An image forming apparatus having a plurality of image forming stations each provided with an image bearing member, a developing device for collecting any untransferred toner on the image bearing member and at the same time, developing an electrostatic image with a toner, and a transfer device for transferring the toner image on the image bearing member to a transfer material, wherein when in a first station and a second station downstream thereof with respect to the movement direction of the transfer material, of the plurality of image forming stations, a toner discharging operation of discharging the toner from each developing device is performed during a non-image forming operation, the toner discharging amount in the second station is controlled so as to be greater than the toner discharging amount in the first station.

1. Field of the Invention
The invention relates to an image forming apparatus using an electrophotographic printing method, an electrostatic recording method or the like, and particularly to an image forming apparatus which collects a toner residual on an image bearing member after the transferring step by developing means and reuses it.
2. Related Background Art
An image forming apparatus such as a copying machine, a printer or a facsimile apparatus using the electrophotographic printing method generally has a cylindrical electrophotographic photosensitive member (photosensitive member) as an image bearing member. Also, the image forming apparatus has a charging device (charging step) for uniformly charging the photosensitive member to a predetermined polarity and potential, and an exposing device (exposing step) as information writing means for forming an electrostatic image on the charged photosensitive member. Also, the image forming apparatus has a developing device (developing step) for visualizing the electrostatic image formed on the photosensitive member as a developer image (toner image) with a toner as a developer, and a transfer device (transferring step) for transferring the toner image from the surface of the photosensitive member to a transfer material. Also, the image forming apparatus has a fixing device (fixing step) for finally fixing the toner image transferred to the transfer material such as recording paper. Further, generally, the image forming apparatus has a cleaning device (cleaning step) for removing any toner (residual developer or untransferred toner) more or less residual on the photosensitive member after the transferring step and cleaning the surface of the photosensitive member. As described above, in the image forming apparatus of the electrophotographic printing type, the photosensitive member is repetitively subjected to an electrophotographic process (the charging step, the exposing step, the developing step, the transferring step and the cleaning step) and is used for image formation.
The untransferred toner is removed from the surface of the photosensitive member by the cleaning device, is collected into the cleaning device and becomes a waste toner. However, from such viewpoints as the preservation of the environment and the effective utilization of resources, it is desirable that such a waste toner does not come out.
From such viewpoints, there has been proposed an image forming apparatus, which returns the untransferred toner, collected in the cleaning device to the developing device and reuses it.
Also, there has been proposed an image forming apparatus of a "cleanerless type" in which the cleaning device is disused and the untransferred toner is removed and collected from on the photosensitive member by "cleaning simultaneous with developing" in the developing device, and is reused.
The cleaning simultaneous with developing collects the untransferred toner on the photosensitive member after the transferring step into the developing device during the developing step after the next step. That is, the photosensitive member to which the untransferred toner adheres is continuedly charged and exposed to thereby form an electrostatic image. Then, during the developing step for this electrostatic image, of the untransferred toner residual on the surface of the photosensitive member, the untransferred toner present on a portion (non-image portion), which should not be developed, is removed and collected into the developing device by fog removal bias. The fog removal bias is the potential difference (fog removal potential difference Vback) between a DC voltage applied to the developing device and the surface potential of the photosensitive member.
Here, the untransferred toner is not constant in the charging amount thereof and therefore, is difficult to intactly collect into the developing device. Therefore, there is a method of applying a bias to a charge assisting member or the like provided downstream of a transfer portion (transfer position) with respect to the rotation direction of the photosensitive member, to thereby uniformize the charging amount of the untransferred toner to a desired charging amount, and collect the untransferred toner by the developing device (Japanese Patent Application Laid-open No. 2004-117960).
According to such a cleanerless type, the untransferred toner is collected by the developing device and is reused for the development of the electrostatic image after the next step. Therefore, the waste toner can be eliminated, and cumbersomeness can be reduced during maintenance. Also, a cleaning member and a waste toner conveying mechanism are unnecessary, and this is also advantageous to the downsizing of the image forming apparatus.
There has also been proposed an image forming apparatus provided with a plurality of image forming portions of such a cleanerless type as described above (Japanese Patent Application Laid-open No. 2004-021178). That is, a plurality of image forming portions each adopting the cleanerless type are disposed along the movement direction (progress direction) of a transfer material. Yellow, magenta, cyan and black toner images are formed by the respective image forming portions, and are successively superposed and transferred to thereby obtain a full-color image formed article (a copy or a print).
However, it has been found that the image forming apparatus provided with a plurality of image forming portions of such a cleanerless type as described above along the movement direction of the transfer material suffers from the following problem.
In the developing device, not only the untransferred toner produced in each image forming portion, but also a toner (re-transferred toner) resulting from the re-transfer of part of a toner image formed by an upstream image forming portion with respect to the movement direction of the transfer material is collected. The re-transfer is the phenomenon that part of the toner image transferred to the transfer material in the upstream image forming portion with respect to the movement direction of the transfer material adheres onto the photosensitive member of a downstream image forming portion in the transferring portion of the downstream image forming portion. In the more downstream image forming portion with respect to the movement direction of the transfer material, the greater becomes the number of upstream image forming portions. Therefore, the more downstream image forming portion is greater in the amount of re-transferred toner, and becomes greater also in the amount of toner collected by the developing device.
Here, the untransferred toner and the re-transferred toner are toners, which could not be borne on the transfer material even if a transfer electric field was applied in the transferring portion of the image forming portion. Therefore, it is often the case that the charging charges of the untransferred toner and the re-transferred toner have a polarity opposite to a regular charging polarity or do not have a polarity. Also, it is often the case that the untransferred toner and the re-transferred toner are different-shaped toners as their toner shape or differ in their toner particle diameter from the mean particle diameter. Further, the re-transferred toner is part of a toner image comprising a toner of a discrete color formed in the upstream image forming portion and therefore, sometimes differs also in the nature of the toner.
The untransferred toner and the re-transferred toner, as described above, are returned to a proper charging amount by the charge assisting member provided downstream of the transferring portion with respect to the rotation direction of the photosensitive member and are collected by the developing device. However, the more downstream image forming portion is greater in the amount of re-transferred toner and therefore, the charge assisting member is liable to be contaminated by the toner and an extraneous additive or the like accumulating thereon. Therefore, the more downstream image forming portion becomes more insufficient in the control of the charging amounts of the untransferred toner and the re-transferred toner.
Thereby, it becomes liable to happen that the toner having passed the charge assisting member is not collected by the developing device or the developer in the developing device is increased in the amount of toner differing from the regular charging polarity. Therefore, a faulty image such as "fog" in which the toner adheres to a white background portion becomes liable to occur.
Also, the re-transferred toner is part of a toner image comprising a toner of a discrete color formed in the upstream image forming portion. Therefore, the mixing of colors occurs in the developing device into which the re-transferred toner has been collected, and it sometimes becomes impossible to reproduce an image of a proper color.


Systems, methods, and devices are provided for a circuit for generating a pulse output having a controllable pulse width. Systems and methods may include a delay line having a plurality of stages. A delay per stage calculation circuit is configured to determine a per-stage delay of the delay line using a first clock input. A pulse generation circuit is configured to generate the pulse output using the delay line based on the per-stage delay using a second clock input, the second clock input having a lower frequency than the first clock input.

Pulse signals are common mechanisms used in digital circuits for a variety of purposes, such as signaling memory read/write times, indicating the occurrence of an event, providing timing synchronization, etc. Proper function of a circuit often dictates that pulse signals be of the designated width. Pulses that are not provided for a long enough time may result in incomplete downstream processes or may not be detected at all. Pulses that are provided for too long a time may result in erroneous downstream circuit operation (e.g., what was meant to be a single pulse may be interpreted as multiple pulses). Thus accurate pulse duration (i.e., width) ensures proper function of a digital circuit. As circuit size scales down and operation speeds increase, power and circuit area efficiency in all aspects, including pulse generation, becomes important.

Systems and methods for generating a controllable-width pulse signal

Taiwan Semiconductor Manufacturing Company Limited


An acrylonitrile solution of maleimide manifesting transparency, precluding coloration and opacification during the course of handling, and excelling in stability, a method for the preparation of the acrylonitrile solution, and an acrylonitrile based copolymer obtained by using the acrylonitrile solution are provided. The acrylonitrile solution of maleimide is such that, when it is subjected to a forced coloration test, the differences xcex94L, xcex94a, xcex94b values (invariably as absolute values) each between L, a, and b values before and after the test are respectively not more than 5, not more than 5, and not more than 10. The acrylonitrile solution of maleimide is prepared by lowering the water content in the acrylonitrile solution to a level of not more than 0.1% by weight, or causing the acrylonitrile solution to permit coexistence therein of a polymerization inhibitor and lowering the water content in the acrylonitrile solution to a level of not more than 0.3% by weight.

1. Field of the Invention
The present invention relates to acrylonitrile solutions of maleimides, a method for the preparation thereof, and acrylonitrile based copolymers obtained by the use of the acrylonitrile solutions.
The maleimides represented by N-phenyl maleimide and the like are used as a heat resistance enhancer for such acrylonitrile based copolymers as acrylonitrile-butadiene-styrene (ABS) resin, acrylonitrile-acrylic rubber-styrene (AAS) resin, acrylonitrile-styrene (AS) resin, and acrylonitrile-chlorinated polyethylene-styrene (ACS) resin.
2 . Description of the Prior Art
The maleimides which are in a solid state at room temperature have been heretofore handled generally in such forms as powder, flakes, and tablets. The maleimides in these solid forms, however, undergo gradual comminution and yield minute particles copiously during the course of transportation and consequently give rise to numerous problems such as deterioration of the work environment. For the solution of these problems, a method for enabling the maleimides to be handled securely in the form of acrylonitrile solutions obtained in advance by dissolving the maleimides together with a polymerization inhibition in acrylonitrile (JP-B-03-12,057) has been proposed. Since this method which permits the maleimides to be handled in the form of acrylonitrile solutions is excellent in having solved the problems mentioned above, it has been finding growing acceptance for industrial applications.
Since the acrylonitrile as the solvent for the acrylonitrile solutions of maleimides constitutes itself the source of the acrylonitrile conpnent of the acrylonitrile based copolymers, the acrylonitrile solutions of maleimides, after being handled as for transportation, are used in their unmodified form for the production of the acrylonitrile based copolymers mentioned above.
The maleimides are yellow and the acrylonitrile solutions obtained by dissolving the maleimides in acrylonitrile are yellow and transparent. So long as the acrylonitrile solutions of maleimides are as yellow and transparent as they were when they were fresh from the production line, the acrylonitrile based copolymers as finished products using the solutions pose no particular problem concerning the color characteristics. In other words, the acrylonitrile based copolymers as the finished products cannot induce such coloration as tends to impair their marketability.
On no occasion, however, the acrylonitrile solutions of maleimides which are fresh from the production line are used immediately for the production of acrylonitrile based copolymers. Generally, the acrylonitrile solutions of maleimides after their production are transported by tank lorries and the like, stored in tanks and the like, or conveyed by the pipeline including pipe, valves, and nozzles (such as, for example, the polymer-feeding line from the storage tank for the acrylonitrile solutions of maleimides) before they are used for the production of acrylonitrile based copolymers. In the present invention, the transportation as by tank lorries, the storage as in tanks, and the conveyance as by the pipeline including pipe, valves, and nozzles (such as, for example, the polymer-feeding line from the storage tank for the acrylonitrile solutions of maleimides) will be referred to collectively as xe2x80x9chandling.xe2x80x9d
After the acrylonitrile solutions of maleimides have been handled over a specific period, they possibly change color from the inherent yellow color to a brown color, for example, gain in the degree of yellowness (namely, darken the yellow color), or occasionally opacify In this invention, these phenomena will be referred to collectively as xe2x80x9cdiscoloration. xe2x80x9d
The acrylonitrile based copolymers obtained as finished products by using the acrylonitrile solutions of maleimides which have been discolored as described above are colored and have markedly impaired marketability. For the purpose of improving these finished products in marketability, the standards or demands imposed on the color of the acrylonitrile solutions of maleimides have been decisively gaining in exactitude in recent years. In the circumstances, such acrylonitrile solutions of maleimides as are appropriately used for the production of acrylonitrile based copolymers which sparingly incur discoloration due to aging during the course of handling, consequently preclude coloration, and excel in the color characteristics are strongly demanded.
Hereinafter, the acrylonitrile solutions of maleimides will be occasionally referred to simply as xe2x80x9cacrylonitrile solutions.xe2x80x9d
An object of this invention, therefore, is to provide such acrylonitrile solutions of maleimides as are appropriately used for the production of acrylonitrile based copolymers which preclude coloration and excel in the color characteristics.
Another object of this invention is to provide a method for the production of the acrylonitrile solutions of maleimides mentioned above.
Yet another object of this invention is to provide acrylonitrile based copolymers of excellent color characteristics and high marketability which are obtained by using the acrylonitrile solutions of maleimides mentioned above.
The objects mentioned above are accomplished by the following aspects (1) to (9) of the present invention.
(1) An acrylonitrile solution of maleimide, characterized by the fact that, in a forced coloration test, the values, xcex94L, xcex94a, and xcex94b, to be calculated in accordance with the following formulas:
xcex94L=|L1xe2x88x92L2|(Absolute value)
xcex94a=|a1xe2x88x92a1|(Absolute value)
xcex94b=|b1xe2x88x92b2|(Absolute value)
wherein L1, a1, and b1 are respectively the values of L, a, and b of the acrylonitrile solution before undergoing the forced coloration test and L2, a2, and b2 are respectively for the values or L, a, and b of the acrylonitrile solution after undergoing the forced coloration test, are respectively not more than 5, not more than 5, and not more than 10.
(2) An acrylonitrile solution of N-phenylmaleimide having azobenzene and N,N-diphenyl hydrazine at a total content of not more than 500 ppm.
(3) A method for the preparation of an acrylonitrile solution set forth in (1) or (2) mentioned above, characterized in that the acrylonitrile solution has a water content of not more than 0.1% by weight.
(4) A method for the preparation of an acrylonitrile solution set forth in (1) or (2) mentioned above, characterized in that the acrylonitrile solution allows the presence therein of at least one member selected from the group consisting of alkyl-substituted hydroxybenzenes and hindered phenols and at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides.
(5) A method for the preparation of an acrylonitrile solution set forth in (1) or (2) mentioned above, characterized in that the acrylonitrile solution has a water content adjusted to a level of not more than 0.3% by weight and allows the presence therein of at least one member selected from the group consisting of alkyl-substituted hydroxybenzenes and hindered phenols, phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides.
(6) A method for the storage of an acrylonitrile solution of maleimide set forth in (1) or (2) mentioned above, characterized in that the molecular oxygen concentration of the gaseous phase portion of the acrylonitrile solution is adjusted to a level in the range of 0.01 to 10% by volume preparatorily to storing the solution as held in contact with a metal.
(7) A method for the preparation of an acrylonitrile solution of maleimide set forth in (1) or (2) mentioned above, comprising the steps of causing a molten maleimide obtained by purifying crude maleimide to allow the presence therein of a primary antioxidant and a secondary antioxidant and subsequently dissolving the solidified maleimide in acrylonitrile.
(8) A method for the preparation of an acrylonitrile solution of maleimide set forth (1) or (2) mentioned above, characterized in that the molten maleimide obtained by purifying crude maleimide is dissolved in acrylonitrile in the presence of a primary antioxidant and a second antioxidant.
(9) An acrylonitrile based copolymer obtained by the use of an acrylonitrile solution set forth in (1) or (2) mentioned above.
It is well known that as one of the methods for quantitatively rating the difference between two colors, the so-called Hunter""s L, a, b method has been proposed by Richard S. Hunter [Richard S. Hunter, The Measurement of Appearance, 2nd Ed., John Wiley and Sons, (1987)]. An instrument generally called a colorimeter which permits direct reading of the L, a, b values according to the Hunter""s L, a, b method mentioned above is marketed and is readily available. We have decided to indicate the degree of discoloration of an acrylonitrile solution of maleimide by using the differences in L, a, and b values determined with a colorimeter designed on the basis of the Hunter""s L, a, b method mentioned above. To be specific, we have established a method of forced coloration test for reproducing the discoloration by aging which occurs when the acrylonitrile solution is actually handled on a commercial scale and rated the degree of discoloration of the acrylonitrile solution in terms of the differences in the L, a, and b values before and after the test. We have consequently found that an acrylonitrile solution giving not more than 5, not more than 5, and not more than 10 respectively as the values of xcex94L, xcex94a, and xcex94b calculated in accordance with the following formulas:
xcex94L=|L1xe2x88x92L2|(Absolute value)
xcex94a=|a1xe2x88x92a1|(Absolute value)
xcex94b=|b1xe2x88x92b2|(Absolute value)
wherein L1, a1, and b1 are respectively the values of L, a, and b before the test mentioned above and L2, a2, and b2 are respectively for the values of L, a, and b after the test, when copolymerized, produces an acrylonitrile based copolymer, more specifically an acrylonitrile-maleimide-containing copolymer, precluding discoloration, excelling in color characteristics, and enjoying high marketability. The acrylonitrile solution of maleimide of this invention incurs no or markedly diminished discoloration by aging during the course of handling thereof.
We made a study in search of the cause for discoloration of the acrylonitrile solutions of maleimides, particularly N-phenyl maleimide. We have consequently demonstrated that the substances responsible for the discoloration are azobenzene (occasionally referred to briefly as xe2x80x9cAZBxe2x80x9d hereinafter) and N,Nxe2x80x2-diphenyl hydrazine (occasionally referred to briefly as xe2x80x9cDPHxe2x80x9d hereinafter). We have further found that acrylonitrile based copolymers, specifically acrylonitrile-N-phenyl maleimide-containing copolymers, obtained with an acrylonitrile solution of N-phenyl maleimide whose total content of AZB and DPH is not more than 500 ppm (based on the weight of the acrylonitrile solution) preclude discoloration and enjoy extremely high marketability.
We seek to explain the formation of AZB and DPH in the acrylonitrile solution of N-phenyl maleimide as follows, though not intent on restricting the present invention by a theoretical discussion. When the acrylonitrile solution of N-phenyl maleimide is stored in a tank made of carbon steel or stainless steel, since the standard industry grade acrylonitrile contains water in a small amount such as, for example, in the approximate range of 0.5 to 1% by weight, this water acts and causes the N-phenyl maleimide to undergo partial hydrolysis and first produce aniline and then this aniline, when activated, leads to the formation of AZB and DPH via the aniline radical.
We have found that the acrylonitrile solution of maleimide having not more than 5, not more than 5, and not more than 10 respectively as the values of xcex94L, xcex94a, and xcex94b and the acrylonitrile solution of N-phenyl maleimide containing AZB and DPH in a total amount of not more than 500 ppm can be prepared by lowering the water content thereof to not more than 0.1 by weight or by adding such an antioxidant as an alkyl-substituted hydroxybenzene and hindered phenol thereto.
Incidentally, the maleimide to be used for the preparation of the acrylonitrile solution of maleimide is generally in the form of flakes of maleimide which are obtained by purifying crude maleimide by distillation in the presence of a polymerization inhibitor thereby obtaining molten maleimide, temporarily storing the molten maleimide in an intermediate tank, and then cooling and solidifying the molten maleimide by the treatment with a flaker, for example. Generally, the flakes of maleimide are stored as placed in a packing container such as, for example, a paper bag, a container bag, or an alumina container. At times, this storage extends over a period of several months. The flakes of maleimide are inevitably exposed to the ambience of air before they are dissolved in acrylonitrile. Specifically, the maleimide is exposed to the ambience of air during the step of storing the molten maleimide in the intermediate tank, the step of cooling and solidifying the molten maleimide into flakes, and the step of storing the flakes of maleimide.
We have been ascertained by their study that the maleimide, when exposed to the ambience of air before it is dissolved in acrylonitrile, is disposed to form readily a peroxide as a source of radical and produce actually the peroxide in a very minute amount and that this peroxide directly passes into the acrylonitrile solution of maleimide, participates in the formation of substances responsible for coloration, and induces unfavorable results such as the discoloration of the acrylonitrile solution of maleimide.
The idea of carrying out the steps mentioned above in the ambience of nitrogen may be conceived for the solution of this problem. This method, however, is incapable of effectively preventing the molten maleimide from being polymerized and is unrealistic from the viewpoint of economy, for example.
We have further continued their study to find that the formation of the peroxide in the maleimide and the discoloration by aging of the acrylonitrile solution of maleimide can be very effectively prevented by quickly adding the combination of such antioxidants as generally defined as a primary antioxidant and a secondary antioxidant to the maleimide which is yet to be solidified, specifically to the maleimide which has been purified by distillation and is still in the molten state.
The present invention provides an acrylonitrile solution of maleimide, characterized by the fact that, in a forced coloration test performed by immersing a sample of the acrylonitrile solution of maleimide in a Pyrex test tube, with a size of 18 mm in inside diameter and 180 mm height, then introducing into the solution a preparatorily polished test piece made of SUS 304 and measuring 50 mm in length, 10 mm in width, and 2 mm in thickness, adjusting the molecular oxygen concentration of the gaseous phase of the test tube to a level in the range of 3 to 10% by volume (providing that the molecular oxygen concentration is obtained of the gas mixture excluding maleimide and acrylonitrile on the basis of volume), placing the test tube in an oil bath set at 70xc2x0 C. and allowing it to stand therein for three days (72 hours), subsequently extracting the test piece from the test tube, and subjecting the acrylonitrile solution to the determination of the values, L , a, and b, the values, xcex94L, xcex94a, and xcex94b, to be calculated in accordance with the following formulas:
xcex94L=|L1xe2x88x92L2|(Absolute value),
xcex94a=|a1xe2x88x92a1|(Absolute value),
xcex94b=|b1xe2x88x92b2|(Absolute value)
wherein L1, a1, and b1 are respectively the values of L, a, and b of the acrylonitrile solution before undergoing the forced coloration test mentioned above and L2, a2, and b2 are respectively for the values of L, a, and b of the acrylonitrile solution after undergoing the forced coloration test, are respectively not more than 5, not more than 5, and not more than 10.
Incidentally, the L, a, and b values of the acrylonitrile solution of maleimide are determined by the following method.
Method for Determination of L, a, and b Values
By the use of a calorimeter produced by Nippon Denshoku Kogyo K. K. and marketed under product code of xe2x80x9cxcexa3-80,xe2x80x9d a sample of the acrylonitrile solution of maleimide is adjusted to a concentration of 30% by weight and subsequently measured for the L, a, and b values by the transmission mode. A commercially available acrylonitrile (guaranteed reagent) is used as a control and the cell used for the test has a thickness of 10 mm.
The maleimides which are used in this invention include N-methyl maleimide, N-ethyl maleimide, N-hexyl maleimide, N-octyl maleimide, N-dodecyl maleimide, N-benzyl maleimide, N-cyclohexyl maleimide, N-phenyl maleimide, N-nitrophenyl maleimide, N-methoxyphenyl maleimide, N-methylphenyl maleimide, N-carboxyphenyl maleimide, N-hydroxyphenyl maleimide, N-chlorophenyl maleimide, N-dimethylphenyl maleimide, N-dichlorophenyl maleimide, N-bromophenyl maleimide, and N-tribromophenyl maleimide, for example. Among other maleimides cited above, N-phenyl maleimide proves particularly advantageous for the use contemplated herein.
This invention does not discriminate the maleimide to be used therein on account of the method to be adopted for the production thereof. The maleimides obtained by varying methods can be used herein. For example, the maleimides obtained by the method which comprises subjecting a maleamic acid, the precursor of a maleimide, to dehydrocyclization with an acid anhydride such as acetic anhydride, the method which comprises heating a maleamic acid together with an acid catalyst under a reduced pressure thereby effecting dehydrocyclization of the maleamic acid, the method which comprises heating a maleamic acid in an organic solvent while expelling from the reaction system the water formed by the resultant dehydrocyclization in the form of an azeotropic mixture with the organic solvent, and the method which comprises preparing as an organic solvent a mixed solvent consisting of an inert organic solvent such as benzene and a non-protonic polar organic solvent such as Nxe2x80x2,N-dimethyl formamide and heating a maleamic acid in the mixed solvent thereby effecting dehydrocyclization of the maleamic acid can be used. The maleimides produced by some, if not all, of these methods contain a residual acid component. This invention tolerates the presence in the maleimide of up to about 5% by weight of such an acid component. It nevertheless prefers the maleimide to be used after being refined until the content of the acid component thereof falls below 0.3% by weight.
Advantageously, the acrylonitrile solution of maleimide of the present invention is such that the values of xcex94L, xcex94a, and xcex94b are respectively not more than 5, not more than 5, and not more than 10, preferably not more than 2, not more than 2, and not more than 4, more preferably not more than 1, not more than 1, and not more than 2, and particularly preferably not more than 0.5, not more than 0.5, and not more than 1. The dissolution of maleimide in acrylonitrile can be implemented by any arbitrary method such as, for example, throwing the maleimide into acrylonitrile. Properly, the solution of maleimide is carried out at a temperature not exceeding the boiling point of acrylonitrile (78.5xc2x0 C.). Since acrylonitrile has a high vapor pressure, it is generally advantageous to carry out the dissolution process at a temperature in the range of 30 to 70xc2x0 C. Generally, the temperature at which the acrylonitrile solution is handled is in the range of 20 to 70xc2x0 C.
The materials of which the facilities (including pipelines) for handling the acrylonitrile solution are made are not limited particularly. The surfaces of the facilities exposed to the acrylonitrile solution may be passivated by glass lining, ceramic coating, etc. For handling the acrylonitrile solution on a commercial scale, it is economically favorable to use facilities which are made of such a general-purpose industrial material as carbon steel or stainless steel.
The concentration of maleimide in the acrylonitrile solution is not particularly limited. It can be suitably selected in consideration of such factors as the temperature of handling, the form of handling (such as transportation or storage), the kind of the acrylonitrile based copolymer to be produced with the acrylonitrile solution, the method of this production, and the production conditions. In some cases, the concentration of maleimide is preferably high as when the acrylonitrile solution is used for the production of an acrylonitrile based copolymer having a high maleimide content, for example. Generally, the concentration of maleimide is in the range of 40 to 90% by weight.
Preferably, the acrylonitrile solution of maleimide of this invention is such that the values of L, a, and b to be determined after the preparation of the solution are in the ranges, L=90 to 100, a=xe2x88x9210 to xe2x88x9230, and b=30 to 50. In the acrylonitrile solutions of maleimide according to this invention, those whose values of L, a, and b determined after the preparation thereof fall within the ranges, L=90 to 100, a=xe2x88x9210 to xe2x88x9230, and b=30 to 50 and whose values of xcex94L, xcex94a, and xcex94b are respectively not more than 5, not more than 5, and not more than 10, particularly preferably not more than 1, not more than 1, and not more than 2.
The acrylonitrile solution of maleimide of this invention can be efficiently produced by the methods which will be described specifically hereinbelow. These methods are adopted advantageously when the acrylonitrile solution of maleimide is handled with facilities which are made of such a general-purpose industrial material as carbon steel or stainless steel.
Method A comprises adjusting the water content in the acrylonitrile solution or maleimide to not more than 0.1% by weight (refer to Example 9).
The acrylonitrile solution of this invention cannot be prepared when the water content exceeds 0.1% by weight (refer to Controls 1 to 3). For the purpose of lowering the water content in the acrylonitrile solution to a level of not more than 0.1% by weight, since the maleimide contains substantially no water, it suffices to lower the water content in the acrylonitrile used as the solvent to a level not more than 0.1% by weight. The water content in the acrylonitrile can be adjusted by any of the known methods such as, for example, precision distillation, physical adsorption by the use of silica gel or molecular sieve, or dehydration by the use of anhydrous sodium sulfate or anhydrous magnesium sulfate. Appropriately, the water content in the acrylonitrile solution is as low as possible. The lower limit of the water content is suitably decided in consideration of the cost for minimizing the water content besides the extent of discoloration by aging which the acrylonitrile solution is expected to tolerate.
It is particularly advantageous to lower the water content in the acrylonitrile solution to a level of not more than 0.05% by weight. When the water content is thus lowered, the acrylonitrile solution to be prepared is such that the values of xcex94L, xcex94a, and xcex94b thereof are respectively not more than 1, not more than 1, and not more than 2.
Method B resides in enabling the acrylonitrile solution to coexist with an antioxidant effective in precluding the generation of peroxide. As the antioxidant, at least one member selected from the group consisting of alkyl-substituted hydroxy benzenes and hindered phenols or at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides can be used by itself. It is, however, effective to use at least one member selected from the group consisting of alkyl-substituted hydroxy benzenes and hindered phenols in combination with at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides. Further, in Method B, the acrylonitrile solution of this invention can be prepared with high efficiency by lowering the water content in the acrylonitrile to be used. In this case, it suffices to lower the water content in the acrylonitrile solution to a level of not more than 0.3% by weight.
Thus, preferred embodiments of Method B are as follows.
(a) The water content in the acrylonitrile solution is lowered to a level of not more than 0.3% by weight and at least one member selected from the group consisting of alkyl-substituted hydroxy benzenes and hindered phenols or at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides is caused to exist in the acrylonitrile solution (refer to Example 12).
(b) The water content in the acrylonitrile solution is lowered to a level of not more than 0.3% by weight and at least one member selected from the group consisting of alkyl-substituted hydroxy benzenes and hindered phenols and at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides is caused to exist in the acrylonitrile solution (refer to Example 11).
In the embodiments (a) and (b) mentioned above, the discoloration by aging of the acrylonitrile solution can be diminished to a still lower level by lowering the water content in the acrylonitrile solution to a level of not more than 0.2% by weight, preferably to a level of not more than 0.1% by weight. Particularly when the water content in the acrylonitrile solution is lowered to a level of not more than 0.05% by weight, the acrylonitrile solution whose values of xcex94L, xcex94a, and xcex94b are respectively not more than 1, not more than 1, and not more than 2 can be prepared.
As typical examples of the alkyl-substituted hydroxy benzene mentioned above, 2,4-dimethyl-6-tert-butylphenol, 4-tert-butyl catechol, 2,5-di-tert-butyl hydroquinone, 2-tert-butyl hydroquinone, and 4,4xe2x80x2-thio-bis(6-tert-butyl-m-cresol) may be cited.
As typical examples of the hindered phenol mentioned above, 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butyl anilino)-1,3,5-triazine, 2,2xe2x80x2-thiobis-(4-methyl-6-tert-butyl phenol), triethylene glycol-bis-[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionatel, pentaerythritol-tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2,2-thio-diethylenebis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,6-hexane diol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], tris-(3,5-di-tort-butyl-4-hydroxybenzyl)-isocyanurate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl) benzene, Nxe2x80x2,Nxe2x80x2-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamide), and 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester may be cited.
Among other hindered phenols enumerated above, 2,4-dimethyl-6-tert-butyl phenol, 4-tert-butyl catechol, 2,5-di-tert-butyl hydroquinone, 2-tert-dibutyl hydroquinone, 4,4xe2x80x2-thio-bis(6-tert-butyl-m-cresol), 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butyl anilino)-1,3,5-triazine, 2,2xe2x80x2-thiobis-(4-methyl-6-tert-butyl phenol), and triethylene glycol-bis-[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] are advantageously used.
As typical examples of the phosphorous ester, triphenyl phosphite, tris(nonylphenyl)phosphite, triethyl phosphite, tris(2-ethylhexyl)phosphite, tridecyl phosphite, tris(tridecyl) phosphite, tristearyl phosphite, diphenyl mono(2-ethylhexyl) phosphite, diphenyl monodecyl phosphite, diphenyl monotridecyl phosphite, dilauryl hydrogen phosphite, dilauryl hydrogen phosphite, diphenyl hydrogen phosphite, tetraphenyl dipropylene glycol phosphite, tetraphenyl tetra(tridecyl)-pentaerythritol tetraphosphite, tetra(tridecyl)-4,4xe2x80x2-isopropylidene diphenyl phosphite, trilauryl trithiophosphite, bis(tridecyl)pentaerythritol diphosphite, bis(nonylphenyl) pentaerythritol phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butyl-phenyl) phosphite, hydrogenated bisphenol A-pentaerythritol phosphite polymer, and hydrogenated bisphenol A-phosphite polymer may be cited.
As typical examples of the phosphoric ester, phosphine and phosphoric acid amide, ethyldiethyl phosphonoacetate, ethyl acid phosphate, xcex2-chloroethyl acid phosphate, butyl acid phosphate, butyl pyrophosphate, butoxyethyl acid phosphate, 2-ethylhexyl acid phosphate, di(2-ethylhexyl) phosphate, ethylene glycol acid phosphate, (2-hydroxyethyl)methacrylate acid phosphate, tris (2-chloroethyl) phosphate, tris(dichloropropyl)phosphate, octyl dichloropropyl phosphate, phenyldichloropropyl phosphate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tricresyl phosphate, triphenyl phosphate, triethyl phosiphine, tri-n-butyl phosphine, tricyclohexyl phosphine, triphenyl phosphine, and hexamethyl phosphoric triamide may be cited.
Among other phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides enumerated above, tris(nonylphenyl) phosphate, distearyl pentaerythritol diphosphite, tristearyl phosphite, and di {2-ethylhexyl} phosphate are advantageously used.
The amount of at least one member selected from the group consisting of the alkyl-substituted hydroxy benzenes and hindered phenols mentioned above to be used is in the range of 0.0001 to 1% by weight, preferably 0.001 to 0.1% by weight, based on the amount of the maleimide. The amount of at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides mentioned above to be used is in the range of 0.0001 to 0.1 by weight, preferably 0.001 to 0.1% by weight, based on the amount of the maleimide. When at least one member selected from the group consisting of alkyl-substituted hydroxy benzenes and hindered phenols is used in combination with at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides, the ratio of combination of the two members is not particularly limited. It may be properly decided so that the amounts of the two members involved fall in the relevant ranges of use mentioned above.
Among the combinations between at least one member selected from the group consisting of alkyl-substituted hydroxy benzenes and hindered phenols and at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides, the following combinations are particularly advantageous.
4-Tert-butyl catechol and distearyl pentaerythritol diphospite,
Triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] and distearyl pentaerythritol diphosphite,
4-Tert-butyl catechol and tristearyl phosphite.
In Method A and Method B mentioned above, the discoloration of the acrylonitrile solution of maleimide can be effectively prevented by adjusting the molecular oxygen concentration of the gaseous phase part of the acrylonitrile solution (providing that the molecular oxygen concentration is obtained of the gas mixture excluding maleimide and acrylonitrile on the basis of volume; this remark similarly applies hereinafter) to a level in the range of 0.01 to 10% by volume.
A deviation from the range mentioned above is unfavorable because the discoloration will not be effectively precluded if the molecular oxygen concentration exceeds 10% by volume and the acrylonitrile solution of maleimide will suffer inclusion of monomers other than maleimide and acrylonitrile and incur discoloration owing to the contamination of containers such as storage tanks if the molecular oxygen concentration is less than 0.01% by volume. It is, therefore, appropriate that the molecular oxygen concentration is in the range of 0.01 to 10% by volume, preferably 0.1 to 8% by volume, and more preferably 1 to 7% by volume. The gas mixture excluding maleimide and acrylonitrile mentioned above generally comprises molecular oxygen and such inert gases as nitrogen, carbon dioxide, helium, and argon. Since nitrogen is advantageously used as the inert gas, the gas mixture consisting of molecular oxygen and nitrogen may be cited as an appropriate example of the gas mixture excluding maleimide and acrylonitrile.
Now, other preferred embodiments of Method A and Method B will be cited below.
(a) The water content in the acrylonitrile solution is lowered to a level of not more than 0.3% by weight and, at the same time, the molecular oxygen concentration in the gaseous phase part of the acrylonitrile solution is adjusted to a level in the range of 0.01 to 10% by volume (refer to Example 13).
(b) The water content in the acrylonitrile solution is lowered to a level of not more than 0.3% by weight, at least one member selected from the group consisting of alkyl-substituted hydroxy benzenes and hindered phenols or at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides is allowed to exist in the acrylonitrile solution, and the molecular oxygen concentration in the gaseous phase part of the acrylonitrile solution is adjusted to a level in the range of 0.01 to 10% by volume (refer to Example 10).
(c) The water content in the acrylonitrile solution is lowered to a level of not more than 0.3% by weight, at least one member selected from the group consisting of alkyl-substituted hydroxy benzenes and hindered phenols and at least one never selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides are allowed to exist in the acrylonitrile solution, and the molecular oxygen concentration in the gaseous phase part of the acrylonitrile solution is adjusted to a level in the range of 0.01 to 10% by volume (refer to Examples 1, 2, 3, and 6).
In the embodiments (a) to (c) mentioned above, the discoloration by aging of the acrylonitrile solution can be diminished to a lower level by lowering the water content in the acrylonitrile solution to a level of not more than 0.2% by weight, preferably 0.1% by weight. Particularly, the acrylonitrile solution whose values of xcex94L, xcex94a, and xcex94b are respectively not more than 1, not more than 1, and not more than 2 can be prepared by lowering the water content in the acrylonitrile solution to a level of not more than 0.05% by weight.
Further in Method A and Method B mentioned above, the discoloration of the acrylonitrile solution can be diminished more effectively by allowing a metal-inactivating agent to exist in the acrylonitrile solution.
As typical examples of the metal-inactivating agent mentioned above, N,Nxe2x80x2-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine, 2,2xe2x80x2-oxamide bis(ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionatel, N,Nxe2x80x2-disalicylidene-1,2-propane diamine, benzotriazole, tollyl triazole, tollyl triazole-potassium salt, and mercapto benzotriazole-sodium salt may be cited. Among other metal-inactivating agents enumerated above, N,Nxe2x80x2-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine, and 2,2xe2x80x2-oxamide bis[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] are advantageously used. These metal-inactivating agents may be used either singly or in the form of a mixture of two or more members. The amount of the metal-inactivating agent to be added is in the range of 0.0001 to 1% by weight, preferably 0.001 to 0.1% by weight. As concrete means to implement the addition of the metal-inactivating agent, the following embodiments may be cited.
(a) The water content in the acrylonitrile solution is lowered to a level of not more than 0.1% by weight and the metal-inactivating gent is added (refer to Example 14).
(b) The water content in the acrylonitrile solution is lowered to a level or not more than 0.1% by weight, the molecular oxygen concentration of the gaseous phase part of the acrylonitrile solution is adjusted to a level in the range of 0.01 to 10% by volume, and the metal-inactivating agent is added (refer to Example 15).
(c) At least one member selected from the group consisting of alkyl-substituted hydroxy benzenes and hindered phenols and at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides are caused to exist in the acrylonitrile solution and the metal-inactivating agent is added (refer to Example 4).
(d) The water content in the acrylonitrile solution is lowered to a level of not more than 0.3% by weight, at least one member selected from the group consisting of alkyl-substituted hydroxy benzenes and hindered phenols or at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides is caused to exist in the acrylonitrile solution, and the metal-inactivating agent is added (refer to Example 14).
(e) At least one member selected from the group consisting of alkyl-substituted hydroxy benzenes and hindered phenols and at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides are caused to exist in the acrylonitrile solution, the molecular oxygen concentration of the gaseous phase part of the acrylonitrile solution is adjusted to a level in the range of 0.01 to 10% by volume, and the metal-inactivating agent is added (refer to Examples 5, 7, and 8).
(f) The water content in the acrylonitrile solution is lowered to a level of not more than 0.3% by weight, at least one member selected from the group consisting of alkyl-substituted hydroxy benzenes and hindered phenols or at least one member selected from the group consisting of phosphorous esters, phosphoric esters, phosphine, and phosphoric acid amides is caused to exist in the acrylonitrile solution, the molecular oxygen concentration of the gaseous phase part of the acrylonitrile solution is adjusted to a level in the range of 0.01 to 10% by volume, and the metal-inactivating agent is added (refer to Example 17).
In the embodiments (a) to (f) mentioned above, the acrylonitrile solution whose values of xcex94L, xcex94a, and xcex94b are respectively not more than 1, not more than 1, and not more than 2 can be prepared by lowering the water content in the acrylonitrile solution to a level of not more than 0.05% by weight.
The acrylonitrile solution of N-phenyl maleimide of this invention whose total content of AZB and DPH is not more than 500 ppm (based on the weight of the acrylonitrile solution) is used advantageously for the production of an acrylonitrile based copolymer, specifically an acrylonitrile-N-phenyl maleimide-containing copolymer, which precludes coloration and excels in color characteristics. The acrylonitrile solution of N-phenyl maleimide whose total content of AZB and DPH is not more than 100 ppm is appropriate in particular. Preferably, the total content of AZB and DPH in the acrylonitrile solution is as low as possible. Depending on the application for which the acrylonitrile solution is intended, it suffices to adjust the total content to the neighborhood of 20 ppm.
The acrylonitrile solution of N-phenyl maleimide whose total content of AZB and DPH is not more than 500 ppm, preferably not more than 100 ppm, can be prepared by adopting without any modification the method which is used for the preparation of the acrylonitrile solution of maleimide whose values of xcex94L, xcex94a, and xcex94b are respectively not more than 5, not more than 5, and not more than 10, preferably not more than 1, not more than 1, and not more than 2.
Now, Method C and Method D which are used particularly advantageously for the preparation of the acrylonitrile solution of maleimide of this invention whose values of xcex94L, xcex94a, and xcex94b are respectively not more than 5, not more than 5, and not more than 10, preferably not more than 1, not more than 1, and not more than 2 will be described below.
By Method C and Method D, the acrylonitrile solution of maleimide which incurs absolutely no discoloration by aging or diminishes the discoloration appreciably can be easily prepared. In other words, these methods permit the acrylonitrile solution of maleimide appropriate for the production of an acrylonitrile based copolymer precluding coloration and excelling in color characteristics to be prepared by a simple procedure.
The maleimide to be used herein is not particularly limited. Any of the maleimides obtained by various known methods can be adopted as already pointed out.
Since the maleimide which is obtained by such a known method (occasionally containing an organic solvent used in the process of reaction) (hereinafter referred to as xe2x80x9ccrude maleimidexe2x80x9d) suffers such extraneous substances as, for example, phosphoric acid that has been used as an acid catalyst to remain therein, it is generally refined by such treatments as washing with water and distillation and converted into a finished maleimide. To be specific, the refinement may be implemented by a series of operations such as, for example, (1) a procedure of washing the crude maleimide with water thereby depriving it of the organic solvent and subsequently distilling the washed maleimide, (2) a procedure of treating the crude maleimide with such an inorganic acid as sulfuric acid, washing the acid-treated maleimide with water, and thereafter separating the organic solvent therefrom, and (3) washing the crude maleimide with water, recrystallizing the washed maleimide as by concentration, and subsequently separating the produced crystals by filtration.
According to Method C, the acrylonitrile solution of maleimide is obtained by causing the finished maleimide obtained in a molten state from the purifying process described above to allow the coexistence therein of a primary antioxidant and a secondary antioxidant, then cooling and solidifying the maleimide, and dissolving the maleimide in a solid state in acrylonitrile.
According to Method D, the acrylonitrile solution of maleimide is obtained by causing the finished maleimide obtained in a molten state from the purifying process described above to be dissolved in acrylonitrile in the presence of a primary antioxidant and a secondary antioxidant.
The term xe2x80x9cprimary antioxidantxe2x80x9d mentioned above is generally defined as a radical chain inhibitor [refer, for example, to Ed. Sawatari et al. xe2x80x9cHandbook on Antioxidants,xe2x80x9d (published by Taiseisha on Oct. 25, 1976)]. The phenol type antioxidants may be cited as representatives. As concrete examples of the primary antioxidant, the following compounds may be cited.
Phenol Types Antioxidant
2,4-Dimethyl-6-tert-butyl phenol, 4-tert-butyl catechol, 4,4xe2x80x2-thio-bis(6-tert-butyl-m-cresol), 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butyl anilino)-1,3,5-triazine, 2,2xe2x80x2-thiobis-(4-methyl-6-tert-butyl phenol), triethylene glycol-bis-[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], pentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2-thio-diethylenebis[3,(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,6-hexane diol-bis[3-(3,5di-tert-butyl-4-hydroxyphenyl)propionate], tris-(3,5-di-tert-butyl-4-hydroxybenzyl)-isocyanurate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl) benzene, N,Nxe2x80x2-hexamethylene bis(3,5-di)-tert-butyl-4-hydroxy-hydrocinnamite), and 3,5-di-tert-butyl-4-hydroxy-benzyl phosphonate-diethyl ester.
Among other primary antioxidants enumerated above, such alkyl-substituted hydroxy benzenes and/or hindered phenols as 2,4-dimethyl-6-tert-butyl phenol, 4-tert-butyl catechol, 4,4xe2x80x2-thio-bis(6-tert-butyl-m-cresol), 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butyl anilino)-1,3,5-triazine, 2,2xe2x80x2-thiobis-(4-methyl-6-tert-butyl phenol), and triethylene glycol-bis-[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] are used advantageously.
The term xe2x80x9csecondary antioxidantxe2x80x9d mentioned above is generally defined as a peroxide decomposing agent (refer, for example, to the xe2x80x9cHandbook on Antioxidantsxe2x80x9d mentioned above). Sulfur type antioxidants and phosphorus type antioxidants are representative. The following compounds may be cited as typical examples of these secondary antioxidants.
Sulfur Type Antioxidants
Dioctyl-3,3xe2x80x2-thiodipropionate, dilauryl-3,3xe2x80x2-thiodipropionate, ditetradecyl-3,3xe2x80x2-thiodipropionate, distearyl-3,3xe2x80x2-thiodipropionate, laurylstearyl-3,3xe2x80x2-thiodipropionate, pentaerythritol tetrakis (xcex2-laurylthiopropionate), ditridecyl-3,3xe2x80x2-thiodipropionate, 2-mercaptobenzoimidazole, and dilauryl sulfide.
Phosphorus Type Antioxidants
Phosphorous Esters
Triphenyl phosphite, tris(nonylphenyl) phosphite, triethyl phosphite, tris(2-ethylhexyl) phosphite, tridecyl phosphite, tris (tridecyl) phosphite, triatearyl phosphite, diphenylmono(2-ethylhexyl) phosphite, diphenyl monodecyl phosphite, diphenyl monotridecyl phosphite, dilauryl hydrogen phosphite, diphenyl ,hydrogen phosphite, tetraphenyl dipropylene glycol phosphate, tetraphenyltetra(tridecyl) pentaerythritol tetraphosphite, tetra (tridecyl)-4,4xe2x80x2-isopropylidene diphenyl phosphite, trilauryl trithiophosphite, bis(tridecyl) pentaerythritol diphosphite, bis (nonylphenyl) pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, hydrogenated bisphenol A-pentaerythritol phosphite polymer, and hydrogenated bisphenol A-phosphite polymer.
Phosphoric Esters, Phosphine and Phosphoric Acid Amides
Ethyldiethyl phosphoroacetate, ethyl acid phosphate, xcex2-chloroethyl acid phosphate, butyl acid phosphate, butyl pyrophosphate, butoxyethyl acid phosphate, 2-ethylhexyl acid phosphate, di(2-othylhexyl) phosphate, ethylene glycol acid phosphate, (2-hydroxyethyl)methacrylate acid phosphate, tris(2-chloroethyl) phosphate, tris(dichloropropyl) phosphate, octyl dichloropropyl phosphate, phenyldichloropropyl phosphate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tricresyl phosphate, triphenyl phosphate, triethyl phosphine, tri-n-butyl phosphine, tricyclohexyl phosphine, triphenyl phosphine and hexamethyl phosphoric triamide.
Among other phosphorus type antioxidants enumerated above, tris(nonylphenyl) phosphite, distearyl pentaerythritol diphosphite, tristearyl phosphite, and di (12-ethylhexyl) phosphate are advantageously used.
Particularly, the combination of 4-tert-butyl catechol with distearyl pentaerythritol diphosphite, the combination of triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] with distearyl pentaerythritol diphosphite, and the combination of 4-tert-butyl catechol with tristearyl phosphite are used appropriately.
The amount of the primary antioxidant to be allowed to exist in the finished maleimide is in the range of 0.0001 to 1% by weight, preferably 0.001 to 0. 1 by weight, based on the amount of the finished maleimide. The amount of the secondary antioxidant to be allowed to exist in the finished maleimide is in the range of 0.0001. to 1% by weight, preferably 0.001 to 0.1% by weight, based on the amount of the finished maleimide. The ratio of the amount of the primary antioxidant to that of the secondary antioxidant is not particularly limited. It may be properly decided so that the amounts of the two antioxidants fall in the relevant ranges of the amount of use mentioned above.
Now, Method C and Method D will be described in greater detail below.
Method C
This method, as described above, comprises causing the molten maleimide obtained by purifying crude maleimide to permit coexistence therein of a primary antioxidant and a secondary antioxidant, namely causing the finished maleimide derived in the molten state from the purifying step to permit coexistence therein of a primary antioxidant and a secondary antioxidant, then solidifying the molten maleimide, and dissolving the solidified maleimide in acrylonitrile. This method will be described below with reference to a case of performing distillation as one of the purifying steps.
The conditions for carrying out the distillation of maleimide have no particular restriction. The distillation can be carried out in accordance with the conventional method under the conventional conditions.
Incidentally, the distillation of maleimide is generally carried out in the presence of a polymerization inhibitor for the purpose of preventing the maleimide from being polymerized. Any of the known polymerization inhibitors can be used therefor. As typical examples of the polymerization inhibitor, methoxy benzoquinone, p-methoxyphenol, phenothiazine, hydroquinone, alkylated diphenyl amines, methylene blue, 4-tert-butyl catechol, 2,5-di-tert-butyl hydroquinone, zinc dimethyldithiocarbamate, dimethyl dithiocarbamic acid, copper dibutyl dithiocarbamate, copper salicylate, thiodipropionic esters, mercaptobenzimidazole, triphenyl phosphite, alkyl phenols, alkyl bisphenols, and hindered phenols may be cited.
The coexistence of the primary antioxidant and the secondary antioxidant in the molten maleimide is accomplished satisfactorily by simply adding the primary antioxidant and the secondary antioxidant to the maleimide obtained in a molten state in consequence of the treatment of distillation. The primary antioxidant and the second antioxidant may be added either simultaneously or separately from each other. When they are added separately of each other, the order in which they are added is not critical. It is particularly appropriate to effect this addition of the primary antioxidant and the secondary antioxidant before the maleimide in the molten state is exposed to the ambient air excessively. Specifically, when the maleimide emanating in the molten state from the top of a distillation column is stored provisionally in a tank, then solidified, and dissolved in the solid state in acrylonitrile, it is advantageous to add the primary antioxidant and the second antioxidant to the maleimide in the molten state before it is put to the provisional storage. More preferably, the primary antioxidant and the secondary antioxidant are added quickly, and particularly immediately to the maleimide emanating in the molten state from the top of the distillation column.
Incidentally, when the primary antioxidant has the function of a polymerization inhibitor to be used during the purifying of crude maleimide by distillation and this polymerization inhibitor (primary antioxidant) remains in the molten maleimide emanating from the distillation column, it is no longer necessary to add the primary antioxidant anew and it suffices to add only the secondary antioxidant to the molten maleimide. Even in this case, it is of course possible to add (supplement) the primary antioxidant with a refill of the same kind or with a primary antioxidant of a different kind. As a typical example of the primary antioxidant which has the function of a polymerization inhibitor as described above, 4-tert-butyl catechol may be cited. The same remarks hold good for the secondary antioxidant.
The maleimide in the molten state which has permitted the primary antioxidant and the second antioxidant to coexist therein is solidified and molded in an arbitrary form such as powder, flakes, or tablets and the maleimide in the solid state is dissolved in acrylonitrile to produce the acrylonitrile solution of the maleimide.
The dissolution in acrylonitrile of the maleimide in the solid state it not always required to be immediately carried out. The solid maleimide, when necessary, may be dissolved in acrylonitrile after being stored for a prescribed length of time. One of the characteristic features of Method C resides in the fact that the acrylonitrile solution or maleimide which defies discoloration even after protracted handling can be prepared by dissolving in acrylonitrile the maleimide which has been stored in the solid state over a period of several months, for example.
Method D
This method, as described above, comprises causing the molten maleimide obtained by purifying crude maleimide to be dissolved in acrylonitrile in the presence of the primary antioxidant and the second antioxidant. This method, similarly to Method C mentioned above, will be described below with reference to a case of performing distillation as one of the purifying processes.
Since the distillation involved in this method is identical to that involved in Method C mentioned above, it will be omitted from the following description. One embodiment of this method comprises adding the primary antioxidant and the secondary antioxidant to the finished maleimide emanating in the molten state from the top of the distillation tower thereby effecting coexistence of the antioxidants in the molten maleimide and then dissolving the molten maleimide in acrylonitrile before being solidified. The coexistence of the primary antioxidant and the secondary antioxidant according to this embodiment can be attained in the same manner as in Method C mentioned above. When such a primary antioxidant as 4-tert-butyl catechol is used, for example, this primary antioxidant may be used as a polymerization inhibitor during the process of distillation and then the secondary antioxidant or, when necessary, both the primary antioxidant and the second antioxidant may be added to the molten maleimide resulting from the distillation for the purpose of the coexistence. In this embodiment, similarly to Method C mentioned above, it is appropriate to add the primary antioxidant and the secondary antioxidant quickly to the molten maleimide emanating from the top of the distillation column.
Another embodiment of Method D comprises either adding the finished maleimide emanating in the molten state from the top of the distillation column simultaneously with the primary antioxidant and the secondary antioxidant to acrylonitrile and dissolving them therein or dissolving the molten maleimide in acrylonitrile having the primary antioxidant and the second antioxidant added in advance thereto. In the case of this embodiment, it is appropriate to have the molten maleimide quickly dissolved in acrylonitrile.
As the acrylonitrile to be used in implementing Method C and Method D, the industry grade acrylonitrile proves appropriate. Generally, the industry grade acrylonitrile contains a small amount of water and this water is thought to constitute a factor for causing the acrylonitrile solution of maleimide to produce a substance responsible for coloration. These methods can use the industry grade acrylonitrile without any trouble. Method C and Method D, therefore, are at a great economic advantage in allowing production of the acrylonitrile solution incurring absolutely no discoloration or appreciably diminished discoloration by aging even by using the industry grade acrylonitrile as the solvent.
In these methods as in Method A and Method B mentioned above, the discoloration of the acrylonitrile solution by aging can be effectively diminished by lowering the molecular oxygen concentration in the gaseous phase part of the acrylonitrile solution in the process of handling (providing that the molecular oxygen concentration is obtained of the gas mixture excluding maleimide and acrylonitrile on the basis of volume) to a level of not more than 10% by volume, preferably in the range of 0.1 to 8% by volume, and more preferably in the range of 1 to 7% by volume.
The gas mixture excluding maleimide and acrylonitrile mentioned above generally comprises molecular oxygen and such inert gases as nitrogen, carbon dioxide, helium, and argon. Since nitrogen is particularly advantageously used as the inert gas, the gas mixture comprising molecular oxygen and nitrogen may be cited as an appropriate example of the gas mixture excluding maleimide and acrylonitrile.
The discoloration of the acrylonitrile solution by aging can be more effectively diminished by allowing the same metal-inactivating agent as mentioned in Method A and Method B to coexist together with the primary antioxidant and the secondary antioxidant in the molten maleimide. The metal-inactivating agent and the amount of addition thereof are the same as those already mentioned in the description of Method A and Method B. This metal-inactivating agent may be added to the acrylonitrile solution of maleimide which has been prepared in accordance with Method C or Method D.
One preferred embodiment of Method C and Method D, therefore, is as follows.
(a) The acrylonitrile solution of maleimide is prepared in accordance with Method C or Method D and the molecular oxygen concentration of the gaseous phase part of this acrylonitrile solution is adjusted to a level of not more than 10% by volume, preferably in the range of 0.1 to 8% by volume, and more preferably in the range of 1 to 7% by volume.
In accordance with Method C and Method D mentioned above, the acrylonitrile solution of maleimide incurring absolutely no discoloration or appreciably diminished discoloration by aging can be prepared conveniently and easily.
Method C and Method D mentioned above are used particularly advantageously for the preparation of the acrylonitrile solution of N-phenyl maleimide whose total content of AZB and DPH is not more than 500 ppn, particularly not more than 100 ppm.
The acrylonitrile solution of maleimide of this invention enjoys transparency and appreciably diminished discoloration. The use of this acrylonitrile solution of maleimide, therefore, permits the production of an acrylonitrile based copolymer, an acrylonitrile-maleimide-containing copolymer to be exact, which precludes coloration and excels in color characteristics. By the same token, the use or the acrylonitrile solution of N-phenyl maleimide of this invention whose total content of AZB and DPH is not more than 500 ppm permits the production of an acrylonitrile based copolymer, an acrylonitrile-N-phenyl maleimide-containing copolymer to be exact, which precludes coloration and excels in color characteristics.
The term xe2x80x9cacrylonitrile based copolymerxe2x80x9d as used in this invention refers to copolymers which are obtained by the use of the acrylonitrile solution of maleimide mentioned above (including the acrylonitrile solution of N-phenyl maleimide mentioned above). The term embraces copolymers of maleimides with acrylonitrile, and copolymers of maleimides with acrylonitrile and monomers which are copolymerizable therewith.
As representative compounds of the copolymerizable monomer, methacrylic esters such as, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, cyclohexyl methacrylate, and isobonyl methacrylate; acrylic esters such as, for example, methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate; aromatic vinyl compounds such as, for example, styrene and xcex1-methyl styrene; and conjugate dienes such as, for example, butadiene may be cited. Among other copolymerizable monomers enumerated above, methyl methacrylate, methyl acrylate, styrene, and xcex1-methyl styrene prove advantageous in exhibiting excellent reactivity and permitting the production of resins which excel in heat-resistance.
As other concrete examples of the copolymer mentioned above, acrylonitrile-butadiene-styrene (ADS) resin, acrylonitrile-acrylic rubber-styrene (AAS) resin, and acrylonitrile-chlorinated polyethylene-styrene (ACS) resin which contain maleimide as one component of copolymer may be cited.
The acrylonitrile based copolymers of this invention are invariably known to the art. They can be easily produced by the known method of polymerization except that the acrylonitrile solution of maleimide of this invention is used in place of the known acrylonitrile solution of maleimide. These acrylonitrile based copolymers, when necessary, can incorporate therein various known additives.
Now, this invention will be described more specifically below with reference to working examples and controls.

Acrylonitrile solutions of maleimides, method for preparation thereof, and acrylonitrile based copolymers obtained by use of the solutions


Disclosed are methods and systems to determine a power plant machine reliability forecast. In an embodiment, a method may comprise obtaining an environmental factor of a power plant machine based on geospatial data of a first area and location data of a second area, obtaining an operating factor of the power plant machine, and determining a reliability forecast based on the obtained environmental factor and the obtained operating factor.

Turbo machines are utilized globally for electric power generation or as mechanical drives for operating pumps and compressors, under a variety of conditions. Gas turbines are a widely used turbo machine used to generate power for electricity and energy to drive a process such as gas compression. During operation, a turbo machine endures high temperatures, high pressure, and high mechanical loads. Due to these stresses, a turbo machine requires maintenance at regular intervals. It is desirable that maintenance of a turbo machine not be performed prematurely in order to keep the turbo machine online for as long as possible and to reduce operational costs. It is also desirable that maintenance of a turbo machine is performed in advance of any component failure.

Method and system for determining power plant machine reliability


A metal fine particle is adhere to a predetermined location on a substrate. A resist film containing a metallic compound dispersed therein is formed on a substrate (101). A patterning of the resist film is conducted by a lithography. The substrate (101) having the patterned resist formed thereon is heated within an oxygen atmosphere to adhere a metal fine particle (106) to the surface of the substrate (101), while removing the resin in the patterned resist.

In recent years, efforts for applying carbon nanotube to electronic devices is actively examined. In order to manufacture such electronic devices, it is necessary to fix carbon nanotube onto a substrate. Typically, processes for obtaining such condition includes a process for fixing the prepared carbon nanotube onto substrate, and a process for adhering metal fine particles that function as a catalyst on a substrate, and allowing a growth of the carbon nanotubes from the metal fine particles.
In these processes, the latter process is beneficial in that a carbon nanotube can be ensured to be disposed at a desired location. When the process for adhering such metal fine particles is adopted, it is required that the metal fine particles should be adhered at desired locations on the substrate with higher controllability. In addition, since the diameter of the formed carbon nanotube is determined by the diameter of the metal fine particles, a critical technical problem would be a reduction in the size of the metal fine particles. More specifically, manufacturing of fine particles having a particle size on the order of the diameter of the carbon nanotube, namely 0.4 nm to several nm, is required, and in particular, a technology for manufacturing fine particles having a minimum size of equal to or less than 1 nm is required.
Patent literature 1 describes a method for providing a pattern of metal fine particles on a substrate. The patent literature describes a technology for aggregating from an aqueous solution containing a metal catalyst ion to form the metal catalyst cluster, by diffusing the aqueous solution containing a metal catalyst ion in a predetermined region on a substrate, and then conducting an annealing process. However, it is difficult to control the size of the fine particles at a level of several nm in this process. Further, it is also difficult to control the quantity of the adhered fine particles.
Meanwhile, dots of a metal can be manufactured on a substrate by employing a fine processing technology for semiconductors. However, the processing dimension is a dot pattern of about 10 nm at minimum, even if the electron beam lithography, which is a fine processing method, is employed, for example. Consequently, the manufacture of a pattern of equal to or less than 10 nm has been conventionally difficult.
On the other hand, a laser ablation process, processes for precipitating metals from a raw material dispersed into a gas phase or a liquid phase or the like have been conventionally employed as a process for manufacturing metal fine particles having a size of equal to or less than 10 nm. Fine particles having particle diameters of equal to or less than 10 nm can be easily obtained by employing these methods. However, it has been difficult to manufacture the metal fine particles at specified locations on the substrate by employing these methods. Consequently, a secondary process for disposing the fine particles on the substrate is required, in addition to the process for manufacturing the fine particles.
[Patent Literature 1]
Japanese Patent Laid-Open No. 2003-168,745

Method for fixing metal particles and method for manufacturing substrate containing metal particles, method for manufacturing substrate containing carbon nanotube, and method for manufacturing substrate containing semiconductor-crystalline rod, employing thereof


A three position weave system selection device for a weaving loom which includes two superposed electromagnets adapted to be selectively activated to control the position of at least one lever articulated relative to the electromagnets. The at least one lever is provided with two magnetic armatures adapted to cooperate selectively with the two electromagnets so as to generate three positions of the at least one lever relative to two mobile hooks of a harness system of the weaving loom.

1. Field of the Invention
The present invention relates to a selection device, to a three-position Jacquard weaving loom weave system, and to a weaving loom equipped with such a weave system.
2. History of the Related Art
A weaving loom incorporating a weave system adapted to generate three positions of the warp yarns, is used for making special fabrics, such as velvet or a carpet.
European Patent Application No. 0 723 041 discloses a three-position Jacquard system in which the mobile hooks associated with a funicular element determining the height of a heddle, may be selected thanks to two superposed electro-magnets. This device is complex and induces repeated deformations of the mobile hooks, which prevents giving them an adequate rigidity to guarantee a sufficient life duration for industrial application and high-speed operation. In addition, the considerable deformations imposed on these hooks require powerful electro-magnets, with the result that the energy used by the loom with which the known weave system is associated and which presents a large number of electro-magnets, is considerable.
It is an object of the present invention to overcome these problems by proposing a three-position weave system selection device which is simple, therefore economical, adapted to operate at high speeds and consuming little energy. According to another aspect of the invention, it aims at providing a selection device capable of operating with hooks adapted to be displaced in pairs, a first hook of each pair being in simple abutment on the second hook of this same pair.

Weaving loom with three-position jacquard selection device


A multi-function glass cleaning apparatus having a container provided With an opening closable by a plug, two principal opposite faces and two side walls, for receiving and storing a cleaning fluid. A handle is formed integrally with the container and defines a hand grasping portion. The hand grasping portion is transverse to the side walls. A first support member is formed integrally with the container on one of the faces thereof for supporting a scraping element which is secured to it. The first support member is parallel to the hand grasping portion and has a trough extending lengthwise thereof. The trough is in communication with the container via a small aperture. A second support member is formed integrally with the container for supporting a wiper which is secured to it. The second support member is parallel to the hand grasping portion and to the first support member. The apparatus has a mechanism for opening and closing the aperture so as to control the rate of feed of the cleaning fluid from the container through the aperture to the scraping element. When the apparatus is being used, the cleaning fluid contained in the container can exit the container through the aperture at a selected rate of feed and flow through the trough to wet the scraping element evenly.

a) Field of the Invention
The present invention relates to a multi-function glass cleaning apparatus.
b) Brief Description of the Prior Art
Known in the art, there is U.S. Pat. No. 2,082,582 of W.H. KLING granted on May 9, 1936. This patent is representative of many patents describing window cleaning devices having a handle perpendicular to a fluid tank which supports a wiper and a scraping element, such as a sponge. In this patent, the tank has a discharge opening in the form of a slot so that the cleaning fluid escaping through the slot will be taken up by a wick. Furthermore, by regulating the tightness of bolts, the rate of feed of the cleaning fluid from the tank to the wick can be adjusted rapidly.
Also known in the art, there is U.S. Pat. No. 2,886,839 of N. LEOPOLDI, granted on May 19, 1959. This patent describes a window cleaning device including a compressible container adapted for serving as a handle for cleaning elements mounted thereon. These elements are a sponge, a rubber blade and a rigid scraper. The container has a small aperture effective for producing a liquid spray when the container is filled with liquid.
Also known in the art, there is U.S. Pat. No. 5,054,945 of J. IGGULDEN et al., granted on Oct. 8, including a bottle used as a handle and having a sponge and a rubber blade attached thereto. The liquid cleaning solution contained in the bottle is discharged through bores therein, and the amount of discharged fluid is controlled by valve means. The valve means allow the liquid cleaning solution to exit the bottle through the bores only under pressure created by squeezing the bottle.
Also known in the art, there are the following patents which describe different glass cleaning devices:
Canadian patents nos.: 70,136 of E.M. FARMER, granted in 1901 258,979 of P. THOMPSON, granted on Mar. 16, 1926 373,714 of W. WESSELER, granted in 1938;
U.S. Pat. Nos.: 1,977,483 of L. KOUKAL, granted on Oct. 16, 1934 4,778,301 of P. SICOTTE, granted on Oct. 18, 1988 4,954,001 of A.E. BILLAT, granted on Sep. 4, 1990
One drawback with the glass cleaning devices shown in the above patents is that the rate of feed of the cleaning fluid from the container to the scraping element, such as the sponge, cannot be adjusted with an adequate precision and thereby a waste of cleaning fluid occurs.


A transmission gear is composed of two gear elements provided with teeth on their circumference. The gear elements are displaceable coaxially in the circumferential direction and with their teeth offset with respect to one another. The elements are also connected with one another shapewise by at least one connecting member in such fashion that when a meshing gear engages the gear elements, the existing tooth flank play is reduced or eliminated. In this way the connecting member connects the gear elements so that they are nondisplaceable with respect to one another in the circumferential direction and causes the displacement of the gear elements with respect to one another by virtue of its thermal expansion.

This application claims the priority of German application 197 21 852.0, filed May 26, 1997 in Germany, the disclosure of which is expressly incorporated by reference herein.
Gear transmissions that operate with zero play are already known in which one gear of a pair of gears that mesh with one another consists of two tooth crowns, one of which transmits the torque while the other compensates for play, said crowns being biased against one another by a spring in the circumferential direction, i.e. movably connected with one another. German Utility Model 74 00 276 describes such a gear transmission, with a gear composed of two gear elements biased against one another.
Previously known engine and transmission designs however suffer from the problem that the housings have thermal expansion characteristics that differ from those of the shafts, bearings, and gears that are employed. This is especially true when steel gears are used in aluminum housings.
Even when gears with very little tooth flank play at ambient temperatures of about 20.degree. C. are deliberately installed, the change in axial spacing that takes place at higher operating temperatures results in a significant increase in tooth flank play. As a result, a clearly perceptible rattling noise can develop.
For this reason, the tooth flank play of a pair of gears that mesh with one another is compensated by an additional gear element mounted coaxially to a gear, said gear element being biased by one or more springs and urged movably in the circumferential direction against the gear.
This has the disadvantage that usually only the idle noise of the gears that are in mesh is influenced in a positive manner. Effective compensation can occur in only one load direction. When loads change, the spring is subjected to excess pressure and thus the rear tooth flank comes in contact. During coasting, this usually means that a rattling noise results. It is also disadvantageous that the spring force produces increased friction on the tooth flanks, which usually is manifested by a squeaking sound.
Therefore a goal of the invention is to provide a transmission gear that compensates for tooth flank play in a pair of gears in a specific manner regardless of the spring forces and thus independently of the torque being transmitted at a given moment by the pair of gears.
This goal is achieved according to preferred embodiments of the invention by providing a transmission gear composed of at least two gear elements provided with teeth on their circumference, said elements being displaceable coaxially in the circumferential direction, with their teeth offset with respect to one another, and connected shapewise with one another by at least one connecting member in such fashion that for engagement of a meshing gear, the existing tooth flank play is reduced or eliminated, wherein the connecting member connects the gear elements so that they are not displaceable in the circumferential direction and, by its thermal expansion, causes shifting of the gear elements with respect to one another in the circumferential direction.
According to the invention, a transmission gear assembly includes of at least. two gear elements provided with teeth on their circumference, said gear elements being displaceable coaxially in the circumferential direction and having teeth that are offset with respect to one another, and connected shapewise with one another by at least one connecting member in such fashion that the existing tooth flank play is reduced or eliminated in order to engage a meshing gear, with the connecting member connecting the gear elements nondisplaceably with one another in the circumferential direction and, by virtue of its thermal expansion, causing shifting of the gear elements with respect to one another in the circumferential direction.
When the gear elements that are mounted displaceably with respect to one another are firmly connected with one another by a connecting member, this has the advantage that their shifting relative to one another is based on a deliberate utilization of different coefficients of thermal expansion of the materials used for the gear elements and the connecting member. In this way, the tooth flank play that results from differences in thermal expansion between the gears and the transmission housing can be compensated extremely well. The connecting member between the gear elements can consist either of a material that has a degree of thermal expansion that is deliberately greater or deliberately smaller than that of the gear elements. By careful positioning and length of the connecting member, complete tooth flank play compensation or clearly reduced tooth flank play can be achieved over the entire operating temperature range from less than -40.degree. C. to far above 200.degree. C.
Advantageously, the gear elements are not tensioned against the gear with which they mesh, but only the play between the toothed flanks is compensated. For this reason, the frictional losses are significantly less than when tooth flank play compensation is performed by spring force. This also has a positive effect on efficiency and wear in the transmission.
In addition, tooth flank play compensation according to the invention is ensured in both directions of rotation of the gear pair. As a result, the rattling noises produced during coasting as well as nonuniformity of rotation are reduced.
In preferred embodiments of the invention, the connecting member is a pull-push rod. This has the advantage that the twist angle between the two gear elements at a given temperature can be determined in advance in simple fashion.
Another advantageous feature of preferred embodiments of the invention is that the connecting member is mounted like a chord between the two gear elements and is connected shapewise at each end with a respective gear element.
A transmission gear constructed according to the invention is also advantageously easy to manufacture.

Transmission gear arrangement for compensating play at the tooth flanks

Bayerische Motoren Werke Aktiengesellschaft


A method for determining an optimal combination of focus bias and spherical aberration compensating value (SA value) in an optical disc drive is provided. Firstly, a first focus bias is set, the SA values are adjusted and the corresponding tracking error signal values are measured. Second-order-approximation is performed to obtain a first maximum value of tracking error signal. Secondly, a second focus bias is set, the SA values are adjusted and the corresponding tracking error signal values are measured. Second-order-approximation is performed to obtain a second maximum value of tracking error signal. Thirdly, a third focus bias is set, the SA values are adjusted and the corresponding tracking error signal values are measured. Second-order-approximation is performed to obtain a third maximum value of the tracking error signal. The three maximum values are compared to obtain the optimal combination of focus bias and SA compensating value in the optical disc drive.

The performance of an optical disc drive is greatly related to the optical quality of the inner system and spherical aberration is one of important factors for degrading the optical quality of the inner system. When the inner optical quality of the optical disc drive is affected with spherical aberration, the focus error signal and the tracking error signal generated by the optical disc drive are easily distorted so that the servo control becomes more difficult and the unfocused condition or off-track condition possibly happens. Moreover, the deformed light spot of the read/write laser light of the optical disc drive resulted from spherical aberration causes more errors in radio frequency signal when reading discs and poor write quality of the optical disc drive.
Please refer to FIG. 1, which is a diagram showing spherical aberration. The main reason why spherical aberration occurs is that an optical path difference Δλ between the marginal rays and the paraxial rays of the laser light exists when the marginal rays and the paraxial rays reaches the foci plane. The light spot at the foci plane becomes elliptic which resulted from spherical aberration. However, the shape of an optical light spot should be round. In addition the energy distribution of the laser light at the foci plane deteriorates because of spherical aberration which results in the affection of the read/write quality of the optical disc drive.
Generally there are two ways to compensate spherical aberration (SA) in an optical system. One is to adopt a liquid crystal SA compensator and the other is to adopt a collimating SA compensator.
The liquid crystal SA compensator is usually composed of liquid crystal material. The refractive index of the liquid crystal SA compensator is varied with the inputted voltage level, thus the laser light which passes through the liquid crystal SA compensator is compensated so that the shape of the light spot which the laser light reaches the optical disc is circular. The second way to compensate spherical aberration is to adopt a collimating SA compensator. The collimating SA compensator is composed of collimating lens. The position of the collimating lens is changed so as to adjust the optical path difference between the marginal rays and the paraxial rays of the laser light so that spherical aberration is compensated.
That is to say, the optical path difference Δλ between the marginal rays and the paraxial rays of the laser light reaching to the foci plane is compensated once the SA compensating value is inputted to the SA compensator.
Please refer to FIG. 2A, FIG. 2B and FIG. 2C, which illustrates simulated spot diagrams of the optical disc drive. As shown in FIG. 2B, the optimal focus point is at position "0" when a cover layer of an optical disc is 0.6 mm and the SA compensating value "0" is provided. When the thickness of the optical disc (DVD) varies from 0.6 mm to 0.55 mm due to process variation, the optimal focus point shifts 50 μm to the negative direction as shown in FIG. 2A, while the thickness of the optical disc (DVD) varies from 0.6 mm to 0.65 mm due to process variation, the optimal focus point shifts 50 μm to the positive direction as shown in FIG. 2A. However, the quality of the optical signal measured in the optimal focus point of FIG. 2A or FIG. 2C is already deteriorated which result in that the spot size in the optimal focus point of FIG. 2A or FIG. 2C is rather bigger than the spot size in the optimal focus point of FIG. 2B.
In other words, the optimal focus point shifts when a spherical aberration exists in the optical system, the corresponding optimal SA compensating value at the shifted focus point is to be acquired so that the spherical aberration can be compensated. Likewise, when the SA compensating value or the optical path difference of the laser light is adjusted which compensates the spherical aberration, the optimal focus point of the optical disc drive would also shifts. Therefore the best way to assure the best read/write quality of the optical disc drive (i.e. assure the optical disc drive positioned at the optimal focus point) is to adjust the variables of focus bias FEbias and SA compensating value SAvalue at the same time.
However, most prior arts only provide methods for determining an optimal SA compensating value. Please refer to FIG. 3, which illustrates a method for adjusting SA compensating value in U.S. Publication 2008/0074973. Firstly, an amplitude of an tracking error signal TEVPP is adopted as an index signal for quantifying spherical aberration. The amplitudes of the tracking error signal corresponding to SA compensating values (SA=A, SA=0, SA=−A) are measured. The optimal SA compensating value SA_peak corresponding to the largest amplitude of the tracking error signal is then acquired by performing second-order approximation of the three measured point. However, if the optimal SA compensating value SA_peak is not within a limited range, the above steps are repeated until the optimal SA compensating value SA_peak within the limited range is acquired. Nevertheless, the above method for adjusting SA compensating value omits the fact of the optimal focus point shifting. Even the spherical aberration is corrected, the focus point corresponding the adjusted SA compensating value is not at the optimal position.
Please refer to FIG. 4, which illustrates an effectiveness diagram of the SA compensating value and the focus bias versus spherical aberration. An index signal for quantifying the spherical aberration is adopted, i.e. an amplitude of reproduction jitter for example. The index signal positioned more inside the ellipse represents that the value of the index signal is close to an extreme value and the image quality of the laser light is optimal. If the optical disc drive sets an initial focus point FBinitial at a deviated area as shown in FIG. 4, the optimal SA compensating value SAoptimal corresponding to the initial focus bias is actually not the optimal SA compensating value of the optical disc drive. The optical disc drive with the optimal SA compensating value SAoptimal does not have best read/write quality because spherical aberration still occurs. Therefore, the focus bias FEbias and the SA compensating value SAvalue are to be adjusted at the same time which ensures the optical disc drive having the best read/write quality.
Hence, U.S. Pat. No. 7,344,077 provides a method for adjusting the focus bias and the SA compensating values at the same time. The method mainly searches different combinations of focus bias and SA compensating value in 2D direction and a quadratic curve approximation is performed on the searched points so that an optimal combination of focus bias and SA compensating value is acquired. The method finds the most optimal combination of focus bias and SA compensating value, however the quadratic curve approximation is too complex and wasting a lot of system resource and memory space. Therefore, How to acquire an optimal combination of focus bias and SA compensating value rapidly and efficiently is the subject matter of the present invention.

Method and apparatus for determining an optimal focus bias and spherical aberration compensating value in an optical disc drive