The present invention relates to electrically-conductive pulp of sulfonated polyaniline blended with para-aramid wherein the para-aramid is a continuous phase in the pulp and the sulfonated polyaniline is a discontinuous phase.

1. Field of the Invention.
This invention relates to an electrically-conductive aramid pulp composition that has high surface area, a high concentration of fibrils and increases strength and high modulus as polymeric reinforcement.
2. Description of Related Art.
U.S. Pat. Nos. 5,788,897 and 5,882,566, issued Aug. 4, 1998 and Mar. 16, 1999, respectively, disclose fibers having a continuous phase of para-aramid and a discontinuous phase of electrically-conductive sulfonated polyaniline.
U.S. Pat. No. 5,094,913, issued Mar. 10, 1992, discloses a pulp refined from fibers having a continuous phase of para-aramid and a discontinuous phase of meta-aramid.
Japanese Patent Publication (Kokai) No. 59/163418, published Sep. 14, 1984, discloses pulp beaten from fibers of a blend of para-aramid and aliphatic polyamide.
This invention includes a composition in the form of a pulp comprising a blend of 65 to 95 weight percent of para-aramid and 5 to 35 weight percent of sulfonated polyaniline (SPA) wherein the para-aramid is present in the composition as a continuous phase and the SPA is dispersed throughout the para-aramid. Pulp particles in the composition generally have a specific surface area of greater than 7.5 m2/g and a Canadian Standard Freeness of less than 150 milliliters.
Paper made from the pulp of this invention exhibits a charge decay rate of less than 5 seconds.
Electrically conductive pulp is a very desirable product for use in reinforcement of packaging films and polymers, generally, and especially where there is a need to drain or dissipate electrical charges. Electrically conductive pulp finds use in applications where handling dielectric pulp, in dry form, results in charged particles that are difficult to handle or are dangerous due to a threat of sparking on discharge.
This invention utilizes an intimate blend of two polymeric materials to provide a pulp that is not only a good reinforcement for other polymers but is, also, electrically conductive to impart electrical conductivity to normally dielectric materials into which it is added for reinforcement. Fibers of combined polymers are known. Particularly fibers of para-aramid combined with other polymersxe2x80x94and even polyaniline polymersxe2x80x94are known. However, there has been, up to now, no suggestion that such fibers might be refined to make conductive pulp materials.
This invention provides a pulp product that is not only an excellent reinforcement material, is also extremely effective for electric charge dissipation. Moreover, the very material good for such charge dissipation is the material that creates ease in pulp manufacture and excellence in pulp quality.
The materials of this pulp product are para-aramid and SPA and the SPA component provides a dual function with the purposes widely divergent and largely unrelated. First, the polyaniline, as a secondary component in the blend, provides points of fracture for refining and pulping forces to achieve efficient and effective manufacture of high quality pulp with fine, long, fibrils. Second, the polyaniline, as a component effectively on the surface of the pulp particles, provides an electrical conductivity that is effective in dissipating electrical charge by contact of the fibrils on adjacent pulp particles.
By xe2x80x9caramidxe2x80x9d is meant a polyamide wherein at least 85% of the amide (xe2x80x94COxe2x80x94NHxe2x80x94) linkages are attached directly to two aromatic rings. Aramid fibers are described in Man-Made Fibersxe2x80x94Science and Technology, Volume 2, Section titled Fiber-Forming Aromatic Polyamides, page 297, W. Black et al., Interscience Publishers, 1968. Aramid fibers are, also, disclosed in U.S. Pat. Nos. 4,172,938; 3,869,429; 3,819,587; 3,673,143; 3,354,127; and 3,094,511.
Para-aramids are the primary polymers of this invention for blending with polyaniline; and poly(p-phenylene terephthalamide) is the preferred para-aramid. By para-aramid is meant the homopolymer resulting from mole-for-mole polymerization of para-phenylene diamine and terephthaloyl chloride and, also, copolymers resulting from incorporation of small amounts of other diamines with the para-phenylene diamine and of small amounts of other diacid chlorides with the terephthaloyl chloride. As a general rule, other diamines and other diacid chlorides can be used in amounts up to as much as about 30 mole percent of the para-phenylene diamine or the terephthaloyl chloride, or perhaps slightly higher, provided only that the other diamines and diacid chlorides have no reactive groups that interfere with the polymerization reaction. Para-aramid, also, means copolymers resulting from incorporation of other aromatic diamines and other aromatic diacid chlorides such as, for example, 2,6-naphthaloyl chloride or chloro- or dichloroterephthaloyl chloride; provided, only that the other aromatic diamines and aromatic diacid chlorides be present in amounts which permit preparation of anisotropic spin dopes. Preparation of para-aramids and processes for spinning fibers from the para-aramids are described in U.S. Pat. Nos. 3,869,429; 4,308,374; 4,698,414; and 5,459,231.
Sulfonated polyaniline of the present invention can be made by in-situ ring-sulfonation. The term xe2x80x9cinsitu ring-sulfonationxe2x80x9d means that the polyaniline is sulfonated during the polymer solutioning process and not isolated from the sulfuric acid solution before the solution is spun into a fiber. Of course, the sulfonation can, also, be achieved in any other way to make sulfonated polyaniline leading to a conductive pulp.
To be effective in practice of this invention, the sulfonated polyaniline must be sulfonated to a degree that will provide adequate conductivity to drain electrical charges. It has been found that sulfonation is required to a sulfur content of at least 8.5 percent, based on total weight of the sulfonated polyaniline. Sulfonation of less than that amount, results in generally inadequate fiber conductivity. It has, also, been found that increased sulfonation yields improved performance up to a sulfonation level of about 15 weight percent sulfur, based on total weight of the sulfonated polyaniline. Sulfonation to a greater degree has been found to be of little additional benefit. It is noted that sulfonation of polyaniline, to a degree of 8.5 to 15 weight percent, corresponds to a mol percent sulfonation of about 30 to 70 percent of the polyaniline repeat units.
The pulp of this invention can be made by so-called air gap spinning of anisotropic spin dope including the para-aramid and the sulfonated polyaniline. Preparation of such spin dope and spinning of fibers to serve as the basis for the pulp used in this invention, can be found in aforementioned U.S. Pat. Nos. 5,788,897 and 5,882,566.
The molecular weight of the polyaniline employed in the pulp of this invention is not critical. Polyaniline of low molecular weight may result in lower solution viscosity and easier processing, however, it might be more readily removed from the fiber in processing or use.
High molecular weight para-aramid is usedxe2x80x94having an inherent viscosity of at least 5. In order to obtain pulp of the desirable high strength and modulus, a spin dope concentration of the para-aramid is employed that results in an anisotropic dope as discussed in U.S. Pat. No. 3,767,756. Spin dopes containing at least 13% by wt. of total polymer content, that is, sulfonated polyaniline plus the p-aramid, meet this requirement. Otherwise the mechanical properties of the spun fiber will not be acceptable for preparation of the pulp to provide antistatic properties.
The concentration of sulfonated polyaniline in para-aramid in the spin solution, and ultimately in the spun fiber and the pulp product, has an important influence on properties. As the content of sulfonated polyaniline increases to and exceeds 40 wt % of the polymer mixture, the tensile strength of the fiber becomes undesirably reduced with no concomitant increase in electrical conductivity. Also, in washing fibers with such a high concentration of polyaniline, some of the insitu ring-sulfonated polyaniline may be extracted.
The ring-sulfonated polyaniline should constitute at least 3 weight percent and preferably more than 5 weight percent of the pulp product to provide a charge decay rate of less than about 5 seconds. The ring-sulfonated polyaniline should constitute from 3 to 40 weight percent and preferably from 5 to 30 weight percent of the fibers, based on the polymer mixture with calculations using unsulfonated polyaniline.
To make the pulp of this invention, fibers that have been spun as described above, are cut into uniform lengths of 0.5 to 2.5 cm and are suspended in water to form a floc that is subjected to high shear conditions to produce pulp. Equipment useful for refining cellulosic fibers, such as refiners having abrading elements that rotate relative to one another, is useful for this purpose. In pulping in accordance with this invention, shearing along boundaries between the para-aramid and polyaniline phases results readily in the formation of high quality pulp particles with excellent pulp length and high degree of fibrillation. The presence of the polyaniline domains provides fracture points in the chopped fiber and leads to ready and more complete fibrillation at reduced energy consumption, wherein pulp particle surfaces are, at least in part, defined by the location of polyaniline domains running through the fibers. As a result of that definition, at least some of the outer surfaces of the pulp have a relatively high concentration of polyaniline and an unexpectedly high electrical conductivity.
One reliable indicator of the degree of fibrillation and the level of surface area of a pulp product is known as xe2x80x9cCanadian Standard Freenessxe2x80x9d (CSF). The CSF of a pulp is reported as a volume of drained water determined as a result of a specified testing procedure explained herein below. Pulp eligible for use in the instant invention generally exhibits a CSF of 0 to 150 ml and preferably 20 to 100 ml. Lower CSF is generally some indication of higher surface area.
The composition of this invention may include a pulp blend combination of the two-component pulp and pulp made from other material. In that case, the composition need only contain as much of the two-component pulp as is required to achieve the desired charge decay rate. Compositions exhibiting a charge decay rate of less than five seconds are within the bounds of this invention. The amount of two-component pulp required to achieve such a charge decay rate varies depending on the amount of sulfur in the sulfonated polyaniline and the amount of sulfonated polyaniline in the two-component pulp. As a general matter, pulp blend compositions must have at least 5 weight percent two-component pulp and less than 95 weight percent of the other pulp material, based on the total weight of the composition.
The pulp component made from other material can be made from any other pulpable material including, for example, cellulosic material, acrylics, para-aramids, and the like. The preferred other pulp material is the para-aramid material, poly(p-phenylene terephthalamide).
Electric Charge Dissipation
The static decay or electric charge dissipation test measures the ability of a material, when grounded, to dissipate a known charge that has been induced on the surface of the material. To test electric charge dissipation of the pulps made in these examples, pulp was made into paper sheets and charge dissipation tests were conducted on the sheets.
Five grams of a pulp were dispersed for five minutes in 1.5 liters of water in a TMI disperser (Testing Machines, Inc., Islandia, N.Y.). The resulting slurry was poured into the head box of a laboratory handsheet machine containing 25 liters of water. A handsheet 30xc3x9730 cm was formed, dewatered, and dried.
Static Decay Rate test specimens, 9xc3x9714 cm, were cut from the handsheets, equilibrated for at least 24 hours at 30% relative humidity, and tested using an ETS Static Decay Meter, Model 406C (Electro-Tech Systems, Inc.).
In conduct of the test, the test specimens are mounted between electrodes of the Meter, a charge of 5000 volts is applied, and, on grounding the electrodes, the time is measured for the charge to drain to 500 volts. This test is Federal Test Method Standard 101B, Method 4046, known as the Static Decay Test. Test results are set out in Table IV.
Sulfur Content
A pulp sample of known weight is combusted with oxygen in a flask; and the generated SO2 and SO3 gases are absorbed in water. Hydrogen peroxide is added to the water to insure that all sulfur is converted to sulfate; and the water is boiled with platinum black to remove any excess H2O2. The resulting solution is combined with an equal volume of isopropanol and titrated with a standardized BaCl2 solution for determination of sulfate concentration. The amount of sulfur is determined based on the sulfate concentration.
Pulp Length
Pulp fiber length is measured using a Kajaani FS-200 instrument (Kajaani Electronics, Kajaani, Finland). An aqueous slurry of pulp fibers is prepared at a concentration adequate for a rate of analysis of 40xcx9c60 fibers per second. The slurry is passed through the capillary of the instrument for exposure to a laser beam and a detector to determine the fiber length. The instrument performs calculations from the detector output and reports three different lengths;xe2x80x94the arithmetic average length, the length-weighted average length; and the weight-weighted average length.
Tensile Properties
Filaments tested for tensile properties are, first, conditioned at 25xc2x0 C., 55% relative humidity for a minimum of 14 hours; and the tensile tests are conducted at those conditions. Tenacity (breaking tenacity), elongation (breaking elongation), and modulus are determined by breaking test filaments on an Instron tester (Instron Engineering Corp., Canton, Mass.).
Tenacity, elongation, and initial modulus, as defined in ASTM D2101-1985, are determined using filament gage lengths of 2.54 cm. Tenacity is reported in grams per denier. The modulus is calculated from the slope of the stress-strain curve at 1% strain and is equal to the stress in grams at 1% strain (absolute) times 100, divided by the test filament denier. Filament denier is determined according to ASTM D1577 using a vibrascope.
Specific Surface Area
Surface areas are determined utilizing a single point BET nitrogen absorption method using a Strohlein surface area meter (Standard Instrumentation, Inc., Charleston, W.Va.). Washed samples of pulp are dried in a tared sample flask, weighed and placed on the apparatus. Nitrogen is adsorbed at liquid nitrogen temperature. Adsorption is measured by the pressure difference between sample and reference flasks (manometer readings) and specific surface area is calculated from the manometer readings, the barometric pressure, and the sample weight.
Canadian Standard Freeness
This is a measure of the drainage of a suspension of 3 grams of fibrous material in 1 liter of water. Measurement and apparatus are according to TAPPI Standard T227 om-94. The fibrous material is dispersed for five minutes in a TMI disperser. Results are reported as volume (ml) of water drained under standard conditions. The measured value is affected by the fineness and flexibility of the fibers and by their degree of fibrillation.


A nonwoven fabric for manufacturing repeatedly re-usable clean-room protective clothing, made of super microfilaments having a titer of less the 0.2 dtex that are produced by water jet splitting multicomponent multisegment filaments having a titer of less than 2 dtex, the primary filaments being spun from the melt, aerodynamically stretched, laid to form a nonwoven fabric, and subjected to water-jet prebonding prior to splitting.

Protective clothing for clean rooms has the function of protecting the products produced or processed in these rooms (e.g. microelectronic parts, pharmaceuticals, optical glass fibers) from people as the xe2x80x9csourcexe2x80x9d of the emission of interfering particles (e.g. dust particles or skin particles, bacteria).
Therefore, the most important requirement of the material for manufacturing such protective clothing is the barrier effect. The protective-clothing material must hold in particles constantly released by the human body (skin particles, hair fragments, bacteria, etc.) as well as fiber fragments detached from a textile garment worn underneath in order to prevent the clean-room air and, thus, the product from being contaminated. Naturally, the material itself may also not release any fiber fragments or other components into the clean-room air.
In addition to the necessary barrier effect, the protective-clothing material must have a high mechanical load-bearing capacity, in particular a high level of resistance to further tearing and abrasions, to minimize the danger of the formation of tears or holes due to outside influences and/or the demands of normal wear. To be able to repeatedly re-use the protective clothing, the material must also be able to undergo washing and cleaning processes customary in the field (e.g. sterilization in an autoclave) with as little damage as possible, i.e., it must be resistant to wet-mechanical wear and pilling and be sufficiently dimensionally stable.
In addition to the barrier effect and (wet) mechanical resistance, the protective-clothing material, in particular for use in clean rooms of the microelectronics industry, must have an anti-static effect, i.e., the material should not become excessively electrostatic as a result of the unavoidable friction when worn or should be able to quickly dissipate or discharge such charges. This is necessary, on the one hand, so that sensitive microelectronics components are not damaged by point-to-point discharging, and, on the other hand, so that dust particles that could accumulate on the material""s surface and potentially be later re-emitted are not pulled in from the ambient air.
In addition, the protective-clothing material should also have a sufficiently high level of wearability, i.e., have a character that is as textile-like as possible with respect to drape, feel, and appearance and should be able to breathe and, if applicable, also be heat-insulating in order to prevent the wearer from sweating or freezing excessively.
It is known to use synthetic fibers or synthetic filaments having an ultra fine titer to manufacture clean-room protective clothing material. In this context, xe2x80x9cultra fine-titeredxe2x80x9d refers to fibers having a titer of less than 1 dtex, which are also referred to a xe2x80x9cmicrofibers.xe2x80x9d The term xe2x80x9csuper microfibersxe2x80x9d may also be used for microfibers having a titer of less than 0.3 dtex.
Typical protective-clothing material on the basis of microfiber or microfilament woven fabrics or microfiber or microfilament knitted fabrics is produced in a plurality of method steps. Microfibers or microfilaments are first spun from raw polymer materials. These are then further processed to form yarns, which undergo a subsequent texturing process if necessary. Finally, the actual protective-clothing material is woven from the (textured) microfiber yarns or microfilament yarns. In the web process, conductive yarns are also able to be woven in the form of a regular pattern, e.g. in stripes or checks, to achieve the required anti-static effect. The conductive yarns contain, for example, core/coat filaments having a soot-containing or graphite-containing core or coat or also metal fibers or metalloid filaments, for example. The necessary barrier function and the high (wet) mechanical load-bearing capacity are achieved by an extremely densely and regularly weaving the microfiber yarns. However, this high web density and the predominantly surface-parallel filament orientation are unfavorable with respect to the material""s breath ability. There are only a few micro pores or micro channels through or via which water vapor can be transported through the woven fabric.
The problematic property combination of barrier effect and breath ability of the protective-clothing material may be achieved by using particle-tight, yet water-vapor permeable, membranes. Such xe2x80x9cmicro porousxe2x80x9d layers may be applied to textile materials of normal density, e.g. By lamination or direct extrusion, to obtain a material having a textile character.
The manufacturing method for high-density, microfilament woven fabrics as well as for composite materials of a breathable barrier membrane and a textile entails multiple steps and is, thus, relatively time consuming. Microfiber nonwoven fabrics present an easily manufactured alternative.
Planar calendered microfilament spun bonded materials on a polyethylene basis are able to satisfy the barrier requirements and are also particularly inexpensive to manufacture. However, such materials are practically air-tight and/or water vapor-tight and have a film-like character, i.e., the wearability is minimal. Moreover, they are only insufficiently wash fast or durable during cleaning, so that their use is limited to one-way or throw-away protective clothing.
Microfiber nonwoven fabrics made from multisegment or multi core staple fibers, which are split up into individual microfibers after the web formation and a possible prebonding via a solvent or water jets, should provide significantly better wearability with a good barrier effect than the abovementioned high-calendered microfilament spun bonded materials.
European Patent 0 624 676 describes, for example, a method for using water jet splitting to manufacture a microfiber nonwoven fabric having an extremely high bulk density and, consequently, also a good barrier effect. However, this nonwoven fabric lacks softness and heat insulation properties. As a result, the use of water jet-bonded nonwoven fabrics for the (protective) clothing industry is considered to be limited. Therefore, another method that does not use the water jet technique is proposed in the indicated patent.
Deviating from the abovementioned patent, PCT Application WO 98 1 23 804 proposes first thermally heat sealing the nonwoven fabric in a point wise manner, prior to the water jet splitting. This is intended to prevent the nonwoven fabric from interlocking with the sieve band of the water-jet aggregate during the water jet splitting and from then being damaged or even destroyed when lifted. In addition, a higher degree of fiber distribution is to be achieved, thereby resulting in improved barrier and touch properties.
European Patent 97 108 364 also strives to expand the scope of application of nonwoven fabrics. The patent describes the manufacture of a nonwoven fabric from very fine filaments, the nonwoven fabric being intended to have properties similar to woven or knitted textiles. The very fine filaments having a titer of 0.005 to 2 dtex are produced via water jet splitting from melt-spun, crimped, or non-crimped multicomponent, multisegment filaments having tinters from 0.3 dtex to 10 dtex. The thus-produced nonwoven fabric can then be after treated in different ways (e.g. Via thermofixing, point calendering, etc.) to attain special working properties. The spun bonded materials produced according to this method are supposed to be particularly suitable for manufacturing articles of clothing and other textile products.
In subsequent tests, it was surprisingly determined that nonwoven fabrics produced according to abovementioned European Patent 97 108 364 are particularly suitable for manufacturing clean-room protective clothing when they are made of super microfilaments having tinters less than 0.2 dtex and are also emboss-calendered. The super microfilaments themselves are produced by water jet splitting multicomponent filaments having a titer of less than 2 dtex that were formed using the melt spinning method, aerodynamically stretched, and prebonded using water jets.
Therefore, the present invention describes a new nonwoven material as well as the method steps for producing it. The nonwoven fabric satisfies all requirements for a repeatedly re-usable clean-room protective-clothing material. It is distinguished by a high barrier effect, a high mechanical load-bearing capacity, high dimensional stability, an efficient anti-static effect, as well as a high level of wearability (breath ability and textile character). These favorable properties are retained to a sufficient extent even after multiple, customary wash or cleaning processes (up to 30 cycles). Until now, the sum of these properties was considered to be impossible for a nonwoven fabric having split super-fine filaments.
The nonwoven fabric is made of super microfilaments having tinters of less than 0.2 dtex that are produced from non-crimped primary filaments having a titer of 1.5 to 2 dtex. Bicomponent multisegment filaments of two incompatible polymers, in particular polyester and polyamide, are preferably used as the primary filaments. This combination is known, and in this respect, reference is made to EP 97 108 364. The proportion of polyester is selected to be greater than that of polyamide, preferably between 60 and 70% by weight. To achieve the necessary anti-static effect, one of the two or both polymers are provided with suitable additives that are permanently effective, i.e., not able to be washed off or out. The anti-static effect can be achieved, e.g. By mixing in soot or graphite or by admixing polymers having a strong hydrophilic character or polymers having (semi) conductive properties, while possibly adding compatibility agents. The primary bicomponent filaments have a cross-section with an orange-like multisegment structure (pie structure). Each segment alternately includes one of the incompatible, additive polymers. This filament cross-section known per se has proven to be favorable for the subsequently described production of the super microfilaments. Following the customary aerodynamic stretching, the primary filaments undergo a further stretching and, at the same time, tempering process (hot-channel stretching) in order to achieve the desired high scuff resistance and low pilling tendency of the nonwoven fabric
The thus-produced primary filaments are laid down in irregular order via special aggregates onto a moving band and are subsequently prebonded, i.e., are mechanically intertwined with one another, using a conventional water jet technique. High-pressure water jets are then applied several times to both sides of the prebonded primary filament nonwoven fabric on perforated drums, the primary filaments practically completely disintegrating into their components, i.e., into the individual super microfilaments, which are simultaneously intermingled with one another in an extremely homogenous manner. This method step produces a microfiber nonwoven fabric that possesses the necessary high barrier effect as a result of its extremely irregular and intermingled fiber structure, yet is also sufficiently permeable for water vapor.
To improve the dimensional stability during washing and cleaning processes, the microfiber nonwoven fabric undergoes a hot-air thermofixation process under tension after the water jet splitting and subsequent drying. The nonwoven fabric is then emboss-calendered in a calender having a special embossing cylinder to further increase the dimensional stability and scuff resistance. The finished nonwoven fabric has a mass per unit area of 80 to 150 g/m2, preferably 95 to 115 g/m2.

Bonded-fiber fabric for producing clean-room protective clothing


A device for respiratory assistance which comprises a tube (4) having at least one auxiliary channel (8) connected to a source of respirable gas (25). The conduit (28) connects the source of respirable gas (25) to the auxiliary channel (8). The device further includes:

The subject of the present invention is a device for respiratory assistance which can be used on patients in whom spontaneous respiration is absent or inadequate, whether or not said patients are placed under artificial respiration.
Various devices are known, such as masks and oral, nasal, endotracheal and tracheotomy probes or cannulas, which are intended to form the junction between an artificial respiration and/or anesthesia apparatus and the respiratory tract of a patient. These devices, essentially in the form of tubes, can, depending on the circumstances, include immobilizing means such as flanges or collars in the vicinity of the proximal end for holding them on the mouth or nose of the patient, or inflatable balloons in the vicinity of the distal end for holding them by friction in the trachea.
The known devices have important disadvantages. Thus, for example, when a tube of a known type is disconnected from the artificial respirator and the patient needs oxygen-enriched air, it is necessary to introduce into said tube a probe which is connected to an oxygen source. Moreover, in cases of inadequate spontaneous respiration, the patient must necessarily remain connected to the respirator until spontaneous respiration has been completely re-established.
To overcome these disadvantages, it has already been proposed, for example in documents EP-A-0 390 684 and EP-A-0 701 834, to provide devices for respiratory assistance which, in addition to the main channel formed by the tube, comprise at least one auxiliary channel, for example formed in the wall of said tube, permitting injection of a jet of respirable gas (oxygen, air or air/oxygen mixture) intended to ventilate the patient, this auxiliary channel opening into the main channel in the vicinity of the distal end of the latter.
Of course, these latter known devices for respiratory assistance include safety means which are able to stop the functioning of the device in the event of overpressure in the respiratory tract of the patient and/or in said tube.
The object of the present invention is to improve said devices for respiratory assistance in order to increase the safety of their use still further.
To this end, according to the invention, the device for respiratory assistance comprising a tube which forms a main channel and which is intended to be connected via its distal end to the respiratory tract of a patient so that said main channel connects the respiratory system of said patient to the outside, said device moreover comprising at least one auxiliary channel connected to a source of respirable gas so as to permit the insufflation of a jet of such a respirable gas into said respiratory system, and opening into said main channel in the vicinity of the distal end of the latter, is distinguished by the fact that, in the conduit connecting said source of respirable gas to said auxiliary channel, it includes:
toward said source, a device for loss of head which is able to limit the flow rate and the pressure of said respirable gas available at the outlet of said source, and to impose on said jet of respirable gas a predetermined flow rate value and a predetermined pressure value; and
toward said auxiliary channel, a calibrated exhaust valve which is able to bring said conduit into communication with the atmosphere when the pressure in said conduit exceeds said predetermined pressure value.
Thus, by virtue of the present invention, the safety system acts at the level of the injection of the jet of respirable gas and advantageously complements the safety systems of the known devices mentioned above which safety systems act at the level of the patient""s airways.
It should be noted that in order to obtain the maximum level of safety sought by the present invention, the combination of the device for loss of head and the calibrated exhaust valve is indispensable. This is because the device for loss of head lowers the flow rate and pressure of the jet of respirable gas so that, when this pressure exceeds said predetermined value, the exhaust valve is able to evacuate the entire jet of respirable gas into the atmosphere. If said device for loss of head were to be omitted, the flow rate and the pressure of the jet of respirable gas would be able to reach values such that said jet would be able at least in part to pass through said calibrated exhaust valve in the direction of the patient""s airways, instead of being evacuated into the atmosphere. This could then result in serious injury to the patient.
Such a device for loss of head can be of any known type, such as needle screw restrictions, channels of small internal diameter, etc., and the same applies to said calibrated exhaust valve, which can be of the type with plunger and pierced cylinder, with a ball or flap charged by a spring, etc.
Said device for loss of head is preferably adjustable in such a way as to make it possible to impose on said jet of respirable gas a plurality of predetermined flow rate values and pressure values. Likewise, it is advantageous for the calibration of said exhaust valve to be adjustable. Thus, it is possible to adapt the device according to the present invention to the particular case of each patient.
Especially in the case where at least part of the conduit connecting the source of respirable gas to the auxiliary channel is incorporated in said tube, the device for loss of head and/or said calibrated exhaust valve could also be incorporated in said tube. However, they are preferably external to it.
By virtue of the device for loss of head, it is particularly easy to provide a humidifier in said conduit connecting the source of respirable gas to the auxiliary channel. This is because this device for loss of head makes it possible to lower the pressure of the jet of respirable gas to a level permitting good humidification thereof. It is thereby possible to prevent the patient""s mucous membrane from drying out. Said humidifier is preferably arranged between the device for loss of head and the calibrated exhaust valve.
Moreover, in order to prevent the jet of humidified respirable gas from directly hitting the mucous membrane, and the risk of its kinetic energy causing trauma to said mucous membrane, it is advantageous if, as is described in European Patent EP-A-0 390 684, at least the distal end of said auxiliary channel opening into the main channel is parallel to the latter and if there are provided, opposite the distal orifice of said auxiliary channel, means for deflecting said jet of respirable ventilation gas toward the inside of said main channel.
Thus, the jet of humidified respirable gas, under low pressure, passing through said auxiliary channel, is deflected toward the axis of the main channel when it penetrates into the latter. Downstream of said deflection means, that is to say inside the main channel, the pressure of said jet of respirable gas falls and the jet emerges at even lower pressure via the distal orifice of the tube. Experience has shown that downstream of the distal outlet of the tube, the pressure is low and is maintained constant throughout the respiratory space. This pressure is dependent on the flow rate of respirable gas in the auxiliary channels. Consequently, with the device for respiratory assistance according to the invention, it is possible, for example, to supply humid oxygen or a humid mixture of air and oxygen directly to the lungs, at the level of the carina, and thereby to suppress the dead space which exists in the current probes and which is about one third of the total respiratory volume of adults and about half the total respiratory volume of premature babies.
The suppression of this dead space corresponds to an increase in performance of the respiratory cycle of more than 25% in all patients and of nearly 50% in certain cases.
When the device according to the invention comprises a plurality of auxiliary channels, it is advantageous for at least some of them to be supplied jointly with respirable gas. Such joint supply of said channels can be achieved by way of a distribution ring which is coaxial with said tube. Moreover, said auxiliary channels which are not jointly supplied can be used for introducing additional gaseous products such as medicinal products.
Thus, it will be seen that the device according to the invention permits, in complete safety:
humidification of the insufflated respirable gas,
long-term intubation of the respiratory assistance device without drying,
injection of medicines or anesthetics during respiratory assistance,
dynamic measurement of pressures, since it suffices to provide auxiliary channels to which appropriate probes are associated,
establishment of a microflow of respirable gas in the auxiliary channels to prevent obstruction of said channels by mucus,
an increase in the volume exchanged, since the pressure is automatically limited and there is no risk of crushing of the pulmonary capillaries,
for the same quantity of oxygen exchanged, a decrease in the amount of oxygen in the mixture, which reduces the secondary effects of the assistance,
the possibility of using respirators which are less expensive then the current respirators.

Abstract: toward the source (25), a device for loss of head (30) which is able to impose on the jet of respirable gas a predetermined flow rate value and a predetermined pressure value; and

Abstract: toward said auxiliary channel (8), a calibrated exhaust valve (32) which is able to bring the conduit (28) into communication with the atmosphere when the pressure in the conduit (28) exceeds said predetermined pressure value.


Elastomers with improved physical properties, particularly hardness, resilience, tear strength, and compression set, may be prepared by the chain extension or moisture cure of isocyanate-terminated prepolymers prepared from a polyol component comprising a high molecular weight, low unsaturation polyoxypropylene diol and a low molecular weight diol. The elastomers are useful for applications such as rollers and other applications for which these physical properties are important.

The present invention pertains to polyurethene and polyurethane/urea heat-cured elastomers prepared by the chain extension or moisture cure of isocyanate-terminated prepolymers. More particularly, the present invention pertains to prepolymers prepared by reacting a stoichiometric excess of a di- or polyisocyanate (other than toluene diisocyanate) with a polyol component comprising a high molecular weight, low unsaturation polyoxypropylene polyol and a very low molecular weight polyol. The subject elastomers have improved hardness, resilience, tear strength, and compression set compared with otherwise similar elastomers having the same hard segment content. Films prepared from the compositions have exceptional tensile and tear strengths.
Polyurethane heat-cured elastomers may, in general, be subdivided into two major classes distinguished by the type of monomeric isocyanate used to prepare the elastomer precursor prepolymer. When methylene diphenylene diisocyanate (MDI) or MDI variants are used to form the prepolymers, the isocyanate group to polyol hydroxyl equivalent ratio may be quite high. The range of isocyanate group content possible provides flexibility in formulating. However, the high reactivity of the MDI isocyanate groups generally requires use of diol chain extenders in cast elastomer systems, as amines with suitable reactivity are not commercially available. To maintain a desirable balance of properties, elastomers prepared from MDI are thus polyurethane elastomers and not polyurethane/urea elastomers which have a distinct status in the art.
Heat-cured polyurethane/urea elastomers should not be confused with reaction injection molded polyurethane/urea (RIM) systems. In the latter, MDI and modified MDIs are generally used in conjunction with a reactive diamine such as diethyltoluene diamine and injected into highly rigid molds at high pressures. Prepolymers are generally not used in such systems except in minor amount, since in the very short period prior to gelation, the rapidly reacting mixture must traverse the entire, often complex mold. Thus, low viscosity systems are desired, in conjunction with very high pressure, short duration injection. RIM processes have acquired a separate status in the art. RIM system are not heat-cured, but rather rapidly cure without heat.
Toluene diisocyanate (TDI) based elastomers are the second major heat-cured elastomer class, and the largest class in terms of elastomer produced. Approximately 65 percent of heat-cured polyurethane elastomers are TDI-based systems. In practice, TDI-based prepolymers having high isocyanate group content are seldom used, and amine rather than diol chain extenders are employed to provide hard segments having urea linkages. The resulting elastomers are thus polyurethane/urea elastomers. High isocyanate group contents are generally avoided with TDI-based prepolymers due to the volatility of TDI.
Due to the limited NCO/OH ratio, the % NCO content of the isocyanate-terminated prepolymers derived from TDI is limited to a maximum of about 10% by weight. At such limited isocyanate contents, formulation flexibility is reduced. Moreover, as the urea hard segment content is related to the isocyanate group content in amine cured systems, preparation of elastomers with high tensile strength and other desirable physical properties is rendered more difficult.
Many attempts have been made to increase polyurethane elastomer physical properties, and many have been successful in elevating certain physical properties, but often at the expense of others. For example, in U.S. Pat. No. 4,934,425 the preparation of polyurethane/urea elastomers having improved dynamic properties is exemplified. The elastomers were prepared from TDI-based prepolymers containing a high molecular weight polytetramethylene ether glycol (PTMEG) of 2000 Da molecular weight and a moderate molecular weight PTMEG of 1000 Da molecular weight. Elastomers prepared from the blended prepolymers showed considerable im provement in resistance to heat build-up in rubber tire applications, indicative of lower hysteresis. However, while dynamic properties improved, no improvement was noted with respect to tensile strength, elongation, or hardness.
In U.S. Pat. No. 3,963,681 the preparation of polyurethane/urea elastomers with improved cut-growth and flex-crack resistance for tire applications is disclosed. The TDI-based prepolymers were prepared from a blend of a very high molecular weight PTMEG (molecular weight above 4500 Da) and a moderate molecular weight PTMEG, the blend having an average molecular weight of between 1000 Da and 4500 Da. The molecular weight of the higher molecular weight PTMEG is required to be higher than the xe2x80x9ccritical molecular weightxe2x80x9d of PTMEG polymers, while the molecular weight of the lower molecular weight component must be less than this value. Tensile strengths as well as cut-growth were improved. However, not all polyether polyols are known to have a xe2x80x9ccritical molecular weight.xe2x80x9d Furthermore, the molecular weights are very critical; blends of 800 Da PTMEG and 3800 Da PTMEG are disclosed as being unsuitable, for example.
U.S. Pat. No. 5,077,371 addressed hardness build in polyurethane/urea cast elastomers. The rate of hardness build is important as cast elastomer parts cannot be demolded prior to developing adequate green strength without risk of damage to the parts. Rapid development of hardness allows more rapid demold. Cure can be completed in an oven outside the mold, and production rates increased correspondingly. The addition of the dimer of toluene diisocyanate (TDI dimer) in amounts of 0.3 to 6 weight percent of total isocyanate to the isocyanate component used to prepare bimodally distributed PTMEG prepolymers was found to increase the rate of hardness build. Unfortunately, of the remaining physical properties, hardness, elongation, and rebound remained virtually unchanged, tensile strength and particularly elongation actually decreased, and only tear strength showed significant improvement. The necessity of preparing the TDI dimer adds additional time and expense to elastomer formulation.
PTMEG has been traditionally used in preparing high performance polyurethane/urea elastomers, as illustrated by the three foregoing U.S. Pat. Nos. 4,934,425, 3,963,681, and 5,077,371. PTMEG is a premium priced polyol. However, PTMEG continues to be used today despite its much greater cost as compared to polyoxyalkylene polyols such as polyoxyethylene glycols and polyoxypropylene glycols, due to the desirable physical properties of the polyurethane which may be obtained through its use.
Moisture-cured polyurethane elastomers are often used as caulks and sealants. Rather than incorporating a diamine to react with isocyanate to form the linking urea hard segments, moisture-cured elastomers rely on the reaction of free isocyanate groups with moisture to form urea linkages. Many moisture-cured films and sealants exhibit relatively low physical properties, particularly tensile strength and/or tear strength, and therefore improvement in these and other properties is desired.
The majority of polyoxyalkylene polyether polyols are polymerized through base catalysis. For example, polyoxypropylene diols are prepared by the base catalyzed oxypropylation of a difunctional initiator such as propylene glycol. During base catalyzed oxypropylation, a competing rearrangement of propylene oxide to allyl alcohol continually introduces an unsaturated, monofunctional, oxyalkylatable species into the reactor. The oxyalkylation of this monofunctional species yields allyl-terminated polyoxypropylene monols. The rearrangement is discussed in Block and Graft Polymerization, Vol. 2, Ceresa, Ed., John Wiley and Sons, pp. 17-21. Unsaturation is measured in accordance with ASTM D-2849-69 xe2x80x9cTesting Urethane Foam Polyol Raw Materials,xe2x80x9d and expressed as milliequivalents of unsaturation per gram of polyol (meq/g).
Due to the continual creation of allyl alcohol and its subsequent oxypropylation, the average functionality of the polyol mixture decreases and the molecular weight distribution broadens. Base-catalyzed polyoxyalkylene polyols contain considerable quantities of lower molecular weight, monofunctional species. In polyoxypropylene diols of 4000 Da molecular weight, the content of monofunctional species may lie between 30 and 40 mol percent. In such cases, the average functionality is lowered to c.a. 1.6 to 1.7 from the nominal, or theoretical functionality of 2.0. In addition, the polyols have a high polydispersity, Mw/Mn due to the presence of the substantial, low molecular weight fractions. Molecular weights and equivalent weights herein in Da (Daltons) are number average molecular weights and number average equivalent weights, respectively, unless specified otherwise.
Some researchers in the past have suggested using low unsaturation, higher functionality polyols to improve elastomer physical properties. See, e.g. U.S. Pat. Nos. 4,239,879 and 5,100,997. For example, A. T. Chen et al., xe2x80x9cComparison of the Dynamic Properties of Polyurethane Elastomers Based on Low Unsaturation Polyoxypropylene Glycols and Poly(tetramethylene oxide) Glycols,xe2x80x9d Polyurethanes World Congress 1993, Oct. 10-13, 1993, pp. 388-399 compared the properties of PTMEG-derived elastomers with those from conventional polyoxypropylene diols and low unsaturation polyoxypropylene diols. In Shore A 90 cast elastomers, PTMEG-MDI pre-polymer-derived, butanediol extended polyurethane elastomers had slightly lower modulus and elongation than low unsaturation polyoxypropylene diol-derived elastomers, however tensile strength of the PTMEG elastomers was considerably higher. For polyurethane/urea cast elastomers, a direct comparison was not possible, as the only PTMEG example used a 1000 Da PTMEG while both low unsaturation polyoxypropylene diol examples employed c.a. 2000 Da molecular weight diols. The PTMEG example had considerably higher physical properties with the exception of elongation, which was to be expected. Notably, conventional, base-catalyzed polyoxypropylene diols produced polyurethane/urea cast elastomers with physical properties virtually indistinguishable from those prepared from low unsaturation diols.
Reducing unsaturation in polyoxyalkylene polyols by lowering catalyst concentration and decreasing the reaction temperature is not feasible, as the reaction rate is so slow that oxypropylation takes days or even weeks, although low unsaturation polyols may be prepared in this manner. Thus, efforts have been expended to discover catalysts which can produce polyoxypropylated products in a reasonable amount of time with little introduction of monofunctionality due to allylic species. In the early 1960""s, for example, double metal cyanide catalysts such as zinc hexacyanocobaltate complexes were developed as illustrated by U.S. Pat. Nos. 3,427,256; 3,427,334; 3,427,335; 3,829,505; and 3,941,849. Despite lowering unsaturation to the range of c.a. 0.018 meq/g, the cost of these catalysts coupled with the necessity of lengthy and expensive catalyst removal steps prevented commercialization.
Use of alternative basic catalysts such as cesium hydroxide and rubidium hydroxide as disclosed in U.S. Pat. No. 3,393,243, and the barium and strontium oxides and hydroxides, as disclosed in U.S. Pat. Nos. 5,010,187 and 5,114,619, enabled modest improvements in unsaturation, however catalyst expense, and in some cases, toxicity, coupled with the but modest improvements offered, mitigated against commercialization. Catalysts such as calcium naphthenate and combinations of calcium naphthenate and tertiary amines have proven successful, as disclosed in U.S. Pat. Nos. 4,282,387, 4,687,851 and 5,010,117, in preparing polyols with unsaturations as low as 0.016 meq/g , and more generally in the range of 0.02 to 0.04 meq/g.
In the 1980""s, double metal cyanide complex (DMC) catalysts were once more revisited, and improvements in catalytic activity and catalyst removal methods encouraged one manufacturer to offer DMC catalyzed polyols having unsaturations in the range of 0.015 to 0.018 meq/g commercially for a brief time. However, base catalysis continued to be the major method of preparing polyoxypropylene polyols, and continues its dominance to the present day.
Recently, however, further major advances in DMC catalysts and polyoxyalkylation processes by the ARCO Chemical Co. have enabled practical preparation of ultra low unsaturation polyoxypropylene polyols. High molecular weight polyols, for example those in the 4000 Da to 8000 Da molecular weight range, typically exhibit unsaturation in the range of 0.004 to 0.007 meq/g when catalyzed by the novel DMC catalysts. At these levels of unsaturation, the amount of monofunctional species is only 2 mol percent or less. Moreover, GPC analysis shows the polyols to be virtually monodisperse, often exhibiting polydispersities less than 1.10. Several such polyols have recently been commercialized as ACCLAIM(trademark) polyols.
However, the advent of low unsaturation, higher functionality polyols has not proven to be the panacea those skilled in the art expected. In many systems, replacement of conventional polyols with very low unsaturation polyols causes system failure, and considerable efforts in reformulation must be expended. In other cases, the low unsaturation polyols could be readily substituted, but expected improvements did not materialize. The reasons for the unexpected difficulties associated with the use of low unsaturation polyols are not known with certainty.
However, the formulation of conventional polyurethane systems employs polyether polyols whose actual and theoretical functionality differ, often considerably. For example, a conventional, base-catalyzed 6000 Da triol may have an actual functionality of only c.a. 2.4 due to the presence of 30 to 40 mol percent monol. Substituting a polyol blend of a low unsaturation, high functionality diol and low unsaturation, high functionality triol to mimic the 2.4 functionality does not provide the same functionality distribution as the conventional polyol. The triol portion of the conventionally catalyzed triol produces three-way branched xe2x80x9ccrosslinkxe2x80x9d sites, while the monofunctional portion acts as a chain terminator. In a diol/triol blend having the same functionality, the number of three-way branched sites is less, but there are no monofunctional chain terminators.
Use of polyols having low content of monofunctional species has been suggested as a method of increasing polymer molecular weight; and increased polymer molecular weight has, in turn, sometimes been cited as desirable in producing higher performance polymers. However, high molecular weight is not necessarily a desirable feature in many polymer systems. As indicated by G. Odian, Principles of Polymerization, John Wiley and Sons, (copyright) 1981, pp. 20-21, for example, often, the molecular weight to be desired is a moderate rather than a high molecular weight. In engineering thermoplastics, for example, higher molecular weights in general increase tensile strength, melt temperature, modulus, and the like, but if the molecular weight is too high, polymer viscosity becomes too great to process. In polyurethanes, molecular weights are far lower than engineering thermoplastics, and polymer morphology and physical properties are influenced by many factors, including amount and nature of hard segment, stereochemistry of isocyanate used, etc. Often, formulations must be chosen to balance conflicting properties. For example, increases in tensile strength are often accompanied by a decrease in elongation.
For example, R. Mascioli, in xe2x80x9cUrethane Applications for Novel High Molecular Weight Polyols,xe2x80x9d 32nd Annual Polyurethane Technical/Marketing Conference, Oct. 1-4, 1989, pp. 139-142, discloses that the substitution of a low unsaturation, 10-11,000 Da triol for a conventional 6000 Da triol in a polyurethane foam formulation resulted in a foam which was stiff and boardy. A softer foam would have been expected, due both to the longer, and therefore more flexible, polyoxypropylene branch length of the triol; and a lower crosslink density. Substitution of higher molecular weight, low unsaturation polyols for conventionally catalyzed polyols whose molecular weight is limited, has also been touted as a means of using less of the more expensive isocyanate in polyurethane manufacture. However, suitable formulations must be developed.
In the area of high resilience polyurethane flexible foams, it has been discovered, as disclosed in copending U.S. application Ser. No. 08/565,516, that substitution of a DMC-catalyzed, low unsaturation polyol for a conventionally, base catalyzed polyol of similar molecular weight and composition in a high resilience polyurethane foam system may result in foam collapse. It is now believed by some that this anomalous behavior may be due to a very small amount of a very high molecular weight component, with a molecular weight in the range of 100,000 Da and higher. This exceptionally high molecular weight component, even though very small in amount, may act as a surfactant and tend to destabilize polyurethane foam, or may serve to increase viscosity, thereby interfering with normal curing mechanisms such as hard segment phase out.
Therefore, the formulation of polyurethane systems which can extol the benefits of the higher molecular weights, higher functionalities, low poly-dispersity, and lower unsaturation and attendant lack of monofunctional species exhibited by low unsaturation polyols such as those prepared through DMC catalysis requires non-obvious and unorthodox reformulation.
The present invention pertains to polyurethane and polyurethane/urea elastomers prepared by chain extension or moisture cure of isocyanate-terminated prepolymers or quasi-prepolymers prepared by reacting a di- or polyisocyanate other than toluene diisocyanate with a mixture containing a high molecular weight, very low unsaturation polyoxypropylene diol and a low molecular weight diol, the mixture having a hydroxyl number between 50 and 200. The chain-extended, cured elastomers surprisingly have improved hardness, resilience, tear strength, and compression set compared with elastomers having similar hard segment content prepared from a prepolymer utilizing a single polyol of equivalent hydroxyl number. The moisture-cured elastomers exhibit exceptional tensile and tear strengths.
The subject invention chain-extended elastomers are prepared by reacting the isocyanate-terminated prepolymer or quasi-prepolymer described hereafter with a chain extender at an isocyanate index of from about 90 to about 120, preferably 95 to 110, and most preferably 100-105. As is well known, the isocyanate index is the ratio of equivalents of isocyanate to equivalents of isocyanate reactive species multiplied by 100. In determining the equivalents of isocyanate reactive species, one mole of hydroxyl or amino groups constitutes one equivalent. The moisture-cured elastomers are cured in the presence of atmospheric moisture or in a humidifying chamber.
The chain-extended cast elastomers are processed by intensively mixing the prepolymer-containing A-side and diol or diamine-containing B-side, degassing under vacuum if necessary, and introducing the mixture into an open or closed mold. The elastomers may be removed from the mold following development of sufficient green strength to allow demolding and handling, and are generally post-cured at slightly elevated temperature. Alternatively, the elastomer may be subjected to cure in the mold itself. Methods of preparing the elastomer per se are conventional, and reference may be made to the appropriate portions of Polyurethane: Chemistry and Technology, J. H. Saunders and K. C. Frisch, Interscience Publishers, New York, 1963; and to the Polyurethane Handbook, Gunter Oertel, Ed., Hanser Publishers, Munich, (copyright) 1985, both of which are incorporated herein by reference. The moisture-cured elastomers may be formulated with traditional fillers, rheology control agents, thixotropes, and the like, or may be extruded or cast as neat films or from solution.
The isocyanate-terminated prepolymers are prepared by reacting a di- or polyisocyanate other than toluene diisocyanate with a polyol component as described below. The prepolymers preferably have an NCO group content of from about 2 to about 12 weight percent.
Suitable di- or polyisocyanates for use in the invention are aromatic, aliphatic, and cycloaliphatic varieties commonly known to those skilled in the art, excluding toluene diisocyanates. Examples include 2,2xe2x80x2-, 2,4xe2x80x2-, or 4,4xe2x80x2-methylenediphenylene diisocyanate (MDI), polymeric MDIs, MDI variants, carbodiimide-modified MDIs, modified di- and polyisocyanates (urea-, biuret-, urethane-, isocyanurate-, allophanate-, carbodiimide-, or uretdione-modified, etc.), hydrogenated MDIs, p-phenylene diisocyanate, TMXDI, isophorone diisocyanate, 1,4-diisocyanatobutane, 1,4-cyclohexanediisocyanate, hexamethylene diisocyanate, and the like, and mixtures thereof. It is also preferable to use commercially available isomers or their mixtures for reasons of economy.
In addition to the prepolymer approach, a quasi-prepolymer method can be used to make the elastomers of the invention. Quasi-prepolymers are made from an excess of the di- or polyisocyanate and a reduced proportion of the polyol component in the same manner as described herein for making prepolymers. Due to the lesser amount of polyol component to isocyanate, however, the % NCO contents of quasi-prepolymers are higher than the % NCO of prepolymers. Isocyanate group contents of from 12 wt. % NCO to 30 wt. % NCO are suitable, for example. Any remaining polyol needed can be introduced together with the chain extender as a blend or in separate streams.
The polyol component to be reacted with the di- or polyisocyanate to form the prepolymer or quasi-prepolymer is a mixture of at least two hydroxyl-functional components, the first being a low molecular weight diol having a molecular weight less than about 400 Da, the second being a low unsaturation polyoxypropylene glycol having a molecular weight of c.a. 2000 Da or higher, such that the mixture of the at least two components has a hydroxyl number in the range of about 50 to about 200.
The low molecular weight diol may be any dihydroxyl functional compound having a molecular weight below about 400 Da. Illustrative, but non-limiting examples, include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propanediol, 2-methyl-1,3-propane diol, neopentyl glycol, 1,3- and 2,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydroquinone bis[2-hydroxyethyl ether], and the various bisphenols and their bis[hydroxyalkyl ether] derivatives. Oxyalkylation products of the above are also useful. Preferably, the low molecular weight diol has a molecular weight below about 200 Da. Mixtures of one or more of such low molecular weight diols are also useful. Minor quantities of low molecular weight trials, tetrols or the like, such as glycerine, trimethylol propane, pentaerythritol, or the like may be added to the low molecular weight diol mixture as long as the amount of trial, tetrol, or higher functionality species is about 10 mol percent or less. xe2x80x9cLow molecular weight diolxe2x80x9d allows such amounts of higher functional species unless indicated otherwise.
The low unsaturation polyoxypropylene glycol has a molecular weight of about 2000 Da or higher, preferably from 2000 Da to 12,000 Da, more preferably from 3000 Da to 10,000 Da, and most preferably from 4000 Da to 8000 Da. The unsaturation must be below 0.020 meq/g, is preferably below 0.015 meq/g, and most preferably below 0.010 meq/g. Unsaturation of from about 0.002 meq/g to about 0.007 meq/g is preferred. To achieve the requisite low unsaturation, any catalytic method which is useful for obtaining the desired molecular weight and unsaturation may be used. However, it is desirable to employ double metal cyanide complex catalysts as the oxyalkylation catalyst. Catalysts of this type are disclosed in U.S. Pat. Nos. 5,470,813 and 5,482,908, for example, and are capable of preparing polyols in the molecular weight range of 2000 Da to 12,000 Da with unsaturation typically in the range of about 0.004 to 0.007 meq/g. More than one low unsaturation polyoxypropylene diol may be used in admixture with the low molecular weight diol components.
The blend of low molecular weight diol and low unsaturation polyoxypropylene diol must have a hydroxyl number between 50 and 200, preferably between 75 and 150, and most preferably in the range of 90 to 120.Hydroxyl number is calculated by adding the weight fractional hydroxyl numbers of the individual components of the mixture, the weight fractional hydroxyl number being the weight fraction of the component multiplied by the component""s hydroxyl number. It must be emphasized that it is the blend of high molecular weight species and low molecular weight species used to prepare the prepolymer which provides the exceptional qualities of the subject invention cast elastomers. These properties cannot be duplicated with single components, nor with bimodal blends not containing species below about 400 Da molecular weight.
Preparation of the prepolymer is by standard techniques. For example, the polyol component and isocyanate component may be mixed thoroughly, generally under a nitrogen blanket, and agitated until the isocyanate group content drops to a steady value, indicating that the reaction is finished. The mixture is advantageously modestly heated, for example to temperatures in the range of 50xc2x0 C. to 70xc2x0 C. Urethane reaction-promoting catalysts such as the various well known tin catalysts, amine catalysts, or other catalysts which promote the reaction between isocyanate and hydroxyl groups may be used if desired. The reaction may be batch, semibatch, or continuous. Examples of prepolymer preparation may be found in Polyurethane: Chemistry and Technology, Polyurethanes Handbook, in U.S. Pat. No. 5,278,274, and, Canadian Published Application 2,088,521, which are herein incorporated by reference.
Chain extenders useful in the subject invention are the conventional diol and diamine chain extenders known to those skilled in the art. Suitable diol chain extenders include, for example, ethylene glycol, 1,4-butanediol, 1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 2-methyl-1,3-propanediol, diethylene glycol, tripropylene glycol, and the like, and mixtures thereof. Suitable diamine chain extenders include aliphatic and aromatic diamines. Preferred diamines are the sterically hindered or electrically deactivated aromatic diamines. Examples of these are the various ring alkylated toluene diamines, methylenedianilines such as 3,5-diethyltoluenediamine (DETA) and like compounds such as those disclosed in U.S. Pat. No. 4,218,543. Examples of aromatic diamines which are rendered less active by electrical effects of ring substituents include 4,4xe2x80x2-methylene-bis(2-chloroaniline) (MOCA or MbOCA) and 4,4-methylene-bis(3-chloro-2,6-diethylaniline) (MCDEA). Diamines without steric hindrance or ring deactivating groups may react too rapidly and cause insufficient pot life to fill the mold, particularly when complex molds are used. The chain extender component may include minor amounts of crosslinkers such as diethanolamine, triethanolamine, and the like.
Catalysts may also be useful in certain systems. Catalysts have been described previously with respect to prepolymer formation, and suitable catalysts are well known to those skilled in the art. Many examples of suitable catalysts may be found in the Polyurethane Handbook, Pp. 90-95, and Polyurethanes: Chemistry and Technology, Pp. 129-217, both incorporated herein by reference.
Conventional additives and auxiliaries may be added as well, including but not limited to fillers, plasticizers, dyes, pigments, UV stabilizers, thermal stabilizers, antioxidants, flame retardants, conductivity agents, internal mold release agents, blowing agents, and the like. When a blowing agent is included, the product is a microcellular elastomer. Suitable blowing agents include reactive ones, such as water, and physical ones, such as volatile hydrocarbons, CFCs, and the like. Mixtures of reactive and physical blowing agents can be used. Polymer solids, for example, vinyl polymer solids as found in polymer polyols and isocyanate-derived solids such as those found in PIPA and PHD polyols may be included as well, for example by using an appropriate polymer polyol dispersion having as its xe2x80x9cbase,xe2x80x9d or xe2x80x9ccarrierxe2x80x9d polyol, a low unsaturation polyoxypropylene diol. If the amount of polymer solids desired is low, a minor quantity of high solids polymer polyol dispersion prepared from a conventionally catalyzed polyol may be used.
The polyoxypropylene diol may contain oxyethylene moieties, introduced, for example, by the random copolymerization or capping with ethylene oxide along with propylene oxide during preparation of the polyol. The amount of ethylene oxide should generally be 40 weight percent or less, preferably less than 20 weight percent, and more preferably about 5 to about 15 weight percent. If the polyoxypropylene diols containing oxyethylene moieties are to be prepared using double metal cyanide complex catalysis, it is preferred that the ethylene oxide be present during a substantial portion of the oxypropylation.
The polyoxypropylene diol may also contain minor amounts of higher alkylene oxides, particularly oxetane, 2,3-butylene oxide, 1,2-butylene oxide, and the like. The amount of higher alkylene oxide should generally be limited to less than about 10 weight percent. Most preferably, the polyoxypropylene diol contains substantially all oxypropylene moieties, or oxypropylene moieties with not more than about 10 weight percent random oxyethylene moieties. The low unsaturation polyoxypropylene diol may also contain a minor amount of a conventionally, base-catalyzed polyoxypropylene diol, provided that the amount of such conventional diol not exceed 20 mol percent of the total high molecular weight diol, and the unsaturation of the high molecular weight portion of the diol mixture be less than 0.020 meq/g, preferably less than 0.015 meq/g.

Polyurethane and polyurethane/urea heat-cured and moisture-cured elastomers with improved physical properties


The present invention relates to a herbicidal composition having a synergistic herbicidal effect against weeds, said herbicidal composition including 3-[(5-difluoromethoxy-1-methyl-3-trifluoromethylpyrazol-4-yl)methylsulfonyl]-4,5-dihydro-5,5-dimethylisoxazole and salts thereof as a component A and a component B selected from the group consisting of paraquat, ametryn, acetochlor, clodinafop-propargyl, diclofop-methyl, cycloxydim, tepraloxydim, tralkoxydim, amidosulfuron, mesosulfuron-methyl, sulfosulfuron, tribenuron-methyl, imazamethabenz-methyl, imazamox, imazapic, florasulam, hexazinone, chlorotoluron, pyraflufen-ethyl, metazachlor, S-metolachlor, isoxaben, fluroxypyr, qinclorac and pinoxaden.

It is disclosed in Patent Document 1 that isoxazoline derivatives or their salts as compounds of Component A to be incorporated in the herbicidal composition of the present invention are safe to rice, wheat, barley, corn, grain sorghum, soybean, cotton, sugar beet, lawn grass, fruits and the like and have excellent herbicidal effects by themselves.
Further, compounds of the after-mentioned Components B and C to be incorporated in the herbicidal composition of the present invention, are known compounds having herbicidal activities, and they are disclosed, for example, in Non-patent Documents 1 to 3.
Further, a group of compounds of the after-mentioned Component D to be incorporated in the herbicidal composition of the present invention, as the case requires, are compounds known as phytotoxicity-reducing agents, and such compounds are disclosed in Non-patent Documents 1 and 2.
Patent Document 2 discloses Examples wherein compounds represented by the formula [I] can be mixed with known herbicidal compounds.
On the other hand, various herbicides have been developed for practical use by the research and development over many years, and such herbicides have contributed to saving of weed-controlling operations or to the improvement of productivity of agricultural or horticultural crop plants. However, even today, it is desired to develop a novel herbicide which is safer and has excellent herbicidal characteristics.
Further, a herbicide to be used for crop plants is desired to be an agent which exhibits sufficient herbicidal effects against a wide range of weeds at a low dose by application to soil or foliage and yet exhibits high selectivity between crop plants and weeds.    Patent Document 1: WO2002/062770    Patent Document 2: WO2004/014138    Non-patent Document 1: Pesticide Manual 14th edition, British Crop Council    Non-patent Document 2: SHIBUYA INDEX 12th Edition, published by SHIBUYA INDEX RESEARCH ASSOCIATION    Non-patent Document 3: Monthly Fine Chemical, vol 35, No. 7 (2006), published by CMC


An achromatic beam shaping prism is disclosed which compensates for a fluctuation in oscillating wavelength of a semiconductor laser source of a recording type optical disc system using a single prism having a diffraction grating with a specified pitch so as to make the beam shaping prism achromatic. Two equations are given for specifying the pitch d or dxe2x80x2 of the diffraction grating, depending on whether the diffraction grating is applied to the output surface or the input surface of the prism, respectively.

In an optical disc recording system, the equalization of intensity distribution (hereinafter termed xe2x80x9cbeam shapingxe2x80x9d) of a laser beam that is output from a semiconductor laser source is desired in order to optimize the shape of a light spot on a disc. For example, beam shaping prisms may be used to either compress or expand the diameter of an incident beam in a specific direction by refracting the beam. Specific examples of such beam shaping prisms are disclosed in Japanese Laid Open Applications H10-268112 and H10-62611. All of these beam shaping prisms are designed so that they not only perform beam shaping, but also can compensate for recording performance degradation caused by wavelength fluctuations of a semiconductor laser that is used to read the optical disc.
Wavelength fluctuations of a semiconductor laser frequently occur at the start of operation of a laser or when the luminous power of the laser is changed. Such wavelength fluctuations are said to be an unavoidable phenomenon in an optical disc system for recording signals on a disc medium when turning the laser ON/OFF. However, in the case where the output of a laser fluctuates from a reference wavelength, the output beam from a beam shaping prism will be emitted at a slightly different inclination as compared with the output beam at the reference wavelength, due to the index of refraction of the beam shaping prism being dependent on wavelength. For a recording-type optical disc system, this becomes a problem in that the position of a reading light spot that is formed on a disc will vary with a change in wavelength. This will cause signal degradation in recording onto a disc as well as in reading from a disc using a photo head.
In the above conventional examples, this problem is solved by using two prisms which are formed of materials that have different, refractive indexes and different dispersions. Thus, by using a pair of prisms that form an achromatic beam shaping system, the angle of an output beam is kept roughly constant so as to prevent a positional fluctuation of a light spot on a disc even when the wavelength of the incident beam fluctuates. Further, a beam shaping optical system that uses two cylindrical lenses in lieu of a pair of prisms has also been known.
An optical system is disclosed in U.S. Pat. No. 5,101,458 which enables the output direction of a beam emitted from a prism to be made substantially constant when the wavelength of an input light beam and the incident angle thereof vary. The technique disclosed in this patent leads light that is output from a waveguide into a prism arranged opposite to the waveguide. The output direction of this light is made constant for a change in wavelength by the action of a diffraction grating formed on the output face of the prism. However, the invention described in the above prior art patent employs both a waveguide and a prism, wherein the prism requires a change of the angle of incidence of the input beam to the prism. Therefore the basic idea of that invention is different from that of the present invention. In the present invention the angle of incidence of the input beam is constant and no waveguide path is needed as a necessary component.
The object of the present invention is to provide an achromatic beam shaping prism in which the output angle of an emitted beam remains substantially the same even when the wavelength of the incident beam changes and which uses a construction that enables both miniaturization and low cost.