A process for the conversion of aromatic hydrocarbons is disclosed which is especially useful for reaction of an alkylating agent, preferably propylene, with an aromatic hydrocarbon. Novel feature is use of a catalyst system comprising TiCl.sub.4 and a Group III-A metal oxide.

1. Field of the Invention
The present invention relates to an improved process for the conversion of an aromatic hydrocarbon in the presence of a titanium tetrachloride catalyst system.
The invention will be described with reference to alkylation, i.e., the synthesis of cumene by alkylation of benzene with propylene in the presence of the catalyst, but will find use in alkylaromatic transalkylation and isomerization as well.
2. Description of the Prior Art
Conversion of aromatic hydrocarbons is well known in industry. Some of the aromatic conversion reactions which occur include alkylation of aromatic hydrocarbons with an alkylating agent such as an olefin, disproportionation of alkylaromatic hydrocarbons and isomerization of alkylaromatic hydrocarbons such as xylenes.
Of special interest, has been the propylation of benzene to cumene. Cumene is used for the production of phenol and acetone. Cumene is also dehydrogenated to form methylstyrene, in a process similar to that used to convert ethylbenzene to styrene. Cumene is also used as a blending component in aviation gasoline because of its high octane number. The consumption of cumene in the U.S.A. was about 350,000 metric tons in 1968. Of this total, 94% was used for the production of phenol or acetone.
It is well known that cumene can be synthesized from benzene and propylene using a catalyst of AlCl.sub.3, SPA or BF.sub.3. SOA is a generally accepted abreviation for solid phosphoric acid catalyst, or phosphoric acid which is adsorbed on kieselguhr or other support.
AlCl.sub.3 is a very popular alkylation catalyst, because of its high activity. Unfortunately, the catalyst operates as a slurry or sludge which is messy to handle on a commercial scale, and also is corrosive. The highly reactive nature of this Friedel-Crafts metal halide catalyst, AlCl.sub.3, is desirable when attempting to aklylate benzene with ethylene, because less active catalyst systems do not work. However, for alkylation with propylene such highly reactive systems are not necessary.
The AlCl.sub.3 catalyst, although not equivalent to a Ziegler-Natta catalyst, is similar, at least for some olefin reactions. AlCl.sub.3 will promote polymerization of both ethylene and propylene, and alkylation of benzene with both ethylene and propylene. These catalysts also promote transalkylation of alkyl groups. This is in contrast to slightly less active systems, such as SPA catalyst, which catalyzes alkylation of benzene with propylene, but does not catalyze transalkylation satisfactorily.
Another highly selective catalyst system has been developed for the alkylation of benzene with olefins. This catalyst comprises boron trifluoride. The boron trifluoride catalyst system is exceptionally active and permits operation with dilute olefin streams, but it requires the continuous addition of BF.sub.3 to maintain catalyst activity. High catalyst activity also leads to oligomerization of olefins, so contact time of olefins with BF.sub.3 catalyst should be as short as possible. This catalyst is also exceptionally water sensitive, as water not only destroys the catalyst, but produces very corrosive solutions which attack downstream processing units. BF.sub.3 also frequently appears in the product, and must be removed therefrom.
Because of the interest in alkylating benzene with olefins, and because of the inadequacies of existing catalyst systems, I studied the work that others had done, and made exhaustive investigations to determine if it would be possible to find a catalyst which would have the activity and selectivity required to produce an acceptable cumene product, while making maximum use of existing petroleum resources.
A highly active catalyst was sought, to permit operation at lower temperatures with less utility cost, cost of construction, and to operate with less catalyst. In new units this would mean smaller, and cheaper reactor vessels, while in existing units it would mean that an increase in capacity could be obtained by changing catalyst in an existing reactor vessel, with minor modifications.
High selectivity is necessary, not only to permit operation with feedstreams which are not 100% pure olefin, but also to maximize production of the desired product, and to minimize production of polymerized olefins, or polyalkylated aromatic compounds.
Accordingly, many catalyst systems were studied to find a catalyst with excellent activity and selectivity, which was not corrosive or destroyed by water.
There has been extensive work done with Ti catalysts, though most work occurred in conjunction with studies of Ziegler-Natta catalysts. The closest prior art known is U.S. Pat. No. 2,381,481 (Class 260-683.15), U.S. Pat. No. 2,951,885 (Class 260-671), U.S. Pat. No. 2,965,686 (Class 260-671) and U.S. Pat. No. 3,153,634 (Class 252-429).
In U.S. Pat. No. 2,381,481, preparation and use of a catalyst prepared by treating alumina gel with fluotitanic acid is disclosed. This catalyst is used for polymerization of olefins to heavier hydrocarbons, and also for alkylation of paraffins with olefins, the latter when operating at high temperatures, between 700.degree. and 900.degree. F. or higher. No mention is made of alkylation of aromatics with olefinic hydrocarbons or transalkylation of polyalkylbenzenes.
In U.S. Pat. No. 2,951,885, there is disclosed the use of titanium trihalide on activated alumina or other activated acidic oxide for alkylation of benzene with olefins. The catalyst is originally a tetrachloride, subsequently reduced to the trichloride with an alkali metal such as sodium, lithium, or potassium. The examples show that this catalyst will alkylate benzene with ethylene.
In U.S. Pat. No. 2,965,686, the thrust of the application was to develop a titanium subchloride catalyst. In Example II, a reaction between cumene and propylene was disclosed using titanium tetrachloride catalyst. The catalyst in Example II was tetrachloride. The catalyst was prepared by activating alumina by evacuation at a temperature of 600.degree. C. for an unspecified period of time. The resultant catalyst was then used in an alkylation reaction for the propylation of cumene to form diisopropylbenzene. This patent is silent as to the type of alumina which was used as the base for the catalyst.
In U.S. Pat. No. 3,153,634, there is disclosed the use of titanium subhalides in a polymerization reaction. The patentee is probably describing a catalyst for production of solid polymer products. On page 3 lines 65-75, the patentee mentions use of benzene as an inert solvent to hold dissolved olefins, rather than as a reactant.
Accordingly, work continued on developing an improved process for the catalytic conversion of aromatic hydrocarbons.
Accordingly, the present invention provides a process for the catalytic conversion of an aromatic hydrocarbon comprising contacting the aromatic hydrocarbon with a reactant at aromatic hydrocarbon conversion conditions in the presence of a catalyst system comprising titanium tetrachloride and alumina wherein the catalyst system is prepared by passing TiCl.sub.4 vapor over activated alumina at a temperature of 100.degree. to 400.degree. C. for 1 to 10 hours.
The catalyst used comprises titanium tetrachloride impregnated on an activated metal oxide which possesses surface hydroxyl groups. Specific examples of these metal oxides will include the Group III-A metal oxides which possess surface hydroxyl groups and which also possess a relatively high surface area such as alumina, gallium oxide, indium oxide, and thallium oxide. Of these compounds, the preferred substrate is alumina, and especially low density, high surface area aluminas such as gamma-alumina or, if so desired, eta-alumina.
The apparent bulk density of the alumina may range from about 0.3 to about 0.7 g/cm.sup.3 or higher with a surface area ranging from about 1 to about 500 m.sup.2 /g. The alumina may be in any shape, one example of the substrate being spheroidal alumina which is prepared by the conventional and commercial oil-drop method as described in U.S. Pat. No. 2,610,314. In addition, it is also contemplated within the scope of this invention that the alumina may be treated to provide greater physical stability, one type of treatment being to impregnate the gamma-alumina with a compound such as barium nitrate, which, upon calcination, is converted into barium oxide. The latter compound will then, as hereinbefore set forth, provide greater physical stability for the alumina. It is also contemplated within the scope of this invention that a commercial gamma-alumina may also be used as the support. However, since this commercial gamma-alumina could contain an excessive amount of water which would consume an excess of titanium tetrahalide without any beneficial effect on the catalyst, in the preferred embodiment of this invention the commercial gamma-alumina is subjected to a predrying step by heating to a temperature in the range of from about 400.degree. to about 550.degree. C. under an inert gas or hydrogen flow for a period of about 1 to about 8 hours.
In order to achieve the maximum activity of the metal oxide support, it is necessary to avoid severe drying of said support. For example, the drying of alumina at temperatures in excess of about 600.degree. such as 650.degree., under vacuum, will seriously deplete the alumina of the hydroxyl groups present thereon. This severe drying step will not only remove the water which is absorbed on the alumina, but will also remove the aforesaid surface hydroxyl groups which are essential to make an active catalyst, said surface hydroxyl groups reacting with the titanium component of the titanium tetrachloride.
The gamma-alumina which has been predried according to the above paragraph is then placed in an appropriate apparatus which may comprise a flask, tube, etc., and a gas mixture of nitrogen and titanium tetrachloride which has been prepared by bubbling nitrogen gas through the liquid titanium tetrachloride at room temperature is passed over the gamma-alumina at temperatures of 25.degree. to 135.degree. . Thereafter the temperature is increased to 550 or more. The passage of the nitrogen-titanium tetrachloride mixture over the alumina is effected about 0.5 to 10 hours or more, the time being dependent upon the amount of gamma-alumina which is present and the flow rate of the titanium tetrachloride-nitrogen gas mixture. It is preferred to pass the titanium tetrachloride or the gaseous mixture over the support at a temperature of about 25.degree. to about 135.degree.. The temperature is then raised to 250.degree. or a desired temperature, either gradually or in a series of steps. The preferred temperature for the heat treatment of this resulting composite is from about 135.degree. to about 550.degree., however, it will be dependent on the temperature which is used in the aromatic hydrocarbon conversion process. Generally, it is preferred that the temperature which is used in the treatment of the composite be equal to, or higher than, the aromatic hydrocarbon conversion temperature. Thereafter the temperature is maintained at this point and a stream of nitrogen is passed over the catalyst composite for an additional period which may range from about 1 to 10 hours. At the end of this time, the finished catalyst is then sealed under an inert atmosphere such as argon, helium, nitrogen, etc., prior to being used.
Alternatively, the catalyst may be prepared by forming a solution of titanium tetrachloride in a polar, non-aqueous organic solvent and impregnating the alumina. Thereafter the impregnated alumina is then treated under a nitrogen flow at temperatures in the range hereinbefore set forth. After subjecting the impregnated substrate to these temperatures for a predetermined period of time, the finished catalyst is also recovered and maintained under an inert atmosphere until use thereof.
It is believed that the important factor in the thermal treating steps is the temperature, rather than the total time, as long as the total period for thermal treatment is reasonably long; around five or six hours. It is believed that the activity of the catalyst is effected by the thermal treatments because the thermal treatments desorb water molecules from the catalyst surface. Water can compete for active sites with the reactants, thus water is to some extent a catalyst poison. However, if catalyst deactivation occurs due to water adsorption, the catalyst can be regenerated by appropriate further thermal treatment under inert gas flow. Any regenerative thermal treatments should probably approximate those of the original thermal treatments, in that heating which is too rapid, or to too high a temperature, may cause hydrolysis of the TiCl.sub.4 component on the catalyst, which would reduce catalyst activity. Another danger of a rapid high temperature catalyst regeneration would be the formation of corrosive gases and liquids due to rapid evolution of H.sub.2 O vapor and chlorine compounds.
It is also contemplated within the scope of this invention that the catalyst system hereinbefore described may, if so desired, be composited on a solid support. The preferred solid supports which may be utilized comprise high surface area inert compounds, some representative examples of which will include silica, magnesia or mixtures of silica with other inorganic oxides such as silica-zirconia, silica-thoria, silica-magnesia-zirconia, etc., charcoal, coal, diatomaceous earths and clays such as fuller's earth, bentonite, montmorillonite, kieselguhr, etc. It is to be understood that these compounds will act only as supports for the catalyst system and will not enter into the catalytic activity of the composite. The catalyst system comprising titanium tetrachloride composited on the Group IIIA metal oxide and the inert support may be composited in any manner known in the art such as by impregnation, deposition, rolling, mixing, etc.
In addition, it is also to be considered within the scope of this invention that one or more promoters may be added to the catalyst system. It is believed that use of one or more promoters selected from the metals of Group VIB or Group VIII of the Periodic Table may be beneficial to the practice of the present invention.
At least about 0.5 weight percent titanium, on an elemental basis, is believed necessary for a significant amount of reaction to occur. The upper limit on titanium is believed to be about 20 wt. %.
When it is desired to use the catalyst system in an alkylaromatic isomerization process, then alkylaromatic isomerization reaction conditions should be used. Reaction conditions are disclosed in U.S. Pat. No. 3,637,881 (Class 260-668a), the teachings of which are incorporated by reference. When it is desired to use the catalyst system of the present invention for alkylaromatic transalkylation then appropriate reaction conditions should also be used. These are disclosed in U.S. Pat. No. 3,720,726 (Class 260-672t), the teachings of which are incorporated by reference. Reaction conditions for the alkylation of aromatic hydrocarbons will be discussed in detail in a latter part of this specification.
The catalyst may be disposed in a reactor vessel as a fixed fluidized or moving bed of catalyst. The reactants may contact the catalyst in upflow, downflow or crossflow fashion, though upflow of reactants over a fixed bed of catalyst is preferred.
The liquid hourly space velocity in the reactor may range from 0.1 to 20. Because catalyst of the present invention is very active for the alkylation reaction, significantly higher space velocities are possible than when using some prior art catalysts, e.g., SPA. To some extent, the liquid hourly space velocity is related to temperature in the reaction zone, in general, a higher LHSV will require higher temperature operation.
The ratios of reactants and other reaction conditions which occur when alkylating benzene with light olefins, and preferably are basically those well known in the art. Pressures may range from 1 to 100 atmospheres, or even higher. It is desirable to maintain pressures high enough to have a liquid phase in the reaction zone. Although it is possible to operate at very high pressure, little advantage is gained thereby, in fact, an increase in pressure seems to have a harmful effect. Preferred pressure seems to be around 20 to 60 atm, with an optimum pressure of about 35 atm.
Temperature effects both the conversion and selectivity of the reaction. Temperature may range between ambient and 250.degree.. At very low temperatures, the catalyst is not sufficiently active to permit the desired reaction to proceed at a satisfactory rate. At very high temperatures, it is believed that the catalyst may be damaged, by formation of carbonaceous materials on the catalyst.
If the reaction is kinetically controlled, an increase in temperature should increase the rate of reaction. As a general statement, this is true, but the temperature dependence may not be as large as expected, if the reaction is limited by mass transport of reactants and products to and from the catalyst surface. Preferred operating temperature is probably about 100.degree. to 200.degree. C.
The catalyst may be disposed in a reactor vessel as a fixed, fluidized or moving bed of catalyst. The reactants may contact the catalyst in upflow, downflow or crossflow fashion, though upflow of reactants over a fixed bed of catalyst is preferred.
The liquid hourly space velocity in the reactor may range from 0.1 to 20. However, higher LHSV is possible depending on the desired conversion level of propylene. Because catalyst of the present invention is believed very active for the alkylation reaction, significantly higher space velocities should be possible than when using some prior art catalysts, e.g., SPA. To some extent, the liquid hourly space velocity is related to temperature in the reaction zone, in general, a higher LHSV will require higher temperature operation.

Titanium tetrachloride as heterogeneous catalyst for isomerization of alkylaromatic hydrocarbon


An implantable lead is provided with at least one extendable member to position therapy delivery elements, which may be electrodes or drug delivery ports, after the lead has been inserted into the body. The lead may formed as a resilient element which is contained in a retainer tube that may be removed to permit the lead to deploy. Alternatively, a non-resilient lead may be provided with a slotted retainer tube. A series of mechanical linkages for expanding and retracting the lead within the human body may be actuated with various mechanisms. A control system may be provided for closed-loop feedback control of the position of the extendable members. The invention also includes a method for expanding an implantable lead in situ.

This invention relates to implantable leads for delivering therapy, in the form of electrical stimulation or drugs, to the human body. Specifically, this invention relates to implantable leads that may be expanded, retracted or adjusted after implantation in the human body. This invention also relates to mechanisms for accomplishing such expansion, retraction or adjustment of such leads in situ. Further, this invention relates to control systems for controlling such expansion, retraction or adjustment of such an implanted lead.
Recent efforts in the medical field have focused on the delivery of therapy in the form of electrical stimulation or drugs to precise locations within the human body. Therapy originates from an implanted source device, which may be an electrical pulse generator, in the case of electrical therapy, or a drug pump, in the case of drug therapy. Therapy is applied through one or more implanted leads that communicate with the source device and include one or more therapy delivery sites for delivering therapy to precise locations within the body. In drug therapy systems, delivery sites take the form of one or more catheters. In electrical therapy systems, they take the form of one or more electrodes wired to the source device. In Spinal Cord Simulation (SCS) techniques, for example, electrical stimulation is provided to precise locations near the human spinal cord through a lead that is usually deployed in the epidural space of the spinal cord. Such techniques have proven effective in treating or managing disease and acute and chronic pain conditions.
Percutaneous leads are small diameter leads that may be inserted into the human body. usually by passing through a Tuohy (non-coring) needle which includes a central lumen through which the lead is guided. Percutaneous leads are advantageous because they may be inserted into the body with a minimum of trauma to surrounding tissue. On the other hand the types of lead structure, including the electrodes or drug-delivery catheters, that may be incorporated into percutaneous leads is limited because the lead diameter or cross-section must be small enough to permit the lead to pass through the Tuohy needle.
Recently, the use of xe2x80x9cpaddlexe2x80x9d leads, like Model 3586 Resume(copyright) Lead or Model 3982 SymMix(copyright) Lead of Medtronic, Inc., which offer improved therapy control over percutaneous leads, have become popular among clinicians. Paddle leads include a generally two-dimensional set of electrodes on one side for providing electrical therapy to excitable tissue of the body. Through selective programmed polarity (i.e., negative cathode, positive anode or off) of particular electrodes, electric current can be xe2x80x9csteeredxe2x80x9d toward or away from particular tissue within the spinal cord or other body areas. Such techniques are described by Holsheimer and Struijk, Stereotact Funct Neurosurg, vol. 56, 199: pp 234-249; Holsheimer and Wesselink, Neurosurgery, vol. 41, 1997: pp 654-660; and Holsheimer, Neurosurgery, vol. 40, 1997: pp 990-999, the subject matter of which is incorporated herein by reference. This feature permits adjustment of the recruitment areas after the lead has been positioned in the body and therefore provides a level of adjustment for non-perfect lead placement. Such techniques are disclosed in U.S. Pat. Nos. 5,643,330, 5,058,584 and 5,417,719, the subject matter of which is incorporated herein by reference. Additionally, the value of a transverse tripole group of electrodes has been demonstrated for spinal cord stimulation, as described by Struijk and Holsheimer, Med and Biol Engng and Comput, July, 1996: pp 273-276; Holsheimer, Neurosurgery, vol. 40, 1997: pp 990-999; Holsheimer et al., Neurosurgery, vol. 20, 1998. This approach allows shielding of lateral nervous tissue with anodes, like the dorsal roots. and steering of fields in the middle under a central cathode by use of two simultaneous electrical pulses of different amplitudes.
One disadvantage recognized in known paddle leads is that their installation, repositioning and removal necessitates laminectomies, which are major back surgeries involving removal of part of the vertebral bone. Laminectomies are required because paddle leads have a relatively large transverse extent compared to percutaneous leads. Thus, implantation, repositioning and removal require a rather large passage through the vertebral bone.
Another disadvantage with paddle leads is that optimal positioning is often difficult during implant. For example, the transverse tripole leads described above work optimally if the central cathode is positioned coincident with the physiological midline of the spinal cord. Such placement is difficult since the doctor cannot see the spinal cord thru the dura during implant. Moreover, lead shifting may occur subsequent to implant, thereby affecting the efficacy of the therapy delivered from the lead.
Yet another disadvantage recognized with paddle leads is that the lead position may change merely with patient movement. For example, when a patient lies down, the spacing between an epidural lead and the spinal cord decreases to a large extent, so that it is often necessary to lower the amplitude of the stimulation by half. It is reasonable to assume that steering effects of a tripole lead might also be affected if the CSF width changes dramatically, or if due to patient twisting or activity, the orientation between the lead and spinal cord changes.
While the prior art has attempted to provide deformable leads, which may provide improved insertion characteristics or enhanced stability once inside the body, they have not succeeded in providing a device which remedies the aforementioned problems. For example, U.S. Pat. No. 4,285,347 to Hess discloses an implantable electrode lead having a distal end portion with a laterally extending stabilizer, preferably in the form of curved loops. Similarly, and U.S. Pat. No. 4,519,403 to Dickhudt discloses an inflatable lead for enhanced contact of the electrode with the dura of the spinal cord._U.S. Pat. No. 5,121,754 to Mullett discloses a device to allow electrodes to move to more lateral positions after insertion, when a stiffening guidewire used during insertion is removed. In Mullett""s device, only one electrode can be found at any particular longitudinal location, since only gentle curves of the lead were designed, and the curves are not adjustable after implant of the lead. Similar problems apply to the device disclosed by O""Neill in U.S. Pat. No. 4,154,247.
Patent Cooperation Treaty (PCT) Publication No. WO 93/04734 to Galley discloses a lead tip that has four spans that will bulge into four different directions when a confining outer catheter is drawn proximally back over the lead body. The publication describes one electrode on the middle of each span. In situ in the epidural space, these four electrodes will form a square or rectangular cross-sectional shape. Two of them might be pressed into the dura (at lateral positions) and the other two would be dorsal, against the vertebral bone. Only the electrodes nearest the spinal cord would be useful for programming. While this could give two electrodes at the same longitudinal position, their medial to lateral locations are difficult to control, and their ability to spread apart depends on the relative stresses in the spans and tissue-like adhesions that may be present. Other malecot-type lead tips have been proposed for positioning of electrodes in the heart (U.S. Pat. No. 4,699,147, Chilson and Smith, 1985; U.S. Pat. No. 5,010,894, Edhag, 1989) or anchoring of lead bodies (U.S. Pat. No. 4,419,819, Dickhudt and Paulson, 1982; U.S. Pat. No. 5,344,439, Otten, 1992) or positioning of ablation electrodes (Desai, U.S. Pat. Nos. 5,215,103, 5,397,339 and 5,365,926). While the aforementioned prior art devices provide various configurations for compact insertion or lead stabilization after implant, they do not offer the advantages and improved efficacy recognized with respect to paddle lead configurations.
It would therefore be desirable to provide a lead structure for stimulation of excitable tissue surfaces which combines the advantages offered by percutaneous leads with respect to minimized trauma during insertion, repositioning and removal with the advantages offered by paddle-type leads with respect to improved efficacy, ability to provide electrodes in places lateral to the axis of the lead and tailoring of treatment.
It would also be desirable to provide a lead structure which permits adjustment of the lead dimensions and therefore the delivery site location in situ for enhanced control of the therapy being applied to the excitable body tissues.
It would be further desirable to provide a paddle lead which is capable of automatically adjusting its width or delivery site spacing automatically in response to patient factors such as body position or activity or in response to a parameter such as muscle contraction or action potentials, which may be characteristic of the stimulation or therapy being applied.
The invention combines the advantages of percutaneous leads with those of paddle leads. In a preferred embodiment, the invention provides a lead structure including a central core portion and at least one flexible, semi-flexible or semi-rigid transversely extending span which may be positioned in a compact position during insertion in which it is wound around or otherwise disposed in close proximity to the central core portion. Each span may also be deployed or shifted to a position in which it extends outward from the central core portion in a transverse direction. Each span has disposed on one surface a number of therapy delivery elements, in the form of electrodes or catheter ports, for delivering therapy in the respective form of electrical or drug therapy to the body. In the compact insertion position, the lead may be easily inserted within a catheter or Tuohy needle. Once the lead has been positioned at the appropriate place in the body, the span or spans may be deployed from the compact position to the extended position in which the therapy delivery elements are positioned in a fashion similar to a paddle lead. The flexibility of the spans also permits the lead to be retracted back to the compact position in the event that the lead must be removed from the body.
In a preferred embodiment, the invention provides a lead which includes a central core portion and at least one flexible paddle extending therefrom and which may be coiled around the core portion when the lead is to be compacted for insertion. As the lead is inserted through a catheter or Tuohy needle, the spans are kept in the compact position by lead rotation in a direction opposite their direction of winding around the central core. Also according to the invention, the spans are deployed by rotating the central core portion in the same direction in which the spans are coiled around the central core portion. Because of the flexibility of the spans, they are caused to move outward, away from the central core as the lead is uncoiled. In another embodiment of the invention, the spans can be formed of a resilient material in which resilient forces develop when the lead is configured in its compact position. The lead is maintained in its compacted form while inside of the insertion tool, i.e. Tuohy needle. The resilient forces cause the spans to extend outward once the lead exits the end of the insertion tool.
An outer concentric retainer tube may be provided in combination with the lead, the outer retainer tube acting to retain the lead in its compact position during insertion. The retainer tube may be provided with a pair of notches on its distal end to aid in the retraction of the lead after deployment. Specifically, the notches are disposed on the distal end of the retainer tube in such a manner that the spans will engage the notches when the central core portion is rotated and pulled toward a proximal end of the retainer tube. The notches retain the spans in position as the central core rotates. thus causing the spans to coil around the central core portion and assume a compact position.
The present invention also provides a lead which may be compacted in a different manner than described above. The lead is comprised of a series of therapy delivery elements which are attached to a thin backing sheet which permits the sheets to be disposed one on top of the other in the compact insertion position and then to expand to a generally planar orientation once the lead is inserted to the appropriate position in the body.
The following are exemplary advantages of adjustable leads constructed according to the preferred embodiments of the invention:
1. The spacing of the sites can be matched to important dimensions of the tissue affected, e.g., the width of the Cerebro-Spinal Fluid (CSF) between the dura and the spinal cord.
2. As the dimensions of the lead tip are changed, the locations of the sites relative to the tissue affected may be advantageously altered. For example, as a paddle""s width is increased the paddle will move toward the spinal cord in the semicircular dorsal part of the epidural space.
3. In cases where the bones or fluid compartments have large widths (e.g., CSF depth at spinal level T7 or T8) or are too wide in a particular patient, the paddle width can be increased appropriately to ensure effective therapy.
4. Changes in paddle width and the accompanying medial and lateral movement of the sites can have a beneficial effect on the therapy. For example, the ability to stimulate only the medial dorsal columns versus the more lateral dorsal roots may provide enhanced therapeutic results.
5. As the patient ages, their pathological condition changes, their degree of fibrosis or scar tissue changes, or the effects of the therapy change, adjustments of the paddle dimension(s) might restore or maintain the benefit.
6. If the paddle""s dimension(s) can be changed after implant, it may be possible to optimize the benefits and minimize undesirable side effects.
7. By changing the paddle""s dimension(s), it may be possible to avoid surgery to replace or reposition the lead.
8. By changing the paddle""s dimension(s), it may be possible to position the sites optimally relative to important physiological locations, e.g., the physiological midline of nervous tissue, or receptors responsive to the drugs being delivered.
9. It may be possible to minimize the use of energy by optimizing efficiency of therapy delivery through adjustment of paddle width.
10. There may be minimal insertion trauma and operating room time and resources needed if it is possible to place a lead with percutaneous techniques, and then expand it in situ.
11. Repositioning of a paddle lead can be done without laminectomy. Removal is also made quicker and less traumatic.
12. With closed loop feedback control of the paddle""s dimension(s), optimal therapy can be maintained with less interference with the patient""s lifestyle.
Another preferred embodiment allows automatic changes in at least one dimension of a paddle lead. Such a system would measure an effect of the stimulation, e.g., a compound action potential caused by stimulation/drugs, a muscle contraction, the direction of gravity, increased activity of the patient, relative motion of vertebral bones, or other effects. Measurement techniques for compound action potentials are disclosed in U.S. Pat. No. 5,702,429 the subject matter of which is incorporated herein by reference. Such a recorded signal should be altered if the lead paddle dimension that is controlled is changed. Then, after filtering, amplifying, integrating and comparing the recorded signal to a previous stored signal, the parts of the lead that control the dimension in question will be moved or activated, causing a change in said dimension, which will restore the effect measured to its original value. This constitutes closed loop feedback control, and can enable to patient to be less affected by changes in the therapy caused by his/her position, activity, etc. Of course there should be governors on the dimensional changes allowed, so that if the measured parameter is very greatly changed, neither the device nor the patient will undergo damage or trauma. The described embodiments show preferred techniques to expand a lead in directions transverse to the main axis of the lead body. The invention also contemplates devices for expanding the lead in a direction substantially parallel to the lead axis.
Other advantages novel features, and the further scope of applicability of the present invention will be set forth in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

Apparatus and method for expanding a stimulation lead body in situ


The present invention is directed to a setting system for use in the making of gelatin desserts comprising gelatin and an anionic hydrocolloid gum wherein the weight ratio of gelatin to anionic hydrocolloid gum is approximately 250-375:1. Through the use of such a setting system, lower gelatin use of up to 10% or more can be realized while achieving an increase in gel strength of up to about 20%.

1. Technical Field
The present invention relates to gelatin desserts and a setting system to be used in the making thereof. More specifically, the setting system in accordance with the present invention comprises gelatin and an anionic hydrocolloid gum wherein the weight ratio of gelatin to gum is approximately 250-375:1. Through the use of a very small amount of anionic hydrocolloid gum in combination with the gelatin, the gel strength of the resulting gelatin product is significantly increased while allowing for about a 10% decrease in the required amount of gelatin. Additionally, the setting system set forth by the present invention provides an improved gelation time in comparison to conventional gelatin setting systems.
2. Prior Art
The production of gelatin represents a very large commercial market in the United States as well as in foreign jurisdictions. Only a few years ago, world gelatin production reached over 115,000 tons, with the United States food industry consuming close to 20,000 tons and having a projected annual growth rate of about 0.5%.
Gelatin, which is a degraded form of collagen, is the main protein gelling agent used in foods. This is due to the fact that gelatin can form gels over a wide range of concentrations, producing a wide range of possible products, such as jellies, mousses, marshmallows and fruit gums. Two main forms of gelatin exist. Gelatin type A and gelatin Type B are both obtained by the partial hydrolysis of collagen, the chief protein component in skin, bones, hides, and white connective tissues of the animal body. Type A is produced by acid processing of collagenous raw material and has an isoelectric point between a pH of 7 and 9. Type B is produced by alkaline or lime processing and has an isoelectric point between a pH of 4.8 and 5.2. Mixtures of Types A and B, as well as gelatins produced by modifications of the above-described processes may exhibit isoelectric points outside of the stated ranges. Most edible gelatin is Type A, but Type B is also used.
The largest use of edible gelatin in the food industry is in the preparation of gelatin desserts in which gelatin is conventionally found in concentrations of about 1.5 to 2.5%. The food industry takes advantage of gelatin""s unique properties such as reversible gel-to-sol transition of aqueous solutions, viscosity of warm aqueous solutions, and capability to act as a protective colloid. Apart from being used in the making of gelatin desserts, gelatin is also used as a source of essential amino acids in dietary supplements and as therapeutic agents. For example, gelatin has been widely used in the treatment of muscular disorders and peptic ulcers, as well as an aid in infant feeding and for promoting nail growth.
Hydrocolloids are mainly responsible for the functional properties of processed food systems and the quality of many foods. Formulated foods usually contain mixtures of hydrocolloids performing structural functions. Hydrocolloids are defined as water soluble polymers with the ability to thicken or gel aqueous systems. The term xe2x80x9chydrocolloidsxe2x80x9d covers polysaccharides (i.e. gums), proteins and starches. Gelatin, discussed above, is a protein-based hydrocolloid, i.e. a polymer made up of amino acids.
D. V. Zasypkin, et al., Food Hydrocoll., 10: 203 (1995) believe that investigations of hydrocolloid interactions in aqueous solutions and gels is necessary for improvement of conventional foods, the development of novel formulated foods and for controlling functional properties of food systems. Increasing attention has been given to the gelation of mixed aqueous solutions of proteins and polysaccharides. This trend reflects the key role of hydrocolloids in structure formation in foods, the increasing number of hydrocolloids used as food additives and the development of new processing methods such as microwave heating, thermoplastic extrusion and high-pressure treatment.
The amount of gelling agent used in food formulations can be reduced by using a mixture of gel forming agents. In addition, a mixture of gel forming agents can allow for a better control of the composition-structure-property relationship of many processed food systems and final food products. V. B. Toltoguzov in Food Hydrocoll. 9: 317 (1995) found that both synergistic and antagonistic effects of mixing biopolymers can occur. The synergistic effect of single-phase mixed solutions of biopolymers is due to the excluded volume effect of macromolecules. In a two-phase system, synergy results from the concentration of the continuous phase rich in stronger gelling agent. The synergistic and antagonistic effects resulting from blending biopolymers are of great importance for the improvement of many foods and also for reducing their cost. The main cause of synergistic effects seems to be thermodynamic incompatibility. The reason is that macromolecules cannot occupy the same volume in solution. This means that each biopolymer can only use some part of the volume of the mixed solution. In solutions, incompatible biopolymers mutually concentrate each other. Thus, each incompatible biopolymer will behave as if it were more concentrated. Since the shear modulus of a gel is usually proportional to the square of its concentration, this means that small additions of a hydrocolloid can increase the elastic modulus of a gel considerably. Excluded volume effects also favor gelation of hydrocolloids. For incompatible biopolymers in mixed solutions, the rate of gelation is higher and the critical concentration for gelation is lower than those for each of them individually. Excluded volume effects depends on the flexibility, shape and size of macromolecules as well as their bulk concentration. On the other hand, antagonistic effect results from the formation of soluble and insoluble complexes that cannot form an additional three-dimensional network. Filled, complex and mixed gels of gelatin with different polysaccharides have been used for the development of a caviar analogue (V. B. Toltoguzov, Nahrung, 23:649 (1979)), multicomponent gels have been used in non-traditional pasta products, meat or fish analogues (V. B. Toltoguzov, Food Hydrocoll., 2: 339 (1988)), and in production of low fat spreads and fat replacers (D. V. Zasypkin, et al., Food Hydrocoll., 10: 203 (1995)).
The essential structure of gelatin is a rod shape triple helix of three polypeptide chains. The main chains are very long (i.e. more than 1000 residues) and the molecular weight is more than 100,000 daltons. In vivo, gelatin""s collagen helices are arranged in small groups or fibrils, which in turn are arranged in bundles. These structures are stabilized by covalent cross-links. During the production of gelatin, cross-links are broken and there may be extensive non-specific main-chain hydrolysis. As a result, gelatin is not a homogeneous product. Solid gelatin can be dissolved in hot water and it forms a gel upon cooling. When heated, the triple helices are largely unraveled and gelatin dissolves as random coils. When the solution is cooled, junction zones are formed by small segments from two or three polypeptide chains reverting to the collagen triple helix-like structure. The total amount of helix formation in the system is very dependent on the rate of cooling, with very slow rates permitting the formation of a greater degree or ordered (helical) structure as compared to faster rates. Gelatin gels are also quite elastic. The rigidity modulus depends on the gelatin concentration, the weight average molecular weight and on the temperature. In gelatin gel matured at high temperatures, only a few collagen-like junctions form and the large remainder of each chain will be disordered so that weak gels are generated. On further cooling of this gel, additional parts of each polypeptide chain become ordered. However, it is not clear if the increase in gel strength results from the growth of the existing junctions or from the formation of new, but less stable, junctions. Nevertheless, observations suggest that a gel matured at a higher temperature, but below the nucleation temperature, prior to chilling to a lower temperature will be stronger, i.e. have greater rigidity than one chilled immediately to the lower temperature. The magnitude of this prematuring effect depends on pH and gelatin concentration, as well as temperature.
The processes of structure formation at different intra and intermolecular levels may be accelerated and intensified by adding polysaccharides. V. B. Toltoguzov et al., Die Starke, 26:130 (1974) have shown that the coil-helix transition for gelatin is markedly accelerated by the addition of a little dextran. At the same time, gelatin gelation proceeds faster. The gelation rate of gelatin has also been increased by the addition of some other polymers such as methylcellulose, starch hydrolysates and polyethyleneglycol (see W. M. Marrs, Prog. Fd Nutr. Sc., 6:25 (1982)). The elastic modulus of filled gelatin gels increased with filler concentration in the single phase region but decreased in the two-phase region because of the increasing imperfection of the gel network.
U.S. Pat. No. 4,517,216 to Shim discloses blends of gellan gum and gelatin which exhibit a synergistic increase in gel strength. In the blends of Shim, the weight:weight ratio of gellan gum to gelatin ranges from 5:1 to 1:5.
U.S. Pat. No. 4,876,105 to Wolf et al. disclose gellan gum/gelatin blends which provide gels with improved setting and melting properties and improved room temperature stability relative to gels prepared using gelatin alone. Wolf et al. disclose a ratio of gellan to gelatin from 1:6 to 1:133, with a ratio of 1:20 to 1:50 being preferred. The gel ingredients also contained a combination of mono- and divalent ions. It is noted that Wolf et al. do not use gellan as an extender for gelatin but as a co-gelling agent. That is, the gellan is added to the existing level of gelatin used. Consequently, the relatively high level addition of gellan will reduce final or equilibrium gel strength if the total amount of gelling agent (i.e. gelatin and gellan) is fixed.
It would still be desirable to comprise a setting system for gelatin solution for use in making gelatin desserts that would not only mimic the texture of gelatin gel and provide increased gel strength and decreased gelation time, but also would allow for economic reasons a reduction in the required amount of gelatin.
The present invention is related to gelatin desserts, and more specifically to the use of anionic hydrocolloid gums as gelatin extenders therein. More particularly, the present invention is directed to a setting system for gelatin desserts comprising gelatin and an anionic hydrocolloid gum wherein the weight ratio of gelatin to anionic hydrocolloid gum is from about 250-375:1. It has surprisingly been found that by using very small amounts of a hydrocolloid gum as gelatin extenders, the resulting gelatin product has an increased gel strength of up to 20%, thereby simultaneously allowing for a lower usage of gelatin on the order of about 10%. Gelation time for the setting system of the present invention is also improved over that of the conventionally used setting system.
The present invention is directed to a setting system for a gelatin solution comprising gelatin and an anionic hydrocolloid gum wherein the weight ratio of gelatin to anionic hydrocolloid gum is from about 250-375:1.
It has surprisingly been found that the use of extremely low concentrations of anionic hydrocolloid gums as gelatin extenders provide a positive effect on gel strength of gelatin. Conventional knowledge indicates a negative effect to gel strength and clarity at normal concentrations. More specifically, it has been found that the use of anionic hydrocolloid gums as gelatin extenders has several advantages over the use of conventionally known gelatin extenders such as maltodextrin. To begin with, a lower use level of the anionic hydrocolloid gums in accordance with the present invention are required as compared to the conventional amounts of gelatin extenders known to those skilled in the art. Further, the anionic hydrocolloid gum gelatin extenders used in accordance with the present invention were found to be less sensitive to gelation/cooling rates, and therefore more suitable in the making of conventional gelatin dessert products. That is, not only does the setting system of the present invention allow for a significant decrease in the amount of gelatin required, i.e. a decrease of 10% or more required gelatin is possible, the resulting gelatin product possesses an increased gel strength of up to 20%. Additionally, gelation time of the setting system of the present invention is improved over that of the conventionally used setting system which uses gelatin extenders.
With the use of the setting system as set forth by the present invention, the required amount of gelatin in the gelatin dessert product can easily be reduced any where from 3-5 to 7-9% depending upon the particular anionic hydrocolloid gum being used. It has been found that this percentage reduction can be increased even further by increasing the pH of the gelatin solution. Also, higher percentage reductions reaching 10% or more can be obtained by using a longer, i.e. slower, gelation rate.
For purposes of the present invention, the gelatin solutions comprise from about 0.8 to about 2.0% gelatin, preferably from about 1.2 to about 1.7% gelatin, and most preferably about 1.5% gelatin. The gelatin solutions of the present invention are also characterized by having a pH of between about 3.8 to about 5.0.
The anionic hydrocolloid gums which are to be used in accordance with the present invention in combination with the gelatin are those hydrocolloid gums falling into the polysaccharide or xe2x80x9cgumxe2x80x9d category. Examples of anionic hydrocolloid gums which may be used in accordance with the present invention include, but are not limited to, xanthan gum, gellan gum, carageenan gum, ghatti gum, tragacanth gum, pectin, alginate, agar and mixtures thereof.
Of the multitude of hydrocolloid gums to choose from, it has further been found that the use of anionic hydrocolloids in the setting systems of the present invention provide superior results. Although neutral gums, such as guar gum, can provide positive results as indicated above, it has been found that the anionic hydrocolloid gums are preferred because of the surprisingly lower level of incorporation, with gellan and xanthan gums being most preferred from this category. As suggested by the two identified preferred gums, one will note that the use of a gelling polymer (such as gellan) as the anionic hydrocolloid is not mandatory. That is, a non-gelling gum such as xanthan gum has been found to work very well in the setting system of the present invention.
For a better understanding of the present invention, reference is made to the following examples, which are intended to be illustrative and not limiting.


The invention relates to an immunoassay apparatus, comprising a dry, porous substrate having at least two sections (1, 2), communicating with one another in the moist state by capillary action, wherein the first section (1) has a marked detection reagent for the substance to be detected and the second section (2) has an immobilized binder reagent for the substance to be detected, and wherein the reaction product comprising the substance to be detected and the marked detection reagent migrates by capillary action from the first section into the second section in the moist state, and is characterized in that the marked detection reagent is a dye-carrying reagent for nicotine or cotinine.

The invention relates to a immunoassay apparatus for detecting nicotine or cotinine.
Nicotine is a primary alkaloid of tobacco; the nicotine content in commercial tobaccos can amount to between 0.3 and 3%, and in heavy grades, up to 7%. However, nicotine is broken down relatively quickly in the body; the primary metabolite of nicotine is cotinine, which is the 2-pyrrolidinone corresponding to nicotine. While nicotine has a biological half-life in human blood of approximately one-half hour, cotinine, which as a secondary alkaloid also occurs in tobacco, has a biological half-life of about 30 to 40 hours and occurs in the blood, serum or urine of smokers in substantially higher concentrations than nicotine. Detecting cotinine is therefore considered to be a reliable indicator of a person""s smoking or nonsmoking.
Since in certain work environments, such as in the chemical or oil industry, smoking can present a considerable risk because of the attendant risk of fire or explosion, on the one hand, and on the other alkaloids not contained in tobacco but other accompanying products produced during smoking are also considered to have a considerable risk to health, there has long been a need, not only in the processing industry but also on the part of insurance companies, for instance, for a quickly performed and reliable test for checking whether persons who say they are nonsmokers are in fact nonsmokers. However, until now, no rests for nicotine or cotinine that could be performed quickly and simply were available.
It is indeed already known that cotinine, as a primary metabolite of nicotine, is suitable for detecting smoking with the aid of immunoassays; for instance, van Vunakis, H. et al., in Am. J. Obstet. Gynecol. 120, 64 ff. (1974) have described a radio immunoassay for detecting nicotine and cotinine in the amniotic fluid of pregnant women smokers, and Bjercke, R. J. et al., in Journal of Immunological Methods, 90 (1986) 203 pp., have described an ELISA test for detecting antibodies to nicotine and cotinine. Although radio immunoassays and ELISA tests are relatively reliable methods for detecting nicotine or cotinine, still they can be performed only by professionals and are time-consuming, and thus are completely unsuitable as a reliable, conveniently performed fast test.
Surprisingly, it has now been discovered that such a fast test for nicotine or cotinine can be performed on the basis of an immunoassay, if an immunoassay apparatus in accordance with the main claim is used.
Immunoassays are highly sensitive determination methods, which are based on the specificity of immunological reactions, primarily antigen and antibody reactions. For qualitative or quantitative analysis, it is necessary to mark one of the reaction partners with a readily detectable and measurable indicator substance, such as radioactive isotopes, enzymes, dyes and fluorescent dyes. Usually this involves solid-phase tests, in which the marker bound to the solid phase is measured. Microtiter slides, as in ELISA tests, or solid substrates, for which nitrocellulose has proven itself in particular, are used as the solid phase. Solid-phase tests are designed such that a solid substrate is subdivided into various sections, and the liquid, aqueous medium to be tested is applied to the initial part of the substrate; the liquid can then move by capillary action of the substrate all the way through the substrate, and excess liquid is rinsed off or caught in a so-called liquid trap. The solid substrate is provided with either marked antigen or marked antibody inside a first section, so that when the substance to be detected, which is in solution, is added an antigen-antibody reaction ensues; the marker can be coupled to either the antigen or the antibody. The antigen-antibody reaction product then migrates with the liquid into a second section, which has either an immobilized antigen or an immobilized antibody, with which the product of the substance to be detected and the antigen or antibody is converted in a competitive reaction, or if a sandwich test is involved, is converted twice. As a result, a concentration of the marker in this region ensues, and the concentration can then be assessed qualitatively or quantitatively with a suitable measuring instrument, or if dyes that are adsorbent in the visible range are used as markers, can be perceived with the naked eye. Excess and therefore unused marked antigens or antibodies may possibly migrate into a third section, in which they are then bound for instance by antigens or antibodies with a different specificity and thus can be used as controls.
Solid-phase immunoassays of the competitive or sandwich type are familiar to one skilled in the art and therefore need not be described in further detail. For instance, such tests are described in detail in European Patent Disclosures EP-A1 0 284 232 or EP B1 0 291 194.
The apparatus according to the invention comprises a so-called xe2x80x9cdipstickxe2x80x9d, that is, a porous substrate in which the coupling product of the detection reagent and the substance to be detected can migrate by capillary action, and which to improve its mechanical properties is in turn secured to a substrate, such as a plastic slide. The substrate, that is, the solid-phase material, may comprise various porous materials that thus dictate capillary action, such as cellulose, polyamide, pretreated papers, and so forth, but preferably nitrocellulose is used. The substrate has a first section, which carries a marked detection reagent for the substance to be detected, which depending on the arrangement of the test is either a marked antibody or a marked antigen. The marking is done with particles, which are preferably either small, dyed plastic particles, especially of polystyrene, or metal sols, and especially gold sol, because even when greatly diluted gold sol has a bluish-red coloring that can be readily seen by the naked eye. When his first section is moistened with the substance to be detected, which is in solution, a coupling product of marked detection reagent and the compound to be analyzed is created; in the moist state of the substrate, this product can migrate out of the first section into the second section. An immobilized binder reagent, which in turn depending on the layout of the test may be a non-marked antibody or a non-marked antigen, is located in the second section.
If desired, the apparatus can also include a third section, namely a control zone, from which it can be told whether the process has proceeded correctly. The marked antigens or antibodies not used by the coupling with the binder reagent can then be converted in this control zone, for instance, with an immobilized antigen or antibody of different specificity, or the control zone may contain a substance which for instance reacts with the aqueous substrate by changing color, so that in one way or another an indication is made that the aqueous solution that was applied in the first section has in fact reached the location of the control strip, so that the reaction can then be considered to have ended.
Preferably, according to the invention the reaction is performed such that an antibody capable of migration is used in the first section and an immobilized antigen is used in the second section; by way of example, antigens and antibodies of the kind described at length in the above-cited work by Bjercke, R. J. et al. can be used. The antibodies are conjugated for use with a marker, especially with gold sol.
If a third section with a control option is desired, then in this third section by way of example a commercially available xe2x80x9canti-mousexe2x80x9d immunoglobulin from rabbits can be used, which is immobilized there if antibodies from the mouse are used in the first section.
To protect the apparatus or dipstrip against environmental factors such as moisture, dust, and so forth, the dipstrip is preferably located in a hood, which encloses the entire strip except for part of the first section. The hood preferably comprises water-repellent, dustproof plastic. In a further preferred embodiment, the hood is in at least two parts, so that the part of the test strip that protrudes out of the hood can also be covered by a removable part of the hood. The part of the test strip that has the first section and that protrudes from the hood or part of the hood is selected such that this part can be saturated with the body fluid to be tested, such as urine in particular, and the saturating fluid then migrates uniformly through the entire strip.

Immunoassay apparatus for detecting nicotine or continine


Disclosed is a method of producing a non-woven web of fibrous or particulate material comprising: formation of a foam slurry; deposition of that slurry onto a foraminous element having a three-dimensional mold; and formation of a web having a three-dimensional shape that is not substantially planar by removal of foam from the slurry through the foraminous element and drying the web. An apparatus therefor is also disclosed. The method may be used in production a variety of products, including automotive pleated fluid and air filters, pleated heating and/or air conditioning (HVAC) filters, shaped breathing mask filters and bacterial filters, laminated cleaning products with super-absorbent middle layers, such as a mop wipe shape to fit a cleaning mop head, and other products.

The invention relates to the utilization of foam processes for making non-woven webs using particular raw materials, and for making particular end products. Foam processes are basically as described in U.S. Pat. Nos. 3,716,449, 3,871,952, and 3,938,782 (the disclosures of which are incorporated by reference herein), and in pending U.S. application Ser. No. 08/923,900 filed Sep. 4, 1997 and U.S. application Ser. No. 09/098,458 filed Jun. 17, 1998, the disclosures of all of which are also incorporated by reference herein.
Foam processes are normally used for making planar forms having a uniform thickness, i.e., two-dimensional shaped forms, during web formation. In accordance with the present invention, a three-dimensional shaped form is created by using a three-dimensional mold during web formation from one or more foam layers. Using a three-dimensional mold, e.g., a wire mesh mold, a pleated or grooved filter product, for example, can be formed directly from a foam having fibers or particles which, when applied to the mold, form the product. A wide variety of products can be produced using the foam processes and three-dimensional molds disclosed herein. For example, three-dimensional molds and foam processes are useful to produce a wide variety of filter products, including automotive pleated fluid and air filters, pleated heating and/or air conditioning (HVAC) filters, shaped breathing mask filters and bacterial filters, laminated cleaning products with super absorbent middle layers, such as a mop wipe shaped to fit a cleaning mop head, and other products.
The present invention can be used to eliminate subsequent mechanical pleating steps or milling steps previously used to create pleats and grooves in a two-dimensional planar web sheet created using two-dimensional planar molds and foam processes. In particular, the present invention obviates the prior art process of mechanically cutting grooves and other shapes to form a three-dimensional planar-shaped product after it has been formed using foam processes. The present invention avoids the prior need for process equipment that shapes the substantially planar intermediate web products formed from two-dimensional molds into a three-dimensional final product. The present invention is particularly suited for use in production of pleated and grooved filter papers, especially those having applications in automobiles.
The foam process of web making is used for making products, e,g., webs using particles or fibers, e.g., short cut fibers, synthetic fiber materials, fibers from mechanical cellulose wood pulp or chemical cellulose wood pulp, or other web materials. Utilizing the foam process, it is possible to produce three-dimensional, non-planar webs from a variety of fibers, particles or combinations of fibers and particles.
One application of the invention relates to the production of pleated or grooved filter paper, particularly for automotive use. Filter paper started to be used in automobiles some 40-50 years ago, and today is standard equipment in every car with a combustion engine. The applications for filter papers today can be divided into the following grade categories: auto air, oil, heavy-duty air (HDA), fuel media, and cabin air. The auto air media/filter paper is designed to trap the particles entering the engine with the air. The HDA filter paper has the same function, but is designed for a more demanding environment with large amounts of dust in the air (e.g., earth moving machines, etc.). An oil media/filter paper is designed to take the particles out of the oil stream entering the engine. The fuel media/filter paper is designed to filter particles from gasoline or diesel fuel before it enters the engine. The cabin air media/filter paper is designed to trap the outside particles before they come into the cabin or compartment where the passengers are sitting. There are also other applications for such filter papers.
Automotive filter papers have previously been produced according to wet-laid processes, which date back to the early part of the 1900s. In the wet-laid process, fibers are broken up under agitation in a pulper. The fibers are then pumped in a liquid slurry through deflakers and refiners to the paper machine. The deflakers and refiners disperse the fibers, and give them a better surface for generating bonding strength. The main components on the paper machine are the wet end and the dry end. Between the pulper and the wet end, various types of wet and dry strength enhancing chemicals are also added. The wet end comprises a headbox and dewatering elements. Typically the headbox has a flat fourdrinier, incline wire, or cylinder type foraminous element. The dewatering elements are designed to suck out water from the slurry to dewater it from roughly a 0.05% fiber consistency to a 25% fiber consistency on a moving wire (foraminous element). After the wet end, the media enters the dry end. The objective there is to dry the filter media from 25% to about a 98-99% fiber consistency.
The filter media is now either impregnated xe2x80x9con-linexe2x80x9d on the same paper machine, or rolled up and impregnated xe2x80x9coff-linexe2x80x9d on a separate impregnation machine. The objective of the impregnation process is to fully saturate the media with a resin or latex (thermosetting or thermoplastic), and thereby give the media its final mechanical strength as well as making it convertible into a filter. The impregnation process basically includes an impregnation unit followed by dryers. The impregnation unit can be a size-press, roll coater, curtain coater, or the like, and the dryers can be any conventional contact/non-contact types. When the media reaches about a 10-15% moisture content, the oil and HDA media types are grooved, giving them a continuous S-shape in the machine direction. Grooving the media type increases the overall filtration surface and helps keep the subsequently formed pleats separated when pleating the media and building the filter element.
After impregnation the media is slit into various slit width sheets before packaging and sending to a customer. At the customer site, the media is mechanically pleated on conventional pleating machines giving the media its final physical configuration before building a filter element containing the filter paper. How the ends of the media are sealed, the media further polymerized, and which characteristics are particularly important, depend on the customer and end application, and these details are conventional.
The process of the U.S. patent application Ser. No. 09/098,458 discusses the manufacture of a planar sheet of filter paper by means of the foam process, and then subsequently the sheet is grooved and pleated to make the actual filter material. The present invention forms the filter paper on a mold, which is grooved, pleated, or grooved and pleated itself. There is no need to perform subsequent mechanical steps of pleating, grooving or otherwise imparting three-dimensional shapes to the web product extracted from the molding process.
Forming products from a fiber or particle foam is advantageous over wet-laid processes. For example, filter paper has been manufactured using a water-laid process. In that process, fibers in a liquid suspension are introduced onto a grooved mold. The depth of the liquid slurry is relatively shallow. Soon after the introduction of the fiber suspension, the slurry surface sinks below the top portion of the lower mold, losing the hermetic seal permitting suction from beneath the mold to avoid removing water from the fibrous slurry. When the seal is lost, the suction acts primarily on the portion of the mold having no contact with the suspended fibers. Consequently, the fiber formation at the bottom of the mold is slow and not optimal. Additionally, there is a possibility that the top portions of the mold would collect a smaller number of fibers than the bottom portions, because the fibers in the liquid slurry tend to settle and concentrate at the bottom of the mold. In contrast, the foam processes disclosed herein involve one or more layers of foam that each form a relatively-deep layer of foam in a three-dimensional mold. Because of the depth of the foam, it is unlikely that the upper surface of the foam will sink below the peaks in the lower mold surfaces. In addition, an upper mold may be used to shape the upper surface of the foam so as to conform to the shape of the underlying lower mold, and thereby avoiding having the tops of a lower mold extend entirely through a foam layer.
Another problem exists with wet-laid processes if the filter paper is manufactured using several different layers, materials, substrates, or combinations thereof. While being introduced on a previous layer (or layers) in dilute suspensions, subsequent layers tend to orient the fibers from a previous layer in the bottoms of the grooves. This causes the final product to have an uneven thickness, which in turn causes a decrease in filtering ability. Foam processes are better suited to layering different foams, where each foam layer has a different consistency of fibers or particles. The foam layers tend to retain randomly oriented fibers, which is often desirable. Alternatively, the fibers in the foam can be oriented parallel to the flow path in the foam injection nozzle. By injecting the foam into the mold vertically from the nozzle, it is possible to preserve the generally-vertical fiber orientation in the foam as deposited in the mold. The vertical fiber orientation in a final web product can be beneficial to form relatively-thick webs and relatively-porous webs.
In these prior art wet-laid and foam processes, there are potential problems caused on the one hand by forming in wet-leid processes, and on the other hand by pleating and grooving the filter paper separately in foam processes. First, increasing process steps cause higher manufacturing costs. Combining several process steps into one, the overall process becomes shorter and, consequently, less expensive. Second, mechanical changes to the formed filter paper may decrease the durability of the final product. Bending a formed planar filter paper to form pleats and grooves creates stress to the bent portions, and that stress may reduce the quality of the final product through rapid deterioration.
The present invention is a foam web manufacture process that uses molds to shape and dry the foam into three-dimensional products, such as three-dimensional filters. These products may be single layered formed from a single application of foam, or a laminate formed of several layers of different foams. In a simplistic description, foam comprises a slurry of air, water, surfactant, and fibers or particles. The type of fibers, particles, or combination of fiber and particles will depend on the product to be produced. For example, the fibers in the foam may be short cut fibers, having an average length of 0.05 mm (millimeters) or less. The fibers or particles conform to a three-dimensional mold as the foam is deposited in the mold. As the foam is deposited on the mold, the water and air (which is in the foam as air bubbles having a wide variety of different diameters) are drained through the mold, extracted and reused. The fibers or particles from the foam are deposited on the mold to form the web product. The fibers or particles are dried on the mold and the completed three-dimensional product is removed from the mold. The web product may be formed from a combination of fibers and particles, or entirely of particles that are deposited from the foam.
The introduction of the foam onto three-dimensional molds is performed in a careful manner, to prevent the problems experienced by the water-laid process. These problems can be prevented, in part, because the consistency of the foam is 1% to 10% (and can be 20% for foams with super-absorbent) fibers) and is higher than the typically 0.01% to 0.5% consistency of the slurry in the conventional water-laid process. As a consequence of the higher consistency, the use of the foam process permits formation of thicker products, such as thicker filter papers or thicker layers of paper in a single stage. If larger consistencies are used in liquid-laid processes, the fibers tend to aggregate and form flocs before web formation occurs. Floc formation decreases the quality of the final product because of the associated fluctuations in thickness and other properties of the filter paper, which in turn cause variations in filtering ability within the same product.
Additionally, the foam requires much less liquid than the liquid-laid process, reducing the water consumption significantly. A reduction in the water consumption decreases the size of equipment needed for transporting liquid downstream of the mold. After the foam is drained from the mold, the foam can be substantially reused. Generally, only fibers and particles, and possibly a surfactant, are added to the reused foam before it is deposited in another mold.
In one embodiment, after foam is introduced onto a bottom mold, a complementary top mold is placed on top. Preferably, the top mold is substantially the inverse of the bottom mold, such that the ridges of the top mold substantially fit in the grooves of the bottom mold. Similarly, the grooves of the top mold fit substantially around the ridges of the bottom mold. The top mold can be used to ensure that the top portions of the bottom mold are covered with foam and thus sealed. Ensuring that foam remains over the top portions of the bottom mold prevents the loss of the seal and the associated problems with suction described above. Additionally, the top mold can be used to apply pressure on the foam, increasing the pressure on the top surface of the foam and assisting the removal of foam from the filter layer.
After the filter layer is substantially formed, the top mold is removed and the filter paper can be either taken to the drying phase or taken to a phase wherein another layer of foam is deposited. Although substantially the same foam material could be deposited using a new headbox in the manner described above, a different foam material can be deposited. Additional layers, for example three or more layers, could be deposited on the formed layers. The number of potential layers is determined partially by the desired properties of the final product.
In another embodiment, the production machine is a batch-type machine, wherein each batch contains at least one bottom mold. For each batch, there is a trough, which contains, for example, five rows and five columns of bottom molds. After the desired amount of foam is deposited using a headbox on the bottom molds in the trough, an insert containing a matching number of top molds is placed on top of the foam. That trough and insert move down the production line, and an empty trough begins the batch process anew.
In another embodiment, the production machine is a continuous-type machine, wherein the bottom and top molds are incorporated into a moving wire, which is also called a foraminous element, and roller system. The bottom mold moving wire contains repeated bottom molds, such that as the bottom mold moves, e.g., laterally or rotationally, new bottom molds are exposed to the headbox. Similar to the batch process, the headbox deposits foam on the bottom molds mounted on the bottom mold moving wire. Thereafter, a complementary top mold attached to a top mold belt is placed on top of a corresponding bottom mold containing foam.
In a further embodiment, after a layer has been formed, the mold is opened. A similar procedure to the ones described above may be done such that another layer is formed. Alternatively, the recently formed layer, or layers, may be run through a blow-drying oven or similar equipment to aid in the drying process.
In yet another embodiment, multiple discrete layers of foam are deposited on the bottom mold before the top mold is placed on top of the foam. After deposition of each layer of foam, some foam may be drawn through the bottom mold without placing the top mold on top. Removing some foam may both ensure the foam maintains a reasonable height in the mold and reduce the overall process time. Alternatively, foam removal may occur after all layers have been deposited. In this embodiment, the top mold is useful when the height of the foam is less than the height of the bottom mold. In such circumstance, without a top mold the seal might be lost if a gap in the foam forms as the top portions of the lower mold extend up through the foam. The top mold prevents gaps in the foam by pressing the foam down into the lower mold, evenly distributing the foam in the lower mold and ensuring that the foam layer maintains a uniform thickness. A top mold is also advantageous to provide better drainage of the foam by adding pressure that forces the foam through the lower and upper molds, which are typically a wire mesh.
In a further embodiment, the foam layers are deposited in a quick sequence in a mold without a large time delay between layer depositions. For example, this can be done using multiple headboxes, each headbox depositing different foam with independent properties. Alternatively, this can be done using a single headbox with the capability of depositing different foams with independent properties. In the second example, the independent foam layers are still deposited sequentially, but the same headbox is used for all layers.
There are multiple advantages to using the present invention, and the following is a non-exhaustive list of benefits. First, the process is relatively fast, and delicate or reactive substances, like active carbon, odor removing substances, salts, super-absorbent products, etc., may be used without substantial degradation or substantial loss of properties. Second, the process can be operated in either batch- or continuous-type machines, providing flexibility in equipment or plant design. Third, the process uses foam, which provides the ability to deposit multiple layers without mixing different layers. Fourth, the process obviates the need to groove or pleat the filter paper after formation. Since the paper is not subjected to bending after formation, the risk of breaking the filter layers is minimal. Fifth, the process is useful with any short fiber, e.g., fibers of 50 mm or less, such as synthetic fibers, mechanically-treated wood pulp or chemically-treated wood pulp.
The present process has advantages over thermo-forming techniques used for shape filters. Thermo-forming is a post mold process to shape a filter element. Thermo-forming processes are unnecessary with the present invention that shapes a filter element using the same mold in which the fibrous foam is solidified into a three-dimensional fiber element. In addition, the foam used with the present process produces a more uniform filter product than does the wet-laid or dry-laid fiber processes typically associated with processes involving thermo-forming. However, thermo-forming can be used on the web product extracted from the mold and produced with the present invention.
While the present invention has been described in connection with the production of filter papers, the invention may be used to manufacture other three-dimensional products using foam. The present invention offers other advantages, which will become apparent to a person of ordinary skill in the art when considered in connection with the accompanying drawings.

Method for foam casting using three-dimensional molds


The proposed device is based on a carbon nanotube oscillator consisting of a finite length outer stationary nanotube and a finite length inner oscillating nanotube. Its main function is to measure changes in the characteristics of the motion of the carbon nanotube oscillating near a sample surface, and profile the roughness of this surface. The device operates in a non-contact mode, thus it can be virtually non-wear and non-fatigued system. It is an alternative to the existing atomic force microscope (AFM) tips used to scan surfaces to determine their roughness.

Carbon nanotubes (CNT) are quasi-one dimensional structures which are obtained by rolling up graphene sheets into cylinders. There are single wall carbon nanotubes, consisting of one sheet, and multi-wall carbon nanotubes, consisting of two or more concentric cylindrical sheets. The particular way of graphene rolling is characterized by a chirality index (n,m), which determines if the rolled graphene is metallic or semiconducting. In addition, CNT can have diameters in the range of 0.5-1.5 nm and lengths up to several micrometers.
CNTs have received much attention due to their potential applications as integrated nanoscale elements in various devices. Low-friction, low-wear multi-wall CNT bearings have been demonstrated. Prior work in the art has shown that if an inner tube from a double wall nanotube is extruded with respect to the stationary outer tube, the inner tube can easily slide or rotate due to the intertube van der Waals (vdW) interaction. Such devices have been reported to have very low friction—at least two orders of magnitude smaller than the vdW forces.
Scanning probe microscopes, such as the Atomic Force Microscope (AFM), are examples of scanning probe imaging and sensing devices. These devices are useful for surface profiling. A non-contact AFM measures the microscopic surface profile of a near-planar target using a nanometer-scale probe that is mounted at the end of a tiny cantilever. Deflection of the cantilever, as the probe is raster-scanned across the surface of the target, is optically measured. The measurements are used to establish a profile of the target surface. However, the resolution of the AFM is limited by the probe tip radius, which is on the order of a few tens of nanometers.
Accordingly, what is needed in the art is a non-contact surface profiling device that provides an improved resolution over the AFM systems currently known in the art.

Carbon nanotube oscillator surface profiling device and method of use


RF-optical metamaterials with (±∈, ±μ) figures-of-merit of interest are constructed from coupled magnetic and dielectric multi-resonant multi-disks (finite-size cylinders) or multi-sphere lattices arranged in a periodic or a random fashion to offer tailored magnetic and electric dipole moments. The present metamaterials include embedded particles arrays that provide coupled magnetic and electronic modes equivalent to L (inductor) and C (capacitor) circuit models. Novel arrangements of these dipole modes (L and C) tailor the transfer function to the physics of interest.

Metamaterials are receiving increasing attention in the scientific community in recent years due to their exciting physical properties and novel potential applications. Metamaterials can be engineered to exhibit negative permittivity and negative permeability over a given frequency range, and thereby provide negative refraction (NR). This can provide a number of benefits in the RF and optical fields.
Most of the previous metamaterial designs have utilized metallic elements, which are very lossy, have very narrow bandwidth, are anisotropic, are not conformal, and are almost impossible to realize for RF and optical devices. The prior techniques also require periodicity as the key to the performance, and this can increase the difficulty of fabrication. Furthermore, one generally needs to establish a large size structure in order to achieve the performance of interest.

Dielectric and magnetic particles based metamaterials