| PATENT ASSIGNEE'S COUNTRY | USA |
| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | 09.01.2001 |
| PATENT TITLE |
Grafted poly(ethylene oxide) compositions |
| PATENT ABSTRACT |
Modifyied poly(ethylene oxide) compositions are disclosed. The poly(ethylene oxide) compositions have improved melt processability and properties and can be used to thermally process articles which have improved properties over articles similarly processed from unmodified poly(ethylene oxide) compositions. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | December 31, 1997 |
| PATENT CLAIMS |
What is claimed is: 1. A poly(ethylene oxide) composition having a polydispersity index less than 10. 2. The poly(ethylene oxide) composition of claim 1, wherein the poly(ethylene oxide) has a melting temperature less than 68.degree. C. 3. The poly(ethylene oxide) composition of claim 2, wherein the poly(ethylene oxide) has a weight-average molecular weight of greater than about 60,000 g/mol. 4. The poly(ethylene oxide) composition of claim 3, wherein the poly(ethylene oxide) has a weight-average molecular weight of greater than about 90,000 g/mol. 5. The poly(ethylene oxide) composition of claim 1, wherein the poly(ethylene oxide) has a polydispersity index less than about 6. 6. A modified poly(ethylene oxide) comprising a poly(ethylene oxide) backbone with polar species grafted onto the poly(ethylene oxide) backbone. 7. The modified poly(ethylene oxide) of claim 6, wherein the polar species is selected from the group consisting of poly(ethylene glycol) methacrylates and 2-hydroxyethyl methacrylate. 8. The modified poly(ethylene oxide) of claim 7, wherein the polar species is a poly(ethylene glycol) methacrylate. 9. The modified poly(ethylene oxide) copolymer of claim 8, wherein the poly(ethylene glycol) methacrylate is a poly(ethylene glycol) ethyl ether methacrylate. 10. The modified poly(ethylene oxide) of claim 9, wherein the poly(ethylene glycol) ethyl ether methacrylate has a number average molecular weight of not greater than about 5,000 grams per mol. 11. The modified poly(ethylene oxide) of claim 7, wherein the polar species is 2-hydroxyethyl methacrylate. 12. The modified poly(ethylene oxide) of claim 6, wherein the modified poly(ethylene oxide) has a polydispersity index less than 10. 13. The moldified poly(ethylene oxide) of claim 6, wherein the modified poly(ethylene oxide) has a melting temperature less than 68.degree. C. 14. The modified poly(ethylene oxide) of claim 6, wherein the modified poly(ethylene oxide) comprises from about 0.1 to about 20 weight percent polar species relative to the weight of the poly(ethylene oxide) backbone. 15. The modified poly(ethylene oxide) of claim 14, wherein the modified poly(ethylene oxide) comprises from about 0.5 to about 10 weight percent polar species relative to the weight of the poly(ethylene oxide) backbone. 16. A grafted poly(ethylene oxide) having a polydispersity index less than 10. 17. The grafted poly(ethylene oxide) of claim 16, wherein the grafted poly(ethylene oxide) has a melting temperature less than 68.degree. C. 18. The grafted poly(ethylene oxide) of claim 17, wherein the grafted poly(ethylene oxide) has a weight-average molecular weight of greater than about 60,000 g/mol. 19. The grafted poly(ethylene oxide) of claim 18, wherein the grafted poly(ethylene oxide) has an apparent viscosity of less than 200 Pascal*seconds at shear rates of not less than 100 second.sup.-1 and not greater than 1,000 second.sup.-1. 20. The grafted poly(ethylene oxide) of claim 16, wherein the grafted poly(ethylene oxide) has a polydispersity index less than about 6. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION The present invention is directed to poly(ethylene oxide) compositions. More particularly, the present invention is directed to improved poly(ethylene oxide) compositions, methods for improving the melt processability of poly(ethylene oxide), and to improved poly(ethylene oxide) films and fibers. BACKGROUND OF THE INVENTION Disposable personal care products such as pantiliners, diapers, tampons etc. are a great convenience. Such products provide the benefit of one time, sanitary use and are convenient because they are quick and easy to use. However, disposal of such products is a concern due to limited landfill space. Incineration of such products is not desirable because of increasing concerns about air quality and the costs and difficulty associated with separating such products from other disposed, non-incineratable articles. Consequently, there is a need for disposable products which may be quickly and conveniently disposed of without dumping or incineration. It has been proposed to dispose of such products in municipal and private sewage systems. Ideally, such products would be flushable and degradable in conventional sewage systems. Products suited for disposal in sewage systems and that can be flushed down conventional toilets are termed "flushable". Disposal by flushing provides the additional benefit of providing a simple, convenient and sanitary means of disposal. Personal care products must have sufficient strength under the environmental conditions in which they will be used and be able to withstand the elevated temperature and humidity conditions encountered during use and storage yet still lose integrity upon contact with water in the toilet. Therefore, a water-disintegratable material having mechanical integrity when dry is desirable. Due to its unique interaction with water and body fluids, poly(ethylene oxide) (hereinafter PEO) is currently being considered as a component material for water-disintegratable films, fibers, and flushable products. PEO, --(CH.sub.2 CH.sub.2 O).sub.n --, is a commercially available water-soluble polymer that can be produced from the ring opening polymerization of the ethylene oxide, ##STR1## Because of its water-soluble properties, PEO is desirable for flushable applications. However, there is a dilemma in melt processing PEO. Low molecular weight PEO resins have desirable melt viscosities and melt pressure properties for melt processing but have limited solid state properties when melt processed into structural articles such as films. An example of a low molecular weight PEO resin is POLYOX.RTM. WSR N-80 PEO which is commercially available form Union Carbide. POLYOX.RTM. WSR N-80 PEO has an approximate molecular weight of 200,000 g/mol as determined by rheological measurements. As used herein, low molecular weight PEO compositions are defined as PEO compositions with an approximate molecular weight of less than and including about 200,000 g/mol. In personal care product industry, flushable thin-gauged films and melt-spun fibers are desired for commercial viability and ease of disposal. The low melt strength and low melt elasticity of low molecular weight PEO limit the ability of the low molecular weight PEO to be drawn into films having a thickness of less than about 1.25 mil. Although low molecular weight PEO can be thermally processed into films, thin-gauged films of less than about 1 mil in thickness cannot be obtained due to the lack of melt strength and melt elasticity of the low molecular weight PEO. Efforts have been attempted to improve the processability of PEO by blending the PEO with a second polymer, a copolymer of ethylene and acrylic acid, in order to increase the melt strength. The PEO/ethylene acrylic acid copolymer blend is able to be processed into films of about 1.2 mils in thickness. However, the blend and resulting film are not water-soluble, especially at high levels of ethylene acrylic acid copolymer, i.e. about 30 weight percent. More importantly, thin films made from low molecular weight PEO are too weak and brittle to be useful for personal care applications. Low molecular weight PEO films have low tensile strength, low ductility, and are too brittle for commercial use. Further, films produced from low molecular weight PEOs become brittle during storage at ambient conditions. Such films shatter and are not suited for commercial applications. High molecular weight PEO resins are expected to produce films with improved mechanical properties compared to films produced from low molecular weight PEO resins. An example of a high molecular weight PEO is POLYOX.RTM. WSR 12K PEO which is commercially available from Union Carbide. POLYOX.RTM. WSR 12K PEO has a reported approximate molecular weight of 1,000,000 g/mol as determined by rheological measurements. As used herein, high molecular weight PEOs are defined as PEOs with an approximate molecular weight of greater than and including about 300,000 g/mol. High molecular weight PEOs have poor processability due to their high melt viscosities and poor melt drawabilities. Melt pressure and melt temperature are significantly elevated during melt extrusion of high molecular weight PEOs. During extrusion of high molecular weight PEOs, severe melt fracture is observed. Only very thick sheets can be made from high molecular weight PEOs. High molecular weight PEOs cannot be thermally processed into films of less than about 3-4 mil in thickness. High molecular weight PEOs suffer from severe melt degradation during extrusion and melt processing. This results in breakdown of the PEO molecules and formation of bubbles in the extrudate. The inherent deficiencies of high molecular weight PEOs make it impossible to utilize high molecular weight PEOs in film applications. Even the addition of high levels of plasticizer to the high molecular weight PEOs do not improve the melt processabilities sufficiently to allow the production of thin films without melt fracture and film breakage occurring. In addition, the use of plasticizer in films causes latent problems due to migration of the plasticizer to the film surface. There is also a dilemma in utilizing PEO in the fiber-making processes. PEO resins of low molecular weights, for example 200,000 g/mol have desirable melt viscosity and melt pressure properties for extrusion processing but cannot be processed into fibers due to their low melt elasticities and low melt strengths. PEO resins of higher molecular weights, for example greater than 1,000,000 g/mol, have melt viscosities that are too high for fiber-spinning processes. These properties make conventional PEOs difficult to process into fibers using conventional fiber-making processes. PEO melt extruded from spinning plates and fiber spinning lines resists drawing and is easily broken. PEO resins do not form thin diameter fibers using conventional melt fiber-making processes. Conventional PEO resins can only be melt processed into strands with diameters in the range of several millimeters. Therefore, PEO compositions with appropriate melt viscosities for processing fibers and with greater melt elasticities and melt strengths are desired. In the personal care industry, flushable melt-spun fibers are desired for commercial viability and ease of disposal. PEO fibers have been produced by a solution casting process. However, it has not been possible to melt process PEO fibers using conventional fiber making techniques such as melt spinning. Melt processing techniques are more desirable than solution casting because melt processing techniques are more efficient and economical. Melt processing of fibers is needed for commercial viability. Prior art PEO compositions cannot be extruded into the melt with adequate melt strength and elasticity to allow attenuation of fibers. Presently, fibers cannot be produced from conventional PEO compositions by melting spinning. Thus, currently available PEO resins are not practical for melt processing, thin films, fibers or personal care applications. What is needed in the art, therefore, is PEO compositions that overcome the difficulties in melt processing. SUMMARY OF THE INVENTION The present invention is directed to methods for improving the processability of PEO. More particularly, the present invention relates to methods of modifying PEO to improve its melt processability by grafting polar vinyl monomers, such as poly(ethylene glycol) methacrylates or 2-hydroxyethyl methacrylate, onto the PEO. The grafting is accomplished by mixing PEO, monomer(s) and initiator and applying heat. In a preferred embodiment, the method of modification is a reactive-extrusion process. PEOs modified in accordance with this invention have improved melt processabilities and can be thermally processed into films, fibers and other articles which have improved properties over films, fibers and articles similarly processed from unmodified PEO compositions. To overcome the disadvantages of the prior art, this invention teaches a method of grafting polar functional groups onto PEO in the melt. Modification of PEO reduces the melt viscosity, melt pressure and melt temperature. Additionally, modification of high molecular weight PEO in accordance with the invention eliminates the severe melt fracture observed when extruding unmodified high molecular weight PEO. This invention provides methods of producing improved, thermally processable PEO resins by modifying PEO. The modified PEO resins can be solidified into pellets for later thermal processing into useful shapes such as thin films and fibers which are in turn useful as components in personal care products. As used herein, the term "graft copolymer" means a copolymer produced by the combination of two or more chains of constitutionally or configurationally different features, one of which serves as a backbone main chain, and at least one of which is bonded at some point(s) along the backbone and constitutes a side chain. As used herein, the term "grafting" means the forming of a polymer by the bonding of side chains or species at some point(s) along the backbone of a parent polymer. (See Sperling, L. H., Introduction to Physical Polymer Science 1986 pp. 44-47 which is incorporated by reference herein in its entirety.) Modification of PEO resins with starting molecular weights of between about 300,000 g/mol to about 8,000,000 g/mol allows the modified PEO resins to be drawn into films with thicknesses of less than 0.5 mil. Modification of PEO resins with starting molecular weights of between about 400,000 g/mol to about 8,000,000 g/mol is preferred for film making. Films drawn from the modified PEO compositions have better softness and greater clarity than films drawn from unmodified low molecular weight PEO. Thermal processing of films from high molecular weight PEO modified in accordance with this invention also results in films with improved mechanical properties over films similarly processed from unmodified low molecular weight PEO films. Modification of PEO resins with starting molecular weights of between about 50,000 g/mol to about 400,000 g/mol allows the modified PEO resins to be extruded into fibers using conventional melt spinning processes. Modification of PEO resins with starting molecular weights of between about 50,000 g/mol to about 200,000 g/mol is preferred for fiber making. The modification of PEO in accordance with this invention improves the melt properties of the PEO allowing the modified PEO to be melted and attenuated into fibers. Thus, the modified PEO can be processed into water-soluble fibers using both meltblown and spunbound processes which are useful for liners, cloth-like outer covers, etc. in flushable personal care products. These and other features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiments. BRIEF DESCRIPTION OF THE FIGURES FIG. 1 compares the melt rheology curve of an unmodified PEO resin of 600,000 g/mol approximate molecular weight, Example 1, and the melt rheology curves of PEO compositions modified from the 600,000 g/mol molecular weight PEO resin, Examples 2-5. FIG. 2 compares the melt rheology curve of unmodified PEO resin of 1,000,000 g/mol approximate molecular weight, Example 6, and the melt rheology curves of PEO compositions modified from the 1,000,000 g/mol molecular weight PEO resin, Examples 7-10. FIG. 3 displays the results of Fourier transform infrared spectra analysis of films from an unmodified PEO of 600,000 g/mol approximate molecular weight, Example 1; a PEO of an initial approximate molecular weight of 600,000 g/mol modified with 4.9 weight % HEMA and 0.28 weight % initiator, Example 3; and a PEO of an initial approximate molecular weight of 600,000 g/mol modified with 4.9 weight % PEG-MA and 0.32 weight % initiator, Example 5. FIG. 4 compares the melt rheology curve of an unmodified PEO resin of 600,000 g/mol approximate molecular weight, Example 1, and the melt rheology curves of PEO compositions modified from the PEO resin having an initial approximate molecular weight of 600,000 g/mol with low monomer and initiator levels, Examples 11-13. FIG. 5 compares the melt rheology curve of an unmodified PEO of 300,000 g/mol approximate molecular weight, Example 14, and the melt rheology curves of PEO compositions modified from the PEO resin having an initial approximate molecular weight of 300,000 g/mol, Examples 15 and 16. FIG. 6 compares the melt rheology curve of an unmodified PEO of 400,000 g/mol approximate molecular weight, Example 17, and the melt rheology curves of PEO compositions modified from the PEO having an initial approximate molecular weight of 400,000 g/mol, Examples 18 and 19. FIG. 7 is a graph comparing the melt viscosities of an unmodified 200,000 g/mol molecular weight PEO, Comparative Example A, versus the melt viscosities of the same PEO resin after modification, Example 32. FIG. 8 is a .sup.13 C-Nuclear Magnetic Resonance spectra of the modified PEO of Example 32. FIG. 9 is a .sup.1 H-Nuclear Magnetic Resonance spectra of the modified PEO of Example 32. DETAILED DESCRIPTION Improved films and fibers can be melt processed using conventional methods from commercially available PEO resins when modified in accordance with this invention. The PEO resins useful for modification for film-making purposes include, but are not limited to, PEO resins having initial reported approximate molecular weights ranging from about 300,000 g/mol to about 8,000,000 g/mol as determined by rheological measurements. Such PEO resins are commercially available from, for example, Union Carbide Corporation and are sold under the trade designations POLYOX.RTM. WSR N-750 and POLYOX.RTM. UCARFLOC.RTM. Polymer 309, respectively. Modification of PEO resins with starting molecular weights from about 300,000 g/mol to about 8,000,000 g/mol are desired and modification of PEO resins with starting molecular weights from about 400,000 g/mol to about 8,000,000 are more desired. Commercially available resins within the desired ranges include, but are not limited to, POLYOX.RTM. WSR N-205 and POLYOX.RTM. WSR N-12K. Fibers can be made using conventional processing methods from commercially available PEO resins when modified in accordance with this invention. The PEO resins useful for modification for fiber-making purposes include, but are not limited to, PEO resins having initial reported approximate molecular weights ranging from about 50,000 g/mol to about 400,000 g/mol. Higher molecular weights are desired for increased mechanical and physical properties and lower molecular weights are desired for ease of processing. Desirable PEO resins for fiber making have molecular weights ranging from 50,000 to 300,000 g/mol before modification and more desired PEO resins for fiber making have molecular weights ranging from 50,000 to 200,000 g/mol before modification. The PEO compositions modified from PEO resins within the above resins provide desirable balances between mechanical and physical properties and processing properties. Two PEO resins within the above preferred ranges are commercially available from Union Carbide Corporation and are sold under the trade designations POLYOX.RTM. WSR N-10 and POLYOX.RTM. WSR N-80. These two resins have reported approximate molecular weights, as determined by rheological measurements, of about 100,000 g/mol and 200,000 g/mol, respectively. Other PEO resins available from, for example, Union Carbide Corporation within the above approximate molecular weight ranges are sold under the trade designations WSR N-750, WSR N-3000, WSR-3333, WSR-205, WSR-N-12K, WSR-N-60K, WSR-301, WSR Coagulant, WSR-303. (See POLYOX.RTM.: Water Soluble Resins, Union Carbide Chemicals & Plastic Company, Inc., 1991 which is incorporated by reference herein in its entirety.) Both PEO powder and pellets of PEO can be used in this invention since the physical form of PEO does not affect its behavior in the melt state for grafting reactions. This invention has been demonstrated by the use of PEO in powder form as supplied by Union Carbide. However, the PEO resins to be modified may be obtained from other suppliers and in other forms, such as pellets. The PEO resins and modified compositions may optionally contain various additives such as plasticizers, processing aids, rheology modifiers, antioxidants, UV light stabilizers, pigments, colorants, slip additives, antiblock agents, etc. which may be added before or after modification. A variety of polar vinyl monomers may be useful in the practice of this invention. The term "monomer(s)" as used herein includes monomers, oligomers, polymers, mixtures of monomers, oligomers and/or polymers, and any other reactive chemical species which is capable of covalent bonding with the parent polymer, PEO. Ethylenically unsaturated monomers containing a polar functional group, such as hydroxyl, carboxyl, amino, carbonyl, halo, thiol, sulfonic, sulfonate, etc. are appropriate for this invention and are desired. Desired ethylenically unsaturated monomers include acrylates and methacrylates. Particularly desirable ethylenically unsaturated monomers containing a polar functional group are 2-hydroxyethyl methacrylate (hereinafter HEMA) and poly(ethylene glycol) methacrylates (hereinafter PEG-MA). A particularly desirable poly(ethylene glycol) methacrylate is poly(ethylene glycol) ethyl ether methacrylate. However, it is expected that a wide range of polar vinyl monomers would be capable of imparting similar effects as HEMA and PEG-MA to PEO and would be effective monomers for grafting. The amount of polar vinyl monomer relative to the amount of PEO may range from about 0.1 to about 20 weight percent of monomer to the weight of PEO. Desirably, the amount of monomer should exceed 0.1 weight percent in order to sufficiently improve the processability of the PEO. More desirably, the amount of monomer should be at the lower end of the above disclosed range in order to decrease costs. A range of grafting levels is demonstrated in the Examples. Typically, the monomer addition levels were between 2.5 percent and 15 percent of the weight of the base PEO resin. This invention has been demonstrated in the following Examples by the use of PEG-MA and HEMA as the polar vinyl monomers. Both the PEG-MA and HEMA were supplied by Aldrich Chemical Company. The HEMA used in the Examples was designated Aldrich Catalog number 12,863-5 and the PEG-MA was designated Aldrich Catalog number 40,954-5. The PEG-MA was a poly(ethylene glycol) ethyl ether methacrylate having a number average molecular weight of approximately 246 grams per mol. PEG-MA with a number average molecular weight higher or lower than 246 g/mol are also applicable for this invention. The molecular weight of the PEG-MA can range up to 50,000 g/mol. However, lower molecular weights are preferred for faster grafting reaction rates. The desired range of the molecular weight of the monomers is from about 246 to about 5,000 g/mol and the most desired range is from about 246 to about 2,000 g/mol. Again, it is expected that a wide range of polar vinyl monomers as well as a wide range of molecular weights of monomers would be capable of imparting similar effects to PEO resins and would be effective monomers for grafting and modification purposes. A variety of initiators may be useful in the practice of this invention. When grafting is achieved by the application of heat, as in a reactive-extrusion process, it is desirable that the initiator generates free radicals through the application of heat. Such initiators are generally referred to as thermal initiators. For the initiator to function as a useful source of radicals for grafting, the initiator should be commercially and readily available, stable at ambient or refrigerated conditions, and generate radicals at reactive-extrusion temperatures. Compounds containing an O--O, S--S, or N.dbd.N bond may be used as thermal initiators. Compounds containing O--O bonds, peroxides, are commonly used as initiators for polymerization. Such commonly used peroxide initiators include: alkyl, dialkyl, diaryl and arylalkyl peroxides such as cumyl peroxide, t-butyl peroxide, di-t-butyl peroxide, dicumyl peroxide, cumyl butyl peroxide, 1,1-di-t-butyl peroxy-3,5,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3 and bis(a-t-butyl peroxyisopropylbenzene); acyl peroxides such as acetyl peroxides and benzoyl peroxides; hydroperoxides such as cumyl hydroperoxide, t-butyl hydroperoxide, p-methane hydroperoxide, pinane hydroperoxide and cumene hydroperoxide; peresters or peroxyesters such as t-butyl peroxypivalate, t-butyl peroctoate, t-butyl perbenzoate, 2,5-dimethylhexyl-2,5-di(perbenzoate) and t-butyl di(perphthalate); alkylsulfonyl peroxides; dialkyl peroxymonocarbonates; dialkyl peroxydicarbonates; diperoxyketals; ketone peroxides such as cyclohexanone peroxide and methyl ethyl ketone peroxide. Additionally, azo compounds such as 2,2'-azobisisobutyronitrile abbreviated as AIBN, 2,2'-azobis(2,4-dimethylpentanenitrile) and 1,1'-azobis(cyclohexanecarbonitrile) may be used as the initiator. This invention has been demonstrated in the following Examples by the use of a liquid, organic peroxide initiator available from Elf Atochem North America, Inc. of Philadelphia, Pa., sold under the trade designation LUPERSOL.RTM. 101. LUPERSOL.RTM. 101 is a free radical initiator and comprises 2,5-dimethyl-2,5-di(t-butylperoxy) hexane. Other initiators and other grades of LUPERSOL.RTM. initiators may also be used, such as LUPERSOL.RTM. 130. A variety of reaction vessels may be useful in the practice of this invention. The modification of the PEO can be performed in any vessel as long as the necessary mixing of PEO, the monomer and the initiator is achieved and enough thermal energy is provided to effect grafting. Desirably, such vessels include any suitable mixing device, such as Bradender Plasticorders, Haake extruders, single or multiple screw extruders, or any other mechanical mixing devices which can be used to mix, compound, process or fabricate polymers. In a desired embodiment, the reaction device is a counter-rotating twin-screw extruder, such as a Haake extruder available from Haake, 53 West Century Road, Paramus, N.J. 07652 or a co-rotating, twin-screw extruder, such as a ZSK-30 twin-screw, compounding extruder manufactured by Werner & Pfleiderer Corporation of Ramsey, N.J. It should be noted that a variety of extruders can be used to modify the PEO in accordance with the invention provided that mixing and heating occur. The ZSK-30 extruder allows multiple feeding, has venting ports and is capable of producing modified PEO at a rate of up to 50 pounds per hour. If a higher rate of production of modified PEO is desired, a commercial-scale ZSK-58 extruder manufactured by Werner & Pfleiderer may be used. The ZSK-30 extruder has a pair of co-rotating screws arranged in parallel with the center to center distance between the shafts of the two screws at 26.2 mm. The nominal screw diameters are 30 mm. The actual outer diameters of the screws are 30 mm and the inner screw diameters are 21.3 mm. The thread depths is 4.7 mm. The lengths of the screws are 1328 mm and the total processing section length was 1338 mm. This ZSK-30 extruder had 14 processing barrels, which are numbered consecutively 1 to 14 from the feed barrel to the die for the purposes of this disclosure. The first barrel, barrel #1, received the PEO and was not heated but cooled by water. The other thirteen barrels were heated. The monomer, HEMA or PEG-MA, was injected into barrel #5 and the initiator was injected into barrel #6. Both the monomer and the initiator were injected via a pressurized nozzle injector, also manufactured by Werner & Pfleiderer. The order in which the PEO, monomer and initiator are added is not critical and the initiator and monomer may be added at the same time or in reverse order. However, the order used in the following Examples is desired. The die used to extrude the modified PEO strands has four openings of 3 mm in diameter which are separated by 7 mm. The modified PEO strands were extruded onto an air-cooling belt and then pelletized. The extruded PEO melt strands were cooled by air on a fan-cooled conveyor belt 20 feet in length. Another extruder suitable as the reaction device includes a Haake extruder. The modified PEO compositions of Examples 31, 32 and 33 suitable for fiber-making purposes were modified by a reactive extrusion process using a Haake extruder. The Haake extruder that was used was a counter-rotating, twin-screw extruder that contained a pair of custom-made, counter rotating conical screws. The Haake extruder had a length of 300 millimeters. Each conical screw had a diameter of 30 millimeters at the feed port and a diameter of 20 millimeters at the die. The monomer and the initiator were added at the feed throat of the Haake extruder contemporaneously with the PEO resin. The Haake extruder comprised six sections as follows: Section 1 comprised a double-flighted forward pumping section having a large screw pitch and high helix angle. Section 2 comprised a double-flighted forward pumping section having a smaller screw pitch than Section 1. Section 3 comprised a double-flighted forward pumping section having a smaller screw pitch than Section 2. Section 4 comprised a double-flighted and notched reverse pumping section where one complete flight was notched. Section 5 comprised a double-flighted and notched forward pumping section containing two complete flights. And, Section 6 comprised a double-flighted forward pumping section having a screw pitch intermediate that of Section 1 and Section 2. |
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