CA1283492C - Interpenetrating polymeric networks comprising polytetrafluoroethylene and polysiloxane - Google Patents
Interpenetrating polymeric networks comprising polytetrafluoroethylene and polysiloxaneInfo
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- CA1283492C CA1283492C CA000521375A CA521375A CA1283492C CA 1283492 C CA1283492 C CA 1283492C CA 000521375 A CA000521375 A CA 000521375A CA 521375 A CA521375 A CA 521375A CA 1283492 C CA1283492 C CA 1283492C
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L27/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers
- C08L27/02—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L27/12—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C08L27/18—Homopolymers or copolymers or tetrafluoroethene
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/005—Shaping by stretching, e.g. drawing through a die; Apparatus therefor characterised by the choice of materials
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
- C08L83/04—Polysiloxanes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2027/00—Use of polyvinylhalogenides or derivatives thereof as moulding material
- B29K2027/12—Use of polyvinylhalogenides or derivatives thereof as moulding material containing fluorine
- B29K2027/18—PTFE, i.e. polytetrafluorethene, e.g. ePTFE, i.e. expanded polytetrafluorethene
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2083/00—Use of polymers having silicon, with or without sulfur, nitrogen, oxygen, or carbon only, in the main chain, as moulding material
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
- C08G77/04—Polysiloxanes
- C08G77/06—Preparatory processes
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
- C08G77/04—Polysiloxanes
- C08G77/12—Polysiloxanes containing silicon bound to hydrogen
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
- C08G77/04—Polysiloxanes
- C08G77/20—Polysiloxanes containing silicon bound to unsaturated aliphatic groups
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- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
INTERPENETRATING POLYMERIC NETWORKS COMPRISING
POLYTETRAFLUOROETHYLENE AND POLYSILOXANE
Abstract of the Disclosure There is provided a composition having interpenetrating matrices comprising (a) a first polymer network characterized by nodes interconnected by fibrils and (b) a second polymer network comprising diorganosiloxy units. In another aspect, there are provided compositions comprising an interpenetrating polymer network of polytetrafluoroethylene and polydiorganosiloxane. Methods for making the foregoing compositions are also provided.
POLYTETRAFLUOROETHYLENE AND POLYSILOXANE
Abstract of the Disclosure There is provided a composition having interpenetrating matrices comprising (a) a first polymer network characterized by nodes interconnected by fibrils and (b) a second polymer network comprising diorganosiloxy units. In another aspect, there are provided compositions comprising an interpenetrating polymer network of polytetrafluoroethylene and polydiorganosiloxane. Methods for making the foregoing compositions are also provided.
Description
1;~8349~
INTERPENETRATING POLYMERIC NETWORKS COMPRISING
POLYTETRAFLUOROETHYLENE AND POLYSILOXANE
Background of the Invention The present invention relates to polymeric structures having interpenetrating matrices in cured form, comprising a polytetrafluoroethylene (PTFE) net-work and a polysiloxane network. More particularly, the present invention relates to interpenetrating polymeric networks wherein a curable silicone composition is mixed with PTFE powder and, thereafter, said silicone is cured while simultaneously stretching the silicone/PTFE
mixture.
Tetrafluoroethylene polymers and, in particular, polytetrafluoroethylene, are gaining more and more uses because of their chemical iner*ness and desirable physical properties such as water repellency and electrical insulating abilities. In one very large area, the field of porous articles, their use has been substantially blocked by the very considerable difficulty of making an article porous and keeping it so while providing it with adequate strength.
Complicated and expensive processes have been devised such as adding a filler to the polymer prior to shaping and then removing the filler after shaping, for example, by leaching it out of the shaped article with a solvent, or by melting or burning it out.
Gore, U.S. Patent Nos. 3,953,566, issued April 27, 1976; 3,962,153, issued June 8, 1976; 4,096,227, issued June 20, 1978; and 4,187,390, issued February 5, 1980, . .
' 349~
INTERPENETRATING POLYMERIC NETWORKS COMPRISING
POLYTETRAFLUOROETHYLENE AND POLYSILOXANE
Background of the Invention The present invention relates to polymeric structures having interpenetrating matrices in cured form, comprising a polytetrafluoroethylene (PTFE) net-work and a polysiloxane network. More particularly, the present invention relates to interpenetrating polymeric networks wherein a curable silicone composition is mixed with PTFE powder and, thereafter, said silicone is cured while simultaneously stretching the silicone/PTFE
mixture.
Tetrafluoroethylene polymers and, in particular, polytetrafluoroethylene, are gaining more and more uses because of their chemical iner*ness and desirable physical properties such as water repellency and electrical insulating abilities. In one very large area, the field of porous articles, their use has been substantially blocked by the very considerable difficulty of making an article porous and keeping it so while providing it with adequate strength.
Complicated and expensive processes have been devised such as adding a filler to the polymer prior to shaping and then removing the filler after shaping, for example, by leaching it out of the shaped article with a solvent, or by melting or burning it out.
Gore, U.S. Patent Nos. 3,953,566, issued April 27, 1976; 3,962,153, issued June 8, 1976; 4,096,227, issued June 20, 1978; and 4,187,390, issued February 5, 1980, . .
' 349~
overcame the difficulties of the prior art by stretching PTFE rods as fast as possible so as to provide tetrafluoroethylene polymer having outstanding combinations of high porosity and high strength.
Moreover, even though the rod was greatly lengthened its diameter remained virtually unchanged throughout its length. The rapid stretching also transformed the hard, shiny rods into a soft, flexible material.
Gore also teaches that there may be included as fillers, silicone fluids having structures represented by the formula ~ R
R3Sl t si t os 3 ~ R / n where n is from 0 to about 2000 and R is an alkyl or aryl radical.
Products based on rapidly stretching highly crystalline poly~etrafluoroethylene include porous films for filters and laminates; fabric laminates of PTFE film bonded to fabric to produce a material having the contradictory properties of impermeability to liquid water and permeability to water vapor, the material being used to make "breathable" rainwear and filters; porous yarn for weaving and braiding into other products such as pump packing; tubes used as replacements for human arteries and veins; and insulation for high performance electric cables.
An interpenetrating polymer network (IPN) is a combination of at least two polymers in network form, at least one of which is synthesized and/or crosslinked in the immediate presence of the other. IPN's can be further classified as sequential IPN's, where the networks are made sequentially, and simultaneous IPN's, where the monomers are mixed together and polymerized by independent and non-interfering 349~
Moreover, even though the rod was greatly lengthened its diameter remained virtually unchanged throughout its length. The rapid stretching also transformed the hard, shiny rods into a soft, flexible material.
Gore also teaches that there may be included as fillers, silicone fluids having structures represented by the formula ~ R
R3Sl t si t os 3 ~ R / n where n is from 0 to about 2000 and R is an alkyl or aryl radical.
Products based on rapidly stretching highly crystalline poly~etrafluoroethylene include porous films for filters and laminates; fabric laminates of PTFE film bonded to fabric to produce a material having the contradictory properties of impermeability to liquid water and permeability to water vapor, the material being used to make "breathable" rainwear and filters; porous yarn for weaving and braiding into other products such as pump packing; tubes used as replacements for human arteries and veins; and insulation for high performance electric cables.
An interpenetrating polymer network (IPN) is a combination of at least two polymers in network form, at least one of which is synthesized and/or crosslinked in the immediate presence of the other. IPN's can be further classified as sequential IPN's, where the networks are made sequentially, and simultaneous IPN's, where the monomers are mixed together and polymerized by independent and non-interfering 349~
routes. Sequential IPN's can also be prepared by swelling a polymer with a monomer and activating agents and, thereafter, polymerizing the monomer in situ.
Since true IPN's require mixing on the molecular level, which is not possible with some polymers due to their well known thermodynamic incompatibility, those skilled in the art often refer to these IPN's as pseudo-IPN's. For purposes of the present invention the terms "interpenetrating polymer network" and "psuedo-interpenetrating polymer network" are used interchangeably and are intended to describe both sequential IPN's and simultaneous IPN's.
Interpenetrating polymeric networks wherein one of the polymers is a polysiloxane are known in the art. Foscante et al, U.S. Patent No. 4,250,074, issued February 10, 1981, discloses an interpenetrating polymer network of a polymerized epoxy resin network intertwined with a polysiloxane network formed by the hydrolytic polycondensation of silane groups. This is achieved by the simultaneous polymerization, at substantially balanced reaction rates, of a mixture of epoxy resin and silane. An amine curing agent forms the epoxy network and water distributed throughout the mixture causes the hydrolytic polycondensation of the silane groups. A preferred method for preparing the IPN is to react epoxy resin with an aminosilane capable of both hydrolytic polycondensation of the silane moiety and amine addition of the oxirane rings of the epoxy resin.
Frisch et al, U.S. Patent No. 4,302,553, issued November 24, 1981, discribes interpenetrating polymeric networks characterized by a single glass transition temperature, comprising at least two separate chemically dissimilar macrocyclic structures of cross-linked polymer chains which do not contain ionizable groups and which are crosslinked by different crosslinking 1~3492 agents which crosslink by different crosslinking mechanisms, the polymer chains of one macrocyclic structure being threaded through, but having substantially no intermolecular chemical bonding with, another macrocyclic structure of the interpenetrating polymer network, with the proviso that the macrocyclic structures have rings of at least 20 ring atoms. Suitable cross-linking polymers typically can be polyfunctional polyurethane, polyepoxides, polyesters, polyamides, polyimides, phenolics, polysiloxanes, polysulfides, acrylics, poly(styrenebutadiene), poly(styrene-acrylonitrile), poly(butadiene-acrylonitrile), polychloro-prene, poly(chloroprene-acrylonitrile) and poly(acryl-onitrile-butadiene-styrene).
Pierce et al, U.S. Patent No. 4,312,920, issued January 26, 1982, provides a blood contacting layer and a blood contacting interface consisting of a solvent cast polyurethane alloyed with a filler-free silicone rubber. The alloy interface comprises an interpenetrating polymer network consisting of poly-urethane and filler-free silicone rubber at the molecular level.
Siegfried et al, U.S. Patent No. 4,468,499, issued August 28, 1984, relates to interpenetrating polymer networks comprised of at least two polymers, the second of which is polymerized in the presence of the first of said polymers, in a mutual solution of said first polymer and a prepolymer or monomer of said second polymer, at least one of said polymers comprising a continuous phase within said composition, said polymers being crosslinked by a non-covalent bonding mechanism selected from the group consisting of (a) ionomeric attraction and (b) block copolymers, each having at least rhree blocks, at least one of said blocks comprising an elastomeric block and at least two of said blocks comprising physically cross-linked glassy blocks, crystalline blocks or hydrogen 349~
Since true IPN's require mixing on the molecular level, which is not possible with some polymers due to their well known thermodynamic incompatibility, those skilled in the art often refer to these IPN's as pseudo-IPN's. For purposes of the present invention the terms "interpenetrating polymer network" and "psuedo-interpenetrating polymer network" are used interchangeably and are intended to describe both sequential IPN's and simultaneous IPN's.
Interpenetrating polymeric networks wherein one of the polymers is a polysiloxane are known in the art. Foscante et al, U.S. Patent No. 4,250,074, issued February 10, 1981, discloses an interpenetrating polymer network of a polymerized epoxy resin network intertwined with a polysiloxane network formed by the hydrolytic polycondensation of silane groups. This is achieved by the simultaneous polymerization, at substantially balanced reaction rates, of a mixture of epoxy resin and silane. An amine curing agent forms the epoxy network and water distributed throughout the mixture causes the hydrolytic polycondensation of the silane groups. A preferred method for preparing the IPN is to react epoxy resin with an aminosilane capable of both hydrolytic polycondensation of the silane moiety and amine addition of the oxirane rings of the epoxy resin.
Frisch et al, U.S. Patent No. 4,302,553, issued November 24, 1981, discribes interpenetrating polymeric networks characterized by a single glass transition temperature, comprising at least two separate chemically dissimilar macrocyclic structures of cross-linked polymer chains which do not contain ionizable groups and which are crosslinked by different crosslinking 1~3492 agents which crosslink by different crosslinking mechanisms, the polymer chains of one macrocyclic structure being threaded through, but having substantially no intermolecular chemical bonding with, another macrocyclic structure of the interpenetrating polymer network, with the proviso that the macrocyclic structures have rings of at least 20 ring atoms. Suitable cross-linking polymers typically can be polyfunctional polyurethane, polyepoxides, polyesters, polyamides, polyimides, phenolics, polysiloxanes, polysulfides, acrylics, poly(styrenebutadiene), poly(styrene-acrylonitrile), poly(butadiene-acrylonitrile), polychloro-prene, poly(chloroprene-acrylonitrile) and poly(acryl-onitrile-butadiene-styrene).
Pierce et al, U.S. Patent No. 4,312,920, issued January 26, 1982, provides a blood contacting layer and a blood contacting interface consisting of a solvent cast polyurethane alloyed with a filler-free silicone rubber. The alloy interface comprises an interpenetrating polymer network consisting of poly-urethane and filler-free silicone rubber at the molecular level.
Siegfried et al, U.S. Patent No. 4,468,499, issued August 28, 1984, relates to interpenetrating polymer networks comprised of at least two polymers, the second of which is polymerized in the presence of the first of said polymers, in a mutual solution of said first polymer and a prepolymer or monomer of said second polymer, at least one of said polymers comprising a continuous phase within said composition, said polymers being crosslinked by a non-covalent bonding mechanism selected from the group consisting of (a) ionomeric attraction and (b) block copolymers, each having at least rhree blocks, at least one of said blocks comprising an elastomeric block and at least two of said blocks comprising physically cross-linked glassy blocks, crystalline blocks or hydrogen 349~
bonded blocks, wherein one of said polymers is a triblock copolymer containing monoalkenyl arene polymer end blocks and the other of said polymers is a monoalkenyl arene monomer copolymerized with an acid forming monomer. The crystalline block can be poly-diphenylsiloxane and the elastomeric block can be polydimethylsiloxane.
Arkles, U.S. Patent No. 4,500,688, issued February 19, 1985, discloses melt processable compositions comprising a silicone component which is vulcanizable by the reaction of a hydride-containing silicone within a polymeric thermoplastic matrix to form a silicone pseudo-interpenetrating polymer network, said vulcanization of said silicone component being initiated during thermoplastic melt-mixing of said component with said matrix. The polymeric thermoplastic matrices include polyamides, thermo-plastic polyurethanes, bisphenol A polycarbonates, styrenics and polyacetals.
Summary of the Invention It is an object of the present invention to provide interpenetrating polymer networks comprising a polydiorganosiloxane network and a polytetrafluoro-ethylene network.
It is another object of the present invention to provide porous materials having improved imper-meability to liquid water and improved air permeability, e.g., breathability.
; Another object of the present invention is to provide materials useful in the manufacture of apparel fabric laminates, geotextiles, geomembranes, filters, and other industrial, medical and electrical applications.
Still another object of the present invention is to provide methods for making polysiloxane - poly-tetrafluoroethylene interpenetrating networks.
i . : :
~349.~
~ 6 - 60SI 1034 In accordance with the present invention there are provided novel compositions comprising a polysiloxane component vulcanized within a polytetrafluoroethylene component to form an interpenetrating polymer network.
There are also provided methods of producing polysiloxane-polytetrafluoroethylene interpenetrating polymer networks by curing a silicone within the polytetrafluoroethylene matrix, particularly at elevated temperatures while simultaneously stretching a mixture of said silicone and polytetrafluoroethylene.
Description of the Invention In accordance with one aspect of the present invention there are provided compositions having interpenetrating matrices in cured form, comprising:
(a) a first polymer network characterized by nodes interconnected by fibrils, and (b) a second polymer network comprising diorganosiloxy units.
Component (a) can be any polymer capable of being stretched, drawn or expanded so as to obtain a microstructure characterized by nodes interconnected by very small fibrils. It is especially preferred that component (a) be polytetrafluoroethylene as taught by Gore in the aforementioned U.S. patents. Poly-ethylene, polyamides, and polyesters are also known to exhibit a fibrillar structure upon being drawn or expanded. The suitability of other polymers for practicing the present invention will be obvious to those skilled in the art or can be ascertained without undue experimentation.
Component (b) can be any curable silicone composition, however, it is preferred that an addition curable silicone composition be employed in the practice of the invention. Generally stated, addition curable silicone compositions comprise (1) a poly-diorganosiloxane having alkenyl unsaturation, (2) an ~349~
organohydrogenpolysiloxane crosslinking agent, and (3) a catalyst for promoting crosslinking of (1) and (2). The principles of this chemistry are well known to those skilled in the art.
Alkenyl-containing polydiorganosiloxanes typically employed in the practice of the present invention can have viscosities up to 100,000,000 centipoise or more at 25C, for example, in accordance with the teaching of U.S. Patent No. 4,061,609, issued December 6, 1977 to Bobear. It has been found that excellent results are obtained when the viscosity of the alkenyl-containing polysiloxane is from about 500 centipoise to 50,000 centipoise at 25C, and especially when the viscosity is from about 3000 centipoise to 6000 centipoise at 25C.
Organohydrogenpolysiloxanes that can be utilized in the present invention may be linear or resinous and have viscosities of between about 25 centipoise and 10,000 centipoise at 25C, with the preferred range being from about 100 centipoise to about 1000 centipoise at 25C.
The curing catalyst can be either an organic peroxide or a precious metal containing material.
Suitable organic peroxides include dibenzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, and dicumyl peroxide. Precious metal containing catalysts can be based on the metals rhodium, ruthenium, palladium, osmium, irridium and platinum. It is particularly preferred that a platinum metal complex be employed as the catalyst, for example, as taught by Ashby in U.S. Patent Nos. 3,159,601 and 3,159,662, both issued December 1, 1964, Lamoreaux in U.S. Patent No.
3,220,972, issued November 11, 1965, Karstedt in U.S.
Patent No. 3,814,730, issued June 4, 1974, and Modic in U.S. Patent No. 3,516,946, issued June 23, 1970.
~3~9~
In an especially preferred embodiment, the addition curable silicone composition further includes a reinforcing organopolysiloxane resin of the type disclosed in U.S. Patent No. 3,284,406, issued November 8, 1966 to Nelson or U.S. Patent No. 3,436,366, issued April l, 1969 to Modic. Briefly, such resins are copolymers of SiO2 units, (CH3)3SiOo 5 units and (CH3)2(CH2=CH)SiOo 5 units, and SiO2 units, (CH3)3SiOo 5 units and (CH3)(CH2=CH)SiO units, respectively.
Particularly preferred organopolysiloxane resins are MDQ resins having vinyl unsaturation on monofunctional siloxane units, difunctional siloxane units, or both.
The use of such reinforcing organopolysiloxane resins is especially desirable when the viscosity of the alkenyl containing polydiorganosiloxane is less than about 5000 centipoise at 25C.
It is also contemplated that there may be included any conventional extending and/or reinforcing fillers. Fumed silica has been found to be particularly effective as a reinforcing filler for the silicone component of the present invention.
In another particularly preferred embodiment of the present invention, the addition curable silicone composition also contains a silane or polysiloxane which functions both as an inhibitor and as an adhesion promoter. One such composition is described in U.S. Patent No. 3,759,968, issued September 18, 1973 to Berger et al as a maleate or fumarate functional silane or polysiloxane. Compositions effective only as an inhibitor are disclosed in U.S. Patent No.
4,256,870, issued March 10, 1981 to Eckberg and aforementioned U.S. Patent 4,061,609. Other suitable inhibitors will be obvious to those skilled in the art.
It is further contemplated that component (b) can be condensation curable silicone composition.
Generally, condensation curable silicone compositions .
349~
are available in either one or two packages and comprise (1) a polydiorganosiloxane having terminal hydrolyzable groups, e.g., hydroxyl or alkoxyl, and (2) a catalyst which promotes condensation curing.
Such compositions are well known in the art, for example, as described in U.S. Patent No. 3,888,815, issued June 10, 1975 to Bessmer et al.
Alternatively, the polysiloxane network can be prepared by the hydrolytic polycondensation of silanes having the general formula Y - Si - (OX)3 where each X is independently selected from the group consisting of hydrogen, alkyl radicals, hydroxyalkyl radicals, alkoxyalkyl radicals, and hydroxyalkoxy-alkyl radicals, and Y is an alkyl radical, OX, where X is as previously defined, or an amino or substituted amino radical. The use of silanes having hydrolyzable groups to form a polysiloxane network of an inter-penetrating polymer network is discussed in greater detail in aforementioned U.S. Patent No. 4,250,074.
The amount of curable silicone composition used in practicing the present invention can range from as little as about 1 part by weight per 10~ parts by weight of component (a) to as much as about 150 parts by weight per 100 parts by weight of component (a).
A particularly preferred embodiment of the present invention utilizes from 1 to 50 parts by weight silicone per 100 parts by weight of component (a).
Optimal results are obtained when from about 5 to about 35 parts by weight of silicone composition are used per 100 parts by weight of polytetrafluoroethylene.
It should be noted that the translucency of the final product increases as the ratio of silicone composition to PTFE increases.
For ease of discussion, preparation of com-positions having interpenetrating matrices in cured ~33492 form will be described only with respect to poly-tetrafluoroethylene and addition curable silicone compositions. Those skilled in the art will appreciate that in order to prevent premature curing of the silicone composition the components must not all be combined until the time of use unless a suitable inhibitor is included (or moisture excluded in the case of condensation curable silicone compositions).
In a preferred embodiment of this invention a one component, addition curable silicone composition containing an amount of inhibitor effective to prevent curing below about 100C is dissolved in a suitable solvent, for example, kerosene or mineral spirits.
The resulting solution is thereafter mixed with polytetrafluoroethylene powder in a tumbler-type mixer suitable for mixing liquids with solids in order to incorporate the desired level of silicone into the PTFE. The semi-dry powder obtained is a mixture of PTFE, silicone composition and solvent which can be pressed into a cylindrical bar or other suitable shape.
The cylindrical bar is then extruded and calendered to provide a film of desired thickness.
A$ter the solvent is removed the film can be stretched to provide a film having a porous microstructure consisting of nodes and fibrils. Although expansion of the film can be carried out at temperatures ranging from room temperature to about 325C, it is preferable that the temperature range from about 250C to about 300C so that the silicone composition cures during the stretching process.
If an inhibitor is not present to prevent premature curing of the silicone composition, it is desirable to prepare a mixture of PTFE and vinyl containing polydiorganosiloxane and a mixture of PTFE
and organohydrogenpolysiloxane, either or both mixtures . . .
~3492 ~ 60SI 1034 also containing a curing catalyst. At the time of use the powders are combined and the final product prepared as if an inhibitor were present.
Because of the presence of the silicone in the extruded PTFE film, stretching was easier as the silicone acted as an internal plasticizer. Consequently, it is not required that stretching be effected as fast as possible, and excellent results have been obtained with stretch rates of only 20~ per second. Of course, this does not preclude stretching at rates of 1000~ per second or more as taught by Gore in U.S. Patent No.
3,953,566, issued April 27, 1976.
Stretched films prepared in accordance with the present invention generally have thicknesses ranging from about 0.5 mils to about 10 mils. Quite surprisingly, however, the resultant materials had larger pore sizes than similar materials prepared solely from PTFE, yet they exhibit improved air permeability and improved resistance to liquid water permeability.
It is also preferred that the expanded products be heated to above the lowest crystalline melting point of the PTFE so as to increase the amorphous content of the polymer, typically to 10%
or more. Such amorphous regions within the crystalline structure appear to greatly inhibit slippage along the crystalline axis and thereby lock fibrils and nodes so that they resist slippage under stress. As a result, a surprising increase in strength is obtained.
In another aspect of the present invention there are provided compositions having interpenetrating matrices in cured form comprising:
(a) a first polymer network comprising 349~
polytetrafluoroethylene, and (b) a second polymer network comprising polydiorganosiloxane.
Components (a) and (b) of this aspect of the invention are the same as described hereinabove, however, the final product is prepared by conventional extrusion techniques rather than by stretching.
Compositions prepared in accordance with the present invention find particular utility as filters, pump packing, insulation for electrical cables, and as laminates useful in the manufacture of breathable wearing apparel.
In order to better enable those skilled in the art to practice the present invention, the following examples are provided by way of illustration and not by way of limitation. All parts and percentages are by weight unless otherwise noted.
EXAMPLES
Silicone compositions comprising the components set forth in Table 1 were prepared ; and identified as silicone A through silicone J.
/
t !
1~3a~92 t` N O O ~i ~
~ Lt7 H ¦ I I ~ , I ~ I O
O ~ l~
Q~ O
o o ~ ~ ~ ct) a ~1 ~ l ~ ~ ~ I I I I
::~ ~4 ~ 9 CO O
~1 1 1 1 l I I I o I
3 ,1 ~ ~ ~1 1 1 1 1 1 1 ,, I I I
.~ o ~
'~ rl .~
o ~1 1 1 1 o ~ o~
~ ~ d~ U~ U~
~ _ ml 1~ I N
l~i !~i ~
l~i ~ o o ~
., 0~r 0 ~
U N a~ ~1 X
.~ 01 ~
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1~3492 Silicone - PTFE compositions were then prepared by dissolving the silicone in kerosene and then mixing this solution with PTFE in a tumbler-type mixer. These compositions are set forth in Table 2 as compositions 1 through 10.
Table 2 - Silicone - PTFE Compositions Weight Weight Weight Weight Composition 1 Kerosene, Silicone, PTFE, CaC03, Number % Kerosene % Silicone2 lbs. lbs. lbs. lbs.
1 17 7 11 4.5 60 2 17 7 1.2 0.5 6.5 3 17 7 1.2 0.5 6.5 4 17 7 1.2 0.5 6.5 17 7 1.2 0.5 6.5 6 17 7 1.2 0.5 6.5 7 17 20 1.2 1.4 5.6 8 17 7 1.2 0.5 6.2 0.35 9 17 7 1.2 0.5 6.5 13 20 1.2 1.4 5.6 1. Kerosene calculated as percent of total solids weight.
2. Silicone level based on percent of final "dried", extruded film.
Extrusions of the foregoing silicone - PTFE
composition were prepared as specified in Table 3.
/
1~3492 Table 3 - PTFE - Silicone Extrudates Extruded Samplel Silicone Stretch Specific Final No. Used (~) Ratio Gravity Width, ins.
lA A(7) 1:1 1.63 6.4 lB A(7) 1:2 1.09 5.9 lC A(7) 1:3 0.87 5.4 lD A(7) 1:4 0.77 4.9 2 D(7) 1:1 1.23 5.5 3 E(7) 1:1 1.29 6.0 4 F(7) 1:1 1.38 5.75 B(7) 1:1 1.32 6.0 6A B+C(7) 1:1 - 5.75 6B B+C(7) 1:3 1.41 5.75 7 A(20) 1:1 1.75 4.0 A(7, 5~ CaCO3) 1:1 1.70 6.0 g G(7) 1:1 1.66 6.75 103 B+C(7) 1:1 1.95 6.0 11 G(20) 1:1 1. All samples used 17% kerosene as a lubricant except 11 which used 13% resulting in a more difficult extrusion.
2. The reduction in specific gravity for lA - lD reflects the difference in longitudinal stretching of the samples.
3. Extrudable PTFE-Silicone mixture stored at 72F for 22 hours before extrusion.
The extruded, calendered and dried PTFE-silicone samples were then stretched from their extruded width of about six inches to 64, 66 or 74 inches. The films were sintered during the stretching operation to prevent shrinking. Moreover, since sintering was effected at 300C, the crosslinkable silicone mixtures were crosslinked during this operation. Physical properties of the stretched film are shown in Table 4 where data on permeability of the stretched films with different silicone additives are compared.
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In Table 4 the stretched film property measure-ments have the following meanings:
Stretch Ratio - Since the extrudate is conveyed over heated drum-rollers during the drying step, longitudinally stretching of the film can be varied by adjusting the speed of the drums. A ratio of 1:1 assumes that no stretching occurs in the machine direction.
Mullen Value - Measures the pounds per square inch of water pressure needed to get penetration of the film. A measure of waterproofness.
The higher the Mullen value the more water-proof is the film. A minimum value of 25 is desired.
Bubble Point - A measure of the pounds per square inch of pressure necessary to produce a bubble in a column of water on the opposite side of the film. This is a measure of the porosity from which the maximum pore size can be calculated.
Air Permeability - Measures the breatheability of the film by the air flow through the membrane expressed in cubic feet per minute per square foot of area.
Moisture-Vapor - This also measures the breatheability Transmission of the film by the number of grams of (MVT) water evaporated per square meter of area over a 24 hour period when air flows across a film in contact with water on the opposite side. The higher the value the greater the breatheability.
The results in Table 4 show that excellent results are obtained in comparison to stretched PTFE which does not have an interpenetrating polydiorganos loxane network.
A detailed set of extraction experiments were then conducted to show that the silicone compositions did cure into the PTFE matrix. Also included in the extraction study were silicones which could not be crosslinked. Thus, weight loss studies before and after extraction with hexane in a Sohxlet extraction appratus show whether an interpenetrating network was formed. The data were collected for both extruded and stretched samples and the results as set forth in Table 5.
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In Table 5, the theoretical weight percent silicone is that amount mixed with PTFE, while the percent silicone extracted is the actual weight loss from the sample after extraction. From these two values percent silicon for the amount originally added (% Si theory) and percent silicon for the amount remaining after extraction (% Si calculated~ were determined. These results were then compared with the percent silicon found by elemental analysis (~ Si found). For sample 5, which contained an uncrosslinkable silicone, essentially all of the silicone was extracted, even after thermal treatment.
A comparison of the stretched PTFE - silicone films shows that for the lA sample essentially none of the silicone could be extracted, whereas for sample 3 most of the silicone was extracted as expected.
Sample 4 showed less extractable silicone than was expected, suggesting that crosslinking occurred through interaction of the material with atmospheric moisture or moisture introduced during processing, since this was a condensation curable silicone.
Next, an extruded sample of PTFE having a 50 mil thickness and containing 20 percent of Silicone G
(Table 1) was cured at 200C for two hours. The resultant material had a Shore A hardness of 90, 484 psi tensile at break and 183% elongation. In addition to being elastomeric, the material was substantially translucent.
Arkles, U.S. Patent No. 4,500,688, issued February 19, 1985, discloses melt processable compositions comprising a silicone component which is vulcanizable by the reaction of a hydride-containing silicone within a polymeric thermoplastic matrix to form a silicone pseudo-interpenetrating polymer network, said vulcanization of said silicone component being initiated during thermoplastic melt-mixing of said component with said matrix. The polymeric thermoplastic matrices include polyamides, thermo-plastic polyurethanes, bisphenol A polycarbonates, styrenics and polyacetals.
Summary of the Invention It is an object of the present invention to provide interpenetrating polymer networks comprising a polydiorganosiloxane network and a polytetrafluoro-ethylene network.
It is another object of the present invention to provide porous materials having improved imper-meability to liquid water and improved air permeability, e.g., breathability.
; Another object of the present invention is to provide materials useful in the manufacture of apparel fabric laminates, geotextiles, geomembranes, filters, and other industrial, medical and electrical applications.
Still another object of the present invention is to provide methods for making polysiloxane - poly-tetrafluoroethylene interpenetrating networks.
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~349.~
~ 6 - 60SI 1034 In accordance with the present invention there are provided novel compositions comprising a polysiloxane component vulcanized within a polytetrafluoroethylene component to form an interpenetrating polymer network.
There are also provided methods of producing polysiloxane-polytetrafluoroethylene interpenetrating polymer networks by curing a silicone within the polytetrafluoroethylene matrix, particularly at elevated temperatures while simultaneously stretching a mixture of said silicone and polytetrafluoroethylene.
Description of the Invention In accordance with one aspect of the present invention there are provided compositions having interpenetrating matrices in cured form, comprising:
(a) a first polymer network characterized by nodes interconnected by fibrils, and (b) a second polymer network comprising diorganosiloxy units.
Component (a) can be any polymer capable of being stretched, drawn or expanded so as to obtain a microstructure characterized by nodes interconnected by very small fibrils. It is especially preferred that component (a) be polytetrafluoroethylene as taught by Gore in the aforementioned U.S. patents. Poly-ethylene, polyamides, and polyesters are also known to exhibit a fibrillar structure upon being drawn or expanded. The suitability of other polymers for practicing the present invention will be obvious to those skilled in the art or can be ascertained without undue experimentation.
Component (b) can be any curable silicone composition, however, it is preferred that an addition curable silicone composition be employed in the practice of the invention. Generally stated, addition curable silicone compositions comprise (1) a poly-diorganosiloxane having alkenyl unsaturation, (2) an ~349~
organohydrogenpolysiloxane crosslinking agent, and (3) a catalyst for promoting crosslinking of (1) and (2). The principles of this chemistry are well known to those skilled in the art.
Alkenyl-containing polydiorganosiloxanes typically employed in the practice of the present invention can have viscosities up to 100,000,000 centipoise or more at 25C, for example, in accordance with the teaching of U.S. Patent No. 4,061,609, issued December 6, 1977 to Bobear. It has been found that excellent results are obtained when the viscosity of the alkenyl-containing polysiloxane is from about 500 centipoise to 50,000 centipoise at 25C, and especially when the viscosity is from about 3000 centipoise to 6000 centipoise at 25C.
Organohydrogenpolysiloxanes that can be utilized in the present invention may be linear or resinous and have viscosities of between about 25 centipoise and 10,000 centipoise at 25C, with the preferred range being from about 100 centipoise to about 1000 centipoise at 25C.
The curing catalyst can be either an organic peroxide or a precious metal containing material.
Suitable organic peroxides include dibenzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, and dicumyl peroxide. Precious metal containing catalysts can be based on the metals rhodium, ruthenium, palladium, osmium, irridium and platinum. It is particularly preferred that a platinum metal complex be employed as the catalyst, for example, as taught by Ashby in U.S. Patent Nos. 3,159,601 and 3,159,662, both issued December 1, 1964, Lamoreaux in U.S. Patent No.
3,220,972, issued November 11, 1965, Karstedt in U.S.
Patent No. 3,814,730, issued June 4, 1974, and Modic in U.S. Patent No. 3,516,946, issued June 23, 1970.
~3~9~
In an especially preferred embodiment, the addition curable silicone composition further includes a reinforcing organopolysiloxane resin of the type disclosed in U.S. Patent No. 3,284,406, issued November 8, 1966 to Nelson or U.S. Patent No. 3,436,366, issued April l, 1969 to Modic. Briefly, such resins are copolymers of SiO2 units, (CH3)3SiOo 5 units and (CH3)2(CH2=CH)SiOo 5 units, and SiO2 units, (CH3)3SiOo 5 units and (CH3)(CH2=CH)SiO units, respectively.
Particularly preferred organopolysiloxane resins are MDQ resins having vinyl unsaturation on monofunctional siloxane units, difunctional siloxane units, or both.
The use of such reinforcing organopolysiloxane resins is especially desirable when the viscosity of the alkenyl containing polydiorganosiloxane is less than about 5000 centipoise at 25C.
It is also contemplated that there may be included any conventional extending and/or reinforcing fillers. Fumed silica has been found to be particularly effective as a reinforcing filler for the silicone component of the present invention.
In another particularly preferred embodiment of the present invention, the addition curable silicone composition also contains a silane or polysiloxane which functions both as an inhibitor and as an adhesion promoter. One such composition is described in U.S. Patent No. 3,759,968, issued September 18, 1973 to Berger et al as a maleate or fumarate functional silane or polysiloxane. Compositions effective only as an inhibitor are disclosed in U.S. Patent No.
4,256,870, issued March 10, 1981 to Eckberg and aforementioned U.S. Patent 4,061,609. Other suitable inhibitors will be obvious to those skilled in the art.
It is further contemplated that component (b) can be condensation curable silicone composition.
Generally, condensation curable silicone compositions .
349~
are available in either one or two packages and comprise (1) a polydiorganosiloxane having terminal hydrolyzable groups, e.g., hydroxyl or alkoxyl, and (2) a catalyst which promotes condensation curing.
Such compositions are well known in the art, for example, as described in U.S. Patent No. 3,888,815, issued June 10, 1975 to Bessmer et al.
Alternatively, the polysiloxane network can be prepared by the hydrolytic polycondensation of silanes having the general formula Y - Si - (OX)3 where each X is independently selected from the group consisting of hydrogen, alkyl radicals, hydroxyalkyl radicals, alkoxyalkyl radicals, and hydroxyalkoxy-alkyl radicals, and Y is an alkyl radical, OX, where X is as previously defined, or an amino or substituted amino radical. The use of silanes having hydrolyzable groups to form a polysiloxane network of an inter-penetrating polymer network is discussed in greater detail in aforementioned U.S. Patent No. 4,250,074.
The amount of curable silicone composition used in practicing the present invention can range from as little as about 1 part by weight per 10~ parts by weight of component (a) to as much as about 150 parts by weight per 100 parts by weight of component (a).
A particularly preferred embodiment of the present invention utilizes from 1 to 50 parts by weight silicone per 100 parts by weight of component (a).
Optimal results are obtained when from about 5 to about 35 parts by weight of silicone composition are used per 100 parts by weight of polytetrafluoroethylene.
It should be noted that the translucency of the final product increases as the ratio of silicone composition to PTFE increases.
For ease of discussion, preparation of com-positions having interpenetrating matrices in cured ~33492 form will be described only with respect to poly-tetrafluoroethylene and addition curable silicone compositions. Those skilled in the art will appreciate that in order to prevent premature curing of the silicone composition the components must not all be combined until the time of use unless a suitable inhibitor is included (or moisture excluded in the case of condensation curable silicone compositions).
In a preferred embodiment of this invention a one component, addition curable silicone composition containing an amount of inhibitor effective to prevent curing below about 100C is dissolved in a suitable solvent, for example, kerosene or mineral spirits.
The resulting solution is thereafter mixed with polytetrafluoroethylene powder in a tumbler-type mixer suitable for mixing liquids with solids in order to incorporate the desired level of silicone into the PTFE. The semi-dry powder obtained is a mixture of PTFE, silicone composition and solvent which can be pressed into a cylindrical bar or other suitable shape.
The cylindrical bar is then extruded and calendered to provide a film of desired thickness.
A$ter the solvent is removed the film can be stretched to provide a film having a porous microstructure consisting of nodes and fibrils. Although expansion of the film can be carried out at temperatures ranging from room temperature to about 325C, it is preferable that the temperature range from about 250C to about 300C so that the silicone composition cures during the stretching process.
If an inhibitor is not present to prevent premature curing of the silicone composition, it is desirable to prepare a mixture of PTFE and vinyl containing polydiorganosiloxane and a mixture of PTFE
and organohydrogenpolysiloxane, either or both mixtures . . .
~3492 ~ 60SI 1034 also containing a curing catalyst. At the time of use the powders are combined and the final product prepared as if an inhibitor were present.
Because of the presence of the silicone in the extruded PTFE film, stretching was easier as the silicone acted as an internal plasticizer. Consequently, it is not required that stretching be effected as fast as possible, and excellent results have been obtained with stretch rates of only 20~ per second. Of course, this does not preclude stretching at rates of 1000~ per second or more as taught by Gore in U.S. Patent No.
3,953,566, issued April 27, 1976.
Stretched films prepared in accordance with the present invention generally have thicknesses ranging from about 0.5 mils to about 10 mils. Quite surprisingly, however, the resultant materials had larger pore sizes than similar materials prepared solely from PTFE, yet they exhibit improved air permeability and improved resistance to liquid water permeability.
It is also preferred that the expanded products be heated to above the lowest crystalline melting point of the PTFE so as to increase the amorphous content of the polymer, typically to 10%
or more. Such amorphous regions within the crystalline structure appear to greatly inhibit slippage along the crystalline axis and thereby lock fibrils and nodes so that they resist slippage under stress. As a result, a surprising increase in strength is obtained.
In another aspect of the present invention there are provided compositions having interpenetrating matrices in cured form comprising:
(a) a first polymer network comprising 349~
polytetrafluoroethylene, and (b) a second polymer network comprising polydiorganosiloxane.
Components (a) and (b) of this aspect of the invention are the same as described hereinabove, however, the final product is prepared by conventional extrusion techniques rather than by stretching.
Compositions prepared in accordance with the present invention find particular utility as filters, pump packing, insulation for electrical cables, and as laminates useful in the manufacture of breathable wearing apparel.
In order to better enable those skilled in the art to practice the present invention, the following examples are provided by way of illustration and not by way of limitation. All parts and percentages are by weight unless otherwise noted.
EXAMPLES
Silicone compositions comprising the components set forth in Table 1 were prepared ; and identified as silicone A through silicone J.
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1~3492 Silicone - PTFE compositions were then prepared by dissolving the silicone in kerosene and then mixing this solution with PTFE in a tumbler-type mixer. These compositions are set forth in Table 2 as compositions 1 through 10.
Table 2 - Silicone - PTFE Compositions Weight Weight Weight Weight Composition 1 Kerosene, Silicone, PTFE, CaC03, Number % Kerosene % Silicone2 lbs. lbs. lbs. lbs.
1 17 7 11 4.5 60 2 17 7 1.2 0.5 6.5 3 17 7 1.2 0.5 6.5 4 17 7 1.2 0.5 6.5 17 7 1.2 0.5 6.5 6 17 7 1.2 0.5 6.5 7 17 20 1.2 1.4 5.6 8 17 7 1.2 0.5 6.2 0.35 9 17 7 1.2 0.5 6.5 13 20 1.2 1.4 5.6 1. Kerosene calculated as percent of total solids weight.
2. Silicone level based on percent of final "dried", extruded film.
Extrusions of the foregoing silicone - PTFE
composition were prepared as specified in Table 3.
/
1~3492 Table 3 - PTFE - Silicone Extrudates Extruded Samplel Silicone Stretch Specific Final No. Used (~) Ratio Gravity Width, ins.
lA A(7) 1:1 1.63 6.4 lB A(7) 1:2 1.09 5.9 lC A(7) 1:3 0.87 5.4 lD A(7) 1:4 0.77 4.9 2 D(7) 1:1 1.23 5.5 3 E(7) 1:1 1.29 6.0 4 F(7) 1:1 1.38 5.75 B(7) 1:1 1.32 6.0 6A B+C(7) 1:1 - 5.75 6B B+C(7) 1:3 1.41 5.75 7 A(20) 1:1 1.75 4.0 A(7, 5~ CaCO3) 1:1 1.70 6.0 g G(7) 1:1 1.66 6.75 103 B+C(7) 1:1 1.95 6.0 11 G(20) 1:1 1. All samples used 17% kerosene as a lubricant except 11 which used 13% resulting in a more difficult extrusion.
2. The reduction in specific gravity for lA - lD reflects the difference in longitudinal stretching of the samples.
3. Extrudable PTFE-Silicone mixture stored at 72F for 22 hours before extrusion.
The extruded, calendered and dried PTFE-silicone samples were then stretched from their extruded width of about six inches to 64, 66 or 74 inches. The films were sintered during the stretching operation to prevent shrinking. Moreover, since sintering was effected at 300C, the crosslinkable silicone mixtures were crosslinked during this operation. Physical properties of the stretched film are shown in Table 4 where data on permeability of the stretched films with different silicone additives are compared.
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In Table 4 the stretched film property measure-ments have the following meanings:
Stretch Ratio - Since the extrudate is conveyed over heated drum-rollers during the drying step, longitudinally stretching of the film can be varied by adjusting the speed of the drums. A ratio of 1:1 assumes that no stretching occurs in the machine direction.
Mullen Value - Measures the pounds per square inch of water pressure needed to get penetration of the film. A measure of waterproofness.
The higher the Mullen value the more water-proof is the film. A minimum value of 25 is desired.
Bubble Point - A measure of the pounds per square inch of pressure necessary to produce a bubble in a column of water on the opposite side of the film. This is a measure of the porosity from which the maximum pore size can be calculated.
Air Permeability - Measures the breatheability of the film by the air flow through the membrane expressed in cubic feet per minute per square foot of area.
Moisture-Vapor - This also measures the breatheability Transmission of the film by the number of grams of (MVT) water evaporated per square meter of area over a 24 hour period when air flows across a film in contact with water on the opposite side. The higher the value the greater the breatheability.
The results in Table 4 show that excellent results are obtained in comparison to stretched PTFE which does not have an interpenetrating polydiorganos loxane network.
A detailed set of extraction experiments were then conducted to show that the silicone compositions did cure into the PTFE matrix. Also included in the extraction study were silicones which could not be crosslinked. Thus, weight loss studies before and after extraction with hexane in a Sohxlet extraction appratus show whether an interpenetrating network was formed. The data were collected for both extruded and stretched samples and the results as set forth in Table 5.
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In Table 5, the theoretical weight percent silicone is that amount mixed with PTFE, while the percent silicone extracted is the actual weight loss from the sample after extraction. From these two values percent silicon for the amount originally added (% Si theory) and percent silicon for the amount remaining after extraction (% Si calculated~ were determined. These results were then compared with the percent silicon found by elemental analysis (~ Si found). For sample 5, which contained an uncrosslinkable silicone, essentially all of the silicone was extracted, even after thermal treatment.
A comparison of the stretched PTFE - silicone films shows that for the lA sample essentially none of the silicone could be extracted, whereas for sample 3 most of the silicone was extracted as expected.
Sample 4 showed less extractable silicone than was expected, suggesting that crosslinking occurred through interaction of the material with atmospheric moisture or moisture introduced during processing, since this was a condensation curable silicone.
Next, an extruded sample of PTFE having a 50 mil thickness and containing 20 percent of Silicone G
(Table 1) was cured at 200C for two hours. The resultant material had a Shore A hardness of 90, 484 psi tensile at break and 183% elongation. In addition to being elastomeric, the material was substantially translucent.
Claims (20)
1. A composition having a porous micro-structure of interpenetrating matrices, comprising:
(a) a polytetrafluoroethylene polymer network characterized by nodes interconnected by fibrils, and (b) a second polymer network comprising diorganosiloxy units, wherein the weight ratio of component (b) to component (a) is from 1:100 to about 20:80.
(a) a polytetrafluoroethylene polymer network characterized by nodes interconnected by fibrils, and (b) a second polymer network comprising diorganosiloxy units, wherein the weight ratio of component (b) to component (a) is from 1:100 to about 20:80.
2. A composition as in claim 1 wherein components (b) is formed from an addition curable silicone composition comprising (1) a polydiorgano-siloxane having alkenyl unsaturation, (2) an organo-hydrogenpolysiloxane crosslinking agent, and (3) a catalyst for promoting crosslinking of (1) and (2).
3. A composition as in claim 2, wherein the viscosity of the polydiorganosiloxane having alkenyl unsaturation is less than 100,000,000 centipoise at 25°C.
4. A composition as in claim 2, wherein the viscosity of the polydiorganosiloxane having alkenyl unsaturation is from about 500 centipoise to about 50,000 centipoise at 25°C.
5. A composition as in claim 2, wherein the viscosity of the polydiorganosiloxane having alkenyl unsaturation is from about 3000 centipoise to about 6000 centipoise at 25°C.
6. A composition as in claim 3, wherein the organohydrogenpolysiloxane has a viscosity of from about 25 centipoise to about 10,000 centipoise at 25°C..
7. A composition as in claim 4, wherein the organohydrogenpolysiloxane has a viscosity of from about 100 centipoise to about 1000 centipoise at 25°C.
8. A composition as in claim 7, wherein the organohydrogenpolysiloxane is substantially linear.
9. A composition as in claim 7, wherein the organohydrogenpolysiloxane is a resin.
10. A composition as in claim 6, wherein the curing catalyst is a platinum containing complex.
11. A composition as in claim 10, further comprising a reinforcing organopolysiloxane resin.
12. A composition as in claim 11, wherein the reinforcing organopolysiloxane resin has vinyl unsaturation on monofunctional siloxane units, difunctional siloxane units, or both.
13. A composition as in claim 6, further comprising a filler.
14. A composition as in claim 13, wherein the filler is fumed silica.
15. A composition as in claim 6, further comprising a cure inhibitor.
16. A composition as in claim 15, wherein the cure inhibitor is a maleate or fumarate functional silane or polysiloxane.
17. A composition as in claim 1 wherein component (b) is formed from a condensation curable silicone composition.
18. A composition having a porous microstructure of interpenetrating matrices, comprising:
(a) a first polymer network characterized by nodes interconnected by fibrils comprising polytetrafluoroethylene, and (b) a second polymer network comprising polydiorganosiloxane, wherein the weight ratio of component (b) to component (a) is from 1:100 to about 7:93.
(a) a first polymer network characterized by nodes interconnected by fibrils comprising polytetrafluoroethylene, and (b) a second polymer network comprising polydiorganosiloxane, wherein the weight ratio of component (b) to component (a) is from 1:100 to about 7:93.
19. A composition as in claim 18, wherein the polydiorganosiloxane is formed from an addition curable silicone composition.
20. A composition as in claim 18, wherein the polydiorganosiloxane is formed from a condensation curable silicone composition.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US79757585A | 1985-11-13 | 1985-11-13 | |
| US797,575 | 1985-11-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1283492C true CA1283492C (en) | 1991-04-23 |
Family
ID=25171222
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000521375A Expired - Fee Related CA1283492C (en) | 1985-11-13 | 1986-10-24 | Interpenetrating polymeric networks comprising polytetrafluoroethylene and polysiloxane |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1283492C (en) |
| WO (1) | WO1987002996A1 (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4849469A (en) * | 1985-02-28 | 1989-07-18 | Ici Americas Inc. | Void control in thermoplastics containing silicone interpenetrating polymer networks |
| JPS6341544A (en) * | 1986-08-04 | 1988-02-22 | バクスター・インターナショナル・インコーポレイテッド | Porous highly expansible fluoropolymers and production thereof |
| US4945125A (en) * | 1987-01-05 | 1990-07-31 | Tetratec Corporation | Process of producing a fibrillated semi-interpenetrating polymer network of polytetrafluoroethylene and silicone elastomer and shaped products thereof |
| JPH07116325B2 (en) * | 1987-02-16 | 1995-12-13 | 日本合成ゴム株式会社 | Rubber composition, crosslinkable rubber composition, oil seal and rubber hose |
| US5506289A (en) * | 1993-07-23 | 1996-04-09 | Gen Electric | Liquid injection molding inhibitors for curable compositions |
| US6451396B1 (en) | 1998-02-13 | 2002-09-17 | Gore Enterprise Holdings, Inc. | Flexure endurant composite elastomer compositions |
| US6770086B1 (en) * | 2000-11-02 | 2004-08-03 | Scimed Life Systems, Inc. | Stent covering formed of porous polytetraflouroethylene |
| US6447918B1 (en) * | 2001-01-30 | 2002-09-10 | Xerox Corporation | Interpenetrating polymer network of polytetra fluoroethylene and silicone elastomer for use in electrophotographic fusing applications |
| WO2008080829A1 (en) * | 2006-12-22 | 2008-07-10 | Bluestar Silicones France | Reinforced silicone elastomer |
| FR2910476A1 (en) * | 2006-12-22 | 2008-06-27 | Rhodia Recherches & Tech | Article, useful for cooling-, oil- and/or hot air- circuits, comprises reinforced silicone elastomer obtained by hardening and/or crosslinking organopolysiloxane composition crosslinkable into elastomer comprising reinforcement |
| CN103937134B (en) * | 2014-04-15 | 2016-04-13 | 东莞市方康电子科技有限公司 | Tetrafluoro emulsion compositions, waterproof ventilated membrane and preparation method thereof |
| CN107880557B (en) * | 2017-12-25 | 2021-02-23 | 广东标美硅氟新材料有限公司 | High-expansion-ratio silicone rubber cold-shrink tube and preparation method and application thereof |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2927908A (en) * | 1960-03-08 | Fluorinated organopolysiloxane rub- | ||
| BE527843A (en) * | 1953-04-03 | |||
| US2934515A (en) * | 1957-07-01 | 1960-04-26 | Dow Corning | Polytetrafluoroethylene-silicone compositions |
| US3207825A (en) * | 1961-07-20 | 1965-09-21 | Gen Electric | Process for extruding polytetrafluoroethylene-silicone rubber composition |
| SE392582B (en) * | 1970-05-21 | 1977-04-04 | Gore & Ass | PROCEDURE FOR THE PREPARATION OF A POROST MATERIAL, BY EXPANDING AND STRETCHING A TETRAFLUORETENE POLYMER PREPARED IN AN PASTE-FORMING EXTENSION PROCEDURE |
| US3962153A (en) * | 1970-05-21 | 1976-06-08 | W. L. Gore & Associates, Inc. | Very highly stretched polytetrafluoroethylene and process therefor |
| US4096227A (en) * | 1973-07-03 | 1978-06-20 | W. L. Gore & Associates, Inc. | Process for producing filled porous PTFE products |
| US3865897A (en) * | 1973-08-03 | 1975-02-11 | Dow Corning | Method of blending polyolefins and polydiorganosiloxane gums and blends thereof |
| US4010136A (en) * | 1975-06-30 | 1977-03-01 | Dow Corning Corporation | Low durometer siloxane elastomers containing polytetrafluoroethylene powder |
| US4347204A (en) * | 1978-12-19 | 1982-08-31 | Olympus Optical Co., Ltd. | Flexible tube and method of manufacturing same |
| US4478665A (en) * | 1980-11-06 | 1984-10-23 | W. L. Gore & Associates, Inc. | Method for manufacturing highly porous, high strength PTFE articles |
| US4336364A (en) * | 1981-07-20 | 1982-06-22 | Dow Corning Corporation | Method of producing organosilicon composition with in situ produced cure inhibitor |
| US4544692A (en) * | 1983-08-29 | 1985-10-01 | Material Sciences Corporation | Polysiloxane and fluorocarbon coating composition |
-
1986
- 1986-10-24 CA CA000521375A patent/CA1283492C/en not_active Expired - Fee Related
- 1986-11-13 WO PCT/US1986/002405 patent/WO1987002996A1/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| WO1987002996A1 (en) | 1987-05-21 |
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