Classifications

• • 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
• • 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

Definitions

• Perfluoroelastomers such as those described hi U.S. Patents 3,682,872, 4,281,092, 4,487,903 and 4,983,697 have properties- that make them attractive for use under unusually severe conditions. These materials are suitable for applications requiring the characteristics of an elastomer and at the same time tolerance for exposure to high temperatures or to aggressive chemicals.
• the mechanical properties of perfluoroelastomers, in common with other elastomers, are conventionally adjusted by varying the ratios of perfluoromonomers in the polymers, by varying the amount of carbon black and other compound ingredients, and by varying the curing, or vulcanizing, chemistry. Certain uses, however, require combinations of properties not attainable by known means. One particularly desirable improvement would be the increase of tensile strength and modulus without sacrifice of compression set.
• the present invention provides cured perfluoroelastomers which exhibit enhanced mechanical properties through the incorporation into the compound of a fluoropolymer modified with a monomer containing a hydroxyl group.
• the instant invention provides a polymer blend comprising, complementally, (a) at least one perfluoroelastomer of tetrafluoroethylene, perfluoroalkyl perfluoro(vinyl ether) and at least one cure site moiety, and
• CF 2 CF[OCF 2 CF(CF 3 )] n (0) p (CF 2 ) m CH 2 OH wherein p is 0 or 1; m is 0 to 10 and n is 0 to 20; and provided that when m is 0, p is 0; and when m is greater than 0, p is 1; and further provided that at least one of n and m is at least 1.
• Perfluoroelastomers used in the present invention are prepared from tetrafluoroethylene, perfluoroalkyl perfluoro(vinyl ether) and at least one cure site moiety.
• minor portions of the tetrafluoroethylene can be replaced by other perhaloolefins, such as chlorotrifluoroethylene.
• Perfluoro(alkyl vinyl ethers) preferred for use in the present invention include perfluoro(methyl vinyl ether) (PMVE) and perfluoro(propyl vinyl ether) (PPVE). Small concentrations of monomers which are not perfluorinated can also be used without significantly changing the desirable characteristics of these perfluoroelastomers.
• Such monomers are incorporated as cure site moieties to obtain desirable crosslin ng characteristics and may be present in concentrations up to about 3 moI%.
• Such monomers can include, for example, bromotetrafluorobutene, bromotrifluoroethylene, and monomers containing cyano groups.
• chain transfer agents which are not perfluorinated can be used in the polymerization reaction to introduce desirable fragments into the polymer for curing purposes, and are considered cure site moieties or monomers in the context of the present invention.
• Such agents include di-iodo compounds that result in bound iodine in the polymer, commonly at the end of the molecule.
• Representative perfluoroelastomers are illustrated in U.S. Patents 3,467,638, 4,281,092, 4,487,903, 4,529,784, 4,948,853 and 4,983,697, each of which is hereby incorporated by reference.
• CF 2 CFOCF 2 CF(CF 3 )OCF 2 CF 2 -CH 2 OH (EVE-OH).
• the fluoropolymers used in this invention contain at least one other fluoromonomer.
• These fluoromonomers include fluoroolefins and fluoro(vinyl ethers).
• Preferred fluoromonomers include TFE, hexafluoropropylene (HFP), PPVE, and PMVE.
• Monomers that do not contain fluorine, such as ethylene (E), can be used in conjunction with a fluorinated monomer.
• Partially fluorinated monomers such as perfluorobutyl ethylene (PFBE) can also be used.
• One illustrative combination with a hydroxy-containing monomer is E/TFE/PFBE.
• Preferred combinations with the hydroxy-containing monomer include TFE alone, TFE/HFP, TFE/PPVE, and TFE/PMVE. These polymers can be prepared by conventional copolymerization techniques.
• the hydroxy-containing fluoropolymers can be either partially- crystalline and classified as fluoroplastics or non-crystalline and classified as fluoroelastomers, depending on the monomers chosen and their proportions, as known to those skilled in the art. If the hydroxy-modified fluoropolymers are elastomeric, they may also contain cure site monomers or fragments with desirable curing characteristics derived from chain transfer agents in polymerization, as discussed above.
• the units in the fluoropolymer derived from hydroxy- containing monomer will constitute about 0.2-20 mol% of the modified fluoropolymer. If the fluoropolymer is a fluoroplastic, the units derived from the hydroxy-containing monomer will constitute about 3-20 mol% and preferably about 5-15 mol% of the hydroxy-modified fluoropolymer. If the fluoropolymer is a fluoroelastomer, the units derived from the hydroxy- containing monomer will constitute about 0.2-10 mol% and preferably about 0.5-5 mol% of the hydros-containing fluoropolymer.
• the amount of hydroxy-containing fluoropolymer used in the present polymer blends is about from 2 to 20 parts by weight, per 100 parts by weight of the polymer blend.
• the hydroxy-modified fluoropolymer will be about from 5 to 15 parts by weight of the blend.
• the blending of the polymeric components of the present invention and compounding of the blends with other components of the compounds can be carried out by conventional blending and compounding techniques.
• the blends of the present invention are typically compounded with one or more of the additives known to be useful in perfluoropolymer compositions, such as pigments, fillers, pore-forming agents and plasticizers. It is particularly advantageous to add carbon black to the fluoroelastomer to increase its modulus.
• tetraphenyltin is customarily used. In the blends of the present invention, it has been found that, with these cure site monomers, triphenyltin hydride is particularly effective.
• blends of the present invention through the incorporation of the hydros-containing fluoropolymer, exhibit significantly increased tensile strength and modulus, without sacrifice of other desirable elastomeric characteristics, such as compression set.
• a 2-liter reactor was purged with nitrogen, and then charged with 1250 ml of deionized water, 50 ml of l,l,2-trichIoro-l,2,2-trifl ⁇ oroethane (CFC-113), and 50 ml of 4% aqueous ammonium persulfate initiator solution.
• TFE 60 g
• the polymer was a partially crystalline fluoroplastic with a melting point of 279°C as determined by differential scanning calorimetry (DSC).
• Polymer B
• a modified perfluoroelastomer was made in a well-stirred 5.4- liter reactor by continuous emulsion polymerization at 70°C. Two aqueous solutions were fed to the reactor. The first solution was fed at the composition rate of 120 ml/hr of water, 1.92 g/hr of ammonium persulfate, 1.3 g/hr of disodium hydrogen phosphate heptahydrate, and 1.4 g/hr of ammonium perfluorooctanoate ("Fluorad" FC-143 from 3M Co.).
• the second solution was fed at the composition rate of 150 ml/hr of water, 1.6 g/hr of sodium sulfite, and 1.7 g/hr of FC-143.
• TFE, perfluoro (methyl vinyl ether) (PMVE) and EVE-OH monomers were fed simultaneously at the rates of 62 g/hr for TFE, 76 g/hr for PMVE, and 2.34 ml/hr for EVE-OH.
• the polymer was isolated by coagulation with magnesium sulfate aqueous solution, then washed and dried in an oven at 80°C for 48 hr.
• Tg glass transition temperature
• compounds of perfluoroelastomer and hydroxy-modified fluoropolymer with other ingredients specified were prepared on a standard two-roll rubber mill with the rolls heated to about 90°C. Ingredients were weighed out, premixed, and then milled for 20-30 minutes.
• the compounded blends were converted to a form suitable for physical testing by compression molding into sheet 15 cm square and 1.9 mm thick. Unless otherwise specified, the sheet was press-cured at 210°C for 10 minutes, and then post-cured in a circulating air oven at 90°C for 6 hr followed by a uniform transition to 305°C over 10 hr and in turn followed by 26 hr at 305°C. Specimens for physical testing were die-cut from the sheet as called for by the test methods summarized in Table 1.
• Polymer A was compounded with a fluoroelastomer identified as Polymer D and other ingredients listed in Table 2.
• Polymer D was a TFE/PMVE/8-CNVE perfluoroelastomer prepared according to the general procedures described in U.S. Patent 4,281,092.
• 8-CNVE is the cure site monomer perfluoro-(8-cyano-5-methyl-3,6-dioxa-l-octene),The compound was molded and tested according to the procedures described above, and the results are summarized in Table 2.
• Table 2 the incorporation of Polymer A in the blend enhanced modulus with modest sacrifice of compression set and tensile strength, a desirable combination of properties.
• Examples 3-8 and Control B Polymer B was compounded with Polymer D and other ingredients as listed in Table 3, using the same procedures as in Examples 1- 2. The compounds were tested as before, and the results are similarly summarized in Table 3.
• Polymer B and Polymer D were compounded with other ingredients including two different curing accelerators as listed in Table 4. While both accelerators in conjunction with Polymer B show enhanced modulus and hardness with little or no sacrifice of compression set and little loss of elongation, the data show triphenyltin hydride to be superior in preserving low compression set. Control Examples D-E
• Polymer D was blended with a commercial non-melt- fabricable TFE polymer (PTFE) of the type known as fine powder, available as Teflon ® TFE fluorocarbon resin grade 6C (Du Pont Co.), and other ingredients as listed in Table 5.
• PTFE non-melt- fabricable TFE polymer
• Teflon ® TFE fluorocarbon resin grade 6C Du Pont Co.
• Polymer C was blended with Polymer E and other ingredients as listed in Table 6.
• Polymer E prepared generally as described in U.S. Patent 3,467,638, was an elastomeric copolymer of TFE and PMVE with 5- pentafluorophenos-perfluoro-(5-methyl-3-oxa-l-pentene) as a cure site monomer.
• the molded sheet was press-cured at 190°C for 30 minutes, then post-cured in a circulating air oven first at 90°C for 6 hr followed by a 10-hr transition to 288°C and finally at 288°C for 26 hr.
• the test results in Table 6 show that addition of the hydroxy-modified fluoroelastomer enhanced mechanical properties without sacrifice of compression set. Examples 15-18 and Control G
• Polymer C was blended with Polymer F and other ingredients as listed in Table 7.
• Polymer F was a copolymer of TFE, PMVE, and BTFB in which BTFB is cure site monomer 4-bromo-3,3,4,4-tetrafluorobutene.
• Perfluoroelastomers of this type and their preparation are described in U.S. Patent 4,035,565.
• the sheet was press-cured at 170°C for 10 minutes, then post-cured in a circulating air oven at 90°C for 2 hr followed by a 6-hr transition to 250°C and finally at 250°C for 18 hr.
• the test results in Table 7 show enhancements of modulus and tensile strength with little change of hardness and modest loss of elongation. Three of the samples exhibit favorable reductions in compression set.

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• Organic Chemistry (AREA)
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• 1993
  • 1993-05-07 EP EP93911181A patent/EP0639208A1/de not_active Withdrawn
  • 1993-05-07 WO PCT/US1993/004380 patent/WO1993022379A1/en not_active Ceased
  • 1993-05-07 JP JP5519651A patent/JPH07506602A/ja active Pending

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