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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
  • C08K5/0025—Crosslinking or vulcanising agents; including accelerators
• • 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
  • C08L83/08—Polysiloxanes containing silicon bound to organic groups containing atoms other than carbon, hydrogen and oxygen

Definitions

• This invention relates to curable compositions of fluoroelastomers containing at least one process aid, more particularly to polyhydroxy curable fluoroelastomer compositions containing at least one aminosilicone process aid,
• Fluoroelastomers are well known in the art. Many are copolymers of vinylidene fluoride (VF 2 ) with at least one other fluorinated comonomer such as hexafluoropropylene (HFP), tetrafluoroethylene (TFE), or a perfluoro(alkyi vinyl ether). Other fluoroelastomers include copolymers of tetrafiuoroethylene with a hydrocarbon olefin such as ethylene or propylene and copolymers of tetraftuoroethylene with a perfluoro(alkyl vinyl ether).
• Fluoroelastomeric compositions can be molded into articles having excellent resistance to aggressive chemicals and high temperatures. They have the disadvantage, however, that compared with other heat resistant elastomers such as silicones, fluoroelastomeric compositions demonstrate relatively poor processability in terms of ease of mixing, ease of molding / demoiding and flow during injection molding processes, To provide better processability, processing aids are usually added to fluoroelastomeric compositions. Commonly used processing aids migrate to the surface during processing and it is generally believed that the processing advantage is provided at the interface between the fluoroelastomeric composition and the metai surfaces of the process equipment, e.g., the mill rolls, extruder screw and barrei, or mold cavities and runners.
• processing aids provide processing advantages in the short term, they eventually result in a deposit at the mold surface which is usually termed mould fouling and eventually causes processing difficulties.
• the surface deposit promotes adhesion between molded components and the mold surface and impairs demolding. It also results in surface defects on molded components such as knit lines. The only remedy is to clean the moid surface at regular intervals which results in a loss of productivity.
• These processing aids can also interfere with bonding performance, in the case of components having meta! bonded inserts, and interfere with the physical properties of molded components, e.g. resulting in increased compression set resistance and lower heat resistance.
• processing aids include hydrocarbon waxes, natural vegetable waxes, fatty acid esters, mono-functional hydrocarbon amines (e.g., octadecyl amine), organosilicones, and long chain alcohols.
• ft is an object of the present invention to provide a curable fluoroelastomer composition having various advantages to prior art compositions, including: - improved compound mixing due to improved mill release (in the case of mill mixing) or rotor release (in the case of internal mixing); - improved processing during molding (injection or compression) defined by an easier flow in the mold, a better mold release (less tendency to stick in the moid), a lower level of mold fouling and hence a reduced frequency of mold cleaning; and - improvement in the physical properties of cured and postcured compositions, e.g, lower compression set.
• an aspect of the present invention is a polyhydroxy curable fluoroeiastomer composition comprising:
• the present invention is directed to polyhydroxy curable fluoroeiastomer compositions that process well (i.e. mix wel! and mold well) while maintaining good physical properties in molded articles made therefrom.
• Fluoroelastomers that are suitable for use in this invention are those that are polyhydroxy curable.
• polyhydroxy curabie is meant fluoroelastomers which are known to crosslink with polyhydroxy curatives such as bisphenol AF.
• Such fluoroelastomers include those having a plurality of carbon-carbon double bonds along the main elastomer polymer chain and also fluoroelastomers which contain sites that may be readily dehydrofluorinated.
• fluoroelastomers include, but are not limited to those which contain adjacent copolymerized units of vinylidene fluoride (VF 2 ) and hexafluoropropylene (HFP) as well as fluoroelastomers which contain adjacent copolymerized units of VF 2 (or tetrafluoroethylene) and a fluorinated comonomer having an acidic hydrogen atom such as 2- hydropentafluoropropylene; 1-hydropentafluoropropylene; trifluoroethylene; 2,3,3,3-tetrafluoroprope ⁇ e; or 3,3,3-trifluoropropene.
• VF 2 vinylidene fluoride
• HFP hexafluoropropylene
• fluoroelastomers which contain adjacent copolymerized units of VF 2 (or tetrafluoroethylene) and a fluorinated comonomer having an acidic hydrogen atom such as 2- hydropentafluoro
• Preferred fluoroelastomers include the copolymers of i) vinylidene fluoride with hexafluoropropylene and, optionally, tetrafluoroethylene (TFE); ii) vinylidene fluoride with a perfluoro(alkyl vinyl ether) such as perfluoro(methyl vinyl ether), 2-hydropentafluoroethylene and optionally, tetrafluoroethylene; iii) tetrafluoroethylene with propylene and 3,3,3- trifluoropropene; and iv) ethylene with tetrafluoroethylene, perfiuoro(methy! vinyl ether) and 3,3,3-trifluoropropylen ⁇ .
• TFE tetrafluoroethylene
• Fluoroelastomers employed in this invention may also, optionally, comprise bromine, iodine or nitrile cure sites, Curable compositions of the invention contain 0.05 to 10 (preferably
• Suitable aminosiiicone fluid process aids that may be employed in this invention are fluids at room temperature, i.e. at 20 0 C, and contain only a single primary amine per poiysiloxane molecule. It is believed that the primary amine group on the process aid reacts with the fiuoroelastomer (during processing or during polyhydroxy curing) so that the process aid becomes grafted to the fluoroelastomer.
• Each aminosiiicone polymer chain may contain only a single primary amine group so that the process aid cannot crosslink the fluoroelastomer. Were the process aid to crosslink the fluoroelastomer, gelation would occur, increasing bulk viscosity, and thus degrading processability.
• the aminosiiicone may, optionally, contain one or more secondary or tertiary amine groups. The latter react more slowly with fluoroelastomer than do primary amines, so that crossiinking and gelation is not an issue.
• the aminosiiicone fluids employed in the invention do not contain silane or alkoxysilane functionality so that the silicone itself does not crosslink.
• the number average molecular weight (Mn), in Daltons, of the mono-functional aminosiiicone is in the range of 500 to 50,000, more preferably in the range of 1000 to 10000.
• Specific examples of aminosi ⁇ cones that.mav,be employed in the compositions of the invention include, b-ut are not limited to
• the curable compositions of the invention contain 0.1 to 20 parts by weight ⁇ preferably 1-5 parts) of polyhydroxy crosslinking agent (including derivatives thereof and salts) per 100 parts fiuoroelastomer.
• polyhydroxy cross-linking agents include di-, tri-, and tetrahydroxybenzenes, naphthalenes, and anthracenes, and bisphenols of the formula
• A is a difunctional aliphatic, cycloaliphatic, or aromatic radical of 1- 13 carbon atoms, or a thio, oxy, carbonyl, sulfinyl, or ⁇ ulfonyl radical; A may optionally be substituted with at least one chlorine or fluorine atom; x is 0 or 1 ; n is 1 or 2; and any aromatic ring of the polyhydroxyiic compound may optionally be substituted with at least one chlorine or fluorine atom, an amino group, a -CHO group, or a carboxyl or acyi radical.
• Preferred polyhydroxy compounds include hexaf!uoroisopropylidene-bis(4-hydroxy-benzene) (i.e.
• bisphenoi AF or "BPAF”
• 4,4 ' -isopropylidene diphenol i.e. "bisphenoi A”
• 4,4 ' - dihydroxydiphenyl suifone 4,4 ' - dihydroxydiphenyl suifone
• 3,3'-diaminobisphenol AF 4,4 ' -isopropylidene diphenol
• A when A is alkylene, it can be for example methylene, ethylene, chloroethylene, fluoroethylene, difluoroethylene, propylidene, isopropylidene, tributylidene, heptachlorobutylidene, hepta- fluorob ⁇ tylidene, pentylidene, hexylidene, and 1 ,1-cyclohexylidene.
• A When A is a cycloalkylene radical, it can be for example 1 ,4-cyciohexylene, 2- chloro-1 ,4-cyclohexylene, cyclopentylene, or 2-fluoro-1 ,4-cyclohexylene. Further, A can be an arylene radical such as m-phenylene, p-phenylene, o-phenylene, methylphenyiene, dimethylphenylene, 1 ,4-naphthylene, 3- fluoro-1 ,4-naphthylene, and 2,6-naphthylene. Polyhydroxyphenols of the formula
• R is H or an alkyl group having 1-4 carbon atoms or an aryl group containing 6-10 carbon atoms and R ' is an alkyl group containing 1-4 carbon atoms also act as effective crossiinking agents.
• examples of such compounds include hydroquinone, catechol, resorcinol, 2- methylresorcinol, 5-methyl-resorcinol, 2-methyihydroquinone, 2,5- dimethylhydroquinone, 2-t-butyl-hydroquinone, 2,4- dihydroxybenzophenone; and such compounds as 1 ,5- dihydroxynaphthalene and 2,6-dihydroxynaphthalene,
• Additional polyhydroxy curing agents include alkali metal salts of bisphenol anions, quaternary ammonium salts of bisphenol anions, tertiary sulfonium salts of bisphenol anions and quaternary phosphonium saits of bisphenol anions, e.g. the salts of bispheno! A and bisphenol AF.
• Specific examples include the disodium salt of bisphenol AF, the dipotassium salt of bisphenol AF 1 the monosodium monopotassium salt of bispheno! AF and the benzyltriphenylphosphonium salt of bisphenol AF.
• Quaternary ammonium and phosphonium salts of bisphenol anions are discussed in U.S. Patents 4,957,975 and 5,648,429.
• derivatized polyhydroxy compounds such as mono- or diesters, and trimethylsilyl ethers are useful crosslinking agents.
• examples of such compositions include, but are not limited to resorcinol monobenzoate, the diacetate of bisphenol AF, the diacetate of sulfonyl diphenol, and the diacetate of hydroquinone.
• the curable compositions of the invention also contain between 0.5 to 30 parts by weight (preferably 0.7 to 10 parts) of an acid acceptor per 100 parts fluoroelastomer.
• the acid acceptor is typically a strong organic base such as Proton Sponge® (available from Aidrich) or an oxirane, or an inorganic base such as a metal oxide, metal hydroxide, or a mixture of 2 or more of the latter.
• Metal oxides or hydroxides which are useful acid acceptors include calcium hydroxide, magnesium oxide, lead oxide, zinc oxide and calcium oxide. Calcium hydroxide and magnesium oxide are preferred.
• Curable compositions of the invention contain 0.1 to 10 (preferably 0.5 to 3) parts by weight per 100 parts fluoroelastomer of a vulcanization (or "cure") accelerator.
• a vulcanization (or "cure") accelerator include tertiary suifonium salts such as [(C e H 5 ) 2 S + (C 6 H 13 )][Ci] " , and [(C 6 Hi 3 ) 2 S(C 6 H 5 )] + [CH 3 CO 2 ]- and quaternary ammonium, phosphonium, and stibonium salts of the formula RSR ⁇ R Z R ⁇ Y* X " .
• Y is phosphorous, nitrogen, or antimony
• R 5 , R 6 , R 7 , and Re are individually C1-C2 0 alkyi, aryl, aralkyl, aikenyl, and the chlorine, fluorine, bromine, cyano, -OR, and -COOR substitute
• benzyltri-phenyiphospho ⁇ ium chloride benzyltriphenylphosphonium bromide, tetrabutylammonium hydrogen sulfate, tetrabutylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium bromide, tributylallylphosphonium chloride, iributyl-2- methoxypropylphosphonium chloride, 1 1 8-diazabicyc
• methyltrioctylammonium chloride methyltributylammonium chloride, tetrapropylammonium chloride, benzyltrioctyjphosphonium bromide, benzyltrioctylphosphonium chloride, methyltrioctylphosphonium acetate, tetraoctylphosphonium bromide, methyitriphenylarsonium tetrafiuoroborate, tetraphenylstibonium bromide, 4-chlorobenzyitriphenyl phosphonium chioride, 8-benzyl ⁇ 1 ,8- diazabicyclo(5.4,0)-7-undecenonium chloride, diphenylmethyltriphenylphosphonium chloride, aliyltriphenyl-phosphonium chioride, tetrabutyiphosphonium bromide, m-trifluoromethyl- benzyltri
• compositions of the invention may be made by blending the ingredients on a two-roll mill, an interna! mixer such as Banbury® mixer, or other conventional equipment used for mixing elastomer compounds,
• the polyhydroxy curable fluoroelastomer compositions of this invention have utility in end uses such as injection, compression, or transfer molded seals, o-rings, and gaskets, extruded tubing and hoses, extruded wire coatings, coatings applied by solvent or flame spray processes, and others.
• Example 1 in this example the tendency of several silicone fluid process aids to crosslink a fluoroelastomer, in the absence of a polyhydroxy curative, was determined by measuring Mooney Scorch, according to the Test method.
• Compounds containing the ingredients listed in Table I were made by blending the ingredients in a Brabender® mixing bowl fitted with cam rotors, operating at 30 rpm with a temperature setpoint of 8O 0 C. Results of the Mooney Scorch tests are also shown in Table I.
• Samples 1 and 2 containing aminosilicones having only one primary amine per polysiloxane molecule, show iittle or no tendency to scorch as indicated by the small difference, or "delta" (0 to 0.2 Mooney units) between the final Mooney after 30 minutes at 149°C and the minimum Mooney value recorded. These Mooney viscosity deltas are essentially the same as those of Control 1 and Control 5, which do not contain any primary amine groups. Thus, the single primary amine per polysiloxane molecule in aminosilicones GP-342 and GP-956 do not cause any crosslinking of the fluoroelastomer. Controls containing aminosilicones having more than one primary amine per polysiloxane molecule all exhibit a Mooney viscosity delta ranging from 1.2 up to 18 units, indicating crosslinking of the fluoroelastomer. O
• 1 phr is parts weight per hundred parts rubber (i.e. fluoroelastomer)
• compositions of the invention containing various amounts of aminosilicone process aid were compared to that of control compositions, absent process aid or containing octadecyl amine process aid.
• Compositions were made by blending the ingredients on a two-roll mill.
• the fluoroelastomer employed in this example was a 60/40 weight ratio copolymer of vinylidene fluoride and hexafluoropropylene having a ML (1 +10) @ 121 a C of 34.
• Compositions (phr), Mooney Scorch data (MS 1+30, 149°C) and compression set of O-rings are shown in Table II, O- rings were press cured at 177°C for 10 minutes and then post cured at 232 0 C for the times indicated in the Table. Compression set testing was conducted using conditions of 200 0 C for 70 hours, 25% compression. The values reported are an average of three specimens. Compression set values of the cured compositions of the invention (Samples 2-4) were comparable to that of Control 9 that did not contain process aid. However, compression set of Control 10 (containing the octadecylamine process aid) was significantly worse (i.e. higher) than that of the cured compositions of the invention. Mooney Scorch data indicates that no premature crosslinking occurred in the samples of the invention (i.e. Sample 4 containing 1 phr aminosilicone had essentially the same final viscosity as Control 9, not containing a process aid).
• injection molding of a curable composition of the invention was conducted on a MIR molding machine having temperature setpoints of 9O 0 C (barrel) and 190 0 C (die). Injection pressure was maintained at a constant 100 bar.
• the moid was a 40 cavity, chrome plated D-214 o-ring mold,
• the curable composition (Sample 5) was made by blending the fluoroelastomers and VC50 in a Banbury mixer operating at 50 rpm, dropped at 13O 0 C.
• the bases, carbon black, and aminosiiicone were then added on a two-roll mill.
• the ingredients and results are shown in Table III.

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• 2009
  • 2009-05-28 US US12/473,414 patent/US7989547B2/en not_active Expired - Fee Related
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