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Fluoroelastomer compositionsRelated Patent Categories: Synthetic Resins Or Natural Rubbers -- Part Of The Class 520 Series, Natural Rubber Compositions Having Nonreactive Materials (dnrm) Other Than: Carbon, Silicon Dioxide, Glass Titanium Dioxide, Water, Hydrocarbon, Halohydrocarbon, Ethylenically Unsaturated Reactant Admixed With A Preformed Reaction Product Derived From: (a) At Least One Polycarboxylic Acid, Ester, Or Anhydride; (b) At Least One Polyhydroxy Compound; And (c) At Least One Fatty Acid Glycerol Ester, Or A Fatty Acid Or Salt Derived From A Naturally Occurring Glyceride, Tall Oil, Or A Tall Oil Fatty Acid, At Least One Solid Polymer Derived From Ethylenic Reactants Only, Polymer Mixture Of Two Or More Solid Polymers Derived From Ethylenically Unsaturated Reactants Only; Or Mixtures Of Said Polymer Mixture With A Chemical Treating Agent; Or Products Or Processes Of Preparing Any Of The Above Mixtures, Solid Polymer Derived From Fluorine-containing Ethylenic ReactantFluoroelastomer compositions description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060189760, Fluoroelastomer compositions. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application is a continuation of U.S. patent application Ser. No. 10/843,440 filed on May 12, 2004, which is a continuation of U.S. application Ser. No. 10/118,066, filed on Apr. 4, 2002, which is a continuation of U.S. application Ser. No. 09/511,949 filed on Feb. 23, 2000, all of which are incorporated by reference herein. [0002] The present invention relates to fluoropolymers essentially formed by a mixture of a fluoroelastomer and a semicrystalline fluoropolymer usable for sealing manufactured articles in the electronic, optical and pharmaceutical industry. [0003] More specifically the present invention relates to fluoropolymers formed by a mixture of a fluoroelastomer and a semicrystalline fluoropolymer, characterized by improved mechanical properties combined with good properties of elastic retention (lower compression set) and very good surface appearance without roughness. It is well known that one of the fluoroelastomer uses is the preparation of O-rings for seals: for this application it is essential that the O-ring surface is smooth. [0004] The use of fluoroelastomers containing polytetrafluoroethylene (PTFE) particles to improve the properties of abrasion-resistance and of hot tearing the obtained manufactured articles is known in the prior art. As described in Japanese patent 57-107,336, the fluoroelastomer abrasion-resistance is improved by physically mixing solid curable fluoroelastomers with PTFE powders having a low molecular weight, in the range 500-200,000 as average molecular weight by number (M.sub.n). Said PTFE is prepared by thermal decomposition at a temperature between 450.degree. C. and 600.degree. C. for prolonged times or by irradiation with ionic radiation of high molecular weight PTFE. An alternative method for obtaining PTFE having a low molecular weight is that to polymerize TFE in the presence of chain transfer agents. The fluoroelastomer and the PTFE powders are mixed in Banbury or in calender. [0005] In U.S. Pat. No. 4,879,362 and U.S. Pat. No. 4,904,726 mixtures of fluoroelastomers with resins of PTFE modified with the addition of comonomers such as hexafluoropropene (HFP), perfluoropropylvinylether (PPVE), etc., are used, in order to avoid PTFE fibrillation problems without losing the reinforcement properties that the PTFE gives to the obtained fluoroelastomers. The comonomer results much more present on the polymeric particle surface, so as to allow an uniform distribution in the fluoroelastomer without the formation of visible agglomerates. The latter should be the cause of fibrillation phenomena. [0006] In EP 708,797 fluoroelastomer compositions formed by a fluoroelastomer and by a semicrystalline fluorinated filler in the form of micropowder which are obtained in curing compounds not containing metal species, are described. Said compositions give a low release of metal species under conditions where an high purity is required, but they show poor mechanical properties. Tests carried out by the Applicant (see the comparative Examples), have shown that the surface of the manufactured articles obtained from said fluoroelastomer compositions shows roughness. It is well known that in the O-ring preparation, typical fluoroelastomer application, surfaces having a low roughness in order to obtain good sealing properties, are required. The semicrystalline fluorinated filler is based on PTFE or PTFE modified with a comonomer and obtained by emulsion or suspension polymerization. The high molecular weight PTFE is subjected to irradiation, as above said, in order to reduce the molecular weight. This makes easier the PTFE milling produced by a suspension process; it eliminates the fibrillation and reduces the PTFE agglomeration obtained by an emulsion process. [0007] The need was felt to have available fluoroelastomer compositions comprising a semicrystalline fluorinated filler having improved properties compared with those of the prior art and specifically with the following property combination: [0008] improved mechanical properties [0009] good elastic retention properties (lower compression set-very good seal) [0010] very good surface appearance roughness free. [0011] The Applicant has unexpectedly and surprisingly found that it is possible to obtain the combination of the above mentioned properties, by incorporating in the fluoroelastomer matrix PTFE particles or its copolymers having well defined sizes as specified hereinafter. [0012] It is therefore an object of the present invention fluoropolymers comprising a fluoroelastomer matrix incorporating therein particles of a semicrystalline fluoropolymer latex formed by tetrafluoroethylene (TFE) homopolymers, or TFE copolymers with one or more monomers containing at least one ethylene unsaturation in amounts ranging from 0.01% to 10% by moles, preferably from 0.05% to 5% by moles, wherein the average particle sizes of the semicrystalline fluoropolymer latex range from 10 to 100 nm, preferably from 10 to 60 nm. Also semycrystalline fluoropolymers wherein the latex particle sizes have the above mentioned value for at least 60% by weight, preferably 70% by weight of the semicrystalline fluoropolymer, can be used. [0013] The invention compositions are obtainable by mixing the semicrystalline fluoropolymer latex with the fluoroelastomer latex and subsequent coagulation. Alternatively the invention compositions can be polymerized in the same reactor in two subsequent steps: in a first step the semicrystalline fluoropolymer with the mentioned nanometric sizes is polymerized and in a second step the fluoroelastomer is polymerized. By operating in this way the fluoroelastomer should cover the semicrystalline fluoropolymer latex particles, allowing to obtain a very good dispersion of the latter in the fluoroelastomer. [0014] The semicrystalline fluoropolymer amount inside the fluoroelastomer matrix is in the range 2%-40% by weight, preferably 5-30% by weight, more preferably 10-20% by weight on the total of the polymeric mixture. [0015] The semicrystalline fluoropolymer particles having the above mentioned sizes are obtainable for example by a polymerization process in an aqueous microemulsion of perfluoropolyoxyalkylenes as described for example in the European patent application EP 99112083.3 in the name of the Applicant, herein incorporated by reference. Microemulsion polymerization methods can also be used, wherein the oil phase is formed by polymerizable unsaturated monomers, as described in U.S. Pat. No. 5,523,346 and in U.S. Pat. No. 5,616,648. [0016] The fluoroelastomers can be prepared by copolymerization of the monomers in aqueous emulsion, according to well known methods in the prior art, in the presence of radical initiators (for example alkaline or ammonium persulphates, perphosphates, perborates, percarbonates), optionally in combination with ferrous, cuprous or silver salts, or of other easily oxidizable metals. In the reaction medium also surfactants of various kind, among which the fluorinated surfactants are particularly preferrred, are usually present. [0017] Alternatively the fluoroelastomers can be prepared in bulk or in suspension, in an organic liquid in which a suitable radical initiator is present, according to well known techniques. [0018] The polymerization reaction is generally carried out at temperatures in the range 25.degree.-150.degree. C., under a pressure up to 10 MPa. [0019] The fluoroelastomers are preferably prepared in microemulsion of perfluoropolyoxyalkylens, according to U.S. Pat. No. 4,789,717 and U.S. Pat. No. 4,864,006. [0020] The Applicant has found that in order to obtain the results of the present invention it is essential that the semi-crystalline fluoropolymer filler latex has the mentioned nanometric sizes, while the size of the latex of the fluoroelastomer is not critical. [0021] When the semi-crystalline fluorinated filler is based on modified PTFE, for its preparation comonomers having an ethylene unsaturation both of hydrogenated and fluorinated type, can be used. Among those hydrogenated, ethylene, propylene, acrylic monomers, for example methylmethacrylate, (meth)acrylic acid, butylacrylate, hydroxyethylhexyl-acrylate, styrene monomers can be mentioned. [0022] Among the fluorinated comonomers we can mention: [0023] perfluoroolefins C.sub.3-C.sub.8, such as hexafluoropropene (HFP), hexafluoroisobutene; [0024] hydrogenated fluorolefins C.sub.2-C.sub.8, such as vinyl fluoride (VF), vinylidene fluoride (VDF), trifluoroethylene, perfluoroalkylethylene CH.sub.2.dbd.CH--R.sub.f, wherein R.sub.f is a perfluoroalkyl C.sub.1-C.sub.6; [0025] chloro- and/or bromo- and/or iodo-fluoroolefins C.sub.2-C.sub.8, such as chlorotrifluoroethylene (CTFE); [0026] (per)fluoroalkylvinylethers (PAVE) CF.sub.2.dbd.CFOR.sub.f, wherein R.sub.f is a (per)fluoroalkyl C.sub.1-C.sub.6, for example CF.sub.3, C.sub.2F.sub.5, C.sub.3F.sub.7; [0027] (per)fluoro-oxyalkylvinylethers CF.sub.2.dbd.CFOX, wherein X is: an alkyl C.sub.1-C.sub.12, or an oxyalkyl C.sub.1-C.sub.12, or a (per)fluorooxyalkyl C.sub.1-C.sub.12 having one or more ether groups, for example perfluoro-2-propoxy-propyl; fluorodioxoles, preferably perfluorodioxoles. [0028] PAVEs are preferred comonomers, specifically perfluoromethyl-, ethyl-, propylvinylether and fluorodioxoles, preferably perfluorodioxoles. [0029] The fluoroelastomers used in the present invention belong to the following classes: [0030] (1) VDF-based copolymers, wherein VDF is copolymerized with at least one comonomer selected from the following: perfluoroolefins C.sub.2-C.sub.8, such as tetrafluoroethylene (TFE) hexafluoropropene (HFP); chloro- and/or bromo- and/or iodo-fluoroolefins C.sub.2-C.sub.8, such as chlorotrifluoroethylene (CTFE) and bromotrifluoroethylene; (per)fluoroalkylvinylethers (PAVE) CF.sub.2.dbd.CFOR.sub.f, wherein R.sub.f is a (per)-fluoroalkyl C.sub.1-C.sub.6, for example trifluoromethyl, bromodifluoromethyl, pentafluoropropyl; perfluorooxyalkylvinylethers CF.sub.2.dbd.CFOX, wherein X is a perfluorooxyalkyl C.sub.1-C.sub.12 having one or more ether groups, for example perfluoro-2-propoxy-propyl; non fluorinated olefins (Ol) C.sub.2-C.sub.8, for example ethylene and propylene; [0031] (2) TFE-based copolymers, wherein TFE is copolymerized with at least one comonomer selected from the following: (per)fluoroalkylvinylethers (PAVE) CF.sub.2.dbd.CFOR.sub.f, wherein R.sub.f is as above defined; perfluoro-oxyalkylvinylethers CF.sub.2.dbd.CFOX, wherein X is as above defined; fluoroolefins C.sub.2-C.sub.8 containing hydrogen and/or chloro and/or bromo and/or iodo atoms; non fluorinated olefins (Ol).sup.- C.sub.2-C.sub.8; perfluorovinylethers containing hydrocyanic groups as described in U.S. Pat. No. 4,281,092, U.S. Pat. No. 5,447,993, U.S. Pat. No. 5,789,489. [0032] Preferably the invention fluoroelastomers contain perfluorinated monomers, and preferably the base structure of these fluoroelastomers is selected from the copolymers of class (2), wherein TFE is polymerized with one or more perfluorinated comonomers as above mentioned. [0033] Within the above defined classes, preferred compositions by moles of the monomers forming the base structure of the fluoroelastomer are the following: [0034] (a) vinylidene fluoride (VDF) 45-85%, hexa-fluoropropene (HFP) 15-45%, tetrafluoroethylene (TFE) 0-30%; [0035] (b) vinylidene-fluoride (VDF) 50-80%, perfluoroalkylvinylether (PAVE) 5-50%, tetrafluoroethylene (TFE) 0-20%; [0036] (c) vinylidene fluoride (VDF) 20-30%, non fluorinated olefins (Ol) C.sub.2-C.sub.8 10-30%, hexafluoropropene (HFP) and/or perfluoroalkylvinylether (PAVE) 18-27%, tetrafluoroethylene (TFE) 10-30%; [0037] (d) tetrafluoroethylene (TFE) 50-80%, perfluoroalkylvinylether (PAVE) 20-50%; [0038] (e) tetrafluoroethylene (TFE) 45-65%, non fluorinated olefins (Ol) C.sub.2-C.sub.8 20-55%, vinylidene fluoride 0-30%; [0039] (f) tetrafluoroethylene (TFE) 32-60% by moles, non fluorinated olefins (Ol) C.sub.2-C.sub.8 10-40%, perfluoroalkylvinylether (PAVE) 20-40%; [0040] (g) tetrafluoroethylene (TFE) 33-75%, perfluoroalkylvinylether (PAVE) 15-45%, vinylidene fluoride (VDF) 5-30%. [0041] Specific particularly preferred compositions are: [0042] (d) TFE 50-80%, PAVE 20-50%; [0043] (g) TFE 33-75%, PAVE 15-45%, VDF 5-30%. Continue reading about Fluoroelastomer compositions... Full patent description for Fluoroelastomer compositions Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Fluoroelastomer compositions patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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