Fluororubber composition

Abstract

A fluororubber composition in which ferroferric oxide having a BET specific surface area of 4.0 m2 / g or less is blended in a fluororubber at a volume fraction of 7.0 vol% or more. For a crosslinked product obtained from the fluororubber composition, a 1 mm sheet can be detected under the conditions of detection sensitivity (Fe: phi 0.6, SUS: phi 1.5) by using a metal detector ND-840 made in the Daixing electronic industry, the compression set after 70 hours at 175 DEG C using an O-ring is 21% or less, and the compression set after 70 hours using the O-ring is 21% or less, and the fluororubber composition can be used for detecting a 1 mm sheet under the conditions of detection sensitivity (Fe: phi 0.6, SUS: phi 1.5). Therefore, the gasket can be effectively used for gaskets, O-shaped rings and the like of food manufacturing equipment, food machinery, automobiles and the like.

Description

Technical Field

[0001] The present invention relates to a fluororubber composition, and more particularly to a fluororubber composition suitable for use as a material for molding a sealing component used in food production equipment and the like. Background Art

[0002] In the field of food manufacturing equipment, sealing components are required to have functions such as heat resistance, water resistance, and oil resistance, and also to comply with various laws and regulations such as the Waterworks Act and the Food Sanitation Act. In particular, fluororubber is suitable for components that are used in strict environments.

[0003] On the other hand, if O-rings or gaskets used in the food manufacturing process are damaged, rubber sheets may be mixed into the food. However, especially for rubber compounds using carbon black or white carbon, which are commonly used as fillers, there is a situation where the filler cannot be prevented from flowing out by metal detectors within the process alone.

[0004] As a countermeasure, patent documents 1 and 2 propose O-rings for food processing plant equipment to which metal oxides (black iron oxide) are added. However, there is no record of product functions and material properties. Here, O-rings used in food manufacturing equipment are not only made of rubber materials that can be detected by metal detectors even in small pieces, but also have excellent compression set resistance properties related to product life.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Utility Model Registration No. 3137050

[0008] Patent Document 2: Utility Model Registration No. 3135558 Summary of the invention

[0009] Technical problem to be solved by the invention

[0010] An object of the present invention is to provide a fluororubber composition which can be detected by a metal detector even when minute rubber pieces are mixed in a manufacturing facility such as a food production line, and which has excellent compression set resistance.

[0011] Solutions to Solve Problems

[0012] The present invention aims to add a fluororubber having a BET specific surface area of ​​4.0 m 2 This is achieved by using a fluororubber composition having a content of ferrosoferric oxide of less than 1 / g.

[0013] Effects of the Invention

[0014] The cross-linked product obtained from the fluororubber composition of the present invention has the effect that even a micro piece, specifically, a piece of 1 mm or less, can be detected by a metal detector and has excellent compression set resistance. DETAILED DESCRIPTION

[0015] As the fluororubber, any of polyol-vulcanizable fluororubber and peroxide-crosslinkable fluororubber can be used, and peroxide-crosslinkable fluororubber is preferably used.

[0016] Examples of the polyol-vulcanizable fluororubber include homopolymers and alternating copolymers of vinylidene fluoride, hexafluoropropylene, pentafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, fluorinated ethylene, perfluoroacrylate, perfluoroalkyl acrylate, perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), perfluoro(propyl vinyl ether), or the like, or copolymers thereof with propylene. Preferably, a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, a tetrafluoroethylene-propylene copolymer, or the like is used. In practice, a commercially available polyol-vulcanizable fluororubber may be used as it is.

[0017] In addition, as a fluororubber that can be crosslinked with peroxide (peroxide crosslinkable fluororubber), as long as the fluorine content is 63 to 71% by weight and the Mooney viscosity is ML 1+10 (121°C) is 20 to 100, and as a crosslinking site, any fluorine-containing elastomer containing iodine and / or bromine in the molecule can be used, and the following copolymer elastomer is preferably used.

[0018] An iodine group and / or a bromine group is introduced into a copolymer elastomer having a copolymer composition of about 50 to 80 mol % of vinylidene fluoride, about 15 to 50 mol % of hexafluoropropylene, and about 30 to 0 mol % of tetrafluoroethylene.

[0019] In practice, commercially available products such as DuPont products Viton GAL200S, GBL200S, GBL600S, GF200S, and GF600S, Solvay Specialty Polymers Japan products Tecnoflon P457, P757, P459, and P952, and Daikin Industries, Ltd. products DAI-EL G952, G901, G902, G912, and G801 can be used as they are.

[0020] An iodine group and / or a bromine group is introduced into a copolymer elastomer having a copolymer composition of about 50 to 85 mol % of 1,1-difluoroethylene, about 5 to 50 mol % of the following perfluorovinyl ether, and about 50 to 0 mol % of tetrafluoroethylene, wherein the perfluorovinyl ether is represented by the general formula CF2=CFORf (Rf: a perfluoroalkyl group having 1 to 10 carbon atoms, preferably a perfluoromethyl group, or a perfluorooxyalkyl group having one or more ether bonds in the carbon chain).

[0021] In fact, DuPont products Viton GLT200S, GLT600S, GBLT200S, GBLT600S, GFLT200S, GFLT600S, Solvay Specialty Polymers Japan products Tecnoflon PL455, PL855, PL557, PL458, PL958, Daikin Industries, Ltd. products DAI-EL LT302, LT301, etc. can be used directly.

[0022] The introduction of iodine groups and / or bromine groups capable of peroxide crosslinking of the fluororubber can be performed by a copolymerization reaction in the presence of a saturated or unsaturated compound containing an iodine group and / or a bromine group.

[0023] In the case of containing bromine and / or iodine groups as side chains of the fluorinated copolymer, examples thereof include copolymers of crosslinking point forming monomers such as perfluoro(2-bromoethyl vinyl ether), 3,3,4,4-tetrafluoro-4-bromo-1-butene, 2-bromo-1,1-difluoroethylene, bromotrifluoroethylene, perfluoro(2-iodoethyl vinyl ether), and iodotrifluoroethylene.

[0024] In the case of containing iodine and / or bromine groups as the ends of the fluorinated copolymer, the general formula X1C n F 2n The terminal halogenated fluoroalkylene compound represented by X2 (X1: F, Br, I, X2: Br, I, n: 1 to 12) is preferably a copolymer in which n is 1 to 6 and contains iodine and / or bromine groups derived from 1-bromoperfluoroethane, 1-bromoperfluoropropane, 1-bromoperfluorobutane, 1-bromoperfluoropentane, 1-bromoperfluorohexane, 1-iodoperfluoroethane, 1-iodoperfluoropropane, 1-iodoperfluorobutane, 1-iodoperfluoropentane, 1-iodoperfluorohexane, etc., from the viewpoint of the balance between reactivity and handling properties.

[0025] In addition, by making X1 and X2 be I and / or Br, crosslinking points can be introduced at the end of the fluorinated copolymer. As the compound, for example, 1-bromo-2-iodotetrafluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, monobromo-monoiodoperfluoropentane, monobromo-monoiodoperfluoro-n-hexane, 1,2-dibromoperfluoroethane, 1,3-dibromoperfluoropropane, 1,4-dibromoperfluorobutane, 1,5-dibromoperfluoropentane, 1,6-dibromoperfluorohexane, 1,2-diiodoperfluoroethane, 1,3-diiodoperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodoperfluoropentane, 1,6-diiodoperfluorohexane, etc. can be cited. These compounds can also be used as chain transfer agents.

[0026] In fluororubber, the BET specific surface area is 4.0m 2 / g or less, preferably 3.0m 2 / g or less, more preferably 2.5m 2 / g or less of ferroferric oxide Fe3O4 is mixed in a volume fraction of 7.0 vol% or more, preferably 8.0 vol% or more. The cross-linked product obtained by such mixing is detected by a metal detector ND-840 manufactured by Nissin Electronics Co., Ltd. in terms of detection sensitivity (Fe: Stainless steel SUS: ) can detect 1mm pieces under the conditions of 175°C and 70 hours using an O-ring. In addition, the compression set after 70 hours at 175°C is less than 21%. Here, if ferroferric oxide Fe3O4 or ferric oxide Fe2O3 with a larger BET specific surface area is used, the desired compression set resistance cannot be guaranteed. In addition, if the volume fraction is less than the above range, the detection of metal becomes difficult. It should be noted that the volume fraction is calculated by considering the specific gravity of the fluororubber and Fe3O4 used.

[0027] When a polyol-vulcanizable fluororubber is used as the fluororubber, a polyol-based vulcanizing agent is preferably used together with a vulcanization accelerator, and when a peroxide-crosslinkable fluororubber is used as the fluororubber, an organic peroxide crosslinking agent is preferably used together with a polyfunctional unsaturated compound.

[0028] For the polyol vulcanizing agent used as a vulcanizing agent for polyol-vulcanizable fluororubber, for example, 2,2-bis(4-hydroxyphenyl)propane [bisphenol A], 2,2-bis(4-hydroxyphenyl)perfluoropropane [bisphenol AF], bis(4-hydroxyphenyl)sulfone [bisphenol S], 2,2-bis(4-hydroxyphenyl)methane [bisphenol F], bisphenol A-bis(diphenyl phosphate), 4,4'-dihydroxydiphenyl, 2,2-bis(4-hydroxyphenyl)butane, etc. can be mentioned, and preferably bisphenol A, bisphenol AF, etc. can be used. They can also be in the form of alkali metal salts or alkaline earth metal salts. These polyol vulcanizing agents are usually used in a ratio of about 2 to 20 parts by weight, preferably about 2.5 to 15 parts by weight per 100 parts by weight of polyol-vulcanizable fluororubber. In addition, the polyol vulcanizing agent can also be used as a masterbatch with fluororubber.

[0029] In addition, as a vulcanization accelerator, a quaternary onium salt as a quaternary phosphonium salt or a quaternary ammonium salt can be used, preferably a quaternary phosphonium salt. These quaternary ammonium salts are used in a ratio of about 0.5 to 10 parts by weight, preferably about 1 to 5 parts by weight per 100 parts by weight of polyol vulcanizable fluororubber. In addition, the vulcanization accelerator can also be used as a masterbatch with fluororubber.

[0030] The quaternary phosphonium salt is a compound represented by the following general formula.

[0031] 〔PR1R2R3R4〕 + X -

[0032] R1 to R4: alkyl, alkoxy, aryl, alkylaryl, aralkyl or polyoxyalkylene having 1 to 25 carbon atoms, or 2 to 3 of them may form a polycyclic structure together with P

[0033] X - :Cl - Br - ,I - 、HSO4 - 、H2PO4 - ,RCOO - ROSO2 - 、CO3 2- Anion

[0034] Specifically, tetraphenylphosphonium chloride, benzyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, triphenylmethoxymethylphosphonium chloride, triphenylmethylcarbonylmethylphosphonium chloride, triphenylethoxycarbonylmethylphosphonium chloride, trioctylbenzylphosphonium chloride, trioctylmethylphosphonium chloride, trioctylethylphosphonium acetate, tetraoctylphosphonium chloride, trioctylethylphosphonium dimethylphosphate, etc. can be used. The quaternary phosphonium salt may be an equimolar compound with an active hydrogen-containing aromatic compound such as a polyhydroxy aromatic compound.

[0035] Quaternary ammonium salts can be used with the general formula

[0036] 〔NR1R2R3R4〕 + X -

[0037] (Among them, R1~R4 and X - The compound represented by the above) is, for example, 1-alkylpyridinium salts, 5-aralkyl-1,5-diazabicyclo[4,3,0]-5-nonenium salts, 8-aralkyl-1,8-diazabicyclo[5,4,0]-7-undecenium salts, etc. are used.

[0038] As the organic peroxide, for example, dicumyl peroxide, cumene hydroperoxide, p-methane hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, di-tert-butyl peroxide, benzoyl peroxide, m-tolyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5 -Di(tert-butylperoxy)hexyne-3, 1,3-di(tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-dibenzoylperoxyhexane, (1,1,3,3-tetramethylbutylperoxy)2-ethylhexanoate, tert-butyl peroxybenzoate, tert-butyl peroxylaurate, di(tert-butylperoxy)adipate, di(2-ethoxyethylperoxy)dicarboxylate, bis-(4-tert-butylcyclohexylperoxy)dicarboxylate, etc.

[0039] When peroxide crosslinking is performed using an organic peroxide, it is preferred to use a multifunctional unsaturated compound in combination. As the multifunctional unsaturated compound, a multifunctional unsaturated compound that improves mechanical strength, compression set, etc., such as tri(methyl)allyl isocyanurate, tri(methyl)allyl cyanurate, triallyl trimellitate, N,N'-m-phenylene bismaleimide, diallyl phthalate, tri(diallylamine)-s-triazine, triallyl phosphite, ethylene glycol di(methyl)acrylate, diethylene glycol di(methyl)acrylate, neopentyl glycol di(methyl)acrylate, trimethylolpropane tri(methyl)acrylate, 1,3-polybutadiene, etc., can be used in a ratio of about 0.1 to 20 parts by weight, preferably about 0.5 to 10 parts by weight per 100 parts by weight of peroxide crosslinkable fluororubber. Here, (methyl)allyl refers to allyl or methallyl. Likewise, (meth)acrylate refers to acrylate or methacrylate.

[0040] To the fluororubber composition composed of the above components, various compounding agents required in terms of vulcanization operation, physical properties and functions can be further added as needed. For example, on the basis of reinforcing agents such as carbon black, fillers such as diatomaceous earth and silica, acid acceptors such as oxides and hydroxides of divalent metals or hydrotalcite, and other necessary compounding agents, the composition is prepared by using any mixing means such as an open roll and a kneading machine, and is vulcanized and molded into a sealing component by hot pressing at 160 to 200°C for 3 to 30 minutes and secondary vulcanization at 150 to 250°C for 0.5 to 24 hours as needed.

[0041] Example

[0042] Hereinafter, the present invention will be described with reference to examples.

[0043] Example 1

[0044]

[0045]

[0046] Among the above components, the components other than the cross-linking agent are kneaded in a closed mixer, and then transferred to an open roll, to which the cross-linking agent is added. After further kneading, press vulcanization is performed at 180° C. for 6 minutes and oven vulcanization (secondary vulcanization) is performed at 230° C. for 22 hours to obtain a cross-linked product.

[0047] The obtained cross-linked product was used to measure normal physical properties, metal detection, and compression set.

[0048] Normal physical properties: JIS K6253 and JIS K6251 standards corresponding to ISO 37

[0049] Metal detection confirmation: Use Nissin Electronics Co., Ltd. metal detector ND-840, with 1 mm slices cut from sulfide as the object, and set the value: Detection: if it can be detected, it is judged as ○, if it cannot be detected, it is judged as ×

[0050] Compression set: According to JIS K6262 corresponding to ISO 815-1, the compression set after 70 hours at 175°C was measured. 21% or less was judged as ○, and 22% or more was judged as ×

[0051] Example 2

[0052] In Example 1, the amount of triiron tetraoxide was changed to 40 parts by mass.

[0053] Example 3

[0054] In Example 1, the amount of triiron tetraoxide was changed to 30 parts by mass.

[0055] Example 4

[0056] In Example 1, as triiron tetraoxide, the same amount (50 parts by mass) of a BET specific surface area of ​​2.1 m 2 / g (specific gravity: 5.2) of iron tetraoxide.

[0057] Comparative Example 1

[0058] In Example 1, the amount of triiron tetraoxide was changed to 20 parts by mass.

[0059] Comparative Example 2

[0060] In Example 1, the amount of triiron tetraoxide was changed to 10 parts by mass.

[0061] Comparative Example 3

[0062] In Example 1, as triiron tetraoxide, the same amount (50 parts by mass) of a BET specific surface area of ​​4.5 m 2 / g of ferroferric oxide (Toda Industrial Products KN-320).

[0063] Comparative Example 4

[0064] In Example 1, as triiron tetraoxide, the same amount (50 parts by mass) of a BET specific surface area of ​​5.5 m 2 / g of iron tetraoxide (titanium industrial product BL-10).

[0065] Comparative Example 5

[0066] In Example 1, as triiron tetraoxide, the same amount (50 parts by mass) of a BET specific surface area of ​​7.0 m 2 / g of ferroferric oxide (Toda Industrial Products KN-370).

[0067] Comparative Example 6

[0068] In Example 1, instead of ferroferric tetraoxide, the same amount (50 parts by mass) of ferric trioxide (Brown #601, a product of Resinocolor Industry Co., Ltd.) was used.

[0069] Comparative Example 7

[0070] In Example 1, the same amount (50 parts by mass) of strontium ferrite powder (SF-D630 product of DOWAF-TECCO., LTD.) was used instead of ferrosoferrate tetraoxide.

[0071] The results obtained in the above embodiments and comparative examples are shown in the following table together with the volume fraction of the metal filler.

[0072] surface

[0073]

[0074] Industrial Applicability

[0075] The crosslinked product obtained from the fluororubber composition of the present invention was detected by using a metal detector ND-840 manufactured by Nissin Electronics Co., Ltd. SUS: ) conditions, a 1 mm piece can be detected. In addition, the compression set of the O-ring after 70 hours at 175°C is less than 21%. Therefore, it can be effectively used for gaskets, O-rings, etc. in food manufacturing equipment, food machinery, automobiles, etc.

Claims

1. A fluororubber composition, wherein: In the fluororubber, a BET specific surface area of ​​4.0 m 2 / g or less of ferroferric oxide.

2. A cross-linked product of the fluororubber composition according to claim 1. The cross-linked product according to claim 2 , which is a sealing member.

4. The cross-linked product according to claim 3, which is used as a sealing member of food production equipment.

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