Sealing material

Abstract

Provided is a fluororubber composition in which triiron tetraoxide having a BET specific surface area of at most 4.0 m2 / g is mixed into a fluororubber in a proportion of at least 7.0 vol% in terms of volume fraction. A crosslinked product obtained using this fluororubber composition can be effectively used in gaskets, O-rings, and the like for food production equipment, food machinery, automobiles, and the like, since it is possible to detect a 1-mm piece of the crosslinked product using the ND-840 metal detector produced by Nissin Electronics under detection sensitivity (Fe: φ0.6, SUS: φ1.5) conditions, and the crosslinked product has a compression set of at most 21% after 70 hours at 175°C when using an O-ring as a sample.

Description

[Technical Field]

[0001] The present invention provides Sealing material More specifically, the present invention relates to a sealing member used in food manufacturing equipment, etc. to Regarding. [Background technology]

[0002] In the field of food manufacturing equipment, sealing components are required to have heat resistance, water resistance, oil resistance, etc., as well as compliance with various laws and regulations such as the Water Supply Act and the Food Sanitation Act, and fluororubber is used for components that are used in particularly harsh environments.

[0003] On the other hand, if O-rings or gaskets used in the food manufacturing process are damaged, there is a risk that rubber fragments will get mixed into the food. However, in rubber compounds that contain carbon black or white carbon, which are commonly used as fillers, metal detectors alone are not enough to prevent the fillers from leaking out.

[0004] As a countermeasure, Patent Documents 1 and 2 propose O-rings for food processing plants that contain metal oxides (black iron oxide). However, they do not disclose any information about the product functions or material properties. O-rings used in food manufacturing equipment are required to be made of a rubber material that can be detected by a metal detector even in minute pieces, and also to have excellent compression set resistance, which is important for the product's lifespan. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Utility Model Registration No. 3137050 [Patent Document 2] Utility Model Registration No. 3135558 Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a rubber material that can be detected by a metal detector even when minute rubber fragments are mixed in manufacturing equipment such as food manufacturing lines, and that has excellent resistance to compression set. Sealing material The purpose is to provide [Means for solving the problem]

[0007] The object of the present invention is to provide a fluororubber having a BET specific surface area. 2.5 m 2 Fluororubber composition containing iron tetroxide in a volume fraction of 7.0 vol% or more A sealing material that is a cross-linked product of the above and conforms to JIS K6262, which corresponds to ISO 815-1, and has a compression set of 21% or less after 70 hours at 175°C. This is achieved by: [Effects of the Invention]

[0008] According to the present invention Sealing material This has the effect that even minute pieces, specifically pieces of 1 mm or less, can be detected by a metal detector, and furthermore, it has excellent resistance to compression set. DETAILED DESCRIPTION OF THE INVENTION

[0009] As the fluororubber, either a polyol-vulcanizable fluororubber or a peroxide-crosslinkable fluororubber can be used, but the peroxide-crosslinkable fluororubber is preferably used.

[0010] Examples of polyol-vulcanizable fluororubbers include homopolymers or alternating copolymers of vinylidene fluoride, hexafluoropropene, pentafluoropropene, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoroacrylic acid esters, perfluoroalkyl acrylates, perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), perfluoro(propyl vinyl ether), etc., or copolymers of these with propylene. Preferably, vinylidene fluoride-hexafluoropropene copolymers, vinylidene fluoride-hexafluoropropene-tetrafluoroethylene terpolymers, tetrafluoroethylene-propylene copolymers, etc. are used, and in practice, commercially available polyol-vulcanizable fluororubbers can be used as they are.

[0011] In addition, peroxide-crosslinkable fluororubber (peroxide-crosslinkable fluororubber) has a fluorine content of 63 to 71% by weight and a Mooney viscosity of ML 1+10 Any fluorine-containing elastomer can be used as long as it has a crosslinking strength (at 121°C) of 20 to 100 and contains iodine and / or bromine in the molecule as crosslinking sites, but the following copolymer elastomers are preferably used. A copolymer elastomer having a copolymer composition of about 50-80 mol% vinylidene fluoride, about 15-50 mol% hexafluoropropene, and about 30-0 mol% tetrafluoroethylene, into which iodine and / or bromine groups have been introduced. In practice, commercially available products such as DuPont's Viton GAL200S, GBL200S, GBL600S, GF200S, and GF600S, Solvay Specialty Polymers Japan's Tecnoflon P457, P757, P459, and P952, and Daikin's Daiel G952, G901, G902, G912, and G801 are used as they are. A copolymer elastomer having a copolymerization composition of about 50 to 85 mol% vinylidene fluoride, about 5 to 50 mol% perfluorovinyl ether represented by the general formula CF2=CFORf (Rf: perfluoroalkyl group having 1 to 10 carbon atoms, preferably perfluoromethyl group or perfluorooxyalkyl group having one or more ether bonds in the carbon chain), and about 50 to 0 mol% tetrafluoroethylene, into which iodine groups and / or bromine groups have been introduced. In practice, DuPont products Viton GLT200S, GLT600S, GBLT200S, GBLT600S, GFLT200S, GFLT600S, Solvay Specialty Polymers Japan products Tecnoflon PL455, PL855, PL557, PL458, PL958, Daikin products Daiel LT302, LT301, etc. are used as they are.

[0012] The introduction of iodine and / or bromine groups that enable peroxide crosslinking of fluororubber can be carried out by copolymerization reaction in the presence of an iodine and / or bromine group-containing saturated or unsaturated compound.

[0013] When a bromine group and / or an iodine group is contained in the side chain of the fluorine-containing 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.

[0014] When an iodine group and / or a bromine group is to be contained at the end of the fluorine-containing copolymer, the fluorine-containing copolymer may be represented by the general formula X1C n F 2nA terminally halogenated fluoroalkylene compound represented by X2 (X1: F, Br, I, X2: Br, I, n: 1 to 12) is used, and from the viewpoint of the balance between reactivity and handling, copolymers containing iodine groups 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., where n: 1 to 6, are preferably used.

[0015] Furthermore, by setting X1 and X2 to I and / or Br, crosslinking points can be introduced at the ends of the fluorine-containing copolymer. Examples of such compounds include 1-bromo-2-iodotetrafluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, monobromomonoiodoperfluoropentane, monobromomonoiodoperfluoro-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, and 1,6-diiodoperfluorohexane. These compounds can also be used as chain transfer agents.

[0016] Fluorine rubber has a BET specific surface area of 2.5m 2Triiron tetroxide (Fe3O4) of 0.1 / g or less is blended at a volume fraction of 7.0 vol% or more, preferably 8.0 vol% or more. This blending allows for the detection of 1 mm pieces of the resulting crosslinked product using a Nissin Electronics ND-840 metal detector under the detection sensitivity conditions (Fe: φ0.6, stainless steel SUS: φ1.5), and the compression set after 70 hours at 175°C using an O-ring is 21% or less. Using triiron tetroxide (Fe3O4) or diiron trioxide (Fe2O3) with a BET specific surface area greater than this would prevent the desired compression set resistance. Furthermore, blending at a volume fraction lower than this makes it difficult to detect the metal. The volume fraction is calculated taking into account the specific gravities of the fluoroelastomer and Fe3O4 used.

[0017] 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.

[0018] Examples of polyol-based vulcanizing agents used as vulcanizing agents for polyol-vulcanizable fluororubbers include 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, and 2,2-bis(4-hydroxyphenyl)butane. Bisphenol A and bisphenol AF are preferred. These may also be in the form of alkali metal salts or alkaline earth metal salts. These polyol-based vulcanizing agents are generally 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. Polyol-based vulcanizing agents can also be used as masterbatches with fluororubber.

[0019] As the vulcanization accelerator, a quaternary onium salt such as a quaternary phosphonium salt or a quaternary ammonium salt is used, preferably a quaternary phosphonium salt. These quaternary onium salts are used in an amount of about 0.5 to 10 parts by weight, preferably about 1 to 5 parts by weight, per 100 parts by weight of the polyol-vulcanizable fluororubber. The vulcanization accelerator is also used as a masterbatch with the fluororubber.

[0020] Quaternary phosphonium salts are compounds represented by the following general formula: [PR1R2R3R4] + X - R1 to R4: an alkyl group, an alkoxyl group, or an aryl group having 1 to 25 carbon atoms; Alkylaryl group, aralkyl group or polyoxyalkylene group or two or three of these together with P form a multi-ring structure. It can also be formed X - :Cl - , Br - , I - , HSO4 - , H2PO4 - , RCOO - , ROSO2 - , CO3 2- Anions such as Specifically, tetraphenylphosphonium chloride, benzyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, triphenylmethoxymethylphosphonium chloride, triphenylmethylcarbonylmethylphosphonium chloride, triphenylethoxycarbonylmethylphosphonium chloride, trioctylbenzylphosphonium chloride, trioctylmethylphosphonium chloride, trioctylethylphosphonium acetate, tetraoctylphosphonium chloride, trioctylethylphosphonium dimethylphosphate, etc. may be used. The quaternary phosphonium salt may also be an equimolar molecular compound with an active hydrogen-containing aromatic compound such as a polyhydroxy aromatic compound.

[0021] Quaternary ammonium salts have the general formula [NR1R2R3R4] + X - (where R1 to R4 and X - is the same as above), 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.

[0022] Examples of organic peroxides include dicumyl peroxide, cumene hydroperoxide, p-methane hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, di-tert-butyl peroxide, benzoyl peroxide, m-toluyl 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 bis-(4-tert-butylcyclohexylperoxy)dicarbonate, di(tert-butylperoxy)hexane, (1,1,3,3-tetramethylbutylperoxy)2-ethylhexanoate, tert-butylperoxybenzoate, tert-butylperoxylaurate, di(tert-butylperoxy)adipate, di(2-ethoxyethylperoxy)dicarbonate, bis-(4-tert-butylcyclohexylperoxy)dicarbonate, etc. are used in a proportion of 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of the peroxide-crosslinkable fluororubber.

[0023] In peroxide crosslinking using an organic peroxide, it is preferable to use a polyfunctional unsaturated compound in combination. Examples of such polyfunctional unsaturated compounds include tri(meth)allyl isocyanurate, tri(meth)allyl cyanurate, triallyl trimellitate, N,N'-m-phenylene bismaleimide, diallyl phthalate, tris(diallylamine)-s-triazine, triallyl phosphite, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and 1,3-polybutadiene. These polyfunctional unsaturated compounds improve mechanical strength and compression set, and are used in an amount 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, "(meth)allyl" refers to allyl or methallyl. Similarly, (meth)acrylate refers to either acrylate or methacrylate.

[0024] To the fluororubber composition comprising the above components, various compounding agents required for vulcanization operation, physical properties, and functionality are further added as needed. For example, a reinforcing agent such as carbon black, a filler such as diatomaceous earth or silica, an acid acceptor such as an oxide, hydroxide, or hydrotalcite of a divalent metal, and other necessary compounding agents are blended, and the composition is prepared by any kneading means such as an open roll or a kneader. The composition is then vulcanized and molded into a sealing member by heat pressing at 160 to 200°C for 3 to 30 minutes and, if necessary, secondary vulcanization at 150 to 250°C for 0.5 to 24 hours. [Example]

[0025] Next, the present invention will be described with reference to examples.

[0026] Example 1 Fluorine rubber (Solvay Specialty Polymers 100 parts by weight) Japan Product P757, specific gravity: 1.825-1.865) Iron tetroxide (Fe3O4) (Titanium Industrial Products BL-SP, 50%) BET specific surface area: 1.1m 2 / g, specific gravity: 4.8-5.2) Austin Black (COAL FILLERS AUSTIN BLACK 325) 5 Barium sulfate (Sakai Chemical Industry Products, Barium Sulfate B-54) 1 Same as above Acid acceptor (Kyowa Chemical Industry Products DHT-4A) 3 Same as above Co-crosslinking agent (Nippon Kasei Products TAIC WH-60) 2.4 〃 Crosslinking agent (NOF Products PERHEXA 25B-40) 1.8 〃 Of the above components, all components except the crosslinking agent were kneaded in an internal mixer, then transferred to an open roll, to which the crosslinking agent was added, and further kneaded. After that, the mixture was press-vulcanized at 180°C for 6 minutes and oven-vulcanized at 230°C for 22 hours (secondary vulcanization) to obtain a crosslinked product.

[0027] The crosslinked product thus obtained was used to measure its normal physical properties, metal detection, and compression set. Normal state physical properties: Compliant with JIS K 6253 and JIS K 6251, which correspond to ISO 37 Metal detection confirmation: Using the Nissin Electronics Metal Detector ND-840, metal was detected from the vulcanized material. For the cut out 1mm piece, setting value: Feφ0.6, Detected with SUSφ1.5 If it is detectable, it is judged as ○, if it is not detectable, it is judged as × Compression set: Compliant with JIS K6262, corresponding to ISO 815-1, 175°C, 70 hours Measure the compression set after If it is 21% or less, it is judged as OK, and if it is 22% or more, it is judged as ×.

[0028] Example 2 In Example 1, the amount of triiron tetroxide used was changed to 40 parts by weight.

[0029] Example 3 In Example 1, the amount of triiron tetroxide used was changed to 30 parts by weight.

[0030] Example 4 In Example 1, iron tetroxide having a BET specific surface area of ​​2.1 m 2 / g (specific gravity: 5.2) was used in the same amount (50 parts by weight).

[0031] Comparative Example 1 In Example 1, the amount of triiron tetroxide used was changed to 20 parts by weight.

[0032] Comparative Example 2 In Example 1, the amount of triiron tetroxide used was changed to 10 parts by weight.

[0033] Comparative Example 3 In Example 1, iron tetroxide having a BET specific surface area of ​​4.5 m 2 The same amount (50 parts by weight) of 1 / g (Toda Kogyo KN-320) was used.

[0034] Comparative Example 4 In Example 1, iron tetroxide having a BET specific surface area of ​​5.5 m 2 The same amount (50 parts by weight) of titanium dioxide powder (Titanium Industrial Products BL-10) was used.

[0035] Comparative Example 5 In Example 1, iron trioxide having a BET specific surface area of ​​7.0 m 2 The same amount (50 parts by weight) of 1 / g (Toda Kogyo KN-370) was used.

[0036] Comparative Example 6 In Example 1, the same amount (50 parts by weight) of diiron trioxide (Resinocolor Industrial Products Brown #601) was used in place of triiron tetroxide.

[0037] Comparative Example 7 In Example 1, the same amount (50 parts by weight) of strontium ferrite powder (DOWA F-Tech product SF-D630) was used in place of triiron tetroxide.

[0038] The results obtained in the above examples and comparative examples are shown in the following table together with the volume fraction of the metal filler. table TIFF0007796225000001.tif65138 [Industrial Applicability]

[0039] The present invention Sealing material It is possible to detect 1mm pieces of this material using the Nissin Electronics Metal Detector ND-840 under the conditions of detection sensitivity (Fe: φ0.6, SUS: φ1.5), and since the compression set after 70 hours at 175°C when used in an O-ring is 21% or less, it is effectively used in gaskets, O-rings, etc. for food manufacturing equipment, food machinery, automobiles, etc.

Claims

1. Fluorine rubber with a BET specific surface area of ​​2.5m 2 A cross-linked product of a fluororubber composition containing triiron tetroxide of 7.0 vol% or more in a volume fraction of 7.0 vol% or less, and a sealing material having a compression set of 21% or less after 70 hours at 175°C in accordance with JIS K6262, which corresponds to ISO 815-1.

2. 2. The sealing member according to claim 1, which is a sealing member for food manufacturing equipment.

3. A sealing member according to claim 1 or 2 which is an O-ring.

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