Flame-retardant rubber composition, flame-retardant rubber crosslinked product, and article

Abstract

To provide a flame-retardant rubber composition which combines flame retardancy, flexibility, and surface properties.SOLUTION: The flame-retardant rubber composition according to one embodiment of the present invention contains a component A: an ethylene-propylene-diene rubber, a component B: a hydrated metal oxide, a component C: a phosphorus-based flame-retardant plasticizer, and a component D: a mineral oil. When the content of the component A is 100 pts.wt., the content of the component B is 80-200 pts.wt., the content of the component C is 1-15 pts.wt., and the content of the component D is 1-30 pts.wt.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a flame-retardant rubber composition, a flame-retardant crosslinked rubber product, and an article. [Background technology]

[0002] Ethylene-propylene-diene rubber (EPDM) is used in a wide range of applications, including automotive parts. Some applications require EPDM to be flame-retardant, and various flame-retardant EPDM-containing compositions have been proposed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special table number 2023-517048 Summary of the Invention [Problem to be solved by the invention]

[0004] The composition disclosed in Patent Document 1 is characterized by not containing mineral oil. However, as a result of intensive research by the present inventors, a new problem was found in that rubber obtained from a composition not containing mineral oil becomes too hard or has poor surface properties.

[0005] An object of one aspect of the present invention is to provide a flame-retardant rubber composition that combines flame retardancy, flexibility, and surface properties. [Means for solving the problem]

[0006] In order to solve the above problems, a flame-retardant rubber composition according to one embodiment of the present invention comprises the following components A to D: Component A: Ethylene-propylene-diene rubber; Component B: Hydrated metal oxides; Component C: phosphorus-based flame-retardant plasticizer; Component D: Mineral oil; When the content of the above component A is taken as 100 parts by weight, the contents of the above components B to D are respectively as follows: Component B: 80~200 parts by weight; Component C: 1~15 parts by weight; Component D: 1 to 30 parts by weight. Effect of the Invention

[0007] According to one aspect of the present invention, there is provided a flame-retardant rubber composition that combines flame retardancy, flexibility, and surface properties. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] An example of an embodiment of the present invention will be described in detail below, but the present invention is not limited to the following embodiments and may be modified in various ways within the scope of the claims. An embodiment that combines technical means described in different embodiments is also included in the technical scope of the present invention.

[0009] Unless otherwise specified in this specification, "A to B" expressing a numerical range means "A or more, and B or less."

[0010] [1. Components contained in the flame-retardant rubber composition] The flame-retardant rubber composition according to one embodiment of the present invention includes component A: ethylene-propylene-diene rubber, component B: hydrated metal oxide, component C: phosphorus-based flame-retardant plasticizer, and component D: mineral oil. The flame-retardant rubber composition may include optional components, such as component E: silane coupling agent and / or component F: filler. The flame-retardant rubber composition may include additives other than those mentioned above. Each of these components may be used alone or in combination of two or more. Each component will be described in detail below.

[0011] [1.1. Component A: Ethylene-propylene-diene rubber] Component A is ethylene-propylene-diene rubber (EPDM), which is a rubber obtained by copolymerizing ethylene, propylene, and diene monomers.

[0012] Examples of diene monomers constituting component A include linear dienes and cyclic dienes. Examples of linear dienes include 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,4-heptadiene, 2-methyl-1,5-hexadiene, 1,4-octadiene, 1,6-octadiene, 1,7-octadiene, 6-methyl-1,5-heptadiene and 7-methyl-1,6-octadiene. Examples of cyclic dienes include cyclohexadiene, cyclooctadiene, dicyclopentadiene, alkyl dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-n-propylidene-2-norbornene, 5-isopropylidene-2-norbornene, 5-(2-methyl-2-butenyl)-2-norbornene, and 6-chloromethyl-5-isopropenyl-2-norbornene. Among these, 5-ethylidene-2-norbornene is preferred because it has a high crosslinking rate and is excellent in the balance of physical properties of the crosslinked body.

[0013] The lower limit of the content of the ethylene-derived units in Component A may be 30% by weight or more or 40% by weight or more, based on 100% by weight of the weight of Component A. The upper limit of the content of the ethylene-derived units in Component A may be 85% by weight or less or 80% by weight or less, based on 100% by weight of the weight of Component A.

[0014] The lower limit of the content of diene monomer derived units in Component A may be 0.5% by weight or more or 1% by weight or more, based on 100% by weight of Component A. The upper limit of the content of ethylene derived units in Component A may be 20% by weight or less or 15% by weight or less, based on 100% by weight of Component A.

[0015] The flame-retardant rubber composition may contain a rubber component other than component A. Examples of rubber other than component A include fluororubber (FKM), natural rubber (NR), styrene-butadiene rubber (SBR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), urethane rubber (U), ethylene acrylic rubber (AEM), acrylic rubber (ACM), and silicone rubber (Q). Among these, at least one type selected from the group consisting of natural rubber (NR), styrene-butadiene rubber (SBR), isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), urethane rubber (U), ethylene acrylic rubber (AEM), acrylic rubber (ACM), and silicone rubber (Q) that do not contain halogens is preferred.

[0016] The rubber components in the flame-retardant rubber composition are preferably mainly composed of component A. In one embodiment, the weight percentage of component A among all the rubber components contained in the flame-retardant rubber composition is 70% by weight or more, 80% by weight or more, or 90% by weight or more. In one embodiment, the flame-retardant rubber composition does not contain any rubber components other than component A.

[0017] [1.2. Component B: Hydrated metal oxides] Component B is a hydrated metal oxide. A hydrated metal oxide is a hydrate of a metal oxide, generally M(OH). n It is expressed by the general formula:

[0018] Examples of component B include aluminum hydroxide, magnesium hydroxide, magnesium / nickel composite hydroxide, and magnesium / zinc composite hydroxide. Among these, aluminum hydroxide and / or magnesium hydroxide are preferred, and aluminum hydroxide is more preferred. These components have a large heat absorption amount during thermal decomposition, and are highly effective in improving flame retardancy.

[0019] Average particle size of component B (D 50 The lower limit of the average particle size (D 50 ) may be 5.0 μm or less, 3.0 μm or less, or 2.0 μm or less. Examples of aluminum hydroxide having an average particle size in the above range include BF013, BF703, BF1403, and BF103 (all of which are manufactured by Nippon Light Metal Co., Ltd.). Examples of magnesium hydroxide having an average particle size in the above range include KISUMA® 5A, 5B, 5E, 5J, 5P / 5L, 8, 5Q-S, and 200-06H (all of which are manufactured by Kyowa Chemical Industry Co., Ltd.).

[0020] Component B may be a surface-treated hydrated metal oxide. For example, component B may be a hydrated metal oxide surface-treated with a silane coupling agent (component E). Inclusion of such component B means, at the same time, inclusion of component E. Component B surface-treated with a silane coupling agent forms a bond with a polymer such as component A, and can change the physical properties of the crosslinked rubber.

[0021] [1.3. Component C: Phosphorus-based flame-retardant plasticizer] Component C is a phosphorus-based flame-retardant plasticizer. A phosphorus-based flame-retardant plasticizer is a flame-retardant plasticizer that has a phosphorus atom and generally takes the form of a phosphoric acid ester.

[0022] Examples of component C include aromatic phosphate esters and aliphatic phosphate esters. Examples of aromatic phosphate esters include triphenyl phosphate, cresyl diphenyl phosphate, tricresyl phosphate, cresyl dixylenyl phosphate, trixylenyl phosphate, and condensates thereof (resorcinol bis(diphenyl phosphate), bisphenol A bis(diphenyl phosphate), resorcinol bis(dixylenyl phosphate), mixed esters of phosphoric acid with [1,1'-biphenyl]4,4'-diol and phenol). Examples of aliphatic phosphate esters include trimethyl phosphate, triethyl phosphate, tributyl phosphate, tris(2-butoxyethyl) phosphate, tris(2-chloroethyl) phosphate, tris(1,2-dichloro-2-propyl) phosphate, and tris(2,3-dibromopropyl) phosphate.

[0023] Component C preferably contains an aromatic compound having excellent flame retardancy. In one embodiment, component C contains an aromatic phosphate ester.

[0024] [1.4. Component D: Mineral oil] Component D is a mineral oil. Mineral oil generally refers to oils derived from petroleum. Examples of component D include process oil, lubricating oil, paraffin oil, liquid paraffin, petroleum asphalt, and petrolatum. Among these, process oil is preferred. Examples of process oil include paraffin-based process oil, naphthene-based process oil, and aromatic process oil. Among these, paraffin-based process oil is preferred.

[0025] [1.5. Component E: Silane coupling agent] Component E is a silane coupling agent. A silane coupling agent is a compound containing silicon atoms and is used to modify the surface of materials. Silane coupling agents generally have a hydrolyzable group (such as an alkoxy group) linked to a silicon atom and a reactive functional group (such as a vinyl group, (meth)acryloyl group, epoxy group, amino group, etc.).

[0026] Examples of component E include alkoxysilanes having a vinyl group (vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, etc.); alkoxysilanes having a (meth)acryloyl group (3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropyltrimethoxysilane). Component E may be an oligomer of these alkoxysilanes.

[0027] Component E improves the physical properties of the crosslinked flame-retardant rubber by binding inorganic components such as component B and component F with polymers such as component A. In one embodiment, component E is blended into the flame-retardant rubber composition as a surface treatment agent for component B and / or component F. In one embodiment, component E is blended into the flame-retardant rubber composition separately from component B and / or component F.

[0028] [1.6. Component F: Filler] Component F is a filler. Examples of the filler include carbon black, silica, calcium carbonate, activated calcium carbonate, fine talc, fine silicic acid, zinc oxide, diatomaceous earth, and clay. These may be surface-treated with a silane coupling agent or the like.

[0029] Among these, carbon black and / or silica are preferred. Examples of carbon black include SAF, ISAF, HAF, FEF, and GPF. Examples of carbon black also include conductive carbon black (acetylene black, ketjen black, etc.). Examples of silica include fumed silica, precipitated silica, and crystalline silica.

[0030] Component F may be a surface-treated filler. For example, component F may be a filler that has been surface-treated with a silane coupling agent (component E). Inclusion of such component F means, at the same time, inclusion of component E. Component F that has been surface-treated with a silane coupling agent can form bonds with polymers such as component A, thereby changing the physical properties of the crosslinked rubber.

[0031] [1.7. Other ingredients] The flame-retardant rubber composition may contain components that can be used in the rubber industry in addition to components A to F. Examples of such components include plasticizers / softeners other than components C or D, antioxidants / stabilizers, processing aids, crosslinking agents, co-crosslinking agents, crosslinking accelerators, crosslinking accelerator assistants, and crosslinking retarders.

[0032] (Plasticizers / Softeners) Examples of plasticizers other than component C or D include coal tar, fatty oils (castor oil, linseed oil, rapeseed oil, soybean oil, coconut oil, etc.), waxes (beeswax, carnauba wax, etc.), higher fatty acids or their salts or esters, naphthenic acid, pine oil, rosin or derivatives thereof, synthetic polymers (terpene resins, petroleum resins, coumarone-indene resins, etc.), ester-based plasticizers (dioctyl phthalate, dioctyl adipate, etc.), microcrystalline wax, poly-α-olefins (liquid polybutadiene, modified liquid polybutadiene, etc.), hydrocarbon-based synthetic lubricating oils, tall oil, and sub(factice).

[0033] Examples of higher fatty acids constituting higher fatty acids or their salts or esters include oleic acid, palmitic acid, stearic acid, lauric acid, linoleic acid, abietic acid, erucic acid, myristic acid, arachic acid, lignoceric acid, and ricinoleic acid. The higher fatty acid may be a saturated or unsaturated fatty acid, and preferably contains an unsaturated fatty acid. The salt of the higher fatty acid is usually a metal salt, preferably an alkali metal salt or an alkaline earth metal salt. Examples of the metal salt include lithium salt, potassium salt, sodium salt, barium salt, calcium salt, magnesium salt, aluminum salt, iron salt, and zinc salt. Specific examples of the higher fatty acid or its salt include ricinoleic acid, palmitic acid, stearic acid, lauric acid, barium stearate, zinc stearate, and calcium stearate.

[0034] (Anti-aging agent / stabilizer) Examples of the antioxidant include amine-based antioxidants, phenol-based antioxidants, and sulfur-based antioxidants.

[0035] Specific examples of amine-based antiaging agents include aromatic amines (phenylbutylamine, N,N-di-2-naphthyl-p-phenylenediamine, etc.) and amine-ketones. Specific examples of phenol-based antiaging agents include monophenols (dibutylhydroxytoluene, etc.), bisphenols, and polyphenols (tetrakis[methylene(3,5-di-t-butyl-4-hydroxy)hydrocinnamate]methane, etc.). Specific examples of sulfur-based antiaging agents include thioethers (bis[2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl]sulfide, etc.), dithiocarbamate salts (nickel dibutyldithiocarbamate, etc.), thiourea, 2-mercaptobenzoylimidazole, 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, dilaurylthiodipropionate, and distearylthiodipropionate.

[0036] (Processing aids) Examples of processing aids include the higher fatty acids or their salts or esters mentioned in the section on plasticizers and softeners. Further examples of processing aids include higher fatty acid amides (such as oleic acid amide).

[0037] (Crosslinking agent) An example of the crosslinking agent is an organic peroxide. Since the organic peroxide does not contain a sulfur-based compound, it does not corrode metals (especially silver or copper) that come into contact with the crosslinked flame-retardant rubber. Examples of the organic peroxide include t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane.

[0038] [1.8. Ingredients that should preferably not be included] From the viewpoint of reducing the environmental load, it is preferable that the flame-retardant rubber composition does not contain a halogen. In this specification, halogen refers to fluorine, chlorine, bromine, iodine or astatine. In this specification, "does not contain a halogen" means that a compound containing a halogen is not used as a raw material for the flame-retardant rubber composition.

[0039] Similarly, from the viewpoint of reducing the environmental load, the flame-retardant rubber composition preferably does not contain antimony trioxide.

[0040] [2. Content of each component in the flame-retardant rubber composition] In the flame-retardant rubber composition, when the content of component A is 100 parts by weight, the lower limit of the content of component B is 80 parts by weight or more, more preferably 90 parts by weight or more, and even more preferably 100 parts by weight or more. In the flame-retardant rubber composition, when the content of component A is 100 parts by weight, the upper limit of the content of component B is 200 parts by weight or less, more preferably 180 parts by weight or less, even more preferably 160 parts by weight or less, and particularly preferably 150 parts by weight or less.

[0041] In the flame-retardant rubber composition, when the content of component A is 100 parts by weight, the lower limit of the content of component C is 1 part by weight or more, and more preferably 3 parts by weight or more. In the flame-retardant rubber composition, when the content of component A is 100 parts by weight, the upper limit of the content of component C is 15 parts by weight or less, and more preferably 13 parts by weight or less.

[0042] In the flame-retardant rubber composition, when the content of component A is 100 parts by weight, the lower limit of the content of component D is 1 part by weight or more, and more preferably 3 parts by weight or more. In the flame-retardant rubber composition, when the content of component A is 100 parts by weight, the upper limit of the content of component D is 30 parts by weight or less, more preferably 25 parts by weight or less, even more preferably 20 parts by weight or less, and particularly preferably 15 parts by weight or less.

[0043] In the flame-retardant rubber composition, the lower limit of the content of component E is preferably 0.01 parts by weight or more, more preferably 0.1 parts by weight or more, and even more preferably 0.5 parts by weight or more, based on 100 parts by weight of the content of component A. In the flame-retardant rubber composition, the upper limit of the content of component E is preferably 10 parts by weight or less, more preferably 7 parts by weight or less, and even more preferably 5 parts by weight or less, based on 100 parts by weight of the content of component A.

[0044] In the flame-retardant rubber composition, the lower limit of the content of component F is preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, and even more preferably 5 parts by weight or more, based on 100 parts by weight of the content of component A. In the flame-retardant rubber composition, the upper limit of the content of component F is preferably 40 parts by weight or less, and more preferably 30 parts by weight or less, based on 100 parts by weight of the content of component A.

[0045] In the flame-retardant rubber composition, when the content of Component A is 100 parts by weight, the lower limit of the total content of the plasticizers (in one embodiment, the total content of Components C and D) is 2 parts by weight or more, and preferably 5 parts by weight or more. In the flame-retardant rubber composition, when the content of Component A is 100 parts by weight, the upper limit of the total content of the plasticizers (in one embodiment, the total content of Components C and D) is 45 parts by weight or less, preferably 35 parts by weight or less, and more preferably 30 parts by weight or less.

[0046] In the flame-retardant rubber composition, the lower limit of the ratio of the content of component B to the total content of the plasticizer (in one embodiment, the ratio of the content of component B to the content of components C and D) is 2.1 or more, preferably 3.0 or more, and even more preferably 5.0 or more. In the flame-retardant rubber composition, the upper limit of the ratio of the content of component B to the total content of the plasticizer (in one embodiment, the ratio of the content of component B to the content of components C and D) is 100.0 or less, preferably 50.0 or less, more preferably 25.0 or less, and even more preferably 15.0 or less.

[0047] In the flame-retardant rubber composition, the lower limit of the ratio of component D to the total content of the plasticizer (in one embodiment, the ratio of component D to the total content of components C and D) is 0.0625 or more, preferably 0.1 or more, and more preferably 0.3 or more. In the flame-retardant rubber composition, when the content of component A is 100 parts by weight, the upper limit of the ratio of the content of component B to the total content of the plasticizer (in one embodiment, the ratio of the content of component B to the contents of components C and D) is 0.94 or less, preferably 0.9 or less, and more preferably 0.87 or less.

[0048] [3. Flame-retardant crosslinked rubber and articles] The flame-retardant crosslinked rubber according to one embodiment of the present invention is obtained by crosslinking the flame-retardant rubber composition according to one embodiment of the present invention. For example, the flame-retardant rubber composition can be produced by kneading each component described in section [1]. A kneader can be used to knead the components. Examples of the kneader include an open roll, a kneader, a planetarium mixer, a Banbury mixer, and an extruder. The kneading temperature may be 25 to 200°C. The kneading time may be 1 minute to 1 hour.

[0049] A flame-retardant crosslinked rubber body can be produced by curing the flame-retardant rubber composition. The curing temperature may be 120 to 200°C. The curing time may be 10 seconds to 120 minutes. The cured molded body may be further subjected to secondary curing. The secondary curing temperature may be 120 to 250°C. The secondary curing time may be 30 minutes to 4 hours.

[0050] An article according to one aspect of the present invention includes the flame-retardant crosslinked rubber according to one aspect of the present invention. The article can be produced by molding and crosslinking the flame-retardant rubber composition. Examples of molding methods include injection molding, transfer molding, casting molding, compression molding, pressing, and extrusion molding. In one embodiment, the article is a gasket. In this specification, the term "gasket" refers to a sealing material that is installed between stationary members.

[0051] [3.1. Physical properties of crosslinked flame-retardant rubber] The flame retardant crosslinked rubber product preferably has a flame retardancy of V-0 or higher according to the UL94 standard. That is, the flame retardancy of the flame retardant crosslinked rubber product is preferably 5VA, 5VB or V-0. In one embodiment, the flame retardancy of the flame retardant crosslinked rubber product is V-0.

[0052] The lower limit of the Shore A hardness of the flame-retardant crosslinked rubber is preferably 50 or more, and more preferably 60 or more. The upper limit of the Shore A hardness of the flame-retardant crosslinked rubber is preferably 80 or less. If the Shore A hardness is within the above range, it can be said that the material has a softness suitable for use as a gasket. In this specification, the Shore A hardness is measured with a Type A durometer based on JIS K6253. For more specific examples of the measurement method, see the Examples of this application. The Shore A hardness of the flame-retardant crosslinked rubber is measured for a flame-retardant crosslinked rubber that has not been subjected to a heat resistance test or a combustion test.

[0053] The upper limit of the compression set of the flame-retardant crosslinked rubber is preferably 80% or less, more preferably 70% or less, even more preferably 60% or less, and particularly preferably 50% or less. In this specification, the compression set is measured using a sample of the flame-retardant crosslinked rubber after a heat resistance test. The heat resistance test method is a modified version of JIS K6262 (see Examples for details). Therefore, the compression set value tends to be larger than when measured according to JIS K6262.

[0054] The tensile strength at break of the flame-retardant crosslinked rubber is preferably 5 MPa or more, more preferably 7 MPa or more. The tensile elongation at break of the flame-retardant crosslinked rubber is preferably 180% or more, more preferably 200% or more. If the tensile properties are within the above ranges, it can be said that the rubber has physical properties suitable for use as a gasket.

[0055] [4. Summary] The present invention includes the following aspects. <1> A flame-retardant rubber composition comprising the following components A to D: Component A: Ethylene-propylene-diene rubber; Component B: Hydrated metal oxides; Component C: phosphorus-based flame-retardant plasticizer; Component D: Mineral oil; When the content of the component A is 100 parts by weight, the contents of the components B to D are as follows: Component B: 80~200 parts by weight; Component C: 1~15 parts by weight; Component D: 1 to 30 parts by weight. <2> When the content of the component A is 100 parts by weight, the content of the component B is less than 180 parts by weight. <1> The flame-retardant rubber composition according to claim 1. <3> The component C contains an aromatic compound. <1> or <2> The flame-retardant rubber composition according to claim 1. <4> The following component E is further contained. <1> ~ <3> The flame-retardant rubber composition according to any one of claims 1 to 5, Component E: Silane coupling agent. <5> The component B contains aluminum hydroxide and / or magnesium hydroxide. <1> The flame-retardant rubber composition according to claim 1. <6> The composition further contains the following component F: <1> ~ <5> The flame-retardant rubber composition according to any one of claims 1 to 5, Component F: Filler. <7> The component F contains carbon black and / or silica. <6> The flame-retardant rubber composition according to claim 1. <8> The flame retardant rubber composition is free of halogens and antimony trioxide. <1> ~ <7> 2. The flame-retardant rubber composition according to claim 1 . <9> <1> ~ <8> 2. A flame-retardant crosslinked rubber product obtained by crosslinking the flame-retardant rubber composition according to any one of claims 1 to 11. <10> Satisfy all of the following physical properties (i) to (iii): <9> The flame-retardant crosslinked rubber according to claim 1, (i) The flame retardancy rating according to the UL94 standard is V-0 or higher; (ii) Shore A hardness between 50 and 80; (iii) The compression set is 80% or less. <11> <9> or <10> An article comprising the flame-retardant crosslinked rubber according to claim 1. <12> It is a gasket, <11> The article described in EXAMPLES

[0056] Hereinafter, one embodiment of the present invention will be described in detail with reference to examples, although the present invention is not limited to these examples.

[0057] [Materials used] Ingredient A Ethylene-propylene-diene rubber (EP33, ENEOS Materials Corporation) ●Ingredient B Hydrated metal oxide 1 (BF013, Nippon Light Metal Co., Ltd., aluminum hydroxide) Hydrated metal oxide 2 (BF013STM, Nippon Light Metal Co., Ltd., aluminum hydroxide treated with silane coupling agent) Hydrated metal oxide 3 (BF013STV, Nippon Light Metal Co., Ltd., aluminum hydroxide treated with silane coupling agent) ●Component C Phosphorus-based flame-retardant plasticizer 1 (TCP, Daihachi Chemical Industry, tricresyl phosphate) Phosphorus-based flame-retardant plasticizer 2 (ADEKA STAB FP-900L, ADEKA Corporation, mixed ester of phosphoric acid with [1,1'-biphenyl]4,4'-diol and phenol) ●Component D Mineral oil (Diana Process Oil PW-380, Idemitsu Kosan Co., Ltd., paraffin-based process oil) ●Ingredient E · Silane coupling agent (KBM-503, Shin-Etsu Chemical Co., Ltd., 3-methacryloxypropyltrimethoxysilane) *Hydrated metal oxides 2 and 3 also contain silane coupling agents. Ingredient F Filler 1 (Seat G-SO, Tokai Carbon Co., Ltd., carbon black) Filler 2 (Nipsil ER, Tosoh Silica Corporation, precipitated silica) Co-crosslinking agent Co-crosslinking agent (Hicross MP, Seiko Chemical Co., Ltd., trimethylolpropane trimethacrylate (TMPTM)) Crosslinking agent Cross-linking agent (Perhexa 25B-40, NOF Corporation, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane) Anti-aging agent · Anti-aging agent (2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ)) Processing aids Processing aid (stearic acid)

[0058] [Examples 1 to 12, Comparative Examples 1 to 9] A crosslinked rubber sheet was prepared according to the following procedure. The crosslinked rubber sheet was used to prepare test pieces for the tests described below. 1. The components except for the crosslinking agent shown in Table 1 were kneaded in a kneader. The temperature during kneading was 50 to 150° C. The kneading time was 10 to 30 minutes. 2. A crosslinking agent was added and kneaded with an open roll. The temperature during kneading was 20 to 100° C. The kneading time was 5 to 30 minutes. 3. An uncrosslinked rubber sheet was produced from the resulting kneaded product. 4. The uncrosslinked rubber sheet was press-crosslinked at 170°C for 10 minutes. 5. Further, secondary crosslinking was carried out for 1 hour at 180° C. In this manner, a crosslinked rubber sheet having a thickness of 2 mm was obtained.

[0059] [Test Method] [1.Surface texture] The surfaces of the uncrosslinked rubber sheets obtained in step 3 of the Examples and Comparative Examples were visually observed and rated according to the following criteria. +: No abnormalities (bloom, bleed, blisters, etc.) are found on the sheet surface. -: Abnormalities are found on the sheet surface.

[0060] [2. Shore A hardness] The Shore A hardness of the crosslinked rubber sheets obtained in step 5 of the Examples and Comparative Examples was measured in accordance with JIS K6253. The specific procedure was as follows. 1. Three 2 mm thick crosslinked rubber sheets were stacked together to prepare a measurement sample. 2. Measurements were performed using a Type A durometer at 23°C and a relative humidity of 50%. The peak value of the durometer was taken as the Shore A hardness.

[0061] [3. Tensile test] A tensile test was performed based on JIS K6251 to measure the tensile stress at break and the tensile elongation at break. As a measurement sample, a No. 3 dumbbell test piece according to JIS K6251, punched out from the crosslinked rubber sheet obtained in step 5 of the examples and comparative examples, was used.

[0062] [4. Heat resistance test] The flame-retardant crosslinked rubber was subjected to a heat resistance test using a method modified from JIS K6262, and then the compression set was measured. The specific procedure was as follows. 1. An O-ring having a wire diameter of 2.4 mm was punched out from the crosslinked rubber sheet obtained in step 5 of each of the Examples and Comparative Examples to prepare a measurement sample. 2. The measurement sample was compressed by 25% and kept in air at 125°C for 70 hours. 3. The compression was released and the compression set of the crosslinked flame-retardant rubber was calculated. A crosslinked flame-retardant rubber with a small compression set value has a high restoring force even after being compressed for a long time.

[0063] The test method used in this embodiment differs from JIS K6262 in the shape of the measurement sample. That is, the measurement sample in JIS K6262 is disk-shaped and has a thickness of 12.5±0.5 mm or 6.3±0.5 mm. On the other hand, the measurement sample used in this embodiment is an O-ring with a wire diameter of 2.4 mm, so the thickness is also 2.4 mm. In general, the thinner the rubber product is, the smaller the recovery when released from compression tends to be. Therefore, the compression set value measured in this embodiment tends to be larger than the value measured based on JIS K6262.

[0064] [5. Combustion test] The flame retardancy was evaluated based on UL94 (vertical flame test). The specific procedure is as follows. 1. A rectangular sample was attached vertically to the clamp. 2. Flame retardancy was evaluated based on the 20mm vertical flame test (IEC60695-11-10B method, ASTM D3801). Specifically, a 20mm flame was applied to the sample for 10 seconds twice, and the burning behavior of the sample was observed. The evaluation criteria are as follows: +: Meets V-0 standards. -: Does not meet V-0 standards.

[0065] 〔result〕 The results are shown in Table 1. [Table 1] JPEG2025076131000002.jpg192142

[0066] The crosslinked rubber products according to the examples contained all of components A to D, and the contents of each component also met the prescribed conditions. As can be seen from Table 1, these crosslinked rubber products were excellent in surface properties, flexibility (Shore A hardness and tensile elongation at break), and flame retardancy, achieving high standards in all respects. Furthermore, these crosslinked rubber products were also excellent in tensile strength and heat resistance.

[0067] Comparing Example 1 and Example 12, in order to improve the tensile elongation at break of the cross-linked rubber product, it is preferable not to compound too much Component B (for example, 180 parts by weight or less is preferable, assuming 100 parts by weight of Component A). Comparing Examples 2, 3 and Examples 6, 7, in order to improve the tensile elongation at break of the cross-linked rubber product, it is preferable to use a non-condensed phosphate ester as Component C (for example, it is preferable to use tricresyl phosphate).

[0068] The cross-linked rubber products according to the Comparative Examples did not contain some of the components A to D, or the content of any of the components did not satisfy the prescribed conditions. As a result, these cross-linked rubber products remained at an insufficient level in any of the surface properties, flexibility, and flame retardancy.

[0069] Specifically, a crosslinked rubber product containing only component C at a high content without component D was too hard (Comparative Example 3) and had blisters on the surface (Comparative Example 6). Conversely, a crosslinked rubber product containing a high content of component D without component C had insufficient flame retardancy (Comparative Example 1). This result did not change even when component B, a flame retardant, was added (Comparative Example 2). A crosslinked rubber product in which the amount of component D was reduced to improve flame retardancy was too hard (Comparative Examples 4 and 5). These results show that in order to achieve high levels of surface properties, flexibility, and flame retardancy in a crosslinked rubber product, it is necessary to compound both components C and D.

[0070] Furthermore, the crosslinked rubber containing too much component B tended to be too hard (Comparative Example 7), while the crosslinked rubber containing too little component B tended to have insufficient flame retardancy (Comparative Example 9). The crosslinked rubber containing an excessive amount of component D and a large amount of component B had poor surface properties (Comparative Example 8). [Industrial Applicability]

[0071] The present invention can be used for rubber parts such as gaskets.

Claims

1. A flame-retardant rubber composition comprising the following components A to D: Component A: ethylene propylene diene rubber; Component B: hydrated metal oxide; Component C: phosphorus-based flame-retardant plasticizer; Component D: mineral oil; When the content of the component A is 100 parts by weight, the contents of the components B to D are as follows: Component B: 80 to 200 parts by weight; Component C: 1 to 15 parts by weight; Component D: 1 to 30 parts by weight.

2. When the content of the component A is 100 parts by weight, the content of the component B is less than 180 parts by weight. The flame retardant rubber composition according to claim 1.

3. The component C contains an aromatic compound. The flame retardant rubber composition according to claim 1.

4. Further comprising the following component E: The flame retardant rubber composition according to claim 1: Component E: A silane coupling agent.

5. The component B contains aluminum hydroxide and / or magnesium hydroxide. The flame retardant rubber composition according to claim 1.

6. The composition further comprises the following component F: The flame retardant rubber composition according to claim 1: Component F: filler.

7. The component F contains carbon black and / or silica. The flame retardant rubber composition according to claim 6.

8. The flame retardant rubber composition is free of halogens and antimony trioxide. The flame retardant rubber composition according to claim 1.

9. A flame-retardant crosslinked rubber product obtained by crosslinking the flame-retardant rubber composition according to any one of claims 1 to 8.

10. Satisfy all of the following physical properties (i) to (iii): The flame-retardant crosslinked rubber according to claim 9: (i) Flame retardancy according to the UL94 standard is V-0 or higher; (ii) a Shore A hardness of 50 to 80; (iii) The compression set is 80% or less.

11. An article comprising the flame-retardant crosslinked rubber according to claim 9.

12. The article of claim 11 which is a gasket.

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