JP2023163484A - Rubber composition and rubber component using the composition - Google Patents

Abstract

To provide a non-halogen-based flame-retardant rubber composition low in smoke emission at combustion, of no generation of harmful halogen-based gas and having physical properties such as weatherability, heat resistance, ozone resistance or the like suitable for applications such as hose, gasket and packing.SOLUTION: Disclosed is a rubber composition including ethylene-α-olefin-nonconjugated polyene-based copolymer rubber and phosphate as a flame retardant. The volume fraction (%) of phosphate is 20 vol% or more but less than 32 vol% based on the volume of rubber composition.SELECTED DRAWING: None

Description

The present invention relates to a rubber composition and a rubber member used in an environment where flame retardancy is required. More specifically, the present invention relates to flame-retardant rubber compositions and rubber members suitable for use as hoses, gaskets, packings, etc. in environments where flame retardancy is required.

When attempting to impart flame retardancy to a rubber material, a technique is known in which a flame retardant is blended into a raw rubber composition. As flame retardants, phosphorus-based flame retardants, halogen-based flame retardants, antimony-based flame retardants, hydrated metal compound-based flame retardants, etc. are known, and especially when halogen-based flame retardants and antimony trioxide are used in combination, excellent flame retardant effects are obtained. It is generally known that it can be obtained. However, in recent years, as environmental awareness has increased, there has been a demand for improvements in flame retardancy, low smoke generation during combustion (low smoke generation), and further reduction in the generation of toxic gases during combustion. . From this point of view, the technique of using a halogen flame retardant and antimony trioxide in combination poses environmental problems.

Patent Document 1 contains polychloroprene rubber and natural rubber as rubber components, uses intumescent phosphate as a flame retardant, does not contain halogen flame retardants and antimony trioxide, and does not generate smoke when burned. To provide a rubber composition for cushioning rubber for railway vehicles, which is environmentally friendly and generates little toxic gas during combustion.

A non-halogen intumescent flame retardant is used as a flame retardant in the composition, but polychloroprene rubber or natural rubber must have good weather resistance and heat resistance in order to be used for hoses, gaskets, packing, etc. , physical properties such as ozone resistance are insufficient. Furthermore, since the polychloroprene rubber component contains chlorine, it cannot be said to be a completely halogen-free rubber composition, and because it releases halogen when burned, it cannot be said to be an environmentally friendly rubber composition. On the other hand, when a hydrated metal compound flame retardant is used in an ethylene-α-olefin-nonconjugated polyene copolymer rubber, it is difficult to obtain sufficient flame retardancy.

JP 2019-1833 Publication

Therefore, the problem to be solved by the present invention is to use a rubber material other than polychloroprene rubber and natural rubber, which produces low smoke when burned and does not generate toxic halogen gas, and which can be used for hoses, gaskets, packing, etc. It is an object of the present invention to provide a non-halogen flame retardant rubber composition having physical properties such as weather resistance, heat resistance, and ozone resistance suitable for

The present inventors have solved the above problem by employing a rubber material that does not contain halogens such as chlorine as a rubber component, and using a phosphate in a specific amount as a flame retardant.
That is, the present invention includes the following.
[1] A rubber composition containing an ethylene-α-olefin-nonconjugated polyene copolymer rubber and a phosphate as a flame retardant, wherein the volume fraction (%) of the phosphate is higher than that of the rubber. A rubber composition having a content of 20% by volume or more and less than 32% by volume based on the volume of the composition.
[2] The ethylene-α-olefin-nonconjugated polyene copolymer rubber is a group consisting of ethylene-propylene-nonconjugated diene copolymer (EPDM) and ethylene-butene-nonconjugated diene copolymer (EBDM). The rubber composition according to [1], wherein the phosphate is at least one selected from the group consisting of melamine and an inorganic phosphorus compound, and a salt consisting of piperazine and an inorganic phosphorus compound.
[3] A rubber member obtained by crosslinking and molding the rubber composition according to [1] or [2].

According to the present invention, a flame-retardant rubber composition suitable for environment-friendly hoses, gaskets, packings, etc. that produces low smoke during combustion and does not generate toxic halogen gases in environments where flame retardancy is required. can provide things.

The rubber composition according to the present invention is a rubber composition containing an ethylene-α-olefin-nonconjugated polyene copolymer rubber and a phosphate as a flame retardant, wherein the volume fraction of the phosphate is (%) is 20% by volume or more and less than 32% by volume based on the volume of the rubber composition. Below, they will be explained in order.

[Ethylene-α-olefin-nonconjugated polyene copolymer rubber]
The α-olefin in the ethylene-α-olefin-nonconjugated polyene copolymer rubber is preferably an α-olefin having 3 to 20 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1- Linear α-olefins such as heptene, 1-octene, 1-nonene, and 1-decene, and branched α-olefins such as 3-methyl-1-butene, 3-methyl-1-pentene, and 4-methyl-1-pentene. - Examples include olefins. Preferred is propylene or 1-butene.

Examples of the non-conjugated polyene include 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, etc. chain nonconjugated diene; cyclohexadiene, dicyclopentadiene, methyltetriindene, 5-vinyl-2-norbornene, 5-(2-propenyl)-2-norbornene, 5-(3-butenyl)-2-norbornene, 5-(4-pentenyl)-2-norbornene, 5-(5-hexenyl)-2-norbornene, 5-(5-heptenyl)-2-norbornene, 5-(7-octenyl)-2-norbornene, 5- Cyclic non-conjugated dienes such as methylene-2-norbornene, 5-ethylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene; 2,3-diisopropylidene-5-norbornene, 2-ethylidene- 3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene, 1,3,7-octatriene, 1,4,9-decatriene, 6,10-dimethyl-1,5,9-undeca Triene, 5,9-dimethyl-1,4,8-decatriene, 4-ethylidene-8-methyl-1,7-nonadiene, 13-ethyl-9-methyl-1,9,12-pentadecatriene, 8, Examples include trienes such as 14,16-trimethyl-1,7,14-hexadecatriene and 4-ethylidene-12-methyl-1,11-pentadecadiene. Preferably it is a linear or cyclic non-conjugated diene.

Therefore, the ethylene-α-olefin-nonconjugated polyene copolymer rubber preferably consists of ethylene-propylene-nonconjugated diene copolymer (EPDM) and ethylene-butene-nonconjugated diene copolymer (EBDM). At least one type selected from the group.

[Flame retardants]
Phosphates used as flame retardants generally include salts of various phosphoric acids and at least one selected from metals, ammonia, aliphatic amines, and aromatic amines.
Phosphate forms a char layer on the rubber surface when ethylene-α-olefin-nonconjugated polyene copolymer rubber is burned, and has a heat insulating effect and a high gas barrier effect, promoting thermal decomposition of the rubber and suppressing decomposed gas. By suppressing the fuel supply to the combustion field due to generation and stopping the combustion cycle, the flame retardance of rubber is improved.

Phosphoric acids constituting the salt include inorganic phosphoric acids such as orthophosphoric acid, phosphorous acid, hypophosphorous acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, and tetraphosphoric acid; phosphonic acid, phosphinicocarboxylic acid, etc. Examples include organic phosphoric acids. Among these, orthophosphoric acid is preferred. Note that phosphoric acid can also be condensed (polyphosphoric acid). Examples of the polyphosphoric acid include chain polyphosphoric acid and cyclic polymetaphosphoric acid. The degree of condensation of these polyphosphoric acids is usually 3 to 50.

Examples of metals include lithium, sodium, magnesium, calcium, barium, iron (II), iron (III), aluminum, and the like. In particular, it is preferable to use magnesium phosphate or ammonium phosphate.
Examples of aliphatic amines include methylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, piperazine, and the like.
Examples of aromatic amines include pyridine, triazine, and melamine.

Among phosphates as flame retardants, intumescent phosphates are preferred.
Intumescent phosphates form an intumescent (foaming expansion layer) on the rubber surface when ethylene-α-olefin-nonconjugated polyene copolymer rubber is burned, and have a high heat insulation effect. The gas barrier effect improves the flame retardancy of rubber by stopping the combustion cycle by suppressing the acceleration of rubber decomposition due to heat and the supply of fuel to the combustion field due to the generation of decomposed gas.

Examples of flame retardants containing magnesium phosphate, ammonium phosphate, etc. include "FP-2500S" manufactured by ADEKA.

Among the phosphates as flame retardants, those containing salts of melamine and inorganic phosphorus compounds and salts of piperazine and inorganic phosphorus compounds are also preferred. More preferred are those containing melamine polyphosphate as melamine and an inorganic phosphorus compound, and piperazine pyrophosphate as a salt of piperazine and an inorganic phosphorus compound.

Examples of flame retardants containing melamine polyphosphate and piperazine pyrophosphate include "FR-303" manufactured by YUIL CHEMITECH.

In order to achieve flame retardancy (equivalent to V-0 according to UL94V standard), it is necessary to contain phosphate as a flame retardant at 20% by volume or more and less than 32% by volume based on the total volume of the rubber composition. preferable. This is because if the amount exceeds 32% by volume, the tensile strength of the rubber member will be less than 9.0 MPa, and cracks may occur in the rubber member when the rubber member is removed from the mold after vulcanization of the rubber composition. . More preferably, it is 20 volume % or more and 30 volume % or less.

[Other additives]

The rubber composition according to the present invention includes, in addition to the rubber component and the phosphate, fillers such as carbon black and clay, plasticizers, vulcanizing agents, vulcanization accelerators, vulcanization accelerators, and vulcanization retarders. , softeners, anti-aging agents, processing aids, and other compounding agents commonly used in the rubber industry may be appropriately blended and used within the range that does not impair the effects of the present invention.

[Plasticizer]
As the plasticizer, known ones can be used, such as petroleum softeners such as paraffin oil, phosphate ester plasticizers, sebacate ester plasticizers, adipic ester plasticizers, and the like.

From the viewpoint of not inhibiting flame retardancy, it is preferable to use a phosphate ester plasticizer. Specific examples of phosphate ester plasticizers include tributyl phosphate (TBP), tris(2-ethylhexyl) phosphate (TOP), tricresyl phosphate (TCP), and tricylenyl phosphate (TXP).

In view of compatibility with the ethylene-α-olefin-nonconjugated polyene copolymer rubber, the SP value (solubility parameter) of the phosphoric acid ester plasticizer is preferably 8.4 (cal/cm ³ ) ^1/2 or less. If the SP value (solubility parameter) is greater than 8.4 (cal/cm ³ ) ^1/2 or greater than 30 parts by weight, it indicates compatibility with the ethylene-α-olefin-nonconjugated polyene copolymer rubber. This causes a phenomenon called bleed, in which the plasticizer oozes out of the rubber composition, resulting in decreased kneading processability, increased defect rate due to mold contamination during vulcanization, and problems with adhesion to metals. In addition, as a product, it is treated as having a poor appearance.

Here, the SP value is a solubility parameter, and a large number of data have been proposed, such as measured values from linear heat of evaporation, solubility, etc., and calculation methods by Small, Fedors, or Hansen. In the invention, values based on the widely known Hoy method are used. Hoy method literature includes H. L. Hoy: J. Paint Tech. , 42 (540), 76-118 (1970), and SP Value Basics, Applications, and Calculation Methods (Yamamoto, Information Technology Organization, 2005).

When the ethylene-α-olefin-nonconjugated polyene copolymer rubber is 100 parts by weight, the plasticizer is preferably 30 parts by weight or less.

[Carbon black]
By incorporating carbon black as a filler into the rubber composition according to the present invention, it is possible to improve mechanical properties such as breaking strength of the resulting rubber member. There are various types of carbon black, and an appropriate one is selected and used depending on the purpose. As the carbon black, any known carbon black can be used, and examples thereof include SAF, ISAF, HAF, MAF, FEF, GPF, SRF, etc., which are furnace blacks commonly used for rubber. Carbon black may be used alone or two or more types may be blended.

Carbon black is preferably at least 10 parts by weight, more preferably at least 20 parts by weight, preferably at least 20 parts by weight, based on 100 parts by weight of the ethylene-α-olefin-nonconjugated polyene copolymer rubber in the rubber composition according to the present invention. It is blended in an amount of 120 parts by weight or less, more preferably 80 parts by weight or less.

There are various commercially available carbon blacks that can be used in the present invention. Examples include SRF grade carbon blacks such as Showblack N762 (Showa Cabot Co., Ltd.), Seast S (Tokai Carbon Co., Ltd.), Diablack R, and Diablack N760M (all produced by Mitsubishi Chemical Corporation).

[Vulcanizing agent]
As the vulcanizing agent, organic peroxides and the like can be used. Any organic peroxide can be used as long as it decomposes at a temperature of 100° C. or higher to generate radicals. The organic peroxide is generally selected in consideration of the film forming temperature, composition adjustment conditions, curing (bonding) temperature, heat resistance of the adherend, and storage stability. In particular, those having a decomposition temperature of 70° C. or higher with a half-life of 10 hours are preferred. If the decomposition temperature is less than 70°C, processability during rubber kneading or rubber molding may deteriorate.

Examples of organic peroxides include peroxycarbonates, diacyl peroxides, dialkyl peroxides, peroxyketals, and alkyl peresters.

Specific examples of organic peroxides include:
2,5-dimethylhexane-2,5-dihydroperoxide,
2,5-dimethyl-2,5-bis(t-butylperoxy)hexane,
t-butylcumyl peroxide,
2,5-dimethyl-2,5-di(t-butylperoxy)hexane,
dicumyl peroxide,
α,α'-bis(t-butylperoxyisopropyl)benzene,
n-butyl-4,4-bis(t-butylperoxy)valerate,
2,2-bis(t-butylperoxy)butane,
1,1-bis(t-butylperoxy)cyclohexane,
1,1-bis(t-butylperoxy)trimethylcyclohexane,
1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,
t-butyl peroxybenzoate,
benzoyl peroxide,
t-butyl peroxyacetate,
methyl ethyl ketone peroxide,
2,5-dimethyl-2,5-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,
1,1-bis(t-butylperoxy)cyclohexane,
methyl ethyl ketone peroxide,
2,5-dimethylhexyl-2,5-bisperoxybenzoate,
t-butyl hydroperoxide,
p-menthane hydroperoxide,
p-chlorobenzoyl peroxide,
hydroxyheptyl peroxide,
chlorohexanone peroxide,
octanoyl peroxide,
decanoyl peroxide,
lauroyl peroxide,
cumyl peroxyoctoate,
succinic acid peroxide,
acetyl peroxide,
t-butyl peroxy (2-ethylhexanoate),
m-tolu oil peroxide,
Mention may be made, without limitation, of t-butyl peroxyisobutyrate, and 2,4-dichlorobenzoyl peroxide.

One type of organic peroxide may be used, or two or more types may be used in combination. Moreover, these can also be used as diluted products or masterbatch products using silica or calcium carbonate as a carrier. All of these are available as commercial products (for example, Percmill D, Percmill D-40, and Percmill D-40MB manufactured by NOF Corporation).

The amount of organic peroxide to be blended is not particularly limited. Preferably, the amount of organic peroxide blended is 1 part by weight or more and 10 parts by weight or less based on 100 parts by weight of the ethylene-α-olefin-nonconjugated polyene copolymer rubber in the rubber composition according to the present invention. It is.

[Vulcanization accelerator]
As a vulcanization accelerator, triallyl isocyanurate, triallyl cyanurate, triallyl isocyanate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, glycidyl methacrylate, diallyl phthalate, Quinone dioximes, bismaleimides, dimethacrylic acid metal salts, diacrylic acid metal salts, sulfur compounds, 1,2-polybutadiene, and the like can be used. All of these are available as commercial products (for example, Sunester TMP manufactured by Sanshin Kagaku Kogyo Co., Ltd.).

The amount of the vulcanization accelerator to be added is not particularly limited. Preferably, the blending amount of the vulcanization accelerator is usually 0.1 to 10 parts by weight, based on 100 parts by weight of the ethylene-α-olefin-nonconjugated polyene copolymer rubber in the rubber composition according to the present invention. Preferably it is 0.5 to 5 parts by weight.

[Vulcanization accelerator]
Examples of vulcanization accelerators include fatty acids such as stearic acid, oleic acid, and cottonseed fatty acids, as well as magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, red lead, white lead, litharge, and hydrotalcite. , and metal oxides such as zinc white.

The amount of the vulcanization accelerator to be added is determined depending on the crosslinking agent used, but is based on 100 parts by weight of the ethylene-α-olefin-nonconjugated polyene copolymer rubber in the rubber composition of the present invention. , usually 0.1 to 10 parts by weight, preferably 0.5 to 3 parts by weight.

[Vulcanization retarder]
Examples of vulcanization retarders include phthalic anhydride, benzoic acid, salicylic acid, N-nitrosodiphenylamine, N-(cyclohexylthio)-phthalimide (CTP), sulfonamide derivatives, diphenylurea, bis(tridecyl)pentaerythritol-diphosphite, etc. Examples include N-(cyclohexylthio)-phthalimide (CTP).

The amount of the vulcanization retarder added is not particularly limited. Preferably, the amount of the vulcanization retarder is usually 0.1 to 10 parts by weight, based on 100 parts by weight of the ethylene-α-olefin-nonconjugated polyene copolymer rubber in the rubber composition of the present invention. Preferably it is 0.5 to 3 parts by weight.

[Softener]
Softeners include process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, petroleum softeners such as petrolatum; coal tar softeners such as coal tar and coal tar pitch; castor oil, linseed oil, rapeseed oil, Vegetable oil-based softeners such as coconut oil; waxes such as tall oil, sabu, beeswax, carnauba wax, and lanolin; aliphatic dibasic acid esters such as bis(2-ethylhexyl) sebacate; tris(2-ethylhexyl) phosphate, etc. Orthophosphoric acid ester; fatty acids and fatty acid salts such as ricinoleic acid, palmitic acid, stearic acid, barium stearate, calcium stearate, zinc laurate; synthetic polymer substances such as petroleum resin, atactic polypropylene, coumaron indene resin, etc. Can be mentioned. All of these are available as commercial products.

The blending amount of the softener is not particularly limited. Preferably, the blending amount of the softener is usually 0.1 to 10 parts by weight, preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the ethylene-α-olefin-nonconjugated polyene copolymer rubber in the rubber composition according to the present invention. The amount is 0.5 to 3 parts by weight.

[Anti-aging agent]
As the anti-aging agent, known anti-aging agents can be used, including amine-ketone anti-aging agents, phenolic anti-aging agents, imidazole anti-aging agents, amine anti-aging agents and the like.
Specifically, commercially available products include Nocrac CD (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., 4,4'-bis(α,α-dimethylbenzyl)diphenylamine), Nocrack 224 (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., 2 , 2,4-trimethyl-1,2-dihydroquinoline polymer).

The amount of anti-aging agent added is not particularly limited. Preferably, the amount of the anti-aging agent blended is usually 0.1 to 10 parts by weight, preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the ethylene-α-olefin-nonconjugated polyene copolymer rubber in the rubber composition according to the present invention. is 0.5 to 5 parts by weight.

[Processing aid]
Processing aids should be selected according to the purpose, and generally well-known higher fatty acids, fatty acid metal salts, fatty acid esters, fatty acid amides, hydrocarbons, etc. may be used alone or in combination. may be used in combination. All of these are available as commercial products.

The amount of the processing aid added is not particularly limited. Preferably, the amount of the anti-aging agent is 0.1 to 10 parts by weight based on 100 parts by weight of the ethylene-α-olefin-nonconjugated polyene copolymer rubber in the rubber composition according to the present invention. Furthermore, silica, calcium carbonate, finely divided talc, finely divided aluminum silicate, and the like may be used as reinforcing agents.

[Method for preparing rubber composition]
The rubber composition according to the present invention can be prepared by blending the above components using a known method for preparing a rubber composition. For example, using a known mixer such as a Banbury mixer, a single- or twin-screw extruder, a kneader, or an internal mixer such as an intermix, softeners, reinforcing agents, anti-aging agents, etc. The conjugated polyene copolymer rubber is kneaded at a temperature of 80 to 170°C for 3 to 10 minutes, and then kneaded as needed at a temperature of 40 to 80°C using rolls such as open rolls or a kneader. It can be prepared by adding a crosslinking agent, crosslinking accelerator, processing aid, etc. and kneading for 5 to 30 minutes.

The rubber composition according to the present invention is suitable for gaskets such as joint sheet gaskets, rubber sheet gaskets, ferrule gaskets (sanitary gaskets), spiral gaskets (semi-metallic gaskets), metal jacket gaskets, metal joints, gland packings, and mechanical gaskets. It is particularly suitable for manufacturing rubber members used for seals, packings such as oil seals, O-rings, etc.

[Rubber member]
The rubber composition obtained by kneading can be crosslinked into a desired rubber member using a known extrusion molding machine, compression molding machine, injection molding machine, transfer molding machine, or the like. The molding conditions are, for example, 150 to 220°C and 1 to 30 minutes.

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples and Comparative Examples.

<Method for preparing rubber composition>
〇Production method of rubber composition The rubber compositions of Examples 1 to 6 and Comparative Examples 1 to 3 were blended with 100 parts by weight of rubber according to the compounding recipe in Table 1, and kneaded using a 6-inch open roll. , a rubber composition was prepared.

Details of each formulation listed in Table 1 are shown below.
a) Rubber component ethylene-propylene-diene copolymer (EPDM); manufactured by JSR, trade name "EP35"
Ethylene-butene-diene copolymer (EBDM); manufactured by Mitsui Chemicals, trade name "K-9330M"
b) Flame retardant Yuil Chemitech Co. , Ltd. Manufactured by product name "FR-303"
Intumescent phosphate (contains magnesium phosphate and ammonium phosphate); manufactured by ADEKA Co., Ltd., product name: ADEKA STAB FP-2500S
c) Carbon black; “Asahi 71” manufactured by Asahi Carbon Co., Ltd.
d) Plasticizer Phosphate ester plasticizer; manufactured by Daihachi Kagaku Kogyo Co., Ltd., trade name "TOP"
e) Anti-aging agent; manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name “Nocrac 224”
f) Processing aid stearic acid; manufactured by New Japan Chemical Co., Ltd., trade name “Stearic Acid 50S”
g) Vulcanizing agent organic peroxide; manufactured by NOF Corporation, trade name “Perc Mill D40”
h) Vulcanization accelerator; manufactured by Sanshin Kagaku Kogyo Co., Ltd., trade name “Sunester TMP”
Each formulation listed in Table 1 is shown below.

<Test piece preparation method and test conditions>
〇 Test piece creation conditions A 2 mm thick sheet-like test piece was obtained by crosslinking the rubber composition obtained by kneading using a press molding machine.

〇Test conditions:
(Normal physical properties)
The hardness of the rubber member was measured using durometer hardness type A in accordance with JIS K6253.
The tensile strength and elongation of the rubber member were measured in accordance with JIS K6251.
The test piece used was a dumbbell type 5 based on JIS K 6251.

(Flame retardancy test)
The flame retardancy of the rubber member was measured in accordance with the UL94V standard.
A test piece of a predetermined size (13 mm x 125 mm x 2 mm) was cut out from the above sheet-like test piece, and the test piece was subjected to a vertical combustion test in accordance with the UL94V standard. Specifically, the test piece was vertically attached to a predetermined clamp, and indirect flame was applied twice for 10 seconds using a 20 mm flame, and the evaluation was made based on the combustion behavior. "Equivalent to V-0" of the UL94V standard was marked as ○, and the others were marked as ×.

(Compression set test)
The heat resistance was evaluated using a compression set test in accordance with JIS K 6262:2018.
A test was conducted for 70 hours under an environment of 25% compression and 150°C, and if the compression set was 40% or less, it was considered heat resistant and rated ○. Others were marked as ×.

(Workability)
Rubber members with a tensile strength of 9.0 MPa or more did not cause tearing defects during demolding during vulcanization molding, and their workability was rated as 0. Rubber members with a tensile strength of less than 9.0 MPa were rated poor in processability because tearing failure occurred.

According to the present invention, a flame-retardant rubber composition suitable for environment-friendly hoses, gaskets, packings, etc. that produces low smoke during combustion and does not generate toxic halogen gases in environments where flame retardancy is required. can provide things.

Claims (3)

A rubber composition containing an ethylene-α-olefin-nonconjugated polyene copolymer rubber and a phosphate as a flame retardant, wherein the volume fraction (%) of the phosphate is A rubber composition having a content of 20% by volume or more and less than 32% by volume based on volume. The ethylene-α-olefin-nonconjugated polyene copolymer rubber is selected from the group consisting of ethylene-propylene-nonconjugated diene copolymer (EPDM) and ethylene-butene-nonconjugated diene copolymer (EBDM). The rubber composition according to claim 1, wherein the phosphoric acid salt contains a salt consisting of melamine and an inorganic phosphorus compound, and a salt consisting of piperazine and an inorganic phosphorus compound. A rubber member obtained by crosslinking and molding the rubber composition according to claim 1 or 2.