Flame-retardant rubber composition

Abstract

Provided is a flame-retardant rubber composition containing one rubber selected from the group consisting of ethylene-butylene-non-conjugated diene rubbers and ethylene-propylene-non-conjugated diene rubbers, the amount of the rubber being less than 100 parts by mass per 100 parts by mass of the rubber component, and the amount of the rubber being less than or equal to 100 parts by mass per 100 parts by mass of the rubber component. The present invention relates to a flame retardant composition containing 220-340 parts by mass of a hydrated metal oxide having an average particle diameter of 0.9-5.0 [mu] m, 20-60 parts by mass of a plasticizer, and 3-6 parts by mass of a crosslinking agent dicumyl peroxide, containing 2-4 parts by mass of a silane coupling agent with respect to 100 parts by mass of the hydrated metal oxide, having flame retardancy of V-0 in flame retardancy standard UL94, having a JIS A hardness of 65-75 in accordance with JIS K-6253-3, having a compression set of 30% or less in accordance with JIS K-6262, and having excellent flame retardancy. In the low-temperature characteristics measured in accordance with JIS K 6261-3: 2017, the temperature at which the shrinkage rate reaches 10% is-50 DEG C or less.

Description

[0001] This application is a divisional application of a patent application with the application number 202180006031.6 (international application number PCT / JP2021 / 000870), the filing date of January 13, 2021, and the invention title of "Flame Retardant Rubber Composition". Technical Field

[0002] The present invention relates to an olefin-based flame retardant rubber composition. Background Art

[0003] Ethylene-α-olefin-non-conjugated diene copolymers typified by ethylene-propylene-diene copolymer rubber are excellent in mechanical properties, heat resistance, weather resistance, etc., and are inexpensive, so they are used in a wide range of applications such as automotive parts, electronic product parts, civil engineering and building materials.

[0004] Recently, as the performance requirements for automobiles, electronic products, etc. have become higher and higher, high functionality is also required for the rubber compositions that make up the sealing materials used in these products. That is, excellent rubber properties such as hardness and compression set, low temperature properties, flame retardancy, etc. are required. In order to realize such a highly functional rubber composition, various technologies for further improving the performance of rubber products containing ethylene-α-olefin-non-conjugated diene copolymers have been developed.

[0005] As technologies for further improving properties such as flame retardancy and reduction of environmental load, for example, Patent Document 1 discloses a flame retardant composition containing ethylene-propylene rubber containing a halogen-based flame retardant. Patent Documents 2 and 3 disclose a halogen-free flame retardant foamed material containing a rubber composition. Patent Document 4 discloses a flame retardant rubber composition that uses a metal hydroxide as a flame retardant and contains an acid-modified polyolefin.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-194232

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2002-293976

[0010] Patent Document 3: Japanese Patent Application Laid-Open No. 2007-204621

[0011] Patent Document 4: Japanese Patent Application Laid-Open No. 2018-16747 Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] However, regarding the flame retardant composition of Patent Document 1, there are concerns about environmental pollution caused by halogen-based flame retardants. Although the foamed materials of Patent Documents 2 and 3 are halogen-free, due to being foamed materials, their rubber properties are poor and they are not suitable for sealing materials. In addition, although the rubber composition of Patent Document 4 is also halogen-free, it is considered that the hardness of the composition made of this composition may increase predictably and the rubber properties are insufficient.

[0014] The present invention has been completed in view of such circumstances. That is, the object of the present invention is to provide a flame retardant rubber composition having excellent flame retardancy and rubber properties and capable of reducing the environmental load.

[0015] Technical means for solving the problem

[0016] In order to solve the above problems, the present inventors studied the types and contents of flame retardants contained in the flame retardant rubber composition. As a result, it was found that by using a hydrated metal oxide as a flame retardant and making the flame retardant rubber composition contain a specified amount of the hydrated metal oxide and a plasticizer, the flame retardancy, rubber properties, etc. of the flame retardant rubber composition can be improved, and the environmental load can be reduced. Based on such an insight, the present invention has been completed.

[0017] That is, the flame retardant rubber composition of the present invention is characterized in that the flame retardant rubber composition contains an ethylene-α-olefin-non-conjugated diene copolymer, a hydrated metal oxide, a silane coupling agent, a plasticizer, and a crosslinking agent, the α-olefin of the above ethylene-α-olefin-non-conjugated diene copolymer has 3 or more carbon atoms, and 180 to 350 parts by mass of the above hydrated metal oxide and 10 to 60 parts by mass of the above plasticizer are contained per 100 parts by mass of the above ethylene-α-olefin-non-conjugated diene copolymer.

[0018] Effects of the invention

[0019] The flame retardant rubber composition of the present invention has excellent flame retardancy and rubber properties and can reduce the environmental load. Detailed implementation mode

[0020] Hereinafter, the embodiments of the present invention will be described in detail. However, the scope of the present invention is not limited to the embodiments described below as specific examples.

[0021] The flame-retardant rubber composition of the present embodiment contains an ethylene-α-olefin-non-conjugated diene copolymer, a hydrated metal oxide, a silane coupling agent, a plasticizer, and a crosslinking agent. By blending a hydrated metal oxide in the components constituting the flame-retardant rubber composition, the environmental load of the flame-retardant rubber composition can be reduced and the flame retardancy can be improved. In addition, by appropriately blending a crosslinking agent and a plasticizer, the kneading processability, rubber properties, etc. of the flame-retardant rubber composition can be improved. Hereinafter, each component constituting the flame-retardant rubber composition will be described.

[0022] (Ethylene-α-olefin-non-conjugated diene copolymer)

[0023] The α-olefin in the ethylene-α-olefin-non-conjugated diene copolymer of the present embodiment is an α-olefin having 3 or more carbon atoms, more preferably an α-olefin having 4 or more carbon atoms. Examples of the α-olefin having 3 or more carbon atoms include, for example, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, etc. By making the number of carbon atoms of the α-olefin 3 or more, the crystallization of polyethylene can be hindered and the elasticity and low-temperature characteristics of the flame-retardant rubber composition can be improved. In addition, by increasing the number of carbon atoms of the α-olefin, the entanglement of the main chain can be reduced, the mobility of the main chain can be increased, and the low-temperature characteristics of the flame-retardant rubber composition can be further improved.

[0024] Examples of the non-conjugated diene include chain non-conjugated dienes such as 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene; cyclic non-conjugated dienes such as cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene; trienes such as 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene, 1,3,7-octatriene, 1,4,9-decatriene, etc.

[0025] (Hydrated metal oxide)

[0026] As the hydrated metal oxide, examples thereof include hydrated metal oxides such as aluminum hydroxide, magnesium hydroxide, hydrated product of magnesium oxide - nickel oxide, hydrated product of magnesium oxide - zinc oxide, etc., and among them, aluminum hydroxide is preferred. Since the heat absorption amount during the thermal decomposition of aluminum hydroxide is higher than that of other hydrated metal oxides, excellent flame retardancy can be exhibited even in a small amount. Therefore, by using aluminum hydroxide as the flame retardant, the amount of the flame retardant can be suppressed and a flame-retardant rubber composition excellent in rubber properties such as hardness and compression set can be produced. The flame retardant can be only one kind or two or more kinds can be used in combination.

[0027] In the flame-retardant rubber composition of the present embodiment, 180 parts by mass to 350 parts by mass of the hydrated metal oxide as the flame retardant is contained with respect to 100 parts by mass of the ethylene - α-olefin - non-conjugated diene copolymer, and preferably 200 parts by mass to 340 parts by mass of the hydrated metal oxide as the flame retardant is contained. The hydrated metal oxide is a halogen-free and antimony-free inorganic flame retardant. By using the hydrated metal oxide as the flame retardant, the flame retardancy of the rubber composition can be improved while reducing the environmental load.

[0028] By setting the content of the hydrated metal oxide to 180 parts by mass or more, the flame retardancy of the flame-retardant rubber composition can be improved. On the other hand, by setting the content of the hydrated metal oxide to 350 parts by mass or less, flexibility suitable for a sealing material or the like can be imparted to the flame-retardant rubber composition.

[0029] As the hydrated metal oxide, it is preferred to use the hydrated metal oxide in a particulate form. The average particle diameter of the hydrated metal oxide is preferably 0.6 μm to 10 μm, more preferably 0.9 μm to 5.0 μm. If the average particle diameter of the hydrated metal oxide is 0.6 μm or more, the dispersion and workability during kneading can be improved. On the other hand, if the average particle diameter of the hydrated metal oxide is 10 μm or less, flame retardancy can be imparted while maintaining the mechanical properties of the rubber material.

[0030] (Silane coupling agent)

[0031] Preferably, the flame-retardant rubber composition contains a silane coupling agent in addition to the hydrated metal oxide, and the hydrated metal oxide is surface-treated with the silane coupling agent. As the silane coupling agent, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane and other vinyl-containing alkoxysilanes or their oligomers can be used. With respect to 100 parts by mass of the hydrated metal oxide, preferably 1 part by mass to 5 parts by mass of the silane coupling agent is contained, and more preferably 2 parts by mass to 4 parts by mass of the silane coupling agent is contained.

[0032] By blending a silane coupling agent in a flame-retardant rubber composition, the compression set of the flame-retardant rubber composition can be improved. Further, by surface-treating a hydrated metal oxide with a silane coupling agent and then blending it, the compatibility of the hydrated metal oxide can be improved and it can be uniformly dispersed in the flame-retardant rubber composition, and the blending amount of the hydrated metal oxide can be suppressed and the increase in the hardness of the flame-retardant rubber composition can be suppressed.

[0033] (Plasticizer)

[0034] In order to improve the processability and rubber properties of a flame-retardant rubber composition, in the flame-retardant rubber composition, 10 to 60 parts by mass of a plasticizer can be blended relative to 100 parts by mass of an ethylene-α-olefin-non-conjugated diene copolymer. The content of the plasticizer is preferably 20 to 60 parts by mass. If the content of the plasticizer is 10 parts by mass or more, appropriate softness can be imparted to the flame-retardant rubber composition, and the applicability to sealing materials and the like can be improved. On the other hand, if the content of the plasticizer is 60 parts by mass or less, the ratio of the flame retardant to the entire flame-retardant rubber composition can be increased and the flame retardancy can be improved.

[0035] As the plasticizer, mineral oils and chemically synthesized oils mainly composed of aliphatic hydrocarbons that are usually used in rubber compositions can be used. For example, as the mineral oil, paraffin-based processing oils are suitable, and as the chemically synthesized oil, poly-α-olefins, α-olefin oligomers, etc. are suitable. Among the exemplified plasticizers, ethylene-α-olefin oligomers are preferred. This is because the blending of the plasticizer may cause a decrease in compression set depending on the type of the plasticizer, and the possibility of a decrease in compression set caused by ethylene-α-olefin oligomers is small.

[0036] Relative to 100 parts by mass of the ethylene-α-olefin-non-conjugated diene copolymer, 10 to 50 parts by mass of an ethylene-α-olefin oligomer is preferably contained, and 20 to 45 parts by mass of an ethylene-α-olefin oligomer is more preferably contained. If the content of the ethylene-α-olefin oligomer is 10 parts by mass or more, appropriate softness can be imparted to the flame-retardant rubber composition and the applicability to sealing materials and the like can be improved. On the other hand, if the content of the ethylene-α-olefin oligomer is 50 parts by mass or less, adhesion of the rubber material to a kneader or the like during kneading processing can be suppressed.

[0037] (Crosslinking agent)

[0038] As the crosslinking agent, crosslinking agents that can usually be used in the crosslinking of rubber compositions can be blended, and among them, organic peroxides are preferred. This is because organic peroxides do not contain sulfur-based compounds and do not corrode metal materials in contact with the flame-retardant rubber composition.

[0039] Examples of the organic peroxide include, for example, tert-butyl peroxide, dicumyl peroxide, tert-butyl cumyl peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, etc. The compounding amount of the organic peroxide is preferably 3 to 6 parts by mass with respect to 100 parts by mass of the ethylene-α-olefin-non-conjugated diene copolymer.

[0040] (Rubber properties)

[0041] The rubber properties are properties such as the hardness, compression set, resilience, elongation rate, etc. of the rubber composition. The hardness of the flame-retardant rubber composition of the present embodiment is preferably 60 to 80 in terms of JIS A hardness, more preferably 65 to 75. If it is 60 or more in terms of JIS A hardness, appropriate strength can be imparted to the flame-retardant rubber composition. On the other hand, if it is 80 or less in terms of JIS A hardness, by imparting appropriate softness to the flame-retardant rubber composition, high sealing performance can be achieved when processed into a sealing material or the like. It should be noted that the JIS A hardness is the hardness measured with a Type A durometer according to JIS K-6253-3.

[0042] In addition, the compression set measured according to JIS K-6262 is preferably 35% or less, more preferably 30% or less. By making the flame-retardant rubber composition have such rubber properties, the sealing performance when the flame-retardant rubber composition is processed into a sealing material or the like is improved.

[0043] (Low-temperature properties)

[0044] In the low-temperature properties of the flame-retardant rubber composition of the present embodiment measured according to JIS K 6261-3:2017, the temperature (TR10) at which the shrinkage rate reaches 10% is preferably -40°C or lower, more preferably -50°C or lower. By making the flame-retardant rubber composition have such low-temperature properties, the applicability to products used in low-temperature environments is improved.

[0045] (Flame retardant)

[0046] The flame retardancy of the flame-retardant rubber composition of the present embodiment is preferably V-0 in the flame retardancy standard UL94. By making the flame-retardant rubber composition have such flame retardancy, the applicability to products used in high-temperature environments, such as gaskets, etc. is improved.

[0047] The flame-retardant rubber composition of the present embodiment can be used as a molding material for sealing materials used under temperature conditions of -40°C to +150°C, such as O-rings, D-rings, X-rings, gaskets, liners, diaphragms, valves, etc. In particular, it can be suitably used as a molding material for sealing materials in contact with high temperatures and heating oils.

[0048] Examples

[0049] Hereinafter, the present invention will be described by way of examples and comparative examples, but these examples do not limit the present invention.

[0050] The raw materials used in the examples and comparative examples are as follows.

[0051] (1) Ethylene-butene-non-conjugated diene rubber (EBDM): Manufactured by Mitsui Chemicals, Inc., EBT K-9330, iodine value 16

[0052] (2) Ethylene-propylene-non-conjugated diene rubber (EPDM): Manufactured by Sumitomo Chemical Co., Ltd., ESPRENE 505A, iodine value 26

[0053] (3) Aluminum hydroxide-1: Manufactured by Nippon Light Metal Co., Ltd., BF013, average particle size 1 μm, not surface-treated with a vinyl-based silane coupling agent

[0054] (4) Aluminum hydroxide-2: Manufactured by Nippon Light Metal Co., Ltd., BF013STV, average particle size 1 μm, surface-treated with a vinyl-based silane coupling agent

[0055] (5) Aluminum hydroxide-3: Dried and pulverized product of Sumitomo Chemical Co., Ltd., AHT#B, average particle size 0.5 μm

[0056] (6) Magnesium hydroxide: Manufactured by Kojima Chemical Industry Co., Ltd., Magseeds N, average particle size 1 μm

[0057] (7) Magnesium oxide: Manufactured by Kyowa Chemical Industry Co., Ltd., Kyowa Mag 150

[0058] (8) Carbon: Manufactured by Asahi Carbon Co., Ltd., Asahi#35G

[0059] (9) Plasticizer-1 (paraffin processing oil): Manufactured by Idemitsu Kosan Co., Ltd., PW-380

[0060] (10) Plasticizer-2 (ethylene-α-olefin oligomer): Manufactured by Mitsui Chemicals, Inc., Lucant HC-2000

[0061] (11) Vinyl-based silane coupling agent: Manufactured by Momentive, STLQUEST A-171

[0062] (12) Crosslinking agent (organic peroxide): Manufactured by NOF Corporation, Percumyl D

[0063] (Method for producing flame-retardant rubber composition)

[0064] Per 100 parts by mass of ethylene-α-olefin-non-conjugated diene copolymer, 250 parts by mass of aluminum hydroxide-2, 20 parts by mass of plasticizer-1, and 22 parts by mass of plasticizer-2 were compounded to prepare the uncrosslinked rubber composition of Example 1. The uncrosslinked rubber composition was prepared using a kneader (closed mixer). For the uncrosslinked rubber compositions of Examples 2 to 9 and Comparative Examples 1 to 14, except that the composition was changed as described in Tables 1 and 2, they were prepared by the same method as in Example 1.

[0065] For the uncrosslinked rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 14, the crosslinking agents described in Tables 1 and 2 were added, kneaded with an open roll, and crosslinked under pressure at 180 °C for 10 minutes using a sheet mold, and then post-cured at 150 °C for 24 hours to obtain 2-mm-thick sheet-shaped crosslinked molded products of the flame-retardant rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 14.

[0066] <Evaluation>

[0067] Using the prepared sheet-shaped crosslinked molded products of the uncrosslinked rubber composition and the flame-retardant rubber composition, various properties described below were evaluated.

[0068] (Mixing processability)

[0069] Regarding the adhesion of the rubber composition to the kneader when kneading the uncrosslinked rubber composition using an open roll and a kneader, it was determined based on the following criteria. In the case of ○ and △, it was considered qualified.

[0070] ○: Not adhered to the kneader and can be discharged

[0071] △: Adhered to the kneader but can be discharged

[0072] (JIS A hardness)

[0073] The JIS A hardness of the flame-retardant rubber composition was measured using a Type A durometer according to JIS K-6253-3.

[0074] (Compression set)

[0075] The compression set of the flame-retardant rubber composition was measured according to JIS K-6262.

[0076] (Low-temperature characteristics)

[0077] According to JIS K 6261-3:2017, the temperature (TR10) at which the shrinkage rate of the flame-retardant rubber composition reaches 10% was measured.

[0078] (Flame retardancy)

[0079] In the flame-retardant test UL94 of the flammability UL94 standard, whether the flame retardancy of the flame-retardant rubber composition was V-1 or V-0 was measured. If it was neither V-1 nor V-0, it was recorded as ×.

[0080] The evaluation results of Examples 1 to 9 were summarized in Table 1, and the evaluation results of Comparative Examples 1 to 14 were summarized in Table 2. It should be noted that in Tables 1 and 2, the mark "present" for the silane coupling agent means that since the surface of aluminum hydroxide was pre-treated with the silane coupling agent, the silane coupling agent was contained, but the content could not be determined.

[0081] [Table 1]

[0082]

[0083]

[0084] From the evaluation results in Table 1, it can be seen that any property of the flame-retardant rubber compositions of Examples 1 to 9 was good. On the other hand, any property among the JIS A hardness, compression set, and flame retardancy of the flame-retardant rubber compositions of Comparative Examples 1 to 14 was poor.

Claims

1. A flame-retardant rubber composition, characterized in that, The flame-retardant rubber composition contains: ethylene-butene-non-conjugated diene rubber or ethylene-propylene-non-conjugated diene rubber, hydrated metal oxide, silane coupling agent, plasticizer, and crosslinking agent, The rubber component of the flame-retardant rubber composition is one rubber selected from the ethylene-butene-non-conjugated diene rubber and the ethylene-propylene-non-conjugated diene rubber, Relative to 100 parts by mass of the rubber component, 220 parts by mass to 340 parts by mass of the hydrated metal oxide and 20 parts by mass to 60 parts by mass of the plasticizer are contained, Relative to 100 parts by mass of the hydrated metal oxide, 2 to 4 parts by mass of the silane coupling agent are contained, The average particle size of the hydrated metal oxide is 0.9 μm to 5.0 μm, The crosslinking agent is dicumyl peroxide, and relative to 100 parts by mass of the rubber component, 3 to 6 parts by mass of the dicumyl peroxide are contained, The flame retardancy is V-0 in the flame retardancy standard UL94, The hardness is 65 to 75 as measured by JIS A hardness according to JIS K-6253-3, The compression set is 30% or less according to JIS K-6262, In the low-temperature property measured according to JIS K 6261-3:2017, the temperature at which the shrinkage rate reaches 10% is -50°C or lower.

2. The flame-retardant rubber composition according to claim 1, wherein The hydrated metal oxide is treated with the silane coupling agent.

3. The flame-retardant rubber composition according to claim 1 or 2, characterized in that, The hydrated metal oxide is aluminum hydroxide.

4. The flame-retardant rubber composition according to claim 1 or 2, characterized in that the plasticizer contains an ethylene-α-olefin oligomer, Relative to 100 parts by mass of the ethylene-α-olefin-non-conjugated diene copolymer, 20 parts by mass to 45 parts by mass of the ethylene-α-olefin oligomer are contained.

5. A sealing member, which is formed by crosslinking and molding the flame-retardant rubber composition according to claim 1 or 2.

6. The flame-retardant rubber composition according to claim 3, characterized in that the plasticizer contains an ethylene-α-olefin oligomer, Relative to 100 parts by mass of the ethylene-α-olefin-non-conjugated diene copolymer, 20 parts by mass to 45 parts by mass of the ethylene-α-olefin oligomer are contained.

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