JP7814092B2 - Ethylene-based copolymer composition and its use - Google Patents

Description

The present invention relates to an ethylene-based copolymer composition containing an ethylene-based copolymer such as an ethylene-α-olefin-non-conjugated polyene copolymer and a specific aluminum hydroxide, and uses thereof.

More specifically, this relates to an ethylene copolymer composition suitable for producing molded articles that have excellent mechanical strength and flame retardancy.

Ethylene-based copolymers such as ethylene-alpha-olefin copolymer (EPR) and ethylene-alpha-olefin-non-conjugated polyene copolymer (EPDM) do not contain unsaturated bonds in the main chain, and therefore have superior weather resistance, heat resistance, and ozone resistance compared to diene-based rubbers. They are widely used in automotive parts, industrial rubber products, electrical insulation, civil engineering and construction materials, rubber-coated fabrics, and other rubber products.

On the other hand, since ethylene copolymers themselves are not flame retardant, for applications requiring flame retardancy, such as the outer covers of railway vehicles, it has been proposed to compound 30 to 90 parts by mass of a flame retardant such as aluminum hydroxide per 100 parts by mass of the rubber component (Patent Document 1).

However, the composition proposed in Patent Document 1 contains natural rubber as the main rubber component, which means that its weather resistance is insufficient, and further improvements in flame retardancy are required.

In addition, in some countries, chloroprene rubber (CR) is used for train canopies due to the need for mechanical strength, tear strength, and oxygen index. However, because CR train canopies emit black smoke and toxic gases (chlorine gas) when burned, the switch to EPDM is being considered.

Japanese Patent Application Laid-Open No. 2006-176659

The object of the present invention is to obtain a composition that is flame retardant and has excellent mechanical properties, using ethylene copolymers such as EPDM, which have previously been difficult to achieve both flame retardancy and mechanical strength, tear strength, and processability.

As a result of extensive research to solve the above-mentioned problems, the present inventors have discovered that a crosslinked body obtained by crosslinking an ethylene copolymer composition characterized by containing ethylene/α-olefin copolymer (A) and aluminum hydroxide (C) having a particle size (median diameter) in the range of 0.1 to 5.0 μm in an amount in the range of 86 to 400 parts by mass per 100 parts by mass of the ethylene/α-olefin copolymer (A) is particularly excellent in mechanical properties and flame retardancy (oxygen index).

The crosslinked product obtained by crosslinking the composition of the present invention has particularly excellent mechanical properties and flame retardancy (oxygen index).

Ethylene/α-olefin copolymer (A)
The ethylene/α-olefin copolymer (A) (hereinafter may be abbreviated as "copolymer (A)"), which is one of the components of the ethylene copolymer composition of the present invention (hereinafter may be referred to as "copolymer composition"), is an ethylene/α-olefin copolymer obtained by random copolymerization of ethylene and an α-olefin having 3 or more carbon atoms.

The above-mentioned α-olefins are typically α-olefins having 3 to 20 carbon atoms, with α-olefins having 3 to 10 carbon atoms such as propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene being preferred, with 1-butene being particularly preferred.

Specific examples of the ethylene/α-olefin copolymer (A) according to the present invention that are preferably used include ethylene/propylene copolymer and ethylene/1-butene copolymer.
The ethylene/α-olefin copolymer (A) according to the present invention has a molar ratio of ethylene to α-olefin (ethylene/α-olefin) in the range of 50/50 to 85/15, preferably 53/47 to 83/17, and particularly preferably 55/45 to 80/20.

The copolymer (A) used in the present invention may be a copolymer of ethylene and an α-olefin with a non-conjugated polyene. As the ethylene-α-olefin-non-conjugated polyene copolymer (A1), which is a copolymer with a non-conjugated polyene, an ethylene-propylene-non-conjugated polyene copolymer, particularly an ethylene-1-butene-non-conjugated polyene copolymer, is preferably used.

The non-conjugated polyene to be copolymerized may be a cyclic or linear non-conjugated polyene. Examples of cyclic non-conjugated polyenes include 5-ethylidene-2-norbornene, dicyclopentadiene, 5-vinyl-2-norbornene, norbornadiene, and methyltetrahydroindene. Examples of linear non-conjugated polyenes include 1,4-hexadiene, 7-methyl-1,6-octadiene, 8-methyl-4-ethylidene-1,7-nonadiene, and 4-ethylidene-1,7-undecadiene. These non-conjugated polyenes may be used alone or in combination of two or more. The copolymerization amount, expressed in iodine value, is desirably 1 to 40, preferably 2 to 35, and more preferably 3 to 30.
These non-conjugated polyenes may be used alone or in combination of two or more.

<Method for producing ethylene/α-olefin (A)>
The ethylene/α-olefin copolymer (A) according to the present invention can be produced using a known polymerization catalyst, such as a Ziegler-Natta catalyst, a vanadium catalyst, or a metallocene catalyst. The polymerization method is not particularly limited, and the copolymer can be a liquid-phase polymerization method such as solution polymerization, suspension polymerization, or bulk polymerization, a gas-phase polymerization, or any other known polymerization method. Furthermore, these copolymers are not limited as long as they exhibit the effects of the present invention, and are also available as commercially available products. Examples of commercially available products include Vistalon (registered trademark) manufactured by ExxonMobil Corporation, Esprene (registered trademark) manufactured by Sumitomo Chemical Co., Ltd., and Mitsui EPT (registered trademark) manufactured by Mitsui Chemicals, Inc.

Aluminum hydroxide (C)
The aluminum hydroxide (C), which is one of the components contained in the ethylene copolymer composition of the present invention, is composed of fine particles having a particle size (median diameter) in the range of 0.1 to 5.0 μm, preferably 0.5 to 3.0 μm, and more preferably 0.5 to 2.0 μm.

Aluminum hydroxide (C) having such a particle size (median diameter) in the range of 0.1 to 5.0 μm is manufactured and sold by Showa Denko K.K. under the trade names Hijilite ^™ , H-21, H-31, H-32, H-42, H-42M, H-43, and H-43M.

<Ethylene-based copolymer composition>
The ethylene-based copolymer composition of the present invention is a composition comprising the ethylene/α-olefin copolymer (A) and 86 to 400 parts by mass, preferably 90 to 300 parts by mass, and more preferably 100 to 300 parts by mass of the aluminum hydroxide (C) per 100 parts by mass of the copolymer (A).

When the ethylene copolymer composition of the present invention contains aluminum hydroxide (C) in the above range, a molded article having excellent processability, mechanical strength and flame retardancy can be obtained.
The copolymer composition of the present invention may contain, in addition to the aluminum hydroxide (C), the modified copolymer (B), a silane coupling agent, a softener, a filler, a crosslinking agent, and other additives such as a processing aid, an activator, a moisture absorbent, a heat stabilizer, a weather stabilizer, an antistatic agent, a colorant, a lubricant, and a thickener.

Furthermore, when the copolymer composition of the present invention contains other polymers, the proportion of the ethylene-α-olefin copolymer (A) in the copolymer composition is generally 20% by mass or more, preferably 30 to 90% by mass.

Graft-modified ethylene/α-olefin copolymer (B) having unsaturated carboxylic acid or its derivative grafted thereon
The copolymer composition according to the present invention may contain, in addition to the copolymer (A), a graft-modified ethylene/α-olefin copolymer (B) to which an unsaturated carboxylic acid or a derivative thereof has been grafted (hereinafter, sometimes abbreviated as "modified copolymer (B)").

In the modified copolymer (B) of the present invention, the graft amount of unsaturated carboxylic acid or its derivative is typically 0.1 to 10% by mass, preferably 1 to 10% by mass, and more preferably 2 to 9% by mass, based on 100% by mass of the modified copolymer (B).

The modified copolymer (B) according to the present invention preferably has a density of 860 kg/m or ^more and ^less than 880 kg/m, more preferably 860 to 875 kg/ ^m , and even more preferably 865 to 875 kg/m ^. When the density of the modified copolymer (B) is within the above range, the ethylene copolymer composition obtained from the copolymer composition according to the present invention has an excellent balance between flexibility and physical properties.

The modified copolymer (B) according to the present invention preferably has a melting point measured by differential scanning calorimetry (DSC) of 20°C or higher but lower than 60°C, or no peak indicating a melting point is observed by differential scanning calorimetry (DSC). When the modified copolymer (B) satisfies this condition, it exhibits excellent dispersibility in the copolymer (A) during kneading and molding. If a peak indicating a melting point is observed by differential scanning calorimetry (DSC), the melting point is more preferably 30°C or higher but lower than 60°C, and even more preferably 40°C or higher but lower than 60°C.

Examples of unsaturated carboxylic acids and/or derivatives thereof used in the present invention include unsaturated compounds having one or more carboxylic acid groups, esters of compounds having a carboxylic acid group with an alkyl alcohol, and unsaturated compounds having one or more carboxylic acid anhydride groups. Examples of unsaturated groups include vinyl groups, vinylene groups, and unsaturated cyclic hydrocarbon groups. Specific examples of such compounds include unsaturated carboxylic acids such as acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, and Nadic Acid™ (endo-cis-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid); or derivatives thereof, such as acid halides, amides, imides, anhydrides, and esters. Specific examples of such derivatives include malenyl chloride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, and glycidyl maleate. These unsaturated carboxylic acids and/or derivatives thereof can be used alone or in combination of two or more. Among these, unsaturated dicarboxylic acids or their acid anhydrides are preferred, with maleic acid, nadic acid, or their acid anhydrides being particularly preferred. The content of the unsaturated carboxylic acid and/or its derivative can be easily controlled, for example, by appropriately selecting the grafting conditions.

There are no particular limitations on the method for grafting a graft monomer selected from unsaturated carboxylic acids and/or their derivatives onto an ethylene-α-olefin copolymer, and any conventionally known graft polymerization method, such as a solution method or melt-kneading method, can be used. For example, there is a method in which the ethylene-α-olefin copolymer is melted and the graft monomer is added thereto to carry out the graft reaction, or a method in which the ethylene-α-olefin copolymer is dissolved in a solvent to form a solution and the graft monomer is added thereto to carry out the graft reaction.

In these methods, graft polymerization in the presence of a radical initiator allows for efficient graft polymerization of graft monomers such as the unsaturated carboxylic acids. In this case, the radical initiator is typically used in an amount of 0.001 to 1 part by mass per 100 parts by mass of the ethylene-α-olefin copolymer.

Such radical initiators include organic peroxides, azo compounds, etc. Such radical initiators include organic peroxides, azo compounds, etc. Specific examples of such radical initiators include benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(peroxidebenzoate)hexyne-3, 1,4-bis(t-butylperoxyisopropyl)benzene, lauroyl peroxide, t-butyl peracetate, 2,5-dimethyl-2,5-di-(t-butylperoxide)hexyne-3, 2,5-dimethyl-2,5-di(t-butylperoxide)hexane, t-butyl perbenzoate, t-butyl perphenyl acetate, t-butyl perisobutyrate, t-butyl per-sec-octoate, t-butyl perpivalate, cumyl perpivalate, t-butyl perdiethyl acetate; azobisisobutyronitrile; and dimethyl azoisobutyrate.

Of these, dialkyl peroxides such as dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 1,4-bis(t-butylperoxyisopropyl)benzene are preferred.

The reaction temperature for graft polymerization reactions using or without a radical initiator is usually set within the range of 60 to 350°C, preferably 150 to 300°C.

The ethylene-α-olefin copolymer (b) used to produce the modified copolymer (B) of the present invention is a copolymer containing units derived from ethylene and units derived from an α-olefin having 3 or more carbon atoms, preferably 3 to 20 carbon atoms, and may be a random copolymer or a block copolymer.

Specific examples of α-olefins include propylene, 1-butene, 4-methyl-1-pentene-1, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-nonadecene, 1-eicosene, 9-methyl-1-decene, 11-methyl-1-dodecene, and 12-ethyl-1-tetradecene. Among these, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene are preferred, with propylene and 1-butene being particularly preferred. These α-olefins may be used alone or in combination.

The content of structural units derived from ethylene in the ethylene/α-olefin copolymer (b) according to the present invention is typically 50.0 mol % or more and less than 100 mol %, preferably 80.0 to 99.5 mol %, and more preferably 90.0 to 99.0 mol %, based on the total structural units contained in the ethylene/α-olefin copolymer.

The density of the ethylene/α-olefin copolymer (b) according to the present invention is preferably such that the density of the graft-modified ethylene/α-olefin copolymer (B) obtained by graft-modifying it falls within the above-mentioned range, specifically 850 to 880 kg/m ³ , more preferably 855 to 875 kg/m ³ .

The melting point of the ethylene/α-olefin copolymer (b) according to the present invention is preferably such that the melting point of the graft-modified ethylene/α-olefin copolymer (B) obtained by graft-modifying it satisfies the above-mentioned conditions. Specifically, the melting point measured by differential scanning calorimetry (DSC) is 20 to 70°C, or no peak indicating a melting point is observed by differential scanning calorimetry (DSC). More preferably, the melting point measured by differential scanning calorimetry (DSC) is 30 to 60°C, or no peak indicating a melting point is observed by differential scanning calorimetry (DSC).

The melt flow rate (MFR; ASTM D 1238, 190°C, 2.16 kg load) of the ethylene/α-olefin copolymer (b) according to the present invention is preferably 0.1 to 100 g/10 min, more preferably 0.2 to 50 g/10 min, and even more preferably 0.3 to 20 g/10 min.

Using a copolymer (B) obtained by graft-modifying an ethylene-α-olefin copolymer (b) whose density, ethylene content, and MFR fall within the above-mentioned ranges results in a good balance between the processability and rubber elasticity of the composition.

When the copolymer composition of the present invention contains the modified copolymer (B), the blending amount of the modified copolymer (B) is 1 to 50 parts by mass, preferably 5 to 30 parts by mass, per 100 parts by mass of the copolymer (A).

<Silane coupling agent>
Examples of the silane coupling agent according to the present invention include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, vinyltrichlorosilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane. silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, N,N'-bis(3-(trimethoxysilyl)propyl)ethylenediamine, polyoxyethylenepropyltrialkoxysilane, polyethoxydimethylsiloxane, p-styryltrimethoxysilane, and 3-acryloxypropyltrimethoxysilane.

When the copolymer composition of the present invention contains a silane coupling agent, the amount is generally 0.1 to 10 parts by mass, preferably 1 to 5 parts by mass, per 100 parts by mass of the total of copolymer (A) and other polymer components that are blended as needed.

<Crosslinking agent>
Examples of crosslinking agents used in the present invention include crosslinking agents that are commonly used when crosslinking rubber, such as organic peroxides, phenolic resins, sulfur-based compounds, hydrosilicone-based compounds, amino resins, quinone or its derivatives, amine-based compounds, azo-based compounds, epoxy-based compounds, isocyanate-based compounds, etc. Among these, crosslinking agents (also called "vulcanizing agents") such as organic peroxides and sulfur-based compounds are preferred.

Examples of organic peroxides include dicumyl peroxide (DCP), di-tert-butyl peroxide, 2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butylperoxybenzoate, tert-butylperoxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, and tert-butylcumyl peroxide.

Of these, bifunctional organic peroxides such as dicumyl peroxide (DCP), 2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and n-butyl-4,4-bis(tert-butylperoxy)valerate are preferred, with dicumyl peroxide (DCP), 2,5-di-(tert-butylperoxy)hexane, and 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane being most preferred.

When an organic peroxide is used as the crosslinking agent, the amount used is generally 0.1 to 20 parts by mass, preferably 0.2 to 15 parts by mass, and more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the total of copolymer (A) and any other polymers that require crosslinking, if added as needed. When the amount of organic peroxide is within the above range, the resulting copolymer composition exhibits excellent crosslinking properties, which is preferable.

When using an organic peroxide as the crosslinking agent, it is preferable to use a crosslinking aid in combination. Examples of crosslinking aids include sulfur; quinone dioxime crosslinking aids such as p-quinone dioxime; acrylic crosslinking aids such as ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate; allyl crosslinking aids such as diallyl phthalate and triallyl isocyanurate; maleimide crosslinking aids; divinylbenzene; and metal oxides such as zinc oxide (e.g., ZnO#1/Zinc Oxide Type 2 (JIS Standard (K-1410)), manufactured by Hakusui Tech Co., Ltd.), magnesium oxide, and zinc oxide (e.g., zinc oxide such as "META-Z102" (trade name; manufactured by Inoue Lime Industry Co., Ltd.)). The amount of crosslinking aid used is typically 0.5 to 10 moles, preferably 0.5 to 7 moles, and more preferably 1 to 5 moles, per mole of organic peroxide.

When a sulfur-based compound (vulcanizing agent) is used as a crosslinking agent, specific examples include sulfur, sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, tetramethylthiuram disulfide, and selenium dithiocarbamate.

When a sulfur-based compound is used as the crosslinking agent, the blending amount is typically 0.3 to 10 parts by mass, preferably 0.5 to 7.0 parts by mass, and more preferably 0.7 to 5.0 parts by mass, per 100 parts by mass of the total of copolymer (A) and any other polymers that require crosslinking, which are blended as needed. When the blending amount of the sulfur-based compound is within the above range, there is no blooming on the surface of the molded article, and excellent crosslinking properties are exhibited.

Next, when a sulfur-based compound is used as the crosslinking agent, it is preferable to use a vulcanization accelerator in combination.
Examples of the vulcanization accelerator include N-cyclohexyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, N,N'-diisopropyl-2-benzothiazole sulfenamide, 2-mercaptobenzothiazole (for example, Suncerer M (trade name; manufactured by Sanshin Chemical Industry Co., Ltd.)), 2-(4-morpholinodithio)benzothiazole (for example, Noccelaer MDB-P (trade name; manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, and 2-(2,6-diethyl-4-morpholinothio)benzothiazole. thiazole-based vulcanization accelerators such as diphenylguanidine, triphenylguanidine, and diorthotolylguanidine; aldehyde amine-based vulcanization accelerators such as acetaldehyde-aniline condensation product and butyraldehyde-aniline condensation product; imidazoline-based vulcanization accelerators such as 2-mercaptoimidazoline; thiourea-based vulcanization accelerators such as diethylthiourea and dibutylthiourea; tetramethylthiuram monosulfide (for example, Sancerer TS ( thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (e.g., Sancerer TT (trade name; manufactured by Sanshin Chemical Industry Co., Ltd.)), tetraethylthiuram disulfide (e.g., Sancerer TET (trade name; manufactured by Sanshin Chemical Industry Co., Ltd.)), tetrabutylthiuram disulfide (e.g., Sancerer TBT (trade name; manufactured by Sanshin Chemical Industry Co., Ltd.)), and dipentamethylenethiuram tetrasulfide (e.g., Sancerer TRA (trade name; manufactured by Sanshin Chemical Industry Co., Ltd.)); zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate Examples of suitable vulcanization accelerators include dithioacid salt vulcanization accelerators such as Sancerar PZ, Sancerar BZ, and Sancerar EZ (trade names, manufactured by Sanshin Chemical Industry Co., Ltd.) and tellurium diethyldithiocarbamate; thiourea vulcanization accelerators such as ethylene thiourea (for example, Sancerar BUR (trade name, manufactured by Sanshin Chemical Industry Co., Ltd.), Sancerar 22-C (trade name, manufactured by Sanshin Chemical Industry Co., Ltd.)), N,N'-diethylthiourea, and N,N'-dibutylthiourea; xanthate vulcanization accelerators such as zinc dibutylxatogenate; and zinc oxide (for example, META-Z102 (trade name, manufactured by Inoue Lime Industry Co., Ltd.), zinc oxide).

The amount of these vulcanization accelerators added is generally 0.1 to 20 parts by mass, preferably 0.2 to 15 parts by mass, and more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the ethylene-α-olefin copolymer and any other polymers that require crosslinking, if added as needed.

<Vulcanization aid>
The vulcanization aid according to the present invention is used when the crosslinking agent is a sulfur-based compound, and examples thereof include zinc oxide (e.g., ZnO#1/Zinc Oxide Type 2, manufactured by Hakusui Tech Co., Ltd.), magnesium oxide, and zinc oxide (e.g., zinc oxide such as "META-Z102" (trade name; manufactured by Inoue Lime Industry Co., Ltd.)).
The amount of the copolymer to be blended is usually 1 to 20 parts by mass per 100 parts by mass of the total of copolymer (A) and other polymers that require crosslinking and are blended as needed.

<Softener>
Specific examples of the softener according to the present invention include petroleum-based softeners such as process oil, lubricating oil, paraffin oil, liquid paraffin, petroleum asphalt, and Vaseline; coal tar-based softeners such as coal tar; fatty oil-based softeners such as castor oil, linseed oil, rapeseed oil, soybean oil, and coconut oil; waxes such as beeswax and carnauba wax; fatty acids or salts thereof such as ricinoleic acid, palmitic acid, stearic acid, barium stearate, and calcium stearate; naphthenic acid, pine oil, rosin, and derivatives thereof; synthetic polymers such as terpene resins, petroleum resins, and coumarone-indene resins; ester-based softeners such as dioctyl phthalate and dioctyl adipate; and other softeners such as microcrystalline wax, liquid polybutadiene, modified liquid polybutadiene, hydrocarbon-based synthetic lubricating oils, tall oil, and sub (factice). Petroleum-based softeners are preferred, and process oils are particularly preferred.

The amount of softener in the copolymer composition is generally 2 to 100 parts by mass, and preferably 10 to 100 parts by mass, per 100 parts by mass of the total of copolymer (A) and other polymer components that are added as needed.

<Inorganic fillers>
Specific examples of the inorganic filler used in the present invention include one or more of light calcium carbonate, heavy calcium carbonate, talc, clay, etc., and among these, heavy calcium carbonate such as "Whiten SB" (trade name; Shiraishi Calcium Co., Ltd.) is preferred.

When the copolymer composition contains an inorganic filler, the amount of inorganic filler is typically 2 to 50 parts by mass, and preferably 5 to 50 parts by mass, per 100 parts by mass of the ethylene-α-olefin-non-conjugated polyene copolymer and any other polymers added as needed. When the amount is within this range, the copolymer composition has excellent kneading processability, and molded articles with excellent mechanical properties can be obtained.

<Reinforcing agent>
Specific examples of the reinforcing agent according to the present invention include carbon black, carbon black surface-treated with a silane coupling agent, silica, calcium carbonate, activated calcium carbonate, finely divided talc, and finely divided silicic acid. When used, the amount of the reinforcing agent is generally 30 to 200 parts by mass, and preferably 50 to 180 parts by mass, per 100 parts by mass of the copolymer and, if necessary, other polymers (A) combined.

<Anti-aging agent (stabilizer)>
The copolymer composition of the present invention can be blended with an antioxidant (stabilizer) to extend the life of a molded article formed therefrom. Examples of such antioxidants include conventionally known antioxidants, such as amine-based antioxidants, phenol-based antioxidants, and sulfur-based antioxidants.

Further examples of antioxidants include aromatic secondary amine antioxidants such as phenylbutylamine and N,N-di-2-naphthyl-p-phenylenediamine; phenolic antioxidants such as dibutylhydroxytoluene and tetrakis[methylene(3,5-di-t-butyl-4-hydroxy)hydrocinnamate]methane; thioether antioxidants such as bis[2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl]sulfide; dithiocarbamate antioxidants such as nickel dibutyldithiocarbamate; and sulfur-based antioxidants such as 2-mercaptobenzoylimidazole, 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, dilaurylthiodipropionate, and distearylthiodipropionate.

These antioxidants can be used alone or in combination of two or more, and the blending amount is typically 0.3 to 10 parts by mass, and preferably 0.5 to 7.0 parts by mass, per 100 parts by mass of the total of copolymer (A) and other polymers. By keeping the blending amount within this range, no blooming occurs on the surface of molded articles obtained from the resulting copolymer composition, and vulcanization inhibition can be suppressed.

<Processing aids>
As the processing aid of the present invention, a wide range of processing aids that are generally compounded with rubber can be used.

Specific examples of processing aids include ricinoleic acid, stearic acid, palmitic acid, lauric acid, barium stearate, zinc stearate, calcium stearate, esters, etc. Of these, stearic acid is preferred.
The amount of the processing aid to be added is usually 10 parts by mass or less, preferably 8.0 parts by mass or less, per 100 parts by mass of the copolymer (A) and other polymers contained in the copolymer composition.

<Activator>
Specific examples of the surfactant include amines such as di-n-butylamine, dicyclohexylamine, and monoelanolamine; surfactants such as diethylene glycol, polyethylene glycol, lecithin, triaryl methylate, and zinc compounds of aliphatic or aromatic carboxylic acids; zinc peroxide preparations; octadecyltrimethylammonium bromide, synthetic hydrotalcite, and special quaternary ammonium compounds.

When an activator is included, the amount thereof is typically 0.2 to 10 parts by mass, and preferably 0.3 to 5 parts by mass, per 100 parts by mass of copolymer (A) and other polymers.

<Moisture absorbent>
Specific examples of moisture absorbents include calcium oxide, silica gel, sodium sulfate, molecular sieves, zeolite, and white carbon.

When a moisture absorbent is contained, the amount thereof is usually 0.5 to 15 parts by mass, preferably 1.0 to 12 parts by mass, per 100 parts by mass of the copolymer (A) and other polymers.
The copolymer composition of the present invention can be prepared by kneading the copolymer (A) and other components, which are blended as necessary, at a desired temperature using a kneading machine such as a mixer, a kneader, a roll, etc. The copolymer (A) of the present invention has excellent kneadability, and therefore the copolymer composition can be prepared satisfactorily.

<Crosslinked product of copolymer composition>
(Crosslinked body)
The crosslinked product of the present invention is a crosslinked product obtained by crosslinking the above-mentioned composition.

The crosslinked product of the present invention is obtained by crosslinking the composition, and therefore has superior mechanical properties such as hardness compared to crosslinked products obtained by crosslinking conventional rubber compositions.
The method for crosslinking the composition is not particularly limited, but for example, the composition can be molded and then crosslinked to obtain a crosslinked product molded into a desired shape.

As a molding method, molding methods such as compression molding, injection molding, and cast molding are preferred because they make it easy to mold the composition into a desired shape.
When molding is carried out by molding, it is preferable from the viewpoint of productivity to carry out crosslinking before removing the composition from the mold, that is, with the mold closed.

The conditions for crosslinking vary depending on the type of crosslinking agent, but crosslinking is usually carried out by heating the composition.
When crosslinking is carried out by heating, the temperature is usually 120 to 270° C., preferably 150 to 180° C., and the heating time is usually 30 seconds to 120 minutes, preferably 5 to 30 minutes.

The crosslinked product of the present invention has excellent hardness and can be used in a variety of applications. The crosslinked product of the present invention may also be used in various applications as a laminate having a layer formed from the crosslinked product.

There are no particular limitations on the method for producing the laminate, but examples include a method in which the composition of the present invention is molded by co-extrusion or the like with other components to obtain a laminate containing a layer formed from the composition of the present invention, and then the composition of the present invention is crosslinked, or a method in which a crosslinked body is prepared and then the crosslinked body is laminated with a layer formed from other components using heat or an adhesive. In the laminate of the present invention, there are no particular limitations on the layer other than the layer formed from the crosslinked body, but examples include nylon or polyester fabrics. Furthermore, the layer other than the layer formed from the crosslinked body may be one layer or two or more layers.

<Applications of crosslinked products and laminates>
The crosslinked body and laminate of the present invention can be used for automobile parts, railway vehicle parts, home appliance parts, civil engineering and building materials parts, miscellaneous goods, daily necessities, etc.

The crosslinked body of the present invention has excellent strength, and therefore the crosslinked body and laminate of the present invention can be suitably used in applications where particular strength is required, such as railway vehicle parts.
Examples of railway vehicle parts include railway vehicle covers such as outer covers and inner covers (through covers).

The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.
The polymers used in the examples and comparative examples are as follows.

[Ethylene/α-olefin copolymer (A)]
(1) Ethylene/1-butene/ENB copolymer (A-1)
MFR = 2 g/10 min (temperature: 190°C, load: 2.16 kg, ASTM D 1238), ethylene content = 77 wt% (ASTM D 3900), iodine value = 22 (ASTM D 6047) (Mitsui Chemicals, Inc., trademark Mitsui Elastomer K-9720).
(2) Ethylene-propylene-ENB copolymer (A-2)
Mooney viscosity = 61 [(ML(1+4) 125°C), ASTM D1646], ethylene content = 65 wt% (ASTM D3900), iodine value = 9.5 (ASTM D6047) [Mitsui Chemicals, Inc., registered trademark Mitsui EPT 3092PM]

[Modified ethylene/α-olefin copolymer (B)]
(1) Maleic anhydride-grafted ethylene/1-butene copolymer (B1)
MFR (190°C, 2.16 kg, ASTM D1238): 1.5 g/10 min, density (ASTM D1505): 872 kg/m ³ , brittleness temperature (ASTM D746): less than -70°C (manufactured by Mitsui Elastomers Singapore Pte Ltd, trade name: Toughmer MD715)

[Aluminum hydroxide (C)]
(1) Aluminum hydroxide (C1): particle size (median diameter) 1.0 μm (manufactured by Showa Denko K.K., trade name: Higilite H-42M)

The other additives used in the examples and comparative examples were the following commercially available products.
(1) Stearic acid (NOF Corporation) (St. A)
(2) Zinc oxide: zinc oxide (manufactured by Hakusui Tech Co., Ltd.) (ZnO#1)
(3) Silica [manufactured by Tosoh Silica Corporation, trade name Nipsil VN3] (Silica VN3)
(4) Carbon black (manufactured by Tokai Carbon Co., Ltd., product name: Seast G-SO) (Seast G-SO)
(5) Silane coupling agent (3-methacryloxypropyltriethoxysilane) [manufactured by Shin-Etsu Chemical Co., Ltd., product name KBM-503] (KBM-503)
(6) Organic peroxide: Dicumyl peroxide (manufactured by Kayaku Akzo Co., Ltd., trade name: Kayacumyl D-40C) (DCP-40C)

Example 1
A compound shown in Table 1 was added to 90 parts by mass of the ethylene/α-olefin/ENB copolymer (A-1) and 10 parts by mass of the maleic anhydride-grafted ethylene/1-butene copolymer (B1), and the mixture was kneaded using a MIXTRON BB MIXER (manufactured by Kobe Steel, Ltd., BB-4 model, volume 2.95 L, rotor 4WH) to obtain a composition.

The composition was kneaded under the conditions of a rotor rotation speed of 50 rpm, a floating weight pressure of 3 kg/cm ² , a kneading time of 5 minutes, and a kneading discharge temperature of 170°C.
Next, after it was confirmed that the temperature of the composition had reached 40°C, 8.5 parts by mass of an organic peroxide was kneaded into the composition using a 14-inch roll to obtain a composition containing a crosslinking agent.

The kneading conditions for the above composition were: roll temperatures (front roll/rear roll) = 65°C/50°C; roll rotation speeds (front roll/rear roll) = 13 rpm/11.5 rpm; roll gap = 5 mm; and a kneading time of 8 minutes.

Next, the composition containing the crosslinking agent was crosslinked at 180° C. for 20 minutes using a press molding machine to prepare sheets (crosslinked body sheets) having thicknesses of 2 mm and 3 mm.
The resulting crosslinked sheet was subjected to measurements of hardness, modulus, tensile stress at break, tensile elongation at break, tear strength and oxygen index (LOI) by the following methods.
The results are shown in Table 1.

[hardness]
The hardness of the sheet of the crosslinked product was measured in accordance with the description of "Hardness test" in Section 7 of JIS K7312 (1996) "Physical testing methods for thermosetting polyurethane elastomer moldings" and the description of Test Type A of "Durometer hardness test" in Section 6 of JIS K6253 (2006) "Vulcanized rubber and thermoplastic rubber - Determination of hardness".

[Modulus, tensile stress at break, tensile elongation at break]
The modulus, tensile stress at break, and tensile elongation at break of the crosslinked sheet were measured by the following methods.
The sheet of the crosslinked product was punched to prepare a No. 3 dumbbell test piece described in JIS K 6251 (1993). A tensile test was carried out using this test piece according to the method specified in JIS K6251, section 3, at a measurement temperature of 25°C and a tensile speed of 500 mm/min, and the tensile stress at an elongation of 25% (25% modulus (M25)), the tensile stress at an elongation of 50% (50% modulus (M50)), the tensile stress at break (TB), and the tensile elongation at break (EB) were measured.

[Tear strength]
An angle-shaped test piece was prepared from a 2 mm thick sheet of the crosslinked product, and the test piece was pulled at a rate of 500 mm/sec to measure the maximum stress value (tear strength) (measurement temperature: 25°C).

[Oxygen index (LOI)]
Using a 3 mm thick sheet of the crosslinked product, the oxygen index (LOI) was measured in accordance with JIS K7201-2 and used as a measure of flame retardancy.

Comparative Example 1
A composition and a crosslinked sheet were obtained in the same manner as in Example 1, except that the ethylene/α-olefin/ENB copolymer (A-2) was used instead of the ethylene/α-olefin/ENB copolymer (A-1) and the maleic anhydride-grafted ethylene/1-butene copolymer (B1) used in Example 1, and the compounding amounts were changed to those shown in Table 1. Using the obtained crosslinked sheet, the physical properties were measured in the same manner as in Example 1.
The results are shown in Table 1.

Comparative Example 2
A composition and a crosslinked sheet were obtained in the same manner as in Example 1, except that the ethylene/α-olefin/ENB copolymer (A-2) was used instead of the ethylene/α-olefin/ENB copolymer (A-1) used in Example 1 and the compound amounts were changed to those shown in Table 1. Using the obtained crosslinked sheet, physical properties were measured in the same manner as in Example 1.
The results are shown in Table 1.

Claims (5)

An ethylene/α-olefin copolymer (A) and 222 to 400 parts by mass of aluminum hydroxide (C) having a particle size (median diameter) of 0.1 to 5.0 μm per 100 parts by mass of the ethylene/α-olefin copolymer (A),
the ethylene/α-olefin copolymer (A) is an ethylene/1-butene/non-conjugated polyene copolymer in which the α-olefin is 1-butene;
An ethylene-based copolymer composition characterized in that the molar ratio of ethylene to 1-butene (ethylene/1-butene) in the ethylene-1-butene-non-conjugated polyene copolymer is in the range of 50/50 or more (however, excluding ethylene-based copolymer compositions in which the intrinsic viscosity [η] of the ethylene-α-olefin copolymer (A) measured in a decalin solution at 135°C is in the range of 7.8 to 13.0 dl/g). A crosslinked product obtained by crosslinking the ethylene copolymer composition described in claim 1. A laminate having a layer formed from the crosslinked product described in claim 2. A railway vehicle part obtained from the crosslinked body described in claim 2 or the laminate described in claim 3. A railway vehicle canopy obtained from the crosslinked body described in claim 2 or the laminate described in claim 3.