Patent Description:
As a technology for improving the vulcanization speed of rubber, as described in Patent Literature <NUM>, it is known that a rubber composition characterized by blending <NUM> to <NUM> parts by mass of silica and <NUM> to <NUM> parts by mass of a cyclic polysulfide represented by formula (<NUM>) with respect to <NUM> parts by mass of diene rubber, and <NUM> to <NUM>% by mass of silane coupling agent with respect to the mass of the silica, <NUM> to <NUM>% by mass of a glycerin mono fatty acid ester derived from a fatty acid having a carbon number of <NUM> to <NUM> with respect to the mass of the silica.

In addition, as a technique for improving the abrasion resistance of a rubber, as described in Patent Literature <NUM>, a composition for chloroprene vulcanized rubber is known. The composition for chloroprene vulcanized rubber comprises <NUM> parts by mass of a polymer for chloroprene vulcanized rubber, <NUM> to <NUM> parts by mass of an acid acceptor, <NUM> to <NUM> parts by mass of a lubricant, <NUM> to <NUM> parts by mass of an antioxidant, <NUM> to <NUM> parts by mass of carbon black, <NUM> to <NUM> parts by mass of a filler other than carbon black, <NUM> to <NUM> parts by mass of a softening agent, <NUM> to <NUM> parts by mass of a processing aid, <NUM> to <NUM> parts by mass of a metal oxide, <NUM> to <NUM> parts by mass of a vulcanization accelerator, wherein the polymer is a copolymer comprising <NUM> to <NUM>% by mass of <NUM>-chloro-<NUM>,<NUM>-butadiene (chloroprene) (C-<NUM>) and <NUM> to <NUM>% by mass of <NUM>,<NUM>-dichloro-<NUM>,<NUM>-butadiene (C-<NUM>); or <NUM> to <NUM>% by mass of <NUM>-chloro-<NUM>,<NUM>-butadiene (chloroprene) (C-<NUM>), <NUM> to <NUM>% by mass of <NUM>,<NUM>-dichloro-<NUM>,<NUM>-butadiene (C-<NUM>) and <NUM> to <NUM>% by mass of a monomer copolymerizable with these (C-<NUM>), as a fraction of each monomer constituting the polymer with respect to <NUM>% by mass of the total amount of all monomers, and the Mooney viscosity (ML1+<NUM> (<NUM>)) of the polymer is in the range of <NUM> to <NUM>.

As a technique for reducing the temperature rise of rubber, as described in Patent Literature <NUM>, a rubber composition is known. The rubber composition comprises more than <NUM> to <NUM> parts by mass of silica with respect to <NUM> parts by mass of total rubber components including two or more kinds of diene rubber, wherein the diene rubber is divided into two or more phases each having a different glass transition temperature, at least one phase of which has a continuous structure, and at least one phase of which has a glass transition temperature of -<NUM> or higher, and <NUM>% or more by mass of the amount of silica per unit volume of the blended rubber is contained in the at least one phase having a glass transition temperature of -<NUM> or higher, and the average aggregate area of the silica contained in the phase is less than <NUM><NUM>.

For rubber compositions containing a chloroprene polymer, it is required to achieve a high degree of compatibility of various properties in a vulcanizate of the rubber composition, and it may be required to provide the vulcanizate having excellent abrasion resistance, low temperature rise in a dynamic environment, excellent vulcanization speed and high productivity.

An object of one aspect of the present invention is to provide a rubber composition having excellent abrasion resistance, low temperature rise in a dynamic environment, excellent vulcanization speed and high productivity. Another object of the present invention is to provide a vulcanizate of the rubber composition. A main object of another aspect of the present invention is to provide a vulcanized molded body of the rubber composition.

One aspect of the present invention relates to a rubber composition comprising <NUM> parts by mass of a chloroprene-based rubber, <NUM> to <NUM> parts by mass of silica, <NUM> part by mass or more and less than <NUM> parts by mass of a hydrate, and <NUM> to <NUM> parts by mass of an organic peroxide, wherein the rubber composition includes <NUM> to <NUM> parts by mass of a silane coupling agent having a double bond in a structure of the silane coupling agent with respect to <NUM> parts by mass of the silica.

Preferably, the chloroprene-based rubber contains a homopolymer of <NUM>-chloro-<NUM>,<NUM>-butadiene or a copolymer of <NUM>-chloro-<NUM>,<NUM>-butadiene and at least one monomer selected from <NUM>,<NUM>-dichloro-<NUM>,<NUM>-butadiene and acrylonitrile.

Preferably, the silane coupling agent having a double bond in the structure of the silane coupling agent is at least one silane coupling agent selected from vinyltrimethoxysilane, vinyltriethoxysilane, <NUM>-(meth)acryloxypropyl methyl dimethoxysilane, <NUM>-(meth)acryloxypropyl methyl trimethoxysilane, <NUM>-(meth)acryloxypropylmethyldiethoxysilane and <NUM>-(meth)acryloxypropylmethyltriethoxysilane.

Preferably, wherein the hydrate is a hydrate releasing H<NUM>O in a temperature range of <NUM> to <NUM>.

Preferably, the hydrate is at least one hydrate selected from a hydrotalcite compound represented by formula (<NUM>), a hydrate, and a metal hydroxide,.

[M<NUM>+<NUM>-xM<NUM>+x(OH)<NUM>]x+[An-x/n·mH<NUM>O]x-     (<NUM>).

Preferably, the hydrate is at least one hydrate selected from hydrotalcite compounds represented by Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O, Mg<NUM>ZnAl<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O, Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O, Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>, Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O, Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O, Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O, and Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O.

Preferably, the organic peroxide is at least one organic peroxide selected from dicumyl peroxide, <NUM>,<NUM>-bis[(t-butylperoxy)isopropyl]benzene, t-butyl α-cumyl peroxide, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-bis(t- butylperoxy)hexane, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-bis(t-butylperoxy)hexyne-<NUM>.

Preferably, the silica has a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of <NUM> to <NUM><NUM>/g.

Another aspect of the present invention relates to a vulcanizate of the rubber composition described above. Another aspect of the present invention relates to a vulcanized molded body of the rubber composition described above.

Preferred embodiments for carrying out the present invention will be described below.

The rubber composition according to the present embodiment comprises (<NUM>) <NUM> parts by mass of a chloroprene-based rubber, (<NUM>) <NUM> to <NUM> parts by mass of silica, (<NUM>) <NUM> part by mass or more and less than <NUM> parts by mass of a hydrate, and (<NUM>) <NUM> to <NUM> parts by mass of an organic peroxide, (<NUM>)wherein the rubber composition includes <NUM> to <NUM> parts by mass of a silane coupling agent having a double bond in a structure of the silane coupling agent with respect to <NUM> parts by mass of the silica.

According to the rubber composition according to the present embodiment, a vulcanizate obtained by vulcanizing the rubber composition can has excellent abrasion resistance and low temperature rise in a dynamic environment.

In recent years, in addition to physical properties such as abrasion resistance and low temperature rise required for rubber parts, improvement in vulcanization speed has been demanded from the viewpoint of productivity. As a result of intensive study in order to meet such requirements, the present inventors have found that vulcanization speed can be improved simultaneously with physical properties such as abrasion resistance and low temperature rise by using a specific amount of silica as a filler, a specific amount of a silane coupling agent having a double bond in a structure of the silane coupling agent with respect to the silica, an organic peroxide as a sulfur agent, and a hydrate instead of magnesium oxide or the like.

A mechanism, which improves vulcanization speed simultaneously with physical properties such as abrasion resistance and low temperature rise by using a specific amount of silica as a filler, a specific amount of a silane coupling agent having a double bond in a structure of the silane coupling agent with respect to the silica, an organic peroxide as a sulfur agent, and a hydrate instead of magnesium oxide or the like, is considered as follows.

First, by protecting the surface of silica added as a filler with a silane coupling agent having a double bond, the dispersibility of the silica is improved. In addition, by using an organic peroxide as a vulcanizing agent, the double bond portion of the silane coupling agent reacts with the rubber portion, and the abrasion resistance, low temperature rise, and reinforcing properties in the resulting vulcanizate are improved. The protection of the silica by the silane coupling agent is achieved by hydrolysis of itself and condensation reaction of the hydrolyzate and the silica. Therefore, by adding the hydrate as well as the silane coupling agent during processing, the heat generated during kneading releases hydrated water (H<NUM>O) from the hydrate, and this released water promotes hydrolysis of the silane coupling agent, which may strengthen the protection of silica and contribute to improved reinforcement properties.

It is also presumed that the decomposition of organic peroxides is accelerated during vulcanization by the desorption of hydration water from the hydrates and the H<NUM>O produced by the chlorine capture reaction of the hydrochloric acid generated from chloroprene-based rubber, thereby increasing the rate of vulcanization.

A chloroprene-based rubber is mainly composed of a chloroprene polymer. The chloroprene polymer is a homopolymer of <NUM>-chloro-<NUM>,<NUM>-butadiene (hereinafter referred to as chloroprene), or a copolymer of chloroprene and other monomers that can be copolymerized with chloroprene, or a mixture of these polymers. Other monomers copolymerizable with chloroprene preferably include for example:.

When a copolymer of chloroprene and other monomers copolymerizable with chloroprene is used as the chloroprene-based rubber, the copolymerization amount of the other monomers is preferably <NUM> parts by mass or less and more preferably <NUM> parts by mass or less, with respect to <NUM> parts by mass of chloroprene. By adjusting the amount of the other monomers to be copolymerized within this range, the effect of copolymerizing these monomers can be exhibited without impairing the properties of the resulting rubber composition.

A chloroprene-based rubber according to one embodiment of the present invention preferably contains a homopolymer of <NUM>-chloro-<NUM>,<NUM>-butadiene or a copolymer of <NUM>-chloro-<NUM>,<NUM>-butadiene and at least one monomer selected from <NUM>,<NUM>-dichloro-<NUM>,<NUM>-butadiene and acrylonitrile. A chloroprene-based rubber according to one embodiment of the present invention may composed of a homopolymer of <NUM>-chloro-<NUM>,<NUM>-butadiene and/or a copolymer of <NUM>-chloro-<NUM>,<NUM>-butadiene and at least one monomer selected from <NUM>,<NUM>-dichloro-<NUM>,<NUM>-butadiene and acrylonitrile. The chloroprene-based rubber of one embodiment of the invention can also be composed of a homopolymer of <NUM>-chloro-<NUM>,<NUM>-butadiene.

Other monomers to be copolymerized with chloroprene are not limited to one type, and the polymer may be a polymer, for example, obtained by copolymerizing three or more types of monomers including chloroprene. Also, the polymer structure of the polymer is not particularly limited.

The chloroprene-based rubber is obtained by emulsion polymerization of raw material monomers including chloroprene as a main component in the presence of a polymerization reaction catalyst, a polymerization initiator, a chain transfer agent, or the like, using rosin or the like as an emulsifying dispersant.

Examples of the catalysts for the polymerization reaction include inorganic peroxides such as potassium sulfate, and organic peroxides such as ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, and diacyl peroxides. Examples of a catalyst activator include sodium sulfite, potassium sulfite, iron(II) oxide, anthraquinone, β-sodium sulfonate, formamidinesulfonic acid, L-ascorbic acid and the like.

The polymerization initiator is not particularly limited and known polymerization initiators generally used for emulsion polymerization of chloroprene monomer, such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, t-butyl hydroperoxide, and the like, is used.

The chain transfer agent is also not particularly limited, and those commonly used for emulsion polymerization of chloroprene can be used.

Specifically, example of the chain transfer agent preferably used include:.

The polymerization temperature of the chloroprene latex is not particularly limited and can be in the range of <NUM> to <NUM>, preferably <NUM> to <NUM>, at which emulsion polymerization is generally performed. The final polymerization rate of the chloroprene-based rubber obtained in the above-described polymerization step is not particularly limited, but is preferably arbitrarily adjusted within the range of <NUM> to <NUM>%. In order to adjust the final conversion, the polymerization may be terminated by adding a polymerization terminator for terminating the polymerization reaction when the desired conversion is achieved.

The polymerization terminator is not particularly limited, and those commonly used can be used. Specific examples of the polymerization terminator include thiodiphenylamine, <NUM>-tertiarybutylcatechol, <NUM>,<NUM>-methylenebis-<NUM>-methyl-<NUM>-tertiarybutylphenol and the like.

Next, unreacted monomers are removed from the polymerization liquid obtained by the polymerization step. The method is not particularly limited, and includes, for example, a steam stripping method. After that, the chloroprene-based rubber is obtained through conventional processes such as adjusting the pH, freeze-coagulating, washing with water, and drying with hot air.

Silica is added to the rubber composition as a filler. It is not particularly limited, for example, wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), and colloidal silica can be used. In the rubber composition of the present invention, use of wet silica is particularly preferred.

The Silica preferably has a CTAB (cetyltrimethylammonium bromide) adsorption specific surface area of <NUM> to <NUM><NUM>/g, especially <NUM> to <NUM><NUM>/g, in terms of processability and physical properties obtained. For example, NipSil AQ (CTAB adsorption specific surface area of <NUM><NUM>/g) manufactured by TOSOH SILICA CORPORATION.

In this description, the CTAB adsorption specific surface area of the silica is a value obtained by measuring the amount of CTAB adsorption on the silica surface according to JIS K <NUM>-<NUM>:<NUM> "Part <NUM>: Determination of specific surface area - CTAB adsorption method".

The amount of the silica added is <NUM> to <NUM> parts by mass, preferably <NUM> to <NUM> parts by mass, more preferably <NUM> to <NUM> parts by mass, with respect to <NUM> parts by mass of the chloroprene-based rubber. The amount of the silica added can be, for example, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> parts by mass and may be in the range between the two values exemplified herein.

The hydrate preferably has a structure that releases H<NUM>O, for example, during kneading operation and vulcanization. The hydrate is more preferably a hydrate that releases H<NUM>O in a temperature range of <NUM> to <NUM>, and even more preferably a hydrate that releases H<NUM>O in a temperature range of <NUM> to <NUM>. Thereby, the reaction between the silane coupling agent and silica is promoted, and improved physical properties and vulcanization speed can be obtained.

The hydrate is not particularly limited, and those used in commercially available rubber compositions can be used. For example, hydrotalcite compounds represented by the following formula (<NUM>), hydrous salts, and metal hydroxides are available.

Examples of the hydrotalcite compound include Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>· <NUM><NUM>O, Mg<NUM>ZnAl<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O, Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O, Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>, Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O, Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O, Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O, and Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O. Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O, Mg<NUM>ZnAl<NUM>(OH)<NUM>CO<NUM>· <NUM><NUM>O are more preferred.

Examples of the hydrous salt include Al<NUM>O<NUM>·<NUM><NUM>O, Al<NUM>O3·H<NUM>O, Na<NUM>SO<NUM>· <NUM><NUM>O, CaSO<NUM>·<NUM><NUM>O, NaHCO<NUM>·Na<NUM>CO<NUM>·<NUM><NUM>O, MgSO<NUM>·<NUM><NUM>O. Al<NUM>O<NUM>·<NUM><NUM>O is more preferred.

Examples of the hydroxide include Ca(OH)<NUM>, Al(OH)<NUM>, Mg(OH)<NUM>, Zn(OH)<NUM>. Mg(OH)<NUM> is more preferred.

The amount of the hydrate added is <NUM> part by mass or more and less than <NUM> parts by mass, preferably <NUM> parts by mass or more and less than <NUM> parts by mass, and more preferably <NUM> to <NUM> parts by mass with respect to <NUM> parts by mass of the chloroprene-based rubber. The amount of hydrate added is, for example, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> parts by mass, and may be in the range between the two values exemplified herein. By using the hydrate in this range, it is possible to obtain a rubber composition excellent in abrasion resistance and low temperature rise.

The organic peroxide is added to the rubber composition as a vulcanization aid and is not particularly limited, and examples include dicumyl peroxide, benzoyl peroxide, <NUM>,<NUM>-bis(t-butylperoxy)-<NUM>,<NUM>,<NUM>-trimethylcyclohexane, diisobutyryl peroxide, cumyl peroxyneodecanoate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, <NUM>,<NUM>,<NUM>,<NUM>-tetramethylbutyl peroxyneodecanoate, di(<NUM>-t-butylcyclohexyl)peroxydicarbonate, di(<NUM>-ethylhexyl) peroxydicarbonate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, di(<NUM>,<NUM>,<NUM>-trimethylhexanoyl) peroxide, dilauroyl peroxide, <NUM>,<NUM>,<NUM>,<NUM>-tetramethylbutyl peroxy-<NUM>-ethylhexanoate, disuccinic peroxide, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-di(<NUM>-ethylhexanoylperoxy)hexane, t-hexylperoxy-<NUM>-ethylhexanoate, di(<NUM>-methylbenzoyl) peroxide, t-butyl peroxy-<NUM>-ethylhexanoate, di(<NUM>-methylbenzoyl) peroxide, benzoyl (<NUM>-methylbenzoyl) peroxide, dibenzoyl peroxide, <NUM>,<NUM>-di(t-butylperoxy)-<NUM>-methylcyclohexane, <NUM>,<NUM>-di(t-hexylperoxy)-<NUM>,<NUM>,<NUM>-trimethylcyclohexane, <NUM>,<NUM>-di(t-hexylperoxy)cyclohexane, <NUM>,<NUM>-di(t-butylperoxy)cyclohexane, <NUM>,<NUM>-di(<NUM>,<NUM>-di-(t-butylperoxy)cyclohexyl)propane, t-hexyl peroxy isopropyl monocarbonate, t-butyl peroxymaleate, t-butyl peroxy-<NUM>,<NUM>,<NUM>-trimethylhexanoate, t-butyl peroxylaurate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy <NUM>-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-di(benzoylperoxy)hexane, t-butyl peroxyacetate, <NUM>,<NUM>-di-(t-butylperoxy)butane, t-butyl peroxybenzoate, n-butyl <NUM>,<NUM>-di-(t-butylperoxy)valerate, <NUM>,<NUM>-bis[(t-butylperoxy)isopropyl]benzene, di-t-hexyl peroxide, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butyl peroxide, p-menthane hydroperoxide, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-bis(t-butylperoxy)hexyne-<NUM>, diisopropylbenzene hydroperoxide, <NUM>,<NUM>,<NUM>,<NUM>-tetramethylbutyl hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide. Among these, one selected from dicumyl peroxide, <NUM>,<NUM>-bis[(t-butylperoxy)isopropyl]benzene, t-butyl α-cumyl peroxide, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-bis(t-butylperoxy)hexane, and <NUM>,<NUM>-Dimethyl-<NUM>,<NUM>-bis(t-butylperoxy)hexin-<NUM> is more preferred and <NUM>,<NUM>-bis[(t-butylperoxy)isopropyl]benzene is particularly preferred.

The amount of the organic peroxide added is <NUM> to <NUM> parts by mass, preferably <NUM> to <NUM> parts by mass, particularly preferably <NUM> to <NUM> parts by mass, with respect to <NUM> parts by mass of the chloroprene-based rubber. The amount of the organic peroxide added is, for example, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> parts by mass, and may be in the range between the two values exemplified herein. By using the organic peroxide within this range, it is possible to obtain a rubber composition having an excellent balance of abrasion resistance, low temperature rise, and vulcanization speed.

In order to improve the dispersibility of the silica in the rubber and the reinforcing effect between the rubber and silica, the rubber composition according to one embodiment of the present invention contains <NUM> to <NUM> parts by mass of the silane coupling agent having a double bond in a structure of the silane coupling agent with respect to <NUM> parts by mass of silica. The content of the silane coupling agent having a double bond in its structure is preferably <NUM> to <NUM> parts by mass, more preferably <NUM> to <NUM> parts by mass, with respect to <NUM> parts by mass of silica. The content of the silane coupling agent having a double bond in its structure is, for example, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> parts by mass, and may be within a range between any two of the numerical values exemplified herein. By using the silane coupling agent having a double bond in its structure within this range, necessary and sufficient effects can be obtained and the occurrence of scorch can be suppressed.

The silane coupling agent having a double bond in its structure is not particularly limited except that it has a double bond in its structure, and those used in commercially available rubber compositions can be used. Examples of the silane coupling agent include vinyl-based coupling agents, styryl-based coupling agents, methacrylic-based coupling agents, and acrylic-based coupling agents. Vinyl-based coupling agents, methacrylic-based coupling agents, and acrylic-based coupling agents are particularly preferable from the viewpoint of processability and reinforcing effect. A silane coupling agent having a double bond in its structure preferably has a (meth)acrylic group in its structure, and even more preferably has a methacrylic group.

Examples of the silane coupling agent having a double bond in its structure include, specifically, vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane, <NUM>-acryloxypropyltrimethoxysilane, <NUM>-(meth)acryloxypropylmethyldimethoxysilane, <NUM>-(meth)acryloxypropylmethyltrimethoxysilane, <NUM>-(meth)acryloxypropylmethyldiethoxysilane, <NUM>-(meth)acryloxypropylmethyltriethoxysilane. Among these, vinyltrimethoxysilane, vinyltriethoxysilane, <NUM>-methacryloxypropylmethyldimethoxysilane, <NUM>-methacryloxypropylmethyltrimethoxysilane, <NUM>-methacryloxypropylmethyldiethoxysilane, <NUM>-methacryloxypropylmethyltriethoxysilane are preferred.

In addition, the rubber composition according to one embodiment of the present invention can also contain a silane coupling agent having no double bond in its structure. The content of the silane coupling agent having no double bond in its structure may be <NUM> to <NUM> parts by mass with respect to <NUM> parts by mass of silica. Moreover, the content of the silane coupling agent having no double bond in its structure is preferably less than the content of the silane coupling agent having a double bond in its structure. In the rubber composition according to one embodiment of the present invention, the content of the silane coupling agent having a double bond in the structure is preferably <NUM> parts by mass or more, more preferably <NUM> parts by mass or more, and even more preferably <NUM> parts by mass or more with respect to <NUM> parts by mass of the total amount of the silica contained in the rubber composition. The rubber composition according to one embodiment of the present invention may not contain a silane coupling agent having no double bond in its structure.

A filler such as carbon black, a reinforcing material, a processing aid, an antioxidant, and the like may be added to the rubber composition as long as the effects of the present invention are not impaired.

Examples of the filler and the reinforcing material include, for example, carbon black, clay, talc, calcium carbonate, and the like. The filler and reinforcing material can be added in amounts that do not impair the heat resistance, and the amounts of these are preferably in the range of <NUM> to <NUM> parts by mass with respect to <NUM> parts by mass of the rubber composition.

Examples of the processing aid include fatty acids such as stearic acid, paraffin-based processing aids such as polyethylene, and fatty acid amides. The amount of the processing aid can be <NUM> to <NUM> parts by mass with respect to <NUM> parts by mass of the rubber composition.

As the antioxidant, general antioxidants such as amine-based antioxidants, imidazole-based antioxidants, metal carbamates, phenol-based antioxidants, and wax can be used. Examples of the antioxidant having a large effect of improving heat resistance include amine-based antioxidant such as <NUM>,<NUM>'-bis(α,α-dimethylbenzyl)diphenylamine, octylated diphenylamine, and the like. In particular, <NUM>,<NUM>'-bis(a,a-dimethylbenzyl)diphenylamine has a great effect of improving heat resistance. These antioxidants can be used alone, or two or more of these can be used in combination.

The plasticizer is not particularly limited as long as it is compatible with the chloroprene-based rubber. Examples of the plasticizer include vegetable oils such as rapeseed oil, phthalate-based plasticizers, DOS, DOA, ester-based plasticizers, ether- and ester-based plasticizers, thioether-based plasticizers, aromatic oils, naphthenic oils, and the like. These can be used alone, or two or more of these can be used in combination according to the properties required for the rubber composition. The amount of the plasticizer to be added is preferably <NUM> to <NUM> parts by mass with respect to <NUM> parts by mass of the rubber composition.

The rubber composition according to one embodiment of the present invention has a vulcanization rate (T90-T10) of preferably <NUM> minutes or less, more preferably <NUM> minutes or less, and further preferably <NUM> minutes or less. Here, the vulcanization speed is calculated by measuring vulcanization time (T90) at <NUM> for <NUM> minutes and the vulcanization time is determined by an oscillation disk rheometer (No. <NUM> lotus rheometer, manufactured by Toyo Seiki Seisaku-sho, Ltd. ), in accordance with the SRIS3102-<NUM> in Standard of the Society of Rubber Industry, Japan.

The rubber composition is obtained by kneading the above compounds at a temperature below the vulcanization temperature. Examples of the kneading device include a mixer, a Banbury mixer, a kneader mixer, two roll mills, and the like.

A vulcanized molded body of the rubber composition is obtained by molding the above rubber composition into various desired shapes and then vulcanizing it, or by molding the rubber composition into various shapes after vulcanizing the rubber composition. Examples of the methods for molding the vulcanized molded body from the rubber composition include methods such as press molding, extrusion molding, and calender molding.

The temperature at which the rubber composition is vulcanized may be appropriately set according to its composition, and is usually in the range of <NUM> to <NUM>, preferably <NUM> to <NUM>. Also, the vulcanization time may be appropriately set depending on the composition and shape of the rubber composition, and is usually in the range of <NUM> to <NUM> minutes.

The vulcanized molded body is obtained by vulcanizing and molding the rubber composition described above and has a good vulcanization rate and is excellent in abrasion resistance and low temperature rise.

The vulcanized molded body according to one embodiment of the present invention preferably has a ΔV of <NUM><NUM> or less, more preferably <NUM><NUM> or less, and even more preferably <NUM><NUM> or less in an Akron abrasion test (<NUM> times abrasion, abrasion volume ΔV, unit: mm<NUM>) in accordance with JIS K <NUM>-<NUM>:<NUM>. Here, the vulcanized molded body may be obtained by press-vulcanizing the rubber composition according to one embodiment of the present invention at <NUM> for <NUM> minutes and may have a diameter of <NUM>, a thickness of <NUM>, and a center hole of <NUM>.

The vulcanized molded body according to one embodiment of the present invention preferably has a temperature rise (ΔT) of <NUM> or less, more preferably <NUM> or less, and even more preferably <NUM> or less. The temperature rise (ΔT) may be measured in accordance with JIS K <NUM>:<NUM>, under the conditions of <NUM>, strain of <NUM> inches, load of <NUM> lb, and frequency of vibration of <NUM>,<NUM> times per minute. Here, the vulcanized molded body may be obtained by press-vulcanizing the rubber composition according to one embodiment of the present invention at <NUM> for <NUM> minutes and may be cylindrical with a diameter of <NUM> and a height of <NUM>.

To a polymerization vessel with an inner volume of <NUM> liters equipped with a heating and cooling jacket and a stirrer, <NUM> parts by mass of chloroprene monomer, <NUM> parts by mass of acrylonitrile monomer, <NUM> parts by mass of diethylxanthogen disulfide, <NUM> parts by mass of pure water, <NUM> parts by mass of potassium rosinate (manufactured by Harima Chemicals Group, Inc. ), <NUM> parts by mass of sodium hydroxide, and <NUM> parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation) were added. <NUM> part by mass of potassium persulfate was added as a polymerization initiator, and emulsion polymerization was carried out at a polymerization temperature of <NUM> under a nitrogen stream. The chloroprene monomer was added in portions from <NUM> seconds after the initiation of polymerization. Based on the change in the heat quantity of the refrigerant for <NUM> seconds from the start of polymerization, the flow rate to be added in portions was adjusted with a solenoid valve. Thereafter, the flow rate was readjusted every <NUM> seconds, and the addition was continuously performed in portions. When the polymerization rate with respect to the total amount of the chloroprene monomer and the acrylonitrile monomer reached <NUM>%, <NUM> parts by mass of phenothiazine as a polymerization terminator was added to terminate the polymerization. Thereafter, unreacted monomers were removed from the reaction solution under reduced pressure to obtain a chloroprene-acrylonitrile copolymer latex.

The above-described polymerization rate [%] of the chloroprene-acrylonitrile copolymer latex was calculated from the dry mass when the chloroprene-acrylonitrile copolymer latex was air-dried. Specifically, it was calculated by the following formula (A). In the formula, "Solid Content Concentration" is the solid content concentration [% by mass], which is obtained by heating <NUM> of the sampled chloroprene-acrylonitrile copolymer latex at <NUM> and removing volatile components such as a solvent (water), a volatile chemical and raw materials. The "Total Charged Amount" is the total amount [g] of raw materials, chamicals and solvent (water) charged into the polymerization vessel from the start of polymerization to a certain time. The "Evaporation Residue" is the mass [g] of chemicals remaining as solid content together with the polymer without being volatilized under conditions of <NUM> among the chemicals and raw materials charged from the start of polymerization to a certain time. The "amount of monomer charged" is the total amount [g] of the amount of the monomer initially charged in the polymerization vessel and the amount of the monomer added in portions from the start of the polymerization to a certain time. In addition, the "monomer" here is the total amount of chloroprene and acrylonitrile.

After adjusting the pH of the above-mentioned chloroprene-acrylonitrile copolymer latex to <NUM> using acetic acid or sodium hydroxide, the chloroprene-acrylonitrile copolymer latex is freeze-coagulated on a metal plate cooled to -<NUM> and demulsified to obtain a sheet. The sheet was washed with water and dried at <NUM> for <NUM> minutes to obtain a solid chloroprene-acrylonitrile copolymer rubber (chloroprene-acrylonitrile copolymer).

The above-mentioned chloroprene-acrylonitrile copolymer rubber was dissolved in THF to prepare a solution with a concentration of <NUM>% by mass, and then the weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of the chloroprene-acrylonitrile copolymer rubber (standard polystyrene equivalent) were measured using a high-speed GPC device (TOSOH HLC-8320GPC: manufactured by Tosoh Corporation). At that time, using TSK guard column HHR-H as a pre-column, using three HSKgelGMHHR-H as analytical columns, the sample pump pressure was set to <NUM>-<NUM> MPa, the flow rate was set to <NUM>/min, the sample was eluted at <NUM>, and detected using a differential refractometer.

The elution time and molecular weight were obtained using a calibration curve prepared by measuring the following nine standard polystyrene samples with known molecular weights.

The chloroprene-acrylonitrile copolymer rubber had a weight average molecular weight (Mw) of <NUM>×<NUM><NUM>g/mol, a number average molecular weight (Mn) of <NUM>×<NUM><NUM>g/mol and a molecular weight distribution (Mw/Mn) of <NUM>.

The content of the acrylonitrile monomer unit contained in the chloroprene-acrylonitrile copolymer rubber was calculated from the content of nitrogen atoms in the chloroprene-acrylonitrile copolymer rubber. Specifically, using an elemental analyzer (SUMIGRAPH 220F: manufactured by Sumika Chemical Analysis Service, Ltd. ), the content of nitrogen atoms in <NUM> of chloroprene-acrylonitrile copolymer rubber was measured, and the content of the monomer unit of acrylonitrile was calculated. The content of the acrylonitrile monomer unit was <NUM>% by mass.

The elemental analysis described above was performed as follows. The temperature of the electric furnace was set to <NUM> for the reaction furnace, <NUM> for the reduction furnace, <NUM> for the column temperature, and <NUM> for the detector temperature. Oxygen gas was flowed at <NUM>/min as combustion gas, and helium gas was flowed at <NUM>/min as carrier gas. Calibration curves were prepared using aspartic acid (<NUM>%), which has a known nitrogen content, as a standard.

The rubber compositions of Examples and Comparative Examples were obtained by kneading the components shown in Table <NUM> or Table <NUM>, that is, <NUM> parts by mass of a plasticizer, <NUM> part by mass of a processing aid, and <NUM> parts by mass of a heat antioxidant with an <NUM>-inch open roll.

Each component used to obtain the rubber composition is as follows.

Silane coupling agent <NUM>: vinyltrimethoxysilane Shin-Etsu Chemical Co. "KBM-<NUM>"
<CHM>.

Hydrotalcite <NUM>: chemical formula Mg<NUM>Al<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O manufactured by Kyowa Chemical Industry Co.

Hydrotalcite <NUM>: chemical formula Mg<NUM>ZnAl<NUM>(OH)<NUM>CO<NUM>·<NUM><NUM>O manufactured by Kyowa Chemical Industry Co.

Magnesium oxide: " Kyowamag (registered trademark) <NUM>" manufactured by Kyowa Chemical Industry Co.

Organic peroxide <NUM>: <NUM>,<NUM>-bis[(t-butylperoxy)isopropyl]benzene manufactured by NOF CORPORATION "Perbutyl (registered trademark) P".

Organic peroxide <NUM>: <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-bis(t-butylperoxy)hexyne-<NUM> manufactured by NOF CORPORATION, product name "Perhexyne (registered trademark) 25B".

Plasticizer: Polyetherester-based "ADEKA CIZER (registered trademark) RS-<NUM>" manufactured by ADEKA Corporation.

Processing aid: stearic acid "Stearic acid <NUM>" manufactured by New Japan Chemical Co.

Heat resistant antioxidant: <NUM>,<NUM>'-bis(α,α-dimethylbenzyl)diphenylamine "Nocrak (registered trademark) CD" manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO.

For the rubber composition described above, vulcanization time (T90) at <NUM> for <NUM> minutes was measured and vulcanization rate (T90-T10) was calculated using an oscillation disk rheometer (No. <NUM> lotus rheometer, manufactured by Toyo Seiki Seisaku-sho, Ltd. ), in accordance with the SRIS3102-<NUM> in Standard of the Society of Rubber Industry, Japan. The results are shown in Tables <NUM> and <NUM>.

The obtained rubber composition was press-vulcanized at <NUM> for <NUM> minutes to prepare a vulcanized molded body having a diameter of <NUM>, a thickness of <NUM>, and a center hole of <NUM>. The obtained vulcanized molded body was subjected to an Akron abrasion test (<NUM> times abrasion, abrasion volume ΔV, unit: mm<NUM>) in accordance with JIS K <NUM>-<NUM>:<NUM>. Those having a ΔV of <NUM><NUM> or less were judged to be good. The results are shown in Tables <NUM> and <NUM>.

The obtained rubber composition was press-vulcanized at <NUM> for <NUM> minutes to prepare a vulcanized molded body having a cylindrical vulcanized molded body having a diameter of <NUM> and a height of <NUM>. The temperature rise (ΔT) of the obtained vulcanized molded body was measured in accordance with JIS K <NUM>: <NUM> under the conditions of <NUM>, strain of <NUM> inches, load of <NUM> lb, and frequency of vibration of <NUM>,<NUM> times per minute. Those having a ΔT of <NUM> or less were judged as acceptable. Tables <NUM> and <NUM> show the results.

Claim 1:
A rubber composition comprising:
<NUM> parts by mass of a chloroprene-based rubber;
<NUM> to <NUM> parts by mass of silica;
<NUM> part by mass or more and less than <NUM> parts by mass of a hydrate; and
<NUM> to <NUM> parts by mass of an organic peroxide, wherein:
the rubber composition includes <NUM> to <NUM> parts by mass of a silane coupling agent having a double bond in a structure of the silane coupling agent with respect to <NUM> parts by mass of the silica.