Diene-based polymer rubber

Abstract

The present invention provides a diene-based polymer rubber, being a conjugated diene-based polymer rubber containing a diene monomer unit and a (meth)acrylic acid ester monomer unit, wherein the (meth)acrylic acid ester monomer unit content is 1-40% mass%.

Description

Diene polymer rubber

[0001] The present invention relates to a diene polymer rubber, and more particularly to a diene polymer rubber capable of giving a cross-linked rubber product that has excellent friction properties on ice and high affinity for water.

[0002] Diene polymer rubbers are produced by emulsion polymerization, in which polymerization is carried out in an aqueous medium in the presence of an emulsifier, or solution polymerization, in which polymerization is carried out in an organic solvent using an anionic polymerization catalyst, and are used in a variety of applications. For example, diene polymer rubbers are suitably used in a variety of applications, such as rubber materials for tires and rubber materials for shoe soles.

[0003] For example, Patent Document 1 discloses a rubber composition for use in tires that has improved friction on ice, characterized in that it contains, per 100 parts by mass of diene rubber, 20 to 70 parts by mass of at least one filler selected from the group consisting of carbon black and white fillers, and 1 to 30 parts by mass of a spherical, non-hollow (meth)acrylic acid alkyl ester polymer having a particle size of 0.1 μm to 100 μm. However, the technology disclosed in Patent Document 1 is only limited in its effect of improving friction on ice, and further improvement in friction on ice (frictionability on ice) has been desired.

[0004] JP 2012-158710 A

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a diene polymer rubber that exhibits high affinity for water and is thereby capable of giving a cross-linked rubber product that has, for example, excellent friction properties on ice.

[0006] The present inventors have conducted studies to achieve the above object and have found that the above problems can be solved by using a diene polymer rubber containing (meth)acrylic acid ester monomer units in a specific content ratio, thereby completing the present invention.

[0007] That is, according to the present invention, there are provided the following diene polymer rubbers and methods for producing the diene polymer rubbers. [1] A conjugated diene polymer rubber containing diene monomer units and (meth)acrylic acid ester monomer units, wherein the content of the (meth)acrylic acid ester monomer units is 1 to 40% by weight. [2] The diene polymer rubber according to [1], characterized in that the glass transition temperature of the diene polymer rubber is -100 to -50°C. [3] The diene polymer rubber according to [1] or [2], characterized in that the (meth)acrylic acid ester monomer units are (meth)acrylic acid alkoxyalkyl ester monomer units. [4] The diene polymer rubber according to any one of [1] to [3], characterized in that the sliding angle is 38° or more. [5] A method for producing the diene polymer rubber according to any one of [1] to [4], comprising a step of polymerizing a monomer mixture containing a diene monomer and a (meth)acrylic acid ester monomer in an aqueous medium in the presence of an emulsifier.

[0008] According to the present invention, it is possible to provide a diene polymer rubber which is capable of giving a cross-linked rubber product which has excellent friction properties on ice and high affinity for water.

[0009] The diene polymer rubber of the present invention contains diene monomer units and (meth)acrylic acid ester monomer units, and the content of the (meth)acrylic acid ester monomer units is 1 to 40% by weight.

[0010] The diene monomer forming the diene monomer unit is not particularly limited, but examples thereof include conjugated diene monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene; and non-conjugated diene monomers such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene. Among these, conjugated diene monomers are preferred, with 1,3-butadiene and isoprene being more preferred, and 1,3-butadiene being even more preferred. These diene monomers may be used alone or in combination of two or more.

[0011] The content of diene monomer units in the diene polymer rubber of the present invention is preferably 60 to 99% by weight, more preferably 70 to 97% by weight, even more preferably 75 to 95% by weight, and particularly preferably 80 to 93% by weight. By making the content of diene monomer units 60% by weight or more, the rubber elasticity of the obtained cross-linked rubber can be made sufficient, and by making the content of diene monomer units 99% by weight or less, the friction properties on ice and affinity for water of the obtained cross-linked rubber can be further improved.

[0012] In the diene polymer rubber of the present invention, the vinyl bond content in the diene monomer units is preferably 5 to 30 mol%, more preferably 8 to 20 mol%, even more preferably 10 to 20 mol%, and particularly preferably 13 to 18 mol%. By setting the vinyl bond content in the diene monomer units to the above upper limit or less, it is possible to appropriately suppress a decrease in performance on ice due to an increase in rubber hardness, while by setting the vinyl bond content in the diene monomer units to the above lower limit or more, it is possible to further increase the strength of the polymer.

[0013] The (meth)acrylic acid ester monomer forming the (meth)acrylic acid ester monomer unit (meaning an acrylic acid ester monomer and / or a methacrylic acid ester monomer; hereinafter, the same applies to methyl (meth)acrylate, etc.) is not particularly limited, but examples thereof include (meth)acrylic acid alkyl ester monomers and (meth)acrylic acid alkoxyalkyl ester monomers, and from the viewpoint of high affinity for water, (meth)acrylic acid alkoxyalkyl ester monomers are preferred.

[0014] The (meth)acrylic acid alkyl ester monomer is not particularly limited, but is preferably an ester of (meth)acrylic acid with an alkanol having 1 to 12 carbon atoms (i.e., a (meth)acrylic acid ester having an alkyl group having 1 to 12 carbon atoms), more preferably an ester of (meth)acrylic acid with an alkanol having 1 to 8 carbon atoms (i.e., a (meth)acrylic acid ester having an alkyl group having 1 to 8 carbon atoms), and even more preferably an ester of (meth)acrylic acid with an alkanol having 2 to 6 carbon atoms (i.e., a (meth)acrylic acid ester having an alkyl group having 2 to 6 carbon atoms).

[0015] Specific examples of the (meth)acrylic acid alkyl ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate. Among these, ethyl (meth)acrylate and n-butyl (meth)acrylate are preferred, ethyl acrylate and n-butyl acrylate are more preferred, and n-butyl acrylate is even more preferred. These may be used alone or in combination of two or more.

[0016] The (meth)acrylic acid alkoxyalkyl ester monomer is not particularly limited, but is preferably an ester of an alkoxyalkyl alcohol having 2 to 12 carbon atoms and (meth)acrylic acid (i.e., a (meth)acrylic acid ester having an alkoxyalkyl group having 2 to 12 carbon atoms), more preferably an ester of an alkoxyalkyl alcohol having 2 to 8 carbon atoms and (meth)acrylic acid (i.e., a (meth)acrylic acid ester having an alkoxyalkyl group having 2 to 8 carbon atoms), and particularly preferably an ester of an alkoxyalkyl alcohol having 2 to 6 carbon atoms and (meth)acrylic acid (i.e., a (meth)acrylic acid ester having an alkoxyalkyl group having 2 to 6 carbon atoms).

[0017] Specific examples of the (meth)acrylic acid alkoxyalkyl ester monomer include methoxymethyl (meth)acrylate, ethoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, and 4-methoxybutyl (meth)acrylate. Among these, 2-ethoxyethyl (meth)acrylate and 2-methoxyethyl (meth)acrylate are preferred, 2-ethoxyethyl acrylate and 2-methoxyethyl acrylate are more preferred, and 2-methoxyethyl acrylate is particularly preferred. These may be used alone or in combination of two or more.

[0018] The content of (meth)acrylic acid ester monomer units in the diene polymer rubber of the present invention is 1 to 40% by weight, preferably 3 to 30% by weight, more preferably 5 to 25% by weight, and even more preferably 7 to 20% by weight. If the content of (meth)acrylic acid ester monomer units is too low, the resulting cross-linked rubber will be inferior in affinity for water and friction on ice, while if the content is too high, the resulting cross-linked rubber will be inferior in expressing rubber elasticity.

[0019] Furthermore, the diene polymer rubber of the present invention may contain aromatic vinyl monomer units in addition to the conjugated diene monomer units and (meth)acrylic acid ester monomer units. Examples of aromatic vinyl monomers for forming the aromatic vinyl monomer units include styrene, methylstyrene, ethylstyrene, t-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, chlorostyrene, bromostyrene, methoxystyrene, dimethylaminomethylstyrene, dimethylaminoethylstyrene, diethylaminomethylstyrene, diethylaminoethylstyrene, cyanoethylstyrene, and vinylnaphthalene. Among these, styrene is preferred.

[0020] The content of aromatic vinyl monomer units in the diene polymer rubber of the present invention is preferably 1 to 25% by weight, more preferably 3 to 20% by weight, and even more preferably 5 to 15% by weight.

[0021] The diene polymer rubber of the present invention may contain other monomer units in addition to the conjugated diene monomer units, (meth)acrylic acid ester monomer units, and aromatic vinyl monomer units contained as needed. Examples of other compounds constituting such other monomer units include chain olefin compounds such as ethylene, propylene, and 1-butene; cyclic olefin compounds such as cyclopentene and 2-norbornene; α,β-ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid, ethylacrylic acid, crotonic acid, and cinnamic acid; α,β-ethylenically unsaturated polycarboxylic acids such as butenedioic acids such as fumaric acid and maleic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, allylmalonic acid, and teraconic acid; and α,β-ethylenically unsaturated polycarboxylic acids such as maleic anhydride, itaconic dicarboxylic anhydride, and citraconic anhydride. anhydrides of saturated polycarboxylic acids; monoalkyl fumarate esters such as monomethyl maleate, monoethyl maleate, monopropyl maleate, mono-n-butyl maleate, monocyclopentyl maleate, monocyclohexyl maleate, monocycloheptyl maleate, monomethyl fumarate, monoethyl fumarate, monopropyl fumarate, and mono-n-butyl fumarate; and α,β-ethylenically unsaturated dicarboxylic acid monoesters such as monocyclopentyl fumarate, monocyclohexyl fumarate, and monocycloheptyl fumarate.

[0022] The bonding pattern of each monomer unit in the diene polymer rubber of the present invention can be various bonding patterns such as block, tapered, random, etc., but a random bonding pattern is preferred. By using a random bonding pattern, the friction on ice and affinity for water of the obtained cross-linked rubber can be further improved.

[0023] The diene polymer rubber of the present invention preferably has a glass transition temperature (Tg) of -100 to -50°C, more preferably -95 to -60°C, even more preferably -90 to -70°C, and particularly preferably -80 to -70°C. If the glass transition temperature is too low, the processability will be poor, while if the glass transition temperature is too high, the resulting cross-linked rubber will have poor friction properties on ice. The glass transition temperature of the diene polymer rubber can be controlled, for example, by selecting the type of (meth)acrylic acid ester monomer used, adjusting the content of (meth)acrylic acid ester monomer units, adjusting the amount of vinyl bonds, or adjusting the type and amount of other monomer units such as aromatic vinyl monomer units.

[0024] The Mooney viscosity (ML1+4) of the diene polymer rubber of the present invention is preferably 10 to 200, more preferably 20 to 150, and particularly preferably 30 to 80. When the Mooney viscosity is within the above range, processability is improved. The Mooney viscosity (ML1+4) is measured at 100°C in accordance with JIS K6300-1:2013.

[0025] The diene polymer rubber of the present invention can be produced by copolymerizing a diene monomer and a (meth)acrylic acid ester monomer, although the method for producing the diene polymer rubber is not particularly limited. The polymerization method is not particularly limited, and known emulsion polymerization or solution polymerization methods may be used. However, from the viewpoint of industrial productivity, emulsion polymerization is preferred. That is, a method in which a monomer mixture containing a diene monomer and a (meth)acrylic acid ester monomer is polymerized in an aqueous medium in the presence of an emulsifier is preferred. In emulsion polymerization, in addition to the emulsifier, a polymerization initiator and a molecular weight modifier may be used, and in addition to these, commonly used polymerization auxiliary materials may also be used.

[0026] The emulsifier is not particularly limited, but a carboxylic acid-based emulsifier can be suitably used. Examples of carboxylic acid-based emulsifiers include fatty acid soaps and rosin acid soaps. Examples of fatty acid soaps include sodium or potassium salts of long-chain aliphatic carboxylic acids having 12 to 18 carbon atoms, such as lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid, as well as mixed aliphatic carboxylic acids. Examples of rosin acid soaps include sodium or potassium salts of disproportionated or hydrogenated natural rosins, such as gum rosin, wood rosin, and tall oil rosin. Examples of natural rosins include those containing abietic acid, levopimaric acid, palustric acid, dehydroabietic acid, tetrahydroabietic acid, and neoabietic acid as main components. The amount of emulsifier used is preferably 0.05 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, per 100 parts by weight of the monomers used in the polymerization.

[0027] The polymerization initiator is not particularly limited as long as it is a radical initiator, but examples thereof include inorganic peroxides such as potassium persulfate, sodium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; organic peroxides such as t-butyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide, t-butylcumyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, t-butylperoxyisobutyrate, and diisopropylbenzene hydroperoxide; and azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, and methyl azobisisobutyrate. These polymerization initiators can be used alone or in combination of two or more. Inorganic or organic peroxides are preferred as the polymerization initiator. When a peroxide is used as the polymerization initiator, it can also be used in combination with a reducing agent as a redox polymerization initiator. The reducing agent is not particularly limited, but examples thereof include compounds containing reduced metal ions such as ferrous sulfate and cuprous naphthenate; sulfinates such as sodium hydroxymethanesulfinate; sulfites such as sodium sulfite, potassium sulfite, sodium hydrogen sulfite, aldehyde sodium hydrogen sulfite, and potassium hydrogen sulfite; etc. The amount of the polymerization initiator to be added is preferably 0.01 to 2 parts by weight based on 100 parts by weight of the monomers used in the polymerization.

[0028] The molecular weight modifier is not particularly limited, but examples thereof include α-methylstyrene dimer; mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, and octyl mercaptan; halogenated hydrocarbons such as carbon tetrachloride, methylene chloride, and methylene bromide; and sulfur-containing compounds such as tetraethylthiuram disulfide, dipentamethylenethiuram disulfide, and diisopropylxanthogen disulfide. Among these, mercaptans are preferred, and t-dodecyl mercaptan is more preferred. These molecular weight modifiers may be used alone or in combination of two or more. The amount of molecular weight modifier used varies depending on the type, but is preferably 0.1 to 1.5 parts by weight, more preferably 0.2 to 1.0 part by weight, per 100 parts by weight of the monomers used in the polymerization.

[0029] As the medium for emulsion polymerization, an aqueous medium such as water is usually used. The amount of the aqueous medium is preferably 80 to 500 parts by weight, more preferably 80 to 300 parts by weight, per 100 parts by weight of the monomers used in the polymerization.

[0030] In emulsion polymerization, if necessary, it is possible to use additional polymerization auxiliary materials such as stabilizers, dispersants, pH adjusters, oxygen scavengers, particle size adjusters, etc. When these are used, the types and amounts used are not particularly limited.

[0031] Examples of methods for adding the monomers include adding the monomers to be used all at once to the reaction vessel, adding them continuously or intermittently as the polymerization progresses, and adding a portion of the monomers and reacting them to a specific conversion rate, followed by adding the remaining monomers continuously or intermittently to polymerize them. Any of these methods may be used. When the monomers are mixed and added continuously or intermittently, the composition of the mixture may be constant or may be varied. Furthermore, the various monomers to be used may be mixed in advance and then added to the reaction vessel, or each may be added separately to the reaction vessel.

[0032] The polymerization temperature during emulsion polymerization is not particularly limited, but is usually 0 to 95° C., and preferably 5 to 70° C. The polymerization time is not particularly limited, but is usually about 5 to 40 hours.

[0033] The polymerization terminator is not particularly limited as long as it is one that is typically used in emulsion polymerization, and specific examples include hydroxylamine compounds such as hydroxylamine, hydroxyamine sulfate, diethylhydroxyamine, hydroxyamine sulfonic acid, and alkali metal salts thereof; sodium dimethyldithiocarbamate; hydroquinone derivatives; catechol derivatives; aromatic hydroxydithiocarboxylic acids such as hydroxydimethylbenzenethiocarboxylic acid, hydroxydiethylbenzenedithiocarboxylic acid, and hydroxydibutylbenzenedithiocarboxylic acid, and aromatic hydroxydithiocarboxylic acid compounds such as alkali metal salts thereof; etc. The amount of the polymerization terminator used is not particularly limited, and is typically 0.05 to 2 parts by weight per 100 parts by weight of the monomers used in the polymerization.

[0034] The diene polymer rubber of the present invention can be obtained by adding an antioxidant, such as a phenolic stabilizer, a phosphorus-based stabilizer, or a sulfur-based stabilizer, to the copolymer latex obtained by emulsion polymerization, if desired, followed by salting out or coagulation with alcohol, filtration, and drying. In this case, the filtration and drying steps following coagulation can be carried out by known methods. The amount of antioxidant to be added is preferably 0.05 to 2 parts by weight per 100 parts by weight of the diene polymer rubber or 100 parts by weight of the monomers used in the polymerization.

[0035] The diene polymer rubber of the present invention has a sliding angle (dynamic contact angle) of preferably 38° or more, more preferably 40° or more, even more preferably 42° or more, and particularly preferably 44° or more. The upper limit of the sliding angle is not particularly limited, but is usually 65° or less. The sliding angle can be measured by dropping a 2 μL water droplet onto a diene polymer rubber molded into a predetermined shape, gradually tilting the diene polymer rubber at a constant speed, and measuring the angle at which the water droplet begins to slide. The angle at which the water droplet begins to slide is defined as the sliding angle (dynamic contact angle). A larger sliding angle indicates better water wettability and a higher affinity for water. In the present invention, it is also preferable that the sliding angle (dynamic contact angle) of a rubber composition or cross-linked rubber obtained using the diene polymer rubber of the present invention is within the above-mentioned range. That is, the sliding angle (dynamic contact angle) of the rubber composition or cross-linked rubber obtained using the diene polymer rubber of the present invention is preferably 38° or more, more preferably 40° or more, even more preferably 42° or more, and particularly preferably 44° or more. The upper limit of the sliding angle is not particularly limited, but is usually 65° or less.

[0036] <Rubber Composition> A rubber composition can be prepared by blending a crosslinking agent with the diene polymer rubber of the present invention.

[0037] Examples of crosslinking agents include sulfur-containing compounds such as sulfur and sulfur halides, organic peroxides, quinone dioximes, organic polyamine compounds, and alkylphenol resins having methylol groups. Of these, sulfur is preferably used. The amount of crosslinking agent blended is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, and particularly preferably 1 to 4 parts by weight, per 100 parts by weight of the polymer components in the rubber composition.

[0038] The rubber composition of the present invention may also contain a filler, and examples of fillers include silica, calcium silicate, aluminum silicate, carbon black, calcium carbonate, talc, aluminum hydroxide, alumina, clay, and mica. Among these, carbon black and silica are preferred, and silica is more preferred, from the viewpoint of being able to further increase the frictional properties on ice and affinity for water of the resulting cross-linked rubber. The fillers may be used alone or in combination of two or more.

[0039] Examples of silica include dry process white carbon, wet process white carbon, colloidal silica, precipitated silica, calcium silicate, and aluminum silicate. Among these, wet process white carbon, which is mainly composed of hydrous silica, is preferred. Carbon-silica dual phase filler, in which silica is supported on the surface of carbon black, may also be used. These silicas may be used alone or in combination of two or more. The nitrogen adsorption specific surface area of ​​the silica used (measured by the BET method in accordance with ASTM D3037-81) is preferably 20 to 400 m ２ / g, more preferably 50 to 220 m ２ / g, particularly preferably 80 to 170 m ２ The pH of the silica is preferably 5 to 10.

[0040] Examples of carbon black include furnace black, acetylene black, thermal black, channel black, and graphite. Examples of channel black include EPC, MPC, and CC. Examples of furnace carbon black include SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF. Examples of thermal black include FT and MT. Each carbon black can be used alone or in combination of two or more types.

[0041] The amount of filler blended in the rubber composition of the present invention is preferably 5 to 90 parts by weight, more preferably 10 to 70 parts by weight, and even more preferably 20 to 65 parts by weight, per 100 parts by weight of the polymer component in the rubber composition. By setting the blending amount of filler within the above range, it is possible to further improve in a balanced manner the abrasion resistance, friction on ice, and affinity for water of the obtained cross-linked rubber product, while ensuring sufficient processability of the rubber composition.

[0042] The rubber composition of the present invention may further contain a silane coupling agent from the viewpoint of further improving the cut resistance, reinforcement, and low loss properties of the resulting cross-linked rubber. The silane coupling agent is not particularly limited, and various silane coupling agents can be used. In the present invention, sulfide-based, mercapto-based, protected mercapto-based (e.g., those having a carbonylthio group), thiocyanate-based, vinyl-based, amino-based, methacrylate-based, glycidoxy-based, nitro-based, epoxy-based, or chloro-based silane coupling agents can be suitably used. Specific examples of the silane coupling agent include bis(3-(triethoxysilyl)propyl)disulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-(triethoxysilyl)propyl)tetrasulfide, bis(3-triethoxysilylpropyl)polysulfide, γ-mercaptopropyltriethoxysilane, 3-[ ethoxybis(3,6,9,12,15-pentaoxaoctacosan-1-yloxy)silyl]-1-propanethiol, 3-octanoylthio-1-propyl-triethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, γ-trimethoxysilylpropylbenzothiazyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-thiocyanatopropyl triethoxysilane, vinyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 3-trimethoxysilylpropyl methacrylate monosulfide, γ-glycidoxypropyltriethoxysilane, 3-nitropropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-chloropropyltrimethoxysilane. Additionally, NXT-Z100, NXT-Z30, NXT-Z45, NXT-Z60, NXT-Z45, and NXT manufactured by Momentive Performance Materials, Inc., and Si69, Si75, and VP Si363 manufactured by Evonik Degussa, Inc. may also be used. These silane coupling agents may be used alone or in combination of two or more.Alternatively, one or more of these may be oligomerized in advance and used in the oligomerized state. The amount of the silane coupling agent to be added is preferably 0.1 to 30 parts by weight, more preferably 1 to 15 parts by weight, based on 100 parts by weight of the filler.

[0043] The rubber composition of the present invention may contain other polymers in addition to the diene polymer rubber of the present invention. Examples of other polymers include natural rubber (which may be modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), highly purified natural rubber (UPNR), and grafted natural rubber), polyisoprene rubber, emulsion-polymerized styrene-butadiene copolymer rubber, solution-polymerized styrene-butadiene copolymer rubber, polybutadiene rubber (which may be high cis-BR or low cis-BR, or which may be polybutadiene rubber containing crystalline fibers made of 1,2-polybutadiene polymer), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, acrylonitrile-styrene-butadiene copolymer rubber, butyl rubber (IIR), ethylene-propylene copolymer, chloroprene rubber, nitrile-chloroprene rubber, and nitrile-isoprene rubber, which are not conjugated diene polymers. Among these, natural rubber, polyisoprene rubber, polybutadiene rubber, and solution-polymerized styrene-butadiene copolymer rubber are preferred, and natural rubber and polybutadiene rubber are more preferred. These polymers can be used alone or in combination of two or more, such as natural rubber and polybutadiene rubber, or natural rubber and styrene-butadiene copolymer rubber.

[0044] Furthermore, in addition to the above components, the rubber composition of the present invention may contain compounding agents such as crosslinking accelerators, crosslinking activators, antioxidants, activators, process oils, plasticizers, lubricants, and tackifiers in required amounts, according to a conventional method.

[0045] When sulfur or a sulfur-containing compound is used as the crosslinking agent, it is preferable to use a crosslinking accelerator and a crosslinking activator in combination. Examples of crosslinking accelerators include sulfenamide-based crosslinking accelerators; guanidine-based crosslinking accelerators; thiourea-based crosslinking accelerators; thiazole-based crosslinking accelerators; thiuram-based crosslinking accelerators; dithiocarbamic acid-based crosslinking accelerators; and xanthogenic acid-based crosslinking accelerators. Among these, those containing sulfenamide-based crosslinking accelerators are preferred. These crosslinking accelerators may be used alone or in combination of two or more. The amount of crosslinking accelerator blended is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, and particularly preferably 1 to 4 parts by weight, per 100 parts by weight of the polymer component in the rubber composition.

[0046] Examples of crosslinking activators include higher fatty acids such as stearic acid, zinc oxide, etc. These crosslinking activators may be used alone or in combination of two or more. The amount of crosslinking activator blended is preferably 0.05 to 20 parts by weight, and particularly preferably 0.5 to 15 parts by weight, per 100 parts by weight of the polymer component in the rubber composition.

[0047] To obtain the rubber composition of the present invention, the components may be kneaded according to a conventional method. For example, the components excluding thermally unstable components such as crosslinking agents and crosslinking accelerators are kneaded with a polymer component containing the diene polymer rubber of the present invention, and then the kneaded mixture is mixed with thermally unstable components such as crosslinking agents and crosslinking accelerators to obtain the desired composition. The kneading temperature for the components excluding thermally unstable components and the polymer component containing the diene polymer rubber of the present invention is preferably 80 to 200°C, more preferably 100 to 180°C, and the kneading time is preferably 30 seconds to 30 minutes. The kneaded mixture is usually mixed with the thermally unstable components after cooling to 100°C or below, preferably 80°C or below.

[0048] <Rubber Cross-Linked Product> A rubber cross-linked product can be obtained by cross-linking the rubber composition containing the diene polymer rubber of the present invention described above.

[0049] The cross-linked rubber product of the present invention can be produced by using a rubber composition containing the diene polymer rubber of the present invention described above, molding the rubber composition into a desired shape using a molding machine such as an extruder, injection molding machine, compressor, or roll, and then heating the resulting composition to cause a cross-linking reaction and fix the shape as a cross-linked rubber product. In this case, cross-linking may be carried out after molding or simultaneously with molding. The molding temperature is usually 10 to 200°C, preferably 20 to 120°C. The cross-linking temperature is usually 100 to 200°C, preferably 130 to 190°C, and the cross-linking time is usually 1 minute to 24 hours, preferably 2 minutes to 12 hours, and particularly preferably 3 minutes to 6 hours.

[0050] Depending on the shape, size, etc. of the cross-linked rubber, the surface may be cross-linked but the interior may not be sufficiently cross-linked, so secondary cross-linking may be carried out by further heating.

[0051] The heating method may be appropriately selected from common methods used for crosslinking rubber, such as press heating, steam heating, oven heating, and hot air heating.

[0052] The cross-linked rubber product of the present invention obtained in this manner is obtained using the diene polymer rubber of the present invention described above, and therefore has excellent friction properties on ice and exhibits high affinity for water. Therefore, by taking advantage of these properties, the cross-linked rubber product of the present invention can be used in a variety of applications, such as materials for various parts of tires; materials for hoses, belts, mats, vibration-proofing rubber, and various other industrial products; impact modifiers for resins; resin film cushioning agents; shoe soles; rubber shoes; golf balls; and toys. In particular, by taking advantage of its excellent friction properties on ice and affinity for water, the cross-linked rubber product of the present invention is preferably used, for example, as tire and shoe sole rubber.

[0053] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. The "parts" are by weight unless otherwise specified. The test methods used in these examples and comparative examples are as follows.

[0054] <Monomer Composition and Vinyl Bond Content> The monomer composition of the diene polymer rubber and the vinyl bond content (mol %) in the diene monomer unit are determined according to JIS K6239:2007. １ It was determined by H-NMR.

[0055] <Mooney Viscosity of Diene Polymer Rubber> The Mooney viscosity (ML1+4) of the diene polymer rubber was measured in accordance with JIS K6300-1:2013 under the following conditions: Test temperature: 100°C Rotor type: L-type Testing machine used: Shimadzu Mooney Viscometer SMV-301, manufactured by Shimadzu Corporation

[0056] <Glass Transition Temperature (Tg) of Diene Polymer Rubber> The glass transition temperature (Tg) of the diene polymer rubber was determined by measuring the temperature from −150° C. to 40° C. at a temperature increase rate of 10° C. / min using a differential scanning calorimeter (DSC, X-DSC7000 manufactured by Hitachi High-Tech Science Corporation).

[0057] <Frictional Properties of Cross-Linked Rubber on Ice> The rubber compositions according to each Example and Comparative Example were molded into test specimens with a diameter of 50 mm and a thickness of 10 mm, and cross-linked at 160°C for 1 hour. The test specimens were then pressed against fixed ice and rotated, and the frictional force generated during rotation was detected with a load cell. The dynamic friction coefficient μ was calculated from the detected frictional force. The measurement temperature was -2°C, and the surface pressure was 12 kgf / cm. ２ The sample rotation peripheral speed was 20 cm / sec. The measurement results were expressed as an index, with the dynamic friction coefficient μ of Comparative Example 1 set to 100. The larger the index value, the larger the dynamic friction coefficient μ and the better the friction properties on ice (the higher and better the coefficient of friction on ice).

[0058] <Sliding Angle of Cross-Linked Rubber> The rubber compositions according to each Example and Comparative Example were molded into 20 mm x 30 mm test plates (thickness: 2 mm) and cross-linked at 160°C for 20 minutes. Then, a 2 μL water droplet was dropped onto the test plate, and the test plate was gradually tilted at a uniform speed. The angle at which the water droplet began to slide down was measured as the sliding angle (dynamic contact angle). A larger sliding angle indicates better water wettability and higher affinity for water. Note that in Examples 4 to 6, only diene polymer rubbers (A-1) to (A-3) were contained as the rubber component, and therefore the sliding angles of the diene polymer rubbers (A-1) to (A-3) themselves are considered to be similar.

[0059] Example 1: A reactor was charged with 200 parts of ion-exchanged water, 4.5 parts of disproportionated potassium rosinate / sodium fatty acid, 0.1 parts of potassium chloride, 10 parts of methoxyethyl acrylate, and 0.3 parts of t-dodecyl mercaptan (molecular weight modifier), in that order. The internal gas was purged with nitrogen three times, and then 90 parts of 1,3-butadiene was charged. The reactor was then maintained at 10°C, and 0.1 parts of diisopropylbenzene hydroperoxide (polymerization initiator), a reducing agent, and an appropriate amount of chelating agent were charged. The polymerization reaction was initiated with stirring. The polymerization reaction was continued with stirring, and when the polymerization conversion rate reached 75%, 0.2 parts of diethylhydroxylamine (polymerization terminator) was added to terminate the polymerization. After the polymerization reaction was terminated, residual monomer was removed under reduced pressure at a water temperature of 60°C. 0.5 parts of alkylated phenol was then added as an antioxidant. The resulting polymer latex was then added to an aqueous calcium chloride solution to coagulate, yielding a crumb-like polymer. The resulting crumb-like polymer was taken out, washed with water, and then dried at 60° C. under reduced pressure to obtain a diene polymer rubber (A-1).

[0060] The obtained diene polymer rubber (A-1) had a 1,3-butadiene unit content of 91% by weight, a methoxyethyl acrylate unit content of 9% by weight, a vinyl bond content in the 1,3-butadiene units of 16 mol%, a Mooney viscosity (ML1+4) of 55, and a glass transition temperature (Tg) of -76°C.

[0061] Example 2 A diene polymer rubber (A-2) was obtained by performing polymerization in the same manner as in Example 1, except that the amount of methoxyethyl acrylate used was changed to 20 parts and the amount of 1,3-butadiene used was changed to 80 parts. The obtained diene polymer rubber (A-2) had a 1,3-butadiene unit content of 82% by weight, a methoxyethyl acrylate unit content of 18% by weight, a vinyl bond content in the 1,3-butadiene units of 15 mol%, a Mooney viscosity (ML1+4) of 43, and a glass transition temperature (Tg) of -72°C.

[0062] Example 3 A diene polymer rubber (A-3) was obtained by performing polymerization in the same manner as in Example 1, except that the amount of methoxyethyl acrylate used was changed to 5 parts and the amount of 1,3-butadiene used was changed to 95 parts. The obtained diene polymer rubber (A-3) had a 1,3-butadiene unit content of 95% by weight, a methoxyethyl acrylate unit content of 5% by weight, a vinyl bond content in the 1,3-butadiene units of 16 mol%, a Mooney viscosity (ML1+4) of 65, and a glass transition temperature (Tg) of -78°C.

[0063] Example 4 In a 250 ml Brabender mixer, 100 parts of the diene polymer rubber (A-1) obtained in Example 1 was masticated for 30 seconds, followed by the addition of 50 parts of silica (manufactured by Tosoh Silica Industrial Co., Ltd., trade name "Nipsil AQ") and 4 parts of a silane coupling agent: bis(3-triethoxysilylpropyl)polysulfide (manufactured by Shin-Etsu Chemical Co., Ltd.). The mixture was kneaded for 1.5 minutes at an initial temperature of 110°C, after which 3 parts of zinc oxide (zinc white), 2 parts of stearic acid, and 2 parts of an antioxidant: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocrac 6C") were added, followed by further kneading for 2.5 minutes, after which the kneaded mixture was discharged from the mixer. The temperature of the kneaded mixture at the end of kneading was 150°C. The resulting kneaded product was then cooled to room temperature and again kneaded for 2 minutes in a Brabender-type mixer at a starting temperature of 110°C, after which the kneaded product was discharged from the mixer. Next, 1.4 parts of sulfur and 1 part of a crosslinking accelerator: N-cyclohexyl-2-benzothiazolylsulfenamide (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Noccela CZ-G") were added to the resulting kneaded product and kneaded using an open roll at 50°C, after which a sheet-shaped rubber composition was obtained. The resulting rubber composition was then used to evaluate the frictional properties on ice of the crosslinked rubber product and the sliding angle of the crosslinked rubber product. The results are shown in Table 1.

[0064] Example 5 A rubber composition was obtained and evaluated in the same manner as in Example 4, except that 100 parts of the diene polymer rubber (A-2) obtained in Example 2 was used instead of 100 parts of the diene polymer rubber (A-1) obtained in Example 1. The results are shown in Table 1.

[0065] Example 6 A rubber composition was obtained and evaluated in the same manner as in Example 4, except that 100 parts of the diene polymer rubber (A-3) obtained in Example 3 was used instead of 100 parts of the diene polymer rubber (A-1) obtained in Example 1. The results are shown in Table 1.

[0066] Example 7 A rubber composition was obtained in the same manner as in Example 4, except that the amount of diene polymer rubber (A-1) obtained in Example 1 was changed from 100 parts to 50 parts, and 25 parts of butadiene rubber (manufactured by UBE, trade name "UBEPOL BR150L") and 25 parts of natural rubber were further compounded, and evaluation was performed in the same manner. The results are shown in Table 1. The butadiene rubber and natural rubber were compounded at the same time as the diene polymer rubber (A-1). In Example 7, the diene polymer rubber (A-1), butadiene rubber, and natural rubber were masticated, and then various compounding ingredients were compounded to obtain a rubber composition.

[0067] Comparative Example 1 A rubber composition was obtained in the same manner as in Example 4, except that 50 parts of a butadiene rubber (manufactured by UBE, trade name "UBEPOL BR150L") and 50 parts of natural rubber were used instead of 100 parts of the diene polymer rubber (A-1) obtained in Example 1, and evaluations were similarly carried out. The results are shown in Table 1. In Comparative Example 1, the butadiene rubber and natural rubber were masticated, and then various compounding ingredients were compounded to obtain a rubber composition.

[0068]

[0069] As shown in Table 1, when a diene polymer rubber having a (meth)acrylic acid ester monomer unit content of 1 to 40% by weight was used, the cross-linked rubber obtained using this had excellent friction properties on ice, a large sliding angle, and a high affinity for water (Examples 4 to 7).

Claims

1. A conjugated diene polymer rubber containing diene monomer units and (meth)acrylic acid ester monomer units, A diene polymer rubber having a content of 1 to 40% by weight of the (meth)acrylic acid ester monomer units.

2. The diene polymer rubber according to claim 1, characterized in that the glass transition temperature of the diene polymer rubber is -100 to -50°C.

3. The diene polymer rubber according to claim 1 or 2, characterized in that the (meth)acrylic acid ester monomer unit is an (meth)acrylic acid alkoxyalkyl ester monomer unit.

4. The diene polymer rubber according to claim 1 or 2, characterized in that the sliding angle is 38° or more.

5. A method for producing a diene polymer rubber according to claim 1 or 2, A method for producing diene polymer rubber, comprising the step of polymerizing a monomer mixture containing a diene monomer and a (meth)acrylic acid ester monomer in an aqueous medium in the presence of an emulsifier.