Rubber composition, vulcanizate of the rubber composition, and vulcanized molded body of the rubber composition

Abstract

Provided is a rubber composition capable of obtaining a vulcanizate having excellent vulcanization rate, wear resistance, and low heat build-up. The rubber composition contains 100 parts by mass of chloroprene rubber, 20 to 80 parts by mass of silica, 1 or more and less than 20 parts by mass of hydrate, 0.3 to 1.4 parts by mass of organic peroxide, and 0.5 to 15 parts by mass of silane coupling agent having a double bond in the structure relative to 100 parts by mass of the silica.

Description

[Technical Field]

[0001] Chloroprene-based rubbers possess excellent mechanical properties, ozone resistance, and chemical resistance, and are widely used in automotive parts, adhesives, and various industrial rubber components. In recent years, the performance requirements for rubber parts have significantly increased. In addition to mechanical properties such as abrasion resistance and low heat generation in dynamic environments, higher vulcanization speeds are also needed to improve productivity. [Background Technology]

[0002] As a technique for increasing the vulcanization speed of rubber, a known rubber composition as described in Patent Document 1 is characterized by comprising, relative to 100 parts by mass of diene rubber, 5 to 200 parts by mass of silica; relative to the silica, 1 to 20% by mass of silane coupling agent; relative to the silica, 1 to 20% by mass of glycerol monofatty acid ester derived from fatty acids having 8 to 24 carbon atoms; and compounded with 0.1 to 10 parts by mass of a cyclic polysulfide represented by the following formula (1).

[0003] Furthermore, as a technique to improve the abrasion resistance of rubber, a vulcanized rubber composition of a known chloroprene-based rubber, as described in Patent Document 2, comprises, when the total mass of all monomers is 100%, a copolymer consisting of 80-97% by mass of 2-chloro-1,3-butadiene (chloroprene) (C-1) and 20-3% by mass of 2,3-dichloro-1,3-butadiene (C-2), or a copolymer consisting of 79.8-96.8% by mass of 2-chloro-1,3-butadiene (chloroprene) (C-1) and 20-3% by mass of 2,3-dichloro-1,3-butadiene (C-2). The copolymer consists of 0.2 to 17% by mass of monomers (C-3) that can be copolymerized with it, and 100 parts by mass of a chloroprene-based vulcanizing rubber polymer having a polymer Mooney viscosity (ML1+4 (100°C)) in the range of 100 to 135, 0.5 to 6 parts by mass of acid absorber, 0.2 to 3 parts by mass of lubricant, 1 to 5 parts by mass of anti-aging agent, 10 to 120 parts by mass of carbon black, 0.1 to 20 parts by mass of filler other than carbon black, 2 to 40 parts by mass of softener, 0.2 to 5 parts by mass of processing aid, 0.5 to 10 parts by mass of metal oxide, and 0.5 to 5 parts by mass of vulcanization accelerator.

[0004] As a technique for improving the low heat generation of rubber, a known rubber composition as described in Patent Document 3 is characterized in that, relative to 100 parts by mass of the total rubber components containing two or more diene rubbers, the composition contains more than 0 parts by mass and less than 100 parts by mass of silica; the diene rubbers are divided into two or more phases having their own glass transition temperatures, wherein at least one phase has a continuous structure; furthermore, at least one phase has a glass transition point of -50°C or higher; at least 80% by weight of the silica per unit volume of the compounded rubber is included in the phase having at least one phase with a glass transition point of -50°C or higher; the average aggregate area of ​​the silica contained in this phase is 2000 nm. 2 the following. [Existing Technical Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2016-113500 [Patent Document 2] Japanese Patent Application Publication No. 2012-211345 [Patent Document 3] Japanese Patent Application Publication No. 2014-196407 [Summary of the Invention] [The problem the invention aims to solve]

[0006] For rubber compositions containing chloroprene polymers, a high degree of compatibility with various properties is required in the vulcanizate of the rubber composition, such as abrasion resistance or low heat generation under dynamic conditions. This may require providing a highly productive vulcanizate with excellent vulcanization rate.

[0007] One aspect of the present invention aims to provide a rubber composition with excellent abrasion resistance or low heat generation under dynamic conditions and excellent vulcanization speed, resulting in high productivity. Another aspect of the present invention aims to provide a vulcanizate of the said rubber composition. A further aspect of the present invention primarily aims to provide a vulcanized molded article of the said rubber composition. [Solutions]

[0008] One aspect of the present invention relates to a rubber composition, wherein the rubber composition contains 100 parts by mass of chloroprene rubber, 20 to 80 parts by mass of silica, 1 or more but less than 20 parts by mass of hydrate, 0.3 to 1.4 parts by mass of organic peroxide, and 0.5 to 15 parts by mass of a silane coupling agent having a double bond in its structure relative to the 100 parts by mass of silica.

[0009] Preferably, the chloroprene-based rubber contains a homopolymer of 2-chloro-1,3-butadiene, or a copolymer of at least one monomer selected from 2,3-dichloro-1,3-butadiene and acrylonitrile with 2-chloro-1,3-butadiene. Preferably, the silane coupling agent having a double bond in the structure is at least one silane coupling agent selected from vinyltrimethoxysilane, vinyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyltrimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, and 3-(meth)acryloyloxypropylmethyltriethoxysilane. Preferably, the hydrate is a hydrate that releases H2O in a temperature range of 100℃ to 250℃. Preferably, the hydrate is at least one hydrate selected from hydrotalcite compounds, hydrated salts, and metal hydroxides represented by the following chemical formula (1).

[0010] [Chemistry 1] [M 2+ 1-× M 3+ x (OH)2] x+ [A n- x / n ·mH2O] x- (M 2+ Selected from Mg 2+ Mn 2+ Fe 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ At least one divalent metal ion M 3+ Selected from Al 3+ Fe 3+ Cr 3+ Co 3+ In 3+ At least one trivalent metal ion A n- Selected from OH - F - Cl - ,Br - NO3 - CO3 2- SO4 2- Fe(CN)6 3- CH3COO - At least one anion X: 0 < X ​​≤ 0.33

[0011] Preferably, the hydrate is selected from Mg 4.3 Al2(OH) 12.6 CO3·3.5H2O, Mg3ZnAl2(OH) 12CO3·3H2O, Mg 4.5 Al2(OH) 13 CO3·3.5H2O, Mg 4.5 Al2(OH) 13 CO3, Mg4Al2(OH) 12 CO3·3.5H2O, Mg6Al2(OH) 16 CO3·4H2O, Mg5Al2(OH) 14 CO3·4H2O, Mg3Al2(OH) 10 At least one hydrate of the hydrotalcite compound represented by CO3·1.7H2O. Preferably, the organic peroxide is at least one organic peroxide selected from dicumyl peroxide, 1,4-bis[(tert-butylperoxide)isopropyl]benzene, tert-butyl-α-cumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane, and 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexyne-3. Preferably, the hexadecyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​the silica is 50–300 m². 2 / g.

[0012] Another aspect of the present invention relates to a vulcanizate of the above-described rubber composition. Another aspect of the present invention relates to a vulcanized molded article of the above-described rubber composition.

Detailed Implementation Methods

[0013] The preferred embodiment of the present invention will be described below. Furthermore, the embodiments described below are representative examples of the present invention and should not be interpreted narrowly as limiting the scope of protection of the present invention.

[0014] <Rubber Composition> The rubber composition described in this embodiment contains (1) 100 parts by mass of chloroprene rubber, (2) 20 to 80 parts by mass of silica, (3) 1 or more but less than 20 parts by mass of hydrate, (4) 0.3 to 1.4 parts by mass of organic peroxide, and (5) 0.5 to 15 parts by mass of silane coupling agent having double bonds in its structure relative to 100 parts by mass of silica.

[0015] According to the rubber composition involved in this embodiment, the rubber composition can be vulcanized to obtain a sulfide, which has excellent abrasion resistance or low heat generation under dynamic conditions.

[0016] In recent years, while rubber components have been required to exhibit properties such as abrasion resistance and low heat generation, from a production standpoint, there is a need to increase the vulcanization speed. The inventors of this invention, through in-depth research to meet these requirements, discovered that by using a specific amount of silica as a filler, employing a specific amount of a silane coupling agent with double bonds in its structure based on the amount of silica, using an organic peroxide as a vulcanizing agent, and using hydrates instead of magnesium oxide, the vulcanization speed can be increased while simultaneously improving properties such as abrasion resistance and low heat generation.

[0017] While not limiting the invention, the mechanism by which improving wear resistance or low heat generation properties while simultaneously increasing vulcanization speed can be considered as follows: First, by using a specific amount of silane coupling agent with double bonds in its structure, based on the amount of silica, using an organic peroxide as a vulcanizing agent, and using hydrates, the surface of the silica added as filler is protected, improving the dispersibility of the silica. Second, by using an organic peroxide as a vulcanizing agent, the double bond portion of the silane coupling agent reacts with the rubber portion, improving the wear resistance, low heat generation, and reinforcing properties of the resulting vulcanizate. Furthermore, the silane coupling agent protects the silica through its own hydrolysis and the condensation reaction of the hydrolysate with the silica. Therefore, by adding the hydrates and silane coupling agents in the same manner during processing, the heat generated during mixing releases hydrated water (H2O) from the hydrates. This released water promotes the hydrolysis of the silane coupling agent, strengthens the protection of the silica, and contributes to improved reinforcing properties. Furthermore, it is speculated that during the vulcanization process, the removal of hydrated water from the hydrate or the H2O generated by the chlorine capture reaction of hydrochloric acid produced from chloroprene rubber promotes the decomposition of organic peroxides and increases the vulcanization rate.

[0018] (1) Chloroprene-based rubber Chloroprene-based rubbers are primarily composed of chloroprene polymers. Chloroprene polymers are homopolymers of 2-chloro-1,3-butadiene (hereinafter referred to as chloroprene), or copolymers of chloroprene with other monomers that may copolymerize with chloroprene, or mixtures of these polymers. Other monomers that may copolymerize with chloroprene include, for example, esters of acrylic acid, such as methyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; esters of methacrylic acid, such as methyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate; hydroxy(meth)acrylates, such as 2-hydroxyethyl(meth)acrylate, 2-hydroxymethyl(meth)acrylate, and 2-hydroxypropyl(meth)acrylate; 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, butadiene, isoprene, ethylene, styrene, and acrylonitrile. As other monomers that may be copolymerized with chloroprene, it is preferred to contain at least one monomer selected from 2,3-dichloro-1,3-butadiene and acrylonitrile.

[0019] When using copolymers of chloroprene with other monomers that can be copolymerized with chloroprene as a chloroprene-based rubber, the copolymerization amount of the other monomers is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, relative to 100 parts by mass of chloroprene. By adjusting the copolymerization amount of the other monomers to this range, the properties of the resulting rubber composition can be preserved, and the copolymerization of these monomers can achieve the desired effect.

[0020] The chloroprene-based rubber of one embodiment of the present invention preferably contains a homopolymer selected from 2-chloro-1,3-butadiene, or a copolymer of at least one monomer selected from 2,3-dichloro-1,3-butadiene and acrylonitrile with 2-chloro-1,3-butadiene. Furthermore, the chloroprene-based rubber of one embodiment of the present invention may include a homopolymer selected from 2-chloro-1,3-butadiene, and / or a copolymer of at least one monomer selected from 2,3-dichloro-1,3-butadiene and acrylonitrile with 2-chloro-1,3-butadiene. The chloroprene-based rubber of one embodiment of the present invention may further include a homopolymer of 2-chloro-1,3-butadiene.

[0021] The other monomers copolymerized with chloroprene are not limited to one type; for example, they can be copolymerized from three or more monomers containing chloroprene. Furthermore, there are no particular limitations on the polymer structure.

[0022] [Manufacturing method of chloroprene-based rubber] Chloroprene-based rubbers can use rosin and other substances as emulsifying dispersants. In the presence of catalysts, polymerization initiators, chain transfer agents, etc., the raw material monomers with chloroprene as the main component are obtained through emulsification polymerization.

[0023] Examples of catalysts for polymerization reactions include inorganic peroxides such as potassium sulfate, organic peroxides such as ketone peroxides, ketal peroxides, hydroperoxides, dialkyl peroxides, and disilicides. Examples of catalyst activators include sodium sulfite, potassium sulfite, iron(II) oxide, anthraquinone, sodium β-sulfonate, methanesulfonic acid, and L-ascorbic acid.

[0024] There are no particular limitations on the polymerization initiator; known polymerization initiators commonly used for the emulsion polymerization of chloroprene monomers can be used, such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, tert-butyl hydrogen peroxide, etc.

[0025] The chain transfer agent is not particularly limited, and chain transfer agents commonly used in the emulsion polymerization of chloroprene can be used. Specifically, long-chain alkyl thiols such as n-dodecyl mercaptan, tert-dodecyl mercaptan, and n-octyl mercaptan, xanthate compounds such as dithiodiisopropyl xanthate and dithiodiethyl xanthate, iodoform, benzyl 1-pyrrole dithiocarbamate (also known as: 1-pyrrole benzyl methyl disulfate), benzyl methyl methyl sulfate, 1-benzyl-N,N-dimethyl-4-aminodithiobenzoate, 1-benzyl-4-methoxydithiobenzoate, 1-phenylethylimidazolium dithiocarbamate (also known as: 1-phenylethylimidazolium methyl sulfate), benzyl-1-(2-pyrrolidone)dithiocarbamate (also known as: benzyl-1-(2-pyrrolidone)carbamate), and benzyl phthalimide are preferred. Amino dithiocarbamate (also known as benzyl phthalimide carbosulfan), 2-cyanopropyl-2-yl-1-pyrrole dithiocarbamate (also known as 2-cyanopropyl-2-yl-1-pyrrole methyl sulfate), 2-cyanobutyl-2-yl-1-pyrrole dithiocarbamate (also known as 2-cyanobutyl-2-yl-1-pyrrole dithioester), benzyl-1-imidazolium dithiocarbamate (also known as benzyl-1-imidazolium carbosulfan), 2-cyanopropyl-2-yl-N,N-dimethyl dithiocarbamate, benzyl-N,N-diethyl dithiocarbamate, cyanomethyl-1-(2-pyrrolidone) dithiocarbamate, 2-(ethoxycarbonyl benzyl) propyl-2-yl-N,N-diethyldithiocarbamate, 1-phenylethyldithiocarbamate, 2-phenylpropyl-2-yldithiocarbamate, 1-acetic acid-1-ethyldithiocarbamate, 1-(4-methoxyphenyl)ethyldithiocarbamate, benzyl dithioacetate, ethoxycarbonylmethyl dithioacetate, 2-(ethoxycarbonyl)propyl-2-yldithiocarbamate, 2-cyanopropyl-2-yldithiocarbamate, tert-butyldithiocarbamate, 2,4,4-trimethylpenta-2-yldithiocarbamate, 2-(4-chlorophenyl)-propyl-2-yldithiocarbamate, 3-vinylbenzyldithiocarbamate, 4-vinylbenzyldithiocarbamate Benzoate esters, benzyl diethoxyphosphine dithiocarboxylate, tert-butyl trithiobenzoate, 2-phenylpropyl-2-yl-4-chlorodithiobenzoate, naphthalene-1-carboxylic acid-1-methyl-1-phenylethyl ester, 4-cyano-4-methyl-4-thiobenzylthiobutyric acid, dibenzyl tetrathiophene dicarboxylate, carboxymethyl dithiobenzoate, poly(ethylene oxide) with dithiobenzoate terminal groups, poly(ethylene oxide) with 4-cyano-4-methyl-4-thiobenzylthiobutyric acid terminal groups, 2-[(2-phenylethylthio)thio]propionic acid, 2-[(2-phenylethylthio)thio]succinic acid, 3,5-dimethyl-1H-pyrazole-1-dithiocarbonate potassium, cyanomethyl-3-5-Dimethyl-1Hpyrazole-1-dithiocarbonate, cyanomethyl-(phenyl)dithiocarbamate, benzyl-4-chlorodithiobenzoate, benzyl-4-chlorodithiobenzoate, 4-nitrobenzyl-4-chlorodithiobenzoate, phenylpropyl-2-yl-4-chlorodithiobenzoate, 1-cyano-1-methylethyl-4-chlorodithiobenzoate, 3-chloro-2-butenyl-4-chloro Dithiobenzoate, 2-chloro-2-butenyl dithiobenzoate, benzyl dithioacetate, 3-chloro-2-butenyl-1H-pyrrole-1-dithiocarboxylic acid, 2-cyanobutane-2-yl-4-chloro-3,5-dimethyl-1H-pyrazole-1-dithiocarbonate, cyanomethyl methyl (phenyl)aminomethyl dithioester, 2-cyano-2-propyl dodecyl trithiocarbonate, dibenzyl trithiocarbonate, butanediol Benzyl trithiocarbonate, 2-[[(butylthio)thiomethyl]thio]propionic acid, 2-[[(dodecylthio)thiomethyl]thio]propionic acid, 2-[[(butylthio)thiomethyl]thio]succinic acid, 2-[[(dodecylthio)thiomethyl]thio]succinic acid, 2-[[(dodecylthio)thiomethyl]thio]-2-methylpropionic acid, 2,2′-[thiocarbonyl dithio]bis[ 2-Methylpropionic acid, 2-amino-1-methyl-2-oxoethylbutyl trithiocarbonate, benzyl-2-[(2-hydroxyethyl)amino]-1-methyl-2-oxoethyl trithiocarbonate, 3-[[[(tert-butyl)thio]thiomethyl]thio]propionic acid, cyanomethyl dodecyl trithiocarbonate, diethylaminobenzyl trithiocarbonate, dibutylaminobenzyl trithiocarbonate, and other thiocarbonyl compounds, etc.

[0026] The polymerization temperature of chloroprene latex is not particularly limited and can be carried out at the typical emulsion polymerization temperature of 0–50°C, preferably within the range of 20–50°C. Furthermore, while the final polymerization rate of the chloroprene-based rubber obtained from the above polymerization steps is not particularly limited, it is preferably adjustable arbitrarily within the range of 30–100%. To adjust the final conversion rate, polymerization can be terminated by adding a polymerization terminator when the desired conversion rate is reached.

[0027] There are no particular limitations on the polymerization terminator; commonly used polymerization terminators can be used. Specifically, these include thiodiphenylamine, 4-tert-butylcatechol, and 2,2-methylenebis-4-methyl-6-tert-butylphenol.

[0028] Next, unreacted monomers are removed from the polymerization solution obtained from the polymerization step. This method is not particularly limited; for example, steam stripping can be used. Afterwards, the pH is adjusted, and the product undergoes conventional freeze-curing, washing, and hot-air drying to obtain chloroprene-based rubber.

[0029] (2) Silicon dioxide Silica is added as a filler to the rubber composition, although there are no particular limitations; for example, wet silica (hydrated silicic acid), dry silica (silicic anhydride), and colloidal silica can be used. The rubber composition of the present invention particularly preferably uses wet silica.

[0030] From the viewpoint of processability and the resulting physical properties, silica is preferably adsorbed using CTAB (hexadecyltrimethylammonium bromide) with a specific surface area of ​​50–300 m². 2 / g, with 80-250m being particularly preferred. 2 / g. As a type of silica, for example, there is NipSil (Nipseal) AQ (CTAB) manufactured by Tosoh Silica Co., Ltd., with an adsorption specific surface area of ​​187m². 2 / g), etc.

[0031] Furthermore, in this specification, the CTAB adsorption specific surface area of ​​silica is the value of the amount of CTAB adsorbed on the silica surface as determined according to JIS K6217-3:2001″ Part 3: Methods for determining specific surface area - CTAB adsorption method″.

[0032] The amount of silica added relative to 100 parts by weight of chloroprene rubber is 20 to 80 parts by weight, preferably 30 to 70 parts by weight, and more preferably 40 to 60 parts by weight. The amount of silica added can be, for example, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80 parts by weight, or can be within any two of the values ​​exemplified here.

[0033] (3) Hydrates The hydrate is preferably a hydrate with a structure that releases H2O during mixing and vulcanization. The hydrate is preferably a hydrate that releases H2O in a temperature range of 100°C to 250°C, and more preferably a hydrate that releases H2O in a temperature range of 100°C to 150°C. This promotes the reaction between the silane coupling agent and silica, resulting in good physical properties or vulcanization speed.

[0034] There are no particular limitations on the hydrate; commercially available rubber compositions may be used, such as hydrotalcite compounds or hydrated salts or metal hydroxides represented by the following chemical formula (1).

[0035] [Chemistry 2] [M 2+ 1-× M 3+ x (OH)2] x+ [A n-x / n ·mH2O] x- (1)

[0036] In the above chemical formula (1), M 2+ Selected from Mg 2+ Zn 2+ At least one divalent metal ion M 3+ Selected from Al 3+ Fe 3+ At least one trivalent metal ion A n- Selected from CO3 2- Cl - NO3 - At least one anion X: 0 < X ​​≤ 0.33.

[0037] As a hydrotalcite compound, Mg can be cited as an example. 4.3 Al2(OH) 12.6 CO3·3.5H2O, Mg3ZnAl2(OH) 12 CO3·3H2O, Mg 4.5 Al2(OH) 13 CO3·3.5H2O, Mg 4.5 Al2(OH) 13 CO3, Mg4Al2(OH) 12 CO3·3.5H2O, Mg6Al2(OH) 16 CO3·4H2O, Mg5Al2(OH) 14 CO3·4H2O, Mg3Al2(OH) 10 CO3·1.7H2O, etc., with Mg being particularly preferred. 4.3 Al2(OH) 12.6 CO3·3.5H2O, Mg3ZnAl2(OH) 12 CO3·3H2O.

[0038] Examples of hydrated salts include Al2O3·3H2O, Al2O3·H2O, Na2SO4·10H2O, CaSO4·2H2O, NaHCO3·Na2CO3·2H2O, and MgSO4·7H2O, with Al2O3·3H2O being particularly preferred.

[0039] Examples of hydroxides include Ca(OH)2, Al(OH)3, Mg(OH)2, and Zn(OH)2, with Mg(OH)2 being particularly preferred.

[0040] The amount of hydrate added relative to 100 parts by weight of chloroprene-based rubber is 1 part by weight or more and less than 20 parts by weight; preferably 2 parts by weight or more and less than 20 parts by weight; more preferably 4 to 10 parts by weight. The amount of hydrate added can, for example, be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19 parts by weight, or can be within any two of the values ​​exemplified here. By using hydrates within this range, rubber compositions with excellent abrasion resistance or low heat generation can be obtained.

[0041] (4) Organic peroxides Organic peroxides added to rubber compositions as vulcanizing aids are not particularly limited, but include, for example, dicumyl peroxide, benzoyl peroxide, 1,1-bis(tert-butylperoxide)-3,5,5-trimethylcyclohexane, diisobutyryl peroxide, cumyl peroxide neodecanoate, di-n-propyl peroxide, diisopropyl peroxide, disec-butyl peroxide, 1,1,3,3-tetramethylbutyl peroxide neodecanoate, di(4-tert-butylcyclohexyl) peroxide, di(2-ethylhexyl) peroxide neodecanoate, tert-hexyl peroxide neodecanoate, tert-butyl peroxide neodecanoate, and tert-butyl... Neoheptanyl peroxide, tert-hexyl peroxypentanoate, tert-butyl peroxypentanoate, di(3,5,5-trimethylhexanoyl)peroxide, dilauroyl peroxide, 1,1,3,3-tetramethylbutyl peroxide-2-ethylhexanoate, disuccinate peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxide)hexane, tert-hexyl peroxide-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, tert-butyl peroxide-2-ethylhexanoate, di(3-methylbenzoyl) peroxide, benzoyl peroxide (3-methylbenzoyl), dibenzoyl peroxide, 1,1-di-tert-butyl 2-Methylcyclohexane peroxide, 1,1-di(tert-hexylperoxide)-3,3,5-trimethylcyclohexane, 1,1-di(tert-hexylperoxide)cyclohexane, 1,1-di-tert-butylperoxidecyclohexane, 2,2-di(4,4-di(tert-butylperoxide)cyclohexyl)propane, tert-hexylperoxide isopropyl monocarbonate, tert-butylperoxide maleic acid, tert-butylperoxide-3,5,5-trimethylhexanoate, tert-butyl peroxylaurate, tert-butylperoxide isopropyl monocarbonate, tert-butylperoxide-2-ethylhexyl monocarbonate, tert-hexylperoxide benzoate, 2,5-dimethyl-2,5-dibenzoyl Hexane peroxide, tert-butyl peroxyacetate, 2,2-di-tert-butyl peroxide, tert-butyl peroxybenzoate, n-butyl 4,4-di(tert-butyl peroxy)valerate, 1,4-bis[(tert-butyl peroxy)isopropyl]benzene, di-tert-hexyl peroxide, 2,5-dimethyl-2,5-bis(tert-butyl peroxy)hexane, tert-butyl isopropylbenzene peroxide, di-tert-butyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-bis(tert-butyl peroxy)hexyn-3, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, tert-butyl hydroperoxide, etc. Preferably, it is selected from at least one of dicumyl peroxide, 1,4-bis[(tert-butylperoxide)isopropyl]benzene, tert-butyl-α-cumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane, and 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexyn-3, with 1,4-bis[(tert-butylperoxide)isopropyl]benzene being particularly preferred.

[0042] The amount of organic peroxide added relative to 100 parts by weight of chloroprene-based rubber is 0.3 to 1.4 parts by weight, preferably 0.4 to 1.3 parts by weight, and particularly preferably 0.4 to 1.2 parts by weight. The amount of organic peroxide added, for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, or 1.4 parts by weight, can be within any two values ​​shown herein. Using organic peroxides within this range, a rubber composition achieving an excellent balance between abrasion resistance, low heat generation, and vulcanization rate can be obtained.

[0043] (5) Silane coupling agents with double bonds in their structure In one embodiment of the present invention, the rubber composition, in order to improve the dispersibility of silica in the rubber and the reinforcing effect between the rubber and silica, uses 0.5 to 15 parts by weight of a silane coupling agent having double bonds in its structure, relative to 100 parts by weight of silica. The content of the silane coupling agent having double bonds in its structure is preferably 0.5 to 15 parts by weight, more preferably 0.5 to 10 parts by weight, relative to 100 parts by weight of silica. The content of the silane coupling agent having double bonds in its structure can, for example, be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts by weight, or can be within any two of the values ​​shown herein. By using a silane coupling agent having double bonds in its structure within this range, the necessary and sufficient effect can be obtained while suppressing scorching.

[0044] Silane coupling agents containing double bonds in their structure are not particularly limited except for the presence of double bonds in their structure; commercially available coupling agents for rubber compositions can be used, such as vinyl-based, styrene-based, methacrylic-based, and acrylic-based coupling agents. From the viewpoint of processability or reinforcing effect, vinyl-based, methacrylic-based, and acrylic-based coupling agents are particularly preferred. Silane coupling agents containing double bonds in their structure are more preferably those containing (meth)acrylic groups, and even more preferably those containing methacrylic groups.

[0045] As silane coupling agents having double bonds in their structure, examples include vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyltrimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, and 3-(meth)acryloyloxypropylmethyldiethoxysilane, with 3-(meth)acryloyloxypropylmethyltriethoxysilane being an example. Among these, vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropylmethyltrimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, and 3-methacryloyloxypropylmethyltriethoxysilane are preferred.

[0046] Furthermore, the rubber composition according to one embodiment of the present invention may also contain a silane coupling agent that does not have double bonds in its structure. The content of the silane coupling agent without double bonds in its structure may be 0.5 to 15 parts by mass relative to 100 parts by mass of silica. Moreover, the content of the silane coupling agent without double bonds in its structure is preferably less than the content of the silane coupling agent with double bonds in its structure. In the rubber composition according to one embodiment of the present invention, when the total amount of silane coupling agent contained in the rubber composition is 100 parts by mass, the content of the silane coupling agent with double bonds in its structure is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and even more preferably 90 parts by mass or more. The rubber composition according to one embodiment of the present invention may not contain a silane coupling agent without double bonds in its structure.

[0047] (6) Other ingredients Within the scope that does not impair the effects of the present invention, fillers such as carbon black, reinforcing materials, processing aids, anti-aging agents, etc. may also be added to the rubber composition.

[0048] As fillers and reinforcing materials, such as carbon black, clay, talc, and calcium carbonate can be used. Within a range that does not impair heat resistance, the preferred amount of these fillers and reinforcing materials is 5 to 100 parts by weight relative to 100 parts by weight of the rubber composition.

[0049] As a processing aid, it can be a fatty acid such as stearic acid or a paraffin-based processing aid such as polyethylene, and examples include fatty acid amides, which can be added up to 0.5 to 5 parts by weight relative to 100 parts by weight of the rubber composition.

[0050] As anti-aging agents, commonly used anti-aging agents include amine-based, imidazole-based, carbamate metal salts, phenolic-based, and wax-based agents. Among anti-aging agents with significant heat resistance improvement effects are amine-based agents such as 4,4′-bis(α,α-dimethylbenzyl)diphenylamine and octyl diphenylamine. In particular, 4,4′-bis(α,α-dimethylbenzyl)diphenylamine has a particularly significant heat resistance improvement effect. These anti-aging agents can be used in one or more combinations.

[0051] As a plasticizer, there are no particular limitations as long as it is compatible with chloroprene-based rubbers. Examples include vegetable oils such as rapeseed oil, phthalate-based plasticizers, DOS, DOA, ester-based plasticizers, ether-ester-based plasticizers, thioether-based plasticizers, aromatic oils, and naphthenic oils. One or more plasticizers can be used in combination depending on the desired properties of the rubber composition. The preferred amount of plasticizer added is 0 to 50 parts by weight relative to 100 parts by weight of the rubber composition.

[0052] According to one embodiment of the present invention, the vulcanization rate (T90-T10) of the rubber composition is determined by measuring the vulcanization time (T90) at 160°C for 60 minutes using an oscillating disk rheometer (NO.292 Rotorless Rheometer, manufactured by Toyo Seiki Co., Ltd.). Preferably, it is 25 minutes or less, more preferably 24 minutes or less, and even more preferably 23 minutes or less.

[0053] <Method for manufacturing rubber composition> The rubber composition can be obtained by mixing the above compounds at a temperature below their vulcanization temperature. Mixing equipment includes mixers, Bambury mixers, mixing blenders, twin-roll mills, etc.

[0054] <Vulcanized Molded Body> The rubber composition can be vulcanized after being molded into various desired shapes, or vulcanized and then molded into various shapes to obtain vulcanized molded bodies of the rubber composition. Molding methods for transforming rubber compositions into vulcanized molded bodies include stamping, extrusion, and calendering.

[0055] The vulcanization temperature of the rubber composition can be appropriately set according to its composition, typically in the range of 140–220°C, preferably in the range of 160–190°C. Furthermore, the vulcanization time can also be appropriately set according to the composition or shape of the rubber composition, typically in the range of 10 to 60 minutes.

[0056] The vulcanized molded body obtained by vulcanizing the above rubber composition has good vulcanization speed, excellent wear resistance or low heat generation.

[0057] The vulcanized molded article according to one embodiment of the present invention, according to JIS K 6264-2:2019, was tested in an Akron abrasion test (1000 abrasion cycles, wear volume ΔV, unit: mm). 3 In this case, ΔV is preferably 80mm. 3 Below, 76mm is preferred. 3 Below, 70mm is further preferred. 3 The following describes a vulcanized molded body, which is obtained by pressing and vulcanizing the rubber composition described in one embodiment of the present invention at 160°C for 40 minutes, resulting in a diameter of 63.6 mm, a thickness of 12.7 mm, and a central hole of 12.7 mm.

[0058] The vulcanized molded body according to one embodiment of the present invention, according to JIS K 6265:2019, has a heat value (ΔT) measured at 40°C, strain 0.175 inches, load 55 psi, and frequency 1,800 cycles per minute, preferably below 35°C, more preferably below 33°C, and even more preferably below 30°C. The vulcanized molded body can be formed by pressing and vulcanizing the rubber composition according to one embodiment of the present invention at 160°C for 40 minutes, resulting in a cylindrical vulcanized molded body with a diameter of 15 mm and a height of 25 mm.

Example

[0059] Manufacturing of chloroprene-acrylonitrile copolymer rubber: In a 3-liter polymerization reactor equipped with a heating and cooling jacket and a stirrer, 24 parts by weight of chloroprene monomer, 24 parts by weight of acrylonitrile monomer, 0.5 parts by weight of dithiodiethyl xanthate, 200 parts by weight of pure water, 5.00 parts by weight of potassium rosinate (manufactured by Harima Chemical Co., Ltd.), 0.40 parts by weight of sodium hydroxide, and 2.0 parts by weight of sodium salt of β-naphthalenesulfonic acid formalin condensate (manufactured by Kao Corporation) were added. 0.1 parts by weight of potassium persulfate was added as a polymerization initiator, and emulsion polymerization was carried out at a polymerization temperature of 40°C under a nitrogen atmosphere. Chloroprene monomer was added in fractions starting 20 seconds after the start of polymerization. The flow rate of each fraction was adjusted using a solenoid valve based on the change in refrigerant calorific value within 10 seconds of the start of polymerization. The flow rate was then adjusted again every 10 seconds, and this fractional addition was continued continuously. When the polymerization rate reached 50% relative to the total amount of chloroprene and acrylonitrile monomers, 0.02 parts by mass of phenothiazine, a polymerization terminator, was added to terminate the polymerization. Subsequently, unreacted monomers were removed from the reaction solution under reduced pressure to obtain a chloroprene-acrylonitrile copolymer latex.

[0060] The polymerization rate [%) of the chloroprene-acrylonitrile copolymer latex is calculated from the dried mass of the chloroprene-acrylonitrile copolymer latex obtained by air drying. Specifically, it is calculated using the following general formula (A). In the formula, "solids concentration" refers to the concentration [mass %] of the solids after heating 2g of the chloroprene-acrylonitrile copolymer latex sample at 130°C to remove volatile components such as solvent (water), volatile chemicals, and raw materials. "Total feed amount" refers to the total amount [g] of raw materials, reagents, and solvent (water) added to the polymerization reactor from the start of polymerization to a certain point. "Evaporation residue" refers to the mass [g] of chemicals [not volatilized] among the chemicals and raw materials added from the start of polymerization to a certain point, which remain as solids along with the polymer at 130°C. "Monomer feed amount" refers to the total amount [g] of the monomer initially added to the polymerization reactor and the monomers added in installments from the start of polymerization to a certain point. It should be noted that the "monomer" here refers to the total amount of chloroprene and acrylonitrile. Polymerization rate = {[(Total feed amount × Solid content concentration / 100) - Evaporation residue] / Monomer feed amount} × 100…(A)

[0061] After adjusting the pH of the chloroprene-acrylonitrile copolymer latex to 7.0 using acetic acid or sodium hydroxide, the latex was emulsified and broken down by freezing it on a metal plate cooled to -20°C to obtain a sheet. The sheet was then washed with water and dried at 130°C for 15 minutes to obtain a solid chloroprene-acrylonitrile copolymer rubber (chloroprene-acrylonitrile copolymer).

[0062] After preparing a 0.1% by mass solution of the above-mentioned chloroprene-acrylonitrile copolymer rubber using THF, the weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the chloroprene-acrylonitrile copolymer rubber were determined using a high-speed GPC apparatus (TOSOH HLC-8320GPC: manufactured by Tosoh Corporation) (converted to standard polystyrene). A TSK HHR-H guard column was used as the pre-column, and three HSKgel GMHHR-H columns were used as the analytical columns. The analysis was performed using a differential refractometer under the following conditions: sample pump pressure 8.0–9.5 MPa, flow rate 1 mL / min, and 40°C.

[0063] The elution time and molecular weight were obtained using a calibration curve, which was constructed by measuring a total of nine points on standard polystyrene samples with known molecular weights. Mw = 8.42 × 10 6 1.09×10 6 7.06×10 5 4.27×10 5 1.90×105 9.64×10 4 3.79×10 4 1.74×10 4 2.63×10 3

[0064] The weight-average molecular weight (Mw) of chloroprene-acrylonitrile copolymer rubber is 473 × 10⁻⁶. 3 g / mol, number-average molecular weight (Mn) is 138 × 10 3 g / mol, molecular weight distribution (Mw / Mn) is 3.4.

[0065] The acrylonitrile monomer unit content in the chloroprene-acrylonitrile copolymer rubber was calculated by determining the nitrogen atom content. Specifically, the nitrogen atom content in 100 mg of chloroprene-acrylonitrile copolymer rubber was determined using an elemental analyzer (Sumigraph 220F: manufactured by Sumika Analysis Center, Co., Ltd.), and the acrylonitrile monomer unit content was calculated. The acrylonitrile monomer unit content was 9.9% by mass.

[0066] The elemental analysis was performed as follows. The furnace temperatures were set as follows: reactor 900°C, reduction furnace 600°C, column temperature 70°C, detector temperature 100°C, oxygen as combustion gas 0.2 mL / min, and helium as carrier gas 80 mL / min. Calibration curves were prepared using aspartic acid (10.52%) with a known nitrogen content as a standard.

[0067] <Example 1> (Preparation of rubber compositions) The rubber compositions of the examples and comparative examples were obtained by mixing the components listed in Table 1 or Table 2, 10 parts by weight of plasticizer, 1 part by weight of processing aid, and 3 parts by weight of heat-resistant and anti-aging agent with an 8-inch open roll.

[0068] The components used to obtain the rubber composition are as follows. Chloroprene rubber polymer 1: The above-mentioned chloroprene-acrylonitrile copolymer rubber Chloroprene Polymer 2: Chloroprene Rubber (a homopolymer of chloroprene), Denka Co., Ltd. "S-40V" Silica: CTAB adsorption specific surface area 187m² 2 / g Tosoh Silica Co., Ltd. "Nipsil AQ" Carbon black: Carbon black (FEF): Product name "Asahi #60" manufactured by Asahicarbon Co., Ltd. Silane coupling agent 1: 3-Methacryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Industry Co., Ltd., "KBM-503v"

[0069]

Transformation 3

[0070] Silane Coupling Agent 2: Vinyltrimethoxysilane, manufactured by Shin-Etsu Chemical Industry Co., Ltd. "KBM-1003"

[0071]

Chemistry 4

[0072] Hydrotalcite 1: Chemical formula Mg 4.3 Al2(OH) 12.6 CO3·3.5H2O Kyowa Chemical Industry Co., Ltd. "DHT-4A" Hydrotalcite 2: Chemical formula Mg3ZnAl2(OH) 12 CO3·3H2O, manufactured by Kyowa Chemical Industry Co., Ltd., "ZHT-4A" Magnesium oxide: Kyowa Chemical Industry Co., Ltd. "Kyowa mag (registered trademark) 150" Organic peroxide 1:1,4-bis[(tert-butylperoxide)isopropyl]benzene, manufactured by Nippon Yushu Co., Ltd. "Perbutyl (registered trademark) P" Organic peroxide 2: 2,5-Dimethyl-2,5-bis(tert-butylperoxyhexyne-3) manufactured by Nippon Oils & Fats Co., Ltd. "Perhexine (registered trademark) 25B" Plasticizer: Polyether ester, manufactured by ADEKA Corporation, "ADEKA CIZER (registered trademark) RS-700". Processing aid: Stearic acid, manufactured by New Nippon Rikka Co., Ltd., "Stearic Acid 50S" Heat-resistant and anti-aging agent: 4,4′-bis(α,α-dimethylbenzyl)diphenylamine, manufactured by Ouchi Shinshin Chemical Industry Co., Ltd. "Nocrac (registered trademark) CD"

[0073] <Evaluating the rate of sulfur addition> According to the Japan Rubber Industry Association standard specification SRIS3102-1977, the vulcanization time (T90) of the above rubber composition was determined using an oscillating disk rheometer (NO.292 Rotorless Rheometer, manufactured by Toyo Seiki Co., Ltd.) at 160°C for 60 minutes, and the vulcanization rate (T90-T10) was calculated. The results are shown in Tables 1 and 2.

[0074] <Abrasion Resistance> The obtained rubber composition was pressed and vulcanized at 160℃ for 40 minutes to prepare a vulcanized molded body with a diameter of 63.6 mm, a thickness of 12.7 mm, and a central hole of 12.7 mm. The obtained vulcanized molded body was subjected to Akron wear testing (1000 wear cycles, wear volume ΔV, unit: mm) according to JIS K 6264-2:2019. 3 ). 80mm 3 The following values ​​are considered good. The results are shown in Tables 1 and 2.

[0075] <Fever> The obtained rubber composition was pressed and vulcanized at 160°C for 40 minutes to prepare cylindrical vulcanized bodies with a diameter of 15 mm and a height of 25 mm. The heat value (ΔT) of the obtained vulcanized bodies was determined according to JIS K 6265:2019 at 40°C, strain of 0.175 inches, load of 55 psi, and vibration frequency of 1,800 vibrations per minute. Values ​​below 35°C are considered acceptable. The results are shown in Tables 1 and 2.

[0076] Table 1

[0077] Table 2

[0078] As shown in Tables 1 and 2, the rubber composition of the present invention can improve vulcanization speed, abrasion resistance, or low heat generation. These properties of the vulcanized molded article make it suitable for use as a molded article for applications such as rubber rollers.

Claims

1. A rubber composition, said rubber composition comprising: 100 parts by weight of chloroprene-based rubber; 20-80 parts by weight of silicon dioxide; More than 1 part by mass and less than 20 parts by mass of hydrate; 0.3–1.4 parts by weight of organic peroxides; Relative to 100 parts by weight of the silicon dioxide, it contains 0.5 to 15 parts by weight of a silane coupling agent having double bonds in its structure. The hydrate is selected from Mg 4.3 Al2(OH) 12.6 CO3·3.5H2O, Mg3ZnAl2(OH) 12 CO3·3H2O, Mg 4.5 Al2(OH) 13 CO3·3.5H2O, Mg4Al2(OH) 12 CO3·3.5H2O, Mg6Al2(OH) 16 CO3·4H2O, Mg5Al2(OH) 14 CO3·4H2O, Mg3Al2(OH) 10 At least one hydrate of the hydrotalcite compound represented by CO3·1.7H2O.

2. The rubber composition according to claim 1, wherein the chloroprene-based rubber contains a homopolymer of 2-chloro-1,3-butadiene, or a copolymer of at least one monomer selected from 2,3-dichloro-1,3-butadiene and acrylonitrile with 2-chloro-1,3-butadiene.

3. The rubber composition according to claim 1 or 2, wherein the silane coupling agent having a double bond in the structure is at least one silane coupling agent selected from vinyltrimethoxysilane, vinyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyltrimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, and 3-(meth)acryloyloxypropylmethyltriethoxysilane.

4. The rubber composition according to claim 1 or 2, wherein the hydrate is a hydrate that releases H2O in a temperature range of 100°C to 250°C.

5. The rubber composition according to claim 1 or 2, wherein the organic peroxide is at least one organic peroxide selected from dicumyl peroxide, 1,4-bis[(tert-butylperoxide)isopropyl]benzene, tert-butyl-α-isocumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane, and 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexyne-3.

6. The rubber composition according to claim 1 or 2, wherein the adsorption specific surface area of ​​the hexadecyltrimethylammonium bromide (CTAB) in the silica is 50-300 m². 2 / g.

7. A sulfide, said sulfide being a sulfide of the rubber composition according to any one of claims 1 to 6.

8. A vulcanized molded body, wherein the vulcanized molded body is a vulcanized molded body of the rubber composition according to any one of claims 1 to 6.

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