JP2022013964A - Rubber composition, vulcanized product and vulcanized molded product of the rubber composition - Google Patents

Abstract

To provide, in the field of chloroprene-based rubber, a rubber composition, vulcanized product and vulcanized molded product thereof that has excellent heat resistance and oil resistance.SOLUTION: Provided is a rubber composition that is characterized by containing a carbon black having an average stacking height LC of 2 nm or more in a C-axis direction of the layer plane in the crystal lattice by 20 to 80 pts.mass, and a zinc powder by 0.2 to 30 pts.mass for 100 pts.mass of a chloroprene rubber having an unsaturated nitrile monomer unit by 3 to 20 mass%. The carbon black preferably is acetylene black, and the unsaturated nitrile monomer preferably is acrylonitrile. The rubber composition can be vulcanized into a vulcanized product or a vulcanized molded product.SELECTED DRAWING: None

Description

The present invention relates to a rubber composition. More specifically, a rubber composition containing chloroprene-based rubber as a rubber component, which is suitable as a material for rubber products used for transmission belts, conveyor belts, air springs, seals, packings, vibration-proof materials, hoses, diaphragms, rubber rolls, and the like. The present invention relates to a vulcanized product and a vulcanized molded product of the rubber composition.

Chloroprene-based rubber has excellent mechanical properties, ozone resistance, and chemical resistance, and is used in a wide range of fields such as automobile parts, adhesives, and various industrial rubber parts by taking advantage of its properties. In recent years, the performance required for industrial rubber parts has increased remarkably, and in addition to the above-mentioned improvements in mechanical properties, ozone resistance, and chemical resistance, excellent rubber processing stability, heat resistance, and cold resistance have been improved. , Compressive permanent distortion, etc. are also required.

In order to satisfy the above-mentioned required characteristics, for example, a technique for improving heat resistance by adding specific carbon black and zinc powder to chloroprene-based rubber (see Patent Document 1), and heat resistance by further combining with a specific plasticizer. A technique for improving the above (see Patent Document 2) has also been proposed.

Japanese Patent Application Laid-Open No. 11-323020 Patent No. 4092270

An object of the present invention is to provide a rubber composition having improved heat resistance and oil resistance at the same time, a vulcanized product thereof, and a vulcanized molded product in the field of chloroprene-based rubber.

In the present invention, carbon black having an average stacking height LC of 2 nm or more in the C-axis direction of the layer plane in the crystal lattice with respect to 100 parts by mass of chloroprene-based rubber having an unsaturated nitrile monomer unit of 3 to 20% by mass. Is a chloroprene-based rubber composition containing 20 to 80 parts by mass and 0.2 to 30 parts by mass of zinc powder.
The chloroprene-based rubber may be a mixture of a chloroprene-based rubber A containing 4 to 40% by mass of an unsaturated nitrile monomer unit and a chloroprene-based rubber B containing no unsaturated nitrile monomer unit.
In the rubber composition according to the present invention, the carbon black is preferably acetylene black.
In the rubber composition according to the present invention, the unsaturated nitrile monomer unit of the chloroprene-based rubber is preferably acrylonitrile.

In the present invention, next, a vulcanized product obtained by vulcanizing the above-mentioned rubber composition according to the present invention and a vulcanization obtained by vulcanizing the above-mentioned rubber composition according to the present invention after or during molding. Provide a molded body.
The vulcanized molded body according to the present invention can be used as a transmission belt, a conveyor belt, an air spring, a seal, a packing, a vibration-proof material, a hose, a diaphragm or a rubber roll.

According to the present invention, in the field of chloroprene-based rubber, it is possible to provide a rubber composition having improved heat resistance and oil resistance at the same time, a vulcanized product thereof, and a vulcanized molded product.

Hereinafter, suitable embodiments for carrying out the present invention will be described. It should be noted that the embodiments described below show an example of a typical embodiment of the present invention, and the scope of the present invention is not narrowly interpreted by this.

<Rubber composition> (first embodiment)
The rubber composition of the present embodiment contains a chloroprene-based rubber having an unsaturated nitrile monomer unit, a specific carbon black, and zinc powder. Further, in addition to the above-mentioned components, the rubber composition of the present embodiment may contain an antiaging agent, carbon black, a softening agent, a filler and the like. Hereinafter, each component will be described in detail.

[Chloroprene rubber]
The chloroprene-based rubber is obtained by copolymerizing a chloroprene monomer and an unsaturated nitrile monomer, and has 3 to 20% by mass of unsaturated nitrile monomer units in its main chain.

Examples of the unsaturated nitrile monomer include acrylonitrile, methacrylonitrile, etacrylonitrile, phenylacrylonitrile, and the like, and these compounds can be used alone or in combination of two or more. Among these, acrylonitrile is preferable from the viewpoint of ease of manufacture and oil resistance.

The amount of the unsaturated nitrile monomer unit contained in the chloroprene-based rubber is 3 to 20% by mass, preferably 5 to 17% by mass, and more preferably 9 to 17% by mass in the total amount of the chloroprene-based rubber. ..
If the amount of the unsaturated nitrile monomer unit is less than 3% by mass, the oil resistance of the obtained vulcanized product does not improve, and if it exceeds 20% by mass, the cold resistance of the obtained vulcanized product deteriorates.

The amount of the unsaturated nitrile monomer unit contained in the chloroprene-based rubber can be calculated from the content of nitrogen atoms in the polymer. Specifically, the nitrogen atom content of 100 mg of chloroprene rubber may be measured using an elemental analyzer (Sumigraph 220F: manufactured by Sumika Chemical Analysis Service, Inc.) to calculate the unsaturated nitrile monomer unit.
The measurement conditions for elemental analysis are as follows. The electric furnace temperature was set to 900 ° C. for the reactor, 600 ° C. for the reduction furnace, 70 ° C. for the column, and 100 ° C. for the detector, and 0.2 ml / min of oxygen was flowed as the combustion gas and 80 ml / min of helium was flowed as the carrier gas. .. The calibration curve was prepared using aspartic acid (10.52%), which has a known nitrogen content, as a standard substance.

The monomer copolymerizing with chloroprene is not limited to one type. For example, in addition to the chloroprene monomer and the unsaturated nitrile monomer, 2 as a monomer copolymerizable with chloroprene. , 3-Dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, isoprene, butadiene and monomers such as acrylic acid, methacrylic acid and esters thereof inhibit the object of the present invention. It may be copolymerized to the extent that it does not occur. Further, the polymer structure of the chloroprene copolymer is not particularly limited, and may be a block copolymer or a statistical copolymer.

For example, a statistical copolymer of acrylonitrile and chloroprene is produced by continuously adding chloroprene or intermittently adding chloroprene 10 times or more after the start of the polymerization reaction. At that time, the time at the start of the polymerization reaction is t (0), n is an integer of 1 or more, and the chloroprene and acrylonitrile at the time dt (n) between the time t (n-1) and the time t (n). Based on the total amount of polymerization conversion, the amount of chloroprene added at time dt (n + 1) between time t (n) and time t (n + 1) was determined, and the ratio of unreacted chloroprene to acrylonitrile was kept constant. Characterized by keeping.

What is a statistical copolymer? C. Randall "POLYMER SEQUENCE DETERMINATION, Carbon-13 NMR Polymer" Academic Press, New York, 1977, 71-78, can be described by Bernoulli's statistical model or by a primary or secondary Marcov statistical model. It means that it is a polymer. When the statistical copolymer of acrylonitrile and chloroprene is composed of a binary monomer, in the following Mayo-Lewis formula (I), other than the chloroprene monomer and the chloroprene monomer at the start of polymerization. Regarding the reactivity ratios r1 and r2 when the ratio with the acrylonitrile monomer is d [M1] / d [M2] and the chloroprene monomer is M1 defined in the following Mayo-Lewis formula (I). , R1 is preferably in the range of 0.3 to 3000, and r2 is preferably in the range of ^10-5 to 3.0 in order to obtain a statistical copolymer.

The polymerization initiator used in the case of emulsion polymerization is not particularly limited, and known polymerization initiators generally used for emulsion polymerization of chloroprene monomers, such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide, and t. -Organic peroxides such as butyl hydroperoxide are used.

The emulsifying agent used in the case of emulsifying polymerization is not particularly limited, and is a known emulsifying agent generally used for emulsifying polymerization of chloroprene monomers, for example, an alkali metal salt of a saturated or unsaturated fatty acid having 6 to 22 carbon atoms, loginic acid or An alkali metal salt of disproportionate loginic acid and an alkali metal salt of a formalin condensate of β-naphthalene sulfonic acid are used.

The molecular weight adjusting agent used in the case of emulsion polymerization is not particularly limited, and known molecular weight adjusting agents generally used for emulsion polymerization of a chloroprene monomer, such as n-dodecyl mercaptan, t-dodecyl mercaptan, n-octyl mercaptan and the like, are used. Long-chain alkyl mercaptans, xanthogen compounds such as diisopropylxantogen disulfide and diethylxanthogen disulfide, iodoform, benzyl1-pyrrole dithiocarbamate (also known as benzyl1-pyrrolcarbodithioate), benzylphenylcarbodithioate, 1-benzyl-N, N Dimethyl-4-aminodithiobenzoate, 1-benzyl-4-methoxydithiobenzoate, 1-phenylethylimidazole dithiocarbamate (also known as 1-phenylethylimidazole carbodithioate), benzyl-1- (2-pyrrolidinone) dithiocarbamate (also known as 1-phenylethylimidazole carbodithioate). Benzyl-1- (2-pyrrolidinone) carbodithioate), benzylphthalimidyldithiocarbamate (also known as benzylphthalimidylcarbodithioate), 2-cyanoprop-2-yl-1-pyrroledithiocarbamate (also known as 2-cyanoprop-) 2-Il-1-pyrrolecarbodithioate), 2-cyanobut-2-yl-1-pyrroledithiocarbamate (also known as 2-cyanobut-2-yl-1-pyrrolcarbodithioate), benzyl-1-imidazole dithiocarbamate) (Also known as benzyl-1-imidazole carbodithioate), 2-cyanoprop-2-yl-N, N-dimethyldithiocarbamate, benzyl-N, N-diethyldithiocarbamate, cyanomethyl-1- (2-pyrrolidone) dithiocarbamate, 2- (ethoxycarbonylbenzyl) prop-2-yl-N, N-diethyldithiocarbamate, 1-phenylethyldithiobenzoate, 2-phenylprop-2-yldithiobenzoate, 1-acetic acid-1-yl-ethyldithiobenzoate , 1- (4-methoxyphenyl) ethyldithiobenzoate, benzyldithioacetate, ethoxycarbonylmethyldithioacetate, 2- (ethoxycarbonyl) prop-2-yldithiobenzoate, 2-cyanoprop-2-yldithiobenzoate, t- Butyldithiobenzoate, 2,4,4-trimethylpenta-2-yldithiobenzoate, 2- (4-chlorophenyl) -prop-2-yldithiobenzoate , 3-vinylbenzyldithiobenzoate, 4-vinylbenzyldithiobenzoate, benzyldiethoxyphosphinyldithioformate, t-butyltrithioperbenzoate, 2-phenylprop-2-yl-4-chlorodithiobenzoate, naphthalene- 1-carboxylic acid-1-methyl-1-phenyl-ethyl ester, 4-cyano-4-methyl-4-thiobenzyl sulfanylbutyric acid, dibenzyltetrathioterephthalate, carboxymethyl dithiobenzoate, poly with dithiobenzoate end group (Ethethylene oxide), 4-cyano-4-methyl-4-thiobenzylsulfanyl Poly (ethylene oxide) having a butyric acid terminal group, 2-[(2-phenylethanth oil) sulfanyl] propanoic acid, 2-[(2) -Phenylethanchi oil) sulfanyl] succinic acid, 3,5-dimethyl-1H-pyrazol-1-carbodithioate potassium, cyanomethyl-3,5-dimethyl-1H pyrazole-1-carbodithioate, cyanomethylmethyl- ( Phenyl) dithiocarbamate, benzyl-4-chlorodithiobenzoate, phenylmethyl-4-chlorodithiobenzoate, 4-nitrobenzyl-4-chlorodithiobenzoate, phenylprop-2-yl-4-chlorodithiobenzoate, 1-cyano- 1-Methylethyl-4-chlorodithiobenzoate, 3-chloro-2-butenyl-4-chlorodithiobenzoate, 2-chloro-2-butenyldithiobenzoate, benzyldithioacetate, 3-chloro-2-butenyl-1H pyrrole -1-Dithiocarboxylic acid, 2-cyanobutane-2-yl-4-chloro-3,5-dimethyl-1H-pyrazole-1-carbodithioate, cyanomethylmethyl (phenyl) carbamodithioate, 2-cyano- 2-propyldodecyltrithiocarbonate, dibenzyltrithiocarbonate, butylbenzyltrithiocarbonate, 2-[[(butylthio) thioxomethyl] thio] propionic acid, 2-[[(dodecylthio) thioxomethyl] thio] propionic acid , 2-[[(Butylthio) thioxomethyl] thio] succinic acid, 2-[[(dodecylthio) thioxomethyl] thio] succinic acid, 2-[[(dodecylthio) thioxomethyl] thio] -2-methylpropionic acid, 2,2 ′-[Carbonothi oil bis (thio)] bis [2-methylpropionic acid], 2-amino-1-methyl-2-o Xoethylbutyltrithiocarbonate, benzyl-2-[(2-hydroxyethyl) amino] -1-methyl-2-oxoethyltrithiocarbonate, 3-[[(t-butyl) thio] thioxomethyl] thio ] Thiocarbonyl compounds such as propionic acid, cyanomethyldodecyltrithiocarbonate, diethylaminobenzyltrithiocarbonate, dibutylaminobenzyltrithiocarbonate are used.

The polymerization temperature and the final conversion of the monomer are not particularly limited, but the polymerization temperature is preferably 0 to 50 ° C, more preferably 20 to 50 ° C. Further, it is preferable that the final conversion of the monomer is in the range of 40 to 95% by mass. In order to adjust the final conversion rate, the polymerization may be stopped by adding a polymerization inhibitor that stops the polymerization reaction when the desired conversion rate is reached.

The polymerization inhibitor is not particularly limited, and known polymerization inhibitors generally used for emulsion polymerization of chloroprene monomers, for example, thiodiphenylamine, 4-tert-butylcatechol, 2,2-methylenebis-4-methyl- 6-Termary butylphenol is used.

The unreacted monomer is removed by, for example, a steam stripping method, and then the pH of the latex is adjusted, and a chloroprene-based rubber is obtained through conventional steps such as freeze-coagulation, washing with water, and hot air drying.

The chloroprene-based rubber is classified into a mercaptan-modified chloroprene rubber, a xanthogen-modified chloroprene rubber, a sulfur-modified chloroprene rubber, a dithiocarbonate-based chloroprene rubber, a trithiocarbonate-based chloroprene rubber, and a carbamate-based chloroprene rubber according to the type of the molecular weight regulator.

The chloroprene-based rubber may be a mixture of a chloroprene-based rubber A containing 4 to 40% by mass of an unsaturated nitrile monomer unit and a chloroprene-based rubber B containing no unsaturated nitrile monomer unit.

<Chloroprene rubber A>
The chloroprene-based rubber A has an unsaturated nitrile monomer unit of 4 to 40% by mass and a chloroprene monomer unit of 60 to 96% by mass.
By adjusting the amount of the unsaturated nitrile monomer unit in the chloroprene rubber A to this range, the production efficiency of the chloroprene rubber A is good, and the amount of the unsaturated nitrile monomer unit in the chloroprene rubber A is adjusted. If it becomes easier. The method for polymerizing the chloroprene-based rubber A may be the same as the method for polymerizing the chloroprene-based rubber. Further, a monomer copolymerizable with the chloroprene may be copolymerized.

<Chloroprene rubber B>
The chloroprene-based rubber B has 80 to 100% by mass of a chloroprene monomer unit and 0 to 20% by mass of other copolymerizable monomer units, and is obtained by mixing with the chloroprene-based rubber A. The amount of unsaturated nitrile monomer unit in the rubber system is diluted and adjusted.
The method for polymerizing the chloroprene-based rubber B may be the polymerization method for the chloroprene-based rubber without adding an unsaturated nitrile monomer, and the copolymerizable monomer can also be copolymerized with the chloroprene. The same monomer as the above-mentioned monomer can be used.

In order to mix the chloroprene-based rubber A and the chloroprene-based rubber B, a kneading device such as a conventionally known mixer, a Banbury mixer, a kneader mixer, or a double roll may be used for mixing.

[Carbon black]
As the carbon black blended in the chloroprene-based rubber composition of the present invention, any of thermal black and acetylene black by the thermal decomposition method, furnace black by the incomplete combustion method, and channel black can be used, but these carbons can be used. In black, it is necessary that the average stacking height LC in the C-axis direction of the layer plane in the crystal is 2 nm or more, and the average stacking height LC in the C-axis direction of the layer plane is 2.5 nm or more in particular. preferable.
Further, it is preferable that the carbon black has an average particle size of 60 nm or less and a DBP oil absorption amount of preferably 100 to 350 ml / 100 g, more preferably 120 to 300 ml / 100 g, and particularly preferably 140 to 300 ml / 100 g.
When the average stacking height LC in the C direction of the layer plane in the crystallite is smaller than 2 nm, the heat resistance of the vulcanized product obtained by vulcanizing the chloroprene-based rubber composition is not insufficient.
Furthermore, among carbon blacks, acetylene black is a carbon black obtained by thermally decomposing acetylene gas, and crystallization is remarkably advanced, the structure is highly developed, the amount of oil absorption is large, and chloroprene-based rubber using acetylene black is used. The composition is most preferable because it has a great effect of improving the heat resistance of the vulcanized product.
The amount of carbon black added is preferably 20 to 80 parts by mass, more preferably 25 to 70 parts by mass with respect to 100 parts by mass of the chloroprene-based rubber. If the amount added exceeds 80 parts by mass, the processability deteriorates, scorch is likely to occur, and the cold resistance of the vulcanized product deteriorates. If the amount added is less than 20 parts by mass, the heat resistance of the vulcanized product decreases.
In addition, carbon black having an average stacking height LC of 2 nm or more in the C-axis direction of the layer planes in the crystal lattice is the main component, but in addition to this, various carbons conventionally used for rubber are used as needed. Can contain black.

[Zinc powder]
The particle size of the zinc powder used in the present invention is preferably one that passes through 200 mesh.
The amount of zinc powder added is preferably 0.2 to 30 parts by mass, more preferably 2 to 20 parts by mass, based on 100 parts by mass of the chloroprene-based rubber. If the amount of zinc powder is less than 0.2 parts by mass, the heat resistance of the vulcanized product is not sufficiently improved, and if it is more than 30 parts by mass, the mechanical properties of the vulcanized product are deteriorated.

[others]
Further, the rubber composition of the present embodiment contains various chemicals usually used in the rubber industry, such as fillers, reinforcing agents, softeners, plasticizers, and antiaging agents, as long as the above-mentioned effects are not impaired. A vulcanizing agent, a vulcanization accelerator, a scorch inhibitor, a processing aid, and the like can be blended.

As the vulcanizing agent that can be added, sulfur, thiourea-based, guanidine-based, thiuram-based, and thiazole-based organic vulcanizing agents generally used for vulcanizing chloroprene-based rubber can be used, but thiourea-based ones are preferable. Examples of the thiourea-based vulcanizing agent include ethylene thiourea, diethyl thiourea, trimethyl thiourea, triethyl thiourea, N, N'-diphenyl thiourea, and the like, and trimethyl thiourea and ethylene thiourea are particularly preferable. Vulcanizing agents such as a mixture of 3-methylthiazolidinethio-2-thiazole and phenylenedimaleimide, dimethylammonium hydrodieneisophthalate or a 1,2-dimercapto-1,3,4-thiadiazole derivative may also be used. can. As these vulcanizing agents, two or more of those listed above may be used in combination. In addition, simple substances such as beryllium, magnesium, zinc, calcium, barium, germanium, titanium, tin, zirconium, antimony, vanadium, bismuth, molybdenum, tungsten, tellurium, selenium, iron, nickel, cobalt, osmium, and these metals. Oxides and hydroxides can be used as sulfides. Among these vulcanizing agents that can be added, calcium oxide, zinc oxide, antimony dioxide, antimony trioxide, and magnesium oxide are particularly preferable because they have a high vulcanizing effect. In addition, two or more of these vulcanizing agents may be used in combination. The vulcanizing agent is preferably added in a range of 0.1 parts by mass or more and 15 parts by mass or less in total with respect to 100 parts by mass of the rubber component.

The filler or reinforcing agent is added to adjust the hardness of the rubber or improve the mechanical strength, and is not particularly limited as long as the effect of the present invention is not impaired. For example, carbon black, silica, clay, etc. Examples include talc and calcium carbonate. The other inorganic filler is not particularly limited, but is limited to alumina (Al ₂ O ₃ ) such as γ-alumina and α-alumina, and alumina monohydrate (Al ₂ O ₃ · H ₂ O) such as boehmite and diaspoa. , Aluminum hydroxide [Al (OH) ₃ ] such as gibsite and bayarite, aluminum carbonate [Al ₂ (CO ₃ ) ₂ ], magnesium hydroxide [Mg (OH) ₂ ], magnesium carbonate (MgCO ₃ ), talc ( _{3MgO ・ 4SiO 2 ・ H2O )} , Attapulsite (5MgO ・ 8SiO2 ・ 9H2O), Titanium White ( _TIO2 ), Titanium Black (TIO2n _-1 ), Calcium Oxide (CaO), Calcium Hydroxide [Ca (Ca (Ca) OH) ₂ ], aluminum oxide magnesium (MgO · Al ₂ O ₃ ), clay (Al ₂ O _{3.2SiO 2} ), kaolin (Al ₂ O _{3.2SiO 2.2H 2 O), pyrophyllite (Al 2 O )} 3.4SiO ₂ · H ₂ O), Bentnite (Al ₂ O _3.4SiO 2.2H ₂ O), Aluminum silicate (Al ₂ SiO ₅ , Al _4.3SiO 4.5H ₂ O, etc.), Magnesium silicate (Al ₂ O _3.4SiO 2.5H ₂ O, etc.) Mg ₂ SiO ₄ , MgSiO ₃ etc.), Calcium silicate (Ca ₂ SiO ₄ etc.), Aluminum silicate calcium (Al ₂ O ₃ · CaO · 2SiO ₂ etc.), Magnesium silicate calcium (CaMgSiO ₄ ), Calcium carbonate (Ca MgSiO 4 etc.) CaCO ₃ ), aluminum oxide (ZrO ₂ ), aluminum hydroxide [ZrO (OH) ₂ · nH ₂ O], zirconium carbonate [Zr (CO ₃ ) ₂ ], charge-correcting hydrogen like various zeolites, and alkali. A crystalline aluminosilicate containing a metal or an alkaline earth metal may be used. Only one kind of filler and reinforcing agent may be used, or two or more kinds may be used in combination. The blending amount of these fillers and reinforcing agents may be adjusted according to the required physical properties of the rubber composition of the present embodiment and the vulcanized molded product thereof, and is not particularly limited, but the rubber of the present embodiment. Usually, a total of 15 parts by mass or more and 200 parts by mass or less can be added to 100 parts by mass of the rubber component in the composition.

The plasticizer is not particularly limited as long as it is a plasticizer compatible with rubber, but for example, vegetable oils such as rapeseed oil, linseed oil, castor oil, and palm oil, phthalate plasticizers, DUP (diundesyl phthalate), and DOS. (Dioctyl sebacate), DOA (Dioctyl adipate), ester plasticizer, ether ester plasticizer, thioether plasticizer, aroma oil, naphthenic oil, lubricating oil, process oil, paraffin, liquid paraffin, vaseline, There are petroleum-based plasticizers such as petroleum asphalt, and one or more can be used according to the characteristics required for the rubber composition of the present embodiment and the vulverized molded product of the composition. The amount of the plasticizer to be blended is not particularly limited, but it can be usually blended in a range of 3 parts by mass or more and 50 parts by mass or less in total with respect to 100 parts by mass of the rubber component in the rubber composition of the present embodiment. ..

When the rubber composition is kneaded or vulcanized, it is added to improve processing characteristics and surface slipperiness, such as making it easier to peel off from rolls, molding dies, screws of extruders, etc. Examples of the processing aid and lubricant include fatty acids such as stearic acid, paraffin-based processing aids such as polyethylene, and fatty acid amides. Only one type of processing aid and lubricant may be used, or two or more types may be used in combination. The amount added is not particularly limited, but is usually 0.5 parts by mass or more and 5 parts by mass or less in total with respect to 100 parts by mass of the rubber component in the rubber composition of the present embodiment.

As an anti-aging agent that improves heat resistance, a primary anti-aging agent that captures radicals and prevents autoxidation, which is used in ordinary rubber applications, and a secondary anti-aging agent that detoxifies hydroperoxide are added. can do. These anti-aging agents can be added at a ratio of 0.1 part by mass or more and 10 parts by mass or less to 100 parts by mass of the rubber component in the rubber composition, preferably 2 parts by mass or more and 5 parts by mass or less. Is the range of. These anti-aging agents can be used not only alone but also in combination of two or more. Examples of the primary anti-aging agent include phenol-based anti-aging agents, amine-based anti-aging agents, acrylate-based anti-aging agents, imidazole-based anti-aging agents, carbamate metal salts, and waxes. Examples of the secondary anti-aging agent include phosphorus-based anti-aging agents, sulfur-based anti-aging agents, and imidazole-based anti-aging agents. Examples of the antiaging agent are not particularly limited, but are limited to N-phenyl-1-naphthylamine, alkylated diphenylamine, octylated diphenylamine, 4,4'-bis (α, α-dimethylbenzyl) diphenylamine, p- (p). -Tolutylsulfonylamide) diphenylamine, N, N'-di-2-naphthyl-p-phenylenediamine, N, N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N -Phenyl-N'-(1,3-dimethylbutyl) -p-phenylenediamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl) -p-phenylenediamine, 1,1,3- Tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4'-butylidenebis- (3-methyl-6-tert-butylphenol), 2,2-thiobis (4-methyl-6) -Tert-Butylphenol), 7-octadecyl-3- (4'-hydroxy-3', 5'-di-tert-butylphenyl) propionate, tetrakis- [methylene-3- (3', 5'-di-tert) -Butyl-4'-hydroxyphenyl) propionate] methane, pentaerythritol-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3- (3-) tert-Butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4- Bis (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine, tris- (3,5-di-tert-butyl-4-hydroxybenzyl) )-Isocyanurate, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis (3,5-di- tert-Butyl-4-hydroxy) -hydrocinnaamide, 2,4-bis [(octylthio) methyl] -o-cresol, 3,5-di-tert-butyl-4-hydroxybenzyl-phosphonate-diethyl ester, tetrakis [Methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane, Octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid ester and 3,9-bis [2- {3- (3-tert-butyl-4-hydroxy-5-methylphenyl) ) Propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, tris (nonyl-phenyl) phosphite, tris (mixed mono- and di-nonylphenyl) ) Phenyl Phenyl, Diphenyl Mono (2-Ethylhexyl) Phenyl Phenyl, Diphenyl Monotridecyl Phenyl Phenyl, Diphenyl Isodecyl Phenyl Phenyl, Diphenyl Isooctyl Phenyl Phenyl, Diphenyl Nonylphenyl Phenyl Phenyl, Triphenyl Phenyl Phenyl, Tris (Tridecyl) Phosphite, Triisodecylphosfite, Tris (2-ethylhexyl) Phosfite, Tris (2,4-di-tert-butylphenyl) Phosfite, Tetraphenyldipropylene glycol diphosphite, Tetraphenyltetra (Tridecyl) Pentaerythritol tetraphosphite, 1,1,3-tris (2-methyl-4-di-tridecylphosfite-5-tert-butylphenyl) butane, 4,4'-butylidenebis (3-methyl- 6-tert-butyl-di-tridecylphosphite), 2,2'-ethylidenebis (4,6-di-tert-butylphenol) fluorophosphite, 4,4'-isopropylidene-diphenolalkyl (C12 ~) C15) Phosphite, Cyclic Neopentantetraylbis (2,4-di-tert-butylphenylphosphite), Cyclic Neopentanetetraylbis (2,6-di-tert-butyl-4-phenylphosphite), Cyclic Neopentantetraylbis (Nonylphenylphosphite), Bis (Nonylphenyl) Pentaerythritol diphosphite, Dibutylhydrogenphosfite, Distealyl pentaerythritol diphosphite and hydrogenated bisphenol A-pentaerythritol phosphite polymer And so on.

A silane coupling agent may be further added in order to enhance the adhesiveness between the rubber component such as the chloroprene-based rubber and the filler or the reinforcing agent and to improve the mechanical strength. The silane coupling agent may be added when the rubber composition is kneaded, or the filler or reinforcing agent may be added in the form of surface treatment in advance. Only one type of silane coupling agent may be used, or two or more types may be used in combination. Although not particularly limited, bis- (3-triethoxysilylpropyl) tetrasulfide, bis- (3-trimethoxynylpropyl) tetrasulfide, bis- (3-methyldimethoxysilylpropyl) tetrasulfide, bis- ( 2-Triethoxysilylethyl) tetrasulfide, bis- (3-triethoxysilylpropyl) disulfide, bis- (3-trimethoxysilylpropyl) disulfide, bis- (3-triethoxysilylpropyl) trisulfide, 3-hexa Noylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoy Lucioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthio Propyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltri Methoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, γ-grindoxypropyltri Methoxysilane, γ-glycidoxypropylmethyldiethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyltetrasulfide, 3-trimethoxysilylpropyl Methacryl monosulfide, methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, trimethylethoxysilane, trimethylmethoxysilane, isobutyltrimethoxysilane, n-decyltrimethoxysilane, phenyltrimethoxysilane, f. Enyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, hex Examples thereof include rutrimethoxysilane, octadecylmethyldimethoxysilane, octadecyltrimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, triffenylchlorosilane, heptadecafluorodecylmethyldichlorosilane, heptadecafluorodecyltrichlorosilane, and triethylchlorosilane. ..

The rubber composition of the present embodiment can be produced by the same method as that of a normal rubber composition. Specifically, it is obtained by kneading chloroprene-based rubber, carbon black, zinc powder and other components at a temperature equal to or lower than the vulcanization temperature with a kneader such as a kneader, banbury or roll.

As described in detail above, the rubber composition of the present embodiment uses a chloroprene-based rubber having an unsaturated nitrile monomer as a rubber component, and contains a specific carbon black and a specific amount of zinc powder. Heat resistance and oil resistance can be improved without reducing mechanical strength and cold resistance. This makes it possible to realize a rubber composition capable of obtaining a vulcanized product having excellent heat resistance and oil resistance.

<Vulcanized product> (second embodiment)
The vulcanized product of the present embodiment is a vulcanized product of the rubber composition of the first embodiment described above. At that time, the vulcanization method of the rubber composition is not particularly limited, and for example, press vulcanization, injection vulcanization, direct kettle vulcanization, indirect kettle vulcanization, direct steam continuous vulcanization, normal pressure continuous vulcanization. Vulcanization may be performed by a vulcanization method such as vulcanization or a continuous vulcanization press.

Further, the vulcanization conditions such as the vulcanization temperature and the vulcanization time are not particularly limited and can be appropriately set, but the vulcanization temperature is 130 to 200 ° C. from the viewpoint of productivity and processing stability. The temperature is preferably 140 to 190 ° C., and more preferably 140 to 190 ° C.

Since the vulcanized product of the present embodiment uses the rubber composition of the first embodiment described above, it is excellent in heat resistance and oil resistance.

<Vulcanized molded product> (third embodiment)
The vulcanized molded product of the present embodiment is obtained by molding the rubber composition of the first embodiment described above into a shape according to a purpose and vulcanizing it at the time of molding or after success. The molding method is not particularly limited, but press molding, injection molding, extrusion molding and the like can be applied. Then, for example, when the molded body is a transmission belt, a conveyor belt, an air spring, a seal, a packing, a vibration-proof material, a hose, a diaphragm, a rubber roll, or the like, it can be formed by press molding, injection molding, extrusion molding, or the like.

Since the vulcanized molded product of the present embodiment uses the rubber composition of the first embodiment described above, it is excellent in heat resistance and oil resistance.

Hereinafter, the present invention will be described in more detail based on Examples. It should be noted that the examples described below show an example of a typical example of the present invention, and the scope of the present invention is not narrowly interpreted by this.

<Manufacturing of chloroprene rubber>
<Manufacturing example 1>
<Chloroprene rubber 1 (acrylonitrile copolymerization amount 5% by mass)>
In a polymer can with an internal volume of 3 liters equipped with a heating / cooling jacket and a stirrer, 32 parts by mass of chloroprene monomer, 14 parts by mass of acrylonitrile monomer, 0.5 parts by mass of diethylxanthogen disulfide, 200 parts by mass of pure water, and loginic acid. 5.00 parts by mass of potassium (manufactured by Harima Kasei Co., Ltd.), 0.40 parts by mass of sodium hydroxide, and 2.0 parts by mass of a sodium salt of β-naphthalenesulfonic acid formarin condensate (manufactured by Kao Co., Ltd.) were added. 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and the polymerization was carried out at a polymerization temperature of 40 ° C. under a nitrogen stream. The addition of the chloroprene monomer starts 20 seconds after the start of the polymerization, the distribution flow rate is adjusted by the solenoid valve based on the change in the calorific value of the refrigerant for 10 seconds from the start of the polymerization, and the flow rate is re-adjusted every 10 seconds thereafter. It was done continuously by adjusting. When the polymerization rate with respect to the total amount of the chloroprene monomer and the acrylonitrile monomer became 50%, the polymerization terminator phenothiazine was added to terminate the polymerization. Then, the unreacted monomer in the reaction solution was removed under reduced pressure to obtain a chloroprene-acrylonitrile copolymer latex.

The polymerization rate of the chloroprene-acrylonitrile copolymer latex was calculated from the dry weight of the chloroprene-acrylonitrile copolymer latex after air-drying. Specifically, it was calculated from the following general formula (I). In the formula, the solid content concentration is the solid content concentration (mass) obtained by heating 2 g of the sampled chloroprene-acrylonitrile copolymer latex at 130 ° C. and excluding volatile components such as solvent (water), volatile chemicals and raw materials. %). The total amount charged is the total amount of raw materials, reagents, and solvent (water) charged in the polymerization can from the start of polymerization to a certain time. The evaporation residue is the mass of the chemicals or raw materials charged from the start of polymerization to a certain time, which remain as solids together with the polymer without volatilizing under the condition of 130 ° C. The amount of the monomer charged is the total amount of the monomer initially charged in the polymerization can and the amount of the monomer divided from the start of the polymerization to a certain time. The monomer referred to here is the total amount of the chloroprene monomer and the acrylonitrile monomer.
Polymerization rate [%] = {(total charge amount [g] x solid content concentration [mass%] / 100)-(evaporation residue [g])} / monomer charge amount [g] x 100 ... I)

The chloroprene-acrylonitrile copolymer latex obtained by the above method was adjusted to pH 7.0 and freeze-coagulated on a metal plate cooled to −20 ° C. to emulsify and fracture. The obtained sheet was washed with water and dried at 130 ° C. for 15 minutes to obtain a solid chloroprene-based rubber 1.

The number average molecular weight Mn, the mass average molecular weight Mw, and the molecular weight distribution (Mw / Mn) of the chloroprene-based rubber 1 are determined by preparing a solution of the chloroprene-based rubber 1 with THF at a sample-adjusted concentration of 0.1% by mass, and then using a high-speed GPC apparatus ( Measured by TOSOH HLC-8320GPC: manufactured by Tosoh Corporation (standard polystyrene conversion). At that time, a TSK guard column HHR-H was used as a pre-column, and three HSKgelGMHHR-Hs were used as an analysis column. did.

For the outflow time and molecular weight, a calibration curve prepared by measuring a total of 9 standard polystyrene samples with known molecular weights listed below was used. (Mw = 8.42 × 106, 1.09 × 106, 7.06 × 105, 4.27 × 105, 1.90 × 105, 9.64 × 104, 3.79 × 104, 1.74 × 104 2.63 × 103)

The amount of the unsaturated nitrile monomer unit contained in the chloroprene-based rubber 1 was calculated from the content of nitrogen atoms in the chloroprene-based rubber 1. Specifically, the nitrogen atom content of 100 mg of chloroprene rubber 1 was measured using an elemental analyzer (Sumigraph 220F: manufactured by Sumika Chemical Analysis Service, Inc.), and the acrylonitrile monomer unit was calculated.
The measurement conditions for elemental analysis were as follows. The electric furnace temperature was set to 900 ° C. for the reactor, 600 ° C. for the reduction furnace, 70 ° C. for the column, and 100 ° C. for the detector, and 0.2 ml / min of oxygen was flowed as the combustion gas and 80 ml / min of helium was flowed as the carrier gas. .. The calibration curve was prepared using aspartic acid (10.52%), which has a known nitrogen content, as a standard substance.

As a result, the number average molecular weight (Mn) of the chloroprene rubber 1 was 130 × 10 ³ g / mol, the weight average molecular weight (Mw) was 442 × 10 ³ g / mol, and the molecular weight distribution (Mw / Mn) was 3.4. rice field. The unit amount of acrylonitrile monomer was 5% by mass.

<Manufacturing example 2>
<Chloroprene rubber 2 (acrylonitrile copolymerization amount 10% by mass)>
In a polymer can with an internal volume of 3 liters equipped with a heating / cooling jacket and a stirrer, 24 parts by mass of chloroprene monomer, 24 parts by mass of acrylonitrile monomer, 0.5 parts by mass of diethylxanthogen disulfide, 200 parts by mass of pure water, and loginic acid. 5.00 parts by mass of potassium (manufactured by Harima Kasei Co., Ltd.), 0.40 parts by mass of sodium hydroxide, and 2.0 parts by mass of a sodium salt of β-naphthalenesulfonic acid formarin condensate (manufactured by Kao Co., Ltd.) were added. 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and the polymerization was carried out at a polymerization temperature of 40 ° C. under a nitrogen stream. The addition of the chloroprene monomer starts 20 seconds after the start of the polymerization, the distribution flow rate is adjusted by the solenoid valve based on the change in the calorific value of the refrigerant for 10 seconds from the start of the polymerization, and the flow rate is re-adjusted every 10 seconds thereafter. It was done continuously by adjusting. When the polymerization rate with respect to the total amount of the chloroprene monomer and the acrylonitrile monomer became 50%, the polymerization terminator phenothiazine was added to terminate the polymerization. Then, the unreacted monomer in the reaction solution was removed under reduced pressure to obtain a chloroprene-acrylonitrile copolymer latex.

The obtained chloroprene-acrylonitrile copolymer latex was freeze-coagulated, washed with water and dried in the same manner as in Production Example 1 to obtain a solid chloroprene-based rubber 2.

As a result of analysis by the same method as in Production Example 1, the number average molecular weight (Mn) of the chloroprene rubber 2 was 139 × 103 g / mol, the weight average molecular weight (Mw) was 480 × 103 g / mol, and the molecular weight distribution (Mw / Mn). Was 3.3. The unit amount of acrylonitrile monomer was 10% by mass.

<Manufacturing example 3>
<Chloroprene rubber 3 (acrylonitrile copolymerization amount 15% by mass)>
In a polymer can with an internal volume of 3 liters equipped with a heating / cooling jacket and a stirrer, 16 parts by mass of chloroprene monomer, 33 parts by mass of acrylonitrile monomer, 0.5 parts by mass of diethylxanthogen disulfide, 200 parts by mass of pure water, and loginic acid. 5.00 parts by mass of potassium (manufactured by Harima Kasei Co., Ltd.), 0.40 parts by mass of sodium hydroxide, and 2.0 parts by mass of a sodium salt of β-naphthalenesulfonic acid formarin condensate (manufactured by Kao Co., Ltd.) were added. 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and the polymerization was carried out at a polymerization temperature of 40 ° C. under a nitrogen stream. The addition of the chloroprene monomer starts 20 seconds after the start of the polymerization, the distribution flow rate is adjusted by the solenoid valve based on the change in the calorific value of the refrigerant for 10 seconds from the start of the polymerization, and the flow rate is re-adjusted every 10 seconds thereafter. It was done continuously by adjusting. When the polymerization rate with respect to the total amount of the chloroprene monomer and the acrylonitrile monomer became 50%, the polymerization terminator phenothiazine was added to terminate the polymerization. Then, the unreacted monomer in the reaction solution was removed under reduced pressure to obtain a chloroprene-acrylonitrile copolymer latex.

The obtained chloroprene-acrylonitrile copolymer latex was freeze-coagulated, washed with water and dried in the same manner as in Production Example 1 to obtain a solid chloroprene-based rubber 3.

As a result of analysis by the same method as in Production Example 1, the number average molecular weight (Mn) of the chloroprene rubber 3 was 131 × 103 g / mol, the weight average molecular weight (Mw) was 451 × 103 g / mol, and the molecular weight distribution (Mw / Mn). Was 3.4. The unit amount of acrylonitrile monomer was 15% by mass.

<Manufacturing example 4>
<Chloroprene rubber 4 (acrylonitrile copolymerization amount 20% by mass)>
In a polymer can with an internal volume of 3 liters equipped with a heating / cooling jacket and a stirrer, 10 parts by mass of chloroprene monomer, 40 parts by mass of acrylonitrile monomer, 0.5 parts by mass of diethylxanthogen disulfide, 200 parts by mass of pure water, and loginic acid. 5.00 parts by mass of potassium (manufactured by Harima Kasei Co., Ltd.), 0.40 parts by mass of sodium hydroxide, and 2.0 parts by mass of a sodium salt of β-naphthalenesulfonic acid formarin condensate (manufactured by Kao Co., Ltd.) were added. 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and the polymerization was carried out at a polymerization temperature of 40 ° C. under a nitrogen stream. The addition of the chloroprene monomer starts 20 seconds after the start of the polymerization, the distribution flow rate is adjusted by the solenoid valve based on the change in the calorific value of the refrigerant for 10 seconds from the start of the polymerization, and the flow rate is re-adjusted every 10 seconds thereafter. It was done continuously by adjusting. When the polymerization rate with respect to the total amount of the chloroprene monomer and the acrylonitrile monomer became 50%, the polymerization terminator phenothiazine was added to terminate the polymerization. Then, the unreacted monomer in the reaction solution was removed under reduced pressure to obtain a chloroprene-acrylonitrile copolymer latex.

The obtained chloroprene-acrylonitrile copolymer latex was freeze-coagulated, washed with water and dried in the same manner as in Production Example 1 to obtain a solid chloroprene-based rubber 4.

As a result of analysis by the same method as in Production Example 1, the number average molecular weight (Mn) of the chloroprene rubber 4 was 135 × 103 g / mol, the weight average molecular weight (Mw) was 457 × 103 g / mol, and the molecular weight distribution (Mw / Mn). Was 3.3. The unit amount of acrylonitrile monomer was 20% by mass.

<Manufacturing example 5>
<Chloroprene rubber 5 (acrylonitrile copolymerization amount 1% by mass)>
In a polymer can with an internal volume of 3 liters equipped with a heating / cooling jacket and a stirrer, 37 parts by mass of chloroprene monomer, 4 parts by mass of acrylonitrile monomer, 0.5 parts by mass of diethylxanthogen disulfide, 200 parts by mass of pure water, and loginic acid. 5.00 parts by mass of potassium (manufactured by Harima Kasei Co., Ltd.), 0.40 parts by mass of sodium hydroxide, and 2.0 parts by mass of a sodium salt of β-naphthalenesulfonic acid formarin condensate (manufactured by Kao Co., Ltd.) were added. 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and the polymerization was carried out at a polymerization temperature of 40 ° C. under a nitrogen stream. The addition of the chloroprene monomer starts 20 seconds after the start of the polymerization, the distribution flow rate is adjusted by the solenoid valve based on the change in the calorific value of the refrigerant for 10 seconds from the start of the polymerization, and the flow rate is re-adjusted every 10 seconds thereafter. It was done continuously by adjusting. When the polymerization rate with respect to the total amount of the chloroprene monomer and the acrylonitrile monomer became 50%, the polymerization terminator phenothiazine was added to terminate the polymerization. Then, the unreacted monomer in the reaction solution was removed under reduced pressure to obtain a chloroprene-acrylonitrile copolymer latex.

The obtained chloroprene-acrylonitrile copolymer latex was freeze-coagulated, washed with water and dried in the same manner as in Production Example 1 to obtain a solid chloroprene-based rubber 5.

As a result of analysis by the same method as in Production Example 1, the number average molecular weight (Mn) of the chloroprene rubber 5 was 136 × 103 g / mol, the weight average molecular weight (Mw) was 460 × 103 g / mol, and the molecular weight distribution (Mw / Mn). Was 3.2. The unit amount of acrylonitrile monomer was 1% by mass.

<Manufacturing example 6>
<Chloroprene rubber 6 (acrylonitrile copolymerization amount 25% by mass)>
In a polymer can with an internal volume of 3 liters equipped with a heating / cooling jacket and a stirrer, 7 parts by mass of chloroprene monomer, 45 parts by mass of acrylonitrile monomer, 0.5 parts by mass of diethylxanthogen disulfide, 200 parts by mass of pure water, and loginic acid. 5.00 parts by mass of potassium (manufactured by Harima Kasei Co., Ltd.), 0.40 parts by mass of sodium hydroxide, and 2.0 parts by mass of a sodium salt of β-naphthalenesulfonic acid formarin condensate (manufactured by Kao Co., Ltd.) were added. 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and the polymerization was carried out at a polymerization temperature of 40 ° C. under a nitrogen stream. The addition of the chloroprene monomer starts 20 seconds after the start of the polymerization, the distribution flow rate is adjusted by the solenoid valve based on the change in the calorific value of the refrigerant for 10 seconds from the start of the polymerization, and the flow rate is re-adjusted every 10 seconds thereafter. It was done continuously by adjusting. When the polymerization rate with respect to the total amount of the chloroprene monomer and the acrylonitrile monomer became 50%, the polymerization terminator phenothiazine was added to terminate the polymerization. Then, the unreacted monomer in the reaction solution was removed under reduced pressure to obtain a chloroprene-acrylonitrile copolymer latex.

The obtained chloroprene-acrylonitrile copolymer latex was freeze-coagulated, washed with water and dried in the same manner as in Production Example 1 to obtain a solid chloroprene-based rubber 6.

As a result of analysis by the same method as in Production Example 1, the number average molecular weight (Mn) of the chloroprene rubber 6 was 135 × 103 g / mol, the weight average molecular weight (Mw) was 459 × 103 g / mol, and the molecular weight distribution (Mw / Mn). Was 3.3. The unit amount of acrylonitrile monomer was 25% by mass.

The chloroprene-based rubbers 1 to 6 obtained by the above method and the compounds shown in Tables 1 to 2 are mixed and dispensed using an 8-inch roll, and press vulcanization is performed at 160 ° C. for 20 minutes. A rubber sheet for evaluation having a sheet length of 200 mm, a sheet width of 15 mm, and a thickness of 2.1 mm was produced.

The compounds used in Tables 1 and 2 are as follows.
Mercaptan-modified chloroprene rubber: Denka Co., Ltd. Raw rubber Mooney viscosity ML _{1 + 4} (100 ° C) = 60
Vulcanization accelerator: Kawaguchi Chemical Industry Co., Ltd. Accelerator (registered trademark) 22-S Ethylene thiourea lubricant / processing aid: Shin Nihon Rika Co., Ltd. Stearic acid 50S
Anti-aging agent A: Nocrack (registered trademark) 6C N-phenyl-N'-(1,3-dimethylbutyl) -p-phenylenediamine anti-aging agent manufactured by Daihachi Chemical Industry Co., Ltd. B: Daihachi Chemical Industry Co., Ltd. Nocrack (registered trademark) CD 4,4'-bis (α, α-dimethylbenzyl) diphenylamine carbon black: manufactured by Tokai Carbon Co., Ltd. Seest SO FEF carbon plasticizer: manufactured by Daihachi Chemical Industry Co., Ltd. Dioctyl sebacate magnesium oxide : Kyowa Chemical Industry Co., Ltd. Kyowa Mug (registered trademark) 150

The following evaluation was performed using the obtained evaluation sheet. The evaluation results are shown in Tables 1 and 2.

<Mechanical strength (tensile strength (TB))>
A test piece was prepared based on JIS K 6250, a tensile test was performed based on JIS K 6251, and the mechanical strength of each vulcanized product was measured. The tensile strength (TB) of 22 MPa or more is particularly good (A), that of 18 MPa or more and less than 22 MPa is good (B), and that of 15 MPa or more and less than 18 MPa is slightly good (C), 15 MPa. Those that were less than were regarded as defective (D).

<Heat resistance>
A test piece was prepared based on JIS K 6250, and the change in hardness after being left in a gear oven at 120 ° C. for 72 hours was measured. The hardness change of less than 8 was particularly good (A), the hardness change of 8 or more and less than 10 was good (B), the hardness change of 10 or more and less than 12 was slightly good (C), and the hardness change was 12 or more. The thing was regarded as defective (D).

<Oil resistance>
A test piece was prepared based on JIS K 6250, an oil resistance test (test conditions: 100 ° C. × 72 hours) was performed using IRM903 oil based on JIS K 6258, and the volume change rate (ΔV) was measured. Those having a ΔV of less than 30% are particularly good (A), those having a ΔV of 30% or more and less than 45% are good (B), those having a ΔV of 45% or more and less than 60% are slightly good (C), 60. Those having a percentage of% or more were regarded as defective (D).

<Cold resistance>
A test piece was prepared based on JIS K 6250, a low temperature torsion test (Geman torsion test) was performed based on JIS K 6261, and the torsion angle at 23 ± 2 ° C. From the angle, the temperature T10 corresponding to that angle was measured. Those with a T10 of less than -25 ° C are particularly good (A), those with a T10 of -25 ° C or higher and lower than -18 ° C are good (B), and those with a T10 of -18 ° C or higher and lower than -10 ° C are slightly better. (C), those having a temperature of −10 ° C. or higher were regarded as defective (D).

<Result>
The results are shown in Tables 1 and 2 below.

From the results shown in Tables 1 and 2, the rubber composition containing 100 parts by mass of chloroprene-based rubber having 3 to 20% by mass of unsaturated nitrile monomer units and a specific amount of specific carbon black and zinc powder was found. It was found that a vulcanized rubber having excellent heat resistance and oil resistance can be obtained. Since the vulcanized rubber has these properties, it can be suitably used as a vulcanized molded product such as a transmission belt, a conveyor belt, an air spring, a seal, a packing, a vibration isolator, a hose, a diaphragm, or a rubber roll.

Claims (6)

Carbon black 20-80 mass with an average stacking height LC of 2 nm or more in the C-axis direction of the layer plane in the crystal lattice with respect to 100 parts by mass of chloroprene-based rubber having 3 to 20% by mass of unsaturated nitrile monomer unit. A rubber composition comprising 0.2 to 30 parts by mass of zinc powder. The rubber according to claim 1, wherein the chloroprene-based rubber is a mixture of a chloroprene-based rubber A containing 4 to 40% by mass of an unsaturated nitrile monomer unit and a chloroprene-based rubber B containing no unsaturated nitrile monomer unit. Composition. The rubber composition according to claim 1 or 2, wherein the carbon black is acetylene black. The rubber composition according to any one of claims 1 to 3, wherein the unsaturated nitrile monomer is acrylonitrile. The vulcanized product of the rubber composition according to any one of claims 1 to 4. The vulcanized molded product of the rubber composition according to any one of claims 1 to 4.