JP2020196784A - Rubber composition, vulcanizate thereof, and molded article - Google Patents

Abstract

To provide a sulfur-modified chloroprene rubber which gives a vulcanizate excellent in scorch resistance and tensile strength and excellent in compression set and wear resistance.SOLUTION: A rubber composition contains, based on 100 pts.mass of the sulfur-modified chloroprene rubber, 0.0005-0.01 pt.mass of a sulfenamide which may have an arbitrary substituent, carbon black having an average particle diameter of 70 nm or less, and 4-12 pts.mass of a diene rubber other than chloroprene rubber. The sulfenamide is preferably one represented by the following chemical formula (1) (where R1 and R2 each independently represent hydrogen or a C1-10 alkyl group; and R1 and R2 may be the same as or different from each other).SELECTED DRAWING: None

Description

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. Further, in recent years, the performance required for industrial rubber parts has been remarkably increased, and in addition to the above-mentioned improvements in mechanical properties, ozone resistance, and chemical resistance, rubber scorch resistance, tensile strength, and compression set resistance are permanent. Improvement of properties and wear resistance is required.

As a technique for improving the scorch resistance of rubber, as described in Patent Document 1, 1 to 10 parts by weight of an amine salt of dithiocarbamic acid and a thiuram-based vulcanization accelerator, guanidine, are added to 100 parts by weight of chloroprene rubber. A rubber composition containing 0.1 to 5 parts by weight of at least one compound selected from the group consisting of a system vulcanization accelerator, a thiazole system vulcanization accelerator and a sulfenamide system vulcanization accelerator is known.

As a technique for improving the tensile strength of rubber, as described in Patent Document 2, 100 parts by mass of chloroprene rubber contains 5 to 20 parts by mass or more of a saturated aliphatic carboxylic acid having a molecular weight of 300 or more. There are known rubber compositions characterized by

In addition, the development of rubber having excellent compression permanent strain resistance and wear resistance is also desired. As a technique for improving the compression resistance and permanent strain resistance, a total of 100 parts by mass of chloroprene rubber and natural rubber described in Patent Document 3 and 0.1 to 10 parts by mass of a copolymer of styrene and butadiene are used. A chloroprene rubber composition containing 0.1 to 3 parts by mass of ethylenethiourea and 0.1 to 3 parts by mass of dipentamethylene thiuram tetrasulfide is known, and a predetermined technique for improving abrasion resistance is known. A modified conjugated diene polymer (see Patent Document 4) obtained by mixing a high molecular weight component having a property and a low molecular weight component having a predetermined property is known.

Japanese Unexamined Patent Publication No. 2016-141736 Japanese Unexamined Patent Publication No. 2013-249409 JP2012-11189A Japanese Unexamined Patent Publication No. 2010-121086

However, there is a problem that the techniques described in Patent Documents 1 to 4 alone are excellent in scorch resistance and tensile strength, and cannot improve compression set resistance and wear resistance.

Therefore, the present invention mainly provides a rubber composition, a vulcanized product and a molded product thereof, which can obtain a vulcanized product having excellent scorch resistance and tensile strength, and also excellent compressive permanent strain resistance and wear resistance. The purpose.

As a result of diligent research to solve this problem, the inventors of the present application used sulfenamide as a plasticizing agent, set the average particle size of carbon black used as a filler in a specific range, and other than chloroprene rubber. By adding a specific amount of the diene-based rubber of the above, we succeeded in improving the scorch resistance and tensile strength, as well as the compressive permanent strain resistance and the abrasion resistance, and completed the present invention.

That is, in the present invention, the amount of sulfenamide which may have an arbitrary substituent is 0.0005 to 0.01 parts by mass with respect to 100 parts by mass of the sulfur-modified chloroprene rubber.
25 to 55 parts by mass of carbon black with an average particle size of 70 nm or less,
It is a rubber composition containing 4 to 12 parts by mass of a diene rubber other than chloroprene rubber.
As the sulfenamide contained in the sulfur-modified chloroprene rubber composition according to the present technology, a sulfenamide represented by the following chemical formula (1) can be used.
(In the chemical formula (1), R ¹ and R ² each independently represent hydrogen or an alkyl group having 1 to 10 carbon atoms. Each of R ¹ and R ² may be the same or different.)
The sulfur-modified chloroprene rubber composition according to the present technology contains 0.1 to 1.5 parts by mass of xanthogen disulfide which may have an arbitrary substituent with respect to 100 parts by mass of the sulfur-modified chloroprene rubber. You can also.
In this case, as the xanthate disulfide, a xanthate disulfide represented by the following chemical formula (2) can be used.
(In the chemical formula (2), R ³ and R ⁴ independently represent alkyl groups having 1 to 4 carbon atoms. Each of R ³ and R ⁴ may be the same or different.)
When xanthogen disulfide is used in the sulfur-modified chloroprene rubber composition according to the present technology, the ratio (B / A) of the sulfenamide content (A) to the xanthate disulfide content (B) is 20 to 20 to A. It can be 2000.
The Mooney viscosity of the sulfur-modified chloroprene rubber can be 20 to 80.

As the diene rubber, it is preferable to use at least one or more diene rubber selected from butadiene rubber, styrene-butadiene rubber and nitrile rubber.

The carbon black has a DBP absorption amount of 80 to 150 ml / 100 g, and an iodine adsorption amount of 40 to 150 mg / g.

The present invention provides a vulcanized product obtained by vulcanizing the above-mentioned rubber composition, and a molded product obtained by vulcanizing the rubber composition after or during molding.

According to the present invention, the present invention provides a rubber composition capable of obtaining a vulcanized product having excellent scorch resistance, tensile strength, compression permanent strain resistance, and abrasion resistance, a vulcanized product thereof, and a molded product. Can be done.

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 typical embodiments of the present invention, and the scope of the present invention is not narrowly interpreted by this.

<Sulfur-modified chloroprene rubber>
Sulfur-modified chloroprene rubber introduces sulfur into the main chain by emulsion polymerization of 2-chloro-1,3-butadiene (hereinafter also referred to as "chloroprene") alone or chloroprene and other monomers in the presence of sulfur. A latex obtained by plasticizing the obtained sulfur-modified chloroprene polymer with sulfenamide which may have an arbitrary substituent, and a sulfur-modified chloroprene rubber obtained by drying and washing this latex by a general method. Including. Hereinafter, the details will be described along with the manufacturing process of the sulfur-modified chloroprene rubber.

<Polymerization process>
The sulfur-modified chloroprene rubber is obtained by emulsion polymerization of chloroprene and sulfur, and if necessary, a monomer copolymerizable with chloroprene.

Examples of the monomer copolymerizable with chloroprene include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, and methacryl. There are acids and esters thereof, and two or more of them can be used in combination. When these monomers are used, they are preferably used within a range that does not impair the characteristics of the obtained sulfur-modified chloroprene rubber, and are preferably 10% by mass or less of all the monomers containing chloroprene. If the amount of these monomers used exceeds 10% by mass, the heat resistance of the obtained sulfur-modified chloroprene rubber may not be improved, or the processing characteristics may be deteriorated.

Among these monomers, for example, 2,3-dichloro-1,3-butadiene can be used to slow down the crystallization rate of the obtained sulfur-modified chloroprene rubber. Sulfur-modified chloroprene rubber, which has a slow crystallization rate, can maintain rubber elasticity even in a low-temperature environment, and can improve, for example, low-temperature compression permanent strain.

The amount of sulfur (S ₈ ) added during emulsion polymerization is preferably 0.01 to 0.6 parts by mass, preferably 0.1 to 0.5 parts by mass, based on 100 parts by mass of the total amount of the monomers to be polymerized. Is more preferable. If the amount of sulfur (S ₈ ) is less than 0.01 parts by mass, the mechanical properties and dynamic properties of the obtained sulfur-modified chloroprene rubber may not be obtained. On the other hand, if the amount of sulfur (S ₈ ) exceeds 0.6 parts by mass, the obtained sulfur-modified chloroprene rubber may become too adhesive to the metal and cannot be processed.

As the emulsifier used for emulsion polymerization, one or more known emulsifiers and fatty acids that can be used for emulsion polymerization of chloroprene can be freely selected and used. Specific examples of the emulsifier include logoic acids, metal salts of aromatic formalin sulphonate, sodium dodecylbenzene sulphonate, potassium dodecylbenzene sulphonate, sodium alkyldiphenyl ether sulphonate, potassium alkyldiphenyl ether sulphonate, and polyoxyethylene. Sodium alkyl ether sulphonate, sodium polyoxypropylene alkyl ether sulphonate, potassium polyoxyethylene alkyl ether sulphonate, potassium polyoxypropylene alkyl ether sulphonate and the like. Of these, it is particularly preferable to use rosin acids. Here, the rosin acids mean rosin acid or disproportionate rosin acid, an alkali metal salt of disproportionate rosin acid, or a compound thereof. A preferably used emulsifier is an aqueous alkaline soap solution consisting of a mixture of an alkali metal salt of unbalanced logonic acid and a saturated or unsaturated fatty acid having 6 to 22 carbon atoms. Examples of the constituents of the disproportionate rosinic acid include sesquiterpenes, 8,5-isopimaric acid, dihydropimaric acid, secodehydroabietic acid, dihydroabietic acid, deisopropyldehydroabietic acid, and demethyldehydroabietic acid.

The pH of the aqueous emulsion at the start of emulsion polymerization is preferably 10.5 or higher. Here, the aqueous emulsion, the emulsion polymerization immediately before the start of, chloroprene and chloroprene monomer copolymerizable with a mixture of emulsifier, sulfur (S ₈₎ or the like. Added after such these monomers and sulfur (S _8), it is also encompassed If dividing the composition varies by addition or the like. By setting the pH to 10.5 or higher, when rosin acids are used as emulsifiers, it is possible to prevent polymer precipitation during polymerization and stably control polymerization. The pH of the aqueous emulsion can be adjusted by the amount of alkaline components such as sodium hydroxide and potassium hydroxide present at the time of emulsion polymerization.

The polymerization temperature of emulsion polymerization is 0 to 55 ° C., preferably 30 to 55 ° C. from the viewpoint of polymerization controllability and productivity.

As the polymerization initiator, potassium persulfate, benzoyl peroxide, ammonium persulfate, hydrogen peroxide and the like, which are used in ordinary radical polymerization, can be used. The polymerization is carried out in a polymerization rate of 60 to 95%, preferably 70 to 90%, and then a polymerization inhibitor is added to terminate the polymerization.

From the viewpoint of productivity, the polymerization rate is preferably 60% or more. Further, the polymerization rate is preferably 95% or less from the viewpoint of suppressing the development of a branched structure and gel formation that affect the processability of the obtained sulfur-modified chloroprene rubber. Examples of the polymerization inhibitor of the polymer include thiodiphenylamine, 4-tert-butylcatechol, 2,2'-methylenebis-4-methyl-6-3-butylphenol and the like. One type of polymerization inhibitor may be used alone, or two or more types may be used in combination.

<Plasticization process>
In the plasticization step, sulfenamide which may have an arbitrary substituent is added to the polymerization solution obtained in the polymerization step, and the polymer in the polymerization solution is plasticized by the sulfenamide. Is.

As the type of sulfenamide to be added, one or more known sulfenamides can be freely used as long as the effects of the present technology are not impaired. In this technique, it is particularly preferable to use sulfenamide represented by the chemical formula (1).

The amount of sulfenamide to be added is 0.2 to 3.0 parts by mass with respect to 100 parts by mass of the polymer in the polymerization solution. By setting the addition amount of sulfenamide to 0.2 parts by mass or more, the scorch resistance, compression permanent strain resistance, and wear resistance of the vulcanized product can be improved. Further, by setting the addition amount of sulfenamide to 3.0 parts by mass or less, the Mooney viscosity of the obtained sulfur-modified chloroprene rubber becomes appropriate, and as a result, the vulcanization moldability can be improved.

In the plasticization step, it is also possible to use xanthogen disulfide which may have an arbitrary substituent in combination. By using xanthogen disulfide, it becomes easy to control the Mooney viscosity of sulfur-modified chloroprene rubber, the scorch resistance is improved, and the physical property balance of the tensile strength, compression set resistance, and abrasion resistance of the obtained vulcanized product is also improved. It will be good. As the type of xanthogen disulfide to be added, one or more known xanthogen disulfides can be freely used as long as the effects of the present technology are not impaired. In this technique, it is particularly preferable to use the xanthate disulfide represented by the chemical formula (2).

When xanthogen disulfide is used, the amount to be added is not particularly limited, but in the present technology, it is preferable to add 0.3 to 6.0 parts by mass with respect to 100 parts by mass of the polymer in the polymerization solution. By setting the amount of xanthogen disulfide added within this range, it becomes easier to control the Mooney viscosity of the sulfur-modified chloroprene rubber, and the vulcanized product obtained has scorch resistance, tensile strength, compressive permanent strain resistance, and abrasion resistance. Further improve.

Further, it is preferable that the ratio (b / a) of the addition amount (a) of sulfenamide to the addition amount (b) of xanthogen disulfide is 0.2 to 30.0. By setting the ratio of the addition amount (b / a) to the above range, the physical property balance of the vulcanized product such as scorch resistance, tensile strength, compression set resistance and wear resistance is further improved.

The polymer solution that has undergone the plasticization step is cooled, adjusted in pH, frozen, dried, etc. by a general method to obtain a sulfur-modified chloroprene rubber. The obtained sulfur-modified chloroprene rubber is characterized by containing 0.0005 to 0.01 parts by mass of unreacted sulfenamide with respect to 100 parts by mass of the sulfur-modified chloroprene rubber. By setting the content of sulfenamide within the range, it contributes to the improvement of the tensile strength, compression set resistance and wear resistance of the vulcanized product.

When xanthogen disulfide which may have an arbitrary substituent is used in the plasticizing step, the content of unreacted xanthogen disulfide present in the obtained sulfur-modified chloroprene rubber is not particularly limited. For example, when 0.3 to 6.0 parts by mass of xanthogen disulfide is added to 100 parts by mass of the polymer in the polymerization solution in the plasticization step, the obtained sulfur-modified chloroprene rubber is sulfur-modified. Unreacted xanthogen disulfide is contained in an amount of 0.1 to 1.5 parts by mass with respect to 100 parts by mass of chloroprene rubber. By setting the content of xanthogen disulfide within the above range, it contributes to the improvement of scorch resistance, tensile strength, compression set resistance and wear resistance of the obtained vulcanized product.

The ratio (B / A) of the sulfenamide content (A) to the xanthate disulfide content (B) is preferably 20 to 2000. By setting the content ratio (B / A) within the range, the physical property balance of scorch resistance, tensile strength, compression set resistance and wear resistance of the obtained vulcanized product is further improved.

[Analysis of the content of plasticizers (compounds represented by chemical formulas (1) and (2))]
The content of the compounds represented by the chemical formulas (1) and (2) in the sulfur-modified chloroprene rubber can be quantified by the following procedure.
After 1.5 g of the obtained sulfur-modified polychloroprene rubber is dissolved in 30 ml of benzene, 60 ml of methanol is added dropwise to precipitate the rubber component, separate it from the solvent, and recover the non-rubber component as a solvent-soluble component. Benzene is dissolved and methanol is added dropwise to the precipitated polymer in the same procedure, the rubber component is separated, the non-rubber component is similarly recovered as a solvent-soluble component, and the first and second solvents are mixed. Then, the volume is adjusted to 200 ml, and this is used as a measurement sample. Inject 20 μL of the measurement sample into a liquid chromatograph (LC Hitachi pump: L-6200, L-600 UV detector: L-4250). The mobile phase of LC is used while changing the ratio of acetonitrile and water, and is flowed at a flow rate of 1 ml / min. As the column, Inertsil ODS-3 (φ4.6 × 150 mm, 5 μm, manufactured by GL Science) is used. The peak detection time of sulfenamide (measurement wavelength: 300 nm) and xanthogen disulfide (measurement wavelength: 280 nm) is confirmed with a standard solution, and a quantitative value is obtained from the calibration curve obtained from the peak area. The contents of the chemical formulas (1) and (2) are determined by comparing this quantitative value with the amount of the sample used for the analysis.

The Mooney viscosity of the sulfur-modified chloroprene rubber is not particularly limited, but is preferably adjusted in the range of 20 to 80. By adjusting the Mooney viscosity of the sulfur-modified chloroprene rubber within this range, the processability of the obtained sulfur-modified chloroprene rubber can be maintained.
In order to adjust the Mooney viscosity of the sulfur-modified chloroprene rubber, the amount of the plasticizer added, the time of the plasticizing step, and the plasticizing temperature may be adjusted.

The sulfur-modified chloroprene rubber can also contain a small amount of stabilizer in order to prevent a change in Mooney viscosity during storage. As the type of stabilizer that can be used in the present invention, one or more known stabilizers that can be used for chloroprene rubber can be freely selected and used. For example, phenyl-α-naphthylamine, octylated diphenylamine, 2,6-di-terrary-butyl-4-phenylphenol, 2,2'-methylenebis (4-methyl-6-tersary-butylphenol), and 4, There are 4'-thiobis- (6-terriary-butyl-3-methylphenol) and the like. Of these stabilizers, 4,4'-thiobis- (6-tertiary-butyl-3-methylphenol) is preferred.

<Carbon black>
Carbon black is added to sulfur-modified chloroprene rubber in order to improve the wear resistance and tensile strength of the obtained molded product. The average particle size of carbon black observed with an electron microscope in accordance with JIS Z8901 is preferably 70 nm or less, and more preferably 20 nm to 50 nm. If the average particle size is out of the above range, a sufficient reinforcing effect cannot be obtained and the tensile strength and wear resistance of the vulcanized rubber are not improved.

Further, the carbon black preferably has a dibutyl phthalate (hereinafter referred to as DBP) absorption amount of 80 ml / 100 g to 150 ml / 100 g in accordance with the oil absorption amount A method of JIS K6217-4, and more preferably 100 ml / 100 g to 140 ml /. It is 100 g. If the amount of DBP absorbed exceeds 150 ml / 100 g, the scorch resistance and tensile strength of the rubber composition will be lowered. If the amount of DBP absorbed is less than 80 ml / 100 g, the wear resistance of the vulcanized rubber will not be improved.

In addition, the carbon black preferably has an iodine adsorption amount of 40 ml / g to 150 ml / g in accordance with JIS K6217-1, and more preferably 50 ml / g to 150 ml / g. If the amount of iodine adsorbed exceeds 150 ml / g, the scorch resistance and compression set resistance are lowered, and if it is less than 40 ml / g, the wear resistance and tensile strength of the vulcanized rubber are not improved.

The amount of carbon black added is 25 to 55 parts by mass with respect to 100 parts by mass of the sulfur-modified chloroprene rubber. If the amount of carbon black blended is less than 25 parts by mass, the wear resistance and tensile strength of the obtained vulcanized product will not improve, and if it exceeds 55 parts by mass, the scorch resistance of the obtained vulcanized product will decrease. Will end up. The amount of carbon black added is preferably 25 to 45 parts by mass, more preferably 30 to 40 parts by mass. Within these ranges, the wear resistance, tensile strength and scorch resistance of the obtained vulcanized product are further improved, which is preferable.

<Diene rubber>
Diene-based rubbers other than chloroprene are added to sulfur-modified chloroprene rubber in order to improve the wear resistance of the obtained molded product. The diene rubber used in the present invention is not particularly limited, and a known diene rubber can be used. Among them, a diene rubber selected from at least one of butadiene rubber, styrene-butadiene rubber, and nitrile rubber is used. It is preferable to use it.

In the present invention, a diene rubber other than the sulfur-modified chloroprene is contained in an amount of 4 to 12 parts by mass with respect to 100 parts by mass of the sulfur-modified chloroprene rubber. If the content is less than 4 parts by mass, a sufficient effect of improving wear resistance cannot be obtained, and if it exceeds 12 parts by mass, a sufficient reinforcing effect cannot be obtained and the tensile strength cannot be improved.

<Vulcanized products / molded products>
For vulcanized products and molded products, the above-mentioned rubber compositions, metal compounds, plasticizers, etc. are mixed with a roll or a Banbury mixer, and then molded into a shape suitable for the purpose, and vulcanized during or after molding. It is obtained by The molding method is not particularly limited, but press molding, injection molding, extrusion molding and the like can be applied. 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 rubber roll, or the like, it can be formed by press molding, injection molding, extrusion molding, or the like.

The metal compound is added to adjust the vulcanization rate of the rubber composition or to adsorb a chlorine source such as hydrogen chloride generated by the dehydrochlorination reaction of the rubber composition to suppress deterioration of the rubber composition. Is. As the metal compound, for example, oxides and hydroxides such as zinc, titanium, magnesium, lead, iron, beryllium, calcium, barium, germanium, zirconium, vanadium, molybdenum, and tungsten can be used. One of these metal compounds may be used alone, or two or more thereof may be used in combination.

The amount of the metal compound added is not particularly limited, but is preferably in the range of 3 to 15 parts by mass with respect to 100 parts by mass of the sulfur-modified chloroprene rubber. By adjusting the amount of the metal compound added within this range, the mechanical strength of the obtained rubber composition can be improved.

Plasticizers are added to reduce the hardness of the rubber composition and improve its low temperature properties. Further, when a sponge is produced using the rubber composition, its texture can be improved. Examples of the plasticizer include dioctyl phthalate, dioctyl adipate {bis (bis (2-ethylhexyl) adipate}}, white oil, silicone oil, naphthenic oil, aroma oil, triphenyl phosphate, and tricresyl phosphate. These plasticizers may be used alone or in combination of two or more.

The amount of the plasticizer added is not particularly limited, but is preferably in the range of 50 parts by mass or less with respect to 100 parts by mass of the sulfur-modified chloroprene rubber. By adjusting the amount of the plasticizer added within this range, the above-mentioned effects can be exhibited while maintaining the tear strength of the obtained rubber composition.

Hereinafter, application examples of the rubber composition will be described.
(Conveyor belt)
A conveyor belt is a mechanical element used in a winding transmission device, and is a component that transmits power from a prime mover to a driven vehicle. It is often used over a pulley set on a shaft. Elastomer materials such as natural rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, and hydride nitrile rubber are used because the belt applied with high tension repeats rotational deformation in order to efficiently transmit power. .. It is known that chloroprene rubber often causes scorch at the molding stage, and extending the scorch time is an important technical issue. Further, since the belt is continuously used in a dynamic environment, a material having excellent wear resistance, tensile strength, and compression set resistance is required in order to improve the reliability of the product.

The rubber composition of the present invention can enhance the scorch resistance and wear resistance, tensile strength and compression set resistance of the conveyor belt. This makes it possible to manufacture a conveyor belt having excellent productivity and durability as compared with the conventional sulfur-modified chloroprene rubber.

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.

<Example 1>
<Sulfur-modified chloroprene rubber>
In a polymerization can with an internal volume of 30 liters, 100 parts by mass of chloroprene, 0.55 parts by mass of sulfur, 120 parts by mass of pure water, 4.00 parts by mass of disproportionated potassium rosinate (manufactured by Harima Kasei Co., Ltd.), 0 parts of sodium hydroxide .60 parts by mass and 0.6 parts by mass of a sodium salt of β-naphthalene sulfonic acid formarin condensate (trade name: Demol N: manufactured by Kao Co., Ltd.) were added. The pH of the aqueous emulsifier before the start of polymerization was 12.8. 0.1 part by mass of potassium persulfate was added as a polymerization initiator, and polymerization was carried out at a polymerization temperature of 40 ° C. under a nitrogen stream. When the conversion rate reached 85%, a polymerization terminator, diethylhydroxyamine, was added to terminate the polymerization to obtain a chloroprene polymerization solution.

In the obtained polymer solution, 5 parts by mass of chloroprene monomer as a solvent and N-cyclohexylbenzothiazole-2-sulfenamide as a plasticizer (trade name "Noxeller CZ" manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.) 1. 5 parts by mass and diisopropylxanthogen disulfide (trade name "Sanbit DIX" manufactured by Sanshin Chemical Industry Co., Ltd.) 3.2 parts by mass, 0.05 parts by mass of sodium salt of β-naphthalenesulfonic acid formalin condensate as a dispersant, emulsifier As a result, a plasticizer emulsion consisting of 0.05 parts by mass of sodium lauryl sulfate was added to obtain a sulfur-modified chloroprene polymer latex before plasticization.

Here, the sodium salt of the β-naphthalene sulfonic acid formalin condensate is a dispersant used for general purposes, and its stability is improved by adding a small amount, and it is stable without aggregation or precipitation in the manufacturing process. Latex can be produced. Further, in this example, a plasticizer is added to the polymerization solution after emulsion polymerization. At that time, in order to enable more stable plasticization, the plasticizer is dissolved in chloroprene added as a solvent. An emulsified state was added by adding sodium lauryl sulfate to the plasticizer solution.

The obtained sulfur-modified chloroprene polymer latex was distilled under reduced pressure to remove unreacted monomers, and the latex was held at a temperature of 50 ° C. for 1 hour with stirring to plasticize the latex to obtain a plasticized latex (hereinafter referred to as “latex”). This plasticized latex is abbreviated as "latex").

The obtained latex was cooled, and the polymer was isolated by a conventional freeze-coagulation method to obtain a sulfur-modified chloroprene rubber.

<Measurement of Mooney viscosity>
With respect to the sulfur-modified chloroprene rubber obtained above, the Mooney viscosity was measured at a preheating time of 1 minute, a rotation time of 4 minutes, and a test temperature of 100 ° C. of the L-shaped rotor in accordance with JIS K 630-1.

<Preparation of sample for evaluation>
The sulfur-modified chloroprene rubber obtained above and the compounds shown in Table 1 were mixed using an 8-inch roll and press-crosslinked at 160 ° C. for 20 minutes to prepare a sample for evaluation.

The compounds listed in Table 1 are as follows: butadiene rubber: BR01 manufactured by JSR Corporation
Styrene-butadiene rubber: Nippon Zeon Corporation Nipol 1502
Nitrile rubber: Nippon Zeon Corporation Nipol 1041
Lubricants / processing aids 1: Stearic acid 50S manufactured by New Japan Chemical Co., Ltd.
Anti-aging agent 1: Nocrack AD-F manufactured by Ouchi Shinko Kagaku Kogyo
Anti-aging agent 2: Nocrack 810-NA manufactured by Ouchi Shinko Kagaku Kogyo
Magnesium oxide: Kyowa Mug 30 manufactured by Kyowa Chemical Industry Co., Ltd.
Filler: Shiraishi Calcium Co., Ltd. Crown Clay Flame Retardant 1: Showa Denko Co., Ltd. Heidi Light H-42M
Flame Retardant 2: Ajinomoto Fine-Techno Co., Ltd. Empara 70
Flame Retardant 3: Ajinomoto Fine-Techno Co., Ltd. Empara 40
Vulcanizing agent: Zinc oxide type 2 vulcanization accelerator manufactured by Sakai Chemical Industry Co., Ltd. 1: Kawaguchi Chemical Industry Co., Ltd. Accelerator 22S
Vulcanization accelerator 2: Noxeller DM manufactured by Ouchi Shinko Kagaku Kogyo
Carbon Black A: Asahi Carbon Co., Ltd. Asahi # 70 Average particle size 28 nm, iodine adsorption amount 80 mg / g, DBP absorption amount 101 ml / 100 g

<Examples 2 to 8 and Comparative Examples 1 to 4>
Sulfur-modified chloroprene rubber was obtained by the same method as in Example 1 by the formulation shown in Tables 1 and 2 below.
The materials used in this example are as follows.
N-tert-Butylbenzothiazole-2-sulfenamide: (trade name "Sunceller NS-G" manufactured by Sanshin Chemical Industry Co., Ltd.)
Diethylxanthate disulfide: (manufactured by Sigma-Aldrich)
Tetraethyl thiuram disulfide: (trade name "Noxeller TET" manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)

<Example 9>
Example 1 except that carbon black A was changed to carbon black B (trade name "Asahi # 60UG" manufactured by Asahi Carbon Co., Ltd., average particle diameter 43 nm, iodine adsorption amount 40 mg / g, DBP absorption amount 110 ml / 100 g) as a filler. An evaluation sample was prepared in the same manner as in the above.

<Example 10>
Example 1 except that carbon black A was changed to carbon black C (trade name "Asahi # 95" manufactured by Asahi Carbon Co., Ltd., average particle diameter 17 nm, iodine adsorption amount 150 mg / g, DBP absorption amount 127 ml / 100 g) as a filler. An evaluation sample was prepared in the same manner as in the above.

<Example 11>
Example 1 except that carbon black A was changed to carbon black D (trade name "Asahi # 52" manufactured by Asahi Carbon Co., Ltd., average particle diameter 60 nm, iodine adsorption amount 19 mg / g, DBP absorption amount 128 ml / 100 g) as a filler. An evaluation sample was prepared in the same manner as in the above.

<Example 12>
Examples except that carbon black A was changed to carbon black E (trade name "Asahi F-200GS" manufactured by Asahi Carbon Co., Ltd., average particle diameter 38 nm, iodine adsorption amount 55 mg / g, DBP absorption amount 180 ml / 100 g) as a filler. An evaluation sample was prepared in the same manner as in 1.

<Example 13>
Example 1 except that carbon black A was changed to carbon black F (trade name "Asahi # 70L" manufactured by Asahi Carbon Co., Ltd., average particle diameter 27 nm, iodine adsorption amount 85 mg / g, DBP absorption amount 75 ml / 100 g) as a filler. An evaluation sample was prepared in the same manner as in the above.

<Comparative example 5>
An evaluation sample was prepared in the same manner as in Example 1 except that the amount of butadiene rubber added was changed from 8 parts by mass to 16 parts by mass.

<Comparative Example 6>
An evaluation sample was prepared in the same manner as in Example 1 except that butadiene rubber was not added.

<Comparative Example 7>
An evaluation sample was prepared in the same manner as in Example 1 except that the amount of carbon black A added was changed from 35 parts by mass to 20 parts by mass.

<Comparative Example 8>
An evaluation sample was prepared in the same manner as in Example 1 except that the amount of carbon black A added was changed from 35 parts by mass to 60 parts by mass.

<Comparative Example 9>
Example 1 and Example 1 except that carbon black A was changed to carbon black G (trade name "Asahi Thermal" manufactured by Asahi Carbon Co., Ltd., average particle diameter 80 nm, iodine adsorption amount 24 mg / g, DBP absorption amount 28 ml / 100 g) as a filler. An evaluation sample was prepared by the same method.

<Evaluation of scorch resistance>
Each sample prepared above was subjected to a Mooney scorch test in accordance with JIS K 630-1.

<Measurement of tensile strength>
A test piece was prepared based on JIS K 6250 (vulcanization conditions: 160 ° C. × 20 minutes), a tensile test was performed based on JIS K 6251, and the tensile strength of each vulcanized product was measured.

<Measurement of compression set>
Each sample prepared above was measured under the test conditions of 100 ° C. and 72 hours according to JIS K 6262.

<Evaluation of wear resistance>
Each sample prepared above was subjected to a DIN wear test in accordance with JIS K 6264-2.

<Result>
The results of the examples are shown in Table 1 below, and the results of the comparative examples are shown in Table 2 below.

<Discussion>
As shown in Tables 1 and 2, it was confirmed that the evaluation samples of Examples 1 to 13 were excellent in scorch resistance and wear resistance, and the heat generation was reduced. Even when sulfenamide was used, in Comparative Example 2 in which the content in the sulfur-modified chloroprene rubber exceeded 0.01 parts by mass, the Mooney viscosity was too low to prepare an evaluation sample.

Comparing with Examples, Example 3 in which xanthogen was not used was inferior in wear resistance, tensile strength, and heat generation to Example 1, and the ratio (B / A) of the xanthate disulfide content (B) was 2000. Example 4 described above was inferior in scorch resistance, compression set resistance, wear resistance, and heat generation property.
Further, in Example 7, the scorch time was longer and the tensile strength was improved as compared with Example 10 in which the DBP absorption amount of carbon black as a filler exceeded 150 ml / 100 g. In addition, Example 7 was superior in wear resistance as compared with Example 9 in which the amount of DBP absorbed was 80 ml / 100 g or less.
In Example 9, since the amount of iodine adsorbed by carbon black, which is a filler, was less than 40 mg / g, the tensile strength, compressive permanent strain resistance, and abrasion resistance were inferior to those of Example 1.

Claims (11)

Sulfenamide was 0.0005 to 0.01 parts by mass with respect to 100 parts by mass of sulfur-modified chloroprene rubber.
Carbon black with an average particle size of 70 nm or less is 25 to 55 parts by mass.
A rubber composition containing 4 to 12 parts by mass of a diene rubber other than chloroprene rubber. The rubber composition according to claim 1, wherein the sulfenamide is represented by the following chemical formula (1).
(In the chemical formula (1), R ¹ and R ² each independently represent hydrogen or an alkyl group having 1 to 10 carbon atoms. Each of R ¹ and R ² may be the same or different.) The rubber composition according to claim 1 or 2, which contains 0.1 to 1.5 parts by mass of xanthate disulfide with respect to 100 parts by mass of the sulfur-modified chloroprene rubber. The rubber composition according to claim 3, wherein the xanthate disulfide is represented by the following chemical formula (2).
(In the chemical formula (2), R ³ and R ⁴ independently represent alkyl groups having 1 to 4 carbon atoms. Each of R ³ and R ⁴ may be the same or different.) The rubber composition according to claim 3 or 4, wherein the ratio (B / A) of the content (A) of the sulfenamide to the content (B) of the xanthate disulfide is 20 to 2000. The rubber composition according to any one of claims 1 to 5, wherein the sulfur-modified chloroprene rubber has a Mooney viscosity of 20 to 80. The rubber composition according to any one of claims 1 to 6, wherein the diene rubber other than the chloroprene rubber is at least one diene rubber selected from butadiene rubber, styrene-butadiene rubber, and nitrile rubber. The rubber composition according to any one of claims 1 to 7, wherein the DBP absorption amount of the carbon black is 80 to 150 ml / 100 g. The rubber composition according to any one of claims 1 to 8, wherein the carbon black has an iodine adsorption amount of 40 to 150 mg / g. A vulcanized product comprising the rubber composition according to any one of claims 1 to 9. A molded product made of the vulcanized product according to claim 10.