JPH11323020A - Chloroprene rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a chloroprene rubber composition capable of giving a vulcanized product having an extremely improved heat resistance by compounding a chloroprene-based rubber with a specific carbon black and zinc powder. SOLUTION: This composition is composed of (A) a chloroprene-based rubber [a homopolymer of chloroprene or a copolymer with another monomer (e.g. 2,3-dichloro-1,3-butadiene), (B) carbon black (any of thermal black and acetylene black by pyrolysis, and furnace black and channel black by an incomplete burning method can be used) having an average piling height Lc in the direction of the C-axis of layer face in a crystallite of 2 nm or more, especially 2.5 nm or more and (C) zinc powder, wherein the component B and the component C are compounded preferably in amounts of 20-80 pts.wt. and 0.2-30 pts.wt., more preferably in mounts of 30-60 pts.wt. and 2-20 pts.wt., respectively based on 100 pts.wt. of the component A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a chloroprene rubber composition, and more particularly to a chloroprene rubber composition which gives a vulcanizate having significantly improved heat resistance.

[0002]

2. Description of the Related Art Several methods have been proposed for improving the heat resistance of vulcanized chloroprene rubber compositions. For example, Japanese Patent Application Laid-Open No. 50-87437 discloses a method for improving heat resistance by adding zinc powder and water to chloroprene rubber. However, in applications such as rubber parts for automobiles, the demand for heat resistance is becoming stricter. Therefore, these known methods are not always satisfactory in heat resistance, and improvement is desired.

[0003]

SUMMARY OF THE INVENTION The present invention is directed to a composition containing chloroprene-based rubber containing specific carbon black and zinc powder, and aims to improve the heat resistance of the vulcanized product.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to improve the heat resistance of the vulcanizates of the chloroprene-based rubber composition. Average stacking height Lc in the C-axis direction
It has been found that this can be achieved by combining carbon black having a particle size of 2 nm or more with zinc powder, and the present invention has been completed.

Hereinafter, the present invention will be described in more detail. The chloroprene rubber in the chloroprene rubber composition of the present invention is mainly composed of chloroprene rubber. In addition to chloroprene rubber, if necessary, natural rubber, SBR, butyl rubber, BR, NBR, EPDM, etc. Can be contained.

The chloroprene rubber of the present invention is obtained by polymerizing a homopolymer of chloroprene or a mixture of chloroprene and at least one other monomer copolymerizable with chloroprene (hereinafter referred to as chloroprene-based monomer). The obtained copolymer (hereinafter often referred to as chloroprene rubber). Examples of monomers copolymerizable with chloroprene include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, sulfur, styrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, and the like. Examples thereof include acrylic acid, methacrylic acid, and esters thereof, and can be used in a range that satisfies the object of the present invention.

[0007] The polymerization method for obtaining the chloroprene rubber used in the present invention is not particularly limited, and any ordinary polymerization method can be used. It can be obtained by emulsion polymerization according to the method used. The emulsifier used in the emulsion polymerization is not particularly limited, and is generally an emulsifier used for emulsion polymerization of chloroprene, for example, an alkali metal salt of a saturated or unsaturated fatty acid having 6 to 22 carbon atoms, rosin acid or heterogeneous acid. Alkali metal salts of rosin acids
For example, an alkali metal salt of a formalin condensate of β-naphthalenesulfonic acid is used.

[0008] Chloroprene rubber is classified into a sulfur-modified type, a mercaptan-modified type, and a xanthogen-modified type according to the type of molecular weight regulator. In the sulfur-modified type, a polymer obtained by copolymerizing sulfur and chloroprene is plasticized with thiuram disulfide to adjust the polymer to a predetermined Mooney viscosity. The mercaptan-modified type uses alkyl mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan and octyl mercaptan as a molecular weight regulator. The xanthogen-modified type uses an alkyl xanthogen compound as a molecular weight regulator.

Specific examples of the alkyl xanthogen compound include dimethyl xanthogen disulfide, diethyl xanthogen disulfide, diisopropyl xanthogen disulfide, diisobutyl xanthogen disulfide and the like. The amount of the alkyl xanthogen compound used is
The chloroprene polymer is selected so that the molecular weight (or Mooney viscosity of chloroprene rubber obtained by isolating the polymer) is appropriate. Although it depends on the structure of the alkyl group and the target molecular weight, it is generally 0.05 to 5.0 parts by weight per 100 parts by weight of the chloroprene monomer.
Preferably, it is used in the range of 0.3 to 1.0 part by weight.

As the polymerization initiator, known organic peroxides generally used for emulsion polymerization of chloroprene such as potassium persulfate, ammonium persulfate, sodium persulfate, hydrogen peroxide and t-butyl hydroperoxide are used. .

In the present invention, the polymerization temperature and the final conversion of the monomer are not particularly limited.
° C, more preferably 20 to 50 ° C. Further, it is preferable to carry out the conversion of the monomer within the range of 60 to 90%, and when the addition rate is reached, the polymerization is stopped by adding a small amount of a polymerization inhibitor.
As the polymerization inhibitor, for example, thiodiphenylamine,
Commonly used inhibitors such as 4-tert-butylcatechol and 2,2-methylenebis-4-methyl-6-tert-butylphenol are used.

Unreacted monomers are removed, for example, by steam stripping, and then the p
After adjusting H, the polymer can be isolated by a conventional method such as freeze coagulation, washing with water, and drying with hot air.

As the chloroprene rubber of the present invention, any modified type can be used. However, the sulfur-modified type is inferior in heat resistance to the polymer itself as compared with the mercaptan-modified and xanthogen-modified types. Therefore, when more heat resistance is required, it is preferable to use the mercaptan-modified and xanthogen-modified types.

As the carbon black compounded in the chloroprene rubber composition of the present invention, any of thermal black and acetylene black by a pyrolysis method, and furnace black and channel black by an incomplete combustion method can be used. In these carbon blacks, it is necessary that the average stacking height Lc of the layer plane in the crystallite in the C axis direction is 2 nm or more,
Those having an average stack height Lc of 2.5 nm or more in the axial direction are particularly preferable. Further, when the average particle size is 60 nm or less,
And the DBP oil absorption is preferably 100 to 350 ml / 1.
00g, more preferably 120-300ml / 100
g, particularly preferably 140 to 300 ml / 100 g of carbon black. If the average stacking height Lc in the C-axis direction of the layer plane in the crystallite is smaller than 2 nm, the heat resistance of the vulcanizate obtained by vulcanizing the chloroprene rubber composition is not sufficient. Further, acetylene black is carbon black obtained by thermally decomposing acetylene gas, crystallization is remarkably advanced and the structure is highly developed, the oil absorption is large, and the chloroprene rubber composition using acetylene black is: The effect of improving the heat resistance of the vulcanized product is large and most preferable. The addition amount of carbon black is preferably from 20 to 80 parts by weight, more preferably from 30 to 60 parts by weight, based on 100 parts by weight of the chloroprene rubber. If the added amount exceeds 80 parts by weight, the workability is deteriorated, scorch is easily caused, and the brittle temperature of the vulcanized product is increased. If the addition amount is less than 20 parts by weight, the tensile strength and modulus of the vulcanized product are reduced.

The particle size of the zinc powder used in the present invention is 20
Those that have passed 0 mesh are preferred. The amount of zinc powder added is 0.2 to 100 parts by weight of the chloroprene rubber.
It is preferably 30 parts by weight, more preferably 2 to 20 parts by weight. When the amount of zinc powder is less than 0.2 parts by weight, the heat resistance of the vulcanized product is not sufficiently improved, and when it is more than 30 parts by weight, the mechanical properties of the vulcanized product are deteriorated.

The vulcanizing agent used in the present invention is not particularly limited, but is preferably a metal oxide, specifically, zinc oxide,
Examples include magnesium oxide, lead oxide, trilead tetroxide, iron trioxide, titanium dioxide, calcium oxide and the like. These can be used in combination of two or more. The added amount of these vulcanizing agents is preferably 3 to 15 parts by weight based on 100 parts by weight of the chloroprene rubber. Further, the vulcanization can be more effectively performed by using in combination with the following vulcanization accelerator.

As the vulcanization accelerator, thiourea-based, guanidine-based, thiuram-based, and thiazole-based vulcanization accelerators generally used for vulcanization of chloroprene rubber can be used, and thiourea-based vulcanization accelerators are preferred. Examples of the thiourea-based vulcanization accelerator include ethylenethiourea, diethylthiourea, trimethylthiourea, triethylthiourea, N, N'-diphenylthiourea, and the like.
Particularly, trimerylthiourea is preferred. The vulcanization accelerators may be used in combination of two or more of the above. The addition amount of these vulcanization accelerators is preferably 0.5 to 5 parts by weight based on 100 parts by weight of the chloroprene rubber.

In the chloroprene rubber composition of the present invention, various additives such as a softening agent, a processing aid, an antioxidant, a lubricant, a filler and the like can be compounded as required.

The selection of the antioxidant also affects the heat resistance. As antioxidants, 4,4'-bis (α, α-dimethylbenzyl) diphenylamine and octylated diphenylamine are effective in heat resistance. They can be used in combination or in combination.

As the heat-resistant plasticizer, ether-thioether plasticizers such as Vulcanol OT (V
ulkanol OT) (trade name, manufactured by Bayer AG), vegetable oil or ester-based plasticizer, ether / ester-based plasticizer, for example, Adekasizer RS-107, RS-7
00, RS-735 (trade name, manufactured by Asahi Denka Kogyo KK) and the like, and one kind or a plurality of kinds can be used in combination according to required characteristics.

In the present invention, the kneading method and the vulcanization of the rubber composition can be carried out by a method commonly used in the rubber industry. Generally, the mixture is mixed by a kneading machine such as a kneader, a Banbury or a roll, and is molded into a shape suitable for the purpose to obtain a molded vulcanizate. Specifically, after each component is kneaded at a temperature equal to or lower than the vulcanization temperature, the kneaded product is formed into various shapes and vulcanized. The temperature and vulcanization time during vulcanization can be set as appropriate. The vulcanization temperature is 1
The temperature is preferably from 40 to 180C, more preferably from 150 to 180C.

The vulcanizates obtained from the chloroprene rubber composition of the present invention are excellent in heat resistance and oil resistance, so that boots, hoses, belts, vibration-proof rubbers, vibration-damping rubbers which require heat resistance and oil resistance are required. It is suitable for industrial parts such as materials, electric wires, gaskets, oil seals and packings, especially for rubber parts for automobiles, which have strict requirements for quality assurance and heat resistance.

[0023]

EXAMPLES The present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples. Example 1, Comparative Examples 1 and 2 According to the compounding recipe shown in Table 1, kneading was carried out using an 8-inch roll to prepare a 2.3 mm thick sheet. This sheet was subjected to press vulcanization under the conditions of 150 ° C. × 20 minutes to produce a vulcanized sheet having a thickness of 2 mm. The physical property test was performed according to JIS K6301.

[0024]

[Table 1]

The materials used in Table 1 are as follows. 1) Mercaptan-modified chloroprene rubber (S-40V) manufactured by Denki Kagaku Kogyo Co., Ltd. 2) Seast 116 (Lc =
1.8 nm or less, DBP oil absorption = 133 ml / 100
g) 3) Denka Black granules (Lc = 3.5 nm, DBP oil absorption = 160 ml / 10, manufactured by Denki Kagaku Kogyo Co., Ltd.)
0g) 4) Bayer (Germany), plasticizer

[0026]

As shown in Table 1, the average stacking height Lc of chloroprene rubber on the layer plane in the crystallite in the C-axis direction is shown.
The chloroprene rubber composition of the present invention containing carbon black having a particle size of 2 nm or more and zinc powder gives a vulcanizate having excellent heat resistance.

Claims (3)

[Claims] 1. A chloroprene-based rubber composition comprising: chloroprene-based rubber; and carbon black and zinc powder having an average stacking height Lc of 2 nm or more in a C-axis direction of a layer plane in a crystallite. 2. The chloroprene-based rubber according to claim 1, wherein 20 to 80 parts by weight of carbon black and 0.2 to 30 parts by weight of zinc powder are blended with respect to 100 parts by weight of the chloroprene-based rubber. Rubber composition. 3. A vulcanizate obtained by vulcanizing the chloroprene rubber composition according to claim 1 or 2.