JP3488310B2 - Chloroprene composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compounding composition of chloroprene rubber widely used as a member for industrial and civil engineering purposes. It relates to the blending of additives used for crosslinking. [0002] Conventionally, as a member for industrial use, civil engineering and construction,
General-purpose rubbers such as natural rubber, styrene-butadiene rubber, and butadiene rubber are used, but such general-purpose rubbers have limitations in weather resistance, ozone resistance, oil resistance, and the like. For this reason, chloroprene rubber is widely used for members requiring high durability. Chloroprene rubber is a chlorinated isoprene rubber produced by a butadiene method or an acetylene method. If this is roughly divided,
It is classified into three types: a mercaptan-modified type, a xanthogen-modified type, and a sulfur-modified type. As a cross-linking agent for chloroprene rubber, magnesium oxide, zinc oxide, lead oxide, and the like are used as main components, and various cross-linking accelerators are used in combination with the main components to increase the cross-linking speed. In recent years, in general applications other than belts, chloroprene rubber of a mercaptan-modified type or a xantogen-modified type has been widely used because of its easy processing. Most of them crosslink chloroprene rubber by using a compounding system in which 4 parts by weight of magnesium oxide and 5 parts by weight of zinc oxide and a thiourea-based crosslinking accelerator are used in combination with 100 parts by weight of chloroprene rubber. . In addition, in this compounding system, when a thiourea-based cross-linking accelerator is used alone, the cross-linking speed is too high. Therefore, a thiazole-based cross-linking accelerator is also used in combination. [0004] However, according to the studies made by the present inventors, such a cured product of the conventional chloroprene composition was not satisfactory with respect to compression set resistance. Furthermore, when a thiazole-based crosslinking accelerator was used in combination with this compounding system, the compression set characteristics were further deteriorated. However, when the chloroprene composition is applied to a building material or a mechanical component material particularly at a portion where pressure is applied, such as a packing material, a sealing material, a joint material, and a cushioning material, it is particularly strong to reduce the compressive strain. Is being requested. An object of the present invention is to provide a composition for molding a vulcanized rubber containing a mercaptan-modified or xanthogen-modified chloroprene rubber as a main component, and particularly to improve the compression set resistance thereof. The present inventors have made intensive efforts to improve the above-mentioned drawbacks, and as a result, based on 100 parts by weight of mercaptan-modified or xantogen-modified chloroprene rubber, (1) dicatechol 0.3 to 3.5 parts by weight of a di-O-tolylguanidine salt of borate, (2) 0.3 to 3.0 parts by weight of a thiourea-based crosslinking accelerator, and (3)
Sulfur, sulfur release type crosslinking accelerator [tetrakis (2-ethyl
Excluding hexyl) thiuram disulfide. ] And one or more sulfur-based crosslinking components selected from the group consisting of sulfur-releasing crosslinking agents in an amount of 0.1 to 5.0 parts by weight as an essential component. That is, as a result of adopting this new composition instead of the conventionally used composition in which a thiourea-based accelerator is mainly added to magnesium oxide and zinc oxide, a compression set test of a cured product was carried out. Found that a remarkable improvement was observed, and reached the present invention. [0008] The chloroprene rubber itself that can be used in the present invention is sold by various companies such as Denki Kagaku Kogyo Co., Ltd., Toyo Soda Co., Ltd., Showa Denko Dupont Co., Ltd., among which mercaptan-modified type and Xantogen. Any grade of chloroprene rubber of the modified type can be used. Of course, it is not affected by the Mooney viscosity or crystallization rate of each product type. Sulfur-modified chloroprene rubbers are not included in the present invention because of their different crosslinking properties. If the amount of the dicatechol borate di-O-tolylguanidine salt of component (1) is less than 0.3 parts by weight, the crosslinking density cannot be increased, and if it exceeds 3.5 parts by weight, Although the crosslink density can be greatly increased,
The crosslinking speed is too high, and the processing stability is lacking, or the cured product after the crosslinking reaction lacks elasticity, which leads to a decrease in tensile strength. (2) The thiourea-based crosslinking accelerator is preferably one or more thiourea-based crosslinking accelerators selected from the group consisting of thiocarbanilide, ethylenethiourea, diethylthiourea, dibutylthiourea, trimethylthiourea and dilaurylthiourea. These can be used in combination. When the amount of the thiourea-based crosslinking accelerator is less than 0.3 parts by weight, the crosslinking density cannot be increased. When the amount exceeds 3.0 parts by weight, the crosslinking density can be greatly increased. Becomes too fast, lacks processing stability,
The cured product after the cross-linking reaction lacks elasticity, leading to a decrease in tensile strength. (3) Sulfur-releasing crosslinking accelerator [Tetraki
(2-ethylhexyl) thiuram disulfide
Good. ] As tetramethylthiuram disulfide,
One or more crosslinking accelerators selected from the group consisting of tetraethylthiuram disulfide, tetrabutylthiuram disulfide, and dipentamethylenethiuram tetrasulfide are preferred. Further, as the sulfur releasing cross-linking agent, one or more sulfur releasing cross-linking agents selected from the group consisting of morpholine disulfide and alkylphenol disulfide are preferable, and these can be used in combination. [0012] Originally, when a sulfur-based material is added to chloroprene rubber, the compression set of the cured product becomes large. However, if each additive is used together within the scope of the present invention, it will be compared with the conventional chloroprene composition. The compression set was significantly reduced. If the addition amount of the sulfur-based crosslinking component is less than 0.1 part by weight, the effect of addition is not at all, and if it exceeds 5 parts by weight, the compression set of the cured product also increases. The chloroprene composition of the present invention contains various additives generally used in the rubber industry, for example, reinforcing agents, fillers, softeners, liquors, antioxidants, processing aids, Tackifiers can be included. The compounding of the crosslinking accelerator employed in the present invention is effective in a crosslinking method using a metal oxide. As the metal oxide, one or more metal oxides selected from the group consisting of zinc oxide, magnesium oxide and lead oxide are preferable, and two or more metal oxides are more preferable. The present invention shows a particularly remarkable effect in a combined system of zinc oxide and magnesium oxide. The total amount of the metal oxide is preferably 8 to 15 parts by weight. Hereinafter, more specific experimental results will be described. A blend having the blend ratio shown in Reference Example 1 in Table 1 was prepared. That is, for 100 g of chloroprene rubber, as additives, 0.5 g of stearic acid, 2 g of an antioxidant,
30 g of carbon black, 20 g of calcium carbonate and 10 g of a softener were added. As a crosslinking system, 5 g of zinc oxide, 4 g of magnesium oxide, di-O- of dicatechol borate
0.5 g of tolylguanidine salt, 1.0 g of trimethyl thiourea, 0.5 g of ethylene thiourea and 1.0 g of tetrakis (2-ethylhexyl) thiuram disulfide
g was blended. Here, the following chloroprene rubbers and additives were used as shown in Table 1. Chloroprene rubber (1): "WXJ" manufactured by Showa Denko Dupont Co., Ltd. Mercaptan-modified antioxidant (2): "AD" manufactured by Ouchi Shinko Chemical Co., Ltd. Carbon black (3): "Asahi II" manufactured by Asahi Carbon Co., Ltd.
35 "Calcium carbonate (4):" Silver W "manufactured by Shiraishi Calcium Co., Ltd. Softener (5):" NM-26 "manufactured by Idemitsu Petrochemical Co., Ltd. The mixture was kneaded at 60 ° C. to obtain a rubber composition. This rubber composition was heated in a mold at 160 ° C. for 40 minutes to cause a crosslinking reaction, thereby obtaining a crosslinking reaction product. This cross-linked reaction product has a thickness of 1 to be used in the JIS compression set test.
A test piece with a 2.7 mm-diameter, 29.0 mm-diameter, right-cylindrical spacer was obtained. The test piece was set in a compression device, compressed by 25%, and kept at 70 ° C. for 22 hours. The test piece was taken out of the compression device, and the thickness t ₁ of the test piece after 30 minutes was measured. The compression set was calculated according to the following equation and is shown in Table 1. CS (%) = (t ₀ −t ₁ ) × 100 / (t ₀ −t ₂ ) CS = compression set (%) t ₀ = the original thickness of the test piece (ie, 12. 7 mm) t ₁ = test pieces of 30 minutes after removal from the compressor thickness (mm) t ₂ = spacer thickness (3.2 mm) [0019] example 1 shown in Table 1, reference example 2,
For each of the blending examples of Example 2 and Reference Example 3 and Comparative Examples 1 to 3 shown in Table 2, a crosslinking reaction product was produced in the same manner, and the compression set thereof was measured. The results are shown in Tables 1 and 2. Was. [Table 1] [Table 2] As can be seen from Table 1, the compression set of the composition of this example was 10% or less. In the case of the compositions of Comparative Examples 1 to 3, the compression set was 19%.
２５25%, which is more than twice as large. Thus, the present invention represents a significant improvement in the compression set test. As described above, the chloroprene rubber composition of the present invention can improve the compression set by as much as 30% or more in comparison with the conventional chloroprene rubber in any temperature range. It is particularly useful as a building material or a machine component material in a part where pressure is applied, such as a packing material, a sealing material, a joint material, or a cushioning material, and its industrial utility value is very large.

Claims (1)

(57) [Claims 1] With respect to 100 parts by weight of a mercaptan-modified or xanthogen-modified chloroprene rubber, (1) 0.3 to 3.5 parts by weight of di-catechol borate di-O- Toluyl guanidine salt (2): 0.3 to 3.0 parts by weight of a thiourea-based crosslinking accelerator,
And (3) 0.1 to 5.0 parts by weight of sulfur, a sulfur-releasing crosslinking accelerator [tetrakis (2-ethylhexyl) thiuramdi)
Excluding sulfide. A chloroprene composition comprising, as an essential component, at least one sulfur-based crosslinking component selected from the group consisting of a sulfur-releasing crosslinking agent.