JPS634580B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides (a) non-sulfur modified chloroprene rubber. (b) Zinc white, magnesium oxide or a mixture thereof. (c) Trithiocyanuric acid and general formula (In the formula, R represents a phenyl group or a tolyl group.)
0.3 to 3 parts by weight of one or more selected from the 1,3-substituted guanidines shown below per 100 parts by weight of rubber. In addition, trithiocyanuric acid/1.
The weight ratio of 3-substituted guanidines is 95/5 to 55/45. The present invention relates to a composition for vulcanizing chloroprene rubber, which is characterized by containing each of the components (a), (b), and (c) above. Chloroprene rubber is a halogen-containing polymer with high weather resistance, ozone resistance, heat resistance, and oil resistance.
General-use types are broadly divided into sulfur-modified chloroprene rubber and non-sulfur-modified chloroprene rubber. Sulfur-modified chloroprene rubber can be vulcanized only with metal oxides such as zinc white or magnesium oxide, but non-sulfur-modified chloroprene rubber is slow to vulcanize and cannot obtain sufficient vulcanized rubber physical properties with metal oxides alone. Can not. Therefore, thioureas such as ethylenethiourea (2-mercaptoimidazoline), diethylthiourea, and trimethylthiourea, or the di-ortho-tolylguanidine salt of dicatecholborate have been used. Trithiocyanuric acid has been shown to be effective as a vulcanization accelerator for chloroprene rubber, as reported in U.S. Patent No.
As is clear in the specification of No. 2804450 (1957),
Compared to the above-mentioned thiourea vulcanization system, this vulcanization accelerator has
There is a strong tendency to burn (scorch). On the other hand, at the vulcanization temperature, the vulcanization rate is slow and vulcanization does not progress tightly. It also has drawbacks such as large compression set. As a result of extensive research by the present inventors to overcome the above-mentioned drawbacks, we found that (1) When 1,3-substituted guanidines are used in the above-mentioned combination ratio with trithiocyanuric acid, the tendency to scorch is reduced. thing. (2) When used alone, 1,3-substituted guanidines have almost no vulcanization accelerating effect, but when used in combination with trithiocyanuric acid, vulcanization progresses sharply and vulcanization increases. To shorten the time. (3) Furthermore, they discovered that the physical properties of vulcanized rubber, especially compression set, can be improved, leading to the completion of the present invention. Trithiocyanuric acid according to the present invention (hereinafter referred to as
TTCA (abbreviated as TTCA) is synthesized from cyanuric chloride and sodium hydrosulfide or sodium sulfide, and is a yellow crystal with a melting point of over 300℃. In addition, the 1,3-substituted guanidines according to the present invention include 1,3-diphenylguanidine (hereinafter abbreviated as DPG) and 1,3-diortho-tolylguanidine (hereinafter abbreviated as DOTG).
is the most suitable. The total amount of these vulcanization accelerators is 0.3 to 100 parts by weight of chloroprene rubber.
The amount is 3.0 parts by weight, preferably 1.0 to 2.0 parts by weight. Also, the weight ratio of TTCA/guanidines is 95/5 to 55/4.
5. Preferably the weight ratio is 90/10 to 60/40. The amount of zinc white or magnesium oxide used as a vulcanizing agent or acid acceptor is usually 4 to 5 parts by weight, but the amount can be increased or decreased as necessary. In addition to the above-mentioned compounding agents, the composition of the present invention may contain, as appropriate, conventional rubber compounding agents such as vulcanization retarders, anti-aging agents, stabilizers, reinforcing agents, and plasticizers. Next, the features of the present invention will be explained in more detail using examples. Examples The formulations are shown in Table 1. trithiocyanuric acid and
Tables 2 and 3 show the effects of non-sulfur modified chloroprene rubber compositions containing 1.3-diortho-tolylguanidine in various proportions on the scorch time and vulcanization rate at 160°C. The compounded rubber was 50± using a 6″φ x 12″ test roll.
The mixture was kneaded at 5°C. Moony Scorch is JIS
Tested at 120°C in accordance with K6300 (1974). The test conditions for the cuylastometer are as follows. The heating time was constant at 160°C x 50 minutes, and if the maximum torque was not reached, the torque value after 50 minutes of heating was taken as the maximum value (Kg-cm). Testing machine: JSR type Cyulast meter Dice: 2mm Shaking width: ±3° Induction period: t ₁₀ (minutes, seconds) Vulcanization time: t ₉₀ (minutes, seconds) Rising speed: R (minutes, seconds) ) Estimated vulcanization time: T = 2t ₉₀ -t ₁₀ (minutes, seconds) Maximum torque value (Kg - cm) = (10 x P / W) Kg x 13.5 cm P: stress from the center line of zero stress Distance to maximum value (cm) W: Effective width of recording paper (cm). The tensile test was based on JIS K6301 (1975).
Physical properties of vulcanized rubber press-cured at 160℃,
The compression set (CS%) after heating at 100°C for 70 hours and the results of the tensile test after heat aging at 100°C for 70 hours using a gear oven are shown in Table 4. Table 1 Non-sulfur modified chloroprene rubber* 100 Zinc white 5 Magnesium oxide 4 Stearic acid 1 Process oil 10 SRF black 50 Vulcanization accelerator Variable notes *Neoprene W (manufactured by Showa Neoprene Co., Ltd.)

[Table] Note) * Trithiocyanuric acid ** 1.3
-Diortho-tolylguanidine

【table】

[Table] Note) * Trithiocyanuric acid ** 1.
3-Diortho-tolylguanidine The above Examples 1 to 4 have shorter vulcanization time (t ₉₀ ), vulcanization rise rate (R), and estimated vulcanization time (T) than TTCA alone (Comparative Examples 1 and 6). It was also found that the maximum torque value was large. It is also seen that as the combined use ratio of DOTG increases, the scorch time (t ₅ ) also increases almost proportionally. Next, Table 4 shows the results of testing the physical properties of the vulcanized rubber of the composition according to the present invention.

[Table] Note) 1) Tensile strength 2) Elongation 3) Modulus 4) Hardness 5) Compression set From the test results in Table 4, the composition according to the present invention has a large modulus and hardness compared to the comparative example. It can be seen that adding sulfur rubber improves compression set. Similarly, Table 5 shows the effects of the composition according to the present invention using 1,3-diphenylguanidine (DPG) in place of DOTG.

[Table] From the test results, it was found that the composition according to the present invention provided a vulcanized rubber with high modulus and hardness, and had excellent compression set.

Claims (1)

[Claims] 1 (a) Non-sulfur modified chloroprene rubber. (b) Zinc white, magnesium oxide or a mixture thereof. (c) Trithiocyanuric acid and general formula (In the formula, R represents a phenyl group or a tolyl group.)
0.3 to 3 parts by weight of one or more selected from the 1,3-substituted guanidines shown below per 100 parts by weight of rubber. In addition, trithiocyanuric acid/1.
The weight ratio of 3-substituted guanidines is 95/5 to 55/45. A composition for vulcanizing chloroprene rubber, comprising each of the components (a), (b), and (c) above.