KR790001995B1 - Ubber compositions - Google Patents

Abstract

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Description

Rubber composition

1 Vulcanization curves at 125 ° C. of the compositions of Examples 1 and 2 and Comparative Examples 1 and 2

2 Vulcanization curves at 125 ° C. of the compositions of Examples 3 and 4 and Comparative Examples 3 and 4

The present invention relates to a vulcanization-promoting rubber composition. When vulcanizing rubber, the addition of a vulcanization accelerator to the rubber shortens the time required for vulcanization or improves the various properties of the vulcanized rubber product under the temperature required for vulcanization and also improves the productivity of the vulcanizer.

However, vulcanization accelerators (hereinafter abbreviated as accelerators) currently on the market have various problems. For example, dithio acid salts or thiolam, which are generally called super accelerators, are vulcanized rapidly at the vulcanization temperature, but are vulcanized by heat in processing processes such as kneading due to their activity. It has the drawback that it is easy to cause so-called scorch. In addition, sulfonamides, commonly referred to as sustained release accelerators, have a low risk of scorch but slow vulcanization rate. In other words, currently known accelerators are known to have a scorch risk proportional to the vulcanization rate.

Therefore, it would be very useful for the rubber industry if it was possible to develop an accelerator system so that the vulcanization proceeded rapidly at the vulcanization temperature without causing scorch at the processing temperature of the rubber. There have been several proposals for this request. For example, there is a method of stabilizing an accelerator so that it is not released if it does not reach a certain temperature.

That is, a method of adsorbing a promoter on the surface of activated carbon and blending it into rubber (US Pat. No. 1,511,984) and barium trithiocarbonate and certain amines that decompose by heating to liberate carbon disulfide, together with sulfur and zinc, There is a method in which dithiocarbamic acid is added and vulcanized under heating.

However, such accelerator systems tend to release accelerators or active ingredients even at the temperatures used to process rubber and consequently the scorch properties are not improved.

A vulcanization method is also proposed in which dithiocarbamic acid is produced at a vulcanization temperature by blending polythio carbonate releasing carbon dioxide sulfide under heating and isocyanate protected amine or amine releasing amine or amine under heating to rubber. (Japanese Patent Laid-Open No. 47-42850). However, the polythiocarbonate used in such a system has a drawback that the vulcanization progresses slowly during the processing process because the decomposition temperature is not sufficiently higher than the temperature used for the processing process and is not very stable to heat.

An object of the present invention is to provide a vulcanization system in which vulcanization proceeds rapidly at a vulcanization temperature without causing a scorch for a sufficiently long time at the vulcanization temperature of rubber.

The vulcanization system of this invention consists of two components. One is a compound that does not thermally decompose over a long time at the processing temperature of rubber but rapidly decomposes at a vulcanization temperature to generate carbon disulfide (hereinafter referred to as a carbon disulfide donor), and another isocyanate-protected amine or imine (hereinafter referred to as Amine donor). By blending these with other compounding agents such as sulfur and zinc, etc., the vulcanizable rubber improves the productivity of rapidly vulcanizing at the vulcanization temperature without causing scorch for a long time during the processing process.

The carbon disulfide donor used in the present invention is an alkylenebisthio carbamic acid metal salt represented by the following general formula (A) or (B) or (C).

(A )

(A)

(B )

(B)

(C )

(C)

Among the above formulas

R ₁ is selected from a hydrogen atom, a methyl group and an ethyl group, and R ₂ is selected from a hydrogen atom, a methyl group, an ethyl group and a propyl group.

M is selected from lithium and sodium potassium, M 'is selected from calcium, manganese, cobalt, nickel, zinc, lead, antimony, bismuth, cadmium and copper, and M "is selected from iron, chromium and aluminum.

Such alkylene bis dithio carbamic acid metal salts can be easily produced according to a known method. For example, in the formula (I), when R ₁ and R ₂ are each hydrogen, it can be easily prepared according to the reaction of ethylenediamine, carbon disulfide and sodium or potassium hydroxide. Furthermore, the compounds of formulas (2) and (3) are easily obtained by the reaction of the compounds of formula (1) with chlorides or sulfates of various metals.

Another component of the present invention, the amine donor, is an isocyanate protected amine (containing imines, hereinafter identical), i.e., an addition compound of secondary amines and isocyanates produced according to the following scheme.

The amine (I) is stabilized in the form of (III), and is free of amines at the vulcanization temperature, regardless of chemical reaction during the rubber processing process, and reacts with the carbon disulfide of electricity, and the dithiocarbamic acid-based accelerator It is synthesized within and vulcanized rapidly. Wherein R ₃ and R ₄ are the same or different monovalent hydrocarbon groups (containing eight carbon atoms), or R ₃ and R ₄ form a divalent hydrocarbon group having 2 to 7 carbon atoms or one or more To form a divalent scattering group containing 2 to 8 carbon atoms having heteroatoms of oxygen, sulfur and nitrogen. Examples of such amines are as follows.

Dimethylamine, diethylamine, di-n-propylamine, di-isopropylamine, di-n-butylamine, di-tert-butylamine, di-tert-butylamine, di-2-ethylhexylamine , N-methyl-N-cyclohexylamine, dicyclohexylamine, diphenylamine, di-trilamine, pyridine, piperidine, piperazine, pyrrole, pyrazole, imidazole, morpholine, pyridine and the like R 'in formula (isocyanate) is a C4-C18 aromatic group or an alkyl group. The aromatic group or alkyl group may further contain an isocyanate group or other substituents. Examples of such isocyanates include the following. Phenyl isocyanate, parachlorophenyl isocyanate, hexamethylene isocyanate, octadecyl isocyanate, 2,4- and 2,6-toluene isocyanate, diphenylmethane-p, p'-diisocyanate, p-phenylenediisocyanate, dichlorodiphenylmethane Diisocyanate, naphthalene-1,5-diisocyanate.

The preparation method of the amine protected by this isocyanate is simple and the objective is produced by simply dissolving and mixing the isocyanate and the amine in a suitable solvent, respectively. It is preferable to use a suitable cooling device because the production of this additive compound generally involves exothermic heat. In the production of the above additive compounds, the amine emission temperature can be varied over a wide range depending on the choice of amine and isocyanate.

In blending the carbon disulfide donor and the amine donor into rubber, zinc, stearic acid, sulfur, fillers, and other agents usually formulated into rubber can be added simultaneously.

The rubber to which the vulcanization system of the present invention can be applied is a rubber having an olefin unsaturated unsaturated bond required as a vulcanizable rubber of the vulcanization accelerator system. Examples thereof include natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, ethylene-propylene-diene terpolymer, and the like. Specific examples are shown below, but the scope of the present invention is not limited to these examples.

[Example 1-2] and [Comparative Example 1-2]

According to the compounding table shown below, the rubber composition was mixed by a conventional method generally recorded in a rubber test method or the like.

TABLE 1

The vulcanization performance was determined using the MPV rheometer vulcanizometer manufactured by Monsanto Co., Ltd. for the above rubber inclusions. The results are shown in Table 2 and FIG.

In the table, Tc represents the optimum vulcanization time and the time required to reach 95% of the maximum torque.

Ts represents the scorch time and represents the time required to reach the torque mentioned above about 3 inches-pounds than the minimum torque.

TABLE 2

Table 2 and FIG. 1 show the formulation using the carbon disulfide donor of the present invention as compared to a compound using a sulfonamide type or thiuram type promoter known in the art.

(1) It exhibits excellent scorch resistance at normal processing temperatures (125 ° C or less).

(2) It is clear that the vulcanization is quite rapid at the temperature (160 ° C or higher) used for normal vulcanization.

In particular, as can be seen even if the order of Tc is changed between Examples 1 and 2 and Comparative Example 1 at 160 ° C to 170 ° C, the vulcanization accelerator of the present invention exhibits particularly excellent properties at high temperatures.

[Examples 3 and 4] and [Comparative Examples 3 and 4]

According to the formulation shown in Table 3, the same test as in Example 1 was conducted. Vulcanization measurement results are shown in Table 4.

[Ryo 3]

TABLE 4

Tables 4 and 2 further illustrate the utility of the present invention by comparing the values of scorch time Ts at 125 ° C. and optimal vulcanization time Tc at 160 ° C. with Example 3 and Comparative Examples 3 and 4.

Example 3

The Mooney characteristics of the formulations of Examples 1,2 and Comparative Examples 1,2 and Comparative Example 4 shown in Tables 1 and 3 were measured according to JISK-6300, and the vulcanization characteristics were measured according to JISK-6301, respectively. . Vulcanization for obtaining a sample for vulcanization measurement was now performed at 149 ° C. The results are shown in Table 5.

TABLE 5

As described above, the vulcanization system comprising the carbon disulfide donor and the amine donor of the present invention is chemically inert at a normal processing temperature, and its scorch stability is a level not seen with conventionally available accelerators. At the vulcanization temperature, vulcanization occurs rapidly, and it has a surprising effect that the time from the vulcanization start until the optimum vulcanization is reached is shorter than the conventional sulfonamide type vulcanization accelerator.

Claims (1)

A rubber composition characterized in that the rubber having olefinic unsaturation contains an alkylenebisthiocarbamic acid metal salt represented by the following general formula A or B or C and an amine-isocyanate addition compound represented by the following general formula D.

(A)

(B)

(C)

(D) Among the above structural formulas R ₁ is hydrogen, methyl, ethyl R ₂ is hydrogen, methyl, ethyl, propyl M is from lithium, sodium, potassium M 'is from calcium, manganese, cobalt, nickel, zinc, lead, antimony, bismuth, cadmium, copper M ″ is one selected from iron, chromium and aluminum, respectively. R ₃ and R ₄ are each one monovalent hydrocarbon group having from to 8 carbon atoms, or R _3, R 2 divalent hydrocarbon group ₄ having from merged 2 to 7 carbon atoms, or R _3, R ₄ are merged and 1 A divalent acid group having 2 to 8 carbon atoms containing at least two oxygen, sulfur or nitrogen atoms, R 'represents an aromatic group or an alkyl group having 4 to 8 carbon atoms, which aromatic group or alkyl group additionally contains an isocyanate group or other substituents.

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