JPS62143950A - Rubber composition - Google Patents

Abstract

PURPOSE:A composition wherein processing properties are improved by reducing viscosity of an unvulcanized rubber composition without changing physical properties of vulcanized rubber, obtained by blending rubber with a polymer or copolymer of a 2-(trialkoxysilyl)-1,3 butadiene. CONSTITUTION:(A) 100pts.wt. rubber blended with (B) 0.5-50pts.wt. of (i) a 2-(trialkoxysilyl)-1,3 butadiene polymer and/or (ii) a copolymer obtained by subjecting a 2-(trialkoxysilyl)-1,3 butadiene, another conjugated diene and/or an aromatic vinyl compound to solution polymerization in the presence of a radical catalyst or an anionic catalyst, (C) 5-200pts.wt. white carbon (wet silica, dry silica or synthetic silicate) and, if necessary, another filler, a reinforcing agent, a softener, etc., to give the aimed rubber composition.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a rubber composition with excellent processability.

[Conventional technology]

When a filler is blended into rubber, the viscosity of the unvulcanized rubber compound increases, which deteriorates the kneading workability and moldability of the compound. This tendency is particularly remarkable when white carbon is mixed.

On the other hand, a softener is usually added to improve processability and workability. Examples of the softening agent include oil-based softening agents such as mineral oil and vegetable oil, fatty acids such as stearic acid and palmitic acid, salts thereof, and factices called subs.

Among these, oil-based softeners act as lubricants between rubber molecules, and if used in an appropriate amount, they can lower the viscosity of unvulcanized rubber compounds, improve processability, and reduce the cost of rubber compounds. It is widely used because it lowers However, in order to obtain an unvulcanized rubber compound with a lower viscosity, a large amount must be blended, and as a result, the modulus of the vulcanized rubber decreases, resulting in a soft rubber with high elongation.

In addition, fatty acids or salts thereof can reduce the viscosity of the unvulcanized rubber compound to some extent by assisting in the dispersion of compounding agents, but even if they are added in large amounts, the viscosity cannot be reduced beyond a certain level.

When a large amount of factice is added to lower the viscosity of unvulcanized rubber, it significantly reduces the strength of the vulcanized rubber, such as the tensile strength.

Therefore, in order to further reduce the viscosity of the unvulcanized rubber, it is possible to add silicone oil or a silane coupling agent. These additives disperse white carbon well and lower the viscosity of unvulcanized rubber, but they have the following problems.

That is, although silicone oil greatly reduces the viscosity of unvulcanized rubber, it also significantly reduces the tensile strength of vulcanized rubber. Also, among silane coupling agents, there are types that have a strong effect on lowering the viscosity of unvulcanized rubber, but this agent is originally added for the purpose of creating a crosslink between the filler and the polymer. Therefore, the resulting vulcanized rubber has high modulus and low elongation.

[Problem that the invention seeks to solve]

In view of the current situation, the present invention relates to a method for reducing the viscosity of an unvulcanized rubber composition without changing the physical properties of the vulcanized rubber as much as possible.

[Means to solve the problem]

Specifically, the present invention relates to 2-(trialkoxysilyl)-
Polymers of 1,3 butadiene or 2-(trialkoxysilyl)-1,3 butadiene and other conjugated dienes and/or
Alternatively, by adding a copolymer with an aromatic vinyl compound, an unvulcanized rubber composition with a lower viscosity can be obtained without significantly changing the physical properties of the vulcanized rubber compared to when no addition is made. This effect is particularly remarkable when white carbon is added.

The rubber used in the present invention is natural rubber or synthetic rubber, and examples of the synthetic rubber include SBR, BR, NBR, EPM,
EPDM, IIR, IR, CR.

ACM, silicone rubber can be used. These types of rubbers may be used alone or in a blend of several types of rubbers.

The polymer of 2-(trialkoxysilyl)-1,3-butadiene or its copolymer only needs to have a molecular weight that does not volatilize during kneading, molding, and vulcanization of the rubber composition, and can be selected from liquid oligomers with low molecular weight. Even rubbery or resinous polymers can be used.

As the alkoxy group of 2-(trialkoxysilyl)-1,3-butadiene, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, or a mixture thereof can be used.

As the conjugated diene or aromatic vinyl compound copolymerized with 2-(trialkoxysilyl)-1,3-butadiene,
Butadiene, isoprene, styrene, α-methylstyrene, P-methylstyrene, etc. can be used. In this polymerization method, solution polymerization using a radical catalyst or an anionic catalyst such as organic lithium, sodium, potassium, etc. is applied.

The amount of the 2-(trialkoxysilyl)-1,3-butadiene polymer or copolymer to be blended is 0.5-50 parts by weight, preferably 0.5-50 parts by weight, based on 100 parts by weight of rubber.
If it is less than 0.5 parts by weight, the viscosity of the unvulcanized rubber composition cannot be effectively lowered, and if it exceeds 50 parts by weight, the physical properties of the vulcanized rubber will be poor compared to when it is not added. This is inferior and falls outside the purpose of the present invention.

The white carbon used in the present invention is wet silica,
Pyrosilica and synthetic silicate are used, and the amount used is 5 to 200 parts by weight per 100 parts of rubber, and 5
If it is less than 200 parts by weight, the reinforcing effect as white carbon will not be sufficient, while if it is used in excess of 200 parts by weight, the viscosity will be low, which is the objective of the present invention, and it will not be possible to knead and mold. It is not possible to obtain an unvulcanized rubber composition with good properties. Other white fillers and reinforcing agents such as carbon black can also be used in combination with these white carbons.

In addition, other softeners, plasticizers,
Vulcanizing agents, vulcanization aids, vulcanization accelerators.

Anti-aging agents 9 coloring agents and the like can be used.

〔Example〕

Example I 75 parts by weight of EPDM, 25 parts by weight of silicone rubber, nib seal VN, (white carbon manufactured by Nippon Silica) 40 parts by weight, PW-380 (paraffin oil manufactured by Idemitsu Kosan) 1
0 parts by weight, 5 parts by weight of Zinc White No. 1, 1 part by weight of stearic acid, and 1 part by weight of an oligomer of 2-()rimethoxysilyl)-1,3-butadiene were mixed in a plastomill for 6 minutes.

The Mooney viscosity of the unvulcanized rubber composition obtained by adding 3 parts by weight of dicumyl peroxide to this mixture and rolling it was measured. Further, this unvulcanized rubber composition was vulcanized at 170° C. for 10 minutes, and then after-cured for 2 hours in a hot air dryer at 150° C. to prepare a vulcanized rubber sheet. The viscosity of the unvulcanized rubber and the physical properties of the vulcanized rubber at this time are
Shown in ■ in the table.

Similarly to (2), various 2-(trimethoxysilyl) 1.
Examples of using 3-butadiene polymer (hereinafter sometimes abbreviated as silyl-butadiene polymer) are shown in Table 1.
~■ Shown.

Comparative Example 1 A rubber composition was obtained in the same manner as in Example 1, except that only the silyl butadiene zelimer of Example 1 was used.

The viscosity of the unvulcanized rubber and the physical properties of the vulcanized rubber at this time are shown in Table 1 (3).

Comparative Example 2 A rubber composition was obtained in the same manner as in Example 1 except that a polybutadiene containing no silyl group was used in place of the silylbutadiene polymer of Example 1. The viscosity of the unvulcanized rubber and the physical properties of the vulcanized rubber at this time are shown in Table 1 (3).

Example 2 The formulation shown in Table 2 (2) except for the vulcanization accelerator and sulfur was mixed in advance in a plastomill. The Mooney viscosity of the unvulcanized rubber composition obtained by adding a vulcanization accelerator and sulfur to this composition and rolling it is shown in the middle row of Table 2 (2).

Further, this unvulcanized rubber composition was press-vulcanized at 170° C. for 10 minutes, and the physical properties of the obtained vulcanized rubber sheet are shown in the lower part of Table 2 (2).

Also, in the same manner as in ■, 2-(trimethoxysilyl)-1,
50 mol% of 2-(trimethoxysilyl)-1,3 butadiene and butadiene 5 instead of 3-butadiene polymer.
Table 2 [Phase] shows the results when using a copolymer with a molecular weight of 200,000 and 0 mol %.

Comparative Example 3 Table 2 (2) shows the results obtained when the silyl butadiene polymer was removed from the rubber composition in Table 2 (2).

Table 2 shows the results when a polybutadiene having no silyl group was used instead of the silyl butadiene polymer in the rubber composition of Comparative Example 4゜■.

Table 2 shows the results when a silane coupling agent was used instead of the silyl butane diene polymer in the rubber composition of Comparative Example 5゜.

Table 2 shows the results when silicone oil was used in place of the silyl and other butadiene polymers in the rubber composition of Comparative Example 6°.

Example 3 The formulation shown in Table 3, excluding the vulcanization accelerator and sulfur, was mixed in a plastomill.

Table 3 shows the Mooney viscosity of the unvulcanized rubber composition obtained by adding a vulcanization accelerator and sulfur to this composition and rolling it.
Phase] is shown in the middle row. In addition, this unvulcanized rubber was heated at 150°C for 20
The physical properties of the vulcanized rubber sheet obtained by press vulcanization for 1 minute are shown in the lower row of Table 3 (2).

Comparative Example 7 Table 3 [Phase] shows the results when only the silyl butadiene polymer was removed from the rubber composition in Table 3 [Phase].

As is clear from Tables 1, 2, and 3, the addition of the silylbutadiene polymer or copolymer does not significantly change the physical properties of the vulcanized rubber composition, and increases the viscosity of the unvulcanized rubber composition. can be lowered.

〔Effect of the invention〕

The rubber composition of the present invention has a low Mooney viscosity and excellent kneading and molding processability when unvulcanized, and when it is vulcanized, it has physical properties with a good balance of stress, strength, and elongation, and has white carbon. It is highly effective in reinforcing rubber and can be suitably used as white or colored rubber products.

Claims (1)

[Claims] (1) For 100 parts by weight of rubber, 2-(trialkoxysilyl)-1.3 butadiene polymer and/or 2-(trialkoxysilyl)-1.
1. A rubber composition comprising 0.5 to 50 parts by weight of a copolymer of 3-butadiene and another conjugated diene and/or an aromatic vinyl compound.