JPH10130430A - Silica-filled vulcanizable rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the processability of an unvulcanized rubber composition without detriment to the properties such as low heat buildup and abrasion resistance by mixing a silica-filled rubber composition with a poly(alkylhydrogendiloxane). SOLUTION: A silica-filled rubber composition is mixed with a poly(alkylhydrogensiloxane) represented by the formula (wherein R<1> is methyl, ethyl or phenyl; R<2> is an alkyl; (m) is 0 or 1 or greater; and (n) is 4 or greater) by means of e.g. a mixer or a poly(alkylhydrogensiloxane) dissolved in a solvent such as acetone is mixed with silica, and the solvent is removed by heating to 60-150 deg.C, whereupon the release effect of the general-purpose rubber is inhibited. The rubber component may be an arbitrary diene rubber alone or in the form of a blend. 100 pts.wt. rubber is mixed with 5-100 pts.wt. silica, CB pts.wt. carbon black having a DBP absorption of 90ml/100g or above and HS pts.wt. poly(alkylhydrogensiloxane) in such amounts as to satisfy relationships I and II.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition,
More specifically, the present invention relates to a vulcanizable silica-containing rubber composition having improved processability before vulcanization. Here, “silica” refers to hydrous silicic acid and silicic anhydride, and the nitrogen specific surface area used for rubber is 50 to 300 m ² /
g, and "vulcanization" includes vulcanization with peroxides in addition to vulcanization with ordinary sulfur.

[0002]

2. Description of the Related Art Rubber compositions comprising silica mixed with various rubbers are known, and are used, for example, as rubber compositions for tire treads having low heat generation and excellent wear resistance.
However, tire treads containing silica have low rolling resistance and good grip on wet roads, but increase the viscosity of unvulcanized compounds, delay vulcanization, and reduce cohesion during the tire manufacturing process, resulting in increased productivity. There was a problem that it became worse. There have been various proposals for solving such a problem, but none of them is practically satisfactory.

For example, diethylene glycol or fatty acid is added (for example, Handbook of Rubber Industry <Fourth Edition>, 517-
P. 518, published in 1994), and addition of a metal carboxylate (for example, Tire Technology I)
International 1995, pp. 107-108), and treatment of silica with a silicone oil in advance (see, for example, JP-A-6-248116) has been proposed. I can not say.

[0004]

Accordingly, the present invention eliminates the above-mentioned problems of the prior art and substantially reduces the characteristics of the silica-containing vulcanizable rubber composition, for example, the characteristics such as low heat build-up and abrasion resistance. An object of the present invention is to provide a silica-containing vulcanizable rubber composition in which the processability of an unvulcanized rubber composition is improved without impairing the composition.

[0005]

According to the present invention, there is provided a silica-containing vulcanizable general-purpose rubber composition obtained by compounding a rubber composition containing silica with a poly (alkyl hydrogen siloxane).

According to a preferred embodiment of the present invention, the vulcanizable rubber composition containing silica further contains a highly oil-absorbing carbon having a DBP oil absorption of 90 ml / 100 g or more and / or a silane coupling agent in the rubber composition. Is provided.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the structure, operation and effect of the present invention will be described in detail. As described above, the tire tread containing silica has good vulcanization properties, but has a drawback that the workability in the unvulcanized state is poor. According to the findings of the present inventors, this is due to silanol groups (≡Si—OH) present on the silica surface, and a structure is formed in the rubber composition due to the cohesive force of the silanol groups to increase the viscosity. Or
An unvulcanized composition due to the phenomenon that vulcanization accelerators are adsorbed due to the polarity of the silanol group and vulcanization is delayed, or the cohesion of the mixture is reduced due to insufficient compatibility with the non-polar rubber. The workability of the steel is reduced. Further, a silane coupling agent is often used in combination with the silica-containing rubber composition to reinforce the rubber.However, a silanol group also exists in the inner cavity of the silica particles, and this is considered as a silane coupling agent. There is a problem that a large amount of the silane coupling agent must be blended because the reaction causes loss of the silane coupling agent and a reduction in the reinforcing effect. As in the prior art, when a polar substance such as diethylene glycol is added thereto, the phenomenon that a polar compounding agent such as a vulcanization accelerator is adsorbed can be prevented to some extent, but cannot be completely prevented, and a silane coupling agent or the like cannot be prevented. Neither was it possible to prevent substances that chemically bond with the silica particles from binding to the lumen.

However, according to the present invention, as described above, by blending a poly (alkyl hydrogen siloxane) into a rubber composition, deterioration of unvulcanization processability, which is a problem of the conventional silica compounding technique, is considered. Can be solved.

The poly (alkyl hydrogen siloxane) compounded in the silica-containing rubber composition according to the present invention is a known substance conventionally used as a silica surface treating agent. Was disadvantageous in the process because it was caused to react in advance with silica at a high temperature. Further, since poly (alkyl hydrogen siloxane) acts as a release agent for general-purpose rubber, it has been prohibited in the conventional rubber industry to add it to a general-purpose rubber composition such as a tire tread. The present inventor has studied the release effect of poly (alkyl hydrogen siloxane) and found that the addition has the effect of improving the unvulcanized properties, and that if the addition method to general-purpose rubber is devised, the release effect is reduced or eliminated. It has been found that when used in combination with a silane coupling agent, there is an effect of improving rubber properties. In the present invention, for example, the processability of the unvulcanized rubber can be improved only by blending it with the silica-containing rubber composition with a mixer or the like. Such poly (alkyl hydrogen siloxane) has, for example, the following general formula:

[0010]

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(Wherein, R ¹ independently represents a methyl group, an ethyl group or a phenyl group, R ² independently represents an alkyl group, m is an integer of 0 or 1 or more, and n is 1 or more. , Preferably an integer of 4 or more), and specific examples include 1,3,5,7,9-pentamethylcyclopentasiloxane and linear poly (methylhydrogensiloxane). Examples of commercially available products include LS-8990 and KF99 manufactured by Shin-Etsu Silicone.

The surface treatment of silica with poly (alkyl hydrogen siloxane) may be performed by mixing both of them, or by mixing poly (alkyl hydrogen siloxane) and silica dissolved in a solvent such as acetone and then air-drying or heating the solvent. Just remove it. The temperature during mixing and removal of the solvent may be room temperature, but heating at 60 to 150 ° C. is more effective. Usually, the surface treatment of silica with a silicone compound is heat-treated at a high temperature of 200 ° C. or more to cause a chemical reaction. For example, even if the treated silica is washed with a solvent such as acetone, most of the silicone compound remains on the silica surface. In the present invention, despite the state where most of the silicone compound is washed away when the treated silica is washed,
The silicone compound does not show a releasing effect on general-purpose rubber.

There is no particular limitation on the type of rubber component to be added to the rubber composition of the present invention, and any rubber conventionally used as a general-purpose rubber composition can be used. Specific examples include, for example, natural rubber (NR), polyisoprene rubber (IR), various styrene-butadiene copolymer rubbers (SBR), various polybutadiene rubbers (BR), acrylonitrile-butadiene copolymer rubber (NBR),
A diene rubber such as butyl rubber (IIR) can be used alone or as an arbitrary blend.

The silica compounded in the silica-containing rubber composition according to the present invention may be a general-purpose filler silica compounded in conventional rubber compositions, such as Nipsil AQ manufactured by Nippon Silica or Nippon Aerosil. Aerosil 20
Commercial products such as 0 can be suitably used. Although the amount of silica is not particularly limited, it is generally preferable to mix 5 to 100 parts by weight with respect to 100 parts by weight of rubber. If the amount of silica is too small, the physical properties of the rubber composition are not expected to be improved much. Conversely, if the amount is too large, the processability decreases, which is not preferable.

According to the present invention, poly (alkyl hydrogen siloxane) is blended into the rubber composition containing silica. When the blending amount is increased to enhance the blending effect of the poly (alkyl hydrogen siloxane). Since poly (alkyl hydrogen siloxane) bleeds after vulcanization and vulcanized rubber causes laminar exfoliation, a highly oil-absorbing carbon, that is, a DBP oil absorption of 90 ml / 100 g or more, preferably 100 to 150 ml / 100 g is used in combination.

According to the present invention, the blending amount HS (parts by weight) of the poly (alkyl hydrogen siloxane) and D are based on 100 parts by weight of the rubber compounded in the rubber composition containing silica.
The blending amount CB (parts by weight) of carbon black having a BP oil absorption of 90 ml / 100 g or more preferably satisfies the following formulas (1) and (2).

HS ≦ (CB / 8) +0.5 (1) HS ≦ 5 (2)

When a silane coupling agent is added to the vulcanizable rubber composition according to the present invention, the abrasion resistance can be further improved as compared with the prior art. The preferred amount of the silane coupling agent in the present invention is 1 to 20% by weight, more preferably 2 to 10% by weight, based on the amount of silica in the composition. If the blending amount of the silane coupling agent is too small, the desired effect cannot be obtained, while if it is too large, scorching (scorch) in the mixing or extrusion process tends to occur, which is not preferable. The silane coupling agent used in the present invention can be any silane coupling agent conventionally used in combination with a silica filler, and typical examples include those shown in Table I.

[0019]

[Table 1]

The rubber composition according to the present invention may be prepared by mixing the above components according to a conventional method, for example, mixing the above components with a Banbury mixer,
It can be obtained by kneading using a kneading machine such as a roll.

The silica-containing rubber composition according to the present invention comprises:
In addition to the above-mentioned essential components, vulcanizing or cross-linking agents, vulcanizing or cross-linking accelerators, various oils, anti-aging agents, fillers, plasticizers, etc. are generally compounded for tires and other general rubbers. Various additives can be compounded, and the compound can be kneaded and vulcanized by a general method to obtain a composition, which can be used for vulcanization or crosslinking. The compounding amounts of these additives can also be conventional general compounding amounts as long as they do not contradict the object of the present invention.

The silica-containing rubber composition according to the present invention can be suitably used in accordance with a conventional method, for example, for producing a pneumatic tire, by utilizing its properties. For example, a composition for a tire tread, a rubber composition for a conveyor belt, It is useful as a rubber composition for vibration rubber, a rubber composition for rubber hose, and the like.

[0023]

EXAMPLES The present invention will be further described with reference to standard examples and examples, but it is needless to say that the scope of the present invention is not limited to these examples.

The following commercially available products were used as the other components in the following standard examples and examples. Natural rubber (NR): RSS # 1 SBR: Nipol NS116 (Nippon Zeon) SBR: Nipol NS114 (Nippon Zeon) Silica: Nipsil AQ (Nippon Silica) Polyalkyl hydrogen siloxane: KF99 (Shin-Etsu Chemical Co., Ltd. Methyl hydrogen siloxane)) Silane coupling agent: Si69 (dexa) (chemical name:
Bis- [3- (triethoxysilyl) -propyl] tetrasulfide) Carbon Black: HAF (Diablack N339 (DBP manufactured by Mitsubishi Chemical Corporation)
Oil absorption 124ml / 100g)) SAF (Mitsubishi Chemical's Diablack A (DBP oil absorption 116ml / 100g))

Wax: microcrystalline wax Powder sulfur: 5% oil-treated powder sulfur Antioxidant 6C: N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine Vulcanization accelerator CZ: N -Cyclohexyl-2-benzothiazylsulfenamide vulcanization accelerator NS: Nt-butyl-2-benzothiazylsulfenamide vulcanization accelerator DPG: diphenylguanidine zinc oxide: zinc white 3 stearic acid: industrial Stearic acid for

Preparation of Sample The vulcanization accelerator and components other than sulfur were kneaded for 3 to 5 minutes in a 1.8-liter closed mixer, and the vulcanization accelerator was added to the masterbatch released when the temperature reached 165 ± 5 ° C. And sulfur were kneaded with an 8-inch open roll to obtain a rubber composition. The unvulcanized physical properties of the obtained rubber composition were measured. Next, this composition was press-vulcanized in a mold at 160 ° C. for 20 minutes to prepare a target test piece (rubber sheet), and the vulcanization properties were evaluated.

The test methods for the unvulcanized and vulcanized properties of the compositions obtained in each example are as follows. Unvulcanized properties 1) Mooney viscosity (ML _{1 + 4} ): JIS K 6300
It measured at 100 degreeC based on. 2) Vulcanization rate: 160 ° C based on JIS K 6300
The time to reach 95% vulcanization was measured at.

The vulcanized physical properties of the vulcanized sheet Skin: To investigate the release effect of the poly (alkyl siloxane), the surface observation of the vulcanized sheet was visually is considered good that there is smooth and glossy.

Standard Examples 1 to 3 and Examples 1 to 5 These are examples showing evaluation results in a system containing silica and carbon black and / or a silane coupling agent. The results are shown in Table II.

[0030]

[Table 2]

[0031]

Examples 1 to 3 show the effect of adding poly (alkyl hydrogen siloxane). The Mooney viscosity and the vulcanization rate are improved as the amount of poly (alkyl hydrogen siloxane) is increased as compared with the standard example 1. I understand. Also, the first embodiment uses the formula (1)
And the formula (2) were satisfied, and it was found that the sheet skin was good and the release effect of poly (alkyl hydrogen siloxane) was suppressed. On the other hand, Examples 2 and 3 can be used only for limited applications because foaming is observed. Example 4
Is 2.5% poly (alkyl hydrogen siloxane)
It is added in parts by weight, improves Mooney viscosity and vulcanization rate as compared with the standard example 2, and satisfies the formulas (1) and (2) because the specific carbon black is used in combination, so that the vulcanized sheet skin is good. It is. Similarly, Example 5 was improved as compared with Standard Example 3, and the wear resistance was also improved because the silane coupling agent was used in combination. in this way,
According to the present invention, the use of poly (alkyl hydrogen siloxane) can remarkably improve the vulcanization delay and viscosity increase due to the silica compounding.

Claims (5)

[Claims] 1. A silica-containing vulcanizable general-purpose rubber composition obtained by compounding a rubber composition containing silica with a poly (alkyl hydrogen siloxane). 2. The rubber composition according to claim 1, further comprising carbon black having a DBP oil absorption of 90 ml / 100 g or more. 3. A blending amount HS (parts by weight) of poly (alkyl hydrogen siloxane) with respect to 100 parts by weight of rubber.
And the blending amount CB (parts by weight) of carbon black and carbon black satisfies the formulas (1) and (2): HS ≦ (CB / 8) +0.5 (1) HS ≦ 5 (2) The rubber composition as described in the above. 4. The rubber composition according to claim 1, further comprising a silane coupling agent. 5. A pneumatic tire using the rubber composition according to any one of claims 1 to 4.