JPH11255964A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition having improved coupling efficiency of a silane coupling agent and vulcanized robber properties without raising the cost, by making the composition include a silica, a silane coupling agent, a specific rubber component and a prescribed sodium pyrophosphate hydrate. SOLUTION: This composition is obtained by compounding (A) a silica [e.g. Nipsil AQ (R) or the like], (B) a silane coupling agent [e.g. (Cn H2n+1 O)3 Si-(CH2 )m - Si-(Cn H2n+1 O)3 ((n) is 1-3; (m) is 1-9; (1) is >=1) of the like], (C) a rubber component composed of a natural rubber(NR) and/or a synthetic rubber (e.g. butyl rubber or the like) and (D) sodium pyrophosphate undecahydrate. In the composition, 3-15 pts.wt. of the component D is mixed based on 100 pts.wt. of the component C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition containing silica and a silane coupling agent.
The present invention relates to a rubber composition capable of improving the coupling efficiency of a silane coupling agent and improving physical properties of a vulcanized rubber.

[0002]

2. Description of the Related Art In recent years, the use of a rubber composition containing silica in the tread portion of a PSR tire in order to achieve both wettability and low RR is rapidly increasing. The rubber composition for a tire tread or the like containing silica contains the above-mentioned merits, but also has disadvantages such as an increase in the number of compounded parts, a decrease in workability, and an increase in cost.

[0003] In general, silica has poor compatibility with polymers and poor dispersion, so that the Mooney viscosity value deteriorates,
This is a problem during scouring and extrusion. In order to improve the dispersibility and the workability, the problem is solved by using a silane coupling agent.

However, the coupling efficiency of the silane coupling agent is small, and in order to make up for it, the amount of silica is increased by 10 to 15% by weight with respect to the amount of silica at present. In addition, since the coupling agent is expensive, there is a problem that a large increase in the amount of the coupling agent leads to a significant increase in cost.

On the other hand, Japanese Patent Application Laid-Open No. Hei 9-118784 discloses 100 parts by weight of a sulfur-curable elastomer, 10 to 250 parts by weight of particulate precipitated silica, and 0.01 to 1.0 part by weight per 1 part by weight of the silica. organosilicon compound having a specific structure parts (the silane coupling agent), sodium thiosulfate pentahydrate _{[Na 2 S 2 O 3 · 5H} 2 O ] 10 to 250
There is disclosed a method of processing a rubber composition, characterized in that a rubber composition consisting of parts by weight is thermomechanically mixed at a rubber temperature in a range of 140 ° C. to 190 ° C. for a mixing time of 1 to 20 minutes.

[0006] The technique disclosed in this publication discloses the proximity technique of the present invention, the purpose of which is to add sodium thiosulfate pentahydrate without sacrificing the properties of the final product. The purpose of the present invention is to shorten the mixing / processing time in the so-called non-pro kneading step, to improve the coupling efficiency of the silane coupling agent of the present invention, and to improve the physical properties of vulcanized rubber. The technical ideas are also different.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is intended to solve the problem. The present invention has been made to improve the coupling efficiency of a silane coupling agent without increasing the cost. An object of the present invention is to provide a rubber composition capable of improving rubber properties.

The present inventors have conducted intensive studies on the above-mentioned conventional problems, and as a result, a desired rubber composition can be obtained by blending a specific compound in a specific amount in a rubber composition containing silica and a silane coupling agent. This led to the completion of the present invention. That is, the present invention resides in the following (1) to (6). (1) In a rubber composition containing silica and a silane coupling agent, sodium pyrophosphate decahydrate [Na ₄ P ₂ O _7. rubber composition characterized in that the 10H ₂ O] by blending 3 to 15 parts by weight. (2) The rubber composition according to the above (1), wherein the amount of the silica is 10 to 100 parts by weight based on 100 parts by weight of the rubber component. (3) The rubber composition according to the above (1), wherein the amount of the silica is 20 to 100 parts by weight based on 100 parts by weight of the rubber component. (4) The rubber composition according to the above (1), wherein the amount of silica is 30 to 100 parts by weight based on 100 parts by weight of the rubber component. (5) The rubber composition according to any one of the above (2) to (4), wherein the amount of the silane coupling agent is 5 to 15% by weight based on the amount of silica. (6) The rubber composition according to any one of the above (1) to (5), wherein the unreacted rate of the silane coupling agent is less than 20%.

[0009]

Embodiments of the present invention will be described below in detail. The rubber composition of the present invention comprises a rubber composition containing silica and a silane coupling agent, wherein sodium pyrophosphate decahydrate [Na ₄ P ₂ O ₇
[10H ₂ O] is 3 to 15 parts by weight, preferably 5 to 1 part by weight.
It is characterized by being mixed with 0 parts by weight.

The silica used in the present invention includes:
For example, synthetic silica by a precipitation method is used. Specifically, Nipsil AQ manufactured by Nippon Silica Kogyo Co., Ltd., ULTR ASIL VN3, BV3 manufactured by Degussa of Germany
370GR, RP1165N manufactured by Rhone Bouland
P, Zeosil 165GR, Zeosil 175
NP, Hisil 233, Hisil manufactured by PPG
200, Hisil 255, etc. (all are trade names), but are not particularly limited. The amount of silica is 10 to 100 parts by weight, preferably 20 to 100 parts by weight, and more preferably 30 to 100 parts by weight, based on 100 parts by weight of the rubber component. The amount of silica is 10
If the amount is less than parts by weight, wettability and reinforcement cannot be obtained.
If the amount is more than 100 parts by weight, workability such as hot extrusion is deteriorated, which is not preferable.

The silane coupling agent used in the present invention is not particularly limited, and a silane coupling agent generally used, for example, bis (3-
Triethoxysilylpropyl) polysulfide, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ -Glycidoxypropyltrimethoxysilane,
γ-glycidoxypropylmethyldiethoxysilane, 3
-Trimethoxysilylpropyl-N, N-dimethylcarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyltetrasulfide, 3-trimethoxysilylpropyl methacrylate monosulfide and the like.

In the present invention, in particular,

Embedded image [Wherein, n is an integer of 1 to 3, m is an integer of 1 to 9, l is 1
Having a distribution of the above integers]. By using this silane coupling agent, specifically, the trade name “Si69” (manufactured by Degussa, Germany) or the like, the coupling agent efficiency can be further improved. Each of the above-mentioned chain sulfur components (-S
The distribution ratio of _1- ) was determined by high performance liquid chromatography (H
It can be calculated from the peak area (%) determined by the PLC) analysis method.

The amount of the silane coupling agent is 5 to 15% by weight, preferably 5 to 10% by weight, based on the weight of silica. When the amount of the silane coupling agent is less than 5% by weight, the coupling effect is small, while on the other hand, 15% by weight.
Exceeding causes gelation of the polymer, which is not preferable. Further, in the present invention, the unreacted rate of the silane coupling agent is preferably less than 20%. When the unreacted rate of the silane coupling agent is less than 20%, the efficiency of the coupling agent can be improved. The unreacted rate of the silane coupling agent was determined by liquid chromatography.

In the present invention, sodium pyrophosphate / 1
The 0-hydrate [Na ₄ P ₂ O ₇ .10H ₂ O] is blended in order to improve the coupling efficiency of the silane coupling agent. If the amount is less than 3 parts by weight with respect to 100 parts by weight of the rubber component, the effect of the present invention cannot be exerted. If the amount exceeds 15 parts by weight, the reinforcing properties (reduced modulus and abrasion resistance) deteriorate, Flown will also occur,
Not preferred. In the present invention, as shown in the following reaction formula,

Embedded image Water portion of sodium pyrophosphate hydrate [10H ₂ O]
There the -OCH ₃ silane coupling agent hydrolyzed to -
When OH is reacted with silica, the coupling efficiency is improved. Since the sodium pyrophosphate hydrate of the present invention is a decahydrate, this reaction occurs efficiently, and the coupling agent efficiency is improved.

As the rubber component used in the present invention, natural rubber (NR) or synthetic rubber can be used alone or by blending them. Examples of the synthetic rubber include synthetic polyisobrene rubber and polybutadiene rubber (B
R), styrene butadiene rubber (SBR), butyl rubber, butyl halide and the like.

In the rubber composition of the present invention, in addition to the above rubber component, silica, a silane coupling agent, and sodium pyrophosphate decahydrate, if necessary, carbon black as a reinforcing filler may be used. Chemicals ordinarily used in the rubber industry, such as a softening agent, an antioxidant, a vulcanizing agent, a vulcanization accelerator, and a vulcanization accelerator may be appropriately compounded.
In the present invention, the above-mentioned sodium pyrophosphate hydrate, silica, and a silane coupling agent are blended together with other chemicals during non-pro kneading.

The carbon black that can be used as the reinforcing filler is SAF, ISAF,
HAF grades can be preferably used, but are not particularly limited. The compounding amount of carbon black is preferably 80 parts by weight or less based on 100 parts by weight of the rubber component. 8 carbon black
If the amount is more than 0 parts by weight, the low heat build-up will be significantly deteriorated. The amount is preferably 40 to 60 parts by weight from the viewpoint of reinforcing properties and low heat generation.

The rubber composition of the present invention is particularly suitable for uses such as treads of tires, but it can be applied to all other uses of ordinary rubber compositions such as conveyor belts and hoses. It is.

[0019]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[Examples 1 to 4 and Comparative Examples 1 to 4] (Study on Coupling Efficiency of Silane Coupling Agent) A rubber composition was prepared at the compounding ratio shown in Table 1 below, and measured by the following measuring method. And the unreacted rate of the silane coupling agent was calculated. The results are shown in Table 1 below.

(Measurement Method of Unreacted Rate) The unreacted rate was calculated from the ratio of the peak area of the extracted unreacted Si69 using liquid phase chromatography. Specifically, unreacted Si69 was extracted with acetone from the unvulcanized rubber composition kneaded with the composition shown in Table 1 below, and its peak area was measured by liquid phase chromatography. The ratio to the peak area was calculated by the same method as described above.

[0022]

[Table 1]

(Consideration of Table 1) As is apparent from the results of Table 1, the rubber compositions containing silica and the silane coupling agent of Examples 1 to 4 which fall within the scope of the present invention were prepared using sodium pyrophosphate / 10 water Japanese [Na ₄ P ₂ O ₇・ 10H
₂ O] was found to improve the coupling efficiency as compared with those of Comparative Examples 1 and 2 not containing sodium pyrophosphate decahydrate. On the other hand, in Comparative Examples 3 and 4, which were added excessively, there was no further improvement in the coupling efficiency.

Examples 5 to 8 and Comparative Examples 5 to 8 Rubber compositions were prepared at the compounding ratios shown in Table 2 below, and Mooney viscosity (ML _{1 + 4} ), M300
(300% tensile elongation stress) and tan δ at 60 ° C. [hysteresis loss characteristics (exothermic)] were measured.

(1) Mooney viscosity (ML _{1 + 4} ) According to JIS K6301, preheating 1 minute, measurement 4 minutes,
It was measured at a temperature of 130 ° C. and expressed as an index relative to the control. The smaller the index value, the lower the Mooney viscosity and the better the processability.

(2) M300 (300% tensile elongation stress) Measured in accordance with JIS K6301-1995.
The larger the index value, the better the tensile stress.

(3) 60 ° C. tan δ [hysteresis loss characteristic (exothermic)] The internal loss (tan δ) was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Co., Ltd., with a tensile strain of 1%, a frequency of 50 Hz and a frequency of 60 Hz. It was measured under the condition of ° C. The test piece was a slab sheet having a thickness of about 2 mm, a width of 5 mm, and a length of 4 cm.
0 g. The smaller the index value, the smaller the steresis loss and the lower the heat generation.

[0028]

[Table 2]

(Consideration of Table 2) As is evident from the results of Table 2, the rubber compositions containing silica and the silane coupling agent of Examples 5 to 8 which fall within the scope of the present invention were prepared by adding sodium pyrophosphate / 10 water Japanese [Na ₄ P ₂ O ₇・ 10H
_The rubber composition containing ₂ O] had a Mooney viscosity (ML _{1 + 4} ) and M300 (300%) which were lower than those of the rubber compositions of Comparative Examples 5 and 6 not containing sodium pyrophosphate decahydrate.
It was found that the tensile stress (elongation during elongation) and tan δ at 60 ° C. [hysteresis loss characteristics (heat generation)] were excellent. Also,
It was found that when combined with the coupling efficiency equivalent to the current one, the silane coupling agent can be reduced, leading to a cost reduction. However, in Comparative Examples 7 and 8 in which sodium pyrophosphate sodium hydrate was excessively added, it was found that the Mooney viscosity increased and the effect of improving M300 could not be expected.

[0030]

According to the present invention, there is provided a rubber composition capable of improving the coupling efficiency of a silane coupling agent and improving the physical properties of a vulcanized rubber without increasing the cost.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 7/00 C08L 7/00

Claims (6)

[Claims] 1. A rubber composition containing silica and a silane coupling agent, wherein 3 to 15 parts by weight of sodium pyrophosphate decahydrate is added to 100 parts by weight of a rubber component composed of natural rubber and / or synthetic rubber. A rubber composition characterized by being compounded. 2. The rubber composition according to claim 1, wherein the amount of the silica is 10 to 100 parts by weight based on 100 parts by weight of the rubber component. 3. The rubber composition according to claim 1, wherein the amount of the silica is 20 to 100 parts by weight based on 100 parts by weight of the rubber component. 4. The rubber composition according to claim 1, wherein the amount of the silica is 30 to 100 parts by weight based on 100 parts by weight of the rubber component. 5. The rubber composition according to claim 2, wherein the amount of the silane coupling agent is 5 to 15% by weight based on the amount of the silica. 6. The unreacted rate of the silane coupling agent is 20.
The rubber composition according to any one of claims 1 to 5, which is less than 10%.