JP3103153B2 - Rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition having improved reinforcing properties, particularly abrasion resistance and low heat build-up, used for tires, hoses, conveyor belts and the like.

[0002]

2. Description of the Related Art Rubber compositions, such as truck and bus tires, which require extremely high durability and low heat generation,
Conventionally, carbon black having high reinforcement such as ISAF has been used. It has been recognized that carbon black is excellent in abrasion resistance as a filler. When the amount is increased, the exothermicity deteriorates. In recent years, as the demand for economic efficiency in the market has increased, obtaining low heat generation and fuel efficiency has become an important point in determining the commercial value.

[0003] For this reason, there has been a limit in using carbon black alone as a filler. For this reason, as a method of improving the low heat buildup conventionally used, the amount of carbon black is reduced, and the amount of silica is increased, for example, the amount of silica is increased.

[0004] Reinforcing the filler with rubber has a structure developed with fine particles having high surface activity such as reinforcing carbon black. Since the interfacial adhesive force between the particle surface and rubber is large, the tension sharing applied to the molecular chain is carried out. Can be averaged microscopically, but for fillers with low surface activity, before taking on the tension share for stress averaging,
It causes interfacial failure between the particle surface and rubber molecules and does not show a reinforcing effect.

[0005] The adhesion of rubber molecules to the particle surface and also the chemical bonding have an advantageous effect on reinforcement of tensile stress, tear strength, abrasion resistance and the like. Chemical bonding with rubber molecules on the particle surface is an important factor, and sufficient consideration must be given to the presence and type of functional groups involved in such chemical bonding on the particle surface.

It is known that the surface of carbon black particles has a functional group that causes a chemical bond with rubber molecules, and many studies have revealed that carboxyl, hydroxyl, ketone, ester, and aldehyde groups are present. And so on. Has been confirmed.

[0007] Silanol groups have a problem of poor wettability with rubber molecules and poor dispersing effect due to -OH groups having hydrophilicity. Therefore, so-called silane coupling such as γ-mercaptopropyltrimethoxysilane is problematic. Due to the agent, one end of the molecular chain is bonded to the silanol group of the silica particles by a condensation reaction by hydrolysis of the trimethoxysilane group, that is, bonded to the silica surface, and the other terminal is mechanically cut during kneading. The functional group (-SH) reacts with the elastomer radical of the produced rubber, and the remaining hydrogen radical is terminated and stabilized by the elastomer radical. It is known that the so-called bound rubber which is insoluble in a solvent such as benzene around the silane particles is increased by 1.5 times as compared with the case where no silane is added. It is known that such a rubber layer has a so-called dense structure having a higher density than an uncrosslinked rubber molecule portion which is easy to move.

However, even when such a silane coupling agent is used in combination with silica to improve the reinforcing property of silica, the effect of the silane coupling agent is limited by the effect of aluminum, which is an impurity in silica. descend.
In addition, there is a group in which two -OH are added to Si, which is also one of the causes of a decrease in coupling efficiency. Therefore, there is a problem that the use of a silane coupling agent in combination with silica does not reach the reinforcing property of carbon black.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to replace a part of carbon black blended with natural rubber and / or a diene-based synthetic rubber with silica to reduce heat build-up and to use a filler made of only carbon black. An object of the present invention is to provide a rubber composition for tires, conveyor belts, and the like, which has at least the same abrasion resistance as the case.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that silica is effectively combined with a silane coupling agent and especially a silylating agent. They have found that they can be solved and have completed this invention.

That is, according to the present invention, 10 to 60 parts by weight of carbon black, 5 to 50 parts by weight of silica, and a silane coupling agent are added in an amount of 2 to 15 parts by weight based on 100 parts by weight of natural rubber and / or diene synthetic rubber. It is a rubber composition obtained by compounding and kneading a silylating agent in an amount of 2 to 45% by weight of a silica compounding amount.

[0012] The rubber composition according to the above item, wherein the silylating agent is at least one selected from the group consisting of compounds represented by the following chemical formulas: [formula 2] [formula 3] and [formula 4]. .

The silica is 25 to 35 parts by weight, and the silane coupling agent is the following chemical formula [Chemical Formula 5] [Chemical Formula 6] (where R is a methyl group or an ethyl group, n is an integer of 1 to 8, and m is 1 to 5).
An integer of 6, X is a mercapto group or an amino group),
The rubber composition according to the preceding item, which is at least one member selected from the group consisting of [Chemical formula 7] and [Chemical formula 8].

In the present invention, as the rubber component, natural rubber or synthetic rubber can be used alone or by blending them. Examples of the synthetic rubber include synthetic polyisoprene rubber, polybutadiene rubber, and styrene butadiene rubber. As carbon black, I
SAF, HAF and the like can be preferably used, but are not particularly limited. As silica, synthetic finely divided anhydrous silicic acid can be preferably used, but is not particularly limited.

[0015] A large number of silanol groups are present on the silica surface, although the degree varies depending on the type. Silanol group is hydrophilic, poor wettability with rubber as described above,
Interaction with rubber is weak. As described above, the role of the silane coupling agent is to act on both the silanol group and the rubber polymer to improve the reinforcing property. However, this silane coupling agent does not contain aluminum, which is an impurity in silica. This is also one of the causes of the decrease in the coupling efficiency.

The silylating agent of the present invention converts the terminal -OH, which lowers the coupling efficiency, into the form of Si-OR by the following reaction.

Embedded image

Embedded image This reaction modifies the silica surface that has been hydrophilic. When the silane coupling agent shown in [Chemical formula 6] or [Chemical formula 7] or [Chemical formula 8] is used, there is a particularly synergistic effect. Heat generation can be made lower than when black is filled alone, and abrasion resistance equal to or more than that when carbon black is filled alone can be maintained.

If the amount of carbon black is less than 10 parts by weight, the reinforcing effect is not sufficient, and if it exceeds 60 parts by weight, not only high heat generation but also abrasion resistance is reduced.
When the amount of silica used is less than 5 parts by weight, the merit of low heat generation due to substitution is small, and when it exceeds 50 parts by weight, workability is deteriorated. Silica is preferably 25 to 35 parts by weight.

When the amount of the silane coupling agent used is less than 2% by weight relative to the weight of silica, the coupling effect is small, and when it exceeds 15% by weight, gelation of the polymer is caused.
When the amount of the silylating agent used is less than 2% by weight with respect to the amount of silica used, the effect of using the silylating agent is not seen, and when it exceeds 45% by weight, the effect of the coupling agent is hindered.

The rubber composition of the present invention contains a compounding agent usually used in the rubber industry, for example, other reinforcing fillers, vulcanizing agents, vulcanization accelerators, antioxidants, softeners and the like. Needless to say, it can be appropriately compounded.

[0020]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. (Rubber physical property measurement method) (1) Abrasion resistance The abrasion resistance index representing abrasion resistance was calculated by the following formula by measuring the amount of abrasion loss using a Lambourn tester. The larger the index, the better the wear resistance.

(2) Exothermicity The tan δ value representing exothermicity was measured by using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd.
The measurement was performed under the conditions of a frequency of 50 Hz and 25 ° C. The test piece was a slab sheet having a thickness of 2 mm and a width of 5 mm, and the initial load was 100 g with the distance between sample sandwiches being 2 cm. Expressed as an index in comparison with the control, the lower the index value, the lower the exothermicity. (Measured values) The measured values of the compositions of Examples and Comparative Examples shown in Tables 1 and 2 are shown in the lower columns of Tables 1 and 2.

[0022]

[Table 1]

[Table 2]

In Tables 1 and 2, * 1 Styrene butadiene copolymer rubber manufactured by Nippon Synthetic Rubber Co., Ltd. * 2 Nipsil AQ manufactured by Nippon Silica Co., Ltd. * 3 Silane coupling agent Si manufactured by Degussa, West Germany
69

Embedded image * 4 Shin-Etsu Chemical Mercaptosilane

Embedded image * 5

Embedded image * 6 N-phenyl-N'-isopropyl-P-phenylenediamine * 7 N-oxydiethylene-2-benzothiazolesulfenamide * 8 Larger is better * 9 Smaller is better

Examples 1 and 2 and Comparative Examples 1 and 2 are SBR
In the compounding of 65 parts by weight of natural rubber and 35 parts by weight of natural rubber, Example 1 contained 3 parts of 45 parts by weight of carbon black of the comparative example.
0 parts were replaced with silica, and a silane coupling agent (based on silica 10%) and a silylating agent (based on silica 30) were used.
%). Example 2 is an example in which a silane coupling agent (3.3% based on silica) and a silylating agent (10% based on silica) were added to Example 1. Comparative Example 1 is an example in which 45 parts by weight of carbon black alone is blended with the same rubber component as in Examples 1 and 2, and no silica, silane coupling agent, or silylating agent is added. Comparative Example 2 is the same as Comparative Example 1, except that 45 parts of carbon black were used.
Example of replacing 30 parts with silica

Example 3 and Comparative Examples 3 and 4 are SBR5
0 parts by weight and 50 parts by weight of natural rubber. In Example 3, 15 parts by weight of carbon black and 30 parts of silica
Parts by weight, silane coupling agent (3.3% of silica),
Example in which a silylating agent (10% of silica) is added. Comparative Example 3 is an example in which the silylating agent was not added in Example 3. Comparative Example 4 is an example in which the silane coupling agent was not added and only the silylating agent (10% of silica) was added in Example 3.

Example 4 and Comparative Example 5 used 15 parts by weight of carbon black and 30 parts by weight of silica in a blend of 35 parts by weight of SBR and 65 parts by weight of natural rubber. Example 4 used a silane coupling agent (15 parts by weight of silica). %) An example in which a silylating agent (16.7% by weight based on silica) is added. Comparative Example 5 is an example in which a silane coupling agent (33.3% by weight with respect to silica, outside the present invention) and a silylating agent (10% by weight with respect to silica) were added.

In Example 5 and Comparative Example 6, 30 parts by weight of SBR and 70 parts by weight of natural rubber were blended. In Example 5, 15 parts by weight of carbon black and 30 parts by weight of silica were used, and a silane coupling agent (based on silica) was used. 3.3
% By weight) An example in which a silylating agent (10% by weight of silica) is added. Comparative Example 6 is an example in which silica was not blended and only carbon black was blended at 45 parts by weight in Example 5. As is clear from Tables 1 and 2, the rubber composition of the present invention has the same or higher abrasion resistance than the comparative example, and has low heat generation. Example 4 and Comparative Example 5 show that when a silane coupling agent is added beyond the range of the present invention, tan δ is reduced, but the abrasion resistance is also deteriorated. Example 5 and Comparative Example 6 show that in Comparative Example 6, when a silane coupling agent or a silylating agent is added without silica, the tan δ decreases, but the abrasion resistance also deteriorates.

[0028]

According to the rubber composition of the present invention, a part of the carbon black compounded in the natural rubber and / or the diene synthetic rubber of the present invention is replaced with silica, and a silane coupling agent and especially a silylating agent are compounded. In the sulphate, abrasion resistance can be reduced to a low heat generation while maintaining the same or higher abrasion resistance as compared with the case where carbon black is blended alone. Therefore, when low fuel efficiency is required in recent years for energy saving, it can greatly contribute to improvement of product performance.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 7/00 C08K 3/04 C08K 3/36 C08K 5/541 C08L 9/00

Claims (3)

(57) [Claims] 1. Carbon black 10 to 60 with respect to 100 parts by weight of natural rubber and / or diene synthetic rubber.
A rubber composition obtained by mixing and kneading parts by weight, 5 to 50 parts by weight of silica, 2 to 15% by weight of a silica compounding amount of a silane coupling agent, and 2 to 45% by weight of a silica compounding amount of a silylating agent. 2. The rubber composition according to claim 1, wherein the silylating agent is at least one member selected from the group consisting of the following compounds [Chemical Formula 1] [Chemical Formula 2] [Chemical Formula 3] and [Chemical Formula 4]. Embedded image Embedded image Embedded image Embedded image 3. Silica is 25 to 35 parts by weight, and the silane coupling agent is a compound represented by the following chemical formula (5) [6] (where R is a methyl group or an ethyl group, n is an integer of 1 to 8, m is 1 to 8). 6
X is a mercapto group or an amino group),
The rubber composition according to claim 2, which is at least one member selected from the group consisting of [Chemical formula 7] and [Chemical formula 8]. Embedded image Embedded image Embedded image Embedded image