JP7058496B2 - Rubber composition - Google Patents

Description

The present invention relates to a rubber composition useful as a raw material for producing a vulcanized rubber capable of maintaining and improving low heat generation while reducing the amount of zinc-containing compound and suppressing thermal deterioration.

In recent years, from the viewpoint of energy saving, fuel-efficient tires have been actively developed in the tire industry, and especially for the development of fuel-efficient tires, the low heat generation performance of the rubber part of the tire tread obtained by vulcanization is used. It is said that improvement is indispensable. In addition, since high durability of tires is also required in the market, for example, even when the tire is aged at a high temperature, the aging resistance is maintained and the tire is thermally deteriorated (thermosetting) even after the aging test. Is required to be suppressed as much as possible.

By the way, in the rubber part such as a tire tread, a vulcanizing agent such as sulfur and a vulcanization accelerator are mixed with a vulcanizing agent such as sulfur as a raw material, and a zinc-containing compound such as zinc oxide is mixed with the rubber composition, and the rubber composition is vulcanized. Manufactured. Of these, metal compounds such as zinc-containing compounds are required to be blended in a reduced amount from the viewpoint of preventing environmental pollution. However, as described in Non-Patent Document 1 below, zinc oxide plays an important role in the vulcanization of rubber, and it is said that if it is lacking, the vulcanization promoting effect is significantly reduced and the vulcanization torque is significantly reduced. ing. Therefore, in reality, metal compounds such as zinc oxide are used as essential materials in the vulcanization of rubber compositions.

The following Patent Document 1 describes a rubber composition for the purpose of improving various physical characteristics of a tire while reducing the amount of zinc oxide, specifically, the content of zinc oxide is 1.0 part by mass or less, and the content of zinc oxide is 1.0 part by mass or less. A rubber composition containing a specific zinc-containing compound has been described.

Japanese Unexamined Patent Publication No. 2012-466202

Tomoyuki Komatsu, Journal of the Japan Rubber Association, Vol. 82, No. 1 (2009), pp. 33-38

However, as a result of diligent studies by the present inventor, it has been found that the technique described in the above patent document has a large content of zinc-containing compounds, and there is a lot of room for improvement from the viewpoint of preventing environmental pollution. In addition, it was found that there is room for improvement in the effect of suppressing thermal deterioration of the vulcanized rubber as well.

The present invention has been made in view of the above circumstances, and an object thereof is a raw material for producing a vulcanized rubber capable of maintaining and improving low heat generation while reducing the amount of zinc-containing compound and suppressing thermal deterioration. To provide a useful rubber composition.

As a result of diligent studies by the present inventor in order to solve the above-mentioned problems, it has been found that the above-mentioned problems can be solved by designing the blending amount of the zinc-containing compound while blending a specific rubber component. Specifically, the present invention has the following configuration.

That is, in the present invention, when the total amount of the rubber component is 100 parts by mass, the amount of the solution-polymerized polystyrene butadiene rubber having the modified molecular ends is 50 parts by mass or more, and the amount of the zinc-containing compound is 0.5. The present invention relates to a rubber composition characterized by being less than parts by mass.

In the present invention, the solution-polymerized polystyrene butadiene rubber having a modified molecular end is particularly focused on as a rubber component, and the amount of the zinc-containing compound is 0.5 mass by mass while using this as the main component, specifically, 50 parts by mass or more. By the compounding design of less than a part, it is possible to suppress thermal deterioration while maintaining and improving the strength physical properties and low heat generation property of the obtained vulcanized rubber.

In the rubber composition, when the blending amount of the solution-polymerized polystyrene butadiene rubber having a modified molecular end is X parts by mass and the blending amount of the zinc-containing compound is Y parts by mass, X / Y> 50. preferable. In this case, it is preferable because the strength physical properties and low heat generation property of the obtained vulcanized rubber and the heat resistance deterioration property can be maintained and improved at a higher level.

The rubber composition preferably does not contain metal oxides from the viewpoint of preventing environmental pollution.

In the rubber composition according to the present invention, when the total amount of the rubber component is 100 parts by mass, the amount of the solution-polymerized polystyrene butadiene rubber having the modified molecular ends is 50 parts by mass or more, and the amount of the zinc-containing compound is added. The present invention relates to a rubber composition, characterized in that the amount is less than 0.5 parts by mass.

Solution-polymerized polystyrene butadiene rubber (hereinafter, also referred to as "S-SBR") is generally obtained by anionic polymerization of a raw material monomer in a hydrocarbon, and is emulsion polymerization obtained by an emulsion polymerization method (radical polymerization method) in water. Compared to polystyrene-butadiene rubber (hereinafter, also referred to as "E-SBR"), it is characterized in that both the molecular weight distribution and the vinyl amount can be controlled. A particular feature of the present invention is the use of S-SBR (hereinafter, also referred to as "modified S-SBR") in which the molecular end of S-SBR is modified. Examples of the S-SBR having a modified molecular end include an amine-modified S-SBR using a diglycidylamine compound or a cyclic amide compound, and an alkoxy-modified S-SBR using a halogenated alkoxysilane or glycidoxypropylmethoxysilane. Can be mentioned. Among these, it is preferable to use amine-modified S-SBR. In order to maintain and improve the low heat buildup of the obtained vulcanized rubber at a higher level, it is preferable that the microstructure of the butadiene portion of the modified S-SBR has a large amount of vinyl groups, and specifically, the amount of vinyl is 30 to 80. It is preferably by mass, more preferably 50 to 80% by mass. Further, when the total amount of the rubber component is 100 parts by mass, the blending amount of the modified S-SBR is 50 parts by mass or more, preferably 65 parts by mass or more, and more preferably 75 parts by mass or more.

The rubber composition according to the present invention may contain a rubber component other than the modified S-SBR as a rubber component, and in particular, in addition to S-SBR whose molecular end is not modified, E-SBR and natural rubber (NR). ) And at least one of polybutadiene rubber (BR), it is preferable because the WET performance of the vulture rubber can be further improved in fatigue resistance and tear resistance in a well-balanced manner. Examples of the diene-based rubber that may be contained in addition to S-SBR, E-SBR, NR and BR whose molecular ends are not modified include polyisoprene rubber (IR), chloroprene rubber (CR), and nitrile rubber (NBR). Can be mentioned. If necessary, a terminal-modified product (for example, terminal-modified SBR) or a product modified to impart desired characteristics (for example, modified NR) can also be preferably used.

In the present invention, examples of the zinc-containing compound include those known to those skilled in the art, and zinc oxide is typically exemplified. In addition to zinc oxide, compounds containing a zinc atom, compounds containing a zinc atom and a sulfur atom, and the like can be mentioned. As described above, from the viewpoint of preventing environmental pollution and further from the viewpoint of maintaining and improving the low heat generation of the obtained vulcanized rubber, when the total amount of the rubber components is 100 parts by mass, the blending amount of the zinc-containing compound is It is preferably less than 0.5 parts by mass, preferably less than 0.2 parts by mass, and preferably does not contain a zinc-containing compound. Similarly, the blending amount of the metal oxide, particularly zinc oxide, is preferably less than 0.5 parts by mass, preferably less than 0.2 parts by mass, and contains the metal oxide, particularly zinc oxide. It is preferable that there is no such thing.

In the present invention, when the blending amount of the modified S-SBR is X parts by mass and the blending amount of the zinc-containing compound is Y parts by mass, when X / Y> 50, the low heat generation performance of the obtained vulcanized rubber is particularly high. It is preferable because it is excellent. From the viewpoint of low heat generation performance of the vulcanized rubber, X / Y> 100 is preferable, and X / Y> 200 is more preferable.

The rubber composition according to the present invention may contain carbon black as a filler. As the carbon black, for example, in addition to carbon black used in the ordinary rubber industry such as SAF, ISAF, HAF, FEF, and GPF, conductive carbon black such as acetylene black and Ketjen black can be used. When the total amount of the rubber component is 100 parts by mass, the rubber composition according to the present invention preferably contains 1 to 80 parts by mass of carbon black, and more preferably 5 to 60 parts by mass.

It is also preferable to contain silica as a filler. As the silica, wet silica, dry silica, sol-gel silica, surface-treated silica and the like used for ordinary rubber reinforcement are used. Of these, wet silica is preferable. The blending amount of silica is preferably 20 to 120 parts by mass, more preferably 40 to 100 parts by mass, when the total amount of the rubber component is 100 parts by mass.

When silica is contained as a filler, it is also preferable to also contain a silane coupling agent. The silane coupling agent is not particularly limited as long as it contains sulfur in the molecule, and various silane coupling agents blended with silica in the rubber composition can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide (for example, "Si69" manufactured by Degusa), bis (3-triethoxysilylpropyl) disulfide (for example, "Si75" manufactured by Degusa), bis (2-tri). Propylsilanes such as ethoxysilylethyl) tetrasulfide, bis (4-triethylsilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) disulfide, γ-mercaptopropyltri Mercaptosilanes such as methoxysilane, γ-mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane, 3-octanoylthio-1-propyltriethoxysilane, 3-propionylthiopropyltri Protected mercaptosilanes such as methoxysilane can be mentioned. The blending amount of the silane coupling agent is preferably 1 to 20 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of silica.

The rubber composition according to the present invention includes a rubber component containing at least a modified S-SBR, carbon black, silica, a silane coupling agent, a vulcanization compound, an antiaging agent, stearic acid, wax, oil, and the like. Softeners, processing aids, etc. can be blended.

As anti-aging agents, aromatic amine-based anti-aging agents, amine-ketone anti-aging agents, monophenol anti-aging agents, bisphenol anti-aging agents, polyphenol anti-aging agents, dithiocarbamic acid, which are usually used for rubber. Anti-aging agents such as salt-based anti-aging agents and thiourea-based anti-aging agents may be used alone or in admixture. The content of the anti-aging agent is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

Examples of the vulcanization-based compounding agent include vulcanization agents such as sulfur and organic peroxides, vulcanization accelerators, vulcanization acceleration aids, and vulcanization retarders.

The sulfur as the vulcanization-based compounding agent may be ordinary sulfur for rubber, and for example, powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used. Considering the physical characteristics and durability of the rubber after vulcanization, the blending amount of sulfur with respect to 100 parts by mass of the rubber component is preferably 0.1 to 10 parts by mass in terms of sulfur content, and more preferably 1 to 3 parts by mass.

As the vulcanization accelerator, a sulfur amide-based vulcanization accelerator, a thiuram-based vulcanization accelerator, a thiazole-based vulcanization accelerator, a thiourea-based vulcanization accelerator, and a guanidine-based vulcanization agent, which are usually used for rubber vulcanization, are used. A vulcanization accelerator such as an accelerator or a dithiocarbamate-based vulcanization accelerator may be used alone or in combination as appropriate. The blending amount of the vulcanization accelerator with respect to 100 parts by mass of the rubber component is preferably 0.1 to 10 parts by mass.

The rubber composition according to the present invention includes a rubber component containing at least a modified S-SBR, carbon black, silica and a silane coupling agent, as well as a vulcanization compound, an antiaging agent, stearic acid, wax, oil and the like. The softener, processing aid, etc. are obtained by kneading using a kneader used in a normal rubber industry such as a Banbury mixer, a kneader, and a roll.

The compounding method of each of the above components is not particularly limited, and compounding components other than the sulfur-based compounding agent such as a sulfur-based vulcanizing agent and a vulcanization accelerator are kneaded in advance to form a masterbatch, and the remaining components are added. Then, a method of further kneading, a method of adding each component in an arbitrary order and kneading, a method of adding all the components at the same time and kneading, and the like may be used.

Hereinafter, examples and the like that specifically show the configuration and effects of the present invention will be described. As the evaluation items in Examples and the like, the rubber samples obtained by heating each rubber composition at 150 ° C. for 30 minutes and vulcanizing were evaluated based on the following evaluation conditions.

(1) Vulcanization behavior measurement test of unvulcanized rubber composition In the vulcanization behavior measurement test of unvulcanized rubber composition by a leometer, MH- when the maximum value of torque is MH and the minimum value is ML. The ML was calculated. The evaluation was performed by exponential evaluation when MH-ML of Reference Examples 1, 3 and 5 and Comparative Example 1-5 was set to 100 for Reference Examples 2, 4 and 6, respectively, and the numerical values were numerical values. If it is low, it means that sulfur vulcanization of the rubber component has not progressed sufficiently.
(2) Tensile properties of vulcanized rubber (initial)
The sample prepared using the JIS No. 3 dumbbell was measured with 100% modulus M100 (MPa) of the obtained vulcanized rubber in accordance with JIS-K 6251. The evaluation is performed by the exponential evaluation when M100 of Reference Examples 1, 3 and 5 and Comparative Example 1-5 is 100 for Reference Examples 2, 4 and 6, respectively, and when the numerical value is low. , Means that sulfur vulcanization of the rubber component has not progressed sufficiently.
(3) Tensile properties of vulcanized rubber (after aging)
The sample prepared using the JIS No. 3 dumbbell was measured with 100% modulus M100 (MPa) of the obtained vulcanized rubber in accordance with JIS-K 6251. This measurement result was taken as the initial M100. Next, the obtained vulcanized rubber was aged by leaving it at 80 ° C. for 4 days, and then 100% modulus M100 (MPa) was measured. This measurement result was designated as M100 after aging. In general, the vulcanized rubber after the aging test becomes harder than before aging (that is, the M100 after aging increases compared to the initial M100). Therefore, when the measurement result of the initial M100 is 100, after aging. The closer M100 is to 100, the more the thermal deterioration is suppressed. The evaluation was performed when the rate of change from the initial M100 to the post-aging M100 of Reference Examples 1, 3 and 5 and Comparative Example 1-5 was 100 for Reference Examples 2, 4 and 6, respectively. When the value is close to 100, it means that the thermal deterioration of the vulcanized rubber is suppressed.
(4) Low heat generation performance of vulcanized rubber Using a viscoelasticity tester manufactured by Toyo Seiki Seisakusho Co., Ltd., a loss coefficient tan δ was obtained under the conditions of initial strain of 10%, dynamic strain of 1%, frequency of 10 Hz, and temperature of 60 ° C. It was measured. The evaluation is performed by exponential evaluation when tan δ of Reference Examples 1, 3 and 5 and Comparative Example 1-5 is 100 for Reference Examples 2, 4 and 6, respectively, and when the numerical value is low. This means that the obtained vulcanized rubber has excellent low heat generation.

(Preparation of rubber composition)
According to the compounding formulations of Tables 1 and 2, the rubber compositions of Reference Example 1-6, Example 1-5 and Comparative Example 1-5 are blended and kneaded using a normal Banbury mixer to prepare the rubber composition. bottom. The compounding agents shown in Tables 1 and 2 are shown below (in Tables 1 and 2, the compounding amount of each compounding agent is indicated by the number of parts by mass with respect to 100 parts by mass of the rubber component).
a) Rubber component modified S-SBR; JSR's "HPR350" (styrene content 20% by mass, butadiene microstructure; cis content 17% by mass, trans content 27% by mass, vinyl content 56% by mass)
S-SBR; "Tuf2831" manufactured by Asahi Kasei Corporation (styrene content 26% by mass, microstructure of butadiene part; cis content 20% by mass, trans content 28% by mass, vinyl content 52% by mass)
E-SBR; JSR's "SBR1502" (styrene content 26% by mass, butadiene microstructure; cis content 12% by weight, trans content 74% by mass, vinyl content 14% by mass)
NR; "RSS # 3"
BR; "BR150B" manufactured by Ube Kosan Co., Ltd. (sys content 96% by mass)
b) Carbon black (N339); "Seast KH" manufactured by Tokai Carbon Co., Ltd.
c) Silica; "Nip Seal AQ" manufactured by Tosoh Silica
d) Silane coupling agent; "Si69" manufactured by Evonik Degussa
e) Oil; "Process NC-140" manufactured by JX Nippon Oil Energy Co., Ltd.
f) Zinc oxide; "Zinc Hana No. 1" manufactured by Mitsui Mining & Smelting Co., Ltd.
g) Stearic acid; Kao Corporation "Lunac S-20"
h) Anti-aging agent; "Antigen 6C" manufactured by Sumitomo Chemical Co., Ltd.
i) Sulfur; "5% oil-containing fine powder sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd.
j) Vulcanization accelerator

From the results of Reference Example 1-2 in Table 1, the rubber composition containing E-SBR as a main component is obtained because sulfur vulcanization of the rubber component does not proceed sufficiently when zinc oxide is not contained. It can be seen that the tensile properties of the vulcanized rubber are significantly deteriorated, and the low heat generation property is also deteriorated. On the other hand, from the comparison results between Reference Example 3 and Reference Example 4, the rubber composition containing S-SBR as a main component sufficiently promotes sulfur vulcanization of the rubber component even when zinc oxide is not contained. It can be seen that the tensile properties of the obtained vulcanized rubber are also improved. Further, it can be seen that the low heat generation property is improved as compared with the case where zinc oxide is not contained. However, in Reference Example 4, it can be seen that the tensile properties after aging are greatly increased and the thermal deterioration is not suppressed. On the other hand, from the comparison results between Comparative Example 1 and Example 1 and the comparison results between Comparative Example 2 and Example 2, when the modified S-SBR was used, almost no change was observed in the tensile properties after aging, and heat was observed. It can be seen that deterioration is suppressed.

Based on the comparison results between Comparative Example 3 and Example 3 in Table 2, the comparison results between Comparative Example 4 and Example 4, and the comparison results between Comparative Example 5 and Example 5, modified S-SBR was used as the main component. In this case, even in the vulcanized rubber of the rubber composition containing NR, BR or E-SBR, the tensile properties after aging are hardly changed, and it can be seen that the thermal deterioration is suppressed. On the other hand, from the results of Reference Example 5-6, a rubber composition containing no modified S-SBR as a main component can be obtained because sulfur vulcanization of the rubber component does not sufficiently proceed when zinc oxide is not contained. It can be seen that the tensile properties of the vulcanized rubber are significantly deteriorated, and the low heat generation property is also deteriorated.

Claims (3)

When the total amount of the rubber component is 100 parts by mass, the compounding amount of the solution-polymerized polystyrene butadiene rubber having the modified molecular ends is 80 parts by mass or more, and carbon black or silica is contained as a filler, and a vulcanizing agent is contained. , A rubber composition characterized by not containing a zinc-containing compound. Claim 1 is characterized in that X / Y> 50 when the blending amount of the solution-polymerized polystyrene butadiene rubber having a modified molecular end is X parts by mass and the blending amount of the zinc-containing compound is Y parts by mass. The rubber composition according to. The rubber composition according to claim 1 or 2, wherein the rubber composition does not contain a metal oxide.