JP2019026758A - Rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the ratio of recycled material in a raw material while improving processability and vulcanized physical characteristics in a rubber composition for a tire using recycled rubber recovered by recycling from waste rubber products. A rubber composition for a tire is provided. SOLUTION: The nitrogen adsorption specific surface area is 30 m2 / g to 80 m2 / g with respect to 100 parts by mass of diene rubber composed of 30 parts by mass to 70 parts by mass of isoprene rubber and 30 parts by mass to 70 parts by mass of butadiene rubber. 30 parts by mass to 70 parts by mass of carbon black, 5 parts to 25 parts by mass of powder recycled rubber, 5 parts by mass to 25 parts by mass of modified recycled rubber functionalized with a thiuram sulfide compound, and sulfur. Is blended so that the pure sulfur content is 0.8 parts by mass to 1.6 parts by mass. [Selection diagram] None

Description

  The present invention relates to a tire rubber composition using recycled rubber recovered from waste rubber products by recycling.

  In recent years, from the viewpoint of environmental protection and cost reduction, a part of used rubber products (waste rubber products) such as tires has been processed into recycled rubber by, for example, pulverization, etc., and this is blended with new rubber and recycled. It is being used. However, since such recycled rubber has inferior physical properties after vulcanization compared to the new rubber, the physical properties after vulcanization of the rubber composition containing the recycled rubber also deteriorated, and it is not practically used. There was a problem of being restricted. In addition, since the physical properties after vulcanization are lowered by recycled rubber, it is difficult to increase the ratio of recycled material in the raw material (the ratio of recycled rubber), and there is a problem that the effect of reducing environmental load is limited.

  For such problems, for example, after the above-mentioned pulverization treatment, desulfurization treatment or functionalization treatment is performed to increase the reactivity of the recycled rubber itself to improve the rubber physical properties after vulcanization. (For example, refer to Patent Document 1). However, even a rubber composition containing a recycled rubber that has undergone such treatment does not provide sufficient physical properties such as elongation at break. For example, when used in pneumatic tires, the workability and vulcanized physical properties There was a problem that performance such as the above could not be obtained sufficiently. For this reason, in rubber compositions using recycled rubber recovered from waste rubber products by recycling, further improvements have been demanded that increase the ratio of recycled materials in raw materials while improving processability and vulcanized physical properties.

Japanese Unexamined Patent Publication No. 2015-212377

  An object of the present invention is a rubber composition for tires using recycled rubber recovered from waste rubber products by recycling, and increases the ratio of recycled materials in raw materials while improving processability and vulcanization physical properties. An object of the present invention is to provide a tire rubber composition that is made possible.

The rubber composition for a tire of the present invention that achieves the above-mentioned object has a nitrogen adsorption ratio with respect to 100 parts by mass of a diene rubber comprising 30 parts by mass to 70 parts by mass of isoprene-based rubber and 30 parts by mass to 70 parts by mass of butadiene rubber. surface area of 30m ² / g~80m ² / g 30 parts by 70 weight parts of carbon black is 5 parts by weight to 25 parts by weight of the powder reclaimed rubber, a functionalized modified recycled rubber thiuram sulfide-based compound 5 It is characterized by blending 25 parts by mass to 25 parts by mass, and blending sulfur so that the pure sulfur content is 0.8 parts by mass to 1.6 parts by mass.

  The rubber composition for tires of the present invention is mainly composed of isoprene-based rubber and butadiene rubber, and is used in combination with powder regenerated rubber and modified regenerated rubber, and contains the above compounding material. Even with such a rubber composition, processability and vulcanized physical properties can be improved. Moreover, since the processability and vulcanized physical properties are improved by the above-described blending, the blended amount of the recycled rubber can be increased as compared with the conventional one, and the ratio of the recycled material in the raw material can be increased.

  In the present invention, it is preferable that the ratio of the blended amount of the powder recycled rubber and the modified recycled rubber is 1: 1 to 1: 2. Thereby, the balance between the powdered recycled rubber and the modified recycled rubber becomes good, which is advantageous for improving processability and vulcanized physical properties while increasing the ratio of recycled material in the raw material (recycled rubber ratio).

  In the present invention, it is preferable that the particle diameter of the powder recycled rubber is 80 mesh or more. This is advantageous for improving processability and vulcanization properties while increasing the ratio of recycled material in the raw material (recycled rubber ratio). In the present invention, the particle diameter of the recycled powder rubber is measured according to JIS K6220. In the present invention, “the particle size is 80 mesh or more” means that 70% by mass or more of the powder recycled rubber is a particle size capable of passing through 80 mesh, and may be a ratio of less than 30% by mass. In other words, it is allowed to include those outside the above particle size range.

  The tire rubber composition of the present invention is preferably used for a sidewall portion of a pneumatic tire, and the pneumatic tire using the tire rubber composition of the present invention for a sidewall portion is recycled rubber in the rubber composition. Even if it is included, excellent running performance equivalent to a conventional pneumatic tire using only a new rubber can be exhibited.

  In the rubber composition for tires of the present invention, the rubber component is a diene rubber and necessarily includes isoprene rubber and butadiene rubber. Examples of the isoprene-based rubber include various natural rubbers, epoxidized natural rubber, and various synthetic polyisoprene rubbers. As the isoprene-based rubber and butadiene rubber, rubbers usually used in tire rubber compositions can be used. These compounding amounts are 30 parts by mass to 70 parts by mass of isoprene-based rubber, 30 parts by mass to 70 parts by mass of butadiene rubber, and preferably 30 parts by mass of isoprene-based rubber when the whole diene rubber is 100 parts by mass. 50 parts by mass and 50 parts by mass to 70 parts by mass of butadiene rubber. If the blending amount of these rubbers is out of the above range, the desired effect of the present invention cannot be obtained sufficiently. In particular, in the present invention, since the recycled rubber described later is blended, the influence of the blending amount of the isoprene-based rubber is large, and when the blending amount of the isoprene-based rubber exceeds 70 parts by mass, the viscosity of the rubber composition is lowered.

  The rubber composition for tires of the present invention may contain a diene rubber other than isoprene rubber and butadiene rubber. Examples of other diene rubbers include styrene-butadiene rubber and acrylonitrile-butadiene rubber. These diene rubbers can be used alone or as any blend.

  The rubber composition for tires of the present invention always contains carbon black. By blending carbon black, the strength of the rubber composition can be increased. The compounding quantity of carbon black is 30 mass parts-70 mass parts with respect to 100 mass parts of diene rubbers, Preferably it is 40 mass parts-60 mass parts. If the blending amount of carbon black is less than 30 parts by mass, the effect of improving the mechanical properties of the rubber composition cannot be obtained sufficiently. When the compounding amount of the carbon black exceeds 70 parts by mass, the exothermic property of the rubber composition is increased, and the rolling resistance is increased when the tire is formed.

Carbon black used in the present invention, the nitrogen adsorption specific surface area N ₂ SA is 30m ² / g~80m ² / g, preferably 40m ² / g~60m ² / g. When the nitrogen adsorption specific surface area N ₂ SA of carbon black is less than 30 m ² / g, mechanical properties such as strength and hardness of the rubber composition are lowered. When the nitrogen adsorption specific surface area N ₂ SA of carbon black exceeds 80 m ² / g, tan δ at 60 ° C. (hereinafter referred to as tan δ (60 ° C.)) of the rubber composition increases. In the present invention, the nitrogen adsorption specific surface area N ₂ SA of carbon black is measured according to JIS K6217-2.

  The rubber composition for tires of the present invention always contains sulfur as a vulcanizing agent. The compounding amount of sulfur is such that the pure sulfur content is 0.8 to 1.6 parts by mass, preferably 1.2 to 1.5 parts by mass with respect to 100 parts by mass of the diene rubber. . If the amount of sulfur is out of the above range, the desired effect of the present invention cannot be obtained sufficiently. In particular, in the present invention, since the reclaimed rubber described later is blended, the influence of the blending amount of sulfur is large, and when the blending amount of sulfur (pure sulfur content) is less than 0.8 parts by mass, the hardness of the rubber composition When the amount of sulfur (pure sulfur content) exceeds 1.6 parts by mass, the elongation at break decreases.

  The rubber composition for tires of the present invention always contains powder recycled rubber and modified recycled rubber. In the present invention, “powder recycled rubber” is a rubber material obtained by pulverizing a part of a used rubber product (waste rubber product) such as a tire, and a modification treatment such as desulfurization treatment or functionalization is performed. It has not been applied. This powder recycled rubber is not highly reactive like desulfurized recycled rubber and modified modified rubber, which will be described later. It is an advantageous material for improving (for example, elongation at break). In the present invention, “modified reclaimed rubber” refers to a part of used rubber products (waste rubber products) such as tires that is pulverized, desulfurized, and then functionalized with a thiuram sulfide compound. This is a rubber material obtained. This modified reclaimed rubber has increased reactivity due to the desulfurization and functionalization of a part of the cross-linked structure in the rubber, resulting in a decrease in hardness, exothermic deterioration, which is a concern when using reclaimed materials, It is an advantageous material for improving problems such as an increase in viscosity of unvulcanized rubber. The thiuram sulfide compounds used for functionalization of the modified recycled rubber include alkyl thiuram sulfide, aryl thiuram sulfide, heterocyclic thiuram sulfide, thiuram disulfide, thiuram polysulfide, tetrabenzyl thiuram disulfide, tetraalkyl thiuram disulfide, tetramethyl. Examples include thiuram disulfide, tetraethylthiuram disulfide, dipentamethylthiuram monosulfide and the like. By using the above-mentioned powder recycled rubber and modified recycled rubber in combination, processability and vulcanized physical properties can be improved even with a rubber composition blended with recycled rubber.

  The compounding amount of the powder recycled rubber is 5 to 25 parts by mass, preferably 10 to 20 parts by mass with respect to 100 parts by mass of the diene rubber. If the blended amount of the powder recycled rubber is less than 5 parts by mass, the physical properties (elongation at break) of the rubber composition are deteriorated. When the blending amount of the powdered recycled rubber exceeds 25 parts by mass, the physical properties (viscosity, hardness, elongation at break, exothermic property) of the rubber composition are deteriorated. The amount of the modified recycled rubber is 5 to 25 parts by mass, preferably 10 to 20 parts by mass with respect to 100 parts by mass of the diene rubber. If the amount of the modified recycled rubber is less than 5 parts by mass, the physical properties (viscosity) of the rubber composition will deteriorate. When the amount of the modified recycled rubber exceeds 25 parts by mass, the physical properties (viscosity, hardness, elongation at break, exothermic property) of the rubber composition are deteriorated.

  By blending a large amount of powdered recycled rubber and modified recycled rubber, the ratio of recycled material in the raw material can be increased, which is advantageous for reducing the environmental burden. Therefore, the total amount of powdered recycled rubber and modified recycled rubber (sum of blended amounts) is preferably 20 parts by mass or more, more preferably 20 parts by mass to 40 parts by mass with respect to 100 parts by mass of the diene rubber. In the conventional rubber composition for tires containing recycled rubber, the amount of recycled rubber is about 10 parts by mass with respect to 100 parts by mass of the diene rubber as the main component of the rubber composition for tires. The recycled material ratio can be greatly increased. If the blended amount of both the powdered recycled rubber and the modified recycled rubber is large and the total amount exceeds 55 parts by mass, the effect of improving the rubber physical properties is limited, and the viscosity, hardness, elongation at break, and exothermicity are reduced.

  Furthermore, the ratio of the blended amount of powder recycled rubber and modified recycled rubber (powder recycled rubber: modified recycled rubber) is preferably 1: 1 to 1: 2, more preferably 1: 1 to 1: 1.5. Good. Thereby, the balance between the powdered recycled rubber and the modified recycled rubber becomes good, which is advantageous for improving processability and vulcanized physical properties while increasing the ratio of recycled material in the raw material (recycled rubber ratio). If the ratio of the blended amount of the powdered recycled rubber and the modified recycled rubber is out of the above range and the blended amount of the powdered recycled rubber is too large relative to the modified recycled rubber, the effect of improving the rubber properties will be limited and the viscosity will be reduced. When the blended amount of the modified recycled rubber is too large relative to the powder recycled rubber, the effect of improving the rubber properties is limited, and the elongation at break decreases.

  The powder recycled rubber used in the present invention preferably has a small particle size. In particular, the particle diameter of the powder recycled rubber is preferably 80 mesh or more, more preferably 100 mesh to 140 mesh. This is advantageous for improving processability and vulcanization properties while increasing the ratio of recycled material in the raw material (recycled rubber ratio). If the particle size of the powder recycled rubber is less than 80 mesh, the particle size is too large and the effect of improving the breaking elongation is limited. The modified recycled rubber is a material that is processed into a sheet shape or a plate shape after the above-described modification treatment, so that the particle size is not considered as in the case of the powder recycled rubber.

  Other compounding agents other than those described above can be added to the rubber composition for tires of the present invention. Other compounding agents include generally reinforcing fillers other than carbon black, vulcanization or crosslinking agents, vulcanization accelerators, anti-aging agents, liquid polymers, thermosetting resins, thermoplastic resins, etc. Various compounding agents used for the tires can be exemplified. The compounding amounts of these compounding agents can be conventional conventional compounding amounts as long as they do not contradict the purpose of the present invention. Moreover, as a kneading machine, a normal rubber kneading machine, for example, a Banbury mixer, a kneader, a roll or the like can be used.

  The rubber composition for tires of the present invention can be suitably used for a sidewall portion of a pneumatic tire. Since the rubber composition for tires of the present invention has good processability and vulcanized physical properties as described above, a pneumatic tire using the rubber composition for tires of the present invention for the sidewall portion is included in the rubber composition. Even if recycled rubber is included in the tire, it is possible to exhibit excellent running performance equivalent to a conventional pneumatic tire using only a new rubber.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  21 types of tire rubber compositions (standard example 1, comparative examples 1 to 9, and examples 1 to 11) having the formulations shown in Tables 1 and 2 were weighed, except for the vulcanization accelerator and sulfur. The mixture was kneaded for 5 minutes with a 1.8 L closed Banbury mixer, and the master batch was discharged at a temperature of 150 ° C. and cooled to room temperature. Thereafter, this master batch was subjected to a 1.8 L closed Banbury mixer, a vulcanization accelerator and sulfur were added and mixed for 2 minutes to prepare a tire rubber composition. Next, the obtained rubber composition for tire was press-vulcanized at 160 ° C. for 20 minutes in a predetermined mold to prepare a vulcanized rubber test piece.

  The obtained 21 kinds of tire rubber compositions were evaluated for viscosity, hardness, elongation at break, and tan δ (60 ° C.) by the following methods.

Viscosity The Mooney viscosity of the obtained rubber composition for tires is based on JIS K6300, using a Mooney viscometer with an L-shaped rotor (38.1 mm diameter, 5.5 mm thickness), preheating time 1 minute, The measurement was performed under the conditions of a rotation time of 4 minutes, 100 ° C., and 2 rpm. The obtained results are shown in the column of “Viscosity” in Tables 1 and 2 as an index with the value of Standard Example 1 being 100. A smaller index value means smaller viscosity and better processability.

Hardness Using the obtained test piece, the rubber hardness at a temperature of 20 ° C. was measured with a durometer type A according to JIS K6253. The obtained results are shown in the column of “Hardness” in Tables 1 and 2 as an index with the value of Standard Example 1 being 100. A larger index value means a higher rubber hardness.

Breaking elongation A JIS No. 3 dumbbell-shaped test piece (thickness 2 mm) was cut out from the obtained test piece in accordance with JIS K6251. It measured on condition of / min. The obtained results are shown in the column of “Elongation at Break” in Tables 1 and 2 as an index with the value of Standard Example 1 being 100. A larger index value means a higher tensile elongation at break.

Tan δ at 60 ° C
Based on JIS K6394, the obtained test piece was subjected to a loss tangent tan δ at a temperature of 60 ° C. under the conditions of an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho. It was measured. The obtained tan δ results are shown in the column of “tan δ (60 ° C.)” in Tables 1 and 2 as an index with the value of Standard Example 1 being 100. A smaller index value means less heat generation.

The types of raw materials used in Tables 1 and 2 are shown below.
・ NR: Natural rubber, STR20
-BR: Butadiene rubber, Nippon Zeon Corporation Nipol BR 1220
CB1: carbon black, show black N550 manufactured by Cabot Japan (nitrogen adsorption specific surface area N ₂ SA: 42 m ² / g)
CB2: carbon black, show black N339 manufactured by Cabot Japan (nitrogen adsorption specific surface area N ₂ SA: 88 m ² / g)
-Modified recycled rubber: EkoDyne manufactured by Lehigh, modified recycled rubber functionalized with tetrabenzylthiuram sulfide-Powdered recycled rubber 1: GF-80 REPROCESSED GROUND RUBBER manufactured by Lehigh (particle size: 80 mesh)
・ Powder reclaimed rubber 2: manufactured by Lehigh 140 MESH GROUND RUBBER (particle size: 140 mesh)
・ Oil: Showa Shell Sekiyu Extract 4 S
・ Stearic acid: Stearic acid 50S manufactured by Nisshin Rika Co., Ltd.
・ Zinc oxide: 3 types of zinc oxide manufactured by Shodo Chemical Industries, Ltd. ・ Anti-aging agent: VULKANOX 4020 manufactured by LANXESS
・ Wax: Nippon Seiwa Co., Ltd. OZOACE-0015A
・ Sulfur: Oil treatment sulfur manufactured by Hosoi Chemical Co., Ltd. (sulfur content: 95%)
・ Vulcanization accelerator: Nouchira CZ-G manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

  As is clear from Tables 1 and 2, the rubber compositions for tires of Examples 1 to 13 improved the viscosity, hardness, elongation at break, and tan δ (exothermic property) at 60 ° C. in a well-balanced manner with respect to Standard Example 1.

On the other hand, since the rubber composition for tires of Comparative Example 1 contains a modified recycled rubber alone as a recycled rubber, the elongation at break decreased. In the rubber composition for tires of Comparative Example 2, although the particle diameter of the powder recycled rubber was 140 mesh, the viscosity was deteriorated because the powder recycled rubber was blended alone as the recycled rubber. In the tire rubber composition of Comparative Example 3, since the blended amount of the powdered recycled rubber was too large, the viscosity, hardness, elongation at break, and tan δ (exothermic property) at 60 ° C. deteriorated. In the tire rubber composition of Comparative Example 4, since the blended amounts of the powdered recycled rubber and the modified recycled rubber were too large, the viscosity, hardness, elongation at break, and tan δ (exothermic property) at 60 ° C. deteriorated. In the rubber composition for tires of Comparative Example 5, the viscosity was deteriorated because the blending amount of natural rubber was too large (the blending amount of butadiene rubber was too small). In the rubber composition for tires of Comparative Example 6, the elongation at break and tan δ were deteriorated because the blending amount of butadiene rubber was too large (the blending amount of natural rubber was too small). In the tire rubber composition of Comparative Example 7, the tan δ deteriorated because the nitrogen adsorption specific surface area N ₂ SA of the carbon black was too large. Since the rubber composition for tires of Comparative Example 8 contained too little sulfur, the elongation at break deteriorated. Since the rubber composition for tires of Comparative Example 9 contained too much sulfur, the hardness and tan δ (exothermic property) at 60 ° C. deteriorated.

Claims (4)

For 100 parts by mass of diene rubber comprising 30 parts by mass to 70 parts by mass of isoprene-based rubber and 30 parts by mass to 70 parts by mass of butadiene rubber,
Nitrogen adsorption specific surface area of 30m ² / g~80m ² / g 30 parts by 70 weight parts of carbon black is 5 parts by weight to 25 parts by weight of powder recycled rubber, modified reproduction functionalized with thiuram sulfide-based compound A rubber composition for tires, wherein 5 to 25 parts by mass of rubber is blended and sulfur is blended so that a pure sulfur content is 0.8 to 1.6 parts by mass.   2. The tire rubber composition according to claim 1, wherein the ratio of the blended amount of the powder recycled rubber and the modified recycled rubber is 1: 1 to 1: 2.   The tire rubber composition according to claim 1 or 2, wherein the particle diameter of the powdered recycled rubber is 80 mesh or more.   A pneumatic tire, wherein the tire rubber composition according to any one of claims 1 to 3 is used for a sidewall portion.