JP5453736B2 - Rubber composition for tire and method for producing the same - Google Patents

Description

  The present invention relates to a tire rubber composition and a method for producing the same. More specifically, the present invention relates to a tire rubber composition that is suitably used as a tread portion forming material for a studless tire and a method for producing the same.

In the following Patent Document 1, a thermoplastic block copolymer having amorphous styrene blocks at both ends and a low molecular weight material are mixed so that the content of the copolymer is 5 to 30% by weight. A rubber composition comprising a gel composition obtained in this manner and a rubber material is described. This rubber composition can contain a large amount of a plasticizer that is a low molecular material, and a low molecular material. Since the retainability is good, the elastic modulus can be controlled to a very low range, and therefore, it can be applied to various fields using the low elastic modulus.
Japanese Patent Laid-Open No. 8-73697

  The thermoplastic block copolymer having an amorphous styrene block at both ends used here has an amorphous styrene block content of 15 to 70% by weight, preferably 20 to 60% in the thermoplastic block copolymer. In the examples, 21% by weight, 30% by weight, and 35% by weight are used. And it is stated that the rubber composition obtained in each Example is a vulcanized rubber that not only has good processability but also has very little bleeding.

In addition, the present applicant has previously described a styrene-butadiene-styrene ternary block copolymer having a solution viscosity (25 ° C.) of 800 to 2500 cps and a styrene content of 5 to 35% by weight based on 100 parts by weight of a diene rubber. Proposing a rubber composition for a tire tread, which is formulated with a weight part or less, and this rubber composition for a tire tread improves the chip cut resistance of the tire and reduces the sliding resistance of the tire. I find out what I can do.
JP 2000-256509 A

  An object of the present invention is a rubber composition for a tire that is suitably used as a molding material for a tread portion of a studless tire, suppresses bleed such as oil blended as a plasticizer, and has a small change in physical properties over time, particularly a small increase rate of aging hardness. It is to provide a product and a manufacturing method thereof.

  The object of the present invention is to provide (A) two types of styrene-butadiene-styrene triblock having a total styrene content of 15 to 25% by weight and 30 to 50% by weight based on (A) 100 parts by weight of diene rubber. This is achieved by a rubber composition for a tire comprising 1 to 30 parts by weight of a copolymer mixture and (C) a plasticizer in an amount of 0.6 to 20 by weight with respect to the component (B). The rubber composition for a tire is a vulcanizable composition obtained by mixing the components (A), (B) and (C) with a mixer and then mixing sulfur and a vulcanization accelerator with a mixer. Method or (B) component previously absorbed with component (C) is mixed with component (A) with a mixer, and then sulfur and a vulcanization accelerator are mixed with the mixer to obtain a vulcanizable composition. Produced by the method, preferably by the latter method.

  The tire rubber composition according to the present invention has a problem that the conventionally proposed tire rubber composition cannot prevent bleeding such as oil blended as a plasticizer and cannot avoid deterioration in tire performance after the second season. Can be improved effectively. That is, the performance required for the rubber for tires includes little change with time. Factors of change in physical properties over time include oxidation, sulfur re-crosslinking, oil bleed, etc.In the present invention, by blending a triblock copolymer mixture that absorbs a plasticizer such as oil and gels, Suppresses bleeds such as oil and reduces changes in physical properties over time.

  That is, the increase in aging hardness indicated by a decrease in the rate of increase in hardness on ice is suppressed without substantially reducing the exothermic property and rolling resistance indicated by the value of tan δ (60 ° C.). Such an effect greatly depends on the weight ratio of the component (C) to the component (B), and is sufficiently exhibited when the value is 0.6 to 20, preferably 1 to 10.

  In addition, when preparing a rubber composition for a tire, when a method of mixing two kinds of styrene-butadiene-styrene triblock copolymer mixtures in which oil or the like as a plasticizer is preliminarily absorbed is mixed with a diene rubber. The absorption efficiency is increased by preliminarily absorbing the plasticizer in the triblock copolymer mixture, and the effect of further suppressing the change in physical properties over time, particularly the increase in aging hardness, is increased. When such a triblock copolymer mixture is used, for example, oil or the like is used in comparison with a case where only one type of triblock copolymer having a total styrene content of 25 to 30% by weight at both ends is used. The amount of plasticizer absorbed can be increased to several times.

The tire rubber composition of the present invention having such characteristics is suitably used as a tread portion forming material of a studless tire after further mixing sulfur and a vulcanization accelerator .

  As the diene rubber of component (A), natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), nitrile rubber (NBR), styrene butadiene rubber ( SBR) or the like is used alone or as a blend rubber, and preferably NR, BR or a blend rubber thereof is used. As SBR, either emulsion polymerization SBR (E-SBR) or solution polymerization SBR (S-SBR) can be used.

As the styrene-butadiene-styrene triblock copolymer as component (B), two types of mixtures having a total styrene content at both ends of 15 to 25% by weight and 30 to 50% by weight are used. These two types of triblock copolymers block-copolymerized in different proportions are 20-40 wt% of the block copolymer of styrene at both ends in a proportion of 15-25 wt% in the triblock copolymer mixture. %, Or 30 to 50% by weight of styrene copolymerized at both ends is used at a rate of 80 to 60% by weight. Actually, a commercially available product is used as it is as a triblock copolymer mixture, and for example, Alpha Japan product α-Gel 1000 is used as it is.

The number average molecular weight Mn of each styrene-butadiene-styrene triblock copolymer forming the mixture is 1 × 10 ⁴ or more, preferably 5 × 10 ⁴ to 40 × 10 ⁴ . If a material having a smaller Mn is used, the affinity with a plasticizer such as oil becomes higher than necessary, and a gel is not formed, that is, the plasticizer holding ability is weakened.

  Further, as the plasticizer of the component (C), a petroleum softener or a fatty oil softener is used. Process oils such as paraffinic oil, naphthenic oil, and aroma oil are used as petroleum softeners, and castor oil, cottonseed oil, soybean oil, palm oil, peanut oil, sesame oil, rapeseed are used as fatty oil softeners. Oil, palm oil, olive oil, pine oil, wax, etc. are used.

  Each of the above components is 1 to 30 parts by weight, preferably 2 to 20 parts by weight of component (B) per 100 parts by weight of diene rubber of component (A), and component (C) is weight to component (B). The ratio is 0.6 to 20, preferably 1 to 20.

  When the component (B) is used in a proportion higher than this, the exothermic property and rolling resistance indicated by tan δ (60 ° C.) are increased, while the proportion less than this suppresses the increase in aging hardness. The object of the present invention is not fully achieved. Also, if the weight ratio of component (C) / component (B) is smaller than this, the exothermic property will deteriorate, while if larger than this, the plasticizer such as oil cannot be absorbed completely, Is likely to occur.

The diene rubber composition further contains 0.5 to 3 parts by weight, preferably 1 to 2 parts by weight of sulfur as a vulcanizing agent per 100 parts by weight of the diene rubber and thiazole (MBT, MBTS, ZnMBT, etc.), sulfene Amides (CBS, DCBS, BBS, etc.), guanidines (DPG, DOTG, OTBG, etc.), thiurams (TMTD, TMTM, TBzTD, TETD, TBTD, etc.), dithiocarbamates (ZTC, NaBDC, etc.), xanthogenic acid 0.5 to 4 parts by weight, preferably 1 to 2.5 parts by weight of a vulcanization accelerator such as a salt system (ZnBX or the like) is used.

In the tire rubber composition comprising the above components, a compounding agent generally used as a compounding agent for rubber, for example, reinforcing agents or fillers such as talc, clay, graphite, calcium silicate, stearic acid, etc. A processing aid such as zinc oxide, a softening agent, a plasticizer, an anti-aging agent and the like are appropriately blended and used as necessary.

  As carbon black, furnace carbon black such as SAF, ISAF, HAF, FEF, GPF, SRF is generally used, and this is generally 3 to 90 parts by weight, preferably 5 to 70 parts by weight per 100 parts by weight of diene rubber. It is used in the ratio. If the blending ratio of carbon black is less than this, the rigidity required for tires cannot be satisfied. On the other hand, if it is used at a blending ratio higher than this, the heat generation becomes high and the low heat build-up property is impaired. .

Silica generally has a BET specific surface area of 30 to 200 m ² / g, preferably 50 to 150 m ² / g. These include the pyrolysis method of silicon halides or organosilicon compounds, the dry method of silica produced by heat reduction of silica sand and the oxidation of vaporized SiO in air, or the pyrolysis method of sodium silicate. Wet process silica to be produced, etc., and wet process silica is preferably used in terms of cost and performance. Actually, a commercial product marketed for the rubber industry can be used as it is.

  The blending ratio is generally 5 to 20 parts by weight per 100 parts by weight of the diene rubber. If the blending ratio of silica is less than this, the viscosity is lowered and the processability is improved, but the elongation at break is lowered. On the other hand, if the blending ratio is higher than this, the processability elastic modulus is deteriorated. It becomes like this. However, the tire rubber composition of the present invention also has an effect that the decrease in elongation at break is suppressed without using silica generally used in this type of tire rubber composition.

Thus, the properties required of silica and dispersibility with diene rubbers (silica has poor affinity with rubber polymers, and silica in rubber forms hydrogen bonds through silanol groups, and silica is incorporated into rubber. In order to increase (having the property of reducing dispersibility), a silane coupling agent is used in a proportion of 2 to 15% by weight, preferably 5 to 10% by weight, based on the weight of silica. The silane coupling agents, polysulfide silane coupling agent having a sulfur chain which reacts with the alkoxysilyl group and the polymer capable of reacting with silanol groups of the silica surface, such as bis (3-triethoxysilylpropyl) tetrasulfide, bis (2 -Triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide and the like are preferably used. If the proportion of silane coupling agent used is less than this, the properties required of silica and dispersibility with diene rubber will not be fully exhibited, while if it is used in a proportion higher than this, workability will deteriorate. To come.

  The composition was prepared by kneading by a general method using a kneader such as a kneader or a Banbury mixer, or a mixer and an open roll, and the obtained composition was used for the diene rubber, additive, and the like. Vulcanization is carried out at a vulcanization temperature corresponding to the type of the vulcanizing agent and the vulcanization accelerator and the blending ratio thereof to form a tread portion of a studless tire.

  The vulcanizable composition is prepared by mixing components other than sulfur and a vulcanization accelerator, that is, a diene rubber, a triblock copolymer mixture, a plasticizer and other compounding components using a closed Banbury mixer or the like. After releasing these mixtures outside the mixer and cooling to room temperature, using a Banbury mixer, open roll, etc., sulfur, a vulcanization accelerator is blended there, using a Banbury mixer, open roll, etc., In this case, it can be said that using a plasticizer such as oil after having been previously absorbed in the triblock copolymer mixture is a very preferable method for further suppressing an increase in aging hardness.

  Next, the present invention will be described with reference to examples.

Comparative example 1 (standard example 1)
Natural rubber (RSS # 3) 50 parts by weight Butadiene rubber (Nippon Zeon product Nipol BR1220) 50 〃
Carbon black (Tokai carbon product seast 6) 35 〃
Triblock copolymer mixture (Alpha Japan product α-Gel 1000) −
Silica (Nippon Silica Industry Products Nip Seal AQ) 25 〃
Silane coupling agent (Dexa product SI69) 2 〃
Zinc oxide (Zondox chemical products, 3 types of zinc oxide) 4 〃
Stearic acid (Japanese oil and fat product beads stearic acid) 2 〃
Anti-aging agent (Flexis product 6PPD) 2 〃
Aroma oil (Fuji Kosan product aroma oil) 20 〃
Sulfur (Tsurumi Chemical Co., Ltd., Jinhua Indian Oil Fine Powdered Sulfur) 1.5 〃
Vulcanization accelerator (Ouchi Emerging Chemical Industry Noxeller CZ-G) 1.5 〃
Among the above components, the components other than sulfur and the vulcanization accelerator are mixed for 5 minutes using a closed Banbury mixer, and these mixtures are discharged to the outside of the mixer and cooled to room temperature. Using a Banbury mixer, sulfur and a vulcanization accelerator were blended and mixed.

The rubber composition for a vulcanizable tire thus obtained was vulcanized at 170 ° C. for 10 minutes to obtain a predetermined vulcanized rubber specimen, and the obtained vulcanized rubber specimen was subjected to the following items. Measurements were made.
Aging / curing increase rate: Rupke sample is subjected to air heat aging test at 80 ° C for 120 hours
In accordance with JIS K6253, the hardness at 20 ° C before and after the aging test
And calculate the rate of increase in hardness, obtained in Standard Example 1 or Standard Example 2.
Expressed as an index with the obtained value as 100
(The smaller this value, the higher the rate of increase in hardness in the air heating aging test.
Shows that the increase in aging hardness over time is suppressed
There)
Exothermic: JIS K6394 compliant, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, initial
Measure tanδ at 60 ° C under the conditions of distortion 10%, amplitude ± 2%, frequency 20Hz,
Shown as an index with the value obtained in Standard Example 1 or Standard Example 2 as 100
(The smaller this value, the lower the heat generation and the better the rolling resistance.
Is shown)

Comparative Example 2
In Comparative Example 1, 0.5 parts by weight of a triblock copolymer mixture (α-Gel 1000) was further used, and the same measurement was performed.

Example 1
In Comparative Example 1, 2 parts by weight of a triblock copolymer mixture (α-Gel 1000) was further used, and the same measurement was performed.

Example 2
In Comparative Example 1, 10 parts by weight of a triblock copolymer mixture (α-Gel 1000) was further used, and the same measurement was performed.

Example 3
In Comparative Example 1, 20 parts by weight of a triblock copolymer mixture (α-Gel 1000) was further used, and the same measurement was performed.

Comparative Example 3
In Comparative Example 1, 40 parts by weight of a triblock copolymer mixture (α-Gel 1000) was further used, and the same measurement was performed.

Comparative Example 4
In Comparative Example 1, 10 parts by weight of a triblock copolymer (a simple substance having a total styrene content at both ends of 24% by weight; JSR product TR2827) was further used, and the same measurement was performed.

  The measurement results of Comparative Examples 1 and 2, Examples 1 to 3, and Comparative Examples 3 to 4 are shown as indices with the standard example 1 being 100.

Comparative Example 5 (Standard Example 2), Comparative Example 6, Examples 4-6, Comparative Examples 7-8
In Comparative Examples 1-2, Examples 1-3, and Comparative Examples 3-4, the same amount (20 parts by weight) of paraffinic oil (Idemitsu Petrochemical Product PW-380) was used instead of the aroma oil. Measurements were made. The measurement results are shown as an index with standard example 2 as 100.

The measurement results obtained in the above Examples and Comparative Examples are shown in the following Table 1 together with the oil / triblock copolymer mixture weight ratio.
Table 1
Oil / copolymer Aging hardness Exothermic
Example Mixture (weight ratio) increase rate (%) (tanδ)
Comparative Example 1-100 100
〃 2 40 100 100
Example 1 10 92 100
〃 2 2 89 101
〃 3 1 88 103
Comparative Example 3 0.5 88 111
４ 4 2 99 102

Comparative Example 5-100 100
６ 6 40 99 100
Example 4 10 87 101
５ 5 2 81 102
６ 6 1 80 104
Comparative Example 7 0.5 79 113
８ 8 2 98 103

  From the above measurement results, it can be seen that by setting the weight ratio of the oil / triblock copolymer mixture to an appropriate range, although the exothermic property is slightly deteriorated, the increase in aging hardness can be largely suppressed. Such an effect is greater when paraffinic oil is used as a plasticizer than aroma oil. In Comparative Example 3 and Comparative Example 7 in which the weight ratio is 0.5, an increase in aging hardness is greatly suppressed, but exothermic deterioration becomes remarkable.

Comparative Example 9, Examples 7-9, Comparative Examples 10-11
In Comparative Example 2, Examples 1 to 3 and Comparative Examples 3 to 4, the same amount of triblock copolymer mixture (40 to 0.5 parts by weight) and aroma oil (20 parts by weight) were used, respectively. After absorption in the block copolymer mixture, mixing, vulcanization and measurement were performed in the same manner. The measurement results are shown as an index with standard example 1 (comparative example 1) as 100.

Comparative Example 12, Examples 10-12, Comparative Examples 13-14
In Comparative Example 9, Examples 7-9 and Comparative Examples 10-11, the same amount of paraffinic oil (PW-380) was used instead of aroma oil, and the same measurement was performed. The measurement results are shown as an index with standard example 2 (comparative example 5) as 100.

The measurement results obtained in Examples 7 to 12 and Comparative Examples 9 to 14 are the oil / triblock copolymer mixture weight ratio, the oil absorbing triblock copolymer mixture amount (the triblock copolymer mixture amount is It is constant in 20 parts by weight, and the balance is the amount of oil absorbed; The values of Standard Example 1 (Comparative Example 1) and Standard Example 2 (Comparative Example 5) to be compared are also shown.
Table 2
Oil / copolymer Oil-absorbing copolymer Aging hardness Exothermic
Example Mixture (weight ratio) Amount of mixture (parts) Increase rate (%) (tanδ)
Comparative Example 1 − − 100 100
〃 9 40 20.5 99 100
Example 7 10 22 87 99
〃 8 2 30 79 100
〃 9 1 40 75 103
Comparative Example 10 0.5 60 74 110
〃 11 2 30 97 101

Comparative Example 5 − − 100 100
〃 12 40 20.5 98 100
Example 10 10 22 82 101
〃 11 2 30 71 101
〃 12 1 40 67 103
Comparative Example 13 0.5 60 66 112
〃 14 2 30 96 102

  From the above results, the same effect as in Table 1 can be pointed out, and it can be seen that the effect of suppressing the increase in aging hardness is further improved.

Claims (7)

  (A) per 100 parts by weight of diene rubber, (B) two styrene-butadiene-styrene triblock copolymer mixtures having a total styrene content of 15 to 25% by weight and 30 to 50% by weight of both ends, 1 to 30 A rubber composition for tires comprising a weight part and (C) a plasticizer in an amount of 0.6 to 20 in a weight ratio to the component (B).   The tire rubber composition according to claim 1, wherein the component (A) diene rubber is natural rubber, butadiene rubber or a blend rubber thereof.   The rubber composition for tires according to claim 1 or 2, wherein the component (C) plasticizer is a petroleum softener or a fatty oil softener. The tire rubber composition according to claim 1, 2 or 3, further comprising sulfur and a vulcanization accelerator and used as a tread portion forming material of a studless tire.   A studless tire having a tread portion formed and vulcanized from the tire rubber composition according to claim 4.   (A) a diene rubber, (B) two styrene-butadiene-styrene triblock copolymer mixtures having a total styrene content of 15 to 25% by weight and 30 to 50% by weight at both ends, and (C) a plasticizer. A method for producing a rubber composition for a vulcanizable tire, comprising mixing with a mixer and then mixing sulfur and a vulcanization accelerator with a mixer.   (B) Two types of styrene-butadiene-styrene triblock copolymer mixtures in which the plasticizer was preabsorbed and (B) the total styrene content at both ends was 15 to 25 wt% and 30 to 50 wt% were ) A method for producing a rubber composition for a vulcanizable tire, comprising mixing with a diene rubber with a mixer and then mixing sulfur and a vulcanization accelerator with a mixer.