JP2009209240A - Rubber composition for regenerated rubber-containing tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a regenerated rubber-containing tire reduced in the decreases of tensile strength and wearing resistance to the minimum, especially suitable for a tire tread. <P>SOLUTION: For 100 pts.wt. of diene rubber excluding the regenerated rubber, the compound quantity α [pts.wt.] of the regenerated rubber is 10-50 pts.wt, the compound quantity β [pts.wt.] of carbon black is defined by formula (1): β=β<SB>0</SB>-3α/8, and the compound quantity γ [pts.wt.] of an oil component is defined by formula (2): γ=γ<SB>0</SB>-α/2. In the formulae (1) and (2), β<SB>0</SB>expresses the numerical range [pts.wt] of 85-110, and γ<SB>0</SB>expresses the numerical range [pts.wt] defined by formula (3): 0.82×(β+3α/8)-22≤γ<SB>0</SB>≤0.82×(β+3α/8)-7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a rubber composition for tires containing recycled rubber, and more specifically, a rubber composition for tires containing recycled rubber with reduced reduction in tensile strength and wear resistance as much as possible, and particularly suitable for tire treads. The present invention relates to a rubber composition for a tire containing rubber.

  In recent years, as conservation of resources and environmental protection have been highlighted as major issues, improvement of the recycling rate is also required for pneumatic tires. For this reason, it has been studied to blend recycled rubber recovered from used tires and tubes into new raw rubber. Recycled rubber is stipulated in JIS K6313, and is a recycle of used automobile tires, tubes and other rubber products, and is a rubber obtained by crushing used rubber products and regenerating desulfurization. is there. However, the rubber composition containing the recycled rubber has a problem in that the physical properties are inevitably deteriorated, and the required tensile strength and wear resistance are deteriorated particularly when used for treads.

As a countermeasure, Patent Document 1 proposes to improve the wear resistance by using a recycled rubber specified by the amount of organic solvent extracted before and after the regeneration desulfurization process. However, in this rubber composition, the amount of recycled rubber is limited to a small amount, and if it is increased, there is a problem that the physical properties are significantly lowered and the wear resistance and tensile strength are deteriorated.
JP 2002-338743 A

  An object of the present invention is to provide a rubber composition for a tire with recycled rubber, in which the decrease in tensile strength and wear resistance is made as small as possible, and particularly a tire with recycled rubber suitable for a tire tread. It is to provide a rubber composition for use.

The rubber composition for tires with recycled rubber of the present invention that achieves the above object is defined by 10 to 50 parts by weight of recycled rubber and carbon black by the following formula (1) with respect to 100 parts by weight of diene rubber excluding the recycled rubber. The blending amount β [parts by weight] and the oil component are blended by blending amount γ [parts by weight] defined by the following formula (2).
β = β ₀ -3α / 8 (1)
γ = γ ₀ −α / 2 (2)
(However, in the formulas (1) and (2), α is the amount of recycled rubber [parts by weight], β ₀ is a value of 85 to 110 [parts by weight], and γ ₀ is a value defined by the following formula (3). [Parts by weight] is expressed.
0.82 × (β + 3α / 8) −22 ≦ γ ₀ ≦ 0.82 × (β + 3α / 8) −7 (3))

For 100 parts by weight of the diene rubber excluding the recycled rubber, sulfur may be blended in a blending amount ξ [parts by weight] defined by the following formula (4).
ξ = ξ ₀ × (200 + α) / 200 (4)
(However, in Formula (4), (alpha) represents the compounding quantity [weight part] of recycled rubber, and (xi) ₀ represents the numerical value [weight part] of 1.8-2.0.)

The carbon black has a nitrogen adsorption specific surface area may 80~100m ² / 50~85 wt% and nitrogen adsorption specific surface area of carbon black g consists 15 to 50 wt% of carbon black 110~130m ² / g.

  This rubber composition for tires containing recycled rubber is suitable for constituting the tread portion of a pneumatic tire.

  The rubber composition for tires with recycled rubber according to the present invention contains 10 to 50 parts by weight of recycled rubber with respect to 100 parts by weight of diene rubber excluding recycled rubber, and carbon black satisfies the relationship of the above formula (1). Since β [parts by weight] and γ [parts by weight] satisfying the relationship of the above formula (2) are blended in the oil component, respectively, by optimizing the blending amounts of carbon black and the oil component, rubber is obtained. It can suppress so that the fall of the tensile strength and abrasion resistance of a composition may be made as small as possible.

  In the rubber composition for tires containing recycled rubber of the present invention, the diene rubber excluding the recycled rubber is not particularly limited, and natural rubber, isoprene rubber, styrene-butadiene rubber, which are usually used for tire rubber compositions, Examples thereof include butadiene rubber, acrylonitrile-butadiene rubber, and butyl rubber. Natural rubber, styrene-butadiene rubber, and butadiene rubber are preferable. These diene rubbers can be used alone or as any blend.

  The recycled rubber used in the present invention is a recycled rubber of automobile tires, tubes and other rubber products defined in JIS K6313, and has the same properties. The type of recycled rubber may be any selected from tube recycled rubber, tire recycled rubber, and other recycled rubber, and a plurality of types may be combined. Of these, tire recycled rubber is preferable.

  The recycled rubber is composed of an organic component such as a low molecular weight rubber subjected to a desulfurization treatment and an inorganic component such as carbon black. However, since the rubber component contained in the recycled rubber has a low molecular weight, the properties such as tensile strength and wear resistance are inferior to those of the diene rubber. Therefore, in the present invention, when the blending amount of the recycled rubber with respect to 100 parts by weight of the diene rubber excluding the recycled rubber is α [parts by weight], (α / 2) [parts by weight] corresponds to the oil component. The estimation is characterized in that (3α / 8) [parts by weight] is estimated as equivalent to carbon black. Thereby, even when recycled rubber is blended, the blending amounts of carbon black and oil components can be optimized, and the decrease in tensile strength and wear resistance of the rubber composition can be minimized. The above coefficients 1/2 and 3/8 are numerical values obtained empirically.

  In the present invention, the blended amount α of the recycled rubber is 10 to 50 parts by weight, preferably 20 to 50 parts by weight, based on 100 parts by weight of the diene rubber excluding the recycled rubber. When the amount of the recycled rubber is less than 10 parts by weight, it is not preferable from the viewpoint of the recycling rate. On the other hand, if the amount of recycled rubber exceeds 50 parts by weight, deterioration of tensile strength and wear resistance cannot be allowed.

When the blending amount of carbon black with respect to 100 parts by weight of diene rubber excluding recycled rubber is β [parts by weight], the blending amount of carbon black β is expressed by the following formula (1) in relation to the blending amount α of recycled rubber. Determined.
β = β ₀ -3α / 8 (1)

In the above formula (1), α represents the amount of recycled rubber [parts by weight], and β represents the amount of carbon black [parts by weight]. β ₀ means a standard blending amount [parts by weight] of carbon black when no recycled rubber is blended, and its numerical range is 85 to 110 [parts by weight], preferably 90 to 100 [parts by weight]. ]. When the blending amount of carbon black is less than (85-3α / 8) parts by weight, the wet braking performance is insufficient. Moreover, when the compounding quantity of carbon black exceeds (110-3α / 8) parts by weight, the exothermic deterioration cannot be allowed.

  When reinforcing fillers such as silica, clay and calcium carbonate are used together with carbon black, the total amount of these reinforcing fillers and carbon black is handled as β.

Carbon black having a nitrogen adsorption specific surface area of preferably 80 to 130 m ² / g may be used. When the nitrogen adsorption specific surface area is less than 80 m ² / g, the wear resistance is insufficient. On the other hand, if the nitrogen adsorption specific surface area exceeds 130 m ² / g, heat generation becomes large, and this is not preferable in terms of cost. The nitrogen adsorption specific surface area of carbon black shall be calculated | required based on JISK6217-2.

In addition, it is preferable to use at least two types of carbon blacks together. Carbon black having a nitrogen adsorption specific surface area of 80 to 100 m ² / g is 50 to 85% by weight and nitrogen adsorption specific surface area is 110 to 130 m ^2. / G of carbon black is preferably 15 to 50% by weight. As shown in the examples in the latter part, in the rubber composition containing the recycled rubber, the two kinds of carbon blacks having different nitrogen adsorption specific surface areas are used in combination at a specific ratio, which is different from the case where the recycled rubber is not blended. The strength can be maximized.

In the present invention, carbon black having a nitrogen adsorption specific surface area of 80 to 100 m ² / g is preferably 50 to 85% by weight, more preferably 50 to 70% by weight, and the nitrogen adsorption specific surface area of 110 to 130 m ² / g. The carbon black of g is preferably 15 to 50% by weight, more preferably 30 to 50% by weight. If the nitrogen adsorption specific surface area and the blending ratio of the two types of carbon black blended in the rubber composition containing recycled rubber are out of the above ranges, the tensile strength cannot be maximized.

In the rubber composition of the present invention, when the blending amount of the oil component with respect to 100 parts by weight of the diene rubber excluding the recycled rubber is γ [parts by weight], the blending amount γ of the oil component is the blending amount α of the recycled rubber and carbon. It is determined by the following formula (2) in relation to the blending amount β of black.
γ = γ ₀ −α / 2 (2)

In the above formula (2), α represents the blending amount of the recycled rubber [parts by weight], γ represents the blending amount of the oil component [parts by weight], and γ ₀ represents the standard blending of the oil component when the recycled rubber is not blended. It means an amount [parts by weight], and takes a numerical range satisfying the relationship of the following formula (3) with the blended amount α of recycled rubber and the blended amount β of carbon black.
0.82 × (β + 3α / 8) −22 ≦ γ ₀ ≦ 0.82 × (β + 3α / 8) −7 (3)

  If the blending amount γ of the oil component is smaller than the numerical range defined in the above formulas (2) and (3), the hardness of the rubber composition becomes too high and the ride comfort deteriorates. On the other hand, when the blending amount of the oil component γ is larger than the numerical range defined in the above formulas (2) and (3), the tensile strength and the wear resistance are deteriorated.

  In the present invention, the oil component refers to the sum of oils such as mineral oil-based softeners and vegetable oil-based softeners added to the rubber composition, and oil components contained in oil-extended rubbers such as oil-extended SBR.

In the rubber composition containing recycled rubber, as described above, since the recycled rubber has a low molecular weight, it functions as an oil component rather than as a rubber component. However, since the recycled rubber has a property of binding to sulfur in the vulcanization process, it is preferable to adjust the amount of sulfur by estimating the consumption of the recycled rubber. Accordingly, when the compounding amount of sulfur with respect to 100 parts by weight of the diene rubber excluding the recycled rubber is ξ [parts by weight], the compounding amount of sulfur ξ is expressed by the following formula (4) in relation to the compounding amount α of the recycled rubber. Determined.
ξ = ξ ₀ × (200 + α) / 200 (4)

In the above formula (4), α means the blending amount [parts by weight] of recycled rubber, and ξ ₀ means the standard blending amount [parts by weight] of sulfur when no recycled rubber is blended. Is 1.8 to 2.0 [parts by weight]. When the blending amount ξ of sulfur is less than (1.8 × (200 + α) / 200) parts by weight, the tensile strength and the wear resistance are lowered and the exothermic property is deteriorated. Moreover, when the compounding amount ξ of sulfur exceeds (2.0 × (200 + α) / 200) parts by weight, the decrease in tensile breaking elongation is undesirably increased.

  The rubber composition for tires containing recycled rubber can contain various additives commonly used in rubber compositions such as vulcanization accelerators, anti-aging agents, and plasticizers. The rubber composition can be kneaded by various methods and used for vulcanization or crosslinking. The blending amounts of these additives may be conventional conventional blending amounts as long as the object of the present invention is not adversely affected.

  The rubber composition for tires containing recycled rubber can be produced by mixing the above components using a known rubber kneading machine such as a Banbury mixer, a kneader, or a roll.

  The rubber composition for tires with recycled rubber according to the present invention suppresses the decrease in tensile strength and wear resistance associated with the blending of recycled rubber. For example, only rubber recycled from rubber composition for tires with recycled rubber is used. The decrease in the tensile strength and wear resistance of the rubber composition excluding is preferably reduced to 30% or less, more preferably 10% or less. Furthermore, the rubber composition for tires with recycled rubber can improve the wet braking performance with respect to the rubber composition excluding only the recycled rubber.

  The rubber composition for tires with recycled rubber described above is preferably applied to a tire tread, and a pneumatic tire having a tread portion made of this rubber composition can maintain excellent durability and wear resistance. .

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

  16 kinds of rubber compositions (Examples 1 to 9 and Comparative Examples 1 to 7) having the compositions shown in Tables 1 and 2 were weighed for the ingredients except for sulfur and vulcanization accelerator, and 1.7 L Banbury. The mixture was kneaded for 4 minutes with a mixer, and the master batch was discharged at a temperature of 160 ° C. and cooled to room temperature. The master batch was subjected to a 1.7 L Banbury mixer, and sulfur and a vulcanization accelerator were added and mixed to prepare a rubber composition for a tire containing recycled rubber.

  The obtained 16 types of rubber compositions (Examples 1-9, Comparative Examples 1-7) were each vulcanized at 150 ° C. for 30 minutes in molds of predetermined shapes to produce test pieces, Various rubber properties were tested by the methods shown.

Tensile strength As the tensile strength of the obtained test piece, the tensile breaking stress was measured according to JIS K6251. The obtained results are shown in Table 1 as indices with Comparative Example 1 as 100 and Table 2 as Example 4 as 100. The larger this value, the greater the tensile strength and the better.

Exothermic (tan δ at 60 ° C)
Based on JIS K6394, the obtained test piece was measured for tan δ under the conditions of an elongation deformation strain rate of 10 ± 2%, a frequency of 20 Hz, and a temperature of 60 ° C. using a viscoelastic spectrometer manufactured by Ueshima Seisakusho. The obtained results are shown in Table 1 as indices with Comparative Example 1 as 100 and Table 2 as Example 4 as 100. The smaller this value, the smaller the tan δ, the lower the heat generation, and the better the fuel efficiency.

Abrasion resistance According to JIS K6264, the obtained test piece was worn under the conditions of a temperature of 20 ° C., a load of 39 N, a slip rate of 30%, and a time of 15 minutes using a lambone wear tester (manufactured by Iwamoto Seisakusho). The amount was measured. The obtained results are shown in Tables 1 and 2 in Table 1, where the reciprocal of Comparative Example 1 is 100, and in Table 2 the reciprocal of Example 4 is 100. A larger index means better wear resistance.

Wet braking performance A pneumatic tire having a tire size of 195 / 65R15 was prepared, which was provided with a tread portion composed of the three types of rubber compositions for tires containing recycled rubber (Example 1, Comparative Examples 1 and 2). Each tire is mounted on a rim (15 x 6.5 JJ), filled with regular air pressure as described in the JATMA Yearbook, mounted on a domestic 2.0 liter class vehicle, and on a submerged asphalt road surface, the initial speed is 100 km / h. The braking distance when driving and braking was measured. The obtained results are shown in Table 1 with the reciprocal of Comparative Example 1 being 100. The larger this value, the shorter the braking distance and the better the wet braking performance.

The types of raw materials used in Tables 1 and 2 are shown below.
SBR: styrene-butadiene rubber, Nipol 1712 manufactured by Nippon Zeon (including 37.5 parts by weight of oil-extended oil with respect to 100 parts by weight of SBR)
Recycled rubber: Muraoka Rubber Co., Ltd. tire Riku purple carbon black-1: Tokai Carbon Co., Ltd. Seest KH (N339, nitrogen adsorption specific surface area 93 m ² / g)
Carbon black-2: N234 (nitrogen adsorption specific surface area 123 m ² / g) manufactured by Cabot Japan
Oil: Aroma oil, Aroma oil manufactured by Fuji Kosan Co., Ltd. Zinc oxide: Zinc oxide, 3 types manufactured by Shodo Chemical Industry Co., Ltd. Stearic acid: Beads stearic acid aging inhibitor manufactured by NOF Corporation
Wax: Sannok Sulfur manufactured by Ouchi Shinsei Chemical Co., Ltd .: Fine powder sulfur vulcanization accelerator with Jinhua Seal Oil manufactured by Tsurumi Chemical Co., Ltd .: Noxeller CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.

Claims (4)

Based on 100 parts by weight of the diene rubber excluding recycled rubber, 10 to 50 parts by weight of recycled rubber, the amount of carbon black defined by the following formula (1) β [parts by weight], and the oil component by the following formula (2) A rubber composition for tires with recycled rubber, which contains a prescribed blending amount γ [parts by weight].
β = β ₀ -3α / 8 (1)
γ = γ ₀ −α / 2 (2)
(However, in the formulas (1) and (2), α is the amount of recycled rubber [parts by weight], β ₀ is a value of 85 to 110 [parts by weight], and γ ₀ is a value defined by the following formula (3). [Parts by weight] is expressed.
0.82 × (β + 3α / 8) −22 ≦ γ ₀ ≦ 0.82 × (β + 3α / 8) −7 (3)) The rubber composition for tires with recycled rubber according to claim 1, wherein a blending amount ξ [parts by weight] defined by the following formula (4) is blended with 100 parts by weight of the diene rubber excluding the recycled rubber.
ξ = ξ ₀ × (200 + α) / 200 (4)
(However, in Formula (4), (alpha) represents the compounding quantity [weight part] of recycled rubber, and (xi) ₀ represents the numerical value [weight part] of 1.8-2.0.) The carbon black of claim nitrogen adsorption specific surface area of 80~100m ² / 50~85 wt% and nitrogen adsorption specific surface area of carbon black g consists 15 to 50 wt% of carbon black 110~130m ² / g The rubber composition for tires containing recycled rubber according to 1 or 2.   A pneumatic tire having a tread portion constituted by the rubber composition for a tire with recycled rubber according to claim 1, 2 or 3.