JP2003192832A - Rubber composition for tread - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for treads capable of making low fuel consumption properties compatible with abrasion resistance and gripping performances in a high dimension. <P>SOLUTION: This rubber composition for the treads comprises ≥10 pts.wt. of silica and 5-20 pts.wt. of a starch/plasticizer composite material in 100 pts.wt. of a rubber component composed of 20-45 wt.% of a natural rubber and/or an isoprene rubber and 25-80 wt.% of a styrene-isoprene-butadiene rubber. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a tread, and more particularly to a rubber composition for a tread excellent in grip performance, rolling resistance and abrasion resistance. . 2. Description of the Related Art In order to reduce the consumption of exhaust gas during driving of automobiles (to reduce fuel consumption), it is desired to reduce the rolling resistance of tires. As an effective means for reducing the rolling resistance, there is a method of reducing the weight ratio of a reinforcing agent such as carbon black or silica to be added to a rubber composition for a tread. However, this technique inevitably reduces wear resistance and grip performance. In addition, styrene-isoprene-
By compounding butadiene rubber (SIBR),
Techniques for improving the balance between grip performance, rolling resistance, and abrasion resistance are known. However, when the rolling resistance of the tire is further reduced, there is a problem that the balance between the wear resistance and the grip performance is lost. [0005] It is an object of the present invention to provide a rubber composition for a tread that can reduce rolling resistance and improve abrasion resistance and grip performance. [0006] In the above-mentioned SIBR blend rubber, in order to further reduce the rolling resistance, a part of silica is replaced with calcium carbonate, aluminum hydroxide, starch / plasticizer / composite material. And evaluated. As a result, rolling resistance could be reduced without sacrificing abrasion resistance and grip performance only when replaced with a starch / plasticizer / composite material. It was also found that there was an optimum amount of substitution. That is, the present invention relates to natural rubber (NR) and / or isoprene rubber (IR) of 20 to 45% by weight.
And styrene-isoprene-butadiene rubber (SIBR)
The present invention relates to a tread rubber composition containing 10 parts by weight or more of silica and 5 to 20 parts by weight of a starch / plasticizer / composite with respect to 100 parts by weight of a rubber component consisting of 25 to 80% by weight. DETAILED DESCRIPTION OF THE INVENTION The rubber composition for a tread of the present invention comprises a rubber component, silica and a starch / plasticizer / composite material. [0009] The rubber component is NR and / or IR
And SIBR. The content of NR and / or IR is 20 to 45% by weight, preferably 25 to 35% by weight in the rubber component.
It is. NR and / or IR content of 20% by weight
If it is less than 45%, it is difficult to maintain wear resistance, and if it exceeds 45% by weight, grip performance may be deteriorated. The SIBR includes a glass transition temperature (T
g) is preferably −80 to −10 ° C., particularly preferably −60 to −20 ° C. Tg is -80 ° C
If the SIBR is less than the above, improvement in grip performance tends not to be expected, and if the SIBR exceeds −10 ° C., sufficient abrasion resistance tends not to be obtained. The content of SIBR is 25 to 8 in the rubber component.
0% by weight, preferably 40-70% by weight. SIB
If the R content is less than 25% by weight or more than 80% by weight, the desired grip performance cannot be obtained, and a significant improvement in rolling resistance cannot be expected. The rubber component in the present invention comprises, as other rubber components, styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene-butadiene rubber (I
BR) and the like. The content of these rubber components is from 0 to 55% by weight, more preferably from 0 to 4% by weight of the rubber components.
It is preferably 0% by weight. If the content of these rubber components exceeds 55% by weight, the desired grip performance cannot be obtained, and the rolling resistance tends not to be sufficiently improved. Further, the content of the other rubber component is as follows:
The weight ratio to the content of the SIBR is 0/100 to 75 /.
25, more preferably 0/100 to 55/45. When the content of the other rubber component exceeds 75/25, the characteristics of SIBR are not sufficiently utilized, and there is a tendency that grip performance and rolling resistance cannot be improved. The silica used in the present invention is not particularly limited, and examples thereof include dry-processed silica (silicic anhydride) and wet-processed silica (silicic anhydride), with wet-processed silica being preferred. Preferable examples of the wet process silica include Ultrasil VN3 manufactured by Degussa and Nippon Silica Co., Ltd.
Nip seal VN3 AQ. The nitrogen adsorption specific surface area of the silica (N ₂ S
A) is preferably from 50 to 300 m ² / g. If the N ₂ SA of the silica is less than 50 m ² / g, the reinforcing effect of the silica tends to be difficult to obtain, and if it exceeds 300 m ² / g, the dispersibility of the silica tends to decrease, and the processability (kneading step) tends to decrease significantly. There is. The amount of the silica is 10
10 parts by weight or more, preferably 20 to 1 part by weight with respect to 0 parts by weight
00 parts by weight. If the amount of silica is less than 10 parts by weight, it is difficult to achieve both grip performance and rolling resistance. If the amount of silica exceeds 100 parts by weight, tan δ at 60 ° C., which is an index of the rolling resistance, does not decrease, and there is a tendency that improvement cannot be expected. The starch / plasticizer used in the present invention
A composite is a blend of starch and a plasticizer. Generally, the mixing of the starch and the plasticizer involves a relatively strong chemical and / or physical interaction between the starch and the plasticizer. It is believed to exist. The starch is usually a sugar chain composed of amylose repeating units (anhydroglucopyranose units linked by glucosidic bonds) and amylopectin repeating units constituting a branched chain structure. Specific examples include plant-derived storage polysaccharides such as corn, potato, rice or wheat. The plasticizer lowers the softening point of starch,
Used to facilitate dispersion in rubber. Therefore, it is preferable to have a melting point sufficiently lower than the softening point of starch. Specifically, less than 180 ° C., preferably 16
Plasticizers having a melting point below 0 ° C. are used. Examples of such a plasticizer include ethylene-vinyl alcohol copolymer, ethylene-acetate-vinyl alcohol terpolymer, ethylene-vinyl acetate copolymer, ethylene-glycidal acrylate copolymer, Ethylene-maleic anhydride-copolymer, cellulose acetate, ester condensate of dibasic organic acid and diol and the like can be mentioned. One or more plasticizers may be contained in the composite material. [0022] The starch and plasticizer can then be prepared according to a mixing method well known to those skilled in the art. For example, the method disclosed in U.S. Pat. No. 5,403,374 is exemplified. The starch content in the starch / plasticizer / composite is generally about 50 to about 400 parts by weight, preferably about 100 to 200 parts by weight, per 100 parts by weight of the plasticizer. The softening point of the starch / plasticizer / composite is
It is generally preferred that the temperature be from about 110 to about 170C. The starch / plasticizer composite is preferably used, for example, as a free-flowing dry powder or in a free-flowing dry pelletized form. The compounding amount of the starch / plasticizer / composite is 5 to 20 parts by weight, preferably 7 to 18 parts by weight, based on 100 parts by weight of the rubber component. If the amount of the starch / plasticizer / composite is less than 5 parts by weight, the effect of the composite is not seen and a reduction in rolling resistance cannot be expected. On the other hand, when the amount of the starch / plasticizer / composite exceeds 20 parts by weight, the abrasion resistance is significantly reduced. In the present invention, by blending the starch / plasticizer / composite with the SIBR blend rubber, compared to the case where the starch / plasticizer / composite is blended with the general-purpose rubber (for example, NR, SBR, BR, etc.). It is possible to expect a further reduction in rolling resistance without sacrificing grip performance and wear resistance in an extremely high dimension. The rubber composition of the present invention may contain any silane coupling agent conventionally used in combination with silica. Specifically, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-
Trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-nitropropyltrimethoxysilane, 3-
Nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-
Chloroethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,
N-dimethylthiocarbamoyltetrasulfide, 2-
Triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-tri Methoxysilylpropyl methacrylate monosulfide and the like. These may be used alone or in combination of two or more. Among these, bis (3-triethoxysilylpropyl) tetrasulfide and the like are preferable from the viewpoint of achieving both the effect of adding the coupling agent and the cost. The silane coupling agent is preferably added in an amount of 4 to 12% by weight based on the silica and the starch / plasticizer / composite. The amount of the silane coupling agent is 4
If the amount is less than 10% by weight, the abrasion resistance tends to decrease remarkably.
If it exceeds 12% by weight, the compounding cost increases, which is not preferable. In the rubber composition of the present invention, as a reinforcing agent,
Further, carbon black can be blended. As carbon black, N ₂ SA is 7
Those having a range of 0 to 200 m ² / g are preferred. If the N ₂ SA of the carbon black is less than 70 m ² / g, a sufficient reinforcing effect tends not to be obtained, and if it exceeds 200 m ² / g, the viscosity during kneading increases, and the processability tends to decrease significantly. The compressed dibutyl phthalate oil absorption of the carbon black is 100 to 150 ml / 100 g.
Are preferred. Examples of the carbon black include HA
F, ISAF, SAF, etc., but are not particularly limited. The compounding amount of the carbon black is preferably 0 to 120 parts by weight based on 100 parts by weight of the rubber component. If the amount of the carbon black exceeds 120 parts by weight, dispersibility and processability tend to be remarkably reduced. The rubber composition of the present invention may further contain, if necessary, a compounding agent usually used in the rubber industry, such as a softening agent, an antioxidant, a vulcanizing agent, a vulcanization accelerator, and a vulcanization accelerator. An agent can be appropriately compounded. The rubber composition of the present invention has an excellent balance of grip performance, rolling resistance and abrasion resistance and can be suitably used as a tread. Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto. The reagents and test methods used in Examples and Comparative Examples are shown below. (Reagent) NR: RSS $ 3 SIBR: GOODYEAR CHEMICA
L) BUDENE SIBR Flex 2550 (BUDENE
SIBRFLEX2550) (Tg: -30 ℃) SBR: JSR Co., Ltd. NS116 Silica: Degussa ultra Jill VN3 (N ₂ SA:
210 m ² / g) Calcium carbonate: Sunlight 700 manufactured by Takehara Chemical Co., Ltd. Aluminum hydroxide: Hygilite H-43 manufactured by Showa Denko Co., Ltd. Starch / plasticizer Composite material: Matter manufactured by Novamont Mater Bi 1128RR (softening point 147 ° C, plasticizer: ethylene-vinyl alcohol copolymer, amount of starch per 100 parts by weight of plasticizer: about 150 parts by weight) Carbon black: N220 silane manufactured by Tokai Carbon Co., Ltd. Coupling agent Process oil: Diana Process PS32 manufactured by Idemitsu Kosan Co., Ltd. Wax: Sannowax antioxidant manufactured by Ouchi Shinko Chemical Co., Ltd .: Santoflex 13 manufactured by Flexis
((N-1,3-dimethylbutyl) -N′-phenyl-
(p-phenylenediamine) Stearic acid: Tung zinc flower of NOF Corporation: Zinc oxide No. 2 manufactured by Mitsui Mining & Smelting Co., Ltd .: Powder sulfur vulcanization accelerator manufactured by Karuizawa Chemical Co., Ltd .: Ouchi Shinko Chemical Noxeller N manufactured by Kogyo Co., Ltd.
(Test Method) Examples 1 to 3 and Comparative Examples 1 to 4 According to the composition shown in Table 1, the components of sulfur and the vulcanization accelerator were mixed with a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd. And kneaded at about 150 ° C. for 4 minutes. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded material, and the mixture was kneaded with a biaxial roller at 80 ° C. for about 4 minutes. The resulting mixture is 17
A vulcanized rubber sample was prepared by vulcanizing at 0 ° C. for 12 minutes. (Abrasion test) A test piece was prepared from the vulcanized rubber sample, and a surface rotation speed of 50 m / min and a load of 1.5 were applied using a Lambourn abrasion tester manufactured by Iwamoto Seisakusho.
The amount of wear was measured at a slip rate of 50% at a slip rate of 15 g / min. The abrasion loss of Comparative Example 1 was set to 100 and expressed as an index. The higher the wear index, the better the wear resistance. (Rolling Resistance) A test piece was prepared from the vulcanized rubber sample, and was subjected to a viscoelastic spectrometer manufactured by Iwamoto Seisakusho under the conditions of a frequency of 10 Hz and a dynamic strain of 2.0% at 60 ° C. The loss tangent (tan δ) was measured. The tan δ of Comparative Example 1 was set to 100 and indicated by an index. The larger the index, the smaller the tan δ and the lower the rolling resistance, and the better. (Grip performance) A test piece was prepared from the above vulcanized rubber sample, and a frequency of 10 Hz and a dynamic strain of 2.0% were measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd.
The loss tangent (tan δ) at 0 ° C. was measured under the following conditions. The tan δ of Comparative Example 1 was set to 100 and indicated by an index. The larger the index, the larger the tan δ and the better the grip performance. Table 1 shows the results. [Table 1] Both Comparative Example 2 containing calcium carbonate and Comparative Example 3 containing aluminum hydroxide were effective in reducing the rolling resistance (tan δ at 60 ° C.), but the wear resistance and wet grip performance were reduced. On the other hand, in Examples 1 to 3 in which the starch / plasticizer / composite was blended, the rolling resistance (60 ° C. tan) was obtained without substantially sacrificing the wear resistance and wet grip performance.
δ) could be greatly reduced. However, Comparative Example 4 containing more than 20 parts by weight of the starch / plasticizer / composite material
In, the wear resistance was significantly reduced. By adding an appropriate amount of starch / plasticizer / composite to the SIBR blend rubber, the fuel economy, abrasion resistance and wet grip performance required for recent tires for passenger cars can be enhanced. A tread rubber composition that can be compatible can be obtained.

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Claims (1)

The present invention relates to a rubber composition comprising 20 to 45% by weight of natural rubber and / or isoprene rubber and 25 to 80% by weight of styrene-isoprene-butadiene rubber and 10% by weight of silica. Parts or more and starch / plasticizer
A tread rubber composition containing 5 to 20 parts by weight of a composite material.