JP2002138163A - Rubber composition for tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for tread enabling to greatly improve ice-gripping performance while maintaining abrasion resistance. SOLUTION: This rubber composition for tread comprises 5 to 40 pts.wt. of polyvinylbutyral having an average molecular weight of 200 to 2000 to 100 pts.wt. of dienic rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition for a tread, and more particularly to a rubber composition for a tread having good ice grip performance.

[0002]

2. Description of the Related Art In recent years, automobile tires have been required to have various performances.
There is a need for a tire that has improved ice grip performance while maintaining wear resistance.

Conventionally, as a method for improving ice grip performance, it has been studied to mix a resin powder such as polyvinyl alcohol or polyacrylic acid with a rubber composition for a tread in order to remove a water film on a road surface on ice. .

[0004] However, these methods have not been able to sufficiently improve the ice grip performance.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber composition for a tread having good ice grip performance while maintaining abrasion resistance.

[0006]

According to the present invention, there is provided a rubber composition for a tread comprising 5 to 40 parts by weight of polyvinyl butyral having an average degree of polymerization of 200 to 2,000 based on 100 parts by weight of a diene rubber. About.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Since the rubber composition of the present invention contains polyvinyl butyral in a diene rubber, it strongly absorbs and removes water existing between the rubber composition and a road surface, and has an area in direct contact with the ice surface. It is large and can be used as a tire tread to improve ice grip performance.

The diene rubber used in the present invention includes, for example, natural rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), and mixtures thereof. be able to.

As the diene rubber, for example, a diene rubber having a glass transition temperature (Tg) of -120 ° C to 10 ° C is preferable. A diene-based rubber having a too high Tg tends to be hard and lack grip performance, and also has a tendency to deteriorate in abrasion resistance. A diene-based rubber having a too low Tg tends to be unable to expect frictional force due to hysteresis loss.

When a tread rubber is finally obtained, for example, a diene rubber having a hardness Hs (20 ° C.) of 35 to 65 is preferable. A diene rubber having too low a hardness tends to have poor wear resistance, and a diene rubber having a too high hardness tends to have low grip performance.

It is desirable to use polyvinyl butyral having an average degree of polymerization of 200 to 2,000, preferably 200 to 1500. If the average degree of polymerization is less than 200, the abrasion resistance decreases, and if it exceeds 2,000, the effect of improving the ice grip performance is not observed.

The degree of butylation of polyvinyl butyral is 30.
It is preferably from 90 to 90 mol%, more preferably from 50 to 75 mol%. If the butylation degree is less than 30 mol%, the effect of improving the ice grip performance tends to be small, and if it exceeds 90 mol%, the abrasion resistance tends to decrease.

The polyvinyl butyral is used in powder form, and preferably has a particle size of 500 μm or less from the viewpoint of abrasion resistance.

The amount of polyvinyl butyral is 5 to 40 parts by weight, preferably 5 to 30 parts by weight, more preferably 5 to 25 parts by weight, based on 100 parts by weight of the diene rubber. If the blending amount of polyvinyl butyral is less than 5 parts by weight, the effect of improving the ice grip performance tends to decrease, and if it exceeds 40 parts by weight, the abrasion resistance tends to decrease.

[0015] The rubber composition of the present invention may further contain a white filler as a filler. Examples of the white filler include silica, clay, alumina, talc, calcium carbonate, zeolite, titanium oxide and the like, and these can be used alone or as a mixture of two or more. Particularly preferred white fillers include silica, clay, aluminum hydroxide, alumina,
Zeolites are mentioned.

The amount of the white filler is preferably 5 to 50 parts by weight, more preferably 10 to 40 parts by weight, based on 100 parts by weight of the diene rubber. If the amount of the white filler is less than 5 parts by weight, grip performance tends to be low, and if it exceeds 50 parts by weight, abrasion resistance tends to be poor.

When a white filler is used, a coupling agent may be used in order to increase the bond between the filler and the diene rubber and improve the abrasion resistance.

As the coupling agent used in the rubber composition of the present invention, a silane coupling agent is preferably used. Specifically, for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilyl) Ethyl) 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-triethyl Ethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylben Benzothiazole tetrasulfide, 3
-Triethoxysilylpropyl benzothiazole tetrasulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, and the like, and bis (3-triethoxy Silylpropyl) tetrasulfide and the like are preferred.

The amount of the silane coupling agent is preferably 5 to 20% by weight based on the white filler. If the amount of the silane coupling agent is less than 5% by weight, the abrasion resistance tends to deteriorate, and if it exceeds 20% by weight, the grip performance tends to deteriorate.

The rubber composition of the present invention may contain carbon black or the like as a filler in addition to the white filler. Examples of carbon black that can be used in the present invention include, but are not limited to, HAF, ISAF, SAF, and the like.

The compounding amount of carbon black is preferably 5 to 100 parts by weight based on 100 parts by weight of the diene rubber. If the amount of carbon black is less than 5 parts by weight, the abrasion resistance tends to be poor, and if it exceeds 100 parts by weight, the grip performance tends to decrease.

The rubber composition of the present invention may further contain a mineral oil such as a paraffinic oil, a naphthenic oil or an aromatic oil. The amount of the mineral oil is preferably 5 to 100 parts by weight based on 100 parts by weight of the diene rubber. If the amount of the mineral oil is less than 5 parts by weight, the grip performance tends to be poor, and if it exceeds 100 parts by weight, the wear resistance tends to be poor.

The rubber composition of the present invention may contain, in addition to the above-mentioned compounding agents, components and additives generally used in the production of rubber compositions for treads, if necessary, in amounts and compounding amounts usually used. Is also good. Specific examples of the components and additives include, for example, vulcanizing agents (sulfur, sulfur chloride compounds, organic sulfur compounds, etc.), vulcanization accelerators (guanidine-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, Sulfenamide-based, thiourea-based, thiuram-based, dithiocarbamate-based, and zandate-based compounds), cross-linking agents (organic peroxide compounds, radical generators such as azo compounds, oxime compounds, nitroso compounds, polyamine compounds, etc.), Reinforcing agents (high impact polystyrene resin, phenol-formaldehyde resin, etc.), antioxidants or anti-aging agents (diphenylamine-based, p-phenylenediamine-based amine derivatives, quinoline derivatives, hydroquinone derivatives, monophenols, diphenols, Thiobisphenols, Emissions hindered phenols, phosphorous and phosphoric acid esters), wax, stearic acid, zinc oxide, softeners, fillers, and plasticizers and the like.

[0024]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

The chemicals used in Examples and Comparative Examples are shown below. Natural rubber: RSS # 3 BR: BR150B manufactured by Ube Industries, Ltd. Carbon black: Diamond Black I manufactured by Mitsubishi Chemical Corporation Silica: Ultrasil VN3 manufactured by Degussa Silane coupling agent: Si69 mineral oil manufactured by Degussa : PS-32 polyvinyl butyral manufactured by Idemitsu Kosan Co., Ltd. 1: Polyvinyl butyral 300 manufactured by Wako Pure Chemical Industries, Ltd. (average degree of polymerization: about 200 to 40)
0) Polyvinyl butyral 2: polyvinyl butyral 1000 manufactured by Wako Pure Chemical Industries, Ltd. (average degree of polymerization: about 900 to 1)
100) Polyvinyl butyral 3: Polyvinyl butyral 2400 manufactured by Wako Pure Chemical Industries, Ltd. (average degree of polymerization: about 2300 to 2300)
2500) Polyvinyl alcohol: Polyvinyl alcohol 500 manufactured by Kishida Chemical (average degree of polymerization: about 500, degree of saponification: 8)
Antioxidant: Nocrack 6 manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
C (N-phenyl-N '-(1,3-dimethylbutyl)
-P-phenylenediamine) Stearic acid: Zinc oxide manufactured by NOF Corporation Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator: Ouchi Shinko Chemical Industry Noxeller C manufactured by
Z (N-cyclohexyl-2-benzothiazolylsulfenamide)

The following is a summary of the test methods performed. (Lambourn abrasion test) An abrasion test was performed using a Lambourn abrasion tester. At that time, the measurement conditions were a measurement temperature of 40 ° C., a load of 1.0 kgf, a slip ratio of 40%, a falling sand amount of 20 g / min, and a measurement time of 4 minutes.

The volume loss was calculated from the weight change of each formulation,
The volume loss (index) of Comparative Example 1 was set to 100 (reference), and the volume loss amount of each compound was indicated by an index using the following formula (Lambourn abrasion index). The larger the index, the better the wear resistance. (Lambourn abrasion index) = (Volume loss of Comparative Example 1) ÷
(Volume loss of each formulation) x 100

(Friction Test on Ice) The surface of a rubber sheet having a thickness of 2 mm was buffed to prepare a sample. Place the buffed surface of this rubber sheet downward so that it comes into contact with ice, put a weight on it so that the vertical drag is 5 kgf / cm ^2, and push it to the point where the speed is 800 mm / min. And the distance (stop distance) from the certain point to the point where the sample stopped was measured.

The stopping distance (index) of Comparative Example 1 was set to 100 (reference), and the stopping distance of each compound was converted into an index by the following formula (ice skid index). The larger the ice skid index, the better the ice grip performance. (Ice skid index) = (stop distance of comparative example 1) ÷
(Stop distance of each formulation) × 100 The temperature of the ice at the time of measurement was −3 ° C.

Examples 1 to 5 and Comparative Examples 1 to 4 Compounds other than sulfur and the vulcanization accelerator shown in Table 1 were kneaded with a 1.7 L Banbury mixer, and then sulfur and the vulcanization accelerator were added. And kneaded with a roll to produce a rubber sheet. This rubber sheet was vulcanized at 170 ° C. for 15 minutes and subjected to the test described above.

The results are shown in Table 1. Average degree of polymerization is 200-
It was found that by blending 5 to 40 parts by weight of polyvinyl butyral of 2000, the ice skid performance was significantly improved without lowering the abrasion resistance (Example 1).
~ 5). On the other hand, even when the blending amount of polyvinyl butyral is too large (Comparative Example 2), when polyvinyl butyral having an average polymerization degree that is too high is blended (Comparative Example 3), and when polyvinyl alcohol is blended (Comparative Example 4), Although the ice skid performance was slightly improved, the improvement effect was small and the abrasion resistance was significantly reduced.

[0032]

[Table 1]

[0033]

According to the rubber composition of the present invention, ice grip performance can be greatly improved while maintaining the wear resistance of the tire.

Claims (1)

[Claims] 1. A rubber composition for a tread, comprising 5 to 40 parts by weight of polyvinyl butyral having an average degree of polymerization of 200 to 2,000 based on 100 parts by weight of a diene rubber.