JP2005146208A - Rubber composition for tire and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition of a tire, in which friction on ice is improved, and provide a pneumatic tire. <P>SOLUTION: The rubber composition for a tire comprises 1 to 20 pts.wt. of nonmetallic fibers having an average fiber diameter of 1 to 100 μm and an average fiber length of 0.1 to 5 mm and 1 to 30 pts.wt. of fillers having two or more protrusions based on 100 pts.wt. of diene rubber. Zinc oxide whisker is preferably used as the filler. The pneumatic tire is produced by using the rubber composition. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tire rubber composition and a pneumatic tire having improved frictional performance on ice on a snowy and snowy road surface.

  Spike tires have been used as tires for running on snowy roads, and chains have been attached to tires. However, environmental problems such as dust problems have occurred, so studless tires have been developed as tires for running on snowy and snowy roads. .

  Compared to the general road surface, the friction coefficient of ice and snow road surface is remarkably reduced and it becomes slippery. Therefore, the studless tire is devised in terms of material and design. For example, the development of rubber compositions containing diene rubbers with excellent low-temperature properties, ingenuity to change the surface irregularities of the tire surface and increase the surface edge components, and the addition of inorganic fillers and fibers that have a scratching effect have been carried out. (For example, see Patent Document 1).

  However, the friction performance on ice on the snowy road surface of the studless tire is still not sufficient as compared with the spike tire, and further improvement is demanded.

JP 2001-39104 A

  An object of the present invention is to provide a rubber composition for a tire and a pneumatic tire having improved friction performance on ice.

  The present invention relates to 1 to 20 parts by weight of non-metallic fibers having an average fiber diameter of 1 to 100 μm and an average fiber length of 0.1 to 5 mm, and 2 or more to 100 parts by weight of diene rubber. It is related with the rubber composition for tires containing 1-30 weight part of fillers which have this protrusion.

  In the tire rubber composition, the filler is preferably a zinc oxide whisker.

  Moreover, this invention relates to the pneumatic tire which consists of said rubber composition for tires.

In the pneumatic tire, the ratio of the complex elastic modulus E1 in the tread thickness direction and the complex elastic modulus E2 in the tire circumferential direction of the rubber piece cut out from the tread portion is an expression:
1.1 ≦ E1 / E2
Is preferably satisfied.

  According to the present invention, non-metallic fibers and a plurality of protrusions on an icy and snowy road surface can be obtained without using a special technique (apparatus) in the tire manufacturing process by blending a filler having non-metallic fibers and a plurality of protrusions. The scratch effect by the filler which has this is acquired. Further, in addition to the scratching effect on the icy and snowy road surface, the water repellent effect of the microprotrusions protruding from the rubber surface can increase the friction coefficient, and a studless tire having excellent on-ice friction performance can be obtained. Further, the wear resistance performance is not greatly reduced.

  The rubber composition for tires of the present invention comprises a diene rubber, a nonmetallic fiber, and a filler having two or more protrusions.

  Usually, the non-metallic fibers in the rubber extruded by the calender roll are oriented in the extrusion direction, so in order to effectively develop the scratching effect of the fibers on the ice, the sheet is produced as a manufacturing method with respect to the extrusion direction. Vertically cut and stand up, or by making the extrusion head into a tube shape, orient the fibers in a direction perpendicular to the extrusion direction, cut the sheet parallel to the extrusion direction, and rotate each by 90 degrees It was necessary to use a special technique (apparatus) such as aligning in the thickness direction of the tread by overlapping again. However, in the present invention, since a fiber having a plurality of protrusions is blended with rubber together with non-metallic fibers to disturb the fiber orientation in the rubber extrusion direction, a special technique (apparatus) is used in tire manufacture. The effect of scratching the ice by non-metallic fibers can be sufficiently obtained.

  In addition, by blending a filler having a plurality of protrusions, the plurality of protrusions show an anchor effect, prevent falling off due to irritation and wear during running, and micro-protrusions appear from the rubber surface. The water film formed between the snowy road surface and the tire can be eliminated, and the frictional performance on ice can be improved.

  As the diene rubber used in the rubber composition of the present invention, any diene rubber is used. For example, natural rubber (NR), polyisoprene rubber (IR), various polybutadiene rubbers (BR), various styrene-butadienes. Diene rubbers such as copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber, polychloroprene rubber (CR), etc., alone or in any proportion. Can be used.

  The non-metallic fiber used in the rubber composition of the present invention has no fear of damaging the road surface, has a small difference between the rubber and the wear rate, and is suitable for ensuring the contact between the tread and the icy and snowy road surface. Of the non-metallic fibers, non-metallic inorganic fibers are preferable. Further, glass fibers or carbon fibers that are broken to an appropriate length in the process of kneading rubber are preferable because they are easy to disperse and orient, and rubber having an appropriate ratio of complex elastic modulus is easily obtained.

  The lower limit of the average fiber diameter of the non-metallic fibers is 1 μm, preferably 3 μm. The upper limit is 100 μm, preferably 50 μm, more preferably 40 μm. When the average fiber diameter is smaller than 1 μm, the fiber cross-sectional area is small, so that a portion with high contact pressure created on the tread surface by fibers oriented in the tread thickness direction cannot be sufficiently produced. On the other hand, when it is larger than 100 μm, the action of pushing off the water film formed between the snowy and snowy road surface and the tire is inferior, so that adhesion and adhesion friction do not work sufficiently.

  The lower limit of the average fiber length of the nonmetallic fiber is 0.1 mm. Moreover, an upper limit is 5 mm, Preferably it is 3 mm, More preferably, it is 2 mm. When the average fiber length is shorter than 0.1 mm, the fiber tends to fall off from the tread surface by running, and the effect of pushing off the water film is reduced. On the other hand, when longer than 5 mm, it becomes difficult to disperse and orient the fibers, and the processability of the rubber is lowered.

  The blending amount of the non-metallic fiber is 1 part by weight with respect to 100 parts by weight of the diene rubber, and the upper limit is 20 parts by weight, preferably 18 parts by weight, more preferably 15 parts by weight. When the blending amount of the non-metallic fiber is less than 1 part by weight, the amount of the fiber that forms the contact pressure on the tread surface is reduced, and the effect of removing the water film and scratching ice becomes insufficient. On the other hand, when the amount exceeds 20 parts by weight, the tread block rigidity becomes too high, and the tread rubber surface cannot follow the icy and snowy road surface, and the adhesion / adhesion friction tends to decrease.

  The filler used in the rubber composition of the present invention exhibits excellent effects in abrasion resistance, heat resistance, thermal conductivity, and the like when blended with a diene rubber.

  The filler has two or more, preferably three or more protrusions. In a filler having no protrusion or having one protrusion, the filler cannot exhibit an anchor effect, and the filler falls off due to stimulation or wear due to tire running or the like.

  Examples of the filler having a plurality of protrusions include zinc oxide whiskers and star sand produced in Okinawa Prefecture. Of these, zinc oxide whiskers are preferably used because they are harder than ice and softer than asphalt.

  The lower limit of the needle-like short fiber length of the filler is preferably 1 μm, and more preferably 10 μm. Further, the upper limit is preferably 5000 μm, more preferably 1000 μm. When the length of the needle-like short fiber of the filler is less than 1 μm, there is a tendency that the improvement of the on-ice friction performance on the snow-ice road surface is not observed. Moreover, when it exceeds 5000 micrometers, there exists a tendency for abrasion resistance to fall remarkably.

  The lower limit of the needle-like short fiber diameter (average value) of the filler is preferably 0.5 μm. Moreover, it is preferable that an upper limit is 2000 micrometers, and it is more preferable that it is 200 micrometers. If the diameter of the needle-like short fiber of the filler is less than 0.5 μm, a sufficient scratching effect cannot be obtained, and the friction performance on ice tends not to be improved. Moreover, when it exceeds 2000 micrometers, there exists a tendency for abrasion resistance to fall remarkably.

  The lower limit of the amount of the filler is 1 part by weight, preferably 5 parts by weight, with respect to 100 parts by weight of the rubber component, and the upper limit is 30 parts by weight, preferably 25 parts by weight, more preferably 10 parts by weight. When the blending amount is less than 1 part by weight, there is a tendency that the friction performance on ice on the snowy and snowy road surface is not improved. Moreover, when it exceeds 30 weight part, there exists a tendency for abrasion resistance to fall.

  In addition, the said filler is polypropylene (PP), polyethylene (PE), polystyrene (PS), polyurethane (PU), polyvinyl alcohol (PVA), silane coupling in order to improve the adhesive force of a filler and diene rubber. You may surface-treat with an agent, a silylating agent, etc.

  The rubber composition for tires of the present invention includes a reinforcing agent (filler), a vulcanizing agent (crosslinking agent), a vulcanization accelerator, various oils, anti-aging, in addition to the diene rubber, non-metallic fiber and filler. Various compounding agents and additives blended for tires or general rubber compositions such as an agent, a softening agent, a plasticizer, and a coupling agent can be blended. Moreover, the compounding quantity of these compounding agents and additives can also be made into a general quantity.

Examples of the reinforcing agent include silica and / or an inorganic filler represented by the general formula (1).
mM · xSiOy · zH ₂ O (1)
(M is at least one selected from metals selected from the group consisting of aluminum, magnesium, titanium, calcium and zirconium, oxides and hydroxides of these metals and their hydrates, and carbonates of these metals. Where m, x, y and z are constants)

  The blending amount of the inorganic filler is preferably 150 parts by weight or less, more preferably 5 to 100 parts by weight with respect to 100 parts by weight of the diene rubber. When it exceeds 150 parts by weight, the workability tends to be lowered.

  When silica is blended, a silane coupling agent is preferably used in combination. The lower limit of the amount of the silane coupling agent is preferably 1 part by weight with respect to 100 parts by weight of silica, more preferably 2 parts by weight, and the upper limit is preferably 20 parts by weight. More preferably, it is a part. When the silane coupling agent is less than 1 part by weight, the viscosity of the unvulcanized rubber composition tends to increase. On the other hand, when the amount exceeds 20 parts by weight, there is no effect of blending the silane coupling agent with respect to the blending amount, and the cost tends to be high.

  Moreover, carbon black is mention | raise | lifted as said reinforcing agent. The lower limit of the amount of carbon black is preferably 5 parts by weight, more preferably 10 parts by weight, and more preferably 150 parts by weight, based on 100 parts by weight of the diene rubber. More preferably, it is a part. If it is less than 5 parts by weight, sufficient reinforcing properties cannot be obtained and the wear resistance tends to be inferior. On the other hand, if it exceeds 150 parts by weight, the workability is lowered and the hardness is increased, so that the frictional performance on ice tends to be lowered.

  The pneumatic tire of the present invention is produced by a usual method using the rubber composition of the present invention. That is, if necessary, the rubber composition of the present invention blended with the additive is extruded in accordance with the shape of each member of the tire at an unvulcanized stage and molded on a tire molding machine by a normal method. By doing so, an unvulcanized tire is formed. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a studless tire.

  The pneumatic tire of the present invention uses the rubber composition of the present invention particularly in the tread portion. As a method for forming the tread, an extrusion process using a normal calender roll can be used. As described in JP 2001-39104 A, a rubber composition in which fibers are dispersed by a calender roll is rolled to obtain a tread. It is preferable to orient the nonmetallic fibers in the tread thickness direction by a method such as folding the obtained rubber sheet.

Specifically, it is preferable that the ratio of the complex elastic modulus E1 in the tread thickness direction and the complex elastic modulus E2 in the tire circumferential direction of the rubber piece cut out from the tread portion satisfies the following formula.
1.1 ≦ E1 / E2
The lower limit of E1 / E2 is preferably 1.1, and more preferably 1.2. Further, the upper limit is more preferably 4, and particularly preferably 3.5. When the ratio is smaller than 1.1, a portion having a high ground pressure cannot be sufficiently formed on the ground surface. As a result, the effect of removing the water film formed between the tire and the icy and snowy road surface is reduced, and adhesion, adhesion friction, scratching, and digging friction are not improved. On the other hand, when El / E2 is larger than 4, the rigidity of the tread block of the tire becomes too high and the tread rubber surface cannot follow the icy and snowy road surface, and there is a tendency for adhesion and adhesion friction to decrease.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not restrict | limited only to these.

The raw materials used in the examples and comparative examples are summarized below.
Natural rubber: RSS # 3 manufactured by Tech Bee Hang
Polybutadiene rubber: UBEPOL-BR150B manufactured by Ube Industries, Ltd.
Carbon black: Showa Black N220 manufactured by Showa Cabot Corporation
Silica: Ultrazil VN3 manufactured by Degussa
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Oil: Idemitsu Kosan Co., Ltd. Dyna Process Oil PS323
Wax: Sunnock wax anti-aging agent manufactured by Ouchi Shinsei Chemical Industry Co., Ltd .: NOCRACK 6C (N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shin Chemical Co., Ltd. )
Stearic acid: Zinc stearate manufactured by NOF Corporation: Zinc Hana No. 1 zinc oxide whisker manufactured by Mitsui Mining & Smelting Co., Ltd .: Panatetra WZ-0501 manufactured by Matsushita Amtech Co., Ltd. Number of needles: 4, needle fiber length: 2 to 50 μm, needle fiber diameter (average value): 0.2 to 3.0 μm)
Glass fiber: Micro chopped strand manufactured by Nippon Sheet Glass Co., Ltd. (average fiber diameter 11 μm, cut length (average fiber length) 3 mm)
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-3 and Comparative Examples 1-5
The compounding ingredients excluding sulfur and vulcanization accelerator shown in Table 1 are kneaded for 3 to 5 minutes using a 1.7 liter closed Banbury mixer, and the compounded rubber is discharged when the temperature reaches 150 ° C. or higher. The base kneaded rubber was used. A rubber composition was obtained by kneading the base kneaded rubber with sulfur and a vulcanization accelerator with an open roll and vulcanizing.

  The obtained rubber composition was extruded into a tread shape with a calender roll by a commonly used method to form a tread, and a 195 / 65R15 size tire was produced. The following test was implemented about the obtained tire. The results are shown in Table 1.

(Complex modulus)
A rubber piece having a thickness of 1.0 mm, a width of 4 mm, and a length of 5 mm was cut out from the tire tread portion to obtain a measurement sample. Under predetermined measurement conditions (temperature 25 ° C., measurement frequency 10 Hz, initial strain 10%, dynamic strain 1%), complex elasticity in the tread thickness direction and circumferential direction using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. Rates (E1 and E2) were measured.

(Friction performance on ice)
The tire was mounted on a 2000 cc domestic FR vehicle, and the braking stop distance on the ice plate from 30 km / hour was determined. The braking stop distance of Comparative Example 1 is shown as an index with the value being 100. The higher the index, the better the friction performance on ice.

(Abrasion resistance)
The tires were mounted on a 2000 cc domestic FR vehicle and the amount of wear after running 30000 km was measured. The value of the amount of wear in Comparative Example 1 was taken as 100 and indicated as an index. The higher the index, the better the wear resistance.

  The results are shown in Table 1, respectively.

  As can be seen from Table 1, Examples 1 to 3 in which both zinc oxide whisker and glass fiber were blended were on ice compared to Comparative Example 2 in which only zinc oxide whisker was blended and Comparative Example 3 in which only glass fiber was blended. The effect of improving friction performance is remarkably large. In Comparative Examples 4 and 5, both zinc oxide whisker and glass fiber are blended in the same manner as in Examples 1 to 3, and excellent friction performance on ice is obtained, but the blending amount of zinc oxide whisker or glass fiber is large. Therefore, the wear resistance was greatly reduced.

Claims (4)

1 to 20 parts by weight of nonmetallic fibers having an average fiber diameter of 1 to 100 μm and an average fiber length of 0.1 to 5 mm, and two or more protrusions with respect to 100 parts by weight of diene rubber A tire rubber composition containing 1 to 30 parts by weight of a filler. The tire rubber composition according to claim 1, wherein the filler is zinc oxide whisker. A pneumatic tire comprising the rubber composition for a tire according to claim 1. The ratio of the complex elastic modulus E1 in the tread thickness direction and the complex elastic modulus E2 in the tire circumferential direction of the rubber piece cut out from the tread portion is an expression:
1.1 ≦ E1 / E2
The pneumatic tire according to claim 3, wherein: