JP2000191830A - Rubber composition and tire using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition capable of effectively being used in a pneumatic tire and, particularly in its tread rubber which meets all of the braking performance on a rainy weather road surface, an ice and snow road surface and the driving stability on a dry road surface. SOLUTION: A rubber composition comprises a matrix rubber having at least one rubber component selected from a natural rubber and a diene type synthetic rubber, and a water soluble polyvinyl alcohol type resin having not less than 95 mol% vinyl alcohol units and vinyl acetate units and, at the same time, 5-30 mol% vinyl acetate units. This composition is applied to the tread rubber of a tire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition and a tire, and more particularly, to a tire having excellent braking performance on rainy roads, braking performance on ice and snow roads, and steering stability on dry roads, which are particularly required by the market. And a rubber composition that can be suitably used for a tread or the like of the tire.

[0002]

2. Description of the Related Art In general, when pneumatic tires accumulate on the road surface, the coefficient of friction between the tires and the road surface is greatly reduced, the braking distance is increased, and an accident is caused. Demands have been increasing in recent years. Conventionally, pneumatic tires have been formed with a drain groove in order to eliminate water on the tire contact surface, and it is known that the braking performance on a rainy road surface as a tire varies greatly depending on the arrangement and volume of the groove. I have. For this reason, many tread grooves have been devised in consideration of other performances of the tire. However, when the volume of the tread groove is increased, the braking performance on a rainy road surface is improved, but the tread rigidity and the effective ground contact area of the tire are reduced, so that the steering stability on a dry road surface tends to be reduced. In recent years, from the viewpoint of tire running stability, it has been desired to further improve braking performance on ice and snow roads or on rainy roads, and at the same time, further improve steering stability on dry roads. Is also strongly desired.

[0003]

Under such circumstances, the present invention satisfies all of the high levels of braking performance on rainy roads, braking on icy and snowy roads, and steering stability on dry roads at the high levels required by the market. It is an object of the present invention to provide a rubber composition which can be effectively used for a pneumatic tire, and particularly for the tread rubber of the tire.

[0004]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have achieved the object by using a rubber containing specific water-soluble short fibers as a tire tread. Was found. That is, in the tire according to the present invention, micro-groove-shaped voids are formed on the tread surface during wear by the water-soluble or desorbing short fibers. It is considered that these micro grooves efficiently remove water on a rainy road surface or water generated by frictional heat with a tire on an ice or snow road surface to a main groove portion (so-called conventional drainage pattern portion) under ground contact. In particular, the braking distance is short on a road surface having a low friction coefficient with a high accident rate. On the other hand, the tread rigidity is softened by melting of fibers near the surface, but the movement of the tread rubber block as a whole is suppressed by restraining the matrix rubber inside the block by the short fibers, and the steering stability on dry road surface is improved. In particular, responsiveness to handling, behavior stability at the time of lane change, and the like are improved. The present invention has been completed based on such findings.

(1) That is, the present invention provides a matrix rubber having at least one rubber component selected from a natural rubber and a diene-based synthetic rubber, and 95 mol% or more of a vinyl alcohol unit and a vinyl acetate unit, A rubber composition comprising a water-soluble polyvinyl alcohol-based resin having a vinyl acetate unit in the range of 5 to 30 mol%. Here, the polyvinyl alcohol-based resin preferably contains 2 to 20 parts by weight based on 100 parts by weight of the rubber component. The polyvinyl alcohol-based resin is preferably short fibers having a length of 1 to 10 mm and a diameter of 10 to 100 μm, and the water-soluble temperature of the resin is preferably 10 ° C. or less. (2) Further, the present invention relates to a tire having a pair of beat portions, a carcass connected to the beat portions in a toroidal shape, and a belt layer and a tread rubber layer for clinching a crown portion of the carcass. A tire wherein the top tread uses the rubber composition of the above (1). (3) The present invention further provides a two-layer tread including a pair of beat portions, a carcass connected to the beat portions in a toroidal shape, a belt layer for clinching a crown portion of the carcass, a top layer, and a base layer. A tire having rubber, wherein at least the base tread rubber uses the rubber composition of the above (1). In the tires (2) and (3), it is preferable that polyvinyl alcohol-based short fibers are oriented in the circumferential direction of the tire in the tread.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION As a material of a water-soluble short fiber used in a rubber composition of the present invention, 95 mol% or more is composed of a vinyl alcohol unit and a vinyl acetate unit, and 5 to 30 mol% of a vinyl acetate unit is contained. A polyvinyl alcohol-based resin within the range is selected in consideration of tire performance and production stability. If the total amount of the vinyl alcohol unit and the vinyl acetate unit is less than 95 mol%, the conventional spinning method such as wet spinning or dry spinning causes a decrease in spinning stability, resulting in a significant decrease in productivity and uneven fineness. Industrially unfavorable.
That is, even if blended with the same number of parts, the rubber physical properties change greatly depending on the fineness of the short fibers, and further, the performance of a tire using such a rubber also changes, so the fineness must be strictly controlled to a certain range. . Therefore, in the polyvinyl alcohol-based resin (hereinafter referred to as PVA-based resin) used in the present invention, the total amount of the vinyl alcohol unit and the vinyl acetate unit is preferably 97 mol% or more, particularly preferably 99 mol% or more.

In the present invention, the modulus of elasticity of the PVA-based resin fiber is not particularly limited, but is 20 g / denier or more in consideration of shape stability during rubber kneading. It is preferable that the PVA-based resin having the above-mentioned composition is also required from this point. Further, the PVA resin according to the present invention has a vinyl acetate unit of 5 units.
It needs to be in the range of 〜30 mol%. 5 mol%
If it is less than 30%, the water solubility is reduced, and if it exceeds 30 mol%, the fiber production stability deteriorates. Therefore, from such a viewpoint, it is more preferably in the range of 10 to 25 mol%. The PVA-based resin in the present invention, that is, the fiber made of the PVA-based resin, is rapidly dissolved in water on any wet road surface environment, and it is important for tire performance stability to form voids on the tire surface, particularly on a low-temperature road surface in winter. It is required to be water-soluble, so that its water-soluble temperature is 10 ° C or less,
Particularly, the temperature is preferably 5 ° C. or lower. PV made of such a resin
The A-based fiber can be obtained by adjusting the ratio of vinyl acetate units, or the degree of polymerization and the degree of crystallization.
In addition, the said aqueous solution temperature puts the fiber which suspended the load of 2 mg / denier in water, started from about 1 degreeC, and started 2 degreeC.
/ Water temperature at the time of melting and melting at the rate of / min.

Next, the content of the PVA resin in the present invention is preferably 2 to 20 parts by weight based on 100 parts by weight of rubber. If the amount is less than 2 parts by weight, the effect of improving the performance is small, and if it exceeds 20 parts by weight, poor dispersion during rubber scouring, poor workability during rubber extrusion (rough skin), cracks in the tire tread, and the like occur. Therefore, three more
-15 parts by weight, particularly preferably 4-10 parts by weight. In the present invention, when using short fibers of the PVA-based resin,
In general, the length of the short fiber is preferably longer from the viewpoint of improving the tire braking performance, but in fact, the longer the fiber is, the more the fiber is pushed in by the pattern in the tire vulcanizer, and the more the rubber scouring is performed. The workability also deteriorates, so it cannot be made extremely long. Therefore, the length of the short fibers depends on the tread pattern, but is preferably 1 to 10 mm, particularly preferably 2 to 5 mm. It is preferable that the fiber diameter is smaller from the viewpoint of improving the tire braking performance, since the number of grooves on the tire surface increases when the same amount is blended, and the groove dispersibility is improved.
However, in the production of fibers, if the fiber is too thin, thread breakage frequently occurs, and the rubber scouring workability also deteriorates. For this reason, the fiber diameter is preferably from 10 to 100 μm, particularly preferably from 15 to 70 μm.

On the other hand, it is preferable that the tread stiffness be high with respect to the handling stability of the dry road of the tire, particularly the response to handling, and the stability of behavior when changing lanes. In the present invention, from the viewpoint of further increasing the tread rigidity, the rubber and the short fibers are preferably bonded. That is, if the fiber and the rubber are not bonded, a gap may be generated at the fiber / rubber interface at the time of input, and the tread rigidity may not be easily exhibited. As a method for bonding the PVA-based resin and the rubber, for example, a silane coupling agent may be blended in the rubber, or the silane coupling agent may be attached to the short fibers by a pretreatment. As the type of the silane coupling agent, those generally used in the rubber industry for bonding silica particles are preferable.
Triethoxysilylpropyl) tetrasulfide or 3-
Trimethoxysilylpropyl-benzothiazole-tetrasulfide and the like are preferably used. The amount of the silane coupling agent is 1 to 100 parts by weight of the rubber component.
Preferably it is 20 parts by weight. If the amount is less than 1 part by weight, a sufficient adhesive force between the short fiber and the rubber cannot be obtained, and if it exceeds 20 parts by weight, it is economically disadvantageous. For the determination of the adhesiveness between the short fiber and the rubber, for example, a vulcanized rubber in which short fibers made of PVA resin are oriented in one direction is cut out at a thickness of about 1 mm perpendicular to the longitudinal direction of the short fibers, and the rubber is cut out. Is fixed with a jig in a state where a constant strain, for example, 100% strain (extended by a factor of 2) is applied, and it can be determined by observing the cut surface with a scanning microscope. When the adhesiveness is weak, voids are formed at the short fiber / rubber interface, resulting in a so-called cat-eye shape. In the present invention, J
It is preferable to use a rubber having a 100% modulus of 1.5 to 1.7 MPa by a measuring method based on IS6251 and to adhere without peeling at 80% or more interfaces in a state where 100% strain is applied. .

[0010] Next, in the rubber composition of the present invention, as the rubber component, a rubber made of at least one selected from natural rubber and diene-based synthetic rubber is used. Any rubber commonly used for use, for example, styrene-butadiene copolymer rubber, polyisoprene rubber, cis-1,4
-Polybutadiene, ethylene-propylene-diene copolymer rubber, butyl rubber and the like. These rubbers can be used alone or as any blend. In the rubber composition, there are no particular restrictions on the components other than those described above. For example, carbon black is preferably used as a reinforcing filler, and can be used in combination with silica. Here, the mixing ratio of the carbon black is 40 to 120 parts by weight, particularly 50 to 11 parts by weight, based on 100 parts by weight of the rubber component for reasons such as workability.
0 parts by weight is preferred. In particular, when carbon black and silica are used together in order to enhance the braking performance on rainy roads, the total amount of carbon black and silica is reduced by 10%.
It is preferably 40 to 120 parts by weight with respect to 0 parts by weight. In this case, the ratio of silica to the total amount of silica and carbon black is preferably 90% by weight or less, particularly preferably 20 to 80% by weight. If the amount of silica exceeds 90% by weight, the reinforcing property (abrasion resistance), particularly the abrasion resistance at a high level of stiffness, is significantly reduced.

[0011] The above rubber composition can be applied to a foamed rubber tread. The foaming rate in this case is 3-4.
It is preferably 0%. Further, as a foaming agent, for example, dinitrosopentamethylenetetramine (DP
T), azodicarbonamide (ADCA), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivative, oxybisbenzenesulfonylhydrazide (OBSH) and the like. The rubber composition of the present invention may be used for a top tread, or may be used as a base rubber having a so-called cap / base structure. In particular, for components requiring high block rigidity, such as base rubber, not only the stability on dry roads is improved, but also the surface fibers dissolve when the base rubber is exposed due to wear, braking performance on rainy roads, and on ice and snow roads. This is preferable because a decrease in braking performance can be suppressed. In the present invention, the directionality can be controlled by orienting the PVA-based resin or fiber in one direction in the rubber extrusion step, so that when used as a product, braking performance on rainy roads, ice and snow on the road The upper braking performance can be greatly improved. In particular, it is preferable to orient the fibers in the tire circumferential direction in order to improve the water rejection in the tire rotation direction rearward in the ground contact surface.

[0012]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited by these examples. [Various Measurement Methods] Performance evaluation of various samples and test tires was performed according to the following methods. (1) Foaming rate Foaming rate Vs is Vs = (ρ ₀ / ρ ₁ -1) × 100
(%). Ρ ₁ is the density of the foamed rubber (g / cm ³ ), and ρ ₀ is the density of the solid phase portion of the foamed rubber (g / cm ³ ).
cm ³ ). (2) Short fiber dispersibility The short fiber dispersibility of the unvulcanized tread rubber during tire production is
The evaluation was made based on the following three criteria of ◎, ◎, and Δ. ：: no problem ○: partially poor fiber dispersion (lumps with a diameter of less than 5 mm) △: poor fiber dispersion at many locations (lumps with a diameter of 5 mm or more)

(3) Brake braking distance on ice The tire is mounted on a passenger car, the vehicle travels 100 km on a dry road and 10 km on a wet road, performs preliminary break-in, and then travels on a flat road on ice, at a speed of 20 km / hr. The brake was depressed to lock the tire, and the distance to the stop was measured. The result was expressed as an index with the reciprocal of the distance taken as 100 for the comparative tire. The larger the value, the better the braking performance on ice. (4) Wet brake braking distance After mounting the tire on a passenger car, the vehicle travels 100 km on a dry road and 10 km on a wet road.
At a speed of 60 km / hr, the brake was depressed to lock the tire, and the distance to stop was measured. The result was expressed as an index with the reciprocal of the distance taken as 100 for the comparative tire. The larger the value, the better the braking performance on a rainy road surface. (5) Dry road steering stability On a test course, two test drivers drove a real vehicle and comprehensively evaluated driving, braking, steering wheel responsiveness, and controllability during steering to evaluate steering stability. Was. The index is indicated by an index when the comparative tire is set to 100. The higher the value, the better.

[Method for Producing a PVA Short Fiber Prototype] (1) Sample A A saponification degree 81 having a vinyl alcohol unit of 81 mol% and a vinyl acetate unit of 19% and a polymerization degree of 750.
Mol% polymer and dimethyl sulfoxide (DMSO)
Are mixed under a reduced pressure nitrogen atmosphere of 100 Torr or less.
The mixture was stirred and dissolved at 90 ° C. for 90 hours to prepare a DMSO solution containing a 40% polyvinyl alcohol-based polymer. This solution was extruded from an extruder set at 90 ° C. to a diameter of 0.1 mm.
It was extruded through a 2 mm nozzle and wet-spun into a mixed solution bath of acetone / DMSO (weight ratio 85/15) kept at 2 ° C. and fixed. Further, the spun fiber is acetone / DMS
Stretching was performed in a mixed solution of O (weight ratio: 98/2), and then DMSO was extracted and removed in heated acetone, and dried with a hot air drier at 80 ° C to produce long fibers. The obtained fiber had a saponification degree of 80% and a water solubility of 3 ° C. and was excellent in low-temperature water solubility. The melting point (Tm) was 191 ° C. This long fiber was cut into a predetermined length with a guillotine cutter to produce a short fiber. In addition, 20 places of the fiber were randomly selected, and the average value measured with an optical microscope was defined as the fiber diameter. (2) Samples B and C In the above method for producing sample A, when spinning a mixed solution of polyvinyl alcohol-based polymer / DMSO,
Samples B and C having the desired fiber diameter were prepared in the same manner as Sample A except that the operation was performed by changing the nozzle diameter.
Was prepared.

[Method of Manufacturing Test Tire] The rubber composition described in Tables 1 and 2 was used for the top tread, and the tread structure was adjusted to the height of the base rubber in the block by the conventional method. A tire having a cap base structure having a height of 50% of the height was prototyped. The maximum temperature during vulcanization is 18
When the temperature during vulcanization of the tread portion was measured with a thermocouple at 0 ° C., the maximum temperature of the tread portion was also 180 ° C. The tires of Examples 1 to 9 and Comparative Examples 1 to 3 were radial tires for passenger cars with a tire size of 205 / 60R15, and the treads were all non-foamed rubber. Example 1
The tires of Nos. 0 to 12 and Comparative Examples 4 and 5 were studless tires for passenger cars with a tire size of 185 / 70R13 and had a foam rubber top tread.

Examples 1 to 10 and Comparative Examples 1 and 2 In the tires of these Examples and Comparative Examples, the rubber compositions containing the water-soluble PVA short fibers described in Table 1 were applied to a non-foamed top tread. This is an example. For the obtained sample and test tire, the short fiber dispersibility,
Wet brake braking distance (wet brake braking performance), ice brake braking distance (ice brake braking performance)
And the dry road steering stability was evaluated. The results are shown in Table 1.

[0017]

[Table 1]

[0018]

[Table 2]

Note) 1) # 1500 manufactured by JSR Corporation 2) # 0120 manufactured by JSR Corporation (37.5% oil exhibition) 3) Seat 7H manufactured by Tokai Carbon Co., Ltd. 4) Nip Seal AQ manufactured by Nippon Silica Industry Co., Ltd. 5) Bis (3-triethoxysilylpropyl) tetrasulfide 6) TMDQ: 2,2,4-trimethyl-1,2-dihydroquinoline polymer 7) IPPD: N-isopropyl-N'-phenyl-p-
Phenylenediamine 8) MBTS: bis-benzothiazolyl-2) disulfide 9) DPG: diphenylguanidine 10) TBBS: Nt-butyl-2-benzothiazolylsulfenamide 11) prototype

Comparative Example 1 is a control tire using a carbon reinforcing compound containing no PVA fiber as a top rubber. Example 1
Is a compound obtained by adding short fibers to the compound of Comparative Example 1. As compared with Comparative Example 1, although the wet braking performance and the stability on the dry road are little improved, the braking performance on ice is greatly improved. Examples 2 to 4 are examples in which the compound of Example 1 was mixed with a variable amount of a silane coupling agent. However, the expression of adhesiveness between the fiber and the rubber improved the block rigidity, and improved wet braking performance and dryness. Road handling stability has been significantly improved. Examples 5 to 7 correspond to Example 3
In this example, the number of PVA short fibers was changed. In the fifth and sixth embodiments, each performance is greatly improved as compared with the third embodiment. However, if the number of parts exceeds 10 parts by weight, the dispersibility of the short fibers is slightly reduced.
It is understood that 0 parts by weight is preferable. Examples 8 and 9 are examples in which the length of the short fiber is changed. Increasing the short fiber length has the same tendency as increasing the number of parts, and although the performance of each tire is in the direction of improvement, if it exceeds 10 mm, a problem occurs in the dispersibility of the short fibers. It turns out that 10 mm is preferable. Comparative Example 2 and Example 10 are compounding examples in which carbon black and silica were used in combination. However, Example 10 according to the present invention was compared with Comparative Example 2 in which no water-soluble PVA short fiber was compounded. It can be seen that each performance is significantly improved by the development of the adhesiveness between the rubber and the rubber, and the improvement of the rain braking performance is particularly large.

Comparative Examples 3 and 4 and Examples 11 to 13 In the tires of these Examples and Comparative Examples, the rubber compositions containing the water-soluble PVA short fibers described in Table 2 were applied to a top tread (foam rubber). This is an example. For the obtained sample and test tire, the foaming rate of the top tread rubber, short fiber dispersibility, wet brake braking distance (wet brake braking performance), brake braking distance on ice (brake braking performance on ice), and drying Road steering stability was evaluated. The results are shown in Table 2.

[0022]

[Table 3]

Note) 1) cis-1,4-polybutadiene (B manufactured by JSR Corporation)
R01) 2) Carbon N220 manufactured by Asahi Carbon Co., Ltd. 4) Bis (3-triethoxysilylpropyl) -tetrasulfide 5) Nocrack 6C manufactured by Ouchi Shinko Chemical Co., Ltd. 6) Dibenzothiazyl disulfide 7) N- Cyclohexyl-2-benzothiazyl-sulfenamide 8) Azodicanrubonamide 9) Otsuka Chemical Co., Ltd. zinc benzenesulfinate 10) Otsuka Chemical Co., Ltd. urea / zinc stearate (85: 1)
5) Blend 11) Prototype

In Example 11, it was confirmed that even when the top tread was foamed rubber, the performance of each tire was significantly improved when the rubber composition of the present invention was used. In particular, the evaluation was performed on a studless tire having a low block rigidity in which a sipe is included in the tire tread, and it is understood that the dry fiber handling stability is greatly improved by the short fiber blending. In Examples 12 and 13, the short fiber diameter was changed. However, when the short fibers were too thick, the handling stability on dry roads was slightly reduced. Furthermore, the short fiber diameter is 5
When it exceeds 0 μm, it tends to take a long time to remove the solvent during fiber production. In addition, as for the tire in which the sample rubber was applied to the base rubber, the test tire was mounted on a passenger car, traveled 30,000 km, and after the base rubber was exposed, the above test was performed. Excellent results were obtained.

[0025]

According to the present invention, a micro-drain is effectively formed on a tread surface on a wet road surface by using a rubber composition containing a specific water-soluble polyvinyl alcohol-based resin as a tread rubber. Tires that can maintain high tread stiffness due to the adhesion between the resin and the rubber, and are excellent in all of braking performance on rainy road surfaces, braking performance on ice and snow road surfaces, and steering stability performance on dry road surfaces. Can be provided.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C08K 5/54 C08K 5/54 C08L 9/00 C08L 9/00 29/04 29/04 B

Claims (10)

[Claims] 1. A matrix rubber having at least one rubber component selected from natural rubber and a diene-based synthetic rubber, 95% by mole or more of a vinyl alcohol unit and a vinyl acetate unit, and 5 to 5 vinyl acetate units. A rubber composition comprising a water-soluble polyvinyl alcohol-based resin in a range of 30 mol%. 2. The rubber composition according to claim 1, comprising 2 to 20 parts by weight of the polyvinyl alcohol resin based on 100 parts by weight of the rubber component. 3. The polyvinyl alcohol resin having a length of 1
The rubber composition according to claim 1, wherein the rubber composition is a short fiber having a diameter of 10 to 10 mm and a diameter of 10 to 100 μm. 4. The rubber composition according to claim 1, wherein the water-soluble temperature of the polyvinyl alcohol resin is 10 ° C. or lower. 5. A rubber component 10 comprising a silane coupling agent.
The rubber composition according to any one of claims 1 to 4, comprising 1 to 20 parts by weight based on 0 part by weight. 6. The rubber composition according to claim 1, comprising 40 to 120 parts by weight of carbon black based on 100 parts by weight of the rubber component. 7. A composition comprising carbon black and silica, wherein the total amount of carbon black and silica is 40 to 120 parts by weight based on 100 parts by weight of the rubber component, and 90% by weight or less of the total amount of carbon black and silica is silica. The rubber composition according to any one of claims 1 to 6, comprising: 8. A tire having a pair of beat portions, a carcass connected to the beat portions in a toroidal shape, a belt layer for tightening a crown portion of the carcass and a tread rubber layer, at least a top tread is required. Item 1
A tire using the rubber composition according to any one of claims 1 to 7. 9. A two-layer tread rubber comprising a pair of beat portions, a carcass connected to the beat portions in a toroidal shape, a belt layer for clinching a crown portion of the carcass, and a top layer and a base layer. A tire having at least a base tread rubber using the rubber composition according to any one of claims 1 to 7. 10. The tire according to claim 7, wherein the polyvinyl alcohol-based short fibers are oriented in a circumferential direction of the tire.