JPH1180437A - Studless tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a studless tire adapted so that protrusions of coarse particles are formed on the surface of the tread to pierce the air bubbles contained in an ice plate to produce the action of scratching the iced road surface and to thereby exhibit excellent antislip effect by forming the tread from a rubber composition containing coarse particles of an RFL resin prepared by drying and solidifying a mixture obtained by adding a rubber latex to a resorcinol/formalin precondensate. SOLUTION: It is desirable that the amount of the rubber latex added to the resorcinol/formalin resin precondensate is 0.01-0.1 time the amount of the precondensate used. The rubber latex is exemplified by a vinylpyridine latex, a styrene/butadiene latex or a natural rubber latex. The coarse particles obtained by grinding the RFL resin (where R is resorcinol, F is formalin, and L is a rubber latex) have a particle diameter of 100-600 μm and a Mohs' hardness of 2.5-3.5. The amount of the RFL resin coarse particles added to the tread rubber is 3-30 pts.wt. per 100 pts.wt. rubber component. The composition is used to form a studless tire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a studless tire mounted on an automobile that sometimes runs on an icy road.

[0002]

2. Description of the Related Art In general, snow on a roadway is compacted by the traffic of a car and becomes compacted snow. The surface of the compacted snow is melted by daylight or the like, the generated water permeates into the compacted snow, and the night temperature becomes 0 ° C. When the temperature falls below, the permeated water freezes and becomes an ice plate containing a large number of air bubbles having a diameter of 100 to 500 μm. Studless tires mounted on cars running on slippery roads covered with ice (hereinafter referred to simply as tires) are made of walnuts, peaches and other fruit shells or nuclei, quartz, granite, alumina, etc. A tread is formed of a rubber composition containing coarse particles having a particle size of 10 to 1000 μm obtained by grinding a hard inorganic material, and the rubber composition is less slippery. While the tire is being used and the tread is being worn, the coarse particles incorporated in the rubber composition that forms the tread (hereinafter, the rubber composition that forms the tread is referred to as tread rubber) disperse the coarse particles. It wears later than the embedded matrix rubber and protrudes from the tread surface. The reason that the tire that formed the tread with the tread rubber containing the coarse particles is not slippery on the frozen road is because the protrusions formed by the coarse particles protruding from the tread surface destroy the surface wall of bubbles scattered just below the surface of the ice plate It is thought to be due to piercing.

[0003]

The shells or nuclei of fruits such as walnuts and peaches, which are compounded with the above-mentioned tread rubber to cause an anti-slip action, and coarse particles of high-hardness inorganic substances such as quartz, granite and alumina are coarse. Since the adhesion to the matrix rubber that disperses and embeds the particles is poor, some of the coarse particles fall off during use of the tire, and the slip resistance decreases.

[0004] It is an object of the present invention to provide a studless tire in which coarse particles incorporated in a rubber composition forming a tread are improved to improve slip resistance on an iced road.

[0005]

If the coarse particles themselves are directly adhered to the matrix rubber in which the coarse particles are dispersed and embedded, the coarse particles do not fall off during use as a tire, and furthermore, when the tires are used on ice roads. Improved slip resistance. That is, the present invention provides a resorcinol-formalin resin precondensate, which is obtained by adding a rubber latex to a dried and solidified RFL resin having a hardness of at least 2.5 on the Mohs scale and having a particle size of 100 to 600 μm. This is a studless tire in which a tread is formed with a rubber composition in which particles are mixed with 3 to 30 parts by weight with respect to 100 parts by weight of rubber.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Generally, it is said that an ice path is more slippery as the temperature is higher, and is most slippery when the surface of ice melts and a thin film of water is formed. The Mohs hardness of an ice plate varies depending on the condition of the ice plate.
At −15 ° C., the Mohs hardness of the ice plate is about 2 to 2.5, and the coarse particles must have a Mohs hardness of at least 2.5 ( Hereinafter, Mohs hardness is simply referred to as hardness). On the other hand, if the hardness of the coarse particles is unnecessarily high, the asphalt whose hardness has decreased due to a rise in temperature may be damaged if it is mounted on a car in winter and used even in summer, so-called crushing. The Mohs hardness is preferably 3.5 or less. As shown in FIG. 1, the resorcinol-formalin resin obtained by heating and drying the resorcinol-formalin resin precondensate changes its hardness when the ratio of the constituent resorcinol to formaldehyde changes, and the hardness becomes 2.5 or more. For this purpose, at least 1.5 mol of formalin in terms of formaldehyde is required for 1 mol of resorcinol. The resorcinol-formalin resin is prepared by adding a rubber latex to the precondensate and heating and drying the RFL resin. As the content of rubber latex such as vinylpyridine latex, styrene-butadiene latex or natural rubber latex increases, the hardness decreases. The amount of the rubber latex added to the resin precondensate is preferably as small as possible so long as an adhesive force that does not fall off from the matrix rubber during traveling by sulfur crosslinking with the rubber component of the matrix rubber is smaller.・ 0.01 of formalin resin precondensate
~ 0.1 times is preferred. In addition, RFL resin is abbreviated as R for resorcinol, F for formalin, and L for rubber latex, which means a resin composed of these.

[0007] The particle size of the coarse particles obtained by pulverizing the RFL resin to be blended with the tread rubber is set to 100 to 600 µm. If the particle size of the coarse particles blended in the tread rubber forming the tire becomes smaller than 100 μm, the protrusions formed by the coarse particles projecting from the tread surface are formed on the ice plate.
Since it is smaller than a bubble having a diameter of 0 to 500 μm, the action of breaking and piercing the surface wall of bubbles scattered just below the surface of the ice plate (hereinafter, the effect of breaking the surface wall of bubbles scattered just below the surface of the ice plate and piercing it) When the diameter is larger than 600 μm, the stress generated by repeated deformation during running of the tire is concentrated, and coarse particles scattered at the bottom of the groove, which is greatly deformed, Since it cannot be deformed following the deformation of the matrix rubber enclosing the coarse particles, the matrix rubber is damaged and cracks occur.

The amount of the RFL resin coarse particles in the tread rubber is 3 to 30 parts with respect to 100 parts by weight of the rubber component (hereinafter, parts by weight are simply referred to as parts). If the compounding amount is less than 3 parts, the scratching action is small, and if it is more than 30 parts, the coarse particles act as foreign substances and damage the matrix rubber to promote abrasion.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the present invention, examples will be described below.

Resorcinol is dissolved in water at the ratio shown in Table 1 expressed in parts by weight, 37% formalin (the amount in parenthesis is converted to formaldehyde) and 10% aqueous sodium hydroxide solution are added, and the mixture is stirred at a temperature of 25 ° C. for 7 hours. To give a resorcinol-formalin resin precondensate, add 41% VP latex (vinylpyridine latex manufactured by Sumitomo ABS Co., Ltd., trade name: PYRATEX L.S., and the amount in parentheses is the amount converted to the solid content) and left for 24 hours Then, it was transferred to a dryer and dried and solidified at a temperature of 250 ° C. for 60 minutes to obtain an RFL resin having a Mohs hardness shown in Table 1.

[0011]

[Table 1]

The RFL resin obtained above was crushed into a basic composition in which the compounding agents shown in Table 2 were blended with the rubbers shown in Table 2 in the proportions shown in Table 2 and the results are shown in Table 3. The coarse particles sieved to the particle size were additionally blended at the ratio shown in the part shown in Table 3 and mixed by a usual method to obtain a trial mixed rubber.

[0013]

[Table 2]

[0014]

[Table 3]

A sample was taken from each of the trial mixed rubbers obtained above and subjected to a wear resistance test using a Lambourn abrasion tester in accordance with JIS K6264. The results were indexed by the following formula and are shown in Table 3. The larger the index, the better. (Amount of wear of mixed rubber with prototype No. 4) × 100 /
(Wear amount of each trial mixed rubber)

A tread was formed with each of the remaining trial mixed rubbers from which the abrasion test sample was collected.
A 0R13 tire was prototyped according to a conventional method. A slip resistance test and a groove crack inspection of each prototype tire were performed under the following conditions. The results are shown in Table 3.

Slip resistance test: When mounted on a passenger car with a displacement of 1600 cc and traveling at a speed of 35 km / h on a road covered with ice sheets, sudden braking is applied, and the distance from the position where the braking is applied to the stop position is measured. It was indexed by the following formula. The larger the index, the better. (Stop distance of prototype No. 4 tire) x 100 / (stop distance of each prototype tire) Groove crack inspection: After mounting on the above-mentioned car and traveling 20,000 km on a non-icing road, crack on the groove bottom of tread pattern An investigation was made as to whether or not a problem had occurred.

In each of the examples, the slip resistance was superior to that of the prototype No. 4 (control) of the comparative example using a tread rubber containing no coarse particles, and no groove crack was generated. Although the abrasion resistance slightly decreased, it was within a practically acceptable range. Compared with the example and the prototype No. 4 (hereinafter, the trial number is simply referred to as a prototype), the trial production 5 using coarse particles having a particle diameter smaller than 100 μm and the trial production 6 having less than 3 parts of coarse particles are resistant. Small improvement in slipperiness, 30 coarse particles
Prototype 7 in which more parts were blended had good slip resistance but inferior wear resistance. Prototype 8 in which coarse particles having a particle size larger than 600 μm were blended had good slip resistance but inferior wear resistance and groove cracking. Prototype 9 in which coarse particles having a low Mohs hardness are blended has little improvement in slip resistance.

[0019]

According to the present invention, the rubber latex is added to the resorcinol-formalin resin precondensate, and the tread is formed from a rubber composition containing a coarse particle obtained by pulverizing a heat-dried solidified product. Projections are formed, and the projections pierce air bubbles contained in the ice plate covering the road surface to prevent slipping, so-called scratching effect on the icy road surface, and exhibit an excellent anti-slip effect.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the ratio of resorcinol and formaldehyde in a resorcinol-formalin resin and Mohs hardness.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C08L 61/06 C08L 61/06

Claims (2)

[Claims] 1. A rubber having a particle diameter of 100 to 600 μm obtained by adding a rubber latex to a resorcinol-formalin resin precondensate and pulverizing a dried and solidified RFL resin to obtain a rubber 10
A studless tire characterized in that a tread is formed with a rubber composition mixed with 3 to 30 parts by weight with respect to 0 part by weight. 2. The studless tire according to claim 1, wherein the coarse particles mixed in the rubber composition forming the tread are coarse particles obtained by pulverizing RFL resin having a Mohs hardness of 2.5 to 3.5.