JPS60147450A - Tire tread rubber composition - Google Patents

Abstract

PURPOSE:To obtain the titled composition giving high coefficient of friction on ice over a wide range of temperatures, by incorporating natural and/or diene synthetic rubber with a combination of low-temperature type plasticizer having specific freezing point and alumina of specific particle diameter range. CONSTITUTION:The objective composition can be obtained by incorporating and kneading (A) 100pts.wt. of natural and/or diene synthetic rubber such as polyisoprene, polybutadiene with (B) 10-80pts.wt. of low-temperature type plasticizer such as di-(2-ethylhexyl)phthalate with a freezing point <=-40 deg.C and (C) 45(pref. 10-30)pts.wt. of alumina with an average size 0.01-0.5(pref. 0.05-0.3)mm.. Said composition gives excellent brake performance on ice over a range of temperatures -5--35 deg.C without impairing its wear resistance, wet-road brake performance and road-protecting ability, thus being suitable as a tread rubber composition for spikeless snow tires.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to tire tread rubber compositions, particularly tread rubber compositions for spikeless tires having excellent high friction properties on ice.

Generally, the rubber composition constituting the tire tread portion hardens at low temperatures and loses its inherent flexibility, resulting in a decrease in road grip. In other words, the vehicle cannot grip the road surface on snow or water and slips. Also, the brakes do not work and the vehicle cannot be controlled using the steering wheel. Snow tires with spikes are used to compensate for this problem, but in recent years snow tires with motorcycles have caused damage to the road surface and the resulting dust generation, floating, and even noise have become social issues. There is an increasing demand for spikeless snow tires with sufficient low-temperature characteristics.

Conventionally, methods for improving the low-temperature properties of rubber and increasing the coefficient of friction on ice include (1) the use of polymers with a large coefficient of friction on ice, (2) the use of large amounts of aromatic oils and naphthenic oils, and (3) sea (2) -Ethylhexyl) (DO^), (2-ethylhexyl) (DOof'), (2-ethylhexyl) azelate (002), (27 ethylhexyl) (DOS), etc. It is known to add plasticizers to rubber compositions.

By the way, icy road surfaces generally have various icy temperatures, and it is particularly important to note that the coefficient of friction of rubber on ice varies considerably depending on the difference in icy temperature. For example, when comparing BR (polybutanoene rubber), which is the same diene-based synthetic rubber, and 5BR (styrene-butadiene copolymer rubber), SDR has a higher coefficient of friction on ice at freezing temperatures around -5°C. Regardless, the magnitude relationship between the coefficients of friction on ice for both reverses around -12℃, and as the temperature gets lower, the coefficient of friction on ice for BR increases (
The friction coefficient of SBR becomes smaller).
generally known. In this case, even if BR and 5ll11 are used as a blend, no special combination effect can be obtained, and the coefficient of friction on ice is inferior to the higher one when BR and SDR are used alone at each temperature.

Also, the use of large amounts of oil and low-temperature plasticizers as mentioned above.

The method using this method is effective in improving the coefficient of friction on ice at ice temperatures lower than around -20°C, but no significant improvement effect is observed on the coefficient of friction on ice at around -5°C.

In this way, when measuring the coefficient of friction on ice of various rubber compositions, the value of the coefficient of friction on ice changes as the ice temperature changes, and it is extremely difficult to obtain a rubber composition with a coefficient of friction on ice over a wide range of ice temperatures. It was difficult.

However, the actual ice temperature of frozen roads varies considerably depending on the season and region. Therefore, there has been a strong desire to develop a tire tread rubber composition that has a high coefficient of friction on ice over the entire freezing temperature range in which spikeless tires are used.

As a result of intensive research aimed at developing a tread rubber composition that satisfies such demands, the present inventors have developed a rubber composition with improved low-temperature properties using a low-temperature plasticizer with a freezing point of 140°C or less. When alumina with a specific particle size range is used in combination with the above, the combined effect of the two appears, and the total temperature ranges from -5°C to -35°C. 1. Wow, 9□5, □□□. f
':fA@yo We have discovered that two things can be obtained, and have arrived at the present invention.

That is, the present invention provides 10 to 80 parts by weight of a low-temperature plasticizer with a freezing point of 140°C or less and an average particle size of 0.01 to
, '5+m, in combination with 5 to 45 parts by weight of alumina.

The low-temperature plasticizer with a freezing point of -4()°C or lower used in the present invention is
(DOA, freezing point □ = 70℃), C (2-ethylhexyl) 7 tallate (DOP, - solid point - 255℃), Di (2-ethylhexyl) azecy) (DOZ, a solid point - 65℃), C ( 2-ethyl to □xyl) sebacate <'D' (l S'.

freezing point -65°C), a-olefin oligomer (1) 80, freezing point -65°C), etc. The total amount of placement is 10 to 80
If it is less than 10 parts by weight, the coefficient of friction on ice at low temperatures will not increase, and if it exceeds 80 parts by weight, the coefficient of friction on ice will tend to decrease at around -5°C. It is undesirable because it has poor viscosity and abrasion resistance.

The alumina used in the present invention has an average particle size of 0.01 to 0.
5m+*, more preferably 0.05-0.3mm.

If it is less than 0.01a++I1, no improvement in the coefficient of friction on ice can be expected, and if it exceeds 0.5fflI11, it is undesirable because it tends to damage the road surface and the abrasion resistance is severely degraded.

The amount of alumina blended in the present invention is 1 o of rubber.

5 to 45 parts by weight, more preferably 10 to 45 parts by weight
If it is less than 65 parts by weight (30 parts by weight), a sufficient improvement in the coefficient of friction on ice cannot be expected, and if it exceeds 45 parts by weight, the abrasion resistance will deteriorate undesirably.

The rubber component in the present invention is natural rubber (NR) and/or diene-based synthetic rubber. Examples of diene-based synthetic rubber include polyisoprene rubber (IR), polybutadiene rubber (8R), and styrene-butadiene rubber (SBR).
and blends thereof are suitable.

The rubber composition of the present invention can be obtained by kneading the above-mentioned components using a conventional processing device such as a roll, a bread ball mixer, a negoo mixer, or the like. In addition to the above components, known vulcanizing agents, vulcanization accelerators, vulcanization accelerators J vulcanization retarders,
Of course, organic peroxides, reinforcing agents, fillers, oils, softeners, plasticizers, anti-aging agents, tackifiers, colorants, etc. can be added.

Hereinafter, the present invention will be explained in detail with reference to Examples and Comparative Examples.

The evaluation method is as follows.

- JIS hardness: Measured according to JIS K6301.

φ Pico friction index: Evaluated using a Pico abrasion tester according to STM D2228, Con) o-le blend No. 1
It was expressed as an index as 00. The larger the number, the better.

・Iceμ (coefficient of friction on ice): Using a friction coefficient measurement test piece manufactured by Hashimoto Seisakusho, the load pressure was 2.7 kg/cI112,
Sliding speed 0. It was measured in lc/sea and expressed as an index with the value of control formulation No. 1 as 100. The larger the number, the better.

・Tire-eLμ: Create a tread with each formulation, and use the tread to create a tire size, l'185/705R.
Fourteen tires were manufactured, and the wet grip properties (Wetμ) of the tires were measured. Measured by UTQGS in the United States
(Tire Quality Grading Standards), the tires were mounted on a test trailer using 5JX14 rims, and the air pressure was 1.8 kg/am2 and the load was 336.
The frictional resistance was measured when the tires were running on a wet asphalt dense-grained road surface under these conditions and the rotation of the tires was locked. The coefficient of friction of the control formulation No. 1 was set as 100 and expressed as an index. The larger the number, the better.

・Road surface damage level: Using a friction coefficient measurement tester made by Iwamoto Seisakusho, the asphalt road surface was subjected to a load pressure of 2.7 k at 30°C.
g/c+a2, operating at a sliding speed of 0.1 cm/see,
Asphalt road surface after rotating the road plate 50 times □
□Eng.□. □1 yo 22. . The road surface damage level (no damage) caused by -7187Nol was set as 1, and the road surface damage level when measured by driving a spike bottle into the control mixture Mol was set as 5, and a 5-level evaluation was performed. The smaller the number, the better □.

Examples and Comparative Examples = Various goss compositions shown in Table 1 were kneaded and then □vulcanized. Each physical property of these rubber compositions was evaluated and the results are shown in Table 1.

In addition, each RQ meeting contains zinc white (
3 parts), stearic acid (3 parts'), anti-aging agent (para-phenylene diamine type, 3 parts), vulcanization accelerator (thiazoles, 1.5 parts), and sulfur (2 parts). did.

Note 1) 5BRI502 Note 2) Evening 7den 1534 Note 3.4) Made by Niren Kako Note 5) Made by Kyodo Oil Note 6) Alumina A: Made by Nikkei Kako, electroformed alumina fine powder (
Particle size #280 product, maximum particle size 147μ or less, average particle size 73.5-62μ) Note 7) Alumina B: Same as above (particle size #2000 product, maximum particle size 17μ or less, average particle size 8.9-7.1μ) Note 8) Aluminum fC: Same as above (particle size #20 product, 840 u
80% or more of particles have a particle size of 168 or more, and a maximum of 168
Note 9) Alumina D: Same as above (particle size #54 product, maximum particle size 500μ or less, 97% or more particle size 210μ or more, 65%
Regarding the evaluation of the rubber materials listed in Table 1, No. 1, which is an example of a typical spikeless/-tire tread composition
, 1 is specifically shown as a control.

Blend No. corresponding to Example, 2.3.5, 8, 15, 1
8゜17 and 18 are both control formulation No.
It can be seen that compared to No. 1, the pico friction index and Netμ are at almost the same level, and Iceμ is very superior over the entire temperature range from -5°C to -35°C.

Blend No. 4 is a comparative example in which only a low temperature plasticizer is blended and no alumina is blended. Compared to control formulation No. 1, Iceμ at -35°C is excellent, but leeμ at 5°C is hardly improved.

Blend No. 14 is a comparative example in which only alumina is blended and no low temperature plasticizer is blended. Compared to control formulation No. 1, the leeμ at -5°C is excellent, but the iceμ at 35°C is hardly improved.

Blend No. 8 is a comparative example in which alumina having an average particle size of less than 0.01-m and a low-temperature plasticizer are combined. Compared to formulation No. 7, there is no improvement in Iceμ around -5°C.

Blend No. 9 is a comparative example in which alumina having an average particle size exceeding 0.5 mI++ is combined with a low temperature plasticizer. This is undesirable because the pico wear index is severely reduced and there is a tendency to damage the road surface.

Blend No. 10 is a comparative example in which the blended amount of alumina is less than 5 coulometric parts. Control formulation No. 1
There is almost no improvement in Iceμ at -5°C.

Blend No. 11 is a comparative example in which the blending amount of alumina exceeds 45 parts. A low pico wear index of 1ζ is undesirable.

Blend No. 12 is a comparative example in which more than 80 parts by weight of a low-temperature plasticizer and alumina are combined.

Compared to Blend No. 6, the [eμ] at -5°C is inferior, and the pico wear index is also lower, which is not preferable.

Blend No. 13 is a comparative example in which the blended amount of the low-temperature plasticizer is less than 10 parts by weight. Ice at -35℃
There is no improvement in μ.

From the above, the tread rubber composition of the present invention has excellent braking power on ice at all temperatures from -5°C to -35°C without deteriorating wear resistance, wet road braking force, and road damage resistance. It can be seen that it has properties that are extremely suitable as a tread rubber composition for spikeless snow tires that do not cause pollution like tires with spikes.

(above) Patent applicant: Toyo Rubber Industries, Ltd. r Agent: Iwao, patent attorney materials

Claims (1)

[Claims] (1) 1 part of a low-temperature plasticizer with a freezing point of 140°C or less per 100 parts by weight of natural rubber and/or tsene-based synthetic rubber
A tire tread rubber composition comprising 0 to 80 parts by weight of alumina and 5 to 45 parts by weight of alumina having an average particle size of 0.01 to 0.5 mm.