JPS62253641A - Rubber composition for tire tread - Google Patents

Abstract

PURPOSE:The titled composition, obtained by blending a neopentyl type polyol ester or a blend thereof with a petroleum based softener as a softener and capable of remarkably improving frictional resistance on frozen road surfaces and sustaining the maneuverability thereof. CONSTITUTION:A composition obtained by blending (A) 100pts.wt. one or more rubbers selected from natural rubber, polyisoprene rubber and diene based rubber, e.g. BR, SBR, etc., with (B) 40-100pts.wt. carbon black and (C) (i) 2-35pts.wt. neopentyl type polyol ester expressed by formula I [R is H, OH, methyl or formula II (R' is 3-21C hydrocarbon group) and at least two are formula II], preferably formula III, IV (R1-R3 are 3-21C alkyl or alkenyl), etc., and optionally (ii) 0-60pts.wt., preferably 0-50pts.wt. petroleum based softener so that the total of the components (i) and (ii) may be 10-90pts.wt. when used together.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention significantly improves frictional resistance on snow or icy road surfaces, maintains its excellent maneuverability over a long period of time, and further reduces volatile content in the tire manufacturing process. The present invention relates to a rubber composition for tire trends that can dramatically reduce the amount of waste and improve the working environment.

[Prior art]

Icy road surfaces are the most slippery and dangerous of the road surfaces on which cars drive. Therefore, in cold regions where vehicles frequently drive on icy roads, automobile tires with metal spikes or chains attached to the tire tread are widely used. However, even in cold regions, roads are rarely frozen all the time during the winter, and in fact, the roads are often free of ice for most of the winter. With the development of automobile transportation, cars in cold regions with tires fitted with spikes or chains are now frequently traveling on roads that are free of ice.Nowadays, spikes and chains can damage roads. Social problems have become apparent, such as the occurrence of dust pollution caused by road damage and the large costs required to repair damaged roads. In order to address this problem, there is a need for the development of tires that can be safely driven on icy roads without the use of spikes or chains. One way to obtain such tires is to develop rubber materials for treads that have high frictional resistance on icy roads.

The main factor that determines the frictional properties of rubber materials is the raw rubber (elastomer) component. When a raw material rubber with a relatively high transition temperature (Tg) is used, the friction i1 resistance increases.

On the other hand, on icy roads, the opposite is true, and natural rubber (N
If a raw material rubber with a low Tg such as R) or polybutadiene rubber (BR) is used, the frictional resistance will increase. BR is
The lower the ice temperature, the greater the effect of increasing frictional resistance, and it is widely used as raw material rubber for the tread rubber of winter tires. There is a limit to its usage. In this way, the frictional resistance on icy roads and the frictional resistance on wet roads are generally considered to have contradictory characteristics, and it is possible to significantly increase the frictional resistance on icy roads without significantly reducing the frictional resistance on wet roads. It was difficult to improve.

As a method to increase frictional resistance on wet road surfaces,
JP-A-7662 proposes the use of a specific process oil. However, the degree of improvement in frictional resistance on icy road surfaces is insufficient compared to the effects of spikes and chains attached to tires, and there is a need to further improve the frictional resistance on icy road surfaces. In addition, as a raw material to increase the frictional resistance on icy road surfaces, JP-A-59-1
No. 26443 describes dioctyl sebacate (DO3).
JP-A-59-206209 discloses the use of synthetic plasticizers such as oleic acid derivatives. However, such synthetic plasticizers
Plasticizer vapor is generated during the tire manufacturing process, especially during the mixing and vulcanization processes, which causes problems such as deterioration of the working environment and deterioration of physical properties.Furthermore, during driving, the rubber temperature may exceed 60 to 1.
In tires that have been used for several years at temperatures as high as 20 degrees Celsius, the softening agent gradually evaporates from the tire surface due to the high temperature (heating), and the physical properties change over time. Ma I? ! It is difficult to maintain resistance, and therefore a softener that volatilizes less when heated is desired.

[Purpose of the invention]

The present invention is a tire tread rubber that significantly increases frictional resistance on icy roads, maintains its maneuverability over a long period of time, and further reduces volatile matter in the tire manufacturing process to improve the working environment. The purpose is to provide the composition. This rubber composition can be used as a trendy rubber material, especially for winter tires or all-season tires.

[Structure of the invention]

Therefore, the present invention provides natural rubber, polyisoprene rubber,
and one or two selected from the group consisting of diene rubber.
Characteristically, 40 to 100 parts by weight of carbon black, 2 to 35 parts by weight of neopentyl type polyol ester represented by the following formula (■), and 0 to 6 parts by weight of a petroleum-based softener are blended with 1 part by weight of rubber 1001i of 1001i or higher. The gist of this invention is a rubber composition for tire treads.

(In the formula, R is a hydrogen atom, a hydroxyl group, a methyl group, or an R'-C-0- (in the formula, R' represents a hydrocarbon group having 3 to 21 carbon atoms), which may be the same or different. However, a small number of R (both two are groups represented by the general formula R'-C-0-, where n is a number from 0 to 2) will be described in detail below regarding the configuration of the present invention.

(1) Raw rubber.

At least one or two or more rubbers selected from natural rubber (NR), polyisoprene rubber (IR), and diene rubber are used. As the diene rubber, for example, polybutadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR) are preferably used, and a blend thereof is preferably used, and the blending ratio is such that NR or IR is 100
~0 parts by weight, BRO ~75 parts by weight, and 5BRO ~70 parts by weight are good0.For example, when the purpose is to significantly increase the frictional resistance on icy roads, NR or IR or 1.2
- BR with a bonding unit content of 20% or less (low vinyl BR)
is used as a raw rubber component. However, low vinyl BR
The lower the temperature, the more pronounced the effect of increasing the frictional resistance on icy roads, but near the melting point of ice, it may conversely reduce the frictional resistance on icy roads, while at the same time increasing the frictional resistance on wet roads. Therefore, it is preferable to limit the amount used to 75% by weight or less of the total raw rubber components.

Although it is necessary to increase the frictional resistance on icy roads, if you want to bring the frictional resistance on wet roads as close as possible to the level of summer tires, use SBR with a bound styrene content of 30% by weight or more. However, if the SBR exceeds 70 parts by weight in 100 parts by weight of raw rubber, the frictional resistance on icy road surfaces will decrease, which is not preferable. Furthermore, in a three-way blend rubber of NR or IR, BR and SBR, S
It is particularly preferable to use BR and BR in a range of 10 to 70% by weight of the raw rubber component because desirable frictional resistance on icy road surfaces can be obtained.

(2) Carbon black.

It may be of the type normally used in Tire Trend.

(3) Neopentyl type polyol ester.

In the present invention, one or more neopentyl-type polyol esters represented by the formula 〇 are blended into the raw material rubber in order to improve the frictional resistance on icy road surfaces. Preferred neopentyl polyol esters are, for example, compounds represented by the following general formulas 〇-■. In addition, in the formula, Ri, Ilt, Ri,
Ri, Rs and P are alkyl groups or alkenyl groups having 3 to 21 carbon atoms, and may be the same or different.

H3 C1[z-0-C-R:+ C11t-0-C-R.

C11□-〇-C-Rz (.

CI□-〇-C-R4 Examples of the polyhydric alcohol constituting the neopentyl type polyol ester include neopentyl glycol, trimethylolethane, trimethylolpropane, pentaerythritol, and diventaerythritol. As the acid constituting the neopentyl type polyol ester, C2
There are ~Cwt saturated fatty acids and unsaturated fatty acids, for example,
butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid,
pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, valmitic acid, heptadecanoic acid, stearic acid, isostearic acid, nonadecanoic acid, heneicoic acid, lauroleic acid, dzu acid, fisetleic acid, myristic acid. acids, zoumaric acid, palmitoleic acid, betrosenic acid, vaccenic acid,
Examples include fatty acids such as gadolenic acid, oleic acid, linoleic acid, and lilunic acid, or mixed fatty acids thereof, but are not particularly limited thereto.

(4) Petroleum-based softener.

The above-mentioned petroleum softener is a paraffinic process oil having a viscosity specific gravity constant (ν, G, C) of 0.80 to 1.00;
A part or all of the petroleum softener, which is a naphthenic process oil or an aromatic process oil, may be impregnated into the raw rubber in advance as an extender oil during the production of the raw rubber.

(5) The rubber composition of the present invention contains 40 to 100 parts by weight of the carbon black, based on 100 parts by weight of the raw material rubber.
It is formed by combining 2 to 35 parts by weight of the neopentyl type polyol ester and the petroleum softener θ to 60 parts by weight.

If the amount of carbon black is less than 40 parts by weight, the abrasion resistance will decrease, and if it exceeds 100 parts by weight, productivity will decrease, which is not preferred.

In addition, the amount of neopentyl type polyol ester is 2
If it is less than 35 parts by weight, the frictional resistance on icy road surfaces will not be sufficiently increased, and if it is more than 35 parts by weight, the abrasion resistance will be significantly lowered, which is not preferable.

Neopentyl type polyol ester may be used alone, but 6 parts by weight of petroleum softener may be added to 100 parts by weight of raw rubber.
0 parts by weight, preferably 50 parts by weight or less can be used. When neopentyl polyol ester is used alone, it can significantly increase the frictional resistance on icy roads, but even when neopentyl polyol ester and a petroleum-based softener are used together, by adjusting the ratio of both, neopentyl It is possible to obtain approximately the same frictional resistance on icy roads as when polyol ester is used alone. The petroleum softener is added to suppress a decrease in frictional resistance on a wet road surface, and if it exceeds 60 parts by weight, the abrasion resistance will decrease, which is not preferable. When using neopentyl-type polyol ester and petroleum-based softener together, the amount of neopentyl-type polyol ester should be 20% in the total amount of softener.
It is preferably contained in an amount of up to 80% by weight.

In the present invention, when the neopentyl type polyol ester and petroleum-based softener are used together, the combined amount is preferably 10 to 90 parts by weight per 100 parts by weight of the raw rubber. If the amount exceeds 90 parts by weight, the frictional resistance will not be sufficiently increased, and the abrasion resistance will drop significantly, which is undesirable.

In addition to the above-mentioned compounding agents, the rubber composition for tire treads of the present invention optionally contains appropriate amounts of compounding agents such as zinc oxide, stearic acid, anti-aging agents, vulcanization accelerators, and sulfur.

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

Performance Examples 1 to 6 and JW'' 1 to 4 Rubber compositions were prepared by kneading raw rubber and various compounding agents in the proportions (parts by weight) shown in Table 1 below in a conventional manner. Press vulcanization was performed at ℃ for 15 minutes to prepare samples for measurement of volatilization amount (heat loss), wear amount (pico wear), and frictional resistance.

The loss on heating is determined by leaving a test piece with a thickness of 2.5 ± 0.5 = +m, width and length of 10 mm each in an oven at 150 ± 2°C for 2 hours for unvulcanized rubber and 24 hours for vulcanized rubber. After that, it was taken out, cooled in a desiccator, and its mass was measured to determine the loss on heating. The results were expressed as an index with the heating loss of Comparative Example 1 as 100. The smaller the value, the smaller the loss on heating, which is better.

In the wear test, the wear loss of Comparative Example 1 was 10
It is expressed as an index as 0, and the larger the index, the better.

Frictional resistance on icy and wet roads was measured using the British Portable Skiffed Tester (AST M E 30).
3). The British Portable Skid Tester is a testing machine developed for the purpose of evaluating the frictional characteristics of roads, and is suitable for measuring the frictional resistance of tire tread materials against various road surfaces. Frictional resistance was measured using a water basin at -8° C. as the frozen road surface and a submerged Safety Walk (manufactured by 3M, outdoor type B) as the wet road surface. The frictional resistance of the frozen road surface was measured on a blank sample immediately after vulcanization and on a sample left in an oven at 70° C. for 10 days. The frictional resistance of Comparative Example 1 is 1
The frictional resistance of the frozen road surface is expressed as an index of 00, and the frictional resistance of the sample before heat treatment in Comparative Example 1 is expressed as 1.
It is expressed as an index set to 00. The larger the frictional resistance index, the greater the frictional resistance, which indicates that it is better.

(Margin below overlapping) In Table 1, Comparative Example 1 has small V, G, and C (viscosity specific gravity constants) that are considered suitable for increasing the frictional resistance of conventional tread rubber materials on icy road surfaces. This is a rubber compound that uses paraffin-based process oil as a softening agent. As shown in Table 1, in Examples 1 to 6 in which neopentyl polyol ester was blended as a softener, the amount of volatilization in unvulcanized and vulcanized rubbers was significantly reduced. When a neopentyl polyol ester and a petroleum softener are used together, the higher the content of the neopentyl polyol ester, the lower the amount of volatilization.

Moreover, Examples 1 to 6 in which neopentyl type polyol ester was blended significantly improved frictional resistance on icy road surfaces. Because there is little volatilization of the softener caused by heating at the same time, there is an advantage that the physical properties after heat treatment, that is, the frictional resistance on icy roads, do not change much, and the high maneuverability during tire manufacturing can be demonstrated for a long period of time. can.

On the other hand, Comparative Example 2 containing an oleic acid derivative (e.g. butyl nioleate) and Comparative Example 3 containing a sebacic acid derivative (e.g. dioctyl sebacate) also have improved frictional resistance compared to petroleum-based softeners, but when heated Because the softening agent volatilizes to a large extent, the frictional resistance after heat treatment decreases, making it impossible to maintain the initial high frictional resistance. Furthermore, oleic acid derivatives and sebacic acid derivatives cause a large loss of heat in unvulcanized rubber;
The softener evaporates during tire manufacturing, worsening the working environment.

〔Effect of the invention〕

As explained above, according to the present invention, frictional resistance on icy road surfaces is improved by using a neopentyl polyol ester or a mixture of a neopentyl polyol ester and a petroleum softener as a softener in a rubber composition for tire trends. It becomes possible to significantly improve athletic performance and maintain that high athletic performance over a long period of time.

At the same time, the volatile content in the tire manufacturing process can be significantly reduced, improving the working environment.

The rubber composition of the present invention having such effects is not only suitable as a trending material for winter tires that run on icy roads, but also has the above characteristics, so it can be used on both general roads and snowy and icy roads. It can also be used as a tread material for all-season tires.

Claims (1)

[Scope of Claims] 40 to 100 parts by weight of carbon black, represented by the following formula, per 100 parts by weight of one or more rubbers selected from the group consisting of natural rubber, polyisoprene rubber, and diene rubber. Neopentyl type polyol ester 2~
A rubber composition for a tire tread, comprising: 35 parts by weight, and 0 to 60 parts by weight of a petroleum softener. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R is a hydrogen atom, a hydroxyl group, a methyl group, or a general formula ▲There are mathematical formulas, chemical formulas, tables, etc.) (represents a hydrocarbon group) and may be the same or different, but at least two of R have the general formula ▲
There are mathematical formulas, chemical formulas, tables, etc. This is the group shown by ▼. n is a number from 0 to 2)