JPS5843807A - Large-sized tire excellent in resistance to side cutting - Google Patents

Abstract

PURPOSE:To improve the durability of a tire, by employing a specified rubber raw polymer as a rubber composition for a side part of a large-sized tire. CONSTITUTION:The rubber raw polymer as a rubber composition for a side part of a large-sized tire comprises a blended rubber of a styrene-butadiene rubber prepared by the solution polymerization and one or more of dien rubbers provided that the relationship between the amounts of stryrene and vinyl in the styrene-butadiene rubber satisfies formula (1) with the composition value X=30- 45, and the styrene-butadiene rubber is 30% or more in the blended rubber. Thus the resistance to cutting and crack and the low heat generating property of the side part can be improved, and therefore the durability of the tire can significantly be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to improving the side cut resistance of large tires for use in truck buses, construction vehicles, industrial vehicles, etc. Specifically, in the rubber compound of the side portion of the tire, It has the same low heat generation property as the conventional one, and further improves cut resistance and crud resistance.

In the first place, off-the-road tires (OFF THE ROAD - abbreviated as OT'R) and truck and bus tires (abbreviated as TB) used in mines, dam construction, etc. have their side parts damaged by rocks scattered on driving roads, mining sites, etc. It is susceptible to cuts, which can not only affect the appearance but also reduce the running life of the tire. In some cases, the cut damage also penetrates the carcass layer on the side of the tire, causing the tire to burst.

Therefore, in order to improve the cut resistance of the side parts, attempts have been made to reinforce the carcass ply of the side parts, increase the rubber thickness of the side parts, and improve the composition of the side part rubber.

Reinforcement of the side carcass plies in these trials;
An increase in the side rubber thickness, etc. will lead to an increase in material costs.
Furthermore, the rolling resistance of the tire increases due to the increase in the thickness of the side part, and furthermore, the heat generation of the side part increases.

Furthermore, in conventional compounding techniques, improvements in the rubber compound of the side portions have been insufficiently effective due to limitations in the heat generation resistance and crack resistance of the rubber.

In other words, improvements in the cut resistance of rubber compounds are limited to heat generation resistance and crack resistance.

In other words, in order to improve the cut resistance of the rubber compound,
Reinforcing fillers (e.g. carbon black, silica, etc.) and resins have been used, but in either case, the heat generated by the rubber increases when subjected to repeated dynamic strain.
This was not preferable in terms of breaking strength.

As described above, it has been extremely difficult to simultaneously improve the cut resistance and heat generation resistance of rubber.

Therefore, the inventors were acutely aware of the need to explore the behavior of the basic polymer in order to eliminate the conventional deficiencies, and as a result of trial and error, they developed solution polymerized styrene-butadiene rubber (abbreviated as S).
-8BR), and found that certain types of molecular star-type polymers are particularly effective.

Furthermore, as a result of research on S-8BH, it was found that - In the rubber compound composition for the side part of large tires, the rubber raw material polymer is composed of one or more -l types of solution polymerized styrene-butadiene rubber and other diene rubbers. It is a blended rubber, and the solution polymerized styrene-butadiene rubber has a composition value in the range of X = 30 to 45 determined by the following formula in terms of the relationship between the amount of styrene and the amount of vinyl, and this polymer is used. By being composed of all rubber raw materials, that is, rubber raw materials containing 30% or more in the blended rubber, the tire side part has low heat generation and is suitable for large tires with excellent cut resistance and crack resistance. It is something that can be relied upon as it has made it possible.

In addition, the value of the composition value X determined by the above composition formula is 3
If it is less than 0, the contribution to the improvement of cut resistance is small, and if it is 45 or more, the glass transition temperature (T2) of the rubber compound becomes high, and the cold resistance of the tire decreases, making it impossible to withstand use in cold regions.

In addition, if the amount of bound styrene in S-8BH is less than 10%,
The contribution of rubber compounds to improvement of cut resistance is small, at 30%.
If it exceeds 100%, the adhesiveness of the unvulcanized rubber will be insufficient and tire molding will be particularly difficult. Therefore, the amount of bound styrene is 15% or more3
It is preferably 0 or less.

Furthermore, if the vinyl content (1,2-bonded butadiene content) in S-8BR is less than 4096% compared to the total butadiene content, crack resistance will be impaired, and if it exceeds 70%, the workability of rolls etc. will deteriorate. Therefore, the amount of vinyl is 40% or more and 70%
The following are preferred.

Further, even if the physical properties of 5-8B'H satisfy the above conditions, if the content of S-8BH in the rubber raw material polymer used is less than 30%, its contribution to cut resistance is small. Therefore, it is necessary to have a composition containing 309b or more of S-8BR in the rubber compounding composition. Also, B-
Among 8BRs, star-type polymers are particularly effective.

Next, the present invention will be specifically explained in detail by giving typical examples.

Tables 1, 2, 3, and 4 show the compositions and physical properties of Examples and Comparative Examples of the present invention.

11' □・) JP-A-58-43807 (3) (note) SBR...Styrene butadiene rubber.

Emulsion polymerization SBR: styrene content 23.5% by weight, stain-prone cold rubber.

NR...Natural rubber solution polymerization 8 B R-(a) (bXCXd) is a star type, and (e) is a linear type, each with a different amount of styrene (- and vinyl amount), so , the composition value X is different.

Anti-aging agent...N-phenyl-N'-inpropyl-
P-phenylenediamine.

Accelerator: N-oxydiethylene-2-benzothiazolesulfenamide.

The physical properties for the above formulation (Table 1) are shown in Table 2.

Table 2 (Physical Properties) (Note) 8BR-1500: Styrene-butadiene rubber, styrene content 23.5% by weight, stain-prone cold rubber, Mooney viscosity 46-58.

The physical properties for the formulations in Table 3 above are shown in Table 4 below.

:S',. 414176. . iAltM*,! :L. .

is compared with 100.

5. Cut resistance is when cutting a knife with a load of 5.5 cm from a height of 60 cm.
A blade with a load of 10# is allowed to fall freely from a height of 30 degrees, and the depth and depth of penetration into the rubber is measured.The degree of resistance is compared with an index.The larger the number, the deeper the penetration. It is shallow and has good cut resistance. (a'l is load 5kg height 60
(7) and (b) are the cut resistance when the load is 10 cm and the height is 30 crn.

5 Exothermicity is measured at room temperature 1 using a Gudrich flexmeter.
It was measured at 00°C. It was also compared using an index, and the smaller the number, the lower the degree of heat generation.

9 Crack resistance is a comparison of the number of cycles until cracking occurs using an index using a deMattia bending fatigue tester under the test conditions specified in JIS-6301, and the higher the number, the better. It is something.

As shown in the test results in the table above, samples A 3, A 4,
Example No. 5 is an example using star-type solution polymerization SBR having the conditions of the present invention, and compared to conventional emulsion polymerization SBH, the cut resistance is almost the same, but the heat generation is reduced,
Cracking resistance has been significantly improved. Therefore, the durability of the side portion is increased in practical terms.

The comparative example of sample A2 is a blending example of a conventional star-type solution polymerized SBH, which has a vinyl content of less than 40% and has performance equivalent to the star-type solution polymerized SDR of the present invention in terms of cut resistance and heat resistance. However, the crack resistance is considerably poor.

Table 3 compares the blended rubber compositions of rubber raw material polymers. Sample/p6A contains 80 parts by weight of natural rubber,
AB is a blend of 20 parts by weight of general 5BR, whereas AB is a blend of 80 parts by weight of natural rubber and solution polymerized 8BR20.
In this case, by blending 20 parts by weight of solution polymerized SBR, the heat generation is significantly reduced, but the cut resistance is insufficient. Sample AC is a blend of 50 parts by weight of natural rubber and 50 parts by weight of general S B' R. - On the other hand, Jf6D is a blend of 50 parts by weight of natural rubber and 50 parts by weight of solution polymerized 5BR. In AD, there is no decrease in cut resistance, which is approximately the same level, but there is a decrease in heat build-up and an improvement in crack resistance. Therefore, it is preferable that the blended rubber contains at least 30% of solution polymerized SBR.

In other words, the polymer composition having the conditions of the present invention has a particularly low heat generation property, and therefore, when compared at the same heat generation level, it has the characteristic that a composition can be obtained that has significantly improved cut resistance than the conventional composition. be. Furthermore, when compared at the same cut resistance level, a composition that generates less heat than the conventional formulation can be obtained.

Next, Table 6 shows the physical properties for the formulations in Table 5, in which silica or resins are added to the formulation examples in Table 1.

Table 5 (composition) (note) Resin <a> is coumaron indene resin.

Resin (b) is cashew nut oil-modified phenolic resin.

The formulation α in Table 5 above is as follows: Sample I61% A5 is the same as in Table 1, Sample I67 is Sample Ya 5 with 10 parts by weight of silica added, and Sample J168 is Sample Ya 5 with 10 parts by weight of silica added. 6
Sample A9 contains 6 parts by weight of resin (b).

] ” □□” As shown in the table above, in the formulation of sample A5, the sample A1, the addition of silica or resins improved the exothermic property compared to the conventional emulsion polymerized SBR formulation sample A1. The cut resistance is compared with the comparative example. That is, Examples of Samples 47, 48 and A9 had almost the same exothermic properties as the Comparative Example of Sample Boiled 1, and the cut resistance was improved by 20 to 30 times. That is, by using the rubber composition of the present invention having the above-mentioned conditions in the side portion of a tire, a large tire with excellent side cut resistance can be obtained.

As shown by the above test results, a large tire constructed with the rubber compounded composition for the side part comprising the constituent elements of the present invention has low heat generation properties in the side part, excellent cut resistance and crack resistance, and is durable. This exhibits an effect that greatly contributes to improving lifespan.

Agent: Patent Attorney Yasushi Oshima

Claims (4)

[Claims] (1) In a rubber compound composition for the side part of a large tire, the rubber raw material polymer is a blended rubber consisting of one or more of solution polymerized styrene-butadiene rubber and other diene rubber, and the solution polymerized styrene・The butadiene rubber has a composition value X = '30 to 45 determined by the following formula, and is characterized by using a composition in which this solution polymerized styrene-butadiene rubber is contained in the blended rubber at 30% 1M. Large tires with excellent side cut resistance. (2) A large tire with excellent side cut resistance according to claim 1, wherein the molecular type of the solution-polymerized styrene-butadiene rubber is a star-type polymer. (3) The amount of bound styrene in the solution polymerized styrene-butadiene rubber is 15% or more and 30% or less. Claim 1
A large tire with excellent side cut resistance as described in the section. (4) A large tire with excellent side cut resistance according to claim 1, wherein the vinyl content of the solution polymerized styrene-butadiene rubber is 40% or more and 10% or less.