JPS5827820B2 - rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rubber composition, and more particularly to a rubber composition that has excellent adhesion to steel cords, particularly water-resistant adhesion and saltwater-resistant adhesion.

In recent years, automobile tires have come to be required to have a high level of performance in terms of safety, high-speed running performance, and durability such as running life, so radial tires that use metal materials for the reinforcing layer are being manufactured in large quantities. It has become.

The adhesion between this metal material, steel cord, and rubber has an important effect on product performance.

To bond a steel cord such as a steel tire to rubber, the surface of the steel cord is often plated with a copper alloy such as brass. It is known that sulfur mixed in the product causes sulfide crosslinking at the interface between rubber and metal, thereby achieving adhesion.

Therefore, the rubber composition coated on the steel cord is a factor in obtaining good adhesion.

Various techniques have been known in the past in order to stably obtain the adhesive properties of this rubber composition.

Representative examples can be roughly divided into the following two types.

That is, white carbon (Hi s i ]),
These are a so-called HRH-based comb composition containing resorcinol and hexamethylenetetramine, and a rubber composition containing a cobalt salt of an organic acid added to the rubber.

However, HRH-based comb compositions generate smoke and odor during Banbury mixing or roll mixing due to the remarkable sublimation property of resorcin, and have the disadvantages of environmental pollution and deterioration of workability.Furthermore, they have poor scorch stability. There were drawbacks such as a reduction in rolling workability and a reduction in adhesive strength due to moisture absorption during unvulcanization.

In addition, the method of blending organic acid cobalt salts into rubber has the disadvantage that adhesive strength decreases after high-temperature vulcanization, long-term vulcanization, or heat aging, and because it contains heavy metals such as cobalt salts, Even after sulfurization, it had the disadvantage of degrading the rubber and reducing the physical properties of the rubber.

If a rubber composition does not contain an HRH system or a cobalt system, it will not have the above disadvantages, but it is difficult to obtain sufficient adhesion to metals by simply increasing the amount of sulfur without including these systems.

Also, N R/B shown in Japanese Patent Application No. 54-59708
The R/POB system (combination system of a blend system of natural rubber and butadiene rubber and paraoxybenzoic acid) is one in which adhesion is not sufficient simply by increasing the amount of sulfur, but is improved by adding BR and POB.

However, while HRH and cobalt systems have the effect of promoting the adhesion reaction between the brass and rubber on the surface of the steel cord, rubber compositions that do not contain these systems exhibit poor performance, such as NR/BR/POB systems. Even if it exhibits good adhesion, it has low reactivity with brass, so it is easily affected by oxidation of the plating surface and lubricant during the wire drawing process in the steel cord manufacturing process, and the amount of lubricant remaining on the surface of the steel cord is particularly high. If there is too much, the adhesion will be extremely poor.

In addition, in systems that do not contain HRH systems or cobalt systems,
In particular, salt water resistance is insufficient compared to cobalt-based products.
There was a drawback.

In cold regions, electrolyte substances such as salt are often sprinkled on roads to prevent them from freezing, and this aqueous electrolyte solution enters the tire tread through trauma, etc., and adheres along the gaps between the steel cords. Salt water resistance is an important property for rubber compositions coated on steel cords, as this may cause deterioration.

As described above, a rubber composition that does not have the disadvantages of conventionally known cobalt-based and HRH-based adhesive compound systems and has excellent adhesion to steel cords has not yet been obtained.

The object of the present invention is to provide a comb composition that has stable adhesion to steel cords, particularly excellent water-resistant adhesion and salt water-resistant adhesion, and is used in steel cord coating rubber for steel tires, etc.

As a result of our research on adhesion stabilization, such as improving the salt water resistant adhesion of rubber compositions containing neither HRH nor cobalt systems such as NR/BR/POB systems and incorporating a large amount of sulfur, we found that these rubber compositions The present invention was achieved by discovering that adding gluten, which is a crude wheat protein, has a remarkable effect on adhesion, especially salt water resistance.

Moreover, since gluten is inexpensive, it is practically preferable as an adhesive stabilizer.

In the present invention, adhesion refers to adhesion that includes initial adhesion, water-resistant adhesion, and salt water-resistant adhesion. The rubber composition improves the adhesion of steel cords, such as water-resistant adhesion, particularly salt water-resistant adhesion, and satisfies the above object.

Raw material rubbers used in the present invention include natural rubber (NR), polyisoprene rubber (IR), and polybucdiene rubber (B).
R), diene rubbers such as styrene-butadiene rubber (SBR), chloroprene rubber (CR), ethylene-propylene-diene terpolymer rubber (EPDM), butyl rubber (IIR), and other widely used rubbers alone or in blends. It is made of rubber.

The gluten used in the present invention is produced using wheat flour as a raw material by a normal method (for example, as described in the Chemical Encyclopedia published by Kyoritsu Publishing), contains about 7 to 8% protein, and has a molecular weight of 11%.
．． It costs between 90,000 and 129,000.

Gluten is blended in an amount of 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the raw material rubber.If it is less than 0.5 parts by weight, the blending effect is small, and even if it exceeds 10 parts by weight, the blending effect is not. few.

In the present invention, sulfur can be optionally blended to the extent that it is blended into ordinary comb compositions, but in order to improve adhesiveness, it is desirable to blend sulfur in a relatively large amount, and the preferred blending amount is 3 to 10 parts by weight per 100 parts by weight of raw rubber. Parts by weight.

If a small amount of sulfur is added, sufficient adhesion will not be obtained; if too much sulfur is added, sulfur will bloom on the rubber surface during unvulcanization, which will not only cause processing problems, but also cause the rubber to become taut after vulcanization. Physical properties such as strength and elongation at break decrease.

Addition of paraoxybenzoic acid (FOB) to the rubber composition of the present invention further stabilizes the adhesion.

In this case, the preferred amount of POB is 0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight.

Less than 0.5 parts by weight and more than 10 parts by weight, respectively, PO
The effect of blending B is small.

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

The preparation of the rubber composition of the example and the first adhesion test were conducted according to the following method.

All amounts in the table are parts by weight.

Preparation of Rubber Composition According to the formulations in Tables 1 and 2, raw rubber and compounding agents other than sulfur and vulcanization accelerator were mixed in a Banbury type mixer, and the remaining compounding ingredients were added to the masterbatch using an open roll to form a rubber composition. It became a thing.

Adhesion test (initial adhesion test) Steel cords (l x
5 structure, strand diameter 0.25 mm) was coated with a rubber composition from both sides and embedded in a width of 12.5 mm.The fabric was then vulcanized at 150 degrees for 130 minutes to prepare a sample for test 1, in accordance with ASTM-D2229. ■ Pulling force when pulling out the wire (kg/finch)
It was evaluated based on the rubber coverage ratio.

In addition, in Example 2, the unvulcanized fabric was
A test sample was vulcanized (overvulcanized) at 50 DEG C. for 190 minutes, and the pull-out force (kg/-2-inch) 2 and rubber coverage were evaluated in the same manner.

(Salt resistance adhesion test 1 test) The above unvulcanized fabric was heated at a temperature of 30°C and a relative humidity of 86%.
After leaving it in the atmosphere for 1 to 2 weeks, it was vulcanized at 1500C for 130 minutes to prepare a second test sample, and the wire was pulled out in accordance with ASTM-D2229, and evaluated by the pulling force (kg/finch) and rubber coverage rate. did.

(Salt water resistance adhesion test) Cut one end of the above ASTM type adhesion test sample (initial adhesion test, test sample after vulcanization) and immerse the cut side to a height of 6 mrft in 20% saline solution. After being left in this state for 4 days, the wire was pulled out in accordance with ASTM-D2229 and evaluated in terms of pulling force (kg/finch) and rubber coverage (maximum).

Examples 1 to 4 and Comparative Example 1 This example shows the adhesion between a rubber containing a large amount of sulfur and a steel cord in which a large amount of lubricant remains. When no gluten is added as in Example 1, the initial adhesion, water-resistant adhesion, and salt water-resistant adhesion are all extremely low.

However, when gluten is added to this system as in Examples 1 to 4, the adhesiveness increases dramatically compared to Comparative Example 1, and the increase in salt water resistance is particularly remarkable.

As the amount of gluten added increases, the adhesiveness improves, but in Example 4 (gluten increasing effect), no gluten increasing effect is observed compared to Example 3 (containing 4 parts by weight of Gludef).

From this, the preferred amount of gluten added is about 1 to 5 parts by weight.

Examples 5 to 8 and Comparative Examples 2 to 4 The present examples compare the effects of adding gluten to NR/BR/POB rubber compositions and HRH rubber compositions and Kobal rubber compositions. In Examples 5 to 8 in which gluten was added, the effect of gluten addition was not so great in terms of initial adhesion and water-resistant adhesion compared to Comparative Example 2 in which no gluten was added, but salt water-resistant adhesion was higher than that of gluten. Improves with increasing weight.

However, similar to the comparison of Examples 3 and 4, Example 8 (containing 10 parts by weight of Gludef) does not show much of an effect of increasing the amount of gluten compared to Example 7 (containing 5 parts by weight of Gludef).

Comparative Example 3 is a cobalt-based rubber composition but has poor initial adhesion during overvulcanization, and Comparative Example 4 is an HRH-based rubber composition but has poor water-resistant adhesion.

From this, it can be seen that the gluten-added rubber compositions of the present invention (Examples 5 to 8) have more stable adhesion than Comparative Examples 2 to 4 in terms of initial adhesion, water-resistant adhesion, and salt water-resistant adhesion. Recognize.

Further, in the present invention, the combination of gluten and POB system further improves the adhesion of the rubber composition to the steel cord.

As explained above, by adding gluten, which is a wheat hull protein, to a rubber composition that does not contain HRH or cobalt-based moieties, stable adhesion to steel cords can be obtained, and in particular, salt water-resistant adhesion is improved. Therefore, it is used for the steel cord coating rubber of steel tires.

Claims (1)

[Claims] 1 Gluten 0.5 to IO per 100 parts by weight of raw rubber
A rubber composition, characterized in that parts by weight are added.