JPS586737B2 - Rubber composition that adheres well to zinc or zinc-plated metal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rubber composition that has excellent adhesion to metals, and in particular, by incorporating a halogen compound and zinc white into the rubber composition, zinc or zinc can be plated on the surface. The present invention relates to a new rubber composition which has excellent adhesion to metals and which can greatly improve adhesion instability due to heat history in the manufacturing process, heat history during vulcanization, etc., and adhesion instability after heat aging.

More specifically, the rubber composition of the present invention can be used for conveyor belts having a galvanized steel cord as a core, as well as for anti-vibration rubbers and rubber linings that utilize galvanized metal. It can also be used for products made by gluing together.

Conventionally, rubber compositions that directly adhere to zinc or zinc-plated metals include rubber substances such as natural rubber,
Rubber compositions in which sulfur and cobalt salts of organic acids are blended into synthetic rubber or a blend of natural rubber and synthetic rubber, or rubber compositions in which sulfur and zinc white are blended into rubber substances are known. Due to the thermal history during vulcanization, adhesion stability was poor, and adhesion failures often occurred.

In particular, when manufacturing conveyor belts, it is necessary to mix and roll a large amount of compound at once, and in addition, the adhesive strength between the steel cord and the rubber composition often decreases due to the heat history caused by overvulcanization when joining the belt after manufacturing. A defect was found that could cause a malfunction.

The present inventors developed a rubber composition that adheres well to zinc or a metal whose surface is plated by vulcanizing it and has adhesive stability against heat. It has been found that it is extremely effective to mix a certain amount or more of each of these.

That is, the object of the present invention is to produce natural rubber (NR), synthetic polyisoprene rubber (IR), styrene-butadiene copolymer rubber (
In a rubber composition consisting of a raw rubber made of one type of rubber (SBR) and polybutadiene rubber (BR) or a mixture thereof, sulfur and a cobalt salt of an organic acid, a chlorine- or bromine-containing organic compound is added to 100 parts by weight of the raw rubber. On the other hand, the amount of halogen is 0.5 parts by weight or more and zinc white is the raw material rubber 10
It is an object of the present invention to provide a rubber composition which has good adhesion to zinc or zinc-plated metal and is blended with 5 parts by weight or more to 0 parts by weight.

The above rubber composition uses natural rubber that can be vulcanized with sulfur, one of diene-based SBR, IR, and BR, or a mixture thereof as a raw material rubber, and contains sulfur and a cobalt salt of an organic acid such as stearic acid, It can be obtained by blending one or more cobalt salts such as octylic acid, rosin acid, and naphthenic acid, and further adding a chlorine compound, a bromine compound, and zinc white.

When the rubber composition of the present invention is pressure-vulcanized on zinc or a metal whose surface is plated with zinc, much higher adhesive strength and adhesive stability against heat can be obtained than with a rubber composition that does not contain chlorine- or bromine-containing organic compounds. .

The organic acid cobalt salt used in the rubber composition of the present invention is preferably blended in an amount of 1 to 10 parts by weight per 100 parts by weight of the raw rubber.

If the cobalt salt of the organic acid is less than 1 part by weight, the adhesiveness will be poor, and if it is more than 10 parts by weight, the processability will be poor in the case of crosstalk.
The aging resistance of the rubber composition tends to deteriorate.

Most preferably, it is used in an amount of 2 to 7 parts by weight.

Suitable organic compounds containing chlorine or bromine in the rubber composition of the present invention include chlorinated paraffin, chlorinated polyolefin, chlorinated rubber, chloroprene rubber, chlorosulfonated polyethylene, hexabromobenzene, brominated alkylphenol resin, etc. It is desirable that the amount of halogen is 0.5 parts by weight or more per 100 parts by weight of rubber.
．． If the amount is less than 5 parts by weight, the adhesion will be poor, and if too much is added, the vulcanization delay will be severe and workability will be poor, so it is desirable to use 0.5 to 40 parts by weight of the halogen.

Note that chloroprene rubber not only improves adhesiveness but is also effective as a raw material rubber.

Next, the zinc white used in the present invention has the effect of greatly improving adhesion loss after overvulcanization, and as is clear from the examples below, 5 parts by weight of zinc white per 100 parts by weight of raw rubber.
It is desirable to add at least 5 parts by weight, and if it is less than 5 parts by weight, the adhesiveness after overvulcanization will decrease.

The rubber composition according to the present invention can be prepared by mixing the respective materials using a conventional mixer such as a Banbury mixer or a roll mixer.
Furthermore, the rubber composition can be easily molded using a calendar or an extruder.

Before pressing the rubber composition onto a zinc metal surface, it is preferable to remove dirt such as oil from the metal surface using, for example, trichlene or triol.

In addition, when the rubber composition of the present invention is pressure-vulcanized on a zinc metal surface, it is carried out under pressure (for example, 5 to 100 kg/cm2) and at a normal vulcanization temperature (for example, 140 to 180 degrees Celsius), and the vulcanization time is It varies depending on the rubber composition and product shape, and generally, as the vulcanization time increases, the adhesiveness improves.

The rubber composition according to the present invention requires general rubber compounding agents such as carbon black, calcium carbonate, clay, aluminum hydroxide, silica-based rubber reinforcing agents, anti-aging agents, pigments, softeners, and vulcanizing agents. Can be added as required.

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

All amounts of the compositions in each example are shown in parts by weight.

Note that the adhesion test in the examples was conducted as follows.

3 steel cords in parallel 500n (vertical) x 500
It is buried in the center of an unvulcanized rubber of r (horizontal) x l 5 mm (thickness), and is pressed and vulcanized in a mold while applying a pressure of about 20 kg/cr2 (vulcanization conditions are shown in the examples).

《For the sample thus obtained, one central cord and two left and right cords were pulled in opposite directions at a speed of 100 mi/min, and the central cord was pulled out to determine the shear adhesive strength per unit of contact between the cord and the rubber and the cord surface. Measure the rubber attachment point (rubber attachment point).

Example 1 Rubber compositions were prepared according to the following formulation examples by changing the type of chlorine-containing organic compound.

Next, an adhesion test of the above rubber composition was conducted using a galvanized cord obtained by twisting seven wires each having a diameter of 0.49 mm and further twisting seven wires.

As is clear from the table above, the adhesion was significantly improved by adding the chlorine-containing organic compound.

Example 2 Rubber compositions were prepared according to the following formulations by varying the amount of the chlorine-containing organic compound.

An adhesion test was conducted on the above rubber composition according to Example 1.

From the table above, it can be seen that when 5 parts or more of chlorinated paraffin is added, the adhesion improves in all cases.

When 60 parts by weight was added, some vulcanization delay was observed and roll adhesion increased, but adhesion was good.

Example 3 A rubber composition was prepared according to the following formulation by adding the amount of zinc white.

An adhesion test was conducted on the above rubber composition according to Example 1.

As shown in the table above, it is desirable to use zinc white in an amount of 5 parts by weight or more, and even if a large amount of zinc white is added in place of carbon black, the effect will not change (Formulation Example 37) Example 4 Rubber composition with the following formulation was prepared.

The results of the adhesion test of the above rubber composition according to Example 1 are as follows.

Vulcanization conditions 153° x 30 minutes Pulling force kg/cm2 72.2 Rubberized points % 90 Vulcanization conditions 153° x 90 minutes Vulcanization conditions 153° x 90 minutes Pulling force kg/cm2 68.0 Rubberized points % 90 Implementation Example 5 A rubber composition was prepared according to the following recipe by changing the type of raw rubber.

An adhesion test was conducted on the above rubber composition according to Example 1.

As shown in the table above, natural rubber, BR other than SBR,
Similarly good results were obtained with a rubber composition containing IR as a raw material rubber.

As described above, the rubber composition of the present invention is prepared by adding sulfur, an organic acid cobalt salt, a chlorine- or bromine-containing organic compound, and zinc white to a raw material rubber made of one of NR, IR, SBR, and BR or a mixture thereof. It has excellent adhesion to zinc or galvanized metals, improves adhesion instability caused by the thermal history of the manufacturing process (mixing, rolling, extrusion) and after heat aging, and can be used under a wide range of vulcanization conditions (
Stable adhesion can be obtained over time and temperature), and the product's adhesive aging resistance is improved.

Claims (1)

[Claims] 1. In a rubber composition consisting of a raw rubber made of one of natural rubber, synthetic polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, or a mixture thereof, sulfur and a cobalt salt of an organic acid, chlorine- or bromine-containing organic The compound is added in an amount of 0.5 parts by weight or more of nologen per 100 parts by weight of the raw material rubber, and the zinc white is added to 10 parts by weight of the raw material rubber.
A rubber composition having good adhesion to zinc or galvanized metal, which is blended in an amount of 5 parts by weight or more to 0 parts by weight.