Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-05-25
2003-09-30
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S204000, C524S348000, C524S349000, C524S351000, C524S352000, C524S323000, C524S492000, C524S493000, C524S612000
Reexamination Certificate
active
06627687
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rubber composition for adhering to steel cords and particularly to a rubber composition for adhering to steel cords which is excellent in adhesion to steel cords.
2. Description of the Related Art
In order to increase the adhesive force of rubber to steel cords plated with brass, bronze, or zinc, a cobalt salt of an organic acid has exclusively been used so far. That is, there exists a technique where blending of the cobalt salt of an organic acid with a rubber composition promotes the formation of an adhesive interface layer onto steel cords, thus to increase the adhesive force.
In recent years, problems have been generated such as deterioration in adhesive force caused by high exothermic heat accompanied by speeding up or power up of vehicles, deterioration in adhesive force caused by thermal history accompanied by prolonged lifetime of tires, or deterioration in adhesive force caused by moisture and heat over a period of time which elapses between manufacture and travel (a storing time from manufacture to use, containing a time of practical use), and thus adhesive properties of a higher level have been demanded.
Although the cobalt is excellent in initial adhesion, heat deterioration (heat aging) causes serious deterioration in adhesive force as described above. The cobalt cannot be satisfying any more adhesion performance of a high level required in recent years. It is probable that the cobalt has a strong action to promote oxidation, and the action thereof to promote the formation of an adhesive layer causes increase in thickness of the adhesive layer in terminal travel to lead to fracture of the rubber layer.
The cobalt is a rare metal, and countries producing the raw material thereof may be politically unstable. Accordingly, the cobalt is disadvantageous in high fluctuation in price and unstable supply of rubber products.
SUMMARY OF THE INVENTION
The invention has been carried out under the aforesaid circumstances. An aim of the invention is to provide a rubber composition for adhering to steel cords without relying only on the cobalt, composition which has excellent heat-resistant adhesion and moist heat-resistant adhesion as well as excellent initial adhesion and performance of a level similar to or higher than that in the related art as to resistance to rubber fracture.
A rubber composition for adhering to steel cords as described in claim
1
is a rubber composition excellent in adhesion to steel cords. The rubber composition is prepared by adding the following component (A) in a metal-converted amount of 0.01 to 10 weight parts to 100 weight parts of a rubber component containing natural rubber and/or a diene synthetic rubber.
(A) A mixture of a compound containing nickel, a compound containing molybdenum, and a compound containing cobalt; a compound containing simultaneously nickel, molybdenum, and cobalt; or a mixture of a compound containing simultaneously two metallic elements selected from nickel, molybdenum, and cobalt and a compound containing the residual metallic element.
A composition as described in claim
2
is prepared by further adding the following component (B) consisting of (b1) and (b2) in the composition as described in claim
1
.
(B) (b1) 0.2 to 20 weight parts of hexamethylenetetramine or a melamine derivative, and (b2) 0.1 to 10 weight parts of at least one selected from the group consisting of phenol resins, resorcin, resorcin derivatives, and cresol resins.
A composition as described in claim
3
is prepared by further adding a compound containing calcium (C) in the composition as described in claim
1
or
2
.
A composition as described in claim
4
is prepared by adding the aforesaid compound containing calcium (C) in an amount of 0.1 to 20% in weight ratio to the aforesaid component (A) in the composition as described in claim
3
.
A composition as described in claim
5
is prepared by further adding silica (D) in the composition as described in any one of claims
1
to
4
.
A composition as described in claim
6
is prepared by adding 1 to 100 weight parts of the aforesaid silica (D) to 100 weight parts of the rubber component in the composition as described in claim
5
.
The invention can provide a rubber composition for adhering to steel cords which has excellent heat-resistant adhesion and excellent moist heat-resistant adhesion as well as excellent initial adhesion and performance of a level similar to or higher than that in the related art as to resistance to rubber fracture.
DETAILED DESCRIPTION OF THE INVENTION
Rubber Components
Examples of rubber components used in the invention include natural rubber and synthetic rubber such as polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene-isobutylene rubber (IIR), ethylene-propylene-diene rubber (EPDM), and modified rubber thereof. These can be used singly or as a mixture of two or more thereof.
Component (A)
The compound containing nickel, the compound containing molybdenum, and the compound containing cobalt can be either an inorganic compound or an organic compound, respectively.
The inorganic compounds include nickel oxide, molybdenum oxide, and cobalt oxide; nickel sulfate, molybdenum sulfate, and cobalt sulfate; nickel phosphate, molybdenum phosphate, and cobalt phosphate; nickel phosphite, molybdenum phosphite, and cobalt phosphite; nickel carbonate, molybdenum carbonate, and cobalt carbonate; and nickel chloride, molybdenum chloride, and cobalt chloride.
The organic compounds include nickel salts, molybdenum salts, and cobalt salts of organic acids; and an organonickel sulfur compound, an organomolybdenum sulfur compound, and an organocobalt sulfur compound.
Herein, preferred nickel salts of organic acids are nickel naphthenate, nickel octylate, nickel propionate, nickel abietate, and nickel acetate in view of excellent adhesion performance.
Preferred molybdenum salts of organic acids are molybdenum naphthenate and/or molybdenum abietate in view of excellent adhesion performance.
Furthermore, the cobalt salts of organic acids are cobalt salts of neodecanoic acid, stearic acid, naphthenic acid, rosin, tall oil acid, oleic acid, linoleic acid, and linolenic acid. Herein, these organic acids can be partly replaced with compounds containing boron such as boric acid.
In component (A), a Ni/Mo ratio (weight converted to metals) is not particularly limited, but preferably is from 2/1 to 20/1. The ratio less than 2/1 may invite problems of being uneconomical (Mo is very costly as compared with Ni) and decreasing hardness (rigidity) of the resulting rubber. Exceeding 20/1 may invite a problem of being unable to acquire sufficient adhesion (Ni cannot compensate deterioration in adhesion).
In these salts of organic acids, it also is possible to blend organic acids. For example, adhesion, particularly moist heat adhesion is preferably improved when component (A) is a mixture of nickel salts of naphthenic acid and octylic acid (naphthenic acid/octylic acid={fraction (1/1)} to ¼ in weight percent) and a molybdenum salt of naphthenic acid.
Naphthenic acid is preferred on the grounds that the high acid value of, for example, 250 mgKOH/g or more further improves the adhesion, particularly the heat-resistant adhesion.
In component (A), it is preferable that the ratio of cobalt to total weight of Ni and Mo is from 1 to 50 weight percent. The ratio of cobalt less than 1 weight percent may not lead to sufficient initial adhesion whereas exceeding 50 weight percent may cause serious decrease in adhesion owing to heat aging or cause decrease in cost merit. Herein, the range is preferably from 10 to 20 weight percent.
Component (B)
A combination of the following components (b1) and (b2) composes component (B) of the invention.
(b1) hexamethylenetetramine or melamine derivatives.
(b2) at least one selected from the group consisting of phenol resins, resorcin, resorcin derivatives, and cresol resins.
An example of the melamine derivatives is hexamethoxymethylmel
Hatano Seiji
Hayashi Hirofumi
Cheung William K
Jordan and Hamburg LLP
Toyo Tire & Rubber Co., Ltd.
Wu David W.
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