JP3323279B2 - Rubber composition for bonding steel cord - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition having good adhesion to a steel cord, and more particularly to an adhesion between a steel cord and a rubber composition after being left under heat aging conditions, and The present invention relates to a rubber composition for bonding a steel cord having good rubber properties after standing under heat aging conditions.

[0002]

2. Description of the Related Art There have been proposed many methods for improving the adhesion between a steel cord and rubber. There are two approaches to improvement, one is brass, zinc,
Alternatively, this is an improvement from the so-called steel cord surface, which is performed by plating with bronze or the like, and the other is an improvement from the viewpoint of the rubber composition. It is well known that the addition of an organic acid metal salt, particularly an organic acid cobalt salt, improves the adhesion between rubber and steel cord. However, diversification and high performance of rubber products using a steel cord as a reinforcing material require not only initial adhesion but also adhesion under various conditions. Taking tires using steel cords for belts and carcass as an example, not only are the initial adhesion high, but also the resistance to deterioration due to heat generated due to high-speed running, and the adhesion that can withstand thermal aging, In addition, resistance to a decrease in adhesion due to moisture absorption during storage is required.

To meet these demands, there are a number of patents that disclose specific organic acid metal salts as adhesion promoters.
As examples of these, particularly as organic acid cobalt salts, US Pat. No. 1919718 discloses acetates and low molecular weight fatty acid salts, especially cobalt stearate, and US Pat.
No. 5 includes cobalt oleate and cobalt citrate; British Patent No. 1169366 discloses cobalt linoleate, cobalt resinate, and the like; US Pat.
No. 8, cobalt salts such as naphthenic acid, octylic acid and tolic acid are disclosed in Japanese Patent Application Laid-Open Nos. 60-15444 and 60-158230, and cobalt borates are disclosed in Japanese Patent Application Laid-Open No. 60-199643. Metal salts of sulfates and the like are disclosed. However, although all have good specific adhesiveness, the above-mentioned initial adhesiveness (including under vulcanization and over vulcanization), adhesion that can withstand heat aging, water-resistant adhesion, and fracture resistance are all balanced. A removed rubber composition has not been obtained. In addition, cobalt salts of organic acids, which have the best performance as an adhesion improver among those skilled in the art, also have a resistance to deterioration due to heat generation due to high speed running in a situation where high performance is required in recent years. Further, there is a demand for an improvement in adhesiveness that can withstand heat aging.

[0004]

DISCLOSURE OF THE INVENTION In view of the above prior art, the present invention has better initial adhesion to a steel cord material, water resistance and fracture resistance than a conventional rubber composition to which a cobalt borate salt is added. It is another object of the present invention to provide a rubber composition having excellent adhesiveness that can withstand heat aging (referred to as heat aging adhesiveness).

[0005]

Means for Solving the Problems As a result of studying the above problems, the present inventors have identified a rubber composition containing a rubber component and an adhesion improver, and identified Co and Ni as metal components of the adhesion improver. By adjusting the ratio, it was found that a rubber composition having adhesiveness to a steel cord, particularly adhesiveness having water resistance and heat aging resistance was obtained, and the present invention was completed. That is,

[0006] Steel cord adhesive rubber composition of the present invention include natural rubber, synthetic polyisoprene or a rubber component comprising at least one of 50 wt% or more selected from Ranaru group 10
At least one adhesive improver selected from metal borates represented by the following general formula (I) per 0 parts by weight.
A rubber composition containing 1 to 15 parts by weight, wherein the metal component weight ratio Co / Ni of the adhesion promoter is 90/10 to 55/45.
It is characterized by being.

Embedded image

The rubber component used in the composition of the present invention contains at least 50% by weight, preferably at least 70% by weight, of natural rubber, synthetic polyisoprene, or a mixed rubber of natural rubber and synthetic polyisoprene. Butadiene rubber, butadiene rubber, chloroprene rubber, butyl rubber and at least one synthetic rubber selected from the synthetic rubber group such as ethylene-propylene rubber is a rubber component comprising less than 50% by weight, preferably less than 30% by weight, Preferred are natural rubber, synthetic polyisoprene, and a mixed rubber of natural rubber and synthetic polyisoprene.

The organic acid metal salt used for the metal borate represented by the above general formula (I) as the adhesion improver of the present invention includes metal versatate, metal naphthenate, metal stearate, and oleic acid. Metal salt, ricinoleic acid metal salt, linoleic acid metal salt, linoleic acid metal salt, dehydrated castor oil acid metal salt, resin acid metal salt, hydroxystearic acid metal salt, abietic acid metal salt, metal cabrylate,
-Metal salts of ethylhexanoic acid, metal salts of octylic acid, metal salts of benzoic acid, metal salts of vivalic acid and the like.

The metal borate as an adhesion improver is a compound represented by the above general formula (1). Specific examples of the monocarboxylic acid having 7 to 11 carbon atoms in the acid group in the general formula (1) include n-heptanoic acid, 2,2-
Dimethylpentanoic acid, 2-ethylpentanoic acid, 4,4-
Dimethylpentanoic acid, n-octanoic acid, 2,2-dimethylhexanoic acid, 2-ethylhexanoic acid, 4,4-dimethylhexanoic acid, 2,4,4-trimethylpentanoic acid, n
-Nonanoic acid, 2,2-dimethylheptanoic acid, 6,6-dimethylheptanoic acid, 3,5,5-trimethylhexanoic acid, n-decanoic acid, 2,2-dimethyloctanoic acid, 7,
7-dimethyloctanoic acid, n-undecanoic acid, "Bersatek" 10 [TM], primarily neodecanoic acid, and Shell International Company Limited in the UK
Synthetic mixture sold by. ].

The metals in the adhesion improver used in the composition of the present invention are Co and Ni, and their weight ratio (Co / N
i) is 90/10 to 55/45, preferably 75/25
６０60/40. If the Co ratio is 55 or less, the initial adhesion is poor, and if the Co ratio is 90 or more, the heat aging adhesion is poor.

The content of the adhesion improver used in the composition of the present invention is 0.1 to 100 parts by weight of the rubber component in the composition.
To 15 parts by weight, preferably 0.2 to 10 parts by weight, more preferably 0.25 to 5 parts by weight, and when expressed in terms of Co content with respect to 100 parts by weight of the rubber component in the composition, 0.05
To 1.0 part by weight, preferably 0.1 to 0.8 part by weight, and more preferably 0.2 to 0.65 part by weight. If the Co content of the adhesion improver is not more than 0.05 part by weight or not less than 1.0 part by weight, the adhesiveness is deteriorated.

In the composition of the present invention, in addition to the above-mentioned rubber component adhesion improver, a compounding agent usually used as a rubber compounding agent, for example, carbon black, process oil, vulcanizing agent, vulcanization accelerator, antiaging agent Etc. can be appropriately compounded.

[0013]

The present invention will be described below in more detail with reference to Examples and Comparative Examples. The physical properties of the rubber compositions obtained in Examples and Comparative Examples were measured by the following methods. (I) Tensile test (100% modulus and elongation at break) The tensile test was performed according to JIS-K-6301. An initial measurement value measured after preparing a test sample vulcanized at 160 ° C. for 20 minutes and a heat aging condition (80 ° C. × 24
(In a gear oven for a period of time), and then measured after heat aging.

(II) Adhesion test Brass-plated steel cord (1 × 5 structure, wire diameter 0.2
5mm) are arranged in parallel at an interval of 12.5mm, and a rubber composition is coated from both sides of the steel cord to prepare a sample (ASTM sample) having an embedding width of 12.5mm. ASTM-D
The steel cord was pulled out in accordance with −2229, and the pulling force at that time was measured. The adhesiveness values in Table 1 are indexed with the value of Comparative Example 1 (where the metal of the adhesion improver is only Co) being 100. A. Initial adhesion: Proper vulcanization of ASTM sample (160
After 20 minutes) and after vulcanization (160 ° C, 40 minutes)
Later measurements were made. I. Unvulcanized water-resistant adhesion: ASTM sample at temperature 30
After standing for 48 hours in a thermo-hygrostat at 86 ° C and a relative humidity of 86%,
After vulcanization at 60 ° C. for 20 minutes, the measurement was performed. C. Water resistance after vulcanization: 160 ° C. for ASTM sample
After vulcanization for 20 minutes, the temperature was measured after standing in a thermo-hygrostat at a temperature of 70 ° C. and a relative humidity of 96% for 96 hours. D. Heat aging adhesion: 160 ° C for ASTM sample, 2
After vulcanization for 0 minutes, heat aging conditions are temperature 100 ° C × 120.
The time was measured after standing in a gear oven.

[0015] Adhesion improvers used in Examples and Comparative Examples were prepared as follows. a) Adhesion improver A (used in Example 1, Comparative Examples 4 and 5) Cobalt hydroxide (2 mol) and nickel hydroxide (1 mol)
Was dissolved in a mixture of versatic acid (3 mol) and acetic acid (3 mol). The water formed during the reaction was removed by heating the mixture at 190 ° C. for 4 hours. The mixed acid soap thus produced was converted to n-butyl orthoborate (1 mol)
And the displaced acetic acid is removed from the reaction mixture by 235.
By heating at 6 ° C. for 6 hours, butyl acetate was distilled off. Upon cooling, the product was obtained consisting of a dark blue, hard, substantially non-tacky solid. b) Adhesion improver B (used in Example 2) Cobalt hydroxide (2.25 mol) and nickel hydroxide (0.75 mol) were dissolved in a mixture of versatic acid (3 mol) and acetic acid (3 mol). . Mix at 190 ° C for 4
Water generated during the reaction was removed by heating for an hour. The mixed acid soap thus produced is reacted with n-butyl orthoborate (1 mol) to replace the substituted acetic acid.
The reaction mixture was heated at 235 ° C. for 6 hours and distilled off as butyl acetate. Upon cooling, the product was obtained consisting of a dark blue, hard, substantially non-tacky solid.

C) Adhesion enhancer C (used in Comparative Example 1) Cobalt hydroxide (3 mol) was dissolved in a mixture of versatic acid (3 mol) and acetic acid (3 mol). Mix 1
Water generated during the reaction was removed by heating at 90 ° C. for 4 hours. The mixed acid soap thus produced was reacted with n-butyl orthoborate (1 mol), and the substituted acetic acid was distilled off as butyl acetate by heating the reaction mixture at 235 ° C. for 6 hours. . When cooled,
The product was obtained consisting of a dark blue, hard, substantially non-tacky solid. d) Adhesion enhancer D (used in Comparative Example 2) Cobalt hydroxide (2.8 mol) and nickel hydroxide (0.
Versatic acid (3 mol), acetic acid (3 mol)
Was dissolved in the mixture. The water formed during the reaction was removed by heating the mixture at 190 ° C. for 4 hours. The mixed acid soap thus produced was reacted with n-butyl orthoborate (1 mol), and the substituted acetic acid was distilled off as butyl acetate by heating the reaction mixture at 235 ° C. for 6 hours. . Upon cooling, the product was obtained consisting of a dark blue, hard, substantially non-tacky solid. e) Adhesion enhancer E (used in Comparative Example 3) Cobalt hydroxide (1 mol) and nickel hydroxide (2 mol)
Was dissolved in a mixture of versatic acid (3 mol) and acetic acid (3 mol). The water formed during the reaction was removed by heating the mixture at 190 ° C. for 4 hours. The mixed acid soap thus produced was converted to n-butyl orthoborate (1 mol)
And the displaced acetic acid is removed from the reaction mixture by 235.
By heating at 6 ° C. for 6 hours, butyl acetate was distilled off. Upon cooling, the product was obtained consisting of a dark blue, hard, substantially non-tacky solid.

Example 1 100 parts by weight of natural rubber, 10 parts by weight of zinc oxide, 2 parts by weight of an antioxidant, 55 parts by weight of HAF carbon black, and 0.4 parts by weight of an adhesion improver A were mixed by a Banbury internal mixer. Then, a master batch was obtained. 6 parts by weight of sulfur and 0.7 parts of vulcanization accelerator DZ were added to the obtained masterbatch.
A part by weight was added and kneaded on an open roll to obtain a rubber composition for bonding steel cord. Table 1 shows the physical property evaluation.

Example 2 and Comparative Examples 1 to 5 The procedure of Example 1 was repeated except that the type of the adhesion improver was changed as shown in Table 1.

[0019]

[Table 1]

[0020]

Industrial Applicability The rubber composition for bonding steel cords of the present invention has an initial adhesion to a steel cord material, water resistance,
It has good fracture resistance and excellent adhesion that can withstand heat aging. Therefore, the rubber composition of the present invention is suitably used for coating steel belts of tires and carcasses. In addition, it can be used for steel coating such as a conveyor belt and a hose.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-59-223737 (JP, A) JP-A-56-159236 (JP, A) JP-A-58-161604 (JP, A) JP-A-60-1985 15444 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 21/00 C08L 7/00 C08L 9/00-9/06 C08K 5/55 C08K 5/09-5/098

Claims (2)

(57) [Claims] 1. A metal borate represented by the following general formula (I) based on 100 parts by weight of a rubber component containing 50% by weight or more of at least one selected from the group consisting of natural rubber and synthetic polyisoprene. A rubber composition comprising 0.1 to 15 parts by weight of at least one adhesive improver,
The metal weight ratio Co / Ni of the adhesion improver is 90/10 to 10/10.
55/45, a rubber composition for bonding steel cord. Embedded image 2. The adhesion improver has a general formula: (Where M represents Co and Ni, X, Y and Z
Is a metal borate represented by the formula (1), which represents an acid group of a monocarboxylic acid having 7 to 11 carbon atoms).