JP3323280B2 - 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 to a steel cord after being left under a heat aging condition, and to a left under a heat aging condition. The present invention relates to a rubber composition for bonding steel cords having good rubber properties afterwards.

[0002]

2. Description of the Related Art Hitherto, many methods for improving the adhesion between a steel cord and rubber have been proposed. There are two approaches to improvement, one is to improve the steel cord surface by plating steel cord with brass, zinc or bronze, and the other is to improve the rubber composition. is there. 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 steel cord as an example for a belt or carcass, tires have high initial adhesion, resistance to thermal degradation caused by high-speed running, and adhesiveness to withstand thermal degradation. For example, resistance to a decrease in adhesion due to moisture absorption is required.

[0003] In order to meet these demands, specific metal salts of organic acids have been disclosed in many patents as adhesion promoters. Examples of these, especially as organic acid cobalt salts,
U.S. Pat. No. 1919718 discloses acetates and low molecular weight fatty acid salts, especially cobalt stearate.
No. 5 includes cobalt oleate and cobalt citrate; British Patent No. 1169366 discloses cobalt linoleate and cobalt resinate; and U.S. Pat.
JP-A-60-15444 and JP-A-60-1
No. 58230 contains cobalt borates.
199643 discloses metal salts of thiosulfates and the like. However, although all of them have good specific adhesiveness, the above-mentioned initial adhesiveness (including under vulcanization and over vulcanization), heat-resistant adhesiveness, water-resistant adhesiveness, and fracture resistance are all balanced. No rubber composition has been obtained. In addition, it is the most proven as an adhesion improver among those skilled in the art, and even for a balanced organic acid cobalt salt,
In a situation where high performance is required in recent years, improvement in resistance to thermal deterioration due to high-speed running and improvement in adhesiveness to withstand heat aging are desired.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, an object of the present invention is to provide an initial bond, a water-resistant bond, and a breakage-resistant material to a steel cord material as compared with a conventional rubber composition containing a cobalt borate salt. An object of the present invention is to provide a rubber composition having good adhesiveness and excellent heat resistance to heat aging (heat aging adhesion).

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies on the above-mentioned problems, and as a result, in a rubber composition containing a rubber component and an adhesion improver, a specific amount of Co and Zn was contained in the metal of the adhesion improver. It has been found that the presence thereof allows the other properties to be maintained, and that the adhesiveness between the rubber component and the steel cord after standing under heat aging conditions (heat aging adhesiveness) is significantly improved. The rubber composition was completed.

That is, the rubber composition for bonding a steel cord according to the present invention is characterized in that at least one selected from the group consisting of natural rubber and synthetic polyisoprene has an organic acid metal content per 100 parts by weight of a rubber component containing 50% by weight or more. A rubber composition containing 0.1 to 15 parts by weight of at least one adhesion enhancer selected from the group consisting of a salt, an organometallic complex and a metal borate, wherein Co is contained in the metal of the adhesion enhancer. Is 96.0-9
It is characterized in that 9.8% by weight and 50 to 5000 ppm of Zn are present. Also, at least one kind of synthetic rubber selected from the group consisting of synthetic rubbers such as styrene-butadiene rubber, butadiene rubber, chloroprene rubber, butyl rubber and ethylene-propylene rubber is used as the rubber component.
Less than 30 parts by weight, preferably less than 30 parts by weight, can be incorporated.

[0007] The adhesion improver used in the composition of the present invention is at least one compound selected from the group consisting of metal salts of organic acids, organic metal complexes and metal borates. The metal salts of organic acids include metal salts of versatic acid, metal salts of naphthenic acid, metal salts of stearic acid, metal salts of oleic acid, metal salts of ricinoleic acid, metal salts of linoleic acid, metal salts of linoleic acid, metal salts of dehydrated castor oil, resins Metal salts of metal acids, metal salts of hydroxystearic acid, metal salts of abietic acid, metal salts of caprylic acid, metal salts of 2-ethylhexanoic acid, metal salts of octylic acid, metal salts of benzoic acid, and metal salts of pivalic acid. Examples include metal complexes of acetylacetone, metal complexes of nonylphenylketone, and metal complexes of acetoacetanilide.

Further, as the metal borate, a general formula

Embedded image (Where M is a metal, X, Y and Z are 7-1 carbon atoms)
(Indicating the acid group of 1 monocarboxylic acid). Specific examples of the above monocarboxylic acids having 7 to 11 carbon atoms 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-dimethylheptane Acid, 3,5,5-trimethylhexanoic acid, n-
Decanoic acid, 2,2-dimethyloctanoic acid, 7,7-dimethyloctanoic acid, n-undecanoic acid, "Versatic" 10 [TM, mainly neodecanoic acid and sold in the UK by Shell International Company Limited Synthetic acid mixture]. Also,
As the metal, other metals such as iron, nickel and manganese may be contained as long as the Co content (96.0 to 99.8% by weight) in the metal of the adhesion improver of the present invention is not impaired. . Metal borates are obtained by adding an organic boron compound to a metal salt of a mixed carboxylic acid mainly containing a cobalt salt of a carboxylic acid.
It is obtained by reacting at a temperature of from 00 to 250 ° C. to remove by-produced volatile esters.

The adhesion enhancer used in the composition of the present invention has a Co content of 96.0% by weight or less in the metal of the adhesion enhancer.
99.8% by weight, preferably 98.0% by weight to 99.5%
%, More preferably 99.5% by weight to 99.3%, and the content of Zn in the metal is 50 ppm to 5000%.
ppm, preferably 80 ppm to 1000 ppm, more preferably 100 ppm to 800 ppm. If the Co content is 98.0 or less, the initial adhesiveness is poor, and if the Co content is 99.8 or more, the heat aging adhesiveness is poor. When the content of Zn is 5000 ppm or more, the initial adhesiveness is deteriorated, and when it is 50 ppm or less, the heat aging adhesiveness is deteriorated. In order to allow an appropriate amount of Zn to be present in the metal of the adhesion improver, a compound containing a large amount of Zn may be used as a synthesis raw material when synthesizing the adhesion improver.

The content of the adhesion improver in the composition of the present invention is 0.1 to 100 parts by weight of the rubber component in the composition.
１５15 parts by weight, preferably 0.2-10, more preferably 0.25-5. In terms of the metal content in the adhesion improver based on 100 parts by weight of the rubber component in the composition, 0.05 to 1.0 part by weight, preferably 0.1 to 1.0 part by weight, in terms of cobalt.
0.8 parts by weight, more preferably 0.2 to 0.65 parts by weight. If the metal content in the composition is 0.05 parts by weight or less or 1.0 parts by weight or more, the adhesiveness becomes poor.

The rubber component used in the composition of the present invention is preferably natural rubber, synthetic polyisoprene, or a mixture of natural rubber and synthetic polyisoprene. However, part of the rubber component can be replaced by styrene butadiene, butadiene rubber chloroprene rubber, butyl rubber, ethylene-propylene rubber up to 50 parts by weight, preferably up to 30 parts by weight.

In the composition of the present invention, in addition to the rubber component and the adhesion improver described above, compounding agents usually used as rubber compounding agents, for example, carbon black, process oil, vulcanizing agents, vulcanization accelerators, anti-aging agents Agents and the like 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. A test sample obtained by vulcanizing the rubber composition at 60 ° C. for 20 minutes
Initial measurement value measured after preparation and 80 ° C as heat aging condition
The measured value after thermal aging was measured after the test sample was left in a gear oven for 24 hours.

(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 a steel cord to make an embedding width of 12.5mm (ASTM sample).
After vulcanization under the prescribed conditions,
Pull out the steel cord in accordance with MD-2229,
The drawing force at that time was measured and determined. In Tables 1 and 2, the values of Comparative Example 2 were indicated as indices with the value of 100 as 100. A. Initial adhesion: Proper vulcanization of ASTM sample (160
C. for 20 minutes) and after overvulcanization (160 ° C. for 40 minutes). I. Unvulcanized water-resistant adhesion: ASTM sample at temperature 30
After standing in a thermo-hygrostat at 86 ° C and a relative humidity of 86% for 96 hours, 1
After vulcanization at 60 ° C. for 20 minutes, the measurement was performed. C. Water resistance after vulcanization: 160 ° C.
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: ASTM sample at 160 ° C, 2
After vulcanization for 0 minutes, the sample was left standing under heat aging conditions (temperature: 100 ° C., 120 hours in a gear oven) and then measured.

[0015] Adhesion improvers used in Examples and Comparative Examples were prepared as follows. a) Adhesion improver A (used in Example 1 and Comparative Examples 4 and 5) 300 cc of an aqueous solution obtained by dissolving sodium hydroxide (1 mol) and industrial naphthenic acid (1 mol) in 1 liter of water
Of toluene was added. An aqueous solution obtained by dissolving cobalt chloride (1 mol) and zinc chloride (6000 ppm) in 500 cc of water was added thereto and reacted at 80 ° C. for 1 hour.
After cooling, the aqueous layer was removed, washed several times with water, and then toluene was vacuum dried to obtain a dark blue solid product whose main component was cobalt naphthenate. The metals in the product include 99% Co and 2%
900 ppm of Zn was present. b) Adhesion improver B (used in Example 2) 300 cc of an aqueous solution obtained by dissolving sodium hydroxide (1 mol) and industrial naphthenic acid (1 mol) in 1 liter of water
Of toluene was added. An aqueous solution obtained by dissolving cobalt chloride (1 mol) and zinc chloride (4000 ppm) in 500 cc of water was added thereto and reacted at 80 ° C. for 1 hour.
After cooling, the aqueous layer was removed, washed several times with water, and then toluene was vacuum dried to obtain a dark blue solid product whose main component was cobalt naphthenate. 99% Co and 1% metal in the product
850 ppm of Zn was present.

C) Adhesion improver C (used in Comparative Example 1) 300 cc of an aqueous solution obtained by dissolving sodium hydroxide (1 mol) and industrial naphthenic acid (1 mol) in 1 liter of water
Of toluene was added. To this, cobalt chloride (0.9 mol), ferric chloride (0.1 mol) and zinc chloride (400 mol)
(0 ppm) in 500 cc of water was added and reacted at 80 ° C. for 1 hour. After cooling, the aqueous layer was removed, washed several times with water, and then toluene was vacuum dried to obtain a dark blue solid product whose main component was cobalt naphthenate. The metals in the product include 94% Co and 1850 ppm Zn.
Existed. d) Adhesion improver D (used in Comparative Example 2) 300 cc of an aqueous solution obtained by dissolving sodium hydroxide (1 mol) and industrial naphthenic acid (1 mol) in 1 liter of water
Of toluene was added. An aqueous solution obtained by dissolving cobalt chloride (1 mol) in 500 cc of water was added thereto and reacted at 80 ° C. for 1 hour. After cooling, the aqueous layer was removed, washed several times with water, and then toluene was vacuum dried to obtain a dark blue solid product whose main component was cobalt naphthenate. The metal in the product had 99.5% Co and no Zn.

E) Adhesion enhancer E (used in Comparative Example 3) 300 cc of an aqueous solution obtained by dissolving sodium hydroxide (1 mol) and industrial naphthenic acid (1 mol) in 1 liter of water
Of toluene was added. An aqueous solution obtained by dissolving cobalt chloride (1 mol) and zinc chloride (50000 ppm) in 500 cc of water was added thereto and reacted at 80 ° C. for 1 hour. After cooling, the aqueous layer was removed, washed several times with water, and then toluene was vacuum dried to obtain a dark blue solid product whose main component was cobalt naphthenate. The metal in the product had 98% Co and 31000 ppm Zn. f) Adhesion enhancer F (used in Example 3 and Comparative Examples 9 and 10) 5000 pp on ELECTRO grade cobalt metal
After mixing m zinc metal, the prepared cobalt hydroxide (3 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 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 obtained a dark blue, hard, substantially non-tacky solid product. The metal in the product contained 99% Co and 2700 ppm Zn.

G) Adhesion enhancer G (used in Example 4) Cobalt hydroxide (3 mol) prepared from a grade of cobalt metal containing 6000 ppm zinc was mixed with versatic acid (3 mol), 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 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 obtained a dark blue, hard, substantially non-tacky solid product. 99% Co in the metal in the product
And 2900 ppm of Zn. h) Adhesion enhancer H (used in Comparative Example 6) 5000 pp on ELECTRO grade cobalt metal
After mixing m zinc metal, the prepared cobalt hydroxide (2.8 mol) and iron hydroxide (0.2 mol) were 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 is reacted with n-butyl orthoborate (1 mol),
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 obtained a dark blue, hard, substantially non-tacky solid product. 94% Co and 22 metal in the product
It contained 00 ppm Zn.

I) Adhesion enhancer I (used in Comparative Example 7) Cobalt hydroxide (3 moles) prepared from ELECTRO grade cobalt metal, versatic acid (3 moles),
Dissolved in a mixture of acetic acid (3 mol). 190 ° C the mixture
For 4 hours to remove water generated during the reaction. 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 obtained a dark blue, hard, substantially non-tacky solid product.
The metals in the product include 99.6% Co and 16 ppm Z
n was included. j) Adhesion improver J (used in Comparative Example 8) 50,000p for ELECTRO grade cobalt metal
After mixing pm of zinc metal, the prepared cobalt hydroxide (3 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 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 obtained a dark blue, hard, substantially non-tacky solid product. The metal in the product contained 98% Co and 31000 ppm Zn.

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 with 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.

Examples 2 to 4 and Comparative Examples 1 to 10 The procedure of Example 1 was repeated except that the adhesion improver was changed as shown in Tables 1 and 2.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

According to the rubber composition for bonding steel cord of the present invention, the effect of a trace amount of zinc contained in the bonding improver contained therein is higher than that of a rubber composition using a conventional bonding improver. It has good initial adhesion, water-resistant adhesion, and fracture resistance, and particularly has excellent adhesion after standing under heat aging conditions. Accordingly, the rubber composition of the present invention is suitably used particularly as a rubber for coating steel on tire belts and carcass. It can also be used for steel coating such as conveyor belts and hoses.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 21/00 C08L 9/00-9/06 C08L 7/00 C08K 5/09-5/098 C08K 5/55

Claims (2)

(57) [Claims] An organic metal salt, an organic metal complex and a metal borate are added to 100 parts by weight of a rubber component containing at least 50% by weight of at least one selected from the group consisting of natural rubber and synthetic polyisoprene. A rubber composition containing 0.1 to 15 parts by weight of at least one adhesion enhancer selected from the group consisting of:
A rubber composition for bonding steel cords, wherein 99.8% by weight and 50 to 5000 ppm of Zn are present. 2. The method according to claim 1, wherein less than 50 parts by weight of the rubber component is at least one kind of synthetic rubber selected from the group consisting of styrene-butadiene rubber, butadiene rubber, chloroprene rubber, butyl rubber and ethylene-propylene rubber. Item 4. A rubber composition for bonding a steel cord according to Item 1.