JP3275419B2 - Rubber composition and method of bonding to steel cord using the same - 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 which is used for automobile tires, conveyor belts, hoses and the like, and is particularly suitable for coating steel cords, and a method for bonding the same to steel cords using the same. Things.

[0002]

2. Description of the Related Art Steel cords for automobile tires, conveyor belts, hoses, etc. are usually plated with brass or zinc as a reinforcing material to improve and maintain the strength and durability of the products. Is widely used. In order to improve the adhesion between the steel cord and the covering rubber made of natural rubber or synthetic rubber, a method of blending an organic acid cobalt salt such as cobalt naphthenate and sulfur with the rubber has been known. I have.

[0003] However, when such a rubber composition is used as a rubber for coating a steel cord, the initial adhesive strength between the rubber and the steel cord is improved, but the heat resistance of the rubber is increased due to the addition of a cobalt salt of an organic acid. Properties and flex crack resistance tended to be significantly inferior.

On the other hand, as a means for improving the heat resistance and flex crack resistance of rubber, a method of blending various amine-based deterioration inhibitors is known. Examples of the amine-based deterioration inhibitor include N-isopropyl-N'-phenyl-p-diaminobenzene and N- (1,3-dimethylbutyl)-
N'-phenyl-p-diaminobenzene, N, N'-diphenyl-p-diaminobenzene, N, N'-ditolyl-p-diaminobenzene, condensate of acetone and diphenylamine, 2,2,4-trimethyl-1 , 2-dihydroquinoline polymers and the like are known.

However, when such a conventional deterioration inhibitor is blended and bonded to a steel cord, not only the deterioration prevention performance such as heat resistance and flex cracking resistance is insufficient, but also the adhesion between the rubber and the steel cord. There was a problem in that it also had an adverse effect on the force, especially on the adhesive performance after the hygrothermal history.

[0006]

In view of such circumstances, the present inventors have conducted various studies to solve the drawbacks of known deterioration inhibitors, and as a result, have found that a given raw material rubber can be used as an organic acid cobalt. By adding a specific amount of salt, sulfur and a specific composition of 2,2,4-trimethyl-1,2-dihydroquinoline polymer, respectively, the adhesion between rubber and steel cord can be improved, and especially, wet heat aging. The present inventors have found that a decrease in the adhesive strength afterward is small, and furthermore, the heat resistance and flex crack resistance of rubber are improved, and the present invention has been completed.

[0007]

That is, the present invention provides a rubber composition obtained by blending the following components with 100 parts by weight of raw rubber selected from natural rubber and diene rubber. .

(1) 0.1 to 1 part by weight of cobalt salt of an organic acid in terms of cobalt, (2) 2 to 10 parts by weight of sulfur, (3) a primary amine content of 1% by weight or less, and a monomer content of 1% by weight or less. 0.5 to 5 parts by weight of a 2,2,4-trimethyl-1,2-dihydroquinoline polymer having a dimer content of 3% by weight or less and a dimer content of 30% by weight or more.

This rubber composition is particularly effective for vulcanization adhesion with a steel cord. Accordingly, the present invention also provides a method for bonding a rubber and a steel cord by bringing the rubber composition into contact with a steel cord and vulcanizing the same. By using such a rubber composition, a steel cord reinforced rubber product excellent in heat resistance and bending crack resistance can be obtained while maintaining high adhesiveness between rubber and steel cord.

A first feature of the present invention is that the primary amine content in the deterioration inhibitor is 1% by weight or less from the viewpoint of preventing the deterioration inhibitor from adversely affecting the adhesion performance between the rubber and the steel cord. It is in the point which was. That is, the primary amine component in the deterioration inhibitor lowers the initial adhesive strength between the rubber and the steel cord, and as a major problem, significantly lowers the adhesive strength after heat history. Easily blooms on the rubber surface in unvulcanized rubber,
It has been found that it causes a decrease in the adhesion between the rubber and the steel cord. Therefore, in the present invention, it is necessary to suppress the primary amine content in the deterioration inhibitor to 1% by weight or less.

A second feature of the present invention is that 2,2,4-trimethyl-1,2-dihydrogen which exhibits a long-lasting excellent deterioration prevention performance from the viewpoint of enhancing the heat resistance and flex crack resistance of rubber. 2,2,4-trimethyl-1,2 containing not less than 30% by weight of a quinoline dimer and not more than 3% by weight of a monomer having a low molecular weight and being easily volatilized.
-Use of a dihydroquinoline polymer as a deterioration inhibitor. In other words, when a rubber is compounded with a deterioration inhibitor,
It is necessary that the dispersant has high dispersibility in rubber,
Also, in consideration of long-term durability such as heat resistance and bending resistance when a rubber product is used, it is necessary that the anti-deterioration agent hardly evaporates from the rubber even under heat aging conditions. Therefore, a low molecular weight deterioration inhibitor is not preferable because it easily evaporates. From these viewpoints, in the present invention, a predetermined amount of a 2,2,4-trimethyl-1,2-dihydroquinoline polymer having a low monomer content and a high dimer content is blended as a deterioration inhibitor. The monomer content is preferably as small as possible, for example, more preferably 1% by weight or less. The higher the dimer content, the better, for example, more preferably 35% by weight or more.

The 2,2,4-trimethyl-1,2-dihydroquinoline polymer is usually produced by reacting aniline with acetone, diacetone alcohol or mesityl oxide in a heated state in the presence of an acidic catalyst. Have been. In general, those having a structure represented by the following formula (I) are mainly used.

[0013]

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In the formula, n represents an integer of 1 or more.

The monomer referred to in the present invention is a compound represented by the above formula (I)
Is a compound of n = 1, and a dimer is a compound of n = 2 in the above formula (I).
As the number increases in the order of 3, 4,..., Trimers, tetramers,. The primary amine is mainly generated from aniline as a raw material, and can have various structures. A typical example is a compound having the following structure.

[0016]

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In the formula, m represents an integer of 1 or more.

Commercially available 2,2,4-trimethyl-1,2-
Since dihydroquinoline polymers are of various grades depending on the manufacturer and product name, those used in the present invention must be carefully selected. In the present invention, as described above, the primary amine content and the monomer content are low, and the dimer content is high in 2,2,4-trimethyl-1,2-.
It is necessary to use a dihydroquinoline polymer, and any polymer satisfying the conditions specified in the present invention may be selected. Such a polymer is preferably produced, for example, as follows.

That is, first, aniline is used in the presence of an acidic catalyst such as hydrochloric acid, hydrobromic acid, hydrofluoric acid, iodine, organic sulfonic acid, boron trifluoride, or a mixture of two or more of these. And 2,2,4-trimethyl-1,2-dihydroquinoline monomer is produced by reacting acetone, diacetone alcohol or mesityl oxide in a heated state, and purifying the resulting reaction product by distillation. . It is preferable that the monomer purity be increased by distillation, and it is generally preferable that the monomer purity is 85% by weight or more, and it is more preferable that the monomer purity is further purified to 90% by weight or more.

The thus purified 2,2,4-trimethyl-1,2-dihydroquinoline monomer is further reacted under heating in the presence of hydrochloric acid or another acidic catalyst as described above to obtain a polymer mixture. Unreacted monomers are removed from the polymer mixture. In the reaction,
For example, when a hydrochloric acid catalyst is used, the concentration of hydrochloric acid is 15 to 25.
% By weight, and hydrochloric acid is added to the total of 2,2,4-trimethyl-1,2-dihydroquinoline monomer as a raw material and other amines contained as impurities. It is preferably used in the range of 0.2 to 0.5 mole times. The reaction temperature is preferably about 80 to 100 ° C. By employing such mild conditions, a polymer having a high dimer content can be obtained. The removal of unreacted monomers is usually carried out by removing low-boiling fractions by distillation.

In the present invention, a 2,2,4-trimethyl-1,2-dihydroquinoline polymer having a specific composition as described above is used. In particular, dimers, trimers and tetramers, that is, the above-mentioned formula (I) N is 2, 3
It is preferable that the polymer containing the polymer represented by (4) and (4) is 75% by weight or more in total, and it is more preferable that the polymer contains 80% by weight or more in total of such dimer, trimer and tetramer.

According to the present invention, such a 2,2,4-trimethyl-1,2-dihydroquinoline polymer having a low content of a primary amine and a monomer and a high content of a dimer is used in accordance with the present invention. It is blended in the range of 0.5 to 5 parts by weight. If the amount is less than 0.5 part by weight, the heat resistance of the rubber is not sufficient, and if it is more than 5 parts by weight, the adhesive performance is undesirably reduced.

The raw rubber used in the present invention is a natural rubber or a diene rubber, and each can be used alone or as a blend of two or more. Examples of the diene rubber include styrene-butadiene copolymer rubber, butadiene rubber, isoprene rubber, chloroprene rubber, ethylene-propylene copolymer rubber, and ethylene-propylene-diene copolymer rubber.

The organic acid cobalt salt to be added to the raw rubber can be one conventionally used in rubber for coating steel cords, for example, cobalt naphthenate, cobalt caprylate, cobalt laurate, tridecylate. Cobalt, cobalt palmitate, cobalt stearate, cobalt oleate, cobalt alanate and the like can be mentioned. The compounding amount of the organic acid cobalt salt is in the range of 0.1 to 1 part by weight as the cobalt amount per 100 parts by weight of the raw rubber. If the amount of cobalt is less than 0.1 part by weight, sufficient adhesion to steel cord cannot be obtained,
If the amount is more than 1 part by weight, the heat resistance and the bending resistance of the rubber decrease, which is not preferable.

The sulfur used in the present invention is generally used in the rubber industry. In many cases, insoluble sulfur is used.
Also, a mixture of various sulfurs may be used. The amount of sulfur is in the range of 2 to 10 parts by weight per 100 parts by weight of the raw rubber. If the amount is less than 2 parts by weight, the adhesion to the steel cord is remarkably reduced, and it is not preferable in terms of rubber reinforcing properties and strength. On the other hand, if the amount is more than 10 parts by weight, the heat resistance and flex cracking resistance of the rubber are remarkably reduced, which is not preferable.

In the present invention, various fillers usually used in the rubber industry, for example, carbon black,
Inorganic fillers such as silica, clay, calcium carbonate, and glass fibers can be added as necessary.
Among them, carbon black is preferably used. The carbon black to be compounded is of a kind usually used in the rubber industry, for example, SAF, ISAF, HA
It can be F, FEF, SRF, GPF, MT, etc. The compounding amount is not particularly limited, but from the viewpoint of reinforcing property and rubber strength, 20 to 100 parts by weight of rubber.
A range of 150 parts by weight is preferred. In addition, it is preferable to mix hydrous silica separately from or in addition to carbon black to improve adhesiveness, and the compounding amount is preferably in the range of 5 to 80 parts by weight per 100 parts by weight of rubber.

Furthermore, various rubber chemicals usually used in the rubber industry, such as other deterioration inhibitors, crosslinking agents, vulcanization accelerators, retarders, deflocculants, softeners, petroleum resins, lubricants, plasticizers Needless to say, a tackifier, an adhesive such as resorcinol or a resorcinol-based resin may be used in combination as needed.

The rubber composition of the present invention thus formulated is particularly effective for uses reinforced with steel cords, and has excellent adhesiveness when applied to various members of automobile tires and other rubber products. Exhibits heat resistance and flex crack resistance. The steel cord used here can be one generally used for automobile tires, conveyor belts, hoses, and the like, and examples thereof include a brass-plated steel cord and a zinc-plated steel cord.

The adhesion between the rubber composition and the steel cord is as follows:
Usually, both are brought into contact with each other in a form in which a steel cord is embedded in an unvulcanized rubber composition, and vulcanization is performed. There are no particular restrictions on the vulcanization conditions, and the vulcanization may be performed under conditions generally used conventionally. The appropriate vulcanization conditions vary considerably depending on the rubber composition used and the intended product, but usually the temperature is about 100 to 200 ° C. and the time is 1 minute to 1 minute.
From the range of about 2 hours, conditions suitable for a rubber composition or a product are selected. For example, in a state in which the rubber composition is in contact with a steel cord, the tire is manufactured through a molding and vulcanization process by applying the rubber composition to a tire, particularly a bead portion or a carcass portion, by a method commonly used in the tire industry. You.

[0030]

EXAMPLES Next, although described in detail with examples for the present invention, the present invention is not intended to be thus limited to these examples. In the following examples,% representing the amount added or the content
Parts and parts are by weight and parts by weight, respectively, unless otherwise noted.

Reference Example 1

In a 500 ml four-necked flask equipped with an acetone introducing device, a thermometer, a stirrer and a condenser, 121 g (1.3 mol) of aniline and 12.4 g of p-toluenesulfonic acid monohydrate (as p-toluenesulfonic acid) 0.065
Mol) and heated. While maintaining the internal temperature at 95 to 100 ° C., 755 g of acetone was introduced in 8 hours. The reaction product was diluted with 100 ml of toluene, neutralized with 2.6 g of caustic soda and 50 ml of water while keeping the temperature at 85 to 95 ° C., allowed to stand, and separated to remove an aqueous layer. The oil layer was washed several times with 100 ml of water, and when the solution became neutral, the toluene layer was separated, the toluene was removed by distillation, and rectification was performed under reduced pressure to obtain an unreacted substance at a boiling point of up to 100 ° C / 10 mmHg. 20 g of an aniline fraction was obtained, and 142.4 g of a monomer fraction was obtained between 100 ° C./10 mmHg and 90 ° C./2 mmHg.

When the monomer fraction was analyzed by gas chromatography, the composition ratio was as follows.

2,2,4-trimethyl-1,2-dihydroquinoline 97.0% Aniline 0.2% Low boiling impurities 2.8%

Subsequently, 100 g of the monomer fraction obtained above, 20.9 g of concentrated hydrochloric acid and 20 parts of water were placed in a 500 ml four-necked flask equipped with a thermometer, a stirrer and a condenser.
ml, and the temperature was raised to 90 ° C. 90 to 100
The mixture was kept under stirring at ℃ for 6 hours. Thereafter, the reaction product was diluted with 100 ml of toluene, neutralized by adding 19.8 g of a 45% aqueous sodium hydroxide solution while maintaining the temperature at 85 to 90 ° C., and allowed to stand for separation to remove the aqueous layer. The toluene layer was washed several times with 100 ml of water.

After the toluene layer was separated and the toluene was removed by distillation, the internal temperature was 200 ° C. and the degree of vacuum was 2 mm.
Distillation was performed under conditions up to Hg to distill off 21.8 g of low-boiling components, thereby obtaining 73.2 g of a 2,2,4-trimethyl-1,2-dihydroquinoline polymer as a residue. This polymer is referred to as a deterioration inhibitor A. Table 1 shows the results of quantifying the components of the deterioration inhibitor A.

The determination of monomers, dimers, trimers and tetramers was carried out by gas chromatography using dibutyl phthalate as an internal standard under the following conditions.

Column: Chromosolve WAW as a carrier was coated with 3% silicon OV-1 as a liquid layer and packed with 3%.
Separation tube of mmφ × 0.5m (manufactured by GL Sciences Inc.) Injection temperature: 350 ° C Column temperature: 10 ° C from 100 ° C to 350 ° C
/ Min Carrier gas: Nitrogen (50 ml / min) Detector: Flame ionization detector

The primary amine content is determined by dissolving the polymer in chloroform, further adding hydrochloric acid and p-dimethylaminobenzaldehyde to prepare a sample solution, and measuring the absorbance of the sample solution with a spectrophotometer (measuring wavelength 440 nm). The blank test value was subtracted from the obtained absorbance, and the blank test value was obtained from a calibration curve.

Reference Example 2

A 500 equipped with an acetone introduction device, a thermometer, a stirrer and a water separator connected at the top to a reflux condenser.
93.1 g (1 mol) of aniline, 27 g (0.27 mol) of concentrated hydrochloric acid and 3 g of n-hexane were placed in a ml four-necked flask and heated. N-hexane was previously put in the water separator. When the internal temperature reaches 85 ° C, the introduction of acetone is started, and 174 g while maintaining the internal temperature at 70 to 90 ° C.
(3 moles) of acetone were introduced over 8 hours. Water generated by the condensation reaction is removed from the flask by azeotropic distillation with n-hexane, and n-hexane and water are separated vertically in the water separator. . After completion of the introduction of acetone, the mixture was neutralized with 15 g of a 28% aqueous sodium hydroxide solution and 100 ml of water while maintaining the temperature at 60 to 80 ° C., diluted with 100 ml of toluene, and filtered through a G3 glass filter precoated with radiolite to obtain a catalyst residue. Was removed. The filtrate was separated after standing, and the aqueous layer was removed.

The oil layer was washed several times with 100 ml of water, and when the solution became neutral, the oil layer was separated, low boiling components such as n-hexane, toluene, unreacted acetone and the like were removed by distillation, and further under reduced pressure. By rectification, the boiling point is 100 ° C / 10
An unreacted aniline fraction of 23 g was obtained up to mmHg, and 2,2,2,100 ° C / 10 mmHg to 90 ° C / 2 mmHg.
57.5 g of 4-trimethyl-1,2-dihydroquinoline monomer fraction (purity of 96.8 by gas chromatography)
%) Was removed and 82.6 g of 2,2,4-trimethyl-
A 1,2-dihydroquinoline polymer was obtained. This polymer is referred to as a deterioration inhibitor X. When the deterioration inhibitor X was quantified in the same manner as in Reference Example 1, the components were as shown in Table 1.

Reference Example 3

After a monomer fraction was obtained in the same manner as in Reference Example 1, 100 g of the monomer fraction was mixed with 60.8 g of concentrated hydrochloric acid.
(0.6 mol) and 30 ml of water
The polymerization reaction and post-treatment were carried out in the same manner as in Reference Example 1, and
By distilling out 4.5 g of low boiling components, 8
0.5 g of a 2,2,4-trimethyl-1,2-dihydroquinoline polymer was obtained. This polymer is referred to as a deterioration inhibitor Y. When the deterioration inhibitor Y was quantified in the same manner as in Reference Example 1, the components were as shown in Table 1.

Reference Example 4

The procedure of Reference Example 1 was repeated, but in the rectification after the monomer condensation, the unreacted aniline fraction having a boiling point of up to 100 ° C./20 mmHg was obtained to obtain 14 g.
The monomer fraction 14 between 20 mmHg and 90 ° C / 2 mmHg
8.6 g were obtained (monomer purity: 84.2%, aniline content: 4.8%). Thereafter, a polymerization reaction and a post-treatment were carried out in the same manner as in Reference Example 1 to obtain 71.6 g of a 2,2,4-trimethyl-1,2-dihydroquinoline polymer as a residue. This polymer is referred to as a deterioration inhibitor Z. Reference Example 1
When quantified in the same manner as in the above, the components were as shown in Table 1.

[0047]

[Table 1]

In addition to these deterioration inhibitors A, X, Y and Z, in the following examples, N- (1,
3-Dimethylbutyl) -N'-phenyl-p-diaminobenzene (deterioration inhibitor V) was also used.

Embodiment 1

[0050]

<Table 2> <Blending formulation> 100 parts of natural rubber (RSS # 1) 45 parts of HAF carbon black (N330) 45 parts of stearic acid 3 parts of hydrated silica (Nipsil VN3 manufactured by Nippon Silica Kogyo) 10 parts of zinc oxide 2 parts of deterioration inhibitor Table 3 Description Cobalt naphthenate (cobalt content 10%) 2 parts Vulcanization accelerator 1.2 parts (N, N-dicyclohexyl-2-benzothiazolesulfenamide) Io 4 parts

As a banbury mixer, 6 made by Toyo Seiki Co., Ltd.
Oil bath temperature 150
Based on the above formulation, carbon black, stearic acid, hydrated silica, zinc white and a deterioration inhibitor were added to natural rubber at a temperature of 50 ° C., and kneaded at a mixer rotation speed of 50 rpm for 15 minutes. The rubber temperature at this time was 160 to 170 ° C. This formulation was then transferred to an open mill and
At a temperature of 0 ° C., the vulcanization accelerator, sulfur and cobalt naphthenate shown in the above formulation were added and kneaded.

A part of the kneaded sample was immediately vulcanized at 145 ° C. for 40 minutes for a heat aging test and a flex cracking resistance test to prepare respective test pieces. Immediately after the preparation of the unvulcanized rubber compound, a brass-plated steel cord was embedded and 145 pressed by a vulcanizing press for the adhesion test.
A test piece was prepared by vulcanization at 40 ° C. for 40 minutes. The remaining samples were left at room temperature for 3 days, embedded with a brass-plated steel cord, and vulcanized under the same conditions as above to obtain a test specimen for an adhesion test.

The rubber properties were tested by the following methods, and the results are shown in Table 3 together with the variable values of the compounding formula.

[0054] As described contact adhesion above, unvulcanized rubber compound created immediately after vulcanization and adhesion test specimens and an unvulcanized rubber formulation 3
Using a test specimen for adhesion test vulcanized after standing for
Adhesion was evaluated by the H test method described in TM D 2138. For the test specimens which were vulcanized and bonded immediately after the preparation of the unvulcanized rubber compound, the adhesive strength was measured before the wet heat aging, and the bond after the wet heat aging at a temperature of 50 ° C. and a relative humidity of 90% for 7 days. Force was also measured. The test results were indicated by the average value of 12 test pieces.

Heat resistance According to JIS K 6301, dumbbell-shaped No. 3 test piece was
After heat aging at 0 ° C. for 72 hours, the tensile strength before and after aging was measured, and the retention of tensile strength was calculated.

[0056] conform to flex crack resistance JIS K 6301, a hole of the original length 2.0 mm in the test piece, using a Demachiya type tester, measuring the length of the crack after 10,000 flex with calipers did.

[0057]

[Table 3]

[0058]

The rubber composition of the present invention is effective for coating a steel cord. When the rubber composition is vulcanized and bonded to a steel cord, the rubber composition has an adhesive property between the rubber and the steel cord. The adhesive strength is reduced, especially after wet heat aging, and good adhesiveness is maintained even after leaving unvulcanized rubber for a long period of time.Furthermore, the heat resistance, flex crack resistance, etc. of rubber Excellent in various properties.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI C08K 5/3437 C08K 5/3437 (56) References JP-A-54-23650 (JP, A) JP-A-53-145854 (JP) , A) JP-A-60-42440 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 21/00 B32B 25/00 C08J 5/04 C08K 3/06 C08K 5/09 C08K 5/3437

Claims (4)

(57) [Claims] (1) To 100 parts by weight of a raw rubber selected from a natural rubber and a diene rubber, (1) a cobalt salt of an organic acid is 0.1 to 1 in terms of a cobalt amount.
(2) 2 to 10 parts by weight of sulfur, and (3) 2,2 having a primary amine content of 1% by weight or less, a monomer content of 3% by weight or less, and a dimer content of 30% by weight or more. A rubber composition comprising 0.5 to 5 parts by weight of a 4-trimethyl-1,2-dihydroquinoline polymer. 2. The rubber composition according to claim 1, wherein the 2,2,4-trimethyl-1,2-dihydroquinoline polymer contains 75% by weight or more in total of dimers, trimers and tetramers. 3. The rubber composition according to claim 1 or 2,
A method of bonding rubber and a steel cord, the method comprising vulcanizing under contact with a steel cord. 4. The method according to claim 3, wherein the rubber and the steel
A steel cord reinforced rubber product that is bonded to a cable.