JP2003026857A - Rubber composition excellent in adhesive property with iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition improved with an adhesive property with an iron base. SOLUTION: This rubber composition contains (i) 100 pts.wt. blended rubber consisting of a natural rubber or at least 1 kind diene-based rubber selected from a group consisting of the natural rubber, a polyisoprene rubber(IR), a styrene-butadiene copolymer rubber(SBR) and a polybutadiene rubber(BR), (ii) 3.5-12 pt.wt. sulfur, (iii) 0.01-2.7 pt.wt. organometallic cobalt salt (provided that based on cobalt element) and (iv) 0.05-10 pt.wt. polysulfide.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition,
More specifically, it relates to a rubber composition having improved adhesion between rubber and iron cloth. This rubber composition is most suitable for use as a coat rubber or an edge tape rubber of a steel cord of a pneumatic tire, and can also be suitably used for a cushion rubber embedded in a conveyor belt.

[0002]

2. Description of the Related Art Conventionally, in order to improve the adhesion between a steel cord and rubber, the organic acid cobalt salt such as cobalt stearate, cobalt naphthenate, and acetylacetone cobalt is blended in the rubber and a large amount of sulfur is blended. Are known (for example, JP-A-5-65370,
JP-A-57-165431 and JP-A-61-167
543, etc.). However, although these technologies can improve the adhesion between rubber and steel cord plated with brass, etc., such as steel cord end (iron part) without plating, etc. Since the adhesiveness of rubber is poor in the part that contacts the fabric,
There is a problem that separation of the steel belt end occurs due to mechanical fatigue of the pneumatic tire after actual running, and the above technique is still insufficient to improve such a problem.

[0003]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a rubber composition having improved adhesion to iron fabric.

[0004]

According to the present invention, (i)
Natural rubber or natural rubber and polyisoprene rubber (IR),
Blend rubber 100 comprising at least one diene rubber selected from the group consisting of styrene-butadiene copolymer rubber (SBR) and polybutadiene rubber (BR)
Parts by weight, (ii) 3.5 to 12 parts by weight of sulfur, (iii) 0.01 to 2.7 parts by weight of organometallic cobalt salt (provided as cobalt element), and (iv) 0.05 to 10 parts by weight of polysulfide compound. A rubber composition comprising a part is provided.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, in order to improve the adhesion between steel cord and rubber, conventionally, a cobalt salt of an organic acid such as cobalt stearate, cobalt naphthenate, and acetylacetone cobalt and a large amount of sulfur are blended. Is proposed. However, according to these techniques, the adhesion between the steel cord plated with brass or the like and the rubber is improved, but since these rubbers also have poor adhesion with the iron material, after the pneumatic tire actually runs. Has not improved the problem of separation of the steel belt end, which may occur due to mechanical fatigue of the steel. Therefore, the present inventors have found that 100 parts by weight of natural rubber or a blend rubber of natural rubber and IR, SBR, and / or BR contains 3.5 to 300% by weight of sulfur.
12 parts by weight, 0.01 to 2.7 parts by weight of an organometallic cobalt salt such as gobaert stearate, cobalt naphthenate, cobalt acetylacetone, and cobalt orthoborate neodecanoate is blended to obtain a polysulfide olefin and a polysulfide fatty acid. It has been found that a rubber composition obtained by blending 0.05 to 10 parts by weight of a polysulfide compound such as polysulfide fatty acid ester and polysulfide oil and fat can be directly vulcanized and adhered to a steel belt end. .

As the rubber component used in the rubber composition according to the present invention, natural rubber conventionally used in the rubber industry has been used, and 80% of this natural rubber is used per the total amount of rubber.
The content of the polyisoprene rubber (I
R), various styrene-butadiene copolymer rubbers (SB
R) and / or polybutadiene rubber (BR) may be a blend rubber containing 20% by weight or less.

The sulfur used in the rubber composition according to the present invention may be any sulfur conventionally blended in a rubber composition for vulcanization, and the blending amount thereof is parts by weight per 100 parts by weight of rubber. (phr) is 3.5 to 12 phr, preferably 5
~ 8 phr. If the blending amount is too small, the desired improvement in the adhesiveness cannot be sufficiently observed, and conversely, if the blending amount is too large, an excessive rubber / iron adhesive layer is formed and the adhesiveness is deteriorated, which is not preferable.

As the organometallic cobalt salt used in the rubber composition according to the present invention, any organometallic cobalt salt conventionally used for improving the adhesiveness of steel cord or the like in the rubber composition can be used. I can give you. Specifically, for example, cobalt-containing organic compounds that form salts with organic compounds such as cobalt stearate, cobalt naphthenate, acetylacetone cobalt, cobalt neodecanoate orthoborate, cobalt oleate, cobalt tall oil, and cobalt resinate. Can be raised. The amount of the organometallic cobalt salt is 0.01 to 2,7 phr, preferably 0.1 to 1.0, in terms of cobalt element.
phr. If the blending amount of the organometallic cobalt salt in the present invention is too small, the desired improvement in adhesiveness cannot be obtained, and conversely, if the blending amount is too large, an excessive rubber / iron adhesive layer is formed and the adhesiveness deteriorates, which is not preferable. These can be used alone or as an arbitrary mixture.

The polysulfide compound used in the rubber composition according to the present invention is, for example, a known commercially available compound that has been conventionally used as a sulfur-based extreme pressure additive for lubricating oil, and is used as a compounding agent for rubber. It has not been used. The polysulfide compound is preferably a polysulfide olefin,
Examples thereof include polysulfide unsaturated hydrocarbon compounds such as polysulfide fatty acid, polysulfide fatty acid ester, and polysulfide oil and fat. These can be used alone or as an arbitrary mixture.
The compounding amount of the polysulfide compound is 0.05 to 10 phr, preferably 2.0 to 7.0 phr. If the compounding amount is too small, the desired effect of improving the adhesiveness is not observed, and conversely if it is too large, it is excessive. Such a rubber / iron adhesive layer is formed and the adhesiveness is lowered, which is not preferable.

As the specific example of the polysulfide compound, those having the following structures can be used. Polysulfide fatty acid ester Oleic acid, elaidic acid, linoleic acid, linolenic acid,
Stearolic acid, ricinoleic acid, ricinoelaidic acid,
Examples include polysulfides of methyl and ethyl ester compounds such as brassic acid and erucic acid. Specifically, for example, a dimer of a fatty acid represented by the formula (I) or a dimer of a fatty acid represented by the formula (II), (III) and (IV) (for example, 3
6%), dimers (eg 47%) and trimers (eg 9)
%) And the like.

[0011]

[Chemical 1]

[0012]

[Chemical 2]

Polysulfide oils and fats For example, those having an intermolecular sulfur crosslinked structure and an intermolecular sulfur crosslinked structure represented by the formulas (V) and (VI) are recognized.

[0014]

[Chemical 3]

The polysulfide olefin formula: _{C n H 2n + 1 -S x} -C n H 2n + 1 ( wherein, n is 3
25 and x is 2 to 5). Specific examples thereof include the following polysulphurized C ₈ olefins.

[0016]

[Chemical 4]

Polysulfated fatty acids : Polysulfides of unsaturated fatty acids such as palmitooleic acid, oleic acid, vaccenic acid, linoleic acid, linolenic acid, eleostearic acid, arachidic acid, arachidonic acid and nervonic acid.

The rubber composition according to the present invention contains, in addition to the above-mentioned essential components, reinforcing agents such as carbon black and silica, other vulcanizing or crosslinking agents, vulcanizing or crosslinking accelerators, various oils, and anti-aging agents. For tires such as agents and plasticizers, various additives that are generally blended for other general rubbers can be blended, and such blends are kneaded and vulcanized by a general method to give a composition, It can be used to vulcanize or crosslink. The compounding amounts of these additives may be the conventional compounding amounts as long as they do not violate the object of the present invention.

[0019]

EXAMPLES The present invention will be further described below with reference to examples, but it goes without saying that the scope of the present invention is not limited to these examples.

Standard Examples 1-2, Examples 1-5 and Comparative Example 1
~ 6 In the formulations (parts by weight) shown in Table I, the vulcanization accelerator and the components other than sulfur were kneaded for 4 to 5 minutes in a 3 liter closed mixer. When the temperature reached 150 ° C., the contents were released, and the obtained masterbatch was kneaded with a vulcanization accelerator and sulfur in an 8-inch open roll to obtain a rubber composition.

[0021]

[Table 1]

The ingredients used in the formulation of Table I are as follows: NR: Natural rubber (RSS # 3, Southland R
tuber Co. , Ltd. ) SBR: Styrene-butadiene copolymer rubber (NIPOL 1502 manufactured by Nippon Zeon Co., Ltd.) CB: Carbon black (Cast 300 manufactured by Tokai Carbon Co., Ltd.) 6C: Antiaging agent (Santof manufactured by Flexis Co., Ltd.)
lex 6PPD) RD: Anti-aging agent (Ouchi Shinko Chemical Industry Co., Ltd. Nocrac 224) Accelerator DZ: Sulfenamide vulcanization accelerator (Ouchi Shinko Chemical Industry Co., Ltd. Nox Cellar DZ-G) PVI: Vulcanization accelerator (made by Flexis Co., Ltd. Santo
flex PVI PS Power Organometallic salt: neodecanoic acid cobalt orthoborate (Co
Sulfur: Insoluble sulfur manufactured by Shikoku Chemicals Co., Ltd.

Polysulfide 1: manufactured by Dainippon Ink and Chemicals, Inc.
GS-100 (polysulfide oil and fat) Polysulfide 2: Dainippon Ink and Chemicals, Inc. GS-225
(Polysulfide oil and fat) Polysulfide 3: GS-230 manufactured by Dainippon Ink and Chemicals, Inc.
(Polysulfide fatty acid ester) Polysulfide 4: Dainippon Ink and Chemicals GS-420
(Polysulfide olefin)

Next, this composition was added to 15 × 15 × 0.2 cm.
The target test piece (rubber sheet) was prepared by press vulcanization in the mold of 160 ° C. for 20 minutes, and the adhesive properties were evaluated by the following methods.

The initial adhesion rubber pull-out and pull-out force of the rubber composition was measured according to ASTM D2229. The results are shown in Table I.

With initial adhesive rubber: A rubber composition is coated and embedded from both sides of unplated steel cords arranged in parallel at intervals of 12.5 mm, and a width of 25
After vulcanizing the mm size fabric at 160 ° C for 20 minutes,
The wire was pulled out and the rubber coverage at that time was evaluated.
The results are the standard example 1 in Examples 1 to 4 and Comparative Examples 1 to 6.
Example 5 was shown as an index with the standard example 2 being 100.
The larger this value is, the higher the adhesive strength is. Pull-out force: 12.5mm intervals are arranged in parallel and the uncoated steel cords are coated with rubber composition from both sides and embedded, and the fabric with a width of 25mm is vulcanized at 160 ° C for 20 minutes, and then the wire. Pull out,
The pulling force at that time was evaluated. The results are shown in Examples 1 to 1.
4 and Comparative Examples 1 to 6 are standard examples 1, and Example 5 is standard example 2
Is shown as an index. The larger this value is, the higher the adhesive strength is.

[0027]

As shown in Table I, the rubber compositions of Standard Examples 1 and 2 showed almost no adhesiveness to the steel cord. On the other hand, in the rubber compositions of Examples 1 to 5, the adhesion to the steel cord was remarkably improved by blending the polysulphurized oil and fat, the polysulphurized fatty acid ester or the polysulphurized olefin.

On the other hand, the rubber compositions of Comparative Examples 1 and 2 had a sulfur content of less than 3.5 phr (parts by weight per 100 parts by weight of rubber), resulting in poor adhesion, while the sulfur content was 12 ph.
If it exceeds r, the rubber becomes too hard, resulting in poor adhesion. The rubber composition of Comparative Example 3 had a polysulfide content of 0.0
Adhesiveness is reduced because it is less than 5 phr, while Comparative Example 4
When the amount of polysulfide compounded exceeds 10 phr, the rubber becomes too hard and the adhesiveness deteriorates. Comparative Examples 5 and 6 show that when the compounding amount of the organic acid cobalt salt is less than 0.01 phr or more than 2.70 phr in terms of cobalt element, the adhesiveness decreases.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 9/00 C08L 9/00 C09J 107/00 C09J 107/00 109/00 109/00 F term (reference) 4J002 AC011 AC031 AC061 AC081 DA046 EG047 EV018 EV098 EZ007 GN01 4J040 CA011 CA041 CA091 DB051 HA236 HD01 HD41 JB09 LA06 MA03 MA12 NA12 NA15 NA16 PA30

Claims (5)

[Claims] 1. (i) At least one diene rubber selected from the group consisting of natural rubber or natural rubber and polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR) and polybutadiene rubber (BR). 100 parts by weight of a blend rubber consisting of (ii) sulfur 3.5 to 12
A rubber composition comprising, by weight, (iii) 0.01 to 2.7 parts by weight of an organometallic cobalt salt (provided that the amount of cobalt element is included), and (iv) a polysulfide compound of 0.05 to 10 parts by weight. 2. The rubber composition according to claim 1, wherein the blending amount of the natural rubber in the blended rubber is 80% by weight or more of the blended rubber. 3. The rubber composition according to claim 1, wherein the organometallic cobalt salt is at least one selected from cobalt stearate, cobalt naphthenate, cobalt acetylacetone, and cobalt orthoborate neodecanoate. 4. The polysulfide compound according to claim 1, wherein the polysulfide compound is at least one selected from the group consisting of polysulfide olefins, polysulfide fatty acids, polysulfide fatty acid esters and polysulfide fats and oils. Rubber composition. 5. A pneumatic tire using the rubber composition according to any one of claims 1 to 4.