JP2018131538A - Rubber composition for metal adhesion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for metal adhesion that well adheres to a metal member such as a steel cord and has low heat build-up properties.SOLUTION: A rubber composition for metal adhesion has a rubber component composed of modified diene rubber 10 mass%-100 mass% and diene rubber 90 mass%-0 mass%. The modified diene rubber is natural rubber and/or isoprene rubber having a graft reaction produce of maleic acid metal salt.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition for metal bonding which has good adhesion to a metal member such as a steel cord and has low heat generation.

  Generally, a pneumatic tire uses a structural member in which a steel cord is coated with a rubber composition (coating rubber). At this time, if the adhesion between the steel cord and the covering rubber is low, the durability of the tire is deteriorated. Therefore, the steel cord is subjected to brass plating, and the coating rubber is mixed with an organic acid cobalt salt to increase the adhesion between the steel cord and the coating rubber (for example, Patent Document 1). reference). However, in rubber compositions containing organic acid cobalt salts, performance such as durability and low heat build-up may not always be obtained sufficiently, and further improvements have been demanded.

JP 2005-53953 A

  An object of the present invention is to provide a rubber composition for metal bonding which has good adhesion to a metal member such as a steel cord and has low heat generation.

  The rubber composition for metal bonding of the present invention that achieves the above object comprises a rubber composition for metal bonding comprising a rubber component consisting of 10% by mass to 100% by mass of a modified diene rubber and 90% by mass to 0% by mass of a diene rubber. The modified diene rubber is natural rubber and / or isoprene rubber having a graft reaction product of metal maleate.

  In the rubber composition for metal bonding of the present invention, as described above, the modified diene rubber has a functional group composed of a graft reaction product of a maleic acid metal salt, so that the conventional modification having a polar group such as maleic anhydride is used. Compared to natural rubber, it is possible to increase the affinity with metal and increase the adhesion to metal members, and to maintain or improve the low heat build-up of the rubber composition at or above the conventional level.

  In the rubber composition for metal bonding of the present invention, carbon black is 20 to 80 parts by mass, zinc oxide is 5 to 12 parts by mass, and sulfur is 5 to 10 parts by mass with respect to 100 parts by mass of the rubber component. It is preferable that a part is blended. Thereby, a favorable physical property can be exhibited as a rubber composition for adhere | attaching the metal member in a tire.

  In the present invention, sodium maleate can be suitably used as the maleate metal salt.

  The rubber composition for metal bonding of the present invention preferably contains an organic acid cobalt salt. As described above, the adhesive rubber composition itself contains cobalt, which increases the affinity for metal and is advantageous for improving the adhesion. Moreover, it is preferable that the rubber composition for metal bonding of this invention is used for adhesion | attachment of the metal member containing cobalt. As described above, when the metal to be bonded contains cobalt, the affinity between the rubber composition for bonding and the metal to be bonded is increased, which is advantageous for improving the adhesion.

  In the rubber composition for tires of the present invention, the rubber component necessarily contains a modified diene rubber. The modified diene rubber is composed of natural rubber and / or isoprene rubber. Constructing the modified diene rubber with natural rubber and / or isoprene rubber is advantageous for improving low heat build-up in a tire rubber composition.

  The modified diene rubber is obtained by grafting a maleic acid metal salt to the above-mentioned natural rubber and / or isoprene rubber, and has a carboxylic acid metal salt contained in the obtained graft reaction product as a functional group. The functional group comprising a carboxylic acid metal salt refers to a metal salt of a carboxyl group represented by -COOM (M is a metal atom). Examples of the metal salt include alkali metal salts such as lithium salt, sodium salt and potassium salt, alkaline earth metal salts such as calcium salt and magnesium salt, and transition metal salts such as iron salt. Preferred are alkali metal salts such as lithium salt, sodium salt and potassium salt, and more preferred are sodium salts.

  Examples of the maleic acid metal salt include an alkali metal salt of maleic acid, an alkaline earth metal salt of maleic acid, a transition metal salt of maleic acid, and the like, preferably an alkali metal salt of maleic acid, more preferably sodium maleate ( Disodium maleate).

The double bond of the maleic acid metal salt reacts with the double bond of the diene rubber at a high temperature to cause a graft reaction. As a result, a metal maleate is added to the diene rubber, and a graft reaction product represented by the chemical formula —CH (COOM) CH ₂ COOM (wherein M is a metal atom) is introduced. This grafting reaction product has two carboxylic acid metal salts (—COOM; M is a metal atom). A modified diene rubber grafted with a maleic acid metal salt is superior in affinity to a metal and can improve adhesion to a metal compared to a modified diene rubber grafted with maleic anhydride. The modified diene rubber added with maleic anhydride requires an operation for ring opening of carboxylic anhydride, but the modified diene rubber added with a maleic acid metal salt does not require such an operation.

  The modified diene rubber of the present invention preferably has a maleic acid metal salt modification rate of 0.1 to 10% by mass, more preferably 0.3 to 5% by mass. By setting the modification rate of the maleic acid metal salt within such a range, it is possible to increase the affinity with the metal and effectively improve the adhesion. In this specification, the modification rate of the maleic acid metal salt is the mass% of the added maleic acid metal salt in 100 mass% of the modified diene rubber.

  The rubber composition for metal bonding of the present invention contains 10% by mass to 100% by mass of the above-described modified diene rubber in 100% by mass of the rubber component, and 90% by mass to 0% by mass of another diene rubber. . As other diene rubbers, rubbers usually used in tire rubber compositions, such as natural rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, ethylene-propylene-diene rubber, and chloroprene rubber, can be used. When the content of the modified diene rubber is less than 10% by mass, the above-mentioned effects due to the use of the modified diene rubber cannot be obtained, and the heat build-up of the tire rubber composition is reduced to a conventional level or less. I can't. Further, the Mooney viscosity of the tire rubber composition cannot be sufficiently reduced, and the molding processability cannot be sufficiently obtained. The amount of the modified diene rubber is preferably 20% by mass to 100% by mass, and more preferably 20% by mass to 80% by mass.

  In the rubber composition for metal bonding of the present invention, carbon black is preferably blended in an amount of 20 to 80 parts by mass, more preferably 30 to 60 parts by mass with respect to 100 parts by mass of the rubber component. Thus, rubber | gum intensity | strength can be made high by mix | blending carbon black. If the blending amount of carbon black is less than 20 parts by weight, the rubber composition will not have sufficient reinforcing properties and the rubber strength will be reduced. When the blending amount of the carbon black exceeds 80 parts by weight, the mixing processability and heat build-up are reduced.

  In the rubber composition for metal bonding of the present invention, zinc oxide is preferably added in an amount of 5 to 12 parts by mass, more preferably 5 to 10 parts by mass with respect to 100 parts by mass of the rubber component described above. Thus, by mix | blending zinc oxide, the physical property at the time of using the rubber composition for metal bonding of this invention for a pneumatic tire can be made favorable. If the blending amount of zinc oxide is less than 5 parts by mass, the rubber hardness may be lowered, and when used for a pneumatic tire, the steering stability may be lowered. When the compounding quantity of zinc oxide exceeds 12 mass parts, there exists a possibility that breaking elongation may fall and it may lead to a separation.

  In the rubber composition for metal bonding of the present invention, sulfur is preferably blended in an amount of 5 to 10 parts by mass, more preferably 5 to 8 parts by mass with respect to 100 parts by mass of the rubber component. Thus, by mix | blending sulfur, the physical property at the time of using the rubber composition for metal bonding of this invention for a pneumatic tire can be made favorable. There exists a possibility that adhesiveness with a metal may fall that the compounding quantity of sulfur is less than 5 mass parts. When the compounding amount of sulfur exceeds 10 parts by mass, there is a risk of aging physical properties being lowered.

  The rubber composition for metal bonding of the present invention can be blended with an organic acid cobalt salt, thereby improving the affinity for the metal and further improving the adhesion to the metal. In addition, when cobalt is contained on the metal side, even if the organic acid cobalt salt is not blended (even if the blending amount of the organic acid cobalt salt is 0 part by mass), the rubber composition for metal bonding of the present invention is used. The thing shows the outstanding affinity with respect to a metal (cobalt containing), and exhibits the outstanding adhesiveness. The compounding amount of the organic acid cobalt salt in the rubber composition for metal bonding when cobalt is not contained on the metal side is preferably 0.1 parts by mass to 3 parts by mass, more preferably 100 parts by mass of the diene rubber. Is preferably 0.5 to 2 parts by mass. When the blending amount of the organic acid cobalt salt is less than 0.1 parts by mass, it is not possible to obtain the effect (further improvement in adhesion to metal) added by blending the organic acid cobalt salt. When the compounding quantity of organic acid cobalt salt exceeds 3 mass parts, the adhesiveness with respect to a metal will fall on the contrary.

  Examples of the organic acid cobalt salt include cobalt naphthenate, cobalt neodecanoate, cobalt stearate, cobalt rosinate, cobalt versatate, cobalt tall oil, cobalt neodecanoate, cobalt acetylacetonate and the like. . The organic acid cobalt salt is preferably an organic acid cobalt salt containing boron. For example, the organic acid cobalt salt may be a composite salt in which a part of the organic acid is replaced with boric acid or the like. The organic acid cobalt salt containing boron has a cobalt content of 20 Cobalt orthoborate that is ˜23 wt% is preferred.

  Examples of the organic acid cobalt salt include DIC Cobalt Naphthenate 10% (Co content 10%), DIC Co. DICnate NBC-2 (Co content 22%), Nippon Kagaku Sangyo Co. Content rate 16.54%), Rhodia Manobond C22.5 and Manobond 680C, Shepherd CoMend A and CoMend B, Dainippon Ink & Chemicals YYNBC-II, and the like.

  Furthermore, when the rubber composition for metal bonding of the present invention is used for bonding a metal member containing cobalt, the effect can be further exhibited. That is, when the metal to be bonded contains cobalt, the affinity between the metal bonding rubber composition of the present invention and the metal to be bonded can be further improved, and the adhesion can be effectively increased. In addition, in this invention, the metal member containing cobalt is cobalt with respect to the metal member which consists of arbitrary metals other than what the metal itself which comprises the metal member (for example, steel cord) contains cobalt. The metal-bonding rubber composition of the present invention can exhibit good adhesiveness to both of them, including those plated with a metal containing.

  In the present invention, the rubber composition for metal bonding can contain a vulcanization accelerator and / or an anti-aging agent. When the rubber composition for metal bonding contains an anti-aging agent, thermal aging during molding can be suppressed, and the mechanical characteristics of the rubber composition for metal bonding can be maintained. In addition, when the metal bonding rubber composition contains a vulcanization accelerator, the modification rate is improved, the Mooney viscosity as the metal bonding rubber composition is reduced, the moldability is improved, and the heat generation is further reduced. be able to.

  In the present specification, the vulcanization accelerator and the anti-aging agent are not particularly limited as long as they are usually used in a tire rubber composition. Examples of the vulcanization accelerator include sulfenamide vulcanization accelerators, thiazole vulcanization accelerators, guanidine vulcanization accelerators, thiuram vulcanization accelerators, and the like. These vulcanization accelerators can be used alone or in combination. Preferred are thiuram vulcanization accelerators and sulfenamide vulcanization accelerators.

  Examples of the sulfenamide-based vulcanization accelerator include N-cyclohexylbenzothiazole sulfenamide, Nt-butylbenzothiazole sulfenamide, N-oxydiethylenebenzothiazole sulfenamide, N, N-dicyclohexylbenzothiazole sulfene. Examples include amide, (morpholinodithio) benzothiazole and the like.

  Examples of thiazole vulcanization accelerators include di-2-benzothiazolyl disulfide, mercaptobenzothiazole, benzothiazyl disulfide, mercaptobenzothiazole zinc salt, (dinitrophenyl) mercaptobenzothiazole, (N, N-diethylthio). Examples thereof include carbamoylthio) benzothiazole.

  Examples of the guanidine vulcanization accelerator include diphenyl guanidine, di (o-tolyl) guanidine, o-tolyl biguanide and the like.

  Examples of the thiuram vulcanization accelerator include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide, tetrakis (2-ethylhexyl) thiuram disulfide, tetrabenzylthiuram disulfide and the like.

  In the rubber composition for metal bonding of the present invention, the blending amount of the vulcanization accelerator is preferably 0.1 parts by mass to 2.0 parts by mass, and more preferably 0.2 parts by mass with respect to 100 parts by mass of the rubber component described above. It is good in it being mass parts-1.5 mass parts. By setting the blending amount of the vulcanization accelerator within the above range, the modification rate can be improved, the Mooney viscosity of the rubber composition can be reduced, the molding processability can be improved, and the exothermic property can be further reduced.

  In the present specification, the anti-aging agent is not particularly limited as long as it is usually used in a rubber composition for tires. An amine anti-aging agent, a phenol anti-aging agent, a phosphorus anti-aging agent is used. Any of imidazole anti-aging agents and thioether anti-aging agents can be added. Examples of the amine-based anti-aging agent include a diarylamine-based anti-aging agent, a diaryl-p-phenylenediamine-based anti-aging agent, a dialkyl-p-phenylenediamine-based anti-aging agent, an alkyl / aryl-p-phenylenediamine-based anti-aging agent, Examples thereof include amine / ketone anti-aging agents. Of these, diaryl-p-phenylenediamine-based antioxidants, dialkyl-p-phenylenediamine-based antioxidants, and alkyl-aryl-p-phenylenediamine-based antioxidants are preferable.

  Examples of the phenol-based antioxidant include monophenol-based antioxidants, alkylene bisphenol-based antioxidants, polyphenol-based antioxidants, thiobisphenol-based antioxidants, hydroquinone-based antioxidants, and the like.

  In the metal bonding rubber composition of the present invention, the blending amount of the antioxidant is preferably 0.5 parts by mass to 5 parts by mass, more preferably 1 part by mass to 3 parts by mass with respect to 100 parts by mass of the rubber component described above. Good part. By setting the blending amount of the anti-aging agent in the above range, it is possible to suppress thermal aging at the time of molding the metal bonding rubber composition and maintain its mechanical characteristics.

  The above-mentioned modified diene rubber contains 0.1 to 10 parts by weight, preferably 0.3 to 5 parts by weight of maleic acid metal salt based on 100 parts by weight of natural rubber and / or isoprene rubber, and has a reinforcing property. It can be manufactured by heating to 145 ° C. to 200 ° C., preferably 150 ° C. to 190 ° C. without grafting, and graft modification. As the maleic acid metal salt, those described above can be used. Further, when the modified diene rubber is produced, the reinforcing filler is not allowed to coexist. Thereby, the graft reaction rate of the maleic acid metal salt with respect to natural rubber and / or isoprene rubber can be made high. By making the compounding amount of the maleic acid metal salt within the above range, the reaction rate to the natural rubber and / or isoprene rubber can be increased, and the remaining unreacted maleic acid metal salt can be suppressed. The reaction rate of the maleic acid metal salt is the amount of the maleic acid metal salt grafted to natural rubber and / or isoprene rubber with respect to the blending amount (preparation amount) of the maleic acid metal salt, and preferably 30 to 80% by mass. Preferably it is 50-80 mass%. Thereby, the modified diene rubber can be produced efficiently.

  In preparing the modified diene rubber, a vulcanization accelerator and / or an antioxidant can be blended. The types and blending amounts of the vulcanization accelerator and the anti-aging agent can be appropriately adjusted so as to be in the above-described range.

  Heat modification of a maleic acid metal salt to natural rubber and / or isoprene rubber can be performed using a heat kneader such as a pressure kneader, a Banbury mixer, a Brabender, a single screw extruder, a twin screw extruder, or the like. .

  Other compounding agents other than the above can be added to the rubber composition for metal bonding of the present invention. Other compounding agents include generally reinforcing fillers other than carbon black, vulcanization or crosslinking agents, vulcanization accelerators, anti-aging agents, liquid polymers, thermosetting resins, thermoplastic resins, etc. Various compounding agents used for the tires can be exemplified. The compounding amounts of these compounding agents can be conventional conventional compounding amounts as long as they do not contradict the purpose of the present invention. Moreover, as a kneading machine, a normal rubber kneading machine, for example, a Banbury mixer, a kneader, a roll or the like can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  Nine types of rubber compositions for metal bonding (comparative examples 1 to 3 and examples 1 to 6) in which the composition shown in Table 2 is a common composition and the composition of natural rubber and modified natural rubber is varied as shown in Table 1 Was prepared. Specifically, among the compounds shown in Tables 1 and 2, a master batch prepared by kneading the components excluding sulfur and the vulcanization accelerator with a 1.7 L closed Banbury mixer for 5 minutes was cooled to room temperature. Was returned to a 1.7 L closed Banbury mixer, and sulfur and a vulcanization accelerator were added and mixed to prepare each rubber composition for metal bonding. In addition, the mixing | blending of Table 2 was represented by the mass part with respect to a total of 100 mass parts of the natural rubber described in Table 1, and modified natural rubber. Using the obtained rubber composition for metal bonding, rubber hardness, heat build-up, and adhesion to metal were measured by the following methods.

Rubber hardness The obtained rubber composition for metal bonding was vulcanized in a predetermined mold at 170 ° C. for 10 minutes to prepare a test piece. Using the obtained test piece, in accordance with JIS K6253, a durometer The rubber hardness at a temperature of 20 ° C. was measured according to Type A. The obtained results are shown in the “Rubber Hardness” column of Table 1 as an index with the value of Comparative Example 1 as 100. A larger index value means better rubber hardness.

Low exothermic property The obtained rubber composition for metal bonding was press-vulcanized at 160 ° C. for 20 minutes in a predetermined mold (150 mm × 150 mm × 2 mm) to produce a test piece, and the obtained test piece was used. In accordance with JIS K6394, a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.) was used as an index of exothermic property at 60 ° C. under the conditions of 10% ± 2% elongation deformation strain, 20 Hz frequency, and 60 ° C. The tan δ was measured. The obtained results are shown in the “low heat generation” column of Table 1 as an index with the value of Comparative Example 1 being 100. The smaller the index, the smaller the tan δ at 60 ° C., and the lower the exothermic property.

Adhesion (initial and after wet heat aging)
A plurality of steel cords were arranged in parallel with each other at intervals of 13 mm, embedded in an unvulcanized metal bonding rubber composition, and vulcanized at 170 ° C. for 15 minutes to prepare test samples. Divide the test sample into two groups, one group is used as it is as a sample for initial wire adhesion evaluation, and the other group is left for 2 weeks under the condition of temperature 70 ° C and humidity 96%. A test sample for later evaluation was used. Using each test sample, perform a steel cord pull-out test in accordance with ASTM-D-2, and visually measure the pulling force during pulling and the rubber coverage (with rubber [%]) on the steel cord. The adhesion property of the rubber composition for metal bonding to the steel cord was evaluated. The obtained results are shown in the columns of “Adhesiveness (initial)” and “Adhesiveness (wet heat)” in Table 1 as indices with the respective values of Comparative Example 1 being 100. The larger these index values, the better the adhesion to steel cord (initial adhesion and adhesion after wet heat aging).

The types of raw materials used in Table 1 and the adjustment methods are shown below.
・ Natural rubber 1: RSS # 3
Natural rubber 2: 100 parts by weight of natural rubber (RSS # 3) is added to a pressure kneader heated to 180 ° C., mixed for 10 minutes, and natural rubber having a thermal history equivalent to the following modified natural rubber 1 to 4 ( Unmodified) was obtained.
-Modified natural rubber 1: In a pressure kneader heated to 180 ° C, 100 parts by mass of natural rubber (RSS # 3), 1 part by mass of disodium maleate (manufactured by Tokyo Chemical Industry Co., Ltd.), anti-aging agent (Flexis Corporation) 1 part by mass of Santoflex 6PPD) was added and mixed for 10 minutes to prepare a modified natural rubber 1 having a modification rate of 0.71% by mass.
Modified natural rubber 2: A modified natural rubber 2 having a modification rate of 0.34% by mass was prepared in the same manner as the modified natural rubber 1 except that the pressure kneader temperature (modification temperature) was set to 150 ° C. .
Modified natural rubber 3: A modified natural rubber 3 having a modification rate of 0.78% by mass was prepared in the same manner as the modified natural rubber 1 except that 1 part by mass of the vulcanization accelerator CBS was added.
Modified natural rubber 4: The modified rate is 0.80% by mass in the same manner as the modified natural rubber 1 except that 1 part by weight of maleic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) is blended instead of sodium maleate. A modified natural rubber 4 was prepared.
(The modification rate was quantified by measurement of infrared spectroscopy using the obtained modified natural rubbers 1 to 4 as samples.)

The types of raw materials used in Table 2 are shown below.
・ CB: Carbon Black, Toast Carbon Co., Ltd. Seest 300
・ Zinc flower: Zinc oxide 3 types manufactured by Shodo Chemical Industry Co., Ltd. ・ Anti-aging agent: Santoflex 6PPD manufactured by Flexis
Cobalt stearate: DICATE NBC-2 manufactured by DIC
・ Sulfur: Kristex HS OT 20 manufactured by Akzo Nobel
・ Vulcanization accelerator CBS: Nouchira CZ manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Vulcanization accelerator DCBS: Sunseller DZ manufactured by Sanshin Chemical Industry Co., Ltd.

  As is clear from Table 1, the rubber compositions of Examples 1 to 6 improved the adhesion to metal (steel cord) while improving the tire hardness and low heat build-up compared to Comparative Example 1. On the other hand, the rubber composition of Comparative Example 2 has a heat history equivalent to that of the modified natural rubber used in Examples 1 to 6, but is an unmodified natural rubber. Sex deteriorated. Since the rubber composition of Comparative Example 3 uses a modified natural rubber modified with maleic anhydride instead of a maleic acid metal salt, the adhesiveness after wet heat aging deteriorated.

Claims (5)

  A rubber composition for metal bonding comprising a rubber component comprising 10% by mass to 100% by mass of a modified diene rubber and 90% by mass to 0% by mass of a diene rubber, wherein the modified diene rubber is a graft of metal maleate A rubber composition for metal bonding, which is a natural rubber and / or isoprene rubber having a reaction product.   Carbon rubber is mixed in an amount of 20 to 80 parts by mass, zinc oxide in an amount of 5 to 12 parts by mass, and sulfur in an amount of 5 to 10 parts by mass with respect to 100 parts by mass of the rubber component. Item 2. A rubber composition for metal bonding according to Item 1.   The rubber composition for metal bonding according to claim 1 or 2, wherein the maleate metal salt is sodium maleate.   The rubber composition for metal bonding according to claim 1, comprising an organic acid cobalt salt.   The rubber composition for metal bonding according to any one of claims 1 to 4, wherein the rubber composition is used for bonding a metal member containing cobalt.