JP4417729B2 - Rubber-steel cord composite and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber-steel cord composite and a pneumatic tire using the same as a reinforcing material.

  Conventionally, steel cords have been used as reinforcing materials for pneumatic tires, belt conveyors and the like, and in order to enhance the reinforcing effect, a technique for improving the adhesion between the steel cord and rubber has been taken. For example, steel cords are plated with brass, bronze, zinc, and the like, and rubber compositions are blended with organic acid cobalt that promotes formation of an adhesive interface layer.

  However, recently due to deterioration under high heat generation due to higher speed and higher horsepower of vehicles, deterioration due to heat history due to longer life of tires, deterioration due to wet heat from manufacturing period to running period, etc. In addition, a high level of adhesion is required. In response to such requirements, the conventional rubber composition containing organic acid cobalt is superior in initial adhesiveness for the reasons described above, but the deterioration in adhesiveness is large due to heat aging, and the recent required performance It's not catching up with. The reason for this is not clear, but it is considered that the organic acid cobalt has a strong oxidation promoting action, so that the promoting action of the adhesive layer formation increases the thickness of the adhesive layer at the end of running and leads to layer destruction.

  In order to improve the adhesion between the steel cord and the rubber, as an improvement measure on the rubber composition side, metals other than cobalt have been studied, such as nickel, but it is more adhesive than cobalt in the initial run and after aging. However, it has not yet been put into practical use. Moreover, although the combination of the organic acid nickel and the organic acid molybdenum is proposed by the following patent documents 1 and 2, it is desired to realize a higher level of adhesion.

On the other hand, as an improvement measure on the steel cord side, increasing the copper content of the brass plating, or promoting the thermal diffusion during plating and increasing the copper ratio of the plating surface, etc., to increase the plating reactivity. Conceivable. This measure has an effect of improving the adhesiveness at the beginning of traveling, but conversely, at the end of traveling, the promoting action of formation of the adhesive layer proceeds excessively, leading to a decrease in adhesiveness.
JP 2002-38113 A JP 2002-69404 A

  The present invention has been made in view of the above points, and in addition to initial adhesiveness, it is excellent in adhesion durability such as heat-resistant adhesiveness and wet heat adhesiveness, and has a high level of adhesive performance both in the initial stage and after aging. It is an object of the present invention to provide a realized rubber-steel cord composite and a pneumatic tire using the same.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor made a metal component molar ratio of the nickel salt and the molybdenum salt of the organic acid to be blended in the rubber composition within a predetermined range, and in the brass plating of the steel cord. By setting the copper / zinc ratio within a predetermined range, it was found that a high level of adhesion performance was exhibited both at the initial stage of running and after aging, and the present invention was completed.

  That is, the rubber-steel cord composite according to the present invention comprises an organic acid metal salt component comprising at least one organic acid metal salt and having a metal molar ratio of nickel to molybdenum of 2/1 to 20/1. A rubber composition comprising 0.01 to 10 parts by weight in terms of metal content with respect to 100 parts by weight of the component, and a steel cord plated with brass having a copper content of 60 to 70% by weight. is there. By combining the nickel / molybdenum ratio of the organic acid metal salt in such a rubber composition and the copper / zinc ratio of brass plating in the steel cord as a specific range, both have a good balance of reactivity, and will be described later. As the results of the examples show, in addition to the initial adhesiveness, the adhesive durability such as wet heat adhesiveness is also excellent.

In the rubber-steel cord composite of the present invention, the organic acid metal salt component includes a metal component having a metal molar ratio of nickel / molybdenum of 2/1 to 20/1, and a salt completely theoretically with the metal. It is obtained from an organic acid component corresponding to 0.7 to 0.8 mole times the organic acid to be formed . When the organic acid nickel and the organic acid molybdenum are combined, generally, unreacted free acid remains at the time of preparation of the metal salt, and the quality varies among lots. In particular, the wet heat adhesion may be deteriorated. This is thought to be because free organic acids break the reactive adhesion layer between rubber and steel cord plating. Therefore, when preparing an organic acid metal salt of nickel and molybdenum, setting the amount of organic acid to the metal within the predetermined range described above, so that free organic acid does not remain, wet heat adhesion Can be more effectively suppressed.

  The pneumatic tire according to the present invention uses the above-described rubber-steel cord composite of the present invention as a reinforcing material, and the adhesion between the rubber and the steel cord is realized at a high level both in the initial stage of travel and after aging. Therefore, a stable reinforcing effect can be exhibited from the beginning of running to after aging.

  As described above, according to the present invention, in addition to the initial adhesiveness, the adhesive performance between the rubber and the steel cord is excellent in adhesion durability such as heat-resistant adhesiveness and wet heat adhesiveness. Adhesive performance can be realized.

  The rubber composition used in the present invention contains a rubber component and an organic acid metal salt component comprising at least one organic acid metal salt and having a metal molar ratio of nickel to molybdenum of 2/1 to 20/1. Is.

  Examples of the rubber components include natural rubber, polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene-isobutylene rubber (IIR), ethylene-propylene-diene rubber (EPDM), and these. Diene-based synthetic rubber such as a modified product of These may be used alone or in combination of two or more.

  The organic acid metal salt component includes a metal component containing nickel and molybdenum, and an organic acid component corresponding to 0.7 to 0.8 moles of the organic acid that theoretically completely forms a salt with the metal. It is preferable to use the resulting organic acid metal salt, particularly a mixture of organic acid nickel and organic acid molybdenum.

  The metal component may be a metal compound such as a metal oxide or an inorganic metal salt, or a simple metal. The molar ratio of nickel to molybdenum (nickel / molybdenum) in the metal component is 2/1 to 20/1, preferably 4/1 to 8/1. When the molar ratio is less than 2/1, economic disadvantages are caused (Mo is more expensive than Ni), and the hardness (rigidity) of the compounded rubber is reduced. On the other hand, if the molar ratio exceeds 20/1, sufficient adhesiveness cannot be obtained (Mo cannot compensate for poor adhesiveness of Ni).

  Examples of the organic acid component include organic acid salts such as organic acids and organic acid alkali metal salts. Examples of the organic acid constituting the organic acid component include naphthenic acid, octylic acid, propionic acid, abietic acid, and acetic acid with respect to nickel, and naphthenic acid and abietic acid with respect to molybdenum. These organic acids may be used in combination, and in that case, the organic acid metal salt may be mixed after preparation.

  The amount of the organic acid component added in preparing the organic acid metal salt is an amount corresponding to 0.7 to 0.8 mole times the amount of the organic acid that theoretically completely forms a salt with the metal of the metal component. is there. When the addition amount of the organic acid is less than 0.7 mole times, the adhesive strength from the initial stage becomes insufficient, and the heat-resistant adhesiveness, wet heat adhesiveness, etc. become insufficient. When the addition amount of the organic acid exceeds 0.8 mol times, unreacted organic acid remains, resulting in poor wet heat adhesion and poor durability. Here, the amount that forms a salt completely in theory is an amount that is calculated stoichiometrically assuming that nickel is divalent and molybdenum is monovalent.

  Examples of a method for preparing such an organic acid metal salt include a metathesis method via an alkali metal salt of an organic acid, a method of heating and melting an organic acid and a metal oxide, a method of reacting a metal sulfate or metal nitrate with an organic acid, etc. Is mentioned. More specifically, for example, it can be prepared as follows. That is, first, a mixture of an organic acid molybdenum salt and an excess organic acid is obtained by a reaction between the organic acid and the inorganic molybdenum salt, and an inorganic nickel salt is added to the mixture, followed by a side decomposition reaction with the organic acid. A mixture of molybdenum salt and organic acid nickel salt is obtained. At that time, if the amount of the organic acid initially charged is 0.7 to 0.8 mol times the theoretical amount with respect to the raw metal (molybdenum and nickel), the organic acid nickel having no residual unreacted organic acid can be obtained. A mixture of molybdenum organic acids is obtained.

  The organic acid metal salt component is blended so that the total weight of nickel and molybdenum is 0.01 to 10 parts by weight with respect to 100 parts by weight of the rubber component. More preferably, the content is such that the total weight of nickel and molybdenum is 0.01 to 2 parts by weight. If the above is less than 0.01 parts by weight, the adhesiveness from the initial stage is insufficient, and if the above is more than 10 parts by weight, the oxidation promoting action becomes too large and the wet heat adhesiveness and aging resistance tend to be inferior.

  In addition to the organic acid metal salt component, a compound containing boron such as boric acid may be blended. By including such a boron compound, the initial adhesiveness is improved, and a roll at the time of manufacture is also provided. It is possible to prevent over-adhesion to the rubber and to improve the elastic modulus of rubber.

  Further, in addition to the organic acid metal salt component, a cobalt compound such as organic acid cobalt can be blended. In that case, the organic acid metal salt component containing the organic acid cobalt at the same time may be prepared by adding cobalt together with nickel and molybdenum during the preparation of the organic acid metal salt. Alternatively, the organic acid metal salt component may be prepared. Apart from this, a cobalt compound may be prepared and used in combination with the rubber composition.

  Furthermore, in addition to the organic acid metal salt component, a general adhesion improver may be added. Examples of such adhesion improvers include (1) 0.2 to 20 parts by weight of hexamethylenetetramine or melamine derivative with respect to 100 parts by weight of the rubber component, and (2) phenol resin or its modified type resorcin or resorcin. Examples include 0.1 to 10 parts by weight of a derivative, a cresol resin, etc. with respect to 100 parts by weight of the rubber component, and (3) a combined system of (1) and (2) above.

  Here, examples of the melamine derivative include hexamethoxymethyl melamine. Examples of the resorcin derivative include resorcin / alkylphenol / formalin copolymer resin, resorcin / formalin reactant, and the like.

  The rubber composition is usually mixed with a filler such as carbon black or silica. For example, 0 to 200 parts by weight of carbon black is mixed with 100 parts by weight of the rubber component, and 0 to 100 parts by weight of silica is mixed with 100 parts by weight of the rubber component. In that case, it is preferable to mix 20 to 200 parts by weight of carbon black and silica in total.

  Here, the silica is not particularly limited, such as dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid) and the like. Further, the carbon black is not particularly limited, and examples thereof include SAF class, ISAF class, HAF class and the like, which have high classification reinforcement according to ASTM D1765.

  The rubber composition may also contain 1 to 10 parts by weight of a vulcanizing agent such as sulfur with respect to 100 parts by weight of the rubber component. Other examples include softeners such as aroma oil and diphenylguanidine. Vulcanization accelerators such as sulfenamide, thiazole based on mercaptobenzothiazole, sulfenamide based on N, N-dicyclohexyldisulfenamide, thiuram based on tetramethylthiuram disulfide Conventional rubber industry such as anti-aging agents such as amine / ketone based on poly (2,2,4-trimethyl-1,2-dihydroquinoline) and diarylamine based on phenyl-α-naphthylamine The compounding agent used in 1 can be appropriately blended in a usual blending amount.

  The rubber-steel cord composite of the present invention can be obtained by vulcanizing and bonding the rubber composition together with the steel cord. The rubber-steel cord composite is vulcanized and molded with the steel cord covered with the rubber composition, and is used as a reinforcing material for a pneumatic radial tire belt, carcass, or various belts. It can be used as a reinforcing material for conveyors.

  Here, in the present invention, a steel cord subjected to brass plating (copper / zinc plating) having a copper content of 60 to 70% by weight is used as the steel cord. The copper / zinc ratio in the brass plating is more preferably 64 to 69% by weight, and further preferably 66 to 69% by weight in terms of copper content. If the copper content exceeds 70% by weight, the reactivity of the brass plating is too high and the reaction layer becomes brittle on the contrary.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Examples 1-6)
100 parts by weight of natural rubber (RSS 3), 60 parts by weight of carbon black N326 (Tokai Carbon Co., Ltd. Seest 300), 8 parts by weight of zinc white (Mitsui Metals Co., Ltd. No. 3), anti-aging agent (ANTAGE 6C from Kawaguchi Chemical Co., Ltd.) 2 parts by weight, 6 parts by weight of insoluble sulfur (manufactured by Shikoku Kasei Co., Ltd.), and 1 part by weight of vulcanization accelerator DZ (Axel DZ-G by Kawaguchi Chemical Co., Ltd.) are used as a common formulation. A mixture of organic acid nickel and organic acid molybdenum was blended in an amount of 0.2 parts by weight in terms of metal content, and kneaded according to a general method using a Banbury mixer to obtain a rubber composition of an example.

  The above-mentioned mixture of organic acid nickel and organic acid molybdenum was synthesized as follows. First, a mixture of molybdenum naphthenate and excess naphthenic acid is obtained by the reaction of naphthenic acid and an inorganic molybdenum salt, and an inorganic nickel salt is added to the mixture, followed by a side decomposition reaction with naphthenic acid. A mixture of molybdenum acid acids was obtained. At that time, the metal molar ratio was nickel / molybdenum = 6/1, and the amount of naphthenic acid charged was 0.7 mol times the theoretical amount of reaction with respect to the amount of raw metal (nickel + molybdenum).

  The rubber composition of the Example obtained above was sheeted to produce a rubber sheet having a thickness of 1.0 mm. 6 types of brass-plated steel cords (structure: 2 + 1 × 0.27 mm) with the copper content shown in Table 1 below are arranged at 12/25 mm intervals and sandwiched between the rubber sheets. The sheets were stacked and vulcanized at 150 ° C. for 30 minutes to prepare rubber-steel cord composite samples of Examples 1 to 6 having two steel cord layers.

  The copper / zinc composition ratio (copper content) of the brass plating is the ratio of copper in the brass plating obtained by fluorescent X-ray measurement. The tube voltage is 40 kV and the tube current is 70 mA using the SXF-1200 model manufactured by Shimadzu Corporation. It is the value measured by.

(Comparative Examples 1-6)
0.2 parts by weight of cobalt stearate as an organic acid metal salt component in terms of metal content is blended with the above-mentioned common blend, and the others are similar to the examples to obtain a rubber composition of a comparative example to produce a rubber sheet. did. And 6 types of brass plated steel cords (structure: 2 + 1 × 0.27 mm) with copper content shown in Table 1 below are arranged at 12/25 mm intervals and sandwiched between the rubber sheets. Two samples were stacked and vulcanized at 150 ° C. for 30 minutes to prepare rubber-steel cord composite samples of Comparative Examples 1 to 6 having two steel cord layers.

(Examination / Evaluation)
About each sample of Examples 1-6 obtained above and Comparative Examples 1-6, the adhesiveness test (initial stage adhesiveness, wet heat adhesiveness) was done. The test and evaluation methods are as follows.

-Initial adhesiveness: The peeling force of the two-layer steel cord was measured for the above sample using an autograph (Shimadzu DCS500), and the rubber coverage of the peeled steel cord was visually confirmed. The peel force was expressed as an index with Comparative Example 1 as 100. A larger value means better adhesion.

-Wet heat adhesion: After leaving the above sample to stand in a steam environment at 105 ° C. for 96 hours, the peel strength of the two-layer steel cord was measured using an autograph, and the rubber coverage of the peeled steel cord was visually observed. Confirmed. The peel force was expressed as an index with Comparative Example 1 as 100. A larger value means better adhesion. The retention rate with respect to the initial adhesiveness is also shown in Table 1.

About each rubber composition of the said Example and a comparative example, heat aging resistance was evaluated. For heat aging resistance, each rubber composition was vulcanized at 150 ° C. for 30 minutes to prepare a test piece having a predetermined shape, and the obtained test piece was left in a gear oven at 90 ° C. for 192 hours, followed by a tensile test (JIS (Based on K6253), and the retention rate of elongation at break relative to the initial stage was measured. The result was displayed by the index | exponent which makes the rubber composition of a comparative example 100. A larger value means better heat aging resistance.

  As shown in Table 1, in Comparative Examples 1 to 6, when the copper content in the brass plating of the steel cord increases and the reactivity increases, the initial adhesiveness tends to improve, but the adhesiveness after aging Was greatly reduced. In contrast, in Examples 1 to 6, a high level of adhesive performance was expressed over a wide range regardless of the brass plating composition of the steel cord, both at the initial stage and after aging. In particular, in Examples 3 to 6, regarding wet heat adhesion, the rubber coverage after peeling was high, and excellent adhesion durability was ensured.

  The rubber-steel cord composite of the present invention can be particularly suitably used as a reinforcing material for a pneumatic tire belt or carcass, but is not limited thereto, and can be used as a reinforcing material for various belt conveyors. it can.

Claims (3)

An organic acid metal salt component consisting of at least one organic acid metal salt and having a metal molar ratio of nickel to molybdenum of 2/1 to 20/1 is 0.01% in terms of metal content with respect to 100 parts by weight of the rubber component. 10 to 10 parts by weight of a rubber composition,
A steel cord plated with brass having a copper content of 60 to 70% by weight;
Made of rubber - a steel cord composite,
The organic acid metal salt component has a metal component molar ratio of nickel to molybdenum of 2/1 to 20/1, and 0.7 to 0 with respect to the organic acid that forms a salt completely with the metal in theory. It is obtained from an organic acid component corresponding to 8 mol times
A rubber-steel cord composite characterized by the above. The rubber of claim 1, wherein the brass plating of the copper content is characterized by a 64 to 69% by weight - steel cord composite. Rubber according to claim 1 or 2 - pneumatic tire characterized by a steel cord composites was used as a reinforcing material.