JPS63245439A - Composite of steel wire with rubber - Google Patents

Abstract

PURPOSE:To obtain the title composite having strong adhesiveness, by coating a zinc- or bronze-plated steel wire with a specified rubber composition. CONSTITUTION:A rubber composition is obtained by mixing 100pts.wt. blend rubber comprising natural rubber or both of this rubber and a synthetic diene rubber with 0.5-8pts.wt. straight phenolic resin of the formula, 0.1-0.5pt.wt. hexamethylenetetramine, 0.3-5pts.wt. cobalt salt (e.g., cobalt naphthenate) and 2.5-10pts.wt. sulfur. A steel wire plated with zinc or bronze of an Sn content of 5-15% is coated with said rubber composition.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to steel wire and rubber used in the bead, belt, or carcass ply of a pneumatic tire, or in the reinforcing part of a belt conveyor or rubber crawler. More particularly, the present invention relates to a steel wire/rubber composite formed by coating a steel wire plated with zinc or bronze with a rubber composition having strong adhesive properties.

(Prior Art) Composites of steel wire and rubber have conventionally been used as reinforcing materials for industrial products such as tires and belt conveyors. Of these, brass plating (
During vulcanization, steel cord made of an alloy of Cu and Zn (approximately 30 to 40% Zn) reacts chemically with the sulfur in the rubber to firmly bond the rubber and wire, so it is used in tire belts and carcass plies. In recent years, it has been widely used as a reinforcing material for parts.

Similarly, adhesion reactions occur during vulcanization of galvanized steel wire or bronze plating, which is an alloy of copper and tin with a tin content of 5 to 15%. It is widely used as a reinforcing material.

When using galvanized wire, the amount of sulfur added to the rubber composition is increased to ensure adhesion between the galvanized wire and the rubber, and the amount of sulfur added to the rubber composition is usually increased to 3 to 15 parts by weight per 100 parts by weight of rubber. Part by weight is added. Also, when bronze-plated wire is used, the sulfur content in the rubber composition is added to a large amount of 5 to 15 parts by weight. Furthermore, in these cases, cobalt naphthenate, cobalt octylate,
A cobalt salt made of an organic cobalt metal salt such as cobalt stearate or cobalt abietate or an inorganic cobalt metal such as cobalt hydroxide may be added, or lead oxide pbo may also be used as an adhesion aid.

(Problems to be Solved by the Invention) However, the current state of the art is that it is not possible to increase the adhesion strength of galvanized wires and bronze-plated wires to rubber to the same extent as the difference in adhesive strength of brass-plated wires.

Furthermore, zinc plating and bronze plating are more easily affected by the moisture in the rubber than brass plating, and when the moisture in the rubber decreases in a low humidity environment in winter, it becomes difficult to maintain adhesive strength.

The cause of such problems has been clarified to some extent by elucidation of the adhesion mechanism between plated wire and rubber during vulcanization. In particular, the adhesion mechanism between brass-plated wire and rubber has become much clearer due to advances in surface analysis technology at the adhesion interface. Cause An Overbiu” Rubber Chemistry and Technology, No. 5
7, pp. 421-456, 1984).

According to this report, the surface of a brass-plated wire before vulcanization is covered with a thin zinc oxide film, but during vulcanization, copper ions in the internal brass plating diffuse to the surface through the zinc oxide film. Furthermore, this copper ion reacts with the sulfur in the rubber, and the copper sulfide Cu, S (X::1.98) becomes fine (
It grows into the rubber in a tree-like manner, resulting in an adhesion between the rubber and the steel wire through a physical anchoring effect.

Cobalt palmitate is used as a technology to improve and stabilize the adhesion between brass-plated wire and rubber.
Cobalt stearate, cobalt oleate, cobalt linoleate, cobalt linoleate, cobalt naphthenate, cobalt abietate, cobalt neoabietate,
Various cobalt salts, such as cobalt levopimarate, cobalt parastophosphate, and cobalt boron salts, are often added to the rubber. According to the above literature, the addition of cobalt salt suppresses the formation of zinc sulfide formed during vulcanization on the surface of brass plating and promotes the formation of copper sulfide, thereby improving and stabilizing the adhesion. However, the detailed mechanism is unknown.

on the other hand. When the surface of a bronze-plated wire made of a Cu-5n alloy and containing about 5 to 15% Sn is analyzed using a surface analyzer such as ESCA, a thin layer of tin oxide is first formed, and then a thin layer of tin oxide is formed on top of that. Generally, a thick layer is formed in which the oxides CuzO1CuO are mixed. Therefore, since the copper oxides Cu, 0, CuO are thickly formed on the surface, it becomes difficult for copper ions to diffuse from the internal bronze plating layer to the surface, and copper sulfation occurs due to the reaction between sulfur in the rubber and copper ions. Objects are not formed properly. As a result, adhesive delamination is likely to occur during vulcanization, which makes adhesion between bronze-plated wire and rubber difficult.

Furthermore, although the surface of galvanized steel wire is covered with a thick film of ZnO, the true adhesion mechanism is unknown.

As a result of various experiments, the present inventors have found that it is necessary to add 2 parts by weight or more of sulfur and the above-mentioned cobalt salt to bond zinc plating and rubber, and that the water content in the rubber is 0.
．． It was revealed that adhesion can be ensured if it is 5% or more. However, the moisture content in rubber is affected by changes in humidity between summer and winter, making it difficult to control the moisture content and making it difficult to stabilize adhesiveness.

When adhering bronze-plated wire to rubber,
If a rubber containing 3 parts by weight or more of sulfur is used, adhesion can be ensured without the addition of cobalt salt, but as with galvanized wire, adhesion cannot be ensured if the water content in the rubber is less than 0.5%.

Therefore, the object of the present invention is to improve the adhesion between galvanized wire and bronze-plated wire and rubber to the same level as that of brass-plated wire, and to maintain stability without being affected by moisture in the rubber, that is, without seasonal fluctuations. The purpose of this invention is to provide a technology that ensures good adhesion.

(Means for Solving the Problems) In order to solve the above problems, the present inventors evaluated the addition of various rubber chemicals to rubber, and found that phenol resin, hexamethylenetetramine and cobalt salt We found that the simultaneous addition of was effective in stabilizing adhesion.
The present invention has now been completed.

That is, the present invention applies 0.5 to 8 parts by weight of phenolic resin and hexamethylenetetramine to 100 parts by weight of natural rubber alone or a blend rubber of natural rubber and synthetic diene rubber to a steel wire plated with zinc or bronze. This relates to a steel wire and rubber composite coated with a rubber composition containing 0.1 to 0.5 parts by weight, 0.3 to 5 parts by weight of cobalt salt, and 2.5 to 10 parts by weight of sulfur. be.

There are two types of phenolic resins, resol type and novolac type, depending on the manufacturing method, and both types are effective for adhesion in the present invention. The phenol resin used in the present invention may be partially modified with cresol, cashew or oil, but is preferably a phenol-based resin such as a straight phenol resin represented by the following formula: This is because, for example, Kutusol-modified phenol resins represented by the following formula: For example, cashew-modified phenolic resins represented by the following formula: This is because the so-called modified phenol resin approaches a so-called alkylphenol resin when the amount of modification is large. This is also because adding an alkylphenol resin such as metacresol resin reduces adhesive activity, which is undesirable. In the present invention, when 0.5 parts by weight or more of the phenol resin is added simultaneously with the cobalt salt and hexamethylenetetramine, the adhesion improving effect appears even on rubbers with a water content of 0.5% or less. However, if more than 8 parts by weight is added, the adhesion improvement effect reaches a plateau, and at the same time, depending on the amount of hexamethylenetetramine added, the curing reaction of the phenolic resin during vulcanization may cause hardening of the rubber, decrease in tensile strength at break, and This is not preferable since the elongation at break is significantly reduced. However, it is difficult to ensure sufficient adhesion by adding phenolic resin alone.

Next, hexamethylenetetramine used in the present invention is known to have a function of helping the thermosetting of the phenolic resin, and there are commercially available products in which hexamethylenetetramine is partially added to the phenolic resin. . The addition of hexamethylenetetramine aids in the thermosetting of the phenolic resin in the rubber, exhibiting a rubber reinforcing effect, and under the simultaneous addition of cobalt salt and phenolic resin, O, L uf
Addition of more than the it part starts to show an adhesion improving effect.

However, if the amount added exceeds 0.5 part by weight, hexamethylenetetramine tends to generate ammonia through thermal decomposition. Therefore, since corrosion of the wire becomes a problem in the long term, it is preferable to add as little amount as possible within a range that can ensure sufficient adhesion.

Further, as the cobalt salt used in the present invention, for example, the various cobalt salts mentioned above can be used.

When the cobalt salt is added at the same time as the phenol resin and hexamethylenetetramine, an effect of improving adhesion can be seen from 0.3 parts by weight. However, if it is added in an amount exceeding 5 parts by weight, no further improvement in adhesive strength is observed and the heat aging properties of the rubber are significantly deteriorated, which is not preferable.

In the present invention, the sulfur content in the rubber composition is specified to be 2.5 parts by weight or more, because stable adhesion cannot be obtained unless it is 2.5 parts by weight or more. but,
Addition of a large amount of sulfur to the rubber composition will significantly worsen the heat aging characteristics of the rubber, so the amount needs to be 10 parts by weight or less.

In addition, when adhering a bronze-plated wire made of a copper-tin alloy with a tin content of about 5 to 15% to rubber, the sulfur content is 2.5 parts by weight or more and the water content in the rubber is If it is 0.5% or more, unlike galvanized wire,
Although adhesion can be ensured to some extent without adding cobalt salt, it becomes difficult to ensure adhesion when the water content in the rubber is less than 0.5%.

(Function) In the present invention, when predetermined amounts of phenol resin, hexamethylenetetramine, and cobalt salt are simultaneously added, the moisture content of bronze and galvanized wires is 0.5% or less. Adhesion is ensured even against wires, and maintains high adhesion strength comparable to that of brass-plated wire.

The optimum addition amount range of each rubber agent is almost the same for long plated wire and galvanized wire.

In addition, when adhering to zinc-plated wire and bronze-plated wire, when the moisture contained in the rubber is 0.5% or more, when phenol resin, hexamethylenetetramine, and cobalt salt are added simultaneously, compared to when they are not added simultaneously. Considerable improvement in adhesion can be seen.

However, when the water content in the rubber exceeds 2%, the adhesive strength to both zinc plating and bronze plating decreases whether or not phenolic resin, hexamethylenetetramine, and cobalt salt are added simultaneously. However, even in Japan's humid summers, the amount of water contained in rubber generally does not exceed 1.5%.

On the other hand, the water content in rubber in winter, when humidity is low, is generally 0.3 to 0.4%. Therefore, in the steel wire and rubber composite of the present invention, stable adhesion without seasonal variations is ensured.

(Example) Next, the present invention will be explained with reference to Examples and Comparative Examples.

・1 ~ 6 ~
13 Various rubber compositions having the compounding ratios (parts by weight) shown in Table 3, and a galvanized piano wire with a wire diameter of 1 mmφ,
Four types of plated steel wire: bronze-plated copper-tin alloy wire with 8% and 12% tin content, and for comparison, brass-plated copper-zinc alloy wire with 35% zinc content. An adhesion test was conducted with

The moisture content of the rubber compositions shown in Table 1 was controlled as follows. That is, a rubber composition with low water content (0
, 5% or less) were made by kneading natural rubber, SBR rubber, and various rubber chemicals with low water content from the beginning in a Banbury mixer. Further, a rubber composition with a high water content (FF content: 10.7 to 1.5%) was prepared by kneading it in a small Banbury mixer and then kneading water on a roll. The water content in the rubber composition thus prepared was measured by the Karl Fischer method.

The adhesive strength between rubber and steel wire is JISK6301.
Measurements were made for each sample prepared by vulcanization under the vulcanization conditions of 150 DEG Cl2O for minutes according to the peel test method. The obtained results are also listed in Table 1.

(Effects of the Invention) As is clear from the adhesive force measurement results in Table 1, in the steel wire and rubber composite of the present invention, as a result of the simultaneous addition of phenol resin, cobalt salt, and hexamethylenetetramine, The effect is that stable and strong adhesion with galvanized wire and bronze-plated wire can be obtained regardless of moisture content.

Claims (1)

[Claims] 1. Zinc or bronze plated steel wire is coated with 0 phenolic resin per 100 parts by weight of natural rubber alone or a blend of natural rubber and synthetic diene rubber.
．． 5-8 parts by weight, hexamethylenetetramine 0.1-0
．． 5 parts by weight, 0.3 to 5 parts by weight of cobalt salt and 2 parts by weight of sulfur.
．． A composite of steel wire and rubber coated with a rubber composition containing 5 to 10 parts by weight.