JPH0551487A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition for an extremely hard tire suitable as a bead filler rubber by compounding a rubber containing a diene rubber with a modified novolak phenolic resin containing a specific hardener. CONSTITUTION:The objective rubber composition for an extremely hard rubber is produced by compounding (A) 100 pts.wt. of a rubber component containing at least one kind of diene rubber with (B) 20-130 pts.wt. (preferably 60-120 pts.wt.) of carbon black and (C) 1-30 pts.wt. (preferably 5-20 pts.wt.) of a rubber- reinforcing agent composed of (C1) a resin produced by modifying a novolak phenolic resin with one or more substances selected from animal or vegetable oils (e.g. rosin oil), unsaturated oils (e.g. linoleic acid), aromatic hydrocarbons (e.g. xylene) and nitrile rubber and (C2) hexamethoxymethylmelamine preparatorily included in the component C1 as a curing agent of the component. A pneumatic tire is manufactured by using the composition as a bead filler and a polyester fiber as the reinforcing cord for a carcass layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for tires, and more particularly to a super hard rubber composition suitable for use as a bead filler rubber and a pneumatic tire using the same.

[0002]

2. Description of the Related Art Various studies have been made on the bead structure of a radial tire so as to satisfy the rigidity and durability required for the tire. Attempts have been made to improve the dynamic performance and durability of tires by disposing a bead reinforcing layer in the bead portion.

On the other hand, by arranging ultra-hard rubber in the bead portion, it is effective to improve the exercise performance.
-16084, French Patent No. 1,260,138, US Pat. No. 4,067,373 and the like are well known.

As described below, these prior arts do not provide a sufficient solution. Therefore, the applicant of the present invention, as described in Japanese Patent Publication No. 57-30856, discloses a novolac type phenolic resin and / or Alternatively, a rubber composition for a bead filler has been proposed in which a novolac-type modified phenolic resin modified with oil or the like and hexamethylenetetramine (hereinafter abbreviated as “hexamine”) are used together with natural rubber or polybutadiene rubber together with carbon black.

In Japanese Patent Publication No. 57-30856, rosin oil is used as a novolac-type modified phenolic resin.
Oils such as tall oil, cashew oil, linole oil, and olein oil, aromatic hydrocarbons such as xylene, and rubber-modified resins such as nitrile rubber are used to compound polyisoprene rubber.

However, these techniques take a form in which a kneaded material of resin and rubber is mixed with a hardening agent and hardened in the rubber. Therefore, in comparison with the usual resin molding in which only the resin and the hardening agent are mixed and hardened. The curing efficiency is poor, and a considerable amount of the resin remains unreacted. To obtain the desired hardness as the bead filler rubber, it is necessary to increase the amount of the resin compounded or increase the amount of the curing agent. there were.

However, if the compounding amount of the resin is increased, the unreacted resin is naturally increased, and these unreacted resins are merely foreign substances and deteriorate the mechanical properties of the rubber composition, particularly the fatigue life and the creep property. In addition, there is a problem in that heat generation becomes large and the breaking life of the tire becomes short.

Further, when the amount of the curing agent is increased, in the case of hexamine, the strength of the polyester fiber, which is widely used as a reinforcing cord for the adjacent carcass layer, is deteriorated due to amine degradation during tire vulcanization or tire running. It is a problem when tires are vulcanized at high temperatures.

Therefore, the applicant of the present invention has made further diligent studies and previously disclosed in JP-A-2-222432 that a novolac-type phenolic resin is modified with an oil such as animal or vegetable oil and that the resin contains hexamine as a curing agent. By internally adding the compound with self-curing property, the reinforcing effect of the rubber can be enhanced, the amount of ammonia generated during vulcanization can be suppressed, and the strength reduction due to amine deterioration of the polyester fiber can be reduced. Proposed.

[0010]

The above-described method of disposing the beat reinforcing layer on the bead portion has a problem that the number of tire manufacturing steps is increased and the productivity is remarkably deteriorated. Also,
In the method of arranging the ultra-hard rubber in the bead portion, the function as the bead filler rubber under the complicated input while the tire is running is fully exerted, and the durability required as a tire on it is provided. There was a problem that little was taken into consideration.

[0011] In addition, as the structure around the bead has been simplified with the demands for improved vulcanization productivity and weight reduction of tires, the load on the bead filler and the ply cord around the bead has become more important. Is coming. Against such a technical tendency, the above-mentioned JP-A-2-22243
In the technique described in Japanese Patent Publication No. 2, although the amount of ammonia generated during vulcanization can be suppressed and tire performance is improved, in high temperature short time vulcanization which is one of the vulcanization productivity improving methods, Ammonia generated in a small amount causes the polyester fiber to gradually deteriorate under high-temperature vulcanization conditions, so that sufficiently satisfactory tire performance cannot be obtained.

An object of the present invention is to increase the hardness of rubber by using a novolac-type modified phenolic resin, particularly in increasing the hardness of rubber in the bead portion of a tire, without increasing the amount of resin or curing agent more than necessary. Therefore, by providing a rubber composition and a tire using the rubber composition, which can completely prevent the mechanical properties of the rubber from being deteriorated due to the presence of the unreacted resin or excess amine, and the amine deterioration of the carcass cord fiber. is there.

[0013]

Means for Solving the Problems The present inventor has conducted earnest research to solve the above problems. As a result, a novolac type phenolic resin was modified with an oil such as animal or vegetable oil, carbon black was used in combination, and hexamethoxymethylmelamine was added to the resin as a curing agent, and ammonia was not generated at all. It has been found that a surprising effect is exhibited by imparting self-curability, and the present invention has been completed.

That is, the present invention selects 20 to 130 parts by weight of carbon black, 100 parts by weight of rubber containing at least one diene rubber, and animal or vegetable oil, unsaturated oil, aromatic hydrocarbon and nitrile rubber. In addition, 1 to 30 parts by weight of a rubber reinforcing agent in which hexamethoxymethyl melamine is internally added as the resin curing agent in a novolac type modified phenolic resin modified with at least one kind is compounded.

A pneumatic tire using the above-mentioned rubber composition as a bead filler.

The pneumatic tire described above uses polyester fiber as a reinforcing cord for the carcass layer.

The rubber containing at least one diene rubber is a rubber containing at least one selected from the group consisting of polyisoprene rubber (including natural rubber), polybutadiene rubber and styrene-butadiene copolymer rubber. is there.

The amount of carbon black used in the present invention is 20 to 130 parts by weight, preferably 60 to 120 parts by weight, and more preferably 6 parts by weight based on 100 parts by weight of the rubber.
5 to 85 parts by weight. If the amount of carbon black is less than 20 parts by weight, the reinforcing effect of the resin is difficult to appear, and if it exceeds 130 parts by weight, the rubber becomes brittle and the durability of the rubber composition is extremely deteriorated, which is not preferable.

The amount of the novolac-modified phenolic resin internally added with hexamethoxymethylmelamine in the present invention is 1 to 30 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the rubber. When the compounding amount of the resin is less than 1 part by weight, there is almost no effect in compounding the resin, and the reinforcing effect cannot be expected. On the other hand, if it exceeds 30 parts by weight, the resin particles form an aggregate in the rubber to cause phase separation, which significantly reduces the physical properties of the rubber composition, which is not preferable.

In the present invention, the novolac-type modified phenolic resin internally added with hexamethoxymethylmelamine,
In addition to carbon black, sulfur, vulcanizing agents, vulcanization accelerators, antioxidants, fillers other than carbon black, such as silica, process oils, etc., which are commonly used in the rubber industry, may be appropriately added. ..

The rubber composition of the present invention comprises a novolak type phenolic resin starting from phenol, cresol or resorcin, rosin oil, tall oil, cashew oil,
Phenol modified with at least one selected from the group consisting of animal and vegetable oils such as linseed oil, unsaturated oils such as linoleic acid, oleic acid and linoleic acid, or aromatic hydrocarbons such as xylene and mesitylene, or rubbers such as nitrile rubber. One of the features is that a system resin is blended.

The most characteristic feature of the present invention is that hexamethoxymethylmelamine is used as a curing agent without using an amine, and a novolac-type modified phenolic resin internally added thereto is used. Conventionally, amines such as hexamine have been used with novolac-type modified phenolic resins, but they are added together with novolac-type modified phenolic resins in rubber, or are those which are internally added in advance. As described above, the unreacted resin causes a decrease in fatigue and a slight amount of ammonia causes deterioration of the polyester fiber.

In the present invention, a novolac-type modified phenolic resin which is hardened without generating ammonia containing hexamethoxymethylmelamine internally is used. Hexamethoxymethylmelamine, which is a curing agent for resins used in the present invention, internally adds an amount necessary for curing the resin. Conventionally, hexamethoxymethyl melamine does not have the effect of lowering the strength of polyester fiber, but the curing efficiency is lower than that of hexamine, so deterioration of mechanical properties caused by the presence of unreacted resin has been a problem. .. In the present invention, by internally adding this hexamethoxymethylmelamine, the curing efficiency increases,
Deterioration of mechanical properties due to unreacted resin disappeared.

The rubber composition of the present invention can be suitably used for tires, particularly for bead fillers for tires. It is suitable as a rubber composition for a bead filler of a tire using polyester fiber as a reinforcing cord for a carcass layer.

[0025]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. (Synthesis Example 1) 200 g of novolak resin (melting point 80 ° C.), 150 g of water and 4 g of gum arabic were charged in a 1-liter glass flask, and the content was heated to 95 ° C. with stirring. Separately, a solution prepared by dissolving 20 g of hexamethoxymethylmelamine in 150 g of water was added thereto, and the reaction was carried out while maintaining the liquid temperature at 95 ° C. for 15 minutes while stirring. Then the contents were lowered to 30 ° C. and after adding 500 g of water,
Solid and liquid were separated by filtration with filter paper and washed with water to obtain resin particles. This resin is depressurized (5 mmHg or less) at 35 ° C.
And dried for 24 hours to obtain modified novolak resin particles. This resin is designated as A. Resin A is an internal addition type of hexamethoxymethylmelamine, but is a resin that has not been modified with animal and vegetable oils, aromatic hydrocarbons, or nitrile rubber.

(Synthesis example 2) 200 g of cashew oil-modified novolac resin (melting point 80 ° C.) was added to a 1-liter glass flask.
150 g of water and 4 g of gum arabic were charged, and the content was heated to 95 ° C. with stirring. Separately, a solution prepared by dissolving 20 g of hexamethoxymethylmelamine in 150 g of water was added thereto, and the reaction was carried out for 15 minutes while maintaining the liquid temperature at 95 ° C while stirring. Next, the content was lowered to 30 ° C., 500 g of water was added, the solid-liquid was separated by filtration with filter paper, and washed with water to obtain resin particles. The resin was dried under reduced pressure (5 mmHg or less) at 35 ° C. for 24 hours to obtain modified novolac resin particles. This resin is designated as B.

(Synthesis Example 3) A modified novolak resin was obtained in the same manner as in Synthesis Example 1 except that the tall oil modified novolac type phenolic resin (melting point: 80 ° C) was used as the resin.
This resin is designated as C.

Various rubber compositions (Examples 1 to 5 and Comparative Examples 1 to 4) having the compounding contents shown in Table 1 were prepared, and hardness, breaking strength, 50% modulus, dynamic elastic modulus E ', dynamic Loss factor (tan δ), influence on fatigue life and polyester fiber cord, lateral stiffness coefficient, special durability drum test, PET
The strong retention rate was evaluated. The results are shown in Table 1.

The evaluation method is as follows. (1) Hardness, breaking strength, 50% modulus Measured according to JIS K 6301. (2) Dynamic elastic modulus, dynamic loss coefficient (tan δ) Viscoelasticity spectrometer (VES-F manufactured by Iwamoto Seisakusho)
Type), the thickness of the sample piece was 2 mm, the width was 4.7 mm, the length was 20 mm, the dynamic strain was 1% in the statically stretched state of 5%, and the frequency was 50 Hz.

(3) Effect on polyester fiber cord Polyester fiber {polyethylene terephthalate (PE
T) Use fiber} Embed the cord in rubber, 160 ℃ ×
After vulcanization under the condition of 90 minutes, the cord was taken out, the cord strength was measured, and the elastic retention ratio was compared with the original cord strength. (4) Fatigue life Using a cyclic fatigue tester manufactured by Sam Electronic Machinery, an initial static load of 30 kg / cm ₂ and dynamic cyclic fatigue were applied to a sample of sample thickness 2 mm and shape JIS-3 type, The number of repetitions until the sample broke was determined.

Next, in order to examine the effect on the tire, FIG.
In a tire 1 of size 165SR13, which has a two-ply steel cord layer as the belt layer 2 and one ply of a layer made of polyethylene terephthalate (PET) fiber of 1500d / 2 as the carcass layer 3, as shown in FIG.
Examples 1, 2, 4 and Comparative Examples 2, shown in Table 1 as the rubber of the bead filler 6 of the test tire 1 in which the folded back 3'of the carcass ply is kept in the low position near the rim flange.
A lateral stiffness test and a special drum test were performed using the compounded rubbers of Nos. 4 and 5, and the results are also shown in Table 1 (continued).

(5) Lateral Stiffness Index A tire was mounted on a 4 1/2 J rim, filled with an internal pressure of 1.7 kg / cm ² , and mounted on a bogie having a serrated surface to prevent slippage.
The vertical load of 20 kg was fixed by pressure, the carriage was pulled in the lateral direction of the tire, and the lateral load generated when the tire lateral displacement was 15 mm was measured. The case where the rubber of Comparative Example 1 was used was 100 and the index was displayed.

(6) Special endurance drum test A tire was assembled on a 4 1/2 J rim, and the strain energy concentrated at the folded end of the carcass ply was about 4 times that of normal running of the actual vehicle. It was crimped on a metal drum with a diameter of 17 m under the conditions and run at a speed of 60 Km / hr, and it was shown as the travel distance until a failure occurred at the folded end of the carcass ply. ..

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

From Table 1, Comparative Example 3 in which a conventional novolac type cashew oil-modified hexamine internally added phenol resin was blended
Compared with the above, in Example 1 in which the resin B containing hexamethoxymethylmelamine (abbreviated as HMMM) was internally added, various physical properties of the rubber were improved. It is considered that this is because a phenol-melamine resin having a higher degree of curing is formed by using HMMM, as compared with the phenolic resin cured by hexamine.

Next, in comparison with Comparative Examples 2 and 4 in which the conventional novolac type phenol resin was compounded, Comparative Example 1 in which the resin A containing HMMM was compounded improved the physical properties of the rubber. This is considered to be due to the fact that the curing reaction efficiency of the resin was improved by internally adding HMMM.

Further, as compared with Comparative Example 5 in which the resin A was blended,
Example 3, in which the resins B and C modified with oil were blended
Even in No. 4, the physical properties of rubber are improved. This is considered to be the effect of the oil modification of the novolac type phenol resin.

As shown in Examples 1 to 4 and Comparative Examples 1 and 5, in the compounding system using HMMM as the curing agent, ammonia was not generated, and thus the amine deterioration of the polyester fiber was not recognized. The result was that the PET retention rate was very high. Even in tire test data, the lateral stiffness index is high, and if the bead filler of the present invention is used,
The steering stability can be further improved. Further, particularly in a tire using polyester fibers for the reinforcing cord of the carcass layer, the deterioration of the polyester fibers due to amine is improved, and the durability around the beads can be improved.

[0042]

The rubber compounded with the novolac-type oil-modified phenolic resin internally added with the hexamethoxymethylmelamine curing agent of the present invention has high hardness, strength at break, 25% modulus, and high dynamic elastic modulus E '. The dynamic heat loss tan δ can also be kept low.

Further, since it is a hexamethoxymethylmelamine curing system, it does not generate ammonia, and therefore it is possible to maintain a high elastic modulus without degrading PET. As a result, the durability of the beads is significantly improved, steering stability is improved, and even in high-temperature short-time vulcanization that enhances productivity, vulcanization can be performed without any adverse effect on PET. It is a technology that can solve two problems that could not be achieved by the conventional technology all at once.

[Brief description of drawings]

FIG. 1 is a partial lateral sectional view of a tire used for performance evaluation of a tire using the bead filler rubber composition of the present invention.

[Explanation of symbols]

 1 tire 2 belt layer 3 carcass layer 3'carcass ply folding back 4 bead part 5 sidewall part 6 bead filler 7 bead wire

Claims (3)

[Claims] 1. Carbon black 20 to 1 to 100 parts by weight of a rubber containing at least one diene rubber.
Hexamethoxymethylmelamine was previously internally added as a resin curing agent to 30 parts by weight of a novolac-type modified phenolic resin modified with at least one selected from animal and vegetable oils, unsaturated oils, aromatic hydrocarbons and nitrile rubber. A rubber composition comprising 1 to 30 parts by weight of a rubber reinforcing agent. 2. A pneumatic tire using the rubber composition according to claim 1 as a bead filler. 3. The pneumatic tire according to claim 2, wherein polyester fiber is used as a reinforcing cord of the carcass layer.