JP2002338743A - Tire tread rubber composition, and tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire tread rubber composition which has improved grip, low heat build-up and abrasion resistance. SOLUTION: The tire tread rubber composition comprises 100 pts.wt. diene based rubber composition and 1-40 pts.wt. reclaimed rubber having a difference in the acetone extraction amount before and after reclamation of <15 wt.% or a difference in the chloroform extraction amount before and after reclamation of <20 wt.%. Preferably, the above reclaimed rubber has a difference in the acetone extraction amount before and after reclaiming of <15 wt.% and, at the same time, a difference in the chloroform extraction amount before and after reclamation of <20 wt.%.

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 a tire tread containing a reclaimed rubber, and a tire using the same. The present invention relates to a tire tread with reduced heat generation and improved wear resistance while maintaining grip performance. The present invention relates to a rubber composition and a tire using the rubber composition.

[0002]

2. Description of the Related Art In recent years, recycling of waste has been strongly demanded from the viewpoint of environmental problems and resource saving. Tires are no exception, and waste tires are subjected to various treatments, such as finely pulverizing them with a crusher to remove fibers and steel and reusing them as rubber powder. Used.

[0003] Among them, the so-called material recycling of the recycling type, which is used again for tires, is very important. A method of recycling waste tires into recycled rubber or rubber powder and reusing the tires has been known for a long time. However, the rubber composition using the recycled rubber generates a large amount of heat, and the wear resistance and the like are greatly reduced. Therefore, the usage amount and the usage ratio of the recycled rubber are decreasing year by year.

[0004] Reclaimed rubber is generally a vulcanized or crosslinked elastic rubber, which is used for a predetermined purpose, and is physically used as a waste rubber product or a rubber waste discharged from a rubber factory. By applying a chemical treatment to impart plasticity and tackiness, it can be used again in the same applications as the raw rubber. It is necessary that the recycled rubber can be used alone, or a rubber product can be produced by the same processing and vulcanization as in the case of the raw rubber. That is,
It is important that the reclaimed rubber be vulcanizable and have good processability.

Attempts have been made to improve rubber properties by using reinforcing fillers in recycled rubber compositions. In particular, carbon black which imparts high reinforcing properties and excellent wear resistance is frequently used as a reinforcing filler. In order to further improve the wear resistance of the pneumatic tire, it is conceivable to increase the filling amount of carbon black or to use carbon black having a smaller particle diameter.
However, in any case, the hysteresis loss due to the carbon black increases, and the heat generation increases.

On the other hand, hydrous silicic acid is known as a filler that simultaneously satisfies grip performance and abrasion resistance with low heat generation. However, hydrous silicic acid has a lower storage modulus of the rubber composition as compared with carbon black having the same nitrogen adsorption specific surface area, and therefore has poor grip performance. As a method of increasing the storage elastic modulus, an increase in the amount of hydrous silicic acid or an increase in the specific surface area can be considered.

For example, Japanese Unexamined Patent Publication No. 6-192480 discloses a tread rubber composition for a retread tire, which comprises 50 to 70 parts by weight of butadiene rubber, 20 to 50 parts by weight of natural rubber, and 10 to 30 parts by weight of styrene butadiene rubber. 140 to 170 m with respect to 100 parts by weight of the rubber component consisting of
² / g nitrogen adsorption specific surface area and 100-135 ml / 1
A rubber composition comprising 45 to 60 parts by weight of carbon black having a dibutyl phthalate oil absorption of 00 g and 2 to 5 parts by weight of an alkylphenol-based resin. The rubber composition has an acetone extraction of 7.5 parts by weight or less. Are disclosed.

Japanese Patent Application Laid-Open No. 8-151482 discloses that polybutadiene having a cis-1,4 bond is α, β
-A tread rubber composition is disclosed in which rubber powder having an average particle diameter of 20 to 600 µm crosslinked with an unsaturated carboxylic acid and a metal ion is blended with a rubber component such as natural rubber, polybutadiene, and polyisoprene.

However, at present, none of the various conventional techniques can provide a rubber composition having a high balance of grip performance, low heat generation and abrasion resistance.

[0010]

SUMMARY OF THE INVENTION The present invention provides a rubber composition for a tire tread which uses recycled rubber in such a situation and which can reduce heat generation and improve abrasion resistance while maintaining grip performance. It is an object of the present invention to provide a product and a tire using the composition for a tread rubber.

[0011]

According to the present invention, the difference in the amount of acetone extracted before and after regeneration is less than 15% by weight or the difference in the amount of chloroform extracted before and after regeneration is 20% by weight based on 100 parts by weight of the diene rubber component. A rubber composition for a tire tread, wherein 1 to 40 parts by weight of a recycled rubber is mixed.

In another invention, the difference in the amount of acetone extracted before and after regeneration is less than 15% by weight and the difference in the amount of chloroform extracted before and after regeneration is less than 20% by weight based on 100 parts by weight of the diene rubber component. A certain recycled rubber
A rubber composition for a tire tread, wherein the rubber composition is blended in an amount of 40 parts by weight.

Further, the present invention is a tire using the rubber composition for a tread rubber.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition of the present invention, by blending a specific reclaimed rubber, reduces heat generation while maintaining grip performance and improves wear resistance. If the heat generation is reduced, the energy loss is reduced and the rolling resistance is reduced, so that the fuel efficiency can be reduced.

In the present invention, the term "reclaimed rubber" refers to vulcanized or crosslinked elastic rubber, rubber products, defective products in factories, rubber wastes in factories, and used rubber wastes, physically and / or chemically. This is to impart plasticity and tackiness by subjecting it to a mechanical treatment so that it can be used again for the same applications as the raw rubber.

[0016] Recycled rubber can be produced by using the most common bread method (oil method), a method using a Banbury mixer / two-screw reaction extruder, a method using microwaves, a method using ultrasonic waves, a method using electron beam irradiation, and the like. Has been developed, but may be reproduced by any method.

The general production of recycled rubber is roughly divided into the following four steps. (1) Garbage sorting process Collect large tires, medium tires, natural rubber tubes, butyl rubber tubes, etc. separately. (2) Pulverization step A step of pulverizing the waste rubber into granules and powders, which comprises coarse grinding and fine grinding. Then, fibers and metals contained in the scrap rubber are removed as much as possible. The standard of the particle size to be pulverized differs depending on the material of the waste rubber and the regeneration desulfurization method. (3) Regeneration desulfurization step The rubber powder, which has been pulverized to a predetermined particle size and from which fibers and metals have been removed, is subjected to a heat treatment to break down sulfur crosslinking and plasticize the rubber.
For example, in the pan method (oil method), a method is used in which a regenerant is mixed with rubber powder pulverized to a predetermined particle size, packed in a container, placed in a regenerative desulfurization tube, and steam is directly blown to regenerate desulfurization at high temperature and pressure. It is. Here, as the regenerating agent, usually two to three kinds of pine tar, tall oil, dipentene, petroleum plasticizer, tackifier and the like are used in combination. The regenerant is the type of scrap,
The amount is usually 5 to 15 parts by weight depending on the conditions of the regeneration desulfurization. The regeneration desulfurization conditions also have a relationship with the boiler pressure. For example, a steam pressure of 15 kg / cm ² is used for 4 to 5 hours. (4) Finishing Step The desulfurized rubber powder is subjected to mechanical treatment, that is, refining and passing through a strainer to completely grind and plasticize the particles, and also remove foreign matters to finish the reclaimed rubber.

In the reclaimed rubber used in the present invention, the difference in the amount of acetone extracted before and after the regeneration is less than 15% by weight, preferably 1%.
It is preferably less than 0% by weight, particularly preferably less than 5% by weight, and the difference in the amount of chloroform extracted before and after regeneration is less than 20% by weight, preferably less than 15% by weight.
When the difference in the amount of acetone extracted exceeds 15% by weight, or when the difference in the amount of chloroform extracted exceeds 20% by weight of the reclaimed rubber, the heat generation increases and the abrasion resistance decreases.

Here, the amounts of acetone and chloroform extracted from the rubber before regeneration and the recycled rubber can be determined by the following methods.

1 mg of the rubber before regeneration and about 2 g of the recycled rubber
Measure correctly to the nearest unit, wrap it in filter paper, or place it in a cylindrical filter paper, place it in the siphon cup of a Knefrell-type or cottle-type extraction device, and place the extract (acetone or chloroform) in a pre-weighed extraction flask. Add 50 ml, assemble the whole apparatus and perform extraction while heating. Heating is adjusted so that the extract in the siphon cup drops and renews about every 3 minutes, and the extraction time is 48 hours continuous.

After the extraction, the extract was heated on a water bath, and after the extract was distilled off, immediately dried in an air bath at 70 ± 5 ° C. for about 2 hours, allowed to cool, weighed, and weighed. The amount of acetone extracted (X) or the amount of chloroform extracted (Y).

Here, assuming that the weight of the extracted rubber with respect to 2 g of the rubber before regeneration is x1 (g), the amount of acetone extracted (X1) is (x1 / 2) × 100 (% by weight).
Becomes On the other hand, if the acetone-extracted weight is x2 (g) with respect to 2 g of the recycled rubber, the acetone extraction amount (X2) is (x2 / 2) × 100 (% by weight). Therefore, in the present invention, (X2-X1) is less than 15% by weight. The amount of chloroform extracted can be determined in the same manner.

The difference in the amount of acetone extracted before and after regeneration is less than 15% by weight, or the difference in the amount of chloroform extracted before and after regeneration is 2%.
Recycled rubber having less than 0% by weight may be, for example, scrap rubber obtained from passenger car tires, truck tires, tubes, solid tires, bicycle tires, footwear, hoses, etc., preferably by the pan method. Manufactured under selected conditions.

The components contained in the extracts obtained by acetone extraction and chloroform extraction are mainly free sulfur, softeners, swelling agents, low molecular weight components generated during regeneration, etc. Increases heat generation and lowers abrasion resistance.

The amount of the recycled rubber is 1 to 40 parts by weight, preferably 1 to 30 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the diene rubber described below. When the amount exceeds 40 parts by weight, heat generation increases and abrasion resistance decreases.

As the diene rubber, natural rubber and / or diene synthetic rubber is used. Here, examples of the diene-based synthetic rubber include styrene-butadiene rubber (SBR), isoprene synthetic rubber (IR), acrylonitrile-butadiene rubber (NBR), isobutylene-isoprene rubber (IIR), and chloroprene rubber (CR). . These rubbers may be used alone,
Alternatively, two or more kinds may be used in combination.

Further, the rubber composition of the present invention preferably contains a reinforcing filler. As a filler for reinforcement,
Although it can be arbitrarily selected from those conventionally used in rubber compositions for tires, carbon black and silica particles are mainly preferred.

The nitrogen adsorption specific surface area of the carbon black is preferably 80~280m ² / g, it is particularly preferably 100 to 200 m ² / g. When the nitrogen adsorption specific surface area is less than 80 m ² / g, abrasion resistance tends to decrease, and when it exceeds 280 m ² / g, heat generation tends to increase.

The amount of the carbon black is 10 to 150 parts by weight based on 100 parts by weight of the diene rubber component.
In particular, it is preferably 15 to 100 parts by weight. If the amount of carbon black is less than 10 parts by weight, abrasion resistance tends to deteriorate, and if it exceeds 150 parts by weight, heat generation tends to increase.

The silica has a nitrogen adsorption specific surface area of 100 to 100.
It is preferably 280 m ² / g. When the nitrogen adsorption specific surface area of silica is less than 100 m ² / g, abrasion resistance tends to decrease, and when it exceeds 280 m ² / g, heat generation tends to increase. The amount of the silica is 5 to 100 parts by weight, particularly 1 to 100 parts by weight of the diene rubber component.
It is preferably from 0 to 80 parts by weight. If the amount of silica is less than 5 parts by weight, the abrasion resistance tends to decrease,
If it exceeds 00 parts by weight, heat generation tends to increase. The reinforcing fillers may be used alone or in combination of two or more.

The rubber composition of the present invention may further contain, in addition to the above-mentioned components, various chemicals usually used in the rubber industry, for example, a vulcanizing agent such as sulfur, various vulcanization accelerators, various softening agents, various antiaging agents. Agents, zinc oxide, stearic acid, antioxidants,
An additive such as an ozone deterioration inhibitor can be blended.

The tire of the present invention is produced by a usual method using the rubber composition of the present invention. That is, if necessary, the rubber composition to which the various compounding agents have been added is extruded in combination with the shape of each member of the tire at an unvulcanized stage, and molded by a normal method on a tire molding machine. To manufacture unvulcanized tires. The unvulcanized tire is heated and pressed in a vulcanizer to produce a tire.

[0033]

EXAMPLES Example 1 and Comparative Examples 1 and 2 Various rubber compositions were obtained by kneading and compounding according to the compounding recipe shown in Table 1. These rubber compositions were press-vulcanized at 170 ° C. for 20 minutes to obtain vulcanized products, which were tested for the following properties.

[0034]

[Table 1]

[0035]

[Table 2]

Hereinafter, various compounding agents used in Examples and Comparative Examples will be described. (Note 1) Styrene-butadiene rubber: SBR1502 manufactured by Japan Synthetic Rubber Co., Ltd. was used.

(Note 2) Carbon black: Show black N220 (nitrogen adsorption specific surface area: 125 m ² / g) manufactured by Showa Cabot Corporation was used.

(Note 3) Recycled rubber A: A vulcanized rubber with 4.5% by weight of acetone extracted and 2.2% by weight of chloroform extracted was subjected to shearing for 5 minutes by a Labo Plastomill controlled at 60 ° C. at 180 ° C. (Extraction amount of acetone: 9.3% by weight, extraction amount of chloroform: 6.2% by weight).

(Note 4) Recycled rubber B: A vulcanized rubber with 4.5% by weight of acetone extracted and 2.2% by weight of chloroform extracted was subjected to shearing for 30 minutes by a Labo Plastomill whose temperature was controlled at 180 ° C. at 60 cc. (Extraction amount of acetone: 19.9% by weight, extraction amount of chloroform: 25.7% by weight).

(Note 5) Recycled rubber C: A vulcanized rubber having an extraction amount of acetone of 4.7% by weight and an extraction amount of chloroform of 2.1% by weight was subjected to shearing for 60 minutes by a Labo Plastomill controlled at 180 ° C. at 60 cc. (Extracting acetone: 18.2% by weight, extracting chloroform: 22.4% by weight).

(Note 6) Recycled rubber D: A vulcanized rubber having an extraction amount of acetone of 4.2% by weight and an extraction amount of chloroform of 2.0% by weight was subjected to shearing for 35 minutes by a Labo Plastomill controlled at 180 ° C. at 60 cc. (Extraction amount of acetone: 19.6% by weight, extraction amount of chloroform: 21.8% by weight).

(Note 7) Stearic acid: Nippon Oil & Fats Co., Ltd.
Was used. (Note 8) Zinc oxide: Zinc flower 1 manufactured by Mitsui Kinzoku Mining Co., Ltd.
No. was used.

(Note 9) Antioxidant: Nocrack 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. was used. The compound name is N-
(1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine.

(Note 10) Aroma oil: JOMO Process X140 manufactured by Japan Energy Co., Ltd. was used.

(Note 11) Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. was used. (Note 12) Vulcanization accelerator: Noxeller CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. was used.

Hereinafter, a method for evaluating a vulcanized rubber will be described. (1) Grip performance A steel radial tire of size 195 / 65R15 using the rubber compositions of Tables 1 and 2 for tread rubber was produced. Using these tires, an actual vehicle was run on a test course on dry asphalt road surface. The test driver evaluated the control stability at the time of steering in actual vehicle running, and displayed an index with Comparative Example 1 as 100. The larger the value, the higher the grip performance on dry road surfaces.

(2) Exothermicity Using a spectrometer manufactured by Ueshima Seisakusho, tan δ was measured at a dynamic strain amplitude of 2%, a frequency of 10 Hz and a temperature of 70 ° C. The reciprocal of the value of tan δ was expressed as an index with Comparative Example 1 being 100. The larger the numerical value, the lower the exothermic property, indicating better.

(3) Abrasion resistance A Lambourn type abrasion tester was used at room temperature and a load of 1.
The wear amount was measured under the conditions of 0 kgf and a slip ratio of 30%. The reciprocal of the amount of abrasion was represented by an index with Comparative Example 1 being 100. The larger the value, the higher the wear resistance.

Table 2 shows the evaluation results of actual vehicle running. From Table 2, it can be seen that the tire having the tread rubber composition using the recycled rubber of the present invention has excellent grip properties, heat generation properties and abrasion resistance.

In Example 1, the difference in acetone extraction before and after regeneration was less than 15% by weight, and the difference in chloroform extraction was 2%.
This is an example in which recycled rubber A is added in an amount of less than 0% by weight, and particularly shows excellent heat generation and low heat generation during tire running. However, when the reclaimed rubber A is compounded in a large amount of 50 parts by weight, the heat generation is reduced as shown in Comparative Example 2.

Example 2 is an example in which the difference in the amount of acetone extracted before and after regeneration is less than 15% by weight and the difference in the amount of chloroform extracted is not less than 20% by weight, and Example 3 is the amount of chloroform extracted before and after regeneration. Is less than 20% by weight and the difference in acetone extraction is not less than 15% by weight. In these cases, grip performance, heat generation and abrasion resistance can be totally satisfied.

The embodiments and examples disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0053]

According to the present invention, a tire having low heat generation and improved abrasion resistance while maintaining grip performance is obtained by blending a predetermined range of the difference in the amount of acetone extracted or the difference in the amount of chloroform extracted before and after regeneration. Can be provided.

Claims (3)

[Claims] 1. The difference in the amount of acetone extracted before and after regeneration with respect to 100 parts by weight of a diene rubber component is 15% by weight.
A rubber composition for a tire tread, comprising 1 to 40 parts by weight of a recycled rubber having a difference of less than 20% by weight or less than 20% by weight of chloroform before and after regeneration. 2. The difference in the amount of acetone extracted before and after regeneration with respect to 100 parts by weight of a diene rubber component is 15% by weight.
A rubber composition for a tire tread, comprising 1 to 40 parts by weight of a reclaimed rubber having a difference in chloroform extraction amount before and after regeneration of less than 20% by weight. 3. A tire using the rubber composition according to claim 1 for a tread rubber.