KR101006195B1 - Rubber composition of tire sidewall - Google Patents

Abstract

The present invention relates to a rubber composition for a tire sidewall, wherein the rubber composition for a tire sidewall comprises 40 to 60 parts by weight of natural rubber; And 50 to 60 parts by weight of carbon black, based on 100 parts by weight of the raw rubber consisting of 40 to 60 parts by weight of high-cis butadiene rubber; 1.4 to 1.8 parts by weight of insoluble sulfur; 0.7 to 0.9 parts by weight of a sulfenamide-based accelerator; 2 to 5 parts by weight of antioxidant; 2 to 5 parts by weight of an ozone inhibitor; And 2 to 5 parts by weight of the adhesive, wherein the high-cis butadiene has a cis-1,4 content of 96% by weight or more, a glass transition temperature (Tg) of -104 to -107 ° C, and the carbon black has a nitrogen adsorption ratio. The surface area is 70 to 90m ² / g and DBP oil absorption is characterized in that 90 to 110cc / 100g.

The rubber composition for a tire sidewall of the present invention has an advantage of improving fatigue resistance, ozone crack resistance and mechanical rigidity, and ease of processing for producing a gum sheet.

Tire sidewall, rubber composition, natural rubber, antioxidant, ozone inhibitor, adhesive

Description

Rubber composition for tire sidewall {RUBBER COMPOSITION OF TIRE SIDEWALL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for tire sidewalls, and to regenerating a new tread on a case of a tire worn with treads during the production of regenerated tires, in order to increase the recycling rate of the appearance of the sidewall or the case. A regenerated sidewall rubber composition is applied in the form of a thin gum sheet.

Sidewall rubber for truck buses may be cracked due to oxygen, ozone, etc., and the chemicals added for resistance thereto may be discolored over time. In addition, the sidewall rubber for truck buses can commonly cause cracking due to fatigue while running and tearing due to trauma.

Accordingly, the sidewalls of tires (hereinafter referred to as tires) having completed tread wear are often difficult to reproduce due to appearance or functional problems. The regenerated tire is a new tread rubber attached to the high tire through the vulcanization process, and there are two regeneration methods, hot cure and cold cure. Thermal vulcanization is a method of attaching a new, unvulcanized tread rubber to a high tire and manufacturing it in a patterned mold mold at a high vulcanization condition of about 130 ° C. or higher. This vulcanized and finished new tread rubber is attached and manufactured using a cushion gum under low temperature vulcanization conditions of 120 ° C. or lower.

Thermal vulcanization uses a steam or electric vulcanization mold to impart a high temperature to vulcanize the unvulcanized tread rubber, which can be vulcanized to the sidewall. Therefore, in the thermal vulcanization method, by attaching and regenerating a reclaimed sidewall rubber to high tires that are difficult to regenerate in appearance, it is possible to secure not only a problem in appearance but also required performance inherent in the sidewall.

In addition to the fatigue and ozone crack resistance and mechanical stiffness, which are inherent characteristics of the sidewall for securing the performance of the regenerated sidewall rubber, the vulcanization tack performance in the regeneration process and the covalent property with the sidewall surface vulcanized during vulcanization and For the preparation of gum sheet through calender work, the condition of proper amount of insoluble sulfur and accelerator suitable for regenerative vulcanization condition is required.

Accordingly, it is an object of the present invention to provide a rubber composition for tire sidewalls that improves fatigue resistance, ozone crack resistance and mechanical stiffness, and ease of processing for producing a gum sheet.

However, technical problems to be achieved by the present invention are not limited to the above-mentioned problems, and other technical problems will be clearly understood by the average technician from the following description.

In order to achieve the above object, the present invention is a natural rubber 40 to 60 parts by weight; And 50 to 60 parts by weight of carbon black, based on 100 parts by weight of the raw rubber consisting of 40 to 60 parts by weight of high-cis butadiene rubber; 1.4 to 1.8 parts by weight of insoluble sulfur; 0.7 to 0.9 parts by weight of a sulfenamide-based accelerator; 2 to 5 parts by weight of antioxidant; 2 to 5 parts by weight of an ozone inhibitor; And 2 to 5 parts by weight of the adhesive, wherein the high-cis butadiene has a cis-1,4 content of 96% by weight or more, a glass transition temperature (Tg) of -104 to -107 ° C, and the carbon black has a nitrogen adsorption ratio. It provides a rubber composition for a tire sidewall, characterized in that the surface area is 70 to 90m ² / g and DBP oil absorption amount is 90 to 110cc / 100g.

The rubber composition for a tire sidewall according to the present invention has an advantage of improving the ozone crack resistance and mechanical stiffness, which is inherent in the sidewall, and improves the ease of processing for producing a gum sheet.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for tire sidewalls used for hot cure for trucks / buses. The present invention relates to natural rubber and high-cis butadiene for securing fatigue and crack resistance and mechanical rigidity, which are inherent to the sidewalls. A certain amount of carbon black having specific colloidal properties and an appropriate ratio of anti-aging agent are added to the raw material rubber made of a mixture of rubber, and processing aids and oils to secure the ease of processing gum sheet are processed. It is a rubber composition comprising an appropriate amount of insoluble sulfur and an accelerator required for adhesion performance through co-vulcanization with a pre-vulcanized rubber suitable for a tack and a regenerative vulcanization condition for securing performance.

Hereinafter, the present invention will be described in more detail.

The present invention is a raw rubber and carbon black made of natural rubber and high-cis butadiene rubber; Insoluble sulfur; Sulfenamide-based accelerators; Antioxidants; Ozone inhibitors; And it provides a rubber composition for a tire sidewall comprising a pressure-sensitive adhesive.

The raw rubber is composed of natural rubber and high-cis butadiene rubber, and the natural rubber is preferably polyisoprene obtained in nature, and in the case of the high-cis butadiene rubber, the cis-1,4 content is preferably 96% by weight. % Or more and a glass transition temperature (Tg) of -104 to -107 ° C may be used.

The raw material rubber is composed of 40 to 60 parts by weight of natural rubber and 40 to 60 parts by weight of high-cis butadiene rubber in order to improve appearance, prevent tearing, and maintain fatigue resistance. If the natural rubber exceeds 60 parts by weight, there is a problem that the fatigue resistance is degraded, the appearance is poor. In addition, if the butadiene exceeds 60 parts by weight, there is a problem that the tear resistance and crack resistance is reduced.

Carbon black added as the reinforcing agent is included in 40 to 80 parts by weight based on 100 parts by weight of the raw rubber. If the carbon black content is less than 40 parts by weight, the rigidity of the tread base is reduced, and tire durability is lowered. If the carbon black content is more than 80 parts by weight, workability is deteriorated due to poor dispersion of carbon black, and heat generation and rotation resistance are increased. Adverse effect occurs.

The carbon black may have a nitrogen adsorption specific surface area of 70 to 90 m ² / g and a DBP oil absorption of 90 to 110 cc / 100 g. If the nitrogen adsorption specific surface area is less than 70 m ² / g, there is a problem that the tensile properties and tearing resistance is lowered, and if the nitrogen adsorption specific surface area exceeds 90 m ² / g, workability is not easy. In addition, when the DBP oil absorption amount is within the above range, tensile properties and tear resistance are improved, and workability is excellent.

Carbon black having such colloidal properties is contained in 50 to 60 parts by weight based on 100 parts by weight of the raw material rubber content. If the carbon black content is less than 50 parts by weight, mechanical properties such as tensile properties are lowered. If the carbon black content is more than 60 parts by weight, workability is deteriorated and fatigue resistance and crack resistance are deteriorated.

The insoluble sulfur is used as a vulcanizing agent, it is included in 1.4 to 1.8 parts by weight based on 100 parts by weight of the raw material rubber content. The use of general sulfur other than the insoluble sulfur generates sulfur bloom, which degrades tack performance.

The sulfenamide-based accelerator is 0.7 to 0.9 weight based on N-cyclohexyl-2-benzothiazyl sulfonamide (CBS) having the best co-curing properties based on 100 parts by weight of the raw material rubber content. It is good to use as wealth. When the sulfenamide-based accelerator is used in the above range, there is an advantage that the adhesion performance is improved.

In the present invention, the insoluble sulfur and the sulfenamide-based accelerator may be used within the range of the above-mentioned content. In particular, the weight ratio of the insoluble sulfur to the sulfenamide-based accelerator is preferably maintained at 1.5: 1. When the insoluble sulfur is out of the range, the sinterability is lowered, when the sulfenamide accelerator is out of the range, the fatigue performance is lowered, and when the insoluble sulfur and the sulfenamide promoter is out of the range, Tack reduction and modulus difference with the surface of the sidewalls are generated, thereby degrading the co-current property.

The antioxidant may be 2,2,4-trimethyl-1,2-dihydroquinoline (2,2,4-trimethyl-1,2-dihydroquinoline: TMQ), based on 100 parts by weight of the raw material rubber content 2 to 5 parts by weight.

The ozone inhibitor may include N- (1.3-dimethylbutyl) -N'-phenylparaphenylenediamine (N- (1.3-dimethybutyl) -N'-phenyl-para-phenylenediamine: (6PPD)), and the amount of raw rubber 2 to 5 parts by weight based on 100 parts by weight.

The pressure-sensitive adhesive may include P-octyl phenol / formaldehyde (P-octyl phenol / formaldehyde), and includes 2 to 5 parts by weight based on 100 parts by weight of the raw material rubber content.

In the present invention, the antioxidant, the ozone inhibitor and the pressure-sensitive adhesive may be used within the range of the above content, in particular, it is most preferable that the weight ratio of the antioxidant to the ozone-to-adhesive is maintained at a ratio of 1: 1.5: 1. .

The weight ratio range of the antioxidant to the ozone to the pressure-sensitive adhesive is a range in which solubility and tack performance are optimized, and the addition of the antioxidant and the ozone-protective agent is necessary for the weather resistance of the sidewall and the solubility between the drugs together with the pressure-sensitive adhesive. If the ratio of the ozone inhibitor is out of the range of the weight ratio, a crack caused by ozone is generated rapidly. If the ratio of the antioxidant is out of the range of the weight ratio, the bloom of the antioxidant ( When the bloom occurs, the tack decreases or the discoloration of the surface of the sidewall after the tire is produced quickly, and the tack performance is deteriorated when the ratio of the pressure-sensitive adhesive is out of the range of the weight ratio. When the weight ratio of the antioxidant, the ozone inhibitor and the pressure-sensitive adhesive is within the above range, the optimum performance required for the rubber composition for regenerated sidewalls can be obtained.

That is, in the present invention, the insoluble sulfur and the sulfenamide-based accelerator are used in the above-described weight ratio, and at the same time, the weight ratio of the antioxidant to the ozone-to-adhesive is used in the above-described range to obtain the effect according to the present invention. Can be.

Meanwhile, the rubber composition for a tire sidewall according to the present invention may further include a process oil as a processing aid to improve processability and ease in manufacturing a gum sheet. The process oil is included in 4 to 7 parts by weight based on 100 parts by weight of the raw material rubber content. When the process oil is less than 4 parts by weight, it is difficult to produce a gum sheet, does not exhibit sufficient flow in the mold during vulcanization, has a disadvantage in fatigue resistance, and has a problem in that the appearance of the sidewall of the finished product is poor. And there is a problem that the adhesion is poor, crack resistance and mechanical properties are degraded, peeling phenomenon with the surface of the high tire.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention and the present invention is not limited to the following examples.

Example 1 and Comparative Examples 1 to 3

A rubber composition was prepared by blending the composition of the rubber composition in the component ratios shown in Table 1 below, followed by vulcanization, to prepare rubber specimens.

Particularly, in Comparative Example 1, the weight ratio of insoluble sulfur to sulfenamide-based accelerators compared to Example 1 (1.5: 1) was 2: 1, and in Comparative Example 2, antioxidant vs. Example 1 (2: 3: 2) was used. The weight ratio of the ozone inhibitor to the pressure-sensitive adhesive was 2: 4: 4, and an excess amount of the ozone-preventive agent and the pressure-sensitive adhesive was used, and in Comparative Example 3, an equivalent amount of powdered sulfur was used instead of insoluble sulfur.

Compounding agent Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Natural rubber 50 50 50 50 Hi-cis Butadiene 50 50 50 50 Carbon Black① 60 60 60 60 Zinc oxide 2 2 2 2 Stearic acid 1.5 1.5 1.5 1.5 Antioxidant ②: Ozone inhibitor ③: Adhesive ④ 2: 3: 2 2: 3: 2 2: 4: 4 2: 3: 2 Wax 2 2 2 2 Process oil 5 5 5 5 Insoluble sulfur: sulfenamide type accelerator ⑤ 1.5: 1.0 2.0: 1.0 1.5: 1.0 0 Powder sulfur: Sulfenamide type accelerator ⑤ 0 0 0 1.5: 1.0

* (Unit: parts by weight)

week)

①: Nitrogen adsorption specific surface area is 70 to 90m ² / g and DBP oil absorption is 90 to 110cc / 100g

②: TMDQ (2,2,4-trimethyl-1,2-dihydroquinoline)

③: 6PPD (N- (1.3-dimethybutyl) -N'-phenyl-para-phenylenediamine)

④: P-Octyl Phenol / formaldehyde Resin

⑤: CBS (N-cyclohexyl-2-benzothiazyl sulfonamide)

The prepared specimens were subjected to vulcanization time, physical properties, and adhesion tests, and subjected to appearance and aging tests by vulcanization using a chamber for thermal vulcanization. The results are shown in Table 2 below.

Compounding agent Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Max. Torque 18.8 23.7 19.1 20.3 Mooney viscosity 45 45 42 44 Tack (Initial, Kg) ⓐ 2.5 2.2 1.8 2.3 Tack (1 week, Kg) 2.3 1.9 1.4 1.3 Adhesive force (Kg) 57 34 41 43 Tensile Strength (kg / cm ² ) 201 215 169 198 Fatigue Resistance (Index) ⓑ 100 81 101 97 Crack Resistance (Index) 100 76 95 98 Heat aging resistance (Index) 100 80 91 97 Ozone crack resistance B-2 C-3 B-2 B-3

week)

※ The vulcanization property is the result of physical properties vulcanized at 150 ℃.

※ ⓐ: Tested after adhesion between unvulcanized gum sheet and vulcanized rubber, initial and 1 week at room temperature.

Ⓑ: Index resin is a more favorable result based on the number of Examples 100.

Ⓒ: Ozone 0.5ppm, 40 ℃, ± 20% Strain, and measurement result after 72 hours exposure at 40Hz.

※ Ozone Resistance Criteria (KS M 6518)

① number of cracks

A: Low number of cracks B: High number of cracks C: Very high number of cracks

① size and depth of crack

1: Invisible, but confirmed by 10 times magnifier

2: visually confirmed

3: deep crack and relatively large (less than 1 mm)

4: deep and large cracks (1 mm or more and less than 3 mm)

5: crack or group of 3mm or more

* No crack is indicated as 0

As shown in Table 2, it can be seen that Example 1 exhibits excellent reclaimed sidewall properties required compared to Comparative Examples 1, 2 and 3.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (2)

40 to 60 parts by weight of natural rubber; And 100 parts by weight of the raw rubber consisting of 40 to 60 parts by weight of high-cis butadiene rubber, Nitrogen adsorption specific surface area of 70 to 90m ² / g and contains 50 to 60 parts by weight of carbon black having a DBP oil absorption of 90 to 110cc / 100g, Insoluble sulfur, sulfenamide-based accelerators, antioxidants, ozone inhibitors, and pressure-sensitive adhesives, The rubber composition for tire sidewalls, wherein the weight ratio of the insoluble sulfur to the sulfenamide-based accelerator is 1.5: 1, and the weight ratio of the antioxidant to the ozone-to-adhesive is 1: 1.5: 1. According to claim 1, wherein the sulfenamide-based accelerator is N-cyclohexyl-2-benzothiazyl sulfonamide (CBS), the antioxidant is 2,2,4-trimethyl- 1,2-dihydroquinoline (2,2,4-trimethyl-1,2-dihydroquinoline: TMQ) and the ozone inhibitor is N- (1.3-dimethylbutyl) -N'-phenylparaphenylenediamine (N- (1.3-dimethybutyl) -N'-phenyl-para-phenylenediamine: (6PPD)), wherein the pressure-sensitive adhesive is P-octylphenol / formaldehyde (P-octyl phenol / formaldehyde).