KR20070000735A - Sidewall insert and bead rubber composition for runflat tire - Google Patents

Abstract

Provided is a sidewall insert and bead rubber composition for a runflat tire which is improved in rolling resistance, fatigue resistance, crack resistance, heat build-up and is lowered in specific gravity. The sidewall insert and bead rubber composition comprises a rubber material which comprises 20-80 wt% of a natural rubber, and 20-80 wt% of a polybutadiene rubber containing 3-35 wt% of syndiotactic 1,2-polybutadiene. Preferably the rubber material comprises further 50 wt% or less of a butadiene rubber. Preferably the composition comprises further 20-70 parts by weight of a filler; 0.5-6 parts by weight of sulfur; 0.5-4 parts by weight of a sulfenamide-based curing accelerator; and 0.5-5 parts by weight of a deterioration preventer based on 100 parts by weight of the rubber material.

Description

        Sidewall insert and bead rubber composition for runflat tire}

        The present invention relates to a run-wall tire sidewall insert and bead rubber composition, and more particularly, to include a polybutadiene containing syndiotactic 1,2-polybutadiene in a predetermined amount to improve the durability and rolling resistance of the tire. It relates to a sidewall insert and bead rubber composition for run flat tires.

        In order to improve the rigidity of the sidewall portion of the conventional run flat tire to obtain the strength required to secure the run flat performance, the reinforcing filler was used in an increased amount or a vulcanizing agent was used in an increased amount. In this case, the specific gravity of the reinforcing filler acts as a main cause of increasing the specific gravity of the rubber product to about 1.8 to 2.0, and there are many problems in reducing the weight of the tire because the weight cannot be lowered.

        In addition, fatigue resistance, crack resistance, and heat resistance were disadvantageous, which resulted in the destruction of rubber without maintaining the required run flat performance. In particular, self-supported run-flat tires could not prevent weight gain due to insert reinforcement.

      Today's tire demand performance is to manufacture and supply tires according to the preferences of various consumers. The most important form of stability is to support the load of the vehicle when the internal pressure of the tire is lost and to be able to safely drive a certain speed and distance.

        The specific gravity of the reinforcing filler is 1.8 to 2.0, which is the most influential factor in the weight of the rubber composition when it is filled according to the conditions used. Therefore, reducing the content of the reinforcing filler has an advantage of obtaining a weight reduction of the rubber composition. However, this cannot be reduced because of the required level of physical properties, and if only the level of physical properties is satisfied, the amount of reinforcing filler can be reduced to make a light rubber composition. That is, there is a need for an individual that can serve as a reinforcing filler, and if such an individual is present, it is possible to manufacture a light rubber composition while maintaining strength.

        In addition, if the stiffness is increased by increasing the amount of vulcanizing agent, it is difficult to secure uniform properties due to insufficient dispersion during on-site processing. Cracking is very disadvantageous, there was a problem in using more than a certain amount.

        Accordingly, the present invention is to improve the run flat performance of the sidewall insert and bead rubber for run flat tires, and to solve the above problems in search of alternative materials that can serve as a reinforcing filler. For sidewall inserts and bead rubber compositions, the application of polybutadiene, including natural rubber and syndiotactic 1,2-polybutadiene, as raw material rubber, avoids the use of excessive vulcanizing agents, It was confirmed that the rubber composition satisfying the physical properties according to the flat performance can be prepared, so that fatigue resistance, crack resistance, and heat resistance can be improved and hardness and tensile strength properties of the same level can be maintained.

        Accordingly, an object of the present invention is to improve the fatigue resistance, crack resistance, heat resistance and low weight of run-flat tires to improve run-flat performance and rolling resistance of the run-wall tire sidewall inserts and bead rubbers. It is to provide a bead rubber composition.

        In order to achieve the object of the present invention, the run-wall tire sidewall insert and bead rubber composition for run-flat tire sidewall insert and bead rubber composition, the raw material rubber is 20 to 80% by weight of natural rubber and syndiotactic 1 It is characterized by comprising 20 to 80% by weight of polybutadiene including, 2-polybutadiene.

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

        The present invention is 20 to 80% by weight of polybutadiene, which is well dispersed in 20 to 80% by weight of natural rubber and syndiotactic 1,2-polybutadiene as a raw material rubber in the common run flat tire sidewall insert and bead rubber composition. It includes, in addition to using butadiene rubber contained within 50% by weight.

        The run-wall tire sidewall insert and the bead rubber composition of the present invention comprises a syndiotactic 1,2-polybutadiene (Syndiotactic 1,2-Polybutadiene) by containing a predetermined amount, the included syndiotactic 1,2-polybutadiene rubber acts as a reinforcing filler that reinforces the existing rubber composition, preventing the weight increase of the tire due to the reinforcing filler, and is excellent in fatigue resistance, crack resistance, and heat resistance. .

        The content of the polybutadiene including the syndiotactic 1,2-polybutadiene rubber as described above is preferably included in the range of 20 to 80% by weight of the total raw rubber, if less than 20% by weight of the syndiotactic 1,2- The role of the reinforcement filler by polybutadiene is difficult to secure the desired level of modulus, and when it exceeds 80% by weight, the content of butadiene and syndiotactic 1,2-polybutadiene is too high, reducing the mixing and extrusion processability, and Cracking property and heat generation performance are reduced.

        In addition, the syndiotactic 1,2-polybutadiene rubber in the polybutadiene including the syndiotactic 1,2-polybutadiene rubber is preferably included in 3 to 35% by weight of the total polybutadiene. If the content of syndiotactic 1,2-polybutadiene rubber is less than 3%, it cannot play a role as a reinforcing filler, and thus, a big difference in performance from general butadiene rubber can not be obtained. No level of performance can be achieved. Most preferably, 10 to 20% by weight of the most appropriate performance can be obtained.

        In addition, the raw material rubber of the present invention may further contain butadiene rubber within 50% by weight of the total raw material rubber in addition to the above components.

        On the other hand, the run-flat tire sidewall insert and bead rubber composition of the present invention is 20 to 70 parts by weight of the filler, 0.5 to 6 parts by weight of sulfur as a vulcanizing agent, and sulfenamide 0.5 to 4 as a vulcanization accelerator, based on 100 parts by weight of the raw material rubber. By weight, 0.5 to 5 parts by weight as a deterioration inhibitor, and these additives are not particularly limited as used in the production of tires in general.

        Hereinafter, the present invention will be described in the following Examples and Test Examples, which do not limit the technical scope of the present invention.

        Example 1 and Comparative Examples 1 to 3

        Next, the rubber composition blended in the composition shown in Table 1 was vulcanized at 160 ° C. for 20 minutes, and the tensile properties, Tanδ, fatigue resistance, crack resistance, heat resistance, and specific gravity of the vulcanized sheet were as follows. It measured, and the result is shown in the following 2.

1. Tensile Properties: Modulus, elongation, and tensile strength were evaluated using a tensile tester (ASTM D 638).

       2. Fatigue resistance: Fatigue life (50% residual rate) was measured using an FF tester.

       3. Crack resistance: The growth rate was determined by measuring the crack length after a certain cycle using a Demattia tester.

       4. tan δ: was measured using a viscoelastic tester.

       5. Specific gravity: It was measured by using an automatic hydrometer.

Table 1

Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Raw material rubber Natural Rubber (STR-20) 30 30 30 30 Polybutadiene with syndiotactic 1,2-polybutadiene ⁽¹⁾ 70 - - - Butadiene Rubber ⁽²⁾ 70 70 70 Carbon Black (GPF) 45 45 65 65 Zinc Oxide (KS # 2) 5 5 5 5 Stearic acid (curable P60) 2 2 2 2 Anti-aging Antioxidant 1 (6PPD) 1.5 1.5 1.5 1.5 Antioxidant 2 (RD) 1.5 1.5 1.5 1.5 Sulfur (powder powder) 3.0 3.0 3.0 3.0 Vulcanization accelerator (TBBS) 1.5 1.5 1.5 2.0 Deterioration inhibitor (Bayer KA9188) 1.0 1.0 1.0 1.0 (1) Polybutadiene containing syndiotactic 1,2 polybutadiene: VCR617 made of UBEPOL (2) Butadiene rubber: KBR01 manufactured by Kumho Petrochemical Co., Ltd. Parts by weight)

Table 2

Properties Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile Properties Shore A 75 65 71 74 Modulus (kgf / cm ² ) 75 40 65 73 Elongation (%) 190 200 150 120 Tensile strength (kgf / cm ² ) 160 145 120 110 Fatigue Resistance (Life Cycle) 6000 6000 1500 500 Crack resistance (growth speed, mm / kc) 0.4 0.4 1.0 2.0 tanδ (80 ° C) 0.04 0.04 0.08 0.07 Specific gravity (g / cc) 1.34 1.35 1.41 1.41

        As can be seen from the results of Table 2, as the present invention, butadiene including syndiotactic 1,2-polybutadiene as a raw material rubber of the conventional run-flat tire sidewall insert and bead rubber composition is contained in a predetermined amount. In this case, it is considered that the physical properties such as tensile properties and fatigue resistance crack resistance are superior to the comparative examples without polybutadiene rubber containing syndiotactic 1,2-polybutadiene. 2-polybutadiene acts as a reinforcing filler, thereby increasing the weight of the rubber to lower specific gravity, and excellent tensile properties, fatigue resistance, crack resistance, and heat resistance.

        On the other hand, in order to measure run flat durability performance and rolling resistance, in the case of run flat durability performance, the tire is left at 2.5 kg / cm 2 of internal pressure after rim assembly for 24 hours at 38 ° C, and the valve is removed and the internal pressure is adjusted to atmospheric pressure. It was the time until the failure occurred by running in a drum (diameter 1.7 m) at 400 kg and a speed of 80 km / h.

        In addition, in the case of the rolling resistance, the tire after the rim assembly (Coast Down SAE J2452) test method using the test after the embodiment was shown to be indexed to 100 by the control.

        The run flat durability and rotational resistance values are shown in Table 3 below.

Table 3

Example 1 Comparative Example 1 Comparative Example 3 Run Flat Durability (Index) 100 10 30 Rolling resistance (exponent) 100 95 70

As can be seen in Table 3, as a result of including the polybutadiene rubber containing syndiotactic 1,2-polybutadiene in the raw material rubber of the conventional run-wall tire sidewall insert and bead rubber composition according to the present invention, The added syndiotactic 1,2-polybutadiene serves as a reinforcing filler and has excellent durability, and can improve fuel economy by reducing rotational resistance through a weight reduction role with a light rubber composition.

        As described in detail above, the present invention reduces the content of the reinforcing filler for the purpose of improving the performance of the run flat tire and increases the weight part of the rubber by increasing the weight part of the rubber by acting as a reinforcement with syndiotactic 1,2-polybutadiene. The rubber composition of the sidewall insert rubber and the bead which improves the tensile properties, fatigue resistance, crack resistance, and heat resistance at the same hardness and modulus at low but satisfies the run flat endurance characteristics and prevents the weight increase to improve the fuel efficiency performance to provide.

Claims (3)

        In the sidewall insert and bead rubber composition for a run flat tire,         The raw rubber is 20 to 80% by weight of natural rubber and 20 to 80% by weight of polybutadiene including syndiotactic 1,2-polybutadiene.         The runflat tire according to claim 1, wherein the syndiotactic 1,2 polybutadiene in the butadiene rubber including the syndiotactic 1,2-polybutadiene is included in an amount of 3 to 35% by weight of the total polybutadiene. Sidewall Inserts and Bead Rubber Compositions.         2. The sidewall insert and bead rubber composition for run flat tires according to claim 1, wherein the raw rubber further comprises butadiene rubber within 50% by weight.