KR100517481B1 - Rubber composition for tire sidewall improving appearance and quality of tire - Google Patents

Abstract

The present invention relates to a rubber composition for tire sidewalls for improving tire appearance and quality, and more particularly, by applying a polyethylene wax different from the wax used in the rubber composition at the time of tire manufacture to the tire rubber composition. In addition, the present invention relates to a rubber composition for tire sidewalls that improves tire appearance and delays cracking of rubber due to ozone aging to improve tire product characteristics.

Description

Rubber composition for tire sidewall to improve tire appearance and quality {RUBBER COMPOSITION FOR TIRE SIDEWALL IMPROVING APPEARANCE AND QUALITY OF TIRE}

The present invention relates to a rubber composition for tire sidewalls for improving tire appearance and quality, and more particularly, by applying a polyethylene wax different from the wax used in the rubber composition at the time of tire manufacture to the tire rubber composition. In addition, the present invention relates to a rubber composition for tire sidewalls that improves tire appearance and delays cracking of rubber due to ozone aging to improve tire product characteristics.

In the manufacture of conventional tires, wax has been used to form a physical barrier on the rubber surface in order to prevent cracking of the rubber due to ozone. The solubility of the waxes in the rubber composition changes with temperature, and the action in the rubber composition is changed by the change in solubility. When a suitable amount of wax is added to the rubber composition to prevent ozone, the wax is completely dissolved in the hot rubber compound, but when the temperature of the compound is lowered under atmospheric conditions, the solubility is lowered to exceed the solubility. The wax can no longer be completely dissolved. Thus, over time, waxes beyond the solubility limit diffuse and migrate to the surface of the rubber composition, thereby forming a protective barrier against ozone over the surface of the rubber composition.

The advantage of the wax is that it is relatively inexpensive, does not discolor, does not affect the vulcanization reaction and is beneficial to the process. There are two types of ozone inhibitor waxes currently in wide use, one is straight chain paraffine wax and the other is branched chain microcrystalline wax. In practice, in principle, a mixture of these two waxes is used as an ozone inhibitor to protect the rubber composition over a wider range of temperatures when either one is used alone.

It is an object of the present invention to improve the appearance of tires by delaying the cracking of rubber due to ozone aging by improving polyethylene tire composition by blending polyethylene wax different from the waxes currently used in tire rubber compositions. To provide a rubber composition for a tire side wall portion.

The rubber composition according to the present invention is characterized in that it comprises 2-3 parts by weight of polyethylene wax in order to improve the appearance of the tire and delay cracking of the rubber due to ozone aging, based on 100 parts by weight of the raw rubber.

In the rubber composition of the present invention, there is no limitation on the type of raw rubber, and natural rubber, synthetic rubber, mixed rubber of natural rubber and synthetic rubber, etc. may be used.

The polyethylene wax used in the rubber composition of the present invention has a molecular weight (MW) of at least two times greater than that of a paraffin wax or a microcrystalline wax, which has conventionally been used to prevent rubber cracking, and has a melting point. (melting point, MP) has a wide range and is lower, equal to, or higher than conventional paraffinic waxes or microcrystalline waxes.

According to the present invention, when the polyethylene wax is used in an amount of less than 2 parts by weight based on 100 parts by weight of the raw material rubber, the effect of improving the appearance of the desired rubber surface and the resistance to ozone is hardly obtained. Considering the high cost compared to using more than 3 parts by weight is not preferable. Therefore, the polyethylene wax used in the rubber composition of the present invention is preferably used in the range of 2 to 3 parts by weight based on 100 parts by weight of the raw material rubber.

As in the present invention, by using a polyethylene wax in place of the wax conventionally used in the rubber composition, the rubber surface appearance improvement effect and the resistance to ozone, without showing a large difference in the physical properties of the rubber composition Appeared to be much better than conventional waxes.

The composition of the present invention may include additives commonly used in tire rubber compositions, and may include, for example, a vulcanizing agent, a vulcanization accelerator, a reinforcing agent, a softening agent, zinc, a process oil, and the like.

The present invention will be described in more detail with reference to the following examples and comparative examples, but the scope of the present invention is not limited to the following examples.

<Examples and Comparative Examples>

Sample Preparation

The physical / chemical properties of the polyethylene wax used in the examples are shown in Table 1 below.

Table 1

Analysis item Wax 1 Wax 2 Wax 3 Molecular Weight (viscosity measurement) 800 800 800 Density (㎏ / ㎥) 881 889 904 Melting point (℃) 57 64 85 Melt Viscosity (mPas) (at 140 ° C) 9 10 11 δ enthalpy (J / g, DSC) 85.80 110.72 166.52

Polyethylene waxes 1-3 having the same molecular weight and different melting points as shown in Table 1 (Examples 1 to 3, respectively) and conventional paraffin waxes (molecular weight = 300 to 400, melting point = 65 ± 3 ° C.) To prepare a rubber composition having a composition of Table 2, each containing Example).

[ Table 2] (Unit: parts by weight)

ingredient Example 1 Example 2 Example 3 Comparative example Raw material rubber 100 100 100 100 Wax 2 2 2 2 Zincification 4.5 4.5 4.5 4.5 Process oil 5 5 5 5 Carbon black 50 50 50 50

Property evaluation

After preparing the specimens in the rubber compositions of Examples 1 to 3 and Comparative Examples shown in Table 2, the physical properties were evaluated, and the results are shown in Table 3 below.

Table 3

Test Items Result item Example 1 Example 2 Example 3 Comparative example Rheo (160 ° C) MAX.Torque 26.3 26.7 27.1 28.3 MIN.torque 8.6 8.5 8.3 9.2 When T40 passes 8.28 8.01 8.14 8.28 When T90 passes 13.74 13.08 13.08 13.47 Final food 15.11 14.39 14.39 14.82 Mooney viscosity 125 ℃ 41 40 39 43 T05 minutes passed 40.40 40.93 40.40 40.40 At the time of T35 minutes 50.53 49.73 49.73 49.87 100 ℃ 52 52 52 51 Initial tension / 3 days later Hardness, Shore method 53/57 53/59 54/59 52/58 100% Modulus (kg / ㎠) 15/24 15/26 16/27 14/27 300% modulus (kg / ㎠) 63/100 63/106 66/109 63/107 Tensile Strength (kg / ㎠) 193/128 195/128 195/137 198/136 Elongation at Break (%) 668/375 670/357 651/371 669/376 Dynamic Flexural Characteristics (DMFC) Row (mm) 7.1 6.8 6.7 7.4 Heat (mm) 10.2 11.3 5.0 14.2

As shown in the physical property test results of Table 3, the effect of the wax on the physical properties of the rubber composition is very small. There was no significant difference in basic properties such as vulcanization and unvulcanized properties.

Ozone Characterization

Ozone evaluation tests were performed on specimens prepared from the rubber compositions of Examples 1 to 3 and Comparative Examples.

For sufficient wax migration, the rubber specimens were left in the dark for 3 days prior to the ozone test and evaluated with no flex / ozone resistant antioxidant added to clearly observe cracks caused by ozone. The ozone test was carried out under the conditions of 50pphm / 40 ° C / 18 hours, the dynamic test, the static test and the O-ring test. After the ozone test was completed, the cracks on the rubber specimens were observed (Fig. 1).

As a result of crack observation, the specimens prepared from the rubber compositions of Examples 1 to 3 were evaluated to have better resistance to ozone than the specimens prepared from the rubber compositions of the comparative examples.

As described above, according to the rubber composition of the present invention, while maintaining and improving the properties of the existing tire is improved ozone resistance to reduce the occurrence of cracks, it is possible to produce a tire product with improved appearance and quality.

1 is a photograph showing the degree of cracking after the ozone characteristic test of the specimen prepared from the rubber composition of the Examples and Comparative Examples of the present invention. In the photograph, A, B, and C correspond to Examples 1 to 3, respectively, and D corresponds to a comparative example.

Claims (1)

A rubber composition for tire sidewalls, comprising 2 to 3 parts by weight of polyethylene wax with respect to 100 parts by weight of raw rubber.