KR20040044762A - Tire rubber composition - Google Patents

Abstract

PURPOSE: Provided is a tire rubber composition with improved tensile or hysteresis properties by adding cystine or cysteine which converts protein included in a natural rubber to an active component to make a bond with carbon black or rubber, thereby preventing the rubber elongation factor from being disintegrated. CONSTITUTION: The tire rubber composition comprises 1-5 phr of any one selected from cystine, cysteine and additives containing cystine or cysteine, based on the 100 pts.wt of a natural rubber as a raw material.

Description

Tire rubber composition

The present invention relates to a tire rubber composition, and more particularly, by adding cystine or cysteine to a composition comprising natural rubber as a raw material rubber, thereby converting the protein in the rubber component into an active ingredient, thereby improving the tensile and hysteresis characteristics of the rubber. It relates to a rubber composition.

The composition of natural rubber consists of 91 to 94% of rubber hydrocarbons, 2 to 3% of proteins, and 2 to 3% of natural lipids.

Among them, proteins are weak to heat and destroyed during mixing, but are not completely decomposed and denatured to exist as substances having no utility. Therefore, it means a loss of 2 to 3 phr of active ingredient.

Therefore, if there is a method for converting such a loss into the active ingredient, it will be possible to improve the physical properties of the rubber composition using natural rubber.

Here, proteins contained in natural rubber can be classified as follows by specific gravity difference.

(1) Rubber particle phase: It binds with 300-500nM particles which make up 26% of rubber-containing proteins. Rubber growth factor (REF) related to the growth of rubber molecules

(2) Cellular fluid phase: It is called C phase and has about 30% of various kinds of proteins with high molecular weight and high anion mobility.

(3) Lutoid particle: It is an insoluble solid in water and about 8 kinds of proteins, also called Bottom Fraction, are Cation Hevamine and Anion Hevein.

Natural rubber naturally undergoes proteolysis, which causes polymerization due to ammonia added to prevent decay and oxidative coupling of thiol groups such as cystine, resulting in low molecular weight proteins from which REF is partially degraded. It binds to rubber particles and complicates the composition of rubber-containing proteins, such as the presence of polymerized new high molecular weight proteins.

Accordingly, the inventors of the present invention, while searching for a method of converting a protein contained in natural rubber into an active ingredient, added cystine or cysteine to the tire rubber composition, and as a result, radicals generated by breaking the disulfide bond of cystine were formed on the carbon black surface. It is induced to react with the active groups and compounds of the to form a bond between the filler and the rubber, and at the same time to prevent the decomposition of the rubber particles (REF) so as not to lose the elongation characteristics to improve the tensile properties or hysteresis characteristics as a result The present invention was completed.

Accordingly, it is an object of the present invention to provide a tire rubber composition in which the protein contained in the natural rubber composition is converted into an active ingredient, thereby improving the tensile and hysteresis characteristics of the tire.

The tire rubber composition of the present invention for achieving the above object is characterized in that it comprises natural rubber as a raw material rubber, added to the selected from cystine, cysteine and additives containing these components.

The present invention will be described in more detail as follows.

In the present invention, in the improvement of the physical properties of the tire rubber composition using natural rubber as a raw material, cystine or cysteine is added to convert proteins contained in natural rubber into active ingredients.

In the present invention, the coupling effect of cystine using cysteine having a unstable and highly sensitive reactivity having a sulfidyl group (-SH) as a reducing agent was used. That is, radicals generated by breaking the disulfide bonds of cystine are induced to react with the active groups or compounds on the surface of the carbon black in the rubber composition to form a bond between the filler and the rubber and at the same time to decompose the rubber growth factor so as not to lose elongation characteristics. It was to prevent. The specific mechanism is shown in Scheme 1 below.

When cystine or cysteine is added to the rubber composition to induce such a reaction, the protein contained in the natural rubber is converted into an effective ingredient, thereby preventing the loss of the active ingredient corresponding to 2 to 3 phr of natural rubber. As a result, tensile properties or hysteresis characteristics can be improved.

The amount of cystine or cysteine added may be 1 to 5 phr based on 100 parts by weight of the raw material rubber. When the content is more than 5 phr, excessive modulus and scorch time are drastically shortened.

The tire rubber composition of the present invention includes a general tire rubber composition, and includes carbon black as a reinforcing agent, zinc oxide, stearic acid, process oil, vulcanizing agent, vulcanization accelerator, and the like.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

Examples 1-5 and Comparative Example 1

Next, the tire rubber composition was manufactured according to a conventional method as the compounding ratio of Table 1, and the rubber properties thereof were measured, and the results are shown in Table 2 below.

Here, the vulcanization time was measured using the MDR2000 rheometer, the Mooney viscosity was measured using the MV2000 Mooney Biscometer, the hardness was measured by Shore A type method, 300% modulus, elongation and tensile strength were measured by an Instron tensile tester. Tanδ was measured by temperature and strain sweep with a rheometric viscoelastic tester. Crack growth was measured by DeMattia method, wear was measured by Lambourn abrasion tester, rebound was measured by Toyoseki's resilience tester.

Example Comparative Example 1 One 2 3 4 5 Natural Rubber (SMR-L) 100 100 100 100 100 100 Carbon black (ISAF) 50 50 50 50 50 50 Zinc oxide 3 3 3 3 3 3 Stearic acid One One One One One One Aromatic oils 3 3 3 3 3 3 Cystine One 2 3 5 10 0 Accelerator (NS) One One One One One One sulfur 2 2 2 2 2 2

Example Comparative Example 1 One 2 3 4 5 MDR @ 150 ℃ Smax 27.3 27.7 28.3 29.1 31.3 28.1 Smin 3.5 3.6 3.7 3.9 4.0 3.3 t ₃₀ 3.0 3.0 3.0 2.9 2.3 5.2 t ₉₀ 6.2 6.3 6.5 5.9 5.2 8.2 MV2000 @ 125 ℃ ML _{1 + 4} 55.1 54.8 55.4 57.4 59.3 49.6 t ₅ 10.2 10.1 10.1 9.3 7.5 14.2 Hardness 65 65 66 67 68 65 300% modulus 168 166 169 173 180 165 Elongation 451 454 452 432 410 443 The tensile strength 273 272 279 283 292 263 tanδ 0 ℃ 0.117 0.120 0.115 0.11 0.108 0.123 60 ℃ 0.082 0.081 0.079 0.073 0.068 0.090 Crack Growth @ 10kc, mm 29.9 30.7 30.9 31.3 32.4 31.1 Rambon wear cc 102 101 100 99 97 100 Rebound @ 60 ℃ 57 59 60 61 63 57

From the results of Table 2, it can be seen that t ₃₀ and t ₉₀ are shortened according to the addition of cystine, so that the vulcanization rate is increased. Cystine is a thiol having a sulfidyl group, and radicals generated by oxidation during the mixing of the complex It appears to play a part in promoting the reaction during formation (2RHS · → RS ~~ @ ~~ SH). However, unlike the increase in general accelerators, the torque (maximum and minimum) values are not increased and there is only a slight increase in the crosslinking density, so that there is almost no deterioration in physical properties.

In addition, it can be seen that the Mooney viscosity (ML _{1 + 4} ) slightly increases with the addition of cystine. The increase of ML _{1 + 4} increases the incorporation with carbon black, that is, carbon during mixing. It can be inferred that a chemical bond is formed between the surface active group of the black and cystine. However, as the amount of cystine is increased, the scorch time is shortened, and excessive use is rather detrimental to processing stability, and additional PVI (PreVulcanization Inhibitor) is used.

On the other hand, the hardness and initial modulus did not change with the addition of cystine, and it can be seen that 300% modulus showed a slightly elevated result at an equivalent level or higher. Elongation and tensile strength increase slightly with the addition of cystine, which has a synergistic effect on overall toughness. The same physical property results are observed in aging. However, when the amount of cystine is increased, the amount of cystine is excessively increased and the elongation is lowered. Therefore, the amount of cystine should be adjusted appropriately (1 to 5 phr). This increase in break energy is believed to be due to the bonding of carbon black and cystine and the bonding of cystine and rubber. In particular, it is assumed that REF, which is involved in rubber elongation, is present in the protein component without being destroyed. Therefore, it can be said that the cystine addition serves as a kind of coupling agent that connects both carbon black and rubber (carbon black-cystine-rubber).

In addition, tan δ results in a decrease in temperature over the entire temperature range, which is caused by a slight decrease in the contact between rubber and carbon black due to the combination of carbon black and cystine, and thus the modulus of carbon black-cystine is not reduced. -Bifunctionality of rubber is likely to play a role.

As a result, the addition of cystine is very effective in reducing exotherm and rolling resistance.

As described above in detail, when cystine or cysteine is added to a tire rubber composition comprising natural rubber as a raw material rubber, the protein contained in natural rubber is converted into an active ingredient to bond carbon black to rubber. It is possible to obtain a rubber for a tire having improved tensile and hysteresis characteristics by preventing the decomposition of the rubber particles so as not to lose the elongation characteristics.

Claims (2)

In the tire rubber composition comprising natural rubber as raw material rubber, A tire rubber composition comprising cysteine, cysteine and an additive containing these components. The tire rubber composition according to claim 1, wherein the cysteine, cysteine, and an additive containing these components are added in an amount of 1 to 5 phr based on 100 parts by weight of the raw rubber.