KR20030049661A - The rubber composition for tire treads - Google Patents

Abstract

PURPOSE: A rubber composition for tire treads is provided to improve processing capability and wear resistance with maintaining excellent braking performance and decreased rotational resistance. CONSTITUTION: The rubber composition for tire treads comprises a base rubber consisting of a solution polymerized styrene-butadiene rubber in which both terminals are modified with an amine and a silane compound, and silica or carbon black as a reinforcing agent. The rubber composition for tire treads is characterized by further comprising 1 to 10 parts by weight of a binder based on 100 parts by weight of the reinforcing agent. The silica or carbon black is preferably contained in the total amount of 100 parts by weight based on 100 parts by weight of the base rubber.

Description

The rubber composition for tire treads

The present invention relates to a rubber tread rubber composition, and more particularly, a solution-polymerized styrene-butadiene rubber (hereinafter referred to as SBR) in which both ends are modified with an amine and a silane compound, and silica or carbon black as a reinforcing agent. The present invention relates to a rubber composition for tire treads that can improve the braking performance, reduce rolling resistance and wear resistance and reduce manufacturing cost without affecting workability by adding a small amount of binder thereto.

In order to reduce the fuel consumption due to recent tires, to improve the stability during braking and to extend the service life of the tire, not only to reduce the rolling resistance of the tread rubber and to improve the braking performance on wet roads, but also to improve the wear resistance performance. Research is being done in a variety of ways.

In general, in order to reduce rolling resistance, the elasticity of the tread rubber material should be increased, while in order to improve tire stability, that is, braking performance on wet roads, a tread rubber material having a large frictional resistance to the road surface during braking, that is, energy loss is required. Should be used.

To satisfy both of these opposing performances: reduced rolling resistance and improved braking performance, emulsion polymerization SBR, high cis-BR, low cis-BR, Although the solution-polymerized SBR obtained by using natural rubber or an organolithium initiator is used alone or in combination, there is a limit in satisfying both performances at the same time.

Specific examples include using rubbers such as BR and natural rubber to reduce resilience, ie reducing rolling resistance, and reducing the use of fillers such as carbon black or increasing the use of vulcanizing agents such as sulfur. It causes a decrease in braking performance. On the contrary, in order to improve braking performance, SBR having high styrene content and high vinyl content should be used and carbon black and oil content should be increased. In this case, however, the increase of fuel consumption is inevitable due to the decrease of repulsive elasticity.

In order to satisfy all of these opposing performances, researches on BR and SBR, which combine high functional groups with rubber black on the rubber molecular chain, have been conducted for a long time. Specifically, by controlling the content of vinyl or styrene, which is a microstructure of SBR or BR, the glass transition temperature of the rubber is increased to improve braking performance, and the number of rubber chain ends is reduced by the coupling reaction after polymerization or mutual attraction with carbon black. Research has been conducted to reduce the movement of rubber chain ends, which is a major factor of rotational resistance, by reacting these high functional groups with rubber chain ends.

U.S. Patent Nos. 4,550,142 and 4,555,547 disclose that braking and rebound elasticity can be improved simultaneously by using BR or SBR containing amine derivatives in tire tread rubber compositions, and U.S. Patent No. 4,397,994 In the case of a rubber composition using BR or SBR in which a rubber molecular chain is coupled to a metal, such as metal, it has a low rolling resistance, and it is disclosed that the result is high braking property and improved workability on wet road surfaces.

In addition, US Pat. No. 5,496,883 uses silica as a reinforcing agent and a solution polymerization SBR and BR having a high vinyl content to simultaneously solve both performances of improving braking performance and reducing rolling resistance.

However, in the case of BR and SBR described above, the functional group is bonded to only one end of the rubber chain and the other end is not bonded to the nature of the initiator used during polymerization, for example, an organic lithium initiator such as n-butyllithium. There is a limit to reducing the movement of the rubber chain ends. As a result, there is a limit to the effect of reducing the rolling resistance. In addition, when the styrene and vinyl content is increased to improve braking property, the glass transition temperature of the rubber is increased, which causes a problem that the wear resistance of the tire is deteriorated.

In addition, when silica is used as a reinforcing agent, it is necessary to use a binder to improve abrasion resistance due to the characteristics of silica, which has a weak bonding strength with rubber. Therefore, it is difficult to control the temperature to prevent scorch problems during mixing and processing caused by the binder. There is this.

In order to solve the above disadvantages, the inventors of the present invention use SBR in which both ends of the rubber chain are modified with amine and silane compound, which not only reduces the rolling resistance of the rubber and improves the braking force on the wet road, but also adds carbon as a reinforcing agent. Since black or silica and the amine and silane compound of the sock end are strongly bonded, they have found that the wear resistance can be improved without using a separate binder, that is, without any problem in processability. 2000-21219).

The rubber composition for tire treads disclosed herein is composed mainly of solution-polymerized styrene-butadiene rubber and butadiene rubber, wherein solution-polymerized styrene-butadiene rubber is modified at both ends with amine and silane compounds, where both ends are amine and silane. The solution-polymerized styrene-butadiene rubber modified with a compound is obtained by polymerizing styrene and butadiene with an anionic polymerization initiator containing an amine functional group and then reacting terminal anions with a silane compound.

As described above, when styrene-butadiene rubber modified at both ends by amine and silane compound is synthesized and applied to tread rubber composition containing carbon black and silica, it can reduce rolling resistance and improve abrasion resistance without problems of workability and braking performance. Could improve.

However, when the binder is not used at all, the viscosity of the composition may be high and may be disadvantageous in processability, and it has been found that there is a limit in improving wear resistance.

The present inventors have confirmed that even if a small amount of the binder is added, the effect of reducing rolling resistance, improving abrasion resistance, and improving braking performance can be seen without problems in processability, thereby completing the present invention.

Accordingly, an object of the present invention is to provide a tire tread that uses both butadiene rubber and styrene-butadiene rubber modified at both ends with amine and silane compounds, and adds a small amount of binder thereto to improve processability and wear resistance. It is to provide a rubber composition.

The rubber composition for tire treads of the present invention for achieving the above object is a rubber composition for tire treads containing carbon black and silica as a reinforcing agent, using solution-polymerized styrene-butadiene rubber and butadiene rubber as raw materials, wherein solution polymerization Styrene-butadiene rubber is characterized in that both ends are modified with amine and silane compound, and the binder contains 1 to 10 parts by weight with respect to 100 parts by weight of the reinforcing agent.

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

The rubber composition for tire tread of the present invention is generally the same as the rubber composition mainly composed of solution-polymerized SBR rubber and butadiene rubber for improving braking property and reducing rolling resistance, and only the solution-polymerized SBR rubber is amine and silane compound at both ends. The modified product is used, and it contains 1 to 10 parts by weight of the binder.

The solution-polymerized SBR rubber in which both ends of the present invention are modified with amine and silane compounds is obtained by polymerizing styrene and butadiene using a compound containing an amine functional group represented by Formula 1 as an anion polymerization initiator, and then terminating anion with Formula 2 It is obtained by reacting with the silane compound represented by.

Here, if the tetraethoxysilane represented by the formula (2) is used as a modifier at the time of terminal modification after polymerization, the degree of terminal denaturation can be increased, and the molecular weight distribution can be easily controlled by controlling the amount of polymerization thereof.

In the case of tetraethoxysilane, there is no side reaction, and the amount of the ethoxy group at the end of the rubber chain can be controlled by controlling the amount of use.

On the other hand, in the present invention, in order to more effectively improve the workability and wear resistance performance, a small amount of the binder is used, and examples of the binder include bis- (triethoxysilyl) -tetrasulfide.

The content is preferably 1 to 10 parts by weight with respect to the content of carbon black or silica added as a reinforcing agent. If the content is less than 1 part by weight, the viscosity of the composition is high, which is detrimental to workability and has a limitation in improving wear resistance. If wealth is exceeded, it is uneconomical for its effect to rise.

Even if a small amount of the binder is added as described above, since the ethoxysilyl group capable of reacting with silica is included at the end of the solution-polymerized styrene-butadiene rubber used in the present invention, the amount of the binder can be reduced. There is no problem in processing because the viscosity rise is also not large, and the improved results in the rotational resistance as well as the wear resistance was confirmed.

On the other hand, the manufacturing process of the solution polymerization SBR of the specific rubber composition of the present invention is as follows;

First, after injecting styrene and butadiene monomer into the polymerization solvent, injecting the initiator represented by the formula (1) at a temperature of 40 ~ 60 ℃ and polymerized for 2 to 4 hours, after the polymerization is completed is represented by the formula (2) The denaturant is injected and further reacted at 50-70 ° C. for 1 hour, and then the reaction is terminated with a polymerization terminator. Then, the reactant is precipitated in isopropyl alcohol or the like containing antioxidant and dried to obtain a solution polymerization SBR in which both ends of the polymer chain are modified with amine and silane compound.

Formula 1

Where

R is a linear or pulverized alkyl group having 1 to 3 carbon atoms,

R 'is a pentyl or isopentyl group.

Formula 2

Si (OR) ₄

Where

R is as described above.

The solution polymerization SBR thus prepared has a styrene content of 10 to 45% by weight and a vinyl content of 25 to 75% by weight for the butadiene portion in order to improve braking property and reduce rolling resistance.

If the styrene content of the SBR and the vinyl content of the butadiene portion are higher than the above ranges, the glass transition temperature of the rubber is increased to increase the rolling resistance, and the wear resistance is lowered. On the other hand, when the styrene content and the vinyl content of the butadiene portion are lower than the above range, the glass transition temperature of the rubber is lowered, so that the braking performance is lowered, therefore, the above range is preferable.

By using such a solution-polymerized SBR rubber with a conventional butadiene rubber to produce a tire tread rubber, the solution-polymerized SBR rubber is preferably contained in 10 to 80 parts by weight of the raw material rubber.

Carbon black and silica are added to the rubber component as a reinforcing agent. As described above, the solution-polymerized SBR modified with amines and silanes is strongly bound through mutual attraction and reaction with the carbon black and silica added as the reinforcing agent. It reduces the movement of the rubber chain and ultimately reduces the rolling resistance and improves the wear resistance.

The content of carbon black and silica is preferably included within 100 parts by weight based on 100 parts by weight of the raw material rubber.

The rubber composition for tire treads prepared by using a solution-polymerized SBR modified at both ends with an amine and an ethoxysilane compound as a rubber component and simultaneously using carbon black and silica as a reinforcing agent is carbon black in which amine and ethoxysilane are reinforcing agents. It can increase the bond with silica, thereby improving the wear resistance and reducing the rolling resistance, and can improve the braking performance by increasing the glass transition temperature of the rubber by controlling the vinyl or styrene content.

In addition to the components described above, tire tread rubber is added by adding components, such as stearic acid, zinc oxide, binder, accelerator, sulfur, aromatic processing oil, etc., which are usually added in the manufacture of tire tread rubber. To make up.

Hereinafter, the present invention will be described in detail with reference to the following examples, the examples are shown for the purpose of illustration only and the present invention is not limited thereto.

Preparation Example) Preparation of solution polymerization SBR in which both ends were modified with amine and silane

Into a stainless steel pressure reactor with a dry volume of 10 liters, 5,000 g of cyclohexane as a solvent, 100 g of tetrahydrofuran for fine structure control, 200 g of styrene as a monomer and 800 g of butadiene were sequentially injected, and then the temperature of the reaction system was maintained at 50 ° C. The initiator represented by Chemical Formula 1 was polymerized for 3 hours by injecting a variable as shown in Table 1 below. After the polymerization was completed, the denaturant represented by Chemical Formula 2 was quantitatively injected as shown in the following Table 1, and further reacted at 60 ° C. for another 1 hour, and then terminated with methyl alcohol. The reactant was precipitated in isopropyl alcohol containing antioxidant and dried to obtain a solution polymerization SBR in which both ends of the polymer chain were modified with amine and silane compounds.

Examples 1-4 and Comparative Examples 1-4)

Next, the rubber composition was prepared by blending in a Banbury mixer at a composition ratio as shown in Table 1.

Example Comparative Example One 2 3 4 One 2 3 4 BR 40 40 40 40 40 40 40 40 SSBR-1 - - - - 60 - 60 - SSBR-2 60 60 60 60 - 60 - 60 Silica 40 40 80 80 40 40 80 80 N330 carbon black 40 40 - - 40 40 - - Binder 3.2 2.0 6.5 4.0 3.2 - 6.5 - Process oil 25 25 25 25 25 25 25 25 Zinc oxide 2.5 2.5 2.0 2.0 2.5 2.5 2.0 2.0 Stearic acid 1.5 1.5 1.0 1.0 1.5 1.5 1.0 1.0 6PPD 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 RD 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Total PHR 216.2 215.0 218.5 216.0 216.2 213.0 218.5 212.0 CZ 1.5 1.5 1.8 / 1.8 1.5 1.5 1.8 1.8 DPG 0.5 0.5 1.8 1.8 0.5 0.5 1.8 1.8 sulfur 2.0 2.0 1.5 1.5 2.0 2.0 1.5 1.5 Total PHR 220.2 219.0 223.6 221.1 220.2 217.0 223.6 217.1 (Note) SSBR-1: A commercially available solution polymerization SBR, one end of which is modified with an amine, 20% styrene content and 60% vinyl content.SSBR-2: A solution polymerization SBR synthesized in Preparation Example, both ends Modified with amine and silane compound, 20% styrene content, 58% vinyl content BR: Commercialized Hysis BR Silica: Nitrogen adsorption surface area 175 mg / g, DBP oil absorption 240ml / 100g 6PPD : N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine RD: poly- (2,2,4-trimethyl-1,2-dihydroquinoline) binder: bis- (trie Toxysilylpropyl) -tetrasulfide CZ: N-cyclohexyl-2-benzothiazyl sulfenamide DPG: diphenylguanidine

Experimental Example

Rubber sheets were prepared using the rubber compositions obtained in Examples and Comparative Examples to prepare specimens for tensile, viscoelastic and Lambbourn wear test, and to test wet skid resistance, rotational resistance and abrasion resistance. A tire of the 195 / 70R14 standard was manufactured.

The rubber specimens and tires thus manufactured were tested for performance in the following manner, and the results are shown in Table 2 below.

(1) Rambon wear index

4.5kg load, surface rotation speed of abrasive stone 100m / s, powder dropping speed 20g / min.

(2) dynamic loss factor (tanδ)

Measured at 10Hz frequency with 0.5% strain using RDS.

(3) tensile strength

The strength at the time of cutting was measured using the Instron tensile tester.

(4) rolling resistance index

A value calculated from the moment of inertia of a tire rotating on a drum with a diameter of 1.7 m, calculated from the following equation.

(5) wear resistance index

After the tires were mounted on the car and traveled 40,000 km, the depth of the remaining groove was measured and indexed by the following equation.

Each index value is based on a comparative value of 100 for the conventional emulsion polymerization SBR (ESBR) having physical properties as shown in Table 1, which is not denatured, and the larger the value, the better the performance.

Example Comparative Example One 2 3 4 One 2 3 4 Rubber property Mooney viscosity 70 72 60 63 70 81 58 92 Tensile Strength (kg / ㎠) 210 215 168 178 208 183 165 157 Rambon Wear Index 108.0 112.0 105.0 108.0 100 87.0 100 91.0 tanδ, 60 ℃ 0.123 0.128 0.099 0.103 0.143 0.130 0.117 0.107 Tire performance Rolling resistance index 108.9 106.9 109.8 109.4 100 105.7 100 106.0 Wear Resistance Index 106.1 114.7 107.6 115.3 100 83.4 100 81.8

Comparative Examples 1 and 2 and Examples 1 and 2 are compositions using carbon blad and silica at the same time, and Comparative Examples 3 and 4 and Examples 3 and 4 are compositions using only silica.

In Comparative Example 1, a solution polymerization SBR in which one end was commercially modified with an amine was used, and in Comparative Example 2, a solution polymerization SBR in which both ends were modified with an amine and a silane compound was used, but a binder was not used. .

Comparative Examples 2 and 4 have a lower rotational resistance than the Comparative Examples 1 and 3 (the higher the index is, the better), the higher the viscosity and the lower the abrasion resistance, and the lower the rotational resistance as it contains a functional group capable of reacting with silica. However, it can be seen that the processability and the wear resistance are thirteen.

Examples 1 and 3 are better in rotational resistance and abrasion resistance than Comparative Examples 1 and 3, while Examples 2 and 4 are slightly disadvantageous in terms of rotational resistance in comparison with Examples 1 and 3, but are very poor in abrasion resistance. Good results were seen. In other words, even if the amount of the binder is reduced, it is a result that illustrates that the manufacturing cost can be lowered because it is not adverse to the performance.

As described in detail above, according to the present invention, when the sock end uses SBR modified with amine and silane compound, includes silica or carbon black as a reinforcing agent, and when a small amount of binder is used together, workability is improved. Abrasion resistance is also improved to prevent the increase of manufacturing cost by using a large amount of the binder.

Claims (5)

In a rubber tread rubber composition containing both solution-polymerized styrene-butadiene rubbers and butadiene rubbers, both ends of which are modified with amine and silane compounds as raw material rubbers, and containing silica or carbon black as reinforcing agents, A rubber composition for tire treads, characterized in that it further comprises 1 to 10 parts by weight with respect to 100 parts by weight of the reinforcing agent. The solution-polymerized styrene-butadiene rubber according to claim 1, wherein both ends of the solution-polymerized styrene-butadiene rubber are polymerized with styrene and butadiene using a compound containing a tertiary amine group represented by the following formula (1) as an anionic polymerization initiator, A rubber composition for tire treads, obtained by reacting a terminal anion with a silane compound represented by the following formula (2). Formula 1 Where R is a linear or pulverized alkyl group having 1 to 3 carbon atoms, R 'is a pentyl or isopentyl group. Formula 2 Si (OR) ₄ Where R is as described above. The solution-polymerized styrene-butadiene rubber in which both ends are modified with amine and silane compound has a styrene content of 10 to 45% by weight and a vinyl content of butadiene to 25 to 75% by weight. Rubber composition for tire tread. The rubber composition for tire treads according to claim 1, wherein the composition comprises 10 to 80 parts by weight of solution-polymerized styrene-butadiene rubber. The rubber composition for tire treads according to claim 1, wherein the composition comprises carbon black or silica within 100 parts by weight as a reinforcing agent based on 100 parts by weight of the raw material rubber.