KR20230063634A - Rubber composition for tire tread and tire manufactured by using the same - Google Patents

Abstract

The present invention discloses a rubber composition for a tire tread and a tire made therefrom. The rubber composition for a tire tread according to the present invention and the tire made therefrom comprises 10 to 100 parts by weight of silica, 10 to 50 parts by weight of carbon black, and 0.5 to 1 part by weight of sulfur, based on 100 parts by weight of raw rubber, wherein the weight ratio of sulfur to the total accelerator is 1:6 to 1:10, and further contains a liquid polymer. According to this, it is possible to optimize the content ratio of sulfur and accelerator used in the rubber vulcanization reaction and improve dry road braking performance while maintaining the wear resistance and low fuel efficiency of rubber by including functionalized liquid polymer.

Description

Rubber composition for tire tread and tire using it {RUBBER COMPOSITION FOR TIRE TREAD AND TIRE MANUFACTURED BY USING THE SAME}

The present invention relates to a rubber composition for tire tread and a tire using the same. It relates to a rubber composition for tire tread that improves braking performance on a dry road while maintaining and a tire using the same.

The main performance requirements of tires include handling, braking performance, anti-abrasion performance, low fuel consumption performance, durability performance, etc. Due to the recent high performance of passenger vehicles, consumers are demanding higher performance of tires and the demand for tire braking performance is increasing.

In order to improve braking performance, one of the most important performance of tires, by adding terpine and petroleum resin-based resin to the tread rubber composition, the adhesiveness and glass transition temperature (Tg) of rubber are increased or contain a high content of styrene. There is a way to increase hysteresis by using a large amount of raw material rubber and carbon black or silica having a small particle diameter.

However, all of the above methods are focused on improving wet road performance, so there is a limit to improving overall braking performance, including dry roads, and there is also a problem in that abrasion performance and fuel economy performance that trade-off with braking performance are reduced. .

Although improvement in dry road braking performance is an absolute and essential performance for safety, a proper solution has not yet been proposed. There is a way to increase hysteresis by increasing the temperature (Tg) or using a large amount of raw rubber containing a high content of styrene and carbon black or silica with a small particle diameter, but this is a method that reduces abrasion performance and fuel economy performance, which are important for tires. result in a decline.

Republic of Korea Registered Patent Publication KR 10-2131424 B1

Therefore, the technical problem to be solved by the present invention is to optimize the content ratio of sulfur and accelerator used in the rubber vulcanization reaction and to improve dry road braking performance while maintaining the wear resistance and low fuel consumption of rubber by including a functionalized liquid polymer To provide a rubber composition for tire tread and a tire using the same.

In order to solve the above-mentioned technical problem, the present invention contains 10 to 100 parts by weight of silica, 10 to 50 parts by weight of carbon black, and 0.5 to 1 part by weight of sulfur based on 100 parts by weight of raw rubber, and the weight ratio of sulfur to total accelerators The ratio is 1:6 to 1:10, and it provides a rubber composition for tire tread, characterized in that it further comprises a liquid polymer.

According to another embodiment of the present invention, the liquid polymer may be a polybutadiene polymer modified with a silane-based compound.

According to another embodiment of the present invention, the liquid polymer may have a molecular weight (Mw) of 5,000 to 30,000.

Meanwhile, the present invention provides a tire including a tread made of the aforementioned rubber composition for tire tread in order to solve the above-described technical problem.

According to the rubber composition for tire tread and the tire using the same according to the present invention, the content ratio of sulfur and accelerator used in the rubber vulcanization reaction is optimized and the dry road surface is maintained while maintaining the wear resistance and low fuel consumption of rubber by including a functionalized liquid polymer. It has the effect of improving the braking performance.

1 is a graph showing the dry μ-peak index of the tread rubber according to the present invention, and the formula y = -0.0046x ² + 0.0787x + 0.8137 (R ² = 0.91: correlation) means a trend line function do.

It should be noted that the technical terms used in the present invention are used only to describe specific embodiments and are not intended to limit the present invention, and the technical terms used in the present invention are not specifically defined in other meanings in the present invention. Unless otherwise specified, it should be interpreted in a meaning generally understood by those skilled in the art, and should not be interpreted in an excessively comprehensive meaning or in an excessively reduced meaning.

In addition, when the technical terms used in the present invention are incorrect technical terms that do not accurately express the spirit of the present invention, they should be replaced with technical terms that those skilled in the art can correctly understand.

In addition, general terms used in the present invention should be interpreted as defined in advance or according to context, and should not be interpreted in an excessively reduced sense.

In addition, the singular expression used in the present invention includes a plurality of expressions unless the context clearly indicates otherwise. It should not be construed as necessarily including all of the various steps, and it should be construed that some components or some steps may not be included, or additional components or steps may be further included.

Figure 1 is a graph showing the dry μ-peak index of the tread rubber according to the present invention, refer to this.

The rubber composition for tire tread according to the present invention includes 10 to 100 parts by weight of silica, 10 to 50 parts by weight of carbon black, and 0.5 to 1 part by weight of sulfur, based on 100 parts by weight of raw rubber, and the weight ratio of sulfur to total accelerator is 1: It is a ratio of 6 to 1:10, and is characterized by further including a liquid polymer.

Here, the raw material rubber may be used individually or in combination with natural rubber or synthetic rubber. For example, the solution polymerized styrene-butadiene rubber contains 30 to 40% by weight of combined styrene based on the total solution polymerized styrene-butadiene rubber And, based on the total solution polymerized styrene-butadiene rubber, the vinyl content of butadiene is 50 to 60% by weight, and the glass transition temperature (Tg) may be -40 to -20 ° C.

In addition, the solution polymerized styrene butadiene rubber may be used without adding oil or with added oil.

In one example, when oil is added to solution polymerized styrene-butadiene rubber, 10 to 40 parts by weight of oil may be added based on 100 parts by weight of the rubber. Flexibility can be supplemented.

Treated Distillate Aromatic Extract (TDAE) oil may be used as an oil that may be added to the solution polymerized styrene-butadiene rubber.

The butadiene rubber that can be used as another synthetic rubber is, for example, butadiene rubber (High Cis -Butadiene rubber), and the butadiene rubber may have a Mooney viscosity of 43 to 47 at 100 ° C., and has an advantageous effect in terms of wear resistance.

On the other hand, reinforcing fillers that can be used include silica and carbon black. The silica has a nitrogen adsorption specific surface area BET (brunauer emmett teller) of 150 to 300 m ² /g and a CTAB (cetyltrimethylammonium bromide) adsorption specific surface area of 140 to 280 m ² /g, it has high dispersibility with respect to raw rubber, and can impart reinforcing performance and processability.

10 to 100 parts by weight of silica may be used based on 100 parts by weight of raw rubber. If it is less than 10 parts by weight, there is a problem in that handling and braking performance are reduced due to a decrease in stiffness. On the contrary, if it exceeds 100 parts by weight, dispersion of silica This is difficult, and there may be a problem in that the overall performance decreases due to the improvement in rigidity and the processability becomes unfavorable.

In addition, the carbon black may have an iodine adsorption value of 100 to 130 mg/g, a DBP oil absorption of 110 to 150 cc/100 g, and a TINT value of 100 to 140.

10 to 50 parts by weight of such carbon black can be used based on 100 parts by weight of raw rubber. If it is less than 10 parts by weight, there is a problem in that handling and braking performance are reduced due to a decrease in stiffness, and if it exceeds 50 parts by weight, the stiffness is reduced. There may be a problem in that overall performance decreases and workability becomes disadvantageous due to a large increase.

Meanwhile, the composition according to the present invention may further include a resin having a high softening point, which imparts rigidity to rubber prepared from the rubber composition, helps to secure braking performance and handling performance on a wet road, and exhibits glass transition The temperature (Tg) may be 50 to 90 ° C, the softening point may be 100 to 140 ° C, and may be one of polymer-friendly aliphatic resins, naphthenic resins, and combinations thereof, Aliphatic-based resins may be, for example, C5-based petroleum resins such as Isoprene, and naphthenic-based resins may be, for example, terpene, dicyclopentadiene (DCPE), and the like. .

In addition, as the vulcanizing agent used in the present invention, a sulfur-based vulcanizing agent may be preferably used, and the sulfur-based vulcanizing agent may be powdered sulfur (S), insoluble sulfur (S), precipitated sulfur (S), colloidal sulfur, etc. Inorganic vulcanizers can be used, and specifically, elemental sulfur or a vulcanizing agent that produces sulfur, for example, amine disulfide, polymeric sulfur, and the like can be used.

The sulfur content is preferably 0.5 to 1 part by weight based on 100 parts by weight of the raw rubber in terms of an appropriate vulcanization effect and lowering the modulus of the rubber to increase the contact area. If the sulfur content is less than 0.5 part by weight, appropriate crosslinking If the reaction is not performed, wear performance may deteriorate, and if it exceeds 1 part by weight, there may be a problem of braking performance deterioration on a dry road surface due to an increase in rubber modulus.

In addition, the vulcanization accelerator used in the present invention means an accelerator that accelerates the vulcanization rate or promotes a delay action in the initial vulcanization step, and the primary vulcanization accelerator is a sulfenamide-based vulcanization accelerator, such as N-cyclohexyl -2-benzothiazylsulfenamide (CBS), N-tert-butyl-2-benzothiazylsulfenamide (TBBS), N,N-dicyclohexyl-2-benzothiazylsulfenamide, N-oxydiethylene Any one selected from the group consisting of -2-benzothiazylsulfenamide, N,N-diisopropyl-2-benzothiazolesulfenamide, and combinations thereof may be used.

Secondary vulcanization accelerators that can be used subsequently are guanidine-based vulcanization accelerators, such as diphenylguanidine, diortotolylguanidine, triphenylguanidine, orthotolylbiguanide, diphenylguanidine phthalate, and combinations thereof. Either one can be used.

On the other hand, the weight ratio of the sulfur to all accelerators constituting the first and second accelerators is preferably 1:6 to 1:10, but if the ratio is less than 1:6, it may be detrimental to the decrease in stiffness and wear performance of the rubber composition. And, if it exceeds 1:10, it may be disadvantageous to the reduction of compounding processability and dry road braking performance.

In addition, the liquid polymer used in the present invention can replace or reinforce oil with a functionalized polymer to impart plasticity to the rubber composition, maximize the dispersion of silica as a reinforcing agent, and form a physical bond with raw rubber to form silica, raw material It is possible to improve abrasion resistance and low fuel consumption by increasing interaction with rubber.

The functionalized polymer may have a molecular weight (Mw) of 5,000 to 30,000, a glass transition temperature (Tg) of -85°C to -95°C, and may be a silane-modified polybutadiene polymer.

The liquid polymer may be used in an amount of 5 parts by weight to 15 parts by weight based on 100 parts by weight of raw rubber. If the amount is less than 5 parts by weight, the silica dispersion effect due to functionalization may be lowered and wear resistance may be lowered, and if the amount exceeds 15 parts by weight

Braking performance may be degraded due to a drop in glass transition temperature, and low fuel efficiency may be deteriorated because an excessive amount of high softening point resin must be used to secure an appropriate glass transition temperature.

The liquid polymer is a silane-modified polybutadiene polymer, which is functionalized by epoxidizing the double bond of polybutadiene and then reacting with the thiol group of the silane compound of Formula 1 below.

<Formula 1>

(R1, R2, R3: C ₁ -C ₁₈ alkyl group, aryl group, C ₁ -C ₆ alkoxy group, C ₅ -C ₇ cycloalkoxy group or phenoxy group, n: 3 to 10 when the alkyl group increases as an integer, silica It is advantageous for dispersion, but if it exceeds 10, the stiffness of rubber may decrease and overall performance may deteriorate.

Here, a silane compound including a polysulfide group (-S _x -) and a thiocyanate group (-SCN) may be used by substituting the thiol group (-SH).

On the other hand, the present invention provides a tire including a tread manufactured using the above-described composition, and the manufacture of tread rubber and the manufacture of a finished tire product can be manufactured according to a conventional tire manufacturing method.

Examples and Comparative Examples

A rubber composition for tire tread was prepared according to the composition shown in Table 1 below.

item Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Example 4 Synthetic rubber (S-SBR) 80 80 80 80 80 80 80 80 Synthetic Rubber (BR) 20 20 20 20 20 20 20 20 silica 80 80 80 80 80 80 80 85 carbon black 25 25 25 25 25 25 25 25 coupling agent 8 8 8 8 8 8 8 8 zinc oxide 3 3 3 3 3 3 3 3 stearic acid 2 2 2 2 2 2 2 2 process oil 10 10 10 10 resin 10 10 10 10 10 10 10 10 liquid polymer 5 10 15 10 brimstone 1.5 0.3 1.5 0.7 0.7 0.7 0.7 0.7 primary accelerator 2 2 2 2 2 2 2 2 secondary accelerator 2 4 4 4 4 4 4 5 Accelerator/Sulfur Ratio 2.7 20.0 4 8.6 8.6 8.6 8.6 10.0

(unit: parts by weight)

1. Synthetic rubber (S-SBR): glass transition temperature -40 ~ -20 ℃, styrene 30 ~ 40wt%, vinyl 50 ~ 60wt%

2. Synthetic rubber (BR): 1,4-butadiene content of 96 wt% or more, glass transition temperature -108 ~ -102 ℃, molecular weight distribution 4 ~ 6

3. Silica: BET value 150~300 m ² /g, CTAB value 140~280 m ² /g

4. Carbon Black: Iodine value 100 ~ 130mg/g, DBP oil absorption 110 ~ 150 cc/100g, TINT value 100 ~ 140

5. Coupling agent: bis(3-triethoxysilylpropyl) tetrasulfide (Si69)

6. Resin (resin): Terpene resin with a softening point of 100 ~ 140 ℃

7. Liquid polymer: A polybutadiene liquid polymer modified with silane having a molecular weight (Mw) of 5,000 to 30,000 and a glass transition temperature (Tg) of -85 ° C to -95 ° C. In Example 2, a silane compound of Formula 3 below, Example 3 of Formula 4, and Example 4 of Formula 5 were used.

<Formula 2>

<Formula 3>

<Formula 4>

<Formula 5>

8. Sulfur : Containing more than 98.5% sulfur, Oil 1% Treated Sulfur

9. Primary accelerator: N-cyclohexyl-2-benzothiazylsulfenamide (CBS)

10. Secondary Accelerator: Diphenyleneguanidine (DPG)

11. Accelerator/sulfur ratio: Means the weight ratio between the total weight of the 1st and 2nd accelerators and sulfur

Experimental example

The rubber composition for tire tread prepared in Comparative Examples and Examples was subjected to a vulcanization process according to a conventional tire manufacturing process to prepare rubber specimens to measure physical properties, and the results are shown in Table 2 below.

item Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Example 4 scorch time (t5) 22 20 13 18 20 22 22 12 Hardness (ShoreA) 70 69 72 71 72 70 68 71 300% modulus 100 70 115 83 95 80 70 90 Tg (℃) -7 -7 -7 -7 -7 -7 -11 -7 60℃ tanδ 0.20 0.25 0.18 0.24 0.22 0.20 0.22 0.19 DIN Wear Index 100 80 105 92 93 101 98 101 Dry μ-peak Index 100 102 104 112 116 118 110 113

- Scorch time (t5) was measured according to ASTM standard D1646, and shows a phenomenon in which plasticity of unvulcanized rubber decreases and elasticity increases as vulcanization progresses slowly. The lower the value, the disadvantageous workability.

- Hardness and 300% modulus were measured according to ASTM standards D2240 and D412, and the higher the hardness, the harder the vulcanized rubber.

- Tg represents the glass transition temperature.

- 60℃ tanδ indicates the fuel consumption characteristics, and the lower the number, the better the performance.

- The DIN wear index was measured at a drum rotation speed of 40 rpm and a load of 10 N using a DIN wear measuring instrument, and the higher the value, the better the wear performance.

- For the Dry μ-peak Index, the maximum value of μ (Coefficient of Friction) between 0 and 40% of the slip ratio (%) of the smooth road surface and the rubber sample was measured using an RTMS measuring instrument, and the higher the value, the better the dry road surface braking. indicates an advantage in performance.

Referring to Table 2, as in the examples, the sulfur content is 0.5 to 1.0 parts by weight, and the weight ratio of sulfur and total accelerator is optimized at a ratio of 1:6 to 1:10, rubber that improves braking performance on dry roads. It was confirmed that the composition was provided.

Referring to Figure 1, as a graph showing the dry μ-peak index, It can be understood that as the dry road braking performance is measured with laboratory equipment (Lab. RTMS equipment), the higher the value, the better the effect. As the accelerator/sulfur weight ratio increases, the dry road braking performance improves. It can be seen that the weight ratio of 1:6 to 1:10 shows the optimal level and the properties decline after passing the inflection point, and the reason for the difference is that Comparative Example 4 and Example 2 have the same accelerator/sulfur weight ratio can be seen as the effect difference according to the liquid polymer addition.

In addition, as in the case of Example 2, it was confirmed that by including an appropriate amount of the functionalized liquid polymer, a rubber composition with significantly improved dry road braking performance was provided while maintaining processability, abrasion resistance, and low fuel consumption equivalent to Comparative Example 1.

Claims (4)

It contains 10 to 100 parts by weight of silica, 10 to 50 parts by weight of carbon black, and 0.5 to 1 part by weight of sulfur based on 100 parts by weight of raw rubber, and the weight ratio of sulfur to all accelerators is 1:6 to 1:10, and the liquid phase A rubber composition for tire tread, characterized in that it further comprises a polymer.
According to claim 1,
The rubber composition for tire tread, characterized in that the liquid polymer is a polybutadiene polymer modified with a silane-based compound.
According to claim 2,
The liquid polymer is a rubber composition for tire tread, characterized in that the molecular weight (Mw) of 5,000 to 30,000.
A tire comprising a tread made of the rubber composition for tire tread according to any one of claims 1 to 3.

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