Tire tread rubber composition with improved wet brake, wear and snow brake performance

Abstract

The present invention provides a tire tread rubber composition having improved wet braking performance in hot summer or cold winter regions while maintaining snowfield braking performance. The tire tread rubber composition may include SBR having excellent low temperature properties and a hydrogenated hydrocarbon resin for improving wet braking, snow braking, and wear performance, as well as a specific vulcanizing agent for supplementing wear / RR performance.

Description

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS]

[0002] This application claims the benefit of Korean Patent Application No. 10-2023-0163145, filed on November 22, 2023, which is hereby incorporated by reference in its entirety. Background of the Invention 1. Field of the Invention

[0004] The present invention relates to a tire tread rubber composition having improved wet braking, wear and snow braking performance compared to existing tire rubber compositions, and more particularly to a tire tread rubber composition comprising a styrene-butadiene rubber (SBR) having excellent low temperature properties and a hydrogenated hydrocarbon resin for improving wet braking, snow braking and wear performance, and a specific vulcanizing agent for supplementing wear / rolling resistance (RR) performance.

[0005] 2. Description of related technologies

[0006] Recently, as the demand for electric vehicles (EV) has rapidly increased, new technologies for tire rubber compositions that take both consumer safety and tire performance into consideration are required in view of tires for EV vehicles having high load capacity and high output.

[0007] In order to overcome the trade-offs between the various properties, for example, wet performance is compromised with snow performance and wear performance, and improving all properties at the same time is therefore a current challenge that is difficult to overcome by conventional technologies. By applying the above technology, it is possible to achieve an optimal tire rubber composition in which wet performance, wear performance and snow performance are significantly improved while also maintaining RR performance.

[0008] For example, Korean Patent Publication No. 10-2005-0051006 discloses a technology of kneading 100 parts by weight ("wt. parts") of SBR rubber with 50 parts by weight of silica and 30 parts by weight of aluminum hydroxide to improve fuel efficiency and wet performance on wet roads at the same time. However, due to the limitation of the rubber composition, the braking performance, wear resistance and process workability are insufficient, and there are limitations in its practical application.

[0009] Korean Patent Publication No. 10-2016-0048406 discloses a technology of adding 10 to 20 parts by weight of aluminum hydroxide and 50 to 60 parts by weight of silica to a rubber component including 60 to 80 parts by weight of SBR rubber, 5 to 20 parts by weight of butyl rubber, and 5 to 20 parts by weight of natural rubber to improve braking performance and fuel efficiency performance. However, due to limitations such as rubber ratio and the total content of silica and aluminum hydroxide, there are limitations in the actual improvement of wet / wear performance.

[0010] In addition, Korean Patent Publication No. 10-2023-0027573 discloses a tire tread rubber composition including a raw rubber and a hydrocarbon resin, which is a rubber composition including a tread rubber composition containing 40 to 80 parts by weight of a hydrocarbon resin and a vulcanizing agent. However, since the above patent is a technology that does not use liquid butadiene and aluminum hydroxide, there are technical limitations on improving wet performance and snow performance.

[0011] [Prior art literature]

[0012] [Patent Document]

[0013] (Patent Document 1) Korean Patent Publication No. 10-2005-0051006

[0014] (Patent Document 2) Korean Patent Publication No. 10-2016-0048406

[0015] (Patent Document 3) Korean Patent Publication No. 10-2023-0027573 SUMMARY OF THE INVENTION

[0017] In view of the above circumstances, an object of the present invention is to provide a tire tread rubber composition which can significantly improve wet performance, wear performance, and snow performance while also maintaining improved fuel efficiency performance.

[0018] In order to achieve the above-mentioned object, according to one aspect of the present invention, a tire tread rubber composition is provided, which, based on 100 parts by weight of raw rubber, comprises 10 to 60 parts by weight ("wt. parts") of liquid polybutadiene, 10 to 50 parts by weight of aluminum hydroxide and 0.5 to 4.0 parts by weight of a vulcanizing agent. If the amount of liquid polybutadiene is less than 10 parts by weight, the effect obtained is extremely small, and if its amount is greater than 60 parts by weight, wet performance may deteriorate. In addition, if less than 10 parts by weight of aluminum hydroxide is used, the effect obtained is extremely small, and if its amount is greater than 50 parts by weight, wear performance may decrease rapidly. In addition, the present invention also provides a tire tread rubber composition comprising the following rubber composition.

[0019] In order to improve wet performance, wear performance and snow performance at the same time, the weight ratio of liquid polybutadiene to aluminum hydroxide is limited to the range of 1:0.25 to 1:3.0. If the ratio of aluminum hydroxide to liquid polybutadiene is less than 0.25, wear performance and snow performance are improved, but wet performance is reduced. If the ratio of aluminum hydroxide used is greater than 3.0 times, wet performance and snow performance are improved, but wear performance is reduced.

[0020] The vulcanizing agent may be included in an amount of 0.5 to 4.0 parts by weight based on 100 parts by weight of the raw rubber. If the content thereof is less than the above range, the effect of improving RR / wear performance is minimal, and if the content thereof is greater than the above range, problems in scorch time stability may occur. The vulcanizing agent is preferably 1,6-bis(n,n-dibenzylthiocarbamoyldisulfide)hexane represented by the following Formula 1, but is not limited thereto.

[0021] To achieve the above object, according to another aspect of the present invention, a tire rubber composition is provided by optimally mixing raw rubber, liquid polybutadiene, aluminum hydroxide and a vulcanizing agent, which can be applied to tires, thereby significantly improving wet / wear / snow performance.

[0022] Furthermore, the present invention provides a tire including the above-mentioned rubber composition.

[0023] In the tire rubber composition of the present invention, the raw rubber may be natural rubber (NR), synthetic rubber or a mixture thereof.

[0024] In the tire tread rubber composition of the present invention, there is no particular limitation on the type of synthetic rubber, and may include, for example, styrene-butadiene rubber, butadiene rubber, butyl rubber, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), epichlorohydrin rubber, nitrile rubber, hydrogenated nitrile rubber, brominated polyisobutylisoprene-co-p-methylstyrene (BIMS) rubber, polyurethane rubber, fluororubber, silicone rubber, styrene-ethylene-butadiene-styrene copolymer rubber, ethylene-propylene rubber, ethylene propylene diene monomer rubber, hypalon rubber, chloroprene rubber, ethylene vinyl acetate rubber and acrylic rubber, etc.

[0025] In the tire tread rubber composition of the present invention, the raw rubber may include 50 to 100 weight % ("wt. %) of styrene-butadiene rubber (containing 10 to 30 weight % of styrene and 1 to 30 weight % of vinyl) based on the total weight of the raw rubber and 0 to 50 weight % of butadiene rubber or natural rubber based on the total weight of the raw rubber. In addition, the styrene-butadiene rubber has a glass transition temperature of -80 to -40°C.

[0026] The liquid polybutadiene may have a molecular weight of 3,000 to 7,000, a vinyl content of 1 to 20%, and a glass transition temperature of -50°C to -100°C. If the molecular weight is less than 3,000, the effect of improving wear properties is minimal. In addition, if the molecular weight exceeds 7,000, the effect of improving wet performance becomes minimal. If less than 10 parts by weight of the liquid polybutadiene is used based on 100 parts by weight of the raw rubber, the effect obtained is minimal, and if the amount thereof is greater than 60 parts by weight, wet performance may deteriorate.

[0027] Aluminum hydroxide can be formed into particles having a size of 0.15 to 1.00 micrometers. If its size is less than 0.15 micrometers, wear performance is effectively improved due to improved dispersibility, but there is a problem of reduced processability. If its size exceeds 1.00 micrometers, wear and tensile strength are rapidly reduced to cause problems. In addition, if the amount of aluminum hydroxide is less than 10 parts by weight, the effect obtained is extremely small, and if the amount is greater than 50 parts by weight, wear performance may be rapidly reduced.

[0028] The weight ratio of the liquid polybutadiene to the aluminum hydroxide used is preferably limited to the range of 1:0.25 to 1:3.0. If the ratio of aluminum hydroxide to liquid polybutadiene is less than 0.25 times, wear and snow performance are improved, but wet performance is reduced, and if the ratio of aluminum hydroxide used is greater than 3.0 times, wet performance and snow performance are improved, but wear performance is reduced.

[0029] The vulcanizing agent may be included in an amount of 0.5 to 4.0 parts by weight based on 100 parts by weight of the raw rubber. If the content is less than the above range, the effect of improving RR / wear performance is minimal, and if the content is greater than the above range, problems in scorch time stability may occur.

[0030] The vulcanizing agent is preferably 1,6-bis(n,n-dibenzylthiocarbamoyldisulfide)hexane represented by the following Formula 1, but is not limited thereto.

[0031] [Formula 1]

[0032]

[0033] In the above formula 1, -S-(CH2)6-S- has excellent vulcanization properties, and its sulfur chain is relatively long compared to sulfur to make it flexible / thermally stable without affecting physical properties, and it can simultaneously act as an accelerator by being generated while decomposing.

[0034] In the tire rubber composition of the present invention, it is preferred to use a rubber having 140 m 2 / g or less in specific surface area, and may be contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of the raw rubber.

[0035] The tire rubber composition of the present invention may include silica for improving the physical properties of the rubber composition. The silica may include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate or colloidal silica, and may be wet silica having the most excellent effect of improving fracture properties and wet grip.

[0036] The silica may have a molecular weight of 90 to 230 m / s as measured by Brunauer-Emmett-Teller (BET). 2 / g of nitrogen adsorption specific surface area, and may be contained in an amount of 60 parts by weight or more and 160 parts by weight or less based on 100 parts by weight of the raw rubber. If the amount is less than the above range, it is difficult to achieve braking performance, and if it exceeds the above range, problems in processability (dispersion) may occur, and wear performance may be greatly reduced.

[0037] In addition, the composition of the present invention may further include a vulcanizing agent and a silane.

[0038] The vulcanizing agent may be sulfur powder, and may be contained in an amount of 1 to 3 parts by weight based on 100 parts by weight of the raw rubber. If the content of the vulcanizing agent is less than the above range, the degree of vulcanization is low, and thus it is difficult to achieve the desired physical properties, and if it exceeds the above range, the degree of vulcanization is too high, and thus the aging properties are greatly reduced.

[0039] Silane can include bifunctional silane, such as TESPT and TESPD, and mercaptosilane, etc. Based on 100 parts by weight of the raw rubber, the silane can be contained in an amount of 5 to 15 parts by weight. When the content of the silane is less than the above range, the degree of vulcanization is low, so the physical properties are reduced, and if it exceeds the above range, the degree of vulcanization is too high, so the aging properties are greatly reduced.

[0040] In addition, the composition may further include ingredients commonly used in the art when manufacturing vehicle tires, such as accelerators.

[0041] The rubber composition of the present invention can significantly improve wet / wear / snow performance through optimal mixing of liquid polybutadiene, aluminum hydroxide and a vulcanizing agent based on 100 parts by weight of the raw rubber, which can be applied to tires.

[0042] In addition, the liquid polybutadiene in the rubber composition of the present invention improves snow / wear performance, but has the disadvantage of reducing wet performance. However, in the present invention, by including a vulcanizing agent that supplements RR and wear performance, wet / wear / snow performance can be improved while maintaining RR performance. DETAILED DESCRIPTION OF THE INVENTION

[0044] The present invention is described in detail below through embodiments and experimental examples.

[0045] However, the Examples and Experimental Examples described below are intended only to illustrate the present invention, and the scope of the present invention is not limited to the following Examples and Experimental Examples.

[0046] <Examples 1 to 4>

[0047] As the raw material rubber, butadiene rubber, natural rubber and styrene-butadiene rubber are used. Specifically, styrene-butadiene rubber including styrene in an amount of 10 to 30% by weight and vinyl in an amount of 1 to 30% and having a glass transition temperature of -70 to -40°C is used.

[0048] A hydrogenated hydrocarbon resin (H2 / DCPD / C9 modifier) ​​having a glass transition temperature of 50° C. to 80° C. and a weight average molecular weight of 600 or more and 1700 or less was used. In addition, 1,6-bis(n,n-dibenzylthiocarbamoyldisulfide)hexane was used as a vulcanizing agent, and Si-69 ([bis(3-triethoxysilyl)propyl]tetrasulfide=TESPT) was used as silica and silane. These components were mixed, and then carbon black, sulfur, CZ (primary accelerator) and DPG (secondary accelerator) were added to the mixture according to the mixing ratio listed in Table 1 below to prepare a tire tread rubber composition sample.

[0049] <Comparative Examples 1 to 6>

[0050] Tire tread rubber composition samples were prepared by the same procedure as in Example, except that the weights of the liquid polybutadiene, aluminum hydroxide, and the vulcanizing agent and the mixing ratio thereof were changed as listed in Table 1 below.

[0051] [Table 1]

[0052]

[0053]

[0054] Comparative Examples 2 and 3: Examples Using Liquid Polybutadiene + Aluminum Hydroxide Comparative Examples 4 and 5: Examples Using Vulcanizing Agents

[0055] Comparative Example 6: Example using a vulcanizing agent (outside the set range)

[0056] <Experimental Example> Evaluation of snow braking, wet road braking, rolling resistance (RR) and wear resistance

[0057] Snow braking, wet braking, rolling resistance (RR), and wear resistance were evaluated using the samples prepared in Examples 1 to 4 and Comparative Examples 1 to 6. Each evaluation method was performed as follows, and the experimental results are shown in Table 1.

[0058] In Table 1 above, the scorch time was evaluated using a rheometer tester, and the unvulcanized rubber was evaluated at 125°C. The scorch time refers to the point at which the rubber starts to be vulcanized. If the scorch time is low, it has a significant impact on the manufacturing quality, and problems in tire safety may occur. Therefore, although it varies depending on the extruder used, the scorch time should preferably be 15 minutes or more.

[0059] Snow braking performance (snow index), wet braking performance (wet index) and RR performance were evaluated using a dynamic mechanical analysis (DMA) tester and were evaluated under temperature sweep conditions (-100°C to +80°C, 11Hz). The evaluation results were then compared with the predicted index values.

[0060] It is beneficial for snow braking performance that the lower the modulus value of E'-30℃, the better the rubber fluidity, and it is beneficial for wet braking performance that the higher the value of E"0℃ (loss modulus / storage modulus ratio), the higher the hysteresis. It is beneficial for RR performance that the lower the value of Tan 60℃, the lower the hysteresis.

[0061] Based on these principles, as shown in Table 1 above, it can be seen that in the samples including only liquid polybutadiene and aluminum hydroxide (Comparative Examples 2 and 3), the snow braking performance and wet braking performance are improved, but the wear performance and RR performance are reduced, and in the samples including only vulcanizing agents (Comparative Examples 4 and 5), only the wear performance and RR performance are improved.

[0062] Comparative Example 6 including a vulcanizing agent (outside the set range) showed improved wear performance and RR performance, but it was difficult to ensure scorch time stability. In contrast, it can be seen that when liquid polybutadiene, aluminum hydroxide and a vulcanizing agent are all applied to samples, such as Examples 1 to 6, snow braking performance, wet braking performance and wear performance are all improved.

Claims

1. A tire tread rubber composition comprising raw rubber, liquid polybutadiene, aluminum hydroxide and a vulcanizing agent, wherein the raw material rubber comprises 50 to 100 parts by weight ("wt. parts") of styrene-butadiene rubber based on the total weight of the raw material rubber, The styrene-butadiene rubber includes styrene in an amount of 10 to 30% by weight and vinyl in an amount of 1 to 30% by weight based on the total weight of the styrene-butadiene rubber, and The liquid polybutadiene rubber is included in an amount of 10 to 60 parts by weight, and the aluminum hydroxide is included in an amount of 10 to 50 parts by weight, based on 100 parts by weight of the raw rubber. 2 . The tire tread rubber composition according to claim 1 , wherein the vulcanizing agent is contained in an amount of 0.5 to 4.0 parts by weight based on 100 parts by weight of the raw rubber.

3. The tire tread rubber composition according to claim 1, wherein the vulcanizing agent is 1,6-bis(n,n-dibenzylthiocarbamoyldithio)hexane represented by the following Formula 1: [Formula 1] 4. The tire tread rubber composition according to claim 1, wherein the aluminum hydroxide is a compound having a size of 0.15 to 1.00 micrometers and represented by the following Formula 2: [Formula 2] 5. The tire tread rubber composition of claim 1, wherein the liquid polybutadiene has a molecular weight of 3,000 to 7,000, a vinyl content of less than 1 to 20%, and a glass transition temperature of -50°C to -100°C. 6 . The tire tread rubber composition according to claim 1 , wherein a weight ratio of the liquid polybutadiene to the aluminum hydroxide is 1:0.25 to 1:3.0.

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