Rubber composition for tire and tire

Abstract

To solve the following problem that, in a rubber composition for a tire, the employment of regenerated carbon black for tire recycling leads to inadequate tensile strength for practical use.SOLUTION: The foregoing problem was solved by a rubber composition for a tire comprising a diene-based rubber, carbon black, regenerated carbon black, and random polypropylene, wherein the melting point of the random polypropylene is 110°C or more and 155°C or less, the melt mass flow rate (MFR) measured at a temperature of 230°C under a load of 2.16 kg is 3 g / 10 min or more, and the content of the regenerated carbon black is more than 10 pts.mass relative to 100 pts.mass of the diene-based rubber.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for tires and a tire, and more particularly to a rubber composition for tires that has practically sufficient breaking strength even when blended with recycled carbon black, and a tire using the same. [Background technology]

[0002] In recent years, with increasing attention being paid to resource conservation and environmental protection, there has been a demand for improved recycling rates for tires as well. To address this, the use of recycled carbon black obtained by pyrolysis of used rubber products such as scrap tires (see, for example, Patent Document 1 below) and recycled carbon black derived from non-petroleum raw materials has been proposed.

[0003] However, recycled carbon black contains impurities derived from the raw materials used in tires, such as reinforcing materials and tire cords, as well as impurities derived from the thermal decomposition process during manufacturing, which poses a problem of significantly reducing the breaking strength of the rubber. For this reason, techniques for adjusting the surface activity of recycled carbon black and selecting the blending amount have been proposed, but these have not yet been able to impart sufficient breaking strength for practical use. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6856781 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a rubber composition for tires that has practically sufficient breaking strength even when blended with recycled carbon black, and a tire using the same. [Means for solving the problem]

[0006] As a result of extensive research, the inventors have discovered that the above-mentioned problems can be solved by providing a rubber composition for tires containing diene rubber, carbon black, recycled carbon black, and random polypropylene, in which the melting point and melt mass flow rate of the random polypropylene are set within specific ranges, and the amount of recycled carbon black blended is set to a specific amount, thereby completing the present invention.

[0007] That is, the present invention provides a rubber composition for tires comprising a diene rubber, carbon black, recycled carbon black, and random polypropylene, wherein the random polypropylene has a melting point of 110°C or higher and 155°C or lower, and a melt mass flow rate (MFR) measured at a temperature of 230°C under a load of 2.16 kg of 3 g / 10 min or higher, and the amount of recycled carbon black blended is more than 10 parts by mass per 100 parts by mass of the diene rubber. The present invention provides a rubber composition for tires, characterized in that The present invention also provides a tire using the rubber composition for a tire. [Effects of the Invention]

[0008] As described above, recycled carbon black contains impurities derived from tire raw materials such as reinforcing materials and tire cords, as well as impurities derived from the thermal decomposition process during manufacturing, resulting in a significant deterioration in breaking strength. As a result of extensive research, the present inventors have found that even when impurities (e.g., ash) are present in recycled carbon black, the occurrence of the above-mentioned problems can be minimized by blending a specific random polypropylene. As a result, according to the present invention, it is possible to provide a rubber composition for tires and a tire that have practically sufficient breaking strength even when recycled carbon black is blended therein. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will now be described in further detail.

[0010] (Diene rubber) The diene rubber used in the present invention is not particularly limited as long as it is one that is commonly used in tire applications, and examples thereof include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and ethylene-propylene-diene terpolymer (EPDM). These may be used alone or in combination of two or more. Furthermore, there are no particular limitations on the molecular weight or microstructure, and the diene rubber may be terminally modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl, or the like, or may be epoxidized. The weight average molecular weight (Mw) of the diene rubber is not particularly limited, but for reasons such as better effects of the present invention, it is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000. In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​calculated as standard polystyrene obtained by gel permeation chromatography (GPC) measurement.

[0011] (carbon black) The carbon black (hereinafter sometimes referred to as CB) used in the present invention has a nitrogen adsorption specific surface area NSA of 60 to 150 m 2 / g is preferred, and 75 to 145m 2 The DBP oil absorption is preferably 100 to 140 ml / 100 g, more preferably 100 to 130 ml / 100 g. The effects of the present invention are further improved by the N2SA and DBP oil absorption of the carbon black being within the above ranges. Note that the carbon black described in this section does not include the recycled carbon black described below.

[0012] (recycled carbon black) The recycled carbon black used in the present invention (hereinafter sometimes referred to as recycled CB) has a difference (ΔDBP) between the DBP oil absorption and the compressed DBP oil absorption (24M4DBP) of less than 20 ml / 100 g, and a nitrogen adsorption specific surface area (N2SA) (unit: m 2 It is preferable that N2SA / IA, which is the ratio of N2SA (unit: mg / g) to iodine adsorption amount IA (unit: mg / g), is in the range of 0.8 or more and less than 2.0.

[0013] From the viewpoint of further enhancing the effects of the present invention, the ΔDBP is preferably 19 ml / 100 g or less, and more preferably 18 ml / 100 g or less. From the viewpoint of further enhancing the effects of the present invention, the N2SA / IA is preferably 0.8 to 1.9, and more preferably 0.8 to 1.7. The DBP oil absorption of the recycled carbon black is preferably 80 to 120 ml / 100 g, and the compressed DBP oil absorption (24M4DBP) is preferably 60 to 100 ml / 100 g.

[0014] In the present invention, DBP oil absorption is measured in accordance with ASTM D2414, compressed DBP (24M4DBP) is measured as 24M4-DBP oil absorption based on JIS K6217-4 (compressed sample), N2SA is measured in accordance with JIS K6217-2, and IA is measured in accordance with JIS K6217-1.

[0015] The compressed DBP oil absorption is measured by breaking down the aggregations of the recycled carbon black, and by measuring the difference from the DBP oil absorption when the aggregations are maintained, it is possible to determine how easily the structure breaks down. The smaller the ΔDBP, the less likely the structure is to collapse, which means that the reinforcing properties of carbon black are not reduced. In the case of recycled carbon black, it is believed that the multiple types of carbon black that were blended into the raw material during tire manufacturing remain intact and maintain their distribution. Therefore, by optimizing the N2SA / IA ratio, recycled carbon black can exhibit sufficient reinforcing properties. The nitrogen adsorption specific surface area N2SA of the recycled carbon black is preferably 65 to 105 m 2 The preferred DBP oil absorption is 70 to 105 ml / 100 g.

[0016] The recycled carbon black used in the present invention can be, for example, the following recycled carbon black. (1) Recycled carbon black derived from natural resources. Natural resources include by-products generated during the manufacturing process of various products, which can be considered renewable raw materials. Examples of such by-products include, but are not limited to, animal and vegetable oils. Animal and vegetable oils refer to animal oils or vegetable oils, including fish oils, fatty oils (liver oils) obtained from the livers of fish such as cod and shark, marine animal oils such as whale oil, and terrestrial animal oils such as beef tallow and lard. Vegetable oils include oils and fats containing fatty acid glycerides extracted from plant seeds, fruits, kernels, etc., and may be drying oils, semi-drying oils, non-drying oils, etc. (2) Recycled carbon black produced by thermally decomposing waste tires and using the resulting pyrolysis oil as a raw material. Commercially available recycled carbon black can be used. (3) Recycled carbon black consisting of residual carbon black produced by the thermal decomposition of waste tires. The thermal decomposition of waste tires can be carried out according to a known method, for example, a thermal decomposition method at a temperature of 300°C or higher, more specifically, 600°C or higher. Such recycled carbon black can be commercially available, for example, PB365 (trade name) manufactured by Enrestec, CONTINUA8000 (manufactured by Birla Carbon), and LN607 (manufactured by Shandong Kaiyuan).

[0017] As described above, recycled carbon black contains impurities, such as ash, and the recycled carbon blacks described in (1) and (2) above contain ash in an amount of 0.5% by mass or less, and more specifically 0.4% by mass or less. The recycled carbon black (3) contains ash in an amount of 1 to 30% by mass, more specifically 3 to 25% by mass. Even when recycled carbon black containing ash is used in this way, the present invention uses a specific random polypropylene, so that deterioration of breaking strength can be significantly suppressed. The ash content is measured by the known ICP method.

[0018] (random polypropylene) The random polypropylene used in the present invention has a melting point of 110° C. or higher and 155° C. or lower, and a melt mass flow rate (MFR) measured at a temperature of 230° C. under a load of 2.16 kg of 3 g / 10 min or higher.

[0019] From the viewpoint of improving the effects of the present invention, the melting point of the random polypropylene is preferably 130°C or higher and 150°C or lower. From the viewpoint of improving the effects of the present invention, the melt mass flow rate (MFR) of the random polypropylene measured at a temperature of 230°C under a load of 2.16 kg is preferably 5 g / 10 min or more, more preferably 20 g / 10 min or more. The upper limit of the MFR is, for example, preferably 5000 g / 10 min or less, more preferably 1000 g / 10 min or less, and particularly preferably 500 g / 10 min or less. In the description of this specification, the melting point is measured by differential scanning calorimetry (DSC) in accordance with ASTM D3418 at a heating rate of 10°C / min, and the melt mass flow rate (MFR) is measured in accordance with the "Test method for melt mass flow rate (MFR) of plastics - thermoplastics" specified in JIS K7210:1999, under the conditions of a temperature of 230°C and a load of 2.16 kg, as described above.

[0020] Suitable types of random polypropylene include, for example, one or more selected from propylene-ethylene random copolymers, propylene-1-butene random copolymers, and propylene-ethylene-1-butene random copolymers. The random polypropylene used in the present invention can optionally contain comonomers other than those mentioned above, as long as the melting point and MFR requirements of the present invention are met. The random polypropylene used in the present invention can also have a hydrolytically condensable silyl group.

[0021] From the viewpoint of improving the effects of the present invention, the density of the random polypropylene is, for example, 0.860 g / cm 3 More than 1.000g / cm 3 Preferably, it is 0.880 g / cm or less. 3 More than 0.980g / cm 3 More preferably, it is 0.890 g / cm or less. 3 More than 0.970g / cm 3 It is particularly preferred that: The density in the present invention can be measured by the method described in JIS K7112. The random polypropylene may have any morphology and / or dispersion state in the rubber composition.

[0022] (Rubber composition blending ratio) The rubber composition for tires of the present invention contains diene rubber, carbon black, recycled carbon black, and random polypropylene, and is characterized in that the amount of recycled carbon black blended exceeds 10 parts by mass per 100 parts by mass of the diene rubber. In the present invention, because a specific random polypropylene is blended, even when the amount of recycled carbon black blended is set to a high level of more than 10 parts by mass per 100 parts by mass of diene rubber, sufficient breaking strength for practical use can be obtained. The amount of recycled carbon black to be compounded is preferably 15 to 35 parts by mass, more preferably 15 to 25 parts by mass, per 100 parts by mass of the diene rubber.

[0023] In addition, from the viewpoint of improving the effects of the present invention, it is preferable that the following blending conditions be satisfied. (i) The total amount of the carbon black and the recycled carbon black is preferably 15 to 150 parts by mass, more preferably 30 to 80 parts by mass, per 100 parts by mass of the diene rubber. (ii) The proportion of the recycled carbon black relative to the total amount of the carbon black and the recycled carbon black is preferably 30% by mass or more, and more preferably 30 to 45% by mass. (iii) The amount of the random polypropylene blended is preferably 1 to 20 parts by mass, more preferably 2 to 10 parts by mass, per 100 parts by mass of the diene rubber.

[0024] (Other ingredients) In addition to the above-mentioned components, the rubber composition for tires of the present invention may contain various additives that are generally compounded in rubber compositions for tires, such as vulcanizing or crosslinking agents, vulcanization or crosslinking accelerators, fillers, antioxidants, plasticizers, and resins, and these additives can be kneaded by a general method to form a composition, which can then be used for vulcanization or crosslinking. The amounts of these additives to be compounded may be conventional amounts, as long as they do not deviate from the object of the present invention.

[0025] The rubber composition for a tire of the present invention has sufficient breaking strength for practical use even when recycled carbon black is used, and therefore can be suitably used for tires. The tire of the present invention is preferably a pneumatic tire, which can be filled with air, an inert gas such as nitrogen, or other gases. [Example]

[0026] The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0027] (Preparation of various polyolefins) The following materials were used as random polypropylene: Random polypropylene A: Novatec PP MG05ES manufactured by Japan Polypropylene Corporation Random polypropylene B: SunAllomer PM731V manufactured by SunAllomer Co., Ltd. Random polypropylene C: SunAllomer PM931M manufactured by SunAllomer Co., Ltd. Random polypropylene D: SunAllomer PM940M manufactured by SunAllomer Co., Ltd. Random polypropylene E: SunAllomer PMA20V manufactured by SunAllomer Co., Ltd. Random polypropylene F: Prime Polypro E-333GV manufactured by Prime Polymer Co., Ltd. The melting points of the various random polypropylenes and the melting points and melt mass flow rates (MFR) measured at a temperature of 230° C. and a load of 2.16 kg are shown in Table 1 below.

[0028] [Table 1]

[0029] Standard Example 1, Examples 1 to 12, and Comparative Examples 1 to 5 Sample preparation In the formulation (parts by mass) shown in Table 1, the components excluding the vulcanization system (vulcanization accelerator, sulfur) were kneaded in a 1.7-liter internal Banbury mixer at 90°C for 5 minutes, then discharged from the mixer and cooled to room temperature. The composition was then placed back into the same Banbury mixer, and the vulcanization system was added and kneaded to obtain a rubber composition. The physical properties of the obtained rubber composition were measured using the test methods shown below. Note that "Reference Example 1, Examples 1 to 8, and Comparative Examples 1 to 5" were formulated and designed for the side tread of heavy-duty tires.

[0030] <Breaking strength> From the vulcanized rubber test pieces prepared as described above, JIS No. 3 dumbbell-shaped test pieces (thickness: 2 mm) were punched out in accordance with JIS K6251, and tests were conducted at a pulling rate of 500 mm / min in an atmosphere of 20°C to measure the tensile strength at break. The results obtained were expressed as an index, with the value of Standard Example 1 being 100. The larger the index, the better the breaking strength. Furthermore, an index of 95 or more can be judged to have sufficient breaking strength for practical use.

[0031] The results are shown in Table 1.

[0032] [Table 2]

[0033] *1:NR(RSS#3) *2: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.) *3: SAF carbon black (Seast 9 manufactured by Tokai Carbon Co., Ltd., nitrogen adsorption specific surface area (N2SA) = 142 m 2 / g, DBP oil absorption = 115ml / 100g) *4: HAF carbon black (Tokai Carbon Co., Ltd., SEAT 3, nitrogen adsorption specific surface area (N2SA) = 79 m 2 / g, DBP oil absorption = 101ml / 100g) *5: Recycled carbon black 1 (Enrestec product name PB365, DBP oil absorption = 88 ml / 100 g, compressed DBP oil absorption (24M4DBP) = 77 ml / 100 g, ΔDBP = 11 ml / 100 g, N2SA = 76 m 2 / g, IA=95mg / g, N2SA / IA=0.8) *6: Recycled carbon black 2 (product name: CONTINUA 8000, manufactured by Birla Carbon, DBP oil absorption = 104 ml / 100 g, compressed DBP oil absorption (24M4DBP) = 85 ml / 100 g, ΔDBP = 19 ml / 100 g, N2SA = 86 m 2 / g, IA=107mg / g, N2SA / IA=0.8) *7: Regenerated carbon black 3 (product name LN607 manufactured by Shandong Kaiyuan Co., Ltd., DBP oil absorption = 89ml / 100g, compressed DBP oil absorption (24M4DBP) = 70ml / 100g, ΔDBP = 19ml / 100g, N2SA = 69m 2 / g, IA=41mg / g, N2SA / IA=1.7) *8: Recycled carbon black 4 (manufactured by RCB nanotechnologies, product name rCB2.2, DBP oil absorption = 98 ml / 100 g, compressed DBP oil absorption (24M4DBP) = 96 ml / 100 g, ΔDBP = 2 ml / 100 g, N2SA = 102 m 2 / g, IA=86mg / g, N2SA / IA=1.2) *9: Recycled carbon black 5 (LDC product name GCB774G, DBP oil absorption = 97 ml / 100 g, compressed DBP oil absorption (24M4DBP) = 77 ml / 100 g, ΔDBP = 22 ml / 100 g, N2SA = 70 m 2 / g, IA=109mg / g, N2SA / IA=0.6) *10: Recycled carbon black 6 (EcoStar product name FN331, DBP oil absorption = 78 ml / 100 g, compressed DBP oil absorption (24M4DBP) = 62 ml / 100 g, ΔDBP = 16 ml / 100 g, N2SA = 62 m 2 / g, IA=29mg / g, N2SA / IA=2.1) *11: Zinc oxide (Zinc oxide type 3 manufactured by Seido Chemical Industry Co., Ltd.) *12: Stearic acid (NOF Corporation Stearic Acid YR) *13: Anti-aging agent (Flexis SANTOFLEX 6PPD) *14: Oil (Nippon Shell Co., Ltd. Extract No. 4 S) *15: Sulfur (Karuizawa Refinery Co., Ltd. oil refinery processing sulfur) *16: Vulcanization accelerator TBBS (Sansera NS-G manufactured by Sanshin Chemical Industry Co., Ltd.)

[0034] From the results in Table 1, it can be seen that the rubber composition of each example contains diene rubber, carbon black, recycled carbon black, and random polypropylene, and the melting point of the random polypropylene is 110°C or higher and 155°C or lower, and the melt mass flow rate (MFR) measured at a temperature of 230°C and a load of 2.16 kg is 3 g / 10 min or higher. Although the amount of recycled carbon black exceeds 10 parts by mass per 100 parts by mass of the diene rubber, the rubber composition has sufficient breaking strength for practical use. On the other hand, in Comparative Examples 1 and 2, the amount of recycled carbon black added is simply increased, and therefore the breaking strength is reduced. In Comparative Example 3, the melt mass flow rate (MFR) of the random polypropylene measured at a temperature of 230° C. and a load of 2.16 kg was below the lower limit specified in the present invention, and therefore the breaking strength was reduced. In Comparative Examples 4 and 5, the amount of recycled carbon black blended is less than the lower limit specified in the present invention, and therefore although the decrease in breaking strength is suppressed, the results are inferior in terms of recyclability.

[0035] Standard Example 2, Examples 13-14 and Comparative Examples 6-9 The breaking strength was measured by repeating the above "Standard Example 1, Examples 1 to 12, and Comparative Examples 1 to 5" except for changing the blending ratio (parts by mass) as shown in Table 2. In Table 2, the results of Standard Example 2 are expressed as an index, with the result being 100. Note that "Standard Example 2, Examples 13 and 14, and Comparative Examples 6 to 9" were blended and designed with the aim of forming cap treads for heavy-duty tires. The results are shown in Table 2.

[0036] [Table 3]

[0037] From the results in Table 2, it can be seen that the rubber composition of each example contains diene rubber, carbon black, recycled carbon black, and random polypropylene, and the melting point of the random polypropylene is 110°C or higher and 155°C or lower, and the melt mass flow rate (MFR) measured at a temperature of 230°C and a load of 2.16 kg is 3 g / 10 min or higher. Although the amount of recycled carbon black exceeds 10 parts by mass per 100 parts by mass of the diene rubber, the rubber composition has sufficient breaking strength for practical use. On the other hand, in Comparative Examples 6 and 7, the amount of recycled carbon black added was simply increased, and therefore the breaking strength was reduced. In Comparative Example 8, the melt mass flow rate (MFR) of the random polypropylene measured at a temperature of 230° C. and a load of 2.16 kg was below the lower limit specified in the present invention, and therefore the breaking strength was reduced. In Comparative Example 9, the amount of recycled carbon black blended is less than the lower limit specified in the present invention, and therefore, although the decrease in breaking strength is suppressed, it is inferior in terms of recyclability.

[0038] The present invention includes the following embodiments. Embodiment 1: A rubber composition for tires comprising a diene rubber, carbon black, recycled carbon black, and random polypropylene, The random polypropylene has a melting point of 110°C or higher and 155°C or lower, and a melt mass flow rate (MFR) measured at a temperature of 230°C and a load of 2.16 kg of 3 g / 10 min or higher; the amount of the recycled carbon black is more than 10 parts by mass per 100 parts by mass of the diene rubber; A rubber composition for tires. Embodiment 2: the difference (ΔDBP) between the DBP oil absorption and the compressed DBP oil absorption (24M4DBP) of the recycled carbon black is less than 20 ml / 100 g; The nitrogen adsorption specific surface area N2SA (unit: m 2 / g) to the iodine adsorption amount IA (unit: mg / g), N2SA / IA is in the range of 0.8 or more and less than 2.0, 2. The rubber composition for a tire according to embodiment 1, wherein the total amount of the carbon black and the recycled carbon black is 15 to 150 parts by mass per 100 parts by mass of the diene rubber. Embodiment 3: The carbon black has a nitrogen adsorption specific surface area N2SA of 60 to 150 m 2 / g and DBP oil absorption of 100 to 140 ml / 100 g. Embodiment 4: 4. The rubber composition for a tire according to any one of embodiments 1 to 3, wherein the random polypropylene is blended in an amount of 1 to 20 parts by mass per 100 parts by mass of the diene rubber. Embodiment 5 5. The rubber composition for a tire according to any one of embodiments 1 to 4, wherein the random polypropylene is selected from a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, and a propylene-ethylene-1-butene random copolymer. Embodiment 6: 6. The rubber composition for a tire according to any one of embodiments 1 to 5, wherein the amount of the recycled carbon black is 30% by mass or more based on the total amount of the carbon black and the recycled carbon black. Embodiment 7: A tire using the rubber composition for a tire according to any one of embodiments 1 to 6.

Claims

1. A rubber composition for tires comprising a diene rubber, carbon black, recycled carbon black, and random polypropylene, The random polypropylene has a melting point of 110°C or higher and 155°C or lower, and a melt mass flow rate (MFR) measured at a temperature of 230°C and a load of 2.16 kg of 3 g / 10 min or higher; the amount of the recycled carbon black is more than 10 parts by mass per 100 parts by mass of the diene rubber; A rubber composition for tires.

2. the difference (ΔDBP) between the DBP oil absorption and the compressed DBP oil absorption (24M4DBP) of the recycled carbon black is less than 20 ml / 100 g; The nitrogen adsorption specific surface area N of the recycled carbon black ２ SA (unit: m ２ / g) to the iodine adsorption amount IA (unit: mg / g), ２ SA / IA is in the range of 0.8 or more and less than 2.0, 2. The rubber composition for tires according to claim 1, wherein the total amount of the carbon black and the recycled carbon black is 15 to 150 parts by mass per 100 parts by mass of the diene rubber.

3. The nitrogen adsorption specific surface area N of the carbon black ２ SA is 60 to 150m ２ 2. The rubber composition for tires according to claim 1, wherein the rubber composition has a viscosity of 100 to 140 ml / 100 g and a DBP oil absorption of 100 to 140 ml / 100 g.

4. 2. The rubber composition for tires according to claim 1, wherein the random polypropylene is blended in an amount of 1 to 20 parts by mass per 100 parts by mass of the diene rubber.

5. 2. The rubber composition for tires according to claim 1, wherein the random polypropylene is selected from the group consisting of a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, and a propylene-ethylene-1-butene random copolymer.

6. 2. The rubber composition for a tire according to claim 1, wherein the proportion of the recycled carbon black is 30% by mass or more based on the total amount of the carbon black and the recycled carbon black.

7. A tire using the rubber composition for tires according to claim 1.

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