Method for manufacturing rubber composition

Abstract

To provide a method for manufacturing rubber composition by which a rubber composition having satisfactory on-ice grip performance and excellent low rolling resistance can be obtained.SOLUTION: A method for manufacturing a rubber composition in which a rubber component (A), carbon black (B), vulcanization accelerator (C) and foaming agent (D) are formulated. In the rubber component (A), the proportion of natural rubber is 30 mass% or more and 60 mass% or less, the proportion of butadiene rubber is 30 mass% or more and 65 mass% or less, the formulation amount of the carbon black (B) is 20 pts.mass or more for 100 pts.mass of the rubber component (A), the formulation amount of the vulcanization accelerator (C) is 1 pt.mass or more and 4 pts.mass or less for 100 pts.mass of the rubber component (A), and the manufacturing method includes a plurality of steps of kneading steps. On a first kneading step, the rubber component (A), a part of or all of the carbon black (B) and a part of the vulcanization accelerator (C) are formulated, and the foaming agent (D) and a part of the vulcanization accelerator (C) are formulated on a kneading step other than the first step.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a rubber composition.

Background Art

[0002] Conventionally, in tires mainly used in winter such as studless tires, various studies have been made particularly on the tread portion of the tire in order to improve braking performance and driving performance (ice performance) on icy and snowy roads.

[0003] For example, Patent Document 1 discloses a rubber component containing natural rubber, polybutadiene rubber, and styrene-butadiene copolymer rubber in predetermined ratios, and 50 to 90 parts by mass of a filler containing silica with respect to 100 parts by mass of the rubber component, and the distribution ratio (Si distribution ratio) of the polybutadiene rubber and the styrene-butadiene copolymer rubber in the total silica to the phase (SB phase) containing them is 50% by mass or more. By applying such a rubber composition to a tread member of a tire, it has been shown that the ice performance is improved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, in recent years, in connection with the global movement to regulate carbon dioxide emissions due to the increasing interest in environmental issues, the demand for low fuel consumption of automobiles has been increasing. In order to meet such demands, tires are required to reduce rolling resistance.

[0006] However, Patent Document 1 does not particularly discuss rolling resistance, and there is room for improvement in the rubber composition described in Patent Document 1 in terms of improving low rolling resistance in addition to ice performance.

[0007] Therefore, an object of the present invention is to provide a method for producing a rubber composition capable of obtaining a rubber composition having good ice grip performance and excellent low rolling resistance.

Means for Solving the Problems

[0008] As a result of intensive studies to solve the above problems, the present inventor has optimized the composition of each material including the rubber component and optimized the input timing of a vulcanization accelerator or the like when kneading the rubber composition, thereby improving the ice grip performance and low rolling resistance, and has completed the present invention. That is, the gist configuration of the present invention for solving the above problems is as follows.

[0009] [1] A method for producing a rubber composition comprising a rubber component (A), carbon black (B), a vulcanization accelerator (C), and a foaming agent (D), wherein the proportion of the natural rubber in the rubber component (A) is 30% by mass or more and 60% by mass or less, and the proportion of the butadiene rubber is 30% by mass or more and 65% by mass or less, the compounding amount of the carbon black (B) is 20 parts by mass or more with respect to 100 parts by mass of the rubber component (A), the compounding amount of the vulcanization accelerator (C) is 1 part by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the rubber component (A), the production method includes a kneading step in a plurality of stages, in the kneading step of the first stage, a part or all of the rubber component (A), a part or all of the carbon black (B), and a part of the vulcanization accelerator (C) are blended, the foaming agent (D) and a part of the vulcanization accelerator (C) are blended in the kneading step of a stage other than the first stage, A method for producing a rubber composition, characterized by the above. According to the method for producing a rubber composition of the present invention, it is possible to obtain a rubber composition that has good grip performance on ice and also has excellent low rolling resistance.

[0010] [2] The method for producing a rubber composition according to [1], wherein the rubber composition further comprises a C5-based resin, and the amount of the C5-based resin is 5 parts by mass or more and 18 parts by mass or less per 100 parts by mass of the rubber component (A). In this case, the grip performance on ice can be further improved, and the adhesion of the rubber composition can be controlled within a range that does not cause problems in workability.

[0011] [3] The method for producing a rubber composition according to [2], wherein the C5 resin is a hydrogenated C5 resin. In this case, the adhesion can be reduced and the manufacturing workability can be improved.

[0012] [4] The method for producing a rubber composition according to any one of [1] to [3], wherein the blending amount of the foaming agent (D) is 5 parts by mass or more and 12 parts by mass or less per 100 parts by mass of the rubber component (A). In this case, grip performance on ice can be effectively improved.

[0013] [5] The method for producing a rubber composition according to any one of [1] to [4], wherein the rubber composition further comprises a softener, and the softener is blended in an amount of 5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the rubber component (A). In this case, the effect of improving grip performance on ice is increased, and the workability in producing the rubber composition and vulcanized rubber is improved. Effect of the Invention

[0014] According to the present invention, there can be provided a method for producing a rubber composition which is capable of obtaining a rubber composition having good grip performance on ice and excellent low rolling resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present invention will be described. However, the description is intended to be an example of the present invention and is not intended to limit the present invention in any way.

[0016] The compounds described in this specification may be derived partially or entirely from fossil resources, from biological resources such as plant resources, or from recycled resources such as used tires, or may be derived from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0017] (Method of manufacturing rubber composition) The method for producing a rubber composition according to one embodiment of the present invention (hereinafter, sometimes referred to as the "production method of the present embodiment") is a method for producing a rubber composition comprising at least a rubber component (A), carbon black (B), a vulcanization accelerator (C), and a foaming agent (D). In terms of the composition of the rubber composition to be produced, the rubber component (A) contains 30% by mass or more and 60% by mass or less of natural rubber and 30% by mass or more and 65% by mass or less of butadiene rubber. The amount of the carbon black (B) is 20 parts by mass or more per 100 parts by mass of the rubber component (A), and the amount of the vulcanization accelerator (C) is 1 part by mass or more and 4 parts by mass or less per 100 parts by mass of the rubber component (A). Further, the production method of the present embodiment includes a plurality of kneading steps, and is characterized in that in a first kneading step, the rubber component (A), a part or all of the carbon black (B), and a part of the vulcanization accelerator (C) are blended; and the foaming agent (D) (all of it) and a part of the vulcanization accelerator (C) are blended in a kneading step other than the first step.

[0018] Regarding the composition of the rubber composition produced by the production method of this embodiment, the rubber component (A) has a ratio of natural rubber of 30% by mass to 60% by mass and a ratio of butadiene rubber of 30% by mass to 65% by mass, so that the compatibility characteristics of the rubber component (A) are good (particularly, the compatibility of the C5 resin that can be used together is improved), and the hysteresis loss at low temperatures is increased. In addition, in the production method of this embodiment, the amount of carbon black (B) blended is 20 parts by mass or more per 100 parts by mass of the rubber component (A), so that the wear performance that has been reduced by foaming can be improved.

[0019] In the manufacturing method of the present embodiment, a multi-stage kneading process (two or more stages including a first stage) is performed, and in the first stage kneading process, in addition to the rubber component (A) and a part or all of the carbon black (B), a part of the vulcanization accelerator (C) is blended. This enhances the reinforcing properties of the carbon black (B) and improves the mixability of the rubber component (A) and the carbon black (B), which results in a reduction in the hysteresis loss of the resulting rubber composition at room temperature and near high temperature, and a reduction in rolling resistance can be achieved. Furthermore, the rubber elastic modulus at low temperatures is reduced, which increases the ground contact area effective for gripping, and as a result, the grip performance on ice can be improved. In the manufacturing method of the present embodiment, a foaming agent (D) is blended in a kneading process other than the first stage, which allows a plurality of good voids to be formed in the rubber composition after vulcanization (vulcanized rubber). The plurality of voids provides appropriate flexibility, and also functions as a drain to remove water that has sprung up on the ice, improving the grip performance on ice of the tire.

[0020] As described above, according to the manufacturing method of this embodiment, a rubber composition having good grip performance on ice and excellent low rolling resistance can be obtained.

[0021] From the viewpoint of further improving the low rolling resistance of the resulting rubber composition, the maximum temperature in the first kneading step is preferably 140 to 190°C, more preferably 145 to 180°C, and even more preferably 150 to 175°C.

[0022] The kneading time in the first kneading step is preferably 1 to 15 minutes. If the kneading time is 1 minute or more, the reinforcing properties of the carbon black (B) can be sufficiently increased, and if the kneading time is 15 minutes or less, excessive reduction in the molecular weight of the rubber component (A) can be suppressed. From the same viewpoint, and further from the viewpoint of productivity, the kneading time in the first kneading step is more preferably 12 minutes or less, further preferably 9 minutes or less, and particularly preferably 6 minutes or less.

[0023] From the viewpoint of forming a good number of voids, the maximum temperature in the kneading step (kneading step other than the first stage) in which the foaming agent (D) is blended is preferably 90 to 130° C., more preferably 95 to 110° C. The kneading time in the kneading step in which the foaming agent (D) is blended is preferably 1 to 10 minutes.

[0024] The maximum temperature in the kneading step of blending a vulcanizing agent (described later) (typically a kneading step other than the first stage, and preferably the same as the kneading step of blending a foaming agent (D)) is preferably 90 to 130° C., more preferably 95 to 110° C., from the viewpoint of suppressing scorch. The kneading time in the kneading step of blending a vulcanizing agent is preferably 1 to 10 minutes.

[0025] <Rubber component (A)> The rubber component (A) used in the manufacturing method of this embodiment contains at least natural rubber (NR), and the ratio of natural rubber in 100% by mass of the rubber component (A) is 30% by mass or more and 60% by mass or less. In addition, the ratio of natural rubber in 100% by mass of the rubber component (A) is preferably 40% by mass or more, and more preferably 45% by mass or more, from the viewpoint of further improving the compatibility characteristics of the rubber component (A) and further improving the grip performance on ice. On the other hand, the upper limit of the ratio of natural rubber in 100% by mass of the rubber component (A) is preferably 55% by mass or less, and more preferably 52% by mass or less. The natural rubber may be unmodified or modified.

[0026] The origin of the natural rubber (NR) is not particularly limited, and examples thereof include those derived from Hevea brasiliensis, guayule, and Russian dandelion. The natural rubber may be modified natural rubber, and examples of the modified natural rubber include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified natural rubber include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. These natural rubbers may be used alone or in combination of two or more.

[0027] The rubber component (A) used in the manufacturing method of this embodiment contains at least butadiene rubber (BR) in addition to the above-mentioned natural rubber (NR), and the proportion of the butadiene rubber in 100% by mass of the rubber component (A) is 30% by mass or more and 65% by mass or less. If the proportion of the butadiene rubber exceeds 65% by mass, durability performance such as crack resistance and grip performance on ice may deteriorate. In addition, the proportion of the butadiene rubber in 100% by mass of the rubber component (A) is preferably 50% by mass or less, more preferably 45% by mass or less, from the viewpoint of further improving the compatibility characteristics of the rubber component and further improving the grip performance on ice. On the other hand, the lower limit of the proportion of the butadiene rubber in 100% by mass of the rubber component (A) is preferably 33% by mass or more, more preferably 35% by mass or more. The butadiene rubber may be unmodified or modified.

[0028] The rubber component (A) used in the manufacturing method of this embodiment may contain other rubber components other than natural rubber (NR) and butadiene rubber (BR). Examples of other rubber components include isoprene rubber (IR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), polysulfide rubber, silicone rubber, fluororubber, and urethane rubber. These other rubber components may be modified. These other rubber components may be used alone or in combination of two or more. These other rubber components may not be used (i.e., the rubber component may consist only of natural rubber (NR) and butadiene rubber (BR)). In particular, the rubber component (A) may not contain styrene-butadiene rubber (SBR).

[0029] In the production method of this embodiment, the rubber component (A) is compounded in the first kneading step among a plurality of kneading steps.

[0030] <Carbon black (B)> In the manufacturing method of the present embodiment, carbon black (B) is used as a filler. The carbon black (B) is not particularly limited, and examples thereof include carbon blacks of grades FEF, SRF, HAF, ISAF, and SAF. The carbon black (B) may be used alone or in combination of two or more. Among these, carbon black (B) is preferably carbon black of grades HAF, ISAF, or SAF.

[0031] The carbon black (B) may be plant-derived carbon black or recycled carbon black. Examples of plant-derived carbon black include carbon black derived from castor oil and rosin oil. Examples of recycled carbon black include carbon black obtained by pyrolysis of used tires and the like, and carbon black obtained from waste oil.

[0032] The carbon black (B) may be plant-derived carbon black or recycled carbon black. Examples of plant-derived carbon black include those derived from castor oil and rosin oil. Examples of recycled carbon black include carbon black obtained by pyrolysis of used tires and the like, and carbon black obtained from waste oil.

[0033] In the manufacturing method of this embodiment, a part or all of the carbon black (B) is blended in the first kneading step of a multi-stage kneading step. That is, a part of the carbon black (B) may be blended in the first kneading step, and the remaining part may be blended in a kneading step other than the first stage (for example, the second stage). Alternatively, the entire carbon black (B) may be blended in the first kneading step.

[0034] In the manufacturing method of this embodiment, the blending amount (total blending amount) of carbon black (B) is 20 parts by mass or more relative to 100 parts by mass of the rubber component (A). If the blending amount of carbon black (B) is less than 20 parts by mass, the durability of a rubber member (such as a tire) using the obtained rubber composition may be insufficient. In addition, the blending amount of carbon black (B) relative to 100 parts by mass of rubber component (A) is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 45 parts by mass or more, and even more preferably 50 parts by mass or more, from the viewpoint of further improving the durability of a rubber member (such as a tire) using the obtained rubber composition. On the other hand, the upper limit of the blending amount of carbon black (B) relative to 100 parts by mass of rubber component (A) is not particularly limited, but is preferably 120 parts by mass or less, more preferably 110 parts by mass or less, and even more preferably 100 parts by mass or less, from the viewpoint of sufficiently maintaining low rolling resistance.

[0035] The amount of carbon black (B) in the first mixing step is preferably 20 parts by mass or more per 100 parts by mass of the rubber component (A). In this range, the effect of improving the reinforcing property of carbon black (B) by using it in combination with vulcanization accelerator (C), and therefore the effect of improving grip performance on ice and / or low rolling resistance, can be further enhanced. From the same viewpoint, the amount of carbon black (B) in the first mixing step is more preferably 30 parts by mass or more per 100 parts by mass of the rubber component (A), further preferably 40 parts by mass or more, and even more preferably 45 parts by mass or more.

[0036] In addition, when the carbon black (B) is blended in a multi-stage kneading process including a first stage, the blending amount of the carbon black (B) in the kneading processes other than the first stage can be more than 0 part by mass, 3 parts by mass or more, or 6 parts by mass or more, and can be 30 parts by mass or less, 25 parts by mass or less, or 20 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0037] <Silica> In the manufacturing method of the present embodiment, in addition to carbon black (B), silica may be further used as a filler. The silica is not particularly limited, and examples thereof include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. The silica may be used alone or in combination of two or more. Further, the silica may not be used (that is, the filler may consist only of carbon black (B)).

[0038] When silica is used in the manufacturing method of the present embodiment, part or all of the silica can be blended in the kneading step of the first stage among the multiple-stage kneading steps. That is, part of the silica can be blended in the kneading step of the first stage, and the remaining part can be blended in the kneading step of a stage other than the first stage (for example, the second stage). Alternatively, all of the silica can be blended in the kneading step of the first stage.

[0039] When silica is used in the manufacturing method of the present embodiment, the blending amount (total blending amount) of the silica is preferably 5 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the rubber component (A). In this case, the ICE performance and the rolling performance can be improved while maintaining the durability performance.

[0040] <Other fillers> In the manufacturing method of the present embodiment, other fillers other than carbon black (B) and silica may be used as the filler. Examples of the other fillers include aluminum hydroxide, clay, alumina, talc, mica, kaolin, glass balloon, glass beads, calcium carbonate, magnesium carbonate, magnesium hydroxide, magnesium oxide, titanium oxide, potassium titanate, barium sulfate, and the like. The other fillers may be used alone or in combination of two or more. Further, the other fillers may not be used (that is, the filler may consist only of carbon black (B) and silica).

[0041] When using other fillers in the manufacturing method of this embodiment, part or all of the other fillers can be blended in the kneading step of the first stage among the multi-stage kneading steps. That is, for the other fillers, a part of them can be blended in the kneading step of the first stage, and the remaining part can be blended in the kneading step of a stage other than the first stage (for example, the second stage). Alternatively, all of the other fillers can also be blended in the kneading step of the first stage.

[0042] <C5 resin> In the manufacturing method of this embodiment, it is preferable to further blend a C5 resin. In other words, the rubber composition manufactured by the manufacturing method of this embodiment preferably further contains a C5 resin. Among resins, the C5 resin has high compatibility with the rubber component (A) having a predetermined composition in this embodiment. Therefore, by further blending the C5 resin, the ice grip performance can be further improved. The C5 resin may be used alone or in combination of two or more.

[0043] In this specification, the "C5 resin" refers to a resin obtained by polymerizing a C5 fraction. The C5 fraction usually includes olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, 3-methyl-1,2-butadiene.

[0044] Examples of the C5 resin include aliphatic hydrocarbon resins and alicyclic hydrocarbon resins. Examples of aliphatic hydrocarbon resins include petroleum resins produced by polymerizing 1,3-pentadiene, which is a C5 petroleum fraction, as a main raw material. For example, the product names of the "Quinton 100" series (A100, B170, K100, M100, R100, N295, U190, S100, D100, U185, P195N, etc.) manufactured by Nippon Zeon Co., Ltd. can be mentioned. In addition, as petroleum resins produced by polymerizing other C5 petroleum fractions, the product names of the "Escorez" series (1102, 1202(U), 1304, 1310, 1315, 1395, etc.) manufactured by ExxonMobil and the product names of the "Hi-Resin" series (G-100X, -T-100X, -C-110X, -R-100X, etc.) manufactured by Mitsui Chemicals, Inc. can be mentioned.

[0045] Examples of alicyclic hydrocarbon resins include cyclopentadiene-based petroleum resins produced using cyclopentadiene extracted from a C5 fraction as a main raw material and dicyclopentadiene-based petroleum resins produced using dicyclopentadiene in a C5 fraction as a main raw material. As the above cyclopentadiene-based petroleum resins, the product names of the "Quinton 1000" series (1325, 1345, etc.) manufactured by Nippon Zeon Co., Ltd. can be mentioned. In addition, as the above dicyclopentadiene-based petroleum resins, the product names of the "Marcarez M" series (M-890A, M-845A, M-990A, etc.) of Maruzen Petrochemical Co., Ltd. can be mentioned.

[0046] The above C5-based resin is preferably a hydrogenated C5-based resin. In this case, since the hydrogenated C5-based resin has higher compatibility with the rubber component (A), elution from the rubber component can be suppressed, and the adhesion can be reduced and the manufacturing workability can be improved as compared with non-hydrogenated C5-based resins.

[0047] When using a C5-based resin in the manufacturing method of this embodiment, all of the C5-based resin can be blended in the kneading step of the first stage among the multi-stage kneading steps. Alternatively, a part of the C5-based resin can be blended in the kneading step of the first stage, and the remaining part can be blended in the kneading step of a stage other than the first stage (for example, the second stage).

[0048] When using a C5 resin in the manufacturing method of this embodiment, the blending amount (total blending amount) of the C5 resin is preferably 5 parts by mass or more and 18 parts by mass or less with respect to 100 parts by mass of the rubber component (A). If the blending amount of the C5 resin is 5 parts by mass or more, a further improvement effect on ice grip performance can be obtained. If it is 18 parts by mass or less, the adhesion of the rubber composition can be suppressed within a range where there is no problem with workability. From the same viewpoint, the blending amount of the C5 resin with respect to 100 parts by mass of the rubber component (A) is more preferably 8 parts by mass or more, still more preferably 12 parts by mass or more, and more preferably 16 parts by mass or less.

[0049] <Softening agent> In the manufacturing method of this embodiment, it is preferable to further blend a softening agent. In other words, the rubber composition produced by the manufacturing method of this embodiment preferably further contains a softening agent. A softening agent is a compounding agent that has the effect of softening the unvulcanized rubber composition and the vulcanized rubber. By further blending a softening agent, the ice grip performance can be further improved. Note that the softening agent is usually liquid at 25 °C (room temperature).

[0050] The softening agent is not particularly limited, and examples include oils and liquid polymers. Among these, oils are preferred. These softening agents may be used alone or in combination of two or more.

[0051] Examples of the oil include petroleum-based oils such as aroma oils, paraffin oils, and naphthene oils; and plant-based oils such as palm oil, castor oil, cottonseed oil, and soybean oil. Among these, petroleum-based oils are preferred as the oil.

[0052] Examples of the liquid polymer include liquid polybutadiene, liquid polyisoprene, and liquid polystyrene-butadiene. The liquid polymer preferably has a weight average molecular weight of 5,000 to 100,000. In addition, in this specification, it is assumed that the above liquid polymer is not included in the rubber component (A) described above.

[0053] When using a softening agent in the production method of this embodiment, all of the softening agent can be compounded in the kneading step of the first stage among the plurality of stages of kneading steps. Alternatively, a part of the softening agent can be compounded in the kneading step of the first stage, and the remaining part can be compounded in the kneading step of a stage other than the first stage (for example, the second stage).

[0054] When using a softening agent in the production method of this embodiment, the compounding amount (total compounding amount) of the softening agent is preferably 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the rubber component (A). If the compounding amount of the above softening agent is 5 parts by mass or more, the effect of improving the ice grip performance becomes greater. On the other hand, if it is 30 parts by mass or less, particularly when adding resin, the viscosity of the rubber composition decreased by the resin can be adjusted (increased), and the production workability of the rubber composition and the vulcanized rubber is improved. From the same viewpoint, the compounding amount of the above softening agent with respect to 100 parts by mass of the rubber component (A) is more preferably 10 parts by mass or more, further preferably 15 parts by mass or more, more preferably 25 parts by mass or less, and further preferably 22 parts by mass or less.

[0055] <Vulcanization accelerator (C)> In the production method of this embodiment, a vulcanization accelerator (C) is used. Examples of the vulcanization accelerator (C) include sulfenamides, thiazoles, thiurams, thioureas, dithiocarbamates, and xanthates. The vulcanization accelerator (C) may be used alone or in combination of two or more.

[0056] Examples of the sulfenamides include N-cyclohexyl-2-benzothiazolylsulfenamide, N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N-methyl-2-benzothiazolylsulfenamide, N-ethyl-2-benzothiazolylsulfenamide, N-propyl-2-benzothiazolylsulfenamide, N-butyl-2-benzothiazolylsulfenamide, N-pentyl-2-benzothiazolylsulfenamide, N-hexyl-2-benzothiazolylsulfenamide, N-pentyl-2-benzothiazolylsulfenamide, N-octyl-2-benzothiazolylsulfenamide, N-2-ethylhexyl-2-benzothiazolylsulfenamide, N-decyl-2-benzothiazolylsulfenamide, N-dodecyl-2-benzothiazolylsulfenamide, N-stearyl-2-benzothiazolylsulfenamide, N,N-dimethyl-2-benzothiazolylsulfenamide, N,N-diethyl-2-benzothiazolylsulfenamide, N,N-dipropyl-2-benzothiazolylsulfenamide, N,N-dibutyl-2-benzothiazolylsulfenamide, N,N-dipentyl-2-benzothiazolylsulfenamide, N,N-dihexyl-2-benzothiazolylsulfenamide, N,N-dipentyl-2-benzothiazolylsulfenamide, N,N-dioctyl-2-benzothiazolylsulfenamide, N,N-di-2-ethylhexylbenzothiazolylsulfenamide, N-decyl-2-benzothiazolylsulfenamide, N,N-didodecyl-2-benzothiazolylsulfenamide, N,N-distearyl-2-benzothiazolylsulfenamide, and the like. Among these, from the viewpoint of reactivity with carbon black (B), N-cyclohexyl-2-benzothiazolylsulfenamide and N-tert-butyl-2-benzothiazolylsulfenamide are preferred.

[0057] Examples of thiazoles include 2-mercaptobenzothiazole, bis(4-methylbenzothiazolyl-2)-disulfide, di-2-benzothiazolyldisulfide, zinc salt of 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, 2-(N,N-diethylthiocarbamoylthio)benzothiazole, 2-(4'-morpholinodithio)benzothiazole, 4-methyl-2-mercaptobenzothiazole, di-(4-methyl-2-benzothiazolyl)disulfide, 5-chloro-2-mercaptobenzothiazole, sodium 2-mercaptobenzothiazole, 2-mercapto-6-nitrobenzothiazole, 2-mercapto-naphtho[1,2-d]thiazole, 2-mercapto-5-methoxybenzothiazole, 6-amino-2-mercaptobenzothiazole, and the like. Among these, from the viewpoint of reactivity with carbon black (B), 2-mercaptobenzothiazole, bis(4-methylbenzothiazolyl-2)-disulfide, and di-2-benzothiazolyldisulfide are preferred.

[0058] Examples of thiurams include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrapropylthiuram disulfide, tetraisopropylthiuram disulfide, tetrabutylthiuram disulfide, tetrapentylthiuram disulfide, tetrahexylthiuram disulfide, tetraheptylthiuram disulfide, tetraoctylthiuram disulfide, tetranonylthiuram disulfide, tetradecylthiuram disulfide, tetradodecylthiuram disulfide, tetrastearylthiuram disulfide, tetrabenzylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, tetramethylthiuram monosulfide, tetraethylthiuram monosulfide, tetrapropylthiuram monosulfide, tetraisopropylthiuram monosulfide, tetrabutylthiuram monosulfide, tetrapentylthiuram monosulfide, tetrahexylthiuram monosulfide, tetraheptylthiuram monosulfide, tetraoctylthiuram monosulfide, tetranonylthiuram monosulfide, tetradecylthiuram monosulfide, tetradodecylthiuram monosulfide, tetrastearylthiuram monosulfide, tetrabenzylthiuram monosulfide, dipentamethylenethiuram tetrasulfide, etc. Among these, from the viewpoint of reactivity with carbon black (B), tetrakis(2-ethylhexyl)thiuram disulfide and tetrabenzylthiuram disulfide are preferred.

[0059] Examples of thioureas include thiourea, N,N'-diphenylthiourea, trimethylthiourea, N,N'-diethylthiourea, N,N'-dimethylthiourea, N,N'-dibutylthiourea, ethylenethiourea, N,N'-diisopropylthiourea, N,N'-dicyclohexylthiourea, 1,3-di(o-tolyl)thiourea, 1,3-di(p-tolyl)thiourea, 1,1-diphenyl-2-thiourea, 2,5-dithiobiurea, guanylthiourea, 1-(1-naphthyl)-2-thiourea, 1-phenyl-2-thiourea, p-tolylthiourea, o-tolylthiourea, etc. Among these, from the viewpoint of reactivity with carbon black (B), thiourea, N,N'-diethylthiourea, trimethylthiourea, N,N'-diphenylthiourea, and N,N'-dimethylthiourea are preferable.

[0060] Examples of dithiocarbamates include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dipropyldithiocarbamate, zinc diisopropyldithiocarbamate, zinc dibutyldithiocarbamate, zinc dipentyldithiocarbamate, zinc dihexyldithiocarbamate, zinc diheptyldithiocarbamate, zinc dioctyldithiocarbamate, zinc di(2-ethylhexyl)dithiocarbamate, zinc didecyldithiocarbamate, zinc didodecyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc dibenzyldithiocarbamate, copper dimethyldithiocarbamate, copper diethyldithiocarbamate, copper dipropyldithiocarbamate, copper diisopropyldithiocarbamate, copper dibutyldithiocarbamate, copper dipentyldithiocarbamate, copper dihexyldithiocarbamate, copper diheptyldithiocarbamate, copper dioctyldithiocarbamate, copper di(2-ethylhexyl)dithiocarbamate, copper didecyldithiocarbamate,Copper didodecyldithiocarbamate, copper N-pentamethylenedithiocarbamate, copper dibenzyldithiocarbamate, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, sodium dipropyldithiocarbamate, sodium diisopropyldithiocarbamate, sodium dibutyldithiocarbamate, sodium dipentyldithiocarbamate, sodium dihexyldithiocarbamate, sodium diheptyldithiocarbamate, sodium dioctyldithiocarbamate, sodium di(2-ethylhexyl)dithiocarbamate, sodium didodecyldithiocarbamate, sodium N-pentamethylenedithiocarbamate, sodium dibenzyldithiocarbamate, ferric dimethyldithiocarbamate, ferric diethyldithiocarbamate, ferric dipropyldithiocarbamate, ferric diisopropyldithiocarbamate, ferric dibutyldithiocarbamate, ferric dipentyldithiocarbamate, ferric dihexyldithiocarbamate, ferric diheptyldithiocarbamate, ferric dioctyldithiocarbamate, ferric di(2-ethylhexyl)dithiocarbamate, ferric didodecyldithiocarbamate, ferric N-pentamethylenedithiocarbamate, ferric dibenzyldithiocarbamate, etc. may be mentioned. Among these, from the viewpoint of reactivity with carbon black (B), zinc dibenzyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc dimethyldithiocarbamate and copper dimethyldithiocarbamate are preferable.

[0061] Examples of xanthates include zinc methylxanthate, zinc ethylxanthate, zinc propylxanthate, zinc isopropylxanthate, zinc butylxanthate, zinc pentylxanthate, zinc hexylxanthate, zinc heptylxanthate, zinc octylxanthate, zinc 2-ethylhexylxanthate, zinc decylxanthate, zinc dodecylxanthate, potassium methylxanthate, potassium ethylxanthate, potassium propylxanthate, potassium isopropylxanthate, potassium butylxanthate, potassium pentylxanthate, potassium hexylxanthate, potassium heptylxanthate, potassium octylxanthate, potassium 2-ethylhexylxanthate, potassium decylxanthate, potassium dodecylxanthate, sodium methylxanthate, sodium ethylxanthate, sodium propylxanthate, sodium isopropylxanthate, sodium butylxanthate, sodium pentylxanthate, sodium hexylxanthate, sodium heptylxanthate, sodium octylxanthate, sodium 2-ethylhexylxanthate, sodium decylxanthate, sodium dodecylxanthate, and the like. Among these, zinc isopropylxanthate is preferred from the viewpoint of reactivity with carbon black (B).

[0062] In the manufacturing method of the present embodiment, a part of the vulcanization accelerator (C) is compounded in the kneading step of the first stage among the multi-stage kneading steps. In the prior art, the vulcanization accelerator was compounded together with a vulcanizing agent such as sulfur in the productive kneading stage after the non-productive kneading. However, in the manufacturing method of the present embodiment, in order to obtain a rubber composition having desired properties, a part of the vulcanization accelerator (C) is compounded in the kneading step of the first stage. That is, in the manufacturing method of the present embodiment, a part of the vulcanization accelerator (C) is compounded in the kneading step of the first stage, and the remaining part is compounded in the kneading step of a stage other than the first stage (for example, the final stage). When such a vulcanization accelerator (C) is compounded in the kneading step of the first stage, it contributes to the improvement of the reinforcing property of the carbon black (B), and when it is compounded in the kneading step of the final stage, it contributes to the promotion of sulfur vulcanization.

[0063] In the manufacturing method of the present embodiment, the compounding amount (total compounding amount) of the vulcanization accelerator (C) is 1 part by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the rubber component (A). If the compounding amount of the vulcanization accelerator (C) is less than 1 part by mass, there is a risk that the effect of compounding the vulcanization accelerator (C) cannot be sufficiently obtained. Further, if the compounding amount of the vulcanization accelerator (C) exceeds 4 parts by mass, it causes an increase in the elastic modulus of the rubber at low temperatures and a decrease in ICE performance.

[0064] Also, the compounding amount of the vulcanization accelerator (C) in the kneading step of the first stage is preferably 0.5 part by mass or more and 2.5 parts by mass or less with respect to 100 parts by mass of the rubber component (A). In this range, the reinforcing property of the carbon black (B) can be improved effectively and efficiently. From the same viewpoint, the compounding amount of the vulcanization accelerator (C) in the kneading step of the first stage is more preferably 0.8 part by mass or more, and more preferably 2 parts by mass or less with respect to 100 parts by mass of the rubber component (A).

[0065] In addition, the compounding amount of the vulcanization accelerator (C) in the kneading step of stages other than the first stage (for example, the final stage) can be more than 0 part by mass, 0.2 part by mass or more, or 0.4 part by mass or more with respect to 100 parts by mass of the rubber component (A), and can also be 2.5 parts by mass or less, 2.0 parts by mass or less, or 1.6 parts by mass or less.

[0066] <Blowing agent (D)> In the production method of this embodiment, a blowing agent (D) is used. Examples of the blowing agent (D) include azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), dinitrosopentastyrenetetramine, benzenesulfonyl hydrazide derivatives, p,p'-oxybisbenzenesulfonyl hydrazide (OBSH), ammonium bicarbonate that generates carbon dioxide, sodium bicarbonate, ammonium carbonate, nitrososulfonyl azo compounds that generate nitrogen, N,N'-dimethyl-N,N'-dinitrosophthalamide, toluenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide, p,p'-oxybisbenzenesulfonyl semicarbazide, and the like. These blowing agents may be used alone or in combination of two or more.

[0067] In the production method of this embodiment, the blowing agent (D) is compounded in the kneading step of stages other than the first stage, particularly in the kneading step of the final stage or the kneading step of the stage immediately before the final stage. That is, the blowing agent (D) is not compounded in the kneading step of the first stage. In addition, the blowing agent (D) can be compounded in the kneading step of the stage where the remaining part of the vulcanization accelerator (C) is compounded.

[0068] In the production method of this embodiment, the compounding amount of the blowing agent (D) is preferably 5 parts by mass or more and 12 parts by mass or less with respect to 100 parts by mass of the rubber component (A). Within this range, a plurality of good voids can be effectively and efficiently formed in the vulcanized rubber composition (vulcanized rubber) after vulcanization, and the ice grip performance can be effectively improved.

[0069] <Blowing aid> In the production method of the present embodiment, in addition to the foaming agent (D), it is preferable to further blend a foaming aid. By using the foaming aid in combination, the foaming reaction can be promoted, the completion degree of the reaction can be increased, and unnecessary deterioration over time can be suppressed. Examples of the foaming aid include urea, zinc stearate, zinc benzenesulfinate, zinc white, etc. These foaming aids may be used alone or in combination of two or more.

[0070] When using a foaming aid in the production method of the present embodiment, the foaming aid can be blended in the kneading step of blending the foaming agent (D).

[0071] <Vulcanizing agent> In the production method of the present embodiment, typically, a vulcanizing agent is blended. As the vulcanizing agent, sulfur is usually used, and examples include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, etc.

[0072] The above vulcanizing agent can typically be blended in the kneading step at a stage other than the first stage, particularly in the kneading step of the final stage. Also, the above vulcanizing agent is preferably blended in the kneading step of blending the foaming agent (D).

[0073] The blending amount of the above vulcanizing agent is preferably 0.1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the rubber component (A). If the blending amount of the vulcanizing agent is 0.1 part by mass or more, vulcanization can proceed sufficiently, and if it is 10 parts by mass or less, the aging resistance of the vulcanized rubber can be suppressed. From the same viewpoint, the blending amount of the vulcanizing agent with respect to 100 parts by mass of the rubber component (A) is more preferably 0.5 part by mass or more, even more preferably 1 part by mass or more, and more preferably 8 parts by mass or less, even more preferably 6 parts by mass or less.

[0074] <Other components> In the manufacturing method of the present embodiment, other components may be blended in addition to those described above. Examples of such other components include silane coupling agents, resins other than C5-based resins, anti-aging agents, zinc white, stearic acid, and other compounding agents commonly used in the rubber industry. They can be appropriately selected within the scope not departing from the object of the present invention and blended in an appropriate amount at an appropriate timing. Moreover, commercially available products can be preferably used as these compounding agents.

[0075] <Uses of the rubber composition> The rubber composition produced by the manufacturing method of the present embodiment has good ice grip performance and excellent low rolling resistance. Therefore, the above rubber composition is preferably used as a rubber composition for at least one type of tire member selected from the tread part (tread contact part, base tread part, etc.), belt part, and case part (particularly, belt coating rubber, inter-belt sheet, belt end covering rubber, belt under-cushion rubber, tread under-cushion rubber, carcass ply coating rubber, and sidewall) of various pneumatic tires for passenger cars, small trucks, light passenger cars, light trucks, and large vehicles (for trucks, buses, construction vehicles, etc.).

[0076] Note that, excluding components such as the foaming agent (D) that decomposes by heating, the ratio (composition) of the blending amounts of the respective components in the manufacturing method of the present embodiment substantially corresponds to the composition of the respective components of the rubber composition produced by the manufacturing method of the present embodiment.

Examples

[0077] Hereinafter, the present invention will be described in more detail with reference to examples. However, these examples are for the purpose of illustrating the present invention and do not limit the present invention in any way.

[0078] According to the compounding formulations at each stage shown in Table 1, kneading was carried out using a Banbury mixer to prepare a rubber composition (vulcanized rubber). In the kneading process of the first stage, the maximum discharge temperature was adjusted to 160 °C and the kneading time was adjusted to 2 - 3 minutes. In the kneading process of the second stage, the maximum discharge temperature was adjusted to 105 °C and the kneading time was adjusted to 1 - 2 minutes. Subsequently, the rubber composition was vulcanized at 145 °C for 33 minutes to obtain a vulcanized rubber in which a plurality of voids derived from the foaming agent were formed.

[0079] (Ice grip performance) Regarding the obtained rubber composition (vulcanized rubber), using a spectrometer manufactured by Ueshima Seisakusho, the storage elastic modulus (E') and loss tangent (tanδ) at a temperature of -20 °C were measured under the conditions of an initial strain of 1%, an initial input of 150 μm, and a frequency of 52 Hz. Taking the measured value of Comparative Example 1 as 100, the measured value of Example 1 was indexed. Also, taking the measurement of Comparative Example 2 as 100, the measured value of Example 2 was indexed. The results are shown in Table 1. The larger these values, especially the value of the storage elastic modulus (E') at a temperature of -20 °C, the better the ice grip performance.

[0080] (Low rolling resistance) Regarding the obtained rubber composition (vulcanized rubber), using a spectrometer manufactured by Ueshima Seisakusho, the loss tangent (tanδ) at a temperature of 40 °C was measured under the conditions of an initial strain of 1%, an initial input of 150 μm, and a frequency of 52 Hz. Taking the measured value of Comparative Example 1 as 100, the measured value of Example 1 was indexed. Also, taking the measurement of Comparative Example 2 as 100, the measured value of Example 2 was indexed. The results are shown in Table 1. The smaller the value, the better the low rolling resistance.

[0081]

Table 1

[0082] *1 Natural rubber: TSR20 *2 Butadiene rubber: manufactured by Ube Elastomer Co., Ltd., "UBEPOL BR150L" *3 Carbon black: HS - HAF grade *4 Silica: Manufactured by Tosoh Silica Corporation, "Nips Seal AQ" *5 Plasticizer: Oil, manufactured by ENEOS Corporation, "Super Oil Y22" *6 C5 resin 1: Hydrogenated C5 resin, manufactured by Synthomer Adhesive Technologies LLC, "Impera (registered trademark) E1780" *7 C5 resin 2: Manufactured by Mitsui Chemicals, Inc., "Hi-Lets T500X" *8 Vulcanization accelerator: Manufactured by Sanshin Chemical Industry Co., Ltd., "Sunceler CM-G" (N-cyclohexyl-2-benzothiazolylsulfenamide), manufactured by NOCIL LIMITED, "PILCURE MBTS" (di-2-benzothiazolyldisulfide) *9 Blowing agent 1: Azodicarbonimide (ADCA) *10 Blowing agent 2: Dinitrosopentamethylenetetramine (DPT)

[0083] From Table 1, it can be seen that the rubber composition of the example obtained according to the production method of the present invention has greatly improved ice grip performance and low rolling resistance in comparison with the rubber composition of the comparative example.

Industrial Applicability

[0084] According to the present invention, it is possible to provide a method for producing a rubber composition capable of obtaining a rubber composition having good ice grip performance and excellent low rolling resistance.

Claims

1. A method for manufacturing a rubber composition containing a rubber component (A), carbon black (B), a vulcanization accelerator (C), and a blowing agent (D), wherein the rubber component (A) has a natural rubber proportion of 30% by mass or more and 60% by mass or less, and a butadiene rubber proportion of 30% by mass or more and 65% by mass or less, the compounding amount of the carbon black (B) is 20 parts by mass or more with respect to 100 parts by mass of the rubber component (A), the compounding amount of the vulcanization accelerator (C) is 1 part by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the rubber component (A), the manufacturing method includes a kneading process in multiple stages, in the kneading process of the first stage, the rubber component (A), part or all of the carbon black (B), and part of the vulcanization accelerator (C) are compounded, the blowing agent (D) and part of the vulcanization accelerator (C) are compounded in the kneading process of stages other than the first stage, characterized in that it is a method for manufacturing a rubber composition.

2. The rubber composition further contains a C ５ -based resin, and the compounding amount of the C ５ -based resin is 5 parts by mass or more and 18 parts by mass or less with respect to 100 parts by mass of the rubber component (A). The method for producing a rubber composition according to claim 1.

3. The above-mentioned C ５ -based resin is a hydrogenated C ５ -based resin, and the method for producing a rubber composition according to claim 2.

4. The method for manufacturing a rubber composition according to any one of Claims 1 to 3, wherein the compounding amount of the blowing agent (D) is 5 parts by mass or more and 12 parts by mass or less with respect to 100 parts by mass of the rubber component (A).

5. The method for manufacturing a rubber composition according to any one of Claims 1 to 3, wherein the rubber composition further contains a softening agent, and the compounding amount of the softening agent is 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the rubber component (A).

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