Silicone compound graft copolymer and rubber composition for tires comprising the same

Abstract

The present invention aims to obtain a modifier suitable for obtaining a lubricating oil, a paint, an adhesive, or the like, which generates less particles and has more excellent smoothness, and to obtain a rubber composition for tires suitable for obtaining a tire having both excellent braking performance and fuel consumption performance. The present invention relates to a silicone compound graft copolymer (X) characterized by containing a main chain portion from an ethylene-α-olefin copolymer (A) and a graft portion from an organic silicon compound (B) containing one or more unsaturated groups, and a rubber composition for tires characterized by containing the silicone compound graft copolymer (X) in a range of 1 to 30 parts by mass with respect to 100 parts by mass of a diene-based rubber containing an aromatic vinyl-conjugated diene copolymer rubber.

Description

Technical Field

[0001] This invention relates to organosilicon graft copolymers and tire rubber compositions comprising the copolymers that exhibit excellent fuel efficiency and braking performance suitable for pneumatic tires.

[0002] More specifically, the invention relates to an organosilicon graft copolymer that provides excellent smoothness when a composition containing the graft copolymer is applied to a substrate when the graft copolymer is used as a modifier for polymers such as resins and elastomers. Background Technology

[0003] Previously, modified olefin polymers obtained by grafting and copolymerizing various unsaturated silane compounds (organosilicon compounds) into high molecular weight olefin polymers such as polyethylene and polypropylene were used as resin modifiers, adhesive agents, and for other applications.

[0004] In particular, in the field of compounding technology of elastomers such as rubber-like polymers, attempts have been made to provide rubber-like polymer compositions with excellent weather resistance, aging resistance and excellent rubber elasticity by compounding ethylene-α-olefin or ethylene-α-olefin copolymers into silicone-containing rubber-like polymers. However, it is known that when only the two are compounded, there is a disadvantage that the mechanical properties of the resulting composition are reduced.

[0005] As a method to improve the above-mentioned shortcomings, a liquid-modified ethylene-based random copolymer is proposed as a modifier, which is a liquid-modified ethylene-based random copolymer formed by grafting an unsaturated silane compound component with 2 to 20 carbon atoms onto an ethylene-based random copolymer composed of ethylene and α-olefins with 3 to 20 carbon atoms. The liquid-modified ethylene-based random copolymer is characterized by: (i) the ethylene content of the ethylene-based random copolymer is in the range of 25 to 75 mol%, and the α-olefin content is in the range of 25 to 75 mol%; (ii) the grafting ratio of the unsaturated silane compound component is in the range of 0.2 to 300 parts by weight relative to 100 parts by weight of the ethylene-based random copolymer; and (iii) the intrinsic viscosity [η] of the liquid-modified ethylene-based random copolymer measured in naphthalene at 135°C is in the range of 0.01 to 1.5 d / g (Patent Document 1).

[0006] On the other hand, depending on the application, it is desirable to include a composition containing a modifier that produces fewer particles and has better smoothness.

[0007] In addition, styrene-butadiene copolymer rubber (SBR) is commonly used as the rubber material for automobile tire treads. For automobile tires, excellent braking performance is required from a safety perspective. In recent years, due to the increasing demand for low fuel consumption in automobiles, research has also focused on improving fuel efficiency in tires. In low-fuel-consumption tires, silica is typically incorporated into the rubber composition of the tire tread to improve braking performance. However, silica has a tendency to aggregate, and aggregated silica contributes to increased rolling resistance (i.e., worsened fuel consumption). Therefore, silane coupling agents are incorporated as dispersants.

[0008] In Patent Document 2, in order to further improve fuel efficiency, a rubber composition containing diene rubber, acid-modified polyolefin and polyolefin was proposed for the purpose of dispersing silica.

[0009] However, it is known that if the ethylene-α-olefin copolymer modified with unsaturated carboxylic acids as proposed in Patent Document 2 is used, problems such as increased viscosity and deterioration of extrudability will arise during molding, raising concerns about reduced braking performance of the resulting tire.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Publication No. 6-2791

[0013] Patent Document 2: Japanese Patent Application Publication No. 2016-030800 Summary of the Invention

[0014] The problem that the invention aims to solve

[0015] The purpose of this invention is to obtain modifiers suitable for producing lubricants, coatings, adhesives, etc., with less particle generation and better smoothness.

[0016] Furthermore, the object of the present invention is to obtain a tire rubber composition suitable for obtaining tires with both excellent braking performance and fuel efficiency.

[0017] Methods for solving problems

[0018] That is, the present invention relates to the following [1] to

[11] . [1]

[0020] The organosilicon graft copolymer (X) is characterized by comprising a main chain portion from an ethylene-α-olefin copolymer (A) and a graft portion from an organosilicon compound (B) containing one or more unsaturated groups. [2]

[0022] The organosilicon graft copolymer (X) as described in item [1] is characterized in that the main chain portion of the ethylene-α-olefin copolymer (A) is an ethylene-α-olefin copolymer (A) with a weight-average molecular weight (Mw) in the range of 2,000 to 14,000, a number-average molecular weight (Mn) in the range of 1,600 to 7,000, and a molecular weight distribution (Mw / Mn) in the range of 1.4 to 2.1. [3]

[0024] The organosilicon graft copolymer (X) as described in item [1] or [2] is characterized in that the main chain portion of the ethylene-α-olefin copolymer (A) is an ethylene-α-olefin copolymer (A) in the range of 41 to 48% by mass of ethylene-derived components (wherein the total amount of the ethylene-derived components and the α-olefin-derived components is set to 100% by mass). [4]

[0026] The organosilicon compound graft copolymer (X) as described in any one of items [1] to [3] is characterized in that the mass of the graft portion from the organosilicon compound (B) is 1% or more and less than 100% [the total mass of the main chain portion and the graft portion is set to 100% by mass]. [5]

[0028] The organosilicon compound graft copolymer (X) as described in any one of items [1] to [4] is characterized in that the organosilicon compound (B) is vinyltrimethoxysilane. [6]

[0030] The organosilicon graft copolymer (X) as described in item [1], wherein the organosilicon graft copolymer (X) has a weight-average molecular weight (Mw) in the range of 1,800 to 13,000, a number-average molecular weight (Mn) in the range of 1,500 to 6,500, and a molecular weight distribution (Mw / Mn) in the range of 1.4 to 2.1. [7]

[0032] The organosilicon graft copolymer (X) as described in any one of items [1] to [6] is characterized in that the content of the following polymeric component in the organosilicon graft copolymer (X) is further 0 to 0.3% by mass, said polymeric component being defined as a component whose molecular weight M, determined by GPC, has a peak in the range defined by 5 ≤ LogM ≤ 6. [8]

[0034] A rubber composition for tires, characterized in that, relative to 100 parts by weight of a diene-based rubber comprising an aromatic vinyl-conjugated diene copolymer, it comprises, in the range of 1 to 30 parts by weight of the organosilicon graft copolymer (X) described in item [1]. [9]

[0036] The tire rubber composition as described in item [8] is characterized in that it further comprises an inorganic filler in the range of 5 to 150 parts by weight.

[10]

[0038] The tire rubber composition as described in item [9], wherein the inorganic filler is silicon dioxide.

[11]

[0040] The tire rubber composition as described in any one of items [8] to

[10] is characterized in that the diene rubber is a mixture of SBR and BR containing SBR as an aromatic vinyl-conjugated diene copolymer rubber and containing the SBR and BR in a ratio of SBR / BR = 100 / 0 to 1 / 99 (mass ratio).

[0041] Invention Effects

[0042] The organosilicon graft copolymer (X) of the present invention does not produce particles. Therefore, by using the organosilicon graft copolymer (X) as a modifier, lubricants, coatings, adhesives and the like with excellent smoothness can be obtained.

[0043] The rubber composition for tires of the present invention has a large tanδ at 0°C and a small tanδ (fading rate) at 60°C, thus enabling the formation of tires with excellent braking performance and fuel consumption performance. Detailed Implementation

[0044] Ethylene-α-olefin copolymer (A)

[0045] The ethylene-α-olefin copolymer (A) forming the main chain of the organosilicon graft copolymer (X) of the present invention is a copolymer of ethylene and α-olefin. The α-olefin constituting the ethylene-α-olefin copolymer (A) is usually an α-olefin with 3 to 20 carbon atoms. Specifically, examples include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene. Among these, propylene, 1-butene, 1-hexene, and 1-octene, which have 3 to 8 carbon atoms, are preferred, and propylene is particularly preferred.

[0046] For the ethylene-α-olefin copolymer (A) of the present invention, it is preferred that the ethylene-derived component is in the range of 39 to 50% by mass, more preferably 41 to 48% by mass, and the α-olefin-derived component is in the range of 50 to 61% by mass, more preferably 52 to 59% by mass (wherein the total amount of the ethylene-derived component and the α-olefin-derived component is set to 100% by mass).

[0047] For the ethylene-α-olefin copolymer (A) of the present invention, it is preferred that the weight-average molecular weight (Mw) is in the range of 2,000 to 14,000, more preferably 2,200 to 13,500, the number-average molecular weight (Mn) is in the range of 1,400 to 7,000, more preferably 1,650 to 6,800, and the molecular weight distribution (Mw / Mn) is in the range of 1.4 to 2.1, more preferably 1.5 to 2.0.

[0048] The ethylene-α-olefin copolymer (A) that meets the above preferred range can produce a coating with excellent surface smoothness when the copolymer (A) is formulated into a coating.

[0049] The content of ethylene-derived components (ethylene content (mass %)), Mn, etc. of the ethylene-α-olefin copolymer (A) involved in this invention are determined by the following method.

[0050] <Ethylene content (mass %)>

[0051] use 13 The C-NMR method, using the following apparatus and conditions, is used to determine the ethylene content (mass %) of ethylene-α-olefin copolymers.

[0052] An ECP500 nuclear magnetic resonance spectrometer (JEOL Ltd.) was used, with a mixed solvent of o-dichlorobenzene / deuterated benzene (80 / 20 volume %) as the solvent. The sample concentration was 55 mg / 0.6 mL, the measurement temperature was 120 °C, and the observed nuclei were... 13 C(125MHz), the sequence was single-pulse proton decoupling, the pulse width was 4.7μs (45° pulse), the repetition time was 5.5 seconds, the cumulative number of times was more than 10,000, and 27.50ppm was used as the reference value for chemical shift for measurement.

[0053] The ethylene content was determined as described above. 13 The C-NMR spectra were derived based on reports by G.J. Ray (Macromolecules, 10, 773 (1977)), J.C. Randall (Macromole cules, 15, 353 (1982)), and K. Kimura (Polymer, 25, 4418 (1984)).

[0054] <Number-average molecular weight, weight-average molecular weight, molecular weight distribution>

[0055] For the number-average molecular weight, weight-average molecular weight, and molecular weight distribution of the ethylene-α-olefin copolymer (A) involved in this invention, a Tosoh HLC-8320GPC was used, and the determination was performed as follows. A TSKgel SuperMultipore HZ-M column (4 columns) was used as the separation column, the column temperature was set to 40°C, tetrahydrofuran (manufactured by FUJIFILM WakoPure Chemical Corporation) was used as the mobile phase, the development rate was 0.35 mL / min, the sample concentration was 5.5 g / L, the sample injection volume was 20 μL, and a differential refractive index meter was used as the detector. Tosoh PStQuick MP-M standard polyethylene was used as the standard polyethylene. Following standard calibration procedures, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) were calculated using a conversion to polystyrene molecular weight, and the molecular weight distribution (Mw / Mn) was calculated from their values.

[0056] <Method for manufacturing ethylene-α-olefin copolymer (A)>

[0057] The ethylene-α-olefin copolymer (A) of the present invention can be manufactured using various known manufacturing methods, specifically, for example, using the methods described in Japanese Patent Application Publication No. 57-123205 and Japanese Patent Application Publication No. 2016-69406.

[0058] Organosilicon Compounds (B)

[0059] The organosilicon compound (B) containing one or more unsaturated groups in the graft portion of the organosilicon compound graft copolymer (X) of the present invention is generally an organosilicon compound containing one or more unsaturated groups having 2 to 20 carbon atoms. Specifically, examples include monovinylsilanes such as vinyltrimethoxysilane (VTMOS), vinyltriethoxysilane, vinyltrimethylsilane, diethylmethylvinylsilane, diacetoxyethylvinylsilane, diethoxymethylvinylsilane, ethoxydimethylvinylsilane, triacetoxyvinylsilane, tri(2-methoxyethoxy)vinylsilane, triphenylvinylsilane, triphenoxyvinylsilane, etc., and polyvinylsilanes such as diphenyldivinylsilane and allyloxydimethylvinylsilane.

[0060] <Organosilicon graft copolymer (X)>

[0061] The organosilicon graft copolymer (X) of the present invention is an organosilicon graft copolymer (X) characterized in that it comprises a main chain portion from the above-mentioned ethylene-α-olefin copolymer (A) and a graft portion from the above-mentioned organosilicon compound (B) containing one or more unsaturated groups.

[0062] For the organosilicon graft copolymer (X) of the present invention, it is preferable that the mass of the graft portion from the organosilicon compound (B) is in the range of 1% or more and less than 100%, more preferably 3 to 50% by mass [the total mass of the main chain portion and the graft portion is set to 100% by mass].

[0063] The amount of grafted organosilicon compound (B) in the organosilicon compound graft copolymer (X) of the present invention was determined by the following method.

[0064] Using a Bruker Biospin AVANCEIIIcryo-270 NMR spectrometer (270 MHz), the following measurements were performed under the following conditions: solvent: deuterated chloroform; measurement temperature: 24.3 °C; spectral width: 15.6 ppm; pulse repetition time: 2.5 seconds; pulse width: 6.5 μsec. 1 H-NMR spectroscopy is used to determine the size of the methoxy group peak in grafted organosilicon compounds (B), such as vinyltrimethoxysilane (VTMOS), and the grafting amount (grafting rate) is calculated from this.

[0065] If the quality of the graft from the organosilicon compound (B) is within the above range, both its affinity with the resin and its affinity with the added filler (silica, etc.) are excellent.

[0066] The organosilicon graft copolymer (X) of the present invention has a number-average molecular weight (Mn) in the range of 1,500 to 7,000, preferably 1,600 to 6,800, more preferably 1,650 to 6,800, and a weight-average molecular weight (Mw) in the range of 2,400 to 13,000, preferably 2,500 to 12,500. Furthermore, the molecular weight distribution Mw / Mn is in the range of 1.4 to 2.1, preferably 1.5 to 2.0.

[0067] Preferably, in the organosilicon graft copolymer (X) of the present invention, the content of the following polymeric component is further 0 to 0.3% by mass, wherein the polymeric component is defined as a component whose molecular weight M, determined by GPC, has a peak in the range defined by 5 ≤ LogM ≤ 6.

[0068] It should be noted that in the determination of the high molecular weight components contained in the organosilicon graft copolymer (X), the analysis software of the EcoSEC-WS GPC workstation manufactured by Tosoh Corporation (HLC-8320GPC) was used to calculate the peak area and peak area ratio, and to calculate the content (mass%) of the high molecular weight components in (X).

[0069] <Method for manufacturing organosilicon graft copolymer (X)>

[0070] The organosilicon graft copolymer (X) of the present invention can be manufactured by reacting the ethylene-α-olefin copolymer (A) involved in the present invention with the aforementioned organosilicon compound (B) containing one or more unsaturated groups in the presence of a free radical initiator.

[0071] The reaction with the organosilicon compound (B) can be carried out in the presence of a solvent or in the absence of a solvent. As a reaction method, for example, the following method can be exemplified: The organosilicon compound (B) containing one or more unsaturated groups and a free radical initiator are continuously or intermittently supplied to a heated ethylene-α-olefin copolymer (A) under stirring, thereby carrying out the reaction. The proportion of the organosilicon compound (B) containing one or more unsaturated groups supplied to the grafting reaction is typically in the range of 1 to 150 parts by mass, preferably 1.2 to 120 parts by mass, relative to 100 parts by mass of the ethylene-α-olefin copolymer (A), and the proportion of the free radical initiator is typically in the range of 0.04 to 5 parts by mass, preferably 0.1 to 1 part by mass, relative to 100 parts by mass of the ethylene-α-olefin copolymer (A). The reaction temperature is in the range of 120 to 200°C, preferably 130 to 180°C, and the reaction time is typically 30 minutes to 10 hours, preferably 1 to 5 hours.

[0072] Organic peroxides are commonly used as free radical initiators in grafting reactions, and particularly preferred are organic peroxides with a half-life of 1 hour and a decomposition temperature in the range of 100 to 180°C. Specifically, examples of organic peroxides include dicumyl peroxide (PERCUMYL D), di-tert-butyl peroxide (PERBUTYL D), 1,1-di(tert-butylperoxide)cyclohexane (PERHEXA C), tert-butylperoxide-2-ethylhexyl monocarbonate (PERBUTYL E), di-tert-hexyl peroxide (PERHEXYL Z), tert-hexyl peroxide (PERHEXYL Z), 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane (PERHEXA 25M), tert-butyl peroxide (PERBUTYL Z), and tert-butylperoxide isopropyl monocarbonate (PERBUTYL I). (It should be noted that the designations in parentheses are product names of Nippon Oil Co., Ltd.)

[0073] <Applications of Organosilicon Graft Copolymer (X)>

[0074] The organosilicon graft copolymer (X) of the present invention can be suitably used for applications such as lubricant additives, coatings, adhesives, compatibilizers, etc.

[0075] Diene-based rubber

[0076] The diene rubber included as one of the components in the rubber composition of the present invention is any rubber having double bonds in its main chain, and is not particularly limited. Specific examples include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), ethylene-propylene-diene copolymer rubber (EPDM), styrene-isoprene rubber, isoprene-butadiene rubber, nitrile rubber, hydrogenated nitrile rubber, etc. One of them may be used alone, but it is preferred to use two or more diene rubbers in combination.

[0077] Among these diene-based rubbers, aromatic vinyl-conjugated diene copolymer rubbers, NR, and BR are preferred from the perspective of good wear resistance and excellent processability.

[0078] Examples of aromatic vinyl-conjugated diene copolymer rubbers included in this invention include styrene-butadiene rubber (SBR), styrene-isoprene rubber, and styrene-butadiene-isoprene rubber (SBIR), with SBR being the preferred choice.

[0079] Among these diene rubbers, SBR alone or a mixture of SBR and BR (composition) is preferred, in the range of SBR / BR = 100 / 0 to 1 / 99 (mass ratio), more preferably SBR / BR = 50 / 50 to 90 / 10 (mass ratio), and even more preferably SBR / BR = 70 / 30 to 80 / 20 (mass ratio).

[0080] The ends of the aforementioned aromatic vinyl-conjugated diene copolymer rubber can be modified using hydroxyl groups, polyorganosiloxane groups, carbonyl groups, amino groups, etc.

[0081] Furthermore, the weight-average molecular weight of the aforementioned aromatic vinyl-conjugated diene copolymer rubber is not particularly limited, but from a processability point of view, it is preferably 100,000 to 2,500,000, more preferably 300,000 to 2,000,000. It should be noted that the weight-average molecular weight (Mw) of the aromatic vinyl-conjugated diene copolymer rubber was determined by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent, converted to standard polystyrene.

[0082] From the viewpoint of processability and wear resistance, the above-mentioned aromatic vinyl-conjugated diene copolymer rubber preferably contains 20 to 50% by mass of aromatic vinyl groups, and more preferably, the content of vinyl bonds in the conjugated diene is 20 to 70% by mass.

[0083] <Rubber Compositions for Tires>

[0084] In the tire rubber composition of the present invention, relative to 100 parts by weight of the diene rubber comprising aromatic vinyl-conjugated diene copolymer, there are 1 to 30 parts by weight, preferably 2 to 20 parts by weight of the above-mentioned organosilicon compound graft copolymer (X).

[0085] For the tire rubber composition of the present invention, by including the above-mentioned organosilicon compound graft copolymer (X) within the above-mentioned range, excellent silica dispersibility, i.e., low fuel consumption performance, can be obtained. When the graft copolymer (X) is less than 1 part by weight relative to 100 parts by weight of diene rubber, sufficient low fuel consumption performance cannot be obtained; when it is more than 30 parts by weight, the hardness of the rubber composition becomes high, and thus the flexibility as a tire is lost.

[0086] Inorganic fillers

[0087] Preferably, the tire rubber composition of the present invention contains an inorganic filler in addition to the above-mentioned organosilicon compound graft copolymer (X).

[0088] Specifically, the inorganic fillers involved in this invention include silica (also known as white carbon black), activated calcium carbonate, light calcium carbonate, heavy calcium carbonate, talc, silicic acid, and clay. These inorganic fillers can be used alone or in combination of two or more.

[0089] Among these inorganic fillers, from the viewpoints of uniform dispersion in the rubber matrix, excellent reinforcement, and versatility (cost), one or more selected from the group consisting of silica are preferred.

[0090] Silicon Dioxide

[0091] The silica involved in this invention is not particularly limited, and any silica known conventionally known to be incorporated into rubber compositions for applications such as tires can be used.

[0092] Specifically, the silica involved in this invention includes, for example, pyrolytic silica, calcined silica, precipitated silica, pulverized silica, molten silica, colloidal silica, etc., and one of them can be used alone or two or more can be used together.

[0093] Furthermore, regarding the silica involved in this invention, from the viewpoint of suppressing silica aggregation, the CTAB adsorption specific surface area is preferably 50 to 300 m². 2 / g, more preferably 80-250m 2 / g. Here, the CTAB adsorption specific surface area is the value obtained by determining the amount of n-hexadecyltrimethylammonium bromide adsorbed onto the silica surface according to JIS K6217-3:2001 "Part 3: Method for determining specific surface area - CTAB adsorption method".

[0094] When the tire rubber composition of the present invention contains inorganic fillers such as silica, the content of silica is preferably 5 to 150 parts by weight, more preferably 10 to 120 parts by weight, and even more preferably 20 to 100 parts by weight, relative to 100 parts by weight of the diene rubber described above.

[0095] Silane coupling agents

[0096] Preferably, the tire rubber composition of the present invention contains a silane coupling agent in addition to the aforementioned organosilicon graft copolymer (X) and inorganic fillers such as silica. The silane coupling agent involved in the present invention is not particularly limited, and any conventionally known silane coupling agent used in rubber compositions for applications such as tires can be used.

[0097] Specifically, examples of silane coupling agents involved in this invention include, for instance, bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, and 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide. Dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropylbenzothiazole tetrasulfide, etc., can be used alone or in combination with two or more. Alternatively, products obtained by pre-oligomerizing one or more of them can also be used.

[0098] In addition to the above-mentioned silane coupling agents, specific examples include thiol-based silane coupling agents such as γ-mercaptopropyltriethoxysilane and 3-[ethoxybis(3,6,9,12,15-pentaoctadecane-1-yloxy)silyl]-1-propanethiol; thiocarboxylate-based silane coupling agents such as 3-octanoylthiopropyltriethoxysilane; and thiocyanate-based silane coupling agents such as 3-thiocyanate-propyltriethoxysilane; etc. One of these can be used alone, or two or more can be used in combination. Alternatively, products obtained by pre-oligomerizing one or more of these agents can also be used.

[0099] Among them, from the viewpoint of improving the reinforcing effect, bis-(3-triethoxysilylpropyl)tetrasulfide and / or bis-(3-triethoxysilylpropyl)disulfide are preferred. Specifically, examples include Si69 [bis-(3-triethoxysilylpropyl)tetrasulfide; manufactured by Evonik Degussa] and Si75 [bis-(3-triethoxysilylpropyl)disulfide; manufactured by Evonik Degussa].

[0100] When the tire rubber composition of the present invention contains the above-mentioned silane coupling agent, its content is preferably 1 part by mass or more, more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the diene rubber containing the aromatic vinyl-conjugated diene copolymer rubber.

[0101] Furthermore, relative to 100 parts by mass of silicon dioxide, the content of the silane coupling agent is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass.

[0102] Carbon Black

[0103] The rubber composition for tires of the present invention preferably further contains carbon black.

[0104] Specifically, the carbon blacks involved in this invention include furnace-processed carbon blacks such as SAF, ISAF, HAF, FEF, GPE, and SRF. One of these carbon blacks can be used alone, or two or more can be used in combination.

[0105] Furthermore, for the carbon black involved in this invention, from the viewpoint of processability during mixing with tire rubber compositions, the nitrogen adsorption specific surface area (N2SA) is preferably 10 to 300 m². 2 / g, more preferably 20-200m 2 / g.

[0106] Here, N2SA is the value obtained by measuring the amount of nitrogen adsorbed on the carbon black surface according to JIS K 6217-2:2001 "Part 2: Calculation of specific surface area - Nitrogen adsorption method - Single point method".

[0107] When the tire rubber composition of the present invention contains the above-mentioned carbon black, its content is preferably 1 to 100 parts by weight, more preferably 5 to 80 parts by weight, relative to 100 parts by weight of the diene rubber containing the aromatic vinyl-conjugated diene copolymer rubber.

[0108] Other Ingredients

[0109] In addition to the above-mentioned components, the tire rubber composition of the present invention may also be combined with additives commonly used in tire rubber compositions, such as: chemical foaming agents such as hollow polymers; vulcanizing agents such as sulfur; vulcanization accelerators such as sulfenamide, guanidine, thiazole, thiourea, and thiuram; vulcanization accelerators such as zinc oxide and stearic acid; waxes; aroma oils; amine anti-aging agents such as p-phenylenediamines (e.g., N,N'-di-2-naphthyl-p-phenylenediamine, N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine, etc.) and ketone-amine condensates (e.g., 2,2,4-trimethyl-1,2-dihydroquinoline, etc.); plasticizers; and so on.

[0110] The amounts of these additives can be set to conventional amounts, as long as they do not violate the purpose of this invention. For example, relative to 100 parts by weight of diene rubber, 0.5 to 5 parts by weight of sulfur, 0.1 to 5 parts by weight of vulcanization accelerator, 0.1 to 10 parts by weight of vulcanization accelerator, 0.5 to 5 parts by weight of anti-aging agent, 1 to 10 parts by weight of wax, and 5 to 30 parts by weight of aromatic oil can be added respectively.

[0111] <Method for manufacturing rubber compositions for tires>

[0112] The method for manufacturing the tire rubber composition of the present invention is not particularly limited. For example, methods for mixing the above-mentioned components using known methods and apparatus (e.g., Banbury mixer, kneader, roller, etc.) can be cited.

[0113] Furthermore, the rubber composition for tires of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0114] Example

[0115] The present invention will now be described in more detail based on embodiments, but the present invention is not limited to these embodiments.

[0116] The following examples and comparative examples show the ethylene-α-olefin copolymer (A), organosilicon graft copolymer (X), diene rubber, etc. used in them.

[0117] [Ethylene-propylene copolymer (A-1)]

[0118] As an ethylene-α-olefin copolymer (A) [represented as "(A)" in Table 1], an ethylene-propylene copolymer (A-1) with Mw of 12,500, Mn of 6,600, Mw / Mn of 1.9, and ethylene content of 44.8% by mass was used.

[0119] Organosilicon graft copolymer (X)

[0120] As the organosilicon graft copolymer (X) [represented as "(X)" in Table 1], the organosilicon graft copolymer (X-1) [hereinafter sometimes simply referred to as "(X-1)"] obtained by the manufacturing method described below is used.

[0121] [Preparation of organosilicon graft copolymer (X-1)]

[0122] 181 g of the ethylene-propylene copolymer (A-1) and 25.5 g of vinyltrimethoxysilane (VTMOS), an organosilicon compound (B) containing one or more unsaturated groups, were loaded into a one-liter glass reaction vessel. After nitrogen purging, the system was sealed. The mixture was stirred at 200 rpm using a double-anchored blade while the temperature was raised to 160°C. 50 mL of a solution obtained by dissolving 1.02 g of dicumyl peroxide (manufactured by Nippon Oil Co., Ltd., product name: PERCUMYL D) in toluene was added dropwise over 60 minutes while stirring at 400 rpm. After the dropwise addition was completed, stirring was continued for another 90 minutes. Then, the stirring speed was reduced to 300 rpm and the mixture was cooled to 50°C. The reactor was depressurized, opened, and the reaction solution was removed. The solvents, toluene and VTMOS, were removed by distillation under reduced pressure using an evaporator. The solution was then vacuum dried at 90°C to obtain the organosilicon graft copolymer (X-1).

[0123] The grafting amount of the VTMOS of the organosilicon compound graft copolymer (X-1) was 11.1% by mass.

[0124] In addition, the obtained organosilicon graft copolymer (X-1) has a weight-average molecular weight (Mw) of 11,600, a number-average molecular weight (Mn) of 6,100, and a molecular weight distribution (Mw / Mn) of 1.9.

[0125] [Ethylene-α-olefin copolymer (A-2)]

[0126] As the ethylene-α-olefin copolymer (A), an ethylene-propylene copolymer (A-2) with Mw of 2,700, Mn of 1,800, Mw / Mn of 1.5, and ethylene content of 42.9% by mass was used.

[0127] Organosilicon graft copolymer (X-2)

[0128] As the organosilicon graft copolymer (X), the organosilicon graft copolymer (X-2) obtained by the manufacturing method described below is used.

[0129] [Preparation of organosilicon graft copolymer (X-2)]

[0130] 177 g of the ethylene-propylene copolymer (A-2) and 25.5 g of vinyltrimethoxysilane (VTMOS), an organosilicon compound (B) containing one or more unsaturated groups, were loaded into a one-liter glass reaction vessel. After nitrogen purging, the system was sealed. The mixture was stirred at 200 rpm using a double-anchored blade while the temperature was raised to 160°C. 50 mL of a solution obtained by dissolving 1.02 g of dicumyl peroxide (manufactured by Nippon Oil Co., Ltd., product name: PERCUMYL D) in toluene was added dropwise over 60 minutes while stirring at 400 rpm. After the dropwise addition was completed, stirring was continued for another 90 minutes. Then, the stirring speed was reduced to 300 rpm and the mixture was cooled to 50°C. The reactor was depressurized, opened, and the reaction solution was removed. The solvents, toluene and VTMOS, were removed by distillation under reduced pressure using an evaporator. The solution was then vacuum dried at 90°C to obtain the organosilicon graft copolymer (X-2).

[0131] The grafting amount of the VTMOS of the organosilicon compound graft copolymer (X-2) was 11.9% by mass.

[0132] In addition, the obtained organosilicon graft copolymer (X-2) has a weight-average molecular weight (Mw) of 2,600, a number-average molecular weight (Mn) of 1,650, and a molecular weight distribution (Mw / Mn) of 1.6.

[0133] [Ethylene-α-olefin copolymer (A-3)]

[0134] As the ethylene-α-olefin copolymer (A), an ethylene-propylene copolymer (A-3) with Mw of 4,800, Mn of 2,800, Mw / Mn of 1.7, and ethylene content of 41.3% by mass was used.

[0135] Organosilicon graft copolymer (X-3)

[0136] As the organosilicon graft copolymer (X), the organosilicon graft copolymer (X-3) obtained by the manufacturing method described below is used.

[0137] [Preparation of organosilicon graft copolymer (X-3)]

[0138] 177 g of the ethylene-propylene copolymer (A-3) and 25.5 g of vinyltrimethoxysilane (VTMOS), an organosilicon compound (B) containing one or more unsaturated groups, were loaded into a one-liter glass reaction vessel. After nitrogen purging, the system was sealed. The mixture was stirred at 200 rpm using a double-anchored blade while the temperature was raised to 160°C. 50 mL of a solution obtained by dissolving 1.02 g of dicumyl peroxide (manufactured by Nippon Oil Co., Ltd., product name: PERCUMYL D) in toluene was added dropwise over 60 minutes while stirring at 400 rpm. After the dropwise addition was completed, stirring was continued for another 90 minutes. Then, the stirring speed was reduced to 300 rpm and the mixture was cooled to 50°C. The reactor was depressurized, opened, and the reaction solution was removed. The solvents, toluene and VTMOS, were removed by distillation under reduced pressure using an evaporator. The solution was then vacuum dried at 90°C to obtain the organosilicon graft copolymer (X-3).

[0139] The grafting amount of the VTMOS of the organosilicon compound graft copolymer (X-3) was 12.1% by mass.

[0140] In addition, the obtained organosilicon graft copolymer (X-3) has a weight-average molecular weight (Mw) of 4,600, a number-average molecular weight (Mn) of 2,750, and a molecular weight distribution (Mw / Mn) of 1.7.

[0141] Organosilicon graft copolymer (X-4)

[0142] As the organosilicon graft copolymer (X), the organosilicon graft copolymer (X-4) obtained by the manufacturing method described below is used.

[0143] [Preparation of organosilicon graft copolymer (X-4)]

[0144] 181 g of the ethylene-propylene copolymer (A-1) and 25.5 g of vinyltrimethoxysilane (VTMOS), an organosilicon compound (B) containing one or more unsaturated groups, were loaded into a one-liter glass reaction vessel. After nitrogen purging, the system was sealed. The temperature was raised to 160°C while stirring at 200 rpm using a double-anchored blade. 50 mL of a solution obtained by dissolving 10.01 g of dicumyl peroxide (manufactured by Nippon Oil Co., Ltd., product name: PERCUMYL D) in toluene was added dropwise over 60 minutes while stirring at 400 rpm. After the dropwise addition was completed, stirring was continued for another 90 minutes. Then, the stirring speed was reduced to 300 rpm and the mixture was cooled to 50°C. The reactor was depressurized, opened, and the reaction solution was removed. The solvents, toluene and VTMOS, were removed by distillation under reduced pressure using an evaporator. The solution was then vacuum dried at 90°C to obtain the organosilicon graft copolymer (X-4).

[0145] The grafting amount of the VTMOS of the organosilicon compound graft copolymer (X-4) was 10.9% by mass.

[0146] Furthermore, for the obtained organosilicon graft copolymer (X-4), bimodality was confirmed in GPC molecular weight determination. The first peak had a weight-average molecular weight (Mw) of 14,600, a number-average molecular weight (Mn) of 6,300, and a molecular weight distribution (Mw / Mn) of 2.3. The second peak had a weight-average molecular weight (Mw) of 458,100, a number-average molecular weight (Mn) of 412,700, and a molecular weight distribution (Mw / Mn) of 1.1.

[0147] The physical properties of the obtained organosilicon graft copolymer (X) were observed using the following methods.

[0148] [Surface observation]

[0149] On two glass plates, each 26 mm long × 26 mm wide, 0.327 g and 0.109 g of an organosilicon graft copolymer (X-1) were coated, respectively (equivalent to film thicknesses of 0.6 mm and 0.2 mm, with a density of 0.838 g / cm³). 3 , ) , by visually observing the presence or absence of particles.

[0150] [Determination of high molecular weight components in organosilicon graft copolymer (X)]

[0151] The high molecular weight components contained in the organosilicon graft copolymer (X) were determined using the method described above.

[0152] [Examples 1-4]

[0153] The surface of the organosilicon graft copolymers (X-1), (X-2), (X-3), and (X-4) obtained by the manufacturing method described above was observed using the method described above. The results showed that no particles were present in any of them. On the other hand, during coating, for (X-1), (X-2), and (X-3), the number of bubbles entering the coating film (0.6 mm thick) was 0, 10, and 90 respectively, less than 100 (good coatability). In contrast, for (X-4), the number of bubbles entering the coating film (0.6 mm thick) was 150, more than 100 but less than 250 (slightly better coatability).

[0154] It should be noted that, in Table 1, the evaluation criteria for coatability are as described below.

[0155] Good: There are more than 0 and less than 100 air bubbles entering the coating (0.6 mm thick).

[0156] Slightly better: The number of air bubbles entering the coating (0.6 mm thick) is more than 100 but less than 250.

[0157] Defect: More than 250 air bubbles penetrate the coating (0.6 mm thick).

[0158] The results are shown in Table 1.

[0159] [Table 1]

[0160] Table 1

[0161]

[0162] Diene-based rubber

[0163] (1) Diene-based rubber-1: Styrene-butadiene rubber (SBR), Nipol (registered trademark) NS116 (manufactured by ZEON Corporation, Japan); [Styrene content = 21%, Mooney viscosity = 45, specific gravity 0.93]

[0164] (2) Diene-based rubber-2: Butadiene rubber (BR) Nipol (registered trademark) 1220 (manufactured by ZEON Corporation, Japan); [Mounney viscosity: 44, specific gravity: 0.90]

[0165] Compounding Agents

[0166] (1) Zinc white: two types of zinc oxide

[0167] (2) Aroma process oil: Diana Process (registered trademark) AH-16 (manufactured by Idemitsu Kogyo)

[0168] (3) Wet silica: Nipsil (trademark) VN3 (Tosoh Silica Corporation)

[0169] (4) Carbon black: Asahi #80 (Asahi Carbon Co., Ltd.)

[0170] (5) Silane coupling agent: Silanogran (trademark) Si69 (manufactured by Techno Preknead HIDACo., Ltd.)

[0171] (6) Vulcanization accelerator (CBS): Sanshin Chemical Industry Co., Ltd. (trademark)

[0172] (7) Vulcanization accelerator (DPG): Sanshin Chemical Industry Co., Ltd. (trademark) DG

[0173] The physical properties of the rubber compositions obtained in the examples and comparative examples were determined using the following methods.

[0174] (1) Compressive permanent strain (CS)

[0175] According to JIS K 6262, a crosslinked body with a diameter of 29 mm and a height (thickness) of 12.5 mm was used as a test piece. The test piece was compressed by 25% relative to its height before loading (12.5 mm) and placed in a Gear oven at 70°C for 22 hours, along with spacers. Afterward, the test piece was removed, allowed to stand at room temperature for 30 minutes, and its height was measured. The compressive settling strain (%) was calculated using the following formula.

[0176] Regarding the compressive permanent strain (0℃), the specimen was placed in a constant temperature bath at 0℃ and treated for 22 hours. Then, the specimen was removed from the constant temperature bath, left for 30 minutes, and its height was measured. The compressive permanent strain (%) was calculated using the following formula.

[0177] Compressive permanent strain (%) = {(t0-t1) / (t0-t2)} × 100

[0178] t0: The height of the test piece before the test.

[0179] t1: Height of the test piece after being treated under the aforementioned conditions and left at room temperature for 30 minutes; t2: Height of the test piece when mounted in the measuring mold.

[0180] (2) Dynamic viscoelasticity test

[0181] For 1 mm thick vulcanized rubber sheets, the temperature dependence of the loss tangent tanδ (an index of vibration damping) was measured using a viscoelastic testing machine (model RDS-2) manufactured by Rheometrics, under the conditions of a measurement temperature of -70 to 100 °C, a frequency of 10 Hz, a strain rate of 1.0%, and a heating rate of 4 °C / min. The tanδ (damping rate) of the rubber composition at 0 °C was used as an index of tire braking performance. A larger tanδ at 0 °C indicates better braking performance. Additionally, the tanδ (damping rate) of the rubber composition at 60 °C was used as an index of vehicle fuel efficiency. A smaller tanδ at 60 °C indicates better fuel efficiency.

[0182] [Example 5]

[0183] Using a 1.7-liter closed Banbury mixer, diene rubber-1, diene rubber-2, graft copolymer (X-1), silica, and silane coupling agent were mixed for 2 minutes in the proportions listed in Table 2. Then, carbon black, aromatic oil, zinc oxide, and stearic acid were added and mixed for another 2 minutes to prepare a masterbatch. A rubber composition obtained by mixing this masterbatch with a vulcanization accelerator and sulfur using an 8-inch open roll with a front and rear roll surface temperature of 50°C was subjected to pressure vulcanization at 170°C for 10 minutes in a 10×10×0.1 cm mold to obtain a vulcanized tire rubber composition. Dynamic viscoelasticity tests were performed using the obtained tire rubber composition. Furthermore, crosslinking was performed at 170°C for 15 minutes to obtain a vulcanized rubber composition with a thickness of 12.5 mm and a diameter of 29 mm. Compression set was measured using the obtained rubber composition. The physical properties of the obtained vulcanized tire rubber composition were measured using the methods described above. The evaluation results are shown in Table 2.

[0184] [Example 6]

[0185] Instead of the tire rubber composition used in Example 5, the formulation amounts described in Table 2 were used, and otherwise the same procedures were followed as in Example 5 to obtain a vulcanized tire rubber composition. The physical properties of the obtained vulcanized tire rubber composition were measured using the methods described above. The evaluation results are shown in Table 2.

[0186] [Example 7]

[0187] Instead of the tire rubber composition used in Example 5, the formulation amounts described in Table 2 were used, and otherwise the same procedures were followed as in Example 5 to obtain a vulcanized tire rubber composition. The physical properties of the obtained vulcanized tire rubber composition were measured using the methods described above. The evaluation results are shown in Table 2.

[0188] [Comparative Example 1]

[0189] The graft copolymer (X-1) used in Example 1 was not used; otherwise, the process was the same as in Example 1 to obtain a vulcanized rubber composition. The physical properties of the obtained vulcanized rubber composition were determined using the methods described above. The evaluation results are shown in Table 2.

[0190] [Table 2] Table 2

[0191] Example 5 Example 6 Example 7 Comparative Example 1 <Fit> Diene-based rubber-1: Nipol NS116R 75 75 75 75 Diene-based rubber-2: Nipol1220 25 25 25 25 Nipsil VN3 36 36 36 36 Si-69 4 4 4 4 Asahi #80 40 40 40 40 Zinc White #1 3 3 3 3 stearic acid 2 2 2 2 AH-16 45 3.5 25 50 Graft copolymer (X-1) 5 12.5 25 - <Physical properties> Compressive permanent strain CS@0℃×22h (%) 14 13 12 14 <Tensile viscoelasticity> tanδ@0℃ 0.33 0.32 0.33 0.34 tanδ@60℃ 0.15 0.15 0.14 0.17

Claims

1. An organosilicon compound graft copolymer (X), characterized in that, It comprises a main chain portion from an ethylene-α-olefin copolymer (A) and a graft portion from an organosilicon compound (B) containing one or more unsaturated groups. The organosilicon graft copolymer (X) has a weight-average molecular weight (Mw) in the range of 2,500 to 12,500, a number-average molecular weight (Mn) in the range of 1,600 to 6,500, and a molecular weight distribution (Mw / Mn) in the range of 1.5 to 1.

9.

2. The organosilicon compound graft copolymer (X) as described in claim 1, characterized in that, The main chain portion of the ethylene-α-olefin copolymer (A) is an ethylene-α-olefin copolymer (A) with a weight average molecular weight (Mw) in the range of 2,000 to 14,000, a number average molecular weight (Mn) in the range of 1,600 to 7,000, and a molecular weight distribution (Mw / Mn) in the range of 1.4 to 2.

1.

3. The organosilicon compound graft copolymer (X) as described in claim 1 or 2, characterized in that, The main chain portion of the ethylene-α-olefin copolymer (A) is an ethylene-α-olefin copolymer (A) in which the ethylene-derived component is in the range of 41 to 48% by mass, wherein the total mass of the ethylene-derived component and the α-olefin-derived component is set as 100 by mass.

4. The organosilicon compound graft copolymer (X) according to any one of claims 1 to 3, characterized in that, The mass of the graft from organosilicon compound (B) is more than 1% and less than 100%, wherein the total mass of the main chain and the graft is set to 100%.

5. The organosilicon compound graft copolymer (X) according to any one of claims 1 to 4, characterized in that, The organosilicon compound (B) is vinyltrimethoxysilane.

6. The organosilicon compound graft copolymer (X) according to any one of claims 1 to 5, characterized in that, In the organosilicon graft copolymer (X), the content of the following polymeric component is further 0 to 0.3% by mass, said polymeric component being defined as a component whose molecular weight M, determined by GPC, has a peak in the range specified by 5 ≤ LogM ≤ 6.

7. A rubber composition for tires, characterized in that, The organosilicon graft copolymer (X) of claim 1 comprises 1 to 30 parts by weight relative to 100 parts by weight of the diene rubber comprising aromatic vinyl-conjugated diene copolymer rubber.

8. The rubber composition for tires as claimed in claim 7, characterized in that, It further includes inorganic fillers in the range of 5 to 150 parts by weight.

9. The rubber composition for tires as claimed in claim 8, wherein, The inorganic filler is silicon dioxide.

10. The rubber composition for tires according to any one of claims 7 to 9, characterized in that, The diene-based rubber is a mixture of SBR and BR containing SBR as an aromatic vinyl-conjugated diene copolymer rubber, and containing SBR and BR in a ratio of SBR / BR=100 / 0~1 / 99 (mass ratio).

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