Vulcanized rubber composition for tires and tires

Abstract

To provide a vulcanized rubber composition for tires that has superior performance on ice.SOLUTION: A vulcanized rubber composition for tires according to the present invention includes a vulcanized rubber composition including a rubber component and a fatty acid amide. The vulcanized rubber composition has a plurality of cavities.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a vulcanized rubber composition for tires and a tire.

Background Art

[0002] When a tire runs on an icy or snowy road surface, the tire slips due to the water film formed between the road surface and the tire, and the braking performance deteriorates. Therefore, in a studless tire, it is required to improve the ice performance such that the grip is effective even on an icy or snowy road surface and it is easy to brake the vehicle.

[0003] As a method for enhancing ice performance, it is known to increase the surface roughness (surface irregularities) of the tread rubber or to improve the flexibility (flexibility and adhesiveness) at low temperatures.

[0004] When the surface roughness is increased, it is considered that the concave portions take in the water film on the ice and the convex portions contact the ice surface, thereby increasing the contact area with the ice surface compared to a tread rubber having a smooth surface. Here, as a method for increasing the surface roughness of the tread rubber, it is common to incorporate a foaming agent or thermally expandable microcapsules into the rubber composition (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the method exemplified in Patent Document 1, while the water film can be taken in as the surface roughness increases, the area that can contact the ice surface decreases. Therefore, it can be said that there is a limit to the effect of improving the ice performance due to the surface roughness.

[0007] Therefore, an object of the present invention is to provide a vulcanized rubber composition for tires having excellent ice performance. Another object of the present invention is to provide a tire with excellent ice performance. [Means for solving the problem]

[0008] The inventors diligently conducted research to further improve ice performance. They discovered that by incorporating fatty acid amides into the vulcanized rubber composition for tires, and by forming multiple voids, a significant improvement in ice performance can be achieved.

[0009] In other words, the vulcanized rubber composition for tires of the present invention is obtained by vulcanizing a rubber composition containing a rubber component and a fatty acid amide, and is characterized by having a plurality of voids. By incorporating the above configuration, excellent ice performance can be achieved.

[0010] Furthermore, in the vulcanized rubber composition for tires of the present invention, it is preferable that the rubber composition contains 0.1 to 10 parts by mass of the fatty acid amide per 100 parts by mass of the rubber component. This is because it is possible to achieve better ice performance without reducing performance such as wear resistance.

[0011] Furthermore, in the vulcanized rubber composition for tires of the present invention, the fatty acid amide is preferably a fatty acid bis-amide, and more preferably an ethylene-bis-fatty acid amide. This is because it enables superior ice performance.

[0012] Furthermore, in the vulcanized rubber composition for tires of the present invention, it is preferable that the rubber composition further comprises a liquid polymer having a polystyrene-equivalent weight-average molecular weight of 5,000 or more and less than 40,000 as measured by gel permeation chromatography. This is because it enables the achievement of even better ice performance.

[0013] Furthermore, in the vulcanized rubber composition for tires of the present invention, it is preferable that the rubber component contains natural rubber. This is because it is possible to further improve performance such as abrasion resistance and low heat generation.

[0014] Furthermore, in the tire vulcanization rubber composition of the present invention, it is preferable that the rubber component contains a modified conjugated diene polymer having a functional group, and it is more preferable that the functional group of the modified conjugated diene polymer has at least one element selected from nitrogen, oxygen, and silicon. This is because it is possible to achieve even better low heat generation.

[0015] Furthermore, in the vulcanized rubber composition for tires of the present invention, it is preferable that the rubber composition further contains a void-introducing agent, and it is more preferable that the void-introducing agent is at least one selected from the group consisting of a foaming agent, a metal sulfate salt, a thermally expandable microcapsule, porous cellulose, and a lignin derivative. This is because it is possible to achieve better ice performance.

[0016] Furthermore, in the vulcanized rubber composition for tires of the present invention, it is preferable that the rubber composition further contains composite fibers, as this enables even better ice performance.

[0017] Furthermore, in the vulcanized rubber composition for tires of the present invention, it is preferable that the porosity of the vulcanized rubber composition is 5 to 45%. This is because it enables better ice performance.

[0018] Furthermore, in the vulcanized rubber composition for tires of the present invention, it is preferable that the rubber composition further contains a filler containing silica and carbon black, and more preferably that the total content of silica and carbon black is 50 to 90 parts by mass per 100 parts by mass of the rubber component. This is because it is possible to achieve better ice performance while maintaining good performance such as wear resistance and low heat generation.

[0019] The tire of the present invention is characterized in that the above-described vulcanized rubber composition for tires is used in the tread portion. By incorporating the above configuration, excellent ice performance can be achieved. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a vulcanized rubber composition for tires having excellent ice performance. Furthermore, according to the present invention, it is also possible to provide a tire with excellent ice performance. [Brief explanation of the drawing]

[0021] [Figure 1] This figure schematically shows a plurality of voids present in a vulcanized rubber composition for tires according to one embodiment of the present invention. [Figure 2] This figure schematically shows a cross-section of voids present in a vulcanized rubber composition for tires according to one embodiment of the present invention. [Modes for carrying out the invention]

[0022] Embodiments of the present invention will be described below with reference to drawings as necessary. <Vulcanized rubber composition for tires> The vulcanized rubber composition for tires of the present invention is a vulcanized rubber composition obtained by vulcanizing a rubber composition containing a rubber component and a fatty acid amide, and is characterized in that the vulcanized rubber composition 10 has a plurality of voids 20, as shown in Figure 1.

[0023] In addition to containing a fatty acid amide, as described later, in the tire vulcanization rubber composition of the present invention, the tire vulcanization rubber composition 10 of the present invention has multiple voids 20, as shown in Figure 1, which significantly improves ice performance when applied to a tire.

[0024] Here, the voids in the tire vulcanized rubber composition of the present invention refer to multiple pores with an average diameter of approximately 1 to 500 μm formed in the tire vulcanized rubber composition, as shown in Figure 1. Furthermore, the diameter of the voids refers to the largest diameter D of the void 20 (if the void is not spherical, the maximum distance D between any two points on the inner wall of the void), as shown in Figure 2. The average diameter of the aforementioned voids is the average value of the diameter D of the voids 20 present in the tire vulcanized rubber composition of the present invention. In this invention, the cross-section of the tire vulcanized rubber composition is observed using a digital microscope (Keyence Corporation "VHX-100"), and the average value of the diameters of all voids present in one field of view (2.5 mm × 2.5 mm) is used. In the tire vulcanized rubber composition of the present invention, the shape and size of the aforementioned voids do not change significantly within a single tire vulcanized rubber composition, so the average value of the voids in one field of view can be used as the average diameter of the voids.

[0025] Furthermore, the porosity of the vulcanized rubber composition for tires of the present invention is preferably 5 to 45%. By setting the lower limit of the porosity to 5%, ice performance can be improved more reliably. From a similar viewpoint, the porosity is preferably 7% or more, and more preferably 15% or more. On the other hand, by setting the upper limit of the porosity to 45%, the decrease in wear resistance can be suppressed more reliably, even when there are multiple voids. From a similar viewpoint, the porosity is preferably 40% or less, and more preferably 37% or less. The void ratio refers to the percentage (volume %) of the volume of voids in the vulcanized rubber composition for tires of the present invention. The method for measuring the void ratio is not particularly limited and can be measured using, for example, a hydrometer (ViBRA hydrometer "DMA-220" manufactured by Shinko Denshi Co., Ltd.).

[0026] Here, the vulcanized rubber composition for tires of the present invention has a plurality of voids, but the method of creating the voids is not particularly limited. Depending on the conditions of the voids and the equipment used to manufacture the vulcanized rubber composition for tires, known techniques can be used to form the voids. For example, as will be described later, one method is to create voids in the vulcanized rubber composition for tires by blending a foaming agent, foaming aid, composite fibers, etc., into the rubber composition before vulcanization. The void ratio can be controlled by changing the vulcanization conditions or by the content of void-introducing agents such as foaming agents and composite fibers.

[0027] The aforementioned vulcanized rubber composition for tires refers to vulcanized rubber obtained by vulcanizing an unvulcanized rubber composition. Furthermore, there are no particular limitations on the vulcanization conditions (temperature, time), and the vulcanization process can be carried out under any conditions depending on the required performance.

[0028] The unvulcanized rubber composition (hereinafter simply referred to as "rubber composition") which forms the basis of the vulcanized rubber composition for tires of the present invention will be described below. The rubber composition comprises a rubber component and a fatty acid amide.

[0029] (Rubber component) The rubber components included in the rubber composition are not particularly limited, but from the viewpoint of wear resistance and reinforcing properties when the vulcanized rubber composition for tires is applied to a tire, it is preferable to include natural rubber (NR). Here, the content of natural rubber in the rubber component is not particularly limited. For example, from the viewpoint of further improving abrasion resistance and ice performance, it is preferable that the content of natural rubber be 30% by mass or more of the rubber component. By using a rubber component containing a certain amount of the aforementioned natural rubber together with a fatty acid amide described later, the ice performance of the vulcanized rubber composition for tires can be more reliably improved. From the same viewpoint, the natural rubber content in the rubber component is preferably 35% by mass or more, and more preferably 40% by mass or more. The upper limit is preferably 100% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less.

[0030] Furthermore, the rubber component may include any synthetic rubber in addition to the natural rubber. For example, it is preferable that the rubber component includes diene-based synthetic rubber, as this provides excellent cut resistance and abrasion resistance.

[0031] Examples of the diene-based synthetic rubber include synthetic polyisoprene (IR), styrene-butadiene copolymer rubber (SBR), and polybutadiene rubber (BR). The diene-based synthetic rubber in the rubber component may be included alone or as a blend of two or more types. Furthermore, the rubber component may also contain non-diene-based synthetic rubber depending on the required performance.

[0032] Furthermore, it is preferable that the rubber component further contains a modified conjugated diene polymer having a functional group. By including a modified conjugated diene polymer having a functional group in the rubber component, the dispersibility of the filler described later can be improved, thereby achieving better wear resistance and ice performance.

[0033] The functional groups of the modified conjugated diene polymer are not particularly limited and can be appropriately selected according to the type of filler and the required performance. For example, the functional groups include those having at least one atom selected from the group consisting of nitrogen, silicon, oxygen, and tin atoms. Furthermore, it is preferable that the modified conjugated diene polymer contains two or more modified conjugated diene polymers having different functional groups.

[0034] Furthermore, the modified conjugated diene polymer is more preferably having alkoxysilane and / or (meth)acrylate as functional groups among the functional groups described above, and is even more preferably containing two types: a modified conjugated diene polymer having alkoxysilane as a functional group and a modified conjugated diene polymer having (meth)acrylate as a functional group. The method for introducing specific functional groups into the conjugated diene polymer is not particularly limited and can be carried out according to known methods depending on the required performance.

[0035] Furthermore, there are no particular restrictions on the modified functional group containing the nitrogen atom, and it can be appropriately selected depending on the purpose. Examples include a substituted amino group represented by the following general formula (I) and a cyclic amino group represented by the following general formula (II). [ka]

[0036] In the formula, R 1 R is an alkyl group, cycloalkyl group, or aralkyl group having 1 to 12 carbon atoms. Here, the alkyl group is preferably a methyl group, ethyl group, butyl group, octyl group, or isobutyl group; the cycloalkyl group is preferably a cyclohexyl group; and the aralkyl group is preferably a 3-phenyl-1-propyl group. 1 These may be of the same kind or different kinds.

[0037] [ka]

[0038] In the formula, R 2 The group is an alkylene group, a substituted alkylene group, an oxyalkylene group, or an N-alkylaminoalkylene group having 3 to 16 methylene groups. Here, the substituted alkylene group includes monosubstituted to octasubstituted alkylene groups, and examples of substituents include linear or branched alkyl groups, cycloalkyl groups, bicycloalkyl groups, aryl groups, or aralkyl groups having 1 to 12 carbon atoms. Here, the alkylene group is preferably trimethylene, tetramethylene, hexamethylene, and dodecamethylene; the substituted alkylene group is preferably hexadecamethylene; the oxyalkylene group is preferably oxydiethylene; and the N-alkylaminoalkylene group is preferably N-alkylazadiethylene.

[0039] There are no particular limitations on the examples of cyclic amino groups represented by general formula (II), and they can be appropriately selected depending on the purpose. For example, 2-(2-ethylhexyl)pyrrolidine, 3-(2-propyl)pyrrolidine, 3,5-bis(2-ethylhexyl)piperidine, 4-phenylpiperidine, 7-decyl-1-azacyclotridecane, 3,3-dimethyl-1-azacyclotetradecane, 4-dodecyl-1-azacyclooctane, 4-(2-phenylbutyl)-1-azacyclooctane, 3-ethyl-5-cyclohexyl-1-azacycloheptane, 4-hexyl-1-azacycloheptane, 9-isoamyl-1-azacycloheptadecane, 2-methyl-1-aza Examples of such groups include cycloheptadecé-9-ene, 3-isobutyl-1-azacyclododecane, 2-methyl-7-t-butyl-1-azacyclododecane, 5-nonyl-1-azacyclododecane, 8-(4'-methylphenyl)-5-pentyl-3-azabicyclo[5.4.0]undecane, 1-butyl-6-azabicyclo[3.2.1]octane, 8-ethyl-3-azabicyclo[3.2.1]octane, 1-propyl-3-azabicyclo[3.2.2]nonane, 3-(t-butyl)-7-azabicyclo[4.3.0]nonane, and 1,5,5-trimethyl-3-azabicyclo[4.4.0]decane, from which one hydrogen atom bonded to the nitrogen atom has been removed. These may be used individually or in combination of two or more.

[0040] Furthermore, there are no particular restrictions on the modified functional group containing the silicon atom, and it can be appropriately selected depending on the purpose. For example, a modified functional group having a silicon-carbon bond formed using a coupling agent represented by the following general formula (III) can be mentioned. This method is preferable because it chemically bonds the rubber component constituting the SB phase with silicon via a silicon-carbon bond, thereby increasing the affinity between the SB phase and the filler, and allowing for the distribution of more filler into the SB phase. Generally, when silicon is simply mixed into a rubber composition, its low affinity with the rubber components results in poor reinforcement of the rubber composition. However, by chemically bonding the rubber components constituting the SB phase with silicon via a silicon-carbon bond, the affinity between the rubber components constituting the SB phase and the filler can be increased, thereby further improving the hysteresis loss of the tire.

[0041] [ka]

[0042] In the formula, Z is silicon, and R 3 Each R is independently selected from the group consisting of alkyl groups having 1 to 20 carbon atoms, cycloalkyl groups having 3 to 20 carbon atoms, aryl groups having 6 to 20 carbon atoms, and aralkyl groups having 7 to 20 carbon atoms, and each R4 is independently chlorine or bromine, a is 0 to 3, b is 1 to 4, and a+b=4. Here, preferred alkyl groups are methyl, ethyl, n-butyl, n-octyl, and 2-ethylhexyl; preferred cycloalkyl groups are cyclohexyl; preferred aryl groups are phenyl; and preferred aralkyl groups are neophyll. 3 These may be of the same kind or different kind. Each R 4 These may be of the same kind or different kinds.

[0043] When the aim is to enhance the interaction of modified rubber with silica, a modifying agent having at least one of the compounds represented by the following general formula (III-1) and general formula (III-2) can be used.

[0044] [ka]

[0045] In the general formula (III-1), R1 and R2 each independently represent a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, a is an integer of 0 to 2, and OR 2 When there are a plurality of them, the plurality of OR 2 may be the same as or different from each other, and the molecule does not contain an active proton.

[0046] Here, specific examples of the compound (alkoxysilane compound) represented by the general formula (III-1) include, for example, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, ethyltriisopropoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltripropoxysilane, propyltriisopropoxysilane, butyltrimethoxysilane, butyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethoxydimethylsilane, methylphenyldimethoxysilane, dimethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, divinyldiethoxysilane, etc. Among these, tetraethoxysilane, methyltriethoxysilane, and dimethyldiethoxysilane are preferred. These may be used alone or in combination of two or more.

[0047]

Chemical formula

[0048] In the general formula (III-2), A 1R is a monovalent group having at least one functional group selected from the group consisting of epoxy, glycidyloxy, isocyanate, imine, carboxylic acid ester, carboxylic acid anhydride, cyclic tertiary amine, acyclic tertiary amine, pyridine, silazane and disulfide, 3 R is a single bond or a divalent hydrocarbon group, 4 and R 5 Each is independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and b is an integer from 0 to 2, OR 5 If there are multiple OR5 molecules, they may be identical or different from each other, and the molecule does not contain an active proton.

[0049] Specific examples of compounds represented by general formula (III-2) include epoxy group-containing alkoxysilane compounds, such as 2-glycidyloxyethyltrimethoxysilane, 2-glycidyloxyethyltriethoxysilane, (2-glycidyloxyethyl)methyldimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, (3-glycidyloxypropyl)methyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyl(methyl)dimethoxysilane. Among these, 3-glycidyloxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane can be preferably used.

[0050] There are no particular limitations on the types of coupling agents that use silicon, and they can be appropriately selected depending on the purpose. Examples include hydrocarbyloxysilane compounds, SiCl4 (silicon tetrachloride), (Ra)SiCl3, (Ra)2SiCl2, (Ra)3SiCl, etc. Ra independently represents an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms. Among these, hydrocarbyloxysilane compounds are preferred from the viewpoint of having a high affinity for silica.

[0051] The hydrocarbyloxysilane compound is not particularly limited and can be appropriately selected depending on the purpose. For example, a hydrocarbyloxysilane compound represented by the following general formula (IV) can be mentioned.

[0052] [ka]

[0053] In the formula, n1+n2+n3+n4=4 (where n2 is an integer from 1 to 4, and n1, n3 and n4 are integers from 0 to 3), A1 is at least one functional group selected from saturated cyclic tertiary amine compound residues, unsaturated cyclic tertiary amine compound residues, ketimine residues, nitrile groups, (thio)isocyanate groups (representing isocyanate groups or thioisocyanate groups; the same applies hereinafter), (thio)epoxy groups, isocyanuric acid trihydrocarbyl ester groups, dihydrocarbyl carbonate ester groups, nitrile groups, pyridine groups, (thio)ketone groups, (thio)aldehyde groups, amide groups, (thio)carboxylic acid ester groups, metal salts of (thio)carboxylic acid esters, carboxylic acid anhydride residues, carboxylic acid halogen compound residues, and first or second amino groups or mercapto groups having hydrolyzable groups, and when n4 is 2 or more, they may be the same or different, and A1 may be a divalent group that forms a cyclic structure when bonded with Si, R 21 R is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when n1 is 2 or more, it may be the same or different, 23 R is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom (fluorine, chlorine, bromine, iodine), and when n3 is 2 or more, it may be the same or different, 22R is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may contain a nitrogen atom and / or a silicon atom. If n2 is 2 or more, they may be the same or different from each other, or they may form a ring together. 24 This is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same or different if n4 is 2 or more. As the hydrolyzable group in the primary or secondary amino group having a hydrolyzable group or the mercapto group having a hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred. In this specification, "monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms" means "monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms." The same applies to divalent hydrocarbon groups.

[0054] Furthermore, the hydrocarbyloxysilane compound represented by general formula (IV) is more preferably a hydrocarbyloxysilane compound represented by the following general formula (V).

[0055] [ka]

[0056] In the formula, p1 + p2 + p3 = 2 (where p2 is an integer between 1 and 2, and p1 and p3 are integers between 0 and 1), A2 is NRa (Ra is a monovalent hydrocarbon group, a hydrolyzable group, or a nitrogen-containing organic group. As a hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred), or sulfur, and R 25 R is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. 27R is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom (fluorine, chlorine, bromine, iodine), 26 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a nitrogen-containing organic group, all of which may contain nitrogen atoms and / or silicon atoms, and when p2 is 2, they may be identical, different, or together form a ring, R 28 This is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.

[0057] Furthermore, the hydrocarbyloxysilane compound represented by general formula (IV) is more preferably a hydrocarbyloxysilane compound represented by the following general formula (VI) or (VII).

[0058] [ka]

[0059] In the formula, q1 + q2 = 3 (where q1 is an integer from 0 to 2 and q2 is an integer from 1 to 3), and R31 is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, R 32 and R 33 Each of these is independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, R 34 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when q1 is 2, it may be the same or different, R 35 q2 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same or different if q2 is 2 or more.

[0060] [ka]

[0061] In the equation, r1 + r2 = 3 (where r1 is an integer from 1 to 3, and r2 is an integer from 0 to 2), and R 36 R is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. 37 is a dimethylaminomethyl group, a dimethylaminoethyl group, a diethylaminomethyl group, a diethylaminoethyl group, a methylsilyl(methyl)aminomethyl group, a methylsilyl(methyl)aminoethyl group, a methylsilyl(ethyl)aminomethyl group, a methylsilyl(ethyl)aminoethyl group, a dimethylsilylaminomethyl group, a dimethylsilylaminoethyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when r1 is 2 or more, it may be the same or different, R 38 is a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when r2 is 2, it may be the same or different.

[0062] Furthermore, it is preferable that the hydrocarbyloxysilane compound represented by general formula (IV) is a compound having two or more nitrogen atoms represented by the following general formula (VIII) or (IX).

[0063] [ka]

[0064] In the formula, TMS is a trimethylsilyl group, and R 40 R is a trimethylsilyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. 41 R is a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. 42This is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. In the formula, TMS is a trimethylsilyl group, and R 43 and R 44 Each is independently a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, R 45 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and multiple R 45 They may be the same or different.

[0065] Furthermore, it is also preferable that the hydrocarbyloxysilane compound represented by general formula (IV) is the hydrocarbyloxysilane compound represented by the following general formula (X).

[0066] [ka]

[0067] In the formula, r1 + r2 = 3 (where r1 is an integer from 0 to 2, and r2 is an integer from 1 to 3), and TMS is a trimethylsilyl group, R 46 R is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. 47 and R 48 Each of these is independently a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. 47 or R 48 They may be the same or different.

[0068] Furthermore, it is preferable that the hydrocarbyloxysilane compound represented by general formula (IV) is the compound represented by the following general formula (XI).

[0069] [ka]

[0070] In the formula, Y is a halogen atom, and R 49 R is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. 50 and R 51 Each of these is independently a hydrolyzable group or a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or R 50 and R 51 They are bonded together to form a divalent organic group, R 52 and R 53 Each of these is independently a halogen atom, a hydrocarbyl oxy group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. 50 and R 51 The hydrolyzable group is preferably a trimethylsilyl group or a tert-butyldimethylsilyl group, with the trimethylsilyl group being particularly preferred.

[0071] The hydrocarbyloxysilane compounds represented by the above general formulas (IV) to (XI) are preferably used when the modified rubber component is produced by anionic polymerization. Furthermore, the hydrocarbyloxysilane compounds represented by general formulas (IV) to (XI) are preferably alkoxysilane compounds.

[0072] There are no particular limitations on suitable modifying agents when modifying diene polymers by anionic polymerization, and they can be appropriately selected depending on the purpose. Examples include 3,4-bis(trimethylsilyloxy)-1-vinylbenzene, 3,4-bis(trimethylsilyloxy)benzaldehyde, 3,4-bis(tert-butyldimethylsilyloxy)benzaldehyde, 2-cyanopyridine, 1,3-dimethyl-2-imidazolidinone, and 1-methyl-2-pyrrolidone. These may be used individually or in combination of two or more.

[0073] The hydrocarbyloxysilane compound is preferably the amide portion of a lithium amide compound used as a polymerization initiator in anionic polymerization. There are no particular restrictions on the lithium amide compound, and it can be appropriately selected depending on the purpose. Examples include lithium hexamethyleneimide, lithium pyrrolidide, lithium piperidide, lithium heptamethyleneimide, lithium dodecamethyleneimide, lithium dimethylamide, lithium diethylamide, lithium dibutylamide, lithium dipropylamide, lithium diheptylamide, lithium dihexylamide, lithium dioctylamide, lithium di-2-ethylhexylamide, lithium didecylamide, lithium-N-methylpiberazide, lithium ethylpropylamide, lithium ethylbutylamide, lithium ethylbenzylamide, lithium methylphenethylamide, and lithium methylphenethylamide. For example, the denaturing agent for the amide portion of lithium hexamethyleneimide is hexamethyleneimine, the denaturing agent for the amide portion of lithium pyrrolidide is pyrrolidine, and the denaturing agent for the amide portion of lithium piperidide is piperidine. These may be used individually or in combination of two or more.

[0074] The modified functional group containing the oxygen atom is not particularly limited and can be appropriately selected depending on the purpose. Examples include alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, and t-butoxy groups; alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups; alkoxyaryl groups such as methoxyphenyl and ethoxyphenyl groups; alkylene oxide groups such as epoxy and tetrahydrofuranyl groups; and trialkylsilyloxy groups such as trimethylsilyloxy, triethylsilyloxy, and t-butyldimethylsilyloxy groups. These may be used individually or in combination of two or more.

[0075] The content of the modified conjugated diene polymer in the rubber component is not particularly limited, but from the viewpoint of achieving better wear resistance and ice performance, it is preferably 10 to 90% by mass, more preferably 20 to 85% by mass, more preferably 28 to 78% by mass, more preferably 38 to 72% by mass, more preferably 40 to 70% by mass, and even more preferably 45 to 65% by mass.

[0076] (Fatty acid amide) Furthermore, the vulcanized rubber composition for tires of the present invention contains a fatty acid amide in the rubber composition. The aforementioned fatty acid amide can promote the imparting of hydrophilicity to the rubber surface and increase viscous resistance, thereby significantly improving the ice performance of the vulcanized rubber composition for tires.

[0077] Here, the content of the fatty acid amide is preferably 0.1 to 10 parts by mass per 100 parts by mass of the rubber component. When the content of the fatty acid amide is 0.1 parts by mass or more per 100 parts by mass of the rubber component, a sufficient improvement in ice performance can be obtained. On the other hand, when the content of the fatty acid amide is 10 parts by mass or less per 100 parts by mass of the rubber component, a decrease in the performance of the rubber composition, such as abrasion resistance and reinforcing properties, can be suppressed. From a similar viewpoint, the content of the fatty acid amide is preferably 0.1 to 8 parts by mass, and more preferably 0.3 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0078] Here, the type of fatty acid amide is not particularly limited as long as it can promote the imparting of hydrophilicity to the rubber surface. Examples include caproic acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, oleic acid amide, erucic acid amide, methylenebisstearamide, ethylenebisstearamide, and the like.

[0079] Furthermore, regarding the fatty acid amide, from the viewpoint of achieving better ice performance, it is preferable that it be a fatty acid bis-amide, and more preferably an ethylene-bis fatty acid amide. Examples of the ethylenebis fatty acid amide include ethylenebisstearate amide and ethylenebisoleate amide.

[0080] (Liquid polymer) The rubber composition preferably further contains, in addition to the rubber components and fatty acid amides described above, a liquid polymer having a polystyrene-equivalent weight-average molecular weight of 5,000 or more and less than 40,000 as measured by gel permeation chromatography. By including the aforementioned liquid polymer, flexibility can be ensured for the rubber composition as a whole. Furthermore, by using it together with the cyclic polyol compounds and fillers described later, a high level of both ice performance and abrasion resistance can be achieved.

[0081] Here, the liquid polymer is a polymer with a polystyrene-equivalent weight-average molecular weight of 5,000 or more and less than 40,000 as measured by gel permeation chromatography, but it is more preferable that it is an unmodified conjugated diene polymer in which the amount of bound styrene is less than 10% and the amount of vinyl bond in the conjugated diene compound portion is 20% or more. The liquid polymer is more likely to be unevenly distributed in the natural rubber phase of the rubber component, and better ice performance can be obtained.

[0082] Furthermore, from the viewpoint of obtaining better ice performance, the vinyl bond content of the conjugated diene compound portion of the liquid polymer is preferably 30% or more, more preferably 40% or more, and even more preferably 45% or more. Furthermore, from the viewpoint of suppressing an increase in rubber hardness, the vinyl bond content of the conjugated diene compound portion of the liquid polymer is preferably 70% or less, more preferably 65% ​​or less, and even more preferably 55% or less.

[0083] Furthermore, the liquid polymer content is preferably 1 to 40 parts by mass per 100 parts by mass of the rubber component. This is because it provides flexibility to the rubber composition, improves the ice performance of the tire equipped with the vulcanized rubber and tread obtained from the rubber composition, and suppresses a decrease in wear resistance. Furthermore, from a similar viewpoint, the content of the liquid polymer is more preferably 3 to 30 parts by mass, even more preferably 5 to 25 parts by mass, and particularly preferably 7 to 20 parts by mass, per 100 parts by mass of the rubber component.

[0084] Furthermore, the liquid polymer is preferably low molecular weight so that it does not form a crosslinked structure with the rubber component (A) even when the rubber composition is vulcanized. Specifically, it is preferable that the polystyrene-equivalent weight-average molecular weight (hereinafter sometimes simply referred to as weight-average molecular weight) measured by gel permeation chromatography is 5,000 or more and less than 40,000. If the weight-average molecular weight of the liquid polymer is less than 5,000, it may make the vulcanized rubber obtained from the rubber composition and the tire tread excessively flexible, impairing wear resistance. If the weight-average molecular weight of the liquid polymer is 40,000 or more, flexibility is lost, and the ice performance of the vulcanized rubber obtained from the rubber composition and the tire with a tread made of the rubber composition may be impaired. Furthermore, from a similar viewpoint, the weight-average molecular weight of the liquid polymer is more preferably 5,500 to 30,000, even more preferably 6,000 to 25,000, and particularly preferably 6,500 to 20,000.

[0085] Furthermore, the liquid polymer is preferably an unmodified conjugated diene polymer. If the amount of bound styrene in the conjugated diene compound portion is less than 10%, sufficient flexibility of the rubber composition can be ensured, and the ice performance of the tire equipped with the vulcanized rubber and tread portion obtained from the rubber composition can be further improved. From a similar viewpoint, the liquid polymer is more preferably 5% or less in terms of the amount of bound styrene in the conjugated diene compound portion, even more preferably 3% or less, and particularly preferably 0%. Furthermore, the reason why the liquid polymer is preferably an unmodified polymer is that it is less likely to interact with the filler described later, suppressing the inclusion of the filler in the natural rubber phase and thus maintaining good ice performance.

[0086] Here, the conjugated diene polymer is not particularly limited as long as it has a specific weight-average molecular weight, the amount of styrene bonded to the conjugated diene compound portion is kept below a certain value, and a specific amount of vinyl bond, but a homopolymer of a conjugated diene compound or a copolymer of an aromatic vinyl compound and a conjugated diene compound is preferred. Examples of conjugated diene compounds as monomers include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, and 1,3-hexadiene, with 1,3-butadiene and isoprene being preferred among these. On the other hand, examples of aromatic vinyl compounds as monomers include styrene, p-methylstyrene, m-methylstyrene, p-tert-butylstyrene, α-methylstyrene, chloromethylstyrene, and vinyltoluene. The liquid polymer is preferably either polybutadiene or polyisoprene, or both, with polybutadiene being more preferred. These monomers may be used individually or in combination of two or more.

[0087] Furthermore, when the liquid polymer is an aromatic vinyl compound-conjugated diene compound copolymer, it is preferable that the amount of aromatic vinyl compound bonded is less than 5% by mass. By limiting the amount of aromatic vinyl compound bonded to less than 5% by mass, it is possible to suppress the increase in rubber hardness and the deterioration of ice performance.

[0088] The method for producing the conjugated diene polymer as a liquid polymer is not particularly limited, and for example, it can be obtained by polymerizing a monomer conjugated diene compound alone, or a mixture of a monomer aromatic vinyl compound and a conjugated diene compound, in a hydrocarbon solvent that is inert to polymerization reactions. Lithium compounds are preferred as polymerization initiators used in the synthesis of the aforementioned conjugated diene polymers, and n-butylthirium is more preferred. When a lithium compound is used as the polymerization initiator, the aromatic vinyl compound and the conjugated diene compound are polymerized by anionic polymerization.

[0089] As described above, there are no particular limitations on the method for producing the conjugated diene polymer using a polymerization initiator. For example, the conjugated diene polymer can be produced by polymerizing monomers in a hydrocarbon solvent that is inert to polymerization reactions. Examples of hydrocarbon solvents inert to polymerization reactions include propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2-butene, cis-2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, and ethylbenzene. These may be used individually or in combination of two or more.

[0090] Furthermore, the polymerization reaction is preferably carried out in the presence of a randomizer. Randomizers can control the microstructure of the conjugated diene compound portion of a (co)polymer, and more specifically, they can control the amount of vinyl bonds in the conjugated diene compound portion of a (co)polymer, or randomize the conjugated diene compound units and aromatic vinyl compound units in the copolymer. Examples of randomizers include dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, ditetrahydrofurylpropane, triethylamine, pyridine, N-methylmorpholine, N,N,N',N'-tetramethylethylenediamine, 1,2-dipiperidinoethane, potassium t-amilate, potassium t-butoxide, and sodium t-amilate. The amount of these randomizers used is preferably in the range of 0.1 to 100 molar equivalents per mole of polymerization initiator.

[0091] Anionic polymerization is preferably carried out by solution polymerization, and the concentration of the monomer in the polymerization reaction solution is preferably in the range of 5 to 50% by mass, and more preferably in the range of 10 to 30% by mass. When a conjugated diene compound and an aromatic vinyl compound are used in combination, the content of the aromatic vinyl compound in the monomer mixture can be appropriately selected according to the amount of aromatic vinyl compound in the target copolymer. Furthermore, the polymerization method is not particularly limited and may be batch or continuous.

[0092] The polymerization temperature for anionic polymerization is preferably in the range of 0 to 150°C, and more preferably in the range of 20 to 130°C. While the polymerization can be carried out under the generated pressure, it is generally preferable to carry it out under a pressure sufficient to keep the monomers used substantially in the liquid phase. When the polymerization reaction is carried out under a pressure higher than the generated pressure, it is preferable to pressurize the reaction system with an inert gas. Furthermore, it is preferable to use raw materials such as monomers, polymerization initiators, and solvents from which reaction inhibitors such as water, oxygen, carbon dioxide, and protic compounds have been removed beforehand.

[0093] The weight-average molecular weight of the liquid polymer, the amount of styrene bound to the conjugated diene compound portion, and the amount of vinyl bonded to the conjugated diene compound portion can be adjusted by the amount of monomer used in polymerization, the degree of polymerization, etc. Furthermore, the amount of styrene bound to the conjugated diene compound portion and the amount of vinyl bonded to the conjugated diene compound portion (sometimes referred to as the microstructure of the liquid polymer) can be determined by infrared spectroscopy (Morello method).

[0094] (Filler) The rubber composition preferably further contains a filler containing at least one of silica and carbon black, in addition to the rubber components and fatty acid amides and a liquid polymer as a preferred component. By including a filler containing at least one of silica and carbon black together with the rubber component, the properties of the vulcanized rubber composition for tires, such as abrasion resistance and ice performance, can be further enhanced. From a similar viewpoint, it is more preferable that the filler contains both the silica and the carbon black.

[0095] Examples of the types of silica mentioned above include wet silica (hydrated silica), dry silica (anhydrous silica), calcium silicate, and aluminum silicate, with wet silica being preferred among these. These silicas may be used individually or in combination of two or more types. Furthermore, precipitated silica can be used as the wet silica. Precipitated silica is silica obtained by first reacting the reaction solution at a relatively high temperature and in a neutral to alkaline pH range during the initial stages of production to grow primary silica particles, and then controlling the pH to the acidic side to aggregate the primary particles.

[0096] Furthermore, the silica is not particularly limited, but for example, if the CTAB specific surface area (cetyltrimethylammonium bromide adsorption specific surface area) is 70 m 2 / g or more, 250m 2 It can be less than / g. Note that the CTAB specific surface area refers to the value measured in accordance with ASTMD3765-92. However, the adsorption cross-section per molecule of cetyltrimethylammonium bromide on the silica surface is 0.35 nm. 2 The specific surface area (m²) is calculated from the amount of adsorption of CTAB. 2 Let the CTAB specific surface area be ( / g). Furthermore, the BET specific surface area of ​​the silica is 100m². 2 / g or more, 250m 2It can be less than or equal to / g. The BET specific surface area is the specific surface area obtained by the BET method, and in this invention, it can be measured in accordance with ASTM D4820-93.

[0097] Furthermore, the silica content is preferably 5 to 90 parts by mass, more preferably 10 to 5070 parts by mass, and even more preferably 20 to 65 parts by mass, per 100 parts by mass of the rubber component. If the silica content is 5 parts by mass or more per 100 parts by mass of the rubber component, the wear resistance and ice performance of the vulcanized rubber composition for tires can be further improved, and if it is 90 parts by mass or less, deterioration of the processability and low rolling resistance of the rubber composition can be suppressed.

[0098] Furthermore, the carbon black is not particularly limited, and examples include GPF, FEF, HAF, N339, IISAF, ISAF, and SAF grade carbon blacks. Among these, ISAF and SAF grade carbon blacks are preferred from the viewpoint of improving the wear resistance of the rubber composition. These carbon blacks may be used individually or in combination of two or more types. Furthermore, the carbon black has a nitrogen adsorption specific surface area (N2SA, measured in accordance with JIS K 6217-2:2001) of 20-250 m². 2 It can be used with a weight of / g, and is suitable for 30-200m 2 It can be used with a weight of / g, and is suitable for 30-150m 2 You can use products that are / g. Furthermore, the carbon black has a dibutyl phthalate (DBP) oil absorption capacity (measured by the method described in JIS K 6217-4:2001 "Method for determining DBP absorption") of 50-200 cm³. 3 It can use items weighing 100g, and is suitable for 60-150cm. 3 You can use products weighing 100g.

[0099] The carbon black content is not particularly limited, but is preferably 5 to 90 parts by mass, more preferably 20 to 80 parts by mass, even more preferably 25 to 70 parts by mass, and particularly preferably 30 to 65 parts by mass per 100 parts by mass of the rubber component. If the carbon black content is 5 parts by mass or more per 100 parts by mass of the rubber component, the abrasion resistance can be further improved, and if it is 90 parts by mass or less, the deterioration of low heat generation can be more reliably suppressed.

[0100] Furthermore, the total content of silica and carbon black is preferably 50 to 90 parts by mass per 100 parts by mass of the rubber component. This is because it is possible to further improve the properties of the vulcanized rubber composition for tires, such as abrasion resistance and ice performance, while maintaining good performance such as low heat generation and processability.

[0101] Furthermore, the mass ratio of the carbon black content to the silica content (carbon black content / silica content) is preferably 0.5 to 2, more preferably 0.5 to 1.5, and even more preferably 0.7 to 1.2. When the mass ratio of carbon black to silica is 0.5 or higher, superior wear resistance and reinforcing properties can be obtained, and when the mass ratio of carbon black to silica is 2 or lower, deterioration of low heat generation properties is not caused.

[0102] Furthermore, the filler may include, in addition to the silica and carbon black mentioned above, the following general formula (XX): nM·xSiO y ·zH2O ··· (XX) The formula may also include inorganic compounds represented by [wherein M is at least one selected from metals chosen from the group consisting of aluminum, magnesium, titanium, calcium, and zirconium, oxides or hydroxides of these metals, hydrates thereof, or carbonates of these metals; n, x, y, and z are integers from 1 to 5, integers from 0 to 10, integers from 2 to 5, and integers from 0 to 10, respectively]. The inorganic compounds of the general formula (XX) mentioned above include alumina (Al2O3) such as γ-alumina and α-alumina, alumina monohydrate (Al2O3·H2O) such as boehmite and diaspore, aluminum hydroxide [Al(OH)3] such as gibbsite and bayerite, aluminum carbonate [Al2(CO3)3], magnesium hydroxide [Mg(OH)2], magnesium oxide (MgO), magnesium carbonate (MgCO3), talc (3MgO·4SiO2·H2O), attapulgite (5MgO·8SiO2·9H2O), titanium white (TiO2), titanium black (TiO2) 2n-1 ), calcium oxide (CaO), calcium hydroxide [Ca(OH)2], magnesium aluminum oxide (MgO·Al2O3), clay (Al2O3·2SiO2), kaolin (Al2O3·2SiO2·2H2O), pyrophyllite (Al2O3·4SiO2·H2O), bentonite (Al2O3·4SiO2·2H2O), aluminum silicate (Al2SiO5, Al4·3SiO4·5H2O, etc.), magnesium silicate (Mg2SiO4, MgSiO3, etc.), k Examples include calcium iodide (Ca2SiO4, etc.), aluminum calcium silicate (Al2O3·CaO·2SiO2, etc.), magnesium calcium silicate (CaMgSiO4), calcium carbonate (CaCO3), zirconium oxide (ZrO2), zirconium hydroxide [ZrO(OH)2·nH2O], zirconium carbonate [Zr(CO3)2], and various zeolites, as well as crystalline aluminosilicates containing hydrogen, alkali metals, or alkaline earth metals to correct the charge. The inorganic compound of general formula (XX) described above preferably has an average particle size of 0.01 to 10 μm, and more preferably 0.05 to 5 μm, from the viewpoint of balancing abrasion resistance and wet performance.

[0103] (Air gap introducing agent) Furthermore, it is preferable that the rubber composition further contains a void-introducing agent in addition to the rubber components and fatty acid amides described above, as well as fillers and liquid polymers as preferred components. Because the rubber composition contains a void-introducing agent, the vulcanized rubber has voids on its surface, inside, or both on its surface and inside. As a result, tires using this vulcanized rubber are flexible and can easily adhere to icy road surfaces. Additionally, water on the road surface is absorbed into the voids on the tire surface, making it easier to remove water from icy and snowy road surfaces, thus improving braking performance on ice.

[0104] Examples of the void-introducing agent include foaming agents, metal sulfate salts, thermally expandable microcapsules, porous cellulose particles, lignin derivatives, etc., and one of these can be used alone or in a mixture of two or more. Furthermore, from the viewpoint of ice performance, it is preferable to use the foaming agent.

[0105] The content of the void-introducing agent in the rubber composition is not particularly limited, but from the viewpoint of obtaining a desired void ratio and maintaining abrasion resistance, it is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 10 parts by mass, and even more preferably 0.5 to 5 parts by mass per 100 parts by mass of the rubber component.

[0106] • Foaming agent The rubber composition contains a foaming agent as a void-introducing agent, which causes bubbles to form in the vulcanized rubber during the vulcanization process, thereby transforming the vulcanized rubber into foamed rubber. Because foamed rubber is flexible, the tire surface made from this foamed rubber adheres more easily to icy road surfaces. Furthermore, the bubbles create holes (foaming pores) on the surface of the vulcanized rubber and the tire surface, which function as drainage channels for water. Examples of foaming agents include, specifically, azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), dinitrosopentastyrenetetramine, benzenesulfonyl hydrazide derivatives, p,p'-oxybisbenzenesulfonyl hydrazide (OBSH), carbonates such as ammonium carbonate, sodium carbonate, and potassium carbonate, and inorganic foaming agents such as bicarbonates (bicarbonates) such as ammonium bicarbonate, sodium bicarbonate, and potassium bicarbonate, as well as nitrogen-generating nitrososulfonyl azo compounds and N,N'-dimethyl-N,N'-dinitrosoftal Examples include amides, toluenesulfonyl hydrazides, p-toluenesulfonyl semicarbazides, and p,p'-oxybisbenzenesulfonyl semicarbazides. Among these, from the viewpoint of ease of manufacturing and processing, it is preferable to use azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), and inorganic blowing agents. These blowing agents may be used individually or in combination of two or more.

[0107] Furthermore, the content of the foaming agent in the rubber composition is not particularly limited, but is preferably 1 to 10 parts by mass, and more preferably 2 to 8 parts by mass, per 100 parts by mass of the rubber component. The rubber composition may further contain foaming aids such as urea, zinc stearate, zinc benzenesulfinate, and zinc oxide. These may be used individually or in combination of two or more. By using foaming aids in combination, the foaming reaction can be promoted, increasing the completeness of the reaction and suppressing unwanted deterioration over time.

[0108] • Metal sulfate When the rubber composition contains a metal sulfate as a void-introducing agent, the metal sulfate protrudes from the tire surface obtained by vulcanizing the rubber composition, performing a claw function without the disadvantage of being abrasive. Subsequently, the metal sulfate gradually exits from the rubber matrix, creating voids that function as storage volumes and passages for draining the water film from the ice surface. Under these conditions, the contact between the tire surface (e.g., the tread surface) and the ice is no longer lubricated, and therefore the coefficient of friction is improved. Magnesium sulfate is an example of a metal sulfate salt.

[0109] The metal sulfate salt is preferably in the form of micrometer-sized particles. Specifically, the average particle size and median particle size (both expressed by mass) are preferably 1 μm to 1 mm, and the median particle size is more preferably 2 μm to 800 μm. When the average and median particle sizes are 1 μm or larger, the target technical effect (i.e., the formation of appropriate fine roughness) is easily achieved. Furthermore, when the average and median particle sizes are 1 mm or smaller, especially when using rubber compositions as treads, the deterioration of aesthetics is suppressed (it is possible to suppress the appearance of overly obvious particles on the tread surface) and the grip performance on melting ice is less likely to be impaired.

[0110] For all these reasons, the median particle size of the metal sulfate salt is preferably 2 μm to 500 μm, and more preferably 5 to 200 μm. This particularly preferred particle size range appears to correspond to the optimal compromise between the desired surface roughness on the one hand and good contact between the rubber composition and ice on the other.

[0111] Furthermore, for the same reasons as above, the content of metal sulfate in the rubber composition is preferably 5 to 40 parts by mass, more preferably 10 to 35 parts by mass, per 100 parts by mass of the rubber component.

[0112] Furthermore, various known methods, such as laser diffraction, can be applied for particle size analysis and calculation of the median particle size of fine particles (or the average diameter of fine particles assuming they are substantially spherical) (see, for example, standard ISO-8130-13 or standard JIS K5600-9-3). Furthermore, particle size analysis by mechanical sieving can also be easily and readily used; the procedure involves sieving a specified amount of sample (e.g., 200 g) on ​​a vibrating table for 30 minutes using various sieve diameters (e.g., according to a progressive ratio equal to 1.26, using meshes of 1000, 800, 630, 500, 400, ..., 100, 80, and 63 μm); weighing the excess size collected in each sieve using a precision balance; estimating the percentage of excess size at each mesh diameter relative to the total mass of the substance from the weighing; and finally calculating the median particle size (or median diameter) or average particle size (or average diameter) from a histogram of the particle size distribution using known methods.

[0113] • Thermally expandable microcapsules The aforementioned thermally expandable microcapsules consist of a shell made of thermoplastic resin containing a thermally expandable substance. The shell of the thermally expandable microcapsules can be formed from a nitrile polymer. Furthermore, the thermally expandable material enclosed within the microcapsule shell has the property of vaporizing or expanding upon heat, and examples include at least one selected from the group consisting of hydrocarbons such as isoalkanes and n-alkanes. Examples of isoalkanes include isobutane, isopentane, 2-methylpentane, 2-methylhexane, and 2,2,4-trimethylpentane, while examples of n-alkanes include n-butane, n-propane, n-hexane, n-heptane, and n-octane. These hydrocarbons may be used individually or in combination. A preferred form of the thermally expandable material is one in which a hydrocarbon that is liquid at room temperature is dissolved in a hydrocarbon that is gaseous at room temperature. By using such a hydrocarbon mixture, sufficient expansion force can be obtained from the low temperature range to the high temperature range within the vulcanization molding temperature range (150°C to 190°C) of unvulcanized tires.

[0114] Examples of such thermally expandable microcapsules include the product names "EXPANCEL 091DU-80" or "EXPANCEL 092DU-120" from Expancel GmbH in Sweden, or the product names "Matsumoto Microsphere F-85D" or "Matsumoto Microsphere F-100D" from Matsumoto Oil & Fat Pharmaceutical Co., Ltd.

[0115] The content of thermally expandable microcapsules in the rubber composition is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0116] • Porous cellulose particles If the rubber composition contains porous cellulose particles as the void-introducing agent, and the porous cellulose particles are exposed on the tire surface obtained by vulcanizing the rubber composition, water on the icy or snowy road surface can be absorbed by the porous cellulose particles, thereby removing water between the tire and the road surface. Furthermore, the presence of cellulose, a polysaccharide, facilitates interaction between the tire and water on the icy or snowy road surface, which can further enhance the interaction between the tire and water caused by the modified polyoxyalkylene glycol.

[0117] The porous cellulose particles are cellulose particles having a porous structure with a void ratio of 75-95%, and when incorporated into a rubber composition, they can significantly improve ice performance. A void ratio of 75% or more in the porous cellulose particles provides excellent ice performance improvement, while a void ratio of 95% or less increases the strength of the particles. The void ratio is more preferably 80-90%. The porosity of the porous cellulose particles can be determined by measuring the volume of a certain mass of sample (i.e., porous cellulose particles) using a graduated cylinder, calculating the bulk density, and then using the following formula. Porosity [%] = {1 - (Bulk density of sample [g / ml]) / (True density of sample [g / ml])} × 100 Here, the true specific gravity of cellulose is 1.5.

[0118] The particle size of the porous cellulose particles is not particularly limited, but from the viewpoint of abrasion resistance, particles with an average particle size of 1000 μm or less are preferably used. The lower limit of the average particle size is not particularly limited, but it is preferably 5 μm or more. The average particle size is more preferably 100 to 800 μm, and even more preferably 200 to 800 μm.

[0119] Preferably, the porous cellulose particles are spherical particles with a major axis / minor axis ratio of 1 to 2. By using such spherical particles, dispersibility in the rubber composition can be improved, contributing to improved ice performance and maintenance of abrasion resistance. The major axis / minor axis ratio is more preferably 1.0 to 1.5.

[0120] The average particle size and the ratio of major axis to minor axis of porous cellulose particles can be determined as follows: By observing porous cellulose particles under a microscope to obtain an image, the major axis and minor axis (or, if the major and minor axes are the same, the length in one axis direction and the length in the axis direction perpendicular to it) of 100 particles are measured using this image, and the average value is calculated to obtain the average particle size. The ratio of major axis to minor axis is obtained by using the average value of the major axis divided by the minor axis.

[0121] Such porous cellulose particles are commercially available from Rengo Co., Ltd. as "Viscopearl," and are also described in Japanese Patent Publication No. 2001-323095, Japanese Patent Publication No. 2004-115284, etc., and can be suitably used. The content of porous cellulose particles in the rubber composition is preferably 0.3 to 20 parts by mass per 100 parts by mass of rubber components. A content of 0.3 parts by mass or more enhances the effect of improving ice performance, while a content of 20 parts by mass or less prevents the rubber hardness from becoming too high and suppresses a decrease in abrasion resistance. The content of porous cellulose particles is more preferably 1 to 15 parts by weight, and even more preferably 3 to 15 parts by mass.

[0122] Lignin derivatives If the rubber composition contains a lignin derivative as the void-introducing agent, the effect of improving ice performance can be enhanced. Here, lignin sulfonates are preferably used as the lignin derivative. Examples of lignin sulfonates include alkali metal salts, alkaline earth metal salts, ammonium salts, and alcoholamine salts of lignin sulfonic acid, and at least one of these can be used. Preferably, alkali metal salts and / or alkaline earth metal salts of lignin sulfonic acid are used, such as potassium salts, sodium salts, calcium salts, magnesium salts, lithium salts, and barium salts, and mixed salts of these may also be used.

[0123] (Foaming agent) Furthermore, if the rubber composition contains a foaming agent as the void-introducing agent, it is preferable to further include a foaming aid. Examples of the foaming aid include urea, zinc stearate, zinc benzenesulfinate, and zinc oxide. These may be used individually or in combination of two or more. By using the aforementioned foaming aid in combination, the foaming reaction can be promoted, increasing the degree of reaction completion and suppressing unwanted deterioration over time.

[0124] Furthermore, the total content of the foaming agent and the foaming aid is preferably 1 to 30 parts by mass per 100 parts by mass of the rubber component. When the total content of the foaming agent and the foaming aid is 1 part by mass or more, the rubber composition can be sufficiently foamed during vulcanization, and a high foaming rate of the vulcanized rubber can be maintained. On the other hand, when the total content of the foaming agent and the foaming aid is 30 parts by mass or less, a decrease in the foaming rate can also be suppressed. As described above, from the viewpoint of suppressing a decrease in foaming rate, the total content of the foaming agent and the foaming aid is preferably 3 parts by mass or more, and more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, as described above, from the viewpoint of suppressing a decrease in foaming rate, the total content of the foaming agent and the foaming aid is preferably 25 parts by mass or less, and more preferably 20 parts by mass or less, per 100 parts by mass of the rubber component.

[0125] In addition, in the rubber composition, the mass ratio (foaming agent:foaming aid) of the foaming agent to the foaming aid is preferably 1:1.1 to 1:3.3. If the mass ratio (foaming agent:foaming aid) is less than 1:1.1, the rubber composition may not foam sufficiently during vulcanization, which may reduce the foaming rate of the vulcanized rubber. On the other hand, if the mass ratio (foaming agent:foaming aid) exceeds 1:3.3, the foaming rate may also decrease. As described above, from the viewpoint of suppressing a decrease in foaming rate, the mass ratio of the foaming agent to the foaming aid (foaming agent:foaming aid) is preferably 1:1.2 or higher, and more preferably 1:1.3 or higher. Furthermore, as described above, from the viewpoint of suppressing a decrease in foaming rate, the mass ratio of the foaming agent to the foaming aid (foaming agent:foaming aid) is preferably 1:3.2 or lower, more preferably 1:3.1 or lower, even more preferably 1:2.9 or lower, even more preferably 1:2.7 or lower, even more preferably 1:2.5 or lower, and particularly preferably 1:2.3 or lower.

[0126] Furthermore, from the viewpoint of the foaming rate of the vulcanized rubber and the ice performance of the tire, the content of the foaming aid is preferably in the range of 4 to 14 parts by mass per 100 parts by mass of the rubber component, and more preferably in the range of 6 to 14 parts by mass.

[0127] (Composite fiber) The rubber composition preferably further contains composite fibers in addition to the rubber components and fatty acid amides described above, and preferred components such as fillers, liquid polymers, void introducers, and foaming aids. By including the aforementioned composite fibers, sufficient affinity with water can be ensured, and particularly when used in tire applications, excellent drainage and ice performance can be provided. Furthermore, it is preferable that the composite fiber is made of a hydrophilic resin with a coating layer formed on its surface. This is because providing a coating layer on the surface of the composite fiber improves the dispersibility of the composite fiber in the rubber composition. Furthermore, the hydrophilic resin is preferably insoluble in water. By using a water-insoluble hydrophilic resin, the dissolution of the composite fibers can be suppressed even when the composite fibers are exposed on the surface of the product (e.g., a tire).

[0128] The hydrophilic resin is not particularly limited as long as it is a resin that can exhibit affinity for water, that is, a resin having a hydrophilic group in its molecule. Specifically, it is preferably a resin containing an oxygen atom, a nitrogen atom, or a sulfur atom. For example, a resin containing at least one group selected from the group consisting of -OH, -C(=O)OH, -OC(=O)R (where R is an alkyl group), -NH2, -NCO, and -SH is a good example. Among these groups, -OH, -C(=O)OH, -OC(=O)R, -NH2, and -NCO are preferred. More specifically, examples of the hydrophilic resin include ethylene-vinyl alcohol copolymers, vinyl alcohol homopolymers, poly(meth)acrylic acid resins or their ester resins (hereinafter, copolymers containing constituent units derived from (meth)acrylic acid and (co)polymers containing constituent units derived from (meth)acrylic acid esters are collectively referred to as (meth)acrylic resins), polyamide resins, polyethylene glycol resins, carboxyvinyl copolymers, styrene-maleic acid copolymers, polyvinylpyrrolidone resins, vinylpyrrolidone-vinyl acetate copolymers, polyester resins, and cellulose resins. Among these, ethylene-vinyl alcohol copolymers, vinyl alcohol homopolymers, poly(meth)acrylic acid resins, polyamide resins, aliphatic polyamide resins, aromatic polyamide resins, polyester resins, polyvinyl alcohol resins, cellulose resins, or (meth)acrylic resins are preferred, with ethylene-vinyl alcohol copolymers being more preferred.

[0129] The surface of the fibers made of the hydrophilic resin preferably has a coating layer made of a low-melting-point resin (hereinafter also referred to as "low-melting-point resin") which has an affinity for rubber components and preferably a melting point lower than the maximum vulcanization temperature. By forming such a coating layer, the affinity of the hydrophilic resin itself for water can be effectively maintained while exhibiting good affinity with the rubber components near the composite fibers. Furthermore, the hydrophilic resin, which is difficult to melt during vulcanization (foaming), can be captured, promoting the formation of voids inside the composite fibers. In other words, good dispersion of the composite fibers in the rubber components can be ensured, allowing the drainage effect due to the hydrophilic resin to be fully exhibited, while also allowing the ice performance improvement effect due to the voids inside the composite fibers to be fully exhibited. In addition, when such low-melting-point resin melts during vulcanization, it becomes a fluid coating layer that contributes to adhesion between the rubber components and the composite fibers, thereby providing good ice performance and abrasion resistance. The thickness of the coating layer may vary depending on the amount of hydrophilic resin blended and the average diameter of the composite fibers, but is preferably 0.001 to 10 μm, more preferably 0.001 to 5 μm. By forming the coating layer with a thickness within the above range, the desired effects of the present invention can be fully realized. Furthermore, the coating layer may be formed over the entire surface of the hydrophilic resin, or on a part of the surface of the hydrophilic resin. Specifically, it is preferable that the coating layer covers at least 50% of the total surface area of ​​the hydrophilic resin.

[0130] Specifically, the low-melting-point resin used in the coating layer is preferably a resin in which the polar component is 50% by mass or less of the total component, and more preferably a polyolefin resin. When the polar component is within the above range relative to the total component, the difference in SP value with the rubber component is appropriate, and it has a melting point that is appropriately lower than the maximum vulcanization temperature, ensuring good affinity with the rubber component while easily melting during vulcanization to promote foaming of the vulcanized rubber. Therefore, it is possible to more reliably improve the dispersibility of the hydrophilic resin fibers in the rubber composition and reliably form cavities inside the composite fibers.

[0131] The polyolefin resin may be branched, linear, or otherwise. It may also be an ionomer resin in which the intermolecules of an ethylene-methacrylic acid copolymer are crosslinked with metal ions. Specifically, examples of the polyolefin resin include polyethylene, polypropylene, polybutene, polystyrene, ethylene-propylene copolymer, ethylene-methacrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-propylene-diene terpolymer, ethylene-vinyl acetate copolymer, and ionomer resins thereof. These may be used individually or in combination of two or more. Among these, polyethylene resins, polypropylene resins, polyolefin ionomers, and maleic anhydride-modified α-polyolefins are preferred as polyolefin resins. When polyolefin ionomers or maleic anhydride-modified α-polyolefins are used, they also adhere to the hydroxyl groups of hydrophilic resins, making it possible to further improve the rubber strength.

[0132] To produce composite fibers made of hydrophilic resin with a coating layer made of the low-melting-point resin, a method can be employed in which these resins are blended using a mixing mill, melt-spun to form undrawn yarn, and then heat-stretched to form fibers. Alternatively, a method can be employed in which the resins are blended using two twin-screw extruders equipped with dies, and then similarly formed into fibers. In this case, the hydrophilic resin and the low-melting-point resin are extruded simultaneously from the two die outlets, from which undrawn yarn is formed. The amount of these resins to be put into the mixing mill or hopper may vary depending on the length and diameter of the resulting composite (fiber), but preferably it is 5 to 300 parts by mass, more preferably 10 to 150 parts by mass, of the low-melting-point resin per 100 parts by mass of the hydrophilic resin. By putting these resins in amounts within the above range, a coating layer capable of exhibiting the desired effect is effectively formed on the surface of the composite (fiber) made of hydrophilic resin obtained after the stretching process.

[0133] Furthermore, the average length of the resulting composite fibers is preferably 0.1 to 500 mm, more preferably 0.1 to 7 mm, and the average diameter is preferably 0.001 to 2 mm, more preferably 0.005 to 0.5 mm. When the average length and average diameter are within the above ranges, there is no risk of the composite fibers becoming excessively entangled with each other, and there is no risk of hindering good dispersibility. The aspect ratio is preferably 10 to 4,000, more preferably 50 to 2,000. The aspect ratio refers to the ratio of the long axis of the composite fiber to the short axis.

[0134] Furthermore, for the resulting composite fiber, the ratio (A / B) of the length A of the cross-section in the major axis direction and the length B of the cross-section in the minor axis direction perpendicular to the major axis direction is preferably greater than 1, more preferably 1.5 or more, even more preferably 1.8 or more, and particularly preferably 2.0 or more. Also, the ratio A / B is preferably 20 or less, even more preferably 15 or less, and particularly preferably 10 or less. By setting it within the above range, the ice performance is further improved. Note that as long as A / B is greater than 1, the cross-sectional shape is not particularly limited and may be elliptical, rectangular, polygonal, irregular, etc.

[0135] Furthermore, the amount of composite fibers made of hydrophilic resin on which the coating layer is formed is preferably 0.1 to 100 parts by mass, more preferably 0.3 to 30 parts by mass, even more preferably 0.5 to 10 parts by mass, and even more preferably 1 to 6 parts by mass, per 100 parts by mass of the rubber component. When the amount of composite fibers made of hydrophilic resin on which the coating layer is formed is within the above range, it is possible to form cavities inside the composite fibers to exhibit good drainage while maintaining sufficient durability. Furthermore, while the content ratio of composite fibers and void introducer is not particularly limited, from the viewpoint of achieving and improving both abrasion resistance and ice performance, the mass ratio of composite fibers to void introducer (void introducer / composite fiber) is preferably 0.5 to 10, more preferably 1 to 8, even more preferably 1.5 to 7, and particularly preferably 2 to 6.

[0136] (Hydrogenated resin) The rubber composition preferably further contains a hydrogenated resin in addition to the rubber components and fatty acid amides described above, as well as fillers, liquid polymers, void introducers, foaming aids, and composite fibers as preferred components. Because the hydrogenated resin readily mixes with rubber components, it can impart the flexibility necessary for grip performance on wet and icy / snowy roads to the tire, thereby improving grip performance on icy / snowy roads, i.e., performance on ice.

[0137] Here, the hydrogenated resin refers to a resin obtained by reducing and hydrogenating a resin. Examples of resins used as raw materials for hydrogenated resins include C5 resins, C5-C9 resins, C9 resins, terpene resins, dicyclopentadiene resins, and terpene-aromatic compound resins. These resins may be used individually or in combination of two or more.

[0138] Examples of the aforementioned C5 resins include aliphatic petroleum resins obtained by (co)polymerizing C5 fractions obtained by the thermal decomposition of naphtha in the petrochemical industry. The C5 fraction typically contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, as well as diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene. Commercially available C5 resins can be used.

[0139] The aforementioned C5-C9 resin refers to a C5-C9 synthetic petroleum resin, and as a C5-C9 resin, for example, petroleum-derived C5-C 11 Examples include solid polymers obtained by polymerizing fractions using Friedel-Crafts catalysts such as AlCl3 and BF3, and more specifically, copolymers mainly composed of styrene, vinyltoluene, α-methylstyrene, indene, etc. As for C5-C9 resins, resins with a low amount of C9 or higher components are preferred from the viewpoint of compatibility with rubber components. Here, "low amount of C9 or higher components" means that the amount of C9 or higher components in the total resin is less than 50% by mass, preferably 40% by mass or less. Commercially available C5-C9 resins can be used.

[0140] The aforementioned C9 resin refers to a C9 synthetic petroleum resin, specifically a solid polymer obtained by polymerizing a C9 fraction using a Friedel-Crafts type catalyst such as AlCl3 or BF3. Examples of C9 resins include copolymers mainly composed of indene, α-methylstyrene, vinyltoluene, etc.

[0141] The aforementioned terpene resins are solid resins obtained by polymerizing turpentine oil, which is obtained simultaneously when rosin is obtained from pine trees, or polymer components separated therefrom, using a Friedel-Crafts type catalyst. Examples include β-pinene resin and α-pinene resin. As a representative example of terpene-aromatic compound resins, terpene-phenol resins can be cited. These terpene-phenol resins can be obtained by reacting terpenes with various phenols using a Friedel-Crafts type catalyst, or by further condensation with formalin. There are no particular restrictions on the terpenes used as raw materials, but monoterpene hydrocarbons such as α-pinene and limonene are preferred, those containing α-pinene are more preferred, and α-pinene is particularly preferred.

[0142] The aforementioned dicyclopentadiene-based resin refers to a resin obtained by polymerizing dicyclopentadiene using, for example, a Friedel-Crafts type catalyst such as AlCl3 or BF3.

[0143] Furthermore, the resin used as a raw material for the hydrogenated resin may include, for example, a resin obtained by copolymerizing a C5 fraction with dicyclopentadiene (DCPD) (C5-DCPD resin). Here, if the dicyclopentadiene-derived component in the total resin is 50% by mass or more, the C5-DCPD resin is considered to be included in the dicyclopentadiene resin. If the dicyclopentadiene-derived component in the total resin is less than 50% by mass, the C5-DCPD resin is considered to be included in the C5 resin. The same applies even if a small amount of a third component or the like is included.

[0144] From the viewpoint of improving the compatibility between the rubber component and the hydrogenated resin and further improving the snow performance of the tire, the hydrogenated resin is preferably at least one selected from the group consisting of hydrogenated C5 resins, hydrogenated C5-C9 resins, and hydrogenated dicyclopentadiene resins (hydrogenated DCPD resins), more preferably at least one selected from the group consisting of hydrogenated C5 resins and hydrogenated C5-C9 resins, and even more preferably a hydrogenated C5 resin. Furthermore, it is preferable that the resin has a hydrogenated DCPD structure or a hydrogenated cyclic structure in at least one monomer.

[0145] Furthermore, the softening point of the hydrogenated resin is preferably higher than 110°C. This is because a softening point of the hydrogenated resin exceeding 110°C can sufficiently reduce the rolling resistance of the tire. From the viewpoint of further lowering the rolling resistance of the tire, the softening point of the hydrogenated resin is preferably 115°C or higher, more preferably 118°C or higher, more preferably 123°C or higher, and even more preferably 125°C or higher. In addition, from the viewpoint of further improving the wet grip performance and snow performance of the tire, the softening point of the hydrogenated resin is preferably 145°C or lower, more preferably 138°C or lower, and even more preferably 133°C or lower.

[0146] Furthermore, the weight-average molecular weight of the hydrogenated resin, in terms of polystyrene, is preferably 200 to 1200 g / mol. This is because if the weight-average molecular weight of the hydrogenated resin, in terms of polystyrene, is 200 g / mol or more, precipitation of the hydrogenated resin from the tire can be suppressed, and if it is 1200 g / mol or less, the hydrogenated resin can be reliably compatible with the rubber component. From the viewpoint of suppressing the precipitation of hydrogenated resin from the tire and suppressing the deterioration of the tire appearance, the weight-average molecular weight of the hydrogenated resin in terms of polystyrene is preferably 500 g / mol or more, more preferably 550 g / mol or more, more preferably 620 g / mol or more, more preferably 670 g / mol or more, more preferably 720 g / mol or more, more preferably 750 g / mol or more, and even more preferably 780 g / mol or more. Furthermore, from the viewpoint of improving the compatibility of the hydrogenated resin with the rubber component and further enhancing the effect of the hydrogenated resin, the weight-average molecular weight of the hydrogenated resin in terms of polystyrene is preferably 1300 g / mol or less, preferably 1100 g / mol or less, preferably 1050 g / mol or less, preferably 950 g / mol or less, preferably 900 g / mol or less, and even more preferably 850 g / mol or less.

[0147] Furthermore, the weight-average molecular weight (Mw) of the hydrogenated resin in terms of polystyrene. HR (Unit is g / mol) Softening point (Ts) of hydrogenated resin HR (Unit is °C) is preferably 0.15 or higher [0.15 ≤ (Ts HR / Mw HR )]. The aforementioned (Ts HR / Mw HR ) is more preferably 0.155 or higher, more preferably 0.158 or higher, more preferably 0.160 or higher, and even more preferably 0.162 or higher, from the viewpoint of further improving the wet grip performance and snow performance of the tire. HR / Mw HR From the viewpoint of suppressing the deterioration of tire performance, the value is preferably 0.2 or less, more preferably 0.185 or less, more preferably 0.178 or less, more preferably 0.172 or less, more preferably 0.168 or less, and even more preferably 0.163 or less.

[0148] Furthermore, the hydrogenated resin content in the rubber composition is preferably 5 to 50 parts by mass per 100 parts by mass of the rubber component. When the hydrogenated resin content is 5 parts by mass or more per 100 parts by mass of the rubber component, the effects of the hydrogenated resin can be fully expressed, while when it is 50 parts by mass or less per 100 parts by mass of the rubber component, the precipitation of hydrogenated resin from the tire can be suppressed. Furthermore, from the viewpoint of further enhancing the effects of the hydrogenated resin, the hydrogenated resin content in the rubber composition is preferably 7 parts by mass or more, and more preferably 9 parts by mass or more, per 100 parts by mass of the rubber component. In addition, from the viewpoint of suppressing the precipitation of hydrogenated resin from the tire and suppressing the deterioration of the tire appearance, the hydrogenated resin content in the rubber composition is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and more preferably 20 parts by mass or less, per 100 parts by mass of the rubber component.

[0149] (Cyclic polyol compounds containing a hydrocarbyl group) Furthermore, the rubber composition preferably further contains, in addition to the rubber components and fatty acid amides described above, as well as fillers, liquid polymers, void introducers, foaming aids, composite fibers, and hydrogenated resins as preferred components, a cyclic polyol compound having a hydrocarbyl group. The cyclic polyol compound having a hydrocarbyl group contained in the rubber composition can significantly improve the abrasion resistance and cut resistance of the vulcanized rubber composition for tires of the present invention. Furthermore, by enhancing the interaction between the rubber molecules of the rubber component and the agent described later, the physical properties of the crosslinked rubber can be homogenized, resulting in improved reinforcing properties. Furthermore, it has become clear that the rubber composition having voids according to the present invention exhibits even greater abrasion resistance and cut resistance. Furthermore, because the cyclic polyol compounds having hydrocarbyl groups have fewer hydrophilic sites compared to compounds such as sorbitol, self-aggregation in the rubber composition can be suppressed, and as a result, the tensile fatigue properties of the vulcanized rubber composition for tires can be well maintained.

[0150] Here, the content of the cyclic polyol compound having a hydrocarbyl group is preferably 0.1 to 5 parts by mass per 100 parts by mass of the natural rubber. When the content of the cyclic polyol compound having a hydrocarbyl group is 0.1 parts by mass or more per 100 parts by mass of the natural rubber, a sufficient improvement in wear resistance can be obtained. On the other hand, when the content of the cyclic polyol compound having a hydrocarbyl group is 5 parts by mass or less per 100 parts by mass of the natural rubber, self-aggregation in the rubber composition can be reliably suppressed, and tensile fatigue resistance can be further improved. From a similar viewpoint, the content of the cyclic polyol compound having a hydrocarbyl group is preferably 0.1 to 3 parts by mass, and more preferably 0.3 to 2.5 parts by mass, per 100 parts by mass of the natural rubber.

[0151] Furthermore, the cyclic polyol compound having a hydrocarbyl group is preferably dispersed in the rubber component, and more preferably dispersed in the natural rubber, from the viewpoint of improving abrasion resistance and cut resistance. The aforementioned cyclic polyol compound having a hydrocarbyl group does not act as a surfactant for other compounding agents, but rather disperses in the rubber to improve abrasion resistance and cut resistance, and is therefore distinct from a surfactant.

[0152] Here, the cyclic polyol compound having the hydrocarbyl group preferably has two or more hydroxyl groups, and more preferably three or more hydroxyl groups. This is because having many hydroxyl groups allows for a stronger interaction between the rubber component and the additive, resulting in superior abrasion resistance and cut resistance. On the other hand, from the viewpoint of suppressing self-aggregation in the rubber due to an increase in hydrophilic parts, it is preferable to have five or fewer hydroxyl groups, and more preferably four or fewer hydroxyl groups.

[0153] Furthermore, the cyclic polyol compound having a hydrocarbyl group is preferably a cyclic polyol compound having a hydrocarbyl ester group. This is because it can achieve better abrasion resistance and cut resistance.

[0154] Furthermore, regarding the cyclic polyol compound having the hydrocarbyl group, from the viewpoint of achieving better wear resistance and cut resistance, the following formula (1): [ka] It is more preferable that the compound be represented by [formula].

[0155] In formula (1) above, A is a hydrocarbyl ester group having 6 to 30 carbon atoms or a hydrocarbyl ether group having 6 to 30 carbon atoms, and it is preferable that the number of carbon atoms in the hydrocarbyl group portion of A is 12 to 24. If the number of carbon atoms in the hydrocarbyl group portion of A in formula (1) is in the range of 12 to 24, wear resistance and cut resistance are further improved while maintaining good tensile fatigue resistance. In formula (1), it is preferable that A is an oxygen atom, either the first atom from the ring portion (i.e., the atom bonded to the ring) or the second atom from the ring portion. Examples of A where the first atom from the ring portion is an oxygen atom include groups represented as -O-A' and -O-CO-A''. Examples of A where the second atom from the ring portion is an oxygen atom include groups represented as -CH2-O-A'' and -CH2-O-CO-A'''. Here, it is preferable that A' is a hydrocarbyl group having 6 to 30 carbon atoms, A'' is a hydrocarbyl group having 5 to 29 carbon atoms, and A''' is a hydrocarbyl group having 4 to 28 carbon atoms. Furthermore, it is even more preferable that A', A'' and A''' are hydrocarbyl groups having 12 to 24 carbon atoms.

[0156] Furthermore, in formula (1) above, X1, X2, X3, and X4 are each independently -OH or -R (where -R is -H or -CH2OH), provided that at least two of X1, X2, X3, and X4 are -OH. When two or more of X1, X2, X3, and X4, preferably three or more of X1, X2, X3, and X4 are -OH, the abrasion resistance and cut resistance of the rubber composition are further improved.

[0157] Furthermore, among the compounds represented by formula (1) above, those with the following formula (2) or formula (3): [ka] [ka] Compounds represented by the above formula (2) are more preferred, and compounds represented by the above formula (2) are particularly preferred. In equations (2) and (3), n is a natural number, preferably in the range of 11 to 23. By incorporating a compound represented by formula (2) or formula (3) as the modified cyclic polyol compound, wear resistance can be further improved.

[0158] The cyclic polyol compound having a hydrocarbyl group is not particularly limited, but can be obtained, for example, by reacting a polyol compound such as sorbitol, sorbitan, glucose, or fructose with an aliphatic alcohol such as octanol, decanol, dodecanol, tetradecanol, or hexadecanol, or an aliphatic carboxylic acid such as lauric acid, myristic acid, palmitic acid, stearic acid, or oleic acid.

[0159] Examples of the aforementioned cyclic polyol compounds having a hydrocarbyl group include ester compounds such as sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, and sorbitan monooleate, and ether compounds such as octyl-β-D-glucopyranoside, decyl-β-D-glucopyranoside, dodecyl-β-D-glucopyranoside, tetradecyl-β-D-glucopyranoside, and hexadecyl-β-D-glucopyranoside. These compounds may be used individually or in combination of two or more. Furthermore, among these compounds, from the viewpoint of achieving a higher level of both extension fatigue resistance and cut resistance, the cyclic polyol compound having a hydrocarbyl group is preferably sorbitan monostearate (sorbitan monoester).

[0160] Furthermore, the melting point of the cyclic polyol compound having the hydrocarbyl group is preferably 40 to 100°C, and more preferably 45 to 90°C. This is because if the melting point of the cyclic polyol compound having the hydrocarbyl group is 100°C or lower, solubility during kneading and vulcanization reactions can be improved, and if it is 40°C or higher, cut resistance at high temperatures can be enhanced.

[0161] (Other ingredients) In addition to the components described above, the rubber composition may contain other compounding agents commonly used in the rubber industry. These other components may include, for example, silane coupling agents, vulcanizing agents, vulcanization accelerators, polyethylene glycol, softeners, antioxidants, zinc oxide, etc., selected as appropriate within a range that does not impair the objectives of the present invention. Commercially available compounding agents can be suitably used.

[0162] Furthermore, when silica is included as the filler mentioned above, it is preferable to further include a silane coupling agent. This is because the cut resistance, reinforcing properties, and low loss effects of silica can be further improved. Any known silane coupling agent can be used as appropriate. Examples of the silane coupling agent include bis(3-triethoxysilylpropyl) polysulfide, 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, 3- Examples include triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide. These silane coupling agents may be used individually or in combination of two or more.

[0163] The content of the silane coupling agent varies depending on the type of silane coupling agent, but it is preferably 0.2 or less by mass ratio to the silica content, more preferably 0.1 or less, and even more preferably 0.09 or less. This is because reducing the content of the silane coupling agent to 0.2 or less by mass ratio to the silica content can further improve the cut resistance of the rubber composition.

[0164] The vulcanization accelerator can be any conventionally known one and is not particularly limited, but examples include sulfenamide-based vulcanization accelerators such as CBS (N-cyclohexyl-2-benzothiadylsulfenamide), TBBS (Nt-butyl-2-benzothiadylsulfenamide), and TBSI (Nt-butyl-2-benzothiadylsulfenimide); guanidine-based vulcanization accelerators such as DPG (diphenylguanidine); thiram-based vulcanization accelerators such as tetraoctylthiuram disulfide and tetrabenzylthiuram disulfide; and zinc dialkyldithiophosphate. The content of the vulcanization accelerator is preferably less than the content of sulfur, and more preferably about 1 to 10 parts by mass per 100 parts by mass of the rubber component.

[0165] Furthermore, the rubber composition may also contain a softening agent, as this enhances the flexibility of the rubber and enables superior wet and ice performance. The softening agent can be any conventionally known agent and is not particularly limited; examples include petroleum-based softening agents such as essential oils, paraffin oil, and naphthenic oil, and plant-based softening agents such as palm oil, castor oil, cottonseed oil, and soybean oil. When using these, one or more may be appropriately selected and used. The softening agent should not contain the fatty acid amides mentioned above. When the aforementioned softening agent is included, from the viewpoint of ease of handling, it is preferable to include a softening agent that is liquid at room temperature such as 25°C, such as a petroleum-based softening agent like an aroma oil, paraffin oil, or naphthenic oil.

[0166] The method for producing the rubber composition is not particularly limited. For example, it can be obtained by blending and kneading the above-mentioned components using known methods.

[0167] <Tires> The tire of the present invention is characterized by using the above-described vulcanized rubber composition for tires of the present invention in the tread portion. By applying the rubber composition to the tread portion, excellent wear resistance can be achieved while maintaining good performance on ice. Herein, the tire of the present invention can be used, for example, as a tire for construction vehicles, a tire for trucks and buses, a tire for aircraft, or a tire for passenger cars, and is particularly preferred as a tire for passenger cars or a tire for trucks and buses. This is because the vulcanized rubber composition for tires used as the material for the tread portion has excellent ice performance and wear resistance, which offers significant advantages when used as a tire for passenger cars or a tire for trucks and buses.

[0168] Furthermore, when using the vulcanized rubber composition for tires of the present invention described above in the tread portion, the tread structure can be, for example, the structure described in the following publications. Japanese Patent Publication No. 2016-203842, Japanese Patent Publication No. 2009-196527, Japanese Patent Publication No. 2000-225815, Japanese Patent Publication No. 2000-264019, Japanese Patent Publication No. 2003-211921, International Publication No. 2014 / 196409

[0169] Furthermore, the tire of the present invention is not particularly limited except for using the above-described vulcanized rubber composition for tires of the present invention in the tire tread portion, and can be manufactured according to conventional methods. In addition to ordinary air or air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium can be used as the gas to fill the tire. [Examples]

[0170] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0171] (Examples 1 and 2, Comparative Example 1) Samples of rubber compositions were prepared by compounding and kneading according to the formulations shown in Table 1 using conventional methods. Each of the obtained samples was subjected to vulcanization treatment to prepare samples of vulcanized rubber compositions for tires, and then the following evaluations (1) to (3) were performed.

[0172] <Rating> (1) Foaming rate (porosity) of vulcanized rubber For each sample of the vulcanized rubber composition for tires, after cutting it at an arbitrary point, the weight of each cut sample of the vulcanized rubber composition for tires was measured using a closed electronic balance, and the difference from the theoretical weight ((theoretical specific gravity / measured specific gravity - 1) × 100) was calculated as the foaming rate (porosity) (%). The obtained foaming rates are shown in Table 1.

[0173] (2) Ice performance of vulcanized rubber For each sample of the vulcanized rubber composition for tires, a test piece with a diameter of 50 mm and a thickness of 10 mm was formed. The frictional force generated when the piece was pressed onto a fixed ice surface and rotated was detected using a load cell, and the coefficient of dynamic friction μ was calculated. The measurement temperature was -2°C, and the surface pressure was 12 kgf / cm². 2 The sample rotation speed was set to 20 cm / sec. In Table 1, the evaluation is shown as an index with the kinetic friction coefficient μ of Comparative Example 1 set to 100. A larger index value indicates a larger kinetic friction coefficient μ and better ice performance.

[0174] (3) Abrasion resistance of vulcanized rubber For each sample of the vulcanized rubber composition for tires, the amount of wear was measured according to Method B of the slip and abrasion test specified in JIS K 7218:1986. The measurement temperature was room temperature (23°C) and the load was 16N. In Table 1, the evaluation is shown as an index with the wear amount of the vulcanized rubber of Comparative Example 1 set to 100. A smaller index value indicates less wear and better wear resistance.

[0175] [Table 1]

[0176] *1 Modified styrene-butadiene rubber: N,N-bis-(trimethylsilyl)-aminopropylmethyldiethoxysilane modified SBR *2 Butadiene rubber: Manufactured by Ube Industries, Ltd., "UBEPOL BR150L" *3 Carbon Black: SAF Grade Carbon Black *4 Silica: Manufactured by Tosoh Silica Industry Co., Ltd., product name "Nipsil AQ" *5 Silane coupling agent: Bis(3-triethoxysilylpropyl) polysulfide, manufactured by Shin-Etsu Chemical Co., Ltd. *6 Foaming agent: Dinitrosopentamethylenetetramine, manufactured by Eiwa Chemical Industries, Ltd., "Cellular ZK" *7 Short fibers: Hydrophilic short fibers prepared by the following method In accordance with Manufacturing Example 3 disclosed in Japanese Patent Publication No. 2012-219245, two twin-screw extruders were used, and 40 parts by mass of polyethylene [Novatec HJ360 (MFR 5.5, melting point 132℃), manufactured by Nippon Polyethylene] and 40 parts by mass of ethylene-vinyl alcohol copolymer [Eval F104B (MFR 4.4, melting point 183℃), manufactured by Kuraray] were put into the hopper. The two materials were simultaneously extruded from the die outlet, and the resulting fibers were cut to a length of 2 mm according to a conventional method to produce hydrophilic short fibers in which a coating layer made of polyethylene was formed on the surface of a core made of ethylene-vinyl alcohol copolymer. *8 Liquid polymer: Liquid polybutadiene with a molecular weight of 7000 and a vinyl content of 49%. *9 Fatty acid amide: Manufactured by NOF Corporation, "ALFLO AD-281F" In addition to the listed ingredients, Table 1 also includes the same amounts of resin, oil, stearic acid, and zinc oxide in each example and comparative example.

[0177] The results in Table 1 show that the vulcanized rubber compositions for tires in each example achieve a higher level of both abrasion resistance and ice performance compared to Comparative Example 1. [Industrial applicability]

[0178] According to the present invention, it is possible to provide a vulcanized rubber composition for tires having excellent ice performance. Furthermore, according to the present invention, it is also possible to provide a tire with excellent ice performance. [Explanation of Symbols]

[0179] 10. Vulcanized rubber composition for tires 20 void

Claims

1. A rubber composition containing rubber components and fatty acid amides is obtained by vulcanization. It has multiple voids, A vulcanized rubber composition for tires, characterized in that the fatty acid amide is a fatty acid bisamide.

2. The vulcanized rubber composition for tires according to claim 1, characterized in that the rubber composition contains 0.1 to 10 parts by mass of the fatty acid amide per 100 parts by mass of the rubber component.

3. The tire vulcanized rubber composition according to claim 1 or 2, characterized in that the fatty acid bisamide is ethylenebis fatty acid amide.

4. The vulcanized rubber composition for tires according to claim 1 or 2, characterized in that the rubber composition further comprises a liquid polymer having a polystyrene-equivalent weight-average molecular weight of 5,000 or more and less than 40,000 as measured by gel permeation chromatography.

5. The vulcanized rubber composition for tires according to claim 1 or 2, characterized in that the rubber component contains natural rubber.

6. The vulcanized rubber composition for tires according to claim 1 or 2, characterized in that the rubber component contains a modified conjugated diene polymer having a functional group.

7. The vulcanized rubber composition for tires according to claim 1 or 2, characterized in that the rubber composition further comprises a void-introducing agent.

8. The vulcanized rubber composition for tires according to claim 7, characterized in that the void introducing agent is at least one selected from the group consisting of a foaming agent, a metal sulfate salt, a thermally expandable microcapsule, porous cellulose, and a lignin derivative.

9. The vulcanized rubber composition for tires according to claim 1 or 2, characterized in that the rubber composition further comprises composite fibers.

10. The tire vulcanized rubber composition according to claim 1 or 2, characterized in that the porosity of the tire vulcanized rubber composition is 5 to 45%.

11. A tire characterized by using the vulcanized rubber composition for tires described in claim 1 or 2 in the tread.

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