JP2017002153A - Rubber composition for tires and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for tires which satisfies all of wet performance, low rolling resistance, and performance on ice and snow roads at excellent levels, and to provide a pneumatic tire using the same.SOLUTION: The rubber composition for tires contains a diene rubber having an average glass transition temperature of -100 to -50°C, an acid-modified polyolefin having a melt flow rate at 230°C of 1.0 g/10 min or less, and silica. The content of the acid-modified polyolefin is 1-30 pts.mass based on 100 pts.mass of the diene rubber. The content of the silica is 80-180 pts.mass based on 100 pts.mass of the diene rubber.SELECTED DRAWING: None

Description

  The present invention relates to a tire rubber composition and a pneumatic tire using the same.

Winter tires that are sometimes used on icy and snowy road surfaces are required to satisfy excellent rolling resistance, wet performance, and icy and snowy road surface performance as well as handling stability and friction resistance.
For such required performance, a method of blending silica with a rubber component constituting a tread portion of a tire is known.
As a winter tire compounded with this silica, for example, in Patent Document 1, “a rubber composition for a tire tread containing a diene rubber component and silica and carbon black, wherein the diene rubber component is (A) an aromatic vinyl. 30 hydroxyl group-containing aromatic vinyl-conjugated diene copolymer containing 20 to 30% by mass of units and 0.1 to 10% by mass of isoprene units, and having a vinyl bond content of 40 to 60 mol% in the conjugated diene part. -80 mass%, (B) 10-50 mass% of high cis-butadiene rubber having a cis-1,4-bond content of 90 mol% or more, and (C) 10-50 mass% of natural rubber The total amount of silica and carbon black is 90 to 150 parts by mass with respect to 100 parts by mass of the diene rubber component. ” Shown ([Claim 1]).

Japanese Patent No. 4666089

  However, since silica has a low affinity with the rubber component and high cohesiveness between the silica components, even if silica is simply added to the rubber component (for example, an aromatic vinyl-conjugated diene copolymer), the silica is contained in the rubber component. Although the wet performance is improved, the low rolling resistance tends not to be sufficiently improved.

  On the other hand, as described above, winter tires are required to have performance on icy and snowy roads. The performance on ice and snow roads is usually expressed by using a rubber component having a low glass transition temperature. However, in order to give wet performance to this, an attempt is made to use a rubber component having a high glass transition temperature (for example, styrene butadiene rubber) in combination. As a result, the glass transition temperature of the entire rubber composition is increased, and the rubber hardness at low temperatures is increased.

  Accordingly, in view of the above circumstances, the present invention has an object to provide a rubber composition for a tire that satisfies all of wet performance, low rolling resistance, and performance on an snowy road, and a pneumatic tire using the same. And

As a result of intensive studies on the above problems, the present inventor obtained an acid-modified polyolefin having a melt mass flow rate at 230 ° C. of 1.0 g / 10 min or less with respect to a diene rubber having an average glass transition temperature of −100 to −50 ° C. By incorporating a specific amount, it was found that even when a large amount of silica is blended in the rubber composition, the dispersibility is improved, and the above problems can be solved, and the present invention has been achieved.
That is, the present inventor has found that the above problem can be solved by the following configuration.

(1) containing a diene rubber having an average glass transition temperature of −100 to −50 ° C., an acid-modified polyolefin having a melt mass flow rate at 230 ° C. of 1.0 g / 10 min or less, and silica,
The content of the acid-modified polyolefin is 1 to 30 parts by mass with respect to 100 parts by mass of the diene rubber,
A tire rubber composition, wherein the silica content is 80 to 180 parts by mass with respect to 100 parts by mass of the diene rubber.
(2) A pneumatic tire using the tire rubber composition according to (1) as a tire tread.
(3) The pneumatic tire according to (2), which is a winter tire.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for tires which satisfy | fills all the wet performance, the low rolling resistance, and the performance on an icy and snowy road can be provided, and a pneumatic tire using the same.

FIG. 1 is a partial cross-sectional schematic view of a tire representing an example of an embodiment of the pneumatic tire of the present invention.

[Rubber composition for tire]
The rubber composition for tires of the present invention (hereinafter also referred to as “rubber composition”) has a diene rubber having an average glass transition temperature of −100 to −50 ° C. and a melt mass flow rate at 230 ° C. of 1.0 g / The acid-modified polyolefin containing 10 min or less and silica, the content of the acid-modified polyolefin is 1 to 30 parts by mass with respect to 100 parts by mass of the diene rubber, and the content of the silica is The amount is 80 to 180 parts by mass with respect to 100 parts by mass of the diene rubber.
The rubber composition of the present invention contains a specific amount of acid-modified polyolefin having a melt mass flow rate at 230 ° C. of 1.0 g / 10 min or less with respect to a diene rubber having an average glass transition temperature of −100 to −50 ° C. Therefore, even if a large amount of silica is added to the rubber composition, its dispersibility is good, and it satisfies wet performance, low rolling resistance, and performance on ice and snow roads at an excellent level, as well as handling stability and wear resistance. Can also be good. The reason is not clear, but it is presumed that it is as follows.

In general, methods for improving wet performance include a method of blending a large amount of silica and a method of blending a diene rubber having a high glass transition temperature. However, when the amount of silica is increased, the wet performance and the handling stability are improved, but the low rolling resistance and the friction resistance tend to be deteriorated. On the other hand, when a diene rubber having a high glass transition temperature is blended, wet performance and handling stability are improved, but on-snow road performance, low rolling resistance, and friction resistance tend to deteriorate.
On the other hand, the rubber composition of the present invention is obtained by adding an acid-modified polyolefin having a melt mass flow rate at 230 ° C. of 1.0 g / 10 min or less to a diene rubber having a low glass transition temperature. The amount of incorporation into the rubber system can be increased and evenly dispersed, so that the wet performance, low rolling resistance, and performance on ice and snow roads are all satisfied at an excellent level, and steering stability and wear resistance are improved. It is thought that it was also possible to improve.
The above-mentioned operational effects are also apparent from the examples described later, that is, it is speculated from the fact that the desired effects are not exhibited in Comparative Example 4 using an acid-modified polyolefin having a melt mass flow rate exceeding 1.0 g / 10 min. Is done. An acid-modified polyolefin having a melt mass flow rate exceeding 1.0 g / 10 min has a smaller molecular weight and a smaller branched structure than an acid-modified polyolefin having a melt mass flow rate of 1.0 g / 10 min or less. For this reason, it is considered that the silica adsorbed on the acid-modified polyolefin tends to re-agglomerate in the system, and accompanying this, the uneven distribution of the acid-modified polyolefin occurs.
Hereinafter, the diene rubber, the acid-modified polyolefin and the preparation method thereof, and other additives including silica will be described in detail.

<Diene rubber>
The diene rubber contained in the rubber composition of the present invention has a double bond in the main chain, and can achieve an average glass transition temperature of -100 to -50 ° C by combining single or plural kinds of diene rubbers. There are no particular limitations as long as it is a natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), aromatic vinyl-conjugated diene copolymer rubber. [For example, styrene-butadiene rubber (SBR), styrene-isoprene rubber, styrene-butadiene-isoprene rubber (SBIR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR)) and the like.
The diene rubber is a derivative in which the end or side chain of each rubber is modified (modified) with an amino group, an amide group, a silyl group, an alkoxy group, a carboxy group, a hydroxy group, an epoxy group, or the like. Also good.

In the present invention, the diene rubber preferably contains at least one selected from the group consisting of aromatic vinyl-conjugated diene copolymer rubber (particularly solution-polymerized SBR) and butadiene rubber, and aromatic vinyl-conjugated diene. It is more preferable to use a copolymer rubber (particularly, solution polymerization SBR) and butadiene rubber in combination.
The total amount of the aromatic vinyl-conjugated diene copolymer and butadiene rubber is suitable for the average glass transition temperature of the diene rubber, and is superior in wet performance, low rolling resistance, and performance on ice and snow roads, and in balance thereof. In view of the above, it is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90 to 100% by mass with respect to the total diene rubber.

Examples of the aromatic vinyl monomer used in the aromatic vinyl-conjugated diene copolymer include styrene; substituted styrene such as α-methylstyrene, 2-methylstyrene, 3-methylstyrene, and 4-methylstyrene. . Of these, styrene is preferred.
Examples of the conjugated diene monomer used in the aromatic vinyl-conjugated diene copolymer include 1,3-butadiene; 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and the like. Substituted butadiene is mentioned. Of these, 2-methyl-1,3-butadiene and 1,3-butadiene are preferred.

The aromatic vinyl-conjugated diene copolymer may be modified, and when it is modified, examples of the modifying group include a hydroxyl group and an N-methylpyrrolidone group.
The hydroxyl group may be primary, secondary or tertiary.
The modifying group can be bonded directly or via an organic group to the aromatic vinyl unit and / or the conjugated diene unit of the aromatic vinyl-conjugated diene copolymer.
At least one modifying group may be present in one molecule of the aromatic vinyl-conjugated diene copolymer.
The aromatic vinyl-conjugated diene copolymer is preferably a hydroxyl group-containing aromatic vinyl-conjugated diene copolymer, more preferably a styrene butadiene rubber terminal-modified with a hydroxyl group.
The aromatic vinyl-conjugated diene copolymer is not particularly limited for its production. When the aromatic vinyl-conjugated diene copolymer is modified, the modification method is not particularly limited. For example, a conventionally well-known thing is mentioned.
The weight average molecular weight of the aromatic vinyl-conjugated diene copolymer is preferably 3.0 × 10 ^{5 to} 20.0 × 10 ⁵ , and preferably 5.0 × 10 ^{5 to} 20.0 × 10 ^5. Is more preferable.
In the present invention, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are values obtained by gel permeation chromatography (GPC) measurement in terms of polystyrene. In addition, as a measuring instrument, three columns (MIXED-B manufactured by Polymer Laboratories) were connected in series, a differential refractometer (RI-8020 manufactured by Tosoh Corporation) as a detector, tetrahydrofuran as an eluent, and 40 ° C. as a column temperature. The following conditions are adopted.

  The amount of the aromatic vinyl-conjugated diene copolymer is 30 to 70 parts by mass in 100 parts by mass of the diene rubber from the viewpoint of being superior in wet performance, low rolling resistance, and performance on ice and snow roads, and in balance thereof. It is preferable that it is 40 to 70 parts by mass.

  The butadiene rubber is preferably a high cis butadiene rubber from the viewpoints of better performance on ice and snow roads and better wear resistance. The cis-1,4-bond content of the high cis-butadiene rubber is preferably 90 mol% or more, more preferably 95 mol% or more, from the viewpoint that it is superior in snow and snow road performance and excellent in wear resistance. preferable.

Butadiene rubber, wet performance, excellent by low rolling resistance, from the viewpoint of excellent wear resistance, the weight-average molecular weight, preferably includes a butadiene rubber of more than ^{6.0 × 10 4, 4.0 × 10} 5 It is preferred to include more than butadiene rubber. The weight average molecular weight of the butadiene rubber is preferably 4.5 × 10 ^{5 to} 1.2 × 10 ⁶ , and more preferably 5.5 × 10 ^{5 to} 1.0 × 10 ⁶ .
The amount of the butadiene rubber is preferably 10 to 50 parts by mass in 100 parts by mass of the diene rubber from the viewpoint of being excellent in low rolling resistance, performance on snowy and snowy roads, and excellent in wear resistance. It is more preferable that

In the present invention, the average glass transition temperature of the diene rubber is −100 to −50 ° C. In such a range, the rubber hardness at a low temperature is maintained flexibly, and the adhesion property to the ice / snow road surface is increased to increase the ice / snow. Road surface performance can be ensured. The average glass transition temperature is −80 to −50 ° C. from the viewpoints of excellent wet performance, low rolling resistance, and snow and snow road performance, and excellent balance between wet performance and snow and snow road performance, steering stability, and wear resistance. It is preferable that it is -70 to -55 ° C.
Here, the average glass transition temperature of the diene rubber is an average value of the glass transition temperature calculated as the sum of the products of the Tg and the blending ratio of each rubber component constituting the diene rubber. That is, in a diene rubber composed of n types (n is an integer of 1 or more), the Tg of any rubber component is Ti [° C.] (i = 1 to n), and the blending ratio is Wi [mass%] (i = 1 to n), the average glass transition temperature of the diene rubber is calculated by the following formula (1).

Average glass transition temperature [° C.] = Σ (Ti × Wi) / ΣWi (1)
(However, ΣWi = 100 [mass%].)

  The glass transition temperature (Tg) of each diene rubber is measured by a differential scanning calorimetry (DSC) under a heating rate condition of 10 ° C./min, and is set as the temperature at the midpoint of the transition region. When each diene rubber contains oil-extended oil, the glass transition temperature of the rubber without oil-extended oil is set.

<Acid-modified polyolefin>
The acid-modified polyolefin contained in the rubber composition of the present invention is a modified polymer having a melt mass flow rate (MFR) of 1.0 g / 10 min or less among modified polymers obtained by modifying polyolefin resins with unsaturated carboxylic acids. .
Here, in the present invention, the melt mass flow rate (MFR) is 230 ° C. under a load of 21.degree. C. according to “Testing method for melt mass flow rate (MFR) of plastic-thermoplastic plastic” defined in JIS K 7210: 1999. It is a value measured under the condition of 2N.

  In the present invention, the melt mass flow rate (MFR) of the acid-modified polyolefin is improved because the dispersibility of the silica is improved so that the wet performance, the low rolling resistance, the performance on snow and snow, the handling stability, and the wear resistance are improved. Is preferably 0.2 to 1.0 g / 10 min, and more preferably 0.4 to 1.0 g / 10 min.

  For reasons of better processability, it is preferably a polyolefin having at least one repeating unit selected from the group consisting of ethylene, propylene, 1-butene and 1-octene, ethylene, propylene and More preferred is a polyolefin having at least one repeating unit selected from the group consisting of 1-butene.

(Polyolefin)
As the polyolefin constituting the skeleton of the acid-modified polyolefin, for example,
Homopolymers such as polyethylene, polypropylene, polybutene and polyoctene;
Ethylene / propylene copolymer, ethylene / 1-octene copolymer, ethylene / 1-butene copolymer, propylene / 1-butene copolymer, propylene / 1-hexene copolymer, propylene / 4-methyl-1 -Pentene copolymer, propylene / 1-octene copolymer, propylene / 1-decene copolymer, propylene / 1,4-hexadiene copolymer, propylene / dicyclopentadiene copolymer, propylene / 5-ethylidene- 2-norbornene copolymer, propylene / 2,5-norbornadiene copolymer, propylene / 5-ethylidene-2-norbornene copolymer, 1-butene / propylene copolymer, 1-butene / 1-hexene copolymer 1-butene / 4-methyl-1-pentene copolymer, 1-butene / 1-octene copolymer, 1-butene -Decene copolymer, 1-butene-1,4-hexadiene copolymer, 1-butene-dicyclopentadiene copolymer, 1-butene-5-ethylidene-2-norbornene copolymer, 1-butene-2 Two-component copolymers such as 5-norbornadiene copolymer and 1-butene-5-ethylidene-2-norbornene copolymer;
Ethylene / propylene / 1-butene copolymer, ethylene / propylene / 1-hexene copolymer, ethylene / propylene / 1-octene copolymer, ethylene / propylene / 1-octene copolymer, ethylene / propylene / 1, 4-hexadiene copolymer, ethylene / propylene / 1,4-hexadiene copolymer, ethylene / propylene / dicyclopentadiene copolymer, ethylene / propylene / dicyclopentadiene copolymer, ethylene / propylene / 5-ethylidene- 2-norbornene copolymer, ethylene / propylene / 5-ethylidene-2-norbornene copolymer, ethylene / propylene / 2, 5-norbornadiene copolymer, ethylene / propylene / 2, 5-norbornadiene copolymer, ethylene / propylene Propylene-5-ethylidene-2-no Borene copolymer, ethylene / propylene / 5-ethylidene-2-norbornene copolymer, 1-butene / ethylene / propylene copolymer, 1-butene / ethylene / 1-hexene copolymer, 1-butene / ethylene / 1-octene copolymer, 1-butene / propylene / 1-octene copolymer, 1-butene / ethylene / 1,4-hexadiene copolymer, 1-butene / propylene / 1,4-hexadiene copolymer, 1-butene / ethylene / dicyclopentadiene copolymer, 1-butene / propylene / dicyclopentadiene copolymer, 1-butene / ethylene / 5-ethylidene-2-norbornene copolymer, 1-butene / propylene / 5 -Ethylidene-2-norbornene copolymer, 1-butene-ethylene-2,5-norbornadiene copolymer, 1-butene・ Multi-components such as propylene / 2,5-norbornadiene copolymer, 1-butene / ethylene / 5-ethylidene-2-norbornene copolymer, 1-butene / propylene / 5-ethylidene-2-norbornene copolymer And the like.

(Unsaturated carboxylic acid)
On the other hand, examples of the unsaturated carboxylic acid that modifies the above-described polyolefin include maleic acid, fumaric acid, acrylic acid, crotonic acid, methacrylic acid, itaconic acid, or acid anhydrides of these acids. .
Of these, maleic anhydride, maleic acid, and acrylic acid are preferably used.

The acid-modified polyolefin may be produced by a usual method, for example, a method for graft polymerization of an unsaturated carboxylic acid to the polyolefin under the usual conditions, for example, stirring under heating, or a commercially available product. May be used.
Examples of commercially available products include maleic anhydride-modified ethylene butene copolymers such as TAFMER MH7020 (MFR: 0.7 g / min, manufactured by Mitsui Chemicals).

  In the present invention, the content of the acid-modified polyolefin is 1 to 30 parts by mass with respect to 100 parts by mass of the diene rubber, and improves the dispersibility of silica to improve wet performance, low rolling resistance, and on ice and snowy roads. For reasons of better performance, steering stability, and wear resistance, it is preferably 3 to 20 parts by mass, particularly preferably 5 to 15 parts by mass.

<Silica>
The silica contained in the rubber composition of the present invention is not particularly limited, and any conventionally known silica compounded in the rubber composition for uses such as tires can be used.
Specific examples of silica include fumed silica, calcined silica, precipitated silica, pulverized silica, fused silica, colloidal silica, and the like. Silica can be used alone or in combination of two or more.

CTAB adsorption specific surface area of the silica, from the viewpoint of obtaining superior wet performance and wear resistance, is preferably greater than 160 m ² / g, and more preferably 170~230m ² / g. Here, the CTAB adsorption specific surface area is measured according to the CTAB adsorption method described in JIS K6217-3: 2001.

  In the present invention, the content of silica is 80 to 1800 parts by mass with respect to 100 parts by mass of the diene rubber, and is superior to the wet performance, low rolling resistance, and performance on ice and snow on the resulting tire, wear resistance, and handling. From the reason that the stability is improved, it is more preferably 80 to 150 parts by mass, and further preferably 90 to 130 parts by mass.

<Other ingredients>
If necessary, the rubber composition of the present invention may further contain an additive within a range that does not impair its effects and purposes. Examples of additives include rubbers other than diene rubbers, silane coupling agents, and fillers other than silica (for example, carbon black, clay, mica, talc, calcium carbonate, aluminum hydroxide, aluminum oxide, titanium oxide). Other rubber compositions for tires such as vulcanization accelerators, resins such as terpene resins, zinc oxide, stearic acid, anti-aging agents, processing aids, aroma oils, process oils, liquid polymers, thermosetting resins, vulcanizing agents, etc. Commonly used for products.

(Carbon black)
The rubber composition of the present invention preferably contains carbon black.
Specific examples of the carbon black include furnace carbon blacks such as SAF, ISAF, HAF, FEF, GPE, and SRF. These may be used alone or in combination of two or more. May be.
Further, the carbon black, from the viewpoint of workability and the like at the time of mixing of the rubber composition is preferably a nitrogen adsorption specific surface area (N ₂ SA) is 10 to 300 m ² / g, with 20 to 200 m ² / g More preferably.
Here, N ₂ SA is a value obtained by measuring the amount of nitrogen adsorbed on the carbon black surface in accordance with JIS K 6217-2: 2001 “Part 2: Determination of specific surface area—nitrogen adsorption method—single point method”. .

  When the carbon black is contained, the content is preferably 1 to 100 parts by mass and more preferably 5 to 80 parts by mass with respect to 100 parts by mass of the diene rubber.

(Silane coupling agent)
The rubber composition of the present invention preferably contains a silane coupling agent.
The said silane coupling agent is not specifically limited, The conventionally well-known arbitrary silane coupling agents currently mix | blended with the rubber composition for uses, such as a tire, can be used.
Specific examples of the silane coupling agent include 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-mercaptopropyltriethoxy Silane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N- Methylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl Methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropylbenzothiazole tetrasulfide These may be used, and these may be used alone or in combination of two or more. Moreover, you may use what made these 1 type, or 2 or more types oligomerize beforehand.

  Specific examples of silane coupling agents other than those described above include, for example, γ-mercaptopropyltriethoxysilane, 3- [ethoxybis (3,6,9,12,15-pentaoxaoctacosan-1-yloxy]. ) Silyl] -1-propanethiol and other mercapto silane coupling agents; 3-octanoylthiopropyltriethoxysilane and other thiocarboxylate silane coupling agents; 3-thiocyanate propyltriethoxysilane and other thiocyanate silane cups Ring agents; and the like. These may be used alone or in combination of two or more. Moreover, you may use what made these 1 type, or 2 or more types oligomerize beforehand.

  Of these, bis- (3-triethoxysilylpropyl) tetrasulfide and / or bis- (3-triethoxysilylpropyl) disulfide is preferably used from the viewpoint of reinforcing effect. Specifically, Examples thereof include Si69 [bis- (3-triethoxysilylpropyl) tetrasulfide; manufactured by Evonik Degussa], Si75 [bis- (3-triethoxysilylpropyl) disulfide; manufactured by Evonik Degussa).

  When the silane coupling agent is contained, the content is preferably 0.1 to 20 parts by mass and more preferably 0.5 to 15 parts by mass with respect to 100 parts by mass of the silica.

<Method for producing rubber composition>
The method for producing the rubber composition of the present invention is not particularly limited, and specific examples thereof include, for example, kneading the above-described components using a known method and apparatus (for example, a Banbury mixer, a kneader, a roll, etc.). The method of doing is mentioned.
The rubber composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.
The rubber composition of the present invention can be used for production of winter tires.

[Pneumatic tire]
Next, the pneumatic tire of the present invention will be described below.
The pneumatic tire of the present invention is a pneumatic tire using the tire rubber composition of the present invention for a tire tread.
The tire rubber composition may be used at least for a tire tread, and the tire rubber composition can be used for, for example, a bead portion and a sidewall portion other than the tire tread.
Hereinafter, a pneumatic tire according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a partial cross-sectional schematic view of a tire representing an example of an embodiment of the pneumatic tire of the present invention. The pneumatic tire of the present invention is not limited to the embodiment shown in FIG.

In FIG. 1, reference numeral 1 represents a bead portion, reference numeral 2 represents a sidewall portion, and reference numeral 3 represents a tire tread.
Further, a carcass layer 4 in which fiber cords are embedded is mounted between the pair of left and right bead portions 1, and the end of the carcass layer 4 extends from the inside of the tire to the outside around the bead core 5 and the bead filler 6. Wrapped and rolled up.
In the tire tread 3, a belt layer 7 is disposed over the circumference of the tire on the outside of the carcass layer 4.
Moreover, in the bead part 1, the rim cushion 8 is arrange | positioned in the part which touches a rim | limb.

The pneumatic tire of the present invention is not particularly limited except that the tire rubber composition of the present invention is used for a tread of a pneumatic tire, and can be produced, for example, according to a conventionally known method. Moreover, as gas with which a tire is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.
The pneumatic tire of the present invention can be used as a winter tire.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.

<Manufacture of rubber composition for tire>
The components shown in the following table were blended in the proportions (parts by mass) shown in the table.
Specifically, first, the components shown in the table below, excluding sulfur and the vulcanization accelerator, are mixed for 10 minutes using a 1.7 liter closed Banbury mixer, and then discharged to room temperature. A master batch was obtained. Furthermore, using the Banbury mixer, sulfur and a vulcanization accelerator were mixed into the obtained master batch to obtain a tire rubber composition.

<Manufacture of vulcanized rubber>
The tire rubber composition (unvulcanized) produced as described above was press-vulcanized at 160 ° C. for 20 minutes in a mold (15 cm × 15 cm × 0.2 cm) to produce a vulcanized rubber sheet.

<Average glass transition temperature of diene rubber>
The diene rubber shown in the following Table 1 was mixed in the ratio (parts by mass) shown in the same table, and the glass transition temperature (Tg) of the obtained diene rubber mixture was 10 ° C./min using a differential thermal analyzer. The midpoint method was used at the rate of temperature increase.

<Melt mass flow rate>
In accordance with “Plastic-thermoplastic melt mass flow rate (MFR) test method” defined in JIS K7210: 1999, measurement was performed under conditions of a temperature of 230 ° C. and a load of 21.2 N.

  The following evaluation was performed using the tire rubber composition and vulcanized rubber produced as described above. The results are shown in Table 1.

<Wet performance (tan δ (0 ° C.))>
About the produced vulcanized rubber sheet, in accordance with JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.) under the conditions of 10% ± 2% elongation deformation strain rate, frequency 20 Hz, temperature 0 ° C. , Tan δ (0 ° C.) was measured, and wet performance was evaluated based on this value. The results were expressed as an index with a standard example of 100. The larger the index, the better the wet performance when used as a tire.

<Low rolling resistance (tan δ (60 ° C.))>
About the produced vulcanized rubber sheet, in accordance with JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.) under the conditions of an elongation deformation strain rate of 10% ± 2%, a frequency of 20 Hz, and a temperature of 60 ° C. , Tan δ (60 ° C.) was measured, and the low rolling resistance was evaluated by this value. The result was expressed as an index with the reciprocal of the value of the standard example as 100. The larger the index, the better the rolling resistance when made into a tire.

<Ice / snow road performance (elastic modulus E ′ (−10 ° C.))>
About the obtained vulcanized rubber sheet, according to JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.), the tensile deformation strain rate is 10% ± 0.5%, the frequency is 20 Hz, and the temperature is −10. E ′ (−10 ° C.) was measured under the condition of ° C., and the performance on icy and snowy roads was evaluated based on this value. The result was expressed as an index with the reciprocal of the value of the standard example as 100. The larger the index, the better the performance on ice and snow.

<Steering stability>
About the obtained vulcanized rubber sheet, hardness (20 ° C.): hardness (type A durometer hardness) at 20 ° C. was measured according to JIS K6253-3, and steering stability was evaluated based on this value. The results are shown as an index with the value of Comparative Example 1 being 100. The larger the index, the higher the hardness and the better the steering stability.

<Abrasion resistance>
The obtained vulcanized rubber sheet was used in accordance with JIS K6264-2: 2005, using a Lambone abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.), temperature 20 ° C., load 39 N, slip rate 30%, time 4 minutes. The amount of wear was measured under the conditions. The obtained results were expressed as an index with the reciprocal of the value of the standard example as 100. Higher index means better wear resistance.

The details of each component shown in Table 1 are as follows.
S-SBR: Nipol NS530 manufactured by Nippon Zeon Co., Ltd. (an aromatic vinyl-conjugated diene copolymer whose terminal is modified with a hydroxyl group, an oil-extended product containing 20 parts by mass of an oil-extended oil with respect to 100 parts by mass of a rubber component, a styrene content of 30 (Mass%, vinyl content 60 mass%, glass transition temperature −25 ° C. without oil-extended oil, glass transition temperature −31 ° C. with oil-extended oil)
BR: Nipol BR1220 manufactured by Nippon Zeon Co., Ltd. (butadiene rubber, cis content 98% by mass, vinyl content 2% by mass, glass transition temperature -105 ° C., weight average molecular weight 4.9 × 10 ⁵ )
・ Silica: Zeosil 1165MP manufactured by Rhodia
Silane coupling agent: bis (3-triethoxysilylpropyl) tetrasulfide, Si69 (Evonik Degussa)
Carbon black: Show black N339 (CTAB adsorption specific surface area = 90 m ² / g, manufactured by Cabot Japan)

・ Zinc oxide: Zinc flower 3 types (manufactured by Shodo Chemical Industries)
・ Stearic acid: Beads stearic acid (manufactured by NOF Corporation)
Aroma oil: Extract No. 4 S (manufactured by Showa Shell Sekiyu KK)
Acid-modified polyolefin 1: Tuffmer MH7020 (maleic anhydride-modified ethylene butene copolymer, MFR: 0.7 g / min) manufactured by Mitsui Chemicals, Inc.
Acid-modified polyolefin 2: Admer QE060 (maleic anhydride-modified polypropylene, MFR: 7 g / min) manufactured by Mitsui Chemicals, Inc.
・ Sulfur: Fine sulfur with Jinhua stamp oil (manufactured by Tsurumi Chemical Co., Ltd.)
・ Vulcanization accelerator: N-cyclohexyl-2-benzothiazolylsulfenamide (Noxeller CZ-G, manufactured by Ouchi Shinsei Chemical Co., Ltd.)

As is clear from the results shown in Table 1, from the comparison between Comparative Example 1 and the standard example, when the amount of silica is increased, the wet performance and the steering stability are more effective than the standard example. However, low rolling resistance and friction resistance tend to deteriorate. On the other hand, as is clear from the comparison between Comparative Example 2 and the standard example, when a diene rubber having a high glass transition temperature is blended, although wet performance and handling stability are improved, performance on ice and snow roads and low rolling resistance are improved. The anti-friction performance tended to deteriorate.
On the other hand, according to the rubber composition for tires prepared in the examples, the silica dispersibility is excellent even when a large amount of silica is blended, and therefore, the performance on ice and snow road, wet performance and low rolling resistance are all excellent. It satisfies the level, and also has excellent handling stability and friction resistance.
As is clear from the comparison between Comparative Example 3 and the standard example, when the acidic polyolefin is blended beyond a predetermined range, the low rolling resistance and the friction resistance are improved due to the improved dispersibility of the silica. Stability performance and wet performance declined.
As is clear from the comparison between Comparative Example 4 and the standard example, when an acid-modified polyolefin having a melt mass flow rate exceeding 1.0 g / min is blended, the above-mentioned acid-modified polyolefin shows some dispersibility of silica. However, wet performance and handling stability decreased. This is presumably because the acid-modified polyolefin used in Comparative Example 4 has a higher melt mass flow rate than the acid-modified polyolefin used in Example 1. That is, in Example 1 using an acid-modified polyolefin having a large molecular weight and / or a large branched structure (in other words, a low melt mass flow rate), the silica adsorbed on the acid-modified polyolefin is prevented from reaggregating and diene When the acid-modified polyolefin as in Comparative Example 4 is used, the silica adsorbed on the acid-modified polyolefin is re-aggregated and the acid-modified polyolefin is unevenly distributed. It is thought that no improvement effect was seen in wet performance and steering stability.
As is clear from the comparison between Comparative Example 5 and the standard example, the addition of the acid-modified polymer improves the low rolling resistance and anti-friction performance, but the amount of silica is small, so the wet performance and steering stability are improved. Decreased.
As is clear from the comparison between Comparative Example 6 and the standard example, since the diene rubber having a high glass transition temperature is blended, although the wet performance and the handling stability are excellent, the snow and snow road surface performance is low, and the acid-modified polyolefin The improvement effect by addition was not seen, but the friction-resistant performance fell.

1 Bead part 2 Side wall part 3 Tire tread part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Rim cushion

Claims (3)

A diene rubber having an average glass transition temperature of −100 to −50 ° C., an acid-modified polyolefin having a melt mass flow rate at 230 ° C. of 1.0 g / 10 min or less, and silica,
The content of the acid-modified polyolefin is 1 to 30 parts by mass with respect to 100 parts by mass of the diene rubber,
A tire rubber composition, wherein the silica content is 80 to 180 parts by mass with respect to 100 parts by mass of the diene rubber.   A pneumatic tire using the tire rubber composition according to claim 1 for a tire tread.   The pneumatic tire according to claim 2, which is a winter tire.