JP6844889B2 - Rubber composition for tire tread and tire - Google Patents

Description

The present invention relates to a rubber composition for a tire tread and a tire.

In recent years, from the viewpoint of reducing the environmental load, it has been desired to utilize recycled raw materials (recycled rubber, recycled powder rubber, etc.) obtained by recycling waste rubber products for tire applications. However, there is a problem that the wear resistance is lowered by simply blending the recycled raw material.
Patent Document 1 includes butadiene rubber for the purpose of providing a rubber composition for a tire cap tread having improved crack resistance, cut resistance and chipping resistance while effectively utilizing vulcanized powder rubber. A rubber composition for a tire cap tread, which comprises a vulcanized powder rubber having a specific particle size and a softening agent, is disclosed with respect to a diene rubber.
Further, Patent Document 2 provides a rubber composition for a tire having improved wear resistance and fatigue resistance without lowering strength, elongation and heat resistance even when recycled powder rubber is blended. 100 parts by weight of a rubber composition containing 50 parts by weight or more of natural rubber, 50 parts by weight or ^{more of carbon black having a nitrogen ratio surface property of 90 m 2} / g or more, 10 to 30 parts by weight of a softener, and a natural rubber content. A rubber composition for a tire containing 3 to 30 parts by weight of sulfide powder rubber having a powder content of 70% by weight or more and a particle size of 500 μm or more and 10% by weight or less is disclosed.
Further, in Patent Document 3, JIS-A hardness after vulcanization is intended to provide a rubber composition for base tread capable of improving riding comfort and reducing noise while maintaining steering stability. A powdered rubber component having a JIS-A hardness of 30 to 60 is blended in a matrix having a value of 65 to 80, and 1 to 10 parts by mass of the powdered rubber is contained with respect to 100 parts by mass of the rubber component of the matrix. A rubber composition for a base tread is disclosed.

Japanese Unexamined Patent Publication No. 2012-116977 Japanese Unexamined Patent Publication No. 11-335488 Japanese Unexamined Patent Publication No. 2010-132772

An object of the present invention is to provide a rubber composition for a tire tread capable of suppressing a decrease in wear resistance even when a large amount of recycled rubber is blended, and a tire using the rubber composition.

As a result of diligent studies by the present inventors, even if a large amount (30 to 60 parts by mass) of recycled rubber is blended with respect to 100 parts by mass of the rubber component, by blending 3.5 parts by mass or more of zinc oxide, We have found that the above problems can be solved.

That is, the present invention relates to the following <1> to <7>.
<1> 30 to 60 parts by mass of recycled rubber and 3.5 parts by mass or more of zinc oxide are blended with 100 parts by mass of a rubber component consisting of at least one selected from the group consisting of natural rubber and synthetic rubber. A rubber composition for a tire tread, which is characterized by becoming.
<2> The rubber composition for tire tread according to <1>, wherein 10 to 20 parts by mass of powdered rubber is further blended with respect to 100 parts by mass of the rubber component.
<3> The rubber composition for tire tread according to <1> or <2>, which further comprises 0.1 to 1.0 parts by mass of a vulcanization retarder with respect to 100 parts by mass of the rubber component.
<4> The tire tread according to any one of <1> to <3>, which is obtained by blending 1.0 to 3.0 parts by mass of a vulcanization accelerator with respect to 100 parts by mass of the rubber component. Rubber composition for.
<5> The rubber composition for a tire tread according to any one of <1> to <4>, wherein the rubber component is a natural rubber or an isoprene rubber.
<6> The rubber composition is formed by blending a vulcanization accelerator and a vulcanization retarder, and the ratio of the blending amounts of the vulcanization accelerator and the vulcanization retarder in the rubber composition (vulcanization accelerator / The rubber composition for a tire tread according to any one of <1> to <5>, wherein the vulcanization retardant) is 1 to 5.
<7> A tire using the rubber composition according to any one of <1> to <6>.

According to the present invention, it is possible to provide a tire tread rubber composition capable of suppressing a decrease in wear resistance even when a large amount of recycled rubber is blended, and a tire using the rubber composition.

Hereinafter, the present invention will be illustrated in detail based on the embodiments thereof. In the following description, the description of "A to B" indicating the numerical range represents the numerical range including the end points A and B, and is "A or more and B or less" (in the case of A <B) or "A". Hereinafter, it represents "B or more" (in the case of A> B).
In addition, parts by mass and% by mass are synonymous with parts by weight and% by weight, respectively.

(Rubber composition for tire tread)
The rubber composition for tire tread of the present invention (hereinafter, also simply referred to as a rubber composition) comprises 100 parts by mass of a rubber component consisting of at least one selected from the group consisting of natural rubber and synthetic rubber. It is characterized by blending 30 to 60 parts by mass and 3.5 parts by mass or more of zinc oxide.
Conventionally, when powdered rubber or recycled rubber is blended with a rubber composition for tire tread, there has been a problem that the reinforcing property of the rubber composition is lowered, and as a result, the wear resistance is lowered. As a result, the amount of recycled raw materials used had to be suppressed, and it was difficult to sufficiently reduce the environmental load.
The present inventors have found through diligent studies that even if a large amount of recycled rubber is blended, the decrease in abrasion resistance is suppressed by setting the zinc oxide content to a specific amount or more, and the present invention has been made. Has been completed. The detailed mechanism is unknown, but some are presumed as follows.
That is, it is presumed that the recycled rubber has a low molecular weight due to deterioration, overheating, etc. in the usage history and the process of regeneration. It is presumed that by blending a larger amount of zinc oxide than before, zinc oxide acts as a vulcanization accelerator and the wear resistance is improved.
Hereinafter, the present invention will be described in more detail.

<Rubber component>
The rubber composition of the present invention comprises a rubber component consisting of at least one selected from the group consisting of natural rubber and synthetic rubber. As the rubber component, natural rubber may be used alone, synthetic rubber may be used alone, or natural rubber and synthetic rubber may be used in combination.
The synthetic rubber is not particularly limited, but a synthetic diene rubber is preferably exemplified. Examples of synthetic diene rubbers include polybutadiene rubber (BR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), ethylene-propylene-diene ternary copolymer rubber, chloroprene rubber, butyl rubber, and halogenated products. Examples thereof include butyl rubber and acrylonitrile-butadiene rubber. These synthetic rubbers may be used alone or in combination of two or more.
In the present invention, as the rubber component, natural rubber and isoprene rubber are preferable, and natural rubber is more preferable.
In the present invention, the total amount of the natural rubber and the isoprene rubber is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more of the total rubber component. It is particularly preferable that it is composed of only natural rubber and / or isoprene rubber, that is, the total amount of natural rubber and isoprene rubber is 100% by mass of the rubber component.

<Recycled rubber>
The rubber composition of the present invention comprises 30 to 60 parts by mass of recycled rubber with respect to 100 parts by mass of the rubber component.
When the blending amount of the recycled rubber is 30 parts by mass or more with respect to 100 parts by mass of the rubber component, it is preferable from the viewpoint of reducing the environmental load, and when it is 60 parts by mass or less, the decrease in wear resistance is suppressed, which is preferable.
The blending amount of the recycled rubber is preferably 35 to 55 parts by mass, and more preferably 40 to 50 parts by mass with respect to 100 parts by mass of the rubber component.

As the recycled rubber used in the present invention, a commercially available recycled rubber can be used. The recycled rubber shall be a recycled rubber of automobile tires, tubes and other rubber products specified in JIS K6313-2012, and shall have the same properties as this. In addition, powdery ones are excluded. In addition, the recycled rubber is desulfurized.
The type of the recycled rubber may be any one selected from the group consisting of the tube recycled rubber, the tire recycled rubber, and other recycled rubber, and a plurality of types may be combined. Among these, tire recycled rubber is preferable.
The method for producing the recycled rubber is not particularly limited, and a known method such as an oil pan method or a recremator method may be adopted.

<Zinc oxide>
The rubber composition of the present invention comprises zinc oxide. Zinc oxide is commonly referred to as zinc oxide.
The rubber composition of the present invention comprises 3.5 parts by mass or more of zinc oxide mixed with 100 parts by mass of the rubber component. When the blending amount of zinc oxide is 3.5 parts by mass or more with respect to 100 parts by mass of the rubber component, a decrease in wear resistance is suppressed, which is preferable.
The blending amount of zinc oxide is preferably 3.5 to 6.5 parts by mass, and more preferably 4 to 6 parts by mass with respect to 100 parts by mass of the rubber component.
The zinc oxide blended in the rubber composition of the present invention preferably has a nitrogen adsorption specific surface area (N ₂ SA) of 3 m ² / g or more and 110 m ² / g or less by the BET method. The specific surface area of zinc oxide is the specific surface area of the nitrogen adsorption method measured according to the BET method specified in ASTM D4567-03 (2007), and will be referred to as "BET specific surface area" below.
^{The BET specific surface area of zinc oxide is more preferably 3 m 2} / g or more and 25 m ² / g or less, and further preferably 5 m ² / g or more and 10 m ² / g or less, from the viewpoint of the influence on the vulcanization rate.

Other components that may be blended in the rubber composition of the present invention will be described below.
<Powdered rubber>
The rubber composition of the present invention preferably contains powdered rubber. By blending the powdered rubber, the increase in the adhesiveness of the unvulcanized rubber composition due to the addition of the recycled rubber is suppressed, and the workability is improved.
Powdered rubber is also called powdered rubber and is vulcanized powdered rubber (recycled powdered rubber) obtained by recycling waste rubber products. The rubber type of the waste rubber used as the raw material of the powdered rubber is not particularly limited, and may include at least one selected from natural rubber and synthetic rubber. The synthetic rubber is preferably a diene rubber, for example, polyisoprene rubber, styrene-butadiene copolymer rubber, high cis-1,4-polybutadiene rubber, low cis-1,4-polybutadiene rubber, ethylene-propylene-diene tri. Examples thereof include a former copolymer, chloroprene rubber, butyl rubber, halogenated butyl rubber, and acrylonitrile-butadiene rubber.

The method for producing the powdered rubber used in the present invention is not particularly limited, but is produced as follows, for example.
Specifically, the rubber raw material processed into chips is subjected to rough crushing, medium crushing, and finish crushing from rough crushed rubber to medium crushed rubber while adding an anti-sticking agent as necessary by fine crushing means. A finely pulverized rubber treatment method having a finely pulverized step (A) for sequentially finishing the finely pulverized rubber and a classification recovery step (B) for classifying the finely pulverized rubber and recovering at least a part thereof as a finely powdered rubber product Illustrated.
Further, to be described in detail, it is preferable that the following three steps are provided.
Pre-crushing step (Y): The rubber chip is processed into finely crushed rubber by a pre-crushing machine which is a pre-crushing means. However, the preliminary pulverization step is a selective step incorporated into the above-mentioned production method as needed.
Fine pulverization step (A): The fine pulverized rubber is pulverized stepwise by a fine pulverizer as a fine pulverizing means while adding an anti-sticking agent as needed, and finally finished into a finely pulverized rubber.
Classification recovery step (B): The finely pulverized rubber is powdered rubber having a predetermined particle size (including fine powder rubber having a particle size smaller than a predetermined particle size) by a classifying machine as a classification means, and other than that. Classify (sort) and collect as a product. For classification, a mesh sieve specified in ASTM D5603-01 (2008) with a predetermined sieve opening may be used.
In the preliminary crushing step (Y), for example, a rubber chip (tire chip) obtained by crushing a cut tire obtained by cutting waste tires (tire reinforcing materials such as beat wires, steel belts and plies) into several pieces to a predetermined size is used. It is put into a preliminary crusher as a rubber raw material and processed into finely crushed rubber by a crushing section provided in the crushing chamber. The rubber chips supplied to the pre-crusher are appropriate, but cutting them to a size of about 1 mm to 8 mm helps to reduce the particle size of the finely crushed rubber. By ripening the rubber chips in advance, fine crushing by the pre-crusher is smoothed, but there is no problem in processing at normal temperature, and whether or not to add preheating is appropriately selected. Will be done.
Further, by repeatedly crushing the rubber chips with a pre-crusher a plurality of times, finely crushed rubber having a small particle size can be produced.
The range of the size of the rubber chip is not limited to 1 mm to 8 mm, but by setting the size of the rubber chip within the above range, the preliminary crushing step (preliminary crushing step (Y) and before the crushing process is not troublesome. The decrease in pulverization efficiency in Y) is suppressed.
As the preliminary crusher, an appropriate extruder such as an extruder for stirring and crushing rubber chips and a roll crusher for crushing with a roll is selected.

In the fine pulverization step (A), the fine pulverized rubber processed by the pre-pulverizer is subjected to rough pulverization to medium pulverization by the fine pulverizer and then finished and pulverized to be processed into fine pulverized rubber. The fine crusher is preferably a roll crushing means in which the rough crushing part, the middle crushing part and the finishing crushing part are continuously arranged from the upper stage (or upstream) to the lower stage (or downstream). The finely pulverized rubber processed in the finish pulverization step is sent to the classifier in the classification recovery step (B).

In the fine crushing step, the anti-sticking agent added as needed is supplied to the stirrer arranged above the rough crushing part, the medium crushing part and the finish crushing part, and is uniformly with the crushed rubber in the stirrer. It is agitated and charged into the rough crushing section, the medium crushing section and the finish crushing section, respectively.
As the anti-sticking agent, a filler (calcium carbonate, alumina, zinc oxide, etc.) or a reinforcing material (carbon black, talc, silica, etc.) is suitable. The type of anti-sticking agent is appropriately selected in consideration of manufacturing cost, use of finely pulverized rubber, and the like.
By adding the anti-sticking agent, the surface of the crushed rubber is coated, the crushed rubbers are suppressed from being adhered and bonded again, and there is an advantage that the classification (sorting) by the classifier becomes efficient and easy. While ensuring this kind of advantage, the small amount of anti-sticking agent added contributes to cost reduction and is convenient for reuse as a raw material for tires.

Further, the raw material rubber crushing method is not limited to the above method, and a method of freezing crushing, a stone mill type crushing method, a crushing method using an extruder, or the like may be adopted. In the method of freezing and pulverizing, it is preferable that the rubber is pulverized in advance with a cutter mill or the like as necessary, and then the rubber is frozen (frozen) with liquid nitrogen or the like and then pulverized.

In the present invention, the particle size of the powdered rubber is preferably 80 mesh or more. Here, the 80-mesh powder rubber means a powder rubber that has passed through an 80-mesh sieve specified in ASTM D563-01 (2008).
The particle size of the powdered rubber is more preferably 40 to 80 mesh, and further preferably 50 to 70 mesh.

The powdered rubber may be used alone or in combination of two or more.
The blending amount of the powdered rubber is preferably 3 to 40 parts by mass, more preferably 5 to 30 parts by mass, and further preferably 10 to 20 parts by mass with respect to 100 parts by mass of the rubber component.
When the blending amount of the powdered rubber is 3 parts by mass or more, the occurrence of rotor adhesion during the production of the rubber composition due to the addition of recycled rubber is suppressed, and good factory workability can be obtained, which is preferable. Further, when the blending amount of the powdered rubber is 40 parts by mass or less, the abrasion resistance is good, which is preferable.

<Vulcanization retarder>
The rubber composition of the present invention preferably contains a vulcanization retarder.
The vulcanization retarder used in the present invention is not particularly limited, but phthalic anhydride, benzoic acid, salicylic acid, N-nitrosodiphenylamine, N, N', N''-tris (isopropylthio) -N, N', Examples include N''-triphenylphosphoric triamide, N-cyclohexylthiophthalimide, and N- (trichloromethylthio) benzenesulfonamide.
Among these, N-cyclohexylthiophthalimide is preferable.

The vulcanization retarder may be used alone or in combination of two or more.
The vulcanization retarder is preferably blended at the same kneading stage as the vulcanization agent and the vulcanization accelerator, that is, at the final stage of kneading.
The blending amount of the vulcanization retarder in the rubber composition of the present invention is preferably 0.03 to 3.0 parts by mass, preferably 0.1 to 1.0 parts by mass with respect to 100 parts by mass of the rubber component. It is more preferable that the amount is 0.3 to 1.0 parts by mass.
When the blending amount of the vulcanization retarder with respect to 100 parts by mass of the rubber component is within the above range, the factory workability is improved, that is, rubber burning is less likely to occur, which is preferable.

<Vulcanization accelerator>
The rubber composition of the present invention preferably contains a vulcanization accelerator.
Examples of the vulcanization accelerator used in the rubber composition of the present invention include guanidines, sulfenamides and thiazoles.
Examples of guanidines include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatecholbolate, and 1,3-di-o-. Examples thereof include cumenyl guanidine, 1,3-di-o-biphenyl guanidine, 1,3-di-o-cumenyl-2-propionyl guanidine, etc., and because of their high reactivity, 1,3-diphenyl guanidine, 1,3- Di-o-tolylguanidine and 1-o-tolylbiguanidine are preferred, and 1,3-diphenylguanidine is more preferred because of its higher reactivity.

Examples of sulfene amides include N-cyclohexyl-2-benzothiazolyl sulfeneamide, N, N-dicyclohexyl-2-benzothiazolyl sulfeneamide, N-tert-butyl-2-benzothiazolyl sulfeneamide, and the like. N-oxydiethylene-2-benzothiazolyl sulphenamide, N-methyl-2-benzothiazolyl sulphenamide, N-ethyl-2-benzothiazolyl sulphenamide, N-propyl-2-benzothiazolyl sulphenamide Fenamide, N-butyl-2-benzothiazolyl sulphenamide, N-pentyl-2-benzothiazolyl sulphenamide, N-hexyl-2-benzothiazolyl sulphenamide, N-pentyl-2-benzothia Zolyl sulphenamide, N-octyl-2-benzothiazolyl sulphen amide, N-2-ethylhexyl-2-benzothiazolyl sulphen amide, N-decyl-2-benzothiazolyl sulphen amide, N-dodecyl- 2-benzothiazolyl sulfene amide, N-stearyl-2-benzothiazolyl sulfene amide, N, N-dimethyl-2-benzothiazolyl sulfene amide, N, N-diethyl-2-benzothiazolyl sulfene Amide, N, N-dipropyl-2-benzothiazolyl sulphenamide, N, N-dibutyl-2-benzothiazolyl sulphenamide, N, N-dipentyl-2-benzothiazolyl sulphenamide, N, N -Dihexyl-2-benzothiazolyl sulphenamide, N, N-diheptyl-2-benzothiazolyl sulphenamide, N, N-dioctyl-2-benzothiazolyl sulphenamide, N, N-di-2- Ethylhexyl benzothiazolyl sulfene amide, N-decyl-2-benzothiazolyl sulfene amide, N, N-didodecyl-2-benzothiazolyl sulfene amide, N, N-distearyl-2-benzothiazolyl sulfene Examples thereof include amides, and N-cyclohexyl-2-benzothiazolyl sulphenamide and N-tert-butyl-2-benzothiazolyl sulphenamide are preferable because of their high reactivity.
Examples of thiazoles include 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, 2-mercaptobenzothiazole zinc salt, 2-mercaptobenzothiazole cyclohexylamine salt, 2- (N, N-diethylthiocarbamoylthio). ) Benzothiazole, 2- (4'-morpholinodithio) benzothiazole, 4-methyl-2-mercaptobenzothiazole, di- (4-methyl-2-benzothiazolyl) disulfide, 5-chloro-2-mercaptobenzothiazole, 2 -Mercaptobenzothiazole sodium, 2-mercapto-6-nitrobenzothiazole, 2-mercapto-naphtho [1,2-d] thiazole, 2-mercapto-5-methoxybenzothiazole, 6-amino-2-mercaptobenzothiazole, etc. 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide are preferable because of their high reactivity.

The vulcanization accelerator may be used alone or in combination of two or more.
The blending amount of the vulcanization accelerator in the rubber composition of the present invention is preferably 0.3 to 3.5 parts by mass, and 1.0 to 3.0 parts by mass with respect to 100 parts by mass of the rubber component. More preferably.
When the blending amount of the vulcanization accelerator with respect to 100 parts by mass of the rubber component is within the above range, the elastic modulus can be secured even when the recycled rubber is applied, which is preferable.

The ratio of the blending amount of the vulcanization accelerator and the vulcanization retarder in the rubber composition (vulcanization accelerator / vulcanization retarder) is preferably 0.1 to 50, preferably 0.5 to 20. It is more preferably present, and further preferably 1 to 5.
When the ratio of the blending amount of the vulcanization accelerator and the vulcanization delay agent (vulcanization accelerator / vulcanization delay agent) is within the above range, the elastic modulus is secured and the factory workability (that is, rubber burning is less likely to occur). ) Can be compatible.

<Other ingredients>
In addition to the above-mentioned components, the rubber composition of the present invention may appropriately contain a vulcanizing agent, a vulcanization accelerating aid (excluding zinc oxide), a filler, an oil, and other compounding agents.
Examples of the vulcanizing agent include sulfur.
Sulfurization accelerators include stearic acid, palmitic acid, myristic acid, lauric acid, arachidic acid, bechenic acid, lignoceric acid, capric acid, pelargonic acid, capric acid, enanthic acid, caproic acid, oleic acid, bacenoic acid, Examples thereof include saturated fatty acids and unsaturated fatty acids such as linoleic acid, linolenic acid and nervonic acid, organic acids containing resin acids such as stearic acid and modified stearic acid, and esters of saturated fatty acids, unsaturated fatty acids and resin acids.
Examples of the filler include silica and carbon black.
Examples of the oil include paraffinic oil, naphthenic oil, aromatic oil and the like.

As other compounding agents, compounding agents usually used in the rubber industry can be appropriately blended as long as the object of the present invention is not impaired. Specific examples thereof include anti-aging agents, softeners, lubricants and the like.

<Use>
The rubber composition of the present invention has excellent wear resistance and is suitable as a tread member of a tire. In particular, it is suitable as a tread member for heavy-duty pneumatic tires such as truck / bus tires and off-the-road tires (for construction vehicles and mining vehicles).
The rubber composition of the present invention is suitable for a tread member of a rehabilitated tire (retread tire), but may be used for a tire tread member of a new tire.
In the manufacture of rehabilitated tires (retread tires), the tread surface of a tire that has worn out and has reached the end of its primary life (hereinafter referred to as "base tire") is buffed, and a pre-vulcanized rehabilitated tread rubber is placed on the tread surface. The method of pasting the part (= precure tire) is known as one of the typical ones. This method is called by a name such as a cold (COLD) method or a precure method. As another method, there is a hot (HOT) method in which unvulcanized tread rubber is placed on a base tire and mold vulcanized.
The rubber composition of the present invention is particularly suitable as a precure red.

[Preparation of rubber composition, tire]
The rubber composition of the present invention can be obtained by kneading the rubber composition of the present invention using a kneader such as a Banbury mixer, a roll, or an internal mixer according to the above-mentioned compounding formulation.
The tire of the present invention is characterized in that the rubber composition of the present invention is used for a tread. The rubber composition of the present invention described above has sufficient wear resistance and can be suitably used for a tread member (grounding tread member).
The tire of the present invention is preferably a pneumatic tire, and examples of the gas to be filled include an ordinary gas or an inert gas such as nitrogen, argon, or helium whose oxygen partial pressure is adjusted.

When the rubber composition of the present invention is used as a tread member of a new tire, the rubber composition of the present invention containing various components as described above is processed into each member at the unvulcanized stage to form a tire. Raw tires are molded by pasting and molding on the machine by a normal method. The raw tire is heated and pressurized in a vulcanizer to obtain a tire.

When the rubber composition of the present invention is attached as a rehabilitated tread rubber portion, the rubber composition of the present invention is vulcanized and molded to obtain a precure tread as a tire member, which is brought to a predetermined length. After cutting, the precure rubber is wrapped around the tire member to be adhered (for example, a base tire). When wrapping the precure tread, either apply cement to the outer peripheral surface of the bonded tire member such as a base tire and attach a sheet-shaped cushion rubber, or directly from the extruder to the bonded tire with a sheet-shaped cushion. It is preferable to apply rubber. The front end and the rear end of the precure tread wrapped around the adhered tire are joined via rubber cement, cushion rubber, or the like.

The rubber composition of the present invention is suitable as a tread member of a tire, but is not limited to this, and may be used for a base tread, a sidewall, a side reinforcing rubber, a bead filler and the like.
In addition to tire applications, the rubber composition of the present invention can be used for anti-vibration rubber, seismic isolation rubber, belts (conveyor belts), rubber crawlers, various hoses, morans, and the like.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

[Compounding ingredients of rubber composition]
The components to be blended in the rubber compositions of each Example and Comparative Example are as follows.
・ Natural rubber: TSR20
-SBR: Emulsion-polymerized styrene-butadiene copolymer rubber, manufactured by JSR Corporation, trade name "JSR 1500"
-BR: Polybutadiene rubber, manufactured by JSR Corporation, product name "BR01"
-Carbon black: N234, manufactured by Tokai Carbon Co., Ltd., product name "Seast 7HM"
-Recycled rubber: Reclaim rubber, manufactured by Muraoka Rubber Industry Co., Ltd.-Powdered rubber: manufactured by Shinsei Rubber Co., Ltd., using the product name "P-50", further sieve 60 mesh (ASTM D5603-01 (2008)). Passed powder rubber / vulcanization retarder: N-cyclohexylthiophthalimide, made by Flexis, trade name "SANTOGARDPVI / PDR / D"
-Vulcanization accelerator: N-cyclohexyl-2-benzothiazolyl sulfeneamide, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name "Noxeller CZ"
-Zinc oxide: 2 types of zinc oxide manufactured by HakusuiTech Co., Ltd. (BET specific surface area 6 m ² / g)

[Evaluation]
The evaluations in the following examples and comparative examples were performed as follows.
(1) Abrasion resistance A lambourn abrasion test was conducted on each sample of the vulcanized rubber composition. The wear resistance was evaluated at room temperature (23 ° C.) according to the standard test conditions of the lambourn wear test specified in JIS K 6264-2: 2005.
Regarding the evaluation, the reciprocal of the amount of wear of the sample of the vulcanized rubber composition of Comparative Example 1-1, Comparative Example 2-1, Comparative Example 3-1 and Comparative Example 4-1 or Comparative Example 5-1 was used. The reciprocal of each wear amount when set to 100 is shown as an index, and the larger the value, the better the wear resistance.

(2) Heat resistance For each sample of the vulcanized rubber composition, the tensile viscoelasticity was measured using a spectro viscoelasticity measuring device. Regarding the evaluation of measuring the loss tangent (tan δ) at a temperature of 23 ° C., an initial strain (static strain) of 5%, a dynamic strain of 1%, and a frequency of 52 Hz, Comparative Example 1-1, Comparative Example 2-1 and Comparative Example 3 -1, The reciprocal of tan δ of each vulcanized rubber composition sample is shown as an index when the reciprocal of tan δ of the vulcanized rubber composition sample of Comparative Example 4-1 or Comparative Example 5-1 is 100. , The larger the index value, the better the heat resistance.

(3) Tear resistance Each rubber composition was applied to tread rubber. A heavy-duty tire of size: 11R22.5 was prototyped according to a conventional method, and the tear resistance was evaluated by the following method.
The obtained tire was mounted on a truck, and the total length of the tear generated in the tire after traveling 100,000 km was measured, and Comparative Example 1-1, Comparative Example 2-1 and Comparative Example 3-1 and Comparative Example 4 It was expressed as an index when the total length of the tires of -1 or Comparative Example 5-1 was 100. The higher the index value, the better the tear resistance. Specifically, the tear resistance index in Examples 1-1 to 1-4 is as follows, and the control of comparison for other Examples is changed to Comparative Examples 2-1 to 5-1. The same is true except for the change.
Tear resistance index = {(total length of tears in Comparative Example 1-1) / (total length of tears in each example)} × 100

(4) Adhesion Adhesion between the unvulcanized rubber composition and the rotor at the lower part of the Banbury mixer was evaluated according to the following criteria. The evaluation points are in the order of A to C, and the factory workability (low rotor adhesion) is good.
A: No rotor adhesion occurred, and the factory workability of the unvulcanized rubber composition was very good.
B: Mild rotor adhesion occurred, but the factory workability of the unvulcanized rubber composition was hardly reduced.
C: Severe rotor adhesion occurred, and the factory workability of the unvulcanized rubber composition was significantly reduced.

(Examples 1-1 to 1-4 and Comparative Example 1-1)
With the formulation shown in Table 1, the compounding components of the above-mentioned rubber composition were kneaded using a Bunbury mixer to prepare a sample rubber composition. In the final stage of kneading, sulfur as a vulcanizing agent, a vulcanization accelerator, and a vulcanization delaying agent were blended.
The obtained rubber composition was vulcanized at 145 ° C. for 30 minutes to prepare a vulcanized rubber composition, and the wear resistance and heat generation resistance were evaluated using the vulcanized rubber composition. The evaluation of Comparative Example 1-1 was evaluated as 100.
Further, a heavy-duty tire was produced using the obtained rubber composition, and the tear resistance was evaluated using Comparative Example 1-1 as a comparative control.

(Examples 2-1 to 2-16 and Comparative Example 2-1)
With the compounding formulations shown in Tables 2 and 3, the compounding components of the above-mentioned rubber composition were kneaded using a Bunbury mixer to prepare a sample rubber composition.
Further, in the same manner as in Example 1-1, the wear resistance and heat resistance were evaluated with the evaluation of Comparative Example 2-1 as 100. Further, in the same manner as in Example 1-1, the tear resistance was evaluated using Comparative Example 2-1 as a comparative control. Furthermore, the adhesion was evaluated.

(Examples 3-1 to 3-4, and Comparative Examples 3-1 and 3-2)
With the formulation shown in Table 4, the compounding components of the above-mentioned rubber composition were kneaded using a Bunbury mixer to prepare a sample rubber composition.
Further, in the same manner as in Example 1-1, the wear resistance and heat resistance were evaluated with the evaluation of Comparative Example 3-1 as 100. Further, in the same manner as in Example 1-1, the tear resistance was evaluated using Comparative Example 3-1 as a comparative control.

(Examples 4-1 to 4-2 and Comparative Example 4-1)
Abrasion resistance, heat generation resistance, tear resistance, and adhesion were evaluated in the same manner as in Example 2-1 except that the rubber component was changed as shown in Table 5. The comparative control was Comparative Example 4-1.

(Examples 5-1 to 5-2 and Comparative Example 5-1)
Abrasion resistance, heat generation resistance, tear resistance, and adhesion were evaluated in the same manner as in Example 2-1 except that the rubber component was changed as shown in Table 6. The comparative control was Comparative Example 5-1.

From the results in Tables 1 to 6, it was shown that each sample of the example had excellent wear resistance.
On the other hand, the rubber composition of the comparative example was inferior in wear resistance.
Further, from the results of Examples 2-2 and 2-5 to 2-9, it was found that the addition of powdered rubber reduced the adhesiveness of the rubber composition and further improved the workability.
Further, from the results of Tables 5 and 6, it was found that when natural rubber is used as the rubber component, a rubber composition having excellent wear resistance, heat generation resistance and tear resistance can be obtained.
Furthermore, from the results of Examples 2-2 and 2-10-2-16, by using a specific amount of the vulcanization retarder and the vulcanization accelerator in combination, the wear resistance, heat generation resistance, and tear resistance can be improved. It has been found that an excellent rubber composition can be obtained.

According to the present invention, it is possible to provide a rubber composition having excellent wear resistance even when a material such as recycled rubber having a small environmental load is blended, and further, according to the present invention, it is excellent. A tire having wear resistance can be provided.

Claims (6)

With respect to 100 parts by mass of a rubber component consisting of at least one selected from the group consisting of natural rubber and synthetic diene rubber.
45-60 parts by mass of recycled tire rubber, 3.5 parts by mass or more of zinc oxide ,
Further, the vulcanization retarder is blended in an amount of 0.1 to 1.0 parts by mass.
Rubber composition for tire tread. The rubber composition for a tire tread according to claim 1, further comprising 10 to 20 parts by mass of powdered rubber in an amount of 100 parts by mass of the rubber component. The rubber composition for tire tread according to claim 1 or 2 , further comprising 1.0 to 3.0 parts by mass of a vulcanization accelerator blended with 100 parts by mass of the rubber component. The rubber composition for a tire tread according to any one of claims 1 to 3 , wherein the rubber component is a natural rubber or an isoprene rubber. The rubber composition is formed by blending a vulcanization accelerator and a vulcanization retarder, and the ratio of the blending amount of the vulcanization accelerator and the vulcanization retarder in the rubber composition (vulcanization accelerator / vulcanization delay). The rubber composition for a tire tread according to any one of claims 1 to 4 , wherein the agent) is 1 to 5. A tire using the rubber composition according to any one of claims 1 to 5.