JPWO2017061441A1 - Rubber composition for tire tread and tire - Google Patents

Abstract

An object of the present invention is to provide a rubber composition for a tire tread that can suppress a decrease in wear resistance even when a large amount of recycled rubber is blended, and a tire using the rubber composition. The rubber composition for a tire tread of the present invention has 30 to 60 parts by mass of recycled rubber and 3 parts of zinc oxide 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 rubber. More than 5 parts by mass is blended. The rubber composition for a tire tread of the present invention is preferably obtained by further blending 10 to 20 parts by mass of powder rubber with respect to 100 parts by mass of the rubber component.

Description

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

In recent years, utilization of recycled raw materials (recycled rubber, recycled powder rubber, etc.) recycled from waste rubber products for tire applications has been desired from the viewpoint of reducing environmental impact. However, there is a problem that wear resistance is lowered by simply blending recycled raw materials.
Patent Document 1 aims to provide a rubber composition for a tire cap tread having improved crack resistance, cut resistance and chipping resistance while effectively utilizing vulcanized powder rubber, and includes butadiene rubber. A rubber composition for a tire cap tread is disclosed in which a vulcanized powder rubber having a specific particle size and a softening agent are blended with a diene rubber.
Patent Document 2 provides a tire rubber composition having improved wear resistance and fatigue resistance without reducing 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 specific surface property of 90 m ² / g or more, 10 to 30 parts by weight of a softener, and a natural rubber content A tire rubber composition comprising 3 to 30 parts by weight of a vulcanized powder rubber having a powder content of 70% by weight or more and a particle size of 500 μm or more of 10% by weight or less is disclosed.
Furthermore, Patent Document 3 discloses a JIS-A hardness after vulcanization for the purpose of providing a rubber composition for base tread that can improve ride comfort and reduce noise while maintaining steering stability. Is a powder rubber component having a JIS-A hardness of 30 to 60 in a matrix of 65 to 80, and 1 to 10 parts by mass of the powder rubber with respect to 100 parts by mass of the rubber component of the matrix. A rubber composition for a base tread is disclosed.

JP 2012-116977 A JP-A-11-335488 JP 2010-132772 A

  An object of the present invention is to provide a rubber composition for a tire tread that can suppress 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 intensive studies, the present inventors have formulated zinc oxide in an amount of 3.5 parts by mass or more, even when blended in a large amount (30-60 parts by mass) of recycled rubber with respect to 100 parts by mass of the rubber component. It has been 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 selected from the group consisting of natural rubber and synthetic rubber. A rubber composition for a tire tread characterized by comprising:
<2> The rubber composition for a tire tread according to <1>, further comprising 10 to 20 parts by mass of powder rubber with respect to 100 parts by mass of the rubber component.
<3> The rubber composition for a tire tread according to <1> or <2>, further comprising 0.1 to 1.0 part by mass of a vulcanization retarder with respect to 100 parts by mass of the rubber component.
<4> Furthermore, the tire tread according to any one of <1> to <3>, wherein 1.0 to 3.0 parts by mass of a vulcanization accelerator is blended with 100 parts by mass of the rubber component. Rubber composition.
<5> The rubber composition for a tire tread according to any one of <1> to <4>, wherein the rubber component is made of natural rubber or isoprene rubber.
<6> The rubber composition is formed by blending a vulcanization accelerator and a vulcanization retarder, and a ratio of blending amounts of the vulcanization accelerator and the vulcanization retarder in the rubber composition (vulcanization accelerator / The rubber composition for tire treads according to any one of <1> to <5>, wherein the vulcanization retarder is 1 to 5.
<7> A tire using the rubber composition according to any one of <1> to <6>.

  ADVANTAGE OF THE INVENTION According to this invention, even if it mix | blends a large amount of recycled rubber, the rubber composition for tire treads which can suppress a wear-resistant fall, and the tire using the said rubber composition can be provided.

Hereinafter, the present invention will be described in detail based on the embodiments. In the following description, the description of “A to B” indicating a numerical range represents a numerical range including A and B as end points, and “A or more and B or less” (when A <B), or “A "B or more" (when A> B).
Moreover, a mass part and mass% are synonymous with a weight part and weight%, respectively.

(Rubber composition for tire tread)
The rubber composition for tire treads of the present invention (hereinafter also simply referred to as a rubber composition) comprises recycled rubber with respect to 100 parts by mass of at least one rubber component selected from the group consisting of natural rubber and synthetic rubber. 30-60 mass parts and 3.5 mass parts or more of zinc oxide are mix | blended, It is characterized by the above-mentioned.
Conventionally, when powder rubber or recycled rubber is blended with a rubber composition for a 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 has to be suppressed, and it has been difficult to sufficiently reduce the environmental load.
The present inventors have intensively studied and found that, even when a large amount of recycled rubber is blended, a decrease in wear resistance is suppressed by setting the zinc oxide content to a specific amount or more. It came to complete. Although the detailed mechanism is unknown, a part is estimated as follows.
That is, it is presumed that the recycled rubber has a low molecular weight due to deterioration, overheating, etc. in the use history and the process of regeneration. By adding zinc oxide in a larger amount than before, it is presumed that zinc oxide functions as a vulcanization acceleration aid and wear resistance is improved.
Hereinafter, the present invention will be described in more detail.

<Rubber component>
The rubber composition of the present invention is formed by blending at least one rubber component 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.
Although it does not specifically limit as a synthetic rubber, A synthetic diene type rubber is illustrated preferably. Synthetic diene rubbers include polybutadiene rubber (BR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), ethylene-propylene-diene terpolymer rubber, chloroprene rubber, butyl rubber, halogenated Examples 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, the rubber component is preferably natural rubber or isoprene rubber, more preferably natural rubber.
In the present invention, the total amount of natural rubber and isoprene rubber is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more of the total rubber component, It is particularly preferable that the rubber is composed only of 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.
The amount of recycled rubber is preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component, and is preferably 60 parts by mass or less, since a decrease in wear resistance is suppressed.
The amount of the recycled rubber is preferably 35 to 55 parts by mass, more preferably 40 to 50 parts by mass with respect to 100 parts by mass of the rubber component.

Commercially available recycled rubber can be used as the recycled rubber used in the present invention. Recycled rubber is a regenerated rubber used for automobile tires, tubes and other rubber products as defined in JIS K6313-2012, and has the same properties as this. Note that powders are excluded. Further, the recycled rubber is subjected to a desulfurization treatment.
The type of recycled rubber may be any selected from the group consisting of tube recycled rubber, tire recycled rubber, and other recycled rubber, and a plurality of types may be combined. Among these, tire recycled rubber is preferable.
It does not specifically limit as a manufacturing method of a recycled rubber, What is necessary is just to employ | adopt well-known methods, such as an oil pan method and a recremeter method.

<Zinc oxide>
The rubber composition of the present invention contains zinc oxide. Zinc oxide is usually referred to as zinc white.
The rubber composition of the present invention is formed by blending 3.5 parts by mass or more of zinc oxide with respect to 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, it is preferable because a decrease in wear resistance is suppressed.
The compounding 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 compounded in the rubber composition of the present invention preferably has a nitrogen adsorption specific surface area (N ₂ SA) by the BET method of 3 m ² / g or more and 110 m ² / g or less. The specific surface area of zinc oxide is a nitrogen adsorption method specific surface area measured according to the BET method defined in ASTM D4567-03 (2007), and is hereinafter referred to as “BET specific surface area”.
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 influence on the vulcanization rate.

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

Although the manufacturing method of the powder rubber used for this invention is not specifically limited, For example, it manufactures as follows.
Specifically, the raw rubber material processed into chips is finely pulverized, and optionally added with an anti-sticking agent, and then roughly crushed, medium crushed, and finished crushed from coarsely crushed rubber to intermediate crushed rubber. A finely pulverized rubber processing method comprising: a finely pulverized step (A) for sequentially finishing 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.
Furthermore, if it demonstrates in detail, it is preferable to provide the following 3 processes.
Pre-grinding step (Y): The rubber chips are processed into finely crushed rubber by a pre-grinding machine which is a pre-grinding means. However, the preliminary pulverization step is a selective step that is incorporated into the production method as necessary.
Fine pulverization step (A): The finely pulverized rubber is pulverized stepwise by a fine pulverizer as a fine pulverization means while adding an anti-sticking agent as necessary to finally finish the finely pulverized rubber.
Classifying and collecting step (B): Using the classifier as a classifying means, the finely pulverized rubber is powder rubber having a predetermined particle diameter (including fine powder rubber having a particle diameter smaller than the predetermined particle diameter) and the others. The product is classified (sorted) and collected as a product. For classification, a mesh sieve defined in ASTM D5603-01 (2008) having a predetermined sieve opening may be used.
In the preliminary pulverization step (Y), for example, rubber chips (tire chips) obtained by crushing cut tires obtained by cutting waste tires (finished from removal of tire reinforcing materials such as beat wires, steel belts and plies) into a predetermined size are obtained. The rubber raw material is put into a preliminary pulverizer and processed into a finely pulverized rubber by a pulverization section provided in the pulverization chamber. The rubber chip supplied to the preliminary pulverizer is appropriate, but cutting to a size of about 1 mm to 8 mm helps to reduce the particle size of the finely pulverized rubber. By pre-ripening the rubber chips, smoothing by the pre-pulverizer is smooth, but there is no problem in processing at normal temperature, and whether or not preheating is added is appropriately selected. Is done.
Further, finely pulverized rubber having a small particle diameter can be produced by repeatedly pulverizing the rubber chip with a preliminary pulverizer a plurality of times.
The range of the size of the rubber chip is not limited to 1 mm to 8 mm, but by making the size of the rubber chip within the above range, the preliminary pulverization step ( The reduction in the grinding efficiency in Y) is suppressed.
As the preliminary pulverizer, an appropriate one such as an extruder for stirring and pulverizing rubber chips and a roll pulverizer for pulverizing with a roll are selected.

  In the fine pulverization step (A), the finely pulverized rubber treated by the preliminary pulverizer is subjected to rough pulverization to intermediate pulverization and finish pulverization by the fine pulverizer to be processed into finely pulverized rubber. The fine pulverizer is preferably a roll pulverizing means in which a rough pulverizing part, a medium pulverizing part and a finish pulverizing 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 pulverization step, the anti-sticking agent added as necessary is supplied to the agitator disposed above the coarse pulverization unit, the medium pulverization unit, and the finish pulverization unit, and uniformly with the pulverized rubber in the agitator. The mixture is stirred and charged into the rough pulverizing part, the medium pulverizing part, and the finishing pulverizing part.
As the anti-sticking agent, fillers (calcium carbonate, alumina, zinc oxide, etc.) and reinforcing materials (carbon black, talc, silica, etc.) are suitable. The type of the anti-sticking agent is appropriately selected in consideration of the manufacturing cost, the use of finely pulverized rubber, and the like.
By adding an anti-sticking agent, the surface of the pulverized rubber is coated, and the crushed rubber is prevented from adhering and bonding again, and there is an advantage that classification (selection) by a classifier becomes efficient and easy. While securing this type of advantage, a small amount of anti-sticking agent contributes to cost reduction and is convenient for reuse as a tire raw material.

  The method for pulverizing the raw rubber is not limited to the above method, and a method of freeze pulverization, a mortar-type pulverization method, a pulverization method using an extruder, or the like may be employed. In the method of freeze pulverization, it is preferable to finely pulverize with a cutter mill or the like as necessary, and then to freeze (freeze) the rubber using liquid nitrogen or the like before pulverization.

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

A powder rubber may be used individually by 1 type, and may use 2 or more types together.
The compounding amount of the powder rubber is preferably 3 to 40 parts by mass, more preferably 5 to 30 parts by mass, and still more preferably 10 to 20 parts by mass with respect to 100 parts by mass of the rubber component.
When the blending amount of the powder rubber is 3 parts by mass or more, the occurrence of adhesion of the rotor during the production of the rubber composition due to the addition of the regenerated rubber is suppressed, and good factory workability is obtained, which is preferable. Moreover, since the abrasion resistance is favorable when the blending amount of the powder rubber is 40 parts by mass or less, it is preferable.

<Vulcanization retarder>
The rubber composition of the present invention preferably comprises 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 ′, N ''-triphenylphosphoric triamide, N-cyclohexylthiophthalimide, and N- (trichloromethylthio) benzenesulfonamide.
Among these, N-cyclohexylthiophthalimide is preferable.

A vulcanization retarder may be used individually by 1 type, and may use 2 or more types together.
The vulcanization retarder is preferably blended at the same kneading stage as that of the vulcanizing agent and the vulcanization accelerator, that is, at the final stage of kneading.
The compounding amount of the vulcanization retarder in the rubber composition of the present invention is preferably 0.03 to 3.0 parts by mass, and 0.1 to 1.0 parts by mass with respect to 100 parts by mass of the rubber component. It is more preferable that it is 0.3 to 1.0 part by mass.
It is preferable that the blending amount of the vulcanization retarder with respect to 100 parts by mass of the rubber component is within the above range because the factory workability is improved, that is, the rubber burn is hardly generated.

<Vulcanization accelerator>
The rubber composition of the present invention preferably comprises 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, dicatechol borate di-o-tolylguanidine salt, 1,3-di-o- Cumenyl guanidine, 1,3-di-o-biphenyl guanidine, 1,3-di-o-cumenyl-2-propionyl guanidine, and the like. Because of their high reactivity, 1,3-diphenyl guanidine, 1,3- Di-o-tolylguanidine and 1-o-tolylbiguanide are preferable, and 1,3-diphenylguanidine is more preferable because of higher reactivity.

Examples of the sulfenamides include N-cyclohexyl-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N-methyl-2-benzothiazolylsulfenamide, N-ethyl-2-benzothiazolylsulfenamide, N-propyl-2-benzothiazolylsulfenamide Phenamide, N-butyl-2-benzothiazolylsulfenamide, N-pentyl-2-benzothiazolylsulfenamide, N-hexyl-2-benzothiazolylsulfenamide, N-pentyl-2-benzothia Zolylsulfenamide, N-octyl-2-benzothiazolylsulfur Enamide, N-2-ethylhexyl-2-benzothiazolylsulfenamide, N-decyl-2-benzothiazolylsulfenamide, N-dodecyl-2-benzothiazolylsulfenamide, N-stearyl-2-benzo Thiazolylsulfenamide, N, N-dimethyl-2-benzothiazolylsulfenamide, N, N-diethyl-2-benzothiazolylsulfenamide, N, N-dipropyl-2-benzothiazolylsulfenamide N, N-dibutyl-2-benzothiazolylsulfenamide, N, N-dipentyl-2-benzothiazolylsulfenamide, N, N-dihexyl-2-benzothiazolylsulfenamide, N, N- Diheptyl-2-benzothiazolylsulfenamide, N, N-dioctyl-2-benzothia Rylsulfenamide, N, N-di-2-ethylhexylbenzothiazolylsulfenamide, N-decyl-2-benzothiazolylsulfenamide, N, N-didodecyl-2-benzothiazolylsulfenamide, N , N-distearyl-2-benzothiazolylsulfenamide and the like, and because of high reactivity, N-cyclohexyl-2-benzothiazolylsulfenamide and N-tert-butyl-2-benzothiazolylsulfenamide Amides are preferred.
Examples of thiazoles include 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, zinc salt of 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, 2- (N, N-diethylthiocarbamoylthio). ) Benzothiazole, 2- (4′-morpholinodithio) benzothiazole, 4-methyl-2-mercaptobenzothiazole, di- (4-methyl-2-benzothiazolyl) disulfide, 5-chloro-2-mercaptobenzothiazole, 2 -Mercaptobenzothiazole sodium, 2-mercapto-6-nitrobenzothiazole, 2-mercapto-naphtho [1,2-d] thiazole, 2-mercapto-5-methoxybenzothiazole, 6-amino-2-mercaptobenzothiazole, etc. Raised 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide are preferred because of their high reactivity.

A vulcanization accelerator may be used individually by 1 type, and may use 2 or more types together.
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, it is preferable because the elastic modulus can be secured even when the recycled rubber is applied.

The blending ratio of the vulcanization accelerator and the vulcanization retarder in the rubber composition (vulcanization accelerator / vulcanization retarder) is preferably 0.1 to 50, and preferably 0.5 to 20. More preferably, it is more preferably 1-5.
When the ratio of the vulcanization accelerator to the vulcanization retarder (vulcanization accelerator / vulcanization retarder) is within the above range, the elastic modulus is secured and the workability of the factory (that is, rubber scoring hardly occurs). ).

<Other ingredients>
In addition to the components described above, a vulcanizing agent, a vulcanization accelerating aid (however, excluding zinc oxide), a filler, oil, and other compounding agents may be appropriately blended with the rubber composition of the present invention.
Examples of the vulcanizing agent include sulfur.
Vulcanization accelerators include stearic acid, palmitic acid, myristic acid, lauric acid, arachidic acid, behenic acid, lignoceric acid, capric acid, pelargonic acid, caprylic acid, enanthic acid, caproic acid, oleic acid, vaccenic acid, Examples include saturated fatty acids and unsaturated fatty acids such as linoleic acid, linolenic acid, and nervonic acid, organic acids including resin acids such as rosin acid and modified rosin 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, and aromatic oil.

  As other compounding agents, compounding agents usually used in the rubber industry can be appropriately compounded as long as the object of the present invention is not impaired. Specifically, anti-aging agents, softeners, lubricants and the like are exemplified.

<Application>
The rubber composition of the present invention is excellent in 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 retread tire (retread tire), but may be used for a tire tread member of a new tire.
In the manufacture of retreaded tires (retread tires), the tread surface of a tire that has been worn out and has finished its primary life (hereinafter referred to as “base tire”) is buffed, and vulcanized retread rubber that has been pre-cured thereon A method of attaching a part (= precure tread) is known as one of representative examples. 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 an 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 tread.

[Preparation of rubber composition, tire]
The rubber composition of the present invention can be obtained by kneading using a kneading machine such as a Banbury mixer, a roll, an internal mixer or the like according to the above-described blending prescription.
The tire of the present invention is characterized by using the rubber composition of the present invention 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 normal or an inert gas such as air, nitrogen, argon, and helium with adjusted oxygen partial pressure.

  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 an unvulcanized stage, and tire molding is performed. It is pasted and molded by a normal method on the machine, and a green tire is molded. The green tire is heated and pressed in a vulcanizer to obtain a tire.

  Further, when the rubber composition of the present invention is applied as a retreaded tread rubber part, the rubber composition of the present invention is vulcanized and molded to obtain a precure tread as a tire member, which has a predetermined length. After cutting, a precure tread is wound around an adherend tire member (for example, a base tire). When winding the precure tread, cement is applied to the outer peripheral surface of a bonded tire member such as a base tire and a sheet-like cushion rubber is applied, or a sheet-like cushion is directly applied to the bonded tire from an extruder. It is preferable to apply rubber. The front and rear ends of the precure tread wound around the adherend tire are joined via rubber cement or cushion rubber.

The rubber composition of the present invention is suitable as a tread member of a tire, but is not limited thereto, and may be used for base treads, sidewalls, side reinforcing rubbers, bead fillers, 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, Moran and the like.

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

[Compounding ingredients of rubber composition]
The components blended in the rubber compositions of the examples and comparative examples 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, trade name “BR01”
・ Carbon black: N234, manufactured by Tokai Carbon Co., Ltd., trade name “SEAST 7HM”
・ Recycled rubber: Reclaim rubber, manufactured by Muraoka Rubber Co., Ltd. ・ Powder rubber: manufactured by Shinsei Rubber Co., Ltd., trade name “P-50”, and further sieved 60 mesh (ASTM D5603-01 (2008)) Passed powder rubber / vulcanization retarder: N-cyclohexylthiophthalimide, made by Flexis, trade name “SANTO GARDDPVI / PDR / D”
・ Vulcanization accelerator: N-cyclohexyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller CZ”
・ Zinc oxide: 2 types of zinc oxide (BET specific surface area 6 m ² / g) manufactured by Hakusuitec Co., Ltd.

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

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

(3) Tear resistance Each rubber composition was applied to a tread rubber. A tire for heavy load having a size of 11R22.5 was prototyped according to a conventional method, and tear resistance was evaluated by the following method.
The obtained tire was mounted on a truck, and the total length of tears generated on the tire after running for 100,000 km was measured. Comparative Example 1-1, Comparative Example 2-1, Comparative Example 3-1, Comparative Example 4 -1 or the index when the total length of the tear of Comparative Example 5-1 is 100. The higher the index value, the better the tear resistance. Specifically, the tear resistance index in Example 1-1 to Example 1-4 is as follows, and Comparative Example 2-1 to Comparative Example 5-1 are used as comparative controls for the other examples. It is the same except for changing.
Resistance to tear resistance = {(total tear length of Comparative Example 1-1) / (total tear length of each example)} × 100

(4) Adhesion The 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: Rotor adhesion did not occur at all, and the factory workability of the unvulcanized rubber composition was very good.
B: Although slight rotor adhesion occurred, the factory workability of the unvulcanized rubber composition hardly decreased.
C: Severe rotor adhesion occurred, and the factory workability of the unvulcanized rubber composition was greatly reduced.

(Examples 1-1 to 1-4 and Comparative Example 1-1)
The compounding composition shown in Table 1 was used to knead the compounding components of the rubber composition described above using a Banbury mixer to prepare a sample rubber composition. In the final stage of kneading, sulfur as a vulcanizing agent, a vulcanization accelerator, and a vulcanization retarder 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 resistance were evaluated using the vulcanized rubber composition. In addition, evaluation of Comparative Example 1-1 was evaluated as 100.
Moreover, the tire for heavy loads was produced using the obtained rubber composition, and tear resistance was evaluated by using Comparative Example 1-1 as a comparative control.

(Examples 2-1 to 2-16 and Comparative Example 2-1)
The compounding ingredients of the rubber composition described above were kneaded using the Banbury mixer with the compounding formulations shown in Tables 2 and 3 to prepare a rubber composition as a sample.
Further, in the same manner as in Example 1-1, the evaluation of Comparative Example 2-1 was set to 100, and the wear resistance and the heat resistance were evaluated. Further, tear resistance was evaluated in the same manner as in Example 1-1 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)
The compounding composition shown in Table 4 was used to knead the compounding components of the rubber composition described above using a Banbury mixer to prepare a sample rubber composition.
Further, in the same manner as in Example 1-1, the evaluation of Comparative Example 3-1 was set to 100, and the wear resistance and the heat resistance were evaluated. Further, tear resistance was evaluated in the same manner as in Example 1-1 using Comparative Example 3-1 as a comparative control.

(Examples 4-1 to 4-2 and Comparative Example 4-1)
Except for changing the rubber component as described in Table 5, the abrasion resistance, heat resistance, tear resistance, and adhesion were evaluated in the same manner as in Example 2-1. The comparative control was Comparative Example 4-1.

(Examples 5-1 to 5-2 and Comparative Example 5-1)
Except for changing the rubber component as described in Table 6, the abrasion resistance, heat resistance, tear resistance, and adhesion were evaluated in the same manner as in Example 2-1. The comparative control was Comparative Example 5-1.

From the results of Tables 1 to 6, it was shown that each sample of the examples was excellent in wear resistance.
On the other hand, the rubber composition of the comparative example was inferior in abrasion resistance.
Moreover, from the results of Examples 2-2 and 2-5 to 2-9, it was found that by adding powdered rubber, the adhesion of the rubber composition was reduced and the workability was further improved.
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 excellent in all of wear resistance, heat resistance and tear resistance can be obtained.
Furthermore, from the results of Examples 2-2 and 2-10 to 2-16, by using a specific amount of the vulcanization retarder and the vulcanization accelerator in combination, the wear resistance, heat resistance, and tear resistance are improved. It was 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. A tire having wear resistance can be provided.

Claims (7)

For 100 parts by mass of a rubber component consisting of at least one selected from the group consisting of natural rubber and synthetic rubber,
30 to 60 parts by mass of recycled rubber, and 3.5 parts by mass or more of zinc oxide,
Rubber composition for tire tread.   Furthermore, the rubber composition for tire treads of Claim 1 formed by mix | blending 10-20 mass parts of powder rubber with respect to 100 mass parts of rubber components.   Furthermore, the rubber composition for tire treads of Claim 1 or 2 formed by mix | blending 0.1-1.0 mass part of vulcanization retarders with respect to 100 mass parts of rubber components.   Furthermore, the rubber composition for tire treads of any one of Claims 1-3 formed by mix | blending 1.0-3.0 mass parts of vulcanization accelerators with respect to 100 mass parts of rubber components.   The rubber composition for a tire tread according to any one of claims 1 to 4, wherein the rubber component is made of natural rubber or isoprene rubber.   The rubber composition comprises a vulcanization accelerator and a vulcanization retarder, and the ratio of the vulcanization accelerator and the vulcanization retarder in the rubber composition (vulcanization accelerator / vulcanization delay). The rubber composition for tire treads according to any one of claims 1 to 5, wherein the agent is 1-5. A tire using the rubber composition according to claim 1.