JP7333208B2 - Rubber composition, rubber composition for tire, rubber composition for crawler, tire and rubber crawler - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition, a rubber composition for tires, a rubber composition for crawlers, a tire and a rubber crawler.

When agricultural vehicles such as tractors and rice transplanters that have completed work in paddy fields, wet fields, upland fields, etc., run on general paved roads, dirt, etc. adhering to lugged running bodies such as tires and crawlers spreads over the road. There was a problem of clutter.
In order to solve this problem, in Patent Document 1, in a lugged traveling body having a plurality of lugs, the surface of the tread is covered with a mud adhesion prevention layer made of two or more layers of elastic bodies with low hardness, thereby removing mud. It is disclosed to prevent the adhesion of Further, Patent Document 2 discloses that 2 to 20 parts by mass of fatty acid amide is compounded in a rubber composition for a rubber crawler in order to obtain a good effect of preventing adhesion of mud to the rubber crawler.

JP-A-11-78406 JP 2009-263403 A

However, with the methods described in Patent Documents 1 and 2, it is difficult to remove mud adhering to tires, rubber crawlers, and the like, and pollution prevention of roads and the like is insufficient.

The present invention provides a tire and a rubber crawler excellent in mud release property, a tire rubber composition from which the tire is obtained, a crawler rubber composition from which the rubber crawler is obtained, and a rubber composition from which the tire and the rubber crawler are obtained. The task is to provide

<1> It contains a rubber component and at least one hydrophilic compound selected from the group consisting of cellulose and cellulose derivatives, and the content of the hydrophilic compound is 5 to 5 parts by mass based on 100 parts by mass of the rubber component. When the content is 30 parts by mass and the content of the hydrophilic compound is 10 parts by mass or less per 100 parts by mass of the rubber component, the rubber composition further contains a water-repellent compound.

<2> The rubber composition according to <1>, wherein the hydrophilic compound has a weight average molecular weight of 150 g/mol to 400000 g/mol.
<3> The rubber composition according to <2>, wherein the hydrophilic compound has a melting point of 200 to 400° C. or has no melting point.

<4> A rubber composition for tires comprising the rubber composition according to any one of <1> to <3>.
<5> A rubber composition for crawlers, comprising the rubber composition according to any one of <1> to <3>.

<6> A tire using the rubber composition according to any one of <1> to <3>.
<7> A rubber crawler using the rubber composition according to any one of <1> to <3>.

INDUSTRIAL APPLICABILITY According to the present invention, a tire and a rubber crawler having excellent mud release properties, a tire rubber composition from which the tire is obtained, a crawler rubber composition from which the rubber crawler is obtained, and a rubber from which the tire and the rubber crawler are obtained A composition can be provided.

<Rubber composition>
The rubber composition of the present invention contains a rubber component and at least one hydrophilic compound selected from the group consisting of cellulose and cellulose derivatives, and the content of the hydrophilic compound is 100 parts by mass of the rubber component. and the content of the hydrophilic compound is 10 parts by mass or less with respect to 100 parts by mass of the rubber component, the water-repellent compound is further included.
By obtaining a tire and a rubber crawler using the rubber composition of the present invention, the tire and the rubber crawler are excellent in mud releasability.
In the present invention, "mud releasability" means ease of removing mud that has already adhered to a tire or the like, and "excellent mud releasability" means that mud adhering to a tire or the like can be removed from the tire or the like. means easy. Mud releasability can be evaluated, for example, by the adhesion force (mud adhesion force) of mud adhering to vulcanized rubber or a tire or the like to the vulcanized rubber.
On the other hand, in the present invention, the resistance to adhesion of mud to a tire or the like is referred to as "mud repellency". Therefore, "excellent mud drainage" means that mud does not easily adhere to the tire or the like and that the mud is easily removed, in other words, the mud easily flows on the surface of the tire or the like without sticking. . Mud-clearing property can be evaluated, for example, by running on mud with a tire or the like and measuring the mass of mud adhering to the tire or the like.

At least one hydrophilic compound selected from the group consisting of cellulose and cellulose derivatives has an affinity for water, while the rubber component is usually hydrophobic. It is considered difficult to dissolve. Therefore, when the vulcanized rubber is obtained from the rubber composition, it is considered that the vulcanized rubber tends to seep out from the vulcanized rubber surface and the vulcanized rubber surface tends to be hydrophilic.
Moreover, since the hydrophilic compound and the rubber component are incompatible with each other, it is considered that the hydrophilic compound is unevenly distributed in the rubber composition to form aggregates. Therefore, even in the vulcanized rubber, the hydrophilic compound is considered to be agglomerated, and by exuding to the vulcanized rubber surface in lumps, the hydrophilicity of the vulcanized rubber surface can be made more pronounced. It is possible.
On the other hand, since cellulose and cellulose derivatives are difficult to dissolve in water, even if the hydrophilic compounds seeping out from the vulcanized rubber surface come into contact with muddy water, they are difficult to dissolve and the hydrophilicity of the vulcanized rubber surface is maintained. is considered possible. Therefore, tires and rubber crawlers, which are processed products of vulcanized rubber obtained from the rubber composition of the present invention, have a hydrophilic surface and can maintain the hydrophilicity. Also, it is considered that the adhering mud can be easily removed from the tire or the like. That is, the tires and rubber crawlers are excellent in mud release.
The details of the present invention will be described below.

[Rubber component]
The rubber composition of the present invention contains a rubber component.
Other rubber components are not particularly limited and can be appropriately selected as desired. Propylene rubber (EPM), ethylene-propylene-nonconjugated diene rubber (EPDM), polysulfide rubber, silicone rubber, fluororubber, synthetic rubber such as urethane rubber, and natural rubber (NR). These rubber components may be used alone or in combination.

Among the above, the rubber composition (rubber composition for tires) when manufacturing a tire from the rubber composition preferably contains synthetic rubber, and the content of the synthetic rubber in the rubber component exceeds 50% by mass. is preferred. Moreover, the rubber composition for tires preferably contains, as a rubber component, at least one synthetic rubber selected from the group consisting of styrene-butadiene rubber (SBR) and polybutadiene rubber (BR).
In addition, the rubber composition (rubber composition for crawlers) in the case of manufacturing the rubber crawler from the rubber composition preferably contains natural rubber (NR), and the content of natural rubber (NR) in the rubber component is 50%. % by weight is preferably exceeded.

[Hydrophilic compound]
The rubber composition of the present invention contains 5 to 30 parts by mass of at least one hydrophilic compound selected from the group consisting of cellulose and cellulose derivatives with respect to 100 parts by mass of the rubber component.
Cellulose and cellulose derivatives have a hydroxyl group (-OH) in their molecules, so while they have an affinity for water, they have low solubility in water, so the hydrophilic compounds that ooze out on the surface of the vulcanized rubber become mud. It is considered that the hydrophilicity of the vulcanized rubber surface can be maintained because it is difficult to dissolve even when in contact with water. Cellulose and cellulose derivatives each independently have a solubility of 10 g or less in 100 g of water at 25° C., and may be 0 g.

Cellulose derivatives are not particularly limited, but include, for example, compounds in which hydroxyl groups of cellulose are esterified or etherified. Specific examples include carboxymethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, methylcellulose, ethylcellulose, ethylhydroxyethylcellulose, and carboxymethylethylcellulose.

As the hydrophilic compound, cellulose alone, cellulose derivatives alone, or a mixture of cellulose and cellulose derivatives may be used. Furthermore, one type of cellulose may be used, or two or more types having different molecular weights and the like may be used. One type of cellulose derivative may be used, or two or more types having different molecular weights, structures, etc. may be used.

The hydrophilic compound preferably has a weight average molecular weight (Mw) of 150 g/mol to 400000 g/mol.
As described above, the hydrophilic compound oozes out onto the surface of the vulcanized rubber, but remains on the surface, thereby facilitating the maintenance of dirt releasability. When the weight-average molecular weight (Mw) of the hydrophilic compound is 150 g/mol or more, the hydrophilic compound tends to stay on the surface of the vulcanized rubber, and the mud releasability is easily maintained. Further, when the weight average molecular weight (Mw) of the hydrophilic compound is 400,000 g/mol or less, the hydrophilic compound tends to ooze out to the surface of the vulcanized rubber, thereby improving the mud removability.
The weight average molecular weight (Mw) of the hydrophilic compound is preferably 300-80000 g/mol.

The hydrophilic compound preferably has a melting point of 200-400° C. or no melting point.
When the hydrophilic compound has a melting point of 200 to 400° C. or does not have a melting point, the hydrophilic compound is less likely to melt even after vulcanization of the rubber composition, and is likely to exhibit mud releasability.

Cellulose and cellulose derivatives may be commercially available products such as granular products and fibrous products. The shape of the product is not particularly limited, but if it is fibrous, even if it oozes out from the surface of the vulcanized rubber, it is considered that it is difficult to fall off from the vulcanized rubber, and it is considered that the dirt release property is easily maintained.

The content of the hydrophilic compound in the rubber composition is 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component.
If the content of the hydrophilic compound is less than 5 parts by mass with respect to 100 parts by mass of the rubber component, it is not possible to obtain the mud release property of the tire and the rubber crawler, and 30 parts by mass with respect to 100 parts by mass of the rubber component. Durability can be maintained by:
The content of the hydrophilic compound in the rubber composition is more preferably 5 to 25 parts by mass, still more preferably 10 to 20 parts by mass, per 100 parts by mass of the rubber component.

In particular, the rubber composition (rubber composition for tires) when manufacturing a tire from the rubber composition preferably contains 7 to 30 parts by mass of a hydrophilic compound with respect to 100 parts by mass of the rubber component. It is more preferable to contain 10 to 20 parts by mass.
Further, the rubber composition (rubber composition for crawlers) for producing rubber crawlers from the rubber composition preferably contains 5 to 10 parts by mass of a hydrophilic compound with respect to 100 parts by mass of the rubber component. , more preferably 5 to 7 parts by mass.

〔filler〕
The rubber composition of the present invention preferably contains a filler.
By containing a filler, the rubber composition can increase the rigidity of tires and rubber crawlers, and is excellent in wear resistance, crack resistance, and the like.
The filler is not particularly limited, but reinforcing fillers such as silica and carbon black are preferably used.

(silica)
The type of silica is not particularly limited, and includes wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), colloidal silica, and the like.
From the viewpoint of low heat build-up, the nitrogen adsorption specific surface area (BET) of silica is preferably 180 m ² /g or less. From the viewpoint of crack resistance, the nitrogen adsorption specific surface area (BET) of silica is preferably 90 m ² /g or more.
The nitrogen adsorption specific surface area is measured by a single point value of the BET method defined by a method conforming to ISO5794/1.
In particular, from the viewpoint of low heat build-up and crack resistance, the nitrogen adsorption specific surface area of the silica contained in the tire rubber composition is preferably 150 m ² /g or less; The silica to be used is preferably 180 m ² /g or less, more preferably 160 m ² /g or less.

The content of silica in the rubber composition is preferably 0 to 80 parts by mass, more preferably 0 to 60 parts by mass, based on 100 parts by mass of the rubber component, from the viewpoint of low heat build-up.
In particular, from the viewpoint of low heat build-up, the content of silica contained in the rubber composition for tires and the rubber composition for crawlers is preferably 0 to 60 parts by mass with respect to 100 parts by mass of the rubber component. , more preferably 0 to 15 parts by mass.

(Carbon black)
The type of carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, SAF and the like.

From the viewpoint of improving tire durability, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 30 m ² /g or more, more preferably 50 m ² /g or more. Further, the N ₂ SA of carbon black is preferably 150 m ² /g or less. When it is 150 m ² /g or less, the dispersibility of carbon black in the rubber composition is excellent.
The N ₂ SA of carbon black can be obtained by Method A of JIS K 6217-2:2001 (Method for determining specific surface area—Nitrogen adsorption method—Single point method).

In particular, from the viewpoint of wear resistance, the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black contained in the rubber composition for tires and the rubber composition for crawlers is preferably 40 to 130 m ² /g. More preferably, it is 70 to 130 m ² /g.

From the viewpoint of improving tire durability, the carbon black preferably has a cetyltrimethylammonium bromide (CTAB) specific surface area of 30 to 150 m ² /g, more preferably 70 to 130 m ² /g.
The CTAB specific surface area of carbon black can be measured by a method conforming to JIS K 6217-3:2001 (Determination of specific surface area - CTAB adsorption method).
In particular, from the viewpoint of wear resistance, the CTAB specific surface area of the carbon black contained in the rubber composition for tires and the rubber composition for crawlers is preferably 30 to 130 m ² /g, and preferably 70 to 130 m ² /g. is more preferable.

From the viewpoint of improving tire durability, the dibutyl phthalate oil absorption (DBP oil absorption) is preferably 50 ml/100 g or more, more preferably 100 ml/100 g or more. From the viewpoint of the processability of the rubber composition, the DBP oil absorption of carbon black is preferably 140 ml/100 g or less.
Incidentally, the DBP oil absorption of carbon black can be determined according to JIS K 6217-4:2001 (Determination of oil absorption).

In particular, from the viewpoint of rubber rigidity, the carbon black contained in the tire rubber composition preferably has a DBP oil absorption of 50 to 150 ml/100 g, more preferably 80 to 120 ml/100 g.
From the viewpoint of rubber rigidity, the carbon black contained in the crawler rubber composition preferably has a DBP oil absorption of 90 to 130 ml/100 g, more preferably 100 to 120 ml/100 g.

The content of carbon black in the rubber composition is preferably 0 to 100 parts by mass, more preferably 30 to 90 parts by mass, per 100 parts by mass of the rubber component.
In particular, from the viewpoint of abrasion resistance, the content of carbon black contained in the rubber composition for tires is preferably 30 to 80 parts by mass, more preferably 40 to 80 parts by mass, with respect to 100 parts by mass of the rubber component. is more preferable.
Further, from the viewpoint of abrasion resistance, the content of carbon black contained in the rubber composition for crawlers is preferably 0 to 80 parts by mass, more preferably 50 to 65 parts by mass, with respect to 100 parts by mass of the rubber component. is more preferable.

The rubber composition of the present invention may contain fillers other than carbon black and silica as fillers, and examples of such fillers include metal oxides such as alumina and titania.

[Silane coupling agent]
When the rubber composition of the present invention contains silica, the rubber composition may further contain a silane coupling agent in order to improve the dispersibility of silica.
The content of the silane coupling agent in the rubber composition of the present invention is preferably 5 to 15% by mass or less relative to the content of silica. When the content of the silane coupling agent is 15% by mass or less with respect to the content of silica, the effect of improving the reinforcing properties of the rubber component and the dispersibility of silica can be obtained, and economic efficiency is hardly impaired. Further, when the content of the silane coupling agent is 5% by mass or more relative to the content of silica, the dispersibility of silica in the rubber composition can be enhanced.

The silane coupling agent is not particularly limited, and bis(3-triethoxysilylpropyl) disulfide, bis(3-triethoxysilylpropyl) trisulfide, bis(3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) disulfide, bis(3-trimethoxysilylpropyl) trisulfide, bis(3-trimethoxysilylpropyl) tetrasulfide, bis(2-triethoxysilylethyl) disulfide, bis(2-tri ethoxysilylethyl) trisulfide, bis(2-triethoxysilylethyl) tetrasulfide, 3-trimethoxysilylpropyl benzothiazole disulfide, 3-trimethoxysilylpropyl benzothiazole trisulfide, 3-trimethoxysilylpropyl benzothiazole tetrasulfide etc. are preferably exemplified.

[Softener]
The rubber composition of the present invention may contain a softening agent.
The inclusion of a softening agent in the rubber composition improves the processability of the rubber composition and imparts flexibility to the vulcanized rubber.
Softeners include process oil, lubricating oil, naphthenic oil, paraffin, liquid paraffin, petroleum asphalt, petroleum-based softeners such as petrolatum, fatty oil-based softeners such as castor oil, linseed oil, rapeseed oil, and coconut oil. Waxes such as wax, carnauba wax, lanolin, and the like. These softeners may be used singly or in combination of two or more.

From the viewpoint of tensile strength and wear resistance, the softening agent contained in the tire rubber composition is preferably aromatic, paraffinic, or naphthenic.
Further, the softener may not be contained, and if it is contained, the softener contained in the rubber composition for crawlers is preferably aromatic or paraffinic from the viewpoint of tensile strength and wear resistance.

The content of the softening agent in the rubber composition is preferably 0 to 100 parts by mass, more preferably 0 to 50 parts by mass, per 100 parts by mass of the rubber component.
In particular, from the viewpoint of tensile strength and wear resistance, the content of the softener contained in the rubber composition for tires is preferably 0 to 50 parts by mass with respect to 100 parts by mass of the rubber component.
From the viewpoint of tensile strength and wear resistance, the content of the softener contained in the rubber composition for crawlers is preferably 0 to 30 parts by mass, more preferably 0 to 15 parts by mass, with respect to 100 parts by mass of the rubber component. Parts by mass are more preferred.

〔resin〕
The rubber composition of the present invention may contain resin.
By including a resin in the rubber composition, the vulcanized rubber can be made flexible, and the grip properties of tires and rubber crawlers can be improved.
Examples of resins include terpene phenol resins, rosin-modified petroleum resins, dicyclopentadiene resins, aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, and aromatic hydrocarbon resins. One or two or more resins may be used.

Terpene phenol resins include YS Polyster T80, YS90L, YS Polyster T115, YS Polyster U115, and Mighty Ace G125 manufactured by Yasuhara Chemical Co.;
As the rosin-modified petroleum resin, Hyrosin S manufactured by Taishamatsu Oil Co., Ltd.;
Aliphatic hydrocarbon resins (C5 resins) include ESCOREZ1102 from Tonex and Hi-Let's T500X from Mitsui Chemicals;
Examples of alicyclic hydrocarbon resins include Nippon Zeon's Quinton 1500, Quinton 1700, and Quinton 1525L;
As the aromatic hydrocarbon resin (C9 resin), Neopolymer L90, Neopolymer 120, Neopolymer E130, Neopolymer 140, Neopolymer 170S, Nisseki Neoresin D-145, etc. of Nippon Petrochemical Co., Ltd. can be used. .
As the aliphatic-aromatic hydrocarbon resin (C5C9 resin), T-REZ R series of Tonen Chemical Co., Ltd., such as RD104, can also be used.

From the viewpoint of cut resistance, processability, etc., the resin contained in the rubber composition for tires is preferably dicyclopentadiene resin, rosin-modified petroleum resin, and aliphatic hydrocarbon.
Moreover, from the viewpoint of cut resistance, workability, etc., the resin contained in the rubber composition for crawlers is preferably a dicyclopentadiene resin, a rosin-modified petroleum resin, and an aliphatic hydrocarbon.

The content of the resin in the rubber composition is preferably 0 to 20 parts by mass, more preferably 1 to 10 parts by mass, per 100 parts by mass of the rubber component.
In particular, from the viewpoint of cut resistance, processability, etc., the content of the resin contained in the rubber composition for tires and the rubber composition for crawlers is 0 to 20 parts by mass with respect to 100 parts by mass of the rubber component. Preferably.

[Vulcanizing agent]
The vulcanizing agent is not particularly limited, and sulfur is usually used, and examples thereof include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur.
In the rubber composition of the present invention, the content of the vulcanizing agent is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. When the content is 0.1 parts by mass or more, vulcanization can be sufficiently advanced, and when the content is 10 parts by mass or less, the aging resistance of the vulcanized rubber can be suppressed.
More preferably, the content of the vulcanizing agent in the rubber composition is 0.5 to 5 parts by mass with respect to 100 parts by mass of the rubber component.
In particular, from the viewpoint of workability and fatigue resistance, the content of the vulcanizing agent contained in the rubber composition for tires and the rubber composition for crawlers is 0.5 to 5 mass parts per 100 mass parts of the rubber component. parts, more preferably 1.0 to 4.0 parts by mass.

[Vulcanization accelerator]
The rubber composition of the present invention may contain a vulcanization accelerator to accelerate the vulcanization of the rubber component.
Examples of vulcanization accelerators include vulcanization accelerators such as guanidine-based, sulfenamide-based, thiuram-based, thiazole-based, aldehydeamine-based, and thiocarbamate-based vulcanization accelerators.

Guanidine-based vulcanization accelerators include, for example, 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, dicatechol borate di-o-tolylguanidine salt, 1, 3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine and the like.
In order to obtain desired vulcanization torque and vulcanization speed, the rubber composition may further contain a vulcanization retarder.

Examples of sulfenamide-based vulcanization accelerators include N-cyclohexyl-2-benzothiazolylsulfenamide, N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzo Thiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N-methyl-2-benzothiazolylsulfenamide, N-ethyl-2-benzothiazolylsulfenamide, N-propyl- 2-benzothiazolylsulfenamide, N-butyl-2-benzothiazolylsulfenamide, N-pentyl-2-benzothiazolylsulfenamide, N-hexyl-2-benzothiazolylsulfenamide, N- Heptyl-2-benzothiazolylsulfenamide, N-octyl-2-benzothiazolylsulfenamide, N-2-ethylhexyl-2-benzothiazolylsulfenamide, N-decyl-2-benzothiazolylsulfenamide Amide, N-dodecyl-2-benzothiazolylsulfenamide, N-stearyl-2-benzothiazolylsulfenamide, 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 phenamide, N,N-dihexyl-2-benzothiazolylsulfenamide, N,N-diheptyl-2-benzothiazolylsulfenamide, N,N-dioctyl-2-benzothiazolylsulfenamide, N, N-di-2-ethylhexylbenzothiazolylsulfenamide, N,N-didecyl-2-benzothiazolylsulfenamide, N,N-didodecyl-2-benzothiazolylsulfenamide, N,N-distearyl -2-benzothiazolylsulfenamide and the like.

Thiuram-based vulcanization accelerators include, for example, tetrakis(2-ethylhexyl)thiuram disulfide, tetrakis(n-dodecyl)thiuram disulfide, tetrakis(benzyl)thiuram disulfide and the like.

Thiazole-based vulcanization accelerators include, for example, dibenzothiazyl disulfide, 2-mercaptobenzothiazole, 2-(2,4-dinitrophenyl)mercaptobenzothiazole, and 2-(2,6-diethyl-4-morpholinothio). benzothiazole and the like.

Aldehydeamine-based vulcanization accelerators include, for example, reaction products of acetaldehyde and aniline, condensates of butyraldehyde and aniline, hexamethylenetetramine, and reaction products of acetaldehyde and ammonia.

The thiocarbamate-based vulcanization accelerators include, for example, dithiocarbamate metal salts such as sodium dithiocarbamate and zinc dithiocarbamate.

The content of the vulcanization accelerator in the rubber composition of the present invention is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component, from the viewpoint of durability of tires and rubber crawlers. .5 to 5 parts by mass is more preferable.
In particular, from the viewpoint of vulcanization speed, the content of the vulcanization accelerator contained in the rubber composition for tires is preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the rubber component. It is more preferably 1.0 to 3.5 parts by mass.
From the viewpoint of vulcanization speed, the content of the vulcanization accelerator contained in the rubber composition for crawlers is preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the rubber component. It is more preferably 1.0 to 3.0 parts by mass.

[Water repellent compound]
The rubber composition of the present invention further contains a water-repellent compound when the content of the hydrophilic compound is 10 parts by mass or less per 100 parts by mass of the rubber component.
When the content of the hydrophilic compound is 10 parts by mass or less with respect to 100 parts by mass of the rubber component, more specifically, the content of the hydrophilic compound is 5 to 10 parts by mass with respect to 100 parts by mass of the rubber component. means that it is a part.
When the rubber composition contains a water-repellent compound, the surface of the vulcanized rubber can be made water-repellent, so mud does not easily adhere to the surfaces of tires and rubber crawlers, resulting in excellent mud-repellency. Therefore, when the content of the hydrophilic compound is a small amount of 10 parts by mass or less with respect to 100 parts by mass of the rubber component, the rubber composition further contains a water-repellent compound, so that the vulcanized rubber has excellent mud releasability. can be obtained.

Here, the water-repellent compound is a compound that can impart water repellency to the surface of the vulcanized rubber obtained from the rubber composition. A compound having a dynamic contact angle (sliding angle) of 20 degrees or less.
The sample plate used for measuring the dynamic contact angle is produced by kneading 10 parts by mass of the sample, 100 parts by mass of natural rubber, and 1.5 parts by mass of sulfur, vulcanizing the mixture, and cutting it into a plate.
The dynamic contact angle of the sample plate is measured by dropping one drop of water onto the sample plate, tilting the sample plate gradually, and measuring the angle at which the water droplet begins to slide down as the dynamic contact angle (sliding angle). .

The water-repellent compound preferably has an aliphatic group having 8 to 30 tire carbon atoms, from the viewpoint of improving mud-repellency of tires and rubber crawlers.
The aliphatic group may be a saturated aliphatic group or an unsaturated aliphatic group, and may be linear, branched, or cyclic. .
From the viewpoint of improving mud-removal properties of tires and rubber crawlers, the aliphatic group is preferably linear or branched, more preferably linear. The number of carbon atoms in the aliphatic group is more preferably 12-27, more preferably 15-23.

From the viewpoint of improving mud-removal properties of tires and rubber crawlers, the water-repellent compound preferably has a weight-average molecular weight of 150 g/mol to 400 g/mol.
Specifically, the water-repellent compound is preferably a fatty acid amide, a silicone resin, a fluororesin, or the like. Among them, a fatty acid amide is more preferable from the viewpoint of improving mud-removal properties of tires and rubber crawlers. More preferred are 12-22 fatty acid amides.
The rubber composition may contain only one type of water-repellent compound, or may contain two or more types.

The content of the water-repellent compound in the rubber composition is preferably 2 to 20 parts by mass with respect to 100 parts by mass of the rubber component.
When the content of the water-repellent compound is 2 to 20 parts by mass with respect to 100 parts by mass of the rubber component, it is easy to improve the mud repellency of tires and rubber crawlers.
The content of the water-repellent compound in the rubber composition is more preferably 2 to 10 parts by mass, still more preferably 2 to 7 parts by mass, per 100 parts by mass of the rubber component.

(Various ingredients)
In addition to the rubber component, hydrophilic compound, filler, softening agent, resin, vulcanizing agent, vulcanization accelerator, and water-repellent compound described above, the rubber composition of the present invention includes, for example, zinc oxide and stearic acid. , anti-aging agents, etc., which are commonly used in the rubber industry, can be appropriately selected and blended within a range that does not impair the object of the present invention. Commercially available products can be suitably used as these various components. In addition, the rubber composition (including the rubber composition for tires and the rubber composition for crawlers) is blended with a rubber component, a hydrophilic compound, and various appropriately selected components, and is mixed with a Banbury mixer, an internal mixer, or an intensive mixer. After kneading using a closed kneading device such as a closed type kneading device such as a roller, a non-sealed kneading device such as a roll, etc., it can be prepared by heating and extruding.

(vulcanized rubber)
A vulcanized rubber is obtained by vulcanizing the rubber composition of the present invention.
As described above, since the hydrophilic compound and the rubber component are incompatible with each other, it is considered that the hydrophilic compound is unevenly distributed in the rubber composition to form aggregates. Therefore, it is considered that the hydrophilic compound is aggregated even in the vulcanized rubber, and it is considered that the surface of the vulcanized rubber is excellent in dirt releasability by aggregating and exuding to the surface of the vulcanized rubber. Such aggregation state of the hydrophilic compound in the vulcanized rubber can be confirmed with a disper grader conforming to ASTM D7723.

The vulcanized rubber of the present invention is obtained by the following formula (I) from the ratio A% of the non-dispersed region in the unit area of the cross section when the cross section of the vulcanized rubber is measured with a disper grader according to ASTM D7723. It is preferred that the Z value obtained is 60 or less.
Z=100−A/0.35 (I)
The larger the Z value, the smaller the proportion of the non-dispersed region in the unit area of the vulcanized rubber cross section, and the smaller the Z value, the larger the proportion of the non-dispersed region in the unit area of the vulcanized rubber cross section. The non-dispersed region is, so to speak, a region of agglomerates in the vulcanized rubber. If there is no agglomerate in the vulcanized rubber, the Z value is 0 or a value close to 0, and the more agglomerates, the higher the Z value. tend to be large.
"Z value is 60 or less" means that the hydrophilic compound is aggregated and present.
From the viewpoint of improving tire and rubber crawler mud release properties, the Z value is more preferably 40 or less, and still more preferably 20 or more.

The Z value tends to decrease when the hydrophilic compound is more incompatible with the rubber component or when the content of the hydrophilic compound in the rubber composition is high. Also, increasing the content of the hydrophilic compound in the rubber composition tends to decrease the Z value.

<Rubber composition for tires, rubber composition for crawlers>
The rubber composition for tires of the present invention includes the rubber composition of the present invention.
Moreover, the rubber composition for crawlers of the present invention includes the rubber composition of the present invention.
Therefore, the tire obtained from the rubber composition for tires of the present invention has excellent mud-releasing properties, and the rubber crawler obtained from the rubber composition for crawlers of the present invention has excellent mud-releasing properties.

<Tire>
The tire of the present invention uses the rubber composition of the present invention.
Therefore, the tire of the present invention has excellent mud-releasing properties. From this point of view, the tire of the present invention is particularly preferably a tire using the rubber composition for the tread.
A tire tread can be produced by vulcanizing the rubber composition or tire rubber composition of the present invention after molding. A tire tread is particularly suitable for use as a tread contact portion.
Further, a tire is manufactured by a conventional tire manufacturing method using the rubber composition or the rubber composition for tires of the present invention for a tread. That is, the rubber composition of the present invention containing various components as described above is processed into a tire tread in an unvulcanized stage, and pasted and molded by a conventional method on a tire molding machine to mold a green tire. be. The raw tire is heated and pressurized in a vulcanizer to obtain a tire.

<Rubber crawler>
The rubber crawler of the present invention uses the rubber composition of the present invention.
Therefore, the rubber crawler of the present invention has excellent mud releasability.
By molding the rubber composition or the rubber composition for crawlers of the present invention with a heated mold having a desired shape such as a guide rubber, an inner peripheral rubber, a lug, etc., a rubber crawler having excellent mud release properties can be obtained.
More specifically, for example, a rubber composition is prepared and molded in an unvulcanized state into the shapes of a guide rubber, an inner peripheral rubber, and a lug rubber. After that, a guide rubber-shaped rubber composition is placed on the inner peripheral rubber-shaped rubber composition, and a lug rubber-shaped rubber composition is further placed at a predetermined position on the guide rubber-shaped rubber composition, The rubber composition may be collectively vulcanized in the mold. In this manufacturing method, the inner peripheral rubber, the guide rubber, and the lug rubber are vulcanized and bonded.

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

<Preparation of rubber composition>
The rubber compositions for tires of Examples 1 and 2 and Comparative Examples 1 to 4 were prepared according to the conventional method using the components and formulation shown in Table 1.
Details of each component in Table 1 are as follows.

(1) Rubber component SBR (oil-extended SBR): oil-extended SBR, manufactured by JSR, trade name "1723"
(Contains 7.5 parts by mass of oil per 100 parts by mass of styrene-butadiene rubber)
BR: Manufactured by JSR, trade name "BR01"

(2) Carbon black: HAF, manufactured by Asahi Carbon Co., Ltd., trade name "Asahi #70"
(CTAB specific surface area = 83 m ² /g, DBP oil absorption = 77 ml/100 g, N ₂ SA = 101 m ² /g)
(3) Cellulose: manufactured by Nippon Paper Industries, trade name “KC Flock”
(4) Sorbitol: manufactured by Kanto Chemical Co., Ltd., trade name "D-Sorbitol"
(5) Oleic acid amide: manufactured by Lion Specialty Chemicals, trade name “Armoslip CP Beads”

(6) Process oil: JXTG Energy Co., Ltd., trade name “A/O MIX”
(7) Vulcanization accelerator: manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name "Noccellar CZ-G"
(8) Sulfur: manufactured by Hosoi Chemical Industry Co., Ltd., trade name “HK200-5”
(9) Stearic acid: trade name “Stearic acid 50S” manufactured by Shin Nippon Rika Co., Ltd.
(10) Zinc oxide: manufactured by Hakusui Tech, trade name “zinc oxide”
(11) Anti-aging agent: manufactured by Sumitomo Chemical Co., Ltd., trade name "Antigen 6C"

Oleic acid amide is a water-repellent compound, since the dynamic contact angle (sliding angle) was 10 degrees in the following dynamic contact angle measurement.

(dynamic contact angle measurement)
3 parts by mass of oleic acid amide, 100 parts by mass of synthetic rubber, and 1.5 parts by mass of sulfur were kneaded and vulcanized into a plate to produce a sample plate.
One drop of water was dropped on the manufactured sample plate, and when the sample plate was gradually tilted, the water began to slide down at 20 degrees.

<Production of vulcanized rubber sheet>
In Examples 1 and 2 and Comparative Examples 1 to 4, the prepared tire rubber compositions were vulcanized to prepare vulcanized rubber sheets of 30 mm×60 mm and 2 mm in thickness.

<Evaluation>
1. Evaluation of mud adhesion (mud releasability) The vulcanized rubber sheets prepared in Examples 1 and 2 and Comparative Examples 1 to 4 were pressed against mud at 25 ° C. for 10 seconds with the same load as the tire load, and the vulcanized rubber Mud stuck to the seat. A spring balance was used to measure the stress when the vulcanized rubber sheet stuck to the mud was pulled out of the mud.
The measured value of Comparative Example 1 is indexed as 100, and each index is shown in Table 1.
The smaller the index value, the smaller the adhesion of mud and the better the mud releasability.

2. Evaluation of mud adhesion amount (mud cleaning property) In Example 1 and Comparative Examples 1 and 3, the prepared vulcanized rubber sheet was attached to the tread rubber of a tire with a tire size of 320/60-26 to make a prototype tire. . The prototype tires were mounted on a passenger car, and the car was run in an oval shape for 1 hour on a muddy unpaved road at a speed of 5 to 10 km/h at a straight distance of 80 m.
In Example 2, Comparative Example 2, and Comparative Example 4, the prepared vulcanized rubber sheets were adhered to the tread rubber of a tire having a tire size of 320/60-26 to obtain a trial tire. A prototype tire is attached to a passenger car, and the vehicle is driven in an oval shape for 1 hour on a muddy unpaved road at a speed of 5 to 10 km/h for a straight distance of 80 m. Scrape off the mud attached to the vulcanized rubber sheet portion of the tire after running, and measure the mass of the scraped mud.
The measured value of Comparative Example 1 is indexed as 100, and each index is shown in Table 1.
The smaller the index value, the less the amount of adhered mud, and the better the mud drainage.

As is clear from Table 1, the tires obtained in Examples are excellent in mud release. Similarly, the rubber crawler manufactured by using the rubber composition of the present invention as a rubber composition for crawlers is considered to be excellent in mud release property.

Since the tire using the rubber composition or the rubber composition for tires of the present invention can be excellent in mud release property, it can be suitably used for various tires such as for passenger cars, light passenger cars, and light trucks. .
In addition, since the rubber crawler using the rubber composition or the rubber composition for crawlers of the present invention can be excellent in mud release, various rubbers for agricultural machinery, construction machinery, civil engineering work machinery, transportation, etc. It can be suitably used for crawlers.

Claims (4)

a rubber component;
and at least one hydrophilic compound selected from the group consisting of cellulose and cellulose derivatives,
The content of the hydrophilic compound is 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component, and the content of the hydrophilic compound is 10 parts by mass or less with respect to 100 parts by mass of the rubber component. A rubber composition for crawlers, optionally further comprising a water-repellent compound,
A rubber composition for crawlers, wherein the water-repellent compound is one or more selected from fatty acid amides, silicone resins, and fluororesins . 2. The rubber composition according to claim 1, wherein the hydrophilic compound has a weight average molecular weight of 150 g/mol to 400000 g/mol. The rubber composition according to claim 2, wherein the hydrophilic compound has a melting point of 200 to 400°C or no melting point. A rubber crawler using the rubber composition according to any one of claims 1 to 3.