JP2016003251A - Rubber composition and shoe outsole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition which is low in hardness and excellent in oil resistance, wear resistance and oil gripping properties and can retain the properties for a relatively long period and a shoe outsole.SOLUTION: A rubber composition comprises a rubber ingredient containing 65 pts. mass of an acrylonitrile-butadiene rubber of an acrylonitrile content of 20-45 mass%, 20-55 pts. mass, relative to 100 pts. mass of the rubber ingredient, of silica and more than 3 pts. mass, relative to 100 pts. mass of silica, of a silane coupling agent having at least a mercapto-containing T-type polysiloxane in the molecular structure.

Description

  The present invention relates to a rubber composition used as a material for forming a rubber product such as an outsole, and a shoe outsole using the same.

Rubber compositions are molded into various shapes and used in various applications.
For example, rubber compositions are widely used after being molded into a shoe sole shape.
Shoes are used in various places. For example, when a person is active on a floor surface to which oil adheres, the oil is slippery. Therefore, a shoe having an outsole having a high anti-slip property is required. In particular, the floor surface of factories, kitchens, gas stations, etc. has a high probability of oil adhesion, and the outsole of shoes used in such places (safety shoes, shoes including work shoes) has an excellent oil grip. It is preferable to have a property and maintain the property for a long time.
However, a rubber outsole that can maintain oil grip performance for a relatively long period of time has not been known.

Patent Document 1 includes 100 parts by mass of a rubber component, 15 to 150 parts by mass of silica, and a silane coupling agent having a specific molecular structure, and the silane coupling agent has a silica compounding amount. A rubber composition containing 1 to 20% by mass is disclosed. Patent Document 1 discloses that the rubber composition has excellent processability, and a tire formed from the rubber composition has excellent wet grip properties (grip properties on water-wet road surfaces) and wear resistance. It is disclosed.
However, the cited document 1 does not suggest any oil grip property, nor does it suggest any rubber composition suitable for a shoe outsole.

WO2009 / 054336

  An object of the present invention is to provide a rubber composition and an outsole of a shoe that have excellent oil grip properties and can maintain them for a relatively long period of time.

The inventors of the present invention have intensively studied for the above purpose, and it has been found that the oil grip property and the hardness have a correlation.
Specifically, the inventors preliminarily performed the following experiment. The experiment was conducted using a rubber composition conventionally used (a rubber composition comprising a mixture of a rubber component consisting only of acrylonitrile butadiene rubber having an acrylonitrile amount of 30.5% by mass, silica, oil, sulfur and a vulcanization accelerator. Was formed into an outsole (rubber product) having a projection design as shown in FIG. The hardness (Shore-A) of this outsole was measured according to JIS K 6253. And in order to obtain the test piece from which hardness differs, several types of outsole which changed the compounding quantity of a silica and oil were produced, and those hardness was measured similarly. Shoes incorporating these outsole were produced. This was worn by an adult male, and the tester performed an operation of stepping one foot forward on a stainless steel floor sprayed with industrial oil, and the oil grip property was evaluated by sensory evaluation at that time. FIG. 2 is a graph of experimental results showing the relationship between the outsole of each hardness and the oil grip property. From the experimental results, when the hardness was around 67, the oil grip property of the rubber product suddenly deteriorated, and the rubber product with a hardness of less than that showed good oil grip property. The oil grip property refers to the property of being difficult to slip with respect to the floor surface on which oil is interposed.

As described above, it has been found that the rubber product having a low hardness is excellent in the oil grip property, but even if the rubber product is excellent in the oil grip property, the rubber product which is easily deteriorated by oil cannot maintain the grip property for a long period of time. Even rubber products having excellent oil grip and oil resistance cannot be used for a long period of time if they are worn early.
Based on the above findings, the inventors of the present invention have further studied earnestly to obtain a rubber composition having low hardness and excellent oil resistance and wear resistance, and completed the present invention.

  The rubber composition of the present invention comprises a rubber component containing 65 parts by mass or more of an acrylonitrile butadiene rubber having an acrylonitrile amount of more than 20% by mass and less than 45% by mass when the total rubber component is 100 parts by mass; A silane coupling agent having 20 to 55 parts by mass of silica and at least a formula (2) in the molecular structure of the following formulas (1) and (2), wherein the silica 100 A silane coupling agent exceeding 3 parts by mass with respect to part by mass.

In the formula (1) and the formula (2), x and y each represent mol%, x is 0 to 30, y is 70 to 100, x + y = 100, R ¹ and R ² is independently hydrogen, hydroxyl group, halogen, substituted or unsubstituted linear or branched alkyl group, substituted or unsubstituted linear or branched alkenyl group, substituted or unsubstituted linear or branched Each of R ³ and R ⁴ independently represents a covalent bond, a substituted or unsubstituted linear or branched alkylene group, a substituted or unsubstituted straight chain, or a substituted or unsubstituted thiol group. It represents a chain or branched alkenylene group or a substituted or unsubstituted linear or branched alkynylene group.
However, when R ³ and R ⁴ are terminal, R ³ and R ⁴ are each independently hydrogen, substituted or unsubstituted linear or branched alkyl group, substituted or unsubstituted linear or branched Or a substituted or unsubstituted linear or branched alkynyl group, R ¹ and R ³ may form a ring, and R ² and R ⁴ form a ring. Also good.

In a preferred rubber composition of the present invention, y in the formula (2) is 80-100.
In a preferable rubber composition of the present invention, the silane coupling agent is contained in an amount of 3.5 to 20 parts by mass with respect to 100 parts by mass of the silica.
In a preferred rubber composition of the present invention, the silane coupling agent is contained in an amount of 4.5 to 8 parts by mass with respect to 100 parts by mass of the silica.
In a preferred rubber composition of the present invention, the silica is contained in an amount of 30 to 50 parts by mass with respect to 100 parts by mass of the rubber component.
In a preferred rubber composition of the present invention, the rubber component comprises only acrylonitrile butadiene rubber having an acrylonitrile amount of more than 20% by mass and less than 45% by mass.
A preferable rubber composition of the present invention is that the rubber component is 70 parts by mass or more and 100 parts by mass of acrylonitrile butadiene rubber having an acrylonitrile amount of more than 20% by mass and less than 45% by mass when the total rubber component is 100 parts by mass. And less than 30 parts by mass of rubber other than acrylonitrile butadiene rubber having the amount of acrylonitrile.
In a preferred rubber composition of the present invention, the amount of acrylonitrile in the acrylonitrile butadiene rubber is 23% by mass to 40% by mass.

According to another aspect of the invention, a shoe outsole is provided.
The outsole of this shoe includes any of the rubber compositions described above.

  The rubber composition of the present invention has low hardness and excellent oil resistance and wear resistance. Rubber products such as shoe outsole containing such a rubber composition have excellent oil grip properties and can maintain the properties for a relatively long period of time.

The photograph figure of the outsole produced by the preliminary test. The graph which shows the relationship between the hardness of rubber | gum, and oil grip property. 1 is a side view of a shoe of one embodiment. Sectional drawing cut | disconnected by the IV-IV line of FIG. The side view of the shoes of other embodiments.

  Hereinafter, the rubber composition of the present invention and rubber products such as shoe outsole using the rubber composition will be described. In the present specification, the description “PPP to QQQ” means “PPP or more and QQQ or less”.

[Rubber composition]
The rubber composition of the present invention includes a rubber component containing acrylonitrile butadiene rubber having an acrylonitrile amount of more than 20% by mass and less than 45% by mass, silica, and a silane coupling agent. The said rubber composition WHEREIN: Content of the said silica is 20 mass parts-55 mass parts with respect to 100 mass parts of rubber components. Moreover, in the said rubber composition, content of the said silane coupling agent exceeds 3 mass parts with respect to 100 mass parts of silica.

<Rubber component>
The rubber component contains 65 parts by mass or more of acrylonitrile butadiene rubber having an acrylonitrile amount of more than 20% by mass and less than 45% by mass when the total rubber component is 100 parts by mass. Hereinafter, acrylonitrile butadiene rubber having an acrylonitrile amount within the above range may be referred to as “predetermined acrylonitrile butadiene rubber”.
The rubber component may contain a rubber other than the predetermined acrylonitrile butadiene rubber on the condition that it contains 65 parts by mass or more of the predetermined acrylonitrile butadiene rubber when the whole is 100 parts by mass. The rubber other than the predetermined acrylonitrile butadiene rubber is an acrylonitrile butadiene rubber having an acrylonitrile content of less than 20%, an acrylonitrile butadiene rubber having an acrylonitrile content of 45% by mass or more, and a rubber (other rubber) other than the acrylonitrile butadiene rubber.

The predetermined acrylonitrile butadiene rubber has an acrylonitrile amount of preferably 23% by mass or more, more preferably 25% by mass or more, further preferably 26% by mass or more, and most preferably 30% by mass at the lower limit. On the other hand, an acrylonitrile butadiene rubber having an acrylonitrile amount of preferably 40% by mass or less, more preferably 38% by mass or less, and further preferably 36% by mass or less is used at the upper limit. By using an acrylonitrile butadiene rubber having an acrylonitrile amount within the above range, a rubber composition having excellent oil resistance can be obtained.
As the predetermined acrylonitrile butadiene rubber, two or more kinds having different acrylonitrile amounts may be used. For example, the predetermined acrylonitrile butadiene rubber may be a mixture of acrylonitrile butadiene rubber having an acrylonitrile content of 25% by mass and acrylonitrile butadiene rubber having an acrylonitrile content of 40% by mass.

  The other rubber is not particularly limited, and examples thereof include isoprene rubber (isoprene rubber includes synthetic and natural isoprene rubber), butadiene rubber (BR), diene rubber such as chloroprene (CR), and styrene butadiene. Diene copolymer rubbers such as rubber (SBR), styrene butadiene styrene rubber (SBSR), styrene isoprene copolymer (SIR), butyl rubber (IIR); units composed of ethylene units and α-olefins having 3 or more carbon atoms; And non-diene rubbers such as ethylene / α-olefin copolymer rubber, urethane rubber, acrylic rubber, and silicone rubber. Each copolymer rubber may be a block copolymer or a random copolymer. The other rubbers may be used alone or in combination of two or more. Preferably, the other rubber includes at least butadiene rubber, and more preferably butadiene rubber is used.

  Here, in order to improve the wear resistance of the rubber product, it is conceivable to add a large amount of butadiene rubber as a rubber component. However, when a large amount of butadiene rubber is used, the oil resistance decreases. Therefore, in the present invention that achieves both wear resistance and oil resistance, it is not appropriate to use a large amount of butadiene rubber as the rubber component. In this respect, the predetermined acrylonitrile butadiene rubber has good compatibility with silica and a silane coupling agent, which will be described later. By using at least the predetermined acrylonitrile butadiene rubber, the rubber has low hardness and excellent wear resistance and oil resistance. A composition may be obtained.

The rubber component contains 65 parts by mass or more of a predetermined acrylonitrile butadiene rubber when the entire rubber component is 100 parts by mass. That is, the rubber component is composed only of a predetermined acrylonitrile butadiene rubber, or when the total rubber component is 100 parts by mass, it exceeds 65 parts by mass and less than 100 parts by mass with a predetermined acrylonitrile butadiene rubber. It consists of a mixture with other rubbers of 35 parts by mass or less. The phrase “consisting only of a predetermined acrylonitrile butadiene rubber” means that a small amount of other rubber that is inevitably contained is allowed to be mixed, and a significant amount of mixing is excluded.
When the rubber component includes a predetermined acrylonitrile butadiene rubber and a rubber other than the predetermined acrylonitrile butadiene rubber, the rubber component is a predetermined amount of 70 parts by mass or more and less than 100 parts by mass when the total rubber component is 100 parts by mass. A mixture of acrylonitrile butadiene rubber and other rubber of more than 0 parts by mass and not more than 30 parts by mass is preferable. Furthermore, a predetermined acrylonitrile butadiene rubber of not less than 75 parts by mass and less than 100 parts by mass, more than 0 parts by mass and 25 parts by mass More preferred is a mixture with other rubbers of less than or equal to 80 parts by weight, and more preferred is a mixture of 80 parts by weight or more and less than 100 parts by weight of a predetermined acrylonitrile butadiene rubber with more than 0 parts by weight and less than or equal to 20 parts by weight.

When the rubber component is composed only of a predetermined acrylonitrile butadiene rubber, the acrylonitrile amount in the rubber component is equal to the acrylonitrile amount of the predetermined acrylonitrile butadiene rubber.
When the rubber component is made of a mixture of a predetermined acrylonitrile butadiene rubber and other rubber, the amount of acrylonitrile in the rubber component is preferably more than 20% by mass and less than 40% by mass, more preferably 23% by mass to 38% by mass. Preferably, 30% by mass to 36% by mass is more preferable.

<Silica>
The silica functions as a reinforcing agent that reinforces the rubber component.
According to the classification based on the production method, the silica is a dry silica obtained by burning silicon tetrachloride in an oxyhydrogen flame; a wet silica obtained by neutralizing an alkali silicate with an acid; a silicon alkoxide A sol-gel method silica obtained by hydrolyzing an acid in an acidic or alkaline water-containing organic solvent; colloidal silica obtained by electrodialysis of an aqueous alkali silicate solution; and the like are known. In this invention, these silica can be used individually by 1 type or in combination of 2 or more types. In particular, since wet silica is easier to handle than other types of silica, it is preferable to use wet silica as the silica.

Although the average particle diameter of the said silica is not specifically limited, For example, it is 5 nm-500 nm, Preferably, it is 10 nm-200 nm, More preferably, it is 20 nm-100 nm. Silica having such a particle size is preferable because of its excellent reinforcing effect. The silica having the average particle diameter can be obtained by a known adjustment method. As the adjustment method, for example, a dry pulverization method for obtaining silica having a target average particle diameter using a jet mill or a ball mill; a silica having a target average particle diameter is obtained using a disper or a homogenizer. Wet-grinding method to be obtained.
The average particle diameter of the silica is a volume average particle diameter, and can be measured using a laser diffraction particle size distribution measuring device (product name “SK Laser Micron Sizer LMS-2000e” manufactured by Seishin Enterprise Co., Ltd.).

  Content of the said silica is 20 mass parts-55 mass parts with respect to 100 mass parts of rubber components. In particular, at the lower limit, the content of silica is preferably 25 parts by mass or more, more preferably 30 parts by mass or more, further preferably 35 parts by mass or more, and most preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. It is. On the other hand, at the upper limit, the content of silica is preferably less than 55 parts by mass and more preferably 50 parts by mass or less with respect to 100 parts by mass of the rubber component. If the amount of silica is too small, the rubber component cannot be sufficiently reinforced and a rubber composition having insufficient wear resistance may be obtained. On the other hand, if the amount of silica is too large, the hardness increases and a rubber composition having poor oil grip properties may be obtained.

<Silane coupling agent>
The silane coupling agent has at least the formula (2) among the following formulas (1) and (2) in the molecular structure. On the condition that the silane coupling agent contains a unit represented by the formula (2), a unit represented by the formula (1) and other units other than the formula (1) and the formula (2) are included. You may have. Hereinafter, this silane coupling agent may be referred to as “predetermined silane coupling agent”.

In Formula (1) and Formula (2), x and y each represent mol%. x is 0-30, and y is 70-100. However, x + y = 100. When x is 0, the predetermined silane coupling agent consists only of units of the formula (2).
In formulas (1) and (2), R ¹ and R ² are each independently hydrogen, hydroxyl group, halogen, substituted or unsubstituted linear or branched alkyl group, substituted or unsubstituted linear or branched An alkenyl group, a substituted or unsubstituted linear or branched alkynyl group, or a substituted or unsubstituted thiol group.
In the formulas (1) and (2), R ³ and R ⁴ each independently represent a covalent bond, a substituted or unsubstituted linear or branched alkylene group, a substituted or unsubstituted linear or branched alkenylene. Or a substituted or unsubstituted linear or branched alkynylene group. However, when R ³ and R ⁴ are terminal, R ³ and R ⁴ are each independently hydrogen, substituted or unsubstituted linear or branched alkyl group, substituted or unsubstituted linear or branched Or a substituted or unsubstituted linear or branched alkynyl group, R ¹ and R ³ may form a ring, and R ² and R ⁴ may form a ring. It may be. That is, R ³ and R ⁴ located at the end may form a ring with R ¹ and R ² respectively, and the predetermined silane coupling agent includes those having such a ring structure at the end. .
In the present specification, the substitution or non-substitution means having a substituent or not having a substituent. The covalent bond means that R ³ and R ⁴ have no group or atom, respectively.

In Formula (1) and Formula (2), x is preferably 0 or more and less than 30, and y is preferably more than 70 and 100 or less, more preferably x is 0 to 25 and y is 75 to 100. , X is 0-20 and y is more preferably 80-100, more preferably x is 10-20 and y is 80-90.
Examples of the halogen include fluorine, chlorine, bromine and the like.
Carbon number of the said linear or branched alkyl group is 1-30, for example, Preferably, it is 1-12, More preferably, it is 1-6, More preferably, it is 1-4. Specific examples of linear or branched alkyl groups having 1 to 30 carbon atoms include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, Examples include tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, octadecyl, etc. It is done.
When the linear or branched alkyl group has a substituent (substituted linear or branched alkyl group), examples of the substituent include an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, A thioalkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, an alkylamino group having 1 to 4 carbon atoms, a phenylamino group having 6 to 20 carbon atoms, an acylamino group having 1 to 4 carbon atoms, and a halogeno group , Nitro group, cyano group, acetamide group, phosphoric acid group, —OH group, —SO ₃ H group, —COOH group, —NH ₂ group, —CONH ₂ group and the like.

  Carbon number of the said linear or branched alkenyl group is 2-30, for example, Preferably, it is 2-12, More preferably, it is 2-6, More preferably, it is 2-4. Specific examples of the linear or branched alkenyl group having 2 to 30 carbon atoms include, for example, vinyl group, 1-propenyl group, 2-propenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 2 -Pentenyl group, 1-hexenyl group, 2-hexenyl group, 1-octenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, octadecenyl group and the like can be mentioned. When the alkenyl group has a substituent (substituted linear or branched alkenyl group), examples of the substituent include the same groups as those exemplified above for the alkyl group.

  Carbon number of the said linear or branched alkynyl group is 2-30, for example, Preferably, it is 2-12, More preferably, it is 2-6, More preferably, it is 2-4. Specific examples of the linear or branched alkynyl group having 2 to 30 carbon atoms include, for example, ethynyl group, propynyl group, butynyl group, pentynyl group, hexynyl group, heptynyl group, octynyl group, noninyl group, decynyl group, undecynyl group. Group, dodecynyl group and the like. When the alkynyl group has a substituent (substituted linear or branched alkynyl group), examples of the substituent include the same groups as those exemplified above for the alkyl group.

  As the thiol group, for example, a thiol group having 0 to 30 carbon atoms is preferable, a thiol group having 1 to 20 carbon atoms is more preferable, and a thiol group having 1 to 10 carbon atoms is further preferable. Specific examples of the thiol group include a mercaptomethyl group, a mercaptoethyl group, a 4-mercaptocyclohexyl group, and a 4-mercaptophenyl group. When the thiol group has a substituent, examples of the substituent include the same groups as those exemplified for the alkyl group.

  Carbon number of the said linear or branched alkylene group is 1-30, for example, Preferably, it is 1-12, More preferably, it is 1-6, More preferably, it is 1-4. Specific examples of the linear or branched alkylene group having 1 to 30 carbon atoms include, for example, methylene group, ethylene group, propylene group, butylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, and decylene. Group, undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group and the like.

  Carbon number of the said linear or branched alkenylene group is 2-30, for example, Preferably, it is 2-12, More preferably, it is 2-6, More preferably, it is 2-4. Specific examples of the linear or branched alkenylene group having 2 to 30 carbon atoms include, for example, vinylene group, 1-propenylene group, 2-propenylene group, 1-butenylene group, 2-butenylene group, 1-pentenylene group, 2 -Pentenylene group, 1-hexenylene group, 2-hexenylene group, 1-octenylene group and the like can be mentioned.

Carbon number of the said linear or branched alkynylene group is 2-30, for example, Preferably, it is 2-12, More preferably, it is 2-6, More preferably, it is 2-4. Specific examples of the linear or branched alkynylene group having 2 to 30 carbon atoms include, for example, ethynylene group, propynylene group, butynylene group, pentynylene group, hexynylene group, heptynylene group, octynylene group, noninylene group, decynylene group, undecynylene group. Group, dodecynylene group and the like.
When the alkylene group, alkenylene group or alkynylene group has a substituent (substituted linear or branched alkenylene group, alkenylene group or alkynylene group), the substituent is the same as those exemplified for the alkyl group. Can be mentioned.

R ¹ and R ^{2 in} formulas (1) and (2) are each preferably a substituted or unsubstituted linear or branched alkyl group, more preferably an unsubstituted linear or branched alkyl group. . In addition, R ³ and R ⁴ in the formulas (1) and (2) are each preferably a substituted or unsubstituted linear or branched alkylene group, more preferably an unsubstituted linear or branched alkylene group. It is.

  The content of the predetermined silane coupling agent exceeds 3 parts by mass with respect to 100 parts by mass of silica. In particular, at the lower limit, the content of the silane coupling agent is preferably 3.5 parts by mass or more, more preferably 4 parts by mass or more, and further preferably 4.5 parts by mass or more with respect to 100 parts by mass of silica. . On the other hand, at the upper limit, the content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and further preferably 8 parts by mass or less with respect to 100 parts by mass of silica. If the amount of the silane coupling agent is too small, the hardness increases and a rubber composition having poor oil grip properties may be obtained. On the other hand, even if a large amount of silane coupling agent is added, the effect of the present invention does not change, so it is not preferable from the viewpoint of cost effectiveness to add too much.

The rubber composition of the present invention may contain various additives in addition to the rubber component, silica as a reinforcing agent, and a predetermined silane coupling agent.
Examples of the additive include softeners, crosslinking agents, crosslinking aids, fillers, weathering agents, antioxidants, ultraviolet absorbers, lubricants, antistatic agents, dispersants, foaming agents, and the like. These are appropriately selected and blended in the rubber composition.
The said crosslinking agent is mix | blended in order to bridge | crosslink a rubber component. A crosslinking agent is not specifically limited, For example, the compound containing sulfur, an organic peroxide, etc. are mentioned. The crosslinking aid is not particularly limited, and examples thereof include zinc oxide, metal oxides other than zinc, metal hydroxides, and fatty acids. The filler is not particularly limited, and examples thereof include calcium carbonate, magnesium carbonate, magnesium oxide, and titanium oxide.

[Composition of shoes and outsole]
3 and 4, a shoe 1a according to an embodiment of the present invention includes an upper 2a that covers an instep, a midsole 3a provided below the upper 2a, and a lower surface of the midsole 3a. And an outsole 5a provided. The midsole 3a is attached to the lower end of the upper 2a. The outsole 5a is attached over the entire lower surface of the midsole 3a. A method for attaching the midsole 3a and the outsole 5a is not particularly limited, and representative examples include adhesion using an adhesive 4a. When the outsole 5a and the midsole 3a have a property of adhering to each other, the outsole 5a and the midsole 3a can be directly adhered. Moreover, the attachment method of the upper 2a and the midsole 3a is not specifically limited, For example, adhesion | attachment using an adhesive agent is mentioned. In the shoe 1a, the lower surface of the outsole 5a is in contact with the ground.

In FIG. 5, a shoe 1b according to another embodiment of the present invention is provided with an upper 2b covering the instep, a midsole 3b provided below the upper 2b, and a lower surface of the midsole 3b. And a plurality of outsole 51b and 52b. In this shoe 1b, the areas of the outsole 51b, 52b are both smaller than the area of the lower surface of the midsole 3b. Therefore, a part of the lower surface of the midsole 3b is exposed. In addition, in the shoe 1b of the example of FIG. 5, although two outsole 51b and 52b (the 1st outsole 51b and the 2nd outsole 52b) whose area is smaller than the midsole 3b are provided, It is not limited to this. For example, only one outsole having a smaller area than the midsole 3b may be provided, or three or more outsole as described above may be provided (none of which is shown).
In FIG. 5, the first outsole 51b is attached to the front of the lower surface of the midsole 3b, and the second outsole 52b is attached to the rear of the lower surface of the midsole 3b. But the arrangement | positioning of an outsole with a small area is not restricted to the front or back of the midsole 3b, It can change suitably. In the shoe 1b, the lower surfaces of the outsole 51b and 52b and a part of the lower surface of the midsole 3b are in contact with the ground.

The lower surfaces of the outsole 5a, 51b, 52b are usually formed in a concavo-convex shape as illustrated. However, it is not limited to such a concavo-convex shape, and the lower surface of all or at least one outsole illustrated may be formed flat (not shown). A plurality of separate studs may be attached to the lower surface of all or at least one outsole illustrated (not shown).
The thicknesses of the outsole 5a, 51b, 52b are not particularly limited, but are usually 1 mm or more, preferably 2 mm to 10 mm. Further, the thickness of the midsole 3a, 3b is not particularly limited, but is usually 3 mm or more, preferably 4 mm to 20 mm.

  The outsole is a bottom member of a shoe that is in contact with the ground, and as described above, the outsole can be appropriately used on the entire lower surface or a part of the shoe. The outsole is not limited to the bottom member that is always in contact with the ground. The concept of the outsole includes a shoe bottom member that does not normally contact the ground but can be deformed by an external force (such as an impact at the time of landing) and contact the ground. Examples of the shoe bottom member that can be deformed by the external force and come into contact with the ground include a reinforcing member such as a shank member. The shank member is a bottom member disposed on the arch portion.

  The rubber composition of the present invention is used for various rubber products. Since the rubber composition is excellent in oil grip properties, it can be suitably used as a material for forming an outsole of an application in an oil environment, for example, a shoe such as work shoes. In a shoe having a plurality of outsole, an outsole containing the rubber composition can be used for a part or all of the plurality of outsole. However, the rubber product obtained by molding the rubber composition of the present invention may be used not only as an outsole, but also as other shoe components including a midsole, and used for applications other than shoe components. May be. Further, rubber products such as outsole may be non-foamed or foamed. When used as an outsole, it is preferably non-foamed.

The shoe outsole can be obtained, for example, as follows.
In the preparation step, a rubber composition containing a rubber component containing a predetermined acrylonitrile butadiene rubber, silica, a predetermined silane coupling agent, and, if necessary, an additive within a range of the above compounding amount is kneaded. . The temperature at the time of kneading | mixing a rubber composition is 120 degreeC-160 degreeC normally. The kneading can be performed using an open roll, a Banbury mixer, a kneader, a twin screw extruder, or the like. Further, sulfur and a vulcanization accelerator are mixed and kneaded, which is usually performed at a temperature of less than 120 ° C.
Next, in the molding step, the kneaded product is put into a suitably shaped mold and heat molded to obtain an outsole. By heating, an outsole having rubber elasticity is obtained. The molding temperature is preferably 140 ° C to 180 ° C, more preferably 150 ° C to 170 ° C.

  The hardness (Shore-A) of rubber products such as outsole thus obtained is preferably less than 67, more preferably 66 or less, and even more preferably 65 or less. Although the minimum of the said hardness is not specifically limited, When using as an outsole, Preferably it is 40 or more, More preferably, it is 45 or more, More preferably, it is 50 or more.

Since the rubber product containing the rubber composition of the present invention has low hardness and excellent oil resistance and wear resistance, excellent oil grip properties can be maintained for a relatively long period of time.
As described in the preliminary experiment, the rubber product having a low hardness has an excellent oil grip property. This is presumed to be because rubber products with low hardness are moderately deformed and bite firmly into the floor. In order to maintain this low hardness, it is conceivable to make the blending amount of silica relatively small, but if so, the strength of the rubber product is lowered.
The inventors of the present invention blended silica to such an extent that the strength as a rubber product can be maintained (20 to 55 parts by mass of silica with respect to 100 parts by mass of the rubber component), and by using a predetermined silane coupling agent, It has been found that a rubber product having excellent wear resistance and low hardness can be obtained.

Specifically, the predetermined silane coupling agent is hydrogen-bonded or covalently bonded to silica at the portions of —OR ¹ and —OR ² , and SCOC ₇ H ₁₅ of the formula (1) and of the formula (2) It is considered that the rubber component is interposed between the silica and the rubber component by hydrogen bonding or covalent bonding with the rubber component at the mercapto group (SH group). The mercapto group of the formula (2) is considered to have high reactivity with a rubber component (particularly, a predetermined acrylonitrile butadiene rubber). Therefore, this predetermined silane coupling agent is considered to have a high ratio of binding to the rubber component and silica. On the other hand, silica itself has the property of agglomerating. For example, even when the silica is dispersed when the rubber composition is kneaded, the silica may be agglomerated again when processed into a rubber product. When the silica is aggregated, the reinforcing effect of the rubber is lowered, so that a large amount of silica must be blended, and the hardness increases. Since the predetermined silane coupling agent is rich in reactivity with the rubber component and silica, it is considered that the aggregation and reaggregation of silica can be suppressed. As described above, since the predetermined silane coupling agent can promote the dispersion of silica, reinforcement of the rubber component can be realized without blending a large amount of silica. Then, since the predetermined silane coupling agent bonded to the dispersed silica bonds to the rubber component, the number of bonding points between the two increases, and the bonding strength of the silane coupling agent to the rubber component and silica is high. It is considered that a rubber product having excellent wear characteristics can be obtained.
Further, by using a rubber component containing a predetermined acrylonitrile butadiene rubber, a rubber product having excellent oil resistance can be obtained.

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

[Materials used]
<Rubber component>
NBR (1): Acrylonitrile butadiene rubber having an acrylonitrile amount of 48% by mass (manufactured by JSR Corporation, trade name “N215SL”).
NBR (2): Acrylonitrile butadiene rubber having an acrylonitrile amount of 35% by mass (manufactured by JSR Corporation, trade name “N230SL”).
NBR (3): Acrylonitrile butadiene rubber having an acrylonitrile amount of 26% by mass (trade name “N240S” manufactured by JSR Corporation).
NBR (4): Acrylonitrile butadiene rubber having an acrylonitrile amount of 20% by mass (trade name “N250S” manufactured by JSR Corporation).
BR: Butadiene rubber (manufactured by Nippon Zeon Co., Ltd., trade name “NIPOL BR1220”).

<Reinforcing agent>
Silica: wet silica having an average particle size of 17 nm. Product name “Ultra Gil VN3” manufactured by Degussa.
<Silane coupling agent>
Silane coupling agent (1): x in the formula (1) is 0 mol% and y in the formula (2) is 100 mol% (that is, only consisting of the formula (2)). Product name “NXT-Z100” manufactured by Momentiv Performance Materials. As the product name “NXT-Z100”, for example, one in which R ^{2 in} the formula (2) is —CH ₂ CH ₃ and R ⁴ is —CH ₂ CH ₂ can be used.
Silane coupling agent (2): x in formula (1) is 20 mol% and y in formula (2) is 80 mol%. However, the product name “NXT-Z100” and the product name “NXT-Z45” to be described later are 7: 4 so that x in the formula (1) is 20 mol% and y in the formula (2) is 80 mol%. What was mixed by (mass ratio) was used.
Silane coupling agent (3): x in formula (1) is 30 mol% and y in formula (2) is 70 mol%. However, the product name “NXT-Z100” and the product name “NXT-Z45” described later are 5: 6 so that x in the formula (1) is 30 mol% and y in the formula (2) is 70 mol%. What was mixed by (mass ratio) was used.
Silane coupling agent (4): x in formula (1) is 40 mol% and y in formula (2) is 60 mol%. However, the product name “NXT-Z100” and the product name “NXT-Z45” described below are 3: 8 so that x in the formula (1) is 40 mol% and y in the formula (2) is 60 mol%. What was mixed by (mass ratio) was used.
Silane coupling agent (5): x in formula (1) is 55 mol% and y in formula (2) is 45 mol%. Product name “NXT-Z45” manufactured by Momentiv Performance Materials. In the product name “NXT-Z45”, for example, R ¹ and R ² in Formula (1) and Formula (2) are both —CH ₂ CH ₃ , R ³ and R in Formula (1) and Formula (2), Any of ⁴ may be —CH ₂ CH ₂ .
Silane coupling agent (6): bis (3-triethoxysilylpropyl) tetrasulfide. Product name “Si69” manufactured by Degussa.
Silane coupling agent (7): 3-mercaptopropyltriethoxysilane. Product name “A1891” manufactured by Momentiv Performance Materials.

<Plasticizer>
Oil: diisononylcyclohexane-1,2-dicarboxylate. Product name "DINCH", manufactured by BASF
<Processing aid>
Stearic acid: New Nippon Rika Co., Ltd., trade name "Stearic acid 50S"
<Crosslinking accelerator>
Zinc oxide: manufactured by Honjo Chemical Co., Ltd., trade name “Active Zinc Hana No. 2”
<Anti-aging agent>
2,6-di-tert-butyl-4-methylphenol: Ouchi Shinsei Chemical Co., Ltd., trade name “NOCRACK 200”
<Activator>
Polyethylene glycol: Product name “PEG # 4000” manufactured by NOF Corporation.
<Crosslinking agent>
Sulfur: manufactured by Hosoi Chemical Industry Co., Ltd., trade name “fine powder sulfur”.
<Crosslinking accelerator>
Cross-linking accelerator (1): 2-benzothiazolyl disulfide. Product name “Noxeller DM-P” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Cross-linking accelerator (2): 2-mercaptobenzothiazole. Product name "Noxeller MP" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Cross-linking accelerator (3): tetramethylthiuram monosulfide. Product name “Noxeller TS” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Cross-linking accelerator (4): N-oxydiethylene-2-benzothiazolylsulfenamide. Product name “Noxeller MSA-G” manufactured by Ouchi Shinsei Chemical Co., Ltd.

[Measurement method of hardness]
Hardness (Shore-A) was measured by the following method based on JIS K 6253.
Using a spring type hardness tester type A, the measurement surface having a thickness of 6 mm or more is brought into contact with the pressure surface of the tester so that the push needle of the tester is perpendicular to the test piece measurement surface. The scale was read immediately after the pressing needle was pressed against the sample with a load of 9.81N. The measurement sample is obtained by stacking a plurality of test pieces formed in Examples and Comparative Examples described later to be 6 mm or more.

[Measurement method of wear resistance index]
It was measured by a DIN abrasion test according to JIS K 6264. Specifically, in the DIN abrasion test, the abrasion volumes of the test pieces of the examples and comparative examples were measured to determine the abrasion resistance. And the abrasion resistance of the comparative example 1 which mix | blended Si69 which is a general purpose silane coupling agent was set to 100, with respect to it, the measurement result of Examples 1-10 and Comparative Examples 2-9 was displayed as an index | exponent. For example, when a certain measurement result (wear volume) is 20% less than the wear volume of Comparative Example 1, the wear resistance index is 120%, and when it is 20% more, the wear resistance index is 80%. . Since the wear resistance index of Example 1 is 110%, the wear volume of Example 1 is 10% smaller than that of Comparative Example 1, and the wear resistance index of Comparative Example 2 is 87%. Therefore, Comparative Example 2 is more than Comparative Example 1. Also, the 13% wear volume was large.

[Measurement method of volume change rate]
In accordance with JIS K6258, the volume change rate was calculated from the following formula by measuring the volume of the test piece after immersing the test piece in isooctane (concentration 100%) for 20 hours under normal temperature and normal pressure.
Volume change rate (%) = {(Volume of test piece after test) / (Volume of test piece before test)} × 100.
The volume change rate is a measure of how much the oil (isooctane) expands and is an index of oil resistance.

[Measurement method of elastic modulus change]
In order to confirm the Payne effect of the test pieces of Examples and Comparative Examples, a change in elastic modulus was measured. Specifically, using a dynamic viscoelasticity measuring apparatus (trade name “MCR301” manufactured by Anton Paar Co., Ltd.), the shear storage elasticity of the test piece was changed while changing the amplitude of shear dynamic strain from 0.01% to 10%. The rate G ′ was measured. The measurement conditions were a temperature of 20 ° C. and a frequency of 0.5 Hz. The change in elastic modulus was calculated from the following formula.
Elastic modulus change ΔG ′ [MPa] = (G ′ when strain is 0.01%) − (G ′ when strain is 10%).
The decrease in elastic modulus due to the Payne effect occurs because silica aggregated inside is destroyed when the rubber is deformed. Therefore, it can be said that the smaller the elastic modulus change ΔG ′, the smaller the amount of silica aggregation.

[Example 1]
Each component is blended with additives such as rubber component, silica, silane coupling agent, and plasticizer in the proportions shown in Table 1, and using a kneader (DS3-10MWB-E type), the discharge temperature is 135 ° C to 155 ° C. The mixture was kneaded under the following temperature conditions. Thereafter, the kneaded product was blended with a crosslinking agent and a crosslinking accelerator (remaining additive) and further kneaded at a temperature of 60 ° C. to 80 ° C. using a 10-inch open roll.
In addition, the breakdown of 24.9 parts by mass of additives is 14 parts by mass of plasticizer, 1.5 parts by mass of processing aid, 3.2 parts by mass of cross-linking accelerator, 1.0 part by mass of anti-aging. Agent, 1.4 parts by weight activator, 2.0 parts by weight crosslinking agent, 0.7 parts by weight crosslinking accelerator (1), 0.6 parts by weight crosslinking accelerator (2), 0.2 parts by weight Part of the crosslinking accelerator (3) and 0.3 part by weight of the crosslinking accelerator (4).
Next, this kneaded product was pressed at 160 ° C. under a pressure of about 15 MPa for about 5 minutes using a press machine to produce a rubber sheet having a length of 125 mm, a width of 215 mm, and a thickness of 2 mm. Further, similarly, a cylindrical rubber piece having a diameter of 16 mm and a thickness of 6 mm was produced. The hardness and volume change rate were measured using the rubber sheet as a test piece, and the wear resistance index and the elastic modulus change were measured using the cylindrical rubber piece as a test piece. The results are shown in Table 1.
In addition, the average value of AN amount in the rubber component in each table is the amount of acrylonitrile with respect to the whole rubber component, and is not the amount with respect to acrylonitrile butadiene rubber alone.

[Examples 2 to 10]
A rubber sheet and a rubber piece were produced in the same manner as in Example 1 except that the rubber component, silica, silane coupling agent and the blending ratio thereof were changed as shown in Tables 1 and 2. In addition, the kind and compounding quantity of the additive in Examples 2 to 10 are the same as those in Example 1. The hardness, volume change rate, wear resistance index, and elastic modulus change of Examples 2 to 10 were measured. The results are shown in Tables 1 and 2.

[Comparative Examples 1 to 9]
A rubber sheet and a rubber piece were produced in the same manner as in Example 1 except that the rubber component, silica, silane coupling agent and the blending ratio thereof were changed as shown in Tables 3 and 4. Note that the types and amounts of additives in Comparative Examples 1 to 9 are the same as those in Example 1. The hardness, volume change rate, wear resistance index, and elastic modulus change of Comparative Examples 1 to 9 were measured. The results are shown in Table 1.
Except having changed each component and those mixture ratios as shown in Table 2, the test piece was produced similarly to Example 1, and the hardness, the abrasion resistance index, and the volume change rate were measured. The results are shown in Table 2.

About evaluation of Table 1 thru | or Table 4, it is as follows.
When the hardness was 65 or less, the oil grip property was evaluated as ◯, and when the hardness exceeded 65, the oil grip property was evaluated as ×.
When the wear resistance index exceeded 100, the wear resistance was evaluated as “good”, and when the wear resistance index was 100 or less, the wear resistance was evaluated as “poor”.
When the volume change rate is less than 5%, the oil resistance is ◎, when the volume change rate is 5% to 12%, the oil resistance is ◯, and when the volume change rate exceeds 12%, the oil resistance is ×.
In addition, "-" in a table | surface represents not having measured. The main factor that determines the volume change rate (oil resistance) is the closeness of the polarities of the rubber composition and the oil, and the polarity of the rubber composition is considered to be almost determined by the rubber component (silica and silane coupling). The agent has little effect on the polarity of the rubber composition). For this reason, it is estimated that the volume change rates of Examples 1, 3, 7 to 10 and Comparative Examples 1 to 4, 7 to 9 having the same rubber component as Example 2 show the same numerical values as in Example 2. As such, these volume change rates were not measured.
The change in elastic modulus was performed to support the estimation of the action of a predetermined silane coupling agent on silica and rubber components. Since this support can be made even if this measurement is not performed for all examples and comparative examples, the elastic modulus change was not measured for some examples.

The rubber products of Examples 1 to 10 were excellent in oil grip properties, wear resistance, and oil resistance. In particular, as in Examples 1 to 4 and 7 to 10, when a rubber component having an average value of acrylonitrile in the rubber component exceeding 30% by mass is used, a rubber product having extremely good oil resistance is obtained. It was.
From Comparative Examples 1 and 2, when a silane coupling agent other than the formula (1) and the formula (2) was used, a rubber product having inferior oil grip properties and / or wear resistance was obtained.
From Comparative Examples 3 and 4, even if the silane coupling agent contains Formula (1) and Formula (2), if y in Formula (2) is less than 70 mol%, the wear resistance is poor. A rubber product was obtained.
From the result of Comparative Example 5, when a rubber component containing acrylonitrile butadiene rubber having an acrylonitrile amount of 48% by mass was used, a rubber product having poor oil grip properties and wear resistance was obtained. The reason why the oil grip property is lowered is presumed that the property of the rubber component approximates that of acrylonitrile resin due to a relatively large amount of acrylonitrile butadiene rubber having a high acrylonitrile ratio, and as a result, the hardness increases. The reason why the wear resistance was lowered is presumed to be that the properties of butadiene rubber having excellent wear resistance could not be sufficiently exhibited because the proportion of acrylonitrile was high and the proportion of butadiene rubber was relatively reduced.
From the result of Comparative Example 6, when an acrylonitrile butadiene rubber having an acrylonitrile amount of 20% by mass was used, a rubber product having inferior oil resistance was obtained. This is presumably because the polarity of the rubber component approached that of trimethylpentane and swelled by using acrylonitrile butadiene rubber having a low ratio of acrylonitrile.

From the result of Comparative Example 7, when the blending amount of the predetermined silane coupling agent was 3 parts by mass with respect to 100 parts by mass of silica, a rubber product having inferior oil grip properties and wear resistance was obtained. The reason why the oil grip property is lowered is presumed to be that the amount of the silane coupling agent relative to the amount of silica is too small and the silica is not sufficiently dispersed and the hardness is increased. In addition, the reason why the wear resistance is lowered is presumed to be that there are too few silane coupling agents with respect to the amount of silica, and the number of bonded sites of silica and rubber components is reduced.
From the result of Comparative Example 8, when the compounding amount of silica was 15 parts by mass with respect to 100 parts by mass of the rubber component, a rubber product having poor wear resistance was obtained. This is presumably because the amount of silica was too small to sufficiently reinforce the rubber component.
From the result of Comparative Example 9, when the amount of silica was 60 parts by mass with respect to 100 parts by mass of the rubber component, a rubber product having inferior oil grip properties was obtained. This is presumably because the amount of silica was too high and the hardness increased.

  The rubber products of Examples 1 to 10 have excellent oil grip properties (low hardness) and excellent wear resistance, as described above, the predetermined silane coupling agent can suppress silica aggregation, Further, it is presumed that the bonding strength to silica and rubber components is high. Such estimation of the present inventors can be confirmed by the Payne effect. The Payne effect is a phenomenon in which the elastic modulus decreases as the strain increases. Due to this Payne effect, when a certain level of strain is applied to a rubber product containing silica, the agglomerated silica is destroyed, and the elastic modulus is lowered. Therefore, it can be said that the smaller the elastic modulus drop when a certain strain or more is applied, the smaller the amount of silica aggregation. For this reason, the present inventors measured the elastic modulus change of the rubber product of each Example and a comparative example. As is apparent from Tables 1 and 2, the rubber products of Examples 1 to 10, which are excellent in oil grip properties and wear resistance, had a small change in elastic modulus.

  The rubber composition of the present invention can be used as a material for forming various rubber products such as shoe outsole.

1a, 1b Shoes 5a, 51b, 52b Shoes outsole

Claims (9)

When the total rubber component is 100 parts by mass, a rubber component containing 65 parts by mass or more of acrylonitrile butadiene rubber having an acrylonitrile amount of more than 20% by mass and less than 45% by mass;
20 to 55 parts by mass of silica with respect to 100 parts by mass of the rubber component;
Among the following formulas (1) and (2), a silane coupling agent having at least the formula (2) in the molecular structure, the silane coupling agent exceeding 3 parts by mass with respect to 100 parts by mass of the silica;
A rubber composition comprising:
In the formula (1) and (2), x and y each represent the mole%, x is 0 to 30, y is from 70 to 100, an x + y = 100, ^{R 1} and R ² is independently hydrogen, hydroxyl group, halogen, substituted or unsubstituted linear or branched alkyl group, substituted or unsubstituted linear or branched alkenyl group, substituted or unsubstituted linear or branched group. Represents an alkynyl group or a substituted or unsubstituted thiol group, and R ³ and R ⁴ each independently represents a covalent bond, a substituted or unsubstituted linear or branched alkylene group, a substituted or unsubstituted linear group Alternatively, it represents a branched alkenylene group or a substituted or unsubstituted linear or branched alkynylene group. However, when R ³ and R ⁴ are terminal, R ³ and R ⁴ are each independently hydrogen, substituted or unsubstituted linear or branched alkyl group, substituted or unsubstituted linear or branched Or a substituted or unsubstituted linear or branched alkynyl group, R ¹ and R ³ may form a ring, and R ² and R ⁴ form a ring. Also good.   The rubber composition according to claim 1, wherein y in the formula (2) is 80 to 100.   The rubber composition according to claim 1 or 2, wherein the silane coupling agent is contained in an amount of 3.5 to 20 parts by mass with respect to 100 parts by mass of the silica.   The rubber composition according to claim 1 or 2, wherein the silane coupling agent is contained in an amount of 4.5 to 8 parts by mass with respect to 100 parts by mass of the silica.   The rubber composition according to any one of claims 1 to 4, wherein the silica is contained in an amount of 30 to 50 parts by mass with respect to 100 parts by mass of the rubber component.   The rubber composition according to any one of claims 1 to 5, wherein the rubber component is composed only of acrylonitrile butadiene rubber having an acrylonitrile amount of more than 20% by mass and less than 45% by mass.   When the rubber component is 100 parts by mass of the entire rubber component, the amount of acrylonitrile is 70% by mass or more and less than 100 parts by mass with an acrylonitrile amount of more than 20% by mass and less than 45% by mass. The rubber composition according to any one of claims 1 to 5, comprising a rubber other than the acrylonitrile butadiene rubber of more than 0 parts by mass and 30 parts by mass or less.   The rubber composition according to any one of claims 1 to 7, wherein an amount of acrylonitrile of the acrylonitrile butadiene rubber is 23% by mass to 40% by mass.   An outsole of a shoe comprising the rubber composition according to any one of claims 1 to 8.