JP6919382B2 - Rubber material for tennis balls and tennis balls - Google Patents

Description

The present invention relates to a rubber material for a tennis ball. In particular, the present invention relates to a rubber material for a tennis ball and a tennis ball used for tennis.

Tennis balls have a core made of rubber material. This core is a hollow sphere. In a tennis ball used in tennis, the core is filled with a compressed gas having a pressure 40 kPa to 120 kPa higher than the atmospheric pressure. This tennis ball is also called a pressure tennis ball (pressure ball).

In playing tennis, a tennis ball with high resilience is advantageous. In addition, a tennis ball having an appropriate resilience performance gives the player a good shot feeling. In a pressurized tennis ball, the internal pressure of the core, which is higher than the atmospheric pressure, provides excellent resilience performance and a good shot feeling. On the other hand, the filled compressed gas gradually leaks from the core due to the internal pressure of the core being higher than the atmospheric pressure. Due to gas leakage, the internal pressure of the core may decrease to near atmospheric pressure. A tennis ball with a reduced core internal pressure is inferior in resilience performance and shot feeling. There is a demand for a tennis ball with little change in resilience performance and shot feeling over time.

Japanese Unexamined Patent Publication No. 61-143455 proposes a rubber material containing a scaly or flat filler as a material for preventing gas leakage.

Japanese Unexamined Patent Publication No. 61-143455

In the rubber material disclosed in JP-A-61-143455, the scaly or flat filler inhibits the permeation of gas and contributes to the prevention of leakage. However, in the case of a scaly or flat plate-shaped filler, the fillers come into contact with each other in the rubber material depending on the blending amount, which causes an increase in the loss tangent tan δ of the rubber material. The loss tangent tan δ of the rubber material correlates with the resilience performance of the tennis ball obtained by using this rubber material. An increase in the loss tangent tan δ reduces the resilience performance of the tennis ball. A tennis ball with reduced resilience performance is also inferior in shot feeling.

In particular, in the case of a tennis ball for competition, the outer shape, weight, rebound performance, etc. are restricted within a predetermined range by the International Tennis Federation from the viewpoint of fairness. Tennis balls whose resilience performance does not meet this requirement cannot be used in official competitions. A rubber material for a tennis ball that has appropriate resilience performance and a good shot feeling and can effectively prevent gas leakage has not yet been proposed.

An object of the present invention is to provide a rubber material for a tennis ball and a tennis ball, which are excellent in resilience performance and shot feeling and have little gas leakage.

The rubber material for tennis balls according to the present invention contains 100 parts by mass of base rubber and 1 part by mass or more and 150 parts by mass or less of a carbon-based filler. The value V1 obtained by multiplying the product of the loss tangent tan δ at 0 ° C. and the nitrogen gas permeability coefficient G at 40 ° C. ^{by 10 10 of this rubber material is 0.90 or less.}

Preferably, the carbon-based filler is selected from the group consisting of carbon black, activated carbon, graphite, graphene, fullerenes and carbon nanotubes. Preferably, the carbon-based filler is graphite or graphene.

Preferably, this value V1 is 0.80 or less.

Preferably, the value V2 obtained by dividing the loss tangent tan δ at 0 ° C. by the flatness DL of the carbon-based filler is 1.00 × 10 ⁻³ or less. The flatness DL is obtained by dividing the average particle size D ₅₀ (μm) of the carbon-based filler by the average thickness T (μm).

Preferably, the rubber material further comprises a coupling agent. Preferably, this coupling agent is
(1) It has a functional group X capable of interacting with a carbon-based filler, a functional group Y capable of interacting with a base rubber, and a spacer group S, and is represented by the general formula XSY. indicated in compound and / or (2) the formula _a 1 _{-B-a 2} shown, the _{a 1} and _{a 2} are each independently a C 3-10 straight, branched or cyclic nitroalkyl It is a group, and this B is a dinitrodiamine compound which is a linear, branched or cyclic alkylene diamino group having 3 to 20 carbon atoms.

Preferably, the functional group X is selected from the group consisting of _{-NR 1} R ₂ , -Ph-OH, -OH, -COOH, ( _{-CO) 2} O, -NCO and -CR ₃ R _{4 O.} Here, R ₁ and R ₂ are independently hydrogen atoms or linear or branched alkyl groups having 1 to 6 carbon atoms, Ph is a phenylene group, and R ₃ and R ₄ are independent, respectively. It is a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms. Preferably, the functional group Y is selected from the group -CR ₅ = CR _6- Z, -S-SO ₃ M ₁ , -S-SO ₂ R ₇ , -SH and -S _n . Here, R ₅ and R ₆ are independently hydrogen atoms or linear or branched alkyl groups having 1 to 6 carbon atoms, Z is a carbonyl group or a carboxyl group, and M ₁ is a hydrogen ion. It is a metal ion, an ammonium ion or a quaternary amine, R ₇ is a methyl group, an ethyl group or a 4-methylphenyl group, and n is an integer of 2 to 4. Preferably, the spacer group S is a linear alkylene group having 2 to 18 carbon atoms, an alicyclic alkylene group having 2 to 18 carbon atoms, a phenylene group (-Ph-) and a phenylene imino group (-Ph-NH-). ) Is selected.

Preferably, the functional group X is a primary amino group (-NH ₂ ). Preferably, the spacer group S is a phenylene imino group (-Ph-NH-). Preferably, the functional group Y is an α, β-unsaturated carbonyl group (-CH = CH-CR ₈ = O). Here, R ₈ is −OM ₂ , and M ₂ is an alkali metal or an alkaline earth metal.

Preferably, the amount of the coupling agent added to the carbon-based filler is 0.1% by mass or more and 50% by mass or less.

Preferably, the base rubber comprises a butadiene rubber and a natural rubber. Preferably, the mass ratio B / N of the butadiene rubber in the base rubber to the natural rubber is 1.4 or less.

Preferably, the sulfur content of this rubber material is 0.01% by mass or more and 10% by mass or less.

Preferably, the shore A hardness Ha of this rubber material is 20 or more and 88 or less. Preferably, the product of the breaking point elongation EB (%) obtained in accordance with JIS K6251 and the hardness Ha of this rubber material is 1,000 or more and 100,000 or less. Preferably, the product of the toluene swelling rate SW (%) obtained in accordance with JIS K6258 and the hardness Ha of this rubber material is 2,500 or more and 50,000 or less.

The tennis ball according to the present invention includes a core made of a rubber material. This rubber material contains 100 parts by mass of base rubber and 1 part by mass or more and 150 parts by mass or less of a carbon-based filler. The value V1 obtained by multiplying the product of the loss tangent tan δ at 0 ° C. and the nitrogen gas permeability coefficient G at 40 ° C. ^{by 10 10 of this rubber material is 0.90 or less.}

In the rubber material according to the present invention, an appropriate amount of carbon-based filler effectively prevents gas leakage. Further, in this rubber material, the loss tangent tan δ at 0 ° C. and the nitrogen gas permeability coefficient G at 40 ° C. are properly balanced. In a tennis ball having a core made of this rubber material, it is possible to achieve both an appropriate repulsion performance and a good shot feeling associated therewith, and a high gas leakage prevention effect.

FIG. 1 is a partially cutaway sectional view of a tennis ball according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

FIG. 1 is a partially cutaway sectional view showing a tennis ball 2 according to an embodiment of the present invention. The tennis ball 2 has a hollow core 4, two felt portions 6 covering the core 4, and a seam portion 8 located in the gap between the two felt portions 6. The thickness of the core 4 is usually about 3 mm to 4 mm. The inside of the core 4 is filled with compressed gas. Two felt portions 6 are attached to the surface of the core 4 with an adhesive.

The core 4 is made of a rubber material. The rubber material according to one embodiment of the present invention is suitably used for forming the core 4. This rubber material contains a base rubber and a carbon-based filler.

Carbon-based fillers consist of a large number of particles. In this rubber material, a large number of particles forming a carbon-based filler are dispersed in a matrix of rubber components. In this rubber material, the carbon-based filler dispersed in the matrix inhibits the movement of gas molecules. The effect of inhibiting the movement of gas molecules by a large number of particles forming a carbon-based filler is great. The gas permeability coefficient of the rubber material containing this carbon-based filler is sufficiently small.

Further, in this rubber material, the loss tangent tan δ at 0 ° C. and the nitrogen gas permeability coefficient G at 40 ° C. are properly balanced. The loss tangent tan δ of the rubber material at 0 ° C. correlates with the repulsive performance of the tennis ball 2 obtained from this rubber material. A tennis ball 2 having high resilience performance can be obtained by using a rubber material having a small loss tangent tan δ at 0 ° C. A tennis ball 2 in which leakage of the filling gas is suppressed can be obtained by using a rubber material having a small nitrogen gas permeation coefficient G at 40 ° C.

The value V1 obtained by multiplying the product of the loss tangent tan δ at 0 ° C. of this rubber material and the nitrogen gas permeability coefficient G (cm ³ · cm / cm ² / sec / cmHg) at ^{40 ° C. by 10 10 is 0.} It is .90 or less. In a rubber material having a value V1 of 0.90 or less, an increase in loss tangent tan δ due to the addition of a carbon-based filler is suppressed. In the tennis ball 2 obtained from this rubber material, it is possible to achieve both an appropriate repulsion performance and a good shot feeling associated therewith, and an effect of preventing leakage of the filling gas. With this tennis ball 2, proper repulsion performance and good shot feeling can be maintained for a long period of time. From this viewpoint, the value V1 is preferably 0.80 or less, more preferably 0.70 or less, and particularly preferably 0.60 or less.

In the present specification, the loss tangent tan δ of the rubber material means the value of the temperature dispersion curve of tan δ obtained by the viscoelastic spectrometer at 0 ° C. The nitrogen gas permeability coefficient G of the rubber material at 40 ° C. is measured according to the differential pressure method described in JIS K7126-1. The details of the measurement method will be described later.

The rubber material having a value V1 of 0.90 or less can be obtained by blending 1 part by mass or more and 150 parts by mass or less of a carbon-based filler with 100 parts by mass of the base rubber. From the viewpoint of preventing leakage of the filling gas, the blending amount of the carbon-based filler is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and particularly preferably 15 parts by mass or more. From the viewpoint of resilience performance and shot feeling, the blending amount of the carbon-based filler is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and particularly preferably 80 parts by mass or less.

In the specification of the present application, the carbon-based filler means a substance having a carbon atom as a main constituent component. Preferably, it means a filler in which 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 98% by mass or more of the constituents thereof are carbon atoms.

In the rubber material according to the present invention, the type of carbon-based filler is not particularly limited, and can be appropriately selected so that the value V1 is 0.90 or less. Specific examples of the carbon-based filler include carbon black, activated carbon, carbon fiber, graphite, graphene, fullerene, carbon nanotubes and the like. The rubber material may contain two or more carbon-based fillers.

From the viewpoint of preventing gas leakage, preferable carbon-based fillers are carbon black, activated carbon, graphite, graphene, fullerenes and carbon nanotubes. Graphite and graphene are more preferred, and graphene is particularly preferred.

Usually, graphene has a single-layer structure in which a large number of carbon atoms are bonded in a plane, and is also called a graphene sheet. Graphene may contain a laminate or aggregate of graphene sheets as long as a value V1 of 0.90 or less is obtained in a predetermined blending amount. From the viewpoint of reducing the gas permeability coefficient, the number of laminated graphene sheets is preferably 100 or less, more preferably 50 or less, and particularly preferably 20 or less.

In the rubber material according to the present invention, the method for producing graphene is not particularly limited. For example, it may be obtained from graphite, graphite oxide or the like by a known method such as a peeling method, an ultrasonic treatment method, a chemical vapor deposition method or an epitaxial growth method. Commercially available graphene may be used as long as the object of the present invention is achieved. Specifically, the product name "xGnP-M-5" of XG Sciences, the product name "G-12" of EM Japan, the product name "GNP-C1" of Graphene Laboratories, and the product name "iGrafen" of iTech. , Etc. are exemplified.

Graphite is a carbon material in which a plurality of graphene sheets are laminated in a slightly displaced state for each layer, and is also referred to as graphite. The type and production method of graphite are not particularly limited as long as a value V1 of 0.90 or less can be obtained in a predetermined blending amount. Examples thereof include natural graphite such as earth-like graphite, scaly graphite, scaly graphite, and semi-scaly graphite, expanded graphite and expanded graphite obtained by processing natural graphite, and artificial graphite obtained by heat-treating amorphous carbon. Be done.

Examples of carbon black include Ketjen black, acetylene black, furnace black, oil furnace black, channel black, and thermal black. Examples of activated carbon include powdered activated carbon, granular activated carbon, crushed carbon, and granular charcoal. Examples of carbon fibers include polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, and vegetable carbon fibers. The carbon fiber may be a long fiber type or a short fiber type.

The carbon nanotubes may be single-walled carbon nanotubes (SWNTs), multi-walled carbon nanotubes (MWNTs), or a mixture thereof. .. Further, the carbon nanotube may have an armchair type structure, a zigzag type structure, a spiral type structure, or a mixture thereof.

In the present specification, the fullerene is meant carbon molecules of globular structure, it is not limited to C ₆₀ fullerene. As long as the effects of the present invention is not inhibited, fullerene polymers may be used which is formed by combining a plurality of C ₆₀ fullerene.

The rubber composition may contain other inorganic fillers as well as carbon-based fillers, as long as the object of the present invention is not impaired. Such inorganic fillers include, for example, talc, kaolinite, bentonite, halosite, montmorillonite, mica, biderite, saponite, hectorite, nontronite, vermiculite, illite, allophane, silica, calcium carbonate, magnesium carbonate, sulfuric acid. Examples include vermiculite and zinc oxide.

When a carbon-based filler is used in combination with another inorganic filler, the total amount of the inorganic filler with respect to 100 parts by mass of the base rubber is preferably 10 parts by mass or more, preferably 20 parts by mass or more, from the viewpoint of resilience performance. More preferably, 25 parts by mass or more is particularly preferable. From the viewpoint of shot feeling, the total amount of the inorganic filler is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, and particularly preferably 70 parts by mass or less.

When the carbon-based filler is used in combination with another inorganic filler, the mixing ratio of the carbon-based filler to the total amount of the inorganic filler is preferably 0.5 mass from the viewpoint of reducing the gas permeability coefficient. % Or more is preferable, 10% by mass or more is more preferable, and 20% by mass or more is particularly preferable. From the viewpoint of shot feeling, the blending ratio of the carbon-based filler is preferably 100% by mass or less, more preferably 80% by mass or less, and particularly preferably 65% by mass or less.

The shape of the particles forming the carbon-based filler is not particularly limited as long as a value V1 of 0.90 or less can be obtained in a predetermined blending amount, but a flat shape is preferable from the viewpoint of reducing the gas permeability coefficient. More preferably, it is a carbon-based filler having a flatness DL of 50 or more, which is obtained by dividing _{the average particle size D 50 (μm) by the average thickness T (μm).} The effect of reducing the gas permeability coefficient by a carbon-based filler having a flatness DL of 50 or more is high. In the rubber material containing the carbon-based filler, gas leakage can be effectively prevented without impairing the resilience performance and the shot feeling. From this viewpoint, the flatness DL of the carbon-based filler is more preferably 100 or more, further preferably 150 or more, and particularly preferably 200 or more. From the viewpoint of dispersibility in the base rubber, the flatness DL is preferably 1000 or less. When the carbon-based filler contains aggregates or aggregates of a plurality of particles, the flatness DL has an average particle diameter D ₅₀ and an average thickness obtained by measuring with the aggregates or aggregates contained. It is calculated from T.

The average particle diameter D ₅₀ of the carbon-based filler is suitably selected depending on the formulation of the type or rubber material. From the viewpoint of reducing the gas permeability coefficient, the average particle size D ₅₀ of the carbon-based filler is preferably 0.1 μm or more, more preferably 0.2 μm or more, and particularly preferably 1.0 μm or more. From the viewpoint of mixing with the base rubber, the average particle size D ₅₀ is preferably 100 μm or less, more preferably 80 μm or less, and particularly preferably 50 μm or less. In the specification of the present application, the average particle size D ₅₀ (μm) is 50 cumulatively from the small diameter side in the particle size distribution measured by a laser diffraction type particle size distribution measuring device (for example, LMS-3000 manufactured by Seishin Enterprise Co., Ltd.). It means the average particle size which is% by volume.

The average thickness T of the carbon-based filler is appropriately selected depending on the type and the composition of the rubber material. From the viewpoint of reducing the gas permeability coefficient, the average thickness T of the carbon-based filler is preferably 1.00 μm or less, more preferably 0.50 μm or less, and particularly preferably 0.20 μm or less. From the viewpoint of mixing with the base rubber, the average thickness T is preferably 0.001 μm or more, more preferably 0.002 μm or more, and particularly preferably 0.003 μm or more. In the specification of the present application, the average thickness T (μm) of the carbon-based filler is measured by microscopic observation with a transmission electron microscope or the like. Specifically, from an image obtained by observing a plurality of particles collected from a carbon-based filler with a transmission electron microscope (for example, H-9500 manufactured by Hitachi High-Technologies Corporation), the carbon-based filler can be used. Particles having a size equivalent to the average particle diameter D ₅₀ are selected and their thickness is measured. The average value of the measured values obtained for the 12 particles is taken as the average thickness T of this carbon-based filler.

Preferably, the rubber material comprises a coupling agent. The coupling agent improves the affinity between the carbon-based filler and the base rubber. In this rubber material, the coupling agent suppresses agglomeration or contact between a large number of particles forming the carbon-based filler. In the tennis ball 2 having the core 4 made of the rubber material, it is possible to avoid the inhibition of the resilience performance and the shot feeling due to the blending of the carbon-based filler.

As such a coupling agent, for example
(1) It has a functional group X capable of interacting with a carbon-based filler, a functional group Y capable of interacting with a base rubber, and a spacer group S, and is represented by the general formula XSY. indicated in compound and / or (2) the formula _a 1 _{-B-a 2} shown, the _{a 1} and _{a 2} are each independently a C 3-10 straight, branched or cyclic nitroalkyl Examples thereof include a dinitrodiamine compound in which B is a linear, branched or cyclic alkylene diamino group having 3 to 20 carbon atoms.

In a rubber material containing the compound (1) represented by the general formula XSY as a coupling agent, the functional group X interacts with the carbon-based filler and the functional group Y interacts with the base rubber. , The affinity between the carbon-based filler and the base rubber is improved.

The type of the functional group X of the compound (1) is not particularly limited as long as it has a function of interacting with a hydroxyl group, a carbonyl group, a carboxyl group, etc. existing on the surface of the carbon-based filler, but the functional group X is preferably functional. Group X is selected from the group consisting of _{-NR 1} R ₂ , -Ph-OH, -OH, -COOH, ( _{-CO) 2} O, -NCO and -CR ₃ R _{4 O.} Here, R ₁ and R ₂ are independently hydrogen atoms or linear or branched alkyl groups having 1 to 6 carbon atoms, Ph is a phenylene group, and R ₃ and R ₄ are independent, respectively. Is a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms.

Examples of R ₁ and R ₂ include linear alkyl groups such as hydrogen atom, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, vinyl group and allyl group, isopropyl group, isobutyl group and s-butyl. Examples thereof include branched alkyl groups such as a group, a t-butyl group, an isopentyl group, a neopentyl group, a t-pentyl group, and an isohexyl group. These linear alkyl groups and branched alkyl groups may further have substituents as long as the effects of the present invention are not impaired.

Examples of R ₃ and R ₄ include linear alkyl groups such as hydrogen atom, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, vinyl group and allyl group, isopropyl group, isobutyl group and s-butyl. Examples thereof include branched alkyl groups such as a group, a t-butyl group, an isopentyl group, a neopentyl group, a t-pentyl group, and an isohexyl group. These linear alkyl groups and branched alkyl groups may further have substituents as long as the effects of the present invention are not impaired.

From the viewpoint of resilience performance and shot feeling, a more preferable functional group X is −NR ₁ R ₂ , and R ₁ and R ₂ are independently hydrogen atoms or linear alkyl groups having 1 to 6 carbon atoms, respectively. NR ₁ R ₂ is more preferable, and a primary amino group (-NH _{2 ) in which R 1} and R ₂ are hydrogen atoms is particularly preferable.

The functional group Y of the compound (1) is a functional group contained in the molecular chain of the base rubber (for example, a carbon-carbon double bond or the like) or a radical generated by cutting the molecular chain of the rubber during vulcanization molding described later. The type is not particularly limited as long as it has a function of interacting with, etc., but preferably, the functional group Y is -CR ₅ = CR _6- Z, -S-SO ₃ M ₁ , -S-. It is selected from the group SO ₂ R ₇ , -SH and -S _n. Here, R ₅ and R ₆ are independently hydrogen atoms or linear or branched alkyl groups having 1 to 6 carbon atoms, Z is a carbonyl group or a carboxyl group, and M ₁ is a hydrogen ion. It is a metal ion, an ammonium ion or a quaternary amine, R ₇ is a methyl group, an ethyl group or a 4-methylphenyl group, and n is an integer of 2 to 4.

Examples of R ₅ and R ₆ include linear alkyl groups such as hydrogen atom, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, vinyl group and allyl group, isopropyl group, isobutyl group and s-butyl. Examples thereof include branched alkyl groups such as a group, a t-butyl group, an isopentyl group, a neopentyl group, a t-pentyl group, and an isohexyl group. These linear alkyl groups and branched alkyl groups may further have substituents as long as the effects of the present invention are not impaired.

Examples of the metal ion of M ₁ include alkali metal ions such as lithium ion, sodium ion and potassium ion, alkaline earth metal ions such as magnesium ion, calcium ion and barium ion, iron ion, copper ion and zinc ion. NS.

From the viewpoint of resilience performance and shot feeling, -CR ₅ = CR _6- Z and -S-SO ₃ M ₁ are more preferable _{as the functional group Y, and R 5} and R ₆ are independently hydrogen atoms or carbon atoms, respectively. _{-CR 5} = CR _6- Z, which is a linear alkyl group of 1 to 6, is more preferable, and α, β-unsaturated carbonyl group (-) in which _{R 5} and R _{6 are hydrogen atoms and Z is a carbonyl group.} CH = CH-CR ₈ = O) is particularly preferable. Here, R ₈ is −OM ₂ , and M ₂ is an alkali metal or an alkaline earth metal. As M ₂ , alkali metals such as lithium, sodium and potassium are preferable, and sodium is particularly preferable.

In compound (1), the functional group X and the functional group Y are bonded via the spacer group S. The type of the spacer group S is not particularly limited as long as it can be bonded to the functional group X and the functional group Y, but preferably, the spacer group S is a linear alkylene group having 2 to 18 carbon atoms and 2 to 18 carbon atoms. It is selected from the alicyclic alkylene group, the phenylene group (-Ph-) and the phenylene imino group (-Ph-NH-).

Examples of the linear alkylene group having 2 to 18 carbon atoms include an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, and a hexamethylene group. Examples of the alicyclic alkylene group having 2 to 18 carbon atoms include a cyclopropylene group, a cyclopentylene group, a cyclohexylene group, a methylcyclohexylene group, and a t-butylcyclohexylene group. As long as the effect of the present invention is not impaired, these linear alkylene group and alicyclic alkylene group may have a substituent such as an alkoxy group, an aryl group, a halogen group and an acyl group.

From the viewpoint of resilience performance and shot feeling, the more preferable spacer group S is a phenylene imino group (-Ph-NH-) or a linear alkylene group having 2 to 18 carbon atoms, and a particularly preferable spacer group is a phenylene imino group. (-Ph-NH-).

A preferred compound (1) in which the functional group X is -NH ₂ , the functional group Y is -CH = CH-C (ONa) = O, and the spacer group S is -Ph-NH- is maleic acid-. 4-Aminoanilide Sodium, Fumaric Acid-4-Aminoanilide Sodium, 4-Amino-Phenyliminoacrylic Acid, Sodium 3-Amino Propanthiosulfonate, Ammonium 3-Amino Propanthiosulfonate, 2-Aminoethanethiol, 5- Aminopentanethiol and the like are exemplified. Sodium 4-aminoanilide maleate is more preferred. For example, sodium maleate-4-aminoanilide, which is commercially available under the trade name "sumilink200" manufactured by Sumitomo Chemical Co., Ltd., can be preferably used.

The rubber composition may contain, if necessary, two or more compounds (1) selected as a coupling agent. In this case, it is preferable that sodium 4-aminoanilide maleate and another compound (1) are used in combination.

Dinitro diamine compounds referred Compound (2) is represented by the general formula _A 1 _{-B-A 2. A 1} and A ₂ of compound (2) are linear, branched or cyclic nitroalkyl groups having 3 to 10 carbon atoms. In the rubber material containing this compound (2) as a coupling agent, the nitro group (-NO _{2 ) contained in A 1} and A ₂ interacts with the carbon-based filler and the base rubber to fill the carbon-based filler. The affinity between the agent and the base rubber is improved. In compound (2), A ₁ and A ₂ may be the same or different, but from the viewpoint of improving affinity, it is preferable that _{A 1} and A _{2 are the same.}

Examples of the linear nitroalkyl group having 3 to 10 carbon atoms include a nitropropyl group, a nitrobutyl group, a nitropentyl group, a nitrohexyl group and the like. Examples of the branched nitroalkyl group include a nitroisopropyl group, a nitroisobutyl group, a nitro-s-butyl group, a nitro-t-butyl group, a nitroisopentyl group and the like. Examples of the cyclic nitroalkyl group include a nitrated cyclopentylene group, a nitrated cyclohexylene group and the like. These linear, branched or cyclic nitroalkyl groups may further have substituents as long as the effects of the present invention are not impaired.

From the viewpoint of shot feeling and repulsion performance, _{the carbon numbers of A 1} and A ₂ are more preferably 3 to 8 and particularly preferably 3 to 6. From the viewpoint of affinity with the carbon-based filler and the base rubber, preferable A ₁ and A ₂ are branched nitroalkyl groups.

Preferably, B of compound (2) is a linear, branched or cyclic alkylene diamino group having 3 to 20 carbon atoms. Examples of the linear alkylenediamino group having 3 to 20 carbon atoms include a propylene diamino group, a butylene diamino group, a pentylene amino group, a hexylene diamino group and the like. Examples of the branched alkylene diamino group include an isopropylene diamino group and an isobutylene diamino group. Examples of the cyclic alkylene diamino group include a dicyclohexylene diamino group, an isophorone diamino group and the like. These linear, branched or cyclic alkylene diamino groups may further have substituents as long as the effects of the present invention are not impaired.

From the viewpoint of resilience performance and shot feeling, the carbon number of B is more preferably 3 to 12, and particularly preferably 3 to 8. From the viewpoint of affinity with the carbon-based filler and the base rubber, preferred B is a linear alkylene diamino group.

As a specific example of the preferable compound (2), _{N, N'-bis (2-methyl-2) in which A 1} and A ₂ are both 2-methyl-2-nitropropyl groups and B is a hexylene diamino group. -Nitropropyl) -1,6-diaminohexane can be mentioned. For example, the trade name "1,6-HEXANEDIAMINE, N1, N6-BIS (2-METHYL-2-NITROPROPYL)" commercially available from 1717 CheMall can be preferably used.

The rubber composition may contain, if necessary, two or more compounds (2) selected as a coupling agent. In this case, it is preferable that N, N'-bis (2-methyl-2-nitropropyl) -1,6-diaminohexane and another compound (2) are used in combination.

Compound (1) and compound (2) may be used in combination as a coupling agent as long as the object of the present invention is achieved.

The amount of the coupling agent added is appropriately selected depending on the type of the coupling agent to be selected, the composition of the rubber material, and the like. From the viewpoint of improving the affinity between the carbon-based filler and the base rubber, the amount of the coupling agent added to the carbon-based filler is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. .0% by mass or more is particularly preferable. From the viewpoint of shot feeling, the amount of the coupling agent added is preferably 50% by mass or less, more preferably 30% by mass or less, and particularly preferably 20% by mass or less. When compound (1) and compound (2) are used in combination as the coupling agent, it is preferable that the total addition amount thereof is set within the above-mentioned range.

From the viewpoint that the effect of the present invention can be easily obtained, the amount of the coupling agent with respect to 100 parts by mass of the base rubber is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, and 0.5 part by mass. More than a portion is particularly preferable. From the viewpoint of shot feeling and cost, the amount of the coupling agent is preferably 15 parts by mass or less, and more preferably 10 parts by mass or less.

In the rubber material according to the present invention, the order or method of blending the carbon-based filler and the coupling agent in the base rubber is not particularly limited. For example, a method of simultaneously adding a carbon-based filler and a coupling agent to the base rubber, a method of sequentially adding a carbon-based filler and a coupling agent to the base rubber, a predetermined amount in advance. A method of adding a mixture of a carbon-based filler and a coupling agent to the base rubber can be appropriately selected and used.

Further, a method of adding a diluted solution of the coupling agent prepared in advance to a predetermined concentration to the base rubber containing the carbon-based filler may be adopted. In this case, the solvent for diluting the coupling agent is appropriately selected depending on the type of the coupling agent, but water, toluene, ethanol, hexane, ethyl acetate, naphtha and the like are preferably used. From the viewpoint of mixing with the base rubber and the carbon-based filler, the concentration of the diluent is preferably 20% by mass or less, more preferably 15% by mass or less. Considering the influence of the diluent on the rubber material, the concentration of the diluent is preferably 1% by mass or more.

Suitable base rubbers include natural rubber, polybutadiene, polyisoprene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, polychloroprene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, isobutylene. -Isoprene copolymers and acrylic rubber are exemplified. More preferred base rubbers are natural rubber and polybutadiene. Two or more of these rubbers may be used in combination.

When natural rubber and polybutadiene are used in combination, the mass ratio B / N of the amount B of the polybutadiene rubber to the amount N of the natural rubber is preferably 1.4 or less, preferably 1.0 or less, from the viewpoint of shot feeling. More preferably, 0.4 or less is particularly preferable. The total amount of the base rubber may be natural rubber.

The rubber material may further include a vulcanizing agent, a vulcanization accelerator and a vulcanization aid. Examples of the vulcanizing agent include sulfur such as powdered sulfur, insoluble sulfur, precipitated sulfur and colloidal sulfur; and sulfur compounds such as morpholine disulfide and alkylphenol disulfide. The blending amount of the vulcanizing agent is adjusted according to the type, but from the viewpoint of resilience performance, 0.5 parts by mass or more is preferable with respect to 100 parts by mass of the base rubber, and 1.0 part by mass or more is more. preferable. The blending amount of the vulcanizing agent is preferably 5.0 parts by mass or less.

Suitable vulverification accelerators include, for example, guanidine compounds, sulfenamide compounds, thiazole compounds, thiuram compounds, thiourea compounds, dithiocarbamic acid compounds, aldehyde-amine compounds, aldehyde-ammonia compounds, imidazolines. Examples thereof include system compounds and xanthate compounds. From the viewpoint of resilience performance, the blending amount of the vulcanization accelerator is preferably 1.0 part by mass or more, and more preferably 2.0 parts by mass or more with respect to 100 parts by mass of the base rubber. The blending amount of the vulcanization accelerator is preferably 6.0 parts by mass or less.

Examples of the vulcanization aid include fatty acids such as stearic acid, metal oxides such as zinc oxide, and fatty acid metal salts such as zinc stearate. The rubber material may further contain additives such as an antioxidant, an antioxidant, a light stabilizer, a softener, a processing aid, and a colorant as long as the effects of the present invention are not impaired.

Preferably, the rubber material contains sulfur. Sulfur contained in the rubber material can contribute to the formation of crosslinked structures. The cross-linking density of the rubber material affects the resilience performance and shot feeling of the tennis ball 2 obtained from this rubber material. From the viewpoint of resilience performance, the sulfur content of this rubber material is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and particularly preferably 1.0% by mass or more. From the viewpoint of shot feeling, the sulfur content is preferably 10% by mass or less, more preferably 8% by mass or less, and particularly preferably 7% by mass or less. In the specification of the present application, the sulfur content of the rubber material is measured according to the oxygen flask combustion method described in the 17th revised Japanese Pharmacopoeia, general test method. The sulfur contained in this rubber material may be sulfur as a simple substance, or may be a sulfur atom contained in a sulfur compound. This sulfur may be derived from a vulcanizing agent or a vulcanization accelerator.

The loss tangent tan δ of this rubber material at 0 ° C. is not particularly limited as long as the above-mentioned value V1 is 0.90 or less. From the viewpoint of obtaining appropriate repulsion performance, the loss tangent tan δ of this rubber material at 0 ° C. is preferably 0.30 or less, more preferably 0.20 or less. Preferably, the loss tangent tan δ at 0 ° C. is 0.05 or more.

The nitrogen gas permeability coefficient G of this rubber material at 40 ° C. is not particularly limited as long as the above-mentioned value V1 is 0.90 or less. From the viewpoint of preventing gas leakage, the nitrogen gas permeation coefficient G of this rubber material at 40 ° C. ^{is preferably 9.0 × 10 -10} (cm ³ · cm / cm ² / sec / cmHg) or less, preferably 8.0 ×. ^10-10 (cm ³ · cm / cm ² / sec / cmHg) or less is more preferable.

From the viewpoint of both gas leakage prevention and repulsion performance, the value V2 obtained by dividing the loss tangent tan δ at 0 ° C. of this rubber material by the flatness DL of the carbon-based filler ^{is preferably 1.00 × 10 -3} or less. , 5.00 × 10 ^-4 or less is more preferable, 2.00 × 10 ^-4 or less is further preferable, and 1.00 × 10 ^-4 or less is particularly preferable. The lower limit is not particularly limited, but a preferable value V2 is 1.00 × ^10-5 or more.

From the viewpoint of resilience performance, the shore A hardness Ha of this rubber material is preferably 20 or more, more preferably 40 or more, and particularly preferably 50 or more. From the viewpoint of shot feeling, the hardness Ha is preferably 88 or less, more preferably 85 or less, and particularly preferably 80 or less. Hardness Ha is measured by a Type A durometer attached to an automatic hardness tester (trade name "Digitest II" by H. Burleys). For the measurement, a slab formed by a hot press and having a thickness of about 2 mm is used. Slabs stored at a temperature of 23 ° C. for 2 weeks are used for measurement. At the time of measurement, three slabs are overlapped.

From the viewpoint of resilience performance, the product (EB × Ha) of the breaking point elongation EB (%) and the shore A hardness Ha of this rubber material is preferably 1,000 or more, more preferably 2,000 or more, and more preferably 5,000. The above is particularly preferable. From the viewpoint of shot feeling, the product (EB × Ha) is preferably 100,000 or less, more preferably 80,000 or less, and particularly preferably 50,000 or less.

The break point elongation EB of the rubber material is measured in accordance with the description of JIS K6251 "Vulcanized rubber and thermoplastic rubber-How to determine tensile properties". From the viewpoint of resilience performance, the breaking point elongation EB of this rubber material is preferably 50% or more, more preferably 100% or more, and particularly preferably 300% or more. From the viewpoint of shot feeling, the breaking point elongation EB is preferably 700% or less.

From the viewpoint of achieving both resilience performance and shot feeling, the product (SW × Ha) of the toluene swelling rate SW (%) and the shore A hardness Ha of this rubber material is preferably 2,500 or more, more preferably 4,000 or more. It is preferable, and 6,000 or more is particularly preferable. From the same viewpoint, the product (SW × Ha) is preferably 50,000 or less, more preferably 40,000 or less, and particularly preferably 30,000 or less.

The toluene swelling rate SW of the rubber material is measured according to the description of JIS K6258 "Vulcanized rubber and thermoplastic rubber-How to determine liquid resistance". The toluene swelling rate SW is an index of the crosslink density of the rubber material. From the viewpoint of shot feeling, the toluene swelling rate SW is preferably 80% or more, more preferably 90% or more, and particularly preferably 100% or more. From the viewpoint of resilience performance, the preferable toluene swelling rate is 300% or less.

As long as the object of the present invention is achieved, the method for producing this rubber material is not particularly limited. For example, unvulcanized rubber, graphene, a coupling agent, and other appropriately selected additives are added to a known kneader such as a Banbury mixer, kneader, or roll and kneaded. It may be a rubber material, or may be a vulcanized rubber material by heating and pressurizing this unvulcanized rubber material. The kneading conditions and the vulcanization conditions are selected according to the composition of the rubber material. The preferred kneading temperature is 50 ° C. or higher and 180 ° C. or lower. The preferred vulcanization temperature is 140 ° C. or higher and 180 ° C. or lower. The vulcanization time is preferably 2 minutes or more and 60 minutes or less.

The method for producing the tennis ball 2 using this rubber material is not particularly limited. For example, two hemispherical half shells are formed by vulcanizing and molding this rubber material in a predetermined mold. These two half shells are bonded together with an ammonium salt and a nitrite contained therein, and then compression-molded to form a core 4 which is a hollow spherical body. Inside the core 4, nitrogen gas is generated by the chemical reaction of ammonium salt and nitrite. This nitrogen gas increases the internal pressure of the core 4. Next, the tennis ball 2 is obtained by previously cutting into a dumbbell shape and attaching the felt portion 6 to which the seam glue is attached to the cross section to the surface of the core 4.

Hereinafter, the effects of the present invention will be clarified by Examples, but the present invention should not be construed in a limited manner based on the description of these Examples.

[Example 1]
In Example 1, graphene was used as the carbon-based filler. First, 80 parts by mass of natural rubber (trade name "SMR CV60"), 20 parts by mass of polybutadiene rubber (JSR's product name "BR01"), 0.51 parts by mass of stearic acid (trade name of Nichiyu Co., Ltd.) "Tsubaki"), 5 parts by mass of zinc oxide (trade name of Shodo Chemical Co., Ltd. "Zinc oxide 2 types"), 4.99 parts by mass of silica (trade name of Toso Silica Co., Ltd. "Nipseal VN3"), 56 mass 10 parts by mass of graphene (XG Sciences product name "xGnP-M-5") and 1.0 part by mass of coupling agent (Sumitomo Chemical Industry Co., Ltd.) (Product name “sumilink200”) was put into a Banbury mixer and kneaded at 90 ° C. for 5 minutes. Next, in the obtained kneaded product, 3.6 parts by mass of sulfur (trade name of Sanshin Chemical Co., Ltd. "Sanfel EX") and 1 part by mass of vulcanization accelerator DPG (trade name of Sanshin Chemical Co., Ltd. "Sun Cellar"). D "), 1 mass of vulcanization accelerator CZ (trade name of Ouchi Shinko Kagaku Co., Ltd." Noxeller CZ ") and 1.88 parts by mass of vulcanization accelerator DM (trade name of Ouchi Shinko Kagaku Co., Ltd." Noxeller DM ") ”) Was added and kneaded at 100 ° C. for 3 minutes using an open roll to obtain an unvulcanized rubber material. This unvulcanized rubber material was press-vulcanized at 150 ° C. for 5 minutes to prepare a sheet-shaped rubber material. In Example 1, the amount of the carbon-based filler was 10 parts by mass, and the amount of the coupling agent added to the carbon-based filler was 10.0% by mass.

[Example 2-13 and Comparative Example 1]
The rubber materials of Examples 2-13 and Comparative Example 1-2 were obtained in the same manner as in Example 1 except that the blending amounts of graphene and the coupling agent were changed to those shown in Table 1-3.

[Comparative Example 2]
A rubber material of Comparative Example 2 was obtained in the same manner as in Example 1 except that the blending amounts of graphene, coupling agent, sulfur and vulcanization accelerator were changed to those shown in Table 2.

[Example 14]
In Example 14, 15 parts by mass of graphene (the above-mentioned “xGnP-M-5”) and 1 part by mass of the coupling agent (the above-mentioned “sumilink200”) are mixed in advance using a commercially available mixer. , A mixture was obtained. The rubber material of Example 14 was obtained in the same manner as in Example 1 except that the obtained mixture was put into a Banbury mixer together with other chemicals. In Example 14, the amount of the carbon-based filler was 15 parts by mass, and the amount of the coupling agent added to the carbon-based filler was 6.7% by mass.

[Example 15]
In Example 15, 1 part by mass of the coupling agent (the above-mentioned “sumilink200”) was diluted 10-fold with distilled water to prepare a diluted solution. The rubber material of Example 15 was the same as in Example 1 except that the blending amount of graphene was 15 parts by mass and the total amount (11 parts by mass) of the obtained diluted solution was put into a Banbury mixer together with other chemicals. Got In Example 15, the amount of the carbon-based filler was 15 parts by mass, and the amount of the coupling agent added to the carbon-based filler was 6.7% by mass.

[Examples 16-18 and Comparative Example 3]
As the carbon-based filler, graphite (trade name "SFG44" of Imeris) or carbon black (trade name "Show Black N330" of Cabot Japan) is used instead of graphene, and the carbon-based filler and coupling agent are used. The rubber materials of Examples 16-18 and Comparative Example 3 were obtained in the same manner as in Example 1 except that the amount of addition was changed to that shown in Table 4-5.

[Comparative Example 4]
Comparative Example in the same manner as in Example 1 except that 15 parts by mass of talc (trade name "Mistron HAR" manufactured by Imerys) was used instead of 10 parts by mass of graphene and no coupling agent was blended. 4 rubber materials were obtained.

[Comparative Example 5]
A rubber material of Comparative Example 5 was obtained in the same manner as in Example 1 except that a carbon-based filler and a coupling agent were not used.

Details of the compounds listed in Table 1-5 are as follows.
SMR CV60: Natural rubber BR01: JSR's polybutadiene rubber Stearic acid: NOF's brand name "Tsubaki"
Zinc oxide: Product name of Shodo Chemical Co., Ltd. "Zinc oxide 2 types"
Silica: Product name "Nipseal VN3" of Toso Silica
Kaolin Clay: Imerys trade name "ECKALITE 120", average particle size (D ₅₀ ) 2.0 μm, average thickness (T) 0.1 μm, flatness (DL) 20
Carbon black: Product name "Show Black N330" from Cabot Japan, average particle size (D ₅₀ ) 0.03 μm, flatness (DL) 1
Graphene: Trade name "xGnP-M-5" from XG Sciences, average particle size (D ₅₀ ) 5.0 μm, average thickness (T) 0.007 μm, flatness (DL) 700
Coupling agent: Sumitomo Chemical Co., Ltd. 4-aminoanilide sodium maleate, trade name "sumilink200"
Graphite (120): Imerys trade name "SFG44", average particle size (D ₅₀ ) 24 μm, average thickness (T) 0.2 μm, flatness (DL) 120
Talc (100): Imerys trade name "Mistron HAR", average particle size (D ₅₀ ) 6.7 μm, average thickness (T) 0.07 μm, flatness (DL) 100
Sulfur: Insoluble sulfur from Sanshin Kagaku Co., Ltd., trade name "Sanfel EX", containing 20% oil Vulcanization accelerator DPG: Sanshin Kagaku Co., Ltd. 1,3-diphenylguanidine, trade name "Sunseller D"
Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazolyl sulfeneamide of Ouchi Shinko Kagaku Co., Ltd., trade name "Noxeller CZ"
Vulcanization accelerator DM: Di-2-benzothiazolyl disulfide from Ouchi Shinko Kagaku Co., Ltd., trade name "Noxeller DM"

[Sulfur content measurement]
The sulfur content of the rubber materials of Examples 1-18 and Comparative Example 1-5 was measured according to the oxygen flask combustion method described in the 17th revised Japanese Pharmacopoeia, General Test Method. After burning 10 mg of rubber material, a total of 55 mL of methanol was added, followed by exactly 20 mL of 0.005 mol / L perchloric acid solution. The sulfur content was quantified by measuring the solution obtained by leaving it for 10 minutes using ion chromatography (HIC-SP manufactured by Shimadzu Corporation). The sulfur content (wt.%) Obtained is shown in Table 1-5.

[Viscoelasticity measurement]
Using the rubber materials of Examples 1-18 and Comparative Example 1-5, test pieces having a thickness of 2 mm, a width of 4 mm, and a length of 30 mm were prepared, respectively. The loss tangent of each test piece at 0 ° C. was measured using a viscoelastic spectrometer (E4000 manufactured by UBM) in a tensile mode, an initial strain of 10%, a frequency of 10 Hz, and an amplitude of 0.05%. The obtained loss tangent is shown as tan δ in Table 6-10 below.

[Measurement of nitrogen gas permeability coefficient]
Using the rubber materials of Examples 1-18 and Comparative Example 1-5, test pieces having a thickness of 2 mm, a width of 4 mm, and a length of 30 mm were prepared, respectively. ^{The nitrogen gas permeability coefficient (cm 3} · cm / cm ² / sec / cmHg) in the thickness direction of each test piece was measured according to the differential pressure method described in JIS K7126-1. For the measurement, a gas permeation tester "GTR-30ANI" manufactured by GTR Tech Co., Ltd. was used. The measurement conditions were a sample temperature of 40 ° C., a permeation cross-sectional area of the measurement cell of 15.2 cm ² , and a differential pressure of 0.2 MPa. All measurements were performed indoors at 23 ± 0.5 ° C. The obtained nitrogen gas permeability coefficient is shown as G in Table 6-10 below.

[hardness]
Using the rubber materials of Examples 1-18 and Comparative Example 1-5, three test pieces having a thickness of 2 mm, a width of 4 mm, and a length of 30 mm were prepared, and each test piece was prepared at a temperature of 23 ° C. Stored for a week. After that, in accordance with the regulations of "ASTM-D 2240-68", the hardness is obtained by pressing an automatic hardness tester (the above-mentioned "Digitest II") equipped with a type A durometer against each of the three test pieces stacked on top of each other. Was measured. The obtained Shore A hardness is shown in Table 6-10 below as Ha.

[Break point elongation]
Using the rubber materials of Examples 1-18 and Comparative Example 1-5, No. 3 dumbbell type test pieces having a thickness of 2 mm were prepared, respectively. A tensile test was carried out at room temperature in accordance with JIS K6251 "Vulcanized rubber and thermoplastic rubber-How to determine tensile properties", and the elongation at the breaking point of each test piece was measured. The obtained measured values are shown in Table 6-10 below as EB (%).

[Toluene swelling degree]
Using the rubber materials of Examples 1-18 and Comparative Example 1-5, test pieces having a thickness of 0.5 mm, a length of 10 mm, and a width of 5 mm were prepared, respectively. Each test piece was immersed in toluene for 24 hours at room temperature, and the degree of toluene swelling (mass change rate (%) = mass after immersion / mass before immersion) was calculated from the mass change of the test piece before and after the immersion. .. The obtained toluene swelling degree is shown in Table 6-10 below as SW (%).

[Manufacturing of tennis balls]
The unvulcanized rubber material obtained in the same manner as in Example 1 was put into a mold and heated at 150 ° C. for 4 minutes to form two half shells. Ammonium chloride, sodium nitrite and water were added to one half shell, then adhered to the other half shell and heated at 150 ° C. for 4 minutes to form a spherical core. A tennis ball was manufactured by laminating two felt portions having seam glue adhered to the cross section of the core surface. Similarly, a tennis ball having a core made of a rubber material of Examples 2-18 and Comparative Example 1-5 was produced.

[durability]
The obtained tennis balls were allowed to stand for 24 hours in an environment of atmospheric pressure, temperature of 20 ° C., and relative humidity of 60%, respectively, and their internal pressure (difference from atmospheric pressure) was measured. The same tennis ball was stored under atmospheric pressure for another 3 months, and then its internal pressure was measured. The rate of decrease in internal pressure before and after 3 months was calculated, and the durability was evaluated according to the following criteria. The results are shown in Table 6-10 below.
S: Less than 10% A: 10% or more and less than 20% B: 20% or more and less than 30% C: 30% or more

[Striking feeling]
After production, each tennis ball left to stand for 24 hours in an environment of atmospheric pressure, temperature of 20 ° C., and relative humidity of 60% was hit by 50 players with a tennis racket, and the shot feeling was heard. The following ratings were given based on the number of players who answered that they had a good shot feeling. The results are shown in Table 6-10 below.
S: 40 or more A: 30-39 B: 20-29 C: 19 or less

As shown in Table 6-10, the rubber material and the tennis ball of the example have a higher evaluation than the rubber material and the tennis ball of the comparative example. From this evaluation result, the superiority of the present invention is clear.

The rubber material described above can also be applied to the production of various hollow balls filled with compressed gas.

2 ... Tennis ball 4 ... Core 6 ... Felt part 8 ... Seam part

Claims (14)

It contains 100 parts by mass of base rubber and 1 part by mass or more and 150 parts by mass or less of a carbon-based filler.
The value V1 obtained by multiplying the product of the loss tangent tan δ at 0 ° C. and the nitrogen gas permeability coefficient G at 40 ° C. ^{by 10 10 is 0.90 or less.}
It also contains a coupling agent, and this coupling agent
(1) It has a functional group X capable of interacting with the carbon-based filler, a functional group Y capable of interacting with the base material rubber, and a spacer group S, and has the general formula XS-. It indicated in compound and / or (2) the formula _a 1 _{-B-a 2} represented by Y, the _{a 1} and _{a 2} are each independently a C 3-10 straight, branched or cyclic A rubber material for tennis balls, which is a nitroalkyl group, wherein B is a dinitrodiamine compound which is a linear, branched or cyclic alkylene diamino group having 3 to 20 carbon atoms. The rubber material according to claim 1, wherein the carbon-based filler is selected from the group consisting of carbon black, activated carbon, graphite, graphene, fullerenes and carbon nanotubes. The rubber material according to claim 1, wherein the carbon-based filler is graphite or graphene. The rubber material according to any one of claims 1 to 3, wherein the value V1 is 0.80 or less. The value V2 obtained by dividing the loss tangent tan δ at 0 ° C. by the flatness DL of the carbon-based filler is 1.00 × 10 ⁻³ or less, and this flatness DL is the average particle of the carbon-based filler. The rubber material according to any one of claims 1 to 4, which is obtained by dividing the diameter D _{50 (μm) by the average thickness T (μm).} The functional group X is selected from the group consisting of _{-NR 1} R ₂ , -Ph-OH, -OH, -COOH, ( _{-CO) 2} O, -NCO and -CR ₃ R _{4 O, where R 1} and R ₂ are independently hydrogen atoms or linear or branched alkyl groups having 1 to 6 carbon atoms, Ph is a phenylene group, and R ₃ and R ₄ are independently hydrogen atoms or or respectively. It is a linear or branched alkyl group having 1 to 6 carbon atoms.
The functional group Y is selected from the group -CR ₅ = CR _6- Z, -S-SO ₃ M ₁ , -S-SO ₂ R ₇ , -SH and -S _n , where R ₅ and R ₆ is an independently hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, Z is a carbonyl group or a carboxyl group, and M ₁ is a hydrogen ion, a metal ion, an ammonium ion or a thyl group. It is a quaternary amine, R ₇ is a methyl group, an ethyl group or a 4-methylphenyl group, and n is an integer of 2-4.
The spacer group S is selected from a linear alkylene group having 2 to 18 carbon atoms, an alicyclic alkylene group having 2 to 18 carbon atoms, a phenylene group (-Ph-) and a phenylene imino group (-Ph-NH-). The rubber material according to any one of claims 1 to 5. The functional group X is a primary amino group (-NH ₂ ).
The spacer group S is a phenylene imino group (-Ph-NH-).
The functional group Y is an α, β-unsaturated carbonyl group (-CH = CH-CR ₈ = O), where R ₈ is -OM ₂ and M ₂ is an alkali metal or an alkaline earth metal. The rubber material according to any one of claims 1 to 5. The rubber material according to any one of claims 1 to 7, wherein the amount of the coupling agent added to the carbon-based filler is 0.1% by mass or more and 50% by mass or less. The base rubber contains butadiene rubber and natural rubber, and the mass ratio B / N of the butadiene rubber in the base rubber to the natural rubber is 1.4 or less according to any one of claims 1 to 8. The rubber material described. The rubber material according to any one of claims 1 to 9, wherein the sulfur content is 0.01% by mass or more and 10% by mass or less. The rubber material according to any one of claims 1 to 10, wherein the shore A hardness Ha is 20 or more and 88 or less. The rubber material according to any one of claims 1 to 11, wherein the product of the breaking point elongation EB (%) obtained in accordance with JIS K6251 and the hardness Ha is 1,000 or more and 100,000 or less. The rubber material according to any one of claims 1 to 12, wherein the product of the toluene swelling rate SW (%) obtained in accordance with JIS K6258 and the hardness Ha is 2,500 or more and 50,000 or less. It has a core made of rubber material and has a core.
The rubber material contains 100 parts by mass of base rubber and 1 part by mass or more and 150 parts by mass or less of a carbon-based filler.
A loss tangent tanδ at 0 ℃ of the rubber material, the product of the nitrogen gas permeation coefficient G at 40 ° C., the value V1 obtained by multiplying the ^{10 10} state, and are 0.90,
The rubber material further contains a coupling agent, and this coupling agent
(1) It has a functional group X capable of interacting with the carbon-based filler, a functional group Y capable of interacting with the base rubber, and a spacer group S, and has the general formula XS-. Compound represented by Y
And / or
(2) represented by the general formula _A 1 _{-B-A 2,} the _{A 1} and _{A 2} are each independently a C 3-10 straight, a nitro branched or cyclic alkyl group of the B There linear C3-20, dinitro diamine compounds der Ru tennis ball is alkylene amino group, branched or cyclic.

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