JP2018089099A - Multi-piece solid gol ball - Google Patents

Abstract

SOLUTION: The present invention provides a multi-piece solid golf ball having an intermediate layer interposed between a core and an outermost layer, the intermediate layer being formed of a thermoplastic resin composition containing (A)ionic olefin-methacrylic acid-unsaturated carboxylic acid ester copolymer, (B)nonionic olefin-acrylic acid copolymer, (C)organic acid or metal salt thereof, and (D)basic inorganic metal compound, and the outermost layer being formed of a thermoplastic resin composition containing (a)specific ionic olefin-unsaturated carboxylic acid copolymer, and (b)specific ionic olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer, in which a ratio (Tanδ) between a tensile storage elasticity modulus (E') and a tensile loss elasticity modulus (E") in a dynamic viscoelasticity test under a specific condition of the resin composition is 0.150 or less.EFFECT: The present invention combines peculiar intermediate layer material and outermost later material, which can obtain a large low-spin effect and increase a carry.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multi-piece solid golf ball in which at least one intermediate layer is interposed between a core and an outermost layer. More specifically, the present invention is formed of a composition containing a high acid content ionomer in the outermost layer. The present invention relates to a golf ball having excellent spin characteristics.

  It has been known so far that when a golf ball is hit with a driver or the like, if the spin applied to the ball is small (low), the flight distance is dominant. In recent years, an ionic composition (ionomer) or the like has been used as a main material as a golf ball cover material as a technical technique for achieving such low spin. In particular, in a golf ball having a multi-layer structure, a highly neutralized ionomer in which acid groups in the resin composition are neutralized at a high ratio is used as the resin material (resin composition) of the inner layer. As a result, the flight distance was increased.

  However, highly neutralized ionomers are often used as the resin material of the inner layer, and it is considered that the effect on low spin cannot be sufficiently exhibited. In addition, since the material characteristics tend to be relatively brittle, as a result, when such a resin material is used, there are factors that cause secondary demerits such as easy ball breakage.

  As techniques for improving the resin material used for the golf ball cover layer, several techniques have been proposed that focus on the deformation behavior of the cover layer when hit with a driver and the loss elastic modulus of the cover material. For example, in Japanese Patent Application Laid-Open No. 2011-254974, the outermost layer is a resin composition, and the ratio (E ″ / G ″) between the tensile loss elastic modulus E ″ and the shear loss elastic modulus G ″ of this resin composition is The technology defined above a certain value is described. In JP-A-2004-65409, the outermost layer is formed of a polymer composition, and the polymer composition is specified by a complex elastic modulus and a loss coefficient in a viscoelastic property measured in a tensile mode at a specific temperature. Golf balls have been proposed. Further, JP-A-2001-137386 discloses a value of loss tangent (tan δ) in a temperature dispersion curve of dynamic viscoelasticity in a tensile mode measured under specific conditions for a cover material in a golf ball composed of a core and a cover. A golf ball having a specific range is proposed.

  However, in the proposed golf ball, the ratio of elastic modulus and the loss tangent (Tan δ) particularly in the cover material of the outermost layer of the ball tend to increase, which means that the resilience elasticity is lowered. For this reason, even if the spin characteristics are optimized, if the rebound resilience is low, the flight distance of the ball will be insufficient as a result. Therefore, the balance between spin performance and rebound resilience is an important factor that determines ball characteristics. In addition, when an ionic thermoplastic resin is used for the outermost layer, a material having a high acid content is often selected particularly for the low spin effect. However, in this case, the durability of the ball may be deteriorated due to the hardness of the blended composition and the inner layer material.

JP 2011-254974 A JP 2004-65409 A JP 2001-137386 A

  The present invention has been made in view of the above circumstances, and in a multi-layered golf ball, a multi-piece solid golf ball that further enhances the low spin effect and improves the durability of the ball by the synergistic effect of each cover layer. The purpose is to provide.

  As a result of intensive studies to achieve the above object, the present inventors have determined that at least one of the intermediate layers in a golf ball having a core, at least one intermediate layer, and an outermost layer is specified. The outermost layer is formed of a highly neutralized ionomer resin material, and the outermost layer is composed of an ionic olefin / unsaturated carboxylic acid copolymer having a high acid content and an ionic olefin / unsaturated carboxylic acid having a low / medium acid content. By forming a blended material with an unsaturated carboxylic acid ester copolymer, it is possible to obtain a ball that further enhances high resilience and low spin performance, and the ball is also excellent in durability. This has been found and the present invention has been made.

Accordingly, the present invention provides the following multi-piece solid golf ball.
[1] In the multi-piece solid golf ball in which at least one intermediate layer is interposed between the core and the outermost layer, the intermediate layer includes the following (A) to (D),
(A) an ionic olefin-methacrylic acid-unsaturated carboxylic acid ester copolymer,
(B) a nonionic olefin-acrylic acid copolymer,
(C) an organic acid or a metal salt thereof,
(D) formed of a thermoplastic resin composition containing a basic inorganic metal compound for neutralizing 80 mol% or more of the acid groups in the components (A) to (C), and the components (A) and ( The blending ratio (mass ratio) with the component B) is (A) :( B) = 50: 50-80: 20, the Shore D hardness of the resin composition is 40-60, and the outermost layer is The following (a) and (b)
(A) The weight average molecular weight (Mw) is 40,000 to 200,000, the weight average molecular weight (Mw) / number average molecular weight (Mn) is 4.0 to 10.0, and an unsaturated carboxylic acid. An ionic olefin-unsaturated carboxylic acid copolymer having a content of 16% by mass or more,
(B) The weight average molecular weight (Mw) is 40,000 to 200,000, the weight average molecular weight (Mw) / number average molecular weight (Mn) is 4.0 to 10.0, and an unsaturated carboxylic acid. Formed of a thermoplastic resin composition containing an ionic olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer having a content of 15% by mass or less, and a combination of the component (a) and the component (b) The ratio (mass ratio) is (a) :( b) = 70: 30 to 90:10, the Shore D hardness of the resin composition is 55 or more, the temperature of the resin composition is 24 ° C., and the frequency is 15 Hz. The ratio (Tanδ) between the tensile storage elastic modulus (E ′) and the tensile loss elastic modulus (E ″) in the dynamic viscoelasticity test measured under a strain of 2.0% is 0.150 or less. Multi-piece solid golf ball characterized by
[2] The core is formed of a rubber composition using polybutadiene as a base rubber, the core has a diameter of 40.0 mm or less, and an initial load of 98 N (10 kgf) is applied to a final load. The multi-piece solid golf ball according to [1], wherein a deflection amount when loaded with 1275N (130 kgf) is 3.0 to 4.5 mm.
[3] The multi-piece solid golf ball according to [1] or [2], wherein, in the cross-sectional hardness of the core, a JIS-C hardness difference value obtained by subtracting the core center hardness H _i from the core surface hardness H ₀ is 20 or more. .
[4] In the cross-sectional hardness of the core, JIS-C hardness H _{15.0 at} a position 15.0 mm outside in the outer circumferential direction from the core center, and JIS-C hardness H _{5.0 at} a position 5.0 mm outside in the outer circumferential direction from the core center. The golf ball according to any one of [1] to [3], wherein a value obtained by subtracting is a positive numerical value.
[5] The golf ball according to any one of [1] to [4], wherein the core has a hysteresis loss rate of 50% or less when compressed at a load cell speed of 500 mm / min and a constant load of 5000 N.
[6] The multi-piece solid golf ball according to any one of [1] to [5], wherein an envelope layer is provided between the core and the intermediate layer.
[7] The multi-piece solid golf ball according to [6], wherein the envelope layer is formed of a thermoplastic resin composition other than ionic, and the Shore D hardness of the resin composition is 50 or less.
[8] Tensile storage modulus (E ′) and tensile loss elasticity in a dynamic viscoelasticity test measured under conditions of a temperature of 24 ° C., a frequency of 15 Hz, and a strain of 2.0% in the resin composition of the intermediate layer. The multi-piece solid golf ball according to any one of [1] to [7], wherein a ratio (Tanδ) to a rate (E ″) is 0.110 or less.
[9] Any one of [1] to [8], wherein the sum of Tan δ of the outermost resin composition and Tan δ of the intermediate layer resin composition measured under the same conditions is 0.250 or less. Multi-piece solid golf ball.

  According to the golf ball of the present invention, not only the highly neutralized ionomer is used as the intermediate layer material, but also the viscoelastic characteristics of the resin material are characterized by using a composition containing a high acid content ionomer as the outermost layer material. The multi-layer golf ball structure in which such an intermediate layer material and outermost layer material are combined has a great effect on low spin and leads to an increase in flight distance. Also, the golf ball of the present invention has excellent durability due to the above configuration.

1 is a schematic cross-sectional view of a golf ball showing an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.
The multi-piece solid golf ball of the present invention is a golf ball in which at least one intermediate layer is interposed between the core and the outermost layer. For example, the golf ball G shown in FIG. 1 is a schematic cross-sectional view showing a golf ball according to one embodiment of the present invention, and includes a core 1, an intermediate layer 2 covering the core 1, and the intermediate layer 2. And an outermost layer 3 to be coated. Although not particularly shown, an envelope layer is provided between the core 1 and the intermediate layer 2 as necessary. In addition, many dimples D are usually formed on the surface of the outermost layer 3 in order to improve aerodynamic characteristics. Hereinafter, each layer will be described in detail.

  The core is preferably formed of a rubber composition containing at least a base rubber, an unsaturated carboxylic acid and / or a metal salt thereof, and a crosslinking initiator.

As the base rubber, it is particularly preferable to use polybutadiene. The polybutadiene preferably has a cis-1,4-bond of 60% (mass%, hereinafter the same) or more, preferably 80% or more, more preferably 90% or more, and most preferably 95% or more. The polybutadiene has a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of preferably 30 or more, preferably 35 or more, and preferably 100 or less, more preferably 90 or less as the upper limit.

  As the polybutadiene, specifically, as the cis-1,4-polybutadiene rubber, high cis BR01, BR11, BR02, BR02L, BR02LL, BR730, BR51 and the like manufactured by JSR can be used.

  The polybutadiene is preferably synthesized from a rare earth element-based catalyst or a Group VIII metal compound catalyst such as Ni or Co from the viewpoint of obtaining a crosslinked molded product of a rubber composition having good resilience.

  The proportion of polybutadiene in the entire rubber composition is preferably 40% by mass or more, more preferably 60% by mass or more, still more preferably 80% by mass or more, and most preferably 90% by mass or more. Moreover, 100 mass% of base rubber may be the said polybutadiene, 98 mass% or less is preferable, More preferably, it is 95 mass% or less.

  In addition to the polybutadiene, other rubber components can be blended with the rubber base material within a range not impairing the effects of the present invention. Examples of the rubber component other than the polybutadiene include polybutadiene other than the polybutadiene, and other diene rubbers such as styrene butadiene rubber, natural rubber, isoprene rubber, and ethylene propylene diene rubber.

  Although there is no restriction | limiting in particular as unsaturated carboxylic acid or its metal salt, For example, (alpha), (beta)-unsaturated carboxylic acid, such as acrylic acid and methacrylic acid, and / or those metal salts can be mix | blended. In this case, examples of the metal include zinc, sodium, potassium, magnesium, lithium, and calcium. However, copper is not included. The α, β-unsaturated carboxylic acid is particularly preferably an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms. Specifically, the α, β-unsaturated carboxylic acid is preferably selected from the group of acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, maleic acid, and fumaric acid. Further, it is preferable to use a metal salt of an α, β-unsaturated carboxylic acid, and it is particularly preferable that the metal salt is a zinc salt.

  The amount of the unsaturated carboxylic acid or metal salt thereof is not particularly limited, but is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and preferably 50 as the upper limit with respect to 100 parts by mass of the base rubber. The blending is not more than part by mass, more preferably not more than 45 parts by mass.

  In particular, an organic peroxide can be suitably used as the crosslinking initiator. Examples of the organic peroxide include 1,1-di (t-butylperoxy) cyclohexane, 1,1-bis-t-butylperoxy-3,3,5-trimethylcyclohexane, dicumyl peroxide, and di (T-Butylperoxy) -meta-diisopropylbenzene, 2,5-dimethyl-2,5-di-t-butylperoxyhexane and the like. These organic peroxides can be used alone or in combination of two or more.

  Although the compounding quantity of the said organic peroxide does not have a restriction | limiting in particular, It is 0.1 mass part or more with respect to 100 mass parts of said base rubber, Preferably it can be 0.3 mass part or more. The upper limit is not particularly limited, but can be 5 parts by mass or less, preferably 2 parts by mass or less.

  Moreover, commercially available anti-aging agent etc. can be added suitably as needed. For example, 2,2'-methylenebis (4-methyl 6-tert-butylphenol) can be used. The blending amount of the antioxidant is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 3 parts by mass or less as an upper limit with respect to 100 parts by mass of the base rubber. . Specifically, “Nocrack NS-6”, “Nocrack NS-5”, “Nocrack NS-30” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. and the like can be mentioned.

  Moreover, decomposition | disassembly of the organic peroxide in a core compounding can be accelerated | stimulated by mix | blending water (or material containing water) directly with the said rubber composition. A golf ball having such a core can achieve low spin, is excellent in durability, and can reduce a change in resilience with time. The water blended in the rubber composition is not particularly limited, and may be distilled water or tap water. In particular, it is preferable to use distilled water containing no impurities. The The amount of water is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 5 parts by mass or less, with respect to 100 parts by mass of the base rubber. More preferably, it is 4 parts by mass or less.

  For example, an organic sulfur compound can be blended with the rubber composition for the purpose of improving the resilience of the rubber cross-linked molded product. Specific examples of such organic sulfur compounds include thiophenols, thionaphthols, halogenated thiophenols or metal salts thereof, more specifically, pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol. , Parachlorothiophenol or metal salts thereof, in particular zinc salts. In this case, the amount of the organic sulfur compound is preferably 0.001 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the base rubber.

  Various inorganic fillers can be blended with the rubber composition in order to adjust the rubber mass. Examples of the inorganic filler include zinc oxide, calcium carbonate, calcium oxide, magnesium oxide, barium sulfate, and silica. In particular, it is preferable to use metal oxides such as zinc oxide, calcium oxide, and magnesium oxide.

  The core can be obtained by vulcanizing and curing the above-described rubber composition in the same manner as a known golf ball rubber composition. Examples of the vulcanization conditions include conditions carried out at a vulcanization temperature of 100 to 200 ° C. and a vulcanization time of 5 to 40 minutes.

  As the diameter of the core, it is recommended that the upper limit is preferably 41.0 mm or less, and the lower limit is preferably 25.0 mm or more, more preferably 30.0 mm or more. If the value is too small, the sufficient low spin effect may not be obtained.

  Further, the amount of deflection when a final load of 1275 N (130 kgf) is applied from a state in which an initial load of 98 N (10 kgf) is applied to the core (heated product) is not particularly limited, but is preferably 2.0 mm or more. More preferably, it is 2.5 mm or more, more preferably 3.0 mm or more, and the upper limit is preferably 6.0 mm or less, more preferably 5.5 mm or less, still more preferably 5.0 mm or less. The If it is larger than the above value, even if the hysteresis loss of the core is improved, the deflection of the product is increased and the resilience may be lowered. On the other hand, if it is smaller than the above value, the hit feeling may become too hard.

  The central hardness of the core is not particularly limited, but is preferably 40 or more, more preferably 43 or more, still more preferably 45 or more according to JIS-C standard, and the upper limit is preferably 70 or less, more preferably. Is 68 or less, more preferably 65 or less. If the center hardness of the core is out of the above range, the durability may be lowered or the low spin effect may not be obtained.

  The surface hardness of the core is not particularly limited, but is preferably 60 or more, more preferably 63 or more, still more preferably 65 or more, and the upper limit is preferably 95 or less, more preferably, according to JIS-C standards. Is 90 or less, more preferably 88 or less. If the surface hardness of the core is too lower than the above range, the resilience will be low and the flight distance may not be sufficiently obtained. On the other hand, when the surface hardness of the core is too higher than the above range, the hit feeling may become too hard or the ball durability may be deteriorated.

  The value of JIS-C hardness difference [(core surface hardness) − (core center hardness)] obtained by subtracting the core center hardness from the core surface hardness is not particularly limited, but is preferably 10 or more, more preferably 13 or more. The upper limit is preferably 15 or more, and the upper limit is preferably 45 or less, more preferably 43 or less, and still more preferably 40 or less. If the value of the hardness difference is too small, the low spin effect cannot be obtained even if the resilience of the product can be secured, and as a result, the flight distance may be impaired. If the hardness difference is too large, the ball durability is remarkably deteriorated.

With respect to the hardness inside the core, JIS-C hardness H _5.0 at a position 5.0 mm outward from the core center in the outer peripheral direction was subtracted from JIS-C hardness H _{15.0 at an} outer position 15.0 mm outward from the core center. The value is preferably a positive numerical value. When the above H _15.0 -H _5.0 value is zero or negative, the hardness of the core hardness is not gradually increased toward the outside. When there is no hardness difference or negative (minus), the energy that should be transmitted to the core at the time of hitting the ball is not transmitted, or the transmitted energy is absorbed inside the core, and the low spin that should be originally obtained The effect may not be obtained.

  The above-mentioned center hardness and cross-sectional hardness at a predetermined position mean the hardness measured at the center and predetermined position of a cross section obtained by cutting the core in half (through the center), It means the hardness measured on the surface (spherical surface) of the core. Moreover, JIS-C hardness means the hardness measured with the spring-type hardness meter (JIS-C type) prescribed | regulated to JISK6301-1975.

  Moreover, the said core prescribes | regulates that the hysteresis loss rate is 50% or less when compressed by load cell speed 500mm / min and constant load 5000N. When the hysteresis loss rate is 50% or more, much of the load energy applied when the ball is hit is dissipated as heat energy. In other words, the energy that should be transmitted to the ball is reduced, which may lead to a decrease in the resilience of the ball product and an increase in the spin rate. In addition, about the measuring method of a hysteresis loss, it carries out, for example using a tension compression testing machine, and is set as the hysteresis loss when a compression load is given in the case of a core (ball). The test conditions are a load cell speed of 500 mm / min and a constant load of 5000 N.

Next, the intermediate layer will be described.
The intermediate layer has the following (A) to (D),
(A) an ionic olefin-methacrylic acid-unsaturated carboxylic acid ester copolymer,
(B) a nonionic olefin-acrylic acid copolymer,
(C) an organic acid or a metal salt thereof,
(D) It is formed by the thermoplastic resin composition containing the basic inorganic metal compound for neutralizing 80 mol% or more of the acid group in said (A)-(C) component.

  The olefin component of the component (A) preferably has 2 to 6 carbon atoms, and particularly preferably ethylene. Moreover, as unsaturated carboxylic acid ester of (A) component, a lower alkyl ester is preferable and especially butyl acrylate (n-butyl acrylate, butyl acrylate) is preferable. Furthermore, in the component (A), the type of the metal salt that neutralizes the acid group may be a 1 to 3 inorganic metal species, specifically zinc, sodium, magnesium, potassium, calcium, In particular, it is preferable to use zinc or sodium.

  (B) As an olefin component of a component, it is preferable that carbon number is 2-6, and especially ethylene is preferable.

  The content (acid content) of the unsaturated carboxylic acid in the component (A) and the component (B) is preferably 15% by mass or less as the upper limit, and 8% by mass or more as the lower limit. preferable. If the acid content is low, a resin material having high resilience may not be obtained. Moreover, when the acid content is increased, the hardness of the resin material may be extremely increased.

  Specific examples of the component (A) and the component (B) include ESCOR, IOTEK, manufactured by ExxonMobil, Nucrel, and Surlyn, manufactured by DuPont and Mitsui DuPont Polychemical.

  The blending ratio (mass ratio) of the component (A) and the component (B) is (A) :( B) = 50: 50-80: 20, preferably 55: 45-75: 25. If the blending ratio of the component (A) and the component (B) is deviated, the ball durability may be deteriorated or the moldability may be deteriorated.

  Component (C) is an organic acid and a metal salt thereof, and the type thereof is not particularly limited, but it is particularly preferable to employ a stearic acid metal salt or an oleic acid metal salt. Examples of the metal stearate include magnesium stearate, calcium stearate, zinc stearate, sodium stearate and the like. Of these, magnesium stearate is particularly preferred.

The component (D) is a basic inorganic metal compound, and types thereof include, for example, Na ⁺ , K ⁺ , Li ⁺ , Zn ²⁺ , Ca ²⁺ , Mg ²⁺ , Cu ²⁺ , and Co ^2+. Can be mentioned. Particularly preferred are Na ⁺ , Zn ²⁺ , Ca ²⁺ and Mg ²⁺ , and more preferred is Mg ²⁺ . These metal salts can be introduced into the resin composition using formate, acetate, nitrate, carbonate, bicarbonate, oxide, hydroxide and the like.

  The component (D) neutralizes 80 mol% or more of the acid groups in the components (A) to (C), preferably 83 mol% or more, more preferably 85 mol% or more. An appropriate amount is blended to neutralize acid groups. A specific compounding amount is 0.5 to 4.0 parts by mass, preferably 0.75 to 3.5 parts by mass with respect to 100 parts by mass of the resin of the component (A) and the component (B).

  In the resin composition containing the components (A) to (D), any additive can be appropriately blended depending on the use, such as a pigment, a dispersant, an anti-aging agent, an ultraviolet absorber, and a light stabilizer. Various additives can be added.

  Moreover, as a method of preparing the resin composition containing the components (A) to (D), a known kneading method can be adopted, and the method of kneading using an extruder is not particularly limited. It can be suitably employed. In this case, as the extruder, both a single screw extruder and a twin screw extruder can be used, but a twin screw extruder having a higher kneading effect can be preferably used. Moreover, the connection type extruder which connected the some extruder can also be used, for example, a two-stage connection type, such as a single screw extruder-a twin screw extruder, a twin screw extruder-a twin screw extruder, etc. is mentioned. .

  The material hardness of the resin composition obtained using these components (A) to (D) is 35 or more in Shore D hardness, preferably 40 or more, more preferably 45 or more. Moreover, the upper limit is 65 or less in Shore D hardness, Preferably it is 60 or less, More preferably, it can be 55 or less. If the material hardness is too low, the spin amount at the time of a full shot increases so that the flight distance may not be obtained, or the durability may deteriorate. Further, if the material hardness is too high, the durability against cracking due to repeated impacts may deteriorate, or the spin rate during full shots may increase and the flight distance may not be achieved.

  The material hardness is a hardness measured using a type D durometer in accordance with ASTM D2240 using a test piece obtained by molding a material to be measured into a sheet having a predetermined thickness (hereinafter described later). The same applies to the material hardness of the envelope layer and the outermost layer).

  The thickness of the intermediate layer is not particularly limited, but is preferably 0.5 mm or more, more preferably 0.8 mm or more, and further preferably 1.0 mm or more. The upper limit is not particularly limited, but is preferably 2.0 mm or less, more preferably 1.8 mm or less, and still more preferably 1.5 mm or less. If the thickness of the intermediate layer is too thin, the durability may deteriorate. Conversely, if the thickness is too thick, the spin rate at the time of a full shot may increase and the flight distance may not be achieved.

  The structure of the intermediate layer is not limited to one layer, and two or more of the same or different types of intermediate layers may be formed within the above range as necessary.

  An envelope layer can be provided between the core and the intermediate layer as necessary. In this case, an envelope layer is directly formed around the core. The envelope layer will be described in detail.

  A known resin can be used as a material for forming the envelope layer, and it is not particularly limited. However, it is particularly preferable that the envelope layer is formed of a thermoplastic resin composition other than ionic. More preferably, one or more selected from the group consisting of thermoplastic elastomers such as urethane, amide, ester, olefin, and styrene can be used. The most preferable is to employ a thermoplastic polyetherester elastomer because high resilience is obtained in a desired hardness range.

  The material hardness of the envelope layer is not particularly limited, but the Shore D hardness can be preferably 50 or less, and more preferably 45 or less. On the other hand, the lower limit value of the material hardness of the envelope layer is usually 15 or more, preferably 20 or more, more preferably 25 or more in Shore D hardness.

  The thickness of the envelope layer is not particularly limited, but is preferably 0.5 mm or more, more preferably 0.8 mm or more. Moreover, about the upper limit, Preferably it is 2.0 mm or less, More preferably, it can be 1.5 mm or less. If the thickness of the envelope layer is too thin, the ball durability may be deteriorated and the hit feeling may be deteriorated. On the other hand, if the envelope layer is too thick, the spin rate at the time of a full shot may increase and the flight distance may not be obtained.

Next, the outermost layer used in the present invention will be described. The outermost layer used in the present invention includes the following (a) and (b),
(A) The weight average molecular weight (Mw) is 40,000 to 200,000, the weight average molecular weight (Mw) / number average molecular weight (Mn) is 4.0 to 10.0, and an unsaturated carboxylic acid. An ionic olefin-unsaturated carboxylic acid copolymer having a content of 16% by mass or more,
(B) The weight average molecular weight (Mw) is 40,000 to 200,000, the weight average molecular weight (Mw) / number average molecular weight (Mn) is 4.0 to 10.0, and an unsaturated carboxylic acid. Is formed by a thermoplastic resin composition containing an ionic olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer having a content of 15% by mass or less.

  The component (a) is an ionic olefin-unsaturated carboxylic acid copolymer. (A) As an olefin component of a component, it is preferable that carbon number is 2-6, and especially ethylene is preferable. Moreover, as unsaturated carboxylic acid of (a) component, it is suitable to employ | adopt either acrylic acid or methacrylic acid, More preferably, it is methacrylic acid. The content (acid content) of the unsaturated carboxylic acid in the component (a) is preferably 25% by mass or less as the upper limit, and preferably 16% by mass or more as the lower limit. If the acid content is lowered, the ratio (Tanδ) of the storage elastic modulus (E ′) and the loss elastic modulus (E ″) is increased, and it is difficult to obtain a low spin effect. The hardness of the resin material becomes extremely high, and it becomes difficult to obtain a desired material hardness.

  (A) The weight average molecular weight (Mw) of a component is 40,000-200,000, Preferably it is 42,000-200,000. In addition, the molecular weight distribution of the component (a), that is, the value of weight average molecular weight (Mw) / number average molecular weight (Mn) is 4.0 to 10.0, preferably 4.0 to 8.5.

  The component (b) is an ionic olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer. (B) As an olefin component of a component, it is preferable that carbon number is 2-6, and especially ethylene is preferable. Moreover, as unsaturated carboxylic acid of (b) component, it is suitable to employ | adopt either acrylic acid or methacrylic acid, More preferably, it is methacrylic acid. Further, the unsaturated carboxylic acid ester of component (b) is preferably a lower alkyl ester, and particularly preferably butyl acrylate (n-butyl acrylate, butyl acrylate). The content (acid content) of the unsaturated carboxylic acid in the component (b) is preferably 15% by mass or less as the upper limit, and preferably 5% by mass or more as the lower limit.

  The weight average molecular weight (Mw) of (b) component is 40,000-200,000, Preferably it is 42,000-200,000. In addition, the molecular weight distribution of the component (a), that is, the value of weight average molecular weight (Mw) / number average molecular weight (Mn) is 4.0 to 10.0, preferably 4.0 to 8.5.

  Both the component (a) and the component (b) are ionic resins. In these components, the type of metal salt that neutralizes the acid group may be any one of 1 to 3 valent inorganic metal species, specifically zinc, sodium, magnesium, potassium, and calcium. Alternatively, it is preferable to use sodium.

  Specific examples of the component (a) and the component (b) include IOTEK manufactured by ExxonMobil, and Surlyn's product series manufactured by DuPont and Mitsui DuPont Polychemical.

  The blending ratio (mass ratio) of the component (a) and the component (b) is (a) :( b) = 70: 30 to 90:10, preferably 70:30 to 85:15. If the ratios (a) and (b) are deviated, the cover may be cracked or the low spin effect may not be obtained.

  In the resin composition containing the component (a) and the component (b), the tensile storage modulus (E ′) in the dynamic viscoelasticity test measured under the conditions of a temperature of 24 ° C., a frequency of 15 Hz, and a strain of 2.0%. And the tensile loss elastic modulus (E ″) ratio (Tan δ) is required to be 0.150 or less. Such a material is suitable for the hardness of the material itself that is optimal for the outermost layer of the golf ball and the material. Combined with a molecular structure that efficiently converts the generated energy into a repulsive force without loss, these actions can give the ball a greater low spin effect and high rebound performance. For example, “EPLEXOR 500N” manufactured by GABO may be employed.

  In the resin composition containing the component (a) and the component (b), any additive can be appropriately blended depending on the application, and various additives can be added in the same manner as described for the intermediate layer material. it can. Moreover, about the preparation method of the resin composition containing (a) component and (b) component, it is the same as that of having demonstrated intermediate | middle layer material.

  The material hardness of the resin composition obtained using these components (a) and (b) is 55 or more in Shore D hardness, preferably 57 or more, more preferably 60 or more. On the other hand, the upper limit of the material hardness of the outermost layer is not particularly limited, but it is preferably 75 or less, more preferably 70 or less in Shore D hardness. If the material hardness of the outermost layer is too low, the spin distance may be excessive or the rebound may be insufficient, resulting in a decrease in flight distance. Further, if the material hardness of the outermost layer is too high, the crack durability may be deteriorated.

  As a method of forming the outermost layer around the intermediate layer using the material of the outermost layer, a known method can be adopted. For example, a sphere having an intermediate layer formed around the core is made into a predetermined injection molding metal. A method of injecting the outermost layer material by placing in a mold and a method of heating and pressure molding by enclosing the sphere with a pair of half cups previously formed into a half shell sphere can be suitably used.

  The thickness of the outermost layer is not particularly limited, but is preferably 0.5 mm or more, more preferably 0.7 mm or more, and further preferably 1.0 mm or more. The upper limit is not particularly limited, but it is preferably 2.0 mm or less, more preferably 1.7 mm or less, and still more preferably 1.5 mm or less. If the thickness of the outermost layer is too thin, the durability may deteriorate. Conversely, if the thickness is too thick, the spin amount at the time of W # 1 strike may increase so that the flight distance may not be obtained.

  Thus, the multi-piece solid golf ball of the present invention combining the intermediate layer formed of the above-described intermediate layer resin material and the outermost layer formed of the above-described outermost layer material has excellent resilience and low spin. The effect is great, the flight distance can be increased, and good durability can be obtained.

  In the present invention, although not particularly limited, in order to further improve the aerodynamic characteristics and improve the flight distance, a large number of dimples can be formed on the surface of the outermost layer in the same manner as a normal golf ball. By optimizing the number and the total number of the dimples, the trajectory is more stable and the flight distance performance is excellent. In order to improve the design and durability of the golf ball, it is optional to perform various treatments such as ground treatment, stamping, painting, etc. on the outermost layer.

  In addition, this invention can be made to follow a golf rule for competition use, As a ball outer diameter, it is a size which does not pass the ring of 42.672 mm inside diameter, 42.80 mm or less, Preferably it is 45.0 as a weight. To 45.93 g.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Examples 1-3 and Comparative Examples 1-9]
Using a core composition composed mainly of polybutadiene common to each example shown in Table 1 below, vulcanization was performed at 155 ° C. for 15 minutes to produce a core having a diameter of 35.2 mm common to each example.

The details of the above blending are as follows.
・ Polybutadiene rubber: Trade name “BR51” (manufactured by JSR)
-Zinc acrylate: manufactured by Nippon Shokubai Co., Ltd.-Organic peroxide: Dicumyl peroxide, trade name "Park Mill D" (manufactured by NOF Corporation)
-Distilled water: Wako Pure Chemical Industries, Ltd.-Anti-aging agent: Trade name "NOCRACK NS-6" (Ouchi Shinsei Chemical Co., Ltd.)
・ Barium sulfate: Trade name “Varico # 100” (manufactured by Hakusuitec)
・ Zinc oxide: Trade name “Three kinds of zinc oxide” (manufactured by Sakai Chemical Industry)
・ Zinc salt of pentachlorothiophenol: Wako Pure Chemical Industries, Ltd.

  About each core produced above, predetermined load deformation amount, hardness distribution, and hysteresis loss rate (%) were evaluated. The results are shown in Tables 3 and 4.

Predetermined load deformation amount of the core This is a value obtained by measuring the deformation amount from the state in which the initial load 98N (10 kgf) is applied to the core until the final load 1275N (130 kgf) is applied. The average value of 30 is shown in Table 3 and Table 4.

Core hardness distribution Although the surface of the core is spherical, a hardness meter needle was set to be substantially perpendicular to the spherical surface, and the core surface hardness H 2 _O was measured by JIS-C hardness according to JIS K6301-1975 standard. The cross-sectional hardness at the core center H _i and the predetermined positions H _5.0 and H _15.0 was measured by cutting the core into a hemispherical shape, making the cross-section flat, and pressing the hardness meter needle vertically on the measurement part. It is shown by the value of JIS-C hardness.

Core hysteresis loss rate (%)
As a tensile and compression tester, the product name “TENSILON RTG-1310” manufactured by A & D Co., Ltd. is used, and the core is set in a jig for measuring the compression load, and the load cell speed is 500 mm / min and the constant load is 5000 N. The hysteresis loss rate (%) of the core of the example was obtained. The number of measurements of one core (N times) was set to 5, and the average values are shown in Tables 3 and 4.

  Next, for each of the cores produced above, three coating layers (enveloping layer, intermediate layer and outermost layer) having the properties shown in Table 2 below were used, and in turn around the cores by injection molding, A multi-layer solid golf ball having a four-layer structure was obtained in which the envelope layer, the intermediate layer, and the outermost layer were coated to a thickness of 1.2 mm, 1.3 mm, and 1.25 mm, respectively. At this time, a common dimple having a predetermined pattern was formed on the outermost layer surface of the balls of all the examples and comparative examples, although not particularly illustrated.

The details of the resin material in the above table are as follows.
“Hytrel 3046”: polyester elastomer, “Surlin 9320” manufactured by Toray DuPont Co., Ltd .: ionomer resin manufactured by DuPont Co., Ltd. (methacrylic acid content 9.6 mass%, ester 23 mass%, neutralized metal Zn)
“AN4221C”: nonionic ethylene-acrylic acid binary copolymer (acrylic acid content 12 mass%), magnesium oxide manufactured by Mitsui DuPont Polychemical Co., Ltd .: “Kyowa Mag MF150”, magnesium stearate manufactured by Kyowa Chemical Industry Co., Ltd .: "Magnesium stearate G", NOF Corporation

The “High Milan” series in the above table is an ionomer resin manufactured by Mitsui DuPont Polychemical Co., Ltd., and details of each brand are as follows.
“High Milan 1605”: 15% by mass of methacrylic acid, neutralized metal Na
“High Milan AM7329”: 15% by mass of methacrylic acid, neutralized metal Zn
“High Milan AM7318”: 18% by mass of methacrylic acid, neutralized metal Na
“High Milan AM7327”: 7.0% by weight of methacrylic acid, 16% by weight of ester, neutralized metal Zn
“High Milan 1706”: 15% by mass of methacrylic acid, neutralized metal Zn
"High Milan 1855": 10% by mass of methacrylic acid, 10% by mass of ester, neutralized metal Zn

  The loss factor (Tan δ) of the resin material is measured by “EPLEXOR 500N” manufactured by GABO under the conditions of a temperature of 24 ° C., a frequency of 15 Hz, and a strain of 2.0%.

  The golf balls of these examples and comparative examples were evaluated for various properties (initial speed, spin rate, durability) as follows. The results are shown in Tables 3 and 4.

[Evaluation of various physical properties of the ball]
Ball deflection (mm)
The amount of deformation (mm) from when the initial load of 98 N (10 kgf) was applied to the golf ball to when the final load of 1275 N (130 kgf) was applied was measured.

Ball spin rate (rpm)
A golf hitting robot equipped with a driver (W # 1), Bridgestone Sports' “PHYZ III (2014 model)” (loft angle: 10.5 °), and hit with a head speed (HS) of 45 m / s The immediately following ball was measured with an initial condition measuring device.

Ball Durability Durability of the golf ball was evaluated by ADC Ball COR Durability Tester manufactured by Automated Design Corporation. This test machine has a function of causing a golf ball to be blown with air pressure and then continuously colliding with two metal plates installed in parallel. The incident speed on the metal plate was 43 m / s. The number of firings required to break the golf ball was measured. The index when the average value (n = 5) of the number of times the ball of Example 1 started to crack was set to 100 (reference value) was obtained, and the results of evaluation based on the following criteria were shown.
<Evaluation criteria>
◎: 90 or more ○: 70 or more and less than 90 ×: less than 70

From the results of Tables 3 and 4 above, it can be seen that the golf ball of this example has a low spin at the time of driver hitting, and is further excellent in initial speed and durability.
On the other hand, Comparative Example 1 has a large amount of spin because there is no component (a) in the outermost layer.
In Comparative Example 2, the amount of spin is large because the mixing ratio of the component (A) and the component (B) in the intermediate layer is not appropriate and the component (a) is not present in the outermost layer.
In Comparative Example 3, the amount of spin is large because the mixing ratio of the component (A) and the component (B) in the intermediate layer is not appropriate.
In Comparative Example 4, since the mixing ratio of the (a) component and the (b) component in the outermost layer is not appropriate and Tan δ is out of the range, the initial speed is slightly low and the spin amount is slightly large.
In Comparative Example 5, the amount of spin is large because there is no component (a) in the outermost layer.
Comparative Example 6 has a large amount of spin because there is no component (a) in the outermost layer.
Comparative Example 7 has poor durability because the intermediate layer is not properly blended and has a high hardness.
In Comparative Example 8, the amount of spin is large because the blending ratio of the component (a) and the component (b) in the outermost layer is not appropriate and Tan δ is out of the range.
In Comparative Example 9, the amount of spin is large because the blending ratio of the (A) component and the (B) component of the intermediate layer is not appropriate and Tan δ is out of the range.

1 Core 2 Intermediate Layer 3 Outermost Layer G Golf Ball D Dimple

Claims (9)

In the multi-piece solid golf ball in which at least one intermediate layer is interposed between the core and the outermost layer, the intermediate layer includes the following (A) to (D),
(A) an ionic olefin-methacrylic acid-unsaturated carboxylic acid ester copolymer,
(B) a nonionic olefin-acrylic acid copolymer,
(C) an organic acid or a metal salt thereof,
(D) formed of a thermoplastic resin composition containing a basic inorganic metal compound for neutralizing 80 mol% or more of the acid groups in the components (A) to (C), and the components (A) and ( The blending ratio (mass ratio) with the component B) is (A) :( B) = 50: 50-80: 20, the Shore D hardness of the resin composition is 40-60, and the outermost layer is The following (a) and (b)
(A) The weight average molecular weight (Mw) is 40,000 to 200,000, the weight average molecular weight (Mw) / number average molecular weight (Mn) is 4.0 to 10.0, and an unsaturated carboxylic acid. An ionic olefin-unsaturated carboxylic acid copolymer having a content of 16% by mass or more,
(B) The weight average molecular weight (Mw) is 40,000 to 200,000, the weight average molecular weight (Mw) / number average molecular weight (Mn) is 4.0 to 10.0, and an unsaturated carboxylic acid. Formed of a thermoplastic resin composition containing an ionic olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer having a content of 15% by mass or less, and a combination of the component (a) and the component (b) The ratio (mass ratio) is (a) :( b) = 70: 30 to 90:10, the Shore D hardness of the resin composition is 55 or more, the temperature of the resin composition is 24 ° C., and the frequency is 15 Hz. The ratio (Tanδ) between the tensile storage elastic modulus (E ′) and the tensile loss elastic modulus (E ″) in the dynamic viscoelasticity test measured under a strain of 2.0% is 0.150 or less. Multi-piece solid golf ball characterized by   The core is formed of a rubber composition using polybutadiene as a base rubber, the core has a diameter of 40.0 mm or less, and an initial load of 98 N (10 kgf) is applied to a final load of 1275 N (130 kgf). The multi-piece solid golf ball according to claim 1, wherein a deflection amount when a load is applied is 3.0 to 4.5 mm. 3. The multi-piece solid golf ball according to claim 1, wherein, in the cross-sectional hardness of the core, a JIS-C hardness difference value obtained by subtracting the core center hardness H _i from the core surface hardness H ₀ is 20 or more. In the cross-sectional hardness of the core, JIS-C hardness H _5.0 at a position 5.0 mm outward from the core center in the outer peripheral direction was subtracted from JIS-C hardness H _{15.0 at} a position 15.0 mm outward in the outer peripheral direction from the core center. The golf ball according to claim 1, wherein the value is a positive numerical value.   The golf ball according to claim 1, wherein the core has a hysteresis loss rate of 50% or less when compressed at a load cell speed of 500 mm / min and a constant load of 5000 N.   The multi-piece solid golf ball according to claim 1, wherein an envelope layer is provided between the core and the intermediate layer.   The multi-piece solid golf ball according to claim 6, wherein the envelope layer is formed of a thermoplastic resin composition other than ionic, and the Shore D hardness of the resin composition is 50 or less.   Tensile storage elastic modulus (E ′) and tensile loss elastic modulus (E) in a dynamic viscoelasticity test measured under conditions of a temperature of 24 ° C., a frequency of 15 Hz, and a strain of 2.0% in the resin composition of the intermediate layer. The multi-piece solid golf ball according to claim 1, wherein the ratio (Tan δ) to “)” is 0.110 or less.   The multi-piece solid golf according to any one of claims 1 to 8, wherein a sum of Tan δ of the outermost resin composition and Tan δ of the intermediate layer resin composition measured under the same condition is 0.250 or less. ball.

Images