Multi-piece solid golf ball

Abstract

In a golf ball having a core, an outermost layer and an intermediate layer therebetween, the intermediate layer is formed of a thermoplastic resin composition that includes (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, and (D) a basic inorganic metal compound, and the outermost layer is formed of a thermoplastic resin composition that includes (a) a specific ionic olefin-unsaturated to carboxylic acid copolymer and (h) a specific ionic olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer. The ratio (tan δ) between the tensile storage modulus (E′) and the tensile loss modulus (E″) in a dynamic viscoelasticity test on the outermost layer-forming resin composition conducted under specific conditions is not more than 0.150. This combination of intermediate layer and outermost layer materials has is a large spin rate-lowering effect on the ball, enabling the ball to travel further.

1 . A multi-piece solid golf ball comprising a core, an outermost layer, and at least one intermediate layer between the core and the outermost layer, wherein the intermediate layer is formed of a thermoplastic resin composition comprising:
 (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, and   (D) a basic inorganic metal compound for neutralizing at least 80 mol % of acid to groups in components (A) to (C),   
       components (A) and (B) having a mixing ratio (by weight) therebetween that satisfies the condition (A):(B)=50:50 to 80:20, which first resin composition has a Shore D hardness of from 40 to 60; and the outermost layer is formed of a thermoplastic resin composition comprising:
 (a) an ionic olefin-unsaturated carboxylic acid copolymer having a weight-average molecular weight (Mw) of from 40,000 to 200,000, a weight-average molecular weight (Mw) to number-average molecular weight (Mn) ratio (Mw/Mn) of from 4.0 to 10.0, and an unsaturated carboxylic acid content of at least 16 wt %, and 
 (b) an ionic olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer having a weight-average molecular weight (Mw) of from 40,000 to 200,000, a weight-average molecular weight (Mw) to number-average molecular weight (Mn) ratio (Mw/Mn) of from 4.0 to 10.0, and an unsaturated carboxylic acid content of not more than 15 wt %, 
 
       components (a) and (b) having a mixing ratio (by weight) therebetween that satisfies the condition (a):(b)=70:30 to 90:10, which outermost layer-forming resin composition has a Shore D hardness of at least 55 and a ratio (tan δ) between the tensile storage modulus (E′) and the tensile loss modulus (E″) in a dynamic viscoelasticity test conducted at a temperature of 24° C., an oscillation frequency of 15 Hz and 2.0% strain of not more than 0.150. 
     
     
         2 . The golf ball of  claim 1 , wherein the core is formed of a rubber composition containing polybutadiene as the base rubber, has a diameter of not more than 40.0 mm, and. has a deflection when compressed under a final load of 1,275 N (130 kgf) from an initial load state of 98 N (10 kgf) of from 3.0 to 4.5 mm. 
     
     
         3 . The golf ball of  claim 1 , wherein the core has a cross-sectional hardness in which the JIS-C hardness difference value obtained by subtracting the core center hardness H i  from the core surface hardness H 0  is at least 20. 
     
     
         4 . The golf ball of  claim 1 , wherein the core has a cross-sectional hardness in which the value obtained by subtracting the JIS-C hardness at a position 5.0 mm peripherally to outward from the core center (H 5.0 ) from the JIS-C hardness at a position 15.0 mm peripherally outward from the core center (H 15.0 ) is a positive numerical value. 
     
     
         5 . The ball of  claim 1 , wherein the core has a hysteresis loss ratio When compressed at a load cell speed of 500 mm/min and under a constant load of 5,000 N of more than 50%. 
     
     
         6 . The golf ball of  claim 1 , further comprising an envelope layer between the core and the intermediate layer. 
     
     
         7 . The golf ball of  claim 1 , wherein the envelope layer is formed of a thermoplastic resin composition that is other than ionic, which envelope layer-forming resin composition has a Shore D hardness of not more than 50. 
     
     
         8 . The golf ball of  claim 1 , wherein the intermediate layer-forming resin composition has a ratio (tan δ) between the tensile storage modulus (E′) and the tensile loss modulus (E″) measured in a dynamic viscoelasticity test conducted at a temperature of 24° C., an oscillation frequency of 15 Hz and 2.0% strain of not more than 0.110. 
     
     
         9 . The golf ball of  claim 1 , wherein the sum of tan δ for the outermost layer-forming resin composition and tan δ for the intermediate layer-forming resin composition, both of which are measured under the same conditions, is not more than 0.250.