Golf ball and process for preparing the same

A golf ball comprising:

• a core having a center and at least one intermediate layer covering the center;
• and
• a cover covering the core,
• wherein at least one piece or one layer of the intermediate layer is formed from a high fluidity intermediate layer composition that has a slab hardness of 65 or more in Shore D hardness and a tensile modulus in a range from 400 MPa to 2000 MPa and contains
• (A) a polyamide resin composition having a flexural modulus in a range from 700 MPa to 4,000 MPa and a melt flow rate (240° C., 2.16 kg) of 5.0 g/10 min or more, and containing (a-1) a polyamide resin and (a-2) a thermoplastic elastomer;
• (B) at least one member selected from the group consisting of a metal-neutralized product of an ethylene-(meth)acrylic acid binary copolymer and a metal-neutralized product of an ethylene-(meth)acrylic acid-(meth)acrylic acid ester ternary copolymer;
• and
• (C) a fluidity improving agent,
• wherein (a-1) the polyamide resin is at least one selected from the group consisting of polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 6T, polyamide 9T, polyamide M5T, polyamide 612 and a polyetherblock amide copolymer;
• (a-2) the thermoplastic elastomer contains at least one member selected from the group consisting of:
• a thermoplastic polyolefin elastomer having at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an anhydride group, a sulfonic acid group, and an epoxy group;
• a thermoplastic polyamide elastomer having at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an anhydride group, a sulfonic acid group, and an epoxy group;
• a thermoplastic polyurethane elastomer having at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an anhydride group, a sulfonic acid group, and an epoxy group;
• and
• a thermoplastic polystyrene elastomer having at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an anhydride group, a sulfonic acid group, and an epoxy group,
• the component (B) is neutralized with at least one metal selected from the group consisting of Li, Na, Ca, Zn, Mg and Cu,
• (C) the fluidity improving agent includes at least one selected from the group consisting of a fatty acid, a metal salt thereof, a nonionic thermoplastic resin having a melt viscosity (190° C.) ranging from 5 Pa·s to 1,000 Pa·s measured by a flow tester, and an ionomer resin having a melt viscosity (190° C.) ranging from 1 Pa·s to 10 Pa·s measured by a brookfield viscometer,
• a content ratio ((A)/(B)) of (A) component to (B) component (a total is 100 mass %) in the high fluidity intermediate layer composition is 20 mass % to 80 mass %/80 mass % to 20 mass %, and a blending amount of (C) the fluidity improving agent in the high fluidity intermediate layer composition is from 1 part to 30 parts by mass with respect to 100 parts by mass of a sum of (A) component and (B) component,
• the intermediate layer has a thickness in a range from 0.8 mm to 2.0 mm,
• the core has a hardness difference (H6−H1) between a core surface hardness H6 and a core center hardness H1 in a range of from 10 to 55 in Shore D, and
• the center has a center surface hardness H2 of 64 or less in Shore D hardness.

A golf ball comprising:

• an inner core consisting of a center and a surrounding layer covering the center,
• at least one intermediate layer covering the inner core, and
• a cover covering the intermediate layer,
• wherein at least one piece or one layer of the intermediate layer is formed from a high fluidity intermediate layer composition that has a melt flow rate (240° C., 2.16 kg) of 5.0 g/10 min or more, a slab hardness of 65 or more in Shore D hardness and a tensile modulus in a range from 400 MPa to 2000 MPa and contains;
• (A) a polyamide resin composition having a flexural modulus in a range from 700 MPa to 4,000 MPa, and containing (a-1) a polyamide resin and (a-2) a thermoplastic elastomer;
• (B) at least one member selected from the group consisting of a metal-neutralized product of an ethylene-(meth)acrylic acid binary copolymer and a metal-neutralized product of an ethylene-(meth)acrylic acid-(meth)acrylic acid ester ternary copolymer;
• and
• (C) a fluidity improving agent,
• wherein (a-1) the polyamide resin is at least one selected from the group consisting of polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 6T, polyamide 9T, polyamide M5T, polyamide 612 and a polyetherblock amide copolymer,
• (a-2) the thermoplastic elastomer contains at least one member selected from the group consisting of:
• a thermoplastic polyolefin elastomer having at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an anhydride group, a sulfonic acid group, and an epoxy group;
• a thermoplastic polyamide elastomer having at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an anhydride group, a sulfonic acid group, and an epoxy group;
• a thermoplastic polyurethane elastomer having at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an anhydride group, a sulfonic acid group, and an epoxy group;
• and
• a thermoplastic polystyrene elastomer having at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an anhydride group, a sulfonic acid group, and an epoxy group,
• the component (B) is neutralized with at least one metal selected from the group consisting of Li, Na, Ca, Zn, Mg and Cu,
• (C) the fluidity improving agent includes at least one selected from the group consisting of a fatty acid, a metal salt thereof, a nonionic thermoplastic resin having a melt viscosity (190° C.) ranging from 5 Pa·s to 1,000 Pa·s measured by a flow tester, and an ionomer resin having a melt viscosity (190° C.) ranging from 1 Pa·s to 10 Pa·s measured by a brookfield viscometer,
• a content ratio ((A)/(B)) of (A) component to (B) component (a total is 100 mass %) in the high fluidity intermediate layer composition is 20 mass % to 80 mass %/80 mass % to 20 mass %, and a blending amount of (C) the fluidity improving agent in the high fluidity intermediate layer composition is from 1 part to 30 parts by mass with respect to 100 parts by mass of a sum of (A) component and (B) component,
• a surface hardness (H6) of the intermediate layer and a surface hardness (H4) of the inner core satisfy the equation:
• H6≧H4, and the cover has a slab hardness (H7) of 45 or less in Shore D hardness, and
• wherein the intermediate layer has a thickness in a range from 0.8 mm to 2.0 mm,
• the inner core has a hardness difference (H4−H1) between an inner core surface hardness H4 and an inner core center hardness H1 in a range of from 10 to 55 in Shore D, and
• the inner core has an inner core surface hardness H4 of 63 or less in Shore D hardness.