Golf ball 2 has a spherical core 4 , a mid layer 6 covering this core 4 , a reinforcing layer 8 covering this mid layer 6 , and a cover 10 covering this reinforcing layer 8 . Base polymer of this mid layer 6 includes an ionomer resin as a principal component. Base polymer of this cover 10 includes a thermoplastic polyurethane elastomer as a principal component. The cover 10 has a thickness Tc of equal to or less than 0.6 mm. The cover 10 has a hardness Hc as measured with a Shore D type hardness scale of equal to or less than 54. The cover 10 has a volume V of equal to or less than 3.0 cm 3 . A product obtained by multiplying the thickness Tc, the hardness Hc and the volume V is equal to or less than 90. The reinforcing layer 8 includes a thermosetting resin as a base polymer. The reinforcing layer has a thickness of 3 μm or greater and 50 μm or less.
1. A golf ball which comprises a spherical core, a mid layer positioned outside of the core, a cover positioned outside of the mid layer, and a reinforcing layer provided between said mid layer and said cover,
said cover having a thickness Tc of equal to or less than 0.5 mm,
said cover having a hardness Hc as measured with a Shore D type hardness scale of equal to or less than 47,
said cover having a volume V of equal to or less than 2.4 cm 3 , and
a product obtained by multiplying the thickness Tc (mm), the hardness Hc and the volume V (cm 3 ) of said cover being equal to or less than 90, and
a product obtained by multiplying the hardness (Hc) and the volume V (cm 3 ) of said cover being equal to or less than 115,
wherein a principal component of the base polymer of said cover is a thermoplastic polyurethane elastomer, and wherein a principal component of the base polymer of said mid layer is an ionomer resin,
wherein an isocyanate component of the thermoplastic polyurethane elastomer is an alicyclic diisocyanate, and
wherein a base polymer of said reinforcing layer is a two-component cured thermosetting resin obtained by curing a bisphenol A type epoxy resin with a polyamide based curing agent containing a polyamide amine or denatured product of the polyamide amine.
2. The golf ball according to claim 1 , wherein said reinforcing layer has a thickness of 3 μm or greater and 50 μm or less.
3. The golf ball according to claim 1 , wherein the product obtained by multiplying the hardness (He) and the volume V (cm 3 ) of said cover is equal to or less than 115 and equal to or greater than 10.
4. The golf ball according to claim 1 , wherein the cover has a thickness Tc equal to or less than 0.4 mm and equal to or greater than 0.1 mm; and the cover has a volume V equal to or less than 2.2 cm 3 and equal to or greater than 0.3 cm 3 .
5. The golf ball according to claim 1 , wherein the cover has a thickness Tc equal to or less than 0.4 mm and equal to or greater than 0.2 mm; and the cover has a volume V equal to or less than 2.2 cm 3 and equal to or greater than 1.0 cm 3 .
6. The golf ball according to claim 1 , wherein the product obtained by multiplying the thickness Tc (mm), the hardness Hc and the volume V (cm 3 ) of said cover being equal to or less than 85, and is equal to or greater than 1.0.
7. The golf ball according to claim 1 , wherein the product obtained by multiplying the thickness Tc (mm), the hardness Hc and the volume V (cm 3 ) of said cover being equal to or less than 60, and is equal to or greater than 1.0.
8. The golf ball according to claim 1 , wherein the isocyanate component is 4,4′-dicyclohexylmethane diisocyanate.
9. The golf ball according to claim 1 , wherein a ratio of epoxy equivalent of the epoxy resin and amine active hydrogen content equivalent of the polyamide based curing agent is 1.0/1.4 or greater and 1.0/1.0 or less.