GOLF BALL HAVING A HOLLOW CENTER
A golf ball includes a spherical inner core shell layer formed from a thermoplastic composition. The shell layer has an outer surface, an inner surface, and an inner diameter to define a hollow center. A thermoplastic outer core layer is formed around the shell layer. An ionomeric inner cover layer and a urethane or urea outer cover layer are formed over the hollow core. The outer cover has a hardness less than the inner cover. The hollow center has a diameter of about 0.15 to 1.1 inches, the shell layer has a surface hardness greater than an inner surface hardness by about 0 to 5 Shore C to define a hardness gradient, and the thermoplastic outer core layer also has a hardness gradient.
1 . A golf ball comprising a hollow core, the golf ball comprising:
a spherical inner core shell layer formed from a first thermoplastic composition, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center;
an outer core layer disposed about the shell layer, the outer core layer comprising a second thermoplastic material;
an inner cover layer disposed about the outer core layer, the inner cover comprising an ionomeric material and having a first hardness; and
an outer cover layer disposed about the inner cover layer, the outer cover comprising a polyurea or a polyurethane and having a second hardness less than the first;
wherein the hollow center has a diameter of about 0.15 to 1.1 inches, the shell layer has a surface hardness greater than an inner surface hardness by about 0 to 5 Shore C to define a first hardness gradient, and the thermoplastic outer core layer has a second hardness gradient different from the first.
2 . The golf ball of claim 1 , wherein the second hardness gradient is about 0 Shore C.
3 . The golf ball of claim 1 , wherein the second hardness gradient is a negative hardness gradient of about 1 to 10 Shore C.
4 . The golf ball of claim 1 , wherein the second hardness gradient is a positive hardness gradient of about 1 to 10 Shore C.
5 . The golf ball of claim 1 , wherein the golf ball has a first volume and the hollow center has a second volume that is about 2% to 30% of the first volume.
6 . The golf ball of claim 1 , wherein the spherical inner core shell layer has a coefficient of restitution less than about 0.700 when measured at an incoming velocity of 125 ft/s.
7 . The golf ball of claim 1 , wherein the outer core layer has a coefficient of restitution, measured at an incoming velocity of 125 ft/s, higher than the coefficient of restitution, measured at an incoming velocity of 125 ft/s, of the inner core shell layer by 10-50%.
8 . A golf ball comprising a hollow core, the golf ball comprising:
a spherical inner core shell layer comprising a first thermoplastic material, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center;
an outer core layer comprising a second thermoplastic material;
an intermediate core layer disposed between the shell layer and the outer core layer, the intermediate layer comprising a third thermoplastic material different from the first and second;
an inner cover layer disposed about the outer core layer, the inner cover comprising an ionomeric material and having a first hardness; and
an outer cover layer disposed about the inner cover layer, the outer cover comprising a polyurea or a polyurethane and having a second hardness less than the first;
wherein the hollow center has a diameter of about 0.15 to 1.1 inches, the shell layer has a surface hardness greater than an inner surface hardness by about 0 to 5 Shore C to define a first hardness gradient, and at least one of the thermoplastic outer core layer or the thermoplastic intermediate layer has a second hardness gradient different from the first.
9 . The golf ball of claim 8 , wherein the second hardness gradient is about 0 Shore C.
10 . The golf ball of claim 8 , wherein the second hardness gradient is a negative hardness gradient of about 1 to 10 Shore C.
11 . The golf ball of claim 8 , wherein the second hardness gradient is a positive hardness gradient of about 1 to 10 Shore C.
12 . A golf ball comprising a hollow core, the golf ball comprising:
a spherical inner core shell layer comprising a first thermoplastic material, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center;
an outer core layer comprising a second thermoplastic material;
an intermediate core layer disposed between the shell layer and the outer core layer, the intermediate core layer comprising a thermoset rubber composition;
an inner cover layer disposed about the outer core layer, the inner cover comprising an ionomeric material and having a first hardness; and
an outer cover layer disposed about the inner cover layer, the outer cover comprising a polyurea or a polyurethane and having a second hardness less than the first;
wherein the hollow center has a diameter of about 0.15 to 1.1 inches, the shell layer has a surface hardness greater than an inner surface hardness by about 0 to 5 Shore C to define a first hardness gradient, and the thermoplastic outer core layer has a second hardness gradient.
13 . The golf ball of claim 12 , wherein the second hardness gradient is about 0 Shore C.
14 . The golf ball of claim 12 , wherein the second hardness gradient is a negative hardness gradient of about 1 to 10 Shore C.
15 . The golf ball of claim 12 , wherein the second hardness gradient is a positive hardness gradient of about 1 to 10 Shore C.
16 . The golf ball of claim 12 , wherein the thermoset intermediate core layer has a surface hardness less than an inner surface hardness to define a negative hardness gradient.
17 . The golf ball of claim 12 , wherein the thermoset intermediate core layer has a surface hardness greater than an inner surface hardness to define a positive hardness gradient.