GOLF BALLS COMPRISING IONOMERS FORMED FROM POST-NEUTRALIZATION OF IN SITU Na/Zn IONOMERS WITH Li OR Ca CATIONS
The present invention is directed to compositions and methods relating to golf balls. In one embodiment, a golf ball can include a core and/or intermediate layer formed from a partially-neutralized in situ ionomer that is neutralized to a first level by a first cation, and is subsequently neutralized by a second, different cation to produce a further, more highly-neutralized ionomer. The further-neutralized ionomer exhibits decreased compression (softer) and/or increased COR (faster) compared to a comparative golf ball that contains a core or layer that is formed from an ionomer that is not subsequently neutralized with a second cation.
1 . A golf ball comprising:
a core;
a cover; and
optionally, an intermediate layer disposed between the core and the cover,
wherein the core or the optional intermediate layer comprises a further-neutralized ionomer having a neutralization greater than 70 wt % formed from a reaction product of:
a partially-neutralized in situ ionomer neutralized to less than 70% by a first and second cation; and
a sufficient amount of a third cation and, optionally, a suitable amount of fatty acid or a salt thereof, the third cation being different from the first and second cations.
2 . The golf ball of claim 1 , wherein the golf ball has a decreased compression, increased COR, or both, compared to a golf ball comprising a conventional ionomer.
3 . The golf ball of claim 2 , wherein the compression is decreased by at least about 2 Atti points.
4 . The golf ball of claim 2 , wherein the COR, when measured at an incoming velocity of 125 ft/s, is increased by at least about 0.004.
5 . The golf ball of claim 1 , wherein the partially-neutralized in situ ionomer comprises a copolymer of ethylene and an α,β-ethylenically unsaturated mono- or dicarboxylic acid.
6 . The golf ball of claim 1 , wherein the first and second cations comprise lithium, sodium, potassium, magnesium, calcium, barium, zinc, bismuth, chromium, cobalt, copper, strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver, aluminum, or tin.
7 . The golf ball of claim 1 , wherein the third cation comprises calcium or lithium.
8 . The golf ball of claim 1 , wherein the first and second cations comprise zinc or sodium and the third cation comprises calcium or lithium.
9 . The golf ball of claim 1 , wherein the in situ ionomer comprises an acrylic acid that is partially neutralized by Na or Zn cations.
10 . The golf ball of claim 1 , wherein a ratio of a melt flow index of the in situ ionomer to a melt flow index of the further-neutralized ionomer is 1 to 20 g/10 min at 190° C. using a 2.16-kg load.
11 . The golf ball of claim 10 , wherein the ratio is 2 to 10 g/10 min.
12 . The golf ball of claim 1 , wherein a ratio of a flexural modulus of the in situ ionomer to a flexural modulus of the further-neutralized ionomer is 0.43 to 0.75.
13 . The golf ball of claim 12 , wherein the ratio is 0.45 to 0.7.
14 . The golf ball of claim 1 , wherein the further-neutralized ionomer composition has a flexural modulus of 65,000 to 90,000 psi.
15 . The golf ball of claim 1 , wherein a ratio of the neutralization level of the in situ ionomer to the neutralization level of the further-neutralized ionomer is 0.3 to 0.9.
16 . The golf ball of claim 15 , wherein the ratio is 0.31 to 0.85.
17 . The golf ball of claim 16 , wherein the ratio is 0.33 to 0.8.
18 . The golf ball of claim 1 , wherein the further-neutralized ionomer is neutralized by at least 80 wt %.
19 . The golf ball of claim 18 , wherein the further-neutralized ionomer is neutralized to 90 to 100 wt %.
20 . A method for manufacturing a golf ball having decreased compression, increased COR, or both, comprising the steps of:
providing a partially-neutralized in situ ionomer neutralized to less than about 70% by a first cation and a second cation; and
further neutralizing the partially-neutralized in situ ionomer with a third cation, different from the first and second cations, to produce a further-neutralized ionomer,
wherein the first and second cations comprise Na or Zn and the third cation comprises Ca or Li, and the further-neutralized ionomer provides decreased compression of at least 2 Atti points, increased COR of at least 0.004, or both, compared to a golf ball comprising a layer formed from a conventional ionomer.