Multi-piece golf ball

1. A multi-piece golf ball comprising a core composed of a center and an envelope layer covering the center and at least one cover covering the core, wherein the center is formed from a center composition containing:

(A) at least one resin component selected from the group consisting of

(a-1) a binary copolymer composed of an olefin and an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms,

(a-2) an ionomer resin consisting of a metal ion-neutralized product of a binary copolymer composed of an olefin and an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms,

(a-3) a ternary copolymer composed of an olefin, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α,β-unsaturated carboxylic acid ester, and

(a-4) an ionomer resin consisting of a metal ion-neutralized product of a ternary copolymer composed of an olefin, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α,β-unsaturated carboxylic acid ester and

(B) a basic metal salt of a fatty acid, wherein the center composition contains (B) the basic metal salt of the fatty acid in an amount range of from 25 parts to 100 parts by mass with respect to 100 parts by mass of (A) the resin component, and

wherein the basic metal salt of the fatty acid is represented by the following general formula (1):

m M 1 O.M 2 (RCOO) 2   (1)

wherein m ranges from 0.3 to 2.0, RCOO represents a residue of the fatty acid, and M 1 and M 2 are magnesium,

wherein the center and surface of the core differ in hardness such that the surface has a hardness that is 10 or more in Shore D higher than the center, and

wherein the envelope layer is formed from a rubber composition.

2. The multi-piece golf ball according to claim 1 , wherein (B) the basic metal salt of the fatty acid is a basic metal salt of a fatty acid having 8 to 30 carbon atoms.

3. The multi-piece golf ball according to claim 1 , wherein a fatty acid component of (B) the basic metal salt of the fatty acid is at least one component selected from the group consisting of lauric acid, stearic acid, behenic acid, oleic acid, and erucic acid.

4. The multi-piece golf ball according to claim 1 , wherein the center composition has a slab hardness ranging from 20 to 80 in Shore D hardness.

5. The multi-piece golf ball according to claim 1 , wherein the center has a diameter ranging from 5 mm to 30 mm.

6. The multi-piece golf ball according to claim 1 , wherein the center composition has a rebound resilience of 40% or more.

7. The multi-piece golf ball according to claim 1 , wherein the envelope layer has a thickness in a range from 0.5 mm to 20 mm.

8. The multi-piece golf ball according to claim 1 , wherein the core has a surface hardness in a range from 40 to 70 in Shore D hardness.

9. The multi-piece golf ball according to claim 1 , wherein the cover comprises at least two layers.

10. The multi-piece golf ball according to claim 1 , wherein the cover consists of an inner cover layer covering the core and an outer cover layer covering the inner cover layer.

11. The multi-piece golf ball according to claim 10 , wherein the inner cover layer contains an ionomer resin and the outer cover layer contains polyurethane.

12. The multi-piece golf ball according to claim 1 , wherein the center composition contains (B) the basic metal salt of the fatty acid in an amount range of from 25 parts to 70 parts by mass with respect to 100 parts by mass of (A) the resin component.

13. The multi-piece golf ball according to claim 1 , wherein m ranges from

0.4 to 2.0.

14. The multi-piece golf ball according to claim 1 , wherein m ranges from

0.7 to 2.0.