A golf ball with improved durability is disclosed herein. The golf ball has a core comprising a polybutadiene material and methyl methacrylate, butadiene, styrene (MBS) with a weight percentage of MBS ranging from 0.5 to 5 weight percent of the core.

In a golf ball for professional golfers and skilled amateurs which has a single-layer core, a cover and at least one intermediate layer therebetween, the sphere obtained by encasing the core with the intermediate layer (intermediate layer-encased sphere) and the ball have a surface hardness relationship which satisfies the condition:

(surface hardness of intermediate layer-encased sphere)>(surface hardness of ball).

The core has a diameter of from 35.5 to 39.5 mm and a distinctive hardness profile that satisfies specific conditions. The ball is endowed with both an excellent flight performance and excellent durability to repeated impact.

A golf ball with a core comprising polybutadiene and graphene is disclosed herein. The golf ball has a single core comprising polybutadiene and graphene. Alternatively, the golf ball has a dual core with an inner core comprising polybutadiene and graphene. Alternatively, the golf ball has a dual core with an outer core comprising polybutadiene and graphene.

An object of the present invention is to provide a golf ball having excellent durability and good shot feeling. The present invention provides a golf ball comprising a core, wherein a difference (crosslinking density at surface of core-crosslinking density at center of core) between a crosslinking density at a surface of the core and a crosslinking density at a center of the core is more than 1.0×10.sup.2 mol/m.sup.3 and less than 9.0×10.sup.2 mol/m.sup.3, and a hardness difference (Hs−Ho) between Hs and Ho is 13.0 or more and 30.0 or less, and the core satisfies H50−Ho>Hs−H50, wherein Hs (Shore C hardness) is a hardness at the surface of the core, Ho (Shore C hardness) is a hardness at the center of the core, and H50 (Shore C hardness) is a hardness at a midpoint between the center of the core and the surface of the core.

A rubber composition for golf balls includes (A) a base rubber, (B) an acrylate ester or methacrylate ester containing an isocyanate group or a blocked isocyanate group, (C) diacrylic acid, dimethacrylic acid or a metal salt thereof, and (D) an organic peroxide. In a golf ball having a core formed of the rubber composition and a cover of one or more layers which encases the core, the rubber composition exhibits a spin rate-lowering effect on shots and can thus improve the flight performance of the ball.

An object of the present disclosure is to provide a rubber composition from which a molded product crosslinked in a short time and having high hardness can be obtained. The present disclosure provides a rubber composition containing (a) a base rubber, (b) a co-crosslinking agent, (c) a crosslinking initiator, and (d) a benzothiazole compound, wherein (d) the benzothiazole compound is a specific benzothiazole compound, and a relationship of {(T2-T1)/(X-18)} ≥ 0.46 is satisfied, wherein X is an amount (parts by mass) of (b) the co-crosslinking agent with respect to 100 parts by mass of (a) the base rubber, T1 is a torque (N.sup..m) at 35 seconds and T2 is a torque (N.sup..m) at 45 seconds from a start of measuring the torque of the rubber composition when conducting a crosslinking test of the rubber composition at a temperature of 170° C.

A method for forming a golf ball core with a nanofiller masterbatch is disclosed herein. The method includes mixing the nanofiller masterbatch, a graphene masterbatch material with other materials to form a core mixture, wherein the masterbatch preferably comprises 1-80% by weight of nanofillers and 20-99% by weight of a carrier polymer.

An object of the present disclosure is to provide a rubber composition from which a crosslinked rubber molded product having good softness and excellent resilience performance can be obtained. The present disclosure provides a rubber composition containing (a) a base rubber, (b) a co-crosslinking agent, (c) a crosslinking initiator, and (d) an organic sulfur compound, wherein (d) the organic sulfur compound includes (d1) a polythiophene compound having two or more thiophene rings in the molecule.

A golf ball core, mantle, and/or cover layer(s) of golf ball having a composition comprising functionalized aluminosilicate particles having a particle size of less than 50 μm is disclosed herein. The aluminosilicate microspheres with an average diameter less than 50 μm are functionalized with, but not limited to, polysulfide, vinyl, amino, epoxy, hydroxyl, carboxyl, methacryloyl, hydrocarbon, mercapto and isocyanate.

A method for forming a golf ball core with a nanofiller masterbatch is disclosed herein. The method includes mixing the nanofiller masterbatch, a graphene masterbatch material with other materials to form a core mixture, wherein the masterbatch preferably comprises 1-80% by weight of nanofillers and 20-99% by weight of a carrier polymer.