A golf ball with a cover layer composed of a blend of non- or partially neutralized copolymeric or terpolymeric ionomer(s), hydroxyl-functionalized styrenic block copolymer and silane coupling agent (SCA). The amount of SCA is preferably between 0.01 and 2.0 weight percent based on the total weight of the polymer composition. The cover layer preferably has a Shore A hardness less than 90.

A golf ball has a core, an inner cover, an outer cover, and dimples. The golf ball satisfies the following mathematical formulas.
Sa=4500+10(A−0.5B−2Cs)≥4000
0.04Sa+160−20≤D≤0.04Sa+160+20 A: a compression (Atti) of the golfball B: a hardness difference (Shore C) between a surface and a center of the core Cs: (Hi×Ti+2Ho×To)/(Ti+2To) D: a total volume (mm.sup.3) of the dimples Hi: a hardness (Shore D) of the inner cover Ho: a hardness (Shore D) of the outer cover Ti: a thickness (mm) of the inner cover To: a thickness (mm) of the outer cover

Multi-piece golf balls containing a multi-layered core structure are provided. The core structure includes a small, heavy inner core (center) having a relatively high specific gravity, an intermediate core layer, and a surrounding outer core layer. The layers of the core structure may have different hardness gradients. In one preferred embodiment, each core layer has a positive hardness gradient. The center of the core comprises a metal material such as copper, steel, brass, tungsten, titanium, aluminum, and alloys thereof. The intermediate core layer is preferably formed from a thermoset composition such as polybutadiene rubber, and the outer core layer is preferably formed from a thermoplastic composition such as an ethylene acid copolymer. The resulting ball has high resiliency and good spin control.

A golf ball includes a core, a mid layer, and a cover. An amount of compressive deformation C3 of the golf ball can be not less than 2.80 mm. The golf ball can satisfy the following mathematical formulas (1) and (2):
C1>(124.8−Hs)/11.5  (1)
C2−C1≥(−1/6*C1+(68−H2)/20+(5−Hd)/100)*T2  (2), where C1 is an amount of compressive deformation (mm) of the core, C2 is an amount of compressive deformation (mm) of a sphere including the core and the mid layer, Hd is Hs−Ho, Ho is a hardness (Shore C) of a center the core, Hs is a hardness (Shore C) of a surface of the core, H2 is a hardness (Shore D) of the mid layer, and T2 is a thickness (mm) of the mid layer.

A golf ball 2 includes a core 4, an inner cover 6, and an outer cover 8. The golf ball 2 satisfies the following mathematical formulas (1), (2), and (3):

5≤(Hi*Ti−Dc*Rc)≤40  (1);

5≤(Hi*Ti−Ho*To)≤40  (2); and

−20≤(Ho*To−Dc*Rc)≤20  (3).

Dc is the amount of compressive deformation (mm) of the core 4,

Rc is the radius (mm) of the core 4,

Hi is the Shore C hardness of the inner cover 6,

Ti is the thickness (mm) of the inner cover 6,

Ho is the Shore C hardness of the outer cover 8, and

To is the thickness (mm) of the outer cover 8.

A method of producing a golf ball applies ultrasonic welding on two half shells to form at least one intermediate layer, at least one cover layer, or at least one intermediate layer and at least one cover layer. The ultrasonic welding may include pressing the two half shells together, delivering a high power electrical signal to a welding stack, and converting the high power electrical signal at the welding stack to ultrasonic energy. The converting may include converting the high power electrical signal into a mechanical vibration, modifying an amplitude of the mechanical vibration to generate a modified mechanical vibration, and applying the modified mechanical vibration to an interface of the two half shells to weld them together ultrasonically. Aspects also relate to golf balls, or one or more layers thereof, made using ultrasonic welding.

A golf ball can include a core, mid layer, and a cover. The golf ball can satisfy the following mathematical formulas (1) and (2),

[00001]$\left(\text{Fw}/\text{Fwn}\right)\le 0.98$

[00002]${\left(\text{Fw}/\text{Fwn}\right)}^2/\left(\text{Fp}/\text{Fpn}\right)\le 0.98$

, wherein Fw represents a maximum vertical force of the golf ball measured under a first condition, Fwn represents a maximum vertical force of a standard ball measured under the first condition, Fp represents a maximum vertical force of the golf ball measured under a second condition, and Fpn represents a maximum vertical force of the standard ball measured under the second condition.

Multi-layered golf balls having at least one layer made of a foamed silicone composition are provided. Multi-layered golf balls having at least one layer made of non-foamed silicone elastomer composition also are provided. For example, three-piece, four-piece, and five-piece golf balls containing different core and cover structures can be made. The foamed silicones have good thermal stability and durability without sacrificing resiliency. The non-foamed silicone elastomers have high elongation, tensile strength, chemical/fluid-resistance, and weatherability properties. These compositions can be used to form any layer, for example, core, intermediate, or cover, in the golf ball.

A golf ball includes a core, a mid layer, and a cover. A ratio R1 calculated by mathematical formula (1): R1=(Df1−Df2)/(Df2−Df3) is not less than 5.00. A ratio R2 calculated by mathematical formula (2): R2=(T2*H2)/H3 is not less than 2.00. A ratio R3 calculated by mathematical formula (3): R3=D1/T3 is not less than 50. In mathematical formulas (1) to (3), Df1 represents an amount of compressive deformation of the core, Df2 represents an amount of compressive deformation of a sphere including the core and the mid layer, Df3 represents an amount of compressive deformation of the golf ball, T2 represents a thickness of the mid layer, H2 represents a hardness of the mid layer, H3 represents a hardness of the cover, D1 represents a diameter of the core, and T3 represents a thickness of the cover.

A golf ball includes a core, a mid layer, and a cover. A ratio R1 calculated by mathematical formula (1): R1=(Df1−Df2)/(Df2−Df3) is not less than 5.00. A ratio R2 calculated by mathematical formula (2): R2=(T2*H2)/H3 is not less than 2.00. A ratio R3 calculated by mathematical formula (3): R3=D1/T3 is less than 50. In mathematical formulas (1) to (3), Df1 represents an amount of compressive deformation of the core, Df2 represents an amount of compressive deformation of a sphere including the core and the mid layer, Df3 represents an amount of compressive deformation of the golf ball, T2 represents a thickness of the mid layer, H2 represents a hardness of the mid layer, H3 represents a hardness of the cover, D1 represents a diameter of the core, and T3 represents a thickness of the cover.