Golf balls are made in a variety of constructions and compositions. Generally, a core is surrounded by a cover, with at least one intermediate layer optionally disposed there between. Examples of conventional golf ball materials range from balata to polybutadiene, ionomer resins, polyurethanes, and/or polyureas. Typically, outer layers are formed about the spherical outer surface of an inner golf ball component via compression molding, casting, or injection molding.
Golf ball manufacturers continuously experiment with constructions and material formulations in order to target, improve and/or preserve aerodynamic and/or inertial properties and achieve desired feel without sacrificing durability. Thinner golf ball layers are often useful for preventing moisture penetration into inner golf ball layers and/or for promoting adhesion between golf ball layers. However, thinner layers can be quite difficult to incorporate reliably during conventional golf ball manufacturing processes such as compression molding or reaction pin injection molding (RPIM). Specifically, when incorporating thin layers, there may be insufficient space to flow out material in RPIM. And compression molding of thin layers can result in “flow lines” at the parting line of the outer material because inner materials can re-melt during the process of applying a very thin outer shell.
For this reason, golf ball manufacturers have sought more flexible processes that can form layers of any desired thickness within golf balls easily and cost effectively. In this regard, conventional thermal spraying techniques such as plasma arc spray, electric arc spray, and flame spray have been considered. See, e.g., U.S. Pat. No. 6,612,939 to Sullivan et al.; and U.S. Pat. No. 8,568,837 to Tomita et al., each of which is hereby incorporated by reference herein in its entirety. However, one drawback with applying golf ball layers via conventional thermal spray methods is that the spray material and the substrate to be coated are vulnerable to damage because each are directly exposed to the heat source as the polymer material is directed onto the substrate's surface. Damage such as unwanted inclusions and/or reduced physical properties of either layer result, which negatively impacts overall golf ball playing characteristics, durability and/or service life span. These drawbacks translate to increased golf ball manufacturing costs. Thus, there is a continued need for methods of making golf balls incorporating layers of any thickness without the risk of a damaging the thin layer material and/or the substrate.
Meanwhile, golf ball manufacturers seek to produce golf balls incorporating single layers that can exhibit multiple desirable properties/characteristics in order to reduce the added manufacturing costs associated with incorporating multiple layers in a golf ball. Ionomer-based formulations typically impart excellent shear and abrasion resistance at Shore D hardnesses of greater than about 60. And castable/injection moldable polyurethane/polyurea formulations can impart both exceptional feel and shear/abrasion resistance at lower hardnesses. Balata, while sometimes difficult to work with, offers great feel. However, combining each of these qualities in a single layer can be challenging.
One golf ball manufacturer tried blending/intermingling the materials of two separate layers into a dimensionally non-distinct blend of those materials via conventional compression molding. See U.S. Pat. No. 9,011,275 of Hebert et al., and related U.S. Patent Publ. No. 2015/0182813, hereby incorporated by reference herein in its entirety. In that golf ball, an original boundary between the two otherwise separate existing layers was eliminated following molding due to differing melt flow rates between the materials of each layer. However, in this approach, two initially separate layers are combined. Thus, there is still a need for golf ball constructions wherein differing materials can be combined initially within and throughout an entire single layer and having any thickness—without the need to modify a boundary between two existing separate layers. Such a unique golf ball formation and construction would be cost effective, improve manufacturing efficiency, and offer new ways for targeting desired properties/playing characteristics.
The golf balls of the present invention and methods of making same consider and solve all of these aforementioned needs.