Multi-Layer Golf Ball

Info

Publication number: 20160250522
Type: Application
Filed: Jan 22, 2016
Publication Date: Sep 1, 2016
Applicant: NIKE, Inc. (Beaverton, OR)
Inventors: Nicholas Yontz (Portland, OR), Chen-Tai Liu (Yun-Lin Hsien)
Application Number: 15/004,368

Abstract

A multi-layer golf ball that provides a consistent feel when struck with different golf clubs has a core center having a diameter D1 and a hardness H1; a first intermediate layer outward from and surrounding the core center; a second intermediate layer outward from and surrounding the first intermediate layer having a diameter D3 and a hardness H3; and a cover outward from and surrounding the second intermediate layer; wherein the ratio of H3 to D3 is at least about 94% of the ratio of H1 to D1 (H3/D3≧0.94 H1/D1).

Description

Description

This Application claims the benefit of U.S. Provisional Application 62/126,249, filed Feb. 27, 2015, which is hereby incorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

The invention concerns multi-layer golf balls. The inventive golf balls are constructed to have a consistent feel when struck with different golf clubs.

INTRODUCTION TO THE DISCLOSURE

This section provides background information related to this disclosure but which may or may not be prior art.

Golf balls have been constructed with multiple layers to improve play characteristics in the short game while maintaining good distance from a tee shot. Golf balls are manufactured using a variety of processes and materials. The response of the ball when struck by a club may vary as a function of the hardness of the materials chosen. For example, a harder ball will typically travel further when struck by a driver than a softer ball. Likewise, a softer ball will typically spin more when struck by a wedge than a harder ball. Using these generalizations, many golfers will select a ball according to their preference for distance or spin control.

Experienced golfers appreciate the feel of a golf ball when struck with a golf club and may select a golf ball for play based in part on whether the ball provides a softer or firmer feel. “Feel” is generally a subjective assessment of the response of the ball when struck by a club, though it is believed to be largely influenced by the sound of the impact, and the acoustic response of the ball may be an important factor in ball selection to some golfers.

Specific details are given to provide a thorough understanding of the disclosed golf ball. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the claims.

The various particular embodiments can be practiced without one or more of the specific details or with other components, materials, and so on. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the embodiments. Reference throughout this specification to “one embodiment,” “an embodiment,” or “embodiments” means that a particular feature, structure, or characteristic is included in at least one embodiment, and the appearances of these phrases in various places throughout this specification do not necessarily all refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in other embodiments.

As used in this description, “a,” “an,” “the,” “at least one,” and “one or more” indicate interchangeably that at least one of the item is present; a plurality of such items may be present unless the context unequivocally indicates otherwise. All numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the technological field with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. In addition, disclosures of ranges are to be understood as specifically disclosing all values and further divided ranges within the range. The terms “comprising,” “including,” and “having” are inclusive and therefore specify the presence of stated features, steps, operations, elements, or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, or components. As used in this specification, the term “or” includes any one and all combinations of the associated listed items. In this description of the invention, for convenience, “polymer” and “resin” are used interchangeably.

The weight-average molecular weight (Mw) and the number-average molecular weight (Mn) refer to molecular weights measured by gel permeation chromatography (GPC) using polystyrene standards.

DRAWING

A drawing is provided and described for illustrative purposes only. The illustrated embodiment is not intended to limit the scope of the present disclosure.

The FIGURE is a cross-section of an embodiment of the disclosed golf ball.

DESCRIPTION

The disclosed golf ball has a core center having a diameter D1 and a hardness H1; a first intermediate layer outward from and surrounding the core center having a diameter D2 and a hardness H2; a second intermediate layer outward from and surrounding the first intermediate layer and having a diameter D3 and a hardness H3; and a cover outward from and surrounding the second intermediate layer having a diameter D4 and a hardness H4. Each of the layers (including the core center as a layer here) has an “effective feel ratio” that is the hardness of the layer (measured on the surface of the layer in situ on a partially-constructed ball or, in the case of the cover, a fully-constructed ball) divided by the diameter of the layer (that is, of the golf ball constructed through that layer, from one point on the surface of the layer through the golf ball center point to an opposite point on the surface of the layer). The effective feel ratio of the second intermediate layer, the ratio of H3 to D3, may be at least about 94% of the effective feel ratio of the core center, the ratio of H1 to D1. The effective feel ratio of the second intermediate layer, the ratio of H3 to D3, may be greater than or equal to the effective feel ratio of the core center, the ratio of H1 to D1 (H3/D3>H1/D1). The effective feel ratio of the second intermediate layer, the ratio of H3 to D3, may be greater than the effective feel ratio of the core center, the ratio of H1 to D1 (H3/D3>H1/D1). For example, the effective feel ratio of the second intermediate layer, the ratio of H3 to D3, may be from 100% up to about 110% or up to about 105% of the effective feel ratio of the core center, the ratio of H1 to D1. In another example, each of the effective feel ratios of the other layers (the ratio of H1 to D1, the ratio of H2 to D2, and the ratio of H4 to D4) may be from about 75% to 100% of the effective feel ratio of the second intermediate laver, the ratio of H3 to D3. The thickness of the second intermediate layer may be at least about 0.65 mm, at least about 0.70 mm, at least about 0.75 mm, or at least about 0.8 mm, and may be up to about 2.0 mm or up to about 1.8 mm or up to about 1.6 mm or up to about 1.5 mm or up to about 1.4 mm. For example, the thickness of the second intermediate layer may from about 0.65 mm to about 2.0 mm or from about 0.7 mm to about 1.8 mm or from about 0.75 mm to about 1.6 mm or from about 0.8 mm to about 1.5 mm.

The disclosed golf ball provides a more consistent feel when struck with a range of golf clubs.

In various examples, the effective feel ratio of the core center, the ratio of H1 to D1, may be from about 75% or from about 80% or from about 85% or from about 90% to 100% of the effective feel ratio of the second intermediate layer, the ratio of H3 to D3. In these or other examples, the effective feel ratio of the first intermediate layer, the ratio of H2 to D2, may be from about 75% or from about 80% or from about 85% or from about 90% to 100% of the effective feel ratio of the second intermediate layer, the ratio of H3 to D3. In these or other examples, the effective feel ratio of the cover, the ratio of H4 to D4, may be from about 75% or from about 80% or from about 85% or from about 90% to 100% of the effective feel ratio of the second intermediate layer, the ratio of H3 to D3.

In general, the core center diameter may be from about 28 mm to about 36 mm, the first intermediate layer thickness may be from about 2.03 mm to about 5.28 mm, the second intermediate layer thickness may be from about 0.65 mm to about 2.0 mm, and the cover thickness may be from about 0.7 mm to about 1.8 mm. The D4 (the cover or golf ball diameter) may be in each case no less than 42.67 mm to comply with the Rules of Golf for competitive play, or from 42.67 mm up to about 45 mm or up to about 44 mm or up to about 43 mm. The second intermediate layer may have a diameter D3 of from about 39.08 mm or from about 39.25 mm or from about 39.5 mm or from about 39.7 mm or from about 40 mm up to about 40.7 mm or up to about 40.8 mm or up to about 41 mm or up to about 41.15 mm or up to about 41.28 mm. For example, the second intermediate layer may have a diameter of from about 39.08 mm up to about 41.28 mm or from about 39.25 mm up to about 41 mm or from about 39.5 mm up to about 40.8 mm or from about 39.7 mm up to about 41.15 mm or from about 40 mm up to about 40.7 mm. The first intermediate layer may have a diameter D2 of from about 35.08 mm or from about 35.5 mm or from about 36 mm or from about 37 mm or from about 37.9 mm up to about 38.9 mm or up to about 39.0 mm or up to about 39.3 mm or up to about 39.6 mm or up to about 39.98 mm. For example, the first intermediate layer may have a diameter D2 of from about 35.08 mm up to about 39.98 mm or from about 35.5 mm up to about 39.6 mm or from about 36 mm up to about 39.3 mm or from about 37 mm up to about 39.0 mm or from about 37.9 mm up to about 38.9 mm. The core center may have a diameter of from about 28 mm to about 36 mm or from about 28 mm to about 32 mm or from about 28 mm to about 31 mm.

Examples of suitable combinations of layer dimensions are provided in Table 1, for which the units are millimeters.

TABLE 1 Core center First intermediate First intermediate Second Cover diameter, layer thickness, layer thickness, intermediate layer thickness, Ex. D1, mm T2, mm T2, mm thickness, T3, mm T4, mm 1 28 5.29 5.28 0.95 1.1 2 29 4.79 4.78 0.95 1.1 3 30 4.29 4.28 0.95 1.1 4 31 3.79 3.78 0.95 1.1 5 32 3.29 3.28 0.95 1.1 6 33 2.79 2.78 0.95 1.1 7 34 2.29 2.28 0.95 1.1 8 28 5.04 5.03 1.2 1.1 9 29 4.54 4.53 1.2 1.1 10 30 4.04 4.03 1.2 1.1 11 31 3.54 3.53 1.2 1.1 12 32 3.04 3.03 1.2 1.1 13 33 2.54 2.53 1.2 1.1 14 34 2.04 2.03 1.2 1.1 15 28 4.64 4.63 2 0.7 16 29 4.14 4.13 2 0.7 17 30 3.64 3.63 2 0.7 18 31 3.14 3.13 2 0.7 19 32 2.64 2.63 2 0.7 20 33 2.14 2.13 2 0.7 21 28 5.99 5.98 0.65 0.7 22 29 5.49 5.48 0.65 0.7 23 30 4.99 4.98 0.65 0.7 24 31 4.49 4.48 0.65 0.7 25 32 3.99 3.98 0.65 0.7 26 33 3.49 3.48 0.65 0.7 27 34 2.99 2.98 0.65 0.7 28 35 2.49 2.48 0.65 0.7 29 28 3.54 3.53 2 1.8 30 29 3.04 3.03 2 1.8 31 30 2.54 2.53 2 1.8 32 31 2.04 2.03 2 1.8 33 28 4.89 4.88 0.65 1.8 34 29 4.39 4.38 0.65 1.8 35 30 3.89 3.88 0.65 1.8 36 31 3.39 3.38 0.65 1.8 37 32 2.89 2.88 0.65 1.8 38 33 2.39 2.38 0.65 1.8

The diameter of the first intermediate layer, D2, is the diameter of the core center, D1, plus two times the thickness T2 of the first intermediate layer: D2=D1+2×(T2); the diameter of the second intermediate layer, D3, is the diameter of the first intermediate layer, D2, plus two times the thickness T3 of the second intermediate layer: D3=D2+2×(T3); and the diameter of the cover D4 is the diameter of the second intermediate layer, D3, plus two times the thickness T4 of the cover, D4=D3+2×(T4), which is the same as the diameter of the golf ball.

The hardnesses and diameters, and thus the relative feel ratios, of the core center, first intermediate layer, second intermediate layer, and cover can be measured in different units. Hardness is measured on a curved surface of the layer. In the case of the cover, which is dimpled, hardness is measured on a land area of the curved surface of the cover. It is understood in this technical field of art that the hardness measured in this way often varies from the hardness of a flat slab of material in a non-linear way that cannot be correlated, for example because of effects of underlying layers. Because of the curved surface, care must be taken to center the golf ball or golf ball subassembly under the durometer indentor (or other applicable measuring device) before a surface hardness reading is obtained and to measure an even area, e.g. on the dimpled surface cover measurements are taken on a land (fret) area between dimples. For example, hardness may be measured using the Shore hardness C or D scale (ASTM D2240C or ASTM D2240D). Hardness may also be measured, for example, with an Asker durometer (ASTM D2240) or as Rockwell hardness (ASTM D785). Diameter may be measured in millimeters, centimeters, inches, mils, and so on. Of course, the hardnesses and diameters of all of the layers are measured in the same way and expressed in the same units in determining the relationships between the second intermediate layer and the other layers.

In particular examples, the golf ball has a core center having a diameter in millimeters D1 and a Shore D hardness H1; a first intermediate :layer outward from and surrounding the core center having a diameter in millimeters D2 and a Shore D hardness H2; a second intermediate layer outward from and surrounding the first intermediate layer and having a diameter in millimeters D3, a thickness in millimeters D3, and a Shore D hardness H3; and a cover outward from and surrounding the second intermediate layer having a diameter in millimeters D4 and a Shore D hardness H4. The thickness of the second intermediate layer, T3, is at least about 0.65 mm. Each of the layers (including the core center as a layer here) has an “effective feel ratio” that is the hardness of the layer (measured on the surface of the layer) divided by the diameter of the layer (that is, of the golf ball constructed through that layer; from one point on the surface of the layer through the golf ball center point to an opposite point on the surface of the layer). The ratio of H3 to D3 may be greater than or equal to the ratio of H1 to D1 (H3/D3≧H1/D1) or may be greater than the ratio of H1 to D1 (H3/D3>H1/D1), for example the ratio of H3 to D3 is equal to the ratio of H1 to D1 or is greater than the ratio of H1 to D1 by no more than about 0.05 (in units of Shore D hardness/mm).

In various examples, the second intermediate layer may have an effective feel ratio of from about 1.5 or from about 1.6 or from about 1.65 or from about 1.68 up to about 1.9 or up to about 1.85 or up to about 1.8 or up to about 1.75, in each case in units of Shore D hardness/mm. Among suitable examples of ranges for the effective feel ratio of the second intermediate layer (H3/D3) are from about 1.5 Shore D hardness/mm) up to about 1.9 Shore D hardness/mm, from about 1.6 Shore D hardness/mm) up to about 1.85 Shore D hardness/mm, from about 1.65 Shore D hardness/mm) up to about 1.8 Shore D hardness/mm, and from about 1.68 Shore D hardness/mm) up to about 1.75 Shore D hardness/mm. The effective feel ratios of the remaining golf ball layers (H1/D1, H2/D2, and H4/D4) may each independently be in a range from equal to the effective feel ratio of the second intermediate layer, H3/D3, to about 0.42 Shore D hardness/mm less than the effective feel ratio of the second intermediate layer, H3/D3. For example, the effective feel ratios of the remaining golf ball layers (H1/D1, H2/D2, and H4/D4) may each independently be in a range from equal to the effective feel ratio of the second intermediate layer, H3/D3, to about 0.3 Shore D hardness/mm less than the effective feel ratio of the second intermediate layer, H3/D3 or to about 0.30 Shore D hardness/mm less than the effective feel ratio of the second intermediate layer, H3/D3 or to about 0.2 Shore D hardness/mm less than the effective feel ratio of the second intermediate layer, H3/D3 or to about 0.15 Shore D hardness/mm less than the effective feel ratio of the second intermediate layer, H3/D3 or to about 0.1 Shore D hardness/mm less than the effective feel ratio of the second intermediate layer, H3/D3, or to about 0.05 Shore D hardness/mm less than the effective feel ratio of the second intermediate layer, H3/D3.

In one embodiment, the second intermediate layer may have an effective feel ratio, H3/D3, of from about 1.65 Shore D hardness/mm to about 1.75 Shore D hardness/mm, the core center may have an effective feel ratio, H1/D1, of from about 1.45 Shore D hardness/mm to about 1.75 Shore D hardness/mm or from about 1.5 Shore D hardness/mm to about 1.7 Shore D hardness/mm, the first intermediate layer may have an effective feel ratio, H2/D2, of from about 1.35 Shore D hardness/mm to about 1.75 Shore D hardness/mm or from about 1.4 Shore D hardness/mm to about 1.6 Shore D hardness/mm, and the cover may have an effective feel ratio, H4/D4, of from about 1.25 Shore D hardness/mm to about 1.6 Shore D hardness/mm or from about 1.3 Shore D hardness/mm to about 1.55 Shore D hardness/mm.

As shown in the FIGURE, a multi-layer golf ball 100 has a core center 110 with a diameter D1 and a surface 115, a first intermediate layer 120 with a diameter D2 and a surface 125 that is radially outward from and surrounds the core center 110, a second intermediate layer 130 with a diameter D3 and a surface 135 that is radially outward from and surround the first intermediate layer 120, and a cover 140 with a diameter D4 and a surface 145 that forms the outermost layer of the golf ball 100. D4 is the actual diameter of the golf ball from a land on one side through the center point of the golf ball to a land on the opposite side. In an embodiment in which the dimple pattern is such that there are no land areas opposite one another on the cover surface, then D4 is taken as the diameter the golf ball would have if the cover were free of dimples (the diameter of the spherical surface the golf ball would have if free of dimples). Surface 115 has a hardness H1. Surface 125 has a hardness H2. Surface 135 has a hardness H3. Surface 145 has a hardness H4. As noted above, H4 is measured on a land (or fret) between dimples.

The coefficient of restitution of the golf ball should be at least 0.78. The golf ball has a suitable initial velocity and distance for various clubs when the golf ball's coefficient of restitution is at least 0.78. The golf ball coefficient of restitution is measured by firing the golf ball by an air cannon at an initial velocity of 40 m/sec at a heavy steel plate about 1.2 meters away from the air cannon. The steel plate is sized to not be moved or deformed by the striking golf ball. A speed monitoring device is located over a distance of 0.6 to 0.9 meters from the cannon. After striking the steel plate, the golf ball rebounds through the speed-monitoring device. The return velocity divided by the initial velocity is the coefficient of restitution (COR). The COR of the core center is measured by testing the formed core center in place of the golf ball. The COR of an intermediate layer is measured by testing the a partially-constructed golf ball formed through the intermediate layer in place of the golf ball. For example, the COR of the first intermediate layer is tested on the first intermediate layer surrounding the core center, while the COR of the second intermediately layer is tested by forming the second intermediate layer around the first intermediate layer and testing the resulting sphere in the COR test method.

The golf ball layers are each independently be made of a thermoplastic composition or a thermoset (i.e., crosslinked to a degree to not be thermoplastic) composition. In general, each layer will include a thermoplastic or thermoset elastomer.

Nonlimiting examples of suitable thermoplastic elastomers that can be used in making the golf ball layers include metal cation ionomers of addition copolymers, metallocene-catalyzed block copolymers of ethylene and α-olefins having 4 to about 8 carbon atoms, thermoplastic polyamide elastomers (PEBA or polyether block polyamides), thermoplastic polyester elastomers, thermoplastic styrene block copolymer elastomers such as poly(styrene-butadiene-styrene), poly(styrene-ethylene-co-butylene-styrene), and poly(styrene-isoprene-styrene), thermoplastic polyurethane elastomers, thermoplastic polyurea elastomers, and dynamic vulcanizates of rubbers in these thermoplastic elastomers and in other thermoplastic matrix polymers.

Useful metal cation ionomers of addition copolymers of ethylenically unsaturated acids include alpha-olefin, particularly ethylene, copolymers with C₃to Cα,β-ethylenically unsaturated carboxylic acids, particularly acrylic or methacrylic acid. The copolymers may also contain one or more further comonomers, for example a softening monomer such as an alkyl acrylate or methacrylate such as a C₁to C₈alkyl acrylate or methacrylate ester. The α,β-ethylenically unsaturated carboxylic acid monomer may be from about 4 weight percent or about 6 weight percent or about 8 weight percent up to about 20 weight percent or up to about 35 weight percent of the copolymer, and the softening monomer, when present, is preferably present in a finite amount, preferably at least about 5 weight percent or at least about 11 weight percent, up to about 23 weight percent or up to about 25 weight percent or up to about 50 weight percent of the copolymer. The hardness of a layer may be increased by using a harder resin, for example an ionomer that is a copolymer of and alpha-olefin and methacrylic acid, optionally with one or more methacrylate comonomers. In general, a higher acid content and higher molecular weight tend to produce a harder polymer.

Nonlimiting specific examples of acid-containing ethylene copolymers include copolymers of ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylic acid/n-butyl acrylate, ethylene/methacrylic acid/isobutyl acrylate, ethylene/acrylic acid/isobutyl acrylate, ethylene/methacrylic acid/n-butyl methacrylate, ethylene/acrylic acid/methyl methacrylate, ethylene/acrylic acid/methyl acrylate, ethylene/methacrylic acid/methyl acrylate, ethylene/methacrylic acid/methyl methacrylate, and ethylene/acrylic acid/n-butyl methacrylate.

The ionomer resin may be a high acid ionomer resin. In general, ionomers prepared by neutralizing acid copolymers including at least about 16 weight % of copolymerized acid residues based on the total weight of the unneutralized ethylene acid copolymer are considered “high acid” ionomers. In these high modulus ionomers, the acid monomer, particularly acrylic or methacrylic acid, is present in about 16 to about 35 weight %. In various embodiments, the copolymerized carboxylic acid may be from about 16 weight %, or about 17 weight % or about 18.5 weight % or about 20 weight % up to about 21.5 weight % or up to about 25 weight % or up to about 30 weight % or up to about 35 weight % of the unneutralized copolymer. A high acid ionomer may be combined with a “low acid” ionomer in which the copolymerized carboxylic acid is less than 16 weight % of the unneutralized copolymer.

The acid moiety in the ethylene-acid copolymer is neutralized by a metal cation. Suitable example cations include lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc, aluminum, or a combination of these cations; in various embodiments alkali metal, alkaline earth metal, or zinc cations are particularly useful. In various embodiments, the acid groups of the ionomer may be neutralized from about 10% or from about 20% or from about 30% or from about 40% to about 60% or to about 70% or to about 75% or to about 80% or to about 90%.

A sufficiently high molecular weight, monomeric organic acid or salt of such an organic acid may be added to the acid copolymer or ionomer so that the acid copolymer or ionomer can be neutralized, without losing processability, to a level above the level that would cause the ionomer alone to become non-melt-processable. An ionomer that is highly neutralized by including such an acid or acid salt is known in the golf ball art as a highly neutralized polymer or highly neutralized acid polymer. The high-molecular weight, monomeric organic acid its salt may be added to the alpha-olefin-unsaturated acid copolymers before they are neutralized or after they are optionally partially neutralized to a level between about 1 and about 100%, provided that the level of neutralization is such that the resulting ionomer remains melt-processable. In generally, when the high-molecular weight, monomeric organic acid is included the acid groups of the copolymer may be neutralized from at least about 40 to about 100%, preferably from at least about 90% to about 100%, and most preferably 100% without losing processability. Such high neutralization, particularly to levels greater than 80%, greater than 90% or greater than 95% or most preferably 100%, without loss of processability can be achieved by (a) melt-blending the ethylene α,β-ethylenically unsaturated carboxylic acid copolymer or a melt-processable salt of the copolymer with an organic acid or a salt of organic acid, and (b) adding a sufficient amount of a cation source up to 110% of the amount needed to neutralize the total acid in the copolymer or ionomer and organic acid or salt to the desired level to increase the level of neutralization of all the acid moieties in the mixture preferably to greater than 90%, preferably greater than 95%, or preferably to 100%. To obtain 100% neutralization, it is preferred to add a slight excess of up to 110% of cation source over the amount stoichiometrically required to obtain the 100% neutralization.

The high molecular weight, monomeric saturated or unsaturated acid may have from 8 or 12 or 18 carbon atoms to 36 carbon atoms or to less than 36 carbon atoms. Nonlimiting suitable examples of the high-molecular weight, monomeric saturated or unsaturated organic acids include stearic, behenic, erucic, oleic, and linoleic acids and their salts, particularly the barium, lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium, strontium, titanium, tungsten, magnesium, or calcium salts of these fatty acids. These may be used in combinations.

Grades of ionomer resins are commercially available from E.I. du Pont de Nemours and Co., Inc. Wilmington, DE under the trademark Surlyn® with hardnesses from about 35-70 Shore D. Highly neutralized acid polymers are also sold by du Pont under the designation HPF with hardnesses from 33 to 55 Shore D.

Thermoplastic polyolefin elastomers may also be used. These are metallocene-catalyzed block copolymers of ethylene and α-olefins having 4 to about 8 carbon atoms prepared by single-site metallocene catalysis of ethylene with a softening comonomer such as hexane-1 or octene-1, for example in a high pressure process in the presence of a catalyst system comprising a cyclopentadienyl-transition metal compound and an alumoxane. Octene-1 is a preferred comonomer to use. These materials are commercially available from ExxonMobil under the tradename Exact and from the Dow Chemical Company under the tradename Engage™. Thermoplastic polyolefin elastomers may be made with hardness at least from about 35 Shore A to about 50 Shore D.

Suitable thermoplastic styrene block copolymer elastomers include poly(styrene-butadiene-styrene), poly(styrene-ethylene-co-butylene-styrene), poly(styrene-isoprene-styrene), and poly(styrene-ethylene-co-propylene) copolymers. These styrenic block copolymers may be prepared by living anionic polymers with sequential addition of styrene and the diene forming the soft block, for example using butyl lithium as initiator. Thermoplastic styrene block copolymer elastomers are commercially available, for example, under the trademark Kraton sold by Kraton Polymers U.S. LLC, Houston, Tex. with hardnesses ranging from 46 to 89 Shore A (approximately 10 to 40 Shore D). Other such elastomers may be made as block copolymers by using polymerizable non-rubber monomers in place of the styrene, including meth(acrylate) esters such as methyl methacrylate and cyclohexyl methacrylate, and other vinyl arylenes, such as alkyl styrenes.

Thermoplastic polyurethane elastomers such as thermoplastic polyester-polyurethanes, polyether-polyurethanes, and polycarbonate-polyurethanes may be used including, without limitation, polyurethanes polymerized using as polymeric diol reactants polyethers and polyesters including polycaprolactone polyesters. These polymeric diol-based polyurethanes are prepared by reaction of the polymeric diol (polyester diol, polyether diol, polycaprolactone diol, polytetrahydrofuran diol, or polycarbonate diol), one or more polyisocyanates, and, optionally, one or more chain extension compounds. Chain extension compounds, as the term is being used, are compounds having two or more functional groups reactive with isocyanate groups, such as the diols, amino alcohols, and diamines. Preferably the polymeric diol-based polyurethane is substantially linear (i.e., substantially all of the reactants are difunctional).

Diisocyanates used in making the polyurethane elastomers may be aromatic or aliphatic. Useful diisocyanate compounds used to prepare thermoplastic polyurethanes include, without limitation, isophorone diisocyanate (IPDI), methylene bis-4-cyclohexyl isocyanate (H₁₂MDI), cyclohexyl diisocyanate (CHDI), m-tetramethyl xylene diisocyanate (m-TMXDI), p-tetramethyl xylene diisocyanate (p-TMXDI), 4,4′-methylene diphenyl diisocyanate (MDI, also known as 4,4′-diphenylmethane diisocyanate), 2,4- or 2,6-toluene diisocyanate (TDI), ethylene diisocyanate, 1,2-diisocyanatopropane, 1,3-diisocyanatopropane, 1,6-diisocyanatohexane (hexamethylene diisocyanate or HDI), 1,4-butylene diisocyanate, lysine diisocyanate, meta-xylylenediioscyanate and para-xylylenediisocyanate (XDI), 4-chloro-1,3-phenylene diisocyanate, 1,5-tetrahydro-naphthalene diisocyanate, 4,4′-dibenzyl diisocyanate, and combinations of these. Nonlimiting examples of higher-functionality polyisocyanates that may be used in limited amounts to produce branched thermoplastic polyurethanes (optionally along with monofunctional alcohols or monofunctional isocyanates) include 1,2,4-benzene triisocyanate, 1,3,6-hexamethylene triisocyanate, 1,6,11-undecane triisocyanate, bicycloheptane triisocyanate, triphenylmethane-4,4′,4″-triisocyanate, isocyanurates of diisocyanates, biurets of diisocyanates, allophanates of diisocyanates, and the like.

Nonlimiting examples of suitable diols that may be used as extenders include ethylene glycol and lower oligomers of ethylene glycol including diethylene glycol, triethylene glycol, and tetraethylene glycol; propylene glycol and lower oligomers of propylene glycol including dipropylene glycol, tripropylene glycol, and tetrapropylene glycol; cyclohexanedimethanol, 1,6-hexanediol, 2-ethyl-1,6-hexanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,3-propanediol, butylene glycol, neopentyl glycol, dihydroxyalkylated aromatic compounds such as the bis (2-hydroxyethyl) ethers of hydroquinone and resorcinol; p-xylene-α,α-diol; the bis(2-hydroxyethyl)ether of p-xylene-α,α′-diol; m-xylene-α,α′-diol, and combinations of these. Other active hydrogen-containing chain extenders that contain at least two active hydrogen groups may be used, for example, dithiols, diamines, or compounds having a mixture of hydroxyl, thiol, and amine groups, such as alkanolamines, aminoalkyl mercaptans, and hydroxyalkyl mercaptans, among others. Suitable diamine extenders include, without limitation, ethylene diamine, diethylene triamine, triethylene tetraamine, and combinations of these. Other typical chain extenders are amino alcohols such as ethanolamine, propanolamine, butanolamine, and combinations of these. The molecular weights of the chain extenders preferably range from about 60 to about 400. Alcohols and amines are preferred.

In addition to difunctional extenders, a small amount of a trifunctional extender such as trimethylolpropane, 1,2,6-hexanetriol and glycerol, or monofunctional active hydrogen compounds such as butanol or dimethylamine, may also be included.

The polyester diols used in forming a thermoplastic polyurethane elastomer are in general prepared by the condensation polymerization of one or more polyacid compounds and one or more polyol compounds. Preferably, the polyacid compounds and polyol compounds are di-functional, i.e., diacid compounds and diols are used to prepare substantially linear polyester diols, although minor amounts of mono-functional, tri-functional, and higher functionality materials can be included to provide a slightly branched, but uncrosslinked polyester polyol component. Suitable dicarboxylic acids include, without limitation, glutaric acid, succinic acid, malonic acid, oxalic acid, phthalic acid, isophthalic acid, hexahydrophthalic acid, adipic acid, maleic acid, suberic acid, azelaic acid, dodecanedioic acid, their anhydrides and polymerizable esters (e.g., methyl esters) and acid halides (e.g., acid chlorides), and mixtures of these. Suitable polyols include those already mentioned, especially the diols. Typical catalysts for the esterification polymerization are protonic acids, Lewis acids, titanium alkoxides, and dialkyltin oxides.

A polymeric polyether or polycaprolactone diol reactant for preparing thermoplastic polyurethane elastomers may be obtained by reacting a diol initiator, e.g., 1,3-propanediol or ethylene or propylene glycol, with a lactone or alkylene oxide chain-extension reagent. Lactones that can be ring opened by an active hydrogen are well-known in the art. Examples of suitable lactones include, without limitation, ε-caprolactone, γ-caprolactone, β-butyrolactone, β-propriolactone, γ-butyrolactone, α-methyl-γ-butyrolactone,β-methyl-γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-decanolactone, δ-decanolactone, γ-nonanoic lactone, γ-octanoic lactone, and combinations of these. In one preferred embodiment, the lactone is ε-caprolactone. Useful catalysts include those mentioned above for polyester synthesis. Alternatively, the reaction can be initiated by forming a sodium salt of the hydroxyl group on the molecules that will react with the lactone ring. In other embodiments, a diol initiator may be reacted with an oxirane-containing compound or cyclic ether to produce a polyether diol to be used in the polyurethane elastomer polymerization. Alkylene oxide polymer segments include, without limitation, the polymerization products of ethylene oxide, propylene oxide, 1,2-cyclohexene oxide, 1-butene oxide, 2-butene oxide, 1-hexene oxide, tert-butylethylene oxide, phenyl glycidyl ether, 1-decene oxide, isobutylene oxide, cyclopentene oxide, 1-pentene oxide, and combinations of these. The oxirane- or cyclic ether-containing compound is preferably selected from ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, and combinations of these. The alkylene oxide polymerization is typically base-catalyzed. The polymerization may be carried out, for example, by charging the hydroxyl-functional initiator compound and a catalytic amount of caustic, such as potassium hydroxide, sodium methoxide, or potassium tert-butoxide, and adding the alkylene oxide at a sufficient rate to keep the monomer available for reaction. Two or more different alkylene oxide monomers may be randomly copolymerized by coincidental addition or polymerized in blocks by sequential addition. Homopolymers or copolymers of ethylene oxide or propylene oxide are preferred. Tetrahydrofuran may be polymerized by a cationic ring-opening reaction using such counterions as SbF₆⁻, AsF₆⁻, PF₆⁻, SbCl₆⁻, BF₄⁻, CF₃SO₃⁻, FSO₃⁻, and ClO₄⁻. Initiation is by formation of a tertiary oxonium ion. The polytetrahydrofuran segment can be prepared as a “living polymer” and terminated by reaction with the hydroxyl group of a diol such as any of those mentioned above. Polytetrahydrofuran is also known as polytetramethylene ether glycol (PTMEG).

Aliphatic polycarbonate diols that may be used in making a thermoplastic polyurethane elastomer may be prepared by the reaction of diols with dialkyl carbonates (such as diethyl carbonate), diphenyl carbonate, or dioxolanones (such as cyclic carbonates having five- and six-member rings) in the presence of catalysts like alkali metal, tin catalysts, or titanium compounds. Useful diols include, without limitation, any of those already mentioned. Aromatic polycarbonates are usually prepared from reaction of bisphenols, e.g., bisphenol A, with phosgene or diphenyl carbonate.

In various embodiments, the polymeric diol preferably has a weight average molecular weight of at least about 500, more preferably at least about 1000, and even more preferably at least about 1800 and a weight average molecular weight of up to about 10,000, but polymeric diols having weight average molecular weights of up to about 5000, especially up to about 4000, may also be preferred. The polymeric diol advantageously has a weight average molecular weight in the range from about 500 to about 10,000, preferably from about 1000 to about 5000, and more preferably from about 1500 to about 4000. The weight average molecular weights may be determined by ASTM D-4274.

The reaction of the polyisocyanate, polymeric diol, and diol or other chain extension agent is typically carried out at an elevated temperature in the presence of a catalyst. Typical catalysts for this reaction include organotin catalysts such as stannous octoate, dibutyl tin dilaurate, dibutyl tin diacetate, dibutyl tin oxide, tertiary amines, zinc salts, and manganese salts. Generally, for elastomeric polyurethanes, the ratio of polymeric diol, such as polyester diol, to extender can be varied within a relatively wide range depending largely on the desired hardness of the final polyurethane elastomer. For example, the equivalent proportion of polyester diol to extender may be within the range of 1:0 to 1:12 and, more preferably, from 1:1 to 1:8. Preferably, the diisocyanate(s) employed are proportioned such that the overall ratio of equivalents of isocyanate to equivalents of active hydrogen containing materials is within the range of 1:1 to 1:1.05, and more preferably, 1:1 to 1:1.02. The polymeric diol segments typically are from about 35% to about 65% by weight of the polyurethane polymer, and preferably from about 35% to about 50% by weight of the polyurethane polymer.

The selection of diisocyanate, extenders, polymeric diols, and the weight percent of the polymeric diols used takes into account the desired specific gravity and hardness of the polyurethane elastomer.

Thermoset polyurethane layers may be made by molding, for example reaction injection molding or compression molding processes, a two-component mixture, one component being isocyanate-functional and the second component being hydroxyl-functional. At least one of the components, generally the isocyanate-functional component, has a functionality greater than two so that the product is crosslinked. For example, the isocyanate composition may be an oligomer, such as an isocyanurate or an isocyanate-functional product of a diisocyanate and a triol, tetraol, or higher polyol, for example trimethylolpropane. The reaction mixture may contain a catalyst such as any of those already mentioned as useful for reaction isocyanate groups with hydroxyl groups.

Suitable thermoplastic polyurea elastomers may be prepared by reaction of one or more polymeric diamines or polyols with one or more of the polyisocyanates already mentioned and one or more diamine extenders. Nonlimiting examples of suitable diamine extenders include ethylene diamine, 1,3-propylene diamine, 2-methyl-pentamethylene diamine, hexamethylene diamine, 2,2,4- and 2,4,4-trimethyl-1,6-hexane diamine, imino-bis(propylamine), imido-bis(propylamine), N-(3-aminopropyl)-N-methyl-1,3-propanediamine), 1,4-bis(3-aminopropoxy)butane, diethyleneglycol-di(aminopropyl)ether), 1-methyl-2,6-diamino-cyclohexane, 1,4-diamino-cyclohexane, 1,3- or 1,4-bis(methylamino)-cyclohexane, isophorone diamine, 1,2- or 1,4-bis(sec-butylamino)-cyclohexane, N,N′-diisopropyl-isophorone diamine, 4,4′-diamino-dicyclohexylmethane, 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane, N,N′-dialkylamino-dicyclohexylmethane, and 3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-dicyclohexylmethane. Polymeric diamines include polyoxyethylene diamines, polyoxypropylene diamines, poly(oxyethylene-oxypropylene) diamines, and poly(tetramethylene ether) diamines. The amine- and hydroxyl-functional extenders already mentioned may be used as well. Generally, as before, trifunctional reactants are limited and may be used in conjunction with monofunctional reactants to prevent crosslinking.

Thermoset polyurea layers may be made similarly to thermoset polyurethane layers, using an amine-functional component in place or (or in combination with) the hydroxyl-functional component.

Suitable thermoplastic polyamide elastomers may be obtained by: (1) polycondensation of (a) a dicarboxylic acid, such as oxalic acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, 1,4-cyclohexanedicarboxylic acid, or any of the other dicarboxylic acids already mentioned with (b) a diamine, such as ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, or decamethylenediamine, 1,4-cyclohexanediamine, m-xylylenediamine, or any of the other diamines already mentioned; (2) a ring-opening polymerization of a cyclic lactam, such as ε-caprolactam or w-laurolactam; (3) polycondensation of an aminocarboxylic acid, such as 6-aminocaproic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, or 12-aminododecanoic acid; or (4) copolymerization of a cyclic lactam with a dicarboxylic acid and a diamine to prepare a carboxylic acid-functional polyamide block, followed by reaction with a polymeric ether diol (polyoxyalkylene glycol) such as any of those already mentioned. Polymerization may be carried out, for example, at temperatures of from about 180° C. to about 300° C. Specific examples of suitable polyamide blocks include NYLON 6, NYLON 66, NYLON 610, NYLON 11, NYLON 12, copolymerized NYLON, NYLON MXD6, and NYLON 46 block copolymer elastomers. Thermoplastic poly(ether amide) block copolymer elastomers (PEBA) are commercially available under the trademark Pebax® from Arkema.

The effects of the type and molecular weights of the soft segment polymeric polyols used in making polyurea elastomers and polyamide elastomers are analogous to the same effects in making thermoplastic polyurethane elastomers.

Thermoplastic polyester elastomers have blocks of monomer units with low chain length that form the crystalline regions and blocks of softening segments with monomer units having relatively higher chain lengths. Thermoplastic polyester elastomers are commercially available under the trademark Hytrel® from E.I. du Pont de Nemours and Co., Inc. Grades with a hardness of about 25 Shore D to about 70 Shore D are available.

Suitable thermoplastic materials may include combinations of thermoplastic elastomers. In one embodiment, the layer material includes a combination of a metal ionomer of a copolymer of ethylene and at least one of acrylic acid and methacrylic acid, a metallocene-catalyzed copolymer of ethylene and an α-olefin having 4 to about 8 carbon atoms, and a metal salt of an unsaturated fatty acid. This material may be prepared as described in Statz et al., U.S. Pat. No. 7,375,151 or as described in Thomas J. Kennedy, III, “Process for Making Thermoplastic Golf Ball Material and Golf Ball with Thermoplastic Material, U.S. Patent Application Publication No. 2014/0274469, the entire contents of both being incorporated herein by reference.

Thermoplastic layer materials may include dispersed domains of cured rubbers, which may be incorporated in a thermoplastic elastomer matrix via dynamic vulcanization of rubbers in any of these thermoplastic elastomers or in other thermoplastic polymers. Examples of such composition are described John C. Chen, U.S. patent application Ser. No. 14/029,136 entitled “Dynamically Crosslinked Thermoplastic Material Process,” filed Sep. 17, 2013; 14/031,626 entitled “Dynamically Crosslinked Thermoplastic Material Process,” filed Sep. 19, 2013; and Ser. No. 14/029,148 entitled “Dynamically Crosslinked Thermoplastic Material Process,” filed Sep. 17, 2013 and in Voorheis et al, U.S. Pat. No. 7,148,279, each of which is incorporated herein by reference. In various embodiments, the first thermoplastic material may include a thermoplastic dynamic vulcanizate of a rubber in a non-elastomeric matrix resin such as polypropylene. Thermoplastic vulcanizates commercially available from ExxonMobil under the tradename Santoprene™ are believed to be vulcanized domains of EPDM in polypropylene and are available in hardnesses of up to 50 Shore D.

The golf ball may have a rubber layer. As the base rubber, a variety of rubbers (thermoplastic elastomer) may be used, such as polybutadiene rubber (BR), styrene-butadiene rubber (SBR), natural rubber (NR), polyisoprene rubber OR), polyurethane rubber (PO, butyl rubber (IIR), vinyl polybutadiene rubber (VBR), ethylene-propylene rubber (EPDM), nitrile rubber (NBR), and silicone rubber. Examples of the polybutadiene rubber (BR) are 1,2-polybutadiene and cis-1,4-polybutadiene. The rubber polymers may be used singly or two or more may be used in combination. The weight-average molecular weight (Mw) may typically be at least 25×10⁴, for example at least 30×10. The weight-average molecular weight (Mw) will typically be not more than 150×10⁴, for example not more than 100×10⁴for sufficient rebound while maintaining workability of the composition.

The cis-1,4 bond content in the diene polymer, although not subject to any particular limitation, is typically at least about 90%, or at least about 93%, or at least about 95%. The trans-1,4 bond content in the diene polymer, although not subject to any particular limitation, is typically not more than 7%, for example not more than about 5% or not more than about 4%, and still more preferably not more than about 3.5% for good ball rebound. The 1,2-vinyl bond of the rubber polymers, although not subject to any particular limitation, is typically not more than 3%, or not more than 2.0%, or not more than 1.5% for good ball rebound.

The diene polymer may be modified with a coupling agent or a polyvalent modifier exemplified by tin, silicon, phosphorus or nitrogen-containing compounds, epoxy group-containing compound, ester compounds and carboxylic acids. Illustrative examples include tin tetrachloride, silicon tetrachloride, phosphorus trichloride, dibutyltin dichloride, dioctyltin bisoctylmaleate (DOTBOM), polyisocyanate compounds, polymethyl methacrylate, maleic acid, and 3-glycidyloxypropyltrimethoxysilane. The coupling agents and polyvalent modifiers react with the diene polymer to improve the cold flow properties and may increase golf ball rebound.

The base rubber may be formulated with any of co-cross linking agents such as unsaturated carboxylic acids or their salts, initiators including organic peroxides, isomerization agents, peptizing agents, sulfur and organic sulfur compounds. As the co-cross linking agent, it is preferable to use, for example, an α,β-ethylenically unsaturated carboxylic acid, for example acrylic acid, methacrylic acid, crotonic acid, maleic acid, or fumaric acid, or a metal salt of an α,β-ethylenically unsaturated carboxylic acid, for example a zinc salt, magnesium salt or calcium salt. The co-crosslinking agent may be used in an amount, for example, based on 100 parts by weight rubber, of about 5 parts or more by weight or about 10 parts by weight or more or 15 parts by weight or more and up to about 70 parts or up to about 50 parts or less by weight or not more than 40 parts by weight or not more than 35 parts by weight. More co-crosslinker increases hardness, but too much may result in poorer durability.

Suitable examples of the organic peroxide include dicumyl peroxide, 1,1-di(t-butylperoxy)-3,3,54rimethylcyclohexane, and 1,1-di(t-butylperoxy)cyclohexane, organic peroxides may be used in combination, for example by using an organic peroxide having a shorter half-life at a given temperature with an organic peroxide having a longer half-life at the given temperature. The organic peroxide or peroxides may be included, although not subject to any particular limitation, is typically at least about 0.05 part by weight, or at least 0.1 part by weight or at least 0.15 part by weight and up to about 3 parts by weight or up to about 2 parts by weight or up to about 1 part by weight or up to about 0.8 part by weight or up to about 0.6 part by weight, in each case based on 100 parts by weight of the base rubber.

Suitable examples of organosulfur compounds include thiophenols, thion.aphthols, halogenated thiophenols, and metal salts thereof illustrative examples include pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol, p-chlorothiophenol, and zinc salts thereof; diphenylpolysulfides, dihenzylpolysulfides, dibenzoylpolysulfides, dibenzothiazoylpolysulfides and dithiobenzoylpolysulfides having 2 to 4 sulfurs; alkylphenyldisulfides; and furan ring-bearing sulfur compounds and thiophene ring-bearing sulfur compounds, particularly diphenyidisulfide or the zinc salt of pentachlorothiophenol. The organosulfur compounds may be at least about 0.05 part by weight or at least about 0.2 part by weight or at least about 0.4 part by weight or at least about 0.7 part by weight or at least about 0.9 part by weight and up to about 5 parts by weight or up to about 4 parts by weight or up to about 3 parts by weight or up to about 2 parts by weight or up to about 1,5 parts by weight, based in each case on 100 parts by weight of the base rubber polymer. The amount used is selected for good rebound at a desired layer hardness.

The vulcanization conditions are exemplified by a vulcanization temperature of from 100 to 200° C. and a vulcanization time of from 10 to 40 minutes.

One or more plasticizers may be incorporated to adjust the hardness of the layer. One example of such a plasticizer is the high molecular weight, monomeric organic acid or its salt that may be incorporated, for example, with an ionomer polymer as already described, including metal stearates such as zinc stearate, calcium stearate, barium stearate, lithium stearate and magnesium stearate. For most thermoplastic elastomers, the percentage of hard-to-soft segments is adjusted if lower hardness is desired rather than by adding a plasticizer.

The surface hardnesses of the layers depend on the polymer selected and may depend on degree of crosslinking (in particular for a thermoset material) and on nonpolymeric materials included. Various fillers may be added to the layer compositions for altering hardness or other properties of the layer. Nonlimiting examples of suitable fillers include clay, talc, asbestos, graphite, glass, mica, calcium metasilicate, barium sulfate, zinc sulfide, aluminum hydroxide, silicates, diatomaceous earth, carbonates (such as calcium carbonate, magnesium carbonate and the like), metals (such as titanium, tungsten, aluminum, bismuth, nickel, molybdenum, iron, copper, brass, boron, bronze, cobalt, beryllium and alloys of these), metal oxides (such as zinc oxide, iron oxide, aluminum oxide, titanium oxide, magnesium oxide, zirconium oxide and the like), particulate synthetic plastics (such as high molecular weight polyethylene, polystyrene, polyethylene ionomeric resins and the like), particulate carbonaceous materials (such as carbon black, natural bitumen and the like), as well as cotton flock, cellulose flock and/or leather fiber. The amount of inorganic filler included may be at least about 1 part by weight or at least about 5 parts by weight or at least about 10 parts by weight or at least about 15 parts by weight up to about 80 parts by weight or up to about 65 parts by weight or up to about 50 parts by weight or up to about 40 parts by weight, in each case based on 100 parts by weight polymer in the layer composition.

Other customary additives can also be included in the layer materials, for example dispersants, antioxidants such as phenols, phosphites, and hydrazides, processing aids, surfactants, stabilizers, and so on.

Layer compositions may be made by conventional methods, such as melt mixing in a single- or twin-screw extruder, a Banbury mixer, an internal mixer, a two-roll mill, or a ribbon mixer. Typically the core center is formed first, then the first intermediate layer is molded around the core center, the second intermediate layer is formed around the first intermediate layer, and the cover is formed around the second intermediate layer. The layers may be formed by injection molding or compression molding with a typical mold temperature in the range of 150° C. to 230° C. The layers may be formed into hemispherical shells that are then compression molded around a core center or other partially-constructed ball to form the next outer layer. The cover may also be formed on the multi-layer inner ball by injection molding, compression molding, casting, and so on. As each outer layer is added, the core center or partially constructed ball of the core center and other layer(s) may be set inside a mold, and the material of the next outer layer may be introduced into the mold. A further layer may also be molded on the partially-constructed ball by pre-molding a pair of hemispherical shells from the layer material by die casting or another molding method, enclosing the partially-constructed ball in the hemispherical shells, and compression molding at, for example, between 120° C. and 170° C. for a period of 1 to 5 minutes to attach the hemispherical shells around the inner partial ball. The partially-constructed ball may be surface-treated before the hemispherical shells are molded around it to increase the adhesion between the partially-constructed ball and hemispherical shells. Nonlimiting examples of suitable surface preparations include mechanical or chemical abrasion, corona discharge, plasma treatment, or application of an adhesion promoter such as a silane or of an adhesive. The cover typically has a dimple pattern and profile to provide desirable aerodynamic characteristics to the golf ball.

The molded layers may be ground to a desired diameter after cooling. Grinding can also be used to remove flash, pin marks, and gate marks due to the molding process.

For example, one of the core center and the first intermediate layer may be made of one of the described rubber compositions, while the other of the core center and the first intermediate layer may be made of a highly neutralized acid polymer composition, optionally further including an ionomer, each as described above. The second intermediate layer may include any of the thermoplastic elastomers described, for example an ionomer, a polyurethane elastomer such as a polyurethane-polycarbonate elastomer, a thermoplastic polyamide elastomer, or a thermoplastic styrene block copolymer elastomer.

The cover may be formulated with a pigment, such as a yellow or white pigment, and in particular a white pigment such as titanium dioxide or zinc oxide. Generally titanium dioxide is used as a white pigment, for example in amounts of from about 0.5 parts by weight or 1 part by weight to about 8 parts by weight or 10 parts by weight based on 100 parts by weight of polymer. In various embodiments, a white-colored cover may be tinted with a small amount of blue pigment or brightener.

The cover may also contain one or more customary additives such as dispersants, hindered amine light stabilizers such as piperidines and oxanalides, ultraviolet light absorbers such as benzotriazoles, triazines, and hindered phenols, antioxidants such as phenols, phosphites, and hydrazides, defoaming agents, processing aids, surfactants, fluorescent materials and fluorescent brighteners, stabilizers, processing aids, and so on. Other exemplary cover materials include dyes such as blue dye, pigments such as titanium dioxide and zinc oxide, and antistatic agents.

In various embodiments, the core center includes a highly neutralized acid polymer composition, the first intermediate layer includes a rubber composition, the second intermediate layer includes an ionomer composition, and the cover includes a thermoplastic or thermoset polyurethane composition.

The golf balls can be of any size, although the USGA requires that golf balls used in competition have a diameter of at least 1.68 inches (42.672 mm) and a weight of no greater than 1.62 ounces (45.926 g). For play outside of USGA competition, the golf balls can have smaller diameters and be heavier. The weight of the golf bail may be from about 40 g or from about 44 g up to about 48 g, and in particularly according to the Rules of Golf for competitive play, preferably not more than 45.93 g.

After a golf ball has been molded, it may undergo various further processing steps such as buffing, painting and marking. In a particularly preferred embodiment of the invention, the golf ball has a dimple pattern that coverage of 65% or more of the surface. The golf ball typically is coated with at least one layer of a durable, abrasion--resistant and relatively non-yellowing finish coat. Optionally, a layer of coating may incorporate various color and effect pigments to give the golf ball a desired appearance. Flake effect pigments produce a gonioapparent effect in a coating layer, described in ASTM F284. Suitable flake effect pigments include metallic flake pigments like aluminum flake pigments including colored aluminum flake pigment, copper flake pigments, zinc flake pigments, stainless steel flake pigments, and bronze flake pigments and pearlescent flake pigments including treated micas like titanium dioxide-coated mica pigments and iron oxide-coated mica pigments to give the coatings a different appearance or color when viewed at different angles. Nonlimiting examples of other suitable pigments include inorganic pigments such as titanium dioxide, carbon black, ocher, sienna, umber, hematite, limonite, red iron oxide, transparent red iron oxide, black iron oxide, brown iron oxide, ferric ammonium ferrocyanide (Prussian blue), and ultramarine, and organic pigments such as metallized and non-metallized azo reds, quinacridone reds and violets, perylene reds, copper phthalocyanine blues and greens, carbazole violet, monoarylide and diarylide yellows, benzimidazolone yellows, tolyl orange, naphthol orange, and so on. The pigment or pigments are preferably dispersed in a resin or polymer or with a pigment dispersant, such as binder resins of the kind already described, according to known methods. In general, the pigment and dispersing resin, polymer, or dispersant are brought into contact under a shear high enough to break the pigment agglomerates down to the primary pigment particles and to wet the surface of the pigment particles with the dispersing resin, polymer, or dispersant. The breaking of the agglomerates and wetting of the primary pigment particles are important for pigment stability and color development. Flake pigments do not agglomerate and may generally be simply stirred into the coating.

EXAMPLES

Four golf balls were prepared as shown in Table 2. Parts are by weight (pbw). The core centers were prepared from highly neutralized acid polymer compositions.

Examples 1 and 2 included barium sulfate to adjust the hardness of the core center material. The hardness of each of the core centers is shown in Table 3. The Shore D hardness was measured on the formed core center spheres. Each of the first intermediate layers of Examples 1-4 was prepared from a cured polybutadiene rubber composition (ZDA crosslinker) containing the stated amounts of zinc oxide and barium sulfate. The hardness of each of the first intermediate layers is shown in Table 3. The Shore D hardness was measured on the surface of the first intermediate layer after it was formed over the core center. Each of the second intermediate layers of Examples 1-4 was prepared from an ionomer resin (ionomer of ethylene acid copolymer) composition. The hardness of each of the second intermediate layers is shown in Table 3. The Shore D hardness was measured on the surface of the second intermediate layer after it was formed over the of the first intermediate layer--core center inner sphere. Finally, a polyurethane cover containing 100 pbw polyurethane and 10 pbw titanium dioxide was formed as the outermost golf ball layer around the second intermediate layer. The hardness of each of the cover layers is shown in Table 3. Example 3 was made with a softer polyurethane. The hardness of the cover surface was measured on a land area between dimples.

TABLE 2 Example 1 Example 2 Example 3 Example 4 Core highly 100 pbw 100 pbw 100 pbw 100 pbw Center neutralized acid polymer BaSO₄ 20 pbw 20 pbw Diameter 28 mm 31 mm 31 mm 31 mm Shore D 49 49 48 48 Hardness first high cis 126.3 pbw 126.3 pbw 126.3 pbw 126.3 pbw interme- polybutadiene diate composition layer zinc oxide 11 pbw 11 pbw 11 pbw 11 pbw barium sulfate 18.5 pbw 18.5 pbw 18.5 pbw 18.5 pbw Diameter 38.6 mm 38.6 mm 38.1 mm 38.6 mm Shore D 54 54 53 58 Hardness second ionomer resin 100 pbw 100 pbw 100 pbw 100 pbw interme- Diameter 40.50 mm 40.50 mm 40.50 mm 40.50 mm diate Shore D 68 68 70 70 layer Hardness Cover Harder TPU 100 pbw 100 pbw 100 pbw Softer TPU 100 pbw TiO₂ 10 pbw 10 pbw 10 pbw 10 pbw Diameter 42.67 mm 42.67 mm 42.67 mm 42.67 mm Shore D 60 60 56 63 Hardness Dimple count 360 360 360 360

In addition, three commercial golf balls were tested: a Titleist ProVIX golf ball, a Callaway Tour iS golf ball, and a Nike 20XI X golf ball. The effective feel ratios for each golf ball tested are shown in Table 3.

TABLE 3 Titleist Callaway Nike Example 1 Example 2 Example 3 Example 4 ProVIX Tour iS 20XI X Core center Shore D hardness 49 49 48 48 49 44.5 50 (H1) Diameter (D1) 28 31 31 31 25 23.8 24.6 H1/D1 1.75 1.58 1.55 1.55 1.96 1.87 2.03 First intermediate layer Shore D hardness 54 54 53 58 61.5 54.5 57 (H2) Diameter (D2) 38.6 38.1 38.6 38.6 39.42 38.5 38.6 H2/D2 1.40 1.42 1.37 1.50 1.56 1.42 1.48 Second intermediate layer Shore D hardness 68 68 70 70 63 63 68 (H3) Diameter (D3) 40.5 40.5 40.5 40.5 41.17 41.73 40.5 H3/D3 1.68 1.68 1.73 1.73 1.53 1.51 1.68 Cover Shore D hardness 60 60 56 63 62 60.5 56 (H4) Diameter (D4) 42.67 42.67 42.67 42.67 42.75 42.79 42.8 H4/D4 1.41 1.41 1.31 1.48 1.45 1.41 1.31 H3/D3 minus −0.07 0.10 0.18 0.18 −0.43 −0.36 −0.35 H1/D1 H3/D3 minus 0.28 0.26 0.36 0.23 −0.03 0.09 0.20 H2/D2 H3/D3 minus 0.27 0.27 0.42 0.25 0.08 0.10 0.37 H4/D4 H1/D1 minus 0.31 0.17 0.24 0.07 0.41 0.46 0.72 H4/D4 Largest difference 0.35 0.27 0.42 0.25 0.51 0.46 0.72 between effective feel ratios

Each of Example golf balls 1, 3, and 4 and the three commercial golf balls was tested for the sound produced in a sound drop test as described in US Patent Application Publication No. 20014/0260635, paragraph [0091] and FIG. 13. The sound drop test was conducted by placing a microphone array such that the stand is facing the drop track and the frequency array at base is 14 inches from the target drop area. All microphones in frequency array must be 14 inches from the target drop area. A test ball is dropped in the target drop area, and the sound of its impact is recorded. The peak frequency, SPL loudness, and spectral centroid of the recorded waveform are calculated. The test results are shown in Table 4.

TABLE 4 SPL Spectral Peak Frequency (kHz) Loudness (dBA) Centroid Example 1 3.167 −43.465 4.280 Titleist ProV1X 3.664 −43.254 3.765 Callaway Tour iS 3.656 −42.991 3.699 Nike 20XI X 4.450 −42.590 4.572 Example 3 3.321 −44.690 3.824 Example 4 3.304 −44.707 3.685

The results of the sound drop test show Example balls 1, 3, and 4 have lower peak frequency and lower SPL loudness values. Balls exhibiting lower peak frequency and lower SPL loudness values are generally perceived by golfers to have excellent sound and feel when hitting shorter shot like chips or putts.

Each of Example golf balls 1, 3, and 4 and the three commercial golf balls were also tested for “feel” in this way. Three experienced golfers struck each test ball with a putter, 9-iron, 6-iron, and driver in that club order. The order in which the balls were tested was random for each player. Each player rated the feel of the test ball when hit with each club on a scale of 1 to 3, with 3 being the best feel. The average of the three players' ratings are recorded in Table 5.

TABLE 5 Feel (1-3, 3 is best feel) Exam- Exam- Titleist Callaway Nike Example 1 ple 3 ple 4 ProV1X Tour iS 20XI X Driver 2.3 2.7 2.7 2.0 1.7 1.7 6-Iron 2.7 2.7 2.7 2.7 1.3 1.0 9-Iron 2.3 2.7 2.3 2.0 1.0 1.3 Putter 1.7 2.7 2.0 2.0 1.0 1.0 Average 2.3 2.7 2.4 2.2 1.3 1.3 Average 2.4 2.7 2.6 2.2 1.3 1.3 without putter Standard 0.4 0.0 0.3 0.3 0.3 0.3 Deviation

The results in Table 5 show that the golf balls of the invention provide a marked improvement in feel and in having a consistently good feel for shots with all golf clubs.

The description is merely exemplary in nature and, thus, variations that do not depart from the gist of the disclosure are a part of the invention. Variations are not to be regarded as a departure from the spirit and scope of the disclosure

Claims

1. A golf ball, comprising:

a core center having a diameter in millimeters Di and a Shore D hardness Hi;

a first inter nediate layer outward from and surrounding the core center having a diameter in millimeters D2 and a Shore D hardness H2;

a second intermediate layer outward from and surrounding the first intermediate layer having a diameter in millimeters D3, a thickness in millimeters T3, and a Shore D hardness H3; and

a cover outward from and surrounding the second intermediate layer having a diameter in millimeters D4 and a Shore D hardness H4;

wherein T3 is at least about 0.65 mm; and

wherein the ratio of H3 to D3 minus the ratio of H1 to D1 (H3/D3−H1/D1) is at least about −0.1 (Shore D hardness/mm).

2. A golf ball according to claim 1, wherein the ratio of H3 to D3 is greater than or equal to the ratio of H1 to D1 (H3/D3≧H1/D1).

3. A golf ball according to claim 2, wherein the ratio of H3 to D3 is equal to the ratio of H1 to D1 or is greater than the ratio of H1 to D1 by no more than about 0.05 (Shore D hardness/mm).

4. A golf ball according to claim 1, wherein the maximum difference in value between the ratios of H1 to D1 (H1/D1), H2 to D2 (H2/D2), H3 to D3 (H3/D3), H4 to D4 (H4/D4) is up to about 0.42 (Shore D hardness/mm).

5. A golf ball according to claim 4, wherein the maximum difference in value between the ratios of H1 to D1 (H1/D1), H2 to D2 (H2/D2), H3 to D3 (H3/D3), H4 to D4 (H4/D4) is up to about 0.30 (Shore D hardness/mm).

6. A golf ball according to claim 1, the ratio of H3 to D3 is greater than or equal to the ratio of H2 to D2 (H3/D3≧H2/D2).

7. A golf ball according to claim 6, wherein the ratio of H3 to D3 is equal to the ratio of H2 to D2 or is greater than the ratio of H2 to D2 by no more than about 0.15 (Shore D hardness/mm).

8. A golf ball according to claim 1, wherein the ratio of H1 to D1 is greater than or equal to the ratio of H4 to D4 (H1/D1≧H4/D4).

9. A golf ball according to claim 8, wherein the ratio of H1 to D1 is equal to the ratio of H4 to D4 or is greater than the ratio of H4 to D4 by no more than about 0.05 (Shore D hardness/mm).

10. A golf ball according to claim 1, wherein T3 is from about 0.65 mm to about 2.0 mm.

11. A golf ball according to claim 1, wherein (a) the core center has a diameter of from about 28 mm to about 36 mm or (b) the first intermediate layer has a thickness of from about 2.04 mm to about 5.99 mm or both (a) and (b).

12. A golf ball according to claim 1, wherein the cover has a thickness of from about 0.7 mm to about 1.8 mm.

13. A golf ball according to claim 1, wherein H3 is from about Shore D 67 to about Shore D 72.

14. A golf ball according to claim 1, wherein H1 is from about Shore D 46 to about Shore D 50.

15. A golf bail, comprising:

a core center having a diameter Di and a hardness H1;

a first intermediate layer outward from and surrounding the core center;

a second intermediatelayer outward from and surrounding the first intermediate layer having a diameter D3 and a hardness H3; and

a cover outward from and surrounding the second intermediate layer;

wherein the ratio of H3 to D3 is at least about 94% of the ratio of H1 to D1 (H3/D3≧0.94 H1/D1).

16. A golf ball according to claim 15, wherein the ratio of H3 to D3 is greater than or equal to the ratio of H1 to D1 (H3/D3≧H1/D1).

17. A golf ball according to claim 16, wherein the ratio of H3 to D3 is from 100% to about 110% of the ratio of H1 to D1.

18. A golf ball according to claim 16, wherein the ratio of H3 to D3 is from 100% to about 105% of the ratio of H1 to D1.

19. A golfball according to claim 17, wherein the second intermediate layer has a thickness of at least about 0.65 mm.

20. A golf ball according to claim 15, wherein the first intermediate layer has a diameter D2 and a hardness H2, the cover has a diameter D4 and a hardness H4: and wherein each of the ratio of H1 to D1, the ratio of H2 to D2, and the ratio of H4 to D4 is from about 75% to 100% of the ratio of H3 to D3.