US20080300069A1

US20080300069A1 - Golf ball with a thermoset polyurethane cover

Info

Publication number: US20080300069A1
Application number: US11/755,466
Authority: US
Inventors: Murali Rajagopalan; Kevin M. Harris
Original assignee: Acushnet Co
Current assignee: Acushnet Co
Priority date: 2007-05-30
Filing date: 2007-05-30
Publication date: 2008-12-04

Abstract

A golf ball with an improved cover layer that is formed over the core, and that is a thermoset polyurethane composition or a thermoset polyurea composition, each formed from reactants comprising respective thermoplastic polyurethane or polyurea and a cross-linking hydrolysable organosilane having the general formula:

- where, R₁, R₂, and R₃are aliphatic alkyl, aromatic alkyl and n≧1; and
- R₄is an organic radical capable of reacting with the polymer backbone moiety, which comprises a cross-linking agent having at least two isocyanate functions. The thermoplastic polyurethane obtained is capable after processing of cross-linking on contact with water molecules to become thermoset. The golf ball can also include an intermediate layer disposed between the core and the cover, where the intermediate layer is composed of a blend of ionomers. The golf ball hydrolysable organosilane cross-linking agent is gamma-methyl aminopropyl methoxy silane.

Description

FIELD OF THE INVENTION

The present invention relates to golf balls and more particularly, the invention is directed to golf balls with an improved cover layer including a thermoset material created from reacting thermoplastic urethane or thermoplastic urea with non-toxic cross-linkable organo-silanes.

BACKGROUND OF THE INVENTION

Conventional golf balls can be divided into two general types or groups: solid balls or wound balls. The difference in play characteristics resulting from these different constructions can be quite significant. These balls, however, have primarily two functional components that make them work. These components are the core and the cover. The primary purpose of the core is to be the “spring” of the ball or the principal source of resiliency. The primary purpose of the cover is to protect the core.
Two-piece solid balls are made with a single-solid core, usually made of a cross-linked polybutadiene or rubber, which is encased by a hard cover material. In these balls, the solid core is the “spring” or source of resiliency. The resiliency of the core can be increased by increasing the crosslink density of the core material. As the resiliency increases, however the compression may also increase making a ball with increased stiffness. Stiffness is a physical attribute defined by load per unit of deflection. In the golf ball art, stiffness is commonly measured using Atti and Rheile “compression” gauges, however, other methods can be used.
Multi-piece solid balls include multi-layer core constructions or multi-layer cover constructions, and combinations thereof. In a golf ball with multi-layer core, the principal source of resiliency is the multi-layer core. In a golf ball with a multi-layer cover, the principal source of resiliency is the single-layer core.
One conventional material used to form golf ball covers is balata, a natural or synthetic trans-polyisoprene rubber. The softness of the balata cover allows the player to achieve spin rates sufficient to more precisely control ball direction and distance, particularly on shorter shots. However, balata covers lack the durability required by the average golfer, and are easily damaged. Accordingly, alternative cover compositions have been developed in an attempt to provide balls with spin rates and a feel approaching those of balata covered balls, while also providing a golf ball with a higher durability and overall distance
Ionomer resins (e.g., copolymers of olefin, such as ethylene, and ethylenically unsaturated carboxylic acids, such as (meth)acrylic acids, wherein the acid groups are partially or fully neutralized by metal ions) have also been used as golf ball cover materials. Ionomer covers may be virtually cut-proof, but in comparison to balata covers, they display inferior spin and feel properties.
Thermoplastic materials are used in golf ball applications, particularly because they are easy to implement and have high performance qualities at ambient temperature. They are also flexible and have a high degree of mechanical resistance. Nevertheless, thermoplastic materials have the drawback of low physical resistance to heat such that the products obtained from said materials have, depending on their use, a short service life. On the other hand, materials known as “thermosetting” materials are difficult to shape, thus even though they may be heat resistant, their use is limited.
Methods have been formulated to form thermoset polyurethane and polyurea materials for use in golf balls. In order to achieve this, the preparation of a thermosetting polymer has been proposed by modifying easily processed thermoplastic polymers to enable the finished product to be cross-linked. One popular method is the reaction of thermoplastic polyurethane or polyurea compositions with a toxic isocyanate monomer like MDI or TDI to create a cross-linking moiety. This is usually achieved by achieved by mixing and extruding a polymer, particularly a polyethylene with a peroxide. However, this type of method not only has the drawback of being possible with only a limited number of polyethylenes, but also of requiring very expensive industrial installations.
Other methods include the use of a high energy radiation to produce a cross-linked TPU, such as irradiating a polymer with doses measuring 80 to 200 KGy. It should, however, be noted that this type of treatment is very expensive and also tends to deteriorate rather than improve the polymers used.
Hebert, et al., U.S. Pat. No. 5,885,172 (“the '172 patent”) discloses a multilayer golf ball giving a “progressive performance” (i.e. different performance characteristics when struck with different clubs at different head speeds and loft angles) and having an outer cover layer formed of a thermoset material with a thickness of less than 0.05 inches and an inner cover layer formed of a high flexural modulus material. The '172 patent provides that the outer cover is made from polyurethane as described in Wu, et al., U.S. Pat. No. 5,692,974, or thermoset polyurethanes such as TDI or methylenebis-(4-cyclohexyl isocyanate) (“HMDI”), or a polyol cured with a polyamine (e.g. methylenedianiline (MDA)), or with a trifunctional glycol (e.g., N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine). The '172 also provides that the inner cover has a Shore D hardness of 65 80, a flexural modulus of at least about 65,000 psi, and a thickness of about 0.020 0.045 inches. Exemplary materials for the inner cover are ionomers, poly-urethanes, polyetheresters (e.g. HYTREL®), polyetheramides (e.g., PEBAX®), polyesters, dynamically vulcanized elastomers, functionalized styrene-butadiene elastomer, metallocene polymer, blends of these materials, nylon or acrylonitrile-butadiene-styrene copolymer.
The problem posed therefore consists in developing a manufacturing procedure for producing polyurethane that maintains the processing conditions of thermoplastic urethane polymers (TPUs) and preserves their mechanical characteristics while adding improved heat resistance.
Therefore, a continuing need remains for novel golf ball construction, and particularly for a golf ball cover that has the desirable and/or optimal combination of performance characteristics, while also having good abrasion durability, good hardness, and friction characteristics that result in favorable spin.

SUMMARY OF THE INVENTION

The present invention is a more durable polyurethane or polyurea material for a golf ball cover. A cover that is formed over the core, and that is a thermoset polyurethane composition or a thermoset polyurea composition, each formed from reactants comprising respective thermoplastic polyurethane or polyurea and a cross-linking hydrolysable organosilane having the general formula:
where, R₁, R₂, and R₃are aliphatic alkyl, aromatic alkyl and n≧1; and
R₄is an organic radical capable of reacting with the polymer backbone moiety, which comprises a cross-linking agent having at least two isocyanate functions. The thermoplastic polyurethane obtained is capable after processing of cross-linking on contact with water molecules to become thermoset.
The golf ball can also include an intermediate layer disposed between the core and the cover, where the intermediate layer is composed of a blend of ionomers.
In one embodiment of the invention the golf ball hydrolysable organosilane cross-linking agent is gamma-methyl aminopropyl methoxy silane.
The thermoset golf ball cover has a Shore D hardness ranging from 20-70D, preferably 35 to 65D, a flexural modulus of 17 to 80 kpsi, preferably from 25 to 70 kpsi, and a thickness ranging from 0.020 inch to 0.065 inch.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, a method is disclosed for forming a golf ball having a cover or intermediate layer that can be a thermoset polyurethane or polyurea after processing of a thermoplastic polyurethane or polyurea. It also relates to the golf ball having a thermoset polyurethane or thermoset polyurea cover or inner cover layer created from the process which is disclosed in U.S. Pat. No. 6,861,491, which is incorporated herein, in its entirety, by reference thereto. Those skilled in the art will recognize that the core may be solid, hollow, multi-piece or liquid-filled, the intermediate layer may be partitioned into additional layers, and the golf ball may have a wound layer without departing from the scope and spirit of the present invention.
As previously discussed thermoplastic materials are used in making golf balls, particularly because they are easy to implement and have high performance qualities at ambient temperature, are flexible and have a high degree of mechanical resistance. Nevertheless, thermoplastic materials have the drawback of low physical resistance to heat such that the products obtained from said materials have, depending on their use, a short service life. All standard TPU compositions generally lose their mechanical characteristics at around 70° C. On the other hand, materials known as “thermosetting” materials are difficult to shape, therefore limiting their use.
The invention incorporates the process of '491 to manufacture golf balls wherein the processing conditions of thermoplastic urethane polymers (TPUs) are maintained while preserving the main mechanical characteristics and adding improved heat resistance that is greater than that of cross-linked polyethylenes. By incorporating this process, the use of toxic isocyanates as cross-linking agents is eliminated, and the lack of abrasion qualities that are inherent with their use.
The method utilized to create the improved thermoset polyurethane (and polyurea) wherein hydrolysable organosilanes are grafted onto macromolecular chains of thermoplastic polyurethane that do not deteriorate the chains. This is achieved by having a cross-linking agent grafting the hydrolysable organosilane onto thermoplastic polyurethane macromolecules, with the hydrolysable organosilane having the general formula:
where, R₁, R₂, and R₃are aliphatic alkyl, aromatic alkyl and n≧1; and
R₄is an organic radical capable of reacting with the polymer backbone moiety, which comprises a cross-linking agent having at least two isocyanate functions. The thermoplastic polyurethane obtained is capable after processing of cross-linking on contact with water molecules to become thermoset.
In an embodiment R₄is selected from the group comprising the radicals NH₂, NH, SH, OH, phenol, epoxy. This list is not limitative and R₄is understood to be any organic radical capable of reacting with an isocyanate function.
Advantageously the cross-linking agent is a diisocyanate with the general formula:
O═C═N—R₅—N═C═O where R₅=organic radical
In selecting both molecules of the organosilane type with R₄=NH₂, NH, SH, OH, phenol, epoxy and molecules of the isocyanate type with functionality greater than or equal to 2 made it possible effectively to graft organosilanes to the macromolecular chains of thermoplastic polyurethane without damaging them. It is to be appreciated that the cross-linking agent can also consist of a triisocyanate function without compromising the scope of the invention.
The method as described has another advantage, viz. the ability to adapt to all types of TPU including esters, ethers, carbonates and caprolactones. In addition, the selected TPU may be aliphatic or aromatic. Finally, it may be in amorphous or semi-crystalline form. In an advantageous embodiment of the invention the organosilane is aminopropyltrimethoxysilane, with the formula:
In this situation reactions between thermoplastic polyurethane or thermoplastic polyurea and isocyanate functions cause, either simultaneously or with a slight time-lag depending on the mixing procedure, the formation of aliophanates and isocyanate-amine reactions according to the reaction scheme below:
This series of reactions makes it possible to affix hydrolysable silane groups onto the polyurethane or polyurea chains without damaging them. The fact of grafting several silanes onto the same thermoplastic polyurethane or polyurea chain can also encourage subsequent cross-linking.
After processing, the thermoplastic polyurethane (or the thermoplastic polyurea) cross-links with humidity by hydrolysis and polycondensation of the silane functions grafted onto the various macro-molecular chains of the TPU in the classic silane hydrolysis and condensation reaction.
The diisocyanate used may advantageously be an aromatic, cycloaliphatic or aliphatic diisocyanate or their dimers.
The diisocyanate selected may advantageously be selected from among the following aromatic diisocyanates: TDI (1-3 diisocyanatomethylbenzene), 2,4′-MDI (1 isocyanato-2(4-isocyanatophenyl)methylbenzene), 4,4′MDI (1,1-methylene bis(4-isocyanatobenzene)), 2,4-TDI (2,4 diisocyanato-1-methylbenzene) or PPDI (1,4-diisocyanatobenzene) or their dimers.
The cycloaliphatic diisocyanate selected may advantageously be H₁₂MDI (1,1-methylene bis(4-isocyanatocyclohexane)). Clearly the above list of diisocyanates that can be implemented in the method of the invention is not exhaustive. The following can be used: HDI (1,6-diisocyanatohexane), CHDI (trans-1,4-diisocyanatocyclohexane), IPDI (5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclo-hexane), TMDI (1,6-diisocyanato-2,2,4 (or 2,4,4)-trimethylhexane), m-TMXDI (1,3-bis(1-isocyanato-1-methylethylbenzene), p-TMXDI (1,4-bis(1-isocyanato-1-methylethylbenzene), NDI (1,5-diisocyanatonaphthalene), polymer MDI (isocyanic acid, polymethylene polyphenylene ester), Desmodur R (1,1′,1″-methyllidynetris(4-isocyanotobenzene)), Desmodur RI (4-isocyanatophenol phosphorothioate (3:1) ester).
The concentration of cross-linking agent required to manufacture the thermoplastic urethane is between 0.1 and 30% by weight of TPU and advantageously between 3 and 4% by weight. For a concentration lower than 1% by weight of TPU, the quantity of cross-linking agent is insufficient to avoid cutting the primary chains of TPU, resulting in loss of thermo-mechanical properties of the cross-linked polymer.
For a concentration higher than 30% the results obtained are no better such that the method becomes financially less attractive.
At the same time, the concentration of organosilane required to obtain polyurethane that can be thermoset after processing is between 0.05 and 15% of TPU by weight, and advantageously 2%. For a concentration lower than 0.5% by weight, the mesh density is insufficient to obtain an insoluble product. For a concentration higher than 15% by weight the price of the ingredients becomes financially less attractive.
In a first embodiment a mixture of thermoplastic polyurethane or thermoplastic polyurea are reacted with a cross-linking agent at temperatures between 120° C. to 220° C. to produce a reagent thermoplastic urethane or a thermoplastic urea; the reagent thermoplastic mixture is then brought into contact with an organosilane; and the resulting grafted thermoplastic is then recovered. The polyurethane or polyurea compositions that are obtained may subsequently be granulated or processed to produce sections of a given shape. This type of reaction may be performed in one or two stages in a variety of reactors such as extruders, calenders, mixing tanks, etc.
When the method of the invention is implemented by extrusion a single- or twin-screw machine is used the profile of which can be easily adapted to each processed TPU. In this situation the extruder comprises at least two mixing zones and at least three heating zones. The maximum temperature applied during the extrusion process is between 120° C. and 220° C. depending on the type of TPU. This is introduced together with the molecule comprising at least one isocyanate function; the hydrolysable organosilane is then introduced into the screw machine.
As explained above, the mixture to be extruded is granulated on removal from the extruder or immediately processed to obtain sections of a given shape. In the granular form the method has the advantage of providing half-finished products for use in other processes such as extrusion, calendering, injection, etc.

PROPHETIC EXAMPLE

A mixture of TPU marketed by Goodrich under the trade-name Estane 58277 together with 2 parts per hundred (phr) of resin of gamma-methyl aminopropyl methoxy silane is introduced into the foot of the hopper of a twin screw extruder at temperatures of 170° C.
The method makes it possible to retain the mechanical characteristics of the original polymer at temperatures higher than 40° C.
Of particular note is the simplicity of the method as it requires no further stages after processing of thermoplastic polyurethane to obtain the cross-linking of the finished product.
While various descriptions of the present invention for making a thermoset polyurethane or thermoset polyurea golf ball cover or intermediate layer are described above, it is understood that the various features of the present invention can be used singly or in combination thereof. For example, the golf ball can include a multi-layer cover. The features of one embodiment can be used with the features of another embodiment. Therefore, this invention is not to be limited to the specifically preferred embodiments depicted therein.
Suitable materials for golf ball core, intermediate and cover layers of the present invention include, but are not limited to, polyethylene, including, for example, low density polyethylene, linear low density polyethylene, and high density polyethylene; polypropylene; rubber-toughened olefin polymers; copolyether-esters; copolyether-amides; polycarbonates; acid copolymers which do not become part of an ionomeric copolymer; plastomers; flexomers; vinyl resins, such as those formed by the copolymerization of vinyl chloride with vinyl acetate, acrylic esters or vinylidene chloride; styrene/butadiene/styrene block copolymers; styrene/ethylene-butylene/styrene block copolymers; acrylonitrile-butadiene-styrene polymers; fluoropolymers; dynamically vulcanized elastomers; ethylene vinyl acetates; ethylene methacrylates and ethylene ethacrylates; ethylene methacrylic acid, ethylene acrylic acid, and propylene acrylic acid; polyvinyl chloride resins; copolymers and homopolymers produced using a metallocene or other single-site catalyst; polyamides, amide-ester elastomers, and graft copolymers of ionomer and polyamide, including, for example, Pebax® thermoplastic polyether block amides, commercially available from Arkema Inc; polyphenylene oxide resins or blends of polyphenylene oxide with high impact polystyrene, such as NORYL® commercially available by General Electric Company of Pittsfield, Mass.; crosslinked transpolyisoprene blends; polyurethanes; polyureas; polyester-based thermoplastic elastomers, such as Hytrel®, commercially available from E. I. du Pont de Nemours and Company, and LOMOD®, commercially available from General Electric Company; polyurethane-based thermoplastic elastomers, such as Elastollan®, commercially available from BASF; natural and synthetic rubbers; partially and fully neutralized ionomers; and combinations thereof. Suitable golf ball materials and constructions also include, but are not limited to, those disclosed in U.S. Pat. Nos. 6,117,025, 6,767,940, and 6,960,630, the entire disclosures of which are hereby incorporated herein by reference.
Particularly preferred materials for outer cover layers of the present invention include castable reactive materials, preferably selected from aliphatic and aromatic thermoset polyurethanes and aliphatic and aromatic thermoset polyureas.
Additionally suitable cover layer materials and methods for forming them are further disclosed, for example, in U.S. Pat. Nos. 5,484,870, 6,818,724, and 6,835,794, the entire disclosures of which are hereby incorporated herein by reference.
The golf ball cover layer or at least one sub-layer thereof (e.g., inner cover layer, outer cover layer) may have a measure water resistance. The compositions may comprise a highly neutralized acid polymer (“HNP”). As used herein, “highly neutralized” refers to the acid polymer after at least 70%, preferably at least 80%, more preferably at least 90%, even more preferably at least 95%, and even more preferably 100%, of the acid groups thereof are neutralized. The HNP may be neutralized by a cation, a salt of an organic acid, a suitable base of an organic acid, or any combination of two or more thereof. Suitable HNPs are salts of homopolymers and copolymers of α,β-ethylenically unsaturated mono- or dicarboxylic acids, and combinations thereof. The term “copolymer,” as used herein, includes polymers having two types of monomers, those having three types of monomers, and those having more than three types of monomers. Preferred acids are (meth) acrylic acid, ethacrylic acid, maleic acid, crotonic acid, fumaric acid, itaconic acid. More preferred acid are (meth) acrylic acid, maleic acid, fumaric acid, and itaconic acid. (Meth) acrylic acid is particularly preferred. As used herein, “(meth) acrylic acid” means methacrylic acid and/or acrylic acid. Likewise, “(meth) acrylate” means methacrylate and/or acrylate. Preferred acid polymers are copolymers of a C₃to C₈α,β-ethylenically unsaturated mono- or dicarboxylic acid and ethylene or a C₃to C₆α-olefin, optionally including a softening monomer. Particularly preferred acid polymers are copolymers of ethylene and an acid selected from (meth) acrylic acid, maleic acid, fumaric acid, and itaconic acid, preferably (meth) acrylic acid. More preferred are copolymers of ethylene and acrylic acid.
The cover layer can have a thickness from 0.020 inch to 0.034 inch, preferably from 0.030 inch to 0.065 inch, more preferably from 0.030 inch to 0.050 inch, most preferably from 00.035 to 0.040 inch. Alternatively, the thickness of the cover layer is 0.50 inch or less, preferably 0.05 inch to 0.2 inch, more preferably 0.05 inch to 0.1 inch. The cover layer may have a flexural modulus of 10,000 to 100,000 psi, preferably 15,000 psi to 80,000 psi, more preferably 20,000 to 50,000 psi. The Shore D hardness of the cover layer may be 90 or less, preferably 20 to 70, more preferably 30 to 65, and further preferably from 40 to 65.
The core of the golf ball may be solid, fluid-filled, gel-filled, or gas-filled, having a single-piece construction or a multi-piece construction that includes a center and one or more outer core layers. Preferred compositions for solid cores include a base rubber (e.g., polybutadiene rubbers having a 1,4-cis content of at least about 40%), a crosslinking agent (e.g., ethylenically unsaturated acids having 3 to 8 carbon atoms and metal salts thereof), an initiator (e.g., peroxides, carbon-carbon initiators, and blends of two or more thereof) and, optionally, one or more additives (e.g., CoR enhancer like halogenated organosulfur compounds). The core may be comprised of a polymer containing an acid group neutralized by an organic acid or a salt thereof, the organic acid or salt thereof being present in an amount sufficient to neutralize the polymer by at least about 80%.
The golf ball core may have a diameter of 0.5 inch or greater, preferably 1 inch or greater, more preferably 1.5 inch or greater, but most preferably 1.53 inch or greater. The core may have an Atti compression of 20 to 120, preferably 30 to 100, more preferably 40 to 90, further preferably 45 to 85, most preferably 50 to 80; alternatively, the compression may be 25 or less, or 20 or less. The core may have a CoR of 0.7 or greater, preferably 0.75 or greater, more preferably 0.77 or greater, further preferably 0.79 or greater, most preferably 0.8 or greater. The core may comprise a center and one or more outer core layers. The outer core layer may have a thickness of 0.5 inch or less, preferably 0.3 inch or less, more preferably 0.25 inch to 0.3 inch.
One, two, or more optional intermediate layers may be disposed between the core and the cover. The intermediate layer may be part of the core as an outer core layer, or part of the cover as an inner cover layer. In one example, an intermediate layer can be formed from a hard, high flexural modulus, resilient material which contributes to the low spin, distance characteristics when they are struck for long shots (e.g. driver or long irons). The material of the intermediate layer can have a Shore D hardness of 55-80, preferably 60-75, more preferably 65-72. The flexural modulus of the intermediate layer can be at least 50,000 psi, preferably from 55,000 psi to 120,000 psi, more preferably from 58,000 psi to 100,000 psi. The thickness of the inner cover layer may be from 0.020 inches to 0.050 inches, preferably from 0.030 inches to 0.040 inches. The intermediate layer preferably has a water vapor transmission rate (WVTR) lower than that of the cover. More preferably, the WVTR of the intermediate layer is no greater than that of an ionomer resin such as Surlyn®, which is in the range of about 0.45 g/(m²× day) to about 0.95 g/(m²× day. The intermediate layer may contain a moisture resistant composition by blending a HNP with one or more thermoplastic polymers and elastomers. Examples of thermoplastic polymers suitable for blending with a HNP are conventional ionomers such as ionomeric materials sold under the trade names DuPont® HPF 1000 and DuPont® HPF 2000, commercially available from E.I. DuPont de Nemours and Company.
The resultant golf balls typically have a CoR of about 0.7 or greater, preferably about 0.75 or greater, more preferably about 0.78 or greater, most preferably about 0.8 or greater. The golf balls also typically have an Atti compression of at least about 40, preferably from about 50 to 120, and more preferably from about 60 to 100. The golf balls typically have dimple coverage greater than about 60 percent, preferably greater than about 65 percent, and more preferably greater than about 75 percent. The diameter of the golf ball is preferably from 1.680 inches to 1.800 inches, more preferably from 1.680 inches to 1.760 inches, most preferably from 1.680 inches to 1.740 inches.
In one example, a golf ball cover layer is formed from a thermoset polyurethane and having a material hardness of Shore D hardness of between 40 and 70. The golf ball has a compression of 90-110. The cover layer has a thickness of 0.03 inches to 0.05 inches (e.g., 0.033 inches, 0.046 inches).
Golf balls of the present invention may have a variety of constructions, typically comprising at least a core and a cover. Optionally, one or more intermediate layers may be disposed between the core and the cover; the core may be a single solid mass, or include a solid, liquid-filled, gel-filled or gas-filled center and one or more outer core layers; and the cover may include an outer cover layer and one or more inner cover layers. Any of the outer core layers, the intermediate layers, or the inner cover layers may be a continuous layer, a discontinuous layer, a wound layer, a molded layer, a lattice network layer, a web or net, an adhesion or coupling layer, a barrier layer, a layer of uniformed or non-uniformed thickness, a layer having a plurality of discrete elements such as islands or protrusions, a solid layer, a metallic layer, a liquid-filled layer, a gas-filled layer, or a foamed layer.
As used herein, the terms “araliphatic,” “aryl aliphatic,” or “aromatic aliphatic” all refer to compounds that contain one or more aromatic moieties and one or more aliphatic moieties, where the reactable functional groups such as, without limitation, isocyanate groups, amine groups, and hydroxyl groups are directly linked to the aliphatic moieties and not directly bonded to the aromatic moieties. Illustrative examples of araliphatic compounds are o-, m-, and p-tetramethylxylene diisocyanate (TMXDI).
The subscript letters such as m, n, x, y, and z used herein within the generic structures are understood by one of ordinary skill in the art as the degree of polymerization (i.e., the number of consecutively repeating units). In the case of molecularly uniformed products, these numbers are commonly integers, if not zero. In the case of molecularly non-uniformed products, these numbers are averaged numbers not limited to integers, if not zero, and are understood to be the average degree of polymerization.
Any numeric references to amounts, unless otherwise specified, are “by weight.” The term “equivalent weight” is a calculated value based on the relative amounts of the various ingredients used in making the specified material and is based on the solids of the specified material. The relative amounts are those that result in the theoretical weight in grams of the material, like a polymer, produced from the ingredients and give a theoretical number of the particular functional group that is present in the resulting polymer.
The golf balls of the present invention should have a moment of inertia (“MOI”) of less than about 85 and, preferably, less than about 83. The MOI is typically measured on model number MOI-005-104 Moment of Inertia Instrument manufactured by Inertia Dynamics of Collinsville, Conn. The instrument is plugged into a PC for communication via a COMM port and is driven by MOI Instrument Software version #1.2.
As used herein, the term “polymer” refers to oligomers, adducts, homopolymers, random copolymers, pseudo-copolymers, statistical copolymers, alternating copolymers, periodic copolymer, bipolymers, terpolymers, quaterpolymers, other forms of copolymers, substituted derivatives thereof, and combinations of two or more thereof. These polymers can be linear, branched, block, graft, monodisperse, polydisperse, regular, irregular, tactic, isotactic, syndiotactic, stereoregular, atactic, stereoblock, single-strand, double-strand, star, comb, dendritic, and/or ionomeric.
Other than in the prophetic example, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for amounts of materials, times and temperatures of reaction, ratios of amounts, values for molecular weight (whether number average molecular weight (“M_n”) or weight average molecular weight (“M_w”), and others in the following portion of the specification may be read as if prefaced by the word “about” even though the term “about” may not expressly appear with the value, amount or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used.
As used herein, the term “flexural modulus” or “modulus” refers to the ratio of stress to strain within the elastic limit (measured in flexural mode) of a material, indicates the bending stiffness of the material, and is similar to tensile modulus. Flexural modulus, typically reported in Pa or psi, is derived in accordance to ASTM D6272-02.
As used herein, the term “water vapor transmission rate” (“WVTR”) refers to the mass of water vapor that diffuses into a material of a given thickness (e.g., 1 mm) per unit area (e.g., 1 m²) per unit time (e.g., 24 h) at a specific temperature (e.g., 38° C.) and humidity differential (e.g., 90% relative humidity). Standard test methods for WVTR include ASTM E96-00, method E, ASTM D1653-03, and ASTM F1249-01.
As used herein, the term “material hardness” refers to indentation hardness of non-metallic materials in the form of a flat slab or button as measured with a durometer. The durometer has a spring-loaded indenter that applies an indentation load to the slab, thus sensing its hardness. The material hardness can indirectly reflect upon other material properties, such as tensile modulus, resilience, plasticity, compression resistance, and elasticity. Standard tests for material hardness include ASTM D2240-02b. Unless otherwise specified, material hardness reported herein is in Shore D. Material hardness is distinct from the hardness of a golf ball portion as measured directly on the golf ball (or other spherical surface). The difference in value is primarily due to the construction, size, thickness, and material composition of the golf ball components (i.e., center, core and/or layers) that underlie the portion of interest. One of ordinary skill in the art would understand that the material hardness and the hardness as measured on the ball are not correlated or convertible.
As used therein, the term “compression,” also known as “Atti compression” or “PGA compression,” refers to points derived from a Compression Tester (ATTI Engineering Company, Union City, N.J.), a scale well known in the art for determining relative compression of a spherical object. Atti compression is approximately related to Riehle compression: Atti compression≈(160−Riehle compression). Compression is a property of a material as measured on a golf ball construction (i.e., on-ball property), not a property of the material per se.
As used herein, the term “coefficient of restitution” or “CoR” for golf balls or subassemblies thereof is defined as the ratio of a ball's rebound velocity to its initial incoming velocity when the ball is fired out of an air cannon into a vertical, stationary, steel plate which provides an impact surface weighing about 100 pounds or about 45 kilograms. The time periods, T_inand T_out, of the ball flight between two separate ballistic light screens placed between the air cannon and the plate are measured to calculate CoR=T_out/T_in. The faster a golf ball rebounds, the higher the CoR it has, the more the total energy it retains when struck with a club, and the longer the ball flies. The reported CoR's initial velocity is about 50 ft/s to about 200 ft/s, and is usually understood to be 125 ft/s, unless otherwise specified. A golf ball may have different CoR values at different initial velocities.
Another CoR measuring method uses a launching device, a circular titanium disk of 200 g and 4-inch in diameter to simulate a golf club, and two separate ballistic light screens placed there between. The impact face of the disk may also be flexible and has its own CoR. From the two time periods, disk mass (M_e), and ball mass (M_b), CoR can be calculated as follows:
$CoR = \frac{(T_{out} / T_{in}) \times (M_{e} + M_{b}) + M_{b}}{M_{e}}$
A “Mooney” viscosity is a unit used to measure the plasticity of raw or unvulcanized rubber. The plasticity in a Mooney unit is equal to the torque, measured on an arbitrary scale, on a disk in a vessel that contains rubber at a temperature of 100° C. and rotates at two revolutions per minute. The measurement of Mooney viscosity is defined according to ASTM D-1646.
As used herein and to conventional practice, the unit “phr” refers to “parts by weight of a respective material per 100 parts by weight of the base polymer or polymer blend.”
All patents and patent applications cited in the foregoing text are expressly incorporated herein by reference in their entirety.
The invention described and claimed herein is not to be limited in scope by the specific embodiments herein disclosed, since these embodiments are intended solely as illustrations of several aspects of the invention. Any equivalent embodiments and various modifications apparent to those skilled in the art are intended to be within the scope of this invention. It is further understood that the various features of the present invention can be used singly or in combination thereof. Such modifications and combinations are also intended to fall within the scope of the appended claims.

Claims

1. A golf ball comprising:

a core; and

a cover formed over the core, the cover composed of a thermoset polyurethane material formed from reactants comprising a thermoplastic polyurethane, a cross-linking agent comprising at least two isocyanate groups, and a hydrolysable organosilane having the general formula;

where, R₁, R₂, and R₃are aliphatic alkyl, aromatic alkyl and n≧1 and

R₄is an organic radical capable of reacting with the polymer backbone moiety, which comprises a cross-linking agent having at least two isocyanate functions. The thermoplastic polyurethane obtained is capable after processing of cross-linking on contact with water molecules to become thermoset.

2. The golf ball according to claim 1 further comprising at least one intermediate layer disposed between the core and the cover.

3. The golf ball according to claim 2 wherein the intermediate layer has a thickness between 0.020 to 0.050 inch.

4. The golf ball according to claim 2, wherein the intermediate layer is composed of a blend of ionomers that include cross-linking polyurethane and polyurea.

5. The golf ball according to claim 1, wherein the hydrolysable organosilane is gamma-methyl aminopropyl methoxy silane.

6. The golf ball according to claim 1, wherein the thermoset polyurethane composition has a Shore D hardness of 20-70.

7. The golf ball according to claim 1, wherein the thermoset polyurethane composition has a flexural modulus of 17,000 to 80,000 psi.

8. The golf ball according to claim 1 wherein the cover has a thickness ranging from 0.030 inch to 0.065 inch.

9. A golf ball comprising:

a core; and

a cover formed over the core, the cover composed of a thermoset polyurea material formed from reactants comprising a thermoplastic polyurea, across-linking agent comprising of at least two isocyanate groups, and a hydrolysable organosilane having the general formula;

where, R₁, R₂, and R₃are aliphatic alkyl, aromatic alkyl and n≧1; and

10. The golf ball according to claim 9 further comprising at least one intermediate layer disposed between the core and the cover.

11. The golf ball according to claim 10 wherein the intermediate layer is composed of a blend of ionomers.

12. The golf ball according to claim 9, wherein the hydrolysable organosilane is gamma-methyl aminopropyl methoxy silane.

13. The golf ball according to claim 9, wherein the thermoset polyurea composition has a Shore D hardness of 20-70.

14. The golf ball according to claim 9, wherein the thermoset polyurea composition has a flexural modulus of 15,000 to 80,000 psi.

15. The golf ball according to claim 9 wherein the cover has a thickness ranging from 0.030 inch to 0.065 inch.

16. A golf ball comprising: a core comprising a polybutadiene mixture, the core having a diameter ranging from 1.35 inches to 1.64 inches and having a PGA compression ranging from 50 to 90; an intermediate layer formed over the core, the intermediate layer composed of a blend of ionomer materials, the intermediate layer having a thickness ranging from 0.020 inch to 0.075 inch, the blend of ionomer materials having a Shore D hardness ranging from 50 to 75 as measured according to ASTM-D2240; and a cover formed over the intermediate layer, the cover composed of a thermosetting polyurethane material formed from reactants comprising a thermoplastic polyurethane and a hydrolysable organosilane, wherein the thermosetting polyurethane material has a Shore D hardness ranging from 30 to 60 as measured according to ASTM-D2240, and a thickness ranging from 0.020 inch to 0.030 inch.