KR20140090568A - Golf ball having a hollow center - Google Patents

Abstract

A golf ball according to the present invention includes a spherical inner core shell layer formed from a thermoset rubber composition, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center. A thermoplastic outer core layer is formed about the shell layer. An optional inner cover layer is formed about the outer core layer, the inner cover including an ionomeric material. An outer cover layer is formed over the core or option inner cover layer, the outer cover including a polyurea or a polyurethane and having a second hardness less than the optional inner cover layer. The hollow center has a diameter of about 0.15 to 1.1 inches.

Description

[0001] GOLF BALL HAVING A HOLLOW CENTER [0002]

The present invention relates to a golf ball having a core with a hollow center surrounded by at least one core layer and at least one cover layer. Any core or cover layer may have a positive or negative hardness gradient, depending on the configuration desired. More particularly, the golf ball comprises a core having a hollow center surrounded by a thermoset "shell layer" and at least one additional thermoplastic core layer.

Recently, virtually all golf balls typically include a solid core surrounded by a cover, and both have a dual core with a solid center and outer core layer, or multiple layers with inner and outer cover layers It is solid construction. The golf ball core and / or center is formed of polybutadiene as the base rubber from the thermosetting rubber composition. The core is typically heated and crosslinked to produce a core having any predetermined characteristic, such as compression or hardness, to provide a mid-to-high, whether a player is an expert, a low handicap player, Whether it is a handicap player or not, it results in a golf ball with characteristics for a particular group of players. From a golf ball manufacturer's point of view it is desirable to have a core that exhibits a wide range of properties such as elasticity, durability, spin and "feel ", which is why golfmakers manufacture and sell golf balls suitable for different levels of ability This is possible.

However, there remains a need for a golf ball configuration that achieves different characteristics. This novel configuration, which did not achieve commercial success in the past, is a golf ball with a hollow core. This means that the innermost portion of the core is hollow surrounded by the shell layer and one or more core and cover layers. Conventionally, many commercially available golf balls were constructed with a non-solid center such as a liquid center, and a very small number of golf balls having a hollow center were constructed.

Among the patent references, there is very little about a golf ball of a hollow core as a generally suitable alternative configuration. For example, U.S. Patent No. 6,315,683 relates to a large size solid golf ball of greater than 1.70 inches in which the hollow core is covered with a single ionomer cover and contains a thermoset rubber layer. More recently, U.S. Patent No. 8,262,508 discloses a golf ball having a generally hollow center, an intermediate layer, an inner cover, and an outer cover. Both the hollow center and the middle layer are formed from a thermoset rubber composition and a conventional " positive hard gradient "(the hardness of the layer is gently obtained in the direction of the interior of the layer). And the core layer has a low surface hardness of 25 to 55 Shore C. The golf ball is covered by a harder ionomer outer cover and a softer ionomer inner cover.

However, the golf ball of the present invention has a hollow core surrounded by a thermosetting 'shell layer', an additional thermoplastic core layer, optionally, one or more thermosetting or thermoplastic intermediate layers and one or more cover layers. The combination of the hollow core configuration with a modification of the hardness gradient of the adjacent thermoplastic and / or thermosetting core layer addresses many of the problems associated with previous attempts in the hollow core construction.

The present invention relates to a golf ball comprising a hollow core. The golf ball comprises a spherical inner core shell layer formed from a first thermoset rubber composition, the shell layer having an inner surface defining an outer surface, an inner surface and a hollow center. The thermoplastic outer core layer is disposed around the shell layer. An optional inner cover layer is disposed around the outer core layer. In one embodiment, the inner cover comprises a ionomer material and has a first hardness. Preferably, the outer cover layer is formed around the optional inner cover layer and comprises a polyurea or preferably a polyurethane. The outer cover layer preferably has a hardness lower than the hardness of the optional inner cover layer.

The hollow center has a diameter of about 0.15 to 1.1 inches. The shell layer has a surface hardness greater than the internal surface hardness by about 3 to 25 Shore C to define the hardness gradient. The thermoplastic outer core layer has a second hardness gradient. Preferably, the shell layer has a surface hardness greater than about 55 Shore C. In one embodiment, the spherical inner core shell layer has a coefficient of restitution of less than about 0.700 as measured at an inlet rate of 125 ft / s. Preferably, the outer core layer has a coefficient of restitution 10-50% greater than the coefficient of restitution of the inner core shell layer when measured at an introduction rate of 125 ft / s.

In one embodiment, the second gradient of hardness is approximately 0 Shore C. In an alternate embodiment, the second gradient of hardness is a negative hardness gradient of about 1 to 10 Shore C. In yet another embodiment, the second hardness gradient is a positive hardness gradient of about 1 to 10 Shore C. The inner cover has a hardness of greater than about 60 Shore D and the outer cover layer has a hardness of less than about 60 Shore D. Alternatively, the golf ball has a first volume and the hollow center has a second volume of about 2% to about 30% of the first volume.

The present invention also relates to a golf ball comprising a hollow core, wherein the golf ball comprises a spherical inner core shell layer formed from a first thermoset rubber composition, the shell layer having an inner surface defining an outer surface, an inner surface and a hollow center . A thermoplastic outer core layer is formed over the shell layer. A thermoplastic intermediate core layer is formed between the shell layer and the outer core layer. An optional inner cover layer is disposed about the outer core layer, the inner cover comprising an innomomer material and having a first hardness. The outer cover layer is preferably disposed about the inner cover layer and comprises a polyurea or polyurethane and has a second hardness less than the first hardness. The hollow center has a diameter of about 0.15 to 1.1 inches and the shell layer has a surface hardness greater than the inner surface hardness by about 3 to 25 Shore C so as to form a first hardness gradient and the thermoplastic outer core layer or thermoplastic intermediate core layer And a second hardness gradient.

In one embodiment, the second gradient of hardness is about 0 Shore C. In an alternate embodiment, the second gradient of hardness is a negative hardness gradient of about 1 to 10 Shore C. In yet another embodiment, the second hardness gradient is a positive hardness gradient of about 1 to 10 Shore C.

The present invention also relates to a golf ball comprising a hollow core, wherein the golf ball comprises a spherical inner core shell layer formed from a first thermoset rubber composition, the shell layer having an inner surface defining an outer surface, an inner surface and a hollow center . A thermoplastic outer core layer is formed on the shell layer. A thermosetting intermediate core layer is disposed between the shell layer and the outer core layer and the intermediate core layer comprises a second thermosetting rubber composition that is the same as or different from the first thermosetting rubber composition. The inner cover layer is optionally disposed around the outer core layer, the inner cover comprising a ionomer material and having a hardness gradient greater than about 60 Shore D. The outer cover layer is disposed on the core or optional inner cover layer and the outer cover comprises polyurea or polyurethane and has a hardness of less than about 60 Shore D. The hollow center has a diameter of about 0.51 to 1.1 inches and the shell layer has a surface hardness greater than the inner surface hardness by about 3 to 25 Shore C to define a first hardness gradient and the thermoplastic outer core layer has a second hardness gradient And the thermosetting intermediate core layer has a third hardness gradient different from the first or second hardness grades.

In one embodiment, the shell layer has a surface hardness greater than about 55 Shore C. Alternatively, the spherical inner core shell layer has a coefficient of restitution less than about 0.700 as measured at an introduction rate of 125 ft / s. The outer core layer also has a coefficient of restitution 10-50% greater than the coefficient of restitution of the inner core shell layer when measured at an inlet rate of 125 ft / s.

In one embodiment, the second gradient of hardness is approximately 0 Shore C. In an alternate embodiment, the second gradient of hardness is a negative hardness gradient of about 3 to 25 Shore C. In another embodiment, the second hardness gradient is a positive hardness gradient of about 3 to 25 Shore C. In a preferred embodiment, the golf ball has a first volume and the hollow center has a second volume of about 2% to about 30% of the first volume.

1A is a diagram illustrating the distance from the center of Shore C hardness to an embodiment of a thermoset (TS) / thermoplastic (TP) hollow core golf ball.
1B is a diagram showing the Shore C hardness versus distance from the center for a second embodiment of a thermoset (TS) / thermoplastic (TP) hollow core golf ball.
2A shows a Shore C hardness versus distance from the center for one embodiment of a thermoset (TS) / thermoplastic (TP) hollow core golf ball.
Figure 2b is a view of the Shore C hardness versus distance from the center for a second embodiment of a thermoset (TS) / thermoplastic (TP) hollow core golf ball.
Figure 3a is a diagram illustrating the Shore C hardness for a distance from the center of a hollow core for an embodiment of a thermoplastic (TP) / thermoplastic (TP) hollow core golf ball.
Figure 3b is a diagram showing the Shore C hardness for the distance from the center of the hollow core for a second embodiment of a thermoplastic (TP) / thermoplastic (TP) hollow core golf ball.

The golf ball of the present invention may comprise a core with a hollow core and at least one outer core layer, an inner cover layer and an outer cover layer, although the golf ball of the present invention may include a core and a multilayer golf ball such as a golf ball having a cover surrounding the core . Any layer of the core or cover layer may comprise more than one layer. The cover layer of the golf ball may be a single layer or it may be formed of a plurality of layers such as an inner cover layer and an outer cover layer.

The hollow core is formed with a thermosetting "shell layer" comprising a spherical hollow portion therein. In a preferred embodiment, the golf ball comprises a thermosetting hollow core and at least two outer core layers, the shell layer is formed of a thermosetting material, the outer core layer is formed of a thermoplastic material, and disposed between the shell layer and the outer core layer The intermediate core layer is formed of a thermoplastic material. In an alternative preferred embodiment, the golf ball comprises a thermosetting hollow core and at least two outer core layers, the shell layer is formed of a thermoset material, the outer core layer is formed of a thermoplastic material, Is formed of a thermosetting material.

The shell, outer core, or intermediate core layer is measured radially inwardly (i.e., from the outer surface / portion of the shell and / or core layer toward the inner surface / portion) from the outer surface or portion of each component toward the innermost portion Soft "hardness gradient (i.e., the outermost surface / portion of the layer is harder than the innermost surface / portion) known as " soft-to-hard" Gradient (i.e., a gradient of "negative"). As used herein, the terms "negative" and " positive "with respect to the gradient of hardness are measured from the hardness value at the outer surface of the component being measured (e.g., the outer surface of the outer core layer) (For example, the inner surface of the core layer) of the component to be formed. For example, if the outer surface of the core layer has a lower hardness value at the inner surface, the hardness gradient is considered to be a gradient of "negative" (small number - large number = negative number) May be disclosed herein as the absolute value of the subtraction result.

The thermoplastic shell, intermediate core layer and outer core layer of the present invention may have a 'positive hardness gradient' or a 'negative hardness gradient' as described above. Alternatively, the TP layer may have a " zero hardness gradient " as defined herein that includes a 0 Shore C hardness gradient of ± 2 Shore C. The TP layer "positive hardness gradient" or "negative hardness gradient" may range from about 0 Shore C to about 10 Shore C, more preferably from about 2 Shore C to about 8 Shore C, and most preferably from about 3 Shore C to about 5 Shore C. < RTI ID = 0.0 >

The thermosetting shell, intermediate core layer and outer core layer of the present invention may have a 'positive hardness gradient' or a 'negative hardness gradient' as described above. Alternatively, the TS layer may have a " zero hardness gradient " as defined herein that includes a 0 Shore C hardness gradient of ± 2 Shore C. The TS layer "positive hardness gradient" or "negative hardness gradient" is in the range of about 1 Shore C to about 30 Shore C, more preferably about 2 Shore C to about 27 Shore C, more preferably about 5 Shore C About 25 Shore C, and most preferably from about 10 Shore C to about 20 Shore C. Other suitable TS 'amount of hardness gradients' or 'negative hardness gradient' core layers can be found in U.S. Patent Nos. 7,537,529 and 7,537,530, the disclosures of which are incorporated herein by reference in their entirety.

A variety of the aforementioned TS and TP hardness gradient layers are contemplated, and a 'positive hardness gradient' and / or a 'negative hardness gradient' may be combined to form the hollow core of the present invention with various layers of such a characteristic.

It is contemplated that the surface hardness of the shell or core layer is obtained from an average of a plurality of measurements taken from opposite hemispheres of a particular layer so as to avoid obtaining measurements on any surface defect or splitting line, such as a hole or protrusion. Hardness measurements are made according to ASTM D-2240 "Indentation Hardness of Rubber and Plastic by Means of a Durometer ". Care should be taken to ensure that they are centered below the durometer indenter before surface hardness readings are made due to the curved surface of the hollow core or core layer. A calibrated digital durometer capable of reading up to 0.1 hardness units is used for all hardness measurements and is set to take a hardness reading after one second after the maximum reading is obtained. The digital durometer shall be attached to the base of the automatic stand so that the weight and attack rate of the durometer is in accordance with ASTM D-2240, and the base of the durometer should be parallel to the base of the automatic stand.

In order to prepare a hollow core for hardness and hardness gradient measurements, the core (with the shell layer or one or two core layers) is gently pressed into a hemispherical holder having an inner diameter approximately finer than the diameter of the core, The core is held in place in the hemispherical portion of the holder while leaving the geometric center plane of the holder at the same time exposed. The core is fixed within the holder by friction and thus does not move during the cutting and grinding steps, but the friction is not excessive so as to cause distortion of the natural shape of the core. The core is fixed such that the dividing line of the core is substantially parallel to the upper end of the holder. The diameter of the core is measured at 90 [deg.] With respect to this orientation prior to fixation. In addition, measurements are made from the bottom of the holder to the top of the core, thus providing a reference point for future calculations. A rough cut is made slightly above the exposed geometric center of the core using a band saw or other suitable cutting tool while ensuring that the core does not move in the holder during this step. The remainder of the core still in the holder is fixed to the base plate of the surface grinder. The exposed 'rough' core surface is ground to a smooth, smooth surface to expose the hollow center of the core, ensuring that exactly half of the original height of the core as measured above is removed to within +/- 0.004 inch, By measuring the height of the bottom portion of the holder relative to the holder.

With the core left in the holder, the center of the core is found at the center square, carefully marked, and the hardness measured at the center mark. The hardness measurement at any distance from the center of the core is measured by measuring and marking the distance from the center with a line radially outward from the center mark and typically in 1 or 2 mm increments. All hardness measurements performed on a plane passing through the center of the hollow are performed with the core still in the holder and its orientation not disturbed so that the test surface is uniformly parallel to the bottom of the holder. The difference in hardness from any predetermined position on the core is calculated by subtracting the hardness at the appropriate reference point at the average surface hardness.

At least one of the shell layer and / or the core layer may be formed from a composition comprising at least one peroxide and at least one thermosetting rubber such as a polybutadiene rubber cured with at least one reactive co- May be a metal salt of an unsaturated carboxylic acid such as acrylic acid or methacrylic acid, a non-metallic co-solvent or a mixture thereof. Preferably, suitable antioxidants are included in the composition. Optional "soft and fast agonists" (sometimes referred to as cis-to-trans catalysts), such as organic sulfur or metal containing organic sulfur or thiol compounds, can also be included in the core composition. Other components known to those skilled in the art can be used and are understood to include, but are not limited to, density controlling fillers, process aids, plasticizers, blowing or blowing aids, sulfur accelerators and / or biperoxides radical sources do.

Base thermosetting rubbers that can be mixed with other rubbers and polymers typically include natural or synthetic rubbers. A good base rubber is 1,4-polybutadiene having a cis structure of at least 40%, preferably more than 80%, and more preferably more than 90%.

Examples of preferred polybutadiene rubbers include BUNA®CB22 and BUNA®CB23, CB1221, CB1220, CB24, and CB21 commercially available from LANXESS Corporation; UBEPOL®360L and UBEPOL®150L and UBEPOL-BR rubbers commercially available from UBE Industries, Ltd. of Tokyo, Japan; KINEX 7245, KINEX 7265 and BUDENE 1207 and 1208 commercially available from Goodyear, Akon, Ohio; SE BR-1220; Europrene ^® NEOCIS ^® BR 40 and BR 60 commercially available from Polimeri Europa; And BR 01, BR 730, BR 735, BR 11, and BR 51 commercially available from Japan Synthetic Rubber Co., Ltd; PETROFLEX®BRNd-40; And KARBOCHEM®ND40, ND45, and ND60 commercially available from Karbochem.

Nd- and Co-catalyst grades from Lanxess Corporation are the best, but all of the following can be used: BUNA CB 21; BUNA CB 22; BUNA CB 23; BUNA CB 24; BUNA CB 25; BUNA CB 29 MES; BUNA CB Nd 40; BUNA CB Nd 40 H; BUNA CB Nd 60; BUNA CB 55 NF; BUNA CB 60; BUNA CB 45 B; BUNA CB 55 B; BUNA CB 55 H; BUNA CB 55 L; BUNA CB 70 B; BUNA CB 1220; BUNA CB 1221; BUNA CB 1203; BUNA CB 45. Also included are JSR (Japan Synthetic Rubber), UBEPOL sold by Ube Industries Inc of Japan, BST sold by BST Elastomers of Thailand; IPCL sold by Indian Petrochemicals Ltd of India; NITSU sold by Karbochem or Karbochem Ltd of South Africa; PETROFLEX from Brazil; LG of Korea; And Kuhmo Petrochemical of Korea.

The base rubber may also include high or medium Mooney viscosity rubbers, or mixtures thereof. The "Mooney" unit is the unit used to measure the plasticity of raw or unvulcanized rubber and is specified in accordance with ASTM D-1646. The Mooney viscosity range is preferably greater than about 40, more preferably in the range of about 40 to 60, and most preferably in the range of about 40 to 52.

Commercial sources of suitable polybutadienes include CB23 (Nd-catalyzed) and CB1221 (Co-catalyzed) of Bayer AG, which has a Mooney viscosity of about 50 and a high linear polybutadiene. If desired, the polybutadiene may be mixed with other known elastomers such as other polybutadiene rubbers, natural rubbers, styrene butadiene rubbers, and / or isoprene rubbers to further modify the properties of the core. When a mixture of elastomers is used, the amount of the other components in the core composition is typically based on 100 parts by weight of the total elastomeric mixture.

In one preferred embodiment, the base rubber comprises Nd-catalyzed polybutadiene, rare earth-catalyzed polybutadiene rubber, or a mixture thereof. If desired, the polybutadiene may be mixed with other elastomers such as natural rubber, polyisoprene rubber and / or styrene-butadiene rubber to further modify the properties of the core. Other suitable base rubbers include thermoset materials such as ethylene propylene diene monomer rubbers, ethylene propylene rubbers, butyl rubbers, halobutyl rubbers, hydrogenated nitrile butadiene rubbers, nitrile rubbers, and silicone rubbers.

Suitable peroxide initiating agents include dicumyl peroxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexane; 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne; 2,5-dimethyl-2,5-di (benzoylperoxy) hexane; 2,2'-bis (t-butylperoxy) -di-iso-propylbenzene; 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane; n-butyl 4,4-bis (t-butyl-peroxy) valerate; t-butyl perbenzoate; Benzoyl peroxide; n-butyl 4,4'-bis (butylperoxy) valerate; Di-t-butyl peroxide; Butyl peroxybenzoate, or 2,5-di- (t-butylperoxy) -2,5-dimethylhexane, lauryl peroxide, t-butyl hydroperoxide, Di (2-t-butyl-peroxyisopropyl) benzene, di-t-amyl peroxide, di-t-butyl peroxide. Preferably, the rubber composition comprises from about 0.25 to about 5.0 parts per hundred peroxide (phr) peroxide, more preferably from 0.5 phr to 3 phr, most preferably from 0.5 phr to 1.5 phr. In a most preferred embodiment, the peroxide is present in an amount of about 0.8 phr. This range of peroxides assumes that peroxides are 100% active without confirmation of any carriers present. Since many commercially available peroxides are sold with the carrier compounds, the actual amount of active peroxide present must necessarily be calculated. Commercially available peroxide initiators include the DICUP ™ family of dicumyl peroxide (including DICUP ™ R, DICUP ™ 40C and DICUP ™ 40KE) available from Crompton (Geo Specialty Chemicals). Similar initiating agents include AkroChem, Lanxess, Flexsys / Harwick and R.T. Available from Vanderbilt. Another commercially available and preferred initiating agent is the mixture of 1,1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane and di (2-t-butylperoxyisopropyl) It is Nobel's TRIGONOX ™ 265-50B. TRIGONOX ™ peroxides are generally sold as carrier compounds.

Suitable reactive co-agents include, but are not limited to, metal salts of diacrylate, dimethacrylate, and monomethacrylate suitable for use in the present invention, and metals include zinc, magnesium, calcium, barium , Tin, aluminum, lithium, sodium, potassium, iron, zirconium, and bismuth. Zinc diacrylate (ZDA) is preferred, but the present invention is not limited thereto. ZDA provides a high initial velocity to the golf ball. The purity of ZDA can be of various grades. For the purposes of the present invention, the lower the amount of zinc stearate present in the ZDA, the higher the purity of ZDA. ZDA containing less than about 10% zinc stearate is preferred. ZDA containing about 4-8% zinc stearate is more preferred. A suitable, commercially available zinc diacrylate is from Sartomer Co. The preferred ZDA concentration that can be used is from about 10 phr to about 40 phr, more preferably from 20 phr to about 35 phr, most preferably from 25 phr to about 35 phr. In a particularly preferred embodiment, the reactive co-agent is present in an amount of from about 29 phr to about 31 phr.

Additional preferred co-agents that may be used alone or in combination with the foregoing include, but are not limited to, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, and the like. Those skilled in the art will appreciate that such co-acting agents may be liquid at room temperature and that it may be advantageous to disperse these compounds in a suitable carrier such that they are readily included in the rubber mixture.

Antioxidants are compounds which inhibit or prevent oxidative degradation of the elastomer and / or inhibit or prevent the reactions promoted by oxygen radicals. Some exemplary antioxidants that may be used in the present invention include, but are not limited to, quinoline type antioxidants, amine type antioxidants, and phenolic type antioxidants. A preferred antioxidant is R.T. Methylene-bis- (4-methyl-6-t-butylphenol) available from Vanderbilt as VANOX® MBPC. Other polyphenol antioxidants include VANOX® T, VANOX® L, VANOX® SKT, VANOX® SWP, VANOX® 13 and VANOX® 1290.

Suitable antioxidants include alkylene-bis-alkyl substituted cresols; Substituted phenols; Alkylene bisphenols; And alkylene trisphenols. The antioxidant is typically present in an amount of from about 0.1 phr to 5 phr, preferably from about 0.1 phr to 2 phr, more preferably from about 0.1 phr to 1 phr. In an alternative embodiment, the antioxidant should be present in an amount that ensures that the hardness gradient of the core layer is "negative ". Preferably, about 0.2 phr to 1 phr, more preferably about 0.3 to 0.8 phr, most preferably 0.4 to 0.7 phr of an antioxidant is added to the core layer formulation. Preferably from about 0.25 phr to about 1.5 phr of peroxide, more preferably from about 0.5 phr to about 1.2 phr, most preferably from about 0.7 phr to about 1.0 phr, as calculated at 100% activity, can be added to the core formulation . The amount of ZDA may be varied to suit the desired compression, spin, and feel of the resulting golf ball. The cure regime may range from about 290 ° F to 350 ° F, more preferably from about 300 ° F to 335 ° F, and the stock may be maintained at the temperature for about 10 minutes to 30 minutes do.

The thermosetting rubber composition may also comprise optional " ductile and fast acting agents ". As used herein, "soft and fast agonists" refer to those materials that are: 1) more ductile (lower compression) than a core at a constant COR, or 2) A higher COR, or any combination thereof. The term " compound " Preferably, the thermosetting core layer composition may contain from about 0.05 phr to about 10.0 phr of a soft and fast agent. In one embodiment, the ductile and fast acting agents are present in an amount from about 0.05 phr to about 3.0 phr, preferably from about 0.05 phr to about 2.0 phr, more preferably from about 0.05 phr to about 1.0 phr. In yet another embodiment, the ductile and fast acting agent is present in an amount from about 2.0 phr to about 5.0 phr, preferably from about 2.35 phr to about 4.0 phr, more preferably from about 2.35 phr to about 3.0 phr. Suitable ductile and fast acting agents include organosulfur compounds, inorganic sulfur compounds, VIA group compounds, or mixtures thereof, including organic sulfur or metal-containing organosulfur compounds, mono-, di-, and polysulfide, thiol, or mercapto compounds But are not limited to, The soft and fast agent components may be a mixture of an organosulfur compound and an inorganic sulfur compound.

Fillers may include processing aids and / or compounds that may be added to the thermosetting rubber layer composition and typically affect the rheological and mixing properties, density-controlled fillers, tear strength, or reinforcing fillers, . The filler may be selected from the group consisting of tungsten, zinc oxide, barium sulphate, silica, calcium carbonate, zinc carbonate, metals, metal oxides and salts, regrind (recycled core material typically polished to about 30 mesh particle size) , Trans-rubber regrind (a recycled core material comprising a high-trans isomer of polybutadiene), and the like. When trans-regrind is present, the amount of trans isomer is preferably between about 10% and 60%. Fillers are generally inorganic and suitable fillers include zinc oxide and tin oxide as well as various metals or metal oxides such as barium sulfate, zinc sulfate, calcium carbonate, barium carbonate, clay, tungsten, tungsten carbide, arrays of silica, . The filler may also include a variety of foam or drag agents that are readily selected by those skilled in the art. The filler may include polymers, ceramics, metals, and glass microspheres, which may be hollow or solid, or filled or unfilled. The filler may be added to one or more layers of the golf ball to control the density of the golf ball.

The thermosetting rubber shell and / or core layer may optionally comprise at least one additive and / or filler. These materials are also appropriately included in the thermoplastic layer of the present invention. Suitable additives and fillers include, but are not limited to, chemical blowing agents such as, but not limited to, chemical blowing agents such as blowing agents, optical brighteners, colorants, fluorescent agents, whitening agents, UV absorbers, light stabilizers, defoaming agents, processing aids, antioxidants, stabilizers, control agents, TiO _2, acid copolymer wax, a surfactant, a performance additive (for example, Honeywell International Inc. from commercially available AC performance additives, particularly the low molecular weight ionomers AC and copolymers, oxidation-treated polyethylene AC, AC and ethylene vinyl acetate (E.g., stearic acid, oleic acid, zinc stearate, magnesium stearate, zinc oleate, and magnesium oleate), fatty acid amides such as ethylenebis-stearamide and ethylenebis-oleamide, , And zinc oxide, tin oxide, barium sulfate, zinc sulfate, calcium oxide, calcium carbonate, zinc carbonate, Fillers such as tungsten, tungsten, tungsten carbide, silica, lead silicate, regrind, clay, mica, talc, nano-filler, carbon black, glass flake, milled glass, floc, fibers, And is not limited to this. Suitable additives are more fully described in U.S. Patent No. 7,041,721, issued May 9, 2006, the contents of which are incorporated herein by reference.

In a particular embodiment, the total amount of additive (s) and filler (s) provided in the particle composition is less than or equal to 20 mass%, or less than or equal to 15 mass%, or less than or equal to 12 mass%, or less than or equal to 10 mass% By mass or less, or 6% by mass or less, or 5% by mass or less, or 4% by mass or less, or 3% by mass or less, or a lower limit of 0 or 2 or 3 or 5% by mass based on the total mass of the particle composition, Is in the range of 9 or 10 or 12 or 15 or 20 mass% based on the total mass. In a particular aspect of this embodiment, the particle composition is selected from the group consisting of carbon black, micro- and nano-scale clay, and CLOISITE (commercially available from Southern Clay Products, Inc., for example) NANOMAX and NANOMER nano clays, commercially available from Nanocor, Inc., and Akzo Nobel Polymer, available from NANOFIL Nanoclay, Nanocor, Micro-and nano-scale talc (e.g., Luzenac America, Inc, < RTI ID = 0.0 > ), Glass (e.g., glass flake, milled glass, micro-glass, or the like) commercially available from LUZENAC HAR And glass fibers), micro- and nano-scale mica and mica-based pigments (for example, IRIODIN pearluster pigments commercially available from The Merck Group) ≪ / RTI > In particular, suitable combinations of fillers include, but are not limited to, micro-scale fillers in combination with nano-scale fillers and organic fillers in combination with inorganic fillers.

For the thermosetting rubber layer of the present invention, the filler and / or additive is contained in an amount of about 50 mass% or less, preferably 30 mass% or less, more preferably 20 mass% or less, and even more preferably 15 % Or less by mass. Alternatively, for the thermoplastic rubber layer of the present invention, the filler and / or additive may be present in an amount of up to about 10% by weight, more preferably up to 6% by weight, more preferably up to 3% by weight, based on the total weight of the composition .

The particle composition optionally comprises at least one melt flow modifier. Suitable melt flow modifiers include materials that increase the melt flow of the composition as measured using the 2160-g mass at 190 占 폚, Condition E, using ASTM D-1238. Examples of suitable melt flow modifiers include fatty acids and fatty acid salts including, but not limited to those disclosed in U.S. Patent No. 5,306,760, the contents of which are incorporated herein by reference; Fatty amides and salts thereof; Polyhydric alcohols including but not limited to those disclosed in U.S. Patent Nos. 7,365,128 and 8,163,823, the contents of which are incorporated herein by reference; U.S. Patent No. 7,642,319, the contents of which are incorporated herein by reference, Polylactic acid, including, but not limited to, those disclosed in U.S. Patent Nos. 5,302, But are not limited to, the modifiers disclosed in U.S. Patent No. 8,163,823 and U.S. Patent Application Publication No. 2009/0203469, the contents of which are incorporated herein by reference. The flow enhancing additives may also include mono-and polyalcohol esters such as montanic acid, esters and salts of montanic acid, bis-stearoylethylenediamine, pentaerythritol tetrastearate, But are not limited to, metallocene-catalyzed polyethylene and polypropylene waxes including anhydrous modified versions, amide waxes such as non-stearamide, and alkylene diamides. Particularly suitable fatty amides include saturated fatty acid monoamides (e.g., lauramide, palmitamide, arachidamide behenamide, stearamide and 12-hydroxystearamide); Unsaturated fatty acid monoamides (e.g., oleamide, erucamide and ricinoleamide); N-substituted fatty acid amides (for example, N-stearyl stearamide, N-behenyl behenamide, N-stearyl behenamide, N-behenyl stearamide, N-oleo oleamide, But are not limited to, stearamide, N-stearyl oleamide, N-stearyl erucamide, erucyl erucamide and erucyl stearamide, N-oleyl palmitamide, methylol amide (more preferably, Amides such as methylene bis-stearamide, ethylene bis-stearamide, ethylene bis-isostearamide, ethylene bis-hydroxystearamide, ethylene bis-behenamide, Hexamethylene bis-hydroxystearamide, N, N'-distearyl adipamide, and N, N'-distearyl cevacamide), unsaturated Fatty acid bis-amides For example, ethylene bis-oleamide, hexamethylene bis-oleamide, N, N'-dioleoyl adipamide, N, N'-dioleyl sebacamide) and saturated and unsaturated fatty acid tetraamides, But are not limited to, ethylene bis-stearamide and ethylene bisoleamide. Suitable examples of commercially available fatty amides include, but are not limited to, commercially available KEMAMIDE B (from Becken < (R) > (Amide / arachidamide), KEMAMIDE W40 (N, N'-ethylene bisstearamide), KEMAMIDE P181 (oleyl palmitamide), KEMAMIDE S (stearamide) KEMAMIDE E (oleamide), KEMAMIDE E (erucamide), KEMAMIDE O (oleamide), KEMAMIDE W45 (N, N'-ethylene bisstearamide) ), ≪ / RTI > KENAMIDE W20 (N, N'- KEMAMIDE E180 (stearyl erucamide), KEMAMIDE E221 (erucyl erucamide), KEMAMIDE S180 (stearyl stearamide), and chemamide KEMAMIDE fatty acids such as S221 (erucyl stearamide); CRODAMIDE OR (oleamide), CRODAMIDE ER (erucamide), CRODAMIDE SR (stearamide) commercially available from Croda Universal Ltd, Such as CRODAMIDE BR (behenamide), CRODAMIDE 203 (oleyl palmitamide), and CRODAMIDE 212 (stearyl erucamide). But are not limited to, CRODAMIDE fatty amides.

The shell layer and the intermediate and outer core layers of the hollow golf ball may also be formed from a thermoplastic such as an ionomer polymer and a high- and fully-neutralized ionomer (HNP). Typically, the acid moiety of the ethylene-based ionomer HNP is preferably neutralized by more than about 80%, more preferably greater than about 90%, and more preferably about 100%. The HNP may also be mixed with a second polymeric component that can be neutralized by the organic fatty acid of the present invention in a conventional manner, or both, if it comprises an acid group. The second polymeric component, which may be partially or fully neutralized, is selected from the group consisting of ionomeric copolymers and terpolymers, ionomer precursors, thermoplastics, polyamides, polycarbonates, polyesters, polyurethanes, polyureas, thermoplastic elastomers, polybutadiene rubbers, It is preferred to include metallocene-catalyzed polymers (grafted and non-grafted), single-site polymers, high-crystalline acid polymers, cationic ionomers, and the like. The HNP polymer typically has a material hardness between about 20 and about 80 Shore D and a flexural modulus between about 3,000 and about 200,000 psi.

Preferably, the HNP is an ionomer and / or an acid precursor thereof, which preferably is totally or partially neutralized with an organic acid copolymer or a salt thereof. The acid copolymers are preferably C _{3 -8} alpha, beta -ethylenically unsaturated carboxylic acids, copolymers such as alpha-olefins such as ethylene, acrylic and methacrylic acid. These optionally include softening monomers such as alkyl acrylates and alkyl methacrylates, wherein the alkyl groups have from 1 to 8 carbon atoms.

The acid copolymer may be represented by an E / X / Y copolymer, wherein E is ethylene, X is an alpha, beta -ethylenically unsaturated carboxylic acid, and Y is a softening comonomer. In a preferred embodiment, X is an acrylic or methacrylic acid, Y is a C _{1 -8} alkyl acrylate or methacrylate ester. X is preferably provided in an amount of about 1 to about 35 mass percent of the polymer, more preferably about 5 to about 30 mass percent of the polymer, and more preferably about 10 to about 20 mass percent of the polymer. Y is preferably provided in an amount of from about 0 to about 50 mass percent of the polymer, more preferably from about 5 to about 25 mass percent, more preferably from about 10 to about 20 mass percent of the polymer.

Specific acid-containing ethylene copolymers include ethylene / acrylic acid / n-butyl acrylate, ethylene / methacrylic acid / n-butyl acrylate, ethylene / methacrylic acid / isobutyl acrylate, ethylene / Acrylic acid / methyl methacrylate, ethylene / acrylic acid / methyl acrylate, ethylene / methacrylic acid / methyl acrylate, ethylene / methacrylic acid / Acid / methyl methacrylate, and ethylene / acrylic acid / n-butyl methacrylate. Preferably, the acid-containing ethylene copolymer is selected from the group consisting of ethylene / methacrylic acid / n-butyl acrylate, ethylene / acrylic acid / n-butyl acrylate, ethylene / methacrylic acid / methyl acrylate, ethylene / / Ethylene / methacrylic acid / ethyl acrylate, and ethylene / acrylic acid / methyl acrylate copolymers. More preferred acid-containing ethylene copolymers include ethylene / (meth) acrylic acid / n-butyl acrylate, ethylene / (meth) acrylic acid / ethyl acrylate, Acrylate copolymer.

The ionomer is typically neutralized with metal cations such as Li, Na, Mg, K, Ca, or Zn. It has been found, however, that by adding a sufficient organic or organic acid salt with an appropriate base to an acid copolymer or ionomer, the ionomer can be neutralized to a greater level for metal cations without loss of processability. Preferably, the acid moiety is neutralized by greater than about 80%, preferably 90 to 100%, more preferably 100%, without losing processability. This is achieved by melt-mixing the ethylene < RTI ID = 0.0 > a, -ethylenically unsaturated < / RTI > caproic acid copolymer, for example with a salt of an organic acid or of an organic acid and by neutralizing all the acid moieties (including acid moieties in the acid copolymer and organic acid) To more than 90% (more preferably, 100%) of the cation source.

Organic acids are typically aliphatic, mono- or multi-functional (saturated, unsaturated or multi-unsaturated) organic acids. Salts of these organic acids may also be used. The salt of the organic acid of the present invention may be selected from barium, lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium, strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver, aluminum, tin or calcium, Salts, especially stearic, behenic, erucic, oleic, linoleic or dimerized derivatives thereof. The organic acids and salts of the present invention are preferably non-migratory (not bloomed to the surface of the polymer at ambient temperature) and non-volatile (not volatilized at the temperatures required for melt-mixing) Do.

In addition, the ionomer of the present invention may be a more conventional ionomer, i. E., An ionomer partially neutralized with a metal cation. The acid moiety in the acid copolymer may be present in an amount of from about 1 to about 90% by cation such as lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc, aluminum, Is at least about 20 to about 75%, and more preferably, about 40 to about 70% neutralized to form an ionomer.

Preferred thermoplastic materials are disclosed in U.S. Patent No. 7,591,742, the disclosure of which is incorporated herein by reference.

The thermoplastic elastomer (TPE) can also be used as a thermoplastic shell or core layer and / or to modify the properties of the shell and / or core layer, or uncured rubber, by mixing with the base thermosetting rubber Can be used. Such TPEs may be any natural or synthetic valata or any trans-polyisoprene, high trans-polybutadiene, or any styrene block copolymer such as styrene ethylene butadiene styrene, styrene-isoprene-styrene, Other single-site catalytic polyolefins such as ethylene-octene or ethylene-butene, or thermoplastic polyurethanes (TPU) comprising copolymers, for example, with silicone. Other TPEs suitable for mixing with the thermosetting rubbers of the present invention include PEBAX (R), which is known to comprise polyetheramide copolymers, HYTREL (R), known to contain polyetherester copolymers, thermoplastic urethanes, and styrene block copolymer elastomers ≪ RTI ID = 0.0 > KRATON (R) < / RTI > In addition, the optional TPE or TPU may comprise functionality suitable for grafting, including maleic or maleic anhydride.

Further, the additional polymer can be optionally incorporated into the base rubber for the shell and core layer. Examples include, but are not limited to, core regrinds, thermoplastic vulcanizates, copoly- meric ionomers, terpolymeric ionomers, polycarbonates, polyamides, copoly- meric polyamides, polyesters, polyvinyl alcohols, acrylonitrile- Styrene-acrylonitrile polymer (SAN) (olefin-acrylonitrile copolymer), styrene-acrylonitrile copolymer (SAN), styrene-acrylonitrile copolymer, polyarylate, polyacrylate, polyphenylene ether, impact-modified polyphenylene ether, high impact polystyrene, Modified SAN and acrylonitrile-styrene-acrylonitrile polymers), styrene-maleic anhydride copolymers, styrenic copolymers, functionalized styrenic copolymers, functionalized styrenic terpolymers, styrenic terpolymers, cellulose Thermosetting elastomers such as polymers, liquid crystalline polymers, ethylene-vinyl acetate copolymers, polyureas, and polysiloxanes It is a metallocene of any of these metal species may include a catalyzed polymer, but is not limited thereto.

-카프로락탐 또는 Ω-라우로락탐과 같은 시클릭 락탐의 고리-열림 중합; (3) 6-아미노카프로산, 9-아미노노나노익 산, 11-아미노운데카노익 산, 또는 12-아미노도데카노익 산과 같은 아미노카르복실산 산의 중축합; 또는 (4) 시클릭 락탐의 디카르복실산 및 디아민과의 공중합. 적합한 폴리아미드의 구체적 예는 나일론 6, 나일론 66, 나일론 610, 나일론 11, 나일론 12, 공중합 나일론, 나일론 MXD6, 및 나일론 46을 포함한다.Also suitable within the scope of the present invention are polyamides suitable for use as the additional polymeric material of the composition, including resins obtained by: (1) (a) oxalic acid, adipic acid, sebacic acid, terephthalic acid, iso Phthalic acid or 1,4-cyclohexanedicarboxylic acid, and (b) a diamine such as ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine or decamethylenediamine, 1,4-cyclohexane Polycondensation of diamines, or m-xylylenediamine; (2)

Ring-opening polymerization of cyclic lactam such as caprolactam or? -Laurolactam; (3) polycondensation of aminocarboxylic acids such as 6-aminocaproic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, or 12-aminododecanoic acid; Or (4) copolymerization of cyclic lactam with dicarboxylic acid and diamine. Specific examples of suitable polyamides include nylon 6, nylon 66, nylon 610, nylon 11, nylon 12, copolymerized nylon, nylon MXD6, and nylon 46.

The hollow interior of the shell layer may have a thickness of from about 0.1 inches to about 1.1 inches, preferably from about 0.2 inches to about 0.9 inches, more preferably from about 0.25 inches to about 0.75 inches, and most preferably from about 0.3 inches to about 0.5 inches Diameter. In one preferred embodiment, the hollow interior of the shell layer has a diameter greater than 0.5 inches. The shell layer has a thickness ranging from 0.01 inch to about 0.4 inch. When a relatively thick shell layer is desired, the shell layer thickness may range from about 0.125 inches to about 0.375 inches, preferably from about 0.2 inches to about 0.3125 inches, more preferably from about 0.25 inches to about 0.3 inches, and most preferably, About 0.26 inches to about 0.275 inches. When it is desired to have a relatively thin shell layer, the shell layer thickness may range from about 0.01 inch to about 0.1 inch, preferably from about 0.02 inch to about 0.075 inch, more preferably from about 0.025 inch to about 0.04 inch, About 0.03 inches to about 0.035 inches. When the shell layer is relatively thin and formed from a thermoplastic material, the TP material is preferably selected (or mixed with a heat resistant TP material) as a refractory material to prevent melting of the layer by subsequent molding of the additional core and / or cover layer .

In consideration of the dimensions of the hollow interior, the hollow core (shell layer, shell layer and outer core layer (s)) of the present invention may be about 0.75 inch to about 1.58 inch, preferably about 1.0 inch to about 1.57 inch, Has an outer diameter of from about 1.3 inches to about 1.56 inches, and most preferably from about 1.4 inches to about 1.55 inches. In a preferred embodiment, the shell layer has an outer diameter of about 0.75 inches, 1.0 inches, 1.20 inches, or 1.30 inches, most preferably 0.75 inches or 1.0 inches. In an alternative embodiment, the outer core layer may have an outer diameter of from about 1.30 inches to about 1.62 inches, preferably from 1.4 inches to about 1.6 inches, and more preferably from about 1.5 inches to about 1.59 inches, And an outer core layer). In a preferred embodiment, the outer core layer has an outer diameter of about 1.51 inches, 1.53 inches, or most preferably 1.550 inches.

The inner and outer cover layers preferably have a thickness of about 0.010 to 0.080 inches, more preferably about 0.015 to 0.060 inches, and most preferably about 0.020 to 0.040 inches. Alternatively, the inner and outer cover layers have a thickness of from about 0.015 inches to about 0.055 inches, more preferably from about 0.02 inches to about 0.04 inches, and most preferably from about 0.025 inches to about 0.035 inches. The inner cover layer, if present, preferably has a hardness of at least about 60 Shore D, more preferably at least about 65 Shore D, and most preferably at least about 70 Shore D. In one embodiment, the outer cover layer is harder than the inner cover layer, but the inner cover layer is preferably harder than the outer cover layer. The outer cover layer preferably has a hardness of about 60 Shore D or less, more preferably about 55 Shore D or less, and most preferably about 50 Shore D or less.

The formation of the shell and outer core layer of the present invention is described in U.S. Patent Nos. 5,480,155, which is incorporated herein by reference in its entirety; 6,315, 683, and 8,262, 508, which are incorporated herein by reference.

In a preferred embodiment, the golf ball of the present invention comprises a hollow core. As noted above, the hollow core comprises a spherical inner core shell layer formed from the first thermosetting rubber composition. The shell layer has an outer surface, an inner surface, and an inner diameter to form a hollow center or interior. In this embodiment, a single thermoplastic outer core layer is disposed around the shell layer to complete the hollow core. A single cover or, preferably, an inner cover layer is formed around the outer core layer. When an inner cover layer is present, an outer cover layer is formed over the inner cover layer. Most preferably, the inner cover is formed from a ionomer material and the outer cover layer is formed from a polyurethane material, and the outer cover layer has a hardness less than the hardness of the inner cover layer. The inner cover preferably has a hardness of greater than about 60 Shore D and the outer cover layer has a hardness of less than about 60 Shore D.

The hollow center has a diameter of about 0.15 to 1.1 inches, preferably about 0.25 to 1.0 inches, more preferably about 0.25 to 0.75 inches, and most preferably about 0.3 to 0.5 inches. In this embodiment, the shell layer has a surface hardness greater than its inner surface hardness by about 3 to 25 Shore C to form a first hardness gradient.

The thermoplastic outer core layer has a second hardness gradient. The shell layer has a surface hardness of greater than about 55 Shore C. The spherical inner core shell layer has a coefficient of restitution (COR) of less than about 0.750 when measured at an introduction rate of 125 ft / s. The COR is preferably less than about 0.700, more preferably from about 0.500 to 0.700, and most preferably from about 0.600 to 0.700. The total core (the combination of hollow core and optional outer core layer) is greater than about 5%, more preferably about 10 to 50%, and more preferably greater than about 10% Most preferably by about 15 to 30%.

In an alternative embodiment, the hardness gradient of the thermoplastic outer core layer has a " zero hardness gradient. &Quot; The zero hardness gradient is typically about 0 Shore C (defined herein as ± 2 Shore C). The hardness gradient of the thermoplastic outer core layer also preferably has a 'negative hardness gradient' of about 1 to 10 Shore C, more preferably about 2 to 8 Shore C, and most preferably about 2 to 5 Shore C Lt; / RTI > Further, the hardness gradient of the thermoplastic outer core layer preferably has a " positive hardness gradient " of about 1 to 10 Shore C, more preferably about 2 to 8 Shore C, and most preferably about 2 to 5 Shore C Lt; / RTI >

The golf ball has a first volume and the hollow center has a second volume. The volume of the hollow center is about 2% to 30% of the golf ball volume, more preferably about 5% to 25% of the golf ball volume, and most preferably about 10% to 20% of the golf ball volume.

Referring to Figures 1A and 1B, two different embodiments of a TS / TP hollow core golf ball are disclosed. Figure 1A shows the hardness profile of a golf ball having a hollow core, an inner polymeric inner cover layer, and a polyurethane outer cover layer. The thermosetting shell layer has a thickness of about 0.375 inches and an outer diameter of about 1.0 inches, and the spherical hollow interior has a diameter of about 0.25 inches. The thermosetting shell layer has a " positive hardness gradient " of about 12 over its thickness. The thermoplastic HNP outer core layer has a thickness of about 0.275 inches and an outer diameter of about 1.55 inches. The thermoplastic HNP outer core layer has a " zero hardness gradient " over its thickness. The inner cover layer has a thickness of about 0.035 inches and the outer cover layer has a thickness of about 0.03 inches. Figure 1B shows the hardness profile of another golf ball having a hollow core, an inner polymeric inner cover layer, and a polyurethane outer cover layer. The thermosetting shell layer has a thickness of about 0.3125 inches and an outer diameter of about 0.75 inches, and the spherical hollow interior has a diameter of about 0.125 inches. The thermosetting shell layer has a " positive hardness gradient " of about 12 over its thickness. The thermoplastic HNP outer core layer has a thickness of about 0.39 inches and an outer diameter of about 1.53 inches. The thermoplastic HNP outer core layer has a " zero hardness gradient " over its thickness. The inner cover layer has a thickness of about 0.045 inches and the outer cover layer has a thickness of about 0.03 inches.

In another embodiment of the present invention, the hollow core further comprises a thermoplastic intermediate core layer disposed between the shell layer and the thermoplastic outer core layer. In another embodiment, the hollow core further comprises a thermosetting intermediate core layer disposed between the shell layer and the outer core layer. The intermediate core layer is formed from a thermosetting rubber composition that may be the same or different from the thermosetting rubber composition used to form the shell layer. Preferably, the hollow center has a diameter of about 0.51 to 1.1 inches, and the shell layer has a surface hardness of greater than about 55 Shore C.

The golf ball of the present invention includes a hollow core formed from a shell layer including a spherical hollow therein. The spherical inner core shell layer is formed of a thermoplastic composition, preferably a conventional ionomer or a fully neutralized ionomer. The shell layer has an inner surface defining an outer surface, an inner surface and a diameter of the hollow center. A single thermosetting outer core layer is formed on the shell layer and comprises a thermosetting rubber composition. The combination of the thermoplastic shell layer and the thermosetting outer core layer forms a TP / TS hollow core. Generally, the inner core layer and the outer core layer are formed on the thermosetting outer core layer. In a preferred embodiment, the inner cover comprises an ionomo material and the outer core comprises a polyurea, more preferably a polyurethane. The outer cover may be more rigid than the inner cover layer, but is preferably more ductile than the inner cover layer.

The hollow center has a diameter of about 0.15 to 1.1 inches, preferably about 0.25 to 1.0 inches, more preferably about 0.25 to 0.75 inches, and most preferably about 0.3 to 0.5 inches. The surface hardness of the thermoplastic shell layer is preferably about 1 to 5 Shore C greater than the hardness of the inner surface of the shell layer to form a first hardness gradient. The thermosetting outer core layer has a second hardness gradient, which is greater than the hardness gradient of the thermoplastic shell layer. In an alternative embodiment, the hardness gradient of the thermosetting outer core layer has a " zero hardness gradient. &Quot; The zero hardness gradient is generally about 0 Shore C (defined herein as ± 2 Shore C). The hardness gradient of the thermosetting outer core layer also has a 'negative hardness gradient', preferably from about 3 to 25 Shore C, more preferably from about 5 to 20 Shore C, most preferably from about 8 to 15 Shore C . The hardness gradient of the thermosetting outer core layer also has a " positive hardness gradient ", preferably from about 3 to 25 Shore C, more preferably from about 5 to 20 Shore C, most preferably from about 8 to 15 Shore C .

Referring to Figures 2A and 2B, two different embodiments of a TP / TS hollow core golf ball are shown. Figure 2a shows the hardness profile of a golf ball having a hollow core, an inner polymeric inner cover layer and a polyurethane outer core layer. The thermoplastic shell layer has a thickness of about 0.375 inches, an outer diameter of about 1.0 inches, and a spherical hollow interior with a diameter of about 0.25 inches. The thermoplastic shell layer has a " zero hardness gradient " across its thickness. The thermosetting outer core layer has a thickness of about 0.275 inches and an outer diameter of about 1.55 inches. The thermosetting outer core layer has a " zero hardness gradient " across its thickness. The inner cover layer has a thickness of about 0.035 inches and the outer cover layer has a thickness of about 0.03 inches. Figure 2B shows the hardness profile for another golf ball having a hollow core, an inner polymeric inner cover layer and a polyurethane outer cover layer. The thermoplastic shell layer has a thickness of about 0.3125 inches and an outer diameter of about 0.75 inches, and the spherical hollow interior has a diameter of about 0.125 inches. The thermoplastic shell layer has a " zero hardness gradient " across its thickness. The thermosetting outer core layer has a thickness of about 0.39 inches and an outer diameter of about 1.53 inches. The thermosetting outer core layer has a " positive hardness gradient " of about 27 Shore C across its thickness. The inner cover layer has a thickness of about 0.045 inches and the outer cover layer has a thickness of about 0.03 inches.

In another embodiment of the present invention, the hollow core further comprises a thermoplastic intermediate core layer disposed between the shell layer and the thermosetting outer core layer. The thermoplastic intermediate core layer may be formed of a thermoplastic material that is the same as or different from the thermoplastic material of the shell layer. In yet another embodiment, the hollow core further comprises a thermosetting intermediate core layer disposed between the thermoplastic shell layer and the thermosetting outer core layer. The intermediate core layer may be formed of a thermosetting rubber composition that is the same as or different from the thermosetting rubber composition used to form the thermosetting outer core layer. In these embodiments, the hollow center preferably has a diameter of about 0.15-1.1 inches, and the thermoplastic shell layer has a first hardness gradient, preferably a positive hardness gradient, of about 1-5 shore C, and the thermosetting outer core layer or the thermosetting intermediate core layer has a second hardness gradient.

The golf ball of the present invention includes a hollow core formed of a shell layer including a spherical hollow portion therein. The spherical inner core shell layer is formed of a thermoplastic composition and is preferably formed of a conventional ionomer or a fully neutralized ionomer. The shell layer has an outer surface, an inner surface and an inner diameter that define the dimensions of the hollow center. A single thermoplastic outer core layer is formed over the shell layer and preferably comprises an ionomer composition. The combination of the thermoplastic shell layer and the thermoplastic outer core layer forms a TP / TP hollow core. Generally, an inner cover layer and an outer cover layer are formed over the thermoplastic outer core layer. In a preferred embodiment, the inner cover comprises an ionomeric material and the outer cover comprises a polyurea, or more preferably a polyurethane. The outer cover is preferably more ductile than the inner cover layer.

The hollow center has a diameter of about 0.15 to 1.1 inches, preferably about 0.25 to 1.0 inches, more preferably about 0.25 to 0.75 inches, and most preferably about 0.3 to 0.5 inches. The surface hardness of the thermoplastic shell layer is preferably about 0-5 Shore C greater than the hardness of the inner surface of the shell layer to form a hardness gradient. The thermoplastic outer core layer also has a hardness gradient equal to or greater than the hardness gradient of the thermoplastic shell layer. In an alternate embodiment, the hardness gradient of the thermoplastic outer core layer has a " zero hardness gradient. &Quot; The zero hardness gradient is generally about 0 Shore C (defined herein as ± 2 Shore C). The hardness gradient of the thermoplastic outer core layer may also have a 'negative hardness gradient', preferably about 1 to 10 Shore C, more preferably about 2 to 8 Shore C, most preferably about 3 to 5 Shore C have. The hardness gradient of the thermoplastic outer core layer may also have a " positive hardness gradient ", preferably about 1 to 10 Shore C, more preferably about 2 to 8 Shore C, most preferably about 3 to 5 Shore C have.

The golf ball has a first volume, and the hollow center has a second volume. The volume of the hollow center is from about 2% to 30%, more preferably from about 5% to 25%, and most preferably from about 10% to 20% of the golf ball volume.

The thermoplastic inner core shell layer has a COR less than about 0.750 when measured at an inlet rate of 125 ft / s. Preferably, the COR is about 0.700, more preferably about 0.500 to 0.700, and most preferably about 0.600 to 0.700. The overall hollow core (a combination of a thermoplastic shell layer and a thermoplastic outer core layer) is greater than about 5%, more preferably from about 10% to about 50%, more preferably greater than about 10% Most preferably by as much as about 15 to 30%.

Referring to Figures 3A-B, two different embodiments of a TP / TP hollow core golf ball are disclosed. Figure 3a shows the hardness profile for a golf ball having a hollow core, an inner core layer and a polyurethane outer core layer. The thermoplastic shell layer has a thickness of about 0.375 inches and an outer diameter of about 1.0 inches, and the spherical hollow interior has a diameter of about 0.25 inches. The thermoplastic outer core layer has a thickness of about 0.275 inches and an outer diameter of about 1.55 inches. The inner cover layer has a thickness of about 0.035 inches and a thickness of about 0.03 inches. Both the thermoplastic shell layer and the thermoplastic outer core layer have a " zero hardness gradient " across their respective thicknesses. Figure 3B shows the hardness profile for another golf ball having a hollow core, an inner cover layer, and a polyurethane outer cover layer. The thermoplastic shell layer has a thickness of about 0.3125 inches and an outer diameter of about 0.75 inches, and the spherical hollow interior has a diameter of about 0.125 inches. The thermoplastic outer core layer has a thickness of about 0.39 inches and an outer diameter of about 1.53 inches. The inner core layer has a thickness of about 0.045 inches and the outer core layer has a thickness of about 0.03 inches. Both the thermoplastic shell layer and the thermoplastic outer core layer have a " zero hardness gradient " across their respective thicknesses.

In another embodiment of the present invention, the hollow core further comprises a thermoplastic intermediate core layer disposed between the thermoplastic shell layer and the thermoplastic outer core layer. In yet another embodiment, the hollow core further comprises a thermosetting intermediate core layer disposed between the thermoplastic shell layer and the thermoplastic outer core layer. The intermediate core layer is preferably formed of a thermosetting rubber composition. In these embodiments, the hollow center preferably has a diameter of about 0.15-1.1 inches, and the thermoplastic shell layer has an inner surface of about 1 to 10 Shore C to form a gradient of hardness, preferably a " positive hardness gradient & And has a larger surface hardness. The thermoplastic outer core layer preferably has a hardness gradient that is different from the hardness gradient of the thermoplastic shell layer or intermediate layer.

In a preferred embodiment, the golf ball of the present invention comprises a hollow core. The hollow core is formed from a spherical inner core shell layer incorporating a spherical hollow therein. The shell layer is formed from a thermosetting rubber composition and has an inner diameter that determines the dimensions of the outer surface, inner surface, and hollow center. In this embodiment, a single outer core layer is formed around the shell layer to form a hollow golf ball core. The outer core layer may also be a rubber composition such as a thermoset material, a shell layer, but is preferably formed from another thermosetting rubber composition. A single cover layer or multiple cover layers are formed over the TS / TS hollow core. Preferably, the inner cover layer and the outer cover layer are formed over the outer core layer. In one embodiment, the inner core comprises an ionomeric material and the outer cover layer comprises a polyurea or, preferably, a polyurethane. The outer cover layer is generally more ductile than the inner cover layer, e.g., the outer cover layer has a hardness of less than about 60 Shore D when the inner cover has a hardness greater than about 60 Shore D.

In this embodiment, the hollow center preferably has a diameter of about 0.51 to 1.1 inches (about 1.3 to 2.8 cm). The surface hardness of the shell layer is preferably greater by about 3 to 25 Shore C than the hardness of the inner surface of the shell layer to form the first hardness gradient. In a preferred embodiment, the thermosetting outer core layer has a different hardness gradient than the hardness gradient of the thermosetting shell layer. Most preferably, the shell layer has a surface hardness of greater than about 55 Shore C.

The thermosetting inner core shell layer has a coefficient of restitution (COR) of less than about 0.750 when measured at an introduction rate of 125 ft / s (about 38.1 m / s). Preferably, the coefficient of restitution is less than about 0.700, more preferably about 0.500 to 0.700, and most preferably about 0.600 to 0.700. The total hollow core (the combination of the thermosetting shell layer and the thermosetting outer core layer) is about 5% larger, more preferably about 5% greater than the inner core shell layer when measured at an inlet rate of 125 ft / s 10 to 50% greater, and most preferably about 15 to 30% greater.

In an alternative, the hardness gradient of the thermosetting outer core layer is a "zero hardness gradient ". The zero hardness gradient is generally approximately 0 Shore C (defined herein as ± 2 Shore C). The hardness gradient of the thermosetting outer core layer can also be a "negative hardness gradient ", and is preferably about 3 to 25 Shore C, more preferably about 5 to 20 Shore C, and most preferably about 8 to 15 Shore C < / RTI > The hardness gradient of the thermosetting outer core layer may also be a "positive hardness gradient ", and is preferably about 3 to 25 Shore C, more preferably about 5 to 20 Shore C, and most preferably about 8 to 15 Shore C < / RTI >

The golf ball has a first volume and the hollow center has a second volume. The volume of the hollow center is between about 2% and 30% of the golf ball volume, more preferably between about 5% and 25% of the golf ball volume, and most preferably between about 10% and 20% of the golf ball volume.

In yet another embodiment of the present invention, the hollow center further comprises a thermoplastic intermediate core layer disposed between the thermosetting shell layer and the thermosetting outer core layer. In yet another embodiment, the hollow center further comprises a thermosetting intermediate core layer disposed between the thermosetting shell layer and the thermosetting outer core layer. The intermediate core layer may be formed from a thermosetting rubber composition that is the same or different from the thermosetting rubber composition used to form the thermosetting shell layer or the thermosetting outer core layer. In this embodiment, the hollow center preferably has a diameter of about 0.15 to 1.1 inches (about 0.38 to 2.79 cm), and the shell layer has a hardness gradient, preferably "positive hardness gradient" And has a surface hardness of about 10 to 25 Shore C. The thermosetting outer core layer preferably has a hardness gradient that is different from the hardness gradient of the shell layer or intermediate layer.

The hollow core of the present invention is covered with at least one cover layer. An intermediate layer such as an inner cover layer may optionally be disposed about the hollow core, and a cover layer may be formed around the intermediate layer as an outer cover layer. While all of the thermoplastic materials disclosed herein may be suitable for the inner cover layer or outer cover layer of the present invention, in the preferred embodiment the outermost cover is a castable polyurea or castable polyurethane; Castable hybrid polyurethane / polyurea; And castable hybrid polyurea / polyurethane. Suitable polyurethanes include those disclosed in U.S. Patent Nos. 5,334,673 and 6,506,851. Suitable polyureas include those disclosed in U.S. Patent Nos. 5,484,870 and 6,835,794. These patents are incorporated herein by reference.

Another suitable polyurethane composition comprises the reaction product of at least one polyisocyanate and at least one curing agent. The curing agent may comprise, for example, one or more polyamines, one or more polyols, or combinations thereof. The polyisocyanate may be combined with at least one polyol to form a prepolymer and then combined with at least one curing agent. Thus, the polyols disclosed herein are suitable for use in one or both of the polyurethane materials, i.e., as part of the prepolymer and for use in the curing agent. More suitable polyurethanes are disclosed in U.S. Patent No. 7,331,878, the contents of which are incorporated herein by reference.

Any polyisocyanate available to those skilled in the art is suitable for use in accordance with the present invention. Exemplary polyisocyanates include 4,4'-diphenylmethane diisocyanate (MDI); Polymeric MDI; Carbodiimide-modified liquid MDI; 4,4'-dicyclohexylmethane diisocyanate (H ₁₂ MDI); p-phenylene diisocyanate (PPDI); m-phenylene diisocyanate (MPDI); Toluene diisocyanate (TDI); 3,3'-dimethyl-4,4'-biphenylene diisocyanate; Isophorone diisocyanate; 1,6-hexamethylene diisocyanate (HDI); Naphthalene diisocyanate; Xylene diisocyanate; p-tetramethylxylene diisocyanate; m-tetraethyl xylylene diisocyanate; Ethylene diisocyanate; Propylene-1,2-diisocyanate; Tetramethylene-1,4-diisocyanate; Cyclohexyl diisocyanate; Dodecane-1,12-diisocyanate; Cyclobutane-1,3-diisocyanate; Cyclohexane-1,3-diisocyanate; Cyclohexane-1,4-diisocyanate; 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane; Methylcyclohexylenediisocyanate; Triisocyanates of HDI; Triisocyanates of 2,4,4-trimethyl-1,6-hexane diisocyanate; Tetracene diisocyanate; Naphthalene diisocyanate; Anthracene diisocyanate; Isocyanates of toluene diisocyanate; Hexamethylene diisocyanate, uretdione of hexamethylene diisocyanate, and hybrids thereof. Polyisocyanates comprising more than one isocyanate group, such as di-isocyanate, tri-isocyanate and tetra-isocyanate, are known to those skilled in the art. Preferably, the polyisocyanate comprises MDI, PPDI, TDI or mixtures thereof, more preferably the polyisocyanate comprises MDI. As disclosed herein, the term MDI is understood to include 4,4'-diphenylmethane diisocyanate, polymeric MDI, carbodiimide-modified liquid MDI, and mixtures thereof, and additionally, use Diisocyanate may be a " low free monomer "and may be a low level, typically less than about 0.1% free monomoisocyanate group, of a" free "isocyanate monomer group by those skilled in the art Able to know. Examples of "low free monomer" diisocyanates include, but are not limited to, low free monomer MDI, low free monomer TDI and low free monomer PPDI. The at least one polyisocyanate should have an unreacted NCO group of less than about 14%. Preferably, the at least one polyisocyanate has an NCO no greater than about 8.0%, more preferably no greater than about 7.8% NCO, most preferably no greater than about 7.5%, and a commonly used amount of about 7.2 Or 7.0, or an NCO level of 6.5%.

Any polyol available to those skilled in the art is suitable for use in accordance with the present invention. Exemplary polyols include, but are not limited to, polyether polyols, hydroxy-terminated polybutadienes (including partially / fully hydrogenated derivatives), polyester polyols, polycaprolactone polyols, and polycarbonate polyols . In one preferred embodiment, the polyol comprises a polyether polyol. Examples include, but are not limited to, polytetramethylene ether glycol (PTMEG), polyethylene propylene glycol, polyoxypropylene glycol, and mixtures thereof. Hydrocarbon chains may have saturated or unsaturated bonds and substituted or unsubstituted aromatic and cyclic groups. Preferably, the polyol of the present invention comprises PTMEG.

In another embodiment, the polyester polyol is included in a polyurethane material. Suitable polyester polyols include polyethylene adipate glycols; Polybutylene adipate glycol; Polyethylene propylene adipate glycol; o-phthalate-1,6-hexanediol; Poly (hexamethylene adipate) glycol; And mixtures thereof. The hydrocarbon chain may have a saturated or unsaturated bond, or a substituted or unsubstituted aromatic and cyclic group.

In another embodiment, the polycaprolactone polyol is included in the material of the present invention. Suitable polycaprolactone polyols include, but are not limited to, 1,6-hexanediol initiated polycaprolactone, diethylene glycol initiated polycaprolactone, trimethylolpropane initiated polycaprolactone, neopentyl glycol initiated polycaprolactone, 1,4- Butanediol-initiated polycaprolactone, and mixtures thereof. The hydrocarbon chain may have a saturated or unsaturated bond, or a substituted or unsubstituted aromatic and cyclic group.

In yet another embodiment, a polycarbonate polyol is included in the polyurethane material of the present invention. Suitable polycarbonates include, but are not limited to, polyphthalate carbonates and poly (hexamethylene carbonate) glycols. The hydrocarbon chain may have a saturated or unsaturated bond, or a substituted or unsubstituted aromatic or cyclic group. In one embodiment, the molecular weight of the polyol is from about 200 to about 4000.

In addition, the polyamine curative is suitable for use in the polyurethane composition of the present invention and improves the cutting, shearing and impact resistance of the resultant ball. Good polyamine curatives include 3,5-dimethylcyano-2,4-toluenediamine and its isomers; 3,5-diethyltoluene-2,4-diamine, such as 3,5-diethyltoluene-2,6-diamine, and isomers thereof; 4-4'-bis- (sec-butylamino) -diphenylmethane; 1,4-bis- (sec-butylamino) -benzene, 4,4'-methylene-bis- (2-chloroaniline); 4,4'-methylene-bis- (3-chloro-2,6-diethylaniline); Polytetramethylene oxide-di-p-aminobenzoate; N, N'-dialkyldiaminodiphenylmethane; p, p'-methylenedianiline; m-phenylenediamine; 4,4'-methylene-bis- (2-chloroaniline); 4,4'-methylene-bis- (2,6-diethylaniline); 4,4'-methylene-bis- (2,3-dichloroaniline); 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane; 2,2 ', 3,3'-tetrachlorodiaminodiphenylmethane; Trimethylene glycol di (di) -p-aminobenzoate; And mixtures thereof. Preferably, the curing agent of the present invention is selected from the group consisting of 3,5-dimethylthio-2, such as ETHACURE 300 commercially available from Albermarle Corporation, Baton Rouge, 4-toluenediamine and isomers thereof. A suitable polyamine curative, including both primary and secondary amines, preferably has a molecular weight in the range of about 64 to about 2000.

At least one of the diol, triol, tetraol or hydroxy-terminated curatives may be added to the polyurethane composition described above. Suitable diols, triols and tetraols are ethylene glycol; Diethylene glycol; Polyethylene glycol; Propylene glycol; Polypropylene glycol; Low molecular weight polytetramethylene ether glycol; 1,3-bis (2-hydroxyethoxy) benzene; 1,3-bis- [2- (2-hydroxyethoxy) ethoxy] benzene; 1,3-bis- {2- [2- (2-hydroxyethoxy) ethoxy] ethoxy} benzene; 1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol; Resorcinol-di- (? -Hydroxyethyl) ether; hydroquinone-di- (? -Hydroxyethyl) ether; And mixtures thereof. Preferred hydroxy-terminated curatives are 1,3-bis (2-hydroxyethoxy) benzene; 1,3-bis- [2- (2-hydroxyethoxy) ethoxy] benzene; 1,3-bis- {2- [2- (2-hydroxyethoxy) ethoxy] ethoxy} benzene; 1,4-butanediol, and mixtures thereof. Preferably, the hydroxy-terminated curative has a molecular weight in the range of about 48 to about 2000. As used herein, molecular weight is an absolute weight average molecular weight and can be understood by those skilled in the art.

Both hydroxy-terminated and amine-curable can include one or more saturated, non-saturated, aromatic and cyclic groups. In addition, the hydroxy-terminated and amine curative can comprise one or more halogen groups. The polyurethane composition may be formed of a hybrid or mixture of curing agents. However, if desired, the polyurethane composition may be formed with a single curing agent.

In a preferred embodiment of the present invention, the saturated polyurethane is used to form one or more cover layers, preferably outer cover layers, and can be selected from castable thermosetting and thermoplastic polyurethanes. In this embodiment, the saturated polyurethanes of the present invention are generally free of aromatic groups or moieties (aromatic groups or moieties). Saturated polyurethanes suitable for use in the present invention are the products of the reaction between at least one polyurethane prepolymer and at least one saturated curing agent. Polyurethane prepolymers are products formed by the reaction between at least one saturated polyol and at least one saturated diisocyanate. As is well known in the art, a catalyst may be employed to promote the reaction between a curing agent and an isocyanate and a polyol, or between a curing agent and a prepolymer.

In addition, the polyurethane can be replaced or mixed with a polyurea material. The polyurea is distinctly different from the polyurethane composition. The polyurea-based composition is preferably saturated in properties. The polyurea composition can be formed from the reaction product of an isocyanate with a cross-linked polyamine prepolymer with a curing agent. For example, the polyurea-based composition of the present invention may be prepared from at least one isocyanate, at least one polyetheramine, and at least one glycol curing agent or at least one diamine curing agent.

Although all embodiments herein may have any known number and pattern of dimples, the number of dimples preferred is 252 to 456, more preferably 330 to 392. The dimples may include any width, depth, and corner angles disclosed in the prior art, and the pattern may include multiple dimples having different widths, depths, and angles of corners. The separating line structure of the pattern may be a straight line or a wavy dividing line (SWPL). Most preferably, the number of dimples is 330, 332 or 392, including dimple sizes of 5 to 7, and the dividing line is SWPL.

In all these embodiments, the single layer core may be replaced by a core having two or more layers, and at least one of the core layers may have a negative hardness gradient. Except for operating examples, or unless otherwise expressly stated, all numerical ranges, amounts, values, and ratios for amounts of materials and others in the specification are to be understood as referring to the terms "about", " Although it may not appear clearly in the scope, it can be understood that the phrase "about" is written. Accordingly, unless stated to the contrary, the numerical limitations set forth in the specification and the appended claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, it is not an attempt to limit the application of the doctrine of equivalents to the scope of the claims, so that each numerical limitation should at least be understood by applying ordinary rounding techniques in terms of reported significant digits.

The numerical values set forth in the specific examples are reported as precisely as possible, even though the numerical ranges and limitations set forth in the broader aspects of the invention are approximations. However, any numerical value inherently contains any errors necessarily resulting from the standard deviation found in each experimental measurement. Furthermore, it is contemplated that when various ranges of numerical ranges are disclosed herein, any combination of these values, including the listed values, may be used.

It is to be understood that the exemplary embodiments of the invention disclosed herein achieve the objects described above, but it is to be understood that many modifications and other embodiments may be devised by those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and embodiments and fall within the spirit and scope of the invention.

Claims (13)

A golf ball comprising a hollow core,
A spherical inner core shell layer formed of a first material, comprising: a spherical inner core shell layer having an outer surface, an inner surface, and an inner diameter defining a hollow center;
An outer core layer disposed around the spherical inner core shell layer and comprising a second material;
An inner cover layer disposed around the outer core layer and comprising an ionomer material,
An outer cover layer disposed about the inner cover layer and comprising a polyurea or polyurethane and having a hardness less than the hardness of the inner cover layer,
Wherein the hollow core has a diameter of about 0.15 to 1.1 inches, the shell layer has a first hardness gradient, and the outer core layer has a second hardness gradient different from the first hardness gradient
Golf ball. The method according to claim 1,
Wherein the first and second materials are thermoplastic
Golf ball. 3. The method of claim 2,
Wherein the first hardness gradient is a positive hardness gradient of less than or equal to 5 Shore C
Golf ball. The method of claim 3,
The second hardness gradient may be a positive hardness gradient or a negative hardness gradient
Golf ball. The method according to claim 1,
Wherein the first material is thermosetting and the second material is thermoplastic
Golf ball. 6. The method of claim 5,
Wherein the first hardness gradient is a positive hardness gradient of about 3 to 25 Shore C
Golf ball. The method according to claim 1,
Wherein the first material is thermoplastic and the second material is a thermosetting < RTI ID = 0.0 >
Golf ball. 8. The method of claim 7,
Wherein the first hardness gradient is a positive hardness gradient of less than or equal to 5 Shore C
Golf ball. 9. The method of claim 8,
The second hardness gradient is a positive hardness gradient of about 3 to 25 Shore C
Golf ball. The method according to claim 1,
Wherein the first material is thermosetting and the second material is also thermosetting
Golf ball. The method according to claim 1,
Wherein the golf ball has a first volume and the hollow center has a second volume that is between about 2% and 30% of the first volume
Golf ball. The method according to claim 1,
Wherein the spherical inner core shell layer has a coefficient of restitution less than about 0.700 when measured at an introduction rate of 125 ft / s
Golf ball. The method according to claim 1,
The outer core layer has a coefficient of restitution measured at an introduction rate of 125 ft / s, which is 10-50% higher than the coefficient of restitution of the inner core shell layer measured at an introduction rate of 125 ft / s
Golf ball.

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