High flex modulus ionomer for improved golf ball durability

Abstract

In one aspect, a golf ball includes a core comprising rubber, and at least one intermediate layer disposed on the core. The intermediate layer comprises at least one ionomer comprising a neutralized ethylene acid copolymer derived from an ethylene monomer and from 7.5 mol% to 15.0 mol% of a carboxylic acid comonomer based on the total mol% of monomers present in the at least one ionomer, wherein the at least one ionomer has a melt index (I2) of 0.5 dg / min to 10.0 dg / min as measured according to ASTM D 1238 (2.16 kg, 190°C), wherein 10 mol% to 50 mol% of the total acid units of the at least one ionomer are neutralized by zinc cations and sodium cations.

Description

Cross-references to related applications

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 574,634, filed on April 4, 2024, the contents of which are incorporated herein by reference in their entirety. Background Technology

[0002] Golf balls are designed to provide an optimal balance of distance and touch without compromising durability. From a materials perspective, the golf ball industry is interested in a variety of resins offering different combinations of coefficient of recovery (COR), compression value, flexural modulus, hardness, scratch resistance, and crack resistance for various performance targets and markets. A simple 2-piece ball consists of a core and an overlay. The core is typically polybutadiene rubber (PBR), while the overlay is often an ionomer. Performance balls are typically constructed with 3 to 5 layers, including a PBR core, an ionomer mantle (i.e., an interlayer), and a polyurethane overlay.

[0003] There is a continued demand for golf balls with higher flexural modulus and improved impact resistance and durability in the golf ball cover and overlay. Summary of the Invention

[0004] The embodiments of this disclosure meet the need for golf balls with higher flexural modulus and improved impact durability by utilizing ionomers or ionomer blends that are neutralized by Na and Zn and contain greater than 7.5 mol% of carboxylic acid comonomers and have a higher molecular weight (i.e., a melt index (I2) of 0.5 dg / min to 10.0 dg / min).

[0005] In one aspect, a golf ball includes a rubber core and at least one intermediate layer disposed on the core. The intermediate layer comprises at least one ionomer comprising a neutralized ethylene copolymer of a carboxylic acid comonomer derived from ethylene monomers and comprising 7.5 mol% to 15 mol% of the total mol% of the monomers present in the at least one ionomer, wherein the at least one ionomer has a melt index (I2) of 0.5 dg / min to 10.0 dg / min as measured according to ASTM D 1238 (2.16 kg, 190 °C), wherein 10 mol% to 50 mol% of the total acid units of the at least one ionomer are neutralized by zinc and sodium cations. Attached Figure Description

[0006] To facilitate the identification of any particular element or action in discussion, the most important number in the reference numbering points to the figure reference where that element was first introduced.

[0007] Figure 1 This is a cross-sectional view of a golf ball according to one embodiment of the present disclosure.

[0008] Figure 2 This is another cross-sectional view of a golf ball according to one embodiment of the present disclosure. Detailed Implementation

[0009] Specific embodiments of this application will now be described. This disclosure may be implemented in various forms and should not be construed as limiting it to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art.

[0010] definition

[0011] "Polymer" refers to a polymeric compound prepared by polymerizing monomers, whether of the same or different types. Therefore, the term polymer encompasses the term homopolymer (used to refer to a polymer prepared from only one type of monomer, where it should be understood that trace impurities may be incorporated into the polymer structure) and the terms copolymer and interpolymer. Trace impurities (e.g., catalyst residues) may be incorporated into and / or within the polymer. A polymer can be a single polymer or a polymer blend.

[0012] As used herein, the term "copolymer" refers to a polymer formed by the polymerization of at least two monomers with different structures. The term "copolymer" includes terpolymers. For example, ethylene copolymers (such as ethylene-propylene copolymers) comprise at least two structurally different monomers (e.g., an ethylene-propylene copolymer comprises copolymer units of at least ethylene monomers and propylene monomers) and may optionally include additional monomers or functional materials or modifiers, such as acid, acrylate, or anhydride functional groups. In other words, the copolymers described herein contain at least two structurally different monomers, and although copolymers may consist of only two structurally different monomers, they do not necessarily consist of only two structurally different monomers and may include additional monomers or functional materials or modifiers.

[0013] As used herein, the term "ionomer" refers to a polymer containing an ionic group, which is a carboxylate, such as ammonium carboxylate, alkali metal carboxylate, alkaline earth metal carboxylate, transition metal carboxylate, and / or combinations of such carboxylates. Such polymers are typically prepared by partially or completely neutralizing the carboxylate groups of a precursor or parent polymer that serves as an acid copolymer as defined herein, for example, by reacting it with a base.

[0014] As used herein, the term "acid copolymer" refers to a polymer comprising copolymer units of an α-olefin, a carboxylic acid, and optionally other suitable comonomers.

[0015] refer to Figure 1The golf ball 100 includes a rubber-containing core 102 and at least one intermediate layer 104 disposed on the core 102. The intermediate layer 104 contains at least one ionomer. This ionomer comprises a neutralized ethylene copolymer derived from ethylene monomers and from a carboxylic acid comonomer at a total molar percentage based on the total molar percentage of the monomers present in the at least one ionomer. The ionomer has a melt index (I2) of 0.5 dg / min to 10.0 dg / min as measured according to ASTM D 1238 (2.16 kg, 190 °C). Furthermore, 10 mol% to 50 mol% of the total acid units of the at least one ionomer are neutralized by zinc and sodium cations.

[0016] The ionomer contains greater than 50 mol% to 92.5 mol% of ethylene, or in other embodiments, a minimum of 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, or 90 mol% of ethylene and a maximum of 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, 90 mol%, or 92.5 mol% of ethylene. As detailed below, the balance of the ionomer may include metal cations as defined below.

[0017] In other embodiments, the ionomer comprises 7.5 mol% to 15 mol% of carboxylic acid, or in other embodiments, a minimum of 7.5 mol%, 8.0 mol%, 8.5 mol%, 9.0 mol%, 9.5 mol%, 10.0 mol%, 10.5 mol%, 11.0 mol%, 11.5 mol%, 12.0 wt%, 12.5 mol%, 13.0 mol%, 13.5 mol%, or 14.0 mol% to a maximum of 8.0 mol%, 8.5 mol%, 9.0 mol%, 9.5 mol%, 10.0 mol%, 10.5 mol%, 11.0 mol%, 11.5 mol%, 12.0 mol%, 12.5 mol%, 13.0 mol%, 13.5 mol%, 14.0 mol%, or 15.0 mol% of carboxylic acid comonomer. Without being theoretically limited, incorporating more than 7.5 mol% of carboxylic acid into the ionomer can result in a greater flexural modulus at the same molecular weight. In one or more embodiments, the ionomer may have a flexural modulus of at least 70 ksi (1000 psi) or 70 kpsi to 150 kpsi as measured according to ASTM D790.

[0018] In other embodiments, the ionomer may contain 20% to 40% by weight of a carboxylic acid, or in other embodiments, a minimum of 20%, 21%, 21.5%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, or 39% by weight, and a maximum of 21%, 21.5%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40% by weight of a carboxylic acid comonomer. The carboxylic acid monomer may include monocarboxylic acids, such as acrylic acid, methacrylic acid, or combinations thereof.

[0019] Furthermore, without being limited by theory, the increase in the durability and stiffness of golf balls is related to the increase in the molecular weight of the ionomer. In one or more embodiments, the ionomer or ionomer blend may have a melt index I2 of 0.5 dg / min to 10 dg / min, or in further embodiments, it may have a melt index (I2) in the range of at least 0.5 dg / min, 1.0 dg / min, 1.5 dg / min, 2.0 dg / min, 3.0 dg / min, 4.0 dg / min, 5.0 dg / min, 6.0 dg / min, 7.0 dg / min, 8.0 dg / min or 9.0 dg / min to at most 1.0 dg / min, 1.5 dg / min, 2.0 dg / min, 3.0 dg / min, 4.0 dg / min, 5.0 dg / min, 6.0 dg / min, 7.0 dg / min, 8.0 dg / min, 9.0 dg / min or 10.0 dg / min. In yet another embodiment, the ionomer may have a melt index of 1.0 dg / min to 2.0 dg / min.

[0020] In one or more embodiments of this disclosure, the pre-neutralized vinyl acetate copolymer has a melt index (I2) of 10.0 dg / min to 60.0 dg / min. In further embodiments, the pre-neutralized vinyl acetate copolymer or its blend (also referred to as the base resin) may have a melt index ranging from a minimum of 10 dg / min, 15 dg / min, 20 dg / min, 25 dg / min, 30 dg / min, 35 dg / min, 40 dg / min, 45 dg / min, 50 dg / min, or 55 dg / min to a maximum of 15 dg / min, 20 dg / min, 25 dg / min, 30 dg / min, 35 dg / min, 40 dg / min, 45 dg / min, 50 dg / min, 55 dg / min, or 60 dg / min. In yet another embodiment, the pre-neutralized vinyl acetate copolymer may have a melt index of 25 dg / min to 35 dg / min.

[0021] In addition to the ethylene copolymers disclosed herein, ionomers may also be terpolymers. In one embodiment, the terpolymer may contain additional comonomers, such as alkyl acrylates and / or alkyl methacrylates.

[0022] The ionomer can be neutralized with sodium cations, which are present in an amount of 0.1 mol% to 3 mol%, or in other embodiments, at least 0.1 mol%, 0.25 mol%, 0.5 mol%, 0.75 mol%, 1.0 mol%, 1.5 mol%, 2.0 mol%, or 2.5 mol%, up to a maximum of 0.25 mol%, 0.5 mol%, 0.75 mol%, 1.0 mol%, 1.5 mol%, 2.0 mol%, 2.5 mol%, or 3.0 mol%. Alternatively, the ionomer can be neutralized with zinc cations, which are present in an amount of 0 mol% to 3 mol%, or in other embodiments, at least 0.1 mol%, 0.25 mol%, 0.5 mol%, 0.75 mol%, 1.0 mol%, 1.5 mol%, 2.0 mol%, or 2.5 mol%, up to a maximum of 0.25 mol%, 0.5 mol%, 0.75 mol%, 1.0 mol%, 1.5 mol%, 2.0 mol%, 2.5 mol%, or 3.0 mol%.

[0023] In addition to zinc and sodium cations, the use of other monovalent metal cations (e.g., lithium), divalent metal cations (e.g., magnesium), trivalent metal cations (e.g., aluminum), or combinations thereof has been considered.

[0024] As stated above, 10 mol% to 50 mol% of the total acid units of the at least one ionomer are neutralized by zinc cations and sodium cations. In further embodiments, the neutralization can range from a minimum of 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, or 45 mol% of neutralized total acid units to a maximum of 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, or 50 mol% of neutralized total acid units.

[0025] Some embodiments may involve a single ionomer neutralized by Zn and Na cations. In other embodiments, the ionomer comprises a blend of a first ionomer and a second ionomer. The first ionomer comprises 7.5 mol% to 15 mol% of a carboxylic acid comonomer based on the total mol% of monomers present in the first ionomer, and has 10 mol% to 50 mol% of the total acid units of the first ionomer neutralized by sodium cations. The second ionomer comprises 7.5 mol% to 15 mol% of a carboxylic acid comonomer based on the total mol% of monomers present in the second ionomer, and 10 mol% to 50 mol% of the total acid units of the second ionomer are neutralized by zinc cations.

[0026] Various amounts of the first and second ionomers within the blend are considered. For example, the blend may contain a first ionomer in an amount ranging from a minimum of 20%, 30%, 40%, 50%, 60%, or 70% to a maximum of 30%, 40%, 50%, 60%, 70%, or 80% by weight. Conversely, the blend may contain a second ionomer in an amount ranging from a minimum of 20%, 30%, 40%, 50%, 60%, or 70% to a maximum of 30%, 40%, 50%, 60%, 70%, or 80% by weight. In another embodiment, the blend may contain 40% to 60% of both the first and second ionomers.

[0027] Similarly, 10 mol% to 50 mol% of the total acid units of the first ionomer are neutralized with sodium cations. In further embodiments, the neutralization of the first ionomer can range from a minimum of 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, or 45 mol% of neutralized acid units to a maximum of 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, or 50 mol% of neutralized acid units. Furthermore, 10 mol% to 50 mol% of the total acid units of the second ionomer are neutralized with zinc cations. In further embodiments, the neutralization of the second ionomer can range from a minimum of 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, or 45 mol% of neutralized acid units to a maximum of 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, or 50 mol% of neutralized acid units. In one or more embodiments, the first ionomer can be neutralized to a greater extent, a smaller extent, or the same extent relative to the second ionomer.

[0028] Acetic acid copolymers can be prepared by standard free radical copolymerization, using high pressure, and in a continuous operation. Monomers are fed into the reaction mixture in proportions related to monomer activity and desired incorporation levels. This achieves a uniform, nearly random distribution of monomer units along the chain. Unreacted monomers can be recovered. Acetic acid copolymers can be prepared according to those methods disclosed in U.S. Patent Nos. 3,404,134, 5,028,674; those methods disclosed in U.S. Patent Nos. 6,500,888; and those methods disclosed in U.S. Patent Nos. 6,518,365.

[0029] Acid copolymer resins can be neutralized by any conventional procedure, such as those disclosed in U.S. Patent Nos. 3,404,134 and 6,518,365, as well as other procedures readily apparent to those skilled in the art. Some of these methods are described in detail in U.S. Patent No. 8,334,033 to Hausmann et al.

[0030] Golf ball construction

[0031] Refer again Figure 1 The core 102 contains polybutadiene rubber. Figure 1 In the two-layer structure, the middle layer 104 can be considered as the outer layer or the cover layer. In, for example... Figure 2In the three-layer embodiment shown, the golf ball 200 may further include an outer layer 106 disposed on an intermediate layer 104 having an ionomer. In one embodiment, the outer layer 106 comprises polyurethane. Furthermore, it is contemplated that the golf ball may have a four-layer, five-layer, or even more-layered construction.

[0032] Golf balls 100 or 200 can have a COR of 0.7 to 0.9 at 125 ft / s. Golf balls 100 or 200 can have an ADC compression value of 50 mils to 100 mils. In addition, golf balls 100 or 200 can have a Shore D hardness of 50 to 75.

[0033] additive

[0034] The composition may additionally contain small amounts of optional materials, including additives for polymeric materials. Examples of suitable additives include, but are not limited to, plasticizers, stabilizers including viscosity stabilizers and hydrolytic stabilizers, and primary and secondary antioxidants such as, for example, IRGANOX. ® 1010. Ultraviolet absorbers and stabilizers, antistatic agents, dyes, pigments or other colorants, flame retardants, lubricants, processing aids, slip additives, release agents, and / or mixtures thereof. Additional optional additives may include acid copolymer waxes, such as, for example, Honeywell wax AC540; TiO2 used as a brightener; fluorescent whitening agents; surfactants; and other components known in the golf ball manufacturing industry that are useful but may not be critical to golf ball performance and / or acceptability. Many such additives are described in the Kirk Othmer Encyclopedia of Chemical Technology, 5th Edition, John Wiley & Sons (Hoboken, 2005).

[0035] Examples of fillers include metals such as titanium, tungsten, aluminum, bismuth, nickel, molybdenum, iron, steel, lead, copper, brass, boron, boron carbide whiskers, bronze, cobalt, beryllium, zinc, and tin; metal oxides, including zinc oxide, iron oxide, aluminum oxide, tin oxide, titanium oxide, magnesium oxide, zinc oxide, and zirconium oxide; and other well-known salts and their oxides. Other commonly used fillers include barium sulfate, lead silicate, tungsten carbide, limestone (heavy calcium carbonate / magnesium carbonate), zinc sulfate, calcium carbonate, zinc carbonate, barium carbonate, clay, tungsten, and mixtures of any of these.

[0036] These additives may be present in the composition in amounts ranging from 0.01% to 15%, 0.01% to 10%, or 0.01% to 5% of the total composition.

[0037] The optional incorporation of such conventional components into the composition can be carried out by any known method, such as by dry blending, by extruding a mixture of various components, by conventional masterbatch technology, etc.

[0038] Golf balls are produced using methods familiar to those skilled in the art, such as injection molding, coating the core with a molded sleeve and / or a cover layer, etc.

[0039] Test methods

[0040] density

[0041] Density was measured according to ASTM D792 and expressed in grams per cubic centimeter. 3 (g / cm) 3 )express.

[0042] Melt index (I2)

[0043] Melt index (I2) is measured according to ASTM D 1238-10 at 190°C and 2.16 kg using Method B, and is expressed as grams eluted per 10 minutes (g / 10min). For ionomer blends, melt index (I2) is the arithmetic mean of the weight percentages of the blend components.

[0044] Coefficient of Recovery (COR)

[0045] The coefficient of restitution (COR) was measured by firing solid resin spheres with a density similar to that of a golf ball from an air cannon at several velocities ranging from approximately 60 ft / s to 180 ft / s. The spheres struck a steel plate positioned three feet away from a point determined by the initial velocity and rebounded through a velocity monitoring device positioned at the same point as the initial velocity measurement. The COR measured each time was determined as the ratio of the rebound velocity to the initial velocity. The individually measured COR values ​​were plotted as a function of the initial velocity, and the COR at 125 ft / s was determined by linear regression. 125 ) and COR at 150ft / s (COR 150 ).

[0046] Shore D hardness

[0047] Shore D hardness was measured on a standard test sample according to ASTM D-2240.

[0048] ADC compression value (mils)

[0049] The ADC compression value, an indicator of compressibility, is the deflection distance of a solid sphere measured after applying a 200-pound compressive load, according to industry-specific testing procedures.

[0050] Flexural modulus

[0051] According to ASTM D790, Method 1, Procedure A, the flexural modulus is measured using a three-point test fixture with a 2-inch span length and a crosshead speed of 0.50 inches / minute. This method provides a measurement of the tangential modulus of elasticity (three-point flexural modulus).

[0052] Durability

[0053] Durability is measured by the loss of COR after repeated firing from an air cannon at the desired velocity onto a steel plate positioned 3 feet away. Failure is defined as when the COR is only 95% of its initial value. The data reports the number of impacts required to reach failure.

[0054] Example

[0055] The following examples are provided to further illustrate the invention in detail, but should not be construed as limiting the scope of the claims. Unless otherwise indicated, all parts and percentages are by weight.

[0056] Preparation of ionomers

[0057] Referring to Table 1, a single cationic ionomer is produced by neutralizing the copolymer of ethylene and methacrylic acid with a metal cationic moiety. Methods for producing ionomers have previously been disclosed in patent literature, such as US 8,334,033, US 3,404,134, and US 6,518,365. The mixed Na / Zn ionomers used in these embodiments are produced by dry blending sodium and zinc ionomers before injection molding solid spheres or overmolding around a polybutadiene rubber (PBR) core to form a two-layer sphere.

[0058] Table 1: Resins

[0059]

[0060] Preparation of solid spheres

[0061] Referring to Table 2 below, solid spheres with a diameter of 1.55 inches were prepared by injection molding at a nozzle temperature of 200°C on a Nissei FNX 180 injection molding machine. Molding conditions for solid spheres are also provided in US 2016 / 0236039, which is incorporated herein by reference in its entirety.

[0062] Table 2: Characteristics of a solid 1.55-inch diameter golf ball

[0063]

[0064] Table 2 shows the benefits of mixed Na / Zn cations (CE6, CE7, CE8, and EX1) to the flexural modulus of ionomers compared to single-cation Na (CE1 and CE2) or Zn (CE3, CE4, and CE5) without significantly altering other key performance properties such as coefficient of recovery (COR), ADC compression value, or hardness. For CE6 and CE7, the flexural modulus is actually higher than that of either individual ionomer used in the blend. For CE8 and EX1, the flexural modulus of the mixed ionomers is between that of the Na ionomers and the Zn ionomers, or comparable to that of the higher-modulus Na ionomer.

[0065] In all cases, the flexural modulus of the mixed Na / Zn ionomers remained surprisingly high, even when the composition consisted of 50% by weight of Zn ionomers with lower flexural modulus. The mixed ionomer EX1 surprisingly exhibited a higher flexural modulus and a higher COR than comparative examples CE6 to CE8, even under lower neutralization conditions.

[0066] Preparation of 2-layer spheres

[0067] Referring to Table 4, injection molding of thermoplastic ionomer resin compositions around a 1.540-inch polybutadiene rubber (PBR) thermosetting ball core is described. Details of molding golf ball sleeve layers or overlay materials around the core are described in US 2005 / 0037866, US 2021 / 0197030, and US 7,375,151. The present invention uses a retractable pin vertical injection molding machine to mold balls to a diameter of 1.68 inches. Properties of a 1.540-inch diameter polybutadiene rubber (PBR) ball core are provided in Table 3.

[0068] Table 3: Properties of 1.54-inch polybutadiene (PBR) cores

[0069]

[0070] Table 4: Two layers of 1.68-inch diameter spheres. Isopolymer molded onto a 1.54-inch diameter sphere core.

[0071]

[0072] For a two-layer 1.68-inch diameter ball molded around a 1.540-inch diameter PBR core, the data in Table 4 show that for the standard Na ionomer and Zn ionomers CE1, CE2, and CE4, a lower flexural modulus tends to contribute to impact durability. However, a high flexural modulus is required because the high flexural modulus layers on the soft core produce a greater spin differential, a desirable characteristic of golf ball construction. Spin differential refers to the difference in spin of a golf ball when hit by a driver club versus when hit by an iron club, where the driver requires a lower spin differential and the iron club requires a higher spin differential. The challenge lies in producing materials with a combination of high flexural modulus and high impact durability. Hybrid Na / Zn ionomers can achieve this, as exemplified by CE7, which exhibits synergistically high flexural modulus and improved impact durability compared to CE1 or CE2. If materials with even higher stiffness (such as CE5) are used instead of CE4 as Zn ionomers, even higher flexural modulus can be obtained with mixed Na / Zn systems containing CE1 or CE2 while retaining or improving impact resistance and durability.

[0073] While specific embodiments of this disclosure have been described and illustrated, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of this disclosure. Therefore, it is intended that all such changes and modifications be covered within the scope of this disclosure in the appended claims.

Claims

1. A golf ball comprising a rubber-component core and at least one intermediate layer disposed on the core, the intermediate layer comprising at least one ionomer, wherein: The at least one ionomer comprises a neutralized ethylene copolymer of a carboxylic acid comonomer derived from ethylene monomers and from 7.5 mol% to 15.0 mol% of the total mol% of the monomers present in the at least one ionomer; The at least one ionomer said therein has a melt index (I2) of 0.5 dg / min to 10.0 dg / min as measured according to ASTM D 1238 (2.16 kg; 190 °C). 10 mol% to 50 mol% of the total acid units of the at least one ionomer are neutralized by zinc cations and sodium cations.

2. The golf ball according to claim 1, wherein the ionomer has a melt index (I2) of 1 dg / min to 5.0 dg / min.

3. The golf ball according to claim 1 or 2, wherein the at least one ionomer comprises 20% to 40% by weight of a carboxylic acid comonomer.

4. The golf ball according to any one of claims 1 to 3, wherein the at least one ionomer comprises 8.0 mol% to 10.0 mol% of a carboxylic acid comonomer.

5. The golf ball according to any one of claims 1 to 4, wherein the at least one ionomer comprises a blend of a first ionomer and a second ionomer, wherein: The first ionomer comprises 7.5 mol% to 15.0 mol% of a carboxylic acid comonomer based on the total weight % of the monomers present in the first ionomer, wherein 10 mol% to 50 mol% of the total acid units of the first ionomer are neutralized by sodium cations; and The second ionomer comprises 7.5 mol% to 15.0 mol% of a carboxylic acid comonomer based on the total weight % of the monomers present in the second ionomer, wherein 10 mol% to 50 mol% of the total acid units of the second ionomer are neutralized by zinc cations.

6. The golf ball of claim 5, wherein the blend comprises 40% to 60% by weight of the first ionomer and 40% to 60% by weight of the second ionomer.

7. The golf ball according to any one of claims 1 to 6, wherein the carboxylic acid monomer comprises one or more of acrylic acid, methacrylic acid, or combinations thereof.

8. The golf ball according to any one of claims 1 to 7, wherein the core comprises polybutadiene rubber.

9. The golf ball according to any one of claims 1 to 8, wherein the golf ball further comprises an outer layer disposed on the intermediate layer.

10. The golf ball according to any one of claims 1 to 9, wherein the outer layer comprises polyurethane.

Images