GOLF BALL

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2024-162311 filed in Japan on Sep. 19, 2024, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a golf ball including a core and a cover, in which a cover material contains a biomass material made of carbon derived from plants (wheat, sugar cane, beet, potatoes, corn, etc.).

BACKGROUND ART

In recent years, efforts have been made to reduce the usage of petroleum-derived plastic materials in order to reduce environmental burden and reduce the consumption of petroleum, which is a non-renewable resource. Also, in the field of golf balls, constituent members of a rubber material and a cover material are formed of plastic made of petroleum as a raw material, and it is desirable to provide an environmentally friendly product if possible. As such a prior art document, for example, Patent Document 1 in particular proposes a golf ball using a biodegradable material as a constituent member. In addition, Patent Documents 2 to 5 propose golf balls using a non-petroleum-based material as a constituent member.

However, although the biodegradable materials and the non-petroleum-based materials described above are environmentally friendly materials, in fact, if used as a part of the material in a golf ball product, it has been difficult to achieve the performance of existing plastic materials produced from petroleum.

Citation List

• • Patent Document 1: JP-A 2006-247224
  • Patent Document 2: JP-A 2008-178683
  • Patent Document 3: JP-A 2008-264038
  • Patent Document 4: JP-A 2009-089854
  • Patent Document 5: JP-A 2009-095660

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a golf ball that includes an environmentally friendly material in a constituent member and may exhibit the same performance as a ball product made of a petroleum-derived plastic material that is conventionally used.

As a result of intensive studies to achieve the above object, the present inventor has found that a golf ball including a core and a cover has performance comparable to that of a golf ball using a conventional petroleum-derived plastic material by forming the cover using polyurethane as a chief material and setting a weight ratio of a biomass material to be within a range of from 10 to 45%, the polyurethane material containing bio-based carbon measured according to the ISO 16620-2 standard, and has completed the present invention.

Accordingly, the present invention provides a golf ball including

• • a core and a cover, wherein the cover is formed of polyurethane as a chief material, the polyurethane contains bio-based carbon measured according to the ISO 16620-2 standard, and a weight ratio of a biomass material containing the bio-based carbon to a total cover amount is from 10 to 45 wt %.

In a preferred embodiment of the golf ball according to the invention, in the cover, a product of the weight ratio of the biomass material and a material hardness (Shore D) is at least 470 and less than 2,010.

In another preferred embodiment of the inventive golf ball, the cover is formed of a resin composition containing the following components (I) and (II):

• • (I) polyurethane, and
  • (II) a (meth)acrylic block copolymer.

In yet another preferred embodiment, a compounding amount of the component (II) is not more than 20 parts by weight per 100 parts by weight of the component (I).

In still another preferred embodiment, a material hardness of the component (II) is not more than 40 on the Shore D hardness scale.

In a further preferred embodiment, the component (II) has a rebound elasticity of not more than 40% as measured according to the JIS-K 6255 standard.

In a yet further preferred embodiment, a melt flow rate (MFR) value of the component (II) is at least 20 g/10 min under measurement conditions of 230° C. and a load of 2.16 kgf (ISO 1133).

In a still further preferred embodiment, in the block copolymer of the component (II), a hard segment is mainly composed of a methyl methacrylate unit, and a soft segment is mainly composed of an n-butyl acrylate unit or an n-butyl acrylate/2-ethylhexyl acrylate unit.

In another preferred embodiment, a content of the methyl methacrylate unit in the block copolymer of the component (II) is from 20 to 50 wt %.

In yet another preferred embodiment, the cover has a thickness of from 0.6 to 1.8 mm.

Advantageous Effects of the Invention

The golf ball of the present invention includes an environmentally friendly material in a constituent member, and may have performance comparable to that of a golf ball using a petroleum-derived plastic material used conventionally.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention is described in more detail.

The golf ball of the present invention includes at least one core layer and at least one cover layer. Hereinafter, each of the above layers is described in detail.

The core may be formed in a single layer or a plurality of layers. As a material of the core, a known rubber material or various resin materials may be used as a substrate. If the core is formed of a rubber material, a known base rubber such as a natural rubber or a synthetic rubber may be used as the base rubber, and more specifically, it is recommended to mainly use polybutadiene, particularly cis-1,4-polybutadiene having at least at least 40% cis structure. In addition, in the base rubber, a natural rubber, a polyisoprene rubber, a styrene butadiene rubber, and the like may be used in combination with the above-described polybutadiene as desired. The polybutadiene may be synthesized by a Ziegler-type catalyst such as a titanium-based catalyst, a cobalt-based catalyst, a nickel-based catalyst, or a neodymium-based catalyst, or by a metal catalyst such as cobalt or nickel.

In the base rubber, a co-crosslinking agent such as an unsaturated carboxylic acid and a metal salt thereof, an inorganic filler such as zinc oxide, barium sulfate, or calcium carbonate, an organic peroxide such as dicumyl peroxide or 1,1-bis(t-butylperoxy)cyclohexane, or the like may be blended. If necessary, a commercially available antioxidant or the like may be appropriately added.

The core may be manufactured by thermally curing a rubber composition containing the above components. For example, a molded body may be manufactured by intensively mixing the rubber composition using a mixing apparatus such as a Banbury mixer or a roll mill, subsequently compression molding or injection molding the mixture using a core mold, and curing the resulting molded body by appropriately heating the molded body at a temperature sufficient for the organic peroxide or the co-crosslinking agent to act, such as at a temperature of from 100 to 200° C., and preferably at a temperature of from 140 to 180° C., for 10 to 40 minutes.

The core has a specific gravity which, although not particularly limited, is preferably at least 1.00, more preferably at least 1.03, and even more preferably at least 1.06. The upper limit is preferably not more than 1.20, more preferably not more than 1.17, and even more preferably not more than 1.14. It is necessary to set a weight of the ball to about 45.0 to 45.6 g in order to ensure good distance performance on shots with a driver, and in such a case, if the specific gravity of the core is smaller than the above range, it is necessary to increase the specific gravities of the intermediate layer and the cover layer, and thus there is a possibility that a spin performance of the ball is impaired by adding a specific gravity adjusting material. On the other hand, if the specific gravity of the core is too large, a moment of inertia becomes too small, and rolling with a putter may worsen.

In the present invention, the cover is formed of polyurethane as a chief material, and in particular, the following components (I) and (II) are preferably contained as a resin composition containing polyurethane as the chief material:

• • (I) polyurethane, and
  • (II) a (meth)acrylic block copolymer. Hereinafter, the components (I) and (II) are described.

[(I) Polyurethane]

The polyurethane may be the chief material of the cover material (resin composition) or a base resin. Details of the polyurethane as this component are as follows.

The structure of polyurethane is composed of a soft segment composed of a polymer polyol (polymeric glycol), which is a long-chain polyol, and a hard segment composed of a chain extender and a polyisocyanate. Here, as the polymer polyol as a raw material, any polymer polyol that is conventionally used in a technique related to a polyurethane material may be used, and is not particularly limited. Examples thereof may include polyester-based polyol, polyether-based polyol, polycarbonate polyol, polyester polycarbonate polyol, polyolefin-based polyol, conjugated diene polymer-based polyol, castor oil-based polyol, silicone-based polyol, and vinyl polymer-based polyol. Specific examples of the polyester-based polyol may include adipate-based polyols such as polyethylene adipate glycol, polypropylene adipate glycol, polybutadiene adipate glycol, and polyhexamethylene adipate glycol, and lactone-based polyols such as polycaprolactone polyol. Examples of the polyether polyol include poly(ethylene glycol), poly(propylene glycol), poly(tetramethylene glycol), and poly(methyltetramethylene glycol). These may be used singly, or two or more may be used in combination.

As the polymer polyol, a polyether-based polyol is preferably used.

In the present invention, not only conventional petroleum-derived polymer polyols but also polymer polyols made of carbon derived from biological resources such as plants (wheat, sugar cane, beet, potatoes, corn, etc.) may be used. That is, a biomass material may be used as a polyol component of the polyurethane. Biomass is a concept representing the amount (mass) of biological resources (bio), and is “renewable organic resources derived from living organisms excluding fossil resources”. Conventionally, biodegradable materials and the like have been present as environmentally friendly golf ball materials, but it has been difficult to exhibit various performances such as flight performance and durability to the same extent as those of existing plastic materials made from petroleum. Therefore, in the present invention, by using a biomass material within a predetermined amount as a raw material of a polyurethane cover, various ball performances may be maintained well, and an environmentally friendly material may be used as a golf ball material.

Specifically, as a raw material of the polyurethane cover, bio-based carbon measured according to the ISO 16620-2 standard is included, and a biomass material containing the bio-based carbon is used so that a weight ratio (hereinafter, also referred to as a “biomass weight ratio”) with respect to a total cover amount falls within a range of from 10 to 45 wt %.

A method for calculating the biomass weight ratio (%) is expressed by the following condition:

Biomass ⁢ weight ⁢ ratio ⁢ ( % ) = { ( weight ⁢ of ⁢ polyol ⁢ in ⁢ resin ) × 
 ( weight ⁢ ratio ⁢ derived ⁢ from ⁢ biomass ⁢ in ⁢ polyol ) / 
 ( total ⁢ weight ⁢ of ⁢ resin ) } × 100

The ISO 16620-2 standard is an international standard for a method for calculating the content of biomass plastic, and is for detecting a synthetic substance using radiocarbon (¹⁴C) analysis. Substances derived solely from a biobase have a constant 14C (radiocarbon) concentration, which is defined in ISO 16620-2 as a 100% bio-basicity. On the other hand, all petroleum-derived materials do not contain ¹⁴C, resulting in a bio-basicity of 0%. That is, bio-based (extracts of plants, animals, and so on) and petroleum-derived industrial products are expressed with a bio-basicity of between 0 and 100% depending on their ratio.

If the biomass weight ratio is less than 10 wt %, it is difficult to say that the material is good for the environment. On the other hand, if the biomass weight ratio of the cover is more than 45 wt %, that is, the biomass weight ratio of the cover is too high, it is difficult to perform adjustment for exhibiting appropriate performance of a golf ball as a urethane material.

A numerical average molecular weight of the polyol is preferably within a range of from 1,000 to 5,000. By using a long-chain polyol having such a numerical average molecular weight, it is possible to reliably obtain a golf ball made of a polyurethane composition excellent in various properties such as productivity and the above-mentioned rebound. The numerical average molecular weight of the long-chain polyol is more preferably within a range of from 1,500 to 4,000, and even more preferably within a range of from 1,700 to 3,500.

The numerical average molecular weight is a numerical average molecular weight calculated based on a hydroxyl value measured in accordance with JIS-K 1557 (the same applies hereinafter.).

As the chain extender, those chain extenders used in conventional techniques related to polyurethanes may be suitably used, and the chain extender is not particularly limited. In the present invention, a low molecular weight compound having two or more active hydrogen atoms capable of reacting with an isocyanate group in a molecule and having a molecular weight of not more than 2,000 may be used, and among low molecular weight compounds, an aliphatic diol having 2 to 12 carbon atoms may be suitably used. Specific examples thereof include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, and among the specific examples, 1,4-butylene glycol may be particularly suitably used.

As the polyisocyanate, those hitherto used in the art related to polyurethane may be suitably used, and are not particularly limited. Specifically, one or more selected from a group consisting of 4,4′-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, 1,5-naphthylene diisocyanate, tetramethylxylene diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, trimethylhexamethylene diisocyanate, 1,4-bis(isocyanatomethyl) cyclohexane, and dimer acid diisocyanate may be used. However, it may be difficult to control a crosslinking reaction during injection molding depending on the type of isocyanate.

In addition, the blending ratio of active hydrogen atoms:isocyanate groups in the polyurethane forming reaction may be appropriately adjusted within a preferable range. Specifically, when the long-chain polyol, the polyisocyanate compound, and the chain extender are reacted to produce a polyurethane, it is preferable to use each component at a ratio such that the isocyanate group contained in the polyisocyanate compound is 0.95 to 1.05 mol, based on 1 mol of active hydrogen atoms of the long-chain polyol and the chain extender.

The method for producing the polyurethane is not particularly limited, and the polyurethane may be produced by either a prepolymer method or a one-shot method using the long-chain polyol, the chain extender, and the polyisocyanate compound by utilizing a known urethanization reaction. Among the methods, it is preferable to perform melt polymerization substantially in the absence of a solvent, and it is particularly preferable to perform production by continuous melt polymerization using a multi-screw extruder.

As the polyurethane described above, it is preferable to use a thermoplastic polyurethane material, and it is particularly preferable to use an ether-based thermoplastic polyurethane material. As the thermoplastic polyurethane material, a commercially available product may be suitably used, and examples thereof include “Pandex” (trade name) manufactured by DIC Covestro Polymer, Ltd., and “Rezamin” (trade name) manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.

A material hardness of the component (I) on the Shore D hardness scale is preferably not more than 52, more preferably not more than 50, and even more preferably not more than 48 in view of spin characteristics and scuff resistance obtained as a golf ball. A lower limit thereof on the Shore D hardness scale is preferably at least 38, and more preferably at least 40 from the viewpoint of moldability.

A rebound elastic modulus of the component (I) is preferably at least 55%, more preferably at least 57%, and even more preferably at least 59% from a comprehensive viewpoint as a golf ball such as initial velocity performance and spin performance at a time of striking. The rebound elastic modulus is measured based on the JIS-K 6255:2013 standard.

The component (I) is the chief material of the resin composition, and is at least 50 wt %, preferably at least 60 wt %, more preferably at least 70 wt %, even more preferably at least 80 wt %, and most preferably at least 90 wt % of the resin composition from the viewpoint of sufficiently imparting the scuff resistance of the urethane resin.

In the present invention, by blending the component (II) described in detail below into the component (I), controllability on approach shots, scuff resistance, and moldability are excellent.

[(II) (Meth)Acrylic Block Copolymer]

In the present specification, the term “(meth)acrylic block copolymer” is used to mean both an acrylic block copolymer and a methacrylic block copolymer.

The (meth)acrylic block copolymer as the component (II) is preferably a block copolymer having at least two blocks constituting the hard segment and at least one block constituting the soft segment. That is, the (meth)acrylic block copolymer used in the present invention is a polymer containing block polymers A and B, and may be represented by a chemical structure of A-B or A-B-A. The (meth)acrylic block copolymer used in the present invention is different in chemical structure from an acrylic copolymer having a general core-shell type.

The block polymer A is a site constituting the hard segment, and specific examples of a monomer unit include methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, phenyl methacrylate, and 2-hydroxyethyl methacrylate, and methyl methacrylate (MMA) is preferably used as a chief component. The block polymer A may be composed of one of the above-mentioned monomer units or two or more of the above-mentioned monomer units in combination.

On the other hand, the block polymer B is a site constituting the soft segment, and specific examples of the monomer unit include acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, benzyl acrylate, phenoxyethyl acrylate, and 2-methoxyethyl acrylate, and it is preferable to use n-butyl acrylate (nBA) as the chief component. The block polymer B may be composed of one of the above-mentioned monomer units or at least two of the above-mentioned monomer units in combination.

The glass transition temperature (Tg) of the block polymer A showing the hard segment is preferably from 80 to 140° C., and more preferably from 100 to 120° C. On the other hand, the glass transition temperature (Tg) of the block polymer B showing the soft segment is preferably from −80 to −20° C., and more preferably from −60 to −40° C.

In the (meth)acrylic block copolymer, a content ratio of the hard segment and the soft segment is preferably from 5:95 to 40:60, and more preferably from 10:90 to 30:70 in weight ratio. As the ratio of the soft segment increases, it may be expected that the resin composition is softened to obtain a desired controllability on approach shots. However, if the ratio of the hard segment is too small, compatibility with a polyurethane resin or the like as a substrate decreases, and moldability may deteriorate.

If the hard segment is composed mainly of a methyl methacrylate unit, a content of the methyl methacrylate unit in the block copolymer of the component (II) is preferably from 20 to 50 wt %. If this value is too low, fluidity becomes very high and the (meth)acrylic block copolymer is not suitable as a molding material. On the other hand, if this value is too high, the resulting molded product may become too hard.

The (meth)acrylic block copolymer may be obtained by polymerizing each monomer unit described above, and examples of a polymerization method include a radical polymerization method, a living anion polymerization method, and a living radical polymerization method. Examples of a polymerization form may include a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a bulk polymerization method.

The weight average molecular weight of the (meth)acrylic block copolymer is not particularly limited, although the weight average molecular weight is preferably at least 10,000, more preferably at least 30,000, and even more preferably at least 45,000, and the upper limit thereof is preferably not more than 200,000, more preferably not more than 150,000, and even more preferably not more than 100,000. As the weight average molecular weight becomes higher, an effect of low rebound is exhibited, and a spin rate is also increased, so that controllability on approach shots is excellent. This weight average molecular weight may be measured by gel permeation chromatography (GPC).

The (meth)acrylic block copolymer used in the present invention is preferably a polymer composed mainly of the methyl methacrylate unit in the hard segment and composed mainly of an n-butyl acrylate unit in the soft segment. As such a (meth)acrylic block copolymer, a commercially available product may be employed, and examples thereof include “KURARITY” manufactured by Kuraray Co., Ltd., and specific examples thereof include trade names “KURARITY LA2114”, “KURARITY LA2140”, “KURARITY LA2250”, “KURARITY LA2270”, “KURARITY LA2330”, and “KURARITY LA4285”.

The material hardness of the component (II) on the Shore D hardness scale is preferably not more than 40, more preferably not more than 38, even more preferably not more than 35, and most preferably not more than 32 from the viewpoint of improving the spin rate on approach shots. The lower limit thereof on the Shore D hardness scale is preferably at least 7, more preferably at least 15, and even more preferably at least 20.

The rebound elastic modulus of the component (II) is preferably not more than 40%, more preferably not more than 35%, and even more preferably not more than 30% from the viewpoint of maintaining the spin rate on approach shots and suppressing the rebound on approach shots to be low to obtain controllability. The lower limit of the rebound elastic modulus is preferably at least 10%, more preferably at least 15%, and even more preferably at least 20%. The rebound elastic modulus is measured based on the JIS-K 6255:2013 standard.

By setting a melt flow rate (MFR) of the component (II) to a high value, a fluidity of the polyurethane resin material may be improved, a molding temperature during molding may be lowered, cutting and deterioration of urethane molecules may be suppressed, and scuff resistance may be further improved. Specifically, the melt flow rate is preferably at least 2 g/10 min, more preferably at least 50 g/10 min, even more preferably at least 100 g/10 min, and most preferably at least 200 g/10 min as a measured value according to the ISO 1133 standard, a test temperature of 230° C., and a test load of 21.18 N (2.16 kgf).

The compounding amount of the component (II) is preferably not more than 20 parts by weight, more preferably not more than 15 parts by weight, and even more preferably not more than 10 parts by weight per 100 parts by weight of the component (I). If the compounding amount exceeds this value, the scuff resistance may be deteriorated. The lower limit of the compounding amount is at least 0.5 part by weight, preferably at least 1 part by weight, and more preferably at least 2 parts by weight per 100 parts by weight of the component (I).

In the resin composition containing the above (I) and (II), other resin materials may be blended in addition to the resin components described above. The purpose of this is to further improve the fluidity of the resin composition for golf balls and improve various physical properties such as rebound and durability to cracking.

The resin composition may be obtained, for example, by mixing the above-described components using various kneaders such as a knead-type twin-screw (or single-screw) extruder, a Banbury mixer, or a kneader.

For low rebound and improvement of the spin rate on approach shots, the rebound elastic modulus of the resin composition is required to be at least 48%, preferably at least 50%, and even more preferably at least 52%, and the upper limit thereof is not more than 72%, preferably not more than 70%, and more preferably not more than 68% in measurement according to the JIS-K 6255:2013 standard.

In addition, the material hardness of the resin composition on the Shore D hardness scale is preferably not more than 50, more preferably not more than 48, and even more preferably not more than 45 from the viewpoint of scuff resistance and application of an appropriate spin rate on approach shots. The lower limit thereof is preferably at least 30, more preferably at least 35, and even more preferably at least 37 on the Shore D hardness scale from the viewpoint of moldability.

In addition, a product of the weight ratio of the biomass material in the resin composition and the material hardness (Shore D) is preferably at least 470 and less than 2,010. For example, if the weight ratio of the biomass material is 35% and the material hardness (Shore D) is 43, the product is “35×43=1,505”. If there is a deviation from the above numerical ranges, the material may not be good for the environment, and the scuff resistance and the spin rate on approach shots may not be sufficient.

The thickness of the cover formed of the resin composition is preferably at least 0.4 mm, more preferably at least 0.5 mm, and even more preferably at least 0.6 mm, and the upper limit thereof is preferably not more than 2.0 mm, and more preferably not more than 1.8 mm. If the cover is too thin, the scuff resistance of the ball on shots with a wedge may worsen. On the other hand, if the cover is too thick, the spin of the ball may be excessively increased, and a desired distance may not be obtained.

The cover has a material hardness on the Shore D hardness scale which, although not particularly limited, is preferably not more than 52, more preferably not more than 50, and even more preferably not more than 48, and the lower limit is preferably at least 40, and more preferably at least 43. By setting the hardness relatively low, the initial velocity of the ball at the time of putting is less likely to be fast, and a variation in a putting distance is reduced. In addition, within the above range, the harder the hardness, the more it is possible to increase the distance due to low spin on full shots with an iron (I #6).

At least one intermediate layer may be formed between the core and the cover.

The intermediate layer is preferably formed of a resin composition. Examples of the resin composition include a resin composition whose chief material is a resin conventionally employed as a material for golf balls. Examples of a base resin of the resin composition include an ionomer-based resin, a polyester resin, a polyurethane resin, a polyamide resin, a polyolefin resin, an olefin-based thermoplastic elastomer, and a styrene-based thermoplastic elastomer. In particular, an ionomer-based resin is preferable from the viewpoints of rebound and moldability.

One kind or two or more kinds of a large number of dimples may be typically formed on a cover surface, and the shape, diameter, depth, number, occupied surface area, and the like of the dimples are appropriately selected.

A method for producing the golf ball is not particularly limited, and the golf ball may be obtained by molding by a known molding method such as injection molding or compression molding. For example, the resin composition for the intermediate layer described above is supplied in a state where the core is set in a mold of an injection molding machine to produce a layer-encased sphere (intermediate layer-encased sphere) in which the core is encased with the intermediate layer, then the intermediate layer-encased sphere is set in a mold of another injection molding machine, and the resin composition for the cover is injected to produce a golf ball encased with the cover.

In addition, a coating layer may be formed on the cover surface. In this case, the coating layer is formed of a coating composition. A base resin of the coating composition is not particularly limited, although examples thereof include a polyurethane resin, an epoxy resin, a polyester resin, an acrylic resin, and a cellulose resin. From the viewpoint of durability of the coating layer, it is preferable to use a two-liquid curable polyurethane resin. In the coating composition, various additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent agent, and a fluorescent brightener may be blended in an appropriate amount as necessary.

A method for applying the coating material to the cover surface is not particularly limited, and a known method may be used, and electrostatic coating, spray gun coating, brush coating, or the like may be adopted.

A ball standard such as the weight and a diameter of the golf ball of the present invention may be appropriately set according to the Rules of Golf.

EXAMPLES

Hereinafter, the present invention is specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Examples 1 to 10 and Comparative Examples 1 to 6

A core composition is prepared by blending rubbers shown in Table 1 common to each of the Examples and Comparative Examples, and vulcanization is performed to prepare a core having a diameter of 38.7 mm and a diameter of 39.3 mm. Zinc oxide and zinc acrylate are blended in appropriate amounts so as to have a predetermined core specific gravity and deflection, and four types of A, B, C, and D are prepared.

TABLE 1
Core blend (pbw)	A, B, C	D

Polybutadiene	100	100
Organic peroxide	1	1
Zinc oxide	Appropriate amount	Appropriate amount
Zinc acrylate	Appropriate amount	Appropriate amount
Water	0.3	0
Zinc salt of	0.2	0.2
pentachlorothiophenol

Details of the above formulations are as follows.

• • Polybutadiene: Trade name “BR 01” (manufactured by ENEOS Materials Corporation)
  • Organic peroxide: Dicumyl peroxide, trade name “Percumyl D” (manufactured by NO Corporation)
  • Zinc oxide: Trade name “Zinc Oxide Grade 3” (manufactured by Sakai Chemical Industry Co., Ltd.)
  • Zinc acrylate: Trade name “ZN-DA85 S” (manufactured by Nippon Shokubai Co., Ltd.)

[Formation of Intermediate Layer and Cover (Outermost Layer)]

Next, in each of the Examples and Comparative Examples, injection molding is performed around a surface of the core with resin materials E to G of the intermediate layer shown in Table 2 using the following injection mold to form an intermediate layer having a thickness of 1.20 mm and a Shore D hardness of 66 to 68.

	TABLE 2
	Intermediate layer blend (pbw)	E	F	G

	Himilan AM7318	85	85	100
	Himilan 1706	15	15
	Trimethylolpropane	1.1	1.1
	Barium sulfate	20	20

Details of the blending components in the above table are as follows.

• • “Himilan AM7318” ionomer resin manufactured by Dow-Mitsui Polychemicals Co., Ltd.
  • “Himilan 1706” ionomer resin manufactured by Dow-Mitsui Polychemicals Co., Ltd.
  • “Trimethylolpropane” manufactured by Tokyo Chemical Industry Co., Ltd.
  • Trade name “Precipitated Barium Sulfate 300” barium sulfate manufactured by Sakai Chemical Industry Co., Ltd.

Next, 16 kinds of urethane resin compositions of C1 to C16 shown in Table 3 and Table 4 are injection molded around the intermediate layer-encased sphere using another injection mold to form a cover (outermost layer) having a thickness of 0.8 mm and a Shore D hardness of 43 to 50.

TABLE 3
Cover blend	C1	C2	C3	C4	C5	C6

Blend	Component (I)	TPU-A	100
(pbw)		TPU-B		100	100	100	100	100
		TPU-C
		TPU-D
		TPU-E
	Component (II)	LA2250	0	0.5	0.5	0.5	0.5	0.5

Physical	Biomass weight ratio (%)	49	45	34	23	11	0
properties	Material hardness (Shore D)	43	43	43	43	43	43
	Biomass weight ratio ×	2107	1935	1462	989	473	0
	Material hardness

TABLE 4
Cover blend	C7	C8	C9	C10	C11	C12	C13	C14	C15	C16

Blend	Component (I)	TPU-A
(pbw)		TPU-B							100	100
		TPU-C	100
		TPU-D		100	100	100	100	100
		TPU-E									100	100
	Component (II)	LA2250	0	5	5	5	5	5	0	0	0	0

Physical	Biomass weight ratio (%)	47	40	30	20	10	0	45	0	41	0
properties	Material hardness (Shore D)	47	47	47	47	47	47	43	43	49	49
	Biomass weight ratio ×	2209	1880	1410	940	470	0	1935	0	2009	0

	Material hardness

In the above table, details of the blending components are as follows.

• • “TPU A” ether-type thermoplastic polyurethane (the polyol component is petroleum-based polyol A and biopolyol A mixed in a predetermined amount ratio) manufactured by DIC Covestro Polymer Ltd.
  • “TPU B” ether-type thermoplastic polyurethane (cover formulations C2 to C5 and C13: the polyol component is petroleum-based polyol B and biopolyol B mixed in a predetermined amount ratio; cover formulations C6 and C14: the polyol component used is only petroleum-based polyol B) manufactured by DIC Covestro Polymer Ltd.
  • “TPU C” ether-type thermoplastic polyurethane (the polyol component is petroleum-based polyol C and biopolyol C mixed in a predetermined amount ratio) manufactured by DIC Covestro Polymer Ltd.
  • “TPU D” ether-type thermoplastic polyurethane (cover formulations C8 to C12: the polyol component is petroleum-based polyol D and biopolyol D mixed in a predetermined amount ratio) manufactured by DIC Covestro Polymer Ltd.
  • “TPU E” ether-type thermoplastic polyurethane (cover formulation C15: the polyol component is petroleum-based polyol E and biopolyol E mixed in a predetermined amount ratio; cover formulation C16: the polyol component used is only petroleum-based polyol E) manufactured by DIC Covestro Polymer Ltd.
  • “LA2250” is a (meth)acrylic block copolymer (hard segment PMMA/soft segment PBA) of the trade name “KURARITY LA” series manufactured by Kuraray Co., Ltd.

The method for calculating the biomass weight ratio (%) in the above tables is expressed by the following condition:

Biomass ⁢ weight ⁢ ratio ⁢ ( % ) = { ( weight ⁢ of ⁢ polyol ⁢ in ⁢ resin ) × 
 ( weight ⁢ ratio ⁢ derived ⁢ from ⁢ biomass ⁢ in ⁢ polyol ) / 
 ( total ⁢ weight ⁢ of ⁢ resin ) } × 100

Methods of measuring the deflection of the core, the material hardness of the intermediate layer, and the material hardness of the cover are as follows.

[Deflection of Core]

The core, which is the subject, is placed on a hard plate, and the deflection when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) is measured. Note that the deflection is a measurement value measured in a room at a temperature of 23.9±2° C. after temperature adjustment to 23.9±1° C. for at least three hours or more in a thermostatic bath. As a measuring device, a high-load compression tester manufactured by MU Instruments Trading Corp. is used, and a down speed of a pressure head that compresses the core is set to 10 mm/s.

[Material Hardnesses of Intermediate Layer and Cover]

The resin material of each layer is molded into a sheet having a thickness of 2 mm and left for two weeks. Thereafter, the Shore D hardness is measured in accordance with the ASTM D2240 standard. For the measurement of the hardness, a “P2” Automatic Rubber Hardness Tester manufactured by Kobunshi Keiki Co., Ltd. is used. A Shore D hardness attachment is attached to measure each hardness. For the hardness value, a maximum value is read. All measurements are carried out in an environment of 23±2° C.

The obtained golf ball of each example is evaluated for the distance on shots with a driver, the spin rate and controllability on approach shots, and scuff resistance by the following methods. The results are shown in Table 5.

[Distance with Driver]

A driver (W #1) is mounted on a swing robot machine, and a distance traveled (total) by a ball when struck at a head speed (HS) of 45 m/s is measured. The club used is a “Tour B XD-5 Driver/loft angle 8.5°” (2017 model) manufactured by Bridgestone Sports Co., Ltd.

[Spin Rate and Controllability on Approach Shots]

A sand wedge is mounted on a swing robot machine, and the spin rate when a ball is struck at an HS of 20 m/s is measured. The spin rate immediately after the ball is struck is measured by a device for measuring initial conditions. The sand wedge used is a “TourStage TW-03/loft angle 570 (2002 model)” manufactured by Bridgestone Sports Co., Ltd.

[Evaluation of Scuff Resistance]

The ball is kept at 23° C. and the swing robot machine is used. The club used is a pitching wedge (PW), each ball is struck five times at a head speed of 33 m/s, and scratches from striking are visually evaluated according to the following criteria.

• • Very good: No scratches or almost no scratches are noticeable.
  • Good: Slight scratches are observed, but the scratches are hardly noticeable.
  • Fair: Surface is slightly fuzzy.
  • NG: Surface is fuzzy or lacks dimples.

	TABLE 5
	Comp.	Example	Comp.	Comp.	Example

		Ex. 1	1	2	3	4	Ex. 2	Ex. 3	5	6
Core	Blend	A	A	A	A	A	A	B	B	B
	Deflection (mm)	3.6	3.6	3.6	3.6	3.6	3.6	3.1	3.1	3.1
	Outer diameter	38.7	38.7	38.7	38.7	38.7	38.7	38.7	38.7	38.7
	(mm)
Intermediate	Material	E	E	E	E	E	E	F	F	F
layer	Thickness (mm)	67	67	67	67	67	67	68	68	68
Cover	Material	C1	C2	C3	C4	C5	C6	C7	C8	C9
	Thickness (mm)	0.8	0.8	0.8	0.8	0.8	0.8	0.8	0.8	0.8
	Material hardness	43	43	43	43	43	43	47	47	47
	(Shore D)
	Biomass weight	49	45	34	23	11	0	47	40	30
	ratio (%)
	Biomass weight ratio ×	2107	1935	1462	989	473	0	2209	1880	1410
	Material hardness
Evaluation	W#1 distance	251	258	258	258	258	259	256	262	263
results	(yards)
	Spin rate on approach	6321	6415	6433	6411	6421	6428	6190	6290	6253
	shots (rpm)
	Controllability	Fair	Very	Very	Very	Very	Very	Fair	Very	Very
	on approach shots		good	good	good	good	good		good	good
	Scuff resistance	NG	Very	Very	Very	Very	Very	NG	Good	Good
			good	good	good	good	good

Example

Comp.

Ex.

Comp.

Ex.

Comp.

			7	8	Ex. 4	9	Ex. 5	10	Ex. 6
	Core	Blend	B	B	B	C	C	D	D

		Deflection (mm)	3.1	3.1	3.1	3.6	3.6	3.45	3.45
		Outer diameter	38.7	38.7	38.7	38.7	38.7	39.3	39.3
		(mm)
	Intermediate	Material	F	F	F	G	G	—	—
	layer	Thickness (mm)	68	68	68	66	66	—	—
	Cover	Material	C10	C11	C12	C13	C14	C15	C16
		Thickness (mm)	0.8	0.8	0.8	0.8	0.8	1.7	1.7
		Material hardness	47	47	47	43	43	49	49
		(Shore D)
		Biomass weight	20	10	0	45	0	41	0
		ratio (%)
		Biomass weight ratio ×	940	470	0	1935	0	2009	0
		Material hardness
	Evaluation	W#1 distance	261	262	262	257	257	242	242
	results	(yards)
		Spin rate on approach	6284	6263	6274	6154	6191	5652	5658
		shots (rpm)
		Controllability	Very	Very	Very	Good	Good	Good	Good
		on approach shots	good	good	good
		Scuff resistance	Good	Good	Good	Very	Very	Good	Good
						good	good

As shown in Table 5, the following points are considered.

When Examples 1 to 4 are compared with Comparative Examples 1 and 2, even in Examples 1 to 4 using a biomass material, the same performance as that of Comparative Example 2 (biomass weight ratio derived from petroleum is 0%) may be obtained. That is, when the biopolyol is used with the biomass weight ratio of the cover resin material within a range of 0 to 45%, the same performance as in Comparative Example 2 may be obtained. On the other hand, in Comparative Example 1, the biomass weight ratio is as large as 49%, and as a result, sufficient performance is not obtained.

When Examples 5 to 8 are compared with Comparative Examples 3 and 4, even in Examples 5 to 8 using a biomass material, the same performance as that of Comparative Example 4 (conventional petroleum-derived material) may be obtained. That is, when the biopolyol is used with the biomass weight ratio of the cover resin material within a range of 0 to 40%, the same performance as in Comparative Example 4 may be obtained. On the other hand, in Comparative Example 3, the biomass weight ratio is as large as 47%, and sufficient performance is not obtained.

When Example 9 is compared with Comparative Example 5, even in Example 9 using a biomass material, the same performance as that of Comparative Example 5 (conventional petroleum-derived material) may be obtained.

When Example 10 is compared with Comparative Example 6, even in Example 10 using a biomass material, the same performance as that of Comparative Example 6 (conventional petroleum-derived material) may be obtained.

Japanese Patent Application No. 2024-162311 is incorporated herein by reference. Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims.