Resin composition, golf ball, and modifier

Abstract

This resin composition contains an ionomer resin (A) obtained by neutralizing the carboxyl groups of an ethylene-unsaturated carboxylic acid copolymer using metal ions, a polyvinyl butyral resin (B), and an ether-type plasticizer (C), and satisfies the following requirements (i)-(iii). (i) The ionomer resin (A) content is 50-99 parts by mass per 100 total parts by mass of the ionomer resin (A) and the polyvinyl butyral resin (B). (ii) The polyvinyl butyral resin (B) content is 1-50 parts by mass per 100 total parts by mass of the ionomer resin (A) and the polyvinyl butyral resin (B). (iii) The ether-type plasticizer (C) content is 25-50 parts by mass per 100 parts by mass of the polyvinyl butyral resin (B).

Description

Resin composition, golf ball, and modifier

[0001] The present disclosure relates to a resin composition, a golf ball, and a modifier.

[0002] Ionomer resins have traditionally been used as golf ball materials because of their excellent properties in terms of durability, impact resilience, and the like.

[0003] Patent Document 1 discloses a golf ball cover composition comprising (A) a rubber-like elastomer composition containing (a) an ionomer resin, (b) a thermoplastic urethane-based material, and (c) a rubber-like elastomer as essential components, and characterized in that the molded product has a Shore D hardness of 45 to 63, and a golf ball having a cover formed from said composition.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-331048

[0005] In recent years, there has been a trend in golf balls to have a lower hardness in the surface layer in order to soften the hardness of the hit feeling and improve the ball controllability when hitting the ball.

[0006] An object of one embodiment of the present disclosure is to provide a resin composition having low hardness and low flexural rigidity, as well as a golf ball and a modifier using the same.

[0007] Means for solving the above problems include the following aspects. <1> A resin composition comprising an ionomer resin (A) obtained by neutralizing the carboxyl groups of an ethylene-unsaturated carboxylic acid copolymer with metal ions, a polyvinyl butyral resin (B), and an ether-type plasticizer (C), and satisfying the following requirements (i) to (iii): (i) The content of the ionomer resin (A) is 50 parts by mass to 99 parts by mass per 100 parts by mass of the total of the ionomer resin (A) and the polyvinyl butyral resin (B). (ii) The content of the polyvinyl butyral resin (B) is 1 part by mass to 50 parts by mass per 100 parts by mass of the total of the ionomer resin (A) and the polyvinyl butyral resin (B). (iii) The content of the ether-type plasticizer (C) is 25 parts by mass to 50 parts by mass per 100 parts by mass of the polyvinyl butyral resin (B). <2> The resin composition according to <1>, having a Shore D hardness of 46.0 or less as measured in accordance with JIS K 7215. <3> The resin composition according to <1> or <2>, having a content of the ether-type plasticizer (C) of 1 part by mass to 25 parts by mass per 100 parts by mass of the resin composition. <4> The resin composition according to any one of <1> to <3>, having a total content of the ionomer resin (A) and the polyvinyl butyral resin (B) of 50 parts by mass or more per 100 parts by mass of the resin composition. <5> The resin composition according to any one of <1> to <4>, wherein the ether-type plasticizer (C) is a polyalkylene glycol derivative or a triethylene glycol derivative. <6> The resin composition according to any one of <1> to <5>, wherein the ethylene-unsaturated carboxylic acid copolymer is an ethylene-unsaturated carboxylic acid copolymer or an ethylene-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer. <7> The resin composition according to any one of <1> to <6>, wherein at least a portion of the metal ions in the ionomer resin (A) are monovalent metal ions. <8> The resin composition according to any one of <1> to <7>, wherein at least a portion of the metal ions in the ionomer resin (A) are divalent metal ions.<9> The resin composition according to any one of <1> to <8>, which has a flexural modulus of 35 MPa or less as measured in accordance with JIS K 7106. <10> A golf ball comprising the resin composition according to any one of <1> to <9> in at least one of a skin layer, an intermediate layer, and a core layer. <11> A modifier comprising the resin composition according to any one of <1> to <9>.

[0008] According to one embodiment of the present disclosure, there are provided a resin composition having low hardness and low bending rigidity, as well as a golf ball and a modifier using the same.

[0009] The resin composition, golf ball, and modifier of the present disclosure will be described below.

[0010] In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in numerical ranges described in the present disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple corresponding substances. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified.

[0011] In the present disclosure, the term "(meth)acrylic" means acrylic or methacrylic.

[0012] <Resin Composition> The resin composition of the present disclosure is a resin composition comprising an ionomer resin (A) obtained by neutralizing the carboxyl groups of an ethylene-unsaturated carboxylic acid copolymer with metal ions, a polyvinyl butyral resin (B), and an ether-type plasticizer (C), and satisfies the following requirements (i) to (iii): (i) the content of the ionomer resin (A) is 50 parts by mass to 99 parts by mass per 100 parts by mass of the ionomer resin (A) and the polyvinyl butyral resin (B); and (ii) the content of the polyvinyl butyral resin (B) is 1 part by mass to 50 parts by mass per 100 parts by mass of the ionomer resin (A) and the polyvinyl butyral resin (B). (iii) The content of the ether-type plasticizer (C) is 25 parts by mass to 50 parts by mass based on 100 parts by mass of the polyvinyl butyral resin (B).

[0013] The resin composition of the present disclosure has the above-described configuration and thus has low hardness and low bending rigidity.

[0014] Each of these will be explained in detail below.

[0015] [Ionomer resin (A) obtained by neutralizing carboxyl groups of an ethylene-unsaturated carboxylic acid copolymer with metal ions] The resin composition of the present disclosure contains an ionomer resin (A) (hereinafter also simply referred to as "ionomer resin (A)") obtained by neutralizing carboxyl groups of an ethylene-unsaturated carboxylic acid copolymer with metal ions.

[0016] The ethylene-unsaturated carboxylic acid copolymer in the ionomer resin (A) is a copolymer in which at least ethylene and an unsaturated carboxylic acid are copolymerized. The copolymer may be a binary copolymer in which ethylene and an unsaturated carboxylic acid are copolymerized, or a terpolymer in which a third monomer is copolymerized in addition to ethylene and an unsaturated carboxylic acid. From the viewpoint of obtaining a resin composition with low hardness and low bending rigidity, a terpolymer in which ethylene, an unsaturated carboxylic acid, and a third constituent unit are copolymerized is preferred.

[0017] The ethylene-unsaturated carboxylic acid copolymer in the ionomer resin (A) may be any of a block copolymer, a random copolymer, and a graft copolymer. From the viewpoint of availability, a binary random copolymer, a ternary random copolymer, a graft copolymer of a binary random copolymer, and a graft copolymer of a ternary random copolymer are preferred, and among these, a binary random copolymer or a ternary random copolymer is more preferred from the viewpoint of economic efficiency.

[0018] When the ionomer resin (A) is a terpolymer, examples of the third monomer other than ethylene and unsaturated carboxylic acid in the ionomer resin (A) include unsaturated carboxylic acid esters; unsaturated hydrocarbons (e.g., propylene, butene, 1,3-butadiene, pentene, 1,3-pentadiene, 1-hexene, etc.); vinyl esters (e.g., vinyl acetate, vinyl propionate, etc.); vinyl sulfate, vinyl nitrate; vinyl halides (e.g., vinyl chloride, vinyl fluoride, etc.); vinyl group-containing primary amine compounds or vinyl group-containing secondary amine compounds. Of these structural units, unsaturated carboxylic acid esters are preferred from the viewpoint of obtaining a resin composition with low hardness and low bending rigidity.

[0019] Examples of unsaturated carboxylic acids that form the structural units of the ethylene-unsaturated carboxylic acid copolymer in the ionomer resin (A) include α,β-unsaturated carboxylic acids, β,γ-unsaturated carboxylic acids, and γ,δ-unsaturated carboxylic acids. Among these, α,β-unsaturated carboxylic acids are preferred from the viewpoint of obtaining a resin composition with low hardness and low bending rigidity. Examples of α,β-unsaturated carboxylic acids include α,β-unsaturated carboxylic acids having 4 to 8 carbon atoms, such as (meth)acrylic acid, itaconic acid, itaconic anhydride, fumaric acid, crotonic acid, maleic acid, and maleic anhydride, or acid anhydrides thereof. Among these, (meth)acrylic acid is preferred as the unsaturated carboxylic acid from the viewpoint of easy availability.

[0020] Examples of the unsaturated carboxylic acid ester, which is the third monomer forming the terpolymer, which is a preferred embodiment of the ethylene-unsaturated carboxylic acid copolymer in the ionomer resin (A), include unsaturated carboxylic acid alkyl esters. The alkyl moiety of the alkyl ester in the unsaturated carboxylic acid alkyl ester preferably has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and even more preferably 1 to 4 carbon atoms. Examples of the alkyl moiety include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-ethylhexyl, and isooctyl.

[0021] Specific examples of unsaturated carboxylic acid alkyl esters include methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, isooctyl acrylate; methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, isooctyl methacrylate; dimethyl maleate, and diethyl maleate.

[0022] Preferable specific examples of the ethylene-unsaturated carboxylic acid copolymer in the ionomer resin (A) include, as binary copolymers, ethylene-(meth)acrylic acid copolymers, and as terpolymers, ethylene-(meth)acrylic acid-(meth)acrylic acid ester copolymers (e.g., ethylene-(meth)acrylic acid-methyl(meth)acrylate copolymer, ethylene-(meth)acrylic acid-ethyl(meth)acrylate copolymer, ethylene-(meth)acrylic acid-isobutyl(meth)acrylate copolymer, ethylene-(meth)acrylic acid-n-butyl(meth)acrylate copolymer, etc.). As the ionomer resin (A), one type may be used alone, or two or more types may be used in combination, as long as the effects of the present disclosure are obtained.

[0023] The content of the unsaturated carboxylic acid-derived structural units contained in the ethylene-unsaturated carboxylic acid copolymer in the ionomer resin (A) is preferably 5% by mass to 25% by mass, more preferably 5% by mass to 20% by mass, and even more preferably 5% by mass to 15% by mass, relative to 100% by mass of the copolymer. When the content of the unsaturated carboxylic acid-derived structural units is within the above range, a resin composition having low hardness and low bending rigidity is easily obtained.

[0024] When the ethylene-unsaturated carboxylic acid copolymer is an ethylene-unsaturated carboxylic acid-unsaturated carboxylic acid ester terpolymer, the content of the unsaturated carboxylic acid ester-derived structural units in the terpolymer is preferably 3% by mass to 30% by mass, and more preferably 5% by mass to 20% by mass, relative to 100% by mass of the copolymer, from the viewpoint of ensuring flexibility. A content of the unsaturated carboxylic acid ester-derived structural units of 3% by mass or more is advantageous in terms of ensuring flexibility, and a content of 30% by mass or less is advantageous in terms of preventing blocking.

[0025] The ionomer resin (A) contained in the resin composition of the present disclosure is a compound in which carboxyl groups contained in an ethylene-unsaturated carboxylic acid copolymer are neutralized with metal ions. At least a portion of the metal ions in the ionomer resin (A) may be monovalent metal ions, such as lithium ions, sodium ions, and potassium ions. At least a portion of the metal ions in the ionomer resin (A) may be divalent metal ions, such as rubidium ions, cesium ions, zinc ions, magnesium ions, and manganese ions. The ionomer resin (A) may contain an ionomer neutralized with a monovalent metal ion and an ionomer neutralized with a divalent metal ion. Among these, from the viewpoint of availability, ionomers neutralized with metal ions selected from zinc ions, magnesium ions, and sodium ions are preferred. From the viewpoint of obtaining a resin composition with low hardness and low bending rigidity, ionomers neutralized with zinc ions are more preferred.

[0026] In the resin composition of the present disclosure, the carboxyl groups of the ethylene-unsaturated carboxylic acid copolymer constituting the ionomer resin (A) are neutralized with metal ions. A neutralization degree of 20% or more tends to provide a better thickening effect. A neutralization degree of 90% or less tends to provide excellent processability and moldability. The neutralization degree is more preferably 15% to 82%, and even more preferably 30% to 75%. The neutralization degree is the ratio (%) of the number of moles of carboxyl groups neutralized with metal ions to the number of moles of carboxyl groups in the ethylene-unsaturated carboxylic acid copolymer.

[0027] In the resin composition of the present disclosure, the content of the ionomer resin (A) is 50 to 99 parts by mass relative to 100 parts by mass of the total of the ionomer resin (A) and the polyvinyl butyral resin (B) described below. When the content of the ionomer resin (A) is 50 to 99 parts by mass relative to 100 parts by mass of the total of the ionomer resin (A) and the polyvinyl butyral resin (B), a resin composition having low hardness and low bending rigidity can be obtained. When the content of the ionomer resin (A) is less than 50 parts by mass relative to 100 parts by mass of the total of the ionomer resin (A) and the polyvinyl butyral resin (B), the scratch resistance of the resin composition may be impaired. When the content of the ionomer resin (A) is more than 99 parts by mass relative to 100 parts by mass of the total of the ionomer resin (A) and the polyvinyl butyral resin (B), a resin composition having low hardness and low bending rigidity may not be obtained. In consideration of the above-mentioned properties, the content of the ionomer resin (A) is preferably 50 parts by mass or more and 99 parts by mass or less, more preferably 50 parts by mass or more and 90 parts by mass or less, still more preferably 50 parts by mass or more and 85 parts by mass or less, and particularly preferably 50 parts by mass or more and 80 parts by mass or less, relative to 100 parts by mass in total of the ionomer resin (A) and the polyvinyl butyral resin (B).

[0028] [Polyvinyl butyral resin (B)] The resin composition of the present disclosure contains a polyvinyl butyral resin (B). By including a predetermined amount of the polyvinyl butyral resin (B), rigidity and flexibility are imparted to the resin composition, and therefore a resin composition having low hardness and low bending rigidity can be obtained.

[0029] The polyvinyl butyral resin (B) is a resin containing a structural unit derived from vinyl butyral (a structural unit having an acetal group). In addition to the structural unit derived from vinyl butyral (a structural unit having an acetal group), the polyvinyl butyral resin (B) also contains a structural unit derived from vinyl alcohol (a structural unit having a hydroxyl group) and a structural unit derived from vinyl acetate (a structural unit having an acetyl group).

[0030] In the polyvinyl butyral resin (B), the content of the vinyl alcohol-derived structural unit is preferably 10% by mass to 15% by mass relative to 100% by mass of the polyvinyl butyral resin (B). By having the content of the vinyl alcohol-derived structural unit be 10% by mass to 15% by mass relative to 100% by mass of the polyvinyl butyral resin (B), a resin composition having low hardness and low bending rigidity is easily obtained.

[0031] In the polyvinyl butyral resin (B), the content of the vinyl acetate-derived structural unit is preferably 1% by mass to 5% by mass relative to 100% by mass of the polyvinyl butyral resin (B). By having the content of the vinyl acetate-derived structural unit be 1% by mass to 5% by mass relative to 100% by mass of the polyvinyl butyral resin (B), a resin composition having low hardness and low bending rigidity is easily obtained.

[0032] In the polyvinyl butyral resin (B), the content of the vinyl butyral-derived structural unit is preferably 80% by mass to 90% by mass relative to 100% by mass of the polyvinyl butyral resin (B). By having the content of the vinyl butyral-derived structural unit be 80% by mass to 90% by mass relative to 100% by mass of the polyvinyl butyral resin (B), a resin composition having low hardness and low bending rigidity is easily obtained.

[0033] From the viewpoint of obtaining a resin composition having low hardness and low bending rigidity, the viscosity of the polyvinyl butyral resin (B) at 20° C. is preferably 10 mPa·s to 200 mPa·s, more preferably 20 mPa·s to 100 mPa·s, and even more preferably 30 mPa·s to 50 mPa·s. The viscosity at 20° C. is a value measured using an E-type rotational viscometer for a 10% ethanol / toluene=1 / 1 solution.

[0034] The polyvinyl butyral resin (B) can be obtained by reacting polyvinyl alcohol (PVA) obtained by saponifying polyvinyl acetate (PVAc) with butyraldehyde in the presence of an acid catalyst (acetalization). More specifically, the polyvinyl butyral resin (B) can be produced by adding appropriate amounts of an acid catalyst (e.g., hydrochloric acid) and butyraldehyde to an aqueous solution of polyvinyl alcohol (PVA) (10% by mass) at 75°C, reacting for a predetermined time, and then neutralizing, washing with water, and drying.

[0035] In the resin composition of the present disclosure, the polyvinyl butyral resin (B) may be one produced by the above-mentioned method, or a commercially available product may be used. Examples of commercially available polyvinyl butyral resins include S-LEC (registered trademark) B series (BL-1, BL-1H, BL-2, BL-2H, BL-5, BL-5Z, BL-10, BL-S, BX-L, BM-1, BM-2, BM-5, BM-S, BH-3, BH-6, BH-S, BX-1, BX-5) (manufactured by Sekisui Chemical Co., Ltd.), Mobital B series (B16H, B20H, B30H, B30HH, B60H, B75H (manufactured by Kuraray Co., Ltd.) and the like, and an appropriate resin may be selected and used from among these.

[0036] In the resin composition of the present disclosure, the content of the polyvinyl butyral resin (B) is 1 to 50 parts by mass per 100 parts by mass of the total of the ionomer resin (A) and the polyvinyl butyral resin (B). When the content of the polyvinyl butyral resin (B) is 1 to 50 parts by mass per 100 parts by mass of the total of the ionomer resin (A) and the polyvinyl butyral resin (B), a resin composition having low hardness and low bending rigidity can be obtained. When the content of the polyvinyl butyral resin (B) is less than 1 part by mass per 100 parts by mass of the total of the ionomer resin (A) and the polyvinyl butyral resin (B), a resin composition having low hardness and low bending rigidity cannot be obtained. When the content of the polyvinyl butyral resin (B) exceeds 50 parts by mass per 100 parts by mass of the total of the ionomer resin (A) and the polyvinyl butyral resin (B), the scratch resistance of the resin composition may be impaired. In consideration of the above-mentioned properties, the content of the polyvinyl butyral resin (B) is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 10 parts by mass or more and 50 parts by mass or less, still more preferably 15 parts by mass or more and 50 parts by mass or less, and particularly preferably 20 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the total of the ionomer resin (A) and the polyvinyl butyral resin (B).

[0037] [Ether-type plasticizer (C)] The resin composition of the present disclosure contains an ether-type plasticizer (C) (hereinafter also simply referred to as "plasticizer (C)"). By containing a predetermined amount of the ether-type plasticizer (C), which is compatible with the polyvinyl butyral resin (B) and can adjust the physical properties of the polyvinyl butyral resin (B), a resin composition having low hardness and low bending rigidity can be obtained.

[0038] Examples of the ether-type plasticizer (C) include polyalkylene glycol derivatives and triethylene glycol derivatives.

[0039] Examples of polyalkylene glycol derivatives include polymers obtained by ring-opening polymerization of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, and oxetane using monohydric alcohols, polyhydric alcohols, monocarboxylic acids, and polycarboxylic acids as polymerization initiators.

[0040] Examples of triethylene glycol derivatives include esters of triethylene glycol with linear or branched carboxylic acids having 4 to 8 carbon atoms, such as triethylene glycol-di-butyrate, triethylene glycol-di-isobutyrate, triethylene glycol-di-pentylate, triethylene glycol-di-2-ethylbutyrate, triethylene glycol-di-caproate, triethylene glycol-di-n-heptanoate, triethylene glycol-di-2-ethylhexoate, and triethylene glycol-di-n-octoate.

[0041] When the above-mentioned ester is used as the triethylene glycol derivative, the carbon number of the carboxylic acid is preferably 4 to 8. If the carbon number of the carboxylic acid is less than 4, the ether-type plasticizer (C) may not be able to approach the polyvinyl butyral resin (B) sufficiently due to the relationship with the propyl group, which is a side chain contained in the vinyl butyral-derived structural unit in the polyvinyl butyral resin (B), and plasticity may be difficult to exhibit. If the carbon number of the carboxylic acid exceeds 8, compatibility with the polyvinyl butyral resin (B) may be significantly impaired.

[0042] The ether-type plasticizer (C) may be used alone or in combination of two or more types, as long as the effects of the present disclosure can be obtained.

[0043] The content of the ether-type plasticizer (C) is 25 to 50 parts by mass per 100 parts by mass of the polyvinyl butyral resin (B). When the content of the ether-type plasticizer (C) is 25 to 50 parts by mass per 100 parts by mass of the polyvinyl butyral resin (B), a resin composition with low hardness and low bending rigidity can be obtained. When the content of the ether-type plasticizer (C) is less than 25 parts by mass, its contribution to the polyvinyl butyral resin (B) is insufficient, and therefore a resin composition with low hardness and low bending rigidity cannot be obtained. When the content of the ether-type plasticizer (C) exceeds 50 parts by mass, the content of the ether-type plasticizer (C) is high, which raises concerns about bleeding. The content of the ether-type plasticizer (C) is preferably 28 to 50 parts by mass, more preferably 30 to 50 parts by mass per 100 parts by mass of the polyvinyl butyral resin (B).

[0044] In the resin composition of the present disclosure, the total content of the ionomer resin (A) and the polyvinyl butyral resin (B) is 50 parts by mass or more per 100 parts by mass of the resin composition, more preferably 60 parts by mass or more, even more preferably 70 parts by mass or more, and particularly preferably 80 parts by mass or more per 100 parts by mass of the resin composition.

[0045] In the resin composition of the present disclosure, the content of the ether-type plasticizer (C) is 1 part by mass to 25 parts by mass relative to 100 parts by mass of the resin composition.

[0046] The resin composition of the present disclosure may contain components other than the ionomer resin (A), polyvinyl butyral resin (B), and ether-type plasticizer (C), as long as the object of the present invention is not impaired. The other components are not particularly limited, but examples include antioxidants, ultraviolet absorbers, wavelength conversion agents, antistatic agents, surfactants, colorants, light stabilizers, foaming agents, lubricants, crystal nucleating agents, crystallization accelerators, crystallization retarders, catalyst deactivators, heat absorbers, heat reflectors, heat dissipation agents, thermoplastic resins, thermosetting resins, inorganic fillers, organic fillers, impact modifiers, slip agents, crosslinking agents, crosslinking aids, silane coupling agents, tackifiers, processing aids, mold release agents, hydrolysis inhibitors, heat stabilizers, antiblocking agents, antifogging agents, flame retardants, flame retardant aids, light diffusing agents, antibacterial agents, antifungal agents, dispersants, and other resins. The other components may be used alone or in combination of two or more. The resin composition of the present disclosure preferably does not contain inorganic nanoparticles.

[0047] (Method for Producing Resin Composition) The method for producing the resin composition of the present disclosure is not particularly limited. The resin composition of the present disclosure can be produced, for example, by a method in which the ionomer (A), the polyvinyl butyral resin (B), and the ether-type plasticizer (C) are supplied to a feeder of a melt kneader so as to achieve a specific ratio, and then melt-kneaded. The melt kneading can be carried out using a kneader such as a single-screw extruder, a twin-screw extruder, a kneader, or a Banbury mixer.

[0048] (Physical Properties of Resin Composition) [MFR] The melt flow rate (MFR) of the resin composition of the present disclosure, measured under conditions of a temperature of 190°C and a load of 2160 g, is preferably 0.1 g / 10 min to 100 g / 10 min, more preferably 0.5 g / 10 min to 50 g / 10 min, and even more preferably 1.0 g / 10 min to 25 g / 10 min, from the viewpoints of fluidity and moldability. The melt flow rate (MFR) is a value measured in accordance with JIS K 7210-1:2014.

[0049] [Shore D Hardness] From the viewpoint of providing a soft feel on impact and improving ball controllability when applied to a golf ball, the Shore D hardness of the resin composition of the present disclosure is preferably 46.0 or less, more preferably less than 45.5, even more preferably less than 45.0, particularly preferably less than 44.5, and most preferably less than 44.0. From the viewpoint of providing impact resilience when the resin composition of the present disclosure is applied to a golf ball, the lower limit of the Shore D hardness is preferably 30.0 or more. The Shore D hardness is a value measured in accordance with JIS K 7215.

[0050] [Bending Rigidity] The bending rigidity of the resin composition of the present disclosure is preferably 35 MPa or less, more preferably 33 MPa or less, and even more preferably 30 MPa or less, from the viewpoint of achieving a soft feel on impact and improved ball controllability when applied to a golf ball. A bending rigidity of 35 MPa or less can achieve low hardness, a good feel on impact, and improved maintenance of distance when applied to a golf ball. On the other hand, the lower limit of the bending rigidity is preferably 9 MPa or more, from the viewpoint of providing rebound resilience when applied to a golf ball. The bending rigidity is a value measured in accordance with JIS K 7106.

[0051] <Golf Ball> As described above, the resin composition of the present disclosure has low hardness and low bending rigidity, and is preferably contained in at least one of the surface layer, intermediate layer, and core layer in the golf ball of the present disclosure. That is, the golf ball of the present disclosure preferably contains the resin composition of the present disclosure in at least one of the surface layer, intermediate layer, and core layer. By containing the resin composition of the present disclosure in at least one of the surface layer, intermediate layer, and core layer, the golf ball of the present disclosure becomes a golf ball with good feel and excellent controllability.

[0052] From the viewpoint of achieving a good feel and maintaining and improving the flight distance of the golf ball, the golf ball of the present disclosure preferably contains the resin composition of the present disclosure in at least one of the surface layer and the intermediate layer among the surface layer, the intermediate layer, and the core layer, and it is particularly preferable that the resin composition be contained in at least the surface layer.

[0053] <Modifier> Furthermore, as described above, the resin composition of the present disclosure has low hardness and low bending rigidity, and is therefore preferably included in the modifier of the present disclosure. That is, the modifier of the present disclosure includes the resin composition of the present disclosure. By including the resin composition of the present disclosure, a modifier applicable to applications requiring low hardness and low bending rigidity can be obtained. The modifier of the present disclosure can be used to modify resins such as polyamide resins and polyester resins, for example, to improve impact resistance and flexibility.

[0054] The modifier of the present disclosure may contain additives in addition to the resin composition of the present disclosure, as long as the additives do not impair the effects of the present disclosure. Examples of additives include pigments, dyes, antioxidants, UV absorbers, light stabilizers, surfactants, surface conditioners, and thixotropic agents.

[0055] The resin composition of the present disclosure has low hardness and bending rigidity, and therefore, in addition to the golf balls and modifiers described above, can be applied to packaging materials, automobile parts, sporting goods, shoe parts, and the like.

[0056] The invention according to one embodiment of the present disclosure will be described in more detail below with reference to examples, but the scope of the invention is not limited to the specific examples shown below.

[0057] The raw materials for the resin compositions of the examples and comparative examples are shown below.

[0058] [Ionomer Resin (A)] Ionomer Resin A1: Zn-type ionomer resin in which 65% of the carboxylic acid groups derived from methacrylic acid of an ethylene-methacrylic acid-isobutyl acrylate copolymer (ethylene:methacrylic acid:isobutyl acrylate=75:8:17 (mass ratio)) have been neutralized.

[0059] [Polyvinyl butyral resin (B)] Polyvinyl butyral resin B1 "S-LEC (registered trademark) BL-5Z" (manufactured by Sekisui Chemical Co., Ltd.)

[0060] [Plasticizer (C)] Plasticizer C1 "Sofval (registered trademark) P-0803N" (manufactured by NOF Corporation) Plasticizer C2 "Sofval (registered trademark) P-0403N" (manufactured by NOF Corporation)

[0061] Examples 1 to 6, Comparative Examples 1 to 5 Using a 30 mmφ twin-screw extruder (manufactured by Ikegai Corporation, product number: PCM30), an ionomer resin (A), a polyvinyl butyral resin (B), and a plasticizer (C) were melt-kneaded and granulated according to the following conditions in the blending ratios shown in Table 1 to obtain pellet-shaped kneaded products. The obtained kneaded products were press-molded at 160°C using a press molding machine and then cooled at 20°C to produce press sheets with a thickness of 3 mm. [Mixing conditions] L / D: 35 Barrel temperature (°C): C1 (120), C2 (140), C3 (160), C4 (170), C5-C9 (180) Die temperature: 180°C Screw rotation speed: 180 rpm Extrusion rate: 10 kg / h C8: Vent open Plasticizer (C) added from C4 vent Screen mesh: 60 / 120 / 60

[0062] [Measurements] The following measurements and evaluations were carried out on the obtained sheets. The results are shown in Table 1.

[0063] [Melt Mass Flow Rate (MFR)] The MFR was measured in accordance with JIS K 7210-1: 2014. Using a melt indexer (manufactured by Toyo Seiki Seisakusho, Ltd.), the measurement was performed in accordance with JIS K 7210-1: 2014 under conditions of a temperature of 190°C and a load of 2160 g.

[0064] [Bending rigidity] The bending rigidity was measured in accordance with JIS K 7106. The obtained sheet was punched into a strip of 20 mm width × 100 mm length to prepare a test piece. The test piece was allowed to stand for 2 weeks in an environment of 23°C and a relative humidity of 50%, and then the bending rigidity was measured in accordance with JIS K 7106 using an Olsen type stiffness tester (manufactured by Toyo Seiki Seisakusho, Ltd.).

[0065] [Shore D Hardness] The Shore D hardness was measured in accordance with JIS K 7215. The obtained sheet was punched into a strip of 20 mm width x 100 mm length to prepare a test piece. The test piece was left to stand for 2 weeks in an environment of 23°C and 50% relative humidity, and then the Shore D hardness was measured in accordance with JIS K 7215 using an automatic rubber hardness tester P2 type (manufactured by Kobunshi Keiki Co., Ltd.).

[0066]

[0067] As can be seen from the results in Table 1, the sheets obtained from the resin compositions of Examples 1 to 6 all had a low Shore D hardness of 46.0 or less and a bending rigidity of 35 MPa or less. Therefore, when applied to golf balls with low hardness and low bending rigidity, a good hitting feel and improved controllability can be achieved despite the low hardness.

[0068] The disclosure of Japanese Patent Application No. 2024-123728, filed on July 30, 2024, is incorporated herein by reference in its entirety. All publications, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual publication, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A resin composition comprising: an ionomer resin (A) obtained by neutralizing the carboxyl groups of an ethylene-unsaturated carboxylic acid copolymer with metal ions; a polyvinyl butyral resin (B); and an ether-type plasticizer (C), and satisfying the following requirements (i) to (iii): (i) the content of the ionomer resin (A) is 50 to 99 parts by mass per 100 parts by mass of the ionomer resin (A) and the polyvinyl butyral resin (B); (ii) the content of the polyvinyl butyral resin (B) is 1 to 50 parts by mass per 100 parts by mass of the ionomer resin (A) and the polyvinyl butyral resin (B); and (iii) the content of the ether-type plasticizer (C) is 25 to 50 parts by mass per 100 parts by mass of the polyvinyl butyral resin (B).

2. The resin composition according to claim 1, which has a Shore D hardness of 46.0 or less as measured in accordance with JIS K 7215.

3. The resin composition according to claim 1, wherein the content of the ether-type plasticizer (C) is 1 to 25 parts by mass per 100 parts by mass of the resin composition.

4. The resin composition according to claim 1, wherein the total content of the ionomer resin (A) and the polyvinyl butyral resin (B) is 50 parts by mass or more per 100 parts by mass of the resin composition.

5. The resin composition according to claim 1, wherein the ether-type plasticizer (C) is a polyalkylene glycol derivative or a triethylene glycol derivative.

6. The resin composition according to claim 1, wherein the ethylene-unsaturated carboxylic acid copolymer is an ethylene-unsaturated carboxylic acid copolymer or an ethylene-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer.

7. The resin composition according to claim 1, wherein at least a portion of the metal ions in the ionomer resin (A) are monovalent metal ions.

8. The resin composition according to claim 1, wherein at least a portion of the metal ions in the ionomer resin (A) are divalent metal ions.

9. The resin composition according to claim 1, which has a flexural rigidity modulus measured in accordance with JIS K 7106 of 35 MPa or less.

10. A golf ball comprising the resin composition according to any one of claims 1 to 9 in at least one of a skin layer, an intermediate layer, and a core layer.

11. A modifier comprising the resin composition according to any one of claims 1 to 9.

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