Golf ball

Abstract

To provide a golf ball improved in durability without substantially lowering resilience.SOLUTION: A golf ball has a core, and a cover of at least one layer positioned outside the core. The cover of the at least one layer is formed of a cover composition containing one or more kinds of an ionomer resin obtained by neutralizing with at least one kind of metal ion selected from Groups I, II, and XII of the periodic table, at least a part of a carboxyl group and / or a dicarboxylic anhydride group in a copolymer (P) containing as the essential constitutional units, a structural unit (A) derived from ethylene and / or 3-20C α-olefin, and a structural unit (B) derived from a monomer having a carboxyl group and / or a dicarboxylic anhydride group. A loss elastic modulus E''at 0°C obtained by measuring the dynamic viscoelasticity of the cover composition in a specific condition is 3.40×107 Pa or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to golf balls with improved durability. [Background technology]

[0002] Examples of golf ball structures include two-piece golf balls having a core and a cover, three-piece golf balls having a core, one intermediate layer encasing the core, and a cover encasing the intermediate layer, and multi-piece golf balls having a core, at least two intermediate layers encasing the core, and a cover encasing the intermediate layer. Ionomer resins are used as materials for each layer of golf balls. Ionomer resins have high rigidity, and when used as components of golf balls, they can produce golf balls with long flight distances. For this reason, ionomer resins are widely used as materials for intermediate layers and covers of golf balls.

[0003] For example, Patent Document 1 discloses a thermoplastic composition comprising: (a) an E / X / Y copolymer (wherein E is ethylene, X is a C3-C8 α,β ethylenically unsaturated carboxylic acid, and Y is a softening comonomer selected from alkyl acrylates and alkyl methacrylates, the alkyl group of which has 1 to 8 carbon atoms), wherein a. the E / X / Y copolymer meets ASTM D-1238, Condition E, having a melt index of at least 75 grams per 10 minutes measured at 190°C using a 2160 gram weight, wherein bX is about 2-30 wt% of said E / X / Y copolymer, Y is about 17-40 wt% of said E / X / Y copolymer, and at least 55% of cX is neutralized with one or more alkali metal, transition metal, or alkaline earth metal cations; and (b) a melt-processable thermoplastic composition consisting essentially of: (a) about 5-50 wt% based on the total of (a) and (b) one or more aliphatic monofunctional organic acids or salts thereof having fewer than 36 carbon atoms, wherein greater than 80% of the total acids in (a) and (b) are neutralized with one or more alkali metal, transition metal, or alkaline earth metal cations.

[0004] Patent Document 2 discloses a golf ball material characterized by a mixture obtained by blending, as essential ingredients, 100 parts by mass of a resin component comprising (a) a base resin comprising (a) an olefin-unsaturated carboxylic acid binary random copolymer and / or a metal ion-neutralized product of an olefin-unsaturated carboxylic acid binary random copolymer, and (b) an olefin-unsaturated carboxylic acid-unsaturated carboxylic ester ternary random copolymer and / or a metal ion-neutralized product of an olefin-unsaturated carboxylic acid-unsaturated carboxylic ester ternary random copolymer in a mass ratio of 100:0 to 25:75, and (e) a non-ionomeric thermoplastic elastomer in a mass ratio of 100:0 to 50:50, with (c) 5 to 80 parts by mass of a fatty acid and / or a derivative thereof having a molecular weight of 280 to 1500, and (d) 0.1 to 10 parts by mass of a basic inorganic metal compound capable of neutralizing unneutralized acid groups in the base resin and component (c).

[0005] Patent Document 3 describes a golf ball having a core and a cover of two or more layers covering the core, in which the first cover layer is formed mainly from (a) a non-ionomer thermoplastic elastomer, and (b) a mixture of an isocyanate compound (b-1) and a thermoplastic resin (b-2) that does not substantially react with isocyanate, and the second cover layer is formed mainly from (c) a metal ion neutralized product of an olefin-unsaturated carboxylic acid binary random copolymer and an olefin-unsaturated carboxylic acid binary random copolymer (c-1), and an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer and an olefin-unsaturated carboxylic acid The golf ball is disclosed as comprising, as its main components, a mixture of one or more base resins selected from (c-2) metal ion-neutralized carboxylic acid-unsaturated carboxylic acid ester ternary random copolymers and (d) a non-ionomeric thermoplastic elastomer in a weight ratio of 100:0 to 50:50; (e) a fatty acid having 18 to 80 carbon atoms and / or a derivative thereof; (f) a metal ion source capable of neutralizing unneutralized acid groups in the components (c) and (e); and (g) a compound having a molecular weight of 20,000 or less and two or more reactive functional groups, wherein the first cover layer and the second cover layer are adjacent to each other.

[0006] Patent Document 4 discloses a golf ball resin composition comprising 100 parts by mass of at least one thermoplastic resin component (A) selected from (a-1) an olefin-unsaturated carboxylic acid random copolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester terpolymer, (a-2) a metal ion-neutralized product of an olefin-unsaturated carboxylic acid random copolymer and / or a metal ion-neutralized product of an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester terpolymer, and (a-3) a thermoplastic elastomer, and 0.1 to 10 parts by mass of at least one wax component (B) selected from (b-1) a fatty acid having 20 to 80 carbon atoms and / or a derivative thereof, and (b-2) a natural wax oxide and / or a natural wax derivative having a neutralization value of 60 to 190 mgKOH / g.

[0007] Patent Document 5 discloses a golf ball resin composition containing (A) at least one selected from the group consisting of (a-1) a binary copolymer of an olefin and an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, (a-2) a metal ion-neutralized binary copolymer of an olefin and an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, (a-3) a terpolymer of an olefin, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α,β-unsaturated carboxylic acid ester, and (a-4) a metal ion-neutralized terpolymer of an olefin, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α,β-unsaturated carboxylic acid ester, and (B) a compound having a hydrocarbon chain, a cationic moiety, and an anionic moiety in its molecule. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2004-524418 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-219195 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-180725 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-348467 [Patent Document 5] Japanese Patent Application Laid-Open No. 2013-78563 Summary of the Invention [Problem to be solved by the invention]

[0009] Golf balls made using ionomer resins have high resilience and can fly long distances, but their durability is not sufficient. 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 with improved durability without substantially reducing resilience. [Means for solving the problem]

[0010] The golf ball of the present invention, which has achieved the above object, is a golf ball having a core and at least one layer of cover positioned on the outside of the core, wherein the at least one layer of cover is formed from a cover composition containing one or more ionomer resins in which at least a portion of the carboxyl groups and / or dicarboxylic anhydride groups in a copolymer (P) containing, as essential structural units, structural units (A) derived from ethylene and / or an α-olefin having 3 to 20 carbon atoms and structural units (B) having carboxyl groups and / or dicarboxylic anhydride groups, are neutralized with at least one metal ion selected from Group 1, 2, or 12 of the Periodic Table, and wherein the loss modulus E'' at 0°C of the cover composition, as measured under the following conditions, is 3.40 x 10 7 Pa or less. <Measurement conditions> Measurement mode: Sine wave tension Measurement temperature range: -100℃~100℃ Heating rate: 4°C / min Excitation frequency: 10Hz Measurement distortion: 0.05% [Effects of the Invention]

[0011] According to the present invention, the durability of the golf ball can be significantly improved without substantially reducing the resilience. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a partially cutaway cross-sectional view showing a golf ball according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The golf ball of the present invention is a golf ball having a core and at least one layer of cover positioned on the outside of the core, wherein the at least one layer of cover is formed from a cover composition containing one or more ionomer resins in which at least a portion of the carboxyl groups and / or dicarboxylic anhydride groups in a copolymer (P) containing, as essential structural units, structural units (A) derived from ethylene and / or an α-olefin having 3 to 20 carbon atoms and structural units (B) having carboxyl groups and / or dicarboxylic anhydride groups are neutralized with at least one metal ion selected from Group 1, Group 2, or Group 12 of the Periodic Table, and the loss modulus E'' at 0°C of the cover composition, as measured by dynamic viscoelasticity under the following conditions, is 3.40×10 7 The cover composition has a loss modulus E″ of 3.40×10 Pa or less at 0° C. 7 In order to satisfy the requirement of 0.1 Pa or less, the ionomer resin contained in the cover composition preferably has a phase angle δ of 50 degrees to 75 degrees when the absolute value of the complex modulus G* is 0.1 MPa as measured with a rotational rheometer described below. <Measurement conditions> Measurement mode: Sine wave tension Measurement temperature range: -100℃~100℃ Heating rate: 4°C / min Excitation frequency: 10Hz Measurement distortion: 0.05%

[0014] First, the ionomer resin used in the present invention will be described. The ionomer resin used in the present invention contains, as essential constituent units, structural units (A) derived from ethylene and / or an α-olefin having 3 to 20 carbon atoms and structural units (B) having carboxyl groups and / or dicarboxylic anhydride groups, and uses a copolymer (P) formed by random copolymerization of these in a substantially linear chain as a base resin, in which at least a portion of the carboxyl groups and / or dicarboxylic anhydride groups of the structural units (B) are neutralized with at least one metal ion selected from Groups 1, 2, or 12 of the periodic table.

[0015] (1) Structural unit (A) The structural unit (A) is at least one structural unit selected from the group consisting of structural units derived from ethylene and structural units derived from an α-olefin having 3 to 20 carbon atoms. That is, the structural unit (A) is a structural unit in the copolymer (P) formed by polymerizing ethylene and / or an α-olefin having 3 to 20 carbon atoms. The α-olefins involved in the present invention have the structural formula: CH2=CHR 18 is an α-olefin having 3 to 20 carbon atoms (R 18 is a hydrocarbon group having 1 to 18 carbon atoms, which may have a linear or branched structure. The α-olefin more preferably has 3 to 12 carbon atoms.

[0016] Specific examples of ethylene and / or α-olefins having 3 to 20 carbon atoms that provide the structural unit (A) include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 3-methyl-1-butene, and 4-methyl-1-pentene, and ethylene may also be used. As ethylene, ethylene derived from petroleum raw materials or non-petroleum raw materials such as plant raw materials can be used.

[0017] The ethylene and / or α-olefin having 3 to 20 carbon atoms that provides the structural unit (A) may be one type or multiple types. Examples of combinations of two types include ethylene-propylene, ethylene-1-butene, ethylene-1-hexene, ethylene-1-octene, propylene-1-butene, propylene-1-hexene, and propylene-1-octene. Examples of combinations of three types include ethylene-propylene-1-butene, ethylene-propylene-1-hexene, ethylene-propylene-1-octene, propylene-1-butene-hexene, and propylene-1-butene-1-octene.

[0018] In the present invention, the structural unit (A) preferably contains an ethylene unit as an essential component and may further contain one or more α-olefin units having 3 to 20 carbon atoms as needed. The ethylene unit in the structural unit (A) may account for 65 mol % to 100 mol % or 70 mol % to 100 mol % of the total moles of the structural unit (A). From the viewpoint of impact resistance, the structural unit (A) may consist solely of structural units derived from ethylene.

[0019] (2) Structural unit (B) The structural unit (B) is a structural unit having a carboxyl group and / or a dicarboxylic anhydride group, and is preferably, for example, a structural unit derived from a monomer having a carboxyl group and / or a dicarboxylic anhydride group. Note that the structural unit (B) may have the same structure as the structural unit derived from a monomer having a carboxyl group and / or a dicarboxylic anhydride group, and as will be described later in the production method, it does not necessarily have to be produced using a monomer having a carboxyl group and / or a dicarboxylic anhydride group.

[0020] Examples of the monomer having a carboxyl group that provides the structural unit (B) include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, norbornene dicarboxylic acid, and bicyclo[2,2,1]hept-2-ene-5,6-dicarboxylic acid.

[0021] Examples of the monomer having a dicarboxylic acid anhydride group that provides the structural unit (B) include maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, 3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride, tetracyclo[6.2.1.1 3,6 .0 2,7 ] Examples of the unsaturated dicarboxylic acid anhydrides include dodec-9-ene-4,5-dicarboxylic acid anhydride and 2,7-octadien-1-yl succinic acid anhydride.

[0022] The monomer having a carboxyl group and / or a dicarboxylic anhydride group that provides the structural unit (B) is preferably a structural unit derived from acrylic acid, methacrylic acid, or 5-norbornene-2,3-dicarboxylic anhydride, in terms of ease of industrial availability, and may particularly be a structural unit derived from acrylic acid. The structural unit derived from the monomer having a carboxyl group and / or a dicarboxylic anhydride group may be of one type or of multiple types.

[0023] The dicarboxylic anhydride group may react with moisture in the air to open the ring and convert a portion of the group into a dicarboxylic acid. However, the dicarboxylic anhydride group may be ring-opened within the scope of the present invention.

[0024] (3) Other structural units (C) The copolymer (P) may contain a structural unit (C) other than the structural units represented by the structural units (A) and (B). Any monomer can be used to provide the structural unit (C), provided it is not included in the monomers that provide the structural units (A) and (B). The monomer that provides the structural unit (C) is not limited as long as it is a compound having one or more carbon-carbon double bonds in its molecular structure, and examples thereof include acyclic monomers represented by the following general formula (1) and cyclic monomers represented by the following general formula (2).

[0025] Acyclic monomers [ka]

[0026] [In general formula (1), T 1 ~T 3 are each independently a hydrogen atom, a hydrocarbon having 1 to 20 carbon atoms, a substituent selected from the group consisting of a hydrocarbon group having 1 to 20 carbon atoms substituted with a hydroxyl group, a hydrocarbon group having 2 to 20 carbon atoms substituted with an alkoxy group having 1 to 20 carbon atoms, a hydrocarbon group having 3 to 20 carbon atoms substituted with an ester group having 2 to 20 carbon atoms, a hydrocarbon group having 1 to 20 carbon atoms substituted with a halogen atom, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an ester group having 2 to 20 carbon atoms, a silyl group having 3 to 20 carbon atoms, a halogen atom, or a cyano group; T 4 is a substituent selected from the group consisting of a hydrocarbon group having 1 to 20 carbon atoms substituted with a hydroxyl group, a hydrocarbon group having 2 to 20 carbon atoms substituted with an alkoxy group having 1 to 20 carbon atoms, a hydrocarbon group having 3 to 20 carbon atoms substituted with an ester group having 2 to 20 carbon atoms, a hydrocarbon group having 1 to 20 carbon atoms substituted with a halogen atom, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an ester group having 2 to 20 carbon atoms, a silyl group having 3 to 20 carbon atoms, a halogen atom, or a cyano group.

[0027] T 1 ~T 4 The carbon skeleton of the hydrocarbon group, substituted alkoxy group, substituted ester group, alkoxy group, aryl group, ester group, and silyl group may have a branch, a ring, and / or an unsaturated bond. T 1 ~T 4 The lower limit of the number of carbon atoms in the hydrocarbon group may be 1 or more, and the upper limit may be 20 or less, or may be 10 or less. T 1 ~T 4 The lower limit of the number of carbon atoms in the substituted alkoxy group may be 1 or more, and the upper limit may be 20 or less, or may be 10 or less. T 1 ~T 4 The lower limit of the number of carbon atoms in the substituted ester group may be 2 or more, and the upper limit may be 20 or less, or may be 10 or less. T 1 ~T 4 The lower limit of the number of carbon atoms in the alkoxy group in the above formula may be 1 or more, and the upper limit may be 20 or less, or may be 10 or less. T 1 ~T 4 The lower limit of the number of carbon atoms in the aryl group in the above formula may be 6 or more, and the upper limit may be 20 or less, or may be 11 or less. T 1 ~T 4 The lower limit of the number of carbon atoms in the ester group in the above formula may be 2 or more, and the upper limit may be 20 or less, or may be 10 or less. T 1 ~T 4 The lower limit of the number of carbon atoms in the silyl group in the above formula may be 3 or more, and the upper limit may be 18 or less, or may be 12 or less. Examples of the silyl group include a trimethylsilyl group, a triethylsilyl group, a tri-n-propylsilyl group, a triisopropylsilyl group, a dimethylphenylsilyl group, a methyldiphenylsilyl group, and a triphenylsilyl group.

[0028] In the ionomer resin, T 1 and T 2 may be a hydrogen atom, T 3 may be a hydrogen atom or a methyl group, T 1 ~T 3 However, both may be hydrogen atoms. 4 may be an ester group having 2 to 20 carbon atoms.

[0029] Specific examples of the acyclic monomer include T monomers containing (meth)acrylic acid esters, etc. 4 is an ester group having 2 to 20 carbon atoms. T 4 is an ester group having 2 to 20 carbon atoms, the acyclic monomer may be an ester group having the structural formula: CH2=C(R 21 )CO2(R 22 ) where R 21 is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, which may have a branched structure, a ring, and / or an unsaturated bond. 22 is a hydrocarbon group having 1 to 20 carbon atoms, which may have a branched, cyclic, and / or unsaturated bond. 22It may contain a heteroatom at any position within the group.

[0030] Structural formula: CH2=C(R 21 )CO2(R 22 ) as a compound represented by R 21 is a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms. 21 is a hydrogen atom or an acrylic acid ester in which R 21 is a methyl group.

[0031] Structural formula: CH2=C(R 21 )CO2(R 22 Specific examples of the compound represented by the formula (I) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, phenyl (meth)acrylate, toluyl (meth)acrylate, and benzyl (meth)acrylate. In the present invention, "(meth)acrylic acid" means "acrylic acid and / or methacrylic acid."

[0032] Specific compounds include methyl acrylate, ethyl acrylate, n-butyl acrylate (nBA), isobutyl acrylate (iBA), t-butyl acrylate (tBA), and 2-ethylhexyl acrylate, and in particular may be n-butyl acrylate (nBA), isobutyl acrylate (iBA), and t-butyl acrylate (tBA). The acyclic monomer may be of one type or of multiple types.

[0033] Cyclic Monomers [ka]

[0034] [In general formula (2), R 1 ~R 12 may be the same or different and are selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 20 carbon atoms; R 9 and R 10 , and R 11 and R 12 may combine with each other to form a divalent organic group, R 9 or R 10 and R 11 or R 12 and may form a ring together. n represents 0 or a positive integer, and when n is 2 or more, R 5 ~R 8 may be the same or different in each repeating unit.

[0035] Examples of the cyclic monomer include norbornene-based olefins, such as compounds having a cyclic olefin skeleton, such as norbornene, vinylnorbornene, ethylidenenorbornene, norbornadiene, tetracyclododecene, and tricyclo[4.3.0.12,5]dec-3-ene, and may also include 2-norbornene (NB) and tetracyclo[6.2.1.13,6.02,7]dodec-4-ene.

[0036] (4) Metal ions Examples of the metal ion of the carboxylate group contained in the ionomer resin include monovalent or divalent metal ions of a group selected from the group consisting of Groups 1, 2, and 12 of the periodic table. Specific examples include ions of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), magnesium (Mg), calcium (Ca), and zinc (Zn). From the viewpoint of ease of handling, sodium (Na) or zinc (Zn) ions are particularly preferred.

[0037] The carboxylate group can be obtained, for example, by hydrolyzing or thermolyzing the ester group of the copolymer, or by reacting the copolymer with a compound containing a metal ion of Group 1, 2, or 12 of the periodic table while the ester group is being hydrolyzed or thermolyzed. The metal ion may be of one type or of multiple types.

[0038] (5) Copolymer (P) The copolymer (P), which serves as the base resin of the ionomer resin used in the present invention, is characterized in that it contains, as essential constituent units, structural units (A) derived from ethylene and / or an α-olefin having 3 to 20 carbon atoms and structural units (B) having a carboxyl group and / or a dicarboxylic anhydride group, and optionally also contains an optional structural unit (C), and these structural units are copolymerized substantially linearly, preferably randomly copolymerized.

[0039] The term "substantially linear" refers to a state in which the copolymer has no branches or the frequency of branched structures is low, and the copolymer can be considered linear. Specifically, as described below, this refers to a state in which the phase angle δ of the copolymer is 50 degrees or more.

[0040] The copolymer (P) must contain at least one type of structural unit (A) and at least one type of structural unit (B), and must contain structural units derived from a total of at least two types of monomers, and may also contain another structural unit (C). The structural units and amounts of the structural units in the copolymer (P) will be described below.

[0041] A structure derived from one molecule of ethylene and / or an α-olefin having 3 to 20 carbon atoms, a monomer having a carboxyl group and / or a dicarboxylic anhydride group, and an arbitrary monomer is defined as one structural unit in the copolymer. The proportion of each structural unit expressed in mol% when the total structural units in the copolymer are taken as 100 mol% is the structural unit amount.

[0042] Structural unit amount of the structural unit (A) derived from ethylene and / or an α-olefin having 3 to 20 carbon atoms: The structural unit amount of the structural unit (A) has a lower limit of 60.0 mol% or more, preferably 70.0 mol% or more, more preferably 80.0 mol% or more, even more preferably 85.0 mol% or more, still more preferably 90.0 mol% or more, and particularly preferably 91.2 mol% or more, and an upper limit of 97.9 mol% or less, preferably 97.5 mol% or less, more preferably 97.0 mol% or less, and even more preferably 96.5 mol% or less.

[0043] When the amount of structural units (A) derived from ethylene and / or an α-olefin having 3 to 20 carbon atoms is 60.0 mol % or more, the toughness of the copolymer is improved, and when it is 97.9 mol % or less, the crystallinity is reduced and the transparency is increased.

[0044] Amount of the structural unit (B) having a carboxyl group and / or a dicarboxylic anhydride group: The lower limit of the amount of the structural unit (B) is selected from the group consisting of 2.0 mol% or more, preferably 2.9 mol% or more, more preferably 3.5 mol% or more, and even more preferably 6.0 mol% or more, and 20.0 mol% or less, preferably 18.0 mol% or less, more preferably 15.0 mol% or less, and even more preferably 10.0 mol% or less.

[0045] If the amount of structural units (B) having a carboxyl group and / or a dicarboxylic anhydride group is 2.0 mol% or more, the copolymer will have good adhesion to different materials with high polarity, and if it is 20.0 mol% or less, the copolymer will tend to have good mechanical properties. If the amount of structural units (B) is 6.0 mol% or more, the coefficient of restitution will be greatly improved, which is preferable. Furthermore, the structural units having a carboxyl group and / or a dicarboxylic anhydride group used may be used alone or in combination of two or more types.

[0046] Amount of structural units (C) derived from other monomers: The upper limit of the amount of the structural unit (C) is selected from 20.0 mol% or less, preferably 15.0 mol% or less, more preferably 10.0 mol% or less, even more preferably 5.0 mol% or less, and particularly preferably 3.6 mol% or less, and there is no particular restriction on the lower limit, which may be 0 mol%. When the amount of the structural unit (C) derived from any monomer is 20.0 mol% or less, the copolymer tends to have sufficient mechanical properties. Furthermore, any of the monomers used may be used alone or in combination of two or more kinds.

[0047] Number of branches per 1,000 carbon atoms in copolymer (P): In the copolymer (P), in order to increase the elastic modulus and obtain sufficient mechanical properties, 13 The number of methyl branches calculated by C-NMR per 1,000 carbon atoms may be an upper limit of 50, 5.0, 1.0, or 0.5, with no particular lower limit, and the lower limit is the better. The number of ethyl branches per 1,000 carbon atoms may be an upper limit of 3.0, 2.0, 1.0, or 0.5, with no particular lower limit, and the lower limit is the better. The number of butyl branches per 1,000 carbon atoms may be an upper limit of 7.0, 5.0, 3.0, or 0.5, with no particular lower limit, and the lower limit is the better.

[0048] Method for measuring the amount of structural units derived from monomers having a carboxy group and / or a dicarboxylic anhydride group and acyclic monomers in copolymer (P), and the number of branches: The amount of structural units derived from a monomer having a carboxy group and / or a dicarboxylic anhydride group and a non-cyclic monomer in the copolymer (P), and the number of branches per 1,000 carbon atoms are 13 It can be determined using C-NMR spectroscopy. 13 C-NMR is measured by the following method.

[0049] 200 mg to 300 mg of sample is placed in an NMR sample tube with an inner diameter of 10 mm, together with 2.4 ml of a mixed solvent of o-dichlorobenzene (C6H4Cl2) and deuterated bromide benzene (C6D5Br) (C6H4Cl2 / C6D5Br = 2 / 1 (volume ratio)) and hexamethyldisiloxane, a chemical shift reference substance, and the tube is purged with nitrogen, then sealed and heated to dissolve into a homogeneous solution, which is used as the NMR measurement sample.

[0050] NMR measurements are carried out at 120°C using an AV400M NMR instrument manufactured by Bruker Japan Ltd. equipped with a 10 mmφ cryoprobe. 13 C-NMR is measured using the inverse gate decoupling method with a sample temperature of 120°C, a pulse angle of 90°, a pulse interval of 51.5 seconds, and an accumulation count of 512 or more.

[0051] The chemical shifts are those of hexamethyldisiloxane. 13 The C signal was set to 1.98 ppm, and the other 13 The chemical shift of the C signal is based on this. 13 In C-NMR, signals specific to the monomers or branches in the copolymer are identified and their intensities are compared, allowing the amount of structural units of each monomer in the copolymer and the number of branches to be analyzed. The positions of the signals specific to the monomers or branches can be determined by reference to publicly known materials, or can be independently identified depending on the sample. Such analytical techniques are commonly known to those skilled in the art.

[0052] Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn): The weight average molecular weight (Mw) of the copolymer (P) has a lower limit of usually 1,000 or more, preferably 6,000 or more, and more preferably 10,000 or more, and an upper limit of usually 2,000,000 or less, preferably 1,500,000 or less, even more preferably 1,000,000 or less, particularly preferably 800,000 or less, and most preferably 100,000 or less.

[0053] If Mw is 1,000 or more, the copolymer tends to have good physical properties such as mechanical strength and impact resistance, and if Mw is 2,000,000 or less, the copolymer has a low melt viscosity and good processability.

[0054] The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the copolymer (P) is usually in the range of 1.5 to 4.0, preferably 1.6 to 3.5, and more preferably 1.9 to 2.3. If Mw / Mn is 1.5 or more, the copolymer has good processability, and if it is 4.0 or less, the copolymer tends to have good mechanical properties. In the present invention, (Mw / Mn) is sometimes expressed as a molecular weight distribution parameter. The method for determining the weight average molecular weight (Mw) and the number average molecular weight (Mn) will be described later.

[0055] Melting point (Tm, °C): The melting point of the copolymer (P) is indicated by the maximum peak temperature of the endothermic curve measured by a differential scanning calorimeter (DSC). When multiple peaks are shown in the endothermic curve obtained by DSC measurement, where the vertical axis is heat flow (mW) and the horizontal axis is temperature (°C), the maximum peak temperature refers to the temperature of the peak with the greatest height from the baseline. When there is only one peak, the maximum peak temperature refers to the temperature of that peak.

[0056] The melting point of the copolymer (P) is preferably 50° C. to 140° C., more preferably 60° C. to 138° C., and most preferably 70° C. to 135° C. If the melting point of the copolymer (P) is within this range, the heat resistance and adhesiveness will be good.

[0057] In the present invention, the melting point can be determined from the absorption curve obtained by using, for example, a DSC (DSC7020) manufactured by SII Nanotechnology Inc., packing approximately 5.0 mg of a sample into an aluminum pan, heating it to 200°C at 10°C / min, holding it isothermally at 200°C for 5 minutes, cooling it to 20°C at 10°C / min, holding it isothermally at 20°C for 5 minutes, and then heating it again to 200°C at 10°C / min.

[0058] Crystallinity (%): The degree of crystallinity of the copolymer (P) as measured by differential scanning calorimetry (DSC) is not particularly limited, but is preferably greater than 0%, more preferably greater than 5%, and even more preferably 7% or more. If the degree of crystallinity exceeds 0%, the copolymer is more likely to exhibit toughness. The degree of crystallinity is also an index of transparency, and higher transparency is preferred, but the upper limit of the degree of crystallinity is not particularly limited.

[0059] In the present invention, the crystallinity can be determined, for example, by determining the heat of fusion (ΔH) from the area of ​​the melting endothermic peak obtained by DSC measurement using the same procedure as in the measurement of the melting point, and dividing the resulting heat of fusion by the heat of fusion of 293 J / g for perfectly crystalline high-density polyethylene (HDPE).

[0060] Molecular structure of copolymer (P): The molecular chain terminal of the copolymer (P) may be a structural unit (A) of ethylene and / or an α-olefin having 3 to 20 carbon atoms, a structural unit (B) having a carboxyl group and / or a dicarboxylic anhydride group, or a structural unit (C) of any monomer.

[0061] Examples of the copolymer (P) include random copolymers, block copolymers, and graft copolymers of structural units (A) of ethylene and / or an α-olefin having 3 to 20 carbon atoms, structural units (B) having a carboxyl group and / or a dicarboxylic anhydride group, and structural units (C) of any monomer. Among these, random copolymers that can contain a large amount of structural units (B) are preferred.

[0062] An example of the molecular structure of a typical ternary copolymer (1) is shown below. A random copolymer is a copolymer of structural units (A) of ethylene and / or an α-olefin having 3 to 20 carbon atoms, structural units (B) having a carboxyl group and / or a dicarboxylic anhydride group, and structural units (C) of any monomer, as shown in the molecular structure example (1) below, in which the probability of finding each structural unit at any position in a molecular chain is independent of the type of adjacent structural units. As shown below, in molecular structure example (1) of copolymer (P), structural units (A) of ethylene and / or an α-olefin having 3 to 20 carbon atoms, structural units (B) having a carboxyl group and / or a dicarboxylic anhydride group, and structural units (C) of any monomer form a random copolymer.

[0063] [ka]

[0064] For reference, an example of the molecular structure (2) of a copolymer into which a structural unit (B) having a carboxyl group and / or a dicarboxylic anhydride group has been introduced by graft modification is also shown. A part of a copolymer in which a structural unit (A) of ethylene and / or an α-olefin having 3 to 20 carbon atoms and a structural unit (C) of an arbitrary monomer are copolymerized is graft-modified with a structural unit (B) having a carboxyl group and / or a dicarboxylic anhydride group.

[0065] [ka]

[0066] Furthermore, the random copolymerization of a copolymer can be confirmed by various methods, and methods for determining the random copolymerization from the relationship between the comonomer content and melting point of the copolymer are described in detail in JP 2015-163691 A and JP 2016-079408 A. From the above documents, it can be determined that the randomness is low when the melting point (Tm, °C) of the copolymer is higher than -3.74 × [Z] + 130 (where [Z] is the comonomer content / mol%).

[0067] The random copolymer (P) preferably has a melting point (Tm, °C) measured by differential scanning calorimetry (DSC) and a total content [Z] (mol%) of the structural unit (B) having a carboxyl group and / or a dicarboxylic anhydride group and the structural unit (C) of an optional monomer, which satisfy the following formula (I): 50 <Tm<-3.74×[Z]+130···(I) If the melting point of the copolymer (Tm, °C) is higher than -3.74 × [Z] + 130 (°C), the random copolymerization is low, resulting in poor mechanical properties such as impact strength, and if the melting point is lower than 50°C, rigidity may be poor.

[0068] Furthermore, from the viewpoint of making the molecular structure of the copolymer (P) linear, it is preferable that the copolymer (P) is produced in the presence of a transition metal catalyst. It is known that the molecular structure of a copolymer varies depending on the production method, such as polymerization by a high-pressure radical polymerization process or polymerization using a metal catalyst. This difference in molecular structure can be controlled by selecting the production method, but the molecular structure can also be estimated from the complex modulus measured with a rotational rheometer, as described in JP 2010-150532 A, for example.

[0069] · Phase angle δ at absolute value of complex modulus G*=0.1MPa: In the copolymer (P) of the present invention, the phase angle δ at an absolute value of the complex modulus G*=0.1 MPa measured with a rotational rheometer may have a lower limit of 50 degrees or more, 51 degrees or more, 54 degrees or more, 56 degrees or more, or 58 degrees or more, and an upper limit of 75 degrees or less, or 70 degrees or less.

[0070] More specifically, when the phase angle δ (G*=0.1 MPa) at the absolute value of the complex modulus G*=0.1 MPa measured with a rotational rheometer is 50 degrees or greater, the molecular structure of the copolymer is linear and contains either no long chain branches or a small amount of long chain branches that does not affect the mechanical strength.

[0071] Furthermore, if the phase angle δ (G*=0.1 MPa) at the absolute value of the complex modulus G*=0.1 MPa measured with a rotational rheometer is lower than 50 degrees, the molecular structure of the copolymer will contain excessive long chain branches, resulting in poor mechanical strength.

[0072] The phase angle δ at the absolute value of the complex modulus G* = 0.1 MPa measured using a rotational rheometer is affected by both the molecular weight distribution and long-chain branching. However, for copolymers with Mw / Mn ≦ 4, more preferably Mw / Mn ≦ 3, it is an indicator of the amount of long-chain branching, and the more long-chain branching there is in the molecular structure, the smaller the δ(G* = 0.1 MPa) value. Furthermore, if the Mw / Mn of a copolymer is 1.5 or higher, the δ(G* = 0.1 MPa) value will not exceed 75 degrees, even if the molecular structure does not contain long-chain branching.

[0073] The complex elastic modulus is measured as follows. The sample was placed in a 1.0 mm thick heat press mold and preheated for 5 minutes in a heat press at a surface temperature of 180°C. Residual gas in the molten resin was then removed by repeatedly applying and depressurizing pressure to 4.9 MPa and holding for 5 minutes. The sample was then transferred to a press at a surface temperature of 25°C and cooled by holding at 4.9 MPa for 3 minutes to create a pressed plate made of the sample approximately 1.0 mm thick. The pressed plate made of the sample was cut into a 25 mm diameter circle and used as a sample. Dynamic viscoelasticity was measured using a Rheometrics ARES rotational rheometer in a nitrogen atmosphere under the following conditions. Plate: φ25mm parallel plate ·Temperature: 160℃ Distortion: 10% Measurement angular frequency range: 1.0 x 10 -2 ~1.0×10 2 rad / s Measurement interval: 5 points / decade Plot the phase angle δ against the common logarithm logG* of the absolute value of the complex elastic modulus G* (Pa), and take the value of δ (degrees) at the point corresponding to logG* = 5.0 as δ (G* = 0.1 MPa). If there is no point corresponding to logG* = 5.0 among the measurement points, use two points around logG* = 5.0 to determine the value of δ at logG* = 5.0 by linear interpolation. Also, if all measurement points have logG* < 5, use the values ​​of the three largest logG* values ​​to extrapolate the value of δ at logG* = 5.0 using a quadratic curve.

[0074] -Production of copolymer (P) The copolymer (P) according to the present invention is preferably produced in the presence of a transition metal catalyst, from the viewpoint of making its molecular structure linear.

[0075] Polymerization catalyst The type of polymerization catalyst used in producing the copolymer (P) is not particularly limited as long as it is capable of copolymerizing the structural unit (A), the structural unit (B), and the optional structural unit (C). For example, a transition metal compound of Groups 5 to 11 having a chelating ligand is preferred, and a transition metal complex of Groups 5 to 11 having a chelating ligand is more preferred.

[0076] Specific examples of preferred transition metals include vanadium atom, niobium atom, tantalum atom, chromium atom, molybdenum atom, tungsten atom, manganese atom, iron atom, platinum atom, ruthenium atom, cobalt atom, rhodium atom, nickel atom, palladium atom, and copper atom. Among these, transition metals of Groups 8 to 11 are preferred, transition metals of Group 10 are more preferred, and nickel (Ni) and palladium (Pd) are particularly preferred. These metals may be used alone or in combination.

[0077] Chelating ligands have at least two atoms selected from the group consisting of P, N, O, and S, and include bidentate or multidentate ligands, and are electronically neutral or anionic. Examples of chelating ligand structures are provided in a review by Brookhart et al. (Chem. Rev., 2000, 100, 1169).

[0078] The chelating ligand preferably includes a bidentate anionic P,O ligand. Examples of the bidentate anionic P,O ligand include phosphorus sulfonic acid, phosphorus carboxylic acid, phosphorus phenol, and phosphorus enolate. Other examples of the chelating ligand include a bidentate anionic N,O ligand. Examples of the bidentate anionic N,O ligand include salicylaldiminate and pyridinecarboxylic acid. Other examples of the chelating ligand include a diimine ligand, a diphenoxide ligand, and a diamide ligand.

[0079] The structure of the metal complex obtained from the chelating ligand is represented by the following structural formula (a) or (b), in which an arylphosphine compound, an arylarsine compound, or an arylantimony compound, which may have a substituent, is coordinated.

[0080] [ka]

[0081] [ka]

[0082] In structural formula (a) and structural formula (b), M represents a transition metal belonging to any of groups 5 to 11 of the periodic table of the elements, that is, the various transition metals described above. X 1 represents oxygen, sulfur, -SO3-, or -CO2-. Y 1 represents carbon or silicon. n represents an integer of 0 or 1. E 1 represents phosphorus, arsenic or antimony. R 53 and R 54 each independently represents hydrogen or a hydrocarbon group having 1 to 30 carbon atoms which may contain a heteroatom. R 55 each independently represents hydrogen, halogen, or a hydrocarbon group having 1 to 30 carbon atoms which may contain a heteroatom. R 56 and R 57 each independently represents hydrogen, halogen, a hydrocarbon group having 1 to 30 carbon atoms which may contain a heteroatom, OR 52 , CO2R 52 , CO2M', C(O)N(R 51 )2, C(O)R 52 , S.R. 52 , SO2R 52 , SOR 52 , OSO2R 52 , P(O)(OR 52 ) 2-y (R 51 )y, CN, NHR 52 , N(R 52 )2, Si(OR 51 ) 3-x (R 51 ) x , OSi(OR 51 ) 3-x (R 51 ) x , NO2, SO3M', PO3M'2, P(O)(OR 52 )2M' or an epoxy-containing group. R 51 represents hydrogen or a hydrocarbon group having 1 to 20 carbon atoms. R 52 represents a hydrocarbon group having 1 to 20 carbon atoms. M' represents an alkali metal, an alkaline earth metal, ammonium, a quaternary ammonium, or a phosphonium; x represents an integer of 0 to 3; and y represents an integer of 0 to 2. In addition, R 56 and R 57may be linked to each other to form an alicyclic ring, an aromatic ring, or a heterocyclic ring containing a heteroatom selected from oxygen, nitrogen, and sulfur, in which case the ring has 5 to 8 members and may or may not have a substituent on the ring. L 1 represents a ligand coordinated to M. Also, R 53 and L 1 may be bonded to each other to form a ring.

[0083] The transition metal complex having a chelating ligand is more preferably a transition metal complex represented by the following structural formula (c).

[0084] [ka]

[0085] [In structural formula (c), M represents a transition metal belonging to any of Groups 5 to 11 of the periodic table of the elements, that is, the various transition metals mentioned above. X 1 represents oxygen, sulfur, -SO3-, or -CO2-. Y 1 represents carbon or silicon. n represents an integer of 0 or 1. E 1 represents phosphorus, arsenic or antimony. R 53 and R 54 each independently represents hydrogen or a hydrocarbon group having 1 to 30 carbon atoms which may contain a heteroatom. R 55 each independently represents hydrogen, halogen, or a hydrocarbon group having 1 to 30 carbon atoms which may contain a heteroatom. R 58 , R 59 , R 60 and R 61 each independently represents hydrogen, halogen, a hydrocarbon group having 1 to 30 carbon atoms which may contain a heteroatom, OR 52 , CO2R 52, CO2M', C(O)N(R 51 )2, C(O)R 52 , S.R. 52 , SO2R 52 , SOR 52 , OSO2R 52 , P(O)(OR 52 ) 2-y (R 51 ) y , CN, NHR 52 , N(R 52 )2, Si(OR 51 ) 3-x (R 51 ) x , OSi(OR 51 ) 3-x (R 51 ) x , NO2, SO3M', PO3M'2, P(O)(OR 52 )2M' or an epoxy-containing group. R 51 represents hydrogen or a hydrocarbon group having 1 to 20 carbon atoms. R 52 represents a hydrocarbon group having 1 to 20 carbon atoms. M' represents an alkali metal, an alkaline earth metal, ammonium, a quaternary ammonium, or a phosphonium; x represents an integer of 0 to 3; and y represents an integer of 0 to 2. In addition, R 58 ~R 61 A plurality of groups appropriately selected from the group consisting of may be linked together to form an alicyclic ring, an aromatic ring, or a heterocyclic ring containing a heteroatom selected from oxygen, nitrogen, or sulfur, in which case the ring has 5 to 8 members and may or may not have a substituent on the ring. L 1 represents a ligand coordinated to M. Also, R 53 and L 1 may be bonded to each other to form a ring.

[0086] Here, typical catalysts of transition metal compounds of Groups 5 to 11 having a chelating ligand include so-called SHOP-based catalysts and Drent-based catalysts. The SHOP catalyst is a catalyst in which a phosphorus-based ligand having an aryl group which may have a substituent is coordinated to nickel metal (see, for example, WO2010-050256). Furthermore, Drent-based catalysts are catalysts in which a phosphorus-based ligand having an aryl group which may have a substituent is coordinated to palladium metal (see, for example, JP-A-2010-202647).

[0087] Polymerization method for copolymer (P): The polymerization method for the copolymer (P) is not limited. Examples of the polymerization method include slurry polymerization in which at least a portion of the produced polymer becomes a slurry in a medium, bulk polymerization in which liquefied monomer itself is used as a medium, gas phase polymerization carried out in vaporized monomer, and high pressure ionic polymerization in which at least a portion of the produced polymer is dissolved in monomer liquefied at high temperature and pressure. The polymerization method may be any of batch polymerization, semi-batch polymerization, and continuous polymerization. Alternatively, living polymerization may be performed, or polymerization may be performed while chain transfer occurs. Furthermore, during polymerization, a so-called chain shuttling agent (CSA) may be used in combination to perform a chain shuttling reaction or coordinated chain transfer polymerization (CCTP). Specific production processes and conditions are disclosed, for example, in JP-A Nos. 2010-260913 and 2010-202647.

[0088] Method for introducing carboxyl groups and / or dicarboxylic anhydride groups into copolymers: There are no particular limitations on the method for introducing carboxyl groups and / or dicarboxylic anhydride groups into the copolymer of the present invention. Carboxyl groups and / or dicarboxylic anhydride groups can be introduced by various methods within the scope of the present invention. Examples of methods for introducing a carboxyl group and / or a dicarboxylic anhydride group include a method of directly copolymerizing a comonomer having a carboxyl group and / or a dicarboxylic anhydride group, and a method of copolymerizing another monomer and then introducing a carboxyl group and / or a dicarboxylic anhydride group by modification.

[0089] Examples of methods for introducing a carboxyl group and / or a dicarboxylic anhydride group by modification include, for example, when introducing a carboxylic acid, a method in which an acrylic acid ester is copolymerized and then hydrolyzed to convert it into a carboxylic acid, and a method in which t-butyl acrylate is copolymerized and then thermally decomposed to convert it into a carboxylic acid.

[0090] A conventionally known acid-base catalyst may be used as an additive to promote the hydrolysis or thermal decomposition reaction. The acid-base catalyst is not particularly limited, and examples thereof include alkali metal or alkaline earth metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; alkali metal or alkaline earth metal carbonates such as sodium bicarbonate and sodium carbonate; solid acids such as montmorillonite; inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid; and organic acids such as formic acid, acetic acid, benzoic acid, citric acid, paratoluenesulfonic acid, trifluoroacetic acid, and trifluoromethanesulfonic acid. Sodium hydroxide, potassium hydroxide, and charcoal are used in terms of reaction acceleration effect, price, and corrosion resistance of equipment. Among these, sodium paratoluenesulfonic acid, paratoluenesulfonic acid, and trifluoroacetic acid are preferred, and paratoluenesulfonic acid and trifluoroacetic acid are more preferred.

[0091] (6) Ionomer resin The ionomer resin used in the present invention is not particularly limited as long as at least a portion of the carboxyl groups and / or dicarboxylic anhydride groups of the structural unit (B) of the copolymer (P) is neutralized with at least one metal ion selected from Groups 1, 2, and 12 of the periodic table.

[0092] ·Ionomer resin structure The ionomer resin used in the present invention has a substantially linear structure, and therefore preferably has a phase angle δ in the range of 50 to 75 degrees when the absolute value of the complex modulus G* is 0.1 MPa as measured with a rotational rheometer. If the phase angle δ (G*=0.1 MPa) is lower than 50 degrees, the molecular structure of the ionomer contains excessive long-chain branches, resulting in poor mechanical strength. Furthermore, even if the molecular structure does not contain long-chain branches, the δ (G*=0.1 MPa) value will not exceed 75 degrees.

[0093] In order to improve the mechanical strength of the ionomer resin used in the present invention, the lower limit of the phase angle δ is preferably 51 degrees or more, more preferably 54 degrees or more, even more preferably 56 degrees or more, and still more preferably 58 degrees or more. The upper limit is not particularly limited, and the closer to 75 degrees the better.

[0094] The complex elastic modulus is measured as follows. The sample was placed in a 1.0 mm thick heat press mold and preheated for 5 minutes in a heat press at a surface temperature of 180°C. Residual gas in the molten resin was removed by repeatedly applying and depressurizing pressure. The sample was then pressurized to 4.9 MPa and held for 5 minutes. The sample was then transferred to a press at a surface temperature of 25°C and cooled by holding the press at 4.9 MPa for 3 minutes to produce a pressed plate made of the sample with a thickness of approximately 1.0 mm. The pressed plate made of the sample was cut into a 25 mm diameter circle to serve as the sample. The dynamic viscoelasticity was measured using a Rheometrics ARES rotational rheometer under a nitrogen atmosphere under the following conditions: Plate: φ25mm parallel plate ·Temperature: 160℃ Distortion: 10% Measurement angular frequency range: 1.0 x 10 -2 ~1.0×10 2 rad / s Measurement interval: 5 points / decade Plot the phase angle δ against the common logarithm logG* of the absolute value of the complex elastic modulus G* (Pa), and take the value of δ (degrees) at the point corresponding to logG* = 5.0 as δ (G* = 0.1 MPa). If there is no point corresponding to logG* = 5.0 among the measurement points, use two points around logG* = 5.0 to determine the value of δ at logG* = 5.0 by linear interpolation. Also, if all measurement points have logG* < 5, use the values ​​of the three largest logG* values ​​to extrapolate the value of δ at logG* = 5.0 using a quadratic curve.

[0095] Metal ions The metal ions contained in the ionomer resin used in the present invention are not particularly limited, and may include metal ions used in conventionally known ionomers. Among these, metal ions are preferably ions of metals in Groups 1, 2, or 12 of the periodic table, and Li + , Na + , K. + , Rb + , Cs + , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Zn 2+ At least one selected from the group consisting of is more preferred. Particularly preferred is Li + , Na + , K. + , Mg 2+ , Ca 2+ , and Zn 2+ , more preferably Na + , and Zn 2+ Among these, the ionomer resin used in the present invention preferably contains two or more of these metal ions, as this provides an excellent balance between strength, durability, resilience performance, and processability. When two types of metal ions are used in combination, they are preferably used in a weight ratio of 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30.

[0096] ·Neutralization degree (mol%) The metal ion content is preferably an amount that neutralizes at least a part or all of the carboxyl groups and / or dicarboxylic anhydride groups in the copolymer as the base polymer, and the preferred degree of neutralization (average degree of neutralization) is 5 to 95 mol%, more preferably 10 to 90 mol%, and even more preferably 10 to 80 mol%. The degree of neutralization can be determined from the ratio of the total molar amount of the valence × molar amount of metal ions to the total molar amount of carboxy groups that may be contained in the carboxy groups and / or dicarboxylic anhydride groups in the copolymer. When forming a carboxylate, the dicarboxylic anhydride group opens its ring to form a dicarboxylic acid, so the total molar amount of the carboxyl groups is calculated assuming that there are 2 mol of carboxyl groups per mol of dicarboxylic anhydride group. 2+ For divalent metal ions such as those mentioned above, 1 mole can form a salt with 2 moles of carboxyl groups, and the total molar amount of molecules with a degree of neutralization is calculated by 2 x the molar amount. A high degree of neutralization results in an ionomer with high tensile strength and tensile stress at break and low tensile strain at break, but tends to result in a low melt flow rate (MFR).On the other hand, a low degree of neutralization results in an ionomer with a moderate MFR, but tends to result in a low tensile modulus and tensile stress at break and high tensile strain at break.

[0097] -Ionomer resin manufacturing method The ionomer resin is obtained by neutralizing a copolymer of ethylene and / or an α-olefin having 3 to 20 carbon atoms / unsaturated carboxylic acid, obtained by the above-mentioned method for introducing carboxyl groups and / or dicarboxylic anhydride groups into the copolymer, with at least one metal ion selected from Group 1, Group 2, or Group 12 of the periodic table. Alternatively, the ionomer resin may be obtained by a thermal conversion step in which an ethylene and / or an α-olefin having 3 to 20 carbon atoms / unsaturated carboxylic acid ester copolymer is heated to convert at least a portion of the ester groups in the copolymer into a metal-containing carboxylate containing at least one metal ion selected from Group 1, Group 2, or Group 12 of the periodic table.

[0098] The temperature at which the ethylene and / or C3-20 α-olefin / unsaturated carboxylic acid ester copolymer is heated may be any temperature at which the ester is converted to a carboxylic acid, and if the heating temperature is too low, the ester is not converted to a carboxylic acid, whereas if the heating temperature is too high, decarbonylation and decomposition of the copolymer proceed. Therefore, the heating temperature in the present invention is preferably 80°C to 350°C, more preferably The temperature is preferably in the range of 100°C to 340°C, more preferably 150°C to 330°C, and even more preferably 200°C to 320°C.

[0099] The reaction time varies depending on the heating temperature, the reactivity of the ester group moiety, etc., but is usually 1 minute to 50 hours, more preferably 2 minutes to 30 hours, even more preferably 2 minutes to 10 hours, still more preferably 2 minutes to 3 hours, and particularly preferably 3 minutes to 2 hours.

[0100] In the above steps, the reaction atmosphere is not particularly limited, but it is generally preferable to carry out the reaction under a stream of inert gas. Examples of inert gases that can be used include nitrogen, argon, and carbon dioxide. A small amount of oxygen or air may be present.

[0101] The reactor used in the above step is not particularly limited as long as it can stir the copolymer substantially uniformly. A glass vessel or autoclave (AC) equipped with a stirrer may be used, or any conventionally known kneader may be used, such as a Brabender Plastograph, a single-screw or twin-screw extruder, a high-intensity screw kneader, a Banbury mixer, a kneader, or a roll.

[0102] The metal ion source for neutralization may be an oxide, hydroxide, carbonate, bicarbonate, acetate, formate, or the like, of a metal of Group 1, 2, or 12 of the periodic table. The metal ion source may be supplied to the reaction system in granular or fine powder form, or may be supplied to the reaction system after being dissolved or dispersed in water or an organic solvent. Alternatively, a masterbatch may be prepared using an ethylene / unsaturated carboxylic acid copolymer or an olefin copolymer as a base polymer and supplied to the reaction system. To ensure smooth reaction, it is preferable to prepare a masterbatch and supply it to the reaction system.

[0103] The reaction with the metal ion source may be carried out by melt-kneading using various types of equipment such as a vent extruder, a Banbury mixer, or a roll mill, and the reaction may be carried out batchwise or continuously. Since the reaction can be carried out smoothly by discharging the water and carbon dioxide gas by-products produced by the reaction using a degasser, it is preferable to carry out the reaction continuously using an extruder equipped with a degasser such as a vent extruder. In the reaction with the metal ion-containing compound, a small amount of water may be injected to promote the reaction.

[0104] Whether or not metal ions have been introduced into the base resin copolymer (P) to form an ionomer can be confirmed by measuring the IR spectrum of the resulting resin and examining the decrease in the peak due to the carbonyl group of the carboxylic acid (dimer). Similarly, the degree of neutralization can be confirmed by calculating from the molar ratio mentioned above, as well as examining the decrease in the peak due to the carbonyl group of the carboxylic acid (dimer) and the increase in the peak due to the carbonyl group of the carboxylate salt group.

[0105] Additives The ionomer resin used in the present invention may be blended with conventionally known additives such as antioxidants, ultraviolet absorbers, lubricants, antistatic agents, colorants, pigments, crosslinking agents, foaming agents, nucleating agents, flame retardants, conductive materials, and fillers, as long as such additives do not deviate from the spirit of the present invention.

[0106] The flexural rigidity (M) of the ionomer resin used in the present invention is preferably 10 MPa or more, more preferably 20 MPa or more, and even more preferably 50 MPa or more, and is preferably 3000 MPa or less, more preferably 2000 MPa or less, and even more preferably 1000 MPa or less. If the flexural rigidity (M) of the ionomer resin is 10 MPa or more, the resilience will be higher, and if it is 3000 MPa or less, the shot feel of the golf ball will be good. Here, the flexural rigidity of the ionomer resin is measured by molding the ionomer resin into a sheet and using the measurement method described below.

[0107] The ionomer resin preferably has a slab hardness of 10 or more, more preferably 20 or more, and even more preferably 30 or more, in Shore D hardness, and preferably 95 or less, more preferably 90 or less, and even more preferably 85 or less. This is because, if the slab hardness of the ionomer resin is within the above range, a golf ball with high resilience performance and a good shot feel can be provided. Here, the Shore D hardness of the ionomer resin is measured by molding the ionomer resin into a sheet and using the measuring method described below.

[0108] The melt flow rate of the ionomer resin (190°C, 2.16 kg load) is preferably 0.01 g / 10 min or more, more preferably 0.05 g / 10 min or more, even more preferably 0.1 g / 10 min or more, and is preferably 500 g / 10 min or less, more preferably 200 g / 10 min or less, even more preferably 100 g / 10 min or less. When the melt flow rate of the ionomer resin (190°C, 2.16 kg load) is 0.01 g / 10 min or more, the fluidity of the cover composition is improved, which allows, for example, the resulting component to be made thinner.

[0109] The cover composition forming the cover of the golf ball of the present invention preferably contains, as ionomer resins, a first ionomer resin that has a phase angle δ of 50 to 75 degrees at an absolute value of complex modulus G* of 0.1 MPa as measured with a rotational rheometer and is neutralized with first metal ions, and a second ionomer resin that has a phase angle δ of 50 to 75 degrees at an absolute value of complex modulus G* of 0.1 MPa as measured with a rotational rheometer and is neutralized with second metal ions different from the first metal ions.

[0110] The first metal ion and the second metal ion are preferably, for example, metal ions of Group 1, 2, or 12 of the periodic table, and Li + , Na + , K. + , Rb + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Ra 2+ and Zn 2+ It is more preferable that the compound is at least one selected from the group consisting of Li + , Na + , K. + , Ca 2+ , and Zn 2+ It is more preferable that the compound is at least one selected from the group consisting of Na + , and Zn 2+ It is particularly preferable that one of the first metal ion and the second metal ion is at least one selected from the group consisting of Na + and the other is Zn 2+ It is preferable that:

[0111] The content of the structural unit (B) in the first ionomer resin and the second ionomer resin is preferably 2.0 mol% or more, more preferably 2.9 mol% or more, even more preferably 3.5 mol% or more, and even more preferably 6.0 mol% or more, and is preferably 20.0 mol% or less, more preferably 18.0 mol% or less, even more preferably 15.0 mol% or less, and even more preferably 10.0 mol% or less.

[0112] The degree of neutralization of the first ionomer resin and the second ionomer resin with metal ions is preferably 5 mol% or more, more preferably 10 mol% or more, and is preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 80 mol% or less.

[0113] The melt flow rate (190° C., 2.16 kg load) of each of the first ionomer resin and the second ionomer resin is preferably 100 g / 10 min or less.

[0114] The combination of the first ionomer resin and the second ionomer resin contained in the cover composition may, for example, be a combination of a first ionomer resin having a degree of neutralization of 50 mol% or less and a second ionomer resin having a degree of neutralization of 50 mol% or less (more preferably a combination of a first ionomer resin having a degree of neutralization of less than 50 mol% and a second ionomer resin having a degree of neutralization of less than 50 mol%); or a combination of a first ionomer resin having a degree of neutralization of 50 mol% or more and a second ionomer resin having a degree of neutralization of more than 50 mol%. Examples of such an embodiment include an embodiment containing a first ionomer resin having a degree of neutralization of more than 50 mol% and a second ionomer resin having a degree of neutralization of more than 50 mol% (more preferably, an embodiment containing a first ionomer resin having a degree of neutralization of 50 mol% or less and a second ionomer resin having a degree of neutralization of more than 50 mol% (more preferably, an embodiment containing a first ionomer resin having a degree of neutralization of less than 50 mol% and a second ionomer resin having a degree of neutralization of more than 50 mol%).

[0115] The blending ratio (mass ratio) of the first ionomer resin to the second ionomer resin is preferably 10 / 90 or more and 90 / 10 or less.

[0116] The cover composition forming the cover of the golf ball of the present invention may contain other resins as resin components in addition to the ionomer resin.

[0117] Specific examples of other resins include ionomer resins commercially available under the trade name "Himilan®" from Dow Mitsui Polychemicals Co., Ltd., thermoplastic polyurethane elastomers commercially available under the trade name "Elastollan®" from BASF Japan Ltd., thermoplastic polyamide elastomers commercially available under the trade name "Pebax®" from Arkema K.K., thermoplastic polyester elastomers commercially available under the trade name "Hytrel®" from Toray Celanese Co., Ltd., and thermoplastic styrene elastomers or thermoplastic polyester-based elastomers commercially available under the trade name "Tefabloc®" from Mitsubishi Chemical Corporation. The above cover materials may be used alone or in combination of two or more types.

[0118] The cover composition of the present invention contains the ionomer resin as a resin component. The content of the ionomer resin component in the resin component is preferably 50% by mass or more, more preferably 75% by mass or more, and even more preferably 90% by mass or more. It is also preferable that the resin component contain only the ionomer resin.

[0119] The cover composition may further contain a flowability modifier. The inclusion of a flowability modifier facilitates molding into golf ball components. Examples of the flowability modifier include fatty acids and / or metal salts thereof.

[0120] The fatty acid is not particularly limited, and examples thereof include saturated fatty acids such as butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, pelargonic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, heptadecanoic acid, stearic acid, icosanoic acid, behenic acid, lignoceric acid, and cerotic acid; and unsaturated fatty acids such as palmitoleic acid, oleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, and arachidonic acid.

[0121] The fatty acid metal salt is not particularly limited, and examples thereof include monovalent metal salts such as fatty acid sodium salts, fatty acid potassium salts, and fatty acid lithium salts; divalent metal salts such as fatty acid magnesium salts, fatty acid calcium salts, fatty acid zinc salts, fatty acid barium salts, and fatty acid cadmium salts; and trivalent metal salts such as fatty acid aluminum salts. Among these, preferred fatty acid metal salts are divalent metal salts of saturated fatty acids such as magnesium stearate, calcium stearate, zinc stearate, barium stearate, and copper stearate.

[0122] The amount of the flowability modifier added is preferably 0.5 parts by weight or more, more preferably 1.5 parts by weight or more, and preferably 30 parts by weight or less, more preferably 25 parts by weight or less, per 100 parts by weight of the resin component of the cover composition. When the amount of flowability modifier added is within the above range, the flowability of the golf ball resin composition is improved, thereby enabling the molding of thin components.

[0123] The cover composition may further contain pigment components such as white pigments (e.g., titanium oxide), blue pigments, and red pigments, weight adjusters such as calcium carbonate and barium sulfate, dispersants, antioxidants, ultraviolet absorbers, light stabilizers, fluorescent materials, or fluorescent brighteners, within limits that do not impair the performance of the cover.

[0124] The content of the white pigment (e.g., titanium oxide) is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less, per 100 parts by mass of the ionomer resin component contained in the cover composition. By making the content of the white pigment 0.5 parts by mass or more, it is possible to impart hiding power to the cover. Furthermore, by making the content of the white pigment 10 parts by mass or less, it is possible to improve the shot feel.

[0125] The golf ball of the present invention has a cover composition containing the ionomer resin, and the loss modulus E'' at 0°C, measured under the following conditions, is 3.40 x 10 7 The loss modulus E'' at 0°C is 3.00 x 10 7 Pa or less, and 7 Pa or less is more preferable, and 2.60 × 10 7 It is more preferable that the loss modulus E'' at 0°C is 3.40 x 10 Pa or less. 7 If the loss modulus E'' at 0°C is not more than 1.00 x 10 Pa, the durability of the golf ball can be significantly improved without substantially reducing the resilience of the golf ball. 6 Pa or more, and 1.20 × 10 6 Pa or more is more preferable, and 1.40 × 10 6 It is more preferable that the viscosity is 100 Pa or more. <Measurement conditions> Measurement mode: Sine wave tension Measurement temperature range: -100℃~100℃ Heating rate: 4°C / min Excitation frequency: 10Hz Measurement distortion: 0.05%

[0126] The golf ball of the present invention is characterized in that the slab hardness (D) and bending rigidity (M) of the cover composition containing the ionomer resin are such that M / D 2 It is preferable that the M / D satisfies ≧0.070. 2is preferably 0.070 or more, more preferably 0.071 or more, and is preferably 0.200 or less, more preferably 0.150 or less. 2 Within the above range, the durability and feel of the golf ball will be improved without reducing the resilience.

[0127] The flexural rigidity (M) of the cover composition is preferably 50 MPa or more, more preferably 60 MPa or more, and even more preferably 70 MPa or more, and is preferably 1000 MPa or less, more preferably 900 MPa or less, and even more preferably 800 MPa or less. A flexural rigidity (M) of 50 MPa or more of the cover composition improves the resilience, while a flexural rigidity of 1000 MPa or less improves the durability and shot feel of the golf ball. The flexural rigidity (M) of the cover composition is measured by molding the cover composition into a sheet and using the measurement method described below. The flexural rigidity (M) of the cover composition can be adjusted, for example, by controlling the content of the structural units (A) and (B) of the ionomer resin, the type of metal ion, the degree of neutralization, etc. It can also be adjusted by changing the amount of filler added to the cover composition.

[0128] The slab hardness (D) of the cover composition is preferably 30 or more, more preferably 35 or more, even more preferably 40 or more, and preferably 90 or less, more preferably 85 or less, and even more preferably 80 or less, in Shore D hardness. A slab hardness of 30 or more in Shore D hardness results in higher resilience, while a slab hardness of 90 or less results in better durability and shot feel. The slab hardness of the cover composition is measured by molding the cover composition into a sheet and using the measurement method described below. The slab hardness of the cover composition can be adjusted, for example, by controlling the content of the structural units (A) and (B) of the ionomer resin, the type of metal ion, the degree of neutralization, etc. It can also be adjusted by changing the amount of anisotropic filler added to the cover composition.

[0129] The cover composition can be obtained by, for example, dry blending the ionomer resin with optional additives, or by melt-mixing the ionomer resin with the additives. Melt-mixing can be performed using a kneader or an extruder (such as a single-screw extruder, twin-screw extruder, or twin-single-screw extruder).

[0130] [Golf balls] The golf ball of the present invention has a core and at least one cover layer positioned outside the core, and the at least one cover layer is formed from a cover composition containing the ionomer resin. The structure of the golf ball is not particularly limited, and examples thereof include a two-piece golf ball having a single-layer core and a cover enclosing the core, and a multi-piece golf ball (such as a three-piece golf ball, four-piece golf ball, or five-piece golf ball) having a core and two or more covers enclosing the core. In the case of a multi-layer cover, the layers of the cover other than the outermost cover layer may be referred to as an intermediate layer, an inner cover layer, or an outer core.

[0131] Examples of the golf ball of the present invention include a two-piece golf ball having a single-layer core and a cover enclosing the single-layer core, wherein the cover is formed from a cover composition containing the ionomer resin; a multi-piece golf ball having a core and a two- or more-layer cover enclosing the core, wherein the outermost cover layer is formed from a cover composition containing the ionomer resin; a golf ball having a single-layer core, at least one inner cover layer enclosing the core, and an outermost cover layer enclosing the inner cover layer, wherein at least one of the inner cover layers is formed from a cover composition containing the ionomer resin; and a golf ball having a single-layer core, at least one inner cover layer enclosing the core, and an outermost cover layer enclosing the inner cover layer, wherein at least one of the inner cover layers and the outermost cover layer are formed from a cover composition containing the ionomer resin. In an embodiment in which at least one inner cover layer is formed from a cover composition containing the ionomer resin, it is preferable that the inner cover layer adjacent to the outermost cover layer be formed from a cover composition containing the ionomer resin.

[0132] A known rubber composition (hereinafter, sometimes simply referred to as a "core rubber composition") can be used for the core. For example, a rubber composition containing a base rubber, a co-crosslinking agent, and a crosslinking initiator can be molded by hot pressing.

[0133] The base rubber preferably uses high-cis polybutadiene with cis bonds of 40% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more, which is advantageous for rebound. The co-crosslinking agent is preferably an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms or a metal salt thereof, more preferably a metal salt of acrylic acid or a metal salt of methacrylic acid. The metal salt is preferably zinc, magnesium, calcium, aluminum, or sodium, more preferably zinc. The amount of co-crosslinking agent used is preferably 20 to 50 parts by weight per 100 parts by weight of the base rubber. Organic peroxides are preferably used as crosslinking initiators. Specific examples include organic peroxides such as dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and di-t-butyl peroxide. Of these, dicumyl peroxide is preferably used. The amount of crosslinking initiator added is preferably at least 0.2 parts by weight, more preferably at least 0.3 parts by weight, and is preferably at most 3 parts by weight, more preferably at most 2 parts by weight, per 100 parts by weight of the base rubber.

[0134] The core rubber composition may further contain an organic sulfur compound. Examples of the organic sulfur compound include compounds belonging to diphenyl disulfides, thiophenols, or thionaphthols. The amount of the organic sulfur compound is preferably at least 0.1 part by mass, more preferably at least 0.3 part by mass, and preferably at most 5.0 parts by mass, more preferably at most 3.0 parts by mass, per 100 parts by mass of the base rubber. The core rubber composition may further contain a carboxylic acid and / or a salt thereof. The carboxylic acid and / or a salt thereof is preferably a carboxylic acid having 1 to 30 carbon atoms and / or a salt thereof. The amount of the carboxylic acid and / or a salt thereof is 1 part by mass or more and 40 parts by mass or less, per 100 parts by mass of the base rubber.

[0135] In addition to the base rubber, co-crosslinking agent, crosslinking initiator, and organic sulfur compound, the core rubber composition may further contain, as appropriate, weight modifiers such as zinc oxide and barium sulfate, antioxidants, color powder, etc. The hot press molding conditions for the core rubber composition may be appropriately set depending on the rubber composition, but typically heating is performed at 130°C to 200°C for 10 to 60 minutes, or in two stages: heating at 130°C to 150°C for 20 to 40 minutes, followed by heating at 160°C to 180°C for 5 to 15 minutes. The shape of the core is not particularly limited, but a spherical shape is preferred.

[0136] The manner in which the cover composition is used to form the cover is not particularly limited, but examples include a manner in which the cover composition is directly injection-molded onto the core, or a manner in which a hollow shell is molded from the cover composition, the core is coated with multiple shells, and then compression-molded (preferably, a method in which a hollow half shell is molded from the cover composition, the core is coated with two half shells, and then compression-molded). The golf ball body with the molded cover is preferably removed from the mold and, as necessary, subjected to surface treatment such as deburring, cleaning, and sandblasting. Marks can also be formed, if desired.

[0137] The thickness of the cover is preferably 4.0 mm or less, more preferably 3.0 mm or less, and even more preferably 2.0 mm or less. If the cover thickness is 4.0 mm or less, the resilience and shot feel of the resulting golf ball will be better. The thickness of the cover is preferably 0.3 mm or more, more preferably 0.5 mm or more, even more preferably 0.8 mm or more, and particularly preferably 1.0 mm or more. If the cover thickness is less than 0.3 mm, the abrasion resistance of the cover may decrease.

[0138] The total number of dimples formed on the cover is preferably 200 to 500. If the total number of dimples is less than 200, the effect of the dimples is difficult to obtain. If the total number of dimples is more than 500, the size of each dimple becomes small, making it difficult to obtain the effect of the dimples. The shape (shape in plan view) of the dimples formed is not particularly limited, and the following may be used alone or in combination: circle; polygon such as approximately triangle, approximately square, approximately pentagon, approximately hexagon; or other irregular shape.

[0139] The golf ball with the molded cover is preferably removed from the mold and, if necessary, subjected to surface treatments such as deburring, cleaning, and sandblasting. A coating film or markings can also be formed as desired. The thickness of the coating film is not particularly limited, but is preferably 5 μm or more, more preferably 7 μm or more, and preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less. If the coating film thickness is less than 5 μm, the coating film is likely to wear away with continued use, while if the coating film thickness exceeds 50 μm, the effect of the dimples is reduced, resulting in a decrease in the flight performance of the golf ball.

[0140] The diameter of the golf ball of the present invention is preferably 40 mm to 45 mm. From the viewpoint of meeting the standards of the United States Golf Association (USGA), a diameter of 42.67 mm or more is particularly preferred. From the viewpoint of reducing air resistance, a diameter of 44 mm or less is more preferred, and 42.80 mm or less is particularly preferred. The mass of the golf ball is preferably 40 g or more and 50 g or less. From the viewpoint of obtaining high inertia, a mass of 44 g or more is more preferred, and 45.00 g or more is particularly preferred. From the viewpoint of meeting the standards of the USGA, a mass of 45.93 g or less is particularly preferred.

[0141] When the golf ball of the present invention has a diameter of 40 mm to 45 mm, the compressive deformation (the amount the golf ball shrinks in the compression direction) when an initial load of 98 N is applied and a final load of 1275 N is applied is preferably 2.0 mm or more, more preferably 2.4 mm or more, even more preferably 2.5 mm or more, and preferably 5.0 mm or less, more preferably 4.5 mm or less, and even more preferably 4.0 mm or less. A golf ball with a compressive deformation of 2.0 mm or more is not too hard and has a good feel at impact. On the other hand, by setting the compressive deformation to 5.0 mm or less, the resilience is improved.

[0142] FIG. 1 is a partially cutaway cross-sectional view showing a golf ball 1 according to one embodiment of the present invention. Golf ball 1 has a spherical core 2 and a cover 3 disposed on the outside of this spherical core 2. A large number of dimples 31 are formed on the surface of cover 3. The portions of the surface of cover 3 other than dimples 31 are lands 32. Cover 3 is formed from a cover composition containing the ionomer resin. [Example]

[0143] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples, and all modifications and embodiments that do not deviate from the spirit of the present invention are included within the scope of the present invention.

[0144] [Evaluation method] (1) Measurement of the phase angle δ (G*=0.1MPa) at the absolute value of the complex elastic modulus G*=0.1MPa 1) Sample preparation and measurement The sample was placed in a 1.0 mm thick heat press mold and preheated for 5 minutes in a heat press at a surface temperature of 180°C. Residual gas in the molten resin was removed by repeatedly applying and depressurizing pressure to 4.9 MPa and holding for 5 minutes. The sample was then transferred to a press at a surface temperature of 25°C and cooled by holding at 4.9 MPa for 3 minutes to produce a pressed plate made of the sample with a thickness of approximately 1.0 mm. The pressed plate made of the sample was cut into a 25 mm diameter circle and used as a sample. Dynamic viscoelasticity was measured using a Rheometrics ARES rotational rheometer under a nitrogen atmosphere under the following conditions: Plate: φ25mm (diameter) parallel plate ·Temperature: 160℃ Distortion: 10% Measurement angular frequency range: 1.0 x 10 -2 ~1.0×10 2 rad / s Measurement interval: 5 points / decade The phase angle δ was plotted against the common logarithm logG* of the absolute value of the complex elastic modulus G* (Pa), and the value of δ (degrees) at the point corresponding to logG* = 5.0 was taken as δ (G* = 0.1 MPa). If there was no point corresponding to logG* = 5.0 among the measurement points, the value of δ at logG* = 5.0 was determined by linear interpolation using two points around logG* = 5.0. Furthermore, if all measurement points had logG* < 5, the value of δ at logG* = 5.0 was extrapolated using a quadratic curve using the values ​​of the three points with the largest logG* values.

[0145] (2) Measurement of weight average molecular weight (Mw) and molecular weight distribution parameter (Mw / Mn) The weight average molecular weight (Mw) was determined by gel permeation chromatography (GPC). The molecular weight distribution parameter (Mw / Mn) was determined by further determining the number average molecular weight (Mn) by gel permeation chromatography (GPC) and calculating the ratio of Mw to Mn. , calculated by Mw / Mn. The measurements were carried out according to the following procedures and conditions.

[0146] 1) Sample pretreatment If the sample contained a carboxylic acid group, it was subjected to esterification treatment, such as methyl esterification using diazomethane or trimethylsilyl (TMS) diazomethane, before use in the measurement. If the sample contained a carboxylic acid base, it was treated with an acid to modify the carboxylic acid base to a carboxylic acid group, and then subjected to the above-mentioned esterification treatment before use in the measurement.

[0147] 2) Preparation of sample solution 3 mg of sample and 3 mL of o-dichlorobenzene were weighed into a 4 mL vial, and the vial was capped with a screw cap and a Teflon (registered trademark) septum, and then shaken for 2 hours at 150°C using a Senshu Scientific SSC-7300 high-temperature shaker. After shaking, it was visually confirmed that there were no insoluble components.

[0148] 3) Measurement A Waters Alliance GPCV2000 was connected to one Showdex HT-G and two Showdex HT-806M high-temperature GPC columns, and measurements were performed using o-dichlorobenzene as the eluent at a temperature of 145°C and a flow rate of 1.0 mL / min.

[0149] 4) Calibration curve The column was calibrated using Showa Denko monodisperse polystyrene (S-7300, S-3900, S-1950, S-1460, S-1010, S-565, S-152, S-66.0, S-28.5, S-5.05, each 0.07 mg / ml solution), n-eicosane, and n-tetracontane under the same conditions as above, and the elution time and the logarithm of the molecular weight were approximated by a quartic equation. The polystyrene molecular weight (MPS) and polyethylene molecular weight (MPE) were converted using the following equation: MPE=0.468×MPS

[0150] (3) Melt flow rate (MFR) MFR was measured in accordance with Table 1-Condition 7 of JIS K-7210 (2018) at a temperature of 190°C and a load of 21.18N (=2.16kgf).

[0151] (4) Melting point and crystallinity The melting point is indicated by the peak temperature of the endothermic curve measured by a differential scanning calorimeter (DSC). Measurements were performed using a DSC (DSC7020) manufactured by SII Nano Technology, Inc. under the following measurement conditions: Approximately 5.0 mg of sample was placed in an aluminum pan, heated to 200°C at 10°C / min, held at 200°C for 5 minutes, and then cooled to 30°C at 10°C / min. After holding at 30°C for 5 minutes, the sample was again heated at 10°C / min. The maximum peak temperature of the absorption curve obtained during this period was taken as the melting point Tm, and the heat of fusion (ΔH) was calculated from the area of ​​the melting endothermic peak. The degree of crystallinity (%) was calculated by dividing this heat of fusion by the heat of fusion of 293 J / g for perfectly crystalline high-density polyethylene (HDPE).

[0152] (5) Bending rigidity (MPa) Test pieces approximately 2 mm thick, 20 mm wide, and 100 mm long were prepared by injection molding using ionomer resin or cover composition. These test pieces were stored for 14 days at a temperature of 23±2°C and a relative humidity of 50±5%. The load scales of the prepared test pieces were measured at bending angles of 3°, 6°, 9°, and 12° using an Olsen-type rigidity tester (manufactured by Toyo Seiki Seisakusho, Ltd.). The horizontal axis represented the bending angle (°) and the vertical axis represented the load scale readings, and the slope of the linear approximation curve was calculated. The measurement conditions were a temperature of 23±2°C, a relative humidity of 50±5%, a bending speed of 60° / min, and a support distance of 50 mm. The bending rigidity was calculated by multiplying the slope value by 8.7078 and dividing the result by the cube of the thickness (cm) of the test piece. In the present invention, bending rigidity is expressed in kgf / cm. 2 was converted into MPa units.

[0153] (6) Slab hardness (Shore D hardness) Ionomer resin or cover composition was injection molded into a sheet approximately 2 mm thick and stored at 23°C for two weeks. Three or more sheets were stacked to avoid the influence of the measurement substrate, and the hardness was measured using an automatic hardness tester (Digitest II, manufactured by H. Burleith Co.). Shore D detector was used.

[0154] (7) Measurement of loss modulus E'' at 0℃ The loss modulus E″ of the cover layer at 0° C. was measured under the following conditions. Device: Dynamic viscoelasticity measuring device Rheogel-E4000 manufactured by UBM Measurement sample: A sheet of approximately 0.5 mm in thickness was prepared using the cover composition by press molding, and a test piece was cut out from this sheet so as to have a width of 4 mm and a clamp distance of 20 mm. Measurement mode: Sine wave tension Measurement temperature range: -100℃~100℃ Heating rate: 4°C / min Measurement data capture interval: 4°C Excitation frequency: 10Hz Measurement distortion: 0.05%

[0155] (8) Measurement of compressive deformation A Yamada compression tester, "SCH," was used to measure the amount of compressive deformation. In this tester, a golf ball is placed on a metal plate. A metal cylinder is gradually lowered toward the golf ball. The golf ball, sandwiched between the bottom of the cylinder and the plate, deforms. The distance traveled by the cylinder from when an initial load of 98 N was applied to the golf ball until a final load of 1275 N was applied was measured. The amount of compressive deformation (mm) is this distance traveled. The speed of the cylinder before the initial load was applied was 0.83 mm / s. The speed of the cylinder after the initial load was applied until the final load was applied was 1.67 mm / s.

[0156] (9) Restitution coefficient A 198.4g metal cylinder was collided with each golf ball at a speed of 45m / s, the speeds of the cylinder and golf ball were measured before and after the collision, and the restitution coefficient of each golf ball was calculated from their respective speeds and masses. Measurements were made for 12 golf balls each, and the average value was used as the restitution coefficient of that golf ball.

[0157] (10)Durability A metal-head W#1 driver (manufactured by Dunlop Sports, XXIO S, loft 11°) was attached to a swing robot M / C manufactured by Golf Laboratory, and each golf ball was hit at a head speed of 45 m / s to measure the number of repeated hits until the golf ball broke. The durability of each golf ball was expressed as an index value for the number of hits for each golf ball, with the number of hits for golf ball No. 1 set as 100 for golf balls No. 2, the number of hits for golf ball No. 3 set as 100 for golf balls No. 4 to No. 8, and the number of hits for golf ball No. 9 set as 100 for golf balls No. 10 to No. 14. The higher the index value, the more durable the golf ball.

[0158] [Preparation of ionomer] <Synthesis of metal complexes> (1) Synthesis of B-27DM / Ni complex The B-27DM / Ni complex was prepared according to Synthesis Example 4 described in WO 2010 / 050256, using the following 2-bis(2,6-dimethoxyphenyl)phosphano-6-pentafluorophenylphenol ligand (B-27DM). Following Example 1 of WO 2010 / 050256, a nickel complex (B-27DM / Ni) was synthesized in which B-27DM and Ni(COD)2 reacted in a 1:1 ratio using bis(1,5-cyclooctadiene)nickel(0) (referred to as Ni(COD)2).

[0159] [ka]

[0160] (2) Synthesis of B-423 / Ni complex The B-423 / Ni complex was prepared using the following 2-bis(2,6-dimethoxyphenyl)phosphano-6-(2,6-diisopropylphenyl)phenol ligand (B-423) in accordance with Synthesis Example 1 described in Japanese Patent No. 6913051. According to Example 1 of Japanese Patent No. 6913051, a nickel complex (B-423 / Ni) was synthesized in which B-423 and Ni(COD)2 reacted in a 1:1 ratio using bis(1,5-cyclooctadiene)nickel(0) (referred to as Ni(COD)2).

[0161] [ka]

[0162] <(Production Examples 1 to 3): Production of Ionomer-Based Resin Precursor> Ethylene / tBu-acrylate copolymer was produced using a transition metal complex (B-27DM / Ni complex or B-423 / Ni complex). An ionomer-based resin precursor was produced by reference to Production Example 1 described in Japanese Patent Publication No. 6750936. The metal complex species, amount of metal complex, amount of trioctylaluminum (TNOA), amount of toluene, comonomer species, amount of comonomer, ethylene partial pressure, polymerization temperature, and polymerization time were all determined according to the conditions listed in Table 1. The physical properties of the resulting ionomer-based resin precursor are shown in Table 2.

[0163] [Table 1]

[0164] [Table 2]

[0165] <(Resins 1 to 3): Production of Ionomer-Based Resins (Copolymers (P))> Internal volume 1.6m 3A SUS316L autoclave equipped with a stirring blade was charged with 100 kg of any one of the copolymers obtained in Production Examples 1 to 3, 2.0 kg of paratoluenesulfonic acid monohydrate, and 173 L of toluene, and the mixture was stirred at 105°C for 4 hours. 173 L of ion-exchanged water was added, stirred, and allowed to stand, after which the aqueous layer was removed. Subsequently, the addition and removal of ion-exchanged water was repeated until the pH of the removed aqueous layer reached 5 or higher. The remaining solution was charged into a twin-screw extruder (L / D = 45.5) equipped with a 42 mm diameter vent device, and the solvent was distilled off by applying a vacuum to the vent. Furthermore, the resin continuously extruded in the form of a strand from the die at the tip of the extruder was cooled in water and cut with a cutter to obtain resin pellets. In the IR spectrum of the obtained resin, a t-Bu group-derived 850 cm -1 The disappearance of the peak around 1730 cm originating from the carbonyl group of the ester -1 The decrease in the peak near 1700 cm originates from the carbonyl group of the carboxylic acid (dimer). -1 An increase in the peak around Decomposition of t-Bu ester and production of carboxylic acid were confirmed, yielding ionomer base resins 1 to 3. The physical properties of the resulting resins are shown in Table 3. In the table, "not detected" means below the detection limit.

[0166] [Table 3]

[0167] <Examples 1 to 11: Production of ionomer resins> 1) Preparation of Na ion source Ethylene / methacrylic acid (MAA) copolymer (Nucrel N1050H, manufactured by Mitsui Dow Polychemicals Co., Ltd.) and sodium carbonate (NaCO) were continuously added to a Toshiba Machine 26mm diameter vented twin-screw extruder (L / D = 64) at a blend ratio of 55 wt% and 45 wt%. The extrusion was carried out at a barrel temperature of 150°C and a screw speed of 150 rpm, while gas and water evolved during the blending were removed through the vent with a vacuum pump. The resin extruded continuously in the form of strands from the die at the end of the extruder was cooled in water and cut with a cutter to obtain pellets for the sodium ion source.

[0168] 2) Preparation of Zn ion source Ethylene / methacrylic acid (MAA) copolymer (Nucrel M1050H, manufactured by Mitsui DuPont Chemical Co., Ltd.) was continuously added to a Toshiba Machine 26mm diameter vented twin-screw extruder (L / D=64) at a blending ratio of 54.5 wt%, zinc oxide 45 wt%, and zinc stearate 0.5 wt%, and extruded at a barrel temperature of 150°C and a screw rotation speed of 150 rpm while removing gas and water generated during mixing through the vent with a vacuum pump. The resin extruded continuously in the form of strands from the die at the tip of the extruder was cooled in water and cut with a cutter to obtain pellets for the Zn ion source.

[0169] 3): Preparation of ionomer One of Resins 1 to 3 and a sodium ion source or a zinc ion source were continuously fed into a Toshiba Machine 26mm diameter vent-equipped twin-screw extruder (L / D = 65) at a blending ratio to achieve a predetermined degree of neutralization, and extrusion was carried out under kneading conditions of a barrel set temperature of 200°C and a screw rotation speed of 150 rpm, while injecting water at a ratio of 4 parts per 100 parts of the resin fed. Gas and water evolved during kneading were removed from the vent with a vacuum pump. Furthermore, the resin extruded continuously in the form of a strand from the die at the tip of the extruder was cooled in water and cut with a cutter to obtain ionomer pellets. In the IR spectrum of the obtained resin, the peak at 1700 cm originating from the carbonyl group of the carboxylic acid (dimer) was observed. -1 The peak around 1560 cm originating from the carbonyl group of the carboxylate group decreases. -1 The peak around 1700 cm originating from the carbonyl group of the carboxylic acid (dimer) increased. -1 The decrease in the peak near the peak indicated that an ionomer with the desired degree of neutralization had been produced. The physical properties of the resulting ionomer are shown in Table 4.

[0170] [Table 4]

[0171] [Manufacturing golf balls] (1) Core preparation A rubber composition having the formulation shown in Table 5 was kneaded and hot-pressed at 170° C. for 30 minutes in upper and lower molds having hemispherical cavities to obtain a core.

[0172] [Table 5]

[0173] Polybutadiene rubber: ENEOS Materials Corporation, "BR-730 (high-cis polybutadiene)" Zinc acrylate: Nisshoku Techno Fine Chemical Co., Ltd., "ZNDA-90S" Zinc oxide: "Ginrei R" manufactured by Toho Zinc Co., Ltd. Barium sulfate: Sakai Chemical Industry Co., Ltd., "Barium Sulfate BD" Dicumyl peroxide: NOF Corporation, "Percumyl (registered trademark) D (dicumyl peroxide)" Diphenyl disulfide: Diphenyl disulfide manufactured by Sumitomo Seika Chemicals

[0174] (2) Making the cover The compounded materials shown in Table 6 were extruded using a twin-screw kneading extruder to prepare pelletized cover compositions. Extrusion was carried out with a screw diameter of 30 mm, a screw rotation speed of 200 rpm, and a screw L / D of 30. The cover composition was heated to 220°C to 250°C at the die of the extruder. The cover composition was injection molded onto the core obtained as described above to form a cover layer (thickness: 1.5 mm). The surface of the resulting golf ball body was sandblasted and marked, and then clear paint was applied. The paint was dried in an oven at 40°C to obtain a golf ball with a diameter of 42.7 mm and a mass of 45.3 g. The evaluation results of the resulting golf ball are shown in Table 6.

[0175] [Table 6]

[0176] The materials used in Table 6 are listed below. Himilan 1605: Mitsui Dow Polychemicals, sodium ion-neutralized ethylene-methacrylic acid copolymer ionomer resin (Shore D hardness 64, flexural modulus: 226 MPa) Himilan AM7329: Manufactured by Mitsui Dow Polychemicals, zinc ion-neutralized ethylene-methacrylic acid copolymer ionomer resin (Shore D hardness 62, flexural modulus: 187 MPa) Surlyn 8150: Sodium ion-neutralized ethylene-methacrylic acid copolymer ionomer resin (Shore D hardness: 68), manufactured by Dow Chemical Company Surlyn 9150: Zinc ion-neutralized ethylene-methacrylic acid copolymer ionomer resin (Shore D hardness: 64), manufactured by Dow Chemical Company Umex 1010: Acid-modified polypropylene resin manufactured by Sanyo Chemical Industries, Ltd.

[0177] As is apparent from the results in Table 6, a golf ball having a core and at least one layer of cover located on the outside of the core, wherein the at least one layer of cover is formed from a cover composition containing one or more ionomer resins in which at least a portion of the carboxyl groups and / or dicarboxylic anhydride groups in copolymer (P) containing, as essential structural units, structural units (A) derived from ethylene and / or an α-olefin having 3 to 20 carbon atoms and structural units (B) derived from a monomer having a carboxyl group and / or a dicarboxylic anhydride group, are neutralized with at least one metal ion selected from Group 1, 2, or 12 of the Periodic Table, and the loss modulus E'' at 0°C, as obtained by measuring the dynamic viscoelasticity of the cover composition under the following conditions, is 3.40 × 10 7 The golf balls of the present invention, which have a loss modulus E'' of 3.40 x 10 Pa or less, exhibited significantly improved durability without a substantial decrease in resilience. In contrast, when comparing No. 1 and No. 2, which have the same core formulation A, No. 1 had a loss modulus E'' of 3.40 x 10 7 Comparing No. 3 to No. 8, which have the same core composition B, the loss modulus E'' of No. 3 and No. 8 is 3.40 × 10 7 Pa, so durability was significantly inferior to No. 4 to No. 7. Comparing No. 9 to No. 14, which have the same core composition C, No. 9 has a loss modulus E'' of 3.40 x 10 7 Since the value exceeded 100 Pa, the durability was significantly inferior to that of Nos. 10 to 14. [Explanation of symbols]

[0178] 1: Golf ball, 2: Spherical core, 3: Cover, 31: Dimples, 32: Land

[0179] A preferred embodiment (1) of the present invention is a golf ball having a core and at least one layer of cover positioned on the outside of the core, wherein the at least one layer of cover is formed from a cover composition containing one or more ionomer resins in which at least a portion of the carboxyl groups and / or dicarboxylic anhydride groups in a copolymer (P) containing, as essential structural units, structural units (A) derived from ethylene and / or an α-olefin having 3 to 20 carbon atoms and structural units (B) having carboxyl groups and / or dicarboxylic anhydride groups are neutralized with at least one metal ion selected from Group 1, 2, or 12 of the Periodic Table, and the loss modulus E'' at 0°C of the cover composition, as measured under the following conditions, is 3.40 × 10 7 A golf ball characterized by a coefficient of friction of 0.001 Pa or less. <Measurement conditions> Measurement mode: Sine wave tension Measurement temperature range: -100℃~100℃ Heating rate: 4°C / min Excitation frequency: 10Hz Measurement distortion: 0.05%

[0180] A preferred embodiment (2) of the present invention is the golf ball of embodiment (1), in which the metal ions are two or more metal ions selected from lithium, sodium, potassium, calcium, and zinc.

[0181] A preferred embodiment (3) of the present invention is a golf ball according to embodiment (1) or (2), wherein the cover composition contains, as the ionomer resin, an ionomer resin having a phase angle δ of 50 degrees to 75 degrees at an absolute value of complex modulus G*=0.1 MPa as measured with a rotational rheometer.

[0182] A preferred embodiment (4) of the present invention is a golf ball according to any one of embodiments (1) to (3), wherein the cover composition contains, as ionomer resins, a first ionomer resin that has a phase angle δ of 50 to 75 degrees when the absolute value of the complex modulus of elasticity G* is 0.1 MPa as measured with a rotational rheometer and that is neutralized with first metal ions, and a second ionomer resin that has a phase angle δ of 50 to 75 degrees when the absolute value of the complex modulus of elasticity G* is 0.1 MPa as measured with a rotational rheometer and that is neutralized with second metal ions different from the first metal ions.

[0183] A preferred embodiment (5) of the present invention is the golf ball of embodiment (4), wherein the content of the structural unit (B) in the first ionomer resin is 2.0 mol % to 20.0 mol % and the degree of neutralization is 5 mol % to 95 mol %.

[0184] A preferred embodiment (6) of the present invention is the golf ball of embodiment (4) or (5), wherein the content of the structural unit (B) in the second ionomer resin is 2.0 mol % to 20.0 mol % and the degree of neutralization is 5 mol % to 95 mol %.

[0185] A preferred embodiment (7) of the present invention is the golf ball of any one of embodiments (4) to (6), wherein the melt flow rates (190° C., 2.16 kg load) of the first and second ionomer resins are 100 g / 10 min or less.

[0186] A preferred embodiment (8) of the present invention is the golf ball of any one of embodiments (4) to (7), in which the cover composition contains a first ionomer resin having a degree of neutralization of 50 mol % or less and a second ionomer resin having a degree of neutralization of 50 mol % or less.

[0187] A preferred embodiment (9) of the present invention is the golf ball according to any one of embodiments (4) to (7), in which the cover composition contains a first ionomer resin having a neutrality of 50 mol % or more and a second ionomer resin having a degree of neutralization greater than 50 mol %.

[0188] A preferred embodiment (10) of the present invention is the golf ball of any one of embodiments (4) to (7), in which the cover composition contains a first ionomer resin having a degree of neutralization of 50 mol % or less and a second ionomer resin having a degree of neutralization of more than 50 mol %.

[0189] A preferred embodiment (11) of the present invention is the golf ball of any one of embodiments (4) to (10), wherein the blending ratio (mass ratio) of the first ionomer resin to the second ionomer resin is 10 / 90 or more and 90 / 10 or less.

[0190] A preferred embodiment (12) of the present invention is the golf ball of any one of embodiments (4) to (11), in which one of the first metal ion and the second metal ion is a sodium ion, and the other is a zinc ion.

[0191] In a preferred embodiment (13) of the present invention, the loss modulus E″ at 0° C. is 3.00×10 7 The golf ball of any one of aspects (1) to (12) has a tensile strength of 100 Pa or less.

[0192] In a preferred embodiment (14) of the present invention, the slab hardness (D: Shore D) and flexural rigidity (M: MPa) of the cover composition are: M / D 2 The golf ball of any one of aspects (1) to (13) satisfies ≧0.070.

Claims

1. The core and and at least one layer of cover positioned outside the core, The at least one layer cover is The cover is formed from a composition containing one or more ionomer resins in which at least a portion of the carboxyl groups and / or dicarboxylic anhydride groups in a copolymer (P) containing, as essential structural units, structural units (A) derived from ethylene and / or an α-olefin having 3 to 20 carbon atoms and structural units (B) having a carboxyl group and / or a dicarboxylic anhydride group are neutralized with at least one metal ion selected from Group 1, Group 2, or Group 12 of the Periodic Table; The dynamic viscoelasticity of the cover composition is measured under the following conditions, and the loss modulus E″ at 0° C. is 3.40×10 ７ A golf ball characterized by having a hardness of 0.001 Pa or less. <Measurement conditions> Measurement mode: Sine wave tension Measurement temperature range: -100℃ to 100℃ Temperature increase rate: 4°C / min Excitation frequency: 10Hz Measured distortion: 0.05%

2. 2. The golf ball according to claim 1, wherein the metal ions are two or more metal ions selected from the group consisting of lithium, sodium, potassium, calcium, and zinc.

3. 2. The golf ball according to claim 1, wherein the cover composition contains, as an ionomer resin, an ionomer resin having a phase angle δ of 50 degrees to 75 degrees at an absolute value of a complex modulus G* of 0.1 MPa as measured with a rotational rheometer.

4. 2. The golf ball of claim 1, wherein the cover composition contains, as ionomer resins, a first ionomer resin that is neutralized with first metal ions and has a phase angle δ of 50 to 75 degrees when the absolute value of the complex modulus of elasticity G* is 0.1 MPa as measured with a rotational rheometer, and a second ionomer resin that is neutralized with second metal ions different from the first metal ions and has a phase angle δ of 50 to 75 degrees when the absolute value of the complex modulus of elasticity G* is 0.1 MPa as measured with a rotational rheometer.

5. 5. The golf ball according to claim 4, wherein the content of the structural unit (B) in the first ionomer resin is 2.0 mol % to 20.0 mol %, and the degree of neutralization is 5 mol % to 95 mol %.

6. 5. The golf ball according to claim 4, wherein the second ionomer resin has a content of the structural unit (B) of 2.0 mol % to 20.0 mol % and a degree of neutralization of 5 mol % to 95 mol %.

7. 7. The golf ball according to claim 5, wherein the first and second ionomer resins have a melt flow rate (190°C, 2.16 kg load) of 100 g / 10 min or less.

8. 5. The golf ball according to claim 4, wherein the cover composition contains a first ionomer resin having a degree of neutralization of 50 mol % or less and a second ionomer resin having a degree of neutralization of 50 mol % or less.

9. 5. The golf ball according to claim 4, wherein the cover composition contains a first ionomer resin having a neutrality of 50 mol % or more and a second ionomer resin having a neutralization degree of more than 50 mol %.

10. 5. The golf ball according to claim 4, wherein the cover composition contains a first ionomer resin having a degree of neutralization of 50 mol % or less and a second ionomer resin having a degree of neutralization of more than 50 mol %.

11. 5. The golf ball according to claim 4, wherein the blending ratio (mass ratio) of the first ionomer resin to the second ionomer resin is 10 / 90 or more and 90 / 10 or less.

12. 5. The golf ball according to claim 4, wherein one of the first metal ion and the second metal ion is a sodium ion and the other is a zinc ion.

13. The loss modulus E″ at 0°C is 3.00×10 ７ 2. The golf ball according to claim 1, wherein the hardness is 0.01 Pa or less.

14. The cover composition has a slab hardness (D: Shore D) and a bending rigidity (M: MPa) of M / D ２ 2. The golf ball according to claim 1, wherein the ρ satisfies ≧0.070.

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