IONOMERIC COMPOSITION FOR GOLF BALLS

Abstract: A melt blend of a polyester or polyamide elastomer and an ionomer wherein the neutralizing cation is a multi-valent metal, the ionomer being modified with an aminoalkyl group containing alicyclic or aromatic compound, and uses thereof, particularly in golf ball covers and cores.

Description: TITLE IONOMERIC COMPOSITION FOR GOLF BALLS BACKGROUND OF THE INVENTION This application claims priority to Japanese Patent Application No. 8-33704 which is incorporated herein by reference. f Field of the Invention " ) The present invention relates to a thermoplastic resin composition having excellent flexibility and rebound resiliency. More specifically, the invention relates to a thermoplastic resin composition that can be favorably used as a cover material and/or a core material of golf balls or as a material for one piece balls, that features excellent injection moldability and that can be reused. (Prior Art) Owing to its excellent rebound resiliency and durability against being cut, ionomer resins made from ethylene-unsaturated carboxylic acid copolymers have been extensively used as cover materials for golf balls. However, the golf balls using a conventional general-purpose hard ionomer as the covering material offer unsatisfactorily low spin performance and undesirable feel at the time of hitting the ball in comparison with golf balls using balata as the covering material. Therefore, attempts have heretofore been made to improve such performance and feel by blending flexibility-imparting components. In order to cope with this, a method has been known to blend the ionomer with a thermoplastic elastomer such as polyester elastomer or polyamide elastomer in order to obtain a composition having flexibility yet exhibiting excellent rebound resiliency. However, such a thermoplastic elastomer is expensive and. besides, the durability of the composition decreases with an increase in the amount of blending thereof: Therefore, it has been desired to decrease the blending amount of the thermoplastic elastomer blended with the ionomer to as low a level as possible. In other words, it has been desired to decrease amount of thermoplastic elastomer while obtaining a composition that exhibits both flexibility and rebound resiliency. By using the conventional general-purpose ionomer, however, the rebound resiliency of the composition decreases with an increase in the blending amount of the ionomer component, and the hardness and the stiffness become too high. Furthermore, a polybutadiene rubber has generally been used as the core material for two-piece balls, center for three-piece balls or as the material of one- piece balls. This cross-linked rubber, however, has problems in regard to moldability and producibility. Besides, the used balls cannot be recycled for another use. A composition of the ionomer and the thermoplastic elastomer is free from such defects and is drawing attention as a core material or as a material for one piece balls accompanied, however, by the problems similar to those of the above-mentioned cover material. SUMMARY OF THE INVENTION The object of the present invention is to find compositions comprising an ionomer and a thermoplastic elastomer that make it possible to obtain balls that exhibit excellent flexibility, excellent rebound resiliency, excellent durability, good feel at the time of hitting the ball, and that can be easily controlled. It has been found that the object can be accomplished when a particular ionomer modified with a particular amine is used. A thermoplastic resin composition is obtained that is suited as a material for golf balls. The present invention is concerned with a thermoplastic resin composition comprising: (A) 10 to 90 parts by weight of a modified composition of a multi-valent metal ionomer made from an ethylene-unsaturated carboxylic acid copoiymer and an alicyclic or aromatic compound having two or more aminoalkyi groups; and -(B) 90 to 10 parts by weight of a thermoplastic elastomer selected from the group consisting of a thermoplastic polyester elastomer and a polyamide elastomer. The thermoplastic resin composition of the present invention exhibits excellent flexibility and rebound resiliency, and lends itself well for being used as a material for forming a center of a three-piece golf ball, core of a two-piece golf ball, for forming a one-piece golf ball, a cover of golf balls, and an outer cover or an inner cover of dual golf balls, making it possible to produce golfs balls having excellent durability, good controllability (higher spin), good feel at the time of hitting, excellent rebound resiliency and improved initial velocity. The present resin composition is thermoplastic and can be easily molded by the injection molding or compression molding, and can be molded and produced very excellently compared with the conventional cross-linked butadiene rubbers, and can further be reused (recycled). Moreover, the present resin composition exhibits excellent resistance against being scratched and scarred, resistance against oils, and exhibits luster. It can be widely used as interior and exterior materials for automobiles, electric wires, cables, building materials, electric appliances, commodities for daily use, or the like. DETAILED DESCRIPTION OF THE INVENTION According to the present invention, an alicyclic or an aromatic compound (and, particularly, a condensed cyclic compound) having two or more aminoalkyi groups is selected out of a variety of amines and is combined with a multi-valent metal ionomer to obtain a modified composition. The ionomer composition modified with the aminoalkyi group-containing compound gives an advantage of improving the rebound resiliency without impairing flexibility of the final composition. The ionomer that is modified is one neutralized with a multi-valent metal. Ionomer neutralized with a monovalent metal when modified with the aminoalkyi compound does not exhibit so much an effect as when a multi-valent ionomer. particularly the zinc ionomer, is modified with the aminoalkyi compound. According to the present invention, the modified ionomer composition (A) is combined with the thermoplastic elastomer (B) selected from the group consisting of a thermoplastic polyester elastomer and a polyamide elastomer. This makes it possible to obtain a material for golf balls that exhibit excellent flexibility, rebound resiliency, durability, good feel at the time of hitting the ball, and that can be easily controlled (improved spin). The multivalent metal ionomer made from an ethylene-unsaturated carboxylic acid copoiymer constituting the composition (A) of the present invention is the ionomer of a random copoiymer of an ethylene and an unsaturated carboxylic acid, or of a random copoiymer of ethylene. unsaturated carboxylic acids, and other copolymerizable monomers. The unsaturated carboxylic acid in the random copoiymer is usually present in an amount of from about 5 to about 30% by weight, preferably, from about 10 to about 25% by weight, and the other copolymerizable monomer is usually present in the amount of from 0 to about 40% by weight, preferably, from 0 to about 25% by weight and, more preferably, from 0 to about 10% by weight. Examples of the unsaturated carboxylic acid include acrylic acid, — methacrylic acid, monomethyl maleate, monoethyl maleate, maleic anhydride and itaconic acid. Among them, acrylic acid or methacrylic acid is particularly preferred. Examples of the other copolymerizable monomer include unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, iso-butyl acrylate, n- butyl acrylate, iso-octyl acrylate, methyl methacrylate, iso-butyl methacrylate and diethyl maleate; vinyl esters such as vinyl acetate and vinyl propionate; and carbon monoxide. In particular, an acrylic acid ester or a methacrylic acid ester is preferred. In the above-mentioned ionomer, the metal ions are those of a multi-valent metal such as zinc, magnesium, calcium, barium, lead, tin, aluminum, copper, cobalt, nickel or the like. In particular, zinc or magnesium is preferred. The ionomer may be one that is co-neutralized with monovalent metal ions so long as it contains such multi-valent metals. The degree of neutralization by such metal ions is usually from 5 to 100% and, preferably, from 20 to 80%. It is further desired that the ionomer has Melt Index of from 0.01 to 20 g/10 min. and, preferably, from 0.1 to 10 g/10 min. at 190°C under a load of 2160 grams. An alicyclic or aromatic compound having two or more aminoalkyi groups is used together with the above-mentioned multi-valent metal ionomer. The amino group of the aminoalkyi group is a primary amino group such as an aminomethyl group, aminoethyl group or aminopropyl group. However, the one having the aminomethyl group is most easily available and is preferred. The alicyclic compound or the aromatic compound may be a monocyclic compound. However, the condensed cyclic compound is preferred since its exhibits excellent effect. Examples of the monocyclic compound include 1,2 (or 1,3 or l ,4)-bis- aminomethyl cyclohexane, and o (or m or p) - xylylene diamine. Examples of the condensed cyclic compound include 2,5 (or 2,6) -bis-aminomethyl-bicyclo[2,2,l ] heptane, 2,6 (or 2,7) -bis-aminomethyl-bicyclo[3,2,l] octane, 2,5 (or 2,6) -bis- aminomethyl-7-dimethylbicyclo[2,2, 1 ] heptane, 2,6-bis-aminomethyl adamantane, and 1 ,4 (or 2,6 or 2,7)-bis-aminomethyl naphthalene. Preferably, the compound having aminoalkyi groups is used at such a ratio of from 0.05 to 1 equivalent and, preferably, from 0.01 to 1 equivalent with respect to the carboxyl groups (inclusive of both free and ionized carboxyl groups). When the aminoalkyi group containing compound is used at a ratio other than in the above range, improvement in the physical properties is not much expected but rather the quality may deteriorate. The composition comprising the multi-valent metal ionomer and the amino compound can be obtained by melt-mixing the two compounds at a temperature not lower than the melting point of the ionomer and, preferably, at a temperature of 160 to 240°C. In such a composition, it is estimated that at least part of the amino group of the amino compound is bonded to a metal of the ionomer or to the free carboxyl group while forming an amine complex or an ammonium salt. According to the present invention, the thermoplastic polyester elastomer or the thermoplastic polyamide elastomer is used together with the above- mentioned composition. Examples of the thermoplastic polyester elastomer include a polyester ether elastomer having, as polymerization units, an aromatic polyester as a hard segment and a polyoxyalkylene glycol as a soft segment, and a polyester ester elastomer having an aromatic polyester as a hard segment and an aliphatic polyester as a soft segment. In the former example, the aromatic polyester polymerization unit is derived from an aromatic dicarboxylic acid component and an aliphatic or alicyclic diol component having a molecular weight of not larger than 250. Typical examples include polyethylene terephthalate and polytetramethylene phthalate. Further, the polymerization unit of polyoxyalkylene glycol is derived from a glycol having 2 to 6 carbon atoms, and has a molecular weight of from 400 to 6000. Typical examples include a polyoxyethylene glycol and a polyoxytetramethylene glycol. The ratio (molar ratio) of ether to ester contained in the polyester ether elastomer is from 10-90 to 90-10 and, preferably, 20-80 to 80-20. The Shore D hardness is not larger than 70 and, preferably, from 20 to 50. As the polyester ester elastomer, there can be used similar compounds with the polyoxyalkylene glycol unit of the polyester ether elastomer replaced by an aliphatic polyester unit such as polytetramethylene adipate or polytetramethylene sebacate. As the polyamide elastomer, there can be used a block copoiymer having, as a hard segment, a polyamide component such as nylon 6, nylon 1 1 , nylon 12, or aromatic polyamide, and having, as a soft segment, a polyoxyalkylene glycol such as polyoxytetramethylene glycol, polyoxypropylene glycol, or fatty acid polyester. It is desired that the polyamide component unit which is the hard segment has an average molecular weight of from 300 to 1 000 and the polyamide component unit which is the soft segment has a molecular weight of from 400 to 6000. The polyamide elastomer has an inherent viscosity of from about 0.8 to about 2.05, has a ratio (molar ratio) of ether (or ester) to amide of from 10-90 to 90-10 and, preferably, 20-80 to 80-20, and has a Shore D hardness of not larger than 60 and, preferably, from 20 to 50. The modified composition (A) comprising the ionomer and the amino compound, and the thermoplastic elastomer (B) are biended at a ratio on the weight basis of from 10/90 to 90/10 and, preferably, from 30/70 to 70/30. though it may vary depending upon the desired properties. As required, the above-mentioned composition may be blended with other thermoplastic resins such as monovalent metal ionomer or linear low-density polyethylene, and a variety of additives such as tackifier, wax. antioxidant. weather resistance stabilizer, photo stabilizer, heat stabilizer, ultraviolet absorber, lubricant, pigment, dye, inorganic filler, etc. Though there is no particular limitation, the resin composition of the present invention can be prepared by a method according to which the composition (A) comprising the multi-valent metal ionomer and the amino compound is prepared by melt-mixing and is then melt-blended with the thermoplastic elastomer (B), or by a method according to which the thermoplastic elastomer (B) is melt-mixed simultaneously at the time of melt-blending the multi-valent metal ionomer and the amino compound together. Besides, any other components may be blended at any step. EXAMPLES The invention will now be described by way of Examples. Tables 1 to 3 show the ionomer resins, amine compound and thermoplastic elastomers used in following Examples and in following Comparative Examples. (Example 1) By using a twin screw extruder (screw diameter of 30 mm, L/D = 25), an Amine Compound 1 of an amount of 5% by weight with respect to Ionomer Resin 1 (0.37 equivalent with respect to carboxyl groups in the acid copoiymer) was fed dropwise by a pump through a feed throat to the Ionomer Resin 1 , and was melt- mixed with the Ionomer Resin 1 at temperature of 200°C and a screw rotation speed of 200 rpm. The resin composition obtained and the Thermoplastic Elastomer 1 were dry-blended at a weight ratio of 40:60, and the mixture was fed to a single screw extruder (screw diameter of 40 mm. L/D = 28) and was melt-blended at a temperature of 200°C and a screw rotation speed of 40 rpm. The resin composition obtained was compression molded into a desired shape, and physical properties were measured in compliance with the methods described below. The results are shown in Table 4. Melt Index: Measured in compliance with JIS K 7210 at a temperature of 190°C under a load of 2160 g. Hardness (Shore D): Measured in compliance with JIS K 7215. Olsen Stiffness: Measured in compliance with JIS K 7106. Rebound resiliency: Measured in compliance with JIS K 6301. (Example 2) Using the procedure of Example 1 , a Thermoplastic Elastomer 2 was used instead of the Thermoplastic Elastomer 1. (Example 3) Using the procedure of Example 1 , a 50/50 blend of the Thermoplastic Elastomer 1 and the Thermoplastic Elastomer 2 was used at the same total weight ratio as the thermoplastic elastomer component of Example 1. (Examples 4 and 5) Using the procedure of Example 1 , the Ionomer Resin 1 was modified with an amine compound, and the Ionomer Resin 2 was modified, too, by the same method. The thus obtained two kinds of resin compositions and the Thermoplastic Elastomer 1 were dry-blended at a blending ratio shown in Table 4, and were melt-blended by the same method as in Example 1. (Comparative Example 1 ) Using the procedure of Example 1. no Amine Compound 1 was used, and the Ionomer Resin 1 which has not been modified and the Thermoplastic Elastomer 1 were melt-blended together to measure the physical properties. The resin composition obtained exhibited rebound resiliency inferior to that of Example 1. Table Ionomer resins used in Examples and in Comparative Examples. Content Kind of Content Kind Degree of Melt Index Kind of acid of acid fmol%) ester of ester fmol% of metal neutralization (%) π Ominϊ Ionomer methacrylic 5.4 - - Zn 59 0.9 Resin 1 acid Ionomer methacrylic J.J iso-butyl 5.2 Zn 70 Resin 2 acid acrylate Table 2 15 Amine compound used in Examples and in Comparative Examples. Chemical name Trade name Manufacturer Amine 2,5(2,6) -bis(aminomethyl)- NDBA Mitsui Toatu Kagaku Compound bicyclo[2,2, 1 jheptane Kogyo K.K. Table 3 Thermoplastic elastomers used in Examples and Comparative Examples. Kind Trade name Manufacturer Thermoplastic polyester elastomer Hytrel® 8122 Toray-Dupont K.K. Elastomer 1 Thermoplastic polyamide elastomer Pebax® 2533 Toray K.K. Elastomer 2 Tqble Resin compositions of Examples and Comparative Examples Ionomer resin Amine compound Therrηoplnstic elastomer Kind Carboxy Added Equivalent Blending Kind Blending group amount ratio ratio (mo|%) (% bv wt.) (% by wt.) (% bv wt Example Ionomer 5.4 5 0.37 40 Thermoplastic 60 1 Resin I 1 Elastomer 1 Example Ionomer 5.4 5 0.37 40 Thermoplastic 60 2 Resin 1 Elastomer 1 Example Ionomer 5.4 5 0.37 40 Thermoplastic 30 3 Resin 1 Elastomer 1 Thermoplastic 30 Elastomer 2 Example Ionomer 5.4 5 0.37 20 Thermoplastic 60 4 Resin 1 Elastomer 1 Ionomer 3.3 5 0.70 20 Resin 2 Example Ionomer 5.4 5 0.37 40 Thermoplastic 40 5 Resin 1 Elastomer 1 Ionomer 3.3 5 0.70 20 Resin 2 Comparative Ionomer 5.4 0 40 Thermoplastic 60 Example 1 Resin 1 Elastomer 1 Table 5 Properties of resin compositions of Examples and Comparative Examples. Melt Index Hardness Olsen Rebound (dg/min) Cshore D) stiffnes resiliency ( Mpϋ) Example 1 3.2 40 83 m 72 Example 2 8.0 39 49 68 Example 3 5.6 36 56 71 Example 4 4.1 37 53 71 Example 5 3.0 38 130 66 Comparative Example 1 2.8 38 37 66

Claims: CLAIMS 1 . A thermoplastic resin composition comprising: (A) 10 to 90 parts by weight of a modified composition of a multi-valent metal ionomer made from an ethylene-unsaturated carboxylic acid copoiymer and an alicyclic or aromatic compound having two or more aminoalkyi groups; and (B) 90 to 10 parts by weight of a thermoplastic elastomer selected from the group consisting of a thermoplastic polyester elastomer and a polyamide elastomer. 2. A thermoplastic resin composition according to claim 1, wherein the multi-valent metal ionomer in the modified composition (A) is a zinc ionomer, and the alicyclic or aromatic compound having two or more aminoalkyi groups is a condensed cyclic compound. 3. A golf ball material comprising the thermoplastic resin composition of claim 1 or 2. 4. A golf ball having a cover comprising the thermoplastic resin of claim 1 or 2. 5. The thermoplastic resin composition of claim 1 wherein the ratio of the aminoalkyl-group-containing alicyclic or aromatic compound to carboxyl groups in the ionomer is from 0.01 : 1 to 1: 1.

Inventors: HOSOAI YASUHISA, YAMAMOTO YOSHIMASA, HOSOAI, YASUHISA, YAMAMOTO, YOSHIMASA
Applicants: DU PONT, HOSOAI YASUHISA, YAMAMOTO YOSHIMASA, E.I. DU PONT DE NEMOURS AND COMPANY, HOSOAI, YASUHISA, YAMAMOTO, YOSHIMASA
Application year: 1997
Main classification: A63B37
IPC codes: A63B37, C08L23, C08L67, C08L77