CA2256690A1 - Soft ionomer compositions and blends thereof for golf ball covers - Google Patents
Soft ionomer compositions and blends thereof for golf ball covers Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
- C08L23/08—Copolymers of ethene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
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Abstract
Novel, soft, low, modulus ehtylene copolymer ionomer compositions containing an acrylate softening monomer, neutralized with magnesium or lithium ions, possess a higher level of resilience at a given level of PGA Compressibility than known ionomers. The advantage is maintained in certain blend compositions with hard ionomers of lithium and magnesium for blends having a neat-sphere PGA Compression below about 155, for blends with hard sodium ionomer, for blends with a neat-sphere PGA Compression below about 155 provided there is at least 50 % soft ionomer, and for stiffer blend compositions having 51-80 % hard ionomer, where the hard ionomer is sodium, potassium or zinc. The soft ionomers and blends are useful for golf ball cover material.
Description
CA 022~6690 1998-ll-2~
TITLE
SOFT IONOMER COMPOSITIONS AND BLENDS THEREOF FOR GOLF
BALL COVERS
CROSS REFERENCE TO RELATED APPLICATIONS
This Application is a Co~tinl~tion-in-Part of copending Application, serial number 08/497,664, filed 6/30l95 which is a continuation-in-part of Application, serial number 08/345,349, filed 11/21/94, which is a Continuation-in-Part of Application serial number 08/077,581, filed 6/18/93 and now flb~n~lo~e~l, and also of copending Application, serial number 08/617,061, 1 o filed 3/18/96.
BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to novel, soft, flexible ethylene copolymer 5 ionomer compositions which have very high resilience combined with good playability. The compositions are useful particularly as covers for golf balls as well as other uses where high resilience is desirable. The ionl merS are copolymers of ethylene, a softening comonomer and (meth)acrylic acid, neutralized with m~gn~eium or lithium. As golf ball cover m~tPri~l they possess ~ 2 o a combination of flexibility and high reqiliPnre. This is an ideal ~lOp~l Ly combination for m~t~ri~l~ used alone or in blends with other ionomers.
Description of Related Art Ethylene copolymer ionomers based on copolymers of ethylene with (meth)acrylic acid, and optionally a third monomer which could be any of a 2 5 vast range of monomers, specifically inrlll~ling vinyl acetate, methyl mrth~r.rylate and ethyl acrylate, were f rst disclosed in U.S. Patent No.
TITLE
SOFT IONOMER COMPOSITIONS AND BLENDS THEREOF FOR GOLF
BALL COVERS
CROSS REFERENCE TO RELATED APPLICATIONS
This Application is a Co~tinl~tion-in-Part of copending Application, serial number 08/497,664, filed 6/30l95 which is a continuation-in-part of Application, serial number 08/345,349, filed 11/21/94, which is a Continuation-in-Part of Application serial number 08/077,581, filed 6/18/93 and now flb~n~lo~e~l, and also of copending Application, serial number 08/617,061, 1 o filed 3/18/96.
BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to novel, soft, flexible ethylene copolymer 5 ionomer compositions which have very high resilience combined with good playability. The compositions are useful particularly as covers for golf balls as well as other uses where high resilience is desirable. The ionl merS are copolymers of ethylene, a softening comonomer and (meth)acrylic acid, neutralized with m~gn~eium or lithium. As golf ball cover m~tPri~l they possess ~ 2 o a combination of flexibility and high reqiliPnre. This is an ideal ~lOp~l Ly combination for m~t~ri~l~ used alone or in blends with other ionomers.
Description of Related Art Ethylene copolymer ionomers based on copolymers of ethylene with (meth)acrylic acid, and optionally a third monomer which could be any of a 2 5 vast range of monomers, specifically inrlll~ling vinyl acetate, methyl mrth~r.rylate and ethyl acrylate, were f rst disclosed in U.S. Patent No.
3,264,272 (Rees). The list of metal ions disclosed as possible neutralizing ionsincluded metals of groups I, II, III, IV-A and VIII of the Periodic Table, including Na, K, Li, Cs, Ag, Hg, Cu, Be, Mg, Ca, Sr, Ba, and many more.
3 o Ionomers with a third monomer exemplified included ethylene/vinyl CA 022~6690 1998-11-2~
acetate/methacrylic acid neutralized with sodium and m~gn~sium, and ethylene/methyl methacrylate/methacrylic acid neutralized with sodium.
The use of 'soft', flexible ionomers, softened by such a third m~ m.-.r, only became of commercial interest around 1987. Alkyl acrylates 5 are the preferred softening monomers, vinyl acetate producing a less stable polymer. The employment of n-butyl acrylate as a softening monomer in terpolymer ionomers is disclosed in U.S. Patent No. 4,690,981 (Statz). This patent lists the possible neutralizing ions as those of groups Ia, Ib, IIa, IIb, IIIa, IVa, VIb and VIII of the periodic table, such as Na, K, Zn, Ca, Mg, Li, Al, Ni 0 and Cr.
U.S. PatentNo. 5,415,939 (~domig~ etal.), filed 12/21/93, çloses soft lithium ionomers and blends of such ionomers with hard ionomers. The parent case of which this present application is a continll~tion-in-part, which was filed 6/18/93, (i.e., prior to this reference), discloses lithium 15 and m~gnesium soft ionomers and blends with hard ionomers.
Many other patents have referred to bipolymer and terpolymer ionc mPr.s of various metals, also in a general way. No terpolymer ionomer using an alkyl acrylate with (meth)acrylic acid and neutralized with either lithium or m~gnesium is known to have been specifically disclosed or 2 o exemplifie~ References to them are merely of the shotgun type, such as those described above.
Golf balls have certain me~cur~hle properties which, directly, strongly affect play characteristics. Most hn~oll~,t ofthese are resilienre and colllplcssibility. High resilience increases the length a golf ball can be driven 2 5 and colllplcssibility increases the playability in terms of 'spin' and 'feel'.
pcesiliPnce and colllpressibility can be measured for the m~teri~l itself, by testing a sphere of the m~t~ri~l. These m~tPri~l properties can affect golf ball play characteristics when used to form the cover of a ball. For ionomers these two ~lo~,.lies, resilience and ccn~lessibility, tend to be inversely related. Thus a3 o highly resilient m~t~.ri~l is generally a harder, less con~ ible m~tP.ri~l, and CA 022~6690 1998-11-2~
vice versa. There has always been a search for a m~t~,ri~l which is better than previously known m~tlori~l~ with respect to this relationship, or lower cost, orhaving ~ tion~l advantages along with a similar balance of these plop~"lies.
One ch~a~ tic, in relation to golf balls, not related directly to the playability but to the general utility of a ball, is the ball's durability in use.
Poor durability is manifest in ball cracking, and cracking at low lcll~clalu~s is a particular problem. The properties of the material itself will affect golf ball durability ~ignific~ntly when the m~tPri~l is used for one-piece balls or for golf ball covers. Balata was an early preferred golf ball cover m~ter~,al because it 0 imparted good spin characteristics with some resilience, as well as good Co~ )rei,sion molding characteristics. However Balata covers impart very poor cut resistance to a ball. Ionomers, which generally impart better durability, soon began to take over a significant portion of the market, most particularly for cover m~t~rj~
There are a large number of patents relating to use of ion~-m~rs as golf ball cover m~teri~l~, almost all of which are concerned with ionomer blends. These are based on the disclosure that, for certain desirable characteristics, blends show synergistic behavior over single ionomers. Two distinct types of ionomer blends have been disclosed. The first type of blend is2 0 that of ionomers neutralized with different metals, and the second is that of blends of hard bipolymer ionomers with soft terpolymer ionomers. The second type of blend may also include the first type of blend; that is to say the soft ionomer may use a different metal ion from the hard jonom~r, Illt~ ,c.:~ed with these combinations is the use of a particular acid as the acid comonomer, 2 5 generally methacrylic acid or acrylic acid. In some cases, either of these acids has been disclosed as being p~cr~ d over the other for some particular utility.
In addition, the amount of acid comonomer may have ~l~c~ d limits, with increasing emph~ on high levels of acid to achieve high resilience Examples of these patents or publications include the following.
WO 98/47957 PCT/u~~ll!o~l8 U.S. Patent No.3,819,768 (Molitor) ~ close~l blends of sodium and zinc hard bipolymer ionomers as cover m~hri~l. Zinc was shown to improve durability in terms of 'cold-crack' resistance. Sodium is generally particularly poor with regard to cold-crack durability.
U.S. Patents 4,884,814 (Sullivan) and 5,120,791 (Sullivan), the former t~rmin~lly .li~cl~im~d with respect to the latter, both disclose blends of hard bipolymer and soft terpolymer ionomers, the second patent limiting the softterpolymer ionomer to acrylic acid based ionomer. The hard ionomers are disclosed as sodium or zinc innom~r~, with lithium and m~gn~sium also 0 disclosed in the second patent. The soft ionomers in both are limited to sodiurn and zinc ionomers. The p~cfelled compositions are sodium zinc blends.
Patent publication WO 95/00212, published Jan. 5, 1995 is the published application of a parent case of the present application. It discloses other blends of hard and soft i- nom~r.~ It discloses that the ions used to neutralize soft ionomers may be sodium, zinc, m~gn~si~lm and lithium. No m~gn~ium or lithium soft ionomers are exemplified.
US. Patent No. 5,298,571 (Statz et al.) discloses blends of hard ionom~rs of zinc, lithiurn, sodium and m~ Blends of zinc and lithium hard ionomers of high acid copolymers are disclosed as having optimum 2 0 resilience. The presence of m~gneCiu-m-- was shown to be a disadvantage for obtaining the highest resiliency in any blend with any or all of zinc, lithium and sodium ionomers. The polymers disclosed are very hard however, and do not generally fall within the range of flexibility or co~ cssibility of interest for the polymers of the present invention.
2 5 Ionomers are disclosed for use as one polymer conlpol1e"~ of a filled three polymer blend useful for centers, cores and one-piece golf balls inU.S. PatentNo. S,155,157 (Statz et al.). Both terpolymer and bipolymer iOllCilll~ S, with various metal ions, are rli~close~l for use as part of the polymer blend, but bipolymers are plcr~ d in each type of use. Sodium and lithium ~ 3 0 hard bipolymers are the only polymers exemrlifie~ The ir nnmPr~ form only CA 022~6690 l998-ll-2~
one polymer coll-polle.ll of a three polymer blend which also included a non-ionomer thermoplastic and an ethylene glycidyl monomer copolymer which acts as a comp~tibilizing agent for the other two polymers.
The golf ball industry is highly co~ tilive, and even a small 5 improvement in a golf ball can have a ~i~nific~nt impact. As the art above shows, there are a vast number variables involved in fortn~ tine ionomlor cover m~teri~l.c Di~cprning which particular manipulation of variables can produce even a small, but real advantage is a ~tmting task.
In general, lithium ionomers are harder than sodium or 10 m~gnesium ionomers and zinc produces the softest ionomers. Lithium and m~gl~P~ n hard ionomers are known, and lithium is a preferred hard ionomer for certain uses. Generally, a virtually llnlimit~d number of ionomer compositions is possible, with any metal, either methacrylic or acrylic or othersuitable carboxylic acid, at any level and, for terpolymer ionom~rs, almost every 15 possible softening monomer. Also possible is an equall~ llnlimite~l number of blend possibilities. The number of possible compositions, based on combinations of the above variables is enormous. The number which possess particularly desirable qualities is however far more limited. Soft ionomers using an alkyl acrylate softening monomer, meth~crylic acid or acrylic acid as 2 o the acid, and lithium and ma~ne~ium as the neutralizing ion do not appear to have ever been made prior to the present invention Thus, while broadly disclosed among a vast range of possible ionomers, there has been no recognition that such ionomers were worth making or that they might possess unique properties compared with other ionomers.
There remains a co.~;.. ,;,-g need for soft iorlnm-~rs, particularly for use as covers for golf balls, which provides the playability imparted by a softer m~t~ri~l~ yet which imparts an hll~lov~d level of rç~ n~e comp~Gd with known soft ionomers. There is also a need for such an jonom~r which can impart some of its resili~nce/playability advantage when blended with hard 3 0 ionomers when used as a component in golf balls.
CA 022~6690 1998-ll-2~
SUMMARY OF THE INVENTION
The invention resides in the discovery that lithium and m~ ions used as the ion in soft innnmer~ produce ionc-m~rS which can 5 show a major i~ lease in the level of colll~les~ibility for a given level of re~ilien~e or, conversely, a higher level of resilience for the same coll~ ssibility. This discovery is magnified even more strongly with acrylic acid ionomers than with methacrylic acid ionnm~rs.
Specifically, there is provided a golf ball comprising a core and a 10 cover, the cover consisting essenti~lly of:
a soft, flexible ionomer having a neat-sphere PGA Conll)lession below about l 55, prepared from a terpolymer which is a first acid copolymer of a) ethylene,b) from 3 to 40 weight percent of an alkyl acrylate, the alkyl group having froml to 8 carbon atoms, and c) from 5 to l 5 weight percent of methacrylic acid or 15 acrylic acid, preferably acrylic acid, the ionomer being made by neutralizing 20 to 80 percent of the acid groups of the acid copolymer with m~g~ ~e~ l or lithium ions.
In a further embodiment, the invention provides golf ball covers based on blends of as low as l 0 weight percent of above ionomer, based on the 2 o blend, with a hard ionomer having a flexural modulus of from 40,000 to l l 0,000 psi, prepared from a bipolymer which is an acid copolymer of ethylene and from 5 to 25 weight percent of mPth~r.rylic acid or acrylic acid, or mix of these, the ionomer made by neutralizing 20 to 80 percent of the acid groups of the acid copolymer preferably with m~gnP~ m ions, but also with lithium, 2 5 provided the neat-sphere PGA Co.ll~lession of the blend does not exceed l 55.
In yet a further embo-lim~nt, ma~ne~ m or lithium soft ionomers, as defined above, may be blended with hard ionomer, based on the acid copolymer defined above, but nPu~li7~(1 with sodium ions, provided there is at least 50 percent of soft ionomer to provide a blend having a PGA
3 0 Colll~le~sion which does not exceed lS5.
W O 98/47957 PCT~US98/08318 In yet a further embodiment there is provided a golf ball co...p. ;~ a core and a cover, where the cover compri~ç~ a blend of, (i) 20 - 49 weight percent of a first polymeric component which is an ionomer forrned from a first acid copolymer consisting of 5 a) ethylene, b) 15 - 25 weight percent of an alkyl acrylate or mix of alkyl acrylates, the alkyl groups having from 1 to 8 carbon atoms, and c) 6 - 12 weight percent of acrylic or methacrylic acid or both, the ionomer neutralized to between 10 and 90 % with m~gnPsium ions, and having a flexural modulus of 3000 to 10,000 psi, a Shore 'D' hardness of 45-55, and a melt index of 0.5 to 5.0 g/10 min, and (ii) 51 - 80 weight percent of a second polymeric component which is an ionomer prepared from a second acid copolymer consisting of, a) ethylene, 5 b) 19-25 weight percent of acrylic acid or methacrylic acid or both, the ionomer formed by neutralizing to b~lweel~ 10 to 90 % with sodium, zinc or potassium ions, the ionomer having a flexural modulus of 70 - 110,000 psi, a Shore 'D' hardness of 65 or greater, and a melt index of 0.5 to 5.0 g/10 min.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a plot of PGA Con~ ;.sion versus COR measured on neat-spheres, showing compositions within the invention con.~ d with other composition~. Figure 2 is a similar plot for the same properties, but measured 2 5 on golf balls having the compositions as cover m~tP.ri~l DETAILED DESCRIPTION OF THE INVENTION
This application is a co,.~ n-in-part oftwo applications.
Applic~tion 08/617,061, filedMarch 18, 1996, is one ofthose applic~tinnc CA 022Ct6690 1998-ll-2C
Part of that application is hereby h~cc.l~oldlcd by ~cr~,.c..ce, as part of the present disclosure. Specifically, Figures l ,2,3 and 4 and the description of those figures or drawings on page 4 of that application, as well as the Description ofSpecific Embodiments starting on page 4, and all subsequent pages through page lO. The claims are spe~ ifi~ ~lly excluded from incorporation, since two sets of claims would then be part of the application. Pages l through page 4, line 3, while part of the priority document, are also excluded from incorporation, since information in those pages is subsumed and/or modified to form part of the present cnntinl-~tion-in-part disclosure.
0 In this disclosure, the term copolymer is used to refer to polymers co~ two or more monomers. The term bipolymer or terpolymer refers to monomers cont~ining only two or three monomers respectively. The phrase 'copolymer of' (various monomers) means a copolymer whose units are derived from the various monomers.
The ionomers ofthis invention are p~.~palcd from 'direct' acid copolymers, that is to say copolymers polymeri7.e~1 by reacting all mon--me.r~
simlllt~neously, as distinct from a graft copolymer, where a monomer or other unit is grafted onto an existing polymer, often by a subsequent polymerization reaction. Methods of plc~a~ g ionomers are well known, and are described in 2 0 U.S. Patent No. 3,264,272, (Rees) which is hereby incorporated by reference.
Methods of ~lcp~;llg the acid copolymers on which the ionomers are based is described in U.S. Patent No. 4,35 l ,93 l, which is also inco~ul~lcd by rcrcl~lce hereby.
The m~tPri~l~ of this inventiûn~ while useful fûr other purposes 2 5 are particularly useful as m~t~ c for use as golf ball covers. This disclosure ~mph~i7~s the particular properties of interest in that end use, the excellent properties so revealed showing the uniqueness of these ionomers. In view of the large difference in the particular properties measured from other in~om~rs, it is believed that other characteristics or properties which related to other particular end uses will also be unique, and thus the compositions will, in many cases, be advantageous for other end uses.
There are different types of golf balls, suited to dirr~.~.ll levels of playing skill and playing conditions. One goal has been to ~ .h~ recilier~-~e, 5 since higher rçqili~nce coll~ol,ds to greater driving length. Higher resilienre is associated with harder balls. Softer balls generally have higher playability or spin. A holy grail has always been to have the best of both worlds, high resilience and high spin. Thus if a softer ball could be made with higher reqilienre than hitherto, it would be highly desirable. The present invention is10 directed to softer m~teri~lq, specifically m~gn~qillm and lithium soft ionomers, as well as blends of these with certain hard ionomers. Both these soft ionomers and blends with hard ionomers can be used for golf ball covers with varying hardness levels.
A common measure of r~silience in the golf ball industry is the 15 Coefflcient of Restitution (COR) of the ball. The COR of a 'neat-sphere' of am~t~ l however can be a useful guide to the utility of that material for golf ball use, particularly for one-piece balls, but also to covers and even, to some extent, to the m~t~ri~l's utility as a component of cores, and centers of balls. However, the COR on a ball clearly depends on the nature of the core, and thus careful 2 o choice of the core is n~cess~ry.
Because ~letçrmin~tion of COR has been carried out under a bewildering variety of conditions, comp~ri.qon with much of the patent or other published data, is difficult. For any particular method however, cor. .~ ;.qons of various m~t~ri~lq can be m~nin~fully made using measu.~e.l.c.,l~ on 'neat-2 5 spheres' of the resin. The phrase neat-sphere in this ~liqclos--re means spheres molded from the resin alone, without filler or additive.
A good correlation of 'playability' or 'spin' of a ball may be made using a test referred to as 'PGA Colnples~ion', which is a standard industry test.
It may be carried out on neat-spheres and, like COR, such a ~ l ;on will 3 0 be the best ch~-;le ;~1 ;on of the nature of the m~teri~l itself. Perhaps collru~ingly, high values of the numbers referred to as PGAConll)lei,sion co-le~,ond to high hardness and stiffn~ss, or lower co.lll.r~s~ibility. Use of the word 'Colll~lea~ion' in relation to the PGA test and the general term 'collllne~ibility' should not be confused, since they are inversely related.
The soft ionomers and many of the ionomer blends of this invention will have a PGAColllples~ion value below about 155, based on neat-resin sphere det~min~tions. For softer golfball m~t~ri~l~, values above 155 are generally too high for the m~tt~ri~l to provide balls with good spin. Preferably, the materials have a PGA Colllpression value below about 140. Resins of this 0 invention, with PGA Colllp~es~ion in the 80 to 120 range show the biggest advantage compared with prior art m~tçr~ Materials with higher PGA
Compression values are in general stiffer, higher modulus materials. However it has been found that, of the two soft ionomers which are the basis of this invention, one of these, the soft m~en.osiurn ionomer, is particularly useful even in higher modulus blends.
While there is no precise correlation between flexural modulus and PGA Coll~ression, resins with flexural modulus of 35,000 psi will have a PGACo-llpl~,ssion in the 130 to 160 range. The increased resiliçnre at a given PGAColllpression value seen in the m~t~ri~l~ of this invention may climini~h at PGA values above about 130. For stiffer blends, such as those having a modulus generally above about 35,000 psi, and a PGA colll~ression above about 150 and even considerably higher, m~gnesium soft ionomers blended with sodium, zinc and pul~lSSiu~ll hard ionomers having a flexural modulus of 70,000 to 110,000 psi, and a Shore 'D' Hardness of 65 or greater, form useful harder cover m~t~ri~l~. In such blends, the amount of hard ionomer is from about 51 to 80 weight percent.
As noted, one other quality is always desirable, and often eQ~enti~l, and that is durability of the m~teri~l in golf ball structures. Typically this is measured on a fini~h~ golf ball, having a cover made of the m~tf-ri~l, 3 0 using a l~e~ted impact test, including tests at low le.llp~ e. De~ ion CA 022~6690 1998-11-2~
of durability on a neat-sphere is generally not so definitive because of the inherent toughness of many neat resins. The durability mea,u,~d on spheres con.~i~ting of neat resin and filler would, of course, be relevant for one-pieceballs. Without at least some durability in a fini~he~l ball, high COR and low PGA Con,~lcssion may be almost without value.
It has now been found, surprisingly, that lithium, the ion which makes the hardest and stiffest of all ionomers, all else being equal, is ideallysuited to make an excellent soft ionomer. Magnesium, which also makes one of the harder ion( mers, is also ideally suited to make an excellent soft ionomer.
Soft ionomers of terpolymer acid copolymers neutralized with these ions have now been found to result in a much improved balance between low PGA
Coll.pl~s~ion and high COR resilience conlpaled with prior art materials. Soft lithium are generally plefel.~d over soft m~grl~sium ionomer~ in single ionomer compositions for covers.
These soft ionomers can particularly also form part of a soft ionomer/hard ionomer blend. If the resulting PGA Co~ ssion of the ionomer blend remains below about 155, this will typically, colre.,~ond to a flexural modulus below about 35,000, though it may exceed this slightly. However, certain blends having a higher flexural modulus than this, specifically when the2 o hard ionomer is sodiurn, potassium or zinc and the soft ionomer is m~g have also been found to be particularly useful.
The acid copolymer precursors of the soft ionomers of this invention are copolymers of ethylene, from 3 to 40 weight percent of alkyl acrylate, whose alkyl group has from 1 to 8 carbons, and from 5 to 15 weight 2 5 percent of methacrylic or acrylic acid. The I~cr~ d alkyl acrylate is n-butyl acrylate. It is to be understood that there can be more than one alkyl acrylate and both acrylic and methacrylic acid present, provided the percent limits for alkyl acrylate and acid are met. Por this reason, the generic term copolyrner isused rather than terpolymer, in referring to the claimed compositions, because 3 o terpolymer implies just three mQnOm~r.~ It is also to be understood the acid copolymer may be a blend of difr~ l soft acid copolymers having ~liffPrinp levels arld/or species of either the softening comonomer, the acid or both. The term 'soft acid copolymer', 'soft flexible innorner' and the like, enco,..l.~qees this possibility. Many pl~ ione of copolymers are sufficiently non-ulfirul"l in com- nnmPr content from molecule to molecule that such 'copolymers' are, in effect, blends anyway.
Below 3% softening comonomer insllff1cient softening (modulus recluçtic-n) occurs, and above 40% the polymer and resultant ionom~r is too soft.
From lO to 30 percent weight is preferred and lS to 25 weight percent is most o pre~lled. Acrylic acid in the soft acid copolymer leads to somewhat more resilient soft ionomers, and is generally preferred.
For soft ionomers and hard ionomers which form blends of the present invention of the percent neutralization of the acid groups present for m~gne~Sillm or lithium ions, or both, is from l O to 90, preferably from 20 to 80%. More preferably the level is from 25 to 65% and most preferably from 30 to 60%. For soft ionomers, the modulus will typically be about 5000 to 35,000 psi. The modulus will be higher for lithium than m~gn~eium, and will increase with the level of acid. The modulus will be lower the higher the amount of alkyl acrylate. The modulus of the soft lithium and m~En~Sillm ionomers 2 o p~ ed here, ranged from about 5000 to 27000 psi, but it is readily possible to prepare m~gJ~Sium and lithium terpolymer ionom~r.~ with a modulus up to 35,000 psi, and even higher. Certain terpolymer ionomer compositions can be made, such ~ ones with very high acid, particularly acrylic acid, using lithium ions and with low amounts of alkyl acrylate which will give higher than 35,000 2 5 psi flexural modulus. However, provided the PGA Coll.p-es~ion of neat-spheres of the soft io~- m~r.q is below about l 55, it will be suitable. It is readily within the skill of the artisan to d~ .i t,c which combinations of mo~
n-olltrali7~tion level and acid type will produce ion~-m~r within the required neat-sphere PGA Col-.plession limits.
CA 02256690 l998-ll-25 In the prior art, it has been common often to refer to 'soft' ionom~rs as possçs~eing a flexural modulus below about lO,000 psi and to 'hard' i(~n~ .s as those with modulus above about 30,000 psi. In this disclosure, the terpolymer ionomers with a softening alkyl acrylate termonom~r are still 5 Icr~red to as 'soft' even when the flexural modulus is much higher As noted above, the soft ionomere of this invention can have a flexural modulus of 35,000, and even in some cases above this.
Typically, to achieve modulus values in the region of 35,000 psi, so that the neat-sphere PGA Compression of the ionomer is as high as l 55, 10 using prior art soft ionomers such as zinc or sodium soft ionomers it would generally be necessary to blend with a hard ionomer. However, it can be seen from the modulus values in Table l, that when lithium and m~gn~Sium are the neutralizing ions, the flexural modulus values can be considerably higher than those of old art zinc and sodium soft ionomers. For this reason, soft ionomers 5 of the present invention are useful alone, even though they may be blended with hard ionomers, as herein defined. The reeilienre advantage at a given PGA
Col,.plession value in the soft ionom~re however, could mean that higher ~liLLIe~s soft ionomers alone would give as good properties as blends of co,..~ ble ~I;rr.,~s~. Blending however can offer cost and various other 2 o advantages, and in practice, often as much hard ionomer as possible, conro~ with a given level of overall stiffn~-ee has been ~rere~ d in the past.
Blending with hard ionomers could however dilute the re,eili~nre advantage at a given PGA Coll.l lession value that these unique soft ionomPrs offer.
For cover material, the modulus should be preferably above 2 5 lO,000 psi. and more preferably above 15,000, h.~e.,li~e of whether using asingle soft ionomer or a soft/hard ionomer blend. When the soft ionomer has a modulus much below lO,000 psi, for cover m~tlori~l.e it is therefore preferable to blend with a hard ionomer so the final modulus falls within the range lO,000 to 35,000 psi when using lithium and m~ .... hard ion- mrrs , .. . .
CA 022~6690 1998-ll-2~
With sodium, zinc and potassium hard ionomPrs, the modulus may be above 35,000 psi.
When the soft i- nnmer is blended with hard ionomer, there should be at least l 0 percent soft ionomer, preferably above 20 percent, or the5 advantages of the particular soft ionomers of this invention will not be reali~d, or will be con.~ider~hly diluted.
The hard ionomers which may be blended with the soft ionomers are lithium, m~gn~ium, sodium, zinc or potassium ionomers. They are derived from acid copolymers of ethylene and, in the case of lithium and m~gJ~4iulll 0 hard ionomers, from 5 to 25 weight percent acid where the acid is m~th~ rylic or acrylic acid, or both, preferably from l 0 to 22 weight percent. In the case of sodium, potassium or zinc hard ionomers, the acid level is preferably l 9 to 25 weight percent. It is to be understood that the hard ionomer may be a blend of more than one hard ionomer each having different levels of and/or dirr~e,lt 5 acids in them, just as for the soft ionomer. The term 'hard acid copolymer', and 'hard stiff ionomer' and the like, encomp~s~s this possibility.
When the composition is a hard ionomer/soft ionomer blend, it is preferable for the hard ionomer to have a higher level of acid than the soft ionomer. Higher acid increases the hardness, so that to produce a blend having 2 o a specific final blend modulus, the higher the acid level in the hard ionomer, the less of it will be required in the blend. The modulus may range from 40,000 to l l0,000 psi. In the case of sodium, zinc and potassium hard ionome~s, the modulus ranges from 70 to l l0,000 psi. In general, when the conlposilion is a blend co~ i.-g hard ionomer, the harder or higher modulus the hard ionom~r, 2 5 whether due to acid level, acid type, neutralizing ion or degree of neutralization, the greater the amount of soft jonom~r possible in the blend, for a given final blend modulus. Since it is the softer terpolymer ionomers which are here clearlyshown to have such an attractive balance of PGA Coll~p.e.,~ion and COR, it may be that the more m~,~ -.. or lithium soft ionomer, the higher the resilience, at3 0 a given PGA Co-~ ,ssion level.
Melt index of either the soft or hard ioïlon~ can be from about O.l to 30 g/lO min., preferably O.l to lO more preferably from O.l to 6 and mostpreferably from 0.5 to 5 .0 g/l 0 min. The melt index of the acid copolymers from which the ionom~s are derived may be from about 20 to 350 g./lO min.
When the compositions of the invention are blends, the p-er~ ,d blends for softer cover m~teri~l.e are lithium soft/m~nesillm hard. l~n~sium/
m~pn~sium and lithium/lithium blends are also attractive. Magnesium soft/lithium hard blends are generally less preferred, and one such blend showeda r1imini~hPd resilience advantage compared with the reverse blend. It is not 0 clear why this should be so. However, the pler~ ,d soft resins, and those used in the elr~mrles, have less acid than the hard resins. Therefore, for a given percent of acid groups neutralized they will have less equivalents of metal present. Thus the number of equivalents of lithium in m~neS;um soft/lithium hard blends will be higher, when there is more acid in the hard ionomer, than inlithium soft/magn~sium hard blends. For blends cont~inin~ both lithium and m~n~sium ions thc.~r~le, it seems that a higher level of m~
equivalents is preferable.
As noted, the hard ionomer may also be a sodium, potassium or zinc ionomer. In the case of zinc and potassium hard ionnmPrs, the amount of 2 o hard ionomer is, by contrast to lithium and m~gn~ium hard ionomers, b~
5 l and 80 weight percent.
It has commonly been ~nme(l that ions in an ionom~r blend are almost comrlet~ly labile, and move freely from polymer chain to polymer chain.
Tllis may be true for a blend of two ionomers based on the sarne acid 2 5 copolymer. However, without c(s""";l",~ ~~t in any particular way, it may not be comrletely true in blends where the underlying acid copolymers of the two ionomers are very dirr~l~,.lt, such as with soft and hard i- n~m~rs. Of course, this will be of no consequence if the metal of the soft and hard ionomer are thesame. It may be of more consequence when the ions are dirr~ . The ions 3 o l~rigin~lly associated with the soft ionomer, may, to some extent, tend to remain CA 022.,6690 1998 - 1 1 - 2., more associated with the soft ionomer in a blend, and this may produce blends with dif~e.lL properties than blends having the reverse ions in the soft and hard components. However, when the underlying acid copolymer is di~~ it may merely mean that higher hlt. .~ / blending is required, such as very high shear extrusion blen~li~, to achieve random distribution of ions throughout the whole composition. In any event, in practice, it has been found that there is a dirr~ ce in properties in soft/hard blends, when the ions for the soft and hard ionomer are reversed.
The ionomers may also contain conv~lional additives such as pigm~nt~, antioxidants, U.V. absorbers, bright~n~r~ and the like.
Testin~e Methods and Criteria.
Flexural modulus is measured using ASTM D790-B, and is measured using a standard 'flex bar' and not on a sphere of m~t~ri~l as for mostother tests.
Coefficient of ~stitlltion~ COR, was measured both on neat-spheres and on fini~he~l balls having a cover of the m~t~ri~l under test. It is measured by firing, either a covered ball having an the ionomer composition as cover or a neat-sphere of the i~-n~m~.r composition, from an air cannon at an initial speed of l 80 ft./sec. as measured by a speed monitoring device over a 2 o tli~t~nce of 3 to 6 feet from the cannon. The ball strikes a steel plate positioned 9 feet away from the cannon, and rebounds through the speed-monit--ring device. The return velocity divided by the initial velocity is the COR.
COR of neat-spheres may fall anywhere b~lwee~ 0.50 and 0.70.
The range on useful covered balls of this invention however, is bet~ about 0.67 and 0.74.
PGA G~ .ession is defined as the lei;~ ce to defom~tion of a golf ball, measured using a standard industry ATTI m~ ne It was measured on a neat-sphere of resin and on balls having a cover of resin. For adequate spin of a ball, when the ionomer is used as a cover Jn~t~ri:~l, the PGA Co...~.e;,;,ion, ]"$g'~'9 S Toêa(o'ZAS ~' ;UI~;TvUIvû~2Lyj-?zS!PêVa!l/uïo;py!A ~Ll Z ~¢NÇKu,àN~E yOOe;ÇOAlIv?~ 3~~~ûh'~E9ï
Durability was measured using a repeat impact test on fini~h~
balls, with the material of the invention as the cover, on a Wilson Ultra'!3 conv~ ;nn~l solid core. Such cores are believed to be made of 1,4-cis polybllt~ n~ cro~linked with peroxides and co-cro~slinking agents such as zinc (meth)acrylate. Durability is measured using the same m~c.~lin~ as for COR, but using an initial velocity of 175 ft./sec. Durability values are the number of hits to break. Durability at low tcn~ laLure3 is especially desirable,and for this reason, durability tests at -20 ~ F were carried out. While good durability only at room lelllpclal~uc is adequate for golf balls used in some 0 locales, low tell~cla~ule durability values, preferably above at least 10, as tested under these conditions, is prer~ d for cold weather use. Durability at room ten~lalule is almost invariably better than durability at -20~F, so that low telllpeldlure durability is a guide to the worst perform~nce to be expected.
Good durability of a m~teri~l, based on tests when the material is used as a cover, may indicate good durability for use as a m~t~ri~l in a one-piece ball.
EXAMPLES.
Table 1 lists various ionomers used in the examples. The list includes soft ionomers which are part of the invention as well as soft ionomers 2 o which are not. It also includes hard ionnm.ors which can be part of a blend of this invention as well as hard ionomers which are not. Flexural modulus is shown, if measured. Note that S8 has a mnd~ of almost 27,000 psi. This is stiff enough even to make a relatively stiff cover m~teri~l by itself, i.e., without blending with a hard ionomer.
2 5 Table 2 lists values of COR and PGA Co~ ,sion on neat-spheres for the compositions indicated. Coln~ali~e examples are numbered with a suffix C. The same values are plotted in Figure 1. Durability of balls which employed the compositions as a cover on a conventinn~l solid core are also shown, if measured.
wo 98/47957 PCT/u~ j8/0~3l8 Figure l shows co~ live examples, outside the invention, indicated by a circle, and examples by a cross. A line is shown, correlating PGA C~ ~ei,~ion and COR values for prior art materials outside this invention, based on previous data (in~lir~t~d by triangles), de~ ;..çd prior to this 5 investigation, together with data on prior art m~t~ri~l~ measured during the present inve.sfig~tion (in-lic~ted by a circle). The line is a 'visually best-fit' line, and is based on materials which differed in their ion or ions, their MI, the acid used (whether acrylic of methacrylic), the amount of acid and, in the case of soft ionomer, the amount of acrylate softening monomtor. The line is a good fit for 10 data up to a PGA Co~ ession of about 140. Above this, there appears to be a poorer correlation with more scatter in the data. Of course, the new soft lithium and m~enesium innomer~ and blends, whether part of this invention or not, are not part of the data on which the line is based, since they are new ionnmçr~.
The fact that such a line can be drawn suggests that, for most 5 ionomers and blends, PGA Compression and COR are uniquely related, largely irrespective of comonomer or ion composition, and depend ess~nti~lly only on the particular level of stiffn~ss of interest. This is except, of course, for the compositions of the present invention.
Surprisingly, when one ~minlos the data for soft ionom~.rs of 2 o m~en.o~ium and lithium, and blends of these ionomers with hard ionomers, there is a dramatic shift to the right or to lower PGA values depending on the axis chosen for comp~ri.~on. Thus, for these soft innnmPrs, and blends cn..l~;ni.~g ~ these soft ionom~rs, there is ap,o~ lly a resilience advantage at a given PGA
Cu~ re;.sion level and vice versa. This will tr~n~l~te to, at the worst equivalent 2 5 or slightly better, but generally signific~ntly better compositions for one-piece balls, and for centers and cores and covers for two- or three-piece balls re~e~live;ly, than previously known compositit~ . Of course the degree of advantage will depend on which of these golf ball appliç~tionc is considered.
Zinc has long been known to provide good durability at low 3 0 t~ ,.dlUI~ s, and compositions of co",p&l~liv~ examples which contain zinc are . , , WO 98/47957 PCT/u~i8lo83lx clearly good in low tclllpcl~ durability as seen from Table 2. Both zinc and sodium soft ionomer~ alone, generally will have a flexural modulus of 5,000 psi or less however. In general, this will be too flexible to be useful alone for use as m~t~ri~l~ of this invention. Zinc hard ionomer blended with lithium soft 5 ionomer does seem to provide good compositions when the PGA Col"~l~;s~ion is above about 140. However, as noted above, the singularity ofthe correlation becomes less definite at high PGA values.
Sodium hard ionomer is known to provide poor low t~ e.~ e durability (example 2C and blend 3C). However it can form the hard ionomer o portion of blends (example 7), provided there is not more than 50 percent of it.
Lithium soft ionomer is not particularly durable at low lc~pc~al~lres (example 2) though not nearly as poor as sodiurn (2C). However its effect on increasing COR at a given PGA level in lithium soft ionomer or in blends of this invention can provide good compositions in this respect.
15 ~gn~ m ionomer as the hard segmlont provides excellent durability.
~gn~ lm soft/magnesium hard blends can thus provide excellent overall compositions (see ~Y~mrle 8).
For use of the m~t~ri~l for golf ball covers, using conventional cores, the advantage can show up in the PGA Compression and COR of the 2 o resulting ball itself. However, because the overall PGA Co",plession and CORis also dependent on the core, not just the cover, the PGA/COR improvement may be somewhat rlimini~hPcl in some cases. Different cores provide somewhat di~e.~ PGA Compression/COR correlations, so that manipulation of core alone can lead to improved balls. Comp~ri~on of cover m~te~ must be 2 5 made on balls which use the same core. As noted above, the rçl~tinn~hir bcl~ ~.n PGA Co~ ession and COR for golf balls provides a line or lines which is shifted far from that observed for neat-spheres.
Table 3 shows PGA Col,~,ei,~ion and COR values measured on golf balls having a Wilson Ultra~ core, and a cover of the m~t~ having the 3 0 composition as indicated by the co,,c~ollding çy~mrle number in Table 2. In Figure 2, the encircled crosses r~pl~selll fini~hP(l ball PGA C~ r~ ion and COR values with prior art covers, and the crosses alone rel.reselll values usingcover m~ttori~l~ ofthe invention. The line drawn is a 'visually-best' line, but there are in~llfflcient data at low PGA values to establish the line with great s cc;ll~illly. It can be seen that, while covers made with soft innom~rs alone, which give PGA values in the 78-81 range, appear to show only a small improvement, if any, when blends are tested, giving PGA in the 83-94 range, the hllpl'uvt;lllent, for the most part is dramatic. It is not clear why e~r~mr'e- 7(PGA 94) shows such a low COR value, and why example 8 (also PGA 94) 0 shows only a small improvement. Nevertheless, it is clear that a dramatic improvement is possible.
.
WO 98147957 Pcr/uss8lo83l8 COMPOSITION OF IONOMERS
# Composition M~nr)m~r MI Ion Neutr Flex Ratios Modulus (%)-S 1 E/nBA/MAA 68l2319 0.6 Zn ~50~2700 S2 E/nBA/MAA 6812319 Na ~504100 S3 E/nBA/MAA 6812319 Mg ~507100 S4 E/nBA/MAA 68123l9 Li ~505000 SS E/nBA/AA 7012218 1.9 Mg ~457800 S6 E/nBA/AA 7012218 0.4 Li ~759500 S7 E/nBA/AA 69.4/18/11.6* 1.6 Mg ~45 16700 S8 E/nBA/AA 69.4/18/11.6* 0.5 Li ~75 26500 Hl E/MAA 80/20 ~1 Na ~79000 H2 E/MAA 85/15 ~1 Na ~5750000 H3 E/MAA 85/15 ~1 Zn ~5748000 H4 E/MAA 85/15 ~1 Mg ~50 H5 E/MAA 85/15 ~4 Li ~50 H6 E/MAA 81/19 ~4 Li ~50 H7 E/MAA 85/15 ~4 Mg ~50 H8 E/MAA 85/15 ~1 Li ~50 H9 E/MAA 80/20 ~1 Mg ~50 H10 E/AA 80/20 ~1 Mg ~50 E = Ethylene, MAA = Methacrylic acid, AA = Acrylic acid, nBA = n-Butyl Acrylate.
Flexural Modulus values in psi.
1 0 Ne~-tr~li7~tiQn values are based on the amount of neutralizing ion in the feed when making the ionomer, ~ it~g complete innnm~i7~tion-$ These comonomer co~lLellL~ are based on best data available. Some uncnnfirm~d data have suggested these comonomer conl~ may be slightly in error.
~
CA 022~6690 1998-11-2~
.
PGA COMPRESSION AND COR OF IONOMER COMPOSITIONS
Ex.# Composition Blend COR PGA Durability Ratio Co.~ e;,~lon Hits/Crack -20~F
lC Sl - 0.511 58 2C S2 - 0.553 67 S3 - 0.593 86 28 2 S4 - 0.584 83 8 3 S5 - 0.618 95 25 4 S6 - 0.656 116 S7 - 0.621 126 6 S8 - 0.672 144 3C Sl/H1 50/50 0.637 140 7 4C S1/H2 50/50 0.645 143 48 5C S2/H3 50/50 0.619 132 50 6C S3/H3 50/50 0.602 127 50 7C S4/H3 50/50 0.621 133 38 8C S5/H3 50/50 0.619 131 50 9C S6/H3 50/50 0.645 139 47 10C S7/H3 75/25 0.618 135 50 1 lC S8/H3 75/25 0.674 148 26 12C S3/H3 75/25 0.590 109 7 S3/H2 50/50 0.645 130 22 8 S3/H4 50/50 0.641 136 50 9 S3/H5 50/50 0.647 142 8 S3/H6 50/50 0.654 146 14 I l S3/H7 75/25 0.620 117 15 13C S1/H2 50/50 0.650 143 50 12 S4/H4 50/50 0.644 141 45 13 SS/H8 50/50 0.638 142 5 14 S5/H4 50/50 0.634 138 50 S6/H9 50/50 0.668 147 44 16 S6/H10 50/50 0.633 132 7 ~ 17 S6/H9 75/25 0.655 126 50 .. . .
PGA COMPRUESSION A~nD COR OF GOLF BALLS
(Cover con~osilion as in Table 2, Ul~a~ Core) s Ex.# COR PGA Co~ .on 1 0.678 79 2 0.673 81 3 0.672 78 7 0.687 94 8 0.681 94 13C 0.693 90 12 0.708 83 13 0.709 87 14 0.711 88 0.714 89 16 0.708 86 17 0.708 85 *rB
. . .
3 o Ionomers with a third monomer exemplified included ethylene/vinyl CA 022~6690 1998-11-2~
acetate/methacrylic acid neutralized with sodium and m~gn~sium, and ethylene/methyl methacrylate/methacrylic acid neutralized with sodium.
The use of 'soft', flexible ionomers, softened by such a third m~ m.-.r, only became of commercial interest around 1987. Alkyl acrylates 5 are the preferred softening monomers, vinyl acetate producing a less stable polymer. The employment of n-butyl acrylate as a softening monomer in terpolymer ionomers is disclosed in U.S. Patent No. 4,690,981 (Statz). This patent lists the possible neutralizing ions as those of groups Ia, Ib, IIa, IIb, IIIa, IVa, VIb and VIII of the periodic table, such as Na, K, Zn, Ca, Mg, Li, Al, Ni 0 and Cr.
U.S. PatentNo. 5,415,939 (~domig~ etal.), filed 12/21/93, çloses soft lithium ionomers and blends of such ionomers with hard ionomers. The parent case of which this present application is a continll~tion-in-part, which was filed 6/18/93, (i.e., prior to this reference), discloses lithium 15 and m~gnesium soft ionomers and blends with hard ionomers.
Many other patents have referred to bipolymer and terpolymer ionc mPr.s of various metals, also in a general way. No terpolymer ionomer using an alkyl acrylate with (meth)acrylic acid and neutralized with either lithium or m~gnesium is known to have been specifically disclosed or 2 o exemplifie~ References to them are merely of the shotgun type, such as those described above.
Golf balls have certain me~cur~hle properties which, directly, strongly affect play characteristics. Most hn~oll~,t ofthese are resilienre and colllplcssibility. High resilience increases the length a golf ball can be driven 2 5 and colllplcssibility increases the playability in terms of 'spin' and 'feel'.
pcesiliPnce and colllpressibility can be measured for the m~teri~l itself, by testing a sphere of the m~t~ri~l. These m~tPri~l properties can affect golf ball play characteristics when used to form the cover of a ball. For ionomers these two ~lo~,.lies, resilience and ccn~lessibility, tend to be inversely related. Thus a3 o highly resilient m~t~.ri~l is generally a harder, less con~ ible m~tP.ri~l, and CA 022~6690 1998-11-2~
vice versa. There has always been a search for a m~t~,ri~l which is better than previously known m~tlori~l~ with respect to this relationship, or lower cost, orhaving ~ tion~l advantages along with a similar balance of these plop~"lies.
One ch~a~ tic, in relation to golf balls, not related directly to the playability but to the general utility of a ball, is the ball's durability in use.
Poor durability is manifest in ball cracking, and cracking at low lcll~clalu~s is a particular problem. The properties of the material itself will affect golf ball durability ~ignific~ntly when the m~tPri~l is used for one-piece balls or for golf ball covers. Balata was an early preferred golf ball cover m~ter~,al because it 0 imparted good spin characteristics with some resilience, as well as good Co~ )rei,sion molding characteristics. However Balata covers impart very poor cut resistance to a ball. Ionomers, which generally impart better durability, soon began to take over a significant portion of the market, most particularly for cover m~t~rj~
There are a large number of patents relating to use of ion~-m~rs as golf ball cover m~teri~l~, almost all of which are concerned with ionomer blends. These are based on the disclosure that, for certain desirable characteristics, blends show synergistic behavior over single ionomers. Two distinct types of ionomer blends have been disclosed. The first type of blend is2 0 that of ionomers neutralized with different metals, and the second is that of blends of hard bipolymer ionomers with soft terpolymer ionomers. The second type of blend may also include the first type of blend; that is to say the soft ionomer may use a different metal ion from the hard jonom~r, Illt~ ,c.:~ed with these combinations is the use of a particular acid as the acid comonomer, 2 5 generally methacrylic acid or acrylic acid. In some cases, either of these acids has been disclosed as being p~cr~ d over the other for some particular utility.
In addition, the amount of acid comonomer may have ~l~c~ d limits, with increasing emph~ on high levels of acid to achieve high resilience Examples of these patents or publications include the following.
WO 98/47957 PCT/u~~ll!o~l8 U.S. Patent No.3,819,768 (Molitor) ~ close~l blends of sodium and zinc hard bipolymer ionomers as cover m~hri~l. Zinc was shown to improve durability in terms of 'cold-crack' resistance. Sodium is generally particularly poor with regard to cold-crack durability.
U.S. Patents 4,884,814 (Sullivan) and 5,120,791 (Sullivan), the former t~rmin~lly .li~cl~im~d with respect to the latter, both disclose blends of hard bipolymer and soft terpolymer ionomers, the second patent limiting the softterpolymer ionomer to acrylic acid based ionomer. The hard ionomers are disclosed as sodium or zinc innom~r~, with lithium and m~gn~sium also 0 disclosed in the second patent. The soft ionomers in both are limited to sodiurn and zinc ionomers. The p~cfelled compositions are sodium zinc blends.
Patent publication WO 95/00212, published Jan. 5, 1995 is the published application of a parent case of the present application. It discloses other blends of hard and soft i- nom~r.~ It discloses that the ions used to neutralize soft ionomers may be sodium, zinc, m~gn~si~lm and lithium. No m~gn~ium or lithium soft ionomers are exemplified.
US. Patent No. 5,298,571 (Statz et al.) discloses blends of hard ionom~rs of zinc, lithiurn, sodium and m~ Blends of zinc and lithium hard ionomers of high acid copolymers are disclosed as having optimum 2 0 resilience. The presence of m~gneCiu-m-- was shown to be a disadvantage for obtaining the highest resiliency in any blend with any or all of zinc, lithium and sodium ionomers. The polymers disclosed are very hard however, and do not generally fall within the range of flexibility or co~ cssibility of interest for the polymers of the present invention.
2 5 Ionomers are disclosed for use as one polymer conlpol1e"~ of a filled three polymer blend useful for centers, cores and one-piece golf balls inU.S. PatentNo. S,155,157 (Statz et al.). Both terpolymer and bipolymer iOllCilll~ S, with various metal ions, are rli~close~l for use as part of the polymer blend, but bipolymers are plcr~ d in each type of use. Sodium and lithium ~ 3 0 hard bipolymers are the only polymers exemrlifie~ The ir nnmPr~ form only CA 022~6690 l998-ll-2~
one polymer coll-polle.ll of a three polymer blend which also included a non-ionomer thermoplastic and an ethylene glycidyl monomer copolymer which acts as a comp~tibilizing agent for the other two polymers.
The golf ball industry is highly co~ tilive, and even a small 5 improvement in a golf ball can have a ~i~nific~nt impact. As the art above shows, there are a vast number variables involved in fortn~ tine ionomlor cover m~teri~l.c Di~cprning which particular manipulation of variables can produce even a small, but real advantage is a ~tmting task.
In general, lithium ionomers are harder than sodium or 10 m~gnesium ionomers and zinc produces the softest ionomers. Lithium and m~gl~P~ n hard ionomers are known, and lithium is a preferred hard ionomer for certain uses. Generally, a virtually llnlimit~d number of ionomer compositions is possible, with any metal, either methacrylic or acrylic or othersuitable carboxylic acid, at any level and, for terpolymer ionom~rs, almost every 15 possible softening monomer. Also possible is an equall~ llnlimite~l number of blend possibilities. The number of possible compositions, based on combinations of the above variables is enormous. The number which possess particularly desirable qualities is however far more limited. Soft ionomers using an alkyl acrylate softening monomer, meth~crylic acid or acrylic acid as 2 o the acid, and lithium and ma~ne~ium as the neutralizing ion do not appear to have ever been made prior to the present invention Thus, while broadly disclosed among a vast range of possible ionomers, there has been no recognition that such ionomers were worth making or that they might possess unique properties compared with other ionomers.
There remains a co.~;.. ,;,-g need for soft iorlnm-~rs, particularly for use as covers for golf balls, which provides the playability imparted by a softer m~t~ri~l~ yet which imparts an hll~lov~d level of rç~ n~e comp~Gd with known soft ionomers. There is also a need for such an jonom~r which can impart some of its resili~nce/playability advantage when blended with hard 3 0 ionomers when used as a component in golf balls.
CA 022~6690 1998-ll-2~
SUMMARY OF THE INVENTION
The invention resides in the discovery that lithium and m~ ions used as the ion in soft innnmer~ produce ionc-m~rS which can 5 show a major i~ lease in the level of colll~les~ibility for a given level of re~ilien~e or, conversely, a higher level of resilience for the same coll~ ssibility. This discovery is magnified even more strongly with acrylic acid ionomers than with methacrylic acid ionnm~rs.
Specifically, there is provided a golf ball comprising a core and a 10 cover, the cover consisting essenti~lly of:
a soft, flexible ionomer having a neat-sphere PGA Conll)lession below about l 55, prepared from a terpolymer which is a first acid copolymer of a) ethylene,b) from 3 to 40 weight percent of an alkyl acrylate, the alkyl group having froml to 8 carbon atoms, and c) from 5 to l 5 weight percent of methacrylic acid or 15 acrylic acid, preferably acrylic acid, the ionomer being made by neutralizing 20 to 80 percent of the acid groups of the acid copolymer with m~g~ ~e~ l or lithium ions.
In a further embodiment, the invention provides golf ball covers based on blends of as low as l 0 weight percent of above ionomer, based on the 2 o blend, with a hard ionomer having a flexural modulus of from 40,000 to l l 0,000 psi, prepared from a bipolymer which is an acid copolymer of ethylene and from 5 to 25 weight percent of mPth~r.rylic acid or acrylic acid, or mix of these, the ionomer made by neutralizing 20 to 80 percent of the acid groups of the acid copolymer preferably with m~gnP~ m ions, but also with lithium, 2 5 provided the neat-sphere PGA Co.ll~lession of the blend does not exceed l 55.
In yet a further embo-lim~nt, ma~ne~ m or lithium soft ionomers, as defined above, may be blended with hard ionomer, based on the acid copolymer defined above, but nPu~li7~(1 with sodium ions, provided there is at least 50 percent of soft ionomer to provide a blend having a PGA
3 0 Colll~le~sion which does not exceed lS5.
W O 98/47957 PCT~US98/08318 In yet a further embodiment there is provided a golf ball co...p. ;~ a core and a cover, where the cover compri~ç~ a blend of, (i) 20 - 49 weight percent of a first polymeric component which is an ionomer forrned from a first acid copolymer consisting of 5 a) ethylene, b) 15 - 25 weight percent of an alkyl acrylate or mix of alkyl acrylates, the alkyl groups having from 1 to 8 carbon atoms, and c) 6 - 12 weight percent of acrylic or methacrylic acid or both, the ionomer neutralized to between 10 and 90 % with m~gnPsium ions, and having a flexural modulus of 3000 to 10,000 psi, a Shore 'D' hardness of 45-55, and a melt index of 0.5 to 5.0 g/10 min, and (ii) 51 - 80 weight percent of a second polymeric component which is an ionomer prepared from a second acid copolymer consisting of, a) ethylene, 5 b) 19-25 weight percent of acrylic acid or methacrylic acid or both, the ionomer formed by neutralizing to b~lweel~ 10 to 90 % with sodium, zinc or potassium ions, the ionomer having a flexural modulus of 70 - 110,000 psi, a Shore 'D' hardness of 65 or greater, and a melt index of 0.5 to 5.0 g/10 min.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a plot of PGA Con~ ;.sion versus COR measured on neat-spheres, showing compositions within the invention con.~ d with other composition~. Figure 2 is a similar plot for the same properties, but measured 2 5 on golf balls having the compositions as cover m~tP.ri~l DETAILED DESCRIPTION OF THE INVENTION
This application is a co,.~ n-in-part oftwo applications.
Applic~tion 08/617,061, filedMarch 18, 1996, is one ofthose applic~tinnc CA 022Ct6690 1998-ll-2C
Part of that application is hereby h~cc.l~oldlcd by ~cr~,.c..ce, as part of the present disclosure. Specifically, Figures l ,2,3 and 4 and the description of those figures or drawings on page 4 of that application, as well as the Description ofSpecific Embodiments starting on page 4, and all subsequent pages through page lO. The claims are spe~ ifi~ ~lly excluded from incorporation, since two sets of claims would then be part of the application. Pages l through page 4, line 3, while part of the priority document, are also excluded from incorporation, since information in those pages is subsumed and/or modified to form part of the present cnntinl-~tion-in-part disclosure.
0 In this disclosure, the term copolymer is used to refer to polymers co~ two or more monomers. The term bipolymer or terpolymer refers to monomers cont~ining only two or three monomers respectively. The phrase 'copolymer of' (various monomers) means a copolymer whose units are derived from the various monomers.
The ionomers ofthis invention are p~.~palcd from 'direct' acid copolymers, that is to say copolymers polymeri7.e~1 by reacting all mon--me.r~
simlllt~neously, as distinct from a graft copolymer, where a monomer or other unit is grafted onto an existing polymer, often by a subsequent polymerization reaction. Methods of plc~a~ g ionomers are well known, and are described in 2 0 U.S. Patent No. 3,264,272, (Rees) which is hereby incorporated by reference.
Methods of ~lcp~;llg the acid copolymers on which the ionomers are based is described in U.S. Patent No. 4,35 l ,93 l, which is also inco~ul~lcd by rcrcl~lce hereby.
The m~tPri~l~ of this inventiûn~ while useful fûr other purposes 2 5 are particularly useful as m~t~ c for use as golf ball covers. This disclosure ~mph~i7~s the particular properties of interest in that end use, the excellent properties so revealed showing the uniqueness of these ionomers. In view of the large difference in the particular properties measured from other in~om~rs, it is believed that other characteristics or properties which related to other particular end uses will also be unique, and thus the compositions will, in many cases, be advantageous for other end uses.
There are different types of golf balls, suited to dirr~.~.ll levels of playing skill and playing conditions. One goal has been to ~ .h~ recilier~-~e, 5 since higher rçqili~nce coll~ol,ds to greater driving length. Higher resilienre is associated with harder balls. Softer balls generally have higher playability or spin. A holy grail has always been to have the best of both worlds, high resilience and high spin. Thus if a softer ball could be made with higher reqilienre than hitherto, it would be highly desirable. The present invention is10 directed to softer m~teri~lq, specifically m~gn~qillm and lithium soft ionomers, as well as blends of these with certain hard ionomers. Both these soft ionomers and blends with hard ionomers can be used for golf ball covers with varying hardness levels.
A common measure of r~silience in the golf ball industry is the 15 Coefflcient of Restitution (COR) of the ball. The COR of a 'neat-sphere' of am~t~ l however can be a useful guide to the utility of that material for golf ball use, particularly for one-piece balls, but also to covers and even, to some extent, to the m~t~ri~l's utility as a component of cores, and centers of balls. However, the COR on a ball clearly depends on the nature of the core, and thus careful 2 o choice of the core is n~cess~ry.
Because ~letçrmin~tion of COR has been carried out under a bewildering variety of conditions, comp~ri.qon with much of the patent or other published data, is difficult. For any particular method however, cor. .~ ;.qons of various m~t~ri~lq can be m~nin~fully made using measu.~e.l.c.,l~ on 'neat-2 5 spheres' of the resin. The phrase neat-sphere in this ~liqclos--re means spheres molded from the resin alone, without filler or additive.
A good correlation of 'playability' or 'spin' of a ball may be made using a test referred to as 'PGA Colnples~ion', which is a standard industry test.
It may be carried out on neat-spheres and, like COR, such a ~ l ;on will 3 0 be the best ch~-;le ;~1 ;on of the nature of the m~teri~l itself. Perhaps collru~ingly, high values of the numbers referred to as PGAConll)lei,sion co-le~,ond to high hardness and stiffn~ss, or lower co.lll.r~s~ibility. Use of the word 'Colll~lea~ion' in relation to the PGA test and the general term 'collllne~ibility' should not be confused, since they are inversely related.
The soft ionomers and many of the ionomer blends of this invention will have a PGAColllples~ion value below about 155, based on neat-resin sphere det~min~tions. For softer golfball m~t~ri~l~, values above 155 are generally too high for the m~tt~ri~l to provide balls with good spin. Preferably, the materials have a PGA Colllpression value below about 140. Resins of this 0 invention, with PGA Colllp~es~ion in the 80 to 120 range show the biggest advantage compared with prior art m~tçr~ Materials with higher PGA
Compression values are in general stiffer, higher modulus materials. However it has been found that, of the two soft ionomers which are the basis of this invention, one of these, the soft m~en.osiurn ionomer, is particularly useful even in higher modulus blends.
While there is no precise correlation between flexural modulus and PGA Coll~ression, resins with flexural modulus of 35,000 psi will have a PGACo-llpl~,ssion in the 130 to 160 range. The increased resiliçnre at a given PGAColllpression value seen in the m~t~ri~l~ of this invention may climini~h at PGA values above about 130. For stiffer blends, such as those having a modulus generally above about 35,000 psi, and a PGA colll~ression above about 150 and even considerably higher, m~gnesium soft ionomers blended with sodium, zinc and pul~lSSiu~ll hard ionomers having a flexural modulus of 70,000 to 110,000 psi, and a Shore 'D' Hardness of 65 or greater, form useful harder cover m~t~ri~l~. In such blends, the amount of hard ionomer is from about 51 to 80 weight percent.
As noted, one other quality is always desirable, and often eQ~enti~l, and that is durability of the m~teri~l in golf ball structures. Typically this is measured on a fini~h~ golf ball, having a cover made of the m~tf-ri~l, 3 0 using a l~e~ted impact test, including tests at low le.llp~ e. De~ ion CA 022~6690 1998-11-2~
of durability on a neat-sphere is generally not so definitive because of the inherent toughness of many neat resins. The durability mea,u,~d on spheres con.~i~ting of neat resin and filler would, of course, be relevant for one-pieceballs. Without at least some durability in a fini~he~l ball, high COR and low PGA Con,~lcssion may be almost without value.
It has now been found, surprisingly, that lithium, the ion which makes the hardest and stiffest of all ionomers, all else being equal, is ideallysuited to make an excellent soft ionomer. Magnesium, which also makes one of the harder ion( mers, is also ideally suited to make an excellent soft ionomer.
Soft ionomers of terpolymer acid copolymers neutralized with these ions have now been found to result in a much improved balance between low PGA
Coll.pl~s~ion and high COR resilience conlpaled with prior art materials. Soft lithium are generally plefel.~d over soft m~grl~sium ionomer~ in single ionomer compositions for covers.
These soft ionomers can particularly also form part of a soft ionomer/hard ionomer blend. If the resulting PGA Co~ ssion of the ionomer blend remains below about 155, this will typically, colre.,~ond to a flexural modulus below about 35,000, though it may exceed this slightly. However, certain blends having a higher flexural modulus than this, specifically when the2 o hard ionomer is sodiurn, potassium or zinc and the soft ionomer is m~g have also been found to be particularly useful.
The acid copolymer precursors of the soft ionomers of this invention are copolymers of ethylene, from 3 to 40 weight percent of alkyl acrylate, whose alkyl group has from 1 to 8 carbons, and from 5 to 15 weight 2 5 percent of methacrylic or acrylic acid. The I~cr~ d alkyl acrylate is n-butyl acrylate. It is to be understood that there can be more than one alkyl acrylate and both acrylic and methacrylic acid present, provided the percent limits for alkyl acrylate and acid are met. Por this reason, the generic term copolyrner isused rather than terpolymer, in referring to the claimed compositions, because 3 o terpolymer implies just three mQnOm~r.~ It is also to be understood the acid copolymer may be a blend of difr~ l soft acid copolymers having ~liffPrinp levels arld/or species of either the softening comonomer, the acid or both. The term 'soft acid copolymer', 'soft flexible innorner' and the like, enco,..l.~qees this possibility. Many pl~ ione of copolymers are sufficiently non-ulfirul"l in com- nnmPr content from molecule to molecule that such 'copolymers' are, in effect, blends anyway.
Below 3% softening comonomer insllff1cient softening (modulus recluçtic-n) occurs, and above 40% the polymer and resultant ionom~r is too soft.
From lO to 30 percent weight is preferred and lS to 25 weight percent is most o pre~lled. Acrylic acid in the soft acid copolymer leads to somewhat more resilient soft ionomers, and is generally preferred.
For soft ionomers and hard ionomers which form blends of the present invention of the percent neutralization of the acid groups present for m~gne~Sillm or lithium ions, or both, is from l O to 90, preferably from 20 to 80%. More preferably the level is from 25 to 65% and most preferably from 30 to 60%. For soft ionomers, the modulus will typically be about 5000 to 35,000 psi. The modulus will be higher for lithium than m~gn~eium, and will increase with the level of acid. The modulus will be lower the higher the amount of alkyl acrylate. The modulus of the soft lithium and m~En~Sillm ionomers 2 o p~ ed here, ranged from about 5000 to 27000 psi, but it is readily possible to prepare m~gJ~Sium and lithium terpolymer ionom~r.~ with a modulus up to 35,000 psi, and even higher. Certain terpolymer ionomer compositions can be made, such ~ ones with very high acid, particularly acrylic acid, using lithium ions and with low amounts of alkyl acrylate which will give higher than 35,000 2 5 psi flexural modulus. However, provided the PGA Coll.p-es~ion of neat-spheres of the soft io~- m~r.q is below about l 55, it will be suitable. It is readily within the skill of the artisan to d~ .i t,c which combinations of mo~
n-olltrali7~tion level and acid type will produce ion~-m~r within the required neat-sphere PGA Col-.plession limits.
CA 02256690 l998-ll-25 In the prior art, it has been common often to refer to 'soft' ionom~rs as possçs~eing a flexural modulus below about lO,000 psi and to 'hard' i(~n~ .s as those with modulus above about 30,000 psi. In this disclosure, the terpolymer ionomers with a softening alkyl acrylate termonom~r are still 5 Icr~red to as 'soft' even when the flexural modulus is much higher As noted above, the soft ionomere of this invention can have a flexural modulus of 35,000, and even in some cases above this.
Typically, to achieve modulus values in the region of 35,000 psi, so that the neat-sphere PGA Compression of the ionomer is as high as l 55, 10 using prior art soft ionomers such as zinc or sodium soft ionomers it would generally be necessary to blend with a hard ionomer. However, it can be seen from the modulus values in Table l, that when lithium and m~gn~Sium are the neutralizing ions, the flexural modulus values can be considerably higher than those of old art zinc and sodium soft ionomers. For this reason, soft ionomers 5 of the present invention are useful alone, even though they may be blended with hard ionomers, as herein defined. The reeilienre advantage at a given PGA
Col,.plession value in the soft ionom~re however, could mean that higher ~liLLIe~s soft ionomers alone would give as good properties as blends of co,..~ ble ~I;rr.,~s~. Blending however can offer cost and various other 2 o advantages, and in practice, often as much hard ionomer as possible, conro~ with a given level of overall stiffn~-ee has been ~rere~ d in the past.
Blending with hard ionomers could however dilute the re,eili~nre advantage at a given PGA Coll.l lession value that these unique soft ionomPrs offer.
For cover material, the modulus should be preferably above 2 5 lO,000 psi. and more preferably above 15,000, h.~e.,li~e of whether using asingle soft ionomer or a soft/hard ionomer blend. When the soft ionomer has a modulus much below lO,000 psi, for cover m~tlori~l.e it is therefore preferable to blend with a hard ionomer so the final modulus falls within the range lO,000 to 35,000 psi when using lithium and m~ .... hard ion- mrrs , .. . .
CA 022~6690 1998-ll-2~
With sodium, zinc and potassium hard ionomPrs, the modulus may be above 35,000 psi.
When the soft i- nnmer is blended with hard ionomer, there should be at least l 0 percent soft ionomer, preferably above 20 percent, or the5 advantages of the particular soft ionomers of this invention will not be reali~d, or will be con.~ider~hly diluted.
The hard ionomers which may be blended with the soft ionomers are lithium, m~gn~ium, sodium, zinc or potassium ionomers. They are derived from acid copolymers of ethylene and, in the case of lithium and m~gJ~4iulll 0 hard ionomers, from 5 to 25 weight percent acid where the acid is m~th~ rylic or acrylic acid, or both, preferably from l 0 to 22 weight percent. In the case of sodium, potassium or zinc hard ionomers, the acid level is preferably l 9 to 25 weight percent. It is to be understood that the hard ionomer may be a blend of more than one hard ionomer each having different levels of and/or dirr~e,lt 5 acids in them, just as for the soft ionomer. The term 'hard acid copolymer', and 'hard stiff ionomer' and the like, encomp~s~s this possibility.
When the composition is a hard ionomer/soft ionomer blend, it is preferable for the hard ionomer to have a higher level of acid than the soft ionomer. Higher acid increases the hardness, so that to produce a blend having 2 o a specific final blend modulus, the higher the acid level in the hard ionomer, the less of it will be required in the blend. The modulus may range from 40,000 to l l0,000 psi. In the case of sodium, zinc and potassium hard ionome~s, the modulus ranges from 70 to l l0,000 psi. In general, when the conlposilion is a blend co~ i.-g hard ionomer, the harder or higher modulus the hard ionom~r, 2 5 whether due to acid level, acid type, neutralizing ion or degree of neutralization, the greater the amount of soft jonom~r possible in the blend, for a given final blend modulus. Since it is the softer terpolymer ionomers which are here clearlyshown to have such an attractive balance of PGA Coll~p.e.,~ion and COR, it may be that the more m~,~ -.. or lithium soft ionomer, the higher the resilience, at3 0 a given PGA Co-~ ,ssion level.
Melt index of either the soft or hard ioïlon~ can be from about O.l to 30 g/lO min., preferably O.l to lO more preferably from O.l to 6 and mostpreferably from 0.5 to 5 .0 g/l 0 min. The melt index of the acid copolymers from which the ionom~s are derived may be from about 20 to 350 g./lO min.
When the compositions of the invention are blends, the p-er~ ,d blends for softer cover m~teri~l.e are lithium soft/m~nesillm hard. l~n~sium/
m~pn~sium and lithium/lithium blends are also attractive. Magnesium soft/lithium hard blends are generally less preferred, and one such blend showeda r1imini~hPd resilience advantage compared with the reverse blend. It is not 0 clear why this should be so. However, the pler~ ,d soft resins, and those used in the elr~mrles, have less acid than the hard resins. Therefore, for a given percent of acid groups neutralized they will have less equivalents of metal present. Thus the number of equivalents of lithium in m~neS;um soft/lithium hard blends will be higher, when there is more acid in the hard ionomer, than inlithium soft/magn~sium hard blends. For blends cont~inin~ both lithium and m~n~sium ions thc.~r~le, it seems that a higher level of m~
equivalents is preferable.
As noted, the hard ionomer may also be a sodium, potassium or zinc ionomer. In the case of zinc and potassium hard ionnmPrs, the amount of 2 o hard ionomer is, by contrast to lithium and m~gn~ium hard ionomers, b~
5 l and 80 weight percent.
It has commonly been ~nme(l that ions in an ionom~r blend are almost comrlet~ly labile, and move freely from polymer chain to polymer chain.
Tllis may be true for a blend of two ionomers based on the sarne acid 2 5 copolymer. However, without c(s""";l",~ ~~t in any particular way, it may not be comrletely true in blends where the underlying acid copolymers of the two ionomers are very dirr~l~,.lt, such as with soft and hard i- n~m~rs. Of course, this will be of no consequence if the metal of the soft and hard ionomer are thesame. It may be of more consequence when the ions are dirr~ . The ions 3 o l~rigin~lly associated with the soft ionomer, may, to some extent, tend to remain CA 022.,6690 1998 - 1 1 - 2., more associated with the soft ionomer in a blend, and this may produce blends with dif~e.lL properties than blends having the reverse ions in the soft and hard components. However, when the underlying acid copolymer is di~~ it may merely mean that higher hlt. .~ / blending is required, such as very high shear extrusion blen~li~, to achieve random distribution of ions throughout the whole composition. In any event, in practice, it has been found that there is a dirr~ ce in properties in soft/hard blends, when the ions for the soft and hard ionomer are reversed.
The ionomers may also contain conv~lional additives such as pigm~nt~, antioxidants, U.V. absorbers, bright~n~r~ and the like.
Testin~e Methods and Criteria.
Flexural modulus is measured using ASTM D790-B, and is measured using a standard 'flex bar' and not on a sphere of m~t~ri~l as for mostother tests.
Coefficient of ~stitlltion~ COR, was measured both on neat-spheres and on fini~he~l balls having a cover of the m~t~ri~l under test. It is measured by firing, either a covered ball having an the ionomer composition as cover or a neat-sphere of the i~-n~m~.r composition, from an air cannon at an initial speed of l 80 ft./sec. as measured by a speed monitoring device over a 2 o tli~t~nce of 3 to 6 feet from the cannon. The ball strikes a steel plate positioned 9 feet away from the cannon, and rebounds through the speed-monit--ring device. The return velocity divided by the initial velocity is the COR.
COR of neat-spheres may fall anywhere b~lwee~ 0.50 and 0.70.
The range on useful covered balls of this invention however, is bet~ about 0.67 and 0.74.
PGA G~ .ession is defined as the lei;~ ce to defom~tion of a golf ball, measured using a standard industry ATTI m~ ne It was measured on a neat-sphere of resin and on balls having a cover of resin. For adequate spin of a ball, when the ionomer is used as a cover Jn~t~ri:~l, the PGA Co...~.e;,;,ion, ]"$g'~'9 S Toêa(o'ZAS ~' ;UI~;TvUIvû~2Lyj-?zS!PêVa!l/uïo;py!A ~Ll Z ~¢NÇKu,àN~E yOOe;ÇOAlIv?~ 3~~~ûh'~E9ï
Durability was measured using a repeat impact test on fini~h~
balls, with the material of the invention as the cover, on a Wilson Ultra'!3 conv~ ;nn~l solid core. Such cores are believed to be made of 1,4-cis polybllt~ n~ cro~linked with peroxides and co-cro~slinking agents such as zinc (meth)acrylate. Durability is measured using the same m~c.~lin~ as for COR, but using an initial velocity of 175 ft./sec. Durability values are the number of hits to break. Durability at low tcn~ laLure3 is especially desirable,and for this reason, durability tests at -20 ~ F were carried out. While good durability only at room lelllpclal~uc is adequate for golf balls used in some 0 locales, low tell~cla~ule durability values, preferably above at least 10, as tested under these conditions, is prer~ d for cold weather use. Durability at room ten~lalule is almost invariably better than durability at -20~F, so that low telllpeldlure durability is a guide to the worst perform~nce to be expected.
Good durability of a m~teri~l, based on tests when the material is used as a cover, may indicate good durability for use as a m~t~ri~l in a one-piece ball.
EXAMPLES.
Table 1 lists various ionomers used in the examples. The list includes soft ionomers which are part of the invention as well as soft ionomers 2 o which are not. It also includes hard ionnm.ors which can be part of a blend of this invention as well as hard ionomers which are not. Flexural modulus is shown, if measured. Note that S8 has a mnd~ of almost 27,000 psi. This is stiff enough even to make a relatively stiff cover m~teri~l by itself, i.e., without blending with a hard ionomer.
2 5 Table 2 lists values of COR and PGA Co~ ,sion on neat-spheres for the compositions indicated. Coln~ali~e examples are numbered with a suffix C. The same values are plotted in Figure 1. Durability of balls which employed the compositions as a cover on a conventinn~l solid core are also shown, if measured.
wo 98/47957 PCT/u~ j8/0~3l8 Figure l shows co~ live examples, outside the invention, indicated by a circle, and examples by a cross. A line is shown, correlating PGA C~ ~ei,~ion and COR values for prior art materials outside this invention, based on previous data (in~lir~t~d by triangles), de~ ;..çd prior to this 5 investigation, together with data on prior art m~t~ri~l~ measured during the present inve.sfig~tion (in-lic~ted by a circle). The line is a 'visually best-fit' line, and is based on materials which differed in their ion or ions, their MI, the acid used (whether acrylic of methacrylic), the amount of acid and, in the case of soft ionomer, the amount of acrylate softening monomtor. The line is a good fit for 10 data up to a PGA Co~ ession of about 140. Above this, there appears to be a poorer correlation with more scatter in the data. Of course, the new soft lithium and m~enesium innomer~ and blends, whether part of this invention or not, are not part of the data on which the line is based, since they are new ionnmçr~.
The fact that such a line can be drawn suggests that, for most 5 ionomers and blends, PGA Compression and COR are uniquely related, largely irrespective of comonomer or ion composition, and depend ess~nti~lly only on the particular level of stiffn~ss of interest. This is except, of course, for the compositions of the present invention.
Surprisingly, when one ~minlos the data for soft ionom~.rs of 2 o m~en.o~ium and lithium, and blends of these ionomers with hard ionomers, there is a dramatic shift to the right or to lower PGA values depending on the axis chosen for comp~ri.~on. Thus, for these soft innnmPrs, and blends cn..l~;ni.~g ~ these soft ionom~rs, there is ap,o~ lly a resilience advantage at a given PGA
Cu~ re;.sion level and vice versa. This will tr~n~l~te to, at the worst equivalent 2 5 or slightly better, but generally signific~ntly better compositions for one-piece balls, and for centers and cores and covers for two- or three-piece balls re~e~live;ly, than previously known compositit~ . Of course the degree of advantage will depend on which of these golf ball appliç~tionc is considered.
Zinc has long been known to provide good durability at low 3 0 t~ ,.dlUI~ s, and compositions of co",p&l~liv~ examples which contain zinc are . , , WO 98/47957 PCT/u~i8lo83lx clearly good in low tclllpcl~ durability as seen from Table 2. Both zinc and sodium soft ionomer~ alone, generally will have a flexural modulus of 5,000 psi or less however. In general, this will be too flexible to be useful alone for use as m~t~ri~l~ of this invention. Zinc hard ionomer blended with lithium soft 5 ionomer does seem to provide good compositions when the PGA Col"~l~;s~ion is above about 140. However, as noted above, the singularity ofthe correlation becomes less definite at high PGA values.
Sodium hard ionomer is known to provide poor low t~ e.~ e durability (example 2C and blend 3C). However it can form the hard ionomer o portion of blends (example 7), provided there is not more than 50 percent of it.
Lithium soft ionomer is not particularly durable at low lc~pc~al~lres (example 2) though not nearly as poor as sodiurn (2C). However its effect on increasing COR at a given PGA level in lithium soft ionomer or in blends of this invention can provide good compositions in this respect.
15 ~gn~ m ionomer as the hard segmlont provides excellent durability.
~gn~ lm soft/magnesium hard blends can thus provide excellent overall compositions (see ~Y~mrle 8).
For use of the m~t~ri~l for golf ball covers, using conventional cores, the advantage can show up in the PGA Compression and COR of the 2 o resulting ball itself. However, because the overall PGA Co",plession and CORis also dependent on the core, not just the cover, the PGA/COR improvement may be somewhat rlimini~hPcl in some cases. Different cores provide somewhat di~e.~ PGA Compression/COR correlations, so that manipulation of core alone can lead to improved balls. Comp~ri~on of cover m~te~ must be 2 5 made on balls which use the same core. As noted above, the rçl~tinn~hir bcl~ ~.n PGA Co~ ession and COR for golf balls provides a line or lines which is shifted far from that observed for neat-spheres.
Table 3 shows PGA Col,~,ei,~ion and COR values measured on golf balls having a Wilson Ultra~ core, and a cover of the m~t~ having the 3 0 composition as indicated by the co,,c~ollding çy~mrle number in Table 2. In Figure 2, the encircled crosses r~pl~selll fini~hP(l ball PGA C~ r~ ion and COR values with prior art covers, and the crosses alone rel.reselll values usingcover m~ttori~l~ ofthe invention. The line drawn is a 'visually-best' line, but there are in~llfflcient data at low PGA values to establish the line with great s cc;ll~illly. It can be seen that, while covers made with soft innom~rs alone, which give PGA values in the 78-81 range, appear to show only a small improvement, if any, when blends are tested, giving PGA in the 83-94 range, the hllpl'uvt;lllent, for the most part is dramatic. It is not clear why e~r~mr'e- 7(PGA 94) shows such a low COR value, and why example 8 (also PGA 94) 0 shows only a small improvement. Nevertheless, it is clear that a dramatic improvement is possible.
.
WO 98147957 Pcr/uss8lo83l8 COMPOSITION OF IONOMERS
# Composition M~nr)m~r MI Ion Neutr Flex Ratios Modulus (%)-S 1 E/nBA/MAA 68l2319 0.6 Zn ~50~2700 S2 E/nBA/MAA 6812319 Na ~504100 S3 E/nBA/MAA 6812319 Mg ~507100 S4 E/nBA/MAA 68123l9 Li ~505000 SS E/nBA/AA 7012218 1.9 Mg ~457800 S6 E/nBA/AA 7012218 0.4 Li ~759500 S7 E/nBA/AA 69.4/18/11.6* 1.6 Mg ~45 16700 S8 E/nBA/AA 69.4/18/11.6* 0.5 Li ~75 26500 Hl E/MAA 80/20 ~1 Na ~79000 H2 E/MAA 85/15 ~1 Na ~5750000 H3 E/MAA 85/15 ~1 Zn ~5748000 H4 E/MAA 85/15 ~1 Mg ~50 H5 E/MAA 85/15 ~4 Li ~50 H6 E/MAA 81/19 ~4 Li ~50 H7 E/MAA 85/15 ~4 Mg ~50 H8 E/MAA 85/15 ~1 Li ~50 H9 E/MAA 80/20 ~1 Mg ~50 H10 E/AA 80/20 ~1 Mg ~50 E = Ethylene, MAA = Methacrylic acid, AA = Acrylic acid, nBA = n-Butyl Acrylate.
Flexural Modulus values in psi.
1 0 Ne~-tr~li7~tiQn values are based on the amount of neutralizing ion in the feed when making the ionomer, ~ it~g complete innnm~i7~tion-$ These comonomer co~lLellL~ are based on best data available. Some uncnnfirm~d data have suggested these comonomer conl~ may be slightly in error.
~
CA 022~6690 1998-11-2~
.
PGA COMPRESSION AND COR OF IONOMER COMPOSITIONS
Ex.# Composition Blend COR PGA Durability Ratio Co.~ e;,~lon Hits/Crack -20~F
lC Sl - 0.511 58 2C S2 - 0.553 67 S3 - 0.593 86 28 2 S4 - 0.584 83 8 3 S5 - 0.618 95 25 4 S6 - 0.656 116 S7 - 0.621 126 6 S8 - 0.672 144 3C Sl/H1 50/50 0.637 140 7 4C S1/H2 50/50 0.645 143 48 5C S2/H3 50/50 0.619 132 50 6C S3/H3 50/50 0.602 127 50 7C S4/H3 50/50 0.621 133 38 8C S5/H3 50/50 0.619 131 50 9C S6/H3 50/50 0.645 139 47 10C S7/H3 75/25 0.618 135 50 1 lC S8/H3 75/25 0.674 148 26 12C S3/H3 75/25 0.590 109 7 S3/H2 50/50 0.645 130 22 8 S3/H4 50/50 0.641 136 50 9 S3/H5 50/50 0.647 142 8 S3/H6 50/50 0.654 146 14 I l S3/H7 75/25 0.620 117 15 13C S1/H2 50/50 0.650 143 50 12 S4/H4 50/50 0.644 141 45 13 SS/H8 50/50 0.638 142 5 14 S5/H4 50/50 0.634 138 50 S6/H9 50/50 0.668 147 44 16 S6/H10 50/50 0.633 132 7 ~ 17 S6/H9 75/25 0.655 126 50 .. . .
PGA COMPRUESSION A~nD COR OF GOLF BALLS
(Cover con~osilion as in Table 2, Ul~a~ Core) s Ex.# COR PGA Co~ .on 1 0.678 79 2 0.673 81 3 0.672 78 7 0.687 94 8 0.681 94 13C 0.693 90 12 0.708 83 13 0.709 87 14 0.711 88 0.714 89 16 0.708 86 17 0.708 85 *rB
. . .
Claims (8)
1. A golf ball comprising a core and a cover, the cover consisting essentially of:
a first polymeric component which is a soft, flexible ionomer having a neat-sphere PGA Compression of below about 155, prepared from a first acid copolymer of;
a) ethylene, b) 3 - 40 weight percent of an alkyl acrylate or mix of alkyl acrylates, the alkyl groups having from 1 to 8 carbon atoms, and c) 5 - 15 weight percent of carboxylic acid which is methacrylic acid or acrylic acid, or a mix of methacrylic and acrylic acid, the ionomer being made by neutralizing 20 to 80 percent of the acid groups of the first acid copolymer with lithium or magnesium ions or both.
a first polymeric component which is a soft, flexible ionomer having a neat-sphere PGA Compression of below about 155, prepared from a first acid copolymer of;
a) ethylene, b) 3 - 40 weight percent of an alkyl acrylate or mix of alkyl acrylates, the alkyl groups having from 1 to 8 carbon atoms, and c) 5 - 15 weight percent of carboxylic acid which is methacrylic acid or acrylic acid, or a mix of methacrylic and acrylic acid, the ionomer being made by neutralizing 20 to 80 percent of the acid groups of the first acid copolymer with lithium or magnesium ions or both.
2. The golf ball of claim 1, wherein the carboxylic acid is acrylic acid.
3. The golf ball of claim 1, wherein the neutralizing ion is magnesium.
4. A golf ball, comprising a core and a cover, the cover consisting essentially of a polymer blend which of, (i) at least 10 weight percent of a first polymeric component which is a soft, flexible ionomer having a neat-sphere PGA Compression of below about 155, prepared from a first acid copolymer of;
a) ethylene, b) 3 - 40 weight percent of an alkyl acrylate or mix of alkyl acrylates, the alkyl groups having from 1 to 8 carbon atoms, and c) 5 - 15 weight percent of carboxylic acid which is methacrylic acid or acrylic acid, or a mix of methacrylic and acrylic acid, the ionomer being made by neutralizing 20 to 80 percent of the acid groups of the first acid copolymer with lithium or magnesium ions or both, and (ii) a second polymeric component which is a hard, stiff ionomer having a flexural modulus of from 40,000 to 110,000 psi, prepared from a second acid copolymer of;
a) ethylene, and b) 5 - 25 weight percent of carboxylic acid which is methacrylic acid or acrylic acid or mix of methacrylic and acrylic acid, the ionomer made by neutralizing 20 to 80 percent of the acid groups of the second acid copolymer with magnesium or lithium ions or both, with the proviso that the neat-sphere PGA Compression of the blend composition does not exceed about 155.
a) ethylene, b) 3 - 40 weight percent of an alkyl acrylate or mix of alkyl acrylates, the alkyl groups having from 1 to 8 carbon atoms, and c) 5 - 15 weight percent of carboxylic acid which is methacrylic acid or acrylic acid, or a mix of methacrylic and acrylic acid, the ionomer being made by neutralizing 20 to 80 percent of the acid groups of the first acid copolymer with lithium or magnesium ions or both, and (ii) a second polymeric component which is a hard, stiff ionomer having a flexural modulus of from 40,000 to 110,000 psi, prepared from a second acid copolymer of;
a) ethylene, and b) 5 - 25 weight percent of carboxylic acid which is methacrylic acid or acrylic acid or mix of methacrylic and acrylic acid, the ionomer made by neutralizing 20 to 80 percent of the acid groups of the second acid copolymer with magnesium or lithium ions or both, with the proviso that the neat-sphere PGA Compression of the blend composition does not exceed about 155.
5. The golf ball of claim 4 wherein the carboxylic acid of the first polymeric component is acrylic acid, the neutralizing ion of the first polymeric component is lithium, and the neutralizing ion of the second polymeric component is magnesium.
6 . A golf ball, comprising a core and a cover, the cover consisting essentially of a polymer blend of;
(i) at least 50 weight percent of a first polymeric component which is a soft, flexible ionomer having a neat-sphere PGA Compression of below about 155, prepared from a first acid copolymer of;
a) ethylene, b) 3 - 40 weight percent of an alkyl acrylate or mix of alkyl acrylates, the alkyl groups having from 1 to 8 carbon atoms, and c) 5 - 15 weight percent of carboxylic acid which is methacrylic acid or acrylic acid, or a mix of methacrylic and acrylic acid, the ionomer being made by neutralizing 20 to 80 percent of the acid groups of the first acid copolymer with lithium or magnesium or both, and (ii) a second polymeric component which is a hard, stiff ionomer having a flexural modulus of from 40,000 to 110,000 psi, prepared from a second acid copolymer of, a) ethylene, and b) 5 - 25 weight percent of carboxylic acid which is methacrylic acid or acrylic acid or mix of methacrylic and acrylic acid, the ionomer made by neutralizing 20 to 80 percent of the acid groups of the second acid copolymer with sodium ions, with the proviso that the neat-sphere PGA Compression of the blend composition does not exceed about 155.
(i) at least 50 weight percent of a first polymeric component which is a soft, flexible ionomer having a neat-sphere PGA Compression of below about 155, prepared from a first acid copolymer of;
a) ethylene, b) 3 - 40 weight percent of an alkyl acrylate or mix of alkyl acrylates, the alkyl groups having from 1 to 8 carbon atoms, and c) 5 - 15 weight percent of carboxylic acid which is methacrylic acid or acrylic acid, or a mix of methacrylic and acrylic acid, the ionomer being made by neutralizing 20 to 80 percent of the acid groups of the first acid copolymer with lithium or magnesium or both, and (ii) a second polymeric component which is a hard, stiff ionomer having a flexural modulus of from 40,000 to 110,000 psi, prepared from a second acid copolymer of, a) ethylene, and b) 5 - 25 weight percent of carboxylic acid which is methacrylic acid or acrylic acid or mix of methacrylic and acrylic acid, the ionomer made by neutralizing 20 to 80 percent of the acid groups of the second acid copolymer with sodium ions, with the proviso that the neat-sphere PGA Compression of the blend composition does not exceed about 155.
7. A golf ball comprising a core and a cover, where the cover comprises a blend of, (i) 20 - 49 weight percent of a first polymeric component which is an ionomer formed from a first acid copolymer consisting of a) ethylene, b) 15 - 25 weight percent of an alkyl acrylate or mix of alkyl acrylates, the alkyl groups having from 1 to 8 carbon atoms, and c) 6 - 12 weight percent of acrylic or methacrylic acid or both, the ionomer neutralized to between 10 and 90 % with magnesium ions, and having a flexural modulus of 3000 to 10,000 psi, a Shore 'D' hardness of 45-55, and a melt index of 0.5 to 5.0 g/10 min., and (ii) 51 - 80 weight percent of a second polymeric component which is an ionomer prepared from a second acid copolymer consisting of, a) ethylene, b) 19-25 weight percent of acrylic acid or methacrylic acid or both, the ionomer formed by neutralizing to between 10 to 90 % with sodium, zinc or potassium ions, the ionomer having a flexural modulus of 70 - 110,000 psi, a Shore 'D' hardness of 65 or greater, and a melt index of 0.5 to 5.0 g/10 min.
8. The golf ball of claim 7 in which the hard ionomer has a Shore 'D' hardness of greater than 70, and the soft ionomer has a Shore 'D' hardeness of greater than 50.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US84376797A | 1997-04-22 | 1997-04-22 | |
| US08/843,767 | 1997-04-22 | ||
| PCT/US1998/008318 WO1998047957A1 (en) | 1997-04-22 | 1998-04-21 | Soft ionomer compositions and blends thereof for golf ball covers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2256690A1 true CA2256690A1 (en) | 1998-10-29 |
Family
ID=25290962
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002256690A Abandoned CA2256690A1 (en) | 1997-04-22 | 1998-04-21 | Soft ionomer compositions and blends thereof for golf ball covers |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JP2000513622A (en) |
| CA (1) | CA2256690A1 (en) |
| WO (1) | WO1998047957A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000073384A2 (en) * | 1999-06-01 | 2000-12-07 | E.I. Du Pont De Nemours And Company | Soft ionomer compositions and blends thereof for golf ball covers |
| WO2002079319A2 (en) * | 2001-03-29 | 2002-10-10 | E.I. Du Pont De Nemours And Company | Soft and resilient ethylene copolymers and their use in golf balls |
| US9446289B2 (en) * | 2013-05-31 | 2016-09-20 | Nike, Inc. | Thermoplastic multi-layer golf ball |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2222277A1 (en) * | 1995-06-30 | 1997-01-23 | E.I. Du Pont De Nemours And Company | Soft ionomer compositions and blends thereof and use thereof as golf ball structural materials |
| GB2311293A (en) * | 1996-03-18 | 1997-09-24 | Wilson Sporting Goods | Golf ball with cover formed from hard and very low modulus ionomer resins |
| JP3748628B2 (en) * | 1996-06-28 | 2006-02-22 | Ｓｒｉスポーツ株式会社 | Golf ball |
-
1998
- 1998-04-21 WO PCT/US1998/008318 patent/WO1998047957A1/en active Application Filing
- 1998-04-21 JP JP10546368A patent/JP2000513622A/en not_active Ceased
- 1998-04-21 CA CA002256690A patent/CA2256690A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| JP2000513622A (en) | 2000-10-17 |
| WO1998047957A1 (en) | 1998-10-29 |
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| Date | Code | Title | Description |
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| FZDE | Discontinued |