Thermoplastic polymer cover for golf balls and golf balls comprising such a cover

Thermoplastic polymer cover for golf balls. The thermoplastic polymer material constituting the cover consists of a poly(ether-ester-amide) sequenced copolycondensate having special characteristics. Such a cover has good mechanical characteristics and confers on the golf balls so covered a satisfactory "feel" and "click".

The invention is directed to a thermoplastic polymer cover for golf balls 
and also relates to golf balls comprising such a cover. 
Golf balls with such a cover are used for practice golf as well as 
competition golf. Such balls usually have a polymer-based cover around a 
nucleus or core of the ball, which may be either of the so-called "wound" 
type, i.e. consisting for example of a central sphere, particularly a 
sphere in rubber, metal or glass, or a sphere made of a bag filled with 
paste, on which is wound a special elastic wire, or of the so-called 
"monoblock" type, i.e. comprising a single sphere or several concentric 
spheres of elastomeric material. 
The polymer material from which golf ball covers are produced is most often 
chosen from among the natural elastomers, such as natural balata or gutta 
percha, or synthetic materials such as synthetic transpolyisoprene, 
neoprene, theremoplastic polymers such as polyethylene or polypropylene, 
ionomer resins, ethylene and vinyl acetate copolymers. The cover thus 
obtained from a polymer material of the above-mentioned type has certain 
drawbacks and particularly an inadequate service-life, a weak breakage 
resistance and inadequate qualities with respect to the "feel" and 
"click". It was indeed proposed to improve the characteristics of the golf 
ball covers by using for said covers polymer compositions, particularly 
based on styrene, butadiene or isoprene elastomeric block copolymer or a 
mixture of an ionomer resin with a chlorosulfonated polyethylene or an 
ethylene and vinyl acetate copolymer. However, the covers prepared from 
these compositions were not judged wholly satisfactory. 
The present invention concerns golf ball covers made of a thermoplastic 
polymer material comprising a specific poly (ether-ester-amide) sequenced 
copolycondensate, said polymer material conferring on the cover an 
extended service-life and a high breakage resistance as well as a 
satisfactory "feel" and "click" to golf balls with such a cover. In 
addition, the sequenced copolycondensate covers can be manufactured by 
injection moulding which enables a high production-rate. The thermoplastic 
polymer material cover for golf balls according to the invention is 
characterized in that the said thermoplastic polymer material consists in 
a poly (ether-ester-amide) sequenced copolycondensate produced from the 
copolycondensation of a .alpha.,.omega.-dicarboxylic copolyamide having an 
average molecular weight comprised between 300 and 15,000 with an 
aliphatic .alpha.,.omega.-dihydroxyl polyalkylene glycol having an average 
molecular weight comprised between 100 and 6,000, the sequenced 
copolycondensate containing 5 to 85% by weight of polyoxyalkylene glycol 
and having a melting point comprised between 80.degree. C. and 150.degree. 
C. and a Shore D hardness ranging between 35 and 70. In the 
afore-mentioned definition, by a poly (ether-ester-amide) sequenced 
copolycondensate is also meant a single poly (ether-ester-amide) sequenced 
copolycondensate having the afore-mentioned characteristics as well as a 
mixture of such sequenced copolycondensates. 
According to one embodiment of the invention the Shore D hardness of the 
sequenced copolycondensate constituting the cover is comprised between 45 
and 60. 
According to another embodiment of the invention the sequenced 
copolycondensate has a melting point comprised between 100.degree. and 
140.degree. C. 
The .alpha.,.omega.-dicarboxylic copolyamide reacting with the 
.alpha.,.omega.-dihydroxyl polyoxyalkylene glycol to constitute the 
sequenced copolycondensate has advantageously a melting point comprised 
between 80.degree. and 150.degree. C., the said melting point being 
preferably comprised between 100.degree. and 140.degree. C. 
The average molecular weights of the copolyamide and polyoxyalkylene 
glycol, which may vary between the afore-mentioned ranges, are preferably 
comprised between 800 and 5,000 for the .alpha.,.omega.-dicarboxylic 
copolyamide and between 200 and 3,000 for the .alpha.,.omega.-dihydroxyl 
polyoxyalkylene glycol. 
In addition, the weight proportion of polyoxyalkylene glycol in the 
sequenced copolycondensate is preferably between 10 and 50% with respect 
to the said sequenced copolycondensate. 
The reaction of the copolycondensation between the 
.alpha.,.omega.-dicarboxylic copolyamide and the 
.alpha.,.omega.-dihydroxyl polyoxyalkylene glycol in order to constitute 
the poly (ether-ester-amide) sequenced copolycondensate constituting the 
golf ball cover according to the invention is effected by contacting, in 
the presence of a catalyst and while stirring, the said reagents, in a 
molten state, that is at temperatures above the melting points of the 
.alpha.,.omega.-dicarboxylic copolyamide and the 
.alpha.,.omega.-dihydroxyl polyoxyalkylene glycol. The temperatures 
selected for this reaction must be sufficient to maintain the molten 
mixture in a state sufficiently fluid to allow by stirring a good contact 
of the reagents. These temperatures, selected above the melting points of 
the dicarboxylic copolyamide and the dihydroxyl polyoxyalkylene glycol may 
be advantageously comprised between 100.degree. and 400.degree. C. and are 
preferably between 200.degree. and 300.degree. C. 
The copolycondensation reaction may be effected, according to requirements, 
under a higher or lower vacuum which may reach 0.05 torr or under inert 
atmospheric pressure at a pressure equal or close to atmospheric pressure. 
In order for the copolycondensation reaction to take place in the most 
favorable conditions for the obtention of the sequenced copolycondensates, 
it is preferable to respect the equimolecularity between the carboxylic 
groups of the .alpha.,.omega.-dicarboxylic copolyamide and the hydroxyl 
groups of the .alpha.,.omega.-dihydroxyl polyoxyalkylene glycol which are 
reacting together. 
The catalyst used to promote the copolycondensation reaction between the 
copolyamide and the polyoxyalkylene glycol can be one of the catalysts 
known in the prior art. In particular, can be used a titanium tetra 
alkoxide based catalyst as described in more details in French Patent 
Application No. 74 18,913 (publication No. 2 273 021) of May 31, 1974 or a 
zirconium or hafnium tetra alkoxide based catalyst as proposed in French 
Patent Application No. 77 26678 of Sept. 2, 1977 in the name of ATO 
CHIMIE, the proportion of the catalyst being that cited in the said 
references. 
The copolycondensation reaction producing a sequenced copolycondensate may 
be carried out as a batch-type or continuous operation and, in the latter 
case, the thin-film technique as described in French Patent Application 
No. 77 39790 of Dec. 30, 1977 in the name of ATO CHIMIE can be used. 
The .alpha.,.omega.-dicarboxylic copolyamide, i.e. having a carboxylic 
group at each of its chain-ends, with a melting point comprised between 
80.degree. and 150.degree. C., and preferably between 100.degree. and 
140.degree. C., is obtained by polycondensating, as is well known in the 
art, a mixture of at least two precursors (or precursor compounds) of 
polyamides selected from among lactams, aliphatic amino acids, and 
aliphatic dicarboxylic acid salts of aliphatic diamines, in the presence 
of a suitable quantity of organic dicarboxylic acid whose carboxylic 
groups are preferably fixed at each end of the molecule; the relative 
proportions of the precursor compounds in the mixture subjected to 
polycondensation, are selected such that the .alpha.,.omega.-dicarboxylic 
copolyamide thus produced has a melting point comprised in the appropriate 
range, namely between 80.degree. and 150.degree. C. and preferably between 
100.degree. and 140.degree. C. 
During the copolycondensation takes place the fixing of the organic 
dicarboxylic acid on the copolyamide macromolecular chain, more 
particularly at its chain-ends; this leads to the obtention of a 
.alpha.,.omega.-dicarboxylic copolyamide. 
The precursor compounds from which the .alpha.,.omega.-dicarboxylic 
copolyamide is formed are preferably selected from the group formed by 
C.sub.6 to C.sub.14 -lactams, C.sub.6 to C.sub.14 -aliphatic amino acids 
for which functional groups are preferably end groups, and C.sub.6 to 
C.sub.14 -aliphatic dicarboxylic acid salts of C.sub.6 to C.sub.14 
-aliphatic diamines and most particularly from the group formed by 
caprolactam, oenantholactam, decanolactam, undecanolactam, dodecanolactam, 
6-amino caproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, 
adipic salts of hexamethylene diamine, azelaic acid sebacic acid and 
1,12-dodecanedioic acid, and adipic acid salts of nonamethylene diamine. 
The organic dicarboxylic acids, which are used in the synthesis reaction of 
a .alpha.,.omega.-dicarboxylic copolyamide, on the one hand permitting the 
fixation of a carboxylic group at each of the copolyamide chain ends and 
acting, on the other hand, as chain-limiters, are C.sub.4 to C.sub.20 
dicarboxylic acids, particularly alkanedioic acids such as, for example, 
succinic, adipic, suberic, azelaic, sebacic, undecanedioic and 
dodecanedioic acids, or dicarboxylic cycloaliphatic or aromatic acids such 
as, for example, terephthalic, isophthalic, 1.4-cyclohexane dicarboxylic 
acid. These organic dicarboxylic acids are used in suitable quantities to 
obtain a copolyamide having an average molecular weight in accordance with 
standard calculations for the polycondensation techniques. 
As afore-mentioned the average molecular weights of the 
.alpha.,.omega.-dicarboxylic copolyamides are between 300 and 15,000, and 
are preferably comprised between 800 and 5,000. 
The .alpha.,.omega.-dicarboxylic polyoxyalkylene glycols, i.e. having a 
hydroxyl group at each of the chain-ends, involve according to the 
invention linear or branched polyoxyalkylene glycols whose alkylene 
radical contains at least two carbon atoms, the copolymers deriving from 
such polyoxyalkylene glycols, and mixtures of such polyoxyalkylene glycols 
and/or their copolymers. Most suitable are polyoxyalkylene glycols, 
polyoxypropylene glycols, polyoxytetramethylene glycols, copolymers 
deriving from such polyoxyalkylene glycols and mixtures of such 
polyoxyalkylene glycols and/or their copolymers. 
As afore-mentioned the average molecular weights of the 
.alpha.,.omega.-polyoxyalkylene glycols can vary between 100 and 6,000, 
and are comprised preferably between 200 and 3,000. 
The proportion of .alpha.,.omega.-dihydroxyl polyoxyalkylene glycol 
reacting with the .alpha.,.omega.-dicarboxylic copolyamide is such that 
the poly(ether-ester-amide) sequenced copolycondensate thus obtained 
contains 5 to 85%, and preferably 10 to 50%, by weight of polyoxyalkylene 
glycol. 
To the sequenced copolycondensate constituting the cover for golf balls 
according to the invention may be incorporated various additives, 
particularly stabilizers against light and heat, antioxidizers, pigments 
such as titanium dioxide or fillers, these additives being used in 
conventional proportions to obtain the required effect. The incorporation 
of additives to the sequenced copolycondensate can be made by mixing a 
mixture of the sequenced copolycondensate and of additives in a mixing 
apparatus, for example a Banbury mixer, at a temperature high enough to 
obtain a homogeneous mass. Furthermore, additives may be added to the 
nascent sequenced copolycondensate which forms during copolycondensation. 
It is also possible in the scope of the invention to incorporate in the 
sequenced copolycondensate a minor quantity of one or several copolymers 
compatible with the sequenced copolycondensate and having a melting point 
and a Shore D hardness comparable to that of the sequenced 
copolycondensate. 
The manufacture of the golf ball cover obtained from the sequenced 
copolycondensate and the application of the cover on any type of core, 
particularly a core of the so-called "wound" type or a core of the 
"monoblock" type, to constitute a golf ball may be realized by known 
techniques of the prior art. 
For example, hemispheric skeletons may be constituted by compression 
moulding a calandered or extruded sheet or small quantities of extruded 
material obtained from the sequenced copolycondensation, then adjusting 
two of these skeletons on the core of the ball, and moulding the structure 
thus produced at a temperature and a pressure such that the said skeletons 
weld together by melting, while during the course of the operation 
printing any suitable design appearing on the outside surface of the 
cover. Furthermore, such hemispheric skeletons may be prepared by 
injection moulding, the two skeletons being adjusted on the core of the 
ball, and the structure moulded as described in the preceding case. 
It is also possible to directly mould by injection the cover on the core 
while in one or several steps constituting a smooth structure which is 
then moulded by compression or to produce a ball whose outside surface 
includes a design. 
The balls produced from the afore-mentioned operations are then subjected 
to finishing processes during which the said balls are polished, and, if 
necessary, painted and marked and are then finally conditioned. 
The methods of control and identification selected to characterize the 
products were the following: 
inherent viscosity (determined at 25.degree. C. at 0.5% by weight solution 
in metacresol) 
tensile strength and extension (measured according to the standard ASTM 
D638 67T) 
VICAT point in .degree.C. (expressed according to the standard ASTM D1525 
65T) 
apparent torsion modulus (measured according to the standard ASTM D1043 61T 
according to the

The invention is illustrated by the following examples which are given only 
as a title of simple illustration without limiting the scope of the 
present invention. Unless specified the proportions are expressed in 
weight percentages relative to the total weight of the constituents of the 
copolycondensate. 
EXAMPLES 1 to 4 
Poly (ether-ester-amide) sequenced copolycondensates are prepared for use 
as golf ball covers by copolycondensation of a 
.alpha.,.omega.-dicarboxylic copolyamide having an appropriate melting 
point and an appropriate average molecular weight (Mn) with an appropriate 
.alpha.,.omega.-dihydroxyl polyoxyalkylene glycol in order to form a 
reaction mixture containing .alpha.,.omega.-dicarboxylic copolyamide and 
.alpha.,.omega.-dihydroxyl polyoxyalkylene glycol as well as 0.2% (in 
weight expressed relatively to the total weight of the said constituents) 
of zirconium tetrabutoxide as catalyst, and by maintaining the said 
reaction mixture during two hours under vigorous stirring at a temperature 
of 260.degree. C. and under a vacuum of 0.1 torr. 
The sequenced copolycondensates thus obtained are the following: 
poly (ether-ester-amide) sequenced copolycondensate resulting from the 
copolycondensation of a .alpha.,.omega.-dicarboxylic copolyamide 
containing 40% by weight of units derived from caprolactam and 60% by 
weight of units derived from undecanoic 11-amino acid and having a melting 
point of 125.degree. C. and an average molecular weight (Mn) equal to 
2,000 with a .alpha.,.omega.-dihydroxyl polytetramethylene glycol having 
an average molecular weight (Mn) equal to 650, the said sequenced 
copolycondensate containing by weight 24.5% polyoxytetramethylene glycol 
and having a melting point of 125.degree. C. and an inherent viscocity 
equal to 1.29 (example 1). This product is designed by the abbreviated 
form PA 6-11/PTMG. 
poly (ether-ester-amide) sequenced copolycondensate obtained from the 
copolycondensation of a .alpha.,.omega.-dicarboxylic copolyamide 
containing by weight 40% of units derived from caprolactam and 60% of 
units derived from undecanoic 11-amino acid and having a melting point of 
126.degree. C. and an average molecular weight equal to 2,000 with a 
.alpha.,.omega.-dihydroxyl polyoxypropylene glycol having an average 
molecular weight equal to 630, the said sequenced copolycondensate 
containing by weight 24% polyoxypropylene glycol and having a melting 
point of 126.degree. C. and an inherent viscocity equal to 0.92 (example 
2). This product is designated by the abbreviated form PA 6-11/PPG. 
poly (ether-ester-amide) sequenced copolycondensate obtained from the 
copolycondensation of a .alpha.,.omega.-dicarboxylic copolyamide 
containing by weight 40% of units derived from caprolactam, 20% of units 
derived from adipic acid salt of hexamethylene diamine, and 40% of units 
derived from dodecalactam and having a melting point of 112.degree. C. and 
an average molecular weight equal to 2,000 with a 
.alpha.,.omega.-dihydroxyl polyoxytetramethylene glycol equal to 650, the 
said sequenced copolycondensate containing by weight 24.5% 
polyoxytetramethylene glycol having a melting point of 112.degree. C. and 
an inherent viscocity equal to 1.32 (example 3). This product is 
designated by the abbreviated form PA 6-6, 6-12/PTMG. 
poly (ether-ester-amide) sequenced copolycondensate obtained from the 
copolycondensation of a .alpha.,.omega.-dicarboxylic copolyamide 
containing by weight 33% of units derived from caprolactam, 33% of units 
derived from undecanoic 11-amino acid and 34% of units derived from 
dodecalactam and having a melting point of 102.degree. C. and an average 
molecular weight equal to 2,460 with hydroxyl polyoxytetramethylene glycol 
having an average molecular weight equal to 740, said sequenced 
copolycondensate containing by weight 23% polyoxytetramethylene glycol and 
having a melting point of 102.degree. C. and an inherent viscocity equal 
to 1.38 (example 4). This product is designated by the abbreviated form PA 
6-11-12/PTMG. 
Golf balls having a core of the so-called "wound" type with a diameter of 
38.6 mms covered by a cover consisting of one of the afore-mentioned 
sequenced copolycondensates and having a thickness of 1.3 mm are 
manufactured according to the following: Two hemispheric skeletons were 
produced by injection moulding of a sequenced copolycondensate. The 
skeletons thus obtained were assembled on the core of the ball and the 
structure thus obtained was then moulded by compression to realize, on the 
one hand, the fusion of the seam of the two hemispheric parts of the 
cover. and, on the other hand, the impression of a design on the surface 
of the said cover; the moulded product obtained was then cooled. The ball 
obtained was then subjected to a polishing process to eliminate the burr. 
The mechanical characteristics of the cover produced from the 
afore-mentioned copolycondensates are grouped together in the table shown 
here-under. 
The cover, whose mechanical characteristics are shown in the table, has 
good to very good breakage resistance and confers in addition on the golf 
balls a satisfactory "feel" and "click". 
In addition, in comparison to a cover of the same dimensions produced from 
a commercial ionomer resin, the cover obtained from a sequenced 
copolycondensate of Example 1 had an abrasion resistance clearly superior 
(losses total only 0.5 cm.sup.3 after 1,000 revolutions for the 
copolycondensates as against 1.2 cm.sup.3 after 1,000 revolutions for the 
ionomer resin). 
TABLE 
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EXAMPLE 1 2 3 4 
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Nature of the sequenced 
-11/PTMG 
-11/PPG 
PAG-G,6-12/ 
-11-12 
copolycondensate PTMG PTMG 
Tension (kg/cm.sup.2): 
flow-point 80 65 75 80 
rupture 245 230 190 200 
Extension (%) 
flow-point 12 10 10 11 
rupture 340 470 365 390 
VICAT point under I kg. 
106 100 73-76 80-82 
(C..degree.) 
Apparent torsion 
550 550 630 550 
modulus: 
Permanent set (%): 
54 60 62 61 
Shore D hardness: 
50-53 50 46 46-48 
Dynstat shock: 
non-notched unbroken 
unbroken 
notched unbroken 
unbroken 
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