Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2002-03-06
2003-12-09
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C473S378000
Reexamination Certificate
active
06660824
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a golf ball covered with a thermosetting polyurethane cover that is excellent in scuff resistance and repulsion property.
2. Description of the Related Art
Ionomer resin covers are mainly used for covers covering golf ball cores because they have superior durability. Golf balls with ionomer resin covers, however, give golfers a larger impact upon a shot than golf balls with Balata covers and hence are likely to impart the golfers with an inferior shot feeling.
In recent years, polyurethane is receiving attention as an inexpensive cover material that has higher durability than Balata covers while imparting golfers with a shot feeling analogous to that imparted by Balata covers. For example, Japanese Patent No. 2662909 discloses a thermosetting polyurethane cover, and Japanese Patent Laid-Open Gazette No. HEI 9-215778 proposes a thermoplastic polyurethane cover.
The art of Japanese Patent No. 2662909 is capable of suppressing a steep increase in viscosity due to the reaction rapidly proceeding between a urethane prepolymer and a polyamine curing agent thereby to enable the molding of a cover by the use of a slow-reactive polyamine curing agent such as 3,5-dimethylthio-2,4-toluenediamine, 3,5-dimethylthio-2,6-toluenediamine, N,N′-dialkyldiaminodiphenylmethane, trimethylene glycol-di-p-aminobenzoate or polytetramethyleneoxide-di-p-aminobenzoate, or a mixture thereof. However, a golf ball with a resulting cover is not satisfactory in terms of repulsion property, spin performance and scuff resistance as compared with golf balls with ionomer resin covers. Thus, further improvements are desired.
Thermoplastic polyurethane elastomer covers are superior in moldability to thermosetting polyurethane covers, but are inferior in wear resistance, tear strength and scuff resistance to thermosetting polyurethane covers because of the lack of crosslinking points.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a golf ball with a thermosetting polyurethane cover that is satisfactory in ball characteristics, particularly, repulsion property and scuff resistance.
A golf ball of the present invention comprises a core and a polyurethane cover covering the core. The polyurethane cover is formed from a cured product prepared by curing a urethane prepolymer having an isocyanate group at a terminal thereof with an amine-type curing agent represented by the following general formula:
H
2
N—R
1
-polyether moiety-R
2
—NH
2
where R
1
and R
2
are independently hydrocarbon groups each having 1 to 6 carbon atoms.
The foregoing and other objects, features and attendant advantages of the present invention will become apparent from the reading of the following detailed description.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be described in detail.
The golf ball of the present invention is characterized that a core comprising a single- or multi-layered vulcanized rubber body or a wound core is covered with a specific polyurethane cover.
The polyurethane cover is formed from a cured product prepared by curing a urethane prepolymer having an isocyanate group as the terminal group thereof (hereinafter referred to as “isocyanate group-terminated urethane prepolymer”) with an amine-type curing agent represented by the following general formula:
H
2
N—R
1
-polyether moiety-R
2
—NH
2
In the formula, R
1
and R
2
are each an intervening group interconnecting the polyether moiety and an amino group. The intervening group is a hydrocarbon chain having 1 to 6 carbon atoms, preferably a linear alkylene group such as ethylene, trimethylene, tetramethylene, pentamethylene or hexamethylene, or a branched alkylene group such as propylene, ethylethylene, butylethylene or dietyletylene.
In the formula of the amine-type curing agent, the polyether moiety is an alkylene oxide group of a linear alkylene glycol such as ethylene glycol, diethylene glycol, polyethylene glycol, methylene glycol, trimethylene glycol or polytetramethylene ether glycol, or a branched alkylene glycol such as propylene glycol, polypropylene glycol, butylene glycol, sec-butyl glycol, hexylene glycol or neopentyl glycol; or a polyether obtained by polymerization of these alkylene glycols. Among such polyether moieties, a polyether moiety represented by the following formula is preferable:
In the above formula, “n”, namely the number of carbon atoms, indicates an integer of 2 to 6 and “N”, namely the number of repeating unit represented by the bracket, indicates an integer of 1 to 40. Specific examples of the preferable alkylene oxide unit include a linear alkylene oxide such as ethylene oxide, trimethylene oxide, tetramethylene oxide, pentamethylene oxide or hexamethylene oxide, or a branched alkylene oxide such as propylene oxide, ethylethylene oxide, butylethylene oxide or diethylethylene oxide. The amine-type curing agent having a polyether moiety represented by the above formula ensures a curing time enough to improve moldability and workability of the cover composition and provide for a cured product having desired physical properties.
Since such an amine-type curing agent does not have any bulky group, polyurethane resulting from the curing reaction using the curing agent is easy to orientation-crystallize and provides a polyurethane cover having high hardness and superior scuff resistance. Though neither any bulky group nor any electron-attractive group acting to lower the reactivity of amino groups exists in a molecule of the curing agent, the amino groups are spaced apart from each other by the polyether moiety and the intervening groups and, hence, the curing agent causes curing at such a speed as to ensure a pot life allowing necessary operations to be performed. Further, the polyether moiety, which can act as a soft segment of the resulting polyurethane, makes it possible to impart the resulting polyurethane with a moderate tensile elongation. Thus, the polyurethane cover is capable of following ball deformation occurring upon a shot, thereby ensuring a golf ball that is less susceptible to break by shots and is excellent in durability.
The amine-type curing agent represented by the formula noted above preferably has a number-average molecular weight of not less than 200. If the number-average molecular weight of the curing agent is less than 200, the curing agent causes the curing reaction to proceed too rapidly due to the absence of any bulky group acting to interfere with the curing reaction or any electron-attractive group acting to lower the reactivity of the amino groups in a molecule of the curing agent. Stated otherwise, the pot life becomes so short that the workability and moldability of the cover composition lower. Further, the urethane bond resulting from the reaction between the curing agent and the NCO group of the urethane prepolymer acts as a hard segment and, hence, if the polyether moiety becomes too small, the resulting polyurethane is rendered hard and is poor in stretchability. Thus, a cover formed from such polyurethane is incapable of following ball deformation occurring upon a shot, resulting in a golf ball that is easy to break by shots and hence cannot ensure desired durability. The upper limit of the number-average molecular weight of the curing agent is preferably 3000, more preferably 2000. If the number-average molecular weight of the curing agent is more than 3000, the resulting polyurethane is too soft to ensure desired repulsion property due to the soft segment of the polyether moiety becoming too large.
Examples of such amine-type curing agents include 4,7,10-trioxytridecane-1,13-diamine, 4,7,10,13-tetraoxyhexadecane-1,16-diamine, 4,9-dioxadodecane-1,12-diamine, 4,9,14-trioxyheptadecane-1,17-diamine, and POLYETHER AMINE D2000 (number-average molecular weight: 2000), POLYETHER AMINE D400 (number-average molecular weight: 400) and POLYETHER AMINE D230 (number-average molecular weight: 230) produced by BASF JAPAN Co.
The isocyanate group-terminated urethane p
Birch & Stewart Kolasch & Birch, LLP
Gorr Rachel
Sumitomo Rubber Industries Limited
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