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Golf ballRelated Patent Categories: Games Using Tangible Projectile, Golf, Ball, Interior Includes Injected Or Compressed MaterialGolf ball description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070167255, Golf ball. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The present invention relates to a golf ball having an excellent rebound. [0002] Many studies have been conducted on the blending and preparation of rubber compositions for use in golf balls and on methods of manufacturing golf ball cores with the express purpose of conferring golf balls with an excellent rebound. See, for example, Patent Document 1: JP-A 2004-167052; Patent Document 2: JP-A 2004-285322; Patent Document 3: JP-B 3639534; and Patent Document 4: JP-A 2005-095493. [0003] For example, JP-A 2004-167052 describes rubber compositions for golf balls which include a base rubber, a co-crosslinking agent, an organic peroxide, an inorganic filler and a processing aid, wherein the base rubber includes a polybutadiene having a cis-1,4 bond content of at least 80% and synthesized using a lanthanide series catalyst, the organic peroxide includes an organic peroxide having a 10-hour half-life temperature of 80 to 100.degree. C., and the processing aid is a fatty acid ester, fatty acid salt or a mixture thereof; and mentions that such compositions have a good processability and enable golf balls having both an excellent rebound and an excellent durability to be obtained. [0004] However, many golfers desire golf balls capable of achieving a longer distance, and so a need exists for the development of golf balls having an even better rebound. SUMMARY OF THE INVENTION [0005] It is therefore an object of the present invention to provide a golf ball having an excellent rebound. [0006] As a result of extensive investigations, we have found that, in the production of a golf ball composed of a material molded under heat from a rubber composition which includes a diene base rubber, an .alpha.,.beta.-unsaturated carboxylic acid and/or metal salt thereof, and an organic peroxide, the foregoing object can be achieved by including within the composition a group of organic peroxides not recognized by those skilled in the art as suitable for crosslinking rubber. [0007] That is, rubber compositions capable of forming a crosslinked structure are commonly used in golf ball production because they confer the golf ball with a suitable hardness. Such a crosslinked structure is generally formed by the action of the .alpha.,.beta.-unsaturated carboxylic acid and/or a metal salt thereof and the organic peroxide upon the diene base rubber. Hence, the organic peroxides selected for this purpose have until now been ones which are known to be suitable for rubber crosslinking. [0008] Here, the organic peroxides supplied by various manufacturers for use in crosslinking rubber are all dialkyl peroxides, peroxyketal-type organic peroxides, or aromatic peroxyester-type organic peroxides (i.e., peroxyester type organic peroxides which include an aromatic ring structure within the chemical structure). Therefore, peroxyester-type organic peroxides which lack an aromatic ring structure in the chemical structure (i.e., aliphatic peroxyester-type organic peroxides) have not been investigated by those skilled in the art who are engaged in the manufacture of golf balls. [0009] Yet, I have discovered that when a peroxide having at the site of an ester linkage an oxygen-oxygen bond capable of radical cleavage (a peroxide having the structural formula R.sup.a--C(.dbd.O)--C--C--R.sup.b), i.e., a peroxyester-type aliphatic peroxide, is used in combination with a diene base rubber and a co-crosslinking agent, there can be obtained from the rubber composition a hot-molded material of exceptional resilience. we have also found that golf balls composed at least in part of such a hot-molded material are capable of exhibiting an exceptional rebound. [0010] Accordingly, the invention provides the following golf balls. [1] A golf ball composed of a material molded under heat from a rubber composition containing (a) a diene base rubber, (b) an .alpha.,.beta.-unsaturated carboxylic acid and/or a metal salt thereof, and (c) an organic peroxide, wherein the organic peroxide (c) includes an aliphatic peroxyester. [0011] [2] The golf ball of [1], wherein the rubber composition contains at least 2 parts by weight of the organic peroxide per 100 parts by weight of the diene base rubber. [0012] [3] The golf ball of [1], wherein the rubber composition additionally comprises (d) an organosulfur compound and/or (e) an inorganic filler. [0013] [4] The golf ball of [1], wherein the .alpha.,.beta.-unsaturated carboxylic acid is acrylic acid or methacrylic acid. [0014] [5] The golf ball of [1], wherein the diene base rubber includes a polybutadiene having a stress relaxation time (T.sub.80), defined as the length of time from the moment when rotor rotation is stopped immediately after measurement of the ML.sub.1+4 (100.degree. C.) value (the Mooney viscosity measured at 100.degree. C. in accordance with ASTM D-1646-96) that is required for the ML.sub.1+4 value to decrease 80%, of at most 4 seconds. [0015] [6] The golf ball of [5], wherein the polybutadiene having a stress relaxation time (T.sub.80) of at most 4 seconds is a polybutadiene prepared by polymerization using a rare-earth catalyst. DETAILED DESCRIPTION OF THE INVENTION [0016] The invention is described more fully below. The golf ball of the invention is a golf ball composed of a material molded under heat from a rubber composition which includes the following components (a) to (c): [0017] (a) a diene base rubber, [0018] (b) an .alpha.,.beta.-unsaturated carboxylic acid and/or a metal salt thereof, and [0019] (c) an organic peroxide which includes an aliphatic peroxyester. [0020] As used herein, "diene base rubber" refers to a base rubber composed primarily of a diene rubber (e.g., polybutadiene rubber (BR), styrene-butadiene rubber (SBR), natural rubber, polyisoprene rubber, ethylene-propylene-diene rubber (EPDM)). The proportion of the base rubber accounted for by the diene rubber is at least 50 wt %, preferably at least 60 wt %, more preferably at least 80 wt %, and may even be 100 wt %. [0021] To achieve a good rebound, it is preferable for component (a) to include a polybutadiene having a stress relaxation time (T.sub.80), defined as the length of time from the moment when rotor rotation is stopped immediately after measurement of the ML.sub.1+4 (100.degree. C.) value (the Mooney viscosity measured at 100.degree. C. in accordance with ASTM D-1646-96) that is required for the ML.sub.1+4 value to decrease 80%, of at most 4 seconds. [0022] The above indicator (T.sub.80) is described in section 13.1.3.1 of ASTM D1646-96. [0023] The term "Mooney viscosity" used herein refers to an industrial indicator of viscosity as measured with a Mooney viscometer, which is a type of rotary plastometer. The unit symbol used is ML.sub.1+4 (100.degree. C.), where "M" stands for Mooney viscosity, "L" stands for large rotor (L-type), "1+4" stands for a pre-heating time of 1 minute and a rotor rotation time of 4 minutes, and "100.degree. C." indicates that measurement was carried out at a temperature of 100.degree. C. [0024] In the practice of the invention, it is desirable for above component (a) to include a polybutadiene (BR1) having a stress relaxation time (T.sub.80) of at most 4 seconds. However, the T.sub.80 value is preferably 3.5 seconds or less, and more preferably 3 seconds or less. The lower limit of the T.sub.80 value is preferably 1 second or more, and most preferably 1.5 seconds or more. At a T.sub.80 value of more than 4 seconds, the rebound decreases. On the other hand, if the T.sub.80 value is too small, problems may arise with workability. [0025] The polybutadiene BR1 has a Mooney viscosity (ML.sub.1+4 (100.degree. C.)) which, while not subject to any particular limitation, is preferably at least 20 but not more than 80. [0026] It is recommended that the polybutadiene BR1 have a cis-1,4 bond content of at least 60%, preferably at least 80%, more preferably at least 90%, and most preferably at least 95%, and a 1,2-vinyl bond content of at most 3%, preferably at most 2%, more preferably at most 1.5%, and most preferably at most 1.3%. At a cis-1,4 bond content or a 1,2-vinyl bond content outside of these ranges, the rebound may decrease. [0027] From the standpoint of rebound, it is preferable for the polybutadiene BR1 in the invention to be a polybutadiene synthesized using a rare-earth catalyst. [0028] A known rare-earth catalyst may be used for this purpose. Exemplary rare-earth catalysts include those made up of a combination of a lanthanide series rare-earth compound, an organoaluminum compound, an alumoxane, a halogen-bearing compound, and an optional Lewis base. [0029] Examples of suitable lanthanide series rare-earth compounds include halides, carboxylates, alcoholates, thioalcoholates and amides of atomic number 57 to 71 metals. Continue reading about Golf ball... Full patent description for Golf ball Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Golf ball patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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