CA1147089A

CA1147089A - Solid golf ball center

Info

Publication number: CA1147089A
Application number: CA000335031A
Authority: CA
Inventors: Thomas A. Molyneaux; Alvon R. Cox
Original assignee: Abbott Laboratories
Current assignee: Abbott Laboratories
Priority date: 1978-09-26
Filing date: 1979-09-05
Publication date: 1983-05-24
Also published as: FR2437223A1; DE2938752A1; JPS5545498A; GB2032287B; CH641966A5; DE2938752C2; FR2437223B3; GB2032287A

Abstract

Abstract:
Radial block copolymers of the butadiene-sty-rene type are utilized in an uncured state to form a solid golf ball center which has high rebound character-istics as well as various durometers. The golf ball cen-ters containing the radial block copolymers can be formu-lated to obtain the specific properties desired by a par-ticular manufacturer and can be manufactured at a lower cost than those presently available.

Description

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Back~round of the Invention This invention relates to thermoplastic polymers which are useful in molding centers for golf balls. ~ore particularly, it relates to the use of thermoplastic polymers composed of block radial polymers of the diene-aryl substituted olefin butadiene-styrene type which con-tains a major portion of a filler material as well as an extender to form a golf ball center having high rebound characteristics as ~Yell as offering versatility in meet-ing manufacturing specifications.
Currently golf balls are produced in the fol-lowing forms:
1. A one component solid construction composed of a homogeneous mass con-sisting of polybutadiene, monomers, fillers, antioxidants, curing agents, etc.

2. A two component golf ball comprising a cover composed of natural rubber (Balata) or plastic (Surlyn ) includ-ing urethanes; and a cor.e composed of a solid homogeneous mass similar to Item ~1.

3. A three component golf hall composed of a cover composed of Balata rubber, plastic (Surlyn*) or similar material;
a winding composed of natural and/or synthetic rubber thread; and a core - made from natural or synthetic polymers.
~. A four component golf ball having a cover as described in Items 2 and 3;
a winding as described in Item 3; a core wall made from natural and/or synthetic rubber; and a liquid center composed of glycerin, polyethylene glycol, salt 501 utions, etc.

* trade mark The golf ball center of the type concerned with in this invention is the Center or Core in Item 3.
Block copolymers of butadiene-styrene and styrene-butadiene-styrene type are described in U. S.
Patent 3,534,965 to produce a solid golf ball. The block copolymers are blended and cured to result in the solid golf ball. Styrene-butadiene copolymers are also vulcanized in a blend with a polytetrahydrofuran to form a molded golf ball in U. S. 3,373,123. In U. S. Patents

4,048,254 and 4,048,255 blends of uncured radial block copolymers are described for use with a third polymeric material for use in making thermoplastic materials for pharmaceutical purposes. The prior art nowhere describes an uncured, butadiene-styrene radial block copolymer hav-ing a specific butadiene and styrene content in combina-tion with a major portion of a filler material for use in the manufacture of a solid golf ball center. Neither does the prior art indicate that an uncured butadiene-styrene radial block copolymer can be employed in formu-lations for composing golf ball centers wherein the use of fillers and extenders can be freely incorporated to obtain centers having high rebound and various durometers.
It is an advantage of the present invention to provide a solid golf ball center composed of an uncured butadiene-styrene radial block copolymer. Other advan-tages are a solid golf ball center containing a major portion of filler material as well as extenders so as to permit versatility in achieving desired properties for a golf ball; a solid golf ball center which can be molded by various molding techniques including injection molding so as to afford rapid production as well as size and weight control; a solid golf ball composition which elim-inates the need for curing and permits the reuse of trim and runner system material.

Summary of the Invention The foregoing advantages are accomplished and the shortcomings of the prior art are overcome by the present solid golf ball center which includes a noncross-s linked butadiene-styrene radial block copolymer having a butadiene content in the range of about 50 - 85% by weight and a styrene content in the range of about 15 - 50~ by weight. A major portion of the golf ball center includes a filler material with the noncross-linked butadiene-styrene radial block copolymer and optionally an extender in the form of an oil. The radial block copolymer will have a molecular weight of at least 150,000 and can be as high as 300,000. In one embodiment of the invention, two radial block copolymers will be employed having different buta-diene-styrene contents. In a preferred embodiment, the filler material will be present in an amount of about 60 -80~ by weight of the golf ball center and the extender present in the range of about 5 - 20% by weight of total center composition.

Description of the Preferred Embodiment The radial block copolymers utilized in the fol-lowing Examples are readily available on the commercial market and are composed of;50 - 85~ by weight of butadiene and 15 - 50~`by weight of styrene. The radial block co-polymers have a molecular weight ranging from 150,000 to 300,000 as measured by inherent viscosity in toluene;
and a specific gravity ranging from 0.92 to 0.95. The preferred radial block copolymers are sold under the trade mark SOLP~ENE and available from the Phillips Petroleum Company.
The invention is disclosed in further detail by means of the following Examples which are set forth for the purpose of illustrating the invention, but, in no way are to be construed as limiting the invention to the pre-cise amounts, ingredients or conditions ind~cated.

i~

- ~ -~xample I
Formula Ingredientsby Parts (phr*) Radial Block Copolymer 75

5 (80:20 But~diene-Styrene) Radial Block Copolymer (70:30 Butadiene-Styrene) 25 ~iller (Barium Sulfate) 220 Extender (Paraffinic Oil) 25 Antioxidant (Hindered Phenol) 1.0 346.0 *Parts/Hundred/Rubber Polymer The barium sulfate and the antioxidant are placed in a Banbury-type internal mixer of suitable capasity. The mixing device is operated for 30 seconds after which the radial block copolymers are added and approximately one-third of the paraffinic oil. Mixing is subsequently effected until three ~inutes after which an additional one-third of the paraffinic oil is added and after four minutes the balance of the paraffinic oil, is added. The mixing unit is operated for an additional minute to bring the total mixing time to five minutes.
After this time, the entire ingredients are dumped from the mixer at a temperature of 100 - 125 degrees C. onto mill rolls which should have a temperature in the range of 75 - 85 C. for the stripping off of the material and its cooling. The cooled material can then be diced into a 1/8 - 3/16 inch cube for later injection molding.
The golf ball centers are then injection molded by any suitable injection molding device and will have a weight in the range of about lS grams to about 22 grams and a diameter of 1-1/32 inch. The solid core center will then be wound in a usual manner with natural and/or synthetic rubber thread and covered with a natural rubber (Balataj, plastic (Surlyn*) or similar material.

* trade mark 8~

Example II

Formula by Ingredients Parts (phr*) Radial Block Copolymer (80:20 Butadiene-Styrene 50 Radial Block Copolymer (70:30 Butadiene-Styrene 50 Filler (Barium Sulfate) 490 Extender (Paraffinic Oil) 100 Antioxidant (Hindered Phenol) 0.5 690.5 *Parts/Hundred/Rubber Polymer The radial block copolymers, the barium sulfate and the antioxidant are placed in a high speed intensive mixer. The added materials are mixed for approximately 30 seconds after which time the paraffinic oil is added with the blender being operated at 1200 rpm. 40 - 50 phr-of oil should be added over approximately 40 - 60 seconds to add 40 - 50 phr of oil. The mixing is continued at 1500 rpm until the compound appears to be free flowing. ~fter this period of time the mixer is operated at 2000 to 2500 rpm for an additional 30 seconds. After approximately l-l/2 minutes of blending, the mixed material is dumped into a ribbon blender and cooled to a temperature of 35 degrees (C). The cooled and mixed material can then be pelletized in the usual manner from an extruder for later injection molding and final fabrication of the golf ball as indicated in Example I.

6--The type of blendlng equiprnent utilized in the Æxamples will depend upon wllat physical form the radial block copolymer is in when supplied. For example, if it is in the form of a bale, a Banbury-type internal mixer would only be used with a cooling facility and take-off. In the instance where it would be supplied in the form of a crumb or pelleted a Banbury mixer could likewise be employed and also a high-speed, intensive dry blender such as a Welex*, Littleford*, He~schel* or equiva-lent equipment with a ribbon blender for cooling. The Banbury mixer will accommodate all three forms and has the advantage that it will accommodate higher use of fil-lers and extenders without fear of separation of the in-gredients from the polymer. In contrast, the dry blend mixing offers the advantage of faster mixing cycles; lower power consumption; elimination of the take-off mill of the Banbury mixer. The material can ~e processed directly from the dry blend into a plastic processing equipment such as an injection molding machine.
Table I indicates additional formulations of the radial block copolymers where only a single radial block copolymer is employed. These formulations as well as those in Table II will be compounded as indicated in 1 Example I and II. Table I also designates the percent of rebound and durometer for these various formulations.
Similarly, Table II lists formulations for two radial block copolymers similar to Examples I and II. Table II illustrates the use of the block copolymers with different butadiene-styrene contents and in ratios in the range of ~5-75:75-25 parts by weight~
It will be seen from the various formulations that the filler material as represented by barium sulfate composes a major portion of the weight of the golf ball center, The amount of this material can range from about ~0~ to about 80~ by weight of the-golf ball center.
While barium sulfate (Barytes) is the preferred filler material the following filler materials could likewise be employed in the same weight range: calcium carbonate, , ~ * trade mark 8~

alumin~m silicate, fumed colloidal silica (Carbosil*), silica, magnesium silicate, carbon black, calcined alumi-num silicate, precipitated hydrated silica, zinc sulfide (Lithophone*), magnesium carbonate, hydrated aluminum silicate, wet ground mica and silicon dioxide.
~ n extender in the form of a paraffinic oil is utilized in the various formulations. If desired, it can be eliminated. If utilized, the amount can range from about 5% to 20% by weight of the golf ball center. While a paraffinic type is preferred and preferably of the - mineral-oil type, other oil-type extenders of the napth-enic variety could likewise be utilized with the aromatic oils being the least desired. This is indicated by the data presented in Table III concerning rebound and duro-meter properties.
In Table IV, the variation in weights of thegolf ball center is indicated in relation to the specific gravity requirecl as well as the weight of the filler material. This Table indicates the versatility in ob-taining the golf ball center with the desired weight.
From the information given in the Tables, itwill be seen that the low styrene content and high buta diene content results in a golf ball center with high rebound capabilities. Those formulations which give high durometers indicate that the use of fillers and extenders can be freely employed to obtain the desired properties of a golf ball center. Specifically, Table III illus-trates that the best golf ball centers for rebound are produced using the higher proportions of extenders with the paraffinic oil being preferred.
From the information presented in Tables I and II, it will be seen that a radial block copolymer having a molecular weight of 160,000 and a butadiene-styrene amount of 80, 20~ respectively is preferred whether the copolymer is used alone or in combination with another radial block copolymer. It will be seen with reference to Table II that the preferred radial block copolymer mixtures of this invention have different molecular weights yet can have the same or different butadiene-styrene amounts. In two of the preferred formulations listed in I ~. * trade mark ,~, Table II, it will be seen that one of the radial block copolymers has a molecular weight of 160,000 or 150,000 and the other has a molecular weight of 300,000.
It will thus be seen that through the present invention there is now provided a formulation for a golf ball center which allows for a large latitude in formu-lation so as to accomplish the specific performance specifications. The utilization of an uncured radial block copolymer also affords injection molding with faster rates in that no curing or time consuming cross linkage need take place. Also, any finished materials which do not meet specifications can be reused, which is not possible when using a cross-linked polymeric material.
Additionally, the injection molding process with the butadiene-styrene thermoelastomers permits precise size and weight control which is not accomplished when util-izing compression molding.
The foregoing invention can now be practiced by those skilled in the art. Such skilled persons will know that the invention is not necessarily restricted to the particular embodiments presented herein. The scope of the invention is given meaning by the preceding description.
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A solid golf ball center having a sub-stantially spherical form with high rebound capabilities and capable of being injection molded comprising:
(a) a noncross-linked, butadiene-styrene radial block copolymer having a butadiene content in the range of about 50% to 85% by weight and a styrene content in the range of about 15% to 50% by weight; and (b) an inorganic filler material;
said filler material composing the major portion by weight not exceeding 80% of said golf ball center, said center being substantially free of curing agents or initiators and said radial block copolymer having a molecular weight of at least 150,000 as measured by gel permeation chroma-tography.

2. The solid golf ball center as defined in Claim 1 including an extender which is a paraffinic or napthenic oil.

3. The solid golf ball center as defined in Claim 1 wherein said golf ball center has a weight in the range of about 15 grams to about 22 grams.

4. The solid golf ball center as defined in Claim 1 wherein said filler material is present in the range of about 60% to about 80% by weight of the golf ball center.

5. The solid golf ball center as defined in Claim 2 wherein said extender is present in an amount in the range of about 5% to 20% by weight of the golf ball center.

6. The solid golf ball center as defined in Claim 1 wherein said butadiene is represented by 85% by weight of isoprene.

7. The solid golf ball center as defined in Claim 4 wherein said filler material is barium sulfate.

8. The solid golf ball center as defined in Claim 1 wherein the butadiene-styrene radial block copoly-mer has a molecular weight of about 160,000.