JP2004027164A - Golf ball - Google Patents

Abstract

A polybutadiene containing 60% by weight or more of cis-1,4-bond and having a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 30 or more is mainly composed of polybutadiene synthesized using a rare earth element-based catalyst. 15 to 50 parts by weight of an unsaturated carboxylic acid and / or a metal salt thereof, 2 parts by weight or more of a processing aid having a maximum melting point of 115 ° C. or lower, and 100 parts by weight of a rubber base material, and an organic peroxide. includes two or more, the half-life in them 155 ° C. is a 1st short organic peroxide (a), the No. 1 long organic peroxide and (b), the half-life of _{(a) a t, (b} ) If the half-life was b _t, the ratio b _{t /} a _t half-life is not less than 7, the total content of the organic peroxide with respect to the base rubber 100 parts by weight of 0.1 to 0 The composition is characterized by comprising a vulcanized molded product of a rubber composition, which is 0.9 parts by weight. Golf balls.
The golf ball of the present invention can be manufactured with good workability, has a short vulcanization time, has high productivity, and has excellent resilience.
[Selection diagram] None

Description

（式中、Ｒ^４は、炭素数１〜２０の炭素原子を含む炭化水素基、ｎは２以上の整数である。）
【００２１】
ハロゲン含有化合物としては、ＡｌＸ_ｎＲ_３−ｎ（ここで、Ｘはハロゲンを示し、Ｒは、炭素数が１〜２０の炭化水素残基であり、例えば、アルキル基、アリール基、アラルキル基であり、ｎは、１、１．５、２又は３を示す）で示されるアルミニウムハライド、Ｍｅ_３ＳｒＣｌ、Ｍｅ_２ＳｒＣｌ_２、ＭｅＳｒＨＣｌ_２、ＭｅＳｒＣｌ_３などのストロンチウムハライド、その他、四塩化ケイ素、四塩化スズ、四塩化チタンなどの金属ハライド等が用いられる。
【００２２】
ルイス塩基は、ランタン系列希土類元素化合物を錯化するのに用いることができ、例えば、アセチルアセトン、ケトンアルコールなどを挙げることができる。
【００２３】
本発明においては、特に、ランタン系列希土類元素化合物としてネオジウム化合物を用いたネオジウム系触媒の使用が、１，４−シス結合が高含量、１，２−ビニル結合が低含量のポリブタジエンゴムを優れた重合活性で得られるので好ましく、これらの希土類元素系触媒の具体例は、特開平１１−３５６３３号公報に記載されているものを好適に挙げることができる。
【００２４】
希土類元素系触媒の存在下でブタジエンを重合させる場合、溶媒を使用しても、溶媒を使用せずにバルク重合あるいは気相重合してもよく、重合温度は通常−３０〜１５０℃、好ましくは１０〜１００℃とすることができる。
【００２５】
本発明の（Ａ）成分のポリブタジエンは、上記の希土類元素系触媒による重合に引き続き、ポリマーの活性末端に末端変性剤を反応させることにより得られるものであってもよい。
【００２６】
ここで、末端変性剤は、公知のものを使用でき、例えば下記▲１▼〜▲６▼に記載した化合物を挙げることができる。
▲１▼　Ｒ^５ _ｎＭ′Ｘ_４−ｎ、Ｍ′Ｘ_４、Ｍ′Ｘ_３、Ｒ^５ _ｎＭ′（−Ｒ^６−ＣＯＯＲ^７）_４−ｎ又はＲ^５ _ｎＭ′（−Ｒ^６−ＣＯＲ^７）_４−ｎ（式中、Ｒ^５及びＲ^６は、同一でも異なっていてもよく、炭素数１〜２０の炭素原子を含む炭化水素基、Ｒ^７は炭素数１〜２０の炭素原子を含む炭化水素基であり、側鎖にカルボニル基又はエステル基を含んでいてもよく、Ｍ′はスズ原子、ケイ素原子、ゲルマニウム原子又はリン原子、Ｘはハロゲン原子、ｎは０〜３の整数を示す）に対応するハロゲン化有機金属化合物、ハロゲン化金属化合物又は有機金属化合物、
▲２▼　分子中に、Ｙ＝Ｃ＝Ｚ結合（式中、Ｙは炭素原子、酸素原子、チッ素原子又はイオウ原子、Ｚは酸素原子、チッ素原子又はイオウ原子を示す）を含有するヘテロクムレン化合物、
▲３▼　分子中に下記結合を含有するヘテロ３員環化合物
【化２】

（式中、Ｙは、酸素原子、チッ素原子又はイオウ原子を示す。）、
▲４▼　ハロゲン化イソシアノ化合物、
▲５▼　Ｒ^８−（ＣＯＯＨ）_ｍ　、Ｒ^９（ＣＯＸ）_ｍ　、Ｒ^１０−（ＣＯＯ−Ｒ^１１）_ｍ　、Ｒ^１２−ＯＣＯＯ−Ｒ^１３、Ｒ^１４−（ＣＯＯＣＯ−Ｒ^１５）_ｍ　、又は下記式で示されるカルボン酸、酸ハロゲン化物、エステル化合物、炭酸エステル化合物又は酸無水物
【化３】

（式中、Ｒ^８〜Ｒ^１６は、同一でも異なっていてもよく、炭素数１〜５０の炭素原子を含む炭化水素基、Ｘはハロゲン原子、ｍは１〜５の整数を示す。）、
▲６▼　Ｒ^１７ _ｌ　Ｍ″（ＯＣＯＲ^１８）_４−ｌ　、Ｒ^１９ _ｌＭ″（ＯＣＯ−Ｒ^２０−ＣＯＯＲ^２１）_４−ｌ、又は下記式で示されるカルボン酸の金属塩
【化４】

（式中、Ｒ^１７〜Ｒ^２３は、同一でも異なっていてもよく、炭素数１〜２０の炭素原子を含む炭化水素基、Ｍ″はスズ原子、ケイ素原子又はゲルマニウム原子、ｌは０〜３の整数を示す。）等を挙げることができる。
【００２７】
以上の▲１▼〜▲６▼に示される末端変性剤の具体例及び反応させる方法は、例えば、特開平１１−３５６３３号公報，特開平７−２６８１３２号公報等に記載されているもの及び方法を挙げることができる。
【００２８】
本発明において、上記ポリブタジエンとしては、分子量分布Ｍｗ／Ｍｎ（Ｍｗ：重量平均分子量、Ｍｎ：数平均分子量）が、２．０以上、好ましくは２．２以上、更に好ましくは２．４以上、最も好ましくは２．６以上であり、上限としては８．０以下、好ましくは７．５以下、更に好ましくは４．０以下、最も好ましくは３．４以下であることが好ましく、Ｍｗ／Ｍｎが小さすぎると作業性が低下し、大きすぎると反発性が低下する場合がある。
【００２９】
本発明は、上記ポリブタジエンを主材としたゴム基材を用いるものであるが、この場合、この主材のポリブタジエンはゴム基材中、５０重量％以上、好ましくは６０重量％以上、更に好ましくは７０重量％以上であることがよい。また、ゴム基材の１００重量％が上記ポリブタジエンであってもよく、９５重量％以下、場合によったら９０重量％以下の含有量とし得る。
【００３０】
なお、上記ポリブタジエン以外のゴム成分としては、上記ポリブタジエン以外のポリブタジエン、例えばＶＩＩＩ族金属化合物触媒を用いて得られたポリブタジエン、その他のジエンゴム、例えばスチレンブタジエンゴム、天然ゴム、イソプレンゴム、エチレンプロピレンジエンゴム等が挙げられ、好ましくはＶＩＩＩ族触媒のポリブタジエンで、ムーニー粘度（ＭＬ_１＋４（１００℃））が５０未満のもの、更に好ましくはＮｉ触媒のポリブタジエンで、ムーニー粘度（ＭＬ_１＋４（１００℃））が５０未満のものである。
【００３１】
次に、（Ｂ）成分の不飽和カルボン酸としては、アクリル酸、メタクリル酸、マレイン酸、フマル酸等が挙げられ、特にアクリル酸、メタクリル酸が好ましい。不飽和カルボン酸の金属塩としては、亜鉛塩、マグネシウム塩等が挙げられ、中でもアクリル酸亜鉛が好適に用いられる。
【００３２】
上記（Ｂ）成分の不飽和カルボン酸／塩の配合量は、上記（Ａ）成分のゴム基材１００部（重量部、以下同じ）に対し、１５部以上、より好ましくは１８部以上、更に好ましくは２１部以上、最も好ましくは２４部以上であり、５０部以下、より好ましくは４５部以下、更に好ましくは４０部以下、最も好ましくは３７部以下とすることが好ましい。
【００３３】
本発明においては、（Ｃ）成分として、最も高い融点が１１５℃以下、好ましくは１１０℃以下、より好ましくは１０８℃以下、更に好ましくは１０５℃以下の加工助剤を配合する。この場合、融点の下限は６０℃以上、より好ましくは７０℃以上、更に好ましくは８０℃以上、最も好ましくは９０℃以上であることが好ましい。
【００３４】
このような加工助剤としては、
（ｉ）高級脂肪酸金属塩、
（ｉｉ）金属錯体、
（ｉｉｉ）有機硫黄化合物、
（ｉｖ）脂肪族炭化水素、
（ｖ）脂肪酸エステル、
（ｖｉ）脂肪アルコール
を含むものが挙げられ、これらの１種を単独で又は２種以上を組み合わせて用いられる。
【００３５】
加工助剤は、（ｉ）高級脂肪酸金属塩が主成分となり、具体的には、アクチプラストＧＴ、アクチプラストＰＰ、アクチプラストＭ、アクチプラストＴ、アクチプラスト８、アクチプラストＳＴ、アフラックス１２、アフラックス４２等があり、好ましくは、アクチプラストＧＴ、アクチプラストＰＰ（いずれもＲｈｅｉｎ　Ｃｈｅｍｉｅ社製）が挙げられる。
【００３６】
更に詳述すると、高級脂肪酸金属塩は、ＲＣＯＯＭからなり、Ｒの炭素数が１１以上、より好ましくは１３以上、更に好ましくは１５以上であり、３１以下、より好ましくは２７以下、更に好ましくは２４以下の高級脂肪酸が好ましく、高級脂肪酸として、具体的には、オレイン酸、なたね油脂肪酸、トール油脂肪酸、ステアリン酸、ラウリン酸、リノール酸、アビエチン酸、エルカ酸、ミリスチン酸、アラキン酸、リグノセリン酸が挙げられ、これらの１種または２種以上を混合して用いられる。なお、脂肪酸としては、飽和脂肪酸でも不飽和脂肪酸でも良いが、飽和脂肪酸を主成分とした方が好ましい。Ｍは、アルカリ土類金属又はアルカリ金属を表し、上記融点となるものであればいずれのものでも良いが、具体的には、Ｎａ、Ｋ、Ｌｉ、Ｂａ、Ｃａ、Ｍｇ、Ａｌ、Ｆｅ、Ｚｎが挙げられ、中でもＺｎ塩が好ましい。
【００３７】
（ｉｉ）金属錯体としては、フタロシアニン型金属錯体であり、具体的には、テトラアザポルフィン又はヘミポルフィラジン金属錯体であり、特に米国特許第３，８３９，２５０号公報の段落４の３７行目から段落５の３行目までに例示されているものが挙げられる。
【００３８】
（ｉｉｉ）有機硫黄化合物としては、例えば、２，２’−ジベンズアミド−ジフェニルジスルフィド（ＤＢＤ）等を用いることが出来る。なお、この（ｉｉｉ）有機硫黄化合物は、予め加工助剤成分の一つとして加工助剤、特に高級脂肪酸金属塩に加えられたものである。
【００３９】
（ｉｖ）脂肪族炭化水素としては、炭素数が１１以上、より好ましくは１３以上、更に好ましくは１５以上であり、３１以下、より好ましくは２７以下、更に好ましくは２４以下であることが好ましい。
【００４０】
（ｖ）脂肪酸エステルは、ＲＣＯＯＲ’からなり、高級脂肪酸エステルが好ましい。Ｒの炭素数が１１以上、より好ましくは１３以上、更に好ましくは１５以上であり、３１以下、より好ましくは２７以下、更に好ましくは２４以下であり、Ｒ’の炭素数が１１以上、より好ましくは１３以上、更に好ましくは１５以上であり、３１以下、より好ましくは２７以下、更に好ましくは２４以下であることが好ましい。
【００４１】
（ｖｉ）脂肪アルコールとしては、高級脂肪アルコールが好ましく、特に炭素数が１１以上、より好ましくは１３以上、更に好ましくは１５以上であり、３１以下、より好ましくは２７以下、更に好ましくは２４以下の高級脂肪アルコールが好ましい。
【００４２】
上記（Ｃ）成分は、（Ａ）成分１００部に対し、２部以上、好ましくは６部以上、より好ましくは８部以上、更に好ましくは１０部以上、最も好ましくは１２部以上で、好ましくは３０部以下、特に好ましくは２７部以下、より好ましくは２４部以下、更に好ましくは２０部以下、最も好ましくは１５部以下である。
【００４３】
（Ｄ）有機過酸化物としては、２種以上を使用し、この場合、１５５℃における半減期が一番短い有機過酸化物を（ａ）、１５５℃における半減期が一番長い有機過酸化物を（ｂ）とし、（ａ）の半減期をａ_ｔ、（ｂ）の半減期をｂ_ｔとした場合、半減期の比ｂ_ｔ／ａ_ｔが７以上、好ましくは８以上、より好ましくは９以上、更に好ましくは１０以上で、２０以下、より好ましくは１８以下、更に好ましくは１６以下、最も好ましくは１４以下である。２種以上の有機過酸化物を用いても、上記範囲を逸脱した場合、反発性、コンプレッション、耐久性に劣ってしまう。
【００４４】
この場合、（ａ）の１５５℃のおける半減期ａ_ｔは、５秒以上、より好ましくは１０秒以上、更に好ましくは１５秒以上で、１２０秒以下、より好ましくは９０秒以下、更に好ましくは６０秒以下が好ましい。（ｂ）の１５５℃のおける半減期ｂ_ｔは、３００秒以上、好ましくは３６０秒以上、更に好ましくは４２０秒以上で、８００秒以下、好ましくは７００秒以下、更に好ましくは６００秒以下が好ましい。
【００４５】
また、上記（ａ），（ｂ）成分を含む有機過酸化物の総配合量は、上記（Ａ）成分１００部に対して０．１部以上、好ましくは０．２部以上、より好ましくは０．３部以上、更に好ましくは０．４部以上であり、０．９部以下、好ましくは０．８部以下、より好ましくは０．７部以下、更に好ましくは０．６部以下である。配合量が少なすぎると、架橋に要する時間が長くなり、生産性の低下が大きく、コンプレッションも大きく低下してしまう。配合量が多すぎると、反発性、耐久性が低下してしまう。
【００４６】
この場合、（ａ）の添加量としては、（Ａ）成分１００部に対し０．０５部以上、より好ましくは０．０８部以上、更に好ましくは０．１部以上で、０．５部以下、より好ましくは０．４部以下、更に好ましくは０．３部以下が好ましい。（ｂ）の添加量としては、（Ａ）成分１００部に対し０．０５部以上、より好ましくは０．１５部以上、更に好ましくは０．２部以上で、０．７部以下、より好ましくは０．６部以下、更に好ましくは０．５部以下が好ましい。
【００４７】
ここで、有機過酸化物として具体的には、ジクミルパーオキサイド、１，１−ビス（ｔ−ブチルパーオキシ）−３，３，５−トリメチルシクロヘキサン、α，α’−ビス（ｔ−ブチルパーオキシ）ジイソプロピルベンゼン等が挙げられる。これら有機過酸化物は市販品を用いることができ、例えば、パークミルＤ（日本油脂社製）、パーヘキサ３Ｍ（日本油脂社製）、Ｌｕｐｅｒｃｏ　２３１ＸＬ（アトケム社製）等が挙げられる。この場合、上記（ａ）成分の有機過酸化物としては、１，１−ビス（ｔ−ブチルパーオキシ）−３，３，５−トリメチルシクロヘキサンが好ましく、（ｂ）成分の有機過酸化物としては、ジクミルパーオキサイドが好ましい。
【００４８】
（Ｅ）成分の有機硫黄化合物としては、例えば、チオフェノール、チオフトール、ハロゲン化チオフェノール又はそれらの金属塩が挙げられる。より具体的には、ペンタクロロチオフェノール、ペンタフルオロチオフェノール、ペンタブロモチオフェノール、パラクロロチオフェノール又はそれらの亜鉛塩、硫黄数が２〜４のジフェニルポリスルフィド、ジベンジルポリスルフィド、ジベンゾイルポリスルフィド、ジベンゾチアゾイルポリスルフィド、ジチオベンゾイルポリスルフィド、アルキルフェニルジスルフィド類、フラン環を有する硫黄化合物類、チオフェン環を有する硫黄化合物類等が挙げられるが、特に、ペンタクロロチオフェノールの亜鉛塩、ジフェニルジスルフィドを好適に用いることができる。その配合量は、ゴム基材１００部に対して０．２部以上、より好ましくは０．３部以上、更に好ましくは０．５部以上、特に好ましくは０．７部以上で、５部以下、より好ましくは４部以下、更に好ましくは３部以下、特に好ましくは２部以下であることが好ましい。
【００４９】
本発明に係るゴム組成物には、無機充填剤を配合することが好ましい。具体的には、酸化亜鉛、硫酸バリウム、炭酸カルシウム等が挙げられ、その配合量は（Ａ）成分１００部に対し、１部以上、より好ましくは３部以上、更に好ましくは５部以上、最も好ましくは７部以上で、１３０部以下、より好ましくは５０部以下、更に好ましくは４５部以下、最も好ましくは４０部以下とすることが好ましい。
【００５０】
なおまた、必要に応じ、老化防止剤を（Ａ）成分１００部に対し、０．０５部以上、より好ましくは０．１部以上、更に好ましくは０．２部以上で、３部以下、より好ましくは２部以下、更に好ましくは１部以下、最も好ましくは０．５部以下を配合することができる。なお、老化防止剤としては市販品を用いることができ、例えば、ノクラックＮＳ−６、同ＮＳ−３０（大内新興化学工業（株）製、ヨシノックス４２５（吉富製薬（株）製）等が挙げられる。
【００５１】
本発明の加硫成形物は、上述したゴム組成物を、公知のゴルフボール用ゴム組成物と同様の方法で加硫・硬化させることによって得ることができる。加硫条件は、例えば、加硫温度１００〜２００℃、加硫時間１０〜４０分にて実施することができる。
【００５２】
本発明において、上記加硫成形物の硬度は、後述する各種ゴルフボールの使用態様に応じて適宜調整することができ、特に制限されるものではなく、断面硬度は、中心から成形物表面までが平坦であっても中心と成形物表面までに硬度差があってもいずれの場合であってもよい。
【００５３】
また、本発明のゴルフボールは、後述する種々のゴルフボール態様を採ることができるが、特にゴルフボールがワンピースゴルフボール又はソリッドコア若しくはソリッドセンターを具備してなるゴルフボールのいずれかである場合、上記ワンピースソリッドゴルフボール、ソリッドコア又はソリッドセンターの９８０Ｎ（１００ｋｇ）荷重負荷時のたわみ量が、通常２．０ｍｍ以上、好ましくは２．５ｍｍ以上、更に好ましくは２．８ｍｍ以上、最も好ましくは３．２ｍｍ以上、上限としては６．０ｍｍ以下、好ましくは５．５ｍｍ以下、更に好ましくは５．０ｍｍ以下、最も好ましくは４．５ｍｍ以下であることが推奨され、変形量が少なすぎると、打感が悪くなると共に、特にドライバーなどのボールに大変形が生じるロングショット時にスピンが増えすぎて飛ばなくなり、軟らかすぎると、打感が鈍くなると共に、反発が十分でなくなり飛ばなくなる上、繰り返し打撃による割れ耐久性が悪くなる場合がある。
【００５４】
本発明のゴルフボールは、上記加硫成形物を構成要素とするもので、ボールの態様は、特に制限されるものではなく、上記加硫成形物がゴルフボールに直接適用されるワンピースゴルフボール、加硫成形物をソリッドコアとし、その表面にカバーが形成されたツーピースソリッドゴルフボール、加硫成形物をソリッドコアとし、２層以上のカバーが形成された３ピース以上のマルチピースソリッドゴルフボール、上記加硫成形物がセンターコアとして適用された糸巻きゴルフボール等の種々の態様を採ることができる。特に、加硫成形物の特性を活かし、製造時の押出し性、製品ゴルフボールに対する反発性付与の観点から、本発明の加硫成形物をソリッドコアとして使用するツーピースソリッドゴルフボール、マルチピースソリッドゴルフボールであることが好適な使用態様として推奨される。
【００５５】
本発明において、加硫成形物を上記ソリッドコアとする場合、ソリッドコアの直径は３０．０ｍｍ以上、好ましくは３２．０ｍｍ以上、更に好ましくは３５．０ｍｍ以上、最も好ましくは３７．０ｍｍ以上であり、上限として４１．０ｍｍ以下、好ましくは４０．５ｍｍ以下、更に好ましくは４０．０ｍｍ以下、最も好ましくは３９．５ｍｍ以下とすることが推奨され、特に、ツーピースソリッドゴルフボールの直径は、３７．０ｍｍ以上、好ましくは３７．５ｍｍ以上、更に好ましくは３８．０ｍｍ以上、最も好ましくは３８．５ｍｍ以上であり、上限として４１．０ｍｍ以下、好ましくは４０．５ｍｍ以下、更に好ましくは４０．０ｍｍ以下、スリーピースソリッドゴルフボールの直径は、３０．０ｍｍ以上、好ましくは３２．０ｍｍ以上、更に好ましくは３４．０ｍｍ以上、最も好ましくは３５．０ｍｍ以上であり、上限として４０．０ｍｍ以下、好ましくは３９．５ｍｍ以下、更に好ましくは３９．０ｍｍ以下とすることが推奨される。
【００５６】
上記ソリッドコアの比重は、通常０．９以上、好ましくは１．０以上、更に好ましくは１．１以上、上限として１．４以下、好ましくは１．３以下、更に好ましくは１．２以下であることが推奨される。
【００５７】
本発明のゴルフボールをツーピースソリッドゴルフボール、マルチピースソリッドゴルフボールとする場合には、上記加硫成形物をソリッドコアとして公知のカバー材、中間層材を射出成形又は加圧成形して形成することができる。
【００５８】
これらカバー材、中間層材の主材として、具体的には、熱可塑性又は熱硬化性のポリウレタン系エラストマー、ポリエステル系エラストマー、アイオノマー樹脂、ポリオレフィン系エラストマー又はこれらの混合物等を挙げることができる。これらは、１種を単独で又は２種以上を混合して用いることができ、特に、熱可塑性ポリウレタン系エラストマー、アイオノマー樹脂を好適に挙げることができる。
【００５９】
上記熱可塑性ポリウレタン系エラストマーとしては、市販品を用いることができ、例えばパンデックスＴ７２９８，同Ｔ７２９５，同Ｔ７８９０、同ＴＲ３０８０、同Ｔ８２９５（ＤＩＣ・バイエルポリマー社製）などのジイソシアネートが脂肪族又は芳香族であるもの等が挙げられる。また、アイオノマー樹脂の市販品としては、サーリン６３２０、同８１２０（米国デュポン社製）、ハイミラン１７０６、同１６０５、同１８５５、同１６０１、同１５５７（三井・デュポンポリケミカル社製）等を例示できる。
【００６０】
更に、上記カバー材又は中間層材の主材に対しては、任意成分として、上記以外の熱可塑性エラストマー等のポリマーを配合することができる。任意成分のポリマーとして、具体的には、ポリアミド系エラストマー、スチレン系ブロックエラストマー、水添ポリブタジエン、エチレン−酢酸ビニル（ＥＶＡ）共重合体等を配合し得る。
【００６１】
この場合、ソリッドコアと２層以上のカバーとを備えたマルチピースソリッドゴルフボールにおいては、
（Ａ）上記ゴム組成物を用いて形成されたソリッドコアの１００ｋｇ荷重負荷時のたわみ量を２．５ｍｍ以上、特に３．０ｍｍ以上で、６．０ｍｍ以下、特に５．５ｍｍ以下とし、またカバー最内層をショアＤ硬度５０以上、特に５５以上で、７０以下、特に６５以下にすると共に、カバー最外層をショアＤ硬度４０以上、特に４３以上で、５５以下、特に５０以下とし、カバー最外層より最内層を硬く形成することが好ましく、これにより、更に高反発でコントロール性に優れたゴルフボールが得られる。
【００６２】
この場合、コアの直径を３０ｍｍ以上、特に３４ｍｍ以上で、４０ｍｍ以下、特に３９ｍｍ以下とし、最内層カバーの厚さを０．５ｍｍ以上、特に１．０ｍｍ以上で、３．０ｍｍ以下、特に２．０ｍｍ以下とし、最外層カバーの厚さを０．５ｍｍ以上、特に１．０ｍｍ以上で、２．５ｍｍ以下、特に２．０ｍｍ以下とし、更にカバー総厚さを１．０ｍｍ以上、特に１．５ｍｍ以上で、５．５ｍｍ以下、特に４．５ｍｍ以下とすることが好ましい。
【００６３】
あるいは、
（Ｂ）上記ゴム組成物を用いて形成されたソリッドコアの１００ｋｇ荷重負荷時のたわみ量を３．０ｍｍ以上、特に３．５ｍｍ以上で、６．０ｍｍ以下、特に５．５ｍｍ以下とし、またカバー最内層をショアＤ硬度８以上、特に３０以上で、４９以下、特に４５以下にすると共に、カバー最外層をショアＤ硬度５６以上、特に５９以上で、７０以下、特に６５以下とし、カバー最内層より最外層を硬く形成することにより、打感が良好で飛び性能に優れたゴルフボールが得られる。
【００６４】
この場合、コアの直径は３０ｍｍ以上、特に３４ｍｍ以上で、４０ｍｍ以下、特に３９ｍｍ以下とし、最内層カバーの厚さを０．５ｍｍ以上、特に１．０ｍｍ以上で、５．０ｍｍ以下、特に２．５ｍｍ以下とし、最外層カバーの厚さを１．０ｍｍ以上、特に１．３ｍｍ以上で、３．０ｍｍ以下、特に２．２ｍｍ以下とし、更にカバー総厚さを１．５ｍｍ以上、特に２．５ｍｍ以上で、８．０ｍｍ以下、特に６．０ｍｍ以下とすることが好ましい。
【００６５】
更に、ツーピースゴルフボールの場合は、上記ゴム組成物にて形成されたコアの１００ｋｇ荷重負荷時のたわみ量を２．０ｍｍ以上、特に２．８ｍｍ以上で、５．０ｍｍ以下、特に４．５ｍｍ以下とし、カバーのショアＤ硬度を３０以上、特に４０以上で、６５以下、特に６２以下とすることが好ましく、これにより飛距離が優位で、かつフィーリングも軟らかいゴルフボールが得られる。
【００６６】
この場合、コアの直径は３７〜４１ｍｍ、特に３９．５〜４０．５ｍｍとすることが好ましい。
【００６７】
本発明のゴルフボールは、競技用としてゴルフ規則に従うものとすることができ、直径４２．６７ｍｍ以上、重量４５．９３ｇ以下に形成することができる。直径の上限として好ましくは４４．０ｍｍ以下、更に好ましくは４３．５ｍｍ以下、最も好ましくは４３．０ｍｍ以下、重量の下限として好ましくは４４．５ｇ以上、特に好ましくは４５．０ｇ以上、更に好ましくは４５．１ｇ以上、最も好ましくは４５．２ｇ以上であることが推奨される。
【００６８】
【発明の効果】
本発明のゴルフボールは、作業性よく製造することができ、また加硫時間も短く、生産性が高い上、反発性に優れたものである。
【００６９】
【実施例】
以下、実施例及び比較例を示し、本発明を具体的に説明するが、本発明は下記の実施例に制限されるものではない。
【００７０】
［実施例、比較例］
表１〜３に示すゴム組成物を用いて、ツーピースゴルフボールのコアを作成した。この場合、コアを外径は３８．９ｍｍ、コアの重量は３６．０ｇであった。このコアにハイミラン１６０１とハイミラン１５５７との重量比１：１の混合物からなるカバー材を射出して、ディンプルを有するゴルフボールを形成し、更にその表面をペイントで被覆し、外径４２．７ｍｍ、重量４５．３ｇのツーピースソリッドゴルフボールを得た。
【００７１】
上記コアの１００ｋｇ荷重たわみ量、反発性、押出し作業性及びゴルフボールの飛び性能を下記方法により評価した。結果を表１〜３に示す。
１００ｋｇ荷重たわみ量
得られたソリッドコアに対し、１００ｋｇ（９８０Ｎ）荷重負荷時の変形量（ｍｍ）を計測した。
反発性
公認機関ＵＳＧＡと同タイプの初速度計で初速度を測定し、実施例１〜１３、比較例２〜１０について、比較例１を基準にしたときの初速度の差を表した。
押出し作業性
押出し作業性については、押出し後のスラグ形状について、下記基準にて評価した。
５：スラグ肌がきれいで非常に良好
４：スラグ肌にややざらつきがあるが良好
３：スラグ肌に毛羽立ちがあるが、押出し可能
２：スラグ肌の毛羽立ちが非常に目立つが、押出し可能
１：スラグ肌の形状不良が起こり、所定量の押出しが困難
飛び性能
打撃マシンにてドライバー（Ｗ＃１，Ｔｏｕｒ　Ｓｔａｇｅ　Ｘ５００，ロフト９°、シャフトＸ，ブリヂストンスポーツ社製）にて、ヘッドスピード４５ｍ／ｓで打撃したときの飛び性能を測定した。
【００７２】
【表１】

【００７３】
【表２】

【００７４】
【表３】

【００７５】
ポリブタジエンＢＲ１８：ＪＳＲ社製、Ｃｉｓ１，４量９６％、ムーニー粘度（ＭＬ_１＋４（１００℃））６０、分子量分布Ｍｗ／Ｍｎ４．２、触媒Ｎｉ
ポリブタジエンＢＲ０１：ＪＳＲ社製、Ｃｉｓ１，４量９５％、ムーニー粘度（ＭＬ_１＋４（１００℃））４４、分子量分布Ｍｗ／Ｍｎ４．２、触媒Ｎｉ
ポリブタジエンＣＢ２２：バイエル社製、Ｃｉｓ１，４量９８％、ムーニー粘度（ＭＬ_１＋４（１００℃））６２、分子量分布Ｍｗ／Ｍｎ７．１、触媒Ｎｄ
ポリブタジエンＨＣＢＮ−１３：ＪＳＲ社製、Ｃｉｓ１，４量９６％、ムーニー（ＭＬ_１＋４（１００℃））粘度５４、分子量分布Ｍｗ／Ｍｎ３．２、触媒Ｎｄ
ポリブタジエンＳＲ８５１０：ファイヤーストンポリマーズ社製、Ｃｉｓ１，４量９６％、ムーニー粘度（ＭＬ_１＋４（１００℃））４５、分子量分布Ｍｗ／Ｍｎ２．５、触媒Ｎｄ
パーヘキサ３Ｍ−４０：１，１−ビス（ｔ−ブチルパーオキシ）−３，３，５−トリメチルシクロヘキサン、日本油脂社製、１５５℃における半減期、４０ｓｅｃ
パークミルＤ：ジクミルパーオキサイド、日本油脂社製、１５５℃における半減期　８ｍｉｎ
アクチプラストＧＴ：Ｒｈｅｉｎ　Ｃｈｅｍｉｅ社製、融点／約１０３℃、飽和脂肪酸の亜鉛塩を主剤とした混合物
アクチプラストＭＳ：Ｒｈｅｉｎ　Ｃｈｅｍｉｅ社製、融点／約１０５℃、高分子の飽和脂肪酸の亜鉛塩を主剤とした活性混合物に、硫黄化合物を加えたもの
アクチプラストＰＰ：Ｒｈｅｉｎ　Ｃｈｅｍｉｅ社製、融点／約１０１℃、飽和脂肪酸の亜鉛塩の混合物
アクチプラストＦ：Ｒｈｅｉｎ　Ｃｈｅｍｉｅ社製、融点／約８５℃、不飽和脂肪酸の亜鉛塩と活性剤との混合物
ステアリン酸亜鉛：融点／約１２４℃
【００７６】
上記の結果より、下記の点が認められる。
比較例１、２：
Ｎｉ系触媒を用いたポリブタジエンであり、加工助剤を添加しないため、反発性、飛距離が低下する。
比較例３：
Ｎｄ系触媒を用いたポリブタジエンであり、加工助剤を添加しないため、作業性が非常に悪い。
比較例４：
加工助剤の添加量が少ないため、反発性、飛距離が低下する。
比較例５：
加工助剤を添加し過ぎたため、たわみ量が大きくなり過ぎ、反発性、飛距離が低下する。
比較例６：
ステアリン酸亜鉛を添加しても、押出し作業性は向上せず、たわみ量が小さく、硬くなり、反発性、飛距離も低下する。
比較例７：
有機過酸化物を単独で使用しているため、反発性が大きく低下してしまう。
比較例８：
Ｎｉ系触媒を用いたポリブタジエンであり、加工助剤を添加しないため、反発性、飛距離が低下する。
比較例９：
ステアリン酸亜鉛を添加しても、押出し作業性は向上せず、たわみ量が小さく、硬くなり、反発性、飛距離も低下する。
比較例１０：
有機過酸化物を単独で使用しているため、反発性が大きく低下してしまう。
【００７７】
これに対し、実施例のものは、押出し作業性が良好である上、反発性、飛び性能が良好なものであった。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a golf ball that can be manufactured with good workability and has excellent resilience.
[0002]
Problems to be solved by the prior art and the invention
Conventionally, in order to impart excellent resilience to golf balls, various improvements have been made to the blending of polybutadiene used as a rubber base material.
[0003]
For example, Japanese Unexamined Patent Publication (Kokai) No. 62-89750 discloses that as a rubber substrate, a polybutadiene having a Mooney viscosity of 70 to 100 synthesized using a Ni or Co catalyst and a Mooney viscosity of 30 to 90 synthesized using a lanthanum catalyst are used. There has been proposed a rubber composition for a solid golf ball, which comprises a polybutadiene or a polybutadiene having a Mooney viscosity of 20 to 50 synthesized using a Ni, Co catalyst.
However, the above proposal requires further improvement in workability at the time of extrusion and resilience.
[0004]
JP-A-2-268778 proposes a golf ball formed by blending a polybutadiene having a Mooney viscosity of less than 50 synthesized with a Group VIII catalyst and a polybutadiene having a Mooney viscosity of less than 50 synthesized with a lanthanide catalyst. However, the resulting golf ball has poor resilience.
[0005]
Japanese Patent Application Laid-Open No. 11-70187 discloses a multi-piece solid golf ball having an intermediate layer formed of polybutadiene having a low Mooney viscosity, and Japanese Patent Application Laid-Open No. 11-319148 uses a Ni, Co catalyst. JP-A-11-164912 discloses a solid golf ball formed of a rubber composition containing a polybutadiene having a Mooney viscosity of 50 to 69 and a polybutadiene having a Mooney viscosity of 20 to 90 synthesized using a lanthanoid catalyst. A solid golf ball formed of a rubber composition having a 1,2 vinyl bond of 2.0% or less and a weight average molecular weight to number average molecular weight ratio Mw / Mn of 3.5 or less, JP-A-63-275356; Japanese Patent Application Laid-Open Publication No. HEI 3-3-200 discloses a golf ball formed of a rubber composition containing polybutadiene having a high Mooney viscosity. No. 5,1985, proposes a golf ball formed of a rubber composition obtained by blending a polybutadiene having a high number average molecular weight and a polybutadiene having a low number average molecular weight. It has the disadvantage that the resilience of the golf ball is poor.
[0006]
Japanese Patent Application Laid-Open No. 61-71070 discloses that two kinds of organic peroxides are used, and Japanese Patent Application Laid-Open No. 62-112574 discloses that a small amount of organic peroxide is used. However, there is a problem that the resilience is not sufficient, and the crosslinking time is delayed, and the productivity is greatly reduced.
[0007]
Generally, polybutadiene synthesized using a rare earth element-based catalyst is said to have high resilience, but this leaves a problem that workability is extremely poor.
In the above-mentioned prior art, workability improvement has been studied based on the mixing ratio of various polybutadienes, but there is a problem that adding polybutadiene having good workability lowers the resilience.
Further, in polybutadiene using a normal Group VIII catalyst, there is a problem that if the amount of the added organic peroxide is reduced, the vulcanization time becomes longer and the productivity is reduced.
[0008]
The present invention has been made in view of the above circumstances, and has good extrudability, can be manufactured with good workability, can shorten the vulcanization time, can improve productivity, and has excellent resilience. The purpose is to provide the ball.
[0009]
Means for Solving the Problems and Embodiments of the Invention
The present inventors have conducted intensive studies in order to achieve the above object. As a result, the inventors of the present invention contained 60% by weight or more of a cis-1,4-bond,_{1 + 4}(100 ° C.)) using a rubber base mainly composed of polybutadiene synthesized using a rare earth element-based catalyst having 30 or more, and based on 100 parts by weight of the rubber base, unsaturated carboxylic acid and / or 15 to 50 parts by weight of the metal salt, 2 parts by weight or more of a processing aid having the highest melting point of 115 ° C. or less, and two or more organic peroxides, of which the half-life at 155 ° C. is the shortest The organic peroxide is (a), the longest organic peroxide is (b), and the half-life of (a) is a_t, The half-life of (b)_tAnd the half-life ratio b_t/ A_tIs not less than 7, and a vulcanized molded product of a rubber composition compounded so that the total content of these organic peroxides is 0.1 to 0.9 parts by weight based on 100 parts by weight of the rubber base material. It has been found that a golf ball excellent in manufacturability and good in resilience can be obtained by using it as a component, in particular, by using a solid core of a solid golf ball. That is, a polybutadiene synthesized using a rare-earth element-based catalyst having high repulsion is used, and at least 2 parts by weight of a fatty acid metal salt having the highest melting point of 115 ° C. or less and two or more organic peroxides having significantly different half-lives. By containing 0.1 to 0.9 parts by weight of the product, the workability can be improved, the vulcanization time can be shortened, the productivity can be improved, and the resilience can be further improved. And found the present invention.
[0010]
Accordingly, the present invention provides the following golf balls.
Claim 1:
It contains 60% by weight or more of cis-1,4-bond and has Mooney viscosity (ML_{1 + 4}The unsaturated carboxylic acid and / or the metal salt thereof is 15 to 50 parts by weight per 100 parts by weight of a rubber base material mainly composed of polybutadiene synthesized using a rare earth element-based catalyst (100 ° C.) of 30 or more. Parts by weight, 2 parts by weight or more of a processing aid having a highest melting point of 115 ° C. or less, and two or more kinds of organic peroxides, of which the organic peroxide having the shortest half-life at 155 ° C. is (a) The longest organic peroxide is (b), and the half-life of (a) is a_t, The half-life of (b)_tAnd the half-life ratio b_t/ A_tIs not less than 7, and a vulcanized molded product of a rubber composition having a total content of these organic peroxides of 0.1 to 0.9 parts by weight based on 100 parts by weight of the rubber base material is a constituent element. A golf ball,
Claim 2:
The golf ball of claim 1, wherein the processing aid comprises a higher fatty acid metal salt.
Claim 3:
The golf ball according to claim 2, wherein the higher fatty acid metal salt has 12 or more carbon atoms.
Claim 4:
The golf ball according to claim 2 or 3, wherein the higher fatty acid metal salt is mainly composed of a saturated fatty acid metal salt.
Claim 5:
The golf ball according to claim 2, wherein the higher fatty acid metal salt contains an unsaturated fatty acid metal salt as a main component.
Claim 6:
The golf ball according to any one of claims 2 to 5, wherein the higher fatty acid metal salt comprises a higher fatty acid zinc salt as a main component.
Claim 7:
The golf ball according to claim 1, wherein the processing aid comprises a metal complex.
Claim 8:
The golf ball according to claim 7, wherein the metal complex is a phthalocyanine-type metal complex.
Claim 9:
The golf ball of claim 1, wherein the processing aid comprises an organic sulfur compound.
Claim 10:
The golf ball according to claim 9, wherein the organic sulfur compound is 2,2'-dibenzamide-diphenyl disulfide.
Claim 11:
The golf ball of claim 1, wherein the processing aid comprises an aliphatic hydrocarbon.
Claim 12:
The golf ball of claim 1, wherein the processing aid comprises a fatty acid ester.
Claim 13:
The golf ball according to claim 12, wherein the fatty acid ester is a higher fatty acid ester.
Claim 14:
The golf ball according to claim 13, wherein the higher fatty acid ester has 12 or more carbon atoms.
Claim 15:
The golf ball of claim 1, wherein the processing aid comprises a fatty alcohol.
Claim 16:
The golf ball according to claim 15, wherein the fatty alcohol is a higher fatty alcohol.
Claim 17:
The golf ball according to claim 16, wherein the higher fatty alcohol has 12 or more carbon atoms.
Claim 18:
The golf ball according to any one of claims 1 to 17, wherein the compounding amount of the processing aid is 2 to 30 parts by weight based on 100 parts by weight of the rubber base material.
Claim 19:
The golf ball according to claim 1, wherein the compounding amount of the organic sulfur compound is 0.2 to 5 parts by weight based on 100 parts by weight of the rubber substrate.
Claim 20:
20. The golf ball according to any one of claims 1 to 19, wherein 50% by weight or more of the rubber base material is polybutadiene synthesized using a rare earth element-based catalyst.
Claim 21:
21. The golf ball according to claim 1, wherein the polybutadiene has a molecular weight distribution Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) of 2.0 to 8.0.
Claim 22:
A solid golf ball having a solid core formed to have a deflection of 2.0 to 6.0 mm under a load of 100 kg using the rubber composition according to any one of claims 1 to 21.
[0011]
Hereinafter, the present invention will be described in more detail.
The golf ball of the present invention
(A) It contains 60% by weight or more of a cis-1,4-bond and has a Mooney viscosity (ML)_{1 + 4}(100 ° C.)) a rubber base material mainly composed of polybutadiene synthesized using a rare earth element-based catalyst having 30 or more,
(B) an unsaturated carboxylic acid and / or a metal salt thereof,
(C) a processing aid having a highest melting point of 115 ° C. or lower,
(D) Organic peroxide
And (E) a vulcanized molded product of a rubber composition which may optionally contain an organic sulfur compound.
[0012]
Here, first, the polybutadiene of the component (A) has a cis-1,4-bond content of at least 60% (% by weight, the same applies hereinafter), preferably at least 80%, more preferably at least 90%, and most preferably at least 95%. % Or more. If the amount of the cis-1,4-bond is too small, the resilience decreases.
[0013]
The polybutadiene has a Mooney viscosity (ML)_{1 + 4}(100 ° C.)) is 30 or more, preferably 38 or more, more preferably 45 or more, most preferably 55 or more, particularly preferably 65 or more, and the upper limit is 140 or less, preferably 120 or less, more preferably 100 or less. It is preferable that
[0014]
The Mooney viscosity referred to in the present invention is an industrial viscosity index (JIS-K6300) measured by a Mooney viscometer, which is a kind of rotational plasticity meter, and ML is used as a unit symbol._{1 + 4}(100 ° C.). M indicates Mooney viscosity, L indicates a large rotor (L type), 1 + 4 indicates a preheating time of 1 minute, and a rotation time of the rotor is 4 minutes, indicating that the measurement was performed at 100 ° C.
[0015]
The polybutadiene used in the present invention needs to be synthesized with a rare earth element-based catalyst, and known rare earth element-based catalysts can be used.
[0016]
For example, a lanthanum series rare earth element compound, an organoaluminum compound, an alumoxane, a halogen-containing compound and, if necessary, a catalyst comprising a combination of a Lewis base can be mentioned.
[0017]
Examples of the lanthanide series rare earth element compounds include metal halides having the atomic numbers of 57 to 71, carboxylate salts, alcoholates, thioalcoholates, and amides.
[0018]
Examples of the organoaluminum compound include, for example, AlR¹R²R³(Where R¹, R²And R³May be the same or different and each represents hydrogen or a hydrocarbon residue having 1 to 8 carbon atoms).
[0019]
The alumoxane preferably includes a compound having a structure represented by the following formula (I) or (II). In this case, Fine Chemicals, 23, (9), 5 (1994); Am. Chem. Soc. , 115, 4971 (1993); Am. Chem. Soc. , 117, 6465 (1995).
[0020]
Embedded image

(Where R⁴Is a hydrocarbon group containing 1 to 20 carbon atoms, and n is an integer of 2 or more. )
[0021]
As a halogen-containing compound, AlX_nR_3-n(Where X represents a halogen, R is a hydrocarbon residue having 1 to 20 carbon atoms, for example, an alkyl group, an aryl group, or an aralkyl group, and n is 1, 1.5, 2 Or 3) aluminum halide, Me₃SrCl, Me₂SrCl₂, MeSrHCl₂, MeSrCl₃And strontium halides, and metal halides such as silicon tetrachloride, tin tetrachloride, and titanium tetrachloride.
[0022]
The Lewis base can be used to complex a lanthanide series rare earth element compound, and examples thereof include acetylacetone and ketone alcohol.
[0023]
In the present invention, in particular, the use of a neodymium-based catalyst using a neodymium compound as a lanthanum series rare earth element compound is superior to polybutadiene rubber having a high content of 1,4-cis bonds and a low content of 1,2-vinyl bonds. Specific examples of these rare earth element-based catalysts include those described in JP-A-11-35633.
[0024]
When butadiene is polymerized in the presence of a rare-earth element-based catalyst, a solvent may be used, bulk polymerization or gas phase polymerization may be performed without using a solvent, and the polymerization temperature is usually -30 to 150 ° C, preferably It can be set to 10 to 100 ° C.
[0025]
The polybutadiene of the component (A) of the present invention may be obtained by reacting a terminal modifier with the active terminal of the polymer, following the polymerization with the rare earth element-based catalyst.
[0026]
Here, as the terminal modifier, known compounds can be used, and examples thereof include the compounds described in the following (1) to (6).
▲ 1 ▼ R⁵ _nM'X_4-n, M'X₄, M'X₃, R⁵ _nM '(-R⁶-COOR⁷)_4-nOr R⁵ _nM '(-R⁶-COR⁷)_4-n(Where R⁵And R⁶May be the same or different, and represent a hydrocarbon group containing 1 to 20 carbon atoms, R⁷Is a hydrocarbon group having 1 to 20 carbon atoms, may have a carbonyl group or an ester group in the side chain, M 'is a tin atom, a silicon atom, a germanium atom or a phosphorus atom, and X is a halogen atom. Atom, n represents an integer of 0 to 3), a halogenated organometallic compound, a halogenated metal compound or an organometallic compound,
(2) Heterocumulene containing a Y ＝ C Z bond (wherein Y represents a carbon atom, an oxygen atom, a nitrogen atom or a sulfur atom, and Z represents an oxygen atom, a nitrogen atom or a sulfur atom) in the molecule. Compound,
(3) Hetero three-membered ring compound containing the following bond in the molecule
Embedded image

(In the formula, Y represents an oxygen atom, a nitrogen atom or a sulfur atom.),
(4) Halogenated isocyano compound,
▲ 5 ▼ R⁸-(COOH)_m, R⁹(COX)_m, R¹⁰-(COO-R¹¹)_m, R¹²-OCOO-R¹³, R¹⁴-(COOCO-R^Fifteen)_mカ ル ボ ン, or a carboxylic acid, acid halide, ester compound, carbonate compound or acid anhydride represented by the following formula
Embedded image

(Where R⁸~ R¹⁶May be the same or different, and represent a hydrocarbon group containing 1 to 50 carbon atoms, X represents a halogen atom, and m represents an integer of 1 to 5. ),
▲ 6 ▼ R¹⁷ _lM ”(OCOR¹⁸)_4-l, R¹⁹ _lM "(OCO-R²⁰-COOR²¹)_4-lOr a metal salt of a carboxylic acid represented by the following formula:
Embedded image

(Where R¹⁷~ R²³May be the same or different and include a hydrocarbon group containing 1 to 20 carbon atoms, M ″ represents a tin atom, a silicon atom or a germanium atom, and l represents an integer of 0 to 3). be able to.
[0027]
Specific examples of the terminal modifier shown in the above (1) to (6) and the method of reacting are described in, for example, JP-A-11-35633, JP-A-7-268132 and the like. Can be mentioned.
[0028]
In the present invention, the polybutadiene has a molecular weight distribution Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) of 2.0 or more, preferably 2.2 or more, more preferably 2.4 or more, and most preferably It is preferably at least 2.6, and the upper limit is preferably at most 8.0, preferably at most 7.5, more preferably at most 4.0, most preferably at most 3.4, and the Mw / Mn is small. If it is too large, the workability may be reduced, and if it is too large, the resilience may be reduced.
[0029]
In the present invention, a rubber base material containing the above-mentioned polybutadiene as a main material is used. In this case, the polybutadiene of the main material is 50% by weight or more, preferably 60% by weight or more, more preferably in the rubber base material. The content is preferably 70% by weight or more. Also, 100% by weight of the rubber substrate may be the polybutadiene, and may have a content of 95% by weight or less, and in some cases 90% by weight or less.
[0030]
As the rubber component other than the polybutadiene, a polybutadiene other than the polybutadiene, for example, a polybutadiene obtained using a Group VIII metal compound catalyst, other diene rubbers, for example, styrene butadiene rubber, natural rubber, isoprene rubber, ethylene propylene diene rubber And the like. Preferably, the polybutadiene of Group VIII catalyst has a Mooney viscosity (ML)_{1 + 4}(100 ° C.)) is less than 50, more preferably a Ni-catalyzed polybutadiene having a Mooney viscosity (ML)_{1 + 4}(100 ° C.)) is less than 50.
[0031]
Next, examples of the unsaturated carboxylic acid as the component (B) include acrylic acid, methacrylic acid, maleic acid, and fumaric acid, and acrylic acid and methacrylic acid are particularly preferable. Examples of the metal salt of an unsaturated carboxylic acid include a zinc salt and a magnesium salt, and among them, zinc acrylate is preferably used.
[0032]
The compounding amount of the unsaturated carboxylic acid / salt of the component (B) is 15 parts or more, more preferably 18 parts or more, based on 100 parts (parts by weight, hereinafter the same) of the rubber base material of the component (A). It is preferably 21 parts or more, most preferably 24 parts or more, 50 parts or less, more preferably 45 parts or less, further preferably 40 parts or less, and most preferably 37 parts or less.
[0033]
In the present invention, as the component (C), a processing aid having a highest melting point of 115 ° C. or lower, preferably 110 ° C. or lower, more preferably 108 ° C. or lower, further preferably 105 ° C. or lower is blended. In this case, the lower limit of the melting point is preferably 60 ° C. or higher, more preferably 70 ° C. or higher, further preferably 80 ° C. or higher, and most preferably 90 ° C. or higher.
[0034]
Such processing aids include:
(I) higher fatty acid metal salt,
(Ii) a metal complex,
(Iii) an organic sulfur compound,
(Iv) aliphatic hydrocarbons,
(V) fatty acid esters,
(Vi) fatty alcohol
And these may be used alone or in combination of two or more.
[0035]
The processing aid comprises (i) a higher fatty acid metal salt as a main component. Specifically, Actiplast GT, Actiplast PP, Actiplast M, Actiplast T, Actiplast 8, Actiplast ST, Aflux 12, Aflux 42 and the like, and preferably, Actiplast GT and Actiplast PP (both manufactured by Rhein Chemie).
[0036]
More specifically, the higher fatty acid metal salt is composed of RCOOM, and the carbon number of R is 11 or more, more preferably 13 or more, still more preferably 15 or more, 31 or less, more preferably 27 or less, still more preferably 24 or more. The following higher fatty acids are preferred.Specific examples of higher fatty acids include oleic acid, rapeseed oil fatty acid, tall oil fatty acid, stearic acid, lauric acid, linoleic acid, abietic acid, erucic acid, myristic acid, arachinic acid, and lignoceric acid. And one or more of these are used as a mixture. The fatty acid may be a saturated fatty acid or an unsaturated fatty acid, but preferably contains a saturated fatty acid as a main component. M represents an alkaline earth metal or an alkali metal, and any metal may be used as long as it has the above melting point. Specifically, Na, K, Li, Ba, Ca, Mg, Al, Fe, Zn And a Zn salt is preferable.
[0037]
(Ii) The metal complex is a phthalocyanine-type metal complex, specifically, a tetraazaporphine or hemiporphyrazine metal complex, and particularly, line 37 in paragraph 4 of US Pat. No. 3,839,250. To the third line of the fifth paragraph.
[0038]
(Iii) As the organic sulfur compound, for example, 2,2'-dibenzamido-diphenyl disulfide (DBD) can be used. The organic sulfur compound (iii) has been previously added to a processing aid, particularly a metal salt of a higher fatty acid, as one of the processing aid components.
[0039]
(Iv) The aliphatic hydrocarbon preferably has 11 or more, more preferably 13 or more, still more preferably 15 or more, 31 or less, more preferably 27 or less, still more preferably 24 or less.
[0040]
(V) The fatty acid ester is composed of RCOOR ', and a higher fatty acid ester is preferable. R has 11 or more, more preferably 13 or more, still more preferably 15 or more, 31 or less, more preferably 27 or less, still more preferably 24 or less, and R 'has 11 or more, more preferably Is preferably 13 or more, more preferably 15 or more, preferably 31 or less, more preferably 27 or less, and further preferably 24 or less.
[0041]
(Vi) As fatty alcohols, higher fatty alcohols are preferred, and particularly those having 11 or more, more preferably 13 or more, still more preferably 15 or more, 31 or less, more preferably 27 or less, and still more preferably 24 or less. Higher fatty alcohols are preferred.
[0042]
Component (C) is at least 2 parts, preferably at least 6 parts, more preferably at least 8 parts, even more preferably at least 10 parts, most preferably at least 12 parts, and preferably at least 12 parts, per 100 parts of component (A). It is 30 parts or less, particularly preferably 27 parts or less, more preferably 24 parts or less, still more preferably 20 parts or less, and most preferably 15 parts or less.
[0043]
(D) Two or more kinds of organic peroxides are used. In this case, the organic peroxide having the shortest half-life at 155 ° C. is (a) the organic peroxide having the longest half-life at 155 ° C. Let the product be (b) and the half-life of (a) be a_t, The half-life of (b)_tAnd the half-life ratio b_t/ A_tIs 7 or more, preferably 8 or more, more preferably 9 or more, still more preferably 10 or more, 20 or less, more preferably 18 or less, still more preferably 16 or less, and most preferably 14 or less. Even if two or more kinds of organic peroxides are used, if they deviate from the above range, the resilience, compression and durability will be poor.
[0044]
In this case, the half life a at 155 ° C. of (a) a_tIs preferably at least 5 seconds, more preferably at least 10 seconds, even more preferably at least 15 seconds, up to 120 seconds, more preferably up to 90 seconds, even more preferably up to 60 seconds. (B) Half-life b at 155 ° C_tIs 300 seconds or more, preferably 360 seconds or more, more preferably 420 seconds or more, and 800 seconds or less, preferably 700 seconds or less, and more preferably 600 seconds or less.
[0045]
The total amount of the organic peroxide containing the components (a) and (b) is 0.1 part or more, preferably 0.2 part or more, more preferably 100 parts of the component (A). 0.3 part or more, more preferably 0.4 part or more, 0.9 part or less, preferably 0.8 part or less, more preferably 0.7 part or less, still more preferably 0.6 part or less. . If the amount is too small, the time required for crosslinking increases, the productivity is greatly reduced, and the compression is greatly reduced. If the amount is too large, the resilience and durability will be reduced.
[0046]
In this case, the amount of (a) added is preferably at least 0.05 part, more preferably at least 0.08 part, even more preferably at least 0.1 part and at most 0.5 part based on 100 parts of component (A). , More preferably 0.4 part or less, further preferably 0.3 part or less. The amount of (b) added is preferably at least 0.05 part, more preferably at least 0.15 part, even more preferably at least 0.2 part and at most 0.7 part, more preferably 100 parts of component (A). Is 0.6 parts or less, more preferably 0.5 parts or less.
[0047]
Here, specific examples of the organic peroxide include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, α, α′-bis (t-butyl). Peroxy) diisopropylbenzene and the like. Commercially available organic peroxides can be used, and examples thereof include Parkmill D (manufactured by NOF Corporation), Perhexa 3M (manufactured by NOF Corporation), and Luperco # 231XL (manufactured by Atochem Corporation). In this case, as the organic peroxide of the component (a), 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane is preferable, and as the organic peroxide of the component (b), Is preferably dicumyl peroxide.
[0048]
Examples of the organic sulfur compound as the component (E) include thiophenol, thiophtol, halogenated thiophenol, and metal salts thereof. More specifically, pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol, parachlorothiophenol or a zinc salt thereof, diphenyl polysulfide having 2 to 4 sulfur atoms, dibenzyl polysulfide, dibenzoyl polysulfide, dibenzo Examples include thiazoyl polysulfide, dithiobenzoyl polysulfide, alkylphenyl disulfides, sulfur compounds having a furan ring, sulfur compounds having a thiophene ring, and particularly, zinc salts of pentachlorothiophenol and diphenyl disulfide are preferably used. be able to. The compounding amount is 0.2 part or more, more preferably 0.3 part or more, further preferably 0.5 part or more, particularly preferably 0.7 part or more, and 5 parts or less based on 100 parts of the rubber base material. It is more preferably 4 parts or less, further preferably 3 parts or less, particularly preferably 2 parts or less.
[0049]
The rubber composition according to the present invention preferably contains an inorganic filler. Specific examples thereof include zinc oxide, barium sulfate, calcium carbonate, and the like. The compounding amount is 1 part or more, more preferably 3 parts or more, still more preferably 5 parts or more, and most preferably 100 parts of the component (A). The content is preferably 7 parts or more, 130 parts or less, more preferably 50 parts or less, further preferably 45 parts or less, and most preferably 40 parts or less.
[0050]
Further, if necessary, the antioxidant is added in an amount of 0.05 part or more, more preferably 0.1 part or more, still more preferably 0.2 part or more, and 3 parts or less, based on 100 parts of the component (A). Preferably not more than 2 parts, more preferably not more than 1 part, most preferably not more than 0.5 part. In addition, a commercially available product can be used as the antiaging agent, and examples thereof include Nocrack NS-6 and NS-30 (manufactured by Ouchi Shinko Chemical Co., Ltd., Yoshinox 425 (manufactured by Yoshitomi Pharmaceutical Co., Ltd.)). Can be
[0051]
The vulcanized molded product of the present invention can be obtained by vulcanizing and curing the above rubber composition in the same manner as a known rubber composition for golf balls. The vulcanization can be carried out, for example, at a vulcanization temperature of 100 to 200 ° C. and a vulcanization time of 10 to 40 minutes.
[0052]
In the present invention, the hardness of the vulcanized molded product can be appropriately adjusted according to the usage mode of various golf balls described below, and is not particularly limited, and the cross-sectional hardness is from the center to the surface of the molded product. It may be flat or may have a difference in hardness between the center and the surface of the molded product.
[0053]
Further, the golf ball of the present invention can take various golf ball embodiments described below, particularly when the golf ball is one of a one-piece golf ball or a golf ball having a solid core or solid center, The deflection of the one-piece solid golf ball, solid core or solid center under a load of 980 N (100 kg) is usually 2.0 mm or more, preferably 2.5 mm or more, more preferably 2.8 mm or more, and most preferably 3. It is recommended that the thickness be 2 mm or more, and the upper limit be 6.0 mm or less, preferably 5.5 mm or less, more preferably 5.0 mm or less, and most preferably 4.5 mm or less. Long shots that worsen and cause large deformations especially on balls such as drivers The spin is no longer fly by too many, and too soft, with the feel is dull, on the rebound will not fly no longer enough, there is a durability to cracking with repeated impact is poor.
[0054]
The golf ball of the present invention has the vulcanized molded product as a constituent element, and the form of the ball is not particularly limited. The one-piece golf ball in which the vulcanized molded product is directly applied to a golf ball, A two-piece solid golf ball having a vulcanized molded product as a solid core and a cover formed on the surface thereof; a three-piece or more multi-piece solid golf ball having a vulcanized molded product as a solid core and having two or more layers of cover; Various modes such as a thread wound golf ball in which the above vulcanized molded product is applied as a center core can be adopted. In particular, two-piece solid golf balls and multi-piece solid golf using the vulcanized molded product of the present invention as a solid core from the viewpoint of extrudability at the time of production and imparting resilience to a product golf ball by utilizing the properties of the vulcanized molded product. A ball is recommended as a preferred mode of use.
[0055]
In the present invention, when the vulcanized molded product is the solid core, the solid core has a diameter of 30.0 mm or more, preferably 32.0 mm or more, more preferably 35.0 mm or more, and most preferably 37.0 mm or more. It is recommended that the upper limit be 41.0 mm or less, preferably 40.5 mm or less, more preferably 40.0 mm or less, and most preferably 39.5 mm or less. In particular, the diameter of a two-piece solid golf ball is 37.0 mm. Or more, preferably 37.5 mm or more, more preferably 38.0 mm or more, most preferably 38.5 mm or more, and the upper limit is 41.0 mm or less, preferably 40.5 mm or less, more preferably 40.0 mm or less. The diameter of the solid golf ball is 30.0 mm or more, preferably 32.0 mm or more. , More preferably 34.0mm or more, and most preferably at least 35.0 mm, 40.0 mm, preferably up 39.5mm or less, and more preferably not be less 39.0 mm.
[0056]
The specific gravity of the solid core is usually 0.9 or more, preferably 1.0 or more, more preferably 1.1 or more, and the upper limit is 1.4 or less, preferably 1.3 or less, more preferably 1.2 or less. It is recommended that there be.
[0057]
When the golf ball of the present invention is used as a two-piece solid golf ball or a multi-piece solid golf ball, the vulcanized molded product is formed as a solid core by injection molding or pressure molding a known cover material and an intermediate layer material. be able to.
[0058]
Specific examples of the main material of these cover materials and intermediate layer materials include thermoplastic or thermosetting polyurethane-based elastomers, polyester-based elastomers, ionomer resins, polyolefin-based elastomers, and mixtures thereof. One of these can be used alone or two or more can be used in combination. In particular, a thermoplastic polyurethane elastomer and an ionomer resin can be preferably used.
[0059]
As the thermoplastic polyurethane-based elastomer, commercially available products can be used. For example, diisocyanates such as Pandex T7298, T7295, T7890, TR3080, and T8295 (manufactured by DIC Bayer Polymer) are aliphatic or aromatic. And the like. Examples of commercially available ionomer resins include Surlyn 6320 and 8120 (manufactured by DuPont, USA), Himilan 1706, 1605, 1855, 1601 and 1557 (manufactured by DuPont-Mitsui Polychemicals).
[0060]
Further, a polymer such as a thermoplastic elastomer other than the above can be blended as an optional component with the main material of the cover material or the intermediate layer material. Specific examples of the optional polymer include polyamide-based elastomers, styrene-based block elastomers, hydrogenated polybutadiene, and ethylene-vinyl acetate (EVA) copolymer.
[0061]
In this case, in a multi-piece solid golf ball having a solid core and a cover of two or more layers,
(A) The amount of deflection of a solid core formed using the above rubber composition under a load of 100 kg is set to 2.5 mm or more, particularly 3.0 mm or more, 6.0 mm or less, particularly 5.5 mm or less, and a cover. The innermost layer has a Shore D hardness of 50 or more, especially 55 or more, and 70 or less, particularly 65 or less, and the outermost layer of the cover has a Shore D hardness of 40 or more, particularly 43 or more, and 55 or less, particularly 50 or less. It is preferable that the innermost layer be formed harder, whereby a golf ball having higher rebound and excellent controllability can be obtained.
[0062]
In this case, the diameter of the core is 30 mm or more, especially 34 mm or more, 40 mm or less, particularly 39 mm or less, and the thickness of the innermost cover is 0.5 mm or more, especially 1.0 mm or more, and 3.0 mm or less, particularly 2.0 mm or less. 0 mm or less, the thickness of the outermost layer cover is 0.5 mm or more, especially 1.0 mm or more, 2.5 mm or less, particularly 2.0 mm or less, and the total cover thickness is 1.0 mm or more, especially 1.5 mm As described above, the thickness is preferably 5.5 mm or less, particularly 4.5 mm or less.
[0063]
Or
(B) The amount of deflection of the solid core formed using the rubber composition under a load of 100 kg is set to 3.0 mm or more, particularly 3.5 mm or more, 6.0 mm or less, particularly 5.5 mm or less, and the cover. The innermost layer has a Shore D hardness of 8 or more, particularly 30 or more, and 49 or less, particularly 45 or less, and the outermost layer of the cover has a Shore D hardness of 56 or more, particularly 59 or more, 70 or less, particularly 65 or less. By forming the outermost layer harder, a golf ball having good hit feeling and excellent flight performance can be obtained.
[0064]
In this case, the diameter of the core is 30 mm or more, especially 34 mm or more, 40 mm or less, particularly 39 mm or less, and the thickness of the innermost layer cover is 0.5 mm or more, particularly 1.0 mm or more, and 5.0 mm or less, particularly 2.0 mm or less. 5 mm or less, the thickness of the outermost layer cover is 1.0 mm or more, especially 1.3 mm or more, 3.0 mm or less, especially 2.2 mm or less, and the total cover thickness is 1.5 mm or more, especially 2.5 mm. As described above, the thickness is preferably 8.0 mm or less, particularly preferably 6.0 mm or less.
[0065]
Furthermore, in the case of a two-piece golf ball, the amount of deflection of the core formed of the rubber composition under a load of 100 kg is 2.0 mm or more, especially 2.8 mm or more, and 5.0 mm or less, especially 4.5 mm or less. It is preferable that the cover has a Shore D hardness of 30 or more, particularly 40 or more, and 65 or less, particularly 62 or less, whereby a golf ball having a superior flight distance and a soft feeling can be obtained.
[0066]
In this case, the diameter of the core is preferably 37 to 41 mm, particularly preferably 39.5 to 40.5 mm.
[0067]
The golf ball of the present invention can conform to the Rules of Golf for competition use and can be formed to have a diameter of not less than 42.67 mm and a weight of not more than 45.93 g. The upper limit of the diameter is preferably 44.0 mm or less, more preferably 43.5 mm or less, most preferably 43.0 mm or less, and the lower limit of the weight is preferably 44.5 g or more, particularly preferably 45.0 g or more, and further preferably 45 mm or less. It is recommended to weigh at least 0.1 g, most preferably at least 45.2 g.
[0068]
【The invention's effect】
The golf ball of the present invention can be manufactured with good workability, has a short vulcanization time, has high productivity, and has excellent resilience.
[0069]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.
[0070]
[Examples and Comparative Examples]
Cores of two-piece golf balls were prepared using the rubber compositions shown in Tables 1 to 3. In this case, the outer diameter of the core was 38.9 mm, and the weight of the core was 36.0 g. A cover material made of a mixture of Himilan 1601 and Himilan 1557 in a weight ratio of 1: 1 is injected into the core to form a golf ball having dimples, and the surface thereof is further coated with paint to have an outer diameter of 42.7 mm. A two-piece solid golf ball weighing 45.3 g was obtained.
[0071]
The above-described cores were evaluated for the deflection amount under a load of 100 kg, the resilience, the extruding workability, and the golf ball flight performance by the following methods. The results are shown in Tables 1 to 3.
100kg load deflection
The amount of deformation (mm) of the obtained solid core under a load of 100 kg (980 N) was measured.
Rebound
The initial speed was measured with an initial speedometer of the same type as that of the official organization USGA, and the difference between the initial speeds of Examples 1 to 13 and Comparative Examples 2 to 10 based on Comparative Example 1 was shown.
Extrusion workability
The extrusion workability was evaluated according to the following criteria for the slag shape after extrusion.
5: Slag skin is clean and very good
4: Slag skin is slightly rough but good
3: The slag has fluff, but can be extruded
2: Fluff on slag skin is very noticeable, but extrudable
1: Poor shape of slag skin occurs, making it difficult to extrude a predetermined amount
Flying performance
The flight performance when hit with a head speed of 45 m / s was measured by a driver (W # 1, Tour Stage X500, loft 9 °, shaft X, manufactured by Bridgestone Sports Co., Ltd.) using a hitting machine.
[0072]
[Table 1]

[0073]
[Table 2]

[0074]
[Table 3]

[0075]
Polybutadiene BR18: JSR, Cis1,4 96%, Mooney viscosity (ML_{1 + 4}(100 ° C.)) 60, molecular weight distribution Mw / Mn 4.2, catalyst Ni
Polybutadiene BR01: manufactured by JSR, Cis1,4 95%, Mooney viscosity (ML_{1 + 4}(100 ° C.)) 44, molecular weight distribution Mw / Mn 4.2, catalyst Ni
Polybutadiene CB22: manufactured by Bayer AG, Cis1,4 98%, Mooney viscosity (ML_{1 + 4}(100 ° C.)) 62, molecular weight distribution Mw / Mn 7.1, catalyst Nd
Polybutadiene HCBN-13: 96% Cis, 4 by JSR, Mooney (ML_{1 + 4}(100 ° C.)) viscosity 54, molecular weight distribution Mw / Mn 3.2, catalyst Nd
Polybutadiene SR8510: Firestone Polymers Co., Ltd., Cis1,4 96%, Mooney viscosity (ML_{1 + 4}(100 ° C.)) 45, molecular weight distribution Mw / Mn 2.5, catalyst Nd
Perhexa 3M-40: 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, manufactured by NOF Corporation, half-life at 155 ° C, 40 sec
Park Mill D: Dicumyl peroxide, manufactured by NOF CORPORATION, half-life at 155 ° C 8 min
Actiplast GT: manufactured by Rhein Chemie, melting point: about 103 ° C., a mixture mainly containing a zinc salt of a saturated fatty acid
Actiplast MS: Rhein @ Chemie, melting point / approximately 105 ° C., active mixture mainly composed of a zinc salt of a high-molecular saturated fatty acid and a sulfur compound added thereto
Actiplast PP: a mixture of zinc salts of saturated fatty acids, melting point / about 101 ° C., manufactured by Rhein Chemie
Actiplast F: manufactured by Rhein Chemie, melting point / about 85 ° C., mixture of zinc salt of unsaturated fatty acid and activator
Zinc stearate: melting point / about 124 ° C
[0076]
From the above results, the following points are recognized.
Comparative Examples 1 and 2:
It is a polybutadiene using a Ni-based catalyst, and since no processing aid is added, resilience and flight distance are reduced.
Comparative Example 3:
It is a polybutadiene using an Nd-based catalyst, and since no processing aid is added, workability is very poor.
Comparative Example 4:
Since the amount of the processing aid added is small, the resilience and the flight distance are reduced.
Comparative Example 5:
Since the processing aid is added too much, the amount of deflection becomes too large, and the resilience and the flight distance decrease.
Comparative Example 6:
Addition of zinc stearate does not improve the extrusion workability, reduces the amount of deflection, becomes hard, and reduces the resilience and the flight distance.
Comparative Example 7:
Since the organic peroxide is used alone, the resilience is greatly reduced.
Comparative Example 8:
It is a polybutadiene using a Ni-based catalyst, and since no processing aid is added, resilience and flight distance are reduced.
Comparative Example 9:
Addition of zinc stearate does not improve the extrusion workability, reduces the amount of deflection, becomes hard, and reduces the resilience and the flight distance.
Comparative Example 10:
Since the organic peroxide is used alone, the resilience is greatly reduced.
[0077]
On the other hand, those of the examples had good extrusion workability and good resilience and flying performance.

Claims (22)

A rubber base material 100 containing polybutadiene as a main component and synthesized using a rare earth element catalyst containing 60% by weight or more of cis-1,4-bonds and having a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 30 or more. 15 to 50 parts by weight of an unsaturated carboxylic acid and / or a metal salt thereof, 2 parts by weight or more of a processing aid having a highest melting point of 115 ° C. or less, and 2 or more kinds of organic peroxides based on parts by weight. half-life in them 155 ° C. is a 1st short organic peroxide (a), the No. 1 long organic peroxide and (b), the half-life of (a) a _t, the half-life of (b) If the b _t, the ratio _b t / _{a t} half-life is not less than 7, 0.1 to 0.9 parts by weight total content of the organic peroxide with respect to the base rubber 100 parts by weight Golf comprising a vulcanized molded product of a rubber composition as a constituent element Lumpur. The golf ball of claim 1, wherein the processing aid comprises a higher fatty acid metal salt. 3. The golf ball according to claim 2, wherein the higher fatty acid metal salt has 12 or more carbon atoms. 4. The golf ball according to claim 2, wherein the higher fatty acid metal salt contains a saturated fatty acid metal salt as a main component. 4. The golf ball according to claim 2, wherein the higher fatty acid metal salt contains an unsaturated fatty acid metal salt as a main component. The golf ball according to any one of claims 2 to 5, wherein the higher fatty acid metal salt comprises a higher fatty acid zinc salt as a main component. The golf ball according to claim 1, wherein the processing aid includes a metal complex. The golf ball according to claim 7, wherein the metal complex is a phthalocyanine-type metal complex. 2. The golf ball according to claim 1, wherein the processing aid contains an organic sulfur compound. 10. The golf ball according to claim 9, wherein the organic sulfur compound is 2,2'-dibenzamide-diphenyl disulfide. 2. The golf ball according to claim 1, wherein the processing aid contains an aliphatic hydrocarbon. 2. The golf ball according to claim 1, wherein the processing aid includes a fatty acid ester. 13. The golf ball according to claim 12, wherein the fatty acid ester is a higher fatty acid ester. 14. The golf ball according to claim 13, wherein the higher fatty acid ester has 12 or more carbon atoms. The golf ball of claim 1, wherein the processing aid comprises a fatty alcohol. The golf ball according to claim 15, wherein the fatty alcohol is a higher fatty alcohol. 17. The golf ball according to claim 16, wherein the higher fatty alcohol has 12 or more carbon atoms. The golf ball according to any one of claims 1 to 17, wherein the amount of the processing aid is 2 to 30 parts by weight based on 100 parts by weight of the rubber substrate. The golf ball according to claim 1, wherein the compounding amount of the organic sulfur compound is 0.2 to 5 parts by weight based on 100 parts by weight of the rubber substrate. 20. The golf ball according to claim 1, wherein 50% by weight or more of the rubber base is polybutadiene synthesized using a rare earth element-based catalyst. 21. The golf ball according to claim 1, wherein the polybutadiene has a molecular weight distribution Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) of 2.0 to 8.0. A solid golf ball having a solid core formed to have a deflection of 2.0 to 6.0 mm under a load of 100 kg using the rubber composition according to any one of claims 1 to 21.