JP2004180720A - Golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a golf ball with excellent workability and to increase the resilience of the golf ball. <P>SOLUTION: The golf ball comprises as a component element a crosslinked mold made of a rubber composition whose essential elements are: (A) a rubber base material consisting of (a) polybutadiene synthesized by using a catalyst of the VIII group and/or a rare earth element catalyst with at least 60 % by weight of cis-1,4-bond, whose Mooney viscosity (ML<SB>1+4</SB>(100°C)) is from 50 to 120, and (b) a solid isoprene rubber with at least 60 % by weight of cis-1,4-bond, whose Mooney viscosity (ML<SB>1+4</SB>(100°C)) is from 70 to 90, with the ratio of (a) to (b) by weight being 96/4-99/1, (B) unsaturated carboxylic acid and/or its metal salt, and (C) organic peroxide. <P>COPYRIGHT: (C)2004,JPO&NCIPI

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。）
【００２５】
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。
【００２６】
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。
【００２７】
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。
【００２８】
また、ランタン系列希土類元素化合物を用いた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、シス含量及びＭｗ／Ｍｎを上記範囲とするために、ブタジエン／ランタン系列希土類元素化合物は、モル比で１，０００〜２００万、特には５，０００〜１００万とすることが好ましく、また、ＡｌＲ^１Ｒ^２Ｒ^３／ランタン系列希土類元素化合物は、モル比で１〜１，０００、特には３〜５００とすることが好ましい。更に、ハロゲン化合物／ランタン系列希土類元素化合物は、モル比で０．１〜３０、特に０．２〜１５であることが好ましい。ルイス塩基／ランタン系列希土類元素化合物は、モル比で０〜３０、特に１〜１０とすることが好ましい。重合にあたっては、溶媒を使用しても、溶媒を使用せずにバルク重合或いは気相重合してもよい。重合温度は、通常、−３０〜１５０℃、好ましくは１０〜１００℃である。
【００２９】
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或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。
【００３０】
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。
【００３１】
変性ポリブタジエンゴムは、上記の重合に引き続き、下記▲１▼〜▲７▼に記載した末端変性剤を使用することができる。
▲１▼ポリマーの活性末端にアルコキシシリル基を持つ化合物を反応させることにより得られる。アルコキシシリル基を持つ化合物としては、エポキシ基又はイソシアナート基を分子内に少なくとも１個有するアルコキシシラン化合物が好適に使用される。具体例としては、３−グリシジルオキシプロピルトリメトキシシラン、３−グリシジルオキシプロピルトリエトキシシラン、（３−グリシジルオキシプロピル）メチルジメトキシシラン、（３−グリシジルオキシプロピル）メチルジエトキシシラン、β−（３，４−エポキシシクロヘキシル）トリメトキシシラン、β−（３，４−エポキシシクロヘキシル）トリエトキシシラン、β−（３，４−エポキシシクロヘキシル）メチルジメトキシシラン、β−（３，４−エポキシシクロヘキシル）エチルジメトキシシラン、３−グリシジルオキシプロピルトリメトキシシランの縮合物、（３−グリシジルオキシプロピル）メチルジメトキシシランの縮合物などのエポキシ基含有アルコキシシラン；３−イソシアナートプロピルトリメトキシシラン、３−イソシアナートプロピルトリエトキシシラン、（３−イソシアナートプロピル）メチルジメトキシシラン、（３−イソシアナートプロピル）メチルジエトキシシラン、３−イソシアナートプロピルトリメトキシシランの縮合物、（３−イソシアナートプロピル）メチルジメトキシシランの縮合物などのイソシアナート基含有アルコキシシラン化合物が挙げられる。
【００３２】
また、上記アルコキシシリル基を持つ化合物を活性末端に反応させる際、反応を促進させるためにルイス酸を添加することもできる。ルイス酸が触媒としてカップリング反応を促進させ、変性ポリマーのコールドフローが改良され貯蔵安定性がよくなる。ルイス酸の具体例としては、ジアルキルスズジアルキルマレート、ジアルキルスズジカルボキシレート、アルミニウムトリアルコキシドなどが挙げられる。
【００３３】
▲２▼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、
▲３▼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、
▲４▼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。）
▲５▼ハロゲン化イソシアノ化合物、
▲６▼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。）
▲７▼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。
【００３４】
以上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、特開２００２−２９３９９６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。
なお、上述した触媒の中では、希土類元素系触媒、特にＮｄ系触媒が好ましい。
【００３５】
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２．３以上、更に好ましくは２．６以上、最も好ましくは２．８以上であり、上限としては８．０以下、好ましくは６．０以下、更に好ましくは５．０以下、最も好ましくは４．０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。
【００３６】
また、本発明で用いるポリブタジエンは、２５℃における５重量トルエン溶液の粘度をη（ｍＰａ・ｓ）としたとき、ηが３００以上、好ましくは３３０以上、より好ましくは３６０以上、更に好ましくは３８０以上、最も好ましくは４００以上であり、１０００以下、好ましくは８００以下、より好ましくは７００以下、更に好ましくは６００以下、最も好ましくは５５０以下であることが望ましい。溶液粘度が低すぎると反発性が低下するおそれがあり、高すぎると作業性が悪くなるおそれがある。
【００３７】
なお、本発明でいう２５℃における５％トルエン溶液の粘度η（ｍＰａ・ｓ）とは、測定対象のポリブタジエン２．２８ｇをトルエン５０ｍｌに溶解した後、標準液として粘度計構成用標準液（ＪＩＳ Ｚ８８０９）を用いて、所定の粘度計により２５℃の条件で測定した値のことをいうものとする。
【００３８】
本発明においては、上記（ａ）成分のポリブタジエンに（ｂ）成分として固形イソプレンゴムを併用する。
この場合、このイソプレンゴムとしては、シス−１，４−結合を６０％以上、好ましくは８０％以上、更に好ましくは９０％以上を含有し、ムーニー粘度（ＭＬ_１＋４（１００℃））が７０以上、好ましくは７５以上、より好ましくは８０以上で、上限として９０以下、好ましくは８５以下のものを使用する。シス−１，４−結合の含有量が低すぎるものは、反発性が低下するおそれがあり、また、ムーニー粘度が低すぎても、反発性が低下するおそれがある。一方、ムーニー粘度が高すぎると、イソプレンゴム添加による作業性改良効果が得られないおそれがある。
【００３９】
上記（ａ）成分と（ｂ）成分の配合割合（ａ）／（ｂ）は、重量比として９６／４以上、好ましくは９６．５／３．５以上で、９９／１以下、好ましくは９８．５／１．５、より好ましくは９８／２以下とすることが必要である。（ｂ）成分が多すぎると、反発性が大きく低下し、（ｂ）成分が少なすぎると、作業性改良効果が得られない。
【００４０】
本発明においては、上記（ａ），（ｂ）成分からなるゴム基材を使用するが、本発明の目的を損なわない限り、他のゴム成分を配合することは任意である。
【００４１】
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。
【００４２】
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、１０部以上、より好ましくは１５部以上、更に好ましくは２０部以上であり、６０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。
【００４３】
（Ｃ）成分の有機過酸化物としては、公知のものを単独使用することができるが、好ましくは２種以上組み合わせて用いることもできる。この場合、特には、反発性の点から２種以上の有機過酸化物を使用し、しかも１５５℃における半減期が一番短い有機過酸化物を（ｃ）、１５５℃における半減期が一番長い有機過酸化物を（ｄ）とし、（ｃ）の半減期をＣ_ｔ、（ｄ）の半減期をｄ_ｔとした場合、半減期の比ｄ_ｔ／ｃ_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、好ましくは１８以下、より好ましくは１６以下、更に好ましくは１４以下であるものを使用することが好適である。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、耐久性に劣る場合がある。
【００４４】
この場合、（ｃ）の１５５℃における半減期ｃ_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秒以下であることが好ましく、（ｄ）の１５５℃における半減期ｄ_ｔは、３００秒以上、より好ましくは３６０秒以上、更に好ましくは４２０秒以上で、８００秒以下、より好ましくは７００秒以下、更に好ましくは６００秒以下であることが好ましい。
【００４５】
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）−３，５，５−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（ｃ）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）−３，５，５−トリメチルシクロヘキサンが好ましく、（ｄ）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。
【００４６】
上記（Ｃ）成分の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、５部以下、好ましくは３部以下、より好ましくは１部以下、更に好ましくは０．８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おそれがある。配合量が多すぎると、反発性、耐久性が低下してしまうおそれがある。
【００４７】
なお、上記（ｃ），（ｄ）成分を併用する場合、（ｃ）成分の添加量は、（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、最も好ましくは０．２部以上で、２．５部以下、より好ましくは１部以下、更に好ましくは０．５部以下、最も好ましくは０．４部以下であることが好ましく、（ｄ）成分の添加量は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、最も好ましくは０．４部以上で、２．５部以下、より好ましくは１．５部以下、更に好ましくは０．７部以下、最も好ましくは０．５部以下であることが好ましい。
【００４８】
本発明のゴム組成物には、（Ｄ）成分として有機硫黄化合物を配合することが好ましい。
【００４９】
（Ｄ）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。
【００５０】
その配合量は、（Ａ）成分のゴム基材１００部に対し、０．１部以上、より好ましくは０．２部以上、更に好ましくは０．４部以上、最も好ましくは０．６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、最も好ましくは２部以下であることが好ましい。その配合量が少なすぎると、反発性を向上させる効果がなく、多すぎると、硬度が軟らかくなりすぎ、十分な反発性が得られない場合がある。
【００５１】
更に、ゴム組成物には、（Ｅ）成分として無機充填剤を配合し得る。
（Ｅ）成分の無機充填剤としては、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できる。配合量が多すぎたり、少なすぎたりすると、適正な重量及び好適な反発性を得ることができない場合が生じる。
【００５２】
なおまた、必要に応じ、老化防止剤を（Ａ）成分１００部に対し、通常０部以上、好ましくは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。
【００５３】
本発明の架橋成形物は、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。
【００５４】
本発明のゴルフボールは、上記架橋成形物を構成要素として具備するもので、ボールの態様は、特に制限されるものではなく、上記架橋成形物がゴルフボールに直接適用されるワンピースソリッドゴルフボール、架橋成形物をソリッドコアとしかつ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、架橋成形物をソリッドコアとしかつその外側に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、上記架橋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、架橋成形物の特性を活かし、製造時の押し出し性、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。
なお、上記架橋成形物をワンピースソリッドゴルフボールやソリッドコア、ソリッドセンターとして使用する場合、それら球体の断面硬度は、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。
【００５５】
また、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る。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。
【００５６】
本発明において、架橋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ソリッドコアの直径は、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。
【００５７】
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。
【００５８】
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、上記架橋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。
【００５９】
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。
【００６０】
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、同Ｔ８２９０（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。
【００６１】
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。
【００６２】
なお、本発明の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は、公知の方法で製造することができ、特に制限されるものではないが、ツーピースや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所定の射出成形用金型内に配備し、ツーピースソリッドゴルフボールの場合には上記カバー材を、マルチピースソリッドゴルフボールの場合には、順に上記中間層材、カバー材を所定の方法に従って射出する公知の方法を好適に採用できる。場合によっては、上記カバー材を加圧成形によって製造することもできる。
【００６３】
マルチピースソリッドゴルフボールの中間層の厚さは、０．５ｍｍ以上、好ましくは１．０ｍｍ以上、上限として３．０ｍｍ以下、好ましくは２．５ｍｍ以下、更に好ましくは２．０ｍｍ以下、最も好ましくは１．６ｍｍ以下であることが推奨される。
【００６４】
また、カバーの厚さは、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のいずれであっても０．７ｍｍ以上、好ましくは１．０ｍｍ以上、上限として３．０ｍｍ以下、好ましくは２．５ｍｍ以下、更に好ましくは２．０ｍｍ以下、最も好ましくは１．６ｍｍ以下であることが推奨される。
【００６５】
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。
【００６６】
【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、反発性に優れたものである。
【００６７】
【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。
【００６８】
［実施例１〜３、比較例１〜５］
表１に示すポリブタジエン（ＢＲ）、イソプレンゴム（ＩＲ）をそれぞれ用い、表２に示すゴム組成にて、１５５℃で２０分間の加硫を行い、ツーピースゴルフボールのコアを作成した。この場合、コアの外径は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、ディンプルを形成し、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。
上記コアの１００ｋｇ（９８０Ｎ）荷重たわみ量、反発性及びゴルフボールの押し出し作業性、飛び性能を下記方法により評価した。結果を表２に示す。
【００６９】
［実施例４，５、比較例６，７］
表３に示す組成で、１７０℃で３０分間の加硫を行い、外径４２．７ｍｍ、重量４５．３ｇのワンピースソリッドゴルフボールを製造し、その性能を評価した。結果を表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１〜３、比較例１〜５については比較例２を基準にし、実施例４，５、比較例６，７については比較例６を基準にしたときの初速度の差を表した。
押し出し作業性の評価
押し出し後のスラグ肌及びスラグ形状について下記基準で評価した。
４ スラグ肌がきれいで非常に良好
３ スラグ肌にややざらつきがあるが良好
２ スラグ肌に毛羽立ちがあるが押し出し可能
１ スラグの形状不良が起こり、所定量の押し出しが困難
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。
【００７０】
【表１】

【００７１】
【表２】

（注）半減期：単位は秒
パーヘキサ３Ｍ−４０：４０％希釈品（実質添加量はパーヘキサ３Ｍ−４０が１００％であるとして計算した値である。）
【００７２】
比較例１：Ｎｉ系触媒を用いて重合したＢＲ単体のため、反発性が良好であるが、作業性が非常に悪い
比較例２：低反発のＮｉ系触媒を用いて重合したＢＲのため、反発性が低い
比較例３：ＩＲが多いため、反発性が低い
比較例４：低ムーニーのＮｉ系触媒を用いて重合したＢＲのため、反発性が低い
比較例５：パーオキサイド単体、ペンタクロロチオフェノールの亜鉛塩を無添加のため反発性が低下
【００７３】
【表３】

比較例６：低反発のＮｉ系触媒を用いて重合したＢＲのため、反発性が低い
比較例７：ＩＲが多いため、反発性も大きく低下[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]
[Prior art]
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 Patent Application Laid-Open No. 62-89750 discloses that a rubber base has 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. 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.
[0004]
However, the above proposal requires further improvement in workability at the time of extrusion and resilience.
[0005]
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.
[0006]
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 1,2-vinyl bond of 2.0% or less, a solid golf ball formed of a rubber composition having a weight average molecular weight to number average molecular weight ratio Mw / Mn of 3.5 or less; JP-A-275356 discloses a golf ball formed of a rubber composition containing high Mooney viscosity polybutadiene. Japanese Patent No. 151985 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.
[0007]
JP-A-6-190083 proposes to use a mixture of a high Mooney viscosity polybutadiene and a high Mooney viscosity isoprene rubber, but the workability and resilience are not satisfactory. Japanese Patent Application Laid-Open No. 60-94434 discloses that a mixture of polybutadiene and zinc acrylate, zinc methacrylate and isoprene rubber in a prescribed ratio is used, but the Mooney viscosity of polybutadiene is described. And the resilience is not satisfactory. Similarly, in the proposal of JP-A-4-1099971, the Mooney viscosity of polybutadiene is low, and the resilience is still not sufficiently satisfactory. JP-A-2-297384 discloses that the resilience is improved by adding an organic sulfur compound or a metal organic sulfur compound.
[0008]
[Patent Document 1]
JP-A-62-89750 [Patent Document 2]
JP-A-2-268778 [Patent Document 3]
JP-A-11-70187 [Patent Document 4]
JP-A-11-319148 [Patent Document 5]
JP-A-11-164912 [Patent Document 6]
JP-A-63-275356 [Patent Document 7]
JP-A-3-151985 [Patent Document 8]
JP-A-6-190083 [Patent Document 9]
JP-A-60-94434 [Patent Document 10]
JP-A-4-1099971 [Patent Document 11]
JP-A-2-297384
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a golf ball that has good pushability, can be manufactured with good workability, and has excellent resilience.
[0010]
Means for Solving the Problems and Embodiments of the Invention
The present inventor has conducted intensive studies to achieve the above object. That is, generally, polybutadiene having a high Mooney viscosity and a high average molecular weight is said to have high resilience, but this is poor in workability (extrusion performance). On the other hand, workability (extrusion performance) is better when the Mooney viscosity is lower and the molecular weight distribution is wider, but it is preferable that the resilience be higher for applications such as golf ball cores. Polybutadiene synthesized using a Group VIII catalyst and / or a rare earth element catalyst having a cis-1,4-bond content of 60% by weight or more and a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 50 to 120 Has very good resilience, but very poor workability, but has a cis-1,4-bond of 60% by weight or more, and a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 70 to 90. The present inventors have found that by using the following solid isoprene rubber in a specific ratio, the workability, particularly the extrudability, can be improved and the cold flow can be suppressed while maintaining the resilience, and the present invention has been accomplished.
[0011]
Accordingly, the present invention provides the following golf balls.
Claim 1:
(A) (a) A group VIII catalyst and / or a rare earth element-based catalyst having 60% by weight or more of cis-1,4-bond and having a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 50 or more and 120 or less. (B) a solid isoprene rubber having 60% by weight or more of cis-1,4-bond and having a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 70 to 90, A rubber substrate wherein the ratio of the component (a) to the component (b) is 96/4 to 99/1 by weight;
(B) an unsaturated carboxylic acid and / or a metal salt thereof,
(C) A golf ball comprising a cross-linked molded article of a rubber composition containing an organic peroxide as an essential component. ,
Claim 2:
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 3:
3. The golf ball according to claim 1, wherein the polybutadiene has a viscosity of η (mPa · s) of 5% by weight toluene solution at 25 ° C., wherein η is 300 or more and 1000 or less. 4.
Claim 4:
4. The golf ball according to claim 1, wherein the rubber composition comprises 0.1 to 5 parts by weight of an organic sulfur compound added to 100 parts by weight of the rubber substrate.
Claim 5:
It contains two or more organic peroxides, of which the organic peroxide having the shortest half-life at 155 ° C is (c), the organic peroxide having the longest is (d), and the half-life of (c) is c. _t, the half-life of (d) when a d _t, the ratio d _{t /} c _t half-life is not less 7 to 20, the total content of 100 parts by weight of material of the rubber group of organic peroxides The golf ball according to any one of claims 1 to 4, which is 0.1 to 5 parts by weight based on the weight of the golf ball.
Claim 6:
The golf ball is a one-piece golf ball or a golf ball having a solid core or a solid center, wherein the cross-linked molded product of the rubber composition forms a one-piece solid golf ball, a solid core or a solid center, and The golf ball according to any one of claims 1 to 5, wherein the one-piece solid golf ball, the solid core or the solid center has a deflection amount of 2.0 to 6.0 mm under a load of 980 N (100 kg).
[0012]
Hereinafter, the present invention will be described in more detail.
The golf ball of the present invention has a crosslinked molded product of a specific rubber composition as a component, and in this case, the rubber composition is
(A) (a) A group VIII catalyst and / or a rare earth element-based catalyst having 60% by weight or more of cis-1,4-bond and having a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 50 or more and 120 or less. (B) a solid isoprene rubber having 60% by weight or more of cis-1,4-bond and having a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 70 to 90, A rubber substrate wherein the ratio of the component (a) to the component (b) is 96/4 to 99/1 by weight;
(B) an unsaturated carboxylic acid and / or a metal salt thereof,
(C) Organic peroxide is an essential component.
[0013]
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.
Further, the content of the 1,2-vinyl bond is preferably 2% or less, more preferably 1.7% or less, and further preferably 1.5% or less. It may decrease.
[0014]
The polybutadiene has a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 50 or more, preferably 51 or more, more preferably 52 or more, most preferably 53 or more, and the upper limit is 120 or less, preferably 90 or less, more preferably 80 or less. Below, it is most preferable that it is 70 or less. If the Mooney viscosity is too low, the cold flow will be large and the resilience will be reduced. If the Mooney viscosity is too high, workability will be greatly reduced.
[0015]
The Mooney viscosity referred to in the present invention is an industrial viscosity index (JIS K6300) measured by a Mooney viscometer, which is one type of rotational plasticity meter, and has a unit symbol of ML _{1 + 4} (100 ° C.). ) Is used. 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.
[0016]
The polybutadiene of the component (a) needs to be synthesized with a Group VIII catalyst and / or a rare earth element catalyst.
More specifically, the following nickel-based catalysts and cobalt-based catalysts can be suitably used as the group VIII catalyst.
[0017]
Here, examples of the nickel-based catalyst include a one-component system such as nickel diatomaceous earth, a two-component system such as Raney nickel / titanium tetrachloride, and a three-component system such as nickel compound / organic metal / boron trifluoride etherate. And the like. In addition, as a nickel compound, reduced nickel with a carrier, Raney nickel, nickel oxide, nickel carboxylate, organic nickel complex salt, etc. are used. As the organic metal, trialkylaluminum such as triethylaluminum, tri-n-propylaluminum, triisobutylaluminum, tri-n-hexylaluminum, n-butyllithium, sec-butyllithium, tert-butyllithium, 1, Examples thereof include alkyl lithium such as 4-dilithium butane, and dialkyl zinc such as diethyl zinc and dibutyl zinc.
[0018]
Examples of the cobalt-based catalyst include cobalt and compounds thereof such as Raney cobalt, cobalt chloride, cobalt bromide, cobalt iodide, cobalt oxide, cobalt sulfate, cobalt carbonate, cobalt phosphate, cobalt phthalate, cobalt carbonyl, and cobalt acetyl. Examples thereof include acetonate, cobalt diethyldithiocarbamate, cobaltanilinium nitrite, and cobalt dinitrosyl chloride.Especially, these compounds are used in combination with dialkylaluminum monochloride such as diethylaluminum monochloride and diisobutylaluminum monochloride, triethylaluminum, and triethylaluminum. -Trialkylaluminums such as n-propylaluminum, triisobutylaluminum, tri-n-hexylaluminum, ethylaluminum sesquik; Aluminum alkyl sesquichloride of chloride etc., can be preferably exemplified a combination of aluminum chloride and the like.
[0019]
When the polymerization is carried out using a Group VIII-based catalyst, particularly a nickel-based catalyst or a cobalt-based catalyst, usually, the solvent is continuously charged to a reactor together with a butadiene monomer. A method in which the reaction pressure is appropriately selected within the range of atmospheric pressure to over 70 atm and the operation is performed so as to obtain the above Mooney viscosity can be mentioned.
On the other hand, as the rare earth element-based catalyst, a known catalyst can be used.
[0020]
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.
[0021]
Examples of the lanthanide series rare earth element compounds include metal halides, carboxylate salts, alcoholates, thioalcoholates, and amides having atomic numbers of 57 to 71.
[0022]
Examples of the organoaluminum compound include AlR ¹ R ² R ³ (where R ¹ , R ² and R ³ may be the same or different, and each is hydrogen or a hydrocarbon residue having 1 to 8 carbon atoms. ) Can be used.
[0023]
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).
[0024]
Embedded image

(In the formula, R ⁴ is a hydrocarbon group containing 1 to 20 carbon atoms, and n is an integer of 2 or more.)
[0025]
The halogen-containing _compounds, AlX _{n R 3-n} (wherein, X is a halogen, R represents a hydrocarbon residue having 1 to 20 carbon atoms, for example, an alkyl group, an aryl group, an aralkyl group And n represents 1, 1.5, 2 or 3), a strontium halide such as Me ₃ SrCl, Me ₂ SrCl ₂ , MeSrHCl ₂ , MeSrCl ₃ , and others, silicon tetrachloride, tetrachloride Metal halides such as tin and titanium tetrachloride are used.
[0026]
The Lewis base can be used to complex a lanthanide series rare earth element compound, and examples thereof include acetylacetone and ketone alcohol.
[0027]
In the present invention, in particular, the use of a neodymium-based catalyst using a neodymium compound as the 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.
[0028]
When butadiene is polymerized in the presence of a rare earth element-based catalyst using a lanthanum series rare earth element compound, the butadiene / lanthanum series rare earth element compound is used in a molar ratio in order to keep the cis content and Mw / Mn within the above ranges. 1,000～200 ten thousand, and particularly preferably be a 5,000～100 ten thousand, ^also, AlR ^{1 R} 2 R ³ / lanthanum series rare earth element compound, 1 to 1,000 by molar ratio, in particular 3 It is preferably 500. Further, the molar ratio of the halogen compound / lanthanum series rare earth element compound is preferably from 0.1 to 30, particularly preferably from 0.2 to 15. The molar ratio of the Lewis base / lanthanum series rare earth element compound is preferably from 0 to 30, particularly preferably from 1 to 10. In the polymerization, a solvent may be used, or bulk polymerization or gas phase polymerization may be performed without using a solvent. The polymerization temperature is usually -30 to 150C, preferably 10 to 100C.
[0029]
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.
[0030]
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.
[0031]
For the modified polybutadiene rubber, following the above polymerization, the terminal modifiers described in the following (1) to (7) can be used.
(1) It can be obtained by reacting a compound having an alkoxysilyl group at the active terminal of the polymer. As the compound having an alkoxysilyl group, an alkoxysilane compound having at least one epoxy group or isocyanate group in a molecule is preferably used. Specific examples include 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, (3-glycidyloxypropyl) methyldimethoxysilane, (3-glycidyloxypropyl) methyldiethoxysilane, β- (3 , 4-Epoxycyclohexyl) trimethoxysilane, β- (3,4-epoxycyclohexyl) triethoxysilane, β- (3,4-epoxycyclohexyl) methyldimethoxysilane, β- (3,4-epoxycyclohexyl) ethyldimethoxy Epoxy group-containing alkoxysilanes such as silane, condensate of 3-glycidyloxypropyltrimethoxysilane, condensate of (3-glycidyloxypropyl) methyldimethoxysilane; 3-isocyanatopropyltrimethoxysilane; Isocyanatopropyltriethoxysilane, (3-isocyanatopropyl) methyldimethoxysilane, (3-isocyanatopropyl) methyldiethoxysilane, condensate of 3-isocyanatopropyltrimethoxysilane, (3-isocyanatopropyl) methyl An isocyanate group-containing alkoxysilane compound such as a condensate of dimethoxysilane is exemplified.
[0032]
When the compound having an alkoxysilyl group is reacted with an active terminal, a Lewis acid may be added to accelerate the reaction. The Lewis acid accelerates the coupling reaction as a catalyst, improving the cold flow of the modified polymer and improving the storage stability. Specific examples of Lewis acids include dialkyltin dialkyl malates, dialkyltin dicarboxylates, and aluminum trialkoxides.
[0033]
_{^{▲ 2 ▼ R 5 n M'X 4}} -n, M'X 4, M'X 3, R 5 n M '(- R 6 -COOR 7) 4-n or _{^{R 5 n M' (- R}} 6 - COR ⁷ ) _4-n (wherein, R ⁵ and R ⁶ may be the same or different and are a hydrocarbon group containing 1 to 20 carbon atoms, and R ⁷ is a 1 to 20 carbon atom Which may contain 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, X is a halogen atom, and n is an integer of 0 to 3. Corresponding to) a halogenated organometallic compound, a metal halide compound or an organometallic compound,
(3) 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,
(4) a 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.)
(5) halogenated isocyano compound,
_{^{▲ 6 ▼ 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, or the following Carboxylic acid represented by the formula, acid halide, ester compound, carbonate compound or acid anhydride,
Embedded image

(In the formula, R ^{8 to} R ¹⁶ may be the same or different, a hydrocarbon group containing 1 to 50 carbon atoms, X is a halogen atom, and m is an integer of 1 to 5.)
_{^{▲ 7 ▼ R 17 l M "}} (OCOR 18) 4-l, R 19 l M" (OCOR 20 -COOR 21) 4-l or metal salt of a carboxylic acid embedded image represented by the following formula,

(In the formula, R ^{17 to} R ²³ may be the same or different, a hydrocarbon group containing a carbon atom having 1 to 20 carbon atoms, M ″ is a tin atom, a silicon atom or a germanium atom, and l is 0 to 3 And an integer of 1).
[0034]
Specific examples of the terminal modifier shown above and the method of reacting are described in, for example, JP-A-11-35633, JP-A-7-268132, JP-A-2002-293996 and the like. Can be mentioned.
In addition, among the above-mentioned catalysts, a rare earth element-based catalyst, particularly, an Nd-based catalyst is preferable.
[0035]
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 2.3 or more, more preferably 2.6 or more, and most preferably It is preferably at least 2.8, and the upper limit is at most 8.0, preferably at most 6.0, more preferably at most 5.0, most preferably at most 4.0, 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.
[0036]
The polybutadiene used in the present invention has a η of 300 or more, preferably 330 or more, more preferably 360 or more, and still more preferably 380 or more, when the viscosity of a 5 weight toluene solution at 25 ° C. is η (mPa · s). It is most preferably 400 or more, 1000 or less, preferably 800 or less, more preferably 700 or less, further preferably 600 or less, and most preferably 550 or less. If the solution viscosity is too low, the resilience may decrease, and if it is too high, the workability may deteriorate.
[0037]
The viscosity η (mPa · s) of a 5% toluene solution at 25 ° C. in the present invention refers to a standard solution for viscometer construction (JIS) as a standard solution after dissolving 2.28 g of a polybutadiene to be measured in 50 ml of toluene. Z8809) and a value measured at 25 ° C. by a predetermined viscometer.
[0038]
In the present invention, a solid isoprene rubber is used in combination as the component (b) with the polybutadiene as the component (a).
In this case, the isoprene rubber contains 60% or more, preferably 80% or more, more preferably 90% or more of cis-1,4-bonds, and has a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 70 or more. It is preferably 75 or more, more preferably 80 or more, and has an upper limit of 90 or less, preferably 85 or less. If the content of the cis-1,4-bond is too low, the resilience may be reduced, and if the Mooney viscosity is too low, the resilience may be reduced. On the other hand, if the Mooney viscosity is too high, the effect of improving workability by adding isoprene rubber may not be obtained.
[0039]
The mixing ratio (a) / (b) of the component (a) and the component (b) is 96/4 or more, preferably 96.5 / 3.5 or more, and 99/1 or less, preferably 98 by weight. 0.5 / 1.5, more preferably 98/2 or less. If the amount of the component (b) is too large, the resilience will be greatly reduced.
[0040]
In the present invention, a rubber substrate composed of the above components (a) and (b) is used, but it is optional to mix other rubber components as long as the object of the present invention is not impaired.
[0041]
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.
[0042]
The compounding amount of the unsaturated carboxylic acid / salt of the component (B) is 10 parts or more, more preferably 15 parts or more, based on 100 parts (parts by weight, the same applies hereinafter) of the rubber base material of the component (A). Preferably it is 20 parts or more, 60 parts or less, more preferably 50 parts or less, further preferably 45 parts or less, most preferably 40 parts or less.
[0043]
As the organic peroxide of the component (C), known organic peroxides can be used alone, but preferably two or more can be used in combination. In this case, in particular, two or more kinds of organic peroxides are used from the viewpoint of resilience, and the organic peroxide having the shortest half-life at 155 ° C is (c) the half-life at 155 ° C. When the long organic peroxide is (d), the half-life of (c) is C _t , and the half-life of (d) is _dt , the half-life ratio d _t / _ct is 7 or more, preferably 8 Above, more preferably 9 or more, still more preferably 10 or more, 20 or less, preferably 18 or less, more preferably 16 or less, and still more 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 may be poor.
[0044]
In this case, the half-life _{c t} at 155 ° C. of (c) is 5 seconds or more, more preferably 10 seconds or more, more preferably at least 15 seconds, 120 seconds or less, more preferably 90 seconds or less, more preferably 60 The half-life _dt of (d) at 155 ° C. is preferably 300 seconds or more, more preferably 360 seconds or more, still more preferably 420 seconds or more, and 800 seconds or less, more preferably 700 seconds or less. , More preferably 600 seconds or less.
[0045]
Here, specific examples of the organic peroxide include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,5,5-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 (c), 1,1-bis (t-butylperoxy) -3,5,5-trimethylcyclohexane is preferable, and as the organic peroxide of the component (d), Is preferably dicumyl peroxide.
[0046]
The total compounding amount of the organic peroxide of the component (C) is 0.1 part or more, preferably 0.2 part or more, more preferably 0.3 part or more, based on 100 parts of the component (A). It is preferably at least 0.4 part, at most 5 parts, preferably at most 3 parts, more preferably at most 1 part, even more preferably at most 0.8 part. If the amount is too small, the time required for cross-linking is prolonged, the productivity is greatly reduced, and the compression may be greatly reduced. If the amount is too large, the resilience and durability may be reduced.
[0047]
When the above components (c) and (d) are used in combination, the amount of the component (c) added is preferably at least 0.05 part, more preferably at least 0.08 part, and more preferably at least 0.08 part, per 100 parts of the component (A). Preferably it is 0.1 part or more, most preferably 0.2 part or more, 2.5 parts or less, more preferably 1 part or less, further preferably 0.5 part or less, most preferably 0.4 part or less. Preferably, the amount of component (d) added is at least 0.05 part, more preferably at least 0.15 part, even more preferably at least 0.2 part, most preferably at least 0.4 part, and at least 2.5 parts. It is preferably 1.5 parts or less, more preferably 0.7 parts or less, and most preferably 0.5 part or less.
[0048]
The rubber composition of the present invention preferably contains an organic sulfur compound as the component (D).
[0049]
Examples of the organic sulfur compound as the component (D) 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, and sulfur compounds having a thiophene ring.In particular, zinc salts of pentachlorothiophenol and diphenyl disulfide are preferably used. Can be.
[0050]
The compounding amount is 0.1 part or more, more preferably 0.2 part or more, further preferably 0.4 part or more, and most preferably 0.6 part or more, based on 100 parts of the rubber base material of the component (A). And 5 parts or less, more preferably 4 parts or less, still more preferably 3 parts or less, and most preferably 2 parts or less. If the amount is too small, there is no effect of improving resilience. If the amount is too large, the hardness becomes too soft and sufficient resilience may not be obtained.
[0051]
Further, the rubber composition may contain an inorganic filler as the component (E).
Examples of the inorganic filler of the component (E) include zinc oxide, barium sulfate, and calcium carbonate. The compounding amount is 1 part or more, more preferably 3 parts or more, and still more preferably 100 parts of the component (A). Can be 5 parts or more, most 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. If the amount is too large or too small, an appropriate weight and suitable resilience may not be obtained.
[0052]
Further, if necessary, the antioxidant may be added in an amount of usually at least 0 part, preferably at least 0.05 part, more preferably at least 0.1 part, further preferably at least 0.2 part, based on 100 parts of component (A). 3 parts or less, more preferably 2 parts or less, still more preferably 1 part or less, and most preferably 0.5 part or less. 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
[0053]
The crosslinked molded product of the present invention can be obtained by vulcanizing and curing the above rubber composition in the same manner as a known golf ball rubber composition. 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.
[0054]
The golf ball of the present invention includes the crosslinked molded article as a constituent element, and the aspect of the ball is not particularly limited, and a one-piece solid golf ball in which the crosslinked molded article is directly applied to a golf ball, A two-piece solid golf ball having a cross-linked molded product as a solid core and a cover formed on the surface thereof, and a three-piece or more multi-piece solid golf ball having a cross-linked molded product as a solid core and having two or more layers of covers formed outside thereof. Various modes such as a thread wound golf ball in which the crosslinked molded article is applied as a center core can be adopted. In particular, two-piece solid golf balls and multi-piece solid golf balls using the vulcanized molded product of the present invention as a solid core, from the viewpoint of extrudability during production and imparting resilience to a product golf ball, making use of the properties of the cross-linked molded product. Is recommended as a preferred mode of use.
When the cross-linked molded article is used as a one-piece solid golf ball, solid core, or solid center, the cross-sectional hardness of the spheres is different even if the center is flat from the center to the molded article surface. Or any case.
[0055]
The deflection of the one-piece solid golf ball, solid core or solid center under a 980 N (100 kg) load is usually 2.0 mm or more, preferably 2.5 mm or more, more preferably 2.8 mm or more, and most preferably. It is recommended that the thickness be 3.2 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. If the amount of deformation is too small, the hit feeling will be worse, and the spin will not increase due to too much spin, especially during long shots where a large deformation occurs in the ball of the driver, etc.If it is too soft, the hit feeling will be dull and the rebound will be sufficient In addition, it may not fly and may have poor durability to cracking due to repeated impact.
[0056]
In the present invention, when the crosslinked molded article 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. The upper limit is 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 the solid core of the two-piece solid golf ball is 37 mm. 0.0 mm or more, preferably 37.5 mm or more, more preferably 38.0 mm or more, most preferably 38.5 mm or more, and as an upper limit of 41.0 mm or less, preferably 40.5 mm or less, more preferably 40.0 mm or less. The diameter of the solid core of a three-piece solid golf ball is 30.0 mm or less. It is preferably at least 32.0 mm, more preferably at least 34.0 mm, most preferably at least 35.0 mm, and at most 40.0 mm, preferably at most 39.5 mm, more preferably at most 39.0 mm. Is recommended.
[0057]
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.
[0058]
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 above-described cross-linked molded product is formed as a solid core by injection molding or pressure molding of a known cover material and intermediate layer material. Can be.
[0059]
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.
[0060]
As the thermoplastic polyurethane elastomer, commercially available products can be used. For example, diisocyanates such as Pandex T7298, T7295, T7890, TR3080, T8295, and T8290 (manufactured by DIC Bayer Polymer) are aliphatic. Or those which are aromatic. 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).
[0061]
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.
[0062]
The two-piece solid golf ball and the multi-piece solid golf ball of the present invention can be produced by a known method, and are not particularly limited. The vulcanized molded product is disposed as a solid core in a predetermined injection mold, and in the case of a two-piece solid golf ball, the cover material is used. A known method of injecting a material according to a predetermined method can be suitably adopted. In some cases, the cover material can be manufactured by pressure molding.
[0063]
The thickness of the intermediate layer of the multi-piece solid golf ball is 0.5 mm or more, preferably 1.0 mm or more, and 3.0 mm or less as an upper limit, preferably 2.5 mm or less, more preferably 2.0 mm or less, and most preferably. It is recommended that it be 1.6 mm or less.
[0064]
Further, the thickness of the cover is 0.7 mm or more, preferably 1.0 mm or more, and 3.0 mm or less as an upper limit, preferably 2.5 mm or less, regardless of whether it is a two-piece solid golf ball or a multi-piece solid golf ball. More preferably, it is recommended to be 2.0 mm or less, and most preferably 1.6 mm or less.
[0065]
The golf ball of the present invention can conform to the Rules of Golf for competition and can be formed to 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.
[0066]
【The invention's effect】
The golf ball of the present invention can be manufactured with good workability and has excellent resilience.
[0067]
【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.
[0068]
[Examples 1 to 3, Comparative Examples 1 to 5]
Using a polybutadiene (BR) and an isoprene rubber (IR) shown in Table 1, vulcanization was performed at 155 ° C. for 20 minutes with a rubber composition shown in Table 2 to prepare a core of a two-piece golf ball. 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 was injected into the core to form dimples, the surface of which was coated with paint, and having an outer diameter of 42.7 mm and a weight of 45.3 g. A two-piece solid golf ball was obtained.
The above-mentioned cores were evaluated for the amount of deflection under a load of 100 kg (980 N), resilience, workability of pushing a golf ball, and flying performance by the following methods. Table 2 shows the results.
[0069]
[Examples 4, 5 and Comparative Examples 6, 7]
The composition shown in Table 3 was vulcanized at 170 ° C. for 30 minutes to produce a one-piece solid golf ball having an outer diameter of 42.7 mm and a weight of 45.3 g, and its performance was evaluated. Table 3 shows the results.
Deflection amount under a load of 100 kg The amount of deformation (mm) of the obtained solid core under a load of 100 kg (980 N) was measured.
Repulsion The initial speed was measured with an initial speedometer of the same type as that of the accredited agency USGA, and Examples 1 to 3 and Comparative Examples 1 to 5 were compared with those of Examples 4 and 5 based on Comparative Example 2. For Examples 6 and 7, the difference in the initial speed with respect to Comparative Example 6 was shown.
Evaluation of extrusion workability The slag skin and slag shape after extrusion were evaluated according to the following criteria.
4 Very good clean slag skin 3 Good but slightly rough slag skin 2 Fluffy slag skin but extrudable 1 Poor shape of slag occurs, making it difficult to push out a predetermined amount
Flying performance Flying performance was measured with a driver (W # 1, Tour Stage X500, loft 9 °, shaft X, manufactured by Bridgestone Sports Co., Ltd.) at a head speed of 45 m / s using a hitting machine. .
[0070]
[Table 1]

[0071]
[Table 2]

(Note) Half-life: The unit is seconds Perhexa 3M-40: 40% diluted product (the actual addition amount is a value calculated assuming that Perhexa 3M-40 is 100%.)
[0072]
Comparative Example 1: BR alone polymerized using a Ni-based catalyst has good resilience but very poor workability Comparative Example 2: BR polymerized using a low-repulsion Ni-based catalyst Comparative Example 3 having low resilience: Low IR due to high IR Comparative Example 4: BR polymerized using a low Mooney Ni-based catalyst, and Comparative Example 5 having low resilience Comparative Example 5: Peroxide alone, pentachloro The resilience is reduced because no zinc salt of thiophenol is added.
[Table 3]

Comparative Example 6: Low resilience due to BR polymerized using a low resilience Ni-based catalyst Comparative Example 7: High resilience due to high IR

Claims (6)

(A) (a) A group VIII catalyst and / or a rare earth element-based catalyst having 60% by weight or more of cis-1,4-bond and having a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 50 or more and 120 or less. (B) a solid isoprene rubber having 60% by weight or more of cis-1,4-bond and having a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 70 to 90, A rubber substrate wherein the ratio of the component (a) to the component (b) is 96/4 to 99/1 by weight;
(B) an unsaturated carboxylic acid and / or a metal salt thereof,
(C) A golf ball comprising a cross-linked molded article of a rubber composition containing an organic peroxide as an essential component. 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. 3. The golf ball according to claim 1, wherein the polybutadiene has a viscosity of 300 to 1,000 when the viscosity of a 5% by weight toluene solution at 25 ° C. is η (mPa · s). 4. 4. The golf ball according to claim 1, wherein a rubber composition is used in which 0.1 to 5 parts by weight of an organic sulfur compound is added to 100 parts by weight of a rubber substrate. It contains two or more organic peroxides, of which the organic peroxide having the shortest half-life at 155 ° C is (c), the organic peroxide having the longest is (d), and the half-life of (c) is c. _t, the half-life of (d) when a d _t, the ratio d _{t /} c _t half-life is not less 7 to 20, the total content of 100 parts by weight of material of the rubber group of organic peroxides The golf ball according to claim 1, wherein the amount is 0.1 to 5 parts by weight. The golf ball is a one-piece golf ball or any one of a golf ball having a solid core or a solid center, and a cross-linked molded product of the rubber composition forms a one-piece solid golf ball, a solid core or a solid center, and The golf ball according to any one of claims 1 to 5, wherein the one-piece solid golf ball, the solid core or the solid center has a deflection amount of 2.0 to 6.0 mm under a load of 980 N (100 kg).