JP2004180729A - One-piece golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf ball with excellent productivity with reduced time of vulcanization and to improve the hitting feel and the resilience of the golf ball. <P>SOLUTION: The one-piece golf ball is made of a vulcanized mold of a rubber composition wherein 100 parts by weight of a rubber base material comprising 60-100 % by weight of polybutadiene synthesized by using 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 at least 40, 10-40 parts by weight of unsaturated carboxylic acid, 10-60 parts by weight of metal oxide, and 0.1-0.8 parts by weight of organic peroxide are compounded. <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。）
【００２２】
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。
【００２３】
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。
【００２４】
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。
【００２５】
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。
【００２６】
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。
【００２７】
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。
【００２８】
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。
【００２９】
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。
【００３０】
▲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。
【００３１】
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。
【００３２】
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。
【００３３】
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、６０％以上、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８５％以上であることがよい。また、ゴム基材の１００％が上記ポリブタジエンであってもよく、９５％以下、場合によったら９０％以下の含有量とし得る。
【００３４】
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る。
【００３５】
この場合、上記ポリブタジエン以外のゴム成分のうちでは、ＶＩＩＩ族の触媒を用いて合成され、ムーニー粘度（ＭＬ_１＋４（１００℃））が５０未満、その２５℃における５重量％トルエン溶液の粘度ηが２００ｍＰａ・ｓ以上、４００ｍＰａ・ｓ以下である第２のポリブタジエンを使用することが、高い反発性、良好な作業性を得ることができる点から好ましい。
【００３６】
上記ＶＩＩＩ族触媒として、具体的には、下記のニッケル系触媒、コバルト系触媒を挙げることができる。
ここで、ニッケル系触媒としては、例えば、ニッケルケイソウ土のような１成分系、ラネーニッケル／四塩化チタンのような２成分系、ニッケル化合物／有機金属／三フッ化ホウ素エーテラートのような３成分系のもの等を挙げることができる。なお、ニッケル化合物としては、担体付還元ニッケル、ラネーニッケル、酸化ニッケル、カルボン酸ニッケル、有機ニッケル錯塩などが用いられる。また、有機金属としては、トリエチルアルミニウム、トリ−ｎ−プロピルアルミニウム、トリイソブチルアルミニウム、トリ−ｎ−ヘキシルアルミニウム等のトリアルキルアルミニウム、ｎ−ブチルリチウム、ｓｅｃ−ブチルリチウム、ｔｅｒｔ−ブチルリチウム、１，４−ジリチウムブタン等のアルキルリチウム、ジエチル亜鉛、ジブチル亜鉛等のジアルキル亜鉛等を挙げることができる。
【００３７】
また、コバルト系触媒としては、コバルト及びその化合物として、ラネーコバルト、塩化コバルト、臭化コバルト、ヨウ化コバルト、酸化コバルト、硫酸コバルト、炭酸コバルト、リン酸コバルト、フタル酸コバルト、コバルトカルボニル、コバルトアセチルアセトネート、コバルトジエチルジチオカルバメート、コバルトアニリニウムナイトライト、コバルトジニトロシルクロリド等を挙げることができ、特にこれらの化合物とジエチルアルミニウムモノクロリド、ジイソブチルアルミニウムモノクロリド等のジアルキルアルミニウムモノクロリド、トリエチルアルミニウム、トリ−ｎ−プロピルアルミニウム、トリイソブチルアルミニウム、トリ−ｎ−ヘキシルアルミニウム等のトリアルキルアルミニウム、エチルアルミニウムセスキクロリド等のアルミニウムアルキルセスキクロリド、塩化アルミニウム等との組み合わせを好適に挙げることができる。
【００３８】
上記ＶＩＩＩ族系触媒、特にニッケル系触媒又はコバルト系触媒を用いて重合する場合は、通常、溶剤、ブタジエンモノマーと併せて連続的に反応機にチャージさせ、例えば、反応温度を５〜６０℃、反応圧力を大気圧から７０数気圧の範囲で適宜選択して、上記ムーニー粘度のものが得られるように操作する方法を挙げることができる。
【００３９】
この場合、第２のポリブタジエンの分子量分布Ｍｗ／Ｍｎ（重量平均分子量）／（数平均分子量）が３．０以上、好ましくは３．３以上、より好ましくは３．６以上、更に好ましくは３．９以上で、６．０以下、好ましくは５．５以下、より好ましくは５．０以下、更に好ましくは４．５以下であることが作業性を低下させずに、反発性を維持する点で好ましい。
【００４０】
上記第２のポリブタジエンのムーニー粘度は、５０未満であり、好ましくは４８以下、より好ましくは４６以下、更に好ましくは４５以下である。この場合、ムーニー粘度の下限としては、１０以上、より好ましくは２０以上、更に好ましくは２５以上、最も好ましくは３０以上であることが好ましい。
また、第２のポリブタジエンの２５℃における５重量％トルエン溶液の粘度ηが１００ｍＰａ・ｓ以上、より好ましくは１２０ｍＰａ・ｓ以上、更に好ましくは１４０ｍＰａ・ｓ以上、特に好ましくは１６０ｍＰａ・ｓ以上、最も好ましくは２００ｍＰａ・ｓ以上で、５００ｍＰａ・ｓ以下、より好ましくは４５０ｍＰａ・ｓ以下、更に好ましくは４００ｍＰａ・ｓ以下、特に好ましくは３５０ｍＰａ・ｓ以下、最も好ましいのは３００ｍＰａ・ｓ以下であることが好ましい。
【００４１】
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℃の条件下で測定した値のことをいうものとする。
【００４２】
上記第２のポリブタジエンの配合量は、ゴム基材中、０％以上、好ましくは５％以上、より好ましくは１０％以上で、４０％以下、より好ましくは３０％以下、更に好ましくは２０％以下、最も好ましくは１５％以下とすることが好ましい。
【００４３】
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。
【００４４】
上記（Ｂ）成分の不飽和カルボン酸の配合量は、上記（Ａ）成分のゴム基材１００部に対し、１０部（重量部、以下同じ）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、４０部以下、より好ましくは３５部以下、更に好ましくは３３部以下、特に好ましくは３０部以下、最も好ましくは２７部以下とすることが好ましい。
【００４５】
（Ｃ）成分の金属酸化物としては、酸化亜鉛、酸化チタンなどが好ましい。
【００４６】
上記（Ｃ）成分の金属酸化物の配合量は、上記（Ａ）成分のゴム基材１００部に対し、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、特に好ましくは４０部以下、最も好ましくは３０部以下とすることが好ましい。
【００４７】
（Ｄ）成分の有機酸化物としては、公知のものを使用することができる。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。
【００４８】
ここで、有機過酸化物としては、単独でも２種以上を組み合わせてもよいが、特に生産性、反発性の点で２種以上を使用することが好ましい。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。
【００４９】
この場合、（ａ）の１５５℃における半減期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秒以下であることが好ましく、（ｂ）の１５５℃における半減期ｂ_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。
【００５０】
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）−３，５，５−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。
【００５１】
また、上記有機過酸化物の総配合量は、上記（Ａ）成分のゴム基材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、０．８部以下、好ましくは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。
【００５２】
上記（ａ），（ｂ）の２種以上を使用する場合、（ａ）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部以下であることが好ましく、（ｂ）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部以下であることが好ましい。
【００５３】
本発明のゴム組成物には、（Ｅ）成分として有機硫黄化合物を配合することが好ましい。
（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。
【００５４】
その配合量は、（Ａ）成分のゴム基材１００部に対し、通常０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０．７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、最も好ましくは２部以下、特に好ましくは１．５部以下であることが必要である。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。
【００５５】
更に、（Ｆ）成分として無機充填剤を配合することができる。（Ｆ）成分の無機充填剤としては、硫酸バリウム、炭酸カルシウム等の酸化物以外のものが挙げられ、その配合量は（Ａ）成分１００部に対し、０部以上で、配合する場合は５部以上、より好ましくは７部以上、更に好ましくは１０部以上、最も好ましくは１３部以上で、８０部以下、より好ましくは６５部以下、更に好ましくは５０部以下、最も好ましくは４０部以下とする。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。
【００５６】
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。
【００５７】
本発明の加硫成形物は、上述したゴム組成物を、公知のワンピースソリッド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。
【００５８】
本発明において、上記加硫成形物（ワンピースゴルフボール）の硬度は、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。
【００５９】
また、本発明のワンピースゴルフボールは、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。
【００６０】
なお、上記ワンピースゴルフボールの比重は、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。
【００６１】
本発明のゴルフボールは、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。
【００６２】
【発明の効果】
本発明のワンピースゴルフボールは、加硫時間が短縮されて生産性が良好であり、しかも打感、反発性に優れたものである。
【００６３】
【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。
【００６４】
［実施例、比較例］
表１に示すポリブタジエン（ＢＲ）を使用し、表２に示すゴム組成物を用いて、１７０℃で３０分間の加硫により、ワンピースゴルフボールを作成した。この場合、ディンプルが形成された表面をペイントで被覆し、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飛び性能を下記方法により評価した。結果を表２に示す。
【００６５】
１００ｋｇ荷重たわみ量
得られたゴルフボールに対し、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、比較例については比較例１を基準にしたときの初速度の差を表した。
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（ＨＳ４５）で打撃したときの飛び性能を測定した。
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
【００６６】
【表１】

【００６７】
【表２】

（注）パーヘキサ３Ｍ−４０：４０％希釈品（実質添加量は括弧内）
【００６８】
比較例１：低反発のＮｉ系触媒を用いて重合したＢＲ単体のため、反発性が低い
比較例２：メタクリル酸が多すぎ、打感が硬い
比較例３：メタクリル酸が少なすぎ、反発性が低い
比較例４：Ｎｉ系触媒を用いて重合したＢＲの添加量が少ないため、反発性が低い
比較例５：有機過酸化物が多いため、反発性が低い[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a one-piece solid golf ball having excellent resilience and giving good flight performance.
[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.
However, with respect to the above proposal, further improvement in resilience is required.
[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 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. I can't say.
[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.
Further, Japanese Patent Application Laid-Open Nos. 2001-149505 to 2001-149507 and 2002-293996 have proposals, but there is still room for improvement in terms of resilience.
[0007]
[Patent Document 1]
JP-A-58-225138 [Patent Document 2]
JP-A-62-89750 [Patent Document 3]
Japanese Patent Application Laid-Open No. 62-112574 [Patent Document 4]
JP-A-63-275356 [Patent Document 5]
JP-A-3-151985 [Patent Document 6]
JP-A-2-268778 [Patent Document 7]
JP-A-11-70187 [Patent Document 8]
JP-A-11-164912 [Patent Document 9]
JP-A-11-319148 [Patent Document 10]
JP-A-61-71070 [Patent Document 11]
JP 2001-149505 A [Patent Document 12]
JP 2001-149506 A [Patent Document 13]
JP 2001-149507 A [Patent Document 14]
JP-A-2002-293996
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and provides a one-piece golf ball that can shorten the vulcanization time, improve productivity, and has a good hit feeling, excellent resilience, and good flight performance. The purpose is to:
[0009]
Means for Solving the Problems and Embodiments of the Invention
The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that rare earths containing 60% by weight or more of cis-1,4-bonds and having a Mooney viscosity (ML _{1 + 4} (100 ° C)) of 40 or more. Using a rubber base mainly composed of polybutadiene synthesized using an elemental catalyst, 10 to 40 parts by weight of an unsaturated carboxylic acid and 10 to 60 parts by weight of a metal oxide with respect to 100 parts by weight of the rubber base. Parts by weight, a rubber composition containing 0.1 to 0.8 parts by weight of an organic peroxide, preferably 0.1 to 5 parts by weight of an organic sulfur compound and 5 to 80 parts by weight of an inorganic filler. And two or more kinds of organic peroxides, of which the organic peroxide having the shortest half-life at 155 ° C. is (a), the organic peroxide having the longest is (b), and the half-life of (a) the _a t, if the half-life of (b) was _{b t,} the ratio of the _{half-b t} / By a _t is a vulcanized molded article components of the blended rubber composition as is 7 to 20, excellent manufacturability and can be shortened vulcanization time, yet feel was good, repulsive It has been found that a one-piece solid golf ball having good properties can be obtained.
[0010]
That is, conventionally, when the amount of the organic peroxide is reduced, the vulcanization time is extended and the productivity is reduced. However, according to the present invention, the vulcanization time can be shortened, and the amount of the organic peroxide is small. It has been found that the present invention can be further improved, and the present invention has been accomplished.
[0011]
Accordingly, the present invention provides the following one-piece golf ball.
Claim 1:
A rubber base containing 60 to 100% by weight of a polybutadiene synthesized using a rare earth element catalyst containing 60% by weight or more of cis-1,4-bond and having a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 40 or more. Rubber composition comprising 10 to 40 parts by weight of unsaturated carboxylic acid, 10 to 60 parts by weight of metal oxide and 0.1 to 0.8 part by weight of organic peroxide, based on 100 parts by weight of material A one-piece golf ball consisting of a vulcanized molded product of
Claim 2:
The one-piece 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:
The one-piece golf ball according to claim 1 or 2, wherein the polybutadiene is a modified polybutadiene rubber synthesized using an Nd-based catalyst and subsequently obtained by reacting a terminal modifier.
Claim 4:
In addition to the above polybutadiene, a polybutadiene synthesized using a Group VIII catalyst as a second polybutadiene is contained in a rubber base material at a ratio of 40% by weight or less, and the second polybutadiene has a Mooney viscosity (ML _{1 + 4} (100 ° C. 4.) The one-piece golf ball according to claim 1, wherein the value of)) is less than 50.
Claim 5:
The one-piece golf ball according to claim 4, wherein the molecular weight distribution Mw / Mn of the second polybutadiene is 3.0 to 6.0, and the viscosity of the 5% by weight toluene solution at 25 ° C is 100 mPa · s or more and 500 mPa · s or less. ,
Claim 6:
The one-piece golf ball according to any one of claims 1 to 5, further comprising an organic sulfur compound in an amount of 0.2 to 5 parts by weight based on 100 parts by weight of the rubber base material.
Claim 7:
It contains two or more kinds of organic peroxides, of which the organic peroxide having the shortest half-life at 155 ° C. is (a), the organic peroxide having the longest is (b), and the half-life of (a) is a _t, the half-life when the set to _{b t,} one-piece golf ball of any one of claims 1 to 6, wherein the ratio _b t / _{a t} half-life of 7 to 20 or less (b).
[0012]
Hereinafter, the present invention will be described in more detail.
The golf ball of the present invention
(A) Rubber containing polybutadiene as a main component synthesized using a rare earth element-based catalyst having a cis-1,4-bond content of 60% by weight or more and a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 40 or more. Base material,
(B) an unsaturated carboxylic acid,
(C) a metal oxide,
(D) an organic peroxide,
Preferably, further (E) an organic sulfur compound,
(F) A composition comprising a vulcanized molded product of a rubber composition containing an inorganic filler.
[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.
[0014]
The polybutadiene has a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 40 or more, preferably 50 or more, more preferably 52 or more, most preferably 54 or more, and the upper limit is 140 or less, preferably 120 or less, more preferably 100 or less. It is most preferably 80 or less.
[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 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.
[0017]
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.
[0018]
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.
[0019]
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.
[0020]
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).
[0021]
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.)
[0022]
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.
[0023]
The Lewis base can be used to complex a lanthanide series rare earth element compound, and examples thereof include acetylacetone and ketone alcohol.
[0024]
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.
[0025]
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.
[0026]
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.
[0027]
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.
[0028]
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.
[0029]
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.
[0030]
_{^{▲ 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).
[0031]
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.
[0032]
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.
[0033]
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 60% or more, preferably 70% or more, more preferably 80% in the rubber base material. Above, most preferably, it is 85% or more. Also, 100% of the rubber substrate may be the above polybutadiene, and may have a content of 95% or less, and in some cases 90% or less.
[0034]
The rubber component other than the polybutadiene includes polybutadiene other than the polybutadiene, for example, polybutadiene obtained using a Group VIII metal compound catalyst, and other diene rubbers such as styrene butadiene rubber, natural rubber, isoprene rubber, and ethylene propylene diene rubber. And the like.
[0035]
In this case, among the rubber components other than the polybutadiene, the rubber component is synthesized using a Group VIII catalyst and has a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of less than 50 and a viscosity η of a 5% by weight toluene solution at 25 ° C. It is preferable to use the second polybutadiene having a pressure of 200 mPa · s or more and 400 mPa · s or less because high resilience and good workability can be obtained.
[0036]
Specific examples of the Group VIII catalyst include the following nickel-based catalysts and cobalt-based catalysts.
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.
[0037]
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.
[0038]
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.
[0039]
In this case, the molecular weight distribution Mw / Mn (weight average molecular weight) / (number average molecular weight) of the second polybutadiene is 3.0 or more, preferably 3.3 or more, more preferably 3.6 or more, and still more preferably 3. It is from 9 or more to 6.0 or less, preferably 5.5 or less, more preferably 5.0 or less, and still more preferably 4.5 or less, in that resilience is maintained without lowering workability. preferable.
[0040]
The Mooney viscosity of the second polybutadiene is less than 50, preferably 48 or less, more preferably 46 or less, and further preferably 45 or less. In this case, the lower limit of the Mooney viscosity is preferably 10 or more, more preferably 20 or more, still more preferably 25 or more, and most preferably 30 or more.
Further, the viscosity η of a 5% by weight toluene solution of the second polybutadiene at 25 ° C. is 100 mPa · s or more, more preferably 120 mPa · s or more, further preferably 140 mPa · s or more, particularly preferably 160 mPa · s or more, and most preferably. Is 200 mPa · s or more, 500 mPa · s or less, more preferably 450 mPa · s or less, further preferably 400 mPa · s or less, particularly preferably 350 mPa · s or less, and most preferably 300 mPa · s or less.
[0041]
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.
[0042]
The compounding amount of the second polybutadiene is 0% or more, preferably 5% or more, more preferably 10% or more, 40% or less, more preferably 30% or less, further preferably 20% or less in the rubber base material. , Most preferably 15% or less.
[0043]
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.
[0044]
The compounding amount of the unsaturated carboxylic acid of the component (B) is at least 10 parts (parts by weight, the same applies hereinafter), more preferably at least 15 parts, even more preferably 100 parts by weight of the rubber base material of the component (A). It is preferably at least 20 parts, at most 40 parts, more preferably at most 35 parts, even more preferably at most 33 parts, particularly preferably at most 30 parts, most preferably at most 27 parts.
[0045]
As the metal oxide of the component (C), zinc oxide, titanium oxide and the like are preferable.
[0046]
The compounding amount of the metal oxide of the component (C) is 10 parts or more, more preferably 15 parts or more, and still more preferably 20 parts or more, based on 100 parts of the rubber base material of the component (A). The content is preferably 50 parts or less, more preferably 45 parts or less, particularly preferably 40 parts or less, and most preferably 30 parts or less.
[0047]
As the organic oxide of the component (D), a known organic oxide can be used. Specific examples of the organic peroxide include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,5,5-trimethylcyclohexane, α, α′-bis (t-butylperoxy). 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).
[0048]
Here, the organic peroxides may be used alone or in combination of two or more, but it is particularly preferable to use two or more in terms of productivity and resilience. In this case, the half-life shortest organic peroxide at 155 ° C. (a), the half-life is longest organic peroxide and (b) at 155 ° C., the half-life of (a) a _t, If the half-life of (b) was _{b t,} the ratio _b t / _{a t} half-life of at least 7, preferably 8 or more, more preferably 9 or more, more preferably 10 or more, 20 or less, more preferably It is 18 or less, more preferably 16 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.
[0049]
In this case, the half-life _{a t} at 155 ° C. of (a) 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 And the half-life b _t at 155 ° C. of (b) is 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.
[0050]
In this case, as the organic peroxide of the component (a), 1,1-bis (t-butylperoxy) -3,5,5-trimethylcyclohexane is preferable, and as the organic peroxide of the component (b), Is preferably dicumyl peroxide.
[0051]
The total amount of the organic peroxide 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 rubber base material of the component (A). More preferably, it is 0.4 part or more, 0.8 part or less, preferably 0.7 part or less, more preferably 0.6 part or less, further preferably 0.5 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.
[0052]
When two or more of the above (a) and (b) are used, the amount of the component (a) added is preferably 0.05 parts or more, more preferably 0.08 parts or more, per 100 parts of the component (A). The content is more preferably 0.1 part or more, 0.5 part or less, more preferably 0.4 part or less, and even more preferably 0.3 part or less. Part or more, more preferably 0.15 part or more, further preferably 0.2 part or more, 0.7 part or less, more preferably 0.6 part or less, further preferably 0.5 part or less. .
[0053]
The rubber composition of the present invention preferably contains an organic sulfur compound as the component (E).
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, and sulfur compounds having a thiophene ring.In particular, zinc salts of pentachlorothiophenol and diphenyl disulfide are preferably used. Can be.
[0054]
The compounding amount is usually at least 0 part, more preferably at least 0.2 part, further preferably at least 0.4 part, most preferably at least 0.7 part, based on 100 parts of the rubber base material of the component (A). 5 parts or less, more preferably 4 parts or less, further preferably 3 parts or less, most preferably 2 parts or less, particularly preferably 1.5 parts or less. If the amount is too small, the effect of improving resilience will not be obtained. If the amount is too large, the hardness will be too soft and sufficient resilience will not be obtained.
[0055]
Further, an inorganic filler can be blended as the component (F). Examples of the inorganic filler of the component (F) include those other than oxides such as barium sulfate and calcium carbonate. The compounding amount is 0 or more parts per 100 parts of the component (A). Parts or more, more preferably 7 parts or more, still more preferably 10 parts or more, most preferably 13 parts or more, 80 parts or less, more preferably 65 parts or less, still more preferably 50 parts or less, and most preferably 40 parts or less. I do. If the amount is too large or too small, an appropriate weight and suitable resilience may not be obtained.
[0056]
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
[0057]
The vulcanized molded product of the present invention can be obtained by vulcanizing and curing the above-described rubber composition in the same manner as a known one-piece solid 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.
[0058]
In the present invention, the hardness of the vulcanized molded product (one-piece golf ball) is not particularly limited, and the cross-sectional hardness is such that the hardness from the center to the surface of the molded product is flat even if the surface is flat from the center to the surface of the molded product. There may be a difference or any case.
[0059]
In addition, the one-piece golf ball of the present invention has a deflection under a load of 980 N (100 kg) of usually 2.0 mm or more, preferably 2.5 mm or more, more preferably 2.8 mm or more, and most preferably 3.2 mm or more. It is recommended that the upper limit is 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. At the same time, when a long shot in which a large deformation occurs in a ball such as a driver, the spin increases too much and the ball does not fly.If it is too soft, the hit feeling becomes dull, the rebound is not enough and it does not fly, and the durability to cracking due to repeated impacts May worsen.
[0060]
The specific gravity of the one-piece golf ball 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. It is recommended that it be no more than 2.
[0061]
The golf ball of the present invention can conform to the Rules of Golf and can be formed with 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.
[0062]
【The invention's effect】
The one-piece golf ball of the present invention has a short vulcanization time, good productivity, and excellent hit feeling and resilience.
[0063]
【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.
[0064]
[Examples and Comparative Examples]
Using the polybutadiene (BR) shown in Table 1 and the rubber composition shown in Table 2, vulcanization was performed at 170 ° C. for 30 minutes to produce a one-piece golf ball. In this case, the surface on which the dimples were formed was coated with paint to obtain a one-piece solid golf ball having an outer diameter of 42.7 mm and a weight of 45.3 g.
The above-described cores were evaluated for the amount of deflection under a load of 100 kg (980 N), resilience, and flight performance of a golf ball by the following methods. Table 2 shows the results.
[0065]
Deflection amount under a load of 100 kg The deformation amount (mm) of the obtained golf ball 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 official agency USGA, and the difference between the initial speed with respect to the example and the comparative example based on the comparative example 1 was shown.
Flying performance Flying performance when hit with a driver (W # 1, Tour Stage X500, Loft 9 °, Shaft X, Bridgestone Sports Co., Ltd.) at a head speed of 45 m / s (HS45) with a hitting machine Was measured.
Evaluation of extrusion workability The slag skin and slag shape after extrusion were evaluated according to the following criteria.
4 Very good and clean slag skin 3 Good but slightly rough slag skin 2 Fluffy slag skin but extrudable
[Table 1]

[0067]
[Table 2]

(Note) Perhexa 3M-40: 40% diluted product (the actual amount added is in parentheses)
[0068]
Comparative Example 1: BR alone polymerized using a low-repulsion Ni-based catalyst, low resilience Comparative Example 2: too much methacrylic acid and hard hitting Comparative Example 3: too little methacrylic acid, resilience Comparative Example 4: Low resilience due to small addition of BR polymerized using a Ni-based catalyst Comparative Example 5: Low resilience due to large amount of organic peroxide

Claims (7)

A rubber base containing 60 to 100% by weight of a polybutadiene synthesized using a rare earth element catalyst containing 60% by weight or more of cis-1,4-bond and having a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of 40 or more. Rubber composition comprising 10 to 40 parts by weight of unsaturated carboxylic acid, 10 to 60 parts by weight of metal oxide and 0.1 to 0.8 part by weight of organic peroxide, based on 100 parts by weight of material A one-piece golf ball made of a vulcanized molded product. The one-piece 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. The one-piece golf ball according to claim 1 or 2, wherein the polybutadiene is a modified polybutadiene rubber synthesized using an Nd-based catalyst and subsequently obtained by reacting a terminal modifier. In addition to the above polybutadiene, a polybutadiene synthesized using a Group VIII catalyst as a second polybutadiene is contained in a rubber base material at a ratio of 40% by weight or less, and the second polybutadiene has a Mooney viscosity (ML _{1 + 4} (100 ° C. 4.) The one-piece golf ball according to claim 1, wherein the number is less than 50. The one-piece golf ball according to claim 4, wherein the molecular weight distribution Mw / Mn of the second polybutadiene is 3.0 to 6.0, and the viscosity of the 5% by weight toluene solution at 25 ° C is 100 mPa · s or more and 500 mPa · s or less. . The one-piece golf ball according to any one of claims 1 to 5, further comprising 0.2 to 5 parts by weight of the organic sulfur compound based on 100 parts by weight of the rubber substrate. It contains two or more kinds of organic peroxides, of which the organic peroxide having the shortest half-life at 155 ° C. is (a), the organic peroxide having the longest is (b), and the half-life of (a) is a _t, the half-life when the set to _{b t,} one-piece golf ball of any one of claims 1 to 6, wherein the ratio _b t / _{a t} half-life of 7 to 20 or less (b).