JP3647389B2 - Polyorganosiloxane foam, foam and method for producing the same - Google Patents

Description

【００２１】
（式中、Ｒ¹は、アルケニル基を表し；Ｒ²は、たがいに同一でも相異なっていてもよく、脂肪族不飽和結合を有しない置換または非置換の１価の炭化水素基を表し；ａは、１または２の整数を表し、ｂは、０〜２の整数を表し、ａ＋ｂは、１〜３の整数である）で示される単位を、分子中に少なくとも２個有するアルケニル基含有ポリオルガノシロキサン１００重量部；
（Ｂ）下記の（Ｂ１）、すなわち（ｉ）と（ii）の組合せ；または（Ｂ２）から選ばれる、（Ａ）を硬化させるための化学物質：
（Ｂ１）（ｉ）一般式：
【００２２】
【化５】

【００２３】
（式中、Ｒ³は、たがいに同一でも相異なっていてもよく、脂肪族不飽和結合を有しない置換または非置換の１価の炭化水素基を表し；ｃは、０〜２の整数を表し、ｄは、１または２の整数を表し、ｃ＋ｄは、１〜３の整数である）で示される単位を、分子中に少なくとも３個有するポリオルガノハイドロジェンシロキサン、（Ａ）成分のアルケニル基１個に対する、ケイ素原子に結合した水素原子の量が、０．５〜５個になる量；
（ii）白金化合物、触媒量；
（Ｂ２）有機過酸化物 ０．１〜１０重量部；
（Ｃ）吸水性ポリマー粉末 ０．００１〜２０重量部；ならびに
（Ｄ）（Ｃ）に吸収されている水 ０．５〜５００重量部
を含むことを特徴とする。
【００２４】
また、本発明の発泡体の製造方法は、前記のポリオルガノシロキサン発泡材を、型成形により、場合によっては型成形の後にさらに加熱する工程を加えて、発泡体を得る方法であり、本発明の発泡体は、そのようにして得られた、ポリオルガノシロキサン架橋体を主成分とする発泡体である。特に、（Ｃ）成分としてビニルカルボン酸アミド繰返し単位から主としてなる架橋ポリマーを用いて、後述のような高温加熱により、圧縮永久ひずみ特性の優れた発泡体が得られる。
【００２５】
【発明の実施の形態】
本発明に用いられる（Ａ）成分は、一般式：
【００２６】
【化６】

【００２７】
（式中、Ｒ¹、Ｒ²、ａおよびｂは、前述のとおり）で示される単位を、分子中に少なくとも２個有するアルケニル基含有ポリオルガノシロキサンである。該（Ａ）成分は、本発明の組成物のベースポリマーであり、ケイ素原子に結合したアルケニル基が、（ｉ）成分中のケイ素原子に結合した水素原子とのヒドロシリル化反応（付加反応）により、または（Ｂ２）成分である有機過酸化物の熱分解によって生ずるラジカルの攻撃を受けて、架橋を行うとともに、他の成分との連携により発泡体に強度を付与する成分である。
【００２８】
（Ａ）成分としては、上記の（Ｉ）式で表される単位を、分子中に少なくとも２個有するポリオルガノシロキサンであれば、その分子構造に特に制限はなく、直鎖状、環状、分岐状のシロキサン骨格を有するものが使用されうるが、合成のしやすさ、および組成物に優れたゴム弾性と機械的性質を付与する点から、直鎖状のものか、直鎖状と分岐状のアルケニル基含有ポリオルガノシロキサンを併用することが好ましい。平均重合度、すなわち分子中のケイ素原子の平均数は、特に限定されないが、通常、３０〜１０，０００の範囲である。重合度が３０未満では、硬化によって得られた発泡体の機械的性質が十分でなく、１０，０００を越えると、未硬化状態における取扱いが困難となる。（Ａ）成分の好ましい平均重合度と、ケイ素原子に結合した有機基中のＲ¹の比率は、目的とするポリオルガノシロキサン発泡材の性質や用途によって異なる。
【００２９】
常温で流動性を示し、射出成形のような量産に適した成形方法に適合する発泡材を得るには、発泡材が適切な粘性を示し、かつ硬化して得られる発泡体が優れた機械的性質を有する必要から、用いる（Ａ）成分は、平均重合度が５０〜２，０００の、常温で液状のものが好ましく、平均重合度が２００〜１，０００のものがさらに好ましい。また、特に優れた機械的性質を有する発泡体を得るために、（Ａ）成分として、直鎖状の液状ポリジオルガノシロキサンと、分岐状のシロキサン構造を有する樹脂状のものを併用することもできる。
【００３０】
発泡材が固体であり、ロールによって素練りした後に成形するものは、優れた機械的強度を示すことから、用いる（Ａ）成分は、平均重合度が３，０００〜８，０００のものが好ましく、平均重合度が５，０００〜７，０００のものがさらに好ましい。Ｒ¹は、発泡体が良好な硬化性と耐熱性を兼ね備えることから、ケイ素原子に結合した全有機基中の０．０２〜５モル％が好ましく、０．０５〜０．５モル％がさらに好ましい。また、発泡体に優れた引裂強さを与えるために、分子中にＲ¹を有さないポリオルガノシロキサンと、Ｒ¹を有するポリオルガノシロキサンを混合して、平均して上記の価にしたものを用いても差支えない。
【００３１】
Ｒ¹としてはビニル、アリル、ブテニルなどが例示され、合成が容易なことからビニル基が好ましい。Ｒ²としては、メチル、エチル、プロピル、ブチル、ペンチル、ヘキシル、オクチル、デシル、ドデシルのような、直鎖状または分岐状のアルキル基；シクロヘキシルのようなシクロアルキル基；２−フェニルエチル、２−フェニルプロピルのようなアラルキル基；フェニルのようなアリール基；ならびにクロロメチル、３，３，３−トリフルオロプロピル、クロロフェニルのような置換された１価の炭化水素基が例示され、合成および取扱いが容易なことから、メチル基が好ましい。ａ、ｂは、それぞれ前述のとおりであり、合成が容易なことから、ａが１であることが好ましい。
【００３２】
このような（Ｉ）式で表される単位は、分子末端、分子中間のいずれに存在してもよいが、硬化して得られる発泡体に良好な機械的性質を付与するには、少なくともその一部は分子末端に、たとえばＲ¹Ｒ² ₂ＳｉＯ_1/2単位のような形式で存在することが好ましい。
【００３３】
（Ａ）成分中の（Ｉ）式で表される単位以外のシロキサン単位において、ケイ素原子に結合した有機基は、たがいに同一でも相異なっていてもよく、Ｒ²として例示したものと同様の１価の置換または非置換の炭化水素基が例示される。（Ａ）成分のケイ素原子に結合した有機基として、前述のＲ¹は別にして、合成および取扱いが容易なことから、８５モル％以上がメチル基であることが好ましく、実質的にすべてがメチル基であることがさらに好ましい。
【００３４】
本発明の発泡材から発泡体を得るには、該発泡材中の（Ａ）成分を、（Ｂ）の作用によって架橋させる。架橋は、次の（１）または（２）の反応によって行うことができるが、これらと他の反応を併用することもできる。
【００３５】
（１）付加反応：（Ｂ）として（Ｂ１）、すなわち、架橋剤である（ｉ）成分と、反応触媒である（ii）成分を組み合わせて用い、（ｉ）成分中のヒドロシリル基と、（Ａ）成分中のＲ¹との間の付加反応によって架橋体が形成される。（Ａ）成分としては、比較的低分子量の、常温で液状のものを用いても、より高分子量のものを用いてもよいが、所望の発泡体を容易に形成できることから、液状のもの、たとえば前述のように、平均重合度が５０〜２，０００のものを用いることが好ましい。
【００３６】
（２）ラジカル反応：（Ｂ）として（Ｂ２）成分を用い、その熱分解によって生成するラジカルにより、（Ａ）成分のＲ¹と、他の分子のケイ素原子に結合した有機基の間の架橋反応によって架橋体が形成される。（Ａ）成分としては、付加反応の場合と同様に、常温で液状のものが好ましい。
【００３７】
本発明に用いられる（ｉ）成分は、一般式：
【００３８】
【化７】

【００３９】
（式中、Ｒ³、ｃおよびｄは、前述のとおり）で表される単位を、１分子中に少なくとも３個有するポリオルガノハイドロジェンシロキサンであり、ケイ素原子に結合した水素原子が、（Ａ）成分中のアルケニル基とのヒドロシリル反応を行う架橋剤として寄与する。
【００４０】
（ｉ）成分としては、１分子中にケイ素原子に直接結合した水素原子を有する単位を、分子中に少なくとも３個有するものであれば、その分子構造に特に制限はなく、直鎖状、環状、分岐状のシロキサン骨格を有するものが使用されうるが、合成のしやすさから直鎖状のものが好ましく、また機械的強度に優れた発泡体を得るためには、（ｉ）成分の少なくとも一部として、Ｒ³ ₂ＨＳｉＯ_1/2単位とＳｉＯ₂単位からなるポリオルガノハイドロジェンシロキサンを用いることが好ましい。
【００４１】
Ｒ³は、たがいに同一でも相異なっていてもよく、脂肪族不飽和結合を有しない置換または非置換の１価の炭化水素基であり、このような基としては、メチル、エチル、プロピル、ブチル、ヘキシル、オクチル、デシル、ドデシルのような、直鎖状または分岐状のアルキル基；シクロヘキシルのようなシクロアルキル基；フェニルのようなアリール基；ならびにクロロメチル、３，３，３−トリフルオロプロピル、クロロフェニルのような置換された１価の炭化水素基が例示され、合成のしやすさからメチル基が好ましい。ｃ，ｄは、それぞれ前述のとおりであり、合成が容易なことから、ｄが１であることが好ましい。
【００４２】
（ｉ）成分中の（II）式で表される単位以外のシロキサン単位において、ケイ素原子に結合した有機基は、たがいに同一でも相異なっていてもよく、Ｒ³と同様なものが例示され、合成のしやすさから、メチル基であることが好ましい。
【００４３】
（ｉ）成分の配合量は、（Ａ）成分のアルケニル基１個に対して、ケイ素原子に結合した水素原子が０．５〜５個になる量である。この値が０．５個未満では、架橋が少なくて機械的強度が弱くなり、５個を越えると、硬化後の物性の変化が大きくなる。
【００４４】
本発明に用いられる（ii）成分は、（Ａ）成分中のアルケニル基と（ｉ）成分中のケイ素原子に結合した水素原子との間の付加反応により、本発明の発泡材を硬化させるために用いられる触媒である。これには、塩化白金酸、アルコールと塩化白金酸から得られる錯体、白金オレフィン錯体、白金ケトン錯体、白金ビニルシロキサン錯体のような白金化合物が使用できる。この（ii）成分は、触媒としての必要量が用いられ、この量は（Ａ）成分に対して、白金原子に換算して、通常０．１〜１，０００ppmとなる量であり、好ましくは０．５〜２００ppmになる量である。０．１ppm未満では、触媒濃度が低いため、硬化が不十分となる。また１，０００ppmを越えて配合しても、それ以上の効果はなく、（ii）成分が貴金属を含み、一般に高価であるために、経済的に好ましくない。
【００４５】
本発明に用いられる（Ｂ２）成分は、有機過酸化物であって、熱分解によりラジカルを発生し、該ラジカルが、（Ａ）成分中のＲ¹をはじめとする有機基を攻撃して、炭素鎖による架橋を形成させるものである。
【００４６】
（Ｂ２）成分としては、ベンゾイルペルオキシド、ｐ−クロロベンゾイルペルオキシド、ｍ−トルイルペルオキシドのようなアシル系ペルオキシド；ジ−tert−ブチルペルオキシド、クミル−tert−ブチルペルオキシド、ジクミルペルオキシド、２，５−ジメチル−２，５−ジ−tert−ブチルペルオキシヘキサンのようなアルキル系ペルオキシド；tert−ブチルペルオキシベンゾアート、tert−ブチルペルオキシ−３，５，５−トリメチルヘキサノアート、tert−ブチルペルオキシイソプロピルカルボナートのようなペルオキシエステル；１，１−ビス（tert−ブチルペルオキシ）−３，５，５−トリメチルシクロヘキサンのようなペルオキシケタールなど、各種の有機過酸化物が用いられ、特に低い圧縮永久ひずみを与えることから、クミル−tert−ブチルペルオキシド、ジクミルペルオキシドおよび２，５−ジメチル−２，５−ジ−tert−ブチルペルオキシヘキサンが好ましい。これらの有機過酸化物は、１種でも、２種以上を併用しても差支えない。
【００４７】
（Ｂ２）成分の配合量は、架橋反応が十分に行われ、また発泡体の耐熱性や物理的性質を損ねないことから、（Ａ）成分１００重量部に対して０．０１〜１０重量部の範囲が好ましく、０．１〜５重量部がさらに好ましい。
【００４８】
本発明に用いられる（Ｃ）成分は、吸水性ポリマー粉末であり、（Ｄ）成分である水を吸収して膨潤した状態で配合され、水を発泡材の系中に均一に細かく分散させるのに有効である。該（Ｃ）成分は、これを配合した発泡材を型成形する際に、成形温度で、および／または成形後の加熱工程における加熱温度で、水を放出して均質な気泡を形成する、本発明の特徴的な成分である。（Ｃ）成分としては、単に親水性であるばかりでなく、水によって水溶液になったり、水の存在で凝集して塊状になるのではなく、個々の粉末が膨潤して微細なゲル状物を形成することが必要である。
【００４９】
このような（Ｃ）成分として用いられる吸水性ポリマーとしては、（メタ）アクリル酸およびそのアルカリ金属塩の重合体、その相互の共重合体や架橋体、ならびにデンプン・（メタ）アクリル酸グラフト共重合体およびそのアルカリ金属塩などが例示され、良好な結果が得られることから、ポリアクリル酸とそのアルカリ金属塩、その架橋体、およびテンプン・アクリル酸グラフト共重合体とそのアルカリ金属塩が好ましく、ポリアクリル酸の部分ナトリウム塩の架橋体、およびデンプン・アクリル酸グラフト共重合体の部分ナトリウム塩が特に好ましい。発泡体を形成するために、（Ｃ）成分を含む発泡材を２００℃まで加熱した後に、ポリアクリル酸の部分ナトリウム塩の架橋体は、なおも吸水能を維持して、吸水性の発泡体が得られるのに対して、デンプン・アクリル酸グラフト共重合体の部分ナトリウム塩は、吸水能を失って、非吸水性の発泡体が得られる。したがって、発泡体の用途によって、これらを選択して用いることが好ましい。
【００５０】
本発明に用いられる（Ｃ）成分としてさらに挙げられるポリマーの例は、一般式：
【００５１】
【化８】

【００５２】
（式中、Ｒ⁴およびＲ⁵は、たがいに独立して水素原子又はメチル基を表す）で示されるＮ−ビニルカルボン酸アミド繰返し単位から主としてなる架橋ポリマーである。ここで、「主としてなる」とは、ポリマー中の繰返し単位の５０％以上、好ましくは７０％以上、さらに好ましくは架橋性単位以外の実質的に１００％が、このような単位からなることを示す。該繰返し単位の例としては、Ｎ−ビニルホルムアミド単位、Ｎ−ビニルアセトアミド単位、Ｎ−ビニル−Ｎ−メチルホルムアミド単位およびＮ−ビニル−Ｎ−メチルアセトアミド単位が挙げられ、Ｎ−ビニルアセトアミド単位が特に好ましい。
【００５３】
上記の架橋ポリマーは、重合によって上記の繰返し単位を構成するモノマーと、分子中に少なくとも２個のビニル基、アリル基、（メタ）アクリル基のような重合性炭素−炭素二重結合を有する架橋性モノマーとを共重合させることによって得られる。このような架橋性モノマーとしては、Ｎ，Ｎ′−メチレンビスアクリルアミド、Ｎ，Ｎ′−１，４−ブチレンビス（Ｎ−ビニルアセトアミド）、Ｎ，Ｎ′−１，１０−デシレンビス（Ｎ−ビニルアセトアミド）、Ｎ，Ｎ′−３−オキサ−１，５−ペンチレンビス（Ｎ−ビニルアセトアミド）、アジピン酸ジビニル、アジピン酸ジアリル、テトラアリルオキシエタン、ペンタエリトリトールテトラアリルエーテル、トリアリルイソシアヌラート、エチレングリコールジ（メタ）アクリラート、ジエチレングリコールジ（メタ）アクリラート、トリエチレングリコールジ（メタ）アクリラート、トリメチロールプロパントリ（メタ）アクリラート、ペンタエリトリトールトリ（メタ）アクリラートなどが例示される。
【００５４】
ポリマー中の、Ｎ−ビニルカルボン酸アミド単位および上記の架橋性モノマーに由来する単位以外の繰返し単位として、各種の繰返し単位を有することができる。このような単位として、（メタ）アクリル酸単位、（メタ）アクリル酸アルカリ金属塩単位、（メタ）アクリル酸アルキルエステル単位、（メタ）アクリル酸ヒドロキシエステル単位、（メタ）アクリルアミド単位、アルキルビニルエーテル単位、マレイン酸単位およびそれから誘導される単位などが挙げられるが、これらに限定されるものではない。
【００５５】
架橋性モノマーは、架橋ポリマーが、適度の水膨潤性を有するように架橋密度を制御するため、モノマー全体に対して、通常０．０００１〜１０モル％、好ましくは０．０００５〜２モル％用いられる。重合は、有機過酸化物のようなラジカル発生剤の存在下に、水溶液重合、懸濁重合、乳化重合などの方法で行うことができる。このようにして得られた、主鎖の重合度が通常１００〜５００，０００、好ましくは５，０００〜１００，０００の架橋性ポリマーの粉末を、本発明の（Ｃ）成分として用いることができる。
【００５６】
（Ｃ）成分としてこのようなＮ−ビニルカルボン酸アミド系の架橋ポリマーを用いることにより、後述のように、高温による加熱工程を経て得られるポリオルガノシロキサン発泡体は、優れた圧縮永久ひずみ特性を有する。
【００５７】
（Ｃ）成分は、粉末状のものが用いられ、その平均粒子径は、細かいものほどセルの微細な発泡体が得られる。粒子径の揃ったものが比較的容易に得られ、取扱いが容易で、細かいセルの発泡体が得られることから、乾燥状態における平均粒子径として、目的に応じて、通常０．１〜５００μmのものから選択して用いられ、１〜１００μmのものが好ましく、２〜６０μmのものがさらに好ましい。
【００５８】
（Ｃ）成分の配合量は、（Ａ）成分１００重量部に対して０．００１〜２０重量部であり、好ましくは０．０５〜５重量部である。０．００１重量部未満では、吸水量が少なく、必要な量の水を配合すると水が分離して、良好な発泡体が得られない。一方、２０重量部を越えても効果は変わらない。
【００５９】
（Ｄ）成分は水であり、（Ｃ）成分に吸収された形で配合される。（Ｄ）成分は、たとえば（Ｃ）成分を（Ｄ）成分中に浸漬することにより、（Ｃ）成分に吸収された形で発泡材に均一に分散し、型成形または成形後の加熱で揮発して、均一に分散した均質なセルを残すために配合されるもので、（ii）成分のヒドロシリル基との反応によって水素を発生させるためのものではない。（Ｄ）成分の配合量は、多いほど高い発泡倍率が得られるが、（Ａ）成分１００重量部に対して０．５〜５００重量部の範囲から選択され、発泡倍率と機械的強度の兼ね合いから、１０〜３００重量部が好ましい。０．５重量部未満では、発泡体が得られず、５００重量部を越えて配合すると、発泡体の機械的強度が大幅に低下する。
【００６０】
また、特に（Ｃ）成分に（Ｄ）成分、すなわち水を多量に吸収させて用いるときは、（Ｃ）成分の吸水した状態を安定に保ち、かつ吸水した（Ｃ）成分の系中への分散を助けるために、（Ｅ）成分として界面活性剤を配合することが好ましい。（Ｅ）成分は、用いる水の中に溶解および／または分散させて（Ｃ）成分を浸漬する、ならびに／あるいは（Ｃ）成分に水を吸収させた後に、（Ｃ）成分に吸収させて配合することが好ましい。なお、（Ｅ）成分を（Ｃ）成分に吸収させるには、たとえば、（Ｃ）成分を常温で液状の（Ｅ）成分中、または加温して液状にした常温で固体の（Ｅ）成分中に浸漬することによって行うことができる。（Ｅ）成分としては、グリセリン脂肪酸エステル、ポリグリセリン脂肪酸エステル、ソルビタン脂肪酸エステル、スクロース脂肪酸エステル、ポリエチレングリコール脂肪酸エステル、ポリオキシエチレングリセリン脂肪酸エステル、ポリオキシエチレンソルビタン脂肪酸エステル、ポリオキシエチレン・ポリオキシプロピレンブロック共重合体、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニルエーテル、ポリオキシエチレン脂肪酸アミドのようなノニオン系界面活性剤；ポリシロキサン・ポリオキシエチレングラフト共重合体のようなシリコーン系界面活性剤；第四級アンモニウム塩のようなカチオン系界面活性剤；アルキルベンゼンスルホン酸塩のようなアニオン系界面活性剤が例示され、１種を用いても、２種以上を併用してもよい。用いる界面活性剤のＨＬＢ値（２種以上を併用するときは、その重量平均ＨＬＢ値）が、５〜１４のものが好ましい。（Ｂ）として（Ｂ１）を用いる場合には、（Ｅ）成分は、（ii）成分の触媒活性を阻害しないものを選択しなければならない。これらのうち、ノニオン系またはシリコーン系の界面活性剤が好ましい。
【００６１】
（Ｅ）成分の配合量は、（Ａ）成分１００重量部に対して、１０重量部以下が好ましく、０．１〜５重量部がさらに好ましい。１０重量部を越えると、発泡体の機械的強度が低下する。
【００６２】
本発明のポリオルガノシロキサン発泡材に、本発明の目的を損なわないかぎり、必要に応じて、希釈剤として、（Ａ）成分や（ｉ）成分に該当しないポリオルガノシキサン、たとえば末端をトリオルガノシリル基やシラノール基で閉塞されたポリオルガノシロキサンを配合することができる。また、必要に応じて、煙霧質シリカ、沈殿シリカ、石英粉末、けいそう土、酸化アルミニウム、酸化亜鉛、酸化鉄、酸化セリウム、マイカ、クレイ、炭酸カルシウム、グラファイトの１種または２種以上の充填剤や顔料を配合することができる。これらの充填剤は、そのまま用いてもよく、疎水化などのために表面処理を行ってもよい。また、発泡体に導電性を付与するために、カーボンブラック、導電性金属酸化物、金属などの導電性充填剤を配合してもよい。さらに、カーボンブラック、二酸化チタン、炭酸亜鉛、炭酸マンガンのような難燃化剤；水酸化セリウムのような耐熱性向上剤など；また付加反応によって硬化させる系では、アセチレンアルコール類、たとえば３−メチル−１−ブチン−３−オール、１−エチニル−１−ヘキサノールのような付加反応の反応抑制剤を配合することができる。
【００６３】
本発明の発泡材は、あらかじめ（Ｄ）成分を吸収して膨潤した（Ｃ）成分を、（Ａ）成分、（Ｂ）として架橋機能に応じて選択された成分、および必要に応じて配合される他の成分を、発泡材の形状に応じて、混練機、ミキサー、ロールなどの混合手段を用いて混合することによって調製することができる。調製された発泡材の保存安定性によっては、（ｉ）成分またはそれを含む配合物を、（ii）成分またはそれを含む配合物と別途に保存して、型成形の直前に両者を混合してもよく、また（Ｂ２）成分またはそれを含む配合物を、（Ａ）成分またはそれを含む配合剤と別途に保存して、型成形の直前に両者を混合してもよい。混合温度は、（Ｄ）成分が揮発しない範囲であれば特に限定されないが、作業性などを考慮して、一般に０〜６０℃、好ましくは２０〜３０℃である。
【００６４】
本発明の発泡体は、本発明の発泡材を、型成形する工程を含む製造方法により、硬化および発泡させて製造される。型成形としては、射出成形、トランスファー成形、プレス成形など、発泡材の性状や目的物の形状に応じて、任意の方法を選択することができる。型成形の方法としては、量産が容易なことから、射出成形が好ましく、（Ａ）成分として液状の、好ましくは平均重合度が１００〜２，０００のポリオルガノシロキサンを用いる液体射出成形が特に好ましい。
【００６５】
型成形を、（１）成形条件における水の揮発温度以上で、かつ発泡材の硬化温度で行うことにより、成形と同時に硬化・発泡を行ってもよく、（２）型成形工程を、常温ないし若干の加温により、発泡材が固体になる程度の部分架橋ないし完全な硬化を行い、次に、加熱工程によって発泡させるとともに、成形の際に部分架橋にとどめた場合は、さらに架橋を進めて硬化を完成させてもよい。（１）の方法の場合の成形温度は、発泡材の架橋機構および（ii）成分または（Ｂ２）成分の種類と量に応じて、通常１５０〜２８０℃の範囲で任意に選択することができるが、好ましくは１５０〜２００℃である。（２）の方法の場合、型成形温度は、５０〜１８０℃が好ましく、加熱工程の加熱温度は、通常１００〜３５０℃の範囲で任意に設定できるが、好ましくは１２０〜３００℃であり、下記を除いてさらに好ましくは１８０〜２５０℃である。この場合、条件に応じて、型成形工程で発泡が行われることもあり、型成形では単に硬化反応が部分的にまたは完全に進行し、加熱工程ではじめて水の揮発による発泡が行われることもある。
【００６６】
なお、（Ｃ）成分として、前述のＮ−ビニルカルボン酸アミド系架橋ポリマーを用いるとき、加熱工程において２２０〜３５０℃、好ましくは２３０〜３００℃に加熱すると、圧縮永久ひずみの小さい発泡体が得られる。このことは、水の分散性をよくするための（Ｅ）成分として、ノニオン系界面活性剤のような、圧縮永久ひずみに影響を与える成分を配合した場合に、特に顕著な効果がある。
【００６７】
（２）のような２段法の利点は、成形条件と発泡条件を別途に設定することにより、より均質な発泡体が得られることである。
【００６８】
【実施例】
以下、実施例および比較例によって、本発明をさらに説明する。これらの例において、部はすべて重量部を表し、粘度は２５℃における粘度を表す。なお、本発明は、これらの実施例によって限定されるものではない。
【００６９】
本発明の実施例および比較例に、（Ａ）成分および（Ｂ）の（ｉ）成分として、下記のシロキサン単位および粘度を有する鎖状ポリシロキサンを用いた。以下の記載で、複数の中間シロキサン単位を有するものは、いずれもランダム共重合体であり、その構造式は、ブロック共重量体を表すものではなく、単にシロキサン単位の数を示したものである。
【００７０】
Ａ−１：両末端がジメチルビニル基で封鎖され、中間単位がジメチルシロキサン単位からなるポリジオルガノシロキサン、粘度１０Pa・s（平均重合度８５０、ビニル基含有量０．１４重量％）；
Ａ−２：両末端がジメチルビニル基で封鎖され、中間単位中、ジメチルシロキサン単位が９５モル％、ジフェニルシロキサン単位が５モル％のポリジオルガノシロキサン、粘度３Pa・s；
Ｂ−１：両末端がトリメチルシリル基で封鎖され、中間単位としてジメチルシロキサン単位とメチルハイドロジェンシロキサン単位を含み、ケイ素原子に結合した水素原子が０．８重量％であるポリメチルハイドロジェンシロキサン、粘度６０mm²/s；
Ｂ−２：両末端がトリメチルシリル基で封鎖され、中間単位がメチルハイドロジェンシロキサン単位からなるポリメチルハイドロジェンシロキサン、粘度２５mm²/s。
【００７１】
また、（ii）成分として、下記の白金化合物を用いた。
Ｐ−１：塩化白金酸と１，３−ジビニル−１，１，３，３−テトラメチルジシロキサンから得られた錯体。
【００７２】
（Ｃ）成分として、下記の吸水性ポリマーを用いた。
Ｃ−１：デンプン・アクリル酸グラフト共重合体の部分ナトリウム塩、中心粒子径２０〜５０μm、平均粒子径３５μm；
Ｃ−２：ポリアクリル酸の部分ナトリウム塩、平均粒子径４０μm；
Ｃ−３：Ｎ−ビニルアセトアミド系架橋ポリマー、平均粒子径３０μm。
【００７３】
（Ｅ）成分として、下記の界面活性剤を用いた。
Ｅ−１：ポリオキシエチレンラウリルエーテル（ＨＬＢ：９．６）；
Ｅ−２：下記の平均構造式を有するポリシロキサン・ポリオキシエチレンブロック共重合体（ＨＬＢ：７．０）。
【００７４】
【化９】

【００７５】
実施例および比較例によって得られた発泡体について、次の評価を行った。
（１）硬さ：硬化物の中央部および端から２cmの部分（以下、端部という）の硬さを、ＪＩＳ Ｋ ６２４９におけるタイプＥデュロメータによって測定した。
（２）発泡倍率および発泡の均一性：中央部および端部をそれぞれ切り取って、発泡倍率を測定した。表１に示す発泡倍率は、中央部の値である。また、中央部／端部の発泡倍率の比を求めた。
（３）セルの平均径：中央部のセルの平均径を、光学顕微鏡を用いて測定した。
【００７６】
実施例１〜４
ポリジオルガノシロキサンＡ−１の１００部に、比表面積が１９０m²／gの沈殿シリカ３０部を加え、ついで混練機で撹拌しながらヘキサメチルジシラザン３部と水１部を加えて、室温で１時間混合した後、減圧下に１５０℃で、さらに１時間の熱処理を行うことにより、沈殿シリカの表面の疎水化処理を行い、マスターバッチを得た。ついで、撹拌を続けながら、Ｂ−１の１、３部、１−エチニル−１−シクロヘキサノール０．５部および白金化合物Ｐ−１の０．６部を逐次添加して、付加反応によって硬化しうるシリコーンゴムベースを調製した。
【００７７】
一方、別の容器に水を取り、これにＣ−１を加えて混合し、Ｃ−１に水を吸収させて、ゲル状に膨潤したＣ−１を得た。なお、実施例２〜４においては、上記のように吸水したＣ−１を、さらに界面活性剤Ｅ−１またはＥ−２に浸漬して、Ｃ−１に界面活性剤を吸収させた。なお、これらの成分の量は、Ａ−１の１００部に対して表１に示された量になるような量である。このようにして吸水し、またはさらに界面活性剤を吸収したＣ−１を、前記のシリコーンゴムベースに添加して混合し、均一に分散させて、表１に示す配合比により、それぞれの発泡材を調製した。
【００７８】
このように調製した発泡材を、１３０mm×１３０mm、厚さ６mmの金型に注型し、密閉、加圧して、１２０℃で１０分加熱することによってプレス成形を行い、ゴム状弾性体を得た。型を開放して弾性体を取り出し、２００℃の乾燥器中で４時間加熱して、スポンジ状に硬化した発泡体を得た。
【００７９】
評価結果は、表１に示すとおりであり、中央部から端部に至るまで、均質で微細なセルからなる発泡体が得られた。
【００８０】
比較例１
実施例１で得られたのと同様のシリコーンゴムベースに、Ｃ−１を配合しないで、単に水１００部を添加して攪拌し、水を分散させることを試みたが、水は系に混和せず、発泡体を得ることはできなかった。
【００８１】
比較例２
実施例１で得られたのと同様のシリコーンゴムベースに、水１００部にＥ−１を２．５部加えて分散させた分散体を添加した以外は、比較例１と同様にして発泡材を調製した。この場合は、水は系に分散したので、以下、実施例１と同様の条件で成形および加熱を行って発泡体を得た。その評価結果は、表１に示すとおりであり、粗く、かつ不均一な発泡体しか得られなかった。
【００８２】
比較例３
Ａ−２の１００部に、ジメチルジクロロシランで表面処理を行った、比表面積が１２０m²/gの煙霧質シリカ１５部、およびＢ−２の２０部を加えて、均一になるまで混合した。ついで、撹拌を続けながら、ｎ−プロパノール２．５部、水２．５部およびＰ−１の０．３部を逐次添加して、発泡材を調製した。１３０mm×１３０mm、厚さ６mmのポリプロピレン製の成形型に、硬化して得られる発泡体が型内に隙間なく充満する量の発泡材を注型し、パーティング面を面圧が３０g/cm²で型締めして、室温において発泡と硬化を進行させて、発泡体を得た。これを、さらに２００℃で４時間加熱して硬化を完成させた。
【００８３】
硬化した発泡体について、評価を行った。評価結果は、表１に示すとおりであり、セルの細かさと均質性は、比較例２よりは優れているが、本発明による実施例１〜４の発泡体には及ばなかった。
【００８４】
実施例５
実施例１と同様にして得られたマスターバッチに、混練機によりtert−ブチルペルオキシイソプロピルカルボナート０．５部を添加して均一になるまで混合し、ラジカル反応によって硬化しうるシリコーンゴムベースを調製した。これに、実施例１と同様の、水７５部を吸収してゲル状に膨潤したＣ−１を０．５部添加して、均一に分散させて、発泡材を調製した。
【００８５】
このようにして調製した発泡材を用いて、型成形条件を１５０℃で１０分とした以外は実施例１と同様にして、硬化した発泡体を得た。発泡体の評価結果は、表１に示すとおりであり、中央部から端部に至るまで、均質で微細なセルからなる発泡体が得られた。
【００８６】
【表１】

【００８７】
（Ｃ）吸水性ポリマーとして、Ｃ−１の代わりにＣ−２またはＣ−３を用い、表２に示す配合比による以外は、実施例１と同様にして、発泡材を調製した。得られた発泡材を用いて、注型、硬化後の加熱を、実施例６および７ではそれぞれ２００℃と２５０℃、実施例８では２５０℃でそれそれ４時間行った以外は、実施例１と同様にして発泡体を作製し、評価を行った。圧縮永久ひずみの測定は、ＪＩＳ Ｋ６２４９に基づき、１８０℃で２２時間の圧縮加熱によって行った。結果は、表２に示すとおりであった。
【００８８】
【表２】

【００８９】
この結果、吸水性ポリマーとしてＣ−３を用いた実施例６および７で得られた発泡材から、２５０℃で加熱する工程を経ることにより、優れた圧縮永久ひずみ特性を有する発泡体が得られた。
【００９０】
【発明の効果】
本発明のポリオルガノシロキサン発泡材は、発泡の際に毒性の高い副生成物を発生する成分を含まず、しかも、これを用いて、内部から表面付近に至る均質で微細なセルを有するシリコーン発泡体を得ることができる。また、気化による発泡に用いる水は、気化熱が高いので、型成形による発泡の制御が容易である。さらに、発泡を成形後の加熱工程によって行うことも可能で、均質なセルを有する発泡体を容易に得ることができる。
【００９１】
このようにして得られた本発明の発泡体は、シリコーンの耐熱性、耐寒性、耐湿性、触感、安全性などの特徴を生かした、柔軟で高機能の断熱材、吸音材、防振剤、クッション、スポンジロール（たとえば、ＯＡ機器用の定着ロール、クリーニングロール、カーボンブラックを配合した導電性の帯電ロール、現像ロール、転写ロール、トナー供給ロール、静電クリーニングロールなど）、パッキン、ガスケット、パッド、気密シール材などの用途、とりわけ、使用中に高温にされされる用途の発泡体などに好適である。さらに、本発明のポリオルガノシロキサン発泡材およびそれを用いて製造された本発明の発泡体は、射出成形のような量産に適した成形方法に適合するので、柔軟性に富み、熱伝導率が低いことを利用した通常のスポンジロール、ならびにトナーの制御や帯電防止に有用な導電性スポンジロールの製造に、きわめて好適である。
【００９２】
吸水性ポリマーとして、Ｎ−ビニルカルボン酸アミド系架橋性ポリマーを用い、２２０℃以上の加熱工程を経て作製された発泡体は、上記の特徴に加えて優れた高温圧縮永久ひずみ特性を有するので、ＯＡ機器の定着ロールなど、高温で圧力がかかる用途に特に適している。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel polyorganosiloxane foam material, and more specifically, by molding and, at the same time or after molding, by foaming and curing by heating, it is uniform without causing high foaming pressure. The present invention relates to a polyorganosiloxane foam material in which a foam having an arbitrary shape having bubbles can be easily obtained; a foam obtained by molding from the foam material; and a method for producing the same.
[0002]
[Prior art]
Various types of polyorganosiloxane foams that cure to form foams are already known. These foaming mechanisms include the following.
[0003]
(1) A foaming agent is blended with a polyorganosiloxane composition that can be cured in a rubbery form, and a foam is obtained by thermal decomposition of the foaming agent, and a sheet-like or bulk-like foam is obtained. The foam is subjected to a processing step for obtaining a desired shape. High molecular weight polydiorganosiloxane is mainly used as the base polymer, and radical crosslinking reaction by organic peroxide is mainly used as the curing mechanism. As a foaming agent, there is a difficulty in that a toxic product such as azobisisobutyronitrile, which produces a toxic product by thermal decomposition, or one that can obtain only a non-uniform foamed state is used. The process is complicated.
[0004]
(2) A liquid polyorganosiloxane is used as a base polymer, a polyorganosiloxane composition having a curing mechanism accompanied by a dehydrogenation reaction is cured at the time of curing, and hydrogen gas generated at that time is taken into the system to produce a foam. And has many advantages such as a simple composition and no toxic decomposition products as in the case of using an organic blowing agent. Therefore, in addition to the heat resistance, cold resistance, and weather resistance inherent to polysiloxane, it is easy to handle, and is therefore widely used as a foam having rubber-like elasticity.
[0005]
Such a foam is used after being processed into various shapes, and as a processing method, a foam that has been primarily processed into a sheet shape or a bulk shape is subjected to a desired process through secondary processing such as cutting. A method of obtaining a shape; and a mold molding in which a material before curing is poured into a mold processed so as to obtain a desired shape and foam-cured in the mold is generally used.
[0006]
The method of obtaining a desired shape through secondary processing such as cutting a foam that has been primarily processed into a sheet or bulk is complicated because it involves two processes, and material loss occurs during secondary processing. Occurrence of the cost becomes a factor of cost increase. Furthermore, from the viewpoint of environmental conservation such as a method for treating waste generated during secondary processing, processing by molding is desirable.
[0007]
The following are known as foamable liquid polyorganosiloxane compositions.
[0008]
Japanese Patent Application Laid-Open No. 51-46352 discloses a foaming property of a mechanism in which a silanol group-containing polyorganosiloxane and a polyorganohydrogensiloxane are cured with a platinum-based catalyst, and a foam is formed by hydrogen gas generated at that time. A polyorganosiloxane composition is disclosed. Furthermore, proposals for improving this foaming mechanism have been made. That is, in JP-A-4-88034, as the above silanol group-containing polyorganosiloxane, (1) a linear polyorganosiloxane having hydroxyl groups bonded to silicon atoms at both ends, and (2) an intermediate silicon atom A foaming polyorganosiloxane composition using a linear polyorganosiloxane having a hydroxyl group only bonded thereto and (3) a branched polyorganosiloxane containing a silanol group is disclosed. A polyorganosiloxane composition using (1) and (2) in combination with an alcohol is disclosed.
[0009]
In Japanese Patent Laid-Open No. 54-135865, when a rubber-like elastic body is obtained by crosslinking by a reaction mechanism in which an alkenyl group-containing polyorganosiloxane and a polyorganohydrogensiloxane are hydrosilylated in the presence of a platinum-based catalyst. A foamable polyorganosiloxane composition is disclosed in which a foam is formed by hydrogen gas generated by the reaction of the polyorganohydrogensiloxane and water in the presence of water. JP-A-2-91131 discloses a foamable polyorganosiloxane composition using a mixture of water and alcohol in place of water, as an improvement of the foaming mechanism and the expansion ratio. JP-A-5-70692 discloses a foamable polyorganosiloxane composition in which a liquid alcohol is used in place of water and a fluorinated silicone foam stabilizer is blended.
[0010]
Japanese Laid-Open Patent Publication No. 57-180641 discloses a foamable polyorganosiloxane composition containing a silanol group-containing polyorganosiloxane, a polyorganohydrogensiloxane, and an aminoxy compound.
[0011]
In these foamable polyorganosiloxane compositions, since the foam retention of the composition itself is insufficient, it is necessary to accelerate the crosslinking reaction against the generation of hydrogen gas in order to improve the foaming ratio. In this final stage, the bubbles cannot be communicated, and the generated hydrogen gas remains in the system even after the crosslinking is completed. Therefore, when foamed and cured in the mold, a high foaming pressure is generated. In addition, since the cross-linking reaction is fast with respect to hydrogen gas generation and the viscosity change of the composition during foaming is large, the size and shape of the generated bubbles are likely to be uneven, and a foam having uniform bubbles can be obtained. Absent. Furthermore, when foaming and curing in a mold due to an increase in the viscosity of the composition in the middle of foaming, it tends to be insufficiently filled due to insufficient flowability, and in order to obtain a foam having a predetermined shape, an excessive amount of the composition is used. Since it is necessary to pour into the mold and a sufficient expansion ratio cannot be obtained, a flexible foam cannot be obtained. In addition, there are problems with the characteristics of the manufacturing apparatus, such as different flexibility depending on the location, and the application is restricted.
[0012]
JP-A-7-196632 and JP-A-8-337670 disclose an alkenyl group-containing polyorganosiloxane having at least one phenyl group bonded to a silicon atom and a polyorganohydrogensiloxane as a platinum catalyst. By the reaction mechanism of hydrosilylation in the presence of alcohol, alcohol is allowed to coexist when cross-linked to obtain a rubber-like elastic body, and hydrogen gas generated by the reaction of the polyorganohydrogensiloxane and alcohol is taken into the system and foamed. A foam-forming polyorganosiloxane composition for forming a body is disclosed.
[0013]
Although this foamable polyorganosiloxane composition has excellent foam-stabilizing properties and a flexible foam having a uniform and high foaming ratio can be obtained, it is a reaction accompanied by heat generation, so that the foam is formed by self-heating during foaming and curing. Resinization may occur. In addition, the foam tends to lose its flexibility when exposed to high temperatures for a long time, and its use is restricted.
[0014]
In order to solve these problems, JP-A-11-130963 discloses a system in which an alkenyl group-containing polyorganosiloxane is cured by an addition reaction with a polyorganohydrogensiloxane. In addition, a foamable polyorganosiloxane composition is disclosed in which a phenyl group bonded to a silicon atom is introduced, polyorganohydrogensiloxane is used in excess, and water and a monovalent or polyhydric alcohol are used. Since the composition is suitable for molding, it gives a foam having excellent processability and heat resistance. However, in order to generate hydrogen during foaming, safety considerations are necessary, and the vicinity of the surface In terms of the uniformity of cells including the above, further superior ones have been demanded.
[0015]
On the other hand, as a technique for combining a water-absorbing resin with a polyorganosiloxane, JP-A 61-236856 discloses hydrophilic or water-soluble organosilanes or organosiloxanes such as silicone rubber and siloxane / polyether copolymers, and A water-absorbing silicone rubber composition comprising a water-absorbing polymer is disclosed. Japanese Patent Application Laid-Open No. 62-89964 discloses a water-absorbing composition that provides a cured product exhibiting stable water absorption by blending an acrylic acid polymer with a liquid silicone rubber composition that cures in a rubbery state. . Japanese Patent Application Laid-Open No. 63-196630 discloses that a silicone rubber and a water-swellable resin are used in combination as a livestock cooling body. Japanese Patent Application Laid-Open No. 2-45566 discloses that an acrylic water-absorbing polymer is blended with an addition reaction curable silicone rubber to improve wettability when used as a dental impression material. Japanese Patent Application Laid-Open No. 2-64160 discloses that a water-absorbing polymer is blended with an aminoxy type silicone rubber to obtain a silicone rubber having high water swelling property. However, it is not disclosed that an uncured silicone rubber composition containing these water-absorbing polymers is used as a foaming material. In addition, International Publication WO 97/38048 and Japanese Patent Application Laid-Open No. 2000-95891 disclose that a hydrous polyolefin resin composition containing a non-crosslinked or crosslinked polyolefin resin and a hydrophilic polymer is pressurized and then placed in a low-pressure atmosphere. Disclosed is a method for producing a foam-molded product by releasing pre-expanded particles to heat and fusing them. However, this publication does not describe that this is applied to a polyorganosiloxane base polymer.
[0016]
Furthermore, when a foam obtained from this type of polyorganosiloxane foam material is used for applications such as a fixing roll of OA equipment, it has been required to have a low compression set at a high temperature.
[0017]
[Problems to be solved by the invention]
An object of the present invention is to provide a polyorgano that can be easily and safely formed into a foam having uniform cells, which is suitable for molding, particularly injection molding, without using a foaming agent that produces a toxic by-product. A siloxane foam material, particularly preferably a foam material that gives a foam having a low compression set at high temperature in addition to the above characteristics; and a foam obtained by molding from the composition, and a method for producing the same It is.
[0018]
[Means for Solving the Problems]
As a result of repeated investigations to achieve the above object, the present inventors have unexpectedly made polyorganosiloxane as a base polymer and cured by addition reaction or radical reaction to form a rubbery elastic body. It is found that the purpose can be achieved by adding a water-absorbing polymer that absorbs water to a compound to be molded, molding this, and optionally adding a step of further heating after molding. The invention has been completed. Furthermore, it has been found that a foam having a small compression set at a high temperature can be obtained by using a crosslinked polymer mainly composed of N-vinylcarboxylic acid amide repeating units as the water-absorbing polymer.
[0019]
That is, the polyorganosiloxane foam material of the present invention is
(A) General formula:
[0020]
[Formula 4]

[0021]
(Wherein R¹Represents an alkenyl group; R²May be the same or different and each represents a substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond; a represents an integer of 1 or 2, and b represents 0 100 parts by weight of an alkenyl group-containing polyorganosiloxane having at least two units represented by an integer of ˜2 and a + b is an integer of 1 to 3);
(B) A chemical substance for curing (A) selected from the following (B1), that is, a combination of (i) and (ii); or (B2):
(B1) (i) General formula:
[0022]
[Chemical formula 5]

[0023]
(Wherein R^ThreeMay be the same or different and each represents a substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond; c represents an integer of 0 to 2, and d represents 1 Or an integer of 2 and c + d is an integer of 1 to 3) polyorganohydrogensiloxane having at least 3 units in the molecule, silicon atom for 1 alkenyl group of component (A) The amount of hydrogen atoms bonded to is 0.5 to 5;
(Ii) platinum compound, catalyst amount;
(B2) Organic peroxide 0.1 to 10 parts by weight;
(C) water-absorbing polymer powder 0.001 to 20 parts by weight; and
(D) 0.5 to 500 parts by weight of water absorbed in (C)
It is characterized by including.
[0024]
The method for producing a foam of the present invention is a method for obtaining a foam by adding a step of further heating the polyorganosiloxane foamed material by molding, in some cases after molding. The foamed body is a foamed body mainly composed of a crosslinked polyorganosiloxane. In particular, a foam having excellent compression set characteristics can be obtained by high-temperature heating as described below using a crosslinked polymer mainly composed of vinylcarboxylic amide repeating units as the component (C).
[0025]
DETAILED DESCRIPTION OF THE INVENTION
The component (A) used in the present invention has a general formula:
[0026]
[Chemical 6]

[0027]
(Wherein R¹, R², A and b are alkenyl group-containing polyorganosiloxane having at least two units represented by The component (A) is a base polymer of the composition of the present invention, and an alkenyl group bonded to a silicon atom undergoes a hydrosilylation reaction (addition reaction) with a hydrogen atom bonded to a silicon atom in the component (i). Or (B2) is a component that is subjected to radical attack caused by thermal decomposition of the organic peroxide that is the component and performs crosslinking, and gives strength to the foam in cooperation with other components.
[0028]
As the component (A), there is no particular limitation on the molecular structure as long as it is a polyorganosiloxane having at least two units represented by the above formula (I) in the molecule, linear, cyclic, branched Those having a siloxane skeleton can be used, but they are either linear or linear and branched in terms of ease of synthesis and imparting excellent rubber elasticity and mechanical properties to the composition. The alkenyl group-containing polyorganosiloxane is preferably used in combination. The average degree of polymerization, that is, the average number of silicon atoms in the molecule is not particularly limited, but is usually in the range of 30 to 10,000. If the degree of polymerization is less than 30, the mechanical properties of the foam obtained by curing are not sufficient, and if it exceeds 10,000, handling in an uncured state becomes difficult. (A) Preferred average degree of polymerization of component and R in the organic group bonded to the silicon atom¹The ratio varies depending on the properties and applications of the target polyorganosiloxane foam material.
[0029]
In order to obtain a foam material that exhibits fluidity at room temperature and is compatible with molding methods suitable for mass production such as injection molding, the foam material exhibits an appropriate viscosity, and the foam obtained by curing has excellent mechanical properties. The component (A) to be used is preferably a liquid at room temperature having an average degree of polymerization of 50 to 2,000, more preferably an average degree of polymerization of 200 to 1,000 because of the necessity to have properties. In order to obtain a foam having particularly excellent mechanical properties, a linear liquid polydiorganosiloxane and a resinous material having a branched siloxane structure can be used in combination as the component (A). .
[0030]
Since the foamed material is solid and is molded after being masticated with a roll, it exhibits excellent mechanical strength. Therefore, the component (A) used preferably has an average degree of polymerization of 3,000 to 8,000. More preferably, the average degree of polymerization is 5,000 to 7,000. R¹Is preferably 0.02 to 5 mol%, more preferably 0.05 to 0.5 mol% in the total organic group bonded to the silicon atom, since the foam has good curability and heat resistance. Also, in order to give the foam an excellent tear strength, R in the molecule¹And a polyorganosiloxane having no R¹It is possible to use a polyorganosiloxane having an average of the above values by mixing.
[0031]
R¹Examples thereof include vinyl, allyl, butenyl and the like, and a vinyl group is preferable because of easy synthesis. R²Examples thereof include linear or branched alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl and dodecyl; cycloalkyl groups such as cyclohexyl; 2-phenylethyl, 2-phenylpropylene Examples include aralkyl groups such as ru; aryl groups such as phenyl; and substituted monovalent hydrocarbon groups such as chloromethyl, 3,3,3-trifluoropropyl and chlorophenyl, which are easy to synthesize and handle Therefore, a methyl group is preferable. a and b are as described above, and a is preferably 1 because synthesis is easy.
[0032]
Such a unit represented by the formula (I) may be present at either the molecular end or in the middle of the molecule, but at least in order to impart good mechanical properties to the foam obtained by curing. Some at the end of the molecule, eg R¹R² ₂SiO_1/2It is preferably present in the form of units.
[0033]
In the siloxane unit other than the unit represented by the formula (I) in the component (A), the organic group bonded to the silicon atom may be the same or different, and R²And monovalent substituted or unsubstituted hydrocarbon groups similar to those exemplified above. As the organic group bonded to the silicon atom of component (A), the aforementioned R¹Apart from that, since it is easy to synthesize and handle, it is preferable that 85 mol% or more is a methyl group, and it is more preferable that substantially all are methyl groups.
[0034]
In order to obtain a foam from the foam material of the present invention, the component (A) in the foam material is crosslinked by the action of (B). Crosslinking can be performed by the following reaction (1) or (2), but these and other reactions can be used in combination.
[0035]
(1) Addition reaction: (B1) is used as (B), that is, (i) component which is a crosslinking agent and (ii) component which is a reaction catalyst are used in combination, and (i) a hydrosilyl group in component, A) R in component¹A cross-linked product is formed by the addition reaction between and. As the component (A), a relatively low molecular weight liquid at room temperature may be used, or a higher molecular weight may be used, but a desired foam can be easily formed. For example, as described above, it is preferable to use one having an average degree of polymerization of 50 to 2,000.
[0036]
(2) Radical reaction: (B) component (B2) is used as (B), and the radical generated by thermal decomposition thereof causes (R) of component (A).¹And a crosslinked body is formed by a crosslinking reaction between organic groups bonded to silicon atoms of other molecules. The component (A) is preferably liquid at room temperature, as in the addition reaction.
[0037]
The component (i) used in the present invention has the general formula:
[0038]
[Chemical 7]

[0039]
(Wherein R^Three, C and d are polyorganohydrogensiloxane having at least three units represented by 1) in a molecule, and a hydrogen atom bonded to a silicon atom is an alkenyl group in component (A). It contributes as a crosslinking agent which performs hydrosilyl reaction with.
[0040]
As the component (i), the molecular structure is not particularly limited as long as it has at least three units having a hydrogen atom directly bonded to a silicon atom in one molecule. In addition, those having a branched siloxane skeleton can be used, but linear ones are preferred from the viewpoint of ease of synthesis, and in order to obtain a foam excellent in mechanical strength, at least component (i) As part, R^Three ₂HSiO_1/2Unit and SiO₂It is preferable to use polyorganohydrogensiloxane composed of units.
[0041]
R^ThreeAre substituted or unsubstituted monovalent hydrocarbon groups which may be the same or different and do not have an aliphatic unsaturated bond, such as methyl, ethyl, propyl, butyl, Linear or branched alkyl groups such as hexyl, octyl, decyl, dodecyl; cycloalkyl groups such as cyclohexyl; aryl groups such as phenyl; and chloromethyl, 3,3,3-trifluoropropyl, A substituted monovalent hydrocarbon group such as chlorophenyl is exemplified, and a methyl group is preferable because of ease of synthesis. c and d are each as described above, and d is preferably 1 because synthesis is easy.
[0042]
In the siloxane unit other than the unit represented by the formula (II) in the component (i), the organic group bonded to the silicon atom may be the same or different, and R^ThreeThe same thing is illustrated and it is preferable that it is a methyl group from the ease of a synthesis | combination.
[0043]
Component (i) is blended in such an amount that 0.5 to 5 hydrogen atoms are bonded to silicon atoms with respect to one alkenyl group in component (A). If this value is less than 0.5, there are few crosslinks and the mechanical strength becomes weak, and if it exceeds 5, the change in physical properties after curing increases.
[0044]
Component (ii) used in the present invention cures the foamed material of the present invention by an addition reaction between an alkenyl group in component (A) and a hydrogen atom bonded to a silicon atom in component (i). It is a catalyst used for. For this, platinum compounds such as chloroplatinic acid, complexes obtained from alcohol and chloroplatinic acid, platinum olefin complexes, platinum ketone complexes, and platinum vinylsiloxane complexes can be used. The component (ii) is used in a necessary amount as a catalyst, and this amount is usually 0.1 to 1,000 ppm in terms of platinum atoms with respect to the component (A), preferably The amount is 0.5 to 200 ppm. If it is less than 0.1 ppm, the catalyst concentration is low and curing is insufficient. Further, even if it exceeds 1,000 ppm, there is no further effect, and the component (ii) contains a noble metal and is generally expensive, which is economically undesirable.
[0045]
The component (B2) used in the present invention is an organic peroxide, which generates radicals by thermal decomposition, and the radicals are R in the component (A).¹It attacks organic groups such as and forms crosslinks by carbon chains.
[0046]
As component (B2), acyl peroxides such as benzoyl peroxide, p-chlorobenzoyl peroxide, and m-toluyl peroxide; di-tert-butyl peroxide, cumyl-tert-butyl peroxide, dicumyl peroxide, 2,5-dimethyl Alkyl peroxides such as 2,5-di-tert-butylperoxyhexane; tert-butylperoxybenzoate, tert-butylperoxy-3,5,5-trimethylhexanoate, tert-butylperoxyisopropylcarbonate Various organic peroxides such as peroxyesters such as 1,1-bis (tert-butylperoxy) -3,5,5-trimethylcyclohexane are used and give particularly low compression set To cumyl-tert- Chill peroxide, dicumyl peroxide and 2,5-dimethyl-2,5-di -tert- butyl peroxy hexane is preferred. These organic peroxides may be used alone or in combination of two or more.
[0047]
Component (B2) is added in an amount of 0.01 to 10 parts by weight per 100 parts by weight of component (A) because the crosslinking reaction is sufficiently performed and the heat resistance and physical properties of the foam are not impaired. The range is preferably 0.1 to 5 parts by weight.
[0048]
The component (C) used in the present invention is a water-absorbing polymer powder, and is blended in a swollen state by absorbing water, which is the component (D), to uniformly and finely disperse the water in the foaming material system. It is effective for. The component (C) is used to form homogeneous bubbles by releasing water at the molding temperature and / or at the heating temperature in the heating step after molding when molding the foamed material containing the component (C). It is a characteristic component of the invention. As the component (C), not only is it hydrophilic, but it becomes an aqueous solution with water or does not aggregate into a lump in the presence of water, but individual powders swell to form a fine gel. It is necessary to form.
[0049]
Such water-absorbing polymers used as the component (C) include polymers of (meth) acrylic acid and alkali metal salts thereof, copolymers and cross-linked products thereof, and starch / (meth) acrylic acid graft copolymers. Polymers and alkali metal salts thereof are exemplified, and good results are obtained. Therefore, polyacrylic acid and alkali metal salts thereof, crosslinked products thereof, and tempun / acrylic acid graft copolymers and alkali metal salts thereof are preferred. Particularly preferred are a crosslinked product of a partial sodium salt of polyacrylic acid, and a partial sodium salt of a starch / acrylic acid graft copolymer. In order to form a foam, after the foam material containing the component (C) is heated to 200 ° C., the crosslinked sodium salt of polyacrylic acid still maintains the water absorption ability and is a water-absorbent foam. On the other hand, the partial sodium salt of the starch / acrylic acid graft copolymer loses the water absorbing ability, and a non-water absorbing foam is obtained. Therefore, it is preferable to select and use these depending on the use of the foam.
[0050]
Examples of the polymer further exemplified as the component (C) used in the present invention are represented by the general formula:
[0051]
[Chemical 8]

[0052]
(Wherein R^FourAnd R^FiveIs a cross-linked polymer mainly composed of N-vinylcarboxylic acid amide repeating units each independently represented by a hydrogen atom or a methyl group. Here, “being mainly” means that 50% or more, preferably 70% or more of the repeating units in the polymer, more preferably substantially 100% other than the crosslinkable units are composed of such units. . Examples of such repeating units include N-vinylformamide units, N-vinylacetamide units, N-vinyl-N-methylformamide units and N-vinyl-N-methylacetamide units, with N-vinylacetamide units being particularly preferred. preferable.
[0053]
The cross-linked polymer is a cross-link having a monomer constituting the above repeating unit by polymerization and a polymerizable carbon-carbon double bond such as at least two vinyl groups, allyl groups, and (meth) acryl groups in the molecule. It can be obtained by copolymerizing a functional monomer. Examples of such crosslinkable monomers include N, N'-methylenebisacrylamide, N, N'-1,4-butylenebis (N-vinylacetamide), N, N'-1,10-decylenebis (N-vinylacetamide). ), N, N′-3-oxa-1,5-pentylenebis (N-vinylacetamide), divinyl adipate, diallyl adipate, tetraallyloxyethane, pentaerythritol tetraallyl ether, triallyl isocyanurate, ethylene glycol Examples include di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and the like.
[0054]
Various repeating units can be used as the repeating unit other than the N-vinylcarboxylic acid amide unit and the unit derived from the crosslinkable monomer in the polymer. As such units, (meth) acrylic acid units, (meth) acrylic acid alkali metal salt units, (meth) acrylic acid alkyl ester units, (meth) acrylic acid hydroxy ester units, (meth) acrylamide units, alkyl vinyl ether units , Maleic acid units and units derived therefrom, but are not limited thereto.
[0055]
The crosslinkable monomer is usually used in an amount of 0.0001 to 10 mol%, preferably 0.0005 to 2 mol%, based on the whole monomer, in order to control the crosslink density so that the crosslinked polymer has an appropriate water swellability. It is done. The polymerization can be carried out by a method such as aqueous solution polymerization, suspension polymerization or emulsion polymerization in the presence of a radical generator such as an organic peroxide. The thus obtained crosslinkable polymer powder having a main chain polymerization degree of usually 100 to 500,000, preferably 5,000 to 100,000, can be used as the component (C) of the present invention. .
[0056]
By using such an N-vinylcarboxylic acid amide-based crosslinked polymer as the component (C), the polyorganosiloxane foam obtained through a heating step at a high temperature has excellent compression set characteristics as described later. Have.
[0057]
As the component (C), a powdery one is used, and the smaller the average particle diameter, the finer the cell foam. Since particles having a uniform particle size can be obtained relatively easily, handling is easy, and a fine cell foam is obtained. The average particle size in a dry state is usually 0.1 to 500 μm depending on the purpose. It is preferably selected from those having a thickness of 1 to 100 μm, more preferably 2 to 60 μm.
[0058]
(C) The compounding quantity of component is 0.001-20 weight part with respect to 100 weight part of (A) component, Preferably it is 0.05-5 weight part. If it is less than 0.001 part by weight, the amount of water absorption is small, and when a necessary amount of water is blended, the water separates and a good foam cannot be obtained. On the other hand, the effect is not changed even if it exceeds 20 parts by weight.
[0059]
Component (D) is water and is blended in the form absorbed by component (C). The component (D) is uniformly dispersed in the foamed material in a form absorbed by the component (C) by, for example, immersing the component (C) in the component (D), and volatilized by heating after molding or molding. Thus, it is blended in order to leave a homogeneously dispersed homogeneous cell, and is not for generating hydrogen by reaction with the hydrosilyl group of component (ii). The higher the blending amount of the component (D), the higher the foaming ratio can be obtained, but it is selected from the range of 0.5 to 500 parts by weight with respect to 100 parts by weight of the component (A), and the balance between the foaming ratio and the mechanical strength. From 10 to 300 parts by weight is preferable. If the amount is less than 0.5 part by weight, a foam cannot be obtained. If the amount exceeds 500 parts by weight, the mechanical strength of the foam is greatly reduced.
[0060]
In particular, when the component (C) is used by absorbing a large amount of the component (D), that is, water, the water absorption state of the component (C) is kept stable, and the water absorption of the component (C) is introduced into the system. In order to assist dispersion, it is preferable to add a surfactant as the component (E). The component (E) is dissolved and / or dispersed in the water to be used and the component (C) is immersed, and / or the component (C) is absorbed by water and then absorbed by the component (C). It is preferable to do. In order to absorb the component (E) in the component (C), for example, the component (C) that is liquid at room temperature or the component (E) that is solid at room temperature that is heated to be liquid. It can be performed by dipping in. As component (E), glycerin fatty acid ester, polyglycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene / polyoxypropylene Nonionic surfactants such as block copolymers, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid amides; silicone surfactants such as polysiloxane / polyoxyethylene graft copolymers A cationic surfactant such as a quaternary ammonium salt; an anionic surfactant such as an alkylbenzene sulfonate; It may be used in combination of two or more. It is preferable that the surfactant used has an HLB value (when using two or more kinds in combination, the weight average HLB value) of 5 to 14. When (B1) is used as (B), the component (E) must be selected so as not to inhibit the catalytic activity of the component (ii). Of these, nonionic or silicone surfactants are preferred.
[0061]
The amount of component (E) is preferably 10 parts by weight or less, more preferably 0.1 to 5 parts by weight, relative to 100 parts by weight of component (A). When it exceeds 10 parts by weight, the mechanical strength of the foam is lowered.
[0062]
In the polyorganosiloxane foam material of the present invention, as long as the purpose of the present invention is not impaired, a polyorganosiloxane that does not correspond to the component (A) or (i), for example, a triorgano end, is used as a diluent. A polyorganosiloxane blocked with a silyl group or silanol group can be blended. In addition, one or more types of fumed silica, precipitated silica, quartz powder, diatomaceous earth, aluminum oxide, zinc oxide, iron oxide, cerium oxide, mica, clay, calcium carbonate, and graphite are filled as necessary. Agents and pigments can be blended. These fillers may be used as they are or may be subjected to a surface treatment for hydrophobization. In order to impart conductivity to the foam, a conductive filler such as carbon black, conductive metal oxide, or metal may be blended. In addition, flame retardants such as carbon black, titanium dioxide, zinc carbonate, manganese carbonate; heat resistance improvers such as cerium hydroxide; and acetylene alcohols such as 3-methyl in systems cured by addition reaction Reaction inhibitors for addition reaction such as -1-butyn-3-ol and 1-ethynyl-1-hexanol can be blended.
[0063]
In the foam material of the present invention, the component (C) swollen by absorbing the component (D) in advance is blended as the component (A), the component selected according to the crosslinking function as (B), and if necessary. Depending on the shape of the foamed material, other components can be prepared by mixing using a mixing means such as a kneader, a mixer, or a roll. Depending on the storage stability of the prepared foamed material, component (i) or a compound containing the component (i) may be stored separately from component (ii) or a compound comprising the component, and both may be mixed immediately before molding. Alternatively, the component (B2) or a formulation containing the component (B2) may be stored separately from the component (A) or a formulation containing the component, and both may be mixed immediately before molding. The mixing temperature is not particularly limited as long as the component (D) does not volatilize, but is generally 0 to 60 ° C., preferably 20 to 30 ° C. in consideration of workability and the like.
[0064]
The foam of the present invention is produced by curing and foaming the foam material of the present invention by a production method including a step of molding. As the mold forming, any method such as injection molding, transfer molding, press molding or the like can be selected according to the properties of the foamed material and the shape of the object. As a mold forming method, injection molding is preferable because mass production is easy, and liquid injection molding using a liquid (preferably polyorganosiloxane having an average degree of polymerization of 100 to 2,000) as component (A) is particularly preferable. .
[0065]
The molding may be performed at the same time as molding by performing (1) above the volatilization temperature of water under molding conditions and at the curing temperature of the foaming material. Perform partial crosslinking or complete curing to the extent that the foam becomes solid with slight heating, then foam it by a heating process, and if it is only partially crosslinked at the time of molding, proceed with further crosslinking Curing may be completed. The molding temperature in the case of the method (1) can be arbitrarily selected in the range of usually 150 to 280 ° C. according to the crosslinking mechanism of the foam material and the type and amount of the component (ii) or the component (B2). However, it is preferably 150 to 200 ° C. In the case of the method (2), the mold molding temperature is preferably 50 to 180 ° C., and the heating temperature in the heating step can be arbitrarily set in the range of usually 100 to 350 ° C., preferably 120 to 300 ° C., More preferably, it is 180-250 degreeC except the following. In this case, depending on the conditions, foaming may be performed in the molding process. In the molding process, the curing reaction may be partially or completely advanced, and foaming may be performed by volatilization of water for the first time in the heating process. is there.
[0066]
In addition, when using the above-mentioned N-vinylcarboxylic acid amide type | system | group crosslinked polymer as (C) component, when it heats at 220-350 degreeC in a heating process, Preferably it is 230-300 degreeC, A foam with a small compression set is obtained. It is done. This is particularly effective when a component that affects compression set, such as a nonionic surfactant, is blended as the component (E) for improving water dispersibility.
[0067]
The advantage of the two-stage method as in (2) is that a more uniform foam can be obtained by separately setting the molding conditions and the foaming conditions.
[0068]
【Example】
Hereinafter, the present invention will be further described by examples and comparative examples. In these examples, all parts represent parts by weight, and the viscosity represents the viscosity at 25 ° C. In addition, this invention is not limited by these Examples.
[0069]
In Examples and Comparative Examples of the present invention, the following polysiloxanes having the following siloxane units and viscosities were used as the component (A) and the component (i) of (B). In the following description, those having a plurality of intermediate siloxane units are all random copolymers, and the structural formula does not represent a block copolymer but simply indicates the number of siloxane units. .
[0070]
A-1: Polydiorganosiloxane having both ends blocked with dimethylvinyl groups and intermediate units composed of dimethylsiloxane units, viscosity 10 Pa · s (average polymerization degree 850, vinyl group content 0.14% by weight);
A-2: a polydiorganosiloxane having both ends blocked with dimethylvinyl groups, 95 mol% of dimethylsiloxane units and 5 mol% of diphenylsiloxane units in the intermediate unit, viscosity of 3 Pa · s;
B-1: Polymethylhydrogensiloxane having both ends blocked with trimethylsilyl groups, containing dimethylsiloxane units and methylhydrogensiloxane units as intermediate units, and 0.8% by weight of hydrogen atoms bonded to silicon atoms, viscosity 60mm²/ s;
B-2: Polymethylhydrogensiloxane having both ends blocked with trimethylsilyl groups and intermediate units consisting of methylhydrogensiloxane units, viscosity 25 mm²/ s.
[0071]
Moreover, the following platinum compound was used as (ii) component.
P-1: A complex obtained from chloroplatinic acid and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane.
[0072]
As the component (C), the following water-absorbing polymer was used.
C-1: Partial sodium salt of starch / acrylic acid graft copolymer, center particle size of 20 to 50 μm, average particle size of 35 μm;
C-2: partial sodium salt of polyacrylic acid, average particle size of 40 μm;
C-3: N-vinylacetamide-based crosslinked polymer, average particle size of 30 μm.
[0073]
The following surfactant was used as (E) component.
E-1: polyoxyethylene lauryl ether (HLB: 9.6);
E-2: Polysiloxane / polyoxyethylene block copolymer having the following average structural formula (HLB: 7.0).
[0074]
[Chemical 9]

[0075]
The following evaluation was performed about the foam obtained by the Example and the comparative example.
(1) Hardness: The hardness of a portion 2 cm from the center and end of the cured product (hereinafter referred to as end) was measured with a type E durometer in JIS K 6249.
(2) Foaming ratio and foaming uniformity: The center part and the end part were cut off, and the foaming ratio was measured. The expansion ratio shown in Table 1 is the value at the center. Further, the ratio of the foaming ratio at the center / end was determined.
(3) Average cell diameter: The average cell diameter at the center was measured using an optical microscope.
[0076]
Examples 1-4
The specific surface area is 190 m on 100 parts of polydiorganosiloxane A-1.²/ G of precipitated silica (30 parts), and then stirring with a kneader, 3 parts of hexamethyldisilazane and 1 part of water were added and mixed for 1 hour at room temperature, then at 150 ° C. under reduced pressure for another hour. By performing the heat treatment, the surface of the precipitated silica was hydrophobized to obtain a master batch. Then, while continuing stirring, 1,3 parts of B-1, 0.5 part of 1-ethynyl-1-cyclohexanol and 0.6 part of platinum compound P-1 were sequentially added and cured by addition reaction. A rubbing silicone rubber base was prepared.
[0077]
On the other hand, water was taken into another container, C-1 was added thereto and mixed, and C-1 was allowed to absorb water to obtain C-1 swollen in a gel form. In Examples 2 to 4, C-1 absorbed as described above was further immersed in surfactant E-1 or E-2 to allow C-1 to absorb the surfactant. In addition, the quantity of these components is an quantity which becomes the quantity shown in Table 1 with respect to 100 parts of A-1. C-1 that has absorbed water or further absorbed the surfactant in this way is added to the silicone rubber base, mixed, and uniformly dispersed, and each foaming material is mixed according to the blending ratio shown in Table 1. Was prepared.
[0078]
The foamed material thus prepared is poured into a mold having a size of 130 mm × 130 mm and a thickness of 6 mm, sealed, pressurized, and heated at 120 ° C. for 10 minutes to obtain a rubber-like elastic body. It was. The mold was opened and the elastic body was taken out and heated in a dryer at 200 ° C. for 4 hours to obtain a foam cured in a sponge shape.
[0079]
The evaluation results are as shown in Table 1, and a foamed body composed of homogeneous and fine cells was obtained from the center to the end.
[0080]
Comparative Example 1
In the same silicone rubber base as obtained in Example 1, 100 parts of water was simply added and stirred without mixing C-1, and water was dispersed, but water was mixed into the system. The foam could not be obtained.
[0081]
Comparative Example 2
A foam material in the same manner as in Comparative Example 1, except that a dispersion obtained by adding 2.5 parts of E-1 to 100 parts of water was added to the same silicone rubber base as obtained in Example 1. Was prepared. In this case, since water was dispersed in the system, foaming was obtained by molding and heating under the same conditions as in Example 1 below. The evaluation results are as shown in Table 1, and only a rough and non-uniform foam was obtained.
[0082]
Comparative Example 3
100 parts of A-2 were surface treated with dimethyldichlorosilane and the specific surface area was 120 m²15 parts of / g fumed silica and 20 parts of B-2 were added and mixed until uniform. Subsequently, 2.5 parts of n-propanol, 2.5 parts of water and 0.3 part of P-1 were successively added while stirring was continued to prepare a foam material. A polypropylene mold with a size of 130 mm x 130 mm and a thickness of 6 mm is poured into the mold so that the foam obtained by curing fills the mold without any gaps. The surface pressure of the parting surface is 30 g / cm.²The mold was clamped and foaming and curing proceeded at room temperature to obtain a foam. This was further heated at 200 ° C. for 4 hours to complete the curing.
[0083]
The cured foam was evaluated. The evaluation results are as shown in Table 1, and the fineness and homogeneity of the cells are superior to those of Comparative Example 2, but did not reach the foams of Examples 1 to 4 according to the present invention.
[0084]
Example 5
To the master batch obtained in the same manner as in Example 1, 0.5 part of tert-butylperoxyisopropyl carbonate was added with a kneader and mixed until uniform, thereby preparing a silicone rubber base that could be cured by radical reaction. did. To this, 0.5 part of C-1 which was absorbed in 75 parts of water and swollen in a gel-like state was added and dispersed uniformly to prepare a foam material.
[0085]
Using the foamed material thus prepared, a cured foam was obtained in the same manner as in Example 1 except that the molding conditions were changed to 150 ° C. for 10 minutes. The evaluation results of the foam were as shown in Table 1, and a foam composed of homogeneous and fine cells was obtained from the center to the end.
[0086]
[Table 1]

[0087]
(C) A foam material was prepared in the same manner as in Example 1 except that C-2 or C-3 was used instead of C-1 and the blending ratio shown in Table 2 was used as the water-absorbing polymer. Example 1 with the exception that the resulting foamed material was cast and heated after curing at 200 ° C. and 250 ° C. in Examples 6 and 7, respectively, and 250 ° C. in Example 8 for 4 hours each. In the same manner, a foam was produced and evaluated. The compression set was measured by compressive heating at 180 ° C. for 22 hours based on JIS K6249. The results were as shown in Table 2.
[0088]
[Table 2]

[0089]
As a result, a foam having excellent compression set characteristics can be obtained from the foamed material obtained in Examples 6 and 7 using C-3 as the water-absorbing polymer, through a process of heating at 250 ° C. It was.
[0090]
【The invention's effect】
The polyorganosiloxane foam material of the present invention does not contain a component that generates a highly toxic by-product during foaming, and also uses this to produce a silicone foam having homogeneous and fine cells extending from the inside to the vicinity of the surface. You can get a body. Further, since water used for foaming by vaporization has a high heat of vaporization, it is easy to control foaming by molding. Furthermore, foaming can be performed by a heating step after molding, and a foam having homogeneous cells can be easily obtained.
[0091]
The foam of the present invention thus obtained is a flexible and highly functional heat insulating material, sound absorbing material, vibration isolator that takes advantage of the heat resistance, cold resistance, moisture resistance, tactile sensation, safety, etc. of silicone. , Cushion, sponge roll (for example, fixing roll for OA equipment, cleaning roll, conductive charging roll containing carbon black, developing roll, transfer roll, toner supply roll, electrostatic cleaning roll, etc.), packing, gasket, It is suitable for applications such as pads and hermetic seal materials, especially for foams that are heated to high temperatures during use. Furthermore, the polyorganosiloxane foam material of the present invention and the foam material of the present invention produced using the same are compatible with a molding method suitable for mass production such as injection molding, and thus have high flexibility and thermal conductivity. The present invention is extremely suitable for the production of ordinary sponge rolls utilizing the low property and conductive sponge rolls useful for toner control and antistatic.
[0092]
As the water-absorbing polymer, an N-vinylcarboxylic acid amide-based crosslinkable polymer and a foam produced through a heating step of 220 ° C. or higher have excellent high temperature compression set characteristics in addition to the above characteristics. It is particularly suitable for applications where pressure is applied at high temperatures, such as fixing rolls for office automation equipment.

Claims (12)

(A) General formula:

Wherein R ¹ represents an alkenyl group; R ² may be the same or different and each represents a substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond; a represents an integer of 1 or 2, b represents an integer of 0 to 2, and a + b is an integer of 1 to 3). 100 parts by weight of organosiloxane;
(B) A chemical substance for curing (A), selected from the following (B1), ie, a combination of (i) and (ii); or (B2):
(B1) (i) General formula:

Wherein R ³ may be the same or different and each represents a substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond; c represents an integer of 0 to 2 And d represents an integer of 1 or 2, and c + d is an integer of 1 to 3). The amount of hydrogen atoms bonded to silicon atoms to 0.5 to 5 per one;
(Ii) platinum compound, catalyst amount;
(B2) Organic peroxide 0.1 to 10 parts by weight;
(C) Water-absorbing polymer powder 0.001-20 parts by weight; and (D) 0.5 to 500 parts by weight of water absorbed in (C). The foamed material according to claim 1, wherein the average degree of polymerization of (A) is from 50 to 2,000. The foam material of Claim 1 or 2 whose average particle diameter of (C) is 1-500 micrometers. (C) is a general formula:

(Wherein R ⁴ and R ⁵ independently represent a hydrogen atom or a methyl group)
The foaming material according to any one of claims 1 to 3, which is a crosslinked polymer mainly composed of an N-vinylcarboxylic acid amide repeating unit represented by formula (1). The foaming material according to claim 4, wherein (C) is a crosslinked polymer containing N-vinylacetamide repeating units and crosslinking units. Furthermore, the foaming material of any one of Claims 1-5 containing 10 weight part or less of (E) surfactant. The manufacturing method of a foam including the process of mold-molding the foaming material of any one of Claims 1-6. The manufacturing method of the foam of Claim 7 which adds the process heated after mold forming. The production method according to claim 8, wherein the crosslinked polymer according to claim 4 is used as (C) and the heating temperature is 220 to 350 ° C. The manufacturing method according to any one of claims 7 to 9 , wherein the molding is injection molding. The foam obtained by the manufacturing method of any one of Claims 7-10 . The foam according to claim 11, which is a sponge roll.