JP3647637B2 - Manufacturing method of resin composition for molding - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、成形用樹脂組成物の製造方法に関し、より詳細には白化、泡、くぼみ等がなく、外観の美麗性に優れたアクリル系人工大理石を提供することができるプレス成形などに好適な成形用樹脂組成物の製造方法に関する。
【０００２】
【従来の技術】
アクリル樹脂に無機充填材を充填したアクリル系人工大理石は、美しい外観と優れた特性を活かして、キッチン天板や各種カウンタートップ、洗面化粧台、シャワートレー、床材、壁材、間仕切板などに広く利用されている。
アクリル系人工大理石の製造方法としては、例えば特公昭５０−２２５８６号公報において提案されているような注型成形法が知られている。一般に注型成形法は、メタクリル酸エステル類を１０〜３０％程度予備重合するか、あるいはメタクリル酸エステル類にメタクリル酸エステル系重合体を溶解した、いわゆるシラップに無機充填材を配合して混合し、その混合物を成形型内の間隙に注入した後、該混合物を常圧下で硬化させて人工大理石製品を得る方法である。しかし、この注型成形法は、硬化時間に長時間を要し生産性が低い上に、モノマー成分が多くモノマー臭気がしたり、注入時等シラップに起因するベタツキ性による取り扱いが不便で汚れが発生しやすいなど良好な作業環境の保全が困難であるといった問題点をもっている。
【０００３】
このような問題点を回避するための方法としてプレス成形法が検討されている。プレス成形法においては、成形材料に形状安定性があることが必要であり、注型成形法において用いられているものと同様の低濃度樹脂シラップに、無機充填材、さらに芳香族ビニル化合物、イソシアネート化合物（特開平５−１２４８４４号公報）、あるいは架橋重合体微粉末（特開平６−３１３０１９号公報）のような増粘剤を添加し組成物に形状安定性を付与する方法が知られている。また、必須成分である多官能（メタ）アクリレートを２０重量％以上含有する単量体、メタクリル系樹脂粉末、硬化剤、無機充填材などを常温又は硬化温度未満の加温下に混練・熟成して得られる成形材料を加圧下に加熱して成形・硬化する方法が提案されている（特公平５−１３８９９号公報）。しかしながら、アクリル系人工大理石用のこれら形状安定性を持つ樹脂組成物は高粘度であり、そのためプレス成形中に樹脂組成物中に残留する空気が十分に脱気できず、成形品表面に白化、泡、くぼみ等が発生し外観が不良となる場合があるなどの問題がある。これらの欠点は、特に美麗性が要求される人工大理石用途においては、商品としての価値を著しく低下させてしまうため、改善が強く望まれている。
【０００４】
【発明が解決しようとする課題】
したがって、本発明の目的は、上記残留空気による問題点を解決した、プレス成形法などに好適なアクリル系人工大理石用等の樹脂組成物の製造方法を提供することにある。
【０００５】
【課題を解決するための手段】
上記目的は、本発明によれば、メタクリル酸エステルを主体とする単量体、メタクリル酸エステル系樹脂、無機充填材、および硬化剤よりなる粘土状の樹脂組成物を、吐出口に減圧室が連結された押出機に供給し、減圧室の入り口部に配置された１個以上の穴を有する目皿を介して減圧下に調整された減圧室に押し出して５５０ｔｏｒｒ以下の減圧下で脱気する成形用樹脂組成物の製造方法によって達成される。
【０００６】
【発明の実施の形態】
以下、本発明を詳細に説明する。
本発明で用いるメタクリル酸エステルを主体とする単量体とは、メタクリル酸エステル単独、またはメタクリル酸エステルを主体としこれと共重合可能な他の不飽和単量体との単量体混合物をいい、メタクリル酸エステルが５０重量％以上であるのが好ましく、メタクリル酸エステルが７０重量％以上であるのがより好ましい。
【０００７】
メタクリル酸エステルとしては、炭素数５〜１８程度のメタクリル酸エステルが好ましく用いられ、具体的には例えばメタクリル酸メチル、メタクリル酸エチル、メタクリル酸プロピル、メタクリル酸ブチル、メタクリル酸２−エチルヘキシル、メタクリル酸シクロヘキシル、メタクリル酸ラウリルなどが挙げられる。これらは１種または２種以上で用いられるが、これらの中でメタクリル酸メチルが特に好ましく用いられる。
【０００８】
また、上記メタクリル酸エステルと共重合可能な他の不飽和単量体としては、特に制限はないが、例えばアクリル酸メチル、アクリル酸エチル、アクリル酸ブチル、アクリル酸２−エチルヘキシル、アクリル酸シクロヘキシル、アクリル酸ラウリルなどのアクリル酸エステル；スチレン、α−メチルスチレンなどの芳香族ビニル化合物；アクリロニトリル、メタクリロニトリル、アクリルアミド、酢酸ビニル、塩化ビニル、アクリル酸、メタクリル酸等の不飽和単量体；エチレングリコールジメタクリレート、１，３−ブチレングリコールジメタクリレート、ネオペンチルグリコールジメタクリレート、トリメチロールプロパントリメタクリレート等の多官能性不飽和単量体などが挙げられる。これらの単量体は１種または２種以上で用いられる。
【０００９】
本発明に用いるメタクリル酸エステル系重合体としては、上述したメタクリル酸エステルを主体とする単量体に溶解するメタクリル酸エステル系重合体であれば特に限定することなく使用できるが、例えば上記メタクリル酸エステルを主体とする単量体を重合して得られたもの、あるいはこれら単量体中の１種以上とその他の重合性単量体を重合して得られたものなどを好ましく挙げることができる。メタクリル酸エステル系重合体の重量平均分子量は、単量体に溶解できるものが使用され、通常５〜６０万、好ましくは７〜３０万、より好ましくは１０〜２０万の範囲である。また、メタクリル酸エステル系重合体の配合割合は、メタクリル酸エステルを主体とする単量体１００重量部に対して、通常１０〜４００重量部、好ましくは１５〜３００重量部である。
また、メタクリル酸エステル系重合体の一部を例えば、特開昭６０−２０２１２８号公報にその製造方法が記載されているアクリル系部分架橋ゲル状重合体に代えて使用することもできる。
【００１０】
本発明に用いる無機充填材としては、例えば水酸化アルミニウム、水酸化マグネシウム、アルミナ、酸化マグネシウム、炭酸カルシウム、シリカ、マイカ、ガラスビーズ等が挙げられるが、その添加により成形品の美観を損なうものでなければ特に制限はされない。これらの無機充填材のなかで、アクリル系人工大理石に必要とされる高級感、耐汚染性能、加工性能などの点から、水酸化アルミニウム、水酸化マグネシウム、シリカ、ガラスビーズが好ましく、とりわけ水酸化アルミニウムが好ましく用いられる。無機充填材の粒子径は通常０．１〜１００μｍであり、より好ましくは１〜３０μｍである。シラン処理など表面処理した無機充填材も好ましく使用される。無機充填材の配合割合は、メタクリル酸エステルを主体とする単量体１００重量部に対して、通常５０〜５００重量部、好ましくは１００〜４００重量部である。
【００１１】
本発明に用いる硬化剤には特に制限はなく、通常のラジカル重合に用いられるベンゾイルパーオキサイド、ラウロイルパーオキサイド、クメンハイドロパーオキサイド、ビス（４−ｔ−ブチルシクロヘキシル）ジカーボネート、１，１−ジ−ｔ−ブチルパーオキシ−３，３，５ートリメチルシクロヘキサン等の有機過酸化物；アゾビスイソブチロニトリル、２，２−アゾビス（２，４−ジメチルバレロニトリル）等のアゾ化合物等が用いられる。これらの硬化剤は１種または２種以上で用いられる。硬化剤の配合割合は、メタクリル酸エステルを主体とする単量体１００重量部に対して、通常１〜１０重量部、好ましくは３〜７重量部である。
【００１２】
また本発明の方法においては、本発明において得られる成形物の靱性や強度の向上あるいはクラックの発生・進行の抑制などの補強効果の発現を目的として、混練時または混合時などに補強単繊維を添加することができる。選択される繊維としては、アスベストやガラス繊維等の無機繊維、アラミド繊維やビニロン繊維などを含む各種有機繊維、カーボン繊維、金属ウィスカーなどである。使用される補強単繊維の形状および添加量は所望される成形品の特徴によりその組合わせが変化するため、これらを厳密に規定することはできないが、例えば、靱性向上やクラック発生の抑制を目的としてビニロン繊維の収束タイプのチョップドストランドを使用する場合には、繊維形状としては、繊維径５〜３００μｍ、繊維長３〜５０ｍｍの範囲にあることが好ましく、また添加量としては、本発明において使用されるメタクリル酸エステルを主体とする単量体１００重量部に対して、５〜２００重量部の範囲にあることが望ましい。添加量が５重量部未満では補強効果を発現させることが困難であり、また添加量が２００重量部を越えると通常の装置による混練が甚だしく困難となる。
【００１３】
また、本発明において、さらに低収縮性や加工特性の向上、意匠性の付与を目的としてメタクリル系部分架橋ゲル状重合体を添加することができる。この目的のため好ましく用いることができるメタクリル系部分架橋ゲル状重合体は、例えば特開昭６０−２０２１２８号公報、特開昭６２−１７０５号公報等に記載されているような、（ａ）アルキルメタクリレ−ト単独、アルキルメタクリレ−トを主成分とするα，β−エチレン性不飽和単量体との単量体混合物およびそれらの重合体を含有するシラップからなる群から選ばれた樹脂原料、および（ｂ）該樹脂原料１００重量部当たり２〜２５０重量部の架橋剤よりなる混合物を部分的に重合させて全重合体含有率が９０重量％を超えない範囲で重合体の含有率を前記混合物中の全重合体含有率よりも４〜７５重量％増加させた部分架橋ゲル状重合体である。アルキルメタクリレ−トには特に制限はなく、上記メタクリル酸エステルとして挙げたものの中から適宜選択することができ、またα，β−エチレン性不飽和単量体および架橋剤についても特に制限はなく、上記メタクリル酸エステルと共重合可能な他の不飽和単量体として挙げたものの中から適宜選択して使用することができる。
【００１４】
メタクリル系部分架橋ゲル状重合体は破砕して用いることが好ましく、通常平均粒径が５ｍｍ以下、好ましくは０．１〜３ｍｍ程度のものが使用される。またメタクリル系部分架橋ゲル状重合体の配合割合は、メタクリル酸エステルを主体とする単量体１００重量部に対して、通常０〜３００重量部、好ましくは１０〜２００重量部、より好ましく１５〜１５０重量部である。
【００１５】
本発明の方法においては、本発明の目的に支障のない範囲で、必要に応じ混練時または混合時などに、各種模様材、着色剤、カップリング剤、光安定剤、酸化防止剤、離型剤、重合調整剤、脱泡剤などの添加剤を併用することができる。また、本発明における混合、混練工程での増粘速度の向上や、樹脂組成物から成形品を製造する際の金型に対する転写性の向上を目的として、本発明において使用される（メタ）アクリル酸エステルを主体とする不飽和単量体に対して不溶かつ膨潤度を有する樹脂組成物を添加することもできる。
【００１６】
本発明において、樹脂組成物は形状保持性のある粘土状の樹脂組成物である必要があり、加圧展延性が好ましくは１５０〜４５０ｃｍ2 、より好ましくは２００〜４００ｃｍ2 の範囲にあるのがよい。ここでいう加圧展延性とは、樹脂組成物を３０．０ｇ秤量し、熱盤温度５０℃に加温したプレス機にて、上熱盤／５０μｍ厚みナイロンフィルム／樹脂組成物／５０μｍ厚みナイロンフィルム／下熱盤の構成で、３トンの加重で６０秒間加圧したときの樹脂組成物の広がり面積である。
【００１７】
形状保持性のある樹脂組成物の製造方法としては、特に制限はないが、メタクリル酸エステルを主体とした単量体、メタクリル酸エステル系重合体および無機充填材を、６５〜１２０℃の温度で混練を行い粘土状物を得、次いで得られた粘土状物に冷却後あるいは冷却過程中において硬化剤を混合して得られる樹脂組成物が、耐候性および美麗性に優れるうえに着色が少なく、好ましいものとして挙げられる。
【００１８】
上記好ましい樹脂組成物の製造において、メタクリル酸エステル系重合体としては、通常上記メタクリル酸エステルを主体とする単量体を、乳化重合法、懸濁重合法、塊状重合法などにより重合したものが用いられる。このような重合方法によって得られたメタクリル酸エステル系重合体は、単量体との混合溶解性の点から、粒子状であることが好ましく、その粒子径は後述する混練に使用できる大きさのものであれば特に限定されるものではないが、通常５ｍｍ以下、より好ましくは０．１〜２ｍｍ程度である。メタクリル酸エステル系樹脂の形状は、通常ビーズ状、ペレット状、粉砕粉粒状等であり、溶解性、取り扱い性などの観点からビーズ状であることが好ましい。
【００１９】
混練温度は、通常６５〜１２０℃の範囲であり、好ましくは７０〜１００℃である。上記温度で混練するために、混練に使用する混練機は、通常ジャケット部などの温度調節部を有し、電熱ヒーター、蒸気、温水または冷却水、温度調節用油などを用いて混練部が所定の温度になるように調節できることが好ましい。
【００２０】
混練方法としては、特に制限はなく本発明の効果を実現できるものであればよく、また混練機としては、回分式二軸混練機、連続式二軸混練機が好ましく用いられる。
回分式二軸混練機としては、例えば、トラフ内に平行に置かれたＺ型、Ｈ型、フィニシュテール型、デイスパージョン型等の２本の混合翼が互いに逆方向に回転し、混合物をせん断、圧縮、引き伸ばしして混練する双腕型ニーダー；双腕型ニーダーに機械的な加圧カバーを備え、加圧カバーを空気圧、液圧等によって圧縮することにより混練物とトラフ壁面または混練物相互間に強いせん断力を発生させて混練を強化した加圧ニーダー；密閉された混合室に原料を投入し、混合室に内蔵した２本のローターが互いに逆方向に回転し、チャンバ壁面とローター間あるいはローター相互間で強いせん断力を与えて混練するインターナルミキサー等が挙げられる。
連続式二軸混練機としては、原料供給部に配置したフィードスクリュー部で原材料を連続的に混練部に送り込み、ローターあるいはニーデングデスク等を配置した混練部にて混練し、混練物を連続的に排出するもので、二軸スクリュー混練機、コンテェニアスニーダー等が好ましく採用される。
混練時間は、混練機の種類、回転数また混練温度により異なるが、一般には２〜１０分が採用される。
【００２１】
上記混練物を得た後に、得られた粘土状物に冷却後あるいは冷却過程中において硬化剤を混合することにより、目的とする樹脂組成物が製造できる。この際、硬化剤を混合する方法としては、特に限定されず、例えば各種混練機、混合機を使用することができる。混合時間としては通常均一に混合できればよく通常数分〜３０分程度、連続式二軸混練機を用いれば１〜５分程度で混合が終了する。このようにして得られた樹脂組成物は、粘土状を呈しており、ベタつきがなく計量等の取り扱いが容易である。
【００２２】
本発明の方法において、上記のように得られた形態保持性を持つ粘土状の樹脂組成物を５５０ｔｏｒｒ以下、好ましくは５０〜４５０ｔｏｒｒの減圧下に脱気することが必要である。脱気圧力が５５０ｔｏｒｒより高い場合、脱気が不十分となり、成形品表面に白化、泡、くぼみ等の欠点が発生する場合があり好ましくない。脱気方法は、減圧された空間に接する樹脂組成物の面積を大きくし、脱気速度を早めることが、生産性向上の観点から望ましい。脱気時間としては、樹脂組成物の組成、形状などにより異なり、通常３０分以下、好ましくは１０分以下である。
【００２３】
脱気の態様としては、粘土状の樹脂組成物を、吐出口に減圧室が連結された押出機に供給し、減圧室の入り口部に配置された１個以上の穴を有する目皿、より好ましくは穴の全開口面積が０．０３〜５ｃｍ２である１個または複数個の穴を有する目皿を介して、５５０ｔｏｒｒ以下の減圧度に調整された減圧室に押し出して脱気する方法である。樹脂組成物は目皿を通ることで、長細い形状となり、表面積が増大して減圧室で効率よく脱気される。減圧室での樹脂組成物の滞留時間は減圧度、径の太さによって異なるが、通常１０秒〜３分である。脱気された樹脂組成物は、減圧室に接続された押出機に供給され、成形に便利な形状に賦形することもできる。
【００２４】
本発明の方法で得られる樹脂組成物は、プレス成形などの方法で賦形・硬化することにより、成形品、特に大理石様の製品を得ることができる。例えばプレス成形の成形条件としては、通常成形圧力１０〜２００ｋｇ／ｃｍ2 、成形温度８０〜１８０℃、成形時間１０分程度である。
【００２５】
【実施例】
以下に、本発明を実施例により詳細に説明する。実施例は本発明の一実施態様を示したものであり、本発明はこれらの例に限定されるものではない。また、加圧展延性およびアクリル系部分架橋重合体の重合体含有率は次の方法により測定・評価した。
【００２６】
（加圧展延性の測定）
樹脂組成物を３０．０ｇ秤量し、熱盤温度５０℃に加温したプレス機にて、上熱盤／５０μｍ厚みナイロンフィルム／樹脂組成物／５０μｍ厚みナイロンフィルム／下熱盤の構成で、３トンの総荷重をかけて６０秒間加圧し、樹脂組成物の広がり面積を面積計［林電工（株）製：自動面積計ＡＡＭ−８型］を用いて測定する。
【００２７】
（加圧展延性の評価）
上記の方法で、樹脂組成物の混練直後と、樹脂組成物を５０μｍの厚みのナイロンフィルムの袋に密閉した状態で約１日室温放置後の加圧加熱による広がり面積（加圧展延性）を測定し、得られた樹脂組成物に１日室温放置による粘度変化があったかどうかを評価した（変化が見られない場合は熟成の必要がないものと評価した）。またナイロンフィルム間で引き伸ばされたフィルム状の樹脂組成物を目視観察し、未溶解重合体の有無を調べた。
【００２８】
（アクリル系部分架橋重合体の重合体含有率測定）
ソックスレー抽出器にハイドロキノンモノメチルエーテルを１０００ＰＰＭ添加溶解したジクロロメタン１５０ｍｌを入れ、抽出用円筒濾紙の中に、部分架橋重合体１５ｇを５ｍｍ以下の粒状に粉砕していれた。５０℃の恒温で抽出器のフラスコを加熱して２０時間還流して抽出した。抽出液を１２００ｍｌのメタノールの中に入れ、再沈してポリマーを析出させた。析出したポリマーを濾紙で濾過して分離し、円筒濾紙のなかに残存するポリマー分と合わせて、５５℃で重量減少がなくなるまで減圧乾燥し、重合体の重量を求め、部分架橋重合体の重量で除して重合体含有率を求めた。
【００２９】
実施例１
メタクリル酸メチル５７重量部にネオペンチルグリコールジメタクリレート４３重量部を混合した液２ｋｇと、水酸化アルミニウム２７４重量部にメタクリル樹脂ビーズ［メタクリル酸メチル９８重量％とアクリル酸メチル２重量％の共重合体、重量平均分子量１１００００、平均粒子径０．３ｍｍ］１０５重量部および石目調模様材４７重量部を混合したもの８．５ｋｇを、９５℃の熱媒で加温されたジャケットをもつ加圧ニーダー［（株）森山製作所製：Ｄ１０−２０型、混合容量１０リッター］に投入し、混練して粘土状物を得た。得られた粘土状物を、ジャケット温度を１５℃に調整した、減圧室を具備した二軸押出機［口径７０φ、Ｌ／Ｄ＝６、回転数６０ｒｐｍ］に供給し、同時に二軸押出機の中間にある硬化剤の投入孔より１，１−ジ−ｔ−ブチルパーオキシ−３，３，５ートリメチルシクロヘキサンを８００ｇ／時間のフィード量で供給し混合して、該粘土状物を冷却しながら減圧室に押し出した。二軸押出機と減圧室の間に、０．６ｃｍ2 の大きさの楕円形の穴が各２０個開いた２個の目皿を設け、粘土状物を断面積が０．６ｃｍ2 のストランド状で減圧室に押し出し、これは重力で減圧室の下部に供給された。減圧室は１１０ｔｏｒｒに調整し脱気した。減圧室の下部に一軸押出機［口径１００φ、Ｌ／Ｄ＝６、回転数５０ｒｐｍ］、さらにその先にシートダイを付け、厚みが２０ｍｍのシート状に賦形された樹脂組成物を得た。粘土状物の減圧室内滞留時間は約１分であった。賦形された樹脂組成物に未溶解ポリマーは見られず、加圧展延性は３０２ｃｍ2 であり、２４時間経過後も変化がなかった。
【００３０】
樹脂組成物１０ｋｇを天板部６００ｍｍ×１０００ｍｍ、５０ｍｍの高さの前垂れおよびバックガードを有する洗面化粧台用金型中に投入し、成形温度１３０℃、加圧樹脂圧１００ｋｇｆ／ｃｍ2 、加圧時間１２分の成形条件において加圧成形を行い、６００ｍｍ×１０００ｍｍ×１０ｍｍのアクリル人工大理石の洗面化粧台を得た。合計５回の成形を行ったが、得られた成形品の表面には、いずれも白化、泡、くぼみなどの成形欠点はなく、極めて美麗であった。
【００３１】
実施例２
メタクリル酸メチル６０重量部、ネオペンチルグリコールジメタクリレート３０重量部、実施例１と同様のメタクリル樹脂ビーズ１０重量部および２，２‘−アゾビス（４−メトキシ−２，４−ジメチルバレロニトリル）０．００３重量部を混合溶解し、２枚のガラス板およびガスケットで１０ｍｍ間隔になるように組み立てられたセルに注入し、６０℃で２時間重合して部分架橋ゲル状重合体を得た。部分架橋重合体の重合体含有率は３８重量％であった。この部分架橋重合体０．５ｋｇ、メチルメタクリレート１．４２５ｋｇ、ネオペンチルグリコールジメタクリレート１．０７５ｋｇ、実施例１と同様のメタクリル樹脂ビーズ２．４重量部、水酸化アルミニウム６．６ｋｇおよび石目調模様材１．１ｋｇを、９５℃の熱媒で加温されたジャケットをもつ実施例１と同様の加圧ニーダーに投入し、混練した。２０分間混練し、次いでこれを５０℃まで冷却後、１，１−ジ−ｔ−ブチルパーオキシ−３，３，５−トリメチルシクロヘキサン１２０ｇ供給して５分間混合し、樹脂組成物を得た。
【００３２】
穴の面積が１．５ｃｍ2 、穴の数が各１６個の目皿を使用し、減圧室の減圧度２５０ｔｏｒｒとし、および二軸押出機内で樹脂組成物の冷却および硬化剤の添加を行わないこと以外は、実施例１と同じ方法により得られた樹脂組成物からシート状の成形用樹脂組成物を得た。
得られた成形用樹脂組成物１０ｋｇを天板部６００ｍｍ×１０００ｍｍ、５０ｍｍの高さの前垂れおよびバックガードを有する洗面化粧台用金型中に投入し、成形温度１３０℃、加圧樹脂圧１００ｋｇｆ／ｃｍ2 、加圧時間１２分の成形条件において加圧成形を行い、６００ｍｍ×１０００ｍｍ×１０ｍｍのアクリル人工大理石の洗面化粧台を得た。合計５回の成形を行ったが、いずれも得られた成形品の表面には、白化、泡、くぼみなどの成形欠点はなく、極めて美麗であった。
【００３３】
実施例３
メタクリル酸メチル６８重量部にネオペンチルグリコールジメタクリレート３２重量部を混合した液３．ｌｋｇと、平均粒径が８μのシラン処理済みの水酸化アルミニウム２１２重景部、実施例１と同様のメタクリル樹脂ビーズ７０重量部、石目調模様材４７里量部および補強用ビニロン繊維［（株）クラレ製：ＲＦ−Ｓ６０２］１９重量部を混合した粉体１１．８ｋｇを９５℃の熱媒で加温されたジャケットを持つ実施例１と同様の加圧二ーダーに投入し、２０分間混練し粘土状物を得た。次いで、得られた粘土状物を、ジャケット温度を１５℃に調整した実施例１と同様の二軸押出機に１２０ｋｇ／時間の速度で供給し、同時に二軸押出機の中間にある硬化剤の投入口より１，１−ジ−ｔ−ブチルパーオキシ−３，３，５−トリメチルシクロヘキサンを８００ｇ／時間のフィード量で供給しつつ、該樹脂組成物を冷却しながら減圧室に押し出した。樹脂組成物は、二軸押出機と減圧室の間に設けられた、４．５ｃｍ2 の大きさの楕円形の穴が各４個開いた２個の目皿を通過し、２５０ｔｏｒｒに調圧された減圧室に押し出され脱気された。減圧室の下部に一軸押出機［口径１００φ、Ｌ／Ｄ：６、回転数５０ｒｐｍ］、さらにその先にシートダイを付け、厚みが２０ｍｍのシート状に賦形された樹脂組成物を得た。粘土状物の減圧室内滞留時間は約１分であった。賦形された樹脂組成物の加圧展延性は３４０ｃｍ2 であり、樹脂組成物中には未溶解ポリマーは見られず、２４時間経過後も加圧展延性は変化がなかった。
【００３４】
得られた成形用樹脂組成物１０ｋｇを天板部６００ｍｍ×１０００ｍｍ、５０ｍｍの高さの前垂れおよびバックガードを有する洗面化粧台用金型中に投入し、成形温度１３０℃、加圧樹脂圧１１０ｋｇｆ／ｃｍ2 、加圧時間１２分の成形条件において加圧成形を行い、６００ｍｍ×１０００ｍｍ×ｌｌｍｍのアクリル人工大理石の洗面化粧台を得た。同様な方法で樹脂組成物を得、合計５回の成形を行ったが、いずれも得られた成形品の表面には、白化、泡、くぼみなどの成形欠点はなく極めて美麗であった。
【００３５】
比較例１
減圧室の減圧度を６６０ｔｏｒｒとする以外は、実施例１と同じ方法によりシート状の成形用樹脂組成物を得た。
得られた成形用樹脂組成物を、実施例１と同じ方法により成形して５個の洗面化粧台の人工大理石成形品を得た。得られた成形品中２個の成形品表面には、成形品の一部に白化、泡、くぼみなどが見られた。
【００３６】
【発明の効果】
本発明の方法は、モノマー、ポリマー、無機充填材および硬化剤を必須成分とするアクリル系の粘土状樹脂組成物に含まれる空気を効率的に脱気してプレス成形などに好適な成形材料を製造する方法であり、成形品の白化、泡、くぼみ等の成形欠点の発生を改善することができるので、高品質のアクリル系人工大理石用の成形用樹脂組成物を製造する方法として好適である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a molding resin composition, and more specifically, suitable for press molding and the like that can provide an acrylic artificial marble that is free of whitening, bubbles, dents, etc. and has excellent appearance. The present invention relates to a method for producing a molding resin composition.
[0002]
[Prior art]
Acrylic artificial marble filled with an inorganic filler in acrylic resin is used for kitchen top plates, various countertops, vanity tops, shower trays, flooring materials, wall materials, partition plates, etc., taking advantage of its beautiful appearance and excellent properties. Widely used.
As a method for producing an acrylic artificial marble, for example, a cast molding method proposed in Japanese Patent Publication No. 50-22586 is known. In general, the cast molding method involves prepolymerizing about 10 to 30% of methacrylic acid esters, or mixing and mixing an inorganic filler in so-called syrup in which a methacrylic acid ester polymer is dissolved in methacrylic acid esters. In this method, the mixture is poured into a gap in the mold, and then the mixture is cured under normal pressure to obtain an artificial marble product. However, this cast molding method takes a long time for curing and is low in productivity, has a large amount of monomer components, has a monomer odor, and is inconvenient to handle due to stickiness caused by syrup during injection, etc. It has a problem that it is difficult to maintain a good working environment, such as being easily generated.
[0003]
As a method for avoiding such problems, a press molding method has been studied. In the press molding method, it is necessary that the molding material has shape stability, the same low-concentration resin syrup as that used in the casting molding method, an inorganic filler, further an aromatic vinyl compound, isocyanate. There is known a method for imparting shape stability to a composition by adding a thickening agent such as a compound (Japanese Patent Laid-Open No. 5-124844) or a crosslinked polymer fine powder (Japanese Patent Laid-Open No. 6-313019). . In addition, a monomer containing 20% by weight or more of an essential component polyfunctional (meth) acrylate, methacrylic resin powder, curing agent, inorganic filler, etc. are kneaded and aged at room temperature or below the curing temperature. There has been proposed a method of molding and curing a molding material obtained by heating under pressure (Japanese Patent Publication No. 5-13899). However, these resin compositions having shape stability for acrylic artificial marble have high viscosity, so that air remaining in the resin composition cannot be sufficiently degassed during press molding, and the surface of the molded product is whitened. There is a problem that bubbles, dents, etc. occur and the appearance may be poor. These disadvantages are strongly desired to be improved, especially in artificial marble applications where beauty is required, since the value as a product is significantly reduced.
[0004]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a method for producing a resin composition for acrylic artificial marble, which is suitable for a press molding method and the like, which solves the problems caused by the residual air.
[0005]
[Means for Solving the Problems]
The above object is achieved according to the present invention, a monomer mainly composed of methacrylic acid ester, methacrylic acid ester resin, an inorganic filler, and a clay-like resin composition comprising the curing agent, the decompression chamber to the discharge port Supply to the connected extruder, push through the eye plate with one or more holes arranged at the inlet of the decompression chamber and push it into the decompression chamber adjusted under reduced pressure, and deaerate under a reduced pressure of 550 torr or less This is achieved by a method for producing a molding resin composition.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The monomer mainly composed of methacrylic acid ester used in the present invention refers to a monomer mixture of methacrylic acid ester alone or other unsaturated monomer mainly composed of methacrylic acid ester and copolymerizable therewith. The methacrylic acid ester is preferably 50% by weight or more, and the methacrylic acid ester is more preferably 70% by weight or more.
[0007]
As the methacrylic acid ester, a methacrylic acid ester having about 5 to 18 carbon atoms is preferably used. Specifically, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid. Examples include cyclohexyl and lauryl methacrylate. These may be used alone or in combination of two or more. Among them, methyl methacrylate is particularly preferably used.
[0008]
The other unsaturated monomer copolymerizable with the methacrylic acid ester is not particularly limited. For example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, Acrylic esters such as lauryl acrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; unsaturated monomers such as acrylonitrile, methacrylonitrile, acrylamide, vinyl acetate, vinyl chloride, acrylic acid, methacrylic acid; ethylene Examples thereof include polyfunctional unsaturated monomers such as glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, neopentyl glycol dimethacrylate, and trimethylolpropane trimethacrylate. These monomers are used alone or in combination of two or more.
[0009]
The methacrylic acid ester polymer used in the present invention can be used without particular limitation as long as it is a methacrylic acid ester polymer that dissolves in the monomer mainly composed of the above methacrylic acid ester. Preferable examples include those obtained by polymerizing monomers mainly composed of esters, or those obtained by polymerizing one or more of these monomers with other polymerizable monomers. . As the weight average molecular weight of the methacrylic acid ester-based polymer, those capable of being dissolved in the monomer are used, and are usually in the range of 5 to 600,000, preferably 70 to 300,000, more preferably 100 to 200,000. The blending ratio of the methacrylic acid ester polymer is usually 10 to 400 parts by weight, preferably 15 to 300 parts by weight with respect to 100 parts by weight of the monomer mainly composed of methacrylic acid ester.
Further, a part of the methacrylic acid ester polymer can be used in place of, for example, an acrylic partially crosslinked gel polymer whose production method is described in JP-A-60-202128.
[0010]
Examples of the inorganic filler used in the present invention include aluminum hydroxide, magnesium hydroxide, alumina, magnesium oxide, calcium carbonate, silica, mica, and glass beads. However, the addition of the inorganic filler deteriorates the appearance of the molded product. If not, there is no particular restriction. Among these inorganic fillers, aluminum hydroxide, magnesium hydroxide, silica, and glass beads are preferable from the viewpoints of high-grade feeling, contamination resistance, and processing performance required for acrylic artificial marble. Aluminum is preferably used. The particle diameter of the inorganic filler is usually 0.1 to 100 μm, more preferably 1 to 30 μm. A surface-treated inorganic filler such as silane treatment is also preferably used. The blending ratio of the inorganic filler is usually 50 to 500 parts by weight, preferably 100 to 400 parts by weight with respect to 100 parts by weight of the monomer mainly composed of methacrylic acid ester.
[0011]
There is no restriction | limiting in particular in the hardening | curing agent used for this invention, The benzoyl peroxide, the lauroyl peroxide, cumene hydroperoxide, bis (4-t- butylcyclohexyl) dicarbonate, 1, 1- di-dioxide used for normal radical polymerization are used. Organic peroxides such as t-butylperoxy-3,3,5-trimethylcyclohexane; azo compounds such as azobisisobutyronitrile and 2,2-azobis (2,4-dimethylvaleronitrile) It is done. These curing agents are used alone or in combination of two or more. The blending ratio of the curing agent is usually 1 to 10 parts by weight, preferably 3 to 7 parts by weight with respect to 100 parts by weight of the monomer mainly composed of methacrylic acid ester.
[0012]
Further, in the method of the present invention, the reinforcing single fiber is added at the time of kneading or mixing for the purpose of improving the toughness and strength of the molded product obtained in the present invention or suppressing the occurrence and progression of cracks. Can be added. Examples of the selected fibers include inorganic fibers such as asbestos and glass fibers, various organic fibers including aramid fibers and vinylon fibers, carbon fibers, and metal whiskers. The combination of the shape and amount of reinforcing single fibers used varies depending on the characteristics of the desired molded product, so these cannot be strictly defined. For example, the purpose is to improve toughness and suppress cracking. As a fiber shape, it is preferable that the fiber shape is in the range of 5 to 300 μm in fiber diameter and 3 to 50 mm in fiber length, and the addition amount is used in the present invention. The amount is preferably in the range of 5 to 200 parts by weight with respect to 100 parts by weight of the monomer mainly composed of methacrylic acid ester. When the addition amount is less than 5 parts by weight, it is difficult to develop a reinforcing effect, and when the addition amount exceeds 200 parts by weight, kneading with a normal apparatus becomes extremely difficult.
[0013]
In the present invention, a methacrylic partially cross-linked gel polymer can be added for the purpose of further improving the low shrinkage property, processing characteristics, and imparting design properties. A methacrylic partially crosslinked gel polymer which can be preferably used for this purpose is, for example, (a) an alkyl as described in JP-A-60-202128, JP-A-62-1705, etc. A resin selected from the group consisting of a methacrylate alone, a monomer mixture with an α, β-ethylenically unsaturated monomer having an alkyl methacrylate as a main component, and a syrup containing a polymer thereof. The content of the polymer in such a range that the total polymer content does not exceed 90% by partially polymerizing the raw material, and (b) a mixture comprising 2 to 250 parts by weight of the crosslinking agent per 100 parts by weight of the resin raw material Is a partially cross-linked gel polymer in which the content of the total polymer in the mixture is increased by 4 to 75% by weight. The alkyl methacrylate is not particularly limited, and can be appropriately selected from those listed as the above methacrylic acid esters. The α, β-ethylenically unsaturated monomer and the crosslinking agent are not particularly limited. , Can be appropriately selected from those listed as other unsaturated monomers copolymerizable with the methacrylic acid ester.
[0014]
The methacrylic partially crosslinked gel polymer is preferably used after being crushed, and usually has an average particle diameter of 5 mm or less, preferably about 0.1 to 3 mm. The blending ratio of the methacrylic partially crosslinked gel polymer is usually 0 to 300 parts by weight, preferably 10 to 200 parts by weight, more preferably 15 to 100 parts by weight of the monomer mainly composed of methacrylic acid ester. 150 parts by weight.
[0015]
In the method of the present invention, various pattern materials, colorants, coupling agents, light stabilizers, antioxidants, mold release, etc., as needed, during kneading or mixing, as long as the object of the present invention is not hindered. Additives such as an agent, a polymerization regulator and a defoaming agent can be used in combination. The (meth) acryl used in the present invention for the purpose of improving the speed of thickening in the mixing and kneading steps in the present invention and improving the transferability to the mold when producing a molded product from the resin composition. It is also possible to add a resin composition that is insoluble and has a degree of swelling with respect to an unsaturated monomer mainly composed of an acid ester.
[0016]
In the present invention, the resin composition needs to be a shape-retaining clay-like resin composition, and the pressure spreadability is preferably in the range of 150 to 450 cm 2 , more preferably 200 to 400 cm 2. Good. Here, the pressure spreadability means that 30.0 g of the resin composition was weighed and heated by a press machine heated to a hot plate temperature of 50 ° C., with an upper hot plate / 50 μm thick nylon film / resin composition / 50 μm thick nylon. It is the spread area of the resin composition when pressed for 60 seconds with a load of 3 tons in the configuration of film / lower heating platen.
[0017]
The method for producing the resin composition having shape retention is not particularly limited, but a monomer mainly composed of a methacrylic ester, a methacrylic ester polymer and an inorganic filler at a temperature of 65 to 120 ° C. A resin composition obtained by kneading to obtain a clay-like material, and then mixing the curing agent after cooling or in the cooling process to the obtained clay-like material is excellent in weather resistance and aesthetics, and is less colored, It is mentioned as preferable.
[0018]
In the production of the preferred resin composition, the methacrylic acid ester polymer is usually obtained by polymerizing a monomer mainly composed of the methacrylic acid ester by an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method or the like. Used. The methacrylic acid ester-based polymer obtained by such a polymerization method is preferably in the form of particles from the viewpoint of mixing solubility with the monomer, and the particle size is such that it can be used for kneading described later. Although it will not specifically limit if it is a thing, Usually, it is 5 mm or less, More preferably, it is about 0.1-2 mm. The shape of the methacrylic ester resin is usually a bead shape, a pellet shape, a pulverized powder particle shape, etc., and is preferably a bead shape from the viewpoints of solubility, handleability, and the like.
[0019]
The kneading temperature is usually in the range of 65 to 120 ° C, preferably 70 to 100 ° C. In order to knead at the above temperature, the kneader used for kneading usually has a temperature control part such as a jacket part, and the kneading part is predetermined using an electric heater, steam, hot water or cooling water, temperature control oil, etc. It is preferable that the temperature can be adjusted to the following temperature.
[0020]
The kneading method is not particularly limited as long as the effects of the present invention can be realized. As the kneader, a batch type biaxial kneader or a continuous biaxial kneader is preferably used.
As a batch type twin-screw kneader, for example, two mixing blades such as Z type, H type, finish tail type, and dispersion type placed in parallel in the trough rotate in opposite directions, Double-arm kneader that kneads by shearing, compressing and stretching; equipped with a mechanical pressure cover on the double-arm kneader and compressing the pressure cover with air pressure, hydraulic pressure, etc. Pressurized kneader that generates strong shearing force between them and strengthens kneading; feeds raw material into a sealed mixing chamber, the two rotors built in the mixing chamber rotate in opposite directions, and the chamber wall and rotor Examples thereof include an internal mixer that kneads by applying a strong shearing force between the rotors or between the rotors.
As a continuous twin-screw kneader, the raw material is continuously fed to the kneading part by the feed screw part arranged in the raw material supply part, and the kneaded product is continuously kneaded in the kneading part in which the rotor or the needing desk is arranged. A twin screw kneader, a continuous kneader or the like is preferably employed.
The kneading time varies depending on the type of kneader, the number of rotations, and the kneading temperature, but generally 2 to 10 minutes are employed.
[0021]
After obtaining the kneaded product, the desired resin composition can be produced by mixing the obtained clay-like material with a curing agent after cooling or during the cooling process. In this case, the method of mixing the curing agent is not particularly limited, and various kneaders and mixers can be used, for example. Mixing time is usually about several minutes to 30 minutes as long as it can be uniformly mixed. If a continuous biaxial kneader is used, mixing is completed in about 1 to 5 minutes. The resin composition thus obtained has a clay-like shape, is not sticky, and is easy to handle such as weighing.
[0022]
In the method of the present invention, it is necessary to degas the clay-like resin composition having the form-retaining property obtained as described above under a reduced pressure of 550 torr or less, preferably 50 to 450 torr. When the deaeration pressure is higher than 550 torr, the deaeration becomes insufficient, and defects such as whitening, bubbles, and dents may occur on the surface of the molded product. In the degassing method, it is desirable from the viewpoint of improving productivity that the area of the resin composition in contact with the decompressed space is increased and the degassing speed is increased. The deaeration time varies depending on the composition and shape of the resin composition, and is usually 30 minutes or less, preferably 10 minutes or less.
[0023]
The status like degassing, perforated plate a clay-like resin composition was fed to an extruder under reduced pressure chamber is connected to the discharge port, having one or more holes arranged in the inlet portion of the vacuum chamber, More preferably, a method of degassing by extruding into a decompression chamber adjusted to a degree of decompression of 550 torr or less through a pan having one or a plurality of holes having a total opening area of 0.03 to 5 cm 2. der Ru. By passing through the eye plate, the resin composition becomes a long and thin shape, increases the surface area, and is efficiently degassed in the decompression chamber. The residence time of the resin composition in the decompression chamber varies depending on the degree of decompression and the diameter, but is usually 10 seconds to 3 minutes. The degassed resin composition is supplied to an extruder connected to a decompression chamber and can be shaped into a shape convenient for molding.
[0024]
The resin composition obtained by the method of the present invention can be molded and cured by a method such as press molding to obtain a molded product, particularly a marble-like product. For example, the molding conditions for press molding are usually a molding pressure of 10 to 200 kg / cm 2 , a molding temperature of 80 to 180 ° C., and a molding time of about 10 minutes.
[0025]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples. The examples show one embodiment of the present invention, and the present invention is not limited to these examples. Further, the pressure spreadability and the polymer content of the acrylic partially crosslinked polymer were measured and evaluated by the following methods.
[0026]
(Measurement of pressure spreadability)
30.0 g of the resin composition was weighed and the press machine heated to a hot platen temperature of 50 ° C. was used, with the configuration of upper hot plate / 50 μm thick nylon film / resin composition / 50 μm thick nylon film / lower hot platen. A total load of tons is applied for 60 seconds, and the spread area of the resin composition is measured using an area meter [manufactured by Hayashi Denko Co., Ltd .: automatic area meter AAM-8 type].
[0027]
(Evaluation of pressure spreadability)
By the above method, the spreading area (pressure spreadability) immediately after kneading the resin composition and by heating under pressure after leaving the resin composition in a nylon film bag with a thickness of 50 μm for about one day at room temperature It was measured and evaluated whether the obtained resin composition had a viscosity change due to standing at room temperature for 1 day (when no change was observed, it was evaluated that no aging was necessary). In addition, the film-like resin composition stretched between nylon films was visually observed to check for the presence of undissolved polymer.
[0028]
(Measurement of polymer content of acrylic partially crosslinked polymer)
150 ml of dichloromethane in which 1000 PPM of hydroquinone monomethyl ether was added and dissolved was placed in a Soxhlet extractor, and 15 g of the partially crosslinked polymer was pulverized into particles of 5 mm or less in the extraction cylindrical filter paper. The extractor flask was heated at a constant temperature of 50 ° C. and refluxed for 20 hours for extraction. The extract was put into 1200 ml of methanol and reprecipitated to precipitate a polymer. The precipitated polymer is separated by filtering with a filter paper, combined with the polymer remaining in the cylindrical filter paper, dried under reduced pressure at 55 ° C. until there is no weight loss, and the weight of the polymer is obtained. The weight of the partially crosslinked polymer The polymer content was determined by dividing by.
[0029]
Example 1
2 kg of a mixture of 57 parts by weight of methyl methacrylate and 43 parts by weight of neopentyl glycol dimethacrylate, 274 parts by weight of aluminum hydroxide and methacrylic resin beads [copolymer of 98% by weight of methyl methacrylate and 2% by weight of methyl acrylate , Weight average molecular weight 110000, average particle diameter 0.3 mm] pressure kneader having a jacket heated with 95 ° C. heating medium, 8.5 kg mixed with 105 parts by weight and 47 parts by weight of a textured pattern material [Corporation made by Moriyama Seisakusho: D10-20 type, mixing volume 10 liters] and kneaded to obtain a clay-like product. The obtained clay-like material was supplied to a twin screw extruder [caliber 70φ, L / D = 6, rotation speed 60 rpm] with a jacket temperature adjusted to 15 ° C. and equipped with a decompression chamber. 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane is fed at a feed rate of 800 g / hour from the intermediate curing agent charging hole, and the clay is cooled. While pushing out to the decompression chamber. Between the twin-screw extruder and the decompression chamber, two eye plates with 20 oval holes each having a size of 0.6 cm 2 are provided, and the clay-like material is a strand having a cross-sectional area of 0.6 cm 2 It was extruded into a decompression chamber in the form of a gas, and this was fed to the lower part of the decompression chamber by gravity. The decompression chamber was adjusted to 110 torr and deaerated. A uniaxial extruder [caliber 100φ, L / D = 6, rotation speed 50 rpm] was attached to the lower part of the decompression chamber, and a sheet die was further attached to the tip, to obtain a resin composition shaped into a sheet having a thickness of 20 mm. The residence time of the clay-like material in the vacuum chamber was about 1 minute. No undissolved polymer was found in the shaped resin composition, the pressure spreadability was 302 cm 2 , and there was no change after 24 hours.
[0030]
10 kg of the resin composition is put into a mold for a vanity having a top plate portion of 600 mm × 1000 mm and a height of 50 mm and a back guard, and a molding temperature is 130 ° C., a pressure resin pressure is 100 kgf / cm 2 , and pressure is applied. Pressure molding was performed under molding conditions for 12 minutes to obtain a vanity for acrylic artificial marble of 600 mm × 1000 mm × 10 mm. The molding was performed 5 times in total, but the surface of the obtained molded product was very beautiful without any molding defects such as whitening, foam, and dent.
[0031]
Example 2
60 parts by weight of methyl methacrylate, 30 parts by weight of neopentyl glycol dimethacrylate, 10 parts by weight of methacrylic resin beads similar to Example 1, and 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) 003 parts by weight of the mixture was mixed and dissolved, poured into a cell assembled with two glass plates and a gasket at an interval of 10 mm, and polymerized at 60 ° C. for 2 hours to obtain a partially crosslinked gel polymer. The polymer content of the partially crosslinked polymer was 38% by weight. 0.5 kg of this partially crosslinked polymer, 1.425 kg of methyl methacrylate, 1.075 kg of neopentyl glycol dimethacrylate, 2.4 parts by weight of methacrylic resin beads similar to Example 1, 6.6 kg of aluminum hydroxide, and a grainy pattern 1.1 kg of the material was put into a pressure kneader similar to Example 1 having a jacket heated with a heating medium at 95 ° C. and kneaded. The mixture was kneaded for 20 minutes and then cooled to 50 ° C., and then 120 g of 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane was supplied and mixed for 5 minutes to obtain a resin composition.
[0032]
Use a countersunk with a hole area of 1.5 cm 2 and a number of holes of 16 each, a vacuum degree of 250 torr in the vacuum chamber, and cooling of the resin composition and no addition of a curing agent in the twin screw extruder Except for this, a sheet-form molding resin composition was obtained from the resin composition obtained by the same method as in Example 1.
10 kg of the obtained molding resin composition was put into a mold for a vanity having a top board portion of 600 mm × 1000 mm and a height of 50 mm and a back guard, a molding temperature of 130 ° C., a pressure resin pressure of 100 kgf / Pressure molding was performed under the molding conditions of cm 2 and a pressing time of 12 minutes to obtain a decorative vanity of 600 mm × 1000 mm × 10 mm acrylic artificial marble. The molding was performed 5 times in total, and the surface of the obtained molded product was extremely beautiful without any molding defects such as whitening, foam, and dent.
[0033]
Example 3
2. Liquid obtained by mixing 32 parts by weight of neopentyl glycol dimethacrylate with 68 parts by weight of methyl methacrylate. 2 kg of silane-treated aluminum hydroxide having an average particle diameter of 8 μm, 70 parts by weight of methacrylic resin beads similar to Example 1, 47 parts by weight of a textured pattern material and reinforcing vinylon fiber [( Kuraray Co., Ltd .: RF-S602] 11.8 kg of powder mixed with 19 parts by weight was charged into a pressure feeder similar to Example 1 having a jacket heated with a heating medium at 95 ° C. for 20 minutes. The mixture was kneaded to obtain a clay-like product. Next, the obtained clay-like material was fed at a rate of 120 kg / hour to the same twin-screw extruder as in Example 1 with the jacket temperature adjusted to 15 ° C., and at the same time, the curing agent in the middle of the twin-screw extruder. While feeding 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane at a feed rate of 800 g / hour from the inlet, the resin composition was extruded into the vacuum chamber while cooling. The resin composition passes through two eye plates each having four oval holes of 4.5 cm 2 provided between the twin screw extruder and the decompression chamber, and the pressure is adjusted to 250 torr. The vacuum chamber was pushed out and degassed. A single screw extruder [caliber: 100φ, L / D: 6, rotation speed: 50 rpm] was attached to the lower part of the decompression chamber, and a sheet die was further attached to the tip to obtain a resin composition shaped into a sheet having a thickness of 20 mm. The residence time of the clay-like material in the vacuum chamber was about 1 minute. The shaped resin composition had a pressure spreadability of 340 cm 2 , no undissolved polymer was found in the resin composition, and the pressure spreadability did not change even after 24 hours.
[0034]
10 kg of the obtained molding resin composition was put into a mold for a vanity having a top plate portion of 600 mm × 1000 mm and a height of 50 mm and a back guard, and a molding temperature of 130 ° C. and a pressurized resin pressure of 110 kgf / Pressure molding was performed under molding conditions of cm 2 and a pressure time of 12 minutes to obtain a vanity for acrylic artificial marble of 600 mm × 1000 mm × ll mm. A resin composition was obtained by the same method and molded a total of 5 times. In all cases, the surface of the obtained molded product was very beautiful with no molding defects such as whitening, bubbles, and dents.
[0035]
Comparative Example 1
A sheet-shaped molding resin composition was obtained in the same manner as in Example 1 except that the degree of vacuum in the vacuum chamber was 660 torr.
The obtained resin composition for molding was molded by the same method as in Example 1 to obtain 5 artificial marble molded products of vanity. On the surface of two of the obtained molded products, whitening, bubbles, dents and the like were observed on a part of the molded product.
[0036]
【The invention's effect】
The method of the present invention provides a molding material suitable for press molding by efficiently degassing air contained in an acrylic clay-like resin composition comprising monomers, polymers, inorganic fillers and curing agents as essential components. This method is suitable for producing a high-quality molding resin composition for acrylic artificial marble because it can improve the occurrence of molding defects such as whitening, foaming, and indentation of molded products. .
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3967698A JP3647637B2 (en) | 1997-02-06 | 1998-02-05 | Manufacturing method of resin composition for molding |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3846897 | 1997-02-06 | ||
| JP9-38468 | 1997-02-06 | ||
| JP3967698A JP3647637B2 (en) | 1997-02-06 | 1998-02-05 | Manufacturing method of resin composition for molding |
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| Publication Number | Publication Date |
|---|---|
| JPH10279698A JPH10279698A (en) | 1998-10-20 |
| JP3647637B2 true JP3647637B2 (en) | 2005-05-18 |
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| JP3967698A Expired - Fee Related JP3647637B2 (en) | 1997-02-06 | 1998-02-05 | Manufacturing method of resin composition for molding |
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