JP4222584B2 - Multi-layer polystyrene resin foam - Google Patents

Description

前記一般式（１）において、Ｒは水素原子またはメチル基を示し、Ｚはハロゲン原子またはメチル基を示し、ｐは０または１〜３の整数である。
【００１８】
前記ポリスチレン系樹脂としては、ポリスチレン、ゴム変性ポリスチレン、スチレン−アクリロニトリル共重合体、スチレン−ブタジエン−アクリロニトリル共重合体、スチレン−アクリル酸共重合体、スチレン−メタクリル酸共重合体、スチレン−メタクリル酸メチル共重合体、スチレン−メタクリル酸エチル共重合体、スチレン−アクリル酸メチル共重合体、スチレン−アクリル酸エチル共重合体、スチレン−無水マレイン酸共重合体、ポリスチレン−ポリフェニレンエーテル共重合体、ポリスチレンとポリフェニレンエーテルとの混合物などが例示される。
【００１９】
上記ポリスチレン系樹脂には、発泡層２の脆性改善等を目的としてスチレン−共役ジエンブロック共重合体や、その水添物を好ましくは３０重量％未満の割合でブレンドしたものや、ポリプロピレン系樹脂や高密度ポリエチレン等のポリオレフィン系樹脂を好ましくは２０重量％未満の割合でブレンドしたものも使用することができる。
【００２０】
本発明においては、ビカット軟化点が１１０℃以上のポリスチレン系樹脂を発泡層２に使用することにより、発泡成形体１の耐熱性を向上させることが好ましい。
尚、本明細書において、樹脂のビカット軟化点はＪＩＳ Ｋ７２０６（試験荷重はＡ法、伝熱媒体の昇温速度は５０℃／時の条件）にて求められる値を指す。
【００２１】
本発明の発泡層２に用いられるポリスチレン系樹脂は、その溶融粘度が１９０℃、剪断速度１００ｓｅｃ^-1の条件下において、２００ｐｏｉｓｅ以上で１０００００ｐｏｉｓｅ未満、好ましくは１０００〜５００００ｐｏｉｓｅである。その溶融粘度が前記範囲より小さいと、発泡時にダイより押出された溶融樹脂が垂れてしまい、発泡層２を得ることが困難になる虞れがある。一方、前記範囲を超えると、粘度が高すぎて押出圧力が上昇して押出発泡成形が困難になり、良質の発泡層２が得られなくなる虞れがある。
【００２２】
本発明の発泡層２に用いられるポリスチレン系樹脂は、２００℃、荷重５ｋｇｆの条件下でのメルトフローレイトが、好ましくは０．８〜３０ｇ／１０分且つ溶融張力が５〜４０ｇｆ、更に好ましくは１．０〜１０ｇ／１０分且つ溶融張力が８〜３５ｇｆであることが多層発泡パリソン６のドローダウン防止、発泡層２の高倍率化及び高厚み化の面から好ましく、気泡膜の破壊や鬆の発生防止に優れた効果がある。このようなポリスチレン系樹脂としては分岐構造を有するポリスチレン系樹脂等が挙げられる。
【００２３】
混合樹脂層３に用いられる樹脂は、ポリスチレン系樹脂と、ポリオレフィン系樹脂又はポリエステル系樹脂との混合物を主成分とし、該混合物が６０重量％以上のものであることが好ましい。
【００２４】
上記混合樹脂層３に用いられるポリスチレン系樹脂は、発泡層２を構成する上記のポリスチレン系樹脂と同じ樹脂を挙げることができる。但し、混合樹脂層３に用いられるポリスチレン系樹脂は、発泡層２に用いられるポリスチレン系樹脂と同一である必要はなく、混合されるポリオレフィン系樹脂又はポリエステル系樹脂の溶融粘度及びメルトフローレイトとの関係において、上記のポリスチレン系樹脂の中から適宜選択される。
【００２５】
上記混合樹脂層３に用いられるポリオレフィン系樹脂としては、低密度ポリエチレン、高密度ポリエチレン、直鎖状低密度ポリエチレン等のポリエチレン系樹脂、ポリプロピレン、プロピレン−エチレンランダム共重合体、プロピレン−1ブテンランダム共重合体、プロピレン−エチレン−ブテンランダム共重合体、プロピレン−エチレンブロック共重合体等のポリプロピレン系樹脂、環状ポリオレフィン等から選択される一種又は二種以上の混合物が挙げられる。
【００２６】
混合樹脂層３に用いられるポリオレフィン系樹脂は、ビカット軟化点が１１２℃以上のものが耐熱性の面で好ましく、該軟化点が１２０℃以上のものがより好ましく、具体的にはポリプロピレン系樹脂、高密度ポリエチレン系樹脂が好ましい。
尚、ビカット軟化点の上限値は特に限定されないが１６５℃程度である。
【００２７】
また、混合樹脂層３に用いられるポリエステル系樹脂としては、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレート、テレフタル酸とエチレングリコールとシクロヘキサンジメタノールとのコポリエステル等から選択される一種又は二種以上の混合物が挙げられる。特に、イーストマンケミカル社製の商品名『Ｅａｓｔａｒ ＰＥＴＧ6763』や『Ｅａｓｔａｒ ＰＥＴＧ5011』等の半結晶化時間が３０分以上のコポリエステル系樹脂が、回収原料を発泡層及び／又は混合樹脂層の原料としてリサイクルできるので好ましい。
【００２８】
本明細書で言う半結晶化時間は、メトロン株式会社（旧コタキ商事株式会社）製のＭＫ−８０１型結晶化速度測定器を使用して測定する。該結晶化速度測定器は、試料の結晶化と光の複屈折の関係より結晶化度を求める装置である。
【００２９】
半結晶化時間の測定は、厚みが０．１±０．０２ｍｍであって、１５×１５ｍｍの四角のフィルムを用意し、該フィルムを顕微鏡用カバーガラスに挟み込んだものを測定試料として、あらかじめ３００℃に加熱した後、１００℃に設定した結晶化浴に投入し、光源ランプの輝度の指示値を３Ｖに設定して測定する。
【００３０】
本明細書で言う半結晶化時間は、上記測定により得られる図３に示すグラフ上の曲線から、複屈折による光の量が一定になった値Ａをグラフ上縦軸から読取り、その値に０．５を乗じたグラフ上縦軸の値Ｂに対応するグラフ上の曲線上の値Ｃを読み取り、該Ｃに対応するグラフ上横軸の値Ｄとして求められる値である。尚、図３中のＥは結晶化浴設定温度、折れ線（II）は結晶化浴の温度である。
【００３１】
混合樹脂層３の主成分を構成するポリスチレン系樹脂と、ポリオレフィン系樹脂又はポリエステル系樹脂とからなる混合物は、（１）ポリスチレン系樹脂２０〜８０重量％と（２）ポリオレフィン系樹脂又はポリエステル系樹脂２０〜８０重量％との混合物（但し、（１）と（２）との合計が１００重量％）であることが好ましく、（１）ポリスチレン系樹脂４０〜８０重量％と、（２）ポリオレフィン系樹脂又はポリエステル系樹脂２０〜６０重量％との混合物（但し、（１）と（２）との合計は１００重量％）であることが発泡層との接着性、混合樹脂層の耐油性等の面でより好ましい。
【００３２】
混合樹脂層３を構成している混合物中のポリスチレン系樹脂が２０重量％未満の場合は、発泡層２と混合樹脂層３との接着性が不十分なものとなり、多層パリソン６の成形後、バリを切り取った切断部分より発泡成形体の発泡層１２と発泡成形体の混合樹脂層１３が界面剥離を起こし、良好な発泡成形体が得られなくなる。
【００３３】
一方、ポリスチレン系樹脂が８０重量％を超える場合は、発泡層２と混合樹脂層３との接着性は満足するが、混合樹脂層３の外側に、混合樹脂層３を構成するポリスチレン系樹脂と混合したポリオレフィン系樹脂又はポリエステル系樹脂と実用に耐えうる熱接着性を示す重合体からなる重合体層４を設ける場合であっても、該重合体層４と混合樹脂層３との接着性が不十分なものとなり、やはり多層パリソン６の成形後、バリを切り取った切断部分より発泡成形体の重合体層１４と発泡成形体の混合樹脂層１３が界面剥離を起こし、良好な成形体とはならない。又、ポリスチレン系樹脂が８０重量％を超える場合は、耐油性等の機能面においても不十分なものとなる。
【００３４】
本発明の混合樹脂層３には、相溶化剤を添加することができる。該相溶化剤としては、ポリスチレン系樹脂と、ポリオレフィン系樹脂又はポリエステル系樹脂とを相溶化し得るものであればよく、従来公知の各種のものを用いることができるが、特にスチレン系熱可塑性エラストマーやスチレン−オレフィン共重合体が好ましい。該スチレン系熱可塑性エラストマーには、ＳＢＳ系又はＳＩＳ系のものや、ＳＥＢＳ系やＳＥＰＳ系のもの等が包含される。
【００３５】
上記ＳＢＳ系又はＳＩＳ系のものは、ハードセグメントとしてポリスチレンの結晶相を有し、ソフトセグメントとしてポリブタジエン又はポリイソプレンがブロック的に共重合された構造を有する。
一方、上記ＳＥＢＳ系やＳＥＰＳ系のものは、上記ＳＢＳ系やＳＩＳ系のものに含まれているポリブタジエン、ポリイソプレンを高度に水素化してその主鎖中の二重結合を飽和させたものである。尚、これらのＳＥＢＳ系や、ＳＥＰＳ系、ＳＢＳ系及びＳＩＳ系等のスチレン系熱可塑性エラストマーについては、「プラスチックエージ」、第１０１頁〜第１０６頁（Ｊｕｎｅ １９８５）に詳述されている。
【００３６】
また、スチレン−オレフィン共重合体としては、エチレンとスチレンのグラフト共重合体、プロピレンとスチレンのグラフト共重合体、エチレン−グリシジルメタクリレート共重合体とスチレンのグラフト共重合体、エチレン−エチルアクリレート共重合体とスチレンのグラフト共重合体、エチレン−酢酸ビニル共重合体とスチレンのグラフト共重合体、エチレン−エチルアクリレート−無水マレイン酸共重合体とスチレンのグラフト共重合体、エチレンとメチルメタクリレートのグラフト共重合体、エチレン−グリシジルメタクリレート共重合体とメチルメタクリレートのグラフト共重合体、エチレン−エチルアクリレート共重合体とメチルメタクリレートのグラフト共重合体、エチレン−酢酸ビニル共重合体とメチルメタクリレートのグラフト共重合体、エチレン−エチルアクリレート−無水マレイン酸共重合体とメチルメタクリレートのグラフト共重合体、エチレンとアクリロニトリル−スチレン共重合体のグラフト共重合体、プロピレンとアクリロニトリル−スチレン共重合体のグラフト共重合体、エチレン−グリシジルメタクリレート共重合体とアクリロニトリル−スチレン共重合体のグラフト共重合体、エチレン−エチルアクリレート共重合体とアクリロニトリル−スチレン共重合体のグラフト共重合体、エチレン−酢酸ビニル共重合体とアクリロニトリル−スチレン共重合体のグラフト共重合体、エチレン−エチルアクリレート−無水マレイン酸共重合体とアクリロニトリル−スチレン共重合体のグラフト共重合体、および、スチレン−エチレンランダム共重合体、スチレン−プロピレンランダム共重合体等が挙げられる。
【００３７】
相溶化剤は、ポリスチレン系樹脂と、ポリオレフィン系樹脂又はポリエステル系樹脂との混合物１００重量部当り、０．１〜４０重量部、好ましくは０．５〜１０重量部の割合で添加することが好ましい。特に、スチレン系熱可塑性エラストマーの場合には、２〜３０重量部の割合で添加するのが好ましい。
【００３８】
上記スチレン系熱可塑性エラストマーからなる相溶化剤を添加すると、ポリスチレン系樹脂発泡層２と混合樹脂層３との接着性が向上し、更に、本発明の発泡成形体１の衝撃強度や脆性も改善される。また、混合樹脂層３の外側に重合体層４を設ける際に、混合樹脂層３と重合体層４との接着性も向上する。
【００３９】
混合樹脂層３に用いられる混合物のメルトフローレイトは、好ましくは０．１５〜３０（ｇ／１０分）、更に好ましくは０．５〜１２（ｇ／１０分）であり、該範囲内において発泡層２に用いられるポリスチレン系樹脂のメルトフローレイトと同程度、若しくはポリスチレン系樹脂に発泡剤を混合することによる可塑化効果を考慮して、該ポリスチレン系樹脂のメルトフローレイトよりも、概ね「ポリスチレン系樹脂のメルトフローレイト＋１０(ｇ／１０分)」を上限として、多少高めのものを選択することが好ましい。
尚、該混合物のメルトフローレイトは、２００℃、荷重５ｋｇｆの条件下において測定した値である。
【００４０】
該混合物のメルトフローレイトが低すぎる場合、ダイ内での流動性が悪いために多層パリソン６の表面平滑性が悪くなったり、場合によってはメルトフラクチャを起こす虞がある。また、ダイ内での発熱も大きくなるため、樹脂の温度が上昇し、積層された発泡層２の気泡構造が破壊され独立気泡率が低下する虞がある。一方、該混合物のメルトフローレイトが高すぎる場合、一般に溶融張力も低下してドローダウンが大きくなるので、大きな多層パリソン６を製造するのが困難となり、大きな発泡成形体を得ることができなくなる虞がある。また、発泡層２の気泡の発泡力が大きいために、気泡が混合樹脂層３に浮き出て混合樹脂層３の表面が凹凸となり外観が悪化する虞もある。
【００４１】
上記重合体層４に用いられる重合体は例えば、低密度ポリエチレン、高密度ポリエチレン、直鎖状低密度ポリエチレン等のポリエチレン系樹脂、ポリプロピレン、プロピレン−エチレンランダム共重合体、プロピレン−1ブテンランダム共重合体、プロピレン−エチレンブロック共重合体、プロピレン−1ブテンブロック共重合体等のポリプロピレン系樹脂、環状ポリオレフィン、ポリカーボネート系樹脂、ポリエステル系樹脂、スチレン系熱可塑性エラストマー、オレフィン系熱可塑性エラストマー、ポリエステル系熱可塑性エラストマー等から選択される一種又は二種以上の混合物からなる熱可塑性重合体が挙げられる。そして、これらの重合体からなる単層又は複層の重合体層４は、混合樹脂層３との積層面において混合樹脂層３との熱接着性があることを要する。
【００４２】
上記熱可塑性重合体の中でも、ポリオレフィン系樹脂及びポリエステル系樹脂が好ましく、耐熱性及び常温での耐衝撃性の面ではポリプロピレン系樹脂が好ましく、低温条件下での耐衝撃性の面では直鎖状低密度ポリエチレンが好ましく、耐熱性及び低温条件下での耐衝撃性の面では高密度ポリエチレンが好ましく、ガスバリヤー性及び常温での耐衝撃性の面ではポリエステル系樹脂が好ましい。
【００４３】
本発明の発泡成形体１において、その発泡成形体の発泡層１２と発泡成形体の混合樹脂層１３との間の剥離強度は１００（ｇｆ／２５ｍｍ）以上であることが好ましく、１５０（ｇｆ／２５ｍｍ）以上であることがより好ましく、２００（ｇｆ／２５ｍｍ）以上という大きな剥離強度を有することが特に好ましい。
また、発泡成形体の発泡層１２の外側に発泡成形体の混合樹脂層１３を介して発泡成形体の重合体層１４が積層されている発泡成形体１において、その該発泡層１２と該重合体層１４との間の剥離強度は１００（ｇｆ／２５ｍｍ）以上であることが好ましく、１５０（ｇｆ／２５ｍｍ）以上であることがより好ましく、２００（ｇｆ／２５ｍｍ）以上という大きな剥離強度を有することが特に好ましい。その剥離強度の上限値は、特に制約されるものではないが、通常３０００（ｇｆ／２５ｍｍ）程度である。このような大きな層間剥離強度を有する発泡成形体は本発明者らによって初めて開発されたものである。
【００４４】
上記接着強度が１００（ｇｆ／２５ｍｍ）未満の場合は、多層パリソン６を金型にて成形する際に発泡成形体の発泡層１２と発泡成形体の混合樹脂層１３とが、又は発泡成形体の混合樹脂層１３と発泡成形体の重合体層１４とが剥離したり、多層パリソン６の成形後、バリを切り取った該切断部分より発泡成形体の発泡層１２と発泡成形体の混合樹脂層１３とが、又は発泡成形体の混合樹脂層１３と発泡成形体の重合体層１４とが界面剥離を起こしてしまう虞がある。
【００４５】
尚、本明細書において発泡成形体の発泡層１２と発泡成形体の混合樹脂層１３との間の剥離強度は得られた発泡成形体１から幅25mmの短冊状試験片を切り出し、ＪＩＳ Ｚ０２３７に準拠し、剥離速度条件３００ｍｍ／ｍｉｎの９０°剥離試験にて測定して求めた値（ｇｆ／２５ｍｍ）である。また、発泡成形体の混合樹脂層１３と、発泡成形体の重合体層１４を有する発泡成形体１の場合は、発泡成形体１から上記試験片と同様の試験片を切り出し、上部つかみにより発泡成形体の重合体層１４のみを引っ張り、上記と同様に剥離試験を行い発泡成形体の発泡層１２と発泡成形体の混合樹脂層１３、または、発泡成形体の混合樹脂層１３と発泡成形体の重合体層１４の間のいずれか片方が剥離する強度を求めた値（ｇｆ／２５ｍｍ）である。
【００４６】
但し、幅25mmの短冊状試験片を切り出すことが出来ない場合は、出来るだけ広幅の短冊状試験片を切り出して上記剥離試験を行い、該切り出した試験片幅あたりの剥離強度を求め、その値に「２５／切り出した試験片の幅（ｍｍ）の係数」を掛算して幅２５mmあたりの剥離強度（ｇｆ／２５ｍｍ）とする。
【００４７】
本発明の発泡成形体１の層間剥離強度を前記のように大きな値とする方法としては、多層パリソン６の混合樹脂層３を構成する混合物の混合状態を表す相構造指数ＰＩ値を０．７超１．３未満、好ましくは０．８〜１．２の範囲に調整することを目安にすればよい。
【００４８】
前記混合樹脂層の相構造指数ＰＩ値は、混合樹脂層のポリスチレン系樹脂と、ポリオレフィン系樹脂又はポリエステル系樹脂との混合状態を示すもので、下記式（７）で定義される。
【数１】
ＰＩ値＝（η_A×φ_B）／（η_B×φ_A） …………（７）
【００４９】
上記式（７）において、φ_Aは混合樹脂層中のポリスチレン系樹脂相の体積分率、η_Aは１８０℃、剪断速度１００ｓｅｃ^-1におけるポリスチレン系樹脂の溶融粘度、φ_Bは混合樹脂層中のポリオレフィン系樹脂相又はポリエステル系樹脂相の体積分率、η_Bは１８０℃、剪断速度１００ｓｅｃ^-1におけるポリオレフィン系樹脂又はポリエステル系樹脂の溶融粘度である。
【００５０】
本発明者らの研究によれば、上記混合樹脂層３のＰＩ値が０．７以下になると、混合樹脂層３中のポリオレフィン系樹脂又はポリエステル系樹脂が、ポリスチレン系樹脂に覆われて接着表面に露出し難くなり、発泡成形体の発泡層１２と発泡成形体の混合樹脂層１３との剥離強度は高い値を示すものの、発泡成形体１の耐油性、衝撃強度等が不十分なものとなってしまう虞がある。
【００５１】
また、発泡成形体の混合樹脂層１３の外側にポリオレフィン系樹脂層又はポリエステル系樹脂層を有する場合それらの層間の剥離強度が不十分となり、多層パリソン６を金型で成形して得られる容器等の発泡成形体において、発泡成形体のバリを切取った部分から発泡成形体の混合樹脂層１３と発泡成形体の重合体層１４とが容易に剥離やすくなる。
【００５２】
一方、ＰＩ値が１．３以上になると、混合樹脂層３中のポリスチレン系樹脂が、ポリオレフィン系樹脂又はポリエステル系樹脂に覆われ接着表面に露出し難くなり、発泡成形体の混合樹脂層１３と発泡成形体の発泡層１２との剥離強度が不十分となり、多層パリソン６から得られる容器等の成形体において、発泡成形体のバリを切取った部分から発泡成形体の発泡層１２と発泡成形体の混合樹脂層１３とが容易に剥離してしまう問題が生じやすくなる。
【００５３】
結局、上記ＰＩ値が０．７超１．３未満の範囲にあると、発泡層３の外面に混合樹脂層３を有する多層パリソン６から成形されてなる発泡成形体１において、発泡成形体の発泡層１２と発泡成形体の混合樹脂層１３との間の剥離強度が高く優れたものとなり、更に外側に発泡成形体の重合体層１４を有する発泡成形体１においては発泡成形体の発泡層１２と、ポリオレフィン系樹脂層又はポリエステル系樹脂層からなる発泡成形体の重合体層１４との間の剥離強度が高く優れたものとなる。
【００５４】
本発明の発泡成形体１において発泡成形体の混合樹脂層１３又は発泡成形体の重合体層１４の更に外側に金属層、不織布又は織布等の繊維層等を設けることも出来る。
【００５５】
また、多層パリソン６の発泡層２、混合樹脂層３、重合体層４は、それらの層を構成している樹脂又は重合体に気泡調整剤、赤外線吸収剤、赤外線反射剤、難燃剤、流動性向上剤、耐候剤、着色剤、熱安定剤、酸化防止剤、充填剤、ゴム等の各種添加剤を必要に応じて適宜配合したものでもよい。又、重合体層４としては、高溶融張力のポリプロピレンや高密度ポリエチレンを用いることが外観良好な発泡成形体１が得られるため好ましい。
【００５６】
また、重合体層４として、オレフィン系熱可塑性エラストマー、スチレン系熱可塑性エラストマーを用いることにより、得られる発泡成形体１の耐衝撃性が更に向上するので好ましい。
【００５７】
本発明の発泡成形体の発泡層１２を覆う発泡成形体の混合樹脂層１３のみ又は、発泡成形体の混合樹脂層１３と発泡成形体の重合体層１４とからなる表皮の厚みは１００μｍ〜１０ｍｍが好ましく、更に好ましくは１００μｍ〜７ｍｍである。表皮の厚みが１００μｍ未満になると表面平滑性が低下するため、発泡成形体１の表面外観が劣る虞がある。また表皮の厚みが１０ｍｍを超えると発泡成形体１全体の重量も重くなることから、用途によっては、軽量とは言い難くなり、また、発泡成形体の発泡層１２の独立気泡率が低くなる虞もある。
【００５８】
発泡成形体の発泡層１２の密度は２０〜５００ｋｇ／ｍ³が好ましく、さらに好ましくは２０〜４００ｋｇ／ｍ³である。発泡成形体の発泡層１２の密度が５００ｋｇ／ｍ³を超えると軽量とは言い難くなり、また断熱性等の物性が低下する虞がある。また発泡成形体の発泡層１２の密度が２０ｋｇ／ｍ³未満であると、発泡層１２を構成している気泡膜が薄くなるので良好な発泡成形体１を得ることができなくなる虞がある。
【００５９】
尚、発泡成形体の発泡層１２の密度は、発泡成形体１より該発泡層１２の一部を切り出し、発泡成形体の発泡層１２から切り出したサンプルの重量を当該サンプルの外径寸法から求められる体積で除することにより算出される。各層の厚みは、発泡成形体断面（必要に応じて顕微鏡により拡大し、拡大された投影図を用いる）より求めることができる。尚、発泡成形体の部分ごとに発泡成形体の発泡層の密度が異なる場合があるため、発泡成形体の底面、側面等の１０箇所以上から発泡成形体の発泡層１２のサンプルを切出して、各々のサンプルについて密度を測定し、最大値及び最小値を除いた値の算術平均をもって発泡成形体の発泡層１２の密度とする。
【００６０】
また、本発明の発泡成形体１の密度は、概ね２０〜８００ｋｇ／ｍ³であり、好ましくは２５〜４００ｋｇ／ｍ³である。発泡成形体１の密度が８００ｋｇ／ｍ³を超えると軽量性や断熱性が低下する虞がある。また、発泡成形体１の密度が２０ｋｇ／ｍ³未満の場合は圧縮強度等の機械的物性が低下する虞がある。
【００６１】
尚、発泡成形体１の密度は、該成形体を水没させて体積を測定し（但し、発泡成形体内部に空隙部が存在する場合であっても求められる発泡成形体の体積より空隙部の容積を差し引くことはしない）、該発泡成形体１の重量を先に求めた体積で除することにより求める。
【００６２】
本発明において発泡成形体の発泡層１２として形成される、多層パリソン６の発泡層２は、前記例示のポリスチレン系樹脂に発泡剤を含有せしめた発泡性溶融樹脂を押出発泡することにより得られる。発泡剤としては、無機発泡剤、揮発性発泡剤、分解型発泡剤のいずれも使用可能であるが、発泡倍率の高い発泡成形体の発泡層１２を得るには揮発性発泡剤を使用することが好ましい。無機発泡剤としては窒素、二酸化炭素等が挙げられる。揮発性発泡剤としては例えば、プロパン、ノルマルブタン、イソブタン、ノルマルペンタン、イソペンタン、ノルマルヘキサン、イソヘキサン、シクロヘキサン等の脂肪族炭化水素、塩化メチル、塩化エチル等の塩化炭化水素、1,1,1,2-テトラフロロエタン、1,1-ジフロロエタン等のフッ化炭化水素等が挙げられる。分解型発泡剤としては、アゾジカルボンアミド等が挙げられる。上記した発泡剤は、２種以上混合して使用可能であり、又、気泡の調整も兼ねて分解型発泡剤を無機発泡剤や揮発性発泡剤に併用することも可能である。
【００６３】
本発明の発泡成形体１の製造方法の一例を図４に基いて説明する。多層パリソン６を製造するには、図４に示すように、多層パリソン６の各層を形成する基材樹脂をそれぞれ別々の押出機（図示しない）により溶融混練し、これらをダイ２１内で積層合流させながら低圧域に押し出すことで多層パリソン６が得られる。必要に応じて押出機とダイ２１の間もしくはダイ２１内には、アキュームレーターを設置してもよい。
【００６４】
多層パリソン６から発泡成形体１を得るには、多層パリソン６を成形後、図４に示すように、押し出された多層パリソン６を両側面から挟むように分割形式の金型２２ａ、２２ｂを閉鎖する。金型を閉鎖すると、金型内面２３ａ、２３ｂにおいて発泡した多層パリソン６が圧縮されて、偏平状に変形しながら金型内面に密着される。次に、図５に示すように金型を閉鎖することによって、多層パリソン６の内側表面同士の少なくとも一部を融着させてキャビティ内において発泡した多層パリソン６が成形されると、本発明の発泡成形体１が得られる。
【００６５】
また、図４に示すように金型に減圧用配管２４を設けることによって、金型内面２３ａ、２３ｂと多層パリソン６の外表面との間を減圧可能に形成された金型を用い、減圧しながら金型を閉鎖して成形すると、多層パリソン６の外表面と金型内面とがよく密着し、金型形状を良好に再現した発泡成形体１を得ることができ、しかも金型内面に模様を有する金型を使用した場合には、発泡成形体１の表面の金型模様転写性も向上する。
【００６６】
また多層パリソンを押し出した直後、パリソンピンチにより多層パリソンを閉鎖し、プリブローにより膨張させた多層パリソンを上記に示すよう成形してもよい。
【００６７】
また、多層パリソン６を深絞り成形する場合には、図６(a)、（ｂ）に示すように、雌型２２ｂの四方の側面部２５が底面部２６を中心に可動できるように、雌型２２ｂを構成することによって、雌型２２ｂの型組み、展開を可能として、雌型２２ｂが展開した状態から、雌型２２ｂの側面部２５を動かして雌型２２を型組みしながら、雄型２２aと雌型２２ｂを閉鎖して成形することが好ましい。
【００６８】
尚、図４〜図６は発泡成形体の製造例を概念的に示す説明図であり、本発明の発泡成形体を製造する具体的な操作手順は、図４〜図６に図示するものに限定されない。
【００６９】
本発明において、発泡層２と混合樹脂層３、更には重合体層４をダイより押出す際に発泡層２の発泡倍率が高い場合、また、混合樹脂層３及び／又は重合体層４が伸びにくい場合、多層パリソン６をダイから押出した直後に多層パリソン６の先端がめくれてしまう場合がある。この多層パリソン６の先端部のめくれは、多層パリソン先端部において発泡層２が高倍率に発泡するのに対して混合樹脂層３等の伸びが追従できないことから発生する現象であって、多層パリソン射出直後に多層パリソン６の先端部のみに発生するものである。ある程度多層パリソン６を形成する樹脂が押出された後は、多層パリソン６自体の自重により下方向に引っ張られるためめくれは発生しなくなる。
【００７０】
多層パリソン６の先端部にめくれが発生した場合、該めくれが発生した部分は成形に用いることが出来ないため、多層パリソン６を長めに押出して、めくれが発生していない部分だけを成形して必要とする大きさの発泡成形体１を得なければならない。この場合、めくれが発生している部分は大きなバリとなるので、効率が悪いばかりでなく、パリソンの重量増によりドローダウン等の悪影響が発生する。
【００７１】
上記めくれを防止するには、混合樹脂層３や重合体層４の押出開始を発泡層２の押出開始よりも早めて、めくれの無い状態で多層パリソン６先端を形成した後、全層を押出すという方法を採用することができる。又、多層パリソン６の先端がダイから押出された直後に、ダイ下部において多層パリソン６の下方先端を金型の型締め方向に多層パリソン６の外側から押すことによって、多層パリソン６内面の少なくとも一部分を接着させる等の手法を用いることによっても、多層パリソン６先端のめくれを防止することができる。このような手法を採用することによって多層パリソン６先端のめくれを防止すれば、成形ロスを少なくできるので押出した多層パリソンを有効に使用することができる。
【００７２】
本発明においては、上記の通り多層パリソン６を成形型に挟み込んで圧縮して成形することにより発泡成形体１を得ることができる。このような方法にて多層パリソン６を使用して、発泡成形体１を得ることにより、発泡成形体の発泡層１２と発泡成形体の混合樹脂層１３、又は該発泡層１２と該混合樹脂層１３と発泡成形体の重合体層１４との接着性は、良好なものとなり剥離強度を大きくすることができる。また、発泡成形体１の混合樹脂層１３、又は該混合樹脂層１３と発泡成形体の重合体層１４の厚みをより均一なものにすることができ、また発泡成形体の発泡層１３において、発泡倍率がより高いもの、より高厚みのもの、より均一な倍率ものを容易に得られる等の優位性がある。
【００７３】
また、本発明においては、例えば図１（ａ）、図１（ｂ）に示すように、多層パリソン６の内側表面同士を完全に密着させて全部を融着させて成形することが、発泡成形体の内部に空隙がないものとなるので寸法安定性及び機械的物性向上の面で好ましい態様である。該発泡成形体の内側表面の融着割合は、本明細書においては融着部面積比（％）で表され、融着部面積比は寸法安定性及び機械的物性向上の面で、６０％以上のものが好ましく、８０％以上のものがより好ましく、９５％以上のものが特に好ましい。融着部面積比の測定方法は、以下の通りである。
【００７４】
発泡成形体を等間隔で１０等分するように発泡成形体製造時の多層パリソン押出方向に直交し、且つ多層パリソン金型圧縮方向に平行な方向で切断する。
次に、切断した発泡成形体の切断面が発泡成形体を形成していた順番通りに切断面が左右方向に位置するように発泡成形体を置き、各成形体切断片の右側の切断面において発泡成形体を形成するために使用した多層パリソンの内面同士が融着している部分の長さ（ｍｍ）を求め、これを２倍した値を融着部長さをＡ（ｍｍ）とする。更に、該右側の切断面において、該多層パリソンの内面同士が融着していないで空隙部を形成している場合、空隙部の内周長さをＢ（ｍｍ）とする。また、各該切断面において前記融着部長さ及び／又は空隙部が複数存在する場合は各々の箇所について融着部長さ又は空隙部の内周長さを求め、各々の合計をＡ又はＢとする。次に［Ａ／（Ａ＋Ｂ）］×１００にて各該切断面の融着部面積比（％）を求める。尚、空隙部がない状態で発泡成形体の当該面積比は１００％となる。そして各該切断面（但し、該多層パリソンの内面融着部自体が存在しない切断面は除く）の融着部面積比の算術平均値をもって発泡成形体の融着部面積比（％）とする。
【００７５】
本発明の発泡成形体はＪＩＳ Ｋ７２１１にて求められる常温での落錘衝撃試験による５０％破壊エネルギーが１Ｊ以上のものが好ましい。更に、低温での落錘衝撃試験による５０％破壊エネルギーが０．５Ｊ以上、特に０．７Ｊ以上が好ましい。
【００７６】
常温又は低温での落錘衝撃試験における５０％破壊エネルギーは、温度２３℃、湿度５５％の恒温恒湿室又は−４０℃の低温槽で、２４時間放置したサイズ縦１００ｍｍ、横１００ｍｍの発泡成形体から切り出した試験片を、温度２３℃、湿度５５％の恒温恒湿室内にて落錘衝撃試験を行い、ＪＩＳ Ｋ７２１１の計算方法により求める。尚、低温での落錘衝撃試験の場合、各試験片を低温槽から取りだしてから測定までを２秒以内で行う。また試験機は（株）東洋精機製作所製Ｎｏ．６２１落錘衝撃試験機を使用し、使用した重錘はＪＩＳ Ｋ７２１１に規定する呼び球２形（直径６３ｍｍ、質量１ｋｇ）の球形の重錘を用いる。
【００７７】
図１(ａ)、（ｂ）は、本発明の発泡成形体の断面形状の一例を示す図面である。図１(ａ)、（ｂ）に示す発泡成形体は、多層発泡パリソンの発泡層内側表面同士を完全に融着させており、容器空間１５が形成されるように金型で成形した容器状の発泡成形体である。
【００７８】
発泡成形体として容器を得る場合、発泡成形体の密度を３０〜４００ｋｇ／ｍ³とすることにより軽量で、断熱性に優れたものとなり、発泡成形体の混合樹脂層１３の厚み、又は、発泡成形体の混合樹脂層１３と発泡成形体の重合体層１４の厚みとの合計の厚みを２００〜５０００μｍとすることにより、耐久性、表面平滑性が高く、外観と軽量性のバランスのとれた容器を得ることができる。
【００７９】
【実施例】
以下、実施例を挙げて本発明をより詳細に説明する。
実施例１
ポリスチレン系樹脂として汎用ポリスチレン（Ａ＆Ｍスチレン株式会社製スタイロンＧ９８０２）を使用し、更に気泡調整剤としてタルクを０．１６重量％混合したものを押出機に供給して溶融混練し、該溶融樹脂に表１に示す量の発泡剤（イソブタンとノルマルブタンとの重量比３５：６５の混合物）を押出機中に圧入し混練して発泡層を形成するための発泡性溶融物とした。
【００８０】
【表１】

【００８１】
一方、ポオレフィン系樹脂として低密度ポリエチレン（日本ユニカー株式会社製ＮＳ−１）と、ポリスチレン系樹脂として汎用ポリスチレン（Ａ＆Ｍスチレン株式会社製スタイロン６７９）と、更に相溶化剤としてスチレン系熱可塑性エラストマー（旭化成工業株式会社製タフテックＨ１０４１）とを表１に示す配合量で混合したものを別の押出機に供給して溶融混練し、混合樹脂層を形成するための非発泡性溶融物とした。
【００８２】
次いで、各押出機により溶融混練された溶融物を押出機とダイの間に設けた各アキュームレーターに充填し、充填完了後、充填された上記非発泡性溶融物と、上記発泡性溶融物とをダイ内で積層合流するようにアキュームレーターにより射出するとともに、ダイから押し出し、発泡層の外面に混合樹脂層が積層された多層パリソンを得た。
【００８３】
次に、押し出された上記多層パリソンを、ダイ直下に設置された図６に示す多分割形式の金型にて挟むように閉鎖して、キャビティ内面において多層パリソンを偏平状に変形させ、更に金型内を減圧して多層パリソンを金型面内に密着させた。このように金型内において多層パリソンを成形し、更に冷却、離型して発泡成形体を取出した。
尚、上記金型には金型内面に梨地加工が施されたものを使用した。
【００８４】
このようにして得られた発泡成形体（開口部の寸法が縦３００ｍｍ×横２６０ｍｍ、底面部の寸法が縦２６０ｍｍ×横１８０ｍｍ、高さが１１０ｍｍ、肉厚約２０ｍｍの円錐台形の容器状）は、収縮、変形などの見られない外観が良好なものであった。
【００８５】
実施例２〜７
表１に示す基材及び実施例１と同様の発泡剤を用いて、表１に示す配合量で、実施例１と同様に発泡成形体を製造した。このようにして得られた発泡成形体は、収縮、変形などの見られない外観が良好なものであった。
【００８６】
実施例８
表１に示す基材及び実施例１と同様の発泡剤を用いて、表１に示す配合量で、実施例１と同様に発泡層を形成するための発泡性溶融物と、混合樹脂層を形成するための非発泡性溶融物を押出機内において作製した。更に、低密度ポリエチレン（日本ユニカー（株）社製 ８００８）を更に別の押出機に供給して、溶融混練し重合体層を形成するための非発泡性溶融物とした。
【００８７】
上記発泡層を形成するための発泡性溶融物と、上記混合樹脂層を形成するための非発泡性溶融物と、上記重合体層を形成するための非発泡性溶融物とをダイ内で積層合流するように押出機とダイとの間に設けたアキュームレーターにより射出するとともに、ダイから押し出し、発泡層の外面に混合樹脂層を介して非発泡樹脂からなる重合体層が積層された多層パリソンを得た。次に該多層パリソンを、ダイ直下に設置された図６に示す形式の金型を用いて、実施例１と同様に成形、冷却、離型して発泡成形体を製造した。このようにして得られた発泡成形体は、収縮、変形などの見られない外観が良好なものであった。
【００８８】
実施例９〜１２
表１に示す基材及び実施例１と同様の発泡剤を用いて、表１に示す配合量で、実施例８と同様に発泡成形体を製造した。このようにして得られた発泡成形体は、収縮、変形などの見られない外観が良好なものであった。
【００８９】
比較例１
表１に示す基材及び実施例１と同様の発泡剤を用いて、表１に示す配合量で、実施例８と同様に発泡層を形成するための発泡性溶融物と、重合体層を形成するための非発泡性溶融物とを作製し（但し、混合樹脂層は形成せず）、これらをダイ内で積層合流するように押出機とダイとの間に設けたアキュームレーターにより射出するとともにダイから押出し、発泡層の外面に重合体層が積層された多層パリソンを得た。次に、実施例１と同様に発泡成形体を製造した。
【００９０】
このようにして得られた発泡成形体は、収縮、変形などの見られない外観が良好なものであったが、耐油性、耐衝撃性において不十分なものであった。
【００９１】
比較例２
表１に示す基材及び実施例１と同様の発泡剤を用いて、表１に示す配合量で、比較例１と同様に発泡成形体を製造した。しかし、成形体は得られたものの、バリを切り取った切断部分より発泡層と重合体層が界面剥離を起こし、良好な発泡成形体が得られなかった。
【００９２】
比較例３
表１に示す基材及び実施例１と同様の発泡剤を用いて、表１に示す配合量で、実施例１と同様に発泡成形体を製造し、外観が良好な成形体が得られたが、耐油性、耐衝撃性において不十分なものであった。
【００９３】
比較例4
表１に示す基材及び実施例１と同様の発泡剤を用いて、表１に示す配合量で、実施例１と同様に発泡成形体を製造したが、成形体は得られたものの、バリを切り取った切断部分より発泡層と混合樹脂層が界面剥離を起こし、良好な発泡成形体は得られなかった。
【００９４】
比較例５
表１に示す基材及び実施例１と同様の発泡剤を用いて、表１に示す配合量で、混合樹脂層をポリスチレン系樹脂層に変更し、比較例４と同様に発泡成形体を製造した。得られた発泡成形体は、外観は良好であったが、耐油性において不十分なものであった。
【００９５】
比較例６、７
表１に示す基材及び実施例１と同様の発泡剤を用いて、表１に示す配合量で、実施例８と同様に発泡成形体を製造した。成形体は得られたものの、バリを切り取った切断部分より重合体層と発泡層が界面剥離を起こし、良好な発泡成形体は得られなかった。尚、比較例６においては、混合樹脂層と重合体層との間、比較例７においては発泡層と混合樹脂層との間で界面剥離が発生した。
【００９６】
実施例１〜１２、比較例１〜７において得られた発泡成形体の、密度、耐溶剤性、常温及び低温の耐衝撃性、剥離強度を測定した結果を表２に示す。
尚、実施例１〜１２において得られた発泡成形体の融着部面積比は、全て１００％であった。
【００９７】
【表２】

【００９８】
実施例１〜１２、比較例１〜７において使用した各種基材のビカット軟化点、樹脂密度、溶融粘度を表３に示す。又、表１、表３において記号で示した各種基材の種類、製造会社名、グレード名を表４に示す。
【００９９】
【表３】

−：測定せず
【０１００】
【表４】

【０１０１】
表１に示した混合樹脂層のＰＩ値の計算例を、実施例１の場合について以下に示す。
ＰＩ値＝（η_A×φ_B）／（η_B×φ_A）
η_A＝ＰＳ（２）の粘度＝１０１００ ［ｐｏｉｓｅ］
φ_A＝ＰＳ（２）の体積分率
η_B＝ＬＤＰＥ（１）の粘度＝１６１００ ［ｐｏｉｓｅ］
φ_B＝ＬＤＰＥ（１）の体積分率
【０１０２】
ここで、
φ_A＝（Ｗ_A/ρ_A）/（Ｗ_A/ρ_A＋Ｗ_B/ρ_B）
＝（０．４/１．０５）/（０．４/１．０５+０．６/０．９２）
＝０．３７
φ_B＝（Ｗ_B/ρ_B）/（Ｗ_A/ρ_A＋Ｗ_B/ρ_B）
＝（０．６/０．９２）/（０．４/１．０５+０．６/０．９２）
＝０．６３
Ｗ_A＝ＰＳ（２）の表１に示す配合量（重量％）/１００＝０．４
ρ_A＝ＰＳ（２）の樹脂密度＝１．０５
Ｗ_B＝ＬＤＰＥ（１）の表１に示す配合量（重量％）/１００＝０．６
ρ_B＝ＬＤＰＥ（１）の樹脂密度＝０．９２
【０１０３】
従って、
ＰＩ値＝（η_A×φ_B）／（η_B×φ_A）
＝（１０１００×０．６３）/（１６１００×０．３７）
＝１．０７
となる。
【０１０４】
尚、本明細書における溶融粘度は、内径が１ｍｍ、長さが１０ｍｍのオリフィスを取付けたチアスト社製「レオビス２１００」を使用して、剪断速度１００ｓｅｃ^-1、樹脂温度１８０℃の条件下で測定した値である。
【０１０５】
表２中の発泡成形体の評価は以下の通りに行なった。
【０１０６】
融着性
多層パリソンを金型に挟んで成形した後、金型より取出し、バリを取り除いたバリ切断部分より発泡成形体の発泡層と発泡成形体の混合樹脂層、又は発泡成形体の混合樹脂層と発泡成形体の重合体層との間において界面剥離が起こり、良好な発泡成形体が得られないものを×、バリ切断部がきちんと融着しており、良好なものを○として評価した。
【０１０７】
耐溶剤性
耐溶剤性は得られた容器内にトルエンを注ぎ、２４時間放置後、発泡成形体の発泡層に穴開きの無いものを○、発泡成形体の発泡層が溶解しているものを×として評価した。
【０１０８】
常温耐衝撃性
常温耐衝撃性は得られた容器から切り出した試験片を、２３℃、湿度５５％の恒温恒湿室の中で２４時間放置した後、ＪＩＳ Ｋ７２１１に準拠して重さ１ｋｇの球形重錘を自由落下させ５０％破壊エネルギーを求め以下の基準にて評価した。
○：５０％破壊エネルギー１Ｊが以上
×：５０％破壊エネルギーが１Ｊ未満
【０１０９】
低温耐衝撃性
低温耐衝撃性は得られた容器から切り出した試験片を-20℃の保冷庫の中で24時間放置したのち取出し、取出してから２秒以内に、ＪＩＳ Ｋ７２１１に準拠して重さ１ｋｇの球形重錘を自由落下させ５０％破壊エネルギーを求め以下の基準にて評価した。
：５０％破壊エネルギーが０．７Ｊ以上
△：５０％破壊エネルギーが０．５Ｊ以上０．７Ｊ未満
×：５０％破壊エネルギーが０．５Ｊ未満
【０１１０】
耐熱性
95℃のオーブン内に24時間放置し、取出し後目視により極端な変形の無いものは耐熱性が良好（○）と評価した。
【０１１１】
【発明の効果】
本発明は、ポリスチレン系樹脂発泡層の外面に（１）ポリスチレン系樹脂２０〜８０重量％と、（２）ポリオレフィン系樹脂又はポリエステル系樹脂２０〜８０重量％との混合物（但し、（１）と（２）との合計は１００重量％）からなる混合樹脂層を有する多層パリソンを、該パリソンの内側表面同士が少なくとも一部において融着するように成形型にて成形して得るという構成を採用したことにより、半成形品を製造後、発泡体を注入する複雑な工程を経ることなくポリスチレン系樹脂発泡成形体を製造することができる。又、本発明によれば、特殊な接着剤を用いないでも、ポリスチレン系樹脂発泡層にポリオレフィン系樹脂又はポリエステル系樹脂と、ポリスチレン系樹脂との混合物からなる層を積層し一体化することができるので、外観が奇麗であり、軽量性、機械的強度、断熱性、緩衝性、防振性、耐油性、耐衝撃性等に優れた多層ポリスチレン系樹脂発泡成形体を提供することができる。又、該発泡成形体を粉砕し溶融して回収し、混合樹脂層等の原料としてリサイクルすることができる。
【０１１２】
本発明の多層ポリスチレン系樹脂発泡成形体は、ポリスチレン系樹脂発泡層の外側に、一定配合の混合樹脂層を介してポリオレフィン系樹脂層が積層されている多層パリソンを、該パリソンの内側表面同士が少なくとも一部において融着するように金型にて成形するという構成を包含する。従って、上記ポリオレフィン系樹脂として高密度ポリエチレンや直鎖状ポリエチレンを使用すれば、前記の効果に加え、低温における耐衝撃性に優れた多層ポリスチレン系樹脂発泡成形体を提供することができる。又、上記ポリオレフィン系樹脂として高密度ポリエチレンやポロプロピレン系樹脂を使用すれば、前記の効果に加え、耐熱性に優れた多層ポリスチレン系樹脂発泡成形体を提供することができる。
【０１１３】
本発明の多層ポリスチレン系樹脂発泡成形体は、ポリスチレン系樹脂発泡層の外側に、一定配合の混合樹脂層を介してポリエステル系樹脂層が積層されている多層パリソンを、該パリソンの内側表面同士が少なくとも一部において融着するように金型にて成形するという構成をも包含する。かかる構成を採用すると、
前記の効果に加え、ガスバリヤー性に優れた多層ポリスチレン系樹脂発泡成形体を提供することができる。
【０１１４】
本発明の多層ポリスチレン系樹脂発泡成形体は、床やドアなどの軽量断熱パネル、ピラーやバンパー、インスツルメントパネルなどの自動車部材、パレット、容器、机、いす、フロート、サーフボード等に利用でき、特にリターナブル容器として好適である。
【図面の簡単な説明】
【図１】図１（ａ）は、発泡層の外面に混合樹脂層を有する本発明の多層ポリスチレン系樹脂発泡成形体の一例を示す縦断面図である。図１（ｂ）は、発泡層の外側に混合樹脂層を介して重合体層を有する本発明の多層ポリスチレン系樹脂発泡成形体の一例を示す縦断面図である。
【図２】図２(ａ)は、発泡層の外面に混合樹脂層を有する多層パリソンの説明図である。図２（ｂ）は、発泡層の外側に混合樹脂層を介して重合体層を有する多層パリソンの説明図である。
【図３】図３は、ポリエステル系樹脂の半結晶化時間を求めるグラフである。
【図４】図４は、本発明発泡成形体の製造方法の一例を説明するための説明図である。
【図５】図５は、本発明発泡成形体の製造方法の一例を説明するための説明図である。
【図６】図６（ａ）は、本発明発泡成形体の製造方法の異なる態様の一例を説明するための説明図である。図６（ｂ）は、本発明発泡成形体の製造方法の異なる態様の一例を説明するための説明図である。
【符号の説明】
１ 多層ポリスチレン系樹脂発泡成形体
２ ポリスチレン系樹脂発泡層
３ 混合樹脂層
４ 重合体層
６ 多層パリソン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer polystyrene-based resin foam molded article used for lightweight insulation panels such as floors and doors, pallets, containers, automobile members and the like.
[0002]
[Prior art]
2. Description of the Related Art Various types of multilayer resin foam molded products in which a thermoplastic resin layer is laminated on the surface of a resin foam layer have been known. As this type of molded body, for example, a molded body having a hollow structure is molded with a thermoplastic resin, and a urethane resin is injected into a cavity inside the molded body or a resin foam particle is filled and molded. There are molded foamed articles (Japanese Patent Publication No. 58-10217, Japanese Patent Laid-Open No. 6-339979, etc.). However, these methods have the problem that the molding of the resin layer on the surface and the formation of the internal foamed layer are separate processes, which complicates the molding process and requires a special molding machine. As a result, the foamed molded article molded by these methods was expensive.
[0003]
Also proposed is a multilayer resin foam molded article obtained by a method in which a hollow multilayer parison having a thermoplastic resin layer on the surface of a resin foam layer is molded while being compressed with a mold and the opposing inner surfaces of the parison are fused. (Japanese Patent Publication No. 62-27978, Japanese Patent Laid-Open No. 6-31449, etc.).
[0004]
However, in the method of molding while compressing the multilayer parison with the above-mentioned mold, the combination of the resin that constitutes the non-foamed resin layer and the resin that constitutes the resin foam layer does not exhibit good adhesion When employed, the molded body obtained by molding the multi-layer parison with the mold by this method is removed from the mold and the burrs are removed. Thus, there has been a problem that the resin foam layer and the non-foam resin layer are easily separated. This is because the resin constituting the resin foam layer can be increased in magnification and thickness, and a polystyrene resin superior in heat insulation and versatility is selected, and the heat resistance, impact characteristics, and oil resistance of the polystyrene resin are selected. When polyolefin resin etc. were selected as resin which comprises a non-foamed resin layer in order to improve property, it appeared notably.
[0005]
The above problem can be solved by adhering a foamed resin layer of polystyrene resin and a non-foamed resin layer of polyolefin resin or the like with an adhesive layer of one-component urethane or the like interposed therebetween. However, a molded article having such a configuration is not economical because it cannot be used as a recycled resin for the same product even when melt-kneaded again, and is not suitable for actual production. Furthermore, depending on the type of the adhesive layer, there is also a problem of odor, so that it cannot be adopted in actual production.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a multilayer polystyrene-based resin foam molded article that does not require a complicated process of injecting a foam after producing a semi-molded product in view of the above-mentioned drawbacks of the prior art. The present invention also provides a polystyrene resin foam layer, a layer made of a polyolefin resin, a layer made of a polyester resin, a polyolefin resin or a mixture of a polyester resin and a polystyrene resin without using a special adhesive. Multi-layer polystyrene with a beautiful appearance and excellent lightness, mechanical strength, heat insulation, shock-absorbing properties, vibration resistance, oil resistance, impact resistance, recyclability, etc. An object of the present invention is to provide a resin-based foamed molded article.
[0007]
[Means for Solving the Problems]
The multilayer polystyrene resin foam molded article of the present invention is formed by molding a multilayer parison having a mixed resin layer on the outer surface of the polystyrene resin foam layer with a molding die so that the inner surfaces of the parison are fused at least partially. The mixed resin layer is a mixture of (1) 20 to 80% by weight of a polystyrene resin and (2) 20 to 80% by weight of a polyolefin resin or a polyester resin (provided that ( The sum of 1) and (2) is 100% by weight). It is preferable that the peel strength between the polystyrene-based resin foam layer and the mixed resin layer of the foam molded article is 100 (gf / 25 mm) or more.
[0008]
Further, the present invention provides a mixture of (3) 20 to 80% by weight of polystyrene resin and (4) 20 to 80% by weight of polyolefin resin (however, (3) and (4 ) And a multi-layer parison having a polyolefin resin layer laminated via a mixed resin layer consisting of 100% by weight) in a mold so that the inner surfaces of the parison are fused at least partially. It includes a multilayer polystyrene-based resin foam molded article obtained by molding. The polyolefin-based resin layer of the foam-molded product is preferably made of a polyolefin-based resin having a Vicat softening point of 112 ° C. or higher, and the peel strength between the polystyrene-based resin foam layer and the polyolefin-based resin layer of the foam-molded product is 100 (gf / 25 mm) or more.
[0009]
Further, the present invention provides a mixture of (5) 20 to 80% by weight of a polystyrene resin and (6) 20 to 80% by weight of a polyester resin (however, (5) and (6 ) With a molding die so that the inner surfaces of the parison are fused at least in part to each other through a mixed resin layer consisting of 100% by weight). A multilayer polystyrene resin foam molded article obtained by molding is also included. The polyester-based resin layer of the foam-molded product is preferably made of a polyester-based resin having a half-crystallization time of 30 minutes or more, and the peel strength between the polystyrene-based resin foam layer and the polyester-based resin layer of the foam-molded product is 100 (gf / 25 mm) or more.
[0010]
The polystyrene resin foam layer of the multilayer polystyrene resin foam molded article is preferably made of a polystyrene resin having a Vicat softening point of 110 ° C. or higher.
[0011]
The phase structure index PI value representing the mixed state of the mixture of the polystyrene resin constituting the mixed resin layer of the multilayer polystyrene resin foamed molded article and the polyolefin resin or the polyester resin is 0.7 <PI value. <1.3 is preferred.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. Fig.1 (a) is a longitudinal cross-sectional view which shows an example of the multilayer polystyrene-type resin foaming molding of this invention which has a mixed resin layer in the outer surface of a foaming layer, Comprising: FIG.1 (b) is on the outer side of a foaming layer. It is a longitudinal cross-sectional view which shows an example of the multilayer polystyrene-type resin foaming molding of this invention by which the polyolefin-type resin layer or the polyester-type resin layer etc. are laminated | stacked through the mixed resin layer. 1 (a) and 1 (b), 1 is a multi-layer polystyrene resin foam molding (hereinafter referred to as "foam molding"), and 12 is a polystyrene resin foam layer (hereinafter referred to as "foam molding") of the foam molding. 1 is a mixed resin layer of the foam molded body, 14 in FIG. 1B is a polyolefin resin layer or a polyester resin layer of the foam molded body (hereinafter referred to as “foam molded body”). Of the polymer layer)).
As shown in FIGS. 1A and 1B, the foam molded body 1 has a foam layer 12 of the foam molded body and a mixed resin layer 13 of the foam molded body covering the entire surface of the foam layer 12.
[0013]
The foam molded body 1 is formed by compressing a multilayer parison having a mixed resin layer on the outer surface of a polystyrene-based resin foam layer with a mold such as a mold. The multi-layer parison has a tubular shape or other hollow shape, and has a shape that can perform the same or similar function as that preformed so that air can be blown in between a mold by blow molding or the like. is there.
[0014]
An example of the multilayer parison in the present invention is shown in FIGS. FIG. 2 (a) is an explanatory view of a multilayer parison having a mixed resin layer on the outer surface of a polystyrene resin foam layer, and FIG. 2 (b) is a polyolefin-based polymer film via a mixed resin layer outside the polystyrene resin foam layer. It is explanatory drawing of the multilayer parison which has a resin layer or a polyester-type resin layer. 2 (a) and 2 (b), 6 is a multilayer parison, 2 is a polystyrene-based resin foam layer (hereinafter referred to as "foam layer"), 3 is a mixed resin layer, and 4 in FIG. 2 (b). Indicates a polyolefin resin layer or a polyester resin layer or the like (hereinafter referred to as “polymer layer”) provided as necessary.
The mixed resin layer 3 and the polymer layer 4 are non-foamed or have a density of 0.4 g / cm. ^Three The above foam or inorganic-filled non-foam is preferably used.
[0015]
In the present invention, the foam molded body 1 has a foam layer 12 of the foam molded body 1 as shown in FIGS. 1A and 1B, and the foam layer 12 corresponds to the foam layer 2 of the multilayer parison 6. To do. The foam molded body 1 has a skin covering the entire surface of the foam layer 12 of the molded body, and the skin is basically a mixed resin layer 13 of the foam molded body or a weight of the mixed resin layer 13 and the foam molded body. The composite resin layer 13 of the foam molded article corresponds to the mixed resin layer 3 of the multilayer parison 6, and the polymer layer 14 of the foam molded article corresponds to the polymer layer 4 of the multilayer parison 6. It is.
[0016]
The polystyrene resin used for the polystyrene resin foam layer 2 includes a styrene homopolymer and a copolymer, and the styrene monomer unit contained in the polymer is at least 25% by weight, preferably 50% by weight. That's it.
[0017]
A preferred polystyrene-based resin used in the present invention is a resin containing at least 25% by weight of a structural unit represented by the following general formula (1) in the resin.
[Chemical 1]

In the general formula (1), R represents a hydrogen atom or a methyl group, Z represents a halogen atom or a methyl group, and p is 0 or an integer of 1 to 3.
[0018]
Examples of the polystyrene resin include polystyrene, rubber-modified polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, and styrene-methyl methacrylate. Copolymer, styrene-ethyl methacrylate copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-maleic anhydride copolymer, polystyrene-polyphenylene ether copolymer, polystyrene and Examples thereof include a mixture with polyphenylene ether.
[0019]
For the purpose of improving the brittleness of the foamed layer 2 and the like, the polystyrene resin is a blend of a styrene-conjugated diene block copolymer or a hydrogenated product thereof preferably in a proportion of less than 30% by weight, a polypropylene resin, What blended polyolefin resin, such as high density polyethylene, preferably in the ratio below 20 weight% can also be used.
[0020]
In the present invention, it is preferable to improve the heat resistance of the foamed molded article 1 by using a polystyrene resin having a Vicat softening point of 110 ° C. or higher for the foamed layer 2.
In the present specification, the Vicat softening point of the resin refers to a value obtained by JIS K7206 (test load is the method A, and the heating rate of the heat transfer medium is 50 ° C./hour).
[0021]
The polystyrene resin used for the foamed layer 2 of the present invention has a melt viscosity of 190 ° C. and a shear rate of 100 sec. ^-1 Under the above conditions, it is 200 poise or more and less than 100,000 poise, preferably 1000 to 50000 poise. If the melt viscosity is smaller than the above range, the molten resin extruded from the die during foaming may sag and it may be difficult to obtain the foamed layer 2. On the other hand, if it exceeds the above range, the viscosity is too high, the extrusion pressure rises and extrusion foam molding becomes difficult, and there is a possibility that a good quality foam layer 2 cannot be obtained.
[0022]
The polystyrene resin used for the foamed layer 2 of the present invention has a melt flow rate of preferably 0.8 to 30 g / 10 minutes and a melt tension of 5 to 40 gf, more preferably 200 ° C. and a load of 5 kgf. 1.0 to 10 g / 10 min and a melt tension of 8 to 35 gf are preferable in terms of preventing the drawdown of the multilayer foamed parison 6 and increasing the magnification and thickness of the foamed layer 2. It has an excellent effect in preventing the occurrence of Examples of such a polystyrene resin include a polystyrene resin having a branched structure.
[0023]
The resin used for the mixed resin layer 3 is preferably composed mainly of a mixture of a polystyrene resin and a polyolefin resin or a polyester resin, and the mixture is preferably 60% by weight or more.
[0024]
Examples of the polystyrene-based resin used for the mixed resin layer 3 include the same resins as the above-mentioned polystyrene-based resin constituting the foamed layer 2. However, the polystyrene resin used for the mixed resin layer 3 does not have to be the same as the polystyrene resin used for the foam layer 2, and the melt viscosity and melt flow rate of the polyolefin resin or polyester resin to be mixed In relation, it selects suitably from said polystyrene-type resin.
[0025]
Examples of the polyolefin resin used in the mixed resin layer 3 include polyethylene resins such as low density polyethylene, high density polyethylene, and linear low density polyethylene, polypropylene, propylene-ethylene random copolymer, and propylene-1 butene random copolymer. Examples thereof include one or a mixture of two or more selected from a polymer, a polypropylene resin such as a propylene-ethylene-butene random copolymer, a propylene-ethylene block copolymer, and a cyclic polyolefin.
[0026]
The polyolefin resin used for the mixed resin layer 3 preferably has a Vicat softening point of 112 ° C. or higher in terms of heat resistance, more preferably has a softening point of 120 ° C. or higher, specifically, a polypropylene resin, High density polyethylene resin is preferred.
The upper limit of the Vicat softening point is not particularly limited, but is about 165 ° C.
[0027]
The polyester resin used for the mixed resin layer 3 is one or two or more selected from polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, a copolyester of terephthalic acid, ethylene glycol, and cyclohexanedimethanol, and the like. A mixture is mentioned. In particular, copolyester resins having a semi-crystallization time of 30 minutes or more, such as the product names “Easter PETG6763” and “Easter PETG5011” manufactured by Eastman Chemical Co., Ltd., are used as the raw material for the foamed layer and / or the mixed resin layer. It is preferable because it can be recycled.
[0028]
The half crystallization time said in this specification is measured using the MK-801 type | mold crystallization rate measuring instrument by Metron Co., Ltd. (former Kotaki Shoji Co., Ltd.). The crystallization rate measuring device is a device for obtaining the crystallinity from the relationship between crystallization of a sample and birefringence of light.
[0029]
The half-crystallization time was measured in advance by preparing a 15 × 15 mm square film having a thickness of 0.1 ± 0.02 mm and sandwiching the film between microscope cover glasses as a measurement sample. After heating to ° C., it is put into a crystallization bath set to 100 ° C., and the brightness indicator value of the light source lamp is set to 3 V and measured.
[0030]
The half crystallization time referred to in this specification is obtained by reading the value A in which the amount of light due to birefringence is constant from the vertical axis on the graph from the curve on the graph shown in FIG. A value C on the curve corresponding to the value B on the vertical axis on the graph multiplied by 0.5 is read, and the value D is obtained as the value D on the horizontal axis on the graph corresponding to C. In FIG. 3, E is the crystallization bath set temperature, and the broken line (II) is the crystallization bath temperature.
[0031]
A mixture comprising a polystyrene resin constituting the main component of the mixed resin layer 3 and a polyolefin resin or a polyester resin comprises (1) 20 to 80% by weight of a polystyrene resin and (2) a polyolefin resin or a polyester resin. It is preferably a mixture of 20 to 80% by weight (provided that the total of (1) and (2) is 100% by weight), (1) 40 to 80% by weight of polystyrene-based resin, and (2) polyolefin-based A resin or a mixture of 20 to 60% by weight of a polyester-based resin (however, the total of (1) and (2) is 100% by weight) such as adhesion to the foamed layer, oil resistance of the mixed resin layer, etc. It is more preferable in terms of surface.
[0032]
When the polystyrene resin in the mixture constituting the mixed resin layer 3 is less than 20% by weight, the adhesion between the foamed layer 2 and the mixed resin layer 3 becomes insufficient, and after the multilayer parison 6 is molded, The foamed layer 12 of the foamed molded product and the mixed resin layer 13 of the foamed molded product cause interfacial peeling from the cut portion from which the burrs are cut, and a good foamed molded product cannot be obtained.
[0033]
On the other hand, when the polystyrene resin exceeds 80% by weight, the adhesiveness between the foamed layer 2 and the mixed resin layer 3 is satisfied, but the polystyrene resin constituting the mixed resin layer 3 on the outside of the mixed resin layer 3 and Even when the polymer layer 4 composed of a mixed polyolefin-based resin or polyester-based resin and a polymer exhibiting thermal adhesiveness that can withstand practical use is provided, the adhesion between the polymer layer 4 and the mixed resin layer 3 is After forming the multi-layer parison 6, the polymer layer 14 of the foamed molded product and the mixed resin layer 13 of the foamed molded product cause interfacial delamination from the cut part from which the burr was cut off. Don't be. On the other hand, when the polystyrene-based resin exceeds 80% by weight, the functional aspect such as oil resistance is insufficient.
[0034]
A compatibilizing agent can be added to the mixed resin layer 3 of the present invention. The compatibilizing agent may be any one that can compatibilize a polystyrene resin and a polyolefin resin or a polyester resin, and various conventionally known ones can be used, and in particular, a styrene thermoplastic elastomer. And styrene-olefin copolymers are preferred. The styrenic thermoplastic elastomer includes SBS type or SIS type, SEBS type or SEPS type.
[0035]
The SBS-based or SIS-based one has a polystyrene crystal phase as a hard segment, and has a structure in which polybutadiene or polyisoprene is block-copolymerized as a soft segment.
On the other hand, the SEBS and SEPS systems are those obtained by highly hydrogenating polybutadiene and polyisoprene contained in the SBS and SIS systems to saturate double bonds in the main chain. . The SEBS type, SEPS type, SBS type and SIS type styrene type thermoplastic elastomers are described in detail in “Plastic Age”, pages 101 to 106 (June 1985).
[0036]
The styrene-olefin copolymer includes ethylene / styrene graft copolymer, propylene / styrene graft copolymer, ethylene / glycidyl methacrylate copolymer / styrene graft copolymer, ethylene / ethyl acrylate copolymer. Graft copolymer of polymer and styrene, graft copolymer of ethylene-vinyl acetate copolymer and styrene, graft copolymer of ethylene-ethyl acrylate-maleic anhydride copolymer and styrene, graft copolymer of ethylene and methyl methacrylate Polymer, ethylene-glycidyl methacrylate copolymer and methyl methacrylate graft copolymer, ethylene-ethyl acrylate copolymer and methyl methacrylate graft copolymer, ethylene-vinyl acetate copolymer and methyl methacrylate group Copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer and methyl methacrylate graft copolymer, ethylene-acrylonitrile-styrene copolymer graft copolymer, propylene-acrylonitrile-styrene copolymer graft copolymer Polymer, graft copolymer of ethylene-glycidyl methacrylate copolymer and acrylonitrile-styrene copolymer, graft copolymer of ethylene-ethyl acrylate copolymer and acrylonitrile-styrene copolymer, ethylene-vinyl acetate copolymer And acrylonitrile-styrene copolymer graft copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer and acrylonitrile-styrene copolymer graft copolymer, and styrene-ethylene random copolymer, Styrene - propylene random copolymer and the like.
[0037]
The compatibilizing agent is preferably added in an amount of 0.1 to 40 parts by weight, preferably 0.5 to 10 parts by weight, per 100 parts by weight of the mixture of polystyrene resin and polyolefin resin or polyester resin. . In particular, in the case of a styrene-based thermoplastic elastomer, it is preferably added at a ratio of 2 to 30 parts by weight.
[0038]
Addition of a compatibilizing agent composed of the styrene thermoplastic elastomer improves the adhesion between the polystyrene resin foam layer 2 and the mixed resin layer 3, and further improves the impact strength and brittleness of the foam molded article 1 of the present invention. Is done. Further, when the polymer layer 4 is provided outside the mixed resin layer 3, the adhesion between the mixed resin layer 3 and the polymer layer 4 is also improved.
[0039]
The melt flow rate of the mixture used for the mixed resin layer 3 is preferably 0.15 to 30 (g / 10 minutes), more preferably 0.5 to 12 (g / 10 minutes). In consideration of the plasticizing effect obtained by mixing a foaming agent with the polystyrene resin in the same degree as the melt flow rate of the polystyrene resin used for the layer 2, it is generally “polystyrene” than the melt flow rate of the polystyrene resin. It is preferable to select a resin resin with a slightly higher value, with the upper limit of the melt flow rate of the resin +10 (g / 10 minutes).
The melt flow rate of the mixture is a value measured under conditions of 200 ° C. and a load of 5 kgf.
[0040]
If the melt flow rate of the mixture is too low, the flowability in the die is poor, so that the surface smoothness of the multilayer parison 6 may be deteriorated, and in some cases, melt fracture may occur. Moreover, since heat generation within the die also increases, there is a possibility that the temperature of the resin rises, the cell structure of the laminated foam layer 2 is destroyed, and the closed cell rate decreases. On the other hand, if the melt flow rate of the mixture is too high, the melt tension is generally lowered and the drawdown is increased, so that it becomes difficult to produce a large multilayer parison 6 and a large foamed molded product may not be obtained. There is. In addition, since the foaming force of the bubbles in the foamed layer 2 is large, the bubbles may float on the mixed resin layer 3 and the surface of the mixed resin layer 3 may become uneven, resulting in a deterioration in appearance.
[0041]
Examples of the polymer used for the polymer layer 4 include polyethylene resins such as low density polyethylene, high density polyethylene, and linear low density polyethylene, polypropylene, propylene-ethylene random copolymer, propylene-1 butene random copolymer. Polypropylene resin such as coalescence, propylene-ethylene block copolymer, propylene-1 butene block copolymer, cyclic polyolefin, polycarbonate resin, polyester resin, styrene thermoplastic elastomer, olefin thermoplastic elastomer, polyester heat The thermoplastic polymer which consists of 1 type, or 2 or more types of mixtures selected from a plastic elastomer etc. is mentioned. And the single layer or multiple layer polymer layer 4 which consists of these polymers needs to have thermal adhesiveness with the mixed resin layer 3 in the lamination | stacking surface with the mixed resin layer 3. FIG.
[0042]
Among the above thermoplastic polymers, polyolefin resins and polyester resins are preferable, polypropylene resins are preferable in terms of heat resistance and impact resistance at normal temperature, and linear resins are in terms of impact resistance under low temperature conditions. Low density polyethylene is preferred, high density polyethylene is preferred in terms of heat resistance and impact resistance under low temperature conditions, and polyester resins are preferred in terms of gas barrier properties and impact resistance at room temperature.
[0043]
In the foam molded article 1 of the present invention, the peel strength between the foam layer 12 of the foam molded article and the mixed resin layer 13 of the foam molded article is preferably 100 (gf / 25 mm) or more, and 150 (gf / 25 mm) or more, more preferably having a large peel strength of 200 (gf / 25 mm) or more.
Further, in the foam molded body 1 in which the polymer layer 14 of the foam molded body is laminated on the outside of the foam layer 12 of the foam molded body via the mixed resin layer 13 of the foam molded body, the foam layer 12 and the weight The peel strength between the combined layers 14 is preferably 100 (gf / 25 mm) or more, more preferably 150 (gf / 25 mm) or more, and a large peel strength of 200 (gf / 25 mm) or more. It is particularly preferred. The upper limit of the peel strength is not particularly limited, but is usually about 3000 (gf / 25 mm). The foamed molded article having such a large delamination strength was first developed by the present inventors.
[0044]
When the adhesive strength is less than 100 (gf / 25 mm), when the multilayer parison 6 is molded with a mold, the foam layer 12 of the foam molded body and the mixed resin layer 13 of the foam molded body or the foam molded body The mixed resin layer 13 and the polymer layer 14 of the foamed molded product are peeled off, or after forming the multilayer parison 6, the foamed layer 12 of the foamed molded product and the mixed resin layer of the foamed molded product are cut from the cut portions from which burrs are cut off. 13 or the mixed resin layer 13 of the foam-molded product and the polymer layer 14 of the foam-molded product may cause interfacial peeling.
[0045]
In this specification, the peel strength between the foamed layer 12 of the foamed molded product and the mixed resin layer 13 of the foamed molded product was cut out from the obtained foamed molded product 1 to a JIS Z0237. This is a value (gf / 25 mm) obtained by measurement in a 90 ° peel test under a peel speed condition of 300 mm / min. Further, in the case of the foam molded body 1 having the mixed resin layer 13 of the foam molded body and the polymer layer 14 of the foam molded body, a test piece similar to the above test piece is cut out from the foam molded body 1 and foamed by the upper grip. Only the polymer layer 14 of the molded body is pulled and a peel test is performed in the same manner as described above, and the foamed layer 12 of the foamed molded body and the mixed resin layer 13 of the foamed molded body, or the mixed resin layer 13 of the foamed molded body and the foamed molded body It is the value (gf / 25mm) which calculated | required the intensity | strength which any one of between the polymer layers 14 peels.
[0046]
However, if it is not possible to cut out a strip-shaped test piece with a width of 25 mm, cut the strip-shaped test piece as wide as possible and perform the above-mentioned peel test, find the peel strength per width of the cut-out test piece, the value Is multiplied by “25 / coefficient of cut-out test piece width (mm)” to obtain a peel strength per 25 mm width (gf / 25 mm).
[0047]
As a method for increasing the delamination strength of the foamed molded article 1 of the present invention as described above, the phase structure index PI value representing the mixed state of the mixture constituting the mixed resin layer 3 of the multilayer parison 6 is 0.7. The adjustment should be made to be within the range of more than 1.3 and preferably in the range of 0.8 to 1.2.
[0048]
The phase structure index PI value of the mixed resin layer indicates a mixed state of the polystyrene resin of the mixed resin layer and the polyolefin resin or the polyester resin, and is defined by the following formula (7).
[Expression 1]
PI value = (η _A × φ _B ) / (Η _B × φ _A ............ (7)
[0049]
In the above equation (7), φ _A Is the volume fraction of the polystyrene resin phase in the mixed resin layer, η _A 180 ° C, shear rate 100 sec ^-1 Melt viscosity of polystyrene resin at _B Is the volume fraction of the polyolefin resin phase or polyester resin phase in the mixed resin layer, η _B 180 ° C, shear rate 100 sec ^-1 It is the melt viscosity of polyolefin resin or polyester resin.
[0050]
According to the study by the present inventors, when the PI value of the mixed resin layer 3 becomes 0.7 or less, the polyolefin resin or the polyester resin in the mixed resin layer 3 is covered with the polystyrene resin and bonded to the surface. Although the peel strength between the foam layer 12 of the foam molded body and the mixed resin layer 13 of the foam molded body shows a high value, the oil resistance, impact strength, etc. of the foam molded body 1 are insufficient. There is a risk of becoming.
[0051]
Further, when a polyolefin resin layer or a polyester resin layer is provided outside the mixed resin layer 13 of the foam molded article, the peel strength between those layers becomes insufficient, and a container obtained by molding the multilayer parison 6 with a mold, etc. In the foamed molded product, the mixed resin layer 13 of the foamed molded product and the polymer layer 14 of the foamed molded product can be easily peeled from the portion where the burr of the foamed molded product is cut off.
[0052]
On the other hand, when the PI value is 1.3 or more, the polystyrene resin in the mixed resin layer 3 is covered with the polyolefin resin or the polyester resin, and is difficult to be exposed on the adhesive surface. The peel strength of the foamed molded product from the foamed layer 12 becomes insufficient, and in the molded product such as a container obtained from the multi-layer parison 6, the foamed layer 12 of the foamed molded product and the foamed molded product from the portion where the burr of the foamed molded product is cut off. The problem that the mixed resin layer 13 of the body easily peels off easily occurs.
[0053]
After all, when the PI value is in the range of more than 0.7 and less than 1.3, in the foam molded body 1 formed from the multilayer parison 6 having the mixed resin layer 3 on the outer surface of the foam layer 3, In the foamed molded product 1 having a high peel strength between the foamed layer 12 and the mixed resin layer 13 of the foamed molded product, and further having a polymer layer 14 of the foamed molded product on the outer side, the foamed layer of the foamed molded product. The peel strength between 12 and the polymer layer 14 of the foamed molded article made of a polyolefin resin layer or a polyester resin layer is high and excellent.
[0054]
In the foamed molded product 1 of the present invention, a metal layer, a fiber layer such as a nonwoven fabric or a woven fabric, and the like can be provided further outside the mixed resin layer 13 of the foamed molded product or the polymer layer 14 of the foamed molded product.
[0055]
In addition, the foamed layer 2, the mixed resin layer 3, and the polymer layer 4 of the multilayer parison 6 are composed of a bubble adjusting agent, an infrared absorber, an infrared reflector, a flame retardant, a fluid, and the resin or polymer constituting the layers. Various additives such as property improvers, weathering agents, colorants, heat stabilizers, antioxidants, fillers, and rubbers may be appropriately blended as necessary. Moreover, as the polymer layer 4, it is preferable to use high melt tension polypropylene or high density polyethylene because the foamed molded article 1 having a good appearance can be obtained.
[0056]
Moreover, it is preferable to use an olefin-based thermoplastic elastomer or a styrene-based thermoplastic elastomer as the polymer layer 4 since the impact resistance of the obtained foamed molded body 1 is further improved.
[0057]
The thickness of the skin composed of only the mixed resin layer 13 of the foam molded body covering the foam layer 12 of the foam molded body of the present invention or the mixed resin layer 13 of the foam molded body and the polymer layer 14 of the foam molded body is 100 μm to 10 mm. Is more preferable, and it is 100 micrometers-7 mm. When the thickness of the epidermis is less than 100 μm, the surface smoothness is lowered, so that the surface appearance of the foam molded article 1 may be inferior. Further, if the thickness of the skin exceeds 10 mm, the weight of the entire foam molded body 1 becomes heavy, so that it may be difficult to say that it is lightweight depending on the application, and the closed cell ratio of the foam layer 12 of the foam molded body may be low. There is also.
[0058]
The density of the foam layer 12 of the foam molded product is 20 to 500 kg / m. ^Three Is more preferable, and 20 to 400 kg / m is more preferable. ^Three It is. The density of the foam layer 12 of the foam molded article is 500 kg / m. ^Three If it exceeds 1, it is difficult to say that it is lightweight, and physical properties such as heat insulation may be deteriorated. The density of the foamed layer 12 of the foamed molded product is 20 kg / m. ^Three If it is less than the range, the cell membrane constituting the foamed layer 12 becomes thin, and there is a possibility that a good foamed molded article 1 cannot be obtained.
[0059]
The density of the foamed layer 12 of the foamed molded product is obtained by cutting out a part of the foamed layer 12 from the foamed molded product 1 and obtaining the weight of the sample cut out from the foamed layer 12 of the foamed molded product from the outer diameter of the sample. It is calculated by dividing by the volume obtained. The thickness of each layer can be obtained from a cross section of the foamed molded body (enlarged with a microscope as necessary and use an enlarged projection view). In addition, since the density of the foamed layer of the foamed molded product may be different for each part of the foamed molded product, cut out a sample of the foamed layer 12 of the foamed molded product from more than 10 locations such as the bottom and side surfaces of the foamed molded product, The density of each sample is measured, and the arithmetic average of values excluding the maximum value and the minimum value is taken as the density of the foamed layer 12 of the foamed molded product.
[0060]
Further, the density of the foamed molded article 1 of the present invention is generally 20 to 800 kg / m. ^Three Preferably 25 to 400 kg / m ^Three It is. The density of the foam molded body 1 is 800 kg / m. ^Three If it exceeds 1, there is a possibility that the lightness and the heat insulating property are lowered. The density of the foam molded body 1 is 20 kg / m. ^Three If it is less than the range, mechanical properties such as compressive strength may be lowered.
[0061]
The density of the foam molded body 1 is determined by submerging the molded body and measuring the volume (however, the void portion is larger than the required volume of the foam molded body even when a void portion is present inside the foam molded body. The volume is not subtracted), and is obtained by dividing the weight of the foamed molded article 1 by the previously obtained volume.
[0062]
The foamed layer 2 of the multilayer parison 6 formed as the foamed layer 12 of the foamed molded product in the present invention is obtained by extrusion foaming a foamable molten resin in which a foaming agent is contained in the exemplified polystyrene resin. As the foaming agent, any of an inorganic foaming agent, a volatile foaming agent, and a decomposable foaming agent can be used, but a volatile foaming agent should be used to obtain the foamed layer 12 of the foamed molded article having a high foaming ratio. Is preferred. Examples of the inorganic foaming agent include nitrogen and carbon dioxide. Examples of the volatile blowing agent include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, normal hexane, isohexane, and cyclohexane, chlorinated hydrocarbons such as methyl chloride and ethyl chloride, 1,1,1, Examples thereof include fluorinated hydrocarbons such as 2-tetrafluoroethane and 1,1-difluoroethane. Examples of the decomposable foaming agent include azodicarbonamide. Two or more kinds of the above-mentioned foaming agents can be mixed and used, and a decomposable foaming agent can be used in combination with an inorganic foaming agent or a volatile foaming agent in order to adjust bubbles.
[0063]
An example of the manufacturing method of the foaming molding 1 of this invention is demonstrated based on FIG. In order to manufacture the multilayer parison 6, as shown in FIG. 4, the base resin forming each layer of the multilayer parison 6 is melt-kneaded by separate extruders (not shown), and these are laminated and joined in the die 21. The multilayer parison 6 is obtained by extruding to a low pressure region. If necessary, an accumulator may be installed between the extruder and the die 21 or in the die 21.
[0064]
In order to obtain the foam molded body 1 from the multilayer parison 6, after the multilayer parison 6 is molded, the divided molds 22a and 22b are closed so as to sandwich the extruded multilayer parison 6 from both sides as shown in FIG. To do. When the mold is closed, the foamed multi-layer parison 6 is compressed on the mold inner surfaces 23a and 23b and is brought into close contact with the mold inner surface while being deformed into a flat shape. Next, as shown in FIG. 5, by closing the mold, at least a part of the inner surfaces of the multilayer parison 6 is fused to form a foamed multilayer parison 6 in the cavity. A foam molded article 1 is obtained.
[0065]
Further, as shown in FIG. 4, by providing a pressure reducing pipe 24 on the mold, the pressure between the inner surfaces 23 a and 23 b of the mold and the outer surface of the multilayer parison 6 can be reduced using a mold. However, when the mold is closed and molded, the outer surface of the multilayer parison 6 and the inner surface of the mold are in close contact with each other, and it is possible to obtain the foamed molded body 1 that reproduces the mold shape well, and the pattern is formed on the inner surface of the mold. In the case where a mold having the above is used, the mold pattern transferability on the surface of the foam molded body 1 is also improved.
[0066]
Alternatively, immediately after the multi-layer parison is extruded, the multi-layer parison closed by a parison pinch and expanded by pre-blow may be molded as shown above.
[0067]
Further, when the multilayer parison 6 is formed by deep drawing, the female side 22 of the female die 22b can be moved around the bottom 26 as shown in FIGS. 6 (a) and 6 (b). By configuring the mold 22b, the female mold 22b can be assembled and expanded. From the state where the female mold 22b is expanded, the side surface 25 of the female mold 22b is moved to mold the female mold 22 while the male mold 22b is assembled. It is preferable to close and mold 22a and female mold 22b.
[0068]
FIGS. 4 to 6 are explanatory views conceptually showing an example of manufacturing a foamed molded product, and specific operating procedures for manufacturing the foamed molded product of the present invention are the same as those shown in FIGS. 4 to 6. It is not limited.
[0069]
In the present invention, when the foaming layer 2 and the mixed resin layer 3 and further the polymer layer 4 are extruded from the die when the foaming layer 2 has a high expansion ratio, the mixed resin layer 3 and / or the polymer layer 4 If it is difficult to stretch, the tip of the multilayer parison 6 may turn up immediately after the multilayer parison 6 is extruded from the die. The turn-up of the tip of the multi-layer parison 6 is a phenomenon that occurs because the foamed layer 2 foams at a high magnification at the tip of the multi-layer parison, but the elongation of the mixed resin layer 3 and the like cannot follow. It occurs only at the tip of the multilayer parison 6 immediately after injection. After the resin forming the multi-layer parison 6 is extruded to some extent, it is pulled downward due to the weight of the multi-layer parison 6 itself, so that no turning occurs.
[0070]
When turning occurs at the tip of the multi-layer parison 6, the portion where the turn is generated cannot be used for molding. Therefore, the multi-layer parison 6 is extruded longer to form only the portion where no turn is generated. The foamed molded body 1 having a required size must be obtained. In this case, the portion where the turn is generated becomes a large burr, which is not only inefficient, but also has an adverse effect such as a drawdown due to an increase in the weight of the parison.
[0071]
In order to prevent the above turning, the start of extrusion of the mixed resin layer 3 and the polymer layer 4 is made earlier than the start of extrusion of the foam layer 2, and after forming the tip of the multilayer parison 6 without turning, the entire layer is pressed. The method of putting out can be adopted. Immediately after the tip of the multilayer parison 6 is pushed out of the die, the lower end of the multilayer parison 6 is pushed from the outside of the multilayer parison 6 in the mold clamping direction at the lower part of the die, thereby at least a part of the inner surface of the multilayer parison 6. It is also possible to prevent the tip of the multilayer parison 6 from being turned over by using a technique such as bonding. If such a technique is used to prevent the tip of the multilayer parison 6 from being turned up, the molding loss can be reduced, and the extruded multilayer parison can be used effectively.
[0072]
In the present invention, as described above, the foamed molded article 1 can be obtained by sandwiching the multilayer parison 6 in a mold and compressing and molding. By using the multilayer parison 6 in such a manner to obtain the foam molded body 1, the foam layer 12 of the foam molded body and the mixed resin layer 13 of the foam molded body, or the foam layer 12 and the mixed resin layer. Adhesiveness between the polymer layer 13 and the polymer layer 14 of the foamed molded article is favorable, and the peel strength can be increased. Further, the thickness of the mixed resin layer 13 of the foam molded body 1 or the mixed resin layer 13 and the polymer layer 14 of the foam molded body can be made more uniform. In the foam layer 13 of the foam molded body, There are advantages such that a foam having a higher expansion ratio, a thicker one, and a more uniform one can be easily obtained.
[0073]
Further, in the present invention, for example, as shown in FIGS. 1 (a) and 1 (b), the inner surfaces of the multilayer parison 6 are completely brought into close contact with each other to be molded together. Since there are no voids inside the body, this is a preferred embodiment in terms of improving dimensional stability and mechanical properties. In the present specification, the fusion ratio of the inner surface of the foamed molded product is represented by a fusion part area ratio (%), and the fusion part area ratio is 60% in terms of improving dimensional stability and mechanical properties. The above is preferable, 80% or more is more preferable, and 95% or more is particularly preferable. The measuring method of the fusion part area ratio is as follows.
[0074]
The foamed molded product is cut in a direction perpendicular to the direction of extrusion of the multilayer parison at the time of manufacturing the foamed molded product and parallel to the direction of compression of the multilayer parison die so that the foamed molded product is equally divided into 10 parts.
Next, place the foam molded body so that the cut surface of the cut foam molded body is positioned in the left-right direction in the order in which the foam molded body was formed, and on the right cut surface of each molded body cut piece The length (mm) of the portion where the inner surfaces of the multilayer parison used to form the foamed molded product are fused is determined, and a value obtained by doubling this is defined as A (mm). Furthermore, in the cut surface on the right side, when the inner surface of the multilayer parison is not fused together to form a void portion, the inner circumferential length of the void portion is B (mm). Further, when there are a plurality of the fusion part lengths and / or gaps in each of the cut surfaces, the fusion part length or the inner circumferential length of the gaps is obtained for each part, and the total of each is A or B. To do. Next, the fused portion area ratio (%) of each cut surface is obtained by [A / (A + B)] × 100. In addition, the said area ratio of a foaming molding is 100% in the state without a space | gap part. And the arithmetic average value of the fusion part area ratio of each of the cut surfaces (excluding the cut surface where the inner surface fusion part of the multilayer parison itself does not exist) is defined as the fusion part area ratio (%) of the foamed molded product. .
[0075]
The foamed molded article of the present invention preferably has a 50% fracture energy of 1 J or more according to a drop weight impact test at room temperature determined by JIS K7211. Further, the 50% fracture energy by a drop weight impact test at a low temperature is preferably 0.5 J or more, particularly 0.7 J or more.
[0076]
The 50% fracture energy in the drop weight impact test at room temperature or low temperature is foam molding with a size of 100 mm in length and 100 mm in width in a constant temperature and humidity chamber with a temperature of 23 ° C. and a humidity of 55% or a low temperature bath of −40 ° C. for 24 hours. The test piece cut out from the body is subjected to a falling weight impact test in a constant temperature and humidity chamber at a temperature of 23 ° C. and a humidity of 55%, and obtained by the calculation method of JIS K7211. In the case of a drop weight impact test at a low temperature, the measurement is performed within 2 seconds after each test piece is taken out of the low temperature bath. The testing machine is No. manufactured by Toyo Seiki Seisakusho. A 621 falling weight impact tester is used, and the weight used is a spherical weight of a nominal ball type 2 (diameter 63 mm, mass 1 kg) defined in JIS K7211.
[0077]
1A and 1B are drawings showing an example of a cross-sectional shape of a foamed molded product of the present invention. The foamed molded body shown in FIGS. 1 (a) and 1 (b) is a container shape in which the foam layer inner surfaces of a multilayer foamed parison are completely fused together and molded with a mold so that a container space 15 is formed. This is a foam molded article.
[0078]
When a container is obtained as a foam molded article, the density of the foam molded article is 30 to 400 kg / m. ^Three It becomes lightweight and excellent in heat insulation, and the total thickness of the mixed resin layer 13 of the foam molded body or the thickness of the mixed resin layer 13 of the foam molded body and the polymer layer 14 of the foam molded body. By setting the thickness to 200 to 5000 μm, it is possible to obtain a container having high durability and surface smoothness and a good balance between appearance and lightness.
[0079]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
General-purpose polystyrene (Stylon G9802 manufactured by A & M Styrene Co., Ltd.) is used as the polystyrene-based resin, and 0.16% by weight of talc mixed as a foam regulator is supplied to the extruder and melt-kneaded. A foaming melt for forming a foamed layer was formed by press-fitting an amount of the foaming agent shown in 1 (a mixture of isobutane and normal butane in a weight ratio of 35:65) into an extruder and kneading.
[0080]
[Table 1]

[0081]
On the other hand, low-density polyethylene (NS-1 manufactured by Nippon Unicar Co., Ltd.) as a polyolefin resin, general-purpose polystyrene (Stylon 679 manufactured by A & M Styrene Co., Ltd.) as a polystyrene resin, and a styrene thermoplastic elastomer (as a compatibilizer) Asahi Kasei Kogyo Co., Ltd. Tuftec H1041) mixed at the blending amount shown in Table 1 was supplied to another extruder and melt-kneaded to obtain a non-foamable melt for forming a mixed resin layer.
[0082]
Next, the melt melt-kneaded by each extruder is filled in each accumulator provided between the extruder and the die, and after the filling is completed, the filled non-foamable melt, the foamable melt, Were injected by an accumulator so as to be joined together in a die, and extruded from the die to obtain a multilayer parison having a mixed resin layer laminated on the outer surface of the foam layer.
[0083]
Next, the extruded multi-layer parison is closed so as to be sandwiched by a multi-part mold shown in FIG. 6 installed directly under the die, and the multi-layer parison is deformed into a flat shape on the inner surface of the cavity. The inside of the mold was depressurized to bring the multilayer parison into close contact with the mold surface. In this way, a multi-layer parison was molded in the mold, further cooled and released from the mold, and the foamed molded product was taken out.
In addition, the said metal mold | die used what the matte finish was given to the inner surface of a metal mold | die.
[0084]
The foamed molded article thus obtained (conical shape of a truncated cone having an opening size of 300 mm × width of 260 mm, a bottom surface size of 260 mm × width of 180 mm, a height of 110 mm, and a wall thickness of about 20 mm) The appearance with no shrinkage or deformation was good.
[0085]
Examples 2-7
Using the base materials shown in Table 1 and the same foaming agent as in Example 1, foamed molded articles were produced in the same manner as in Example 1 with the compounding amounts shown in Table 1. The foamed molded article thus obtained had a good appearance with no shrinkage or deformation.
[0086]
Example 8
Using the base material shown in Table 1 and the same foaming agent as in Example 1, with the blending amount shown in Table 1, the foamable melt for forming the foam layer in the same manner as in Example 1, and the mixed resin layer A non-foamable melt to form was made in an extruder. Further, low-density polyethylene (8008 manufactured by Nippon Unicar Co., Ltd.) was supplied to another extruder to melt and knead to form a non-foamable melt for forming a polymer layer.
[0087]
A foamable melt for forming the foam layer, a non-foamable melt for forming the mixed resin layer, and a non-foamable melt for forming the polymer layer are laminated in a die. A multilayer parison in which a polymer layer made of non-foamed resin is laminated on the outer surface of the foamed layer via a mixed resin layer while being injected by an accumulator provided between the extruder and the die so as to merge Got. Next, the multilayer parison was molded, cooled and released in the same manner as in Example 1 using a mold of the type shown in FIG. The foamed molded article thus obtained had a good appearance with no shrinkage or deformation.
[0088]
Examples 9-12
Using the base materials shown in Table 1 and the same foaming agent as in Example 1, foamed molded articles were produced in the same manner as in Example 8 with the compounding amounts shown in Table 1. The foamed molded article thus obtained had a good appearance with no shrinkage or deformation.
[0089]
Comparative Example 1
Using the base material shown in Table 1 and the same foaming agent as in Example 1, the foaming melt for forming the foam layer in the same manner as in Example 8 and the polymer layer in the blending amounts shown in Table 1 A non-foamable melt for forming is prepared (but no mixed resin layer is formed), and these are injected by an accumulator provided between the extruder and the die so as to be laminated and joined in the die. At the same time, it was extruded from a die to obtain a multilayer parison having a polymer layer laminated on the outer surface of the foam layer. Next, a foam molded article was produced in the same manner as in Example 1.
[0090]
The foamed molded product thus obtained had a good appearance with no shrinkage or deformation, but was insufficient in oil resistance and impact resistance.
[0091]
Comparative Example 2
Using the base material shown in Table 1 and the same foaming agent as in Example 1, foamed molded articles were produced in the same manner as in Comparative Example 1 with the compounding amounts shown in Table 1. However, although a molded product was obtained, the foamed layer and the polymer layer were peeled off from the cut portion from which burrs were cut, and a good foamed molded product could not be obtained.
[0092]
Comparative Example 3
Using the base material shown in Table 1 and the same foaming agent as in Example 1, a foamed molded product was produced in the same manner as in Example 1 with the blending amount shown in Table 1, and a molded product with a good appearance was obtained. However, the oil resistance and impact resistance were insufficient.
[0093]
Comparative Example 4
Using the same base material as shown in Table 1 and the same foaming agent as in Example 1, a foamed molded product was produced in the same manner as in Example 1 with the compounding amounts shown in Table 1. The foamed layer and the mixed resin layer were peeled from the cut portion from which the film was cut off, and a good foamed molded article could not be obtained.
[0094]
Comparative Example 5
Using the base material shown in Table 1 and the same foaming agent as in Example 1, the mixed resin layer was changed to a polystyrene-based resin layer at the blending amount shown in Table 1, and a foam molded article was produced in the same manner as in Comparative Example 4. did. The obtained foamed molded article had a good appearance but was insufficient in oil resistance.
[0095]
Comparative Examples 6 and 7
Using the base materials shown in Table 1 and the same foaming agent as in Example 1, foamed molded articles were produced in the same manner as in Example 8 with the compounding amounts shown in Table 1. Although a molded product was obtained, the polymer layer and the foamed layer were peeled off from the cut portion from which burrs were cut, and a good foamed molded product was not obtained. In Comparative Example 6, interfacial peeling occurred between the mixed resin layer and the polymer layer, and in Comparative Example 7, separation between the foamed layer and the mixed resin layer occurred.
[0096]
Table 2 shows the results of measuring the density, solvent resistance, normal temperature and low temperature impact resistance, and peel strength of the foamed molded products obtained in Examples 1 to 12 and Comparative Examples 1 to 7.
In addition, all the fusion part area ratios of the foaming molding obtained in Examples 1-12 were 100%.
[0097]
[Table 2]

[0098]
Table 3 shows the Vicat softening point, resin density, and melt viscosity of various substrates used in Examples 1 to 12 and Comparative Examples 1 to 7. Table 4 shows the types of base materials, manufacturing company names, and grade names indicated by symbols in Tables 1 and 3.
[0099]
[Table 3]

-: Not measured
[0100]
[Table 4]

[0101]
A calculation example of the PI value of the mixed resin layer shown in Table 1 is shown below for Example 1.
PI value = (η _A × φ _B ) / (Η _B × φ _A )
η _A = Viscosity of PS (2) = 10100 [poise]
φ _A = Volume fraction of PS (2)
η _B = Viscosity of LDPE (1) = 16100 [poise]
φ _B = Volume fraction of LDPE (1)
[0102]
here,
φ _A = (W _A / ρ _A ) / (W _A / ρ _A + W _B / ρ _B )
= (0.4 / 1.05) / (0.4 / 1.05 + 0.6 / 0.92)
= 0.37
φ _B = (W _B / ρ _B ) / (W _A / ρ _A + W _B / ρ _B )
= (0.6 / 0.92) / (0.4 / 1.05 + 0.6 / 0.92)
= 0.63
W _A = Blending amount (% by weight) shown in Table 1 of PS (2) / 100 = 0.4
ρ _A = Resin density of PS (2) = 1.05
W _B = Blending amount (% by weight) shown in Table 1 of LDPE (1) / 100 = 0.6
ρ _B = Resin density of LDPE (1) = 0.92
[0103]
Therefore,
PI value = (η _A × φ _B ) / (Η _B × φ _A )
= (10100 × 0.63) / (16100 × 0.37)
= 1.07
It becomes.
[0104]
The melt viscosity in this specification is a shear rate of 100 sec using “Leobis 2100” manufactured by Chiast Corp. with an orifice having an inner diameter of 1 mm and a length of 10 mm. ^-1 The value measured under the condition of a resin temperature of 180 ° C.
[0105]
Evaluation of the foamed molded product in Table 2 was performed as follows.
[0106]
Fusion property
After molding with a multi-layer parison sandwiched between molds, take out from the mold and remove the burrs from the burr cutting part. Interfacial delamination occurred between the polymer layers of the molded product, and a case where a good foamed molded product could not be obtained was evaluated as x, and the burr cut portion was properly fused.
[0107]
Solvent resistance
Solvent resistance was evaluated by pour toluene into the obtained container and let it stand for 24 hours, then evaluate that the foamed layer of the foamed molded product had no holes, and that the foamed layer of the foamed molded product was dissolved as x. did.
[0108]
Room temperature shock resistance
The room temperature impact resistance is obtained by leaving a test piece cut out from the obtained container in a constant temperature and humidity chamber at 23 ° C. and 55% humidity for 24 hours, and then applying a spherical weight of 1 kg in accordance with JIS K7211. A 50% fracture energy was obtained by free-falling and evaluated according to the following criteria.
○: 50% destruction energy 1J or more
X: 50% destruction energy is less than 1J
[0109]
Low temperature impact resistance
The low-temperature impact resistance is obtained by leaving a test piece cut out from the obtained container in a -20 ° C cool box for 24 hours, and then taking it out within 2 seconds after taking it out. The weight was allowed to fall freely and the 50% fracture energy was determined and evaluated according to the following criteria.
: 50% fracture energy is 0.7J or more
Δ: 50% fracture energy 0.5J or more and less than 0.7J
X: 50% fracture energy is less than 0.5J
[0110]
Heat-resistant
The sample was left in an oven at 95 ° C. for 24 hours and, after removal, the one without extreme deformation was evaluated as having good heat resistance (◯).
[0111]
【The invention's effect】
The present invention provides a mixture of (1) 20 to 80% by weight of polystyrene resin and (2) 20 to 80% by weight of polyolefin resin or polyester resin (provided that (1) and Adopted a configuration in which a multi-layer parison having a mixed resin layer (total with (2)) is obtained by molding with a mold so that the inner surfaces of the parison are fused at least partially. As a result, a polystyrene-based resin foam molded article can be produced without going through a complicated process of injecting the foam after producing the semi-molded product. Further, according to the present invention, a layer made of a mixture of a polyolefin resin or a polyester resin and a polystyrene resin can be laminated and integrated on the polystyrene resin foam layer without using a special adhesive. Therefore, it is possible to provide a multilayer polystyrene-based resin foam molded article having a beautiful appearance and excellent in lightness, mechanical strength, heat insulation, buffering, vibration proofing, oil resistance, impact resistance, and the like. Further, the foamed molded product can be pulverized, melted and recovered, and recycled as a raw material for a mixed resin layer or the like.
[0112]
The multilayer polystyrene resin foam molded article of the present invention comprises a multilayer parison in which a polyolefin resin layer is laminated on the outside of a polystyrene resin foam layer with a mixed resin layer of a certain composition, and the inner surfaces of the parison are It includes a configuration in which it is molded with a mold so as to be fused at least partially. Therefore, if high-density polyethylene or linear polyethylene is used as the polyolefin resin, it is possible to provide a multilayer polystyrene resin foam molded article having excellent impact resistance at low temperatures in addition to the above effects. If a high-density polyethylene or polypropylene resin is used as the polyolefin resin, it is possible to provide a multilayer polystyrene resin foam molded article having excellent heat resistance in addition to the above effects.
[0113]
The multilayer polystyrene resin foam molded article of the present invention comprises a multilayer parison in which a polyester resin layer is laminated on the outside of a polystyrene resin foam layer with a mixed resin layer of a certain composition, and the inner surfaces of the parison are A configuration in which molding is performed with a mold so as to be fused at least partially is also included. When such a configuration is adopted,
In addition to the above effects, it is possible to provide a multi-layer polystyrene resin foam molded article having excellent gas barrier properties.
[0114]
The multi-layer polystyrene resin foam molded article of the present invention can be used for lightweight thermal insulation panels such as floors and doors, automotive parts such as pillars, bumpers and instrument panels, pallets, containers, desks, chairs, floats, surfboards, etc. Suitable as a returnable container.
[Brief description of the drawings]
FIG. 1 (a) is a longitudinal sectional view showing an example of a multilayer polystyrene resin foam molded article of the present invention having a mixed resin layer on the outer surface of a foam layer. FIG.1 (b) is a longitudinal cross-sectional view which shows an example of the multilayer polystyrene-type resin foaming molding of this invention which has a polymer layer through a mixed resin layer on the outer side of a foaming layer.
FIG. 2 (a) is an explanatory diagram of a multilayer parison having a mixed resin layer on the outer surface of a foam layer. FIG.2 (b) is explanatory drawing of the multilayer parison which has a polymer layer through a mixed resin layer on the outer side of a foaming layer.
FIG. 3 is a graph for determining a half crystallization time of a polyester resin.
FIG. 4 is an explanatory view for explaining an example of a method for producing a foamed molded product of the present invention.
FIG. 5 is an explanatory diagram for explaining an example of a method for producing a foamed molded product of the present invention.
FIG. 6 (a) is an explanatory diagram for explaining an example of different aspects of the method for producing a foamed molded product of the present invention. FIG.6 (b) is explanatory drawing for demonstrating an example of the different aspect of the manufacturing method of this invention foaming molding.
[Explanation of symbols]
1 Multi-layer polystyrene resin foam molding
2 Polystyrene resin foam layer
3 Mixed resin layer
4 Polymer layer
6 Multi-layer parison

Claims (9)

A foamed molded article obtained by molding a multilayer parison having a mixed resin layer on the outer surface of a polystyrene-based resin foam layer with a molding die so that inner surfaces of the parison are fused at least partially, The mixed resin layer is a mixture of (1) 20 to 80% by weight of a polystyrene-based resin and (2) 20 to 80% by weight of a polyolefin-based resin or a polyester-based resin (provided that the total of (1) and (2) is 100% by weight) %) Is a multilayer polystyrene resin foam molded article. The multilayer polystyrene resin foam molded article according to claim 1, wherein the peel strength between the polystyrene resin foam layer and the mixed resin layer constituting the molded article is 100 (gf / 25 mm) or more. The multilayer polystyrene resin foam molded article according to claim 1. A mixture of (3) 20 to 80% by weight of polystyrene resin and (4) 20 to 80% by weight of polyolefin resin (however, the sum of (3) and (4) is 100) on the outside of the polystyrene resin foam layer. A multilayer parison obtained by molding a multilayer parison having a polyolefin resin layer laminated via a mixed resin layer composed of a weight%) with a molding die so that the inner surfaces of the parison are fused at least partially. Polystyrene resin foam molding. The multilayer polystyrene resin foam molded article according to claim 3, wherein the polyolefin resin layer is made of a polyolefin resin having a Vicat softening point of 112 ° C or higher. A mixture of (5) 20 to 80% by weight of polystyrene resin and (6) 20 to 80% by weight of polyester resin (however, the sum of (5) and (6) is 100) on the outside of the polystyrene resin foam layer. And a multilayer parison obtained by molding a multilayer parison having a polyester resin layer laminated through a mixed resin layer (weight%) with a molding die so that the inner surfaces of the parison are fused at least partially. Polystyrene resin foam molding. 6. The multilayer polystyrene resin foam molded article according to claim 5, wherein the polyester resin layer comprises a polyester resin having a half crystallization time of 30 minutes or more. The multilayer polystyrene resin foam molded article according to any one of claims 3 to 6, wherein the peel strength between the polystyrene resin foam layer constituting the molded article and the polyolefin resin layer or the polyester resin layer is 100. The multilayer polystyrene resin foam molded article according to any one of claims 3 to 6, which is (gf / 25mm) or more. The multi-layer polystyrene resin foam molded article according to any one of claims 1 to 7, wherein the polystyrene resin foam layer is made of a polystyrene resin having a Vicat softening point of 110 ° C or higher. A phase structure index PI value representing a mixed state of a mixture of a polystyrene resin and a polyolefin resin or a polyester resin constituting the mixed resin layer is 0.7 <PI value <1.3. The multilayer polystyrene-based resin foam molded article according to any one of claims 1 to 8.

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