JP3959866B2

JP3959866B2 - Injection molding apparatus for molding multilayer molded article and injection molding method of multilayer molded article

Info

Publication number: JP3959866B2
Application number: JP26608898A
Authority: JP
Inventors: 勝也丸山; 毅原; 義弘寺田; 貴夫太田
Original assignee: Mitsubishi Gas Chemical Co Inc
Current assignee: Mitsubishi Gas Chemical Co Inc
Priority date: 1997-09-25
Filing date: 1998-09-21
Publication date: 2007-08-15
Anticipated expiration: 2018-09-21
Also published as: JPH11165330A

Description

【０００１】
【発明の属する技術分野】
本発明は、多層成形品を成形するための射出成形装置、及び、多層成形品の射出成形方法に関する。
【０００２】
【従来の技術】
近年、熱可塑性樹脂を用いた容器が、軽量化、破裂に対する安全性等の利点から、化粧品、食品、飲料などの容器として広範に使用されている。特に、ポリエチレンテレフタレート樹脂（以下、ＰＥＴ樹脂と略す場合がある）から成る容器の開発が、二軸延伸ブロー成形技術の向上により急速に進展している。しかしながら、ＰＥＴ樹脂を主体とする熱可塑性ポリエステル樹脂から成る二軸配向した容器も、万全の性能を具備しているわけではない。即ち、特に容器に充填すべき内容物がガス遮断性を容器に対して高度に要求する飲料品である場合には、酸素ガスや炭酸ガス等に対するガスバリヤー性能がＰＥＴ樹脂から成形された容器には不足しているため、内容物の風味を損なう等の欠点を有している。最近では、容器の小型化により、容器のガスバリヤー性に対する要求が一層高くなっている。
【０００３】
このような要求に対して、熱可塑性ポリエステル樹脂と、熱可塑性ガスバリヤー性樹脂であるメタキシリレン基含有ポリアミド樹脂（以下ＭＸナイロン樹脂と略す場合がある）との各々を可塑化、溶融する２つの射出シリンダーを備え、単一の金型を有する射出成形装置を用い、１回の成形サイクルにおいて、溶融熱可塑性ポリエステル樹脂を射出し、溶融熱可塑性ポリエステル樹脂を射出し続けながら溶融ＭＸナイロン樹脂を射出し、溶融ＭＸナイロン樹脂の射出完了後も溶融熱可塑性ポリエステル樹脂を射出し続けることによって、熱可塑性ポリエステル樹脂／ＭＸナイロン樹脂／熱可塑性ポリエステル樹脂の３層構造を有するパリソンを成形する技術が、特開昭５７−１２８５２０号から公知である。尚、このような射出成形方法を同時射出成形方法と呼ぶ。
【０００４】
また、上記方法と同様であるが、特定の条件下、例えば熱可塑性ポリエステル樹脂とＭＸナイロン樹脂とを、熱可塑性ポリエステル樹脂、ＭＸナイロン樹脂、熱可塑性ポリエステル樹脂の順に射出することにより、熱可塑性ポリエステル樹脂／ＭＸナイロン樹脂／熱可塑性ポリエステル樹脂／ＭＸナイロン樹脂／熱可塑性ポリエステル樹脂の５層構造を有するパリソンを成形する技術が、特開昭６０−２４０４０９号から公知である。尚、このような射出成形方法を交互射出成形方法と呼ぶ。
【０００５】
また、近年、ＰＥＴ樹脂を主体とした容器を回収し粒状化して回収ＰＥＴ樹脂として再利用する技術の開発も進められている。このような回収ＰＥＴ樹脂（パリソン成形時の不良品の再利用ＰＥＴ樹脂やパリソン成形時に一旦使用した後の再生ＰＥＴ樹脂を含む）を用いて飲料容器用のパリソンを成形する場合、ＰＥＴ樹脂層／回収ＰＥＴ樹脂層／ＰＥＴ樹脂層の３層構造、あるいは、ＰＥＴ樹脂層／回収ＰＥＴ樹脂層／ＰＥＴ樹脂層／回収ＰＥＴ樹脂層／ＰＥＴ樹脂層の５層構造とする必要がある。
【０００６】
これらの特許公開公報に開示された技術により、ポリエチレンテレフタレート樹脂から成る容器と同等の外観及び機械的性能を有し、しかも、酸素ガスや炭酸ガスに対するバリヤー性が大きく向上した多層容器（多層ボトル）を製造することが可能となり、現在、使用されるに至っている。
【０００７】
従来、２つ以上の射出シリンダーを用いて２種類以上の樹脂から多層成形品（例えば、多層容器の前駆体である多層パリソン）を成形する場合、キャビティが設けられた金型と、少なくとも２つの射出シリンダーとを備えた射出成形装置を使用する。例えば、２つの射出シリンダーとを備えた射出成形装置においては、各射出シリンダーの内部とキャビティとを結ぶ各樹脂流路（第１の溶融樹脂が流れる第１の樹脂流路及び第２の溶融樹脂が流れる第２の樹脂流路）は、キャビティに開口したゲート部の上流の合流部で合流する構造を有している。尚、金型内に位置する第１の樹脂流路及び第２の樹脂流路の部分はホットランナー構造を有する。また、合流部よりも上流の樹脂流路の部分は、通常、多重管構造となっている。そして、射出シリンダー内に配設されたスクリューは、溶融樹脂の射出時及び保圧時以外には、樹脂流路から圧力が加わると後退する構造となっており、樹脂流路内の溶融樹脂が射出シリンダー内に逆流する。
【０００８】
【発明が解決しようとする課題】
このような構造を有する射出成形装置においては、キャビティ内を第１及び第２の溶融樹脂で完全に充填するために、多層成形品の最外層を構成する第１の溶融樹脂を第１の樹脂流路を経由してキャビティ内に射出したとき、第１の樹脂流路を流れる第１の溶融樹脂は第２の樹脂流路内に流入するが、この際の第１の溶融樹脂の流入量は一定ではない。その結果、キャビティ内に射出すべき第１の溶融樹脂の量が不安定となったり、第１の溶融樹脂の最初の射出時、合流部近傍の第２の樹脂流路内に存在する第２の溶融樹脂と第１の溶融樹脂とが混ざり合った状態でキャビティ内に射出されるため、多層成形品の最外層を構成しない第２の樹脂が最外層表面に出現するといった問題が生じる。
【０００９】
このような第１の溶融樹脂が第２の樹脂流路へ流入することを防止するために、従来の技術においては、第２の溶融樹脂を射出するための射出シリンダーのノズル部に、油圧作動方式のシャットオフ弁を配設している。第２の溶融樹脂の射出時のみシャットオフ弁を開き、それ以外の場合においては、シャットオフ弁を閉じることによって、第１の溶融樹脂が第２の樹脂流路へ流入することを防止している。
【００１０】
ところで、シャットオフ弁による溶融樹脂の流れの制御を行う場合、第２の樹脂流路への第１の溶融樹脂の流入は防止することができるが、逆に、第１の溶融樹脂の射出時、樹脂流路の合流部近傍において第１の溶融樹脂と第２の溶融樹脂との混合が生じたり、射出状態にない第２の溶融樹脂が射出されつつある第１の溶融樹脂に巻き込まれる結果、合流部近傍の第２の溶融樹脂がキャビティ内に流入し、例えば、第２の樹脂が多層成形品の表面に出現するといった問題が生じる。即ち、多層成形品の最外層を構成しない第２の樹脂が最外層表面に出現するといった問題が生じる。
【００１１】
特開昭６１−２０６６１２号公報には、第１の樹脂流路１１と第２の樹脂流路１２を有し、第２の樹脂流路１２に逆止弁１３が備えられた射出成形用ホットランナー金型が開示されている。そして、第１の樹脂材料Ａの注入の際、キャビティ２２は樹脂によって完全に充填されるが、第２の樹脂流路１２には逆止弁１３が設けられているので、第１の樹脂材料Ａによって第２の樹脂材料Ｂが逆流することはないとされている。
【００１２】
本発明の目的は、少なくとも２種類の樹脂から成形され、各樹脂から構成された樹脂層が積層された多層成形品であって、多層成形品の最外層を構成しない樹脂が最外層表面に出現することを確実に防止し得る、言い換えれば、多層成形品の最外層を構成する樹脂層によって多層成形品の最外層を構成しない樹脂が確実に封鎖された構造を有する多層成形品を成形するための射出成形装置及び多層成形品の射出成形方法を提供することにある。
【００１３】
【課題を解決するための手段】
上記の目的を達成するための本発明の多層成形品を成形するための射出成形装置は、
（ａ）キャビティが設けられたキャビティブロックと、ホットランナーブロックとを有する金型、
（ｂ）少なくとも第１の射出シリンダー及び第２の射出シリンダー、
（ｃ）第１の射出シリンダーの内部とキャビティとを結ぶ第１の樹脂流路、
及び、
（ｄ）第２の射出シリンダーの内部とキャビティとを結ぶ第２の樹脂流路、
を備え、
金型内に位置する第１の樹脂流路及び第２の樹脂流路の部分はホットランナーブロック内に設けられ、
第１の樹脂流路と第２の樹脂流路とは、キャビティに開口したゲート部の上流の合流部で合流する構造を有する射出成形装置であって、
第２の樹脂流路を経由して第２の溶融樹脂をキャビティ内に射出した後、第１の樹脂流路内の第１の溶融樹脂を第２の樹脂流路内に流入させる逆流手段が設けられており、
該逆流手段は、第１の樹脂流路内の第１の溶融樹脂が第２の樹脂流路内の第２の溶融樹脂に及ぼす圧力によって動作することを特徴とする。ここで、上流とは射出シリンダー側を意味し、下流とはキャビティ側を意味する。以下においても同様である。
【００１４】
上記の目的を達成するための本発明の第１の態様に係る多層成形品の射出成形方法は、上記の本発明の多層成形品を成形するための射出成形装置を使用した交互射出成形方法である。即ち、上記の目的を達成するための本発明の第１の態様に係る多層成形品の射出成形方法は、
（ａ）キャビティが設けられたキャビティブロックと、ホットランナーブロックとを有する金型、
（ｂ）少なくとも第１の射出シリンダー及び第２の射出シリンダー、
（ｃ）第１の射出シリンダーの内部とキャビティとを結ぶ第１の樹脂流路、
及び、
（ｄ）第２の射出シリンダーの内部とキャビティとを結ぶ第２の樹脂流路、
を備え、
金型内に位置する第１の樹脂流路及び第２の樹脂流路の部分はホットランナーブロック内に設けられ、
第１の樹脂流路と第２の樹脂流路とは、キャビティに開口したゲート部の上流の合流部で合流する構造を有する射出成形装置であって、
第２の樹脂流路を経由して第２の溶融樹脂をキャビティ内に射出した後、第１の樹脂流路内の第１の溶融樹脂を第２の樹脂流路内に流入させる逆流手段が設けられており、
該逆流手段は、第１の樹脂流路内の第１の溶融樹脂が第２の樹脂流路内の第２の溶融樹脂に及ぼす圧力によって動作する射出成形装置を用いた多層成形品の射出成形方法であって、
（Ａ）第１の射出シリンダー内で溶融させた第１の溶融樹脂を、第１の樹脂流路を介してキャビティ内に射出した後、第１の溶融樹脂の射出を中断し、
（Ｂ）第２の射出シリンダー内で溶融させた第２の溶融樹脂を、第２の樹脂流路を介してキャビティ内に射出した後、第２の溶融樹脂の射出を終了し、次いで、
（Ｃ）第１の射出シリンダー内で溶融させた第１の溶融樹脂を、第１の樹脂流路を介してキャビティ内に射出し、第１の溶融樹脂の射出中若しくは射出完了後、逆流手段の動作によって第１の樹脂流路内の第１の溶融樹脂を第２の樹脂流路内に流入させる、
工程から成ることを特徴とする。
【００１５】
本発明の第１の態様に係る多層成形品の射出成形方法においては、射出成形条件にも依存するが、多層成形品の主たる部分を、第１の樹脂層／第２の樹脂層／第１の樹脂層／第２の樹脂層／第１の樹脂層の５層構成とすることができる。あるいは又、多層成形品の主たる部分の一部分を、第１の樹脂層／第２の樹脂層／第１の樹脂層／第２の樹脂層／第１の樹脂層の５層構成とし、多層成形品の主たる部分の他の部分を、第１の樹脂層／第２の樹脂層／第１の樹脂層の３層構成とすることもできる。これらの場合、多層成形品の主たる部分以外の部分は、第１の樹脂層によって構成される。
【００１６】
図１４、図１５及び図１６に、本発明の第１の態様に係る多層成形品の射出成形方法における射出圧力等の時間変化を示す。尚、図１４〜図２１中の「逆流手段の状態」において、「閉状態」とは、第２の射出シリンダーの内部とキャビティとが逆流手段によって非連通状態となっていることを意味し、「開状態」とは、第２の射出シリンダーの内部とキャビティとが逆流手段によって連通状態となっていることを意味し、「逆流」とは、第１の樹脂流路内の第１の溶融樹脂が第２の樹脂流路内の第２の溶融樹脂に及ぼす圧力によって逆流手段が動作しており、第１の樹脂流路内の第１の溶融樹脂が第２の樹脂流路内に流入し、その結果、第２の溶融樹脂が第２の射出シリンダーに向かって流れる状態を意味する。本発明の第１に係る多層成形品の射出成形方法において、第１の溶融樹脂の射出完了後に逆流手段の動作によって第１の樹脂流路内の第１の溶融樹脂が第２の樹脂流路内に流入する場合には、具体的には、第１の射出シリンダーによって保圧を行い、併せて、第１の溶融樹脂の射出完了後に逆流手段の動作によって第１の樹脂流路内の第１の溶融樹脂を第２の樹脂流路内に流入させる（図１６参照）。また、第１の溶融樹脂の射出中に逆流手段の動作によって第１の樹脂流路内の第１の溶融樹脂が第２の樹脂流路内に流入し始めた場合には、第１の溶融樹脂の第２の樹脂流路内への流入完了の時点は、第１の溶融樹脂の射出中であってもよいし（図１４参照）、射出完了と同時であってもよいし、射出完了後の保圧期間中であってもよい（図１５参照）。
【００１７】
上記の目的を達成するための本発明の第２の態様に係る多層成形品の射出成形方法は、上記の本発明の多層成形品を成形するための射出成形装置を使用した同時射出成形方法である。即ち、上記の目的を達成するための本発明の第２の態様に係る多層成形品の射出成形方法は、
（ａ）キャビティが設けられたキャビティブロックと、ホットランナーブロックとを有する金型、
（ｂ）少なくとも第１の射出シリンダー及び第２の射出シリンダー、
（ｃ）第１の射出シリンダーの内部とキャビティとを結ぶ第１の樹脂流路、
及び、
（ｄ）第２の射出シリンダーの内部とキャビティとを結ぶ第２の樹脂流路、
を備え、
金型内に位置する第１の樹脂流路及び第２の樹脂流路の部分はホットランナーブロック内に設けられ、
第１の樹脂流路と第２の樹脂流路とは、キャビティに開口したゲート部の上流の合流部で合流する構造を有する射出成形装置であって、
第２の樹脂流路を経由して第２の溶融樹脂をキャビティ内に射出した後、第１の樹脂流路内の第１の溶融樹脂を第２の樹脂流路内に流入させる逆流手段が設けられており、
該逆流手段は、第１の樹脂流路内の第１の溶融樹脂が第２の樹脂流路内の第２の溶融樹脂に及ぼす圧力によって動作する射出成形装置を用いた多層成形品の射出成形方法であって、
（Ａ）第１の射出シリンダー内で溶融させた第１の溶融樹脂を、第１の樹脂流路を介してキャビティ内に射出し、
（Ｂ）第１の溶融樹脂の射出中に、第２の射出シリンダー内で溶融させた第２の溶融樹脂を第２の樹脂流路を介してキャビティ内に射出し、
（Ｃ）第２の溶融樹脂の射出完了後であって第１の溶融樹脂の射出中若しくは射出完了後、逆流手段の動作によって第１の樹脂流路内の第１の溶融樹脂を第２の樹脂流路内に流入させる、
工程から成ることを特徴とする。
【００１８】
図１７、図１８及び図１９に、本発明の第２の態様に係る多層成形品の射出成形方法における射出圧力等の時間変化を示す。第１の溶融樹脂の射出完了後に逆流手段の動作によって第１の樹脂流路内の第１の溶融樹脂が第２の樹脂流路内に流入する場合には、具体的には、第１の射出シリンダーによって保圧を行い、併せて、第１の溶融樹脂の射出完了後に逆流手段の動作によって第１の樹脂流路内の第１の溶融樹脂を第２の樹脂流路内に流入させる（図１９参照）。また、第１の溶融樹脂の射出中に逆流手段の動作によって第１の樹脂流路内の第１の溶融樹脂が第２の樹脂流路内に流入し始めた場合には、第１の溶融樹脂の第２の樹脂流路内への流入完了の時点は、第１の溶融樹脂の射出中であってもよいし（図１７参照）、射出完了と同時であってもよいし、射出完了後の保圧期間中であってもよい（図１８参照）。
【００１９】
本発明の第２の態様に係る多層成形品の射出成形方法においては、工程（Ｂ）において、第１の溶融樹脂の単位時間当たりの射出量を第２の溶融樹脂の単位時間当たりの射出量よりも多くすることが好ましい。射出成形条件にも依存するが、多層成形品の主たる部分を、第１の樹脂層／第２の樹脂層／第１の樹脂層の３層構成とすることができる。あるいは又、多層成形品の主たる部分の一部分を、第１の樹脂層／第２の樹脂層／第１の樹脂層の３層構成とすることができる。これらの場合、多層成形品の主たる部分以外の部分は、第１の樹脂層によって構成される。
【００２０】
上記の目的を達成するための本発明の第３の態様に係る多層成形品の射出成形方法は、上記の本発明の多層成形品を成形するための射出成形装置を使用した射出成形方法であり、
（Ａ）第１の射出シリンダー内で溶融させた第１の溶融樹脂を、第１の樹脂流路を介してキャビティ内に射出した後、第１の溶融樹脂の射出を終了し、
（Ｂ）第２の射出シリンダー内で溶融させた第２の溶融樹脂を、第２の樹脂流路を介してキャビティ内に射出した後、第２の溶融樹脂の射出を終了し、次いで、
（Ｃ）第１の射出シリンダーによって保圧を行い、併せて、逆流手段の動作によって第１の樹脂流路内の第１の溶融樹脂を第２の樹脂流路内に流入させる、
工程から成ることを特徴とする。図２０に、本発明の第３の態様に係る多層成形品の射出成形方法における射出圧力等の時間変化を示す。
【００２１】
上記の目的を達成するための本発明の第４の態様に係る多層成形品の射出成形方法は、上記の本発明の多層成形品を成形するための射出成形装置を使用した同時射出成形方法であり、
（Ａ）第１の射出シリンダー内で溶融させた第１の溶融樹脂を、第１の樹脂流路を介してキャビティ内に射出し、
（Ｂ）第１の溶融樹脂の射出中に、第２の射出シリンダー内で溶融させた第２の溶融樹脂を第２の樹脂流路を介してキャビティ内に射出し、
（Ｃ）第１の溶融樹脂の射出と第２の溶融樹脂の射出を略同時に完了した後、第１の射出シリンダーによって保圧を行い、併せて、逆流手段の動作によって第１の樹脂流路内の第１の溶融樹脂を第２の樹脂流路内に流入させる、
工程から成ることを特徴とする。図２１に、本発明の第４の態様に係る多層成形品の射出成形方法における射出圧力等の時間変化を示す。
【００２２】
本発明の多層成形品を成形するための射出成形装置、若しくは、本発明の第１〜第４の態様に係る多層成形品の射出成形方法においては、逆流手段は、第１の樹脂流路内の第１の溶融樹脂を第２の樹脂流路内に一定量流入させることが好ましい。また、第２の樹脂流路を経由して第２の溶融樹脂をキャビティ内に射出しているとき及び射出完了後には、第２の射出シリンダーの内部とキャビティとは逆流手段によって連通状態となり、第１の樹脂流路内の第１の溶融樹脂が第２の樹脂流路内に所定量流入した後、第２の射出シリンダーの内部とキャビティとは逆流手段によって非連通状態となることが好ましい。尚、所定量と一定量との間には、（所定量）≦（一定量）の関係がある。あるいは又、第２の樹脂流路を経由して第２の溶融樹脂をキャビティ内に射出しているとき及び射出完了後には、第２の射出シリンダーの内部とキャビティとは逆流手段によって連通状態となり、第１の樹脂流路内の第１の溶融樹脂が第２の樹脂流路内に流入し始めた後、第２の射出シリンダーの内部とキャビティとは逆流手段によって非連通状態となることが好ましい。
【００２３】
本発明の多層成形品を成形するための射出成形装置、若しくは、本発明の第１〜第４の態様に係る多層成形品の射出成形方法においては、逆流手段は、樹脂流路の合流部と第２の射出シリンダーとの間の第２の樹脂流路に設けられていることが好ましい。この場合、逆流手段は、第２の射出シリンダーのノズル部と金型との間、若しくは、第２の射出シリンダーのノズル部に配設されていることが特に好ましい。
【００２４】
本発明の多層成形品を成形するための射出成形装置、若しくは、本発明の第１〜第４の態様に係る多層成形品の射出成形方法においては、一定量の第１の溶融樹脂を第２の樹脂流路内に流入させるという観点から、また、構造の簡素化の観点から、逆流手段を逆流制御弁とすることが好ましい。逆流制御弁として、ボール形式逆流制御弁又はスライド形式逆流制御弁を挙げることができる。
【００２５】
本発明の多層成形品を成形するための射出成形装置、若しくは、本発明の第１〜第４の態様に係る多層成形品の射出成形方法においては、第２の樹脂流路内に流入させる第１の溶融樹脂の体積は、キャビティの体積の５乃至５０％、好ましくは５乃至３５％、より好ましくは５乃至２５％とすることが望ましい。第２の樹脂流路内に流入する第１の溶融樹脂の体積がキャビティの体積の５％未満では、多層成形品の最外層を構成しない樹脂が最外層表面に出現することを防止することが困難となる。一方、射出条件にも依るが、第１の溶融樹脂を第２の樹脂流路内に流入させることにより、多層成形品の各層を構成する樹脂層に乱れが発生するが、これらの乱れを確実に防止するためには、第２の樹脂流路内に流入する第１の溶融樹脂の体積がキャビティの体積の３５％以下、特に２５％以下であることが望ましい。キャビティの体積の５０％を越える場合には、多層成形品の各層を構成する樹脂層に、実用上、問題となる程度の乱れが多々発生する虞がある。
【００２６】
本発明の多層成形品を成形するための射出成形装置、若しくは、本発明の第１〜第４の態様に係る多層成形品の射出成形方法においては、成形すべき多層成形品は如何なる構造、形状のものであってもよく、例えば、多層容器（多層ボトル）を成形するための前駆体であるパリソンを挙げることができる。この場合、第１の樹脂流路を経由してキャビティ内に射出された第１の溶融樹脂によってパリソンの最外層が形成されることが好ましい。また、成形すべき多層成形品として、その他、自動車用バンパー、自動車用ドアハンドルを挙げることができる。また、成形品に強度と外観性等の異なった機能を付与するために、多層成形技術によって複数の樹脂を組み合わせた多層成形品を挙げることもできる。
【００２７】
本発明の第１〜第４の態様に係る多層成形品の射出成形方法においては、第２の樹脂として、ガスバリヤー性を有する熱可塑性樹脂（ガスバリヤー性樹脂）、回収ポリエチレンテレフタレート樹脂（パリソン成形時に一旦使用した後の再生ポリエチレンテレフタレート樹脂を含む）、着色ポリエチレンテレフタレート樹脂から成る群から選択された少なくとも１種の樹脂を挙げることができる。
【００２８】
ここで、ガスバリヤー性樹脂は、メタキシリレン基含有ポリアミド樹脂（ＭＸナイロン樹脂）、エチレン−酢酸ビニル共重合樹脂ケン化物、ポリアクリルニトリル樹脂、ポリ塩化ビニリデン樹脂から成る群から選択された少なくとも１種の樹脂であることが好ましいが、中でも、ＭＸナイロン樹脂とすることが一層好ましい。
【００２９】
ＭＸナイロン樹脂とは、メタキシリレンジアミン単独、又は、メタキシリレンジアミン及び全量の３０％以下のパラキシリレンジアミンを含む混合キシリレンジアミンと炭素数６〜１０のα・ω−脂肪族ジカルボン酸とから得られる構成単位を少なくとも７０モル％以上含有する重合体を意味する。これらの重合体の例としては、ポリメタキシリレンアジパミド、ポリメタキシリレンセバカミド、ポリメタキシリレンスベラミド等のような単独重合体、メタキシリレン／パラキシリレンアジパミド共重合体、メタキシリレン／パラキシリレンスベラミド共重合体のような共重合体、あるいは、これらの単独若しくは共重合体成分と、ヘキサメチレンジアミンのような脂肪族ジアミン、ピペラジン等の脂環族ジアミン、パラ−ビス−（２−アミノエチル）ベンゼン等の芳香族ジアミン、テレフタル酸等の芳香族ジカルボン酸、ε−カプロラクタム等のラクタム、ω−アミノヘプタン酸等のω−アミノカルボン酸、パラ−アミノ安息香酸等の芳香族アミノカルボン酸等との共重合を例示することができる。また、これらの重合体に、例えば、ナイロン６、ナイロン６６、ナイロン６１０、ナイロン１１等の重合体を含有させてもよい。
【００３０】
これらのＭＸナイロン樹脂の相対粘度は１．５以上が適当であり、好ましくは２．０〜４．０である。尚、相対粘度（η_rel）は、樹脂１ｇ／９６％硫酸１００ｍｌの条件にて、２５゜Ｃにて測定したときの粘度である。
【００３１】
一方、本発明の第１〜第４の態様に係る多層成形品の射出成形方法において、第１の樹脂として、ポリエチレンテレフタレート、ポリエチレン−２，６−ナフタレート（ＰＥＮ）等の熱可塑性ポリエステル樹脂；熱可塑性共重合ポリエステル樹脂；ポリオレフィン系樹脂；脂肪族ポリアミド樹脂；ポリカーボネート樹脂；ポリアクリルニトリル樹脂；ポリ塩化ビニル樹脂；ポリスチレン樹脂から成る群から選択された少なくとも１種の樹脂を挙げることができるが、中でも、熱可塑性ポリエステル樹脂を用いることが好ましい。また、必要に応じて２種の樹脂をブレンドしたもの、例えば、ポリエチレンテレフタレート樹脂とポリエチレン−２，６−ナフタレート樹脂とをブレンドしたものを使用することもできる。
【００３２】
ここで、ポリエチレンテレフタレートとは、通常、酸成分の８０モル％以上、好ましくは９０モル％以上がテレフタル酸であり、グリコール成分の８０モル％以上、好ましくは９０モル％以上がエチレングリコールであるポリエステルを意味し、残部の他の酸成分としてはイソフタル酸、ジフェニルエ−テル−４，４−ジカルボン酸、ナフタレン−１，４又は２，６−ジカルボン酸、アジピン酸、セバシン酸、デカン−１，１０−ジカルボン酸、ヘキサヒドロテレフタル酸を、また、他のグリコール成分としてはプロピレングリコール、１，４−ブタンジオール、ネオペンチルグリコール、ジエチレングリコール、シクロヘキサンジメタノール、２，２−ビス（４−ヒドロキシエトキシフェニル）プロパン等を例示することができる。更には、オキシ酸として、Ｐ−オキシ安息香酸等を含有するポリエステル樹脂を挙げることもできる。
【００３３】
また、ポリエチレン−２，６−ナフタレートは、エチレン−２，６−ナフタレートの他に、他のエステル形成単位を２０モル％以下、好ましくは１０モル％以下で含有してもよい。他のエステル形成単位を構成するジカルボン酸として、フタル酸、イソフタル酸、テレフタル酸、１，４−ナフタレンジカルボン酸、１，５−ナフタレンジカルボン酸、２，５−ナフタレンジカルボン酸、２，７−ナフタレンジカルボン酸、４，４’−ジフェニルカルボン酸、３，４’−ジフェニルカルボン酸等の芳香族ジカルボン酸；コハク酸、アジピン酸、セバシン酸、ドデカンジオン酸等の脂肪族ジカルボン酸；１，４−シクロヘキサンジカルボン酸、１，３−シクロヘキサンジカルボン酸、デカリンジカルボン酸、テトラリンジカルボン酸等の脂肪族ジカルボン酸を好適なものとして挙げることができる。また、他のエステル形成単位を構成するジオールとして、プロピレングリコール、トリメチレングリコール、ジエチレングリコール、１，４−ブタンジオール等の脂肪族グリコール；１，３−シクロヘキサンジメタノール、１，４−シクロヘキサンジメタノール、１，６−シクロヘキサンジオール等の脂肪族グリコール；ビスフェノールＡ等の芳香族グリコールを好適なものとして挙げることができる。上記のようなポリエチレン−２，６−ナフタレートは、例えば、少量の安息香酸、ベンゾイル安息香酸、ベンジルオキシ安息香酸、メトキシポリエチレングリコール等の単官能化合物によって分子末端を封止されていてもよい。また、グリセリン、トリメシン酸、ペンタエリスリトール等の多官能化合物を極く少量含んでいてもよい。
【００３４】
これらの熱可塑性ポリエステル樹脂の固有粘度は０．４０以上が適当であり、好ましくは０．５０〜１．４である。固有粘度が０．４０未満では、得られる積層成形品（例えば、多層容器）の機械的強度が不十分となる他、例えば多層成形品を透明な非晶質状態で得ることが困難となる。尚、固有粘度（η）は、フェノール／テトラクロロエタン＝６／４（重量比）の混合溶媒を使用して、３０゜Ｃにて測定したときの粘度である。
【００３５】
熱可塑性共重合ポリエステル樹脂とは、テレフタル酸、イソフタル酸、１，４−ナフタレンジカルボン酸、１，５−ナフタレンジカルボン酸、２，５−ナフタレンジカルボン酸、２，６−ナフタレンジカルボン酸、２，７−ナフタレンジカルボン酸等の酸成分と、エチレングリコール、プロピレングリコール、１，３−シクロヘキサンジメタノール、１，４−シクロヘキサンジメタノール、１，３−ビス（２−ヒドロキシエトキシ）ベンゼン、１，４−ビス（２−ヒドロキシエトキシ）ベンゼン等のジオール成分の中から、少なくとも２つの成分を共重合して成る熱可塑性共重合ポリエステル樹脂である。これらの熱可塑性共重合ポリエステル樹脂は、必要に応じて、他の熱可塑性ポリエステル樹脂と混合して使用してもよい。
【００３６】
本発明の第１〜第４の態様に係る多層成形品の射出成形方法においては、熱可塑性ポリエステル樹脂、特にポリエチレンテレフタレート樹脂（ＰＥＴ樹脂）と、ＭＸナイロン樹脂との組み合わせが最も好ましい。その理由は、樹脂の有する透明性、機械的強度、射出成形性、延伸ブロー成形性の全てにおいて優れているためである。また、両樹脂の熱的性質が近いため、成形温度条件の設定が容易である。この場合、ポリエチレンテレフタレート樹脂とＭＸナイロン樹脂の溶融粘度が接近していることが好ましく、例えば固有粘度０．７〜０．８のポリエチレンテレフタレート樹脂を使用する場合、相対粘度２．７前後のＭＸナイロン樹脂を使用することが望ましい。他のガスバリヤー性樹脂を使用する場合にも、その溶融粘度はポリエチレンテレフタレート樹脂の溶融粘度に近い値を有することが好ましい。
【００３７】
更には、本発明の第１〜第４の態様に係る多層成形品の射出成形方法においては、必要に応じて、第１の樹脂や第２の樹脂、あるいは、多層成形品を構成する各樹脂層を形成するための樹脂に、着色剤、紫外線吸収剤、帯電防止剤、酸化防止剤、滑剤、核剤、抗菌剤等を配合することができる。
【００３８】
本発明の射出成形装置においては、第１の樹脂流路内の第１の溶融樹脂を第２の樹脂流路内に流入させる逆流手段が設けられている。それ故、第１の溶融樹脂をキャビティ内に射出する際、樹脂流路の合流部近傍の第２の樹脂流路には、前回の成形サイクルにおいて第２の樹脂流路内に流入した第１の溶融樹脂が既に存在することになる。従って、樹脂流路の合流部近傍において、射出された第１の溶融樹脂と第２の樹脂流路内に存在する第２の溶融樹脂との混合が生じたり、射出状態にない第２の溶融樹脂が射出されつつある第１の溶融樹脂に巻き込まれるといった現象の発生を防止することができる結果、例えば、第２の樹脂が多層成形品の表面に出現するという問題の発生を確実に回避することができる。
【００３９】
本発明の第１〜第４の態様に係る射出成形方法においては、第１の樹脂流路内の第１の溶融樹脂を第２の樹脂流路内に流入させる逆流手段が設けられた本発明の射出成形装置を用いる。それ故、工程（Ａ）において第１の溶融樹脂をキャビティ内に射出する際、樹脂流路の合流部近傍の第２の樹脂流路には、前回の成形サイクルにおいて第２の樹脂流路内に流入した第１の溶融樹脂が既に存在することになる。従って、樹脂流路の合流部近傍において、射出された第１の溶融樹脂と第２の樹脂流路内に存在する第２の溶融樹脂との混合が生じたり、射出状態にない第２の溶融樹脂が射出されつつある第１の溶融樹脂に巻き込まれるといった現象の発生を防止することができる結果、例えば、第２の樹脂が多層成形品の表面に出現するという問題の発生を確実に回避することができる。
【００４０】
本発明において、逆流手段を逆流制御弁から構成すれば、射出成形装置の大型化、複雑化を回避することができるし、樹脂流路からの溶融樹脂の漏れ発生等が生じることもない。逆流制御弁をボール形式逆流制御弁とすれば、ボールが流体圧力によって移動するだけであり、構造が極めて簡素であり、可動部及び摺動部が無い。尚、ボール形式逆流制御弁による流体の制御は、溶融樹脂の流れの制御だけでなく、他の液体やガス体に対しても行うことができる。従来の開閉弁は、外部からの油圧や空気圧等によって電磁バルブやシリンダーを動かし、これらの回転や往復運動によって流体流路を強制的に開閉している。そのため、構造や作動制御が複雑となり、耐久性に乏しい。
【００４１】
【実施例】
以下、図面を参照して、実施例に基づき本発明を説明する。
【００４２】
（実施例１）
実施例１における多層成形品を成形するための射出成形装置（以下、単に射出成形装置と呼ぶ）の概念図を図１及び図２に示す。尚、図１は、射出成形を全く行っていない状態の射出成形装置を示し、図２は、多層成形品の成形直前の第１の溶融樹脂４０Ａ、第２の溶融樹脂４０Ｂの計量済みの射出成形装置の状態を示している。
【００４３】
この射出成形装置は、金型２０と、２つの射出シリンダー１０Ａ，１０Ｂと、第１の射出シリンダー１０Ａの内部とキャビティ２５とを結ぶ第１の樹脂流路２３Ａと、第２の射出シリンダー１０Ｂの内部とキャビティ２５とを結ぶ第２の樹脂流路２３Ｂとを備えている。金型２０は、キャビティ２５が設けられたキャビティブロック２１と、ホットランナーブロック２２から構成されている。キャビティブロック２１は、複数のブロックが組み合わされて構成されている。そして、金型２０内に位置する第１の樹脂流路２３Ａ及び第２の樹脂流路２３Ｂの部分は、ホットランナーブロック２２内に設けられている。更に、第１の樹脂流路２３Ａと第２の樹脂流路２３Ｂとは、キャビティ２５に開口したゲート部２４の上流の合流部で合流する構造を有する。また、第１及び第２の射出シリンダー１０Ａ，１０Ｂのノズル部を参照番号１２Ａ，１２Ｂで示す。第１の樹脂流路２３Ａと第２の樹脂流路２３Ｂとの合流部より上流（射出シリンダー側）における第１の樹脂流路２３Ａ及び第２の樹脂流路２３Ｂの一部分は、二重管構造となっている。この二重管構造の樹脂流路における内側の管状の第２の樹脂流路２３Ｂ内にはゲートカットピン２６が配設されている。ゲートカットピン２６は空気圧シリンダー２７の作動によってキャビティ２５に近づく方向及び遠ざかる方向に移動可能である。二重管構造の樹脂流路における外側の第１の樹脂流路２３Ａとキャビティ２５との連通、及び、二重管構造の樹脂流路における内側の管状の第２の樹脂流路２３Ｂとキャビティ２５との連通は、ゲートカットピン２６の移動によって制御することができる。即ち、ゲートカットピン２６を前進端に位置させると、第１の樹脂流路２３Ａとキャビティ２５との連通、及び、第２の樹脂流路２３Ｂとキャビティ２５との連通が遮断される。また、ゲートカットピン２６を後進端に位置させると、第１の樹脂流路２３Ａとキャビティ２５との連通、及び、第２の樹脂流路２３Ｂとキャビティ２５との連通が確保される。尚、図１には、ゲートカットピン２６がゲート部２４から抜き出された状態（後進端に位置する状態）を示す。また、図２には、ゲートカットピン２６がゲート部２４に挿入された状態（前進端に位置する状態）を示す。ここで、図２において、参照番号４０Ａは、第１の射出シリンダー１０Ａから第１の樹脂流路２３Ａ及びゲート部２４を介してキャビティ２５に射出される第１の溶融樹脂を示し、参照番号４０Ｂは、第２の射出シリンダー１０Ｂから第２の樹脂流路２３Ｂ及びゲート部２４を介してキャビティ２５に射出される第２の溶融樹脂を示す。また、参照番号４０ａは、前回の射出時に流入し、第２の樹脂流路２３Ｂ内に残された第１の溶融樹脂４０Ａの残り（図中、白四角印で表現する）を示す。尚、キャビティブロック２１の内部には冷却水を流す配管が配設され、ホットランナーブロック２２の内部にはヒータが配設されているが、かかる配管やヒータの図示は省略した。
【００４４】
本発明の射出成形装置においては、第２の溶融樹脂４０Ｂを第２の樹脂流路２３Ｂを経由してキャビティ２５内に射出した後、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａを第２の樹脂流路２３Ｂ内に一定量流入させる逆流手段が設けられている。この逆流手段は、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂに及ぼす圧力によって動作する。実施例１の射出成形装置においては、この逆流手段は、第１及び第２の樹脂流路２３Ａ，２３Ｂの合流部より上流の第２の樹脂流路２３Ｂに設けられた逆流制御弁であり、具体的には、この逆流制御弁はボール形式の逆流制御弁３０Ｂである。尚、逆流制御弁３０Ｂは、第２の射出シリンダー１０Ｂのノズル部１２Ｂと金型２０との間に配設されているが、ノズル部１２Ｂ内に配設されていてもよい。
【００４５】
従来のボールチェッキ弁（逆止弁）は、溶融樹脂の逆流を防止するために設けられている。一方、実施例１における逆流制御弁３０Ｂは、一定量の第２の溶融樹脂４０Ｂを逆流させ得る構造を有する。具体的には、図６の（Ａ）に模式的な端面図を示すように、逆流制御弁３０Ｂは、中空部３２を有する円筒管部３１と、中空部３２内に格納されたボール３４から構成されている。中空部３２の下流側（金型側）の端部から上流側（射出シリンダー側）に向かっての所定の中空部３２の部分の直径はボール３４の直径よりも大きい。この中空部３２の部分を拡径部３３と呼ぶ。中空部３２の拡径部３３以外の部分の直径は、ボール３４の直径とほぼ等しい。
【００４６】
第２の射出シリンダー１０Ｂから第２の溶融樹脂４０Ｂをキャビティ２５に向かって送り出す際には、図６の（Ｂ）に示すように、ボール３４は中空部３２の下流側端部の拡径部３３に第２の溶融樹脂４０Ｂの圧力によって押し付けられる。従って、第２の樹脂流路２３Ｂを経由して第２の溶融樹脂４０Ｂをキャビティ２５内に射出しているとき及び射出完了後には、第２の射出シリンダー１０Ｂの内部とキャビティ２５とは逆流制御弁３０Ｂによって連通状態となる。ボール３４と拡径部３３との間の隙間を通って第２の溶融樹脂４０Ｂはキャビティ２５に向かって流れる。
【００４７】
一方、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂに及ぼす圧力によって、第２の溶融樹脂４０Ｂは逆流する。そして、第２の溶融樹脂４０Ｂが逆流制御弁３０Ｂ内を逆流する際には、逆流する第２の溶融樹脂４０Ｂの圧力によってボール３４は中空部３２の上流側端部に向かって移動させられ、最終的には、中空部３２の上流側端部に押し付けられる（図６の（Ｃ）参照）。ボール３４と中空部３２の上流側端部との間には隙間が存在しない。従って、図６の（Ｃ）に示した状態においては、これ以上、第２の溶融樹脂４０Ｂの逆流が生じることはない。言い換えれば、ボール３４が円筒管部３１の拡径部３３から中空部３２の上流側端部に移動する間に、第２の溶融樹脂４０Ｂは逆流制御弁３０Ｂ内を逆流する。この逆流する第２の溶融樹脂４０Ｂの体積は、概ね、ボール３４の断面積及びボール３４の移動距離の積によって規定され、一定量である。言い換えれば、この逆流する第２の溶融樹脂４０Ｂの体積は、概ね、中空部３２の体積からボール３４の体積を減じた値と略等しく、一定量である。従って、ボール３４の直径及びボール３４の移動距離を適切に選択、設定することにより、第２の樹脂流路２３Ｂ内に流入する第１の溶融樹脂４０Ａの体積を規定することができる。即ち、第２の樹脂流路２３Ｂ内に流入する第１の溶融樹脂４０Ａの体積を、キャビティの体積の５乃至５０％、好ましくは５乃至３５％、一層好ましくは５乃至２５％とするためには、ボール３４の直径及びボール３４の移動距離を適切に選択、設定すればよい。言い換えれば、ボール３４の断面積及びボール３４の移動距離の積は、第２の樹脂流路２３Ｂ内に流入する第１の溶融樹脂４０Ａの体積とほぼ等しい。尚、図６の（Ｂ）及び（Ｃ）において、第２の溶融樹脂４０Ｂの流れる方向を矢印で示した。
【００４８】
尚、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し始めると、ボール３４が円筒管部３１の拡径部３３から中空部３２の上流側端部に向かって移動する。第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に所定量流入したとき、ボール３４は拡径部３３と拡径部３３以外の部分の境界に達する、中空部３２の拡径部３３以外の部分にボール３４が侵入した時点で、中空部３２の拡径部３３以外の部分の直径はボール３４の直径とほぼ等しいので、第２の射出シリンダー１０Ｂの内部とキャビティ２５とは逆流制御弁３０Ｂによって非連通状態となる。
【００４９】
図６の（Ｂ）の矢印Ａ−Ａに沿った円筒管部３１の模式的な断面図を図７の（Ａ）及び（Ｂ）に示す。図７の（Ａ）及び（Ｂ）に示した構造においては円筒管部３１の拡径部３３の内面の４カ所から、突起部３３Ａが円筒管部３１の軸線と平行な方向にボール受け部３１Ｃ近傍まで延びており、ボール３４は突起部３３Ａの頂点若しくは頂面に接触しながら移動する。また、図６の（Ｂ）の矢印Ａ−Ａに沿った円筒管部３１の拡径部３３の変形例を、図７の（Ｃ）及び（Ｄ）に示す。図７の（Ｃ）及び（Ｄ）に示した構造においては円筒管部３１の拡径部３３の内面の３カ所から、突起部３３Ａが円筒管部３１の軸線と平行な方向にボール受け部３１Ｃ近傍まで延びている。図７の（Ａ）及び（Ｃ）に示した構造においては、突起部３３Ａの断面形状は円形を一部切り欠いた形状である。また、図７の（Ｂ）及び（Ｄ）に示した構造においては、突起部３３Ａの断面形状は略矩形である。第２の溶融樹脂４０Ｂは、ボール３４と突起部３３Ａと拡径部３３の内面によって囲まれた空間内を流動する。尚、突起部３３Ａの断面形状、突起部３３Ａの数、円筒管部３１の軸線に垂直な面でかかる空間を切断したときの空間の形状は、図７の（Ａ）〜（Ｄ）に示した形状や数に限定するものではない。更には、図６の（Ｂ）の矢印Ｂ−Ｂに沿ったボール受け部３１Ｃの模式的な断面図を図７の（Ｅ）に示す。また、図６の（Ｂ）の矢印Ｂ−Ｂに沿ったボール受け部３１Ｃの部分の変形例を図７の（Ｆ）、（Ｇ）及び（Ｈ）の模式的な断面図に示す。図７の（Ｅ）〜（Ｈ）に示すように、中空部３２の下流側端部に設けられたボール受け部３１Ｃと円筒管部３１との間には、円筒管部３１の軸線と平行な方向に延びる空間３１Ｂが設けられており、かかる空間３１Ｂは拡径部３３に連通しており、第２の溶融樹脂４０Ｂはこれらの空間３１Ｂ内を流動する。ボール受け部３１Ｃと円筒管部３１は一体に作製してもよいし、個別に作製してもよい。尚、円筒管部３１の軸線に垂直な面でかかる空間３１Ｂを切断したときの空間３１Ｂの形状や数は、図７の（Ｅ）〜（Ｈ）に示した形状や数に限定するものではない。
【００５０】
第１及び第２の射出シリンダー１０Ａ，１０Ｂに配設されたスクリュー１１Ａ，１１Ｂのそれぞれは、樹脂を可塑化、溶融すると同時にプランジャの作用も有する形式のインラインスクリュー方式である。以下、図８を参照して、第２の射出シリンダー１０Ｂを例にとり説明を行うが、図９に示すように、第１の射出シリンダー１０Ａも同様の構造とすることができる。スクリュー１１Ｂは、減速歯車１３を介して油圧モータ１４によって回転させられる。ホッパ１５からスクリュー１１Ｂに投入された第２の樹脂は、加熱シリンダー１０Ｂ、スクリュー１１Ｂによって加熱、可塑化、溶融、計量され、加熱シリンダー１０Ｂとスクリュー１１Ｂの先端の間に形成された空隙１６に蓄えられる。スクリュー１１Ｂの後端には射出ラム１７Ｂが取り付けられており、射出ラム１７Ｂは射出用油圧シリンダー１８Ｂによって圧力が加えられる。射出用油圧シリンダー１８Ｂによって射出ラム１７Ｂに圧力を加えることにより、スクリュー１１Ｂが前方に押し出され第２の溶融樹脂に圧力が加わる結果、空隙１６に蓄えられた第２の溶融樹脂は、逆流制御弁３０Ｂ、第２の樹脂流路２３Ｂ及びゲート部２４を経由して、キャビティ２５に射出される。尚、図８において、参照番号１９は射出装置前進後退用シリンダー、参照番号１９Ａ，１９Ｂは油圧配管、参照番号１９Ｃは圧力計である。
【００５１】
以下、図２〜図５を参照して、実施例１の射出成形装置を用いた本発明の第１の態様に係る多層成形品の射出成形方法を説明する。尚、この射出成形方法は交互射出成形方法である。図１４に、実施例１の多層成形品の射出成形方法における射出圧力等の時間変化を示す。
【００５２】
［工程−１００］
図２に示した第１及び第２の溶融樹脂４０Ａ，４０Ｂの計量済みの状態から、多層成形品（実施例１においてはパリソン）を成形するために、空気圧シリンダー２７を作動させてゲートカットピン２６を後退させ、ゲートカットピン２６をゲート部２４から抜き出し、後進端に位置させ、ゲート部２４を開く。そして、第１の射出シリンダー１０Ａ内で溶融させた第１の溶融樹脂４０Ａの一部を、第１の樹脂流路２３Ａを介してキャビティ２５内に射出する。即ち、射出用油圧シリンダー１８Ａによって射出ラム１７Ａに圧力を加えることによりスクリュー１１Ａを前方に押し出す。これによって、第１の射出シリンダー１０Ａ内で溶融された第１の溶融樹脂４０Ａの一部は、第１の樹脂流路２３Ａ及びゲート部２４を経由してキャビティ２５内に射出される。この状態を模式的に図３に示す。尚、図３において、参照番号４０ａは、前回の射出時に流入し、第２の樹脂流路２３Ｂ内に残された第１の溶融樹脂４０Ａの残り（図中、白四角印で表現する）を示す。
【００５３】
例えば、キャビティ２５における溶融樹脂充填率がキャビティ２５の体積の例えば７０％以下においては、第１の溶融樹脂４０Ａをキャビティ２５内に射出する際には、第１の溶融樹脂４０Ａの射出に起因した第２の射出シリンダー１０Ｂに向かう圧力が、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂには殆ど加わらない。それ故、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが第２の射出シリンダー１０Ｂに向って逆流することはない。
【００５４】
尚、多層成形品の最外層を形成するために第１の溶融樹脂４０Ａを第１の樹脂流路２３Ａを経由してキャビティ２５内に射出するより以前に、即ち、この［工程−１００］より以前に（具体的には、例えば前回の成形サイクルにおいて）、多層成形品の最外層ではない層を形成するための溶融樹脂以外の溶融樹脂（実施例１においては、第１の溶融樹脂４０Ａ）が、合流部より上流の第２の樹脂流路２３Ｂに既に一定量流入している。
【００５５】
［工程−１１０］
そして、第１の溶融樹脂４０Ａを中止する。即ち、第１の射出シリンダー１０Ａにおける射出用油圧シリンダー１８Ａによる射出ラム１７Ａへの加圧を中止する。そして、第２の射出シリンダー１０Ｂ内で溶融させた第２の溶融樹脂４０Ｂを、第２の樹脂流路２３Ｂを介してキャビティ２５内に射出する。即ち、第２の射出シリンダー１０Ｂにおいて、射出用油圧シリンダー１８Ｂによって射出ラム１７Ｂに圧力を加えることによりスクリュー１１Ｂを前方に押し出す。これによって、第２の射出シリンダー１０Ｂ内で溶融された第２の溶融樹脂４０Ｂは、第２の樹脂流路２３Ｂ及びゲート部２４を経由してキャビティ２５内に射出される。第２の溶融樹脂４０Ｂの射出途中の状態を模式的に図４に示す。キャビティ２５内に射出された第２の溶融樹脂４０Ｂは、射出条件にも依るが、既にキャビティ２５の一部分を充填した第１の溶融樹脂４０Ａの中央部を前進する。前回の成形サイクルにおいて流入し、第２の樹脂流路２３Ｂ内に残された第１の溶融樹脂４０ａも、第２の溶融樹脂４０Ｂと一緒にキャビティ２５内に射出される。尚、図４には第１の溶融樹脂４０ａの図示は省略した。
【００５６】
尚、３つの射出シリンダーを備えた射出成形装置を用い、［工程−１１０］に引き続き、第３の射出シリンダー内で溶融させた第３の樹脂を、第３の樹脂流路を介してキャビティ内に射出してもよい。この場合、例えば、第３の樹脂を、第１の樹脂と同種の樹脂あるいは異種の樹脂とすることができる。
【００５７】
［工程−１２０］
第２の溶融樹脂４０Ｂの射出が完了したならば、第２の射出シリンダー１０Ｂにおける射出用油圧シリンダー１８Ｂによる射出ラム１７Ｂへの加圧を中止する。そして、第１の射出シリンダー１０Ａ内で溶融させた第１の溶融樹脂４０Ａの残りを、第１の樹脂流路２３Ａ及びゲート部２４を介してキャビティ２５内に射出する。即ち、第１の射出シリンダー１０Ａにおいて、射出用油圧シリンダー１８Ａによって射出ラム１７Ａに圧力を加えることによりスクリュー１１Ａを前方に押し出す。これによって、第１の射出シリンダー１０Ａ内で溶融された第１の溶融樹脂４０Ａは、第１の樹脂流路２３Ａ及びゲート部２４を経由してキャビティ２５内に射出される。第１の溶融樹脂４０Ａの射出完了時点における状態を模式的に図５に示す。尚、射出すべき第１の溶融樹脂４０Ａの残りの量は、キャビティ２５の全てを充填するのに充分な量及び第２の樹脂流路２３Ｂ内に流入する量の合計とする。キャビティ２５内に射出された第１の溶融樹脂４０Ａは、射出条件にも依るが、既にキャビティ２５の一部分を充填した第２の溶融樹脂４０Ｂの中央部を前進する。
【００５８】
このとき、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂに対して第２の射出シリンダー１０Ｂに向かう圧力が第１の溶融樹脂４０Ａによって加わる。それ故、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが第２の射出シリンダー１０Ｂに向って逆流する。その結果、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａの一部が第２の樹脂流路２３Ｂ内に流入する。先に説明したとおり、第２の溶融樹脂４０Ｂの逆流によってボール３４が円筒管部３１の拡径部３３から中空部３２の上流側端部に移動させられる。この逆流する第２の溶融樹脂４０Ｂの体積は一定量である。従って、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入する量も一定量となる。尚、第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂の部分を参照番号４０ａで示し、白四角印で表現した。このとき、第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂４０ａと第２の溶融樹脂４０Ｂとは、射出成形条件に依っては、殆ど混ざり合わない場合もあるし、混ざり合う場合もある。また、射出成形条件に依っては、この工程では、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａの一部が第２の樹脂流路２３Ｂ内に流入する現象が生ぜず、次の保圧期間中において、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａの一部が第２の樹脂流路２３Ｂ内に流入する現象が生じる場合もある。また、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａの一部が第２の樹脂流路２３Ｂ内に流入し終わる時点は、射出成形条件に依って、第１の溶融樹脂４０Ａの射出中の場合があるし、次の保圧期間中となる場合もある。
【００５９】
［工程−１３０］
第１の溶融樹脂４０Ａの射出完了後、第１の射出シリンダー１０Ａによって保圧を行う。その後、ゲートカットピン２６を前進させ、ゲートカットピン２６によってゲート部２４を閉じる。そして、キャビティ２５内の樹脂を冷却した後、金型２０を開き、多層成形品であるパリソンを取り出す。こうして得られた多層成形品の主たる部分（パリソンの側面の主たる部分）は、射出条件にも依るが、第１の樹脂４０Ａ／第２の樹脂４０Ｂ／第１の樹脂４０Ａ／第２の樹脂４０Ｂ／第１の樹脂４０Ａの５層構造である。また、多層成形品の主たる部分以外の部分は、第１の樹脂層によって構成される。
【００６０】
第２の樹脂流路２３Ｂ内に流入する第１の溶融樹脂４０Ａの体積は、キャビティ２５の体積の５乃至５０％であることが好ましい。第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂４０ａは、第２の溶融樹脂４０Ｂの射出時に、第２の溶融樹脂４０Ｂと共にキャビティ２５内に射出される。第２の樹脂流路２３Ｂ内に流入する第１の溶融樹脂４０ａの体積がキャビティ２５の体積の５０％以下ならば、第２の溶融樹脂４０Ｂと共にキャビティ内に射出される第１の溶融樹脂４０ａが多層成形品の特性に何ら悪影響を与えることがない。尚、第２の樹脂流路２３Ｂ内に流入する第１の溶融樹脂４０ａの体積がキャビティ２５の体積の２５％以下ならば、多層成形品の各層を構成する樹脂層に乱れが発生することを確実に防止することができる。第２の樹脂流路２３Ｂ内に流入する第１の溶融樹脂４０ａの体積がキャビティ２５の体積の２５％を越え、５０％以下の場合には、多層成形品の各層を構成する樹脂層に若干の乱れが発生する場合があるが、実用上問題となる乱れではない。第２の樹脂流路２３Ｂ内に流入する第１の溶融樹脂４０ａの体積がキャビティ２５の体積の５０％を越える場合には、多層成形品の各層を構成する樹脂層に、実用上、問題となる程度の乱れが発生する場合がある。
【００６１】
一方、第２の樹脂流路２３Ｂ内に流入する第１の溶融樹脂４０ａの体積がキャビティ２５の体積の５％未満の場合、例えば［工程−１００］において第１の溶融樹脂４０Ａをキャビティ２５内に射出する際、前回の射出時に流入しそして第２の樹脂流路２３Ｂ内に残された第１の溶融樹脂４０ａ、更には、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが、キャビティ２５内に射出される第１の溶融樹脂４０Ａに巻き込まれ、第２の溶融樹脂４０Ｂもキャビティ２５内に流入する。その結果、キャビティ２５内で第１の溶融樹脂４０Ａと第２の溶融樹脂４０Ｂの混合が生じ、第２の樹脂４０Ｂが多層成形品の最外層表面に出現するといった問題が生じる場合がある。
【００６２】
先に説明したように、第１の樹脂流路内の第１の溶融樹脂が第２の樹脂流路内に流入する現象は、常に起こるわけではなく、キャビティ２５内における溶融樹脂充填率が例えば７０％を越える場合に発生する。従って、［工程−１００］において、キャビティ２５における溶融樹脂充填率がキャビティ２５の体積の例えば７０％以下においては、第１の溶融樹脂４０Ａをキャビティ２５内に射出する際には、第１の溶融樹脂４０Ａの射出に起因した第２の射出シリンダー１０Ｂに向かう圧力が、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂには殆ど加わらず、第２の樹脂流路２３Ｂ内に第１の溶融樹脂４０Ａが流入することはない。また、［工程−１１０］においても、第２の樹脂流路２３Ｂ及びゲート部２４を経由して第２の溶融樹脂４０Ｂをキャビティ２５内に射出したとき、キャビティ２５における溶融樹脂充填率が例えば７０％を越えない場合には、第２の溶融樹脂４０Ｂをキャビティ２５内に射出する際、第２の溶融樹脂４０Ｂの射出に起因した第１の射出シリンダー１０Ａに向かう圧力が、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａには殆ど加わらない。それ故、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第１の射出シリンダー１０Ａに向って逆流することはない。第１の射出シリンダー１０Ａのノズル部１２Ａあるいはノズル部１２Ａと金型２０との間に逆流を防止するための弁を配設する必要はないが、場合によっては、かかる弁を射出シリンダー１０Ａのノズル部１２Ａあるいはノズル部１２Ａと金型２０との間に配設してもよい。この場合の弁は、逆流制御弁３０Ｂと同様の構造であってもよいし、従来の溶融樹脂の逆流を防止するボールチェッキ弁（逆止弁）であってもよい。
【００６３】
尚、射出条件によっては、［工程−１２０］においてキャビティ２５内に射出された第１の溶融樹脂４０Ａは、既にキャビティ２５の一部分を充填した第２の溶融樹脂４０Ｂの中央部を前進するが第２の溶融樹脂４０Ｂから成る樹脂層の先端部分にまでは到達せず、図１０の（Ａ）にパリソンの模式的な断面図を示すように、多層成形品の主たる部分（パリソンの側面の主たる部分）の一部分は、第１の樹脂４０Ａ／第２の樹脂４０Ｂ／第１の樹脂４０Ａ／第２の樹脂４０Ｂ／第１の樹脂４０Ａの５層構造の部分であり、多層成形品の主たる部分の他の部分は、第１の樹脂４０Ａ／第２の樹脂４０Ｂ／第１の樹脂４０Ａの３層構造の部分の３層構成とすることもできる。あるいは又、射出条件によっては、図１０の（Ｂ）に示すように、パリソンの側面が３層／５層／３層等の構造を有するパリソンを成形することも可能である。
【００６４】
尚、図１４、図１５及び図１６に交互射出成形方法における射出圧力等の時間変化を示すように、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａの一部が第２の樹脂流路２３Ｂ内に流入する現象が第１の溶融樹脂４０Ａの射出中に生じるか（図１４及び図１５参照）、射出完了後に生じるか（図１６参照）は、射出成形条件に依存する。尚、第１の溶融樹脂４０Ａの射出完了後に逆流手段の動作によって第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入する場合には、具体的には、第１の射出シリンダー１０Ａによって保圧を行い、併せて、第１の溶融樹脂４０Ａの射出完了後に逆流手段の動作によって第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａを第２の樹脂流路２３Ｂ内に流入させる（図１６参照）。また、第１の溶融樹脂４０Ａの射出中に逆流手段の動作によって第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し始めた場合には、第１の溶融樹脂４０Ａの第２の樹脂流路２３Ｂ内への流入完了の時点は、第１の溶融樹脂４０Ａの射出中であってもよいし（図１４参照）、射出完了と同時であってもよいし、射出完了後の保圧期間中であってもよい（図１６参照）。
【００６５】
また、本発明の第２の態様に係る多層成形品の射出成形方法である同時射出成形方法に基づく射出を行えば、即ち、［工程−１１０］において、第１の溶融樹脂４０Ａをキャビティ２５に射出し続けながら、第２の溶融樹脂４０Ｂを一定量だけキャビティ２５に射出すれば、図１１の（Ａ）にパリソンの模式的な断面図を示すように、多層成形品の主たる部分（パリソンの側面の主たる部分）が、第１の樹脂層／第２の樹脂層／第１の樹脂層の３層構造のパリソンが得られる。場合によっては、図１１の（Ｂ）にパリソンの模式的な断面図を示すように、多層成形品の主たる部分（パリソンの側面の主たる部分）の一部分が、第１の樹脂層／第２の樹脂層／第１の樹脂層の３層構成のパリソンを得ることもできる。尚、図１７、図１８及び図１９に射出圧力等の時間変化を示すように、第２の溶融樹脂４０Ｂの射出完了後であって第１の溶融樹脂４０Ａの射出中若しくは射出完了後、逆流手段の動作によって第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａを第２の樹脂流路２３Ｂ内に流入させる。第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａの一部が第２の樹脂流路２３Ｂ内に流入する現象が第１の溶融樹脂４０Ａの射出中に生じるか（図１７及び図１８参照）、射出完了後に生じるか（図１９参照）は、射出成形条件に依存する。尚、第１の溶融樹脂４０Ａの射出完了後に逆流手段の動作によって第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入する場合には、具体的には、第１の射出シリンダー１０Ａによって保圧を行い、併せて、第１の溶融樹脂４０Ａの射出完了後に逆流手段の動作によって第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａを第２の樹脂流路２３Ｂ内に流入させる（図１９参照）。また、第１の溶融樹脂４０Ａの射出中に逆流手段の動作によって第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し始めた場合には、第１の溶融樹脂４０Ａの第２の樹脂流路２３Ｂ内への流入完了の時点は、第１の溶融樹脂４０Ａの射出中であってもよいし（図１７参照）、射出完了と同時であってもよいし、射出完了後の保圧期間中であってもよい（図１８参照）。
【００６６】
更には、場合によっては、［工程−１２０］を省略することもできる。この場合、本発明の第３の態様に係る多層成形品の射出成形方法である交互射出成形方法においては、［工程−１１０］において、第２の溶融樹脂４０Ｂをキャビティ２５に射出し、キャビティ２５内を第２の溶融樹脂４０Ｂで完全に満たす。また、本発明の第４の態様に係る多層成形品の射出成形方法である同時射出成形方法においては、［工程−１１０］において、第１の溶融樹脂４０Ａをキャビティ２５に射出し続けながら、第２の溶融樹脂４０Ｂをキャビティ２５に射出し、キャビティ２５内を第１の溶融樹脂４０Ａ及び第２の溶融樹脂４０Ｂで完全に満たす。そして、これらの場合、［工程−１３０］において、第１の射出シリンダー１０Ａによる保圧を行う。この第１の射出シリンダー１０Ａによる保圧によって、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂに対して第２の射出シリンダー１０Ｂに向かう圧力が第１の溶融樹脂４０Ａによって加わる。その結果、逆流手段が動作し、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが第２の射出シリンダー１０Ｂに向って逆流し、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａの一部が第２の樹脂流路２３Ｂ内に流入する（図２０及び図２１参照）。
【００６７】
尚、逆流制御弁として、図６の（Ａ）〜（Ｃ）に示したボール形式逆流制御弁の代わりに、図１２の（Ａ）〜（Ｃ）に示すスライド形式逆流制御弁５０を用いることもできる。このスライド形式逆流制御弁５０は、一定量の第２の溶融樹脂４０Ｂを逆流させ得る構造を有する。具体的には、図１２の（Ａ）に模式的な端面図を示すように、逆流制御弁５０は、中空部５２を有する円筒管部５１と、中空部５２内に格納された弁体５４と、バー５５から構成されている。バー５５は円筒管部５１の中心部にその軸線に沿って配設され、支持体５６Ａ，５６Ｂによって円筒管部５１に取り付けられている。第２の溶融樹脂４０Ｂは、支持体５６Ａ，５６Ｂを自由に通過し得る。弁体５４の中心部はバー５５に滑動自在に取り付けられている。中空部５２の下流側（金型側）の端部から上流側（射出シリンダー側）に向かっての所定の中空部５２の部分の断面積は弁体５４の断面積よりも大きい。この中空部５２の部分を拡径部５３と呼ぶ。中空部５２の拡径部５３以外の部分の断面形状は、弁体５４の断面形状とほぼ等しい。
【００６８】
第２の射出シリンダー１０Ｂから第２の溶融樹脂４０Ｂをキャビティ２５に向かって射出する場合には、図１２の（Ｂ）に示すように、弁体５４は中空部５２の下流側端部の支持体５６Ａに第２の溶融樹脂４０Ｂの圧力によって押し付けられる。従って、第２の樹脂流路２３Ｂを経由して第２の溶融樹脂４０Ｂをキャビティ２５内に射出しているとき及び射出完了後には、第２の射出シリンダー１０Ｂの内部とキャビティ２５とは逆流制御弁５０によって連通状態となる。弁体５４と拡径部５３との間の隙間を通って第２の溶融樹脂４０Ｂはキャビティ２５に向かって流れる。
【００６９】
一方、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂに及ぼす圧力によって、第２の溶融樹脂４０Ｂは逆流する。そして、第２の溶融樹脂４０Ｂが逆流制御弁５０内を逆流する際には、第２の樹脂流路２３Ｂに流入する第１の溶融樹脂４０Ａの圧力によって弁体５４は中空部５２の上流側端部に向かって移動させられ、最終的には、中空部５２の上流側端部に押し付けられる（図１２の（Ｃ）参照）。弁体５４と中空部５２の上流側端部との間には隙間が存在しない。従って、図１２の（Ｃ）に示した状態においては、これ以上、第２の溶融樹脂４０Ｂの逆流が生じることはない。言い換えれば、弁体５４が円筒管部５１の中空部５２の下流側端部から上流側端部に移動する間に、第２の溶融樹脂４０Ｂは逆流制御弁５０内を逆流する。この逆流する第２の溶融樹脂４０Ｂの体積は、概ね、弁体５４が移動する中空部５２の部分の断面積及び弁体５４の移動距離の積によって規定され、一定量である。言い換えれば、この逆流する第２の溶融樹脂４０Ｂの体積は、概ね、中空部５２の体積から弁体５４の体積を減じた値と略等しく、一定量である。従って、弁体５４が移動する中空部５２の部分の断面積及び弁体５４の移動距離を適切に選択、設定することにより、第２の樹脂流路２３Ｂ内に流入する第１の溶融樹脂４０Ａの体積を規定することができる。言い換えれば、弁体５４が移動する中空部５２の部分の断面積及び弁体５４の移動距離の積は、第２の樹脂流路２３Ｂ内に流入する第１の溶融樹脂４０Ａの体積とほぼ等しい。図１２の（Ｂ）及び（Ｃ）において、第２の溶融樹脂４０Ｂの流れる方向を矢印で示した。尚、第２の溶融樹脂４０Ｂの流れる方向に垂直な面で切断したときの弁体５４及び中空部５２の形状は円形であることが好ましいが、かかる形状に限定されず、矩形等、任意の形状とすることができる。
【００７０】
尚、第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し始めると、弁体５４が中空部５２を上流側端部に向かって移動する。第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に所定量流入したとき、弁体５４は、拡径部５３と拡径部５３以外の部分の境界に達する。中空部５２の拡径部５３以外の部分に弁体５４が侵入した時点で、中空部５２の拡径部５３以外の部分の断面形状は弁体５４の断面形状とほぼ等しいので、第２の射出シリンダー１０Ｂの内部とキャビティ２５とは逆流制御弁５０によって非連通状態となる。
【００７１】
図１２の（Ｂ）の矢印Ａ−Ａに沿った円筒管部５１の模式的な断面図を図１３の（Ａ）に示す。また、図１２の（Ｂ）の矢印Ｂ−Ｂに沿った円筒管部５１の模式的な断面図を図１３の（Ｂ）に示す。支持体５６Ａは中央部が円盤状であり、周囲から４本の腕が延び、これらの腕の先端部が円筒管部５１の内面に達している。支持体５６Ａと円筒管部５１は一体に作製してもよいし、個別に作製してもよい。支持体５６Ａの中心部にはバー５５が固定されている。尚、支持部５６Ａの構造は、図１３の（Ａ）及び（Ｂ）に示した構造に限定されるものではなく、支持体５６Ａの中央部の形状、腕の数は、任意である。
【００７２】
実施例１においては、２つの射出シリンダーを備え、２つの射出シリンダーのそれぞれの内部とキャビティとを結ぶ２つの樹脂流路を有する射出成形装置を例にとり説明を行ったが、射出シリンダーの数は３つ以上であってもよく、この場合には、射出シリンダーの数と同じ数の樹脂流路を設ければよい。そして、［工程−１１０］と［工程−１２０］との間で、第３、第４・・・の射出シリンダーから溶融した第３、第４・・・の樹脂をキャビティ２５へと射出すればよい。この場合、１つの樹脂流路が第１の樹脂流路に相当し、残りの樹脂流路が第２の樹脂流路に相当する。尚、第２の樹脂流路のそれぞれに流入する第１の溶融樹脂の体積が、キャビティの体積の５乃至５０％、好ましくは５乃至３５％、より好ましくは５乃至２５％であることが望ましい。また、金型に設けられたキャビティの数は１つに限定されず、任意である。キャビティの数が複数の場合、第１の樹脂流路及び第２の樹脂流路のそれぞれをキャビティの数だけ分岐し、分岐された各樹脂流路を各キャビティに開口した各ゲート部と結べばよい。この場合、本発明の射出成形装置においては、逆流手段の下流で樹脂流路を分岐することが好ましい。尚、第２の樹脂流路のそれぞれに流入する第１の溶融樹脂の体積が、キャビティの体積の５乃至５０％、好ましくは５乃至３５％、より好ましくは５乃至２５％であることが望ましい。
【００７３】
実施例１においては、第２の樹脂流路２３Ｂ内にゲートカットピン２６が配設されている構造としたが、ゲート部の構造や、ゲート部における溶融樹脂の温度を適宜設定することによって、ゲートカットピンを省略することもできる。
【００７４】
また、実施例１においては、射出シリンダー内で樹脂の可塑化、溶融、計量を行い、射出シリンダーから溶融樹脂の射出を行ったが、ポット式（シューティング・ポット式あるいは加熱ポット式とも呼ばれる）の成形装置を用いることもできる。このポット式の成形装置においては、樹脂の可塑化、溶融、計量をシリンダー内で行い、溶融樹脂を射出用ポット内に充填する。シリンダーと射出用ポットとの間には逆止弁が配設されている。射出用ポット内に充填された溶融樹脂には射出用シリンダーから圧力が加えられ、樹脂流路及びゲート部を介して溶融樹脂がキャビティ内に射出される。このようなポット式の成形装置においても、射出用ポットとキャビティとを結ぶ第２の樹脂流路に逆流手段を配設すればよい。
【００７５】
以下、実施例２〜実施例１１及び比較例１〜比較例３により、本発明を更に詳細に説明する。尚、これらの実施例及び比較例における温度条件を以下の表１に示すが、特に断りの無い限り、表１の温度条件を採用した。また、これらの実施例及び比較例においては、図１に示した実施例１の射出成形装置を使用した。
【００７６】
【表１】
射出シリンダー１０Ａにおける第１の溶融樹脂４０Ａの温度：２７０゜Ｃ
射出シリンダー１０Ｂにおける第２の溶融樹脂４０Ｂの温度：２６０゜Ｃ
ホットランナーブロック内の第１及び第２の樹脂流路の温度：２７０゜Ｃ
キャビティブロック内の冷却水の温度：１５゜Ｃ
【００７７】
ポリエチレンテレフタレート樹脂の固有粘度（η）は、フェノール／テトラクロロエタン＝６／４（重量比）の混合溶媒を使用して、３０゜Ｃにて測定した。一方、ポリメタキシリレンアジパミド樹脂の相対粘度（η_rel）は、樹脂１ｇ／９６％硫酸１００ｍｌの条件にて、２５゜Ｃにて測定した。また、層間接着強度の測定は、剥離方向１８０度、剥離速度２０ｍｍ／分、試料寸法１０ｍｍ（幅）×１００ｍｍ（長さ）にて行った。
【００７８】
（実施例２）
第１の樹脂４０Ａとして、固有粘度０．７５のポリエチレンテレフタレート樹脂（ＰＥＴ樹脂。日本ユニペット株式会社製のＲＴ５４３Ｃ）を用い、第２の樹脂４０Ｂとして、相対粘度２．７のポリメタキシリレンアジパミド樹脂（Ｎ−ＭＸＤ６樹脂。三菱瓦斯化学株式会社製の＃６００７）を使用した。そして、実施例１にて説明した各工程に基づき、ＰＥＴ樹脂、Ｎ−ＭＸＤ６樹脂、ＰＥＴ樹脂を交互に射出し、５層構成のパリソンを交互射出成形方法（本発明の第１の態様に係る多層成形品の射出成形方法）に基づき成形した。パリソンの長さを１１０ｍｍ、肉厚を４．５ｍｍ、外形直径を２６．５ｍｍとした。尚、このようなパリソンに基づき二軸延伸ブロー成形法にて得られる多層ボトルの寸法は、全長２００ｍｍ、外径７５ｍｍ、容積６００ミリリットルである。
【００７９】
第１の樹脂流路２３Ａと第２の樹脂流路２３Ｂとの合流部より上流（射出シリンダー側）における第１の樹脂流路２３Ａ及び第２の樹脂流路２３Ｂの一部分は、二重管構造となっており、この部分の長さを１２０ｍｍとした。この二重管構造の樹脂流路における外側の第１の樹脂流路２３Ａの外径を１８ｍｍ、内径を１４ｍｍとした。一方、この二重管構造の樹脂流路における内側の管状の第２の樹脂流路２３Ｂの直径を８ｍｍとした。また、円柱状のゲートカットピン２６の外径を４ｍｍとした。
【００８０】
第１の射出シリンダー１０Ａとしては内径５０ｍｍのものを使用して、第１の樹脂４０Ａ（ＰＥＴ樹脂）を可塑化し、溶融した。また、第２の射出シリンダー１０Ｂとしては内径４０ｍｍのものを使用し、第２の樹脂４０Ｂ（Ｎ−ＭＸＤ６樹脂）を可塑化し、溶融した。逆流手段としてボール形式逆流制御弁３０Ｂを使用した。金型２０には４つのキャビティ２５が設けられており、各樹脂流路２３Ａ，２３Ｂを、逆流制御弁３０Ｂよりも下流で分岐させて、各々のキャビティ２５に開口したゲート部２４へと繋げた。
【００８１】
射出成形前には、前回の射出時に第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂４０ａがキャビティ２５の体積の５％に相当する量だけ第２の樹脂流路２３Ｂ内に残っていた。
【００８２】
先ず、［工程−１００］と同様にして、第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５の体積の３０％に相当する量だけキャビティ２５に射出した。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入することはなかった。
【００８３】
次いで、［工程−１１０］と同様にして、第２の射出シリンダー１０Ｂから第２の溶融樹脂４０Ｂ（溶融Ｎ−ＭＸＤ６樹脂）をキャビティ２５に射出した。射出した第２の溶融樹脂４０Ｂの量を、キャビティ２５の体積の５％に相当する量とした。前回の射出時に第２の樹脂流路２３Ｂ内に流入し、キャビティ２５の体積の５％に相当する量だけ残っていた第１の溶融樹脂４０ａもキャビティ２５に射出された。この際にも、第２の溶融樹脂４０Ｂ及び第１の溶融樹脂４０ａが第１の樹脂流路２３Ａ内に流入することはなかった。
【００８４】
続いて、［工程−１２０］と同様にして、第１の射出シリンダー１０Ａから第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５に射出した。射出した第１の溶融樹脂４０Ａの量を、キャビティ２５を溶融樹脂で充填するためのキャビティ２５の体積の６０％に相当する量と、第２の樹脂流路２３Ｂ内に第１の溶融樹脂４０Ａが流入する量の合計とした。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが逆流し、第２の射出シリンダー１０Ｂ内のスクリュー１１Ｂが後退したが、逆流制御弁３０Ｂの作動によって、第２の樹脂流路２３Ｂへの第１の溶融樹脂４０Ａの流入はキャビティ２５の体積の５％にとどまった。
【００８５】
次に、第１の射出シリンダー１０Ａにより、１５秒間保圧した後、空気圧シリンダー２７を作動させてゲートカットピン２６を前進させてゲート部２４を閉じた。その後、１０秒間冷却した後、金型を開き、積層成形品であるパリソンを金型から取り出した。得られたパリソンは、図５に示したと同様に、ＰＥＴ樹脂層／Ｎ−ＭＸＤ６樹脂層／ＰＥＴ樹脂層／Ｎ−ＭＸＤ６樹脂層／ＰＥＴ樹脂層の５層構造であり、樹脂層に乱れの無い、きれいな樹脂層が形成されていた。また、Ｎ−ＭＸＤ６樹脂層がパリソンの最外層表面（パリソンの内側表面及び外側表面）に出現する現象も全く認められなかった。得られた多層パリソンを１００゜Ｃに加熱して、二軸延伸ブロー成形法にて多層ボトルを製造したところ、外観良好な多層ボトルが得られた。
【００８６】
（実施例３）
ボール３４の直径は実施例２にて使用した逆流制御弁３０Ｂのボール３４の直径と同じであるが、ボール３４の移動距離が実施例２にて使用した逆流制御弁３０Ｂよりも長いボール形式逆流制御弁３０Ｂに交換した以外は、実施例２の射出成形装置を用いてパリソンの成形を行った。
【００８７】
射出成形前には、前回の射出時に第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂４０ａがキャビティ２５の体積の１５％に相当する量だけ第２の樹脂流路２３Ｂ内に残っていた。
【００８８】
先ず、［工程−１００］と同様にして、第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５の体積の４０％に相当する量だけキャビティ２５に射出した。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入することはなかった。
【００８９】
次いで、［工程−１１０］と同様にして、第２の射出シリンダー１０Ｂから第２の溶融樹脂４０Ｂ（溶融Ｎ−ＭＸＤ６樹脂）をキャビティ２５に射出した。射出した第２の溶融樹脂４０Ｂの量を、キャビティ２５の体積の５％に相当する量とした。前回の射出時に第２の樹脂流路２３Ｂ内に流入し、キャビティ２５の体積の１５％に相当する量だけ残っていた第１の溶融樹脂４０ａもキャビティ２５に射出された。この際にも、第２の溶融樹脂４０Ｂ及び第１の溶融樹脂４０ａが第１の樹脂流路２３Ａ内に流入することはなかった。
【００９０】
続いて、［工程−１２０］と同様にして、第１の射出シリンダー１０Ａから第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５に射出した。射出した第１の溶融樹脂４０Ａの量を、キャビティ２５を溶融樹脂で充填するためのキャビティ２５の体積の４０％に相当する量と、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂの逆流する量に相当する量の合計とした。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが逆流し、第２の射出シリンダー１０Ｂ内のスクリュー１１Ｂが後退したが、逆流制御弁３０Ｂの作動によって、第２の樹脂流路２３Ｂへの第１の溶融樹脂４０Ａの流入はキャビティ２５の体積の１５％にとどまった。
【００９１】
次に、第１の射出シリンダー１０Ａにより、１５秒間保圧した後、空気圧シリンダー２７を作動させてゲートカットピン２６を前進させてゲート部２４を閉じた。その後、１０秒間冷却した後、金型を開き、積層成形品であるパリソンを金型から取り出した。得られたパリソンは、図５に示したと同様に、ＰＥＴ樹脂層／Ｎ−ＭＸＤ６樹脂層／ＰＥＴ樹脂層／Ｎ−ＭＸＤ６樹脂層／ＰＥＴ樹脂層の５層構造であり、樹脂層に乱れの無い、きれいな樹脂層が形成されていた。また、Ｎ−ＭＸＤ６樹脂層がパリソンの最外層表面（パリソンの内側表面及び外側表面）に出現する現象も全く認められなかった。また、外観良好な多層ボトルが得られた。
【００９２】
（実施例４）
第２の樹脂４０Ｂとして、Ｎ−ＭＸＤ６樹脂の代わりに、エチレン−酢酸ビニル共重合樹脂ケン化物（ＥＶＯＨ。クラレ株式会社製のＥＶＡＬＥＦ−Ｅ）を用いた。実施例４に於ける温度条件を、以下の表２に示す。ボール３４の直径は実施例３にて使用した逆流制御弁３０Ｂのボール３４の直径と同じであるがボール３４の移動距離が実施例３にて使用した逆流制御弁３０Ｂよりも長いボール形式逆流制御弁３０Ｂに交換した点を除き、実施例２と同様の射出成形装置にて射出成形を行った。
【００９３】
【表２】
射出シリンダー１０Ａにおける第１の溶融樹脂４０Ａの温度：２７０゜Ｃ
射出シリンダー１０Ｂにおける第２の溶融樹脂４０Ｂの温度：２３０゜Ｃ
ホットランナーブロック内の第１及び第２の樹脂流路の温度：２７０゜Ｃ
キャビティブロック内の冷却水の温度：１５゜Ｃ
【００９４】
射出成形前には、前回の射出時に第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂４０ａがキャビティ２５の体積の２５％に相当する量だけ第２の樹脂流路２３Ｂ内に残っていた。
【００９５】
先ず、［工程−１００］と同様にして、第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５の体積の４０％に相当する量だけキャビティ２５に射出した。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入することはなかった。
【００９６】
次いで、［工程−１１０］と同様にして、第２の射出シリンダー１０Ｂから第２の溶融樹脂４０Ｂ（溶融ＥＶＯＨ樹脂）をキャビティ２５に射出した。射出した第２の溶融樹脂４０Ｂの量を、キャビティ２５の体積の５％に相当する量とした。前回の射出時に第２の樹脂流路２３Ｂ内に流入し、キャビティ２５の体積の２５％に相当する量だけ残っていた第１の溶融樹脂４０ａもキャビティ２５に射出された。この際にも、第２の溶融樹脂４０Ｂ及び第１の溶融樹脂４０ａが第１の樹脂流路２３Ａ内に流入することはなかった。
【００９７】
続いて、［工程−１２０］と同様にして、第１の射出シリンダー１０Ａから第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５に射出した。射出した第１の溶融樹脂４０Ａの量を、キャビティ２５を溶融樹脂で充填するためのキャビティ２５の体積の３０％に相当する量と、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂの逆流する量に相当する量の合計とした。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが逆流し、第２の射出シリンダー１０Ｂ内のスクリュー１１Ｂが後退したが、逆流制御弁３０Ｂの作動によって、第２の樹脂流路２３Ｂへの第１の溶融樹脂４０Ａの流入はキャビティ２５の体積の２５％にとどまった。
【００９８】
次に、第１の射出シリンダー１０Ａにより、１５秒間保圧した後、空気圧シリンダー２７を作動させてゲートカットピン２６を前進させてゲート部２４を閉じた。その後、１０秒間冷却した後、金型を開き、積層成形品であるパリソンを金型から取り出した。得られたパリソンは、図５に示したと同様に、ＰＥＴ樹脂層／ＥＶＯＨ樹脂層／ＰＥＴ樹脂層／ＥＶＯＨ樹脂層／ＰＥＴ樹脂層の５層構造であり、樹脂層に乱れの無い、きれいな樹脂層が形成されていた。また、ＥＶＯＨ樹脂層がパリソンの最外層表面（パリソンの内側表面及び外側表面）に出現する現象も全く認められなかった。また、外観良好な多層ボトルが得られた。
【００９９】
（実施例５）
ボール３４の直径は実施例２にて使用した逆流制御弁３０Ｂのボール３４の直径と同じであるが、ボール３４の移動距離が実施例２にて使用した逆流制御弁３０Ｂよりも長いボール形式逆流制御弁３０Ｂに交換した点、第１の射出シリンダー１０Ａのノズル部１２Ａに従来の逆止弁を設けた点を除き、実施例２と同様の射出成形装置にて射出成形を行った。尚、第２の樹脂４０ＢとしてＮ−ＭＸＤ６樹脂の代わりに回収ＰＥＴ樹脂を用いた。
【０１００】
射出成形前には、前回の射出時に第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂４０ａがキャビティ２５の体積の１０％に相当する量だけ第２の樹脂流路２３Ｂ内に残っていた。
【０１０１】
先ず、［工程−１００］と同様にして、第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５の体積の５０％に相当する量だけキャビティ２５に射出した。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入することはなかった。
【０１０２】
次いで、［工程−１１０］と同様にして、第２の射出シリンダー１０Ｂから第２の溶融樹脂４０Ｂ（回収ＰＥＴ樹脂）をキャビティ２５に射出した。射出した第２の溶融樹脂４０Ｂの量を、キャビティ２５の体積の２０％に相当する量とした。前回の射出時に第２の樹脂流路２３Ｂ内に流入し、キャビティ２５の体積の１０％に相当する量だけ残っていた第１の溶融樹脂４０ａもキャビティ２５に射出された。この際、第１の射出シリンダー１０Ａのノズル部１２Ａに従来の逆止弁が設けられているので、第２の溶融樹脂４０Ｂ及び第１の溶融樹脂４０ａが第１の樹脂流路２３Ａ内に流入することはなかった。
【０１０３】
続いて、［工程−１２０］と同様にして、第１の射出シリンダー１０Ａから第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５に射出した。射出した第１の溶融樹脂４０Ａの量を、キャビティ２５を溶融樹脂で充填するためのキャビティ２５の体積の２０％に相当する量と、第２の樹脂流路２３Ｂ内に第１の溶融樹脂４０Ａが流入する量の合計とした。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが逆流し、第２の射出シリンダー１０Ｂ内のスクリュー１１Ｂが後退したが、逆流制御弁３０Ｂの作動によって、第２の樹脂流路２３Ｂへの第１の溶融樹脂４０Ａの流入はキャビティ２５の体積の１０％にとどまった。
【０１０４】
次に、第１の射出シリンダー１０Ａにより、１５秒間保圧した後、空気圧シリンダー２７を作動させてゲートカットピン２６を前進させてゲート部２４を閉じた。その後、１０秒間冷却した後、金型を開き、積層成形品であるパリソンを金型から取り出した。得られたパリソンは、図５に示したと同様に、ＰＥＴ樹脂層／回収ＰＥＴ樹脂層／ＰＥＴ樹脂層／回収ＰＥＴ樹脂層／ＰＥＴ樹脂層の５層構造であり、樹脂層に乱れの無い、きれいな樹脂層が形成されていた。また、回収ＰＥＴ樹脂層がパリソンの最外層表面に出現する現象も全く認められなかった。得られた多層パリソンを１００゜Ｃに加熱して、二軸延伸ブロー成形法にて多層ボトルを製造したところ、外観良好な多層ボトルが得られた。
【０１０５】
（実施例６）
ボール３４の直径は実施例４にて使用した逆流制御弁３０Ｂのボール３４の直径と同じであるが、ボール３４の移動距離が実施例４にて使用した逆流制御弁３０Ｂよりも長いボール形式逆流制御弁３０Ｂに交換した点、第１の射出シリンダー１０Ａのノズル部１２Ａに従来の逆止弁を設けた点を除き、実施例２と同様の射出成形装置にて射出成形を行った。尚、第２の樹脂４０ＢとしてＮ−ＭＸＤ６樹脂の代わりに、回収ＰＥＴ樹脂を用いた。
【０１０６】
射出成形前には、前回の射出時に第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂４０ａがキャビティ２５の体積の５０％に相当する量だけ第２の樹脂流路２３Ｂ内に残っていた。
【０１０７】
先ず、［工程−１００］と同様にして、第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５の体積の３０％に相当する量だけキャビティ２５に射出した。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入することはなかった。
【０１０８】
次いで、［工程−１１０］と同様にして、第２の射出シリンダー１０Ｂから第２の溶融樹脂４０Ｂ（回収ＰＥＴ樹脂）をキャビティ２５に射出した。射出した第２の溶融樹脂４０Ｂの量を、キャビティ２５の体積の１０％に相当する量とした。前回の射出時に第２の樹脂流路２３Ｂ内に流入し、キャビティ２５の体積の５０％に相当する量だけ残っていた第１の溶融樹脂４０ａもキャビティ２５に射出された。この際、第１の射出シリンダー１０Ａのノズル部１２Ａに従来の逆止弁が設けられているので、第２の溶融樹脂４０Ｂ及び第１の溶融樹脂４０ａが第１の樹脂流路２３Ａ内に流入することはなかった。
【０１０９】
続いて、［工程−１２０］と同様にして、第１の射出シリンダー１０Ａから第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５に射出した。射出した第１の溶融樹脂４０Ａの量を、キャビティ２５を溶融樹脂で充填するためのキャビティ２５の体積の１０％に相当する量と、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂの逆流する量に相当する量の合計とした。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが逆流し、第２の射出シリンダー１０Ｂ内のスクリュー１１Ｂが後退したが、逆流制御弁３０Ｂの作動によって、第２の樹脂流路２３Ｂへの第１の溶融樹脂４０Ａの流入はキャビティ２５の体積の５０％にとどまった。
【０１１０】
次に、第１の射出シリンダー１０Ａにより、１５秒間保圧した後、空気圧シリンダー２７を作動させてゲートカットピン２６を前進させてゲート部２４を閉じた。その後、１０秒間冷却した後、金型を開き、積層成形品であるパリソンを金型から取り出した。得られたパリソンは、ＰＥＴ樹脂層／回収ＰＥＴ樹脂層／ＰＥＴ樹脂層／回収ＰＥＴ樹脂層／ＰＥＴ樹脂層の５層構造を有し、各層を構成する樹脂層に若干の乱れが発生したが、実用上問題となる乱れではなかった。また、回収ＰＥＴ樹脂層がパリソンの最外層表面に出現する現象も全く認められなかった。得られた多層パリソンを１００゜Ｃに加熱して、二軸延伸ブロー成形法にて多層ボトルを製造したところ、外観良好な多層ボトルが得られた。
【０１１１】
（実施例７）
実施例２と同じ樹脂を使用し、実施例２の射出成形装置を用いて、射出成形を行った。尚、温度条件は表１と同様とした。実施例７が実施例２と相違する点は、実施例２が交互射出成形方法であったのに対して、実施例７においては同時射出成形方法（本発明の第２の態様に係る多層成形品の射出成形方法）を採用した点にある。
【０１１２】
射出成形前には、前回の射出時に第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂４０ａがキャビティ２５の体積の５％に相当する量だけ第２の樹脂流路２３Ｂ内に残っていた。
【０１１３】
先ず、［工程−１００］と同様にして、第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５の体積の２０％に相当する量だけキャビティ２５に射出した。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入することはなかった。
【０１１４】
次いで、キャビティ２５への第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）の射出を続行しながら、第２の射出シリンダー１０Ｂから第２の溶融樹脂４０Ｂ（溶融Ｎ−ＭＸＤ６樹脂）をキャビティ２５に射出した。射出した第２の溶融樹脂４０Ｂの量を、キャビティ２５の体積の５％に相当する量とした。前回の射出時に第２の樹脂流路２３Ｂ内に流入し、キャビティ２５の体積の５％に相当する量だけ残っていた第１の溶融樹脂４０ａもキャビティ２５に射出された。この際にも、第２の溶融樹脂４０Ｂ及び第１の溶融樹脂４０ａが第１の樹脂流路２３Ａ内に流入することはなかった。
【０１１５】
その後、キャビティ２５への第２の溶融４０Ｂ樹脂の射出を中止した。そして、キャビティ２５への第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）の射出を続行し、キャビティ２５内を溶融樹脂で完全に充填した。射出した第１の溶融樹脂４０Ａの量を、キャビティ２５を溶融樹脂で充填するためのキャビティ２５の体積の７０％に相当する量と、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂの逆流する量に相当する量の合計とした。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが逆流し、第２の射出シリンダー１０Ｂ内のスクリュー１１Ｂが後退したが、逆流制御弁３０Ｂの作動によって、第２の樹脂流路２３Ｂへの第１の溶融樹脂４０Ａの流入はキャビティ２５の体積の５％にとどまった。
【０１１６】
次に、第１の射出シリンダー１０Ａにより、１５秒間保圧した後、空気圧シリンダー２７を作動させてゲートカットピン２６を前進させてゲート部２４を閉じた。その後、１０秒間冷却した後、金型を開き、積層成形品であるパリソンを金型から取り出した。得られたパリソンは、図１１の（Ａ）に示したと同様に、ＰＥＴ樹脂層／Ｎ−ＭＸＤ６樹脂層／ＰＥＴ樹脂層の３層構造であり、樹脂層に乱れの無い、きれいな樹脂層が形成されていた。また、Ｎ−ＭＸＤ６樹脂層がパリソンの最外層表面（パリソンの内側表面及び外側表面）に出現する現象も全く認められなかった。得られた多層パリソンを１００゜Ｃに加熱して、二軸延伸ブロー成形法にて多層ボトルを製造したところ、外観良好な多層ボトルが得られた。
【０１１７】
（実施例８）
逆流手段を図１２の（Ａ）に示したスライド形式逆流制御弁５０に換えた以外は、実施例２の射出成形装置を用い、実施例２と同様の射出形成条件にてパリソンの成形を行った。
【０１１８】
射出成形前には、前回の射出時に第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂４０ａがキャビティ２５の体積の２０％に相当する量だけ第２の樹脂流路２３Ｂ内に残っていた。
【０１１９】
先ず、［工程−１００］と同様にして、第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５の体積の３０％に相当する量だけキャビティ２５に射出した。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入することはなかった。
【０１２０】
次いで、［工程−１１０］と同様にして、第２の射出シリンダー１０Ｂから第２の溶融樹脂４０Ｂ（溶融Ｎ−ＭＸＤ６樹脂）をキャビティ２５に射出した。射出した第２の溶融樹脂４０Ｂの量を、キャビティ２５の体積の５％に相当する量とした。前回の射出時に第２の樹脂流路２３Ｂ内に流入し、キャビティ２５の体積の２０％に相当する量だけ残っていた第１の溶融樹脂４０ａもキャビティ２５に射出された。この際にも、第２の溶融樹脂４０Ｂ及び第１の溶融樹脂４０ａが第１の樹脂流路２３Ａ内に流入することはなかった。
【０１２１】
続いて、［工程−１２０］と同様にして、第１の射出シリンダー１０Ａから第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５に射出した。射出した第１の溶融樹脂４０Ａの量を、キャビティ２５を溶融樹脂で充填するためのキャビティ２５の体積の４５％に相当する量と、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂの逆流する量に相当する量の合計とした。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが逆流し、第２の射出シリンダー１０Ｂ内のスクリュー１１Ｂが後退したが、逆流制御弁５０の作動によって、第２の樹脂流路２３Ｂへの第１の溶融樹脂４０Ａの流入はキャビティ２５の体積の２０％にとどまった。
【０１２２】
次に、第１の射出シリンダー１０Ａにより、１５秒間保圧した後、空気圧シリンダー２７を作動させてゲートカットピン２６を前進させてゲート部２４を閉じた。その後、１０秒間冷却した後、金型を開き、積層成形品であるパリソンを金型から取り出した。得られたパリソンは、図５に示したと同様に、ＰＥＴ樹脂層／Ｎ−ＭＸＤ６樹脂層／ＰＥＴ樹脂層／Ｎ−ＭＸＤ６樹脂層／ＰＥＴ樹脂層の５層構造であり、樹脂層に乱れの無い、きれいな樹脂層が形成されていた。また、Ｎ−ＭＸＤ６樹脂層がパリソンの最外層表面（パリソンの内側表面及び外側表面）に出現する現象も全く認められなかった。また、外観良好な多層ボトルが得られた。
【０１２３】
（実施例９）
第１の樹脂４０Ａとして、固有粘度０．７５のＰＥＴ樹脂と、固有粘度０．５０のポリエチレン−２，６−ナフタレート樹脂（ＰＥＮ樹脂）とを９０／１０の重量割合でブレンドした樹脂を使用し、温度条件を以下の表３に示す条件とした以外は、実施例２の射出成形装置を用いて射出成形を行った。
【０１２４】
【表３】
射出シリンダー１０Ａにおける第１の溶融樹脂４０Ａの温度：２９０゜Ｃ
射出シリンダー１０Ｂにおける第２の溶融樹脂４０Ｂの温度：２６０゜Ｃ
ホットランナーブロック内の第１及び第２の樹脂流路の温度：２９０゜Ｃ
キャビティブロック内の冷却水の温度：１５゜Ｃ
【０１２５】
射出成形前には、前回の射出時に第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂４０ａがキャビティ２５の体積の５％に相当する量だけ第２の樹脂流路２３Ｂ内に残っていた。
【０１２６】
先ず、［工程−１００］と同様にして、第１の溶融樹脂４０Ａ（溶融ＰＥＴ・ＰＥＮ樹脂）をキャビティ２５の体積の３０％に相当する量だけキャビティ２５に射出した。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入することはなかった。
【０１２７】
次いで、［工程−１１０］と同様にして、第２の射出シリンダー１０Ｂから第２の溶融樹脂４０Ｂ（溶融Ｎ−ＭＸＤ６樹脂）をキャビティ２５に射出した。射出した第２の溶融樹脂４０Ｂの量を、キャビティ２５の体積の５％に相当する量とした。前回の射出時に第２の樹脂流路２３Ｂ内に流入し、キャビティ２５の体積の５％に相当する量だけ残っていた第１の溶融樹脂４０ａもキャビティ２５に射出された。この際にも、第２の溶融樹脂４０Ｂ及び第１の溶融樹脂４０ａが第１の樹脂流路２３Ａ内に流入することはなかった。
【０１２８】
続いて、［工程−１２０］と同様にして、第１の射出シリンダー１０Ａから第１の溶融樹脂４０Ａ（溶融ＰＥＴ・ＰＥＮ樹脂）をキャビティ２５に射出した。射出した第１の溶融樹脂４０Ａの量を、キャビティ２５を溶融樹脂で充填するためのキャビティ２５の体積の６０％に相当する量と、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂの逆流する量に相当する量の合計とした。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが逆流し、第２の射出シリンダー１０Ｂ内のスクリュー１１Ｂが後退したが、逆流制御弁３０Ｂの作動によって、第２の樹脂流路２３Ｂへの第１の溶融樹脂４０Ａの流入はキャビティ２５の体積の５％にとどまった。
【０１２９】
次に、第１の射出シリンダー１０Ａにより、１５秒間保圧した後、空気圧シリンダー２７を作動させてゲートカットピン２６を前進させてゲート部２４を閉じた。その後、１０秒間冷却した後、金型を開き、積層成形品であるパリソンを金型から取り出した。得られたパリソンは、ＰＥＴ・ＰＥＮ樹脂層／Ｎ−ＭＸＤ６樹脂層／ＰＥＴ・ＰＥＮ樹脂層／Ｎ−ＭＸＤ６樹脂層／ＰＥＴ・ＰＥＮ樹脂層の５層構造であり、樹脂層に乱れの無い、きれいな樹脂層が形成されていた。また、Ｎ−ＭＸＤ６樹脂層がパリソンの最外層表面（パリソンの内側表面及び外側表面）に出現する現象も全く認められなかった。得られた多層パリソンを１１０゜Ｃに加熱して、二軸延伸ブロー成形法にて多層ボトルを製造したところ、外観良好な多層ボトルが得られた。
【０１３０】
（実施例１０）
第１の射出シリンダー１０Ａのノズル部１２Ａに従来の逆止弁を設けた点を除き、実施例２と同じ樹脂を使用し、実施例２の射出成形装置を用いて、射出成形を行った。尚、温度条件は表１と同様とした。実施例２が本発明の第１の態様に係る交互射出成形方法であったのに対して、実施例１０においては、本発明の第３の態様に係る多層成形品の射出成形方法（交互射出成形方法）を採用した。
【０１３１】
射出成形前には、前回の射出時に第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂４０ａがキャビティ２５の体積の１０％に相当する量だけ第２の樹脂流路２３Ｂ内に残っていた。
【０１３２】
先ず、［工程−１００］と同様にして、第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５の体積の７０％に相当する量だけキャビティ２５に射出した。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入することはなかった。
【０１３３】
次いで、キャビティ２５への第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）の射出を終了し、［工程−１１０］と同様にして、第２の射出シリンダー１０Ｂ内で溶融させた第２の溶融樹脂４０Ｂ（溶融Ｎ−ＭＸＤ６樹脂）を、第２の樹脂流路２３Ｂを介してキャビティ２５内に射出した。射出した第２の溶融樹脂４０Ｂの量を、キャビティ２５の体積の２０％に相当する量とした。前回の射出時に第２の樹脂流路２３Ｂ内に流入し、キャビティ２５の体積の１０％に相当する量だけ残っていた第１の溶融樹脂４０ａもキャビティ２５に射出された。
【０１３４】
第２の溶融樹脂４０Ｂの射出を終了した後、第１の射出シリンダー１０Ａによって１５秒間の保圧を行い、併せて、ボール形式逆流制御弁３０Ｂの動作によって第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａを第２の樹脂流路２３Ｂ内に流入させた。即ち、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが逆流し、第２の射出シリンダー１０Ｂ内のスクリュー１１Ｂが後退したが、逆流制御弁３０Ｂの作動によって、第２の樹脂流路２３Ｂへの第１の溶融樹脂４０Ａの流入はキャビティ２５の体積の１０％にとどまった。
【０１３５】
その後、空気圧シリンダー２７を作動させてゲートカットピン２６を前進させてゲート部２４を閉じた。そして、１０秒間冷却した後、金型を開き、積層成形品であるパリソンを金型から取り出した。ゲート部に対応するパリソンの部分以外のパリソンの表面には、Ｎ−ＭＸＤ６樹脂層の出現は認められなかった。得られた多層パリソンを１００゜Ｃに加熱して、二軸延伸ブロー成形法にて多層ボトルを製造したところ、外観良好な多層ボトルが得られた。
【０１３６】
（実施例１１）
第１の射出シリンダー１０Ａのノズル部１２Ａに従来の逆止弁を設けた点を除き、実施例２と同じ樹脂を使用し、実施例２の射出成形装置を用いて、射出成形を行った。尚、温度条件は表１と同様とした。実施例２が本発明の第１の態様に係る交互射出成形方法であったのに対して、実施例１１においては、本発明の第４の態様に係る多層成形品の射出成形方法（同時射出成形方法）を採用した。
【０１３７】
射出成形前には、前回の射出時に第２の樹脂流路２３Ｂ内に流入した第１の溶融樹脂４０ａがキャビティ２５の体積の２０％に相当する量だけ第２の樹脂流路２３Ｂ内に残っていた。
【０１３８】
先ず、［工程−１００］と同様にして、第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５の体積の４０％に相当する量だけキャビティ２５に射出した。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入することはなかった。
【０１３９】
引き続き、第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５の体積の２０％に相当する量だけキャビティ２５に射出しながら、第２の射出シリンダー１０Ｂから第２の溶融樹脂４０Ｂ（溶融Ｎ−ＭＸＤ６樹脂）をキャビティ２５に射出した。射出した第２の溶融樹脂４０Ｂの量を、キャビティ２５の体積の２０％に相当する量とした。前回の射出時に第２の樹脂流路２３Ｂ内に流入し、キャビティ２５の体積の２０％に相当する量だけ残っていた第１の溶融樹脂４０ａもキャビティ２５に射出された。
【０１４０】
第１の溶融樹脂４０Ａの射出と第２の溶融樹脂４０Ｂの射出を略同時に完了した後、第１の射出シリンダー１０Ａによって１５秒間の保圧を行い、併せて、ボール形式逆流制御弁３０Ｂの動作によって第１の樹脂流路２３Ａ内の第１の溶融樹脂４０Ａを第２の樹脂流路２３Ｂ内に流入させた。即ち、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入し、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂが逆流し、第２の射出シリンダー１０Ｂ内のスクリュー１１Ｂが後退したが、逆流制御弁３０Ｂの作動によって、第２の樹脂流路２３Ｂへの第１の溶融樹脂４０Ａの流入はキャビティ２５の体積の２０％にとどまった。
【０１４１】
その後、空気圧シリンダー２７を作動させてゲートカットピン２６を前進させてゲート部２４を閉じた。そして、１０秒間冷却した後、金型を開き、積層成形品であるパリソンを金型から取り出した。ゲート部に対応するパリソンの部分以外のパリソンの表面には、Ｎ−ＭＸＤ６樹脂層の出現は認められなかった。得られた多層パリソンを１００゜Ｃに加熱して、二軸延伸ブロー成形法にて多層ボトルを製造したところ、外観良好な多層ボトルが得られた。
【０１４２】
（比較例１）
ボール３４の直径は実施例６にて使用した逆流制御弁３０Ｂのボール３４の直径と同じであるが、ボール３４の移動距離が実施例６にて使用した逆流制御弁３０Ｂよりも長いボール形式逆流制御弁３０Ｂに交換して、実施例２と同じ樹脂及び実施例２と同じ射出成形装置を用いてパリソンの成形を行った。第２の樹脂流路２３Ｂへの第１の溶融樹脂４０Ａの流入がキャビティ２５の体積の６０％以上にも達し、しかも、射出成形サイクル毎に大きく変動した。第２の射出シリンダー１０Ｂにおける第２の溶融樹脂４０Ｂの計量値を増加させたが安定した成形を行うことができず、得られた５層のパリソンは層構造が非常に乱れたものであった。
【０１４３】
（比較例２）
逆流手段を、溶融樹脂の逆流を防止する従来のボールチェッキ弁（逆止弁）に交換した。そして、実施例２と同じ樹脂及び実施例２の射出成形装置を用いてパリソンの成形を行った。
【０１４４】
先ず、［工程−１００］と同様にして、第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５の体積の６０％に相当する量だけキャビティ２５に射出した。この際、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入することはなかった。
【０１４５】
次いで、［工程−１１０］と同様にして、第２の射出シリンダー１０Ｂから第２の溶融樹脂４０Ｂ（溶融Ｎ−ＭＸＤ６樹脂）をキャビティ２５に射出した。射出した第２の溶融樹脂４０Ｂの量を、キャビティ２５の体積の１０％に相当する量とした。
【０１４６】
続いて、［工程−１２０］と同様にして、第１の射出シリンダー１０Ａから第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）をキャビティ２５に射出した。射出した第１の溶融樹脂４０Ａの量を、キャビティ２５を溶融樹脂で充填するためのキャビティ２５の体積の３０％に相当する量とした。この際、従来の逆止弁を使用しているので、第１の溶融樹脂４０Ａが第２の樹脂流路２３Ｂ内に流入することはなかった。
【０１４７】
次に、第１の射出シリンダー１０Ａにより、１５秒間保圧した後、空気圧シリンダー２７を作動させてゲートカットピン２６を前進させてゲート部２４を閉じた。その後、１０秒間冷却した後、金型を開き、積層成形品であるパリソンを金型から取り出した。ＰＥＴ樹脂層／Ｎ−ＭＸＤ６樹脂層／ＰＥＴ樹脂層／Ｎ−ＭＸＤ６樹脂層／ＰＥＴ樹脂層の５層構造のパリソンが得られた。パリソンの表面にはＮ−ＭＸＤ６樹脂層の出現が認められた。
【０１４８】
（比較例３）
逆流手段を、従来の油圧シリンダー作動にて開閉動作するシャットオフ弁に変えた以外は、実施例２と同様の方法にてパリソンの成形を行った。即ち、第２の射出シリンダー１０Ｂのノズル部１２Ｂに、油圧シリンダーの作動にて開閉するシャットオフ弁を配設し、［工程−１１０］の完了後、直ちに油圧シリンダーを作動させてシャットオフ弁を閉じ、第２の溶融樹脂４０Ｂの第２の射出シリンダー１０Ｂ内への逆流を防止した。第２の樹脂流路２３Ｂへの第１の溶融樹脂４０Ａの流入はキャビティ２５の体積の０〜０．９％であった。その結果、［工程−１００］と同様の工程において第１の溶融樹脂４０Ａ（溶融ＰＥＴ樹脂）の射出の際、第２の樹脂流路２３Ｂ内の第２の溶融樹脂４０Ｂ（溶融Ｎ−ＭＸＤ６樹脂）が同伴されてキャビティ２５内に流入し、得られた５層のパリソンの開口部付近の第１の樹脂４０Ａ（ＰＥＴ樹脂）から構成された樹脂層表面に第２の樹脂４０Ｂ（Ｎ−ＭＸＤ６樹脂）が出現していた。
【０１４９】
以上、本発明を、好ましい実施例に基づき説明したが、本発明はこれらに限定されるものではない。実施例１にて説明した射出成形装置は例示であり、適宜、設計変更することができる。また、各実施例にて説明した射出成形装置や射出成形条件も例示であり、適宜、設計変更・条件変更することができるし、実施例にて使用した樹脂も例示である。［工程−１１０］において、溶融樹脂４０Ａを射出し続けながら溶融樹脂４０Ｂの射出を行い、溶融樹脂４０Ｂの射出完了後も溶融樹脂４０Ａを射出し続ける、同時射出成形方法を実行してもよい。実施例においては、逆流手段内を第２の溶融樹脂が逆流したが、逆流手段の配設位置によっては、逆流手段内を第２の溶融樹脂だけでなく第１の溶融樹脂が逆流する場合もあり得る。
【０１５０】
本発明における逆流手段は、断続的に２種類の液体（比較的粘度の高い液体等から構成された流動体を含む）を切り替える場合にも適用することができる。更には、本発明における逆流手段は、断続的に２種類のガス体を切り替える場合にも適用することができる。断続的に切り替える際、最初に使用する液体若しくはガス体中に、第２番目に使用する液体若しくはガス体の混入を避けたい分野に、特に有効であり、石油化学の分野、食品製造分野（菓子の製造分野や食品加工分野等）、化学品製造装置、排水処理設備等への適用が可能である。以下、具体的に適用可能な分野を列挙する。
（１）原油採取設備における原油と海水の切換装置において、海水中に原油が流入することを避ける場合
（２）菓子の製造において、２色の高粘度のクリーム等を切り替えて使用するときに、或る色のクリームが他の色のクリームに混入することを避ける場合
（３）水産加工等の食品加工分野において、真水中に海水が混入することを避ける場合
（４）化学品製造装置において、最終製品と粗製品の貯蔵設備への配管を共通に使用するとき、最終製品に粗製品が混入することを避ける場合
（５）イオン交換装置において、液体の吸着ライン及び脱着ラインの切り替えを行う場合
（６）高純度のガス製造設備において、ガスの流れを断続的に切り替えてガス製造設備を運転するとき、高純度のガス中に原料ガスあるいは粗ガスが混入することを避ける場合
【０１５１】
【発明の効果】
本発明の射出成形装置あるいは本発明の射出成形方法においては、第１の溶融樹脂の射出時、樹脂流路の合流部近傍において、多層成形品の外層を形成する第１の溶融樹脂と第２の樹脂流路内に存在する多層成形品の内層を形成する第２の溶融樹脂との混合が生じたり、射出状態にない第２の溶融樹脂が射出されつつある第１の溶融樹脂に巻き込まれるといった現象の発生を防止することができる。その結果、例えば、第２の樹脂が多層成形品の表面に出現するという問題の発生を確実に回避することができる。樹脂として、例えば熱可塑性ポリエステル樹脂とガスバリヤー性樹脂とから構成された多層成形品であるパリソンを成形すれば、二軸延伸ブロー成形することによって、ガスバリヤー性、透明性、機械的強度に優れた多層容器を製造することができる。しかも、第２の樹脂流路内に流入する第１の溶融樹脂の量の上限を規定することによって、多層成形品の各層を構成する樹脂層に乱れが発生することを確実に防止することができる。
【０１５２】
尚、逆流手段を逆流制御弁から構成すれば、射出成形装置の大型化、複雑化を回避することができるし、樹脂流路からの溶融樹脂の漏れ発生等が生じることもない。更には、逆流手段の作動が迅速であり、しかも、第２の樹脂流路への一定量の第１の溶融樹脂の流入を確実に生じさせることができる。
【図面の簡単な説明】
【図１】実施例１における射出成形装置の概念図であって、射出成形を全く行っていない状態の射出成形装置を示す図である。
【図２】実施例１における射出成形装置の概念図であって、多層成形品の成形直前の第１及び第２の溶融樹脂の計量済みの射出成形装置の状態を示す図である。
【図３】実施例１の射出成形装置を用いた多層成形品の射出成形方法を説明するためのキャビティ等の概念図である。
【図４】図３にに引き続き、実施例１の射出成形装置を用いた多層成形品の射出成形方法を説明するためのキャビティ等の概念図である。
【図５】図４に引き続き、実施例１の射出成形装置を用いた多層成形品の射出成形方法を説明するためのキャビティ等の概念図である。
【図６】実施例１における逆流手段である逆流制御弁の模式的な端面図である。
【図７】図６の（Ｂ）の矢印Ａ−Ａに沿った逆流制御弁の円筒管部の模式的な断面図、及び、図６の（Ｂ）の矢印Ｂ−Ｂに沿った逆流制御弁の円筒管部の模式的な断面図である。
【図８】第２の射出シリンダーの構造を示す模式的な断面図である。
【図９】第１の射出シリンダーの構造を示す模式的な断面図である。
【図１０】パリソンの模式的な断面図である。
【図１１】パリソンの模式的な断面図である。
【図１２】スライド形式逆流制御弁の模式的な端面図である。
【図１３】図１２の（Ｂ）の矢印Ａ−Ａに沿った円筒管部の模式的な断面図、及び、図１２の（Ｂ）の矢印Ｂ−Ｂに沿った円筒管部の模式的な断面図である。
【図１４】本発明の第１の態様に係る多層成形品の射出成形方法における射出圧力等の時間変化を示すグラフである。
【図１５】本発明の第１の態様に係る多層成形品の射出成形方法における射出圧力等の時間変化を示すグラフである。
【図１６】本発明の第１の態様に係る多層成形品の射出成形方法における射出圧力等の時間変化を示すグラフである。
【図１７】本発明の第２の態様に係る多層成形品の射出成形方法における射出圧力等の時間変化を示すグラフである。
【図１８】本発明の第２の態様に係る多層成形品の射出成形方法における射出圧力等の時間変化を示すグラフである。
【図１９】本発明の第２の態様に係る多層成形品の射出成形方法における射出圧力等の時間変化を示すグラフである。
【図２０】本発明の第３の態様に係る多層成形品の射出成形方法における射出圧力等の時間変化を示すグラフである。
【図２１】本発明の第４の態様に係る多層成形品の射出成形方法における射出圧力等の時間変化を示すグラフである。
【符号の説明】
１０Ａ，１０Ｂ・・・射出シリンダー
１１Ａ，１１Ｂ・・・スクリュー
１２Ｂ・・・射出シリンダー１０Ｂのノズル部
１３・・・減速歯車
１４・・・油圧モータ
１５・・・ホッパ
１６・・・空隙
１７Ａ，１７Ｂ・・・射出ラム
１８Ａ，１８Ｂ・・・射出用油圧シリンダー
１９・・・射出装置前進後退用シリンダー
１９Ａ，１９Ｂ・・・油圧配管
１９Ｃ・・・圧力計
２０・・・金型
２１・・・キャビティブロック
２２・・・ホットランナーブロック
２３Ａ，２３Ｂ・・・樹脂流路
２４・・・ゲート部
２５・・・キャビティ
２６・・・ゲートカットピン
２７・・・空気圧シリンダー
３０Ｂ，５０・・・逆流制御弁
３１，５１・・・円筒管部
３２，５２・・・中空部
３３，５３・・・拡径部
３４・・・ボール
４０Ａ，４０Ｂ・・・樹脂又は溶融樹脂
４０ａ・・・他の樹脂流路内に流入した第１の溶融樹脂
５４・・・弁体
５５・・・バー
５６Ａ，５６Ｂ・・・支持体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection molding apparatus for molding a multilayer molded article and an injection molding method for a multilayer molded article.
[0002]
[Prior art]
In recent years, containers using thermoplastic resins have been widely used as containers for cosmetics, foods, beverages and the like because of advantages such as weight reduction and safety against bursting. In particular, the development of containers made of polyethylene terephthalate resin (hereinafter may be abbreviated as PET resin) is progressing rapidly due to improvements in biaxial stretch blow molding technology. However, a biaxially oriented container made of a thermoplastic polyester resin mainly composed of a PET resin does not have perfect performance. That is, especially when the contents to be filled in the container are beverages that require a high gas barrier property for the container, the gas barrier performance against oxygen gas, carbon dioxide gas, etc. is improved in a container molded from PET resin. Is deficient, and thus has the disadvantage of impairing the flavor of the contents. Recently, the demand for gas barrier properties of containers has become higher due to the miniaturization of containers.
[0003]
In response to such demands, two injections that plasticize and melt each of a thermoplastic polyester resin and a metaxylylene group-containing polyamide resin (hereinafter sometimes abbreviated as MX nylon resin) which is a thermoplastic gas barrier resin. Using an injection molding machine equipped with a cylinder and having a single mold, in one molding cycle, the molten thermoplastic polyester resin is injected, and the molten MX nylon resin is injected while continuing to inject the molten thermoplastic polyester resin. A technique for molding a parison having a three-layer structure of thermoplastic polyester resin / MX nylon resin / thermoplastic polyester resin by continuously injecting molten thermoplastic polyester resin even after completion of injection of molten MX nylon resin No. 57-128520. Such an injection molding method is called a simultaneous injection molding method.
[0004]
Further, the method is the same as the above method, but the thermoplastic polyester resin and MX nylon resin are injected in the order of thermoplastic polyester resin, MX nylon resin, and thermoplastic polyester resin under specific conditions, for example, thermoplastic polyester resin. JP-A-60-240409 discloses a technique for molding a parison having a five-layer structure of resin / MX nylon resin / thermoplastic polyester resin / MX nylon resin / thermoplastic polyester resin. Such an injection molding method is called an alternate injection molding method.
[0005]
In recent years, the development of a technique for collecting and granulating containers mainly composed of PET resin and reusing them as recovered PET resin has been promoted. In the case of forming a parison for a beverage container using such recovered PET resin (including a reused PET resin for defective products at the time of parison molding and a recycled PET resin once used at the time of parison molding), the PET resin layer / A three-layer structure of recovered PET resin layer / PET resin layer or a five-layer structure of PET resin layer / recovered PET resin layer / PET resin layer / recovered PET resin layer / PET resin layer is required.
[0006]
Multi-layer containers (multi-layer bottles) having the same appearance and mechanical performance as containers made of polyethylene terephthalate resin and greatly improved barrier properties against oxygen gas and carbon dioxide gas by the techniques disclosed in these patent publications Can be manufactured and is now in use.
[0007]
Conventionally, when a multilayer molded product (for example, a multilayer parison that is a precursor of a multilayer container) is molded from two or more kinds of resins using two or more injection cylinders, a mold provided with a cavity, and at least two An injection molding device with an injection cylinder is used. For example, in an injection molding apparatus equipped with two injection cylinders, each resin flow path (the first resin flow path and the second molten resin through which the first molten resin flows) connects the inside of each injection cylinder and the cavity. The second resin flow path through which the gas flows) has a structure that merges at the merge portion upstream of the gate portion that is open to the cavity. In addition, the part of the 1st resin flow path and 2nd resin flow path which are located in a metal mold | die has a hot runner structure. In addition, the resin flow channel portion upstream of the merge portion usually has a multiple tube structure. The screw disposed in the injection cylinder has a structure that retreats when pressure is applied from the resin flow path, except during the injection and holding of the molten resin, and the molten resin in the resin flow path Back flow into the injection cylinder.
[0008]
[Problems to be solved by the invention]
In the injection molding apparatus having such a structure, in order to completely fill the cavity with the first and second molten resins, the first molten resin constituting the outermost layer of the multilayer molded product is used as the first resin. When injected into the cavity via the flow path, the first molten resin flowing through the first resin flow path flows into the second resin flow path, and the inflow amount of the first molten resin at this time Is not constant. As a result, the amount of the first molten resin to be injected into the cavity becomes unstable, or when the first molten resin is injected for the first time, the second molten resin is present in the second resin flow path near the junction. Since the molten resin and the first molten resin are mixed and injected into the cavity, there arises a problem that the second resin that does not constitute the outermost layer of the multilayer molded product appears on the outermost layer surface.
[0009]
In order to prevent such first molten resin from flowing into the second resin flow path, in the conventional technique, a hydraulic operation is performed on the nozzle portion of the injection cylinder for injecting the second molten resin. A shut-off valve of the type is provided. The shutoff valve is opened only when the second molten resin is injected, and in other cases, the shutoff valve is closed to prevent the first molten resin from flowing into the second resin flow path. Yes.
[0010]
By the way, when the flow of the molten resin is controlled by the shutoff valve, the first molten resin can be prevented from flowing into the second resin flow path, but conversely, when the first molten resin is injected. As a result, the first molten resin and the second molten resin are mixed in the vicinity of the joining portion of the resin flow path, or the second molten resin that is not in the injection state is caught in the first molten resin being injected. The second molten resin in the vicinity of the merging portion flows into the cavity, and for example, the second resin appears on the surface of the multilayer molded product. That is, there arises a problem that the second resin that does not constitute the outermost layer of the multilayer molded product appears on the outermost layer surface.
[0011]
Japanese Patent Application Laid-Open No. 61-206612 discloses a hot for injection molding having a first resin flow path 11 and a second resin flow path 12, and a check valve 13 provided in the second resin flow path 12. A runner mold is disclosed. When the first resin material A is injected, the cavity 22 is completely filled with the resin, but since the check valve 13 is provided in the second resin flow path 12, the first resin material A is provided. The second resin material B does not flow back due to A.
[0012]
An object of the present invention is a multilayer molded product formed from at least two types of resins and laminated with a resin layer composed of each resin, and a resin that does not constitute the outermost layer of the multilayer molded product appears on the outermost layer surface. In other words, in order to mold a multilayer molded article having a structure in which a resin that does not constitute the outermost layer of the multilayer molded article is securely sealed by the resin layer that constitutes the outermost layer of the multilayer molded article. And an injection molding method for a multilayer molded product.
[0013]
[Means for Solving the Problems]
An injection molding apparatus for molding the multilayer molded article of the present invention for achieving the above object
(A) a mold having a cavity block provided with a cavity and a hot runner block;
(B) at least a first injection cylinder and a second injection cylinder;
(C) a first resin flow path connecting the inside of the first injection cylinder and the cavity;
as well as,
(D) a second resin flow path connecting the inside of the second injection cylinder and the cavity;
With
The first resin flow channel and the second resin flow channel located in the mold are provided in the hot runner block,
The first resin flow path and the second resin flow path are injection molding devices having a structure in which the first resin flow path and the second resin flow path are merged at a merge section upstream of the gate section opened in the cavity,
Back flow means for injecting the first molten resin in the first resin flow path into the second resin flow path after injecting the second molten resin into the cavity via the second resin flow path Provided,
The backflow means is operated by a pressure exerted on the second molten resin in the second resin flow path by the first molten resin in the first resin flow path. Here, upstream means the injection cylinder side, and downstream means the cavity side. The same applies to the following.
[0014]
An injection molding method for a multilayer molded article according to the first aspect of the present invention for achieving the above object is an alternate injection molding method using the injection molding apparatus for molding the multilayer molded article of the present invention. is there. That is, the injection molding method of a multilayer molded product according to the first aspect of the present invention for achieving the above object is as follows:
(A) a mold having a cavity block provided with a cavity and a hot runner block;
(B) at least a first injection cylinder and a second injection cylinder;
(C) a first resin flow path connecting the inside of the first injection cylinder and the cavity;
as well as,
(D) a second resin flow path connecting the inside of the second injection cylinder and the cavity;
With
The first resin flow channel and the second resin flow channel located in the mold are provided in the hot runner block,
The first resin flow path and the second resin flow path are injection molding devices having a structure in which the first resin flow path and the second resin flow path are merged at a merge section upstream of the gate section opened in the cavity,
Back flow means for injecting the first molten resin in the first resin flow path into the second resin flow path after injecting the second molten resin into the cavity via the second resin flow path Provided,
The reverse flow means is an injection molding of a multilayer molded article using an injection molding device that operates by pressure exerted by the first molten resin in the first resin flow path on the second molten resin in the second resin flow path. A method,
(A) After injecting the first molten resin melted in the first injection cylinder into the cavity through the first resin flow path, the injection of the first molten resin is interrupted,
(B) After injecting the second molten resin melted in the second injection cylinder into the cavity through the second resin flow path, the injection of the second molten resin is terminated,
(C) The first molten resin melted in the first injection cylinder is injected into the cavity through the first resin flow path, and the reverse flow means is injected during or after the injection of the first molten resin. The first molten resin in the first resin channel is caused to flow into the second resin channel by the operation of
It consists of a process.
[0015]
In the method for injection molding a multilayer molded product according to the first aspect of the present invention, the main part of the multilayer molded product is divided into the first resin layer / second resin layer / first, depending on the injection molding conditions. 5 resin layers / second resin layer / first resin layer. Alternatively, a part of the main part of the multilayer molded product has a five-layer configuration of first resin layer / second resin layer / first resin layer / second resin layer / first resin layer, and multilayer molding is performed. The other part of the main part of the product may have a three-layer configuration of first resin layer / second resin layer / first resin layer. In these cases, the portion other than the main portion of the multilayer molded product is constituted by the first resin layer.
[0016]
FIGS. 14, 15 and 16 show temporal changes such as injection pressure in the injection molding method for multilayer molded articles according to the first aspect of the present invention. 14 to 21, the “closed state” means that the interior of the second injection cylinder and the cavity are not in communication with each other by the backflow means. “Open state” means that the inside of the second injection cylinder and the cavity are in communication with each other by the backflow means, and “backflow” means the first melting in the first resin flow path. The reverse flow means is operated by the pressure exerted by the resin on the second molten resin in the second resin flow path, and the first molten resin in the first resin flow path flows into the second resin flow path. As a result, it means that the second molten resin flows toward the second injection cylinder. In the first method for injection molding a multilayer molded product according to the present invention, the first molten resin in the first resin flow path is changed to the second resin flow path by the operation of the backflow means after the completion of the injection of the first molten resin. In the case of flowing into the inside, specifically, the pressure is held by the first injection cylinder, and at the same time, after the completion of the injection of the first molten resin, the operation of the backflow means causes the first in the first resin flow path. One molten resin is caused to flow into the second resin flow path (see FIG. 16). In addition, when the first molten resin in the first resin flow channel starts to flow into the second resin flow channel by the operation of the backflow means during the injection of the first molten resin, The point of time when the inflow of the resin into the second resin flow path is completed may be during the injection of the first molten resin (see FIG. 14), may be simultaneously with the completion of the injection, or the injection is completed. It may be during a later pressure holding period (see FIG. 15).
[0017]
An injection molding method for a multilayer molded article according to the second aspect of the present invention for achieving the above object is a simultaneous injection molding method using the injection molding apparatus for molding the multilayer molded article of the present invention. is there. That is, an injection molding method of a multilayer molded product according to the second aspect of the present invention for achieving the above object is as follows:
(A) a mold having a cavity block provided with a cavity and a hot runner block;
(B) at least a first injection cylinder and a second injection cylinder;
(C) a first resin flow path connecting the inside of the first injection cylinder and the cavity;
as well as,
(D) a second resin flow path connecting the inside of the second injection cylinder and the cavity;
With
The first resin flow channel and the second resin flow channel located in the mold are provided in the hot runner block,
The first resin flow path and the second resin flow path are injection molding devices having a structure in which the first resin flow path and the second resin flow path are merged at a merge section upstream of the gate section opened in the cavity,
Back flow means for injecting the first molten resin in the first resin flow path into the second resin flow path after injecting the second molten resin into the cavity via the second resin flow path Provided,
The reverse flow means is an injection molding of a multilayer molded article using an injection molding device that operates by pressure exerted by the first molten resin in the first resin flow path on the second molten resin in the second resin flow path. A method,
(A) Injecting the first molten resin melted in the first injection cylinder into the cavity through the first resin flow path,
(B) During the injection of the first molten resin, the second molten resin melted in the second injection cylinder is injected into the cavity through the second resin flow path,
(C) After the completion of the injection of the second molten resin and during the injection of the first molten resin or after the completion of the injection, the first molten resin in the first resin flow path is removed by the operation of the backflow means. Let it flow into the resin flow path,
It consists of a process.
[0018]
FIGS. 17, 18 and 19 show temporal changes in injection pressure and the like in the injection molding method for multilayer molded articles according to the second aspect of the present invention. In the case where the first molten resin in the first resin flow path flows into the second resin flow path by the operation of the backflow means after the completion of the injection of the first molten resin, specifically, The holding pressure is performed by the injection cylinder, and the first molten resin in the first resin flow path is caused to flow into the second resin flow path by the operation of the backflow means after completion of the injection of the first molten resin ( (See FIG. 19). In addition, when the first molten resin in the first resin flow channel starts to flow into the second resin flow channel by the operation of the backflow means during the injection of the first molten resin, The point of time when the inflow of the resin into the second resin flow path is completed may be during the injection of the first molten resin (see FIG. 17), may be simultaneously with the completion of the injection, or the injection is completed. It may be during a later pressure holding period (see FIG. 18).
[0019]
In the method for injection molding a multilayer molded article according to the second aspect of the present invention, in step (B), the injection amount per unit time of the first molten resin is set to the injection amount per unit time of the second molten resin. It is preferable to increase the amount. Although it depends on the injection molding conditions, the main part of the multilayer molded product can have a three-layer configuration of first resin layer / second resin layer / first resin layer. Alternatively, a part of the main part of the multilayer molded product can be configured as a three-layer structure of the first resin layer / second resin layer / first resin layer. In these cases, the portion other than the main portion of the multilayer molded product is constituted by the first resin layer.
[0020]
An injection molding method for a multilayer molded article according to the third aspect of the present invention for achieving the above object is an injection molding method using an injection molding apparatus for molding the multilayer molded article of the present invention. ,
(A) After injecting the first molten resin melted in the first injection cylinder into the cavity through the first resin flow path, the injection of the first molten resin is terminated,
(B) After injecting the second molten resin melted in the second injection cylinder into the cavity through the second resin flow path, the injection of the second molten resin is terminated,
(C) Holding pressure by the first injection cylinder, and simultaneously flowing the first molten resin in the first resin flow path into the second resin flow path by the operation of the backflow means.
It consists of a process. FIG. 20 shows changes over time in injection pressure and the like in the injection molding method for multilayer molded articles according to the third aspect of the present invention.
[0021]
An injection molding method for a multilayer molded article according to the fourth aspect of the present invention for achieving the above object is a simultaneous injection molding method using the injection molding apparatus for molding the multilayer molded article of the present invention. Yes,
(A) Injecting the first molten resin melted in the first injection cylinder into the cavity through the first resin flow path,
(B) During the injection of the first molten resin, the second molten resin melted in the second injection cylinder is injected into the cavity through the second resin flow path,
(C) After completing the injection of the first molten resin and the injection of the second molten resin substantially simultaneously, holding pressure is performed by the first injection cylinder, and the first resin flow path is also operated by the operation of the backflow means. The first molten resin is allowed to flow into the second resin flow path,
It consists of a process. FIG. 21 shows changes over time in the injection pressure and the like in the multilayer molded product injection molding method according to the fourth aspect of the present invention.
[0022]
In the injection molding apparatus for molding the multilayer molded product of the present invention or the multilayer molded product injection molding method according to the first to fourth aspects of the present invention, the backflow means is provided in the first resin flow path. It is preferable to flow a certain amount of the first molten resin into the second resin flow path. Further, when the second molten resin is injected into the cavity via the second resin flow path and after completion of the injection, the inside of the second injection cylinder and the cavity are in communication with each other by the backflow means, After a predetermined amount of the first molten resin in the first resin flow channel flows into the second resin flow channel, the inside of the second injection cylinder and the cavity are preferably brought out of communication by the backflow means. . There is a relationship of (predetermined amount) ≦ (constant amount) between the predetermined amount and the constant amount. Alternatively, when the second molten resin is injected into the cavity via the second resin flow path and after the injection is completed, the inside of the second injection cylinder and the cavity are in communication with each other by the backflow means. After the first molten resin in the first resin flow path starts to flow into the second resin flow path, the inside of the second injection cylinder and the cavity may be in a non-communication state by the backflow means. preferable.
[0023]
In the injection molding apparatus for molding the multilayer molded product of the present invention, or the injection molding method of the multilayer molded product according to the first to fourth aspects of the present invention, the backflow means includes a confluence portion of the resin flow path and It is preferable to be provided in the second resin flow path between the second injection cylinder. In this case, it is particularly preferable that the backflow means is disposed between the nozzle portion of the second injection cylinder and the mold or in the nozzle portion of the second injection cylinder.
[0024]
In the injection molding apparatus for molding the multilayer molded article of the present invention or the multilayer molded article injection molding method according to the first to fourth aspects of the present invention, a predetermined amount of the first molten resin is added to the second molten resin. From the viewpoint of flowing into the resin flow path and from the viewpoint of simplification of the structure, the back flow means is preferably a back flow control valve. Examples of the backflow control valve include a ball type backflow control valve and a slide type backflow control valve.
[0025]
In the injection molding apparatus for molding the multilayer molded product of the present invention or the injection molded method of the multilayer molded product according to the first to fourth aspects of the present invention, the second resin flowed into the second resin flow path. The volume of the molten resin 1 is 5 to 50%, preferably 5 to 35%, more preferably 5 to 25% of the volume of the cavity. When the volume of the first molten resin flowing into the second resin flow path is less than 5% of the volume of the cavity, it is possible to prevent the resin that does not constitute the outermost layer of the multilayer molded product from appearing on the outermost layer surface. It becomes difficult. On the other hand, although depending on the injection conditions, when the first molten resin flows into the second resin flow path, turbulence occurs in the resin layers constituting each layer of the multilayer molded product. In order to prevent this, it is desirable that the volume of the first molten resin flowing into the second resin flow path is 35% or less, particularly 25% or less of the volume of the cavity. When it exceeds 50% of the volume of the cavity, there is a possibility that many disturbances causing a problem in practice occur in the resin layers constituting each layer of the multilayer molded product.
[0026]
In the injection molding apparatus for molding the multilayer molded product of the present invention, or the multilayer molded product injection molding method according to the first to fourth aspects of the present invention, the multilayer molded product to be molded has any structure and shape. For example, the parison which is a precursor for shape | molding a multilayer container (multilayer bottle) can be mentioned. In this case, it is preferable that the outermost layer of the parison is formed by the first molten resin injected into the cavity through the first resin flow path. In addition, examples of the multilayer molded product to be molded include an automobile bumper and an automobile door handle. In addition, in order to impart different functions such as strength and appearance to the molded product, a multilayer molded product in which a plurality of resins are combined by a multilayer molding technique can also be exemplified.
[0027]
In the method for injection molding of multilayer molded articles according to the first to fourth aspects of the present invention, as the second resin, a thermoplastic resin having a gas barrier property (gas barrier resin), a recovered polyethylene terephthalate resin (parison molding) And at least one resin selected from the group consisting of colored polyethylene terephthalate resin (sometimes including recycled polyethylene terephthalate resin once used).
[0028]
Here, the gas barrier resin is at least one selected from the group consisting of a metaxylylene group-containing polyamide resin (MX nylon resin), a saponified ethylene-vinyl acetate copolymer resin, a polyacrylonitrile resin, and a polyvinylidene chloride resin. A resin is preferable, but MX nylon resin is more preferable among them.
[0029]
MX nylon resin is metaxylylenediamine alone or mixed xylylenediamine containing metaxylylenediamine and 30% or less of paraxylylenediamine and α-ω-aliphatic dicarboxylic acid having 6 to 10 carbon atoms. And a polymer containing at least 70 mol% or more of structural units obtained from the above. Examples of these polymers include homopolymers such as polymetaxylylene adipamide, polymetaxylylene sebacamide, polymetaxylylene veramide, metaxylylene / paraxylylene adipamide copolymer, metaxylylene. / Copolymers such as paraxylylene beramide copolymer, or homo- or copolymer components thereof, aliphatic diamines such as hexamethylene diamine, alicyclic diamines such as piperazine, para-bis- (2-Aminoethyl) aromatic diamines such as benzene, aromatic dicarboxylic acids such as terephthalic acid, lactams such as ε-caprolactam, ω-aminocarboxylic acids such as ω-aminoheptanoic acid, and fragrances such as para-aminobenzoic acid Copolymerization with a group aminocarboxylic acid or the like can be exemplified. Moreover, you may make these polymers contain polymers, such as nylon 6, nylon 66, nylon 610, nylon 11, for example.
[0030]
The relative viscosity of these MX nylon resins is suitably 1.5 or more, preferably 2.0 to 4.0. The relative viscosity (η _rel ) Is the viscosity measured at 25 ° C. under the conditions of 1 g of resin / 100% sulfuric acid 100 ml.
[0031]
On the other hand, in the injection molding method for multilayer molded articles according to the first to fourth aspects of the present invention, the first resin is a thermoplastic polyester resin such as polyethylene terephthalate, polyethylene-2,6-naphthalate (PEN); Examples thereof include at least one resin selected from the group consisting of a plastic copolyester resin; a polyolefin resin; an aliphatic polyamide resin; a polycarbonate resin; a polyacrylonitrile resin; a polyvinyl chloride resin; It is preferable to use a thermoplastic polyester resin. Moreover, what blended two types of resin as needed, for example, what blended polyethylene terephthalate resin and polyethylene-2,6- naphthalate resin can also be used.
[0032]
Here, the polyethylene terephthalate is usually a polyester in which 80 mol% or more, preferably 90 mol% or more of the acid component is terephthalic acid, and 80 mol% or more, preferably 90 mol% or more of the glycol component is ethylene glycol. And the remaining other acid components include isophthalic acid, diphenyl ether-4,4-dicarboxylic acid, naphthalene-1,4 or 2,6-dicarboxylic acid, adipic acid, sebacic acid, decane-1, 10-dicarboxylic acid, hexahydroterephthalic acid, and other glycol components include propylene glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, 2,2-bis (4-hydroxyethoxyphenyl) ) Propane and the like can be exemplified. Furthermore, examples of the oxyacid include a polyester resin containing P-oxybenzoic acid and the like.
[0033]
Polyethylene-2,6-naphthalate may contain other ester forming units in an amount of 20 mol% or less, preferably 10 mol% or less in addition to ethylene-2,6-naphthalate. Examples of dicarboxylic acids constituting other ester forming units include phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, and 2,7-naphthalene. Aromatic dicarboxylic acids such as dicarboxylic acid, 4,4′-diphenylcarboxylic acid, 3,4′-diphenylcarboxylic acid; aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, dodecanedioic acid; 1,4- Suitable examples include aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, decalin dicarboxylic acid, and tetralindicarboxylic acid. In addition, as diols constituting other ester forming units, aliphatic glycols such as propylene glycol, trimethylene glycol, diethylene glycol, 1,4-butanediol; 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, Preferred examples include aliphatic glycols such as 1,6-cyclohexanediol; aromatic glycols such as bisphenol A. The polyethylene-2,6-naphthalate as described above may have its molecular ends sealed with a monofunctional compound such as a small amount of benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid, methoxypolyethylene glycol, and the like. Further, it may contain a very small amount of a polyfunctional compound such as glycerin, trimesic acid and pentaerythritol.
[0034]
The intrinsic viscosity of these thermoplastic polyester resins is suitably 0.40 or more, preferably 0.50 to 1.4. When the intrinsic viscosity is less than 0.40, the mechanical strength of the obtained laminated molded product (for example, a multilayer container) becomes insufficient, and for example, it becomes difficult to obtain the multilayer molded product in a transparent amorphous state. The intrinsic viscosity (η) is a viscosity measured at 30 ° C. using a mixed solvent of phenol / tetrachloroethane = 6/4 (weight ratio).
[0035]
The thermoplastic copolyester resin is terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7 -Acid components such as naphthalenedicarboxylic acid, ethylene glycol, propylene glycol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,3-bis (2-hydroxyethoxy) benzene, 1,4-bis It is a thermoplastic copolymer polyester resin obtained by copolymerizing at least two components among diol components such as (2-hydroxyethoxy) benzene. These thermoplastic copolyester resins may be used by mixing with other thermoplastic polyester resins as necessary.
[0036]
In the method for injection molding of multilayer molded articles according to the first to fourth aspects of the present invention, a combination of thermoplastic polyester resin, particularly polyethylene terephthalate resin (PET resin) and MX nylon resin is most preferable. This is because the resin has excellent transparency, mechanical strength, injection moldability, and stretch blow moldability. Moreover, since the thermal properties of both resins are close, setting of molding temperature conditions is easy. In this case, it is preferable that the melt viscosity of the polyethylene terephthalate resin and the MX nylon resin are close to each other. For example, when a polyethylene terephthalate resin having an intrinsic viscosity of 0.7 to 0.8 is used, MX nylon having a relative viscosity of about 2.7. It is desirable to use a resin. Even when other gas barrier resins are used, the melt viscosity thereof preferably has a value close to that of the polyethylene terephthalate resin.
[0037]
Furthermore, in the injection molding method of the multilayer molded product according to the first to fourth aspects of the present invention, the first resin, the second resin, or each resin constituting the multilayer molded product, if necessary. A colorant, an ultraviolet absorber, an antistatic agent, an antioxidant, a lubricant, a nucleating agent, an antibacterial agent, and the like can be blended with the resin for forming the layer.
[0038]
In the injection molding apparatus of the present invention, backflow means is provided for allowing the first molten resin in the first resin flow path to flow into the second resin flow path. Therefore, when the first molten resin is injected into the cavity, the first resin that has flowed into the second resin flow channel in the previous molding cycle enters the second resin flow channel in the vicinity of the joining portion of the resin flow channel. The molten resin already exists. Accordingly, in the vicinity of the joining portion of the resin flow path, mixing of the injected first molten resin and the second molten resin existing in the second resin flow path occurs, or the second melt that is not in the injection state As a result of preventing the occurrence of the phenomenon that the resin is caught in the first molten resin being injected, for example, the occurrence of the problem that the second resin appears on the surface of the multilayer molded product is surely avoided. be able to.
[0039]
In the injection molding method according to the first to fourth aspects of the present invention, the present invention is provided with backflow means for allowing the first molten resin in the first resin flow path to flow into the second resin flow path. The injection molding apparatus is used. Therefore, when the first molten resin is injected into the cavity in the step (A), the second resin flow path in the vicinity of the joining portion of the resin flow path has the second resin flow path in the previous molding cycle. The first molten resin that has flowed into the tank already exists. Accordingly, in the vicinity of the joining portion of the resin flow path, mixing of the injected first molten resin and the second molten resin existing in the second resin flow path occurs, or the second melt that is not in the injection state As a result of preventing the occurrence of the phenomenon that the resin is caught in the first molten resin being injected, for example, the occurrence of the problem that the second resin appears on the surface of the multilayer molded product is surely avoided. be able to.
[0040]
In the present invention, if the backflow means is composed of a backflow control valve, it is possible to avoid an increase in size and complexity of the injection molding apparatus, and there is no occurrence of leakage of molten resin from the resin flow path. If the backflow control valve is a ball-type backflow control valve, the ball only moves by fluid pressure, the structure is extremely simple, and there are no moving parts and sliding parts. The fluid control by the ball type backflow control valve can be performed not only for the flow of the molten resin but also for other liquids and gas bodies. A conventional on-off valve moves an electromagnetic valve or a cylinder by external hydraulic pressure or air pressure, and forcibly opens and closes a fluid flow path by rotating or reciprocating these valves. Therefore, the structure and operation control are complicated, and the durability is poor.
[0041]
【Example】
Hereinafter, the present invention will be described based on examples with reference to the drawings.
[0042]
Example 1
A conceptual diagram of an injection molding apparatus (hereinafter simply referred to as an injection molding apparatus) for molding a multilayer molded article in Example 1 is shown in FIGS. 1 shows the injection molding apparatus in a state where injection molding is not performed at all, and FIG. 2 shows metered injections of the first molten resin 40A and the second molten resin 40B immediately before the molding of the multilayer molded product. The state of the molding apparatus is shown.
[0043]
This injection molding apparatus includes a mold 20, two injection cylinders 10A and 10B, a first resin flow path 23A connecting the inside of the first injection cylinder 10A and the cavity 25, and a second injection cylinder 10B. A second resin flow path 23B connecting the inside and the cavity 25 is provided. The mold 20 includes a cavity block 21 provided with a cavity 25 and a hot runner block 22. The cavity block 21 is configured by combining a plurality of blocks. The first resin flow path 23 A and the second resin flow path 23 B located in the mold 20 are provided in the hot runner block 22. Furthermore, the first resin flow path 23 A and the second resin flow path 23 B have a structure that merges at a merge portion upstream of the gate portion 24 that opens to the cavity 25. The nozzle portions of the first and second injection cylinders 10A and 10B are denoted by reference numerals 12A and 12B. A portion of the first resin flow path 23A and the second resin flow path 23B upstream (on the injection cylinder side) from the joining portion of the first resin flow path 23A and the second resin flow path 23B has a double tube structure. It has become. A gate cut pin 26 is disposed in the inner tubular second resin flow path 23B in the resin flow path of the double tube structure. The gate cut pin 26 can be moved in a direction toward and away from the cavity 25 by operation of the pneumatic cylinder 27. Communication between the outer first resin flow path 23A and the cavity 25 in the double pipe structure resin flow path, and the inner tubular second resin flow path 23B and cavity 25 in the double pipe structure resin flow path. Communication with can be controlled by movement of the gate cut pin 26. That is, when the gate cut pin 26 is positioned at the forward end, the communication between the first resin flow path 23A and the cavity 25 and the communication between the second resin flow path 23B and the cavity 25 are blocked. In addition, when the gate cut pin 26 is positioned at the reverse end, communication between the first resin flow path 23A and the cavity 25 and communication between the second resin flow path 23B and the cavity 25 are ensured. FIG. 1 shows a state where the gate cut pin 26 is extracted from the gate portion 24 (a state where the gate cut pin 26 is located at the backward movement end). FIG. 2 shows a state where the gate cut pin 26 is inserted into the gate portion 24 (a state where the gate cut pin 26 is positioned at the forward end). Here, in FIG. 2, reference numeral 40A indicates the first molten resin injected from the first injection cylinder 10A into the cavity 25 through the first resin flow path 23A and the gate portion 24, and reference numeral 40B. These show the 2nd molten resin inject | poured into the cavity 25 through the 2nd resin flow path 23B and the gate part 24 from the 2nd injection cylinder 10B. Reference numeral 40a indicates the remainder of the first molten resin 40A that flows in at the time of the previous injection and remains in the second resin flow path 23B (represented by white square marks in the figure). In addition, although the piping which flows cooling water is arrange | positioned inside the cavity block 21, and the heater is arrange | positioned inside the hot runner block 22, illustration of this piping and heater was abbreviate | omitted.
[0044]
In the injection molding apparatus of the present invention, the second molten resin 40B is injected into the cavity 25 via the second resin flow path 23B, and then the first molten resin 40A in the first resin flow path 23A. Is provided with a backflow means for allowing a certain amount to flow into the second resin flow path 23B. This reverse flow means operates by the pressure exerted on the second molten resin 40B in the second resin flow path 23B by the first molten resin 40A in the first resin flow path 23A. In the injection molding apparatus of Example 1, the backflow means is a backflow control valve provided in the second resin flow path 23B upstream from the merge portion of the first and second resin flow paths 23A, 23B. Specifically, this backflow control valve is a ball-type backflow control valve 30B. The backflow control valve 30B is disposed between the nozzle portion 12B of the second injection cylinder 10B and the mold 20, but may be disposed in the nozzle portion 12B.
[0045]
A conventional ball check valve (check valve) is provided to prevent the backflow of molten resin. On the other hand, the backflow control valve 30B in the first embodiment has a structure capable of backflowing a certain amount of the second molten resin 40B. Specifically, as shown in a schematic end view of FIG. 6A, the backflow control valve 30B includes a cylindrical pipe portion 31 having a hollow portion 32 and a ball 34 stored in the hollow portion 32. It is configured. The diameter of the portion of the predetermined hollow portion 32 from the end portion on the downstream side (mold side) of the hollow portion 32 toward the upstream side (injection cylinder side) is larger than the diameter of the ball 34. This portion of the hollow portion 32 is referred to as an enlarged diameter portion 33. The diameter of the hollow portion 32 other than the enlarged diameter portion 33 is substantially equal to the diameter of the ball 34.
[0046]
When the second molten resin 40B is sent out from the second injection cylinder 10B toward the cavity 25, the ball 34 has an enlarged diameter portion at the downstream end of the hollow portion 32, as shown in FIG. 33 is pressed by the pressure of the second molten resin 40B. Therefore, when the second molten resin 40B is injected into the cavity 25 via the second resin flow path 23B and after the injection is completed, the inside of the second injection cylinder 10B and the cavity 25 are controlled in reverse flow. A communication state is established by the valve 30B. The second molten resin 40 B flows toward the cavity 25 through the gap between the ball 34 and the enlarged diameter portion 33.
[0047]
On the other hand, the second molten resin 40B flows backward due to the pressure exerted on the second molten resin 40B in the second resin flow path 23B by the first molten resin 40A in the first resin flow path 23A. When the second molten resin 40B flows back in the backflow control valve 30B, the ball 34 is moved toward the upstream end of the hollow portion 32 by the pressure of the backflowing second molten resin 40B. Finally, it is pressed against the upstream end of the hollow portion 32 (see FIG. 6C). There is no gap between the ball 34 and the upstream end of the hollow portion 32. Therefore, in the state shown in FIG. 6C, the backflow of the second molten resin 40B does not occur any more. In other words, while the ball 34 moves from the enlarged diameter portion 33 of the cylindrical tube portion 31 to the upstream end portion of the hollow portion 32, the second molten resin 40B flows back through the backflow control valve 30B. The volume of the second molten resin 40B that flows backward is generally defined by the product of the cross-sectional area of the ball 34 and the moving distance of the ball 34, and is a constant amount. In other words, the volume of the second molten resin 40B that flows backward is substantially equal to a value obtained by subtracting the volume of the ball 34 from the volume of the hollow portion 32, and is a constant amount. Therefore, by appropriately selecting and setting the diameter of the ball 34 and the moving distance of the ball 34, the volume of the first molten resin 40A flowing into the second resin flow path 23B can be defined. That is, in order to set the volume of the first molten resin 40A flowing into the second resin flow path 23B to 5 to 50%, preferably 5 to 35%, more preferably 5 to 25% of the cavity volume. In this case, the diameter of the ball 34 and the moving distance of the ball 34 may be appropriately selected and set. In other words, the product of the cross-sectional area of the ball 34 and the moving distance of the ball 34 is approximately equal to the volume of the first molten resin 40A flowing into the second resin flow path 23B. 6B and 6C, the direction in which the second molten resin 40B flows is indicated by an arrow.
[0048]
When the first molten resin 40A in the first resin flow path 23A starts to flow into the second resin flow path 23B, the ball 34 is upstream from the enlarged diameter portion 33 of the cylindrical tube portion 31 to the hollow portion 32. Move towards the side edge. When the first molten resin 40A in the first resin flow path 23A flows into the second resin flow path 23B by a predetermined amount, the ball 34 reaches the boundary between the enlarged diameter portion 33 and a portion other than the enlarged diameter portion 33. When the ball 34 enters the portion other than the enlarged diameter portion 33 of the hollow portion 32, the diameter of the portion other than the enlarged diameter portion 33 of the hollow portion 32 is substantially equal to the diameter of the ball 34, and thus the second injection cylinder 10B. And the cavity 25 are brought into a non-communication state by the backflow control valve 30B.
[0049]
7A and 7B are schematic cross-sectional views of the cylindrical tube portion 31 taken along the arrow AA in FIG. In the structure shown in FIGS. 7A and 7B, the ball receiving portion 33A is projected from four locations on the inner surface of the enlarged diameter portion 33 of the cylindrical tube portion 31 in the direction parallel to the axis of the cylindrical tube portion 31. It extends to the vicinity of 31C, and the ball 34 moves while contacting the apex or top surface of the protrusion 33A. Moreover, the modification of the enlarged diameter part 33 of the cylindrical pipe part 31 along arrow AA of (B) of FIG. 6 is shown to (C) and (D) of FIG. In the structure shown in FIGS. 7C and 7D, the ball receiving portion 33 A has a protruding portion 33 A in a direction parallel to the axis of the cylindrical tube portion 31 from three locations on the inner surface of the enlarged diameter portion 33 of the cylindrical tube portion 31. It extends to the vicinity of 31C. In the structure shown in FIGS. 7A and 7C, the cross-sectional shape of the protrusion 33A is a shape obtained by partially cutting a circle. Further, in the structure shown in FIGS. 7B and 7D, the cross-sectional shape of the protrusion 33A is substantially rectangular. The second molten resin 40 B flows in a space surrounded by the balls 34, the protruding portion 33 A, and the inner surface of the enlarged diameter portion 33. The cross-sectional shape of the projection 33A, the number of projections 33A, and the shape of the space when the space is cut by a plane perpendicular to the axis of the cylindrical tube portion 31 are shown in FIGS. It is not limited to different shapes and numbers. Further, FIG. 7E shows a schematic cross-sectional view of the ball receiving portion 31C along the arrow BB in FIG. Moreover, the modification of the part of the ball | bowl receiving part 31C along arrow BB of (B) of FIG. 6 is shown to typical sectional drawing of (F), (G), and (H) of FIG. As shown in FIGS. 7E to 7H, the ball receiving portion 31 C provided at the downstream end of the hollow portion 32 and the cylindrical tube portion 31 are parallel to the axis of the cylindrical tube portion 31. Spaces 31B extending in various directions are provided, the spaces 31B communicate with the enlarged diameter portion 33, and the second molten resin 40B flows in the spaces 31B. The ball receiving portion 31C and the cylindrical tube portion 31 may be manufactured integrally or individually. It should be noted that the shape and number of the space 31B when the space 31B is cut along a plane perpendicular to the axis of the cylindrical tube portion 31 is not limited to the shapes and numbers shown in FIGS. Absent.
[0050]
Each of the screws 11A and 11B disposed in the first and second injection cylinders 10A and 10B is an in-line screw type in which the resin is plasticized and melted and also has a plunger action. Hereinafter, the second injection cylinder 10B will be described as an example with reference to FIG. 8. However, as shown in FIG. 9, the first injection cylinder 10A may have the same structure. The screw 11B is rotated by the hydraulic motor 14 via the reduction gear 13. The second resin charged into the screw 11B from the hopper 15 is heated, plasticized, melted and measured by the heating cylinder 10B and the screw 11B, and stored in the gap 16 formed between the heating cylinder 10B and the tip of the screw 11B. It is done. An injection ram 17B is attached to the rear end of the screw 11B, and pressure is applied to the injection ram 17B by an injection hydraulic cylinder 18B. By applying pressure to the injection ram 17B by the hydraulic cylinder 18B for injection, the screw 11B is pushed forward and pressure is applied to the second molten resin. As a result, the second molten resin stored in the gap 16 becomes the backflow control valve. It is injected into the cavity 25 via 30B, the second resin flow path 23B and the gate portion 24. In FIG. 8, reference numeral 19 is an injection device forward / backward cylinder, reference numerals 19A and 19B are hydraulic piping, and reference numeral 19C is a pressure gauge.
[0051]
Hereinafter, with reference to FIGS. 2-5, the injection molding method of the multilayer molded product which concerns on the 1st aspect of this invention using the injection molding apparatus of Example 1 is demonstrated. This injection molding method is an alternate injection molding method. FIG. 14 shows changes over time in the injection pressure and the like in the injection molding method for the multilayer molded article of Example 1.
[0052]
[Step-100]
In order to form a multilayer molded product (a parison in the first embodiment) from the weighed state of the first and second molten resins 40A and 40B shown in FIG. 26 is retracted, and the gate cut pin 26 is extracted from the gate portion 24, positioned at the reverse end, and the gate portion 24 is opened. Then, a part of the first molten resin 40A melted in the first injection cylinder 10A is injected into the cavity 25 through the first resin flow path 23A. That is, the screw 11A is pushed forward by applying pressure to the injection ram 17A by the injection hydraulic cylinder 18A. As a result, a part of the first molten resin 40A melted in the first injection cylinder 10A is injected into the cavity 25 via the first resin flow path 23A and the gate portion 24. This state is schematically shown in FIG. In FIG. 3, reference numeral 40a indicates the remainder of the first molten resin 40A that flows in at the time of the previous injection and remains in the second resin flow path 23B (represented by white square marks in the figure). Show.
[0053]
For example, when the molten resin filling rate in the cavity 25 is 70% or less of the volume of the cavity 25, for example, when the first molten resin 40A is injected into the cavity 25, it is caused by the injection of the first molten resin 40A. The pressure toward the second injection cylinder 10B is hardly applied to the second molten resin 40B in the second resin flow path 23B. Therefore, the second molten resin 40B in the second resin flow path 23B does not flow backward toward the second injection cylinder 10B.
[0054]
In addition, in order to form the outermost layer of the multilayer molded product, the first molten resin 40A is injected into the cavity 25 via the first resin flow path 23A, that is, from this [Step-100]. Previously (specifically, for example, in the previous molding cycle), a molten resin other than a molten resin for forming a layer that is not the outermost layer of the multilayer molded product (first molten resin 40A in Example 1). However, a certain amount has already flowed into the second resin flow path 23B upstream from the junction.
[0055]
[Step-110]
Then, the first molten resin 40A is stopped. That is, pressurization to the injection ram 17A by the injection hydraulic cylinder 18A in the first injection cylinder 10A is stopped. Then, the second molten resin 40B melted in the second injection cylinder 10B is injected into the cavity 25 through the second resin flow path 23B. That is, in the second injection cylinder 10B, the screw 11B is pushed forward by applying pressure to the injection ram 17B by the injection hydraulic cylinder 18B. As a result, the second molten resin 40B melted in the second injection cylinder 10B is injected into the cavity 25 via the second resin flow path 23B and the gate portion 24. A state in the middle of injection of the second molten resin 40B is schematically shown in FIG. The second molten resin 40B injected into the cavity 25 advances forward in the center of the first molten resin 40A that has already filled a part of the cavity 25, depending on the injection conditions. The first molten resin 40a that flows in in the previous molding cycle and remains in the second resin flow path 23B is also injected into the cavity 25 together with the second molten resin 40B. In FIG. 4, the first molten resin 40a is not shown.
[0056]
In addition, using the injection molding apparatus provided with three injection cylinders, following [Step-110], the third resin melted in the third injection cylinder is put into the cavity through the third resin flow path. May be injected. In this case, for example, the third resin can be the same kind of resin as the first resin or a different kind of resin.
[0057]
[Step-120]
When the injection of the second molten resin 40B is completed, the pressurization to the injection ram 17B by the injection hydraulic cylinder 18B in the second injection cylinder 10B is stopped. The remainder of the first molten resin 40A melted in the first injection cylinder 10A is injected into the cavity 25 through the first resin flow path 23A and the gate portion 24. That is, in the first injection cylinder 10A, the screw 11A is pushed forward by applying pressure to the injection ram 17A by the injection hydraulic cylinder 18A. Thus, the first molten resin 40A melted in the first injection cylinder 10A is injected into the cavity 25 via the first resin flow path 23A and the gate portion 24. A state at the time of completion of injection of the first molten resin 40A is schematically shown in FIG. The remaining amount of the first molten resin 40A to be injected is the sum of the amount sufficient to fill the entire cavity 25 and the amount flowing into the second resin flow path 23B. The first molten resin 40A injected into the cavity 25 moves forward through the center of the second molten resin 40B that has already filled a part of the cavity 25, depending on the injection conditions.
[0058]
At this time, the pressure toward the second injection cylinder 10B is applied by the first molten resin 40A to the second molten resin 40B in the second resin flow path 23B. Therefore, the second molten resin 40B in the second resin flow path 23B flows backward toward the second injection cylinder 10B. As a result, a part of the first molten resin 40A in the first resin flow path 23A flows into the second resin flow path 23B. As described above, the ball 34 is moved from the enlarged diameter portion 33 of the cylindrical tube portion 31 to the upstream end portion of the hollow portion 32 by the back flow of the second molten resin 40B. The volume of the second molten resin 40B that flows backward is a fixed amount. Accordingly, the amount of the first molten resin 40A in the first resin flow path 23A flowing into the second resin flow path 23B is also a constant amount. In addition, the part of the 1st molten resin which flowed in the 2nd resin flow path 23B was shown with the reference number 40a, and was represented by the white square mark. At this time, the first molten resin 40a and the second molten resin 40B that have flowed into the second resin flow path 23B may hardly mix or may mix depending on the injection molding conditions. There is also. Further, depending on the injection molding conditions, in this step, a phenomenon in which a part of the first molten resin 40A in the first resin flow path 23A flows into the second resin flow path 23B does not occur. During the pressure holding period, a phenomenon may occur in which a part of the first molten resin 40A in the first resin flow path 23A flows into the second resin flow path 23B. Further, when a part of the first molten resin 40A in the first resin flow path 23A finishes flowing into the second resin flow path 23B, the first molten resin 40A of the first molten resin 40A depends on the injection molding conditions. There is a case where the injection is in progress, and there is a case where it is during the next pressure holding period.
[0059]
[Step-130]
After completion of the injection of the first molten resin 40A, pressure holding is performed by the first injection cylinder 10A. Thereafter, the gate cut pin 26 is advanced, and the gate portion 24 is closed by the gate cut pin 26. And after cooling the resin in the cavity 25, the metal mold | die 20 is opened and the parison which is a multilayer molded product is taken out. The main part of the multilayer molded product thus obtained (the main part of the side surface of the parison) depends on the injection conditions, but the first resin 40A / second resin 40B / first resin 40A / second resin 40B. / A five-layer structure of the first resin 40A. Moreover, parts other than the main part of a multilayer molded product are comprised by the 1st resin layer.
[0060]
The volume of the first molten resin 40A flowing into the second resin flow path 23B is preferably 5 to 50% of the volume of the cavity 25. The first molten resin 40a that has flowed into the second resin flow path 23B is injected into the cavity 25 together with the second molten resin 40B when the second molten resin 40B is injected. If the volume of the first molten resin 40a flowing into the second resin flow path 23B is 50% or less of the volume of the cavity 25, the first molten resin 40a injected into the cavity together with the second molten resin 40B. However, there is no adverse effect on the properties of the multilayer molded article. If the volume of the first molten resin 40a flowing into the second resin flow path 23B is 25% or less of the volume of the cavity 25, the resin layer constituting each layer of the multilayer molded product may be disturbed. It can be surely prevented. When the volume of the first molten resin 40a flowing into the second resin flow path 23B exceeds 25% of the volume of the cavity 25 and is 50% or less, the resin layer constituting each layer of the multilayer molded product is slightly However, this is not a problem that causes a practical problem. When the volume of the first molten resin 40a flowing into the second resin flow path 23B exceeds 50% of the volume of the cavity 25, there is a practical problem in the resin layers constituting each layer of the multilayer molded product. A certain degree of disturbance may occur.
[0061]
On the other hand, when the volume of the first molten resin 40a flowing into the second resin flow path 23B is less than 5% of the volume of the cavity 25, for example, the first molten resin 40A is placed in the cavity 25 in [Step-100]. The first molten resin 40a that flows in at the previous injection and is left in the second resin flow path 23B, and further, the second molten resin 40B in the second resin flow path 23B are injected. The second molten resin 40 B flows into the cavity 25 by being wound into the first molten resin 40 A injected into the cavity 25. As a result, there is a case where the first molten resin 40A and the second molten resin 40B are mixed in the cavity 25 and the second resin 40B appears on the outermost layer surface of the multilayer molded product.
[0062]
As described above, the phenomenon that the first molten resin in the first resin flow channel flows into the second resin flow channel does not always occur, and the molten resin filling rate in the cavity 25 is, for example, Occurs when exceeding 70%. Therefore, in [Step-100], when the molten resin filling rate in the cavity 25 is, for example, 70% or less of the volume of the cavity 25, the first molten resin 40A is injected into the cavity 25 when the first molten resin 40A is injected. The pressure toward the second injection cylinder 10B resulting from the injection of the resin 40A is hardly applied to the second molten resin 40B in the second resin flow path 23B, and the first pressure in the second resin flow path 23B. The molten resin 40A does not flow in. Also in [Step-110], when the second molten resin 40B is injected into the cavity 25 via the second resin flow path 23B and the gate portion 24, the molten resin filling rate in the cavity 25 is, for example, 70. If the second molten resin 40B is injected into the cavity 25, the pressure toward the first injection cylinder 10A caused by the injection of the second molten resin 40B is the first resin flow. Almost no addition to the first molten resin 40A in the path 23A. Therefore, the first molten resin 40A in the first resin flow path 23A does not flow backward toward the first injection cylinder 10A. Although it is not necessary to arrange a valve for preventing backflow between the nozzle portion 12A of the first injection cylinder 10A or the nozzle portion 12A and the mold 20, in some cases, such a valve is used as a nozzle of the injection cylinder 10A. The portion 12A or the nozzle portion 12A and the mold 20 may be disposed. The valve in this case may have the same structure as the backflow control valve 30B, or may be a ball check valve (a check valve) that prevents the backflow of a conventional molten resin.
[0063]
Depending on the injection conditions, the first molten resin 40A injected into the cavity 25 in [Step-120] moves forward through the center of the second molten resin 40B that has already filled a part of the cavity 25. The main part of the multilayer molded product (the main part of the side surface of the parison is not shown in FIG. 10A), as shown in the schematic cross-sectional view of the parison. Part) is a part of a five-layer structure of first resin 40A / second resin 40B / first resin 40A / second resin 40B / first resin 40A, and is a main part of a multilayer molded product The other part can also have a three-layer structure of a three-layer structure of the first resin 40A / second resin 40B / first resin 40A. Alternatively, depending on the injection conditions, as shown in FIG. 10 (B), it is possible to mold a parison having a structure such that the side surface of the parison is 3 layers / 5 layers / 3 layers.
[0064]
As shown in FIGS. 14, 15 and 16 with respect to time changes such as injection pressure in the alternate injection molding method, a part of the first molten resin 40A in the first resin flow path 23A is the second resin. Whether the phenomenon of flowing into the flow path 23B occurs during the injection of the first molten resin 40A (see FIGS. 14 and 15) or after the completion of the injection (see FIG. 16) depends on the injection molding conditions. In addition, when the first molten resin 40A in the first resin flow path 23A flows into the second resin flow path 23B by the operation of the backflow means after the injection of the first molten resin 40A is completed, The first injection cylinder 10A holds the pressure, and after the injection of the first molten resin 40A is completed, the first molten resin 40A in the first resin flow path 23A is removed by the operation of the backflow means. 2 flows into the resin flow path 23B (see FIG. 16). Also, when the first molten resin 40A in the first resin flow path 23A starts to flow into the second resin flow path 23B by the operation of the backflow means during the injection of the first molten resin 40A, The time point when the first molten resin 40A is completely flown into the second resin flow path 23B may be during the injection of the first molten resin 40A (see FIG. 14) or at the same time as the completion of the injection. Alternatively, it may be during a pressure holding period after completion of injection (see FIG. 16).
[0065]
Moreover, if injection based on the simultaneous injection molding method which is an injection molding method of the multilayer molded product according to the second aspect of the present invention is performed, that is, in [Step-110], the first molten resin 40A is made into the cavity 25. If the second molten resin 40B is injected into the cavity 25 by a certain amount while continuing to be injected, as shown in FIG. 11A, a schematic cross-sectional view of the parison is shown. A parison having a three-layer structure of the first resin layer / second resin layer / first resin layer is obtained. In some cases, as shown in the schematic cross-sectional view of the parison in FIG. 11B, a part of the main portion of the multilayer molded article (the main portion of the side surface of the parison) may be the first resin layer / second A parison having a three-layer structure of resin layer / first resin layer can also be obtained. As shown in FIG. 17, FIG. 18 and FIG. 19 with respect to the time change of the injection pressure and the like, after the completion of the injection of the second molten resin 40B and during the injection of the first molten resin 40A or after the completion of the injection, The first molten resin 40A in the first resin flow path 23A is caused to flow into the second resin flow path 23B by the operation of the means. Whether a phenomenon in which a part of the first molten resin 40A in the first resin flow path 23A flows into the second resin flow path 23B occurs during the injection of the first molten resin 40A (FIGS. 17 and 18). Whether it occurs after completion of injection (see FIG. 19) depends on the injection molding conditions. In addition, when the first molten resin 40A in the first resin flow path 23A flows into the second resin flow path 23B by the operation of the backflow means after the injection of the first molten resin 40A is completed, The first injection cylinder 10A holds the pressure, and after the injection of the first molten resin 40A is completed, the first molten resin 40A in the first resin flow path 23A is removed by the operation of the backflow means. 2 flows into the resin flow path 23B (see FIG. 19). Also, when the first molten resin 40A in the first resin flow path 23A starts to flow into the second resin flow path 23B by the operation of the backflow means during the injection of the first molten resin 40A, The time point when the first molten resin 40A is completely flown into the second resin flow path 23B may be during the injection of the first molten resin 40A (see FIG. 17) or at the same time as the completion of the injection. Alternatively, it may be during a pressure holding period after completion of injection (see FIG. 18).
[0066]
Furthermore, in some cases, [Step-120] can be omitted. In this case, in the alternate injection molding method which is an injection molding method of the multilayer molded product according to the third aspect of the present invention, in [Step-110], the second molten resin 40B is injected into the cavity 25, and the cavity 25 is injected. The interior is completely filled with the second molten resin 40B. In the simultaneous injection molding method, which is an injection molding method for a multilayer molded product according to the fourth aspect of the present invention, the first molten resin 40A is continuously injected into the cavity 25 in [Step-110]. The second molten resin 40B is injected into the cavity 25, and the cavity 25 is completely filled with the first molten resin 40A and the second molten resin 40B. In these cases, in [Step-130], the pressure is maintained by the first injection cylinder 10A. Due to the holding pressure by the first injection cylinder 10A, the pressure toward the second injection cylinder 10B is applied to the second molten resin 40B in the second resin flow path 23B by the first molten resin 40A. As a result, the backflow means operates, the second molten resin 40B in the second resin flow path 23B flows back toward the second injection cylinder 10B, and the first melt in the first resin flow path 23A. Part of the resin 40A flows into the second resin flow path 23B (see FIGS. 20 and 21).
[0067]
As the backflow control valve, a slide type backflow control valve 50 shown in FIGS. 12A to 12C is used instead of the ball type backflow control valve shown in FIGS. 6A to 6C. You can also. This slide type backflow control valve 50 has a structure capable of backflowing a certain amount of the second molten resin 40B. Specifically, as shown in a schematic end view of FIG. 12A, the backflow control valve 50 includes a cylindrical pipe portion 51 having a hollow portion 52 and a valve body 54 stored in the hollow portion 52. And a bar 55. The bar 55 is disposed along the axis of the central portion of the cylindrical tube portion 51, and is attached to the cylindrical tube portion 51 by supports 56A and 56B. The second molten resin 40B can freely pass through the supports 56A and 56B. A central portion of the valve body 54 is slidably attached to the bar 55. The cross-sectional area of the portion of the predetermined hollow portion 52 from the end portion on the downstream side (die side) of the hollow portion 52 toward the upstream side (injection cylinder side) is larger than the cross-sectional area of the valve body 54. This portion of the hollow portion 52 is referred to as an enlarged diameter portion 53. The cross-sectional shape of the portion other than the enlarged diameter portion 53 of the hollow portion 52 is substantially equal to the cross-sectional shape of the valve body 54.
[0068]
When the second molten resin 40B is injected from the second injection cylinder 10B toward the cavity 25, the valve body 54 supports the downstream end of the hollow portion 52 as shown in FIG. The body 56A is pressed by the pressure of the second molten resin 40B. Therefore, when the second molten resin 40B is injected into the cavity 25 via the second resin flow path 23B and after the injection is completed, the inside of the second injection cylinder 10B and the cavity 25 are controlled in reverse flow. A communication state is established by the valve 50. The second molten resin 40 B flows toward the cavity 25 through the gap between the valve body 54 and the enlarged diameter portion 53.
[0069]
On the other hand, the second molten resin 40B flows backward due to the pressure exerted on the second molten resin 40B in the second resin flow path 23B by the first molten resin 40A in the first resin flow path 23A. When the second molten resin 40B flows back in the backflow control valve 50, the valve body 54 is upstream of the hollow portion 52 by the pressure of the first molten resin 40A flowing into the second resin flow path 23B. It is moved toward the end portion, and finally pressed against the upstream end portion of the hollow portion 52 (see FIG. 12C). There is no gap between the valve body 54 and the upstream end of the hollow portion 52. Therefore, in the state shown in FIG. 12C, the backflow of the second molten resin 40B does not occur any more. In other words, the second molten resin 40 B flows back in the backflow control valve 50 while the valve body 54 moves from the downstream end of the hollow portion 52 of the cylindrical pipe portion 51 to the upstream end. The volume of the second molten resin 40 B flowing backward is generally defined by the product of the cross-sectional area of the hollow portion 52 where the valve body 54 moves and the movement distance of the valve body 54, and is a constant amount. In other words, the volume of the second molten resin 40B that flows backward is substantially equal to a value obtained by subtracting the volume of the valve body 54 from the volume of the hollow portion 52, and is a constant amount. Accordingly, the first molten resin 40A flowing into the second resin flow path 23B is selected by appropriately selecting and setting the cross-sectional area of the portion of the hollow portion 52 to which the valve body 54 moves and the moving distance of the valve body 54. Can be defined. In other words, the product of the cross-sectional area of the hollow portion 52 where the valve element 54 moves and the movement distance of the valve element 54 is substantially equal to the volume of the first molten resin 40A flowing into the second resin flow path 23B. . In FIGS. 12B and 12C, the direction in which the second molten resin 40B flows is indicated by an arrow. In addition, it is preferable that the shape of the valve body 54 and the hollow part 52 when it cut | disconnects in a surface perpendicular | vertical to the direction through which the 2nd molten resin 40B flows is circular. It can be a shape.
[0070]
When the first molten resin 40A in the first resin flow path 23A starts to flow into the second resin flow path 23B, the valve body 54 moves through the hollow portion 52 toward the upstream end. When a predetermined amount of the first molten resin 40A in the first resin flow path 23A flows into the second resin flow path 23B, the valve body 54 is a boundary between the diameter expanded portion 53 and a portion other than the diameter expanded portion 53. To reach. Since the cross-sectional shape of the portion other than the enlarged diameter portion 53 of the hollow portion 52 is substantially equal to the sectional shape of the valve body 54 when the valve body 54 enters the portion other than the enlarged diameter portion 53 of the hollow portion 52, The inside of the injection cylinder 10 B and the cavity 25 are brought into a non-communication state by the backflow control valve 50.
[0071]
FIG. 13A shows a schematic cross-sectional view of the cylindrical tube portion 51 along the arrow AA in FIG. FIG. 13B shows a schematic cross-sectional view of the cylindrical tube portion 51 taken along the arrow BB in FIG. The support 56 A has a disk shape at the center, and four arms extend from the periphery, and the tips of these arms reach the inner surface of the cylindrical tube portion 51. The support 56A and the cylindrical tube portion 51 may be manufactured integrally or individually. A bar 55 is fixed to the center of the support 56A. The structure of the support portion 56A is not limited to the structure shown in FIGS. 13A and 13B, and the shape of the central portion of the support body 56A and the number of arms are arbitrary.
[0072]
In the first embodiment, an explanation has been given by taking an example of an injection molding apparatus that includes two injection cylinders and has two resin flow paths that connect the interior of each of the two injection cylinders and the cavity. The number of injection cylinders is as follows. There may be three or more. In this case, the same number of resin flow paths as the number of injection cylinders may be provided. Then, between [Step-110] and [Step-120], the molten third, fourth,... Resin is injected into the cavity 25 from the third, fourth,. Good. In this case, one resin flow path corresponds to the first resin flow path, and the remaining resin flow paths correspond to the second resin flow paths. The volume of the first molten resin flowing into each of the second resin flow paths is desirably 5 to 50%, preferably 5 to 35%, more preferably 5 to 25% of the volume of the cavity. . Further, the number of cavities provided in the mold is not limited to one and is arbitrary. When the number of cavities is plural, the first resin flow path and the second resin flow path are branched by the number of cavities, and the branched resin flow paths are connected to the gate portions opened in the cavities. Good. In this case, in the injection molding apparatus of the present invention, it is preferable to branch the resin flow channel downstream of the backflow means. The volume of the first molten resin flowing into each of the second resin flow paths is desirably 5 to 50%, preferably 5 to 35%, more preferably 5 to 25% of the volume of the cavity. .
[0073]
In the first embodiment, the gate cut pin 26 is arranged in the second resin flow path 23B. However, by appropriately setting the structure of the gate portion and the temperature of the molten resin in the gate portion, The gate cut pin can be omitted.
[0074]
In Example 1, the resin was plasticized, melted and measured in the injection cylinder, and the molten resin was injected from the injection cylinder. However, the pot type (also called shooting pot type or heating pot type) was used. A molding apparatus can also be used. In this pot type molding apparatus, plasticization, melting, and metering of a resin are performed in a cylinder, and the molten resin is filled in an injection pot. A check valve is disposed between the cylinder and the injection pot. Pressure is applied from the injection cylinder to the molten resin filled in the injection pot, and the molten resin is injected into the cavity through the resin flow path and the gate portion. Also in such a pot type molding apparatus, the backflow means may be disposed in the second resin flow path connecting the injection pot and the cavity.
[0075]
Hereinafter, the present invention will be described in more detail with reference to Examples 2 to 11 and Comparative Examples 1 to 3. In addition, although the temperature conditions in these Examples and Comparative Examples are shown in Table 1 below, the temperature conditions in Table 1 were adopted unless otherwise specified. In these examples and comparative examples, the injection molding apparatus of Example 1 shown in FIG. 1 was used.
[0076]
[Table 1]
Temperature of first molten resin 40A in injection cylinder 10A: 270 ° C
Temperature of second molten resin 40B in injection cylinder 10B: 260 ° C
Temperature of first and second resin flow paths in hot runner block: 270 ° C
Cooling water temperature in the cavity block: 15 ° C
[0077]
The intrinsic viscosity (η) of the polyethylene terephthalate resin was measured at 30 ° C. using a mixed solvent of phenol / tetrachloroethane = 6/4 (weight ratio). Meanwhile, the relative viscosity of polymetaxylylene adipamide resin (η _rel ) Was measured at 25 ° C. under the condition of 1 g of resin / 100 ml of 96% sulfuric acid. Moreover, the measurement of interlayer adhesive strength was performed at a peeling direction of 180 degrees, a peeling speed of 20 mm / min, and a sample size of 10 mm (width) × 100 mm (length).
[0078]
(Example 2)
As the first resin 40A, a polyethylene terephthalate resin (PET resin; RT543C manufactured by Nihon Unipet Co., Ltd.) having an intrinsic viscosity of 0.75 is used. A mid resin (N-MXD6 resin, # 6007 manufactured by Mitsubishi Gas Chemical Company, Inc.) was used. And based on each process demonstrated in Example 1, PET resin, N-MXD6 resin, and PET resin are inject | poured alternately, and the parison of 5 layer structure is formed by the alternate injection molding method (the 1st aspect of this invention) Molded based on injection molding method of multilayer molded product). The length of the parison was 110 mm, the wall thickness was 4.5 mm, and the outer diameter was 26.5 mm. In addition, the dimension of the multilayer bottle obtained by a biaxial stretch blow molding method based on such a parison is a total length of 200 mm, an outer diameter of 75 mm, and a volume of 600 ml.
[0079]
A portion of the first resin flow path 23A and the second resin flow path 23B upstream (on the injection cylinder side) from the joining portion of the first resin flow path 23A and the second resin flow path 23B has a double tube structure. The length of this part was 120 mm. The outer diameter of the outer first resin flow path 23A in the double-pipe resin flow path was 18 mm, and the inner diameter was 14 mm. On the other hand, the diameter of the inner tubular second resin flow path 23B in the resin flow path of the double tube structure was 8 mm. The outer diameter of the cylindrical gate cut pin 26 was 4 mm.
[0080]
The first injection cylinder 10A having an inner diameter of 50 mm was used to plasticize and melt the first resin 40A (PET resin). The second injection cylinder 10B having an inner diameter of 40 mm was used, and the second resin 40B (N-MXD6 resin) was plasticized and melted. A ball-type backflow control valve 30B was used as the backflow means. The mold 20 is provided with four cavities 25, and the resin flow paths 23A and 23B are branched downstream of the backflow control valve 30B and connected to the gate portions 24 opened in the cavities 25. .
[0081]
Before the injection molding, the first molten resin 40a flowing into the second resin flow path 23B at the previous injection remains in the second resin flow path 23B by an amount corresponding to 5% of the volume of the cavity 25. It was.
[0082]
First, in the same manner as in [Step-100], the first molten resin 40A (molten PET resin) was injected into the cavity 25 by an amount corresponding to 30% of the volume of the cavity 25. At this time, the first molten resin 40A did not flow into the second resin flow path 23B.
[0083]
Next, in the same manner as in [Step-110], the second molten resin 40B (molten N-MXD6 resin) was injected into the cavity 25 from the second injection cylinder 10B. The amount of the second molten resin 40B injected was an amount corresponding to 5% of the volume of the cavity 25. The first molten resin 40a that flowed into the second resin flow path 23B at the previous injection and remained in an amount corresponding to 5% of the volume of the cavity 25 was also injected into the cavity 25. Also at this time, the second molten resin 40B and the first molten resin 40a did not flow into the first resin flow path 23A.
[0084]
Subsequently, in the same manner as in [Step-120], the first molten resin 40A (molten PET resin) was injected into the cavity 25 from the first injection cylinder 10A. The amount of the first molten resin 40A injected is equivalent to an amount corresponding to 60% of the volume of the cavity 25 for filling the cavity 25 with the molten resin, and the first molten resin 40A in the second resin flow path 23B. The total amount of inflow. At this time, the first molten resin 40A flows into the second resin flow path 23B, the second molten resin 40B in the second resin flow path 23B flows backward, and the screw in the second injection cylinder 10B. 11B was retracted, but the flow of the first molten resin 40A into the second resin flow path 23B was limited to 5% of the volume of the cavity 25 by the operation of the backflow control valve 30B.
[0085]
Next, after holding for 15 seconds by the first injection cylinder 10A, the pneumatic cylinder 27 was operated to advance the gate cut pin 26 and close the gate portion 24. Thereafter, after cooling for 10 seconds, the mold was opened, and the parison as a laminated molded product was taken out from the mold. The obtained parison has a five-layer structure of PET resin layer / N-MXD6 resin layer / PET resin layer / N-MXD6 resin layer / PET resin layer, as shown in FIG. A clean resin layer was formed. In addition, a phenomenon in which the N-MXD6 resin layer appeared on the outermost layer surface of the parison (the inner surface and the outer surface of the parison) was not observed at all. When the obtained multilayer parison was heated to 100 ° C. and a multilayer bottle was produced by a biaxial stretch blow molding method, a multilayer bottle having a good appearance was obtained.
[0086]
(Example 3)
The diameter of the ball 34 is the same as the diameter of the ball 34 of the backflow control valve 30B used in the second embodiment, but the moving distance of the ball 34 is longer than that of the backflow control valve 30B used in the second embodiment. A parison was molded using the injection molding apparatus of Example 2 except that the control valve 30B was replaced.
[0087]
Before the injection molding, the first molten resin 40a flowing into the second resin flow path 23B at the previous injection remains in the second resin flow path 23B by an amount corresponding to 15% of the volume of the cavity 25. It was.
[0088]
First, in the same manner as in [Step-100], the first molten resin 40A (molten PET resin) was injected into the cavity 25 by an amount corresponding to 40% of the volume of the cavity 25. At this time, the first molten resin 40A did not flow into the second resin flow path 23B.
[0089]
Next, in the same manner as in [Step-110], the second molten resin 40B (molten N-MXD6 resin) was injected into the cavity 25 from the second injection cylinder 10B. The amount of the second molten resin 40B injected was an amount corresponding to 5% of the volume of the cavity 25. The first molten resin 40 a that flowed into the second resin flow path 23 B at the previous injection and remained in an amount corresponding to 15% of the volume of the cavity 25 was also injected into the cavity 25. Also at this time, the second molten resin 40B and the first molten resin 40a did not flow into the first resin flow path 23A.
[0090]
Subsequently, in the same manner as in [Step-120], the first molten resin 40A (molten PET resin) was injected into the cavity 25 from the first injection cylinder 10A. The amount of the injected first molten resin 40A is equal to the amount corresponding to 40% of the volume of the cavity 25 for filling the cavity 25 with the molten resin, and the second molten resin 40B in the second resin flow path 23B. The total amount corresponding to the amount of reverse flow of was taken. At this time, the first molten resin 40A flows into the second resin flow path 23B, the second molten resin 40B in the second resin flow path 23B flows backward, and the screw in the second injection cylinder 10B. 11B moved backward, but the flow of the first molten resin 40A into the second resin flow path 23B was limited to 15% of the volume of the cavity 25 by the operation of the backflow control valve 30B.
[0091]
Next, after holding for 15 seconds by the first injection cylinder 10A, the pneumatic cylinder 27 was operated to advance the gate cut pin 26 and close the gate portion 24. Thereafter, after cooling for 10 seconds, the mold was opened, and the parison as a laminated molded product was taken out from the mold. The obtained parison has a five-layer structure of PET resin layer / N-MXD6 resin layer / PET resin layer / N-MXD6 resin layer / PET resin layer, as shown in FIG. A clean resin layer was formed. In addition, a phenomenon in which the N-MXD6 resin layer appeared on the outermost layer surface of the parison (the inner surface and the outer surface of the parison) was not observed at all. In addition, a multilayer bottle with good appearance was obtained.
[0092]
Example 4
As the second resin 40B, an ethylene-vinyl acetate copolymer resin saponified product (EVOH, EVAL EF-E manufactured by Kuraray Co., Ltd.) was used instead of the N-MXD6 resin. The temperature conditions in Example 4 are shown in Table 2 below. The diameter of the ball 34 is the same as the diameter of the ball 34 of the backflow control valve 30B used in the third embodiment, but the moving distance of the ball 34 is longer than that of the backflow control valve 30B used in the third embodiment. Except that the valve 30B was replaced, injection molding was performed using the same injection molding apparatus as in Example 2.
[0093]
[Table 2]
Temperature of first molten resin 40A in injection cylinder 10A: 270 ° C
Temperature of second molten resin 40B in injection cylinder 10B: 230 ° C
Temperature of first and second resin flow paths in hot runner block: 270 ° C
Cooling water temperature in the cavity block: 15 ° C
[0094]
Before the injection molding, the first molten resin 40a flowing into the second resin flow path 23B at the previous injection remains in the second resin flow path 23B by an amount corresponding to 25% of the volume of the cavity 25. It was.
[0095]
First, in the same manner as in [Step-100], the first molten resin 40A (molten PET resin) was injected into the cavity 25 by an amount corresponding to 40% of the volume of the cavity 25. At this time, the first molten resin 40A did not flow into the second resin flow path 23B.
[0096]
Next, in the same manner as in [Step-110], the second molten resin 40B (molten EVOH resin) was injected into the cavity 25 from the second injection cylinder 10B. The amount of the second molten resin 40B injected was an amount corresponding to 5% of the volume of the cavity 25. The first molten resin 40 a that flowed into the second resin flow path 23 B at the previous injection and remained in an amount corresponding to 25% of the volume of the cavity 25 was also injected into the cavity 25. Also at this time, the second molten resin 40B and the first molten resin 40a did not flow into the first resin flow path 23A.
[0097]
Subsequently, in the same manner as in [Step-120], the first molten resin 40A (molten PET resin) was injected into the cavity 25 from the first injection cylinder 10A. The amount of the first molten resin 40A injected is equivalent to 30% of the volume of the cavity 25 for filling the cavity 25 with the molten resin, and the second molten resin 40B in the second resin flow path 23B. The total amount corresponding to the amount of reverse flow of was taken. At this time, the first molten resin 40A flows into the second resin flow path 23B, the second molten resin 40B in the second resin flow path 23B flows backward, and the screw in the second injection cylinder 10B. 11B moved backward, but the flow of the first molten resin 40A into the second resin flow path 23B was limited to 25% of the volume of the cavity 25 by the operation of the backflow control valve 30B.
[0098]
Next, after holding for 15 seconds by the first injection cylinder 10A, the pneumatic cylinder 27 was operated to advance the gate cut pin 26 and close the gate portion 24. Thereafter, after cooling for 10 seconds, the mold was opened, and the parison as a laminated molded product was taken out from the mold. The obtained parison has a five-layer structure of PET resin layer / EVOH resin layer / PET resin layer / EVOH resin layer / PET resin layer, as shown in FIG. Was formed. Moreover, the phenomenon in which the EVOH resin layer appears on the outermost layer surface of the parison (the inner surface and the outer surface of the parison) was not recognized at all. In addition, a multilayer bottle with good appearance was obtained.
[0099]
(Example 5)
The diameter of the ball 34 is the same as the diameter of the ball 34 of the backflow control valve 30B used in the second embodiment, but the moving distance of the ball 34 is longer than that of the backflow control valve 30B used in the second embodiment. Injection molding was performed by the same injection molding apparatus as in Example 2 except that the control valve 30B was replaced and a conventional check valve was provided in the nozzle portion 12A of the first injection cylinder 10A. Note that a recovered PET resin was used as the second resin 40B instead of the N-MXD6 resin.
[0100]
Before the injection molding, the first molten resin 40a flowing into the second resin flow path 23B at the previous injection remains in the second resin flow path 23B by an amount corresponding to 10% of the volume of the cavity 25. It was.
[0101]
First, in the same manner as in [Step-100], the first molten resin 40A (molten PET resin) was injected into the cavity 25 by an amount corresponding to 50% of the volume of the cavity 25. At this time, the first molten resin 40A did not flow into the second resin flow path 23B.
[0102]
Next, in the same manner as in [Step-110], the second molten resin 40B (recovered PET resin) was injected into the cavity 25 from the second injection cylinder 10B. The amount of the injected second molten resin 40B was set to an amount corresponding to 20% of the volume of the cavity 25. The first molten resin 40a that flowed into the second resin flow path 23B at the previous injection and remained in an amount corresponding to 10% of the volume of the cavity 25 was also injected into the cavity 25. At this time, since the conventional check valve is provided in the nozzle portion 12A of the first injection cylinder 10A, the second molten resin 40B and the first molten resin 40a flow into the first resin flow path 23A. I never did.
[0103]
Subsequently, in the same manner as in [Step-120], the first molten resin 40A (molten PET resin) was injected into the cavity 25 from the first injection cylinder 10A. The amount of the first molten resin 40A injected is equivalent to an amount corresponding to 20% of the volume of the cavity 25 for filling the cavity 25 with the molten resin, and the first molten resin 40A in the second resin flow path 23B. The total amount of inflow. At this time, the first molten resin 40A flows into the second resin flow path 23B, the second molten resin 40B in the second resin flow path 23B flows backward, and the screw in the second injection cylinder 10B. 11B moved backward, but the flow of the first molten resin 40A into the second resin flow path 23B was limited to 10% of the volume of the cavity 25 by the operation of the backflow control valve 30B.
[0104]
Next, after holding for 15 seconds by the first injection cylinder 10A, the pneumatic cylinder 27 was operated to advance the gate cut pin 26 and close the gate portion 24. Thereafter, after cooling for 10 seconds, the mold was opened, and the parison as a laminated molded product was taken out from the mold. The obtained parison has a five-layer structure of PET resin layer / recovered PET resin layer / PET resin layer / recovered PET resin layer / PET resin layer, as shown in FIG. A resin layer was formed. Moreover, the phenomenon in which the recovered PET resin layer appeared on the outermost layer surface of the parison was not observed at all. When the obtained multilayer parison was heated to 100 ° C. and a multilayer bottle was produced by a biaxial stretch blow molding method, a multilayer bottle having a good appearance was obtained.
[0105]
(Example 6)
The diameter of the ball 34 is the same as the diameter of the ball 34 of the backflow control valve 30B used in the fourth embodiment, but the moving distance of the ball 34 is longer than that of the backflow control valve 30B used in the fourth embodiment. Injection molding was performed by the same injection molding apparatus as in Example 2 except that the control valve 30B was replaced and a conventional check valve was provided in the nozzle portion 12A of the first injection cylinder 10A. Note that a recovered PET resin was used as the second resin 40B instead of the N-MXD6 resin.
[0106]
Before the injection molding, the first molten resin 40a flowing into the second resin flow path 23B at the previous injection remains in the second resin flow path 23B by an amount corresponding to 50% of the volume of the cavity 25. It was.
[0107]
First, in the same manner as in [Step-100], the first molten resin 40A (molten PET resin) was injected into the cavity 25 by an amount corresponding to 30% of the volume of the cavity 25. At this time, the first molten resin 40A did not flow into the second resin flow path 23B.
[0108]
Next, in the same manner as in [Step-110], the second molten resin 40B (recovered PET resin) was injected into the cavity 25 from the second injection cylinder 10B. The amount of the injected second molten resin 40B was set to an amount corresponding to 10% of the volume of the cavity 25. The first molten resin 40 a that flowed into the second resin flow path 23 B at the previous injection and remained in an amount corresponding to 50% of the volume of the cavity 25 was also injected into the cavity 25. At this time, since the conventional check valve is provided in the nozzle portion 12A of the first injection cylinder 10A, the second molten resin 40B and the first molten resin 40a flow into the first resin flow path 23A. I never did.
[0109]
Subsequently, in the same manner as in [Step-120], the first molten resin 40A (molten PET resin) was injected into the cavity 25 from the first injection cylinder 10A. The amount of the first molten resin 40A injected is equivalent to 10% of the volume of the cavity 25 for filling the cavity 25 with the molten resin, and the second molten resin 40B in the second resin flow path 23B. The total amount corresponding to the amount of reverse flow of was taken. At this time, the first molten resin 40A flows into the second resin flow path 23B, the second molten resin 40B in the second resin flow path 23B flows backward, and the screw in the second injection cylinder 10B. 11B moved backward, but the flow of the first molten resin 40A into the second resin flow path 23B was limited to 50% of the volume of the cavity 25 by the operation of the backflow control valve 30B.
[0110]
Next, after holding for 15 seconds by the first injection cylinder 10A, the pneumatic cylinder 27 was operated to advance the gate cut pin 26 and close the gate portion 24. Thereafter, after cooling for 10 seconds, the mold was opened, and the parison as a laminated molded product was taken out from the mold. The obtained parison has a 5-layer structure of PET resin layer / recovered PET resin layer / PET resin layer / recovered PET resin layer / PET resin layer, and some disturbance occurred in the resin layers constituting each layer. It was not a turbulence that would be a problem in practice. Moreover, the phenomenon in which the recovered PET resin layer appeared on the outermost layer surface of the parison was not observed at all. When the obtained multilayer parison was heated to 100 ° C. and a multilayer bottle was produced by a biaxial stretch blow molding method, a multilayer bottle having a good appearance was obtained.
[0111]
(Example 7)
The same resin as in Example 2 was used, and injection molding was performed using the injection molding apparatus in Example 2. The temperature conditions were the same as in Table 1. Example 7 differs from Example 2 in that Example 2 was an alternate injection molding method, whereas Example 7 was a simultaneous injection molding method (multilayer molding according to the second aspect of the present invention). Product injection molding method).
[0112]
Before the injection molding, the first molten resin 40a flowing into the second resin flow path 23B at the previous injection remains in the second resin flow path 23B by an amount corresponding to 5% of the volume of the cavity 25. It was.
[0113]
First, in the same manner as in [Step-100], the first molten resin 40A (molten PET resin) was injected into the cavity 25 by an amount corresponding to 20% of the volume of the cavity 25. At this time, the first molten resin 40A did not flow into the second resin flow path 23B.
[0114]
Next, while continuing the injection of the first molten resin 40A (molten PET resin) into the cavity 25, the second molten resin 40B (molten N-MXD6 resin) was injected into the cavity 25 from the second injection cylinder 10B. . The amount of the second molten resin 40B injected was an amount corresponding to 5% of the volume of the cavity 25. The first molten resin 40a that flowed into the second resin flow path 23B at the previous injection and remained in an amount corresponding to 5% of the volume of the cavity 25 was also injected into the cavity 25. Also at this time, the second molten resin 40B and the first molten resin 40a did not flow into the first resin flow path 23A.
[0115]
Thereafter, the injection of the second molten 40B resin into the cavity 25 was stopped. Then, the injection of the first molten resin 40A (molten PET resin) into the cavity 25 was continued, and the cavity 25 was completely filled with the molten resin. The amount of the first molten resin 40A injected is equivalent to 70% of the volume of the cavity 25 for filling the cavity 25 with the molten resin, and the second molten resin 40B in the second resin flow path 23B. The total amount corresponding to the amount of reverse flow of was taken. At this time, the first molten resin 40A flows into the second resin flow path 23B, the second molten resin 40B in the second resin flow path 23B flows backward, and the screw in the second injection cylinder 10B. 11B was retracted, but the flow of the first molten resin 40A into the second resin flow path 23B was limited to 5% of the volume of the cavity 25 by the operation of the backflow control valve 30B.
[0116]
Next, after holding for 15 seconds by the first injection cylinder 10A, the pneumatic cylinder 27 was operated to advance the gate cut pin 26 and close the gate portion 24. Thereafter, after cooling for 10 seconds, the mold was opened, and the parison as a laminated molded product was taken out from the mold. The obtained parison has a three-layer structure of PET resin layer / N-MXD6 resin layer / PET resin layer, as shown in FIG. 11A, and a clean resin layer with no disturbance in the resin layer is formed. It had been. In addition, a phenomenon in which the N-MXD6 resin layer appeared on the outermost layer surface of the parison (the inner surface and the outer surface of the parison) was not observed at all. When the obtained multilayer parison was heated to 100 ° C. and a multilayer bottle was produced by a biaxial stretch blow molding method, a multilayer bottle having a good appearance was obtained.
[0117]
(Example 8)
Except that the backflow means is changed to the slide type backflow control valve 50 shown in FIG. 12A, the parison is molded under the same injection molding conditions as in the second embodiment using the injection molding apparatus of the second embodiment. It was.
[0118]
Before the injection molding, the first molten resin 40a flowing into the second resin flow path 23B at the previous injection remains in the second resin flow path 23B by an amount corresponding to 20% of the volume of the cavity 25. It was.
[0119]
First, in the same manner as in [Step-100], the first molten resin 40A (molten PET resin) was injected into the cavity 25 by an amount corresponding to 30% of the volume of the cavity 25. At this time, the first molten resin 40A did not flow into the second resin flow path 23B.
[0120]
Next, in the same manner as in [Step-110], the second molten resin 40B (molten N-MXD6 resin) was injected into the cavity 25 from the second injection cylinder 10B. The amount of the second molten resin 40B injected was an amount corresponding to 5% of the volume of the cavity 25. The first molten resin 40 a that flowed into the second resin flow path 23 B at the previous injection and remained in an amount corresponding to 20% of the volume of the cavity 25 was also injected into the cavity 25. Also at this time, the second molten resin 40B and the first molten resin 40a did not flow into the first resin flow path 23A.
[0121]
Subsequently, in the same manner as in [Step-120], the first molten resin 40A (molten PET resin) was injected into the cavity 25 from the first injection cylinder 10A. The amount of the first molten resin 40A injected is equivalent to 45% of the volume of the cavity 25 for filling the cavity 25 with the molten resin, and the second molten resin 40B in the second resin flow path 23B. The total amount corresponding to the amount of reverse flow of was taken. At this time, the first molten resin 40A flows into the second resin flow path 23B, the second molten resin 40B in the second resin flow path 23B flows backward, and the screw in the second injection cylinder 10B. 11B moved backward, but the flow of the first molten resin 40A into the second resin flow path 23B was limited to 20% of the volume of the cavity 25 by the operation of the backflow control valve 50.
[0122]
Next, after holding for 15 seconds by the first injection cylinder 10A, the pneumatic cylinder 27 was operated to advance the gate cut pin 26 and close the gate portion 24. Thereafter, after cooling for 10 seconds, the mold was opened, and the parison as a laminated molded product was taken out from the mold. The obtained parison has a five-layer structure of PET resin layer / N-MXD6 resin layer / PET resin layer / N-MXD6 resin layer / PET resin layer, as shown in FIG. A clean resin layer was formed. In addition, a phenomenon in which the N-MXD6 resin layer appeared on the outermost layer surface of the parison (the inner surface and the outer surface of the parison) was not observed at all. In addition, a multilayer bottle with good appearance was obtained.
[0123]
Example 9
As the first resin 40A, a resin in which a PET resin having an intrinsic viscosity of 0.75 and a polyethylene-2,6-naphthalate resin (PEN resin) having an intrinsic viscosity of 0.50 are blended at a weight ratio of 90/10 is used. The injection molding was performed using the injection molding apparatus of Example 2 except that the temperature conditions were the conditions shown in Table 3 below.
[0124]
[Table 3]
Temperature of first molten resin 40A in injection cylinder 10A: 290 ° C
Temperature of second molten resin 40B in injection cylinder 10B: 260 ° C
Temperature of the first and second resin flow paths in the hot runner block: 290 ° C
Cooling water temperature in the cavity block: 15 ° C
[0125]
Before the injection molding, the first molten resin 40a flowing into the second resin flow path 23B at the previous injection remains in the second resin flow path 23B by an amount corresponding to 5% of the volume of the cavity 25. It was.
[0126]
First, in the same manner as in [Step-100], the first molten resin 40A (molten PET / PEN resin) was injected into the cavity 25 by an amount corresponding to 30% of the volume of the cavity 25. At this time, the first molten resin 40A did not flow into the second resin flow path 23B.
[0127]
Next, in the same manner as in [Step-110], the second molten resin 40B (molten N-MXD6 resin) was injected into the cavity 25 from the second injection cylinder 10B. The amount of the second molten resin 40B injected was an amount corresponding to 5% of the volume of the cavity 25. The first molten resin 40a that flowed into the second resin flow path 23B at the previous injection and remained in an amount corresponding to 5% of the volume of the cavity 25 was also injected into the cavity 25. Also at this time, the second molten resin 40B and the first molten resin 40a did not flow into the first resin flow path 23A.
[0128]
Subsequently, in the same manner as in [Step-120], the first molten resin 40A (molten PET / PEN resin) was injected into the cavity 25 from the first injection cylinder 10A. The amount of the first molten resin 40A injected is equivalent to 60% of the volume of the cavity 25 for filling the cavity 25 with the molten resin, and the second molten resin 40B in the second resin flow path 23B. The total amount corresponding to the amount of reverse flow of was taken. At this time, the first molten resin 40A flows into the second resin flow path 23B, the second molten resin 40B in the second resin flow path 23B flows backward, and the screw in the second injection cylinder 10B. 11B was retracted, but the flow of the first molten resin 40A into the second resin flow path 23B was limited to 5% of the volume of the cavity 25 by the operation of the backflow control valve 30B.
[0129]
Next, after holding for 15 seconds by the first injection cylinder 10A, the pneumatic cylinder 27 was operated to advance the gate cut pin 26 and close the gate portion 24. Thereafter, after cooling for 10 seconds, the mold was opened, and the parison as a laminated molded product was taken out from the mold. The obtained parison has a five-layer structure of PET / PEN resin layer / N-MXD6 resin layer / PET / PEN resin layer / N-MXD6 resin layer / PET / PEN resin layer, and the resin layer is not disturbed and clean. A resin layer was formed. In addition, a phenomenon in which the N-MXD6 resin layer appeared on the outermost layer surface of the parison (the inner surface and the outer surface of the parison) was not observed at all. When the obtained multilayer parison was heated to 110 ° C. and a multilayer bottle was produced by the biaxial stretch blow molding method, a multilayer bottle having a good appearance was obtained.
[0130]
(Example 10)
Except that the conventional check valve was provided in the nozzle portion 12A of the first injection cylinder 10A, the same resin as in Example 2 was used, and injection molding was performed using the injection molding apparatus in Example 2. The temperature conditions were the same as in Table 1. While Example 2 was the alternate injection molding method according to the first aspect of the present invention, Example 10 was an injection molding method (alternate injection) of the multilayer molded article according to the third aspect of the present invention. The molding method was adopted.
[0131]
Before the injection molding, the first molten resin 40a flowing into the second resin flow path 23B at the previous injection remains in the second resin flow path 23B by an amount corresponding to 10% of the volume of the cavity 25. It was.
[0132]
First, in the same manner as in [Step-100], the first molten resin 40A (molten PET resin) was injected into the cavity 25 by an amount corresponding to 70% of the volume of the cavity 25. At this time, the first molten resin 40A did not flow into the second resin flow path 23B.
[0133]
Next, the injection of the first molten resin 40A (molten PET resin) into the cavity 25 is finished, and the second molten resin 40B melted in the second injection cylinder 10B in the same manner as in [Step-110]. (Melted N-MXD6 resin) was injected into the cavity 25 through the second resin flow path 23B. The amount of the injected second molten resin 40B was set to an amount corresponding to 20% of the volume of the cavity 25. The first molten resin 40a that flowed into the second resin flow path 23B at the previous injection and remained in an amount corresponding to 10% of the volume of the cavity 25 was also injected into the cavity 25.
[0134]
After finishing the injection of the second molten resin 40B, the first injection cylinder 10A holds the pressure for 15 seconds, and at the same time, the operation of the ball-type backflow control valve 30B causes the first resin flow path 23A to move in the first resin passage 23A. One molten resin 40A was allowed to flow into the second resin flow path 23B. That is, the first molten resin 40A flows into the second resin flow path 23B, the second molten resin 40B in the second resin flow path 23B flows backward, and the screw 11B in the second injection cylinder 10B. However, due to the operation of the backflow control valve 30B, the flow of the first molten resin 40A into the second resin flow path 23B was limited to 10% of the volume of the cavity 25.
[0135]
Thereafter, the pneumatic cylinder 27 was operated to advance the gate cut pin 26 and close the gate portion 24. And after cooling for 10 seconds, the metal mold | die was opened and the parison which is a laminated molded product was taken out from the metal mold | die. The appearance of the N-MXD6 resin layer was not observed on the surface of the parison other than the parison portion corresponding to the gate portion. When the obtained multilayer parison was heated to 100 ° C. and a multilayer bottle was produced by a biaxial stretch blow molding method, a multilayer bottle having a good appearance was obtained.
[0136]
(Example 11)
Except that the conventional check valve was provided in the nozzle portion 12A of the first injection cylinder 10A, the same resin as in Example 2 was used, and injection molding was performed using the injection molding apparatus in Example 2. The temperature conditions were the same as in Table 1. Example 2 was the alternate injection molding method according to the first aspect of the present invention, whereas Example 11 was an injection molding method (simultaneous injection) of the multilayer molded product according to the fourth aspect of the present invention. The molding method was adopted.
[0137]
Before the injection molding, the first molten resin 40a flowing into the second resin flow path 23B at the previous injection remains in the second resin flow path 23B by an amount corresponding to 20% of the volume of the cavity 25. It was.
[0138]
First, in the same manner as in [Step-100], the first molten resin 40A (molten PET resin) was injected into the cavity 25 by an amount corresponding to 40% of the volume of the cavity 25. At this time, the first molten resin 40A did not flow into the second resin flow path 23B.
[0139]
Subsequently, while injecting the first molten resin 40A (molten PET resin) into the cavity 25 by an amount corresponding to 20% of the volume of the cavity 25, the second molten resin 40B (molten N−) is injected from the second injection cylinder 10B. MXD6 resin) was injected into the cavity 25. The amount of the injected second molten resin 40B was set to an amount corresponding to 20% of the volume of the cavity 25. The first molten resin 40 a that flowed into the second resin flow path 23 B at the previous injection and remained in an amount corresponding to 20% of the volume of the cavity 25 was also injected into the cavity 25.
[0140]
After completing the injection of the first molten resin 40A and the injection of the second molten resin 40B substantially simultaneously, the first injection cylinder 10A holds the pressure for 15 seconds, and also the operation of the ball type backflow control valve 30B. Thus, the first molten resin 40A in the first resin flow path 23A was caused to flow into the second resin flow path 23B. That is, the first molten resin 40A flows into the second resin flow path 23B, the second molten resin 40B in the second resin flow path 23B flows backward, and the screw 11B in the second injection cylinder 10B. However, due to the operation of the backflow control valve 30B, the flow of the first molten resin 40A into the second resin flow path 23B was limited to 20% of the volume of the cavity 25.
[0141]
Thereafter, the pneumatic cylinder 27 was operated to advance the gate cut pin 26 and close the gate portion 24. And after cooling for 10 seconds, the metal mold | die was opened and the parison which is a laminated molded product was taken out from the metal mold | die. The appearance of the N-MXD6 resin layer was not observed on the surface of the parison other than the parison portion corresponding to the gate portion. When the obtained multilayer parison was heated to 100 ° C. and a multilayer bottle was produced by a biaxial stretch blow molding method, a multilayer bottle having a good appearance was obtained.
[0142]
(Comparative Example 1)
The diameter of the ball 34 is the same as the diameter of the ball 34 of the backflow control valve 30B used in the sixth embodiment, but the moving distance of the ball 34 is longer than that of the backflow control valve 30B used in the sixth embodiment. The parison was molded using the same resin as in Example 2 and the same injection molding apparatus as in Example 2 by replacing the control valve 30B. The inflow of the first molten resin 40A into the second resin flow path 23B reached 60% or more of the volume of the cavity 25, and fluctuated greatly every injection molding cycle. Although the measured value of the second molten resin 40B in the second injection cylinder 10B was increased, stable molding could not be performed, and the resulting 5-layer parison had a very disturbed layer structure. .
[0143]
(Comparative Example 2)
The backflow means was replaced with a conventional ball check valve (check valve) that prevents backflow of the molten resin. The parison was molded using the same resin as in Example 2 and the injection molding apparatus in Example 2.
[0144]
First, in the same manner as in [Step-100], the first molten resin 40A (molten PET resin) was injected into the cavity 25 by an amount corresponding to 60% of the volume of the cavity 25. At this time, the first molten resin 40A did not flow into the second resin flow path 23B.
[0145]
Next, in the same manner as in [Step-110], the second molten resin 40B (molten N-MXD6 resin) was injected into the cavity 25 from the second injection cylinder 10B. The amount of the injected second molten resin 40B was set to an amount corresponding to 10% of the volume of the cavity 25.
[0146]
Subsequently, in the same manner as in [Step-120], the first molten resin 40A (molten PET resin) was injected into the cavity 25 from the first injection cylinder 10A. The amount of the first molten resin 40A injected was an amount corresponding to 30% of the volume of the cavity 25 for filling the cavity 25 with the molten resin. At this time, since the conventional check valve is used, the first molten resin 40A did not flow into the second resin flow path 23B.
[0147]
Next, after holding for 15 seconds by the first injection cylinder 10A, the pneumatic cylinder 27 was operated to advance the gate cut pin 26 and close the gate portion 24. Thereafter, after cooling for 10 seconds, the mold was opened, and the parison as a laminated molded product was taken out from the mold. A parison having a five-layer structure of PET resin layer / N-MXD6 resin layer / PET resin layer / N-MXD6 resin layer / PET resin layer was obtained. Appearance of the N-MXD6 resin layer was observed on the surface of the parison.
[0148]
(Comparative Example 3)
The parison was molded in the same manner as in Example 2 except that the backflow means was changed to a shutoff valve that opened and closed by a conventional hydraulic cylinder operation. That is, a shut-off valve that opens and closes by the operation of the hydraulic cylinder is arranged in the nozzle portion 12B of the second injection cylinder 10B, and immediately after [Step-110] is completed, the hydraulic cylinder is operated and the shut-off valve is turned on. Closed to prevent the backflow of the second molten resin 40B into the second injection cylinder 10B. The inflow of the first molten resin 40A into the second resin flow path 23B was 0 to 0.9% of the volume of the cavity 25. As a result, when the first molten resin 40A (molten PET resin) is injected in the same step as [Step-100], the second molten resin 40B (molten N-MXD6 resin) in the second resin flow path 23B is injected. ) Entrained and flows into the cavity 25, and the second resin 40B (N-MXD6) is formed on the surface of the resin layer composed of the first resin 40A (PET resin) in the vicinity of the opening of the obtained five-layer parison. Resin) appeared.
[0149]
As mentioned above, although this invention was demonstrated based on the preferable Example, this invention is not limited to these. The injection molding apparatus described in the first embodiment is an example, and the design can be changed as appropriate. In addition, the injection molding apparatus and the injection molding conditions described in each example are also examples, and the design change / condition change can be appropriately performed, and the resin used in the examples is also an example. In [Step-110], a simultaneous injection molding method may be executed in which the molten resin 40B is injected while continuing to inject the molten resin 40A, and the molten resin 40A is continuously injected even after the injection of the molten resin 40B is completed. In the embodiment, the second molten resin flows back in the backflow means. However, depending on the position of the backflow means, not only the second molten resin but also the first molten resin may flow back in the backflow means. possible.
[0150]
The backflow means in the present invention can also be applied when intermittently switching between two types of liquids (including fluids composed of liquids with relatively high viscosity). Furthermore, the backflow means in the present invention can also be applied when switching between two types of gas bodies intermittently. When switching intermittently, it is particularly effective in the field where it is desired to avoid mixing the liquid or gas body to be used secondly and the liquid or gas body to be used secondly. The petrochemical field, food manufacturing field (confectionery) Production field, food processing field, etc.), chemical manufacturing equipment, wastewater treatment equipment, etc. The fields that can be specifically applied are listed below.
(1) When the crude oil and seawater switching equipment is used to avoid the inflow of crude oil into the seawater
(2) In the production of confectionery, when switching between two high-viscosity creams, etc., to avoid mixing one color cream into another color cream
(3) In the food processing field such as marine products processing, when seawater is not mixed in fresh water
(4) When using pipes to the storage facility for the final product and the crude product in the chemical production equipment, to avoid mixing the crude product into the final product
(5) When switching between liquid adsorption line and desorption line in an ion exchange device
(6) In high-purity gas production equipment, when operating gas production equipment by intermittently switching the gas flow, avoiding mixing of raw material gas or crude gas in high-purity gas
[0151]
【The invention's effect】
In the injection molding apparatus of the present invention or the injection molding method of the present invention, when the first molten resin is injected, the first molten resin and the second molten resin that form the outer layer of the multilayer molded product in the vicinity of the joining portion of the resin flow path. Mixing with the second molten resin that forms the inner layer of the multilayer molded article existing in the resin flow path, or the second molten resin that is not in the injection state is caught in the first molten resin that is being injected Such a phenomenon can be prevented. As a result, for example, it is possible to reliably avoid the occurrence of the problem that the second resin appears on the surface of the multilayer molded article. For example, if a parison, which is a multilayer molded article composed of a thermoplastic polyester resin and a gas barrier resin, is molded as a resin, it is excellent in gas barrier properties, transparency, and mechanical strength by biaxial stretch blow molding. Multi-layer containers can be manufactured. In addition, by defining an upper limit of the amount of the first molten resin flowing into the second resin flow path, it is possible to reliably prevent the resin layers constituting each layer of the multilayer molded product from being disturbed. it can.
[0152]
If the backflow means is composed of a backflow control valve, it is possible to avoid an increase in size and complexity of the injection molding apparatus, and there is no occurrence of leakage of molten resin from the resin flow path. Furthermore, the operation of the backflow means is quick, and a certain amount of the first molten resin can be surely caused to flow into the second resin flow path.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of an injection molding apparatus according to a first embodiment, showing an injection molding apparatus in a state where no injection molding is performed.
FIG. 2 is a conceptual diagram of an injection molding apparatus in Example 1 and shows a state of an injection molding apparatus that has already weighed first and second molten resins just before molding a multilayer molded product.
3 is a conceptual diagram of cavities and the like for explaining an injection molding method of a multilayer molded article using the injection molding apparatus of Example 1. FIG.
4 is a conceptual diagram of cavities and the like for explaining an injection molding method of a multilayer molded product using the injection molding apparatus of Example 1 following FIG. 3. FIG.
5 is a conceptual diagram of cavities and the like for explaining an injection molding method of a multilayer molded product using the injection molding apparatus of Example 1 following FIG. 4;
FIG. 6 is a schematic end view of a backflow control valve which is a backflow means in the first embodiment.
7 is a schematic cross-sectional view of a cylindrical tube portion of the backflow control valve along arrow AA in FIG. 6B, and backflow control along arrow BB in FIG. 6B. It is typical sectional drawing of the cylindrical pipe part of a valve.
FIG. 8 is a schematic cross-sectional view showing the structure of a second injection cylinder.
FIG. 9 is a schematic cross-sectional view showing a structure of a first injection cylinder.
FIG. 10 is a schematic cross-sectional view of a parison.
FIG. 11 is a schematic cross-sectional view of a parison.
FIG. 12 is a schematic end view of a slide type backflow control valve.
13 is a schematic cross-sectional view of the cylindrical tube portion along arrow AA in FIG. 12B, and a schematic view of the cylindrical tube portion along arrow BB in FIG. FIG.
FIG. 14 is a graph showing temporal changes in injection pressure and the like in the multilayer molded product injection molding method according to the first embodiment of the present invention.
FIG. 15 is a graph showing temporal changes in injection pressure and the like in the multilayer molded product injection molding method according to the first aspect of the present invention.
FIG. 16 is a graph showing temporal changes in injection pressure and the like in the multilayer molded product injection molding method according to the first aspect of the present invention.
FIG. 17 is a graph showing temporal changes in injection pressure and the like in the injection molding method for multilayer molded articles according to the second embodiment of the present invention.
FIG. 18 is a graph showing temporal changes in injection pressure and the like in the multilayer molded product injection molding method according to the second embodiment of the present invention.
FIG. 19 is a graph showing temporal changes in injection pressure and the like in the injection molding method for multilayer molded articles according to the second embodiment of the present invention.
FIG. 20 is a graph showing temporal changes in injection pressure and the like in the injection molding method for multilayer molded articles according to the third aspect of the present invention.
FIG. 21 is a graph showing changes over time in injection pressure and the like in the injection molding method for multilayer molded articles according to the fourth aspect of the present invention.
[Explanation of symbols]
10A, 10B ... Injection cylinder
11A, 11B ... Screw
12B ... Nozzle part of injection cylinder 10B
13 ... Reduction gear
14 ... Hydraulic motor
15 ... Hopper
16 ... Void
17A, 17B ... Injection ram
18A, 18B ... Hydraulic cylinder for injection
19 ... Injection device forward / backward cylinder
19A, 19B ... Hydraulic piping
19C ... Pressure gauge
20 ... Mold
21 ... Cavity block
22 ... Hot runner block
23A, 23B ... resin flow path
24 ... Gate part
25 ... Cavity
26 ... Gate cut pin
27 ... Pneumatic cylinder
30B, 50 ... Backflow control valve
31, 51 ... Cylinder tube part
32, 52 ... hollow part
33, 53 ... Diameter expansion part
34 ... Ball
40A, 40B ... Resin or molten resin
40a: first molten resin flowing into another resin flow path
54 ... Valve
55 ... Bar
56A, 56B ... Support

Claims

(A) a mold having a cavity block provided with a cavity and a hot runner block;
(B) at least a first injection cylinder and a second injection cylinder;
(C) a first resin flow path connecting the inside of the first injection cylinder and the cavity;
as well as,
(D) a second resin flow path connecting the inside of the second injection cylinder and the cavity;
With
The first resin flow channel and the second resin flow channel located in the mold are provided in the hot runner block,
The first resin flow path and the second resin flow path are injection molding devices having a structure in which the first resin flow path and the second resin flow path are merged at a merge section upstream of the gate section opened in the cavity,
Back flow means for injecting the first molten resin in the first resin flow path into the second resin flow path after injecting the second molten resin into the cavity via the second resin flow path Provided,
The reverse flow means operates by the pressure exerted on the second molten resin in the second resin flow path by the first molten resin in the first resin flow path,
The injection molding apparatus for molding a multilayer molded product, wherein the backflow means is a ball type backflow control valve or a slide type backflow control valve.

2. The injection for molding a multilayer molded article according to claim 1, wherein the backflow means causes a fixed amount of the first molten resin in the first resin flow path to flow into the second resin flow path. Molding equipment.

When the second molten resin is injected into the cavity via the second resin flow path and after completion of the injection, the inside of the second injection cylinder and the cavity are in communication with each other by the backflow means, and the first After the predetermined amount of the first molten resin in the resin flow path flows into the second resin flow path, the interior of the second injection cylinder and the cavity are in a non-communication state by the backflow means. An injection molding apparatus for molding the multilayer molded article according to claim 1.

When the second molten resin is injected into the cavity via the second resin flow path and after completion of the injection, the inside of the second injection cylinder and the cavity are in communication with each other by the backflow means, and the first After the first molten resin in the resin flow path starts to flow into the second resin flow path, the inside of the second injection cylinder and the cavity are in a non-communication state by the backflow means. An injection molding apparatus for molding the multilayer molded article according to claim 1.

The backflow means is provided in the second resin flow path between the joining portion of the resin flow path and the second injection cylinder, for molding a multilayer molded article according to claim 1 Injection molding equipment.

6. The multilayer molded article according to claim 5, wherein the backflow means is disposed between the nozzle portion of the second injection cylinder and the mold or in the nozzle portion of the second injection cylinder. Injection molding equipment for molding.

The injection molding for molding a multilayer molded article according to claim 1, wherein the volume of the first molten resin flowing into the second resin flow path is 5 to 50% of the volume of the cavity. apparatus.

The injection molding for molding a multilayer molded article according to claim 7, wherein the volume of the first molten resin flowing into the second resin flow path is 5 to 25% of the volume of the cavity. apparatus.

2. The injection molding apparatus for molding a multilayer molded product according to claim 1, wherein the multilayer molded product is a parison.

10. The injection for molding a multilayer molded article according to claim 9, wherein the outermost layer of the parison is formed by the first molten resin injected into the cavity through the first resin flow path. Molding equipment.

(A) a mold having a cavity block provided with a cavity and a hot runner block;
(B) at least a first injection cylinder and a second injection cylinder;
(C) a first resin flow path connecting the inside of the first injection cylinder and the cavity;
as well as,
(D) a second resin flow path connecting the inside of the second injection cylinder and the cavity;
With
The first resin flow channel and the second resin flow channel located in the mold are provided in the hot runner block,
The first resin flow path and the second resin flow path are injection molding devices having a structure in which the first resin flow path and the second resin flow path are merged at a merge section upstream of the gate section opened in the cavity,
Back flow means for injecting the first molten resin in the first resin flow path into the second resin flow path after injecting the second molten resin into the cavity via the second resin flow path Provided,
The reverse flow means operates by the pressure exerted on the second molten resin in the second resin flow path by the first molten resin in the first resin flow path,
The backflow means is an injection molding method of a multilayer molded article using an injection molding apparatus which is a ball type backflow control valve or a slide type backflow control valve,
(A) After injecting the first molten resin melted in the first injection cylinder into the cavity through the first resin flow path, the injection of the first molten resin is interrupted,
(B) After injecting the second molten resin melted in the second injection cylinder into the cavity through the second resin flow path, the injection of the second molten resin is terminated,
(C) The first molten resin melted in the first injection cylinder is injected into the cavity through the first resin flow path, and the reverse flow means is injected during or after the injection of the first molten resin. The first molten resin in the first resin channel is caused to flow into the second resin channel by the operation of
A method for injection molding a multilayer molded article, comprising a step.

The injection molding method for a multilayer molded article according to claim 11, wherein a fixed amount of the first molten resin in the first resin flow path is caused to flow into the second resin flow path by the backflow means.

When the second molten resin is injected into the cavity via the second resin flow path and after completion of the injection, the inside of the second injection cylinder and the cavity are in communication with each other by the backflow means, and the first After the predetermined amount of the first molten resin in the resin flow path flows into the second resin flow path, the interior of the second injection cylinder and the cavity are in a non-communication state by the backflow means. The method for injection molding a multilayer molded article according to claim 11.

When the second molten resin is injected into the cavity via the second resin flow path and after completion of the injection, the inside of the second injection cylinder and the cavity are in communication with each other by the backflow means, and the first After the first molten resin in the resin flow path starts to flow into the second resin flow path, the inside of the second injection cylinder and the cavity are in a non-communication state by the backflow means. The method for injection molding a multilayer molded article according to claim 11.

The main part of the multilayer molded article has a five-layer structure of first resin layer / second resin layer / first resin layer / second resin layer / first resin layer. 11. A method for injection molding a multilayer molded article according to item 11.

A part of the main part of the multilayer molded product has a five-layer configuration of the first resin layer / second resin layer / first resin layer / second resin layer / first resin layer, The other part of the main part has a three-layer structure of a first resin layer / second resin layer / first resin layer, and the injection molding method for a multilayer molded article according to claim 11.

The multilayer molding product injection molding method according to claim 11, wherein the backflow means is provided in a second resin flow path between a joining portion of the resin flow path and the second injection cylinder.

18. The multilayer molded article according to claim 17, wherein the backflow means is disposed between the nozzle portion of the second injection cylinder and the mold or in the nozzle portion of the second injection cylinder. Injection molding method.

12. The method for injection molding a multilayer molded product according to claim 11, wherein the volume of the first molten resin flowing into the second resin flow path is 5 to 50% of the volume of the cavity.

The method for injection molding a multilayer molded article according to claim 19, wherein the volume of the first molten resin flowing into the second resin flow path is 5 to 25% of the volume of the cavity.

The multilayer molded article injection molding method according to claim 11, wherein the multilayer molded article is a parison.

The method for injection molding a multilayer molded article according to claim 21, wherein the outermost layer of the parison is formed by the first molten resin injected into the cavity through the first resin flow path.

The first resin is at least selected from the group consisting of thermoplastic polyester resin, thermoplastic copolyester resin, polyolefin resin, aliphatic polyamide resin, polycarbonate resin, polyacrylonitrile resin, polyvinyl chloride resin, and polystyrene resin. The method for injection molding of a multilayer molded product according to claim 11, wherein the method is one type of resin.

The injection of a multilayer molded article according to claim 11, wherein the second resin is at least one resin selected from the group consisting of a gas barrier resin, a recovered polyethylene terephthalate resin, and a colored polyethylene terephthalate resin. Molding method.

The gas barrier resin is at least one resin selected from the group consisting of a metaxylylene group-containing polyamide resin, a saponified ethylene-vinyl acetate copolymer resin, a polyacrylonitrile resin, and a polyvinylidene chloride resin. The method for injection molding a multilayer molded article according to claim 24.

(A) a mold having a cavity block provided with a cavity and a hot runner block;
(B) at least a first injection cylinder and a second injection cylinder;
(C) a first resin flow path connecting the inside of the first injection cylinder and the cavity;
as well as,
(D) a second resin flow path connecting the inside of the second injection cylinder and the cavity;
With
The first resin flow channel and the second resin flow channel located in the mold are provided in the hot runner block,
The first resin flow path and the second resin flow path are injection molding devices having a structure in which the first resin flow path and the second resin flow path are merged at a merge section upstream of the gate section opened in the cavity,
Back flow means for injecting the first molten resin in the first resin flow path into the second resin flow path after injecting the second molten resin into the cavity via the second resin flow path Provided,
The reverse flow means operates by the pressure exerted on the second molten resin in the second resin flow path by the first molten resin in the first resin flow path,
The backflow means is an injection molding method of a multilayer molded article using an injection molding apparatus which is a ball type backflow control valve or a slide type backflow control valve,
(A) Injecting the first molten resin melted in the first injection cylinder into the cavity through the first resin flow path,
(B) During the injection of the first molten resin, the second molten resin melted in the second injection cylinder is injected into the cavity through the second resin flow path,
(C) After the completion of the injection of the second molten resin and during the injection of the first molten resin or after the completion of the injection, the first molten resin in the first resin flow path is removed by the operation of the backflow means. Let it flow into the resin flow path,
A method for injection molding a multilayer molded article, comprising a step.

27. The method for injection molding a multilayer molded article according to claim 26, wherein a fixed amount of the first molten resin in the first resin flow path is caused to flow into the second resin flow path by the backflow means.

When the second molten resin is injected into the cavity via the second resin flow path and after completion of the injection, the inside of the second injection cylinder and the cavity are in communication with each other by the backflow means, and the first After the predetermined amount of the first molten resin in the resin flow path flows into the second resin flow path, the interior of the second injection cylinder and the cavity are in a non-communication state by the backflow means. 27. A method for injection molding a multilayer molded article according to claim 26.

When the second molten resin is injected into the cavity via the second resin flow path and after completion of the injection, the inside of the second injection cylinder and the cavity are in communication with each other by the backflow means, and the first After the first molten resin in the resin flow path starts to flow into the second resin flow path, the inside of the second injection cylinder and the cavity are in a non-communication state by the backflow means. 27. A method for injection molding a multilayer molded article according to claim 26.

27. The method for injection molding of a multilayer molded article according to claim 26, wherein the main part of the multilayer molded article has a three-layer configuration of first resin layer / second resin layer / first resin layer.

27. The injection molding of a multilayer molded article according to claim 26, wherein a part of a main portion of the multilayer molded article has a three-layer configuration of a first resin layer / second resin layer / first resin layer. Method.

27. The injection molding method for a multilayer molded article according to claim 26, wherein the backflow means is provided in a second resin flow path between the joining portion of the resin flow path and the second injection cylinder.

33. The multilayer molded article according to claim 32, wherein the backflow means is disposed between the nozzle portion of the second injection cylinder and the mold or in the nozzle portion of the second injection cylinder. Injection molding method.

27. The method for injection molding a multilayer molded article according to claim 26, wherein the volume of the first molten resin flowing into the second resin flow path is 5 to 50% of the volume of the cavity.

The method for injection molding a multilayer molded article according to claim 34, wherein the volume of the first molten resin flowing into the second resin flow path is 5 to 25% of the volume of the cavity.

27. The method for injection molding a multilayer molded article according to claim 26, wherein the multilayer molded article is a parison.

The method for injection molding a multilayer molded article according to claim 36, wherein the outermost layer of the parison is formed by the first molten resin injected into the cavity through the first resin flow path.

The first resin is at least selected from the group consisting of thermoplastic polyester resin, thermoplastic copolyester resin, polyolefin resin, aliphatic polyamide resin, polycarbonate resin, polyacrylonitrile resin, polyvinyl chloride resin, and polystyrene resin. 27. The method for injection molding a multilayer molded article according to claim 26, wherein the injection molding method is one kind of resin.

27. The injection of a multilayer molded article according to claim 26, wherein the second resin is at least one resin selected from the group consisting of a gas barrier resin, a recovered polyethylene terephthalate resin, and a colored polyethylene terephthalate resin. Molding method.

The gas barrier resin is at least one resin selected from the group consisting of a metaxylylene group-containing polyamide resin, a saponified ethylene-vinyl acetate copolymer resin, a polyacrylonitrile resin, and a polyvinylidene chloride resin. 40. A method of injection molding a multilayer molded article according to claim 39.

(A) a mold having a cavity block provided with a cavity and a hot runner block;
(B) at least a first injection cylinder and a second injection cylinder;
(C) a first resin flow path connecting the inside of the first injection cylinder and the cavity;
as well as,
(D) a second resin flow path connecting the inside of the second injection cylinder and the cavity;
With
The first resin flow channel and the second resin flow channel located in the mold are provided in the hot runner block,
The first resin flow path and the second resin flow path are injection molding devices having a structure in which the first resin flow path and the second resin flow path are merged at a merge section upstream of the gate section opened in the cavity,
Back flow means for injecting the first molten resin in the first resin flow path into the second resin flow path after injecting the second molten resin into the cavity via the second resin flow path Provided,
The reverse flow means operates by the pressure exerted on the second molten resin in the second resin flow path by the first molten resin in the first resin flow path,
The backflow means is an injection molding method of a multilayer molded article using an injection molding apparatus which is a ball type backflow control valve or a slide type backflow control valve,
(A) After injecting the first molten resin melted in the first injection cylinder into the cavity through the first resin flow path, the injection of the first molten resin is terminated,
(B) After injecting the second molten resin melted in the second injection cylinder into the cavity through the second resin flow path, the injection of the second molten resin is terminated,
(C) Holding pressure by the first injection cylinder, and simultaneously flowing the first molten resin in the first resin flow path into the second resin flow path by the operation of the backflow means.
A method for injection molding a multilayer molded article, comprising a step.

(A) a mold having a cavity block provided with a cavity and a hot runner block;
(B) at least a first injection cylinder and a second injection cylinder;
(C) a first resin flow path connecting the inside of the first injection cylinder and the cavity;
as well as,
(D) a second resin flow path connecting the inside of the second injection cylinder and the cavity;
With
The first resin flow channel and the second resin flow channel located in the mold are provided in the hot runner block,
The first resin flow path and the second resin flow path are injection molding devices having a structure in which the first resin flow path and the second resin flow path are merged at a merge section upstream of the gate section opened in the cavity,
Back flow means for injecting the first molten resin in the first resin flow path into the second resin flow path after injecting the second molten resin into the cavity via the second resin flow path Provided,
The reverse flow means operates by the pressure exerted on the second molten resin in the second resin flow path by the first molten resin in the first resin flow path,
The backflow means is an injection molding method of a multilayer molded article using an injection molding apparatus which is a ball type backflow control valve or a slide type backflow control valve,
(A) Injecting the first molten resin melted in the first injection cylinder into the cavity through the first resin flow path,
(B) During the injection of the first molten resin, the second molten resin melted in the second injection cylinder is injected into the cavity through the second resin flow path,
(C) After completing the injection of the first molten resin and the injection of the second molten resin substantially simultaneously, holding pressure is performed by the first injection cylinder, and the first resin flow path is also operated by the operation of the backflow means. The first molten resin is allowed to flow into the second resin flow path,
A method for injection molding a multilayer molded article, comprising a step.