JP2004034491A

JP2004034491A - Method for injection-molding molded product and mold assembly

Info

Publication number: JP2004034491A
Application number: JP2002194287A
Authority: JP
Inventors: Akihiro Kokubo; 小久保　章博; Akimasa Kaneishi; 兼石　彰雅
Original assignee: Mitsubishi Engineering Plastics Corp
Current assignee: Mitsubishi Engineering Plastics Corp
Priority date: 2002-07-03
Filing date: 2002-07-03
Publication date: 2004-02-05

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for injection-molding a molded product by which the problems involved in a conventional SCORIM process are solved. <P>SOLUTION: This method uses a mold assembly constituted of a first resin flow path 14A, a second resin flow path 14B, a cavity 18, a first gate part 15A, a second gate part 15B, first pressurizing means 20A and 21A and second pressurizing means 20B and 21B. The method comprises the processes that (a) after injecting a molten thermoplastic resin 30 into the cavity 18, (b) a pressure P<SB>l</SB>and a pressure P<SB>2</SB>(provided, however, that P<SB>l</SB>>P<SB>2</SB>>0) are applied to the molten thermoplastic resin 30 in the first resin flow path 14A and the second resin flow path 14B by the first pressurizing means 20A and the second pressurizing means 20B, respectively, and next, a pressure P<SB>1</SB>' and a pressure P<SB>2</SB>'(provided, however, that P<SB>2</SB>'> P<SB>1</SB>'>0) are repeatedly applied to the molten thermopolastic resin 30 in the first resin flow path 14A and the second resin flow path 14B by the first pressurizing means 20A and the second pressurizing means 20B, respectively. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、成形品の射出成形方法及び金型組立体に関し、更に詳しくは、所謂ＳＣＯＲＩＭ（Ｓｈｅａｒ　Ｃｏｎｔｒｏｌｌｅｄ　ＯＲｉｅｎｔａｔｅｄ　Ｉｎｊｅｃｔｉｏｎ　Ｍｏｌｄｉｎｇ）法の改良、及び、係る改良されたＳＣＯＲＩＭ法の実施に適した金型組立体に関する。
【０００２】
【従来の技術】
従来の射出成形法によって長尺形状の成形品を製造すると、成形品の表面にひけが発生したり、成形品に反りが発生し、成形品の寸法精度が著しく損なわれることが知られている。また、１カ所にゲート部が設けられた金型を使用して長尺形状の成形品を成形する場合、ゲート部から離れたキャビティの部分（樹脂充填末端）内の溶融樹脂に保圧圧力が加わり難く、成形品の寸法精度が損なわれる。
一方、２カ所以上にゲート部が設けられた金型を使用して長尺形状の成形品を成形する場合、成形品にウエルドが発生し易い。ウエルドが発生した成形品の部分は、外観不良、強度低下、寸法精度の低下などを引き起こす。特に、板状や繊維状等の強化材や充填材を配合した樹脂組成物を用いる場合、キャビティ内に射出された溶融樹脂組成物内における強化材や充填材の配向方向は一様ではなく、成形品の形状（開口部の有無、肉厚の変化）、ゲート部の位置等によって複雑に変化する。その結果、成形品の寸法精度が著しく低下したり、成形品の強度ばらつきが生じ易い。このような問題を解決するために、金型温度や射出速度、保圧圧力等の種々の成形条件を変更する方法が種々試みられているが、その効果は小さい。
【０００３】
このような従来の射出成形の課題を解決するための一方法として、特開昭６１−１７９１５号公報には、モールドキャビティに供給された溶融樹脂組成物の少なくとも一部に剪断力を加えつつ、溶融樹脂組成物を固化させることから成る射出成形方法（ＳＣＯＲＩＭ法）、並びに、剪断力を加える成形装置が開示されている。この成形方法によれば、射出用シリンダーから射出された溶融樹脂組成物でモールドキャビティ内を充填する。その後、剪断力を加える装置である２つのピストンにてモールドキャビティ内の溶融樹脂組成物に交互に剪断力を加えながら、樹脂組成物を固化させる。このように、モールドキャビティ内の溶融樹脂組成物に剪断力を加えることによって、固化しかけた熱可塑性樹脂が再溶融する結果、モールドキャビティ内に射出された溶融樹脂組成物内における強化材や充填材の配向方向を一様とすることができるし、ウエルドの発生を抑制することができる。
【０００４】
【発明が解決しようとする課題】
特開昭６１−１７９１５号公報に開示された射出成形方法（ＳＣＯＲＩＭ法）は、上述の従来の射出成形方法の問題点を解決するための有効な方法である。しかしながら、一方のピストンにてモールドキャビティ内の溶融樹脂組成物に圧力を加えるとき、他方のピストンによってはモールドキャビティ内の溶融樹脂組成物に圧力を加えていないので、得られた成形品の外観や寸法精度が不十分である場合が生じたり、ひけの発生を確実に防止することが困難である虞がある。また、剪断力を保持しながらモールドキャビティ内の樹脂組成物を固化させるので、成形品に応力が残り易いといった問題がある。
【０００５】
従って、本発明の目的は、従来のＳＣＯＲＩＭ法における上記の問題点を解消し、優れた外観、優れた寸法精度を有し、ひけが無く、残留応力の残り難い成形品を成形し得る射出成形方法、及び、係る射出成形方法の実施に適した金型組立体を提供することにある。
【０００６】
【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第１の態様に係る成形品の射出成形方法は、
（Ａ）射出用シリンダーに連通した第１樹脂流路及び第２樹脂流路、
（Ｂ）キャビティ、
（Ｃ）第１樹脂流路に連通し、キャビティに開口した第１ゲート部、
（Ｄ）第２樹脂流路に連通し、キャビティに開口した第２ゲート部、
（Ｅ）第１樹脂流路内の溶融熱可塑性樹脂に圧力を加えるための第１加圧手段、及び、
（Ｆ）第２樹脂流路内の溶融熱可塑性樹脂に圧力を加えるための第２加圧手段、
を備えた金型組立体を使用した成形品の射出成形方法であって、
（ａ）射出用シリンダーにて可塑化、溶融された熱可塑性樹脂を、第１樹脂流路及び第１ゲート部を介してキャビティ内に射出した後、
（ｂ）第１樹脂流路内の溶融熱可塑性樹脂に第１加圧手段により圧力Ｐ_１を加え、第２樹脂流路内の溶融熱可塑性樹脂に第２加圧手段により圧力Ｐ_２（但し、Ｐ_１＞Ｐ_２＞０）を加えることで、キャビティ内の溶融熱可塑性樹脂に対して第１ゲート部から第２ゲート部に向かう方向に剪断力を与えて、キャビティ内の溶融熱可塑性樹脂を第１ゲート部から第２ゲート部に向かう方向に流動させ、次いで、第１樹脂流路内の溶融熱可塑性樹脂に第１加圧手段により圧力Ｐ_１’を加え、第２樹脂流路内の溶融熱可塑性樹脂に第２加圧手段により圧力Ｐ_２’（但し、Ｐ_２’＞Ｐ_１’＞０）を加えることで、キャビティ内の溶融熱可塑性樹脂に対して第２ゲート部から第１ゲート部に向かう方向に剪断力を与えて、キャビティ内の溶融熱可塑性樹脂を第２ゲート部から第１ゲート部に向かう方向に流動させる操作を繰り返す、
工程から成ることを特徴とする。
【０００７】
本発明の第１の態様に係る成形品の射出成形方法においては、第２ゲート部には開閉手段が設けられており、前記工程（ａ）において第２ゲート部は開閉手段によって閉じられており、前記工程（ｂ）において第２ゲート部は開閉手段によって開かれている構成とすることができる。このような構成とすることで、工程（ａ）において溶融熱可塑性樹脂を第１樹脂流路及び第１ゲート部を介してキャビティ内に射出したとき、溶融熱可塑性樹脂が第２ゲート部や第２樹脂流路内に侵入することを確実に防止することができる。尚、このような構成を採用する場合、第１樹脂流路及び第２樹脂流路を、例えばホットランナーから構成することが好ましい。
【０００８】
上記の目的を達成するための本発明の第２の態様に係る成形品の射出成形方法は、
（Ａ）射出用シリンダーに連通した樹脂流路、
（Ｂ）キャビティ、
（Ｃ）樹脂流路に連通し、キャビティに開口したゲート部、
（Ｄ）キャビティに連通した樹脂溜り、
（Ｅ）樹脂流路内の溶融熱可塑性樹脂に圧力を加えるための第１加圧手段、及び、
（Ｆ）樹脂溜り内の溶融熱可塑性樹脂に圧力を加えるための第２加圧手段、
を備えた金型組立体を使用した成形品の射出成形方法であって、
（ａ）射出用シリンダーにて可塑化、溶融された熱可塑性樹脂を、樹脂流路及びゲート部を介してキャビティ内に射出した後、
（ｂ）樹脂流路内の溶融熱可塑性樹脂に第１加圧手段により圧力Ｐ_１を加え、樹脂溜り内の溶融熱可塑性樹脂に第２加圧手段により圧力Ｐ_２（但し、Ｐ_１＞Ｐ_２＞０）を加えることで、キャビティ内の溶融熱可塑性樹脂に対してゲート部から樹脂溜りに向かう方向に剪断力を与えて、キャビティ内の溶融熱可塑性樹脂をゲート部から樹脂溜りに向かう方向に流動させ、次いで、樹脂流路内の溶融熱可塑性樹脂に第１加圧手段により圧力Ｐ_１’を加え、樹脂溜り内の溶融熱可塑性樹脂に第２加圧手段により圧力Ｐ_２’（但し、Ｐ_２’＞Ｐ_１’＞０）を加えることで、キャビティ内の溶融熱可塑性樹脂に対して樹脂溜りからゲート部に向かう方向に剪断力を与えて、キャビティ内の溶融熱可塑性樹脂を樹脂溜りからゲート部に向かう方向に流動させる操作を繰り返す、
工程から成ることを特徴とする。
【０００９】
上記の目的を達成するための本発明の第３の態様に係る成形品の射出成形方法は、
（Ａ）射出用シリンダーに連通した樹脂流路、
（Ｂ）キャビティ、
（Ｃ）樹脂流路に連通し、キャビティに開口したゲート部、
（Ｄ）キャビティに連通した第１樹脂溜り、
（Ｅ）キャビティに連通した第２樹脂溜り、
（Ｆ）第１樹脂溜り内の溶融熱可塑性樹脂に圧力を加えるための第１加圧手段、及び、
（Ｇ）第２樹脂溜り内の溶融熱可塑性樹脂に圧力を加えるための第２加圧手段、
を備えた金型組立体を使用した成形品の射出成形方法であって、
（ａ）射出用シリンダーにて可塑化、溶融された熱可塑性樹脂を、樹脂流路及びゲート部を介してキャビティ内に射出した後、
（ｂ）第１樹脂溜り内の溶融熱可塑性樹脂に第１加圧手段により圧力Ｐ_１を加え、第２樹脂溜り内の溶融熱可塑性樹脂に第２加圧手段により圧力Ｐ_２（但し、Ｐ_１＞Ｐ_２＞０）を加えることで、キャビティ内の溶融熱可塑性樹脂に対して第１樹脂溜りから第２樹脂溜りに向かう方向に剪断力を与えて、キャビティ内の溶融熱可塑性樹脂を第１樹脂溜りから第２樹脂溜りに向かう方向に流動させ、次いで、第１樹脂溜り内の溶融熱可塑性樹脂に第１加圧手段により圧力Ｐ_１’を加え、第２樹脂溜り内の溶融熱可塑性樹脂に第２加圧手段により圧力Ｐ_２’（但し、Ｐ_２’＞Ｐ_１’＞０）を加えることで、キャビティ内の溶融熱可塑性樹脂に対して第２樹脂溜りから第１樹脂溜りに向かう方向に剪断力を与えて、キャビティ内の溶融熱可塑性樹脂を第２樹脂溜りから第１樹脂溜りに向かう方向に流動させる操作を繰り返す、
工程から成ることを特徴とする。
【００１０】
上記の好ましい形態を含む本発明の第１の態様〜第３の態様に係る成形品の射出成形方法（以下、これらを総称して、単に、本発明の射出成形方法と呼ぶ場合がある）にあっては、工程（ｂ）において、最初に、Ｐ_１＞Ｐ_２＞０とするか、Ｐ_２’＞Ｐ_１’＞０とするかは、本質的に任意であり、どちらを採用してもよく、両者共に本願発明に包含される。
【００１１】
本発明においては、Ｐ_１，Ｐ_２’，Ｐ_２，Ｐ_１’は成形条件により任意に設定することができるが、Ｐ_１＝Ｐ_２’、Ｐ_２＝Ｐ_１’を満足することが好ましい。そして、このような形態を含む本発明の射出成形方法にあっては、Ｐ_２／Ｐ_１の値は、１／１０乃至９／１０、好ましくは１／１０乃至５／１０であり、Ｐ_１’／Ｐ_２’の値は、１／１０乃至９／１０、好ましくは１／１０乃至５／１０であることが望ましい。また、（Ｐ_１−Ｐ_２）若しくは（Ｐ_２’−Ｐ_１’）の値として、例えば、１××１０^６Ｐａ乃至１．５×１０^８Ｐａ、好ましくは５×１０^６Ｐａ乃至８×１０^７Ｐａを例示することができる。更には、Ｐ_１，Ｐ_２’の値として、それぞれ、例えば、２×１０^６Ｐａ乃至１．６×１０^８Ｐａ、好ましくは３×１０^７Ｐａ乃至１×１０^８Ｐａを例示することができ、Ｐ_２，Ｐ_１’の値として、それぞれ、例えば、１×１０^６Ｐａ乃至１．５×１０^８Ｐａ、好ましくは２×１０^７Ｐａ乃至９×１０^７Ｐａを例示することができる。
【００１２】
上記の各種の好ましい形態を含む本発明の射出成形方法においては、工程（ｂ）の完了後、第１加圧手段及び第２加圧手段によってキャビティ内の溶融熱可塑性樹脂に圧力Ｐ_０を加えることが好ましい。即ち、第１加圧手段及び第２加圧手段によって保圧工程を実行することが好ましい。これによって、キャビティ内の溶融熱可塑性樹脂の冷却に伴う体積減少を補償することができる。
【００１３】
上記の目的を達成するための本発明の第１の態様に係る金型組立体は、
（Ａ）射出用シリンダーに連通した第１樹脂流路及び第２樹脂流路、
（Ｂ）キャビティ、
（Ｃ）第１樹脂流路に連通し、キャビティに開口した第１ゲート部、
（Ｄ）第２樹脂流路に連通し、キャビティに開口した第２ゲート部、
（Ｅ）第１樹脂流路内の溶融熱可塑性樹脂に圧力を加えるための第１加圧手段、及び、
（Ｆ）第２樹脂流路内の溶融熱可塑性樹脂に圧力を加えるための第２加圧手段、
を備えた金型組立体であって、
第２ゲート部には開閉手段が設けられていることを特徴とする。
【００１４】
上記の目的を達成するための本発明の第２の態様に係る金型組立体は、
（Ａ）射出用シリンダーに連通した樹脂流路、
（Ｂ）キャビティ、
（Ｃ）樹脂流路に連通し、キャビティに開口したゲート部、
（Ｄ）キャビティに連通した樹脂溜り、
（Ｅ）樹脂流路内の溶融熱可塑性樹脂に圧力を加えるための第１加圧手段、及び、
（Ｆ）樹脂溜り内の溶融熱可塑性樹脂に圧力を加えるための第２加圧手段、
を備えたことを特徴とする。
【００１５】
上記の目的を達成するための本発明の第３の態様に係る金型組立体は、
（Ａ）射出用シリンダーに連通した樹脂流路、
（Ｂ）キャビティ、
（Ｃ）樹脂流路に連通し、キャビティに開口したゲート部、
（Ｄ）キャビティに連通した第１樹脂溜り、
（Ｅ）キャビティに連通した第２樹脂溜り、
（Ｆ）第１樹脂溜り内の溶融熱可塑性樹脂に圧力を加えるための第１加圧手段、及び、
（Ｇ）第２樹脂溜り内の溶融熱可塑性樹脂に圧力を加えるための第２加圧手段、
を備えたことを特徴とする。
【００１６】
本発明の第１の態様に係る射出成形方法あるいは金型組立体にあっては、開閉手段として、バルブゲート式ホットランナーを例示することができる。ここで、バルブゲートは、シャットオフピンとシリンダーピストンから構成され、例えば、油圧シリンダーとシリンダーピストンの作動によってシャットオフピンがゲート部を開閉する構造を有する。
【００１７】
本発明の第１の態様に係る射出成形方法あるいは金型組立体にあっては、射出用シリンダーを１つとし、第１樹脂流路及び第２樹脂流路をこの１つの射出用シリンダーに連通させることが、構成の簡素化といった観点から望ましいが、このような構成に限定するものではなく、射出用シリンダーを２つとし、第１樹脂流路を一方の射出用シリンダーに連通させ、第２樹脂流路を他方の射出用シリンダーに連通させてもよく、この場合、これらの２つの射出用シリンダーから溶融熱可塑性樹脂をキャビティ内に射出すればよい。
【００１８】
第１の態様に係る射出成形方法あるいは金型組立体における第１樹脂流路及び第２樹脂流路、あるいは又、本発明の第２の態様若しくは第３の態様に係る射出成形方法あるいは金型組立体における樹脂流路は、例えば、スプルーとコールドランナーの組合せ、あるいは又、ホットランナーから構成することができる。尚、これらの樹脂流路をホットランナーから構成する場合、第１の態様に係る射出成形方法あるいは金型組立体における第１ゲート部、第２の態様に係る射出成形方法あるいは金型組立体におけるゲート部及びキャビティに開口した樹脂溜りの開口部、第３の態様に係る射出成形方法あるいは金型組立体におけるキャビティに開口した第１樹脂溜りの開口部及びキャビティに開口した第２樹脂溜りの開口部を、例えば、バルブゲートで開閉自在とすることが好ましい。
【００１９】
本発明の第１の態様〜第３の態様に係る射出成形方法あるいは金型組立体においては、第１ゲート部や第２ゲート部、ゲート部の構造は、本質的に任意であり、成形すべき成形品の形状等に基づき決定すればよく、例えば、オープンタイプ構造、ダイレクト構造、サイドゲート構造、オーバーラップゲート構造、トンネルゲート構造、ピンポイントゲート構造を例示することができる。
【００２０】
本発明の第１の態様〜第３の態様に係る射出成形方法あるいは金型組立体においては、第１加圧手段及び第２加圧手段として、油圧シリンダーとピストンの組合せを例示することができる。そして、この場合、第１樹脂流路内や第２樹脂流路内、樹脂流路内、樹脂溜り内、第１樹脂溜り内、あるいは、第２樹脂溜り内に、ピストンを配置すればよい。
【００２１】
本発明の射出成形方法においては、工程（ｂ）を数回、具体的には、例えば３回乃至５回、繰り返すことが好ましい。繰り返しの周期は、１秒乃至６０秒に１回（１Ｈｚ乃至１／６０Ｈｚ）以上、好ましくは、１Ｈｚ乃至１／５Ｈｚとすることが望ましい。工程（ｂ）を繰り返すとき、Ｐ_１，Ｐ_２，Ｐ_１’，Ｐ_２’の値を一定としてもよいし、変化させてもよい。
【００２２】
また、本発明の射出成形方法にあっては、成形品の容積をＶとしたとき、上記工程（ｂ）において、０．０５Ｖ乃至０．５Ｖの量、好ましくは０．１Ｖ乃至０．４Ｖの量だけ、キャビティ内で、成形品の長手方向に相当する方向に沿って溶融熱可塑性樹脂を流動させることが望ましい。
【００２３】
本発明の第１の態様〜第３の態様に係る射出成形方法あるいは金型組立体によって成形される成形品は、如何なる形状とすることもできるが、例えば、長さＬと幅Ｗの割合Ｌ／Ｗが２以上である成形品を成形することが好ましい。
【００２４】
このようなＬ／Ｗが２以上である成形品を成形する場合、本発明の第１の態様に係る射出成形方法あるいは金型組立体においては、成形品の長手方向の一方の端部を形成すべきキャビティの部分あるいはその近傍に第１ゲート部を配置し、成形品の長手方向の他方の端部を形成すべきキャビティの部分あるいはその近傍に第２ゲート部を配置することが好ましい。具体的には、成形品の長手方向の一方の端部を形成すべきキャビティの部分から第１ゲート部までの距離を、０乃至０．１Ｌとすることが好ましく、成形品の長手方向の他方の端部を形成すべきキャビティの部分から第２ゲート部までの距離を、０乃至０．１Ｌとすることが好ましい。
【００２５】
あるいは又、このようなＬ／Ｗが２以上である成形品を成形する場合、本発明の第２の態様に係る射出成形方法あるいは金型組立体においては、成形品の長手方向の一方の端部を形成すべきキャビティの部分あるいはその近傍にゲート部を配置し、成形品の長手方向の他方の端部を形成すべきキャビティの部分あるいはその近傍に樹脂溜りを開口させることが好ましい。具体的には、成形品の長手方向の一方の端部を形成すべきキャビティの部分からゲート部までの距離を、０乃至０．１Ｌとすることが好ましく、成形品の長手方向の他方の端部を形成すべきキャビティの部分から樹脂溜りの開口部までの距離を、０乃至０．１Ｌとすることが好ましい。尚、補助のゲート部を更に有していてもよい。この場合、補助のゲート部と連通する樹脂流路内の溶融熱可塑性樹脂に圧力を加えるための加圧手段を設ける必要は無い。
【００２６】
あるいは又、このようなＬ／Ｗが２以上である成形品を成形する場合、本発明の第３の態様に係る射出成形方法あるいは金型組立体においては、成形品の長手方向の一方の端部を形成すべきキャビティの部分あるいはその近傍に第１樹脂溜りを開口させ、成形品の長手方向の他方の端部を形成すべきキャビティの部分あるいはその近傍に第２樹脂溜りを開口させることが好ましい。具体的には、成形品の長手方向の一方の端部を形成すべきキャビティの部分から第１樹脂溜りの開口部までの距離を、０乃至０．１Ｌとすることが好ましく、成形品の長手方向の他方の端部を形成すべきキャビティの部分から第２樹脂溜りの開口部までの距離を、０乃至０．１Ｌとすることが好ましい。尚、ゲート部を配置する位置は本質的には任意である。更には、ゲート部の数も本質的には任意であり、１あるいは２以上とすることができる。
【００２７】
本発明の射出成形方法での使用に適した樹脂として、結晶性熱可塑性樹脂や非晶性熱可塑性樹脂を挙げることができ、具体的には、ポリエチレン樹脂、ポリプロピレン樹脂等のポリオレフィン系樹脂；ポリアミド６、ポリアミド６６、ポリアミドＭＸＤ６等のポリアミド系樹脂；ポリオキシメチレン（ポリアセタール，ＰＯＭ）樹脂；ポリエチレンテレフタレート（ＰＥＴ）樹脂、ポリブチレンテレフタレート（ＰＢＴ）樹脂等のポリエステル系樹脂；ポリフェニレンサルファイド樹脂；ポリスチレン樹脂、ＡＢＳ樹脂、ＡＥＳ樹脂、ＡＳ樹脂といったスチレン系樹脂；メタクリル系樹脂；ポリカーボネート樹脂；変性ＰＰＥ樹脂；ポリスルホン樹脂；ポリエーテルスルホン樹脂；ポリアリレート樹脂；ポリエーテルイミド樹脂；ポリアミドイミド樹脂；ポリイミド系樹脂；ポリエーテルケトン樹脂；ポリエーテルエーテルケトン樹脂；ポリエステルカーボネート樹脂；液晶ポリマーを例示することができる。
【００２８】
更には、ポリマーアロイ材料から成る熱可塑性樹脂を用いることができる。ここで、ポリマーアロイ材料は、少なくとも２種類の熱可塑性樹脂をブレンドしたもの、又は、少なくとも２種類の熱可塑性樹脂を化学的に結合させたブロック共重合体若しくはグラフト共重合体から成る。ポリマーアロイ材料は、単独の熱可塑性樹脂のそれぞれが有する特有な性能を合わせ持つことができる高機能材料として広く使用されている。少なくとも２種類の熱可塑性樹脂をブレンドしたポリマーアロイ材料を構成する熱可塑性樹脂として、ポリスチレン樹脂、ＡＢＳ樹脂、ＡＥＳ樹脂、ＡＳ樹脂といったスチレン系樹脂；ポリエチレン樹脂、ポリプロピレン樹脂等のポリオレフィン系樹脂；メタクリル樹脂；ポリカーボネート樹脂；ポリアミド６、ポリアミド６６、ポリアミドＭＸＤ６等のポリアミド系樹脂；変性ＰＰＥ樹脂；ポリブチレンテレフタレート樹脂やポリエチレンテレフタレート樹脂等のポリエステル樹脂；ポリオキシメチレン樹脂；ポリスルホン樹脂；ポリイミド樹脂；ポリフェニレンサルファイド樹脂；ポリアリレート樹脂；ポリエーテルスルホン樹脂；ポリエーテルケトン樹脂；ポリエーテルエーテルケトン樹脂；ポリエステルカーボネート樹脂を挙げることができる。２種類の熱可塑性樹脂をブレンドしたポリマーアロイ材料として、ポリカーボネート樹脂とＡＢＳ樹脂とのポリマーアロイ材料を例示することができる。尚、このような樹脂の組合せを、ポリカーボネート樹脂／ＡＢＳ樹脂と表記する。以下においても同様である。更に、少なくとも２種類の熱可塑性樹脂をブレンドしたポリマーアロイ材料として、ポリカーボネート樹脂／ＰＥＴ樹脂、ポリカーボネート樹脂／ＰＢＴ樹脂、ポリカーボネート樹脂／ポリアミド系樹脂、ポリカーボネート樹脂／ＰＢＴ樹脂／ＰＥＴ樹脂、変性ＰＰＥ樹脂／ＨＩＰＳ樹脂、変性ＰＰＥ樹脂／ポリアミド系樹脂、変性ＰＰＥ樹脂／ＰＢＴ樹脂／ＰＥＴ樹脂、変性ＰＰＥ樹脂／ポリアミドＭＸＤ６樹脂、ポリオキシメチレン樹脂／ポリウレタン樹脂、ＰＢＴ樹脂／ＰＥＴ樹脂を例示することができる。
【００２９】
尚、以上に説明した各種の熱可塑性樹脂に、安定剤、紫外線吸収剤、離型剤、染顔料等を添加することができるし、ガラスビーズ、マイカ、カオリン、炭酸カルシウム等の無機充填材、あるいは有機充填材を添加することもできる。
【００３０】
更には、以上に説明した各種の熱可塑性樹脂に無機繊維を添加したものを使用することもできる。ここで、無機繊維として、ガラス繊維、カーボン繊維、ウォラストナイト、ホウ酸アルミニウムウィスカー繊維、チタン酸カリウムウィスカー繊維、塩基性硫酸マグネシウムウィスカー繊維、珪酸カルシウムウィスカー繊維及び硫酸カルシウムウィスカー繊維から成る群から選択された少なくとも１種の材料を挙げることができる。
【００３１】
熱可塑性樹脂中の無機繊維の重量％として、５重量％乃至５０重量％を例示することができる。成形品の強度を重視する場合には、無機繊維の平均長さを、５μｍ乃至５ｍｍ、好ましくは１０μｍ乃至０．４ｍｍとし、成形品の写像性（鏡面性）を重視する場合には、５μｍ乃至０．４ｍｍ、より好ましくは５μｍ乃至０．２ｍｍ、一層好ましくは５μｍ乃至０．１ｍｍとすることが望ましい。また、これらの場合、無機繊維の平均直径を、０．０１μｍ乃至１５μｍ、より好ましくは０．０２μｍ乃至１０μｍ以下、一層好ましくは０．０５μｍ乃至５μｍ以下とすることが望ましい。
【００３２】
尚、無機繊維の平均長さは、重量平均長さを意味する。無機繊維の長さの測定は、熱可塑性樹脂を溶解する液体に無機繊維を含有する成形用ペレット若しくは成形品を浸漬して樹脂成分を溶解するか、ガラス繊維の場合、６００゜Ｃ以上の高温で樹脂成分を燃焼させて、残留する無機繊維を顕微鏡等で観察して測定することができる。通常、無機繊維を写真撮影して人が測長するか、専用の繊維長測定装置を使用して無機繊維の長さを求める。数平均長さでは微小に破壊された繊維の影響が大き過ぎるので、重量平均長さを採用することが好ましい。重量平均長さの測定に際しては、あまりに小さく破砕された無機繊維の破片を除いて測定する。無機繊維の公称直径の２倍よりも長さが短くなると測定が難しくなるので、例えば公称直径の２倍以上の長さを有する無機繊維を測定の対象とする。
【００３３】
本発明の第１の態様〜第３の態様に係る射出成形方法にあっては、Ｐ_１＞Ｐ_２＞０、及び、Ｐ_２’＞Ｐ_１’＞０の条件で、キャビティ内において溶融熱可塑性樹脂を流動させるが故に、キャビティ内の溶融熱可塑性樹脂には常に第１加圧手段及び第２加圧手段から対向する圧力が加わった状態となる結果、優れた外観、優れた寸法精度を有し、ひけが無く、残留応力の小さい成形品を成形することが可能となる。
【００３４】
【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。
【００３５】
（実施例１）
実施例１は、本発明の第１の態様に係る成形品の射出成形方法に関する。
【００３６】
実施例１の金型組立体の概念図を図１に示す。実施例１の金型組立体１０は、（Ａ）射出用シリンダー１１に連通した第１樹脂流路１４Ａ及び第２樹脂流路１４Ｂ、
（Ｂ）キャビティ１８、
（Ｃ）第１樹脂流路１４Ａに連通し、キャビティ１８に開口した第１ゲート部１５Ａ、
（Ｄ）第２樹脂流路１４Ｂに連通し、キャビティ１８に開口した第２ゲート部１５Ｂ、
（Ｅ）第１樹脂流路１４Ａ内の溶融熱可塑性樹脂に圧力を加えるための第１加圧手段、及び、
（Ｆ）第２樹脂流路１４Ｂ内の溶融熱可塑性樹脂に圧力を加えるための第２加圧手段、
を備えている。
【００３７】
より具体的には、金型組立体１０は、固定金型部１２及び可動金型部１３を有し、固定金型部１２と可動金型部１３を型締めすることによってキャビティ１８が形成される。第１樹脂流路１４Ａ及び第２樹脂流路１４Ｂは、固定金型部１２内に設けられ、所謂ホットランナーから構成されている。また、第１加圧手段は、油圧シリンダー２１Ａと、油圧シリンダー２１Ａに取り付けられ、油圧シリンダー２１Ａの作動に基づき第１樹脂流路１４Ａ内で前後に移動（摺動）させられるピストン２０Ａから構成されている。一方、第２加圧手段は、油圧シリンダー２１Ｂと、油圧シリンダー２１Ｂに取り付けられ、油圧シリンダー２１Ｂの作動に基づき第２樹脂流路１４Ｂ内で前後に移動（摺動）させられるピストン２０Ｂから構成されている。第１ゲート部１５Ａ及び第２ゲート部１５Ｂはオープンタイプ構造を有する。そして、成形品の長手方向の長さをＬとしたとき、成形品の長手方向の一方の端部を形成すべきキャビティ１８の部分１８Ａから第１ゲート部１５Ａまでの距離は０．０５Ｌであり、成形品の長手方向の他方の端部を形成すべきキャビティ１８の部分１８Ｂから第２ゲート部１５Ｂまでの距離は０．０５Ｌである。
【００３８】
以下、金型組立体等の概念図である図２〜図４を参照して実施例１の射出成形方法を説明するが、実施例１においては、熱可塑性樹脂として、ガラス繊維を２０重量％添加したポリカーボネート樹脂（三菱エンジニアリングプラスチックス株式会社製、ノバレックス７０２５ＧＲ２０）を使用し、長さ（Ｌ）３００ｍｍ、幅（Ｗ）１５ｍｍ、厚さ３ｍｍの成形品（容積Ｖ＝１３．５ｃｍ^３）を成形した。尚、図２〜図４においては、射出用シリンダー１１の図示を省略した。
【００３９】
［工程−１００］
まず、射出用シリンダー１１にて可塑化、溶融された熱可塑性樹脂３０を、第１樹脂流路１４Ａ及び第１ゲート部１５Ａを介してキャビティ１８内に射出し、キャビティ１８内を溶融熱可塑性樹脂３０で完全に充填し、更に、溶融熱可塑性樹脂３０で第２ゲート部１５Ｂ及び第２樹脂流路１４Ｂを充填した（図２参照）。射出条件を、以下の表１に例示する。尚、溶融熱可塑性樹脂３０の射出時、第１加圧手段を構成するピストン２０Ａを後進端に位置させ、第２加圧手段を構成するピストン２０Ｂを前進端に位置させる。溶融熱可塑性樹脂３０の射出によってこれらのピストン２０Ａ，２０Ｂの位置が変化しないように、油圧シリンダー２１Ａ，２１Ｂを制御する。
【００４０】
［表１］
樹脂温度：３００゜Ｃ
金型温度：８０゜Ｃ
射出圧力：１．５×１０^８Ｐａ
射出時間：３．５秒
【００４１】
［工程−１１０］
キャビティ１８への溶融熱可塑性樹脂３０の射出完了と同時に、油圧シリンダー２１Ａ，２１Ｂを作動させて、ピストン２０Ａを前進端へと移動させ、このピストン２０Ａの動きと同期して、ピストン２０Ｂを後進端へと移動させた。このとき、第１樹脂流路１４Ａ内の溶融熱可塑性樹脂３０に第１加圧手段（具体的には、ピストン２０Ａ）により圧力Ｐ_１（＝９×１０^７Ｐａ）を加え、第２樹脂流路１４Ｂ内の溶融熱可塑性樹脂３０に第２加圧手段（具体的には、ピストン２０Ｂ）により圧力Ｐ_２（＝２×１０^７Ｐａ）を加えることで、キャビティ１８内の溶融熱可塑性樹脂３０に対して第１ゲート部１５Ａから第２ゲート部１５Ｂに向かう方向に剪断力を与えて、キャビティ１８内の溶融熱可塑性樹脂３０を第１ゲート部１５Ａから第２ゲート部１５Ｂに向かう方向に流動させた。この状態を図３に示す。ピストン２０Ａ，２０Ｂの移動時間を１．５秒とした。キャビティ１８内の溶融熱可塑性樹脂３０を、約５ｃｍ^３、第１ゲート部１５Ａから第２ゲート部１５Ｂに向かう方向に移動させた。
【００４２】
［工程−１２０］
ピストン２０Ａが前進端に達し、ピストン２０Ｂが後進端に達したならば（図３参照）、直ちに、第１樹脂流路１４Ａ内の溶融熱可塑性樹脂３０に第１加圧手段（具体的には、ピストン２０Ａ）により圧力Ｐ_１’（＝２×１０^７Ｐａ）を加え、第２樹脂流路１４Ｂ内の溶融熱可塑性樹脂３０に第２加圧手段（具体的には、ピストン２０Ｂ）により圧力Ｐ_２’（＝９×１０^７Ｐａ）を加えることで、キャビティ１８内の溶融熱可塑性樹脂３０に対して第２ゲート部１５Ｂから第１ゲート部１５Ａに向かう方向に剪断力を与えて、キャビティ１８内の溶融熱可塑性樹脂３０を第２ゲート部１５Ｂから第１ゲート部１５Ａに向かう方向に流動させた。
この状態を図４に示す。ピストン２０Ａ，２０Ｂの移動時間を１．５秒とした。
キャビティ１８内の溶融熱可塑性樹脂３０を、約５ｃｍ^３、第２ゲート部１５Ｂから第１ゲート部１５Ａに向かう方向に移動させた。
【００４３】
［工程−１３０］
ピストン２０Ａが後進端に達し、ピストン２０Ｂが前進端に達したならば（図４参照）、直ちに、［工程−１１０］、［工程−１２０］を順次繰り返す。こうして、［工程−１１０］、［工程−１２０］を１回の操作としたとき、５回の操作を行った。５回の操作に要した時間は１５秒である。
【００４４】
［工程−１４０］
その後、第１加圧手段及び第２加圧手段（具体的には、ピストン２０Ａ，２０Ｂ）によってキャビティ１８内の溶融熱可塑性樹脂３０に圧力Ｐ_０（＝５×１０^７Ｐａ）を加えた。そして、キャビティ内の溶融熱可塑性樹脂３０の冷却、固化を行った。圧力Ｐ_０を加える時間を５秒間とし、次いで、第１加圧手段及び第２加圧手段によってキャビティ１８内の溶融熱可塑性樹脂３０に圧力を加える操作を中止した。その後、２０秒が経過した後、金型組立体を開き、成形品を取り出した。
【００４５】
成形品は、優れた外観、優れた寸法精度を有しており、ガラス繊維は成形品の長手方向に配向していた。また、ひけや反りは認められなかった。成形品の平面度を測定した結果を、表３に示す。尚、平面度は、ミツトヨ社製の三次元測定機Ｇｅｏｐａｋ７００を用い、成形品の表面の１４点にて測定した平均値である。
【００４６】
（比較例１Ａ）
比較例１Ａにおいては、実施例１の［工程−１００］を実行した後、直ちに、射出用シリンダー１１によってキャビティ１８内の溶融熱可塑性樹脂３０に保圧（５×１０^７Ｐａ）を２０秒間加えた。その後、２０秒が経過した後、金型組立体を開き、成形品を取り出した。
【００４７】
得られた成形品を観察したところ、ガラス繊維は成形品の長手方向に配向していたが、樹脂流動末端である、第２ゲート部１５Ｂの近傍におけるキャビティ１８内の溶融熱可塑性樹脂３０に十分な保圧圧力が加わらないが故に、第２ゲート部１５Ｂの近傍に対応する成形品の部分にひけ及び反りが発生していた。成形品の平面度を測定した結果を、表３に示す。
【００４８】
（比較例１Ｂ）
比較例１Ｂにおいては、実施例１の［工程−１００］を実行した後、更に、［工程−１１０］〜［工程−１４０］を実行した。但し、［工程−１１０］〜［工程−１３０］において、Ｐ_１＝９×１０^７Ｐａ、Ｐ_２＝０Ｐａ、Ｐ_２’＝９×１０^７Ｐａ、Ｐ_１’＝０Ｐａとした。
【００４９】
得られた成形品を観察したところ、ガラス繊維は成形品の長手方向に配向していたが、第１ゲート部１５Ａ及び第２ゲート部１５Ｂの近傍に対応する成形品の部分にひけ及び反りが発生していた。成形品の平面度を測定した結果を、表３に示す。
【００５０】
（実施例２）
実施例２は、本発明の第１の態様に係る射出成形方法及び本発明の第１の態様に係る金型組立体に関する。図５に概念図を示す実施例２の金型組立体１０Ａは、第２ゲート部１５Ｂに開閉手段が設けられている点が、実施例１の金型組立体１０と相違する。また、第１ゲート部１５Ａにも開閉手段が設けられている。その他の構造は、実施例１の金型組立体と同じである。ここで、開閉手段は、シャットオフピン１６Ａ，１６Ｂと油圧シリンダー１７Ａ，１７Ｂから構成され、油圧シリンダー１７Ａ，１７Ｂの作動によってシャットオフピン１６Ａ，１６Ｂが第１及び第２ゲート部１５Ａ，１５Ｂを開閉する形式のバルブゲートから構成されている。尚、図５においては、第１ゲート部１５Ａが開かれ、第２ゲート部１５Ｂが閉じられた状態を示す。第１樹脂流路１４Ａ及び第２樹脂流路１４Ｂは、ホットランナーから構成されているが、詳細な図示は省略した。
【００５１】
以下、金型組立体等の概念図である図６〜図９を参照して実施例２の射出成形方法を説明するが、実施例２においては、熱可塑性樹脂として、ガラス繊維を２０重量％添加した変性ＰＰＥ樹脂（三菱エンジニアリングプラスチックス株式会社製、ユピエースＧＨ２０）を使用し、長さ（Ｌ）２００ｍｍ、幅（Ｗ）１０ｍｍ、厚さ３ｍｍの成形品（容積Ｖ＝６ｃｍ^３）を成形した。尚、図６〜図９においては、射出用シリンダー１１の図示を省略した。また、図６〜図９において、前回の射出成形により第２樹脂流路１４Ｂ内に残された溶融熱可塑性樹脂を、参照番号３０Ａで示す。
【００５２】
［工程−２００］
まず、射出用シリンダー１１にて可塑化、溶融された熱可塑性樹脂３０を、第１樹脂流路１４Ａ及び第１ゲート部１５Ａを介してキャビティ１８内に射出し、キャビティ１８内を溶融熱可塑性樹脂３０で完全に充填した（図６参照）。射出条件を、以下の表２に例示する。尚、溶融熱可塑性樹脂３０の射出時、第１加圧手段を構成するピストン２０Ａを後進端に位置させ、第２加圧手段を構成するピストン２０Ｂを前進端に位置させる。溶融熱可塑性樹脂３０の射出によってピストン２０Ａの位置が変化しないように、油圧シリンダー２１Ａを制御する。また、第１ゲート部１５Ａは開かれ、第２ゲート部１５Ｂは閉じられた状態にある。
【００５３】
［表２］
樹脂温度：２８０゜Ｃ
金型温度：７０゜Ｃ
射出圧力：１．２×１０^８Ｐａ
射出時間：４．２秒
【００５４】
［工程−２１０］
キャビティ１８への溶融熱可塑性樹脂３０の射出完了と同時に、油圧シリンダー１７Ｂを作動させてシャットオフピン１６Ｂを後退させ、第２ゲート部１５Ｂを開いた（図７参照）。同時に、油圧シリンダー２１Ａ，２１Ｂを作動させて、ピストン２０Ａを前進端へと移動させ、このピストン２０Ａの動きと同期して、ピストン２０Ｂを後進端へと移動させた。このとき、第１樹脂流路１４Ａ内の溶融熱可塑性樹脂３０に第１加圧手段（具体的には、ピストン２０Ａ）により圧力Ｐ_１（＝９×１０^７Ｐａ）を加え、第２樹脂流路１４Ｂ内の溶融熱可塑性樹脂３０，３０Ａに第２加圧手段（具体的には、ピストン２０Ｂ）により圧力Ｐ_２（＝２×１０^７Ｐａ）を加えることで、キャビティ１８内の溶融熱可塑性樹脂３０に対して第１ゲート部１５Ａから第２ゲート部１５Ｂに向かう方向に剪断力を与えて、キャビティ１８内の溶融熱可塑性樹脂３０を第１ゲート部１５Ａから第２ゲート部１５Ｂに向かう方向に流動させた。この状態を図８に示す。ピストン２０Ａ，２０Ｂの移動時間を１．５秒とした。キャビティ１８内の溶融熱可塑性樹脂３０を、約３ｃｍ^３、第１ゲート部１５Ａから第２ゲート部１５Ｂに向かう方向に移動させた。
【００５５】
［工程−２２０］
ピストン２０Ａが前進端に達し、ピストン２０Ｂが後進端に達したならば（図８参照）、直ちに、第１樹脂流路１４Ａ内の溶融熱可塑性樹脂３０に第１加圧手段（具体的には、ピストン２０Ａ）により圧力Ｐ_１’（＝２×１０^７Ｐａ）を加え、第２樹脂流路１４Ｂ内の溶融熱可塑性樹脂３０，３０Ａに第２加圧手段（具体的には、ピストン２０Ｂ）により圧力Ｐ_２’（＝９×１０^７Ｐａ）を加えることで、キャビティ１８内の溶融熱可塑性樹脂３０に対して第２ゲート部１５Ｂから第１ゲート部１５Ａに向かう方向に剪断力を与えて、キャビティ１８内の溶融熱可塑性樹脂３０を第２ゲート部１５Ｂから第１ゲート部１５Ａに向かう方向に流動させた。この状態を図９に示す。ピストン２０Ａ，２０Ｂの移動時間を１．５秒とした。キャビティ１８内の溶融熱可塑性樹脂３０を、約３ｃｍ^３、第２ゲート部１５Ｂから第１ゲート部１５Ａに向かう方向に移動させた。
【００５６】
［工程−２３０］
ピストン２０Ａが後進端に達し、ピストン２０Ｂが前進端に達したならば（図９参照）、直ちに、［工程−２１０］、［工程−２２０］を順次繰り返す。こうして、［工程−２１０］、［工程−２２０］を１回の操作としたとき、５回の操作を行った。５回の操作に要した時間は１５秒である。
【００５７】
［工程−２４０］
その後、第１加圧手段及び第２加圧手段（具体的には、ピストン２０Ａ，２０Ｂ）によってキャビティ１８内の溶融熱可塑性樹脂３０に圧力Ｐ_０（＝４×１０^７Ｐａ）を加えた。そして、キャビティ内の溶融熱可塑性樹脂３０の冷却、固化を行った。圧力Ｐ_０を加える時間を１５秒間とし、次いで、第１加圧手段及び第２加圧手段によってキャビティ１８内の溶融熱可塑性樹脂３０に圧力を加える操作を中止した。その後、２０秒が経過した後、金型組立体を開き、成形品を取り出した。
【００５８】
成形品は、優れた外観、優れた寸法精度を有しており、ガラス繊維は成形品の長手方向に配向していた。また、ひけや反りは認められなかった。成形品の平面度を測定した結果を、表３に示す。
【００５９】
（比較例２Ａ）
比較例２Ａにおいては、実施例２の［工程−２００］を実行した後、射出用シリンダー１１によってキャビティ１８内の溶融熱可塑性樹脂３０に保圧（４×１０^７Ｐａ）を１５秒間加えた。その後、２０秒が経過した後、金型組立体を開き、成形品を取り出した。
【００６０】
得られた成形品を観察したところ、ガラス繊維は成形品の長手方向に配向していたが、樹脂流動末端である、第２ゲート部１５Ｂの近傍におけるキャビティ１８内の溶融熱可塑性樹脂３０に十分な保圧圧力が加わらないが故に、第２ゲート部１５Ｂの近傍に対応する成形品の部分にひけ及び反りが発生していた。成形品の平面度を測定した結果を、表３に示す。
【００６１】
（比較例２Ｂ）
比較例２Ｂにおいては、実施例２の［工程−２００］を実行した後、更に、［工程−２１０］〜［工程−２４０］を実行した。但し、［工程−２１０］〜［工程−２３０］において、Ｐ_１＝９×１０^７Ｐａ、Ｐ_２＝０Ｐａ、Ｐ_２’＝９×１０^７Ｐａ、Ｐ_１’＝０Ｐａとした。
【００６２】
得られた成形品を観察したところ、ガラス繊維は成形品の長手方向に配向していたが、第１ゲート部１５Ａ及び第２ゲート部１５Ｂの近傍に対応する成形品の部分にひけ及び反りが発生していた。成形品の平面度を測定した結果を、表３に示す。
【００６３】
（実施例３）
実施例３は、本発明の第２の態様に係る成形品の射出成形方法及び本発明の第２の態様に係る金型組立体に関する。
【００６４】
実施例３の金型組立体の概念図を図１０に示す。実施例３の金型組立体１０Ｂは、
（Ａ）射出用シリンダー１１に連通した樹脂流路１４、
（Ｂ）キャビティ１８、
（Ｃ）樹脂流路１４に連通し、キャビティ１８に開口したゲート部１５、
（Ｄ）キャビティ１８に連通した樹脂溜り４４、
（Ｅ）樹脂流路１４内の溶融熱可塑性樹脂に圧力を加えるための第１加圧手段、及び、
（Ｆ）樹脂溜り４４内の溶融熱可塑性樹脂に圧力を加えるための第２加圧手段、
を備えている。
【００６５】
より具体的には、金型組立体１０Ｂは、固定金型部１２及び可動金型部１３を有し、固定金型部１２と可動金型部１３を型締めすることによってキャビティ１８が形成される。樹脂流路１４及び樹脂溜り４４は、固定金型部１２内に設けられ、樹脂流路１４は、所謂ホットランナーから構成されている。また、第１加圧手段は、油圧シリンダー２１Ａと、油圧シリンダー２１Ａに取り付けられ、油圧シリンダー２１Ａの作動に基づき樹脂流路１４内で前後に移動（摺動）させられるピストン２０Ａから構成されている。一方、第２加圧手段は、油圧シリンダー２１Ｂと、油圧シリンダー２１Ｂに取り付けられ、油圧シリンダー２１Ｂの作動に基づき樹脂溜り４４内で前後に移動（摺動）させられるピストン２０Ｂから構成されている。ゲート部１５はダイレクト構造を有する。そして、成形品の長手方向の長さをＬとしたとき、成形品の長手方向の一方の端部を形成すべきキャビティ１８の部分１８Ａからゲート部１５までの距離は０．０５Ｌであり、成形品の長手方向の他方の端部を形成すべきキャビティ１８の部分１８Ｂから樹脂溜り４４の開口部までの距離は０．０５Ｌである。
【００６６】
以下、金型組立体等の概念図である図１１〜図１３を参照して実施例３の射出成形方法を説明するが、実施例３においては、実施例１と同じ熱可塑性樹脂を使用し、実施例１と同じ形状の成形品を成形した。尚、図１１〜図１３においては、射出用シリンダー１１の図示を省略した。
【００６７】
［工程−３００］
まず、射出用シリンダー１１にて可塑化、溶融された熱可塑性樹脂３０を、樹脂流路１４及びゲート部１５を介してキャビティ１８内に射出し、キャビティ１８内を溶融熱可塑性樹脂３０で完全に充填し、更に、溶融熱可塑性樹脂３０で樹脂溜り４４を充填した（図１１参照）。射出条件を、表１に示したと同様とした。尚、溶融熱可塑性樹脂３０の射出時、第１加圧手段を構成するピストン２０Ａを後進端に位置させ、第２加圧手段を構成するピストン２０Ｂを前進端に位置させる。溶融熱可塑性樹脂３０の射出によってこれらのピストン２０Ａ，２０Ｂの位置が変化しないように、油圧シリンダー２１Ａ，２１Ｂを制御する。
【００６８】
［工程−３１０］
キャビティ１８への溶融熱可塑性樹脂３０の射出完了と同時に、油圧シリンダー２１Ａ，２１Ｂを作動させて、ピストン２０Ａを前進端へと移動させ、このピストン２０Ａの動きと同期して、ピストン２０Ｂを後進端へと移動させた。このとき、樹脂流路１４内の溶融熱可塑性樹脂３０に第１加圧手段（具体的には、ピストン２０Ａ）により圧力Ｐ_１（＝９×１０^７Ｐａ）を加え、樹脂溜り４４内の溶融熱可塑性樹脂３０に第２加圧手段（具体的には、ピストン２０Ｂ）により圧力Ｐ_２（＝２×１０^７Ｐａ）を加えることで、キャビティ１８内の溶融熱可塑性樹脂３０に対してゲート部１５から樹脂溜り４４に向かう方向に剪断力を与えて、キャビティ１８内の溶融熱可塑性樹脂３０をゲート部１５から樹脂溜り４４に向かう方向に流動させた。この状態を図１２に示す。ピストン２０Ａ，２０Ｂの移動時間を１．５秒とした。キャビティ１８内の溶融熱可塑性樹脂３０を、約５ｃｍ^３、ゲート部１５から樹脂溜り４４に向かう方向に移動させた。
【００６９】
［工程−３２０］
ピストン２０Ａが前進端に達し、ピストン２０Ｂが後進端に達したならば（図１２参照）、直ちに、樹脂流路１４内の溶融熱可塑性樹脂３０に第１加圧手段（具体的には、ピストン２０Ａ）により圧力Ｐ_１’（＝２×１０^７Ｐａ）を加え、樹脂溜り４４内の溶融熱可塑性樹脂３０に第２加圧手段（具体的には、ピストン２０Ｂ）により圧力Ｐ_２’（＝９×１０^７Ｐａ）を加えることで、キャビティ１８内の溶融熱可塑性樹脂３０に対して樹脂溜り４４からゲート部１５に向かう方向に剪断力を与えて、キャビティ１８内の溶融熱可塑性樹脂３０を樹脂溜り４４からゲート部１５に向かう方向に流動させた。この状態を図１３に示す。ピストン２０Ａ，２０Ｂの移動時間を１．５秒とした。キャビティ１８内の溶融熱可塑性樹脂３０を、約５ｃｍ^３、樹脂溜り４４からゲート部１５に向かう方向に移動させた。
【００７０】
［工程−３３０］
ピストン２０Ａが後進端に達し、ピストン２０Ｂが前進端に達したならば（図１３参照）、直ちに、［工程−３１０］、［工程−３２０］を順次繰り返す。こうして、［工程−３１０］、［工程−３２０］を１回の操作としたとき、５回の操作を行った。５回の操作に要した時間は１５秒である。
【００７１】
［工程−３４０］
その後、第１加圧手段及び第２加圧手段（具体的には、ピストン２０Ａ，２０Ｂ）によってキャビティ１８内の溶融熱可塑性樹脂３０に圧力Ｐ_０（＝５×１０^７Ｐａ）を加えた。そして、キャビティ内の溶融熱可塑性樹脂３０の冷却、固化を行った。圧力Ｐ_０を加える時間を５秒間とし、次いで、第１加圧手段及び第２加圧手段によってキャビティ１８内の溶融熱可塑性樹脂３０に圧力を加える操作を中止した。その後、２０秒が経過した後、金型組立体を開き、成形品を取り出した。
【００７２】
成形品は、優れた外観、優れた寸法精度を有しており、ガラス繊維は成形品の長手方向に配向していた。また、ひけや反りは認められなかった。成形品の平面度を測定した結果を、表３に示す。
【００７３】
（比較例３Ａ）
比較例３Ａにおいては、実施例３の［工程−３００］を実行した後、直ちに、射出用シリンダー１１によってキャビティ１８内の溶融熱可塑性樹脂３０に保圧（５×１０^７Ｐａ）を２０秒間加えた。その後、２０秒が経過した後、金型組立体を開き、成形品を取り出した。
【００７４】
得られた成形品を観察したところ、ガラス繊維は成形品の長手方向に配向していたが、樹脂流動末端である、樹脂溜り４４の近傍におけるキャビティ１８内の溶融熱可塑性樹脂３０に十分な保圧圧力が加わらないが故に、樹脂溜り４４の近傍に対応する成形品の部分にひけ及び反りが発生していた。成形品の平面度を測定した結果を、表３に示す。
【００７５】
（比較例３Ｂ）
比較例３Ｂにおいては、実施例３の［工程−３００］を実行した後、更に、［工程−３１０］〜［工程−３４０］を実行した。但し、［工程−３１０］〜［工程−３３０］において、Ｐ_１＝９×１０^７Ｐａ、Ｐ_２＝０Ｐａ、Ｐ_２’＝９×１０^７Ｐａ、Ｐ_１’＝０Ｐａとした。
【００７６】
得られた成形品を観察したところ、ガラス繊維は成形品の長手方向に配向していたが、ゲート部１５及び樹脂溜り４４の近傍に対応する成形品の部分にひけ及び反りが発生していた。成形品の平面度を測定した結果を、表３に示す。
【００７７】
（実施例４）
実施例４は、実施例３の変形である。図１４に概念図を示す実施例４の金型組立体１０Ｃは、樹脂溜り４４に開閉手段が設けられている点が、実施例３の金型組立体１０Ｂと相違する。また、ゲート部１５にも開閉手段が設けられている。
その他の構造は、実施例３の金型組立体と同じである。ここで、開閉手段は、実施例２にて説明したと同様の構成、構造を有する。尚、図１４においては、ゲート部１５が開かれ、樹脂溜り４４が閉じられた状態を示す。樹脂流路１４は、ホットランナーから構成され、樹脂溜り４４内の熱可塑性樹脂も溶融状態とされる機構を有しているが、詳細な図示は省略した。
【００７８】
以下、金型組立体等の概念図である図１５〜図１８を参照して実施例４の射出成形方法を説明するが、実施例４においては、実施例２と同じ熱可塑性樹脂を使用し、実施例２と同じ形状の成形品を成形した。尚、図１５〜図１８においては、射出用シリンダー１１の図示を省略した。また、図１５〜図１８において、前回の射出成形により第２樹脂溜り４４内に残された溶融熱可塑性樹脂を、参照番号３０Ａで示す。
【００７９】
［工程−４００］
まず、射出用シリンダー１１にて可塑化、溶融された熱可塑性樹脂３０を、樹脂流路１４及びゲート部１５を介してキャビティ１８内に射出し、キャビティ１８内を溶融熱可塑性樹脂３０で完全に充填した（図１５参照）。射出条件を、表２に示したと同様とした。尚、溶融熱可塑性樹脂３０の射出時、第１加圧手段を構成するピストン２０Ａを後進端に位置させ、第２加圧手段を構成するピストン２０Ｂを前進端に位置させる。溶融熱可塑性樹脂３０の射出によってピストン２０Ａの位置が変化しないように、油圧シリンダー２１Ａを制御する。また、ゲート部１５は開かれ、樹脂溜り４４は閉じられた状態にある。
【００８０】
［工程−４１０］
キャビティ１８への溶融熱可塑性樹脂３０の射出完了と同時に、油圧シリンダー４７を作動させてシャットオフピン４６を後退させ、樹脂溜り４４をキャビティ１８と連通させた（図１６参照）。同時に、油圧シリンダー２１Ａ，２１Ｂを作動させて、ピストン２０Ａを前進端へと移動させ、このピストン２０Ａの動きと同期して、ピストン２０Ｂを後進端へと移動させた。このとき、樹脂流路１４内の溶融熱可塑性樹脂３０に第１加圧手段（具体的には、ピストン２０Ａ）により圧力Ｐ_１（＝９×１０^７Ｐａ）を加え、樹脂溜り４４内の溶融熱可塑性樹脂３０，３０Ａに第２加圧手段（具体的には、ピストン２０Ｂ）により圧力Ｐ_２（＝２×１０^７Ｐａ）を加えることで、キャビティ１８内の溶融熱可塑性樹脂３０に対してゲート部１５から樹脂溜り４４に向かう方向に剪断力を与えて、キャビティ１８内の溶融熱可塑性樹脂３０をゲート部１５から樹脂溜り４４に向かう方向に流動させた。この状態を図１７に示す。ピストン２０Ａ，２０Ｂの移動時間を１．５秒とした。キャビティ１８内の溶融熱可塑性樹脂３０を、約２ｃｍ^３、ゲート部１５から樹脂溜り４４に向かう方向に移動させた。
【００８１】
［工程−４２０］
ピストン２０Ａが前進端に達し、ピストン２０Ｂが後進端に達したならば（図１７参照）、直ちに、樹脂流路１４内の溶融熱可塑性樹脂３０に第１加圧手段（具体的には、ピストン２０Ａ）により圧力Ｐ_１’（＝２×１０^７Ｐａ）を加え、樹脂溜り４４内の溶融熱可塑性樹脂３０，３０Ａに第２加圧手段（具体的には、ピストン２０Ｂ）により圧力Ｐ_２’（＝９×１０^７Ｐａ）を加えることで、キャビティ１８内の溶融熱可塑性樹脂３０に対して樹脂溜り４４からゲート部１５に向かう方向に剪断力を与えて、キャビティ１８内の溶融熱可塑性樹脂３０を樹脂溜り４４からゲート部１５に向かう方向に流動させた。この状態を図１８に示す。ピストン２０Ａ，２０Ｂの移動時間を１．５秒とした。キャビティ１８内の溶融熱可塑性樹脂３０を、約２ｃｍ^３、樹脂溜り４４からゲート部１５に向かう方向に移動させた。
【００８２】
［工程−４３０］
ピストン２０Ａが後進端に達し、ピストン２０Ｂが前進端に達したならば（図１８参照）、直ちに、［工程−４１０］、［工程−４２０］を順次繰り返す。こうして、［工程−４１０］、［工程−４２０］を１回の操作としたとき、５回の操作を行った。５回の操作に要した時間は１５秒である。
【００８３】
［工程−４４０］
その後、第１加圧手段及び第２加圧手段（具体的には、ピストン２０Ａ，２０Ｂ）によってキャビティ１８内の溶融熱可塑性樹脂３０に圧力Ｐ_０（＝４×１０^７Ｐａ）を加えた。そして、キャビティ内の溶融熱可塑性樹脂３０の冷却、固化を行った。圧力Ｐ_０を加える時間を１５秒間とし、次いで、第１加圧手段及び第２加圧手段によってキャビティ１８内の溶融熱可塑性樹脂３０に圧力を加える操作を中止した。その後、２０秒が経過した後、金型組立体を開き、成形品を取り出した。
【００８４】
成形品は、優れた外観、優れた寸法精度を有しており、ガラス繊維は成形品の長手方向に配向していた。また、ひけや反りは認められなかった。成形品の平面度を測定した結果を、表３に示す。
【００８５】
（比較例４Ａ）
比較例４Ａにおいては、実施例４の［工程−４００］を実行した後、射出用シリンダー１１によってキャビティ１８内の溶融熱可塑性樹脂３０に保圧（４×１０^７Ｐａ）を１５秒間加えた。その後、２０秒が経過した後、金型組立体を開き、成形品を取り出した。
【００８６】
得られた成形品を観察したところ、ガラス繊維は成形品の長手方向に配向していたが、樹脂流動末端である、樹脂溜り４４の近傍におけるキャビティ１８内の溶融熱可塑性樹脂３０に十分な保圧圧力が加わらないが故に、樹脂溜り４４の近傍に対応する成形品の部分にひけ及び反りが発生していた。成形品の平面度を測定した結果を、表３に示す。
【００８７】
（比較例４Ｂ）
比較例４Ｂにおいては、実施例４の［工程−４００］を実行した後、更に、［工程−４１０］〜［工程−４４０］を実行した。但し、［工程−４１０］〜［工程−４３０］において、Ｐ_１＝９×１０^７Ｐａ、Ｐ_２＝０Ｐａ、Ｐ_２’＝９×１０^７Ｐａ、Ｐ_１’＝０Ｐａとした。
【００８８】
得られた成形品を観察したところ、ガラス繊維は成形品の長手方向に配向していたが、ゲート部１５及び樹脂溜り４４の近傍に対応する成形品の部分にひけ及び反りが発生していた。成形品の平面度を測定した結果を、表３に示す。
【００８９】
（実施例５）
実施例５は、本発明の第３の態様に係る成形品の射出成形方法及び本発明の第３の態様に係る金型組立体に関する。
【００９０】
実施例５の金型組立体の概念図を図１９に示す。実施例５の金型組立体１０Ｄは、
（Ａ）射出用シリンダー１１に連通した樹脂流路１４、
（Ｂ）キャビティ１８、
（Ｃ）樹脂流路１４に連通し、キャビティ１８に開口したゲート部１５、
（Ｄ）キャビティ１８に連通した第１樹脂溜り４４Ａ、
（Ｅ）キャビティ１８に連通した第２樹脂溜り４４Ｂ、
（Ｆ）第１樹脂溜り４４Ａ内の溶融熱可塑性樹脂に圧力を加えるための第１加圧手段、及び、
（Ｇ）第２樹脂溜り４４Ｂ内の溶融熱可塑性樹脂に圧力を加えるための第２加圧手段、
を備えている。
【００９１】
より具体的には、金型組立体１０Ｄは、固定金型部１２及び可動金型部１３を有し、固定金型部１２と可動金型部１３を型締めすることによってキャビティ１８が形成される。樹脂流路１４、第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂは固定金型部１２内に設けられ、樹脂流路１４は所謂スプルー及びコールドランナーから構成されている。また、第１加圧手段は、油圧シリンダー２１Ａと、油圧シリンダー２１Ａに取り付けられ、油圧シリンダー２１Ａの作動に基づき第１樹脂溜り４４Ａ内で前後に移動（摺動）させられるピストン２０Ａから構成されている。一方、第２加圧手段は、油圧シリンダー２１Ｂと、油圧シリンダー２１Ｂに取り付けられ、油圧シリンダー２１Ｂの作動に基づき第２樹脂溜り４４Ｂ内で前後に移動（摺動）させられるピストン２０Ｂから構成されている。ゲート部１５はダイレクト構造を有する。そして、成形品の長手方向の長さをＬとしたとき、成形品の長手方向の一方の端部を形成すべきキャビティ１８の部分１８Ａから第１樹脂溜り４４Ａの開口部までの距離は０．０５Ｌであり、成形品の長手方向の他方の端部を形成すべきキャビティ１８の部分１８Ｂから第２樹脂溜り４４Ｂの開口部までの距離は０．０５Ｌである。
【００９２】
以下、金型組立体等の概念図である図２０〜図２２を参照して実施例５の射出成形方法を説明するが、実施例５においては、実施例１と同じ熱可塑性樹脂を使用し、実施例１と同じ形状の成形品を成形した。尚、図２０〜図２２においては、射出用シリンダー１１の図示を省略した。
【００９３】
［工程−５００］
まず、射出用シリンダー１１にて可塑化、溶融された熱可塑性樹脂３０を、樹脂流路１４及びゲート部１５を介してキャビティ１８内に射出し、キャビティ１８内を溶融熱可塑性樹脂３０で完全に充填し、更に、溶融熱可塑性樹脂３０で第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂを充填した（図２０参照）。射出条件を、表１に示したと同様とした。尚、溶融熱可塑性樹脂３０の射出時、第１加圧手段を構成するピストン２０Ａを後進端に位置させ、第２加圧手段を構成するピストン２０Ｂを前進端に位置させる。溶融熱可塑性樹脂３０の射出によってこれらのピストン２０Ａ，２０Ｂの位置が変化しないように、油圧シリンダー２１Ａ，２１Ｂを制御する。
【００９４】
［工程−５１０］
キャビティ１８への溶融熱可塑性樹脂３０の射出完了と同時に、油圧シリンダー２１Ａ，２１Ｂを作動させて、ピストン２０Ａを前進端へと移動させ、このピストン２０Ａの動きと同期して、ピストン２０Ｂを後進端へと移動させた。このとき、第１樹脂溜り４４Ａ内の溶融熱可塑性樹脂３０に第１加圧手段（具体的には、ピストン２０Ａ）により圧力Ｐ_１（＝９×１０^７Ｐａ）を加え、第２樹脂溜り４４Ｂ内の溶融熱可塑性樹脂３０に第２加圧手段（具体的には、ピストン２０Ｂ）により圧力Ｐ_２（＝２×１０^７Ｐａ）を加えることで、キャビティ１８内の溶融熱可塑性樹脂３０に対して第１樹脂溜り４４Ａから第２樹脂溜り４４Ｂに向かう方向に剪断力を与えて、キャビティ１８内の溶融熱可塑性樹脂３０を第１樹脂溜り４４Ａから第２樹脂溜り４４Ｂに向かう方向に流動させた。この状態を図２１に示す。ピストン２０Ａ，２０Ｂの移動時間を１．５秒とした。キャビティ１８内の溶融熱可塑性樹脂３０を、約５ｃｍ^３、第１樹脂溜り４４Ａから第２樹脂溜り４４Ｂに向かう方向に移動させた。また、ゲート部１５内の溶融熱可塑性樹脂３０には、キャビティ１８からゲート部１５に溶融熱可塑性樹脂３０が逆流しない程度の圧力を加え続けた。
【００９５】
［工程−５２０］
ピストン２０Ａが前進端に達し、ピストン２０Ｂが後進端に達したならば（図２１参照）、直ちに、第１樹脂溜り４４Ａ内の溶融熱可塑性樹脂３０に第１加圧手段（具体的には、ピストン２０Ａ）により圧力Ｐ_１’（＝２×１０^７Ｐａ）を加え、第２樹脂溜り４４Ｂ内の溶融熱可塑性樹脂３０に第２加圧手段（具体的には、ピストン２０Ｂ）により圧力Ｐ_２’（＝９×１０^７Ｐａ）を加えることで、キャビティ１８内の溶融熱可塑性樹脂３０に対して第２樹脂溜り４４Ｂから第１樹脂溜り４４Ａに向かう方向に剪断力を与えて、キャビティ１８内の溶融熱可塑性樹脂３０を第２樹脂溜り４４Ｂから第１樹脂溜り４４Ａに向かう方向に流動させた。この状態を図２２に示す。ピストン２０Ａ，２０Ｂの移動時間を１．５秒とした。キャビティ１８内の溶融熱可塑性樹脂３０を、約５ｃｍ^３、第２樹脂溜り４４から第１樹脂溜り４４Ａに向かう方向に移動させた。また、ゲート部１５内の溶融熱可塑性樹脂３０には、キャビティ１８からゲート部１５に溶融熱可塑性樹脂３０が逆流しない程度の圧力を加え続けた。
【００９６】
［工程−５３０］
ピストン２０Ａが後進端に達し、ピストン２０Ｂが前進端に達したならば（図２２参照）、直ちに、［工程−５１０］、［工程−５２０］を順次繰り返す。こうして、［工程−５１０］、［工程−５２０］を１回の操作としたとき、５回の操作を行った。５回の操作に要した時間は１５秒である。
【００９７】
［工程−５４０］
その後、第１加圧手段及び第２加圧手段（具体的には、ピストン２０Ａ，２０Ｂ）によってキャビティ１８内の溶融熱可塑性樹脂３０に圧力Ｐ_０（＝５×１０^７Ｐａ）を加えた。そして、キャビティ内の溶融熱可塑性樹脂３０の冷却、固化を行った。圧力Ｐ_０を加える時間を５秒間とし、次いで、第１加圧手段及び第２加圧手段によってキャビティ１８内の溶融熱可塑性樹脂３０に圧力を加える操作を中止した。その後、２０秒が経過した後、金型組立体を開き、成形品を取り出した。
【００９８】
成形品は、優れた外観、優れた寸法精度を有しており、ガラス繊維は成形品の長手方向に配向していた。また、ひけや反りは認められなかった。成形品の平面度を測定した結果を、表３に示す。
【００９９】
（比較例５Ａ）
比較例５Ａにおいては、実施例５の［工程−５００］を実行した後、直ちに、射出用シリンダー１１によってキャビティ１８内の溶融熱可塑性樹脂３０に保圧（５×１０^７Ｐａ）を２０秒間加えた。その後、２０秒が経過した後、金型組立体を開き、成形品を取り出した。
【０１００】
得られた成形品を観察したところ、ガラス繊維は成形品の長手方向に配向していたが、樹脂流動末端である、第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂの近傍におけるキャビティ１８内の溶融熱可塑性樹脂３０に十分な保圧圧力が加わらないが故に、第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂの近傍に対応する成形品の部分にひけ及び反りが発生していた。成形品の平面度を測定した結果を、表３に示す。
【０１０１】
（比較例５Ｂ）
比較例５Ｂにおいては、実施例５の［工程−５００］を実行した後、更に、［工程−５１０］〜［工程−５４０］を実行した。但し、［工程−５１０］〜［工程−５３０］において、Ｐ_１＝９×１０^７Ｐａ、Ｐ_２＝０Ｐａ、Ｐ_２’＝９×１０^７Ｐａ、Ｐ_１’＝０Ｐａとした。
【０１０２】
得られた成形品を観察したところ、ガラス繊維は成形品の長手方向に配向していたが、ゲート部１５の近傍に対応する成形品の部分にひけ及び反りが発生していた。成形品の平面度を測定した結果を、表３に示す。
【０１０３】
（実施例６）
実施例６は、実施例５の変形である。図２３に概念図を示す実施例６の金型組立体１０Ｅは、第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂに開閉手段が設けられている点が、実施例５の金型組立体１０Ｄと相違する。また、ゲート部１５にも開閉手段（図示せず）が設けられている。その他の構造は、実施例５の金型組立体と同じである。ここで、開閉手段は、実施例２にて説明したと同様の構成、構造を有する。尚、図２３においては、第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂが閉じられた状態を示す。樹脂流路１４は、スプルーとホットランナーの組合せから構成され、第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂ内の熱可塑性樹脂も溶融状態とされる機構を有しているが、詳細な図示は省略した。
【０１０４】
以下、金型組立体等の概念図である図２４〜図２７を参照して実施例６の射出成形方法を説明するが、実施例６においては、実施例２と同じ熱可塑性樹脂を使用し、実施例２と同じ形状の成形品を成形した。尚、図２４〜図２７においては、射出用シリンダー１１の図示を省略した。また、図２４〜図２７において、前回の射出成形により第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂ内に残された溶融熱可塑性樹脂を、参照番号３０Ａで示す。更には、溶融熱可塑性樹脂３０の一部はキャビティ１８と第１樹脂溜り４４Ａあるいは第２樹脂溜り４４Ｂとの間を流動し、溶融熱可塑性樹脂３０Ａの一部もキャビティ１８と第１樹脂溜り４４Ａあるいは第２樹脂溜り４４Ｂとの間を流動するが、図２６及び図２７においてはこのような溶融熱可塑性樹脂３０，３０Ａの流動状態の図示を省略した。
【０１０５】
［工程−６００］
まず、射出用シリンダー１１にて可塑化、溶融された熱可塑性樹脂３０を、樹脂流路１４及びゲート部１５を介してキャビティ１８内に射出し、キャビティ１８内を溶融熱可塑性樹脂３０で完全に充填した（図２４参照）。射出条件を、表２に示したと同様とした。尚、溶融熱可塑性樹脂３０の射出時、第１加圧手段を構成するピストン２０Ａを後進端に位置させ、第２加圧手段を構成するピストン２０Ｂを前進端に位置させる。第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂは閉じられた状態にある。
【０１０６】
［工程−６１０］
キャビティ１８への溶融熱可塑性樹脂３０の射出完了と同時に、油圧シリンダー４７Ａ，４７Ｂを作動させてシャットオフピン４６Ａ，４６Ｂを後退させ、第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂをキャビティ１８と連通させた（図２５参照）。同時に、油圧シリンダー２１Ａ，２１Ｂを作動させて、ピストン２０Ａを前進端へと移動させ、このピストン２０Ａの動きと同期して、ピストン２０Ｂを後進端へと移動させた。このとき、第１樹脂溜り４４Ａ内の溶融熱可塑性樹脂３０，３０Ａに第１加圧手段（具体的には、ピストン２０Ａ）により圧力Ｐ_１（＝９×１０^７Ｐａ）を加え、第２樹脂溜り４４Ｂ内の溶融熱可塑性樹脂３０，３０Ａに第２加圧手段（具体的には、ピストン２０Ｂ）により圧力Ｐ_２（＝２×１０^７Ｐａ）を加えることで、キャビティ１８内の溶融熱可塑性樹脂３０に対して第１樹脂溜り４４Ａから第２樹脂溜り４４Ｂに向かう方向に剪断力を与えて、キャビティ１８内の溶融熱可塑性樹脂３０を第１樹脂溜り４４Ａから第２樹脂溜り４４Ｂに向かう方向に流動させた。この状態を図２６に示す。ピストン２０Ａ，２０Ｂの移動時間を１．５秒とした。キャビティ１８内の溶融熱可塑性樹脂３０を、約２ｃｍ^３、第１樹脂溜り４４Ａから第２樹脂溜り４４Ｂに向かう方向に移動させた。
【０１０７】
［工程−６２０］
ピストン２０Ａが前進端に達し、ピストン２０Ｂが後進端に達したならば（図２６参照）、直ちに、第１樹脂溜り４４Ａ内の溶融熱可塑性樹脂３０，３０Ａに第１加圧手段（具体的には、ピストン２０Ａ）により圧力Ｐ_１’（＝２×１０^７Ｐａ）を加え、第２樹脂溜り４４Ｂ内の溶融熱可塑性樹脂３０，３０Ａに第２加圧手段（具体的には、ピストン２０Ｂ）により圧力Ｐ_２’（＝９×１０^７Ｐａ）を加えることで、キャビティ１８内の溶融熱可塑性樹脂３０に対して第２樹脂溜り４４Ｂから第１樹脂溜り４４Ａに向かう方向に剪断力を与えて、キャビティ１８内の溶融熱可塑性樹脂３０を第２樹脂溜り４４Ｂから第１樹脂溜り４４Ａに向かう方向に流動させた。この状態を図２７に示す。ピストン２０Ａ，２０Ｂの移動時間を１．５秒とした。キャビティ１８内の溶融熱可塑性樹脂３０を、約２ｃｍ^３、第２樹脂溜り４４Ｂから第１樹脂溜り４４Ａに向かう方向に移動させた。
【０１０８】
［工程−６３０］
ピストン２０Ａが後進端に達し、ピストン２０Ｂが前進端に達したならば（図２７参照）、直ちに、［工程−６１０］、［工程−６２０］を順次繰り返す。こうして、［工程−６１０］、［工程−６２０］を１回の操作としたとき、５回の操作を行った。５回の操作に要した時間は１５秒である。
【０１０９】
［工程−６４０］
その後、第１加圧手段及び第２加圧手段（具体的には、ピストン２０Ａ，２０Ｂ）によってキャビティ１８内の溶融熱可塑性樹脂３０に圧力Ｐ_０（＝４×１０^７Ｐａ）を加えた。そして、キャビティ内の溶融熱可塑性樹脂３０の冷却、固化を行った。圧力Ｐ_０を加える時間を１５秒間とし、次いで、第１加圧手段及び第２加圧手段によってキャビティ１８内の溶融熱可塑性樹脂３０に圧力を加える操作を中止した。その後、２０秒が経過した後、金型組立体を開き、成形品を取り出した。
【０１１０】
成形品は、優れた外観、優れた寸法精度を有しており、ガラス繊維は成形品の長手方向に配向していた。また、ひけや反りは認められなかった。成形品の平面度を測定した結果を、表３に示す。
【０１１１】
（比較例６Ａ）
比較例６Ａにおいては、実施例６の［工程−６００］を実行した後、射出用シリンダー１１によってキャビティ１８内の溶融熱可塑性樹脂３０に保圧（４×１０^７Ｐａ）を１５秒間加えた。その後、２０秒が経過した後、金型組立体を開き、成形品を取り出した。
【０１１２】
得られた成形品を観察したところ、ガラス繊維は成形品の長手方向に配向していたが、樹脂流動末端である、第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂの近傍におけるキャビティ１８内の溶融熱可塑性樹脂３０に十分な保圧圧力が加わらないが故に、第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂの近傍に対応する成形品の部分にひけ及び反りが発生していた。成形品の平面度を測定した結果を、表３に示す。
【０１１３】
（比較例６Ｂ）
比較例６Ｂにおいては、実施例６の［工程−６００］を実行した後、更に、［工程−６１０］〜［工程−６４０］を実行した。但し、［工程−６１０］〜［工程−６３０］において、Ｐ_１＝９×１０^７Ｐａ、Ｐ_２＝０Ｐａ、Ｐ_２’＝９×１０^７Ｐａ、Ｐ_１’＝０Ｐａとした。
【０１１４】
得られた成形品を観察したところ、ガラス繊維は成形品の長手方向に配向していたが、第１樹脂溜り４４Ａ及び第２樹脂溜り４４Ｂの近傍に対応する成形品の部分にひけ及び反りが発生していた。成形品の平面度を測定した結果を、表３に示す。
【０１１５】
［表３］
平面度（ｍｍ）
実施例１　　　０．１０
比較例１Ａ　　０．３０
比較例１Ｂ　　０．１５
実施例２　　　０．０８
比較例２Ａ　　０．２０
比較例２Ｂ　　０．１０
実施例３　　　０．１１
比較例３Ａ　　０．３１
比較例３Ｂ　　０．１７
実施例４　　　０．０９
比較例４Ａ　　０．２２
比較例４Ｂ　　０．１２
実施例５　　　０．１３
比較例５Ａ　　０．３２
比較例５Ｂ　　０．１８
実施例６　　　０．１０
比較例６Ａ　　０．２４
比較例６Ｂ　　０．１２
【０１１６】
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。実施例にて説明した金型組立体の構成、構造、実施例にて使用した熱可塑性樹脂、射出成形条件、成形品の大きさ、形状等は例示であり、適宜変更することができる。例えば、樹脂溜りや第１樹脂溜り、第２樹脂溜りの数は１つに限定されない。
【０１１７】
実施例１及び実施例２においては、第１ゲート部１５Ａのみから溶融熱可塑性樹脂３０をキャビティ１８に射出したが、図２８に実施例１の変形例を示すように、第１ゲート部１５Ａ及び第２ゲート部１５Ｂから溶融熱可塑性樹脂３０をキャビティ１８に射出してもよい。このような構成においては、キャビティ１８内を溶融熱可塑性樹脂で完全に充填してもよいし、不完全に充填してもよい。キャビティ１８内を溶融熱可塑性樹脂で不完全に充填した場合、加圧手段の動作により樹脂流路内の溶融熱可塑性樹脂がキャビティ１８内に流入し、これによって、キャビティ１８内は溶融熱可塑性樹脂で完全に充填される。尚、このような射出方法を実施例２に適用することもできる。
【０１１８】
また、図２９に実施例１の変形例を示すように、成形品の長手方向の一方の端部を形成すべきキャビティ１８の部分１８Ａから第１ゲート部１５Ａまでの距離を０とし、成形品の長手方向の他方の端部を形成すべきキャビティ１８の部分１８Ｂから第２ゲート部１５Ｂまでの距離を０とすることもできる。尚、このようなゲート部の構造を、実施例２〜実施例６にて説明した金型組立体に適用することもできる。
【０１１９】
更には、図３０に実施例５の変形例を示すように、成形品の長手方向の一方の端部を形成すべきキャビティ１８の部分１８Ａから第１樹脂溜り４４Ａまでの距離を０とし、成形品の長手方向の他方の端部を形成すべきキャビティ１８の部分１８Ｂから第２樹脂溜り４４Ｂまでの距離を０とすることもできる。尚、このような樹脂溜りの構造を、実施例３〜実施例４、実施例６にて説明した金型組立体に適用することもできる。ここで、図３０に示す金型組立体においては、金型組立体は、２カ所（第１ゲート部１５Ａ、第２ゲート部１５Ｂ）のゲート部を有するが、このようなゲート部の構造に限定するものではなく、ゲート部の数は１つであっても、３以上であってもよい。このような複数のゲート部を有する構成においては、キャビティ１８内を溶融熱可塑性樹脂で完全に充填してもよいし、不完全に充填してもよい。キャビティ１８内を溶融熱可塑性樹脂で不完全に充填した場合、加圧手段の動作により樹脂溜り内の溶融熱可塑性樹脂がキャビティ１８内に流入し、これによって、キャビティ１８内は溶融熱可塑性樹脂で完全に充填される。
【０１２０】
【発明の効果】
本発明の第１の態様〜第３の態様に係る射出成形方法にあっては、キャビティ内に射出された溶融熱可塑性樹脂は、Ｐ_１＞Ｐ_２＞０、及び、Ｐ_２’＞Ｐ_１’＞０の条件で、キャビティ内を流動する。即ち、キャビティ内の溶融熱可塑性樹脂には常に第１加圧手段及び第２加圧手段から対向する圧力が加わった状態となっている。その結果、優れた外観、優れた寸法精度を有し、ひけが無く、残留応力の残り難い成形品を成形することが可能となる。しかも、複数のゲート部からキャビティ内に溶融熱可塑性樹脂を射出した場合であっても、ウエルドが発生し難い。
【図面の簡単な説明】
【図１】図１は、実施例１の金型組立体の概念図である。
【図２】図２は、実施例１の射出成形方法を説明するための金型組立体等の概念図である。
【図３】図３は、図２に引き続き、実施例１の射出成形方法を説明するための金型組立体等の概念図である。
【図４】図４は、図３に引き続き、実施例１の射出成形方法を説明するための金型組立体等の概念図である。
【図５】図５は、実施例２の金型組立体の概念図である。
【図６】図６は、実施例２の射出成形方法を説明するための金型組立体等の概念図である。
【図７】図７は、図６に引き続き、実施例２の射出成形方法を説明するための金型組立体等の概念図である。
【図８】図８は、図７に引き続き、実施例２の射出成形方法を説明するための金型組立体等の概念図である。
【図９】図９は、図８に引き続き、実施例２の射出成形方法を説明するための金型組立体等の概念図である。
【図１０】図１０は、実施例３の金型組立体の概念図である。
【図１１】図１１は、実施例３の射出成形方法を説明するための金型組立体等の概念図である。
【図１２】図１２は、図１１に引き続き、実施例３の射出成形方法を説明するための金型組立体等の概念図である。
【図１３】図１３は、図１２に引き続き、実施例３の射出成形方法を説明するための金型組立体等の概念図である。
【図１４】図１４は、実施例４の金型組立体の概念図である。
【図１５】図１５は、実施例４の射出成形方法を説明するための金型組立体等の概念図である。
【図１６】図１６は、図１５に引き続き、実施例４の射出成形方法を説明するための金型組立体等の概念図である。
【図１７】図１７は、図１６に引き続き、実施例４の射出成形方法を説明するための金型組立体等の概念図である。
【図１８】図１８は、図１７に引き続き、実施例４の射出成形方法を説明するための金型組立体等の概念図である。
【図１９】図１９は、実施例５の金型組立体の概念図である。
【図２０】図２０は、実施例５の射出成形方法を説明するための金型組立体等の概念図である。
【図２１】図２１は、図２０に引き続き、実施例５の射出成形方法を説明するための金型組立体等の概念図である。
【図２２】図２２は、図２１に引き続き、実施例５の射出成形方法を説明するための金型組立体等の概念図である。
【図２３】図２３は、実施例６の金型組立体の概念図である。
【図２４】図２４は、実施例６の射出成形方法を説明するための金型組立体等の概念図である。
【図２５】図２５は、図２４に引き続き、実施例６の射出成形方法を説明するための金型組立体等の概念図である。
【図２６】図２６は、図２５に引き続き、実施例６の射出成形方法を説明するための金型組立体等の概念図である。
【図２７】図２７は、図２６に引き続き、実施例６の射出成形方法を説明するための金型組立体等の概念図である。
【図２８】図２８は、実施例１の金型組立体の変形例の概念図である。
【図２９】図２９は、実施例１の金型組立体の別の変形例の概念図である。
【図３０】図３０は、実施例５の金型組立体の変形例の概念図である。
【符号の説明】
１０，１０Ａ，１０Ｂ，１０Ｃ，１０Ｄ，１０Ｅ・・・金型組立体、１１・・・射出用シリンダー、１２・・・固定金型部、１３・・・可動金型部、１４・・・樹脂流路、１４Ａ・・・第１樹脂流路、１４Ｂ・・・第２樹脂流路、１５・・・ゲート部、１５Ａ・・・第１ゲート部、１５Ｂ・・・第２ゲート部、１６Ａ，１６Ｂ，４６，４６Ａ，４６Ｂ・・・シャットオフピン、１７Ａ，１７Ｂ，４７，４７Ａ，４７Ｂ・・・油圧シリンダー、１８・・・キャビティ、２０Ａ，２０Ｂ・・・ピストン、２１Ａ，２１Ｂ・・・油圧シリンダー、３０，３０Ａ・・・溶融熱可塑性樹脂、４４・・・樹脂溜り、４４Ａ・・・第１樹脂溜り、４４Ｂ・・・第２樹脂溜り[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for injection molding a molded article and a mold assembly, and more particularly, to an improvement of a so-called SCORIM (Shear Controlled Oriented Injection Molding) method, and a mold assembly suitable for implementing the improved SCORIM method. About three-dimensional.
[0002]
[Prior art]
It is known that when a long-sized molded product is manufactured by a conventional injection molding method, sinkage occurs on the surface of the molded product, or the molded product is warped, and the dimensional accuracy of the molded product is significantly impaired. . When a long-sized molded product is molded using a mold provided with a gate portion at one place, the holding pressure is applied to the molten resin in the cavity portion (resin-filled end) away from the gate portion. It is difficult to add, and the dimensional accuracy of the molded product is impaired.
On the other hand, when a long-sized molded product is molded using a mold having gate portions provided at two or more locations, welds are likely to occur in the molded product. The part of the molded product where the weld has occurred causes poor appearance, reduced strength, reduced dimensional accuracy, and the like. In particular, when using a resin composition containing a reinforcing material or filler such as plate-like or fibrous, the orientation direction of the reinforcing material or filler in the molten resin composition injected into the cavity is not uniform, It varies in a complicated manner depending on the shape of the molded product (the presence or absence of an opening, a change in wall thickness), the position of a gate, and the like. As a result, the dimensional accuracy of the molded product is significantly reduced, and the strength of the molded product tends to vary. In order to solve such a problem, various methods of changing various molding conditions such as a mold temperature, an injection speed, and a holding pressure have been tried, but the effect is small.
[0003]
As one method for solving the problem of such conventional injection molding, JP-A-61-17915 discloses a method of applying a shearing force to at least a part of a molten resin composition supplied to a mold cavity. An injection molding method (SCORIM method) comprising solidifying a molten resin composition, and a molding apparatus for applying a shearing force are disclosed. According to this molding method, the inside of the mold cavity is filled with the molten resin composition injected from the injection cylinder. Thereafter, the resin composition is solidified while alternately applying a shearing force to the molten resin composition in the mold cavity by two pistons, which are devices for applying a shearing force. As described above, by applying a shearing force to the molten resin composition in the mold cavity, the solidified thermoplastic resin is re-melted, and as a result, the reinforcing material and filler in the molten resin composition injected into the mold cavity are reduced. Can be made uniform, and the occurrence of welds can be suppressed.
[0004]
[Problems to be solved by the invention]
The injection molding method (SCORIM method) disclosed in JP-A-61-17915 is an effective method for solving the above-mentioned problems of the conventional injection molding method. However, when pressure is applied to the molten resin composition in the mold cavity by one of the pistons, pressure is not applied to the molten resin composition in the mold cavity by the other piston. There may be cases where the dimensional accuracy is insufficient, or it is difficult to reliably prevent sink marks from occurring. In addition, since the resin composition in the mold cavity is solidified while maintaining the shearing force, there is a problem that stress is likely to remain in the molded product.
[0005]
Accordingly, an object of the present invention is to solve the above-mentioned problems in the conventional SCORIM method, and to provide an injection molding capable of forming a molded product having excellent appearance, excellent dimensional accuracy, no sink marks, and less residual stress. It is an object of the present invention to provide a method and a mold assembly suitable for carrying out such an injection molding method.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an injection molding method for a molded article according to the first aspect of the present invention comprises:
(A) a first resin flow path and a second resin flow path communicating with an injection cylinder;
(B) a cavity,
(C) a first gate portion communicating with the first resin flow path and opening to the cavity;
(D) a second gate portion communicating with the second resin flow path and opening to the cavity;
(E) first pressurizing means for applying pressure to the molten thermoplastic resin in the first resin flow path, and
(F) a second pressurizing means for applying pressure to the molten thermoplastic resin in the second resin flow path;
A method for injection molding a molded article using a mold assembly having
(A) After injecting the thermoplastic resin plasticized and melted by the injection cylinder into the cavity through the first resin flow path and the first gate portion,
(B) A pressure P is applied to the molten thermoplastic resin in the first resin flow path by the first pressing means. ₁ Is added to the molten thermoplastic resin in the second resin flow path by the second pressure means. ₂ (However, P ₁ > P ₂ > 0), a shearing force is applied to the molten thermoplastic resin in the cavity in a direction from the first gate portion to the second gate portion, and the molten thermoplastic resin in the cavity is removed from the first gate portion. The molten thermoplastic resin in the first resin flow path is caused to flow in the direction toward the second gate portion, and then the pressure P is applied to the molten thermoplastic resin by the first pressing means. ₁ ', And the pressure P is applied to the molten thermoplastic resin in the second resin flow path by the second pressing means. ₂ '(However, P ₂ '> P ₁ '> 0), a shearing force is applied to the molten thermoplastic resin in the cavity in a direction from the second gate portion to the first gate portion, so that the molten thermoplastic resin in the cavity is removed from the second gate portion. Repeating the operation to flow in the direction from
It is characterized by comprising a process.
[0007]
In the method for injection-molding a molded article according to the first aspect of the present invention, the second gate portion is provided with opening / closing means, and in the step (a), the second gate portion is closed by the opening / closing means. In the step (b), the second gate portion may be opened by opening / closing means. With such a configuration, when the molten thermoplastic resin is injected into the cavity via the first resin flow path and the first gate portion in the step (a), the molten thermoplastic resin is injected into the second gate portion or the second gate portion. 2 It is possible to reliably prevent intrusion into the resin flow path. When such a configuration is adopted, it is preferable that the first resin flow path and the second resin flow path are formed of, for example, a hot runner.
[0008]
In order to achieve the above object, an injection molding method for a molded article according to the second aspect of the present invention comprises:
(A) a resin flow path communicating with the injection cylinder,
(B) a cavity,
(C) a gate portion communicating with the resin flow path and opening to the cavity;
(D) a resin reservoir communicating with the cavity,
(E) first pressurizing means for applying pressure to the molten thermoplastic resin in the resin flow path, and
(F) second pressurizing means for applying pressure to the molten thermoplastic resin in the resin reservoir;
A method for injection molding a molded article using a mold assembly having
(A) After injecting the thermoplastic resin plasticized and melted by the injection cylinder into the cavity through the resin flow path and the gate portion,
(B) A pressure P is applied to the molten thermoplastic resin in the resin flow path by the first pressing means. ₁ Is added to the molten thermoplastic resin in the resin reservoir by the second pressure means. ₂ (However, P ₁ > P ₂ > 0), a shearing force is applied to the molten thermoplastic resin in the cavity from the gate toward the resin reservoir, and the molten thermoplastic resin in the cavity is directed from the gate toward the resin reservoir in the cavity. Then, the molten thermoplastic resin in the resin flow path is subjected to a pressure P by the first pressing means. ₁ 'And apply a pressure P to the molten thermoplastic resin in the resin reservoir by the second pressing means. ₂ '(However, P ₂ '> P ₁ By applying '> 0), a shear force is applied to the molten thermoplastic resin in the cavity in a direction from the resin reservoir toward the gate portion, and the molten thermoplastic resin in the cavity is directed from the resin reservoir to the gate portion. Repeat the operation to flow to
It is characterized by comprising a process.
[0009]
In order to achieve the above object, an injection molding method for a molded article according to a third aspect of the present invention comprises:
(A) a resin flow path communicating with the injection cylinder,
(B) a cavity,
(C) a gate portion communicating with the resin flow path and opening to the cavity;
(D) a first resin reservoir communicating with the cavity,
(E) a second resin reservoir communicating with the cavity,
(F) first pressurizing means for applying pressure to the molten thermoplastic resin in the first resin reservoir, and
(G) second pressurizing means for applying pressure to the molten thermoplastic resin in the second resin reservoir;
A method for injection molding a molded article using a mold assembly having
(A) After injecting the thermoplastic resin plasticized and melted by the injection cylinder into the cavity through the resin flow path and the gate portion,
(B) A pressure P is applied to the molten thermoplastic resin in the first resin reservoir by the first pressing means. ₁ Is applied to the molten thermoplastic resin in the second resin reservoir by the second pressing means. ₂ (However, P ₁ > P ₂ > 0), a shear force is applied to the molten thermoplastic resin in the cavity in a direction from the first resin reservoir toward the second resin reservoir, and the molten thermoplastic resin in the cavity is removed from the first resin reservoir. The resin is caused to flow in a direction toward the second resin reservoir, and then a pressure P is applied to the molten thermoplastic resin in the first resin reservoir by the first pressing means. ₁ To the molten thermoplastic resin in the second resin reservoir by the second pressing means. ₂ '(However, P ₂ '> P ₁ '> 0), a shear force is applied to the molten thermoplastic resin in the cavity in a direction from the second resin reservoir toward the first resin reservoir, and the molten thermoplastic resin in the cavity is removed from the second resin reservoir. Repeating the operation of flowing in a direction toward the first resin reservoir from
It is characterized by comprising a process.
[0010]
Injection molding methods for molded articles according to the first to third aspects of the present invention including the above preferred embodiments (hereinafter, these may be collectively simply referred to as the injection molding method of the present invention). In step (b), first, P ₁ > P ₂ > 0 or P ₂ '> P ₁ Whether or not '> 0 is essentially arbitrary, and either one may be adopted, and both are included in the present invention.
[0011]
In the present invention, P ₁ , P ₂ ', P ₂ , P ₁ 'Can be set arbitrarily according to the molding conditions. ₁ = P ₂ ', P ₂ = P ₁ 'Is preferably satisfied. And, in the injection molding method of the present invention including such a mode, P ₂ / P ₁ Is 1/10 to 9/10, preferably 1/10 to 5/10, and P ₁ '/ P ₂ It is desirable that the value of 'is 1/10 to 9/10, preferably 1/10 to 5/10. Also, (P ₁ -P ₂ ) Or (P ₂ '-P ₁ '), For example, 1 × 10 ⁶ Pa to 1.5 × 10 ⁸ Pa, preferably 5 × 10 ⁶ Pa to 8 × 10 ⁷ Pa can be exemplified. Furthermore, P ₁ , P ₂ ', For example, 2 × 10 ⁶ Pa to 1.6 × 10 ⁸ Pa, preferably 3 × 10 ⁷ Pa to 1 × 10 ⁸ Pa can be exemplified, and P ₂ , P ₁ ', For example, 1 × 10 ⁶ Pa to 1.5 × 10 ⁸ Pa, preferably 2 × 10 ⁷ Pa to 9 × 10 ⁷ Pa can be exemplified.
[0012]
In the injection molding method of the present invention including the above various preferable embodiments, after the step (b) is completed, the pressure P is applied to the molten thermoplastic resin in the cavity by the first pressing means and the second pressing means. ₀ Is preferably added. That is, it is preferable that the pressure holding step is performed by the first pressure unit and the second pressure unit. This makes it possible to compensate for a decrease in volume due to cooling of the molten thermoplastic resin in the cavity.
[0013]
To achieve the above object, a mold assembly according to a first aspect of the present invention comprises:
(A) a first resin flow path and a second resin flow path communicating with an injection cylinder;
(B) a cavity,
(C) a first gate portion communicating with the first resin flow path and opening to the cavity;
(D) a second gate portion communicating with the second resin flow path and opening to the cavity;
(E) first pressurizing means for applying pressure to the molten thermoplastic resin in the first resin flow path, and
(F) a second pressurizing means for applying pressure to the molten thermoplastic resin in the second resin flow path;
A mold assembly comprising:
The second gate portion is provided with opening / closing means.
[0014]
A mold assembly according to a second aspect of the present invention for achieving the above object,
(A) a resin flow path communicating with the injection cylinder,
(B) a cavity,
(C) a gate portion communicating with the resin flow path and opening to the cavity;
(D) a resin reservoir communicating with the cavity,
(E) first pressurizing means for applying pressure to the molten thermoplastic resin in the resin flow path, and
(F) second pressurizing means for applying pressure to the molten thermoplastic resin in the resin reservoir;
It is characterized by having.
[0015]
A mold assembly according to a third aspect of the present invention for achieving the above object,
(A) a resin flow path communicating with the injection cylinder,
(B) a cavity,
(C) a gate portion communicating with the resin flow path and opening to the cavity;
(D) a first resin reservoir communicating with the cavity,
(E) a second resin reservoir communicating with the cavity,
(F) first pressurizing means for applying pressure to the molten thermoplastic resin in the first resin reservoir, and
(G) second pressurizing means for applying pressure to the molten thermoplastic resin in the second resin reservoir;
It is characterized by having.
[0016]
In the injection molding method or the mold assembly according to the first aspect of the present invention, a valve gate type hot runner can be exemplified as the opening / closing means. Here, the valve gate includes a shut-off pin and a cylinder piston. For example, the valve gate has a structure in which the shut-off pin opens and closes the gate by the operation of a hydraulic cylinder and a cylinder piston.
[0017]
In the injection molding method or the mold assembly according to the first aspect of the present invention, one injection cylinder is used, and the first resin flow path and the second resin flow path are communicated with the one injection cylinder. Although it is desirable from the viewpoint of simplification of the configuration, the present invention is not limited to such a configuration. The resin flow path may be communicated with the other injection cylinder. In this case, the melted thermoplastic resin may be injected into the cavity from these two injection cylinders.
[0018]
The first resin flow path and the second resin flow path in the injection molding method or the mold assembly according to the first aspect, or the injection molding method or the mold according to the second or third aspect of the present invention. The resin flow path in the assembly can be composed of, for example, a combination of a sprue and a cold runner, or alternatively, a hot runner. When these resin flow paths are formed of hot runners, the first gate portion in the injection molding method or the mold assembly according to the first aspect, or the injection molding method or the mold assembly according to the second aspect. The opening of the resin reservoir opening in the gate and the cavity, the opening of the first resin reservoir opening in the cavity and the opening of the second resin reservoir opening in the cavity in the injection molding method or the mold assembly according to the third aspect. It is preferable that the part can be opened and closed by, for example, a valve gate.
[0019]
In the injection molding method or the mold assembly according to the first to third aspects of the present invention, the structures of the first gate portion, the second gate portion, and the gate portion are essentially arbitrary, and the molding is performed. What is necessary is just to determine based on the shape of the to-be-molded article, etc. For example, an open type structure, a direct structure, a side gate structure, an overlap gate structure, a tunnel gate structure, and a pinpoint gate structure can be illustrated.
[0020]
In the injection molding method or the mold assembly according to the first to third aspects of the present invention, a combination of a hydraulic cylinder and a piston can be exemplified as the first pressing means and the second pressing means. . In this case, the piston may be arranged in the first resin channel, the second resin channel, the resin channel, the resin reservoir, the first resin reservoir, or the second resin reservoir.
[0021]
In the injection molding method of the present invention, it is preferable to repeat the step (b) several times, specifically, for example, three to five times. It is desirable that the repetition cycle be once or more (1 Hz to 1/60 Hz) once every 1 to 60 seconds, and more preferably 1 to 1/5 Hz. When step (b) is repeated, P ₁ , P ₂ , P ₁ ', P ₂ The value of 'may be fixed or may be changed.
[0022]
In the injection molding method of the present invention, when the volume of the molded product is V, the amount of 0.05 V to 0.5 V, preferably 0.1 V to 0.4 V in the step (b) is used. It is desirable to flow the molten thermoplastic resin in the cavity by a quantity along a direction corresponding to the longitudinal direction of the molded article.
[0023]
The molded article molded by the injection molding method or the mold assembly according to the first to third aspects of the present invention can have any shape. For example, the ratio L of the length L to the width W is L. It is preferable to mold a molded product having / W of 2 or more.
[0024]
When molding such a molded product having L / W of 2 or more, in the injection molding method or the mold assembly according to the first aspect of the present invention, one end in the longitudinal direction of the molded product is formed. Preferably, the first gate portion is disposed at or near the cavity to be formed, and the second gate portion is disposed at or near the cavity at which the other end in the longitudinal direction of the molded product is to be formed. Specifically, it is preferable that the distance from the portion of the cavity where one end in the longitudinal direction of the molded product is to be formed to the first gate portion is 0 to 0.1 L, and the other in the longitudinal direction of the molded product. It is preferable that the distance from the portion of the cavity in which the end portion is formed to the second gate portion is 0 to 0.1 L.
[0025]
Alternatively, when molding such a molded product having L / W of 2 or more, in the injection molding method or the mold assembly according to the second aspect of the present invention, one end of the molded product in the longitudinal direction is used. It is preferable to arrange the gate portion at or near the cavity where the portion is to be formed, and to open the resin reservoir at or near the cavity where the other end in the longitudinal direction of the molded product is to be formed. Specifically, it is preferable that the distance from the cavity portion where one end in the longitudinal direction of the molded article is to be formed to the gate portion be 0 to 0.1 L, and the other end in the longitudinal direction of the molded article be used. It is preferable that the distance from the portion of the cavity where the portion is to be formed to the opening of the resin reservoir is 0 to 0.1 L. Incidentally, an auxiliary gate portion may be further provided. In this case, there is no need to provide a pressurizing means for applying pressure to the molten thermoplastic resin in the resin flow path communicating with the auxiliary gate portion.
[0026]
Alternatively, when molding such a molded product having L / W of 2 or more, in the injection molding method or the mold assembly according to the third aspect of the present invention, one end in the longitudinal direction of the molded product is provided. A first resin reservoir is opened at or near the cavity where the part is to be formed, and a second resin reservoir is opened at or near the cavity where the other end in the longitudinal direction of the molded product is to be formed. preferable. Specifically, it is preferable that the distance from the cavity portion where one end in the longitudinal direction of the molded product is to be formed to the opening of the first resin reservoir is 0 to 0.1 L. It is preferable that the distance from the portion of the cavity where the other end in the direction is to be formed to the opening of the second resin reservoir is 0 to 0.1 L. The position where the gate portion is arranged is essentially arbitrary. Further, the number of gate portions is essentially arbitrary, and may be one or two or more.
[0027]
Examples of the resin suitable for use in the injection molding method of the present invention include a crystalline thermoplastic resin and an amorphous thermoplastic resin, and specifically, a polyolefin resin such as a polyethylene resin and a polypropylene resin; a polyamide. 6, polyamide resins such as polyamide 66 and polyamide MXD6; polyoxymethylene (polyacetal, POM) resins; polyester resins such as polyethylene terephthalate (PET) resins and polybutylene terephthalate (PBT) resins; polyphenylene sulfide resins; polystyrene resins; Styrene resins such as ABS resin, AES resin, and AS resin; methacrylic resin; polycarbonate resin; modified PPE resin; polysulfone resin; polyether sulfone resin; polyarylate resin; Bromide resin; polyimide resins; polyether ketone resins; polyether ether ketone resins; polyester carbonate resin; can be exemplified a liquid crystal polymer.
[0028]
Further, a thermoplastic resin made of a polymer alloy material can be used. Here, the polymer alloy material is composed of a blend of at least two kinds of thermoplastic resins, or a block copolymer or a graft copolymer in which at least two kinds of thermoplastic resins are chemically bonded. Polymer alloy materials are widely used as high-performance materials that can combine the unique properties of each of the single thermoplastic resins. As thermoplastic resins constituting a polymer alloy material in which at least two kinds of thermoplastic resins are blended, styrene resins such as polystyrene resin, ABS resin, AES resin and AS resin; polyolefin resins such as polyethylene resin and polypropylene resin; methacrylic resin Polycarbonate resins; polyamide resins such as polyamide 6, polyamide 66 and polyamide MXD6; modified PPE resins; polyester resins such as polybutylene terephthalate resin and polyethylene terephthalate resin; polyoxymethylene resins; polysulfone resins; polyimide resins; polyphenylene sulfide resins; Polyarylate resin; Polyether sulfone resin; Polyether ketone resin; Polyether ether ketone resin; Polyester carbonate resin Can. As a polymer alloy material in which two kinds of thermoplastic resins are blended, a polymer alloy material of a polycarbonate resin and an ABS resin can be exemplified. Incidentally, such a combination of resins is referred to as polycarbonate resin / ABS resin. The same applies to the following. Further, as a polymer alloy material in which at least two kinds of thermoplastic resins are blended, polycarbonate resin / PET resin, polycarbonate resin / PBT resin, polycarbonate resin / polyamide resin, polycarbonate resin / PBT resin / PET resin, modified PPE resin / HIPS Resin, modified PPE resin / polyamide resin, modified PPE resin / PBT resin / PET resin, modified PPE resin / polyamide MXD6 resin, polyoxymethylene resin / polyurethane resin, and PBT resin / PET resin.
[0029]
In addition, stabilizers, ultraviolet absorbers, release agents, dyes and pigments can be added to the various thermoplastic resins described above, and glass beads, mica, kaolin, inorganic fillers such as calcium carbonate, Alternatively, an organic filler can be added.
[0030]
Furthermore, those obtained by adding inorganic fibers to the various thermoplastic resins described above can also be used. Here, as the inorganic fiber, selected from the group consisting of glass fiber, carbon fiber, wollastonite, aluminum borate whisker fiber, potassium titanate whisker fiber, basic magnesium sulfate whisker fiber, calcium silicate whisker fiber and calcium sulfate whisker fiber. At least one type of material may be used.
[0031]
The weight percentage of the inorganic fibers in the thermoplastic resin is, for example, 5% by weight to 50% by weight. When importance is placed on the strength of the molded product, the average length of the inorganic fibers is set to 5 μm to 5 mm, preferably 10 μm to 0.4 mm. It is desirable that the thickness be 0.4 mm, more preferably 5 μm to 0.2 mm, and still more preferably 5 μm to 0.1 mm. In these cases, the average diameter of the inorganic fibers is desirably 0.01 μm to 15 μm, preferably 0.02 μm to 10 μm, and more preferably 0.05 μm to 5 μm.
[0032]
The average length of the inorganic fibers means the weight average length. The length of the inorganic fiber can be measured by dissolving the resin component by immersing a molding pellet or a molded article containing the inorganic fiber in a liquid in which the thermoplastic resin is dissolved, or by using a glass fiber at a high temperature of 600 ° C. or more. And the residual inorganic fibers can be observed and measured with a microscope or the like. Usually, the length of the inorganic fiber is obtained by photographing the inorganic fiber and measuring the length by a person, or using a dedicated fiber length measuring device. It is preferable to use the weight average length because the number average length has too great an effect of the finely broken fibers. In the measurement of the weight average length, the measurement is performed except for fragments of inorganic fibers that are too small and crushed. If the length is shorter than twice the nominal diameter of the inorganic fiber, the measurement becomes difficult. For example, an inorganic fiber having a length twice or more the nominal diameter is measured.
[0033]
In the injection molding method according to the first to third aspects of the present invention, P ₁ > P ₂ > 0 and P ₂ '> P ₁ Under the condition of '> 0, since the molten thermoplastic resin flows in the cavity, the molten thermoplastic resin in the cavity is always in a state where opposing pressures are applied from the first pressing means and the second pressing means. As a result, it is possible to mold a molded article having excellent appearance, excellent dimensional accuracy, no sink marks, and small residual stress.
[0034]
【Example】
Hereinafter, the present invention will be described based on embodiments with reference to the drawings.
[0035]
(Example 1)
Example 1 Example 1 relates to the injection molding method for a molded article according to the first aspect of the present invention.
[0036]
FIG. 1 is a conceptual diagram of a mold assembly according to the first embodiment. The mold assembly 10 according to the first embodiment includes (A) a first resin flow path 14A and a second resin flow path 14B that communicate with the injection cylinder 11,
(B) cavity 18,
(C) a first gate portion 15A communicating with the first resin flow path 14A and opening to the cavity 18;
(D) a second gate portion 15B communicating with the second resin flow path 14B and opening to the cavity 18,
(E) first pressurizing means for applying pressure to the molten thermoplastic resin in the first resin flow path 14A, and
(F) second pressurizing means for applying pressure to the molten thermoplastic resin in the second resin flow path 14B;
It has.
[0037]
More specifically, the mold assembly 10 has a fixed mold part 12 and a movable mold part 13, and the cavity 18 is formed by clamping the fixed mold part 12 and the movable mold part 13. You. The first resin flow path 14A and the second resin flow path 14B are provided in the fixed mold part 12, and are constituted by so-called hot runners. The first pressurizing means includes a hydraulic cylinder 21A and a piston 20A attached to the hydraulic cylinder 21A and moved (slid) back and forth in the first resin flow path 14A based on the operation of the hydraulic cylinder 21A. ing. On the other hand, the second pressurizing means includes a hydraulic cylinder 21B and a piston 20B attached to the hydraulic cylinder 21B and moved (slid) back and forth in the second resin flow path 14B based on the operation of the hydraulic cylinder 21B. ing. The first gate unit 15A and the second gate unit 15B have an open type structure. When the length of the molded product in the longitudinal direction is L, the distance from the portion 18A of the cavity 18 where one end in the longitudinal direction of the molded product is to be formed to the first gate portion 15A is 0.05L. The distance from the portion 18B of the cavity 18 where the other end in the longitudinal direction of the molded product is to be formed to the second gate portion 15B is 0.05L.
[0038]
Hereinafter, the injection molding method of the first embodiment will be described with reference to FIGS. 2 to 4 which are conceptual diagrams of a mold assembly and the like. In the first embodiment, 20% by weight of glass fiber is used as a thermoplastic resin. Using the added polycarbonate resin (NOVAREX 7025GR20 manufactured by Mitsubishi Engineering-Plastics Co., Ltd.), a molded product having a length (L) of 300 mm, a width (W) of 15 mm, and a thickness of 3 mm (volume V = 13.5 cm) ³ ) Was molded. 2 to 4, illustration of the injection cylinder 11 is omitted.
[0039]
[Step-100]
First, the thermoplastic resin 30 plasticized and melted by the injection cylinder 11 is injected into the cavity 18 through the first resin flow path 14A and the first gate portion 15A, and the inside of the cavity 18 is melted thermoplastic resin. Then, the second gate portion 15B and the second resin flow path 14B were filled with the molten thermoplastic resin 30 (see FIG. 2). The injection conditions are illustrated in Table 1 below. At the time of injection of the molten thermoplastic resin 30, the piston 20A constituting the first pressurizing means is located at the backward end, and the piston 20B constituting the second pressurizing means is located at the forward end. The hydraulic cylinders 21A and 21B are controlled so that the positions of the pistons 20A and 20B do not change due to the injection of the molten thermoplastic resin 30.
[0040]
[Table 1]
Resin temperature: 300 ° C
Mold temperature: 80 ° C
Injection pressure: 1.5 × 10 ⁸ Pa
Injection time: 3.5 seconds
[0041]
[Step-110]
Simultaneously with the completion of the injection of the molten thermoplastic resin 30 into the cavity 18, the hydraulic cylinders 21A and 21B are operated to move the piston 20A to the forward end, and in synchronization with the movement of the piston 20A, move the piston 20B to the reverse end. Moved to At this time, the pressure P is applied to the molten thermoplastic resin 30 in the first resin flow path 14A by the first pressurizing means (specifically, the piston 20A). ₁ (= 9 × 10 ⁷ Pa), and the pressure P is applied to the molten thermoplastic resin 30 in the second resin flow path 14B by the second pressing means (specifically, the piston 20B). ₂ (= 2 × 10 ⁷ By applying Pa), a shearing force is applied to the molten thermoplastic resin 30 in the cavity 18 in a direction from the first gate portion 15A to the second gate portion 15B, so that the molten thermoplastic resin 30 in the cavity 18 is removed. The fluid was caused to flow from the first gate 15A toward the second gate 15B. This state is shown in FIG. The movement time of the pistons 20A and 20B was 1.5 seconds. The molten thermoplastic resin 30 in the cavity 18 is about 5 cm ³ , In the direction from the first gate portion 15A to the second gate portion 15B.
[0042]
[Step-120]
As soon as the piston 20A has reached the forward end and the piston 20B has reached the reverse end (see FIG. 3), the first pressurizing means (specifically, the first pressurizing means) is applied to the molten thermoplastic resin 30 in the first resin flow path 14A. , The pressure P due to the piston 20A) ₁ '(= 2 × 10 ⁷ Pa), and the pressure P is applied to the molten thermoplastic resin 30 in the second resin flow path 14B by the second pressing means (specifically, the piston 20B). ₂ '(= 9 × 10 ⁷ By applying Pa), a shearing force is applied to the molten thermoplastic resin 30 in the cavity 18 in a direction from the second gate portion 15B toward the first gate portion 15A, so that the molten thermoplastic resin 30 in the cavity 18 is removed. The fluid was caused to flow in a direction from the second gate portion 15B to the first gate portion 15A.
This state is shown in FIG. The movement time of the pistons 20A and 20B was 1.5 seconds.
The molten thermoplastic resin 30 in the cavity 18 is about 5 cm ³ , And moved in the direction from the second gate portion 15B to the first gate portion 15A.
[0043]
[Step-130]
As soon as the piston 20A reaches the backward end and the piston 20B reaches the forward end (see FIG. 4), [Step-110] and [Step-120] are immediately repeated. Thus, when [Step-110] and [Step-120] were performed as one operation, five operations were performed. The time required for the five operations is 15 seconds.
[0044]
[Step-140]
Thereafter, the pressure P is applied to the molten thermoplastic resin 30 in the cavity 18 by the first pressing means and the second pressing means (specifically, the pistons 20A and 20B). ₀ (= 5 × 10 ⁷ Pa) was added. Then, the molten thermoplastic resin 30 in the cavity was cooled and solidified. Pressure P ₀ Was applied for 5 seconds, and then the operation of applying pressure to the molten thermoplastic resin 30 in the cavity 18 by the first pressing means and the second pressing means was stopped. After the elapse of 20 seconds, the mold assembly was opened and the molded product was taken out.
[0045]
The molded article had excellent appearance and excellent dimensional accuracy, and the glass fibers were oriented in the longitudinal direction of the molded article. No sink marks or warpage were observed. Table 3 shows the results of measuring the flatness of the molded product. Note that the flatness is an average value measured at 14 points on the surface of the molded product using a three-dimensional measuring device Geopak700 manufactured by Mitutoyo Corporation.
[0046]
(Comparative Example 1A)
In Comparative Example 1A, immediately after performing [Step-100] of Example 1, the injection cylinder 11 immediately held the molten thermoplastic resin 30 in the cavity 18 under pressure (5 × 10 5). ⁷ Pa) was added for 20 seconds. After the elapse of 20 seconds, the mold assembly was opened and the molded product was taken out.
[0047]
Observation of the obtained molded product showed that the glass fibers were oriented in the longitudinal direction of the molded product. However, the glass fibers were not sufficiently dispersed in the molten thermoplastic resin 30 in the cavity 18 near the second gate portion 15B, which is the end of the resin flow. Since a large holding pressure was not applied, sink and warp occurred in a portion of the molded product corresponding to the vicinity of the second gate portion 15B. Table 3 shows the results of measuring the flatness of the molded product.
[0048]
(Comparative Example 1B)
In Comparative Example 1B, after [Step-100] of Example 1 was performed, [Step-110] to [Step-140] were further performed. However, in [Step-110] to [Step-130], P ₁ = 9 × 10 ⁷ Pa, P ₂ = 0Pa, P ₂ '= 9 × 10 ⁷ Pa, P ₁ '= 0 Pa.
[0049]
When the obtained molded product was observed, the glass fibers were oriented in the longitudinal direction of the molded product. Had occurred. Table 3 shows the results of measuring the flatness of the molded product.
[0050]
(Example 2)
Example 2 Example 2 relates to the injection molding method according to the first aspect of the present invention and the mold assembly according to the first aspect of the present invention. The mold assembly 10A of the second embodiment whose conceptual diagram is shown in FIG. 5 is different from the mold assembly 10 of the first embodiment in that the second gate portion 15B is provided with opening / closing means. The first gate unit 15A is also provided with opening / closing means. Other structures are the same as those of the mold assembly of the first embodiment. Here, the opening / closing means includes shut-off pins 16A and 16B and hydraulic cylinders 17A and 17B, and the shut-off pins 16A and 16B open and close the first and second gate portions 15A and 15B by operating the hydraulic cylinders 17A and 17B. The valve gate is configured as follows. FIG. 5 shows a state in which the first gate unit 15A is opened and the second gate unit 15B is closed. The first resin flow path 14A and the second resin flow path 14B are constituted by hot runners, but detailed illustration is omitted.
[0051]
Hereinafter, the injection molding method of the second embodiment will be described with reference to FIGS. 6 to 9 which are conceptual diagrams of a mold assembly and the like. In the second embodiment, 20% by weight of a glass fiber is used as a thermoplastic resin. Using the added modified PPE resin (Mitsubishi Engineering Plastics Co., Ltd., Iupiace GH20), a molded product having a length (L) of 200 mm, a width (W) of 10 mm, and a thickness of 3 mm (volume V = 6 cm) ³ ) Was molded. 6 to 9, illustration of the injection cylinder 11 is omitted. 6 to 9, the molten thermoplastic resin left in the second resin flow path 14B by the previous injection molding is indicated by reference numeral 30A.
[0052]
[Step-200]
First, the thermoplastic resin 30 plasticized and melted by the injection cylinder 11 is injected into the cavity 18 through the first resin flow path 14A and the first gate portion 15A, and the inside of the cavity 18 is melted thermoplastic resin. Completely filled at 30 (see FIG. 6). The injection conditions are illustrated in Table 2 below. At the time of injection of the molten thermoplastic resin 30, the piston 20A constituting the first pressurizing means is located at the backward end, and the piston 20B constituting the second pressurizing means is located at the forward end. The hydraulic cylinder 21A is controlled so that the injection of the molten thermoplastic resin 30 does not change the position of the piston 20A. The first gate unit 15A is open, and the second gate unit 15B is closed.
[0053]
[Table 2]
Resin temperature: 280 ° C
Mold temperature: 70 ° C
Injection pressure: 1.2 × 10 ⁸ Pa
Injection time: 4.2 seconds
[0054]
[Step-210]
Simultaneously with the completion of the injection of the molten thermoplastic resin 30 into the cavity 18, the hydraulic cylinder 17B was operated to retract the shut-off pin 16B, and the second gate 15B was opened (see FIG. 7). At the same time, the hydraulic cylinders 21A and 21B were operated to move the piston 20A to the forward end, and in synchronization with the movement of the piston 20A, moved the piston 20B to the reverse end. At this time, the pressure P is applied to the molten thermoplastic resin 30 in the first resin flow path 14A by the first pressurizing means (specifically, the piston 20A). ₁ (= 9 × 10 ⁷ Pa), and the pressure P is applied to the molten thermoplastic resin 30, 30A in the second resin flow path 14B by the second pressing means (specifically, the piston 20B). ₂ (= 2 × 10 ⁷ By applying Pa), a shearing force is applied to the molten thermoplastic resin 30 in the cavity 18 in a direction from the first gate portion 15A to the second gate portion 15B, so that the molten thermoplastic resin 30 in the cavity 18 is removed. The fluid was caused to flow from the first gate 15A toward the second gate 15B. This state is shown in FIG. The movement time of the pistons 20A and 20B was 1.5 seconds. The molten thermoplastic resin 30 in the cavity 18 is about 3 cm ³ , In the direction from the first gate portion 15A to the second gate portion 15B.
[0055]
[Step-220]
As soon as the piston 20A reaches the forward end and the piston 20B reaches the reverse end (see FIG. 8), the first pressurizing means (specifically, the first pressurizing means) is applied to the molten thermoplastic resin 30 in the first resin flow path 14A. , The pressure P due to the piston 20A) ₁ '(= 2 × 10 ⁷ Pa), and the pressure P is applied to the molten thermoplastic resin 30, 30A in the second resin flow path 14B by the second pressing means (specifically, the piston 20B). ₂ '(= 9 × 10 ⁷ By applying Pa), a shearing force is applied to the molten thermoplastic resin 30 in the cavity 18 in a direction from the second gate portion 15B toward the first gate portion 15A, so that the molten thermoplastic resin 30 in the cavity 18 is removed. The fluid was caused to flow in a direction from the second gate portion 15B to the first gate portion 15A. This state is shown in FIG. The movement time of the pistons 20A and 20B was 1.5 seconds. The molten thermoplastic resin 30 in the cavity 18 is about 3 cm ³ , And moved in the direction from the second gate portion 15B to the first gate portion 15A.
[0056]
[Step-230]
As soon as the piston 20A reaches the backward end and the piston 20B reaches the forward end (see FIG. 9), [Step-210] and [Step-220] are immediately repeated. Thus, when [Step-210] and [Step-220] were performed as one operation, five operations were performed. The time required for the five operations is 15 seconds.
[0057]
[Step-240]
Thereafter, the pressure P is applied to the molten thermoplastic resin 30 in the cavity 18 by the first pressing means and the second pressing means (specifically, the pistons 20A and 20B). ₀ (= 4 × 10 ⁷ Pa) was added. Then, the molten thermoplastic resin 30 in the cavity was cooled and solidified. Pressure P ₀ Was applied for 15 seconds, and then the operation of applying pressure to the molten thermoplastic resin 30 in the cavity 18 by the first pressing means and the second pressing means was stopped. After the elapse of 20 seconds, the mold assembly was opened and the molded product was taken out.
[0058]
The molded article had excellent appearance and excellent dimensional accuracy, and the glass fibers were oriented in the longitudinal direction of the molded article. No sink marks or warpage were observed. Table 3 shows the results of measuring the flatness of the molded product.
[0059]
(Comparative Example 2A)
In Comparative Example 2A, after performing [Step-200] of Example 2, the injection cylinder 11 is used to hold the molten thermoplastic resin 30 in the cavity 18 under pressure (4 × 10 4). ⁷ Pa) was added for 15 seconds. After the elapse of 20 seconds, the mold assembly was opened and the molded product was taken out.
[0060]
Observation of the obtained molded product showed that the glass fibers were oriented in the longitudinal direction of the molded product. However, the glass fibers were not sufficiently dispersed in the molten thermoplastic resin 30 in the cavity 18 near the second gate portion 15B, which is the end of the resin flow. Since a large holding pressure was not applied, sink and warp occurred in a portion of the molded product corresponding to the vicinity of the second gate portion 15B. Table 3 shows the results of measuring the flatness of the molded product.
[0061]
(Comparative Example 2B)
In Comparative Example 2B, after [Step-200] of Example 2 was performed, [Step-210] to [Step-240] were further performed. However, in [Step-210] to [Step-230], P ₁ = 9 × 10 ⁷ Pa, P ₂ = 0Pa, P ₂ '= 9 × 10 ⁷ Pa, P ₁ '= 0 Pa.
[0062]
When the obtained molded product was observed, the glass fibers were oriented in the longitudinal direction of the molded product. Had occurred. Table 3 shows the results of measuring the flatness of the molded product.
[0063]
(Example 3)
Example 3 Example 3 relates to an injection molding method for a molded article according to the second aspect of the present invention and a mold assembly according to the second aspect of the present invention.
[0064]
FIG. 10 is a conceptual diagram of a mold assembly according to the third embodiment. The mold assembly 10B according to the third embodiment includes:
(A) a resin flow path 14 communicating with the injection cylinder 11,
(B) cavity 18,
(C) a gate portion 15 communicating with the resin flow path 14 and opening to the cavity 18;
(D) a resin reservoir 44 communicating with the cavity 18,
(E) first pressurizing means for applying pressure to the molten thermoplastic resin in the resin flow path 14;
(F) second pressurizing means for applying pressure to the molten thermoplastic resin in the resin reservoir 44,
It has.
[0065]
More specifically, the mold assembly 10B has a fixed mold portion 12 and a movable mold portion 13, and the cavity 18 is formed by clamping the fixed mold portion 12 and the movable mold portion 13. You. The resin flow path 14 and the resin reservoir 44 are provided in the fixed mold part 12, and the resin flow path 14 is formed of a so-called hot runner. The first pressurizing means includes a hydraulic cylinder 21A and a piston 20A attached to the hydraulic cylinder 21A and moved (slid) back and forth in the resin flow path 14 based on the operation of the hydraulic cylinder 21A. . On the other hand, the second pressurizing means includes a hydraulic cylinder 21B and a piston 20B attached to the hydraulic cylinder 21B and moved (slid) back and forth in the resin reservoir 44 based on the operation of the hydraulic cylinder 21B. The gate section 15 has a direct structure. When the length of the molded product in the longitudinal direction is L, the distance from the portion 18A of the cavity 18 where one end in the longitudinal direction of the molded product is to be formed to the gate portion 15 is 0.05L. The distance from the portion 18B of the cavity 18 where the other end in the longitudinal direction of the article is to be formed to the opening of the resin reservoir 44 is 0.05L.
[0066]
Hereinafter, the injection molding method of the third embodiment will be described with reference to FIGS. 11 to 13 which are conceptual diagrams of a mold assembly and the like. In the third embodiment, the same thermoplastic resin as that of the first embodiment is used. A molded product having the same shape as in Example 1 was molded. Note that the injection cylinder 11 is not shown in FIGS.
[0067]
[Step-300]
First, the thermoplastic resin 30 plasticized and melted by the injection cylinder 11 is injected into the cavity 18 via the resin flow path 14 and the gate portion 15, and the inside of the cavity 18 is completely filled with the molten thermoplastic resin 30. After filling, the resin pool 44 was further filled with the molten thermoplastic resin 30 (see FIG. 11). The injection conditions were the same as those shown in Table 1. At the time of injection of the molten thermoplastic resin 30, the piston 20A constituting the first pressurizing means is located at the backward end, and the piston 20B constituting the second pressurizing means is located at the forward end. The hydraulic cylinders 21A and 21B are controlled so that the positions of the pistons 20A and 20B do not change due to the injection of the molten thermoplastic resin 30.
[0068]
[Step-310]
Simultaneously with the completion of the injection of the molten thermoplastic resin 30 into the cavity 18, the hydraulic cylinders 21A and 21B are operated to move the piston 20A to the forward end, and in synchronization with the movement of the piston 20A, move the piston 20B to the reverse end. Moved to At this time, the pressure P is applied to the molten thermoplastic resin 30 in the resin flow path 14 by the first pressing means (specifically, the piston 20A). ₁ (= 9 × 10 ⁷ Pa), and the pressure P is applied to the molten thermoplastic resin 30 in the resin sump 44 by the second pressing means (specifically, the piston 20B). ₂ (= 2 × 10 ⁷ By applying Pa), a shearing force is applied to the molten thermoplastic resin 30 in the cavity 18 in a direction from the gate portion 15 toward the resin reservoir 44, and the molten thermoplastic resin 30 in the cavity 18 is removed from the gate portion 15. It was made to flow in the direction toward the resin pool 44. This state is shown in FIG. The movement time of the pistons 20A and 20B was 1.5 seconds. The molten thermoplastic resin 30 in the cavity 18 is about 5 cm ³ , And moved in a direction from the gate portion 15 toward the resin reservoir 44.
[0069]
[Step-320]
As soon as the piston 20A reaches the forward end and the piston 20B reaches the backward end (see FIG. 12), the first pressurizing means (specifically, the piston 20A) the pressure P ₁ '(= 2 × 10 ⁷ Pa), and the pressure P is applied to the molten thermoplastic resin 30 in the resin sump 44 by the second pressing means (specifically, the piston 20B). ₂ '(= 9 × 10 ⁷ By applying Pa), a shearing force is applied to the molten thermoplastic resin 30 in the cavity 18 in a direction from the resin reservoir 44 toward the gate portion 15, and the molten thermoplastic resin 30 in the cavity 18 is removed from the resin reservoir 44. It was made to flow in the direction toward the gate section 15. This state is shown in FIG. The movement time of the pistons 20A and 20B was 1.5 seconds. The molten thermoplastic resin 30 in the cavity 18 is about 5 cm ³ , And moved in a direction from the resin reservoir 44 to the gate portion 15.
[0070]
[Step-330]
As soon as the piston 20A reaches the backward end and the piston 20B reaches the forward end (see FIG. 13), [Step-310] and [Step-320] are immediately repeated. Thus, when [Step-310] and [Step-320] were set to one operation, five operations were performed. The time required for the five operations is 15 seconds.
[0071]
[Step-340]
Thereafter, the pressure P is applied to the molten thermoplastic resin 30 in the cavity 18 by the first pressing means and the second pressing means (specifically, the pistons 20A and 20B). ₀ (= 5 × 10 ⁷ Pa) was added. Then, the molten thermoplastic resin 30 in the cavity was cooled and solidified. Pressure P ₀ Was applied for 5 seconds, and then the operation of applying pressure to the molten thermoplastic resin 30 in the cavity 18 by the first pressing means and the second pressing means was stopped. After the elapse of 20 seconds, the mold assembly was opened and the molded product was taken out.
[0072]
The molded article had excellent appearance and excellent dimensional accuracy, and the glass fibers were oriented in the longitudinal direction of the molded article. No sink marks or warpage were observed. Table 3 shows the results of measuring the flatness of the molded product.
[0073]
(Comparative Example 3A)
In Comparative Example 3A, immediately after performing [Step-300] of Example 3, the injection cylinder 11 was used to hold the molten thermoplastic resin 30 in the cavity 18 with a pressure (5 × 10 3). ⁷ Pa) was added for 20 seconds. After the elapse of 20 seconds, the mold assembly was opened and the molded product was taken out.
[0074]
When the obtained molded article was observed, the glass fibers were oriented in the longitudinal direction of the molded article. However, the glass fiber was sufficiently retained in the molten thermoplastic resin 30 in the cavity 18 near the resin pool 44, which is the terminal of the resin flow. Since no pressure was applied, sink and warp occurred in the portion of the molded product corresponding to the vicinity of the resin reservoir 44. Table 3 shows the results of measuring the flatness of the molded product.
[0075]
(Comparative Example 3B)
In Comparative Example 3B, after [Step-300] of Example 3 was performed, [Step-310] to [Step-340] were further performed. However, in [Step-310] to [Step-330], P ₁ = 9 × 10 ⁷ Pa, P ₂ = 0Pa, P ₂ '= 9 × 10 ⁷ Pa, P ₁ '= 0 Pa.
[0076]
Observation of the obtained molded product showed that the glass fibers were oriented in the longitudinal direction of the molded product, but sink and warpage occurred in the portion of the molded product corresponding to the vicinity of the gate portion 15 and the resin reservoir 44. . Table 3 shows the results of measuring the flatness of the molded product.
[0077]
(Example 4)
The fourth embodiment is a modification of the third embodiment. The mold assembly 10C of the fourth embodiment whose conceptual diagram is shown in FIG. 14 is different from the mold assembly 10B of the third embodiment in that the resin reservoir 44 is provided with opening / closing means. The gate unit 15 is also provided with opening / closing means.
Other structures are the same as those of the mold assembly of the third embodiment. Here, the opening / closing means has the same configuration and structure as described in the second embodiment. FIG. 14 shows a state in which the gate portion 15 is opened and the resin reservoir 44 is closed. The resin flow path 14 is composed of a hot runner and has a mechanism for also melting the thermoplastic resin in the resin reservoir 44, but is not shown in detail.
[0078]
Hereinafter, the injection molding method of the fourth embodiment will be described with reference to FIGS. 15 to 18 which are conceptual diagrams of a mold assembly and the like. In the fourth embodiment, the same thermoplastic resin as in the second embodiment is used. A molded product having the same shape as in Example 2 was molded. 15 to 18, the illustration of the injection cylinder 11 is omitted. 15 to 18, the molten thermoplastic resin left in the second resin reservoir 44 by the previous injection molding is indicated by reference numeral 30A.
[0079]
[Step-400]
First, the thermoplastic resin 30 plasticized and melted by the injection cylinder 11 is injected into the cavity 18 via the resin flow path 14 and the gate portion 15, and the inside of the cavity 18 is completely filled with the molten thermoplastic resin 30. Filled (see FIG. 15). The injection conditions were the same as shown in Table 2. At the time of injection of the molten thermoplastic resin 30, the piston 20A constituting the first pressurizing means is located at the backward end, and the piston 20B constituting the second pressurizing means is located at the forward end. The hydraulic cylinder 21A is controlled so that the injection of the molten thermoplastic resin 30 does not change the position of the piston 20A. Further, the gate portion 15 is opened, and the resin reservoir 44 is in a closed state.
[0080]
[Step-410]
Simultaneously with the completion of the injection of the molten thermoplastic resin 30 into the cavity 18, the hydraulic cylinder 47 was operated to retract the shut-off pin 46, and the resin reservoir 44 was communicated with the cavity 18 (see FIG. 16). At the same time, the hydraulic cylinders 21A and 21B were operated to move the piston 20A to the forward end, and in synchronization with the movement of the piston 20A, moved the piston 20B to the reverse end. At this time, the pressure P is applied to the molten thermoplastic resin 30 in the resin flow path 14 by the first pressing means (specifically, the piston 20A). ₁ (= 9 × 10 ⁷ Pa), and a pressure P is applied to the molten thermoplastic resin 30, 30A in the resin sump 44 by the second pressing means (specifically, the piston 20B). ₂ (= 2 × 10 ⁷ By applying Pa), a shearing force is applied to the molten thermoplastic resin 30 in the cavity 18 in a direction from the gate portion 15 toward the resin reservoir 44, and the molten thermoplastic resin 30 in the cavity 18 is removed from the gate portion 15. It was made to flow in the direction toward the resin pool 44. This state is shown in FIG. The movement time of the pistons 20A and 20B was 1.5 seconds. The molten thermoplastic resin 30 in the cavity 18 is about 2 cm ³ , And moved in a direction from the gate portion 15 toward the resin reservoir 44.
[0081]
[Step-420]
As soon as the piston 20A reaches the forward end and the piston 20B reaches the reverse end (see FIG. 17), the first pressing means (specifically, the piston 20A) the pressure P ₁ '(= 2 × 10 ⁷ Pa), and a pressure P is applied to the molten thermoplastic resin 30, 30A in the resin sump 44 by the second pressing means (specifically, the piston 20B). ₂ '(= 9 × 10 ⁷ By applying Pa), a shearing force is applied to the molten thermoplastic resin 30 in the cavity 18 in a direction from the resin reservoir 44 toward the gate portion 15, and the molten thermoplastic resin 30 in the cavity 18 is removed from the resin reservoir 44. It was made to flow in the direction toward the gate section 15. This state is shown in FIG. The movement time of the pistons 20A and 20B was 1.5 seconds. The molten thermoplastic resin 30 in the cavity 18 is about 2 cm ³ , And moved in a direction from the resin reservoir 44 to the gate portion 15.
[0082]
[Step-430]
As soon as the piston 20A reaches the backward end and the piston 20B reaches the forward end (see FIG. 18), [Step-410] and [Step-420] are immediately repeated. Thus, when [Step-410] and [Step-420] were performed as one operation, five operations were performed. The time required for the five operations is 15 seconds.
[0083]
[Step-440]
Thereafter, the pressure P is applied to the molten thermoplastic resin 30 in the cavity 18 by the first pressing means and the second pressing means (specifically, the pistons 20A and 20B). ₀ (= 4 × 10 ⁷ Pa) was added. Then, the molten thermoplastic resin 30 in the cavity was cooled and solidified. Pressure P ₀ Was applied for 15 seconds, and then the operation of applying pressure to the molten thermoplastic resin 30 in the cavity 18 by the first pressing means and the second pressing means was stopped. After the elapse of 20 seconds, the mold assembly was opened and the molded product was taken out.
[0084]
The molded article had excellent appearance and excellent dimensional accuracy, and the glass fibers were oriented in the longitudinal direction of the molded article. No sink marks or warpage were observed. Table 3 shows the results of measuring the flatness of the molded product.
[0085]
(Comparative Example 4A)
In Comparative Example 4A, after performing [Step-400] of Example 4, the injection cylinder 11 holds the molten thermoplastic resin 30 in the cavity 18 under pressure (4 × 10 4). ⁷ Pa) was added for 15 seconds. After the elapse of 20 seconds, the mold assembly was opened and the molded product was taken out.
[0086]
When the obtained molded article was observed, the glass fibers were oriented in the longitudinal direction of the molded article. However, the glass fiber was sufficiently retained in the molten thermoplastic resin 30 in the cavity 18 near the resin pool 44, which is the terminal of the resin flow. Since no pressure was applied, sink and warp occurred in the portion of the molded product corresponding to the vicinity of the resin reservoir 44. Table 3 shows the results of measuring the flatness of the molded product.
[0087]
(Comparative Example 4B)
In Comparative Example 4B, after [Step-400] of Example 4 was performed, [Step-410] to [Step-440] were further performed. However, in [Step-410] to [Step-430], P ₁ = 9 × 10 ⁷ Pa, P ₂ = 0Pa, P ₂ '= 9 × 10 ⁷ Pa, P ₁ '= 0 Pa.
[0088]
Observation of the obtained molded product showed that the glass fibers were oriented in the longitudinal direction of the molded product, but sink and warpage occurred in the portion of the molded product corresponding to the vicinity of the gate portion 15 and the resin reservoir 44. . Table 3 shows the results of measuring the flatness of the molded product.
[0089]
(Example 5)
Example 5 Example 5 relates to the injection molding method for a molded article according to the third aspect of the present invention and the mold assembly according to the third aspect of the present invention.
[0090]
FIG. 19 shows a conceptual diagram of the mold assembly of the fifth embodiment. The mold assembly 10D of the fifth embodiment includes:
(A) a resin flow path 14 communicating with the injection cylinder 11,
(B) cavity 18,
(C) a gate portion 15 communicating with the resin flow path 14 and opening to the cavity 18;
(D) a first resin reservoir 44A communicating with the cavity 18,
(E) a second resin reservoir 44B communicating with the cavity 18,
(F) first pressurizing means for applying pressure to the molten thermoplastic resin in the first resin reservoir 44A, and
(G) a second pressing means for applying pressure to the molten thermoplastic resin in the second resin reservoir 44B;
It has.
[0091]
More specifically, the mold assembly 10D has a fixed mold part 12 and a movable mold part 13, and a cavity 18 is formed by clamping the fixed mold part 12 and the movable mold part 13. You. The resin flow path 14, the first resin pool 44A and the second resin pool 44B are provided in the fixed mold part 12, and the resin flow path 14 is composed of a so-called sprue and cold runner. The first pressurizing means includes a hydraulic cylinder 21A and a piston 20A attached to the hydraulic cylinder 21A and moved (slid) back and forth in the first resin reservoir 44A based on the operation of the hydraulic cylinder 21A. I have. On the other hand, the second pressurizing means includes a hydraulic cylinder 21B and a piston 20B attached to the hydraulic cylinder 21B and moved (slid) back and forth in the second resin reservoir 44B based on the operation of the hydraulic cylinder 21B. I have. The gate section 15 has a direct structure. When the length of the molded product in the longitudinal direction is L, the distance from the portion 18A of the cavity 18 where one end in the longitudinal direction of the molded product is to be formed to the opening of the first resin reservoir 44A is 0.1 mm. The distance from the portion 18B of the cavity 18 where the other end in the longitudinal direction of the molded product is to be formed to the opening of the second resin reservoir 44B is 0.05L.
[0092]
Hereinafter, the injection molding method of the fifth embodiment will be described with reference to FIGS. 20 to 22 which are conceptual diagrams of a mold assembly and the like. In the fifth embodiment, the same thermoplastic resin as that of the first embodiment is used. A molded product having the same shape as in Example 1 was molded. 20 to 22, illustration of the injection cylinder 11 is omitted.
[0093]
[Step-500]
First, the thermoplastic resin 30 plasticized and melted by the injection cylinder 11 is injected into the cavity 18 via the resin flow path 14 and the gate portion 15, and the inside of the cavity 18 is completely filled with the molten thermoplastic resin 30. The first resin reservoir 44A and the second resin reservoir 44B were filled with the molten thermoplastic resin 30 (see FIG. 20). The injection conditions were the same as those shown in Table 1. At the time of injection of the molten thermoplastic resin 30, the piston 20A constituting the first pressurizing means is located at the backward end, and the piston 20B constituting the second pressurizing means is located at the forward end. The hydraulic cylinders 21A and 21B are controlled so that the positions of the pistons 20A and 20B do not change due to the injection of the molten thermoplastic resin 30.
[0094]
[Step-510]
Simultaneously with the completion of the injection of the molten thermoplastic resin 30 into the cavity 18, the hydraulic cylinders 21A and 21B are operated to move the piston 20A to the forward end, and in synchronization with the movement of the piston 20A, move the piston 20B to the reverse end. Moved to At this time, the pressure P is applied to the molten thermoplastic resin 30 in the first resin reservoir 44A by the first pressurizing means (specifically, the piston 20A). ₁ (= 9 × 10 ⁷ Pa), and the pressure P is applied to the molten thermoplastic resin 30 in the second resin reservoir 44B by the second pressing means (specifically, the piston 20B). ₂ (= 2 × 10 ⁷ By applying Pa), a shearing force is applied to the molten thermoplastic resin 30 in the cavity 18 in a direction from the first resin reservoir 44A to the second resin reservoir 44B, and the molten thermoplastic resin 30 in the cavity 18 is removed. It was made to flow in the direction from the first resin reservoir 44A to the second resin reservoir 44B. This state is shown in FIG. The movement time of the pistons 20A and 20B was 1.5 seconds. The molten thermoplastic resin 30 in the cavity 18 is about 5 cm ³ , And moved in a direction from the first resin reservoir 44A to the second resin reservoir 44B. Further, pressure was applied to the molten thermoplastic resin 30 in the gate portion 15 such that the molten thermoplastic resin 30 did not flow backward from the cavity 18 to the gate portion 15.
[0095]
[Step-520]
As soon as the piston 20A reaches the forward end and the piston 20B reaches the reverse end (see FIG. 21), the first pressing means (specifically, the first pressurizing means) is applied to the molten thermoplastic resin 30 in the first resin reservoir 44A. Pressure P by piston 20A) ₁ '(= 2 × 10 ⁷ Pa), and the pressure P is applied to the molten thermoplastic resin 30 in the second resin reservoir 44B by the second pressing means (specifically, the piston 20B). ₂ '(= 9 × 10 ⁷ By applying Pa), a shearing force is applied to the molten thermoplastic resin 30 in the cavity 18 in a direction from the second resin reservoir 44B to the first resin reservoir 44A, so that the molten thermoplastic resin 30 in the cavity 18 is removed. It was made to flow in the direction from the second resin reservoir 44B to the first resin reservoir 44A. This state is shown in FIG. The movement time of the pistons 20A and 20B was 1.5 seconds. The molten thermoplastic resin 30 in the cavity 18 is about 5 cm ³ , And moved in the direction from the second resin reservoir 44 to the first resin reservoir 44A. Further, pressure was applied to the molten thermoplastic resin 30 in the gate portion 15 such that the molten thermoplastic resin 30 did not flow backward from the cavity 18 to the gate portion 15.
[0096]
[Step-530]
As soon as the piston 20A reaches the backward end and the piston 20B reaches the forward end (see FIG. 22), [Step-510] and [Step-520] are immediately repeated in sequence. Thus, when [Step-510] and [Step-520] were set as one operation, five operations were performed. The time required for the five operations is 15 seconds.
[0097]
[Step-540]
Thereafter, the pressure P is applied to the molten thermoplastic resin 30 in the cavity 18 by the first pressing means and the second pressing means (specifically, the pistons 20A and 20B). ₀ (= 5 × 10 ⁷ Pa) was added. Then, the molten thermoplastic resin 30 in the cavity was cooled and solidified. Pressure P ₀ Was applied for 5 seconds, and then the operation of applying pressure to the molten thermoplastic resin 30 in the cavity 18 by the first pressing means and the second pressing means was stopped. After the elapse of 20 seconds, the mold assembly was opened and the molded product was taken out.
[0098]
The molded article had excellent appearance and excellent dimensional accuracy, and the glass fibers were oriented in the longitudinal direction of the molded article. No sink marks or warpage were observed. Table 3 shows the results of measuring the flatness of the molded product.
[0099]
(Comparative Example 5A)
In Comparative Example 5A, immediately after performing [Step-500] of Example 5, the injection cylinder 11 was used to hold the molten thermoplastic resin 30 in the cavity 18 under pressure (5 × 10 5). ⁷ Pa) was added for 20 seconds. After the elapse of 20 seconds, the mold assembly was opened and the molded product was taken out.
[0100]
Observation of the obtained molded product showed that the glass fibers were oriented in the longitudinal direction of the molded product. Since sufficient holding pressure was not applied to the thermoplastic resin 30, sinks and warpage occurred in portions of the molded product corresponding to the vicinity of the first resin reservoir 44A and the second resin reservoir 44B. Table 3 shows the results of measuring the flatness of the molded product.
[0101]
(Comparative Example 5B)
In Comparative Example 5B, after [Step-500] of Example 5 was executed, [Step-510] to [Step-540] were further executed. However, in [Step-510] to [Step-530], P ₁ = 9 × 10 ⁷ Pa, P ₂ = 0Pa, P ₂ '= 9 × 10 ⁷ Pa, P ₁ '= 0 Pa.
[0102]
Observation of the obtained molded product showed that the glass fibers were oriented in the longitudinal direction of the molded product, but sink and warp occurred in the portion of the molded product corresponding to the vicinity of the gate portion 15. Table 3 shows the results of measuring the flatness of the molded product.
[0103]
(Example 6)
The sixth embodiment is a modification of the fifth embodiment. The mold assembly 10E of the sixth embodiment whose conceptual view is shown in FIG. 23 is different from the mold assembly 10D of the fifth embodiment in that opening and closing means are provided in the first resin reservoir 44A and the second resin reservoir 44B. Different. The gate unit 15 is also provided with opening / closing means (not shown). Other structures are the same as those of the mold assembly of the fifth embodiment. Here, the opening / closing means has the same configuration and structure as described in the second embodiment. FIG. 23 shows a state where the first resin reservoir 44A and the second resin reservoir 44B are closed. The resin flow path 14 is composed of a combination of a sprue and a hot runner, and has a mechanism in which the thermoplastic resin in the first resin sump 44A and the second resin sump 44B is also in a molten state. Omitted.
[0104]
Hereinafter, the injection molding method of the sixth embodiment will be described with reference to FIGS. 24 to 27 which are conceptual diagrams of a mold assembly and the like. In the sixth embodiment, the same thermoplastic resin as that of the second embodiment is used. A molded product having the same shape as in Example 2 was molded. 24 to 27, the illustration of the injection cylinder 11 is omitted. 24 to 27, the molten thermoplastic resin left in the first resin reservoir 44A and the second resin reservoir 44B by the previous injection molding is indicated by reference numeral 30A. Further, part of the molten thermoplastic resin 30 flows between the cavity 18 and the first resin reservoir 44A or the second resin reservoir 44B, and part of the molten thermoplastic resin 30A also flows between the cavity 18 and the first resin reservoir 44A. Alternatively, it flows between the second resin reservoir 44B and the flow state of the molten thermoplastic resin 30, 30A is omitted in FIGS. 26 and 27.
[0105]
[Step-600]
First, the thermoplastic resin 30 plasticized and melted by the injection cylinder 11 is injected into the cavity 18 via the resin flow path 14 and the gate portion 15, and the inside of the cavity 18 is completely filled with the molten thermoplastic resin 30. Filled (see FIG. 24). The injection conditions were the same as shown in Table 2. At the time of injection of the molten thermoplastic resin 30, the piston 20A constituting the first pressurizing means is located at the backward end, and the piston 20B constituting the second pressurizing means is located at the forward end. The first resin reservoir 44A and the second resin reservoir 44B are in a closed state.
[0106]
[Step-610]
At the same time when the injection of the molten thermoplastic resin 30 into the cavity 18 is completed, the hydraulic cylinders 47A and 47B are operated to retract the shut-off pins 46A and 46B, and the first resin reservoir 44A and the second resin reservoir 44B communicate with the cavity 18. (See FIG. 25). At the same time, the hydraulic cylinders 21A and 21B were operated to move the piston 20A to the forward end, and in synchronization with the movement of the piston 20A, moved the piston 20B to the reverse end. At this time, the pressure P is applied to the molten thermoplastic resin 30, 30A in the first resin reservoir 44A by the first pressing means (specifically, the piston 20A). ₁ (= 9 × 10 ⁷ Pa), and a pressure P is applied to the molten thermoplastic resin 30, 30A in the second resin reservoir 44B by the second pressurizing means (specifically, the piston 20B). ₂ (= 2 × 10 ⁷ By applying Pa), a shearing force is applied to the molten thermoplastic resin 30 in the cavity 18 in a direction from the first resin reservoir 44A to the second resin reservoir 44B, and the molten thermoplastic resin 30 in the cavity 18 is removed. It was made to flow in the direction from the first resin reservoir 44A to the second resin reservoir 44B. FIG. 26 shows this state. The movement time of the pistons 20A and 20B was 1.5 seconds. The molten thermoplastic resin 30 in the cavity 18 is about 2 cm ³ , And moved in a direction from the first resin reservoir 44A to the second resin reservoir 44B.
[0107]
[Step-620]
As soon as the piston 20A reaches the forward end and the piston 20B reaches the reverse end (see FIG. 26), the first pressurizing means (specifically, the first pressurizing means) is applied to the molten thermoplastic resin 30, 30A in the first resin reservoir 44A. Is the pressure P by the piston 20A). ₁ '(= 2 × 10 ⁷ Pa), and a pressure P is applied to the molten thermoplastic resin 30, 30A in the second resin reservoir 44B by the second pressurizing means (specifically, the piston 20B). ₂ '(= 9 × 10 ⁷ By applying Pa), a shearing force is applied to the molten thermoplastic resin 30 in the cavity 18 in a direction from the second resin reservoir 44B to the first resin reservoir 44A, so that the molten thermoplastic resin 30 in the cavity 18 is removed. It was made to flow in the direction from the second resin reservoir 44B to the first resin reservoir 44A. This state is shown in FIG. The movement time of the pistons 20A and 20B was 1.5 seconds. The molten thermoplastic resin 30 in the cavity 18 is about 2 cm ³ , And moved in the direction from the second resin reservoir 44B to the first resin reservoir 44A.
[0108]
[Step-630]
As soon as the piston 20A reaches the backward end and the piston 20B reaches the forward end (see FIG. 27), [Step-610] and [Step-620] are immediately repeated. Thus, when [Step-610] and [Step-620] were set as one operation, five operations were performed. The time required for the five operations is 15 seconds.
[0109]
[Step-640]
Thereafter, the pressure P is applied to the molten thermoplastic resin 30 in the cavity 18 by the first pressing means and the second pressing means (specifically, the pistons 20A and 20B). ₀ (= 4 × 10 ⁷ Pa) was added. Then, the molten thermoplastic resin 30 in the cavity was cooled and solidified. Pressure P ₀ Was applied for 15 seconds, and then the operation of applying pressure to the molten thermoplastic resin 30 in the cavity 18 by the first pressing means and the second pressing means was stopped. After the elapse of 20 seconds, the mold assembly was opened and the molded product was taken out.
[0110]
The molded article had excellent appearance and excellent dimensional accuracy, and the glass fibers were oriented in the longitudinal direction of the molded article. No sink marks or warpage were observed. Table 3 shows the results of measuring the flatness of the molded product.
[0111]
(Comparative Example 6A)
In Comparative Example 6A, after performing [Step-600] of Example 6, the injection cylinder 11 was used to hold the molten thermoplastic resin 30 in the cavity 18 under pressure (4 × 10 6). ⁷ Pa) was added for 15 seconds. After the elapse of 20 seconds, the mold assembly was opened and the molded product was taken out.
[0112]
Observation of the obtained molded product showed that the glass fibers were oriented in the longitudinal direction of the molded product, but that the glass fiber was melted in the cavity 18 near the first resin reservoir 44A and the second resin reservoir 44B, which are the resin flow ends. Since sufficient holding pressure was not applied to the thermoplastic resin 30, sinks and warpage occurred in portions of the molded product corresponding to the vicinity of the first resin reservoir 44A and the second resin reservoir 44B. Table 3 shows the results of measuring the flatness of the molded product.
[0113]
(Comparative Example 6B)
In Comparative Example 6B, after [Step-600] of Example 6 was performed, [Step-610] to [Step-640] were further performed. However, in [Step-610] to [Step-630], P ₁ = 9 × 10 ⁷ Pa, P ₂ = 0Pa, P ₂ '= 9 × 10 ⁷ Pa, P ₁ '= 0 Pa.
[0114]
Observation of the obtained molded product showed that the glass fibers were oriented in the longitudinal direction of the molded product, but sink and warp occurred in portions of the molded product corresponding to the vicinity of the first resin reservoir 44A and the second resin reservoir 44B. Had occurred. Table 3 shows the results of measuring the flatness of the molded product.
[0115]
[Table 3]
Flatness (mm)
Example 1 0.10
Comparative Example 1A 0.30
Comparative Example 1B 0.15
Example 2 0.08
Comparative Example 2A 0.20
Comparative Example 2B 0.10
Example 3 0.11
Comparative Example 3A 0.31
Comparative Example 3B 0.17
Example 4 0.09
Comparative Example 4A 0.22
Comparative Example 4B 0.12
Example 5 0.13
Comparative Example 5A 0.32
Comparative Example 5B 0.18
Example 6 0.10
Comparative Example 6A 0.24
Comparative Example 6B 0.12
[0116]
Although the present invention has been described based on the preferred embodiments, the present invention is not limited to these embodiments. The configuration and structure of the mold assembly described in the examples, the thermoplastic resin used in the examples, the injection molding conditions, the size and the shape of the molded product are merely examples, and can be changed as appropriate. For example, the number of the resin pool, the first resin pool, and the second resin pool is not limited to one.
[0117]
In the first embodiment and the second embodiment, the molten thermoplastic resin 30 is injected into the cavity 18 only from the first gate portion 15A. However, as shown in a modification of the first embodiment in FIG. The molten thermoplastic resin 30 may be injected into the cavity 18 from the second gate 15B. In such a configuration, the inside of the cavity 18 may be completely filled with the molten thermoplastic resin or may be incompletely filled. When the inside of the cavity 18 is incompletely filled with the molten thermoplastic resin, the operation of the pressurizing means causes the molten thermoplastic resin in the resin flow path to flow into the cavity 18, whereby the inside of the cavity 18 is filled with the molten thermoplastic resin. Completely filled. Note that such an injection method can be applied to the second embodiment.
[0118]
As shown in a modification of the first embodiment in FIG. 29, the distance from the portion 18A of the cavity 18 where the one end in the longitudinal direction of the molded product is to be formed to the first gate portion 15A is set to 0, The distance from the portion 18B of the cavity 18 where the other end in the longitudinal direction is to be formed to the second gate portion 15B can be set to zero. Incidentally, such a structure of the gate portion can be applied to the mold assembly described in the second to sixth embodiments.
[0119]
Further, as shown in a modification of the fifth embodiment in FIG. 30, the distance from the portion 18A of the cavity 18 where one end in the longitudinal direction of the molded product is to be formed to the first resin reservoir 44A is set to 0, The distance from the portion 18B of the cavity 18 where the other end in the longitudinal direction of the article is to be formed to the second resin reservoir 44B may be set to zero. In addition, such a structure of the resin reservoir can also be applied to the mold assemblies described in the third to fourth and sixth embodiments. Here, in the mold assembly shown in FIG. 30, the mold assembly has two gate portions (a first gate portion 15A and a second gate portion 15B). There is no limitation, and the number of gate units may be one or three or more. In the configuration having such a plurality of gate portions, the inside of the cavity 18 may be completely filled with the molten thermoplastic resin or may be incompletely filled. When the cavity 18 is incompletely filled with the molten thermoplastic resin, the operation of the pressurizing means causes the molten thermoplastic resin in the resin reservoir to flow into the cavity 18, whereby the cavity 18 is filled with the molten thermoplastic resin. Completely filled.
[0120]
【The invention's effect】
In the injection molding method according to the first to third aspects of the present invention, the molten thermoplastic resin injected into the cavity is made of P ₁ > P ₂ > 0 and P ₂ '> P ₁ Under the condition of '> 0, it flows in the cavity. That is, opposing pressure is always applied to the molten thermoplastic resin in the cavity from the first pressing unit and the second pressing unit. As a result, it is possible to mold a molded article having excellent appearance, excellent dimensional accuracy, no sink marks, and little residual stress. In addition, even when the molten thermoplastic resin is injected into the cavity from the plurality of gate portions, weld is unlikely to occur.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a mold assembly according to a first embodiment.
FIG. 2 is a conceptual diagram of a mold assembly and the like for describing an injection molding method according to a first embodiment.
FIG. 3 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the first embodiment, following FIG. 2;
FIG. 4 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the first embodiment, following FIG. 3;
FIG. 5 is a conceptual diagram of a mold assembly according to a second embodiment.
FIG. 6 is a conceptual diagram of a mold assembly and the like for describing an injection molding method according to a second embodiment.
FIG. 7 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the second embodiment, following FIG. 6;
FIG. 8 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the second embodiment, following FIG. 7;
FIG. 9 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the second embodiment, following FIG.
FIG. 10 is a conceptual diagram of a mold assembly according to a third embodiment.
FIG. 11 is a conceptual diagram of a mold assembly and the like for describing an injection molding method according to a third embodiment.
FIG. 12 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the third embodiment, following FIG. 11;
FIG. 13 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the third embodiment, following FIG. 12;
FIG. 14 is a conceptual diagram of a mold assembly according to a fourth embodiment.
FIG. 15 is a conceptual diagram of a mold assembly and the like for explaining an injection molding method according to a fourth embodiment.
FIG. 16 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the fourth embodiment, following FIG. 15;
FIG. 17 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the fourth embodiment, following FIG. 16;
FIG. 18 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the fourth embodiment, following FIG. 17;
FIG. 19 is a conceptual diagram of a mold assembly according to a fifth embodiment.
FIG. 20 is a conceptual diagram of a mold assembly and the like for describing an injection molding method according to a fifth embodiment.
FIG. 21 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the fifth embodiment, following FIG. 20;
FIG. 22 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the fifth embodiment, following FIG. 21;
FIG. 23 is a conceptual diagram of a mold assembly according to a sixth embodiment.
FIG. 24 is a conceptual diagram of a mold assembly and the like for describing an injection molding method according to a sixth embodiment.
FIG. 25 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the sixth embodiment, following FIG. 24;
FIG. 26 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the sixth embodiment, following FIG. 25;
FIG. 27 is a conceptual diagram of a mold assembly and the like for explaining the injection molding method of the sixth embodiment, following FIG. 26;
FIG. 28 is a conceptual diagram of a modified example of the mold assembly according to the first embodiment.
FIG. 29 is a conceptual diagram of another modified example of the mold assembly of the first embodiment.
FIG. 30 is a conceptual diagram of a modified example of the mold assembly according to the fifth embodiment.
[Explanation of symbols]
10, 10A, 10B, 10C, 10D, 10E: mold assembly, 11: injection cylinder, 12: fixed mold portion, 13: movable mold portion, 14: resin Channel, 14A: first resin channel, 14B: second resin channel, 15: gate section, 15A: first gate section, 15B: second gate section, 16A, 16B, 46, 46A, 46B ... shut-off pin, 17A, 17B, 47, 47A, 47B ... hydraulic cylinder, 18 ... cavity, 20A, 20B ... piston, 21A, 21B ... hydraulic Cylinder, 30, 30A: molten thermoplastic resin, 44: resin reservoir, 44A: first resin reservoir, 44B: second resin reservoir

Claims

(A) a first resin flow path and a second resin flow path communicating with an injection cylinder;
(B) a cavity,
(C) a first gate portion communicating with the first resin flow path and opening to the cavity;
(D) a second gate portion communicating with the second resin flow path and opening to the cavity;
(E) first pressurizing means for applying pressure to the molten thermoplastic resin in the first resin flow path, and
(F) a second pressurizing means for applying pressure to the molten thermoplastic resin in the second resin flow path;
A method for injection molding a molded article using a mold assembly having
(A) After injecting the thermoplastic resin plasticized and melted by the injection cylinder into the cavity through the first resin flow path and the first gate portion,
(B) the pressure P ₁ exerted by the first pressure unit to the molten thermoplastic resin in the first resin passage, the pressure P _{2 (where} the second pressure means in the molten thermoplastic resin in the second resin flow path , P ₁ > P ₂ > 0), a shear force is applied to the molten thermoplastic resin in the cavity in a direction from the first gate portion to the second gate portion, and the molten thermoplastic resin in the cavity is provided. Flows in the direction from the first gate portion to the second gate portion, and then a pressure P ₁ ′ is applied to the molten thermoplastic resin in the first resin flow path by the first pressurizing means, so that By applying a pressure P ₂ ′ (where P ₂ ′> P ₁ ′> 0) to the molten thermoplastic resin of the above by the second pressurizing means, the molten thermoplastic resin in the cavity can be moved from the second gate portion to the second thermoplastic resin. 1 Apply shearing force in the direction toward the gate to melt the thermoplastic resin in the cavity. Repeating the operation of causing the fat to flow from the second gate to the first gate,
A method for injection molding a molded article, comprising:

Opening / closing means is provided in the second gate portion,
2. The method according to claim 1, wherein in the step (a), the second gate unit is closed by an opening / closing unit, and in the step (b), the second gate unit is opened by an opening / closing unit. 3. Injection molding method for molded products.

_{3. The method according} to claim ₁ , wherein P ₁ = P ₂ ′ and P ₂ = P ₁ ′ are satisfied.

The value of P ₂ / _{P 1} is 1/10 to 9/10, the value of _{P 1} '/ _{P 2'} is the preceding claims, characterized in that it is 1/10 to 9/10 4. The injection molding method for a molded article according to any one of the above items 3.

After completion of step (b), any one of claims 1 to 4, characterized in that applying pressure P ₀ in the molten thermoplastic resin in the cavity by the first pressure means and second pressure means The injection molding method of the molded article according to the above.

(A) a resin flow path communicating with the injection cylinder,
(B) a cavity,
(C) a gate portion communicating with the resin flow path and opening to the cavity;
(D) a resin reservoir communicating with the cavity,
(E) first pressurizing means for applying pressure to the molten thermoplastic resin in the resin flow path, and
(F) second pressurizing means for applying pressure to the molten thermoplastic resin in the resin reservoir;
A method for injection molding a molded article using a mold assembly having
(A) After injecting the thermoplastic resin plasticized and melted by the injection cylinder into the cavity through the resin flow path and the gate portion,
(B) A pressure P ₁ is applied to the molten thermoplastic resin in the resin flow path by the first pressing means, and a pressure P ₂ (where P ₁ > P) is applied to the molten thermoplastic resin in the resin reservoir by the second pressing means. ₂ > 0), a shear force is applied to the molten thermoplastic resin in the cavity in a direction from the gate portion toward the resin reservoir, and the molten thermoplastic resin in the cavity is directed from the gate portion to the resin reservoir. Then, a pressure P ₁ ′ is applied to the molten thermoplastic resin in the resin flow path by the first pressurizing means, and a pressure P ₂ ′ (however, , P ₂ ′> P ₁ ′> 0), a shearing force is applied to the molten thermoplastic resin in the cavity in a direction from the resin reservoir toward the gate portion, and the molten thermoplastic resin in the cavity is Flow in the direction from the pool to the gate Repeat the operation to move,
A method for injection molding a molded article, comprising:

The method according to claim 6, wherein P ₁ = P ₂ ′ and P ₂ = P ₁ ′ are satisfied.

7. The value of P ₂ / P ₁ is 1/10 to 9/10, and the value of P ₁ ′ / P ₂ ′ is 1/10 to 9/10. 8. The injection molding method of a molded article according to 7.

After completion of step (b), any one of claims 6 to 8, characterized in that applying pressure P ₀ in the molten thermoplastic resin in the cavity by the first pressure means and second pressure means The injection molding method of the molded article according to the above.

(A) a resin flow path communicating with the injection cylinder,
(B) a cavity,
(C) a gate portion communicating with the resin flow path and opening to the cavity;
(D) a first resin reservoir communicating with the cavity,
(E) a second resin reservoir communicating with the cavity,
(F) first pressurizing means for applying pressure to the molten thermoplastic resin in the first resin reservoir, and
(G) second pressurizing means for applying pressure to the molten thermoplastic resin in the second resin reservoir;
A method for injection molding a molded article using a mold assembly having
(A) After injecting the thermoplastic resin plasticized and melted by the injection cylinder into the cavity through the resin flow path and the gate portion,
(B) the pressure P ₁ exerted by the first pressure unit to the molten thermoplastic resin in the first resin within the reservoir, the pressure P ₂ by the second pressurizing unit to a molten thermoplastic resin in the second resin in the reservoir _(where, P ₁ > P ₂ > 0), a shearing force is applied to the molten thermoplastic resin in the cavity in a direction from the first resin reservoir toward the second resin reservoir, and the molten thermoplastic resin in the cavity is removed from the first resin reservoir. The resin is caused to flow in the direction from the first resin reservoir toward the second resin reservoir, and then a pressure P ₁ ′ is applied to the molten thermoplastic resin in the first resin reservoir by the first pressurizing means, thereby causing the molten thermoplastic resin in the second resin reservoir to flow. By applying a pressure P ₂ ′ (however, P ₂ ′> P ₁ ′> 0) to the resin by the second pressing means, the molten thermoplastic resin in the cavity is transferred from the second resin reservoir to the first resin reservoir. The shearing force is applied in the direction of Repeating the operation of causing the fat to flow from the second resin reservoir toward the first resin reservoir,
A method for injection molding a molded article, comprising:

P ₁ = _{P 2} injection molding method of a molded article according to claim 10, characterized by satisfying the _{_{', P 2 = P 1'}} .

The value of P ₂ / _{P 1} is 1/10 to 9/10, the value of _{P 1} '/ _{P 2'} is claim 10 or claim characterized in that it is a 1/10 to 9/10 12. The injection molding method for a molded article according to item 11.

After completion of step (b), any one of claims 10 to 12, characterized in that applying pressure P ₀ in the molten thermoplastic resin in the cavity by the first pressure means and second pressure means The injection molding method of the molded article according to the above.

(A) a first resin flow path and a second resin flow path communicating with an injection cylinder;
(B) a cavity,
(C) a first gate portion communicating with the first resin flow path and opening to the cavity;
(D) a second gate portion communicating with the second resin flow path and opening to the cavity;
(E) first pressurizing means for applying pressure to the molten thermoplastic resin in the first resin flow path, and
(F) a second pressurizing means for applying pressure to the molten thermoplastic resin in the second resin flow path;
A mold assembly comprising:
A mold assembly, wherein an opening / closing means is provided in the second gate portion.

(A) a resin flow path communicating with the injection cylinder,
(B) a cavity,
(C) a gate portion communicating with the resin flow path and opening to the cavity;
(D) a resin reservoir communicating with the cavity,
(E) first pressurizing means for applying pressure to the molten thermoplastic resin in the resin flow path, and
(F) second pressurizing means for applying pressure to the molten thermoplastic resin in the resin reservoir;
A mold assembly comprising:

(A) a resin flow path communicating with the injection cylinder,
(B) a cavity,
(C) a gate portion communicating with the resin flow path and opening to the cavity;
(D) a first resin reservoir communicating with the cavity,
(E) a second resin reservoir communicating with the cavity,
(F) first pressurizing means for applying pressure to the molten thermoplastic resin in the first resin reservoir, and
(G) second pressurizing means for applying pressure to the molten thermoplastic resin in the second resin reservoir;
A mold assembly comprising: