JP2004017629A

JP2004017629A - Molding method for resin molded body

Info

Publication number: JP2004017629A
Application number: JP2002180259A
Authority: JP
Inventors: Tomomi Hasegawa; 長谷川　智巳; Yasumasa Shibata; 柴田　康雅; Hiroshi Furukawa; 古川　泰士
Original assignee: NGK Insulators Ltd; Idemitsu Petrochemical Co Ltd
Current assignee: NGK Insulators Ltd; Idemitsu Petrochemical Co Ltd
Priority date: 2002-06-20
Filing date: 2002-06-20
Publication date: 2004-01-22
Anticipated expiration: 2022-06-20
Also published as: JP4036689B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding method for a resin molded body capable of efficiently and integrally molding the resin molded body in the case where a region high in flow resistance of a resin making the resin hard to flow exists in a cavity of a mold when the resin molded body is injection molded. <P>SOLUTION: The inside of the cavity 5 of the mold 10 is divided into a plurality of regions according to easiness in flowing of the resin to be filled in the cavity 5. One region in a plurality of divided regions is partitioned by making it abut against by moving one or more movable blocks 3 to a decoration side mold part 1. Primary resin is injected into the region 5a partitioned by a movable block 3. The movable block 3 is successively evacuated from the inside of the cavity. A resin on and after secondary is successively injected into the other regions (5b) shut up by the movable block 3 inside the cavity 5. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】本発明は、樹脂成形体の成形方法に関し、さらに詳しくは、樹脂成形体を射出成形するときに、金型のキャビティ内に、樹脂の流れ抵抗が大きく流れ難い領域がある場合に、その樹脂成形体を効率的に一体成形することができる樹脂成形体の成形方法に関する。
【０００２】
【従来の技術】樹脂成形体の射出成形法は、プラスチック材料（樹脂）を加熱溶融してスクリュー又はプランジャー等により金型のキャビティ内に射出し、金型内で冷却固化又は加熱硬化させて樹脂成形体を得るものである。この射出成形法により、金型のキャビティの形状に忠実な精度の高い樹脂成形体を得ることができる。
【０００３】しかし、このような射出成形法も、得られる樹脂成形体が部分的に細かい構造を有し、その部分に対応する金型のキャビティが細く及び／又は入り組んだ構造である場合に、キャビティ内に射出された樹脂がその部分に充填され難くなり、充填に時間を要したり、高い充填圧を要したり、充填されない部分が残存するという問題があった。
【０００４】このように、金型のキャビティ内に樹脂を射出した場合に、樹脂が流れ難いため充填され難い部分がある場合には、その樹脂が充填され難い部分に相当する樹脂成形体を別の金型で成形し、さらにもとの樹脂成形体から樹脂が充填され難い部分を除いた樹脂成形体を別の金型で成形し、得られた二つの樹脂成形体を組み合わせることにより目的の樹脂成形体を得ることができる。しかし、このように、二つの樹脂成形体又は、さらに複雑な構造の場合には三つ以上の樹脂成形体を別々の金型を用いて別々に射出成形して、得られた樹脂成形体を組み合わせて一つの樹脂成形体とする場合には、二又はそれ以上の金型を準備し、それぞれ別々に射出成形し、最後に得られた射出成形体を組み合わせて一つにしなければならないため、両者がピッタリ嵌り合わないという問題があった。
【０００５】そこで、このような、部分的に細かい構造を有する樹脂成形体を一つの金型で射出成形することにより一体成形しようとすると、樹脂が充填され難い部分に樹脂を強制的に充填しなければならないため、高圧を要したり、その部分を加熱して樹脂の粘度を低下させる等の余分な操作を必要とし、複雑な装置を必要としたり、生産性が低下するという問題があった。
【０００６】たとえば、自動車のドアトリムには、図３に示すように、スピーカー設置位置に網状部が形成され、スピーカーからの音を良好に伝達できるようにしている場合があるが、ドアトリムを射出成形により一体成形する場合には、金型のキャビティの網状部に相当する領域の方が、その他の部分に相当する領域よりも樹脂が流れ難く、網状部に相当する領域に樹脂を充填し難いため、網状部に相当する領域だけを加熱して樹脂の流動を良好にする必要があり、非常に効率が悪いという問題があった。
【０００７】
【発明が解決しようとする課題】本発明は上述の問題に鑑みなされたものであり、樹脂成形体を射出成形するときに、金型のキャビティ内に、樹脂の流れ抵抗が大きく流れ難い領域がある場合に、その樹脂成形体を効率的に一体成形することができる樹脂成形体の成形方法を提供することを目的とする。
【０００８】
【課題を解決するための手段】上記目的を達成するため、本発明によって以下の樹脂成形体の成形方法が提供される。
［１］　樹脂を金型のキャビティ内に射出して樹脂成形体を一体成形する樹脂成形体の成形方法であって、前記金型のキャビティ内を、前記キャビティ内に充填される前記樹脂の流れ難さに対応して複数の領域に区分けして、区分けされた前記複数の領域のうちの一の領域を、一以上の可動ブロックを意匠側金型部に移動させてそこに当接させることによって仕切るとともに、前記可動ブロックによって仕切られた領域に一次樹脂を射出し、次いで、前記可動ブロックをキャビティ内から順次退避させ、前記キャビティ内部の前記可動ブロックによって塞がれていた他の領域に順次二次以降の樹脂を射出することを特徴とする樹脂成形体の成形方法。
［２］　前記複数の領域に射出するそれぞれの前記樹脂を見切り部で接合することを特徴とする［１］に記載の樹脂成形体の成形方法。
［３］　前記複数の領域に射出する前記樹脂のうち、少なくとも前記一の領域に射出する樹脂の色及び／又は材質が、他の領域に射出する樹脂の色及び／又は材質と異なるものである［１］又は［２］に記載の樹脂成形体の成形方法。
［４］　前記可動ブロックと前記意匠側金型部との間の突き合わせ隙間（ｔ１）を、０．１ｍｍ以下とする［１］〜［３］のいずれかに記載の樹脂成形体の成形方法。
［５］　前記金型が前記可動ブロックの移動を制止するストッパーを備えてなる［１］〜［４］のいずれかに記載の樹脂成形体の成形方法。
［６］　前記ストッパーが、前記非意匠側金型部に設けた、前記可動ブロックと当接する当接ブロックである［５］に記載の樹脂成形体の成形方法。
［７］　前記当接ブロックを構成する材料の硬度が、前記可動ブロックを構成する材料の硬度よりも小である［６］に記載の樹脂成形体の成形方法。
［８］　前記見切り部に対応する意匠側金型部の先端部の断面平面部分の幅（Ｗ）が、０．５ｍｍ以下であるとともに、前記可動ブロックの長さ（Ｌ）が、前記見切り部よりも、前記複数の樹脂のうち先の射出順位の樹脂側に、０．１ｍｍ以上延長されてなる［２］〜［７］のいずれかに記載の樹脂成形体の成形方法。
［９］　前記可動ブロックと前記意匠側金型部との間の突き合わせ隙間（ｔ２）が、０ｍｍより大で、且つ０．１ｍｍ以下である［８］に記載の樹脂成形体の成形方法。
［１０］　前記金型が前記可動ブロックの移動を制限するストッパーを備えてなる［８］又は［９］に記載の樹脂成形体の成形方法。
［１１］　前記ストッパーが前記非意匠側金型部に設けた、前記可動ブロックと当接する当接ブロックである［１０］に記載の樹脂成形体の成形方法。
［１２］　前記当接ブロックを構成する材料の硬度が、前記可動ブロックを構成する材料の硬度よりも小である［１１］に記載の樹脂成形体の成形方法。
［１３］　前記可動ブロック近傍において、一次樹脂が固化し始めた直後から、遅くとも一次樹脂の可動ブロック近傍が完全に固化する前に、前記可動ブロックを前記キャビティ内から退避させたのち、前記キャビティ内部の残る空間に二次樹脂を射出して一次樹脂中に潜り込ませる［１］〜［１２］のいずれかに記載の樹脂成形体の成形方法。
［１４］　前記二次樹脂が潜り込む一次樹脂の可動ブロック近傍が、厚肉部である［１３］に記載の樹脂成形体の成形方法。
［１５］　前記可動ブロックの一次樹脂と接する側端が、意匠面側から非意匠面側に向かうに従って次第に肉薄になるように斜めに形成され、その斜めの面に凹凸が形成されてなる［１］〜［１４］のいずれかに記載の樹脂成形体の成形方法。
［１６］　前記可動ブロックが、少なくとも二以上のブロックからなり、各ブロック片は、二次樹脂が射出される前に前記キャビティ内から退避した際に、非意匠面と平坦な面になる［１５］に記載の樹脂成形体の成形方法。
［１７］　前記可動ブロックが、一次樹脂を射出する前記一の領域の可動ブロック近傍を、厚さ方向に垂直、且つ見切り線に垂直な方向に対してアンダーカットになるように区画する形状に形成されてなる［１］〜［１６］のいずれかに記載の樹脂成形体の成形方法。
【０００９】このように、樹脂成形体を射出成形により一体成形する場合に、金型のキャビティ内を複数の領域に区分けして、その領域を可動ブロックで仕切り、可動ブロックを移動（退避）させながら樹脂を射出充填するようにしたため、キャビティ内の各領域に適した射出条件により樹脂を射出充填することができるため、流動性の悪い領域（樹脂の流れ抵抗の大きい領域）に樹脂を射出する場合にも高圧を要することなく、効率的に充填することができる。
【００１０】
【発明の実施の形態】以下、本発明の実施の形態を図面を参照しながら具体的に説明するが、本発明は以下の実施の形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲で、当業者の通常の知識に基づいて、適宜設計の変更、改良等が加えられることが理解されるべきである。
【００１１】図１（ａ）〜（ｄ）は、本発明の樹脂成形体の成形方法の一の実施の形態に使用する金型を模式的に示す断面図である。本実施の形態は、樹脂を金型のキャビティ内に射出するときに樹脂の流れ抵抗が大きい（流れ難い）一の領域と、他の一の領域（樹脂の流れ抵抗が小さい（流れ易い）領域）から構成されるキャビティを有する金型を使用して、樹脂成形体を一体成形する樹脂成形体の成形方法である。
【００１２】本実施の形態の樹脂成形体の成形方法は、図１（ａ）に示す、意匠側金型部１、非意匠側金型部２及び可動ブロック３を備えてなる金型１０を使用して、射出成形により樹脂成形体を成形するものである。金型１０のキャビティ５は、図１（ｂ）に示す樹脂の流れ抵抗が小さい領域５ａと、樹脂の流れ抵抗が大きい領域５ｂとの二つの領域に区分けされる。樹脂の充填方法は、まず、図１（ｂ）に示すように、可動ブロック３を意匠側金型部１に突き合わせるように移動することによってキャビティ５を仕切り、可動ブロック３、意匠側金型部１及び非意匠側金型部２の間にキャビティ５ａを形成する。そして、一次樹脂４ａをキャビティ５ａ内に射出する。このとき、キャビティ５ａは、樹脂の流れ抵抗が小さい領域であるため、大きな射出圧力をかけなくても容易に樹脂を射出し充填することができる。次に、図１（ｃ）に示すように、可動ブロック３を引き下げて（退避させて）、一次樹脂４ａ、意匠側金型部１及び非意匠側金型部２の間（可動ブロック３によって塞がれていた領域）に樹脂の流れ抵抗が大きいキャビティ５ｂを形成する。そして、二次樹脂４ｂをキャビティ５ｂ内に射出して、一次樹脂４ａと、見切り部６で接合する。これにより、樹脂の流れ抵抗が小さい領域と樹脂の流れ抵抗が大きい領域に別々に樹脂を充填することができ、それぞれの領域に適した条件で樹脂を射出・充填することができるため、射出圧力を過剰に大きくする必要がなく、バリの発生等を防止することができる。また、一つの金型で成形する場合より、短時間で樹脂を充填することができ、充填効率を向上させることができる。
【００１３】一次樹脂４ａ、二次樹脂４ｂはともに、溶融状態で金型１０のキャビティ５に射出、充填され、金型１０内で冷却されて樹脂成形体の形状となる。金型１０内で形成された樹脂成形体形状物は、金型１０から取り出し、通常の方法で表面処理等を施して樹脂成形体として完成させる。
【００１４】本発明において、キャビティ５に樹脂が充填されるときの流れ抵抗の大きさは、一定量の樹脂をキャビティ５に充填したときの型締め力で表される。
【００１５】本実施の形態では、金型１０のキャビティ５が、キャビティ５ａとキャビティ５ｂの二つの領域から構成される（二つの領域に区分けされる）場合について説明したが、本発明の樹脂成形体の成形方法においては、金型のキャビティは三以上の領域に区分けされていてもよく、その場合には三以上の領域を一以上の可動ブロックを意匠側金型部に突き合わせるように移動することによって領域毎に仕切り、可動ブロックによって仕切られた領域に一次樹脂を射出し、その後、可動ブロックを順次退避させ、キャビティ内の可動ブロックで塞がれていた領域に順次二次以降の樹脂を射出し、各領域に射出する樹脂を見切り部で接合するようにしてもよい。
【００１６】本実施の形態の樹脂成形体の成形方法においては、図１（ｃ）に示す、一次樹脂４ａと二次樹脂４ｂとは、色及び／又は材質が異なるものであってもよい。たとえば、一次樹脂４ａに添加する顔料と二次樹脂４ｂに添加する顔料とを異ならせて２色の樹脂成形体とすることができ、また、一次樹脂４ａと二次樹脂４ｂとをそれぞれ機能の異なる樹脂とし、部分的に機能の異なる一体成形による樹脂成形体を得ることができる。一次樹脂４ａと二次樹脂４ｂの樹脂の機能及び添加する顔料を同時に異ならせてもよい。また、金型のキャビティが三以上の領域から構成される場合には、少なくとも一つの領域に射出する樹脂の色及び／又は材質が異なるものであってもよい。たとえば、少なくとも一つの領域に射出する樹脂に添加する顔料と他の領域に射出する樹脂に添加する顔料とを異ならせて多色成形品とすることができ、また、少なくとも一つの領域に射出する樹脂を、他の領域に射出する樹脂とは異なる機能の樹脂とすることにより、部分的に機能の異なる一体成形による樹脂成形体を得ることができる。
【００１７】本実施の形態は、図３に示すような、スピーカー設置位置等に網状部が形成された自動車のドアトリムの製造に好適に適用することができる。図３に示す自動車のドアトリム３１は、自動車のドアの内面に装着され、ドア内部に埋込設置されたスピーカーからの音が良好に伝達されるように、多数の網目を有する網状部３２が形成されている。このような網状部３２が形成されたドアトリム３１を射出成形により一体成形する場合には、金型のキャビティの網状部３２に相当する領域における樹脂の流れ難さ（流れ抵抗）が、その他の部分３３に相当する領域における樹脂の流れ難さ（流れ抵抗）より大きく、網状部３２に相当する領域に樹脂を充填し難い。そのため、ドアトリム３１の網状部３２に相当する金型のキャビティを図１（ｃ）の５ｂとし、その他の部分３３に相当する金型のキャビティを図１（ｃ）の５ａとして、上記本実施の形態の成形方法を適用することにより、網状部３２も効率的に成形することができ、ドアトリム３１を高圧で樹脂を充填することなく、効率的に一体成形することができる。このとき、ドアトリム３１の網状部３２を形成する樹脂（４ｂ）をその他の部分３３を形成する樹脂（４ａ）とは異なった吸音性に優れた材質のものとしてもよい。また、樹脂４ａと樹脂４ｂのそれぞれに添加する顔料を違うものとし、２色の成形体としてもよい。
【００１８】本実施の形態の樹脂成形体の成形方法に使用する金型は、図１（ｂ）に示すように、可動ブロック３と意匠側金型部１との間の突き合わせ隙間（ｔ１）が、０．１ｍｍ以下であることが好ましい。この場合、可動ブロック３と意匠側金型部１との間の突き合わせ隙間（ｔ１）は、０ｍｍであってもよい。すなわち、可動ブロック３と意匠側金型部１とを完全に接触させた状態であってもよい。
【００１９】このように構成することによって、構成が簡易であるとともに、可動ブロック３と意匠側金型部１との間の突き合わせ隙間（ｔ１）が０．１ｍｍ以下であるため、一次樹脂４ａの、二次樹脂に対応するキャビティ５ｂ内への進入が防止され、樹脂接合部の見切り部６が端麗で、意匠性に優れた樹脂成形体を得ることが可能となる。なお、非意匠側金型部２は、金型表面に意匠を施して、第２の意匠側金型部としてもよい。また、可動ブロック３は、通常、図１（ａ）〜（ｄ）に示すように、非意匠側金型部２に設けることが多いが、意匠側金型部１に設けて、移動して非意匠側金型部２に突き合わされるように構成したものであってもよい。
【００２０】本発明に用いられる樹脂は、特に制限されるものではなく、その流動性の如何に拘わらず、あらゆる種類の熱可塑性樹脂を用いることができる。
【００２１】また、その他の成形条件については、通常の射出成形の場合と同様な条件を用いることができ、金型のキャビティの各領域に適した射出圧力で射出成形するとよい。
【００２２】図１（ａ）及び（ｂ）に示すように、本実施の形態においては、可動ブロック３の移動を制止するストッパー７をさらに備えたものとすることが、可動ブロック３と意匠側金型部１との間の突き合わせ隙間（ｔ１）を特定範囲内に確保するため、及び耐久性をさらに向上させるために好ましい。
【００２３】この場合、ストッパー７は、可動ブロック３と当接する当接ブロック７ａとすることが好ましく、さらに、当接ブロック７ａを構成する材料の硬度を、可動ブロック３を構成する材料の硬度よりも小とすることがさらに好ましい。このように構成することによって、可動ブロック３と当接ブロック７ａとの当接、衝合による摩耗を当接ブロック７ａ側だけに限定して、摩耗した当接ブロック７ａだけを取り替えることにより、容易に可動ブロック３と意匠側金型部１との間の突き合わせ隙間（ｔ１）を特定の範囲に確保することができる。
【００２４】上記ストッパー７（当接ブロック７ａ）は、金型内の、たとえば、非意匠側金型部２上に設けてもよく、また、金型外の所定箇所に、ストロークエンドブロック等を設けたものであってもよい。また、図１（ｄ）に示すように、可動ブロック３に設けて、非意匠側金型２と当接させてもよい。
【００２５】図２（ａ）〜（ｃ）は、本発明の樹脂成形体の成形方法の他の実施の形態に使用する金型を模式的に示す断面図である。本実施の形態の樹脂成形体の成形方法は、図２（ａ）に示す、意匠側金型部１１、非意匠側金型部１２及び可動ブロック１３を備えてなる金型２０を使用して、射出成形により樹脂成形体を成形するものである。金型２０のキャビティ１５は、図２（ｂ）に示す樹脂の流れ抵抗が小さい（流れ易い）領域１５ａと、図２（ｃ）に示す樹脂の流れ抵抗が大きい（流れ難い）領域１５ｂとの二つの領域から構成される（二つの領域に区分けされる）。樹脂の充填方法は、まず、図２（ｂ）に示すように、可動ブロック１３を意匠側金型部１１に突き合わせるように移動することによってキャビティ１５を仕切り、可動ブロック１３、意匠側金型部１１及び非意匠側金型部１２の間にキャビティ１５ａを形成する。そして、一次樹脂１４ａをキャビティ１５ａ内に射出する。このとき、キャビティ１５ａは、樹脂の流れ抵抗が小さい領域であるため、射出圧力を高圧にしなくても容易に樹脂を射出し充填することができる。次に、図２（ｃ）に示すように、可動ブロック１３を引き下げて（退避させて）、一次樹脂１４ａ、意匠側金型部１１及び非意匠側金型部１２の間（可動ブロック１３によって塞がれていた領域）にキャビティ１５ｂを形成する。そして、二次樹脂１４ｂをキャビティ１５ｂ内に射出して、一次樹脂１４ａと、見切り部（線）１６で接合する。このとき、キャビティ１５ｂは、樹脂の流れ抵抗が大きい領域であるが、この部分だけに樹脂を充填すればよいため、高圧をかけずに樹脂を充填することができ、且つ短時間で樹脂を充填することができ、充填効率を向上させることができる。
【００２６】一次樹脂１４ａ、二次樹脂１４ｂはともに、溶融状態で金型２０のキャビティ１５に射出、充填され、金型２０内で冷却されて樹脂成形体の形状となる。金型２０内で形成された樹脂成形体形状物は、金型２０から取り出し、通常の方法で表面処理等を施して樹脂成形体として完成させる。
【００２７】本実施の形態では、図２（ａ）〜（ｃ）に示すように、見切り部１６に対応する意匠側金型部１１の先端部の断面平面部分の幅（Ｗ）が、０．５ｍｍ以下であるとともに、可動ブロックの長さ（Ｌ）が、見切り部１６よりも、複数の樹脂のうち一次樹脂１４ａ側に、０．１ｍｍ以上延長されてなることが好ましい。
【００２８】このように意匠側金型部１１の先端部の断面平面部分の幅（Ｗ）が、０．５ｍｍ以下と狭い場合には、この部分の耐久性が問題となり易いので、この部分には耐摩耗性の高い材料を用いるか、又は耐摩耗性の表面処理等を施すことが好ましい。
【００２９】上述のように、意匠側金型部１１の先端部の断面平面部分の幅（Ｗ）が狭い場合には、可動ブロックの長さ（Ｌ）を、見切り部１６よりも、一次樹脂１４ａ側に、０．１ｍｍ以上延長することによって、構成が簡易であるとともに、一次樹脂１４ａの、二次樹脂に対応するキャビティ１５ｂ内への進入が防止され、樹脂接合部の見切り部１６が端麗で、意匠性に優れた樹脂成形体を得ることが可能となる。
【００３０】この場合、可動ブロック１３と意匠側金型部１１との間の突き合わせ隙間（ｔ２）が０ｍｍより大であるため両者は当接することがなく、耐久性を向上させることが可能であるとともに、突き合わせ隙間（ｔ１）が０．１ｍｍ以下であるため、一次樹脂１４ａの、二次樹脂に対応するキャビティ１５ｂ内への進入を防止し、樹脂接合部の見切り部１６が端麗で、意匠性に優れた樹脂成形体を得る上で好ましい。
【００３１】この場合も、上述の場合と同様に、可動ブロックの移動を制限するストッパー（図示せず）をさらに備えたものとすること、ストッパーとして、非意匠側金型部に設けた、可動ブロックと当接する当接ブロックとすること、及び当接ブロックを構成する材料の硬度を、可動ブロックを構成する材料の硬度よりも小とすること等が好ましい。
【００３２】図４（ａ）、（ｂ）は、本発明の樹脂成形体の成形方法の他の実施の形態に使用する金型を模式的に示す断面図である。本実施の形態の樹脂成形体の成形方法は、図４（ａ）に示す、意匠側金型部４１、非意匠側金型部４２及び可動ブロック４３を備えてなる金型４０を使用して、射出成形により樹脂成形体を成形するものである。金型４０のキャビティ４５は、図４（ａ）に示す樹脂の流れ抵抗が小さい（流れ易い）領域（キャビティ）４５ａと、樹脂の流れ抵抗が大きい（流れ難い）領域（キャビティ）４５ｂとの二つの領域から構成される（二つの領域に区分けされる）。
【００３３】本実施の形態では、４５ａの可動ブロック４３近傍に肉厚部４６が形成されている。キャビティ４５ａに一次樹脂４４ａを充填し、可動ブロック４３近傍において、一次樹脂４４ａが固化し始めた直後から、遅くとも一次樹脂４４ａの可動ブロック４３近傍が完全に固化する前に、可動ブロック４３をキャビティ４５ａ内から退避させた後、キャビティ４５ｂに二次樹脂４４ｂを射出して一次樹脂４４ａ中に潜り込ませるようにする。これにより、見切り線が良好で、意匠性に優れた一体成形品が得られると同時に、二次樹脂４４ｂが一次樹脂４４ａ中に潜り込んだ状態で接合される。
【００３４】図５（ａ）、（ｂ）は、本発明の樹脂成形体の成形方法の他の実施の形態に使用する金型を模式的に示す断面図である。本実施の形態の樹脂成形体の成形方法は、図５（ａ）に示す、意匠側金型部５１、非意匠側金型部５２及び可動ブロック５３を備えてなる金型５０を使用して、射出成形により樹脂成形体を成形するものである。金型５０のキャビティ５５は、図５（ａ）に示す樹脂の流れ抵抗が小さい（流れ易い）領域（キャビティ）５５ａと、樹脂の流れ抵抗が大きい（流れ難い）領域（キャビティ）５５ｂとの二つの領域から構成される（二つの領域に区分けされる）。
【００３５】本実施の形態では、可動ブロック５３の先端が斜めに、つまり、可動ブロック５３の一次樹脂５４ａと接する側端が、意匠面側から非意匠面側に向かうに従って、次第に肉薄になるように斜めに形成されている。そして、その斜めの面に凹凸５６が形成されている。これにより、キャビティ５５ａに一次樹脂５４ａを射出した後、一次樹脂５４ａの可動ブロック５３近傍が固化した後に、可動ブロック５３の退避によって生じたキャビティ５５ｂに二次樹脂５４ｂを射出すると、二次樹脂５４ｂが一次樹脂５４ａの非意匠面側に流れ込み、一次樹脂５４ａを非意匠面側から意匠面側へ向かって押圧する結果、キャビティ５５との隙間が塞がれる。同時に一次樹脂５４ａと二次樹脂５４ｂとの接合面には凹凸５６が形成されているから、接合強度を向上させることができる。
【００３６】尚、本実施の形態において、可動ブロック５３の先端を直線上に斜めにカットする他に、図６に示すように可動ブロック６３の先端を階段状にカットしてもよい。図６において、６０は金型、６１は意匠側金型部、６２は非意匠側金型部、６４ａは一次樹脂、６４ｂは二次樹脂、６５ａ及び６５ｂはキャビティをそれぞれ示す。
【００３７】また、図７に示すように、可動ブロック７３を二つの可動ブロック片７３ａと７３ｂとによって構成し、各ブロック片が、二次樹脂が射出される前にキャビティ７５内から退避した際に、非意匠面と平坦な面になるようにすることにより、非意匠面が平坦な成形品を得ることができる。図７において、７０は金型、７１は意匠側金型部、７２は非意匠側金型部、７４ａは一次樹脂、７４ｂは二次樹脂、７５ａ及び７５ｂはキャビティをそれぞれ示す。
【００３８】図８（ａ）、（ｂ）は、本発明の樹脂成形体の成形方法の他の実施の形態に使用する金型を模式的に示す断面図である。本実施の形態の樹脂成形体の成形方法は、図８（ａ）に示す、意匠側金型部８１、非意匠側金型部８２及び可動ブロック８３を備えてなる金型８０を使用して、射出成形により樹脂成形体を成形するものである。金型８０のキャビティ８５は、図８（ａ）に示す樹脂の流れ抵抗が小さい（流れ易い）領域（キャビティ）８５ａと、樹脂の流れ抵抗が大きい（流れ難い）領域（キャビティ）８５ｂとの二つの領域から構成される。
【００３９】本実施の形態では、可動ブロック８３が一次樹脂８４ａを射出する領域（キャビティ８５ａ）の可動ブロック８３近傍を、厚さ方向に垂直、且つ見切り線に垂直な方向に対してアンダーカットになるように（アンダーカット部８６を形成するように）区画する形状に形成されている。本実施の形態においては、可動ブロック８３の退避後に二次樹脂８４ｂを射出すると、可動ブロック８３は非意匠面に、一次樹脂８４ａのアンダーカット部８６が配置されるような構造をしているため、二次樹脂８４ｂが一次樹脂８４ａの非意匠面側に入り、一次樹脂８４ａ近傍部を意匠側金型部８１に押し付ける力が働き、一次樹脂８４ａと意匠側金型部８１との隙間に二次樹脂８４ｂが浸入し難くなるため、見切り線も向上する。
【００４０】
【実施例】以下、本発明を実施例により具体的に説明するが、本発明はこれら実施例に限定されるものではない。
【００４１】図３に示す自動車のドアトリムを以下のようにして作製した。このドアトリムは、射出成形時に、網状部の樹脂の流れ抵抗が、網状部以外の部分の樹脂の流れ抵抗より、大きいものである。
【００４２】
（実施例１）
図３に示す自動車のドアトリムを、図１に示す金型を使用して作製したときの、網状部以外の部分に樹脂が一定量充填されたときの内圧を測定し、型締め力を算出した。結果を表１に示す。
【００４３】成形条件は、以下の通りである。
【００４４】網状部以外の部分について、射出温度を２２０℃、射出圧力を９０ＭＰａ、使用樹脂をポリプロピレン、樹脂の充填量を１０００ｃｍ^３とした。また、網状部以外の部分に相当するキャビティの、金型が型締めされる方向に投影した投影図の面積は２９０５ｃｍ^２であった。
【００４５】
（比較例１）
図３に示す自動車のドアトリムを、通常の一体成形用金型を使用して、網状部及び網状部以外の部分に相当するキャビティを同時に充填する（一度の射出で両方のキャビティを充填する）方法で作製し、樹脂が一定量充填されたときの内圧を測定し、型締め力を算出した。結果を表１に示す。
【００４６】成形条件は以下の通りである。
【００４７】射出温度、射出圧力、使用樹脂及び樹脂の充填量は、実施例１と同様にした。キャビティ全体の、金型が型締めされる方向に投影した、投影図の面積は３０８７ｃｍ^２であった。
【００４８】
【表１】

【００４９】表１より、実施例１の型締め力のほうが、比較例１の型締め力より小さく、実施例１のほうが低い圧力で樹脂を充填することができるため、小さい型締め力で金型を型締めすることができることがわかる。
【００５０】
【発明の効果】以上説明したように、本発明によって、樹脂成形体を射出成形するときに、金型のキャビティ内に、樹脂の流れ抵抗が大きく、樹脂が流れ難い領域がある場合に、その樹脂成形体を高圧を要さず、効率的に一体成形することができる樹脂成形体の成形方法を提供することができる。
【図面の簡単な説明】
【図１】本発明の樹脂成形体の成形方法の一の実施の形態に使用する金型を模式的に示す断面図で、（ａ）は可動ブロックを意匠側金型部に突き合わせるように移動する前の状態、（ｂ）は可動ブロックを意匠側金型部に突き合わせるように移動した後の状態、（ｃ）は複数の樹脂を射出した状態、（ｄ）はストッパー（当接ブロック）を可動ブロックに設定した例をそれぞれ示す。
【図２】本発明の樹脂成形体の成形方法の他の実施の形態に使用する金型を模式的に示す断面図で、（ａ）は可動ブロックを意匠側金型部に突き合わせるように移動する前の状態、（ｂ）は可動ブロックを意匠側金型部に突き合わせるように移動した後の状態、（ｃ）は複数の樹脂を射出した状態をそれぞれ示す。
【図３】自動車のドアトリムを模式的に示す平面図である。
【図４】本発明の樹脂成形体の成形方法の他の実施の形態に使用する金型を模式的に示す断面図で、（ａ）は可動ブロックを意匠側金型部に突き合わせるように移動した後の状態、（ｂ）は複数の樹脂を射出した状態をそれぞれ示す。
【図５】本発明の樹脂成形体の成形方法の他の実施の形態に使用する金型を模式的に示す断面図で、（ａ）は可動ブロックを意匠側金型部に突き合わせるように移動した後の状態、（ｂ）は複数の樹脂を射出した状態をそれぞれ示す。
【図６】本発明の樹脂成形体の成形方法の他の実施の形態に使用する金型を模式的に示す断面図で、（ａ）は可動ブロックを意匠側金型部に突き合わせるように移動した後の状態、（ｂ）は複数の樹脂を射出した状態をそれぞれ示す。
【図７】本発明の樹脂成形体の成形方法の他の実施の形態に使用する金型を模式的に示す断面図で、（ａ）は可動ブロックを意匠側金型部に突き合わせるように移動した後の状態、（ｂ）は複数の樹脂を射出した状態をそれぞれ示す。
【図８】本発明の樹脂成形体の成形方法の他の実施の形態に使用する金型を模式的に示す断面図で、（ａ）は可動ブロックを意匠側金型部に突き合わせるように移動した後の状態、（ｂ）は複数の樹脂を射出した状態をそれぞれ示す。
【符号の説明】
１…意匠側金型部、２…非意匠側金型部、３…可動ブロック、４…複数の樹脂、４ａ…先の射出順位の樹脂（一次樹脂）、４ｂ…後の射出順位の樹脂（二次樹脂）、５…キャビティ、５ａ…一次樹脂に対応するキャビティ、５ｂ…二次樹脂に対応するキャビティ、６…見切り部、７…ストッパー、７ａ…当接ブロック、１０…金型、１１…意匠側金型部、１２…非意匠側金型部、１３…可動ブロック、１４…複数の樹脂、１４ａ…一次樹脂、１４ｂ…二次樹脂、１５…キャビティ、１５ａ…一次樹脂に対応するキャビティ、１５ｂ…二次樹脂に対応するキャビティ、１６…見切り部、２０…金型、３１…ドアトリム、３２…網状部、３３…ドアトリムの網状部以外の部分、４０…金型、４１…意匠側金型部、４２…非意匠側金型部、４３…可動ブロック、４４ａ…先の射出順位の樹脂（一次樹脂）、４４ｂ…後の射出順位の樹脂（二次樹脂）、４５ａ，４５ｂ…キャビティ、４６…肉厚部、５０…金型、５１…意匠側金型部、５２…非意匠側金型部、５３…可動ブロック、５４ａ…一次樹脂、５４ｂ…二次樹脂、５５，５５ａ，５５ｂ…キャビティ、５６…凹凸、６０…金型、６１…意匠側金型部、６２…非意匠側金型部、６３…可動ブロック、６４ａ…一次樹脂、６４ｂ…二次樹脂、６５，６５ａ，６５ｂ…キャビティ、７０…金型、７１…意匠側金型部、７２…非意匠側金型部、７３…可動ブロック、７３ａ，７３ｂ…可動ブロック片、７４ａ…一次樹脂、７４ｂ…二次樹脂、７５，７５ａ，７５ｂ…キャビティ、８０…金型、８１…意匠側金型部、８２…非意匠側金型部、８３…可動ブロック、８３ａ，８３ｂ…可動ブロック片、８４ａ…一次樹脂、８４ｂ…二次樹脂、８５，８５ａ，８５ｂ…キャビティ、８６…アンダーカット部、ｔ１，ｔ２…可動ブロックと意匠側金型部との間の突き合わせ隙間、Ｌ…可動ブロックの長さ、Ｗ…意匠側金型部の先端部の断面平面部分の幅。[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a resin molded article, and more particularly, to a method for injection molding of a resin molded article, in which a region where the flow resistance of the resin is large and which is difficult to flow is formed in a cavity of a mold. In some cases, the present invention relates to a method for molding a resin molded body that can efficiently integrally mold the resin molded body.
[0002]
2. Description of the Related Art In a resin injection molding method, a plastic material (resin) is heated and melted, injected into a cavity of a mold by a screw or a plunger or the like, and cooled and solidified or heated and cured in the mold. This is to obtain a resin molded body. By this injection molding method, it is possible to obtain a highly accurate resin molded body that is faithful to the shape of the cavity of the mold.
[0003] However, such an injection molding method also has a problem in that the obtained resin molded body has a partially fine structure, and the cavity of a mold corresponding to the part has a narrow and / or complicated structure. There is a problem that the resin injected into the cavity becomes difficult to be filled in the portion, which requires a long time for filling, a high filling pressure, and a portion that is not filled remains.
[0004] As described above, when the resin is injected into the mold cavity and there is a portion that is difficult to be filled because the resin is hard to flow, a resin molded body corresponding to the portion that is difficult to be filled with the resin is separated. Molding with a mold, further molding the resin molded body from the original resin molded body except for the portion that is difficult to be filled with resin with another mold, and combining the obtained two resin molded bodies A resin molding can be obtained. However, as described above, two resin molded articles or, in the case of a more complicated structure, three or more resin molded articles are separately injection-molded using different molds, and the obtained resin molded articles are obtained. When combined into one resin molded body, two or more molds are prepared, injection molded separately for each, and the finally obtained injection molded body must be combined into one, There was a problem that they did not fit perfectly.
[0005] Therefore, when such a resin molded body having a partially fine structure is to be integrally molded by injection molding with one mold, the resin is forcibly filled in a portion where the resin is hardly filled. Therefore, there is a problem that a high pressure is required, an extra operation such as heating the portion to lower the viscosity of the resin is required, a complicated apparatus is required, and productivity is reduced. .
For example, in a door trim of an automobile, as shown in FIG. 3, there is a case where a mesh portion is formed at a speaker installation position so that sound from the speaker can be transmitted well, but the door trim is injection-molded. In the case of integral molding, the resin in the region corresponding to the mesh portion of the mold cavity is more difficult to flow than the region corresponding to the other portion, and the resin corresponding to the region corresponding to the mesh portion is more difficult to fill. In addition, it is necessary to heat only the region corresponding to the mesh portion to improve the flow of the resin, and there is a problem that the efficiency is extremely low.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. When injection molding a resin molding, there is a region in the cavity of a mold where the flow resistance of the resin is large and it is difficult to flow. In some cases, an object of the present invention is to provide a method for molding a resin molded body that can efficiently integrally mold the resin molded body.
[0008]
In order to achieve the above object, the present invention provides the following method for molding a resin molded article.
[1] A method of molding a resin molded body by integrally injecting a resin molded body by injecting a resin into a cavity of a mold, wherein a flow of the resin to be filled in the cavity in the cavity of the mold. Dividing into a plurality of areas corresponding to the difficulty, and moving one or more movable blocks to the design-side mold portion to abut one of the divided areas in the plurality of areas. Along with the partition, the primary resin is injected into an area partitioned by the movable block, and then the movable block is sequentially retracted from the inside of the cavity, and sequentially into another area which is closed by the movable block inside the cavity. A method for molding a resin molded body, comprising injecting a secondary or subsequent resin.
[2] The method for molding a resin molded article according to [1], wherein the respective resins injected into the plurality of regions are joined at a cut-off portion.
[3] Among the resins injected into the plurality of regions, the color and / or material of the resin injected into at least the one region is different from the color and / or material of the resin injected into the other region. The method for molding a resin molded article according to [1] or [2].
[4] The method for molding a resin molded article according to any one of [1] to [3], wherein a butt gap (t1) between the movable block and the design-side mold portion is 0.1 mm or less.
[5] The method for molding a resin molded article according to any one of [1] to [4], wherein the mold includes a stopper for stopping movement of the movable block.
[6] The method for molding a resin molded article according to [5], wherein the stopper is a contact block provided on the non-design side mold portion and in contact with the movable block.
[7] The method for molding a resin molded article according to [6], wherein a hardness of a material forming the contact block is smaller than a hardness of a material forming the movable block.
[8] The width (W) of the cross-sectional plane portion of the tip of the design-side mold portion corresponding to the parting-off portion is 0.5 mm or less, and the length (L) of the movable block is the parting-off portion. The method for molding a resin molded article according to any one of [2] to [7], wherein the resin is extended by 0.1 mm or more to the resin side of the earlier injection order among the plurality of resins.
[9] The method for molding a resin molded article according to [8], wherein a butt gap (t2) between the movable block and the design-side mold portion is greater than 0 mm and 0.1 mm or less.
[10] The method for molding a resin molded article according to [8] or [9], wherein the mold includes a stopper for restricting movement of the movable block.
[11] The method for molding a resin molded article according to [10], wherein the stopper is a contact block provided on the non-design side mold portion and in contact with the movable block.
[12] The method for molding a resin molded article according to [11], wherein a hardness of a material forming the contact block is lower than a hardness of a material forming the movable block.
[13] The movable block is retracted from the cavity immediately after the primary resin starts to solidify in the vicinity of the movable block and before the movable block of the primary resin completely solidifies at the latest, and then the interior of the cavity is removed. The method for molding a resin molded article according to any one of [1] to [12], wherein the secondary resin is injected into a space where the remaining resin remains, and is sunk into the primary resin.
[14] The method for molding a resin molded article according to [13], wherein a portion near the movable block of the primary resin into which the secondary resin enters is a thick portion.
[15] The movable block is formed obliquely so that the side end in contact with the primary resin becomes gradually thinner from the design surface side to the non-design surface side, and the oblique surface is formed with irregularities [1]. ] The molding method of the resin molded article according to any one of [14] to [14].
[16] The movable block includes at least two or more blocks, and each block piece becomes a non-design surface and a flat surface when retracted from the cavity before the secondary resin is injected [15] ] The method for molding a resin molded article according to [1].
[17] The movable block is formed into a shape that partitions the vicinity of the movable block in the one area where the primary resin is injected so as to be undercut in a direction perpendicular to the thickness direction and perpendicular to the parting line. The method for molding a resin molded article according to any one of [1] to [16].
As described above, when the resin molded body is integrally molded by injection molding, the inside of the mold cavity is divided into a plurality of regions, the regions are partitioned by the movable block, and the movable block is moved (evacuated). While the resin is injected and filled, the resin can be injected and filled according to the injection conditions suitable for each area in the cavity, so that the resin is injected into an area with poor fluidity (an area where the flow resistance of the resin is large). Even in this case, the filling can be performed efficiently without requiring high pressure.
[0010]
Embodiments of the present invention will be specifically described below with reference to the drawings. However, the present invention is not limited to the following embodiments and departs from the spirit of the present invention. It should be understood that design changes, improvements, etc. may be made as appropriate based on the ordinary knowledge of those skilled in the art without departing from the scope of the present invention.
FIGS. 1A to 1D are cross-sectional views schematically showing a mold used in one embodiment of the method for molding a resin molded article of the present invention. In this embodiment, one region where the flow resistance of the resin is large (hard to flow) when the resin is injected into the cavity of the mold, and another region (the region where the flow resistance of the resin is small (easy to flow)). This is a method for molding a resin molded body by integrally molding the resin molded body using a mold having a cavity composed of the following.
The method for molding a resin molded article according to the present embodiment comprises a mold 10 having a design-side mold part 1, a non-design-side mold part 2, and a movable block 3 shown in FIG. It is used to mold a resin molded body by injection molding. The cavity 5 of the mold 10 is divided into two regions: a region 5a where the flow resistance of the resin is small and a region 5b where the flow resistance of the resin is large as shown in FIG. As shown in FIG. 1 (b), the cavity is partitioned by moving the movable block 3 so as to abut the design side mold part 1, and the movable block 3 and the design side mold are first filled with the resin. A cavity 5a is formed between the part 1 and the non-design side mold part 2. Then, the primary resin 4a is injected into the cavity 5a. At this time, since the cavity 5a is a region where the flow resistance of the resin is small, the resin can be easily injected and filled without applying a large injection pressure. Next, as shown in FIG. 1 (c), the movable block 3 is pulled down (retracted), and between the primary resin 4a, the design side mold part 1 and the non-design side mold part 2 (by the movable block 3). The cavity 5b having a large flow resistance of the resin is formed in the (blocked area). Then, the secondary resin 4b is injected into the cavity 5b and joined to the primary resin 4a at the parting-off portion 6. As a result, the resin can be separately filled into a region where the flow resistance of the resin is small and a region where the flow resistance of the resin is large, and the resin can be injected and filled under conditions suitable for each region. Need not be excessively large, and the occurrence of burrs and the like can be prevented. Further, the resin can be filled in a shorter time than in the case of molding with one mold, and the filling efficiency can be improved.
Both the primary resin 4a and the secondary resin 4b are injected and filled into the cavity 5 of the mold 10 in a molten state, and are cooled in the mold 10 to form a resin molded body. The resin molded article formed in the mold 10 is taken out of the mold 10 and subjected to a surface treatment or the like by a usual method to complete a resin molded article.
In the present invention, the magnitude of the flow resistance when the cavity 5 is filled with resin is represented by the mold clamping force when a certain amount of resin is filled into the cavity 5.
In the present embodiment, the case where the cavity 5 of the mold 10 is composed of two regions of the cavity 5a and the cavity 5b (divided into two regions) has been described. In the method of molding a body, the cavity of the mold may be divided into three or more regions, in which case the three or more regions are moved so that one or more movable blocks abut against the design side mold part. The primary resin is injected into the area partitioned by the movable block, and then the movable block is sequentially retracted, and the secondary and subsequent resins are sequentially removed into the area closed by the movable block in the cavity. May be injected, and the resin injected into each area may be joined at a parting-off portion.
In the method for molding a resin molded article of the present embodiment, the primary resin 4a and the secondary resin 4b shown in FIG. 1 (c) may be different in color and / or material. For example, a pigment to be added to the primary resin 4a and a pigment to be added to the secondary resin 4b can be made different from each other to form a two-color resin molded product. Further, the primary resin 4a and the secondary resin 4b have different functions. By using different resins, it is possible to obtain a resin molded body by integral molding partially having different functions. The functions of the resins of the primary resin 4a and the secondary resin 4b and the pigment to be added may be simultaneously different. When the cavity of the mold is composed of three or more regions, the color and / or material of the resin injected into at least one region may be different. For example, a multi-color molded article can be formed by making the pigment added to the resin injected into at least one region different from the pigment added to the resin injected into another region, and also injected into at least one region. By using a resin having a function different from that of the resin to be injected into other regions, a resin molded body formed by integral molding having partially different functions can be obtained.
The present embodiment can be suitably applied to the manufacture of a door trim for an automobile having a net portion formed at a speaker installation position or the like as shown in FIG. The car door trim 31 shown in FIG. 3 is mounted on the inner surface of a car door, and has a mesh portion 32 having a large number of meshes so that sound from a speaker embedded in the door can be transmitted well. Have been. When the door trim 31 provided with such a net portion 32 is integrally formed by injection molding, the difficulty of resin flow (flow resistance) in a region corresponding to the net portion 32 of the mold cavity is reduced by other portions. It is larger than the difficulty of flowing resin (flow resistance) in the region corresponding to 33, and it is difficult to fill the region corresponding to the mesh portion 32 with resin. Therefore, the mold cavity corresponding to the mesh portion 32 of the door trim 31 is denoted by 5b in FIG. 1C, and the mold cavity corresponding to the other portions 33 is denoted by 5a in FIG. By applying the molding method of the embodiment, the mesh portion 32 can also be efficiently molded, and the door trim 31 can be integrally molded efficiently without filling the resin with high pressure. At this time, the resin (4b) forming the mesh portion 32 of the door trim 31 may be made of a material having a different sound absorbing property from the resin (4a) forming the other portion 33. Alternatively, the pigment added to each of the resin 4a and the resin 4b may be different, and a two-color molded article may be used.
As shown in FIG. 1B, the mold used in the method of molding a resin molded body according to the present embodiment is a butt gap (t1) between the movable block 3 and the design side mold part 1. Is preferably 0.1 mm or less. In this case, the butting gap (t1) between the movable block 3 and the design side mold part 1 may be 0 mm. That is, the movable block 3 and the design side mold part 1 may be in a state of being completely contacted.
With this configuration, the configuration is simple and the butting gap (t1) between the movable block 3 and the design side mold portion 1 is 0.1 mm or less. In addition, the entry into the cavity 5b corresponding to the secondary resin is prevented, and the parting-off portion 6 of the resin joining portion is clear, so that a resin molded body excellent in design can be obtained. The non-design side mold part 2 may be a second design side mold part by applying a design to the surface of the mold. The movable block 3 is usually provided in the non-design side mold part 2 as shown in FIGS. 1A to 1D. It may be configured so as to abut against the non-design side mold part 2.
The resin used in the present invention is not particularly limited, and any kind of thermoplastic resin can be used regardless of its fluidity.
As for other molding conditions, the same conditions as in normal injection molding can be used, and it is preferable to perform injection molding at an injection pressure suitable for each region of the mold cavity.
As shown in FIGS. 1 (a) and 1 (b), in the present embodiment, a stopper 7 for stopping the movement of the movable block 3 may be further provided. It is preferable to secure the butting gap (t1) with the mold part 1 within a specific range and to further improve the durability.
In this case, it is preferable that the stopper 7 is a contact block 7a which is in contact with the movable block 3, and the hardness of the material forming the contact block 7a is more than the hardness of the material forming the movable block 3. It is even more preferable that the value be small. With this configuration, the wear caused by the contact and abutment between the movable block 3 and the contact block 7a is limited to only the contact block 7a side, and it is easy to replace only the worn contact block 7a. In this way, the butting gap (t1) between the movable block 3 and the design-side mold portion 1 can be secured in a specific range.
The stopper 7 (contact block 7a) may be provided in the mold, for example, on the non-design side mold portion 2, or a stroke end block or the like may be provided at a predetermined position outside the mold. It may be provided. Further, as shown in FIG. 1 (d), the non-design side mold 2 may be provided in the movable block 3 to make contact with the non-design side mold 2.
FIGS. 2A to 2C are cross-sectional views schematically showing a mold used in another embodiment of the method for molding a resin molded article of the present invention. The method for molding a resin molded article according to the present embodiment uses a mold 20 having a design-side mold portion 11, a non-design-side mold portion 12, and a movable block 13 shown in FIG. A resin molded article is formed by injection molding. The cavity 15 of the mold 20 includes a region 15a in which the flow resistance of the resin is small (easy to flow) as shown in FIG. 2B and a region 15b in which the flow resistance of the resin is large (hard to flow) as shown in FIG. It is composed of two areas (divided into two areas). As shown in FIG. 2 (b), the cavity is partitioned by moving the movable block 13 such that the movable block 13 abuts on the design side mold part 11, and the movable block 13 and the design side mold are first filled with the resin. A cavity 15a is formed between the part 11 and the non-design side mold part 12. Then, the primary resin 14a is injected into the cavity 15a. At this time, since the cavity 15a is a region where the flow resistance of the resin is small, the resin can be easily injected and filled without increasing the injection pressure. Next, as shown in FIG. 2C, the movable block 13 is pulled down (retracted), and between the primary resin 14a, the design-side mold portion 11 and the non-design-side mold portion 12 (by the movable block 13). The cavity 15b is formed in the (blocked area). Then, the secondary resin 14b is injected into the cavity 15b, and is joined to the primary resin 14a at the parting-off portion (line) 16. At this time, the cavity 15b is a region where the flow resistance of the resin is large, but since only this portion needs to be filled with the resin, the resin can be filled without applying high pressure, and the resin can be filled in a short time. And the filling efficiency can be improved.
The primary resin 14a and the secondary resin 14b are both injected and filled into the cavity 15 of the mold 20 in a molten state, and cooled in the mold 20 to have a shape of a resin molded body. The resin molded article formed in the mold 20 is taken out of the mold 20 and subjected to a surface treatment or the like by an ordinary method to complete a resin molded article.
In the present embodiment, as shown in FIGS. 2A to 2C, the width (W) of the cross-sectional plane portion at the tip of the design-side mold portion 11 corresponding to the parting-off portion 16 is 0. It is preferable that the length (L) of the movable block is not less than 0.5 mm and the length (L) of the movable block is extended to the primary resin 14a side of the plurality of resins by 0.1 mm or more.
In the case where the width (W) of the sectional plane portion at the tip of the design-side mold portion 11 is as narrow as 0.5 mm or less, the durability of this portion tends to be a problem. It is preferable to use a material having high abrasion resistance or to perform abrasion resistance surface treatment or the like.
As described above, when the width (W) of the sectional plane portion at the tip of the design side mold portion 11 is small, the length (L) of the movable block is set to be smaller than that of the parting portion 16 by the primary resin. By extending 0.1 mm or more to the side 14a, the configuration is simple, the primary resin 14a is prevented from entering the cavity 15b corresponding to the secondary resin, and the parting-off portion 16 of the resin joint is clean. Thus, it is possible to obtain a resin molded body having excellent design properties.
In this case, since the butting gap (t2) between the movable block 13 and the design-side mold portion 11 is larger than 0 mm, they do not come into contact with each other, and the durability can be improved. At the same time, since the butting gap (t1) is 0.1 mm or less, the primary resin 14a is prevented from entering the cavity 15b corresponding to the secondary resin, and the parting-off portion 16 of the resin joining portion is neat and has a good design. It is preferable to obtain a resin molded product excellent in the above.
In this case, as in the case described above, a stopper (not shown) for restricting the movement of the movable block should be further provided, and the stopper provided on the non-design side mold portion should be provided. It is preferable that the contact block is in contact with the block, and the hardness of the material forming the contact block is smaller than the hardness of the material forming the movable block.
FIGS. 4A and 4B are cross-sectional views schematically showing a mold used in another embodiment of the method for molding a resin molded article of the present invention. The method for molding a resin molded body according to the present embodiment uses a mold 40 having a design-side mold portion 41, a non-design-side mold portion 42, and a movable block 43, as shown in FIG. A resin molded article is formed by injection molding. The cavity 45 of the mold 40 includes a region (cavity) 45a where the flow resistance of the resin is small (easy to flow) and a region (cavity) 45b where the flow resistance of the resin is large (hard to flow) as shown in FIG. It is composed of two areas (divided into two areas).
In this embodiment, a thick portion 46 is formed in the vicinity of the movable block 43 of 45a. The cavity 45a is filled with the primary resin 44a, and immediately after the primary resin 44a starts to be solidified in the vicinity of the movable block 43, the movable block 43 is filled with the cavity 45a at the latest before the vicinity of the movable block 43 of the primary resin 44a is completely solidified. After being retracted from the inside, the secondary resin 44b is injected into the cavity 45b so as to be sunk into the primary resin 44a. As a result, an integral molded product having a good parting line and excellent design can be obtained, and at the same time, the secondary resin 44b is joined in a state of being sunk into the primary resin 44a.
FIGS. 5A and 5B are cross-sectional views schematically showing a metal mold used in another embodiment of the method for molding a resin molded article of the present invention. The method for molding a resin molded body according to the present embodiment uses a mold 50 having a design-side mold portion 51, a non-design-side mold portion 52, and a movable block 53, as shown in FIG. A resin molded article is formed by injection molding. The cavity 55 of the mold 50 includes a region (cavity) 55a in which the flow resistance of the resin is small (easy to flow) and a region (cavity) 55b in which the flow resistance of the resin is large (hard to flow) as shown in FIG. It is composed of two areas (divided into two areas).
In the present embodiment, the end of the movable block 53 is slanted, that is, the side end in contact with the primary resin 54a of the movable block 53 becomes gradually thinner from the design surface side to the non-design surface side. It is formed diagonally. And the unevenness 56 is formed in the diagonal surface. Thereby, after injecting the primary resin 54a into the cavity 55a, solidifying the vicinity of the movable block 53 of the primary resin 54a, and then injecting the secondary resin 54b into the cavity 55b generated by the retreat of the movable block 53, the secondary resin 54b Flows into the non-design surface side of the primary resin 54a and presses the primary resin 54a from the non-design surface side toward the design surface side, so that the gap with the cavity 55 is closed. At the same time, the unevenness 56 is formed on the joint surface between the primary resin 54a and the secondary resin 54b, so that the joint strength can be improved.
In this embodiment, in addition to cutting the tip of the movable block 53 obliquely on a straight line, the tip of the movable block 63 may be cut in a stepwise manner as shown in FIG. 6, reference numeral 60 denotes a mold, 61 denotes a design side mold part, 62 denotes a non-design side mold part, 64a denotes a primary resin, 64b denotes a secondary resin, and 65a and 65b denote cavities, respectively.
As shown in FIG. 7, the movable block 73 is composed of two movable block pieces 73a and 73b, and each block piece is retracted from the cavity 75 before the secondary resin is injected. In addition, by making the non-design surface flat, a molded product having a flat non-design surface can be obtained. 7, reference numeral 70 denotes a mold, 71 denotes a design side mold portion, 72 denotes a non-design side mold portion, 74a denotes a primary resin, 74b denotes a secondary resin, and 75a and 75b denote cavities, respectively.
FIGS. 8A and 8B are cross-sectional views schematically showing a mold used in another embodiment of the method for molding a resin molded article of the present invention. The method for molding a resin molded body according to the present embodiment uses a mold 80 having a design-side mold portion 81, a non-design-side mold portion 82, and a movable block 83, as shown in FIG. A resin molded article is formed by injection molding. The cavity 85 of the mold 80 includes a region (cavity) 85a in which the flow resistance of the resin is small (easy to flow) and a region (cavity) 85b in which the flow resistance of the resin is large (hard to flow) shown in FIG. It consists of two areas.
In the present embodiment, the area near the movable block 83 in the region (cavity 85a) where the movable block 83 injects the primary resin 84a is undercut perpendicular to the thickness direction and perpendicular to the parting line. It is formed in such a shape as to partition (to form the undercut portion 86). In the present embodiment, when the secondary resin 84b is injected after the movable block 83 is retracted, the movable block 83 has a structure in which the undercut portion 86 of the primary resin 84a is arranged on the non-design surface. Then, the secondary resin 84b enters the non-design surface side of the primary resin 84a, and a force that presses the vicinity of the primary resin 84a against the design-side mold portion 81 acts, so that the gap between the primary resin 84a and the design-side mold portion 81 is reduced. Since the next resin 84b does not easily enter, the parting line is also improved.
[0040]
EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.
The automobile door trim shown in FIG. 3 was manufactured as follows. In this door trim, at the time of injection molding, the flow resistance of the resin in the mesh portion is larger than the flow resistance of the resin in portions other than the mesh portion.
[0042]
(Example 1)
When the door trim of the automobile shown in FIG. 3 was manufactured using the mold shown in FIG. 1, the internal pressure was measured when a fixed amount of resin was filled in portions other than the mesh portion, and the mold clamping force was calculated. . Table 1 shows the results.
The molding conditions are as follows.
For the portions other than the mesh portion, the injection temperature was 220 ° C., the injection pressure was 90 MPa, the resin used was polypropylene, and the filling amount of the resin was 1000 cm. ³ And In addition, the area of the projection corresponding to the portion other than the mesh portion, which is projected in the direction in which the mold is clamped, is 2905 cm. ² Met.
[0045]
(Comparative Example 1)
A method of simultaneously filling the cavities corresponding to the mesh portion and the portion other than the mesh portion of the door trim of the automobile shown in FIG. 3 using a normal integral molding die (filling both cavities with one injection). The internal pressure when the resin was filled in a fixed amount was measured, and the mold clamping force was calculated. Table 1 shows the results.
The molding conditions are as follows.
The injection temperature, the injection pressure, the resin used and the filling amount of the resin were the same as in Example 1. The projected area of the entire cavity in the direction in which the mold is clamped is 3087 cm. ² Met.
[0048]
[Table 1]

According to Table 1, the mold clamping force of Example 1 is smaller than the mold clamping force of Comparative Example 1, and the resin of Example 1 can be filled with a lower pressure. It can be seen that the mold can be clamped.
[0050]
As described above, according to the present invention, when a resin molded body is injection-molded, when there is a region where the flow resistance of the resin is large and the resin is difficult to flow in the cavity of the mold, the injection molding is performed. It is possible to provide a method for molding a resin molded body that can efficiently be integrally molded without requiring high pressure.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a mold used in one embodiment of a method for molding a resin molded body of the present invention, wherein FIG. 1 (a) shows a movable block abutting on a design side mold portion. A state before the movement, (b) a state after the movable block is moved so as to abut against the design side mold part, (c) a state where a plurality of resins are injected, and (d) a stopper (abutting block). ) Are set as movable blocks.
FIG. 2 is a cross-sectional view schematically showing a mold used in another embodiment of the method for molding a resin molded article of the present invention, in which (a) shows a movable block abutting on a design side mold section. (B) shows a state after moving the movable block so as to abut the design side mold part, and (c) shows a state where a plurality of resins are injected.
FIG. 3 is a plan view schematically showing an automobile door trim.
FIG. 4 is a cross-sectional view schematically showing a mold used in another embodiment of the method for molding a resin molded body of the present invention, wherein FIG. (B) shows a state after a plurality of resins have been injected.
FIG. 5 is a cross-sectional view schematically showing a mold used in another embodiment of the method for molding a resin molded body of the present invention, in which (a) shows a movable block abutting on a design side mold portion. (B) shows a state after a plurality of resins have been injected.
FIG. 6 is a cross-sectional view schematically showing a mold used in another embodiment of the method of molding a resin molded body according to the present invention, wherein (a) shows a movable block abutting on a design-side mold portion. (B) shows a state after a plurality of resins have been injected.
FIG. 7 is a cross-sectional view schematically showing a mold used in another embodiment of the method for molding a resin molded body of the present invention, where (a) shows a movable block abutting on a design side mold portion. (B) shows a state after a plurality of resins have been injected.
FIG. 8 is a cross-sectional view schematically showing a mold used in another embodiment of the method for molding a resin molded body according to the present invention, wherein (a) shows a movable block abutting on a design side mold portion. (B) shows a state after a plurality of resins have been injected.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Design side mold part, 2 ... Non-design side mold part, 3 ... Movable block, 4 ... Plural resins, 4a ... Resin of first injection order (primary resin), 4b ... Resin of next injection order ( 5: cavity, 5a: cavity corresponding to primary resin, 5b: cavity corresponding to secondary resin, 6: parting-off part, 7: stopper, 7a: contact block, 10: mold, 11 ... Design side mold part, 12 ... non-design side mold part, 13 ... movable block, 14 ... plural resins, 14a ... primary resin, 14b ... secondary resin, 15 ... cavity, 15a ... cavity corresponding to primary resin, 15b: cavity corresponding to the secondary resin, 16: parting-off portion, 20: mold, 31: door trim, 32: mesh portion, 33: portion other than the mesh portion of the door trim, 40: mold, 41: design side mold Part, 42: Non-design side mold part, 43: Possible Block, 44a: resin in the first order of injection (primary resin), 44b: resin in the second order of injection (secondary resin), 45a, 45b: cavity, 46: thick part, 50: mold, 51: design side Mold part, 52: Non-design side mold part, 53: Movable block, 54a: Primary resin, 54b: Secondary resin, 55, 55a, 55b: Cavity, 56: unevenness, 60: Mold, 61: Design side Mold part, 62: Non-design side mold part, 63: Movable block, 64a: Primary resin, 64b: Secondary resin, 65, 65a, 65b: Cavity, 70: Mold, 71: Design side mold part, 72: Non-design side mold part, 73: movable block, 73a, 73b: movable block piece, 74a: primary resin, 74b: secondary resin, 75, 75a, 75b: cavity, 80: mold, 81: design side Mold part, 82 ... Non-design side mold part, 8 .. Movable block, 83a, 83b movable block piece, 84a primary resin, 84b secondary resin, 85, 85a, 85b cavity, 86 undercut part, t1, t2 movable block and design side mold part , L: length of the movable block, W: width of the cross-sectional plane portion at the tip of the design-side mold portion.

Claims

A method for molding a resin molded body by integrally molding a resin molded body by injecting a resin into a cavity of a mold,
The cavity of the mold is divided into a plurality of regions corresponding to the difficulty of flowing the resin filled in the cavity,
One of the divided areas is partitioned by moving one or more movable blocks to the design-side mold part and abutting the movable block on the one side, and the primary area is divided into the areas partitioned by the movable blocks. Inject resin,
Next, the movable block is sequentially retracted from the inside of the cavity, and the secondary and subsequent resins are sequentially injected into another region which is closed by the movable block inside the cavity, and a method for molding a resin molded body is provided. .

The method of molding a resin molded body according to claim 1, wherein each of the resins injected into the plurality of regions is joined at a cut-off portion.

The color and / or material of the resin injected into at least one of the resins injected into the plurality of regions is different from the color and / or material of the resin injected into another region. Or the method of molding a resin molded article according to 2.

The method for molding a resin molded product according to any one of claims 1 to 3, wherein a butting gap (t1) between the movable block and the design-side mold portion is 0.1 mm or less.

The method according to any one of claims 1 to 4, wherein the mold includes a stopper for stopping the movement of the movable block.

The method of molding a resin molded product according to claim 5, wherein the stopper is a contact block provided on the non-design side mold portion and in contact with the movable block.

The method for molding a resin molded body according to claim 6, wherein the hardness of the material forming the contact block is lower than the hardness of the material forming the movable block.

The width (W) of the sectional plane portion of the tip portion of the design-side mold portion corresponding to the parting-off portion is 0.5 mm or less, and the length (L) of the movable block is greater than that of the parting-off portion. The method for molding a resin molded article according to any one of claims 2 to 7, wherein the resin is extended by 0.1 mm or more to the resin side of the earlier injection order among the plurality of resins.

The method of molding a resin molded product according to claim 8, wherein a butting gap (t2) between the movable block and the design-side mold portion is larger than 0 mm and 0.1 mm or less.

The method according to claim 8, wherein the mold includes a stopper that restricts movement of the movable block.

The method according to claim 10, wherein the stopper is a contact block provided on the non-design side mold portion and in contact with the movable block.

The method of molding a resin molded body according to claim 11, wherein a hardness of a material forming the contact block is lower than a hardness of a material forming the movable block.

In the vicinity of the movable block, immediately after the primary resin starts to solidify, and before the movable block of the primary resin is completely solidified at the latest, the movable block is retracted from the cavity, and the remaining space in the cavity is left. The method for molding a resin molded article according to any one of claims 1 to 12, wherein a secondary resin is injected into the primary resin to be sunk into the primary resin.

The method according to claim 13, wherein a portion near the movable block of the primary resin into which the secondary resin enters is a thick portion.

The side end in contact with the primary resin of the movable block is formed diagonally so as to become gradually thinner from the design surface side to the non-design surface side, and the diagonal surface is formed with irregularities. The method for molding a resin molded article according to any one of the above.

The said movable block consists of at least two or more blocks, and each block piece becomes a non-design surface and a flat surface when retreating from the inside of a cavity before secondary resin is injected. Molding method of the resin molded article.

The movable block is formed in a shape that partitions the vicinity of the movable block in the one area for injecting the primary resin so as to be undercut in a direction perpendicular to a thickness direction and a direction perpendicular to a parting line. A method for molding a resin molded article according to any one of claims 1 to 16.