JP3574174B2 - Molding method of multilayer molded body - Google Patents

Molding method of multilayer molded body Download PDF

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Publication number
JP3574174B2
JP3574174B2 JP11339094A JP11339094A JP3574174B2 JP 3574174 B2 JP3574174 B2 JP 3574174B2 JP 11339094 A JP11339094 A JP 11339094A JP 11339094 A JP11339094 A JP 11339094A JP 3574174 B2 JP3574174 B2 JP 3574174B2
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Prior art keywords
molten resin
injected
pressure
pressurized gas
hollow portion
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JPH07299841A (en
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茂生 新宮
芳博 大原
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Asahi Kasei Chemicals Corp
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Asahi Kasei Chemicals Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/1703—Introducing an auxiliary fluid into the mould
    • B29C45/1704—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles
    • B29C45/1705—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles using movable mould parts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
    • B29C45/1418—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles the inserts being deformed or preformed, e.g. by the injection pressure

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)

Description

【０００１】
【産業上の利用分野】
本発明は、例えば自動車、一般機械、電気・電子機器等の分野に広く利用される複層成形体の成形方法に関する。
【０００２】
【従来の技術】
樹脂層の表面にファブリックあるいはレザーなどの表皮層を有する複層成形体は、その改善された表面性ゆえに各種産業分野において需要が増している。
【０００３】
かかる複層成形体の成形方法としては、表皮層をセットした金型キャビティ内に、金型キャビティを不完全に閉じた状態で溶融樹脂を注入し、その後金型キャビティを完全に閉じて成形する、いわゆるスタンピングあるいは圧縮成形方法が知られており、各種の複層成形体が実用に供されている。
【０００４】
一方、溶融樹脂中に高圧のガスを注入して成形する、例えば特公昭５７−１４９６８号に代表されるいわゆる中空射出成形方法が、成形体の“ひけ”や変形を防止し外観を向上，改善できる成形方法として広く応用されだしている。
【０００５】
また、上記のスタンピングあるいは圧縮成形方法と中空射出成形方法を組み合わせた方法が特開平４−７４６１７号，特開平４−２５５３１４号などで提案されている。
【０００６】
【発明が解決しようとする課題】
しかしながら、従来提案されている方法では、単なるスタンピングあるいは圧縮成形方法による場合よりも成形体の状態は改善されるものの、以下のような問題点が有った。
【０００７】
例えば、金型が僅かに開いた状態で溶融樹脂を注入し、金型を完全に閉じて溶融樹脂を圧縮した後にガスを注入する方法では、樹脂の充填圧力が高いためにガスの注入が不完全な状態になりやすく、中空部の形成による効果が十分に発揮されない場合が有った。
【０００８】
また、特開平４−７４６１７号で提案されているように、金型が僅かに開いた状態で溶融樹脂を注入し、樹脂を注入しつつ或は加圧成形に至る過程でガスを注入する方法では、金型締めの過程における樹脂圧にばらつきが生じやすく、樹脂中に形成される中空部が不規則に変形し、特に非対称形の成形体を成形する場合には所定の位置以外の不必要な部分に中空部が形成され、成形体の外観や品質の低下さらには強度低下を招きやすい。
【０００９】
また、特開平４−２５５３１４号で提案されているように、金型が僅かに開いた状態で溶融樹脂を注入し、金型締めの完了前あるいは完了と同時にガスを注入し、さらにガスを注入しつつ金型を僅かに開く方法では、中空部の変形は比較的少ないものの、成形体の寸法精度が低下するため、精密部品の成形には適さない。
【００１０】
本発明は上記の問題点に着目してなされたものであって、その目的とするところは、中空部の形成を容易にし、成形品の“ひけ”や変形を改善し優れた外観を確保し得ると共に、型再現性に優れ精密部品の成形にも十分に対応することのできる複層成形体の成形方法を提供することにある。
【００１１】
【課題を解決するための手段及び作用】
このために請求項１の発明では、少なくとも、樹脂層と表皮層からなる複層成形体の成形方法において、
表皮層を配置、溶融樹脂を注入した不完全に閉じた状態の金型キャビティを段階的に閉じ、金型キャビティが不完全に閉じている段階で溶融樹脂中に加圧ガスを注入して予備中空部を形成し、金型キャビティを完全に閉じた段階で予備中空部に更に加圧ガスを注入し金型キャビティが完全に閉じたままの状態で最終的な中空部を形成することを特徴とする複層成形体の成形方法としているものである。
【００１２】
本発明の成形方法においては、金型キャビティが不完全に閉じている段階で、金型キャビティ内の溶融樹脂中に加圧ガスを注入し、予備中空部を形成する。この段階では溶融樹脂の圧力は比較的低圧であるため、容易に且つ確実に加圧ガスを注入することができる。
【００１３】
そして、金型キャビティを完全に閉じた段階で、上記の予備中空部に更に加圧ガスを注入する。この段階では溶融樹脂は比較的高圧であるものの、すでに形成されている予備中空部に加圧ガスを注入するものであるため、容易に且つ確実に加圧ガスを注入することができ、最終的な中空部の形状をある程度制御することができる。すなわち、予め形成した予備中空部に更に加圧ガスを注入することにより、該予備中空部を核として、最終的な中空部に成長させることができるのである。
【００１４】
通常、予備中空部は、金型キャビティを閉じていくに従い、その過程において生ずる樹脂圧のばらつきにより変形する。特に非対称形の成形体を成形する場合には上記の現象が顕著に現れる。
【００１５】
このため、本発明においては、予備中空部は必要最低限の大きさで形成するのが好ましい。
【００１６】
予備中空部が大き過ぎると、金型キャビティを完全に閉じた段階では、その形状が大きく変形していることが多い。このように変形した予備中空部に加圧ガスを注入すると、最終的に形成される中空部も予定していた形状にならず不必要な部分にまで中空部が形成されがちである。
【００１７】
また本発明においては、溶融樹脂中に注入される加圧ガスの圧力を、各段階における溶融樹脂の圧力に応じて制御することが好ましい。
【００１８】
すなわち、溶融樹脂が低圧の段階においては、低圧の加圧ガスでも容易に圧入することができるため低圧に制御する。これによりガスの注入量をより厳密に制御することができ、予備中空部を所望の大きさで形成することができる。そして溶融樹脂が高圧の段階では、より高圧の加圧ガスを注入して中空部を成長させる。
【００１９】
以上のように本発明によれば、溶融樹脂中への加圧ガスの注入を極めて容易に良好な状態で行うことができ、中空部の大きさや形状を制御して不必要な部位に中空が形成されるのを防止することができる。このため、複層成形品の“ひけ”や変形を防止し更なる外観の向上が成されると共に、不必要な中空部が形成されることによる強度低下を防止することができる。
【００２０】
【実施例】
以下に実施例をもって本発明を説明する。
【００２１】
本例の成形工程について図１を用いて説明する。
【００２２】
先ず、図１（ａ）に示されるように、可動型１と固定型２からなる金型キャビティを不完全に閉じた状態で、表皮層３をセットし、溶融樹脂４を注入するか、又は溶融樹脂４を注入し、表皮層３をセットする。不完全に閉じた状態とは、図１（ａ）のように可動型１と固定型２が完全に離合した状態に限らず、図１（ｂ）のように可動型１と固定型２の一部は噛み合うが、いわゆるパーティング面は噛み合わない状態であっても良く、さらにはキャビティを複数のブロックで構成した場合には、パーティング面は噛み合うが一部のブロックに圧縮可能な圧縮代が残っている状態であっても良い（不図示）。
【００２３】
尚、キャビティを複数のブロックで構成するには、例えば可動型１と固定型２の少なくとも一方を複数のブロックに分割すればよい。そして、各ブロック毎に油圧機構やバネ機構等の開閉機構を備えることで、各ブロック毎に段階的に閉じることができる。
【００２４】
表皮層３としては、織布、不織布、繊維、紙、金属や熱可塑性樹脂及び熱可塑性エラストマーのシートまたはフィルム等を用いることができる。また、ポリオレフィン系，ポリスチレン系，ポリ塩化ビニル系等の熱可塑性樹脂製、ポリウレタン系等の熱硬化性樹脂製あるいはゴム製の発泡体を用いることができる。さらに、これらを単独でもしくは２種以上を積層して用いることもできる。
【００２５】
溶融樹脂４の注入は、樹脂ノズル（不図示）或は金型に設けた樹脂供給ライン（不図示）等から行うが、特にその方法は限定されない。
【００２６】
溶融樹脂４としては熱硬化性樹脂を用いることもできるが、熱可塑性樹脂が好ましく用いられる。熱可塑性樹脂としては、例えば、ポリエチレン、ポリプロピレン、ポリスチレン、ＡＢＳ樹脂、ＡＳ樹脂、ポリ塩化ビニル、ポリアミド、ポリアセタール、ポリカーボネイト、変性ポリフェニレンエーテル、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリフェニレンスルフィド、ポリイミド、ポリアミドイミド、ポリエーテルイミド、ポリアリレート、ポリサルフォン、ポリエーテルサルフォン、ポリエーテルエーテルケトン、液晶ポリマー、テトラフルオロエチレン、熱可塑性エラストマー等が挙げられる。さらには、これらの熱可塑性樹脂の混合体や、耐熱性及び機械的強度をアップする目的で、無機及び／又は有機の充填材を配合した樹脂を用いることもできる。
【００２７】
金型キャビティ内に溶融樹脂４を注入した後、図１（ｃ）のように金型キャビティは一段階閉じられる。そして、加圧ガス注入機構５により溶融樹脂４の圧力に応じて比較的低圧に制御された加圧ガスを、ガス注入口６より溶融樹脂４中に注入して、予備中空部７を形成する。
【００２８】
加圧ガスの注入を停止した後、図１（ｄ）のように金型キャビティを完全に閉じる。この時、溶融樹脂の量が多過ぎると、樹脂圧が必要以上に高くなり、成形体に残留応力が発生したり、表皮層が潰れたりし好ましくない。また、溶融樹脂の量が少な過ぎると、樹脂層と表皮層との十分な接着性が得られない。このため、溶融樹脂の量は、金型キャビティを完全に閉じた状態で、ほぼ金型キャビティの容積から表皮層の容積を差し引いた容積に見合う量であることが好ましい。
【００２９】
そして、前記と同様にして溶融樹脂４の圧力に応じて比較的高圧に制御された加圧ガスを溶融樹脂４中の予備中空部７に注入して、最終的な中空部８を形成する。
【００３０】
最後に、溶融樹脂４が冷却，固化された後、樹脂中の加圧ガスを回収又は排出し、金型を開き、樹脂層中に中空部８が形成された複層成形体を取り出す。
【００３１】
溶融樹脂４中に注入する加圧ガスとしては、成形の温度及び圧力下で、成形に用いる溶融樹脂と反応又は混合されないものが使用される。例えば、窒素、空気などが用いられるが、特に限定はされない。
【００３２】
注入する加圧ガスの圧力は、通常１０〜３５０Ｋｇ／ｃｍ２ 程度であり、好ましくは３０〜３００Ｋｇ／ｃｍ２ である。
【００３３】
本例は金型キャビティを２段階に閉じる例であるが、本発明においてはこの段数に特に制限はなく、最終的な成形体の大きさや形状等により適宜決められるものである。
【００３４】
金型キャビティを３段階以上に閉じる場合には、予備中空部７の形成を段階的に行うこともできる。例えば金型キャビティを３段階に閉じ、第一の段階で第一段階予備中空部を形成した後、第二の段階でこれとは別の新たな予備中空部を形成したり、第一段階予備中空部に加圧ガスを注入して第二段階予備中空部を形成してもよい。このような場合においても、金型キャビティを完全に閉じた段階で、これらの予備中空部に加圧ガスを注入して、最終的な中空部８を形成する。
【００３５】
加圧ガスの圧力を各段階における溶融樹脂４の圧力に応じて制御する方法としては、例えば、圧縮状態にある溶融樹脂４の圧力を金型面に設けた圧力検出器で検出し、これを直ちに加圧ガス注入機構５にフィードバックし、該機構内に設けられている圧力調節弁（不図示）の開閉を調節することで、溶融樹脂４の圧力に対して予め決められた圧力となるように加圧ガスの圧力を制御することができる。あるいは金型キャビティの容量と注入される溶融樹脂量との関係から、可動型１の移動量と加圧ガスの圧力との対応を予め決めておき、該移動量をフィードバックすることによって同様に制御することもできる。
【００３６】
【発明の効果】
以上説明したように、スタンピングあるいは圧縮成形方法を応用し、更に中空射出成形方法を組み合わせた本発明の成形方法においては、溶融樹脂中への加圧ガスの注入を極めて容易に良好な状態で行うことができ、中空部の大きさや形状を制御して不必要な部位に中空が形成されるのを防止することができる。このため、“ひけ”や変形を防止し更なる外観の向上が成されると共に、不必要な部位に中空部が形成されることによる強度低下を防止することができる。
【００３７】
また、加圧成形の最終段階で金型を開くこともないため、型再現性に優れ精密部品の成形にも十分に対応することができる。
【図面の簡単な説明】
【図１】本発明の一実施例の工程を説明するための図である。
【符号の説明】
１ 可動型
２ 固定型
３ 表皮層
４ 溶融樹脂
５ 加圧ガス注入機構
６ ガス注入口
７ 予備中空部
８ 中空部[0001]
[Industrial applications]
The present invention relates to a method for forming a multilayer molded article widely used in the fields of, for example, automobiles, general machines, electric / electronic devices, and the like.
[0002]
[Prior art]
Multilayer molded articles having a skin layer such as fabric or leather on the surface of a resin layer are in increasing demand in various industrial fields because of their improved surface properties.
[0003]
As a molding method of such a multilayer molded body, a molten resin is poured into a mold cavity in which a skin layer is set, with the mold cavity being incompletely closed, and then the mold cavity is completely closed and molded. A so-called stamping or compression molding method is known, and various types of multilayer molded articles have been put to practical use.
[0004]
On the other hand, a so-called hollow injection molding method represented by Japanese Patent Publication No. 57-14968, in which a high-pressure gas is injected into a molten resin, for example, prevents "sinking" and deformation of a molded product and improves and improves the appearance. It has been widely applied as a possible molding method.
[0005]
Further, a method in which the above stamping or compression molding method is combined with a hollow injection molding method is proposed in Japanese Patent Application Laid-Open Nos. 4-74617 and 4-255314.
[0006]
[Problems to be solved by the invention]
However, in the conventionally proposed method, although the state of the molded body is improved as compared with the case of simple stamping or compression molding, there are the following problems.
[0007]
For example, in the method of injecting molten resin with the mold slightly opened, injecting gas after completely closing the mold and compressing the molten resin, gas injection is impossible due to high filling pressure of the resin. In some cases, it was likely to be in a complete state, and the effect of forming the hollow portion was not sufficiently exhibited.
[0008]
Further, as proposed in Japanese Patent Application Laid-Open No. 4-74617, a method of injecting a molten resin in a state where a mold is slightly opened and injecting a gas while injecting the resin or in a process leading to pressure molding. In this case, the resin pressure during the mold clamping process tends to fluctuate, and the hollow portion formed in the resin is deformed irregularly. Particularly when molding an asymmetrical molded body, unnecessary portions other than the predetermined position are unnecessary. The hollow part is formed in a suitable part, and the appearance and quality of the molded article are likely to be reduced, and the strength is liable to be reduced.
[0009]
Further, as proposed in Japanese Patent Application Laid-Open No. 4-255314, a molten resin is injected with the mold slightly opened, and a gas is injected before or simultaneously with the completion of the mold clamping, and further a gas is injected. While the method of slightly opening the mold while opening the mold has a relatively small deformation of the hollow portion, the dimensional accuracy of the molded body is reduced, and thus is not suitable for molding precision parts.
[0010]
The present invention has been made in view of the above-mentioned problems, and aims at facilitating the formation of a hollow portion, improving the "sink" and deformation of a molded product, and ensuring an excellent appearance. It is another object of the present invention to provide a method for forming a multilayer molded article which is excellent in mold reproducibility and can sufficiently cope with the molding of precision parts.
[0011]
Means and Action for Solving the Problems
For this purpose, in the invention of claim 1, at least in a method of forming a multilayer molded body comprising a resin layer and a skin layer,
The skin layer is placed, the mold cavity in the incompletely closed state where the molten resin is injected is closed stepwise, and the pressurized gas is injected into the molten resin when the mold cavity is incompletely closed to reserve Forming a hollow part, injecting further pressurized gas into the preliminary hollow part when the mold cavity is completely closed, and forming the final hollow part with the mold cavity completely closed. The method for forming a multilayer molded article is as follows.
[0012]
In the molding method of the present invention, a pressurized gas is injected into the molten resin in the mold cavity when the mold cavity is incompletely closed to form a preliminary hollow portion. At this stage, the pressure of the molten resin is relatively low, so that the pressurized gas can be easily and reliably injected.
[0013]
Then, when the mold cavity is completely closed, pressurized gas is further injected into the preliminary hollow portion. At this stage, although the molten resin has a relatively high pressure, the pressurized gas is injected into the already formed preliminary hollow portion, so that the pressurized gas can be easily and reliably injected. The shape of the hollow portion can be controlled to some extent. That is, by further injecting a pressurized gas into the preliminary hollow portion formed in advance, it is possible to grow the final hollow portion with the preliminary hollow portion as a nucleus.
[0014]
Usually, as the mold cavity is closed, the preliminary hollow portion is deformed due to a variation in resin pressure generated in the process. In particular, when an asymmetrical shaped body is formed, the above-mentioned phenomenon is remarkably exhibited.
[0015]
For this reason, in the present invention, it is preferable that the preliminary hollow portion be formed with a minimum necessary size.
[0016]
If the preliminary hollow portion is too large, the shape is often greatly deformed when the mold cavity is completely closed. When the pressurized gas is injected into the thus deformed preliminary hollow portion, the hollow portion finally formed does not have the intended shape, and the hollow portion tends to be formed to an unnecessary portion.
[0017]
Further, in the present invention, it is preferable to control the pressure of the pressurized gas injected into the molten resin according to the pressure of the molten resin in each step.
[0018]
That is, when the molten resin is at a low pressure, the pressure is controlled to be low because even a low-pressure pressurized gas can be easily injected. This makes it possible to more strictly control the gas injection amount, and to form the preliminary hollow portion with a desired size. Then, when the molten resin is at a high pressure, a hollow gas is grown by injecting a higher pressure gas.
[0019]
As described above, according to the present invention, the injection of the pressurized gas into the molten resin can be performed extremely easily and in a favorable state, and the size and shape of the hollow portion are controlled so that the hollow portion is unnecessary. It can be prevented from being formed. For this reason, it is possible to prevent "sink" and deformation of the multilayer molded product, to further improve the appearance, and to prevent a decrease in strength due to the formation of an unnecessary hollow portion.
[0020]
【Example】
Hereinafter, the present invention will be described with reference to examples.
[0021]
The molding process of this embodiment will be described with reference to FIG.
[0022]
First, as shown in FIG. 1A, the skin layer 3 is set and the molten resin 4 is injected with the mold cavity composed of the movable mold 1 and the fixed mold 2 incompletely closed, or The molten resin 4 is injected, and the skin layer 3 is set. The incompletely closed state is not limited to the state in which the movable mold 1 and the fixed mold 2 are completely separated from each other as shown in FIG. 1A, and the state of the movable mold 1 and the fixed mold 2 as shown in FIG. A part may be engaged, but the so-called parting surface may not be engaged. Further, when the cavity is composed of a plurality of blocks, the parting surface is engaged but can be compressed into some blocks. May be left (not shown).
[0023]
In order to form the cavity with a plurality of blocks, for example, at least one of the movable mold 1 and the fixed mold 2 may be divided into a plurality of blocks. By providing an opening / closing mechanism such as a hydraulic mechanism or a spring mechanism for each block, each block can be closed step by step.
[0024]
As the skin layer 3, a woven fabric, a nonwoven fabric, a fiber, a paper, a metal or a sheet or film of a thermoplastic resin and a thermoplastic elastomer can be used. Further, a foam made of a thermoplastic resin such as polyolefin, polystyrene, or polyvinyl chloride, a thermosetting resin such as a polyurethane, or a rubber can be used. Further, these may be used alone or in a combination of two or more.
[0025]
The molten resin 4 is injected from a resin nozzle (not shown) or a resin supply line (not shown) provided in a mold, but the method is not particularly limited.
[0026]
Although a thermosetting resin can be used as the molten resin 4, a thermoplastic resin is preferably used. As the thermoplastic resin, for example, polyethylene, polypropylene, polystyrene, ABS resin, AS resin, polyvinyl chloride, polyamide, polyacetal, polycarbonate, modified polyphenylene ether, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polyimide, polyamide imide, poly Examples include ether imide, polyarylate, polysulfone, polyether sulfone, polyether ether ketone, liquid crystal polymer, tetrafluoroethylene, and thermoplastic elastomer. Furthermore, a mixture of these thermoplastic resins, or a resin in which an inorganic and / or organic filler is blended for the purpose of increasing heat resistance and mechanical strength can also be used.
[0027]
After injecting the molten resin 4 into the mold cavity, the mold cavity is closed one step as shown in FIG. Then, a pressurized gas controlled at a relatively low pressure by the pressurized gas injection mechanism 5 according to the pressure of the molten resin 4 is injected into the molten resin 4 from the gas injection port 6 to form the preliminary hollow portion 7. .
[0028]
After the injection of the pressurized gas is stopped, the mold cavity is completely closed as shown in FIG. At this time, if the amount of the molten resin is too large, the resin pressure becomes unnecessarily high, so that a residual stress is generated in the molded body and the skin layer is crushed, which is not preferable. On the other hand, if the amount of the molten resin is too small, sufficient adhesion between the resin layer and the skin layer cannot be obtained. For this reason, it is preferable that the amount of the molten resin is an amount that substantially matches the volume obtained by subtracting the volume of the skin layer from the volume of the mold cavity when the mold cavity is completely closed.
[0029]
Then, similarly to the above, a pressurized gas controlled to a relatively high pressure according to the pressure of the molten resin 4 is injected into the preliminary hollow portion 7 in the molten resin 4 to form a final hollow portion 8.
[0030]
Finally, after the molten resin 4 is cooled and solidified, the pressurized gas in the resin is recovered or discharged, the mold is opened, and the multilayer molded body having the hollow portion 8 formed in the resin layer is taken out.
[0031]
As the pressurized gas to be injected into the molten resin 4, a gas that does not react with or mix with the molten resin used for molding under the temperature and pressure of molding is used. For example, nitrogen, air, and the like are used, but there is no particular limitation.
[0032]
The pressure of the pressurized gas to be injected is usually about 10 to 350 Kg / cm 2 , preferably 30 to 300 Kg / cm 2 .
[0033]
This embodiment is an example in which the mold cavity is closed in two stages. However, in the present invention, the number of stages is not particularly limited, and is appropriately determined according to the size and shape of the final molded body.
[0034]
When the mold cavity is closed in three or more steps, the preliminary hollow portion 7 can be formed stepwise. For example, the mold cavity is closed in three stages, a first stage preliminary hollow portion is formed in the first stage, and another new preliminary hollow portion is formed in the second stage, or the first stage preliminary hollow portion is formed. A second stage preliminary hollow portion may be formed by injecting a pressurized gas into the hollow portion. Even in such a case, when the mold cavity is completely closed, pressurized gas is injected into these preliminary hollow portions to form a final hollow portion 8.
[0035]
As a method of controlling the pressure of the pressurized gas according to the pressure of the molten resin 4 in each stage, for example, the pressure of the molten resin 4 in a compressed state is detected by a pressure detector provided on a mold surface, and this is detected. Immediately feeding back to the pressurized gas injection mechanism 5 and adjusting the opening and closing of a pressure adjustment valve (not shown) provided in the mechanism, the pressure of the molten resin 4 becomes a predetermined pressure. The pressure of the pressurized gas can be controlled. Alternatively, the correspondence between the moving amount of the movable mold 1 and the pressure of the pressurized gas is determined in advance from the relationship between the capacity of the mold cavity and the amount of the injected molten resin, and the same control is performed by feeding back the moving amount. You can also.
[0036]
【The invention's effect】
As described above, in the molding method of the present invention in which the stamping or compression molding method is applied and the hollow injection molding method is further combined, the injection of the pressurized gas into the molten resin is performed very easily in a good state. By controlling the size and shape of the hollow portion, it is possible to prevent the hollow portion from being formed at an unnecessary portion. For this reason, it is possible to prevent "sinking" and deformation, to further improve the appearance, and to prevent a decrease in strength due to the formation of a hollow portion at an unnecessary portion.
[0037]
Further, since the mold is not opened at the final stage of the pressure molding, the mold has excellent mold reproducibility and can sufficiently cope with the molding of precision parts.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a process in one embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 1 movable type 2 fixed type 3 skin layer 4 molten resin 5 pressurized gas injection mechanism 6 gas injection port 7 spare hollow section 8 hollow section

Claims (2)

少なくとも、樹脂層と表皮層からなる複層成形体の成形方法において、
表皮層を配置、溶融樹脂を注入した不完全に閉じた状態の金型キャビティを段階的に閉じ、金型キャビティが不完全に閉じている段階で溶融樹脂中に加圧ガスを注入して予備中空部を形成し、金型キャビティを完全に閉じた段階で予備中空部に更に加圧ガスを注入し金型キャビティが完全に閉じたままの状態で最終的な中空部を形成することを特徴とする複層成形体の成形方法。At least, in a method of molding a multilayer molded body comprising a resin layer and a skin layer,
The skin layer is arranged, the mold cavity in the incompletely closed state where the molten resin is injected is closed stepwise, and pressurized gas is injected into the molten resin when the mold cavity is incompletely closed to reserve After forming the hollow part, pressurized gas is further injected into the preliminary hollow part when the mold cavity is completely closed, and the final hollow part is formed with the mold cavity completely closed. Molding method of a multilayer molded body. 溶融樹脂中に注入される加圧ガスの圧力を、各段階における溶融樹脂の圧力に応じて制御することを特徴とする請求項１に記載の複層成形体の成形方法。The method according to claim 1, wherein the pressure of the pressurized gas injected into the molten resin is controlled according to the pressure of the molten resin in each step.
JP11339094A 1994-05-02 1994-05-02 Molding method of multilayer molded body Expired - Lifetime JP3574174B2 (en)

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Application Number Priority Date Filing Date Title
JP11339094A JP3574174B2 (en) 1994-05-02 1994-05-02 Molding method of multilayer molded body

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US6106260A (en) * 1995-03-03 2000-08-22 Sumitomo Chemical Company, Limited Mold useful in the production of hollow thermoplastic molded articles
DE60008220T2 (en) * 1999-03-23 2004-07-08 Rhodia Engineering Plastics S.A. COMPOSITE ITEMS WITH A RIGID PART AND A PART THERMOPLASTIC MATERIAL, AND PRODUCTION METHOD
FR2791297B1 (en) * 1999-03-23 2001-06-01 Rhodia Engineering Plastics Sa MANUFACTURED ARTICLE BASED ON A THERMOPLASTIC MATERIAL COMPRISING A RIGID ELEMENT
JP4942704B2 (en) * 2008-06-11 2012-05-30 株式会社ファルテック Manufacturing method of synthetic resin molded products
JP5954553B2 (en) * 2014-07-18 2016-07-20 太平洋通商株式会社 Method for manufacturing storage frame

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