JP2012143997A - Heat resistant packaging container having excellent transparency, and method of manufacturing the same - Google Patents

Heat resistant packaging container having excellent transparency, and method of manufacturing the same Download PDF

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JP2012143997A
JP2012143997A JP2011005466A JP2011005466A JP2012143997A JP 2012143997 A JP2012143997 A JP 2012143997A JP 2011005466 A JP2011005466 A JP 2011005466A JP 2011005466 A JP2011005466 A JP 2011005466A JP 2012143997 A JP2012143997 A JP 2012143997A
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sheet
polyethylene terephthalate
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forming
laminated sheet
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JP5693979B2 (en
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Tomonori Sugimura
知則 杉村
Shigeru Takahashi
盛 高橋
Hiromichi Inagaki
宏道 稲垣
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Risupack Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide a packaging container made from a multilayer sheet, the packaging container being excellent in transparency and shape forming degree.SOLUTION: The packaging container is obtained by hot shaping a laminate sheet having a two or three layer structure formed by laminating a core layer having both surfaces of a front surface and a back surface and a skin layer provided to at least one of both surfaces of the core layer. The core layer of the laminate sheet is composed of an unstretched sheet of amorphous polyethylene terephthalate (A-PET) having a specific melting point Tm (generally 260°C). The skin layer of the laminate sheet is composed of a stretched film of polyethylene terephthalate (OPET film). The packaging container having excellent transparency and shape forming degree is obtained by shaping the laminated sheet while heating the sheet so that the temperature of the skin layer becomes ≥200°C and below the melting point Tm of the amorphous polyethylene terephthalate in the heat forming.

Description

本発明は、二層以上の多層構造を有する積層シートを熱成形して得られる包装用容器と、その包装用容器の製造方法とに関する。   The present invention relates to a packaging container obtained by thermoforming a laminated sheet having a multilayer structure of two or more layers, and a method for producing the packaging container.

食品用容器等の包装用容器として、ポリエステルやポリプロピレン等の熱可塑性樹脂からなる樹脂シートに熱盤成形や真空・圧空成形などの熱成形を施して得られるものが知られている。当初、容器成形用のシートとしては、二軸配向ポリエステルの単層シート(特許文献1,2参照)や二軸延伸ポリエチレンテレフタレートの単層シート(特許文献3参照)が主流であり、シートの延伸条件や成形条件を工夫することで耐熱性等に優れた成形品(容器)が提供されていた。   2. Description of the Related Art Known packaging containers for food containers and the like are obtained by subjecting a resin sheet made of a thermoplastic resin such as polyester or polypropylene to thermoforming such as hot plate molding or vacuum / pressure forming. Initially, as the sheet for forming a container, a monolayer sheet of biaxially oriented polyester (see Patent Documents 1 and 2) and a single layer sheet of biaxially stretched polyethylene terephthalate (see Patent Document 3) are mainly used. By devising conditions and molding conditions, molded products (containers) having excellent heat resistance and the like have been provided.

しかしながら、予め延伸加工された単層シートに更に熱成形を施して容器を製造した場合、形状が比較的シンプルな容器(例えば、浅い皿型トレー)ならば、熱成形によって金型とおりの正確な形状を再現することができるが、いわゆる深物(深さのある容器)のように多少なりとも形状に複雑性がある容器になると、金型どおりの正確な形状を付与することが難しいという難点があった。これは、熱成形自体が、延伸済みのシートを更に引き伸ばす処理となることから、熱成形段階での変形の自由度が既に不足していることに起因する。このような事情から近年では、性質の異なる二つ又は三つの樹脂層を積層してなる多層シートを用い、これを熱成形して包装用容器を得ることが主流となっている。   However, when a container is manufactured by further thermoforming a single-layer sheet that has been stretched in advance, if the container has a relatively simple shape (for example, a shallow dish-type tray), it is accurate as the mold by thermoforming. The shape can be reproduced, but it is difficult to give the exact shape as the mold if the container is somewhat complicated in shape like a so-called deep object (a container with depth). was there. This is due to the fact that the degree of freedom of deformation at the thermoforming stage is already insufficient because thermoforming itself is a process of further stretching the stretched sheet. Under these circumstances, in recent years, it has become the mainstream to obtain a packaging container by using a multilayer sheet obtained by laminating two or three resin layers having different properties and thermoforming this.

例えば、特許文献4(特許第4223700号公報)は、非晶性PETの内側層4および結晶性PETの外側層5からなると共に各層が非晶状態の積層シートを、結晶性PETの結晶化温度以下の温度で熱成形することによって容器を成形し、次いで、その容器を外側からヒーターで結晶性PETの結晶化温度(120℃又はそれ以上)に加熱して、結晶性PETを熱結晶化させる、という耐熱PET容器の製造方法を開示する(同文献の請求項1,段落0009〜0015参照)。この方法によれば、非晶状態のPETを熱成形しているので、深絞り成形が容易になる(同文献の段落0024参照)。加えて、結晶性PETの結晶化によって、当該PET容器の耐熱性、剛性、耐衝撃性を向上させることができる(同文献の段落0023参照)。   For example, Patent Document 4 (Japanese Patent No. 4223700) discloses a laminated sheet composed of an inner layer 4 of amorphous PET and an outer layer 5 of crystalline PET, and each layer is in an amorphous state, and the crystallization temperature of crystalline PET. The container is molded by thermoforming at the following temperature, and then the container is heated from the outside to the crystallization temperature of crystalline PET (120 ° C. or higher) with a heater to thermally crystallize the crystalline PET. A method for producing a heat-resistant PET container is disclosed (see claim 1, paragraphs 0009 to 0015). According to this method, since amorphous PET is thermoformed, deep drawing is facilitated (see paragraph 0024 of the same document). In addition, crystallization of crystalline PET can improve the heat resistance, rigidity, and impact resistance of the PET container (see paragraph 0023 of the same document).

特許文献5(特開2009−280218号公報)は、A−PET(Amorphous PET,非晶PET)のシートを一次延伸して得た延伸A−PETシートと、未延伸A−PETフィルム又はシートとをドライラミネートで一体化した積層シートを、熱成形機の金型にて80〜150℃で加熱成形して二次延伸し、この二次延伸による配向結晶化によって結晶化を高めたことを特徴とする耐熱透明A−PET容器を開示する(同文献の要約、請求項1及び5参照)。この方法によれば、高耐熱性と高透明性とを有する食品容器が得られるとのことである。なお、特許文献5の段落0042では、二次延伸の延伸温度の上限値を150℃とした理由として、「150℃を超えると、シートのドローダウンが大きくなり成形された時に成形体にシワが発生する」ことをあげているが、理由はそれだけに止まらない。即ち多層PETシート製容器の開発者の間には、A−PET多層シートを150℃を超えて高温加熱すると、透明性が急激に低下するとの一般認識がある(図2参照)。このため、そのような一般認識に従い、特許文献5でも二次延伸の上限温度を150℃に抑制したものと思われる。   Patent Document 5 (Japanese Patent Laid-Open No. 2009-280218) discloses a stretched A-PET sheet obtained by first stretching a sheet of A-PET (Amorphous PET), and an unstretched A-PET film or sheet. A laminated sheet integrated with a dry laminate was heat-formed at 80 to 150 ° C. in a thermoforming machine mold and subjected to secondary stretching, and crystallization was enhanced by orientation crystallization by this secondary stretching. A heat-resistant transparent A-PET container is disclosed (see summary of the same document, claims 1 and 5). According to this method, a food container having high heat resistance and high transparency can be obtained. In paragraph 0042 of Patent Document 5, the reason why the upper limit of the stretching temperature of the secondary stretching is 150 ° C. is as follows: “If it exceeds 150 ° C., the drawdown of the sheet becomes large and the molded product is wrinkled when it is molded. The reason is not only that. That is, among developers of multilayer PET sheet containers, there is a general recognition that when an A-PET multilayer sheet is heated to a high temperature exceeding 150 ° C., the transparency is drastically reduced (see FIG. 2). For this reason, it seems that in accordance with such general recognition, Patent Document 5 also suppresses the upper limit temperature of secondary stretching to 150 ° C.

特公昭59−51407号公報Japanese Patent Publication No.59-51407 特公昭62−18339号公報Japanese Patent Publication No.62-18339 特許第4172878号公報Japanese Patent No. 4172878 特許第4223700号公報Japanese Patent No. 4223700 特開2009−280218号公報JP 2009-280218 A

しかしながら、従前の積層シート由来の耐熱容器にも、いくつかの欠点がある。
特許文献4の耐熱PET容器にあっては、外側層5を結晶化することによって耐熱性が付与されるものの、色は透明から白色になってしまう(同文献の段落0013参照)。特許文献4はその段落0014において「外側層5は熱結晶化により、透明から白色に変わるため着色する必要はない。」と述べて樹脂の白化を肯定的にとらえているが、PET製容器の主な用途である食品用容器の分野では、内容物の目視確認性を確保するとの観点から、樹脂の白化つまり不透明化は、あまり好ましいものではない。
However, conventional heat-resistant containers derived from laminated sheets also have some drawbacks.
In the heat resistant PET container of Patent Document 4, although heat resistance is imparted by crystallization of the outer layer 5, the color changes from transparent to white (see paragraph 0013 of the same document). Patent Document 4 states in its paragraph 0014 that “the outer layer 5 changes from transparent to white due to thermal crystallization and does not need to be colored.” In the field of food containers, which is the main application, whitening of the resin, that is, opacification, is not very preferable from the viewpoint of ensuring visual confirmation of the contents.

特許文献5のA−PET容器では耐熱性と透明性との両立を図っているが、一次延伸A−PETシート(文献5の実施例1では、厚さ0.26mm)をコア層とする多層シートを用いているにもかかわらず、透明性確保等の観点から、加熱成形時(二次延伸時)の加熱温度が最大でも150℃以下に抑制されている。このため、実際の製造現場では、賦形性(成形用金型とおりの正確な形状を確保できるという特性)があまり良くない、または賦形性を良くするために加熱時間を長くする必要が生じて生産性が良くない、といった欠点がある。   In the A-PET container of Patent Document 5, both heat resistance and transparency are achieved, but a multi-layer having a primary stretched A-PET sheet (in Example 1 of Document 5, thickness 0.26 mm) as a core layer. Despite the use of the sheet, the heating temperature at the time of heat forming (secondary stretching) is suppressed to 150 ° C. or less at the maximum from the viewpoint of ensuring transparency. For this reason, at the actual manufacturing site, the formability (characteristic that can ensure the exact shape as the molding die) is not so good, or it is necessary to lengthen the heating time in order to improve the shapeability. The disadvantage is that productivity is not good.

つまり、従前の多層シート由来の耐熱容器の製造技術にあっては、容器の透明性の確保と、製造プロセスでの良好な賦形性の確保とを両立できているとは言い難い。   That is, it is difficult to say that the conventional technology for manufacturing heat-resistant containers derived from multilayer sheets can achieve both of ensuring the transparency of containers and ensuring good formability in the manufacturing process.

本発明の目的は、透明性及び賦形性に優れた積層シート由来の包装用容器と、その包装用容器の製造方法を提供することにある。   An object of the present invention is to provide a packaging container derived from a laminated sheet excellent in transparency and formability, and a method for producing the packaging container.

[発明着想の原点]
後ほど「発明を実施するための形態」の欄で詳述するように、本願の発明者は、ポリエチレンテレフタレート(PET)樹脂を主体とした多層積層シートの熱成形において、熱成形品の透明性および賦形性に図1のグラフに示すような極めて意外な傾向性があることを発見した。本発明はこの新発見に基づいてなされたものである。
[The origin of the inventive idea]
As will be described in detail later in the section “DETAILED DESCRIPTION OF THE INVENTION”, the inventors of the present application are concerned with the transparency of thermoformed products in the thermoforming of multilayer laminated sheets mainly composed of polyethylene terephthalate (PET) resin. It has been found that the formability has a very unexpected tendency as shown in the graph of FIG. The present invention has been made based on this new discovery.

[課題解決の手段]
請求項1に係る発明は、表裏両面を有するコア層と、該コア層の片面又は両面に設けられたスキン層とを積層してなる2層又は3層構造の積層シートを、熱盤成形、真空成形、圧空成形または真空圧空成形から選択される熱成形により賦形して得られる包装用容器であって、
前記積層シートのコア層が、特定の融点(Tm)を有する非晶ポリエチレンテレフタレートの未延伸シートからなると共に、前記積層シートのスキン層が、ポリエチレンテレフタレートの延伸フィルムからなり、前記熱成形の際に、前記スキン層の温度が200℃以上、前記非晶ポリエチレンテレフタレートの融点(Tm)未満の温度となるように前記積層シートを加熱しつつ成形することにより、賦形性及び透明性を両立させたことを特徴とする包装用容器である。
[Means for solving problems]
The invention according to claim 1 is a two-layer or three-layer laminated sheet obtained by laminating a core layer having both front and back surfaces and a skin layer provided on one or both sides of the core layer. A packaging container obtained by shaping by thermoforming selected from vacuum forming, pressure forming or vacuum / pressure forming,
While the core layer of the laminated sheet is composed of an unstretched sheet of amorphous polyethylene terephthalate having a specific melting point (Tm), the skin layer of the laminated sheet is composed of a stretched film of polyethylene terephthalate, and during the thermoforming The laminate sheet is molded while being heated so that the temperature of the skin layer is 200 ° C. or higher and lower than the melting point (Tm) of the amorphous polyethylene terephthalate, thereby achieving both formability and transparency. This is a packaging container.

請求項2に係る発明は、
A)特定の融点(Tm)を有する非晶ポリエチレンテレフタレートの未延伸シートを準備するシート準備工程と、
B)ポリエチレンテレフタレートの延伸フィルムを準備するフィルム準備工程と、
C)前記非晶ポリエチレンテレフタレートの未延伸シートをコア層とし、該コア層の片面に前記ポリエチレンテレフタレートの延伸フィルムをスキン層として積層してなる2層構造の積層シートを形成する積層シート形成工程と、
D)前記積層シートを、そのスキン層を下側にして、スキン層の温度が200℃以上、前記非晶ポリエチレンテレフタレートの融点(Tm)未満の温度となるように加熱すると共に、この加熱された積層シートを、熱盤成形、真空成形、圧空成形または真空圧空成形から選択される熱成形により容器形状に賦形する熱成形工程と、
を経て製造することを特徴とする包装用容器の製造方法である。
The invention according to claim 2
A) a sheet preparation step of preparing an unstretched sheet of amorphous polyethylene terephthalate having a specific melting point (Tm);
B) a film preparation step of preparing a stretched film of polyethylene terephthalate;
C) A laminated sheet forming step of forming a laminated sheet having a two-layer structure in which an unstretched sheet of amorphous polyethylene terephthalate is used as a core layer, and a stretched film of polyethylene terephthalate is laminated on one side of the core layer as a skin layer; ,
D) The laminated sheet was heated with the skin layer facing down so that the temperature of the skin layer was 200 ° C. or higher and lower than the melting point (Tm) of the amorphous polyethylene terephthalate. A thermoforming step of shaping the laminated sheet into a container shape by thermoforming selected from hot plate forming, vacuum forming, pressure forming or vacuum pressure forming;
It is a manufacturing method of the packaging container characterized by manufacturing through this.

請求項3に係る発明は、
A)特定の融点(Tm)を有する非晶ポリエチレンテレフタレートの未延伸シートを準備するシート準備工程と、
B)ポリエチレンテレフタレートの延伸フィルムを準備するフィルム準備工程と、
C)前記非晶ポリエチレンテレフタレートの未延伸シートをコア層とし、該コア層の両面に前記ポリエチレンテレフタレートの延伸フィルムをスキン層として積層してなる3層構造の積層シートを形成する積層シート形成工程と、
D)前記積層シートを、そのスキン層の温度が200℃以上、前記非晶ポリエチレンテレフタレートの融点(Tm)未満の温度となるように加熱すると共に、この加熱された積層シートを、熱盤成形、真空成形、圧空成形または真空圧空成形から選択される熱成形により容器形状に賦形する熱成形工程と、
を経て製造することを特徴とする包装用容器の製造方法である。
The invention according to claim 3
A) a sheet preparation step of preparing an unstretched sheet of amorphous polyethylene terephthalate having a specific melting point (Tm);
B) a film preparation step of preparing a stretched film of polyethylene terephthalate;
C) a laminated sheet forming step of forming a laminated sheet having a three-layer structure in which the amorphous polyethylene terephthalate unstretched sheet is used as a core layer, and the polyethylene terephthalate stretched film is laminated on both sides of the core layer as a skin layer; ,
D) Heating the laminated sheet so that the temperature of the skin layer is 200 ° C. or higher and lower than the melting point (Tm) of the amorphous polyethylene terephthalate, and heating the laminated sheet, A thermoforming step of forming into a container shape by thermoforming selected from vacuum forming, pressure forming or vacuum pressure forming;
It is a manufacturing method of the packaging container characterized by manufacturing through this.

本発明に係る包装用容器および包装用容器の製造方法によれば、2層又は3層構造の積層シート由来の容器において、熱成形時の良好な賦形性と、成形後に得られる容器の透明性確保とを見事に両立させることができる。   According to the packaging container and the manufacturing method of the packaging container according to the present invention, in a container derived from a laminated sheet having a two-layer or three-layer structure, good formability at the time of thermoforming and transparency of the container obtained after molding It is possible to achieve a good balance between ensuring sex.

シート温度と容器の透明性及び賦形性との相関関係(新知見)を模式的に示すグラフ。The graph which shows typically the correlation (new knowledge) with sheet | seat temperature, the transparency of a container, and a shaping property. シート温度と容器の透明性及び賦形性との相関関係(従来知見)を模式的に示すグラフ。The graph which shows typically the correlation (conventional knowledge) with sheet | seat temperature, the transparency of a container, and a shaping property. 積層シートの試作例を示し、(a)は三層構造の積層シートの部分断面図、(b)は二層構造の積層シートの部分断面図。The example of a lamination sheet is shown, (a) is a fragmentary sectional view of a lamination sheet of a three layer structure, (b) is a fragmentary sectional view of a lamination sheet of a two layer structure. 容器のヘーズ(透明性)とシート温度との関係を示すグラフ。The graph which shows the relationship between the haze (transparency) of a container, and sheet | seat temperature. 三層構造シートの金型への良好な付着状況を模式的に示す断面図。Sectional drawing which shows typically the favorable adhesion state to the metal mold | die of a three-layer structure sheet. 二層構造シートの金型への不良な付着状況を模式的に示す断面図。Sectional drawing which shows typically the bad adhesion state to the metal mold | die of a two-layer structure sheet.

(用語の定義)この明細書においては各用語を次のような意味で用いる。
「シート」とは厚さが100μm以上の厚膜状物をいい、「フィルム」とは厚さが100μm未満の薄膜状物をいう。また、非晶ポリエチレンテレフタレートを指して「A−PET」ということがあり(A−PETのAは非晶質(Amorphous)の意味)、延伸処理したポリエチレンテレフタレートを指して「OPET」ということがある。また、「容器」という場合、容器の本体のみならず、容器の蓋体も含まれる。
(Definition of terms) In this specification, each term is used in the following meaning.
“Sheet” refers to a thick film having a thickness of 100 μm or more, and “film” refers to a thin film having a thickness of less than 100 μm. In addition, it may refer to amorphous polyethylene terephthalate and may be referred to as “A-PET” (A in A-PET means amorphous), and may refer to stretched polyethylene terephthalate as “OPET”. . The term “container” includes not only the main body of the container but also the lid of the container.

以下に、本発明を実施するにあたり好ましい形態について説明する。
本発明に係る包装用容器を製造する方法は、シート準備工程(A)、フィルム準備工程(B)、積層シート形成工程(C)および熱成形工程(D)からなる。
Hereinafter, preferred modes for carrying out the present invention will be described.
The method for producing a packaging container according to the present invention comprises a sheet preparation step (A), a film preparation step (B), a laminated sheet formation step (C), and a thermoforming step (D).

シート準備工程(A)では、特定の融点Tmを有する非晶ポリエチレンテレフタレートの未延伸シートを準備する。非晶ポリエチレンテレフタレート(A−PET)の融点Tmは一般的には260℃とされている。A−PETの未延伸シートは、例えば、ペレット状のA−PET樹脂を原料としてこれを押出し成形装置にて溶融し、Tダイ法等により押出し成形することで得られる。A−PETシートの厚さは、好ましくは100μm〜1mmである。A−PETシートの厚さが100μmを下回ると、熱成形後に得られる容器の肉厚が薄くなりすぎて、容器の強度や剛性の面で必要な性能確保が難しくなる。他方、A−PETシートの厚さが1mmを超えると、熱成形における賦形性を悪化させるおそれがある。なお、「未延伸」とは、押出し成形等で得られたA−PETシートに対し延伸加工が施されていないことを意味する。   In the sheet preparation step (A), an unstretched sheet of amorphous polyethylene terephthalate having a specific melting point Tm is prepared. The melting point Tm of amorphous polyethylene terephthalate (A-PET) is generally 260 ° C. The unstretched sheet of A-PET can be obtained, for example, by using a pellet-shaped A-PET resin as a raw material, melting it in an extrusion molding apparatus, and extrusion molding it by a T-die method or the like. The thickness of the A-PET sheet is preferably 100 μm to 1 mm. If the thickness of the A-PET sheet is less than 100 μm, the thickness of the container obtained after thermoforming becomes too thin, and it becomes difficult to ensure the required performance in terms of the strength and rigidity of the container. On the other hand, when the thickness of the A-PET sheet exceeds 1 mm, the shapeability in thermoforming may be deteriorated. “Unstretched” means that the A-PET sheet obtained by extrusion molding or the like has not been stretched.

フィルム準備工程(B)では、ポリエチレンテレフタレートの延伸フィルムを準備する。ここで、延伸フィルムとは、未延伸状態のPETフィルムに対して延伸加工を施したフィルムをいう。本発明では、延伸フィルムとして二軸延伸したフィルムを用いることが好ましい。そして、その場合の延伸倍率としては、X方向およびY方向(X方向と直交する方向)のそれぞれにおいて、3〜4倍であることが好ましい。この延伸PETフィルムは、熱成形後の容器の耐熱性を担保する。なお、延伸加工後のフィルム(延伸フィルム)の厚さは、好ましくは5〜20μm、より好ましくは10〜15μmである。延伸フィルムの厚さが5μmを下回ると、延伸加工時に破れを生じたり、熱成形後の容器の耐熱性が低下したりする不都合がある。他方、延伸フィルムの厚さが20μmを超えると、熱成形における賦形性を悪化させるおそれがある。   In the film preparation step (B), a stretched film of polyethylene terephthalate is prepared. Here, the stretched film refers to a film obtained by stretching an unstretched PET film. In the present invention, it is preferable to use a biaxially stretched film as the stretched film. And as a draw ratio in that case, it is preferable that it is 3 to 4 times in each of a X direction and a Y direction (direction orthogonal to a X direction). This stretched PET film ensures the heat resistance of the container after thermoforming. The thickness of the stretched film (stretched film) is preferably 5 to 20 μm, more preferably 10 to 15 μm. When the thickness of the stretched film is less than 5 μm, there is a disadvantage that the film is torn during stretching or the heat resistance of the container after thermoforming is lowered. On the other hand, when the thickness of the stretched film exceeds 20 μm, the shapeability in thermoforming may be deteriorated.

積層シート形成工程(C)では、2層又は3層構造の積層シートを形成する。具体的には、前記非晶ポリエチレンテレフタレートの未延伸シートをコア層とし、該コア層の片面又は両面に前記ポリエチレンテレフタレートの延伸フィルムをスキン層として積層することで、2層又は3層構造の積層シートが形成される。積層化の手法としては、コア層とスキン層との間に接着剤を介在させつつ両層を貼り合せるラミネート加工ないしドライラミネート加工を採用することができる。   In the laminated sheet forming step (C), a laminated sheet having a two-layer or three-layer structure is formed. Specifically, the non-stretched sheet of amorphous polyethylene terephthalate is used as a core layer, and the stretched film of polyethylene terephthalate is laminated as a skin layer on one or both sides of the core layer to form a two-layer or three-layer structure. A sheet is formed. As a laminating method, a laminating process or a dry laminating process in which both layers are bonded together with an adhesive interposed between the core layer and the skin layer can be employed.

熱成形工程(D)では、上記の2層又は3層構造の積層シートを熱成形により容器形状に賦形する。熱成形の手法としては、熱盤成形、真空成形、圧空成形または真空圧空成形のいずれかを選択することができる。熱盤成形とは、熱板によるシートの片面加熱後、該加熱シートを移動させることなく熱板上方に配置された金型で成形する手法をいう。これに対し、真空成形、圧空成形および真空圧空成形とは、ヒーターゾーン(加熱領域)においてシートの(上下)両面を加熱後、成形ゾーンに該加熱シートを移動させ、成形ゾーンに設けられた金型にシートを付着させて成形する手法をいう。   In the thermoforming step (D), the laminated sheet having the two-layer or three-layer structure is shaped into a container shape by thermoforming. As the thermoforming method, any one of hot plate forming, vacuum forming, pressure forming, or vacuum / pressure forming can be selected. Hot plate molding refers to a technique in which a sheet is heated with one side of a sheet by a hot plate and then molded with a mold placed above the hot plate without moving the heated sheet. On the other hand, vacuum forming, pressure forming, and vacuum / pressure forming are performed by heating the (upper and lower) surfaces of the sheet in the heater zone (heating region), then moving the heated sheet to the forming zone, and providing the gold provided in the forming zone. A technique for forming a sheet by attaching it to a mold.

工程(D)の熱成形においては、成形用金型に密着させる前の事前加熱として、積層シートを、そのスキン層の温度が200℃以上で且つ前記非晶ポリエチレンテレフタレートの融点(Tm)未満の範囲のいずれかの温度となるように加熱する。
積層シートの加熱温度を上述の範囲に設定した理由は以下のとおりである。
In the thermoforming of the step (D), as preheating before adhering to the molding die, the temperature of the skin layer is 200 ° C. or higher and less than the melting point (Tm) of the amorphous polyethylene terephthalate. Heat to any temperature in the range.
The reason why the heating temperature of the laminated sheet is set in the above range is as follows.

従来、PET主体の多層シートを用いて製造される容器の開発者(当業者)の間では、図2に示すように、多層シートの加熱温度が150℃を超えるあたりから容器の透明性が急激に低下する傾向にあるとの認識が一般的であった。つまり、150℃よりも高温領域では、加熱温度の上昇と共に透明性が低下する傾向が維持されるものと当業者は信じていた。実のところ、当業者間で使用されている市販の熱盤成形機や真空圧空成形機には、装置メーカー側の安全に対する配慮から、加熱温度の上限を規制する昇温リミッターが付加されており、一般にこの昇温リミッターの作用により200℃以上の温度に加熱できないようになっている。このため、当業者の誰もが、PET主体の多層シートを200℃以上に加熱して熱成形を試みようとはしなかった。   2. Description of the Related Art Conventionally, among developers (persons skilled in the art) of containers manufactured using a multilayer sheet mainly composed of PET, as shown in FIG. It was generally recognized that there was a tendency to decrease. In other words, those skilled in the art believed that in the region higher than 150 ° C., the tendency for transparency to decrease with increasing heating temperature was maintained. As a matter of fact, a temperature rise limiter that regulates the upper limit of the heating temperature is added to commercial hot plate molding machines and vacuum / pneumatic molding machines used by those skilled in the art for safety considerations by equipment manufacturers. In general, the temperature rise limiter prevents heating to a temperature of 200 ° C. or higher. For this reason, no one skilled in the art has attempted to thermoform by heating a PET-based multilayer sheet to 200 ° C. or higher.

しかしながら、本願の発明者は、多層の積層シートにおいては、OPETによるスキン層によってあたかも水風船のようにコア層が保持され、200℃以上に加熱しても垂れ下がらない(ドローダウンしない)のではないかと考えたため、熱盤成形機から昇温リミッターを取り外して熱成形を行うという実験を思い付き、実際にそれを試みた。その結果、図1に示すような意外な結果を得た。即ち、積層シートの加熱温度が150℃以上、200℃未満の領域では、従前の一般認識どおり容器の透明性は極めて悪いままであったが、約200℃に達するあたりから急に透明性が向上し、200〜260℃の高温領域では、150℃未満の低温領域とほぼ同程度の透明性を確保できることが判明した。併せて、熱成形時の賦形性(成形用金型とおりの正確な形状を確保できるという特性)については、100℃から260℃付近までの温度範囲にわたり、温度が高いほど賦形性が良くなるとの傾向性を確認できた。つまり、200℃以上260℃未満の温度領域では、熱成形で得られる容器の透明性と賦形性とが両立し得ることを発見したのである。   However, the inventor of the present application said that in the multilayer laminated sheet, the core layer is held like a water balloon by the skin layer by OPET and does not sag even when heated to 200 ° C. or higher (does not draw down). Because of this, I came up with an experiment to remove the temperature rise limiter from the hot plate molding machine and perform thermoforming, and actually tried it. As a result, an unexpected result as shown in FIG. 1 was obtained. In other words, in the region where the heating temperature of the laminated sheet is 150 ° C. or higher and lower than 200 ° C., the transparency of the container remained extremely poor as previously recognized, but the transparency suddenly improved when it reached about 200 ° C. In addition, it has been found that in the high temperature region of 200 to 260 ° C., it is possible to ensure almost the same degree of transparency as the low temperature region of less than 150 ° C. In addition, with regard to the formability during thermoforming (characteristic that can ensure the exact shape as the molding die), the shapeability is better as the temperature is higher over the temperature range from 100 ° C to around 260 ° C. I was able to confirm the tendency. In other words, it has been discovered that in the temperature range of 200 ° C. or higher and lower than 260 ° C., the transparency and shapeability of the container obtained by thermoforming can be compatible.

このように本発明によれば、ポリエチレンテレフタレート(PET)主体の多層の積層シートを用いた場合でも、熱成形により得られる成形品(容器)について透明性を損なうことなく、良好な賦形性を確保することができる。また、積層シートを構成するスキン層にPET製の延伸フィルムを採用したことで、食品用容器に求められる程度の耐熱性(耐熱温度約100℃)を確保することができる。   As described above, according to the present invention, even when a multi-layer laminate sheet mainly composed of polyethylene terephthalate (PET) is used, the molded product (container) obtained by thermoforming has good formability without impairing transparency. Can be secured. Moreover, the heat resistance (heat-resistant temperature about 100 degreeC) of the grade calculated | required by the container for foodstuffs is securable by employ | adopting the stretched film made from PET for the skin layer which comprises a lamination sheet.

[積層シートの作製]
ペレット状のA−PET樹脂(三房巷社製:商品名「CZ−333」)を溶融後、押出し成形機で押出し成形して厚さ250μmのA−PETシートを得た。その一方で、市販の二軸延伸PETフィルム(東洋紡績株式会社製:商品名「東洋紡エステルフィルム E5100」)を調達した。この二軸延伸PETフィルムは、12倍延伸品(X方向に3倍、Y方向に4倍)であり、厚さは12μmである。
[Production of laminated sheet]
Pellet-shaped A-PET resin (manufactured by Sanbo Co., Ltd .: trade name “CZ-333”) was melted and then extruded with an extruder to obtain an A-PET sheet having a thickness of 250 μm. Meanwhile, a commercially available biaxially stretched PET film (manufactured by Toyobo Co., Ltd .: trade name “Toyobo Ester Film E5100”) was procured. This biaxially stretched PET film is a 12-fold stretched product (3 times in the X direction and 4 times in the Y direction) and has a thickness of 12 μm.

試作例1:三層構造の積層シート
上記A−PETシートの両面にウレタン系接着剤を塗布した後、それぞれの塗布面上に上記市販の二軸延伸PETフィルムを重ね合わせてラミネート機にかけることにより、図3(a)に示すように、厚さ250μmのA−PETシートの両面に、厚さ12μmの二軸延伸PETフィルム(OPETフィルム)をドライラミネートしてなる三層構造の積層シートを得た。これを「試作例1の三層構造積層シート」とする。
Prototype Example 1: Three-layer Laminated Sheet After applying urethane adhesive on both sides of the A-PET sheet, overlay the commercially available biaxially stretched PET film on each coated surface and apply to a laminating machine As shown in FIG. 3 (a), a laminated sheet having a three-layer structure obtained by dry laminating a 12 μm thick biaxially stretched PET film (OPET film) on both sides of a 250 μm thick A-PET sheet. Obtained. This is referred to as “Trilayer Structure Laminated Sheet of Prototype Example 1”.

試作例2:二層構造の積層シート
上記A−PETシートの片面にウレタン系接着剤を塗布した後、その塗布面上に上記市販の二軸延伸PETフィルムを重ね合わせてラミネート機にかけることにより、図3(b)に示すように、厚さ250μmのA−PETシートの片面に、厚さ12μmの二軸延伸PETフィルム(OPETフィルム)をラミネートしてなる二層構造の積層シートを得た。これを「試作例2の二層構造積層シート」とする。
Prototype Example 2: Two-layer Laminated Sheet After applying a urethane-based adhesive on one side of the A-PET sheet, the commercially available biaxially stretched PET film is overlaid on the coated surface and applied to a laminating machine. As shown in FIG. 3B, a laminated sheet having a two-layer structure obtained by laminating a 12 μm thick biaxially stretched PET film (OPET film) on one side of a 250 μm thick A-PET sheet was obtained. . This is referred to as “two-layer laminated sheet of prototype example 2”.

実験1(透明性確保のための試作実験)
試作例1の三層構造積層シートを、昇温リミッターを取り外した熱盤成形機(株式会社浅野研究所製:高速熱板加熱式圧空成形機CLS54H)を用いて熱成形することにより、加熱時のシート温度と、得られた容器の透明性との関係を調べる試作実験を行った。なお、実験時には熱盤成形機における付形用金型の温度を30〜40℃に維持した。試作した容器は、縦165mm×横165mm×高さ25mmの矩形状容器の蓋体である。それぞれの加熱温度で得られた各容器(蓋体)につき、その天面にあたる部分のヘーズ(%)をJIS K7105のプラスチックの光学的特性試験方法に基づいて測定した。ヘーズは透明性の指標であり、その%値が小さいほど透明性が高くなる。この試作実験の結果を表1に示す。また、表1をグラフ化したものを図4に示す。尚、表1では、目視による透明性の評価(「○」「△」「×」の三段階評価)をも行った。この目視評価において「○」は透明性良好を、「△」は透明性やや不良を、「×」は透明性不良を示す。評価「×」は、食品用透明容器としての使用には耐え得ないほどに透明性が悪いことを示す。評価「△」及び「○」は、食品用透明容器として使用可能な範囲内にあることを示す。
Experiment 1 (Prototype experiment to ensure transparency)
When the three-layer structure laminated sheet of Prototype Example 1 is heated by using a hot plate molding machine (manufactured by Asano Laboratory Co., Ltd .: high-speed hot plate heating type pneumatic molding machine CLS54H) from which the temperature rise limiter is removed, A prototype experiment was conducted to investigate the relationship between the sheet temperature and the transparency of the resulting container. In the experiment, the temperature of the shaping mold in the hot plate molding machine was maintained at 30 to 40 ° C. The prototyped container is a rectangular container lid of length 165 mm × width 165 mm × height 25 mm. For each container (lid) obtained at each heating temperature, the haze (%) of the portion corresponding to the top surface was measured based on the plastic optical property test method of JIS K7105. Haze is an index of transparency. The smaller the% value, the higher the transparency. Table 1 shows the results of this prototype experiment. A graph of Table 1 is shown in FIG. In Table 1, the evaluation of transparency by visual observation (three-step evaluation of “◯”, “Δ”, “×”) was also performed. In this visual evaluation, “◯” indicates that the transparency is good, “Δ” indicates that the transparency is slightly poor, and “X” indicates that the transparency is poor. Evaluation "x" shows that transparency is so bad that it cannot be used as a transparent container for food. The evaluations “Δ” and “◯” indicate that they are in a range that can be used as a transparent food container.

Figure 2012143997
Figure 2012143997

表1及び図4から、熱盤成形におけるシート加熱温度が200℃以上の領域においても容器の透明性が比較的良好になることを確認できる。   From Table 1 and FIG. 4, it can confirm that the transparency of a container becomes comparatively favorable also in the area | region whose sheet | seat heating temperature in hot plate molding is 200 degreeC or more.

実験2(賦形性についての試作実験)
試作例1及び2の積層シートを、昇温リミッターを取り外した熱盤成形機(上記実験1と同じもの)を用いて熱成形することにより、加熱時のシート温度と、賦形性の良し悪しとの関係を調べる試作実験を行った。なお、実験時には熱盤成形機における付形用金型の温度を30〜40℃に維持した。試作した容器は、上記実験1の容器(蓋体)と同形同寸の矩形状容器の蓋体である。
Experiment 2 (Prototype experiment on shaping)
The laminated sheets of Prototype Examples 1 and 2 are thermoformed using a hot plate molding machine (same as Experiment 1 above) with the temperature rise limiter removed, so that the sheet temperature during heating and the shapeability are good or bad. A prototype experiment was conducted to investigate the relationship between In the experiment, the temperature of the shaping mold in the hot plate molding machine was maintained at 30 to 40 ° C. The prototype container is a lid of a rectangular container having the same shape and the same size as the container (cover) of Experiment 1 above.

賦形性については、熱盤成形機の付形用金型に対する積層シートの付着性の良否(目視観察)に基づき、「○」「△」「×」の三段階で評価した。この三段階評価において、
「○」は、加熱シートの金型への引き付け付着が良好で、金型形状とおりの賦形が実現していることを示す。
「△」は、加熱シートの金型への引き付け付着がやや甘く、金型形状とおりの賦形が部分的に実現していないことを示す。
「×」は、加熱シートの金型への引き付け付着が非常に甘く、金型形状とおりの賦形が全く実現していないことを示す。
表2に、試作例1の三層構造積層シートを用いた場合の賦形性の評価結果を示す。
表3に、試作例2の二層構造積層シートを用いた場合の賦形性の評価結果を示す。
The formability was evaluated in three stages, “◯”, “Δ”, and “×”, based on the adhesiveness (visual observation) of the laminate sheet to the shaping die of the hot plate molding machine. In this three-level evaluation,
“◯” indicates that the heated sheet is attracted and adhered to the mold, and that the shaping according to the shape of the mold is realized.
“Δ” indicates that the attracting adhesion of the heating sheet to the mold is slightly sweet, and the shaping according to the mold shape is not partially realized.
“X” indicates that the attracting adhesion of the heating sheet to the mold is very sweet, and shaping according to the mold shape is not realized at all.
Table 2 shows the evaluation results of the formability when the three-layer structure laminated sheet of Prototype Example 1 is used.
In Table 3, the evaluation result of the shaping property at the time of using the two-layer structure laminated sheet of Prototype Example 2 is shown.

Figure 2012143997
Figure 2012143997

Figure 2012143997
Figure 2012143997

表2の実施例2-1及び実施例2-2では、賦形性の評価が「○」となっている。これは、図5に模式的に示すように、金型10のキャビティ11に対し、加熱された三層積層シートが緊密に付着して成形が行われたことを意味する。特に、容器(蓋体)の天面の四隅位置に対応する金型キャビティの各コーナー部12においても、積層シートの三層全体がコーナー部12に緊密に付着して成形が行われたことを意味するものである。尚、表3の実施例3-1から3-4についても同様である。   In Example 2-1 and Example 2-2 in Table 2, the evaluation of formability is “◯”. This means that, as schematically shown in FIG. 5, the heated three-layer laminated sheet is closely attached to the cavity 11 of the mold 10 and molding is performed. In particular, in each corner portion 12 of the mold cavity corresponding to the four corner positions of the top surface of the container (lid body), the entire three layers of the laminated sheet were closely adhered to the corner portion 12 and the molding was performed. That means. The same applies to Examples 3-1 to 3-4 in Table 3.

表3の失敗例ア及び失敗例イでは賦形性の評価が「×」となっているが、これは熱盤の温度が低すぎて、シート全体として金型形状とおりの賦形が全くできなかったという意味である。また、表3の失敗例ウ及び失敗例エでは、賦形性の評価が「△」となっている。これは、図6に模式的に示すように、加熱された二層積層シートは概して金型10のキャビティ11に付着するものの、容器(蓋体)の天面の四隅位置に対応する金型キャビティの各コーナー部12においてシートの付着性が部分的に良くなかったという意味である。具体的には、二層構造積層シートをその下側に配置した熱板に、OPET層を(鉛直方向の)下側にして直接加熱させ、該加熱シートを移動させることなく熱板上方に配置された金型に成形させたものである。金型の表面に直接接触するA−PET層についてはコーナー部12においても金型への良好な付着性を示したが、該コーナー部では、OPET層がA−PET層に追従できず、A−PET層とOPET層との間に剥離(隙間)が生じ、結果的にOPET層が金型形状とおりに賦形されなかった。尚、表3から、試作例2の二層シートを良好に熱盤成形するためには、熱盤表面(シート表面)で160℃以上の温度が必要である。   In the failure example a and failure example i in Table 3, the evaluation of the formability is “x”, but this is because the temperature of the hot plate is too low and the entire sheet can be shaped as the mold shape. It means no. In addition, in the failure example C and failure example D in Table 3, the evaluation of the formability is “Δ”. As schematically shown in FIG. 6, although the heated two-layer laminated sheet generally adheres to the cavity 11 of the mold 10, the mold cavity corresponding to the four corner positions of the top surface of the container (lid body). This means that the sheet adhesion at each corner 12 was partially poor. Specifically, the two-layered laminated sheet is directly heated on the lower side of the OPET layer (vertical direction) on the lower side of the hot plate, and the upper side of the hot plate is moved without moving the heated sheet. Molded into a molded mold. The A-PET layer that is in direct contact with the surface of the mold showed good adhesion to the mold at the corner portion 12, but the OPET layer could not follow the A-PET layer at the corner portion. -Peeling (gap) occurred between the PET layer and the OPET layer, and as a result, the OPET layer was not shaped according to the mold shape. From Table 3, a temperature of 160 ° C. or higher is required on the surface of the hot platen (sheet surface) in order to satisfactorily hot plate the two-layer sheet of Prototype Example 2.

上記表2及び表3に示した各実施例について、賦形性および透明性に関する評価を一覧化したものを表4に示す。表4における透明性の評価およびヘーズ(%)の測定は実験1に準ずる。   Table 4 shows a list of evaluations relating to formability and transparency for each of the examples shown in Tables 2 and 3 above. The evaluation of transparency and the measurement of haze (%) in Table 4 are in accordance with Experiment 1.

Figure 2012143997
Figure 2012143997

表4の各実施例によれば、試作例1又は2の積層シートを用いて200℃以上の温度で熱盤成形することにより、賦形性および透明性ともに優れた容器(蓋体)を得ることができる。   According to each Example of Table 4, the container (lid body) excellent in both formability and transparency is obtained by hot plate molding at a temperature of 200 ° C. or higher using the laminated sheet of Prototype Example 1 or 2. be able to.

[変更例]上記の実施例1-1から実施例3-4では熱盤成形を行ったが、熱盤成形に代えて、真空成形、圧空成形または真空圧空成形を採用してもよい。その場合でも上記の実験結果と同様の結果(ないし傾向性)が得られることは言うまでもない。なお、二層構造積層シートを熱成形工程(D)のヒーターゾーン(加熱領域)で加熱させるとき、コア層を保持させるため、OPETによるスキン層を(鉛直方向の)下側にした方が良い。   [Modification] Although hot platen molding is performed in the above-described Examples 1-1 to 3-4, vacuum molding, pressure molding, or vacuum / pressure molding may be employed instead of hot plate molding. In this case, it goes without saying that the same result (or tendency) as the above experimental result can be obtained. When the two-layer laminated sheet is heated in the heater zone (heating region) of the thermoforming step (D), it is better to have the skin layer made of OPET down (in the vertical direction) to hold the core layer. .

10 熱盤成形機の金型
11 金型のキャビティ
12 金型のキャビティのコーナー部
10 Mold of Hot Plate Molding Machine 11 Cavity of Mold 12 Corner of Cavity of Mold

Claims (3)

表裏両面を有するコア層と、該コア層の片面又は両面に設けられたスキン層とを積層してなる2層又は3層構造の積層シートを、熱盤成形、真空成形、圧空成形または真空圧空成形から選択される熱成形により賦形して得られる包装用容器であって、
前記積層シートのコア層が、特定の融点(Tm)を有する非晶ポリエチレンテレフタレートの未延伸シートからなると共に、前記積層シートのスキン層が、ポリエチレンテレフタレートの延伸フィルムからなり、
前記熱成形の際に、前記スキン層の温度が200℃以上、前記非晶ポリエチレンテレフタレートの融点(Tm)未満の温度となるように前記積層シートを加熱しつつ成形することにより、賦形性及び透明性を両立させたことを特徴とする包装用容器。
A laminated sheet having a two-layer or three-layer structure formed by laminating a core layer having both front and back surfaces and a skin layer provided on one or both surfaces of the core layer is formed by hot plate forming, vacuum forming, pressure forming, or vacuum pressure forming. A packaging container obtained by shaping by thermoforming selected from molding,
The core layer of the laminated sheet is made of an unstretched sheet of amorphous polyethylene terephthalate having a specific melting point (Tm), and the skin layer of the laminated sheet is made of a stretched film of polyethylene terephthalate,
By shaping the laminated sheet while heating so that the temperature of the skin layer is 200 ° C. or higher and lower than the melting point (Tm) of the amorphous polyethylene terephthalate during the thermoforming, A packaging container characterized by having both transparency.
A)特定の融点(Tm)を有する非晶ポリエチレンテレフタレートの未延伸シートを準備するシート準備工程と、
B)ポリエチレンテレフタレートの延伸フィルムを準備するフィルム準備工程と、
C)前記非晶ポリエチレンテレフタレートの未延伸シートをコア層とし、該コア層の片面に前記ポリエチレンテレフタレートの延伸フィルムをスキン層として積層してなる2層構造の積層シートを形成する積層シート形成工程と、
D)前記積層シートを、そのスキン層を下側にして、スキン層の温度が200℃以上、前記非晶ポリエチレンテレフタレートの融点(Tm)未満の温度となるように加熱すると共に、この加熱された積層シートを、熱盤成形、真空成形、圧空成形または真空圧空成形から選択される熱成形により容器形状に賦形する熱成形工程と、
を経て製造することを特徴とする包装用容器の製造方法。
A) a sheet preparation step of preparing an unstretched sheet of amorphous polyethylene terephthalate having a specific melting point (Tm);
B) a film preparation step of preparing a stretched film of polyethylene terephthalate;
C) A laminated sheet forming step of forming a laminated sheet having a two-layer structure in which an unstretched sheet of amorphous polyethylene terephthalate is used as a core layer, and a stretched film of polyethylene terephthalate is laminated on one side of the core layer as a skin layer; ,
D) The laminated sheet was heated with the skin layer facing down so that the temperature of the skin layer was 200 ° C. or higher and lower than the melting point (Tm) of the amorphous polyethylene terephthalate. A thermoforming step of shaping the laminated sheet into a container shape by thermoforming selected from hot plate forming, vacuum forming, pressure forming or vacuum pressure forming;
The manufacturing method of the packaging container characterized by manufacturing through this.
A)特定の融点(Tm)を有する非晶ポリエチレンテレフタレートの未延伸シートを準備するシート準備工程と、
B)ポリエチレンテレフタレートの延伸フィルムを準備するフィルム準備工程と、
C)前記非晶ポリエチレンテレフタレートの未延伸シートをコア層とし、該コア層の両面に前記ポリエチレンテレフタレートの延伸フィルムをスキン層として積層してなる3層構造の積層シートを形成する積層シート形成工程と、
D)前記積層シートを、そのスキン層の温度が200℃以上、前記非晶ポリエチレンテレフタレートの融点(Tm)未満の温度となるように加熱すると共に、この加熱された積層シートを、熱盤成形、真空成形、圧空成形または真空圧空成形から選択される熱成形により容器形状に賦形する熱成形工程と、
を経て製造することを特徴とする包装用容器の製造方法。
A) a sheet preparation step of preparing an unstretched sheet of amorphous polyethylene terephthalate having a specific melting point (Tm);
B) a film preparation step of preparing a stretched film of polyethylene terephthalate;
C) a laminated sheet forming step of forming a laminated sheet having a three-layer structure in which the amorphous polyethylene terephthalate unstretched sheet is used as a core layer, and the polyethylene terephthalate stretched film is laminated on both sides of the core layer as a skin layer; ,
D) Heating the laminated sheet so that the temperature of the skin layer is 200 ° C. or higher and lower than the melting point (Tm) of the amorphous polyethylene terephthalate, and heating the laminated sheet, A thermoforming step of forming into a container shape by thermoforming selected from vacuum forming, pressure forming or vacuum pressure forming;
The manufacturing method of the packaging container characterized by manufacturing through this.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6218339B2 (en) * 1978-07-24 1987-04-22 Mitsubishi Plastics Ind
JP2000109038A (en) * 1998-10-05 2000-04-18 Risu Pack Co Ltd Packaging container made of laminated sheet
JP2004010711A (en) * 2002-06-05 2004-01-15 Toray Ind Inc Biaxially oriented polyester film for molding container and method for producing the film
JP4172878B2 (en) * 1999-06-10 2008-10-29 東洋アルミエコープロダクツ株式会社 Method for forming biaxially stretched polyethylene terephthalate sheet

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6218339B2 (en) * 1978-07-24 1987-04-22 Mitsubishi Plastics Ind
JP2000109038A (en) * 1998-10-05 2000-04-18 Risu Pack Co Ltd Packaging container made of laminated sheet
JP4172878B2 (en) * 1999-06-10 2008-10-29 東洋アルミエコープロダクツ株式会社 Method for forming biaxially stretched polyethylene terephthalate sheet
JP2004010711A (en) * 2002-06-05 2004-01-15 Toray Ind Inc Biaxially oriented polyester film for molding container and method for producing the film

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