JP3692288B2 - Polypropylene-based resin laminated foam, method for producing the same, and molded article using the same - Google Patents

Description

【００８９】
またＣＰＰフィルムとしては、下記４種のフィルムの中から１種を選択して用いた。
〈フィルムＣ−１〉
プロピレンの単独重合体からなる、厚み２０μｍのＣＰＰフィルム〔東洋紡績社製の商品名Ｐ−１１１１〕。
〈フィルムＣ−２〉
プロピレンの単独重合体からなる、厚み２５μｍのＣＰＰフィルム〔東洋紡績社製の商品名Ｐ−１１１１〕。
〈フィルムＣ−３〉
プロピレンの単独重合体からなり、顔料を練りこむことで赤色に着色された、厚み２５μｍのＣＰＰフィルム〔東洋紡績社製の商品名Ｐ−１１１１〕。
〈フィルムＣ−４〉
プロピレンの単独重合体からなる、厚み３０μｍのＣＰＰフィルム〔東洋紡績社製の商品名Ｐ−１１１１〕。
【００９０】
さらにＯＰＰフィルムとしては、下記６種のフィルムの中から１種を選択して用いた。
〈フィルムＯ−１〉
プロピレンの単独重合体からなる、熱収縮温度１４２℃、厚み７μｍのＯＰＰフィルム〔東レ社製〕。
〈フィルムＯ−２〉
プロピレンの単独重合体からなる、熱収縮温度１４２℃、厚み１０μｍのＯＰＰフィルム〔東レ社製〕。
〈フィルムＯ−３〉
プロピレンの単独重合体からなる、熱収縮温度１３８℃、厚み２５μｍのＯＰＰフィルム〔東洋紡績社製の商品名Ｐ−２１６１〕。
〈フィルムＯ−４〉
プロピレン−エチレンランダム共重合体からなる、熱収縮温度１１８℃、厚み４０μｍのＯＰＰフィルム〔サントックス社製の商品名ＳＦ−２１〕。
〈フィルムＯ−５〉
プロピレンの単独重合体からなる、熱収縮温度１３８℃、厚み５０μｍのＯＰＰフィルム〔東洋紡績社製の商品名Ｐ−２１６１〕。
〈フィルムＯ−６〉
プロピレンの単独重合体からなる、熱収縮温度１３８℃、厚み６０μｍのＯＰＰフィルム〔東洋紡績社製の商品名Ｐ−２１６１〕。
【００９１】
ＯＰＰフィルムの熱収縮温度は、下記の方法で測定した。
〈ＯＰＰフィルムの熱収縮温度測定〉
１０ｃｍ角に切り出したフィルムを、恒温槽（オーブン）にて、設定温度で１０分間、加熱したのち、槽外に取り出し、フィルムのＭＤ方向とＴＤ方向の寸法を測定した。なお恒温槽の設定温度は９０℃から１５０℃まで１０℃刻みで設定して、上記の測定を各設定温度ごとに行った。
【００９２】
そして横軸に設定温度、縦軸に収縮率〔＝（加熱前の寸法−加熱後の寸法）÷加熱前の寸法×１００〕をとったグラフを、フィルムのＭＤ方向とＴＤ方向のそれぞれについてプロットして、このいずれかの方向の収縮率が５％に達する温度をグラフから読み取って熱収縮温度とした。
なおＯ−４のＯＰＰフィルムは、先に述べたように比較的融点の低いプロピレン系共重合体にて形成されたもので、それ以外の他の、汎用のＯＰＰフィルムより熱成形時の伸びが良く、良好な成形品が得られるものであった。
【００９３】
実施例１
〈発泡シートの作製〉
表１のＰＰ１のポリプロピレン系樹脂１００重量部と、気泡調整剤〔ベーリンガー社製の商品名ハイドロセロールＨＫ−７０〕０．４重量部とをドライブレンドし、この混合物を、第１および第２の２台の押出機を有するタンデム押出機（口径φ９０−φ１１５）のホッパーに供給し、当該ホッパーに接続された第１押出機内で溶融、混合しつつ、発泡剤としてのブタン（イソブタン／ノルマルブタン＝６５／３５）を圧入した。ブタンの圧入量は、樹脂１００重量部あたり２．０重量部とした。
【００９４】
そしてさらに溶融、混合した溶融混合物を、第１押出機から第２押出機に連続的に供給し、当該第２押出機内で均一に冷却したのち、第２押出機の先端に接続した、口径２４０ｍｍの円筒状ダイから、毎時１２０ｋｇの吐出量で、大気中に連続的に、円筒状に押し出しながら発泡させた。
次に、得られた円筒状の発泡体を、２４℃の水で冷却された、直径６７２ｍｍのマンドレルに沿わせて円筒の内部から冷却し、また円筒の外形より大きいエアリングからエアーを吹き付けて円筒の外部から冷却したのち、円周上の２点でカッターによって切開して、密度０．２５ｇ／ｃｍ³、厚み１．５ｍｍ、幅１０４５ｍｍの長尺の発泡シートを作製した。
【００９５】
〈積層発泡体の製造〉
上記で作製した発泡シートの片面に、ＣＰＰフィルムとしての、同幅の長尺のフィルムＣ−２と、ＯＰＰフィルムとしての、同幅の長尺のフィルムＯ−１とを、図２(b)に示す同時ラミネートによるサーマルラミネート法で積層、接着して積層発泡体を製造した。積層の条件は下記のとおりとした。またＣＰＰフィルムの厚みは、ＯＰＰフィルムの厚みの３５７％であった。
【００９６】
予熱ヒータＨ１による発泡シート１の予熱温度：６５℃
加熱ローラＲａの加熱温度：１９０℃
ニップローラＲｂのニップ圧力：６ｋｇ／ｃｍ²
各層の送り速度：１０ｍ／分
〈成形品の製造〉
上記積層発泡体を、そのＯＰＰフィルム側が容器の内面側となるようにプラグアシスト成形して、成形品としての前記パスタ容器を製造した。
【００９７】
実施例２
〈発泡シートの作製〉
表１のＰＰ２のポリプロピレン系樹脂１００重量部を用いたこと以外は実施例１と同様にして、密度０．３４ｇ／ｃｍ³、厚み１ｍｍ、幅１０４５ｍｍの長尺の発泡シートを作製した。
〈積層発泡体の製造〉
上記で作製した発泡シートの片面に、ＣＰＰフィルムとしての、同幅の長尺のフィルムＣ−３と、ＯＰＰフィルムとしての、同幅の長尺のフィルムＯ−３とを、図２(a)に示す逐次ラミネートによるサーマルラミネート法で積層、接着して積層発泡体を製造した。積層の条件は下記のとおりとした。またＣＰＰフィルムの厚みは、ＯＰＰフィルムの厚みの１００％であった。
【００９８】
予熱ヒータＨ１による発泡シート１の予熱温度：７０℃
加熱ローラＲ１ａの加熱温度：１９０℃
ニップローラＲ１ｂのニップ圧力：６ｋｇ／ｃｍ²
加熱ローラＲ２ａの加熱温度：１９０℃
ニップローラＲ２ｂのニップ圧力：６ｋｇ／ｃｍ²
各層の送り速度：１０ｍ／分
〈成形品の製造〉
上記積層発泡体を、そのＯＰＰフィルム側が容器の内面側となるように、実施例１と同様にプラグアシスト成形して、成形品としての前記パスタ容器を製造した。
【００９９】
実施例３
〈発泡シートの作製〉
表１のＰＰ３のポリプロピレン系樹脂１００重量部を用いたこと以外は実施例１と同様にして、密度０．３３ｇ／ｃｍ³、厚み１．０２ｍｍ、幅１０４５ｍｍの長尺の発泡シートを作製した。
〈積層発泡体の製造〉
上記で作製した発泡シートの片面に、ＣＰＰフィルムとしての、同幅の長尺のフィルムＣ−２と、ＯＰＰフィルムとしての、同幅の長尺のフィルムＯ−１とを、図２(a)に示す逐次ラミネートによるサーマルラミネート法で積層、接着して積層発泡体を製造した。積層の条件は実施例２と同様とした。またＣＰＰフィルムの厚みは、ＯＰＰフィルムの厚みの３５７％であった。またＣＰＰフィルムの発泡シート側の表面に、あらかじめグラビア印刷によって印刷層を形成することで、発泡シートとＣＰＰフィルムとの界面に上記印刷層を介装した。
【０１００】
〈成形品の製造〉
上記積層発泡体を、そのＯＰＰフィルム側が容器の内面側となるように、実施例１と同様にプラグアシスト成形して、成形品としての前記パスタ容器を製造した。
実施例４
ＣＰＰフィルムとして、そのＯＰＰフィルム側の表面に、あらかじめグラビア印刷によって印刷層を形成したものを用いて、ＣＰＰフィルムとＯＰＰフィルムとの界面に上記印刷層を介装したこと以外は実施例３と同様にして積層発泡体、およびパスタ容器を製造した。
【０１０１】
実施例５
ＯＰＰフィルムとして、発泡シートと同幅の長尺のフィルムＯ−３を用いたこと以外は実施例４と同様にして積層発泡体、およびパスタ容器を製造した。ＣＰＰフィルムの厚みは、ＯＰＰフィルムの厚みの１００％であった。
実施例６
ＯＰＰフィルムとして、発泡シートと同幅の長尺のフィルムＯ−４を用いたこと以外は実施例３と同様にして積層発泡体、およびパスタ容器を製造した。ＣＰＰフィルムの厚みは、ＯＰＰフィルムの厚みの６２．５％であった。
【０１０２】
実施例７
実施例２で製造したのと同じ発泡シートの片面に、ＣＰＰフィルムとしての、同幅の長尺のフィルムＣ−４と、ＯＰＰフィルムとしての、同幅の長尺のフィルムＯ−５とを、図２(a)に示す逐次ラミネートによるサーマルラミネート法で積層、接着して積層発泡体を製造し、実施例１と同様にプラグアシスト成形してパスタ容器を製造した。積層の条件は実施例２と同様とした。またＣＰＰフィルムの厚みは、ＯＰＰフィルムの厚みの６０％であった。またＯＰＰフィルムのＣＰＰフィルム側の表面に、あらかじめグラビア印刷によって印刷層を形成することで、ＣＰＰフィルムとＯＰＰフィルムとの界面に上記印刷層を介装した。
【０１０３】
実施例８
〈発泡シートの作製〉
表１のＰＰ４のポリプロピレン系樹脂１００重量部を用いたこと以外は実施例１と同様にして、密度０．４６ｇ／ｃｍ³、厚み０．８９ｍｍ、幅１０４５ｍｍの長尺の発泡シートを作製した。
〈積層発泡体の製造〉
上記で作製した発泡シートの片面に、ＣＰＰフィルムとしての、同幅の長尺のフィルムＣ−４と、ＯＰＰフィルムとしての、同幅の長尺のフィルムＯ−２とを、図２(b)に示す同時ラミネートによるサーマルラミネート法で積層、接着して積層発泡体を製造した。積層の条件は実施例１と同様とした。またＣＰＰフィルムの厚みは、ＯＰＰフィルムの厚みの３００％であった。またＣＰＰフィルムの発泡シート側の表面に、あらかじめグラビア印刷によって印刷層を形成することで、発泡シートとＣＰＰフィルムとの界面に上記印刷層を介装した。
【０１０４】
〈成形品の製造〉
上記積層発泡体を、そのＯＰＰフィルム側が容器の内面側となるように、実施例１と同様にプラグアシスト成形して、成形品としての前記パスタ容器を製造した。
比較例１
ＣＰＰフィルムを省略して、発泡シートと、ＯＰＰフィルムとしてのフィルムＯ−３とを直接に積層したこと以外は実施例５と同様にして積層発泡体、およびパスタ容器を製造した。
【０１０５】
比較例２
ＯＰＰフィルムの、発泡シート側の表面に、あらかじめグラビア印刷によって印刷層を形成することで、発泡シートとＯＰＰフィルムとの界面に上記印刷層を介装したこと以外は比較例１と同様にして積層発泡体、およびパスタ容器を製造した。
比較例３
実施例３で製造したのと同じ発泡シートの片面に、ＣＰＰフィルムとしての、同幅の長尺のフィルムＣ−１と、ＯＰＰフィルムとしての、同幅の長尺のフィルムＯ−６とを、図２(a)に示す逐次ラミネートによるサーマルラミネート法で積層、接着して積層発泡体を製造し、実施例１と同様にプラグアシスト成形してパスタ容器を製造した。積層の条件は実施例２と同様とした。またＣＰＰフィルムの厚みは、ＯＰＰフィルムの厚みの３３．３％であった。またＣＰＰフィルムの発泡シート側の表面に、あらかじめグラビア印刷によって印刷層を形成することで、発泡シートとＣＰＰフィルムとの界面に上記印刷層を介装した。
【０１０６】
以上の結果を表２にまとめた。
【０１０７】
【表２】

【０１０８】
表より、ＣＰＰフィルムを省略して発泡シートとＯＰＰフィルムとを直接に積層した比較例１、２はともに、熱成形後の加熱調理時にＯＰＰフィルムの浮き上がりが多数発生し、特に両層の間に印刷層を設けた比較例２は、熱成形時にも僅かながらＯＰＰフィルムの浮き上がりが発生することが確認された。
またＣＰＰフィルムを介装したものの、その厚みが、ＯＰＰフィルムの厚みの４０％未満であった比較例３は、ＯＰＰフィルムの厚みが６０μｍと大きいことも相まって、熱成形時からＯＰＰフィルムの浮き上がりが多数発生した。また熱成形性もやや不良であった。
【０１０９】
これに対し各実施例はいずれも、熱成形時にＯＰＰフィルムの浮き上がりが見られず、また加熱調理時にも殆どの実施例でＯＰＰフィルムの浮き上がりが見られない上、成形性、断熱性ともに実用可能なレベルに達していることが確認された。
また各実施例のうち、同じＣＰＰフィルムとＯＰＰフィルムを組み合わせた実施例１、３および４を比較すると、発泡シートの密度および厚みの相違に起因して、断熱性の結果こそ実施例１が極めて良好で、実施例３、４が良好という違いがあったものの、ＯＰＰフィルムの浮き上がりは、熱成形時および加熱調理時のいずれの時点でも全く見られず、このことから本発明の構成によれば、印刷層の有無やその形成位置に拘らず、ＯＰＰフィルムの密着性を著しく向上できることがわかった。
【０１１０】
またＯＰＰフィルムの厚みを違えることで、ＣＰＰフィルムの厚みの、ＯＰＰフィルムの厚みに対する割合を変化させた実施例３〜６、あるいは実施例２、７を比較すると、いずれも実用可能な範囲内であるものの、上記割合が大きくなるほど、ＯＰＰフィルムの浮き上がりが減少して、その密着性が向上することが確認された。
また各実施例の中でＯＰＰフィルムの厚みが特に大きい実施例６、７を比較すると、実施例７に見るように汎用のＯＰＰフィルムを用いた場合は、その厚みゆえに成形性が僅かに低下するが、実施例６に示すように、前述した伸びのよいＯＰＰフィルムを用いることで、成形性を改善できることが確認された。
【０１１１】
さらに実施例８の結果より、発泡シートを前記樹脂(B)のみで形成した場合には、当該発泡シートを樹脂(A)のみ、もしくは樹脂(A)(B)で形成した場合に比べて、密度の小さい、高い断熱性を有する積層発泡体こそ得られないものの、中程度の密度を有する積層発泡体を形成できる、その場合にも本発明の構成を採用することで、ＯＰＰフィルムの密着性を向上できることが確認された。
【０１１２】
【発明の効果】
以上、詳述したように本発明によれば、電子レンジ調理等に使用できる耐熱性、耐油性、断熱性を有し、かつ高温時の剛性にすぐれる上、熱成形時や、熱成形後の加熱調理時等に隅部などでＯＰＰフィルムが浮き上がる問題が改善された、新規なポリプロピレン系樹脂積層発泡体と、その効率的な製造方法と、上述した各特性に優れた良好な成形品とを提供できるという特有の作用効果を奏する。
【図面の簡単な説明】
【図１】同図(a)は、本発明のポリプロピレン系樹脂積層発泡体の、実施の形態の一例を示す拡大断面図、同図(b)は、上記積層発泡体を熱成形した際の、隅部の状態を示す拡大断面図である。
【図２】上記例の積層発泡体を、サーマルラミネート法によって製造する工程を説明する図であって、同図(a)は逐次ラミネートによるサーマルラミネート法、同図(b)は同時ラミネートによるサーマルラミネート法の説明図。
【図３】積層発泡体から製造される成形品の一例としてのパスタ容器を示す図であって、同図(a)は平面図、同図(b)は縦断面図である。
【図４】同図(a)は、従来の積層発泡体を熱成形した際の、隅部の理想的な状態を示す拡大断面図、同図(b)は、上記従来の積層発泡体を熱成形した際の、隅部にOPPフィルムの浮き上がりが生じた状態を示す拡大断面図である。
【符号の説明】
１ 発泡シート
２ ＣＰＰフィルム
３ 印刷層
４ ＯＰＰフィルム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel polypropylene-based resin laminate foam, a method for producing the same, and a molded article suitably used for food packaging containers and the like using the laminate foam.
[0002]
[Prior art]
Conventionally, as for food packaging containers such as lunch boxes and salmon sold at convenience stores and supermarkets, and other general packaging containers, those made of expanded polystyrene have been widely used in consideration of heat retention, heat insulation, strength, etc. It was.
However, recently, with the spread of microwave ovens to general households, or the spread of cooking services such as lunch boxes using microwave ovens at convenience stores, it is especially useful for food packaging containers and foam polystyrene containers. High heat resistance and oil resistance that cannot be achieved have been demanded.
[0003]
As a food packaging container excellent in heat resistance and oil resistance and capable of cooking in a microwave oven, a polypropylene sheet non-foamed container filled with a filler such as talc is generally used.
However, since the container is non-foamed, its heat insulation is insufficient, and there is a problem that the wall surface and the bottom surface of the container become high temperature when the container is taken out after cooking with a microwave oven.
[0004]
Further, since the container contains a large amount of filler, there is a problem that recycling is difficult.
Therefore, a polypropylene resin foam sheet having excellent heat resistance and oil resistance compared to expanded polystyrene, excellent heat insulation because it has a foam structure, and also excellent recyclability because it contains no filler in most cases. It has been studied to produce food packaging containers by thermoforming.
[0005]
However, a container made by thermoforming the above-mentioned polypropylene resin foam sheet alone has low rigidity, and the strength is greatly reduced particularly in a high temperature state after cooking by heating with a microwave oven. In a container having a wide opening, such as a curry container or a spaghetti container, there is a problem that the entire container is bent and deformed by the weight of the contents, and the contents are easily spilled.
Therefore, at present, the weight per unit area of the foam sheet is increased to cope with bending and deformation at a high temperature, but this causes a new problem of increasing the cost of the container.
[0006]
In addition, when a container is manufactured by thermoforming the polypropylene resin foam sheet, the sheet is drastically drooped in the heating zone of the molding apparatus, or the sheet corrugates. There is also a problem that it becomes impossible to manufacture a good container evenly. In particular, this tendency is stronger as the foam sheet having a larger weight per unit area is used.
Therefore, in order to solve such a problem with the foam sheet alone, for example, in Japanese Patent No. 2904337 or Japanese Patent Application Laid-Open No. 11-170455, a biaxially stretched polypropylene system similar to a polypropylene resin foam sheet is used. It has been proposed to use a laminated foam in which a resin film (hereinafter abbreviated as “OPP film”) is laminated.
[0007]
Since such a laminated foam is obtained by improving the rigidity of the container at high temperature by laminating films, it is prevented from being greatly bent and deformed during cooking, and the weight of the foam sheet can be reduced by this lamination. It is considered that the problems in the manufacturing process can be solved.
[0008]
[Problems to be solved by the invention]
However, as a result of investigations by the inventors, it has been clarified that the conventional laminated foam has the following problems.
That is, when a container is manufactured by thermoforming a conventional laminated foam, it is provided at the corner of the rising from the bottom of the container to the side wall, or at the bottom or side wall of the container for reinforcement, design, etc. As shown in FIG. 4B, the foam sheet 1 and the OPP film 2 are not integrally molded as shown in FIG. 4A at the rising corners of the ribs. However, there is a problem that the OPP film 2 is lifted off the foam sheet 1 by locally peeling at the interface between the two.
[0009]
Even if the container can be molded beautifully without being lifted up, if the container is stored for a long period of time, or is cooked by a microwave oven or the like with food stored inside, the OPP film 2 is still removed from the foam sheet 1. There was a problem of floating up.
The problem of floating of the OPP film at the corners or the like is that the printing layer 3 for improving the design property, particularly at the interface between the foamed sheet 1 and the OPP film 2, as shown in FIGS. It was generated remarkably when it was provided.
[0010]
The object of the present invention is to have heat resistance, oil resistance and heat insulation that can be used for cooking in a microwave oven, etc., and excellent in rigidity at high temperature, and at the time of thermoforming and cooking after thermoforming. An object of the present invention is to provide a novel polypropylene-based resin laminated foam in which the problem that the OPP film is lifted at a part or the like is improved, and a method for producing the same.
Another object of the present invention is to provide a novel molded product that can be suitably used for food packaging containers and the like because of its excellent properties described above.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the inventors have raised the OPP film at the corners when the conventional laminated foam is thermoformed or when the container after thermoforming is used for cooking. As a result of examining easy causes, the following facts were found.
That is, in the process of manufacturing a food packaging container or the like by thermoforming the laminated foam, the laminated foam is stretched along the shape of the container while receiving heat. In this process, the stretched foam is applied to the OPP film 2. Contrary to the force (shown by solid line arrows in FIGS. 4 (a) and (b)), the force of thermal contraction to ease stretching [shown by the dashed line arrows in FIGS. 4 (a) and (b)] ] Occurs.
[0012]
This force concentrates on the corner of the container where the amount of stretch of the laminated foam is the largest, and as a result, the foam sheet 1 and the OPP film 2 that are not originally so close to each other are separated from each other at the corner. As a result, the OPP film 2 is lifted as indicated by white arrows in FIG.
In particular, when the printing layer 3 is formed at the interface between the two, the printing layer 3 further reduces the adhesion of the OPP film 2 to the foam sheet 1 and promotes the peeling. The resulting lift is even more prominent.
[0013]
Moreover, even if it can be molded beautifully without being lifted at the time of thermoforming, since the shrinkage force is accumulated as stress in the OPP film 2, when stored over a long period of time as described above, As a result of the OPP film 2 gradually contracting to relieve the accumulated stress, the OPP film 2 is peeled off and lifted off, particularly at the corners. Further, when cooking, the OPP film 2 contracts rapidly, and as a result, the OPP film 2 peels off and rises at the corners.
[0014]
Therefore, the inventors of the polypropylene resin laminate foam in order to suppress the thermal shrinkage of the OPP film during heating, which causes peeling, and to increase the adhesion between each layer constituting the laminate foam more than before. The layer structure was further examined.
As a result, when the OPP film is laminated on the polypropylene resin foam sheet via an unstretched polypropylene resin film (hereinafter abbreviated as “CPP film”) having a thickness of 40% or more of the thickness of the OPP film. The CPP film is a film having a uniform thickness made of a polypropylene resin similar to the foam sheet and the OPP film,
(1) It adheres to both the foam sheet and the OPP film uniformly and with good adhesion, and functions to increase the adhesion at the interface of each layer than before,
(2) In such a close contact state, the OPP film functions to absorb the force of heat shrinkage due to heating and suppress the heat shrinkage.
Even if a printing layer is provided at the interface between the foam sheet and the CPP film, or the interface between the CPP film and the OPP film, the peeling of the OPP film and the resulting lift are more The inventors have found that it can be surely prevented, and have completed the present invention.
[0015]
Therefore, in the polypropylene resin laminate foam of the present invention, a biaxially stretched polypropylene resin film (OPP film) is formed on at least one side of a polypropylene resin foam sheet, and the thickness of the biaxially stretched polypropylene resin film is 40% or more. It is characterized by being laminated through an unstretched polypropylene-based resin film (CPP film) having a thickness of 5 mm.
In the present invention, the thickness of the CPP film is limited to 40% or more of the thickness of the OPP film. If the thickness of the CPP film is within this range, the functions (1) and (2) are sufficiently exhibited. Therefore, it is possible to reliably prevent the OPP film from being lifted at corners or the like, but these functions cannot be obtained when the thickness of the CPP film is less than the above range.
[0016]
The polypropylene resin laminated foam of the present invention can be produced by various conventionally known methods. However, a foam sheet, a CPP film, and an OPP film prepared in advance are directly bonded by a thermal laminating method. It is most preferable to manufacture by the manufacturing method of the present invention, which is laminated and thermally bonded.
When the above layers are heat-bonded via, for example, a hot-melt adhesive, the melting temperature of the hot-melt adhesive is generally the thermoforming temperature of the polypropylene resin, or cooking food by a microwave oven. Since the temperature is much lower than the temperature, etc., when the container is manufactured by thermoforming, or when the container is cooked together with the food inside the microwave oven, the hot melt adhesive melts and the adhesive strength decreases significantly. As a result, there is a risk of causing peeling at the corners and lifting due to the above-described thermal contraction of the OPP film.
[0017]
Further, for example, a polypropylene resin in a molten state is extruded between the foam sheet and the OPP film to form an intermediate layer corresponding to the CPP film, and at the same time, the foam sheet and the OPP film are interposed through the intermediate layer. When the extrusion laminating method that laminates and adheres is adopted, the very high temperature (typically around 280 ° C) polypropylene resin extruded in the molten state between the foam sheet and the OPP film is cooled. Until the intermediate layer is formed, a larger amount of heat is applied to the foamed sheet and the OPP film than the thermal laminating method.
[0018]
For this reason, the laminated foam produced has a higher tension, particularly due to the accumulation of shrinkage force generated in the OPP film, as compared with the case produced by other lamination methods, and the laminated foam was thermoformed. In some cases, immediately after the molding, the OPP film hardly peels off and rises due to the action of the intermediate layer, but when stored over a long period of time, it gradually increases over time and rapidly when cooked. As a result of the shrinkage of the OPP film 2, there is a risk that the OPP film 2 may peel off and rise, particularly at the corners.
[0019]
Further, in the above extrusion laminating method, it is difficult to reduce the thickness of the intermediate layer due to manufacturing restrictions, and the thickness of the intermediate layer becomes as large as about 100 μm. This requires a large amount of heat, which further increases the stress accumulated in the OPP film and further promotes peeling and lifting of the OPP film at the corners, etc. There is also the problem of lengthening.
[0020]
On the other hand, according to the production method of the present invention, without using a hot melt adhesive, and without exposing the foamed sheet and the OPP film to a high temperature for a long time as in the extrusion laminating method, for example, As will be described later, a polypropylene resin laminate foam can be produced by heating only for a very short time while passing between a hot roll and a nip roll, and the thickness of the CPP film can be formed by an extrusion lamination method. It can be made smaller than the layer, all the above-mentioned problems can be solved, and the above-described polypropylene-based resin laminated foam excellent in each characteristic can be efficiently produced.
[0021]
Furthermore, since the molded article of the present invention is manufactured by thermoforming the above-mentioned polypropylene resin laminate foam, it can be suitably used for food packaging containers suitable for microwave cooking.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below.
<Polypropylene-based resin laminated foam and its manufacturing method>
For example, as shown in FIG. 1 (a), the polypropylene-based resin laminate foam of the present invention has an OPP film 2 on at least one side (in the figure, one side but includes both sides) of a polypropylene-based resin foam sheet 1. Are laminated via a CPP film 4 having a thickness of 40% or more of the thickness of the OPP film 2. Reference numeral 3 in the figure is a printing layer for improving the design properties. In the figure, it is formed at the interface between the foamed sheet 1 and the CPP film 4, but is printed at the interface between the CPP film 4 and the OPP film 2. Layer 3 may be formed.
[0023]
In the laminated foam, the CPP film 4 interposed between the foamed sheet 1 and the OPP film 2 is uniformly adhered to both the foamed sheet 1 and the OPP film 2 as described above. In order to prevent the thermal contraction of the OPP film 2 by absorbing the force of the OPP film 2 to be thermally contracted by heating in the close contact state, as well as improving the adhesive force at the interface of each layer than before. To work.
[0024]
Therefore, by thermoforming, the foamed sheet 1, the OPP film 2, the printed layer 3, and the CPP film 4 do not cause peeling of the OPP film 2 and the accompanying lifting at the corners or the like. As shown in (b), it is integrally molded neatly. Further, the OPP film 2 is prevented from being peeled off or lifted by the passage of time after molding or heat during cooking.
(Foam sheet 1)
Of the laminated foams, the polypropylene resin constituting the foam sheet 1 is preferably a non-crosslinked polypropylene resin, and as such a non-crosslinked polypropylene resin,
(A) a polypropylene resin having a free-end long-chain branch in the molecule and a melt tension of 6 g or more and 40 g or less (hereinafter referred to as “resin (A)”), and
(B) Polypropylene resin having a melt tension of 0.01 g or more and less than 6 g and a ratio Mw / Mn of weight average molecular weight Mw to number average molecular weight Mn of 3 to 8 [hereinafter referred to as “resin (B)” ]
At least one selected from the group consisting of is preferably used.
[0025]
Among these, the preferable range of the melt tension of the resin (A) is 6 g or more and 40 g or less. If the resin tension is less than 6 g, good foamability cannot be obtained. This is because there is a possibility that the extrudability may be deteriorated due to extreme deterioration or easy formation of a gel. The melt tension of the resin (A) is particularly preferably 20 to 30 g even within the above range, considering the balance between foamability and extrusion or composition.
[0026]
Examples of the resin (A) having such a free-end long chain branch include trade names Pro-fax PF-814 and Pro-fax SD-632, which are sold as foaming grades from Montel SDK Sunrise. It is done.
The resin (A) has good foamability when foamed by extrusion foaming or the like, for example, its density is 0.3 g / cm.^ThreeIt is suitable for forming a foam sheet 1 having a low density, a high expansion ratio, and particularly excellent heat insulation.
[0027]
Therefore, the above-mentioned resin (A) may be used alone to form the foamed sheet 1. However, since the resin (A) is expensive and may increase the product cost, the resin is usually used as a polypropylene resin. It is preferable to form the foamed sheet 1 by using (A) and the resin (B) in combination. Even in that case, it is possible to form the foam sheet 1 having a relatively low density and a high expansion ratio and excellent heat insulation.
The preferred range of the melt tension of the resin (B) is 0.01 g or more and less than 6 g as described above, since the tension is too low if it is less than 0.01 g, the resulting foam sheet 1 is open-celled. On the other hand, if it is 6 g or more, the melt viscosity of the resin becomes high and it becomes difficult to lower the resin temperature to near the melting point. As a result, an open cell structure tends to be obtained. It is because there exists a possibility that it may fall. In view of the balance between the tension and the melt viscosity, the resin (B) has a melt tension of preferably 0.1 g or more and less than 6 g, and more preferably 0.1 g or more and less than 3 g, even within the above range. Is more preferable.
[0028]
Examples of such a resin (B) include those satisfying the above conditions among general-purpose polypropylene resins such as a homopolymer of propylene and an ethylene-propylene copolymer.
The ratio of the resin (A) to the total amount of the resin (A) and the resin (B) is preferably 10 to 50% by weight as described above, and more preferably 10 to 40% by weight. . The reason for this is as follows.
[0029]
That is, the resin (A) improves the foaming property of the non-crosslinked general-purpose polypropylene resin, that is, the resin (B), which is usually not very foamable by the action of free-end long chain branching introduced into the molecule. It contributes to obtaining the foam sheet 1 having heat insulation, oil resistance and heat resistance.
However, a polypropylene resin having a free end long chain branch has a problem that it is inferior in rigidity as compared to a general-purpose polypropylene resin having no free end long chain branch. Moreover, since the polypropylene resin having a free-end long chain branch is expensive, the production cost of the product is increased.
[0030]
Therefore, the ratio of the resin (A) to the total amount of the resin (A) and the resin (B) is preferably 50% by weight or less, particularly 40% by weight or less as described above. On the other hand, the foamability of the resin (B) is improved, and the density is 0.3 g / cm as in the case of the resin (A) alone.^ThreeIn order to form a foam sheet 1 having a low density, a high expansion ratio, and excellent heat insulation, the ratio of the resin (A) to the total amount of the resin (A) and the resin (B) is 10% by weight. % Or more is preferable.
[0031]
As described above, although the resin (B) is usually not very foamable, for example, its density is 0.3 g / cm.^ThreeIt is possible to manufacture the foam sheet 1 having a relatively low expansion ratio as described above. Therefore, the foam sheet 1 may be formed by using the resin (B) alone as a polypropylene resin.
The foam sheet 1 is manufactured by melt-kneading the above polypropylene resin together with a foaming agent using an extruder, for example, and then extrusion-foaming through a mold connected to the tip of the extruder.
[0032]
There are circular slit dies, T-shaped dies, etc., but a cylindrical foam obtained by extrusion foaming through a circular slit die is cut at one or two or more locations on the circumference of the foam sheet 1. Preferably it is manufactured.
Examples of the foaming agent used for extrusion foaming include various volatile foaming agents, decomposable foaming agents, carbon dioxide, nitrogen gas, and water.
Among these, examples of the volatile blowing agent include one or more hydrocarbons such as propane, butane and pentane, and halogenated hydrocarbons such as tetrafluoroethane, chlorodifluoroethane and difluoroethane. Preferably used. As butane, normal butane or isobutane may be used alone, or normal butane and isobutane may be used in any proportion.
[0033]
Examples of the decomposable foaming agent include inorganic foaming agents such as an organic foaming agent such as azodicarbonamide and dinitrosopentamethylenetetramine, a combination of an organic acid such as citric acid or a salt thereof, and a bicarbonate such as sodium bicarbonate. Type foaming agents.
One of these foaming agents may be used alone, or two or more thereof may be used in combination.
[0034]
In addition, when melt-kneaded with a polypropylene-based resin in advance or with an extruder, for example, talc, or citric acid and sodium bicarbonate, such as a bubble adjusting agent for adjusting the size of bubbles when foaming, Various additives such as pigments, stabilizers, fillers, antistatic agents and the like may be appropriately added within a range not impairing the effects of the present invention. Among them, the filler is added to improve the strength of the molded product, rigidity at high temperature, durability and heat resistance. Examples of the filler include talc, calcium carbonate, silica, alumina, and titanium oxide. And inorganic fillers such as clay. The addition amount of the inorganic filler is preferably 5 to 50 parts by weight with respect to 100 parts by weight of the polypropylene resin.
[0035]
The foamed sheet 1 thus formed has a density of 0.1 to 0.85 g / cm.^ThreeIs preferred.
The density of the foam sheet 1 is 0.1 g / cm^ThreeIs less than 0.85 g / cm, the strength of the molded product and the rigidity at high temperatures may decrease.^ThreeIf it exceeds, the heat insulating property of the molded product may be lowered. The density of the foamed sheet 1 is 0.18 to 0.6 g / cm, particularly within the above range, considering the balance between strength and rigidity of the molded product and heat insulation.^ThreeIs preferred.
[0036]
Further, the thickness of the foam sheet 1 is preferably 0.3 to 5 mm, more preferably 0.5 to 3 mm in consideration of thermoformability, although it depends on the specifications of the target molded product.
(OPP film 2)
Examples of the polypropylene resin used as the basis of the OPP film 2 constituting the polypropylene resin laminated foam together with the foam sheet 1 include a propylene homopolymer, and a block copolymer of propylene and another resin. Or a random copolymer or the like may be used alone or in admixture of two or more.
[0037]
As other olefins other than propylene, ethylene or an α-olefin having 4 to 10 carbon atoms (1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, etc.) or 2 More than species.
Particularly suitable polypropylene resins include, for example, propylene homopolymer, propylene-ethylene random copolymer, propylene-ethylene-α-olefin random copolymer, and propylene component and propylene-ethylene random copolymer component. Examples thereof include a block copolymer.
[0038]
In addition, other resins may be mixed with the polypropylene resin as long as the effects of the present invention are not impaired.
Examples of the other resins include homopolymers or copolymers such as ethylene and α-olefin, olefin resins such as polyolefin wax and polyolefin elastomer, and hydrocarbon resins such as petroleum resins and terpene resins. However, it is used individually by 1 type or in mixture of 2 or more types.
[0039]
In addition, the above-mentioned polypropylene-based resin is intended to provide an antistatic agent, an antifogging agent, an antiblocking agent, an antioxidant, a light stabilizer, a crystal nucleating agent, a lubricant, a slipperiness and an antiblocking property as necessary. You may add suitably various additives, such as surfactant and a filler, in the range which does not impair the effect of this invention.
The OPP film 2 is obtained by, for example, melt-kneading the above-described polypropylene resin using an extruder, and then extruding the extruded film into a film shape through a die connected to the tip of the extruder. It is manufactured by stretching (biaxial stretching) sequentially or simultaneously in two directions: a direction (longitudinal direction, MD) and a direction perpendicular to the direction (transverse direction, TD).
[0040]
Among these, as the sequential biaxial stretching method, for example, a resin melted by using an extruder is extruded into a film shape from a T die connected to the tip of the extruder, cooled and solidified on a cooling roll, and then a heating roll stretching machine is used. And stretching in the MD direction, followed by stretching in the TD direction using a tenter transverse stretching machine. Examples of the simultaneous biaxial stretching method include a tenter method and a tubular inflation method.
The stretch amount of the OPP film 2 is not particularly limited, but the area stretch ratio, that is,
Area stretch ratio = (MD direction stretch ratio) × (TD direction stretch ratio)
Is preferably 4 to 50 times.
[0041]
When the area stretch ratio is less than 4 times, the effect of improving the drawdown of the laminated foam or the improvement of the strength of the molded product, the rigidity at high temperature, etc. due to the lamination of the OPP film 2 becomes insufficient. There is a fear. On the other hand, when the area stretch ratio exceeds 50 times, the thermoformability of the laminated foam may be lowered. The area stretch ratio is 15 to 35 times, especially within the above range, considering the balance between the effect of improving drawdown, the effect of improving the strength and rigidity of the molded product, and the thermoformability of the laminated foam. Preferably there is.
[0042]
Moreover, it is preferable that the draw ratio of MD direction and TD direction is 2-10 times.
If the draw ratio is less than 2, the effect of improving the drawdown of the laminated foam or the effect of improving the strength of the molded product, the rigidity at high temperature, etc. due to the lamination of the OPP film 2 may be insufficient. There is. On the other hand, when the draw ratio exceeds 10 times, the thermoformability of the laminated foam may be lowered. The draw ratio in the MD direction and the TD direction is particularly within the above range in consideration of the effect of improving drawdown, the effect of improving the strength and rigidity of the molded product, and the thermoformability of the laminated foam. It is preferably 3 to 9 times.
[0043]
The thickness of the OPP film 2 is preferably 5 to 50 μm.
If the thickness is less than 5 μm, the effect of improving the drawdown of the laminated foam and preventing the occurrence of corrugation or the effect of improving the rigidity of the molded product at high temperature may be insufficient. When the OPP film 2 is exceeded, a large amount of heat is generated when a laminated foam is produced by laminating the OPP film 2 on the foam sheet 1 or when a molded product is produced by thermoforming the produced laminated foam. Since it is necessary, the production efficiency is deteriorated, and the foamed sheet 1 is attacked by heat, and a part stretched locally at the time of thermoforming may be generated. The thickness of the OPP film 2 is particularly preferably 6 to 45 μm even within the above range, considering the balance of the above characteristics.
[0044]
Further, for example, a general OPP film formed of a propylene homopolymer is excellent in transparency and surface gloss, and the transparency and gloss tend to improve as the thickness decreases. Moreover, it is excellent in mechanical strength and can exhibit sufficient strength even if the thickness is small. And since the elongation at the time of thermoforming is low, there exists a tendency for thermoformability to fall, so that thickness becomes large. For this reason, when a general OPP film is used, the thickness is preferably as small as possible. Considering the balance between the transparency, gloss, mechanical strength, and thermoformability, it is particularly 6 to 25 μm even within the above range. Is preferred.
[0045]
Recently, an OPP film having a significantly improved elongation has been developed, although the mechanical strength is slightly lower than that of a general OPP film. Such an OPP film is, for example, a propylene-ethylene random copolymer having an ethylene content of 1 to 4% by weight or an ethylene content of 0.5 to 3.0 as described in JP-A-7-241906. It is formed from a propylene-based copolymer having a relatively low melting point, such as a propylene-ethylene-1-butene random copolymer having a 1% -butene content of 4 to 15% by weight. Compared with the OPP film, the elongation at the time of thermoforming is good, deep drawing and the like are possible, and a good molded product can be obtained. However, since the mechanical strength is slightly low as described above, it is preferable that the thickness is as large as possible in order to produce a molded product having sufficient strength and rigidity. Preferably there is.
[0046]
The surface of the OPP film 2 may be subjected to a surface treatment such as a corona discharge treatment in order to improve, for example, printability.
The OPP film 2 is not limited to a single layer, for example, a laminated film in which two or more OPP films such as OPP films made of polypropylene resins having different compositions or OPP films having different draw ratios are laminated. It can also be used. In that case, it is preferable to set the thickness of each layer so that the total thickness of all the OPP films falls within the above-described preferable range.
[0047]
Further, the OPP film 2 may be laminated with other films having different compositions, such as a film made of an ethylene-vinyl alcohol copolymer, for the purpose of improving gas barrier properties, etc., within a range not impairing the effects of the present invention. Good.
(CPP film 4)
Examples of the polypropylene resin used as the basis of the CPP film 4 interposed between the OPP film 2 and the foamed sheet 1 include the same polypropylene resin as in the case of the OPP film 2. The point that other resins can be mixed with the polypropylene resin within a range not impairing the effects of the invention is the same, and the types of the other resins are the same as in the case of the OPP film 2. Further, the types of additives that may be added to the polypropylene resin are the same as in the previous case.
[0048]
The CPP film 4 is produced by melting and kneading a polypropylene resin using an extruder and then extruding the film through a mold connected to the tip of the extruder without substantially stretching.
The thickness of the CPP film 4 is limited to 40% or more of the thickness of the OPP film 2 for the reason described above.
The thickness of the CPP film 4 is preferably 500% or less of the thickness of the OPP film 2 even within the above range.
[0049]
When the thickness of the CPP film 4 exceeds 500% of the thickness of the OPP film 2, the CPP film 4 is too thick and the effect of relaxing the heat shrinkage force of the OPP film 2 becomes excessive. There is a possibility that drawdown, corrugation and the like are likely to occur in the laminated foam. The thickness of the CPP film 4 is within the above range in consideration of the balance between the effect of relaxing the heat shrinkage force of the OPP film 2 and the effect of preventing the draw down and corrugation from occurring in the laminated foam during thermoforming. Of these, 50 to 450% of the thickness of the OPP film 2 is particularly preferable.
[0050]
The specific thickness of the CPP film 4 is preferably 5 to 80 μm.
If the thickness is less than 5 μm, the function of adhering to both the foamed sheet 1 and the OPP film 2 uniformly and with good adhesion and increasing the adhesion at the interface of each layer than before, or such an adhesion state In this case, since the function of absorbing the heat shrinkage of the OPP film 2 by heating and suppressing the heat shrinkage is not sufficiently exerted, the peeling and lifting of the OPP film 2 at the corners and the like are ensured. There is a risk that it cannot be prevented. On the other hand, when the thickness exceeds 80 μm, a large amount of heat is required when thermoforming the laminated foam, and the stress accumulated in the OPP film 2 is further increased. In addition to the possibility of further promoting the peeling and lifting in the process, there is a possibility that the thermoforming cycle becomes longer. In addition, the foamed sheet 1 is attacked by heat, and a part stretched locally at the time of thermoforming may be generated, which may deteriorate the appearance of the molded body. The thickness of the CPP film 4 is particularly preferably 10 to 50 μm even within the above range, considering the balance of the above characteristics.
[0051]
The surface of the CPP film 4 may be subjected to a surface treatment such as a corona discharge treatment in order to improve, for example, printability.
The CPP film 4 is not limited to a single layer, and a laminated film obtained by laminating two or more layers of CPP films such as CPP films made of polypropylene resins having different compositions can also be used. In that case, it is preferable to set the thickness of each layer so that the total thickness of all the CPP films falls within the above-described preferable range.
[0052]
Further, similar to the case of the OPP film 2, the CPP film 4 may be laminated with other films having different compositions such as a film made of an ethylene-vinyl alcohol copolymer for the purpose of improving gas barrier properties. .
The total thickness of the CPP film 4 and the OPP film 2 laminated thereon is preferably 20 to 120 μm.
If the thickness is less than 20 μm, the effect of improving the strength of the molded product and the rigidity at high temperature may be insufficient. Conversely, if the thickness exceeds 120 μm, many of the laminated foams may be thermoformed. The amount of heat is required, and the foamed sheet 1 is attacked by heat, resulting in a part that is locally stretched during thermoforming. The total thickness of the OPP film 2 and the CPP film 4 is preferably 30 to 90 μm even within the above range, considering the balance of these characteristics.
[0053]
(Print layer 3)
The printing layer 3 for improving the designability is one of the interfaces of each layer located between the foam sheet 1 and the OPP film 2, specifically, the foam sheet 1 and the CPP film 4 as described above. It is formed at one or both of the interface and the interface between the CPP film 4 and the OPP film 2.
More specifically,
(i) The surface of the foam sheet 1 on the CPP film 4 side,
(ii) The surface of the CPP film 4 on the foam sheet 1 side,
(iii) The surface of the OPP film 2 side of the CPP film 4,
(iv) The surface of the OPP film 2 on the CPP film 4 side,
In any of the above, the printing layer 3 is formed in advance prior to the lamination, and the printing layer 3 is formed at the predetermined position by laminating and bonding them.
[0054]
Of these, the formation of the printing layer 3 on any one of the surfaces (ii) to (iv) excluding the surface of the foamed sheet 1 in (i) is excellent in smoothness and gives beautiful printing. This is preferable because it is possible.
On the other hand, considering the effect of improving adhesiveness, it is preferable to form the printing layer 3 on the interface between the foamed sheet 1 and the CPP film 4, that is, on the surface of either (i) or (ii).
[0055]
In the configurations (i) to (iv) described above, since the printing layer 3 is viewed through the transparent and glossy OPP film 2, an appearance that emits a beautiful color coupled with the gloss of the OPP film 2 is obtained. Since this appearance is maintained even in a container after thermoforming, a container having excellent design properties can be obtained.
For example, when the printed layer 3 having a red or black pattern is formed on any one of the above surfaces by gravure printing or the like, a container having a color like a lacquer is obtained.
[0056]
In addition, a more beautiful appearance can be formed together with the printing layer 3 by kneading and coloring a pigment as a base layer of the printing layer 3.
Further, by forming the printing layer 3 at two interfaces that can be seen from the outside of the same OPP film 2, a more beautiful appearance can be formed by superimposing the two printing layers 3.
Further, a unique and beautiful appearance can be formed by merely kneading and coloring the foam sheet 1, the OPP film 2, and the CPP film 4 without forming the printing layer 3. For example, if the pigment is kneaded into the CPP film 4 and colored in red or black, the color will be seen through the transparent and glossy OPP film 2, and therefore, combined with the gloss of the OPP film 2, A container having such a color is obtained.
[0057]
As a printing method for forming the printing layer 3, in addition to the above gravure printing, various conventionally known printing methods that can use ink that can be printed on each surface can be employed. is there.
Further, as the pigment kneaded in each layer, any of various pigments excellent in compatibility and dispersibility with the polypropylene resin can be used.
(Laminated foam)
In the laminated foam of the present invention, as described above, the OPP film 2 is disposed on one or both sides of the polypropylene resin foam sheet 1 via the CPP film 4 having a thickness of 40% or more of the thickness of the OPP film 2. In addition to the lamination, the printing layer 3 is formed at any interface of each layer.
[0058]
That is, the laminated foam of the present invention basically includes the following 14 kinds of laminated structures (I) to (XIV) (in practice, here, as described above, the OPP film 2 and the CPP film 4). Variations due to the laminated structure and the like are added, but the description becomes complicated, so the OPP film 2 and CPP film 4 in the following classifications include all those having such a laminated structure in addition to those of a single layer. ).
(I) Three-layer structure of OPP film 2 / CPP film 4 / foamed sheet 1.
[0059]
(II) A four-layer structure of OPP film 2 / printing layer 3 / CPP film 4 / foamed sheet 1.
(III) Four-layer structure of OPP film 2 / CPP film 4 / printing layer 3 / foamed sheet 1.
(IV) 5-layer structure of OPP film 2 / printing layer 3 / CPP film 4 / printing layer 3 / foamed sheet 1.
[0060]
(V) 5 layer structure of OPP film 2 / CPP film 4 / foamed sheet 1 / CPP film 4 / OPP film 2.
(VI) 6-layer structure of OPP film 2 / printing layer 3 / CPP film 4 / foamed sheet 1 / CPP film 4 / OPP film 2.
(VII) 6-layer structure of OPP film 2 / CPP film 4 / printing layer 3 / foamed sheet 1 / CPP film 4 / OPP film 2.
[0061]
(VIII) 7-layer structure of OPP film 2 / printing layer 3 / CPP film 4 / printing layer 3 / foamed sheet 1 / CPP film 4 / OPP film 2.
(IX) 7-layer structure of OPP film 2 / printing layer 3 / CPP film 4 / foamed sheet 1 / CPP film 4 / printing layer 3 / OPP film 2.
(X) 7-layer structure of OPP film 2 / CPP film 4 / printing layer 3 / foamed sheet 1 / printing layer 3 / CPP film 4 / OPP film 2.
[0062]
(XI) 7-layer structure of OPP film 2 / printing layer 3 / CPP film 4 / foamed sheet 1 / printing layer 3 / CPP film 4 / OPP film 2.
(XII) Eight-layer structure of OPP film 2 / printing layer 3 / CPP film 4 / printing layer 3 / foamed sheet 1 / CPP film 4 / printing layer 3 / OPP film 2.
(XIII) 8 layer structure of OPP film 2 / printing layer 3 / CPP film 4 / printing layer 3 / foamed sheet 1 / printing layer 3 / CPP film 4 / OPP film 2.
[0063]
(XIV) 9-layer structure of OPP film 2 / printing layer 3 / CPP film 4 / printing layer 3 / foamed sheet 1 / printing layer 3 / CPP film 4 / printing layer 3 / OPP film 2.
(Method for producing laminated foam)
As a method for producing the laminated foam of the present invention by laminating the above layers, the thermal laminating method is suitably employed as described above.
[0064]
For example, a case where a laminated foam in which an OPP film is laminated on one side of the foamed sheet 1 via the CPP film 4 as in the above (I) to (IV) is continuously produced by the thermal laminating method is taken as an example. Further, the sequential lamination shown in FIG. 2 (a) and the simultaneous lamination shown in FIG. 2 (b) can be adopted.
Of these, in the thermal laminating method by sequential laminating shown in FIG. 2 (a), the foamed sheet 1 that has been manufactured by extrusion foaming in advance and wound in a roll shape is first preheated while being fed from the roll 10 at a constant speed. After preheating to 50 to 90 ° C. through the heater H1, it is supplied to a first roller pair R1 comprising a heating roller R1a and a nip roller R1b.
[0065]
There, this is also produced by extrusion molding in advance, and if necessary, the CPP film 4 wound in a roll shape with the printing layer 3 applied on either side or both sides thereof, While being fed from the roll 40 at a constant speed, it is supplied to the first roller pair R1 through the guide roller GR1, and laminated by heating and pressurizing continuously while being superposed on one surface of the foam sheet 1.
Suitable conditions for laminating by the first roller pair R1 are: the passing speed of the foam sheet 1 and the CPP film 4 is 5 to 15 m / min, the heating temperature of the heating roller R1a is 180 to 210 ° C., and the nip pressure of the nip roller R1b is 4 to 10 kg / min. cm²It is.
[0066]
Next, the laminate is fed to a second roller pair R2 composed of a heating roller R2a and a nip roller R2b while being fed at a constant speed.
There, it was also extruded and then biaxially stretched and manufactured, and OPP was wound into a roll with the printing layer 3 applied on either side or both sides as necessary. The film 2 is supplied from the roll 20 at a constant speed to the second roller pair R2 via the guide roller GR2, and the laminate of the foam sheet 1 and the CPP film 4 on the CPP film 4 side is supplied. Laminate by continuous heating and pressurization while superposing on the surface.
[0067]
If it does so, the laminated foam by which the OPP film was laminated | stacked through the CPP film 4 on the single side | surface of the foam sheet 1 as mentioned above will be manufactured continuously.
Suitable conditions for lamination by the second roller pair R2 are the same as described above. That is, the passing speed of the foam sheet 1, the CPP film 4 and the OPP film 2 is 5 to 15 m / min, the heating temperature of the heating roller R2a is 180 to 210 ° C., and the nip pressure of the nip roller R2b is 4 to 10 kg / cm.²It is.
[0068]
On the other hand, in the thermal laminating method by simultaneous laminating shown in FIG. 2 (b), the foamed sheet 1 manufactured by extruding and foaming in the same manner as described above and wound in a roll shape is fed from the roll 10 at a constant speed. First, after preheating to 50 to 90 ° C. through the preheating heater H1, it is supplied to a roller pair R composed of a heating roller Ra and a nip roller Rb.
There, CPP film 4 which was manufactured by extruding in advance and wound in a roll shape with printing layer 3 on either side or both sides as necessary, and extruding in advance After that, the biaxially stretched OPP film 2 that is manufactured in a roll shape with the printing layer 3 on either side or both sides as necessary is rolled into each roll. While being fed out from 40 and 20 at a constant speed, they are superposed on the guide roller GR and supplied to the roller pair R.
[0069]
Then, when the foamed sheet 1, the CPP film 4, and the OPP film 2 are laminated in this order and continuously heated and pressed to laminate, a laminated foam in which the above layers are laminated in this order is continuously produced.
The preferred conditions for laminating with the roller pair R are the same as described above. That is, the passing speed of the foam sheet 1, the CPP film 4 and the OPP film 2 is 5 to 15 m / min, the heating temperature of the heating roller Ra is 180 to 210 ° C., and the nip pressure of the nip roller Rb is 4 to 10 kg / cm.²It is.
[0070]
The foam sheet 1 is directly extruded and foamed from an extruder directly connected to the apparatus shown in FIGS. (A) and (b). In the case of FIG. (A), the first roller pair R1 is used. In this case, the roller pair R may be supplied. In that case, since the foam sheet 1 immediately after foaming has residual heat, the preheater heater H1 can be omitted.
<Molding>
Examples of the thermoforming method for producing the molded product of the present invention from the above-mentioned laminated foam include various conventionally known methods such as vacuum forming and pressure forming, or matched mold forming and plug assist forming as applications thereof. The molding method can be employed.
[0071]
The molded article of the present invention thus produced has heat resistance, oil resistance, and chemical resistance because the foam sheet 1, CPP film 4, and OPP film 2 constituting the container are all formed of a polypropylene resin. It is excellent and easy to recycle.
In addition, since the foamed sheet 1 is contained, the heat insulating property and the heat retaining property are excellent, and since the foamed sheet 1 has a structure reinforced by the OPP film 2, it is excellent in rigidity at high temperature and impact resistance at low temperature. ing.
[0072]
Moreover, a CPP film 4 is interposed between the foamed sheet 1 and the OPP film 2, and the function of the CPP film 4 allows for, as described above, during thermoforming, during storage after molding, during cooking, etc. The OPP film 2 is reliably prevented from being lifted off at the corners of the molded product. In particular, even if the printing layer 3 that has been conventionally considered to be inferior in adhesiveness is provided, the above-described peeling or lifting does not occur.
In particular, when the printing layer 3 is provided at any of the interfaces of the layers located between the foam sheet 1 and the OPP film 2 or when a pigment is kneaded and colored in the CPP film 4 or the like, it is transparent and glossy. Since the underlying printed layer 3 and coloring can be seen through the OPP film 2, the appearance that gives off a beautiful color combined with the gloss of the OPP film 2 can be obtained, and the container has an excellent design. In particular, when it is colored with a red or black pigment, or when it is a gravure-printed pattern or the like, it emits a color like a lacquer ware and becomes a particularly preferable container.
[0073]
Therefore, although the molded article of the present invention is suitable as various containers, the food, which is the contents, is delivered from the delivery center to each store in a state of being refrigerated or frozen, and taken back to the store or home. It is most suitable for food packaging containers such as convenience stores that are directly cooked in a microwave oven.
A pasta container C as an example of a molded product is shown in FIGS.
The illustrated pasta container C includes a shallow bowl-shaped container body C1, and a collar part C2 for fitting a lid (not shown) extending outward from the upper end opening of the container body C1, The reinforcing rib C3 projecting upward from the bottom of the container main body C1 is manufactured by thermoforming the laminated foam of the present invention as described above.
[0074]
The pasta container C is conventionally manufactured by, for example, manufacturing a laminated foam by thermoforming the OPP film so that the OPP film is located inside the container using a mold having a recess corresponding to the outer shape of the pasta container C, or manufacturing the pasta container C. During the subsequent storage, cooking, etc., the above-described peeling and lifting of the OPP film occurred frequently at the corner C4 of the rising edge of the rib C3 surrounded by the one-dot chain line in the figure, but the configuration of the present invention was adopted. By doing so, these problems can be solved.
[0075]
【Example】
Hereinafter, the present invention will be described based on examples and comparative examples.
In addition, each characteristic of the polypropylene resin used by each Example of this invention and the comparative example, the foam sheet, the laminated foam body manufactured, and a molded article was measured and evaluated by the following method, respectively.
<Melt tension measurement>
The melt tension of the polypropylene resin was measured as follows using a measuring device [Capillograph PMD-C] manufactured by Toyo Seiki Seisakusho.
[0076]
That is, in a state where the sample resin was heated to 230 ° C. and melted, the piston descending speed was constant at 10 mm / min from the piston extrusion type plastometer nozzle (2.095 mm in diameter and 8 mm in length) of the above apparatus. While extruding into a string while maintaining the speed, the string is passed through a tension detection pulley located 35 cm below the nozzle, and then the winding speed is about 66 m / min using a winding roll.²The sample resin was wound up while gradually increasing at a certain acceleration, and the tension at the time when the string-like material was cut was used as the melt tension of the sample resin.
[0077]
<Density measurement of foam sheet>
The density of the foam sheet is determined by measuring the weight and volume of the foam sheet, and the weight (g) / volume (cm^Three).
<Evaluation of thermoformability of laminated foam>
The thermoformed formability of the laminated foam is determined by the pasta container as a molded product produced by plug-assist molding of the laminated foam so that the OPP film side surface is inside the container [FIGS. 3 (a) (b) The outer appearance of those having an outer diameter of 200 mm and an outer diameter of 30 mm] was visually observed and evaluated in the following three stages.
[0078]
X: Breaking or the like occurred, and the product could not be formed into a predetermined shape. Poor thermoformability.
(Triangle | delta): The elongation at the time of shaping | molding was bad and the part with thin thickness produced locally. Somewhat poor thermoformability.
◯: A good molded article having good elongation at molding, uniform thickness and high dimensional accuracy was obtained. Good thermoformability.
[0079]
<Uplift evaluation of OPP film>
The presence or absence of lifting of the OPP film during thermoforming and cooking was evaluated according to the following criteria.
(During thermoforming)
As described above, pasted containers having the same shape and the same dimensions are continuously manufactured by plug assist molding so that the surface on the OPP film side is the inner side of the container in the same manner as described above. Every time, 100 samples randomly extracted from each sample were visually observed, and the presence or absence of lifting of the OPP film was evaluated according to the following criteria.
[0080]
A: No lifting of the OPP film was observed in all 100 samples. Very good adhesion of OPP film.
○: Uplift of the OPP film was observed in 10 or less of the 100 samples. Good adhesion of OPP film.
Δ: OPP film was lifted in more than 10 samples but not more than 10 out of 100 samples, but there was no practical problem. Good adhesion of OPP film.
[0081]
X: The lifting of the OPP film was observed in more than 20 samples out of 100. Poor adhesion of OPP film.
(When cooking)
Ten samples of the OPP film that are not lifted are extracted from the samples of the above examples and comparative examples, 200 cc of hot water (98 ° C.) is added to each sample, and heated in a microwave oven with an output of 500 W for 4 minutes. Then, it observed visually and evaluated the presence or absence of the lifting of an OPP film according to the following reference | standard.
[0082]
A: The lifting of the OPP film was not observed at all in all 10 samples. Very good adhesion of OPP film.
○: The lifting of the OPP film was observed in 2 or less of the 10 samples. Good adhesion of OPP film.
Δ: OPP film was lifted in more than 2 samples but not more than 5 out of 10 samples, but there was no practical problem. Good adhesion of OPP film.
[0083]
X: Lifting of the OPP film was observed in more than 5 samples out of 10. Poor adhesion of OPP film.
<Insulation evaluation of molded products>
After putting 200 cc of hot water (98 ° C.) into the containers of each of the above Examples and Comparative Examples and heating them in a microwave oven with an output of 500 W for 2 minutes, the container immediately after heating was taken out from the microwave oven with bare hands. The thermal insulation was evaluated according to the following criteria.
[0084]
(Double-circle): It was able to take out without a problem without almost feeling heat. Very good thermal insulation.
○: It was able to be taken out without any problem as long as it felt warm. Good thermal insulation.
Δ: felt hot and could not hold for a long time. Somewhat poor insulation.
X: It was hot and could not be taken out with bare hands. Insulation failure.
Moreover, in each of the following Examples and Comparative Examples, in order to produce a foam sheet, the following A-1 resin belonging to the resin (A), and the following B-1 and B-2 belonging to the resin (B) Any one of polypropylene resins PP1 to PP4 each containing a resin shown in Table 1 was used.
<Resin A-1>
Propylene-ethylene block copolymer manufactured by Montelu SDK Sunrise, Inc., trade name SD632.
[0085]
Melt tension: 21.9g
Melt index (MI) value: 3
Density: 0.90 g / cm^Three
<Resin B-1>
Propylene homopolymer manufactured by Montelu SDK Sunrise, Inc., trade name PM600A.
[0086]
Melt tension: 0.8g
MI value: 7.5
Density: 0.90 g / cm^Three
<Resin B-2>
Propylene homopolymer manufactured by Montelu SDK Sunrise, Inc., trade name PL500A.
[0087]
Melt tension: 1.8g
MI value: 3.3
Density: 0.90 g / cm^Three
[0088]
[Table 1]

[0089]
As the CPP film, one of the following four types of films was selected and used.
<Film C-1>
A 20-μm thick CPP film (trade name P-1111 manufactured by Toyobo Co., Ltd.) made of a propylene homopolymer.
<Film C-2>
A CPP film (trade name P-1111 manufactured by Toyobo Co., Ltd.) made of a homopolymer of propylene and having a thickness of 25 μm.
<Film C-3>
A 25-μm thick CPP film (trade name P-1111 manufactured by Toyobo Co., Ltd.) made of a homopolymer of propylene and colored red by kneading a pigment.
<Film C-4>
A 30-μm-thick CPP film (trade name P-1111 manufactured by Toyobo Co., Ltd.) made of a homopolymer of propylene.
[0090]
Further, as the OPP film, one of the following six kinds of films was selected and used.
<Film O-1>
An OPP film (made by Toray Industries, Inc.) made of a propylene homopolymer and having a heat shrink temperature of 142 ° C. and a thickness of 7 μm.
<Film O-2>
An OPP film (manufactured by Toray Industries, Inc.) having a heat shrink temperature of 142 ° C. and a thickness of 10 μm made of a propylene homopolymer.
<Film O-3>
An OPP film (trade name P-2161 manufactured by Toyobo Co., Ltd.) made of a homopolymer of propylene and having a heat shrink temperature of 138 ° C. and a thickness of 25 μm.
<Film O-4>
An OPP film made of a propylene-ethylene random copolymer and having a heat shrinkage temperature of 118 ° C. and a thickness of 40 μm (trade name SF-21 manufactured by Santox).
<Film O-5>
An OPP film (trade name P-2161 manufactured by Toyobo Co., Ltd.) made of a propylene homopolymer and having a heat shrink temperature of 138 ° C. and a thickness of 50 μm.
<Film O-6>
An OPP film (trade name P-2161 manufactured by Toyobo Co., Ltd.) made of a homopolymer of propylene and having a heat shrink temperature of 138 ° C. and a thickness of 60 μm.
[0091]
The heat shrink temperature of the OPP film was measured by the following method.
<Measurement of heat shrink temperature of OPP film>
The film cut into a 10 cm square was heated in a thermostatic bath (oven) at a set temperature for 10 minutes, then taken out of the bath, and the dimensions of the film in the MD direction and the TD direction were measured. The set temperature of the thermostatic bath was set in increments of 10 ° C. from 90 ° C. to 150 ° C., and the above measurement was performed for each set temperature.
[0092]
A graph with the set temperature on the horizontal axis and the shrinkage ratio [= (size before heating−size after heating) ÷ size before heating × 100] on the vertical axis is plotted for each of the MD direction and the TD direction of the film. Then, the temperature at which the shrinkage rate in either direction reached 5% was read from the graph and defined as the heat shrinkage temperature.
The O-4 OPP film is formed of a propylene-based copolymer having a relatively low melting point as described above, and the elongation during thermoforming is higher than that of other general-purpose OPP films. Good and good molded products were obtained.
[0093]
Example 1
<Production of foam sheet>
100 parts by weight of a polypropylene resin of PP1 in Table 1 and 0.4 parts by weight of a cell regulator [trade name Hydrocerol HK-70 manufactured by Boehringer Co., Ltd.] are dry blended, and this mixture is mixed with the first and second components. Of butane as a blowing agent (isobutane / normal butane) = 65/35). The amount of butane injected was 2.0 parts by weight per 100 parts by weight of the resin.
[0094]
Further, the melted and mixed molten mixture is continuously supplied from the first extruder to the second extruder, cooled uniformly in the second extruder, and then connected to the tip of the second extruder. From the cylindrical die, foaming was performed while continuously extruding into a cylindrical shape at a discharge rate of 120 kg / hour.
Next, the obtained cylindrical foam is cooled from the inside of the cylinder along a mandrel having a diameter of 672 mm cooled with water at 24 ° C., and air is blown from an air ring larger than the outer shape of the cylinder. After cooling from the outside of the cylinder, it is cut with a cutter at two points on the circumference, and the density is 0.25 g / cm.^ThreeA long foam sheet having a thickness of 1.5 mm and a width of 1045 mm was produced.
[0095]
<Manufacture of laminated foam>
A long film C-2 having the same width as the CPP film and a long film O-1 having the same width as the OPP film are provided on one side of the foamed sheet prepared above. A laminated foam was produced by laminating and adhering by the thermal laminating method by simultaneous laminating shown in FIG. The conditions for lamination were as follows. The thickness of the CPP film was 357% of the thickness of the OPP film.
[0096]
Preheating temperature of the foam sheet 1 by the preheating heater H1: 65 ° C.
Heating temperature of the heating roller Ra: 190 ° C.
Nip pressure of nip roller Rb: 6 kg / cm²
Feed speed of each layer: 10m / min
<Manufacture of molded products>
The laminated foam was plug-assisted molded so that the OPP film side was the inner surface side of the container, and the pasta container as a molded product was manufactured.
[0097]
Example 2
<Production of foam sheet>
The density was 0.34 g / cm in the same manner as in Example 1 except that 100 parts by weight of the PP2 polypropylene resin in Table 1 was used.^ThreeA long foam sheet having a thickness of 1 mm and a width of 1045 mm was produced.
<Manufacture of laminated foam>
A long film C-3 having the same width as the CPP film and a long film O-3 having the same width as the OPP film are provided on one side of the foamed sheet prepared above. A laminated foam was produced by laminating and adhering by the thermal laminating method using sequential lamination as shown in FIG. The conditions for lamination were as follows. The thickness of the CPP film was 100% of the thickness of the OPP film.
[0098]
Preheating temperature of the foam sheet 1 by the preheating heater H1: 70 ° C.
Heating temperature of the heating roller R1a: 190 ° C.
The nip pressure of the nip roller R1b: 6 kg / cm²
Heating temperature of heating roller R2a: 190 ° C
Nip pressure of nip roller R2b: 6 kg / cm²
Feed speed of each layer: 10m / min
<Manufacture of molded products>
The laminated foam was plug-assisted molded in the same manner as in Example 1 so that the OPP film side was the inner surface side of the container, and the pasta container as a molded product was manufactured.
[0099]
Example 3
<Production of foam sheet>
The density was 0.33 g / cm in the same manner as in Example 1 except that 100 parts by weight of the PP3 polypropylene resin in Table 1 was used.^ThreeA long foam sheet having a thickness of 1.02 mm and a width of 1045 mm was produced.
<Manufacture of laminated foam>
A long film C-2 having the same width as a CPP film and a long film O-1 having the same width as an OPP film are provided on one side of the foamed sheet prepared above as shown in FIG. A laminated foam was produced by laminating and adhering by the thermal laminating method using sequential lamination as shown in FIG. The lamination conditions were the same as in Example 2. The thickness of the CPP film was 357% of the thickness of the OPP film. Moreover, the said printing layer was interposed in the interface of a foam sheet and a CPP film by previously forming the printing layer by the gravure printing on the surface at the side of the foam sheet of a CPP film.
[0100]
<Manufacture of molded products>
The laminated foam was plug-assisted molded in the same manner as in Example 1 so that the OPP film side was the inner surface side of the container, and the pasta container as a molded product was manufactured.
Example 4
The same as in Example 3 except that a CPP film having a printed layer previously formed by gravure printing on the surface of the OPP film was used and the printed layer was interposed at the interface between the CPP film and the OPP film. Thus, a laminated foam and a pasta container were produced.
[0101]
Example 5
A laminated foam and a pasta container were produced in the same manner as in Example 4 except that a long film O-3 having the same width as the foam sheet was used as the OPP film. The thickness of the CPP film was 100% of the thickness of the OPP film.
Example 6
A laminated foam and a pasta container were produced in the same manner as in Example 3 except that a long film O-4 having the same width as the foam sheet was used as the OPP film. The thickness of the CPP film was 62.5% of the thickness of the OPP film.
[0102]
Example 7
On one side of the same foam sheet produced in Example 2, a long film C-4 having the same width as a CPP film and a long film O-5 having the same width as an OPP film, A laminated foam was produced by laminating and adhering by the thermal laminating method by sequential lamination shown in FIG. 2 (a), and a pasta container was produced by plug assist molding in the same manner as in Example 1. The lamination conditions were the same as in Example 2. The thickness of the CPP film was 60% of the thickness of the OPP film. Moreover, the said printing layer was interposed in the interface of a CPP film and an OPP film by previously forming the printing layer by the gravure printing on the surface at the side of the CPP film of an OPP film.
[0103]
Example 8
<Production of foam sheet>
The density was 0.46 g / cm in the same manner as in Example 1 except that 100 parts by weight of the PP4 polypropylene resin in Table 1 was used.^ThreeA long foam sheet having a thickness of 0.89 mm and a width of 1045 mm was produced.
<Manufacture of laminated foam>
On one side of the foamed sheet prepared above, a long film C-4 having the same width as the CPP film and a long film O-2 having the same width as the OPP film are shown in FIG. A laminated foam was produced by laminating and adhering by the thermal laminating method by simultaneous laminating shown in FIG. The lamination conditions were the same as in Example 1. The thickness of the CPP film was 300% of the thickness of the OPP film. Moreover, the said printing layer was interposed in the interface of a foam sheet and a CPP film by previously forming the printing layer by the gravure printing on the surface at the side of the foam sheet of a CPP film.
[0104]
<Manufacture of molded products>
The laminated foam was plug-assisted molded in the same manner as in Example 1 so that the OPP film side was the inner surface side of the container, and the pasta container as a molded product was manufactured.
Comparative Example 1
A laminated foam and a pasta container were produced in the same manner as in Example 5 except that the CPP film was omitted and the foamed sheet and the film O-3 as the OPP film were directly laminated.
[0105]
Comparative Example 2
Laminate in the same manner as in Comparative Example 1 except that the printed layer is formed on the surface of the OPP film on the foamed sheet side by gravure printing in advance, and the printed layer is interposed at the interface between the foamed sheet and the OPP film. Foam and pasta containers were produced.
Comparative Example 3
On one side of the same foamed sheet produced in Example 3, a long film C-1 having the same width as a CPP film and a long film O-6 having the same width as an OPP film, A laminated foam was produced by laminating and adhering by the thermal laminating method by sequential lamination shown in FIG. 2 (a), and a pasta container was produced by plug assist molding in the same manner as in Example 1. The lamination conditions were the same as in Example 2. The thickness of the CPP film was 33.3% of the thickness of the OPP film. Moreover, the said printing layer was interposed in the interface of a foam sheet and a CPP film by previously forming the printing layer by the gravure printing on the surface at the side of the foam sheet of a CPP film.
[0106]
The above results are summarized in Table 2.
[0107]
[Table 2]

[0108]
From the table, in Comparative Examples 1 and 2 in which the CPP film is omitted and the foamed sheet and the OPP film are directly laminated, a large number of the OPP film floats during cooking after thermoforming, especially between the two layers. In Comparative Example 2 provided with the print layer, it was confirmed that the OPP film was slightly lifted even during thermoforming.
Moreover, although the thickness of the OPP film was less than 40% of the thickness of the OPP film, the thickness of the OPP film was 60 μm, and the thickness of the OPP film increased from the time of thermoforming. Many occurred. The thermoformability was also somewhat poor.
[0109]
In contrast, in each of the examples, there is no lifting of the OPP film during thermoforming, and there is no lifting of the OPP film in most embodiments during cooking, and both formability and heat insulation are practical. It was confirmed that this level was reached.
Moreover, when Examples 1, 3 and 4 which combined the same CPP film and OPP film among each Example are compared, due to the difference in the density and thickness of the foamed sheet, the result of the heat insulation is the result of Example 1. Although it was good and there was a difference that Examples 3 and 4 were good, the lifting of the OPP film was not observed at all at the time of thermoforming and cooking, and from this, according to the configuration of the present invention. It was found that the adhesion of the OPP film can be remarkably improved regardless of the presence or absence of the printing layer and the formation position thereof.
[0110]
Further, when Examples 3 to 6 or Examples 2 and 7 in which the ratio of the thickness of the CPP film to the thickness of the OPP film was changed by changing the thickness of the OPP film were compared, both were within the practical range. However, it was confirmed that as the ratio increased, the lift of the OPP film decreased and the adhesion was improved.
Further, when Examples 6 and 7 in which the thickness of the OPP film is particularly large in each example are compared, when a general-purpose OPP film is used as seen in Example 7, the moldability is slightly lowered due to the thickness. However, as shown in Example 6, it was confirmed that the moldability can be improved by using the above-described OPP film having good elongation.
[0111]
Furthermore, from the result of Example 8, when the foam sheet was formed only from the resin (B), compared to the case where the foam sheet was formed from the resin (A) alone or the resin (A) (B), Although it is not possible to obtain a laminated foam having a low density and a high heat insulating property, it is possible to form a laminated foam having a medium density. In this case, the adhesiveness of the OPP film can be obtained by adopting the configuration of the present invention. It was confirmed that it can be improved.
[0112]
【The invention's effect】
As described above in detail, according to the present invention, heat resistance, oil resistance, heat insulation that can be used for cooking in a microwave oven, and the like are excellent in rigidity at high temperature, and at the time of thermoforming or after thermoforming. A novel polypropylene-based resin laminate foam that has improved the problem of the OPP film floating at the corners, etc. during cooking, an efficient manufacturing method thereof, and a good molded product excellent in each of the above-mentioned properties There is a specific effect that can be provided.
[Brief description of the drawings]
FIG. 1 (a) is an enlarged sectional view showing an example of an embodiment of a polypropylene resin laminated foam of the present invention, and FIG. 1 (b) is a diagram when the laminated foam is thermoformed. It is an expanded sectional view which shows the state of a corner.
FIGS. 2A and 2B are diagrams illustrating a process for producing the laminated foam of the above example by a thermal laminating method, in which FIG. 2A is a thermal laminating method by sequential lamination, and FIG. 2B is a thermal laminating by simultaneous lamination. Explanatory drawing of the lamination method.
FIGS. 3A and 3B are views showing a pasta container as an example of a molded product manufactured from a laminated foam, in which FIG. 3A is a plan view and FIG. 3B is a longitudinal sectional view.
FIG. 4 (a) is an enlarged sectional view showing an ideal state of a corner when a conventional laminated foam is thermoformed, and FIG. 4 (b) shows the conventional laminated foam. FIG. 5 is an enlarged cross-sectional view showing a state in which the OPP film is lifted at the corner when thermoformed.
[Explanation of symbols]
1 Foam sheet
2 CPP film
3 Print layer
4 OPP film

Claims (9)

A biaxially stretched polypropylene resin film is laminated on at least one surface of a polypropylene resin foam sheet via an unstretched polypropylene resin film having a thickness of 40% or more of the thickness of the biaxially stretched polypropylene resin film. A polypropylene resin laminate foam characterized by the following. The biaxially stretched polypropylene resin film has a thickness of 5 to 50 µm, the unstretched polypropylene resin film has a thickness of 5 to 80 µm, and the total thickness of both films is 20 to 120 µm. Polypropylene-based resin laminate foam. 2. The polypropylene-based resin laminated foam according to claim 1, wherein a printed layer is provided at any of the interfaces of the respective layers located between the foamed sheet and the biaxially stretched polypropylene-based resin film. 4. The polypropylene resin laminate foam according to claim 3, wherein the printed layer is provided at an interface between the foam sheet and the unstretched polypropylene resin film. 2. The polypropylene resin laminated foam according to claim 1, wherein the unstretched polypropylene resin film is colored by kneading a pigment into the polypropylene resin forming the film. Foam sheet
(A) 10-50% by weight of a polypropylene resin having a free-end long-chain branch in the molecule and a melt tension of 6 g or more and 40 g or less,
(B) 90 to 50% by weight of a polypropylene resin having a melt tension of 0.01 g or more and less than 6 g and a ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn of 3 to 8 is mixed; The polypropylene-based resin laminate foam according to claim 1, which is formed by extrusion foaming. The polypropylene-based resin laminate foam according to claim 1, wherein the density of the foam sheet is 0.1 to 0.85 g / cm ³ . A method for producing the polypropylene resin laminate foam according to any one of claims 1 to 7, wherein a foam sheet, an unstretched polypropylene resin film, and a biaxially stretched polypropylene resin film prepared in advance are thermally laminated. A method for producing a polypropylene-based resin laminate foam, characterized by directly laminating and adhering by a method. A molded article produced by thermoforming the polypropylene resin laminated foam according to any one of claims 1 to 7.

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