JP2005088200A - Styrenic resin laminated foamed sheet and molded container comprising the same - Google Patents
Styrenic resin laminated foamed sheet and molded container comprising the same Download PDFInfo
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Abstract
Description
本発明はインスタントらーめん容器等に使用される軽量で、強度の優れたスチレン系樹脂積層発泡シートに関する。 The present invention relates to a lightweight and strong styrene-based resin laminated foam sheet used for instant ramen containers and the like.
インスタントらーめん容器等の容器には、スチレン系樹脂発泡シートの表面にスチレン系樹脂非発泡フィルム層を積層したスチレン系樹脂積層発泡シートが軽量で、断熱性が高く、高強度の割れ難い容器が得られるため、多量に使用されている。しかし、これら食品は価格が安いことから容器価格の低減が課題であり、発泡シート層の軽量化やフィルム層の薄肉化が要求されてきた。また、近年の容器リサイクル法の施行によりこの要求は更に強いものとなっている。 For containers such as instant ramen containers, a styrene resin laminated foam sheet in which a styrene resin non-foamed film layer is laminated on the surface of a styrene resin foam sheet is light, has high heat insulation, and has a high strength and is difficult to break. Therefore, it is used in large quantities. However, the price of these foods is low, and hence the reduction of the container price is an issue, and the weight reduction of the foamed sheet layer and the thinning of the film layer have been required. In addition, this requirement has been further strengthened by the recent enforcement of the Container Recycling Law.
しかし、単純に発泡シート層を軽量化しただけでは、当然成形容器の強度が低下し、成形工程で容器が折れ破損したり、シワが生じ外観が損なわれる等の問題が発生する。また、スチレン樹脂積層発泡シートのフィルム面を容器の外側となる様に成形し、その容器外面に曲面印刷を施し、容器に意匠性を与えることは広く行われているが、フィルムを薄膜化しすぎると得られた容器の表面の平滑性が損なわれるため、印刷飛び等が発生し、容器外観が大きく損なわれる。 However, simply reducing the weight of the foam sheet layer naturally reduces the strength of the molded container, which causes problems such as breakage and breakage of the container in the molding process, wrinkles, and loss of appearance. Moreover, it is widely practiced to form the styrene resin laminated foam sheet so that the film surface is on the outside of the container, and then apply curved printing to the outer surface of the container to give the container design, but the film is too thin. Since the smoothness of the surface of the obtained container is impaired, printing skipping or the like occurs, and the appearance of the container is greatly impaired.
これらの問題を回避しつつ、市場の軽量化の要求に応えるため、発泡シート表面の強度を上げる方法が提案されている（例えば特許文献１を参照）。しかし、この方法は発泡シート単体をトレーなどの浅い形状に成形する場合には有効だが、積層発泡シートを丼など深い形状の容器に成形する場合には、成形性が大幅に低下したり、フィルムと発泡シートの接着性が低下するといった問題が生じる。更には、両面にフィルムを積層することも提案されている(例えば特許文献２)。しかし、この方法は強度の向上と引き替えに製造コストの増加や、生産性の悪化を招くという問題があった。また、これらの方法とは別に、丼容器成形を対象に、残存発泡剤量、表層の密度を特定の範囲内に調整することによる高強度化が提案されている(例えば特許文献３)。しかし、同発明は天地圧縮強度の向上を対象とするものであり、リップ圧縮強度、突き刺し強度等成形容器に要求されている全ての要件を満たすための方法については示唆されていない。 このため、スチレン系樹脂積層発泡シートの目付を３８０〜４２０ｇ／ｍ2程度とすることが限界であり、軽量化した容器を求める市場の要求に応えるのに充分ではなかった。
本発明は、軽量で強度、曲面印刷適正に優れた容器に成形することが可能な、成形性に優れたスチレン系樹脂積層発泡シートおよびその成形容器を提供することを目的とする。 An object of the present invention is to provide a styrene-based resin laminated foam sheet having excellent moldability and a molded container that can be molded into a container that is lightweight and has excellent strength and curved surface printing.
発明者らは、スチレン系樹脂積層発泡シートから成形される容器の天地圧縮強度、リップ圧縮強度、突き刺し強度等の強度向上に関し、鋭意研究した結果、積層発泡シートの曲げ強度が高ければ、成形品の強度、特にリップ圧縮強度が向上できることを見出した。また、積層発泡シートの曲げ強度は、それを構成する発泡シートと非発泡フィルムのそれぞれの目付、発泡シートの表層部(特にフィルムを積層していない面)の密度、残存発泡剤量によって決まることを見出し、本発明に至った。 As a result of diligent research regarding the improvement of the strength of the container formed from the styrene-based resin laminated foam sheet, such as the vertical compression strength, the lip compression strength, and the piercing strength, It was found that the strength, particularly the lip compression strength, can be improved. In addition, the bending strength of the laminated foam sheet is determined by the basis weight of the foam sheet and non-foamed film constituting it, the density of the surface layer portion of the foam sheet (particularly, the surface on which the film is not laminated), and the amount of residual foaming agent. And found the present invention.
すなわち、本発明は、
目付が１９０〜２３０ｇ／ｍ2、残存発泡剤量が０．４５〜０．５５モル／ｋｇ、フィルムを積層しない面の表面から厚み１５０μｍの部分の密度が０．２５〜０．３５ｇ／ｃｍ3であるスチレン系発泡シートに目付が７０〜１３０ｇ／ｍ2のスチレン系樹脂非発泡フィルムを積層した積層発泡シートであって、ＪＩＳ−Ｋ７２２１に準拠した方法で積層発泡シートのフィルム面側から変形を与えた時の曲げ最大荷重が３．５Ｎ以上である、厚み１．８〜２．３ｍｍ、目付２８０〜３６０ｇ／ｍ2のスチレン系樹脂積層発泡シート（請求項１）、
スチレン系樹脂発泡シートのフィルムを積層する面の表面から厚み１５０μｍの部分の密度が０．３５〜０．４５ｇ／ｃｍ3である請求項１記載のスチレン系樹脂積層発泡シート（請求項２）、
少なくとも一方の表面に塗布量が０．０３〜０．１０ｇ／ｍ2のシリコーンオイルを塗布した請求項１または２に記載のスチレン系樹脂積層発泡シート（請求項３）、
および、請求項１〜３いずれかに記載のスチレン系樹脂積層発泡シートを成形して得られる容器（請求項４）
に関する。
That is, the present invention
The basis weight is 190 to 230 g / m 2 , the residual foaming agent amount is 0.45 to 0.55 mol / kg, and the density of the portion having a thickness of 150 μm from the surface on which the film is not laminated is 0.25 to 0.35 g / cm 3. Is a laminated foam sheet in which a non-foamed styrene resin film having a basis weight of 70 to 130 g / m 2 is laminated on the styrene foam sheet, and is deformed from the film surface side of the laminated foam sheet by a method according to JIS-K7221. The styrene-based resin laminated foam sheet having a thickness of 1.8 to 2.3 mm and a basis weight of 280 to 360 g / m 2 having a bending maximum load of 3.5 N or more when applied (Claim 1),
The styrene resin laminated foam sheet according to claim 1, wherein the density of the portion having a thickness of 150 μm from the surface of the surface on which the film of the styrene resin foam sheet is laminated is 0.35 to 0.45 g / cm 3 .
The styrene-based resin laminated foam sheet according to claim 1 or 2, wherein a silicone oil having an application amount of 0.03 to 0.10 g / m 2 is applied to at least one surface (Claim 3).
And the container obtained by shape | molding the styrene resin laminated foam sheet in any one of Claims 1-3 (Claim 4).
About.
本発明によるスチレン系樹脂発泡積層シートを成形することにより、軽量で強度が高く、曲面印刷適正に優れた容器が得られる。 By molding the styrene-based resin foam laminated sheet according to the present invention, a container having a light weight, high strength and excellent curved surface printing is obtained.
スチレン系樹脂積層発泡シートを成形した容器の物性としては天地圧縮強度、リップ圧縮強度、突き刺し強度が求められるが、この内、天地圧縮強度、リップ圧縮強度には曲げ変形に対する強度が高い事が必要である。そのため、強度の高い容器を得るためにはＪＩＳ−Ｋ７２２１に準拠した方法で測定した最大曲げ荷重が３．５Ｎ以上である必要がある。具体的には、先端部の半径が５ｍｍ支持台に長さ１５０ｍｍ×巾２５ｍｍに切り出したサンプルをフィルム面が上になるように乗せ、先端部の半径が５ｍｍの加圧楔で１０ｍｍ／ｍｉｎで変形を与えて測定を行う。この測定を積層発泡シートの巾方向、長手方向に各５点測定を行い、最大曲げ荷重の平均を求める。 The physical properties of containers made of styrene resin laminated foam sheets are required to have top and bottom compression strength, lip compression strength, and piercing strength. Of these, top and bottom compression strength and lip compression strength must have high strength against bending deformation. It is. Therefore, in order to obtain a container with high strength, the maximum bending load measured by a method according to JIS-K7221 needs to be 3.5 N or more. Specifically, a sample cut to a length of 150 mm × width 25 mm is placed on a support base having a radius of 5 mm at the tip portion so that the film surface is on top, and a pressure wedge with a tip radius of 5 mm is 10 mm / min. Measurement is performed with deformation. This measurement is performed for each of the five points in the width direction and the longitudinal direction of the laminated foam sheet, and the average of the maximum bending load is obtained.
この最大曲げ荷重が３．５Ｎ未満の場合には十分な天地圧縮強度、リップ圧縮強度を有する容器を得ることができない。また、最大曲げ荷重は高ければ高い程、容器強度は向上するが、本発明に於ける積層発泡シートでは６．０Ｎが限界であった。もし、これ以上の曲げ強度を有するシートが得られたとしても、強度が高くなる反面、脆く、割れやすくなり実用には適さない。 When this maximum bending load is less than 3.5 N, a container having sufficient top and bottom compression strength and lip compression strength cannot be obtained. Further, the higher the maximum bending load, the better the container strength, but 6.0 N was the limit in the laminated foam sheet of the present invention. Even if a sheet having a bending strength higher than this is obtained, the strength is increased, but on the other hand, it is fragile and easily broken, which is not suitable for practical use.
スチレン系樹脂発泡シートとは、ポリスチレン単独重合樹脂、スチレンを主成分とする（メタ）アクリル酸、無水マレイン酸、アクリロニトリル、アクリル（メタ）アクリレート等のビニル系モノマー及びブタジエン、イソプレン等のジエン系モノマーとの共重合樹脂、及びこれらの樹脂間、並びに、これら樹脂とポリフェニレンオキサイド等との混合樹脂よりなるポリスチレン系樹脂と、タルク等の造核剤、並びに、必要に応じて流動パラフィン等の可塑剤、エチレンビスステアリルアミド、ステアリン酸マグネシウム、脂肪酸エステル等の滑剤等を押出機内で混合・溶融した後ブタン等の発泡剤を圧入し、発泡適正温度に冷却後、サーキュラーダイより押出発泡させて得られる。 The styrene resin foam sheet is a polystyrene homopolymer resin, a vinyl monomer such as (meth) acrylic acid, maleic anhydride, acrylonitrile, acrylic (meth) acrylate and the like, and a diene monomer such as butadiene and isoprene. And polystyrene resins made of a mixed resin of these resins and polyphenylene oxide, nucleating agents such as talc, and, if necessary, plasticizers such as liquid paraffin It is obtained by mixing and melting a lubricant such as ethylenebisstearylamide, magnesium stearate, fatty acid ester, etc. in an extruder, press-fitting a blowing agent such as butane, cooling to an appropriate foaming temperature, and then extruding and foaming from a circular die. .
本発明における、強度に優れた目付２８０〜３６０ｇ／ｍ2の積層発泡シートを得るためには、発泡シートの目付は１９０〜２３０ｇ／ｍ2であることが必要である。目付が１９０ｇ／ｍ2未満であれば、いくら非発泡フィルムを厚くしても積層発泡シートの曲げ強度が不足する。更に、目付が低い状態で成形に必要な積層シートの厚みを確保しようとした場合、発泡シートの密度が低くなるため、破断しやすくなり、丼などの深絞り形状への成形には適さなくなる。また、目付が２３０ｇ／ｍ2を越える場合にはフィルムを薄くしなければならず、突き刺し強度が低下したり、曲面印刷適正が損なわれる等の問題が生じる。 In order to obtain a laminated foam sheet having a basis weight of 280 to 360 g / m 2 excellent in strength in the present invention, the basis weight of the foam sheet needs to be 190 to 230 g / m 2 . If the basis weight is less than 190 g / m 2 , the bending strength of the laminated foamed sheet will be insufficient no matter how thick the non-foamed film is. Further, when it is attempted to secure the thickness of the laminated sheet necessary for molding with a low basis weight, the density of the foamed sheet becomes low, so that it tends to break and becomes unsuitable for forming into a deep drawing shape such as a wrinkle. Further, when the basis weight exceeds 230 g / m 2 , the film must be thinned, resulting in problems such as reduced puncture strength and impaired curved surface printing.
押出発泡にて発泡シートを製造する際、発泡シート表面に空気を吹き付けて急冷することにより、発泡シート表面の密度を高くすることができる。目標とする表面の密度を得るためには、押出直後のシート表面温度、押出樹脂吐出量、シート引き取り速度等に合わせて、冷却空気の温度、風量、風速そして吹き付け位置を適宜調整すればよい。この発泡シートの表層部の密度は表層部（表面から１５０μｍの部分）を、±１５μｍ以内の精度で削り出し、その重さを測定することで求められる。 When producing a foam sheet by extrusion foaming, the density of the foam sheet surface can be increased by blowing air to the foam sheet surface and quenching. In order to obtain a target surface density, the temperature of the cooling air, the air volume, the air speed, and the spraying position may be appropriately adjusted in accordance with the sheet surface temperature immediately after extrusion, the extrusion resin discharge amount, the sheet take-up speed, and the like. The density of the surface layer portion of the foamed sheet is determined by cutting out the surface layer portion (portion 150 μm from the surface) with an accuracy within ± 15 μm and measuring the weight.
ここで、フィルムを積層しない面については、表面から厚み１５０μｍの部分の密度が０．２５〜０．３５ｇ／ｃｍ3であることが必要である。これは、表面に剛直な層を形成することとなり、この層の補強効果により積層発泡シートの曲げ強度を向上することができる。表層１５０μｍの部分の密度が０．２５ｇ／ｃｍ3未満であれば、補強効果が不十分となり、強度、特にリップ圧縮強度が低下する。また、０．３５ｇ／ｃｍ3を越えると発泡シート表面の伸びが極端に低下し、ナキ、割れなどの成形不良が発生する。 Here, about the surface which does not laminate | stack a film, it is necessary for the density of the part of thickness 150 micrometers from the surface to be 0.25-0.35 g / cm < 3 >. This forms a rigid layer on the surface, and the bending strength of the laminated foamed sheet can be improved by the reinforcing effect of this layer. If the density of the surface layer of 150 μm is less than 0.25 g / cm 3 , the reinforcing effect is insufficient, and the strength, particularly the lip compression strength is lowered. On the other hand, if it exceeds 0.35 g / cm 3 , the elongation of the surface of the foamed sheet is extremely lowered, and molding defects such as cracks and cracks occur.
また、フィルムを積層する面の表面から１５０μｍの部分の密度は０．３５〜０．４５ｇ／ｃｍ3であることが好ましい。密度が０．３５ｇ／ｃｍ3以上であれば、成形時の加熱によりフィルムを積層した発泡シート表面に直径５０μｍ程度の微細な気泡が生じる。これにより容器フィルム積層面の表面平滑性が向上し、曲面印刷適正が良好な容器を得ることができる。また、容器の突き刺し強度も向上する。一方、密度が０．４５ｇ／ｃｍ3を越えると、フィルム積層時に加えられる熱で前述の微細な気泡が生じる。積層発泡シート段階でこの微細気泡が生じると、成形時の加熱によりこの微細気泡が拡大、更には連泡化する。これにより、容器表面に凹凸が生じ、容器の外観、表面平滑性が大きく損なわれることとなる。 Moreover, it is preferable that the density of the part of 150 micrometers from the surface of the surface which laminates | stacks a film is 0.35-0.45 g / cm < 3 >. If the density is 0.35 g / cm 3 or more, fine bubbles having a diameter of about 50 μm are generated on the surface of the foam sheet on which the film is laminated by heating during molding. Thereby, the surface smoothness of a container film lamination surface improves, and a container with favorable curved-surface printing suitability can be obtained. Moreover, the puncture strength of the container is also improved. On the other hand, if the density exceeds 0.45 g / cm 3 , the fine bubbles described above are generated by the heat applied during film lamination. When the fine bubbles are generated in the laminated foam sheet stage, the fine bubbles are expanded by the heating at the time of molding, and are further formed into a continuous bubble. Thereby, irregularities are generated on the surface of the container, and the appearance and surface smoothness of the container are greatly impaired.
発泡シートの残存発泡剤量は押出時に圧入する発泡剤の量、及び押出時の樹脂温度によって主に決まる。また、前述の表層部分の密度を上げることは、発泡シート表面からの発泡剤散逸を抑える効果もあり、残存発泡剤量の確保にも有効である。 The amount of foaming agent remaining in the foamed sheet is mainly determined by the amount of foaming agent that is pressed during extrusion and the resin temperature during extrusion. Further, increasing the density of the surface layer portion described above also has an effect of suppressing dissipation of the foaming agent from the surface of the foamed sheet, and is effective in securing the amount of residual foaming agent.
発泡シートに残存する発泡剤ガスが多くなれば多くなるほど発泡シートの気泡内のガス圧力が高くなり、発泡シートの曲げ強度が向上する。十分に強度の高い容器を得るためには、残存発泡剤量が０．４５〜０．５５モル／ｋｇである必要である。残存発泡剤量が０．４５モル／ｋｇ未満であれば天地圧縮強度、リップ強度が低下する。また、残存発泡剤量が０．５５モル／ｋｇを越える場合には積層時に発泡シートから発泡剤ガスが散逸して積層界面に空隙が生じ、成形の加熱時にフィルムと発泡シートの界面が剥離し、いわゆるデラミ現象を生じさせ、容器外観が大きく損なわれることとなる。また、前述の積層時の加熱による微少気泡の発生の原因ともなる。 As the amount of the foaming agent gas remaining in the foamed sheet increases, the gas pressure in the bubbles of the foamed sheet increases, and the bending strength of the foamed sheet improves. In order to obtain a sufficiently high strength container, the amount of the remaining foaming agent needs to be 0.45 to 0.55 mol / kg. If the amount of residual foaming agent is less than 0.45 mol / kg, the top and bottom compression strength and the lip strength are lowered. In addition, when the amount of residual foaming agent exceeds 0.55 mol / kg, the foaming agent gas is dissipated from the foamed sheet at the time of lamination, resulting in a gap at the lamination interface, and the interface between the film and the foamed sheet is peeled off during heating of molding. In other words, the so-called delamination phenomenon occurs, and the appearance of the container is greatly impaired. Moreover, it becomes a cause of generation | occurrence | production of the microbubble by the heating at the time of the above-mentioned lamination | stacking.
積層発泡シート中の発泡剤の散逸を抑え、長期間強度物性を維持するために、発泡シートの独立気泡率は８５％以上が好ましく、９０％以上であることがより好ましい。発泡シートの独立気泡率はBECKMAN製 Model930等のAir Comparison Pycnometerにて測定することができる。独立気泡率が８５％未満の場合には、発泡シートの残存発泡剤の散逸が早くなり、気泡内の圧力の維持が難しく、強度や成形時の加熱による二次発泡力も低下することがある。 In order to suppress the dissipation of the foaming agent in the laminated foam sheet and maintain the strength properties for a long time, the closed cell ratio of the foam sheet is preferably 85% or more, and more preferably 90% or more. The closed cell ratio of the foam sheet can be measured with an Air Comparison Pycnometer such as Model 930 manufactured by BECKMAN. When the closed cell ratio is less than 85%, the remaining foaming agent in the foamed sheet is quickly dissipated, it is difficult to maintain the pressure in the air bubbles, and the secondary foaming force due to strength and heating during molding may be reduced.
発泡シート表面に積層するスチレン系樹脂非発泡フィルムには、上記スチレン系樹脂発泡シートに使用されるスチレン系樹脂が使用でき、発泡シートと同種の樹脂でも異種の樹脂でも良いが、スチレンモノマーとジエン系モノマーとの共重合樹脂よりなるゴム成分を含有するスチレン系樹脂フィルム、特にハイインパクトポリスチレン樹脂を原料としたフィルムが、発泡シートとの接着性、フィルムの耐衝撃性の面から好ましい。 For the non-foamed styrene resin film laminated on the surface of the foamed sheet, the styrenic resin used in the above-mentioned styrenic resin foamed sheet can be used. A styrene-based resin film containing a rubber component made of a copolymer resin with a series monomer, particularly a film made of a high-impact polystyrene resin as a raw material is preferable from the viewpoint of adhesion to a foam sheet and impact resistance of the film.
発泡シート表面へのフィルムの積層は、Ｔダイを使用してフィルム樹脂を発泡シート表面上にフィルム状に押出し積層する方法が適用される。押出フィルムを一層だけ積層しても良いし、押出フィルムを介して更に外面に熱可塑性樹脂非発泡フィルムを積層しても良い。この際、フィルム樹脂温度が低すぎる場合には発泡シートとの接着力が確保できなくなり、高すぎる場合にはフィルムの持つ熱により、発泡シートのフィルム接着を行う表面に微細な気泡が発生し、成形時の接着不良やヤケの原因となったり、更に外面に積層する熱可塑性樹脂非発泡フィルムが膨張・収縮を起こしてシワが発生する。このため、Ｔダイから押出されるフィルム樹脂の温度は使用する樹脂の流動性により適宜選定する必要がある。例えばハイインパクトポリスチレン樹脂の場合には、２１０〜２４０℃であることが好ましい。 For the lamination of the film on the surface of the foamed sheet, a method of extruding and laminating a film resin on the surface of the foamed sheet using a T die is applied. Only one layer of extruded film may be laminated, or a thermoplastic resin non-foamed film may be laminated on the outer surface through the extruded film. At this time, if the film resin temperature is too low, it becomes impossible to secure the adhesive force with the foam sheet, and if it is too high, fine bubbles are generated on the surface of the foam sheet that adheres to the film due to the heat of the film, This may cause adhesion failure and burns during molding, and the thermoplastic resin non-foamed film laminated on the outer surface will expand and contract to cause wrinkles. For this reason, it is necessary to select suitably the temperature of the film resin extruded from a T-die according to the fluidity of the resin used. For example, in the case of a high impact polystyrene resin, the temperature is preferably 210 to 240 ° C.
押出フィルムを一層だけ積層する場合には、非発泡フィルムの目付は７０〜１３０ｇ／ｍ2である必要がある。７０ｇ／ｍ2未満の場合には突き刺し強度が不足し、曲面印刷適正が損なわれる。また、１３０ｇ／ｍ2を越える場合には、フィルムが重くなった分、発泡シートの目付を下げることとなり、積層発泡シートの曲げ強度の低下を招く。 In the case of laminating the extruded film only one layer, the basis weight of the non-foamed film is required to be 70~130g / m 2. If it is less than 70 g / m 2 , the puncture strength is insufficient, and the curved surface printing suitability is impaired. On the other hand, if it exceeds 130 g / m 2 , the basis weight of the foamed sheet will be lowered as the film becomes heavier, leading to a decrease in the bending strength of the laminated foamed sheet.
押出フィルムを介して外面に積層する熱可塑性樹脂非発泡フィルムには、スチレン系樹脂以外にも、ポリエチレン、ポリプロピレン等のポリオレフィン樹脂やＰＥＴ等の食品包装用途に適用可能な素材であれば何でも用いることが可能である。また、予め印刷を施した該フィルムを積層することにより、成形容器に意匠性を付与することも可能である。また、Ｔダイ法やインフレ法等で製造されるこれらのフィルムは製造工程に於いて、ある程度の延伸が行われるため、これを積層することはリップ圧縮強度の向上効果も期待できる。押出フィルムを介して積層する熱可塑性樹脂非発泡フィルムの目付は２０〜４０ｇ／ｍ2とし、フィルム層全体の目付を７０〜１３０ｇ／ｍ2とすることが好ましい。熱可塑性樹脂非発泡フィルムの目付が２０ｇ／ｍ2未満の場合、積層時にフィルムにシワが発生しやすくなり、安定的な生産が困難となる。また、４０ｇ／ｍ2を越えると、フィルム自体のコストが高くなり、費用対効果の面から意味がない。 For the non-foamed thermoplastic resin film laminated on the outer surface via an extruded film, use any material other than styrene resins, as long as it is applicable to food packaging applications such as polyolefin resins such as polyethylene and polypropylene, and PET. Is possible. In addition, it is possible to impart designability to the molded container by laminating the pre-printed film. Moreover, since these films manufactured by the T-die method, the inflation method, and the like are stretched to some extent in the manufacturing process, it is also expected to improve the lip compression strength by laminating them. The basis weight of the thermoplastic resin non-foamed film laminated via the extruded film is a 20 to 40 g / m 2, it is preferable that the basis weight of the entire film layer and 70~130g / m 2. If the basis weight of the thermoplastic resin non-foamed film is less than 20 g / m 2 , wrinkles are likely to occur in the film during lamination, and stable production becomes difficult. On the other hand, if it exceeds 40 g / m 2 , the cost of the film itself becomes high, which is meaningless from the viewpoint of cost effectiveness.
従来、容器成形後の容器積み重ね時のブロッキング(容器が重なったまま分離しなくなる)や内容物充填ラインでの滑り性を考慮して、成形前もしくは成形後にシリコーンオイルが塗布されているが、成形前にシリコーンを塗布することで、金型とシートが接触した際の滑り性が良くなり、容器の肉周り(底部と口元の密度バランス)を均一化することが可能となる。特に、軽量化した積層発泡シートの場合、従来の重目付のシートに比べ伸び易く、容器口元が軽くなるため、リップ圧縮強度が損なわれる事となる。このため、シリコーンオイル塗布により肉周りを均一化することが好ましい。シリコーン塗布を行う面はフィルム積層面、フィルム非積層面のどちらでも良く、また、両面に塗布しても良い。シリコーンオイルの塗布は、積層工程で行っても良いし、成形工程で成形直前に行っても良い。塗布の方法としては、霧箱方式、噴霧方式、ロールコーター方式など一般的な方法を用いることができる。シリコーンオイルの塗布量は、０．０３〜０．１０ｇ／ｍ2であることが好ましい。塗布量が０．０３ｇ／ｍ2未満では滑り性向上の効果が認められない場合があり、０．１０ｇ／ｍ2を越える量を塗布しても更なる効果は発現しないばかりか、フィルム非積層面に塗布した場合には発泡シート表面の耐熱性低下(ヤケの発生)が生じたり、フィルム積層面に塗布した場合には曲面印刷時の印刷不良が生じることがある。 Conventionally, silicone oil is applied before or after molding in consideration of blocking during container stacking after container molding (contains containers that do not separate while overlapping) and slipping in the content filling line. By applying silicone in advance, the slipping property when the mold and the sheet come into contact with each other is improved, and it is possible to make the circumference of the container (the density balance between the bottom and the mouth) uniform. In particular, in the case of a laminated foam sheet that has been reduced in weight, the lip compression strength is impaired because it is easier to stretch than the conventional heavy weight sheet and the container mouth becomes lighter. For this reason, it is preferable to make the circumference of the meat uniform by applying silicone oil. The surface on which the silicone is applied may be either a film laminated surface or a film non-laminated surface, or may be applied to both surfaces. The application of silicone oil may be performed in a lamination process or may be performed immediately before molding in a molding process. As a coating method, a general method such as a cloud chamber method, a spray method, or a roll coater method can be used. The application amount of silicone oil is preferably 0.03 to 0.10 g / m 2 . If the coating amount is less than 0.03 g / m 2 , the effect of improving the slipping property may not be recognized. Even if the amount exceeding 0.10 g / m 2 is applied, no further effect is exhibited, and the film is not laminated. When it is applied to the surface, the heat resistance of the foam sheet surface may be reduced (discoloration), and when it is applied to the film laminated surface, printing failure may occur during curved surface printing.
この様にして得られた積層発泡シートは広く一般的に行われている方法で容器に成形することができる。即ち、赤外線ヒーター等で加熱し、積層発泡シートを二次発泡させた後、金型で勘合して容器形状を付与した後、シートから容器を打ち抜く方法である。この際の金型設計により、適正なシートの二次発泡厚みが決まる。一般に丼形状への成形を行う場合には４．５〜５．５ｍｍ程度の二次厚みが求められ、これに合わせて発泡シートの一次厚みを決める必要がある。積層発泡シートの強度を十分引き出すためには、積層発泡シートの最大二次厚み(加熱してシートに焼けが発生する直前の二次発泡厚み)の８０〜９０％程度の二次厚みとなるように加熱して成形を行うことが望ましく、そのため、積層発泡シートの厚みは１．８〜２．３ｍｍである必要がある。厚みが１．８ｍｍ未満であれば、成形時の加熱を強くする必要があり、過剰な加熱による容器強度の低下や外観不良を招く。また、２．３ｍｍを越える場合には、成形時に十分な加熱を行うことができず、加熱不足で積層発泡シートの伸びが不足し、ナキ等の成形不良が発生する。 The laminated foam sheet obtained in this way can be formed into a container by a widely used method. In other words, after heating with an infrared heater or the like to secondarily foam the laminated foamed sheet, the container is shaped by fitting with a mold and then punched out from the sheet. The appropriate secondary foam thickness of the sheet is determined by the mold design at this time. In general, when forming into a bowl shape, a secondary thickness of about 4.5 to 5.5 mm is required, and it is necessary to determine the primary thickness of the foam sheet in accordance with this. In order to sufficiently draw out the strength of the laminated foamed sheet, the secondary thickness is about 80 to 90% of the maximum secondary thickness of the laminated foamed sheet (secondary foamed thickness immediately before heating and burning of the sheet). It is desirable to perform heating and molding, and therefore, the thickness of the laminated foam sheet needs to be 1.8 to 2.3 mm. If the thickness is less than 1.8 mm, it is necessary to increase the heating at the time of molding, which leads to a decrease in container strength and poor appearance due to excessive heating. On the other hand, when the thickness exceeds 2.3 mm, sufficient heating cannot be performed at the time of molding, and the expansion of the laminated foamed sheet is insufficient due to insufficient heating, resulting in molding defects such as cracking.
以下に具体的な実施例を揚げて説明する。 Hereinafter, specific examples will be described.
（実施例１〜４）
懸濁重合により作成したポリスチレン樹脂を用い、イソブタン８５％を含有するブタンガスを発泡剤として、表１に示すスペックを有する巾１０５０ｍｍの押出発泡シートを作成した。尚、得られた発泡シートの独立気泡率は全て９０％以上であった。
(Examples 1-4)
Using a polystyrene resin prepared by suspension polymerization, an extruded foam sheet having a width of 1050 mm having the specifications shown in Table 1 was prepared using butane gas containing 85% isobutane as a foaming agent. In addition, all the closed cell ratios of the obtained foam sheet were 90% or more.
これら発泡シートの残存発泡剤量は発泡シートを密閉容器にいれて、減圧した後、加熱して内部に残留しているガス成分を採取、島津製ガスクロにてＰＥＧ２０Ｍカラム＋ＤＮＰカラムを用いて測定した結果より算出した。目付は１０ｃｍ角のサンプルを巾方向１０点切り出し、その重量を測定して求めた。 The amount of foaming agent remaining in these foamed sheets was measured using a PEG20M column and a DNP column in a gas chromatograph manufactured by Shimadzu after putting the foamed sheet into a sealed container and reducing the pressure and heating to collect the gas components remaining inside. Calculated from the results. The basis weight was determined by cutting a 10 cm square sample at 10 points in the width direction and measuring the weight.
得られた発泡シートに押出ラミネート法によりＡ＆Ｍ製ハイインパクトポリスチレン樹脂４７５Ｄを用いたフィルムを表１．に示す目付となるように積層した。積層において押出フィルムの表面温度を非接触式表面温度計を用いて測定した結果、巾方向で２２５±３℃であった。また、実施例４では、９０ｇ／ｍ2の押出フィルムを介して大石産業製ＨＩＰＳフィルムＳＰＨ３０(３０μｍ=３２ｇ／ｍ2)を積層し、三層の積層発泡シートを得た。更に積層後、同積層工程にて、グラビアコーターを用い信越シリコーン製シリコーンオイルＴＳＭ６３４４をフィルム積層面側の表面に塗布した。 Table 1 shows a film using A & M high impact polystyrene resin 475D by extrusion lamination to the obtained foamed sheet. It laminated | stacked so that it might become the fabric weight shown to. As a result of measuring the surface temperature of the extruded film using a non-contact type surface thermometer in the lamination, it was 225 ± 3 ° C. in the width direction. In Example 4, a HIPS film SPH30 (30 μm = 32 g / m 2 ) manufactured by Oishi Sangyo Co., Ltd. was laminated through a 90 g / m 2 extruded film to obtain a three-layer laminated foam sheet. Furthermore, after the lamination, in the same lamination step, a silicone oil TSM 6344 made of Shin-Etsu silicone was applied to the surface on the film lamination surface side using a gravure coater.
得られた積層発泡シートを浅野研究所製のＦＬＣ３型連続成形機に供給し、日清食品「どん兵衛」類似の容器(口径１４４ｍｍ×深さ７５ｍｍ、３６個／ショット)に積層発泡シートのフィルム積層面が外側となる様に成形した。成形時の二次厚みは４．８〜５．０ｍｍとなるように加熱条件を調整した。得られた容器について以下の方法にて天地圧縮強度、リップ圧縮強度、突き刺し強度を測定した。測定は１ショット３６個について行い、その平均値を表１に示した。
天地圧縮強度：口部を下に、２枚の板間に容器を挟み、底部から１００ｍｍ／ｍｉｎの速度で圧縮した時の降伏強度
リップ圧縮強度：容器口部ＴＤ方向の両端部を支え、一方の端を１００ｍｍ／ｍｉｎの速度で80mm圧縮した時の最大荷重
突き刺し強度：容器底部の内側表面から、直径１．５ｍｍの針を１００ｍ／ｍｉｎで突き刺し、貫通させた際の最大荷重
また、成形性は容器成形時にナキ(局所的に発泡シートが引き延ばされる現象)、デラミ(成形加熱時に発泡シートとフィルムが剥離する現象)が生じず、外観良好な成形が可能かどうかを評価した。印刷性は容器成形２日後に曲面印刷を施し、インクのカスレや飛びが無いかどうかを目視で評価した。
The obtained laminated foam sheet is supplied to the FLC3 continuous molding machine manufactured by Asano Laboratories, and the film of the laminated foam sheet is placed in a container similar to Nissin Foods “Donbei” (caliber 144 mm × depth 75 mm, 36 pcs / shot). It shape | molded so that a lamination surface might become an outer side. The heating conditions were adjusted so that the secondary thickness during molding was 4.8 to 5.0 mm. The top and bottom compression strength, lip compression strength, and puncture strength of the obtained container were measured by the following methods. The measurement was performed on 36 shots, and the average value is shown in Table 1.
Top and bottom compression strength: Yield strength when the container is sandwiched between two plates with the mouth down and compressed from the bottom at a speed of 100 mm / min. Lip compression strength: Supports both ends in the container mouth TD direction, Load puncture strength when the end of the tube is compressed 80 mm at a speed of 100 mm / min: the maximum load when a needle with a diameter of 1.5 mm is pierced from the inner surface of the bottom of the container at 100 m / min and penetrated. Was evaluated whether it was possible to mold with good appearance without causing naki (a phenomenon in which the foamed sheet was stretched locally) and delami (a phenomenon in which the foamed sheet and the film were peeled off during molding and heating) during container molding. As for printability, curved surface printing was performed two days after the container was formed, and it was visually evaluated whether there was any ink smearing or jumping.
得られた結果を表１にまとめた。 The results obtained are summarized in Table 1.
比較例１よりも積層するフィルムを薄くしたのが比較例２である。また、トレー容器成形用の高強度発泡シートグレードに厚膜のフィルムを積層したのが比較例３である。どちらも品質のバランスが取れておらず、強度も不足した容器となった。 Comparative Example 2 is a thinner film than Comparative Example 1. In Comparative Example 3, a thick film was laminated on a high strength foamed sheet grade for forming a tray container. Neither was balanced in quality, and the containers lacked strength.
比較例４〜５は発泡シート、フィルムの目付は実施例と同等である。比較例４では非ラミ面の表面の密度が低すぎて、積層発泡シートの最大曲げ荷重が低くなり、容器では特にリップ圧縮強度が不足した。また、比較例５では非ラミ面の表面の密度が高すぎ、最大曲げ荷重は高いが、成形時にナキが発生し、容器の強度としては不十分なものとなった。また、残存揮発分が高すぎたため、成形時に発泡シートとフィルムが剥離するデラミ現象が発生し、印刷性も損なわれた。 In Comparative Examples 4 to 5, the foam sheet and the basis weight of the film are the same as those in the example. In Comparative Example 4, the density of the non-laminated surface was too low, the maximum bending load of the laminated foam sheet was low, and the lip compression strength was particularly insufficient in the container. In Comparative Example 5, the density of the non-lamellar surface was too high and the maximum bending load was high, but cracks occurred during molding, which was insufficient as the strength of the container. Moreover, since the residual volatile matter was too high, a delamination phenomenon in which the foamed sheet and the film peeled during molding occurred, and printability was also impaired.
比較例６、７は比較例４と同じ積層発泡シートであるが、シリコーンオイル塗布を行わなかった比較例６では、底部に肉周りが集中し天地圧縮強度、突き刺し強度は向上した反面、口元が引き延ばされたため、ナキが発生するとともに、リップ圧縮強度が大幅に損なわれた。シリコーンオイル塗布量が多すぎた比較例７では、印刷時にインクはじきによる印刷不良が生じ、外観が非常に悪くなった。
Comparative Examples 6 and 7 are the same laminated foam sheets as Comparative Example 4, but in Comparative Example 6 where the silicone oil application was not performed, the circumference of the meat was concentrated on the bottom and the compression strength and piercing strength were improved, but the mouth was As it was stretched, cracks occurred and the lip compression strength was greatly impaired. In Comparative Example 7 in which the amount of silicone oil applied was too large, printing failure occurred due to ink repelling during printing, and the appearance was very poor.
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| JP2010228182A (en) * | 2009-03-26 | 2010-10-14 | Sekisui Plastics Co Ltd | Polystyrene-based resin laminated foamed sheet and molded body |
| JP2012030571A (en) * | 2010-06-28 | 2012-02-16 | Sekisui Plastics Co Ltd | Biodegradable resin laminated foamed sheet, peripheral side frame material for lunch box and the lunch box |
| WO2019150702A1 (en) * | 2018-01-30 | 2019-08-08 | 株式会社吉野工業所 | Delamination container |
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| JP6870162B1 (en) * | 2020-09-17 | 2021-05-12 | 積水化成品工業株式会社 | Polystyrene resin foam sheet and polystyrene resin foam container |
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