【発明の詳細な説明】[Detailed description of the invention]
本発明は緩衝効果等の優れた横方向に熱収縮性
を有する発泡材料に関する。
従来、熱収縮性を有する例えば発泡シート・フ
イルム等の発泡材料は、その原料をポリスチレン
を使用したものが主流をしめ、特にこれがビン等
の容器類の外装に用いることにより、破ビン防止
効果と緩衝効果を発揮するので有用な包装材料と
して周知である。
ところが、前記ポリスチレンからなる熱収縮性
を有する発泡材料は、その原料の特性から衝撃に
弱く脆いものであり、例えばビン等のラベル用と
して装着しても、その洗浄工程や充填工程、更に
は輸送中に発泡材料が破損するという欠点があり
又、同材料表面に印刷を施こしても鮮明に表出で
きず、その上発泡材料が端縁から層状になつて部
分的に剥離する等の現象がみられた。
更に発泡ポリスチレン材は延伸の際、その脆さ
が原因でテンター等による横方向の延伸がしにく
く、比較的延伸を行い易いロール延伸等による縦
延伸が主流であるため、例えばこの材料をビン等
の外装として使用する際、自動機への適応が制限
され、従前の横延伸フイルム用（例えばPVC
用）自動機には適応できず、新たに縦延伸フイル
ム用自動機を準備せねばならないことも考えら
れ、又使用面でも、例えばビンに被覆して熱収縮
させビンに密着させる筒状体を作成する工程が、
横延伸材に比しどうしても煩雑化する等の問題点
もあつた。
このような技術背景をもとに、本発明者等は特
願昭57―110084号にて前記問題点の解決を提案し
たところであるが、その材料を使用して例えば前
記同様の筒状体を作成し、これをビンに被覆して
熱収縮させ、ビンに密着したものは、経時の緊縛
力に不足してゆるんでくることが判明し、一方印
刷性に若干劣ることを知見した。
この発明は、前記新たな問題点を解決するため
になされたものであり、横方向に熱収縮性を有す
る発泡材料として、エチレン含有量が１〜10モル
％のエチレン―プロピレン共重合体と、弾性改質
用重合体、及び発泡剤とを配合した組成物を装膜
し、しかる後横方向に延伸してなることを、この
発明の要旨とするものである。
以下本発明について詳述する。
本発明で使用するエチレン―プロピレン共重合
体は、通常エチレン含有量１〜10モル％、好まし
くは２〜６モル％のもので、このさい10モル％を
越えると製造された発泡材料がべたついてブロツ
キングを起し易くなつて好ましくなく、また、１
モル％未満ではその性質がポリプロピレンに近づ
き、従つて延伸しても収縮率が小さく、熱収縮性
部材として不満足である上に発泡セルが破れて毛
羽立ち現象を起し易くなる。なお前記共重合体中
にはエチレンがランダムに入つているものが好ま
しい。この際、前記共重合体の使用量は効果の表
われる量を適宜に加えれば良いが、好ましくは全
重合体量に対し50〜95重量％程度でよい。
次に本発明で使用する弾性改質用重合体は、発
泡材料の発泡セルに弾性を付与するために添加す
るもので、この重合体を添加しない場合は発泡の
際の内部圧力に耐えられず発泡セルが膨脹し易く
なるので微細な発泡構造のものが得られない。
この重合体は発泡時のセルに弾性を付与する性
質を有するものが好ましく、例示すれば低・中・
高密度ポリエチレン、ポリブテン、エチレン―酢
酸ビニル共重合体、エチレン―エチルアクリレー
ト、エチレン―１―ブテン共重合体、プロピレン
―１―ブテン共重合体、不飽和カルボン酸および
その誘導体等の極性基を有する変性ポリオレフイ
ン、１：２型ポリブタジエン、直鎖状低密度ポリ
エチレン（Ｌ―Ｌ DPE）等が代表的なもので
ある。この際より好ましい弾性改質用重合体とし
ては、酢酸ビニル含有量３〜40重量％のエチレン
―酢酸ビニル共重合体、エチレン含有量85〜95モ
ル％（密度0.86〜0.91ｇ／cm3、結晶化度３〜20
％）のエチレン―１―ブテンランダム共重合体、
等を例示できる。なおこの弾性改質用重合体の使
用量は少なくともその効果が表われる量を加えれ
ば良く、好ましくは全重合体量に対し５〜50重量
％程度で良い。
又本発明で使用する発泡剤は、公知のものであ
れば如何なるものでも良く、適応可能な発泡剤と
してその種類を例示すると、揮発性のものとして
ペンタン、ブタン等、有機系のものとしてヒドラ
ジン系、ニトロソ系、アゾ系等が、又無機系のも
のとして重炭酸ソーダ、炭酸アンモニヤ等があ
る。この際より好ましい例としては前記アゾ系発
泡剤ではアゾジカルボンアミド、アゾビスイソブ
チロニトリル等、無機系発泡剤では重炭酸ナトリ
ウム、炭酸アンモン等の炭酸塩とクエン酸、洒石
酸等の有機酸とからなるものをあげることができ
る。なおこの発泡剤の使用量は少なくともその効
果が表われる量を加えれば良いが、エチレン含有
量１〜10モル％のエチレン―プロピレン共重合体
と、弾性改質用重合体との合計量（全重合体量）
100重量部に対し、0.2〜５重量部、更に好ましく
は0.5〜２重量部程度を例示できる。上記発泡剤
は本発明に係るエチレン―プロピレン共重合体に
直接ブレンドしたり、濃度の高い発泡剤を含むマ
スターペレツトを加えてブレンドしたり、予じめ
前記共重合体中に発泡剤を適宜量練り込んで用い
たりすればよく、その用法には特に制限はない。
なお、本発明では上記３者からなる成分の他に
適宜の添加剤や充填剤等を加えることもあり、例
えば滑剤、帯電防止剤等を必要に応じ加えて物性
の改善を図ることも適宜行い得、必要ならば顔料
を添加することにより希望する着色も可能であ
る。
本発明に係る発泡材料とは、フイルム、シート
状のもの等を例示でき、特にその形状を限定する
ものでないが、フイルムやシート状のものは延伸
操作が容易に出来るので好適な一例である。
本発明は上記各成分を配合した組成物を製膜
し、しかる後、横方向に延伸が行われる。ここ
で、横方向に延伸を行うのは横方向に熱収縮性を
付与するためであり、「横方向に熱収縮する」に
は発泡材料を製造する方向に対して直角の巾方向
に延伸を行うことにより達成され、この横延伸を
行うためには、組成物を製膜し発泡後、もしくは
発泡し製膜後（場合によつては延伸中に発泡させ
てもよい）に行えばよいが、フラツトシート状発
泡材料をテンターにより行えば最も好ましい結果
が得られる。なお横方向の延伸手段は前記のもの
に限定されるものではない。次に延伸温度である
が、これは適宜選択でき、例えば100〜130℃が好
ましい。また延伸倍率は必要に応じその大きさを
選定するが３〜10倍程度でよく、上記の各数値条
件で延伸を行えば好ましい横方向の熱収縮性を有
する発泡材料が得られることになる。この際、発
泡材料の製膜時や延伸時のたるみ防止等のため若
干縦方向にテンシヨンがかかり、その結果配向が
起るため、一般に縦方向にも若干熱収縮性を有す
ることになるが全て本発明に包含される。
本発明に係る発泡材料を作成する１例として、
押出機によりフイルムもしくはシート状に製膜し
横延伸する方法を以下に述べる。
先ず、エチレン含有量１〜10モル％のエチレン
―プロピレン共重合体と、弾性改質用重合体及び
発泡剤を配合した組成物をダイス内で発泡しない
程度に押出成形機の条件設定を行い、ダイスから
フラツトシート状に押出させる。そしてこの際同
時に発泡するようにすれば好適である。しかる後
横延伸を行うが、延伸手段については前述の通り
である。
本発明に係る発泡材料の用途としては、ビン等
に用いる印刷された外装用熱収縮性発泡ラベルと
して最も多用され、延伸方向がビン等の円周方向
と一致するように筒状化して用いれば良いが、そ
の他各種容器、各種物品の包装用材料として多用
されその応用範囲は広く特に制限はない。こうし
た用途からみても発泡材料はシートもしくはフイ
ルム状態で用いることが最も好ましいわけであ
る。
本発明は以上の通りであり、本発明に係る発泡
材料は例えばビン等の外装用ラベルとして用いる
と、特に破ビン防止効果や緩衝効果に優れる。ま
た強度等の諸物性にも優れ、従来のものの如く脆
くないので、例えば筒状体としても折りたたむこ
とが可能で、折りたたみの際に生じた折目は熱収
縮の際に消滅するという特性もある上に、材料の
端縁から層状となつて剥離し易いという欠点もな
く強靭である等の如く顕著な効果を奏する。更に
本発明材料は、熱伝導率が良好であるので、熱収
縮させる際の熱エネルギーが少なくてすむ他、耐
薬品性、耐候性等にも優れており、印刷インキの
溶剤等による強度低下や紫外線による強度低下も
起りにくい等の効果も奏する。
特に本発明に係る発泡材料は横方向に熱収縮性
を有するので、例えば従来から使用されている自
動機、例えば熱収縮ラベルを容器類の外周に被覆
し、容器類の円周方向に熱収縮させて密着させる
自動ラベル挿入機の機構に適用する際も、センタ
ーシールによる長尺の連続した筒状体を予じめ作
成し（この状態で扁平に折りたたんで保管してお
くこともできる）ておくことが可能であり、これ
を容器類の外周に挿入被覆する際、適宜長さにカ
ツトして筒状体として用いればよく、従つて従来
機の機構を適用できるのに対し、従来の縦方向に
熱収縮する発泡材料を用いる場合、センターシー
ルによる長尺の連続した筒状体を予じめ作成して
おくことができず、長尺フイルムを適寸にカツト
した後に個々の筒状体を予じめ作成しておくか、
自動ラベル挿入機に挿入の際、筒状体も同時に作
成する必要がある等のために、従来機の機構をそ
のまま適用することができないのであり、こうし
た点でも本発明の材料は格別な効果を有する。
以上の説明を図面で示したものが第１図と第２
図である。第１図は本発明に係る横方向に熱収縮
性を有する発泡材料によるものであり、１は長尺
フイルム、２は長尺筒状体、３はセンターシー
ル、４は個々にカツトされた筒状体、５は容器、
６は熱収縮させて容器５上に密着した筒状体（ラ
ベル）、矢印は収縮方向を示す。第２図は従来の
縦方向に熱収縮性を有する発泡材料によるものを
示したもので、１′は長尺フイルム、２′は個々に
カツトされたフイルム、４′はカツトされたフイ
ルム２′をセンターシール３′して個々の筒状体と
したもの、５，６は第１図と同一であり、矢印は
同じく収縮方向を示したもので、これらの図面か
ら本発明の発泡材料から筒状体を形成する際、従
来のものに比し極めて能率の良いことが理解でき
る。
以下本発明の実施例を比較例と共に挙げる。
〈実施例 １〉
エチレン含有量4.5モル％のエチレン―プロピ
レンランダム共重合体70重量％と、酢酸ビニル含
有量15重量％のエチレン―酢酸ビニル共重合体
（弾性改質用重合体）30重量％の配合物100重量部
に対し、重炭酸ナトリウムとクエン酸の混合物か
らなる発泡剤１重量部を配合し、押出成型機のダ
イスを通してフラツトシート状押出製膜を行つ
た。この際、ダイスより押出した時に発泡するよ
うに条件設定を行つたところ、厚さ1000μの発泡
シートを得た。しかる後、テンターにより温度
110〜120℃で横方向に約５倍に延伸したところ、
厚さ200μの横方向に熱収縮する発泡フイルムを
得た。この際、発泡剤の重炭酸ナトリウムが分解
して気泡を生じさせた。
〈実施例 ２〉
弾性改質用重合体としてエチレン含有量92モル
％、密度0.90ｇ／cm3、結晶化度約10％のエチレン
―１―ブテンランダム共重合体を用いる以外は実
施例１と同様にして、同様の発泡フイルムを得
た。
〈実施例 ３〉
発泡剤として重炭酸ナトリウムとクエン酸を使
用（使用量20重量％）してなる主成分が、ポリエ
チレンであるマスターペレツト５重量部（発泡剤
成分は１重量部）を用いる以外は実施例１と同様
の配合物を用い、押出製膜して厚さ1000μのフラ
ツト状発泡シートを得た。しかる後、テンターに
て温度110〜120℃で横方向に約５倍に延伸したと
ころ、厚さ200μの横方向に熱収縮する発泡フイ
ルムを得た。
〈比較例 １〉
エチレン含有量4.5モル％のエチレン―プロピ
レンランダム共重合体100重量部に重炭酸ナトリ
ウムとクエン酸とからなる発泡剤１重量部を配合
した組成物を、実施例１と同様に処理し発泡フイ
ルムを得た。このフイルムは発泡状態が悪くセル
がところどころ破裂して表面が毛羽立つて見える
上に、延伸の際の縦割れによる解繊化がところど
ころに見られる不良品であつた。
〈比較例 ２〉
ポリスチレンに比較例１と同様の発泡剤を同量
加え、同様に製膜し、110℃の温度で３倍にロー
ル延伸を行つたところ、縦方向に熱収縮する厚さ
200μの発泡フイルムを得た。この際、同様に押
出製膜した原反シートをテンターにより横方向に
３倍に延伸する実験を試みたが、テンタークリツ
プにより原反シートの耳部が破壊されたり、中央
部で破断されて十分な延伸ができなかつた。
以上の実施例１、２、３と比較例１、２で得ら
れた発泡フイルムの各物性を下記第１表と第２表
に掲げる。
TECHNICAL FIELD The present invention relates to a foamed material having excellent cushioning effect and heat shrinkability in the lateral direction. Conventionally, heat-shrinkable foamed materials such as foamed sheets and films have mainly been made from polystyrene as a raw material, and when used for the exterior of containers such as bottles, it has been particularly effective in preventing bottles from breaking. It is well known as a useful packaging material because it exhibits a cushioning effect. However, the heat-shrinkable foam material made of polystyrene is weak and fragile due to the characteristics of its raw material, and even if it is used as a label for a bottle, for example, it will be difficult to clean, fill, or transport. There is a disadvantage that the foamed material is damaged during printing, and even if the surface of the material is printed, it cannot be clearly printed, and furthermore, the foamed material forms a layer from the edges and partially peels off. was seen. Furthermore, when stretching polystyrene foam material, it is difficult to stretch it in the horizontal direction using a tenter or the like due to its brittleness, and longitudinal stretching using roll stretching, etc., which is relatively easy to stretch, is the mainstream. When used as the exterior of
It may not be possible to use an automatic machine for longitudinally stretched film, and it may be necessary to prepare a new automatic machine for longitudinally stretched film. The process of creating
There were also problems such as the fact that it was inevitably more complicated than the horizontally stretched material. Based on this technical background, the present inventors have proposed a solution to the above-mentioned problem in Japanese Patent Application No. 110084/1984, and using the material, for example, a cylindrical body similar to the above-mentioned one can be manufactured. It was found that those that were prepared, coated on a bottle, heat-shrinked, and tightly attached to the bottle became loose due to insufficient binding force over time, and on the other hand, the printability was slightly inferior. This invention was made to solve the above-mentioned new problem, and uses an ethylene-propylene copolymer having an ethylene content of 1 to 10 mol% as a foam material having heat shrinkability in the transverse direction; The gist of the present invention is to coat a composition containing an elasticity-modifying polymer and a foaming agent, and then stretch it in the transverse direction. The present invention will be explained in detail below. The ethylene-propylene copolymer used in the present invention usually has an ethylene content of 1 to 10 mol%, preferably 2 to 6 mol%; if the ethylene content exceeds 10 mol%, the produced foam material becomes sticky. This is undesirable as it tends to cause blocking, and 1
If it is less than mol %, its properties approach those of polypropylene, and therefore, even when stretched, the shrinkage rate is small, making it unsatisfactory as a heat-shrinkable member, and moreover, the foam cells tend to break and fluffing occurs. Preferably, the copolymer contains ethylene randomly. At this time, the amount of the copolymer to be used may be an appropriate amount that exhibits the effect, but preferably about 50 to 95% by weight based on the total amount of the polymer. Next, the elasticity-modifying polymer used in the present invention is added to impart elasticity to the foam cells of the foam material, and if this polymer is not added, it will not be able to withstand the internal pressure during foaming. Since the foam cells tend to expand, a fine foam structure cannot be obtained. This polymer preferably has the property of imparting elasticity to the cells during foaming, examples of which include low, medium,
Contains polar groups such as high-density polyethylene, polybutene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, ethylene-1-butene copolymer, propylene-1-butene copolymer, unsaturated carboxylic acid and its derivatives, etc. Typical examples include modified polyolefin, 1:2 type polybutadiene, and linear low density polyethylene (LL DPE). In this case, more preferred elasticity-modifying polymers include ethylene-vinyl acetate copolymers with a vinyl acetate content of 3 to 40% by weight, ethylene content of 85 to 95 mol% (density of 0.86 to 0.91 g/cm 3 , crystalline degree of 3~20
%) of ethylene-1-butene random copolymer,
etc. can be exemplified. The amount of the elasticity-modifying polymer to be used may be at least an amount that exhibits its effect, and preferably about 5 to 50% by weight based on the total amount of the polymer. The blowing agent used in the present invention may be any known blowing agent. Examples of applicable blowing agents include pentane, butane, etc. as volatile ones, and hydrazine type as organic ones. , nitroso-based, azo-based, etc., and inorganic ones such as sodium bicarbonate and ammonia carbonate. In this case, more preferable examples include azo blowing agents such as azodicarbonamide and azobisisobutyronitrile, and inorganic blowing agents such as carbonates such as sodium bicarbonate and ammonium carbonate and organic I can list things consisting of acids. The amount of this blowing agent used should be at least the amount that exhibits its effect, but the total amount of the ethylene-propylene copolymer with an ethylene content of 1 to 10 mol% and the elasticity-modifying polymer (total amount) Polymer amount)
For example, 0.2 to 5 parts by weight, more preferably 0.5 to 2 parts by weight, per 100 parts by weight. The above blowing agent may be directly blended with the ethylene-propylene copolymer according to the present invention, or blended with the addition of master pellets containing a high concentration of blowing agent, or the blowing agent may be appropriately added to the copolymer in advance. It may be used by kneading a certain amount, and there is no particular restriction on its usage. In addition, in the present invention, appropriate additives, fillers, etc. may be added in addition to the above three components, and for example, lubricants, antistatic agents, etc. may be added as necessary to improve physical properties. If necessary, desired coloring can be achieved by adding a pigment. Examples of the foamed material according to the present invention include those in the form of a film or sheet, and the shape is not particularly limited, but a film or sheet-shaped material is a suitable example because it can be easily stretched. In the present invention, a composition containing the above components is formed into a film, and then stretched in the transverse direction. Here, the purpose of stretching in the transverse direction is to impart heat shrinkability in the transverse direction, and "heat shrinking in the transverse direction" means stretching in the width direction perpendicular to the direction in which the foam material is manufactured. In order to perform this lateral stretching, it may be carried out after the composition is formed into a film and foamed, or after foaming and film formation (in some cases, foaming may be performed during stretching). The most favorable results are obtained by tentering the foam material in the form of a flat sheet. Note that the lateral stretching means is not limited to those described above. Next, the stretching temperature can be selected as appropriate, and is preferably 100 to 130°C, for example. Further, the stretching ratio may be selected from 3 to 10 times depending on the necessity, and if stretching is carried out under the above-mentioned numerical conditions, a foamed material having preferable lateral heat shrinkability can be obtained. At this time, a slight tension is applied in the vertical direction to prevent the foam material from sagging during film formation or stretching, and as a result, orientation occurs, so it generally has some heat shrinkability in the vertical direction as well. Included in the present invention. As an example of creating a foam material according to the present invention,
A method of forming a film or sheet using an extruder and laterally stretching it will be described below. First, the conditions of the extrusion molding machine were set to such an extent that a composition containing an ethylene-propylene copolymer with an ethylene content of 1 to 10 mol%, an elasticity-modifying polymer, and a foaming agent would not foam in the die. Extrude it into a flat sheet from a die. At this time, it is preferable to foam at the same time. Thereafter, transverse stretching is performed, and the stretching means is as described above. The foamed material according to the present invention is most often used as a printed exterior heat-shrinkable foamed label for bottles, etc., and it can be used in a cylindrical shape so that the stretching direction coincides with the circumferential direction of the bottle, etc. Although it is good, it is also widely used as a packaging material for various containers and various articles, and its application range is wide and there are no particular restrictions. Considering these uses, it is most preferable to use the foamed material in the form of a sheet or film. The present invention is as described above, and when the foamed material according to the present invention is used, for example, as an exterior label for a bottle or the like, it is particularly excellent in bottle breakage prevention effect and cushioning effect. It also has excellent physical properties such as strength, and is not brittle like conventional products, so it can be folded into a cylindrical shape, for example, and the creases that occur during folding disappear when heat shrinks. Moreover, it does not have the disadvantage that it forms a layer from the edge of the material and is easily peeled off, and has remarkable effects such as being strong and strong. Furthermore, the material of the present invention has good thermal conductivity, so it requires less thermal energy during heat shrinkage, and also has excellent chemical resistance and weather resistance, and is resistant to strength loss due to printing ink solvents, etc. It also has the advantage of being less likely to lose its strength due to ultraviolet rays. In particular, since the foamed material according to the present invention has heat-shrinkability in the lateral direction, for example, a conventionally used automatic machine, for example, can coat the outer periphery of the container with a heat-shrinkable label and heat-shrink it in the circumferential direction of the container. When applying it to the mechanism of an automatic label insertion machine that allows the labels to fit tightly together, a long continuous cylindrical body with a center seal is created in advance (it can also be folded flat and stored in this state). When inserting and covering the outer periphery of containers, it is sufficient to cut it to an appropriate length and use it as a cylindrical body. Therefore, the mechanism of conventional machines can be applied, whereas the conventional vertical When using a foam material that heat shrinks in the direction, it is not possible to create a long continuous cylindrical body in advance using a center seal, and the individual cylindrical bodies are cut after cutting the long film to the appropriate size. Create it in advance, or
When inserting into an automatic label insertion machine, the cylindrical body also needs to be created at the same time, so the mechanism of the conventional machine cannot be applied as is, and the material of the present invention has special effects in this respect as well. have Figures 1 and 2 show the above explanation in drawings.
It is a diagram. Fig. 1 shows a foamed material having heat shrinkability in the lateral direction according to the present invention, where 1 is a long film, 2 is a long cylindrical body, 3 is a center seal, and 4 is an individually cut cylinder. shaped body, 5 is a container,
6 is a cylindrical body (label) that is heat-shrinked and tightly attached to the container 5, and the arrow indicates the direction of shrinkage. Fig. 2 shows a conventional foamed material having heat shrinkability in the longitudinal direction, where 1' is a long film, 2' is an individually cut film, and 4' is a cut film 2'. 5 and 6 are the same as in Fig. 1, and the arrows also indicate the direction of shrinkage. From these drawings, it can be seen that the cylinders are made from the foamed material of the present invention. It can be seen that when forming a shaped body, it is extremely efficient compared to conventional methods. Examples of the present invention will be listed below along with comparative examples. <Example 1> 70% by weight of an ethylene-propylene random copolymer with an ethylene content of 4.5 mol% and 30% by weight of an ethylene-vinyl acetate copolymer (elasticity modification polymer) with a vinyl acetate content of 15% by weight 1 part by weight of a blowing agent consisting of a mixture of sodium bicarbonate and citric acid was added to 100 parts by weight of the mixture, and the mixture was extruded into a flat sheet through a die of an extrusion molding machine. At this time, conditions were set so that it would foam when extruded from the die, and a foamed sheet with a thickness of 1000 μm was obtained. After that, the temperature is controlled by a tenter.
When stretched approximately 5 times in the transverse direction at 110 to 120°C,
A foamed film with a thickness of 200 μm that is heat-shrinkable in the transverse direction was obtained. At this time, the foaming agent, sodium bicarbonate, decomposed and produced bubbles. <Example 2> Same as Example 1 except that an ethylene-1-butene random copolymer with an ethylene content of 92 mol%, a density of 0.90 g/cm 3 and a crystallinity of about 10% was used as the elasticity-modifying polymer. A similar foamed film was obtained in the same manner. <Example 3> Using 5 parts by weight of master pellets whose main component is polyethylene (the blowing agent component is 1 part by weight), which is made by using sodium bicarbonate and citric acid as blowing agents (amount used: 20% by weight) A flat foamed sheet having a thickness of 1000 μm was obtained by extrusion using the same formulation as in Example 1 except for this. Thereafter, the film was stretched by about 5 times in the transverse direction using a tenter at a temperature of 110 to 120°C to obtain a foamed film having a thickness of 200 μm and heat-shrinkable in the transverse direction. <Comparative Example 1> A composition in which 1 part by weight of a blowing agent consisting of sodium bicarbonate and citric acid was blended with 100 parts by weight of an ethylene-propylene random copolymer with an ethylene content of 4.5 mol% was prepared in the same manner as in Example 1. A foamed film was obtained by processing. This film had a poor foaming condition, with cells bursting in some places and a fluffy surface, and was a defective product in which fibrillation due to longitudinal cracks during stretching was observed in some places. <Comparative Example 2> The same amount of the same blowing agent as in Comparative Example 1 was added to polystyrene, a film was formed in the same manner, and the film was stretched three times as much with rolls at a temperature of 110°C.
A foamed film of 200μ was obtained. At this time, we attempted an experiment in which a raw sheet formed by extrusion was stretched 3 times in the horizontal direction using a tenter, but the edges of the raw sheet were destroyed by the tenter clips, or the raw sheet was broken in the center. It was not possible to stretch the film. The physical properties of the foamed films obtained in Examples 1, 2, and 3 and Comparative Examples 1 and 2 are listed in Tables 1 and 2 below.
【表】
上記の第１表から本発明の実施例１、２、３の
各発泡材料は強靭で、引裂強度に優れ、衝撃強度
が抜群で、伸度も適度に備わつた極めて実用的な
熱収縮性材料であることが立証された。これに対
し比較例１のものは満足な材料とならなかつたし
比較例２の従来品は横延伸は不可能であり、縦延
伸されたものも衝撃強度その他諸物性が極めて悪
く、緩衝効果がもう一つ不充分であつた。
更に本発明実施例１、２、３のものは、熱伝導
率が良好のため、収縮の際の熱エネルギーが少な
くてすむので、被包装物（例えばビン）を予熱す
る工程が不要であつたり、低温予熱で行える他、
被包装物を冷蔵庫等で冷却する時も早く冷えるこ
とも考えられる。
〈実施例 ４〉
実施例１、２、３で得た発泡フイルムを熱収縮
性ラベルとしてビンに被覆させるため、表面に印
刷を施した後、巾22.5cmの長尺帯にスリツトし、
センターシールを施して折り径11cmの長尺筒状体
を得た。これを長さ11cmにカツトして筒状体とな
し、ビンに被覆し熱収縮させてビン表面にこれを
密着させた。この際熱収縮の方向はビンの円周方
向であり、ビンの横方向にも若干収縮した。
〈比較例 ３〉
比較例２で得た発泡フイルムを熱収縮性ラベル
として実施例４と同様のビンに被覆させるため、
印刷を施し、次いで巾11cmの長尺帯にスリツトし
た後、フイルムの長尺方向と直角の方向に22.5cm
にカツトして長さ22.5cm、巾11cmの長方形のフイ
ルムを作成した。この長方形フイルムにセンター
シールを施して折り径11cm、長さ11cmの筒状体を
作成して実施例４と同様にビン表面に密着させ
た。
以上の実施例４と比較例３からも解る如く、実
施例４のものは筒状体を作成するのが極めて能率
的で、従来の自動ラベル挿入機の機構を用いるこ
とにより連続してビンに密着させることが可能で
あるのに対し、比較例３のものは筒状体の作成が
極めて煩雑で非能率的である上に、特別な自動ラ
ベル挿入機を作成しないと密着させることができ
なかつた。[Table] From Table 1 above, the foamed materials of Examples 1, 2, and 3 of the present invention are tough, have excellent tear strength, excellent impact strength, and have moderate elongation, making them extremely practical. It was proven to be a heat-shrinkable material. On the other hand, the material of Comparative Example 1 was not a satisfactory material, and the conventional product of Comparative Example 2 could not be stretched horizontally, and even the material stretched longitudinally had extremely poor impact strength and other physical properties, and the cushioning effect was poor. There was one more thing that was insufficient. Furthermore, since the products of Examples 1, 2, and 3 of the present invention have good thermal conductivity, they require less thermal energy during shrinkage, so there is no need to preheat the packaged item (for example, a bottle). , which can be done with low temperature preheating,
It is also conceivable that the packaged items may cool down quickly when they are cooled in a refrigerator or the like. <Example 4> In order to coat a bottle with the foamed film obtained in Examples 1, 2, and 3 as a heat-shrinkable label, the surface was printed and then slit into a long strip with a width of 22.5 cm.
A center seal was applied to obtain a long cylindrical body with a fold diameter of 11 cm. This was cut to a length of 11 cm to form a cylindrical body, which was then coated on a bottle and heat-shrinked to adhere it to the bottle surface. At this time, the direction of heat shrinkage was in the circumferential direction of the bottle, and there was also some shrinkage in the lateral direction of the bottle. <Comparative Example 3> In order to cover the same bottle as in Example 4 with the foamed film obtained in Comparative Example 2 as a heat-shrinkable label,
After printing and then slitting into long strips 11 cm wide, 22.5 cm in the direction perpendicular to the length of the film.
A rectangular film with a length of 22.5 cm and a width of 11 cm was created. This rectangular film was center-sealed to create a cylindrical body with a fold diameter of 11 cm and a length of 11 cm, and was brought into close contact with the bottle surface in the same manner as in Example 4. As can be seen from the above Example 4 and Comparative Example 3, it is extremely efficient to create a cylindrical body in Example 4, and it can be continuously inserted into bottles by using the mechanism of a conventional automatic label insertion machine. On the other hand, in Comparative Example 3, the production of the cylindrical body is extremely complicated and inefficient, and it cannot be made in close contact without creating a special automatic label insertion machine. Ta.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図と第２図は本発明に係る発泡材料と従来
の発泡材料を使用してビンに筒状体を熱収縮被着
する場合の工程説明図である。
１…本発明に係る横方向に熱収縮性を有する発
泡材料、２…長尺筒状体、５…容器、６…熱収縮
して容器上に密着した筒状体、１′…従来の縦方
向に熱収縮性を有する発泡材料。
FIGS. 1 and 2 are explanatory diagrams of the process of heat-shrinking a cylindrical body onto a bottle using the foamed material according to the present invention and a conventional foamed material. DESCRIPTION OF SYMBOLS 1... Foamed material having heat-shrinkability in the transverse direction according to the present invention, 2... Elongated cylindrical body, 5... Container, 6... Cylindrical body that is heat-shrinked and tightly adheres to the container, 1'... Conventional vertical Foam material that has heat shrinkability in the direction.