JPS60135242A - Heat-shrinkable composite film and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-shrinkable composite film having an opaque pearlescent luster. More specifically, a heat-shrinkable composite having an opaque pearl-like luster, which has a heat-shrinkable foamed film as a base layer and a surface layer made of an unfoamed heat-shrinkable film formed on at least one side of the base layer. Regarding film.

Exterior of packaged goods, tight packaging to prevent impact of contents,
Anisotropic or isotropic heat-shrinkable plastic film (shrink film) stretched in one or two directions for use in binding packaging, label packaging 9 that serves both to protect glass bottles and containers and to display products. Shrink wrapping using has been widely used for a long time. Furthermore, in recent years, with advances in shrink packaging technology, heat-shrinkable foam films with a cushioning effect have been used as a way to protect items that are easily damaged by slight impacts, such as glasses, bottles, kelp, vases, and vases, from damage. It started to be done.

By directly shrink-wrapping these items using this heat-shrinkable foam film, the following conventional methods can be used: a) Wrapping and stringing of cushioning materials such as cardboard, thin paper, and expanded polystyrene around the item; , bondage packaging using bands, tape, etc.) Amount of goods using partitions in cardboard cases.

iii) There is no need to store the item in a thick foam molded product that matches the shape of the item, simplifying the packaging process, streamlining the packaging process, reducing transportation space, etc., and reducing costs. You can get big benefits.

Conventionally, polystyrene expanded stretched film has been well known as this type of heat-shrinkable foamed film.For example, it is used as a two-pel-cum-preservation film for glass bottles such as carbonated beverages, and is used to print patterns, trademarks, and boss marks on the circumferential side of the container. It is widely practiced to wrap a stretched polystyrene film printed with a label, etc., and then heat-shrink it so that it adheres tightly to the bottle (hereinafter, packaging that functions as both a label and a preservative film is referred to as label packaging). However, polystyrene expanded stretched film has poor impact resistance, so if a bottle under internal pressure, such as a carbonated drink υ bottle, is dropped while wrapped in the film, the damaged bottle may tear the film and cause the bottle to fall. It is dangerous because the fragments are scattered widely.

On the other hand, stretched films obtained from polypropylene and ethylene-propylene copolymers containing mainly propylene have better impact resistance than polystyrene, and are used as unbalanced heat-yield films for label packaging (Japanese Patent Laid-Open No. 5
5-108951), a multilayer heat-shrinkable film with two to three layers of heat-sealability (Japanese Patent Laid-Open No. 57-495)
No. 54) and the like have been proposed, but the buffering effect as a protective film cannot necessarily be said to be sufficient.

The present inventors have conducted various studies on polyglopylene-based expanded stretched films that have excellent impact resistance, shock-absorbing properties, and heat shrinkability, and have found that specific crystalline propylene (α-olefin/copolymer), low-density polyethylene, or After creating a raw foam sheet from a composition containing specific amounts of ethylene-vinyl acetate copolymer, an organic decomposable blowing agent, and a metal salt of higher fatty acid, the sheet is stretched 8 times or more in at least one direction. The foamed stretched film has excellent heat-shrinkability and cushioning effect.The closer the stretching temperature is to the coagulation and melting point of the crystalline propylene-α-olefin copolymer, which is the main component of the composition, the less opaque it becomes, and the more the contents are The problem was that it appeared translucent, which negatively affected the product image. Furthermore, when heat sealing is applied, the heat and pressure of the seal bar melts the foamed part and returns it to its non-foamed state, making only the sealed part transparent and making it look even worse. It had drawbacks.

As a result of further studies on these improvements, the present inventors blended specific amounts of a polystyrene resin, an organic decomposable blowing agent, and a metal salt of a higher fatty acid into a specific crystalline propylene-α-olefin copolymer. A raw resilient foam sheet obtained by melt-extruding the composition under specific conditions is stretched in at least one direction by a factor of 4 or more so that the stretching ratio in the i direction is 4 times higher than the stretching ratio in the direction perpendicular to this. A heat-shrinkable composite film is a heat-shrinkable composite film that has a structure in which a specific non-foamed heat-shrinkable film is laminated on at least one side of a heat-shrinkable foamed film.

The present invention was achieved by discovering that it has excellent buffering action and impact resistance, as well as a pearl-like luster with a sense of opacity, and that the above-mentioned drawbacks can be overcome.

That is, one of the aspects of the present invention is that the crystal melting point is 115 to 145°.
The crystalline propylene-α-olefin copolymer of C is 97
~78% by weight, 3-20% by weight of polystyrene resin, 0.1-1.0ii% of organic decomposable blowing agent, and 0.03-1.0% by weight of metal salt of higher fatty acid. At least one side of the base material layer consisting of a heat-shrinkable foam layer which heat-shrinks significantly in one direction and in the perpendicular direction, obtained from the crystalline propylene-α-olefin copolymer separately obtained from the crystalline propylene-α-olefin copolymer. Non-foaming, one direction perpendicular to this)
The gist of the present invention is a heat-shrinkable composite film characterized in that a surface layer is formed by laminating thin heat-shrinkable layers with the same shrinking direction.

Another aspect of the present invention is a crystal melting point of 115-145
The crystalline globylene-α-olefin copolymer at 9 °C
7-98% by weight and polystyrene resin 3-20% by weight
A composition consisting of 0.1 to 1.0% by weight of an organically decomposed blowing agent and 0.03 to 1.0% by weight of a metal salt of a higher fatty acid*
is melt-extruded at a temperature higher than the decomposition temperature of the blowing agent, and heated to 50°C.
Then, the crystalline propylene-α-olefin copolymer is separately melt-extruded and laminated on at least one side of the foamed unstretched base material layer to form a foamed unstretched base material layer. The crystalline melting point of the crystalline propylene-α-olefin copolymer is 10 to 10.
Formed from the foamed unstretched base material layer by stretching in at least one direction at least 4 times the stretching ratio in one direction at a temperature lower than 60°C so that the stretching ratio in one direction is 4 times or more the stretching ratio in the direction perpendicular to this. On at least one side of the base layer made of a heat-shrinkable foam layer that heat-shrinks in at least one direction, a surface layer made of an unfoamed thin heat-shrinkable layer that heat-shrinks in at least one direction is formed from the unstretched surface layer. The gist of the present invention is a method for producing a heat-shrinkable composite film, which is characterized by forming a composite structure in which the shrinkage direction coincides with that of the base layer to form a laminated composite structure.

Each component and blending ratio of the composition used to form the base layer (hereinafter sometimes referred to as base layer composition) in the present invention will be explained.

The crystalline propylene-α-olefin copolymer has a crystal melting point in the range of 115 to 145°C, and is composed of propylene containing 70% by weight or more of a propylene component and ethylene or/and α-olefin having 4 to 8 carbon atoms. Copolymers with olefins are preferred, and ethylene-propylene random copolymers and ethylene-propylene-butene-1 ternary copolymers are the most preferred because they allow the foaming state of the base material layer to be adjusted extremely finely and uniformly. preferable.

Here, the crystal melting point (hereinafter sometimes abbreviated as Tm) is a sample measured at 10° in a crab atmosphere using a scanning differential calorimeter.
It refers to the peak temperature of the mosquito fever curve as the crystal melts by increasing the temperature at a rate of C/min. Crystalline propylene
If the Tm of the α-olefin copolymer exceeds 145° C., foaming becomes non-uniform and stretch breakage is likely to occur, and heat shrinkability is also insufficient. Further, if Tm is less than 115°C, it is not preferable because the film becomes too flexible and workability is significantly reduced, or the film tends to stick.

Considering the above-mentioned physical properties and in addition to the productivity of heat-shrinkable composite films, among the crystalline propylene-α-olefin copolymers whose component composition and crystal melting point are within the above range, the ethylene component has 4 to 7 polymers. World% Tm is 125-140
°C ethylene/propylene random copolymer, and ethylene component is 0.5 to 6 M% and butene-1 component is 1 to 1%.
Particularly preferred is an ethylene-propylene-butene-1 terpolymer having a content of 15% by weight and a Tm of 120 to 140°C. These copolymers have shrinkage characteristics suitable for use in the final heat-shrinkable composite film particularly for label packaging, and are also inexpensive as raw material resins. In addition, the melt 70-rate (MFR) of the crystalline propylene-α-olefin copolymer is in the range of o, i to 20, and the extrusion/molding conditions (extruder screw shape , extrusion temperature, withdrawal speed, etc.). The crystalline propylene-α-olefin copolymer is the main component of the base layer and accounts for 97 to 78% by weight of the base layer composition.
If the amount is less than % by weight, the effect of the present invention will be insufficient.

As the polystyrene resin, a styrene homopolymer or a copolymer with a styrene content of 70% or more and a softening point (ring and ball method) of 50°C or higher is used, especially polystyrene (including rubber blends), acrylonitrile, etc. - Styrene copolymers and styrene/inbutylene copolymers are preferred. The blending ratio of the polystyrene resin in the base layer composition is preferably 3 to 20% by weight, particularly preferably 5 to 15% by weight. By blending the polystyrene resin in the composition for the base layer, the base layer obtained therefrom, and therefore the heat-shrinkable composite film of the present invention, exhibits a pearl-like luster with an opaque feel. Also, even if the composite film is heat-sealed, the opacity of the sealed portion can be maintained.

If the above blending ratio does not reach 3% by weight, the opacity will be insufficient, and if it exceeds 20% by weight, stretch breakage will not easily occur, and the opacity will be accentuated and the pearl-like luster will be lost, which is not preferable. .

The organic decomposable blowing agent is solid at room temperature and has a decomposition temperature higher than the Tm of the crystalline propylene-α-olefin copolymer, and when heated above the decomposition temperature, nitrogen,
A compound that decomposes while generating carbon dioxide gas, ammonia gas, etc. is used. A specific example is azodicarbonamide.

Examples include metal salts of azodicarbonamide, hydrazodicarbonamide, NN'-dinitrosopentamethylenetetramine, p-)luenesulfonyl hydrazide, and the like. The blending ratio of these blowing agents in the base layer composition is 0.
．． 1 to 1.0% by weight, if it does not reach 0.1% by weight, the amount of foaming will be small and the cushioning effect of the heat-shrinkable composite film will be poor; if it exceeds 1.0% by weight, foaming will occur. It is difficult to form a foamed unstretched base material layer by proceeding too much.
:During stretching, stretching breaks occur frequently, making stretching difficult, and the resulting product will be of significantly poor quality, which is undesirable.

As a foaming agent, azodicarbonamide fc0.2-0
．． Most preferably, the amount is 6% by weight.

Stearic acid is a metal salt of higher fatty acids.

Higher fatty acids such as 12-hydroxystearic acid and periodic table 18 (sodium, lithium, etc.), la (calcium,
(magnesium, etc.), (2)b (zinc, etc.), Il[b (aluminum, etc.) salts with metals can be formed. Specific examples thereof include sodium stearate, lithium 12-hydroxystearate, calcium stearate.

Calcium 12-hydroxystearate, magnesium stearate, etc. are shown. The blending ratio of the metal salt of higher fatty acid in the base layer composition is 0.08 to 1.0% by weight. If the above-mentioned blending ratio does not reach 0.08% by weight, the dispersion of the blowing agent will be poor and foaming will be non-uniform, while if it exceeds 1.0% by weight, it will be extremely difficult to feed into the extruder.

An antioxidant is added to the base layer composition as necessary.

Ultraviolet absorbers, antistatic agents, slip agents, pigments, etc. may be added.

Crystalline propylene-α- used for the surface layer in the present invention
The olefin copolymer used is the same as the crystalline propylene-α-olefin copolymer, which is the main component of the base layer, in order to improve the shrinkage characteristics as a heat-shrinkable composite film. If necessary, anti-aging agents, ultraviolet absorbers + %'i% inhibitors, sliving agents, lubricants, and pigments may be added to the base propylene-α-olefin copolymers used for earrings, slitter pieces, etc.

The heat-shrinkable composite film according to the present invention (hereinafter sometimes simply referred to as composite film) is obtained by melt-extruding a base layer composition comprising each of the components described above in one direction and in a direction perpendicular to this. At least one side of the base material layer consisting of a heat-shrinkable foam layer that is highly heat-shrinkable is coated with a material separately obtained from the same copolymer as the crystalline propylene-α-olefin copolymer in the composition for the base material layer. A surface layer is formed by laminating non-foamed heat-shrinkable thin layers that shrink by a large amount υ in one direction and in a direction perpendicular to the heat-shrinkable layer, with the shrinking directions matching. This composite film has a surface layer formed on one or both sides of the base layer, but this surface layer may be subjected to surface treatment such as corona discharge treatment. The thickness of the base material layer is preferably 50 to 99% of the total thickness of the composite film, especially 70 to 90%.
% is preferred. Typically, the total thickness of the composite film is 0.05
~0.4M, apparent specific gravity 0.2~0.75.120°
If the thermal contraction rate in one direction in C is 10% or more,
It is sufficient in terms of heat shrinkability and cushioning effect, and the surface layer not only sufficiently increases impact resistance due to its non-foamed and excellent strength and elongation, but also further enhances the pure-like luster of the base material layer. In addition to having a flattering effect, its good printability makes it possible to print extremely beautiful prints on the surface of the composite film.

Among the heat-shrinkable composite films according to the present invention, the following are particularly suitable for label packaging. In other words, the total thickness is 1), the specific gravity is 0.3 to 0, the heat shrinkage rate in one direction at 120°C is 20% or more, and the thermal contraction rate in the direction perpendicular to this is 20% or more It has a heat shrinkage rate of 4 times or more and is considered to be cold. If the thickness is 0.101 m or more, the impact resistance for label packaging is sufficient, and the foam cells are uniform and the appearance is satisfactory as a label. If the thickness exceeds 0.25 mm, the time required for heat shrinkage is too long, making it difficult to work with a large number of bottles, etc., and the shape of the curved portion after shrinkage may become uneven, which may impair the appearance. There is. If the apparent specific gravity is 0.3 or more, the foam cells will be fine9 and the pearl-like luster will be excellent and suitable for labels.

Bottles with an apparent specific gravity exceeding 0.7 may not have sufficient cushioning effect for label packaging, and may be taut if two or more bottles are dropped in a row from a vending machine. There is a risk of rupture due to collision with the bottle. Regarding heat shrinkage, due to the nature of label packaging for bottles, etc., it is necessary that the heat shrinkage in only one direction be especially large.Therefore, if the heat shrinkage rate in one direction at 120°C does not reach 20%,
The amount of shrinkage is insufficient and the adhesion of the label to the bottle is incomplete.

It is also important for label packaging that the heat shrinkage rate in one direction is at least four times the heat shrinkage rate in the perpendicular direction. For example, when a film cylinder is made from a composite film, placed in a bottle, and heat-shrinked, it is desirable to shrink only in the cylindrical direction. If the shrinkage in the cylinder axis direction is large in addition to the shrinkage in the circumferential direction, it becomes difficult to keep the film surface clean, resulting in distortions in the printed pattern9, uneven printed characters, and the edges of the film. The curved shape will spoil the appearance. Therefore, a film cylinder may be created by aligning the direction in which the composite film has a heat shrinkage rate of 20% or more with the circumferential direction, and the direction perpendicular thereto with the cylinder axis direction. In this way, for label packaging, it is necessary to have unbalanced heat shrinkability, which is a large heat shrinkage in one direction and a small heat shrinkage rate in a direction perpendicular to this direction, with virtually no dimensional change.

As can be seen from the manufacturing method described below, the heat-shrinkable composite film according to the present invention generally has the shape of a long film, but the direction in which it shrinks more υ is the width of the long film. It is preferable for the composite film to shrink in the width direction, so that it can be used for various purposes. Therefore, it is preferable that the base layer and the surface layer constituting the composite film also shrink in the width direction.

The heat-shrinkable composite film according to the present invention can be manufactured by the following method. .

That is, first, the above-described base layer composition is melted at a temperature equal to or higher than the decomposition temperature of the blowing agent contained in the composition and extruded. This melting/extrusion temperature is usually above, but close to, the decomposition temperature of the blowing agent. Since the extruded cell has countless foamed cells, it is rapidly cooled to 50°C or less to form a foamed unstretched base material layer, and it is also included as a main component in the composition for the base material layer. The same copolymer as the propylene-olefin copolymer (hereinafter sometimes referred to as surface layer propylene copolymer) is separately melted and extruded. An unstretched composite sheet is obtained by laminating them to form an unstretched surface layer. As described above, there are the following methods for laminating the foamed unstretched base material layer and the unfoamed unstretched surface layer.

One method is to melt and extrude the base material composition alone as described above, rapidly cool it to obtain a raw resilient foam sheet, and then extrude this raw resilient foam sheet as a foamed unstretched base material layer on at least one side of the base material. In this method, a propylene copolymer for the surface layer is melted and extruded by a lamination method, and then cooled to form an unstretched surface layer. The other method uses a coextrusion method to melt and extrude the composition for the base layer and the propylene copolymer for the surface layer using separate extruders in a T-die kept at an appropriate temperature. This is a method in which the materials are laminated into a predetermined configuration in a molten state and then rapidly cooled. In this step, conditions are adjusted so that the foamed unstretched base material layer of the resulting unstretched composite sheet has an apparent specific gravity of 0.3 to 0.8 and a thickness of 0.15 H or more.

The thus obtained unstretched composite sheet is stretched at a stretching ratio in one direction at a temperature 10 to 6θ°C lower than the crystalline melting point Tm of the crystalline propylene-α-olefin copolymer, which is the main component of the unstretched composite sheet. Stretch in at least one direction [4 times or more] so that the stretching ratio is 4 times or more the stretching ratio in the direction perpendicular to this. In the case of uniaxial stretching, the stretching ratio in one direction is 4 to 10 times the stretching ratio in the vertical or horizontal direction, and in the case of biaxial stretching, the stretching ratio in one direction is at least 4 times the stretching ratio in the direction perpendicular to the stretching ratio. It is preferable to perform the stretching simultaneously or sequentially so that the area magnification becomes 6 to 30 times. In the case of axial stretching, the preferred stretching conditions are Tm of the propylene-α-olefin copolymer) 20 to 60″
C: Stretch 4 to 8 times at low temperature. In addition, in the case of biaxial stretching, the Tm of the propylene-α-olefin copolymer is 30 to
After stretching 1.05 to 2.0 times on or between two or more heating rolls kept at a temperature 60°C lower, the horizontal/vertical stretching ratio is set to 4 or more at a temperature slightly higher than the stretching temperature. It is preferable to use a sequential stretching method in which the film is stretched 6 to 10 times in the transverse direction in a tenter. The stretched composite film is heat-treated in a conventional manner under tension or in a slightly relaxed state as required, and then cooled by air cooling, cooling rolls, cooling belts, etc. to obtain the heat-shrinkable composite sheet of the present invention. can get. After cooling in the above step, surface treatment such as corona discharge treatment may be performed in the air or in an inert gas.

In the stretching process, although the main component of the unstretched composite sheet is a foamed unstretched base material layer that is easily broken by stretching, it is the foamed unstretched base material that enables stretching at such a high stretching ratio as described above. This is because an unstretched surface layer of a propylene-α-olefin copolymer having excellent strength and elongation is laminated on at least one side of the layer, and this allows for a wide range of stretching conditions for the unstretched composite sheet. After high shrinkage, no non-uniform shrinkage occurs on the surface due to differences in the shrinkage direction of each layer.

Incidentally, as the stretching method, a commonly practiced method can be used, but the following should be taken into consideration. With the tubular one-sided method, it is generally desirable to make the foam cells uniform and adjust the thickness when foaming polypropylene resin. In addition, in the vertical (longitudinal) - axial stretching of the T-die method, the heat shrinkage rate in the longitudinal direction is large, so it tends to shrink at room temperature after core winding, resulting in poor rolled shape of the heat-shrinkable composite film. In addition, when the product composite film is heat-shrinked, in some cases, it may not shrink in the transverse (width) direction but instead elongate, and the breaking strength in the transverse (width) direction is small, making it easy to tear. It is difficult to use the longitudinal direction of the composite film as it is for shrink wrapping purposes, as the longitudinal direction of the container. Furthermore, when widening the die is carried out as a method of increasing productivity, it is difficult to control uniform foaming in the width direction of the foamed fabric due to the widening of the die.

On the other hand, the T-die stretching method, which mainly involves IA stretching in the transverse (width direction) with no or only slight stretching in the vertical (length direction), does not have the above-mentioned difficulties, and the product composite film This is an extremely preferable stretching method that is particularly suitable for shrink wrapping applications, and furthermore, the above-mentioned adjustment of the foamed material is easy, and a wide heat-shrinkable composite film with good winding shape can be efficiently produced.

As described above, the heat-shrinkable composite film according to the present invention has (1) the use of a specific composition in the base material layer, which results in extremely fine and uniform foaming, and excellent cushioning properties; (2) the base material By blending polystyrene resin into the layer, a transparent pearl-like luster was obtained, and (3) transparency of the sealed area due to heat sealing was prevented.
(4) By providing a non-foamed heat-shrinkable surface layer of crystalline propylene-μ·-olefin copolymer, the extremely excellent gloss of the surface layer enhances the pearl-like luster of the base layer, and (5) Extremely clear printing is now possible.
(6) The surface layer can be stretched at a high stretching ratio and has a large heat shrinkage rate; (6) It is extremely useful not only for label packaging but also for tapes, decorative packaging, slow-motion packaging, etc. It has the effect of In addition, the method for producing a heat-shrinkable composite film according to the present invention not only provides the heat-shrinkable composite film obtained above with the above-mentioned effects, but also provides (7) a foamed unstretched base material layer and a non-foamed By laminating the unstretched surface layer of the composite sheet and stretching the resulting unstretched composite sheet, it has the following effects: it reduces stretch breakage and enables stable production at a low stretch ratio and high speed. .

EXAMPLES The present invention will be explained in more detail below using Examples and Comparative Examples, but the present invention is not limited to the following Examples. In addition, the characteristic values in the following Examples and Comparative Examples were measured by the following method.

(+) Melt 70-rate (MFR): JISK72
10-1976 ■Polypropylene and hygropylene-α-olefin copolymer under Condition 14 (280°C12,16#f) ■Polyethylene and ethylene-vinyl acetate copolymer under Condition 4 (
190°C 12,16A: ri f).

(Appearance ratio M: JIS K7112-19'
l'l B method (pycnometer method) Distilled water is used as the immersion liquid.

0il) 120°C shrinkage rate: Film i cut into strips with length lQc* and width 1m, immersed in a silicone oil bath at 120°C for 30 seconds, taken out, and calculated the axis ratio of length in each direction. Expressed in (%).

4V) Total light transmittance: JIS K-6714 (v) Printability: Printed in a grid pattern using a commercially available printing ink for polypropylene (Polypro Color manufactured by Toyo Ink (1)) with a gravure printing machine, Observe the printing condition. Q: If there is no shading, no bleeding, and the print is clear. △: There is no shading, but there is some shading. If there is no shading, but there is some smearing and it is unclear, △: The printing has clear shading. Cases where the base grains are unclear due to bleeding or ink bleeding are indicated as ×.

' in the width and length directions of the cl/D foamed film
Visually observe the presence or absence of uneven foaming and its uniformity.If there is no uneven foaming and the foamed cells are fine and uniform, it is judged as gold.If the foaming cells are slightly uneven and the foamed cells are coarse, it is judged as Δ.If there is a lot of uneven foaming and the foamed cells are coarse and the cells are coarse. Uniform samples are indicated as ×.

Example 1 Ethylene content is 4.0″wt%, butene-1 content is 5.0″wt%.
2% by weight + ethylene-propylene-butene-1 terpolymer with Tm of 130°C and MFR of 11.5 (0% 2.6-di-t-butyl-p-cresol as antioxidant)
．． Contains 15% by weight) 89.4% by weight, polystyrene (trade name Styron 679, manufactured by Asahi Dow ■) 10'Nt%, azodicarbonamide (decomposed at 190°C) 0.8N fluorescent %, calcium stearate o, azz %, mixed in a Henschel mixer, melt-extruded into strands at a resin temperature of 165°C, cooled and cut to obtain an unfoamed base layer composition. This composition for the base material layer was melt-extruded at 195°C through an extruder and a T-die, and rapidly cooled with a cooling roll kept at 30°C to obtain a raw material with a thickness of 1.0 mm and an apparent specific gravity of 0.78. A resilient foam sheet was obtained. This raw rebound foam sheet was used as a foamed unstretched base material layer, and one side thereof was coated with ethylene propylene butene-1, which was the same as that used in the composition for the base material layer.
The terpolymer was melt-extruded at 220°C and laminated as an unstretched surface layer to a thickness of 0.1518H on the above-mentioned raw rebound foam sheet between a metal roll and a silicone rubber roll kept at 30°C. A stretched composite sheet was stretched 8 times in the horizontal direction in a tenter of
- An axially stretched heat-shrinkable composite film according to the present invention was obtained. The stretching of the unstretched composite sheet was extremely stable with no stretching breakage, and the thickness was uniform, which was better than that obtained by stretching the original rebound foam seal alone. The resulting heat-shrinkable composite film has a thickness of 0.181M and an apparent specific gravity of 0.
The heat shrinkage rate at 65,120°C is 3% in the vertical direction and 42% in the horizontal direction, and the foaming condition is good. Impermeable E! It had a pearl-like luster with an A feel. In addition, when the base pattern was printed on the surface layer of this composite film, the printing was dark and clear. Apply this printing film to a height of 11 cm using an impulse sealer with the printed surface facing outward and the horizontal direction facing the circumferential direction.
After sealing it into a cylindrical shape with a diameter of 75 mm and a height of 120 mm, it was covered with a paper tube having a height of 120 mm and a diameter of 7 Q+++x.
Heated at 20°C for 7 seconds. As a result, the cylindrical direction of the film is in close contact with the regular body, there is no shrinkage in the height direction, no distortion is seen in the printing base, and it is opaque enough to completely shield the regular body. A beautiful close-contact package with a pearl-like luster was obtained. Furthermore, the portion sealed with impulse sealer also had sufficient opacity.

Examples 2-8. Comparative Examples 1 to 9 Seven types of compositions shown in Table 1 were prepared as base layer compositions. - Same as olefin copolymer, ethylene content is 3.5% by weight, butene-1 content is 4.5% by weight, Tm is 182°C, MFR
An ethylene-propylene-butene-1 terpolymer with a 10.0% copolymer was used, and 0.2M'tA't% of 2.6-di-t-butyl-p-cresol and 0.05% of calcium stearate were used. A composition for the surface layer was prepared by blending % leaves and 0.1% by weight of erucic acid amide. The above compositions for the base layer, for the surface layer, and for the surface layer were individually melt-extruded using two extruders, and the T was kept at 190°C.
Laminated in a molten state in a die, the layers are passed between two cooling rolls kept at 20"C and quenched while being pressed together to form a foamed unstretched base material layer in the center and m layers of unfoamed unstretched material on both sides. An unstretched composite sheet with 8 layers in the shape of a sandwich consisting of a stretched surface layer (
A thickness l, 5 vtttt) was obtained. This composite sheet is processed using a small pantada rough drawing device (T).

M, stretching temperature 100°C using Long Co. (made of lead)
After stretching 1.5 times in the vertical direction at
．． 12jM) of seven types of biaxially stretched heat-shrinkable composite films according to the present invention were obtained. In addition, for comparison, a composite film was biaxially stretched in the same manner as in the above example, except that the composition shown in the column of composition for base layer in Table 1 was used as a composition corresponding to the composition for base layer. I got it. Table 1 shows the foaming state, apparent specific gravity, total light transmittance, and opacity of the sealed portion of these composite films. To check the opacity of the seal, after sealing each sample with a 5-width impulse sealer, place the seal on a piece of paper with literature printed on it. The letters that are unclear but can be distinguished are expressed as Δ, and the letters that are transparent and easily distinguishable are expressed as '6x. As is clear from Table 1, the composite film according to the present invention showed a good foaming state, had an excellent shielding effect, and did not exhibit any transparency phenomenon due to heat sealing.

Notes on Table 1.

*1: Ethylene-propylene-butene-1 terpolymer; ethylene content ia, 51UCfit%, butene-1
Content 4.5 M, 'It%, , Trn 182°C,
MF'R10,0 *2: Manufactured by Asahi Dow ■, product name "Styron 679" *8:
Manufactured by Asahi Dow ■, product name "Styron 475" *4: Asahi Dow 4ζ) packaging, product name "Tyryl 767" *5: Ethylene.
Vinyl acetate copolymer iMFR4.0, vinyl acetate content 14% by weight *6: Low density polyethylene iMFR5.0, density 0.9
18 *7: High density polyethylene iMFR4,2, dense &0.9
56 *8: Azodicarbonamide *9 Calcium nistearate *10: 2.6-di-t-butyl-p-cresol Examples 9 to 11. Comparative Examples 10 to 14 A styrene-butadiene copolymer was added to the crystalline propylene-α-olefin copolymer shown in Table 2 (including 0.155 UC of 2,6-di-t-butyl-p-cresol as a partitioning agent). Three types of compositions for base material layers were prepared by blending 7% by weight of composite rubber blend polystyrene (trade name: Pastylon 475'' manufactured by Asahi Dow ■), 0.25% by weight of azodicarbonamide, and 0.3% by weight of calcium stearate. This composition was passed through an extruder and a T-die at 195°C.
After melt extrusion at a resin temperature of 25° C., the resin was rapidly cooled while being pressed using an air knife on a cooling roll kept at 25° C. to obtain three types of raw rebound foam sheets each having a thickness of 0.85 mm. Each raw rebound foam sheet was used as a foamed unstretched base material layer, and one side of the base material layer was coated with the same crystalline propylene-α-olefin copolymer (also containing an antioxidant) as used in the composition for each base material layer. The raw repulsion foam sheet was melt extruded and held between a metal roll and a silicone rubber roll for 40 minutes.
An unstretched composite sheet (total thickness: 0.90ffffl) of 8 seconds was obtained by forming an unstretched surface layer with a C area of 7. Each composite sheet was stretched 7.2 times in the horizontal direction at the stretching temperatures shown in Table 2 using a small pan tag 2-fold stretching device (T, M Long (made in Japan)), and uniaxially stretched to a thickness of 0.18 ffff. Stretched heat-shrinkable composite films according to the present invention were obtained (Examples 9 to 11).For comparison, the above three types of original rebound foam sheets (Comparative Examples 12 to 14) and those of Examples 9 to 11 were obtained. Polypropylene shown in Table 1: / (ratio M11110
) (!: Ethylene-propylene random copolymer (specific example 11) (both contain a single-wave inhibitor as above)
A total of 5 types of raw resilient foam sheets, each having a thickness of 0.85 my obtained by using a propylene-α-olefin copolymer in layer 9, are laminated with an unstretched surface layer. Using the same stretching equipment as above, the film was stretched 7.2 times in the horizontal direction at the stretching temperature shown in Table 2 to a thickness of 0.12M.
A uniaxially stretched foamed film having a thickness of 0.12 mm was obtained (Comparative Examples 10 to 14). At this time, the stretchability and appearance of each sample was in a foamed state with a specific gravity of 9.

Printability and heat shrinkage rate at 120°CK are shown in Table 2.

The stretchability was expressed as the number of stretching breaks (unit: 1 time) when stretching was repeated 10 times under the same stretching conditions.

As is clear from Table 2, the heat-shrinkable composite film of the present invention has a wider range of stretching temperatures, finer and more uniform foaming, and better printability than a film with only a base layer without a surface layer. It was observed that the opaque pearl-like luster, which is a feature of the present invention, was further enhanced.

Practical Examples 12-15, Comparative Grid 15-18 Ethylene with an ethylene content of 4.0 M%, a butene-1 content of 5.2% heavy oil, a Tm of 130°C, and an MFR of 11.5.
Propylene-butene-1 terpolymer (2.6-di-t-butyl-p-cresol 0.15
Polystyrene (trade name: ``Styron 6'79'' 7-weight, manufactured by Asahi Dow), 0.25% by weight of andicarbonamide, and 0.25% by weight of calcium stearate.
i amount% was blended to obtain a composition for profiteering IW. This composition was melt extruded through an extruder and a T-die at 185°C, rapidly cooled on a cooling roll kept at 20°C, and the thickness was 0.8°C.
A raw rebound foam sheet with an appearance of 5 mm and an appearance of 69 mm was obtained. On one side of this sheet, the same ethylene-propylene-butene-1 terpolymer as used in the base material J durable composition was melt-extruded and laminated to a thickness of 0.910 mm to form an unstretched composite sheet. , small pantograph type stretching machine (T,
M, Long Co. ((a) 10 in each direction using W>+
By stretching at a stretching temperature of 0°C and changing the stretching ratio in the vertical and horizontal directions as shown in Figure 3, various composite films with different vertical and horizontal orientations with a heat shrinkage rate of 120°C were obtained. Created. In the same manner as in Example 1, these composite films were formed into a full cylindrical shape, covered with the same paper sheet, and heated at 220°C for 7 hours.
Heated for seconds. Table 3 shows the shrinkage state of the composite film at this time and the presence or absence of distortion of the printed substrate.

Table 3 that's all

Claims (8)

[Claims] (1) Crystalline propylene-α-olefin copolymer with a crystalline melting point of 115 to 145°C is 97 to 78i lid%, polystyrene resin is 3 to 20% by weight, and organic decomposition type blowing agent is 0%.
．． 1 to 1.0% by weight and 0.03 to 0.03% of metal salts of higher fatty acids
The crystalline globilene α- A non-foamed heat-shrinkable thin layer separately obtained from an olefin copolymer that heat-shrinks more greatly in one direction than in the perpendicular direction is laminated with the shrinking direction aligned to form a surface layer. A heat-shrinkable composite film featuring: (2) The crystalline polypyrene-α-olefin copolymer is an ethylene-propylene random copolymer containing t-70% by weight or more of a propylene component.
) The heat-shrinkable composite film described in item 1. (3) Heat shrinkability according to claim (1), wherein the crystalline propylene-α-olefin copolymer is an ethylene-propylene-butene-1Ex copolymer containing 7ON% or more of a propylene component. composite film. (4) The total thickness of the heat-shrinkable composite film is 0.05-0.
4gg, with an apparent specific gravity of 0.2 to 0.75.The heat shrinkage rate in one direction at 120°C is 10% or more and is 4 times or more the heat shrinkage rate in the direction perpendicular to this. (1
) to (3). (5) The method according to any one of claims (1) to (4), wherein the thickness of the heat-shrinkable foam layer is 50 to 99% of the total thickness of the heat-shrinkable composite film. Heat-shrinkable composite film. (6) Claims (1) to (5) in which the heat-shrinkable composite film is a long film, and the base layer and the surface layer are heat-shrinkable in both the width direction and the length direction. The heat-shrinkable composite film described in any of the preceding items. (7) 97 to 78% by weight of crystalline propylene-α-olefin copolymer with crystal melting point of 115 to 145°C, 3 to 20ii% of polystyrene resin, and 0% of organic decomposable blowing agent
．． 1 to 1.0% by weight and 0.03 to 0.03% of metal salts of higher fatty acids
1.0% by weight of the foaming agent is melt-extruded at a temperature higher than the decomposition temperature of the blowing agent and rapidly cooled to 50°C or lower to form a foamed unstretched base material layer, and the crystalline propylene-α-olefin A separately melt-extruded copolymer is laminated on at least one side of the foamed unstretched base material layer to form an unfoamed unstretched surface layer, and the unstretched composite sheet thus obtained is laminated with the crystalline propylene-α- By stretching at least 4 times in one direction at a temperature 10 to 60°C lower than the crystal melting point of the olefin copolymer so that the stretching ratio in one direction is 4 times or more the stretching ratio in the direction perpendicular to this. C. On at least one side of the base material layer made of a heat-shrinkable foam layer formed from the above-mentioned foamed unstretched base layer, at least one side of the non-foamed base material layer formed from the above-mentioned unstretched surface layer. 1. A method for producing a heat-shrinkable composite film, comprising forming a composite structure in which a surface layer consisting of a thin heat-shrinkable layer is laminated with its shrinking direction aligned with that of a base layer. (8) The method for producing a heat-shrinkable composite film according to claim (7), wherein the unstretched composite sheet is stretched in a direction perpendicular to the melt-extruded longitudinal stretching ratio to four times or more. .