JPH06297618A - Heat-shrinkable foam cushioning material - Google Patents

Abstract

PURPOSE:To provide a heat-shrinkable foam cushioning material with wider temp. condition and improved shrinking force over conventional products while heat seal strength is kept by laminating integrally a foam cushioning material and a heat-shrinkable film or a heat-shrinkable composite film. CONSTITUTION:Either a heat-shrinkable film 6 produced by performing film forming, crosslinking and drawing of an ethylene resin film of an ethylene copolymer resin such as EVA(ethylene-vinyl acetate copolymer resin) with large crosslinking effect and EEA(ethylene-ethyl acrylate copolymer resin) and an ethylene resin, or a heat-shrinkable composite film produced by laminating the heat-shrinkable film 6 and another film is integrally laminated with a non- crosslinked foam cushioning material 10 with soft cushioning properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cushioning wrapping material, and particularly to a cushioning wrapping material when tight packing is required.

[0002]

2. Description of the Related Art There has never been attempted a technique in which a film made of a crosslinked resin is attached to a bubble cushioning material to impart heat shrinkability. Japanese Utility Model Publication No. 4-6894 is known as a heat-shrinkable cushioning material in which heat-shrinkability is imparted to the bubble cushioning material itself.

Japanese Utility Model Publication No. 4-6894 exemplifies, as a specific manufacturing method thereof, steps of molding a bubble cushioning material, crosslinking by electron beam irradiation, and stretching. Since the backing film is heat-sealed to the cap film and the bubble cushioning material is molded and then cross-linked, both films are cross-linked. After heat-sealing and packaging the object to be packaged by, for example, a two-sided seal, a three-sided seal, a four-sided seal, etc., the shrinkage tunnel causes heat shrinkage, but the heat seal strength cannot be increased. In general, a crosslinked resin tends to have a higher shrinkage temperature than that before crosslinking. Therefore, there is a problem in that the surface of the object to be packaged is also exposed to a high temperature when it is attempted to shrink the portion of the bubble cushioning material that is in direct contact with the object to be packaged. Further, since it is stretched after molding, the illustrated columnar convex protrusion (bottom area = 0.8 square centimeter, that is, diameter = about 10 mm and height = 4 m
In m), when it is uniaxially stretched 4 times, the cylindrical shape is significantly deformed. In other words, the height of the cylindrical airtight chamber =
It becomes as low as about 1 mm, the diameter in the stretching direction is transformed into an ellipse, and the film thickness becomes thin. Since the airtightness of the airtight chamber cannot be maintained with the thin film, the cushioning property is practically lost and it cannot be put to practical use.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-shrinkable bubble cushioning material having a wider range of temperature conditions and a stronger shrinkage force than conventional products while maintaining heat-sealing strength.

[0005]

The present invention will be described with reference to FIGS. 1 to 6, but the present invention is not limited thereto.

[0006]

[Figure 1]

FIG. 1A is a sectional view showing a first embodiment of the heat-shrinkable bubble cushioning material, and FIG. 1B is a perspective view showing the first embodiment of the heat-shrinkable bubble cushioning material. Reference numeral 1 is a heat-shrinkable bubble buffer material, 2 is a cap film, 3 is a back film, 5 is a bubble chamber, 6 is a heat-shrinkable film, and 10 is a bubble buffer material.

In FIG. 1, a non-crosslinking resin is used as a material for the cap film 2 and the back film 3. As the non-crosslinking resin, a polyolefin resin, particularly an ethylene resin is preferable in view of the material of the heat-shrinkable film 6, which will be described later, and in view of processability and cost.

As a material for the heat-shrinkable film 6 shown in FIG. 1, a crosslinked thermoplastic synthetic resin is used. As the thermoplastic synthetic resin, any of polyethylene resin, polypropylene resin, polyvinyl chloride and the like can be used, but the same as the back film 3 and the liner film 4 in order to increase the heat fusion strength in the case of the extrusion lamination method. Ethylene resins are especially preferred. Ethylene-based resins include ethylene copolymer resins and polyethylene resins.
Examples of the ethylene copolymer resin include ethylene / vinyl acetate copolymer resin (EVA) and ethylene / ethyl acrylate copolymer resin (EEA). As the polyethylene resin, linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE) and the like can be used.

The cap film 2 and the back film 3 are attached to each other to manufacture the bubble cushioning material 10 having the shape shown in FIG. The cap film 2 is heated to a temperature at which a flat film can be molded, and then vacuum-molded into a cap shape (as shown in FIG. 1B) using, for example, a molding roll, and the heated back film 3 is heated and heated. Laminate under pressure. Similarly, the heat-shrinkable film 6 and the back film 3 are bonded together to manufacture the heat-shrinkable bubble cushioning material 1 shown in FIG. As a method for laminating the heat-shrinkable film 6 and the back film 3, there are an extrusion lamination method, an adhesive lamination method and the like. The extrusion lamination method is a method in which, when the cap film 2 and the back film 3 are laminated, the heat-shrinkable film 6 is adhered to the back film 3 in a heated state. The adhesive lamination method is a method in which the heat-shrinkable film 6 and the backing film 3 are bonded together with an adhesive (not shown). Here, as the adhesive agent, in addition to the adhesive agent generally referred to, an adhesive agent, a thermoplastic resin having an affinity for both of the two films 6 and 3, and the like are used.

The heat-shrinkable film 6 is attached to the liner film 4
The case of bonding with is illustrated in FIG. However, unlike the backing film 3 (FIG. 1 etc.), the liner film 4 may be omitted, and the heat-shrinkable film 6 is attached to the top of the capping film 2 (in FIG. 6, the portion where the liner film 4 is attached). ) May be directly attached. To directly bond the heat-shrinkable film 6 and the top of the liner film 4 or the cap film 2 to each other, it is preferable to use an adhesive lamination method. In the case of the extrusion lamination method, the thickness of the liner film 4 is set to the heat shrinkable film 6, 7
The thickness is preferably less than or equal to.

The crosslinked film has a gel fraction of 50 to 9
It is crosslinked in the range of 5%. Since the cross-linking widens the processing temperature range indicated by the difference between the lower temperature limit for heat fusion and the shrinkage initiation temperature, the extrusion lamination method requires less shrinkage during bonding. When the gel fraction is less than 50%, the heat shrinkage rate is insufficient. If the gel fraction exceeds 95%, the transparency, appearance, etc. will deteriorate significantly.

[0013]

[Fig. 2]

FIG. 2A is a sectional view showing a second embodiment of the heat-shrinkable bubble cushioning material, and FIG. 2B is a perspective view showing a second embodiment of the heat-shrinkable bubble cushioning material. 1-3, 5,
6 and 10 are the same as in FIG. Further, 4 is a liner film.

Cap film 2 and back film 3
The bubble cushioning material 10 shown in FIG. 1, which is composed of two films, is called a two-layer bubble cushioning material 10. On the other hand, the bubble cushioning material 10 shown in FIG. 2, which is composed of a cap film 2, a backing film 3, a liner film 4 and three films, is called a three-layer bubble cushioning material 10.

[0016]

[Figure 3]

FIG. 3 is a cross-sectional view showing a third embodiment of the heat-shrinkable bubble cushioning material, wherein 1-3, 5, 6, 10 are shown in FIG.
4 is the same as in FIG.

The bubble cushioning material 10 shown in FIG. 3 has a structure in which the two-layer bubble cushioning material 10 (FIG. 1) and the three-layer bubble cushioning material 10 (FIG. 2) are overlapped, and the bubble chamber 5 is doubled. . 2 above
For the three-layer bubble cushioning material 10 and the three-layer bubble cushioning material 10, FIG.
The structure of the bubble cushioning material 10 shown in is referred to as a five-layer bubble cushioning material.

[0019]

[Figure 4]

FIG. 4 is a cross-sectional view showing a fourth embodiment of the heat-shrinkable air bubble cushioning material, and 1 to 5, 5 and 10 are the same as those in FIG. Further, 7 is a heat-shrinkable composite film, 8 is a crosslinked portion, and 9 is a non-crosslinked portion.

The heat-shrinkable bubble cushioning material 1 of FIG. 4 has substantially the same structure as the heat-shrinkable bubble cushioning material 1 of FIG. 1 shows a heat-shrinkable bubble cushioning material 1 in which a heat-shrinkable film 6 is attached to a two-layer bubble cushioning material 10, while FIG. 4 shows a heat-shrinkable composite film 7 attached to the same two-layer bubble cushioning material 10. The combined heat-shrinkable bubble cushioning material 1. The heat-shrinkable composite film 7 is
This is a multilayer film in which a crosslinked portion 8 and a non-crosslinked portion 9 are integrally laminated. When laminating with the bubble cushioning material 10, for example, the non-cross-linking portion 9 surface of the heat-shrinkable composite film 7 and the back film 3 surface of the bubble cushioning material 10 are laminated together in view of mutual affinity. preferable.

[0022]

[Figure 5]

FIG. 5 is a sectional view showing a fifth embodiment of the heat-shrinkable air bubble cushioning material, wherein 1 to 5, 5 and 10 are the same as in FIG. 1, 4 is the same as in FIG. Is similar to FIG.

[0024]

[Figure 6]

FIG. 6 is a cross-sectional view showing a sixth embodiment of the heat-shrinkable air bubble cushioning material, wherein 1-3, 5, 6, 10 are shown in FIG.
4 is the same as in FIG.

[0026]

Embodiment 1 A cap film 2, a back film 3,
The heat-shrinkable film 6 was extruded and laminated by a lamination method to manufacture the heat-shrinkable bubble cushioning material 1 shown in FIG. The thickness of the cap film 2 is 60 μm, and that of the back film 3
Was 30 μm and the heat-shrinkable film 6 was 20 μm.
A linear low-density polyethylene cross-linked product alone was used as the heat-shrinkable film 6. As the test method, a general contraction measurement method using a glycerin bath was used. When it was heated at about 125 to 130 ° C, it shrank by about 34%.

[0027]

Example 2 A heat-shrinkable composite buffer film 1 shown in FIG. 4 was manufactured by bonding a heat-shrinkable composite film 7 to the back film 3 side of the air bubble buffer material 10 by an adhesive lamination method. The cap film 2 had a thickness of 60 μm, the back film 3 had a thickness of 30 μm, and the heat-shrinkable composite film 7 had a thickness of 25 μm. The breakdown of the thickness of the heat-shrinkable composite film 7 was 15 μm in the crosslinked portion 8 and 10 μm in the non-crosslinked portion 9. As the heat-shrinkable composite film 7, both the crosslinked portion 8 and the non-crosslinked portion 9 were made of ethylene / vinyl acetate copolymer resin. Glycerin bath heated at about 125-130 ℃, about 3
It contracted by 1%.

[0028]

The function of the heat-shrinkable film 6 and the heat-shrinkable composite film 7 will be described first.
A chain polymer, for example, high-pressure polyethylene is a thermoplastic resin, and the molecules of the chain polymer are covalently bonded to each other by means of irradiating it with an electron beam or the like, so-called cross-linking. When crosslinked, it becomes insoluble and heat resistance and mechanical strength are improved. The degree of insolubility is indicated by a gel fraction, and a high gel fraction means a large number of covalent bonds. The chain polymer polyethylene resin has a gel fraction of 50 to 95.
% Can be significantly crosslinked. When the crosslinked chain polymer is stretched, the molecule is deformed and elongated, and when it is softened by heating, it exhibits a property like rubber-like elasticity that tends to return to its original state. Stretching the uncrosslinked chain polymer extends the crystals of the folded structure and improves the tensile strength, but even if it is softened by heating, the crosslinked chain polymer exhibits rubber-like elasticity and shrinks. Differently, the contraction force and contraction rate are small. At the time of extrusion lamination in which the heat shrinkable film 6 and the back film 3 are bonded together, the heat shrinkable film 6 shrinks if it is softened, but the back film 3 is heated unless it is heated to near the melting point.
And does not fuse. Therefore, the back film 3 side of the heat-shrinkable film 6 is heated to a temperature at which it can be fused, and the other side is sufficiently cooled with a chill roll or the like for bonding. In this way, the heat-shrinkable film 6 is supercooled on one side, but the back film 3
It is fused and does not easily shrink. However, since there are many insoluble portions due to cross-linking, the fusion is not complete fusion but insufficient fusion, but fusion occurs to the extent that there is no practical problem. Therefore, the range between the heat fusion lower limit temperature and the heat shrinkage start temperature becomes wider. Heat resistance is improved during shrink wrapping. Further, since it is insoluble, unlike the cap film 2, the back film 3 and the liner film 4 which compose the bubble cushioning material 10 by heating, they are plasticized unless they are heated to an unnecessarily high temperature such as carbonization. It is not elastic and only shows rubber elasticity. Therefore, there is no problem even if a wide temperature range is taken up to a high temperature until the bubble chamber 5 does not collapse, and as described above, the contraction shows a rubber elastic property and the contraction rate is large.
In addition, the contraction force also increases. For heat seal strength,
Since there are many insoluble portions, the sealing strength, that is, the fusion strength, is not improved.

In the case of packaging with the heat-shrinkable bubble cushioning material 1 shown in FIGS. 1 to 5, the heat-shrinkable film 6 or the heat-shrinkable composite film 7 is on the back film 3 side, and therefore the cap film 2 (FIG. 2, In FIG. 5, the liner film 4) surface is in contact with the object to be packaged. An air bubble cushioning material 10 composed of the cap film 2 and the backing film 3 (FIGS. 1 and 4), and a bubble cushioning material 10 composed of the cap film 2, the backing film 3 and the liner film 4 (FIGS. 2, 3 and 4). In 5), since it is not crosslinked and is not subjected to a positive stretching by providing a stretching step, it is less likely to undergo heat shrinkage than the heat-shrinkable film 6 or the heat-shrinkable composite film 7. The object to be packaged is wrapped with the heat-shrinkable air bubble cushioning material 1, heat-sealed with the heat-shrinkable film 6 or the heat-shrinkable composite film 7 on the outside, and heat-shrinked in the shrink tunnel, whereby the heat-shrinkable film 6 or Only the heat-shrinkable composite film 7 shrinks, and the portion of the bubble cushioning material 10 composed of the cap film 2, the back film 3 and the liner film 4 hardly shrinks. As a result, the back film 3 has a wrinkled shape in association with the heat shrinkage of the heat shrinkable film 6 or the heat shrinkable composite film 7, but the cap film 2 is only slightly mechanically deformed. However, the deformation of the liner film 4 is smaller than that of the cap film 2. The bubble chamber 5 also has a slightly inclined shape, but the essential shape of the bubble chamber 5 does not change. This action is
The same applies to the heat-shrinkable bubble cushioning material 1 shown in FIG. 6 as well as the heat-shrinkable bubble cushioning material 1 shown in FIG. In the case of packaging with the heat-shrinkable air bubble cushioning material 1 shown in FIG. 6, the back film 3 is in contact with the object to be packaged. When the heat-shrinkable film 6 or the heat-shrinkable composite film 7 is pasted on the liner film 4 side (exemplified in FIG. 6), it is deformed by heat more than when it is pasted on the back film 3 side (illustrated in FIGS. 1 to 5). Grows larger. At the time of packaging, the heat-shrinkable film 6 or the heat-shrinkable composite film 7 on the outer surface of the heat-shrinkable bubble cushioning material 1 is
Heat shrinks as described above. As a result of the heat shrinkage, the heat-shrinkable film 6 or the heat-shrinkable composite film 7 increases the thickness of the film, making it easier to absorb the impact from the outside.

When the heat-shrinkable film 6 or the heat-shrinkable composite film 7 is pasted on the liner film 4 side (illustrated in FIG. 6), it is pasted on the back film 3 side (illustrated in FIGS. 1 to 5). It has different characteristics. In FIG.
Even if the heat-shrinkable film 6 is heat-shrinked after packaging, the shrinkage deformation of the back film 3 and the cap film 2 is not so large as in the case of the heat-shrinkable film 6 alone. on the other hand,
When the heat-shrinkable film 6 is provided on the liner film 4 side as shown in FIG. 6, only the top portion of the cap film 2 resists the shrinkage deformation of the heat-shrinkable film 6.
Compared to the case of FIG. 1 which is thick and resists over the entire area of the backing film 3, the shrinkage of the cap film 2 and below is large in accordance with the shrinkage of the heat-shrinkable film 6. This phenomenon is shown in FIG.
Even if the liner film 4 is provided as described above, if the thickness of the liner film 4 corresponding to the top of the cap film 2 is thin, the heat-shrinkable film 6 accompanies the contraction deformation of the cap film 2 or less. There is no change in the principle that the bubble cushioning material 10 easily contracts and deforms.

[0031]

The heat-shrinkable film 6 and the heat-shrinkable composite film 7 used in the present invention each have a gel fraction of 50 to 95.
% Of the cross-linked portion 8 is stretched, and is superior to the heat-shrinkable films 6 and 7 of the non-cross-linked portion 9 material which exhibits rubber-like elasticity and has a large shrinkage force and a large shrinkage ratio and a low shrinking force and a shrinkage ratio. As described in the section of action, in the extrusion lamination step, fusion can be performed even at a low temperature, and further, shrinking to a high temperature is difficult. That is, when the fusion temperature is low and the shrinkage lower limit temperature is high, the temperature range in which extrusion lamination can be performed can be widened. Similarly, the shrinking start temperature required for tight packing is low, and the lower limit temperature at which the bubble chamber 5 is crushed due to the high temperature is high, so that the temperature range during heat shrink wrapping is wide and the wrapping operation is easy. Become. When the heat-shrinkable film 6 and the heat-shrinkable composite film 7 are provided on the liner film 4 side, the heat-shrinkable bubble cushioning material 1 is largely deformed during heat shrinkage.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a heat-shrinkable air bubble cushioning material.

FIG. 1 is a perspective view showing a first embodiment of a B heat-shrinkable bubble cushioning material.

FIG. 2 is a cross-sectional view showing a second embodiment of the heat-shrinkable air bubble cushioning material.

FIG. 2 is a perspective view showing a second embodiment of the B-heat-shrinkable bubble cushioning material.

FIG. 3 is a cross-sectional view showing a third embodiment of the heat-shrinkable bubble cushioning material.

FIG. 4 is a sectional view showing a fourth embodiment of the heat-shrinkable bubble cushioning material.

FIG. 5 is a sectional view showing a fifth embodiment of the heat-shrinkable bubble cushioning material.

FIG. 6 is a cross-sectional view showing a sixth embodiment of the heat-shrinkable bubble cushioning material.

[Explanation of symbols]

 1 heat-shrinkable air bubble cushioning material 2 cap film 3 backing film 4 liner film 5 air bubble chamber 6 heat shrinkable film 7 heat shrinkable composite film 8 crosslinked portion 9 non-crosslinked portion 10 air bubble buffering material

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[Procedure amendment]

[Submission date] February 14, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1A is a cross-sectional view showing a first embodiment of a heat-shrinkable bubble cushioning material. 3B is a perspective view showing a first embodiment of the heat-shrinkable bubble cushioning material. FIG.

FIG. 2A is a sectional view showing a second embodiment of the heat-shrinkable bubble cushioning material. B is a perspective view showing a second embodiment of the heat-shrinkable air bubble cushioning material.

FIG. 3 is a cross-sectional view showing a third embodiment of the heat-shrinkable bubble cushioning material.

FIG. 4 is a sectional view showing a fourth embodiment of the heat-shrinkable bubble cushioning material.

FIG. 5 is a sectional view showing a fifth embodiment of the heat-shrinkable bubble cushioning material.

FIG. 6 is a cross-sectional view showing a sixth embodiment of the heat-shrinkable bubble cushioning material.

[Explanation of reference numerals] 1 heat-shrinkable air bubble cushioning material 2 cap film 3 backing film 4 liner film 5 air bubble chamber 6 heat shrinkable film 7 heat shrinkable composite film 8 crosslinked portion 9 non-crosslinked portion 10 air bubble cushioning material

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Figure 3]

[Figure 4]

[Figure 6]

[Fig. 2]

[Figure 5]

Claims (2)

[Claims] 1. A heat-shrinkable bubble-cushioning material comprising a heat-shrinkable film, which is a cross-linked film, attached to one surface of a bubble-cushioning material made of a non-crosslinked resin. 2. A gel fraction made of an ethylene resin, which is one of a polyethylene resin, an ethylene / vinyl acetate copolymer resin, an ethylene / ethyl acrylate copolymer resin, or a mixture of these resins, as a raw material. The heat-shrinkable bubble cushioning material according to claim 1, wherein a crosslinked film in the range of 95% is used as the heat-shrinkable film.