JPS61178820A - Packaging method using expandable heat-shrinkable sheet - 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 (Part I of the Invention) Specifically, the present invention is directed to forming a desired printed portion on the surface of a heat-shrinkable sheet in advance with a foamable ink containing heat-foamable resin particles on the surface of the sheet. A foaming method characterized by packaging an object with a heat-shrinkable sheet, then heat-treating it to form a foam layer on the printed part, and then wrapping it with a heat-shrinkable sheet that closely fits the shape of the object. This invention relates to a packaging method using a heat-shrinkable sheet.

(Prior Art) Conventionally, there has been known a packaging method that uses a heat-shrinkable sheet provided with a foam layer to provide a cushioning effect.

However, since the foam layer is bulky, it not only requires a large space for storing and transporting the packaging material and packaging machinery, but also is not easy to work and operate. In addition, the foam layer may inhibit sheet welding (heat sealing) during bag making, or the foam layer may not soften sufficiently due to its poor thermal conductivity, causing the heat-shrinkable sheet to conform to the shape of the packaged item. However, it has the disadvantage that it is difficult to make a close contact.

(Objective of the Invention) The present invention has been developed through intensive research in view of the above circumstances, and the present invention is based on the following: A desired printed area is provided on the surface of a heat-shrinkable sheet using foamable ink, and this unfoamed foamable heat-shrinkable sheet is applied. Therefore, this packaging material is not bulky and has good thermal conductivity, and furthermore, it is possible to form a foam layer with a desired different thickness on the printed part. It is an object of the present invention to provide a packaging method that has improved sheet weldability, adhesion to the packaged object, and cushioning properties, and exhibits unprecedented effects.

(Structure of the Invention) The heat-shrinkable sheet of the present invention may be of any known type (
The material is vinyl chloride resin, polypropylene resin, polyethylene resin, etc., the thickness is 0.01~0.07 mm, the shrinkage rate is 40~85 inches, and the shrinkage temperature is 160~220℃.
, the time required for contraction is 2-5 seconds. Further, its characteristics are appropriately adjusted and selected to suit the foaming ink, the foaming temperature and foaming rate of the thermally foamable resin particles, etc., which will be described later.

The heat-expandable resin particles according to the present invention are particles of a thermoplastic resin with low gas permeability that includes or contains a well-known expansion agent, and has a particle size of 1 to 500 μm, preferably 10 to 10 μm.
0μ, and the shape is preferably approximately spherical. In addition, the content of the expanding agent is preferably 10 to 20% by weight when the expanding agent is a low-boiling liquid expanding agent described below (hereinafter, weight - is abbreviated as wt%), and 20 to 50% by weight for a decomposable expanding agent. It is.

Low-boiling liquid expansion agents include propane, butane, isophane,
Pentane, isopentane, neopentane.

Low-molecular hydrocarbons such as hexane and heptane, halogenated hydrocarbons such as trichloromonofluoromethane, dichlorodifluoromethane, and dichlorotetrafluoroethane, and petroleum ethers are applicable. ,
2'-azobisisobutyronitrile, azodicarbonamide, azocarboxylic acid dialkyl ester, diazoaminobenzene.

Paratoluenesulfonyl hydrazide, sodium bicarbonate, ammonium bicarbonate, etc. are chemically thermally decomposed to generate gas, and are applied together with a decomposition accelerator if necessary.

Polymer resins with low gas permeability such as polyvinylidene chloride, polyacrylonitrile, polyester, polyamide, polyurethane, and polycarbonate are used as thermoplastic resins, and for the purpose of modification, divinylbenzene, Esters of methacrylic acid, esters of acrylic acid.

Vinyl acetate, vinyl chloride, styrene, etc. are applied together with various polymerization initiators and stabilizers.

In order to obtain the thermally foamable resin particles, for example, a low-boiling point liquid expanding agent and a thermoplastic resin monomer may be mixed and polymerized under pressure, or the decomposable expanding agent and the thermoplastic resin may be mixed in a solvent. After mixing and dissolving the resin in the non-solvent, the resin may be pulverized in the non-solvent.

The foaming ink according to the present invention is a mixture of the thermally foamable resin particles and a well-known aqueous emulsion such as ethylene-vinyl acetate copolymer emulsion, vinyl acetate-acrylic acid ester copolymer emulsion, or polyacrylic acid ester emulsion. It is composed of a dry-type print binder or an organic solvent-type print binder made of a drying organic solvent that does not attack the heat-foamable resin particles and a thermoplastic resin. The type of resin in the print binder, the resin content, and the content of heat-foamable resin particles in the print binder are appropriately adjusted depending on the characteristics such as adhesion to the heat-shrinkable film, thickness of the foam layer, and strength of the foam film. be done. Generally, the resin content in the print binder is 20 to 50 wt%, and the content of thermally foamable resin particles is 1
0 to 50 wt% is suitable.

Here, in the present invention, particularly preferred foaming inks include:
Expanding agents are butane, isobutane, and pentane.

It is a copolymer resin consisting of vinylidene chloride and acrylonitrile as the main components of a thermoplastic resin with a low content of isopentane and an expansion agent content of 10 to 20%.
Particles of thermally foamable resin having a particle size of 5 to 50 μm are used, and the particles are contained in an aqueous emulsion type print binder, which is an ethylene-vinyl acetate copolymer emulsion, at 20 to 50 wt%. .

The above thermally foamable resin particles are heated at a temperature of 110-140°C for 5 seconds to
When heated for 1 minute, the particle size expands 4 to 5 times, and the thickness of the foamed ink printed on a heat-shrinkable sheet similarly expands 5 to 15 times.

Next, the packaging method of the present invention will be described.

First, screen printing or roll printing is performed using foam ink on the inner or outer surface of the packaged heat-shrinkable sheet to provide printed portions that will become desired characters and designs. Here, by using foaming inks with different colors or contents of thermally foamable resin particles, and by adjusting the thickness of the printed layer, foam layers of various different colors or thicknesses can be mixed. It is also possible to form it by

Next, the foamable ink in the printed area is dried at a temperature lower than the shrinkage temperature of the heat-shrinkable sheet and the foaming temperature of the heat-foamable resin particles (<50 to 70°C) to create an unfoamed foamable heat-shrinkable sheet.

Using this foamed heat-shrinkable sheet, wrap the packaged item in a slightly larger size, and weld the open end of the sheet with a heat plate to create an airtight seal with a volume that is 1.2 to 1.5 times the volume of the packaged item. After storing the packaged item in a bag, the item is passed through a normal tunnel-shaped heating device, and the temperature at which the foamable ink foams is 11.
Heat treatment is performed at 0 to 140°C for 5 to 30 seconds, and then holes are formed in a part of the bag-shaped heat-shrinkable sheet using needle-like protrusions, and the temperature at which the heat-shrinkable sheet contracts is 160-22°C.
Heat treatment may be performed at 0° C. for 4 to 5 seconds to shrink and mold the foamed heat-shrinkable sheet into close contact with the shape of the packaged item.

Although the heating device used for the above heat treatment is not specified, a hot air tunnel-shaped heating device with good thermal conductivity is preferable. Further, when a far-infrared lamp is used as a heat source, the heat treatment time is shortened, and it is suitable for performing the foaming process and the shrinking process continuously.

Note that the heat treatment temperature is appropriately adjusted depending on the characteristics of the heat-shrinkable sheet and the foamed ions.

(Example of the invention) The present invention will be explained below with reference to Examples.

Example 1 Vinylidene chloride-acrylonitrile copolymer with a particle size of 10 to 20 μm containing butane (15 wt%) (resin content 40 μm)
Using a foaming ink consisting of 70 wt% (wt%), screen printing was performed on the surface of a polypropylene heat-shrinkable sheet (2) (thickness: 0.05 mm), excluding the welded parts, to create a polka dot pattern. A printed portion (1 g) (thickness 0.05 mm) was provided.

Next, after drying the printed area with warm air at a temperature of 50 to 60°C, wrap the paper containing cosmetics (3) with this sheet in a slightly larger size with the printed area (1a) inside, and then wrap it in the usual manner. The open end was welded airtight. This product is passed through a hot air tunnel whose heat source is a far-infrared lamp, and first heat-treated with hot air at a temperature of 130°C for 10 seconds to form a foam layer (1b ), and at the same time, the sheet (2) was slightly heat-shrinked to give the sheet (2) a balloon-like shape. Here, since the sheet is inflated like a balloon, the heat treatment of the printed portion +11 is carried out quickly and unevenly.

Subsequently, a through hole was formed in a part of the sheet that was inflated like a balloon with needle-like protrusions in the hot air tunnel, and the sheet was continuously heated for 4 to 5 seconds with hot air at a temperature of 170 to 180°C. Then, the sheet (2) was tightly wrapped on the paper.

A transparent polypropylene sheet having a foam layer with a polka dot pattern was used to beautifully package the paper bag, and the foam layer sufficiently performed its function as a cushioning material.Example 2 The foamable resin particles of Example 1 were A cosmetic was obtained in the same manner as in Example 1, except that the treatment temperature and time to form a particle size layer containing 2,2'-azobisisobutyronitrile (40 wt%) were 110°C and 20 seconds. It was possible to tightly package the paper with a transparent polypropylene sheet having a polka dot pattern foam layer (thickness: 0.2 to 0.3 x m).

(Effects of the Invention) As described above, in the packaging method of the present invention, the packaging material does not become bulky, a large space is not required for storing and transporting the packaging material, and packaging machinery, and work and operation are facilitated. Also,
Not only is the sheet welding property, the adhesion between the packaged item and the sheet good, and the cushioning property good, but also it is possible to provide a packaged product with a beautiful appearance. Furthermore, printing process 1 using foam ink
By carrying out the foaming process and shrinking process continuously,
It is possible to provide a useful packaging method with fewer types of materials and simplified processes.

[Brief explanation of drawings]

Each figure is an explanatory view showing one embodiment of the present invention. Figure 1 is a diagram of a sheet printed with foam ink packaged in a packaged object, Figure 2 is a diagram of the formation of a foam layer after heating, Figure 3 is a diagram of the final packaging state after heat-shrinking the sheet.

Claims (1)

[Claims] 1. A step of printing desired characters and designs on the surface of a heat-shrinkable sheet with foaming ink containing heat-foamable resin particles, and making the packaged item airtight using the heat-shrinkable sheet. A process of packaging to form a package, heating the package in a heating device to form a foam layer on the printed part of the heat shrink sheet, and then providing a through hole in a part of the heat shrink sheet. 1. A packaging method using a foamable heat-shrinkable sheet, which comprises the following step of shrink-molding the heat-shrinkable sheet in close contact with the shape of an object to be packaged. 2. A packaging method using a foamable heat-shrinkable sheet according to claim 1, wherein the heat-foamable resin particles are thermoplastic resin particles containing a low-boiling liquid expansion agent. 3. A packaging method using a foamable heat-shrinkable sheet according to claim 1, wherein the heat-foamable resin particles are thermoplastic resin particles containing a decomposable expansion agent. 4. Claim 2, wherein the low-boiling liquid expanding agent is at least one of butane, isobutane, pentane, and isopentane, and the thermoplastic resin is a copolymer resin consisting of vinylidene chloride and acrylonitrile as main components. A packaging method using the foamable heat-shrinkable sheet described above.