JPS61178819A - 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 (IF) The present invention provides a method for printing a desired print on the surface of a heat-shrinkable sheet with an ultraviolet curable foaming ink containing heat-foamed particles, and packaging an object with the sheet. A foamable heat-shrinkable sheet is characterized in that a foam layer is formed on the printed portion by irradiation with ultraviolet rays, and then the heat-shrinkable sheet is brought into close contact with the object to be packaged in a heating device for packaging. Regarding the packaging method used.

(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.

(Purpose of the Invention) The present invention has been developed through intensive research in view of the above circumstances, and has been developed by providing a desired printed area on the surface of a heat-shrinkable sheet with ultraviolet curable foaming ink, and using the unfoamed foamed heat-shrinkable By applying the sheet and serving it as a packaging material for the packaged item, this packaging material does not become bulky, has good thermal conductivity, and also has good sheet weldability, adhesion to the packaged item, and cushioning properties. It is an object of the present invention to provide a packaging method that is improved in terms of the packaging method and exhibits unprecedented effects.

(Structure of the Invention) The packaging method of the present invention includes the steps of printing desired characters and designs on the surface of a heat-shrinkable sheet with ultraviolet curable foaming ink containing heat-foamed particles, and wrapping the sheet using this sheet. A process of packaging an object to form a package, irradiating the package with ultraviolet rays to form a foam layer on the printed part of the sheet, and then tightly fitting the sheet to the shape of the packaged object in a heating device. The method is characterized in that it consists of a step of shrink-molding.

(Specific configuration of the invention) The heat-shrinkable sheet according to the present invention may be a well-known one,
The material is vinyl chloride resin, polypropylene resin, polyethylene resin, etc., and the thickness is 0.01~0.07go.
++, shrinkage rate is 40-85%, shrinkage temperature is 160-22
At 0°C, the time required for shrinkage is 2 to 6 seconds. Further, its characteristics are appropriately adjusted and selected to suit the foaming ink, the foaming temperature and foaming rate of thermally foamed particles, etc., which will be described later.

The thermally foamed 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 100 μm.
The shape is preferably approximately spherical, and the content of the swelling agent is 10 to 10.

20% by weight (hereinafter, weight% is abbreviated as wt%) is suitable.

Low-boiling liquid expansion agents include propane, butane, isobutane,
Pentane, impentane, neopentane.

Low-molecular hydrocarbons such as hexane and heptane, halogenated hydrocarbons such as trichloromonofluoromethane, dichlorodifluoromethane, and dichlorotetrafluoroethane, and petroleum ethers are applicable.

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 foamed particles, for example, a low-boiling liquid expansion agent and a thermoplastic resin may be mixed and suspension polymerized under pressure.

The ultraviolet curable foaming ink according to the present invention comprises the thermally foamable particles and a print binder whose main components are a well-known ultraviolet curable prepolymer and a photopolymerization initiator,
The print binder is selected to be one that does not attack the film-forming resin of the thermally foamed particles.

For the print binder, prepolymers such as polyester acrylate, epoxy acrylate, and urethane acrylate, and polymerization initiators such as thioxanthone (+ amine), benzophenone, and ketal are used. For example, adipic acid 1,6 -Hexanediol/acrylic acid, phthalic anhydride/propylene oxide/acrylic acid.

Bisphenol A, epichlorohydrin, acrylic acid,
Coelectric prepolymers such as polyester, tolylene diisocyanate, and 2-hydroxyethyl acrylate, and polymerization initiators such as isopropylthioxanthone, benzophenone, and benzyl dimethyl ketal are used.

The content of thermally foamed particles in the ultraviolet curable foamed ink is appropriately adjusted depending on the characteristics such as adhesion to the heat-shrinkable sheet, thickness of the foamed layer, and strength of the foamed film, and is usually 20 to 60wt.
tl- is preferred. This foaming ink also contains viscosity modifiers and diluents as needed.

Crosslinking Strengthening Agent 1 A coloring agent, a pigment stabilizer, etc. are blended.

The ultraviolet irradiation device used in the present invention is a well-known device, and a line light source type particularly suitable for irradiation in a flow process on a belt conveyor is employed. In addition, xenon lamps, low-pressure, medium-pressure, and high-pressure mercury lamps can also be used, but in particular, one to five high-power (4 to 20 KW) high-pressure mercury lamps can be used for short periods of time (5 to 10 seconds). It is preferable to foam the thermally foamed particles in the foamed ink and harden the print binder at the same time, and form a foamed layer with a thickness of 5 to 10 times the thickness of the printed layer on the printed portion of the surface of the heat-shrinkable sheet. can.

As is well known, the wavelength characteristics of a lamp are adjusted by filling a mercury lamp with various halogen metals, which are selected and adopted to match the ultraviolet curable prepolymer and photopolymerization initiator.

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

First, a desired printed portion is provided by screen printing or roll printing with foam ink except for the portion of the heat-shrinkable sheet that will be welded to the inner or outer surface of the package. This sheet is used to wrap a somewhat larger object, and the open end of the sheet is welded using a heat plate. Next, 1 to 5 high-pressure mercury lamps of usually 4KW to 20:9 are used on a belt conveyor, distance from the lamps is 10 to 25 cm, processing speed (conveyor speed) is 2 to 10 m/I1 m, lamp output is 30 to 160 W/w. The sheet is irradiated with ultraviolet rays under the following conditions, and the surface temperature of the sheet is adjusted to 70°C by the radiant heat of the ultraviolet rays, and the print binder in the printed area is cured while the sheet does not shrink due to heat, and the thermally foamed particles are expanded. to form a foam layer.

That is, it was essential to heat the thermally foamed particles to a temperature of 110 to 150°C to expand them, but in the packaging method of the present invention, the radiant heat of the ultraviolet rays and the heat generated by curing the print binder are used to expand the thermally foamed particles. It has become possible to form a foam layer on the surface of a heat-shrinkable sheet while the heat-shrinkable sheet does not shrink or only slightly shrinks.

Subsequently, the above-mentioned package is preferably passed through a tunnel-shaped heating device and heat-treated at a temperature of 160 to 220° C. for 4 to 6 seconds to transform the sheet with the foam layer into the form of a packaged product. It is sufficient if they are brought into close contact and shrink-molded.

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 ink.

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

Example 1 Particle size 10 to 20 μm containing butane (15 wt%)
An ultraviolet curable foam consisting of heat-foamed particles of polyvinylidene chloride-acryloni (J) copolymer resin, 40 wt%, and a print binder, 60 wt%. Using ink, screen printing was performed on the surface of a heat-shrinkable polypropylene sheet (thickness: 0.05 tm), excluding the welded areas, to provide a printed area (thickness: 0.05 m) with a polka dot pattern.

Next, a glass cylindrical bottle (with a plastic cap) containing a lotion was wrapped in a slightly larger size with the printed part inside, and the open end was welded in a conventional manner to form a package.

This package was placed on a rotary table and heated using a metal halide lamp (output 120 W/(up)) in the wavelength range of 250 to 400 nm, which mainly contains Fe, at a conveyor speed of 5 m/- from a distance of 20 (IB). The surface temperature of the sheet was 65 to 70°C, almost no thermal contraction of the sheet was observed, and the thickness of the polka dot pattern was 0.3 to 0.4 tx.
A foam layer of T was formed along the circumferential wall of the cylindrical bottle. Subsequently, the temperature is 180, where the heat source is a far infrared lamp.
4 on a belt conveyor in a hot air tunnel of ℃~200℃
The sheet was passed through the bottle for ~5 seconds to undergo continuous heat treatment, and the bottle was packaged with the sheet in close contact with the bottle.

A glass bottle of lotion was beautifully packaged using a transparent polypropylene sheet having a foam layer with a polka dot pattern, and the foam layer fully exhibited its function as a cushioning material.

(Effects of the Invention) As described above, in the packaging method of the present invention, the packaging material does not become bulky, and a large space is not required for storing and transporting the packaging material, as well as packaging machinery, and the work operation becomes easy. Moreover, not only the sheet weldability, the adhesion between the packaged object and the sheet, and the cushioning properties are good, but also a packaged article with a beautiful appearance can be provided. Furthermore, by continuously carrying out the printing process using foam ink, the foaming process, and the sheet shrinking process, it is possible to provide a useful packaging method that uses fewer types of materials and simplifies the process.

Claims (3)

[Claims] (1) The process of printing desired characters and designs on the surface of a heat-shrinkable sheet using ultraviolet curable foaming ink containing heat-foamable particles, and wrapping the packaged item using this sheet to form a package. and irradiating the packaged item with ultraviolet rays to form a foam layer on the printed portion of the sheet, followed by shrink-molding the sheet in close contact with the shape of the packaged item in a heating device. A packaging method using a foamable heat-shrinkable sheet, characterized by: (2) A packaging method using a foamable heat-shrinkable sheet according to claim 1, wherein the heat-foamed particles are thermoplastic resin particles containing a low-boiling point liquid expansion agent. (3) The second claim in which 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 a foamable heat-shrinkable sheet as described in 2.