JPS59230720A - Covering method of heat shrinking label - Google Patents

Abstract

PURPOSE:To achieve the covering a shrinking label accurately and with an uniform tightness by heating the label in which a laminate sheet having a low temperature foaming resin layer on a heat shrinking substrate film is formed cyrindrical with the resin layer inward on a specified conditon after a bottle or the like is covered therewith. CONSTITUTION:A label in which a laminate sheet having a low temperature foaming resin layer 2 on a heat shrinking substrate film 1 is formed cylindrical with the resin layer 2 inward on a bottle or the like to cover by shrinking. Here, the covering of the heat shrinking label is done by heating it below the temperature that meets the expression sigmaf=20te/tf as given when the tensile strength sigmaf[kg/cm<2>] of the heat shrinking substrate 1 in the weak direction at a certain temperature is expressed by the thickness tf[mu] of the substrate film before heating and the dry thickness te[mu] until the thickness of the low temperature foaming resin layer 2 increases more than 1.5 times.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of coating heat-shrinkable labels. More specifically, the present invention relates to a method of covering and adhering a foamable shrinkable label, which protects a container such as a glass bottle that is easily damaged by impact, and at the same time functions as a decorative or display label.

Shrink wrapping or label covering made of only heat-shrinkable film is well known, but those made of a single film tend to shift position after wrapping and lack cushioning properties, making it difficult to retain and remove the film. It was inferior.

Therefore, a method has been proposed in which a composite sheet is formed into a cylindrical shape and has a layer that simultaneously expands during shrinkage coating by heating. However, in this case, the cylindrical body was placed over a bottle, etc.! When simply heated, the low-humidity foaming ink not only foams in the thickness direction, but also tries to foam in the direction perpendicular to the thickness, that is, in the plane direction, which creates a force that stretches the shrinkable film that has become flexible due to heating. , the film may be stretched non-uniformly by σ1, resulting in unevenness, or may be stretched entirely, resulting in problems such as not coming into close contact with the surface of the glass bottle.

The present invention solves these problems and provides a coating method capable of reliably shrink-coating a shrinkable label having a foam layer with high cushioning properties in a uniform and tightly adhered state.

That is, in the present invention, a label is formed by forming a laminated sheet in which a heat-shrinkable base film is provided with a low-temperature foamable resin layer into a cylindrical shape with the resin layer inside, and the label is placed over a bottle or the like and heated to shrink. When coating, the tensile strength of the heat-shrinkable base film at a certain temperature in the direction where the tensile strength is weak is σf[
kg/i], and the thickness of the heat-shrinkable base film before heating is 1. (2), the thickness of the low-temperature foamable resin layer is telAI, and the temperature is below that satisfies σf = 20tc/lf and the thickness of the low-temperature foamable resin layer is 1
．． This is a heat-shrinkable label coating method characterized by heating until the temperature increases by 5 times or more.

, will be explained below with reference to the attached drawings.

Figure 1 is a graph showing the relationship between heating temperature ('C) and increase in foam layer thickness (double) of the label, Figure 2 is heating temperature ('C)
The tensile strength of the heat-shrinkable base film is kg/c! l)
FIG. 3 is a cross-sectional view showing an example of a label before heating used in the present invention.

If the heating temperature is higher than the temperature that satisfies σ = 20tc/lf, unevenness will occur on the label surface, and if the thickness of the low-temperature foaming resin layer is less than 1.5 times, the cushioning properties will be poor. Since the writing conditions are not improved, the heating conditions of the present invention are required. The reason for this is not necessarily clear, but in the label shown in FIG. 3, as the heat-shrinkable base film 1 increases in size as shown in FIG.
When the temperature exceeds a certain level, the base film 1 is stretched in the direction of weak tensile strength, causing unevenness.

The heat-shrinkable base film used in the present invention is made of various thermoplastic resins such as polyvinyl chloride, polyethylene terephthalate, and polyethylene, and has a stretching ratio of 1.5 times or less in the axial direction when made into a label. Examples include heat-shrinkable films that are 1.3 times or more thicker in the circumferential direction.

In addition, the low humidity foamable resin formed on this base film is
As the foaming material, for example, a capsule-shaped foaming agent having a particle size of 5 to 20 microns is used, in which resin particles are encapsulated with low-boiling point carbonized tree leaf gas such as isobutane, ethane, propane, hexane, or the like. If the particle size is less than 5 μm, it is technically difficult to manufacture, and if it is more than 20 μm, the film-like surface becomes poor and the foaming temperature increases, which is not preferable. Resin particles include vinylidene chloride, methyl methacrylate, acrylonitrile, etc. It is important to adjust the amount of hydrocarbon gas and resin depending on the type of base film and select a blowing agent with a foaming temperature suitable for the base film. It is. That is, the shrink processing hot air temperature is 190 to 230 depending on the shrink processing humidity of the base film.
In the case of base films such as polyethylene, polyvinyl chloride, etc., which have a length of 'C x 10 seconds, the blowing agent is
A relatively low-temperature foaming agent that foams at 120°C for 1 to 2 minutes is particularly suitable; in this case, the resin particles contain 65 to 85% vinylidene chloride and 15 to 3% acrylonitrile.
A mixture of resin particles of about 5% is suitable and gives good results.

Low-temperature foamable resin is made by adding a synthetic resin binder to the above-mentioned foaming agent. You can choose as you like, but for polyvinyl chloride, polyester + polyisocyanate,
Silicone resin, polyvinyl acetate, vinyl chloride/vinyl acetate copolymer, etc., polyethylene terephthalate includes polyester + polyisocyanate, polyethyleneimine,
Polyisocyanates, polyvinyl acetate, vinyl chloride/vinyl acetate copolymers, vinyl acetate/ethylene copolymers, polyacrylates, polyacrylic esters, and acrylate/vinyl acetate copolymers, polyester monomers and catalytic systems for polystyrene; Examples include polymethyl methacrylate monomer, cyanoacrylate, polystyrene and polyamide (persamide type).

Organic solvents used for dissolving such synthetic resin binders include aromatics such as toluene, xylene, alcohols such as isopropanol, isopropyl alcohol, acetic acid esters, tetrahydrocarbons, tetrahydrofuran, etc. It may be selected depending on the type of synthetic resin binder.

The appropriate amount of the blowing agent to be added is 5 to 30 parts by weight, preferably 10 to 15 parts by weight, per 100 parts by weight of the synthetic resin base. If the amount is less than 5 parts by weight, foaming will be insufficient, and if it is more than 30 parts by weight, the adhesion to the base film 1 will be poor, which is not preferable.

Next, to obtain the laminated sheet for labels used in the present invention, the synthetic resin binder is stirred in an organic solvent at room temperature to obtain a resin solution. Mixing may be performed under humidification if necessary.

Next, the capsule-shaped foamed particles adjusted to foam according to the shrinking processing temperature of the shrinkable base film are added to this resin solution, and the powdered resin particles are uniformly dispersed in the resin solution by stirring. The obtained low-temperature foamable resin is applied onto a shrinkable base film by a commonly used method such as gravure, and then dried at room temperature (below 40°C) for about 1 minute to form a close contact with Q-. at least in the stretching direction (
When formed into a cylindrical shape, it must shrink by 30% or more in the circumferential direction. Therefore, when the tensile strength at humidity for shrinking by 30% is σf3o [yu/crl], σ ≧2
The material of the film, the thickness of the film,
It is practically preferable to configure the label sheet by selecting the coating thickness of the foamable resin layer.

The label sheet thus obtained is formed into a cylindrical shape, placed over a bottle, preheated to usually 50°C in a preheating furnace, sent to a shrink tunnel controlled at a predetermined temperature, and heated and shrunk according to the conditions of the present invention. In this case, a label having an excellent appearance and a uniform foam layer without wrinkles and having excellent mild impact properties can be tightly coated. The present invention will be explained in more detail with reference to Examples below.

Example 1 15% by weight of an acrylic resin (BR102 manufactured by Mitsubishi Rayon Co., Ltd.) was added to a mixed solution of 50% by weight of isopropyl alcohol and 20% by weight of ethyl acetate/I/I to obtain a resin solution with stirring at room temperature. To this resin solution, 15% by weight of capsule-shaped foamed particles (Microfere F-30 manufactured by Matsumoto Yushi Co., Ltd.), which are made of mixed resin particles containing vinylidene chloride and acridinitrile (7:3) and isobutane gas sealed, were added, and the mixture was heated to room temperature. The mixture was stirred so that the foamed particles were uniformly dispersed in the resin liquid.

This dispersion was applied by gravure onto a vertically axially stretched polyvinyl chloride film (Hishirex 502 manufactured by Mitsubishi Plastics Co., Ltd.) with a thickness of 50 μm and a stretching ratio of 2.5 times, dried for 1 minute at room temperature, and foamed to a film thickness of 50 μm. Form the foamable resin layer into a cylindrical shape with a circumference of 222cm with the foamable resin layer on the inside.
It was placed on a 1300 cc bottle and heated in a hot air oven at 20'O ℃ to a predetermined temperature in the range of 85 ℃ to 105 ℃ to cause shrinkage and foaming, and the increase in the thickness of the foam layer was measured. The results were plotted on the graph of FIG. 1 to obtain a curve H1.

At 105° C. (point 81 in FIG. 1), unevenness occurred on the label surface.

Example 2 The same dispersion as in Example 1 was applied to a longitudinally axially stretched styrene-butadiene copolymer film with a thickness of 50μ and a stretching ratio of 4°0 to form a foamed layer with a thickness of 50μ. When we performed the same evaluation as above, we found that at 100℃ (82 points in Figure 1)
Irregularities were observed on the film surface.

Next, when the polyvinyl chloride film of Example 1 and the styrene-butadiene copolymer film of Example 2 were made into cylindrical labels, the tensile strength in the transverse direction corresponding to the axial direction was measured, and the results are shown in Figure 2. , the polyvinyl chloride film is Ml, and the styrene-butadiene copolymer film C1 is M.

The curve was Transverse tensile strength of polyvinyl chloride film at 81 points (105°C), 81 points (100°C)
The tensile strength of the copolymer film at
, = 50μ, and the foamable resin layer thickness tc = 50
Since μ, 50 σ/ = 20 tc/lf = 20 x 100 = 20, satisfying the formula, it is understood that polyvinyl chloride needs to be heated at 105°C or lower, and polystyrene needs to be heated at 100°C or lower.

In addition, the tensile strength was also determined in the longitudinal direction (stretching direction) of the film, and a curve of T1 was obtained for the polyvinyl chloride film, and a curve of T2 was obtained for the styrene-butadiene copolymer film. It was greater than the tensile strength.

The temperature measurement method during shrinkage processing in Examples 1 and 2 is as follows.

A temperature-indicating tape that indicates the temperature by color change is attached to the portion of the cylindrical film that is not coated with the foamable resin, and the film is visually observed to see if a predetermined temperature has been reached.

Example 3 The same dispersion as shown in Example 1 was applied to a shrinkable polystyrene film (DXLOI manufactured by Mitsubishi Plastics Co., Ltd.) with a thickness of 50 μm (stretching ratio: 4.0) using gravure so that the film had a dry thickness of 15 μm. After coating, it was dried for 1 minute at room temperature to obtain a label sheet. This sheet was formed into a cylindrical shape with a diameter of 111 tnx with the foamed resin layer on the inside, and a cylinder with a height of about 14 cm, a waist circumference of about 6.5 cm, and a capacity of 30 cm.
Cover it with a 0CC bottle and preheat it to 50℃, then heat it to 200℃.
When heat-shrinked for 10 seconds, the foaming ratio was approximately 15.
A wrinkle-free covering with good cushioning properties was obtained, which was twice as uniformly foamed.

Example 4 15% by weight of an acrylic resin (BR102 manufactured by Mitsubishi Rayon Co., Ltd.) was added to a mixed solution of 50% by weight of isopropyl alcohol and 20% by weight of ethyl acetate, and the mixture was stirred at room temperature to obtain a resin solution.

Capsule-shaped foamed particles (Microfere F-40 manufactured by Matsumoto Yushi Co., Ltd.) are made by encapsulating isobutane gas in mixed resin particles containing vinylidene chloride as a main component and a small amount of methyl methacrylate and acrylonitrile in this resin solution.
15% by weight was added and stirred at room temperature so that the foamed particles were uniformly dispersed in the resin liquid.

This dispersion was applied to a polyvinyl chloride film with a thickness of 50μ and a stretching ratio of v2.5 (Hishit, 7x50, manufactured by Mitsubishi! Co., Ltd.).
2) After coating by gravure, a foamable resin layer having a thickness of 15 μm was formed by drying at room temperature for 1 minute to obtain a label sheet.

Place this sheet with the foam resin layer on the inside.
It was formed into a 11M cylindrical shape, placed on a bottle of the same size as in Example 1, preheated to 50°C, and subjected to shrinkage processing at a hot air temperature of 230°C for 10 seconds, resulting in a uniform foam with a foaming ratio of about 15 times. A covering body was obtained in which a foamed label with no wrinkles and good cushioning properties was tightly coated.

In Example 3.4, the base film has approximately the same thickness as in Example 1.2, but because the low-temperature foamable resin layer is as thin as 15 μm, the tensile strength of the base film is σ−″−20 tc. /
Since each small temperature diameter of 1f = 6 (kg/ffl) can be heated to a high temperature, even if the low temperature foaming resin layer is sufficiently heated to a high magnification of 15 times, there will be no unevenness on the label. Does not occur.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between heating temperature and the amount of increase in the foam layer thickness of the label, and FIG. 2 is a graph showing the relationship between heating temperature and tensile strength. FIG. 3 is a cross-sectional view showing an example of a label before heating used in the present invention.OHX...Relationship between the increase in thickness of the foam layer (fold) and the heating temperature M1...The side of the polyvinyl chloride film Relationship between directional tensile strength and heating temperature M2... Relationship between lateral tensile strength and heating temperature of styrene-butadiene copolymer film T1... Relationship between longitudinal tensile strength of polyvinyl chloride film and heating temperature T...Relationship between lateral tensile strength and heating temperature of styrene-butadiene copolymer film 1...Heat-shrinkable base film 2...Low-temperature foamable resin layer Patent applicant Mitsubishi Plastics Co., Ltd. Agent Patent attorney Yoshio Kimura Figure 1 no 9% 31jc ('C/ - Figure 2 Shioguchisha 5LK ('C) - Figure 3 Procedural amendment ζ/IA issued) Showa evening? Z month Saturday and Sunday, Commissioner of the Patent Office 1. Display of the case 1929 patent application No. 1 I4-7F No. 2, title of the invention Huangdai Mata φ voice 1. Relationship between patent applicant

Claims (1)

[Claims] A label made of a laminated sheet with a heat-shrinkable base film and a low-temperature foamable resin layer formed into a cylindrical shape with the resin layer inside is placed on a bottle, etc. and heated to shrink. When coating, the tensile strength in the direction where the tensile strength is weak at a certain temperature of the heat-shrinkable base film is σI Ckl? /ad)
. The thickness of the heat-shrinkable base film before heating is 1. (2)
. When the dry thickness of the low temperature foamable resin layer is tc (capital). At a temperature that satisfies σ -20tc/tf or less, the thickness of the low-temperature foamable resin layer is 1,
A method for covering a heat-shrinkable label, the method comprising heating the label until the temperature increases by 5 times or more.