KR102437851B1 - Heat Shrinkable Film for Label and Process of Preparing Same - Google Patents

Abstract

Disclosed in the present invention is a heat shrinkable film for a label composed of a PP layer (10) forming an intermediate layer and a pair of PET layers (20, 30) bonded to both sides of the PP layer to form an outer layer. The PP layer (10) and the pair of PET layers (20, 30) are bonded to each other by co-extruding an adhesive (compatibility agent) (15, 25) together. In the heat shrinkable film having a three-layered structure of the present invention, the PP layer (10) has a thickness of 80 to 90%, and the PET layers (20, 30) each have a thickness of 10 to 5%, so that the heat shrinkable film has the specific gravity less than 1. According to the present invention, water separation can be performed for the label, so that PET bottles can be easily recycled.

Description

Heat Shrinkable Film for Label and Process of Preparing Same

The present invention relates to a heat-shrinkable film used for forming labels on the outer periphery of various containers such as synthetic resin containers, glass bottles, aluminum cans, and the like. More specifically, the present invention relates to a heat-shrinkable film having a multilayer structure suitable for use as a film for labels of various containers.

The heat-shrinkable film is used for labels formed to surround the outer periphery of various synthetic resin containers such as polyester (PET) bottles, glass bottles, and aluminum cans (hereinafter collectively referred to as 'containers'). That is, the necessary contents are printed on the heat-shrinkable film, the printed film is adhered to the center in a cylindrical shape (called tubing or seaming), and the label is attached to the outer periphery of the container by applying hot air from the outside to shrink it.

As such, a heat-shrinkable film for manufacturing a label attached to be wrapped around the outer periphery of a container by heat shrinkage must satisfy various physical property conditions in consideration of the working process, quality, or appearance. Such physical properties include heat resistance, printability, adhesiveness, shrinkage, etc., and these properties must all be satisfied before it can be used as a label film.

Among the synthetic resin films known so far, PVC film is known to be the most suitable as a heat-shrinkable film for labels. PVC film has been widely used as a heat-shrinkable film for labels because its physical properties such as heat resistance, printability, adhesion, and stretchability are suitable for label films. However, PVC film has fatal flaws in environmental pollution because it generates environmental hormones. Therefore, Korea and Japan have already legally regulated the use of PVC film for label purposes, and other foreign countries are also in the process of regulating their use by law.

Therefore, it can be said that PET film and PS film were developed for the purpose of replacing PVC film for labels. PET film or PS film does not have the same environmental pollution problem as PVC film, and there is no problem of recovery or recycling, but there are many problems that need to be overcome in order to be used for labels.

The PET film has a specific gravity of about 1.3 and has good heat resistance, printability, and adhesion, but has a drawback in that overshrinkage occurs during heat shrinkage. If overshrinkage occurs, the container is crushed or deformed in the case of a synthetic resin container, not a glass bottle or aluminum can. Since PET film has good heat resistance, it has the advantage that it can be used even when sterilization is required at high temperatures such as fruit juice, usually at 95°C.

On the other hand, the PS film has good low-temperature shrinkability, has a specific gravity of about 1.05, is light, and does not cause over-shrinkage. Because of its good low-temperature shrinkability, it is suitable for use as a label for containers of dairy products such as milk or yogurt. Because overshrinkage does not occur, it is possible to maintain a beautiful appearance after heat shrinkage. However, since the PS film has difficult printability, there is a problem that an ink suitable for printing needs to be developed, and the adhesiveness is also difficult, which causes a problem in the tubing (or seaming) process.

In order to solve the above problems, the present inventor forms a PS-based film layer in an intermediate layer, and co-extrudes to form an outer layer, which is a PET-based film layer, on both sides of the intermediate layer. Heat shrinkability having a three-layer structure The film was developed and patented as Patent No. 10-1156607 (applied on Nov. 3, 2009).

However, although the heat shrinkable film of Patent No. 10-1156607 satisfies all physical properties for use as a label, it was found that there is a problem in recycling PET bottles. PET bottles with labels are cut and shredded into small pieces during recycling to separate the label from the main PET piece. When shredded PET pieces are put in water, PET with a specific gravity of about 1.3 sinks to the bottom, and the label floats on the water so that the label and PET can be easily removed. However, the heat-shrinkable film of Patent No. 10-1156607 has a PET specific gravity of about 1.3 and a PS specific gravity of about 1.05, so the shredded label does not float on the water but sinks with PET and separates the label by water separation. Can not.

Therefore, the present inventors have developed a heat-shrinkable film having a specific gravity of less than 1 to enable separation of labels by number, thereby leading to the development of a heat-shrinkable film of the present invention that can facilitate recycling of PET bottles.

An object of the present invention is to provide a new heat-shrinkable film for labels that can facilitate recycling of PET bottles by providing a heat-shrinkable film having a specific gravity of less than 1 to enable water separation of labels.

Another object of the present invention is to provide a heat-shrinkable film for a label that has a specific gravity of less than 1 and can satisfy the heat-resistance, printability, stretchability, and shrinkability of heat-shrinkable labels.

Another object of the present invention is to form a PP (polypropylene)-based film in an intermediate layer, and co-extrusion so that a PET (polyester)-based film is laminated on both sides of the heat for a label that can be produced without loss in the manufacturing process To provide a shrinkable film.

All of the above and other objects of the present invention can be achieved by the present invention described below.

The heat-shrinkable film for labels of the present invention is characterized in that it consists of a PP layer 10 forming an intermediate layer, and a pair of PET layers 20 and 30 bonded to both sides of the PP layer to form an outer layer. .

The PP layer 10 is composed of PP of the following structural formula,

-[-CH ₂ CH(CH ₃ )-] _n -

(Where n is the degree of polymerization of an integer)

PET of the PET layers 20 and 30 is PET-G (glycol modified polyethylene terephthalate) of the following structural formula:

(Where m and n are integer polymerization degrees).

The PP layer 10 and the pair of PET layers 20 and 30 are adhered to each other by co-extruding the adhesives (compatibility agents) 15 and 25 together.

The heat-shrinkable film for labels of the present invention is co-extruded into five layers, all of the PP layer 10, a pair of adhesives 15, 25, and a pair of PET layers 20, 30, but the adhesives 15, 25 occupies less than 0.5% by weight of the entire film, so it is described as having a structure of substantially the PP layer 10 and a pair of PET layers 20 and 30, that is, three layers.

The heat-shrinkable film having a three-layer structure of the present invention is characterized in that the PP layer 10 forms a thickness of 80 to 90%, and the PET layers 20 and 30 form a thickness of 10 to 5%, respectively. In the heat-shrinkable film having such a configuration, assuming that the specific gravity of PP is 0.9 and that of PET is 1.3, the film has a specific gravity of 0.94 to 0.98.

Hereinafter, the specific content of the present invention will be described in detail with reference to the accompanying drawings.

The present invention provides a heat-shrinkable film having a specific gravity of less than 1 to facilitate the recycling of PET bottles by enabling water separation of the label, and has a specific gravity of less than 1 and provides heat resistance, printability, and flexibility, which are the requirements for heat-shrinkable labels. The effect of the invention of providing a heat-shrinkable film for a label that can be produced without loss in the manufacturing process by forming a PP film layer in the middle layer and co-extruding the PET film layer on both sides, satisfying the newness and shrinkability have

1 is a schematic enlarged cross-sectional view of the heat-shrinkable film of the present invention formed by co-extrusion into five layers.

The present invention relates to a heat-shrinkable film used to form a label on the outer periphery of various containers such as synthetic resin containers, glass bottles, aluminum cans, and the like. It relates to a heat-shrinkable film for labels having a multilayer structure manufactured by co-extruding a pair of PET layers (20, 30) forming an outer layer.

1 is a schematic enlarged cross-sectional view of a heat-shrinkable film of the present invention formed by co-extrusion into five layers.

As shown in the enlarged cross-sectional view of FIG. 1 , the heat-shrinkable film for labels is a very thin film having a thickness t of about 40 μm, but has a laminated structure of five layers in the present invention. The heat-shrinkable film for labels of the present invention is co-extruded into five layers, all of the PP layer 10, a pair of adhesives 15, 25, and a pair of PET layers 20, 30, but the adhesives 15, 25 occupies less than 0.5% by weight of the entire film, so it is described as having a structure of substantially the PP layer 10 and a pair of PET layers 20 and 30, that is, three layers.

The heat-shrinkable film having a three-layer structure of the present invention is characterized in that the PP layer 10 forms a thickness of 80 to 90%, and the PET layers 20 and 30 form a thickness of 10 to 5%, respectively. When the thickness of each of the PET layers 20 and 30 exceeds 10%, the specific gravity of the film approaches 1.0 or becomes larger than 1.0, making water separation impossible. On the other hand, if the thickness of each of the PET layers 20 and 30 is less than 5%, it is not preferable because printability, heat resistance, or elasticity are affected. In the heat-shrinkable film having such a configuration, assuming that the specific gravity of PP is 0.9 and that of PET is 1.3, the film has a specific gravity of 0.94 to 0.98. Since the specific gravity of the label is less than 1, when water separation is performed, the label floats on the water and the PET sinks down, making it easy to separate the label. Since the label is easily removed, the recycling rate of PET bottles can be increased that much.

The PP layer 10 is composed of PP of the following structural formula:

-[-CH ₂ CH(CH ₃ )-] _n -

In the above formula, n is the degree of polymerization of an integer.

PP has a specific gravity of about 0.90 to 0.92 depending on the degree of polymerization. Because PP is located in the intermediate layer, it has no relation to printability, but it satisfies all of the requirements for a label such as heat resistance, stretchability, and shrinkability, and in particular, since the specific gravity is less than 1, it is used to produce the film for a label of the present invention having a specific gravity of less than 1. Suitable.

PET of the PET layers 20 and 30 is PET-G (glycol modified polyethylene terephthalate) of the following structural formula:

In the above formula, m and n are integer polymerization degrees.

PET has a specific gravity of about 1.25 to 1.30 depending on the degree of polymerization. Since the PET layers 20 and 30 have been used for the outer layer in the heat-shrinkable film of Patent No. 10-1156607, all of the requirements for a label such as heat resistance, printability, stretchability, and shrinkability are satisfied.

The PP layer 10 and the pair of PET layers 20 and 30 are adhered to each other by co-extruding the adhesives (compatibility agents) 15 and 25 together. The adhesive or compatibilizer is for bonding the PP layer 10 and the PET layers 20 and 30 to each other, and the PP layer 10, a pair of adhesives 15 and 25, and a pair of PET layers 20, 30) It is co-extruded so that it consists of all 5 layers. The technique of co-extrusion of the synthetic resin is a known technique and can be easily carried out by those skilled in the art to which the present invention pertains.

The film produced by co-extrusion goes through a stretching process to complete a heat-shrinkable film for labels. The finished film is printed with necessary contents depending on the product, and the printed film is attached to the container through cutting and tubing or seaming processes.

The present invention will be further embodied by the following examples, which are not intended to limit the protection scope of the present invention, but are described for illustrative purposes.

Example 1

To form the PP layer, a commercially available PP polymer having a specific gravity of 0.9 and a molecular weight of 40,000 was used, and to form the PET layer, PET-G, a product of Eastman Kodak, USA, having a specific gravity of 1.3 was used. A compatibilizer (adhesive) was added between the PP layer and the PET layer, co-extruded, and stretched to prepare a film having a three-layer structure in which a PP-based film and a PET-based film were laminated. By controlling the extrusion amount of PP and PET, the thickness of the PP layer 10 was 80%, and the thickness of each of the PET layers 20 and 30 was 10% to prepare a film. The specific gravity of this film was 0.98.

Example 2

In the same manner as in Example 1, except for preparing a film having a thickness of 85% of the PP layer 10 and a thickness of each of the PET layers 20 and 30 of 7.5% by controlling the extrusion amounts of PP and PET, the film was prepared in the same manner as in Example 1. was prepared. The specific gravity of this film was 0.96.

Example 3

In the same manner as in Example 1, except for preparing a film having a thickness of 90% of the PP layer 10 and a thickness of each of the PET layers 20 and 30 of 5% by controlling the extrusion amounts of PP and PET, the film was prepared. The specific gravity of this film was 0.94.

All of the films for labels of Examples 1-3 have a specific gravity of less than 1, and when water is separated from PET having a specific gravity of 1.3, the label floats on the water and the PET sinks down, so that the label can be easily separated.

All simple modifications and alterations of the present invention should be construed as falling within the protection scope of the present invention, and the following claims will specifically limit the protection scope of the present invention.

10: PP layer 20, 30: a pair of PET layer
15, 25: adhesive (compatibility agent)

Claims (8)

PP layer 10 forming an intermediate layer; and
a pair of PET layers 20 and 30 bonded to both sides of the PP layer to form an outer layer;
is composed of
In order to improve the adhesion between the PP layer and the pair of PET layers, an adhesive (compatibility agent) is further included between each layer, and the PP layer 10 has a thickness of 80 to 90%, and the PET layer (20, 30) each has a thickness of 10 to 5% and a specific gravity of less than 1, the heat-shrinkable film for labels.
The heat-shrinkable film for labels according to claim 1, wherein the PP layer (10) is composed of PP of the following structural formula:
-[-CH ₂ CH(CH ₃ )-] _n -
In the above formula, n is the degree of polymerization of an integer.
[Claim 3] The heat-shrinkable film for labels according to claim 2, wherein the pair of PET layers (20, 30) is composed of PET-G (glycol modified polyethylene terephthalate) of the following structural formula:

In the above formula, m and n are integer polymerization degrees.
delete delete delete A PP layer 10 forming an intermediate layer, and a pair of PET layers 20 and 30 bonded to both sides of the PP layer to form an outer layer are formed, and PP and PET are bonded to the PP layer and the PET layer. , and co-extruding an adhesive (compatibility agent), wherein the PP layer 10 has a thickness of 80 to 90%, and the PET layers 20 and 30 each have a thickness of 10 to 5%, , A method for producing a heat-shrinkable film for a label, characterized in that the specific gravity is less than 1.
The method of claim 7, further comprising the step of stretching the film after the co-extrusion step.

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