KR20120052056A - Environment-friendly thermoresistant heat shrinkable film - Google Patents

Abstract

PURPOSE: A heat-shrinkable film is provided to have excellent heat-shrinkable property, thermal resistance, and anti-blocking property, and moderate shrinkage stress, thereby reducing carbon dioxide through the application of carbon dioxide, and not exhausting harmful material. CONSTITUTION: A heat-shrinkable film comprises a base material layer containing an aliphatic polycarbonate resin, a heat-resistant polymer membrane in which one side or both sides of the base material layers are coated. The shrinkage ratio of the film along main shrinkage direction at 90 °C for 10 seconds is 30% or more, and the film is elongated at least along one direction. The aliphatic polycarbonate resin is obtained by the copolymerization of carbon dioxide and an epoxide compound selected from a group consisting of alkylene oxide, cycloalkene oxide, and a mixture thereof.

Description

Eco-friendly heat resistant heat shrink film {ENVIRONMENT-FRIENDLY THERMORESISTANT HEAT SHRINKABLE FILM}

The present invention relates to an environment-friendly heat shrink film used for labeling or food packaging overlap of food and beverage containers.

As general-purpose heat-shrinkable films, polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyester (PET) and the like derived from petroleum are widely used. However, they are produced from petroleum, have high energy consumption, generate large amounts of carbon dioxide, and emit environmentally harmful substances during disposal after use.

For example, polyvinyl chloride (PVC) film not only contains chlorine in the molecule, but also contains additives such as various plasticizers, and thus generates harmful substances such as dioxins when incinerated, thereby making it a lot of restrictions on use. In addition, polypropylene (PP), polystyrene (PS), polyester (PET), etc., are used for packaging purposes, and when they are landfilled, they accumulate with little degradation due to chemical and biological stability. It causes the problem of soil pollution.

In order to make up for the shortcomings of plastic films that do not decompose, various studies have recently been made on methods of producing films using environmentally friendly aliphatic polycarbonates utilizing high biodegradable polylactic acid (PLA) or carbon dioxide of the resin itself. It is becoming.

However, PLA is limited in label use because the crystallinity is high, the shrinkage rate is fast, and the shrinkage stress is too low, so that the shrinkage finish is not good. In addition, since the aliphatic polycarbonate is an amorphous resin having a low Tg (glass transition temperature), there is a problem in that heat resistance and mechanical properties are insufficient for use as a film alone.

In addition, PET has excellent mechanical properties due to its stable molecular structure, but due to its high shrinkage stress, PET is limited to use for labeling a flexible bottle made of PE, PP, and the like.

Accordingly, there is a demand for the development of a new heat-shrinkable film in which the disadvantages of the existing heat-shrinkable film are compensated for.

Therefore, an object of the present invention is to provide a film that is useful for environmentally friendly, excellent heat shrinkability and excellent heat resistance for use in labels or packaging materials.

In order to achieve the above object, the present invention comprises a substrate layer containing an aliphatic polycarbonate resin, and a heat-resistant polymer film coated on one or both sides of the substrate layer, when placed in a 90 ℃ constant temperature water bath for 10 seconds in the main shrinkage direction Shrinkage of 30% or more, and at least one direction stretched, to provide an environmentally friendly heat shrink film.

In addition, the present invention provides a heat shrink label or packaging material comprising the eco-friendly heat shrink film.

Eco-friendly heat shrink film according to the present invention is excellent in heat resistance, heat shrinkage and anti-blocking properties and suitable for the shrinkage stress, can be used for labeling of food and beverage containers or food packaging overlap, reducing carbon dioxide through the use of carbon dioxide It is eco-friendly because it does not emit environmentally harmful substances even when incinerated.

The film according to the present invention includes a base layer containing an aliphatic polycarbonate resin and a heat resistant polymer film coated on one or both sides of the base layer, and the shrinkage ratio in the main shrinkage direction when placed in a 90 ° C. constant temperature water bath for 10 seconds. It is 30% or more, It is characterized by extending | stretching in at least one direction.

The aliphatic polycarbonate resin used in the substrate layer may be prepared by copolymerizing carbon dioxide with an epoxide compound selected from the group consisting of alkylene oxide, cycloalkene oxide, and mixtures thereof. In this case, as the polymerization catalyst, a zinc precursor such as diethyl zinc (US Pat. No. 3,585,168), a complex compound containing an onium salt (Korean Patent No. 10-0853358), or a cobalt catalyst may be used.

Specific examples of the epoxide compound include ethylene oxide, propylene oxide, butene oxide, pentene oxide, hexene oxide, octene oxide, decene oxide, dodecene oxide, tetradecene oxide, hexadecene oxide, octadecene oxide, butadiene monooxide, 1 , 2-epoxide-7-octene, cyclopentene oxide, cyclohexene oxide, cyclooctene oxide, cyclododecene oxide, 2,3-epoxide norbornene, limonene oxide and mixtures thereof.

When copolymerizing aliphatic polycarbonate resin, the pressure of carbon dioxide may be from normal pressure to 100 atmospheres, preferably 5 to 30 atmospheres. In addition, the polymerization temperature may be 20 ℃ to 120 ℃, preferably 50 ℃ to 90 ℃.

As a method of copolymerizing an aliphatic polycarbonate resin, there exist a batch polymerization method, a semi-batch polymerization method, a continuous polymerization method, etc. When using a batch or semi-batch polymerization method, the reaction time may be 1 hour to 24 hours, preferably 1.5 hours to 4 hours, and when using the continuous polymerization method, the average residence time of the catalyst is likewise 1.5 hours to 4 hours. It is preferable to set it as time.

Specific examples of the aliphatic polycarbonate resin include preferably polyethylene carbonate, polypropylene carbonate and mixtures thereof.

The number average molecular weight (Mn) of the aliphatic polycarbonate resin used in the present invention may be 50,000 to 500,000. Here, the number average molecular weight (Mn) means the number average molecular weight measured by GPC by correcting the polystyrene of a single molecular weight distribution with a standard.

In general, aromatic polycarbonates are very dangerous from the manufacturing process because they are manufactured using the toxic substances bisphenol-A and phosgene, while aliphatic polycarbonates utilize carbon dioxide to reduce carbon dioxide emitted to the atmosphere. It also has the advantage of contributing to. In addition, aromatic polycarbonates do not cause natural decomposition and emit environmentally harmful substances when incinerated, but aliphatic polycarbonates can be decomposed into carbon dioxide and water upon incineration.

In the present invention, such a non-crystalline aliphatic polycarbonate can be used as the substrate layer to ensure a sufficient shrinkage rate for labeling.

In the film of the present invention, a heat resistant polymer film is coated on one side or both sides of the base layer to improve heat resistance.

Such a heat resistant polymer film preferably contains a polymer resin having a glass transition temperature (Tg) of 60 ° C or higher. More preferably, the polymer resin has a weight average molecular weight (Mw) of 1,000 to 20,000 and a softening point of 100 ° C to 150 ° C. Examples of the polymer resin include polyester resins. Examples of the polymer resin include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polyethylene adipate, and polyhydroxyal. Resins comprising at least one polyester repeating unit selected from the group consisting of cannoates are possible.

It is preferable that the thickness of such a heat resistant polymer film is 0.001 micrometer-30.0 micrometers.

Since the heat resistant polymer film is amorphous, the problem that can be easily fused by applying heat can be solved through the heat resistant polymer film coating, and thus can be used as a single film. In addition, during the film drawing process and hot filling process, it exhibits anti-blocking property to prevent the films from sticking together.

To the base layer and the heat resistant polymer film, ordinary electrostatic agents, antistatic agents, antioxidants, heat stabilizers, sunscreens, antiblocking agents, other inorganic lubricants, and the like can be added within a range that does not impair the effects of the present invention.

It is preferable that the total thickness of the film of this invention is 5 micrometers-500 micrometers.

The heat shrinkable film according to the present invention may be manufactured by melt extruding and cooling the aliphatic polycarbonate resin to obtain an unstretched film, coating a heat resistant polymer film on one or both surfaces thereof, and then stretching and heat setting the film.

At this time, it is possible to produce a bidirectional shrinkage film by biaxially stretching the unstretched sheet in the longitudinal direction and the transverse direction, or to uniaxially stretch in only one of the longitudinal direction and the transverse direction to produce the unidirectional shrinkage film.

In addition, the coating of the heat-resistant polymer film, may be coated using the water-based emulsion resin of the heat-resistant polymer, the coating process may be Mayer (Mayer Bar) coating, Gravure (Gravure) coating, Micro Gravure coating, lip It may be performed by a method such as a die die coating, a slot die coating, a comma coating, a reverse kiss coating, or the like.

In addition, the melt extrusion temperature is preferably 150 ℃ to 280 ℃, the temperature of the stretching process is preferably 30 ℃ to 90 ℃, the stretching ratio for each direction is preferably 1.5 times to 10.0 times and 2.5 times to It is more preferable that it is 5.0 times. In addition, the heat setting temperature is preferably 50 ℃ to 150 ℃. When the process conditions are within the above range, it is possible to more easily implement the heat shrink rate pursued in the present invention.

In the case of the bidirectional shrinkage film, in order to balance the shrinkage in both directions, the relaxation after heat setting may be reduced to 0.01% to 5%. It is also possible to give back relaxation from -0.01% to -5.0% to impart adequate shrinkage stress.

Such a heat shrink film according to the present invention is excellent in heat shrinkage, shrinkage stress, friction coefficient and heat resistance.

When the film of this invention is left for 10 second in 90 degreeC constant temperature water bath, the shrinkage rate of the main contraction direction shows 30% or more. When the heat shrinkage is in the above range, it is easy to apply the film to various types of containers and uses.

In addition, preferably, the maximum shrinkage stress is 1.0N to 9.0N when placed for 10 seconds in a 90 ℃ constant temperature water bath. When the maximum shrinkage stress is in the above range, the finish can be better after the heat shrink of the film, it can also be applied to a flexible bottle of PE or PP material.

Further, preferably, the coefficient of kinetic friction measured according to ASTM D1894 is less than 0.70 and the static friction coefficient is less than 0.65. When the coefficient of friction is within the above range, it is possible to more effectively prevent the films from sticking together during the stretching process or hot filling.

Such a heat shrink film of the present invention is suitable as a heat shrink label or packaging material use. Such heat shrinkable labels or packaging materials are preferably usable for labeling of food and beverage containers or for overlapping of food packaging. For example, when used as a heat-shrinkable label can be produced by stretching in one direction, when used as a packaging material such as overlap can be produced by stretching in both directions.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

The film according to the present invention and the prior art was prepared as follows, and the configuration and process of each film are summarized in Table 1 below.

Example 1 Preparation of Uniaxially Stretched Film Coated with One Surface of Heat Resistant Polymer (PPC)

As the base layer resin, polypropylene carbonate resin (QPAC40, Empower Co., Ltd.), which is an aliphatic polycarbonate obtained by alternating copolymerization of carbon dioxide and propylene oxide, was used.

The resin was melt extruded at 180 ° C. and cooled on a casting roll at 10 ° C. to obtain an unstretched film.

On one side of the unstretched film, a polyester water-based emulsion resin (product name: W0035, Nippon Synthetic Chemical Co., Ltd.) having a Tg of 75 ° C., a viscosity of 2500 cP, and a Mw 7,000 was coated using a coater (Mayer bar coater # 3). It was.

The coated film was laterally stretched four times at 65 ° C., and then heat-set at 50 ° C. to prepare a film having a total thickness of 50 μm coated with a heat resistant polymer film having a thickness of 0.5 μm.

Example 2 Preparation of Uniaxially Stretched Film Coated with Heat-Resistant Polymer Membrane (PEC)

Polyethylene carbonate resin (QPAC25, Empower Co., Ltd.) which is an aliphatic polycarbonate obtained by alternating copolymerization of carbon dioxide and propylene oxide was used as the base layer resin.

The resin was melt extruded at 160 ° C. and cooled on a casting roll at 8 ° C. to obtain an unstretched film.

On both sides of the unstretched film, a polyester water-based emulsion resin (trade name: WR901, Japan Synthetic Chemicals Co., Ltd.) having a Tg of 70 ° C., a viscosity of 1400 cP, and a Mw of 16,000 was coated on both sides using a coater (Mayer bar coater # 6). Coated on.

The coated film was laterally stretched three times at 55 ° C., and then heat-set at 50 ° C. to prepare a film having a total thickness of 50 μm coated with a heat resistant polymer film having a thickness of 0.2 μm.

Comparative Example 1: Preparation of Uniaxially Stretched Film (PPC)

As the base layer resin, polypropylene carbonate resin (QPAC25, Empower Co., Ltd.), which is an aliphatic polycarbonate obtained by alternating copolymerization of carbon dioxide and propylene oxide, was used.

The resin was melt extruded at 190 ° C. and cooled on a casting roll at 30 ° C. to obtain an unstretched film.

The unoriented film was laterally stretched five times at 60 ° C., and then heat-set at 80 ° C. to produce a film having a total thickness of 50 μm.

Comparative Example 2: Preparation of Uniaxially Stretched Film (PET)

Polyethylene terephthalate resin (SKC) was used as the base material layer resin.

The resin was melt extruded at 280 ° C. and cooled on a casting roll at 15 ° C. to obtain an unstretched film.

The unoriented film was laterally stretched 7 times at 90 ° C., and then heat-set at 120 ° C. to produce a film having a total thickness of 50 μm.

After performing the physical property measurement and performance evaluation for the films prepared according to the Examples and Comparative Examples in the following manner, the results are shown in Table 1 below.

(1) heat shrinkage

The film sample was cut into a length of 200 mm and a width of 15 mm in the direction to measure the shrinkage rate, treated in a constant temperature water bath maintained at a temperature of 90 ° C. for 10 seconds, and then the change in length was measured. Calculated.

Equation 1

Thermal contraction rate (%) = (length before heat treatment-length after heat treatment) / length before heat treatment x 100

(2) shrinkage stress

The maximum stress was measured when soaked in a 90 ° C. constant temperature water bath for 10 seconds using a shrinkage stress tester (QM150S, Cumsys) equipped with a load cell.

(3) heat resistance

After labeling the film in the bottle, when the 70 ℃ liquid is filled in the bottle, it was confirmed whether or not blocking occurs between the bottles and evaluated by the following criteria.

Excellent: Bottles are not fused at all.

Good: Bottles stick together but can be removed after cooling.

Poor: Bottles do not fuse together.

(4) coefficient of friction

The coefficient of friction of the film was measured in accordance with ASTM 1894 using a static / kinetic coefficient of friction measuring instrument (QM110C, Curmsys).

division unit Example 1 Example 2 Comparative Example 1 Comparative Example 2 Configuration Base layer resin - PPC PEC PPC PET Heat resistant polymer membrane has exist has exist - - fair Elongation ratio Longitudinal direction ship - - - - Transverse ship 4 3 5 7 Heat setting temperature ℃ 50 50 80 120 Properties Thermal contraction rate (main contraction direction) % 40 45 20 25 Maximum Shrinkage Stress N 2.0 1.5 2.5 9.2 Dynamic friction coefficient 0.50 0.53 0.80 0.70 Heat resistance Great Good Bad Good

As can be seen in Table 1, the film of Examples 1 to 2 according to the present invention is excellent in the heat shrinkage in the main shrinkage direction compared to the film of Comparative Examples 1 and 2, the shrinkage stress is also suitable as a heat shrink film. In addition, the coefficient of kinetic friction is low and excellent in heat resistance, it can be seen that it is suitable for the label or overlapping packaging material for containers such as food and beverage.

Claims (10)

A base layer comprising an aliphatic polycarbonate resin, and a heat-resistant polymer film coated on one or both sides of the base layer, when placed in a 90 ℃ constant temperature water bath for 10 seconds, the shrinkage in the main shrinkage direction is 30% or more, at least one direction Stretched, eco-friendly heat shrink film.
The method of claim 1,
Eco-friendly heat shrink film, characterized in that the aliphatic polycarbonate resin is obtained by copolymerization of carbon dioxide and epoxide compound selected from the group consisting of alkylene oxide, cycloalkene oxide and mixtures thereof.
The method of claim 1,
Eco-friendly heat shrink film, characterized in that the aliphatic polycarbonate resin is selected from the group consisting of polyethylene carbonate, polypropylene carbonate and mixtures thereof.
The method of claim 1,
Eco-friendly heat shrink film, characterized in that the aliphatic polycarbonate resin has a number average molecular weight (Mn) of 50,000 to 500,000.
The method of claim 1,
Eco-friendly heat shrink film, characterized in that the heat-resistant polymer film comprises a polymer resin having a glass transition temperature of 60 ℃ or more.
The method of claim 5,
Eco-friendly heat shrink film, characterized in that the polymer resin is a polyester resin having a weight average molecular weight of 1,000 to 20,000 and a softening point of 100 ℃ to 150 ℃.
The method of claim 1,
The heat resistant polymer film has a thickness of 0.01 μm to 30.0 μm, wherein the environment-friendly heat shrink film.
The method of claim 1,
The eco-friendly heat-shrink film is stretched at a draw ratio of 1.5 times to 10.0 times at a stretching temperature of 30 ℃ to 90 ℃ with respect to at least one of the longitudinal direction and the transverse direction, characterized in that it is heat-set at 50 ℃ to 150 ℃ , Eco-friendly heat shrink film.
The method of claim 1,
The eco-friendly heat shrink film, the maximum shrinkage stress is 1.0N to 9.0N when placed in a 90 ℃ constant temperature water bath, characterized in that the coefficient of kinetic friction 0.65 or less, eco-friendly heat shrink film.
A heat shrink label or packaging material comprising the environmentally friendly heat shrink film of claim 1.