KR100762546B1 - Heat shrinkable and biodegradable film - Google Patents

Abstract

A heat shrinkable and biodegradable film is provided to realize excellent thickness uniformity, printability, shrinking property, post-processability, impact property and flexibility, while improving tensile elongation after shrinking. A heat shrinkable and biodegradable film is based on a polylactic acid (polymer A) comprising L-lactic acid units and D-lactic acid units in a ratio of 100:0-92:8 or 0:100 to 8:92, and further comprises a copolymerized polyester (polymer B) in an amount of 2-20 wt%. The heat shrinkable and biodegradable film has a biodegradability of at least 90% and a shrinkage of at least 50% along the main shrinking direction, and shows an elongation after shrinking of at least 100% along the direction perpendicular to the main shrinking direction.

Description

Biodegradable Heat Shrink Film {HEAT SHRINKABLE AND BIODEGRADABLE FILM}

The present invention relates to a biodegradable heat-shrinkable film, and more particularly, to include a biodegradable component and completely decompose upon embedding, and to excellent basic properties such as thickness uniformity, printing property, shrinkage property, and post-processing property. In addition, the present invention relates to a biodegradable heat-shrinkable film having low impact resistance in a direction perpendicular to the main contraction direction and having low failure failure due to external impact.

Heat-shrinkable film is not only used for plastic containers containing polyester or polystyrene, for labeling glass bottles, batteries or electrolytic capacitors, but also for the entire covering of packaging containers, and for various purposes such as packing or tight packing of stationery or multiple containers. It is used. As such a heat-shrinkable film, polyvinyl chloride, polystyrene, a polyester film, etc. are used a lot.

In order to use the heat-shrinkable film for various packaging materials or labels, not only basic properties such as heat resistance, solvent resistance, weather resistance, printing characteristics, transparency, etc., but also excellent post-processability such as sealing property and shrinkage uniformity are required. However, in the case of polyvinyl chloride or polystyrene heat-shrinkable films, which are widely used as conventional heat-shrink film materials, there is a problem that heat resistance, chemical resistance, weather resistance, and heat shrinkage characteristics are not sufficient. In particular, the polyvinyl chloride heat-shrinkable film contains a chlorine component, so the environmental friendliness at the time of incineration disposal is very poor. Because polystyrene film has poor printability and cannot use ink for general plastic film, special ink must be used, and it is difficult to store because of its high natural shrinkage rate, and it is heat-resistant in case of filling high temperature contents or heat sterilization of contents. There is a problem that can not be used because of vulnerability.

The heat shrinkable polyester film generally used is polyethylene terephthalate, which is excellent in heat resistance and weather resistance and also excellent in shrinkage rate, but it has very low impact resistance in the direction perpendicular to the main shrinkage direction (lateral direction) (longitudinal direction). In the post-processing process such as the labeling process, breakage in the longitudinal direction may occur, which may reduce productivity.In particular, in the finished product in which the contents are filled after the entire coating on the glass bottle container, in the transverse direction and the longitudinal direction by the external impact. There is a problem that the breakage (rupture) occurs, which greatly reduces the value of the product.

On the other hand, polypropylene, nylon, and polyethylene terephthalate, which are used as film materials with good mechanical properties due to their relatively stable molecular structure, are accumulated and hardly decomposed due to chemical and biological stability when they are landfilled. In addition, shorter landfills have caused shorter lives and problems with global soil pollution.

In order to compensate for the disadvantages of plastics that do not decompose, a film made of 20% to 40% of a decomposable resin such as starch in a hardly decomposable plastic is decomposed after a certain period of time. However, such a film is deteriorated in mechanical properties under the influence of the mixed decomposable resin, there is a disadvantage that there is no heat resistance. Further, after a certain period of time, only the degradable resin mixed in the film is selectively decomposed, and in the case of the overall film, there is a disadvantage in that it accumulates in the soil as it is only physically chopped.

In order to solve the above problems, recently, a stretched film using polylactic acid, which is an aliphatic polyester having high biodegradability of the resin itself, has been developed. Polylactic acid is generally present as a random copolymer between two optical isomers of L-lactic acid and D-lactic acid. Since the random copolymer does not have crystallinity, the random copolymer may be manufactured as a blown film in an amorphous state and used for a general encapsulation, which does not require heat resistance and mechanical properties.

Japanese Patent Laid-Open Nos. 2001-151906, 2001-011214, and 2003-119367 propose biodegradable heat shrink films having polyesters in polylactic acid having good heat shrinkage. However, such a biodegradable heat shrinkable film has a sufficient shrinkage rate but has a problem in that the impact resistance in the transverse direction and the longitudinal direction is very weak after shrinkage as a uniaxially stretched film, and thus the film easily ruptures due to impact during transportation. In addition, the Republic of Korea Patent Publication No. 2005-79041 proposes a film having a good heat shrinkage produced by mixing an aromatic polyester with polylactic acid, but the biodegradability is less than 80% due to the mixing of the aromatic polyester It is a biodegradable film which is not a landfill when disposed of and causes residues to contaminate the environment.

Accordingly, an object of the present invention is not only excellent in thickness uniformity, printing characteristics, shrinkage characteristics, and post-processing properties required for biodegradable and heat-shrinkable films, but also in the main shrinking direction and orthogonal direction even after labeling (shrink). Elongation is improved to provide a biodegradable heat-shrinkable film excellent in impact resistance and flexibility, characterized in that the rupture phenomenon due to external impact during transportation does not appear in the finished product state after labeling.

In order to achieve the above object, in the present invention, a copolymer of polylactic acid (polymer A) having a composition ratio of L-lactic acid unit and D-lactic acid unit is 100: 0 to 92: 8 or 0: 100 to 8:92 Ester (Polymer B) in the range of 2 to 20% by weight, biodegradability is 90% or more, the main shrinkage rate is 50% or more, characterized in that the elongation after stretching in the direction orthogonal to the main shrinkage direction 100% or more To provide a biodegradable heat shrink film.

Hereinafter, the present invention will be described in more detail.

The biodegradable heat-shrinkable film of the present invention is composed of polylactic acid (polymer A) having a composition ratio of L-lactic acid unit and D-lactic acid unit of 100: 0 to 92: 8 or 0: 100 to 8:92, and the copolymerized polyester ( It is characterized in that the uniaxially stretched film containing the polymer B) in the range of 2 to 20% by weight.

In the present invention, in order to obtain a film having excellent stretchability at the time of uniaxial stretching (lateral stretching) and having a high shrinkage rate, any one of the above units in the random copolymer of L-lactic acid unit and D-lactic acid unit is within 8 mol%. Included polylactic acid (polymer A) is used. When the content of any one lactic acid unit in the polylactic acid (Polymer A) exceeds 8 mol%, the polylactic acid has very amorphous properties, so that a stretched film having a uniform thickness cannot be obtained or stretched excessively when stretching at a normal drawing ratio. There is a problem that normal filmmaking is difficult.

In addition, the polylactic acid preferably has a weight average molecular weight of 120,000 to 180,000. If the weight average molecular weight is less than 120,000, heat resistance and mechanical properties are not properly expressed, and if the weight average molecular weight is greater than 180,000, the viscosity is too high to process a properly drawn film.

When the copolymerized polyester (polymer B) used in the present invention is mixed with the polymer A and melt extruded, the polymer B is dispersed in the polymer A, wherein the polymer B, which is a dispersed particle, has a main shrinkage direction ( Longitudinally) and orthogonal (longitudinal) is distributed long to serve as a support to reinforce the mechanical properties in the longitudinal direction.

The copolyester (polymer B) usable in the present invention is preferably an aliphatic or aromatic polyester copolymerized with polyoxyalkylene glycol, and 5 to 20 parts by weight of poly based on 100 parts by weight of the dicarboxylic acid which is a component of the polyester. It is preferable to include oxyalkylene glycol. Specific examples of the polyoxyalkylene glycol include polyoxypropylene glycol, polyoxytetramethylene glycol, and the like, and specific examples of polyester include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polybutylene succinate. Etc.

In addition, the polymer B preferably has a melting temperature of 180 ° C to 240 ° C, and an intrinsic viscosity of 0.6 dl / g to 0.9 dl / g for kneading in the extruder with the polymer A.

The polymer B is preferably included in an amount ranging from 2% by weight to 20% by weight in the biodegradable heat shrink film of the present invention. If the polymer B is mixed in an amount of less than 2% by weight, the dispersed particles are too small to serve as a support in the longitudinal direction, so the elongation after shrinkage of the film becomes less than 10%, resulting in a cracking failure, and more than 20% by weight. When mixed in an amount of, the dispersed particles are not sufficiently kneaded with the polymer A, which is a main component, so that voids are formed at the interface of the heterogeneous polymer, thereby easily tearing the film. When voids occur, the film becomes opaque and loses commercial viability and mechanical properties drop sharply.

In the present invention, in order for the polymer B to function as a support, it is preferable that the polymer B, which is a dispersed particle, is dispersed to have an L / W of 2 to 5. At this time, L (µm) is an average value of the longitudinal length of the dispersed particles observed in the longitudinal cross section of the stretched film, and W (µm) is an average value of the dispersed particle width. In the produced film, when the dispersed particles are arranged with the proper shape in the longitudinal direction of the film, it acts as a support in the longitudinal direction so that cracking does not occur after shrinkage. If the L / W of the dispersed particles present in the prepared film is less than 2, the dispersed particles have a shape close to a sphere, and thus do not function as a support in the longitudinal direction, and thus the elongation after shrinkage of the film is less than 10%. When the L / W is greater than 5, the dispersed particles have a shape that is very thinly arranged, and thus the elongation after the shrinkage of the film becomes less than 10% because it does not serve as a support in the longitudinal direction.

In the present invention, if necessary, known additives such as dispersants, electrostatic agents, antistatic agents, sunscreens, antiblocking agents, and other inorganic lubricants may be used within the scope of not impairing the effects of the present invention. In addition, a known antistatic agent or slip agent coating treatment may be applied to remove static electricity on the surface of the film.

The biodegradable heat shrinkable film according to the present invention can be obtained by uniaxially stretching the melt extrudates of Polymer A and Polymer B in a conventional manner, and is characterized by having a biodegradability of 90% or more. Biodegradation shows the rate of decomposition compared to the standard substance (cellulose) in the same period, and the Ministry of Environment of Korea is defined as biodegradable when the biodegradation degree is more than 90%.

In addition, the biodegradable heat shrink film according to the invention is characterized in that the main shrinkage (lateral direction) is 50% or more. If the main shrinkage is less than 50%, the shrinkage is so small that it cannot be applied to a container that requires a high shrinkage of various shapes, thereby degrading its value as a commodity.

In addition, the biodegradable heat-shrink film according to the present invention is characterized in that the elongation after shrinkage in the direction (vertical direction) perpendicular to the main contraction direction is 100% or more. In general, the film uniaxially stretched in the transverse direction has a very weak mechanical property in the longitudinal direction, so that the label is easily broken due to transportation shock after shrinkage. At this time, if the elongation of the direction (orthogonal direction) orthogonal to the main shrinkage direction after shrinkage is 100% or more, the film has an elongated property and thus has impact resistance, so the film is not easily broken by external impact during transportation, but after shrinkage If the elongation in the longitudinal direction is less than 100%, the stretching property of the film is small, so that the film is broken when exposed to external impact.

The biodegradable heat shrinkable film according to the present invention is also characterized in that the specific gravity indicating the crystallinity of the film is 1.20 g / cm 3 to 1.30 g / cm 3. The heat-shrink film of the present invention is prepared by mixing heterogeneous polymers rather than a single material, and there should be no voids at the interface between the polylactic acid as a main component and the copolyester as a subcomponent. If the specific gravity of the film in which the polymer B is mixed is less than 1.20 g / cm 3, voids are formed at the interface of the two polymers. have.

The biodegradable heat shrinkable film according to the present invention preferably has a thickness of 30 μm to 70 μm, and when it has such a range of thickness, excellent stretching uniformity and heat shrink uniformity, ink adhesiveness, solvent when used for label or food packaging It is excellent in adhesiveness and the like.

The biodegradable heat shrinkable film of the present invention prepared as described above is completely decomposed upon embedding and has an environmentally friendly property, but also has excellent thickness uniformity, printing property, shrinkage property, and post-processability which are basically required for the heat shrinkable film. Rather, the tensile elongation in the orthogonal direction of the main shrinkage direction is improved after labeling (shrinkage), thereby exhibiting excellent characteristics that the label does not appear to be ruptured by external impact during transportation in the finished product state after labeling.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are not intended to limit the present invention, but are not limited thereto. Measurement of physical properties and various performance evaluations of the films prepared in Examples and Comparative Examples of the present invention were performed by the following method.

(1) Melting temperature (T _m, ℃)

Using a differential scanning thermal analyzer (Perkin Elmer, DSC-7), the crystal melting temperature was measured at a rate of 20 ° C. per minute.

(2) film thickness

After measuring five times at intervals of 5 cm in the longitudinal and transverse directions of the biodegradable heat-shrink film, the average thickness and thickness deviation were respectively calculated according to the following equation.

Thickness average (μm) = average value of 10 measurements

Thickness Deviation (%) = (Max-Min) / Average Thickness × 100

(3) L / W of dispersed particles

The longitudinal section of the biodegradable heat shrink film was photographed using a scanning electron microscope (SEM) (JSM-840A manufactured by JEOL). Using the SEM photograph obtained above, the length (L) and the width (W) of the total dispersed particles in the range of 50 μm ² of the cross section were measured, and then L / W was calculated from these average values.

(4) specific gravity

According to the measuring method of JIS Z8807, it was measured by CAS submersible hydrometer (DMC-220H).

(5) main contraction rate

After cutting into a width of 15 mm and a length of 300 mm with respect to the main shrinkage direction (lateral direction) of the biodegradable heat-shrinkable film, heat-treated for 10 seconds in hot water maintained at a temperature of 90 ° C, and measuring the length (L _f ) The main shrinkage rate was calculated according to the equation.

Main shrinkage (%) = [(300-L _f ) / 300] × 100

(6) elongation after shrinkage

The biodegradable heat-shrink film was 150 mm long and 100 mm wide using MEK (methylethyl ketone) to bond a central portion to prepare a tube-shaped label. The label was placed in a cylindrical glass bottle of 100 mm in length and 61.8 mm in diameter so that the upper and lower portions of the label protruded out of the container, and were labeled for 20 seconds in hot water at 90 ° C. After the labeled glass bottle was left to cool at room temperature (25 ° C.) for 3 hours, the shrunk label was removed from the container. Tensile elongation in the direction (longitudinal) orthogonal to the main shrinkage direction of the separated label was measured three times using Instron's UTM 6021 according to the ASTM D882 method, and the average value was taken as the elongation after shrinkage.

(7) biodegradation rate (%)

It was measured according to the ASTM D5338 method.

Example 1

93 wt% of polymer A having a composition ratio of L-lactic acid and D-lactic acid of 95: 5, and a composition ratio of terephthalic acid, 1,4-butanediol and polyoxypropylene glycol at 100: 90: 10 and a melting temperature of 220 ° C. 7 wt% of polymer B was mixed, and then melt extruded in a T-die having a melt extrusion temperature of 240 ° C., and then unstretched with a thickness of 190 μm by electrostatic adhesion and quenching to a cooling roll having a 20 ° C. cooling water circulated. A sheet was obtained. The unstretched sheet thus obtained was stretched 4.0 times at 75 ° C. using a tenter transverse stretching machine to prepare a biodegradable heat shrink film having a thickness of 50 μm.

The thickness average, thickness variation, L / W of the dispersed particles, specific gravity, main shrinkage rate, elongation after shrinkage and biodegradation of the prepared film are measured and shown in Table 1 below.

Comparative Examples 1 to 3

A uniaxially oriented film was obtained in the same manner as in Example 1 except that the composition ratio of L-lactic acid and D-lactic acid and the mixing ratio of polymer A and polymer B were different as described in Table 1 below. The measurement is shown in Table 1 below.

As shown in Table 1, the biodegradable heat shrinkable film prepared according to the present invention has excellent biodegradability and excellent thickness uniformity, printing property, shrinkage property, and the like, which are basically required for the heat shrinkable film, and labeling. Later, it can be seen that the impact resistance in the direction perpendicular to the main contraction direction is improved.

As described above, the biodegradable heat shrinkable film according to the present invention is completely decomposed upon embedding and has an environmentally friendly property, while thickness uniformity, printing property, shrinkage property, and post-processability which are basically required for the heat shrinkable film. Not only is the back light excellent, but the impact resistance in the direction perpendicular to the main shrinkage direction after labeling (shrinkage) is enhanced, so that the failure failure due to external impact during transportation in the finished product coated on the entire glass container is low. And very useful for packaging and the like.

Claims (10)

L-lactic acid unit and D-lactic acid unit composition ratio of 100: 0 to 92: 8 or 0: 100 to 8:92 polylactic acid (polymer A) as a main component and 2 to 20 weight of copolyester (polymer B) Biodegradable heat-shrink film, characterized in that in the range of%, the biodegradability is 90% or more, the main contraction rate is 50% or more and the elongation after stretching in the direction orthogonal to the main contraction direction. The method of claim 1, Biodegradable heat shrink film, characterized in that the weight average molecular weight of Polymer A is 120,000 to 180,000. The method of claim 1, Biodegradable heat-shrink film characterized in that polymer B is an aliphatic or aromatic polyester copolymerized with polyoxyalkylene glycol. The method of claim 3, wherein Biodegradable heat-shrink film, characterized in that the polyoxyalkylene glycol is used in an amount of 5 to 20 parts by weight based on 100 parts by weight of the dicarboxylic acid component of the polyester. The method of claim 3, wherein Biodegradable heat shrink film, characterized in that the aliphatic or aromatic polyester is selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate and polybutylene succinate. The method of claim 1, Biodegradable heat-shrink film, characterized in that the polymer B, the melting temperature is 180 ℃ to 240 ℃. The method of claim 1, Biodegradable heat-shrink film, characterized in that Polymer B has an intrinsic viscosity of 0.6 dl / g to 0.9 dl / g. The method of claim 1, Polymer B has a range of L / W (where L (μm) is the average of the longitudinal lengths of the dispersed particles observed in the longitudinal cross section of the film, and W (μm) is the average of the widths of the dispersed particles) in the range of 2 to 5. Biodegradable heat-shrink film, characterized in that dispersed in the polymer A. The method of claim 1, A biodegradable heat shrink film, characterized by a specific gravity of 1.20 g / cm 3 to 1.30 g / cm 3. The method of claim 1, Biodegradable heat shrink film, characterized in that the thickness of 30 ㎛ to 70 ㎛.