KR20090077154A - Heat shrinkable film retaining biodegradability and preparing process thereof - Google Patents

Abstract

The present invention relates to a method for producing a biodegradable heat shrinkable film and a heat shrinkable film that can be used as a packaging material such as coating, binding, exterior, label, etc., the biodegradable heat shrinkable film of the present invention is polylactic acid 95.0 To 99.9% by weight and a polylactic acid impact modifier of 0.1 to 5.0% by weight of the film composition, the heat shrinkage rate for 10 seconds in hot water at 90 ℃ is characterized in that the film is at least 30% in at least one of the longitudinal direction and the width direction of the film. It is done.

The heat-shrinkable film having the biodegradability of the present invention configured as described above is a heat-shrinkable film having excellent biodegradability using polylactic acid as a main raw material, and having excellent uniformity in appearance after shrinkage, thereby making a heat-shrinkable film made of a raw material of a conventional synthetic resin series. Not only is it an industrially viable alternative, it is also industrially useful as it is biodegradable at the time of disposal by consumers using environmentally friendly polylactic acid extracted from plant resources.

Description

Heat shrinkable film retaining biodegradability and preparing method thereof

The present invention relates to a biodegradable heat-shrinkable film and a method for producing the same, and more particularly, to a biodegradable heat-shrinkable film and a heat-shrinkable film that can be used as a packaging material such as coating, binding, exterior, and labeling. It is about.

In general, synthetic plastics are used for various purposes all over the world as packaging materials that are indispensable to modern life because of their excellent properties and cheap and light properties. However, synthetic plastics having the above-mentioned characteristics are environmental problems due to their advantages and disadvantages of poor decomposition, and thus, various countries have recently been interested in finding solutions to them. In other words, the conventional methods of landfilling, incineration and regeneration have been mainly used for treating synthetic plastics, but these methods could not completely solve the environmental pollution problem.

Therefore, attention is now focused on the development of so-called degradable plastics, which makes it possible to decompose the used plastic by itself. Currently, various kinds of degradable plastics have been developed from various technologies and raw materials. Among them, polylactic acid (hereinafter referred to as 'PLA') is produced in large quantities and inexpensively by the fermentation method of L-lactic acid, and decomposed under composting conditions. Its fast speed, resistance to mold, and good odor resistance to food are expanding its range of applications.

On the other hand, in the case of the heat-shrinkable film, coating, binding, or exterior of various containers, plastic bottles, glass bottles, and various rod-shaped articles (pipes, rods, wood) and the like, in particular, a part of these caps, shoulders, barrels, or the like, or It is used for the purpose of covering the entire surface, marking, protecting, binding, and improving the value of the product.It is widely used in the field of integrated packaging such as boxes, bottles, plates, rods, and notebooks. It is true.

Such heat-shrinkable film was used to improve product image, increase advertising effect, and increase product protection effect by using heat-shrinkable film composed of materials such as vinyl chloride, polystyrene, polypropylene, polyester, and polyolefin. Various printing, deposition, coating, and lamination make it impossible to recycle materials and rely only on disposal by incineration, causing the same problems as general packaging plastics as described above.

Therefore, Japanese Patent Publication Nos. 2001-151906, 2001-011214, and 2003-119367 disclose shrink films and sheets using polylactic acid and polyester to solve the conventional problems as described above. In the present invention, the polyester content is more than 9wt% or more than 25wt% in the total composition, and considering the compatibility between polylactic acid and aliphatic polyester, it is a difficult composition ratio to maintain transparency, which is an advantage of polylactic acid, or an aliphatic polyester. -The biodegradability of the aliphatic-aromatic polyester is not clear since the aromatic content is used and the aromatic content is not described, and thus the transparency of the film composition is also high, and the transparency of the polylactic acid with a haze of 7 to 8% is achieved. The disadvantage is that it is difficult to maintain.

Accordingly, the present invention solves the problems of the conventional heat-shrinkable film as described above, while maintaining excellent transparency and biodegradability, and provides a heat-shrinkable film having a particularly good low-temperature shrinkability and excellent biodegradability after shrinkage. It is to.

Another object of the present invention is to provide a method capable of easily producing a heat-shrinkable film having good low-temperature shrinkability while maintaining excellent transparency and biodegradability as described above and excellent in uniformity in appearance after shrinkage.

Heat shrinkable film having a biodegradable of the present invention for achieving the above object;

A film composition composed of 95.0 to 99.9% by weight of polylactic acid and 0.1 to 5.0% by weight of polylactic acid impact modifier, wherein the thermal contraction rate for 10 seconds in hot water at 90 ° C. is 30% in at least one of the length and width directions of the film. It is characterized by the above.

According to another configuration of the present invention, the polylactic acid is obtained by polymerizing lactic acid (lactic acid), the polylactic acid used in the present invention is composed of L-lactic acid, D-lactic acid or L, D-lactic acid, Number average molecular weight is 10,000 or more, these polylactic acid is characterized in that it can be used alone or in combination.

According to another configuration of the present invention, the polylactic acid shock-improving agent is an aromatic-aliphatic polyester or an aliphatic polyester or a copolymer composed of an aliphatic polyester and a polylactic acid, characterized in that they are composed alone or in combination.

According to another configuration of the present invention, the aromatic-aliphatic polyester is an aromatic component of dicarboxylic acid or derivative thereof of ROOC-Ar-COOR '(R, R' is hydrogen or alkyl group) structure of terephthalic acid, phthalic acid, iso Phthalic acid, naphthalene 2,6-dicarboxylic acid, diphenylsulfonic acid dicarboxylic acid, diphenylmethanedicarboxylic acid, diphenyletherdicarboxylic acid, diphenoxyethanedicarboxylic acid, cyclohexanedicarboxylic acid At least one selected from the group consisting of an acid or an alkylene ester thereof, and an aliphatic dicarboxylic acid or a derivative thereof may include ROOC (CH ₂ ) nCOOR '(R, R' is hydrogen or an alkyl group, n is 2 to 14; At least one member selected from the group consisting of succinic acid, glutaric acid, malonic acid, oxalic acid, adipic acid, sebacic acid, azelaic acid, nonanedicarboxylic acid and their alkyl or aryl ester derivatives Glycols are HO- (CH ₂ ) n-O Ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol or propylene glycol, 1,4-cyclohexane having a structure of H (n is an integer of 2 or more) A group consisting of alkylene glycol or polyalkylene glycol composed of diol, hexamethylene glycol, polyethylene glycol, triethylene glycol, neopentyl glycol, and tetramethylene glycol or a branched structure represented by the general formula (1) can be formed. 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,2- which are aliphatic dihydric alcohols Hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,2-octanediol, 1,3-octanediol, 1,4-octanediol, 1,5-octane It is characterized in that the group consisting of diols, 1,6-octanediol and the like can be used.

General formula (1)

In General Formula (1), R ₁ is an alkylene group of C ₂ to C ₈ , and R ₂ is an alkyl group of C ₂ to C ₈ .

In the aromatic-aliphatic polyester component, the aromatic component should be adjusted to 10 to 50 mol%, preferably 30 mol% is the best. If the aromatic is 10 mol% or less, there is no improvement in terms of enhancing the flexibility of the film.

According to another configuration of the present invention, the aliphatic polyester is an aliphatic dicarboxylic acid or derivative thereof ROOC (CH ₂ ) n COOR '(R, R' is hydrogen or an alkyl group, n is an integer of 2 to 14) structure At least one selected from the group consisting of succinic acid, glutaric acid, malonic acid, oxalic acid, adipic acid, sebacic acid, azelaic acid, nonanedicarboxylic acid and alkyl or aryl ester derivatives thereof, and glycols are HO Ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol or propylene glycol having a structure of-(CH ₂ ) n-OH (n is an integer of 2 or more) , A group consisting of alkylene glycol and polyalkylene glycol composed of 1,4-cyclohexanediol, hexamethylene glycol, polyethylene glycol, triethylene glycol, neopentyl glycol, and tetramethylene glycol or represented by the following general formula (1) Capable of forming branch structure 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,2-hexane which are aliphatic dihydric alcohols Diol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,2-octanediol, 1,3-octanediol, 1,4-octanediol, 1,5-octanediol , Characterized in that the group consisting of 1,6-octanediol and the like can be used.

According to another configuration of the present invention, the copolymer made of the aliphatic polyester and the polylactic acid is a block copolymer, and the aliphatic polyester is as described above.

In the manufacturing process of the heat-shrinkable film according to the present invention, it is possible to add an ether ester plasticizer, an oxyacid ester plasticizer, or a glycol plasticizer as a plasticizer for the purpose of improving secondary processability as other additives. Examples thereof include ethylene glycol, propylene glycol, polyethylene glycol, sorbitol, glycerin (glycerol), methoxypolyethylene glycol, tri-n-butyl citrate, and the like. It is also possible to mix and use two or more types of these mixtures.

In addition, as the nucleating agent, inorganic particles such as titanium dioxide including talc, silica, kaolin, calcium carbonate, alumina, zirconia, zeolite, and the like may be used, and the inorganic particles used in the nucleating agent may be used in combination with an organic lubricant. As the organic lubricant, an aliphatic hydrocarbon lubricant, an aliphatic amide lubricant, or the like is used.

In addition, a crosslinking agent may be used for the purpose of lowering the melt tension during molding into a film. Examples of the crosslinking agent that may be added to the resin include an organic peroxide compound, a metal complex, an epoxy compound, and an isocyanate compound.

In addition, depending on the application, a substance such as a sunscreen, an antibacterial / deodorant, a heat stabilizer, a light stabilizer, a flame retardant, an antistatic agent, an antioxidant, or a pigment may be used as an additive.

As described above, the content of the polylactic acid impact improving agent according to the present invention should be 0.1 to 5.0% by weight, which is more than 5.0% by weight in the transparency of the film is a problem that the transparency worsens sharply, preferably polylactic acid shock Although it is preferable not to use an improving agent, when the flexibility of the film is insufficient in the manufacturing process of the film, it is not preferable because of difficulty in manufacturing due to continuous breakage during film production. The heat shrinkage rate of the film should be maintained at 30% or more in at least one direction of the film length direction and the width direction. When the heat shrinkage rate of the film is 30% or less, it is difficult to apply to various applications, and thus the practicality of the product is poor. The polylactic acid, polylactic acid impact improving agent and other additives are fed into a twin screw extruder (TWIN SCREW EXTRUDER) at a constant mixing ratio through a feeder and melt-extruded while removing moisture by high vacuum, and cooling and solidifying them. A biodegradable heat-shrinkable film can be produced by preparing a sheet and stretching in either the longitudinal direction of the film or the width direction of the film, or by stretching in both directions at an appropriate draw ratio.

The heat-shrinkable film having the biodegradability of the present invention configured as described above is a heat-shrinkable film having excellent biodegradability using polylactic acid as a main raw material, and having excellent uniformity in appearance after shrinkage. Not only is it an industrially viable alternative, it is also industrially useful as it is biodegradable when disposed of by consumers using eco-friendly PLA extracted from plant resources as a raw material.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to the following Examples. In addition, the characteristics evaluation method of the FILM manufactured according to the following Examples and Comparative Examples are as follows.

(1) heat shrinkage

The specimen was cut and sampled into a square shape to be 100 mm in the length direction and 100 mm in the width direction, and the sample was heat-treated for 10 seconds in hot water at 90 ° C., and the shrinkage was measured, and the average value was repeated 20 times. Defined. The longitudinal direction of the film was represented by MD, and the width direction was represented by TD.

(2) appearance after shrinkage

The prepared shrink film was made to be used as a label on the shoulder portion of a 1.5L plastic bottle container, and then put on the container and shrinked for 30 seconds in an air oven at 150 ° C. If the defect is 1 or less, good (0), 5 or less (△), if more than 5 it was marked as bad (×). In addition, the appearance defects were identified by the number of shrinkage plaques, wrinkles, upper and lower end curls, print-shaped distortion for each label.

(3) Transparency (HAZE: ASTM D 1003)

HAZE was obtained under ASTM D 1003 analysis conditions.

(4) Mechanical Strength (Tensile Strength; ASTM D 882)

Using a tensile tester, the temperature was measured at a tensile rate of 500 mm / min at a temperature of 20 ± 2 ° C and a relative humidity of 65 ± 2%, and the longitudinal direction of the film was expressed in MD and the width in TD.

(5) Flexibility (elongation; ASTM D 882)

The elongation until break of the film was determined under the same conditions as the tensile strength, and the length direction of the film was expressed in MD, and the width direction was expressed in TD.

(6) Exploded View (KS M 3100-1)

Compute the test material under the same conditions using TLC grade cellulose with a particle size of 20 µm or less as the standard sample, and calculate the biodegradability of the test material from the cumulative amount of carbon dioxide released for 45 days (using the formula below). When the biodegradability of the test substance was calculated in%, 80% or more was expressed as 1, 80 to 50% was expressed as 2, and 50% or less.

D _t = [{(CO ₂ ) _T- (CO ₂ ) _B } / ThCO ₂ ] × 100

(CO ₂ ) _T : Accumulated amount of carbon dioxide from the container containing the test substance

(CO ₂ ) _B : Accumulated amount of carbon dioxide from containers containing compost

ThCO ₂ : Calculation of Theoretical Carbon Dioxide

ThCO ₂ = M _TOT × C _TOT × (44/12)

M _TOT : Total dry solids (g) of test substance added at the beginning of the analysis

C _TOT : Ratio of organic carbon in the total dry solids of the test substance (g / g)

                 44,12: molecular weight of carbon dioxide and atomic weight of carbon

Example 1

As the polylactic acid (PLA) and polylactic acid impact modifier, the polybutylene adipate terephthalate (PBAT) having an aromatic content of 30 mol% as an aromatic-aliphatic polyester is used to supply 99 wt% PLA and 1 wt% PBAT, respectively. The raw material is continuously put into the twin screw extruder that can be melted and extruded while removing moisture by high vacuum and melted and discharged through T-DIE. The discharged sheet is cooled and solidified on the casting roll. The sheet was preheated at 110 ° C., stretched three times in the transverse direction at 100 ° C., and heat-set at 100 ° C. to prepare a heat shrinkable film having a biodegradability of 50 μm. The heat shrinkage, appearance after shrinkage, transparency, mechanical strength, flexibility, and resolution of the films prepared as described above were measured by the above method, and the results are shown in Table 1 below.

Example 2

Except for using polybutylene succinate (PBS), an aliphatic polyester, instead of PBAT as a polylactic acid impact improving agent, a film was prepared in the same manner as in Example 1 to obtain thermal shrinkage, appearance after shrinkage, transparency, and mechanical properties of the film. Strength, flexibility, and resolution were measured by the above method, and the results are shown in Table 1 below.

Example 3

Heat shrinkage rate of the film was prepared by the same method as Example 1 except that 1 wt% of polybutylene succinate (PBS) and polylactic acid copolymer (PBS-PLA COPOLYMER) was used instead of PBAT as a polylactic acid impact improving agent. The appearance, transparency, mechanical strength, flexibility, and resolution after shrinkage were measured by the above method, and the results are shown in Table 1 below.

Example 4

The same method as Example 1 except that 97 wt% polylactic acid (PLA) and 3 wt% of polybutylene succinate (PBS) and polylactic acid (PBS-PLA COPOLYMER) was used instead of PBAT as an impact modifier for polylactic acid. The film was prepared by measuring the heat shrinkage, the appearance state after shrinkage, transparency, mechanical strength, flexibility, resolution of the film by the above method, the results are shown in Table 1 below.

Example 5

Except 95 wt% polylactic acid (PLA) and 5 wt% polybutylene succinate (PBS) and polylactic acid copolymer (PBS-PLA COPOLYMER) instead of PBAT as a polylactic acid impact modifier. The film was prepared by measuring the heat shrinkage, the appearance state after shrinkage, transparency, mechanical strength, flexibility, resolution of the film by the above method, the results are shown in Table 1 below.

Comparative Example 1

Except for using 100% by weight of polylactic acid (PLA) without a polylactic acid impact improving agent, the film was prepared in the same manner as in Example 1, and the thermal shrinkage, appearance after shrinkage, transparency, mechanical strength, flexibility, and degradability of the film were It was measured, and the results are shown in Table 1 below.

Comparative Example 2

The same method as Example 1 except that 90 wt% of polylactic acid (PLA) and 10 wt% of polybutylene succinate (PBS) and polylactic acid (PBS-PLA COPOLYMER) was used instead of PBAT as an impact modifier for polylactic acid. The film was prepared by measuring the heat shrinkage, the appearance state after shrinkage, transparency, mechanical strength, flexibility, resolution of the film by the above method, the results are shown in Table 1 below.

division Example-1 Example-2 Example-3 Example-4 Example-5 Comparative Example-1 Comparative Example-2 Composition (wt%) PLA 99 99 99 97 95 100 90 PBAT One - - - - - - PBS - One - - - - - PBS-PLACopolymer - - One 3 5 - 10 Heat Shrinkage (%) MD 1.9 2.0 2.1 1.8 1.6 4.8 1.3 TD 49.2 47.0 47.9 50.0 53.8 25.0 57.5 Appearance after shrinking ○ ○ ○ ○ ○ △ ○ HAZE (%) 1.7 1.3 0.9 2.2 4.8 0.6 23.3 Tensile Strength (㎏ / ㎠) MD 5.0 5.2 5.1 6.9 8.8 5.2 4.9 TD 31.9 31.3 31.2 29.4 28.7 32.1 28.5 Elongation (%) MD 4.6 4.0 4.1 5.2 5.9 3.9 6.3 TD 88.3 86.0 86.9 92.0 99.8 40.5 113.0 Exploded View (%) 93 94 94 92 90 94 87

Claims (6)

A film composition composed of 95.0 to 99.9% by weight of polylactic acid and 0.1 to 5.0% by weight of polylactic acid impact modifier, wherein the thermal contraction rate for 10 seconds in hot water at 90 ° C. is 30% in at least one of the length and width directions of the film. The heat shrinkable film which has biodegradability characterized by the above. The method of claim 1, wherein the polylactic acid is composed of L-lactic acid, D-lactic acid or L, D-lactic acid, the number average molecular weight of 10,000 or more biodegradable, characterized in that these polylactic acid is used alone or in combination Heat-shrinkable film containing. According to claim 1, wherein the polylactic acid shock-improving agent is an aromatic-aliphatic polyester or a copolymer composed of aliphatic polyester or aliphatic polyester and polylactic acid, biodegradable heat shrinkability, characterized in that they are composed alone or in combination film. The aliphatic component according to claim 3, wherein the aromatic-aliphatic polyester is an aromatic component and at least one member selected from dicarboxylic acids or derivatives thereof having a structure of ROOC-Ar-COOR '(R, R' is hydrogen or an alkyl group). Wherein at least one member selected from dicarboxylic acids or derivatives thereof having a structure of ROOC- (CH ₂ ) n -COOR '(R, R' is hydrogen or an alkyl group, n is an integer of 2 to 14), and glycols are selected from HO- Biodegradable, characterized in that a group consisting of diols or polyalkylene glycols of (CH ₂ ) n-OH (n is an integer of 2 or more) or aliphatic dihydric alcohols of the structure represented by the following general formula (1) is used. A heat shrinkable film having a; General formula (1) R ₁ in the general formula (1) is an alkylene group of C ₂ ~ C _8, R ₂ is an alkyl group of C ₂ ~ C _8. The method of claim 3, wherein the aliphatic polyester is selected from dicarboxylic acids or derivatives of the structure ROOC- (CH ₂ ) n-COOR '(R, R' is hydrogen or an alkyl group, n is an integer of 2 to 14) structure Glycols consist of diols or polyalkylene glycols of HO- (CH ₂ ) n-OH (n is an integer of 2 or more) or aliphatic dihydric alcohols of the structure represented by the following general formula (1). Bioshrinkable heat shrinkable film, characterized in that the group is used; General formula (1) R ₁ in the general formula (1) is an alkylene group of C ₂ ~ C _8, R ₂ is an alkyl group of C ₂ ~ C _8. The bioshrinkable heat shrinkable film of claim 1, wherein the film has a thickness of 30 to 200 μm.