KR20210095005A - Biodegradable pla label and film having improved transparency and heat-shrinkable, and method of manufacturing the same - Google Patents

Abstract

Provided are a biodegradable PLA film with improved transparency and heat-shrinkable properties, and a manufacturing method thereof. The biodegradable PLA film contains 33-88 wt% of polylactic acid (PLA), 3-20 wt% of polyhydroxyalkanoate (PHA), 3-20 wt% of a non-toxic plasticizer, 0.2-5 wt% of silica, 1-5 wt% of a dispersant, 0.2-5 wt% of a slip agent, 0.1-10 wt% of a chain extender and 0.1-2 wt% of an antioxidant, wherein the film has a thickness of 20-60 μm and has heat-shrinkable properties.

Description

Biodegradable PLA label and film having improved transparency and heat shrinkability, and method of manufacturing the same

The present invention relates to a biodegradable PLA label and film suitable for packaging articles having improved transparency and heat shrinkability, and a method for manufacturing the same.

Plastic films such as PE (Polyethylene) and PET (Poly Ethylene Terephthalate) have become common and are being mass-produced and used for various purposes such as packaging of goods or food. However, due to global warming, environmental pollution of plastics, which are recently becoming issues around the world, accumulation in animals, and microplastic problems, the rejection of conventional plastics such as PET is growing. Therefore, there is a growing demand for biodegradable bio-resin produced from renewable plant resources.

In general, as raw materials for biodegradable resins, natural polymers such as polylactic acid (PLA), polyhydroxybutyrate (PHB), cellulose (Cellulose), starch (Starch), chitin (Chitin), chitosan (Chitosan) There are also PBS, PBSA, PBAT, and PCL from petroleum. Among them, PLA is a biodegradable and biocompatible polymer that can be obtained from renewable raw materials such as starch and sugar cane, and has excellent mechanical strength and transparency, so that it is being developed for use in food containers. Because PLA is composed of lactic acid, a biometabolite, it is completely metabolized when decomposed (KFDA: Guide for Evaluation of Mechanical Properties, Physicochemical and Biological Safety (2009), Korea Institute of Science and Technology Information 2002: PLA is a drug release agent. Biocompatible resin being used, FCN=food contact notification NO178 certified).

However, PLA, as a semi-crystalline polymer, has brittleness, a slow crystallization rate and a long molding time, so productivity is poor, and gas barrier, water barrier is low. Therefore, in order to make labels or films with PLA, it is important to have crystallinity, crystal grain size, penetration barrier, mechanical properties, transparency, heat shrinkability, etc. suitable for the intended use.

On the other hand, the primary structure of the polymer resin is a structure determined by chemical bonds having various structural arrangements according to polymerization conditions. It is an aggregate of molecular chains and has crystalline and amorphous structures. The crystal structure affects the primary and secondary structures, and the degree of crystallinity of polymer resins depends on the primary structure. The agglomeration structure of the crystal depends on the conditions of crystallization, such as the molten state, pressure, and temperature. The bonds between the polymer resin chains are affected by the external environment and are affected by the degree of polymerization of the polymer resin, the shape and three-dimensional structure of the chain, the chemical structure of the repeating unit, and the intramolecular attraction. Therefore, the degree of crystallinity, crystal grain size, penetration barrier, mechanical properties, and transparency vary depending on the processing conditions by heat, pressure, etc. according to polymerization of polymer resin and compound manufacturing. For example, the penetration barrier property largely depends on the primary structure, which is a structure determined by the chemical bonding of the polymer resin, and also depends on the secondary structure, which is the molecular structure of the solid. In this case, the solid structure means a degree of crystallinity and a degree of molecular orientation. As such, the structure and properties of polymer resins may vary greatly depending on molding or processing conditions, and in particular, it is more difficult to prepare a resin having desired properties using PLA, which has weak penetration barrier properties.

A related prior document, Republic of Korea Patent Publication No. 10-0909776, discloses a shrinkable film blended with PLA and PBS, but has poor transparency and a thickness of 200 μm or more, making it difficult to package a plastic bottle in a film form. .

Korean Intellectual Property Office Registered Patent Publication No. 10-0909776

An object of the present invention to solve this problem is to provide a biodegradable PLA film that can be used as a shrinkable film or label suitable for packaging goods by improving flexibility, penetration barrier, heat shrinkability, etc. while maintaining the transparency of PLA. .

Another object of the present invention for solving the above problem is to provide a method for manufacturing such a PLA film.

The problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

The biodegradable PLA film according to an embodiment of the present invention for solving the above problems is polylactic acid (PLA) 33-88 wt%, polyhydroxyalkanoate (PHA) 3-20 wt%, Contains 3-20 wt% of a non-toxic plasticizer, 0.2-5 wt% of silica, 1-5 wt% of a dispersant, 0.2-5 wt% of a slip agent, 0.1-10 wt% of a chain extender and 0.1-2 wt% of an antioxidant and has a thickness of 20-60 μm, and has heat shrinkability.

In addition, it may have one or more of the following characteristics (1) to (8).

(1) Tensile strength: 1500-5000 N/cm ² (MD direction) / 1000-4000 N/cm ² (TD direction)

(2) Tear strength: 1000-4000 N/cm (MD direction) / 1000-3500 N/cm (TD direction)

(3) Elongation: 50 % (MD direction) or more / 100 % or more (TD direction)

(4) Dynamic friction coefficient: 0.2-0.5

(5) Turbidity: 5.0% or less

(6) Heat shrinkage (75 ℃/30 sec): 12-30%

(7) Oxygen permeability: 30 cc/m ² ·24 hr·atm or less

(8) Biodegradability: more than 90% for 180 days

Meanwhile, the PHA is P3HB-4HB (P(3-hydroxybutyrate)-(4-hydroxybutyrate)), the non-toxic plasticizer is polyethylene glycol, the slip agent is erucamide, and/or the dispersant is ethylenebis(stearic acid amide) ) (Ethylenebis(stearamide); EBS).

The method for producing a biodegradable PLA film according to an embodiment of the present invention for solving the above other problems is PLA 33-88 wt%, PHA 3-20 wt%, non-toxic plasticizer 3-20 wt%, silica 0.2-5 wt% %, 1-5 wt% of a dispersant, 0.2-5 wt% of a slip agent, 0.1-10 wt% of a chain extender, and 0.1-2 wt% of an antioxidant in an extruder at 160-200 °C, in the die of the extruder Preparing pellets with the extruded extrudate, extruding the pellets with a T-die extruder at 160-210 ° C. and passing through a cooling roll at 20-40 ° C. to prepare a sheet having a thickness of 100-200 μm After preheating the sheet to 70-90 ℃, stretching 2-5 times in the MD direction and 1-3 times in the TD direction (1-3 times or 1-2 times in the MD direction depending on the processing conditions; It can be stretched 2-5 times in the TD direction) through a cooling roll to prepare a film having a thickness of 20-60 μm.

In addition, one or more of the following methods (a) to (c) may be satisfied.

(a) the non-toxic plasticizer is introduced in the middle part of the extruder

(b) preparing the pellets by quenching the extrudate

(c) the temperature of the cooling roll passed after the stretching is 30-50 ℃

The details of other embodiments are included in the detailed description.

The biodegradable PLA film according to embodiments of the present invention can be used as a film or label suitable for packaging goods because mechanical properties such as flexibility, penetration barrier, heat shrinkability, etc. are greatly improved while maintaining excellent transparency.

In addition, according to other embodiments of the present invention, it is possible to manufacture a PLA film having the above properties.

Effects according to the embodiments of the present invention are not limited by the contents exemplified above, and more various effects are included in the present specification.

1 is a flowchart showing an apparatus and a process for manufacturing a biodegradable PLA film according to an embodiment of the present invention.
Figure 2 is a graph showing the relationship between the tensile strength and turbidity according to the thickness of the biodegradable PLA film measured according to the experimental example of the present invention.
3 is a graph showing the thermal shrinkage and oxygen permeability according to the PLA content and the cooling roll temperature of the biodegradable PLA film measured according to the experimental example of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. In adding reference numerals to components in each drawing, it should be noted that the same components are given the same reference numerals as much as possible even though they are indicated in different drawings.

In the description of the embodiment of the present invention, if it is determined that a detailed description of a related known configuration or function interferes with the understanding of the embodiment of the present invention, the detailed description thereof will be omitted.

In addition, in describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the components from other components, and the essence, order, or order of the components are not limited by the terms.

The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, 'and/or' includes each and every combination of one or more of the mentioned items. The singular also includes the plural, unless the phrase specifically states otherwise.

As used herein, 'comprises' and/or 'comprising' does not exclude the presence or addition of one or more other components in addition to the stated components. Numerical ranges indicated using 'to' or '-' indicate numerical ranges including the values stated before and after them as the lower and upper limits, respectively. 'About' or 'approximately' means a value or numerical range within 20% of the value or numerical range recited thereafter.

As used herein, 'penetration barrier' means a property that does not penetrate or permeate gas (gas) or moisture, and has substantially the same meaning as gas barrier and/or water barrier properties. have

Hereinafter, the present invention will be described in detail.

The biodegradable PLA film according to an embodiment of the present invention contains 33-88 wt% of polylactic acid (PLA), 3-20 wt% of polyhydroxyalkanoate (PHA), and 3-20 wt% of a non-toxic plasticizer. %, 0.2-5 wt% of silica, 1-5 wt% of a dispersant, 0.2-5 wt% of a slip agent, 0.1-10 wt% of a chain extender and 0.1-2 wt% of an antioxidant.

In the present specification, that the PLA film includes the above components means that the components or the composition are mixed, melted, extruded, injected and/or molded through steps such as to include a case in which the PLA film is manufactured.

The PLA film of the present invention may preferably be a heat shrinkable PLA film or label suitable for packaging articles.

The thickness of the PLA film may be 100 μm or less, preferably 20-60 μm. If the thickness is thinner than 20 μm, the tensile strength may be too weak, and if it is thicker than 60 μm, transparency may be lost.

PLA (Polylactic acid)

PLA is a main component for producing the biodegradable PLA film of the present invention, and is a biodegradable natural polymer obtained from starch, sugar cane, and the like. PLA has excellent mechanical strength and transparency, but it has a brittleness and a slow crystallization rate, so the molding time is long and productivity is low. In addition, PLA itself does not have good gas barrier, water barrier, which can be represented by water permeability or oxygen permeability. Therefore, it is important to improve weak properties while maintaining excellent properties by mixing with appropriate PHA, non-toxic plasticizer, and dispersing agent in an appropriate amount.

Such PLA may be included in 33-88 wt%, preferably 50-88 wt%. More preferably, it may be included in 75-85 wt%, and when the content of PLA is within the above range, it can be seen that the efficiency of increasing the heat shrinkage rate considering oxygen permeability is the best.

PHA (Polyhydroxyalkanoate, Polyhydroxyalkanoate)

PHA is added to improve the easily brittle properties of the aforementioned PLA. By mixing PHA, a biodegradable raw material, it is possible to improve the impact resistance of PLA resin while maintaining its biodegradability and transparency.

PHA may be included in 3-20 wt%, preferably in 10-15 wt%. In addition, the weight ratio of PLA and PHA may be 8:1 to 4:1. If the weight ratio is greater than 8:1, the elongation improvement may be insignificant, and if it is less than 4:1, the loss of transparency may be large compared to the elongation improvement effect. there is.

These PHAs include polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxyoctanoate (PHO) and their It may include one or more selected from the group consisting of copolymers.

Preferably, the PHA comprises at least one selected from the group consisting of poly-3-hydroxybutyrate (P3HB) and poly-4-hydroxybutyrate (P4HB). It may be PHB.

More preferably, the PHA may be P3HB-4HB (P(3-hydroxybutyrate)-(4-hydroxybutyrate)), which is a copolymer obtained by copolymerizing P4HB with a homopolymer of P3HB. Since P3HB has the property of being easily broken like PLA, it is possible to improve impact resistance, flexibility, elongation, tensile strength/elongation, moldability, etc. by copolymerizing P4HB with elasticity.

Non-toxic plasticizer

Non-toxic plasticizers can impart flexibility and stretchability to PLA resin. In addition, since the crystallization rate is increased by dropping the glass transition temperature, melting temperature, and crystallization temperature of PLA, while not affecting the crystallinity, transparency can be maintained while improving moldability. In addition, it is possible to prevent loss of transparency by using a plasticizer with low migration that can prevent the whitening of PLA resin.

The non-toxic plasticizer may be included in an amount of 3-20 wt%, preferably 10-15 wt%. If the non-toxic plasticizer is less than 3 wt%, the effect of improving flexibility, stretchability and/or moldability may be insignificant, and if it exceeds 20 wt%, transparency may be affected.

The non-toxic plasticizer may include one or more of a polyol and a citric acid ester. In an exemplary embodiment, the polyol may be selected from the group consisting of ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, trimethylolpropane, and pentaerythritol. and the citric acid ester may be selected from the group consisting of Triethyl citrate (TEC), Acetyl triethyl citrate (ATEC), Tributyl citrate (TBC), Acetyl tributyl citrate (ATBC) and Acetyl tris(2-ethylhexyl) citrate (ATEHC). there is.

silica

Silica can make the molten resin extruded from the T-die easily separated without sticking to the cooling roll when the PLA sheet or film is molded into a T-die. In addition, it acts as a nucleating agent to increase the crystallization rate, and the smaller the silica particle size, the better the crystallinity.

Silica may be included in 0.2-5 wt%, preferably 0.5-3 wt%. If the content of silica is less than 0.5 wt%, it may be difficult to prevent the molten resin of PLA from adhering to the cooling roll, and if it exceeds 3 wt%, stretchability, transparency, etc. may be deteriorated.

As silica it is possible to use commercially available silica powders such ^{as Sylobloc ®} , Sylosiv ^® , Shieldex ^® , Perkasil ^® or Sylowhite ^{® .} However, the present invention is not limited thereto.

slip agent

A slip agent is also added to prevent the PLA melt extruded from the T-die from sticking to the cooling rolls.

The slip agent may be included in an amount of 0.2-5 wt%, preferably 0.5-3 wt%. If the content of the slip agent is less than 0.5 wt%, it may be difficult to prevent the PLA molten resin from adhering to the cooling roll, and if it exceeds 3 wt%, stretchability, transparency, etc. may be deteriorated.

The slip agent may include an amide-based compound such as oleamide or erucamide (Erucamide or Erucic amide).

dispersant

The dispersant has polarity and is mixed with PLA to maintain transparency, and is not mixed with water to improve penetration barrier properties. In addition, when a PLA sheet or film is molded with a T-die, the molten resin extruded from the T-die can be easily separated without sticking to the cooling roll.

These dispersants may be included in 1-5 wt%, preferably in 1-3 wt%. If the content of the dispersant is less than 1 wt%, the penetration barrier effect may be small, and if it exceeds 5 wt%, impact resistance may be deteriorated. In particular, when the content of the dispersant is within the range of 1-5 wt%, the penetration barrier improvement efficiency may be the best compared to the impact resistance reduction.

As a dispersant, an amide-based wax such as ethylenebis(stearamide) (EBS) may be used. In addition, it may include a metallic fatty acid, specifically, calcium stearate, zinc stearate, magnesium stearate, aluminum stearate, calcium oleate, zinc oleate, magnesium oleate, aluminum oleate, calcium palmitate, zinc palmitate, magnesium palmitate and It may include one or more selected from the group consisting of aluminum palmitate.

chain extender

Chain extenders are added to improve the mechanical properties of PLA and PHA by improving the bonding strength. The chain extender may increase molecular weight, increase melt viscosity, and improve moldability such as stretchability.

The chain extender may be included in an amount of 0.1-10 wt%, preferably 0.2-2 wt%. When the content of the compatibilizer is less than 0.1 wt%, the effect of improving mechanical properties is insignificant, and when the content of the compatibilizer exceeds 10 wt%, transparency and penetration barrier properties may be deteriorated.

The chain extender may include Joncryl 4468C.

antioxidant

Antioxidants are added to prevent decomposition or yellowing of the PLA resin or the composition during PLA resin production by heat.

The antioxidant may include at least one selected from the group consisting of phenolic antioxidants, phosphorus antioxidants, amine antioxidants, and thio antioxidants. Specifically, phosphoric acid such as phosphoric acid, trimethyl phosphate or triethyl phosphate; 2,6-di-t-butyl-p-cresol, octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, tetrabis[methylene-3-(3, 5-di-t-butyl-4-hydroxyphenyl)propionate]methane or bis[3,3-bis-(4'-hydroxy-3'-tert-butylphenyl)butanoic acid]glycol ester hindered phenol type; amines such as phenyl-α-naphthylamine, N,N′-diphenyl-p-phenylenediamine or N,N′-di-β-naphthyl-p-phenylenediamine; and thio antioxidants such as dilauryl disulfide, dilauryl thiopropionate, distearyl thiopropionate or tetramethylthiuram disulfide tetrabis[methylene-3-(laurylthio)propionate]methane; can be heard In an exemplary embodiment, Songnox 1010 (Songwon Industries) may be used as the phenolic antioxidant, and Songnox 1680 (Songwon Industries) may be used as the phosphorus antioxidant, but is not limited thereto.

These antioxidants may be included in 0.1-2 wt%, preferably 0.1-1 wt%. In an exemplary embodiment, as the antioxidant, the phenolic antioxidant and the phosphorus antioxidant may be included in an amount of 0.1-1 wt%, preferably 0.1-0.5 wt%, respectively, but is not limited thereto.

1 is a flow chart showing an apparatus and a process for producing a biodegradable PLA film of the present invention. Hereinafter, a method of manufacturing a biodegradable PLA film according to another embodiment of the present invention will be described in detail with reference to FIG. 1 .

First, PLA 33-88 wt%, PHA 3-20 wt%, silica 0.2-5 wt%, dispersant 1-5 wt%, slip agent 0.2-5 wt%, chain extender 0.1-10 wt% and antioxidant 0.1 After mixing -2 wt% with a super mixer 10 or the like, it is put into the main hopper 21 of the extruder 20 maintained at 160-200 °C.

3-20 wt% of non-toxic plasticizer can also be mixed with PLA and the like and put into the main hopper 21, but it is preferable to put it into the side feeder 22 connected to the middle of the extruder to prevent thermal decomposition of the non-toxic plasticizer. . When non-toxic plasticizers are thermally decomposed, mechanical properties such as flexibility and penetration barrier properties of PLA films may be deteriorated. To this end, the side feeder 22 is preferably connected at the rear end of the melting zone of the extruder 20, but is not limited thereto.

The raw materials pass through the extruder 20 and are melted, kneaded, dispersed, etc., and unreacted substances and gases are removed from the vacuum vent 23 . The raw material mixture that has undergone this process is extruded from the die 24 of the extruder 20 . This extrudate is quenched by passing it through a water tank 30 containing cooling water, and moisture and the like are removed to prepare pellets (1). At this time, if the extrudate is not quenched with cooling water, the transparency may deteriorate.

The prepared pellets (1) are put into a T-die extruder 40 at a temperature of 160-210 ℃, and the molten resin extruded from the T-die 41 is cooled on a 20-40 ℃ cooling roll 50 ) to prepare a sheet with a thickness of 100-200 μm.

PLA, like PET, exhibits heat-shrinkage characteristics when it is oriented in a stretching direction, so in order to manufacture a heat-shrinkable film or label, the manufactured sheet must be uniaxially or biaxially stretched through a stretching process. When stretching in only one direction, since shrinkage and packaging properties in the non-stretched direction may be deteriorated, biaxial stretching is preferable.

As such a stretching process, the prepared sheet is preheated to 70-90° C., then stretched 2-5 times in the longitudinal direction (MD direction) with the stretching device 60, and 1-3 times in the width direction (TD direction) Alternatively, the film or label having a thickness of 20-60 μm is prepared by stretching 1-2 times and then cooling with a cooling roll 70 at 30-50 ° C. Alternatively, depending on the processing conditions, it may be stretched 1-3 times or 1-2 times in the MD direction, and 2-5 times in the TD direction.

Since molecular orientation and crystallinity during stretching affect thermal shrinkage, it is important to maintain transparency and improve mechanical properties by refining the crystal grain size while maintaining the crystallinity at 15-50%. However, the higher the crystallinity, the lower the biodegradability, so it is possible to prevent the deterioration of biodegradability while improving the mechanical properties by using environmentally friendly additives such as PHA and non-toxic plasticizers like the PLA film of the present invention.

The biodegradable PLA film of the present invention as described above may satisfy one or more of the following properties, preferably three or more, more preferably five or more when the thickness is 20-60 μm.

(1) Tensile strength: 1500-5000 N/cm ² (MD direction) / 1000-4000 N/cm ² (TD direction), preferably 2500-4500 N/cm ² (MD direction) / 2000-3500 N/ cm ² (TD direction)

(2) Tear strength: 1000-4000 N/cm (MD direction) / 1000-3500 N/cm (TD direction), preferably 2000-3500 N/cm (MD direction) / 1500-3000 N/cm ( TD direction)

(3) Elongation: 50% (MD direction) or more / 100% or more (TD direction), preferably 65% (MD direction) or more / 130% or more (TD direction),

(4) Dynamic friction coefficient: 0.2-0.5, preferably 0.3-0.4

(5) Turbidity: 5.0% or less, preferably 3.0% or less

(6) Heat shrinkage (75° C./30 sec): 12-30%, preferably 15-25%

(7) Oxygen permeability: 30 cc/m ² ·24 hr·atm or less, preferably 20 cc/m ² ·24 hr·atm or less

(8) biodegradability: 90% or more for 180 days, preferably 93% or more for 180 days

Hereinafter, embodiments of the present invention will be described in more detail through specific preparation examples and experimental examples. However, the following Preparation Examples and Experimental Examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Preparation Example: PLA Film Manufacturing

75.9 wt% PLA LX-175 (Total Corbion), 15 wt% P3HB-4HB (CJ CheilJedang), 0.5 wt% erucamide (Kao), 2 wt% Sylobloc ^® (Grace division), 0.4 wt% Joncryl 4468C ( BASF), 1 wt% EBS (Leochem), 0.1 wt% Songnox 1010 (Songwon Industry), and 0.1 wt% Songnox 1680 (Songwon Industry) are mixed in a super mixer for 2-5 minutes, followed by a temperature of 160-200 ℃ was put into the main hopper of the extruder holding the.

Using a liquid injection pump, 5 wt% of polyethylene glycol 400 (Lotte Chemical) is supplied to the side feeder connected to the middle part of the extruder to uniformly mix with other components in the extruder, and unreacted substances through a vacuum vent. and gas were removed. After the extrudate extruded from the die was quenched in a water bath, it was put into a dehumidifying dryer and dried to obtain a moisture content of 0.02-0.03 wt% to prepare PLA pellets.

The prepared PLA pellets were put into a T-die extruder at a temperature of 160-210 ℃, and the extruded molten resin was cooled with a cooling roll of 30 ℃ to prepare a PLA sheet having a thickness of 180 μm. After passing the prepared PLA sheet through a hot air tunnel preheated to 75 ℃, stretched twice in the MD direction, stretched 1.5 times in the TD direction, and then passed through a cooling roll at 40 ℃ to prepare a PLA film having a thickness of 60 μm.

Experimental Example 1: Comparison of physical properties of PLA film and PE shrink film

Physical properties such as tensile strength, thermal shrinkage rate, and turbidity of the PLA film of the present invention (Example 1) and the conventional PE shrink film (Comparative Example) prepared in the same manner as in the Preparation Example were measured based on the following method. , the results are shown in Table 1 below.

- Tensile strength and tear strength: ASTM D638

- Dynamic coefficient of friction: ASTM D1984

- Turbidity: ASTM D1003

- Biodegradability: ASTM D5338

- Heat shrinkage rate: After cutting the film into a square of 100 mm in length and 100 mm in width, heat shrinking it in hot water at 75 ° C. for 30 seconds, measuring the numerical values in the MD direction and TD direction, and then heat it according to Equation 1 below. Shrinkage was calculated.

[Equation 1]

Properties Example 1 comparative example Tensile strength (N/cm ² ) MD = 3950
TD = 3030 MD = 3480
TD = 2750 Tear strength (N/cm) MD = 2950
TD = 2255 MD = 3250
TD = 2590 dynamic coefficient of friction 0.32 0.33 Turbidity (%) 2.0 1.8 Heat Shrinkage (%): 75℃/30sec 18 15 biodegradability 93% or more in 180 days not biodegradable

As shown in Table 1, the PLA film of the present invention has physical properties equivalent to or higher than that of the PE film, even though it is a biodegradable resin that decomposes 93% or more within 180 days, and in particular, because it has excellent thermal shrinkage, It can be seen that it can be used as an eco-friendly shrinkable film or label replacing the degradable resin.

Experimental Example 2: Comparison of physical properties according to weight ratio of PLA and PHA

In order to find out the change in the physical properties of the PLA film according to the weight ratio of PLA and PHA, the PLA film was prepared in the same manner as in Preparation Example by varying the content ratio by weight of PLA and PHA as shown in Table 2 below (Example 2) -1 to Examples 2-4). Elongation and turbidity were measured for the prepared specimens, and the results are shown in Table 3 below. Elongation was measured according to ASTM D638.

Example PLA content (wt%): PHA content (wt%) Example 2-1 10:1 Example 2-2 8:1 Example 2-3 4:1 Example 2-4 2:1

Example Elongation (%) Turbidity (%) Example 2-1 MD = 64
TD = 131 1.6 Example 2-2 MD = 71
TD = 138 1.7 Example 2-3 MD = 88
TD = 156 1.9 Example 2-4 MD = 90
TD = 163 2.3

As shown in Table 3 above, it can be seen that the higher the ratio of PHA to PLA, the better the elongation, while the turbidity tends to be somewhat higher, and the content ratio of PLA and PHA is within the range of about 8:1 to 4:1. It can be seen that the effect of improving elongation considering the increase in turbidity is the best.

Experimental Example 3: Comparison of physical properties according to thickness of PLA film

In order to find out the change in physical properties according to the thickness of the PLA film, a PLA film was prepared in the same manner as in Preparation Example, but the PLA film was prepared in various thicknesses as shown in Table 4 below by varying the degree of stretching of the PLA sheet (Example) 3-1 to Example 3-7), tensile strength and turbidity in the MD direction were measured.

Example Film thickness (μm) Example 3-1 5 Example 3-2 10 Example 3-3 30 Example 3-4 50 Example 3-5 70 Example 3-6 90 Example 3-7 110

Figure 2 is a graph showing the tensile strength and turbidity according to the thickness of the PLA film based on the measurement results. As shown in FIG. 2, as the film becomes thicker, the tensile strength increases, but the transparency decreases. Because of the large increase, it can be seen that the PLA film has optimal properties when the thickness is 20-60 μm.

Experimental Example 4: Comparison of physical properties according to PLA content and temperature of cooling rolls

In order to find out the change in physical properties depending on the content of PLA and the temperature of the cooling roll, a PLA film was prepared in the same manner as in Preparation Example, but the PLA content and the temperature of the cooling roll for cooling the PLA film were different, as shown in Table 5 below. After preparing a PLA film (Examples 4-1 to 4-15), heat shrinkage and oxygen permeability were measured. Oxygen permeability was measured according to ASTM D3985.

PLA (wt%) Cooling roll temperature (℃) 5 20 40 70 Example 4-1 Example 4-6 Examples 4-11 80 Example 4-2 Example 4-7 Example 4-12 85 Example 4-3 Examples 4-8 Examples 4-13 90 Example 4-4 Examples 4-9 Examples 4-14 95 Example 4-5 Example 4-10 Examples 4-15

3 is a graph showing the thermal shrinkage rate and oxygen permeability of the PLA film based on the measurement results. As shown in FIG. 3, the higher the PLA content, the higher the thermal shrinkage rate, but the oxygen barrier property is lower. In addition, the lower the cooling roll temperature, the lower the thermal shrinkage. If the temperature of the cooling roll is too high, the temperature of the PLA raw material increases, and the PLA raw material itself may stick to the cooling roll due to its stickiness.

Experimental Example 5: Comparison of ease of roll separation according to the content of slip agent and silica

In order to examine the ease of separation of the PLA film from the cooling roll according to the content of the slip agent and the silica, the PLA film was prepared in the same manner as in the Preparation Example by varying the contents of the ^{slip agent erucamide and the silica Sylobloc ® as shown in Table 6 below.} While manufacturing the film, it was confirmed that the PLA sheet or film adhered to the cooling roll (Examples 5-1 to 5-6).

Example Erucamide (wt%) Sylobloc ^® (wt%) ease of separation Example 5-1 0.1 0.5 × Example 5-2 0.5 0.5 △ Example 5-3 One 0.5 ◎ Example 5-4 2 0.5 ◎ Example 5-5 One One ◎ Example 5-6 One 0.1 ×

◎: Good separation, △: Partial separation, ×: Difficulty in separation As shown in Table 6 above, it can be seen that the PLA film was easy to separate from the cooling roll when the content of the slip agent or silica was at least 0.5 wt%.

Experimental Example 6: Comparison of physical properties according to the time of addition of non-toxic plasticizer

In order to examine the difference in the physical properties of the PLA film according to the time of addition of the non-toxic plasticizer, 5 wt% of polyethylene glycol 400, a non-toxic plasticizer, was added to the super mixer and main hopper together with PLA, etc., in the same manner as in Preparation Example. PLA films were prepared. Table 7 below shows the results of comparison with the PLA film of Example 1 by measuring the tensile strength and elongation of the prepared PLA film (Example 6).

Example Tensile strength (kg/cm ² ) Elongation (%) Example 6 MD = 353.1
TD = 237.5 MD = 65
TD = 122 Example 1 MD = 402.8
TD = 309.0 MD = 85
TD = 150

As shown in Table 7, when polyethylene glycol 400, a non-toxic plasticizer, is mixed with components such as PLA from the beginning, it can be seen that the tensile strength and elongation are somewhat decreased, which is a low molecular weight non-toxic plasticizer such as polyethylene glycol 400. If it is input from the front end of the extruder, it suggests that it may be decomposed by receiving excessive heat history. In the above, the embodiments of the present invention have been mainly described, but these are merely examples and do not limit the present invention. Those of ordinary skill in the art will know that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the embodiments of the present invention.

Therefore, it should be understood that the scope of the present invention includes changes, equivalents or substitutes of the technical ideas exemplified above. For example, each component specifically shown in the embodiment of the present invention may be implemented by modification. And differences related to such modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

Claims (5)

Polylactic acid (PLA) 33-88 wt%;
Polyhydroxyalkanoate (PHA) 3-20 wt%;
3-20 wt% of a non-toxic plasticizer;
0.2-5 wt% of silica;
1-5 wt% dispersant;
0.2-5 wt% of slip agent;
0.1-10 wt of chain extender; and
0.1-2 wt% of an antioxidant;
Biodegradable PLA film with a thickness of 20-60 μm and heat shrinkability. According to claim 1,
A biodegradable PLA film having at least one of the following properties (1) to (8).
(1) Tensile strength: 1500-5000 N/cm ² (MD direction) / 1000-4000 N/cm ² (TD direction)
(2) Tear strength: 1000-4000 N/cm (MD direction) / 1000-3500 N/cm (TD direction)
(3) Elongation: 50 % (MD direction) or more / 100 % or more (TD direction)
(4) Dynamic friction coefficient: 0.2-0.5
(5) Turbidity: 5.0% or less
(6) Heat shrinkage (75 ℃/30 sec): 12-30%
(7) Oxygen permeability: 30 cc/m ² ·24 hr·atm or less
(8) Biodegradability: more than 90% for 180 days According to claim 1,
The PHA is P3HB-4HB (P(3-hydroxybutyrate)-(4-hydroxybutyrate)),
The non-toxic plasticizer is polyethylene glycol,
The slip agent is erucamide, and/or
The dispersant is ethylenebis (stearic acid amide) (Ethylenebis (stearamide); EBS) biodegradable PLA film. PLA 33-88 wt%, PHA 3-20 wt%, non-toxic plasticizer 3-20 wt%, silica 0.2-5 wt%, dispersant 1-5 wt%, slip agent 0.2-5 wt%, chain extender 0.1-10 adding wt% and 0.1-2 wt% of antioxidant to an extruder at 160-200 °C;
preparing pellets from the extrudate extruded from the die of the extruder;
extruding the pellets with a T-die extruder at 160-210° C. and passing a cooling roll at 20-40° C. to prepare a sheet having a thickness of 100-200 μm; and
Biodegradability comprising the step of preheating the sheet to 70-90° C., stretching it 2-5 times in the MD direction and 1-3 times in the TD direction, and then passing it through a cooling roll to prepare a film having a thickness of 20-60 μm Method of making PLA film. 5. The method of claim 4,
A method for producing a biodegradable PLA film that satisfies one or more of the following (a) to (c) methods.
(a) the non-toxic plasticizer is introduced in the middle part of the extruder
(b) preparing the pellets by quenching the extrudate
(c) the temperature of the cooling roll passed after the stretching is 30-50 ℃

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