KR20120016416A - Environmental friendly multi-layer barrier film and preparation method thereof - Google Patents

Abstract

PURPOSE: An eco-friendly multilayered barrier film and a method for manufacturing the same are provided to enable free thickness control of a first resin layer and to ensure biodegradation. CONSTITUTION: A multilayered barrier film comprises: a first resin layer formed of polyvinyl alcohol(PVOH) with 170-220 °C of melting temperature; and a second resin layer which is formed at both sides of the first resin layer and contains PET(polyethylene terephthalate). The multilayered barrier film has a second resin layer/first resin layer/second resin layer, a second resin layer/first resin layer/first resin layer/second resin layer, or second resin layer/first resin layer/second resin layer/first resin layer/second resin layer.

Description

Eco-friendly multilayer barrier film and its manufacturing method {ENVIRONMENTAL FRIENDLY MULTI-LAYER BARRIER FILM AND PREPARATION METHOD THEREOF}

The present invention relates to an environmentally friendly multilayer film having excellent gas barrier properties, which can be used as a packaging material, and a manufacturing method thereof.

Thermoplastic resin films such as polypropylene films and polyethylene terephthalate films derived from petroleum have excellent mechanical strength and are widely used as packaging films because of their excellent workability.

However, due to the low barrier to gas, its use is limited for applications where the package must be kept very safe from the action of external gases, in particular atmospheric oxygen, or the gas composition in the package must be kept constant. to be.

Accordingly, in order to impart gas barrier functions such as oxygen barrier property, laminating a resin layer having gas barrier property such as polyvinyl alcohol (PVOH) system on the film surface of the thermoplastic resin film has been developed.

Korean Laid-Open Patent Publication No. 2001-21633 has a configuration in which a coating layer comprising a water-dispersible copolyester having PVOH and a sulfonyloxy moiety includes a polyester base film having a thickness of 5 to 50 μm formed on one side thereof, and having transparency. A composite polyester film having excellent barrier properties and resistance to mechanical stress is disclosed.

In addition, Korean Patent Laid-Open Publication No. 2004-37065 discloses that a gas barrier layer made of a hydrolyzate of silicon alkoxide, a layered silicate, and a PVOH-based resin is coated on a base layer made of a thermoplastic resin film and silicon alkoxy is interposed between the layers of the internal silicate. The film | membrane is comprised so that a film | membrane exists and the film excellent in gas barrier property is disclosed also in the high humidity exceeding 90% RH.

In addition, Korean Laid-Open Patent Publication No. 2002-92812 has a structure in which a gas barrier layer made of PVOH-based resin, silicon alkoxide hydrolyzate and polyethylene oxide is laminated on one side of the thermoplastic resin film and a sealing layer is laminated on the opposite side. As a result, a film excellent in appearance and excellent in gas barrier properties even under high humidity is disclosed.

However, the conventional method of implementing barrier properties by laminating PVOH resin by coating has a limitation that coating is not possible beyond a certain thickness, and the thicker the thickness, the weaker the coating adhesion, and the protective layer. In order to laminate the film, an additional lamination process is required after film production, which causes a problem in that the production efficiency is lowered. Therefore, the development of an improved barrier film that can solve the above problems by laminating a PVOH resin layer without coating.

Republic of Korea Patent Publication No. 2001-21633 Republic of Korea Patent Publication No. 2004-37065 Republic of Korea Patent Publication No. 2002-92812

Accordingly, it is an object of the present invention to provide a novel multilayer barrier film having improved gas barrier properties and a method of manufacturing the same.

According to the above object, the present invention comprises a first resin layer made of polyvinyl alcohol (PVOH) having a melting temperature (Tm) of 170 to 220 ℃; And a second resin layer formed on both sides of the first resin layer and made of polylactic acid (PLA) or polyethylene terephthalate (PET) having a melting temperature of 205 ° C. or less.

According to another object of the present invention, the present invention provides a) a polyvinyl alcohol (PVOH) resin having a melting temperature (Tm) of 170 to 220 ° C as a first resin, and a polylactic acid (PLA) resin or melting temperature of 205 as a second resin. Melting a polyethylene terephthalate (PET) resin that is below < RTI ID = 0.0 > And b) co-extrusion the molten first resin and the second resin in step a) to obtain a sheet in which the second resin layer is laminated on both sides of the first resin layer, and then stretching and heat setting the sheet to obtain a multilayer film. Alternatively, the first resin and the second resin melted in step a) are respectively extruded, stretched and heat-set to obtain a first sheet and a second sheet, and then an adhesive layer is coated on both sides of the first sheet, and the second sheet. It provides a method for producing a multilayer barrier film of the present invention, comprising the step of obtaining a multilayer film by bonding.

The multilayer film of the present invention is excellent in biodegradability by using an environmentally friendly resin, has excellent barrier property against gas, and has a protective layer, so that physical properties are not easily degraded, and the thickness of the barrier layer can be adjusted to provide barrier properties. Can be further improved.

1 is a result of measuring the oxygen air permeability of the barrier film obtained in Examples and Comparative Examples over time.

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

In the film of the present invention, polyvinyl alcohol (PVOH) used as the resin forming the barrier layer (first resin layer) is not biomass but is biodegradable resin.

In general, since the PVOH resin has a similar melting temperature (Tm) and decomposition temperature (Td), it is impossible to obtain a film by an extrusion process. Therefore, in order to use PVOH resin as a barrier film, the coating method was mainly used conventionally. However, when the coating method is used, the coating is not possible beyond a specific thickness, and as the thickness becomes thick, there is a disadvantage in that the adhesive strength of the coating is weakened, and there is a problem in that the protective layer is difficult to be laminated. Thus, in the present invention, using a PVOH resin modified so that the melting temperature (Tm) is 170 to 220 ℃, to produce a PVOH layer through an extrusion process.

More preferably, the PVOH resin used in the present invention has a melting temperature of 180 to 200 ° C and a decomposition initiation temperature of at least 10 ° C or higher than the melting temperature. Moreover, it is preferable that polymerization degree is the range of 300-3,000.

As a result, the thickness can be freely adjusted to further improve the barrier property. Preferably, the thickness of the barrier layer (first resin layer) is 100 nm to 100 μm. This is a numerical value compared with that of the conventional PVOH barrier layer manufactured using the coating method, which had to be about 1 μm or less. As a result, the film of the present invention can improve the barrier property to the gas, the air permeability to oxygen according to ASTM D3985 is preferably 10cc / m ² / day or less.

Since the film of the present invention has a multilayer structure of three or more layers in which a PVOH layer is used as a barrier layer (first resin layer) and a protective layer (second resin layer) is disposed on both sides, PVOH is directly exposed to the external environment. To prevent physical properties from deteriorating. In the conventional film, since there is no protective layer, the direct printing on the PVOH-coated film affects the PVOH, resulting in poor barrier properties.

In the present invention, the protective layer (second resin layer) is made of polylactic acid (PLA) or polyethylene terephthalate (PET). In the case of using PET as the protective layer, since the melting temperature of general PET has a high decomposition starting temperature of PVOH, it is difficult to apply it to the coextrusion process. In the present invention, the modified PET is modified so that the melting temperature is lower than that of PVOH. use. Preferably the melting temperature of PET is preferably 170 to 205 ℃.

The preferred weight average molecular weight (Mw) of PLA used in the present invention is 50,000 to 300,000, and the preferred weight average molecular weight (Mw) of PET is 10,000 to 60,000.

In the barrier film of the present invention, the three-layer film can be configured as a protective layer / barrier layer / protective layer, and more than three layers of the protective layer / barrier layer / barrier layer / protective layer, protective layer / barrier layer. A configuration such as a protective layer / barrier layer / protective layer is possible.

When the thickness of each resin layer becomes thick, the bonding force between the resin layers may be reduced, and thus an adhesive layer may be further included between the resin layers. For example, the structure of the protective layer / adhesive layer / barrier layer / adhesive layer / protective layer can be considered. As said adhesive layer, the layer which consists of resin chosen from polyethylenimine, a polyurethane, etc. can be used.

In the film of the present invention, the thickness of the protective layer (second resin layer) is preferably 1 to 150 µm, and the thickness of the entire multilayer barrier film is preferably 5 to 200 µm. Nano-lamination is also possible through thickness control, in which case the adhesion between the layers can be better.

The multilayer barrier film of the present invention comprises a) melting a PVOH resin having a melting temperature (Tm) of 170 to 220 ° C as a first resin, and a PLA resin or a PET resin having a melting temperature of 205 ° C or less as a second resin, respectively. step; And b) extruding and heat-setting the melted first and second resins.

In step b), the first resin and the second resin may be laminated by co-extrusion, or may be laminated by extruding and then bonding each using an adhesive layer.

In the case of using co-extrusion in step b), the molten first resin and the second resin are co-extruded to obtain a sheet in which the second resin layer is laminated on both sides of the first resin layer, followed by stretching and heat setting. Can be.

In addition, in the case of using the adhesive layer in step b), the melted first resin and the second resin are respectively extruded, stretched and heat-set to obtain the first sheet and the second sheet, and then the adhesive layers are formed on both sides of the first sheet. Coating and bonding the second sheet.

In the manufacturing method, the temperature in the melt extrusion process is preferably 170 to 250 ° C, more preferably 170 to 220 ° C.

Such a multilayer barrier film of the present invention has better gas barrier properties than the conventional one, and in particular, the thickness of the PVOH layer can be adjusted to further improve barrier properties, and the physical properties including the protective layer are not easily reduced. In addition, it is environmentally friendly, and in particular, when using PLA as the protective layer resin, the entire multilayer film may be 100% biodegradable.

Therefore, the multilayer barrier film of the present invention can be used in fields requiring environmental friendliness and barrier properties, for example, food packaging materials.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited to the following examples.

In the following Examples 1-3, the following was used as raw material resin.

PVOH PLA PET manufacturer Nippon gohsei Nature works SKC product name Nichigo G-polymer 4032D XTP10 Tg (占 폚) 75 60 85 Tc (℃) 93 110 130 Tm (占 폚) 183 170 205 Decomposition start temperature (℃) 240 ↑ 240 ↑ 300 ↑ Mw 20,000 ~ 80,000 150,000 ~ 200,000 3.50,000-40,000

Example 1: Preparation of PLA / PVOH / PLA Multi-layer Coextrusion Film

As the first resin, a polyvinyl alcohol resin (G-POLYMER, Nippon Gohsei) having a melting temperature of 183 ° C was used, and a polylactic acid resin (4032D, NatureWorks) having a melting temperature of 170 ° C was used as the second resin.

Each of the raw material resins was melt extruded at 220 ° C. such that the thickness ratio of the second resin layer / first resin layer / second resin layer was 5: 1: 1 through three extruders, and then laminated in three layers in a feed block. .

The unstretched laminated sheet was brought into close contact with a casting roll at 15 ° C. and stretched at 80 ° C. with a 3.0% longitudinal draw ratio, and stretched at 90 ° C. with a transverse draw ratio 3.8 times. This was heat-set at 100 ° C. to obtain a biaxially stretched three-layer coextrusion film having a thickness of 20 μm.

Example 2: Preparation of PET / PVOH / PET Multi-layer Coextrusion Film

Polyvinyl alcohol resin (G-POLYMER, Nippon Gohsei) having a melting temperature of 183 ° C was used as the first resin, and polyethylene terephthalate resin (XTP10, SKC) having a melting temperature of 205 ° C was used as the second resin. .

Each of the raw material resins were 220 ° C. (first resin layer) and 240 ° C. (second resin) so that the thickness ratio of the second resin layer / first resin layer / second resin layer was 5: 1: 5 through three extruders. Resin extrusion) and then laminated in three layers in the feed block.

The unstretched laminated sheet was brought into close contact with a casting roll at 15 ° C. and stretched at 80 ° C. with a 3.0% longitudinal draw ratio, and stretched at 90 ° C. with a transverse draw ratio 3.8 times. This was heat-set at 100 ° C. to obtain a biaxially stretched three-layer coextrusion film having a thickness of 20 μm.

Example 3: Preparation of PLA / Adhesive Layer / PVOH / Adhesive Layer / PLA Multilayer Bonding Film

As the first resin, a polyvinyl alcohol resin (G-POLYMER, Nippon Gohsei) having a melting temperature of 183 ° C was used, and a polylactic acid resin (4032D, NatureWorks) having a melting temperature of 170 ° C was used as the second resin. As the adhesive resin, a polyurethane resin having a melting temperature of 205 ° C was used.

The first resin and the second resin were melt-extruded through an extruder to have a thickness ratio of 5: 1 at 220 ° C., respectively, and brought into close contact with a casting roll at 15 ° C. to be stretched at 80 ° C. in a longitudinal draw ratio of 3.0 times, and 90 times in a transverse draw ratio of 3.8 times. After stretching at < RTI ID = 0.0 > C, < / RTI > The second sheet / first sheet / second sheet were laminated in the order of coating, and the adhesive resin was coated between the sheets, followed by bonding to prepare a multilayer bonding film having a thickness of 20 μm.

In the following Comparative Examples 1-5, the following was used as raw material resin.

PVOH PLA PET EVOH PVdC manufacturer OCI Nature works SKC Kuraray Asahi Kasei product name POLINOL 4032D CTF41 EVAL PVDC LATEX Tg (占 폚) 85 60 80 48 -17 Tc (℃) 110 130 Tm (占 폚) 230 170 255 160 200 Decomposition start temperature (℃) 200 ↑ 240 ↑ 300 ↑ 220 ↑ 200 ↑ Mw 20,000 ~ 80,000 150,000 ~ 200,000 3.50,000-40,000 150,000-30,000 50,000 ~ 100,000

Comparative Example 1: Preparation of PVOH Single Layer Coating Film (Base Film-PLA)

The polylactic acid resin (4032D, NatureWorks) whose melting temperature was 170 degreeC was melt-extruded at 220 degreeC, contact | adhered to the casting roll of 15 degreeC, and extended | stretched at 80 degreeC by 3.0 times of longitudinal stretch ratio. After coating a solution containing 3% by weight of polyvinyl alcohol (POLINOL, OCI) having a melting temperature of 225 to 230 ° C with a wet thickness of 16.4 μm using a Mayer rod # 6, It extended | stretched at 130 degreeC by 3.8 times. It was heat set at 230 ° C. to obtain a biaxially oriented coated film having a thickness of 20 μm.

Comparative Example 2: Preparation of PVOH Single Layer Coating Film (Base Film-PET)

A polyethylene terephthalate resin (CTF41, SKC) having a melting temperature of 255 ° C. was melt-extruded at 285 ° C., brought into close contact with a casting roll at 15 ° C., and stretched at 80 ° C. with a 3.0 times longitudinal drawing ratio. A solution containing 3% by weight of polyvinyl alcohol (POLINOL, OCI Co., Ltd.) having a melting temperature of 225 to 230 ° C. was coated with a wet thickness of 16.4 μm using a Mayer rod # 6, thereby extending transverse ratio 3.8. Stretched at 130 degreeC by boat. It was heat set at 230 ° C. to obtain a biaxially oriented coated film having a thickness of 20 μm.

Comparative Example 3: Preparation of PLA Single Layer Film

Polylactic acid resin (4032D, NatureWorks) having a melting temperature of 170 ° C was melt-extruded at 220 ° C. The resultant was brought into close contact with a casting roll at 15 ° C. and stretched at 80 ° C. with a longitudinal draw ratio of 3.0 times and at 90 ° C. with a transverse draw ratio of 3.8. It was heat set at 100 ° C. to obtain a biaxially stretched monolayer film having a thickness of 20 μm.

Comparative Example 4: Preparation of EVOH Multi-layer Coextrusion Film

EVOH (EVAL, Kuraray) having a melting temperature of 160 ° C. was used as the first resin, and polylactic acid resin (4032D, NatureWorks) having a melting temperature of 170 ° C. was used as the second resin.

Each of the raw material resins was melt extruded at 220 ° C. such that the thickness ratio of the second resin layer / first resin layer / second resin layer was 5: 1: 1 through three extruders, and then laminated in three layers in a feed block. .

The unstretched laminated sheet was brought into close contact with a casting roll at 15 ° C., and stretched at 70 ° C. at a 3.0 times longitudinal stretch ratio, and stretched at 90 ° C. at a transverse draw ratio 3.8 times. This was heat-set at 100 ° C. to obtain a biaxially stretched trilayer coextrusion film having a thickness of 20 μm.

Comparative Example 5: Preparation of PVdC Coating Film (Base Film-PET)

A polyethylene terephthalate resin (CTF41, SKC) having a melting temperature of 255 ° C. was melt-extruded at 285 ° C., was brought into close contact with a casting roll at 15 ° C., and stretched at 105 ° C. with 3.0 times the longitudinal drawing ratio. On it, a solution containing 50 wt% of PVdC resin (PVDC LATEX, Asahi Kasei) having a melting temperature of 200 ° C. was coated with a wet thickness of 16.4 μm using a Mayer rod # 8, and then transversely. It extended | stretched at 130 degreeC by draw ratio 3.8 times. It was heat set at 230 ° C. to obtain a biaxially oriented coated film having a thickness of 20 μm.

Test Example

Test Example 1 Evaluation of Air Permeability to Oxygen

For the films obtained in the above examples and comparative examples, the air permeability to oxygen was measured using an air permeability meter (OX-TRAN, MOCON) according to ASTM D3985 in the air. Furthermore, after printing on the surface of each film, air permeability was measured in the same manner. The results are shown in Table 3 below.

division Example Comparative example One 2 3 One 2 3 4 5 Specularity
(cc / ㎡ / day) Unprinted 10 8 14 15 15 900 15 20 After printing 12 8 16 20 20 920 16 20

As shown in Table 3, the barrier film of the embodiment according to the present invention can be seen that the barrier property against oxygen is more excellent than the barrier film of the comparative example prepared in a conventional manner. In addition, while the barrier film of Example maintains low air permeability even after printing, it can be seen that in Comparative Examples 1 to 3 without the protective layer, the barrier property is greatly reduced after printing.

Test Example 2 Evaluation of Air Permeability to Oxygen Under Humidity

For the films obtained in the above Examples and Comparative Examples, the air permeability to oxygen was measured using an air permeability meter (OX-TRAN, MOCON) according to ASTM D1434 at 25 ° C., 1 atm and 50% RH. The results are shown in Table 4 below.

division Example Comparative example One 2 3 One 2 3 4 5 Specularity
(cc / ㎡ / day)
11
9
15
900
40
900
16
20

As shown in Table 4, it can be seen that the barrier film of the embodiment according to the present invention is superior to the barrier property against oxygen even under a high humidity of 50% RH than the barrier film of the comparative example prepared in a conventional manner. In the case of Comparative Example 1, the PVOH coating layer collapsed under 50% RH, and showed a value similar to that of Comparative Example 3.

Test Example 3 Evaluation of Changes in Air Efficiency Over Time

For the films obtained in the above Examples and Comparative Examples, using the air permeability measuring instrument (OX-TRAN, MOCON Co., Ltd.) according to ASTM D3985, the air permeability was measured continuously at daily intervals in the air and the results are shown in FIG. It was.

As shown in FIG. 1, it can be seen that even after time passes, the barrier film of the example according to the present invention is generally superior to the barrier property against oxygen than the barrier film of the comparative example manufactured in a conventional manner. In the case of Comparative Examples 1 and 3 were too large (1000cc level) compared to other values it could not be shown together.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, It is to be understood that the invention may be practiced within the scope of the appended claims.

Claims (9)

A first resin layer made of polyvinyl alcohol (PVOH) having a melting temperature (Tm) of 170 to 220 ° C; And a second resin layer formed on both sides of the first resin layer and made of polylactic acid (PLA) or polyethylene terephthalate (PET) having a melting temperature of 205 ° C. or less.
The method of claim 1,
The multilayer barrier film, characterized in that the multilayer coextrusion film or multilayer bonding film.
The method of claim 1,
The thickness of the first resin layer is characterized in that the 100nm to 100㎛, multilayer barrier film.
The method of claim 1,
The multilayer barrier film, the multi-layer barrier film, characterized in that the air permeability according to ASTM D3985 is 10 cc / ㎡ / day or less.
The method of claim 1,
The multilayer barrier film,
Second resin layer / first resin layer / second resin layer;
A second resin layer / first resin layer / first resin layer / second resin layer; or
It has a structure of 2nd resin layer / 1st resin layer / 2nd resin layer / 1st resin layer / 2nd resin layer, The multilayer barrier film characterized by the above-mentioned.
The method of claim 1,
The multilayer barrier film, characterized in that further comprising an adhesive layer between the first resin layer and the second resin layer.
The method of claim 6,
The adhesive layer is a multilayer barrier film, characterized in that consisting of a resin selected from polyethyleneimine and polyurethane.
a) polyvinyl alcohol (PVOH) resin having a melting temperature (Tm) of 170 to 220 ° C as a first resin, and polylactic acid (PLA) resin as a second resin or polyethylene terephthalate (PET) resin having a melting temperature of 205 ° C or less Melting each of them; And
b) co-extrusion the molten first resin and the second resin in step a) to obtain a sheet in which the second resin layer is laminated on both sides of the first resin layer, and then stretching and heat setting the sheet to obtain a multilayer barrier film. ; Alternatively, the first resin and the second resin melted in step a) are respectively extruded, stretched and heat-set to obtain a first sheet and a second sheet, and then an adhesive layer is coated on both sides of the first sheet and the second sheet is bonded. The method of manufacturing the multilayer barrier film of claim 1 comprising the step of obtaining a multilayer barrier film.
The method of claim 8,
Melt extrusion temperature of the first resin is 170 to 250 ℃ manufacturing method of a multilayer barrier film.

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