Gas barrier multilayer film

Abstract

The gas barrier multilayer film according to the present disclosure is biodegradable and at the same time has excellent gas barrier properties, and has the advantage of being able to store and dispense food for a long period of time due to its excellent gas barrier properties when applied to a food packaging material. In addition, due to its biodegradable property under soil and marine conditions, it can be used as a biodegradable, environmentally friendly packaging material.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Korean Patent Application No. 10-2023-0094875 filed on July 20, 2023 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure provides a multi-layer film that is eco-friendly and has gas barrier properties. Background Art

[0004] The frequent occurrence of natural disasters in recent years has made us realize that the severity of environmental pollution and the resulting climate change are major issues that must be given top priority. Among them, reducing the use of disposable plastics is a policy that every country is pursuing as an environmental pollution improvement activity that can be implemented on a daily basis.

[0005] As part of this policy, the use of eco-friendly or biodegradable plastics is also recommended, and various plastics that can be biodegraded in soil or the ocean are being studied and developed. However, in the case of food packaging, which accounts for the majority of plastics, materials that can block gases such as oxygen and moisture must be used to prevent food from being denatured during distribution and to preserve it for a long time, and in the case of these gas barrier materials, most of them are based on petrochemicals and are not biodegradable. Therefore, in order to achieve eco-friendly food packaging materials applying biodegradable materials, food packaging companies usually add a metal layer to impart barrier properties, or preferentially apply biodegradable plastic materials to products that do not require barrier properties.

[0006] Therefore, the present disclosure relates to a multilayer film capable of blocking oxygen and moisture based on PGA→(polyglycolic acid), which is one of biodegradable polymer materials, and confirms that biodegradable food packaging is possible through such a multilayer film, thereby completing the present invention. Summary of the invention

[0007] [Technical issues]

[0008] An object of the present invention is to provide a multilayer film which is eco-friendly and has gas barrier properties.

[0009] Another object of the present invention is to provide a method for manufacturing a gas barrier multilayer film.

[0010] [Technical solution]

[0011] In order to achieve the above objectives, according to the present disclosure, the following gas barrier multi-layer film is provided.

[0012] A gas barrier multilayer film comprising: a substrate layer (Ts), and a gas barrier layer (Tb) formed on the substrate layer,

[0013] wherein the gas barrier layer (Tb) comprises 40% to 60% by volume of polyglycolic acid based on the total volume of the gas barrier layer, and

[0014] The gas barrier multilayer film satisfies the following mathematical formula 1:

[0015] [Mathematical formula 1]

[0016] 0.38≤D(Tb) / D(Ts)<4.89

[0017] In mathematical formula 1,

[0018] D(Tb) is the thickness of the gas barrier layer, and

[0019] D(Ts) is the thickness of the substrate layer.

[0020] The gas barrier multilayer film disclosed herein comprises at least two layers, and comprises a substrate layer (Ts) and a gas barrier layer (Tb) formed on the substrate layer. The gas barrier layer (Tb) comprises polyglycolic acid (PGA) as a biodegradable polymer, thereby making it biodegradable and environmentally friendly, and the gas barrier layer and the substrate layer complement each other to exhibit excellent gas barrier properties.

[0021] The present invention will be described in detail below.

[0022] The term "gas barrier layer (Tb)" used herein refers to a layer containing 40% to 60% by volume of polyglycolic acid (PGA) based on the total volume of the gas barrier layer. Polyglycolic acid is a biodegradable polymer, so that the gas barrier multilayer film according to the present disclosure can be used in an environmentally friendly manner. If the content of polyglycolic acid contained in the gas barrier layer is less than 40% by volume, it is difficult to achieve an effective gas barrier effect, and if the content of polyglycolic acid contained in the gas barrier layer exceeds 60% by volume, there is a problem that melt processability is reduced during processing and the decomposition phenomenon of polyglycolic acid is aggravated.

[0023] Preferably, the weight average molecular weight (Mw) of polyglycolic acid is 80000 to 220000. When the weight average molecular weight of polyglycolic acid is less than 80000, there may be a problem of being difficult to extrusion molding due to low melt viscosity, and the mechanical properties of molded products such as molded films are insufficient. In addition, when the weight average molecular weight is higher than 220000, polyglycolic acid may significantly change color, which may cause the appearance of molded products such as films, and may require more energy for melt processing, making effective processing difficult. More preferably, the weight average molecular weight (Mw) of polyglycolic acid is 100000 to 200000.

[0024] Preferably, the molecular weight distribution (polydispersity index, PDI) of polyglycolic acid is 1.5 to 4.5. The molecular weight distribution of polyglycolic acid is an important factor in the production of polyglycolic acid, and when the molecular weight distribution is less than 1.5, it is necessary to accurately control the polymerization conditions, which may lead to difficulties in the production of economic products. In addition, when the molecular weight distribution of polyglycolic acid is greater than 4.5, there may be a problem of accelerated decomposition during melt processing due to low molecular weight polyglycolic acid. More preferably, the molecular weight distribution of polyglycolic acid is 2.0 to 4.0.

[0025] The gas barrier layer may include various polymers except polyglycolic acid, and preferably includes poly(butylene adipate-co-butylene terephthalate) (PBAT). More preferably, the gas barrier layer includes polyglycolic acid and poly(butylene adipate-co-butylene terephthalate), and based on the total volume of the gas barrier layer, includes them in an amount of 40 volume % to 60 volume % and 60 volume % to 40 volume %. Preferably, the weight average molecular weight of poly(butylene adipate-co-butylene terephthalate) is 90000 to 180000. If the weight average molecular weight of poly(butylene adipate-co-butylene terephthalate) is less than 90000, there may be a problem that the mechanical properties of the produced film may be significantly deteriorated, and due to low melt viscosity, difficulties may occur in methods such as film molding. If the weight average molecular weight of poly(butylene adipate-co-butylene terephthalate) is greater than 180,000, it may be difficult to efficiently melt the resin in an extrusion molding process.

[0026] As used herein, the term "substrate layer (Ts)" is used to support a gas barrier layer, wherein the gas barrier layer is formed on the substrate layer. Preferably, the substrate layer is made of a biodegradable polyester or a mixture thereof. Examples of biodegradable polyesters include poly(butylene adipate-co-butylene terephthalate) (PABT), polylactic acid (PLA) and polybutylene succinate (PBS). Preferably, the weight average molecular weight of poly(butylene adipate-co-butylene terephthalate) is 90,000 to 180,000, the weight average molecular weight of polylactic acid is 110,000 to 190,000, and the weight average molecular weight of polybutylene succinate is 120,000 to 200,000.

[0027] In particular, the gas barrier multilayer film according to the present disclosure is characterized by satisfying the above-mentioned Mathematical Formula 1. Mathematical Formula 1 represents the thickness ratio between the gas barrier layer and the substrate layer, and is expressed as "D(Tb) / D(Ts)". If the D(Tb) / D(Ts) value is less than 0.38, the thickness of the gas barrier layer is made into a very thin film during melt processing, which may cause a problem of significant deterioration in gas barrier performance. In addition, if the D(Tb) / D(Ts) value is 4.89 or greater, there is a problem that the thickness of the substrate layer is made into a relatively horizontal film, which significantly reduces the melt bonding strength between the films, making it difficult to produce packaging materials. In the case of a gas barrier layer, there may be a problem that it is difficult to achieve an economically suitable gas barrier layer due to the problem of making a thick film.

[0028] In another aspect, the thickness of the gas barrier layer is 10 μm to 500 μm. In addition, the thickness of the substrate layer is 8 μm to 450 μm.

[0029] Preferably, the gas barrier multilayer film according to the present disclosure satisfies the following Mathematical Formula 2:

[0030] [Mathematical formula 2]

[0031] 0.01≤OTR(Tb) / OTR(Ts)≤0.52

[0032] In mathematical formula 2,

[0033] OTR(Tb) is the oxygen transmission rate of the gas barrier layer, and

[0034] OTR(Ts) is the oxygen transmission rate of the substrate layer.

[0035] Mathematical formula 2 represents the ratio of oxygen permeability between the gas barrier layer and the substrate layer, and is expressed as "OTR(Tb) / OTR(Ts)". The unit of oxygen permeability is "cc / m 2·day·kPa", and the measuring method is specifically described in the examples provided below. If the OTR(Tb) / OTR(Ts) value is less than 0.01, there is a problem in that it is difficult to realize a multilayer film due to the reduction in mechanical properties of the gas barrier layer, and if the OTR(Tb) / OTR(Ts) value is greater than 0.52, there is a problem in that the substrate layer is peeled off during the deformation process of the multilayer film since the substrate layer is made into a thin film, and it is difficult to realize an economical and effective gas barrier layer due to excessive thickening of the gas barrier layer.

[0036] Preferably, the gas barrier multilayer film according to the present disclosure satisfies the following Mathematical Formula 3:

[0037] [Mathematical formula 3]

[0038] 0.014≤WVTR(Tb) / WVTR(Ts)≤0.61

[0039] In mathematical formula 3,

[0040] WVTR(Tb) is the water vapor transmission rate of the gas barrier layer, and

[0041] WVTR(Ts) is the water vapor transmission rate of the substrate layer.

[0042] Mathematical formula 3 represents the ratio of the water vapor transmission rate between the gas barrier layer and the base material layer, and is expressed as "WVTR (Tb) / WVTR (Ts)". The unit of water vapor transmission rate is "g / m 2 ·day", and the measurement method is specifically described in the examples provided below. If the WVTR(Tb) / WVTR(Ts) value is less than 0.014, there is a problem that it is difficult to realize a multilayer film due to the reduction in the mechanical properties of the gas barrier layer, and if the WVTR(Tb) / WVTR(Ts) value is greater than 0.61, there may be a problem similar to the above-mentioned oxygen permeability, that is, since the substrate layer is made into a thin film, the substrate layer is peeled off during the deformation process of the multilayer film, and it is difficult to realize an economical and effective gas barrier layer due to excessive thickening of the gas barrier layer.

[0043] On the other hand, the gas barrier multilayer film according to the present disclosure may further include various layers as needed in addition to the above-mentioned substrate layer and gas barrier layer. That is, the gas barrier multilayer film according to the present disclosure may further include an additional substrate layer, an additional gas barrier layer or an inorganic layer. For example, on a gas barrier multilayer film including a substrate layer and a gas barrier layer, an additional substrate layer may be included to protect the gas barrier layer, or a substrate layer and a gas barrier layer may be further included to further enhance the gas barrier effect, or an inorganic layer may be added to improve the printing visibility of the packaging material or to improve the sliding properties of the film, thereby preventing the film roll from sticking. These examples are schematically represented as follows. At this time, the substrate layer and the gas barrier layer are as described above, and the inorganic layer refers to TiO 2 , alumina, silicon oxide, etc.

[0044] -Base layer / gas barrier layer / base layer

[0045] -Base layer / gas barrier layer / inorganic layer / base layer

[0046] -Base layer / gas barrier layer / base layer / gas barrier layer

[0047] -Base layer / gas barrier layer / base layer / gas barrier layer / base layer

[0048] Furthermore, according to the present disclosure, there is provided a method for manufacturing a gas barrier multilayer film according to the present disclosure, the method comprising: step 1 of separately making a substrate layer and a gas barrier layer film; and step 2 of laminating the respective films produced in step 1.

[0049] In step 1, a gas barrier multilayer film can be prepared by melting the components constituting the base layer and the gas barrier layer to prepare a film, and for example, it can be prepared by a blown film method. In step 2, a gas barrier multilayer film can be prepared by laminating each film prepared in the above step 1 and then laminating them using a heat press or the like.

[0050] [Beneficial Effects]

[0051] As described above, the gas barrier multilayer film according to the present disclosure is biodegradable and has excellent gas barrier properties at the same time, and when applied to food packaging materials, it has the advantage of being able to store and distribute food for a long time due to its excellent gas barrier properties. In addition, due to its biodegradable properties under soil and marine conditions, it can be used as a biodegradable eco-friendly packaging material. DETAILED DESCRIPTION

[0052] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the following examples. However, the following examples are provided only for illustrative purposes and are not intended to limit the scope of the present disclosure thereby.

[0053] Manufacturing example

[0054] The corresponding polymer blends were prepared in the proportions shown in Table 1 below using a co-rotating intermeshing twin-screw extruder (BA-19, Bautek) having a screw diameter of 19 mm, an aspect ratio (L / D, length / diameter) of 40 and 7 heated barrels.

[0055] Specifically, the barrel temperature was sequentially set to 180 to 230° C. at intervals of 20° C., and the strands extruded under the conditions of 200 rpm and 3 kg / hr feed were cooled in a 20° C. water bath and passed through a pelletizer to produce polymer blend pellets.

[0056] In the case of composition #8, polymer blend pellets were prepared under the same conditions, except that the barrel temperature was sequentially set to 140° C. to 190° C. at intervals of 20° C. At this time, Joncryl ADR 4401 (BASF) was used as a compatibilizer to increase the compatibility between the resins, and 1.0 phr was added to compositions #1 to #7, #9 and #10, respectively, and 0.1 phr was added to composition #8.

[0057] In addition, 0.1 phr of PEP36 (ADEKA) was added to compositions #1 to #7, #9 and #10 as a pentaerythritol-based antioxidant to improve thermal stability. In addition, in order to prepare a polymer composite material containing an inorganic substance, 30 wt % of TiO 2 (Sigma Aldrich) was added to poly(butylene adipate-co-butylene terephthalate) (PABT).

[0058] [Table 1]

[0059]

[0060] Examples and Comparative Examples

[0061] For each composition prepared in the manufacturing example, a film having a thickness of 30 μm was prepared using a film blowing machine (30 mm Air Die, Collin) at 230° C., 60 rpm and a BUR (blow up ratio) of 1.3. However, for composition #8 and the inorganic composite, a film having a thickness of 30 μm was prepared at 170° C., 60 rpm and a BUR (blow up ratio) of 1.3.

[0062] The prepared films were laminated in the configurations shown in Tables 2 and 3 below, and then a multilayer film was prepared using a heat press (Wabash, US) under the conditions of 40° C., 5 MPa, and 6 minutes.

[0063] Each of the produced multilayer films was subjected to the following evaluations, and are shown in Tables 2 to 4 below.

[0064] (1) Oxygen Transmission Rate (OTR)

[0065] For each film, the oxygen transmission rate (OTR) was measured using an OTR (oxygen transmission rate) device from Systech Illinois at a temperature of 23° C. and a ΔP of 1 atm for 2 days.

[0066] (2) Water vapor transmission rate (WVTR)

[0067] For each film, the water vapor transmission rate (WVTR) was measured at a temperature of 37.8°C and a relative humidity of 90% for 2 days using an AquaSense 7101 WVTR (water vapor transmission rate) device from Systech Illinois. When the oxygen transmission rate of each film was measured to be 100 cc / m 2 At high levels of ·day·kPa or higher, the water vapor transmission rate is not measured.

[0068] [Table 2]

[0069] project Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Number of layers 2 2 2 2 2 2 Layer 1 #3 #3 #3 #4 #4 #4 Layer 2 #8 #7 #9 #8 #7 #9 <![CDATA[OTR(cc / m 2 ·day·kPa)]]> 3 4 2 4 5 4 <![CDATA[WVTR(g / m 2 ·Day)]]> 4 4 3 6 6 4

[0070] [Table 3]

[0071]

[0072] [Table 4]

[0073] project Example 7 Example 8 Example 9 Example 10 Comparative Example 9 Comparative Example 10 Number of layers 3 4 5 6 3 3 Layer 1 #9 #9 #9 #9 #9 #8 Layer 2 #3 Inorganic layer #3 Inorganic layer #8 #9 Layer 3 #8 #3 #8 #3 #9 #8 Layer 4 - #8 #3 #8 - - Layer 5 - - #8 #3 - - Layer 6 - - - #8 - - <![CDATA[OTR(cc / m 2 ·day·kPa)]]> 3 2 <1 <1 21 44 <![CDATA[WVTR(g / m 2 ·Day)]]> 4 2 1 <1 22 51

Claims

1. A gas barrier multilayer film comprising: a substrate layer (Ts), and a gas barrier layer (Tb) formed on the substrate layer, wherein the gas barrier layer (Tb) comprises poly(butylene adipate-co-butylene terephthalate) and polyglycolic acid, and comprises 40% to 60% by volume of polyglycolic acid based on the total volume of the gas barrier layer, and The gas barrier multilayer film satisfies the following mathematical formula 1: [Mathematical formula 1] 0.38≤D(Tb) / D(Ts)<4.89 In mathematical formula 1, D(Tb) is the thickness of the gas barrier layer, and D(Ts) is the thickness of the substrate layer.

2. The gas barrier multilayer film according to claim 1, wherein The gas barrier multilayer film satisfies the following mathematical formula 2: [Mathematical formula 2] 0.01≤OTR(Tb) / OTR(Ts)≤0.52 In mathematical formula 2, OTR(Tb) is the oxygen transmission rate of the gas barrier layer, and OTR(Ts) is the oxygen transmission rate of the substrate layer.

3. The gas barrier multilayer film according to claim 1, wherein The gas barrier multilayer film satisfies the following mathematical formula 3: [Mathematical formula 3] 0.014≤WVTR(Tb) / WVTR(Ts)≤0.61 In mathematical formula 3, WVTR(Tb) is the water vapor transmission rate of the gas barrier layer, and WVTR(Ts) is the water vapor transmission rate of the substrate layer.

4. The gas barrier multilayer film according to claim 1, wherein The gas barrier layer comprises 40 to 60 volume % of polyglycolic acid and 60 to 40 volume % of poly(butylene adipate-co-butylene terephthalate), respectively, based on the total volume of the gas barrier layer.

5. The gas barrier multilayer film according to claim 1, wherein The substrate layer is made of biodegradable polyester or a mixture thereof.

6. The gas barrier multilayer film according to claim 5, wherein: The biodegradable polyester is poly(butylene adipate-co-butylene terephthalate) (PABT), polylactic acid (PLA) or polybutylene succinate (PBS).

7. The gas barrier multilayer film according to claim 1, wherein The thickness of the gas barrier layer is 5 μm to 50 μm.

8. The gas barrier multilayer film according to claim 1, wherein The thickness of the substrate layer is 5 μm to 60 μm.

9. The gas barrier multilayer film according to claim 1, wherein The gas barrier multilayer film further comprises an additional substrate layer, an additional gas barrier layer or an inorganic layer.

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