Gas barrier multilayer film

Abstract

A gas barrier multilayer film according to the present invention has both biodegradability and an excellent gas barrier property, and, if applied to a food packaging material, the excellent gas barrier property enables food to be stored and distributed for a long period of time. In addition, the gas barrier multilayer film is biodegradable under soil and marine conditions, and thus can be utilized as a biodegradable eco-friendly packaging material.

Description

Gas barrier multilayer film

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0094875, filed July 20, 2023, the entire disclosure of which is incorporated herein by reference.

[0003]

[0004] The present invention provides a multilayer film that is environmentally friendly and has excellent gas barrier properties.

[0005] The recent and frequent occurrence of natural disasters has highlighted the severity of environmental pollution and the resulting climate change as serious issues requiring urgent action. Reducing the use of single-use plastics is a practical, everyday approach to improving environmental pollution, and many countries are implementing policies to address this issue.

[0006]

[0007] As part of these policies, the use of eco-friendly or biodegradable plastics is also being recommended, and various plastics that can biodegrade in soil or the ocean are being researched and developed. However, in the case of food packaging, which is largely made of plastic, materials capable of blocking gases such as oxygen and moisture are essential to prevent food deterioration during distribution and long-term preservation. However, most of these gas barrier materials are made from petrochemical raw materials and are non-biodegradable. Accordingly, food packaging companies are generally implementing eco-friendly food packaging using biodegradable materials by adding metal layers to enhance barrier properties, or are preferentially applying biodegradable plastic materials to products that do not require barrier properties.

[0008]

[0009] Accordingly, the present invention relates to a multilayer film capable of blocking oxygen and moisture based on PGA (Polyglycolic acid), which is one of biodegradable polymer materials, and the present invention was completed by confirming that biodegradable food packaging material can be implemented through such a multilayer film.

[0010] The present invention provides a multilayer film that is environmentally friendly and has excellent gas barrier properties.

[0011] In addition, the present invention provides a method for manufacturing the gas barrier multilayer film.

[0012] To solve the above problem, the present invention provides the following gas barrier multilayer film:

[0013] In a gas barrier multilayer film comprising a substrate layer (Ts); and a gas barrier layer (Tb) formed on the substrate layer,

[0014] The above gas barrier layer (Tb) contains 40 to 60 volume% of poly(glycolic acid; PGA) relative to the total volume of the gas barrier layer (Tb),

[0015] The above gas barrier multilayer film satisfies the following mathematical formula 1:

[0016] Gas barrier multilayer film:

[0017] [Mathematical Formula 1]

[0018] 0.38 ≤ D(Tb) / D(Ts) < 4.89

[0019] In the above mathematical formula 1,

[0020] D(Tb) is the thickness of the gas barrier layer,

[0021] D(Ts) is the thickness of the above substrate layer.

[0022]

[0023] The gas barrier multilayer film of the present invention comprises at least two layers, namely, a substrate layer (Ts); and a gas barrier layer (Tb) formed on the substrate layer. Among these, the gas barrier layer (Tb) comprises a biodegradable polymer, polyglycolic acid (PGA), so that it is biodegradable and thus environmentally friendly, and further exhibits excellent gas barrier properties through the mutual complementation of the gas barrier layer and the substrate layer.

[0024]

[0025] The present invention is described in detail below.

[0026]

[0027] The term "gas barrier layer (Tb)" used in the present invention refers to a layer containing 40 to 60 vol% of poly(glycolic acid); PGA based on the total volume of the gas barrier layer. The polyglycolic acid is a biodegradable polymer, and through this, the gas barrier multilayer film according to the present invention can be used in an environmentally friendly manner. When the content of polyglycolic acid contained in the gas barrier layer is less than 40 vol%, it is difficult to achieve an effective gas barrier effect, and when the content of polyglycolic acid contained in the gas barrier layer exceeds 60 vol%, there is a problem that the melt processability is lowered and the decomposition phenomenon of polyglycolic acid is aggravated during processing.

[0028]

[0029] Preferably, the weight average molecular weight (Mw) of the polyglycolic acid is 80,000 to 220,000. When the weight average molecular weight of the polyglycolic acid is less than 80,000, extrusion molding may be difficult due to low melt viscosity, and furthermore, there may be a problem that the mechanical properties of the molded product, such as a film, are insufficient. In addition, when the weight average molecular weight is higher than 220,000, significant discoloration of the polyglycolic acid may occur, which may result in appearance problems of the molded product, such as a film. In addition, more energy is required for melt processing, which may make efficient processing difficult. More preferably, the weight average molecular weight (Mw) of the polyglycolic acid is 100,000 to 200,000.

[0030]

[0031] Preferably, the molecular weight distribution (Polydispersity Index, PDI) of the polyglycolic acid is 1.5 to 4.5. The molecular weight distribution of the polyglycolic acid is an important factor in the production of polyglycolic acid. If the molecular weight distribution is less than 1.5, precise control of polymerization conditions is required, which may make it difficult to produce the product economically. In addition, if the molecular weight distribution of the polyglycolic acid exceeds 4.5, a problem of accelerated decomposition during melt processing may occur due to the low molecular weight of the polyglycolic acid. More preferably, the molecular weight distribution of the polyglycolic acid is 2.0 to 4.0.

[0032]

[0033] The gas barrier layer may contain various polymers other than polyglycolic acid, and preferably contains poly(butylene adipate-co-terephthalate) (PBAT). More preferably, the gas barrier layer contains polyglycolic acid and poly(butylene adipate-co-terephthalate), and contains 40 to 60 vol% and 60 to 40 vol%, respectively, based on the total volume of the gas barrier layer. Preferably, the weight average molecular weight of the poly(butylene adipate-co-terephthalate) is 90,000 to 180,000. If the weight average molecular weight of the poly(butylene adipate-co-terephthalate) is less than 90,000, the mechanical properties of the produced film may be significantly deteriorated, and difficulties may arise in processes such as film molding due to low melt viscosity. If the weight average molecular weight of the poly(butylene adipate-co-terephthalate) exceeds 180,000, effective resin melting may be difficult in the extrusion molding process.

[0034]

[0035] The term "base layer (Ts)" used in the present invention serves to support the gas barrier layer, and the gas barrier layer is formed on the base layer. Preferably, the base layer is made of a biodegradable polyester or a mixture thereof. Examples of the biodegradable polyester include poly(butylene adipate-co-terephthalate) (PABT), polylactic acid (PLA), and polybutylene succinate (PBS). Preferably, the weight average molecular weight of the poly(butylene adipate-co-terephthalate) is 90,000 to 180,000, the weight average molecular weight of the polylactic acid is 110,000 to 190,000, and the weight average molecular weight of the polybutylene succinate is 120,000 to 200,000.

[0036]

[0037] In particular, the gas barrier multilayer film according to the present invention is characterized by satisfying the above mathematical formula 1. The mathematical formula 1 refers to the ratio of the thickness of 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 may become very thin during melt processing, which may cause a problem in that the gas barrier properties may be significantly reduced. In addition, if the D(Tb) / D(Ts) value is 4.89 or more, the thickness of the substrate layer may become significantly thin, which may cause a problem in that the melt adhesive strength between films may be significantly reduced, making it difficult to manufacture packaging materials. In addition, in the case of the gas barrier layer, there may be a problem in that it may be difficult to implement an economically appropriate gas barrier layer due to the problem in that the gas barrier layer becomes a thick film.

[0038]

[0039] Meanwhile, the thickness of the gas barrier layer is 10 to 500 μm. In addition, the thickness of the substrate layer is 8 to 450 μm.

[0040]

[0041] Preferably, the gas barrier multilayer film according to the present invention satisfies the following mathematical expression 2:

[0042] [Equation 2]

[0043] 0.01 ≤ OTR(Tb) / OTR(Ts) ≤ 0.52

[0044] In the above mathematical expression 2,

[0045] OTR(Tb) is the oxygen permeability of the gas barrier layer,

[0046] OTR(Ts) is the oxygen permeability of the above-mentioned substrate layer.

[0047]

[0048] The above mathematical expression 2 means the ratio of the oxygen permeability of the gas barrier layer and the substrate layer, and is expressed as "OTR(Tb) / OTR(Ts)". The unit of the oxygen permeability is "cc / m 2·day·kPa", and the measurement method thereof is specified in the following examples. If the OTR(Tb) / OTR(Ts) value is less than 0.01, there is a problem that it is difficult to implement a multilayer film due to a decrease in the mechanical properties of the gas barrier layer, and if the OTR(Tb) / OTR(Ts) value is more than 0.52, there is a problem that the substrate layer may peel off when the multilayer film is deformed due to the substrate layer becoming thin, and there is a problem that it is difficult to implement an economically effective gas barrier layer due to excessive thickening of the gas barrier layer.

[0049]

[0050] Preferably, the gas barrier multilayer film according to the present invention satisfies the following mathematical expression 3:

[0051] [Equation 3]

[0052] 0.014 ≤ WVTR(Tb) / WVTR(Ts) ≤ 0.61

[0053] In the above mathematical formula 3,

[0054] WVTR(Tb) is the moisture permeability of the gas barrier layer,

[0055] WVTR(Ts) is the moisture permeability of the above-mentioned substrate layer.

[0056]

[0057] The above mathematical expression 3 means the ratio of the moisture permeability of the gas barrier layer and the substrate layer, and is expressed as "WVTR(Tb) / WVTR(Ts)". The unit of the moisture permeability is "g / m 2.day", and its measurement method is specified in the examples below. If the WVTR(Tb) / WVTR(Ts) value is less than 0.014, there is a problem that it is difficult to implement a multilayer film due to a decrease in the mechanical properties of the gas barrier layer, and if the WVTR(Tb) / WVTR(Ts) value is more than 0.61, as in the case of the oxygen permeability above, a problem that the substrate layer peels off when the multilayer film is deformed due to the substrate layer becoming thinner may occur, and there is a problem that it is difficult to implement an economically effective gas barrier layer due to the excessive thickening of the gas barrier layer.

[0058]

[0059] Meanwhile, the gas barrier multilayer film according to the present invention may additionally include various layers as needed in addition to the substrate layer and gas barrier layer described above. That is, the gas barrier multilayer film according to the present invention may additionally 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 an additional substrate layer and a gas barrier layer may be included to further enhance the gas barrier effect, or an inorganic layer may be added for the purpose of improving the print visibility of packaging materials or improving the slipperiness of the film to prevent film roll blocking, and examples of these are schematically represented as follows. In this case, the substrate layer and the gas barrier layer are as described above, and the inorganic layer refers to TiO2, aluminum oxide, silicon oxide, or the like.

[0060] - Base layer / gas barrier layer / base layer

[0061] - Base layer / Gas barrier layer / Inorganic layer / Base layer

[0062] - Base layer / gas barrier layer / base layer / gas barrier layer

[0063] - Base layer / Gas barrier layer / Base layer / Gas barrier layer / Base layer

[0064]

[0065] In addition, the present invention provides a method for manufacturing a gas barrier multilayer film according to the present invention, the method comprising: a step (step 1) of manufacturing a substrate layer and a gas barrier layer film; and a step (step 2) of laminating each film manufactured in step 1.

[0066]

[0067] The above step 1 can be manufactured by a method of manufacturing a film by melting the components constituting the substrate layer and the gas barrier layer, and can be manufactured using a blown film process, for example. The above step 2 can be manufactured by laminating the respective films manufactured in the above step 1 and then laminating them using a hot press or the like.

[0068] As described above, the gas-barrier multilayer film according to the present invention is both biodegradable and possesses excellent gas-barrier properties. When applied to food packaging, its superior gas-barrier properties enable long-term storage and distribution of food. Furthermore, its biodegradability in soil and marine conditions makes it suitable for use as a biodegradable, eco-friendly packaging material.

[0069] Hereinafter, embodiments of the present invention will be described in more detail in the following examples. However, the following examples are merely illustrative of embodiments of the present invention, and the content of the present invention is not limited by the following examples.

[0070]

[0071] Manufacturing example

[0072] Using a co-rotating intermeshing twin screw extruder (BA-19, Bautek) consisting of a screw diameter of 19 mm, an aspect ratio (L / D, Length / Diameter) of 40, and 7 heating barrels, each polymer blend was manufactured at the ratios shown in Table 1 below.

[0073]

[0074] Specifically, the barrel temperature was sequentially set from 180℃ to 230℃ at 20℃ intervals, and the extruded strand was cooled in a 20℃ water bath under the conditions of 200 rpm and 3 kg / hr feeding, and then polymer blend pellets were manufactured through a pelletizer.

[0075]

[0076] For Composition #8, polymer blend pellets were manufactured under the same conditions, except that the barrel temperature was sequentially set from 140℃ to 190℃ at 20℃ intervals. At this time, Joncryl ADR 4401 (BASF) was used as a compatibilizer to increase compatibility between resins, and 1.0 phr was added to Compositions #1 to #7, #9, and #10, and 0.1 phr was added to Composition #8.

[0077]

[0078] In addition, to improve thermal stability, 0.1 phr of PEP 36 (ADEKA), a pentaerythritol-based antioxidant, was added to compositions #1 to #7, #9, and #10. In addition, to manufacture a polymer composite including an inorganic material, 30 wt% of TiO2 (Sigma Aldrich) was added to poly(butylene adipate-co-terephthalate) (PABT) under the conditions of sequentially setting the barrel temperature from 140°C to 190°C at 20°C intervals, 200 rpm, and 3 kg / hr feeding as described above.

[0079] Polymer product name (manufacturer) Composition (vol%) #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11PGAMI15 (Samyang) 10065.655.145.035.317.00--55.155.1PBATEcoflex C1200 (BASF) 034.444.955.064.783.010080---PLA4032D (NatureWorks)-------20---PBSFZ79AC (PTT-MCC)--------100--PETSKYPET BL8050 (SK Chemicals)---------44.9-PBTKH2100A (HENGLI)----------44.9

[0080]

[0081] Examples and Comparative Examples

[0082] For each composition manufactured in the manufacturing example above, a film having a thickness of 30 μm was manufactured under the conditions of 230°C, 60 rpm, and BUR (Blow-up Ratio) 1.3 using a blown film machine (30 mm Air Die, Collin). However, in the case of composition #8 and the inorganic composite, a film having a thickness of 30 μm was manufactured under the conditions of 170°C, 60 rpm, and BUR (Blow-up Ratio) 1.3.

[0083]

[0084] Each of the films manufactured above was laminated in the configuration shown in Tables 2 and 3 below, and then a multilayer film was manufactured using a Hot Press (Wabash, US) under the conditions of 40°C, 5 MPa, and 6 minutes.

[0085]

[0086] The following evaluations were conducted on each manufactured multilayer film, and are shown in Tables 2 to 4.

[0087]

[0088] (1) Oxygen permeability (OTR)

[0089] For each film, the oxygen transmission rate (OTR) was measured using an OTR (Oxygen Transmittance Rate) device from Systech Illinois at 23℃ and ΔP 1 atm for 2 days.

[0090]

[0091] (2) Water vapor transmission rate (WVTR)

[0092] For each film, the water vapor transmission rate (WVTR) was measured using an AquaSense 7101 WVTR (Water Vapor Transmittance Rate) device from Systech Illinois at 37.8℃ and 90% relative humidity for 2 days. The oxygen transmission rate of each film was 100 cc / m 2 Water permeability was not measured when measured at high levels greater than .day.kPa.

[0093]

[0094] Item Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Layer Number 2 2 2 2 2 Layer 1 # 3 # 3 # 3 # 4 # 4 # 4 Layer 2 # 8 # 7 # 9 # 8 # 7 # 9 OTR (cc / m 2 .day.kPa)342454WVTR(g / m 2 .day)443664

[0095]

[0096] Item Comparison Example 1 Comparison Example 2 Comparison Example 3 Comparison Example 4 Comparison Example 5 Comparison Example 6 Comparison Example 7 Comparison Example 8 Layer Number 1 1 1 1 2 2 2 Layer 1 # 3 # 6 # 7 # 8 # 9 # 7 # 10 # 11 Layer 2----- # 3 # 8 # 8 OTR (cc / m 2 .day.kPa)151031091172920Failure 1) FailureWVTR(g / m 2 .day)16---3324FailureFailure1) Failure: The compatibility between polymers was poor, so it was not manufactured into a film.

[0097]

[0098] Item Example 7 Example 8 Example 9 Example 10 Comparative Example 9 Comparative Example 10 Layer Number 345633 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--OTR(cc / m 2 .day.kPa)32< 1< 12144WVTR(g / m 2 .day)421< 12251

Claims

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

2. In paragraph 1, The above gas barrier multilayer film satisfies the following mathematical formula 2: Gas barrier multilayer film: [Equation 2] 0.01 ≤ OTR(Tb) / OTR(Ts) ≤ 0.52 In the above mathematical expression 2, OTR(Tb) is the oxygen permeability of the gas barrier layer, OTR(Ts) is the oxygen permeability of the above-mentioned substrate layer.

3. In paragraph 1, The above gas barrier multilayer film satisfies the following mathematical formula 3: Gas barrier multilayer film: [Equation 3] 0.014 ≤ WVTR(Tb) / WVTR(Ts) ≤ 0.61 In the above mathematical formula 3, WVTR(Tb) is the moisture permeability of the gas barrier layer, WVTR(Ts) is the moisture permeability of the above-mentioned substrate layer.

4. In paragraph 1, The above gas barrier layer comprises polyglycolic acid and poly(butylene adipate-co-terephthalate) in an amount of 40 to 60% by volume and 60 to 40% by volume, respectively, relative to the total volume of the gas barrier layer. Gas barrier multilayer film.

5. In paragraph 1, The above substrate layer is made of biodegradable polyester or a mixture thereof. Gas barrier multilayer film.

6. In paragraph 5, The above biodegradable polyester is poly(butylene adipate-co-terephthalate) (PABT), polylactic acid (PLA), or polybutylene succinate (PBS). Gas barrier multilayer film.

7. In paragraph 1, The thickness of the above gas barrier layer is 5 to 50 ㎛, Gas barrier multilayer film.

8. In paragraph 1, The thickness of the above substrate layer is 5 to 60 ㎛, Gas barrier multilayer film.

9. In paragraph 1, The above gas barrier multilayer film further comprises an additional substrate layer, an additional gas barrier layer, or an inorganic layer. Gas barrier multilayer film.