JP2006198842A - Gas barrier composite film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas barrier composite film excellent in the gas barrier properties of oxygen, carbon dioxide and steam. <P>SOLUTION: The gas barrier composite film comprises an α-1,4-glucan layer constituted of α-1,4-glucan and/or its modified matter and the water-resistant layer provided at least on one side of the α-1,4-glucan layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a composite film having excellent gas barrier properties. More specifically, the present invention relates to a gas barrier composite film having an α-1,4-glucan layer composed of α-1,4-glucan and / or a modified product thereof, and a water-resistant layer.

  Conventionally, as a packaging material, for example, a film of a thermoplastic synthetic resin such as polyolefin, polyester, polystyrene, or polyvinyl chloride is used. However, these films generally have insufficient barrier properties against oxygen and carbon dioxide, and in particular, food packaging materials (for example, fresh meats and seafood, refrigerated foods, frozen foods, dairy products, beverages, (Fruits and vegetables, snack foods, dried foods, noodles, cooked rice, miso, pickles, etc.), toiletry materials, chemical packaging materials, etc. are desired to be improved. In addition, when used as a coating material for burns and wounds, there is a drawback that it does not satisfy the required oxygen barrier property and also lacks compatibility with the human body.

  Therefore, a film made of an ethylene vinyl alcohol copolymer, polyamide or the like with improved gas barrier properties has been developed. However, these films are products manufactured by a process under high temperature and high humidity such as retort sterilization, and there is a problem in performance as a packaging material for products that require long-term storage.

  In addition, the demand for products that are friendly to the global environment has increased, and polyglycolic acid, polylactic acid, polycaprolactone, and the like have been developed as biodegradable films. For example, Japanese Patent Laid-Open No. 10-80990 (Patent Document 1) describes a composite film in which a thermoplastic film is laminated on a film formed from polyglycolic acid. However, the film of polylactic acid and polycaprolactone has a problem that it is inferior in the barrier property of gas such as oxygen, carbon dioxide, and water vapor. In addition, the polyglycolic acid film has an excellent barrier property against the gas, but has a problem that it is disadvantageous in terms of economy because it has low film strength and is expensive.

Japanese Patent Laid-Open No. 10-80990

  An object of the present invention is to provide a composite film having excellent barrier properties against oxygen, carbon dioxide, and water vapor. Furthermore, it is providing the biodegradable gas barrier composite film with low environmental impact.

The present invention
an α-1,4-glucan layer composed of α-1,4-glucan and / or a modified product thereof, and a water-resistant layer provided on at least one surface of the α-1,4-glucan layer;
The gas barrier composite film having the above is provided, whereby the above object is achieved.

  The molecular weight of α-1,4-glucan is preferably 100 kDa to 6000 kDa.

  Further, α-1,4-glucan is preferably enzyme-synthesized α-1,4-glucan.

  The modification of the α-1,4-glucan modified product is preferably a chemical modification selected from the group consisting of esterification, etherification, and crosslinking.

  Furthermore, the water-resistant layer is preferably composed of a biodegradable resin.

  Furthermore, the water-resistant layer is preferably composed of a biodegradable resin made from renewable resources.

  The composite film of the present invention has a water-resistant layer on at least one side of an α-1,4-glucan and / or an α-1,4-glucan layer made of a modified product thereof excellent in gas barrier properties and film strength properties. It has a structure and is excellent in gas barrier properties and other physical performances. And the composite film of this invention has the characteristics that it is excellent in gas barrier property, even if it is very thin. Moreover, by using a renewable resource as a raw material for the water-resistant layer, biodegradability can be imparted and the environmental load can be reduced.

  The present inventors have already found that α-1,4-glucan having biodegradability and / or a modified film thereof has excellent film strength with a single layer (WO 02/06507 A1). ). The present inventors examined the gas permeability of the film made of α-1,4-glucan in more detail. Surprisingly, the gas permeability of the film made of α-1,4-glucan It has been found for the first time that it is remarkably lower than the gas permeability of petroleum-based films and biodegradable films, and has excellent barrier properties against oxygen, nitrogen, carbon dioxide, ethylene, and the like.

  However, a film made of α-1,4-glucan has a problem that water resistance and water vapor blocking properties are not sufficient, and the usable range is limited as it is. Thus, as a result of intensive studies, it was found that a composite film having excellent barrier properties against water vapor and other gases can be obtained by forming a water-resistant layer on at least one surface of a film made of α-1,4-glucan. It was.

The composite film of the present invention is
an α-1,4-glucan layer composed of α-1,4-glucan and / or a modified product thereof, and a water-resistant layer provided on at least one surface of the α-1,4-glucan layer;
A composite film having excellent gas barrier properties.

α-1,4-glucan layer The α-1,4-glucan layer contained in the composite film of the present invention is composed of α-1,4-glucan and / or a modified product thereof.

  The term “α-1,4-glucan”, as used herein, is a sugar having D-glucose as a constituent unit and linked only by α-1,4-glucoside bonds. Is a saccharide having at least two saccharide units. α-1,4-glucan is a linear molecule. α-1,4-glucan is also called linear glucan. The number of sugar units contained in one molecule of α-1,4-glucan is called the degree of polymerization. In this specification, the term “degree of polymerization” refers to the weight average degree of polymerization unless otherwise specified. In the case of α-1,4-glucan, the weight average degree of polymerization is calculated by dividing the weight average molecular weight by 162.

  The term “dispersion degree Mw / Mn” is the ratio of the number average molecular weight Mn to the weight average molecular weight Mw (that is, Mw ÷ Mn). Except for special cases such as proteins, a high molecular compound has a molecular weight that is not single and has a certain range regardless of whether it is derived from natural or non-natural origin. Therefore, in order to show the degree of dispersion of the molecular weight of the polymer compound, the dispersion degree Mw / Mn is usually used in the field of polymer chemistry. This degree of dispersion is an indicator of the breadth of the molecular weight distribution of the polymer compound. In the case of a polymer compound having a completely single molecular weight, Mw / Mn is 1, and Mw / Mn becomes a value larger than 1 as the molecular weight distribution increases. In this specification, the term “molecular weight” refers to weight average molecular weight (Mw) unless otherwise specified.

  The α-1,4-glucan of the present invention is a polymer having a structure in which glucose is linearly bonded. This can be produced from natural starch, by enzymatic methods, etc., by methods known in the art.

  As a method for obtaining α-1,4-glucan from natural starch, for example, isoamylase or pullulanase known as a debranching enzyme is used only for the α-1,6-glucoside bond of amylopectin present in natural starch. There is a method of obtaining amylose by selectively acting and decomposing amylopectin (so-called starch enzymatic decomposition method). Another example is a method in which an amylose / butanol complex is precipitated and separated from starch paste.

  In addition, α-1,4-glucan can be prepared using a known enzyme synthesis method. As an example of the enzyme synthesis method, there is a method in which amylosucrase (EC 2.4.1.4) is allowed to act using sucrose as a substrate.

  Another example of the enzyme synthesis method is a method using glucan phosphorylase (α-glucan phosphorylase, EC 2.4.1.1; usually referred to as phosphorylase). Phosphorylase is an enzyme that catalyzes a phosphorolysis reaction.

In the present invention, it is preferable to use enzyme-synthesized α-1,4-glucan, and it is particularly preferable to use α-1,4-glucan that is enzymatically synthesized using glucan phosphorylase. Enzymatic synthesis α-1,4-glucan synthesized with glucan phosphorylase has the following characteristics:
(1) Narrow molecular weight distribution (Mw / Mn is 1.1 or less);
(2) Those having an arbitrary degree of polymerization (about 60 to about 37000) can be obtained by appropriately controlling the production conditions;
(3) is completely linear and does not contain the slight branching structure found in amylose fractionated from natural starch;
(4) Like natural starch, it is composed only of glucose residues, and α-1,4-glucan, its degradation intermediates, and final degradation products are not toxic to living bodies;
(5) Low permeability of oxygen, nitrogen, carbon dioxide, ethylene, etc .;
(6) Even if the moisture in the film fluctuates, physical properties such as strength hardly change;
(7) If necessary, chemical modification similar to starch is possible;
(8) Film strength characteristics comparable to petroleum-based plastics such as polyethylene, polypropylene and polyester.

Since the enzyme-synthesized α-1,4-glucan synthesized with glucan phosphorylase has the above characteristics, the following advantages are obtained when it is used as a film or sheet:
(A) safely decomposed and metabolized after use;
(B) Gas barrier properties can be controlled by controlling the molecular weight or the degree of chemical modification substitution;
(C) protects the contents from external damage with excellent film properties;

  Those obtained by modifying the above α-1,4-glucan can also be used. Examples of such modifications include esterification, etherification and crosslinking.

  Esterification is, for example, reaction of α-1,4-glucan with an esterification reagent (eg, acid anhydride, organic acid, acid chloride, ketene or other esterification reagent) in various solvents or without solvent. Can be done. By such esterification, for example, a modified acylated ester such as acetate ester or propionate ester can be obtained.

  Etherification can be performed, for example, by reacting α-1,4-glucan with an etherifying agent (for example, alkyl halide, dialkyl sulfate, etc.) in the presence of an alkali. By such etherification, for example, modified products of carboxymethyl ether, hydroxypropyl ether, hydroxymethyl ether, methyl ether, and ethyl ether are obtained.

  Crosslinking can be performed, for example, by reacting α-1,4-glucan with a crosslinking agent (formalin, epichlorohydrin, glutaraldehyde, various diglycidyl ethers, various esters, etc.).

  As the α-1,4-glucan, those that have not been modified or those that have been modified may be used alone or in combination. Two or more α-1,4-glucan modifications may be used in combination.

  The α-1,4-glucan and / or modified product constituting the α-1,4-glucan layer preferably has a polymerization degree of about 620 to 37000 (molecular weight of 100 kDa to 6000 kDa), and more preferably about 1240 to about 1240. It is preferably 12400 (molecular weight 200 kDa to 2000 kDa). When the degree of polymerization is lower than 620, the strength and flexibility of the α-1,4-glucan layer may be inferior. Moreover, when a polymerization degree exceeds 37000, there exists a possibility that the yield in the synthesis | combination of (alpha) -1, 4- glucan may become low. Moreover, since the viscosity becomes high, there is a possibility that molding becomes difficult. However, when α-1,4-glucan having various degrees of polymerization is used in combination, the range is not limited to the above range of degree of polymerization. The balance of each property can be adjusted by using α-1,4-glucan having various degrees of polymerization.

  The molecular weight distribution Mw / Mn of α-1,4-glucan and / or a modified product thereof is preferably 1.2 or less, and more preferably 1.1 or less. When the molecular weight distribution Mw / Mn exceeds 1.2, the molecular weight distribution becomes wide, the gas barrier property and the film physical property may be lowered, and the excellent characteristics of α-1,4-glucan may not be exhibited.

  The thickness of the α-1,4-glucan layer is not particularly limited, but is usually 1-1000 μm, preferably 5-100 μm. Furthermore, the α-1,4-glucan layer can exhibit a sufficient gas barrier property even if it is about 10 to 50 μm thick.

  The α-1,4-glucan layer of the present invention may contain a softening agent. Examples of the softening agent include glycerin, monoacetin, diacetin, triacetin, polyvinyl alcohol, polyethylene glycol, starch, dextrin, sucrose fatty acid ester, glycerin fatty acid ester and the like. By including such a softening agent, the physical properties of the obtained film can be improved.

  The α-1,4-glucan layer of the present invention may contain a lubricant such as a surfactant. Examples of lubricants include sodium lauryl sulfate, sucrose fatty acid ester, glycerin fatty acid ester, polyvinyl alcohol, polyoxyethylene sorbitan fatty acid ester, sorbitan monostearate, lecithin, carnauba wax, shellac and the like. By using such a lubricant, the moldability of the composite film can be improved, and stickiness can be improved.

  The α-1,4-glucan layer of the present invention may contain a colorant and a pigment for the purpose of imparting discrimination and light shielding properties. Examples of colorants and pigments include yellow ferric oxide, ferric oxide, edible red No. 2 aluminum lake, edible red No. 3, edible red No. 102, edible red No. 104, edible red No. 105, edible red No. 106, Food yellow No. 4, food yellow No. 5, food green No. 3, food blue No. 1, food blue No. 2, copper chlorofin sodium, copper chlorofin, titanium oxide and the like can be mentioned.

  As a method for preparing the α-1,4-glucan layer, it can be prepared by a method such as extrusion molding, injection molding, casting, or drying a thin film gel using a commonly used production apparatus.

Examples of the material constituting the water-resistant layer of the water-resistant layer composite film include thermoplastic resins and waxes.

  The thermoplastic resin is not particularly limited. For example, polyolefin (eg, polyethylene, polypropylene, ethylene vinyl acetate copolymer, etc.), polyester (eg, polyethylene terephthalate, polylactic acid, polysuccinate, etc.), polystyrene , Polyvinyl chloride, polycarbonate, polyamide, polyurethane, ethylene vinyl alcohol copolymer, polyvinylidene chloride, polyglycolic acid, polycaprolactone, α-1,4-glucan modified product, cellulose acetate and the like. Examples of the wax include paraffin wax, tung oil, and beeswax. These thermoplastic resins and waxes may be used alone or in combination of two or more.

  More preferably, the water-resistant layer is composed of a biodegradable resin. Because α-1,4-glucan is excellent in biodegradability, the composite film obtained is excellent in biodegradability by forming the water-resistant layer from a biodegradable resin. Examples of biodegradable resins include polylactic acid, polyglycolic acid, polycaprolactone, poly-3-hydroxybutyric acid, poly-3-hydroxyalkanoic acid, polybutylene succinate, polyethylene succinate and other polyesters, starch, pullulan , Polysaccharides such as cellulose, chitin and chitosan and modified products thereof, polyamides such as polyglutamic acid and polylysine, gluten, collagen and gelatin, polyvinyl alcohol, polyethylene glycol, polyurethane and the like, and their block copolymers and terpolymers, graft polymers Etc. These biodegradable resins may be used alone or in combination of two or more.

  Although there is no restriction | limiting in particular in the thickness of a water-resistant layer, Usually, 1-1000 micrometers, Preferably, it is 5-100 micrometers, More preferably, it is 10-50 micrometers.

  As a method for preparing the water-resistant layer of the present invention, when the water-resistant layer is composed of a thermoplastic resin, it is usually used by a method such as extrusion molding, injection molding, casting or drying a thin film gel. It can be prepared using a manufacturing apparatus. Moreover, when a water-resistant layer is comprised from a wax, a water-resistant layer can be formed by the method of apply | coating a wax to any one side or both surfaces of (alpha) -1, 4- glucan layer.

Composite film The composite film of the present invention comprises:
an α-1,4-glucan layer composed of α-1,4-glucan and / or a modified product thereof, and a water-resistant layer provided on at least one surface of the α-1,4-glucan layer;
Have

  The water-resistant layer may be provided on only one surface of the α-1,4-glucan layer, or may be provided on both surfaces of the α-1,4-glucan layer. When providing a water-resistant layer on both sides of the α-1,4-glucan layer, these water-resistant layers may be composed of the same component or may be composed of different components.

The method for producing the composite film is not particularly limited. For example, (1) a method of separately producing an α-1,4-glucan layer and a water-resistant layer and bonding them together,
(2) A method of providing the other layer on one layer (film) of the α-1,4-glucan layer and the water-resistant layer, for example, by extrusion coating,
(3) a method of co-extrusion of an α-1,4-glucan layer and a water-resistant layer,
(4) A method of coating one layer (film) of the α-1,4-glucan layer and the water-resistant layer with the other layer melted or made into a solution,
Etc.

  In the method (1), examples of the method of bonding the α-1,4-glucan layer and the water-resistant layer include a method of bonding using an adhesive, a method of bonding by heat melting, and the like. As an adhesive that can be used, a synthetic adhesive or a natural adhesive can be used. Specifically, although not particularly limited, for example, emulsion adhesive (vinyl acetate resin type, EVA resin type, acrylic resin type, etc.), pressure sensitive adhesive (solvent type, emulsion type, etc.), silicone type, etc. Examples thereof include an adhesive and a photocurable adhesive. Furthermore, α-1,4-glucan and / or a modified product thereof used in the present invention can also be used as an adhesive.

  As the composite film of the present invention, for example, in a gas barrier composite film having a polyethylene / polyamide / polyethylene layer structure, a film of α-1,4-glucan and / or a modified product thereof is used instead of polyamide. Examples are given. The composite film thus obtained can achieve the purpose of long-term storage in applications such as packaging materials. In addition to oxygen, nitrogen and carbon dioxide, α-1,4-glucan can also block the permeation of ethylene involved in ripening fruits and the like. Then, as a water resistant layer, a compostable composite film can be prepared by combining with biodegradable resin such as polylactic acid, biomax, polysuccinic acid ester, polycaprolactone and the like. Furthermore, when it is combined with α-1,4-glucan and / or a modified product thereof, polylactic acid, etc., which are renewable resources, a composite film having not only gas barrier properties but also less burden on the global environment can be produced.

  Furthermore, the film characteristics of α-1,4-glucan and / or a modified product thereof are particularly excellent in tensile strength. α-1,4-glucan and / or a modified product thereof can provide a film having an excellent barrier property against the above gas even if it is a single layer, however, there is a drawback that water resistance and moisture resistance are insufficient. is there. By using a composite film as in the present invention, a composite film having excellent water resistance and moisture resistance, and excellent physical strength and gas barrier properties can be obtained.

  The following examples further illustrate the present invention, but the present invention is not limited thereto. In the examples, “parts” and “%” are based on weight unless otherwise specified.

  In the test examples, a method for preparing purified glucan phosphorylase derived from potato tubers, a method for preparing sucrose phosphorylase derived from Streptococcus mutans, a method for calculating the yield (%) of α-1,4-glucan, a weight average molecular weight (Mw) and a number average The measuring method of molecular weight (Mn) followed the method known by description of Unexamined-Japanese-Patent No. 2002-345458. Specifically, the molecular weight of the synthesized glucan was measured as follows. First, the synthesized glucan is completely dissolved in 1N sodium hydroxide, neutralized with an appropriate amount of hydrochloric acid, and about 300 μg of glucan is subjected to gel filtration chromatography using a differential refractometer and a multi-angle light scattering detector in combination. To determine the weight average molecular weight. Specifically, Shodex SB806M-HQ (manufactured by Showa Denko) is used as a column, and a multi-angle light scattering detector (DAWN-DSP, manufactured by Wyatt Technology) and a differential refractometer (Shodex RI-71, manufactured by Showa Denko) are used as detectors. ) Were used in this order. The column was kept at 40 ° C., and 0.1 M sodium nitrate solution was used as an eluent at a flow rate of 1 mL / min. The obtained signals were collected using data analysis software (trade name ASTRA, manufactured by Wyatt Technology), and analyzed using the same software to determine the weight average molecular weight and the number average molecular weight.

  The degree of substitution of acetylated α-1,4-glucan was measured by the following method according to the description of “Starch / Related Sugar Experimental Method” (Nakamura et al., 1986, Japan Society for the Science of Publishing). 1 g of the sample was precisely weighed into a 300 ml Erlenmeyer flask, and 50 ml of 75% ethanol was added and dispersed. To this was added 40 ml of 0.5N aqueous sodium hydroxide solution, which was sealed and shaken at room temperature for 48 hours. Excess alkali was titrated with 0.5N hydrochloric acid, and the degree of substitution (DS) was determined from the difference from the blank. The degree of substitution (DS) is the average number of substituted hydroxyl groups per anhydroglucose residue.

  The gas permeability test was carried out by the following method by a differential pressure method based on Japanese Industrial Standard JIS K7126 “Gas permeability test method for plastic film and sheet”. The apparatus includes a permeation cell for allowing gas to permeate the test piece, a pressure detector for detecting a pressure change caused by the permeated gas, a test gas supplier for supplying oxygen to the permeation cell, a vacuum pump, and the like. The pressure detector was measured with the accuracy of 1 Pa using NEW Palmyl vacuum gauge PVD-9500-L21 by Sato Vacuum Co., Ltd. The diameter of the transmission surface was 30 mm, and the test piece was dried for 48 hours or more using silica gel in a desiccator. The test conditions were a room temperature of 20 ° C. and a test temperature of 25 ° C. In the test method, one side (low pressure side) separated by the test piece was kept in vacuum, gas was introduced to the other (high pressure side) at about 1 atm, and the pressure on the low pressure side was recorded to obtain a transmission curve. The pressure change on the low pressure side per unit time was determined from the steady state slope of the permeation curve, and the gas permeability and gas permeation coefficient were calculated. In addition, the average value measured three places was used for the thickness of the test piece.

  The measurement of water vapor permeability is as follows using a water vapor permeability measuring device CR-2011 by a moisture sensitive sensor method based on Japanese Industrial Standard JIS K7129 “Water vapor permeability test method for plastic films and sheets (instrument measurement method)”. It was done by the method.

  Distilled water was put into the lower cell, and a Kapton test piece was inserted between the upper cell and the lower cell. After confirming that the temperature of the upper cell and the lower cell reached 40 ± 0.5 ° C., the relative humidity of the upper cell was adjusted by adjusting the nitrogen gas flow rate. H. The measurement was started after it became constant at 1% RH or less. Unit relative humidity range R.P. H. The water vapor transmission time of 2.5% to 5% was read, and the measurement was repeated until the error became a constant value of ± 5.0% or less. In addition, as a standard sample, the biaxially stretched polypropylene film (made by Daicel Chemical Industries Ltd.) was used.

  The water vapor permeability was calculated by the formula (1).

（１）

(1)

In the formula, WVTR: water vapor permeability of the test piece [g / (m ² · 24 h)]
S: Water vapor permeability of standard sample [g / (m ² · 24h)]
C: Time required for the unit sample relative humidity range [s]
T: Time required for the unit relative humidity range of the test piece [s]
F: Transmission area of standard sample / transmission area of test piece.

Production Example 1 : Synthesis of α-1,4-glucan Reaction solution (1) containing 15 mM phosphate buffer (pH 7.0), 106 mM sucrose, and malto-oligosaccharide mixture (Tetrap H, manufactured by Hayashibara) 5.4 mg / liter Liter) and purified glucan phosphorylase derived from potato tuber (1 unit / ml) and Streptococcus mutans-derived sucrose phosphorylase (1 unit / ml) were added and incubated at 37 ° C. for 16 hours. , 4-glucan yield (%), weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined. As a result, α-1,4-glucan having a weight average molecular weight of 1250 kDa and a molecular weight distribution (Mw / Mn) of 1.03 was obtained.

Production Example 2 : Synthesis of acetylated α-1,4-glucan In 80 g of dimethyl sulfoxide, the α-1,4-glucan obtained in Test Example 1 was dissolved at a concentration of 5% by weight, and 2 g of sodium carbonate was obtained. After adding, 10 g of vinyl acetate was added and reacted at 40 ° C. for 60 minutes. After the reaction, ethanol was added to precipitate the product. After filtration, the product was washed several times with water and purified. The degree of substitution of the obtained acetylated α-1,4-glucan was 0.56.

Preparation of α-1.4-glucan layer monolayer film and gas permeability test Each solution obtained in Examples 1 and 2 was cast on a substrate and dried with a drier kept at 30 ° C. A film having a thickness of about 30 μm was obtained. A gas permeability test was conducted on the two types of films thus obtained and a commercially available resin film. As shown in Table 1, the gas barrier property of α-1,4-glucan represented by the gas permeability coefficient (P × 10 ¹² ) indicates oxygen 0.016 and carbon dioxide 0.13, and cellophane oxygen 0 .12, 10 times better than those of carbon dioxide 2.88. Furthermore, there is a difference of 100 times or more for polylactic acid, polyglycolic acid, and hydroxypropylcellulose. In addition, polylactic acid and hydroxypropylcellulose are inferior to 8.4 and 42, respectively, with respect to α-1,4-glucan ethylene 0.37.

The α-1,4-glucan modified product has a gas permeability coefficient of 0.061 from DS: 0 to DS: 0 as the substitution degree DS increases by esterification or etherification of the hydroxyl group of glucose as a structural unit. .56 of 1.2 (P × 10 ¹² ), that is, the gas barrier property is lowered. These results suggest that gas barrier films having different performances can be obtained even in a single layer film. Furthermore, when it approaches DS: 3, water resistance improves and it can be used as a laminate film for forming a water-resistant layer against α-1,4-glucan.

  In addition, the α-1,4-glucan modified product is excellent in compatibility with ordinary thermoplastic resins and adhesiveness, so it can be used as an adhesive or adhesive layer to improve the adhesion between each layer of the film. May be.

Example 1
A commercially available polylactic acid film 35 μm was heated and pressure-bonded at 80 ° C. to one side of an acetylated α-1,4-glucan film about 30 μm thick obtained in Example 2 to obtain a composite film.

Example 2
A commercially available cellulose acetate film of 35 μm was heated and pressure-bonded at 80 ° C. on both sides of a film of about 30 μm thick acetylated α-1,4-glucan obtained in Example 2 to obtain a composite film.

Example 3
A commercially available polyethylene film 20 μm was heated and pressure-bonded at 80 ° C. using an EVA adhesive on both sides of the α-1,4-glucan film about 30 μm thick obtained in Example 1 to obtain a composite film. It was.

Example 4
A commercially available polylactic acid film of 30 μm was laminated on one side of the α-1,4-glucan film of about 30 μm thickness obtained in Example 1 using an EVA adhesive. The other side of the α-1,4-glucan film was coated with beeswax to obtain a composite film.

Test 2 : Preparation of composite film and gas permeability test The composite films of Examples 1 to 4 were tested in the same manner as Test 1. The results are shown in Table 2. In Table 2, the test results of films made of polylactic acid, polyglycolic acid, cellophane or hydroxypropyl cellulose shown in Table 1 are shown as Comparative Examples 1 to 4, respectively.

The composite film of the present invention has excellent properties such as high barrier properties against oxygen, carbon dioxide, and water vapor. For this reason, the product to be packaged can be stored for a long time. Furthermore, the composite film of the present invention has an advantage of high affinity with the human body. Furthermore, a biodegradable gas barrier composite film can be provided, thereby reducing the burden on the environment. The composite film of the present invention is particularly suitable as various packaging materials and medical materials.

Claims (6)

an α-1,4-glucan layer composed of α-1,4-glucan and / or a modified product thereof, and a water-resistant layer provided on at least one side of the α-1,4-glucan layer;
A gas barrier composite film comprising:   The gas barrier composite film according to claim 1, wherein the molecular weight of α-1,4-glucan is 100 kDa to 6000 kDa.   The gas barrier composite film according to claim 1 or 2, wherein the α-1,4-glucan is an enzymatically synthesized α-1,4-glucan.   The gas barrier composite film according to any one of claims 1 to 3, wherein the modification of the α-1,4-glucan modified product is a chemical modification selected from the group consisting of esterification, etherification, and crosslinking.   The gas barrier composite film according to any one of claims 1 to 4, wherein the water-resistant layer is composed of a biodegradable resin. The gas barrier composite film according to any one of claims 1 to 5, wherein the water-resistant layer is composed of a biodegradable resin made from renewable resources.