Degradable high-barrier-property composite film, high-barrier-property composite material comprising same, and manufacturing method of degradable high-barrier-property composite film and high-barrier-property composite material

Abstract

A degradable high-barrier composite film, a high-barrier composite material comprising the same, and a method for manufacturing the same, the degradable high-barrier composite film comprising: a first polymer film layer comprising a first polymer material and a first plasticizer; the first polymer film layer comprises a first polymer material and a first plasticizer, the second polymer film layer comprises a second polymer material and a second plasticizer, the first polymer film layer and the second polymer film layer are mutually stacked, the first polymer material and the second polymer material are biodegradable materials, the first polymer material has gas barrier property and heat sealability, and the second polymer material has gas barrier property and heat sealability. The second polymer material has hydrophobicity, and wherein the gas passing rate of the high barrier composite film is less than 0.1 cm < 3 > / (m < 2 >. 24hr. 0.1 MPa).

Description

Technical Field

[0001] The present invention relates to a composite film and a method for manufacturing the same, and in particular to a high-barrier composite film composed of two or more degradable polymers having gas barrier properties, heat sealability and hydrophobicity, and a method for manufacturing the same. The present invention also relates to a high-barrier composite material comprising the composite film and a method for manufacturing the same. Background Art

[0002] At present, the world produces about 350 million tons of plastic products every year, but the recycling rate is less than 10%. In particular, disposable plastic products are the main source of plastic pollution to the environment, of which more than 50% are used for packaging purposes, especially flexible packaging such as film bags. Therefore, replacing traditional plastic materials with degradable materials has become a very important industrial trend to solve plastic pollution. Currently commonly used degradable materials, such as polylactic acid PLA (Polylactic Acid), polybutylene adipate terephthalate PBAT (Polybutylene Adipate Terephthalate) and polybutylene butyrate PBS (Polybutylene Succinate), have been used to manufacture film products, but because their physical properties such as mechanical strength and transparency cannot be compared with traditional plastics, especially the gas barrier performance is much lower than that of traditional plastics, which limits the applicability of these degradable materials.

[0003] In the current plastic packaging application field, high barrier films are a very important and rapidly growing type, which are mainly used in the packaging of products that are sensitive to oxygen and / or water vapor, such as food, cosmetics, medical supplies, and electronic / communication / optical products. For the packaging of these products, it is very important to reduce spoilage and increase the shelf life of the product, and / or avoid rust to maintain stable product quality.

[0004] Therefore, the packaging of these products requires not only excellent barrier properties, but also good heat-sealing properties to meet the needs of airtight storage; and good printability to achieve the requirements of beautifying the appearance; in addition, superior mechanical properties are required to ensure the integrity of the transportation process.

[0005] In view of the high gas barrier requirements of composite films, generally speaking, the oxygen transmission rate (OTR) must be less than 1.5 cm 3 / (m 2 .24hrs.0.1MPa), plastic materials commonly used to provide high gas barrier properties include polyvinylidene chloride (PVDC) and ethylene-vinyl alcohol copolymer (EVOH).

[0006] Table 1: Requirements for high barrier films in different packaging applications

[0007]

[0008] (Data source: https: / / zhuanlan.zhihu.com / p / 447273480 )

[0009] The barrier properties of commonly used barrier materials to gases (such as oxygen) and water vapor are shown in Table 2 below.

[0010] Table 2. Oxygen permeability and water vapor permeability of commonly used barrier materials

[0011]

[0012] (Data source: Plastic Industry Development Center website data, https: / / www.pidc.org.tw / news_column_show.php? id=51 )

[0013] However, up to now, due to the limitations of the physical properties of degradable materials themselves, there is no material on the market that can simultaneously meet the requirements of degradability, heat sealability and excellent mechanical properties and can be made into a high-barrier film for use alone.

[0014] In order to meet the gas barrier requirements of different application fields, the current trend of industrial development is to develop multi-type, multi-functional and multi-layer composite films. The manufacturing process of composite films has been developed, which generally includes dry composite method, coating composite method, co-extrusion composite method and evaporation composite method.

[0015] In the dry lamination method, various boards, sheets or films are used as the substrate, and adhesive is coated on the surface of the substrate using a roller. After drying to produce adhesion, it is pressed and laminated.

[0016] In the coating composite method, barrier materials that are difficult to process into films alone, such as polyvinyl alcohol (PVA), polyvinylidene chloride (PVDC) and polyvinylidene chloride (PVDC), are coated on the surface of a suitable substrate after adding appropriate solvents and additives.

[0017] In the co-extrusion composite method, two or more materials are heated and melted in different screw flow channels, and the molten materials are brought together to the same die head and welded to form a multi-layer composite film.

[0018] In addition, the evaporation composite method is a technology that combines a plastic film substrate with an inorganic material. The dense inorganic layer gives better barrier properties. The more common evaporation composite method, such as vacuum aluminum plating technology, vaporizes aluminum wire at high temperature under high vacuum conditions, and precipitates and gathers aluminum vapor on the surface of the plastic film to form a barrier layer.

[0019] At present, among the above methods, the technology of using co-extrusion composite method to manufacture multi-layer composite films has been increasingly widely used in the industry. In addition to a wide range of material selection, the thickness of each layer can also be adjusted according to demand, effectively reducing the use of expensive materials. Such composite films can be used in a wide range of needs.

[0020] Based on the requirements of heat sealing, mechanical properties and cost, multi-layer composite films are usually manufactured by multi-layer co-extrusion (for example, polypropylene-EVOH-polypropylene three-layer composite film can provide a high barrier film with both polypropylene mechanical properties and heat sealing strength).

[0021] Co-extrusion technology can be applied to blow molding, cast film or stretch film equipment. Under the requirements of functionality, this technology not only has high output, but also can reduce film thickness, and takes into account the sustainable environmental protection requirements of energy conservation and reducing packaging waste. Combining the above-mentioned processing processes, co-extrusion lamination is a low-cost, high-output, and widely used option.

[0022] In the field of film manufacturing, the manufacturing technology of multi-layer co-extrusion film is already very mature. The most common is three-axis co-extrusion, which can produce up to three layers of film. Recently, there are 11-axis co-extrusion equipment that can produce up to 11 layers of film at a time.

[0023] Regarding the high gas barrier properties required for packaging films, according to public literature, polyvinyl alcohol (PVA) is the plastic material with the best known gas barrier properties. The film made from it is a water-soluble, highly transparent, glossy, biodegradable and heat-sealable high gas barrier film. However, due to its water solubility and easy ductility, the applicability of polyvinyl alcohol alone processed into packaging films is limited.

[0024] In view of the mechanical properties required for packaging films, films made from cellulose acetate have the characteristics of being biologically derived, degradable, highly transparent, having good gloss, excellent mechanical strength, being easy to print, and having good oil resistance, water resistance, and resistance to organic solvents. However, although cellulose acetate films have good gas barrier properties, they still cannot meet the high gas barrier requirements for packaging films. At the same time, cellulose acetate films have poor heat sealing properties and are not easy to be made into airtight packaging bags, which limits the application of cellulose acetate as a flexible packaging material.

[0025] In industrial applications, in the process of using polyvinyl alcohol or cellulose acetate to make thin films, solution coating is usually used, and the film is dried and then rolled up. Since this solution coating process uses a large amount of solvent (such as water or flammable organic solvent), extra attention should be paid to operational safety and environmental protection issues. It is also time-consuming, energy-consuming, and has limited production, making this method difficult to be widely used in general plastic material processing equipment. Summary of the invention

[0026] In view of this, the main purpose of the present invention is to provide a degradable high-barrier composite film and a method for manufacturing the same. Specifically, the composite film is a double-layer or multi-layer composite film mainly composed of a degradable polymer with high gas barrier and heat-sealability (such as polyvinyl alcohol) and a hydrophobic degradable polymer (such as cellulose acetate), thereby utilizing the advantages of various materials at the same time and improving the disadvantages of each film being formed separately.

[0027] Furthermore, another object of the present invention is to manufacture a biodegradable high barrier composite film by co-extrusion lamination, replacing the traditional solvent die-casting or coating method, so as to simplify the process and eliminate the need for using flammable organic solvents, thereby improving operational safety.

[0028] In addition, another object of the present invention is to provide a new option of sustainable packaging material, wherein the pollution to the natural environment can be reduced by using degradable polymers.

[0029] According to the above object of the present invention, there is provided a degradable high barrier composite film, comprising:

[0030] a first polymer film layer comprising a first polymer material and a first plasticizer; and

[0031] The second polymer film layer comprises a second polymer material and a second plasticizer, wherein:

[0032] The first polymer film layer and the second polymer film layer are stacked on each other, and

[0033] The first polymer material and the second polymer material are both biodegradable materials, the first polymer material has gas barrier properties and heat sealability, the second polymer material has hydrophobicity, and wherein,

[0034] The gas permeability of the high barrier composite film is less than 0.1 cm 3 / (m 2 ·24hrs·0.1MPa).

[0035] According to the present invention, there is also provided a high barrier composite material, comprising:

[0036] substrate; and

[0037] The high barrier composite film as described above is attached to the substrate.

[0038] Wherein, the substrate comprises paper, plastic or metal.

[0039] According to the present invention, there is also provided a method for manufacturing a degradable high-barrier composite film, comprising:

[0040] a pellet preparation step, mixing the first polymer material and the second polymer material with the first plasticizer and the second plasticizer, respectively, and extruding them to form the first polymer pellet and the second polymer pellet; and

[0041] In the film preparation step, the first polymer particles and the second polymer particles are co-extruded to form a degradable high-barrier composite film.

[0042] According to the present invention, there is also provided a method for manufacturing a high barrier composite material, comprising:

[0043] The above-mentioned steps of preparing the colloid particles and preparing the film; and

[0044] The film laminating step is to laminate the degradable high barrier composite film onto a substrate, wherein the substrate comprises paper, plastic or metal.

[0045] In the degradable high barrier composite film and its manufacturing method of the present invention, two or more degradable polymer materials having gas barrier properties, heat sealability and hydrophobicity are used to manufacture the composite film by co-extrusion without using organic solvents, which can improve the shortcomings of each film forming separately and reduce the pollution to the natural environment. In addition, the manufactured composite film has excellent barrier properties, especially the gas barrier rate (GTR) can reach less than 0.1cm 3 / (m 2 .24hrs.0.1MPa) level. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a structural diagram of an embodiment of the degradable high-barrier composite film of the present invention;

[0047] Figure 2A and Figure 2B They are respectively structural diagrams of another embodiment of the degradable high-barrier composite film of the present invention;

[0048] Figure 3 It is a structural diagram of another embodiment of the degradable high-barrier composite film of the present invention;

[0049] Figure 4 is a structural diagram of an embodiment of the high barrier composite material of the present invention;

[0050] Figure 5 It is a flow chart of the method for manufacturing the degradable high-barrier composite film of the present invention;

[0051] Figure 6is a flow chart of a method for manufacturing a high barrier composite material of the present invention;

[0052] Figure 7 Shows polyvinyl alcohol pellets produced by hot melt extrusion;

[0053] Figure 8 Showing cellulose acetate pellets produced by hot melt extrusion; and

[0054] Fig. 9 This is an electron microscope scanning image of an embodiment of the degradable high-barrier composite film of the present invention.

[0055]

Explanation of symbols

[0056] 10: First polymer film layer

[0057] 20: Second polymer film layer

[0058] 30: third polymer film layer

[0059] 40: Base material

[0060] S10: Preparation step of colloid particles

[0061] S20: Thin film preparation step

[0062] S30: Film Lamination Step DETAILED DESCRIPTION

[0063] Hereinafter, the degradable high-barrier composite film of the present invention, the high-barrier composite material including the composite film, and the method for producing the same will be described with reference to the accompanying drawings.

[0064] In the absence of any contradiction, the technical features in any embodiment described in the specification of the present invention may be applicable to other embodiments of the present invention.

[0065] In order to achieve the above objectives, the present invention uses two or more biodegradable polymers to prepare at least two layers of high barrier composite films, one of which has high gas barrier properties and heat sealability, and the other is hydrophobic, while utilizing the advantages of various materials and improving the disadvantages of each material forming a single film.

[0066] like Figure 1 As shown, in one embodiment of the present invention, the present invention provides a degradable high-barrier composite film, comprising a first polymer film layer 10 and a second polymer film layer 20 stacked on each other.

[0067] The first polymer film 10 includes a first polymer material and a first plasticizer, and the second polymer film layer 20 includes a second polymer material and a second plasticizer. Both the first polymer material and the second polymer material are biodegradable materials, which will decompose into carbon dioxide and water in the soil, and thus will not remain in the soil to cause irreversible environmental pollution.

[0068] Polyvinyl alcohol is the plastic material with the best known gas barrier properties. The film made from it is a film with good water solubility, high transparency, good gloss, good toughness, and good ductility. It is highly stable against solvents such as animal and vegetable oils, petroleum-based hydrocarbons, esters, ketones, or higher alcohols, and is therefore one of the best anti-solvent materials. In addition, polyvinyl alcohol film has good heat sealing properties, so it can be used in high gas barrier films for resistance heat sealing and high-frequency heat sealing.

[0069] Therefore, in the present invention, in order to meet the high gas barrier requirements of the composite film, the first polymer material may be polyvinyl alcohol (PVA), the alkalinity of which is generally between 70% and 99%, and the molecular weight of which is generally between 24,500 and 120,000.

[0070] The performance of the polyvinyl alcohol film layer is affected by the alkalinity and polymerization degree of the raw materials. The alkalinity represents the degree to which the hydrophobic acetate groups are replaced by hydrophilic groups. The higher the alkalinity, the higher the adhesion of the polyethylene film layer to the surface with greater polarity. The polymerization degree represents the size of the molecular weight. As the polymerization degree increases, the mechanical strength of the polyvinyl alcohol film layer increases, while the permeability decreases (that is, the barrier property increases). Therefore, the mechanical properties and barrier properties of the polyvinyl alcohol film layer can be changed by adjusting the alkalinity and polymerization degree of polyvinyl alcohol.

[0071] However, although polyvinyl alcohol has good gas barrier properties and heat sealability, due to its hydrophilicity, the gas barrier properties of the film made from it will be affected by the moisture content of the contact environment, and due to the easy ductility of polyvinyl alcohol film, the applicability of polyvinyl alcohol alone processed into a high gas barrier film is limited. Therefore, it is necessary to process polyvinyl alcohol and another material into a composite film to improve the above problems.

[0072] On the other hand, films made from cellulose acetate have the characteristics of being biologically derived, high transparency, good gloss, excellent mechanical strength, easy printing, and good oil resistance, water resistance and organic solvent resistance.

[0073] Therefore, in the present invention, in order to meet the requirements of degradability, mechanical properties and hydrophobicity of the composite film, the second polymer material can be cellulose acetate, with a combined acid content of 50% to 58% and a molecular weight of 20,000 to 120,000.

[0074] The combined acid content of the commercially available plastic grade cellulose diacetate is between 50% and 58%, and it is mostly used in textile and plastic material processing products. Cellulose acetate with a combined acid content of less than 50% is usually not used for film making. Cellulose acetate with a combined acid content greater than 58% is cellulose triacetate, which is often used in optical films. Although its physical properties after processing are better, the cost is higher.

[0075] Preferably, the cellulose acetate raw material used in the present invention is plastic material grade cellulose diacetate with a combined acid ratio of about 53% to 55%.

[0076] However, although cellulose acetate film has good gas barrier properties, it has almost no ductility and still cannot meet the requirements of high gas barrier film. At the same time, due to the poor heat sealing property of cellulose acetate film, it is not easy to make airtight packaging bags, which limits the application of cellulose acetate as a flexible packaging material. Therefore, it is necessary to process cellulose acetate and another material into a composite film to improve the above problems.

[0077] Therefore, the present invention provides a degradable high-barrier composite film, which combines the high gas barrier and heat-sealability of polyvinyl alcohol film and the advantages of water resistance, oil resistance and resistance to most organic solvents of cellulose acetate film, and improves the disadvantages of polyvinyl alcohol film being not water-resistant and cellulose acetate film being poor in barrier and heat-sealability.

[0078] The degradable high-barrier composite film of the present invention can be widely used in packaging materials with high gas barrier requirements such as food, cosmetics, medicines, electronic and optical components or products in terms of barrier properties, so as to extend the shelf life, control freshness, and improve safety and convenience; in terms of degradability, it can replace traditional plastic materials, reduce environmental pollution, and achieve environmental sustainability and environmental friendliness.

[0079] In addition, in order to increase the plasticity of the polymer material and facilitate the co-extrusion process, each polymer material layer also contains its own plasticizer.

[0080] Specifically, in the first polymer film layer 10, the content of the first plasticizer is between 15wt% and 35wt%, wherein the first plasticizer includes at least one of small molecule polyols (such as glycerol), polyethylene glycol, glycerides and citrates.

[0081] For polyvinyl alcohol as the first polymer material, crystals will be formed due to the many hydrogen bonds between molecules. Here, the main function of the plasticizer is to destroy the hydrogen bonds, thereby increasing the plasticity of the first polymer material. Therefore, a small molecule plasticizer is usually selected as the first plasticizer because the small molecule plasticizer has a functional group that forms a strong hydrogen bond. The most commonly used plasticizers are small molecule polyols, small molecule polyethylene glycols, and monosaccharides. If the plasticizer is not a molecule with such a structure, it is not suitable for use as the plasticizer of the present invention.

[0082] Therefore, triacetin can be selected as the first plasticizer to provide a plasticizing effect while reducing the hydrophilicity of polyvinyl alcohol.

[0083] Specifically, in the second polymer film layer 20, the content of the second plasticizer is between 10wt% and 25wt%, wherein the second plasticizer includes at least one of phthalate (Diethyl Phathalate, DEP), glycerides and citrates.

[0084] For cellulose acetate as the second polymer material, based on safety considerations, triacetyl glyceride, which can be used as a food additive, can be selected as the second plasticizer. On the other hand, citrate esters (such as triethyl citrate or acetyl triethyl citrate) are also safe and environmentally friendly plasticizers, but the cost is relatively high.

[0085] In one embodiment, the thickness of the composite film of the present invention is between 0.02 mm and 0.06 mm, wherein the thickness ratio of the first polymer film layer 10 to the second polymer film layer 20 is between 1:4 and 4:1, and the first polymer film layer 10 can be a heat-sealing layer.

[0086] Although in Figure 1 The illustrated embodiment only includes a single first polymer film layer 10 and a single second polymer film layer 20. However, in the present invention, at least one of the first polymer film layer and the second polymer film layer may be multiple layers, and the first polymer film layer and the second polymer film layer are alternately stacked.

[0087] For example, in Figure 2A In another embodiment shown, the high barrier composite film is formed by alternatingly stacking two first polymer film layers 10 and a single second polymer film layer 20 to form a structure of first polymer film layer 10 / second polymer film layer 20 / first polymer film layer 10 .

[0088] In the embodiment where the first polymer film layer 10 is used as two outer layers, the composite film of the present invention can be heat-sealed to form a sealed packaging bag; alternatively, the first polymer film layer 10 as one of the outer layers can be directly attached to a substrate such as paper, and the first polymer film layer 10 as the other outer layer can be heat-sealed to form a sealed paper bag package, thereby greatly increasing the barrier properties of the paper / film composite material.

[0089] However, the first polymer film layer 10 made of polyvinyl alcohol is not suitable for contact with water-containing items. Such a first polymer film layer 10, when used as another outer layer of the above-mentioned paper / film composite material, is only suitable for packaging dry products, such as coffee powder / grains, candies, biscuits, etc.

[0090] For example, in Figure 2B In another embodiment shown, the high barrier composite film is composed of a single first polymer film layer 10 and two second polymer film layers 20 alternately stacked to form a second polymer film layer 20 / first polymer film layer 10 / second polymer film layer 20 structure.

[0091] In the embodiment where the second polymer film layer 20 is used as two outer layers, although the composite film cannot be heat-sealed, the second polymer film layer 20 made of cellulose acetate can come into contact with aqueous items without dissolving. Therefore, the second polymer film layer 20 as one of the outer layers can be glued and attached to paper, and the second polymer film layer 20 as the other outer layer can be heat-sealed to form a sealed paper bag package, which can be further applied to the packaging of water-containing products, such as disposable small packages of shampoo, shower gel, etc.

[0092] like Figure 3 As shown, in another embodiment of the present invention, compared to Figure 1 In the illustrated embodiment, the high barrier composite film of the present invention may further include a third polymer film layer 30. The third polymer film layer 30 may include a third polymer material having heat sealability, and the third polymer film layer 30 may also be a heat seal layer.

[0093] Specifically, the first polymer material and the second polymer material may be co-extruded to form a composite film including a first polymer film layer 10 and a second polymer film layer 20, and then the composite film and the third polymer film layer 30 may be dry-laminated to form a composite film in a final form.

[0094] Alternatively, the first polymer material, the second polymer material and the third polymer material may be simultaneously made into a composite film including the first polymer film layer 10, the second polymer film layer 20 and the third polymer film layer 30 by a one-step co-extrusion composite method.

[0095] Although Figure 3 The embodiment shown is a structure of a first polymer film layer 10 / a second polymer film layer 20 / a third polymer film layer 30, but the structure of the high barrier composite film of the present invention is not limited thereto, and the third polymer film layer 30 can be used as any outer layer of the high barrier composite film or be located between any two layers as an intermediate layer.

[0096] Specifically, the third polymer material can be an adhesive, such as acrylic resin, or other biodegradable materials, such as at least one of polybutylene adipate terephthalate (PBAT), polylactic acid (PLA) or polybutylene butyrate (PBS) having heat sealability or a combination thereof.

[0097] Although the above descriptions are all for two-layer or three-layer high-barrier composite films, the high-barrier composite film of the present invention is not limited thereto, and may also be a high-barrier composite film in which four, five, six or more layers of first polymer film layers 10 and second polymer film layers 20 are alternately stacked, which may also include one or more third polymer film layers 30 as outer layers or intermediate layers.

[0098] The degradable high-barrier composite film of the present invention can be used alone as a high-barrier film, or can be composited with other substrates for use according to application requirements.

[0099] Therefore, if Figure 4 As shown, in one embodiment of the present invention, the present invention also provides a high barrier composite material made of the above-mentioned high barrier composite film, including: a substrate 40; and the above-mentioned high barrier composite film, adhered to the substrate 40, wherein the substrate 40 may include materials such as paper, plastic or metal, but is not limited thereto.

[0100] Although Figure 4 The high barrier composite film in the high barrier composite material shown in the figure only comprises a first polymer film layer 10 and a second polymer film layer 20, but the present invention is not limited thereto. The high barrier composite film in the high barrier composite material can be any of the above-mentioned high barrier composite films (e.g. Figures 1 to 3 Any embodiment shown or any implementation mentioned above).

[0101] In addition, you can Figure 4 The composite film side of the high barrier composite material shown is further coated with a water-soluble acrylic resin as an adhesive layer.

[0102] To manufacture the above-mentioned degradable high barrier composite film, such as Figure 5As shown, the present invention provides a method for manufacturing a degradable high-barrier composite film, including a colloid particle preparation step S10 and a film preparation step S20.

[0103] In the pellet preparation step S10 , the first polymer material and the second polymer material are mixed with the first plasticizer and the second plasticizer respectively, and extruded (for example, using a twin-screw extruder) to prepare the first polymer pellet and the second polymer pellet respectively.

[0104] In the film preparation step S20, the first polymer particles and the second polymer particles are co-extruded (eg, hot melt co-extruded) to prepare the degradable high barrier composite film of the present invention. Specifically, the co-extrusion method may be casting, stretching or blow molding.

[0105] The polyvinyl alcohol film layer as the first polymer film layer 10 and the cellulose acetate film layer as the second polymer film layer 20 both have the characteristics of high transparency, good glossiness and biodegradability. However, since the melting points of these two materials are close to the temperature of thermal decomposition, if they are to be processed by the hot melt method used for general plastic materials, appropriate plasticizers must be added first and then hot melt extrusion must be used to form plastic pellets.

[0106] However, since the processing technology and conditions are not easy to master, the current manufacturing process of cellulose acetate film mainly uses the solvent casting method. This process mainly dissolves cellulose acetate in an organic solvent, the most commonly used organic solvent is acetone, to form a viscous fiber glue liquid (Vicose), and then extrude it through a T-type die, roll it in turn, remove the organic solvent, and then roll it up after drying it into a film.

[0107] On the other hand, the manufacturing process of polyvinyl alcohol film is to dissolve polyvinyl alcohol in water in a certain proportion, and then use coating or solvent casting process. Based on functional requirements, the polyvinyl alcohol solution is applied to a film or substrate of other materials, and after drying, it becomes a film with high gas barrier properties, for example, polypropylene-polyvinyl alcohol-polypropylene composite film, which gives the polyvinyl alcohol film waterproofness and better mechanical properties.

[0108] However, the disadvantage of the solvent casting process is that a large amount of flammable organic solvents must be used, so extra attention must be paid to environmental protection and work safety issues and concerns. In addition, it is impossible to use equipment for general plastic industry film making, such as hot melt extrusion casting, stretching and blow molding process equipment. This will greatly increase the manufacturing cost of cellulose acetate film, thereby limiting the industrialization and popularity of cellulose acetate film.

[0109] Therefore, the present invention uses a co-extrusion composite method to manufacture a composite film, wherein the "co-extrusion composite method" refers to a processing method in which polymer particles are heated and plasticized into a melt through an extrusion screw, and then passed through a filter screen, a metering pump, and a die head to form various flat products or semi-finished products, and the film thickness can be controlled according to demand. The co-extrusion composite method can be applied to equipment such as casting, stretching or blow molding.

[0110] Therefore, the present invention uses a co-extrusion lamination method to manufacture a composite film, replacing the traditional process of using solvents to dissolve polyvinyl alcohol or cellulose acetate into a stock solution for coating and then drying to form a film. It can not only be applied to general plastic material processing machinery and equipment, but also can eliminate environmental pollution and industrial safety issues caused by organic solvents, greatly improving the applicability of the industry. Most importantly, the present invention provides a high-barrier composite film that is degradable and can be applied to the industry, as an effective solution for sustainable packaging materials.

[0111] like Figure 6 As shown, the present invention also provides a method for manufacturing a high barrier composite material including the high barrier composite film, comprising: the aforementioned colloid particle preparation step S10 and film preparation step S20, and film lamination step S30.

[0112] In the film laminating step S30, the degradable high barrier composite film of the present invention may be further laminated (for example, using a dry lamination method) onto other substrates, wherein the substrate may include paper, plastic or metal, but is not limited thereto.

[0113] In the present invention, since the polymer raw material is first granulated, the raw material in the form of granules is conducive to subsequent processing and application. Therefore, the composite film can be manufactured by a general plastic hot melt processing process, without the need for solvent die casting or coating process to form a film, which can simplify the manufacturing process and reduce the use of flammable organic solvents.

[0114] At the same time, in the present invention, there is no need to replace the existing plastic processing equipment, thereby eliminating the cost of adding equipment. The co-extrusion composite method used in the present invention can use a variety of different materials to manufacture multi-layer composite films according to needs, with high efficiency and large output, and is also conducive to the control of film thickness.

[0115] Experimental methods

[0116] In order to verify the efficacy of the present invention, the following experiments were conducted to test the degradability, mechanical properties, heat-sealing strength after bonding with a substrate, and barrier properties of the composite film.

[0117] Production of polyvinyl alcohol granules

[0118] In order to reduce the influence of environmental humidity on the barrier properties and mechanical properties of polyvinyl alcohol, partially alkalized polyvinyl alcohol with an alkalinity of 88% and a molecular weight of about 24500 was selected as the first polymer material. In addition, since both glycerol and polyethylene glycol are hygroscopic, triacetyl glycolide with low hydrophilicity was selected as the first plasticizer in consideration of reducing the influence of environmental humidity on the barrier properties and mechanical properties of polyvinyl alcohol.

[0119] The raw material ratios used in the polyvinyl alcohol granules are 75wt% to 90wt% of polyvinyl alcohol and 10wt% to 25wt% of triacetin.

[0120] The polyvinyl alcohol and triacetin are first mixed evenly in a mixer, and then kneaded and granulated in a twin-screw extruder. The screw diameter of the extruder is 75 mm, the aspect ratio (L / D) is 26, and the heating temperature range is between 160 and 230°C. The appearance of the obtained granules is as follows: Figure 7 Its hot melt index (Melting FLow Index, MI) is 3.8 to 4.8 (200°C, 2.16kg).

[0121] Production of Cellulose Acetate Granules

[0122] Plastic material grade cellulose diacetate with a combined acid ratio of about 53% to 55% is selected as the second polymer material. Based on environmentally friendly considerations, glycerides and citrates are more suitable second plasticizers. In this experimental method, triacetyl glyceride is selected as the second plasticizer.

[0123] The raw material ratios used in the cellulose acetate granules are 65wt% to 85wt% of cellulose acetate and 15wt% to 35wt% of triacetin.

[0124] The cellulose acetate and triacetin are first mixed evenly in a mixer, and then kneaded and granulated in a twin-screw extruder. The screw diameter of the extruder is 75 mm, the aspect ratio (L / D) is 26, and the heating temperature range is between 160 and 230°C. The appearance of the obtained granules is as follows Figure 8 , and its hot melt index (Melting FLow Index, MI) is 3.5 to 4.8 (230°C, 2.16kg).

[0125] Manufacturing of composite films

[0126] The most commonly used three-axis co-extrusion equipment was selected to prepare composite films with AB (Example 1) and ABA (Example 2) structures, respectively, wherein A is a polyvinyl alcohol film layer and B is a cellulose acetate film layer. Based on considerations of cost, heat sealing or mechanical properties, the thickness of each film layer can be adjusted as required.

[0127] Example 1

[0128] Under optimal conditions after equipment adjustment, a double-layer composite film with an AB structure was obtained, with an average thickness of 0.03 mm, wherein the thickness ratio of the polyvinyl alcohol film layer to the cellulose acetate film layer was 5:3.

[0129] Example 2

[0130] Under optimal conditions after equipment adjustment, a three-layer composite film with an ABA structure was produced with an average thickness of 0.045 mm, wherein the thickness ratio of the polyvinyl alcohol film layer to the cellulose acetate film layer was 3:4:3.

[0131] Example 3

[0132] The three-layer composite film of Example 2 and the white kraft paper (63 g / cm 2 ) were bonded to obtain a three-layer composite film / paper bonding sample.

[0133] Example 4

[0134] Using a roller device, the double-layer composite film of Example 1 and the white kraft paper (63 g / cm 2 ) Double-layer composite film / paper laminated samples were prepared by hot pressing.

[0135] Example 5

[0136] After the equipment was adjusted, an acrylic resin was coated on the double-layer composite film (cellulose acetate film layer side) of Example 1 under the optimal conditions to obtain a three-layer composite film having a structure of cellulose acetate film layer / polyvinyl alcohol film layer / acrylic resin film layer stacked in sequence. Subsequently, a roller device was used to press the three-layer composite film (polyvinyl alcohol film layer side) against a white kraft paper (63 g / cm 2 )The three-layer composite film / paper laminated sample was prepared by hot pressing.

[0137] Example 6

[0138] The same three-layer composite film and white kraft paper as in Example 5 were used and the lamination was performed in the same manner, except that the lamination pressure was adjusted to 5 GPa.

[0139] Biodegradability test

[0140] According to the international standard NF T51-800, the degradation rate of the double-layer composite film of Example 1 was tested at an ambient temperature of 25±5°C. After 175 days, the degradation rate of the composite film was 80%. The results confirmed that the high barrier composite film of the present invention has excellent biodegradability.

[0141] Mechanical properties

[0142] Under the conditions of a temperature of 25±3°C and a relative humidity of 55±5%RH, the mechanical properties of the double-layer composite film of Example 1 were tested, and the results confirmed that the high barrier composite film of the present invention has good mechanical properties and anti-extension properties (MD is the longitudinal direction and TD is the transverse direction).

[0143] Table 3 Mechanical properties of AB mode double-layer composite film (Example 1)

[0144]

[0145] Heat seal strength

[0146] The composite film side of Example 2 was heat sealed as the heat sealing layer, and then the heat sealing strength was tested in accordance with the requirements of the light industry standard QB / T 2358-98 "Test method for heat sealing strength of plastic film packaging bags" of the People's Republic of China. With a sample with a width of 25 mm, the heat sealed part was opened 180°, and the heat sealing strength measured was 12 to 15 N / 25 mm.

[0147] Gas barrier properties (gas transmission rate, GTR)

[0148] According to the national standard of the People's Republic of China GB / T 1038 "Test method for gas permeability of plastic film and sheet", the composite materials of Examples 3 to 6 were tested for gas permeability at a temperature of 23°C and a relative humidity of 50%RH. The results are shown in Tables 4 and 5.

[0149] It can be seen from Table 4 that the gas barrier property of the high barrier composite material (Example 3) of the present invention can reach 0.1386 cm 3 / (m 2 .24hrs.0.1MPa), and has significantly better gas barrier properties than the single-layer cellulose acetate film (Comparative Example 1, prepared by casting method). The results confirm that the composite material made of the degradable high-barrier composite film of the present invention can prevent gas from passing through to achieve the required sealing performance.

[0150] In addition, it can be seen from Table 5 that the composite materials obtained by roller lamination (Examples 4 to 6, especially Example 4) have a lower gas permeability (oxygen permeability) than Example 3 obtained by manual processing. Moreover, it can be seen from the comparison results of Example 5 and Example 6 that more excellent gas barrier properties can be obtained under heavy pressure (5 GPa).

[0151] Table 4. Gas barrier properties of film / paper laminated samples

[0152]

[0153] Table 5. Gas barrier properties of composite film / paper laminated samples

[0154]

[0155] Water vapor resistance (water vapor transmission rate, WVTR)

[0156] According to the National Standard of the People's Republic of China GB / T 21529 "Determination of water vapor transmission rate of plastic films and sheets", the water vapor transmission rate of the composite materials of Examples 3 to 6 was tested at a temperature of 38°C and a relative humidity of 90%. The results are shown in Tables 6 and 7.

[0157] It can be seen from Table 6 that the water vapor barrier of the high barrier composite material (Example 3) of the present invention can reach 35.9599 g / (m 2 .24hrs), and has significantly better water vapor barrier properties than the single-layer cellulose acetate film (Comparative Example 1). The results confirm that the composite material made of the high barrier composite film of the present invention can block more water vapor and reduce the risk of moisture deterioration of the contents in the package.

[0158] In addition, it can be seen from Table 7 that the composite materials obtained by roller pressing (Examples 4 to 6, especially Example 4) have lower water vapor transmission rate than Example 3 obtained by manual processing. Moreover, from the comparison results of Examples 4 to 6, it can be seen that the water vapor barrier property is not significantly affected under heavy pressure (5 GPa) and light pressure (1 GPa).

[0159] Table 6. Water vapor barrier performance of film / paper laminated samples

[0160]

[0161] Table VII. Water vapor barrier performance of film / paper laminated samples

[0162]

[0163] Fig. 9FIG. 1 is an electron microscope scanning image of an embodiment of the degradable high barrier composite film of the present invention, which is an ABAB composite film produced by co-extrusion. Fig. 9 As shown, the thickness of the composite film is about 0.057 mm, wherein the thicknesses of the two A layers (polyethylene film layers) are 9.369 μm and 26.464 μm, respectively, and the thicknesses of the two B layers (cellulose acetate film layers) are 10.323 μm and 10.810 μm, respectively.

[0164] In summary, the degradable high barrier composite film of the present invention or the composite material made thereof has the following advantages:

[0165] (1) The high gas barrier and heat-sealability properties of the first polymer film (e.g., polyvinyl alcohol film) combined with the hydrophobicity and mechanical strength of the second polymer film (e.g., cellulose acetate film) improve the shortcomings of each film alone;

[0166] (ii) In order to increase industrial applicability, the polymer raw materials are first granulated. The raw materials in the form of granules are conducive to subsequent processing and application, which can simplify the procedures and do not require the use of flammable organic solvents. At the same time, the co-extrusion composite method can use a variety of different materials to manufacture multi-layer composite films according to needs without replacing the existing plastic material processing equipment. It has high efficiency and large output, and is also conducive to the control of film thickness;

[0167] (3) All raw materials are made of biodegradable polymer materials, which can reduce pollution to the environment; and

[0168] (iv) Most importantly, the composite film produced by co-extrusion has excellent barrier properties, especially the gas barrier rate (GTR) can reach less than 0.1cm 3 / (m 2 .24hrs.0.1MPa) level.

[0169] Although the preferred embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will clearly understand that without departing from the spirit or scope of the present invention disclosed in the appended claims, they should still be included in the scope of protection intended by the present invention.

Claims

1. A degradable high barrier composite film, comprising: a first polymer film layer comprising a first polymer material and a first plasticizer; as well as The second polymer film layer comprises a second polymer material and a second plasticizer, wherein: The first polymer film layer and the second polymer film layer are stacked on each other, and The first polymer material and the second polymer material are both biodegradable materials, the first polymer material has gas barrier properties and heat sealability, the second polymer material has hydrophobicity, and wherein, The gas permeability of the high barrier composite film is less than 0.1 cm 3 / (m 2 ·24hrs·0.1MPa).

2. The high barrier composite film according to claim 1, wherein: At least one of the first polymer film layer and the second polymer film layer is a plurality of layers, and The first polymer film layers and the second polymer film layers are stacked alternately.

3. The high barrier composite film according to claim 1, wherein: The first polymer material is polyvinyl alcohol, the alkalinity of which is between 70% and 99%, the molecular weight of which is between 24,500 and 120,000, and The second polymer material is cellulose acetate, with a bound acid content of 50% to 58% and a molecular weight of 20,000 to 120,000.

4. The high barrier composite film according to claim 1, wherein In the first polymer film layer, the content of the first plasticizer is between 15wt% and 35wt%, wherein The first plasticizer includes at least one of small molecule polyols, polyethylene glycol, glycerides and citrates, and In the second polymer film layer, the content of the second plasticizer is between 10wt% and 25wt%, wherein The second plasticizer includes at least one of dimethyl phthalate, diethyl phthalate, glycerides and citrates.

5. The high barrier composite film according to claim 1, further comprising a third polymer film layer, wherein the third polymer film layer comprises a third polymer material having heat sealability.

6. The high barrier composite film according to claim 5, wherein: The third polymer material includes at least one of acrylic resin, polybutylene adipate terephthalate, polylactic acid and polybutylene butyrate, or a combination thereof.

7. The high barrier composite film according to claim 1, wherein: The thickness of the high barrier composite film is between 0.02 mm and 0.06 mm, and the thickness ratio of the first polymer film layer to the second polymer film layer is between 1:4 and 4:

1.

8. A high barrier composite material comprising: Base material; as well as The high barrier composite film according to any one of claims 1 to 7, which is bonded to the substrate, wherein the substrate comprises paper, plastic or metal.

9. A method for producing a degradable high-barrier composite film, comprising: a step of preparing colloid particles, comprising mixing the first polymer material and the second polymer material according to any one of claims 1 to 7 with the first plasticizer and the second plasticizer according to any one of claims 1 to 7, respectively, and extruding them to form first polymer colloid particles and second polymer colloid particles, respectively; and The film preparation step is to prepare a degradable high-barrier composite film by co-extruding the first polymer particles and the second polymer particles.

10. A method for producing a high barrier composite material, comprising: The colloid preparation step and the film preparation step as claimed in claim 9; as well as The film laminating step is to laminate the degradable high barrier composite film onto a substrate, wherein the substrate comprises paper, plastic or metal.

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