Composite membrane as well as preparation method and application thereof

Abstract

The invention discloses a composite membrane as well as a preparation method and application thereof. The composite film comprises a self-lubricating modified layer, a hydrolysis-resistant modified layer and a weather-resistant modified layer, the hydrolysis-resistant modified layer is positioned between the self-lubricating modified layer and the weather-resistant modified layer; the self-lubricating modified layer, the hydrolysis-resistant modified layer and the weather-resistant modified layer are prepared from the following raw materials: a first biodegradable material and a lubricant, a second biodegradable material and a chain extender, a third biodegradable material, an antioxidant, an ultraviolet light absorber and a light stabilizer; the first, second and third biodegradable materials independently include at least PBAT. The composite film provided by the invention has excellent environment-friendly property and packaging property as well as good compostable degradation property, mechanical property, self-lubricating property, hydrolysis resistance and weather resistance, can protect the appearance of a product from being scratched, can meet the environment-friendly and dustproof requirements of a product packaging material, and has a wide application prospect. And particularly, the packaging box has a wide application prospect in packaging or transportation of household appliances.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of packaging materials, in particular to a composite film and a preparation method and application thereof. BACKGROUND

[0002] When polyethylene (such as low-density polyethylene, high-density polyethylene, foamed pearl wool) based packaging materials are used as dustproof and scratch-resistant film bags for household appliances (such as air conditioners, refrigerators, washing machines, etc.), inappropriate recycling methods and abandonment will lead to widespread plastic pollution and microplastic pollution in the natural environment.

[0003] In order to further improve the environmental friendliness of the packaging film material for household appliances, while ensuring the good packaging performance of the packaging material, various solutions have been proposed in the related field of the industry. In the prior art, nano-zinc oxide is added as a reinforcing agent to improve the strength of PBAT (polybutylene adipate terephthalate), but the mechanical properties of the obtained PBAT film still cannot meet the requirements of packaging and transportation of household appliances. In the prior art, crystalline PLA and powder materials with lamellar structure characteristics are added to make the film material have good water vapor barrier performance, but the mechanical properties are low, the life remains good for only 12 months, the hydrolysis resistance is poor, and it is also difficult to meet the extreme storage environment requirements of household appliances. Moreover, the above-mentioned film materials still have the problem of insufficient self-lubricating performance, which can easily cause scratches on high-gloss appearance plastic parts, thereby affecting the appearance quality of the products. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art.

[0005] In view of the environmental friendliness and the requirements of product packaging, the present application adopts lubrication modification, chain extension modification and weather resistance modification to improve the self-lubricating performance, hydrolysis resistance and weather resistance of the PBAT-based film, and further improves the mechanical properties of the film material through a multi-layer co-extrusion process, thereby obtaining a composite film with excellent environmental friendliness and packaging performance.

[0006] To this end, one of the purposes of the present application is to propose a composite film which has good compostable degradation characteristics, mechanical properties, self-lubricating performance, hydrolysis resistance and weather resistance, can protect the appearance of the product from scratches, can meet the environmental friendliness and dustproof requirements of product packaging materials, and has a broad application prospect in packaging or transportation of household appliances.

[0007] The second purpose of the present application is to propose a preparation method of the above-mentioned composite film.

[0008] The third purpose of the present application is to propose a packaging material having the above-mentioned composite film.

[0009] A fourth object of the present invention is to provide an application of the above-mentioned composite film.

[0010] A first embodiment of the present invention provides a composite film comprising a self-lubricating modified layer, a hydrolysis-resistant modified layer, and a weather-resistant modified layer;

[0011] The anti-hydrolysis modified layer is located between the self-lubricating modified layer and the weathering modified layer;

[0012] The raw materials for preparing the self-lubricating modified layer include a first biodegradable material and a lubricant;

[0013] The raw materials for preparing the hydrolysis-resistant modified layer include a second biodegradable material and a chain extender;

[0014] The raw materials for preparing the weather-resistant modified layer include a third biodegradable material, an antioxidant, an ultraviolet absorber and a light stabilizer;

[0015] The first biodegradable material, the second biodegradable material, and the third biodegradable material independently include at least PBAT.

[0016] The composite film according to the embodiment of the present invention has at least the following beneficial effects:

[0017] In response to the needs of environmental friendliness and product packaging (such as dustproof or scratchproof), the present invention provides a composite film made of PBAT, a biodegradable material, as a base material. This composite film has excellent compostability, mechanical properties, self-lubricating properties, hydrolysis resistance and weather resistance. It can protect the product appearance from scratches and can effectively avoid appearance quality problems caused by friction between the film and the product surface during packaging or transportation.

[0018] Specifically, in view of the problem that the self-lubricating performance of the film product is insufficient, which easily leads to scratches on the high-gloss appearance of the plastic part, thereby affecting the appearance quality of the product, by adding a lubricant to PBAT to form a self-lubricating modified layer, the self-lubricating performance of the film material can be greatly improved, thereby effectively avoiding the potential scratch risk of the high-gloss appearance of the household appliance product. In view of the problem that the hydrolysis resistance of the PBAT material is poor, by using PBAT and a chain extender to prepare a chain-extended modified PBAT material to form a hydrolysis-resistant modified layer, the acid value of the PBAT can be greatly reduced, thereby greatly improving the hydrolysis resistance of the film material. In view of the problem that the weather resistance of the PBAT material is poor, by using PBAT and an antioxidant, an ultraviolet absorber and a light stabilizer to prepare a weather-resistant modified PBAT material to form a weather-resistant modified layer, the weather resistance of the film material can be improved. The above new material technology is used to prepare a composite film, which has no effect on the original parts, the size, angle, number and specification of the parts. However, by using the composite film with the compostable degradation feature, the environmental friendly feature of the material can be greatly improved.

[0019] According to some embodiments of the present application, the first biodegradable material, the second biodegradable material and the third biodegradable material are independently selected from PBAT, or a combination of PBAT and at least one of PLA (poly lactic acid), PBS (polybutylene succinate), PBSA (polybutylene succinate adipate), PHA (polyhydroxyalkanoate), PPC (polypropylene carbonate) and PGA (polyglycolic acid). The materials used are biodegradable materials, have compostable degradation, and can improve the environmental friendly feature of the film material.

[0020] According to some embodiments of the present application, the composite film comprises a self-lubricating modified layer, a hydrolysis-resistant modified layer and a weather-resistant modified layer arranged in sequence from inside to outside. The inner layer is in contact with the product, and the inner layer is arranged as the self-lubricating modified layer, which can obtain good self-lubricating effect, thereby effectively avoiding the possible appearance quality problem of the product; the outer layer is the outer exposed surface, and the outer layer is arranged as the weather-resistant modified layer, which can enhance the weather resistance and light aging resistance of the composite film for the outer exposed surface.

[0021] According to some embodiments of the present application, the mass ratio of the preparation raw material of the self-lubricating modified layer, the preparation raw material of the hydrolysis-resistant modified layer and the preparation raw material of the weather-resistant modified layer is 1:(0.8-1.2):(0.8-1.2). By using such a ratio to prepare a multi-layer composite film material, good packaging performance is obtained.

[0022] According to some embodiments of the present application, the acid value of the anti-hydrolysis modified layer is 3 mgKOH / g-8 mgKOH / g. The anti-hydrolysis modified layer is a product prepared by using the second biodegradable material and the chain extender. The anti-hydrolysis modified layer with such an acid value has good hydrolysis resistance.

[0023] According to some embodiments of the present application, the mass percentage of the lubricant in the raw materials for preparing the first biodegradable material is 0.5%-1.5%. By adding the lubricant in such a proportion, the lubricating property of the PBAT material can be effectively improved, so that the PBAT-based film has good self-lubricating property, and the appearance quality problem caused by the friction between the film and the product appearance surface during transportation can be effectively avoided.

[0024] According to some embodiments of the present application, the lubricant includes at least one of silicone oil, silicone powder, fatty acid amide, stearic acid, stearate, montanate, paraffin, polyethylene wax, erucic acid amide, oleic acid amide, ethylene bis-stearamide, pentaerythritol stearate, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid copolymer. The self-lubricating modified layer prepared by using these kinds of lubricants has good self-lubricating property.

[0025] According to some embodiments of the present application, the mass percentage of the chain extender in the raw materials for preparing the second biodegradable material is 0.5%-1.5%. By adding the chain extender in such a proportion, the acid value of the PBAT can be greatly reduced, so that the hydrolysis resistance of the material is greatly improved.

[0026] According to some embodiments of the present application, the chain extender includes at least one of polycaprolactone and polybasic epoxy chain extender. The anti-hydrolysis modified layer prepared by using these kinds of chain extenders has good hydrolysis resistance.

[0027] According to some embodiments of the present application, the mass percentage of the antioxidant, the ultraviolet absorber and the light stabilizer in the raw materials for preparing the third biodegradable material is independently 0.2%-0.5%. By adding the antioxidant, the ultraviolet absorber and the light stabilizer in such a proportion, the weather resistance of the PBAT material can be improved.

[0028] According to some embodiments of the present application, the antioxidant includes at least one of hindered amine antioxidant and hindered phenol antioxidant.

[0029] According to some embodiments of the present application, the ultraviolet absorber includes at least one of salicylate ultraviolet absorber, benzophenone ultraviolet absorber, benzotriazole ultraviolet absorber, substituted acrylonitrile ultraviolet absorber, triazine ultraviolet absorber and hindered amine ultraviolet absorber.

[0030] According to some embodiments of the present application, the light stabilizer comprises at least one of a light screening agent, a quenching agent, a hindered amine light stabilizer.

[0031] By using the above-mentioned antioxidants, ultraviolet absorbers and light stabilizers to form the weathering modification layer, the weather resistance of the PBAT film can be improved.

[0032] According to some embodiments of the present application, the thickness of the composite film is 10-35 microns. The composite film with such thickness has good compostable degradation characteristics, mechanical properties, self-lubricating properties, hydrolysis resistance and weather resistance.

[0033] The second aspect of the present application provides a preparation method of the composite film of the first aspect of the present application, comprising the following steps:

[0034] The first biodegradable material and the lubricant are mixed to obtain a first component; the second biodegradable material and the chain extender are blended and modified to obtain a second component; the third biodegradable material, the antioxidant, the ultraviolet absorber and the light stabilizer are blended and modified to obtain a third component;

[0035] The first component, the second component and the third component are subjected to multi-layer co-extrusion blown film to obtain the composite film.

[0036] The preparation method of the composite film according to the embodiments of the present application has at least the following beneficial effects:

[0037] The multi-layer co-extrusion scheme of the present application obtains a multi-layer co-extrusion PBAT-based composite film with better mechanical properties. The multi-layer co-extrusion technology realizes forced orientation of PBAT molecular chains in the transverse and longitudinal directions of the film material, thereby greatly improving the mechanical properties of the composite film and forming a compostable film material with good packaging performance.

[0038] According to some embodiments of the present application, in the step of blending and modifying the second biodegradable material and the chain extender, the blending and modification temperature is 150-170 DEG C. By using such a processing temperature for chain extension modification to form a hydrolysis resistance modification layer, the hydrolysis resistance of the composite film can be better.

[0039] According to some embodiments of the present application, in the step of blending and modifying the third biodegradable material, the antioxidant, the ultraviolet absorber and the light stabilizer, the blending and modification temperature is 150-170 DEG C. By using such a processing temperature for weathering modification to form a weathering modification layer, the weather resistance of the composite film can be better.

[0040] According to some embodiments of the present application, the extrusion temperature of the multi-layer co-extrusion blown film is 150-170℃. By co-extruding the multi-layer at such a processing temperature to form a PBAT-based composite film material, the mechanical properties of the composite film can be greatly improved.

[0041] The third aspect of the present application provides a packaging material comprising the composite film of the first aspect of the present application.

[0042] The packaging material according to the embodiments of the present application has at least the following beneficial effects:

[0043] The packaging material provided by the present application has good compostable degradation characteristics, mechanical properties, self-lubricating properties, hydrolysis resistance and weather resistance, which can effectively avoid appearance quality problems of products and greatly improve the environmental friendly characteristics of the packaging material.

[0044] According to some embodiments of the present application, the packaging material is a dust cover bag or a scratch-resistant cover bag for household appliances. As a dust cover bag or a scratch-resistant cover bag for household appliances, the packaging material has good environmental friendly characteristics and packaging performance, which can meet the requirements of dust prevention or scratch prevention of household appliances and avoid appearance quality problems of household appliances.

[0045] The fourth aspect of the present application provides the application of the composite film of the first aspect of the present application in packaging or transportation of household appliances.

[0046] The application of the composite film according to the embodiments of the present application in packaging or transportation of household appliances has at least the following beneficial effects:

[0047] The composite film provided by the present application has excellent environmental friendly characteristics and packaging performance, which can meet the requirements of dust prevention or scratch prevention of household appliances and effectively avoid appearance quality problems of household appliances, and has a wide application prospect in packaging and transportation of household appliances.

[0048] Additional aspects and advantages of the present application will be given in part in the following description, will become apparent in part from the following description, or will be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 is a schematic diagram of the composite film in an embodiment of the present application.

[0050] Reference signs:

[0051] Self-lubricating modified layer 100,

[0052] Hydrolysis-resistant modified layer 200,

[0053] Weather-resistant modified layer 300. DETAILED DESCRIPTION

[0054] The embodiments of the present application will be described in detail below with reference to the drawings, the embodiments described by reference to the drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation to the present application.

[0055] In the description of the present application, it should be understood that the terms "thickness", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation to the present application. In addition, the features defined as "first", "second", "third" can explicitly or implicitly include one or more of the features.

[0056] One aspect of the present application provides a composite film. Below, the composite film of the embodiments of the present application is described with reference to the drawings. Figure 1 The composite film of the embodiments of the present application is described.

[0057] With reference to Figure 1 The composite film of the embodiments of the present application includes a self-lubricating modified layer 100, a hydrolysis-resistant modified layer 200, and a weather-resistant modified layer 300. The hydrolysis-resistant modified layer 200 is located between the self-lubricating modified layer 100 and the weather-resistant modified layer 300. The raw material for preparing the self-lubricating modified layer 100 includes a first biodegradable material and a lubricant. The raw material for preparing the hydrolysis-resistant modified layer 200 includes a second biodegradable material and a chain extender. The raw material for preparing the weather-resistant modified layer 300 includes a third biodegradable material, an antioxidant, an ultraviolet absorber, and a light stabilizer. The first biodegradable material, the second biodegradable material, and the third biodegradable material each independently includes at least PBAT. The composite film made of PBAT as the base material has good compostable degradation characteristics, mechanical properties, self-lubricating properties, hydrolysis resistance, and weather resistance, can protect the appearance of the product from scratches, and can effectively avoid appearance quality problems caused by friction between the film and the appearance of the product during packaging or transportation.

[0058] According to the embodiments of the present application, the first biodegradable material, the second biodegradable material, and the third biodegradable material are each independently selected from PBAT or a combination of PBAT and at least one of PLA, PBS, PBSA, PHA, PPC, and PGA. In some embodiments of the present application, the first biodegradable material, the second biodegradable material, and the third biodegradable material are each independently selected from PBAT or a combination of PBAT and at least one of PLA and PBS, i.e., a blended base material of PBAT and PLA / PBS. The biodegradable material can be PBAT alone or a composite material formed by taking PBAT as the base material and blending with PLA, PBS, etc. These materials all have compostable degradation characteristics and can improve the environmental friendliness of the film material.

[0059] In some specific embodiments of the present invention, the first biodegradable material is PBAT. Using only PBAT as the biodegradable material to prepare the self-lubricating modified layer reduces costs, and the resulting PBAT-based composite film material has good self-lubricating properties.

[0060] In some specific embodiments of the present invention, the second biodegradable material is PBAT. Using only PBAT as the biodegradable material to prepare the hydrolysis-resistant modified layer reduces costs, and the resulting PBAT-based composite film material has good hydrolysis resistance.

[0061] In some specific embodiments of the present invention, the third biodegradable material is PBAT. Using only PBAT as the biodegradable material to prepare the weather-resistant modified layer reduces costs, and the resulting PBAT-based composite film material has good weather resistance.

[0062] In some embodiments of the present invention, the composite film of the present invention includes a self-lubricating modified layer 100, an anti-hydrolysis modified layer 200, and a weather-resistant modified layer 300, arranged sequentially from the inside to the outside. In some specific embodiments of the present invention, the composite film of the present invention includes the self-lubricating modified layer 100, the anti-hydrolysis modified layer 200, and the weather-resistant modified layer 300, arranged sequentially from the product contact surface to the exposed surface, i.e., the self-lubricating modified layer 100 is the product contact surface, and the weather-resistant modified layer 300 is the exposed surface. By providing the three base layers of the self-lubricating modified layer 100, the anti-hydrolysis modified layer 200, and the weather-resistant modified layer 300, each layer is used to enhance the self-lubricating ability of the film material to protect the product appearance from scratches, enhance the hydrolysis resistance of the PBAT film, and enhance the weather resistance of the PBAT film. Specifically, to address the problem of film scratching the high-gloss finish of home appliances, a self-lubricating modified layer is placed on the product-contacting surface. By applying lubrication modification to the layer closest to the product, a film material with excellent self-lubrication properties is achieved, effectively avoiding potential product appearance quality issues. For packaging scenarios where film leakage occurs, a weathering modified layer is placed on the exposed surface to enhance the composite film's weather resistance and light aging resistance.

[0063] According to an embodiment of the present application, the mass ratio of the raw material for preparing the self-lubricating modified layer, the raw material for preparing the hydrolysis-resistant modified layer, and the raw material for preparing the weather-resistant modified layer is 1:(0.8-1.2):(0.8-1.2). In some embodiments of the present application, the mass ratio of the raw material for preparing the self-lubricating modified layer, the raw material for preparing the hydrolysis-resistant modified layer, and the raw material for preparing the weather-resistant modified layer is 1:(0.9-1.1):(0.9-1.1). In some specific embodiments of the present application, the mass ratio of the raw material for preparing the self-lubricating modified layer, the raw material for preparing the hydrolysis-resistant modified layer, and the raw material for preparing the weather-resistant modified layer is 1:1:1, i.e., the three are in equal mass ratio. By using such a proportion to prepare the multi-layer composite film material, good packaging performance is achieved.

[0064] According to an embodiment of the present application, the acid value of the hydrolysis-resistant modified layer is 3-8 mgKOH / g. In some embodiments of the present application, the acid value of the hydrolysis-resistant modified layer is 4-6 mgKOH / g. The hydrolysis-resistant modified layer with such an acid value has good hydrolysis resistance.

[0065] According to an embodiment of the present application, the mass percentage of the lubricant in the raw material for preparing the first biodegradable material is 0.5%-1.5%. In some examples, the mass percentage of the lubricant can be selected from 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%. In the raw material for preparing the self-lubricating modified layer, by adding such a proportion of lubricant, the lubricating performance of the PBAT material can be effectively improved, so that the PBAT-based film has good self-lubricating performance, and appearance quality problems caused by friction between the film and the product appearance surface during transportation can be effectively avoided.

[0066] According to an embodiment of the present application, the lubricant includes at least one of silicone oil, silicone powder, fatty acid amide, stearic acid, stearate, montanate, paraffin, polyethylene wax, erucic acid amide, oleic acid amide, ethylene bis-stearamide, pentaerythritol stearate, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid copolymer. In some embodiments of the present application, the lubricant includes at least one of silicone powder, fatty acid amide, stearic acid, stearate, erucic acid amide, oleic acid amide, ethylene bis-stearamide, and pentaerythritol stearate. By using these kinds of lubricants to prepare the self-lubricating modified layer, the self-lubricating performance of the film can be better.

[0067] In some embodiments of the present application, the raw material for preparing the self-lubricating modified layer is the first biodegradable material and the lubricant. In some examples, the first biodegradable material is PBAT. In this way, by using only PBAT and the lubricant to prepare the self-lubricating modified layer, the PBAT-based composite film material prepared thereby can have good self-lubricating performance.

[0068] According to an embodiment of the present application, the mass percentage of the chain extender in the preparation raw material of the second biodegradable material is 0.5% to 1.5%. In some examples, the mass percentage of the chain extender can be selected from 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%. In the preparation raw material of the anti-hydrolysis modification layer, by adding the chain extender in such a proportion, the acid value of PBAT can be greatly reduced, thereby greatly improving the hydrolysis resistance of the material.

[0069] According to an embodiment of the present application, the chain extender includes at least one of polycaprolactone and a multi-epoxy chain extender. By using these kinds of chain extenders to make the anti-hydrolysis modification layer, the hydrolysis resistance of the film can be better.

[0070] In some embodiments of the present application, the acid value of the second biodegradable material is 10 mgKOH / g to 40 mgKOH / g. In some specific embodiments of the present application, the acid value of the second biodegradable material is 13 mgKOH / g to 38 mgKOH / g. The acid value of the raw material of the second biodegradable material is high, and the hydrolysis resistance is poor, so by adding the chain extender for chain extension modification, the acid value of the second biodegradable material can be reduced, thereby effectively improving the hydrolysis resistance of the material.

[0071] In some embodiments of the present application, the preparation raw material of the anti-hydrolysis modification layer is the second biodegradable material and the chain extender. In some examples, the second biodegradable material is PBAT. In this way, by using only PBAT and the chain extender to prepare the anti-hydrolysis modification layer, the PBAT-based composite film material made of PBAT can have good hydrolysis resistance.

[0072] According to an embodiment of the present application, the mass percentage of the antioxidant, the ultraviolet absorber, and the light stabilizer in the preparation raw material of the third biodegradable material is independently 0.2% to 0.5%. In some examples, the mass percentage of the antioxidant, the ultraviolet absorber, or the light stabilizer can be selected from 0.2%, 0.3%, 0.4%, or 0.5%, respectively. In the preparation raw material of the weather-resistant modification layer, by adding the antioxidant, the ultraviolet absorber, and the light stabilizer in such a proportion, the weather resistance of the material can be improved.

[0073] According to an embodiment of the present application, the antioxidant includes at least one of a hindered amine antioxidant, a hindered phenol antioxidant. In some embodiments of the present application, the antioxidant includes at least one of antioxidant 168, 245, 264, 300, 626, 702, 703, 1010, 1024, 1076, 1098, 1135, 2246, 3114, B215, B225, B900, B911. By using such a kind of antioxidant, the material can have good antioxidant effect.

[0074] According to an embodiment of the present application, the ultraviolet absorber includes at least one of a salicylate ultraviolet absorber, a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a substituted acrylonitrile ultraviolet absorber, a triazine ultraviolet absorber, a hindered amine ultraviolet absorber. In some embodiments of the present application, the ultraviolet absorber includes at least one of UV-P, UV-9, UV-21, UV-24, UV-104, UV-234, UV-242, UV-284, UV-292, UV-326, UV-327, UV-328, UV-329, UV-360, UV-531, UV-770, UV-5411. By using such a kind of ultraviolet absorber, the material can have good light aging resistance, and can further improve the weather resistance to meet the requirements of exposed packaging scenarios.

[0075] According to an embodiment of the present application, the light stabilizer includes at least one of a light screen, a quencher, a hindered amine light stabilizer. In some embodiments of the present application, the light stabilizer includes at least one of light stabilizer 119, 292, 622, 770, 783, 791, 944. By using such a kind of light stabilizer, the material can have good light aging resistance, and can further improve the weather resistance to meet the requirements of exposed packaging scenarios.

[0076] In some embodiments of the present application, the preparation raw material of the weather resistance modified layer is a third biodegradable material, an antioxidant, an ultraviolet absorber, and a light stabilizer. In some examples, the third biodegradable material is PBAT. In this way, only PBAT is used to prepare the weather resistance modified layer with the antioxidant, the ultraviolet absorber, and the light stabilizer, and the prepared PBAT-based composite film material can have good weather resistance.

[0077] According to an embodiment of the present application, the thickness of the composite film is 10 microns to 35 microns. In some embodiments of the present application, the thickness of the composite film is 12 microns to 32 microns. The composite film with such thickness has good compostable degradation characteristics, mechanical properties, self-lubricating properties, hydrolysis resistance, and weather resistance.

[0078] In some embodiments of the present application, the composite film has at least three layers, i.e., at least comprises a self-lubricating modified layer, a hydrolysis-resistant modified layer and a weather-resistant modified layer. In some specific embodiments of the present application, the composite film is made of a self-lubricating modified layer, a hydrolysis-resistant modified layer, a weather-resistant modified layer and other modified materials, and the film material has a structure of three or more layers.

[0079] In some embodiments of the present application, the composite film has a transverse tensile strength of 30-40 MPa. In some specific embodiments of the present application, the composite film has a transverse tensile strength of 32-38 MPa.

[0080] In some embodiments of the present application, the composite film has a longitudinal tensile strength of 29-38 MPa. In some specific embodiments of the present application, the composite film has a longitudinal tensile strength of 30-36 MPa.

[0081] In some embodiments of the present application, the composite film has a transverse elongation at break of 500-950%. In some specific embodiments of the present application, the composite film has a transverse elongation at break of 540-940%.

[0082] In some embodiments of the present application, the composite film has a longitudinal elongation at break of 270-350%. In some specific embodiments of the present application, the composite film has a longitudinal elongation at break of 280-340%.

[0083] In some embodiments of the present application, the composite film has a fusion strength of 9-16 N / mm. In some specific embodiments of the present application, the composite film has a fusion strength of 10-15 N / mm.

[0084] Another aspect of the present application provides a method for preparing the composite film of the embodiments.

[0085] According to the embodiments of the present application, the method for preparing the composite film comprises the following steps:

[0086] The first biodegradable material and the lubricant are mixed to obtain a first component; the second biodegradable material and the chain extender are blended and modified to obtain a second component; the third biodegradable material, the antioxidant, the ultraviolet absorber and the light stabilizer are blended and modified to obtain a third component;

[0087] The first component, the second component and the third component are subjected to multi-layer co-extrusion blown film to obtain the composite film.

[0088] According to the embodiment of the present application, in order to solve the problem of insufficient mechanical properties of PBAT material, a multi-layer co-extrusion PBAT film with better mechanical properties is obtained through the multi-layer co-extrusion scheme; the multi-layer co-extrusion technology realizes the forced orientation of PBAT molecular chain in the transverse and longitudinal directions of the film material, thereby greatly improving the mechanical properties of the composite film, forming a compostable film material with good packaging performance.

[0089] According to the embodiment of the present application, the first component forms a self-lubricating modified layer, the second component forms a hydrolysis-resistant modified layer, and the third component forms a weather-resistant modified layer.

[0090] According to the embodiment of the present application, in the step of blending and modifying the second biodegradable material and the chain extender, the temperature of the blending and modification is 150-170°C. In some embodiments of the present application, in the step of blending and modifying the second biodegradable material and the chain extender, the temperature of the blending and modification is 150-160°C. In some examples, the temperature of the blending and modification in this step can be selected from 150°C, 152°C, 155°C, 157°C or 160°C. By such a processing temperature for chain extension modification, the hydrolysis-resistant modified layer is made, which can make the hydrolysis resistance of the composite film better.

[0091] According to the embodiment of the present application, in the step of blending and modifying the third biodegradable material, the antioxidant, the ultraviolet absorber and the light stabilizer, the temperature of the blending and modification is 150-170°C. In some embodiments of the present application, in the step of blending and modifying the third biodegradable material, the antioxidant, the ultraviolet absorber and the light stabilizer, the temperature of the blending and modification is 150-160°C. In some examples, the temperature of the blending and modification in this step can be selected from 150°C, 152°C, 155°C, 157°C or 160°C. By such a processing temperature for weather resistance modification, the weather-resistant modified layer is made, which can make the weather resistance of the composite film better.

[0092] According to the embodiment of the present application, the extrusion temperature of the multi-layer co-extrusion blown film is 150-170°C. In some embodiments of the present application, the extrusion temperature of the multi-layer co-extrusion blown film is 155-165°C. In some specific embodiments of the present application, the multi-layer co-extrusion blown film is carried out in a multi-layer co-extrusion blown film system, and the control of the feeding section temperature, the compression section temperature, the homogenization section temperature and the die temperature is respectively 153-157°C, 163-167°C, 163-167°C and 163-167°C. By such a processing temperature for multi-layer co-extrusion, the PBAT-based composite film material is formed, which can greatly improve the mechanical properties of the composite film.

[0093] Another aspect of the present application provides a packaging material. According to an embodiment of the present application, the packaging material comprises the composite film of the aforementioned embodiments. The packaging material has good compostable degradation characteristics, mechanical properties, self-lubricating properties, hydrolysis resistance and weather resistance, can effectively avoid appearance quality problems of the product, and can greatly improve the environmental friendly characteristics of the packaging material.

[0094] According to an embodiment of the present application, the packaging material is a dust cover bag or a scratch-resistant cover bag for household appliances. As a dust cover bag or a scratch-resistant cover bag for household appliances, the packaging material has good environmental friendly characteristics and packaging performance, can meet the requirements of dustproof or scratch-resistant for household appliances, and avoid appearance quality problems of the household appliance product.

[0095] Another aspect of the present application provides the application of the composite film of the aforementioned embodiments in packaging or transportation of household appliances. The composite film has excellent environmental friendly characteristics and packaging performance, can meet the requirements of dustproof or scratch-resistant for household appliances, can effectively avoid appearance quality problems of the household appliance product, and has a broad application prospect in packaging and transportation of household appliances.

[0096] According to the aforementioned embodiments of the present application, the household appliances include air conditioners, refrigerators or washing machines. These kinds of household appliances have white high light appearance surfaces, and the use of the composite film of the embodiments for packaging or transportation can protect the appearance of the household appliance product from scratching and avoid appearance quality problems in the packaging or transportation process.

[0097] The content of the present application is further described in detail through specific embodiments. The raw materials, reagents or devices used below can be obtained from conventional commercial channels unless otherwise specified. Unless otherwise specified, the test or test method is a conventional method in the art.

[0098] The raw materials used in the embodiments / Comparative Examples are described below:

[0099] Polycaprolactone, CAS: 24980-41-4;

[0100] Multi-epoxy chain extender, styrene-methyl methacrylate-glycidyl methacrylate copolymer, CAS: 1191261-43-4;

[0101] Multi-epoxy chain extender, BASF chain extender ADR-4468;

[0102] Hindered phenol antioxidant, XH-245, CAS: 36443-68-2;

[0103] Benzotriazole ultraviolet absorber, UV-360, CAS: 103597-45-1;

[0104] Light stabilizer, Tinuvin® 119, CAS: 106990-43-6;

[0105] Lubricant, oleic acid amide, CAS: 301-02-0.

[0106] The above raw materials are commercially available products and are used directly without further treatment.

[0107] The following test method standards are as follows:

[0108] The mechanical properties and elongation at break were tested in accordance with the standard GB / T 40933-2021 "Plastic Products Film and Sheet Thermoplastic Plastic Film Test Guide".

[0109] The fusion strength test was carried out in accordance with the standard QB / T 2358-1998 "Plastic Film Packaging Bag Heat Seal Strength Test Method".

[0110] Example 1

[0111] In this example, PBAT with an acid value of 13.1 mgKOH / g was used as the base material, and 0.5% polycaprolactone chain extender based on the mass of PBAT was added for blending modification at a processing temperature of 150°C to obtain component 1. After testing, the acid value of component 1 was reduced to 4.3 mgKOH / g.

[0112] PBAT raw material, and 0.3% hindered phenol antioxidant, 0.3% benzotriazole ultraviolet absorber and 0.3% light stabilizer based on the mass of PBAT were added for blending modification at a processing temperature of 150°C to obtain component 2.

[0113] PBAT raw material, and 1% lubricant based on the mass of PBAT were mixed to obtain component 3.

[0114] Components 1, 2 and 3 were put into a multi-layer co-extrusion blown film system in equal mass proportions, and the feeding section temperature, compression section temperature, homogenization section temperature and die temperature were 155°C, 165°C, 165°C and 165°C, respectively, to obtain the composite film of Example 1 by multi-layer co-extrusion blowing. The mass ratio of component 1, component 2 and component 3 was 1:1:1, and the thickness of the obtained composite film was about 25 microns.

[0115] The film of Example 1 has a transverse tensile strength of 36.10 MPa, a longitudinal tensile strength of 35.63 MPa, a transverse elongation at break of 938.51%, a longitudinal elongation at break of 333.67%, a fusion strength of 14.75 N / mm, a mechanical property (transverse / longitudinal tensile strength) retention rate of more than 75% after being placed in an environment of 85°C and 85% humidity for 192 hours, a mechanical property (transverse / longitudinal tensile strength) retention rate of more than 85% after being placed in a conventional environment for 24 months, no scratches on the air conditioner high-gloss appearance panel after the film is rubbed back and forth for more than 30 times under a load of 1 kg weight, and degradable organic matter of more than 90%.

[0116] Example 2

[0117] PBAT with an acid value of 20.8 mgKOH / g is used as a base material, 1% of styrene-methyl methacrylate-glycidyl methacrylate copolymer by mass of PBAT is added, and blending modification is performed at a processing temperature of 155°C to obtain component 1; detection shows that the acid value of component 1 is reduced to 5.8 mgKOH / g.

[0118] PBAT raw materials, 0.2% of hindered phenol antioxidant, 0.4% of benzotriazole ultraviolet absorber and 0.3% of light stabilizer by mass of PBAT are added, and blending modification is performed at a processing temperature of 155°C to obtain component 2.

[0119] PBAT raw materials and 1% of lubricant by mass of PBAT are mixed to obtain component 3.

[0120] Component 1, component 2 and component 3 are put into a multi-layer co-extrusion film blowing system in equal mass proportions, and a composite film of Example 2 is obtained by multi-layer co-extrusion blowing according to feeding section temperature, compression section temperature, homogenization section temperature and die temperature of 155°C, 165°C, 165°C and 165°C respectively. The mass ratio of component 1, component 2 and component 3 is 1:1:1, and the thickness of the obtained composite film is about 25 microns.

[0121] The film of Example 2 has a transverse tensile strength of 33.18 MPa, a longitudinal tensile strength of 30.28 MPa, a transverse elongation at break of 666.24%, a longitudinal elongation at break of 337.13%, a fusion strength of 12.72 N / mm, a mechanical property (transverse / longitudinal tensile strength) retention rate of more than 75% after being placed in an environment of 85°C and 85% humidity for 192 hours, a mechanical property (transverse / longitudinal tensile strength) retention rate of more than 85% after being placed in a conventional environment for 24 months, no scratches on the air conditioner high-gloss appearance panel after the film is rubbed back and forth for more than 30 times under a load of 1 kg weight, and degradable organic matter of more than 90%.

[0122] Example 3

[0123] PBAT with an acid value of 37.2 mgKOH / g as the base material, 1.5% of polybasic epoxy chain extender ADR-4468 by mass of PBAT was added, and blending modification was carried out at a processing temperature of 160°C to obtain component 1; detection showed that the acid value of component 1 was reduced to 4.9 mgKOH / g;

[0124] PBAT raw material, and 0.5% of hindered phenol antioxidant, 0.4% of benzotriazole ultraviolet absorber and 0.3% of light stabilizer were added according to the mass of PBAT, and blending modification was carried out at a processing temperature of 160°C to obtain component 2;

[0125] PBAT raw material, and 1% of lubricant was added according to the mass of PBAT, and mixing was carried out to obtain component 3;

[0126] Component 1, component 2 and component 3 were put into a multi-layer co-extrusion blown film system in equal mass ratio, and the feeding section temperature, compression section temperature, homogenization section temperature and die temperature were 155°C, 165°C, 165°C and 165°C respectively, and the composite film of example 3 was obtained by multi-layer co-extrusion blowing. The mass ratio of component 1, component 2 and component 3 was 1:1:1, and the thickness of the obtained composite film was about 25 microns.

[0127] Test showed that the transverse tensile strength of the film obtained in example 3 could reach 32.47 MPa, the longitudinal tensile strength could reach 30.14 MPa, the transverse elongation at break could reach 542.14%, the longitudinal elongation at break could reach 287.34%, the fusion strength could reach 10.87 N / mm; after placing in an environment of 85°C and 85% humidity for 192 hours, the retention rate of mechanical properties (transverse / longitudinal tensile strength) could reach more than 75%; after placing in a conventional environment for 24 months, the retention rate of mechanical properties (transverse / longitudinal tensile strength) could reach more than 85%; the film could be rubbed back and forth for more than 30 times under the load of a 1kg weight, and there was no scratch on the high light appearance panel of the air conditioner; the degradable organic matter was more than 90%.

[0128] Comparative example 1

[0129] PBAT with an acid value of 13.1 mgKOH / g as the base material, 1.5% of polycaprolactone chain extender by mass of PBAT was added, and blending modification was carried out at a processing temperature of 150°C to obtain component 1;

[0130] PBAT raw material, and 0.3% of hindered phenol antioxidant, 0.3% of benzotriazole ultraviolet absorber and 0.3% of light stabilizer were added according to the mass of PBAT, and blending modification was carried out at a processing temperature of 150°C to obtain component 2;

[0131] The component 1, component 2 and PBAT raw material were put into a multi-layer co-extrusion blown film system in a mass ratio of 1:1:1, and a composite film of Comparative Example 1 was obtained by multi-layer co-extrusion blowing according to the feeding section temperature, compression section temperature, homogenization section temperature and die temperature of 155℃, 165℃, 165℃ and 165℃ respectively. Among them, component 2 was used to prepare the outer layer, component 1 was used to prepare the middle layer, and PBAT raw material was used to prepare the inner layer. The mass ratio of component 1, component 2 and PBAT raw material was 1:1:1, and the thickness of the obtained composite film was about 25 microns.

[0132] Tested, the film of Comparative Example 1 had a transverse tensile strength of 36.57 MPa, a longitudinal tensile strength of 34.89 MPa, a transverse elongation at break of 920.78%, a longitudinal elongation at break of 327.15%, a fusion strength of 13.25 N / mm, a mechanical property (transverse / longitudinal tensile strength) retention rate of more than 75% after being placed in an environment of 85℃ and 85% humidity for 192 hours, a mechanical property (transverse / longitudinal tensile strength) retention rate of more than 85% after being placed in a conventional environment for 24 months, obvious scratching marks on the air conditioner high-gloss appearance panel after the film was rubbed back and forth for more than 30 times under a load of 1kg weight, and more than 90% of degradable organic matter.

[0133] Comparative Example 2

[0134] In this comparative example, PBAT with an acid value of 13.1 mgKOH / g was used as the base material, 1.5% polycaprolactone chain extender based on the mass of PBAT was added, and blending modification was carried out at a processing temperature of 150℃ to obtain component 1; 0.3% hindered phenol antioxidant, 0.3% benzotriazole ultraviolet absorber and 0.3% light stabilizer were added based on the mass of component 1, and blending modification was carried out at a processing temperature of 150℃ to obtain weather-resistant modified component 1.

[0135] The weather-resistant modified component 1 was put into an extrusion blown film system, and a single-layer film of Comparative Example 2 was obtained by extrusion blow molding according to the feeding section temperature, compression section temperature, homogenization section temperature and die temperature of 155℃, 165℃, 165℃ and 165℃ respectively. Among them, the thickness of the obtained single-layer film was about 25 microns.

[0136] Tested, the film of Comparative Example 2 had a transverse tensile strength of 16.13 MPa, a longitudinal tensile strength of 28.30 MPa, a transverse elongation at break of 540.51%, a longitudinal elongation at break of 426.89%, a fusion strength of 7.97 N / mm, a mechanical property (transverse / longitudinal tensile strength) retention rate of more than 50% after being placed in an environment of 85℃ and 85% humidity for 192 hours, a mechanical property (transverse / longitudinal tensile strength) retention rate of more than 70% after being placed in a conventional environment for 24 months, obvious scratching marks on the air conditioner high-gloss appearance panel after the film was rubbed back and forth for more than 30 times under a load of 1kg weight, and more than 90% of degradable organic matter.

[0137] Comparative Example 3

[0138] The PBAT with an acid value of 20.8 mgKOH / g was used as the base material, and 1% of the mass of the PBAT was added with styrene-methyl methacrylate-glycidyl methacrylate copolymer to obtain component 1 by blending modification at a processing temperature of 155°C.

[0139] The PBAT raw material, and 0.2% of the mass of the PBAT was added with a hindered phenol antioxidant, 0.4% of the mass of the PBAT was added with a benzotriazole ultraviolet absorber, and 0.3% of the mass of the PBAT was added with a light stabilizer to obtain component 2 by blending modification at a processing temperature of 155°C.

[0140] The component 1, the component 2, and the PBAT raw material were put into a multi-layer co-extrusion film blowing system in equal mass proportions, and the feeding section temperature, the compression section temperature, the homogenization section temperature, and the die temperature were 155°C, 165°C, 165°C, and 165°C, respectively, to obtain the composite film of the comparative example 3 by multi-layer co-extrusion blowing. The component 2 was used to make the outer layer, the component 1 was used to make the middle layer, and the PBAT raw material was used to make the inner layer. The mass ratio of the component 1, the component 2, and the PBAT raw material was 1:1:1, and the thickness of the obtained composite film was about 25 microns.

[0141] The test results showed that the transverse tensile strength of the film of the comparative example 3 was 32.46 MPa, the longitudinal tensile strength was 30.87 MPa, the transverse elongation at break was 620.45%, the longitudinal elongation at break was 358.76%, the fusion strength was 13.05 N / mm, the mechanical property (transverse / longitudinal tensile strength) retention rate was more than 75% after being placed in an environment of 85°C and 85% humidity for 192 hours, the mechanical property (transverse / longitudinal tensile strength) retention rate was more than 85% after being placed in a conventional environment for 24 months, the air conditioning high light appearance panel had obvious scratch marks after the film was rubbed back and forth for more than 30 times under a load of 1 kg weight, and the degradable organic matter was more than 90%.

[0142] Comparative Example 4

[0143] The HDPE (high density polyethylene) was used as the base material to blow the film, and the thickness of the film was about 25 microns.

[0144] The film of Comparative Example 4 has a transverse tensile strength of 22.14 MPa, a longitudinal tensile strength of 16.58 MPa, a transverse elongation at break of 237.15%, a longitudinal elongation at break of 140.30%, a fusion strength of 7.80 N / mm, a mechanical property (transverse / longitudinal tensile strength) retention rate of more than 90% after being placed in an environment of 85 ℃ and 85% humidity for 192 hours, a mechanical property (transverse / longitudinal tensile strength) retention rate of more than 90% after being placed in a normal environment for 24 months, obvious scratches on the air conditioner high-gloss appearance panel after being rubbed back and forth for more than 30 times under a load of 1 kg, and no degradable organic matter.

[0145] The composite film structure prepared in Examples 1-3 is shown in the schematic diagram Figure 1 .

[0146] The test results of the film materials prepared in Examples 1-3 and Comparative Examples 1-4 are shown in Table 1 below.

[0147] Table 1: Film test results of examples and comparative examples

[0148]

[0149] According to the above test results, compared with the existing polyethylene packaging material (see Comparative Example 4), the composite film of Examples 1-3 has better compostable degradation characteristics, mechanical properties, self-lubricating properties, hydrolysis resistance and weather resistance, and can protect the appearance of the product from scratches. Comparative Example 1 does not add a lubricant, which will cause the air conditioner high-gloss appearance panel to have obvious scratches, resulting in appearance quality problems; Comparative Example 2 uses a single-layer film made of modified raw materials, which has poor mechanical properties and is not as good as the packaging performance of the examples; Comparative Example 3 differs from Example 2 only in that no lubricant is added. As can be seen from the test results, the air conditioner high-gloss appearance panel of Comparative Example 3 has obvious scratches, while the air conditioner high-gloss appearance panel of Example 2 has no scratches, indicating that the film of Example 2 has self-lubricating properties and can protect the appearance of the product from scratches.

[0150] The preparation raw material of the weather-resistant modification layer of the composite film of the examples of the present application adds an antioxidant, an ultraviolet absorber and a light stabilizer. The ultraviolet absorber and the light stabilizer are added to meet the requirement of the exposed packaging material. By adding the ultraviolet absorber and the light stabilizer, the light aging resistance of the composite film can be enhanced. If the ultraviolet absorber and the light stabilizer are not added for light aging resistance modification, the film sample without light aging resistance will be broken within the same light aging test time.

[0151] The composite film prepared by using various modified materials has no influence on the original parts, the size, angle, quantity and specification of the parts. However, the environmental friendly property of the material can be greatly improved by using the composite film with compostable degradation property.

[0152] The composite film with excellent environmental friendly property and packaging performance provided by the embodiment of the present application can be used as a packaging material. For example, the composite film can be used as a dustproof and scratchproof film bag for air conditioners, refrigerators, washing machines and other household appliances, which can meet the dustproof or scratchproof requirements of the household appliances and avoid the appearance quality problems of the household appliances. The composite film has a wide application prospect in the packaging or transportation of household appliances.

[0153] In the description of the present specification, the description referring to the terms "some embodiments", "some specific embodiments" or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiments or examples are contained in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0154] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A composite membrane, characterized in that Including self-lubricating modified layer, anti-hydrolysis modified layer and weathering modified layer; The anti-hydrolysis modified layer is located between the self-lubricating modified layer and the weathering modified layer; The raw materials for preparing the self-lubricating modified layer include a first biodegradable material and a lubricant; The raw materials for preparing the hydrolysis-resistant modified layer include a second biodegradable material and a chain extender; The raw materials for preparing the weather-resistant modified layer include a third biodegradable material, an antioxidant, an ultraviolet absorber and a light stabilizer; The first biodegradable material, the second biodegradable material, and the third biodegradable material independently include at least PBAT.

2. A composite membrane according to claim 1, characterized in that The first biodegradable material, the second biodegradable material, and the third biodegradable material are independently selected from PBAT, or a combination of PBAT and at least one of PLA, PBS, PBSA, PHA, PPC, and PGA.

3. A composite membrane according to claim 1, characterized in that The composite film comprises a self-lubricating modified layer, an anti-hydrolysis modified layer and a weather-resistant modified layer which are sequentially arranged from the inside to the outside.

4. A composite membrane according to claim 1, characterized in that: The mass ratio of the raw materials for preparing the self-lubricating modified layer, the raw materials for preparing the anti-hydrolysis modified layer and the raw materials for preparing the weathering modified layer is 1:(0.8-1.2):(0.8-1.2).

5. A composite membrane according to claim 1, characterized in that: The acid value of the hydrolysis-resistant modified layer is 3 mgKOH / g to 8 mgKOH / g.

6. A composite membrane according to any one of claims 1 to 4, characterized in that: The mass percentage of the lubricant to the mass percentage of the raw materials for preparing the first biodegradable material is 0.5% to 1.5%.

7. A composite membrane according to claim 6, characterized in that: The lubricant includes at least one of silicone oil, silicone powder, fatty acid amide, stearic acid, stearate, montanate, paraffin, polyethylene wax, erucamide, oleamide, ethylene bisstearamide, pentaerythritol stearate, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid copolymer.

8. A composite membrane according to any one of claims 1 to 5, characterized in that: The mass percentage of the chain extender to the mass percentage of the raw materials for preparing the second biodegradable material is 0.5% to 1.5%.

9. A composite membrane according to claim 8, characterized in that: The chain extender includes at least one of polycaprolactone and polyvalent epoxy chain extender.

10. A composite membrane according to any one of claims 1 to 4, characterized in that: The weight percentage of the antioxidant, the ultraviolet absorber and the light stabilizer to the weight percentage of the raw materials for preparing the third biodegradable material is 0.2% to 0.5%.

11. A composite membrane according to claim 10, characterized in that: The antioxidant includes at least one of a hindered amine antioxidant and a hindered phenol antioxidant.

12. A composite membrane according to claim 10, characterized in that: The ultraviolet absorber includes at least one of a salicylate ultraviolet absorber, a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a substituted acrylonitrile ultraviolet absorber, a triazine ultraviolet absorber, and a hindered amine ultraviolet absorber.

13. A composite membrane according to claim 10, characterized in that: The light stabilizer includes at least one of a light shielding agent, a quencher, and a hindered amine light stabilizer.

14. A composite membrane according to any one of claims 1 to 5, characterized in that: The thickness of the composite film is 10 microns to 35 microns.

15. A method for preparing the composite membrane according to any one of claims 1 to 14, characterized in that: The following steps are involved: mixing a first biodegradable material and a lubricant to obtain a first component; blending and modifying a second biodegradable material and a chain extender to obtain a second component; blending and modifying a third biodegradable material, an antioxidant, an ultraviolet absorber, and a light stabilizer to obtain a third component; The first component, the second component and the third component are subjected to multi-layer co-extrusion blown film to obtain the composite film.

16. The preparation method according to claim 15, characterized in that In the step of blending and modifying the second biodegradable material and the chain extender, the blending and modification temperature is 150° C. to 170° C.

17. The preparation method according to claim 15, characterized in that In the step of blending and modifying the third biodegradable material, the antioxidant, the ultraviolet absorber and the light stabilizer, the blending and modification temperature is 150° C. to 170° C.

18. The preparation method according to claim 15, characterized in that The extrusion temperature of the multi-layer co-extrusion blown film is 150° C. to 170° C.

19. A packaging material, characterized in that: The composite film comprises the composite film according to any one of claims 1 to 14.

20. The packaging material according to claim 19, characterized in that The packaging material is a dust-proof bag or an anti-scratch bag for household appliances.

21. Use of the composite film according to any one of claims 1 to 14 in the packaging or transportation of household appliances.

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