A degradable water- and oil-blocking double-layer film and preparation method thereof

Abstract

The present invention provides a degradable water- and oil-blocking double-layer film and a preparation method thereof, and belongs to the technical field of food packaging. In the present invention, a degradable oil-blocking-based biomaterial is prepared into a first film liquid, and a plasticizer is added to obtain a third film liquid; a degradable water-blocking-based biomaterial is prepared into a second film liquid, and a plasticizer is added to obtain a fourth film liquid; the third film liquid is prepared into a gel, and the fourth film liquid is evenly coated on the gel and dried to form a film, thereby obtaining a degradable water- and oil-blocking double-layer film. The double-layer film has good mechanical properties, extremely low water vapor permeability, and will not have oil permeation for at least 10 days.

Description

Technical Field

[0001] The invention belongs to the technical field of food packaging, and in particular relates to a degradable water- and oil-blocking double-layer film and a preparation method thereof. Background Art

[0002] Food packaging paper is often coated or laminated to improve its waterproof and oil-proof properties to meet its functional requirements for contact with water-based and oily foods. Traditional waterproof and oil-proof films are mainly plastic polymers produced from petroleum-based raw materials. For example, polypropylene, polyethylene and polyethylene terephthalate are used to form a dense film on the surface of paper to prevent water and paper from contacting, thereby achieving a waterproof and oil-proof effect. These polymers are non-renewable and non-degradable. With the extensive use of disposable tableware, the environmental problems caused are becoming increasingly serious; and toxic substances in the packaging may also enter the food through chemical migration, resulting in increasingly significant food safety issues. At the same time, the existing food packaging materials have poor water and oil barrier properties, which can easily cause the food to become damp or its inherent quality to deteriorate. Therefore, it is very necessary to study degradable, renewable, safe and environmentally friendly food packaging materials. Summary of the invention

[0003] The present invention provides a method for preparing a degradable water- and oil-blocking double-layer film. The method uses degradable bio-based raw materials to prepare a film having excellent water- and oil-blocking properties.

[0004] In order to achieve the above object, the present invention specifically adopts the following technical solutions:

[0005] A method for preparing a degradable water- and oil-blocking double-layer film comprises the following steps:

[0006] S1, dissolving the oil-blocking biomaterial in a first solvent to prepare a first membrane liquid; dissolving the water-blocking biomaterial in a second solvent to prepare a second membrane liquid; the oil-blocking biomaterial is a natural polysaccharide; the water-blocking biomaterial is at least one of zein, soy protein, ethyl cellulose, chitosan, and waterborne polyurethane;

[0007] S2, adding a plasticizer to the first membrane liquid, mixing evenly, to obtain a third membrane liquid; adding a plasticizer to the second membrane liquid, mixing evenly, to obtain a fourth membrane liquid;

[0008] S3, pouring the third film liquid into a mold, drying, and obtaining a film or a gel; placing the fourth film liquid on the film or the gel, drying, and obtaining a degradable water- and oil-blocking double-layer film.

[0009] Natural polysaccharides have good film-forming properties, contain a large number of hydrophilic groups, and have weak hydrophobicity. Therefore, they can be used to block lipophilic substances. Natural proteins such as zein and soy protein and water-insoluble cellulose derivatives such as ethyl cellulose all have a large number of hydrophobic groups and weak hydrophilicity, so they can be used to block hydrophilic substances.

[0010] In a preferred embodiment, the oil-blocking biomaterial is at least one of konjac glucomannan, deacetyl konjac glucomannan, agar, pectin, curdlan, gellan gum, carrageenan, gum arabic, locust bean gum, and guar gum.

[0011] In a preferred embodiment, the mass concentration of the oil-blocking biomaterial in the first membrane liquid is 1% to 1.35%.

[0012] In a preferred embodiment, the mass volume percentage of the water-blocking biomaterial in the second membrane liquid is 5% to 15%.

[0013] In a preferred embodiment, the first solvent is water.

[0014] In a preferred embodiment, the second solvent is 70% to 95% (v / v) ethanol or 1% (v / v) acetic acid aqueous solution.

[0015] In a preferred embodiment, the oil-blocking biomaterial is dissolved in the first solvent at a temperature of 25 to 95°C.

[0016] In a preferred embodiment, a plasticizer accounting for 10% to 20% of the mass of the oil-resistant biomaterial is added to the first membrane liquid.

[0017] In a preferred embodiment, a plasticizer accounting for 10% to 30% of the mass of the water-blocking biomaterial is added to the second membrane liquid.

[0018] In a preferred embodiment, the plasticizer is added to the first membrane liquid, and the mixture is mixed evenly at 25 to 95° C. to obtain the third membrane liquid.

[0019] In a preferred embodiment, the plasticizer is added to the second membrane liquid, and the mixture is mixed uniformly at 25-60° C. to obtain the fourth membrane liquid.

[0020] In a preferred embodiment, the plasticizer includes at least one of glycerol and triethyl citrate.

[0021] In a preferred embodiment, the ratio of the mass of the fourth membrane liquid to the mass of the third membrane liquid is 1:(3-5).

[0022] In a preferred embodiment, when the natural polysaccharide in step S1 is konjac glucomannan, step S2 further comprises the step of adding an alkaline solution to the mixed solution of the first membrane liquid and the plasticizer.

[0023] In a further preferred embodiment, the alkaline solution is a 1 wt% to 6 wt% sodium carbonate solution, and the ratio of the volume of the sodium carbonate solution to the total volume of the first membrane liquid and the plasticizer is 1:20.

[0024] The present invention also provides a degradable water- and oil-blocking double-layer film prepared according to any of the preparation methods described above.

[0025] The technical solution of the present invention has the following beneficial effects: (1) The present invention adopts a natural polymer material with a wide range of sources, renewable and degradable as a raw material to prepare a double-layer film with excellent mechanical properties and good water and oil barrier properties. The water vapor permeability of the double-layer film is less than 11(10 -13 g cm / cm 2 ·s·Pa), and there will be no oil penetration for at least 10 days; tensile strength>36MPa, elongation at break>15%. (2) The method of the present invention is simple in process and easy to operate, and is suitable for industrial production of food packaging materials. (3) The use of the double-layer film of the present invention to prepare food packaging materials can prevent the quality of food from deteriorating due to interference from external oil and water during transportation and storage, and can also prevent the loss and leakage of moisture and oil in the packaged food, thereby playing a relatively sealing role. (4) The material of the double-layer film of the present invention is biodegradable and more environmentally friendly. DETAILED DESCRIPTION

[0026] The following content is combined with the embodiments to clearly and completely describe the technical solution of the present application so that those skilled in the art can fully understand the present application. Obviously, the described embodiments are only some preferred embodiments of the present application, rather than all embodiments. Any equivalent transformation or substitution made to the following implementation modes by those of ordinary skill in the art without creative work belongs to the protection scope of the present application.

[0027] In the following examples, a degradable water- and oil-blocking double-layer film was prepared according to the following steps:

[0028] S1. Dissolve the oil-blocking biomaterial in water at 25 to 95°C to prepare a first membrane solution with a mass concentration of 1% to 1.35%; dissolve the water-blocking biomaterial in 70% to 95% (volume ratio) ethanol or 1% (volume ratio) acetic acid aqueous solution to prepare a second membrane solution with a mass volume percentage of 5% to 15%. The oil-blocking biomaterial is a natural polysaccharide, such as at least one of konjac glucomannan (KGM), deacetylated konjac glucomannan (DKGM), agar, pectin, curdlan, gellan gum, carrageenan, gum arabic, locust bean gum, and guar gum; the water-blocking biomaterial is at least one of zein, soy protein, ethyl cellulose, chitosan, and water-based polyurethane.

[0029] S2. Add 10% to 20% of the mass of the oil-blocking biomaterial to the first membrane liquid, mix evenly at 25 to 95° C. (e.g., mechanical stirring for 0.5 to 1.5 hours), and obtain a third membrane liquid; add 10% to 30% of the mass of the water-blocking biomaterial to the second membrane liquid, mix evenly at 25 to 60° C. (e.g., magnetic stirring for 20 to 40 minutes), and obtain a fourth membrane liquid. The plasticizer is glycerol or triethyl citrate.

[0030] S3, pour the third film liquid into the mold, dry at 40-70°C to obtain a gel; evenly apply the fourth film liquid on the gel, cool it into a gel, and dry it at 60-80°C to obtain a degradable water- and oil-blocking double-layer film. The mass ratio of the fourth film liquid to the mass ratio of the third film liquid is 1:(3-5).

[0031] Furthermore, when the natural polysaccharide in step S1 is konjac glucomannan, step S2 further includes the step of adding 1wt% to 6wt% sodium carbonate solution to the mixed solution of the first membrane liquid and the plasticizer. The ratio of the volume of the sodium carbonate solution to the total volume of the first membrane liquid and the plasticizer is 1:20.

[0032] The bio-based materials and various reagents used in the examples are all common raw materials on the market and can be purchased through commercial channels. Konjac glucomannan uses konjac glucomannan powder with a molecular weight of 9.67×10 5 Da. Zein is analytically pure. Agar is analytically pure, with a gel strength of 800-1200 g / cm 2 The specification of ethyl cellulose is analytically pure, and the viscosity is 60-80 mPa·s. The specification of pectin is analytically pure, and the galacturonic acid content is >74%. The specification of chitosan is analytically pure, and the molecular weight is 20×10 4 Da.

[0033] In the embodiment, the water permeability test of the degradable water- and oil-blocking double-layer film adopts a water vapor permeability tester (model: W3 / 031, Jinan Languang Electromechanical Technology Co., Ltd.), referring to GB / T 1037-2021 "Plastic Film and Thin Sheet Water Vapor Permeability Performance Determination Cup Weight Gain and Weight Loss Method", and fills a 25mm×65mm thin plate cup with deionized water (20mL), then seals it with a film sample and places it in a test box. The temperature of the test box is controlled at 25°C and the relative humidity is controlled at 50%. The method of oil permeability test is as follows: Use a sealing machine to seal the three sides of the film sample to make a film bag, add 0.5mL of soybean oil to the bag, and seal the bag with a sealing machine. Place the packaged film bag on oil-absorbing paper and observe the oil leakage on the oil-absorbing paper. The mechanical properties test method is as follows: refer to the ASTM-D882-91 standard test method, use a tensile machine to test the tensile strength and elongation at break of the film sample, the film sample size is 5mm×50mm, the film sample is installed between the clamps, and the test is performed with an initial clamp spacing of 50mm and a tensile speed of 0.5mm / s. The maximum tensile force (unit: N) is divided by the area of ​​the film sample (unit: m 2 ), and the tensile strength is obtained. Elongation at break = (length after stretching - initial length) / initial length × 100%.

[0034] Example 1

[0035] A method for preparing a degradable water- and oil-blocking double-layer film comprises the following steps:

[0036] S1. Take an appropriate amount of konjac glucomannan (KGM) and dissolve it in 60°C water to prepare a first membrane solution with a konjac glucomannan concentration of 1wt%; take an appropriate amount of zein (Zein) and dissolve it in 90% (v / v) ethanol to prepare a second membrane solution with a zein concentration of 6% (w / v).

[0037] S2. Add glycerol accounting for 10% of the mass of konjac glucomannan to the first membrane liquid, and stir mechanically for 1.5 hours in a water bath at 60° C. to obtain a third membrane liquid; add glycerol accounting for 15% of the mass of zein to the zein membrane liquid, and stir magnetically for 30 minutes at 40° C. to obtain a fourth membrane liquid.

[0038] S3, pour the third film liquid into the mold, dry at 60°C to obtain a gel; while the gel is still sticky, evenly apply the fourth film liquid on the gel, cool it to make it gel, and then dry it at 60°C to obtain a degradable water- and oil-blocking double-layer film. The mass ratio of the fourth film liquid to the mass of the third film liquid is 1:3.5.

[0039] The water and oil permeability of the double-layer film prepared in step S3 was tested, and the water vapor permeability was measured to be 9.23±0.57 (10 -13 g cm / cm 2 ·s·Pa), and no oil penetration occurred in 10 days.

[0040] Example 2

[0041] A method for preparing a degradable water- and oil-blocking double-layer film comprises the following steps:

[0042] S1. Take an appropriate amount of agar (analytical grade, gel strength 800-1200 g / cm 2 ) was dissolved in 60°C water to prepare a first membrane solution with an agar concentration of 1wt%; an appropriate amount of zein was dissolved in 90% (v / v) ethanol to prepare a second membrane solution with a zein concentration of 6% (w / v).

[0043] S2. Add glycerol accounting for 10% of the mass of agar to the first membrane liquid, and stir mechanically for 1 hour in a water bath at 60° C. to obtain a third membrane liquid; add glycerol accounting for 15% of the mass of zein to the second membrane liquid, and stir magnetically for 30 minutes at 40° C. to obtain a fourth membrane liquid.

[0044] S3, pouring the third film liquid into the mold, drying at 60°C to obtain a gel; uniformly coating the fourth film liquid on the gel, cooling the fourth film liquid to form a gel, and then drying at 60°C to obtain a degradable water- and oil-blocking double-layer film. The mass ratio of the fourth film liquid to the mass ratio of the third film liquid is 1:3.5.

[0045] The water and oil permeability of the double-layer film prepared in step S3 was tested, and the water vapor permeability was measured to be 8.20±0.39 (10 -13 g cm / cm 2 ·s·Pa), and no oil penetration occurred in 14 days.

[0046] Example 3

[0047] A method for preparing a degradable water- and oil-blocking double-layer film comprises the following steps:

[0048] S1. Dissolve agar in 60°C water, stir mechanically at 60°C for 15 min, then add konjac glucomannan to the solution, and continue stirring for 75 min to obtain a first membrane liquid. The mass ratio of konjac glucomannan to agar is 24:76, and the solute concentration in the first membrane liquid is 1.35wt%. Take an appropriate amount of zein and dissolve it in 90% (v / v) ethanol to prepare a second membrane liquid with a zein concentration of 6% (w / v).

[0049] S2. Add glycerol accounting for 10% of the solute mass to the first membrane liquid, and stir mechanically for 1.5 hours in a water bath at 60°C to obtain a third membrane liquid; add glycerol accounting for 15% of the mass of corn alcohol-soluble protein to the second membrane liquid, and stir magnetically for 30 minutes at 40°C to obtain a fourth membrane liquid.

[0050] S3, pouring the third film liquid into the mold, drying at 60°C to obtain a gel; uniformly coating the fourth film liquid on the gel, cooling the fourth film liquid to form a gel, and then drying at 60°C to obtain a degradable water- and oil-blocking double-layer film. The mass ratio of the fourth film liquid to the mass ratio of the third film liquid is 1:3.5.

[0051] The water and oil permeability of the double-layer film prepared in step S3 was tested, and the water vapor permeability was measured to be 8.84±0.75 (10 -13 g cm / cm 2 ·s·Pa), and no oil penetration occurred in 14 days.

[0052] Example 4

[0053] A method for preparing a degradable water- and oil-blocking double-layer film comprises the following steps:

[0054] S1. Dissolve agar in 60°C water, stir mechanically at 60°C for 15 min, then add konjac glucomannan to the solution, continue stirring for 75 min, and obtain a first membrane liquid. The mass ratio of konjac glucomannan to agar is 24:76, and the solute concentration in the first membrane liquid is 1.35wt%. Take an appropriate amount of zein and dissolve it in 70% (v / v) ethanol to prepare a second membrane liquid with a zein concentration of 6% (w / v).

[0055] S2. Add 10% glycerol to the first membrane liquid, stir mechanically for 1.5h in a water bath at 60°C, then add 5.25% sodium carbonate solution to the solution, continue stirring for 5min, and obtain the third membrane liquid. The sodium carbonate solution provides an alkaline environment to induce the removal of the acetyl group of konjac glucomannan, so that the molecular chains are closely arranged to increase the hydrophobicity of the subsequent film. Add 15% glycerol to the second membrane liquid, stir magnetically for 30min at 40°C, and obtain the fourth membrane liquid; the ratio of the volume of the 5.25% sodium carbonate solution to the total volume of the first membrane liquid and 10% glycerol is 1:20.

[0056] S3, pouring the third film liquid into the mold, drying at 60°C to obtain a gel; uniformly coating the fourth film liquid on the gel, cooling the fourth film liquid to make it gel, and drying at 60°C to obtain a degradable water- and oil-blocking double-layer film. The mass ratio of the fourth film liquid to the mass ratio of the third film liquid is 1:3.5.

[0057] The mechanical properties of the double-layer film prepared in step S3 were tested, and the tensile strength was measured to be (36.23±3.64) MPa, and the elongation at break was (15.98±2.43)%. The water and oil permeability of the double-layer film prepared in step S3 was tested, and the water vapor permeability was measured to be 8.24±0.60(10 -13 g cm / cm 2 ·s·Pa), and no oil penetration occurred in 14 days.

[0058] Example 5

[0059] A method for preparing a degradable water- and oil-blocking double-layer film comprises the following steps:

[0060] S1. Dissolve agar in 60°C water, stir mechanically at 60°C for 15 min, then add konjac glucomannan to the solution, continue stirring for 75 min, and obtain a first membrane liquid. The mass ratio of konjac glucomannan to agar is 24:76, and the solute concentration in the first membrane liquid is 1.35wt%. Take an appropriate amount of ethyl cellulose and dissolve it in 90% (v / v) ethanol to prepare a second membrane liquid with an ethyl cellulose concentration of 5% (w / v).

[0061] S2, add glycerol accounting for 10% of the solute mass to the first membrane liquid, and stir mechanically for 1.5 hours in a water bath at 60°C to obtain a third membrane liquid; add triethyl citrate accounting for 15% of the mass of ethyl cellulose to the second membrane liquid, and stir magnetically for 30 minutes at 40°C to obtain a fourth membrane liquid;

[0062] S3, pouring the third film liquid into the mold, drying at 60°C to obtain a gel; uniformly coating the fourth film liquid on the gel, cooling the fourth film liquid to make it gel, and drying at 60°C to obtain a degradable water- and oil-blocking double-layer film. The mass ratio of the fourth film liquid to the mass ratio of the third film liquid is 1:3.5.

[0063] The water and oil permeability of the double-layer film prepared in step S3 was tested, and the water vapor permeability was measured to be 6.77±0.42 (10 -13 g cm / cm 2 ·s·Pa), and no oil penetration occurred in 14 days.

[0064] Example 6

[0065] A method for preparing a degradable water- and oil-blocking double-layer film comprises the following steps:

[0066] S1. Dissolve agar in 60°C water, stir mechanically at 60°C for 15 min, then add konjac glucomannan to the solution, continue stirring for 75 min, and obtain a first membrane liquid. The mass ratio of konjac glucomannan to agar is 24:76, and the solute concentration in the first membrane liquid is 1.35wt%. Take an appropriate amount of zein and dissolve it in 90% (v / v) ethanol to prepare a second membrane liquid with a zein concentration of 8% (w / v).

[0067] S2. Add 10% glycerol by mass to the first membrane liquid, stir mechanically for 1.5 hours in a water bath at 60°C, then add 5.25% sodium carbonate solution, continue stirring for 5 minutes to obtain the third membrane liquid; add 15% triethyl citrate by mass of ethyl cellulose to the second membrane liquid, stir magnetically for 30 minutes at 40°C to obtain the fourth membrane liquid. The volume ratio of the 5.25% sodium carbonate solution to the total volume of the first membrane liquid and 10% glycerol is 1:20.

[0068] S3, pouring the third film liquid into the mold, drying at 60°C to obtain a gel; uniformly coating the fourth film liquid on the gel, cooling the fourth film liquid to make it gel, and drying at 60°C to obtain a degradable water- and oil-blocking double-layer film. The mass ratio of the fourth film liquid to the mass ratio of the third film liquid is 1:3.5.

[0069] The mechanical properties of the double-layer film prepared in step S3 were tested, and the tensile strength was measured to be (54.69±3.34)MPa, and the elongation at break was (17.45±1.74)%. The water and oil permeability of the double-layer film prepared in step S3 was tested, and the water vapor permeability was measured to be 6.63±0.36(10 -13 g cm / cm 2 ·s·Pa), and no oil penetration occurred in 14 days.

[0070] Example 7

[0071] A method for preparing a degradable water- and oil-blocking double-layer film comprises the following steps:

[0072] S1. Dissolve pectin in water at 25° C. to prepare a first membrane solution with a pectin concentration of 1.2 wt %; take an appropriate amount of zein and dissolve it in 95% (v / v) ethanol to prepare a second membrane solution with an ethyl cellulose concentration of 10% (w / v).

[0073] S2, adding 15% of the mass of glycerol to the first membrane liquid and mechanically stirring it in a water bath at 25°C for 1 hour to obtain a third membrane liquid; adding 10% of the mass of ethyl cellulose to the second membrane liquid, magnetically stirring it at 40°C for 30 minutes to obtain a fourth membrane liquid;

[0074] S3, pour the third film liquid into the mold, dry at 40°C to obtain a gel; evenly apply the fourth film liquid on the gel, cool the fourth film liquid to make it gel, and dry at 70°C to obtain a degradable water- and oil-blocking double-layer film. The mass ratio of the fourth film liquid to the mass of the third film liquid is 1:3.

[0075] The water and oil permeability of the double-layer film prepared in step S3 was tested, and the water vapor permeability was measured to be 10.35±0.66 (10 -13 g cm / cm 2 ·s·Pa), and no oil penetration occurred in 14 days.

[0076] Example 8

[0077] A method for preparing a degradable water- and oil-blocking double-layer film comprises the following steps:

[0078] S1. Dissolve konjac glucomannan in 95° C. water to prepare a first membrane solution with a konjac glucomannan concentration of 1 wt %; take an appropriate amount of chitosan and dissolve it in a 1% (v / v) acetic acid aqueous solution to prepare a second membrane solution with a chitosan concentration of 15% (w / v).

[0079] S2, adding glycerol accounting for 20% of the mass of the solute to the first membrane liquid and mechanically stirring in a water bath at 95°C for 1.5 hours to obtain a third membrane liquid; adding glycerol accounting for 30% of the mass of chitosan to the second membrane liquid, magnetically stirring at 40°C for 30 minutes to obtain a fourth membrane liquid;

[0080] S3, pour the third film liquid into the mold, dry at 70°C to obtain a gel; evenly apply the fourth film liquid on the gel, cool the fourth film liquid to form a gel, and dry at 80°C to obtain a degradable water- and oil-blocking double-layer film. The mass ratio of the fourth film liquid to the mass of the third film liquid is 1:5.

[0081] The water and oil permeability of the double-layer film prepared in step S3 was tested, and the water vapor permeability was measured to be 7.53±0.89 (10 -13 g cm / cm 2 ·s·Pa), and no oil penetration occurred in 14 days.

[0082] The inventors found in the experimental process that, in addition to konjac glucomannan, agar, and pectin, natural polysaccharides such as curdlan, gellan gum, carrageenan, gum arabic, locust bean gum, and guar gum as oil-blocking biomaterials, or / and soybean protein and aqueous polyurethane as water-blocking biomaterials, can all be used to successfully prepare degradable water-blocking and oil-blocking double-layer films according to the methods in the above embodiments, and achieve the same or substantially the same effects as in the above embodiments. Konjac glucomannan can be deacetylated by using an alkaline solution to obtain deacetylated konjac glucomannan, especially when deacetylated by using a 1wt% to 6wt% sodium carbonate aqueous solution, the effect is better.

[0083] The above-described embodiments are only preferred embodiments of the present application and are not intended to limit the scope of protection of the present application. For any person skilled in the art, the present application may have various changes and modifications. Any simple equivalent changes and modifications made based on the scope of protection of the present application and the contents of the specification should be included in the scope of protection of the present application.

Claims

1. A method for preparing a degradable water- and oil-blocking double-layer film, characterized in that: The following steps are involved: S1, dissolving the oil-blocking biomaterial in a first solvent to prepare a first membrane liquid; dissolving the water-blocking biomaterial in a second solvent to prepare a second membrane liquid; the water-blocking biomaterial is at least one of zein, soy protein, ethyl cellulose, and aqueous polyurethane; the oil-blocking biomaterial is at least one of konjac glucomannan, deacetyl konjac glucomannan, agar, pectin, curdlan, gellan gum, carrageenan, gum arabic, locust bean gum, and guar gum; the mass concentration of the oil-blocking biomaterial in the first membrane liquid is 1% to 1.35%; the mass volume percentage of the water-blocking biomaterial in the second membrane liquid is 5% to 15%; S2, adding a plasticizer to the first film liquid, mixing evenly, to obtain a third film liquid; adding a plasticizer to the second membrane liquid and mixing them evenly to obtain a fourth membrane liquid; S3, pouring the third film liquid into a mold, drying, and obtaining a gel; evenly coating the fourth film liquid on the gel, drying, and obtaining a degradable water- and oil-blocking double-layer film; the ratio of the mass of the fourth film liquid to the mass of the third film liquid is 1:(3~5).

2. The method for preparing the degradable water- and oil-blocking double-layer film according to claim 1, characterized in that: The first solvent is water; or / and the second solvent is 70% to 95% (v / v) ethanol or 1% (v / v) acetic acid aqueous solution.

3. The method for preparing the degradable water- and oil-blocking double-layer film according to claim 1, characterized in that: Adding a plasticizer accounting for 10% to 20% of the mass of the oil-blocking biomaterial to the first membrane liquid; or / and adding a plasticizer accounting for 10% to 30% of the mass of the water-blocking biomaterial to the second membrane liquid.

4. The method for preparing the degradable water- and oil-blocking double-layer film according to claim 1, characterized in that: The plasticizer includes at least one of glycerol and triethyl citrate.

5. The method for preparing the degradable water- and oil-blocking double-layer film according to claim 1, characterized in that: When the oil-blocking biomaterial in step S1 is konjac glucomannan, step S2 further comprises the step of adding an alkaline solution to the mixed solution of the first membrane liquid and the plasticizer.

6. The method for preparing the degradable water- and oil-blocking double-layer film according to claim 5, characterized in that: The alkaline solution is a 1wt% to 6wt% sodium carbonate solution, and the ratio of the volume of the sodium carbonate solution to the total volume of the first membrane liquid and the plasticizer is 1:

20.

7. The method for preparing the degradable water- and oil-blocking double-layer film according to claim 1, characterized in that: The oil-resistant biomaterial is dissolved in the first solvent at 25-95° C.; or / and the plasticizer is added to the first membrane liquid and mixed evenly at 25-95° C.; or / and the plasticizer is added to the second membrane liquid and mixed evenly at 25-60° C.

8. The degradable water- and oil-blocking double-layer film prepared by the preparation method according to any one of claims 1 to 7.