Macromolecular breathable film material and preparation method thereof

Abstract

The invention discloses a macromolecular breathable film material and a preparation method thereof. The macromolecular breathable film material is prepared from the following components in parts by weight: 2.6 to 3.1 parts of epsilon-caprolactone, 27 to 30 parts of L-lactide and 0.6 to 0.9 part of metal-polyphenol network coated fiber crystals. The mode of preparing a star initiator through epsilon-caprolactone is provided, the air permeability of the polylactic acid material is improved, meanwhile, microcrystalline cellulose is used for preparing metal-polyphenol network coated fiber crystals to serve as a reinforcing agent, and then the mechanical property and the antibacterial property are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and specifically refers to a polymer breathable film material and a preparation method thereof. Background Art

[0002] At present, most of the film materials used in packaging are non-biodegradable or petroleum-based plastics, such as polyvinylidene chloride, polystyrene and polyvinyl chloride. With the development of society, the widespread use of petroleum-based polymers in the packaging of various products has caused increasing pressure on the environment, and the resulting global warming, white pollution and other problems have also followed one after another; with the rapid development of polymer materials and the continuous improvement of consumer demand, it is urgent to develop environmentally friendly and degradable packaging materials to replace traditional petroleum-based plastics. Polylactic acid, starch, methyl cellulose, chitosan, soy protein, gelatin and polyhydroxyalkanoates are environmentally friendly biomaterials. Among them, polylactic acid is a transparent, crystalline, compostable synthetic polymer with excellent properties such as high mechanical strength, strong thermoplasticity and good heat resistance. It has been widely used in packaging fields such as shopping bags, fruit boxes, yogurt and disposable beverage cups. Its raw materials can be produced by fermentation of agricultural products or agricultural by-products such as corn, wheat and rice, and can be completely decomposed by microorganisms in nature. Therefore, it has received widespread attention as a completely biodegradable, renewable and environmentally friendly material.

[0003] The existing technology currently has the following main problems: the air permeability, mechanical properties and antibacterial properties of the current polymer film are poor. Summary of the invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a polymer breathable film material and a preparation method thereof. In order to solve the problem of poor air permeability of the polymer film, the present invention proposes to improve the air permeability of the polylactic acid material by preparing a star-shaped initiator through ε-caprolactone, and at the same time prepare a metal-polyphenol network-coated fiber crystal with microcrystalline cellulose as a reinforcing agent, thereby achieving the improvement of mechanical properties and antibacterial properties.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: The present invention proposes a polymer breathable film material, which includes the following components in parts by weight: 2.6-3.1 parts of ε-caprolactone, 27-30 parts of L-lactide, and 0.6-0.9 parts of metal-polyphenol network-coated fiber crystals.

[0006] Preferably, the method for preparing the metal-polyphenol network coated fiber crystal comprises the following steps:

[0007] (1) Add microcrystalline cellulose in an amount of 0.09-0.11 g / mL to a 65 wt% sulfuric acid solution, stir in a water bath, then add 5 times the volume of distilled water to stop acid hydrolysis, centrifuge to obtain the precipitate, and prepare a 0.1 wt% suspension with deionized water, dialyze with deionized water to a neutral pH, and rotary evaporate at 50°C to obtain a nano-microcrystalline cellulose suspension with a concentration of 0.4 wt%;

[0008] (2) 3-aminopropyltriethoxysilane and 80 wt% ethanol were mixed to obtain a modifier, and then the 0.4 wt% nano-microcrystalline cellulose suspension obtained in step (1) was mixed with the modifier, magnetically stirred at 50 rpm for 2 h, the pH was adjusted to 3 with acetic acid, the precipitate was collected by centrifugation, washed with 95 wt% ethanol, and dried to obtain modified nano-microcrystalline cellulose;

[0009] 3-aminopropyltriethoxysilane forms hydrogen bonds with the hydroxyl groups of the surface hydroxyl groups after hydrolysis and dehydration condensation or forms ether bonds after dehydration and condensation;

[0010] (3) The modified nanocrystalline cellulose obtained in step (2) is prepared into a 0.1 wt% modified nanocrystalline cellulose suspension, zinc chloride is added, and after mixing evenly, two times the molar amount of proanthocyanidins as zinc chloride is added to obtain a mixed solution, followed by adding an equal volume of 3-morpholinepropanesulfonic acid buffer with a pH of 8 to the mixed solution, shaking the reaction at 800 rpm for 1-1.5 h, centrifuging at 11000 rpm for 10 min, collecting the precipitate, filtering, and washing with deionized water to obtain a metal-polyphenol network-coated fiber crystal.

[0011] Preferably, in step (1), the water bath stirring temperature is 45-55°C and the time is 1.5-2.5h;

[0012] Preferably, in step (1), the centrifugal speed is 11000-12000 rpm and the time is 8-12 min.

[0013] Preferably, in step (2), the volume ratio of 3-aminopropyltriethoxysilane to 80wt% ethanol is 1:0.5-0.6;

[0014] Preferably, in step (2), the volume ratio of the 0.4 wt% nano-microcrystalline cellulose suspension obtained in step (1) to the modifier is 1:0.3-0.4;

[0015] Preferably, in step (2), the centrifugal speed is 11000-12000 rpm and the time is 8-12 min.

[0016] Preferably, in step (3), the amount of zinc chloride added is 0.12-0.14 mmol / L.

[0017] The present invention also provides a method for preparing a polymer breathable film material, which specifically comprises the following steps:

[0018] S1, adding ε-caprolactone into a reactor, adding glycerol and stannous octoate, heating the reaction under argon protection, cooling to room temperature, washing with 95wt% ethanol, and drying to obtain a star initiator;

[0019] S2, adding L-lactide into a reactor, and then adding the star initiator obtained in S1 and stannous octoate, heating for reaction under argon protection, cooling to room temperature, washing with 95wt% ethanol, and drying to obtain a copolymer;

[0020] S3. Dissolve the copolymer obtained in S2 in chloroform, then add the metal-polyphenol network-coated fiber crystals, mix well and pour into a polystyrene dish, vacuum dry to obtain a polymer breathable film material.

[0021] Preferably, in S1, the mass ratio of ε-caprolactone, glycerol and stannous octoate is 30:0.6-0.8:1-1.2;

[0022] Preferably, in S1, the heating reaction temperature is 120-130°C and the time is 5-6h.

[0023] Preferably, in S2, the mass ratio of L-lactide, star initiator and stannous octoate is 20:2-2.2:0.1-0.12;

[0024] Preferably, in S2, the heating reaction temperature is 120-130°C and the time is 30-36h.

[0025] Preferably, in S3, the amount of the copolymer obtained in S2 added to chloroform is 0.019-0.021 g / mL.

[0026] The beneficial effects achieved by the present invention are as follows: the present invention uses ε-caprolactone as a monomer, glycerol as a trifunctional initiator, and stannous octoate as a catalyst to synthesize in an argon atmosphere to prepare a three-arm star polymer, namely a star initiator; then uses the three-arm star polymer as an initiator, L-lactide as a monomer, and stannous octoate as a catalyst to synthesize a copolymer in an argon atmosphere, thereby promoting the formation of a microphase separation microstructure, establishing a microphase separation structure with an island morphology as a gas permeation channel, and improving the air permeability of a film material; using microcrystalline cellulose and 3-aminopropyltriethoxysilane to prepare nano-microcrystalline cellulose with amino groups on the surface, namely modified nano-microcrystalline cellulose, thereby improving the surface metal ion adsorption capacity, promoting the polymerization of proanthocyanidins on the surface to form a metal-polyphenol network to encapsulate the nano-microcrystalline cellulose, and obtaining a metal-polyphenol network-coated fiber crystal; and using it as a reinforcing agent, while improving the mechanical properties of the film material, the material is given good antibacterial properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The results of the air permeability test of Examples 1-3 of the present invention and Comparative Example 1 are shown in FIG.

[0028] Figure 2 The results of mechanical property tests of Examples 1-3 and Comparative Example 2 of the present invention are shown in FIG.

[0029] Figure 3 The graph is a result of the antibacterial performance test of Examples 1-3 of the present invention and Comparative Examples 2-3.

[0030] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein may be applied to the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only and are not intended to limit the content of this application.

[0033] The experimental methods in the following examples are conventional methods unless otherwise specified; the experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0034] Example 1

[0035] A polymer breathable film material comprises the following components in parts by weight: 2.6 parts of ε-caprolactone, 27 parts of L-lactide, and 0.6 parts of metal-polyphenol network-coated fiber crystals.

[0036] The preparation method of metal-polyphenol network coated fiber crystal comprises the following steps:

[0037] (1) Add microcrystalline cellulose at an addition amount of 0.09 g / mL to a 65 wt% sulfuric acid solution, stir in a water bath at 45°C for 1.5 h, then add 5 times the volume of distilled water to stop acid hydrolysis, centrifuge at 11000 rpm for 8 min to obtain a precipitate, and prepare a 0.1 wt% suspension with deionized water, dialyze with deionized water to a neutral pH, and rotary evaporate at 50°C to obtain a nano-microcrystalline cellulose suspension with a concentration of 0.4 wt%;

[0038] (2) 3-aminopropyltriethoxysilane and 80 wt% ethanol were mixed at a volume ratio of 1:0.5 to obtain a modifier, and then the 0.4 wt% nanocrystalline cellulose suspension obtained in step (1) was mixed with the modifier at a volume ratio of 1:0.3, magnetically stirred at 50 rpm for 2 h, the pH was adjusted to 3 with acetic acid, and the precipitate was centrifuged at 11000 rpm for 8 min, washed with 95 wt% ethanol, and dried to obtain modified nanocrystalline cellulose;

[0039] (3) The modified nanocrystalline cellulose obtained in step (2) is prepared into a 0.1 wt% modified nanocrystalline cellulose suspension, zinc chloride is added in an amount of 0.12 mmol / L, and after mixing evenly, anthocyanidins twice the molar amount of zinc chloride are added to obtain a mixed solution, and then an equal volume of 3-morpholinepropanesulfonic acid buffer with a pH of 8 is added to the mixed solution, and the reaction is shaken at 800 rpm for 1 h, and centrifuged at 11000 rpm for 10 min to obtain a precipitate, which is filtered and washed with deionized water to obtain a metal-polyphenol network-coated fiber crystal.

[0040] The present invention also provides a method for preparing a polymer breathable film material, which specifically comprises the following steps:

[0041] S1, adding ε-caprolactone into a reactor, adding glycerol and stannous octoate, the mass ratio of ε-caprolactone, glycerol and stannous octoate is 30:0.6:1, heating at 120°C for 5h under argon protection, cooling to room temperature, washing with 95wt% ethanol, and drying to obtain a star initiator;

[0042] S2, adding L-lactide to a reactor, and then adding the star initiator and stannous octoate obtained in S1, the mass ratio of L-lactide, star initiator and stannous octoate is 20:2:0.1, heating at 120° C. for 30 h under argon protection, cooling to room temperature, washing with 95 wt% ethanol, and drying to obtain a copolymer;

[0043] S3. The copolymer obtained in S2 is dissolved in chloroform at an addition amount of 0.019 g / mL, and then the metal-polyphenol network-coated fiber crystal is added. After mixing evenly, the mixture is poured into a polystyrene dish and vacuum dried to obtain a polymer breathable film material.

[0044] Example 2

[0045] A polymer breathable film material comprises the following components in parts by weight: 3.1 parts of ε-caprolactone, 30 parts of L-lactide, and 0.9 parts of metal-polyphenol network-coated fiber crystals.

[0046] The preparation method of metal-polyphenol network coated fiber crystal comprises the following steps:

[0047] (1) Add microcrystalline cellulose at a dosage of 0.11 g / mL to a 65 wt% sulfuric acid solution, stir in a water bath at 55°C for 2.5 h, then add 5 times the volume of distilled water to stop acid hydrolysis, centrifuge at 12000 rpm for 12 min to obtain a precipitate, and prepare a 0.1 wt% suspension with deionized water, dialyze with deionized water to a neutral pH, and rotary evaporate at 50°C to obtain a nano-microcrystalline cellulose suspension with a concentration of 0.4 wt%;

[0048] (2) 3-aminopropyltriethoxysilane and 80 wt% ethanol were mixed in a volume ratio of 1:0.6 to obtain a modifier, and then the 0.4 wt% nanocrystalline cellulose suspension obtained in step (1) was mixed with the modifier in a volume ratio of 1:0.4, magnetically stirred at 50 rpm for 2 h, the pH was adjusted to 3 with acetic acid, centrifuged at 12000 rpm for 12 min to obtain a precipitate, washed with 95 wt% ethanol, and dried to obtain modified nanocrystalline cellulose;

[0049] (3) The modified nanocrystalline cellulose obtained in step (2) is prepared into a 0.1 wt% modified nanocrystalline cellulose suspension, zinc chloride is added in an amount of 0.14 mmol / L, and after mixing evenly, anthocyanidins twice the molar amount of zinc chloride are added to obtain a mixed solution, and then an equal volume of 3-morpholinepropanesulfonic acid buffer with a pH of 8 is added to the mixed solution, and the reaction is shaken at 800 rpm for 1.5 h, and centrifuged at 11000 rpm for 10 min to obtain a precipitate, which is filtered and washed with deionized water to obtain a metal-polyphenol network-coated fiber crystal.

[0050] The present invention also provides a method for preparing a polymer breathable film material, which specifically comprises the following steps:

[0051] S1, adding ε-caprolactone into a reactor, adding glycerol and stannous octoate, the mass ratio of ε-caprolactone, glycerol and stannous octoate is 30:0.8:1.2, heating at 130°C for 6h under argon protection, cooling to room temperature, washing with 95wt% ethanol, and drying to obtain a star initiator;

[0052] S2, adding L-lactide to a reactor, and then adding the star initiator and stannous octoate obtained in S1, the mass ratio of L-lactide, star initiator and stannous octoate is 20:2.2:0.12, heating at 130° C. for 36 h under argon protection, cooling to room temperature, washing with 95 wt% ethanol, and drying to obtain a copolymer;

[0053] S3. The copolymer obtained in S2 is dissolved in chloroform at an addition amount of 0.021 g / mL, and then the metal-polyphenol network-coated fiber crystal is added. After mixing evenly, the mixture is poured into a polystyrene dish and vacuum dried to obtain a polymer breathable film material.

[0054] Example 3

[0055] A polymer breathable film material comprises the following components in parts by weight: 3 parts of ε-caprolactone, 29 parts of L-lactide, and 0.8 parts of metal-polyphenol network-coated fiber crystals.

[0056] The preparation method of metal-polyphenol network coated fiber crystal comprises the following steps:

[0057] (1) Add microcrystalline cellulose at a dosage of 0.1 g / mL to a 65 wt% sulfuric acid solution, stir in a water bath at 50°C for 2 h, then add 5 times the volume of distilled water to stop acid hydrolysis, centrifuge at 11500 rpm for 10 min to obtain a precipitate, and prepare a 0.1 wt% suspension with deionized water, dialyze with deionized water to a neutral pH, and rotary evaporate at 50°C to obtain a nano-microcrystalline cellulose suspension with a concentration of 0.4 wt%;

[0058] (2) 3-aminopropyltriethoxysilane and 80 wt% ethanol were mixed at a volume ratio of 1:0.55 to obtain a modifier, and then the 0.4 wt% nanocrystalline cellulose suspension obtained in step (1) was mixed with the modifier at a volume ratio of 1:0.35, and magnetically stirred at 50 rpm for 2 h, and the pH was adjusted to 3 with acetic acid, and the precipitate was obtained by centrifugation at 11500 rpm for 10 min, and washed with 95 wt% ethanol, and dried to obtain modified nanocrystalline cellulose;

[0059] (3) The modified nanocrystalline cellulose obtained in step (2) is prepared into a 0.1 wt% modified nanocrystalline cellulose suspension, zinc chloride is added in an amount of 0.13 mmol / L, and after mixing evenly, anthocyanidins twice the molar amount of zinc chloride are added to obtain a mixed solution, and then an equal volume of 3-morpholinepropanesulfonic acid buffer with a pH of 8 is added to the mixed solution, and the reaction is shaken at 800 rpm for 1.2 h, and centrifuged at 11000 rpm for 10 min to obtain a precipitate, which is filtered and washed with deionized water to obtain a metal-polyphenol network-coated fiber crystal.

[0060] The present invention also provides a method for preparing a polymer breathable film material, which specifically comprises the following steps:

[0061] S1, adding ε-caprolactone into a reactor, adding glycerol and stannous octoate, the mass ratio of ε-caprolactone, glycerol and stannous octoate is 30:0.7:1.1, heating and reacting at 125°C under argon protection for 5.5h, cooling to room temperature, washing with 95wt% ethanol, and drying to obtain a star initiator;

[0062] S2, adding L-lactide to a reactor, and then adding the star initiator and stannous octoate obtained in S1, the mass ratio of L-lactide, star initiator and stannous octoate is 20:2.1:0.11, heating at 125°C for 33h under argon protection, cooling to room temperature, washing with 95wt% ethanol, and drying to obtain a copolymer;

[0063] S3. The copolymer obtained in S2 is dissolved in chloroform at an addition amount of 0.02 g / mL, and then the metal-polyphenol network-coated fiber crystal is added. After mixing evenly, the mixture is poured into a polystyrene dish and vacuum dried to obtain a polymer breathable film material.

[0064] Comparative Example 1

[0065] This comparative example provides a thin film material, which is different from Example 1 only in that no star-shaped initiator is prepared in the components, and the other components and component contents are the same as those in Example 1.

[0066] Comparative Example 2

[0067] This comparative example provides a thin film material, which differs from Example 1 only in that the components do not contain metal-polyphenol network-coated fiber crystals, and the remaining components and component contents are the same as those in Example 1.

[0068] Comparative Example 3

[0069] This comparative example provides a thin film material, which differs from Example 1 only in that 3-aminopropyltriethoxysilane is not included in the components, and the remaining components and component contents are the same as those in Example 1.

[0070] Experimental example

[0071] 1. Air permeability test

[0072] Examples 1-3 and Comparative Example 1 were prepared into test samples with a thickness of 0.8 mm. The air permeability of the samples was measured by a differential pressure gas permeometer. The test temperature was 20° C. and the area was Φ97 mm. The carbon dioxide permeability and oxygen permeability of the samples were recorded.

[0073] Figure 1 The results of the air permeability test of Examples 1-3 and Comparative Example 1 of the present invention are shown in the figure. The carbon dioxide permeability (cm 3 ·m·m −2 ·h −1 ·Pa −1 ) are 8.9, 8.8, 8.9, 6.3 respectively, oxygen permeability (cm 3 ·m·m −2 ·h −1 ·Pa −1) are 1.3, 1.3, 1.3, and 0.9, respectively; the carbon dioxide permeability and oxygen permeability of Examples 1-3 are significantly higher than those of Comparative Example 1, indicating that the preparation and use of the star-type initiator improves the air permeability of the film material.

[0074] 2. Mechanical properties test

[0075] Examples 1-3 and Comparative Example 2 were prepared into specimens with a length of 50 mm and a width of 10 mm, and tensile tests were performed using an intelligent electronic tensile testing machine at a tensile speed of 6 mm / min, and the tensile strength and elongation at break of the samples were recorded.

[0076] Figure 2 It is a result graph of the mechanical properties test of Examples 1-3 of the present invention and Comparative Example 2. As shown in the figure, the tensile strengths of Examples 1-3 and Comparative Example 1 are 37.4 MPa, 38.6 MPa, 36.5 MPa, and 28.3 MPa, respectively, and the elongations at break are 286.6%, 287.1%, 283.9%, and 203.5%, respectively; the tensile strength and elongation at break of Examples 1-3 are significantly higher than those of Comparative Example 2, indicating that the preparation and use of the metal-polyphenol network-coated fiber crystals improve the mechanical properties of the film material.

[0077] 3. Antibacterial performance test

[0078] The concentration is 1.2×10 8 1 mL of each CFU / mL Escherichia coli and Salmonella solution was inoculated into 100 mL of liquid culture medium, and 0.2 g of the materials obtained in Examples 1-3 and Comparative Examples 2-3 were added to the experimental group, and nothing was added to the control group. The culture was carried out under natural light at a constant temperature and shaking for 10 h, and the total number of colonies was determined, and the antibacterial rate was calculated:

[0079] Inhibition rate = (number of colonies in the control group - number of colonies in the experimental group) / number of colonies in the control group × 100%.

[0080] Figure 3 This is a graph showing the results of the antibacterial performance test of Examples 1-3 and Comparative Examples 2-3 of the present invention. As shown in the figure, the antibacterial rates of Escherichia coli in Examples 1-3 and Comparative Example 1 are 99.6%, 99.8%, 99.3%, 2.3%, and 83.6%, respectively, and the antibacterial rates of Salmonella are 99.9%, 99.8%, 99.6%, 1.9%, and 86.1%, respectively; the antibacterial rates of Escherichia coli and Salmonella in Examples 1-3 are significantly higher than those in Comparative Examples 2-3, indicating that the preparation and use of the metal-polyphenol network-coated fiber crystals and the use of 3-aminopropyltriethoxysilane improve the antibacterial properties of the film material.

[0081] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

[0082] The present invention and its implementation methods are described above, which is not restrictive. The drawings are only one of the implementation methods of the present invention, and the actual application is not limited thereto. In short, if ordinary technicians in the field are inspired by it and design methods and embodiments similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A polymer breathable film material, characterized in that: The invention comprises the following components in parts by weight: 2.6-3.1 parts of ε-caprolactone, 27-30 parts of L-lactide, and 0.6-0.9 parts of metal-polyphenol network coated fiber crystals; The method for preparing the metal-polyphenol network coated fiber crystal comprises the following steps: (1) Add microcrystalline cellulose in an amount of 0.09-0.11 g / mL to a 65 wt% sulfuric acid solution, stir in a water bath, then add 5 times the volume of distilled water to stop acid hydrolysis, centrifuge to obtain the precipitate, and prepare a 0.1 wt% suspension with deionized water, dialyze with deionized water to a neutral pH, and rotary evaporate at 50°C to obtain a nano-microcrystalline cellulose suspension with a concentration of 0.4 wt%; (2) 3-aminopropyltriethoxysilane and 80 wt% ethanol were mixed to obtain a modifier, and then the 0.4 wt% nano-microcrystalline cellulose suspension obtained in step (1) was mixed with the modifier, magnetically stirred at 50 rpm for 2 h, the pH was adjusted to 3 with acetic acid, the precipitate was collected by centrifugation, washed with 95 wt% ethanol, and dried to obtain modified nano-microcrystalline cellulose; (3) The modified nanocrystalline cellulose obtained in step (2) is prepared into a 0.1 wt% modified nanocrystalline cellulose suspension, zinc chloride is added, and after mixing evenly, two times the molar amount of proanthocyanidins as zinc chloride is added to obtain a mixed solution, followed by adding an equal volume of 3-morpholinepropanesulfonic acid buffer with a pH of 8 to the mixed solution, shaking the reaction at 800 rpm for 1-1.5 h, centrifuging at 11000 rpm for 10 min, collecting the precipitate, filtering, and washing with deionized water to obtain a metal-polyphenol network-coated fiber crystal.

2. The polymer breathable film material according to claim 1, characterized in that: In step (1), the water bath stirring temperature is 45-55°C for 1.5-2.5 hours; the centrifugal speed is 11000-12000 rpm for 8-12 minutes.

3. The polymer breathable film material according to claim 2, characterized in that: In step (2), the volume ratio of 3-aminopropyltriethoxysilane to 80wt% ethanol is 1:0.5-0.6; the volume ratio of the 0.4wt% nanocrystalline cellulose suspension obtained in step (1) to the modifier is 1:0.3-0.4; the centrifugal speed is 11000-12000rpm, and the time is 8-12min.

4. The polymer breathable film material according to claim 3, characterized in that: In step (3), the amount of zinc chloride added is 0.12-0.14 mmol / L.

5. A method for preparing a polymer breathable film material according to claim 1, characterized in that: The specific steps include: S1, adding ε-caprolactone into a reactor, adding glycerol and stannous octoate, heating the reaction under argon protection, cooling to room temperature, washing with 95wt% ethanol, and drying to obtain a star initiator; S2, adding L-lactide into a reactor, and then adding the star initiator obtained in S1 and stannous octoate, heating for reaction under argon protection, cooling to room temperature, washing with 95wt% ethanol, and drying to obtain a copolymer; S3. Dissolve the copolymer obtained in S2 in chloroform, then add the metal-polyphenol network-coated fiber crystals, mix well and pour into a polystyrene dish, vacuum dry to obtain a polymer breathable film material.

6. The method for preparing a polymer breathable film material according to claim 5, characterized in that: In S1, the mass ratio of ε-caprolactone, glycerol and stannous octoate is 30:0.6-0.8:1-1.2; the heating reaction temperature is 120-130° C., and the time is 5-6 hours.

7. The method for preparing a polymer breathable film material according to claim 6, characterized in that: In S2, the mass ratio of L-lactide, star initiator and stannous octoate is 20:2-2.2:0.1-0.12, the heating reaction temperature is 120-130°C, and the time is 30-36h.

8. The method for preparing a polymer breathable film material according to claim 7, characterized in that: In S3, the copolymer obtained in S2 is added in chloroform in an amount of 0.019-0.021 g / mL.

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