Waterproof coating prepared based on waste down and preparation method thereof

Abstract

The application relates to a waterproof coating prepared based on waste eiderdown and a preparation method thereof, and belongs to the cross technical field of high-value-added utilization of waste eiderdown resources and waterproof coating. The waterproof coating prepared based on waste eiderdown is composed of the following components in parts by weight: waste eiderdown-based prepolymer 20-30 parts, long-chain alkane organic alcohol 8-12 parts, polybasic organic amine 8-12 parts, polybasic organic aldehyde 5-8 parts, emulsifier 1-3 parts, defoaming agent 0.1-0.2 parts, catalyst 0.8-1.6 parts and deionized water 20-30 parts. The preparation steps of the waste eiderdown-based prepolymer include impurity removal, protein extraction and carboxyl modification. Long-chain alkane is introduced as a hydrophobic group on the molecular surface of the coating, and short-chain amino is used as a hydrophilic group, so that the coating has the performance of preventing liquid water and resisting water vapor, and the base material is endowed with all-around waterproof performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the cross technical field of high value-added utilization of waste down resources and waterproof coating, in particular to a waterproof coating prepared based on waste down and a preparation method thereof. BACKGROUND

[0002] As a kind of household garbage, down in waste down jackets is often discarded, which not only brings certain burden to the environment, but also causes waste of resources. Down, coming from duck and goose, is mainly composed of keratin protein, which is a natural biological macromolecule with rich amino groups (referring to "Research and application of near-infrared spectroscopy in identification of down feather types", China Textile Inspection, 2024, (12): 50-53, Sun Jin, Zhao Rui, Fang Songchen, etc.), which can be used as a reactive site to synthesize new coatings. In addition, the waterproof coatings on the market at present mainly introduce long-chain alkanes as hydrophobic groups on the surface of polymers to achieve waterproof purpose. Chinese patent publication No.

CN119842295A

CN119823626A

[0003] In view of the above-mentioned deficiencies, the purpose of the present application is to provide a waterproof coating prepared based on waste down and a preparation method thereof, which uses waste down as raw material, successfully grafts carboxyl groups on the amino groups on the surface of the molecular chain, then introduces long-chain alkane groups into the molecular chain by esterification reaction, and in the carboxyl modification process, the molar ratio of carboxyl group to amino group is required to be greater than that of amino group, so that part of the amino groups in the waste down molecular chain are not modified as short-chain hydrophilic groups. Finally, the aldehyde group reacts with part of the amino groups in the down molecular chain to form a network cross-linked structure with polybasic organic amine in the formula to form a coating film.

[0004] The specific technical solution is as follows:

[0005] The application discloses a waterproof coating prepared from waste eiderdown, which is prepared from the following components in parts by weight: waste eiderdown-based prepolymer 20-30 parts, long-chain alkane organic alcohol 8-12 parts, polybasic organic amine 8-12 parts, polybasic organic aldehyde 5-8 parts, emulsifier 1-3 parts, defoaming agent 0.1-0.2 parts, catalyst 0.8-1.6 parts and deionized water 20-30 parts.

[0006] S1 impurity removal: the collected waste eiderdown is immersed in a mixed solution of acetone / methanol with a mass ratio of 1:1, stirring is carried out at a stirring speed of 200-500 revolutions / minute for 18-30 hours, then the waste eiderdown is rinsed with anhydrous ethanol and dried in an oven at 30-40 DEG C overnight to obtain dry and clean eiderdown;

[0007] S2 protein extraction: 8 mol of urea, 0.2 mol of sodium pyrosulfite and 1 mol of sodium hydroxide are dissolved in 200 mL of distilled water, then the obtained clean eiderdown is soaked in the mixed solution of urea / sodium pyrosulfite / sodium hydroxide, and the protein decomposition is promoted by treating at a stirring speed of 500-800 revolutions / minute and a temperature of 80-100 DEG C for 12-18 hours, after the reaction is completed, the eiderdown residue is removed by filtering with a 120-mesh stainless steel screen, the filtrate is centrifuged, then the centrifuged filtrate is dialyzed to remove urea, sodium pyrosulfite and sodium hydroxide, and a purified protein solution is obtained; the mass ratio of the eiderdown to the mixed solution of urea / sodium pyrosulfite / sodium hydroxide is 1:20-30;

[0008] S3 carboxyl modification: the obtained purified protein solution is added into organic aldehyde acid and dilute sulfuric acid with a concentration of 5wt%-10wt%, the pH of the mixed solution is adjusted to 1-3, then the mixed solution is refluxed at 80-90 DEG C for 6-8 hours, after the reaction is completed, the temperature is lowered to 25-30 DEG C, 1 mol / L sodium hydroxide solution is added to make the pH of the mixed solution 7-9, then the salt in the mixed solution is removed by dialysis, and a waste eiderdown-based prepolymer modified by carboxyl is obtained.

[0009] In some embodiments, the long-chain alkane organic alcohol is selected from one or more of cetyl alcohol, stearyl alcohol and heneicosyl alcohol.

[0010] In some embodiments, the polybasic organic amine is selected from one or more of hexamethylenetetramine, ethylenediamine and hexanediamine.

[0011] In some embodiments, the polybasic organic aldehyde is selected from one or more of glutaraldehyde, malondialdehyde and succindialdehyde.

[0012] In some embodiments, the emulsifier is selected from one or more of sodium stearate, sodium stearoyl glutamate and potassium cetyl phosphate.

[0013] In some embodiments, the defoaming agent is selected from one or more of sucrose fatty acid ester, polyglycerol fatty acid ester.

[0014] In some embodiments, the catalyst is selected from one or more of antimony trioxide, tin acetate.

[0015] In some embodiments, the organic aldehyde acid in S3 is selected from one or more of glyoxylic acid, malonic acid, 3-carboxy-1-butyraldehyde, 4-carboxy-1-pentanal, 4-carboxy-1-methyl-1-pentanal.

[0016] In some embodiments, the molar ratio of the purified protein liquid to the organic aldehyde acid in S3 is determined according to the amino concentration in the purified protein liquid, so that the molar ratio of the amino in the purified protein liquid to the organic aldehyde acid is 1:0.4-0.6.

[0017] The application also provides a preparation method of the waterproof coating prepared based on waste eiderdown.

[0018] S1 In a multifunctional reaction kettle, according to the formula weight, long-chain alkane organic alcohol, deionized water, emulsifier and defoaming agent are sequentially added, then nitrogen is introduced while stirring at a speed of 500-1000 revolutions per minute for 10-30 minutes to prepare an emulsion, and the stirring is continued for 10-30 minutes to obtain a uniform mixture, and the nitrogen is continuously introduced for 5-10 minutes;

[0019] S2 The waste eiderdown-based prepolymer is added, the nitrogen introduction is stopped, heating is performed to 120-150 DEG C, and the stirring is continued for 1-3 hours, then the catalyst is added, the temperature is raised to 200-220 DEG C to initiate esterification, and the reaction is kept for 4-8 hours, during which the water vapor generated is separated by a water trap;

[0020] S3 After the reaction is completed, the temperature is lowered to 30-40 DEG C, then polybasic organic aldehyde and polybasic organic amine are sequentially added, the stirring is continued for 3-6 hours, during which the water vapor generated is separated by a water trap, after the reaction is completed, the formula amount of deionized water is added, so that the viscosity of the mixed solution is 9000-12000 cps / 25 DEG C, then the stirring is continued at a speed of 800-1000 revolutions per minute for 30-60 minutes, and the waterproof coating prepared based on waste eiderdown is obtained.

[0021] The application has the following advantages:

[0022] (1) The waste eiderdown is used as a production raw material, the cost is low, the pollution of the waste eiderdown to the environment can be reduced, the high-value utilization of waste is realized, and a new insight is provided for the resource utilization of the waste eiderdown;

[0023] (2) The formula does not involve the use of organic solvents, and the use of subsequent coatings will not produce gases harmful to human health, in line with the green and environmentally friendly production concept;

[0024] (3) The present application introduces long-chain alkane as a hydrophobic group and short-chain amino as a hydrophilic group on the surface of the coating molecules, so that the coating has both liquid water resistance and water vapor resistance, and the substrate material has all-round waterproof performance. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Chemical reaction formula schematic diagram of the preparation process of the waterproof coating prepared based on waste down;

[0026] Figure 2 From left to right are the front scanning electron micrographs of the films of the waterproof coatings prepared based on waste down of examples 8, 9 and 10, respectively;

[0027] Figure 3 From left to right are the cross-sectional scanning electron micrographs of the films of the waterproof coatings prepared based on waste down of examples 8, 9 and 10, respectively;

[0028] Figure 4 Biodegradation test results of the polysaccharide acrylic resins prepared in examples 12-14. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings, technical process steps, specific implementation conditions and materials. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0030] Example 1

[0031] The collected waste down was immersed in a mixed solution of acetone / methanol with a mass ratio of 1:1, mixed for 30 hours at a stirring speed of 200 revolutions / minute, then the waste down was rinsed with anhydrous ethanol and dried in an oven at 30°C overnight to obtain dry and clean down; 8 mol of urea, 0.2 mol of sodium metabisulfite and 1 mol of sodium hydroxide were dissolved in 200 mL of distilled water, then the obtained clean down was immersed in the mixed solution of urea / sodium metabisulfite / sodium hydroxide, the mass ratio of down to the mixed solution of urea / sodium metabisulfite / sodium hydroxide was 1:20, the treatment was carried out at a stirring speed of 500 revolutions / minute and a temperature of 80°C for 18 hours to promote protein decomposition, after the reaction was completed, the filtrate was obtained by filtering with a 120-mesh stainless steel screen, the waste down residue was removed by centrifugation, then the centrifuged filtrate was dialyzed to remove urea, sodium metabisulfite and sodium hydroxide, and a purified protein solution was obtained.

[0032] Example 2

[0033] The collected waste down was immersed in a mixed solution of acetone / methanol with a mass ratio of 1:1, mixed for 24 hours at a stirring speed of 300 revolutions / minute, then the waste down was rinsed with anhydrous ethanol and dried in an oven at 35°C overnight to obtain dry and clean down; 8 mol of urea, 0.2 mol of sodium metabisulfite and 1 mol of sodium hydroxide were dissolved in 200 mL of distilled water, then the obtained clean down was immersed in the mixed solution of urea / sodium metabisulfite / sodium hydroxide, the mass ratio of down to the mixed solution of urea / sodium metabisulfite / sodium hydroxide was 1:25, the treatment was carried out at a stirring speed of 800 revolutions / minute and a temperature of 90°C for 15 hours to promote protein decomposition, after the reaction was completed, the filtrate was obtained by filtering with a 120-mesh stainless steel screen, the waste down residue was removed by centrifugation, then the centrifuged filtrate was dialyzed to remove urea, sodium metabisulfite and sodium hydroxide, and a purified protein solution was obtained.

[0034] Example 3

[0035] The collected waste down feather was immersed in a mixed solution of acetone / methanol with a mass ratio of 1:1, stirred at a speed of 500 rpm for 18 hours, then washed with anhydrous ethanol, and dried in an oven at 40°C overnight to obtain dry and clean down feather; 8 mol of urea, 0.2 mol of sodium metabisulfite and 1 mol of sodium hydroxide were dissolved in 200 mL of distilled water, then the obtained clean down feather was immersed in the mixed solution of urea / sodium metabisulfite / sodium hydroxide, the mass ratio of down feather to the mixed solution of urea / sodium metabisulfite / sodium hydroxide was 1:30, and the mixed solution was treated at a stirring speed of 800 rpm and a temperature of 100°C for 12 hours to promote protein decomposition; after the reaction was completed, the solution was filtered with a 120-mesh stainless steel screen, the filtrate was taken, and the waste down feather residue was removed by centrifugation, then the centrifuged filtrate was dialyzed to remove urea, sodium metabisulfite and sodium hydroxide, and a purified protein solution was obtained.

[0036] Example 4

[0037] The purified protein solution obtained in Example 1 was added to glyoxylic acid and dilute sulfuric acid with a concentration of 10 wt%, the pH of the mixed solution was adjusted to 1, then the mixed solution was refluxed at 80°C for 8 hours, after the reaction was completed, the temperature was lowered to 30°C, 1M sodium hydroxide solution was added to make the pH of the mixed solution 7, then the salts in the mixed solution were removed by dialysis to obtain a carboxyl-modified waste down feather-based prepolymer, and in this embodiment, the molar ratio of amino groups in the purified protein solution to glyoxylic acid was 1:0.4.

[0038] Example 5

[0039] The purified protein solution obtained in Example 2 was added to malonic acid and dilute sulfuric acid with a concentration of 8 wt%, the pH of the mixed solution was adjusted to 2, then the mixed solution was refluxed at 90°C for 7 hours, after the reaction was completed, the temperature was lowered to 25°C, 1M sodium hydroxide solution was added to make the pH of the mixed solution 8, then the salts in the mixed solution were removed by dialysis to obtain a carboxyl-modified waste down feather-based prepolymer, and in this embodiment, the molar ratio of amino groups in the purified protein solution to malonic acid was 1:0.5.

[0040] Example 6

[0041] The purified protein solution obtained in Example 3 was added to 3-carboxy-1-butyraldehyde and dilute sulfuric acid with a concentration of 10 wt%, the pH of the mixed solution was adjusted to 3, then the mixed solution was refluxed at 90°C for 6 hours, after the reaction was completed, the temperature was lowered to 30°C, 1M sodium hydroxide solution was added to make the pH of the mixed solution 9, then the salts in the mixed solution were removed by dialysis to obtain a carboxyl-modified waste down feather-based prepolymer, and in this embodiment, the molar ratio of amino groups in the purified protein solution to 3-carboxy-1-butyraldehyde was 1:0.6.

[0042] Example 7

[0043] The purified protein solution prepared in Examples 1-6 was subjected to amino content testing. 1 mL of the purified protein solution prepared in Examples 1-6 was taken and subjected to color development reaction in ninhydrin solution, and then the absorbance of the solution after the reaction was tested by spectrophotometry. According to the Lambert-Beer law and the standard sample, the amino content of the solution prepared in Examples 1-6 was 0.89 mmol g -1 , 0.92 mmol g -1 , 0.96 mmol g -1 , 0.58 mmol g -1 , 0.49 mmol g -1 and 0.41 mmol g -1 , respectively.

[0044] The waste down-based prepolymer prepared in Examples 4-6 was subjected to carboxyl content testing. The free carboxyl content of the waste down-based prepolymer was determined by conductometric titration. 50 mg of the waste down-based prepolymer was taken, 10 ml (0.01 M) of HC1 was added, and ultrasonic treatment was performed for 4 hours. Finally, the suspension was titrated with NaOH (0.01 M).

[0045]

[0046] In the formula, C NaOH is the concentration of NaOH (0.01 M), V NaOH is the volume of NaOH required for titration of HC1, and m is the dry weight of the waste down-based prepolymer. The results showed that the free carboxyl content of the waste down-based prepolymer prepared in Examples 4, 5 and 6 was 0.24 mmol g -1 , 0.42 mmol g -1 and 0.45 mmol g -1 , respectively.

[0047] Example 8

[0048] As Figure 1As shown, in the multifunctional reactor, according to the formula weight, the cetyl alcohol, deionized water, sodium stearate and sucrose fatty acid ester were added in turn, then nitrogen was introduced while stirring at a speed of 500 rpm for 30 minutes to prepare an emulsion, and continue to stir for 30 minutes to obtain a uniform mixture, continue to introduce nitrogen for 10 minutes; add the waste down feather-based prepolymer, stop the nitrogen introduction, heat to 120°C, continue to stir for 3 hours, add antimony trioxide, heat to 200°C to initiate esterification reaction, and keep the reaction for 8 hours, during which the generated water vapor is separated by a water trap; after the reaction is completed, cool to 30°C, add glutaraldehyde and hexamethylene tetramine in turn, continue to stir and keep the reaction for 6 hours, during which the generated water vapor is separated by a water trap, after the reaction is completed, add the formula amount of deionized water to make the viscosity of the mixed solution 9000 cps / 25°C, then continue to stir at a stirring speed of 800 rpm for 60 minutes, to obtain the waterproof coating prepared based on waste down feather. The prepared waterproof coating prepared based on waste down feather is coated on a glass plate, and cured into a film at a temperature of 80°C and a humidity of 40-60%. The prepared film is tested by scanning electron microscopy, the front surface is shown in Figure 2 As shown in FIG. 8a, the surface is dense and smooth, and almost no holes; the scanning electron microscopy of the cross section is shown in Figure 3 FIG. 8b, there is no layered structure, almost as a whole, the above results show that the prepared waterproof coating prepared based on waste down feather is dense after film formation, which is beneficial to the waterproof performance in later period.

[0049] Table 1 Raw material ratio for synthesizing the waterproof coating prepared based on waste down feather of Example 8

[0050] Waste down base prepolymer 20 parts Hexadecanol 8 parts Hexamethylenetetramine 8 parts Glutaraldehyde 5 parts Sodium stearate 1 part Sucrose fatty acid ester 0.1 part Antimony trioxide 0.8 parts Deionized water 20 parts

[0051] The waste down feather-based prepolymer in Table 1 is prepared by the method described in Example 4.

[0052] According to GB / T 6739-1996 "Pencil Test Method for Coating Film Hardness", the strength of the film after the waterproof coating prepared based on waste down feather is tested by manual method, and the test results show that the film strength is >B.

[0053] According to GB / T 23985-2009 "Determination of Volatile Organic Compounds (VOC) Content in Color Paint and Varnish by Difference Method", the film prepared by the prepared waterproof coating prepared based on waste down feather is tested for VOC, and the result is VOC≤8.19 g / L.

[0054] Example 9

[0055] As shown in Figure 1As shown, in the multifunctional reactor, according to the formula weight, octadecyl alcohol, deionized water, sodium stearoyl glutamate and polyglycerol fatty acid ester were added in turn, then nitrogen was introduced while stirring at a speed of 800 rpm for 20 minutes to prepare an emulsion, and the stirring was continued for 20 minutes to obtain a uniform mixture, and the nitrogen was continued to be introduced for 8 minutes; the waste down feather-based prepolymer was added, the nitrogen introduction was stopped, heated to 130°C, and the stirring was continued for 2 hours, tin acetate was added, heated to 210°C to initiate esterification, and the reaction was kept for 6 hours, during which the water vapor generated was separated by a water trap; after the reaction was completed, the temperature was lowered to 35°C, and malondialdehyde and ethylenediamine were added in turn, and the reaction was kept for 4 hours with stirring, during which the water vapor generated was separated by a water trap, after the reaction was completed, the formula amount of deionized water was added to make the viscosity of the mixed solution 10000 cps / 25°C, and then the stirring was continued for 45 minutes at a stirring speed of 900 rpm to obtain the waterproof coating prepared based on waste down feather. The prepared waterproof coating prepared based on waste down feather was coated on a glass plate, and cured into a film at a temperature of 80°C and a humidity of 40-60%. The prepared film was tested by scanning electron microscopy, and the front surface was shown in Figure 2 b, the surface was dense and smooth, and almost no holes; the scanning electron microscopy of the cross section was shown in Figure 3 b, there was no layered structure, and almost an integral, the above results showed that the waterproof coating prepared based on waste down feather was dense after film formation, which was beneficial to the waterproof performance in later period.

[0056] Table 2 Raw material ratio for synthesizing the waterproof coating prepared based on waste down feather of example 9

[0057]

[0058]

[0059] The waste down feather-based prepolymer in table 2 was prepared by the method described in example 5.

[0060] According to GB / T 6739-1996 "Pencil test method for film hardness", the strength of the film of the waterproof coating prepared based on waste down feather was tested by manual method, and the test results showed that the film strength was >B.

[0061] According to GB / T 23985-2009 "Determination of volatile organic compounds (VOC) content of color paint and varnish-difference method", the film of the waterproof coating prepared based on waste down feather was tested for VOC, and the results showed that VOC≤6.47 g / L.

[0062] Example 10

[0063] As shown in Figure 1As shown, in the multifunctional reactor, according to the formula weight, in turn, add the twenty-one alkyl alcohol, deionized water, potassium cetyl phosphate and sucrose fatty acid ester, then in the nitrogen into the time, and at 1000 rpm stirring speed for 10 minutes, prepared emulsion, continue to stir for 10 minutes to obtain a homogeneous mixture, continue to pass into the nitrogen for 5 minutes; add the waste down feather-based prepolymer, stop the nitrogen into the heating to 150 ℃, continue to stir for 1 hour, add antimony trioxide, heating to 220 ℃ to initiate esterification reaction, keep the reaction for 4 hours, during which the water vapor generated by the water separator; after the reaction is completed, the temperature is lowered to 40 ℃, in turn, add butanedial and hexanediamine, continue to stir for 3 hours, during which the water vapor generated by the water separator, after the reaction is completed, add the formula amount of deionized water, so that the viscosity of the mixed solution is 12000 cps / 25 ℃, then continue to stir for 30 minutes at a stirring speed of 1000 rpm, to obtain the waterproof coating prepared based on the waste down feather. The prepared waterproof coating prepared based on the waste down feather is coated on a glass plate, and cured into a film at a temperature of 80 ℃ and a humidity of 40-60%. The prepared film is tested by scanning electron microscopy, and the front surface is shown in FIG. 1C, which is dense and smooth, and almost no hole; the scanning electron microscopy of the cross section is shown in FIG. 1C, which has no layered structure and is almost an integral whole, and the above results show that the prepared waterproof coating prepared based on the waste down feather is dense after film formation, which is beneficial to the waterproof performance in the later period. Figure 2 Figure 3

[0064]

[0065]

[0066]

[0067] The waste down feather-based prepolymer in Table 3 is prepared by the method described in Example 6.

[0068] According to GB / T 6739-1996 "Pencil Test Method for Coating Film Hardness", the strength of the waterproof coating prepared based on the waste down feather after film formation is tested by manual method, and the test results show that the film strength is > B.

[0069] According to GB / T 23985-2009 "Determination of the Content of Volatile Organic Compounds (VOC) in Color Paint and Varnish by Difference Method", the film prepared from the prepared waterproof coating prepared based on the waste down feather is tested for VOC, and the result is VOC≤9.25 g / L.

[0070] Test Example 11

[0071] ​​​The films prepared by the waterproof coating prepared based on waste down prepared in examples 8, 9 and 10 were subjected to liquid water and water vapor protection tests. First, the liquid water protection was mainly tested by the contact angle, and the results are shown in Figure 4 Table 1. The contact angles of the waterproof coating films prepared in examples 8, 9 and 10 were 119.5°, 121.8° and 122.4°, respectively, all showing hydrophobicity, indicating good liquid water protection performance. The water vapor protection was mainly tested by the water vapor transmission rate, and the specific reference standard method was ASTM F1249. The water vapor transmission rates of the waterproof coating films prepared in examples 8, 9 and 10 were 845.9 g / (m2·24h), 815.7 g / (m2·24h) and 859.6 g / (m2·24h), respectively, indicating that the waterproof coating films prepared in examples 8, 9 and 10 had smaller water vapor transmission rates and good water vapor protection performance.

[0072] Skilled persons should know that although the present application has been described according to the above specific embodiments, the inventive idea of the present application is not limited to this application, and any modification using the inventive idea will be included in the scope of protection of the present patent.

Claims

1. A waterproof coating prepared on the basis of waste down, characterized in that, The waterproof coating prepared from waste down is composed of, by weight fraction, 20-30 parts of waste down-based prepolymer, 8-12 parts of long-chain alkane organic alcohol, 8-12 parts of polybasic organic amine, 5-8 parts of polybasic organic aldehyde, 1-3 parts of emulsifier, 0.1-0.2 parts of defoaming agent, 0.8-1.6 parts of catalyst, and 20-30 parts of deionized water; the preparation method of the waste down-based prepolymer comprises the following steps: S1 impurity removal: the collected waste down is immersed in a mixed solution of acetone / methanol with a mass ratio of 1:1, stirred at a speed of 200-500 revolutions per minute for 18-30 hours, then rinsed with anhydrous ethanol, and dried in an oven at 30-40℃ overnight to obtain dry and clean down; S2 protein extraction: 8 mol of urea, 0.2 mol of sodium metabisulfite, and 1 mol of sodium hydroxide are dissolved in 200 mL of distilled water, then the obtained clean down is immersed in the mixed solution of urea / sodium metabisulfite / sodium hydroxide, treated at a stirring speed of 500-800 revolutions per minute and a temperature of 80-100℃ for 12-18 hours to promote protein decomposition, filtered with a 120-mesh stainless steel screen after the reaction is completed, centrifuged to remove the waste down residue, then the centrifuged filtrate is dialyzed to remove urea, sodium metabisulfite, and sodium hydroxide, and a purified protein solution is obtained; the mass ratio of the down to the mixed solution of urea / sodium metabisulfite / sodium hydroxide is 1:20-30; S3 carboxyl modification: the obtained purified protein solution is added to organic aldehyde acid and dilute sulfuric acid with a concentration of 5wt%-10wt%, the pH of the mixed solution is adjusted to 1-3, then the mixed solution is refluxed at 80-90℃ for 6-8 hours, cooled to 25-30℃ after the reaction is completed, 1 mol / L of sodium hydroxide solution is added to make the pH of the mixed solution 7-9, then the salts in the mixed solution are removed by dialysis to obtain carboxyl-modified waste down-based prepolymer.

2. A waterproof coating prepared based on waste down as claimed in claim 1, wherein, The long-chain alkane organic alcohol is selected from one or more of cetyl alcohol, stearyl alcohol, and heneicosyl alcohol.

3. A waterproof coating prepared based on waste down as claimed in claim 1, wherein, The polybasic organic amine is one or more of hexamethylenetetramine, ethylenediamine, and hexanediamine.

4. A waterproof coating prepared based on waste down as claimed in claim 1, wherein, The polybasic organic aldehyde is selected from one or more of glutaraldehyde, malondialdehyde, and succindialdehyde.

5. A waterproof coating prepared based on waste down as claimed in claim 1, wherein, The emulsifier is selected from one or more of sodium stearate, sodium stearoglutamate, and potassium cetyl phosphate.

6. A waterproof coating prepared based on waste down as claimed in claim 1, wherein, The defoaming agent is selected from one or more of sucrose fatty acid ester and polyglycerol fatty acid ester.

7. A water repellent coating prepared based on waste down as claimed in claim 1, wherein, The catalyst is selected from one or more of antimony trioxide and tin acetate.

8. A water repellent coating prepared based on waste down as claimed in claim 1, wherein, The organic aldehyde acid in S3 is selected from one or more of glyoxylic acid, propionic aldehyde acid, 3-carboxyl-1-butyl aldehyde, 4-carboxyl-1-pentyl aldehyde, and 4-carboxyl-1-methyl-1-pentyl aldehyde.

9. A water repellent coating prepared based on waste down as claimed in claim 1, wherein, The molar ratio of the purified protein solution to the organic aldehyde acid in S3 is determined according to the amino concentration in the purified protein solution, so that the molar ratio of the amino in the purified protein solution to the organic aldehyde acid is 1:0.4-0.

6.

10. The method for preparing a waterproof coating based on waste down according to any one of claims 1-9, characterized in that, The preparation method comprises the following steps: S1 in a multifunctional reaction kettle, according to the formula weight, in turn, add long chain alkane organic alcohol, deionized water, emulsifier and defoaming agent, then while the nitrogen is imported, and at 500~1000 rpm speed stirring 10~30 minutes, prepared emulsion, continue to stir 10~30 minutes to get a uniform mixture, continue to import 5~10 minutes of nitrogen; S2 add waste down feather base prepolymer, stop the nitrogen is imported, heating to 120~150 ℃, continue to stir 1~3 hours, add catalyst, heating to 200~220 ℃ to initiate esterification reaction, keep the reaction for 4~8 hours, during the period with water separator to separate the generated water vapor; S3 after the reaction is completed, cooling to 30~40 ℃, in turn, add polyaldehyde and polyamine, continue to stir and keep the reaction for 3~6 hours, during the period with water separator to separate the generated water vapor, after the reaction is completed, add the formula amount of deionized water, so that the viscosity of the mixed solution is 9000~12000 cps / 25 ℃, then continue to stir at 800~1000 rpm speed for 30~60 minutes, get the waterproof coating prepared based on waste down feather.

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