A multifunctional fluorinated modified polyurethane with excellent transmittance and preparation method thereof

Abstract

The present invention belongs to the field of polyurethane preparation, and in particular to a multifunctional fluorinated modified polyurethane with excellent transmittance and a preparation method thereof. The preparation method of the present invention comprises the following steps: under the conditions of nitrogen and reflux, syringaldehyde is added to an aqueous sodium hydroxide solution, heated in a water bath and stirred, and then 3-chloro-1,2-propylene glycol is dripped therein, reacted, extracted, washed, and dried to obtain syringaldehyde diol; then syringaldehyde diol is mixed with carbonate, and after adding a catalyst, reacted under certain conditions to obtain syringaldehyde carbonate; then syringaldehyde carbonate and amine substances are added to a solvent, stirred for reaction, and dried to obtain a multifunctional fluorinated modified polyurethane. The multifunctional fluorinated modified polyurethane has excellent comprehensive performance, can meet the requirements of some special scenes for polyurethane, and further expands the scope of application of non-isocyanate polyurethane.

Description

Technical Field

[0001] The invention belongs to the field of polyurethane preparation, and particularly relates to a multifunctional fluorinated modified polyurethane with excellent transmittance and a preparation method thereof. Background Art

[0002] Most traditional polyurethane materials are obtained by the reaction of isocyanates and polyols. Isocyanates are highly toxic, and the phosgene used in their preparation is also a highly toxic and lethal substance. This poses a great threat to the health of production personnel and the environment. Strict safety measures and protection are required during production, transportation, storage and use, which increases costs and operational difficulties. Non-isocyanate polyurethanes use cyclic carbonates and amine compounds as the main raw materials. The sources of raw materials are relatively wide, and they do not involve highly toxic isocyanates, which is safer. In addition, the reaction conditions are relatively mild, and a large amount of gas will not be produced during the reaction, and the reaction conditions are also easier to control. Due to the unique performance characteristics of non-isocyanate polyurethanes, they have application potential in some fields that require high environmental protection, water resistance, and flexibility, such as water-based coatings, adhesives, elastomers, biomedical materials, etc.

[0003] Patent CN 109593451 A discloses a bisphenol AF-based hydrophobic and oleophobic non-isocyanate polyurethane coating and its preparation method and application. The method uses bisphenol AF and perfluoroepoxy compounds as raw materials, synthesizes bisphenol AF and perfluorocyclic carbonate in a CO2 atmosphere, and further prepares a high-performance non-isocyanate polyurethane coating with different amine curing agents. The non-isocyanate polyurethane coating prepared by the invention has very good hydrophobic and oleophobic properties and corrosion resistance, and also has high hardness, excellent impact resistance and chemical resistance. Patent CN 118126314A discloses a method for preparing non-isocyanate polyurethane-epoxy acrylate, using monoethanolamine, cyclic carbonate, anhydride and multifunctional epoxy monomer as raw materials, and synthesizing a non-isocyanate polyurethane-epoxy acrylate by ring-opening reaction of cyclic carbonate with amino group, hydroxyl with anhydride, carboxyl with epoxy. The substance has high photocuring activity and paint film hardness, as well as good wear resistance and adhesion, and has achieved good technical effects.

[0004] However, in some special occasions, such as the field of OLED protective film, non-isocyanate polyurethane is also required to have good high transmittance, softness, water and oxygen isolation and thermal stability. Therefore, it is of great significance to develop multifunctional non-isocyanate polyurethane materials and expand the application scope of non-isocyanate polyurethane. Summary of the invention

[0005] The invention discloses a multifunctional fluorinated modified polyurethane with excellent transmittance and a preparation method thereof. The invention uses bio-based syringaldehyde as a raw material, and by controlling the process conditions of a chemical reaction, converts the bio-based syringaldehyde into syringaldehyde-based carbonate, and then reacts with amine substances to generate a multifunctional fluorinated modified polyurethane with excellent comprehensive performance. The requirements for polyurethane in some special scenarios can be met, and the application scope of non-isocyanate polyurethane is further expanded.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention provides a method for preparing a multifunctional fluorinated modified polyurethane having excellent transmittance, comprising the following preparation steps:

[0008] (1) In an inert gas atmosphere, syringaldehyde is added to an aqueous sodium hydroxide solution, heated in a water bath at 75-85° C. with stirring for 1-1.5 hours, 3-chloro-1,2-propanediol is then added dropwise thereto, the temperature is raised to 90-110° C., the reaction is stirred, extracted, washed, and dried to obtain syringaldehyde diol;

[0009] (2) mixing the syringaldehyde diol of step (1) with carbonate, adding a catalyst, reacting under reflux for 7-8 hours in an inert gas atmosphere, washing, filtering, and drying to obtain syringaldehyde carbonate;

[0010] (3) adding the syringaldehyde carbonate and amine substance of step (2) into a solvent, stirring and reacting at 40-90° C. to obtain a multifunctional fluorinated modified polyurethane.

[0011] In some embodiments, in step (1), the molar ratio of syringaldehyde to 3-chloro-1,2-propanediol is 1:(1-1.2).

[0012] Preferably, in step (1), the molar ratio of syringaldehyde to 3-chloro-1,2-propanediol is 1:1.1.

[0013] In some embodiments, in step (2), the molar ratio of syringaldehyde diol to carbonate is 1:(5-9).

[0014] Preferably, in step (2), the molar ratio of syringaldehyde diol to carbonate is 1:(6-8).

[0015] In some embodiments, in step (3), the amine substance includes a fluorine-containing amine substance and a diamine substance.

[0016] Preferably, in step (3), the mass ratio of the fluorine-containing amine substance to the diamine substance is 1:(1-2).

[0017] More preferably, the diamine substance is one or more of alkyl diamine, aromatic diamine and cyclohexane diamine.

[0018] In some embodiments, in step (3), the amount of the amine substance used is 5-10 wt % of the syringaldehyde carbonate.

[0019] Preferably, the amount of the amine substance used can be selected according to the desired performance of the product.

[0020] In some embodiments, the preparation steps of the fluorine-containing amine substance are:

[0021] The fluorine-containing acrylate is dissolved in an organic solvent, stirred evenly at 30-80° C., and a triamine substance is added under an inert gas atmosphere to react for 18-48 hours to obtain a fluorine-containing amine substance.

[0022] In some embodiments, the fluorine-containing acrylate is selected from one or more of trifluoroethyl acrylate, trifluoroethyl methacrylate, hexafluorobutyl acrylate, and hexafluorobutyl methacrylate.

[0023] In some embodiments, the triamine substance is selected from one or more of tris(2-aminoethyl)amine, tris[2-(methylamino)ethyl]amine, and polyetheramine.

[0024] In some embodiments, the molar ratio of the fluorinated acrylate to the triamine substance is 1:(1-1.1).

[0025] Preferably, the molar ratio of the fluorine-containing acrylate to the triamine substance is 1:1.05.

[0026] In some embodiments, the carbonate is selected from dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and propylene carbonate.

[0027] In some embodiments, the solvent is preferably one of DMF, THF, and DCM.

[0028] Another aspect of the present invention provides a multifunctional fluorinated modified polyurethane prepared by the preparation method described in the above scheme.

[0029] First, the present invention prepares a fluorine-containing amine substance for use in the synthesis of polyurethane. The present invention allows a fluorine-containing acrylate containing C=C and a fluorine-containing group in its structure to undergo an addition reaction with an alkyl triamine substance under certain conditions to generate a fluorine-containing amine substance. Under alkaline conditions, the amino group in the alkyl triamine acts as a nucleophilic reagent to attack the β-position carbon atom of C=C in the fluorine-containing acrylate. This is probably because the β-position carbon atom of C=C carries a partial positive charge under the influence of the electron-withdrawing acrylate group and the fluorine-containing group, and is easily attacked by the nucleophilic reagent, the double bond is opened, and the fluorine-containing amine substance is finally formed after steps such as proton transfer. This reaction introduces the fluorine-containing group into the amine structure, so that it has good low surface energy, water resistance and thermal stability, and also has an amino active site for subsequent reaction with syringaldehyde carbonate to generate polyurethane.

[0030] Secondly, due to the presence of active groups such as phenolic hydroxyl groups in the molecular structure of syringaldehyde, in the present invention, under alkaline conditions, the hydrogen atoms of the phenolic hydroxyl groups in the syringaldehyde molecules will be taken away by sodium hydroxide to form phenol oxygen anions with stronger nucleophilicity and reactivity, and to form active intermediates; then under specific reaction conditions, 3-chloro-1,2-propanediol is dripped in, and its chlorine atoms have a certain tendency to leave, and the hydroxyl groups can participate in the reaction as nucleophilic reagents, and react with the active intermediates of syringaldehyde to produce syringaldehyde diols with higher reactivity. Then, the hydroxyl groups in the syringaldehyde diols attack the carbonyl carbon in the carbonate as nucleophilic reagents, and after the hydroxyl groups are combined with the carbonyl carbons, syringaldehyde carbonates are generated. This reaction causes the hydroxyl groups in the structure of the syringaldehyde diols to combine with carbonates, introduces carbonate groups, and further changes the structure and reactivity of the molecules, which is conducive to the subsequent reaction with amine substances to form polyurethanes.

[0031] Finally, the active carbonate group in syringaldehyde carbonate reacts with the amino group in diamine substances and the amino group in fluorine-containing amine substances, and the hydrogen atom on the amino group combines with the carbonyl oxygen atom in the carbonate group, and the nitrogen atom of the amino group combines with the carbonyl carbon, and after the addition reaction, a carbamate bond is formed. As the reaction proceeds, the carbonate group of syringaldehyde carbonate continuously reacts with the amino group in diamine substances and fluorine-containing amine substances, and the molecular chains continue to grow and cross-link with each other. Diamine substances can play a role in chain extension between molecular chains, and fluorine-containing amine substances not only participate in chain growth and cross-linking, but also introduce fluorine-containing groups into the polyurethane structure, and finally form a multifunctional fluorinated modified polyurethane. Its special structure gives itself good mechanical properties, water and oxygen isolation properties and excellent softness, and can be well used in the field of OLED protective films.

[0032] From the preparation process, in the synthesis of multifunctional fluorinated modified polyurethane, step (3) uses amine substances for reaction, which include fluorinated amine substances and diamine substances. The introduction of fluorinated amine substances makes the molecular chain have a certain flexibility. The presence of fluorinated groups changes the spatial structure and interaction of the molecular chain. At the same time, the polyurethane molecular chain formed by the participation of amine substances in the reaction contains soft segment structures. These soft segment structures are usually composed of flexible segments such as polyether or polyester, just like springs, which can be freely stretched and bent to a certain extent, so that the material has good softness. And the length, structure and hard and soft segment distribution of the multifunctional fluorinated modified polyurethane molecular chain segment generated by the reaction are reasonable, and the material will not become hard due to excessive cross-linking, which is conducive to maintaining the softness of the material.

[0033] In addition, fluorine-containing acrylates (trifluoroethyl acrylate, trifluoroethyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate) are used in the raw materials, in which the fluorine atom has a strong electronegativity. The introduction of fluorine-containing groups changes the electron cloud distribution around the polyurethane molecular chain, reducing the material's affinity for water molecules and oxygen molecules. The fluorine-containing groups form a structure similar to a "protective layer" on the surface of the molecular chain, which increases the difficulty for water molecules and oxygen molecules to enter the interior of the material. The multifunctional fluorinated modified polyurethane molecular chain structure constructed through multi-step reactions in the preparation process is relatively dense, which reduces the gaps and channels inside the material, making it difficult for water molecules and oxygen molecules to diffuse inside the material, thereby effectively isolating water and oxygen.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention uses bio-based syringaldehyde as a raw material, and converts it into syringaldehyde carbonate by controlling the process conditions of the chemical reaction, and then reacts with amine substances to generate a multifunctional fluorinated modified polyurethane with excellent comprehensive performance, which not only avoids the use of toxic isocyanate substances, but also further expands the application scope of non-isocyanate polyurethane.

[0036] 2. The present invention causes a fluorinated acrylate containing C=C and a fluorinated group in its structure to undergo a Michael addition reaction with an alkyltriamine substance under certain conditions to generate a fluorinated amine substance, and introduces the fluorinated group into the amine structure, so that it has good low surface energy, water resistance and thermal stability, and also has amino active sites for subsequent reaction with syringaldehyde carbonate to generate polyurethane, thereby improving the performance of the polyurethane. DETAILED DESCRIPTION

[0037] Now describe in detail various exemplary embodiments of the present invention, this detailed description should not be considered as limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing a particular embodiment, and are not used to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the range.

[0038] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. Various modifications and variations may be made to the specific embodiments of the present invention specification without departing from the scope or spirit of the present invention, which will be apparent to those skilled in the art. Other embodiments obtained from the present invention specification will be apparent to the technician. The present application specification and examples are exemplary only.

[0039] The words “include,” “including,” “have,” or “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0040] It should be noted that the post-processing steps such as "extraction", "distillation under reduced pressure" and "stirring" appearing in the following embodiments are routine operations for those skilled in the art and can be selected according to actual operations.

[0041] The mass fractions described in the following embodiments may be grams, kilograms, tons or other mass units.

[0042] The catalyst used in the present invention is anhydrous potassium carbonate; the other reagents used can be obtained by purchase.

[0043] Preparation Example 1

[0044] The preparation steps of fluorine-containing amine substances are as follows:

[0045] 0.1 mol of trifluoroethyl acrylate was dissolved in 200 mL of THF, and the mixture was stirred at 30° C., and 0.1 mol of tris(2-aminoethyl)amine was added under a nitrogen atmosphere. The mixture was refluxed for 48 hours to obtain fluorine-containing amine substances.

[0046] Preparation Example 2

[0047] The preparation steps of fluorine-containing amine substances are as follows:

[0048] 0.1 mol of trifluoroethyl methacrylate was dissolved in 200 mL of THF, and the mixture was stirred at 60° C., and 0.105 mol of tri[2-(methylamino)ethyl]amine was added under a nitrogen atmosphere. The mixture was refluxed for 30 h to obtain fluorine-containing amine substances.

[0049] Preparation Example 3

[0050] The preparation steps of fluorine-containing amine substances are as follows:

[0051] 0.1 mol of hexafluorobutyl acrylate was dissolved in 300 mL of THF, and the mixture was stirred evenly at 80° C. 0.11 mol of polyetheramine T403 was added under nitrogen atmosphere, and the mixture was refluxed for 18 h to obtain fluorine-containing amine substances.

[0052] Preparation Example 4

[0053] The preparation steps of the fluorine-containing amine substance are the same as those in Preparation Example 2, except that 0.12 mol of tri[2-(methylamino)ethyl]amine is used.

[0054] Example 1

[0055] A method for preparing a multifunctional fluorinated modified polyurethane with excellent transmittance comprises the following preparation steps:

[0056] (1) Under a nitrogen atmosphere, 0.2 mol of syringaldehyde was added to 100 mL of a 7.5 wt% sodium hydroxide aqueous solution, heated in a water bath at 80° C. with stirring for 1.25 h, and then 0.22 mol of 3-chloro-1,2-propanediol was added dropwise thereto, the temperature was raised to 100° C., and the mixture was stirred for 4 h. The mixture was extracted with an equal volume of n-butanol, and the organic phase was washed with 20 mL of deionized water, concentrated by rotary evaporation to half of the original volume, and then dried with a mixed solvent (ethyl acetate and n-hexane in a mass ratio of 1:1), allowed to stand for 15 min, and dried at 45° C. to constant weight to obtain syringaldehyde diol;

[0057] (2) 0.15 mol of syringaldehyde diol from step (1) was mixed with 1 mol of dimethyl carbonate, 0.25 wt% of the catalyst in the system was added, and the mixture was refluxed for 7.5 h under a nitrogen atmosphere, washed with anhydrous ethanol three times, filtered, and dried at 45° C. to constant weight to obtain syringaldehyde carbonate;

[0058] (3) 30 g of syringaldehyde carbonate and 2.1 g of amine substance in step (2) were added to 65 g of DMF, and the mixture was stirred and reacted at 60° C. for 12 h to obtain a multifunctional fluorinated modified polyurethane.

[0059] The amine substance used comprises the fluorine-containing amine substance obtained in Preparation Example 1 and 4,4'-diaminodiphenylmethane in a mass ratio of 1:1.5.

[0060] Example 2

[0061] A method for preparing a multifunctional fluorinated modified polyurethane with excellent transmittance comprises the following preparation steps:

[0062] (1) Under a nitrogen atmosphere, 0.2 mol of syringaldehyde was added to 100 mL of a 7 wt% sodium hydroxide aqueous solution, heated in a water bath at 75° C. with stirring for 1.5 h, and then 0.2 mol of 3-chloro-1,2-propanediol was added dropwise thereto, the temperature was raised to 90° C., and the reaction was stirred for 4.5 h. After extraction with an equal volume of n-butanol, the organic phase was washed with 20 mL of deionized water, concentrated by rotary evaporation to half of the original volume, and then dried with a mixed solvent (ethyl acetate and n-hexane in a mass ratio of 1:1), allowed to stand for 10 min, and dried at 45° C. to constant weight to obtain syringaldehyde diol;

[0063] (2) 0.15 mol of syringaldehyde diol from step (1) was mixed with 0.9 mol of ethyl methyl carbonate, 0.3 wt% of the catalyst in the system was added, and the mixture was refluxed for 7 h under a nitrogen atmosphere, washed with anhydrous ethanol three times, filtered, and dried at 45° C. to constant weight to obtain syringaldehyde carbonate;

[0064] (3) 30 g of syringaldehyde carbonate and 1.5 g of amine substance in step (2) were added to 60 g of DMF, and the mixture was stirred and reacted at 40° C. for 18 h to obtain a multifunctional fluorinated modified polyurethane.

[0065] The amine substance used comprises the fluorine-containing amine substance obtained in Preparation Example 1 and 1,6-hexanediamine in a mass ratio of 1:1.

[0066] Example 3

[0067] A method for preparing a multifunctional fluorinated modified polyurethane with excellent transmittance comprises the following preparation steps:

[0068] (1) Under nitrogen atmosphere, 0.2 mol of syringaldehyde was added to 100 mL of 8 wt% sodium hydroxide aqueous solution, heated in a water bath at 85° C. with stirring for 1 h, and then 0.24 mol of 3-chloro-1,2-propanediol was added dropwise thereto, the temperature was raised to 110° C., and the reaction was stirred for 3.5 h. After extraction with an equal volume of n-butanol, the organic phase was washed with 20 mL of deionized water, concentrated by rotary evaporation to half of the original volume, and then dried with a mixed solvent (ethyl acetate and n-hexane in a mass ratio of 1:1), allowed to stand for 20 min, and dried at 45° C. to constant weight to obtain syringaldehyde diol;

[0069] (2) mixing 0.1 mol of syringaldehyde diol from step (1) with diethyl carbonate, adding 0.35 wt% of the catalyst of the system, reacting under reflux at 90-100° C. for 7-8 h in an inert gas atmosphere, washing with anhydrous ethanol three times, filtering, and drying at 45° C. to constant weight to obtain syringaldehyde carbonate;

[0070] (3) Add 30 g of syringaldehyde carbonate and 3 g of amine substance in step (2) to 70 g of DMF, and stir and react at 90° C. for 4 h to obtain a multifunctional fluorinated modified polyurethane.

[0071] The amine substance used comprises the fluorine-containing amine substance obtained in Preparation Example 1 and IPDA in a mass ratio of 1:2.

[0072] Example 4

[0073] A method for preparing a multifunctional fluorinated modified polyurethane with excellent transmittance, the specific implementation method is the same as that of Example 1, except that the fluorine-containing amine substance used is obtained from Preparation Example 2.

[0074] Example 5

[0075] A method for preparing a multifunctional fluorinated modified polyurethane with excellent transmittance, the specific implementation method is the same as that of Example 1, except that the fluorine-containing amine substance used is obtained from Preparation Example 3.

[0076] Example 6

[0077] A method for preparing a multifunctional fluorinated modified polyurethane with excellent transmittance, the specific implementation method is the same as that of Example 1, except that the fluorine-containing amine substance used is obtained from Preparation Example 4.

[0078] Example 7

[0079] A method for preparing a multifunctional fluorinated modified polyurethane with excellent transmittance, the specific implementation method is the same as that of Example 1, except that the amine substance used comprises trifluoroethyl acrylate obtained in Preparation Example 1 and 4,4'-diaminodiphenylmethane in a mass ratio of 1:1.5.

[0080] Example 8

[0081] A method for preparing polyurethane with excellent transmittance, the specific implementation method is the same as that of Example 1, except that an equal mass of 4,4'-diaminodiphenylmethane is used instead of the amine substance.

[0082] Example 9

[0083] A method for preparing polyurethane with excellent transmittance, the specific implementation method is the same as that of Example 2, except that an equal mass of 1,6-hexanediamine is used instead of the amine substance.

[0084] Example 10

[0085] A method for preparing polyurethane with excellent transmittance, the specific implementation method is the same as that of Example 3, except that an equal mass of IPDA is used instead of the amine substance.

[0086] Performance Testing

[0087] The multifunctional fluorinated modified polyurethane / polyurethane obtained in each embodiment was dried and sprayed on a PET substrate, and cured at 130° C. for 2 minutes to obtain each test sample with a thickness of 100 μm; and then the light transmittance, transmittance, thermal stability, elongation at break, and water absorption of each test sample were tested.

[0088] Light transmittance: measured by photoelectric haze meter model NDH2000;

[0089] Transmittance: measured by spectrophotometer UV3100, wavelength range 400-700nm;

[0090] Thermal stability: Use TGA to detect the decomposition temperature of each sample to be tested;

[0091] Elongation at break: Tested in strict accordance with GB / T 1040-2006 "Test method for tensile properties of plastics";

[0092] Water permeability: tested strictly in accordance with GB / T 1037-2021 standard;

[0093] Oxygen permeability: tested strictly in accordance with GB / T 19789-2021 standard.

[0094] The specific test results are shown in Table 1.

[0095] Table 1

[0096]

[0097] It can be seen from Table 1 that the multifunctional fluorinated modified polyurethane prepared in Examples 1-5 has excellent comprehensive properties, excellent mechanical properties, good light transmittance and transmittance, high thermal stability, and good flexibility and water and oxygen isolation.

[0098] Compared with Example 1, the composition of the amine substances in Examples 6 and 7 is changed, wherein the content and position of the fluorine functional group may change, resulting in changes in the cross-linking reaction between the amine substances and the syringaldehyde carbonate, thereby causing a decrease in the comprehensive performance of the multifunctional fluorinated modified polyurethane; and the preparation process in Examples 8-10 is a preparation method of ordinary polyurethane, and the comprehensive performance of the prepared polyurethane is significantly reduced.

[0099] The above is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present application. Although the present application is disclosed as above in the preferred embodiment, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. A method for preparing a multifunctional fluorinated modified polyurethane with excellent transmittance, characterized in that: The method comprises the following preparation steps: (1) In an inert gas atmosphere, syringaldehyde is added to an aqueous sodium hydroxide solution, heated in a water bath at 75-85° C. with stirring for 1-1.5 hours, 3-chloro-1,2-propanediol is then added dropwise thereto, the temperature is raised to 90-110° C., the reaction is stirred, extracted, washed, and dried to obtain syringaldehyde diol; (2) mixing the syringaldehyde diol of step (1) with carbonate, adding a catalyst, reacting under reflux for 7-8 hours in an inert gas atmosphere, washing, filtering, and drying to obtain syringaldehyde carbonate; (3) adding the syringaldehyde carbonate and amine substance of step (2) into a solvent, stirring and reacting at 40-90° C. to obtain a multifunctional fluorinated modified polyurethane.

2. The method for preparing the multifunctional fluorinated modified polyurethane according to claim 1, characterized in that: In the step (1), the molar ratio of syringaldehyde to 3-chloro-1,2-propanediol is 1:(1-1.2).

3. The method for preparing the multifunctional fluorinated modified polyurethane according to claim 1, characterized in that: In the step (2), the molar ratio of syringaldehyde diol to carbonate is 1:(5-9).

4. The method for preparing the multifunctional fluorinated modified polyurethane according to claim 1, characterized in that: In the step (3), the amine substances include fluorine-containing amine substances and diamine substances.

5. The method for preparing the multifunctional fluorinated modified polyurethane according to claim 1, characterized in that: In the step (3), the amount of the amine substance used is 5-10 wt % of the syringaldehyde carbonate.

6. The method for preparing the multifunctional fluorinated modified polyurethane according to claim 4, characterized in that: The preparation steps of the fluorine-containing amine substance are: The fluorine-containing acrylate is dissolved in an organic solvent, stirred evenly at 30-80° C., and a triamine substance is added under an inert gas atmosphere to react for 18-48 hours to obtain a fluorine-containing amine substance.

7. The method for preparing the multifunctional fluorinated modified polyurethane according to claim 6, characterized in that: The fluorine-containing acrylate is selected from one or more of trifluoroethyl acrylate, trifluoroethyl methacrylate, hexafluorobutyl acrylate, and hexafluorobutyl methacrylate.

8. The method for preparing the multifunctional fluorinated modified polyurethane according to claim 6, characterized in that: The triamine substance is selected from one or more of tris(2-aminoethyl)amine, tris[2-(methylamino)ethyl]amine, and polyetheramine.

9. The method for preparing the multifunctional fluorinated modified polyurethane according to claim 7, characterized in that: The molar ratio of the fluorine-containing acrylate to the triamine substance is 1:(1-1.1).

10. A multifunctional fluorinated modified polyurethane prepared by the preparation method of the multifunctional fluorinated modified polyurethane according to any one of claims 1 to 9.

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