A preparation method for converting biomass into fluorine-containing thermoplastic elastomer

Abstract

The present invention belongs to the technical field of fluorine thermoplastic elastomer preparation, and specifically relates to a preparation method for converting biomass into fluorine-containing thermoplastic elastomer. The present invention first prepares highly dispersed micro-nano cellulose by treating cellulose with a multi-element low eutectic solvent, and then prepares highly dispersed cellulose by ultrasonic and centrifugal treatment, and then prepares a cellulose skeleton by surface modification, and then polymerizes the obtained cellulose skeleton with an organic fluorine monomer and a dynamic cross-linking monomer under the action of an initiator to obtain a fluorine monomer modified dynamic single-bridged fluorine polymer, or polymerizes the obtained cellulose skeleton with an organic fluorine monomer, a dynamic cross-linking monomer, and a non-dynamic cross-linking monomer under the action of an initiator to obtain a fluorine monomer modified dynamic and non-dynamic double-bridged fluorine polymer. Compared with commonly used fluorinated polymers, the fluorine polymer thermoplastic elastomer prepared by the method of the present invention has adjustable mechanical properties, is highly modifiable, is easy to heat-process, and can be recycled and reused.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine-containing thermoplastic elastomer preparation, and particularly relates to a preparation method for fluorine-containing thermoplastic elastomer by converting biomass. Background Art

[0002] As the most abundant biomass material in the world, cellulose is often unable to be effectively dispersed due to its many hydrogen bonds, and current solutions are also limited to using ionic liquids (such as 1-allyl-3-methylimidazolium chloride and / or 1-ethyl-3-methylimidazolium acetate, etc.) to carry out solvent dispersion. Unfortunately, this ionic liquid is extremely expensive, and requires control variables to prevent preparation failure during the preparation process, causing it to be unable to be applied in certain limited conditions (such as university laboratories, enterprises, etc.). Therefore, it is necessary to develop new dispersing solvents to avoid the use of ionic liquids.

[0003] As a representative of thermoplastic elastomers, fluoroelastomers are widely used in polymer composites due to their numerous advantages, including high temperature resistance, oil resistance, chemical corrosion resistance, and aging resistance. However, existing fluoroelastomers, due to their single molecular structure design and limited crosslinking methods, have insufficient mechanical properties and are no longer able to meet the requirements of practical applications. This has also greatly restricted the further development of fluoroelastomers in more fields. At the same time, most current fluoroelastomers are limited to linear structures, which easily cause chain entanglements in the polymer molecular chain. This entanglement affects the mechanical property design of fluoroelastomers. Therefore, how to further improve the mechanical properties of fluoroelastomers from the perspective of molecular structure design is of great significance for the development of high-performance engineering polymer composites. It is clear that it is necessary to develop new process solutions to eliminate the impact of this chain entanglement on the molecular design capabilities of fluoroelastomers, thereby improving the mechanical properties of fluoroelastomers. Summary of the Invention

[0004] To overcome the shortcomings of the aforementioned prior art, the present invention proposes a method for converting biomass into a fluorothermoplastic elastomer. This method first involves treating cellulose with a polynary deep eutectic solvent (DES) to weaken intermolecular hydrogen bonds, thereby obtaining a well-dispersed cellulose and avoiding the use of ionic liquids. A polymer is then prepared using cellulose as a backbone and cellulose side chains as active sites, eliminating chain entanglement and resulting in a fluoroelastomer with exceptional mechanical properties (e.g., a low entanglement plateau modulus). This method also provides a high degree of molecular designability for this fluoropolymer.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The present invention provides a method for converting biomass into a fluorine-containing thermoplastic elastomer, the method comprising the following steps:

[0007] S1. treating cellulose with a multi-component deep eutectic solvent to obtain micro-dispersed cellulose, wherein the multi-component deep eutectic solvent comprises choline chloride, oxalic acid, malonic acid, and water;

[0008] S2, dispersing the micro-dispersed cellulose in water, and preparing highly dispersed cellulose by ultrasonic and centrifugal treatment;

[0009] S3, dispersing highly dispersed cellulose in an organic solvent, and surface-modifying the highly dispersed cellulose using bromopropionyl bromide, 4-dimethylaminopyridine, triethylamine, lauryl mercaptan, and carbon disulfide;

[0010] S4, using the modified cellulose as a polymer backbone, adding an organic fluorine monomer, a dynamic crosslinking monomer, and an initiator thereto, and causing the system to undergo a polymerization reaction by heating and ultrasonic treatment to prepare a single-bridged fluorinated thermoplastic elastomer;

[0011] Alternatively, a double-bridged fluorinated thermoplastic elastomer is prepared by using modified cellulose as a polymer backbone, adding an organic fluorine monomer, a dynamic crosslinking monomer, and an initiator, and then adding a non-dynamic crosslinking monomer after heating and reacting. The system is then subjected to ultrasonic treatment to cause a polymerization reaction.

[0012] The structural formula of the single-bridged fluorinated thermoplastic elastomer is as follows:

[0013]

[0014] Among them, the side chain n1 value is 300-600, and n2 value is 10-200;

[0015] The structural formula of the double-bridged fluorinated thermoplastic elastomer is as follows:

[0016]

[0017] Among them, the side chain n1 value range is 300-600, n2 value range is 10-200, and n3 is 1-3.

[0018] The present invention first prepares highly dispersible micro-nano cellulose by treating cellulose with a multi-element low eutectic solvent, then modifies the micro-nano cellulose to prepare a cellulose skeleton, and then modifies the cellulose skeleton with a fluorine monomer and a dynamic cross-linking monomer to obtain a dynamic single-bridged fluorinated polymer thermoplastic elastomer, or modifies the cellulose skeleton with a fluorine monomer and a dynamic / non-dynamic cross-linking monomer to obtain a dynamic and non-dynamic double-bridged fluorinated polymer thermoplastic elastomer. The main components of the thermoplastic elastomer are highly dispersible micro-nano cellulose, a fluorine monomer, a dynamic cross-linking monomer and / or a non-dynamic cross-linking monomer. Compared with commonly used fluorinated polymers, this fluorine polymer thermoplastic elastomer has adjustable mechanical properties, is highly modifiable, and is easy to heat process. Among them, among the fluorine monomers, the rich CF makes the material selective in hydrophobic properties, excellent thermal stability, and aging resistance. The dynamic cross-linking monomer and / or the non-dynamic cross-linking monomer make the mechanical properties of the thermoplastic material adjustable.

[0019] Preferably, the mass ratio of the cellulose to the multi-component deep eutectic solvent is 1-3:50-150; in the multi-component deep eutectic solvent, the molar ratio of choline chloride, oxalic acid, malonic acid, and water is 1-2:0.2-0.5:1-2:1-2.

[0020] Preferably, the source of the cellulose includes one or more of cotton, bagasse, and rice bran.

[0021] Preferably, the treatment temperature in S1 is not higher than 90° C., and the treatment time is 2 h to 5 h.

[0022] Preferably, the ultrasonic time in S2 is 0.5-3h, the ultrasonic interval is 1-3s off and 1-3s on; the centrifugal speed is 5000-12000r / min, and the time is 3-10min.

[0023] Preferably, S3 is a method of dispersing highly dispersed cellulose in an organic solvent using a solvent exchange method; the surface modification method of S3 is as follows: after dispersing the highly dispersed cellulose in an organic solvent, 2-10 parts of bromopropionyl bromide and 0.1 parts of 4-dimethylaminopyridine are added to 1 part of the highly dispersed system, and the mixture is heated at 50-70°C for 1-3 hours to obtain modified cellulose A; 1 part of A is dissolved in DMSO, and 1-2 parts of triethylamine, 0.5-2 parts of lauryl mercaptan, and 1-2 parts of carbon disulfide are added, and the mixture is heated at 30-50°C for 20-30 hours to obtain modified cellulose B.

[0024] More preferably, the specific operation of dispersing highly dispersed cellulose in an organic solvent using a solvent exchange method is as follows: the cellulose aqueous dispersion is rapidly frozen using liquid nitrogen for 7-15 minutes, and then the solvent is removed by freeze-drying for 2-4 days to obtain highly dispersed cellulose powder; then 1-3 g of highly dispersed cellulose is taken and injected with 20-40 g of N,N-dimethylformamide for solvent exchange, and after the exchange, the cellulose is ultrasonically treated for 7-20 minutes (1-3 s off, 1-3 s on).

[0025] Preferably, in S4, the organic fluorine monomer is selected from 2,4,6-trifluorobenzyl methacrylate, 1H,1H,2H,2H-perfluorooctanol acrylate, 2-(perfluorobutyl)ethyl acrylate, perfluoroalkylethyl acrylate, pentafluorobenzyl methacrylate, 1H,1H-perfluorooctyl acrylate, (perfluorocyclohexyl) methacrylate, 1H,1H-perfluoropropyl methacrylate, 1H,1H,2H,2H-perfluorodecyl acrylate, 1H,1H,7H-dodecafluoroheptyl acrylate, 2-(perfluorooctyl)ethyl methacrylate, 2-(perfluorohexyl)ethyl methacrylate, 2-(perfluorobutyl)ethyl methacrylate, 2-(perfluorodecyl)ethyl methacrylate, 1H,1H,11H-perfluoroundecyl acrylate, 2,2,3,3-tetrafluoro At least one of propyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, 3-(perfluoro-5-methylhexyl)-2-hydroxypropyl methacrylate, 2-methyl-2-(trifluoromethylsulfonamide)propyl methacrylate, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexafluorononyl acrylate, hexafluorobutyl acrylate, 2,2,2-trifluoroethyl acrylate, tetrafluoropropyl acrylate, octafluoropentyl acrylate, heptafluorobutyl acrylate, pentafluorophenol acrylate, isopropyl heptafluoroisoacrylate, dodecafluoroheptyl acrylate, and 2,2,3,3,3-pentafluoropropyl acrylate; the dynamic crosslinking monomer is selected from acrylamide, the non-dynamic crosslinking monomer is selected from N,N'-methylenebisacrylamide, and the initiator is selected from azobisisobutyronitrile.

[0026] Preferably, the mass ratio of the organic fluorine monomer to the modified cellulose is 50-500:1, the molar ratio of the dynamic crosslinking monomer to the organic fluorine monomer is 5-60:80-100, and the molar mass of the non-dynamic crosslinking monomer accounts for 0.1%-0.3% of the molar mass of the organic fluorine monomer and the dynamic crosslinking monomer.

[0027] Preferably, in S4, the heating reaction temperature is 60-80°C, the time is 10-20 hours, stirring is performed during the reaction process, and the stirring speed is 100-150 r / min; the ultrasonic treatment interval is 0.5-2 hours, and the ultrasonic time is 5-10 minutes.

[0028] Preferably, in S4, the non-dynamic cross-linking monomer is added dropwise for more than 3 hours.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention discloses a preparation method for converting biomass into a fluorine-containing thermoplastic elastomer, wherein cellulose is first treated with a multi-element low eutectic solvent to obtain highly dispersed micro-nano cellulose, and then subjected to ultrasonic and centrifugal treatment to prepare highly dispersed cellulose, and then the highly dispersed cellulose is surface-modified to obtain a cellulose skeleton, and then the obtained cellulose skeleton is polymerized with an organic fluorine monomer and a dynamic cross-linking monomer under the action of an initiator to obtain a fluorine monomer-modified dynamic single-bridged fluoropolymer, or the obtained cellulose skeleton is polymerized with an organic fluorine monomer, a dynamic cross-linking monomer, and a non-dynamic cross-linking monomer under the action of an initiator to obtain a fluorine monomer-modified dynamic and non-dynamic double-bridged fluoropolymer. Compared with commonly used fluorinated polymer thermoplastic elastomers, the fluorinated polymer thermoplastic elastomer prepared by the method of the present invention has adjustable mechanical properties, is highly modifiable, is easy to heat-process, and can be recycled and reused. Specifically, the present invention has the following advantages:

[0031] (1) Due to the strong hydrogen bonding between cellulose, direct modification on the cellulose surface must give priority to ionic liquids (such as 1-allyl-3-methylimidazolium chloride and / or 1-ethyl-3-methylimidazolium acetate) for dissolution and dispersion, but the preparation of such ionic liquids is extremely complicated and their application is limited. To this end, the present invention uses a low eutectic solvent to weaken the forces between cellulose molecules, and performs solvent exchange by a solvent exchange method. At the same time, by adjusting the ratio in the low eutectic solvent, the non-esterification of the active hydroxyl groups is ensured, thereby obtaining cellulose in a well-dispersed state. This method avoids the use of expensive ionic liquids and reduces production costs. At the same time, the cellulose in this dispersed state can ensure that no stratification occurs for more than 3 months.

[0032] (2) The present invention can produce a fluorinated thermoplastic elastomer with adjustable mechanical properties through simple ultrasonic treatment, expanding the application range of fluoropolymers and ensuring the selectivity of fluoropolymer materials for use under extreme conditions. Furthermore, the elastomer has good thermoplasticity and is recyclable and reusable, avoiding waste of fluoropolymers.

[0033] (3) Studies have shown that the elongation at break of the thermoplastic elastomer prepared by the present invention can reach over 400%, the strength can be adjusted within a wide range, and the tensile properties are excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A comparison of micro-dispersed cellulose (left) and highly dispersed cellulose (right);

[0035] Figure 2 This is a stability comparison chart of highly dispersed cellulose on day 0 and day 90;

[0036] Figure 3 The infrared spectra of highly dispersed cellulose, A, and B are shown;

[0037] Figure 4 is the NMR spectrum of product A;

[0038] Figure 5 is the NMR spectrum of product B;

[0039] Figure 6 is a diagram of the mechanical properties of the product in Example 1;

[0040] Figure 7 is the NMR spectrum of fluorinated thermoplastic elastomer 1;

[0041] Figure 8 is the mechanical properties diagram of fluorinated thermoplastic elastomer 2;

[0042] Figure 9 is the mechanical properties diagram of fluorinated thermoplastic elastomer 3;

[0043] Figure 10 is the NMR spectrum of fluorinated thermoplastic elastomer 4;

[0044] Figure 11 is a diagram of the mechanical properties of fluorinated thermoplastic elastomer 4;

[0045] Figure 12 is a graph of the mechanical properties of fluorinated thermoplastic elastomer 5;

[0046] Figure 13 is the mechanical properties diagram of fluorinated thermoplastic elastomer 6;

[0047] Figure 14 is a graph of the mechanical properties of fluorinated thermoplastic elastomer 7;

[0048] Figure 15 is a graph of the mechanical properties of fluorinated thermoplastic elastomer 8;

[0049] Figure 16 is a graph of the mechanical properties of fluorinated thermoplastic elastomer 9;

[0050] Figure 17The recyclability of fluorinated thermoplastic elastomer 9;

[0051] Figure 18 This is the infrared spectrum of the highly dispersed cellulose of Comparative Example 1. DETAILED DESCRIPTION

[0052] The following is a further description of specific embodiments of the present invention. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0053] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0054] Example 1: A method for converting biomass into a fluorinated thermoplastic elastomer

[0055] (1) 2 g of cotton-derived microcrystalline cellulose was mixed with 50 g of a polyvalent deep eutectic solvent (choline chloride: oxalic acid: malonic acid: water) in a molar ratio of 1:0.2:1:1 and heated at 80°C for 3 h. After the reaction, 52 g of the mixture was filtered and washed three times in 150 mL of anhydrous ethanol to obtain microdispersed cellulose.

[0056] Figure 1 (Left) A micro-dispersed cellulose aqueous solution shows that this micro-dispersed cellulose cannot maintain suspension stability, has poor dispersion, and undergoes significant stratification within 1 hour.

[0057] (2) 2 g of finely dispersed cellulose was redissolved in 150 g of water and sonicated for 1 h (2 s off, 2 s on). The sonicated product was centrifuged at 10,000 r / min for 5 min. The supernatant was collected after centrifugation and the precipitate was redispersed. The precipitate was poured into 40 mL of deionized water and sonicated again for more than 1 min. The supernatant was collected again after centrifugation. This operation was repeated 4 times to obtain highly dispersed cellulose. The yield of the calculated solid content was 43.76%.

[0058] Figure 1(Right) is a picture of the aqueous solution of highly dispersed cellulose. If only ultrasound is used without centrifugation, the long-term stability of the cellulose cannot be guaranteed. According to the test, it will show obvious stratification within 1 day. At the same time, one of the reasons for repeating the centrifugal ultrasound treatment of the precipitate after centrifugation is to ensure the yield. The second reason is that cellulose flocculation may occur during the treatment process. This repeated ultrasound can solve the flocculation problem very well. According to the test, this highly dispersed cellulose aqueous dispersion can remain stable for more than 3 months ( Figure 2 ).

[0059] (3) The solvent of highly dispersed cellulose was changed by solvent exchange method: 150 mL of cellulose aqueous dispersion was rapidly frozen using 500 mL of liquid nitrogen for 10 min. The solvent was then removed using a freeze dryer with a freezing temperature of -60 °C for 3 days. After removal, highly dispersed cellulose powder was obtained. Then, 1 g of highly dispersed cellulose was injected into 30 g of N,N-dimethylformamide for solvent exchange. After the exchange, the cellulose was ultrasonically treated for 10 min (2 s off, 2 s on).

[0060] (4) Surface modification of highly dispersed cellulose: 6 g of bromopropionyl bromide and 0.1 g of 4-dimethylaminopyridine were added to a DMF dispersion of 1 g of highly dispersed cellulose, and the mixture was heated to 60°C and reacted for 2 h to obtain product A. 1 g of A was dissolved in 30 g of DMSO and 0.8 mol of triethylamine, 0.8 mol of lauryl mercaptan, and 1.6 mol of carbon disulfide were added, and the mixture was heated to 40°C and reacted for 24 h to obtain product B.

[0061] (5) Take 24 mg of B, 0.8 mg of azobisisobutyronitrile, 0.267 g of acrylamide, 7.13 g of 2,2,2-trifluoroethyl acrylate and 20 mL of dioxane in a reaction tube, and freeze-thaw and vacuum the reaction tube three times (vacuum the reaction tube and pass nitrogen, then take 500 mL of liquid nitrogen and put the reaction tube into it, take it out after 5 minutes, and then put the reaction tube in 60°C warm water to thaw for 5 minutes. Repeat this process three times). After the treatment, place it in an oil bath and adjust the reaction temperature to 70°C. React for 17 hours. Keep the stirring speed at 130 r / min during the reaction. After the reaction, perform intermittent ultrasonication in an ultrasonic instrument. The ultrasonication interval is 0.5 hours each time. A total of 4 ultrasonications are performed, and the total ultrasonication time is 8 minutes. After the reaction, the product is precipitated in n-hexane to obtain 6.21 g of fluorinated thermoplastic elastomer 1. The structure of fluorinated thermoplastic elastomer 1 is shown below:

[0062]

[0063] Among them, n1=397, n2=23.

[0064] Figure 3 The infrared spectra of highly dispersed cellulose, A, and B are shown. It can be seen that highly dispersed cellulose still maintains a complete active hydroxyl group, specifically at 1730 cm -1 There is no absorption peak, indicating that the esterification reaction is small. The strong absorption peak in A indicates that a strong esterification reaction has occurred, indicating that A is successfully synthesized, while B has a strong absorption peak at 2900 cm -1 A strong absorption peak appeared near the end, indicating that a long alkyl chain had been attached, indicating that B was successfully synthesized.

[0065] Figure 4 This is the NMR spectrum of A. The chemical shift at NMR 1.76 is the methyl peak of the acyl bromide, further indicating that A was successfully synthesized.

[0066] Figure 5 This is the NMR spectrum of B. The chemical shift at NMR 1.36 is a strong methylene peak of thiol, further indicating that B was successfully synthesized.

[0067] Figure 6 Figure 1 is a graph showing the mechanical properties of fluorinated thermoplastic elastomer 1. The ultimate elongation of fluorinated thermoplastic elastomer 1 is 2000%, and the strength is 0.42 MPa, indicating overall softness.

[0068] Figure 7 This is the NMR spectrum of fluorinated thermoplastic elastomer 1. In the figure, the chemical shift near NMR 7.0 indicates the amino splitting peak of the acrylamide monomer, and the chemical shift near 4.65 indicates the methylene peak of the 2,2,2-trifluoroethyl acrylate monomer. These results indicate that the elastomer was successfully synthesized.

[0069] Example 2: A method for converting biomass into a fluorinated thermoplastic elastomer

[0070] Steps (1) to (4) are the same as those in Example 1, except for step (5), which is specifically as follows:

[0071] Take 24mg B, 0.8mg azobisisobutyronitrile, 0.444g acrylamide, 6.74g 2,2,2-trifluoroethyl acrylate and 20mL dioxane in a reaction tube, and freeze-thaw and vacuum the reaction tube three times (vacuum the reaction tube and pass nitrogen, then take 500mL liquid nitrogen and place the reaction tube in it, take it out after 5 minutes, and then place the reaction tube in 60℃ warm water to thaw for 5 minutes. Repeat this process three times). After the treatment, place it in an oil bath and adjust the reaction temperature to 70℃. React for 17 hours. Keep the stirring speed at 130r / min during the reaction. After the reaction, intermittent ultrasonication is performed in an ultrasonic instrument. The ultrasonic interval is 0.5h each time, and the ultrasonication is performed 4 times in total. The total ultrasonication time is 8 minutes. After the reaction, the product is precipitated in n-hexane to obtain 5.84g of fluorinated thermoplastic elastomer 2. The structure of fluorinated thermoplastic elastomer 2 is shown below:

[0072]

[0073] Among them, n1=362, n2=37.

[0074] Figure 8 Figure 2 shows the mechanical properties of fluorinated thermoplastic elastomer 2. Its ultimate elongation is 1105% and its strength is 1.9 MPa. Compared to fluorinated thermoplastic elastomer 1, increasing the acrylamide monomer content also changes its mechanical properties, with its elongation at break decreasing by 895% but its strength increasing by 1.48 MPa.

[0075] Example 3: A method for converting biomass into a fluorinated thermoplastic elastomer

[0076] Steps (1) to (4) are the same as those in Example 1, except for step (5), which is specifically as follows:

[0077] 24 mg of B, 0.8 mg of azobisisobutyronitrile, 0.621 g of acrylamide, 6.36 g of 2,2,2-trifluoroethyl acrylate and 20 mL of dioxane were placed in a reaction tube, and the reaction tube was subjected to freeze-thaw vacuum treatment three times (the reaction tube was vacuumed and nitrogen was introduced, then 500 mL of liquid nitrogen was taken and the reaction tube was placed in it, taken out after 5 minutes, and then the reaction tube was placed in warm water at 60°C to thaw for 5 minutes. This process was repeated three times). After the treatment, the reaction temperature was adjusted to 70°C in an oil bath, and the reaction was carried out for 17 hours. The stirring speed was maintained at 130 r / min during the reaction. After the reaction, intermittent ultrasonication was performed in an ultrasonic instrument, with an interval of 0.5 hours between each ultrasonication, a total of 4 ultrasonications, and a total ultrasonication time of 8 minutes. After the reaction, the product was precipitated in n-hexane to obtain 5.72 g of fluorinated thermoplastic elastomer 3. The structure of fluorinated thermoplastic elastomer 3 is shown below:

[0078]

[0079] Among them, n1=351, n2=44.

[0080] Figure 9 Figure 3 shows the mechanical properties of fluorinated thermoplastic elastomer 3. It has an ultimate elongation of 930% and a strength of 3.41 MPa. Compared to fluorinated thermoplastic elastomer 2, further increasing the acrylamide monomer content also changes the mechanical properties, with the elongation at break decreasing by 175% but the strength increasing by 1.51 MPa.

[0081] Example 4: A method for converting biomass into a fluorinated thermoplastic elastomer

[0082] Steps (1) to (4) are the same as those in Example 1, except for step (5), which is specifically as follows:

[0083] Place 24 mg of B, 0.8 mg of azobisisobutyronitrile, 0.267 g of acrylamide, 7.13 g of 2,2,2-trifluoroethyl acrylate, and 20 mL of dioxane in a reaction tube and freeze-thaw the tube three times (evacuate the tube and purge it with nitrogen. Then, place the tube in 500 mL of liquid nitrogen, remove it after 5 minutes, and thaw it in 60°C warm water for 5 minutes. Repeat this process three times). After this treatment, adjust the reaction temperature to 70°C in an oil bath and react for 17 hours, maintaining a stirring speed of 130 rpm. Dissolve 0.023 g of N,N'-methylenebisacrylamide in 5 mL of dioxane and slowly add it dropwise to the reaction tube, ensuring that the addition time is at least 3 hours. After the dropwise addition, intermittent ultrasonication was performed in an ultrasonic instrument for a total of 3 times, with an ultrasonic interval of 1 hour and a total ultrasonic time of 4 minutes. After the reaction was completed, the product was precipitated in n-hexane to obtain 6.20 g of fluorinated thermoplastic elastomer 4. The structure of fluorinated thermoplastic elastomer 4 is shown below:

[0084]

[0085] Among them, n1=391, n2=25, n3=1.3.

[0086] Figure 10 Figure 4 shows the mechanical properties of fluorinated thermoplastic elastomer 4. Its ultimate elongation is 982% and its strength is 2.61 MPa. Compared to fluorinated thermoplastic elastomer 1, the addition of only a small amount of non-dynamic crosslinking monomer alters its mechanical properties, reducing its elongation at break to 1018% while increasing its strength to 2.19 MPa.

[0087] Figure 11 This is the NMR spectrum of fluorinated thermoplastic elastomer 4. Multiple split peaks appear between chemical shifts 5 and 7. The split peak at chemical shift 6.2 is the methylene peak of N,N'-methylenebisacrylamide, indicating that fluorinated thermoplastic elastomer 4 was successfully synthesized.

[0088] Example 5: A method for converting biomass into a fluorinated thermoplastic elastomer

[0089] Steps (1) to (4) are the same as those in Example 1, except for step (5), which is specifically as follows:

[0090] 72 mg of B, 0.8 mg of azobisisobutyronitrile, 0.267 g of acrylamide, 7.13 g of 2,2,2-trifluoroethyl acrylate and 20 mL of dioxane were placed in a reaction tube, and the reaction tube was subjected to freeze-thaw vacuum treatment three times (the reaction tube was vacuumed and nitrogen was introduced, then 500 mL of liquid nitrogen was taken and the reaction tube was placed in it, taken out after 5 minutes, and then the reaction tube was placed in warm water at 60°C to thaw for 5 minutes. This process was repeated three times). After the treatment, the reaction temperature was adjusted to 70°C in an oil bath, and the reaction was carried out for 17 hours. The stirring speed was maintained at 130 r / min during the reaction. After the reaction, intermittent ultrasonication was performed in an ultrasonic instrument, with an interval of 0.5 hours between each ultrasonication, a total of 4 ultrasonications, and a total ultrasonication time of 8 minutes. After the reaction, the product was precipitated in n-hexane to obtain 6.48 g of fluorinated thermoplastic elastomer 5. The structure of fluorinated thermoplastic elastomer 5 is shown below:

[0091]

[0092] Among them, n1=409, n2=26.

[0093] Figure 12 Figure 5 shows the mechanical properties of fluorinated thermoplastic elastomer 5. It has an ultimate elongation of 2032% and a strength of 1.07 MPa. Compared to fluorinated thermoplastic elastomer 1, increasing the cellulose content also alters its mechanical properties. While the elongation at break remains largely unchanged, the strength increases by 0.65 MPa.

[0094] Example 6: A method for converting biomass into a fluorinated thermoplastic elastomer

[0095] Steps (1) to (4) are the same as those in Example 1, except for step (5), which is specifically as follows:

[0096] 128 mg of B, 0.8 mg of azobisisobutyronitrile, 0.267 g of acrylamide, 7.13 g of 2,2,2-trifluoroethyl acrylate and 20 mL of dioxane were placed in a reaction tube, and the reaction tube was subjected to freeze-thaw vacuum treatment three times (the reaction tube was vacuumed and nitrogen was introduced, then 500 mL of liquid nitrogen was taken and the reaction tube was placed in it, taken out after 5 minutes, and then the reaction tube was placed in warm water at 60°C to thaw for 5 minutes. This process was repeated three times). After the treatment, the reaction temperature was adjusted to 70°C in an oil bath, and the reaction was carried out for 17 hours. The stirring speed was maintained at 130 r / min during the reaction. After the reaction, intermittent ultrasonication was performed in an ultrasonic instrument, with an ultrasonic interval of 0.5 hours each time, a total of 4 ultrasonications, and a total ultrasonication time of 8 minutes. After the reaction, the product was precipitated in n-hexane to obtain 6.09 g of fluorinated thermoplastic elastomer 6. The structure of fluorinated thermoplastic elastomer 6 is shown below:

[0097]

[0098] Among them, n1=385, n2=21.

[0099] Figure 13 Figure 6 shows the mechanical properties of fluorinated thermoplastic elastomer 6. It has an ultimate elongation of 632% and a strength of 2.34 MPa. Compared to fluorinated thermoplastic elastomer 5, further increasing the cellulose content also changes the mechanical properties, with the elongation at break decreasing by 1400% but the strength increasing by 1.27 MPa.

[0100] Example 7: A method for converting biomass into a fluorinated thermoplastic elastomer

[0101] Steps (1) to (4) are the same as those in Example 1, except for step (5), which is specifically as follows:

[0102] Take 24mg B, 0.8mg azobisisobutyronitrile, 0.71g acrylamide, 9.44g hexafluorobutyl acrylate and 20mL dioxane in a reaction tube, and perform freeze-thaw vacuum treatment on the reaction tube three times (vacuum the reaction tube and pass nitrogen, then take 500mL liquid nitrogen and place the reaction tube in it, take it out after 5 minutes, and then place the reaction tube in 60℃ warm water to thaw for 5 minutes. Repeat this process three times). After the treatment, place it in an oil bath and adjust the reaction temperature to 70℃. React for 17 hours, and maintain the stirring speed at 130r / min during the reaction. After the reaction, intermittent ultrasonication is performed in an ultrasonic instrument, with an ultrasonic interval of 0.5h each time, a total of 4 ultrasonications, and a total ultrasonication time of 8 minutes. After the reaction, the product is precipitated in n-hexane to obtain 6.21g of fluorinated thermoplastic elastomer 7. The structure of fluorinated thermoplastic elastomer 7 is shown below:

[0103]

[0104] Among them, n1=344, n2=97.

[0105] Figure 14 Figure 7 shows the mechanical properties of fluorinated thermoplastic elastomer 7. Its ultimate elongation is 713% and its strength is 2.97 MPa. Compared to fluorinated thermoplastic elastomer 1, increasing the acrylamide monomer content and changing the organic fluorine monomer also alters its mechanical properties. Elongation at break decreases by 1287%, but its strength increases by 2.55 MPa.

[0106] Example 8: A method for converting biomass into a fluorinated thermoplastic elastomer

[0107] Steps (1) to (4) are the same as those in Example 1, except for step (5), which is specifically as follows:

[0108] Take 24mg B, 0.8mg azobisisobutyronitrile, 1.066g acrylamide, 8.26g hexafluorobutyl acrylate and 20mL dioxane in a reaction tube, and freeze-thaw and vacuum the reaction tube three times (vacuum the reaction tube and pass nitrogen, then take 500mL liquid nitrogen and place the reaction tube in it, take it out after 5 minutes, and then place the reaction tube in 60℃ warm water to thaw for 5 minutes. Repeat this process three times). After the treatment, place it in an oil bath and adjust the reaction temperature to 70℃. React for 17 hours, and maintain the stirring speed at 130r / min during the reaction. After the reaction, intermittent ultrasonication is performed in an ultrasonic instrument, with an ultrasonic interval of 0.5h each time, a total of 4 ultrasonications, and a total ultrasonication time of 8 minutes. After the reaction, the product is precipitated in n-hexane to obtain 8.8g of fluorinated thermoplastic elastomer 8. The structure of fluorinated thermoplastic elastomer 8 is shown below:

[0109]

[0110] Among them, n1=336, n2=131.

[0111] Figure 15 Figure 8 shows the mechanical properties of fluorinated thermoplastic elastomer 8. It has an ultimate elongation of 616% and a strength of 3.67 MPa. Compared to fluorinated thermoplastic elastomer 7, further increasing the acrylamide monomer content and varying the organic fluorine monomer content also alters the mechanical properties, with the elongation at break decreasing by 97% while the strength increasing by 0.7 MPa.

[0112] Example 9: A method for converting biomass into a fluorinated thermoplastic elastomer

[0113] Steps (1) to (4) are the same as those in Example 1, except for step (5), which is specifically as follows:

[0114] Place 24 mg of B, 0.8 mg of azobisisobutyronitrile, 1.066 g of acrylamide, 8.26 g of hexafluorobutyl acrylate, and 20 mL of dioxane in a reaction tube and freeze-thaw and evacuate the tube three times (evacuate the tube and purge with nitrogen. Then, place the tube in 500 mL of liquid nitrogen, remove it after 5 minutes, and thaw it in 60°C warm water for 5 minutes. Repeat this process three times). After this treatment, adjust the reaction temperature to 70°C in an oil bath and react for 17 hours, maintaining a stirring speed of 130 rpm. Then, dissolve 0.023 g of N,N'-methylenebisacrylamide in 5 mL of dioxane and slowly add it dropwise to the reaction tube, ensuring that the addition time is at least 3 hours. After the dropwise addition, intermittent ultrasonication was performed in an ultrasonic instrument for a total of 3 times, with an ultrasonic interval of 1 hour and a total ultrasonic time of 4 minutes. After the reaction was completed, the product was precipitated in n-hexane to obtain 8.1 g of fluorinated thermoplastic elastomer 9. The structure of fluorinated thermoplastic elastomer 9 is shown below:

[0115]

[0116] Among them, n1=302, n2=118, n3=2.

[0117] Figure 16 Figure 9 shows the mechanical properties of fluorinated thermoplastic elastomer 9. It has an ultimate elongation of 437% and a strength of 4.32 MPa. Compared to fluorinated thermoplastic elastomer 8, the addition of a non-dynamic crosslinking monomer also alters its mechanical properties, with its elongation at break decreasing by 179% but its strength increasing by 0.65 MPa.

[0118] Figure 17 The recyclability of the fluorinated thermoplastic elastomer 9 is demonstrated by placing the broken fluorinated thermoplastic elastomer 9 in a vacuum hot press at a temperature of 135°C, a pressure of 3 MPa, and a vacuum of 0.1 MPa. The hot press is then continued for 5 minutes, followed by removal and cold pressing for 3 minutes. After this operation, the fluorinated thermoplastic elastomer 9 can be recovered.

[0119] Comparative Example 1: A method for converting biomass into a fluorinated thermoplastic elastomer

[0120] Steps (2) to (5) are the same as those in Example 1, except for step (1), which is specifically as follows:

[0121] 2 g of microcrystalline cellulose was mixed with 50 g of a polyvalent deep eutectic solvent (choline chloride: oxalic acid: malonic acid = 1:0.2:1 molar ratio) and heated at 80°C for 4 hours. After the reaction, the mixture was filtered and washed three times with anhydrous ethanol to obtain microdispersed cellulose.

[0122] Finally, 6.82 g of fluorinated thermoplastic elastomer was prepared. The structure of the fluorinated thermoplastic elastomer is as follows:

[0123]

[0124] Among them, n1=431, n2=27.

[0125] Compared with Examples 1-9, the yield of the highly dispersed cellulose obtained in Comparative Example 1 has a solid content of 21.25%, while the yield of the highly dispersed cellulose in the examples is 43.76%.

[0126] Figure 18 This is the infrared spectrum of the highly dispersed cellulose of comparative example 1. It can be clearly seen that the cellulose -1 The presence of an absorption peak near the reaction zone indicates that multiple active hydroxyl groups are esterified, which is not conducive to the subsequent reaction of highly dispersed cellulose with bromopropionyl bromide.

[0127] In summary, the fluorinated polymer thermoplastic elastomer prepared by the method of the present invention is highly modifiable and has adjustable mechanical properties. The mechanical properties of the fluorinated thermoplastic elastomer can be modified to meet various requirements by varying the content of dynamic crosslinking monomers, adding non-dynamic crosslinking monomers, increasing the cellulose content, or varying the organic fluorine monomers. Furthermore, the fluorinated polymer thermoplastic elastomer prepared by the method of the present invention is easy to heat-process and can be recycled and reused, avoiding waste of fluoropolymers.

[0128] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations of these embodiments may be made without departing from the principles and spirit of the present invention, and the changes still fall within the scope of protection of the present invention.

Claims

1. A method for converting biomass into a fluorinated thermoplastic elastomer, characterized in that: The following steps are involved: S1. treating cellulose with a multi-component deep eutectic solvent to obtain micro-dispersed cellulose, wherein the multi-component deep eutectic solvent comprises choline chloride, oxalic acid, malonic acid, and water; S2, dispersing the micro-dispersed cellulose in water, and preparing highly dispersed cellulose by ultrasonic and centrifugal treatment; S3, dispersing highly dispersed cellulose in an organic solvent, and surface-modifying the highly dispersed cellulose using bromopropionyl bromide, 4-dimethylaminopyridine, triethylamine, lauryl mercaptan, and carbon disulfide; S4, using the modified cellulose as a polymer backbone, adding an organic fluorine monomer, a dynamic crosslinking monomer, and an initiator thereto, and causing the system to undergo a polymerization reaction by heating and ultrasonic treatment to prepare a single-bridged fluorinated thermoplastic elastomer; Alternatively, a double-bridged fluorinated thermoplastic elastomer is prepared by using modified cellulose as a polymer backbone, adding an organic fluorine monomer, a dynamic crosslinking monomer, and an initiator, and then adding a non-dynamic crosslinking monomer after heating and reacting. The system is then subjected to ultrasonic treatment to cause a polymerization reaction. The structural formula of the single-bridged fluorinated thermoplastic elastomer is shown below: Among them, the side chain n1 value is 300-600, and n2 value is 10-200; The structural formula of the double-bridged fluorinated thermoplastic elastomer is as follows: Among them, the side chain n1 value range is 300-600, n2 value range is 10-200, and n3 is 1-3.

2. The method for converting biomass into fluorinated thermoplastic elastomer according to claim 1, characterized in that: The mass ratio of the cellulose to the multi-component deep eutectic solvent is 1-3:50-150; in the multi-component deep eutectic solvent, the molar ratio of choline chloride, oxalic acid, malonic acid and water is 1-2:0.2-0.5:1-2:1-2.

3. The method for converting biomass into fluorinated thermoplastic elastomer according to claim 1, characterized in that: The sources of the cellulose include one or more of cotton, bagasse, and rice bran.

4. The method for converting biomass into fluorinated thermoplastic elastomer according to claim 1, characterized in that: The treatment temperature in S1 is not higher than 90°C, and the treatment time is 2h-5h.

5. The method for converting biomass into fluorine-containing thermoplastic elastomer according to claim 1, characterized in that: The ultrasonic time in S2 is 0.5-3h, the ultrasonic interval is 1-3s off and 1-3s on; the centrifugal speed is 5000-12000r / min, and the time is 3-10min.

6. The method for converting biomass into fluorinated thermoplastic elastomer according to claim 1, characterized in that: S3 utilizes a solvent exchange method to disperse highly dispersed cellulose in an organic solvent; the surface modification method of S3 is as follows: after dispersing the highly dispersed cellulose in an organic solvent, 2-10 parts of bromopropionyl bromide and 0.1 parts of 4-dimethylaminopyridine are added to 1 part of the highly dispersed system, and the mixture is heated at 50-70°C for 1-3 hours to obtain modified cellulose A; 1 part of A is dissolved in DMSO, and 1-2 parts of triethylamine, 0.5-2 parts of lauryl mercaptan, and 1-2 parts of carbon disulfide are added, and the mixture is heated at 30-50°C for 20-30 hours to obtain modified cellulose B.

7. The method for converting biomass into fluorine-containing thermoplastic elastomer according to claim 1, characterized in that: In S4, the organic fluorine monomer is selected from 2,4,6-trifluorobenzyl methacrylate, 1H,1H,2H,2H-perfluorooctanol acrylate, 2-(perfluorobutyl)ethyl acrylate, perfluoroalkylethyl acrylate, pentafluorobenzyl methacrylate, 1H,1H-perfluorooctyl acrylate, (perfluorocyclohexyl) methacrylate, 1H,1H-perfluoropropyl methacrylate, 1H,1H,2H,2H-perfluorodecyl acrylate, 1H,1H,7H-dodecafluoroheptyl acrylate, 2-(perfluorooctyl)ethyl methacrylate, 2-(perfluorohexyl)ethyl methacrylate, 2-(perfluorobutyl)ethyl methacrylate, 2-(perfluorodecyl)ethyl methacrylate, 1H,1H,11H-perfluoroundecyl acrylate, 2,2,3,3-tetrafluoropropyl At least one of methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, 3-(perfluoro-5-methylhexyl)-2-hydroxypropyl methacrylate, 2-methyl-2-(trifluoromethylsulfonamide)propyl methacrylate, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexafluorononyl acrylate, hexafluorobutyl acrylate, 2,2,2-trifluoroethyl acrylate, tetrafluoropropyl acrylate, octafluoropentyl acrylate, heptafluorobutyl acrylate, pentafluorophenol acrylate, isopropyl heptafluoroisoacrylate, dodecafluoroheptyl acrylate, and 2,2,3,3,3-pentafluoropropyl acrylate; the dynamic crosslinking monomer is selected from acrylamide, the non-dynamic crosslinking monomer is selected from N,N'-methylenebisacrylamide, and the initiator is selected from azobisisobutyronitrile.

8. The method for converting biomass into fluorine-containing thermoplastic elastomer according to claim 1, characterized in that: The mass ratio of the organic fluorine monomer to the modified cellulose is 50-500:1, the molar ratio of the dynamic crosslinking monomer to the organic fluorine monomer is 5-60:80-100, and the molar mass of the non-dynamic crosslinking monomer accounts for 0.1%-0.3% of the molar mass of the organic fluorine monomer and the dynamic crosslinking monomer.

9. The method for converting biomass into fluorinated thermoplastic elastomer according to claim 1, characterized in that: In S4, the heating reaction temperature is 60-80°C and the time is 10-20 hours. Stirring is performed during the reaction at a stirring speed of 100-150 r / min. The ultrasonic treatment is performed at an ultrasonic interval of 0.5-2 hours and a ultrasonic time of 5-10 minutes.

10. The method for converting biomass into fluorine-containing thermoplastic elastomer according to claim 1, characterized in that: In S4, the non-dynamic cross-linking monomer is added dropwise for more than 3 hours.

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