Preparation method for converting biomass into fluorine-containing thermoplastic elastomer

Abstract

The invention belongs to the technical field of preparation of fluorothermoplastic elastomers, and particularly relates to a preparation method for converting biomass into a fluorothermoplastic elastomer. The preparation method comprises the following steps: treating cellulose with a multi-element eutectic solvent to prepare high-dispersity micro-nano cellulose, carrying out ultrasonic and centrifugal treatment to prepare high-dispersity cellulose, carrying out surface modification to prepare a cellulose skeleton, and polymerizing the obtained cellulose skeleton with an organic fluorine monomer and a dynamic crosslinking monomer under the action of an initiator to obtain the high-dispersity cellulose. And polymerizing 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 so as to prepare a fluorine monomer modified dynamic single-bridged fluoropolymer, or polymerizing 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 so as to prepare a fluorine monomer modified dynamic and non-dynamic double-bridged fluoropolymer. Compared with a common fluorinated polymer, the fluoropolymer thermoplastic elastomer prepared by the method disclosed by the invention has the advantages of adjustable mechanical properties, high modifiability, easiness in hot processing and capability of being recycled and reused.

Description

Technical Field

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

[0002] As the most abundant biomass material in the world, cellulose is often unable to be effectively dispersed due to the large number of hydrogen bonds, and the current solution is also limited to the use of ionic liquids (such as 1-allyl-3-methylimidazolium chloride and / or 1-ethyl-3-methylimidazolium acetate, etc.) for solvent dispersion. Unfortunately, this ionic liquid is extremely expensive, and it is necessary to control variables during the preparation process to prevent preparation failure, resulting in its inability 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 one of the representatives of thermoplastic elastomers, fluoroelastomers are widely used in polymer composites due to their many advantages such as high temperature resistance, oil resistance, chemical corrosion resistance, and aging resistance. However, due to the single molecular structure design and limited cross-linking methods, the existing fluoroelastomers have insufficient mechanical properties and can no longer meet the requirements of practical applications, which greatly limits the further development of fluoroelastomers in more fields. At the same time, most of the current fluoroelastomers are limited to linear structures, which can easily cause chain entanglement of polymers on the 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 engineering high-performance polymer composites. It can be seen that it is necessary to develop new process solutions to eliminate the influence of this chain entanglement on the molecular design ability of fluoroelastomers, thereby improving the mechanical properties of fluoroelastomers. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the present invention proposes a preparation method for converting biomass into a fluorinated thermoplastic elastomer, firstly, cellulose is simply treated with a multi-element low eutectic solvent (DES) to weaken the force of hydrogen bonds between molecules, thereby obtaining cellulose in a well-dispersed state and avoiding the use of ionic liquids. Then, cellulose is used as a skeleton and a polymer is prepared with cellulose side chains as active sites, thereby eliminating chain entanglement and obtaining a fluorinated elastomer with special mechanical properties (such as low entanglement platform modulus), and at the same time, this fluorinated polymer is endowed with a high degree of molecular designability.

[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 preparing a fluorine-containing thermoplastic elastomer by converting biomass, the method comprising the following steps:

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

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

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

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

[0011] Alternatively, the modified cellulose is used as a polymer skeleton, an organic fluorine monomer, a dynamic crosslinking monomer and an initiator are added thereto, a non-dynamic crosslinking monomer is added after a heating reaction, and then an ultrasonic treatment is performed to cause the system to undergo a polymerization reaction, thereby preparing a double-bridged fluorinated thermoplastic elastomer;

[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 ranges from 300-600, n2 ranges from 10-200, and n3 ranges from 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 obtain 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 low eutectic solvent is 1-3:50-150; in the multi-component low 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, 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 by 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 by solvent exchange is: using liquid nitrogen to quickly freeze the cellulose aqueous dispersion for 7-15 minutes, and then removing the solvent by freeze drying for 2-4 days to obtain highly dispersed cellulose powder; then taking 1-3g of highly dispersed cellulose and injecting 20-40g of N,N-dimethylformamide for solvent exchange, and then ultrasonically treating the cellulose after the exchange for 7-20min (1-3s off, 1-3s 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-dodecyl 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 temperature of the heating reaction is 60-80°C, the time is 10-20h, stirring is performed during the reaction, and the stirring speed is 100-150r / min; the ultrasonic interval of the ultrasonic treatment is 0.5-2h, 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 interaction 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 active hydroxyl groups is ensured, thereby obtaining cellulose with a good dispersion 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 obtain a fluorinated thermoplastic elastomer with adjustable mechanical properties through simple ultrasonic treatment, which expands the application range of fluoropolymers and ensures the selectivity of fluoropolymer materials under extreme conditions. At the same time, the elastomer has good thermoplasticity and can be recycled and reused, avoiding the waste of fluoropolymers.

[0033] (3) Studies have shown that the elongation at break of the thermoplastic elastomer prepared by the present invention can reach more than 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 high-dispersible cellulose on the 0th day and the 90th day;

[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 It is the mechanical property diagram of the product in Example 1;

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

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

[0042] Fig. 9 is a diagram of mechanical properties of fluorinated thermoplastic elastomer 3;

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

[0044] Fig.11 is a diagram of mechanical properties of fluorinated thermoplastic elastomer 4;

[0045] Fig.12 is a diagram of mechanical properties of fluorinated thermoplastic elastomer 5;

[0046] Fig.13 is a diagram of mechanical properties of fluorinated thermoplastic elastomer 6;

[0047] Fig.14 is a diagram of mechanical properties of fluorinated thermoplastic elastomer 7;

[0048] Fig.15 is a diagram of mechanical properties of fluorinated thermoplastic elastomer 8;

[0049] Fig.16 is a diagram of mechanical properties of fluorinated thermoplastic elastomer 9;

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

[0051] Fig.18 This is the infrared spectrum of the high-dispersed cellulose of Comparative Example 1. DETAILED DESCRIPTION

[0052] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can 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 microcrystalline cellulose from cotton was mixed with 50 g of a polynary low eutectic solvent, and heated at 80° C. for 3 h, wherein the polynary low eutectic solvent was choline chloride: oxalic acid: malonic acid: water = 1:0.2:1:1 (molar ratio). After the reaction was completed, 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) is a picture of the aqueous solution of micro-dispersed cellulose. It can be seen that this micro-dispersed cellulose cannot guarantee suspension stability, the dispersion state is poor, and obvious stratification will occur within 1 hour.

[0057] (2) 2 g of finely dispersed cellulose was redissolved in 150 g of water and ultrasonicated for 1 h (2 s off, 2 s on). The ultrasonicated product was centrifuged at 10,000 r / min for 5 min. The supernatant was taken after centrifugation and the precipitate was redispersed. The precipitate was poured into 40 mL of deionized water and ultrasonicated again for more than 1 min. The supernatant was taken again after centrifugation. This operation was repeated 4 times to obtain highly dispersed cellulose. The solid content yield was calculated to be 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 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 well. According to the test, this highly dispersed cellulose aqueous dispersion can be kept without stratification 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 quickly frozen with 500 mL of liquid nitrogen for 10 min. The solvent was then removed by freeze dryer with a freezing temperature of -60 °C for 3 days to obtain highly dispersed cellulose powder. Then 1 g of highly dispersed cellulose was injected with 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 the DMF dispersion system of 1 g of highly dispersed cellulose, and the mixture was heated to 60°C 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 for 24 h to obtain product B.

[0061] (5) 24 mg B, 0.8 mg azobisisobutyronitrile, 0.267 g acrylamide, 7.13 g 2,2,2-trifluoroethyl acrylate and 20 mL dioxane were placed in a reaction tube, and the reaction tube was subjected to freeze-thaw vacuum treatment three times (the reaction tube was vacuum treated, 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, and this process was repeated three times). After the treatment, the reaction temperature was adjusted to 70°C in an oil bath pot, 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 ultrasound was carried out in an ultrasonic instrument, with an interval of 0.5 hours each time, and a total of 4 ultrasounds, with a total ultrasound time of 8 minutes. After the reaction, the product was 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 in Figure 1. It can be seen that highly dispersed cellulose still maintains a complete active hydroxyl group, specifically 1730cm -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 peak at 2900cm -1 A strong absorption peak appeared near it, 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, which further indicates 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, which further indicates that B was successfully synthesized.

[0067] Figure 6 The figure is a mechanical property diagram of the fluorinated thermoplastic elastomer 1. The ultimate elongation of the fluorinated thermoplastic elastomer 1 is 2000%, the strength is 0.42 MPa, and the overall performance is soft.

[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 monomer acrylamide, and the chemical shift near 4.65 indicates the methylene peak of the monomer 2,2,2-trifluoroethyl acrylate. The above results show 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 vacuumize the reaction tube three times (vacuum the reaction tube, pass nitrogen, then take 500mL liquid nitrogen and put the reaction tube in it, take it out after 5 minutes, and then put the reaction tube in 60℃ warm water to thaw for 5 minutes, and repeat this process three times). After the treatment, place it in an oil bath pot and adjust the reaction temperature to 70℃, react for 17h, and keep the stirring speed at 130r / min during the reaction. After the reaction, intermittent ultrasound is performed in an ultrasonic instrument, each ultrasound interval is 0.5h, a total of 4 ultrasounds, and the total ultrasound 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 as follows:

[0072]

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

[0074] Figure 8 The figure is the mechanical properties of fluorinated thermoplastic elastomer 2. The ultimate elongation of fluorinated thermoplastic elastomer 2 is 1105%, and the strength is 1.9MPa. Compared with fluorinated thermoplastic elastomer 1, the mechanical properties also change after increasing the acrylamide monomer content, and the elongation at break decreases by 895%, but the strength increases by 1.48MPa.

[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] Take 24mg B, 0.8mg azobisisobutyronitrile, 0.621g acrylamide, 6.36g 2,2,2-trifluoroethyl acrylate and 20mL dioxane in a reaction tube, and freeze-thaw and vacuumize the reaction tube three times (vacuum the reaction tube, pass nitrogen, then take 500mL liquid nitrogen and put the reaction tube in it, take it out after 5 minutes, and then put the reaction tube in 60℃ warm water to thaw for 5 minutes, and repeat this process three times). After the treatment, place it in an oil bath pot and adjust the reaction temperature to 70℃, react for 17h, and keep the stirring speed at 130r / min during the reaction. After the reaction, intermittent ultrasound is performed in an ultrasonic instrument, each ultrasound interval is 0.5h, a total of 4 ultrasounds, and the total ultrasound time is 8 minutes. After the reaction, the product is precipitated in n-hexane to obtain 5.72g of fluorinated thermoplastic elastomer 3. The structure of fluorinated thermoplastic elastomer 3 is as follows:

[0078]

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

[0080] Fig. 9 The figure is the mechanical properties of fluorinated thermoplastic elastomer 3. The ultimate elongation of fluorinated thermoplastic elastomer 3 is 930%, and the strength is 3.41MPa. Compared with fluorinated thermoplastic elastomer 2, the mechanical properties also change after further increasing the acrylamide monomer content, and the elongation at break decreases by 175%, but the strength increases by 1.51MPa.

[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] Take 24mg B, 0.8mg azobisisobutyronitrile, 0.267g acrylamide, 7.13g 2,2,2-trifluoroethyl acrylate and 20mL dioxane in a reaction tube, and freeze-thaw and vacuumize the reaction tube three times (vacuum the reaction tube, pass nitrogen, then take 500mL liquid nitrogen and put the reaction tube in it, take it out after 5 minutes, and then put the reaction tube in 60℃ warm water to thaw for 5 minutes, and repeat this process three times). After the treatment, place it in an oil bath pot and adjust the reaction temperature to 70℃, react for 17h, and keep the stirring speed at 130r / min during the reaction. Then take 0.023g N,N'-methylenebisacrylamide and dissolve it in 5mL dioxane, and slowly add it to the reaction tube, ensuring that the drop time is more than 3h. 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] Fig.10 The figure is the mechanical properties of fluorinated thermoplastic elastomer 4. The ultimate elongation of fluorinated thermoplastic elastomer 4 is 982%, and the strength is 2.61MPa. Compared with fluorinated thermoplastic elastomer 1, the mechanical properties also change after adding only a small amount of non-dynamic crosslinking monomer, and the elongation at break is reduced to 1018%, but the strength is increased to 2.19MPa.

[0087] Fig.11 This is the NMR spectrum of fluorinated thermoplastic elastomer 4. There are multiple split peaks between chemical shift 5-7, and 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] Take 72mg B, 0.8mg azobisisobutyronitrile, 0.267g acrylamide, 7.13g 2,2,2-trifluoroethyl acrylate and 20mL dioxane in a reaction tube, and freeze-thaw and vacuumize the reaction tube three times (vacuum the reaction tube, pass nitrogen, then take 500mL liquid nitrogen and put the reaction tube in it, take it out after 5 minutes, and then put the reaction tube in 60℃ warm water to thaw for 5 minutes, and repeat this process three times). After the treatment, place it in an oil bath pot and adjust the reaction temperature to 70℃, react for 17h, and keep the stirring speed at 130r / min during the reaction. After the reaction, intermittent ultrasound is performed in an ultrasonic instrument, each ultrasound interval is 0.5h, a total of 4 ultrasounds, and the total ultrasound time is 8 minutes. After the reaction, the product is precipitated in n-hexane to obtain 6.48g of fluorinated thermoplastic elastomer 5. The structure of fluorinated thermoplastic elastomer 5 is as follows:

[0091]

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

[0093] Fig.12 The figure is the mechanical properties of fluorinated thermoplastic elastomer 5. The ultimate elongation of fluorinated thermoplastic elastomer 5 is 2032%, and the strength is 1.07MPa. Compared with fluorinated thermoplastic elastomer 1, the mechanical properties also change after increasing the cellulose content. The elongation at break does not change much, but the strength increases by 0.65MPa.

[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] Take 128mg B, 0.8mg azobisisobutyronitrile, 0.267g acrylamide, 7.13g 2,2,2-trifluoroethyl acrylate and 20mL dioxane in a reaction tube, and freeze-thaw and vacuumize the reaction tube three times (vacuum the reaction tube, pass nitrogen, then take 500mL liquid nitrogen and put the reaction tube in it, take it out after 5 minutes, and then put the reaction tube in 60℃ warm water to thaw for 5 minutes, and repeat this process three times). After the treatment, place it in an oil bath pot and adjust the reaction temperature to 70℃, react for 17h, and keep the stirring speed at 130r / min during the reaction. After the reaction, intermittent ultrasound is performed in an ultrasonic instrument, with an interval of 0.5h each time, a total of 4 ultrasounds, and a total ultrasound time of 8 minutes. After the reaction, the product is precipitated in n-hexane to obtain 6.09g of fluorinated thermoplastic elastomer 6. The structure of fluorinated thermoplastic elastomer 6 is shown below:

[0097]

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

[0099] Fig.13 The figure is a mechanical property diagram of fluorinated thermoplastic elastomer 6. The ultimate elongation of fluorinated thermoplastic elastomer 6 is 632% and the strength is 2.34MPa. Compared with fluorinated thermoplastic elastomer 5, the mechanical properties also change after further increasing the cellulose content, and the elongation at break decreases by 1400%, but the strength increases by 1.27MPa.

[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 freeze-thaw and vacuumize the reaction tube three times (vacuum the reaction tube, pass nitrogen, then take 500mL liquid nitrogen and put the reaction tube in it, take it out after 5 minutes, and then put the reaction tube in 60℃ warm water to thaw for 5 minutes, and repeat this process three times). After the treatment, place it in an oil bath pot and adjust the reaction temperature to 70℃, react for 17h, and keep the stirring speed at 130r / min during the reaction. After the reaction, intermittent ultrasound is performed in an ultrasonic instrument, with an interval of 0.5h each time, a total of 4 ultrasounds, and a total ultrasound 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] Fig.14 The figure is the mechanical properties of fluorinated thermoplastic elastomer 7. The ultimate elongation of fluorinated thermoplastic elastomer 7 is 713%, and the strength is 2.97MPa. Compared with fluorinated thermoplastic elastomer 1, the mechanical properties are changed after increasing the acrylamide monomer content and changing the organic fluorine monomer. The elongation at break is reduced by 1287%, but the strength is increased by 2.55MPa.

[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 vacuumize the reaction tube three times (vacuum the reaction tube, pass nitrogen, then take 500mL liquid nitrogen and put the reaction tube in it, take it out after 5 minutes, and then put the reaction tube in 60℃ warm water to thaw for 5 minutes, and repeat this process three times). After the treatment, place it in an oil bath pot and adjust the reaction temperature to 70℃, react for 17h, and keep the stirring speed at 130r / min during the reaction. After the reaction, intermittent ultrasound is performed in an ultrasonic instrument, with an interval of 0.5h each time, a total of 4 ultrasounds, and a total ultrasound 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] Fig.15 The figure is a mechanical property diagram of fluorinated thermoplastic elastomer 8. The ultimate elongation of fluorinated thermoplastic elastomer 8 is 616%, and the strength is 3.67MPa. Compared with fluorinated thermoplastic elastomer 7, the mechanical properties also change after further increasing the acrylamide monomer content and changing the organic fluorine monomer content, and the elongation at break decreases by 97%, but the strength increases by 0.7MPa.

[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] Take 24mg B, 0.8mg azobisisobutyronitrile, 1.066g acrylamide, 8.26g hexafluorobutyl acrylate and 20mL dioxane in a reaction tube, and freeze-thaw and vacuumize the reaction tube three times (vacuum the reaction tube, pass nitrogen, then take 500mL liquid nitrogen and put the reaction tube in it, take it out after 5 minutes, and then put the reaction tube in 60℃ warm water to thaw for 5 minutes, and repeat this process three times). After the treatment, place it in an oil bath pot and adjust the reaction temperature to 70℃, react for 17h, and keep the stirring speed at 130r / min during the reaction. Then take 0.023g N,N'-methylenebisacrylamide and dissolve it in 5mL dioxane, and slowly add it to the reaction tube, ensuring that the drop time is more than 3h. 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] Fig.16 The figure is a diagram of the mechanical properties of fluorinated thermoplastic elastomer 9. The ultimate elongation of fluorinated thermoplastic elastomer 9 is 437% and the strength is 4.32MPa. Compared with fluorinated thermoplastic elastomer 8, the mechanical properties also change after adding non-dynamic crosslinking monomers, the elongation at break decreases by 179%, but the strength increases by 0.65MPa.

[0118] Fig.17 The specific operation is as follows: the broken fluorinated thermoplastic elastomer 9 is placed in a vacuum hot press, and the temperature of the hot press is adjusted to 135 degrees Celsius, the pressure is 3MPa, and the vacuum degree is 0.1MPa. After hot pressing for 5 minutes, it is taken out and cold pressed for 3 minutes. After the above 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 multi-component low eutectic solvent, and heated at 80° C. for 4 h, wherein the multi-component low eutectic solvent was choline chloride: oxalic acid: malonic acid = 1:0.2:1 (molar ratio). After the reaction was completed, the mixture was filtered and washed three times in anhydrous ethanol to obtain micro-dispersed 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 solid content yield of the highly dispersed cellulose obtained in Comparative Example 1 is 21.25%, while the yield of the highly dispersed cellulose in the Examples is 43.76%.

[0126] Fig.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 nearby 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 changed to meet different requirements by changing the content of dynamic crosslinking monomers, adding non-dynamic crosslinking monomers, increasing the cellulose content, changing the organic fluorine monomers, etc. At the same time, the fluorinated polymer thermoplastic elastomer prepared by the present invention is easy to heat process and can be recycled and reused, avoiding the 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. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope 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 low eutectic solvent to obtain micro-dispersed cellulose, wherein the multi-component low eutectic solvent comprises choline chloride, oxalic acid, malonic acid and water; S2, dispersing the micro-dispersed cellulose in water, and preparing the highly dispersed cellulose by ultrasonic and centrifugal treatment; S3, dispersing the highly dispersed cellulose in an organic solvent, and modifying its surface using bromopropionyl bromide, 4-dimethylaminopyridine, triethylamine, lauryl mercaptan and carbon disulfide; S4, using the modified cellulose as a polymer skeleton, adding an organic fluorine monomer, a dynamic cross-linking monomer and an initiator thereto, and polymerizing the system by heating reaction and ultrasonic treatment to prepare a single-bridged fluorinated thermoplastic elastomer; Alternatively, the modified cellulose is used as a polymer skeleton, an organic fluorine monomer, a dynamic crosslinking monomer and an initiator are added thereto, a non-dynamic crosslinking monomer is added after a heating reaction, and then an ultrasonic treatment is performed to cause the system to undergo a polymerization reaction, thereby preparing a double-bridged fluorinated thermoplastic elastomer; The structural formula of the single-bridged fluorinated thermoplastic elastomer is as follows: 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 ranges from 300-600, n2 ranges from 10-200, and n3 ranges from 1-3.

2. The method for preparing a fluorinated thermoplastic elastomer by converting biomass into the fluorinated thermoplastic elastomer according to claim 1, characterized in that: The mass ratio of the cellulose to the multi-component low eutectic solvent is 1-3:50-150; in the multi-component low 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 preparing a fluorinated thermoplastic elastomer by converting biomass into the 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 preparing a fluorinated thermoplastic elastomer by converting biomass into the 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 preparing a fluorinated thermoplastic elastomer by converting biomass into the fluorinated thermoplastic elastomer according to claim 1, characterized in that: S2: The ultrasonic time is 0.5-3h, the ultrasonic interval is 1-3s off, 1-3s on; the centrifugal speed is 5000-12000r / min, and the time is 3-10min.

6. The method for preparing a fluorinated thermoplastic elastomer by converting biomass into the fluorinated thermoplastic elastomer according to claim 1, characterized in that: S3 is a method of dispersing highly dispersed cellulose in an organic solvent by a solvent exchange method; the surface modification method of S3 is as follows: after dispersing 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 preparing a fluorinated thermoplastic elastomer by converting biomass into the fluorinated 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-dodecyl 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 preparing a fluorinated thermoplastic elastomer by converting biomass into the fluorinated 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 preparing a fluorinated thermoplastic elastomer by converting biomass into the fluorinated thermoplastic elastomer according to claim 1, characterized in that: In S4, the heating reaction temperature is 60-80°C, the time is 10-20h, stirring is performed during the reaction, and the stirring speed is 100-150r / min; the ultrasonic treatment has an ultrasonic interval of 0.5-2h and an ultrasonic time of 5-10 minutes.

10. The method for preparing a fluorinated thermoplastic elastomer by converting biomass into the fluorinated 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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