A method for preparing chemically recyclable polyaldehyde ester, its product, and the chemical recycling method.

Abstract

This invention discloses a method for preparing chemically recyclable polyaldehyde esters. Using linear aldehydes and cyclic anhydrides as raw materials, and Lewis acids or protic acids as catalysts, chemically recyclable polyaldehyde esters are prepared through alternating copolymerization. The general structural formula of the linear aldehyde is as follows: R is selected from alkyl groups with 1 to 20 carbon atoms, alkenyl groups with 2 to 20 carbon atoms, alkynyl groups, terpenyl groups with 5 to 20 carbon atoms, cycloalkyl groups with 3 to 20 carbon atoms, aromatic groups with 5 to 20 carbon atoms, and the above groups containing heteroatoms. This invention discloses a method for successfully preparing polyaldehyde esters from linear aldehydes. The method is simple and controllable, and the product obtained is a fully alternating polyaldehyde ester with a well-defined chain structure. More importantly, the polyaldehyde ester prepared by this method is chemically recyclable; it can be completely depolymerized and converted into raw material monomers through simple pyrolysis, thus achieving the chemical recycling of the polyaldehyde ester.

Description

Technical Field

[0001] This invention relates to the technical field of polymer materials, and in particular to a method for preparing chemically recyclable polyaldehyde ester, its product, and the chemical recycling method. Background Technology

[0002] Since Hermann Staudinger first proposed the concept of polymers based on covalent bonds in 1920, polymer science has undergone a century of development, and polymers have become an indispensable material in social development. While synthetic polymer materials bring enormous convenience to humankind, the contradiction between them and the sustainable development of human society is becoming increasingly prominent: first, raw materials rely on non-renewable fossil resources, while industrial production emits large amounts of CO2; second, carbon-chain polymers with carbon-carbon bonds as their main chain are extremely stable, and under natural conditions, they can take hundreds or even thousands of years to degrade into smaller molecules.

[0003] Epoxy anhydrides are common compounds that can be prepared by heating corresponding (bio-based) dicarboxylic acids to induce intramolecular dehydration. Anionic copolymerization of epoxy anhydrides and epoxides is an emerging method for synthesizing polyesters, offering advantages such as atom economy, easily controllable structure, and mild polymerization conditions. To date, more than 20 types of epoxy anhydrides and epoxides have been reported to participate in copolymerization, resulting in over 400 different types of polyesters synthesized.

[0004] Chinese patent document CN 113861395 A discloses a polyester with a main chain containing acetal groups and its preparation method, which is prepared by alternating copolymerization of cyclic acetals and cyclic anhydrides. Unlike cyclic acetals, linear aldehydes are linear molecules without ring strain. As a natural and widely bioavailable monomer, such as lily aldehyde, perillaldehyde, and citric acid aldehyde, they are considered one of the most promising monomers of the 21st century. Polymers prepared from aldehydes are expected to replace traditional petroleum-based materials and have good development prospects. However, unfortunately, in current research, apart from formaldehyde, which has been widely studied and confirmed to undergo cationic homopolymerization to prepare polyoxymethylene and copolymerization with other cyclic acetals to prepare copolymerized polyoxymethylene (In Polyoxymethylene Handbook, 2014; pp 21-51), other linear aldehydes are difficult or even impossible to homopolymerize or copolymerize due to their low polymerization enthalpy change (Macromolecules 2021, 54, 9165-9173). Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention discloses a method for successfully preparing polyaldehyde esters using linear aldehydes and cyclic anhydrides as raw materials. The method is simple and controllable, and the product obtained is a fully alternating polyaldehyde ester with a well-defined chain structure. More importantly, the polyaldehyde ester prepared by this method is chemically recyclable and can be completely depolymerized and converted into raw materials through simple pyrolysis, thus realizing the chemical recycling of polyaldehyde esters.

[0006] The specific technical solution is as follows:

[0007] A method for preparing a chemically recyclable polyaldehyde ester, comprising:

[0008] The chemically recyclable polyaldehyde ester was prepared by alternating copolymerization using linear aldehydes and cyclic anhydrides as raw materials and Lewis acids or protic acids as catalysts.

[0009] The linear aldehyde has the following general structural formula:

[0010]

[0011] In the formula, R is selected from branched alkyl or straight alkyl with 1 to 20 carbon atoms, branched alkenyl or straight alkenyl with 2 to 20 carbon atoms, branched alkynyl or straight alkynyl with 2 to 20 carbon atoms, branched terpenyl or straight terpenyl with 5 to 20 carbon atoms, branched cycloalkyl or straight cycloalkyl with 3 to 20 carbon atoms, aromatic groups with 5 to 20 carbon atoms, and the above groups containing one or more heteroatoms selected from O, S, N, Si, P, F, Cl, Br, and I.

[0012] When R is selected from branched alkenyl or straight alkenyl with 2 to 20 carbon atoms, the alkenyl cannot form conjugation with the double bond in the aldehyde group;

[0013] When R is selected from a branched alkynyl or straight-chain alkynyl with 2 to 20 carbon atoms, the alkynyl group cannot form a conjugation with the double bond in the aldehyde group;

[0014] The cyclic anhydride is selected from six-membered cyclic anhydrides and / or seven-membered cyclic anhydrides;

[0015] If the six-membered cyclic anhydride contains substituents, the substituents cannot be directly connected alicyclic substituents.

[0016] If the seven-membered cyclic anhydride contains substituents, the substituents cannot be directly connected alicyclic substituents.

[0017] Through extensive experimentation, the inventors discovered that only when screening for special six-membered cyclic anhydrides and / or seven-membered cyclic anhydrides with both large ring strain and small steric hindrance, the enthalpy change of the ring-opening polymerization of cyclic anhydrides can compensate for the entropy change in the linear aldehyde polymerization process, thereby initiating a copolymerization reaction and achieving the copolymerization of linear aldehydes.

[0018] Therefore, the present invention has certain requirements for the structure of cyclic anhydrides. First, six-membered and / or seven-membered cyclic anhydrides with large ring strain are selected. At the same time, in order to ensure small steric hindrance, if the cyclic anhydride contains substituents, the substituents cannot be directly connected alicyclic substituents.

[0019] Preferably, the linear aldehyde is selected from one or more of straight-chain alkyl groups with 1 to 20 carbon atoms, cyclohexaneformaldehyde, benzaldehyde, 2,3-dichlorobenzaldehyde, and lily aldehyde; these preferred aldehyde monomers are widely available chemically or biologically, easily obtained in large quantities, and convenient to store and transport. Particularly important is that these preferred aldehyde monomers have simple structures and are thermodynamically easier to polymerize.

[0020] Preferably, the cyclic anhydride is selected from one or more of glutaric anhydride, diethylene glycol anhydride, thiodiethylene glycol anhydride, 3-methylglutaric anhydride, 3,3-dimethylglutaric anhydride, 2,2-dimethylglutaric anhydride, 3-isobutylglutaric anhydride, hexafluoroglutaric anhydride, and adipic anhydride. These preferred cyclic anhydride monomers are inexpensive, readily available, and common industrial products, and are convenient to store and transport. Furthermore, these preferred cyclic anhydride monomers exhibit good reactivity and excellent effects with the linear aldehyde monomer.

[0021] Preferably, the molar ratio of cyclic anhydride to linear aldehyde is 0.1–10:1; more preferably, it is 0.5–1.5:1, and preferably, within this range, the polymerization product can be guaranteed to have a degree of alternation of ≥99%. More preferably, it is 1.0–1.5:1, at which the polymerization reaction has a higher conversion rate and the polymer product has a higher molecular weight.

[0022] Preferably, the molar ratio of catalyst to cyclic anhydride is 1:5 to 10000; more preferably, it is 1:50 to 7500, and this range ensures high polymerization efficiency. More preferably, it is 1:100 to 7500, and even more preferably, it is 1:1000 to 7500. With the continuous optimization of the above molar ratio, the conversion rate of the polymerization reaction is higher, and higher molecular weight polymer products can be prepared.

[0023] Preferably, the alternating copolymerization reaction is carried out at -20 to 60°C under autogenous pressure for 0.05 to 12 hours; more preferably, the temperature of the alternating copolymerization reaction is -20 to 25°C; even more preferably, it is -20 to 0°C. Experiments have shown that the special characteristic of this polymerization reaction is that low temperatures are more conducive to the polymerization reaction; as the polymerization reaction temperature decreases, the conversion rate of the polymerization reaction is higher, and polymeric products with higher molecular weights can be prepared.

[0024] Further experiments revealed that in this polymerization reaction, when R is selected from aromatic groups with 5 to 20 carbon atoms, and aromatic groups with 5 to 20 carbon atoms containing one or more heteroatoms from O, S, N, Si, P, F, Cl, Br, and I, the polymerization reaction requires a lower temperature (-20 to 0°C).

[0025] In this alternating copolymerization reaction, the Lewis acid is selected from one or more of BF3, B(C6F5)3, InCl3, InBr3, SnCl4, AlCl3, SbCl5, PF5, CF3SO3Et, and Ph3CPF6;

[0026] The protic acid is selected from one or more of HBF4, HClO4, CF3COOH, CF3SO4H, FSO4H, and concentrated sulfuric acid.

[0027] Preferably, the catalyst is selected from InCl3 and / or InBr3. Experiments have shown that this preferred catalyst exhibits higher catalytic activity compared to other catalyst types, and can produce polymer products with higher molecular weights under the same conditions.

[0028] This invention also discloses a chemically recyclable polyaldehyde ester prepared according to the above method:

[0029] The chemically recyclable polyaldehyde ester has a fully alternating structure, with an ester unit content of ≥99%, and each repeating unit contains an aldehyde group.

[0030] The present invention also discloses a method for chemically recycling polyaldehyde ester, wherein the chemically recyclable polyaldehyde ester prepared according to the above method is pyrolyzed under vacuum conditions at 160-180°C.

[0031] Preferably, the vacuum is evacuated to a vacuum level of <0.1 kPa.

[0032] The chemically recyclable polyaldehyde ester prepared by the above method can be quantitatively degraded through the simple and mild pyrolysis described above, with a conversion rate of >99% and an aldehyde yield of ≥88%.

[0033] Preferably, the selected chemically recyclable polyaldehyde ester uses linear aldehyde substituents selected during preparation from aromatic groups with 5 to 20 carbon atoms, or aromatic groups with 5 to 20 carbon atoms containing one or more heteroatoms selected from O, S, N, Si, P, F, Cl, Br, and I.

[0034] Experiments have shown that chemically recyclable polyaldehyde esters prepared from linear aldehydes containing aromatic groups, aromatic heterocycles, or substituents are easier to chemically recycle, require lower pyrolysis temperatures and shorter times, and have higher aldehyde yields (≥95%).

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) Based on extensive experimental research, this invention is the first to realize the alternating cationic copolymerization of linear aldehyde monomers and cyclic anhydride monomers. Since the two monomer raw materials are easy to prepare, widely available from biological sources and cheap and readily available, this polymerization reaction has great practical value.

[0037] (2) The polyaldehyde ester prepared by this invention has a fully alternating structure and a regular structure, and has broad application prospects in food packaging, biological and electronic fields.

[0038] (3) The polyaldehyde ester prepared by the present invention has excellent degradation performance. Under static vacuum and relatively mild conditions (160-180°C), it can be returned from the polymer to the monomer, completing the closed-loop recovery of the monomer. The polymer conversion rate is >99% and the monomer recovery rate is >88%. Attached Figure Description

[0039] Figure 1 The polyaldehyde ester prepared in Example 1 1 H NMR spectrum;

[0040] Figure 2 The polyaldehyde ester prepared in Example 1 13 C NMR spectrum;

[0041] Figure 3 The polyaldehyde ester prepared in Example 2 1 H NMR spectrum;

[0042] Figure 4 The polyaldehyde ester prepared in Example 2 13 C NMR spectrum;

[0043] Figure 5 The polyaldehyde ester prepared in Example 3 1 H NMR spectrum;

[0044] Figure 6 The polyaldehyde ester prepared in Example 3 13 C NMR spectrum;

[0045] Figure 7 The polyaldehyde ester prepared in Example 4 1 H NMR spectrum;

[0046] Figure 8 The polyaldehyde ester prepared in Example 4 13 C NMR spectrum;

[0047] Figure 9 The polyaldehyde ester prepared in Example 6 1H NMR spectrum;

[0048] Figure 10 The polyaldehyde ester prepared in Example 6 13 C NMR spectrum;

[0049] Figure 11 The polyaldehyde ester prepared in Example 7 1 H NMR spectrum;

[0050] Figure 12 The polyaldehyde ester prepared in Example 7 13 C NMR spectrum;

[0051] Figure 13 The polyaldehyde ester prepared in Example 8 1 H NMR spectrum;

[0052] Figure 14 The polyaldehyde ester prepared in Example 8 13 C NMR spectrum;

[0053] Figure 15 The polyaldehyde ester prepared in Example 9 1 H NMR spectrum;

[0054] Figure 16 The polyaldehyde ester prepared in Example 9 13 C10 NMR spectrum. Detailed Implementation

[0055] The present invention will be described in further detail below with reference to embodiments and comparative examples, but the implementation of the present invention is not limited thereto.

[0056] Example 1: Alternating copolymerization of acetaldehyde and glutaric anhydride to form fully alternating polyaldehyde ester

[0057] Before polymerization, 10 mL Shrek tubes were incubated at 110 °C for 2 hours to remove moisture and then cooled to room temperature in a glove box. A certain mass of InBr3, acetaldehyde, glutaric anhydride, and 1 mL of dichloromethane were added sequentially to the Shrek tubes. The molar ratio of InBr3 / acetaldehyde / glutaric anhydride was 1 / 100 / 100. The reaction was carried out at 25 °C under autogenous pressure for 0.1 h. After the reaction, the crude product was dissolved in dichloromethane, and then the polymer was precipitated in a 100 mL mixture of methanol and sodium phenolate (sodium phenolate molar concentration 5%). This washing process was repeated three times, and the product was dried under vacuum to constant weight. The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the results are shown in Table 1.

[0058] The polyaldehyde ester prepared in this embodiment 1 H NMR spectrum as shown Figure 1 As shown, 13 CNMR spectrum as shown Figure 2As shown. Observation Figure 1 and Figure 2 As can be seen from the figure, no peak corresponding to polyaldehyde linkages is observed, indicating that the obtained product has a completely alternating linkage structure.

[0059] Degradation performance test:

[0060] The sublimator was heated at 110°C for approximately 12 hours to remove moisture and then cooled to room temperature in a glove box. The polyaldehyde ester prepared in this embodiment was added to the sublimator, which was then sealed and evacuated under vacuum for 30 minutes until the vacuum level was <0.1 kPa to remove air. The apparatus was then sealed again. The reaction was carried out at 180°C under autogenous pressure for 12 hours. After the reaction was completed, the lower layer of raw material and the upper layer of sublimation product in the sublimator were taken and weighed. The purity was tested by NMR, and the test results are shown in Table 2.

[0061] Comparative Example 1

[0062] Before the polymerization reaction, 10 mL Shrek tubes were dried at 110°C for 2 hours to remove moisture and then cooled to room temperature in a glove box. A certain mass of InBr3, acetaldehyde, maleic anhydride, and 1 mL of dichloromethane were added sequentially to the Shrek tubes. The molar ratio of InBr3 / acetaldehyde / maleic anhydride was 1 / 100 / 100. The reaction was carried out at 25°C under autogenous pressure for 12 hours.

[0063] The product after the reaction was a colorless liquid. No precipitate was formed in 100 mL of a mixture of methanol and sodium phenolate (sodium phenolate molar concentration of 5%), indicating that no polymerization reaction occurred in the system. The molecular weight and molecular weight distribution of the polymer were determined by gel chromatography, and the test results are shown in Table 1.

[0064] The test results further confirm that acetaldehyde does not copolymerize with maleic anhydride, a representative of five-membered cyclic anhydrides.

[0065] Comparative Example 2

[0066] The preparation process is basically the same as that in Comparative Example 1, except that the reaction system is placed at 100°C and reacted under autogenous pressure for 12 hours.

[0067] The product after the reaction was a colorless liquid. No precipitate was formed in 100 mL of a mixture of methanol and sodium phenolate (sodium phenolate molar concentration of 5%), indicating that no polymerization reaction occurred in the system. The molecular weight and molecular weight distribution of the polymer were determined by gel chromatography, and the test results are shown in Table 1.

[0068] The test results confirm that even when the reaction temperature is increased, acetaldehyde does not copolymerize with maleic anhydride, a representative of five-membered cyclic anhydrides.

[0069] Comparative Example 3

[0070] The preparation process is basically the same as in Example 1, except that:

[0071] Replace acetaldehyde with an equimolar amount of cinnamaldehyde, and place the reaction system at 25°C under autogenous pressure for 12 hours.

[0072] The product after the reaction was a colorless liquid. No precipitate was formed in 100 mL of a mixture of methanol and sodium phenolate (sodium phenolate molar concentration of 5%), indicating that no polymerization reaction occurred in the system. The molecular weight and molecular weight distribution of the polymer were determined by gel chromatography, and the test results are shown in Table 1.

[0073] Based on the test results, it can be determined that glutaric anhydride does not undergo a copolymerization reaction with cinnamaldehyde, which has conjugated unsaturated bonds.

[0074] Comparative Example 4

[0075] The preparation process is basically the same as in Example 1, except that:

[0076] Replace acetaldehyde with an equimolar amount of furanaldehyde, and place the reaction system at 25°C under autogenous pressure for 12 hours.

[0077] The product after the reaction was a colorless liquid. No precipitate was formed in 100 mL of a mixture of methanol and sodium phenolate (sodium phenolate molar concentration of 5%), indicating that no polymerization reaction occurred in the system. The molecular weight and molecular weight distribution of the polymer were determined by gel chromatography, and the test results are shown in Table 1.

[0078] The test results confirm that glutaric anhydride does not copolymerize with furanaldehyde, which has conjugated unsaturated bonds.

[0079] Example 2: Cyclohexane-formaldehyde / glutaric anhydride alternating copolymerization to form fully alternating polyaldehyde ester

[0080] The preparation process is basically the same as in Example 1, except that:

[0081] Replace acetaldehyde with an equimolar amount of cyclohexane-formaldehyde, and place the reaction system at 25°C under autogenous pressure for 0.5 hours.

[0082] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0083] The polyaldehyde ester prepared in this embodiment 1 H NMR spectrum as shown Figure 3 As shown, 13 CNMR spectrum as shown Figure 4 As shown. Observation Figure 3 and Figure 4 As can be seen from the figure, no peak corresponding to polyaldehyde linkages is observed, indicating that the obtained product has a completely alternating linkage structure.

[0084] Example 3: Alternating copolymerization of eicosaldehyde and glutaric anhydride to form a fully alternating polyaldehyde ester

[0085] The preparation process is basically the same as in Example 1, except that:

[0086] Replace acetaldehyde with an equimolar amount of eicosanaldehyde, and place the reaction system at 25°C under autogenous pressure for 0.5 hours.

[0087] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0088] The polyaldehyde ester prepared in this embodiment 1 H NMR spectrum as shown Figure 5 As shown, 13 CNMR spectrum as shown Figure 6 As shown. Observation Figure 5 and Figure 6 As can be seen from the figure, no peak corresponding to polyaldehyde linkages is observed, indicating that the obtained product has a completely alternating linkage structure.

[0089] Example 4: Alternating copolymerization of benzaldehyde and glutaric anhydride to form fully alternating polyaldehyde ester

[0090] The preparation process is basically the same as in Example 1, except that:

[0091] Replace acetaldehyde with an equimolar amount of benzaldehyde, and place the reaction system at 0°C under autogenous pressure for 0.5 hours.

[0092] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0093] The polyaldehyde ester prepared in this embodiment 1 H NMR spectrum as shown Figure 7 As shown, 13 CNMR spectrum as shown Figure 8 As shown. Observation Figure 7 and Figure 8 As can be seen from the figure, no peak corresponding to polyaldehyde linkages is observed, indicating that the obtained product has a completely alternating linkage structure.

[0094] Degradation performance test:

[0095] The sublimator was heated at 110°C for approximately 12 hours to remove moisture and then cooled to room temperature in a glove box. The polyaldehyde ester prepared in this embodiment was added to the sublimator, which was then sealed and placed under vacuum for 30 minutes until the vacuum level was <0.1 kPa to remove air. The apparatus was then sealed again. The reaction was carried out at 160°C under autogenous pressure for 3 hours. After the reaction was completed, the lower layer of raw material and the upper layer of sublimation product in the sublimator were taken and weighed. The purity was tested by NMR, and the test results are shown in Table 2.

[0096] Example 5: Alternating copolymerization of benzaldehyde and glutaric anhydride to form a fully alternating polyaldehyde ester

[0097] The preparation process is basically the same as in Example 4, with the only difference being:

[0098] The reaction system was placed at 25°C and reacted under autogenous pressure for 0.5 hours.

[0099] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0100] Example 6: Alternating copolymerization of 2,3-dichlorobenzaldehyde / glutaric anhydride to form a fully alternating polyaldehyde ester

[0101] The preparation process is basically the same as in Example 1, except that:

[0102] Replace acetaldehyde with an equimolar amount of 2,3-dichlorobenzaldehyde, and place the reaction system at -20°C under autogenous pressure for 12 hours.

[0103] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0104] The polyaldehyde ester prepared in this embodiment 1 H NMR spectrum as shown Figure 9 As shown, 13 CNMR spectrum as shown Figure 10 As shown. Observation Figure 9 and Figure 10 As can be seen from the figure, no peak corresponding to polyaldehyde linkages is observed, indicating that the obtained product has a completely alternating linkage structure.

[0105] Degradation performance test:

[0106] The sublimator was heated at 110°C for approximately 12 hours to remove moisture and then cooled to room temperature in a glove box. The polyaldehyde ester prepared in this embodiment was added to the sublimator, which was then sealed and placed under vacuum for 30 minutes until the vacuum level was <0.1 kPa to remove air. The apparatus was then sealed again. The reaction was carried out at 160°C under autogenous pressure for 3 hours. After the reaction was completed, the lower layer of raw material and the upper layer of sublimation product in the sublimator were taken and weighed. The purity was tested by NMR, and the test results are shown in Table 2.

[0107] Example 7: Alternating copolymerization of lily aldehyde and glutaric anhydride to form fully alternating polyaldehyde ester

[0108] The preparation process is basically the same as in Example 1, except that:

[0109] Replace acetaldehyde with an equimolar amount of lily aldehyde, and place the reaction system at 25°C under autogenous pressure for 0.5 hours.

[0110] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0111] The polyaldehyde ester prepared in this embodiment 1 H NMR spectrum as shown Figure 11 As shown, 13 CNMR spectrum as shown Figure 12 As shown. Observation Figure 11 and Figure 12 As can be seen from the figure, no peak corresponding to polyaldehyde linkages is observed, indicating that the obtained product has a completely alternating linkage structure.

[0112] Example 8: Alternating copolymerization of acetaldehyde and 3-methylglutaric anhydride to form a fully alternating polyaldehyde ester

[0113] The preparation process is basically the same as in Example 1, except that:

[0114] Replace glutaric anhydride with an equimolar amount of 3-methylglutaric anhydride, and place the reaction system at 25°C under autogenous pressure for 0.5 hours.

[0115] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0116] The polyaldehyde ester prepared in this embodiment 1 H NMR spectrum as shown Figure 13 As shown, 13 CNMR spectrum as shown Figure 14 As shown. Observation Figure 13 and Figure 14 As can be seen from the figure, no peak corresponding to polyaldehyde linkages is observed, indicating that the obtained product has a completely alternating linkage structure.

[0117] Comparative Example 5

[0118] The preparation process is basically the same as in Example 1, except that:

[0119] Replace glutaric anhydride with an equimolar amount of 3,3-tetramethyleneglutaric anhydride, and place the reaction system at 25°C under autogenous pressure for 12 hours.

[0120] The product after the reaction was a colorless liquid. No precipitate was formed in 100 mL of a mixture of methanol and sodium phenolate (sodium phenolate molar concentration of 5%), indicating that no polymerization reaction occurred in the system. The molecular weight and molecular weight distribution of the polymer were determined by gel chromatography, and the test results are shown in Table 1.

[0121] Based on the test results, it can be determined that acetaldehyde does not undergo a copolymerization reaction with 3,3-tetramethyleneglutaric anhydride, which has significant steric hindrance.

[0122] Comparative Example 6

[0123] The preparation process is basically the same as in Example 1, except that:

[0124] Replace glutaric anhydride with an equimolar amount of 1,1-cyclohexyldiacetic anhydride, and place the reaction system at 25°C under autogenous pressure for 12 hours.

[0125] The product after the reaction was a colorless liquid. No precipitate was formed in 100 mL of a mixture of methanol and sodium phenolate (sodium phenolate molar concentration of 5%), indicating that no polymerization reaction occurred in the system. The molecular weight and molecular weight distribution of the polymer were determined by gel chromatography, and the test results are shown in Table 1.

[0126] Based on the test results, it can be determined that acetaldehyde does not undergo a copolymerization reaction with 1,1-cyclohexyldiacetic anhydride, which has large steric hindrance.

[0127] Example 9: Alternating copolymerization of acetaldehyde and adipic anhydride to form fully alternating polyaldehyde ester

[0128] The preparation process is basically the same as in Example 1, except that:

[0129] Replace glutaric anhydride with an equimolar amount of adipic anhydride, and place the reaction system at 25°C under autogenous pressure for 0.5 hours.

[0130] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0131] The polyaldehyde ester prepared in this embodiment 1 H NMR spectrum as shown Figure 15 As shown, 13 CNMR spectrum as shown Figure 16 As shown. Observation Figure 15 and Figure 16 As can be seen from the figure, no peak corresponding to polyaldehyde linkages is observed, indicating that the obtained product has a completely alternating linkage structure.

[0132] Examples 10-11: Alternating copolymerization of acetaldehyde and glutaric anhydride to form fully alternating polyaldehyde esters

[0133] The preparation process is basically the same as in Example 1, with the only difference being:

[0134] The catalyst was replaced with equimolar amounts of BF3 and TfOH, respectively.

[0135] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0136] Example 12: Alternating copolymerization of acetaldehyde and glutaric anhydride to form fully alternating polyaldehyde ester

[0137] The preparation process is basically the same as in Example 1, with the only difference being:

[0138] Replace the molar ratio of InBr3 / acetaldehyde / glutaric anhydride with 1 / 50 / 50.

[0139] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0140] Example 13: Alternating copolymerization of acetaldehyde and glutaric anhydride to form fully alternating polyaldehyde ester

[0141] The preparation process is basically the same as in Example 1, except that:

[0142] Replace the molar ratio of InBr3 / acetaldehyde / glutaric anhydride with 1 / 1000 / 1000, and place the reaction system at 25°C under autogenous pressure for 6 hours.

[0143] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0144] Example 14: Alternating copolymerization of acetaldehyde and glutaric anhydride to form fully alternating polyaldehyde ester

[0145] The preparation process is basically the same as in Example 1, except that:

[0146] Replace the molar ratio of InBr3 / acetaldehyde / glutaric anhydride with 1 / 7500 / 7500, and place the reaction system at 25°C under autogenous pressure for 12 hours.

[0147] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0148] Examples 15-16: Alternating copolymerization of acetaldehyde and glutaric anhydride to form fully alternating polyaldehyde esters

[0149] The preparation process is basically the same as in Example 1, with the only difference being:

[0150] Replace the molar ratio of InBr3 / acetaldehyde / glutaric anhydride with 1 / 50 / 100 and 1 / 150 / 100, respectively.

[0151] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0152] Examples 17-19: Alternating copolymerization of acetaldehyde and glutaric anhydride to form fully alternating polyaldehyde esters

[0153] The preparation process is basically the same as in Example 1, with the only difference being:

[0154] The reaction temperatures of the reaction system were replaced with 0℃, 40℃, and 60℃, respectively.

[0155] The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography, and the test results are shown in Table 1.

[0156] Table 1

[0157]

[0158]

[0159]

[0160] 1 M n Number-average molecular weight, determined by gel permeation chromatography; 2 PDI: Molecular weight distribution, determined by gel permeation chromatography.

[0161] Table 2

[0162]

[0163] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above detailed methods.

Claims

1. A method for preparing a chemically recyclable polyaldehyde ester, characterized in that, include: The chemically recyclable polyaldehyde ester was prepared by alternating copolymerization using linear aldehydes and cyclic anhydrides as raw materials and Lewis acids or protic acids as catalysts. The linear aldehyde has the following general structural formula: In the formula, R is selected from branched alkyl or straight alkyl with 1 to 20 carbon atoms, branched alkenyl or straight alkenyl with 2 to 20 carbon atoms, branched alkynyl or straight alkynyl with 2 to 20 carbon atoms, branched terpenyl or straight terpenyl with 5 to 20 carbon atoms, branched cycloalkyl or straight cycloalkyl with 3 to 20 carbon atoms, aromatic groups with 5 to 20 carbon atoms, and the above groups containing one or more heteroatoms selected from O, S, N, Si, P, F, Cl, Br, and I. When R is selected from branched alkenyl or straight alkenyl with 2 to 20 carbon atoms, the alkenyl cannot form conjugation with the double bond in the aldehyde group; When R is selected from a branched alkynyl or straight-chain alkynyl with 2 to 20 carbon atoms, the alkynyl group cannot form a conjugation with the double bond in the aldehyde group; The cyclic anhydride is selected from one or more of glutaric anhydride, diethylene glycol anhydride, thiodiethylene glycol anhydride, 3-methylglutaric anhydride, 3,3-dimethylglutaric anhydride, 2,2-dimethylglutaric anhydride, 3-isobutylglutaric anhydride, hexafluoroglutaric anhydride, and adipic anhydride.

2. The method for preparing chemically recyclable polyaldehyde ester according to claim 1, characterized in that: The molar ratio of cyclic anhydride to linear aldehyde is 0.1~10:1; The molar ratio of catalyst to cyclic anhydride is 1:5~10000; The alternating copolymerization reaction was carried out at -20 to 60°C under autogenous pressure for 0.05 to 12 hours.

3. The method for preparing chemically recyclable polyaldehyde ester according to claim 1, characterized in that: The Lewis acid is selected from one or more of BF3, B(C6F5)3, InCl3, InBr3, SnCl4, AlCl3, SbCl5, PF5, CF3SO3Et, and Ph3CPF6; The protic acid is selected from one or more of HBF4, HClO4, CF3COOH, CF3SO4H, FSO4H, and concentrated sulfuric acid.

4. The method for preparing chemically recyclable polyaldehyde ester according to claim 1, characterized in that: The linear aldehyde is selected from one or more of the following: linear alkyl substituted alkyl aldehydes with 1 to 20 carbon atoms, cyclohexane formaldehyde, benzaldehyde, 2,3-dichlorobenzaldehyde, and lily aldehyde.

5. The method for preparing chemically recyclable polyaldehyde ester according to claim 4, characterized in that: The molar ratio of cyclic anhydride to linear aldehyde is 0.5~1.5:1; The molar ratio of catalyst to cyclic anhydride is 1:50~7500.

6. The method for preparing chemically recyclable polyaldehyde ester according to claim 5, characterized in that: The catalyst is selected from InCl3 and / or InBr3.

7. The method for preparing chemically recyclable polyaldehyde ester according to claim 1, characterized in that: The alternating copolymerization reaction was carried out at -20 to 25°C under autogenous pressure for 0.1 to 12 hours.

8. A chemically recyclable polyaldehyde ester prepared according to any one of claims 1 to 7, characterized in that: The chemically recyclable polyaldehyde ester has a fully alternating structure, with an ester unit content of ≥99%, and each repeating unit contains an aldehyde group.

9. A method for the chemical recycling of polyaldehyde esters, characterized in that, The chemically recyclable polyaldehyde ester according to claim 8 is pyrolyzed under vacuum conditions at 160-180°C.

10. The method for chemically cycling polyaldehyde ester according to claim 9, characterized in that, The chemically recyclable polyaldehyde ester is prepared by using linear aldehydes whose substituents are selected from aromatic groups with 5 to 20 carbon atoms, or aromatic groups with 5 to 20 carbon atoms containing one or more heteroatoms selected from O, S, N, Si, P, F, Cl, Br, and I.

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