Chemically recyclable biodegradable PPDO-based polyurethane material, and preparation method and application thereof

Abstract

The invention belongs to the technical field of preparation and application of polyurethane, and particularly relates to a chemically recyclable biodegradable PPDO (poly (p-dioxanone))-based polyurethane material as well as a preparation method and application thereof. According to the invention, PPDO with biodegradability and chemical recoverability is used as a main raw material, and a polyurethane material is prepared through a chain extension reaction; carbon groups, ether bonds and the like in a PPDO molecular chain can form multiple intermolecular interaction with carbamate bonds, and the polyurethane material has excellent and adjustable mechanical strength and relatively high thermal stability under the microphase separation action of polyurethane; the cyclic ester monomer in a polyurethane molecular chain can be recovered through simple pyrolysis and is used for preparing a polyurethane material again, so that complete recovery and closed-loop circulation are realized; and when being discarded in the environment, the compound can be completely biodegraded into small molecular compounds which are harmless to the environment.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation and application of polyurethane, and specifically relates to a chemically recyclable biodegradable PPDO-based polyurethane material, a preparation method and an application thereof. Background Art

[0002] The full name of polyurethane is polyurethane (PU), which is a polymer with repeated urethane ( - NHCOO - ) group. At present, commercial polyurethanes are mainly isocyanate polyurethanes, which are multi-block copolymers formed by the gradual polymerization of organic diisocyanates or polyisocyanates and dihydroxy or polyhydroxy compounds. They have the characteristics of easy molecular structure design and adjustable performance. The diverse structure, excellent performance and easy processing and molding of polyurethane make it widely used in many fields. It is usually used as plastics, rubbers, fibers, adhesives, synthetic leathers and waterproof materials. The output of polyurethane ranks sixth among global polymer materials, and its global annual output in 2022 has exceeded 75 million tons. However, the vast majority of polyurethanes currently used are non-degradable under natural conditions, difficult to recycle, and will cause problems such as environmental pollution and waste of resources.

[0003] Many countries in the world have enacted laws to restrict the use of disposable non-degradable plastics, which has greatly promoted the research and development of degradable and recyclable polyurethane. The recycling of polymers is mainly divided into physical recycling and chemical recycling. Physical recycling refers to the separation of specific polymers from waste mixtures by physical means, and then physical processing (such as hot pressing). However, physically recycled polymers are prone to yellowing due to the presence of various additives, and the appearance quality is reduced after processing. Chemical recycling of polymers refers to the process of degrading polymers into small molecules or oligomers by chemical means, and then repolymerizing them to obtain new polymers. Even polymers that are colored, contain additives or foreign materials can be recycled as valuable raw materials and then converted into new polymers for high-end applications, thus realizing a closed loop of plastic recycling.

[0004] At present, research on the chemical recycling of polyurethane is still in its infancy. Semetey et al. (ACS Omega 2021, 6, 4175-4183) reported the chemical recycling of polyether polyurethane by destroying the carbamate bond in polyurethane. However, since the carbamate bond is relatively stable, it requires harsh conditions (strong alkali and high temperature) to destroy the chemical bond, and the product is a mixture, which is extremely difficult to separate and is not conducive to industrialization. Therefore, it is still very important to develop polyurethane materials that are both recyclable and biodegradable.

[0005] The controllable introduction of ester bonds in the main chain of polymers, especially ester bonds in aliphatic polyesters, can give the material degradable and potentially recyclable properties under specific (acidic, alkaline or biological) conditions. Among them, PPDO, as a kind of aliphatic polyester, has ether bonds in the chain segments that make it flexible, while also having good degradation properties and recyclability. However, the performance of a single polymer cannot be adjusted, which limits its application. Therefore, it is currently a problem that needs to be solved to propose a biodegradable PPDO-based polyurethane material that can be chemically recycled and a preparation method thereof. Summary of the invention

[0006] In view of this, in order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a chemically recyclable biodegradable PPDO-based polyurethane material, a preparation method and an application thereof. The method of the present invention utilizes PPDO to polymerize with other aliphatic polycyclic esters, thereby giving the material adjustable degradation performance and recyclability, and having good mechanical strength and thermal stability.

[0007] A method for preparing a chemically recyclable biodegradable PPDO-based polyurethane material comprises the following steps

[0008] The polydioxanone prepolymer and the aliphatic polyester prepolymer are mixed to obtain a mixture, the mixture is heated, and a chain extender is added to react to obtain a chemically recyclable and biodegradable PPDO-based polyurethane material.

[0009] Furthermore, the aliphatic polyester prepolymer is any one or more of polycaprolactone, polylactide and polyglycolide.

[0010] Furthermore, the chain extender is any one or more of diisocyanates such as 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, toluene diisocyanate or xylylene diisocyanate.

[0011] Furthermore, the temperature of the heating process is 120-220° C., and the reaction time is 5-300 min.

[0012] Furthermore, the polydioxanone prepolymer and the aliphatic polyester prepolymer have hydroxyl groups at both ends and a molecular weight of 1000 to 20000 Da.

[0013] A chemically recyclable biodegradable PPDO-based polyurethane material comprises a PPDO prepolymer, an aliphatic polyester prepolymer and a chain extender.

[0014] Furthermore, the mass ratio of the aliphatic polyester prepolymer is 1% to 50%.

[0015] The invention discloses an application of a chemically recyclable biodegradable PPDO-based polyurethane material. The chemically recyclable biodegradable PPDO-based polyurethane material is applied in the preparation of biomedical materials, textiles, general plastics, daily chemicals and recyclable materials.

[0016] Beneficial Effects

[0017] (1) The present invention provides a chemically recyclable biodegradable PPDO-based polyurethane material, wherein the carbon groups and ether bonds in the PPDO molecular chain can form multiple molecular interactions with the carbamate bonds, so that the obtained polyurethane material has excellent mechanical strength and high thermal stability.

[0018] (2) According to the method for preparing a chemically recyclable biodegradable PPDO-based polyurethane material provided by the present invention, the crystallinity of the polyurethane can be regulated by changing the chain segment ratio of the aliphatic polyester prepolymer. The presence of other aliphatic polycyclic ester chains reduces the intermolecular forces between the PPDO chains, hinders the orderly arrangement of the molecular chains, and reduces the orderliness of the molecular chains. Therefore, the crystalline area is reduced, thereby effectively reducing the crystallinity of the polyurethane material.

[0019] (3) Through the application of a chemically recyclable biodegradable PPDO-based polyurethane material provided by the present invention, the polyurethane material has good degradation performance and can be completely biodegraded into small molecule compounds that are harmless to the environment. It can be used as an environmentally friendly material. The polyurethane can recover the cyclic ester monomers in the polyurethane molecular chain through simple pyrolysis and be used again to prepare the polyurethane material, thereby achieving complete recovery and closed-loop circulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0021] Figure 1 1H NMR spectra of PPDO-PLA segmented polyurethanes in Examples 1 to 3 of the present invention;

[0022] Figure 2 The thermogravimetric (TG) curve of the PPDO-PLA segmented polyurethane in Examples 1 to 3 of the present invention;

[0023] Figure 3 is a differential scanning calorimetry (DSC) diagram of the PPDO-PLA segmented polyurethane in Examples 1 to 3 of the present invention;

[0024] Figure 4 1 is a stress-strain curve diagram of the PPDO-PLA segmented polyurethane in Examples 1 to 3 of the present invention;

[0025] Figure 5 This is a graph showing the mass loss variation during the degradation process of the PPDO-PLA segmented polyurethane in Examples 1 to 3 of the present invention;

[0026] Figure 6 This is a scanning electron microscope image of a monofilament fiber prepared from the PPDO-PLA segmented polyurethane material in Example 2 of the present invention;

[0027] Figure 7 This is the 1H NMR spectrum of the PPDO-PLA segmented polyurethane material recovery and separation product in Example 8 of the present invention;

[0028] Figure 8 This is a comparison chart of the thermal properties of the repolymerized polyurethane material and the original polyurethane material in Example 8 of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with embodiments 1 to 5 of the present invention and the attached Figures 1 to 8 , the technical solution of the present invention is clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The present invention provides a method for preparing a chemically recyclable biodegradable PPDO-based polyurethane material, comprising the following steps: weighing PPDO (polydioxanone) and PLA (polylactic acid), mixing the two evenly and adding them into a three-necked flask, heating them until they are completely melted, and then adding a chain extender to carry out a chain extension reaction, the reaction process is carried out under the protection of an inert gas N2, and polyurethane is obtained.

[0031] Example 1

[0032] Weigh 45g of PPDO and 5g of PLA, mix them evenly and add them into a three-necked flask, heat them to 180°C, and add 1,6-hexamethylene diisocyanate to carry out chain extension reaction after they are completely melted. The reaction is carried out under the protection of inert gas N2 for 1h to obtain polyurethane.

[0033] Example 2

[0034] Weigh 40g of PPDO and 10g of PLA, mix them evenly and add them into a three-necked flask, heat them to 160°C, and add 1,6-hexamethylene diisocyanate after they are completely melted to carry out chain extension reaction. The reaction is carried out under the protection of inert gas N2 for 1h to obtain polyurethane.

[0035] from Figure 6 It can be seen that Figure 6 This is a scanning electron microscope image of the monofilament fiber prepared from the PPDO-PLA segmented polyurethane material in this embodiment.

[0036] Example 3

[0037] Weigh 25g of PPDO and 25g of PLA, mix them evenly and add them into a three-necked flask, heat them to 160°C, and after they are completely melted, add 1,-hexamethylene diisocyanate to carry out chain extension reaction. The reaction is carried out under the protection of inert gas N2 for 1h to obtain polyurethane.

[0038] from Figure 1 It can be seen that Figure 1 1H NMR diagram of PPDO-PLA segmented polyurethane in this example; Figure 1 As shown, in addition to the characteristic peaks of PPDO and PLA, δ=7.4ppm is the proton peak of NH in the carbamate group; indicating that the method of the present invention can successfully prepare a PPDO-PLA based block polyurethane. Figure 2 It can be seen that Figure 2 is the thermogravimetric (TG) diagram of the PPDO-PLA segmented polyurethane in Examples 1, 2, and 3; Figure 2 As shown, the obtained PPDO-PLA block polyurethane has higher thermal stability.

[0039] from Figure 3 It can be seen that Figure 3 is the differential scanning calorimetry (DSC) diagram of the PPDO-PLA segmented polyurethane in Examples 1, 2, and 3; Figure 3 As shown in the figure, the melting enthalpy of the obtained PPDO-PLA segmented polyurethane decreases with the increase of PLA content. This is because the presence of other aliphatic polycyclic ester chains reduces the intermolecular forces between PPDO chains, hinders the orderly arrangement of the molecular chains, and reduces the orderliness of the molecular chains. Therefore, the crystalline area is reduced, thereby effectively reducing the crystallinity of the polyurethane material.

[0040] from Figure 4 It can be seen that Figure 4 are the mechanical properties of the PPDO-PLA segmented polyurethanes in Examples 1, 2, and 3; Figure 4 As shown, the mechanical properties of the obtained PPDO-PLA segmented polyurethane increase with the increase of PLA content, while the elongation at break decreases with the increase of PLA content, indicating that the mechanical properties of the polyurethane material can be adjusted by adjusting the PLA content in the polyurethane material of the present invention.

[0041] Figure 5 The mass loss variation rule of the degradation process of PPDO-PLA segmented polyurethane in Examples 1, 2 and 3 is shown in FIG. Figure 5 It can be seen from the figure that the degradation performance of the polyurethane material can be adjusted by adjusting the content of PLA in the polyurethane material of the present invention.

[0042] Example 4

[0043] Weigh 45g of PPDO and 5g of PCL, mix them evenly and add them into a three-necked flask, heat them to 220°C, and add 1-6-hexamethylene diisocyanate after they are completely melted to carry out chain extension reaction. The reaction is carried out under the protection of inert gas N2 for 1h to obtain polyurethane.

[0044] Example 5

[0045] Weigh 45 g of PPDO and 5 g of PGA, mix them evenly and add them into a three-necked flask, heat them to 220°C, and add 1,6-hexamethylene diisocyanate after they are completely melted to carry out chain extension reaction. The reaction is carried out under the protection of inert gas N2 for 1 hour to obtain polyurethane.

[0046] The polyurethane sample obtained in Example 1 is cut into pieces and added to a reaction bottle with stannous octoate and the mixture is stirred. Using a vacuum distillation device, the reaction bottle is heated to 180°C for 6 hours. Since the boiling point and melting point of lactide and p-dioxanone monomers are different, p-dioxanone monomer and lactide monomer can be separated by controlling the cooling temperature of the recovery device to obtain pure p-dioxanone monomer and lactide monomer. The p-dioxanone monomer and lactide monomer obtained above are used again to prepare the polyurethane material according to the preparation method described in Example 1 of the present invention to obtain a repolymerized product.

[0047] from Figure 7 It can be seen that the relatively pure monomers obtained by simple depolymerization and separation can realize the recovery of polyurethane. Figure 8 It can be seen that the performance of the polyurethane obtained by repolymerization is almost the same as that of the original polyurethane material, which proves that the polyurethane material can be recycled in a closed loop.

[0048] The chemically recyclable biodegradable PPDO-based polyurethane material provided by the present invention demonstrates excellent technical effects. Through the multiple intermolecular interactions formed by the carbon group, ether bond and carbamate bond in the PPDO molecular chain, the material has excellent mechanical strength and thermal stability. In addition, during the material preparation process, by adjusting the segment ratio of the aliphatic polyester prepolymer, the polyurethane crystallinity is effectively reduced, the molecular chain order is optimized, and its performance is improved. In terms of application, the material can be completely biodegraded into environmentally harmless small molecule compounds, and the cyclic ester monomers in the polyurethane molecular chain can be recovered by simple pyrolysis and reused in preparation, achieving a completely closed-loop cycle, showing significant environmental protection and resource recycling value.

Claims

1. A method for preparing a chemically recyclable biodegradable PPDO-based polyurethane material, characterized in that: The following steps are involved: The polydioxanone prepolymer and the aliphatic polyester prepolymer are mixed to obtain a mixture, the mixture is heated, and a chain extender is added to react to obtain a chemically recyclable and biodegradable PPDO-based polyurethane material.

2. The method for preparing a chemically recyclable biodegradable PPDO-based polyurethane material according to claim 1, characterized in that: The aliphatic polyester prepolymer is any one or any combination of polycaprolactone, polylactide and polyglycolide.

3. The method for preparing a chemically recyclable biodegradable PPDO-based polyurethane material according to claim 1, characterized in that: The chain extender is any one or several of diisocyanates such as 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, toluene diisocyanate or xylylene diisocyanate.

4. The method for preparing a chemically recyclable biodegradable PPDO-based polyurethane material according to claim 1, characterized in that: The temperature of the heating process is 120-220° C., and the reaction time is 5-300 minutes.

5. The method for preparing a chemically recyclable biodegradable PPDO-based polyurethane material according to claim 1, characterized in that: The polydioxanone prepolymer and the aliphatic polyester prepolymer have hydroxyl groups at both ends and a molecular weight of 1000-20000 Da.

6. A chemically recyclable biodegradable PPDO-based polyurethane material obtained by the preparation method according to any one of claims 1 to 5, characterized in that: The materials include PPDO prepolymer, aliphatic polyester prepolymer and chain extender.

7. The chemically recyclable biodegradable PPDO-based polyurethane material according to claim 6, characterized in that: The mass ratio of the aliphatic polyester prepolymer is 1% to 50%.

8. The use of a chemically recyclable biodegradable PPDO-based polyurethane material according to claim 6, characterized in that: The chemically recyclable biodegradable PPDO-based polyurethane material is used in the preparation of biomedical materials, textiles, general plastics, daily chemicals and recyclable materials.

Images