CO2-based thermoplastic polyurethane and preparation method thereof

Abstract

The invention discloses CO2-based thermoplastic polyurethane and a preparation method thereof. The method adopts a one-pot two-step reaction and comprises the following steps: firstly, performing ring-opening copolymerization on alpha-ethylidene-delta-vinyl-delta-valerolactone (EVP) (from telomerization of CO2 and 1, 3-butadiene) and a cyclic monomer (cyclic lactone or cyclic carbonate) to prepare unsaturated copolyester polyol with a side chain containing carbon-carbon double bonds; and taking the polyol as a soft segment, and reacting with diisocyanate and a chain extender to obtain the thermoplastic polyurethane. Controllable transformation of the material from a crystalline state to an amorphous state and from a plastomer to a high-elastic body is realized by regulating and controlling the EVP content (0-19 mol%). The obtained material can be selectively subjected to bulk depolymerization under the action of a catalyst, is efficiently recovered into EVP and a cyclic monomer, and has good chemical recovery performance. Meanwhile, side chain double bonds provide reaction sites for subsequent functionalization, so that the polymer has good application prospects in the fields of elastomers, adhesives, biomedical materials and the like.

Description

Technical Field

[0001] This invention relates to the fields of polymer materials and chemical engineering, specifically to a CO2-based thermoplastic polyurethane and its preparation method. Background Technology

[0002] Polyurethane materials, due to their outstanding performance in elasticity, abrasion resistance, and processability, have been widely used in various fields such as elastomers, adhesives, coatings, and biomedicine. Based on the different chemical structures of their soft segments, polyurethanes are mainly divided into two categories: polyether-based and polyester-based. Compared to polyether-based polyurethanes, polyester-based polyurethanes generally exhibit better thermal stability and mechanical strength. However, traditional polyester soft segments lack modifiable functional groups, limiting further expansion of material properties and functional applications.

[0003] α-Ethylene-δ-vinyl-δ-valerolactone (EVP) is a green monomer with atom economy, obtained by telomerization of CO2 and 1,3-butadiene. This monomer contains one lactone ring and two carbon-carbon double bonds with different reactivity, allowing for the preparation of unsaturated polyesters with double bonds in the side chains via ring-opening polymerization, providing reaction sites for subsequent functionalization modifications. However, due to the low ring strain of EVP, its ring-opening polymerization faces certain thermodynamic and kinetic challenges. To overcome this bottleneck, a copolymerization strategy has been adopted, copolymerizing EVP with monomers with higher ring strain (such as ε-caprolactone and β-butyrolactone). The enthalpy change released during ring-opening of the high-strain monomer drives the ring-opening insertion of EVP under mild conditions (ACS Macro Letters, 2021, 10: 1055-1060; Macromolecules, 2025, 58: 3497-3508). Currently, there are no reports on the use of EVP-based copolyester polyols in the preparation of thermoplastic polyurethanes.

[0004] In view of this, the present invention provides a CO2-based thermoplastic polyurethane and its preparation method. Compared with the prior art, the present invention has the following advantages: (1) By introducing EVP into the polyurethane main chain and controlling the EVP content (0~19 mol%), the polyurethane material is transformed from a crystalline state to an amorphous state and from a plastic body to a highly elastic body. (2) Thermoplastic polyurethane can be selectively depolymerized and recycled into monomers in the presence of a catalyst, realizing efficient chemical recycling. (3) The carbon-carbon double bonds of EVP provide a structural basis for subsequent functionalization modification and have broad application prospects in the fields of elastomers, adhesives, coatings and biomedical materials. Summary of the Invention

[0005] The purpose of this invention is to provide a CO2-based thermoplastic polyurethane and its preparation method, comprising the following steps: (1) Dissolve the polyol initiator, alkali and urea in an organic solvent and stir and mix them at -20 ~ 50 ℃. Add the mixture of α-ethylene-δ-vinyl-δ-valerol with cyclic lactone and cyclic carbonate to the above mixed solution and polymerize at -20 ~ 50 ℃ for a period of time. Add an acidic substance to terminate the reaction and add the reaction solution to methanol to precipitate and obtain CO2-based copolyester polyol. (2) CO2-based copolyester polyol is mixed with isocyanate, a catalyst is added, and the mixture is reacted at 60-100 °C for 1-6 h to obtain isocyanate-terminated prepolymer; (3) Add a chain extender to the prepolymer and react at 10~80 °C for 10~24 h to obtain the CO2-based thermoplastic polyurethane; In the above preparation method, the chemical structure of the CO2-based thermoplastic polyurethane is shown in formula (Ⅰ):

[0006] Its characteristic is that m and n are natural numbers greater than or equal to 5, and x and y are natural numbers greater than or equal to 5; wherein R2 has the following structure:

[0007] R3 has the following structure:

[0008] R4 has the following structure: .

[0009] In the above preparation method, the polyol initiator in step (1) is one or more of ethylene glycol, propylene glycol, 1,4-phenyldiethanol, glycerol, pentaerythritol, 1,6-hexanediol, diethylene glycol, or trihydroxypropane; the base is an alkali metal compound or an organophosphorus nitrile base catalyst, specifically potassium hydride, sodium hydride, potassium methoxide, sodium methoxide, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo(4.4.0)dec-5-ene (TBD), hexa[tris(dimethylamine)phosphazene]tripolyphosphazene ({[(NMe2)3P=N]2P=N}3), phosphazene ligand P4-tert-butyl ([(NMe2)3P=N]3P=NtBu, t-BuP4), phosphazene ligand P2-tert-butyl ([(NMe2)3P=N](NMe2)2P=NtBu, t-BuP2); the cyclic ester and carbonate are one of ε-caprolactone, δ-valerolactone, γ-butyrolactone, cyclopentadecanolactone and trimethylene carbonate, ethylene carbonate, and propylene carbonate; the acidic substance is at least one of acetic acid, benzoic acid, hydrochloric acid, sulfuric acid, phosphoric acid, and diphenyl phosphate.

[0010] In the above preparation method, the urea mentioned in step (1) is a co-catalyst with the following structure:

[0011] In the above preparation method, the molar ratio of the strong base to the polyol initiator in step (1) is 0.1 / 1 to 5 / 1; the molar ratio of the strong base to the co-catalyst is 1 / 0.2 to 1 / 2; and the molar ratio of EVP to cyclic lactone or cyclic carbonate is 1 / 9 to 9 / 1.

[0012] In the above preparation method, the catalyst in step (2) is selected from N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, triethylamine, triethylenediamine, N,N-dimethylbenzylamine, N-ethylmorpholine, N-methylmorpholine, N,N'-diethylpiperazine, pyridine, 4-dimethylaminopyridine, dibutyltin dilaurate, and stannous octoate. The isocyanate is toluene diisocyanate, methylcyclohexyl diisocyanate, isophorone diisocyanate, terephthalic diisocyanate, 4,4'-diisocyanate-3,3'-dimethyl-1,1'-biphenyl, cyclohexyldimethylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and 1,5-naphthalene diisocyanate.

[0013] In the above preparation method, the molar ratio of isocyanate to polyol initiator in step (2) is 1 / 1 to 5 / 1; the catalyst accounts for 0.01 to 10 wt% of the polyol mass.

[0014] In the above preparation method, in step (3), the molar ratio of the chain extender to the polyol initiator is 0.2 / 1 to 6 / 1. Attached Figure Description

[0015] Figure 1 The image shows the infrared spectrum of the polyurethane prepared in Example 1.

[0016] Figure 2 The image shows the GPC diagrams of the polyurethanes prepared in Examples 1, 2, and 3.

[0017] Figure 3 The image shows the tensile curves of the polyurethanes prepared in Examples 1, 2, and 3, with a tensile rate of 50 mm / min.

[0018] Figure 4 The polyurethane prepared in Example 3 1 H NMR spectrum.

[0019] Figure 5 This is a comparison chart of the lap shear strengths of the three polyurethanes (Examples 1, 2, and 3) measured in Example 10. Figure 6 This refers to the recovery of polyurethane (Example 2) and the recovered products in Example 11. 1 H NMR superimposed spectrum. Detailed Implementation

[0020] The following embodiments illustrate the present invention in detail, but the present invention is not limited to these embodiments.

[0021] Unless otherwise specified, all materials and reagents used in the following implementation examples are commercially available.

[0022] Example 1 1,5,7-Triazabicyclo(4.4.0)dec-5-ene (0.8 mmol, 111.2 mg), co-catalyst U5 (0.4 mmol, 179.2 mg), and 1,4-phenyldiethanol (2.4 mmol, 331.2 mg) were added to a reaction tube and dissolved in 11.6 mL of tetrahydrofuran. The mixture was equilibrated at -10 °C for 10 min. Then, α-ethylidene-δ-vinyl-δ-valerolactone (12 mmol, 1.56 mL) and ε-caprolactone (60 mmol, 5.3 mL) were added using a syringe. After reacting for 3 h under nitrogen protection, a small amount of acetic acid was added to terminate the reaction. The product was precipitated in ice-cold methanol to obtain poly(EVP- co -CL) diol. NMR calculations showed that the molar content of EVP was 6%, and the molecular weight was 3.7 kg / mol. The above poly(EVP- co -CL)(2 g, 0.57 mmol) was added to a reaction flask, and the mixture was stirred in an oil bath at 80 °C for 10 min. Then, isoflurane diisocyanate (253 mg, 1.1 mmol), dibutyltin dilaurate (4 mg, 0.2 wt%), and 4 mL of [amount missing] were added. N, N -Dimethylacetamide was reacted for 3 h to obtain an isocyanate-terminated prepolymer. The mixture was then cooled to 40 °C, and adipic acid dihydrazide (99 mg, 0.57 mmol) and 12 mL of [amount missing] were added. N, N -Dimethylacetamide, reacted for 13 h. The reaction solution was precipitated with methanol to obtain polyurethane. The infrared spectrum showed that the characteristic peak of isocyanate disappeared, indicating that the reaction was complete. Figure 1 GPC analysis showed that the number-average molecular weight of the polyurethane was 21.6 kg / mol, and the molecular weight distribution was 2.83 ( ). Figure 2 The polyurethane with this EVP content exhibits excellent mechanical properties, with a tensile strength of 34 MPa, an elongation at break of 1000%, and significant yielding behavior. Figure 3 The bond strength is 4.76 MPa, as shown. Figure 5 As shown.

[0023] Example 2 Except for the monomer feeding ratio, the remaining steps were the same as in Example 1. (24 mmol, 3.1 mL) α-ethylidene-δ-vinyl-δ-valerolactone and (48 mmol, 5.3 mL) ε-caprolactone were added. The resulting poly(EVP-co-CL) had an EVP molar fraction of 11% and a Mn of 3.8 kg / mol. The final polyurethane had a Mn of 29.0 kg / mol and a K of 3.24 (see Example 1). Figure 2 The material exhibits elastomeric behavior, with a tensile strength of 33 MPa and an elongation at break of 1079% (see...). Figure 3 The bond strength is 1.57 MPa (see...). Figure 5 ).

[0024] Example 3 Except for the monomer feeding ratio, the remaining steps were the same as in Example 1. (36 mmol, 4.7 mL) α-ethylidene-δ-vinyl-δ-valerolactone and (48 mmol, 5.3 mL) ε-caprolactone were added. The resulting poly(EVP-co-CL) had an EVP molar fraction of 19% and a Mn of 3.8 kg / mol. The final polyurethane had a Mn of 31.4 kg / mol and a K of 2.91 (see...). Figure 2 The material has a tensile strength of 2 MPa and an elongation at break of 1856% (see...). Figure 3 Its ¹H NMR spectrum is shown in [reference needed]. Figure 6 The bond strength is 0.72 MPa (see...). Figure 5 ).

[0025] Example 4 Except for the monomer type, the remaining steps were the same as in Example 1. (25 mmol, 4.8 mL) α-ethylidene-δ-vinyl-δ-valerolactone and (48 mmol, 3.7 mL) γ-butyrolactone were added. Under this catalytic system, γ-butyrolactone participated in the copolymerization reaction to form poly(EVP-co-BL). The resulting polymer had an EVP molar fraction of 16% and a Mn content of 3.8 kg / mol, and the corresponding polyurethane was further prepared.

[0026] Example 5 Except for the monomer type, the remaining steps were the same as in Example 1. (25 mmol, 4.7 mL) α-ethylidene-δ-vinyl-δ-valerolactone and (25 mmol, 5.3 mL) trimethylene carbonate were added. The resulting poly(EVP-co-TMC) had an EVP molar fraction of 12% and a Mn content of 3.9 kg / mol, and the corresponding polyurethane was further prepared.

[0027] Example 6 1,5,7-Triazabicyclo(4.4.0)dec-5-ene (0.8 mmol, 111.2 mg), co-catalyst U5 (0.4 mmol, 179.2 mg), and 1,4-phenyldiethanol (2.4 mmol, 331.2 mg) were added to a reaction tube and dissolved in 11.6 mL of tetrahydrofuran. The mixture was equilibrated at -10 °C for 10 min. Then, α-ethylidene-δ-vinyl-δ-valerolactone (12 mmol, 1.56 mL) and ε-caprolactone (60 mmol, 5.3 mL) were added using a syringe. After reacting for 3 h under nitrogen protection, a small amount of acetic acid was added to terminate the reaction. The reaction solution was precipitated in ice-cold methanol to obtain poly(EVP- co -CL) diol. NMR calculations showed that the molar content of EVP was 6%, and the molecular weight was 3.7 kg / mol. The above poly(EVP- co -CL)(0.8 g, 0.21 mmol) was added to a reaction flask, and the mixture was stirred in an 80 °C oil bath for 10 min. Then, hexamethylene diisocyanate (70.6 mg, 0.42 mmol), dibutyltin dilaurate (2 mg, 0.2 wt%), and 1 mL of [amount missing] were added. N, N The reaction with dimethylacetamide for 3 h yielded an isocyanate-terminated prepolymer. The mixture was then cooled to 40 °C, and adipic acid dihydrazide (36.5 mg, 0.21 mmol) and 5 mL of [unspecified solution] were added. N, N -Dimethylacetamide, reacted for 14 h. The reaction solution was precipitated with methanol to obtain polyurethane.

[0028] Example 7 1,5,7-Triazabicyclo(4.4.0)dec-5-ene (0.8 mmol, 111.2 mg), co-catalyst U5 (0.4 mmol, 179.2 mg), and 1,4-phenyldiethanol (2.4 mmol, 331.2 mg) were added to a reaction tube and dissolved in 11.6 mL of tetrahydrofuran. The mixture was equilibrated at -10 °C for 10 min. Then, α-ethylidene-δ-vinyl-δ-valerolactone (12 mmol, 1.56 mL) and ε-caprolactone (60 mmol, 5.3 mL) were injected using a syringe. After reacting for 3 h under nitrogen protection, a small amount of acetic acid was added to terminate the reaction. The reaction solution was precipitated in ice-cold methanol to obtain poly(EVP- co -CL) diol. NMR calculations showed that the molar content of EVP was 6%, and the molecular weight was 3.7 kg / mol. The above poly(EVP- co-CL)(0.92 g, 0.25 mmol) was added to the reaction flask, and the mixture was stirred in an 80 °C oil bath for 10 min. Then, 4,4'-dicyclohexylmethane diisocyanate (130 mg, 0.5 mmol), dibutyltin dilaurate (2 mg, 0.2 wt%), and 2 mL of [unspecified substance] were added. N, N -Dimethylacetamide was reacted for 3 h to obtain an isocyanate-terminated prepolymer. The mixture was then cooled to 40 °C, and (43.5 mg, 0.25 mmol) adipicohydrazide and 6 mL of [unspecified solution] were added. N, N -Dimethylacetamide, reacted for 15 h. The reaction solution was precipitated with methanol to obtain polyurethane.

[0029] Example 8 1,5,7-Triazabicyclo(4.4.0)dec-5-ene (0.8 mmol, 111.2 mg), co-catalyst U5 (0.4 mmol, 179.2 mg), and 1,4-phenyldiethanol (2.4 mmol, 331.2 mg) were added to a reaction tube and dissolved in 11.6 mL of tetrahydrofuran. The mixture was equilibrated at -10 °C for 10 min. Then, α-ethylidene-δ-vinyl-δ-valerolactone (12 mmol, 1.56 mL) and ε-caprolactone (60 mmol, 5.3 mL) were injected using a syringe. After reacting for 3 h under nitrogen protection, a small amount of acetic acid was added to terminate the reaction. The reaction solution was precipitated in ice-cold methanol to obtain poly(EVP- co -CL) diol. NMR calculations showed that the molar content of EVP was 6%, and the molecular weight was 3.7 kg / mol. The above poly(EVP- co -CL)(0.88 g, 0.24 mmol) was added to a reaction flask, and the mixture was stirred in an oil bath at 80 °C for 10 min. Then, isoflurane diisocyanate (105.1 mg, 0.48 mmol), dibutyltin dilaurate (2 mg, 0.2 wt%), and 2 mL of [amount missing] were added. N, N -Dimethylacetamide was reacted for 3 h to obtain an isocyanate-terminated prepolymer. The mixture was then cooled to 40 °C, and 1,4-butanediol (21.3 mg, 0.24 mmol) and 9 mL of [unspecified solution] were added. N, N The reaction mixture was reacted with dimethylacetamide for 15 h. The reaction solution was then precipitated with methanol to obtain polyurethane.

[0030] Example 9 1,5,7-Triazabicyclo(4.4.0)dec-5-ene (0.8 mmol, 111.2 mg), co-catalyst U5 (0.4 mmol, 179.2 mg), and 1,4-phenyldiethanol (2.4 mmol, 331.2 mg) were added to a reaction tube and dissolved in 11.6 mL of tetrahydrofuran. The mixture was equilibrated at -10 °C for 10 min. Then, α-ethylidene-δ-vinyl-δ-valerolactone (12 mmol, 1.56 mL) and ε-caprolactone (60 mmol, 5.3 mL) were injected using a syringe. After reacting for 3 h under nitrogen protection, a small amount of acetic acid was added to terminate the reaction. The reaction solution was precipitated in ice-cold methanol to obtain poly(EVP- co -CL) diol. NMR calculations showed that the molar content of EVP was 6%, and the molecular weight was 3.7 kg / mol. The above poly(EVP- co -CL)(1 g, 0.27 mmol) was added to a reaction flask, and the mixture was stirred in an oil bath at 80 °C for 10 min. Then, isoflurane diisocyanate (119.4 mg, 0.54 mmol), dibutyltin dilaurate (4 mg, 0.2 wt%), and 2 mL of [amount missing] were added. N, N -Dimethylacetamide was reacted for 3 h to obtain an isocyanate-terminated prepolymer. The mixture was then cooled to 40 °C, and 7 mL of 3,3'-dichloro-4,4'-diaminophenylmethane (71.8 mg, 0.27 mmol) and 7 mL of [unspecified ingredient] were added. N, N -Dimethylacetamide, reacted for 15 h. The reaction solution was precipitated with methanol to obtain polyurethane.

[0031] Example 10 Using polyurethanes with different EVP contents obtained in Examples 1–3 as adhesives, the lap shear strength was tested using single lap joints (aluminum plate / polyurethane / aluminum plate) according to ASTM D3164-03 standard. The lap area size was 25 mm × 12.5 mm. After the samples were left to stand overnight at room temperature (23 ± 2 ℃), they were tested using a universal testing machine at a tensile rate of 5.0 mm / min. The results show that the lap shear strength gradually decreases with increasing EVP content. See [details omitted]. Figure 5 .

[0032] Example 11 The polyurethane obtained in Example 2 was shredded, mixed with 5 wt% stannous octoate, and added to a dry reaction flask. Under reduced pressure distillation, the reaction was carried out at 170 °C for 16 h, recovering α-ethylidene-δ-vinyl-δ-valerolactone and ε-caprolactone, with a yield of approximately 94%. The original polyurethane, recovered products, and monomers were... 1 The H NMR spectrum overlay is shown in the image. Figure 6 .

Claims

1. A CO2-based thermoplastic polyurethane and its preparation method, characterized in that, Includes the following steps: (1) Dissolve the polyol initiator, alkali and urea in an organic solvent and stir and mix them at -20 ~ 50 ℃. Add α-ethylidene-δ-vinyl-δ-valerolactone (EVP) to the above mixed solution after mixing with cyclic lactone or cyclic carbonate. Polymerize at -20 ~ 50 ℃ for a period of time. Add an acidic substance to terminate the reaction. Add the reaction solution to methanol to precipitate and obtain CO2-based copolyester polyol. (2) CO2-based copolyester polyol is mixed with isocyanate, a catalyst is added, and the mixture is reacted at 60-100 °C for 1-6 h to obtain isocyanate-terminated prepolymer; (3) Add chain extender to prepolymer and react at 10~80 °C for 6~24 h to obtain CO2-based thermoplastic polyurethane.

2. The method according to claim 1, characterized in that, The chemical structure of the CO2-based thermoplastic polyurethane is shown in formula (Ⅰ): Its characteristic is that m and n are natural numbers greater than or equal to 5, and x and y are natural numbers greater than or equal to 5. R2 has the following structure: R3 has the following structure: R4 has the following structure:

3. The method according to claim 1, characterized in that, In the above preparation method, the polyol initiator in step (1) is one or more of ethylene glycol, propylene glycol, 1,4-phenyldiethanol, glycerol, pentaerythritol, 1,6-hexanediol, diethylene glycol, or trihydroxypropane; the base is an alkali metal compound or an organophosphorus nitrile base catalyst, selected from potassium hydride, sodium hydride, potassium methoxide, sodium methoxide, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo(4.4.0)dec-5-ene (TBD), hexa[tris(dimethylamine)phosphazene]tripolyphosphazene ({[(NMe2)3P=N]2P=N}3), phosphazene ligand P4-tert-butyl ([(NMe2)3P=N]3P=NtBu, The cyclic monomers are ε-caprolactone, δ-valerolactone, γ-butyrolactone, cyclopentadecanolactone, trimethylene carbonate, ethylene carbonate, or propylene carbonate; the acidic substances are acetic acid, benzoic acid, hydrochloric acid, sulfuric acid, phosphoric acid, or diphenyl phosphate.

4. The method according to claim 1, characterized in that, In the above preparation method, the urea in step (1) has one of the following structures:

5. The method according to claim 1, characterized in that, In step (1), the molar ratio of the base to the polyol initiator is 0.1 / 1 to 5 / 1; the molar ratio of the base to the cocatalyst is 1 / 0.2 to 1 / 2; and the molar ratio of the EVP to the cyclic lactone or cyclic carbonate is 1 / 9 to 9 / 1.

6. The method according to claim 1, characterized in that, The catalyst in step (2) is selected from N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, triethylamine, triethylenediamine, N,N-dimethylbenzylamine, N-ethylmorpholine, N-methylmorpholine, N,N'-diethylpiperazine, pyridine, 4-dimethylaminopyridine, dibutyltin dilaurate, and stannous octoate; the isocyanate is selected from toluene diisocyanate, methylcyclohexyl diisocyanate, isophorone diisocyanate, terephthalic diisocyanate, 4,4'-diisocyanate-3,3'-dimethyl-1,1'-biphenyl, cyclohexyldimethylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, 1 5-Naphthalene diisocyanate; the chain extender is a diol or diamine compound selected from one or more of ethylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, adipate dihydrazide, p-phenylenediamine, 4,4′-diaminodiphenylmethane or 3,3′-dichloro-4,4′-diaminodiphenylmethane.

7. The method according to claim 1, characterized in that, In the above preparation method, the molar ratio of isocyanate to polyol initiator in step (2) is 1 / 1 to 5 / 1; the mass of the catalyst accounts for 0.01 to 10 wt% of the mass of the polyol.

8. The method according to claim 1, characterized in that, In the above preparation method, the molar ratio of the chain extender to the polyol initiator in step (3) is 0.2 / 1 to 6 / 1.

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