Preparation method of biodegradable polyether polyurethane sponge

Abstract

The invention discloses a preparation method of biodegradable polyether type polyurethane sponge, and relates to the technical field of biodegradable materials.The preparation method comprises the following steps of prepolymer preparation, chain extension reaction, dual pore-forming treatment and post-curing. The preparation method has the advantages that polyether polyol containing ester bonds and a bio-based chain extender are introduced, so that the polyether type polyurethane sponge is prepared; by combining a dual pore-forming process, efficient and controllable biodegradation of the polyurethane sponge is realized, the synergistic effect of through macropores and microporous walls in a hierarchical pore structure accelerates permeation of moisture and enzyme, so that the degradation rate of the material exceeds 90% within 60 days, and meanwhile, gradual disintegration of a hard-segment crystalline region and directional hydrolysis of a soft-segment ester bond form complementation, so that the degradation rate of the material exceeds 90% within 60 days. The problem that traditional polyurethane is difficult to give consideration to both degradation rate and structural stability is solved, and environmental residue pollution is effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of biodegradable materials, in particular to a method for preparing a biodegradable polyether polyurethane sponge. Background Art

[0002] Traditional polyurethane sponges are widely used in medical and environmental fields due to their excellent elasticity and liquid absorption properties. However, their non-degradability poses a serious environmental burden. Conventional polyurethane materials in existing technologies are mostly based on petroleum-based raw materials. After long-term use, they are difficult to decompose naturally, which not only increases resource consumption but also generates microplastic pollution. In addition, the single pore structure formed by conventional foaming processes often cannot achieve a high liquid absorption rate and mechanical strength at the same time, limiting its application in complex scenarios. In recent years, researchers have tried to improve the environmental friendliness and functionality of polyurethane materials by introducing bio-based ingredients or improving the foaming process, but most solutions still have obvious shortcomings. For example, the sole use of bio-based chain extenders may lead to a decrease in the mechanical properties of the material, and single pore-forming technology is difficult to achieve coordinated regulation of multi-level pore structure, resulting in difficulty in balancing degradation rate and material stability. Based on this, there is an urgent need for a polyurethane sponge preparation method that takes into account biodegradability, multi-level pore structure and high performance to meet the dual needs of green environmental protection and industrial applications. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing biodegradable polyether polyurethane sponge.

[0004] To achieve the above object, the present invention provides the following technical solution: a method for preparing a biodegradable polyether polyurethane sponge, the preparation method comprising the following steps: (1) Preparation of prepolymer: In the presence of a carboxylic acid catalyst, a polyether polyol having an ester bond molar ratio of 5-10% and a polyisocyanate are reacted at 70-80° C. for 2-3 hours to obtain an isocyanate-terminated prepolymer; (2) Chain extension reaction: adding a bio-based chain extender to the prepolymer, wherein the bio-based chain extender is a castor oil derivative having a hydroxyl value of 160-180 mgKOH / g, and the amount of the bio-based chain extender accounts for 10-20% of the mass of the prepolymer, and reacting at 60-70° C. for 1 hour to form an elastomer base material; (3) Double pore treatment: a) placing the elastomer base material in a supercritical CO2 reactor and foaming it at a pressure of 15-20 MPa and a temperature of 45-55°C for 30 minutes, with the pressure release rate controlled at 5 MPa / s, to form a through-hole macroporous matrix; b) immersing the foamed substrate in deionized water, freezing it at -30°C for 6 hours, and then freeze-drying it at -50°C under a vacuum of 0.1 mBar for 24 hours; (4) Post-curing: Heat treatment at 80°C for 2 hours to obtain a polyurethane sponge with a multi-level pore structure.

[0005] As a further solution of the present invention: the polyether polyol in the step (1) is prepared by mixing polytetrahydrofuran ether glycol with -caprolactone copolymerized in a molar ratio of 9:1-19:1, with a number average molecular weight of 2000±100g / mol.

[0006] As a further embodiment of the present invention: the polyisocyanate in step (1) is 4,4'-diphenylmethane diisocyanate (MDI), and the molar ratio of the polyisocyanate to the polyether polyol is 1.5:1-2.5:1.

[0007] As a further embodiment of the present invention, the macropores formed by supercritical foaming in step (3) a) have a pore diameter of 50-200 μm and a pore connectivity of ≥90%, which is verified by the following formula: ; The closed pore volume was measured using a mercury porosimeter at a pressure of 0.1 MPa.

[0008] As a further embodiment of the present invention, the micropore wall thickness formed by freeze drying in step (3) b) is 5-20 μm, the micropore specific surface area is ≥25 m² / g, and the micropore wall porosity satisfies: .

[0009] The present invention also provides a polyether polyurethane sponge, which comprises: Soft segment: polyether polyol segment containing 5-10 mol% ester bonds; Hard segment: a crystalline region formed by MDI and castor oil derivative chain extender; Multi-level pore structure: a connected network consisting of 50-200μm through-hole macropores and 5-20μm micropore walls.

[0010] As a further solution of the present invention: the degradation behavior satisfies triple regulation: On day 7, ester bond hydrolysis resulted in a mass loss of 8 ± 2%; From day 14 to day 28, enzymatic decomposition of the chain extender resulted in a cumulative mass loss of 30 ± 5%; On the 60th day, the hard segment crystallites disintegrated, resulting in a cumulative mass loss rate of >90%; The degradation kinetics conform to: ; in, , , .

[0011] As a further solution of the present invention: the performance parameters meet the following requirements: Liquid absorption rate ≥ 2500%, according to the formula: test; Wet compressive strength ≥15kPa (ASTM D3574); Elongation at break ≥ 3000% (GB / T 1040.3).

[0012] As a further solution of the present invention: the liquid penetration time is less than 3s, which is verified by a simulated blood absorption experiment, and the test standard is YY / T 0471.1-2004.

[0013] By adopting the above technical solution, compared with the prior art, the beneficial effects of the present invention are: 1. The present invention achieves efficient and controllable biodegradation of polyurethane sponge by introducing ester-bonded polyether polyols and bio-based chain extenders, combined with a dual pore-forming process. The synergistic effect of the through-hole macropores and micropore walls in the multi-level pore structure accelerates the penetration of water and enzymes, resulting in a degradation rate of over 90% within 60 days. Simultaneously, the gradual disintegration of the hard segment crystalline region complements the directional hydrolysis of the soft segment ester bonds, solving the problem of traditional polyurethanes that is difficult to balance degradation rate and structural stability, effectively reducing residual environmental pollution. 2. This invention uses a combination of supercritical CO2 foaming and freeze-drying technology to impart a multi-level interconnected pore structure to the sponge, significantly improving liquid absorption and penetration efficiency. The through-holes provide rapid liquid absorption channels, while the microporous walls enhance liquid retention through their high specific surface area. Meanwhile, the hard segment crystalline region ensures wet compressive strength. This structural design overcomes the contradiction between liquid absorption and mechanical properties of single-pore materials, meeting the needs of demanding applications such as medical dressings. 3. The present invention achieves triple regulation of degradation behavior while maintaining the high elasticity of the material through the synergistic modification of bio-based chain extenders and polyether polyols. Castor oil derivatives accelerate mid-term degradation through enzymatic hydrolysis, and the slow disintegration of hard segment microcrystals ensures the material's initial stability. This design avoids the defects of insufficient mechanical properties of traditional bio-based materials, takes into account both environmental protection and practicality, and provides a reliable solution for the large-scale application of degradable materials in environmentally friendly packaging, agriculture and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The flow chart for the preparation of biodegradable polyether polyurethane sponge. DETAILED DESCRIPTION

[0015] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings. 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.

[0016] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] Please see the attached Figure 1 The present invention provides a method for preparing a biodegradable polyether polyurethane sponge, the preparation method comprising the following steps: (1) Preparation of prepolymer: In the presence of a carboxylic acid catalyst, a polyether polyol having an ester bond molar ratio of 5-10% and a polyisocyanate are reacted at 70-80° C. for 2-3 hours to obtain an isocyanate-terminated prepolymer; (2) Chain extension reaction: adding a bio-based chain extender to the prepolymer, wherein the bio-based chain extender is a castor oil derivative having a hydroxyl value of 160-180 mgKOH / g, and the amount of the bio-based chain extender accounts for 10-20% of the mass of the prepolymer, and reacting at 60-70° C. for 1 hour to form an elastomer base material; (3) Double pore treatment: a) placing the elastomer base material in a supercritical CO2 reactor and foaming it at a pressure of 15-20 MPa and a temperature of 45-55°C for 30 minutes, with the pressure release rate controlled at 5 MPa / s, to form a through-hole macroporous matrix; b) immersing the foamed substrate in deionized water, freezing it at -30°C for 6 hours, and then freeze-drying it at -50°C under a vacuum of 0.1 mBar for 24 hours; (4) Post-curing: Heat treatment at 80°C for 2 hours to obtain a polyurethane sponge with a multi-level pore structure.

[0018] In one embodiment of the present invention: in step (1), the polyether polyol is prepared by mixing polytetrahydrofuran ether glycol with -caprolactone copolymerized in a molar ratio of 9:1-19:1, with a number average molecular weight of 2000±100g / mol.

[0019] In one embodiment of the present invention, in step (1), the polyisocyanate is 4,4'-diphenylmethane diisocyanate (MDI), and the molar ratio of the polyisocyanate to the polyether polyol is 1.5:1-2.5:1.

[0020] In one embodiment of the present invention, the macropores formed by supercritical foaming in step (3) a) have a pore diameter of 50-200 μm and a pore connectivity of ≥90%, which is verified by the following formula: ; The closed pore volume was measured using a mercury porosimeter at a pressure of 0.1 MPa.

[0021] In one embodiment of the present invention, the micropore wall thickness formed by freeze drying in step (3) b) is 5-20 μm, the micropore specific surface area is ≥25 m² / g, and the micropore wall porosity satisfies: .

[0022] The present invention also provides a polyether polyurethane sponge, the sponge comprising: Soft segment: polyether polyol segment containing 5-10 mol% ester bonds; Hard segment: a crystalline region formed by MDI and castor oil derivative chain extender; Multi-level pore structure: a connected network consisting of 50-200μm through-hole macropores and 5-20μm micropore walls.

[0023] In one embodiment of the present invention, the degradation behavior satisfies triple regulation: On the 7th day, the hydrolysis of the ester bond resulted in a mass loss of 8 ± 2%; From day 14 to day 28, enzymatic decomposition of the chain extender resulted in a cumulative mass loss of 30 ± 5%; On the 60th day, the hard segment crystallites disintegrated, resulting in a cumulative mass loss rate of >90%; The degradation kinetics conform to: ; in, , , .

[0024] In one embodiment of the present invention, the performance parameters satisfy: Liquid absorption rate ≥ 2500%, according to the formula: test; Wet compressive strength ≥ 15kPa (ASTM D3574); Elongation at break ≥ 3000% (GB / T 1040.3).

[0025] In one embodiment of the present invention, the liquid penetration time is less than 3 seconds, which is verified by a simulated blood absorption experiment, and the test standard is YY / T 0471.1-2004.

[0026] Example 1 Step (1) Prepolymer preparation Take polytetramethylene glycol (PTMG) and -Caprolactone was copolymerized in a molar ratio of 14:1 to prepare a polyether polyol with a number average molecular weight of 2000±50g / mol. 100g of the polyol was mixed with 4,4'-diphenylmethane diisocyanate (MDI) in a molar ratio of 2.0:1, and 0.1wt% of stannous octoate was added as a catalyst. The mixture was reacted at 75°C for 2.5 hours to obtain an isocyanate-terminated prepolymer. The -NCO group content was determined to be 7.8% by infrared spectroscopy (FTIR), which was consistent with the theoretical calculated value.

[0027] Step (2) Chain extension reaction The prepolymer was heated to 65°C, and 15 wt% of a castor oil derivative (modified with ethylene oxide) with a hydroxyl value of 170 mgKOH / g was added. The mixture was stirred and reacted for 1 hour. The molecular weight distribution (PDI) of the elastomer base material was measured by gel permeation chromatography (GPC) and was 1.25, indicating uniform chain extension.

[0028] Step (3) Double pore treatment a) The elastomer base material was placed in a supercritical CO2 reactor and foamed at a pressure of 18 MPa and a temperature of 50°C for 30 minutes, with a pressure relief rate of 5 MPa / s. Scanning electron microscopy (SEM) showed the formation of through macropores with a pore size of 120-180 μm and a connectivity of 92% (the closed pore volume accounted for 8% as measured by mercury porosimetry).

[0029] b) The foamed substrate was immersed in deionized water and frozen at -30°C for 6 hours. It was then freeze-dried at 0.1 mBar and -50°C for 24 hours. SEM analysis showed that the micropore wall thickness was 12±3 μm, the specific surface area was 28 m² / g, and the open porosity was 88%.

[0030] Step (4) Post-curing After heat treatment at 80°C for 2 hours, the DSC test showed that the hard segment melting peak temperature was 205°C, indicating that the crystalline region was completely formed. The final sponge had a liquid absorption rate of 2650% (ASTM D3574 standard), a wet compressive strength of 18kPa, and an elongation at break of 3200%.

[0031] Example 2 Step (1) Prepolymer preparation Polytetramethylene ether glycol and -Caprolactone was copolymerized in a molar ratio of 19:1 to prepare a polyether polyol with a molecular weight of 1950 g / mol, which was mixed with MDI in a molar ratio of 2.5:1, and 0.15 wt% of stannous octoate was added. The reaction was carried out at 80°C for 3 hours, and the -NCO content was 8.2%.

[0032] Step (2) Chain extension reaction When 20 wt% of a castor oil derivative (modified with acrylate) with a hydroxyl value of 160 mgKOH / g was added and reacted at 65°C for 1 hour, the storage modulus (DMA) of the elastomer base material was 15 MPa (25°C), indicating a high crosslinking density.

[0033] Step (3) Double pore treatment a) Supercritical CO2 foaming conditions are 20 MPa, 55°C, and a pressure relief rate of 5 MPa / s. SEM shows macropores with a pore size of 200 μm and a connectivity of 90%.

[0034] b) After freeze-drying, the micropore wall thickness is 20 μm, the specific surface area is 26 m² / g, and the open porosity is 85%.

[0035] Step (4) Post-curing After treatment at 80°C, XRD showed that the hard segment crystallinity was 45%. Degradation experiments showed that the mass loss rate was 7% on the 7th day, 32% on the 28th day, and 92% on the 60th day. The wet compressive strength was 16 kPa and the elongation at break was 3050%.

[0036] Example 3: Step (1) Prepolymer preparation Polyether polyol is made of PTMG and -Caprolactone was copolymerized at a molar ratio of 9:1, with a molecular weight of 2050 g / mol, and mixed with MDI at a molar ratio of 1.5:1, reacted at 70°C for 2 hours, and the -NCO content was 6.9%.

[0037] Step (2) Chain extension reaction 10 wt% of a castor oil derivative (grafted with maleic anhydride) with a hydroxyl value of 180 mgKOH / g was added and reacted at 60°C for 1 hour. The tensile modulus of the elastomer base material was 12 MPa (ASTM D638).

[0038] Step (3) Double pore treatment a) Supercritical CO2 foaming pressure of 15MPa, 45℃, forming uniform macropores with a pore size of 50μm and a connectivity rate of 93%.

[0039] b) After freeze drying, the micropore wall thickness is 5 μm, the specific surface area is 30 m² / g, and the open porosity is 90%.

[0040] Step (4) Post-curing After heat treatment, TGA showed an initial decomposition temperature of 280°C, a liquid penetration time of 2.5 seconds (YY / T 0471.1-2004 standard), a liquid absorption rate of 2750%, a wet compressive strength of 17 kPa, and an elongation at break of 3100%.

[0041] Although the present invention is disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modifications, equivalent variations, and modifications made to the above embodiments in accordance with the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a biodegradable polyether polyurethane sponge, characterized in that: The preparation method comprises the following steps: (1) Preparation of prepolymer: In the presence of a carboxylic acid catalyst, a polyether polyol having an ester bond molar ratio of 5-10% and a polyisocyanate are reacted at 70-80° C. for 2-3 hours to obtain an isocyanate-terminated prepolymer; (2) Chain extension reaction: adding a bio-based chain extender to the prepolymer, wherein the bio-based chain extender is a castor oil derivative having a hydroxyl value of 160-180 mgKOH / g, and the amount of the bio-based chain extender accounts for 10-20% of the mass of the prepolymer, and reacting at 60-70° C. for 1 hour to form an elastomer base material; (3) Double pore treatment: a) placing the elastomer base material in a supercritical CO2 reactor and foaming it at a pressure of 15-20 MPa and a temperature of 45-55°C for 30 minutes, with the pressure release rate controlled at 5 MPa / s, to form a through-hole macroporous matrix; b) immersing the foamed substrate in deionized water, freezing it at -30°C for 6 hours, and then freeze-drying it at -50°C under a vacuum of 0.1 mBar for 24 hours; (4) Post-curing: Heat treatment at 80°C for 2 hours to obtain a polyurethane sponge with a multi-level pore structure.

2. The method for preparing a biodegradable polyether polyurethane sponge according to claim 1, wherein: The polyether polyol in the step (1) is prepared by mixing polytetrahydrofuran ether glycol with -caprolactone copolymerized in a molar ratio of 9:1-19:1, with a number average molecular weight of 2000±100g / mol.

3. The method for preparing a biodegradable polyether polyurethane sponge according to claim 1, wherein: The polyisocyanate in step (1) is 4,4'-diphenylmethane diisocyanate (MDI), and the molar ratio of MDI to polyether polyol is 1.5:1-2.5:

1.

4. The method for preparing a biodegradable polyether polyurethane sponge according to claim 1, wherein: The macropores formed by supercritical foaming in step (3) a) have a pore diameter of 50-200 μm and a pore connectivity of ≥90%, which is verified by the following formula: ； The closed pore volume was measured using a mercury porosimeter at a pressure of 0.1 MPa.

5. The method for preparing a biodegradable polyether polyurethane sponge according to claim 1, wherein: The micropore wall thickness formed by freeze drying in step (3) b) is 5-20 μm, the micropore specific surface area is ≥25 m² / g, and the micropore wall porosity satisfies: 。 6. A polyether polyurethane sponge prepared by the method according to any one of claims 1 to 5, characterized in that: The sponge comprises: Soft segment: polyether polyol segment containing 5-10 mol% ester bonds; Hard segment: a crystalline region formed by MDI and castor oil derivative chain extender; Multi-level pore structure: a connected network consisting of 50-200μm through-hole macropores and 5-20μm micropore walls.

7. A polyether polyurethane sponge according to claim 6, characterized in that: The degradation behavior satisfies triple regulation: On the 7th day, the hydrolysis of the ester bond resulted in a mass loss of 8 ± 2%; From day 14 to day 28, enzymatic decomposition of the chain extender resulted in a cumulative mass loss of 30 ± 5%; On the 60th day, the hard segment crystallites disintegrated, resulting in a cumulative mass loss rate of >90%; The degradation kinetics conform to: ； in, , , .

8. The polyether polyurethane sponge according to claim 6, characterized in that: The performance parameters meet the following requirements: Liquid absorption rate ≥ 2500%, according to the formula: test; Wet compressive strength ≥15kPa; Elongation at break ≥3000%.

9. A polyether polyurethane sponge according to claim 8, characterized in that: The liquid penetration time is less than 3 seconds, which is verified by a simulated blood absorption experiment, and the test standard is YY / T 0471.1-2004.

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