Medical polyurethane foam material and preparation method thereof

Abstract

The invention discloses a preparation method of a medical polyurethane foam material, relates to the technical field of polyurethane foam dressings, and belongs to the patent classification number A61L15 / 00. The preparation method comprises the following steps: coating the surface of a polymer with a hydrophilic coupling agent to obtain pretreated polymer microspheres, and adding polyoxypropylene glycol, diphenylmethane diisocyanate, azodicarbonamide and dibutyltin dilaurate into a reaction kettle for heating reaction to obtain a polyurethane prepolymer; adding the pretreated polymer microspheres into the polyurethane prepolymer to obtain a mixed material; and pouring the mixed material into a mold, carrying out foaming molding, and carrying out curing treatment at room temperature so as to obtain the medical polyurethane foam material. The polyurethane foam material prepared by the invention has good water absorption and air permeability.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane foam dressings, belonging to the patent classification number A61L15 / 00, and specifically relates to a medical polyurethane foam material and a preparation method thereof. Background Art

[0002] In the modern medical system, as the core product for wound care, the performance of medical dressings directly affects the rehabilitation process and prognosis of patients. Medical polyurethane foam dressings are widely used in the care of chronic wounds (such as diabetic foot ulcers, pressure ulcers), postoperative incisions, and traumatic wounds due to their advantages of soft texture, strong adhesion, and effective isolation from external contamination. However, with the refined development of clinical needs and the increasing requirements of patients for the quality of wound healing, the limitations of traditional medical polyurethane foam dressings in water absorption and breathability have gradually emerged, becoming the key bottleneck restricting their further development.

[0003] From the perspective of water absorption, the molecular structure and pore characteristics of traditional polyurethane foam dressings result in limited absorption capacity for wound exudate. Polyurethane itself is a hydrophobic polymer material, and its surface has a weak affinity for water molecules, making it unable to quickly absorb the tissue fluid exuded from the wound into the dressing interior. In actual clinical applications, for wounds with a large amount of exudate (such as deep burns, infected wounds), such dressings are difficult to absorb a large amount of exudate in a short time, resulting in the liquid remaining on the wound surface, which not only easily forms a breeding ground for bacteria but also may cause wound tissue edema, hindering the migration and proliferation of new cells, thus delaying wound healing. In addition, the pore distribution of existing polyurethane foam dressings is uneven. Some pores are too large, causing the liquid to easily diffuse horizontally inside the dressing and unable to form an effective longitudinal absorption channel; some pores are too small, restricting the liquid penetration rate and resulting in low overall water absorption efficiency and liquid absorption saturation of the dressing. At the same time, traditional dressings lack effective fixation ability for the liquid. Slight external forces (such as patient turning over, limb movement) may cause the absorbed exudate to overflow again, contaminating the skin around the wound and increasing the risk of cross-infection.

[0004] In terms of breathability, the breathability of traditional medical polyurethane foam dressings far fails to meet the physiological requirements for wound healing. The wound healing process requires a relatively moist and oxygen-rich microenvironment. Sufficient oxygen supply contributes to the bactericidal effect of white blood cells, the proliferation of fibroblasts, and the synthesis of collagen. However, traditional polyurethane foam dressings have strong airtightness, and their dense internal structure hinders the entry of oxygen and the discharge of carbon dioxide. When the dressing covers the wound surface, a hypoxic or even anoxic environment is extremely likely to form locally at the wound, which not only inhibits the normal metabolism and repair function of cells but also promotes the large-scale reproduction of anaerobic bacteria, leading to wound infection. In addition, insufficient breathability of the dressing will also cause the temperature of the wound surface to rise, accelerate water evaporation, making the local wound environment that originally needs to be kept moist become dry, thus affecting the migration and epithelialization process of epidermal cells and resulting in delayed wound healing. Summary of the Invention

[0005] The purpose of the present invention is to provide a medical polyurethane foam material and its preparation method to solve the technical problems of poor water absorption and breathability of the polyurethane foam material proposed in the above background technology.

[0006] To achieve the above purpose, the present invention provides the following technical solutions: A preparation method of a medical polyurethane foam material includes the following steps: S1. Hydrophilically treat the surface of polymer microspheres, coat their surfaces with a hydrophilic coupling agent to improve the compatibility and dispersibility of the polymer microspheres with the polyurethane matrix, and obtain pretreated polymer microspheres; S2. Add polyoxypropylene glycol, diphenylmethane diisocyanate, azodicarbonamide, and dibutyltin dilaurate into a reaction kettle, stir and mix evenly, and heat and react to obtain a polyurethane prepolymer; S3. Add the pretreated polymer microspheres into the polyurethane prepolymer, continue to stir to make the pretreated polymer microspheres evenly dispersed in the polyurethane prepolymer, and obtain a mixed material; S4. Pour the mixed material into a mold, carry out foaming and molding, then place it at room temperature for curing treatment, and obtain a medical polyurethane foam material after drying.

[0007] In the technical solution of the present invention, first, the polymer microspheres are subjected to surface hydrophilization treatment with a hydrophilic coupling agent to change their surface properties, improve the compatibility and dispersibility with the polyurethane matrix, and obtain pretreated polymer microspheres; then, under the catalysis of dibutyltin dilaurate, polypropylene glycol and diphenylmethane diisocyanate react to form a polyurethane prepolymer; subsequently, the pretreated polymer microspheres are added to the polyurethane prepolymer, and are stirred to be uniformly dispersed to form a mixed material; finally, the mixed material is poured into a mold, heated to decompose azodicarbonamide for foaming and molding, then cured at room temperature to improve the molecular chain crosslinking, and dried to remove moisture and volatile substances, so as to obtain a polyurethane foam material with water absorption and air permeability properties and meeting medical requirements.

[0008] Preferably, in the step S1, the hydrophilic coupling agent is γ-glycidoxypropyltrimethoxysilane.

[0009] Preferably, in the step S2, the mass ratio of polypropylene glycol to diphenylmethane diisocyanate is 1:1.2 - 1.5.

[0010] Preferably, in the step S3, the addition amount of the pretreated polymer microspheres is 10% of the mass of the polyurethane prepolymer.

[0011] Preferably, in the step S4, the foaming and molding temperature is 70 - 75 °C, and the pressure is 0.5 - 0.7 MPa.

[0012] Preferably, in the step S1, the preparation method of the polymer microspheres includes the following steps: S11. Add acrylic acid and acrylamide to deionized water, stir and dissolve, then dropwise add polyvinyl alcohol aqueous solution, add N,N'-methylenebisacrylamide, and stir to react to obtain a prepolymerization reaction solution; S12. Add nano-silica aerogel to the prepolymerization reaction solution, stir evenly to obtain a mixed solution; S13. Add potassium persulfate to deionized water and stir to dissolve to obtain a potassium persulfate initiator solution. Slowly drop the potassium persulfate initiator solution into the mixed solution, heat and stir to react, and obtain polymer microspheres after centrifugal separation, washing and drying.

[0013] In the technical solution of the present invention, when preparing polymer microspheres, acrylic acid and acrylamide are first dissolved in deionized water, an aqueous solution of polyvinyl alcohol is added dropwise as a dispersant, N,N'-methylenebisacrylamide is added as a crosslinking agent, and stirring is carried out to form a pre-polymerization reaction solution; then nano-silica aerogel is added, which is dispersed therein by its unique structure and acts with the prepolymer; finally, a solution of potassium persulfate as an initiator is added dropwise, and potassium persulfate decomposes under heating to generate free radicals to initiate the polymerization of monomers, forming a three-dimensional network structure through the crosslinking agent. After centrifugal separation, washing, and drying, super-hydrophilic polymer microspheres are finally obtained.

[0014] The polymer microspheres are polymerized from acrylic acid and acrylamide, and the molecular chains are rich in a large number of strongly hydrophilic groups such as carboxyl groups and amide groups, and have a three-dimensional network structure. When the polymer microspheres are dispersed in polyurethane, the hydrophilic groups on their surface can form hydrogen bonds with water molecules, attracting the water molecules to approach; at the same time, their network structure can accommodate water molecules, enabling the water to penetrate into the interior of the polyurethane. In addition, the polymer microspheres after hydrophilic treatment have good compatibility with the polyurethane matrix. After the two are combined, the hydrophilicity of the microspheres can induce the rearrangement of the molecular chains on the surface of the polyurethane, increasing the exposure degree of the hydrophilic groups on the surface of the polyurethane, thereby changing the overall hydrophilicity of the polyurethane and making it easier to contact and interact with water, endowing the polyurethane foam material with super water-absorbing properties.

[0015] The polymer microspheres themselves have a certain pore structure, which can realize gas exchange. The pores of the polymer microspheres themselves cooperate with the original pores of the polyurethane to construct a more complex and efficient gas transmission network. However, there are problems such as uneven pore size distribution and poor connectivity of some pores in the polymer microspheres. The nano-silica aerogel particles have extremely high porosity and specific surface area, and their nano-scale porous structure is extremely rich and uniform. When the nano-silica aerogel particles are doped into the super-hydrophilic polymer microspheres, the pore structures of the two can be complementary. The nano-pores of the nano-silica aerogel particles can be filled in the gaps of the original pores of the polymer microspheres, optimizing the pore distribution, increasing the connectivity of the pores, and forming a more dense and unobstructed gas transmission channel network. This enables more alternative paths for the gas to diffuse inside the microspheres, reducing the hindrance to gas diffusion, thereby improving the overall air permeability.

[0016] Preferably, in the step S11, the mass ratio of acrylic acid to acrylamide is 3:1 - 2.

[0017] Preferably, in the step S12, the addition amount of nano-silica aerogel is 13 - 18% of the total mass of acrylic acid and acrylamide.

[0018] In the technical solution of the present invention, as described above, the nanopores of the nano-silica aerogel particles can be filled in the gaps of the original pores of the polymer microspheres, optimizing the pore distribution, increasing the connectivity of the pores, and forming a denser and smoother gas transmission channel network, thereby improving the air permeability of the polyurethane foam material. To make the polyurethane foam material have good air permeability, a sufficient amount of nano-silica aerogel particles must be doped in the polyurethane foam material. Therefore, the present invention controls the addition amount of the nano-silica aerogel to be greater than 13% of the total mass of acrylic acid and acrylamide. As the addition amount of the nano-silica aerogel continues to increase, the air permeability of the polyurethane foam increases slowly. However, the research team of the present invention unexpectedly found that when the addition amount of the nano-silica aerogel increases to a certain amount, that is, when the addition amount of the nano-silica aerogel is greater than 18% of the total mass of acrylic acid and acrylamide, the water absorption performance of the polyurethane foam material suddenly drops significantly. Through research, it is found that this is because after excessive addition of nano-silica, the nano-silica aerogel occupies too much reaction space, hindering the reaction between monomers such as acrylic acid and acrylamide and initiators and cross-linking agents, resulting in incomplete polymerization reaction, insufficient cross-linking degree, and the uncross-linked or insufficiently cross-linked parts curl and fold, wrapping some hydrophilic groups inside, reducing the contact area between the hydrophilic groups and water, thereby reducing the hydrophilicity of the polymer. In addition, due to insufficient cross-linking degree, the polymer cannot form a tight three-dimensional network structure, which limits the swelling property of the polymer in water and makes it difficult for water molecules to enter the polymer interior to fully interact with the hydrophilic groups. Therefore, the present invention strictly controls the addition amount of the nano-silica aerogel within the range of 13%-18% of the total mass of acrylic acid and acrylamide.

[0019] Preferably, in the step S13, the heating reaction temperature is 70-80 °C.

[0020] A medical polyurethane foam material is prepared by the above method.

[0021] Compared with the prior art, the beneficial effects of the present invention are: 1. By performing surface hydrophilization treatment on the polymer microspheres, their compatibility with the polyurethane matrix is good, and the polymer microspheres are polymerized from acrylic acid and acrylamide rich in strong hydrophilic groups such as carboxyl groups and amide groups, and have a three-dimensional network structure. After being dispersed in the polyurethane, the hydrophilic groups on the surface of the microspheres form hydrogen bonds with water molecules, the network structure accommodates water molecules, and induces the rearrangement of the molecular chains on the surface of the polyurethane, increasing the exposure of hydrophilic groups, thereby endowing the polyurethane foam material with super water absorption performance, which can effectively absorb wound exudate and keep the wound dry.

[0022] 2. The polymer microspheres cooperate with the original pores of the polyurethane, and the doped nano-silica aerogel particles, with their abundant and uniform nano-porous structure, fill the original pore gaps of the polymer microspheres, optimize the pore distribution, increase the connectivity, construct a denser and smoother gas transmission network, significantly improve the air permeability of the polyurethane foam material, facilitate gas exchange at the wound site, and improve the wound microenvironment.

[0023] 3. During the preparation of the polymer microspheres, the addition amount of nano-silica aerogel is controlled within a certain range to avoid hindering the monomer reaction and reducing the crosslinking degree due to excessive addition, and prevent a significant decrease in the hydrophilicity of the polymer. Within this addition amount range, both good air permeability of the polyurethane foam material and its stable hydrophilic property are ensured, achieving a balanced optimization of water absorption and air permeability, and better meeting the requirements of medical dressings. Detailed implementation manners

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] The specifications of the raw materials used in the specific embodiments are as follows: Acrylic acid, purity ≥ 99%, electronic grade, without inhibitor; acrylamide, purity ≥ 98%, biological grade; polyvinyl alcohol, alcoholysis degree 88% - 90%, molecular weight 10000 - 15000; N,N'-methylenebisacrylamide, purity ≥ 99%; nano-silica aerogel, particle size 10 - 30 nm, specific surface area ≥ 500 m 2 / g; potassium persulfate, analytical pure, purity ≥ 99.5%; polyoxypropylene glycol, molecular weight 1000 - 2000, hydroxyl value 50 - 60 mg KOH / g, water content ≤ 0.05%; diphenylmethane diisocyanate, purity ≥ 98%, NCO content ≥ 30%, industrial grade; azodicarbonamide, particle size 5 - 10 μm; dibutyltin dilaurate, tin content 18% - 19%, chemically pure.

[0026] Example 1 Preparation of polymer microspheres: Step S11: Prepare a 500 mL four-necked flask, and install a stirrer, a thermometer and a reflux condenser. Add 300 mL of deionized water to the flask, turn on the stirrer and raise the temperature to 60 °C. Weigh 15 g of acrylic acid and 9 g of acrylamide and add them to the flask, and continue stirring until completely dissolved to form a homogeneous monomer solution. Then, slowly drop 20 mL of a 5% polyvinyl alcohol aqueous solution into the flask. After the dropping is complete, continue stirring for 30 minutes to evenly disperse the dispersant. Then, weigh 0.1 g of N,N'-methylenebisacrylamide and add it to the flask, and stir for 15 minutes to ensure that the crosslinking agent is fully dispersed, obtaining a prepolymerization reaction solution.

[0027] Step S12: Weigh 3.84 g of nano-silica aerogel (16% of the total mass of acrylic acid and acrylamide), and slowly add it to the above prepolymerization reaction solution. Stir at a speed of 200 r / min for 40 minutes to evenly disperse the nano-silica aerogel in the reaction solution, obtaining a mixed solution.

[0028] Step S13: Prepare a 50 mL beaker, add 10 mL of deionized water, and then weigh 0.2 g of potassium persulfate and add it thereto, and stir to dissolve to obtain a potassium persulfate initiator solution. Slowly drop the initiator solution into the mixed solution, and control the dropping rate at 2 drops per second. The dropping process lasts for 15 minutes. After the dropping is complete, raise the temperature of the reaction system to 75 °C, maintain this temperature and stir the reaction at a speed of 150 r / min for 3 hours. After the reaction is completed, transfer the reaction solution to a centrifuge tube, and centrifuge at a speed of 4000 r / min for 15 minutes to separate out the microsphere precipitate. Wash the precipitate 3 times with deionized water, and perform centrifugal separation after each washing. Finally, place the washed microspheres in a vacuum drying oven and dry them at 50 °C to constant weight to obtain polymer microspheres.

[0029] A method for preparing a medical polyurethane foam material, comprising the following steps: Step S1: Add 20 g of polymer microspheres to a conical flask, weigh 2 g of γ-glycidoxypropyltrimethoxysilane, dissolve it in 300 mL of absolute ethanol to prepare a coupling agent solution. Pour the coupling agent solution into the conical flask and ultrasonically disperse for 20 minutes to allow the microspheres to fully contact the coupling agent solution. Then place the conical flask in a constant temperature water bath at 40 °C and stir the reaction at a speed of 120 r / min for 4 hours. After the reaction is completed, collect the microspheres by filtration and wash them 3 times with absolute ethanol to remove the unreacted coupling agent. Finally, dry the microspheres in a vacuum drying oven at 50 °C for 12 hours to obtain pretreated polymer microspheres.

[0030] Step S2: Add 20 g of polypropylene glycol and 29 g of diphenylmethane diisocyanate into the reaction kettle, then add 1 g of azodicarbonamide and 0.05 g of dibutyltin dilaurate. Start stirring and stir the mixture at a speed of 180 r / min for 15 minutes to make the materials evenly mixed. Then raise the temperature of the reaction kettle to 80 °C and react at this temperature for 2 hours to obtain a polyurethane prepolymer.

[0031] Step S3: Add the pretreated polymer microspheres into the polyurethane prepolymer. The addition amount of the pretreated polymer microspheres is 10% of the mass of the polyurethane prepolymer. Continue to stir at a speed of 150 r / min for 30 minutes to make the pretreated polymer microspheres evenly dispersed in the polyurethane prepolymer, obtaining a mixed material.

[0032] Step S4: Quickly pour the mixed material into a preheated mold with the size of 10 cm × 10 cm × 2 cm. Put the mold into a hot press molding machine and carry out foaming molding under the conditions of a temperature of 73 °C and a pressure of 0.6 MPa, and maintain these conditions for 30 minutes. After the foaming is completed, take out the mold from the hot press molding machine and place it at room temperature for 24 hours for curing treatment. After the curing is completed, take out the foam from the mold and place it in a blast drying oven, and dry it to a constant weight at 60 °C to obtain a medical polyurethane foam material.

[0033] Example 2 Preparation of polymer microspheres: Step S11: Prepare a 500 mL four-necked flask and install a stirrer, a thermometer and a reflux condenser. Add 300 mL of deionized water into the flask, start stirring and raise the temperature to 60 °C. Weigh 15 g of acrylic acid and 6 g of acrylamide and add them into the flask, and continuously stir until completely dissolved to form a uniform monomer solution. Then, slowly drop 20 mL of a 5% aqueous solution of polyvinyl alcohol into the flask. After the dropping is completed, continue to stir for 30 minutes to make the dispersant evenly dispersed. Then, weigh 0.1 g of N,N'-methylenebisacrylamide and add it into the flask, and stir for 15 minutes to ensure that the crosslinking agent is fully dispersed, obtaining a prepolymerization reaction solution.

[0034] Step S12: Weigh 2.94 g of nano-silica aerogel (14% of the total mass of acrylic acid and acrylamide), and slowly add it into the above prepolymerization reaction solution. Stir at a speed of 200 r / min for 40 minutes to make the nano-silica aerogel evenly dispersed in the reaction solution, obtaining a mixed solution.

[0035] Step S13: Prepare a 50 mL beaker, add 10 mL of deionized water, and then weigh 0.2 g of potassium persulfate and add it thereto. Stir to dissolve to obtain a potassium persulfate initiator solution. Slowly drop the initiator solution into the mixed solution, control the dropping rate at 2 drops per second, and the dropping process lasts for 15 minutes. After the dropping is completed, raise the temperature of the reaction system to 75 °C, maintain this temperature and stir and react at a rotation speed of 150 r / min for 3 hours. After the reaction is completed, transfer the reaction solution to a centrifuge tube, centrifuge at a rotation speed of 4000 r / min for 15 minutes to separate out the microsphere precipitate. Wash the precipitate with deionized water 3 times, and perform centrifugal separation after each washing. Finally, place the washed microspheres in a vacuum drying oven and dry them at 50 °C to constant weight to obtain polymer microspheres.

[0036] A preparation method of a medical polyurethane foam material, comprising the following steps: Step S1: Add 20 g of polymer microspheres to a conical flask, weigh 2 g of γ-glycidoxypropyltrimethoxysilane, dissolve it in 300 mL of absolute ethanol to prepare a coupling agent solution. Pour the coupling agent solution into the conical flask and ultrasonically disperse for 20 minutes to allow the microspheres to fully contact with the coupling agent solution. Then place the conical flask in a constant temperature water bath at 40 °C and stir and react at a rotation speed of 120 r / min for 4 hours. After the reaction is completed, collect the microspheres by filtration and wash them 3 times with absolute ethanol to remove the unreacted coupling agent. Finally, dry the microspheres in a vacuum drying oven at 50 °C for 12 hours to obtain pretreated polymer microspheres.

[0037] Step S2: Add 20 g of polyoxypropylene glycol and 25 g of diphenylmethane diisocyanate to the reaction kettle, and then add 1 g of azodicarbonamide and 0.05 g of dibutyltin dilaurate. Start stirring and stir and mix at a rotation speed of 180 r / min for 15 minutes to uniformly mix the materials. Then raise the temperature of the reaction kettle to 80 °C and react at this temperature for 2 hours to obtain a polyurethane prepolymer.

[0038] Step S3: Add the pretreated polymer microspheres to the polyurethane prepolymer, and the addition amount of the pretreated polymer microspheres is 10% of the mass of the polyurethane prepolymer. Continue to stir at a rotation speed of 150 r / min for 30 minutes to uniformly disperse the pretreated polymer microspheres in the polyurethane prepolymer to obtain a mixed material.

[0039] Step S4: Rapidly pour the mixed material into a preheated mold with dimensions of 10 cm × 10 cm × 2 cm. Place the mold in a hot press molding machine and perform foaming molding under the conditions of a temperature of 73 °C and a pressure of 0.6 MPa, and maintain these conditions for 30 minutes. After foaming is completed, remove the mold from the hot press molding machine and place it at room temperature for 24 hours for curing treatment. After curing is completed, take out the foam from the mold and place it in a blast drying oven, and dry it to a constant weight at 60 °C to obtain a medical polyurethane foam material.

[0040] Example 3 Preparation of polymer microspheres: Step S11: Prepare a 500 mL four-necked flask and install a stirrer, a thermometer, and a reflux condenser. Add 300 mL of deionized water to the flask, turn on the stirrer and raise the temperature to 60 °C. Weigh 15 g of acrylic acid and 7 g of acrylamide and add them to the flask, and continue stirring until completely dissolved to form a uniform monomer solution. Then, slowly drop 20 mL of a 5% aqueous solution of polyvinyl alcohol into the flask. After dropping, continue stirring for 30 minutes to evenly disperse the dispersant. Then, weigh 0.1 g of N,N'-methylenebisacrylamide and add it to the flask, and stir for 15 minutes to ensure that the cross-linking agent is fully dispersed to obtain a prepolymerization reaction solution.

[0041] Step S12: Weigh 3.3 g of nano-silica aerogel (15% of the total mass of acrylic acid and acrylamide), and slowly add it to the above prepolymerization reaction solution, and stir at a speed of 200 r / min for 40 minutes to evenly disperse the nano-silica aerogel in the reaction solution to obtain a mixed solution.

[0042] Step S13: Prepare a 50 mL beaker, add 10 mL of deionized water, and then weigh 0.2 g of potassium persulfate and add it thereto, and stir to dissolve to obtain a potassium persulfate initiator solution. Slowly drop the initiator solution into the mixed solution, and control the dropping rate at 2 drops per second. The dropping process lasts for 15 minutes. After dropping, raise the temperature of the reaction system to 75 °C, maintain this temperature and stir the reaction at a speed of 150 r / min for 3 hours. After the reaction is completed, transfer the reaction solution to a centrifuge tube and centrifuge at a speed of 4000 r / min for 15 minutes to separate out the microsphere precipitate. Wash the precipitate with deionized water 3 times, and perform centrifugal separation after each washing. Finally, place the washed microspheres in a vacuum drying oven and dry them to a constant weight at 50 °C to obtain polymer microspheres.

[0043] A preparation method of a medical polyurethane foam material, comprising the following steps: Step S1: Add 20 g of polymer microspheres into a conical flask. Weigh 2 g of γ-glycidoxypropyltrimethoxysilane, dissolve it in 300 mL of absolute ethanol to prepare a coupling agent solution. Pour the coupling agent solution into the conical flask and ultrasonically disperse for 20 minutes to ensure full contact between the microspheres and the coupling agent solution. Then place the conical flask in a constant temperature water bath at 40 °C and stir and react at a speed of 120 r / min for 4 hours. After the reaction, collect the microspheres by filtration and wash them 3 times with absolute ethanol to remove the unreacted coupling agent. Finally, dry the microspheres in a vacuum drying oven at 50 °C for 12 hours to obtain pretreated polymer microspheres.

[0044] Step S2: Add 20 g of polyoxypropylene glycol and 27 g of diphenylmethane diisocyanate into the reaction kettle, and then add 1 g of azodicarbonamide and 0.05 g of dibutyltin dilaurate. Start stirring and stir and mix at a speed of 180 r / min for 15 minutes to make the materials evenly mixed. Then raise the temperature of the reaction kettle to 80 °C and react at this temperature for 2 hours to obtain a polyurethane prepolymer.

[0045] Step S3: Add the pretreated polymer microspheres into the polyurethane prepolymer. The addition amount of the pretreated polymer microspheres is 10% of the mass of the polyurethane prepolymer, and continue to stir at a speed of 150 r / min for 30 minutes to make the pretreated polymer microspheres evenly dispersed in the polyurethane prepolymer to obtain a mixed material.

[0046] Step S4: Quickly pour the mixed material into a preheated mold with the size of 10 cm × 10 cm × 2 cm. Place the mold in a hot press molding machine and carry out foaming molding under the conditions of a temperature of 73 °C and a pressure of 0.6 MPa, and maintain these conditions for 30 minutes. After foaming is completed, take out the mold from the hot press molding machine and place it at room temperature for 24 hours for curing treatment. After curing, take out the foam from the mold and place it in a blast drying oven and dry it to constant weight at 60 °C to obtain a medical polyurethane foam material.

[0047] Example 4 Preparation of polymer microspheres: Step S11: Prepare a 500 mL four-necked flask and install a stirrer, a thermometer and a reflux condenser. Add 300 mL of deionized water into the flask, start stirring and raise the temperature to 60 °C. Weigh 15 g of acrylic acid and 10 g of acrylamide and add them into the flask, and continuously stir until completely dissolved to form a uniform monomer solution. Then slowly drop 20 mL of a 5% aqueous solution of polyvinyl alcohol into the flask. After dropping, continue to stir for 30 minutes to make the dispersant evenly dispersed. Then weigh 0.1 g of N,N'-methylenebisacrylamide and add it into the flask and stir for 15 minutes to ensure full dispersion of the crosslinking agent to obtain a prepolymerization reaction solution.

[0048] Step S12: Weigh 4.5 g of nano-silica aerogel (18% of the total mass of acrylic acid and acrylamide), and slowly add it to the above-mentioned prepolymerization reaction solution. Stir at a speed of 200 r / min for 40 minutes to uniformly disperse the nano-silica aerogel in the reaction solution, obtaining a mixed solution.

[0049] Step S13: Prepare a 50 mL beaker, add 10 mL of deionized water, and then weigh 0.2 g of potassium persulfate and add it thereto. Stir to dissolve to obtain a potassium persulfate initiator solution. Slowly drip the initiator solution into the mixed solution, with the dripping rate controlled at 2 drops per second, and the dripping process lasts for 15 minutes. After the dripping is completed, raise the temperature of the reaction system to 80 °C, maintain this temperature and stir and react at a speed of 150 r / min for 3 hours. After the reaction is completed, transfer the reaction solution to a centrifuge tube, centrifuge at a speed of 4000 r / min for 15 minutes to separate out the microsphere precipitate. Wash the precipitate 3 times with deionized water, and perform centrifugal separation after each washing. Finally, place the washed microspheres in a vacuum drying oven and dry them to a constant weight at 50 °C to obtain polymer microspheres.

[0050] A preparation method of a medical polyurethane foam material, comprising the following steps: Step S1: Add 20 g of polymer microspheres to a conical flask. Weigh 2 g of γ-glycidoxypropyltrimethoxysilane, dissolve it in 300 mL of absolute ethanol to prepare a coupling agent solution. Pour the coupling agent solution into the conical flask and ultrasonically disperse for 20 minutes to allow the microspheres to fully contact the coupling agent solution. Then place the conical flask in a constant temperature water bath at 40 °C and stir and react at a speed of 120 r / min for 4 hours. After the reaction is completed, collect the microspheres by filtration and wash them 3 times with absolute ethanol to remove the unreacted coupling agent. Finally, dry the microspheres in a vacuum drying oven at 50 °C for 12 hours to obtain pretreated polymer microspheres.

[0051] Step S2: Add 20 g of polyoxypropylene glycol and 30 g of diphenylmethane diisocyanate to the reaction kettle, and then add 1 g of azodicarbonamide and 0.05 g of dibutyltin dilaurate. Start stirring and stir and mix at a speed of 180 r / min for 15 minutes to uniformly mix the materials. Then raise the temperature of the reaction kettle to 80 °C and react at this temperature for 2 hours to obtain a polyurethane prepolymer.

[0052] Step S3: Add the pretreated polymer microspheres to the polyurethane prepolymer, with the addition amount of the pretreated polymer microspheres being 10% of the mass of the polyurethane prepolymer, and continue to stir at a speed of 150 r / min for 30 minutes to uniformly disperse the pretreated polymer microspheres in the polyurethane prepolymer, obtaining a mixed material.

[0053] Step S4: Rapidly pour the mixed materials into a preheated mold with dimensions of 10 cm × 10 cm × 2 cm. Place the mold in a hot press molding machine and perform foam molding under the conditions of a temperature of 75 °C and a pressure of 0.7 MPa, and maintain these conditions for 30 minutes. After the foaming is completed, take the mold out of the hot press molding machine and place it at room temperature for 24 hours for curing treatment. After the curing is completed, take the foam out of the mold and place it in a blast drying oven, and dry it at 60 °C to a constant weight to obtain a medical polyurethane foam material.

[0054] Example 5 Preparation of polymer microspheres: Step S11: Prepare a 500 mL four-necked flask, and install a stirrer, a thermometer, and a reflux condenser. Add 300 mL of deionized water to the flask, turn on the stirrer and raise the temperature to 60 °C. Weigh 15 g of acrylic acid and 5 g of acrylamide and add them to the flask, and continuously stir until completely dissolved to form a uniform monomer solution. Then, slowly drop 20 mL of a 5% aqueous solution of polyvinyl alcohol into the flask. After the dropping is completed, continue to stir for 30 minutes to evenly disperse the dispersant. Then, weigh 0.1 g of N,N'-methylenebisacrylamide and add it to the flask, and stir for 15 minutes to ensure that the cross-linking agent is fully dispersed to obtain a pre-polymerization reaction solution.

[0055] Step S12: Weigh 2.6 g of nano-silica aerogel (13% of the total mass of acrylic acid and acrylamide), and slowly add it to the above pre-polymerization reaction solution, and stir at a speed of 200 r / min for 40 minutes to evenly disperse the nano-silica aerogel in the reaction solution to obtain a mixed solution.

[0056] Step S13: Prepare a 50 mL beaker, add 10 mL of deionized water, and then weigh 0.2 g of potassium persulfate and add it thereto, and stir to dissolve to obtain a potassium persulfate initiator solution. Slowly drop the initiator solution into the mixed solution, and control the dropping rate at 2 drops per second, and the dropping process lasts for 15 minutes. After the dropping is completed, raise the temperature of the reaction system to 70 °C, maintain this temperature and stir the reaction at a speed of 150 r / min for 3 hours. After the reaction is completed, transfer the reaction solution to a centrifuge tube, and centrifuge at a speed of 4000 r / min for 15 minutes to separate out the microsphere precipitate. Wash the precipitate with deionized water 3 times, and perform centrifugal separation after each washing. Finally, place the washed microspheres in a vacuum drying oven and dry them at 50 °C to a constant weight to obtain polymer microspheres.

[0057] A preparation method of a medical polyurethane foam material, comprising the following steps: Step S1: Add 20 g of polymer microspheres into a conical flask. Weigh 2 g of γ-glycidoxypropyltrimethoxysilane and dissolve it in 300 mL of absolute ethanol to prepare a coupling agent solution. Pour the coupling agent solution into the conical flask and ultrasonically disperse for 20 minutes to ensure full contact between the microspheres and the coupling agent solution. Then place the conical flask in a constant temperature water bath at 40 °C and stir and react at a speed of 120 r / min for 4 hours. After the reaction, collect the microspheres by filtration and wash them 3 times with absolute ethanol to remove the unreacted coupling agent. Finally, dry the microspheres in a vacuum drying oven at 50 °C for 12 hours to obtain pretreated polymer microspheres.

[0058] Step S2: Add 20 g of polypropylene glycol and 24 g of diphenylmethane diisocyanate into a reaction kettle, and then add 1 g of azodicarbonamide and 0.05 g of dibutyltin dilaurate. Start stirring and stir and mix at a speed of 180 r / min for 15 minutes to make the materials evenly mixed. Then raise the temperature of the reaction kettle to 80 °C and react at this temperature for 2 hours to obtain a polyurethane prepolymer.

[0059] Step S3: Add the pretreated polymer microspheres into the polyurethane prepolymer. The addition amount of the pretreated polymer microspheres is 10% of the mass of the polyurethane prepolymer, and continue to stir at a speed of 150 r / min for 30 minutes to make the pretreated polymer microspheres evenly dispersed in the polyurethane prepolymer, obtaining a mixed material.

[0060] Step S4: Quickly pour the mixed material into a preheated mold with dimensions of 10 cm × 10 cm × 2 cm. Place the mold in a hot press molding machine and carry out foaming molding under the conditions of a temperature of 70 °C and a pressure of 0.5 MPa, and maintain these conditions for 30 minutes. After foaming is completed, take out the mold from the hot press molding machine and place it at room temperature for 24 hours for curing treatment. After curing is completed, take out the foam from the mold and place it in a blast drying oven and dry it to a constant weight at 60 °C to obtain a medical polyurethane foam material.

[0061] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that polymer microspheres are not added during the preparation process of the medical polyurethane foam material, and the remaining steps are the same.

[0062] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the polymer microspheres are not pretreated with a hydrophilic coupling agent during the preparation process of the medical polyurethane foam material, and the remaining steps are the same.

[0063] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that nano-silica aerogel is not added during the preparation process of the polymer microspheres, and the remaining steps are the same.

[0064] Comparative Example 4 The difference between Comparative Example 4 and Example 4 lies in that the addition amount of nano-silica aerogel is 19% of the total mass of acrylic acid and acrylamide, and the remaining steps are the same.

[0065] Comparative Example 5 The difference between Comparative Example 5 and Example 4 lies in that the addition amount of nano-silica aerogel is 20% of the total mass of acrylic acid and acrylamide, and the remaining steps are the same.

[0066] Performance test: 1. Water absorption performance test: The water absorption performance of the medical polyurethane foam material was measured by the weighing method. First, the prepared foam material was cut into specimens with dimensions of 5 cm × 5 cm × 1 cm, placed in a forced-air drying oven at 60 °C and dried to a constant weight, and its initial mass was recorded. Then, the specimens were completely immersed in deionized water and soaked for 30 minutes. During this period, the specimens were gently squeezed every 5 minutes to remove internal air bubbles and promote water absorption. After taking out the specimens, the surface water was quickly blotted dry with filter paper and immediately weighed, and the mass was recorded. According to the formula: water absorption rate = (mass after water absorption - initial mass) / initial mass × 100%, the water absorption rate of the material was calculated. Each specimen was tested 5 times and the average value was taken. The test results are shown in Table 1.

[0067] 2. Air permeability performance test: Referring to the standard of GB / T5453-1997 "Textiles - Determination of fabric air permeability", the air permeability tester was used for testing. The foam material was cut into circular specimens with a diameter of 7 cm, fixed on the test chamber of the instrument, the test area was set to 50 cm², the test pressure difference was 100 Pa, and under the environmental conditions of a temperature of 25 °C and a relative humidity of 65%, the air flow rate (unit: mm / s) passing through the specimen per unit time was measured. Each specimen was tested 13 times and the average value was taken. The test results are shown in Table 1.

[0068] 3. Biocompatibility performance test: The MTT method was used to evaluate the biocompatibility of the materials. The medical polyurethane foam materials were cut into small pieces and extracted by soaking in sterile PBS solution for 24 hours to prepare the extraction solution. Logarithmic growth phase L929 mouse fibroblasts were taken and inoculated into 96-well plates at a density of 1×104 cells per well. After culturing for 24 hours, the original culture medium was discarded, and the extraction solution was added respectively. Six replicates were set for each concentration. At the same time, a blank control group (containing only the culture medium) and a positive control group (containing 0.1% Triton X-100) were set. After continuing to culture for 24 hours, 20 μL of MTT solution (5 mg / mL) was added to each well, incubated for 4 hours, the culture medium was discarded, 150 μL of dimethyl sulfoxide was added, and shaken for 10 minutes to fully dissolve the crystals. The absorbance (OD value) was measured at a wavelength of 570 nm using an enzyme-linked immunosorbent assay reader. According to the formula: cell survival rate = (absorbance of the experimental group - absorbance of the blank group) / (absorbance of the negative control group - absorbance of the blank group) × 100%, the cell survival rate was calculated to evaluate the effect of the materials on cell growth. The test results are shown in Table 1.

[0069] Table 1: Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a medical polyurethane foam material, characterized in that, It includes the following steps: S1. Perform surface hydrophilization treatment on the polymer microspheres, and coat their surfaces with a hydrophilic coupling agent to improve the compatibility and dispersibility of the polymer microspheres with the polyurethane matrix, thereby obtaining pretreated polymer microspheres; S2. Add polyoxypropylene glycol, diphenylmethane diisocyanate, azodicarbonamide, and dibutyltin dilaurate into a reaction kettle, stir and mix them evenly, and then heat and react to obtain a polyurethane prepolymer; S3. Add the pretreated polymer microspheres into the polyurethane prepolymer, and continue stirring to make the pretreated polymer microspheres evenly dispersed in the polyurethane prepolymer, thereby obtaining a mixed material; S4. Pour the mixed material into a mold, perform foaming and molding, then place it at room temperature for curing treatment, and after drying, obtain a medical polyurethane foam material.

2. The preparation method of a medical polyurethane foam material according to claim 1, characterized in that, In the step S1, the hydrophilic coupling agent is γ-glycidoxypropyltrimethoxysilane.

3. The preparation method of a medical polyurethane foam material according to claim 1, characterized in that, In the step S2, the mass ratio of polyoxypropylene glycol to diphenylmethane diisocyanate is 1:1.2 - 1.

5.

4. The preparation method of a medical polyurethane foam material according to claim 1, characterized in that, In the step S3, the addition amount of the pretreated polymer microspheres is 10% of the mass of the polyurethane prepolymer.

5. The preparation method of a medical polyurethane foam material according to claim 1, characterized in that, In the step S4, the foaming and molding temperature is 70 - 75°C, and the pressure is 0.5 - 0.7 MPa.

6. The preparation method of a medical polyurethane foam material according to claim 1, characterized in that, In the step S1, the preparation method of the polymer microspheres includes the following steps: S11. Add acrylic acid and acrylamide into deionized water, stir and dissolve them, then dropwise add a polyvinyl alcohol aqueous solution, add N,N'-methylenebisacrylamide, and stir and react to obtain a pre-polymerization reaction solution; S12. Add nano-silica aerogel into the pre-polymerization reaction solution, stir evenly to obtain a mixed solution; S13. Add potassium persulfate into deionized water and stir to dissolve it to obtain a potassium persulfate initiator solution. Slowly drop the potassium persulfate initiator solution into the mixed solution, heat and stir to react, and after centrifugal separation, washing, and drying, obtain polymer microspheres.

7. The preparation method of a medical polyurethane foam material according to claim 6, characterized in that, In the step S11, the mass ratio of acrylic acid to acrylamide is 3:1 - 2.

8. The preparation method of a medical polyurethane foam material according to claim 6, characterized in that, In the step S12, the addition amount of nano-silica aerogel is 13 - 18% of the total mass of acrylic acid and acrylamide.

9. The preparation method of a medical polyurethane foam material according to claim 6, characterized in that, In the step S13, the heating reaction temperature is 70 - 80°C.

10. A medical polyurethane foam material, characterized in that, Prepared by the method according to any one of claims 1 - 9.

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