High-porosity polyurethane foam as well as preparation method and application thereof

Abstract

The invention discloses high-porosity polyurethane foam and a preparation method and application thereof.The high-porosity polyurethane foam is provided with macropores with the pore diameter ranging from 500 micrometers to 2000 micrometers and micropores with the pore diameter ranging from 10 micrometers to 100 micrometers at the same time, the volume ratio of the macropores to the micropores is (10-50): 1, the overall porosity of the polyurethane foam is larger than 96%, and the expansion multiple is larger than 75. The high-porosity polyurethane foam is prepared in a mode of combining freezing polymerization and a soluble salt template, a multi-stage pore channel is constructed through the synergistic effect of salt dissolution and ice crystal growth, an original pore channel structure formed by low-temperature reaction is kept to the maximum extent through freeze drying, and the high-porosity polyurethane foam is prepared. Meanwhile, the glass transition temperature Tg of the polyurethane foam material is close to the body temperature through the design of a polyurethane molecular structure, and the polyurethane foam material has the characteristic that the body temperature can recover the memory shape and is suitable for being used as a biomedical device for minimally invasive embolism.

Description

Technical Field

[0001] This application relates to the field of polyurethane materials technology, and in particular to a high-porosity polyurethane foam, its preparation method, and its application. Background Technology

[0002] The structure and properties of polyurethane (PU) materials can be flexibly designed by adjusting the types, proportions and distributions of diisocyanates, chain extenders and oligomeric diols. At the same time, polyurethane materials have excellent mechanical properties, resilience, good processing performance, excellent biocompatibility, adhesiveness and antithrombotic properties, and occupy a pivotal position in medical biomaterials.

[0003] Implantable medical devices based on shape memory polyurethane foam can maintain a temporary compressed state below body temperature. After being stored in this compressed state, they are implanted into the surgical site via a catheter. Upon contact with blood, they expand spontaneously, achieving rapid filling or fixation support. Compared to traditional open surgery, this type of minimally invasive surgery significantly reduces costs and complications. Implantable filler medical devices place stringent requirements on the foam material. In addition to possessing shape memory properties near body temperature, they must also meet requirements such as extremely low density, high porosity, high open-cell ratio, high compression / expansion performance, and good support properties.

[0004] Existing polyurethane foams are mostly prepared using chemical foaming methods (such as water and ammonium bicarbonate) or physical pore-forming agents (such as microspheres, soluble pore-forming agent templates, and freeze polymerization). Chemical foaming utilizes gases generated from reactions or the decomposition of foaming agents for foaming; the pore structure and distribution depend on the precise control of gas generation and gelation rates, requiring high-precision processing. Microsphere foaming utilizes the vaporization of low-boiling-point gases encapsulated within microspheres, causing the microspheres to expand and foam, resulting in a closed-cell structure with a low compressibility. The soluble pore-forming agent template method involves... The process involves injecting a precursor solution into a stacked template of soluble porogen particles for curing, followed by removal of the soluble porogen particles to form a porous structure. However, the porous structure is limited by the size, shape, and stacking morphology of the salt particles, making it difficult to prepare pores smaller than 20 μm. While the pore size and shape of the resulting foam material can be flexibly adjusted, some closed pores exist, leading to a low compression ratio. Freeze-polymerization, on the other hand, involves solvent ice crystals below the solvent's melting point expelling solute molecules, which then accumulate in small, unfrozen areas and undergo a curing reaction. When the ice crystals melt, a polymer foam material is obtained. The pore structure is directly related to the type and amount of solvent, as well as the ice crystal growth rate. The resulting pores exhibit a locally oriented porous structure, mostly consisting of through-pores with small diameters. Foam materials prepared using a single foaming technique struggle to meet requirements for extremely low density, high porosity, high open-cell ratio, and high compression / expansion performance. Summary of the Invention

[0005] Based on this, this application provides a high-porosity polyurethane foam and its preparation method, the resulting polyurethane foam having high porosity and high compressibility and expansion performance.

[0006] A high-porosity polyurethane foam, wherein the polyurethane foam has macropores with a pore size of 500-2000 μm and micropores with a pore size of 10-100 μm, the volume ratio of macropores to micropores is 10-50:1, and the overall porosity of the polyurethane foam is greater than 96% and the expansion ratio is greater than 75.

[0007] The polyurethane foam provided in this application has extremely high porosity and expansion ratio. After being implanted into the target site through a catheter, it expands on its own, playing a role in rapid filling or fixed support.

[0008] Several alternative methods are provided below, but they are not intended as additional limitations on the overall solution above. They are merely further additions or optimizations. Provided there are no technical or logical contradictions, each alternative method can be combined individually with respect to the overall solution above, or multiple alternative methods can be combined with each other.

[0009] Optionally, the Tg of the polyurethane foam is 37℃~41℃.

[0010] The glass transition temperature of polyurethane foam is close to that of human body temperature. Polyurethane foam can be compressed to a very small volume when heated, and then fixed into a temporary shape at low temperature. It can then be implanted into the target site through a catheter. Under body temperature, it can expand and return to its original shape on its own, making it suitable as a minimally invasive embolization biomedical device.

[0011] This application also discloses a method for preparing the high-porosity polyurethane foam, comprising the following steps:

[0012] (1) Dissolve diisocyanate, macromolecular diol, small molecule polyol and catalyst in solvent to obtain polyurethane precursor liquid;

[0013] (2) Inject the polyurethane precursor liquid into a mold filled with water-soluble inorganic salt particles;

[0014] (3) The polyurethane precursor liquid is polymerized and cured at a temperature below the melting point of the solvent;

[0015] (4) Freeze-drying to remove solvent;

[0016] (5) Remove water-soluble inorganic salt particles by dissolving them in water to obtain the high-porosity polyurethane foam.

[0017] In step (3), the polymerization reaction is carried out at a temperature lower than the melting point of the solvent. When the temperature of the precursor liquid before polymerization is lower than the freezing point of the system, most of the solvent crystallizes to form fine ice crystal particles. Small molecule reactants and a small amount of solvent are squeezed out of the ice crystals and concentrated in the gaps between the ice crystals to form a high-concentration micro liquid phase. The reactants solidify in this liquid phase to form pore walls. After the reaction is completed, the ice crystals melt to produce a porous structure.

[0018] The preparation method provided in this application employs both water-soluble inorganic salt particles and freeze polymerization below the solvent melting point to create pores. These two methods form a controllable construction of multi-level channels, which improves porosity, enhances pore structure, makes the pore structure uniformly distributed, and ensures good pore connectivity.

[0019] Optionally, the diisocyanate is at least one selected from 1,6-hexanediisocyanate (HDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), trimethylhexanediisocyanate (TMHDI), and L-lysine diisocyanate (LDI).

[0020] The number-average molecular weight of the macromolecular diol is 200 to 2000, and the macromolecular diol is at least one of polyethylene glycol (PEG), polycaprolactone diol (PCL-Diol), polyglycolic acid diol (PGA-Diol), polyhydroxybutyrate diol (PHB-Diol), polylactic acid diol (PLA-Diol), and polytetrahydrofuran (PTMG).

[0021] The small molecule polyol is at least one of triethanolamine (TEA), N,N,N',N'-tetratetra(2-hydroxypropyl)ethylenediamine (HPED), pentaerythritol (PER), and tri(hydroxymethyl)ethane (TME).

[0022] Optionally, the catalyst is at least one of organotin compounds, dibutyltin dilaurate (DBTDL), and stannous octoate.

[0023] Optionally, the solvent is dimethyl sulfoxide (DMSO), 1,4-dioxane, or carbon tetrachloride. The melting point of the solvent should not be too low; otherwise, the low temperature of the freeze polymerization will result in a slow or difficult polymer formation process.

[0024] Optionally, the molar ratio of the total amount of hydroxyl groups in the macromolecular diol and the small molecule polyol to the isocyanate groups in the diisocyanate is 0.95 to 1.05:1.

[0025] Optionally, the molar ratio of the macromolecular polyol to the small molecule polyol is 0.05 to 0.2:1.

[0026] Optionally, the total mass of the diisocyanate, macromolecular diol, and small molecule polyol is m1, the mass of the solvent is m2, and the ratio of m2 to m1 is in the range of 0.5 to 10:1.

[0027] Optionally, the mass of the catalyst is m3, and the ratio of m3 to m1 ranges from 0.05% to 2%.

[0028] Optionally, in step (2), the water-soluble inorganic salt particles are at least one of sodium chloride particles, potassium chloride particles, and sodium carbonate particles.

[0029] Optionally, in step (2), the particle size of the water-soluble inorganic salt particles is less than 2000 μm. Preferably, it is 200–1500 μm.

[0030] Optionally, in step (2), the water-soluble inorganic salt particles adopt two particle sizes, one of which is a large particle size of 800-1500 μm and the other is a small particle size of 200-300 μm, with a mass ratio of large particle size to small particle size of 2-3:1.

[0031] Water-soluble inorganic salt particles are used to form macropores in polyurethane foam. Micropores are formed on the pore walls by freeze-polymerized ice crystals. The thickness of the macropore walls determines the space for the ice crystals. The pore wall thickness is closely related to the particle size and packing density of the water-soluble inorganic salt particles. If the macropore walls are too thin, there is insufficient space to accommodate the ice crystals and form a micropore structure; if the macropore walls are too thick, the porosity is directly affected. Therefore, the macropore walls need to be as thin as possible while still being able to accommodate the ice crystals to form a complete micropore structure. The presence of the micropore structure increases the strength of the pore walls, and this increase in strength depends on the optimization of structural stress. Simultaneously, the polyurethane foam also needs to possess shape memory properties, meaning the pore structure is not easily damaged during compression and recovery. To simultaneously satisfy porosity, mechanical properties, and shape memory functions, precise control over the size and distribution of both macropores and micropores is required.

[0032] Optionally, in step (2), the polyurethane precursor liquid is injected into a mold filled with water-soluble inorganic salt particles, specifically including the following steps:

[0033] (2-1) Add 1% to 2% water by mass to water-soluble inorganic salt particles, stir evenly, pack into a mold and compact, dry at 70-100℃ for 3 to 5 hours to obtain water-soluble inorganic salt particle template.

[0034] (2-2) A portion of the polyurethane precursor liquid is injected into the water-soluble inorganic salt particle template, and the polyurethane precursor liquid is made to enter the pores of the water-soluble inorganic salt particles by means of vibration or vacuum degassing.

[0035] (2-3) Repeat step (2-2) until the pores of the water-soluble inorganic salt particles are filled with polyurethane precursor liquid.

[0036] Add 1% to 2% water by mass to water-soluble inorganic salt particles, stir evenly, pack into a mold and compact, place in an oven to dry for a certain period of time, so that they are tightly bonded and stacked, but without destroying the crystal morphology of the inorganic salt particles.

[0037] Because of the high bulk density of water-soluble inorganic salt particles, the polyurethane precursor solution does not easily enter the gaps between the water-soluble inorganic salt particles. Therefore, it is necessary to use vibration or vacuum degassing to assist the polyurethane precursor solution in entering the gaps between the water-soluble inorganic salt particles. Depending on the viscosity of the polyurethane precursor solution, the bulk density of the water-soluble inorganic salt particles, and the pore size of the prepared product, the polyurethane precursor solution is injected into the gaps between the water-soluble inorganic salt particles in small amounts and multiple times.

[0038] Optionally, in step (3), the temperature range of the polymerization reaction is -40 to 5°C, and the polymerization reaction time is 8 to 96 hours.

[0039] Optionally, in step (4), after the freeze polymerization reaction is completed, the mold is removed and the solvent is sublimated by freeze drying to remove the solvent.

[0040] Optionally, in step (5), water-soluble inorganic salt particles are removed by dissolving in water at 0–40°C.

[0041] When removing water-soluble inorganic salt particles, the process can be carried out at room temperature or in ice water, and the dissolution rate can be accelerated with the help of auxiliary means such as a shaking table. Preferably, in step (5), the water-soluble inorganic salt particles are removed by dissolving in water at 0-10°C. Dissolving and removing water-soluble inorganic salt particles at a lower temperature is beneficial to maintaining the morphology of polyurethane foam, avoiding the problem of pore structure collapse and deformation caused by softening of polymer chains due to high temperature, and better maintaining the pore morphology and porosity.

[0042] After removing the water-soluble inorganic salt particles in step (5), the polyurethane foam is vacuum dried at a low temperature (0-10℃) or room temperature to obtain the high-porosity polyurethane foam. Preferably, after removing the water-soluble inorganic salt particles in step (5), vacuum drying is performed at a low temperature. Low-temperature drying helps maintain the morphology of the polyurethane foam and avoids the problem of pore structure collapse and deformation caused by the softening of polymer chain segments due to high temperature. The morphology and porosity of the pores can be better maintained.

[0043] Compared with the prior art, this application has at least the following advantages:

[0044] (1) High porosity: Combining the advantages of freeze polymerization and soluble salt template method, a through-pore structure with macropores (500-2000 μm, derived from the dissolution of water-soluble inorganic salt particles) and micropores (10-100 μm, derived from the sublimation of solvent ice crystals) is obtained, which greatly improves the porosity.

[0045] (2) Pore size is precisely controllable and has a narrow distribution: The pore size is mainly determined by the particle size of water-soluble inorganic salt particles and the freezing polymerization process. By selecting water-soluble inorganic salt particles of different sizes, controlling the ice crystal growth rate, and the type and concentration of polyurethane precursor liquid, the pore size and distribution of polyurethane foam can be precisely controlled.

[0046] (3) Excellent material properties: The prepared foam has low density, high compression / expansion ratio, better support performance and the ability to recover its shape at body temperature. Attached Figure Description

[0047] Figure 1 This is a SEM image of Embodiment 1 of this application;

[0048] Figure 2 This is a SEM image of Comparative Example 1 of this application;

[0049] Figure 3 This is a SEM image of Comparative Example 2 of this application;

[0050] Figure 4 This is a DSC diagram of Embodiment 1 of this application;

[0051] Figure 5 This is a DMA (shape memory property) diagram of Embodiment 1 of this application. Detailed Implementation

[0052] Various exemplary embodiments of this application are now described in detail. This detailed description should not be considered as a limitation of this application, but rather as a more detailed description of certain aspects, features, and implementations of this application.

[0053] It should be understood that the terminology used in this application is merely for describing particular embodiments and is not intended to limit the application. Furthermore, for numerical ranges in this application, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0054] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art described herein. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0055] Various modifications and variations can be made to the specific embodiments described in this application without departing from the scope or spirit of this application, as will be apparent to those skilled in the art. Other embodiments derived from this application will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0056] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0057] The technical solution of this application will be further described below through embodiments.

[0058] Example 1 (Frozen polymerization + salt template synergistic pore formation)

[0059] A method for preparing high-porosity polyurethane foam includes the following steps:

[0060] (a) Diisocyanate TMHDI (50 mmol, 10.94 g), macromolecular diol PEG (Mn = 400, 2.5 mmol, 1 g), small molecule polyol TEA (20 mmol, 3.01 g), small molecule polyol HPED (8 mmol, 1.91 g), and catalyst DBTDL (0.017 g) were dissolved in solvent dimethyl sulfoxide DMSO (84.33 g) and stirred to dissolve, thus obtaining a polyurethane precursor solution.

[0061] (b) Add 2% water by mass to water-soluble inorganic salt particles (particle size about 800 μm), stir evenly, pack into a mold and compact, dry at 80°C for 4 hours to obtain water-soluble inorganic salt particle template.

[0062] A portion of the polyurethane precursor solution is injected into the water-soluble inorganic salt particle template. Vibration is used to allow the polyurethane precursor solution to enter the pores of the water-soluble inorganic salt particles. This process is repeated multiple times until the pores of the water-soluble inorganic salt particles are filled with the polyurethane precursor solution.

[0063] (c) The water-soluble inorganic salt particle template filled with polyurethane precursor liquid is reacted at -15°C for 24 hours to cure, forming a polyurethane / salt composite.

[0064] (d) The polyurethane / salt composite was demolded and freeze-dried using a freezer (sample temperature -20℃) to remove the solvent by sublimation.

[0065] (e) The product obtained by freeze-drying and removing solvent in step (d) is immersed in water to dissolve and remove sodium chloride particles, and then freeze-dried using a freezer (sample temperature -20°C) to obtain polyurethane foam.

[0066] Examples 2-5

[0067] The amounts of each raw material used in Examples 2 to 5 are shown in Table 2, and the reaction conditions are shown in Table 3. For items not listed in the tables, the same raw materials and reaction conditions as in Example 1 are used.

[0068] Table 1

[0069]

[0070] Table 2

[0071]

[0072]

[0073] Table 3

[0074] Comparative Example 1 (Porosity created by salt template)

[0075] (a) TMHDI (50 mmol, 10.94 g), PEG (Mn = 400, 2.5 mmol, 1 g), TEA (20 mmol, 3.01 g), HPED (8 mmol, 1.91 g), catalyst DBTDL (0.017 g), and solvent dimethyl sulfoxide (DMSO) (84.33 g) were stirred and dissolved to obtain a polyurethane precursor solution.

[0076] (b) Add 2% water by mass to water-soluble inorganic salt particles (particle size about 800 μm), stir evenly, pack into a mold and compact, dry at 80°C for 4 hours to obtain water-soluble inorganic salt particle template.

[0077] A portion of the polyurethane precursor solution is injected into the water-soluble inorganic salt particle template. Vibration is used to allow the polyurethane precursor solution to enter the pores of the water-soluble inorganic salt particles. This process is repeated multiple times until the pores of the water-soluble inorganic salt particles are filled with the polyurethane precursor solution.

[0078] (c) The water-soluble inorganic salt particle template filled with polyurethane precursor liquid is reacted at 35°C for 12 hours to cure, forming a polyurethane / salt composite.

[0079] (d) The polyurethane / salt composite was demolded and the sample was taken out and soaked in a large amount of deionized water to completely replace and remove the solvent DMSO and sodium chloride particles in the sample. After drying, polyurethane foam was obtained.

[0080] Comparative Example 2 (salt-free template, frozen polymerization to create pores)

[0081] (a) TMHDI (50 mmol, 10.94 g), PCL-Diol (Mn = 530, 2.5 mmol, 1.32 g), TEA (20 mmol, 3.01 g), HPED (8 mmol, 1.91 g), and catalyst DBTDL (0.017 g) were dissolved in 84.33 g of dimethyl sulfoxide (DMSO) solvent and stirred to dissolve, thus obtaining a polyurethane precursor solution;

[0082] (b) The polyurethane precursor solution was cured by reacting at -15°C for 24 hours, freeze-dried, and the solvent was removed by sublimation to obtain porous polyurethane.

[0083] Performance Characterization

[0084] The polyurethane shape memory foams prepared in each embodiment were characterized, and the characterization results are detailed in Table 4. The main characterization test methods are as follows:

[0085] 1. Calculation of surface density and porosity

[0086] According to GB / T 634-2009 Determination of Apparent Density of Foamed Plastics and Rubber, the apparent density of the sample is tested according to the following steps, and the porosity of the sample is calculated by comparing the theoretical density.

[0087] 1) Sample preparation

[0088] Cut the foam material into regular geometric shapes (cubic prisms) with accurately measurable volume. The original pore structure should not be altered during cutting; ensure a smooth surface without any residual skin layer. The total volume of the sample should be at least 100 cm³. 3 Each group should have at least 5 parallel samples; dry in an oven at 80°C for 12 hours to constant weight, cool to room temperature in a desiccator (and let stand for at least 16 hours), weigh the samples to an accuracy of 0.5% g, in g.

[0089] 2) Apparent density determination

[0090] Measure the three dimensions of the sample with vernier calipers (accuracy 0.01 mm), and take the average value at least three positions for each dimension. Calculate the volume V.

[0091] Apparent density: ρ = m / V (unit: mg / cm³) 3 ), take the average value.

[0092] 3) Porosity calculation (theoretical density comparison method)

[0093] The density ρ of the polyurethane bulk material was obtained using the same method described above. PU ;

[0094] Porosity formula: ε=(1-ρ / ρ PU )×100%

[0095] 2. Expansion ratio of shape memory polymers

[0096] 1) Heating: Heat the sample to a programmed temperature above its glass transition temperature, 60-70℃.

[0097] 2) Loading / Deformation: Applying external pressure to the specimen to compress its volume to a minimum;

[0098] 3) Cooling / fixing: While keeping the external force constant, cool the sample to a temperature much lower than its glass transition temperature (-20 to 10°C), fix the temporary shape, and remove the external force.

[0099] Measure the temporary volume: At this moment, measure the volume of the sample in the temporary shape (Vtemporary).

[0100] Recovery: The unconstrained sample is reheated to the recovery temperature (60-70℃), and its final recovered volume (V permanent) is measured.

[0101] Volume expansion ratio = V permanent / V temporary

[0102] Each sample must be tested in at least 3 groups, and the average value should be taken.

[0103] 3. Glass transition temperature Tg

[0104] The glass transition temperature (Tg) of foam materials was determined using a synchronous thermal analyzer according to GB / T 19466.2-2004, following the steps below.

[0105] 1) Sample preparation

[0106] Take 5–10 mg of representative foam sample (avoiding the skin layer), embrittle it with liquid nitrogen, grind it into uniform particles, and seal it to prevent moisture absorption. Before testing, accurately weigh it to 0.01 mg, place it in a standard aluminum crucible, and seal it with a pressure cap (puncture micropores to release pyrolysis gases).

[0107] 2) Test program

[0108] Thermal history elimination: Under a nitrogen atmosphere (50 mL / min), the temperature was increased from room temperature to 120 °C at a rate of 10 °C / min and held at that temperature for 5 min to eliminate the thermal history.

[0109] 3) Tg determination: The temperature was then increased to 120℃ at a rate of 5℃ / min, and the curve was recorded.

[0110] 4. Characterization of the pore structure of foam materials (SEM)

[0111] The foam material sample was placed in a sputtering coating apparatus and sputtered with gold for 60 seconds at a distance of 3 cm. The microstructure of the foam material was imaged using a low-vacuum scanning electron microscope (SEM).

[0112] 5. Dynamic Thermomechanical Analysis (DMA) - Shape Memory Properties

[0113] Using a dynamic thermomechanical analyzer in "controlled stress" mode, the shape memory cycle of the material was tested, and the shape memory retention rate and recovery rate were calculated. The force-thermal cycle program is as follows:

[0114] First, heat the sample to 80℃ and perform isothermal tensile testing on the sample at a certain strain rate. When the strain reaches 7.5%, stop loading and then reduce the temperature to -20℃ at 5℃ / min. Unload and hold for 5 min, and calculate the shape retention rate.

[0115] The sample is then heated to 80℃ at a rate of 5℃ / min and held for 10min. The sample will recover its shape. The shape recovery rate is calculated. This is one thermomechanical cycle. The same procedure is repeated multiple times.

[0116] Table 4

[0117] Serial Number <![CDATA[Density (mg / cm 3 )]]> Porosity expansion factor Glass transition temperature Tg Example 1 32.2 97.2％ 83.2 40℃ Example 2 21.85 98.1％ 89.5 40℃ Example 3 35.65 96.9％ 76.3 37℃ Example 4 36.8 96.8％ 75.4 39℃ Example 5 40.25 96.5％ 80.1 41℃ Comparative Example 1 112.7 90.2％ 56.2 40℃ Comparative Example 2 143.75 87.5％ 40.4 37℃

[0118] Figure 1 The image shows a SEM image of the pore structure of the polyurethane foam in Example 1. It can be seen that in addition to the macropore structure (approximately 750 μm in diameter) formed by salt template pore formation, there are also pores (approximately 20 μm in diameter) formed by ice crystals from freeze polymerization on the pore walls. The image also shows that the foam exhibits a mixed pore structure of closed and open cells. By adjusting the particle size distribution of the salt particles and regulating the freeze polymerization pore formation process parameters, the pore structure, porosity, and distribution can be controlled, thereby effectively regulating the expansion ratio of the material.

[0119] Figure 2 The SEM image of the pore structure of the polyurethane foam in Comparative Example 1 shows that only the pore structure formed by the salt template is visible. Figure 3 The image shows the SEM image of the pore structure of the foam in Comparative Example 2, which is the pore structure produced by simple freeze polymerization.

[0120] Figure 4 The image shows the DSC diagram of the polyurethane foam prepared in Example 1. As can be seen from the figure, the glass transition temperature of the prepared shape memory foam material is about 40°C, which is close to body temperature. This allows the material to quickly recover from temporary deformation in the human body environment.

[0121] Figure 5 The shape memory properties of the polyurethane foam prepared in Example 1 were tested using DMA. Based on the obtained data, the shape fixation rate Rf of the sample was calculated to be 95.5%, and the shape recovery rate was 94.68%. After multiple cycles, the shape memory properties (shape fixation rate and recovery rate) of the material remained basically unchanged, indicating that the material has good shape memory properties.

[0122] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A high-porosity polyurethane foam, characterized in that, The polyurethane foam has both macropores with a pore size of 500-2000 μm and micropores with a pore size of 10-100 μm, the volume ratio of macropores to micropores is 10-50:1, and the overall porosity of the polyurethane foam is greater than 96% and the expansion ratio is greater than 75.

2. The high-porosity polyurethane foam as described in claim 1, characterized in that, The Tg of the polyurethane foam is 37℃~41℃.

3. A method for preparing a high-porosity polyurethane foam, characterized in that, Includes the following steps: (1) Dissolve diisocyanate, macromolecular diol, small molecule polyol and catalyst in solvent to obtain polyurethane precursor liquid; (2) Inject the polyurethane precursor liquid into a mold filled with water-soluble inorganic salt particles; (3) The polyurethane precursor liquid is polymerized and cured at a temperature below the melting point of the solvent; (4) Freeze-drying to remove solvent; (5) Remove water-soluble inorganic salt particles by dissolving them in water to obtain the high-porosity polyurethane foam.

4. The method for preparing high-porosity polyurethane foam as described in claim 3, characterized in that, The diisocyanate is at least one of 1,6-hexanediisocyanate, 4,4'-dicyclohexylmethane diisocyanate, trimethylhexanediisocyanate, and L-lysine diisocyanate. The number-average molecular weight of the macromolecular diol is 200 to 2000, and the macromolecular diol is at least one of polyethylene glycol, polycaprolactone diol, polyglycolic acid diol, polyhydroxybutyrate diol, polylactic acid diol, and polytetrahydrofuran. The small molecule polyol is at least one of triethanolamine, N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine, pentaerythritol, and tris(hydroxymethyl)ethane.

5. The method for preparing high-porosity polyurethane foam as described in claim 3, characterized in that, The total molar ratio of the hydroxyl groups of the macromolecular diol and the small molecule polyol to the isocyanate groups in the diisocyanate is 0.95 to 1.05:

1.

6. The method for preparing high-porosity polyurethane foam as described in claim 3, characterized in that, The total mass of the diisocyanate, macromolecular diol, and small molecule polyol is m1, the mass of the solvent is m2, and the ratio of m2 to m1 is in the range of 0.5 to 10:

1.

7. The method for preparing high-porosity polyurethane foam as described in claim 3, characterized in that, In step (2), the particle size of the water-soluble inorganic salt particles is less than 2000 μm.

8. The method for preparing high-porosity polyurethane foam as described in claim 3, characterized in that, In step (2), the polyurethane precursor liquid is injected into a mold filled with water-soluble inorganic salt particles, specifically including the following steps: (2-1) Add 1% to 2% water by mass to water-soluble inorganic salt particles, stir evenly, pack into a mold and compact, dry at 70-100℃ for 3 to 5 hours to obtain water-soluble inorganic salt particle template. (2-2) A portion of the polyurethane precursor liquid is injected into the water-soluble inorganic salt particle template, and the polyurethane precursor liquid is made to enter the pores of the water-soluble inorganic salt particles by means of vibration or vacuum degassing. (2-3) Repeat step (2-2) until the pores of the water-soluble inorganic salt particles are filled with polyurethane precursor liquid.

9. The method for preparing high-porosity polyurethane foam as described in claim 3, characterized in that, In step (3), the temperature range of the polymerization reaction is -40 to 5℃, and the polymerization reaction time is 8h to 96h.

10. An implantable medical device, characterized in that, It is made using high-porosity polyurethane foam as described in any one of claims 1 to 2.

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