A multilayer composite, a method of manufacture and use thereof

Abstract

The application provides a multilayer composite material, a preparation method and application thereof, and relates to the technical field of medical materials.The multilayer composite material comprises, from bottom to top, at least a lower surface layer, an intermediate layer and an upper surface layer in sequence; the raw material components of the lower surface layer and the upper surface layer respectively comprise PCL, and the raw material component of the intermediate layer comprises PCL or PLA; the density of the upper surface layer and the density of the lower surface layer are respectively lower than the density of the intermediate layer; and the upper surface layer and the lower surface layer are respectively supercritical foaming materials.The multilayer composite material can realize non-foaming or less foaming of the intermediate layer and relatively sufficient foaming of the upper surface layer and the lower surface layer.The multilayer composite material can be used as a dressing, an orthopedic fixing plate material, a carrier of a bioactive component and the like.

Description

Technical Field

[0001] This invention belongs to the field of medical technology and relates to a multilayer composite material, its preparation method, and its application. Background Technology

[0002] Biodegradable polymer materials, including polylactic acid (PLA) and polycaprolactone (PCL), possess excellent biocompatibility and degradability, and have a very broad application prospect in the biomedical field, with ongoing in-depth research. Supercritical foaming materials, characterized by their light weight, good resilience, and good cushioning properties, have already achieved widespread application in multiple fields.

[0003] Supercritical foaming is an effective way to optimize the performance and broaden the applications of biodegradable polymer materials. Chinese patent CN117777643A discloses a biodegradable supercritical foamed material of PBAT, obtained by supercritical foaming of a copolymer of butylene adipate and butylene terephthalate under the action of an initiator, chain extender, and additives. Chinese patent CN119060514A discloses a supercritical foamed PLA material, comprising PLA, a peroxide initiator, and a chain extender. US patent US20120065604A1 discloses a biodegradable hemostatic sponge composed of biodegradable, absorbable polylactic acid with open-cell micropores less than 100 μm in diameter and auxiliary moisture-absorbing materials selected from collagen, chitosan, and starch.

[0004] Existing supercritical foamed biodegradable polymer materials are generally produced through uniform foaming of the entire material. There are few reports of obtaining supercritical foamed materials with varying foam densities in different areas through a single supercritical foaming process. However, some applications of supercritical foamed materials require high foaming degree, low density, and good skin-friendliness on the surface, while the core requires low foaming degree, high density, and good support. Therefore, existing supercritical foamed materials need further optimization to improve their performance and / or broaden their applications. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a multilayer composite material, its preparation method, and its applications.

[0006] The technical solution of the present invention is as follows:

[0007] A multilayer composite material comprising, from bottom to top, at least a lower surface layer, an intermediate layer and a top surface layer;

[0008] The raw material components of the lower and upper surface layers respectively contain PCL;

[0009] The raw material components of the intermediate layer include PCL and / or PLA;

[0010] The density of the upper surface layer and the density of the lower surface layer are respectively lower than the density of the middle layer;

[0011] The upper and lower surfaces are both made of supercritical foaming materials.

[0012] Preferably, the density of the intermediate layer is not less than 0.9 g / cm³. 3 ;

[0013] The density of the upper surface layer and the density of the lower surface layer each do not exceed 0.5 g / cm³. 3 .

[0014] More preferably, the intermediate layer is a supercritical foaming material;

[0015] The density of the upper surface layer and the density of the lower surface layer each do not exceed 0.2 g / cm³. 3 .

[0016] Preferably, the weight-average molecular weight of the PCL in the upper surface layer is lower than that of the PCL or PLA in the middle layer.

[0017] The weight-average molecular weight of the PCL in the lower surface layer is lower than that of the PCL or PLA in the middle layer.

[0018] More preferably, the weight-average molecular weight of the PCL in the upper layer and the weight-average molecular weight of the PCL in the lower layer do not exceed 50% of the weight-average molecular weight of the PCL or PLA in the intermediate layer.

[0019] More preferably, the weight-average molecular weight of the PCL or PLA is not less than 40,000;

[0020] The weight-average molecular weight of the PCL in the upper layer and the weight-average molecular weight of the PCL in the lower layer do not exceed 20,000 respectively.

[0021] Preferably, the raw material components of the upper and lower surface layers each contain chitosan at a weight percentage not exceeding 12%.

[0022] The raw material components of the upper and lower surface layers each contain a water-soluble polymer with a weight percentage not exceeding 2%.

[0023] The raw material components of the upper and lower surface layers each contain no more than 15% polyurethane elastomer by weight.

[0024] The raw material components of the intermediate layer contain fillers accounting for no more than 10% by weight;

[0025] Preferably, the thickness of the upper surface layer and the thickness of the lower surface layer are 0.05mm-5mm respectively;

[0026] The thickness of the intermediate layer is 0.1-10 mm.

[0027] A method for preparing a multilayer composite material according to any of the above embodiments, wherein a composite layer material having at least three layers is prepared by melt co-extrusion process;

[0028] The composite layer material is subjected to supercritical foaming to obtain the multilayer composite material.

[0029] An application of the multilayer composite material described in any of the above embodiments, as a dressing, as an orthopedic fixation plate, or as a carrier of bioactive ingredients.

[0030] The beneficial effects of this invention are:

[0031] (1) The present invention uses biodegradable polymer materials (the main material of the upper and lower layers is PCL, and the main material of the middle layer is PCL or PLA) to prepare a multi-layer composite material. The upper and lower layers are both supercritical foaming materials and their densities are lower than those of the middle layer. Due to their low density and supercritical foaming, the upper and lower layers have low mechanical strength, a soft touch to the skin, and good skin affinity, and can be in direct contact with the skin. The middle layer has high density and high mechanical strength, and can play a supporting role.

[0032] (2) The PCL in the upper and lower surface layers has a low weight-average molecular weight, while the PCL or PLA in the middle layer has a high weight-average molecular weight. During supercritical foaming, the supercritical fluid can easily penetrate into the upper and lower surface layers, but it is not easy to penetrate into the middle layer, which is conducive to forming a density difference between the middle layer and the upper and lower surface layers. By controlling the supercritical foaming temperature between the melting point of the PCL or PLA in the middle layer and the melting point of the PCL in the upper and lower surface layers, the supercritical foaming can be further optimized, and the upper and lower surface layers can achieve better foaming, while the middle layer does not foam or foams little.

[0033] (3) The upper, middle and lower layers contain different raw material components, which can optimize the performance of multilayer composite materials. For example, the presence of chitosan in the upper and lower layers can improve antibacterial properties, the presence of water-soluble polymers in the upper and lower layers can improve hydrophilicity, and the presence of inorganic fillers in the middle layer can improve mechanical strength, etc. Attached Figure Description

[0034] Figure 1 This is a cross-sectional image of the multilayer composite material obtained in Example 1.

[0035] Figure 2 This is a cross-sectional image of the multilayer composite material obtained in Example 2. Detailed Implementation

[0036] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0037] On the one hand, the present invention proposes a multilayer composite material, which comprises at least a lower surface layer, an intermediate layer and an upper surface layer from bottom to top;

[0038] The raw material components of the lower and upper surface layers each contain PCL;

[0039] The raw material components of the intermediate layer include PCL or PLA;

[0040] The density of the upper and lower surface layers is lower than that of the middle layer;

[0041] The upper and lower layers are both made of supercritical foaming materials.

[0042] PCL (polycaprolactone) has good biocompatibility, enabling it to interact well with human tissues (such as skin) without triggering immune or inflammatory responses. In the multilayer composite material of this invention, both the upper and lower layers are supercritical foaming materials containing PCL, exhibiting relatively low density, good skin affinity, and good breathability when in contact with human skin. The middle layer (containing PCL or PLA) has high density and high mechanical strength, providing excellent support. Furthermore, adjusting the foaming degree of the middle layer can adjust its mechanical strength, thus providing different support structures for different application scenarios.

[0043] In some embodiments, the density of the intermediate layer is not less than 0.9 g / cm³. 3 ;

[0044] The density of the upper surface layer and the density of the lower surface layer do not exceed 0.5 g / cm³. 3 .

[0045] The intermediate layer can be either unfoamed or supercritically foamed, but its density must not be less than 0.9 g / cm³. 3 This provides better support; the lower density of the upper and lower layers helps improve the skin-friendliness of the outer surfaces of both the upper and lower layers (the outer surface being the surface in contact with the skin).

[0046] For example, if the intermediate layer is foamed, the degree of foaming can be low, and the density can be 0.9 g / cm³. 3 0.95g / cm 3 1g / cm 3 1.05g / cm 3 1.1g / cm 3 1.15g / cm 3For the upper and lower layers, the degree of foaming is relatively high, and the density can be 0.5 g / cm³. 3 0.45g / cm 3 0.4g / cm 3 0.35g / cm 3 0.3g / cm 3 0.25g / cm 3 0.2g / cm 3 0.15g / cm 3 0.1g / cm 3 wait.

[0047] In some embodiments, the intermediate layer is a supercritical foamed material;

[0048] The density of the upper surface layer and the density of the lower surface layer do not exceed 0.2 g / cm³. 3 .

[0049] For the intermediate layer, the density can be no less than 0.5 g / cm³. 3 For example, the density could be 0.5 g / cm³. 3 0.55g / cm 3 0.6g / cm 3 0.65g / cm 3 0.7g / cm 3 0.75g / cm 3 0.8g / cm 3 0.85g / cm 3 0.9g / cm 3 0.95g / cm 3 1g / cm 3 For the upper and lower surface layers, the density can be 0.2 g / cm³. 3 0.18g / cm 3 0.15g / cm 3 0.12g / cm 3 0.1g / cm 3 0.08g / cm 3 wait.

[0050] For a supercritical fluid with a density lower than that of the upper and lower layers than that of the middle layer, at least the following four methods can be adopted: Method (1): Since the supercritical fluid first penetrates the upper and lower layers and then the middle layer, controlling the penetration time of the supercritical fluid can make it mainly penetrate the upper and lower layers and less penetrate the middle layer; Method (2): The higher the molecular weight of PCL and / or PLA, the more difficult it is for the supercritical fluid to penetrate. Therefore, the middle layer uses a material with a higher molecular weight, and the upper and lower surfaces use materials with a lower molecular weight, so that the supercritical fluid can penetrate the upper and lower layers and then less penetrate the middle layer; Method (3): The middle layer uses PCL or PLA with a higher density, and the upper and lower layers use PCL with a relatively lower density, so that the supercritical fluid is less likely to penetrate the middle layer after penetrating the upper and lower layers; (4) For biodegradable polymer materials such as PCL and PLA, the temperature of the supercritical fluid (i.e., the supercritical foaming temperature) is lower than the melting point Tm of the biodegradable polymer material, making it difficult for the supercritical fluid to penetrate and thus difficult to carry out supercritical foaming. The temperature of the supercritical fluid is higher than the Tm of the biodegradable polymer material, making it easier for the supercritical fluid to penetrate. Therefore, the intermediate layer uses a material with high Tm (such as high molecular weight and high crystallinity), while the upper and lower layers use materials with low Tm (such as low molecular weight and low crystallinity). Alternatively, for example, the intermediate layer uses PLA with high Tm (and high mechanical strength), while the upper and lower layers use PCL with low Tm (and low mechanical strength). The supercritical foaming temperature is between high Tm and low Tm, which allows the supercritical fluid to penetrate the upper and lower layers, but it is difficult to penetrate the intermediate layer.

[0051] In some embodiments, the weight-average molecular weight Mw of the PCL used in the upper layer (upper layer Mw) is lower than the Mw of the PCL or PLA used in the middle layer (middle layer Mw).

[0052] The Mw of the PCL used in the bottom layer (bottom layer Mw) is lower than the Mw of the PCL or PLA used in the middle layer (middle layer Mw).

[0053] Using the above scheme, such as method (2), the Mw of the intermediate layer is higher than that of the upper and lower surface layers, making it relatively difficult for the fluid to penetrate into the intermediate layer, resulting in less foaming or no foaming in the intermediate layer. Moreover, generally speaking, for the same material, the higher the Mw, the higher the melting point Tm. Therefore, as in method (4), it is possible to achieve foaming of the upper and lower surface layers, while the intermediate layer is less likely to foam or does not foam.

[0054] In some embodiments, the molecular weight (Mw) of the upper and lower surface layers does not exceed 50% of the molecular weight (Mw) of the intermediate layer. The Mw of the intermediate layer is significantly higher than that of the upper and lower surface layers; this larger molecular weight difference is more conducive to achieving sufficient foaming of the upper and lower surface layers and less or no foaming of the intermediate layer. For example, the Mw of the upper and lower surface layers does not exceed 50%, 45%, 40%, 35%, 30%, 25%, 20%, etc., of the molecular weight (Mw) of the intermediate layer.

[0055] Further preferred, the intermediate layer Mw is not less than 40,000; for example, for the intermediate layer PLA, Mw can be 40,000-120,000; for the intermediate layer PCL, Mw can be 100,000-200,000.

[0056] The Mw for the upper and lower layers should not exceed 20,000 each. For example, if the upper and lower layers are both PLA, the Mw can be 5,000-20,000; if the upper and lower layers are both PCL, the Mw can be 5,000-20,000.

[0057] For the multilayer composite material in this invention, the characteristics of two or more materials can be combined. For example, PLA has higher mechanical strength than PCL and has a better supporting effect. Therefore, the middle layer of the multilayer composite material can be PLA, and the upper and lower layers can be PCL respectively. The middle layer has high mechanical strength and a more significant supporting effect, while the upper and lower layers have good flexibility and skin-friendliness.

[0058] In some embodiments, the raw material components of the upper and lower surface layers each contain chitosan at a weight percentage not exceeding 12%; chitosan is a natural antibacterial agent that can provide good antibacterial properties for multilayer composite materials.

[0059] The raw material components of the upper and lower layers each contain no more than 2% by weight of water-soluble polymers; the water-soluble polymers can be polyethylene glycol, etc., which can improve the hydrophilicity of the outer surface of the multilayer composite material and improve its compatibility with the skin.

[0060] The raw material components of the upper and lower layers each contain no more than 15% polyurethane elastomer by weight; the polyurethane elastomer can give the upper and lower layers better flexibility and impact resistance, such as significantly improving the compression resilience of the multilayer composite material.

[0061] The raw material components of the intermediate layer contain fillers with a weight ratio not exceeding 10%; adding fillers to the intermediate layer can improve mechanical strength and enhance the supporting effect; the fillers can be inorganic fillers, such as talc, hydroxyapatite, kaolin, wollastonite, graphene, carbon nanotubes, etc., or organic fillers, such as PE micro powder, PTFE micro powder, etc.

[0062] In some embodiments, the thickness of the upper surface layer and the thickness of the lower surface layer are 0.05mm-5mm, respectively;

[0063] The thickness of the intermediate layer is 0.1-10mm.

[0064] For example, the thickness of the top and bottom layers can be 0.05mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, etc.; the thickness of the intermediate layer can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, etc.

[0065] On the other hand, the present invention also proposes a method for preparing a multilayer composite material according to any of the above embodiments, wherein a composite layer material having at least three layers is prepared by melt co-extrusion process;

[0066] The composite layer material is subjected to supercritical foaming to obtain a multilayer composite material.

[0067] Using the above preparation method, a multi-layered composite material can be pre-prepared and then subjected to supercritical foaming, which can conveniently yield a multi-layered composite material. Melt co-extrusion is a conventional technique in this field; for example, the materials for the upper, middle, and lower layers are melted separately and then co-extruded using a co-extrusion die. PCL and PLA are both polyester materials, therefore they have good compatibility in the molten state. Composite materials formed through melt co-extrusion exhibit high bonding strength between adjacent layers.

[0068] Furthermore, the present invention also proposes an application of the multilayer composite material described in any of the above embodiments, for use as a dressing, as an orthopedic fixation plate, or as a carrier of bioactive ingredients.

[0069] For example, when used as a dressing, the density of the upper and lower layers can be relatively low, such as 0.1-0.3 g / cm³. 3 The density of the intermediate layer can be relatively high, for example, 0.5-0.6 g / cm³. 3The thickness of the top, middle, and bottom layers can be 0.05-0.2mm respectively. It has good flexibility, excellent breathability, and can be bent. When used as an orthopedic fixation plate, the density of the top and bottom layers can be lower, for example, 0.1-0.4g / cm³. 3 It is skin-friendly and breathable, with a high density in the middle layer, for example, not less than 0.9g / cm³. 3 Even the middle layer can be non-foamed or made of materials with high mechanical strength (such as PLA), which are not easily deformed. The thickness of the upper and lower layers can be 0.1-0.5 mm, and the thickness of the middle layer can be 0.1-5 mm. When used as a carrier of bioactive ingredients, the thickness of the upper and lower layers can be 0.05-0.1 mm, and the thickness of the middle layer can be 0.1-1 mm.

[0070] The technical solution of the present invention will be further described and illustrated below with reference to various embodiments. Unless otherwise specified, the parts mentioned in the following embodiments are parts by weight.

[0071] Example 1

[0072] The multilayer composite material consists of a lower surface layer, an intermediate layer, and an upper surface layer from bottom to top. The materials of the lower surface layer, intermediate layer, and upper surface layer are all pure PCL, and they are labeled PCL1, PCL2, and PCL3, respectively. PCL1 and PCL3 both have a Mw of 20,000 and a Tm of approximately 58℃; PCL2 has a Mw of 50,000 and a Tm of approximately 61.5℃.

[0073] PCL1, PCL2 and PCL3 are melted at 90-100℃ using a twin-screw extruder, and then co-extruded using a co-extrusion die to form a three-layer composite material.

[0074] The three-layer composite material was subjected to supercritical foaming with CO2 fluid at a foaming temperature of 59.5±0.5℃ (between 58℃ and 61.5℃), a foaming pressure of 18MPa, a holding time of 2h, and then rapidly depressurized at a rate of 1.5MPa / s to obtain a multilayer composite material.

[0075] The cross-sectional structure of the multilayer composite material obtained in this embodiment is shown in the attached figure. Figure 1 As shown, it exhibits a distinct three-layer structure. The thickness of the top, bottom, and middle layers is 0.1 mm. The top and bottom layers show significant foaming, while the middle layer shows virtually no foaming. The measured densities of the top and bottom layers are both 0.42-0.43 g / cm³. 3 .

[0076] Comparative Example 1

[0077] The multilayer composite material consists of a lower surface layer and an upper surface layer from bottom to top; both the lower and upper surface layers are made of pure PCL and are designated PCL1 and PCL2, respectively. PCL1 has a Mw of 20,000 and a Tm of approximately 58°C; PCL2 has a Mw of 50,000 and a Tm of approximately 61.5°C.

[0078] PCL1 and PCL2 are melted at 90-100℃ using a twin-screw extruder, and then co-extruded using a co-extrusion die to form a two-layer composite material.

[0079] The above-mentioned bilayer composite material was supercritically foamed using CO2 fluid at a foaming temperature of 59.5±0.5℃ (between 58℃ and 61.5℃), a foaming pressure of 18MPa, a holding time of 2h, and then rapidly depressurized at a rate of 1.5MPa / s to obtain the bilayer composite material.

[0080] The bilayer composite material obtained in this embodiment exhibits a distinct bilayer structure, with both the upper and lower layers having a thickness of 0.1 mm. The lower layer shows a significantly higher degree of foaming than the upper layer. The measured density of the lower layer is 0.41-0.42 g / cm³. 3 The density of the upper surface layer is 0.86-0.87 g / cm³. 3 .

[0081] Therefore, based on the results of Example 1 and Comparative Example 1, it can be seen that the present invention sets a material that is difficult to supercritically foam in the intermediate layer, which can reduce the degree of foaming, or even achieve no foaming.

[0082] Example 2

[0083] The multilayer composite material consists of a lower surface layer, an intermediate layer, and an upper surface layer from bottom to top. The lower and upper surface layers are made of pure PCL and are designated as PCL1 and PCL2, respectively. The intermediate layer is made of pure PLLA. PCL1 and PCL2 both have a Mw of 60,000 and a Tm of approximately 62℃. PLLA has a Mw of 50,000 and a Tm greater than 140℃.

[0084] PCL1, PCL2, and PLLA are melted using a twin-screw extruder. The melting temperatures of PCL1 and PCL2 are 90-110℃, and the melting temperature of PLLA is 180-200℃. They are then co-extruded using a co-extrusion die to form a three-layer composite material.

[0085] The three-layer composite material was subjected to supercritical foaming with CO2 fluid at a foaming temperature of 70℃ (between 62℃ and 140℃), a foaming pressure of 20MPa, a holding time of 2.5h, and then rapidly depressurized at a rate of 1.5MPa / s to obtain a multilayer composite material.

[0086] The cross-sectional structure of the multilayer composite material obtained in this embodiment is shown in the attached figure. Figure 2 As shown, it exhibits a distinct three-layer structure. The thickness of the top, bottom, and middle layers is 0.1 mm. The top and bottom layers show significant foaming, while the middle layer shows virtually no foaming. The measured densities of the top and bottom layers are both 0.17-0.18 g / cm³. 3 .

[0087] Example 3

[0088] The multilayer composite material consists of a lower surface layer, an intermediate layer, and an upper surface layer from bottom to top. The materials of the lower surface layer, intermediate layer, and upper surface layer are all pure PCL, and they are labeled PCL1, PCL2, and PCL3, respectively. PCL1 and PCL3 both have a Mw of 20,000 and a Tm of approximately 58°C; PCL2 has a Mw of 100,000 and a Tm of approximately 62°C.

[0089] PCL1, PCL2 and PCL3 are melted at 90-100℃ using a twin-screw extruder, and then co-extruded using a co-extrusion die to form a three-layer composite material.

[0090] The three-layer composite material was subjected to supercritical foaming with CO2 fluid at a foaming temperature of 62±0.5℃, a foaming pressure of 20MPa, and a holding time of 2h. Then, the pressure was rapidly released at a rate of 1.5MPa / s to obtain a multilayer composite material.

[0091] The multilayer composite material obtained in this embodiment exhibits a distinct three-layer structure. The upper and lower surface layers are 0.15 mm thick and both show significant foaming, while the middle layer is 0.5 mm thick and exhibits slight foaming. The measured densities of the upper and lower surface layers are both 0.28-0.29 g / cm³. 3 The density of the intermediate layer is 0.95-0.96 g / cm³. 3 .

[0092] Example 4

[0093] The three-layer composite material in Example 3 was subjected to supercritical foaming with CO2 fluid at a foaming temperature of 63±0.5℃, a foaming pressure of 20MPa, and a holding time of 2h. Then, the pressure was rapidly released at a rate of 1.5MPa / s to obtain a multilayer composite material.

[0094] The multilayer composite material obtained in this embodiment exhibits a distinct three-layer structure. The upper and lower surface layers are both 0.18 mm thick and show significant foaming, while the middle layer is 0.65 mm thick and shows slight foaming. The measured densities of the upper and lower surface layers are both 0.22-0.23 g / cm³. 3 The density of the intermediate layer is 0.74-0.75 g / cm³. 3 .

[0095] Example 5

[0096] The multilayer composite material consists of a lower surface layer, an intermediate layer, and an upper surface layer from bottom to top. The lower and upper surface layers are composed of pure PCL, chitosan, and polyethylene glycol-200 in a weight ratio of 1:0.1:0.01, and are designated PCL1 and PCL2, respectively. The intermediate layer is composed of pure PCL and calcium hydroxyphosphate in a weight ratio of 1:0.05, and is designated PCL3. The Mw of pure PCL in PCL1 and PCL2 is 20,000, and the Tm is approximately 58℃; the Mw of pure PCL in PCL3 is 100,000, and the Tm is approximately 62℃.

[0097] PCL1, PCL2, and PCL3 are melted using a twin-screw extruder. The melting temperatures of PCL1 and PCL2 are 90-110℃, and the melting temperature of PCL3 is 110-130℃. They are then co-extruded using a co-extrusion die to form a three-layer composite material.

[0098] The three-layer composite material was subjected to supercritical foaming with CO2 fluid at a foaming temperature of 60±0.5℃ (between 58℃ and 62℃), a foaming pressure of 20MPa, a holding time of 3h, and then rapidly depressurized at a rate of 1.5MPa / s to obtain a multilayer composite material.

[0099] The multilayer composite material obtained in this embodiment exhibits a distinct three-layer structure. The thickness of both the upper and lower surface layers is 0.2 mm, and both show significant foaming. The thickness of the middle layer is 0.3 mm, and it exhibits virtually no foaming. The measured densities of the upper and lower surface layers are both 0.25-0.26 g / cm³. 3 .

[0100] Example 6

[0101] The multilayer composite material consists of a lower surface layer, an intermediate layer, and a top surface layer from bottom to top. All three layers are made of pure PCL and are designated PCL1, PCL2, and PCL3, respectively. PCL1 has a molecular weight (Mw) of 20,000 and a temperature range (Tm) of approximately 58°C; PCL2 has a Mw of 50,000 and a Tm of approximately 61.5°C; and PCL3 has a Mw of 10,000 and a Tm of approximately 57°C.

[0102] PCL1, PCL2 and PCL3 are melted at 90-100℃ using a twin-screw extruder, and then co-extruded using a co-extrusion die to form a three-layer composite material.

[0103] The three-layer composite material was subjected to supercritical foaming with CO2 fluid at a foaming temperature of 59.5±0.5℃ (between 58℃ and 61.5℃), a foaming pressure of 19MPa, a holding time of 2h, and then rapidly depressurized at a rate of 2MPa / s to obtain a multilayer composite material.

[0104] The multilayer composite material obtained in this embodiment has a distinct three-layer structure: a bottom layer with a thickness of 0.05 mm, a middle layer with a thickness of 0.2 mm, and a top layer with a thickness of 0.05 mm. Both the top and bottom layers show significant foaming, while the middle layer exhibits virtually no foaming. The density of the top layer was measured to be 0.30-0.31 g / cm³. 3 The density of the lower surface layer is 0.38-0.39 g / cm³. 3 .

[0105] Example 7

[0106] The difference between this embodiment and Embodiment 6 is that in Embodiment 6, 5% by weight of polyester-type TPU (hardness 85A) was added to PCL1 and PCL3 respectively, while PCL2 remained unchanged. The remaining steps remained the same.

[0107] Example 8

[0108] The difference between this embodiment and Embodiment 6 is that in Embodiment 6, 15% by weight of the polyester-type TPU from Embodiment 7 was added to PCL1 and PCL3 respectively, while PCL2 remained unchanged. The remaining steps remained the same.

[0109] The multilayer composite materials in Examples 6-8 were tested for compression resilience according to the method of GB / T 6669-2008. The test conditions were: compression to 50% of the original thickness at 25°C, holding for 10 minutes, releasing, and testing again after 30 minutes of release. Higher compression resilience indicates better flexibility. The results are shown in Table 1 below.

[0110] Table 1 Compression Rebound Rate / %

[0111]

[0112] As shown in Table 1 above, adding TPU to the upper and lower layers can improve the flexibility of the multilayer composite material.

[0113] Example 9

[0114] Following the preparation method of Example 6, the three-layer composite material was adjusted to obtain a multilayer composite material with a distinct three-layer structure: a bottom layer with a thickness of 1 mm, a middle layer with a thickness of 3 mm, and a top layer with a thickness of 1 mm. The middle layer showed virtually no foaming, while the top and bottom layers exhibited significant foaming. The density of the top layer was measured to be 0.31-0.32 g / cm³. 3 The density of the lower surface layer is 0.39-0.40 g / cm³. 3 .

[0115] Example 10

[0116] Following the preparation method of Example 6, the three-layer composite material was adjusted to obtain a multilayer composite material with a distinct three-layer structure: a bottom layer thickness of 3 mm, a middle layer thickness of 10 mm, and a top layer thickness of 5 mm. The middle layer showed virtually no foaming, while the top and bottom layers exhibited significant foaming. The density of the top layer was measured to be 0.32-0.33 g / cm³. 3 The density of the lower surface layer is 0.41-0.42 g / cm³. 3 .

[0117] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited to the above embodiments, which are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent and the description should still fall within the scope of the present invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A multilayer composite material, characterized in that, It contains at least a bottom layer, a middle layer, and a top layer from bottom to top; The raw material components of the lower and upper surface layers respectively contain PCL; The raw material components of the intermediate layer include PCL or PLA; The density of the upper surface layer and the density of the lower surface layer are respectively lower than the density of the middle layer; The weight-average molecular weight of the PCL in the upper surface layer is lower than that of the PCL or PLA in the middle layer. The weight-average molecular weight of the PCL in the lower surface layer is lower than that of the PCL or PLA in the middle layer. The upper and lower surfaces are both made of supercritical foaming materials.

2. The multilayer composite material according to claim 1, characterized in that, The density of the intermediate layer is not less than 0.9 g / cm 3 ; The density of the upper surface layer and the density of the lower surface layer each do not exceed 0.5 g / cm³. 3 .

3. The multilayer composite material according to claim 2, characterized in that, The intermediate layer is a supercritical foaming material; The density of the upper surface layer and the density of the lower surface layer each do not exceed 0.2 g / cm³. 3 .

4. The multilayer composite material according to claim 1, characterized in that, The weight-average molecular weight of the PCL in the upper layer and the weight-average molecular weight of the PCL in the lower layer do not exceed 50% of the weight-average molecular weight of the PCL or PLA in the middle layer.

5. The multilayer composite material according to claim 4, characterized in that, The weight-average molecular weight of the PCL or PLA in the intermediate layer is not less than 40,000. The weight-average molecular weight of the PCL in the upper layer and the weight-average molecular weight of the PCL in the lower layer do not exceed 20,000 respectively.

6. The multilayer composite material according to claim 1, characterized in that, The raw material components of the upper and lower surface layers each contain chitosan at a weight percentage not exceeding 12%. The raw material components of the upper and lower surface layers each contain a water-soluble polymer with a weight percentage not exceeding 2%. The raw material components of the upper and lower surface layers each contain no more than 15% polyurethane elastomer by weight. The raw material components of the intermediate layer contain fillers accounting for no more than 10% by weight.

7. The multilayer composite material according to claim 1, characterized in that, The thickness of the upper surface layer and the thickness of the lower surface layer are 0.05mm-5mm respectively; The thickness of the intermediate layer is 0.1-10 mm.

8. A method for preparing a multilayer composite material according to any one of claims 1-7, characterized in that, A composite layer material with at least three layers was prepared using a melt co-extrusion process. The composite layer material is subjected to supercritical foaming to obtain the multilayer composite material.

9. An application of the multilayer composite material according to any one of claims 1-7, characterized in that, It can be used as a dressing, as an orthopedic fixation plate, or as a carrier of bioactive ingredients.

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