A photocurable polylactic acid composite material, its preparation method and application

Abstract

This invention discloses a photocurable polylactic acid (PLA) composite material, its preparation method, and its applications, belonging to the field of biodegradable polymer materials technology. It comprises the following raw materials in parts by weight: 70-99.4 parts of PLA, 0.5-20 parts of a photodimerizing agent, and 0.1-10 parts of a compatibilizer. The photodimerizing agent is a monomer capable of undergoing a [2+2] photocycloaddition reaction under ultraviolet irradiation to generate a cyclobutane derivative. No small-molecule photoinitiator is required; a three-dimensional network is formed through direct cyclobutane crosslinking between photodimerizing agents (such as coumarin derivatives and cinnamic acid derivatives). The aforementioned photocurable PLA composite material maintains the biodegradability of PLA while significantly improving its toughness, modulus, and heat distortion temperature. It can be applied to fields such as 4D printing (light-driven shape change), photowelding / repair of products, and light-controlled regulation of drug release rates.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable polymer materials technology, specifically relating to a photocurable polylactic acid composite material, its preparation method, and its application. Background Technology

[0002] Polylactic acid (PLA) has shown broad application prospects in many fields due to its good biocompatibility and biodegradability. However, its inherent brittleness and poor heat resistance severely limit its development. Introducing photocuring technology is an effective strategy to improve PLA performance. Currently, most photocurable PLA systems rely on (meth)acrylate monomers and free radical photoinitiators.

[0003] This traditional system has several inherent flaws: 1) Biosafety concerns: Small molecule photoinitiators and their photolysis products may have cytotoxicity and sensitization, and are not suitable for strict biomedical scenarios such as in vivo implantation.

[0004] 2) Oxygen inhibition effect: Oxygen in the air quenches free radicals, resulting in incomplete curing and stickiness of the material surface.

[0005] 3) Large polymerization shrinkage: When the double bonds of acrylate are converted into single bonds, significant volume shrinkage occurs, which can easily lead to product deformation and internal stress concentration.

[0006] 4) Single function: Once the cross-linked network is formed, it is irreversible, making it difficult to reprocess or regulate the function of the material. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a photocurable polylactic acid composite material, its preparation method, and its application, thereby solving the problems in the prior art.

[0008] The objective of this invention can be achieved through the following technical solutions: A photocurable polylactic acid composite material, comprising the following raw materials in parts by weight: Polylactic acid 70~99.4 parts; Photodimerizing agent 0.5~20 parts; Compatibilizer 0.1~10 parts; The photodimer is a monomer that can undergo a [2+2] photocycloaddition reaction under ultraviolet irradiation to generate a cyclobutane derivative.

[0009] Furthermore, the compatibilizer is one or a combination of two of maleic anhydride-grafted polylactic acid and glycidyl methacrylate-grafted polylactic acid.

[0010] Furthermore, the photodimerizing agent is one or more combinations of coumarin derivatives, cinnamic acid and its derivatives.

[0011] Further, the cinnamic acid derivative is one or more combinations of: 4-hydroxycinnamic acid, 3,4-dihydroxycinnamic acid, 3-methoxy-4-hydroxycinnamic acid, methyl p-hydroxycinnamate, 4-hydroxy-3,5-dimethoxycinnamic acid, octyl methoxycinnamate, acryloyloxyethyl cinnamate, cholesterol cinnamate, polyvinyl alcohol cinnamate, polyethylene glycol cinnamic acid, cinnamic acid-based compounds, and polymers containing cinnamic acid structures; The coumarin derivatives are one or more combinations of 7-ethoxycoumarin, 7-hydroxy-4-methylcoumarin, 7-(2-methacryloylethoxy)-4-methylcoumarin, 7-(4-vinylbenzyloxy)-4-methylcoumarin, coumarin-based compounds, and polymers containing coumarin structures.

[0012] The above-mentioned method for preparing photocurable polylactic acid composite material includes the following steps: Polylactic acid, photodimerizing agent and compatibilizer are mixed evenly to obtain a mixture; The mixture is added to an extruder, and after melting, extrusion, strip drawing, air cooling, and pelletizing, a photocurable polylactic acid composite material is obtained.

[0013] Furthermore, the extruder is a twin-screw extruder, wherein the screw length-to-diameter ratio of the twin-screw extruder is 48:1 to 56:1, the extrusion temperature is 180℃ to 220℃, and the extrusion speed is 200 to 400 rpm.

[0014] The above-mentioned molding and curing method for photocurable polylactic acid composite materials includes: The photocurable polylactic acid material is thermoplastically processed into a product. By irradiating the product with ultraviolet light, the photodimerizing agent undergoes a [2+2] photocycloaddition crosslinking reaction, thereby achieving product curing.

[0015] Furthermore, the thermoplastic processing is injection molding, extrusion molding, or fused deposition modeling 3D printing; The wavelength range of the ultraviolet irradiation is 250-360nm, and the light intensity is 5-200mW / cm². 2 The irradiation time is 10-300 seconds.

[0016] A photocurable polylactic acid product prepared by the above-described molding and curing method, wherein the product has a cyclobutane three-dimensional network structure formed by direct cross-linking of the photodimerizing agent under ultraviolet light irradiation.

[0017] The above-mentioned photocurable polylactic acid composite materials are used in 4D printing, photowelding / repair of products, and photo-controlled regulation of drug release rate.

[0018] The beneficial effects of this invention are: 1. This invention eliminates the cytotoxicity and sensitization risks associated with small molecule photoinitiators and their photolysis products by employing a [2+2] photocycloaddition dimerization mechanism (such as introducing coumarin or cinnamic acid groups) to replace the traditional (meth)acrylate monomers and free radical systems. This technique enables the material to overcome the limitations of traditional photocurable resins and is expected to be safely applied in extremely demanding biomedical scenarios such as in vivo implantation.

[0019] 2. Utilizing the unique stepwise polymerization mechanism of light dimerization, the surface curing and stickiness problems caused by the quenching of free radicals by air oxygen in traditional systems are effectively avoided, achieving oxygen-free polymerization inhibition and a dry, smooth surface quality. Simultaneously, the extremely low volume shrinkage rate resulting from double bond conversion under this mechanism avoids product deformation and internal stress concentration caused by large shrinkage in traditional acrylate systems, significantly improving the dimensional accuracy of the products.

[0020] 3. This invention utilizes ultraviolet irradiation to induce a reaction in photodimer monomers, directly crosslinking them within the polylactic acid matrix to form a cyclobutane three-dimensional network structure, effectively overcoming the inherent brittleness and poor heat resistance of polylactic acid. This specific physical crosslinking network allows the composite material to maintain biodegradability while significantly and substantially improving its toughness, modulus, and heat distortion temperature.

[0021] 4. This invention utilizes the molecular property of specific dimers (such as coumarin dimers) that can undergo reversible depolymerization after absorbing higher-energy ultraviolet light, breaking the inherent limitations of traditional cross-linked networks, which are irreversible and difficult to reprocess once formed. This specific chemical configuration endows the material with the ability of photoreversible cross-linking. Based on this, the material of this invention has the potential to be applied in the following scenarios: 4D printing (light-driven shape change), photowelding / repair of products, and light-controlled regulation of drug release rates. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] A photocurable polylactic acid composite material, wherein the raw materials for preparing the photocurable polylactic acid composite material include, by weight: Polylactic acid 70~99.4 parts; Photodimerizing agent 0.5~20 parts; Compatibilizer 0.1~10 parts; The photodimer is a monomer that can undergo a [2+2] photocycloaddition reaction to generate a cyclobutane derivative under ultraviolet irradiation.

[0024] The polylactic acid mentioned is commercially available general-purpose polylactic acid; The photodimer is one or more combinations of coumarin derivatives, cinnamic acid and its derivatives.

[0025] Specifically, the photodimerizing agent is one or more combinations of cinnamic acid, 4-hydroxycinnamic acid, 3,4-dihydroxycinnamic acid, 3-methoxy-4-hydroxycinnamic acid, methyl p-hydroxycinnamate, 4-hydroxy-3,5-dimethoxycinnamic acid, octyl methoxycinnamate, acryloyloxyethyl cinnamate, cholesterol cinnamate, polyvinyl alcohol cinnamate, polyethylene glycol cinnamic acid, cinnamic acid-based compounds, and polymers containing cinnamic acid structures; 7-ethoxycoumarin, 7-hydroxy-4-methylcoumarin, 7-(2-methacryloylethoxy)-4-methylcoumarin, 7-(4-vinylbenzyloxy)-4-methylcoumarin, coumarin-based compounds, and polymers containing coumarin structures.

[0026] The compatibilizer is one or a combination of two of maleic anhydride-grafted polylactic acid and glycidyl methacrylate-grafted polylactic acid.

[0027] Methods for preparing photocurable polylactic acid composite materials include: S1, Polylactic acid, photodimerizing agent and compatibilizer are mixed evenly according to the above mass parts to obtain a mixture; S2, the mixture is added to the extruder, and after melting, extrusion, strip drawing, air cooling and pelletizing, a photocurable polylactic acid composite material can be obtained.

[0028] The extruder is a twin-screw extruder with a screw length-to-diameter ratio of 48:1 to 56:1, an extrusion temperature of 180℃ to 220℃, and an extrusion speed of 200 to 400 rpm.

[0029] After the photocurable polylactic acid composite material is thermoplastically processed into a product, it is exposed to ultraviolet light, causing the photodimerization monomers to undergo a cross-linking reaction, thereby achieving product curing.

[0030] The thermoplastic processing is injection molding, extrusion molding, or fused deposition modeling 3D printing; the wavelength range of the ultraviolet irradiation is 250-360nm, the light intensity is 5-200mW / cm², and the irradiation time is 10-300s.

[0031] The aforementioned photocurable polylactic acid composite material can be widely used in 3D printing, biomedicine, smart and environmentally friendly packaging, and photo-repairable products.

[0032] The technical solution of the present invention will be described below through the following embodiments and comparative examples; the specific information of the raw materials used in the following embodiments and comparative examples is as follows: Polylactic acid (PLA) (NatureWorks, USA, 4032D; Total-Corbion, Thailand, L175; Pullis, PT101; Fengyuan, FY801); Photodimerizing agents (Wuhan Nengmaike, 4-hydroxycinnamic acid; Shanghai Yisen, 7-hydroxy-4-methylcoumarin) Compatibilizers (Shenghao Rubber & Plastics, glycidyl methacrylate-grafted polylactic acid SH500, maleic anhydride-grafted polylactic acid SH600) Photoinitiator (BASF, Irgacure 819).

[0033] Example 1 9.94 kg of polylactic acid (PT101), 0.05 kg of 4-hydroxycinnamic acid, and 0.01 kg of glycidyl methacrylate-grafted polylactic acid were mixed evenly. The mixture was then added to a twin-screw extruder for melt extrusion, stranding, air cooling, and pelletizing. The pellets were dried at 100°C for 4 hours and then injection molded into standard test strips and square pieces. The test strips were placed under a UV point light source (wavelength 280 nm, light intensity 50 mW / cm²). 2 Irradiation for 120 seconds yielded polylactic acid material. The twin-screw extruder described above had a length-to-diameter ratio of 48, and the screw temperature was 220℃.

[0034] Example 2 8.5 kg of polylactic acid (PT101), 1 kg of 7-hydroxy-4-methylcoumarin, and 0.5 kg of maleic anhydride-grafted polylactic acid were mixed evenly. The mixture was then added to a twin-screw extruder for melt extrusion, stranding, air cooling, and pelletizing. The pellets were dried at 100°C for 4 hours and then injection molded into standard test strips and square pieces. The test strips were placed under a UV point light source (wavelength 365 nm, light intensity 50 mW / cm²). 2 Irradiation for 120 seconds yielded polylactic acid material. The twin-screw extruder described above had an aspect ratio of 52, and the screw temperature was 210℃.

[0035] Example 3 8.5 kg of polylactic acid (PT101), 0.5 kg of 4-hydroxycinnamic acid, 0.5 kg of 7-hydroxy-4-methylcoumarin, 0.25 kg of glycidyl methacrylate-grafted polylactic acid, and 0.25 kg of maleic anhydride-grafted polylactic acid were mixed evenly. The mixture was then added to a twin-screw extruder for melt extrusion, stranding, air cooling, and pelletizing. The pellets were dried at 100°C for 4 hours and then injection molded into standard test strips and square pieces. The test strips were placed under a UV point light source (wavelength 365 nm, light intensity 50 mW / cm²). 2 Irradiation for 120 seconds yielded polylactic acid material. The twin-screw extruder described above had an aspect ratio of 56, and the screw temperature was 180℃.

[0036] Example 4 The cured sample prepared in Example 2 (PLA + 7-hydroxy-4-methylcoumarin + compatibilizer, cured according to the conditions, properties shown in Table 1) was placed under a higher energy UV point light source (wavelength 254nm, light intensity 50mW / cm²). 2 The irradiation time was 300 seconds, and polylactic acid material with reversible depolymerization was obtained.

[0037] Comparative Example 1 Comparative Example 1 is Pullis PT101.

[0038] Comparative Example 2 8.5 kg of polylactic acid (PT101), 1 kg of trimethylolpropane triacrylate, and 0.5 kg of Irgacure 819 photoinitiator were mixed evenly. The mixture was then added to a twin-screw extruder for melt extrusion, stranding, air cooling, and pelletizing. The pellets were dried at 100°C for 4 hours and then injection molded into standard test strips and square pieces. The test strips were placed under a UV point light source (wavelength 365 nm, light intensity 50 mW / cm²). 2 Irradiation for 120 seconds yielded polylactic acid material. The twin-screw extruder described above had an aspect ratio of 52, and the screw temperature was 210℃.

[0039] Experimental Test The standard specimens and square pieces of Examples 1-4 and Comparative Examples 1-2 were injection molded respectively. After being placed for 24 hours, the cantilever beam notched impact performance test (GB / 1843-2008), flexural modulus test (GB / T 9341-2008), volume shrinkage test (GB / T 17037.4-2003) and heat distortion temperature test (GB / T1634.1-2019) were carried out. The results are shown in Table 1.

[0040] Table 1 Comparison of mechanical properties between the embodiments and the comparative examples As can be seen from Table 1: Examples 1, 2, and 3 achieved superior toughness, flexural modulus, and heat distortion temperature compared to the conventional system (Comparative Example 2) without the need for a photoinitiator. After curing, Examples 1, 2, and 3 exhibited a dry, smooth surface with low volume shrinkage, effectively overcoming the surface stickiness caused by oxygen inhibition in Comparative Example 2 and the significant volume shrinkage in the traditional acrylate system due to the conversion of double bonds to single bonds. Example 1, a cinnamic acid derivative, required relatively harsh reaction conditions and lower efficiency, necessitating higher-energy ultraviolet light. Example 2, a coumarin derivative, possessed a conjugated ring within its molecule, resulting in a more stable photoexcited state, higher quantum yield in the dimerization reaction, longer absorption wavelength, and higher reaction efficiency. Furthermore, the coumarin core itself is an ultraviolet absorbing group, and the cross-linked network formed after curing also functions as an ultraviolet stabilizer, resulting in superior weather resistance. Example 3 involved a cinnamic acid derivative and a coumarin derivative. Since the cinnamic acid derivative could not undergo a [2+2] photoaddition reaction under high-wavelength ultraviolet light, only the coumarin derivative participated in photodimerization crosslinking in Example 3. The actual effective crosslinking density was lower than in Example 2 (pure coumarin system), resulting in slightly lower mechanical properties compared to Example 2, but still significantly better than Comparative Example 1 (pure PLA) and Comparative Example 2 (traditional acrylate system). In Example 4, after irradiation with 254 nm ultraviolet light, the properties essentially returned to the level of pure PLA, demonstrating the disintegration of the crosslinking network and reversible depolymerization of the material. The photocurable polylactic acid composite material prepared by this invention has the potential for application in fields such as 4D printing (photo-driven shape change), photo-welding / repair of products, and photo-controlled regulation of drug release rates.

[0041] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0042] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A photocurable polylactic acid composite material, characterized in that, Includes the following quantities of raw materials: Polylactic acid 70~99.4 parts; Photodimerizing agent 0.5~20 parts; Compatibilizer 0.1~10 parts; The photodimer is a monomer that can undergo a [2+2] photocycloaddition reaction under ultraviolet irradiation to generate a cyclobutane derivative.

2. The photocurable polylactic acid composite material according to claim 1, characterized in that, The compatibilizer is one or a combination of two of maleic anhydride-grafted polylactic acid and glycidyl methacrylate-grafted polylactic acid.

3. The photocurable polylactic acid composite material according to claim 1, characterized in that, The photodimer is one or more combinations of coumarin derivatives, cinnamic acid and its derivatives.

4. The photocurable polylactic acid composite material according to claim 3, characterized in that, The cinnamic acid derivatives are one or more combinations of the following: 4-hydroxycinnamic acid, 3,4-dihydroxycinnamic acid, 3-methoxy-4-hydroxycinnamic acid, methyl p-hydroxycinnamate, 4-hydroxy-3,5-dimethoxycinnamic acid, octyl methoxycinnamate, acryloyloxyethyl cinnamate, cholesterol cinnamate, polyvinyl alcohol cinnamate, polyethylene glycol cinnamic acid, cinnamic acid-based compounds, and polymers containing cinnamic acid structures. The coumarin derivatives are one or more combinations of 7-ethoxycoumarin, 7-hydroxy-4-methylcoumarin, 7-(2-methacryloylethoxy)-4-methylcoumarin, 7-(4-vinylbenzyloxy)-4-methylcoumarin, coumarin-based compounds, and polymers containing coumarin structures.

5. The method for preparing the photocurable polylactic acid composite material according to any one of claims 1-4, characterized in that, Includes the following steps: Polylactic acid, photodimerizing agent and compatibilizer are mixed evenly to obtain a mixture; The mixture is added to an extruder, and after melting, extrusion, strip drawing, air cooling, and pelletizing, a photocurable polylactic acid composite material is obtained.

6. The method for preparing photocurable polylactic acid composite material according to claim 5, characterized in that, The extruder is a twin-screw extruder with a screw length-to-diameter ratio of 48:1 to 56:1, an extrusion temperature of 180℃ to 220℃, and an extrusion speed of 200 to 400 rpm.

7. The molding and curing method for the photocurable polylactic acid composite material according to any one of claims 1-4, characterized in that, include: The photocurable polylactic acid material is thermoplastically processed into a product. By irradiating the product with ultraviolet light, the photodimerizing agent undergoes a [2+2] photocycloaddition crosslinking reaction, thereby achieving product curing.

8. The molding and curing method according to claim 7, characterized in that, The thermoplastic processing is injection molding, extrusion molding, or fused deposition modeling 3D printing; The wavelength range of the ultraviolet irradiation is 250-360nm, and the light intensity is 5-200mW / cm². 2 The irradiation time is 10-300 seconds.

9. A photocurable polylactic acid product prepared by the molding and curing method according to claim 7 or 8, characterized in that: The product has a three-dimensional cyclobutane network structure formed by direct cross-linking of the photodimerizing agent under ultraviolet light irradiation.

10. The application of the photocurable polylactic acid composite material according to any one of claims 1-4 in the preparation of 4D printing, photowelding / repair of products, and photo-controlled regulation of drug release rate.

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