CN116478517A - Biomedical fully degradable polylactic acid polymer-based composite product and preparation method thereof - Google Patents
Biomedical fully degradable polylactic acid polymer-based composite product and preparation method thereof Download PDFInfo
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Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
- C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B9/00—Making granules
- B29B9/02—Making granules by dividing preformed material
- B29B9/06—Making granules by dividing preformed material in the form of filamentary material, e.g. combined with extrusion
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/76—Measuring, controlling or regulating
- B29C45/77—Measuring, controlling or regulating of velocity or pressure of moulding material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/76—Measuring, controlling or regulating
- B29C45/78—Measuring, controlling or regulating of temperature
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76003—Measured parameter
- B29C2945/7604—Temperature
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2201/00—Properties
- C08L2201/06—Biodegradable
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2203/00—Applications
- C08L2203/02—Applications for biomedical use
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
- C08L2205/025—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
- Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics
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Abstract
The invention provides a biomedical fully degradable polylactic acid polymer-based composite product and a preparation method thereof. According to the weight portion, 85-90 portions of polylactic acid polymer and 5-15 portions of polydioxanone are mixed, then the single screw extruder is used for carrying out premelting blending treatment, and the double screw extruder is used for carrying out secondary premelting blending treatment, and then the micro injection molding is used for preparing the polylactic acid polymer matrix composite product. The preparation method only adopts polylactic acid polymer and poly-p-dioxanone which are poor in original compatibility as raw materials to prepare a composite product, and the polylactic acid polymer-based composite micro-product which has full degradation characteristic and combines mechanical property and biocompatibility can be prepared on the basis of not adding compatilizer/toughening agent and other auxiliary agents/fillers.
Description
Technical Field
The invention belongs to the technical field of biomedical high molecular products and molding processing thereof, relates to a biomedical fully degradable polylactic acid polymer-based composite product and a preparation method thereof, and in particular relates to a fully degradable polylactic acid polymer-based composite micro product prepared by a micro injection molding process.
Background
Polylactic acid polymer is the highest cost performance biodegradable material, has good biocompatibility, can be completely biodegraded, has good mechanical properties, meets the basic requirements of manufacturing various medical instruments, and is widely applied. However, the characteristics of high hardness, poor toughness and the like lead to the situation that the workpiece is easy to fracture due to high brittleness in the application scene requiring toughness, such as bone screws, vascular clamps, medical micro-catheters and micro-needle arrays. In addition, the medical products and devices which are in direct contact with the circulatory system of the human body have higher requirements on material selection: on the basis of ensuring good biocompatibility, the preparation meets the requirements of completely biodegradability and simple formula components, and can be widely applied. Among the toughening methods of PLA, blending by a tough polymer material complementary to the mechanical properties is an effective method. However, materials with good toughness, such as PBAT, polydioxanone (PPDO), have poor compatibility with PLA due to their good flexibility in molecular chains, and compatibilizers must be added to improve the toughening effect of PLA systems. In prior studies, arruda et al added a multifunctional epoxy chain extender Joncryl ADR4368 as a compatibilizer to PLA/PBAT systems (Arruda LC, magaton M, brettas RES, et al Influence of chain extender on mechanical, thermal and morphological properties of blown films of PLA/PBAT blends [ J ]. Polymer Testing,2015,43,27-37); xu et al add silica based Janus nanoplatelets as compatibilizers to PLA/PPDOS to enhance their toughening effect (Xu Z, lin J, chen J, et al Synthesis, characterization and its compatibilization on Polymer blends of arched Janus nanosheets [ J ]. Polymer Testing,2021,98). If PLA and such ductile materials are directly blended to prepare a composite material, under the condition of no addition of any compatilizer, the prepared PLA/PBAT, PLA/PPDOS and other blends have low phase separation (Yeh JT, tsou CH, huang CY, chen KN, wu CS, chai WL, compatible and crystallization properties of poly (lactic acid)/poly (butyl acrylate-co-terephtalate) blends, journal of Applied Polymer Science,2010,116,680) when the content of PBAT or PPDO reaches 5wt%, and the phase interface bonding strength is low, so that the mechanical properties of the corresponding composite material, particularly the impact toughness and the elongation at break, are greatly reduced. The toughness of medical and health devices such as bone screws, microneedle arrays and the like is difficult to meet the requirement due to contradiction with the aim of toughening and modifying PLA, and the medical and health devices can be broken in the use process, so that the application of the medical and health devices is limited.
However, in the prior art of toughening modification, commonly used compatibilizers/toughening agents, such as multifunctional epoxides (Joncryl ADR 4368), multi-walled carbon nanotubes (Hemmati M, rahimi GH, kaganj A B, et al Rheiologic and Mechanical Characterization of Multi-Walled Carbon Nanotubes/Polypropylene Nanocomposites [ J ], journal of Macromolecular Science Part B,2008,47 (6), 1176-1187), or silane-based compatibilizers. Such compatibilizers/tougheners are not biodegradable and in vivo degradation of PLA-based articles containing the added compatibilizers can lead to direct exposure of the compatibilizers to in vivo environments, the metabolic processes of well-biocompatible epoxide or silane-based compatibilizers remain to be investigated, while unpurified carbon nanotubes present biocompatibility and cytotoxicity problems (Sun Lan, zhang Yingge, biocompatibility of carbon nanotubes [ J ], journal of biomedical engineering, 2008, (03), 742-746).
Therefore, if the polylactic acid polymer-based composite material with good biocompatibility and full degradation is provided, and the characteristics of good mechanical properties are simultaneously considered, the polylactic acid polymer-based composite material is expected to be popularized and used as a next-generation biomedical instrument material.
Disclosure of Invention
The invention aims to solve the problems in the background art and provide a biomedical fully degradable polylactic acid polymer-based composite product and a preparation method thereof.
In order to achieve the above object, the present invention is realized by adopting the technical scheme comprising the following technical measures.
The preparation method of the biomedical fully degradable polylactic acid polymer-based composite product comprises the following steps:
(1) The following raw materials are mixed according to parts by weight and used as a mixture:
85-95 parts of polylactic acid polymer (PLP),
5 to 15 Parts of Polydioxanone (PPDO),
wherein, the total of polylactic acid polymer and polydioxanone is 100 parts;
(2) Carrying out premelting blending treatment on the mixture obtained in the step (1), specifically, carrying out melting blending extrusion granulation on the mixture by using a single screw extruder to obtain a pretreated polylactic acid polymer matrix composite material;
(3) Carrying out secondary premelting blending treatment on the pretreated polylactic acid polymer-based composite material obtained in the step (2), specifically, carrying out melt blending extrusion granulation on the pretreated polylactic acid polymer-based composite material by utilizing a double screw extruder to obtain a polylactic acid polymer-based composite material subjected to secondary pretreatment; wherein the screw speed of the twin-screw extruder is not lower than 60rpm;
(4) Preparing the polylactic acid polymer-based composite material subjected to secondary pretreatment obtained in the step (3) into a polylactic acid polymer-based composite product by micro injection molding; wherein, the technological parameters of the miniature injection molding are as follows: the injection speed is 50-200 mm/s, the die temperature is 30-60 ℃, the injection pressure is 1000-1500 bar, and the melt temperature is 180-200 ℃.
In this context, the polylactic acid-based polymer (PLP) and the polydioxanone (PPDO) used in step (1) may each be selected from conventional commercial raw materials, such as conventional chemical raw material grade polylactic acid-based polymers and polydioxanone; in one of the solutions, the raw material used is preferably a medical grade chemical raw material in order to be better suited for the preparation of biomedical devices.
It should be noted that in the technical solution of the present invention, the raw materials in the step (1) are formed by polylactic acid polymer and polydioxanone, and no third raw material component of other filler/auxiliary agent is added, especially no compatilizer/compatibilizer/plasticizer/flexibilizer is added.
The specific choice of the polylactic acid-based polymer (PLP) in step (1) herein is any one of the polylactic acid-based polymers (PLP) known in the art, such as polylactic acid (PLA, also known as polylactide), polylactic acid-glycolic acid copolymer (PLGA, also known as polylactide-glycolide copolymer), and the like. In one preferable embodiment, the polylactic acid polymer (PLP) in the step (1) is polylactic acid.
It should be noted that the mixture obtained in step (1) needs to be sufficiently dried before the pre-melt blending treatment, and if necessary, before the pre-melt blending treatment, the drying treatment may be referred to the conventional drying treatment method for polymer materials in the prior art, for example, the mixture is dried in vacuum at 40 to 80 ℃ for 6 to 12 hours.
In the step (2), the pre-melt blending treatment is specifically that the mixture is melt blended and extruded to form granules by a single screw extruder, wherein the melt blending and extrusion granulation by the single screw extruder can be referred to the description of the prior art, and the specific process parameters of the pre-melt blending treatment can be referred to the description of the prior art, especially the process parameters of the single screw melt blending and extrusion granulation of the polylactic acid polymer with the main raw material component in the conventional polylactic acid polymer material or the mixed material; the melt-blending extrusion granulation treatment may be performed at a conventional screw rotation speed based on the general principle of melt-blending extrusion granulation at a temperature selected to be higher than the melting temperature of the polylactic acid polymer.
In one technical scheme, in the step (2), the mixture is melted, blended, extruded and granulated by a single screw extruder, and specific technological parameters are as follows: the melting temperature is 180-200 ℃, and the rotating speed of the screw is 20-30 rpm.
In the step (3), the secondary premelting and blending treatment is specifically that the pretreated polylactic acid polymer-based composite material is subjected to melt blending extrusion granulation by a twin-screw extruder, wherein the melt blending extrusion granulation by the twin-screw extruder is performed, and the other process parameters except the screw rotation speed can be referred to the description of the prior art, in particular, the process parameters of the twin-screw melt blending extrusion granulation of the polylactic acid polymer material which is the main raw material component in the conventional polylactic acid polymer material or the mixed material; the melt-blending extrusion granulation treatment may be performed at a screw speed of not less than 60rpm, with the temperature being selected to be higher than the melting temperature of the polylactic acid-based polymer, based on the usual principle of melt-blending extrusion granulation.
In one of the technical schemes, in the step (3), the pretreated polylactic acid polymer-based composite material is subjected to melt blending extrusion granulation by a double screw extruder, and specific technological parameters are as follows: the melting temperature is 180-200 ℃, and the screw rotating speed is 60-100 rpm.
Based on the above preferred technical scheme, when the polylactic acid polymer (PLP) is polylactic acid, it should be noted that the pre-melt blending treatment and the secondary pre-melt blending treatment are adopted mainly because the compatibility between PLA and PPDO is poor, and the screw rotation speed in the secondary melt blending treatment of twin-screw extrusion cannot be lower than 60rpm, which is obviously improved compared with the conventional process parameters, so as to further enable the PLA/PPDO with poor compatibility to achieve uniform submicron dispersion and prevent agglomeration. If any one melt blending treatment is absent or the screw rotation speed is too low in the double screw extrusion treatment, the size of the disperse phase of the PLA/PPDOS blending system is increased and the disperse phase is unevenly distributed, the in-situ fiber forming phenomenon is difficult to occur in the subsequent micro injection molding strong shear force field, the generation of a shishi-kebab structure is adversely affected, and the toughening effect on PLA is difficult to achieve.
In addition, it should be noted that the pre-treated polylactic acid polymer-based composite material obtained in the step (2) and the secondarily pre-treated polylactic acid polymer-based composite material obtained in the step (3) should be sufficiently dried before the next process treatment, and if necessary, before the next process treatment, the drying treatment should be performed, and reference may be made to the conventional drying treatment method for the polymer material in the prior art, for example, the composite material is dried in vacuum at 40 to 80 ℃ for 6 to 12 hours.
The invention is characterized in that the inventor of the invention discovers that after the PLA/PPDO composite material is fully pre-melted and blended, the finished product obtained by micro injection molding process has good mechanical property under the condition of no need of adding compatilizer/toughening agent or other auxiliary agents, which breaks the inherent thinking that the compatilizer/toughening agent is needed to be added when two polymer materials with poor compatibility are melted and blended by the technicians in the field. The unique strong shearing force field effect of the miniature injection molding process is utilized to lead the disperse phase to form fiber in situ under the shearing force effect, and the submicron fibers uniformly dispersed in the matrix lead the product to achieve the toughening effect which is difficult to realize compared with the traditional processing method.
The inventor verifies that the improvement of the mechanical property is stable through repeated experiments, and finds the principle through an electron microscope, and discovers that in the micro injection molding process, PPDOs form micro-nano fiber structures after micro injection molding and play a key role in the subsequent generation of a sh-kebab structure. The polylactic acid-based composite material subjected to full premelting blending treatment can be found that PLA and PPDOs are distributed in a sea-island structure through electron microscopy, and a certain gap exists between a disperse phase and a matrix, so that the compatibility of the PLA and the PPDOs is poor. However, when the polylactic acid-based composite material is formed into a sample by a micro injection molding process, the PPDOS dispersed phase is stretched along the melt flow direction to form a submicron fibrous structure with larger length-diameter ratio, and a clear shish-kebab highly oriented crystalline structure is formed along the melt flow direction. Wherein, the shish structure is composed of submicron fibers of PPDO disperse phase, and the kebab structure is composed of PLA platelets, and the formation mechanism is that a very strong shear stress field exists in micro injection molding, wherein, the shear force induces crystallization.
The discovery fully verifies that the PLA and the PPDOs can form a sh-kebab highly oriented crystal structure through a micro injection molding process after being fully premelted and blended on the premise of poor compatibility, thereby having excellent mechanical properties on the premise of not adding a compatilizer/toughening agent.
The polylactic acid polymer-based composite article finally prepared in the step (4) is a conventional article which can be molded in a micro injection molding process, and mainly depends on the selection of a mold thereof, including biomedical devices such as bone screws, vascular clamps, medical microcatheters, nasal micro-fasteners and microneedle arrays; but also non-biomedical devices such as micro-gears, microelectromechanical components, etc.
The invention has the following beneficial effects:
(1) According to the technical scheme, only polylactic acid polymers and polydioxanone which are poor in original compatibility are used as raw materials to prepare the composite product, and a brand-new technological mode is developed on the basis that no compatilizer/toughening agent and other auxiliary agents/fillers are added to prepare the biomedical fully-degradable polylactic acid polymer-based composite micro-product.
(2) The polylactic acid polymer-based composite product prepared by the technical scheme of the invention has the characteristic of full degradation, excellent mechanical property and biocompatibility, and is expected to be popularized and used as a next-generation biomedical instrument material.
Drawings
FIG. 1 is an SEM image of a PPDO/PLA microneedle array prepared in example 1 of the invention. It can be seen that the prepared microneedle array has complete structure, good replica and smooth surface.
FIG. 2 is a drawing showing the quenched section SEM image (b) and the quenched section SEM image (a) of pure PLA of the secondarily pretreated polylactic acid-based composite material obtained in step (3) in the example of the present invention. It is evident from the figure that PLA and PPDO have poor compatibility and, although sufficiently melt-blended, still have some gaps between them.
FIG. 3 is a SEM image (b) of a quenched section of a PPDO/PLA spline prepared in example 1 of the invention along the melt flow direction and a SEM image (a) of a quenched section of a pure PLA spline.
FIG. 4 shows an SEM image (b) of a quenched section in the melt flow direction after etching and an SEM image (a) of a quenched section after etching of a pure PLA spline, which are obtained in example 1 of the present invention. For plot (a) of pure PLA, only the crystal structure of the transverse lamellar (kabab) forms after etching the pure PLA mini injection molded tensile bars. However, as shown in figure (b), it is apparent that there is a clear sh-kebab highly oriented crystalline structure formed along the melt flow direction for PLA/PPDO blended mini-injection molded samples.
FIG. 5 is a graph showing the comparison of mechanical properties of PPDO/PLA splines prepared in example 9 of the present invention and pure PLA splines. It can be seen that the pure PLA samples show brittle fracture, whereas the curves with PPDO content of 10% show typical crystalline polymer ductile fracture. The stress of pure PLA rises in a direct proportion with the strain before the strain reaches 5%; the stress strain curve of the 90/10 PLA/PPDOmicro injection molded sample showed significant turning at about 3% and a thin neck due to yield. In particular, the breaking elongation of the graph (d) is obviously improved. The elongation at break of the pure PLA is 3.9%, and the elongation at break of the samples with 10% PPDOs, which characterize toughness, is obviously improved to 45.4%.
FIG. 6 is a graph showing the compressive load contrast of PPDO/PLA microneedles prepared in example 1 of the present invention and pure PLA microneedles. It can be seen that when the PPDOs were added in an amount of 10%, the crush load was 7.5N at the maximum and the crush displacement was 0.132mm at the maximum, which was far higher than that of the pure PLA specimen (the crush load was 3.23N and the crush displacement was 0.66 mm).
Detailed Description
For a further understanding of the present invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are merely intended to illustrate further features and advantages of the invention and are not limiting of the invention claims. Those skilled in the art can, with the benefit of this disclosure, suitably modify the process parameters to achieve this. It is expressly noted that all such similar substitutions and modifications will be apparent to those skilled in the art, and are deemed to be included within the present invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those skilled in the relevant art that variations and modifications can be made in the methods and applications described herein, and in the practice and application of the techniques of this invention, without departing from the spirit or scope of the invention. While the following terms are believed to be well understood by those of ordinary skill in the art, the following definitions are set forth to aid in the description of the presently disclosed subject matter.
The preparation method of the biomedical fully degradable polylactic acid polymer-based composite product comprises the following steps:
(1) The following raw materials are mixed according to parts by weight and used as a mixture:
85-95 parts of polylactic acid polymer (PLP),
5 to 15 Parts of Polydioxanone (PPDO),
wherein, the total of polylactic acid polymer and polydioxanone is 100 parts;
(2) Carrying out premelting blending treatment on the mixture obtained in the step (1), specifically, carrying out melting blending extrusion granulation on the mixture by using a single screw extruder to obtain a pretreated polylactic acid polymer matrix composite material;
(3) Carrying out secondary premelting blending treatment on the pretreated polylactic acid polymer-based composite material obtained in the step (2), specifically, carrying out melt blending extrusion granulation on the pretreated polylactic acid polymer-based composite material by utilizing a double screw extruder to obtain a polylactic acid polymer-based composite material subjected to secondary pretreatment; wherein the screw speed of the twin-screw extruder is not lower than 60rpm;
(4) Preparing the polylactic acid polymer-based composite material subjected to secondary pretreatment obtained in the step (3) into a polylactic acid polymer-based composite product by micro injection molding; wherein, the technological parameters of the miniature injection molding are as follows: the injection speed is 50-200 mm/s, the die temperature is 30-60 ℃, the injection pressure is 1000-1500 bar, and the melt temperature is 180-200 ℃.
In this context, the polylactic acid-based polymer (PLP) and the polydioxanone (PPDO) used in step (1) may each be selected from conventional commercial raw materials, such as conventional chemical raw material grade polylactic acid-based polymers and polydioxanone; in one embodiment, the feedstock used is preferably medical grade chemical feedstock for better suitability for use in the preparation of biomedical devices.
It should be noted that in the technical solution of the present invention, the raw materials in the step (1) are formed by polylactic acid polymer and polydioxanone, and no third raw material component of other filler/auxiliary agent is added, especially no compatilizer/compatibilizer/plasticizer/flexibilizer is added.
In one embodiment, the specific choice of the polylactic acid-based polymer (PLP) in the step (1) is any one of the polylactic acid-based polymers (PLP) known in the art, such as polylactic acid (PLA, also known as polylactide), polylactic acid-glycolic acid copolymer (PLGA, also known as polylactide-glycolide copolymer), and the like. In one preferred embodiment, the polylactic acid-based polymer (PLP) in step (1) is polylactic acid.
It should be noted that the mixture obtained in step (1) is sufficiently dried before the pre-melt blending treatment, and if necessary, before the pre-melt blending treatment, the drying treatment may be performed by referring to a conventional drying treatment method for polymer materials in the prior art, and in one embodiment, the mixture is dried under vacuum at 40 to 80 ℃ for 6 to 12 hours.
In one embodiment, the polylactic acid-based polymer (PLP) in step (1) is 85 to 95 parts, for example 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95 parts, or any range or point value therebetween; the polydioxanone (PPDO) is 5 to 15 parts, for example 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, or any range or point value therebetween.
In the step (2), the pre-melt blending treatment is specifically that the mixture is melt blended and extruded to form granules by a single screw extruder, wherein the melt blending and extrusion granulation by the single screw extruder can be referred to the description of the prior art, and the specific process parameters of the pre-melt blending treatment can be referred to the description of the prior art, especially the process parameters of the single screw melt blending and extrusion granulation of the polylactic acid polymer with the main raw material component in the conventional polylactic acid polymer material or the mixed material; the melt-blending extrusion granulation treatment may be performed at a conventional screw rotation speed based on the general principle of melt-blending extrusion granulation at a temperature selected to be higher than the melting temperature of the polylactic acid polymer.
In one embodiment, in the step (2), the mixture is melt blended, extruded and granulated by using a single screw extruder, and specific process parameters are as follows: the melting temperature is 180-200 ℃, and the rotating speed of the screw is 20-30 rpm. Wherein the melting temperature is 180 to 200 ℃, such as 180 ℃, 185 ℃, 190 ℃, 195 ℃,200 ℃, or any range or point value therebetween; screw speed is 20-30 rpm, e.g. 20rpm, 22rpm, 24rpm, 26rpm, 28rpm, 30rpm or any range or point value in between.
In the step (3), the secondary premelting and blending treatment is specifically that the pretreated polylactic acid polymer-based composite material is subjected to melt blending extrusion granulation by a twin-screw extruder, wherein the melt blending extrusion granulation by the twin-screw extruder is performed, and the other process parameters except the screw rotation speed can be referred to the description of the prior art, in particular, the process parameters of the twin-screw melt blending extrusion granulation of the polylactic acid polymer material which is the main raw material component in the conventional polylactic acid polymer material or the mixed material; the melt-blending extrusion granulation treatment may be performed at a screw speed of not less than 60rpm, with the temperature being selected to be higher than the melting temperature of the polylactic acid-based polymer, based on the usual principle of melt-blending extrusion granulation.
In one embodiment, in the step (3), the pretreated polylactic acid polymer-based composite material is subjected to melt blending extrusion granulation by using a twin-screw extruder, and specific process parameters are as follows: the melting temperature is 180-200 ℃, and the screw rotating speed is 60-100 rpm. Wherein the melting temperature is 180 to 200 ℃, such as 180 ℃, 185 ℃, 190 ℃, 195 ℃,200 ℃, or any range or point value therebetween; screw speed is 60 to 100rpm, for example 60rpm, 70rpm, 80rpm, 90rpm, 100rpm or any range or point value therebetween.
Based on the above preferred technical scheme, when the polylactic acid polymer (PLP) is polylactic acid, it should be noted that the pre-melt blending treatment and the secondary pre-melt blending treatment are adopted mainly because the compatibility between PLA and PPDO is poor, and the screw rotation speed in the secondary melt blending treatment of twin-screw extrusion cannot be lower than 60rpm, which is obviously improved compared with the conventional process parameters, so as to further enable the PLA/PPDO with poor compatibility to achieve uniform submicron dispersion and prevent agglomeration. If any one melt blending treatment is absent or the screw rotation speed is too low in the double screw extrusion treatment, the size of the disperse phase of the PLA/PPDOS blending system is increased and the disperse phase is unevenly distributed, the in-situ fiber forming phenomenon is difficult to occur in the subsequent micro injection molding strong shear force field, the generation of a shishi-kebab structure is adversely affected, and the toughening effect on PLA is difficult to achieve.
It should be noted that the pre-treated polylactic acid polymer-based composite material obtained in step (2) and the secondarily pre-treated polylactic acid polymer-based composite material obtained in step (3) should be sufficiently dried before the next process treatment, and if necessary, before the next process treatment, the drying treatment should be performed, and reference may be made to a conventional drying treatment method for a polymer material in the prior art, in one embodiment, the composite material is vacuum-dried at 40 to 80 ℃ for 6 to 12 hours.
In one embodiment, the process parameters of the micro injection molding in the step (4) are as follows: injection speeds of 50 to 200mm/s, for example 50mm/s, 60mm/s, 70mm/s, 80mm/s, 90mm/s, 100mm/s, 110mm/s, 120mm/s, 130mm/s, 140mm/s, 150mm/s, 160mm/s, 170mm/s, 180mm/s, 190mm/s, 200mm/s or any range or point value therebetween; the mold temperature is 30-60 ℃, such as 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, or any range or point value therebetween; injection pressures of 1000 to 1500bar, for example 1000bar, 1100bar, 1200bar, 1300bar, 1400bar, 1500bar or any range or point value in between; the melt temperature is 180 to 200 ℃, such as 180 ℃, 185 ℃, 190 ℃, 195 ℃,200 ℃ or any range or point value therebetween.
The invention is characterized in that the inventor of the invention discovers that after the PLA/PPDO composite material is fully pre-melted and blended, the finished product obtained by micro injection molding process has good mechanical property under the condition of no need of adding compatilizer/toughening agent or other auxiliary agents, which breaks the inherent thinking that the compatilizer/toughening agent is needed to be added when two polymer materials with poor compatibility are melted and blended by the technicians in the field. The unique strong shearing force field effect of the miniature injection molding process is utilized to lead the disperse phase to form fiber in situ under the shearing force effect, and the submicron fibers uniformly dispersed in the matrix lead the product to achieve the toughening effect which is difficult to realize compared with the traditional processing method.
The inventor verifies that the improvement of the mechanical property is stable through repeated experiments, and finds the principle through an electron microscope, and discovers that in the micro injection molding process, PPDOs form micro-nano fiber structures after micro injection molding and play a key role in the subsequent generation of a sh-kebab structure. The polylactic acid-based composite material subjected to full premelting blending treatment can be found that PLA and PPDOs are distributed in a sea-island structure through electron microscopy, and a certain gap exists between a disperse phase and a matrix, so that the compatibility of the PLA and the PPDOs is poor. However, when the polylactic acid-based composite material is formed into a sample by a micro injection molding process, the PPDOS dispersed phase is stretched along the melt flow direction to form a submicron fibrous structure with larger length-diameter ratio, and a clear shish-kebab highly oriented crystalline structure is formed along the melt flow direction. Wherein, the shish structure is composed of submicron fibers of PPDO disperse phase, and the kebab structure is composed of PLA platelets, and the formation mechanism is that a very strong shear stress field exists in micro injection molding, wherein, the shear force induces crystallization.
The discovery fully verifies that the PLA and the PPDOs can form a sh-kebab highly oriented crystal structure through a micro injection molding process after being fully premelted and blended on the premise of poor compatibility, thereby having excellent mechanical properties on the premise of not adding a compatilizer/toughening agent.
The polylactic acid polymer-based composite article finally prepared in the step (4) is a conventional article which can be molded in a micro injection molding process, and mainly depends on the selection of a mold thereof, including biomedical devices such as bone screws, vascular clamps, medical microcatheters, nasal micro-fasteners and microneedle arrays; but also non-biomedical devices such as micro-gears, microelectromechanical components, etc.
The present application will be explained in further detail with reference to examples. However, those skilled in the art will appreciate that these examples are provided for illustrative purposes only and are not intended to limit the present application.
Examples
Embodiments of the present application will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only for illustration of the present application and should not be construed as limiting the scope of the present application. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention. The present application should not be construed as limited to the particular embodiments described.
1. Raw materials
PLA: nature Works 4032D, mn=10W, melting point about 170deg.C, glass transition temperature about 60deg.C, melt flow rate 7g/10min (210 deg.C, 2.16 kg), supplied by Suzhou Kaisha engineering plastics Co., ltd;
PPDO: mn=25W, melting point about 109 ℃, glass transition temperature about-10 ℃, melt intrinsic viscosity 2.0dl/g (measured by Ubbelohde viscometer), shenzhen Boli biological materials Co., ltd.
2. Preparation method
(1) The following raw materials are mixed according to parts by weight and used as a mixture:
85-95 parts of polylactic acid (PLA),
5 to 15 Parts of Polydioxanone (PPDO),
wherein, the total amount of polylactic acid and polydioxanone is 100 parts;
(2) Carrying out premelting blending treatment on the mixture obtained in the step (1), specifically, carrying out melting blending extrusion granulation on the mixture by using a single screw extruder to obtain a pretreated polylactic acid-based composite material; the specific technological parameters of the single screw extruder are as follows: the melting temperature is 180 ℃, and the screw rotating speed is 30rpm;
(3) Carrying out secondary premelting blending treatment on the pretreated polylactic acid-based composite material obtained in the step (2), specifically, carrying out melt blending extrusion granulation on the pretreated polylactic acid-based composite material by using a double-screw extruder to obtain a polylactic acid-based composite material subjected to secondary pretreatment; the specific technological parameters of the twin-screw extruder are as follows: the melting temperature is 180 ℃, and the screw rotating speed is 80rpm;
(4) Preparing the polylactic acid-based composite material subjected to secondary pretreatment obtained in the step (3) into a polylactic acid-based composite product by micro injection molding; wherein, the technological parameters of the miniature injection molding are as follows: the injection speed is 50-200 mm/s, the die temperature is 30-60 ℃, the injection pressure is 1000-1500 bar, and the melt temperature is 180-200 ℃;
the size parameters of the prepared microneedle array were: the diameter of the substrate is 12mm, and the thickness is 0.9mm; the bottom of the microneedle tip has a diameter of 0.3mm and a height of 0.6mm, and is distributed in a 6×6 array.
3. Test method
3.1 Scanning Electron Microscope (SEM)
The blend melt extrudate or mini-tensile sample was placed in liquid nitrogen for complete immersion for 10min and quenched in the melt flow direction. To more clearly observe the crystalline structure in the micro injection molded bars, the bars quenched in the melt flow direction were etched at 25℃for 24 hours in 0.05mol/L NaOH methanol solution to remove amorphous PLA. And ultrasonically cleaning the etched sample bar in distilled water for 5min to remove surface impurities. Finally, the sample was subjected to a metal spraying treatment, and the microscopic morphology of the sample was observed under an acceleration voltage of 5kV using a JSM-5900LV type SEM from JEOL corporation of Japan.
3.2 tensile test
Mini tensile samples were tested using a model 5567 universal materials tester from Instron, usa, and tested at room temperature at 25 ℃ at a tensile speed of 1mm/min, 5 replicates per sample were measured and averaged.
3.3 compression test
Microneedle array compression experiments were performed using an Electro Force 3220SERIES type II tester from Bose Inc. of America, where the compression displacement and compression frequency were 0.15mm and 0.2Hz, respectively.
Examples 1 to 3 and comparative example 1
Examples 1 to 3 and comparative example 1 were based on the fact that the ratio of polylactic acid to polydioxanone was different as a variable, and the mechanical properties of the obtained samples were prepared, and the process parameters of the micro injection molding were: the injection speed is 100mm/s, the die temperature is 40 ℃, the injection pressure is 1500bar, and the melt temperature is 190 ℃; specific comparative properties are shown in Table 1 below
TABLE 1 influence of PPDO content on PLA/PPDO blend physical Properties
From the above experimental comparison, it was surprisingly found that when the PPDO content was 10wt%, the sample had a significant increase in elongation at break and compressive load, which was approximately 2-fold greater than that of comparative example 1, and the increase was beyond our expectation without the addition of compatibilizers/toughening agents and other adjuvants, which fully demonstrated the potential for excellent mechanical properties.
Examples 4 to 6
Examples 4 to 6 are based on the melt temperature difference in micro injection molding as a variable, and the mechanical properties of the obtained samples were prepared, at this time, the PLA/PPDOS ratio was fixed to 90/10, and the other micro injection molding process parameters were: the injection speed is 100mm/s, the die temperature is 40 ℃, and the injection pressure is 1500bar; specific comparative properties are shown in table 2 below:
TABLE 2 influence of melt temperature on PLA/PPDOS blend physical Properties
Through the experimental comparison, the elongation at break of the sample can be further obviously improved when the temperature of the melt is selected to be 180 ℃.
Examples 7 to 8, comparative example 2
Examples 7 to 8 and comparative example 2 are based on the fact that the temperature of the mold in the micro injection molding is different as a variable, and the mechanical properties of the obtained sample are prepared, at the moment, the PLA/PPDOs are fixed to be 90/10, and the other micro injection molding process parameters are as follows: injection speed 100mm/s, injection pressure 1500bar, melt temperature 180 ℃; specific comparative properties are shown in table 3 below:
TABLE 3 influence of die temperature on PLA/PPDOS blend physical Properties
Through the experimental comparison, the elongation at break of the sample can be further remarkably improved when the temperature of the die is selected to be 40 ℃. When the mold temperature was selected at 80 ℃, experiments found that the reproducibility of the results of elongation at break in the tensile test was poor, the reason for this was presumably that the mold temperature at 80 ℃ was close to the melting temperature of ppdi and higher than the crystallization temperature of ppdi, and thus the crystallization of the sample after the injection molding was completed may not be completed yet, the degree of crystallization was uncontrollable, and the elongation at break difference distance of each spline was large. Therefore, although the improvement of the mold temperature is favorable for PLA crystallization and the improvement of the breaking elongation of the miniature injection molding sample in theory, the production period is prolonged, the demolding process is difficult to control, and the continuous production is influenced, so that the mechanical property of the sample is not improved by singly using the mode of improving the mold temperature.
Examples 9 to 11, comparative example 3
Examples 9 to 11 are based on the injection speed difference in micro injection molding as a variable, and the mechanical properties of the obtained samples were prepared, at which time the PLA/PPDOS content was fixed at 90/10, and the other micro injection molding process parameters were: the temperature of the die is 40 ℃, the injection pressure is 1500bar, and the temperature of the melt is 180 ℃; specific comparative properties are shown in table 4 below:
TABLE 4 influence of injection speed on PLA/PPDOS blend physical Properties
Comparative example 3 in the above table is a spline prepared using pure PLA.
Through the above experimental comparison, it was found that the elongation at break of the sample could be further significantly improved when the injection speed was selected at 200 mm/s.
Claims (8)
1. The preparation method of the biomedical fully degradable polylactic acid polymer-based composite product is characterized by comprising the following steps of:
(1) The following raw materials are mixed according to parts by weight and used as a mixture:
85-95 parts of polylactic acid polymer,
5 to 15 parts of polydioxanone,
wherein, the total of polylactic acid polymer and polydioxanone is 100 parts;
(2) Carrying out premelting blending treatment on the mixture obtained in the step (1), specifically, carrying out melting blending extrusion granulation on the mixture by using a single screw extruder to obtain a pretreated polylactic acid polymer matrix composite material;
(3) Carrying out secondary premelting blending treatment on the pretreated polylactic acid polymer-based composite material obtained in the step (2), specifically, carrying out melt blending extrusion granulation on the pretreated polylactic acid polymer-based composite material by utilizing a double screw extruder to obtain a polylactic acid polymer-based composite material subjected to secondary pretreatment; wherein the screw speed of the twin-screw extruder is not lower than 60rpm;
(4) Preparing the polylactic acid polymer-based composite material subjected to secondary pretreatment obtained in the step (3) into a polylactic acid polymer-based composite product by micro injection molding; wherein, the technological parameters of the miniature injection molding are as follows: the injection speed is 50-200 mm/s, the die temperature is 30-60 ℃, the injection pressure is 1000-1500 bar, and the melt temperature is 180-200 ℃.
2. The method of manufacture of claim 1, wherein: the polylactic acid polymer in the step (1) is polylactic acid.
3. The method of manufacture of claim 1, wherein: in the step (2), the mixture is subjected to melt blending extrusion granulation by using a single screw extruder, and specific technological parameters are as follows: the melting temperature is 180-200 ℃, and the rotating speed of the screw is 20-30 rpm.
4. The method of manufacture of claim 1, wherein: in the step (3), the pretreated polylactic acid polymer-based composite material is subjected to melt blending extrusion granulation by using a double-screw extruder, and specific technological parameters are as follows: the melting temperature is 180-200 ℃, and the screw rotating speed is 60-100 rpm.
5. The method of manufacture of claim 1, wherein: the mixture obtained in the step (1), the pre-treated polylactic acid polymer-based composite material obtained in the step (2) and the polylactic acid polymer-based composite material subjected to the secondary pre-treatment in the step (3) are subjected to drying treatment before the next process treatment.
6. The method of manufacturing according to claim 5, wherein: the drying treatment is vacuum drying for 6-12 h at 40-80 ℃.
7. The method for preparing a biomedical fully degradable polylactic acid polymer-based composite product according to claim 1, wherein the polylactic acid polymer-based composite product is prepared.
8. The method for producing a biomedical fully degradable polylactic acid polymer-based composite product according to claim 2, wherein the polylactic acid-based composite product is produced.
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