A vacuum pressure infiltration polymer / glass ceramic composite material, its preparation method and application

Abstract

The present invention relates to a vacuum pressure infiltration polymer / glass-ceramic composite material, its preparation method and application, belonging to the technical field of composite material preparation. The preparation method of the present invention has the following characteristics during the process: (1) Adding a pore-forming agent to form pores and adopting a two-step sintering method (pre-sintering and calcination) of pre-sintering first, then forming and finally sintering to prepare porous glass-ceramics; (2) Using a simple and efficient vacuum / pressure infiltration device and infiltration method to prepare glass-ceramic / polymer composites. The separating funnel, suction bottle and vacuum pump in the infiltration device construct a vacuum system. First, make the porous structure of the glass-ceramics reach a vacuum state, absorb the monomer solution into the pores through the capillary force, and then press the monomer solution into the pores of the glass-ceramics through the pressurization of the load-bearing syringe; the vacuum / pressure infiltration improves the infiltration effect through the strictly procedural conversion of the infiltration liquid pressure.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of composite materials, and relates to a vacuum pressure infiltration polymer / glass ceramic composite material, a preparation method thereof and an application thereof. Background Art

[0002] Dental materials, as hard materials in biomaterials, are required to maintain stability and durability in the specific environment of the human oral cavity after being implanted into the oral cavity. Therefore, the following conditions need to be met: (1) Good biocompatibility and minimal biochemical reactions. Properties such as no adverse irritation, no toxicity, no interference with immune function, no allergic reactions, no carcinogenicity, no teratogenicity, no inflammatory reactions, no infection, no rejection, etc.; (2) Stable physical and chemical properties. Dental materials are immersed in saliva for a long time, and saliva contains proteins, inorganic acids, organic acids, and various ions, etc. In this complex environment, dental materials need to have physical and chemical properties such as anti-dissolution and anti-corrosion; (3) Superior mechanical properties. Teeth, as the main functional organs for chewing, should have high strength, good wear resistance and high toughness, and their mechanical properties should be similar to those of natural teeth; (4) High biomimicry. Natural dentin is essentially an organic / inorganic composite material composed of inorganic components of hydroxyapatite and proteins. Only when artificial dental materials are similar to natural teeth in structure and composition can they be functionally matched with natural teeth. High aesthetic similarity. With the development of dental technology and the improvement of people's quality of life, dental materials should not only perform the most basic functions of teeth, but also have the same aesthetics as natural teeth. Therefore, dental materials should have a very high surface finish and realistic color; in addition, in order to achieve the required dimensional accuracy, dental materials should have the property of being easy to process and form. In order to seek dental materials that meet the above various requirements, materials scientists and medical workers have made unremitting efforts for many years and developed a variety of dental materials and have been applied clinically. At present, the dental restoration materials used clinically mainly include metal materials, polymer materials represented by cured resins and their composite materials, and ceramic materials.

[0003] Metal dental materials are the earliest developed and applied among all dental materials. Although metal materials have very high mechanical properties, and their strength and wear resistance can meet the use requirements of dental materials, they have fatal disadvantages in terms of physical and chemical properties such as physiological toxicity and corrosion, and aesthetics.

[0004] Compared with metal restorative materials, polymer restorative materials do not produce cytotoxicity or allergic reactions due to metal dissolution. Polymer materials have relatively low mechanical strength but high toughness. Commonly used ones include bisphenol A glycidyl methacrylate (Bis-GMA), urethane dimethacrylate (UDMA), polymethyl methacrylate (PMMA), etc. However, polymer restorative materials such as cured resins still have many disadvantages, such as large shrinkage after curing, incomplete curing, low strength, poor wear resistance, easy aging, etc., and it is difficult to be used for large-area restorations such as posterior tooth filling, thus limiting their application in clinical restorations.

[0005] Ceramic materials such as zirconia, alumina, and glass ceramics have been widely used in the field of all-ceramic restorative dentistry due to their good biocompatibility, wear resistance, and aesthetic properties. Glass ceramics are an inorganic composite material between ceramics and glass. In recent years, glass ceramics (such as lithium disilicate) have become an important dental restorative material due to their high mechanical strength, excellent aesthetic properties, and outstanding biocompatibility. However, the inherent defects of ceramic materials (such as high brittleness and weak ability to decompose local stress) make the probability of ceramic restorations cracking in clinical applications relatively high and the service life shortened. In addition, compared with natural teeth, traditional ceramic materials have higher elastic modulus and hardness, which are likely to cause excessive wear of the contralateral teeth, resulting in a large loss of dental hard tissue, destruction of the anatomical morphology, abnormal occlusion curve, and even temporomandibular joint disorders. Therefore, improving the strength and toughness of dental ceramic materials has become a research hotspot for materials scientists.

[0006] Natural teeth have a hierarchical structure composed of organic components and inorganic components. This composite composed of protein organic matrix and hydroxyapatite endows teeth with high mechanical properties. Therefore, it is of great clinical significance to combine ceramic materials and polymer materials to simulate the mechanical behavior of the natural tooth structure and prepare a dental restorative material that combines the advantages of both and matches the properties of natural tooth tissues. The combination of glass ceramics and polymers can introduce ceramic crystal phases into the amorphous glass phase and form a three-phase interpenetrating network structure of glass, ceramic microcrystals, and polymers, greatly improving the mechanical properties of the composite material. Existing research has shown that polymer-infiltrated glass ceramic networks have a structure closer to natural teeth than existing dental resin composites and better fracture toughness and damage tolerance than glass ceramics.

[0007] Compared with glass ceramics and resin composites, the mechanical properties of polymer-infiltrated glass ceramics are more improved and can be used as a better dental restoration material. To prepare such a composite material, first, a biocompatible glass ceramic needs to be prepared, and then it is combined with a high molecular monomer compound through a polymerization reaction to form a composite material. The most direct and simplest method for preparing a polymer / glass ceramic composite material is the direct mixing method of polymer and glass ceramic powder, that is, mixing the polymer material and the glass ceramic powder in a certain proportion and then performing thermal curing. For example, Dhuha H. Mohammed et al. first ground lithium disilicate glass ceramic into fine powder, and the fine powder was surface-treated with ethanol and organosilane respectively to increase the interfacial bonding strength between the polymer and the glass ceramic. Then, the surface-treated lithium disilicate glass ceramic powder was ultrasonically dispersed and mixed with polymethyl methacrylate (PMMA) monomer and initiator, and then thermally cured at a certain temperature to form a composite material. However, although the direct mixing method of polymer and glass ceramic powder is simple in preparation method, this material is still a polymer-based composite material formed by inorganic non-metallic particles dispersed in the polymer. The glass ceramic phase itself does not form an integrated network structure and does not have the bionic structural characteristics of natural teeth, so its mechanical properties are not prominent.

[0008] Generally, porous ceramics are more suitable for preparing ceramic / polymer composites by impregnation method, and mainly adopt the following methods: (1) Freeze-drying pore-forming infiltration method (The freeze-drying preparation method uses the condition that water freezes into ice at ultra-low temperature and pores are formed after ice sublimation to obtain a porous ceramic green body (scaffold), which is then sintered at high temperature to become a porous ceramic framework. The microstructure of the ceramic phase can be controlled by controlling the solid content in the ceramic slurry and the freezing conditions (freezing rate, sintering temperature, etc.). Then, the porous ceramic is evacuated in a closed space and then immersed in the impregnation liquid for vacuum impregnation of the polymer, and the ceramic / polymer composite is obtained after curing. For example, the ceramic resin composite is obtained by infiltrating and curing the ceramic scaffold after vacuum high-temperature sintering with epoxy resin); (2) Slip casting vacuum impregnation method (A mixture of ceramic powder and water with a certain volume ratio is ground into a slurry by a planetary ball mill, and the slurry is poured into a plaster mold. The strong absorption of water by the plaster is used to obtain particle agglomeration, and then it is dried and sintered at a certain temperature to obtain a sintered ceramic framework with an open pore structure. Then, the ceramic framework is immersed in a polymer monomer mixed solution in a vacuum environment, and a composite material is formed by polymerization reaction at a certain temperature); (3) 3D printing impregnation method (A certain proportion of photocurable resin, dispersant, ceramic powder and photoinitiator TPO are ball-milled to finally obtain a ceramic slurry. The ceramic slurry is added to a 3D printer, and a green body with a smooth and fully connected porous structure in a periodic three-dimensional space is printed by 3D printing technology. The green body is degreased and sintered to obtain a porous ceramic framework. Subsequently, the porous ceramic framework is evacuated and impregnated with a silane coupling agent. Then, the porous ceramic framework is semi-immersed in the polymer monomer solution, and the polymer monomer solution is impregnated by vacuum assistance, and then the polymer is cured by keeping warm at a certain temperature for a period of time).

[0009] However, there are certain defects when applying the above various methods for ceramics to glass ceramics, mainly reflected in the following aspects: (1) Freeze-drying, slip casting, and 3D printing all belong to wet forming methods, which are more suitable for the forming of ceramic slurries such as Al2O3. For the preparation of glass ceramics, since it is necessary to mix glass powder with a dispersion liquid and then perform long-term ball milling, the preparation process is long and the cost is relatively high. Among them, freeze-drying and slip casting use water as the dispersion medium, and the glass phase in the glass ceramics will be strongly eroded by water during the ball milling process, affecting subsequent sintering and the transformation and formation of the crystal phase; (2) The dehydration speed of freeze-drying and slip casting is uneven in all directions, resulting in very low green body strength, depressions, cracks, and warping deformation. The process is not easy to control, the connection of powder particles is weak, and the green body is easily broken with a little carelessness, and the dimensional stability is poor; Since freeze-drying and slip casting use water as the pore-forming agent, it is difficult to regulate the porosity and pore size. The pore size is too small to form an interconnected pore structure, and it is generally only suitable for the forming of ceramic slurries. For glass slurries, due to the high-temperature melting of glass during the sintering of the formed green body, these small pores are easily blocked, bringing difficulties to subsequent polymer infiltration; (3) 3D printing requires first printing a green body with a reticulated through-hole from a ceramic powder particle dispersion containing a photocurable resin, and then sintering the green body into a porous ceramic framework through debinding and sintering. This method requires advanced 3D printing equipment and technology, and the preparation process is long and the cost is high. (4) The method of directly immersing a porous ceramic in a vacuum state in an infiltration liquid or sucking the infiltration liquid into the porous ceramic by vacuum pumping will result in low infiltration efficiency due to insufficient internal and external pressure differences of the porous material, limited capillary force, and poor pore connectivity.

[0010] Since the glass softening temperature is lower than that of ceramics, the viscosity decrease during the sintering process will cause pore sealing or blind holes to appear, and it is difficult to form a three-dimensional interconnected pore structure in the prepared glass ceramics, affecting the infiltration and filling of the polymer phase. In view of the above disadvantages of the preparation methods, it is necessary to study a dry forming method for glass ceramics that can simply and quickly construct a connected porous structure, optimize the heat treatment process to prepare a porous glass ceramic skeleton with adjustable pores suitable for polymer infiltration, and design a convenient and efficient polymer infiltration device and method to prepare glass ceramic / polymer dental composites. Summary of the Invention

[0011] In view of this, one of the objectives of the present invention is to provide a preparation method for a vacuum pressure infiltrated polymer / glass ceramic composite material; the second objective of the present invention is to provide a vacuum pressure infiltrated polymer / glass ceramic composite material; the third objective of the present invention is to provide an application of a vacuum pressure infiltrated polymer / glass ceramic composite material in oral rehabilitation medicine.

[0012] To achieve the above objectives, the present invention provides the following technical solutions:

[0013] 1. A method for preparing a polymer / glass-ceramic composite by vacuum pressure impregnation, the preparation method comprising the following steps:

[0014] (1) Crystallization heat treatment and sintering of porous glass-ceramics: Place the glass fragments formed from the precursor glass in a crucible, and heat it in a muffle furnace at a rate of 2 - 5 °C / min to the glass transition temperature (T g ) and the crystallization temperature (T p ) of the precursor glass. After holding for a certain time, cool it in the furnace to allow the glass fragments to crystallize preliminarily. Then grind and pass through a 200 - 300 mesh sieve to obtain the preliminarily crystallized glass powder. Add a pore-forming agent and glycerol in sequence, stir evenly, put it into a mold, press and form, then relieve pressure, demold, and dry to form a green body. Place it in a muffle furnace, heat it to 450 - 500 °C, hold for 3 h to remove the binder and degrade and volatilize the pore-forming agent, and then heat it to the initial melting temperature (T mx ) of the glass, hold for a certain time to sinter the green body into glass-ceramics, and cool it in the furnace to obtain porous glass-ceramics;

[0015] (2) Preparation of polymer / glass-ceramic composite by vacuum / pressure impregnation method: Use the porous glass-ceramics prepared in step (1), and polish or etch the surface layer with a 5 - 15% by mass hydrofluoric acid solution to remove a 0.5 - 1 mm thick surface layer, ultrasonically clean it with water for 10 - 30 min to expose the internal pores, treat the pore surface of the glass-ceramics by impregnating with a silane coupling agent, dry it in an oven at 105 - 110 °C for 3 - 5 h to obtain the porous glass-ceramics treated with the silane coupling agent. Then impregnate the polymer monomer solution into the porous glass-ceramics, and then first pre-polymerize at 60 - 80 °C, and then carry out a thermal polymerization reaction at 90 - 120 °C to polymerize the impregnated polymer monomers into a polymer and fill it in the pores of the porous glass-ceramics, which is the polymer / glass-ceramic composite prepared by vacuum pressure impregnation.

[0016] Preferably, in step (1), the glass fragments formed from the precursor glass are prepared as follows: Place the raw materials constituting the precursor glass in a ball mill tank for ball milling to form a mixture, place the mixture in a crucible, heat it to the melting temperature (T m ) at a rate of 5 - 10 °C / min, hold for 2 - 5 h, fully melt it into glass liquid, and pour it on an iron plate to cool or quench it with water to form glass fragments;

[0017] The precursor glass includes any one or several of the composition systems SiO2 - Al2O3 - K2O, Li2O - SiO2, or SiO2 - Al2O3 - MgO - K2O.

[0018] Preferably, in step (1), the mass of the pore-forming agent is 10 - 50% of the mass of the glass powder;

[0019] The mass of the glycerol is 5-10% of the total mass of the glass powder and the pore former.

[0020] Preferably, in step (1), the pore former is any one of polymethyl methacrylate microspheres, polystyrene microspheres, polyvinyl alcohol or urea with a diameter of 5-100 μm.

[0021] Preferably, in step (1), the tableting is dry pressing at 10-15 MPa and then holding the load for 2-3 min;

[0022] The heating rate is 2-5 °C / min.

[0023] Preferably, in step (2), the specific method of infiltration is as follows: Connect the separatory funnel and the aspirator bottle with high airtightness, close and communicate them through a valve, connect the aspirator bottle with a vacuum pump. First, close the valve of the separatory funnel, pour the polymer monomer solution into the separatory funnel, place the porous glass ceramic in the aspirator bottle, turn on the vacuum pump to extract the air in the aspirator bottle, make the internal air pressure reach -0.07 to -0.1 MPa and maintain it for 1-3 h to completely extract the air in the porous glass ceramic. Keep the vacuum and open the valve of the separatory funnel to make the polymer monomer solution slowly flow into the aspirator bottle until the polymer monomer solution partially submerges the porous glass ceramic, close the valve of the separatory funnel and infiltrate under vacuum for 0.5-2 h. Then, continue to open the valve to add the polymer monomer solution under vacuum conditions until the surface of the porous glass ceramic is completely submerged, and close the vacuum pump to infiltrate under normal pressure for 1-5 h.

[0024] Preferably, in step (2), when the polymer monomer solution infiltrates into the porous glass ceramic, the following steps are also included: Fix the syringe on the bracket, place a weight of 2-8 kg on the piston handle of the syringe and infiltrate for 1-6 h. The pressure of the weight will be transmitted to the polymer monomer solution through the piston shaft, so that the monomer solution penetrates into the pores of the glass ceramic under the action of pressure, enhancing the infiltration effect of the monomer solution.

[0025] Preferably, in step (2), the polymer monomer solution is prepared as follows: Mix the polymer monomer and the diluent according to a mass ratio of 1:0.5-1, and then add benzoyl peroxide (BPO), and stir at room temperature for 1-2 h to fully dissolve the benzoyl peroxide.

[0026] The mass of the benzoyl peroxide is 0.3-1 wt% of the total mass of the polymer monomer and the diluent. The polymer monomer is an acrylic polymer monomer, and the acrylic polymer monomer is any one of methacrylate, bisphenol A glycidyl methacrylate or ethylene glycol dimethacrylate.

[0027] The diluent is polyurethane dimethacrylate (UDMA) or triethylene glycol dimethacrylate (TEGDMA).

[0028] 2. A vacuum pressure infiltration polymer / glass-ceramic composite material prepared by the above preparation method.

[0029] 3. Application of the above vacuum pressure infiltration polymer / glass-ceramic composite material in oral medical restoration.

[0030] The beneficial effects of the present invention are as follows: The present invention discloses a preparation method of a vacuum pressure infiltration polymer / glass-ceramic composite material. The process of this preparation method has the following characteristics: (1) Adding a pore-forming agent to form pores and adopting a two-step sintering method of pre-sintering first, then forming and finally sintering to prepare porous glass ceramics (pre-sintering is to convert part of the glass phase into a crystal phase to avoid the sealing of pores and serious shrinkage deformation of the glass-ceramic sintered body due to the reduction of the viscosity of the glass phase; for the preparation of porous ceramics, since there is generally no glass phase, it only needs to be calcined at the sintering temperature). (2) Using a simple and efficient vacuum / pressure infiltration device and infiltration method to prepare a glass-ceramic / polymer composite material. The separating funnel and the suction bottle in this infiltration device are connected to a vacuum pump to construct a vacuum system. First, the porous structure of the glass ceramic reaches a vacuum state, and the monomer solution is absorbed into the pores through capillary force, and then the monomer solution is pressed into the pores of the glass ceramic through the pressurization of a load-bearing syringe; the vacuum / pressure infiltration improves the infiltration effect through a strictly procedural conversion of the infiltration liquid pressure.

[0031] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent description, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following description. Description of the Drawings

[0032] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0033] Figure 1 is the differential scanning calorimetry analysis result of 65SiO2-28Li2O-2K2O-1.5ZnO-1.5P2O5-2Al2O3;

[0034] Figure 2 is the XRD pattern of lithium silicate glass ceramic;

[0035] Figure 3 is the process diagram of vacuum infiltration in the preparation method of the present invention;

[0036] Figure 4Device diagram for vacuum / pressure infiltration of GMA monomer in Example 2;

[0037] Figure 5 SEM cross-sectional micrographs of lithium silicate glass-ceramic, porous lithium silicate glass-ceramic, and polymer-infiltrated lithium silicate glass-ceramic composites prepared in the examples, where a is the lithium silicate glass-ceramic, b is the porous lithium silicate glass-ceramic, and c is the vacuum-pressure infiltrated polymer / glass-ceramic composite prepared in Example 2. Detailed implementation mode

[0038] The following specific examples illustrate the implementation modes of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following examples only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following examples and the features in the examples can be combined with each other.

[0039] Example 1

[0040] A vacuum-pressure infiltrated polymer / glass-ceramic composite is prepared specifically according to the following steps:

[0041] 1. Preparation of glass fragments: Weigh quartz sand, Li2CO3, potassium carbonate, ZnO, ammonium dihydrogen phosphate, and Al(OH)3 according to the molar percentage composition of 65SiO2 - 28Li2O - 2K2O - 1.5ZnO - 1.5P2O5 - 2Al2O3. After mixing, put them into a ball mill jar and grind thoroughly on a ball mill for 1 h. Put the obtained mixture into an alumina crucible and heat it in a high-temperature electric furnace at a rate of 10 °C / min to 1500 °C and hold for 3 h to fully melt various raw material powders to obtain a glass melt, and then water-quench it (directly pour it into water for quenching) into glass fragments.

[0042] 2. Preparation of lithium silicate porous glass-ceramic:

[0043] (1) Perform differential scanning calorimetry analysis on 65SiO2 - 28Li2O - 2K2O - 1.5ZnO - 1.5P2O5 - 2Al2O3 glass. The results are as Figure 1 shown. According to Figure 1 the glass transition temperature and glass crystallization temperature shown in the DSC curve in

[0044] (2) Tabletting: Grind the glass fragments processed in step (1) into glass powder with an agate mortar (grind until it can pass through a 200-mesh sieve hole), add spherical polymethyl methacrylate particles with a particle size of 200 mesh as a pore-forming agent (where the mass of the polymethyl methacrylate microspheres is 50% of the mass of the glass powder), drop glycerol (where the mass of glycerol is 7% of the total mass of the polymethyl methacrylate spherical particles and the glass powder), stir evenly to granulate, then pour it into a mold, and dry-press and form it under a pressure of 15 MPa with a holding time of 2 min using a tabletting machine. After releasing the pressure and demolding, dry it in an oven at 70 °C for 3 h to obtain a green body;

[0045] (3) Place the green body prepared in step (2) into a muffle furnace, heat it to 450 °C at a rate of 3 °C / min and hold for 3 h to remove the binder, then heat it to 800 °C at a rate of 3 °C / min and hold for 1 h, and finally heat it to 900 °C at a rate of 3 °C / min and hold for 1 h, and cool it with the furnace to obtain lithium silicate glass-ceramics. Perform XRD analysis on the lithium silicate glass-ceramics, as Figure 2 shown. The analysis results show that there are three main crystal phases in the obtained lithium silicate glass-ceramics, namely lithium metasilicate (Li2SiO3), lithium disilicate (Li2Si2O5), and spodumene (LiAlSi2O6).

[0046] 3. Preparation of PMMA infiltrated lithium silicate glass-ceramic composites:

[0047] (1) Infiltrate silane coupling agent: Remove the sealing layer on the surface of the lithium silicate glass-ceramics. First, polish the surface with 200 - 800# silicon carbide sandpaper to remove about 1 mm thick surface sealing layer, then etch it with a 10% HF solution for 15 min, then ultrasonically clean it with deionized water for 20 min and dry it. Mix 3-(methacryloyloxy)propyltrimethoxysilane, deionized water, and absolute ethanol in a ratio of 1:9:1, and magnetically stir it at room temperature for 1 h to hydrolyze the silane into an infiltration solution. Pour the hydrolyzed silane solution into a separatory funnel and close the valve of the separatory funnel. Then place the glass-ceramics upright in a suction flask, evacuate it with a vacuum pump until the air pressure reaches -0.085 MPa and maintain it for 1 h. Keep the vacuum and open the valve of the separatory funnel to make the liquid slowly flow into the suction flask until the infiltration liquid partially submerges the glass-ceramics, then close the valve of the separatory funnel and perform vacuum infiltration for about 1 h. Then open the valve under vacuum to add the infiltration solution until the glass-ceramics are completely submerged, close the vacuum pump, and infiltrate it at normal pressure for 1 h. Then place the glass-ceramics infiltrated with silane into an oven and dry it at a temperature of 120 °C for 3 h, and cool it to room temperature to obtain the porous glass-ceramics treated with silane coupling agent (this infiltration process is as Figure 3 shown);

[0048] (2) Vacuum / pressure impregnation of polymer: Dibutyl phthalate (DBP) and methyl methacrylate (MMA) were mixed at a ratio of 1:15, and then 1 wt% benzoyl peroxide (BPO) was added to the total mass. The mixture was stirred magnetically for 1 h at room temperature to prepare a PMMA monomer solution, and the valve of the separatory funnel was closed. The porous glass ceramics treated with silane coupling agent were placed sideways in a vacuum bottle, and the vacuum pump was turned on to extract the air in the bottle until the internal pressure reached -0.085 MPa and maintained for 3 h. Then, the vacuum was maintained and the valve of the separatory funnel was opened to allow the liquid to slowly flow into the vacuum bottle until the monomer solution partially submerged the porous glass ceramics. The valve of the separatory funnel was closed for vacuum impregnation for about 1 h. Turn off the vacuum pump and infiltrate at normal pressure for 1 hour to allow the monomer solution to penetrate into the porous glass ceramic block under vacuum through capillary action; then, seal the nipple of the syringe barrel with a screw-on sealing cap, pour the vacuum-infiltrated porous glass ceramic and PMMA monomer solution into the syringe, push the syringe piston, turn the syringe upside down, remove the screw-on sealing cap, slowly push the piston in, exhaust the air at the top of the liquid in the syringe, and then seal the syringe nipple with a screw-on sealing cap. Finally, fix the syringe on the bracket, place a 3kg weight on the syringe piston handle and infiltrate for 6 hours.

[0049] (3) Thermal curing: After the monomer solution is impregnated, the glass ceramics and the solution in the syringe are placed in a container and heated in a constant temperature water bath at 80°C for 30 min to prepolymerize into a viscous liquid. The impregnated glass ceramics are then taken out and placed in an oven at 50°C for 5 h and then heated to 90°C for 1 h for polymerization reaction and then cooled to room temperature to obtain a vacuum pressure impregnation polymer / glass ceramic composite material.

[0050] Example 2

[0051] A vacuum pressure infiltration polymer / glass ceramic composite material is prepared according to the following steps:

[0052] 1. Preparation of glass fragments: quartz sand, Li2CO3, potassium carbonate, ZnO, ammonium dihydrogen phosphate and Al(OH)3 were weighed according to the molar percentage composition of 65SiO2-28Li2O-2K2O-1.5ZnO-1.5P2O5-2Al2O3, mixed and put into a ball mill, and fully ground on the ball mill for 1 hour. The obtained mixture was put into an alumina crucible, and the temperature was increased to 1500°C in a high-temperature electric furnace at a rate of 10°C / min and kept warm for 3 hours to fully melt various raw material powders to obtain glass liquid, which was quenched into glass fragments.

[0053] 2. Preparation of lithium silicate porous glass ceramics:

[0054] (1) The 65SiO2-28Li2O-2K2O-1.5ZnO-1.5P2O5-2Al2O3 glass was subjected to differential scanning calorimetry analysis. The results are as follows:Figure 1 As shown in Figure 1 Figure 1 According to the glass transition temperature and glass crystallization temperature shown in the DSC curve, put the above glass fragments into a crucible and heat them in a muffle furnace to 630 °C at a rate of 2-5 °C / min successively, hold for 3 h, and then cool with the furnace to allow the glass fragments to crystallize preliminarily, reducing the amorphous glass phase in the glass and increasing the crystalline phase;

[0055] (2) Tabletting: Grind the glass fragments treated in step (1) into glass powder with an agate mortar (grind until it can pass through a 200-mesh sieve opening), add spherical polymethyl methacrylate particles with a particle size of 200 meshes as a pore-forming agent (where the mass of the polymethyl methacrylate microspheres is 50% of the mass of the fine glass powder), add glycerol with a total mass of 7% (where the mass of glycerol is 7% of the total mass of the polymethyl methacrylate spherical particles and the fine glass powder), stir evenly to granulate, then pour it into a mold, and dry-press and form it under a pressure of 15 MPa with a press for 2 min, relieve the pressure, demold, and dry it in an oven at 70 °C for 3 h to obtain a green body;

[0056] (3) Put the green body prepared in step (2) into a muffle furnace, heat it to 450 °C at a rate of 3 °C / min, hold for 3 h to remove the binder, then heat it to 800 °C at a rate of 3 °C / min and hold for 1 h, and finally heat it to 900 °C at a rate of 3 °C / min and hold for 1 h, and cool with the furnace to obtain lithium silicate glass-ceramics. Perform XRD analysis on the lithium silicate glass-ceramics. The analysis results show that there are three main crystal phases in the obtained lithium silicate glass-ceramics, namely lithium metasilicate (Li2SiO3), lithium disilicate (Li2Si2O5), and spodumene (LiAlSi2O6).

[0057] 3. Preparation of GMA-impregnated lithium silicate glass-ceramic composite materials:

[0058] (1) Impregnation with silane coupling agent: Remove the sealing layer on the surface of lithium silicate glass-ceramics. First, polish the surface with 200 - 800# silicon carbide sandpaper to remove about 1 mm thick surface sealing layer, then etch with 10% HF solution for 15 min, followed by ultrasonic oscillation cleaning with deionized water for 20 min and then drying. Mix 3-(methacryloyloxy)propyltrimethoxysilane, deionized water, and absolute ethanol in a ratio of 1:9:1, and magnetically stir at room temperature for 1 h to hydrolyze the silane into an impregnation solution. Pour the hydrolyzed silane solution into a separating funnel and close the valve of the separating funnel. Then place the glass-ceramics upright in a suction flask, evacuate with a vacuum pump until the pressure reaches -0.1 MPa and maintain for 1 h. Keep the vacuum and open the valve of the separating funnel to allow the liquid to slowly flow into the suction flask until the impregnation liquid partially submerges the glass-ceramics. Close the valve of the separating funnel and perform vacuum impregnation for about 1 h. Then, open the valve under vacuum to add impregnation liquid until the glass-ceramics are completely submerged, and close the vacuum pump to perform impregnation at atmospheric pressure for 1 h. Then place the glass-ceramics impregnated with silane in an oven and dry at 120 °C for 3 h, and cool to room temperature to obtain porous glass-ceramics treated with silane coupling agent;

[0059] (2) Vacuum / pressure impregnation of GMA monomer: Mix bisphenol A glycidyl methacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) in a mass ratio of 1:1, and then add 1 wt% benzoyl peroxide (BPO) of their total mass. Magnetically stir at room temperature for 1 h to fully dissolve BPO to prepare a GMA monomer solution, and close the valve of the separating funnel. Place the porous glass-ceramics treated with silane coupling agent upright in a suction flask, open the vacuum pump to extract the air in the flask, make the internal pressure reach -0.1 MPa and keep for 3 h. Then keep the vacuum and open the valve of the separating funnel to allow the liquid to slowly flow into the suction flask until the monomer solution partially submerges the porous glass-ceramics. Close the valve of the separating funnel and perform vacuum impregnation for about 1 h. Close the vacuum pump and perform impregnation at atmospheric pressure for 1 h to allow the monomer solution to penetrate into the porous glass-ceramics block through capillary action under vacuum; Subsequently, seal the nipple of the syringe barrel with a screw cap, remove the piston of the syringe barrel, pour the porous glass-ceramics impregnated with monomer solution and the GMA monomer solution into the syringe barrel together, and push the piston of the syringe barrel. Invert the syringe barrel upwards, remove the nipple sealing cap, slowly push the piston to expel the air at the upper end of the liquid in the syringe, then screw the screw cap tightly to block the nipple of the syringe barrel. Finally, fix the syringe on a bracket and place a 5 kg weight on the piston handle of the syringe for impregnation for 6 h (the device is as Figure 4 shown);

[0060] (3) After the glass-ceramics are impregnated with the monomer, the polymer polymerizes into a viscous liquid at 70 °C. Take out the glass-ceramics and perform a polymerization reaction curing for 8 h in an oven at 110 °C to obtain a GMA / lithium silicate glass-ceramics composite material.

[0061] The cross-sectional scanning electron micrographs of the lithium silicate glass-ceramic, porous lithium silicate glass-ceramic, and polymer-infiltrated lithium silicate glass-ceramic composite prepared in Example 2 above are as follows Figure 5 shown, where a is the lithium silicate glass-ceramic, b is the porous lithium silicate glass-ceramic, and c is the polymer-infiltrated lithium silicate glass-ceramic composite. From Figure 5 a in it can be seen that the precipitated lithium silicate grains are in the shape of plates and are arranged in an interlocking structure by intersecting with each other. This structural feature endows the glass-ceramic phase with relatively high mechanical strength. From Figure 5 b in it can be seen that the porous lithium silicate glass-ceramic contains internally connected pores, and there are penetrating branched pore channels on the inner wall of the pores, forming a three-dimensional maze-like connected pore network. From Figure 5 c in it can be seen that the light gray is the glass-ceramic phase and the dark gray is the polymer phase. The internal pores of the polymer / glass-ceramic composite are filled with the polymer, and the continuous glass-ceramic phase and polymer phase form an interpenetrating network structure.

[0062] It was detected that for the composites obtained by infiltrating polymers into the porous glass-ceramics with a porosity of less than 30% in Example 1 and Example 2, compared with the non-porous glass-ceramics, their flexural strength is basically stable, the elastic modulus is reduced, the fracture toughness is increased by about 3 times, the friction and wear are significantly reduced, and the mechanical properties are closer to those of natural teeth. Therefore, it has good application prospects in oral medical restoration.

[0063] In summary, the present invention discloses a preparation method of a vacuum-pressure infiltrated polymer / glass-ceramic composite. The preparation method has the following characteristics during the process: (1) Adding a pore-forming agent to form pores and adopting a two-step sintering method of pre-sintering first, then shaping and finally sintering to prepare the porous glass-ceramic (pre-sintering is to convert part of the glass phase into the crystal phase to avoid the sealing of pores and serious shrinkage deformation of the glass-ceramic sintered body caused by the reduction of the viscosity of the glass phase; for the preparation of porous ceramics, since there is generally no glass phase, it only needs to be calcined at the sintering temperature). (2) Using a simple and efficient vacuum / pressure infiltration device and infiltration method to prepare the polymer / glass-ceramic composite. The separating funnel and the suction bottle in the infiltration device construct a vacuum system. First, the porous structure of the glass-ceramic reaches the vacuum state, and the monomer solution is absorbed into the pores through the capillary force, and then the monomer solution is pressed into the pores of the glass-ceramic through the pressurization of the load-bearing syringe; the vacuum / pressure infiltration improves the infiltration effect through the strictly procedural conversion of the infiltration liquid pressure. Therefore, the vacuum-pressure infiltrated polymer / glass-ceramic composite prepared by the present invention has cutting, polishing, and bonding properties, can meet the processing requirements of CAD / CAM, and has good application prospects in oral restorative medicine.

[0064] In addition, the preparation method of the present invention also has the following characteristics: (1) The dry pressing forming process of adding pore-forming agent to the powder is simple, and the pore size and porosity can be adjusted by the particle size and dosage of the pore-forming agent. It has the characteristics of high green body strength, stable size, and small shrinkage. The performance of the prepared glass-ceramic composite material can meet the processing requirements of CAD / CAM; (2) The two-step sintering method of pre-sintering first and then sintering can effectively reduce the problems of pore sealing and finished product shrinkage and deformation caused by glass melting. After pre-sintering, part of the glass phase is transformed into the crystal phase. The dry pressing formed green body reduces the pore sealing and shrinkage and deformation of the glass liquid during the secondary sintering. The appropriate residual glass phase helps the crystal grains to form neck connections, which is conducive to the formation of the glass-ceramic sintered body; (3) The polymer infiltration device is simple, efficient, and low-cost. By vacuum, a negative pressure is first formed in the pores of the glass-ceramic, and then the infiltration liquid is slowly added in batches. The infiltration liquid is sucked in through upper suction and the capillary force of the pores. In addition, the infiltration pressure is adjusted by the load weight above the piston handle of the syringe to promote the further infiltration of the infiltration liquid into the pores of the glass-ceramic. These two measures strengthen the infiltration effect and improve the filling rate of the polymer in the glass-ceramic.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for preparing a vacuum pressure infiltration polymer / glass ceramic composite material, characterized in that, The preparation method comprises the following steps: (1) Crystallization heat treatment and sintering of porous glass ceramics: Place the glass fragments formed from the precursor glass in a crucible, heat it in a muffle furnace at a rate of 2-5 °C / min to a temperature between the glass transition temperature and the crystallization temperature of the precursor glass, keep it warm and then cool it with the furnace to allow the glass fragments to crystallize preliminarily. Then grind it and pass it through a sieve with 200-300 meshes to obtain the preliminarily crystallized glass powder. Add a pore-forming agent and glycerol in sequence, stir evenly, put it into a mold, press it into a sheet, relieve the pressure, demold, and dry it to form a green body. Place it in a muffle furnace, heat it to 450-500 °C, keep it warm for 3 h to remove the binder and degrade and volatilize the pore-forming agent, then heat it to the initial melting temperature of the glass, keep it warm to sinter the green body into glass ceramics, and cool it with the furnace to obtain porous glass ceramics; The precursor glass includes any one or several of the composition systems SiO2-Al2O3-K2O, Li2O-SiO2, or SiO2-Al2O3-MgO-K2O; The mass of the pore-forming agent is 10-50% of the mass of the glass powder; the mass of the glycerol is 5-10% of the total mass of the glass powder and the pore-forming agent; The pore-forming agent is any one of polymethyl methacrylate microspheres, polystyrene microspheres, polyvinyl alcohol, or urea with a diameter of 5-100 μm; (2) Preparation of polymer / glass ceramic composites by vacuum / pressure infiltration method: Use grinding and polishing or etching with a 5-15% hydrofluoric acid solution to remove the skin layer with a thickness of 0.5-1 mm from the porous glass ceramics prepared in step (1), ultrasonically clean it with water for 10-30 min to expose the internal pores, treat the pore surface of the glass ceramics by infiltrating a silane coupling agent, dry it in an oven at 105-110 °C for 3-5 h to obtain the porous glass ceramics treated with the silane coupling agent. Then infiltrate the polymer monomer solution into the porous glass ceramics, and then first carry out pre-polymerization at 60-80 °C, and then carry out a thermal polymerization reaction at 90-120 °C to polymerize the infiltrated polymer monomer to form a polymer, which is filled in the pores of the porous glass ceramics, that is, a vacuum pressure infiltrated polymer / glass ceramic composite.

2. The preparation method according to claim 1, characterized in that, In step (1), the glass fragments formed from the precursor glass are prepared as follows: Place the raw materials constituting the precursor glass in a ball mill tank for ball milling to form a mixture, place the mixture in a crucible, heat it to the melting temperature at a rate of 5-10 °C / min, keep it warm for 2-5 h, fully melt it into a glass melt, pour it on an iron plate to cool or quench it with water to form glass fragments.

3. The preparation method according to claim 1, characterized in that, In step (1), the pressing into a sheet is dry pressing at 10-15 MPa and then keeping the load for 2-3 min; The heating rate is 2-5 °C / min.

4. The preparation method according to claim 1, characterized in that, In step (2), the specific method of infiltration is: Connect the separatory funnel and the aspirator bottle with high airtightness. They are closed and connected through a valve. The aspirator bottle is connected to a vacuum pump. First, close the valve of the separatory funnel, pour the polymer monomer solution into the separatory funnel, place the porous glass ceramic in the aspirator bottle, turn on the vacuum pump to extract the air in the aspirator bottle, so that the internal air pressure reaches -0.07~-0.1 MPa and is maintained for 1~3 h to completely extract the air in the porous glass ceramic. Keep the vacuum and open the valve of the separatory funnel to slowly let the polymer monomer solution flow into the aspirator bottle until the polymer monomer solution partially submerges the porous glass ceramic. Close the valve of the separatory funnel and perform vacuum impregnation for 0.5~2 h. Then, continue to open the valve under vacuum conditions and add the polymer monomer solution until the surface of the porous glass ceramic is completely submerged. Turn off the vacuum pump and impregnate at normal pressure for 1~5 h.

5. The preparation method according to claim 1, characterized in that, In step (2), when the polymer monomer solution infiltrates into the porous glass ceramic, the following steps are also included: Fix the syringe on the bracket, place a weight of 2~8 kg on the piston handle of the syringe and impregnate for 1~6 h. The pressure of the weight will be transmitted to the polymer monomer solution through the piston shaft, so that the monomer solution penetrates into the pores of the glass ceramic under the action of pressure, strengthening the impregnation effect of the monomer solution.

6. The preparation method according to claim 1, characterized in that, In step (2), the polymer monomer solution is prepared according to the following method: Mix the polymer monomer and the diluent in a mass ratio of 1:0.5~1, and then add benzoyl peroxide and stir at room temperature for 1~2 h until benzoyl peroxide is completely dissolved. The mass of the benzoyl peroxide is 0.3~1 wt% of the total mass of the polymer monomer and the diluent. The polymer monomer is an acrylic polymer monomer, and the acrylic polymer monomer is any one of methacrylate, bisphenol A glycidyl methacrylate or ethylene glycol dimethacrylate. The diluent is polyurethane dimethacrylate or triethylene glycol dimethacrylate.

7. A vacuum pressure infiltration polymer / glass ceramic composite material prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the vacuum pressure infiltration polymer / glass ceramic composite material according to claim 7 in oral medical restoration.

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