Photosensitive resin for photocuring additive manufacturing and ceramic slurry prepared from photosensitive resin

Abstract

The invention discloses photosensitive resin for photocuring additive manufacturing and ceramic slurry prepared from the photosensitive resin, and the photosensitive resin is prepared from the following components in parts by weight: 7 to 50 parts of prepolymer, 3 to 100 parts of monofunctional monomer, 30 to 95 parts of low-functional monomer, 0.5 to 50 parts of high-functional monomer, 0.4 to 10 parts of dispersing agent, 0.01 to 5 parts of photoinitiator, 2 to 20 parts of plasticizer, 0.01 to 0.11 part of light absorbent and / or 0.01 to 1.5 parts of polymerization inhibitor, wherein the prepolymer accounts for more than 15% of the total weight of the photosensitive resin. The photosensitive resin is low in viscosity, meanwhile, the prepared slurry has the characteristic of low viscosity, and a printed piece has a smooth surface; x / Y plane overexposure can be inhibited, and the photocuring precision is improved; the problems of deformation of the printed green body, cracking caused by decomposition and elimination of organic matters and the like can be effectively solved, the ceramic green body is high in density, and a thin-wall structure can be printed.

Description

Technical Field

[0001] The present invention relates to the technical field of dental material production, and in particular to a photosensitive resin for photocuring additive manufacturing and a ceramic slurry prepared therefrom. Background Art

[0002] 3D printing, also known as additive manufacturing, is a cutting-edge manufacturing technology that integrates digital modeling technology, information technology, materials science, chemistry and many other fields. The Economist magazine calls it the "third industrial revolution". In recent years, with the development of aerospace, biomedicine and other fields, traditional processing methods can no longer fully meet human requirements. The demand for personalized and customized products has further pushed 3D printing technology to the national strategic level.

[0003] Ceramic materials are widely used in aerospace, electronics, biomedicine and other fields due to their high hardness, high strength, high corrosion resistance and wear resistance. However, it is difficult to form complex precision ceramic parts with traditional processes. 3D printing, as a new molding technology, has great advantages in preparing high-precision parts of arbitrary shapes and can meet personalized needs. 3D printing ceramic slurry is mainly composed of ceramic powder and liquid photosensitive resin, and is finally made into printed parts through processes such as photocuring, body degreasing and sintering. As an important component of ceramic slurry, photosensitive resin has an important influence on printing accuracy, shrinkage rate and mechanical properties of ceramic blanks. In recent years, it has attracted the attention of a large number of domestic and foreign researchers, and various ceramic slurry systems have been introduced one after another.

[0004] In order to prepare high-density, low-shrinkage ceramic parts, the ceramic slurry must have a high solid content. The higher the solid content of the slurry, the greater the viscosity of the slurry, which is not conducive to the printing and laying process, which directly affects the printing accuracy. If a high-viscosity resin is used to prepare the ceramic slurry, the slurry viscosity will further increase, hindering the further optimization and improvement of the slurry solid content. Therefore, the preparation of a low-viscosity photosensitive resin system is a necessary condition for the preparation of high-solid content ceramic parts. At the same time, the photosensitive resin must also have low volatility, low irritating odor and low toxicity.

[0005] CN106007671B discloses a ceramic composite material for 3D printing, which includes the following components by weight: 20 to 45 parts of acrylate monomer; 121 to 165 parts of ceramic powder; 10 to 20 parts of spirocarbonate expansion monomer; 2 to 14 parts of dispersant; 1 to 3 parts of photoinitiator; 0 to 3 parts of photoinhibitor; and 1 to 3 parts of ultraviolet light absorber. The invention utilizes the expansion monomer to produce volume expansion during the polymerization process initiated by the cationic photoinitiator, thereby reducing the shrinkage and internal stress generated by the slurry during curing, so that the printed parts have smaller deformation, better dimensional accuracy and fewer microcrack defects.

[0006] CN108083817B discloses a ceramic slurry for photocuring 3D printing, which includes the following components: ceramic powder, dispersant, acrylate monomer combination, organic additive, photoinitiator; wherein: the acrylate monomer combination includes at least two acrylate monomers, and the weight ratio of the acrylate monomer combination to the ceramic powder is 0.14-0.175; the weight of the dispersant is 0.05%-5% of the weight of the ceramic powder; the weight ratio of the organic additive to the acrylate monomer combination is 0.1-0.5; the weight ratio of the photoinitiator to the acrylate monomer combination is 0.002-0.01. The invention has a high solid content (ceramic powder weight ratio is between 78%-85%) through effective control and coordination of the distribution ratio of each component, and the green body has a high density.

[0007] CN109081890B discloses a photosensitive resin and its preparation method and application. The raw material components of the photosensitive resin include a main material and auxiliary materials. The main material includes a mixture of any one of a multifunctional monomer and an oligomer with a monofunctional monomer. The auxiliary materials include a photoinitiator and an ultraviolet absorber. The amount of the photoinitiator accounts for 0.5-1% of the total mass of the main material, and the amount of the ultraviolet absorber accounts for 0.5-1% of the total mass of the main material. The invention adopts a main material including a mixture of any one of a multifunctional monomer and an oligomer with a monofunctional monomer. The auxiliary materials include a photoinitiator and an ultraviolet absorber. The invention has a simple formula, is easy to prepare, saves costs, and has the characteristics of low viscosity, low shrinkage and fast curing rate.

[0008] CN110627501B discloses a photocurable 3D printing ceramic slurry and its preparation method and application. The ceramic slurry comprises ceramic powder, photocurable resin, photoinitiator and dispersant. The photocurable resin is composed of the following components by mass percentage: 10-60wt% of bisphenol A epoxy acrylate, 10-60wt% of trimethylolpropane triacrylate, 10-60wt% of tripropylene glycol diacrylate and 10-60wt% of isobornyl methacrylate. The rheological properties of the slurry are adjusted by selecting active diluents with different functionalities and adjusting their proportions to meet the needs of photocurable molding. The molded sample is degreased and sintered to obtain a highly dense zirconia ceramic with a relative density of 98.8%.

[0009] There is no effective solution in the prior art for achieving a higher solid content in the printing slurry without causing a significant impact on the slurry spreading during the printing process.

[0010] Since ceramic powder materials are often added to the printing slurry, the powder particles suspended in the slurry will scatter in the X / Y plane during the light curing process, resulting in overexposure of the print, affecting the printing accuracy. When suppressing overexposure of the print, it is likely to reduce the light penetration ability, thereby reducing the curing depth and making the green strength of the printed part insufficient. There is no report on how to solve the problem of ceramic printing slurry being easily scattered in the XY plane to prevent overexposure while ensuring sufficient curing thickness.

[0011] During the printing process, the solidification and cross-linking of the slurry will cause shrinkage stress inside the green body, causing deformation of the printed green body, resulting in separation between the printed layers and the printing base plate and the printing platform. Therefore, the printed green body is required to have low shrinkage deformation stress. There is no effective solution in the prior art.

[0012] The printing slurry is composed of ceramic powder and organic components. During the debinding, degreasing and sintering process, the organic resin component softens under the action of heat, and the green body is very easy to deform under the dual action of gravity and thermal stress. In addition, in the initial stage of degreasing, low-melting-point organic matter will volatilize in the green body due to the inability to be discharged from the body, resulting in high pressure, causing cracking, deformation and other defects in the ceramic green body. Therefore, the degreasing rate needs to be strictly controlled, which requires that the printing slurry contains resin components that are easy to debind. As the temperature of the debinding process continues to rise, organic matter with different melting points is gradually decomposed and removed, leaving a through pore channel inside the printed part, which is conducive to the subsequent decomposition and removal of organic matter without cracking and other problems. In addition, the green body of the printed part has high density and high strength to ensure that the printed part can be successfully printed during the printing process. How to solve the problems of cracking caused by the decomposition and removal of organic matter to improve the green body strength of the printed part to ensure the successful printing of high-density ceramic green bodies in the top-pull printer, as well as the printing of thin-walled structures, has not been reported. Summary of the invention

[0013] The purpose of the present invention is to provide a photosensitive resin for photocuring additive manufacturing and a ceramic slurry prepared therefrom. The photosensitive resin has low viscosity, and the prepared slurry has low viscosity characteristics, and the printed part has a smooth surface; it can suppress overexposure of the X / Y plane and improve the photocuring accuracy; it can effectively solve the problems of deformation of the printed green body and cracking caused by the decomposition and removal of organic matter. The ceramic green body has a high density and can print thin-walled structures.

[0014] The technical solution adopted by the present invention to solve its technical problem is: A photosensitive resin for photocuring additive manufacturing, which is composed of 7 to 50 parts of prepolymer, 3 to 100 parts of monofunctional monomer, 30 to 95 parts of low-functional monomer, 0.5 to 50 parts of high-functional monomer, 0.4 to 10 parts of dispersant, 0.01 to 5 parts of photoinitiator, 2 to 20 parts of plasticizer, 0.01 to 0.11 parts of light absorber and / or 0.01 to 1.5 parts of polymerization inhibitor; wherein the prepolymer accounts for more than 15% of the total weight of the photosensitive resin. Preferably, the prepolymer accounts for more than 20% of the total weight of the photosensitive resin.

[0015] In the present invention, the proportion of prepolymer is controlled to be more than 15% to inhibit shrinkage deformation and improve dimensional accuracy. At the same time, low-viscosity monomers (monofunctional monomers, low-functional monomers) and plasticizers are used to achieve a low viscosity effect; high-functional monomers have a fast curing speed to ensure the cured thickness in the Z direction; light absorbers / inhibitors are added to the resin to regulate the excitation and transfer of free radicals in the monomers and prepolymers during the photocuring process, inhibit overexposure in the X / Y plane, and improve the photocuring accuracy.

[0016] Through high prepolymer content and high-functionality monomers, a strong spatial cross-linked network structure with high strength and low shrinkage is formed. At the same time, plasticizers are used to achieve the effect of low stress residue and inhibit debinding sintering cracking.

[0017] The high functionality monomer combined with the low functionality monomer and the monofunctional monomer forms a difference in curing time, thereby increasing the green density.

[0018] Preferably, the prepolymer is selected from one or more of acrylate, polyester acrylate, polyurethane acrylate and epoxy acrylate.

[0019] Preferably, the monofunctional monomer is selected from one or more of o-phenylphenoxyethyl acrylate (OPPEA), cyclotrimethylolpropane acrylate (CTFA), ethoxyphenol acrylate (PHEA), isooctyl acrylate (IOA), methoxyethyl acrylate (MEA), ethyl methacrylate (EMA), and isobutyl methacrylate (IBMA).

[0020] Preferably, the low-functionality monomer is selected from one or more of dipropylene glycol diacrylate (DPGDA), 1,6-hexanediol diacrylate (HDDA), polyethylene glycol diacrylate (PEGDA), neopentyl glycol diacrylate (NPGDA), tetraethylene glycol diacrylate (TTEGDA), 1,6-hexanediol dimethacrylate (HDDMA), and triethylene glycol dimethacrylate (TEGDMA); The high-functionality monomer is selected from one or more of pentaerythritol triacrylate (PETA), (3-propoxy)propylene glycol triacrylate (GPTA), pentaerythritol tetraacrylate (PETTA), ethoxylated pentaerythritol tetraacrylate (PPTTA), dipentaerythritol hexaacrylate (DPHA), and trimethylolpropane trimethacrylate (TMPTMA).

[0021] Preferably, the dispersant is selected from sodium polyacrylate (PAA-Na), ammonium polyacrylate (PAA-NH 4 ), ammonium citrate (AC), oleic acid (OA), hyperdispersant (Solsperse-28000 / 5000 / 38500), copolymer dispersant containing acidic groups (DISPERBYK-102 / 110 / 111, KOS-110, HY-610, HLD-F6623), block copolymer dispersant containing pigment affinity groups (DISPERBYK-161 / 162 / 163 / 164 / 166 / 167 / 170 / 190), structured acrylic copolymer (DISPERBYK-2009 / 2010 / 2010 / 2015 / 2022 / 2025) or more thereof.

[0022] Preferably, the photoinitiator is selected from one or more of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-phenyl acetone-1, 2-hydroxy-2-methyl-p-hydroxyethyl ether phenyl acetone-1, and 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide.

[0023] Preferably, the plasticizer is selected from one or more of fatty acid esters (dioctyl adipate, dioctyl sebacate, diisooctyl sebacate), polyethylene glycol, polypropylene glycol, tributyl citrate, diisononyl cyclohexane 1,2-dicarboxylate and epoxidized soybean oil.

[0024] Preferably, the light absorber is selected from one or more of phenyl salicylate, phenyl o-hydroxybenzoate, benzophenone-2, 2-hydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4,4-dimethoxybenzophenone, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-chlorobenzotriazole, pentaerythritol tetrakis(2-cyano-3,3-diphenylacrylate), 2-ethylhexyl 2-cyano-3,3-diphenylacrylate, UV-1577, UV-1164, UV-400, triazine-5, UV-770, and UV-622; The polymerization inhibitor is selected from one or more of p-methoxyphenol (MEHQ), N-nitrosophenylhydroxylamine aluminum salt, hydroquinone (HQ), and 2,6-di-tert-butyl-p-cresol (MTBHQ).

[0025] Light absorber categories: salicylates (phenyl salicylate, phenyl o-hydroxybenzoate), benzophenones (benzophenone-2, 2-hydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4,4-dimethoxybenzophenone), benzotriazoles (2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-chlorobenzotriazole), substituted acrylonitriles (pentaerythritol tetra(2-cyano)pyrrolidone), 2-cyano-3,3-diphenylacrylate), 2-ethylhexyl 2-cyano-3,3-diphenylacrylate), triazines (UV-1577, UV-1164, UV-400 and triazine-5) and hindered amines (bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (UV-770), poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol) succinate (UV-622)).

[0026] Preparation process of photosensitive resin: First, add the components of the photosensitive resin into a mixing container in proportion, and put it into a mixing device for mixing. After mixing, filter the photosensitive resin into another container. The mesh size of the filter medium is 5~300 mesh, and you can choose either a screen or a filter.

[0027] The mixing device is preferably one of a vacuum homogenizer, a ball mill, a sand mill, and a three-roll mill; Mixing speed: 100 ~500rpm / min; Mixing time: 0.5~3h; The viscosity of the photosensitive resin is 1 mPa·s to 50 mPa·s, and preferably the viscosity is less than 20 mPa·s.

[0028] A ceramic slurry for photocuring additive manufacturing, wherein, by weight percentage, the ceramic powder accounts for 70-90wt% and the photosensitive resin accounts for 10-30wt%.

[0029] Preferably, the material of the ceramic powder is selected from one or more of aluminum oxide, zirconium oxide, magnesium oxide, silicon nitride and lithium disilicate.

[0030] The beneficial effects of the present invention are: 1. The prepared photosensitive resin has low viscosity, and the prepared slurry has low viscosity characteristics, and the printed part has a smooth surface; 2. High dimensional accuracy, stable shrinkage rate, and curing depth can be maintained at 2~3 times the thickness of the printing layer; 3. The average green strength of printed parts can reach 90MPa, and the average strength of printed sintered parts can reach 800MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1is a comparison chart of the performance test results of Examples 1-10; Figure 2 It is a comparison diagram of the products processed by Example 4 and Comparative Example 1; Figure 3 It is a comparison diagram of the products processed by Example 4 and Comparative Example 2; Figure 4 It is a comparison diagram of the products processed by Example 4 and Comparative Example 4; Figure 5 It is the measurement chart of curing accuracy and curing depth of single-layer print (unit: mm); Figure 6 It is a vertical printout of the print; Figure 7 is an appearance diagram of the sintered part (3 unit bridges) in Example 4; Figure 8 This is a measurement diagram of the inner surface accuracy of the sintered part (3 unit bridges) in Example 4; Fig. 9 This is a diagram showing the edge accuracy measurement of the sintered part (3 unit bridges) in Example 4. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described in detail below through specific embodiments.

[0034] In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0035] Embodiment 1: The photosensitive resin is prepared by weight: 7 parts of prepolymer (polyurethane acrylate), 3 parts of monofunctional monomer (isooctyl acrylate (IOA)), 30 parts of low-functional monomer (polyethylene glycol diacrylate (PEGDA)), 0.5 parts of high-functional monomer (ethoxylated pentaerythritol tetraacrylate (PPTTA)), 0.4 parts of dispersant (KOS-110), 0.01 parts of photoinitiator (2-hydroxy-2-methyl-phenylacetone-1), 0.01 parts of light absorber (2,2-dihydroxy-4,4-dimethoxybenzophenone), and 2 parts of plasticizer (polypropylene glycol) are put into a ball mill and mixed at 200 rpm / min for 1 hour. After mixing, the photosensitive resin is filtered through a 200-mesh filter into another ball mill to obtain a photosensitive resin with a viscosity of 36.7 mPa·s. Preparation of ceramic printing slurry: Add ceramic powder (zirconia) according to the total mass of the slurry to the mixed photosensitive resin at 80wt% and mix it in a ball mill for a second time at 300rpm / min for 2h. After mixing, filter the slurry with a 200-mesh filter into a plastic container for vacuum degassing for 1h with a vacuum degree of 0.1kPa to finally obtain an ideal ceramic printing slurry. The slurry viscosity is 16.136Pa·s 3D printing: First, place the stable ceramic printing slurry in the material cylinder of a sunken 405nm DLP printer for photocuring printing. The thickness of each printing layer is 50μm, and the printing exposure is 8s. Repeat the UV curing process until a complete printed green body is printed. Then use a 50Hz ultrasonic cleaner to clean the residual printing slurry on its surface for 5min, and repeat the cleaning 3 times. After cleaning, use a microwave dryer to dry the printed green body. Finally, use a grinding and polishing tool to remove the support structure on the printed part, and obtain a printed part with a good surface condition. The single-layer cured thickness is 0.12mm, which is 2.4 times the printing layer thickness of 50μm. The rectangular holes and 0.5mm round holes are partially visible, and the green strength of the printed part is not less than 70MPa.

[0036] Debinding of printed parts: first, the dried printed parts were placed in a crucible, and then placed in a debinding furnace, and the temperature was increased from room temperature to 120°C at a heating rate of 0.5°C / min, and then kept warm for 2 hours; then the temperature was increased to 220°C at a heating rate of 0.4°C / min, and then kept warm for 2 hours; then the temperature was increased to 350°C at a heating rate of 0.5°C / min, and kept warm for 2 hours; then the temperature was increased to 410°C at a heating rate of 0.3°C / min, and kept warm for 2 hours; then the temperature was increased to 620°C at a heating rate of 0.5°C / min, and kept warm for 2 hours, and then cooled to room temperature with the furnace to obtain the debinding printed parts. The printed parts did not crack after debinding.

[0037] High-temperature sintering of printed parts: First, place the debinding printed parts in a crucible, and then put them into a sintering furnace for high-temperature sintering. First, heat the temperature from room temperature to 350°C at a heating rate of 2°C / min, and then keep it warm for 2h; then heat it to 500°C at a heating rate of 2°C / min, and keep it warm for 2h; then heat it to 650°C at a heating rate of 5°C / min, and keep it warm for 2h; then heat it to 1200°C at a heating rate of 15°C / min, and keep it warm for 0.5h, and then heat it to 1550°C at a heating rate of 25°C / min, and keep it warm for 2h, and then cool it to room temperature with the furnace to obtain the final sintered printed parts. The strength of the printed parts is not less than 720MPa, and the sintered density is 6.01g / cm 3 .

[0038] Embodiment 2: The photosensitive resin is prepared by weight: 50 parts of prepolymer (polyurethane acrylate), 100 parts of monofunctional monomer (isooctyl acrylate (IOA)), 95 parts of low-functional monomer (polyethylene glycol diacrylate (PEGDA)), 50 parts of high-functional monomer (ethoxylated pentaerythritol tetraacrylate (PPTTA)), 10 parts of dispersant (KOS-110), 5 parts of photoinitiator (2-hydroxy-2-methyl-phenylacetone-1), 0.11 parts of light absorber (2,2-dihydroxy-4,4-dimethoxybenzophenone), and 20 parts of plasticizer (polypropylene glycol) are put into a ball mill and mixed at 200 rpm / min for 1 hour. After mixing, the photosensitive resin is filtered through a 200-mesh filter into another ball mill to obtain a photosensitive resin with a viscosity of 45.7 mPa·s. Preparation of ceramic printing slurry: Add ceramic powder (zirconia) according to the total mass of the slurry to the mixed photosensitive resin at 80wt% and mix it in a ball mill for a second time at 300rpm / min for 2h. After mixing, filter the slurry with a 200-mesh filter into a plastic container for vacuum degassing for 1h with a vacuum degree of 0.1kPa to finally obtain an ideal ceramic printing slurry. The slurry viscosity is 28.113Pa·s 3D printing: First, place the stable ceramic printing slurry in the material cylinder of a sunken 405nm DLP printer for photocuring printing. The thickness of each printing layer is 50μm, and the printing exposure is 8s. Repeat the UV curing process until a complete printed green body is printed. Then use a 50Hz ultrasonic cleaner to clean the residual printing slurry on its surface for 5min, and repeat the cleaning 3 times. After cleaning, use a microwave dryer to dry the printed green body. Finally, use a grinding and polishing tool to remove the support structure on the printed part, and obtain a printed part with a good surface condition. The single-layer cured thickness is 0.16mm, which is 3.4 times the printing layer thickness of 50μm. The rectangular holes and 0.5mm round holes are partially visible, and the green strength of the printed part is not less than 82MPa.

[0039] Debinding of printed parts: first, the dried printed parts were placed in a crucible, and then placed in a debinding furnace, and the temperature was increased from room temperature to 120°C at a heating rate of 0.5°C / min, and then kept warm for 2 hours; then the temperature was increased to 220°C at a heating rate of 0.4°C / min, and then kept warm for 2 hours; then the temperature was increased to 350°C at a heating rate of 0.5°C / min, and kept warm for 2 hours; then the temperature was increased to 410°C at a heating rate of 0.3°C / min, and kept warm for 2 hours; then the temperature was increased to 620°C at a heating rate of 0.5°C / min, and kept warm for 2 hours, and then cooled to room temperature with the furnace to obtain the debinding printed parts. The printed parts did not crack after debinding.

[0040] 5. High-temperature sintering of printed parts: First, place the printed parts after debinding in a crucible, and then put them into a sintering furnace for high-temperature sintering. First, heat up from room temperature to 350°C at a heating rate of 2°C / min, and then keep it warm for 2h; then heat up to 500°C at a heating rate of 2°C / min, and keep it warm for 2h; then heat up to 650°C at a heating rate of 5°C / min, and keep it warm for 2h; then heat up to 1200°C at a heating rate of 15°C / min, and keep it warm for 0.5h, and then heat up to 1550°C at a heating rate of 25°C / min, and keep it warm for 2h, and then cool to room temperature with the furnace to obtain the final sintered printed parts. The strength of the printed parts is not less than 741MPa, and the sintered density is 6.01g / cm 3 .

[0041] Embodiment 3: The photosensitive resin was prepared by weight: 22 parts of prepolymer (polyurethane acrylate), 4 parts of monofunctional monomer (isooctyl acrylate (IOA)), 30 parts of low-functional monomer (polyethylene glycol diacrylate (PEGDA)), 21 parts of high-functional monomer (ethoxylated pentaerythritol tetraacrylate (PPTTA)), 16 parts of dispersant (KOS-110), 1 part of photoinitiator (2-hydroxy-2-methyl-phenylacetone-1), 0.07 parts of light absorber (2,2-dihydroxy-4,4-dimethoxybenzophenone), and 5 parts of plasticizer (polypropylene glycol) were put into a ball mill and mixed at 200 rpm / min for 1 hour. After mixing, the photosensitive resin was filtered through a 200-mesh filter into another ball mill to obtain a photosensitive resin with a viscosity of 16.5 mPa·s. Preparation of ceramic printing slurry: Add ceramic powder (zirconia) according to the total mass of the slurry to the mixed photosensitive resin at 80wt% and mix it in a ball mill for a second time at 300rpm / min for 2h. After mixing, filter the slurry with a 200-mesh filter into a plastic container for vacuum degassing for 1h with a vacuum degree of 0.1kPa to finally obtain an ideal ceramic printing slurry. The slurry viscosity is 14.472Pa·s 3D printing: First, place the stable ceramic printing slurry in the material cylinder of a sunken 405nm DLP printer for photocuring printing. The thickness of each printing layer is 50μm, and the printing exposure is 8s. Repeat the UV curing process until a complete printed green body is printed. Then use a 50Hz ultrasonic cleaner to clean the residual printing slurry on its surface for 5min, and repeat the cleaning 3 times. After cleaning, use a microwave dryer to dry the printed green body. Finally, use a grinding and polishing tool to remove the support structure on the printed part, and obtain a printed part with a good surface condition. The single-layer cured thickness is 0.17mm, which is 3.4 times the printing layer thickness of 50μm. The rectangular holes and 0.5mm round holes are clearly visible, and the green strength of the printed part is not less than 91MPa.

[0042] Debinding of printed parts: first, the dried printed parts were placed in a crucible, and then placed in a debinding furnace, and the temperature was increased from room temperature to 120°C at a heating rate of 0.5°C / min, and then kept warm for 2 hours; then the temperature was increased to 220°C at a heating rate of 0.4°C / min, and then kept warm for 2 hours; then the temperature was increased to 350°C at a heating rate of 0.5°C / min, and kept warm for 2 hours; then the temperature was increased to 410°C at a heating rate of 0.3°C / min, and kept warm for 2 hours; then the temperature was increased to 620°C at a heating rate of 0.5°C / min, and kept warm for 2 hours, and then cooled to room temperature with the furnace to obtain the debinding printed parts. The printed parts did not crack after debinding.

[0043] 5. High-temperature sintering of printed parts: First, place the printed parts after debinding in a crucible, and then put them into a sintering furnace for high-temperature sintering. First, heat up from room temperature to 350°C at a heating rate of 2°C / min, and then keep it warm for 2h; then heat up to 500°C at a heating rate of 2°C / min, and keep it warm for 2h; then heat up to 650°C at a heating rate of 5°C / min, and keep it warm for 2h; then heat up to 1200°C at a heating rate of 15°C / min, and keep it warm for 0.5h, and then heat up to 1550°C at a heating rate of 25°C / min, and keep it warm for 2h, and then cool to room temperature with the furnace to obtain the final sintered printed parts. The strength of the printed parts is not less than 841MPa, and the sintered density is 6.03g / cm 3 .

[0044] Embodiment 4: The photosensitive resin was prepared by weight: 21 parts of prepolymer (polyurethane acrylate), 4 parts of monofunctional monomer (isooctyl acrylate (IOA)), 5 parts of low-functional monomer (polyethylene glycol diacrylate (PEGDA)), 5 parts of high-functional monomer (ethoxylated pentaerythritol tetraacrylate (PPTTA)), 16 parts of dispersant (KOS-110), 0.4 parts of photoinitiator (2-hydroxy-2-methyl-phenylacetone-1), 0.07 parts of light absorber (2,2-dihydroxy-4,4-dimethoxybenzophenone), and 25 parts of plasticizer (polypropylene glycol) were put into a ball mill and mixed at 200 rpm / min for 1 hour. After mixing, the photosensitive resin was filtered through a 200-mesh filter into another ball mill to obtain a photosensitive resin with a viscosity of 9.4 mPa·s. Preparation of ceramic printing slurry: Add ceramic powder (zirconia) according to 80wt% of the total mass of the slurry into the mixed photosensitive resin and mix it in a ball mill for a second time at 300rpm / min for 2h. After mixing, filter the slurry with a 200-mesh filter into a plastic container for vacuum defoaming for 1h with a vacuum degree of 0.1kPa to finally obtain an ideal ceramic printing slurry. The slurry viscosity is 11.472Pa·s; 3D printing: First, place the stable ceramic printing slurry in the material cylinder of a sunken 405nm DLP printer for photocuring printing. The thickness of each printing layer is 50μm, and the printing exposure is 8s. Repeat the UV curing process until a complete printed green body is printed. Then use a 50Hz ultrasonic cleaner to clean the residual printing slurry on its surface for 5min, and repeat the cleaning 3 times. After cleaning, use a microwave dryer to dry the printed green body. Finally, use a grinding and polishing tool to remove the support structure on the printed part, and obtain a printed part with a good surface condition. The single-layer cured thickness is 0.19mm, which is 3.8 times the printing layer thickness of 50μm. The rectangular holes and 0.5mm round holes are clearly visible, and the green strength of the printed part is not less than 94MPa.

[0045] Accelerated debinding of printed parts: first, the dried printed parts were placed in a crucible, and then placed in a debinding furnace and heated from room temperature to 120°C at a heating rate of 2°C / min, and then kept warm for 1 hour; then heated to 220°C at a heating rate of 0.8°C / min, and then kept warm for 1 hour; then heated to 350°C at a heating rate of 0.8°C / min, and kept warm for 1 hour; then heated to 410°C at a heating rate of 0.8°C / min, and kept warm for 1 hour; then heated to 620°C at a heating rate of 2°C / min, and kept warm for 1 hour, and then cooled to room temperature with the furnace to obtain the debinded printed parts. The printed parts did not crack after debinding.

[0046] High-temperature sintering of printed parts (method 1): First, place the printed parts after debinding in a crucible, and then put them into a sintering furnace for high-temperature sintering. First, heat up from room temperature to 350℃ at a heating rate of 2℃ / min, and then keep it warm for 2h; then heat up to 500℃ at a heating rate of 2℃ / min, and keep it warm for 2h; then heat up to 650℃ at a heating rate of 5℃ / min, and keep it warm for 2h; then heat up to 1200℃ at a heating rate of 15℃ / min, and keep it warm for 0.5h, and then heat up to 1550℃ at a heating rate of 25℃ / min, and keep it warm for 2h, and then cool to room temperature with the furnace to obtain the final sintered printed parts. (Method 2): First, heat the temperature from room temperature to 400℃ at a heating rate of 20℃ / min, and then keep it at this temperature for 20min; then heat the temperature to 1550℃ at a heating rate of 85℃ / min, keep it at this temperature for 20min, and then cool it to 300℃ with the furnace. Take out the printed part and place it at room temperature to cool it down to obtain the final sintered printed part. The strength of the printed part is not less than 917MPa, and the sintered density is 6.06g / cm 3 .

[0047] Embodiment 5: The difference between this embodiment and embodiment 4 is that the prepolymer is epoxy acrylate, the viscosity of the photosensitive resin is 8.1 mPa·s, the viscosity of the slurry is 10.012 Pa·s, the cured thickness of the single-layer print is 0.17 mm, which is 3.4 times the thickness of the print layer of 50 μm, the rectangular holes and the 0.5 mm round holes are clearly visible, the green strength of the print is not less than 97 MPa, the print does not crack after debinding, the strength of the print is not less than 837 MPa, and the sintered density is 6.05 g / cm 3 .

[0048] Embodiment 6: The difference between this embodiment and embodiment 4 is that the monofunctional monomer is methoxyethyl acrylate (MEA), the viscosity of the photosensitive resin is 5.1 mPa·s, the viscosity of the slurry is 6.134 Pa·s, the cured thickness of the single-layer print is 0.17 mm, which is 3.4 times the thickness of the print layer of 50 μm, the rectangular holes and the 0.5 mm round holes are clearly visible, the green strength of the print is not less than 93 MPa, the print does not crack after debinding, the strength of the print is not less than 846 MPa, and the sintered density is 6.04 g / cm 3 .

[0049] Embodiment 7: The difference between this embodiment and embodiment 4 is that the low-functionality monomers are dipropylene glycol diacrylate (DPGDA) and neopentyl glycol diacrylate (NPGDA), the ratio of the two is 1:1, the viscosity of the photosensitive resin is 6.3 mPa·s, the viscosity of the slurry is 8.252 Pa·s, the cured thickness of the single-layer print is 0.18 mm, which is 3.6 times the thickness of the print layer of 50 μm, the rectangular holes and the 0.5 mm round holes are clearly visible, the green strength of the print is not less than 101 MPa, the print does not crack after debinding, the strength of the print is not less than 942 MPa, and the sintered density is 6.07 g / cm 3 .

[0050] Embodiment 8: The difference between this embodiment and embodiment 4 is that the high-functionality monomers are pentaerythritol triacrylate (PETA) and trimethylolpropane trimethacrylate (TMPTMA), the ratio of the two is 1:1, the viscosity of the photosensitive resin is 9.9 mPa·s, the viscosity of the slurry is 12.351 Pa·s, the cured thickness of the single-layer print is 0.20 mm, which is 4.0 times the thickness of the print layer of 50 μm, the rectangular holes and the 0.5 mm round holes are clearly visible, the green strength of the print is not less than 95 MPa, the print does not crack after debinding, the strength of the print is not less than 928 MPa, and the sintered density is 6.05 g / cm 3 .

[0051] Example 9: The difference between this example and Example 4 is that the light absorber is replaced by an inhibitor (N-nitrosophenylhydroxylamine aluminum salt), the viscosity of the photosensitive resin is 9.6 mPa·s, the viscosity of the slurry is 12.017 Pa·s, the cured thickness of the single-layer print is 0.13 mm, which is 2.6 times the thickness of the printed layer of 50 μm, the rectangular holes and 0.2 mm round holes are clearly visible, the green strength of the print is not less than 93 MPa, the print does not crack after debinding, the strength of the print is not less than 904 MPa, and the sintered density is 6.03 g / cm 3 .

[0052] Embodiment 10: The difference between this embodiment and embodiment 4 is that: the light absorber (UV-1577) and the polymerization inhibitor (p-methoxyphenol (MEHQ)) are added at the same time, the ratio of the two is 1:1, the viscosity of the photosensitive resin is 9.1 mPa·s, the viscosity of the slurry is 11.195 Pa·s, the cured thickness of the single-layer print is 0.14 mm, which is 2.8 times the thickness of the print layer of 50 μm, the rectangular holes and the 0.2 mm round holes are clearly visible, the green strength of the print is not less than 87 MPa, the print does not crack after debinding, the strength of the print is not less than 897 MPa, and the sintered density is 6.02 g / cm 3 .

[0053] Embodiment 11: The difference between this embodiment and embodiment 4 is that: The prepolymer is: acrylate; Monofunctional monomer: o-phenylphenoxyethyl acrylate (OPPEA); The low functionality monomer is preferably: 1,6-hexanediol diacrylate (HDDA); The high functionality monomer is preferably: (3-propoxy) glycerol triacrylate (GPTA); The dispersant is: sodium polyacrylate (PAA-Na); The photoinitiator is: 1-hydroxycyclohexyl phenyl ketone; The light absorber is: phenyl salicylate; The plasticizer is dioctyl adipate. The effect is similar to that of Example 4.

[0054] Embodiment 12: The difference between this embodiment and embodiment 4 is that: The prepolymer is a mixture of polyester acrylate and polyurethane acrylate in a mass ratio of 1:1; The monofunctional monomers are: cyclotrimethylolpropane acrylate (CTFA); The low-functionality monomers are: tetraethylene glycol diacrylate (TTEGDA); The high-functionality monomers are: pentaerythritol tetraacrylate (PETTA); Dispersant: ammonium polyacrylate (PAA-NH 4 ) and ammonium citrate (AC) in a 1:1 mass ratio; The photoinitiator is a mixture of 2-hydroxy-2-methyl-p-hydroxyethyl ether phenyl acetone-1 and 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide in a mass ratio of 1:1; The light absorber is a mixture of benzotriazoles (2-(2-hydroxy-5-methylphenyl)benzotriazole and 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-chlorobenzotriazole) in a mass ratio of 1:1; The plasticizer is a mixture of polyethylene glycol and tributyl citrate in a mass ratio of 1:1. The effect is similar to that of Example 4.

[0055] Embodiment 13: The difference between this embodiment and embodiment 4 is that: The monofunctional monomer is a mixture of ethoxyphenol acrylate (PHEA), ethyl methacrylate (EMA) and isobutyl methacrylate (IBMA) in a mass ratio of 1:1:1; The low-functionality monomer is: a mixture of 1,6-hexanediol dimethacrylate (HDDMA) and triethylene glycol dimethacrylate (TEGDMA) in a 1:1 mass ratio; The high-functionality monomers are: dipentaerythritol hexaacrylate (DPHA); The dispersants were: oleic acid (OA); The photoinitiator is: 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide; The light absorber is preferably a mixture of pentaerythritol tetrakis(2-cyano-3,3-diphenylacrylate) and 2-cyano-3,3-diphenylacrylate-2-ethylhexyl ester) in a mass ratio of 1:1; The plasticizer is: cyclohexane 1,2-diisononyl dicarboxylate. The effect is similar to that of Example 4.

[0056] Embodiment 14: The difference between this embodiment and embodiment 4 is that: The dispersants were: Solsperse-28000; The light absorber is: bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (UV-770); The plasticizer is epoxidized soybean oil. The effect is similar to that of Example 4.

[0057] Embodiment 15: The difference between this embodiment and embodiment 4 is that: Dispersant: DISPERBYK-161; The light absorber is: poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate (UV-622); The plasticizer is dioctyl sebacate. The effect is similar to that of Example 4.

[0058] Embodiment 16: The difference between this embodiment and embodiment 10 is that: The inhibitor is: 2,6-di-tert-butyl-p-cresol (MTBHQ); The material of the ceramic powder is alumina.

[0059] Embodiment 17: The difference between this embodiment and embodiment 4 is that: In the ceramic slurry, ceramic powder accounts for 70wt% and photosensitive resin accounts for 30wt%.

[0060] The material of the ceramic powder is magnesium oxide.

[0061] Embodiment 18: The difference between this embodiment and embodiment 4 is that: In the ceramic slurry, ceramic powder accounts for 90wt% and photosensitive resin accounts for 10wt%.

[0062] The material of the ceramic powder is silicon nitride.

[0063] Embodiment 19: The difference between this embodiment and embodiment 4 is that: The material of the ceramic powder is lithium disilicate.

[0064] The performance test results of Examples 1-10 are shown in Figure 1 . It can be seen from Examples 1 to 4 that the prepolymer can effectively reduce the curing shrinkage rate during the photocuring process, improve the dimensional accuracy of the molded parts and reduce the internal stress, which helps to reduce the volume shrinkage during the curing process; from the comparison of Examples 3, 4, 7 and 8, it can be seen that by applying the prepolymer and a variety of monomers with different functionalities to the ceramic printing slurry at the same time, a strong spatial cross-linked network structure can be formed, and a difference in curing time is formed, so that the green and sintered density and strength of the printed parts have excellent performance; from the comparison of Examples 3 and 4, it can be seen that the addition of plasticizer can reduce the residual stress generated by printing and curing, and even if the debinding and sintering temperature rise rates are increased, cracking will not occur.

[0065] Comparative Example 1: The prepolymer (polyurethane acrylate) in Example 4 was replaced with the spirocarbonate expansion monomer (3,9-diethyl-3,9-dihydroxymethyl-1,5,7,11-tetraoxaspiroundecane) in CN106007671B, and other process conditions remained unchanged to explore its effect on the shrinkage deformation and dimensional accuracy of the printed parts: 0.5mm round holes were visible, but single-layer printing was severely warped ( Figure 2 ).

[0066] Comparative Example 2: In Example 4, no plasticizer was added, and other process conditions remained unchanged. The effect of the plasticizer on the viscosity of the photosensitive resin and the ceramic slurry was investigated, and whether cracking occurred during debinding sintering was investigated: the viscosity of the photosensitive resin was 19.1 mPa·s, the viscosity of the slurry was 18.426 Pa·s, and cracking occurred during debinding sintering ( Figure 3 ), indicating that the increase of plasticizer can reduce the viscosity of photosensitive resin and slurry, and inhibit the occurrence of debinding sintering cracking.

[0067] Comparative Example 3: The high-functionality monomer (ethoxylated pentaerythritol tetraacrylate (PPTTA)) in Example 4 was replaced with a crosslinker monomer (ethoxylated bisphenol A acrylate) with a rigid structure in CN108249930B, and other process conditions remained unchanged to explore its effect on the Z-direction cured thickness: the single-layer cured thickness was 0.18 mm, which was 3.6 times the printed layer thickness of 50 μm. Although the single-layer cured thickness of Comparative Example 3 was close to that of Example 4, the toughness of the printed part decreased.

[0068] Comparative Example 4: In Example 4, no prepolymer was added, and other process conditions remained unchanged to explore its effect on green density: the green strength of the printed part decreased from no less than 94 MPa to no less than 76 MPa, and the shrinkage deformation of the single-layer printed part was aggravated ( Figure 4 ).

[0069] Attached Figure 5 The actual measurement results of the single-layer curing accuracy and curing depth of ceramic printing slurry in Example 4 are shown. The printing layer thickness is set to 50μm. The overexposure and curing accuracy of the printing are judged by observing whether the rectangular holes and circular holes of different diameters can be successfully printed (the diameters of the 6 circular holes from top to bottom are 2mm, 1.5mm, 1mm, 0.75mm, 0.5mm and 0.2mm respectively, and the length and width of the rectangular hole are 10mm and 0.5mm respectively). Figure 5It can be seen that the curing depth of the printed part can reach 2~3 times the thickness of the printed layer (the curing depths of the printed parts from left to right are 0.16mm, 0.15mm, and 0.14mm respectively), indicating that the ceramic slurry has good light curing ability; the 0.5mm hole on the left side of each printed part and the 0.5mm wide rectangular hole in the upper right corner can also be printed well, indicating that the ceramic slurry has high printing accuracy and the overexposure is not obvious.

[0070] Attached Figure 6 The vertical printing diagram of the printout of the solution of Example 4 (printout height: contact dimension with the printing platform>1:1), the printout thickness is 0.1~0.2mm. Figure 6 It can be seen that the green body of the printed part has good strength, without collapse or deformation, and can be printed successfully even if the thickness of the printed part is very thin.

[0071] Attached Figure 7 , Attachment Figure 8 and attached Fig. 9 They are respectively the appearance diagram, inner surface accuracy measurement diagram and edge accuracy measurement diagram of the printed sintered part (3 unit bridges) in Example 4. Figure 7 It can be seen that the bridge of the printed part (3 units) has a good smooth surface after sintering, and no cracking occurs. The 3D deviation of the printed sintered part was analyzed by using reverse engineering software (Geomagic Studio 2013) to detect the distance between the scan data and the CAD data in each selected area, and to generate a color difference map. The root mean square (RMS) was calculated according to the following formula: Among them, X 1,i represents the measurement point i in the CAD data, X 2,i represents the measurement point i in the scan data, and n is the total number of measurement points. RMS indicates how far the deviation between two different data sets is from zero. It is a general method to evaluate the error average by directly comparing two data sets in the same coordinate system. A low RMS value indicates that the fabricated restoration has high-dimensional authenticity. After calculation, the average deviation value (RMS) of the inner surface of the 3D printed 3-unit bridge is 0.0977mm, which meets the clinical requirement of ≤300 µm; the average deviation value (RMS) of the crown edge suitability is 0.0748mm, which meets the clinical requirement of ≤120 µm, indicating that the print has good dimensional accuracy and the shrinkage rate of the print is controllable.

[0072] The above-described embodiment is only a preferred solution of the present invention and does not limit the present invention in any form. There are other variations and modifications without exceeding the technical solution described in the claims.

Claims

1. A photosensitive resin for photocurable additive manufacturing, characterized in that: The composition is as follows by weight: 7 to 50 parts of prepolymer, 3 to 100 parts of monofunctional monomer, 30 to 95 parts of low-functional monomer, 0.5 to 50 parts of high-functional monomer, 0.4 to 10 parts of dispersant, 0.01 to 5 parts of photoinitiator, 2 to 20 parts of plasticizer, 0.01 to 0.11 parts of light absorber and / or 0.01 to 1.5 parts of inhibitor; wherein the prepolymer accounts for more than 15% of the total weight of the photosensitive resin.

2. The photosensitive resin according to claim 1, characterized in that: The prepolymer is selected from one or more of acrylate, polyester acrylate, polyurethane acrylate and epoxy acrylate.

3. The photosensitive resin according to claim 1, characterized in that: The monofunctional monomer is selected from one or more of o-phenylphenoxyethyl acrylate, cyclotrimethylolpropane acrylate, ethoxyphenol acrylate, isooctyl acrylate, methoxyethyl acrylate, ethyl methacrylate, and isobutyl methacrylate.

4. The photosensitive resin according to claim 1, characterized in that: The low-functionality monomer is selected from one or more of dipropylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, neopentyl glycol diacrylate, tetraethylene glycol diacrylate, 1,6-hexanediol dimethacrylate, and triethylene glycol dimethacrylate; The high-functionality monomer is selected from one or more of pentaerythritol triacrylate, (3-propoxy)propylene glycol triacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, and trimethylolpropane trimethacrylate.

5. The photosensitive resin according to claim 1, characterized in that: The dispersant is selected from one or more of sodium polyacrylate, ammonium polyacrylate, ammonium citrate, oleic acid, super dispersant, copolymer dispersant containing acidic groups, block copolymer dispersant containing pigment affinity groups, and structured acrylic copolymer.

6. The photosensitive resin according to claim 1, characterized in that: The photoinitiator is selected from one or more of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-phenyl acetone-1, 2-hydroxy-2-methyl-p-hydroxyethyl ether phenyl acetone-1, and 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide.

7. The photosensitive resin according to claim 1, characterized in that: The plasticizer is selected from one or more of fatty acid esters, polyethylene glycol, polypropylene glycol, tributyl citrate, cyclohexane 1,2-diisononyl dicarboxylate and epoxidized soybean oil.

8. The photosensitive resin according to claim 1, characterized in that: The light absorber is selected from one or more of phenyl salicylate, phenyl o-hydroxybenzoate, benzophenone-2, 2-hydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4,4-dimethoxybenzophenone, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-chlorobenzotriazole, pentaerythritol tetrakis(2-cyano-3,3-diphenylacrylate), 2-ethylhexyl 2-cyano-3,3-diphenylacrylate, UV-1577, UV-1164, UV-400, triazine-5, UV-770, and UV-622; The polymerization inhibitor is selected from one or more of p-methoxyphenol, N-nitrosophenylhydroxylamine aluminum salt, hydroquinone, and 2,6-di-tert-butyl-p-cresol.

9. A ceramic slurry for photocuring additive manufacturing, characterized in that: In terms of weight percentage, the ceramic powder accounts for 70-90wt%, and the photosensitive resin according to claim 1 accounts for 10-30wt%.

10. The ceramic slurry according to claim 9, characterized in that: The material of the ceramic powder is selected from one or more of aluminum oxide, zirconium oxide, magnesium oxide, silicon nitride and lithium disilicate.

Images