Photosensitive water-washing resin for 3D printing and preparation method thereof

Abstract

The present application relates to the technical field of water washing resin, and particularly relates to a photosensitive water washing resin for 3D printing and a preparation method thereof. First, isophorone diisocyanate, polytetrahydrofuran and hydrophilic dimethylol propionic acid are used to form a prepolymer, then a photosensitive monomer trimethylolpropane monoallyl ether is embedded on the side chain of the prepolymer, chain extension is performed by using p-benzoquinone dioxime and bis-selenium chain extenders, and end capping is performed by using multifunctional POSS. First, graphite phase carbon nitride containing nitrogen defects is prepared, then a magnetic iron composite graphite phase carbon nitride is obtained by using a chemical co-precipitation method, the magnetic iron composite graphite phase carbon nitride is mercapto-functionalized by using sodium dimethyl dithiocarbamate, and multifunctional POSS and polyethylene glycol diacrylate are introduced on the surface of the graphite phase carbon nitride, so that the water washability of the photosensitive water washing resin is further improved, and the photosensitive water washing resin after solidification has excellent anti-aging property and wear resistance.

Description

Technical Field

[0001] This invention relates to the field of water-washing resin technology, specifically a photosensitive water-washing resin for 3D printing and its preparation method. Background Technology

[0002] With societal development, precision and lightweight 3D printing are widely used across various industries. Photosensitive resin is a crucial raw material affecting the speed of 3D printing and product formation. Existing common photosensitive resins are primarily oil-based, generally requiring volatile organic solvents such as isopropanol or acetone to remove excess uncured liquid, resulting in significant environmental pollution. Therefore, more environmentally friendly photosensitive water-washable resins for 3D printing are gradually attracting the attention of researchers.

[0003] Photosensitive water-washable resins used in 3D printing are mainly water-based polyurethane or water-based polyurethane acrylate. Although they are green and environmentally friendly, they have a large shrinkage rate after photocuring, resulting in poor product dimensional accuracy. In addition, when exposed to air for a long time, they will age and be damaged due to prolonged exposure to ultraviolet light, which will significantly reduce the product's lifespan. Summary of the Invention

[0004] The purpose of this invention is to provide a photosensitive water-washable resin for 3D printing and its preparation method, so as to solve the problems in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A photosensitive water-washable resin for 3D printing, comprising, by weight, 47-63 parts modified waterborne polyurethane, 1-3 parts photoinitiator, 18-25 parts diluent, and 1-5 parts modified graphitic carbon nitride.

[0006] Furthermore, the photoinitiator is a TPO-type photoinitiator.

[0007] Furthermore, the diluent is one or more of the following: acrylomorpholine, hydroxyethyl methacrylate, hydroxyethyl acrylate, glyceryl triacrylate, and polyethylene glycol diacrylate.

[0008] Furthermore, the preparation of modified graphitic carbon nitride includes the following steps: 1) Melamine, potassium hydroxide and deionized water are mixed, dried, heated to 550℃ and kept at that temperature for 4 hours, cooled, ground, washed and dried to obtain graphitic carbon nitride containing nitrogen defects. 2) Mix nitrogen-deficient graphitic carbon nitride with deionized water, add ferric sulfate heptahydrate and sodium borohydride at 38-42℃, keep warm for 1-2 hours, wash until pH is neutral, keep warm at 78-82℃ for 22-24 hours to obtain composite graphitic carbon nitride. 3) Mix composite graphitic carbon nitride, ethanol, deionized water, and sodium dimethyl dithiocarbamate, stir at 58-62℃ for 1-2 hours, wash until pH is neutral, filter, and dry to obtain mercapto-graphitic carbon nitride. 4) Under a nitrogen atmosphere, mercapto-based graphitic carbon nitride and anhydrous tetrahydrofuran were mixed and added to polyethylene glycol diacrylate, multifunctional POSS, 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone, and anhydrous tetrahydrofuran. The mixture was then treated with ultraviolet light, rotary evaporated, ethanol was added, and the mixture was centrifuged, washed, and dried to obtain modified graphitic carbon nitride.

[0009] Furthermore, the mass ratio of mercaptographite carbon nitride, polyethylene glycol diacrylate, and multifunctional POSS is 1.6:1.2:1.4.

[0010] Furthermore, the preparation of modified waterborne polyurethane includes the following steps: S1: Mix selenocysteine ​​hydrochloride and deionized water, add potassium hydroxide and stir for 1-2 hours, extract with dichloromethane 3-5 times, add anhydrous magnesium sulfate and stir for 10-12 hours, filter and rotary evaporate to obtain diselenium chain extender. S2: Mix isophorone diisocyanate, polytetrahydrofuran, dimethylolpropionic acid and dibutyltin dilaurate, add a mixture of tetrahydrofuran, trimethylolpropane monoallyl ether and p-benzoquinone dioxime, heat to 68-72℃ and keep warm for 2-3 hours, add a mixture of diselenyl chain extender and tetrahydrofuran, continue to keep warm for 2-3 hours, add a mixture of tetrahydrofuran, hydroquinone and multifunctional POSS, continue to keep warm for 4-5 hours, cool to 48-52℃, add triethylamine and keep warm for 1-2 hours, add deionized water and ethylenediamine, emulsify for 20-30 minutes, evaporate under reduced pressure to obtain modified waterborne polyurethane.

[0011] Furthermore, the working conditions for ultraviolet light treatment are: irradiation with 365nm ultraviolet light for 2-3 hours.

[0012] Furthermore, in the preparation of modified waterborne polyurethane, the mass ratio of p-benzoquinone dioxime, diselenole chain extender, and multifunctional POSS is 1:0.4:1.1.

[0013] Furthermore, the preparation of a multifunctional POSS includes the following steps: (1) Under a nitrogen atmosphere, D,L-lactide, hydroxyethyl methacrylate and stannous isooctanoate are mixed, heated to 108-112°C and kept at that temperature for 2-3 hours, chloroform is added, and the mixture is washed 3-5 times with hydrochloric acid aqueous solution and ultrapure water, then evaporated and dried to obtain an intermediate preparation. (2) Under a nitrogen atmosphere, the intermediate preparation and toluene are mixed, and a mixture of γ-glycidyl ether oxysilyl sesquioxane and toluene is added. The mixture is then transferred to a 0°C ice-water bath and kept warm for 15-20 min. Boron trifluoride ethyl ether is added, and the mixture is allowed to stand for 30-40 min. The temperature is then raised to 18-25°C and kept warm for 46-48 h. The mixture is then rotary evaporated under vacuum, and chloroform is added. The mixture is washed 3-5 times with sodium bicarbonate and ultrapure water, separated into layers, filtered, and rotary evaporated under vacuum. Anhydrous ethanol is added, and the mixture is centrifuged and washed to obtain the multifunctional POSS.

[0014] Furthermore, a method for preparing a photosensitive water-washable resin for 3D printing includes the following steps: under a nitrogen atmosphere, a photoinitiator, modified waterborne polyurethane, a diluent, and modified graphitic carbon nitride are ultrasonically mixed to obtain a photosensitive water-washable resin for 3D printing.

[0015] The beneficial effects of this invention are: This invention provides a photosensitive water-washable resin for 3D printing and its preparation method. The prepared photosensitive water-washable resin has excellent self-healing properties and anti-aging and wear resistance after photocuring. When applied to 3D printing, the product has high dimensional accuracy and good durability, meeting the industry requirements.

[0016] To address the issue of high shrinkage rates after photocuring of existing photosensitive water-washable resins, this invention first forms a prepolymer using isophorone diisocyanate, polytetrahydrofuran, and hydrophilic dimethylolpropionic acid. Then, the photosensitive monomer trimethylolpropane monoallyl ether is embedded into the side chain of the prepolymer. Compared to introducing double bonds at the end groups, this provides more photocrosslinking sites, resulting in a denser network after curing. p-Benzoquinone dioxime and diselenoside chain extenders are used for chain extension. p-Benzoquinone dioxime is introduced into the main chain in a copolymeric form, extending the conjugated structure within the system and thus improving its light absorption capacity, while also acting as a photothermal conversion agent. Compared to disulfide bonds, diselenoside bonds have a more dynamic... With enhanced reversibility, the introduction of diselenium chain extender enables the cured 3D printing material to rapidly self-heal under mild conditions. Multifunctional POSS is used for end-capping, where multifunctional POSS is a macromonomer containing epoxy groups, hydroxyl groups, and unsaturated double bonds at the end groups, prepared by reacting mixed lactide with hydroxyl ester under a catalyst. Then, epoxy cage-type POSS is grafted using the reaction of hydroxyl groups with epoxy. The introduction of multifunctional POSS further enhances the complexity of the crosslinking network, thereby improving the mechanical strength, anti-aging properties, and wear resistance of the cured photosensitive washable resin.

[0017] This invention uses graphitic carbon nitride as a filler to improve the mechanical properties of photosensitive water-washable resins. To enhance the dispersion uniformity and visible light response of the graphitic carbon nitride in the water-washable resin, the precursor melamine is first treated with potassium hydroxide to prepare nitrogen-defective graphitic carbon nitride. Potassium hydroxide treatment increases the interlayer spacing of the carbon nitride, which is beneficial for photocatalytic performance. Then, a chemical co-precipitation method is used to obtain magnetic iron composite graphitic carbon nitride, which is then thiolized with sodium dimethyl dithiocarbamate. The magnetic iron... The introduction of thiol as a bridge, along with the introduction of magnetic iron, enables the water-washed resin to align in an orderly manner under the influence of an external magnetic field. This further enhances the photo-induced self-healing ability of the water-washed resin, while also improving its strength and toughness, thereby effectively increasing the service life of 3D printed products. Then, using the thiol-olefin click reaction, multifunctional POSS and polyethylene glycol diacrylate are introduced onto the surface of graphitic carbon nitride, further improving the washability of the photosensitive water-washed resin and giving the cured photosensitive water-washed resin excellent anti-aging and wear resistance. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0020] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0021] Example 1: A method for preparing a photosensitive water-washable resin for 3D printing, comprising the following steps: under a nitrogen atmosphere, a photoinitiator, modified waterborne polyurethane, a diluent, and modified graphitic carbon nitride are ultrasonically mixed to obtain a photosensitive water-washable resin for 3D printing. The composition of the photosensitive water-washable resin by mass parts is: 47 parts modified waterborne polyurethane, 1 part photoinitiator, 18 parts diluent, and 1 part modified graphitic carbon nitride. The photoinitiator is a TPO-type photoinitiator; the diluent is acrylomorpholine; The preparation of modified graphitic carbon nitride includes the following steps: 1) Mix 7.5g melamine, 0.5g potassium hydroxide and 15mL deionized water, dry, heat to 550℃ and keep warm for 4h, cool, grind, wash and dry to obtain graphitic carbon nitride containing nitrogen defects; 2) Mix 5g of graphitic carbon nitride containing nitrogen defects with 125mL of deionized water, add 50mL of 0.2mol / L ferric sulfate heptahydrate and 75mL of 40g / L sodium borohydride at 38℃, keep warm for 1h, wash until pH is neutral, keep warm at 78℃ for 24h to obtain composite graphitic carbon nitride. 3) Mix 2.5g of composite graphitic carbon nitride, 100mL of ethanol, 50mL of deionized water and 2.5g of sodium dimethyl dithiocarbamate, stir at 58℃ for 2h, wash until pH is neutral, filter and dry to obtain mercapto-graphitic carbon nitride. 4) Under a nitrogen atmosphere, 1.6 g of mercapto-based graphitic carbon nitride and 10 mL of anhydrous tetrahydrofuran were mixed and added to 1.2 g of polyethylene glycol diacrylate, 1.4 g of multifunctional POSS, 0.04 g of 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone and 10 mL of anhydrous tetrahydrofuran. The mixture was treated with ultraviolet light, rotary evaporated, and 200 mL of ethanol was added. The mixture was then centrifuged, washed, and dried to obtain modified graphitic carbon nitride. The working conditions for ultraviolet light treatment are: irradiation with 365nm ultraviolet light for 2 hours; The preparation of modified waterborne polyurethane includes the following steps: S1: Mix 5g selenocysteine ​​hydrochloride and 25mL deionized water, add 3g potassium hydroxide and stir for 1h, extract three times with 100mL dichloromethane, add anhydrous magnesium sulfate, stir for 10h, filter and rotary evaporate to obtain diselenium chain extender. S2: Mix 5.3g isophorone diisocyanate, 10g polytetrahydrofuran, 0.8g dimethylolpropionic acid and 2 drops dibutyltin dilaurate, add 8mL tetrahydrofuran, 7.4g trimethylolpropane monoallyl ether and 2g p-benzoquinone dioxime, heat to 68℃ and keep warm for 3h, add 0.8g diselenide chain extender and 3mL tetrahydrofuran, continue to keep warm for 2h, add 5mL tetrahydrofuran, 0.5g hydroquinone and 2.2g multifunctional POSS, continue to keep warm for 4h, cool to 48℃, add 0.3g triethylamine and keep warm for 2h, add 50mL deionized water and 0.1g ethylenediamine, emulsify for 20min, evaporate under reduced pressure to obtain modified waterborne polyurethane; The preparation of a multifunctional POSS includes the following steps: (1) Under a nitrogen atmosphere, 10g of D,L-lactide, 4.5g of hydroxyethyl methacrylate and 64μL of stannous isooctanoate were mixed, heated to 108°C and kept warm for 3h, 50mL of chloroform was added, and the mixture was washed three times with 1mol / L hydrochloric acid aqueous solution and ultrapure water, then rotary evaporated and dried to obtain the intermediate preparation. (2) Under a nitrogen atmosphere, 7.5g of intermediate preparation and 40mL of toluene were mixed, and a mixture of 1g of γ-glycidyl oxysilyl sesquioxane and 13mL of toluene was added. The mixture was transferred to an ice-water bath at 0℃ and kept warm for 15min. 105μL of boron trifluoride ether was added, and the mixture was allowed to stand for 30min. The temperature was raised to 18℃ and kept warm for 48h. The mixture was rotary evaporated under vacuum, and 50mL of chloroform was added. The mixture was washed three times with sodium bicarbonate and ultrapure water with a mass concentration of 2%. The mixture was separated into layers, filtered, and rotary evaporated under vacuum. 50mL of anhydrous ethanol was added, and the mixture was centrifuged and washed to obtain multifunctional POSS.

[0022] Example 2: A method for preparing a photosensitive water-washable resin for 3D printing, comprising the following steps: under a nitrogen atmosphere, a photoinitiator, modified waterborne polyurethane, a diluent, and modified graphitic carbon nitride are ultrasonically mixed to obtain a photosensitive water-washable resin for 3D printing. The composition of the photosensitive water-washable resin by mass parts is: 53 parts modified waterborne polyurethane, 2 parts photoinitiator, 21 parts diluent, and 3 parts modified graphitic carbon nitride. The photoinitiator is a TPO-type photoinitiator; the diluent is acrylomorpholine; The preparation of modified graphitic carbon nitride includes the following steps: 1) Mix 7.5g melamine, 0.5g potassium hydroxide and 15mL deionized water, dry, heat to 550℃ and keep warm for 4h, cool, grind, wash and dry to obtain graphitic carbon nitride containing nitrogen defects; 2) Mix 5g of graphitic carbon nitride containing nitrogen defects with 125mL of deionized water, add 50mL of 0.2mol / L ferric sulfate heptahydrate and 75mL of 40g / L sodium borohydride at 40℃, keep warm for 1.5h, wash until pH is neutral, keep warm at 80℃ for 23h to obtain composite graphitic carbon nitride. 3) Mix 2.5g of composite graphitic carbon nitride, 100mL of ethanol, 50mL of deionized water and 2.5g of sodium dimethyl dithiocarbamate, stir at 60℃ for 1.5h, wash until pH is neutral, filter and dry to obtain mercapto-graphitic carbon nitride. 4) Under a nitrogen atmosphere, 1.6 g of mercapto-based graphitic carbon nitride and 10 mL of anhydrous tetrahydrofuran were mixed and added to 1.2 g of polyethylene glycol diacrylate, 1.4 g of multifunctional POSS, 0.04 g of 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone and 10 mL of anhydrous tetrahydrofuran. The mixture was treated with ultraviolet light, rotary evaporated, and 200 mL of ethanol was added. The mixture was then centrifuged, washed, and dried to obtain modified graphitic carbon nitride. The working conditions for ultraviolet light treatment are: irradiation with 365nm ultraviolet light for 2.5 hours; The preparation of modified waterborne polyurethane includes the following steps: S1: Mix 5g selenocysteine ​​hydrochloride and 25mL deionized water, add 3g potassium hydroxide and stir for 1.5h, extract 4 times with 100mL dichloromethane, add anhydrous magnesium sulfate, stir for 11h, filter and rotary evaporate to obtain diselenium chain extender. S2: Mix 5.3g isophorone diisocyanate, 10g polytetrahydrofuran, 0.8g dimethylolpropionic acid and 2 drops dibutyltin dilaurate, add 8mL tetrahydrofuran, 7.4g trimethylolpropane monoallyl ether and 2g p-benzoquinone dioxime, heat to 70℃ and keep warm for 2.5h, add 0.8g diselenide chain extender and 3mL tetrahydrofuran, continue to keep warm for 2.5h, add 5mL tetrahydrofuran, 0.5g hydroquinone and 2.2g multifunctional POSS, continue to keep warm for 4.5h, cool to 50℃, add 0.3g triethylamine and keep warm for 1.5h, add 50mL deionized water and 0.1g ethylenediamine, emulsify for 25min, evaporate under reduced pressure to obtain modified waterborne polyurethane; The preparation of a multifunctional POSS includes the following steps: (1) Under a nitrogen atmosphere, 10g of D,L-lactide, 4.5g of hydroxyethyl methacrylate and 64μL of stannous isooctanoate were mixed, heated to 110°C and kept at that temperature for 2.5h, 50mL of chloroform was added, and the mixture was washed 4 times with 1mol / L hydrochloric acid aqueous solution and ultrapure water, then rotary evaporated and dried to obtain the intermediate preparation. (2) Under a nitrogen atmosphere, 7.5g of intermediate preparation and 40mL of toluene were mixed, and a mixture of 1g of γ-glycidyl oxysilyl sesquioxane and 13mL of toluene was added. The mixture was transferred to an ice-water bath at 0℃ and kept warm for 18min. 105μL of boron trifluoride ether was added, and the mixture was allowed to stand for 35min. The temperature was raised to 22℃ and kept warm for 47h. The mixture was rotary evaporated under vacuum, and 50mL of chloroform was added. The mixture was washed 4 times with sodium bicarbonate and ultrapure water with a mass concentration of 2%. The mixture was separated into layers, filtered, rotary evaporated under vacuum, and 50mL of anhydrous ethanol was added. The mixture was centrifuged and washed to obtain multifunctional POSS.

[0023] Example 3: A method for preparing a photosensitive water-washable resin for 3D printing, comprising the following steps: under a nitrogen atmosphere, a photoinitiator, modified waterborne polyurethane, a diluent, and modified graphitic carbon nitride are ultrasonically mixed to obtain a photosensitive water-washable resin for 3D printing. The composition of the photosensitive water-washable resin by mass parts is: 63 parts modified waterborne polyurethane, 3 parts photoinitiator, 25 parts diluent, and 5 parts modified graphitic carbon nitride. The photoinitiator is a TPO-type photoinitiator; the diluent is acrylomorpholine; The preparation of modified graphitic carbon nitride includes the following steps: 1) Mix 7.5g melamine, 0.5g potassium hydroxide and 15mL deionized water, dry, heat to 550℃ and keep warm for 4h, cool, grind, wash and dry to obtain graphitic carbon nitride containing nitrogen defects; 2) Mix 5g of graphitic carbon nitride containing nitrogen defects with 125mL of deionized water, add 50mL of 0.2mol / L ferric sulfate heptahydrate and 75mL of 40g / L sodium borohydride at 42℃, keep warm for 2h, wash until pH is neutral, keep warm at 82℃ for 22h to obtain composite graphitic carbon nitride. 3) Mix 2.5g of composite graphitic carbon nitride, 100mL of ethanol, 50mL of deionized water and 2.5g of sodium dimethyl dithiocarbamate, stir at 62℃ for 1h, wash until pH is neutral, filter and dry to obtain mercapto-graphitic carbon nitride. 4) Under a nitrogen atmosphere, 1.6 g of mercapto-based graphitic carbon nitride and 10 mL of anhydrous tetrahydrofuran were mixed and added to 1.2 g of polyethylene glycol diacrylate, 1.4 g of multifunctional POSS, 0.04 g of 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone and 10 mL of anhydrous tetrahydrofuran. The mixture was treated with ultraviolet light, rotary evaporated, and 200 mL of ethanol was added. The mixture was then centrifuged, washed, and dried to obtain modified graphitic carbon nitride. The working conditions for ultraviolet light treatment are: irradiation with 365nm ultraviolet light for 3 hours; The preparation of modified waterborne polyurethane includes the following steps: S1: Mix 5g selenocysteine ​​hydrochloride and 25mL deionized water, add 3g potassium hydroxide and stir for 2h, extract 5 times with 100mL dichloromethane, add anhydrous magnesium sulfate, stir for 12h, filter and rotary evaporate to obtain diselenium chain extender. S2: Mix 5.3g isophorone diisocyanate, 10g polytetrahydrofuran, 0.8g dimethylolpropionic acid and 2 drops dibutyltin dilaurate, add 8mL tetrahydrofuran, 7.4g trimethylolpropane monoallyl ether and 2g p-benzoquinone dioxime, heat to 72℃ and keep warm for 2h, add 0.8g diselenide chain extender and 3mL tetrahydrofuran, continue to keep warm for 3h, add 5mL tetrahydrofuran, 0.5g hydroquinone and 2.2g multifunctional POSS, continue to keep warm for 5h, cool to 52℃, add 0.3g triethylamine and keep warm for 1h, add 50mL deionized water and 0.1g ethylenediamine, emulsify for 30min, evaporate under reduced pressure to obtain modified waterborne polyurethane; The preparation of a multifunctional POSS includes the following steps: (1) Under a nitrogen atmosphere, 10g of D,L-lactide, 4.5g of hydroxyethyl methacrylate and 64μL of stannous isooctanoate were mixed, heated to 112°C and kept warm for 2h, 50mL of chloroform was added, and the mixture was washed 5 times with 1mol / L hydrochloric acid aqueous solution and ultrapure water, then rotary evaporated and dried to obtain the intermediate preparation. (2) Under a nitrogen atmosphere, 7.5g of intermediate preparation and 40mL of toluene were mixed, and a mixture of 1g of γ-glycidyl oxysilyl sesquioxane and 13mL of toluene was added. The mixture was transferred to an ice-water bath at 0℃ and kept warm for 20min. 105μL of boron trifluoride ether was added, and the mixture was allowed to stand for 40min. The temperature was raised to 25℃ and kept warm for 46h. The mixture was rotary evaporated under vacuum, and 50mL of chloroform was added. The mixture was washed 5 times with sodium bicarbonate and ultrapure water with a mass concentration of 2%. The mixture was separated into layers, filtered, rotary evaporated under vacuum, and 50mL of anhydrous ethanol was added. The mixture was centrifuged and washed to obtain multifunctional POSS.

[0024] Comparative Example 1: Using Example 3 as the control group, the modified graphite phase carbon nitride was replaced with composite graphite phase carbon nitride, and other processes were normal.

[0025] Comparative Example 2: Using Example 3 as the control group, the bis(2-hydroxyethyl) disulfide was used to replace the bisselenium chain extender, and the other processes were normal.

[0026] Comparative Example 3: Using Example 3 as the control group, no multifunctional POSS was prepared, and other processes were normal.

[0027] Source of raw materials used: D,L-lactide JS3902: Hubei Jusheng Technology Co., Ltd.; TPO photoinitiator (2,4,6-trimethylbenzoyl-diphenylphosphine oxide) T107643, acrylmorpholine A151729, melamine M108433, ferric sulfate heptahydrate I434044, sodium dimethyl dithiocarbamate S106280, tetrahydrofuran T431419, 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone M130040, selenocysteine ​​hydrochloride D303521, isophorone diisocyanate I109582, polytetrahydrofuran P118599, dibutyltin dilaurate D 100274, p-benzoquinone dioxime P476965, trimethylolpropane monoallyl ether T487225, polyethylene glycol diacrylate P109708, dimethylolpropionic acid B104539, triethylamine T103285, ethylenediamine E112132, hydroquinone H108945, hydroxyethyl methacrylate H140643, stannous isooctanoate T100108, γ-glycidyl etheroxysilyl sesquioxane G140436, boron trifluoride ethyl ether B431395: Aladdin reagent; potassium hydroxide, sodium borohydride, ethanol, dichloromethane, anhydrous magnesium sulfate, chloroform, hydrochloric acid, toluene, sodium bicarbonate, analytical grade: Sinopharm Group reagent.

[0028] Performance testing: The water-washing resins prepared in the examples and comparative examples were cured, and the test results of the cured products are shown in Table 1. The curing conditions are as follows: the finished product is obtained after photocuring under an external magnetic field; the external magnetic field strength is 45mT and the time is 8s; the working conditions for photocuring are: irradiation with light of wavelength 365nm for 30s. Mechanical property testing: The sample was cut into strips 35mm long, 4mm wide, and 2mm thick. The mechanical properties of the sample were tested using a universal testing machine at a tensile rate of 50mm / min. Self-healing performance testing: A sample 35mm long, 35mm wide, and 2mm thick was cut, and a 15mm long, 2µm wide, and 1mm deep scratch was made on it. It was then placed under a 150W infrared lamp at a distance of 20cm for 6 hours. The tensile properties were compared with those of the original sample to evaluate its self-healing ability. Self-healing rate = σ 修复后抗拉强度 / σ 原始抗拉强度×100%; Abrasion resistance: Cut a sample 100mm long, 20mm wide, and 2mm thick. Use 800-grit sandpaper to place the sample on the surface, and then place a 50g weight on top to press it down. Move the sample horizontally on the sandpaper at a speed of 2cm / min. A back-and-forth movement of 4cm constitutes one cycle. Repeat 10 cycles. Compare with the sample before friction. A change rate of tensile strength less than 2% is acceptable (including 2%), otherwise it is unacceptable; Aging resistance: Cut a sample 100mm long, 20mm wide, and 2mm thick. Irradiate it under a 365nm ultraviolet lamp at a distance of 20cm for 12 hours. Compare with the sample before irradiation. A change rate of tensile strength less than 5% is acceptable (including 5%), otherwise it is unacceptable. Table 1 This invention provides a photosensitive water-washable resin for 3D printing and its preparation method. As shown in Table 1 above, the photosensitive water-washable resin prepared in Examples 1-3 of this application has good self-healing properties under light and anti-aging and wear resistance after being subjected to mechanical damage. When applied to 3D printing, the product has high dimensional accuracy and good durability, meeting industry requirements.

[0029] Comparing Example 3 with Comparative Examples 1 and 3, this invention uses graphitic carbon nitride as a filler to improve the mechanical strength of photosensitive water-washing resin. To improve the dispersion uniformity and visible light response of graphitic carbon nitride in the water-washing resin, the precursor melamine was first treated with potassium hydroxide to prepare graphitic carbon nitride containing nitrogen defects. Potassium hydroxide treatment can increase the interlayer spacing of carbon nitride, which is beneficial to the expression of photocatalytic performance. Then, magnetic iron composite graphitic carbon nitride was obtained by chemical coprecipitation, and sodium dimethyl dithiocarbamate was used to further refine it. Thiolization is achieved by introducing magnetic iron as a bridge to thiolate the resin. Simultaneously, the introduction of magnetic iron allows the water-washable resin to align in an orderly manner under an applied magnetic field, further enhancing its photoinduced self-healing ability, strength, and toughness, thus effectively extending the lifespan of 3D printed products. Then, using a thiol-olefin click reaction, multifunctional POSS and polyethylene glycol diacrylate are introduced onto the surface of graphitic carbon nitride, further improving the washability of the photosensitive water-washable resin and giving the cured resin excellent anti-aging and wear resistance.

[0030] Comparing Example 3 with Comparative Examples 2 and 3, to address the issue of high shrinkage after photocuring of existing photosensitive water-washable resins, this invention first forms a prepolymer using isophorone diisocyanate, polytetrahydrofuran, and hydrophilic dimethylolpropionic acid. Then, the photosensitive monomer trimethylolpropane monoallyl ether is embedded into the side chain of the prepolymer. Compared to introducing double bonds at the end groups, this provides more photocrosslinking sites, resulting in a denser network after curing. p-benzoquinone dioxime and diselenoside chain extenders are used for chain extension. The p-benzoquinone dioxime is introduced into the main chain in a copolymeric form, extending the conjugated structure within the system and thus improving its light absorption capacity, while also acting as a photothermal conversion agent. Compared to disulfide bonds... The diselenium bond exhibits stronger dynamic reversibility, thus the introduction of diselenium chain extender enables the cured 3D printing material to rapidly self-heal under mild conditions. In the self-healing polyurethane, multifunctional POSS is used for end-capping. Multifunctional POSS is prepared by reacting mixed lactide with hydroxyl 2-methacrylate under a catalyst, resulting in a macromonomer containing epoxy groups, hydroxyl groups, and unsaturated double bonds at the end groups, serving as an intermediate preparation. Then, epoxy cage-type POSS is grafted using the reaction of hydroxyl groups with epoxy. The introduction of multifunctional POSS further enhances the complexity of the crosslinking network, thereby improving the mechanical strength, anti-aging properties, and wear resistance of the cured photosensitive washable resin.

[0031] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the present invention's specification under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A photosensitive water-washable resin for 3D printing, characterized in that, The composition of the photosensitive water-washable resin by mass parts is as follows: 47-63 parts modified waterborne polyurethane, 1-3 parts photoinitiator, 18-25 parts diluent, and 1-5 parts modified graphitic carbon nitride.

2. The photosensitive water-washable resin for 3D printing according to claim 1, characterized in that, The photoinitiator is a TPO-type photoinitiator.

3. The photosensitive water-washable resin for 3D printing according to claim 1, characterized in that, The diluent is one or more of the following: acrylomorpholine, hydroxyethyl methacrylate, hydroxyethyl acrylate, glyceryl triacrylate, and polyethylene glycol diacrylate.

4. The photosensitive water-washable resin for 3D printing according to claim 1, characterized in that, The preparation of modified graphitic carbon nitride includes the following steps: 1) Melamine, potassium hydroxide and deionized water are mixed, dried, heated to 550℃ and kept at that temperature for 4 hours, cooled, ground, washed and dried to obtain graphitic carbon nitride containing nitrogen defects. 2) Mix nitrogen-deficient graphitic carbon nitride with deionized water, add ferric sulfate heptahydrate and sodium borohydride at 38-42℃, keep warm for 1-2 hours, wash until pH is neutral, keep warm at 78-82℃ for 22-24 hours to obtain composite graphitic carbon nitride. 3) Mix composite graphitic carbon nitride, ethanol, deionized water, and sodium dimethyl dithiocarbamate, stir at 58-62℃ for 1-2 hours, wash until pH is neutral, filter, and dry to obtain mercapto-graphitic carbon nitride. 4) Under a nitrogen atmosphere, mercapto-based graphitic carbon nitride and anhydrous tetrahydrofuran were mixed and added to polyethylene glycol diacrylate, multifunctional POSS, 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone, and anhydrous tetrahydrofuran. The mixture was then treated with ultraviolet light, rotary evaporated, ethanol was added, and the mixture was centrifuged, washed, and dried to obtain modified graphitic carbon nitride.

5. The photosensitive water-washable resin for 3D printing according to claim 1, characterized in that, The preparation of modified waterborne polyurethane includes the following steps: S1: Mix selenocysteine ​​hydrochloride and deionized water, add potassium hydroxide and stir for 1-2 hours, extract with dichloromethane 3-5 times, add anhydrous magnesium sulfate and stir for 10-12 hours, filter and rotary evaporate to obtain diselenium chain extender. S2: Mix isophorone diisocyanate, polytetrahydrofuran, dimethylolpropionic acid and dibutyltin dilaurate, add a mixture of tetrahydrofuran, trimethylolpropane monoallyl ether and p-benzoquinone dioxime, heat to 68-72℃ and keep warm for 2-3 hours, add a mixture of diselenyl chain extender and tetrahydrofuran, continue to keep warm for 2-3 hours, add a mixture of tetrahydrofuran, hydroquinone and multifunctional POSS, continue to keep warm for 4-5 hours, cool to 48-52℃, add triethylamine and keep warm for 1-2 hours, add deionized water and ethylenediamine, emulsify for 20-30 minutes, evaporate under reduced pressure to obtain modified waterborne polyurethane.

6. The photosensitive water-washable resin for 3D printing according to claim 4, characterized in that, The working conditions for ultraviolet light treatment are: irradiation with 365nm ultraviolet light for 2-3 hours.

7. The photosensitive water-washable resin for 3D printing according to claim 4, characterized in that, The mass ratio of mercapto-graphite carbon nitride, polyethylene glycol diacrylate, and multifunctional POSS is 1.6:1.2:1.

4.

8. The photosensitive water-washable resin for 3D printing according to claim 5, characterized in that, In the preparation of modified waterborne polyurethane, the mass ratio of p-benzoquinone dioxime, diselenole chain extender, and multifunctional POSS is 1:0.4:1.

1.

9. A photosensitive water-washable resin for 3D printing according to claim 4 or 5, characterized in that, The preparation of a multifunctional POSS includes the following steps: (1) Under a nitrogen atmosphere, D,L-lactide, hydroxyethyl methacrylate and stannous isooctanoate are mixed, heated to 108-112°C and kept at that temperature for 2-3 hours, chloroform is added, and the mixture is washed 3-5 times with hydrochloric acid aqueous solution and ultrapure water, then evaporated and dried to obtain an intermediate preparation. (2) Under a nitrogen atmosphere, the intermediate preparation and toluene are mixed, and a mixture of γ-glycidyl ether oxysilyl sesquioxane and toluene is added. The mixture is then transferred to a 0°C ice-water bath and kept warm for 15-20 min. Boron trifluoride ethyl ether is added, and the mixture is allowed to stand for 30-40 min. The temperature is then raised to 18-25°C and kept warm for 46-48 h. The mixture is then rotary evaporated under vacuum, and chloroform is added. The mixture is washed 3-5 times with sodium bicarbonate and ultrapure water, separated into layers, filtered, and rotary evaporated under vacuum. Anhydrous ethanol is added, and the mixture is centrifuged and washed to obtain the multifunctional POSS.

10. A method for preparing a photosensitive water-washable resin for 3D printing according to any one of claims 1-8, characterized in that, The process includes the following steps: under a nitrogen atmosphere, a photoinitiator, modified waterborne polyurethane, a diluent, and modified graphitic carbon nitride are ultrasonically mixed to obtain a photosensitive water-washable resin for 3D printing.

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