Preparation method of sodium carbonate nanoparticle suspension for 3d printing

Abstract

The invention provides a preparation method of a sodium carbonate nanoparticle suspension for 3d printing. The preparation method comprises the following steps: surface activation: carrying out heat treatment on sodium carbonate powder; pre-dissolving a dispersing agent: adding the dispersing agent into an organic medium in batches, and stirring; grinding treatment: grinding the sodium carbonate powder subjected to heat treatment and an organic medium, and cooling; preliminary filtration: filtering the ground sodium carbonate powder and an organic medium through a filter screen; in the stirring process, the filtered sodium carbonate powder is added into the filtered organic medium, a pre-dissolved dispersing agent is synchronously added, mixed slurry is formed, and then continuous stirring is conducted; ultrasonic treatment: performing ultrasonic oscillation treatment on the mixed slurry to form a suspension; concentration: concentrating the suspension liquid; filtering: filtering the suspension through a plurality of filter membranes in sequence; and stabilizing treatment: stirring the filtered suspension in a closed container to obtain the final sodium carbonate nanoparticle suspension.

Description

Technical Field

[0001] The present invention relates to the field of 3D printing, and more particularly to a method for preparing a sodium carbonate nanoparticle suspension for 3D printing. Background Art

[0002] Direct material inkjet 3D printing constructs complex three-dimensional structures by layer-by-layer deposition of functional materials (such as sodium carbonate nanoparticles), and is applied to the manufacture of ceramics, electronic devices, and biomaterials.

[0003] Among them, sodium carbonate nanoparticles are used as soluble support materials, and the suspension is required to have high dispersibility (D50 < 150 nm, suitable for a 20-micron nozzle), appropriate rheology (viscosity 5 - 20 mPa·s, surface tension 30 - 50 mN / m), and wettability with a nickel substrate (surface energy ~45 mN / m). However, the high surface energy of the existing sodium carbonate nanoparticle suspension easily leads to particle aggregation, making it difficult to prepare and store a high-concentration (>20 wt%) sodium carbonate nanoparticle suspension stably. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a sodium carbonate nanoparticle suspension for 3D printing to solve the above technical problems.

[0005] To solve the above technical problems, the present invention provides a method for preparing a sodium carbonate nanoparticle suspension for 3D printing, including the following steps: Surface activation: placing sodium carbonate powder in a vacuum tube furnace for heat treatment to remove organic matter and crystal water on the powder surface; Dispersant pre-dissolution: adding the dispersant in batches to an organic medium and stirring; Grinding treatment: grinding the heat-treated sodium carbonate powder and the organic medium, and cooling; Preliminary filtration: filtering the ground sodium carbonate powder and the organic medium through a filter screen; Slurry premixing: during stirring, adding the filtered sodium carbonate powder to the filtered organic medium, and synchronously adding the pre-dissolved dispersant to form a mixed slurry, and then continuously stirring for a specified time; Ultrasonic treatment: using ultrasonic oscillation to treat the mixed slurry to form a suspension; Concentration: concentrating the suspension to a target concentration; Filtration: filtering the suspension through a number of filter membranes in sequence, and the filtration pore sizes of the number of filter membranes gradually decrease; Stabilization treatment: stirring the filtered suspension in a closed container for a specified time to obtain the final sodium carbonate nanoparticle suspension.

[0006] Further, the sodium carbonate powder is composed of nanoscale sodium carbonate particles with a purity of ≥99%, and an average particle size of 50 - 300 mm; the organic medium is a mixture of propylene glycol monomethyl ether and cyclohexanone with a mass ratio of 3:2, or a mixture of ethanol and ethylene glycol with a mass ratio of 4:1; the dispersant is graphene oxide or a hydroxyl-terminated polymer or a polyelectrolyte complex, and the molecular weight of the dispersant is 5000 - 10000.

[0007] Further, 1 - 10 wt% of glycerol is added to the organic medium.

[0008] Further, during surface activation, the sodium carbonate powder is heat-treated at 50 - 80°C for 6 - 10 hours; during pre-dissolution of the dispersant, the stirring speed is 500 - 1000 rpm, and stirring is carried out for 40 minutes.

[0009] Further, during grinding treatment, the sodium carbonate powder and the organic medium are added to a planetary ball mill at a solid content ratio of 15 wt%, and ball milling is carried out at 400 rpm for 3 hours with grinding balls having a ball-to-material ratio of 5:1, and then cooled to less than 40°C.

[0010] Further, during premixing of the slurry, the stirring speed is 1000 - 2000 rpm, and after forming a mixed slurry with a solid content of 20% - 40%, continuous stirring is carried out for 120 minutes.

[0011] Further, during concentration, the target concentration is 20 - 40 wt%; during filtration, the filter membrane material is hydrophilic polyethersulfone or polyvinylidene fluoride, the filter membrane thickness is 100 - 150 μm, and before filtration, the filter membrane is pre-washed with the mixed slurry.

[0012] Further, during filtration, pressure filtration is carried out, controlling the pressure within the range of 0.1 - 0.3 MPa, and controlling the temperature of the mixed slurry at 20 - 25°C.

[0013] Further, 0.1 - 1 wt% of a rheology regulator is added to the sodium carbonate nanoparticle suspension, and the rheology regulator is polyvinyl alcohol or polyethylene oxide.

[0014] Further, quality monitoring is carried out on the final sodium carbonate nanoparticle suspension, and the quality monitoring includes laser particle size analysis, rheology detection, and TEM observation.

[0015] The beneficial effects of the present invention are as follows: 1. By adding 1 - 10 wt% of glycerol to improve storage stability; 2. Controlling the molecular weight between 5000 and 10000 to ensure the electrostatic stabilization effect on nanoparticles; 3. Heat treatment can effectively remove the adsorbed organic matter and crystal water on the particle surface, thereby improving the activity of the powder. 4. Sequentially performing grinding treatment, preliminary filtration, and slurry premixing can reduce the powder agglomeration degree. Combining with ultrasonic oscillation can further refine the particles and improve the dispersion uniformity. 5. By concentrating the suspension to increase the concentration and combining with membrane filtration, large particle substances in the suspension can be effectively removed. By pre-wetting the filter membrane, the slurry loss caused by filter membrane adsorption can be reduced. 6. By adding a rheology regulator, the viscosity and fluidity of the sodium carbonate nanoparticle suspension are adjusted. Specific embodiments

[0016] The technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention belong to the protection scope of the present invention.

[0018] It can be understood that the term "one" should be understood as "at least one" or "one or more". That is, in one embodiment, the number of one element can be one, while in other embodiments, the number of this element can be multiple. The term "one" cannot be understood as a limitation on the number.

[0019] The present invention provides a preparation method for a sodium carbonate nanoparticle suspension for 3D printing, including the following steps: Raw material preparation: Sodium carbonate nanoparticles: Select nanoscale sodium carbonate with a purity ≥ 99%. The primary particle size is characterized by transmission electron microscopy (TEM), and the average particle size is 50 - 300 nm. It is preferably self-made by chemical precipitation method or gas phase method. After preparation, it is dried and the compatibility with the organic medium is enhanced through hydrophobic modification.

[0020] Organic medium: Select a mixture of propylene glycol monomethyl ether and cyclohexanone (mass ratio 3:2), or a mixture of ethanol and ethylene glycol (mass ratio 4:1) to balance volatility and viscosity. 1 - 10 wt% of glycerol can be added to improve storage stability.

[0021] Dispersant system: Self-made functionalized graphene oxide (containing carboxyl and hydroxyl groups, 0.5 - 2 wt%), hydroxyl-terminated polymer (such as PEG, 0.1 - 0.5 wt%), polyelectrolyte complex (such as polyacrylic acid and chitosan, 0.2 - 0.8 wt%). The molecular weight needs to be between 5000 and 10000 to ensure the electrostatic stabilization effect on the nanoparticles.

[0022] Other additives: 0.1% - 0.3 wt% defoamer (such as polydimethylsiloxane) or pH regulator (such as dilute hydrochloric acid / sodium hydroxide) can be added to optimize the stability of the slurry.

[0023] Dispersion and preparation of sodium carbonate nanoparticle suspension: Surface activation: Place sodium carbonate powder in a vacuum tube furnace and heat-treat it at 50 - 80 °C for 6 - 10 hours to remove adsorbed organic matter and crystal water on the surface and improve the powder activity.

[0024] Pre-dissolution of dispersant: Add the dispersant to the organic medium in batches and stir at 500 - 1000 rpm for 40 minutes to form a homogeneous solution.

[0025] Ball milling treatment: The powder and the organic medium (solid content 15 wt%) are placed in a planetary ball mill, using zirconia grinding balls (1 mm, ball-to-material ratio 5:1), ball mill at 400 rpm for 3 hours, and cool (<40 °C).

[0026] Initial filtration: Filter through a 5-micron stainless steel filter screen to remove impurities.

[0027] Slurry pre-mixing: Under medium-high speed stirring (1000 - 2000 rpm), slowly add the activated sodium carbonate powder to the organic medium, and at the same time add the pre-dissolved dispersant to form a mixed slurry with a solid content of 20% - 40%; pre-disperse for 120 minutes to reduce the powder agglomeration degree; Ultrasonic treatment: Use ultrasonic with a power of 300 - 1000 W and a frequency of 20 kHz to treat for 20 minutes to further refine the particles and improve the dispersion uniformity to form a suspension.

[0028] Defoaming treatment: Add 0.1% - 0.3 wt% polydimethylsiloxane to the suspension and stir at low speed (100 - 300 rpm) for 10 - 15 minutes to eliminate bubbles.

[0029] pH adjustment: Use dilute hydrochloric acid or sodium hydroxide solution (0.1 mol / L), add dropwise in small amounts and multiple times to adjust the pH of the suspension to 6 - 8, and stir (300 - 500 rpm) for 20 - 30 minutes to ensure the stability of the system.

[0030] Concentration and filtration: Concentration by rotary evaporator: Concentrate the suspension to the target concentration of 20 - 40 wt%.

[0031] Membrane filtration: The membrane material is made of hydrophilic polyethersulfone (PES) or polyvinylidene fluoride (PVDF) to avoid reaction with nano sodium carbonate slurry. The membrane thickness is controlled at 100~150 μm to ensure mechanical strength.

[0032] Optimization of filter membrane pore size gradient: Initially, a filter membrane with a pore size of 10μm is used for coarse filtration to quickly remove coarse particles with a particle size of >10μm; subsequently, according to the particle distribution in the slurry (such as the results of laser particle size analyzer detection), switch to a 5μm filter membrane for fine filtration. For example, if there are many agglomerated particles >1000 nm in the slurry, a filter membrane with a pore size of 3μ nm is selected.

[0033] Membrane pretreatment: Use slurry to pre-moisten the membrane before filtration to reduce slurry loss caused by membrane adsorption. Use the membrane to remove large particles and impurities, and adjust the pore size if necessary to optimize the filtration effect.

[0034] Among them, during filtration, various process parameters of filtration are controlled: ①Operation pressure: Use pressurized filtration and control the operation pressure within the range of 0.1~0.3 MPa. Too low pressure will reduce the filtration efficiency, while too high pressure may cause damage to the filter membrane or deformation of particles.

[0035] Data example: record the filtration flux under different pressures, for example, the flux is 50 L / (m²・h) at 0.2 MPa, and the flux increases to 70 L / (m²・h) at 0.3 MPa, but the membrane fouling rate increases by 15%.

[0036] ② Temperature control: Keep the slurry temperature at 20~25℃ during the filtration process to avoid temperature fluctuations that may cause particle agglomeration or changes in membrane performance. Temperature stability can be achieved through a constant temperature water bath circulation system.

[0037] ③Filtration method: Cross-flow filtration is used instead of dead-end filtration. The high-speed flow of slurry on the surface of the filter membrane (flow rate 1~2 m / s) reduces the deposition of particles on the membrane surface and extends the service life of the filter membrane.

[0038] Stabilization treatment: Stir the suspension slowly in a closed container for 8 - 12 hours to allow the dispersant to fully combine with the particles.

[0039] 0.1 - 1 wt% of rheology modifier (such as polyvinyl alcohol or polyethylene oxide) is added to adjust the viscosity and fluidity according to the usage scenario; in one embodiment of the present scheme, 0.3 wt% of polyvinyl alcohol can be used, with a viscosity of 5-20 mPa·s, a surface tension of 30-50 mN / m, and a 20 micron nozzle (Dimatix DMP-2850).

[0040] Quality inspection: Laser particle size analysis: Ensure that D50 < 150 nm and the particle size distribution range is 50 - 200 nm; Rheological property detection: The viscosity range is 5 - 20 mPa·s; TEM observation: Verify the dispersion uniformity and morphology of the particles.

[0041] It is worth mentioning that during the above filtration process, it can be linked with the quality inspection steps to enable the monitoring of the filtration effect and the dynamic adjustment of the pore size. For example: Online monitoring index: Combine the laser particle size analyzer to detect the particle size in the filtrate. If particles larger than 300 nm are detected, replace the filter membrane with a smaller pore size.

[0042] Pore size adjustment strategy, establish the "pore size - particle distribution" mapping relationship: If the proportion of particles larger than 1000 nm in the slurry is > 5%, first perform rough filtration with a 1000 nm filter membrane; If there are still particles with a size of 500 - 800 nm in the filtrate, switch to a 500 nm filter membrane for secondary filtration.

[0043] The final sodium carbonate nanoparticle suspension is stored in a light - proof environment at 4 - 25°C and stirred thoroughly before use to ensure uniformity; during actual printing, the printing resolution is < 50 microns, the water washing removal time is < 5 minutes, the wettability of the nickel substrate (contact angle < 90°), and the surface energy of the nickel substrate used is 45 mN / m.

[0044] This solution prepares the sodium carbonate nanoparticle suspension according to the above steps, and the test results of its parameter performance are as follows:

[0045] Final component proportion range: Sodium carbonate nanoparticles: 10% - 50 wt% Organic medium (diethylene glycol monomethyl ether and cyclohexanone, 3:2): 42.2% - 88.7 wt% Diethylene glycol monomethyl ether: 25.3% - 53.2 wt% Cyclohexanone: 16.9% - 35.5 wt% Glycerol: 0.5% - 9 wt% Dispersant: 0.1% - 1.5 wt% Rheology regulator: 0.1% - 1 wt% Defoamer and pH regulator: 0.2% - 0.6 wt% The present invention is not limited to the above-described optimal embodiments. Any person can obtain other various forms of products under the inspiration of the present invention. However, no matter what changes are made in its shape or structure, as long as there are technical solutions that are the same as or similar to those of the present application, they all fall within the protection scope of the present invention.

Claims

1. A preparation method of a sodium carbonate nanoparticle suspension for 3D printing, characterized in that, It includes the following steps: Surface activation: Place the sodium carbonate powder in a vacuum tube furnace for heat treatment to remove the organic matter and crystal water on the powder surface; Dispersant pre-dissolution: Add the dispersant to the organic medium in batches and stir; Grinding treatment: Grind the heat-treated sodium carbonate powder and the organic medium, and then cool; Preliminary filtration: Filter the ground sodium carbonate powder and the organic medium through a filter screen; Slurry premixing: During stirring, add the filtered sodium carbonate powder to the filtered organic medium, and simultaneously add the pre-dissolved dispersant to form a mixed slurry, and then continue stirring for a specified time; Ultrasonic treatment: Use ultrasonic oscillation to treat the mixed slurry to form a suspension; Concentration: Concentrate the suspension to the target concentration; Filtration: Filter the suspension through several filter membranes in sequence, and the filtration pore sizes of the several filter membranes gradually decrease; Stabilization treatment: Stir the filtered suspension in a closed container for a specified time to obtain the final suspension of sodium carbonate nanoparticles.

2. The preparation method of the sodium carbonate nanoparticle suspension for 3D printing according to claim 1, characterized in that: The sodium carbonate powder uses nano-level sodium carbonate particles with a purity of ≥99%, and the average particle size is 50 - 300 mm; the organic medium uses a mixture of propylene glycol monomethyl ether and cyclohexanone with a mass ratio of 3:2, or a mixture of ethanol and ethylene glycol with a mass ratio of 4:1; the dispersant uses graphene oxide or a hydroxyl-terminated polymer or a polyelectrolyte complex, and the molecular weight of the dispersant is 5000 - 10000.

3. The preparation method of the sodium carbonate nanoparticle suspension for 3D printing according to claim 1, characterized in that: 1 - 10 wt% of glycerol is added to the organic medium.

4. The preparation method of the sodium carbonate nanoparticle suspension for 3D printing according to claim 1, characterized in that: During surface activation, the sodium carbonate powder is heat-treated at 50 - 80 °C for 6 - 10 hours; during dispersant pre-dissolution, the stirring speed is 500 - 1000 rpm and stirring is carried out for 40 minutes.

5. The preparation method of the sodium carbonate nanoparticle suspension for 3D printing according to claim 1, characterized in that: During grinding treatment, add the sodium carbonate powder and the organic medium to a planetary ball mill according to a solid content of 15 wt%, and use grinding balls with a ball-to-material ratio of 5:1 to carry out ball milling at 400 rpm for 3 hours, and then cool to less than 40 °C.

6. The preparation method of the sodium carbonate nanoparticle suspension for 3D printing according to claim 1, wherein: During slurry premixing, the stirring speed is 1000 - 2000 rpm. After forming a mixed slurry with a solid content of 20% - 40%, continue stirring for 120 minutes.

7. The preparation method of the sodium carbonate nanoparticle suspension for 3D printing according to claim 1, characterized in that: During concentration, the target concentration is 20 - 40 wt%; during filtration, the filter membrane material uses hydrophilic polyethersulfone or polyvinylidene fluoride, the filter membrane thickness is 100 - 150 μm, and before filtration, the filter membrane is pre-washed with the mixed slurry.

8. The preparation method of the sodium carbonate nanoparticle suspension for 3D printing according to claim 1, characterized in that: During filtration, pressure filtration is carried out, controlling the pressure within the range of 0.1 - 0.3 MPa, and controlling the temperature of the mixed slurry at 20 - 25 °C.

9. The preparation method of the sodium carbonate nanoparticle suspension for 3D printing according to claim 1, wherein: 0.1 - 1 wt% of a rheology modifier is added to the suspension of sodium carbonate nanoparticles, and the rheology modifier is polyvinyl alcohol or polyethylene oxide.

10. The preparation method of the sodium carbonate nanoparticle suspension for 3D printing according to claim 1, characterized in that: Quality monitoring is carried out on the final suspension of sodium carbonate nanoparticles, and the quality monitoring includes laser particle size analysis, rheology detection, and TEM observation.

Images