Enhanced ink for binder jet printing and preparation method and application thereof

Abstract

The invention provides enhanced ink for binder jet printing and a preparation method and application thereof, and relates to the technical field of binder jet printing. The enhanced ink comprises the following components in percentage by mass: 5%-15% of a high-molecular binder, 0.5%-5% of a small-molecular additive, 10%-15% of a humidifying agent, 8%-10% of a flatting agent, 0.1%-1% of a surfactant and the balance of a solvent. The preparation method comprises the following steps: dissolving the high-molecular binder in the solvent, adding the rest components, and uniformly mixing. The micromolecular additive is introduced into the high-molecular binder, the interface bonding force is enhanced through chemical or physical action, and the strength of the green body after printing is remarkably improved.

Description

Technical Field

[0001] The present application relates to the technical field of binder jet printing, and in particular to an enhanced ink for binder jet printing, a preparation method thereof, and an application thereof. Background Art

[0002] Binder jet additive manufacturing technology, as an efficient and low-cost powder metallurgy forming process, has been widely used in the field of metal part preparation in recent years. This technology selectively bonds metal powders by layer-by-layer spraying of polymer-based binder ink, and realizes near-net shaping of metal parts through debinding and sintering processes.

[0003] Currently, the binders commonly used in the industrial sector for printing metals, ceramics, and composite materials are mainly organic binders, such as furan resin, phenolic resin, etc. These binders will release a large amount of volatile organic compounds (VOCs) during the spraying and curing processes, which not only pollute the environment but may also affect the health of operators. In addition, the binder is prone to crystallization or curing at the nozzle, resulting in nozzle clogging and affecting printing stability and production efficiency.

[0004] To reduce VOC emissions and improve environmental performance, water-based binders have gradually attracted attention, such as polyvinyl alcohol (PVA), polyacrylic acid (PAA), etc. However, water-based binders also have some defects. For example, the green body after curing has insufficient flexural strength and is prone to cracking. Especially during the printing process of thin-walled precision parts, it is more likely to deform or break in the subsequent debinding and sintering stages. In addition, the storage stability of water-based binders is poor, and long-term storage may lead to hydrolysis, aggregation, or component separation, affecting spraying performance. Researchers have tried to improve the bonding strength and stability of water-based binders by adding nano-fillers or surfactants, etc., but these modification methods often affect rheological properties and increase the difficulty of spraying. Therefore, how to develop a binder system with high bonding strength, good storage stability, and environmental protection characteristics is still an important challenge faced by binder jet additive manufacturing technology. Summary of the Invention

[0005] In order to improve the problems of low bonding strength and poor storage stability of the current water-based binders, the present application provides an enhanced ink for binder jet printing, a preparation method thereof, and an application thereof.

[0006] In the first aspect, the present application provides an enhanced ink for binder jet printing, adopting the following technical solution: An enhanced ink for binder jet printing, in terms of mass percentage, comprises the following components: 5% - 15% of a polymer binder, 0.5% - 5% of a small molecule additive, 10% - 15% of a humectant, 8% - 10% of a leveling agent, 0.1% - 1% of a surfactant, and the balance is a solvent.

[0007] The enhanced ink provided by this application adds small molecule additives on the basis of a polymer binder to enhance the interfacial bonding force with metal powder and promote the formation of a more compact cross-linked structure, thereby significantly improving the flexural strength of the material without exacerbating the carbon residue problem. The binder system including small molecule additives serves as the continuous phase to construct a stable three-dimensional bonding network, providing necessary macroscopic structural support for the green body. The wetting agent maintains the wettability of the ink by regulating the evaporation rate of the solvent, preventing printing defects caused by local drying during powder spreading. The leveling agent promotes the uniform spreading of the liquid film, thereby reducing interlayer defects and improving printing quality. The surfactant synergistically regulates the ink-powder interfacial energy, enhances the wettability of metal particles, and optimizes the adhesion state between particles. The solvent is not only used to dissolve polymer and small molecule components to ensure uniform mixing of the system, but also adjusts the viscosity and surface tension of the ink to optimize its rheological properties and improve printing stability and final forming quality.

[0008] Optionally, the small molecule additive is a small molecule compound containing at least one group among amino group, carboxyl group or hydroxyl group.

[0009] Optionally, the small molecule additive is selected from any one of triethanolamine, ethylenediamine, hexamethylenediamine, citric acid, succinic acid, glycerol or ethanolamine.

[0010] The small molecule additive provided by this application has polar groups, and thus can form chemical adsorption or hydrogen bond interaction with the surface of metal powder to enhance the interfacial bonding force; specifically, the amino group can undergo coordination with the surface of metal oxide to form a stable metal-amine complex, reducing the interfacial energy, the carboxyl group forms a hydrogen bond network with the surface hydroxyl group of the metal through protonation, and the hydroxyl group enhances the physical entanglement between the polymer binder and metal particles through van der Waals force and hydrogen bond.

[0011] Optionally, the polymer binder is selected from any one of polyvinyl alcohol, polyacrylic acid or acrylate resin.

[0012] This application utilizes the polymer chains of the polymer binder to form a continuous network through physical entanglement and chemical bonding. The small molecule additive fills the network gaps and strengthens the interfacial bonding. By using the synergistic mechanism of the two, the interfacial bonding force and sintering density between the polymer binder and metal powder can be improved.

[0013] Optionally, the wetting agent is selected from one or more of triethylene glycol, ethylene glycol, propylene glycol, glycerol.

[0014] This application uses a humectant to adjust the wettability of the binder, which can prevent the unstable spraying phenomenon caused by the too-fast drying of the ink. An appropriate amount of humectant can improve the fluidity and spreading property of the ink during the printing process, and its content should be controlled within 10% - 15% to avoid the adverse effect of the relative reduction of the solvent content on the stability of the base material.

[0015] Optionally, the leveling agent is selected from one or more of ethylene glycol monobutyl ether, 1,2 - hexanediol, n - propanol, and propylene glycol monobutyl ether.

[0016] This application uses a leveling agent to increase the spreading property and permeability of the polymer binder on the surface of metal powder, and promote the uniform diffusion of droplets. An appropriate amount of leveling agent can improve the diffusibility of the binder droplets, ensuring that the green body after printing has good structural integrity and flexural strength. The content of the leveling agent should be controlled within 8% - 10% to avoid the problem of unstable spraying caused by excessive use.

[0017] Optionally, the surfactant is selected from any two of hydrocarbon surfactants, fluorocarbon surfactants, and silicone surfactants.

[0018] Optionally, the hydrocarbon surfactant is selected from any one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, N - alkyl betaine, nonylphenol polyoxyethylene ether, and sorbitan fatty acid ester; The fluorocarbon surfactant is selected from any one of Capstone FS31, Capstone FS66, Capstone FS81, and Capstone FS3100; The silicone surfactant is selected from any one of Silwet L - 77, Silwet HS 312, Silwet DA - 40, and Silwet STIK - 2.

[0019] In this application, the role of the surfactant is to reduce the surface tension of the ink, improve the spraying performance, wettability of the ink, and the uniform spreading property of the droplets on the surface of the metal powder after printing. By reasonably matching different types of surfactants, the performance of the ink can be further improved. Among them, the hydrocarbon surfactant has good surface activity and wetting effect. The fluorocarbon surfactant has extremely low surface tension and excellent wetting performance, which is suitable for improving the spreading property of droplets on the surface of the printing substrate. The silicone surfactant has a unique molecular structure, combining low surface tension and high wettability, which is suitable for further optimizing the rheological properties and interfacial properties of the ink.

[0020] In a second aspect, this application provides a method for preparing the enhanced ink for binder jet printing described above. First, dissolve the polymer binder in a solvent, and then add the remaining components and mix them evenly.

[0021] In a third aspect, the present application provides an application of the enhanced ink in binder jet printing of metal powders.

[0022] In summary, the present application includes at least one of the following beneficial effects: 1. In the present application, small molecule additives are introduced into the polymer binder, and the interfacial bonding force is enhanced through chemical or physical actions, significantly improving the green strength after printing.

[0023] 2. Experiments have shown that compared with traditional inks, the flexural strength of the cured material is increased by 10%-30%, meeting higher performance requirements. Detailed implementation manners

[0024] Example 1 Example 1 provides an enhanced ink for binder jet printing. Each 100 g of the enhanced ink contains the following raw material components: 10 g of polyvinyl alcohol, 2 g of ethylenediamine, 2 g of ethylene glycol, 2 g of n-propanol, 0.2 g of sodium dodecyl sulfate, 0.2 g of Silwet L-77, and 83.6 g of deionized water. The preparation method of the enhanced ink is as follows: Add polyvinyl alcohol to deionized water, and stir magnetically at a constant temperature of 40 °C for 2 hours until completely dissolved. Subsequently, add ethylenediamine, ethylene glycol, n-propanol, sodium dodecyl sulfate, and Silwet L-77 in sequence, and stir and mix at 300 r / min for 30 minutes to obtain the finished ink.

[0025] Example 2 Example 2 is basically the same as Example 1, except that in Example 2, an equal mass of citric acid is used to replace ethylenediamine.

[0026] Example 3 Example 3 is basically the same as Example 1, except that in Example 2, an equal mass of glycerol is used to replace ethylenediamine.

[0027] Example 4 Example 4 is basically the same as Example 1, except that in Example 4, an equal mass of polyacrylic acid is used to replace polyvinyl alcohol.

[0028] Example 5 Example 5 is basically the same as Example 4, except that in Example 5, an equal mass of citric acid is used to replace ethylenediamine.

[0029] Example 6 Example 6 is basically the same as Example 4, except that in Example 6, an equal mass of glycerol is used to replace ethylenediamine.

[0030] Example 7 Example 7 is basically the same as Example 1, except that in Example 7, an equal mass of acrylic resin is used to replace polyvinyl alcohol.

[0031] Example 8 Example 8 is basically the same as Example 7, except that in Example 8, an equal mass of citric acid is used to replace ethylenediamine.

[0032] Example 9 Example 9 is basically the same as Example 7, except that in Example 9, an equal mass of glycerol is used to replace ethylenediamine.

[0033] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that in Comparative Example 1, an equal mass of deionized water is used to replace ethylenediamine.

[0034] Comparative Example 2 Comparative Example 2 is basically the same as Example 4, except that in Comparative Example 2, an equal mass of deionized water is used to replace ethylenediamine.

[0035] Comparative Example 3 Comparative Example 3 is basically the same as Example 7, except that in Comparative Example 3, an equal mass of deionized water is used to replace ethylenediamine.

[0036] Examples 10 - 11 Examples 10 - 11 are basically the same as Example 1, except that in Examples 10 - 11, the dosages and types of each component are different from those in Example 1. For details, see Table 1.

[0037] Table 1 Dosages of each raw material in Examples 1, 10 - 11 Performance detection The enhanced inks prepared by binder jet printing in the above examples and comparative examples were subjected to performance detection. The detection items included flexural strength test, residual carbon content test, and stability test.

[0038] First, the enhanced ink was used for binder jet printing of metal powder. The metal powder was 316L, and the finished product was obtained after high - temperature curing. The curing temperature was 250°C and the time was 2h.

[0039] (1) Flexural strength test: Three - point bending test was adopted. The distance between the three - point bending supports was 20mm. The size of the prepared test block was a cuboid with dimensions of 30mm×12mm×9mm (length×width×height). The load was applied at a speed of 1mm / min, and the flexural strength was calculated. The specific test results are shown in Table 2.

[0040] (2) Method for testing residual carbon content: Test with an Eltra high-frequency infrared carbon-sulfur analyzer according to the standard requirements. The sample is first preheated to the specified temperature and then completely burned with the assistance of oxygen. The carbon content in the combustion gas is detected in real time by high-frequency infrared to ensure accurate data.

[0041] Table 2 Performance test results of each example and comparative example It can be seen from the results in Table 2 that in the polyvinyl alcohol and polyacrylic acid systems, the presence of the small molecule additive ethylenediamine significantly improves the flexural strength, which may play a role by promoting the cross-linking of polymer chains or improving the interfacial bonding between the ink and metal powder. Moreover, the introduction of the small molecule additive does not cause an increase in the residual carbon content, probably because its small molecule characteristics are more easily completely decomposed at high temperatures.

[0042] The above are all the preferred embodiments of this application. The protection scope of this application is not limited accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. An enhanced ink for binder jet printing, characterized in that: Calculated by mass percentage, the following components are included: 5% to 15% of polymer binder, 0.5% to 5% of small molecule additive, 10% to 15% of wetting agent, 8% to 10% of leveling agent, 0.1% to 1% of surfactant, and the balance is solvent.

2. The enhanced ink for binder jet printing according to claim 1, characterized in that: The small molecule additive is a small molecule compound containing at least one of an amine group, a carboxyl group or a hydroxyl group.

3. The enhanced ink for binder jet printing according to claim 1, characterized in that: The small molecule additive is selected from any one of triethanolamine, ethylenediamine, hexamethylenediamine, citric acid, succinic acid, glycerol or ethanolamine.

4. The enhanced ink for binder jet printing according to claim 1, characterized in that: The polymer binder is selected from any one of polyvinyl alcohol, polyacrylic acid or acrylate resin.

5. The enhanced ink for binder jet printing according to claim 1, characterized in that: The humidifying agent is selected from one or more of triethylene glycol, ethylene glycol, propylene glycol and glycerol.

6. The enhanced ink for binder jet printing according to claim 1, characterized in that: The leveling agent is selected from one or more of ethylene glycol butyl ether, 1,2-hexanediol, n-propanol, and propylene glycol butyl ether.

7. The enhanced ink for binder jet printing according to claim 1, characterized in that: The surfactant is selected from any two of hydrocarbon surfactants, fluorocarbon surfactants and silicone surfactants.

8. The enhanced ink for binder jet printing according to claim 7, characterized in that: The hydrocarbon surfactant is selected from any one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, N-alkyl betaine, nonanol polyoxyethylene ether, and sorbitan fatty acid ester; The fluorocarbon surfactant is selected from any one of Capstone FS31, Capstone FS66, Capstone FS81, and CapstoneFS3100; The organic silicon surfactant is selected from any one of Silwet L-77, Silwet HS 312, Silwet DA-40 and Silwet STIK-2.

9. The method for preparing an enhanced ink for binder jet printing according to any one of claims 1 to 8, characterized in that: First dissolve the polymer binder in the solvent, then add the remaining components and mix well.

10. Use of the enhanced ink according to any one of claims 1 to 8 in binder jet printing of metal powder.

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