Composite binder as well as preparation method and use method thereof

Abstract

The invention discloses a composite binder which comprises the following components in percentage by mass: 10%-40% of polyacrylic acid, 5%-30% of polyacrylamide, 0.1%-3% of a wetting agent, 1%-5% of an accelerant, 0.05%-3% of a pH regulator and 30%-70% of a solvent. According to the composite binder disclosed by the invention, the polyacrylic acid and the polyacrylamide are used as main components, and the polyacrylic acid and the polyacrylamide are heated to generate chemical cross-linking curing in the printing and green body drying processes, so that the composite binder has the characteristics of high bonding strength, low viscosity and the like; active groups in the accelerant and polyacrylic acid or polyacrylamide are further subjected to cross-linking reaction and curing in the green body drying process of the 3D printing metal product, and the bonding strength of the adhesive is remarkably improved; a wetting agent is added into a bonding system, so that the wetting effect is good; the binder system only takes water as a solvent medium, and the VOC detection value is obviously lower than that of a traditional binder containing an organic solvent.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and particularly to a composite binder for binder jet 3D printing, a preparation method thereof, and a usage method thereof. Background Art

[0002] In the industrialization process of binder jet metal powder 3D printing technology, the research and development of binders occupies a core and crucial position. Currently, there are many intractable problems in the binder system, which seriously restrict the further development of this technology. The bonding strength of the binder is insufficient, resulting in the green body printed with metal powder being easily damaged during the powder cleaning process; the wettability of the binder is poor, resulting in the formation of droplet spherical aggregates during printing, which affects the inkjet stability; the viscosity of the binder is too high, resulting in poor inkjet printing effect, difficult cleaning of the print head, and even nozzle clogging and frame loss; the binder component contains organic solvents, and the volatilization of organic solvents leads to an increase in VOC, which is not conducive to environmental protection.

[0003] For example, the invention patent with the application number CN202110744828.8 discloses an aqueous binder for binder jet 3D printing, with the matrix being polyvinyl alcohol, the reinforcing agent being polyacrylic acid, and the solvents being water and ethers. Among them, there is only a non - chemical bond, hydrogen bond, between polyvinyl alcohol and polyacrylic acid, and the interaction force is weak, resulting in a low bonding strength of the binder. The viscosity of the binder is too high and the wetting effect is poor, resulting in a rough texture on the surface of the 316L parts printed and sintered. In addition, the low - boiling - point alcohol quick - drying agent and ether penetrant added to the binder will volatilize during the printing process, causing the on - site VOC value to increase during printing, which is not conducive to environmental protection. Summary of the Invention

[0004] Based on this, in order to solve the technical problems such as insufficient bonding strength, too high viscosity, poor wettability, and too high VOC of the existing binder for metal binder jet 3D printing, the present invention provides a composite binder with high bonding strength, excellent wettability, low viscosity, and low VOC emissions, a preparation method thereof, and a usage method thereof.

[0005] In order to solve the above - mentioned technical problems, the present invention adopts the following technical solutions:

[0006] A composite binder, calculated by mass percentage, includes: 10% - 40% polyacrylic acid, 5% - 30% polyacrylamide, 0.1% - 3% wetting agent, 1% - 5% promoter, 0.05% - 3% pH regulator, and 30% - 70% solvent.

[0007] Further, the promoter includes one or more of agar, glucose, citric acid, carboxymethyl cellulose, and glycerol.

[0008] Further, the wetting agent includes one or more of sodium diisooctyl sulfosuccinate, polyether-modified polyorganosiloxane, isooctyl alcohol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether, and octylphenol polyoxyethylene ether.

[0009] Further, the solid content of the polyacrylic acid is 10% - 50%.

[0010] Further, the solid content of the polyacrylamide is 10% - 50%.

[0011] Further, the solvent is water.

[0012] Further, the pH regulator is an organic base.

[0013] Further, the pH regulator is at least one of triethylamine, ethylenediamine, triethanolamine, diisopropylethylamine, and sodium ethoxide.

[0014] In a second aspect, the present application also provides a preparation method, which is applied to any of the above-mentioned composite binders. The preparation method includes the following steps:

[0015] S1. Add the solvent into the reaction kettle, start stirring, add the polyacrylamide, heat up to 40°C - 60°C, and stir for 1h - 2h;

[0016] S2. Add the polyacrylic acid and stir for 1h - 2h;

[0017] S3. Add the accelerator, heat up to 70°C - 90°C, and stir for 1h - 3h;

[0018] S4. Cool down to below 30°C, add the wetting agent and the pH regulator, and stir for 0.5h - 2h.

[0019] In a third aspect, the present application also provides a usage method, which is applied to any of the above-mentioned composite binders. The composite binder is used for metal binder jet 3D printing.

[0020] The method of the present invention has the following beneficial effects compared with the prior art:

[0021] The composite binder disclosed in the present invention uses polyacrylic acid and polyacrylamide as the main components. During printing and green body drying, polyacrylic acid and polyacrylamide are chemically crosslinked and cured by heat, having the characteristics of high bonding strength and low viscosity, and having an obvious improvement effect on enhancing the green body strength, printing accuracy, and surface quality of 3D printed metal products; the active groups in the accelerator further crosslink and react with polyacrylic acid or polyacrylamide during the green body drying process of 3D printed metal products, significantly improving the bonding strength of the binder.

[0022] The composite binder disclosed by the present invention adds a wetting agent to the binding system, which can not only reduce the surface tension of the binder to improve the inkjet effect during printing, but also improve the wetting effect of the binder on metal powder, effectively improve the printing accuracy, enhance the green body quality and reduce printing defects. At the same time, the wetting agent can also help the binder penetrate into the metal powder faster, reduce the penetration time of the binder, and thus improve the printing efficiency. Detailed implementation mode

[0023] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to relevant embodiments. The preferred embodiments of the present invention are given in the embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0025] One of the purposes of the present invention is to disclose a composite binder. By mass percentage, the composite binder includes: 10% - 40% polyacrylic acid, 5% - 30% polyacrylamide, 0.1% - 3% wetting agent, 1% - 5% accelerator, 0.05% - 3% pH regulator, and 30% - 70% solvent. Among them, the polyacrylic acid is an aqueous solution of low molecular weight polyacrylic acid (the molecular weight is between 1000 and 10000), and its solid content is between 10% and 50%. The polyacrylamide is an aqueous solution of low molecular weight polyacrylamide (the molecular weight is between 100,000 and 300,000), and its solid content is between 10% and 50%. The carboxyl group of polyacrylic acid and the amino group of polyacrylamide undergo an amidation reaction during the printing and drying heating process to form an interpenetrating network structure, which can significantly improve the binding effect of the binder on metal powder and increase the green body strength of metal 3D printing products by 40% - 50%. Both polymer raw materials in the binder system are water-soluble materials, so the binder system uses only water as the solvent medium. Through the design of this environmentally friendly formula without organic solvents, the emissions of volatile organic compounds (VOCs) during the printing operation are reduced by 60% - 90%.

[0026] The promoter is a hydrogen bond donor, specifically it can be one or more of agar, glucose, citric acid, carboxymethyl cellulose, glycerol, etc. The active groups in the promoter undergo further cross-linking reactions with polyacrylic acid or polyacrylamide in the binder, enhancing the interaction force of the binder network structure. While ensuring the strength of the printed green body, it can also reduce the viscosity of the binder by 20% - 30%. The wetting agent can be one or more of sodium diisooctyl sulfosuccinate, polyether-modified polyorganosiloxane, isooctyl alcohol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether, octylphenol polyoxyethylene ether, etc.; adding a small amount of wetting agent to the binder system reduces the surface tension of the binder to 23 mN / m - 30 mN / m and reduces the contact angle by 20% - 40%, thereby achieving a breakthrough improvement in wetting performance. During the 3D printing process, it can reduce the formation of spherical aggregates during inkjet printing, ensure a high degree of uniformity in the morphology of ink droplets during continuous spraying, and at the same time increase the penetration rate of the binder in the metal powder, improving the printing efficiency. The pH regulator is an organic base, preferably at least one of triethylamine, ethylenediamine, triethanolamine, diisopropylethylamine, sodium ethoxide, etc. The addition of the pH regulator can adjust the pH value of the binder system, making the pH value of the final binder product between 6 and 8, which can not only store the binder stably for a long time, but also avoid corrosion and debonding of the print head, extending the service life of the print head.

[0027] The second object of the present invention is to provide a preparation method, which is applied to the composite binder described in any of the above embodiments. This preparation method may include the following steps:

[0028] S1. Add 30% - 70% of the solvent into the reaction kettle, start stirring, and add 5% - 30% of polyacrylamide, heat up to 40°C - 60°C, and stir for 1 h - 2 h;

[0029] S2. Add 10% - 40% of polyacrylic acid into the reaction kettle and stir for 1 h - 2 h;

[0030] S3. Add 1% - 5% of the promoter into the reaction kettle, heat up to 70°C - 90°C, and stir for 1 h - 3 h;

[0031] S4. Cool down to below 30°C, add 0.1% - 3% of the wetting agent and 0.05% - 3% of the pH regulator into the reaction kettle, and stir for 0.5 h - 2 h to obtain the composite binder of the present invention.

[0032] The third object of the present invention is to provide a usage method, which is applied to the composite binder described above. This composite binder can be used for metal binder jet 3D printing.

[0033] Example 1

[0034] A composite binder, by mass percentage, includes: 36% polyacrylic acid (solid content 20%), 30% polyacrylamide (solid content 10%), 1% isomeric tridecanol polyoxyethylene ether, 1% citric acid, 2% triethylamine, and 30% deionized water.

[0035] The preparation method of the composite binder in this example may include the following steps:

[0036] S1. Add 30% deionized water into the reaction kettle, start stirring, add 30% polyacrylamide, heat up to 40°C, and stir for 1.5 h;

[0037] S2. Add 36% polyacrylic acid into the reaction kettle and stir for 1 h;

[0038] S3. Add 1% citric acid into the reaction kettle, heat up to 60°C, and stir for 3 h;

[0039] S4. Cool down to below 30°C, add 1% isomeric tridecanol polyoxyethylene ether and 2% triethylamine into the reaction kettle, and stir for 2 h to obtain the composite binder of this example.

[0040] Example 2

[0041] A composite binder, by mass percentage, includes: 40% polyacrylic acid (solid content 10%), 5% polyacrylamide (solid content 50%), 2% sodium diisooctyl sulfosuccinate, 2% glucose, 3% diisopropylethylamine, and 48% tap water.

[0042] The preparation method of the composite binder in this example may include the following steps:

[0043] S1. Add 48% tap water into the reaction kettle, start stirring, add 5% polyacrylamide, heat up to 60°C, and stir for 1 h;

[0044] S2. Add 40% polyacrylic acid into the reaction kettle and stir for 2 h;

[0045] S3. Add 2% glucose into the reaction kettle, heat up to 90°C, and stir for 2 h;

[0046] S4. Cool down to below 30°C, add % sodium diisooctyl sulfosuccinate and 3% diisopropylethylamine into the reaction kettle, and stir for 1 h to obtain the composite binder of the present invention.

[0047] Example 3

[0048] A composite binder, by mass percentage, includes: 26% polyacrylic acid (solid content 40%), 17.9% polyacrylamide (solid content 20%), 0.1% isooctanol polyoxyethylene ether, 5% hydroxyethyl cellulose, 1% sodium ethoxide, and 50% deionized water.

[0049] The preparation method of the present composite binder may include the following steps:

[0050] S1. Add 50% deionized water into the reaction kettle, start stirring, and add 17.9% polyacrylamide, heat up to 50 °C, and stir for 2 h;

[0051] S2. Add 26% polyacrylic acid into the reaction kettle and stir for 1 h;

[0052] S3. Add 5% hydroxyethyl cellulose into the reaction kettle, heat up to 80 °C, and stir for 2 h;

[0053] S4. Cool down to below 30 °C, add 0.1% isooctyl polyoxyethylene ether and 1% sodium ethoxide into the reaction kettle, and stir for 1 h to obtain the composite binder of the present invention.

[0054] Example 4

[0055] A composite binder, by mass percentage, includes: 28% polyacrylic acid (solid content 30%), 5% polyacrylamide (solid content 40%), 3% polyether-modified polyorganosiloxane, 3% agar, 1% triethanolamine, and 60% deionized water.

[0056] The preparation method of the present composite binder may include the following steps:

[0057] S1. Add 60% deionized water into the reaction kettle, start stirring, and add 5% polyacrylamide, heat up to 40 °C, and stir for 2 h;

[0058] S2. Add 28% polyacrylic acid into the reaction kettle and stir for 1.5 h;

[0059] S3. Add 3% agar into the reaction kettle, heat up to 90 °C, and stir for 3 h;

[0060] S4. Cool down to below 30 °C, add 3% polyether-modified polyorganosiloxane and 1% triethanolamine into the reaction kettle, and stir for 2 h to obtain the composite binder of the present invention.

[0061] Example 5

[0062] A composite binder, by mass percentage, includes: 10% polyacrylic acid (solid content 50%), 12.95% polyacrylamide (solid content 30%), 3% octylphenol polyoxyethylene ether, 4% glycerol, 0.05% ethylenediamine, and 70% tap water.

[0063] The preparation method of the present composite binder may include the following steps:

[0064] S1. Add 70% tap water into the reaction kettle, start stirring, add 12.95% polyacrylamide, heat up to 60 °C, and stir for 2 h;

[0065] S2. Add 10% polyacrylic acid into the reaction kettle and stir for 1.5 h;

[0066] S3. Add 4% glycerol into the reaction kettle, heat up to 70 °C, and stir for 3 h;

[0067] S4. Cool down to below 30 °C, add 3% octylphenol polyoxyethylene ether and 0.05% ethylenediamine into the reaction kettle, and stir for 2 h to obtain the composite binder of the present invention.

[0068] To further demonstrate the excellent performance of the composite binders of the embodiments of the present invention, an existing metal binder for binder jet 3D printing is used as Comparative Example 1 to verify the excellent performance of the composite binders of the embodiments of the present invention.

[0069] Add the binders of Embodiments 1-5 of the present invention and Comparative Example 1 into the printer respectively for binder jet 3D printing of stainless steel metal parts.

[0070] It should be noted that the printing parameters of Embodiments 1-5 and Comparative Example 1 are the same.

[0071] The specific experimental results are shown in Table 1:

[0072] Table 1 Experimental Results

[0073]

[0074] The above embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A composite binder, characterized in that, By mass percentage, it includes: 10% - 40% polyacrylic acid, 5% - 30% polyacrylamide, 0.1% - 3% wetting agent, 1% - 5% accelerator, 0.05% - 3% pH regulator and 30% - 70% solvent.

2. The composite binder according to claim 1, characterized in that, The accelerator includes one or more of agar, glucose, citric acid, carboxymethyl cellulose, glycerol.

3. The composite binder according to claim 1, characterized in that, The wetting agent includes one or more of sodium diisooctyl sulfosuccinate, polyether modified polyorganosiloxane, isooctyl alcohol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether, octylphenol polyoxyethylene ether.

4. The composite binder according to claim 1, characterized in that, The solid content of the polyacrylic acid is 10% - 50%.

5. The composite binder according to claim 1, wherein The solid content of the polyacrylamide is 10% - 50%.

6. The composite binder according to claim 1, characterized in that, The solvent is water.

7. The composite binder according to claim 1, wherein The pH regulator is an organic base.

8. The composite binder according to claim 7, characterized in that, The pH regulator is at least one of triethylamine, ethylenediamine, triethanolamine, diisopropylethylamine, sodium ethoxide.

9. A preparation method, which is applied to the composite binder according to any one of claims 1 to 8, and is characterized in that, It includes the following steps: S1. Add the solvent into the reaction kettle, start stirring, and add the polyacrylamide, heat up to 40°C - 60°C, and stir for 1h - 2h; S2. Add the polyacrylic acid and stir for 1h - 2h; S3. Add the accelerator, heat up to 70°C - 90°C, and stir for 1h - 3h; S4. Cool down to below 30°C, add the wetting agent and pH regulator, and stir for 0.5h - 2h.

10. A method of use, applied to the composite binder according to any one of claims 1 to 8, characterized in that, The composite binder is used for metal binder jet 3D printing.

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