Binder for 3D printing as well as preparation method and use method of binder

Abstract

The invention discloses a binder for 3D printing, which is prepared from the following components in parts by weight: 15 to 60 parts of polyvinyl alcohol, 80 to 160 parts of solvent, 0.5 to 2 parts of cosolvent and 0.2 to 2 parts of surfactant, the polyvinyl alcohol is low-molecular-weight polyvinyl alcohol and high-molecular-weight polyvinyl alcohol; the average molecular weight of the low molecular weight polyvinyl alcohol is 13000 to 50000, and the average molecular weight of the high molecular weight polyvinyl alcohol is 50000 to 150000. According to the binder for 3D printing disclosed by the invention, polyvinyl alcohol is adopted as a base material, and metal powder is solidified; the high-molecular-weight polyvinyl alcohol and the low-molecular-weight polyvinyl alcohol are matched, so that the strength of a printed green body can be ensured, the content of residual carbon in sintering is effectively reduced, and the sintering performance is improved; the wettability of the binder on the surface of the metal powder can be improved through the solvent, and it is ensured that the viscosity and fluidity of the binder are within a proper range; and the cosolvent and the surfactant are added, so that the bonding uniformity of the binder system is effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of additive manufacturing technology, and in particular to a 3D printing adhesive and a preparation method and a use method thereof. Background Art

[0002] The basic principle of binder jet 3D printing technology is to lay down layers of powdered material and then bind the powder particles together by spraying a binder to form a three-dimensional object. In this process, the performance of the binder plays a crucial role in print quality. Existing binders often retain high carbon content during the debinding and sintering processes after printing, which can lead to various problems in the quality and performance of printed parts.

[0003] High residual carbon levels can reduce part density. During the debinding and sintering processes, residual carbon takes up space, hindering the close bonding of powder particles. This prevents ideal part density and compromises part quality. Furthermore, high residual carbon levels can introduce impurities into printed parts. During the debinding and sintering processes, residual carbon can react with other elements to form impurity phases. These impurity phases can affect the part's microstructure and performance, reducing its purity and quality. Summary of the Invention

[0004] Based on this, in order to solve the above technical problems, the present invention provides a low-residual carbon binder for 3D printing and a preparation method and a use method thereof.

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

[0006] A binder for 3D printing comprises, by weight, 15 to 60 parts of polyvinyl alcohol, 80 to 160 parts of a solvent, 0.5 to 2 parts of a cosolvent, and 0.2 to 2 parts of a surfactant; the polyvinyl alcohol is low molecular weight polyvinyl alcohol and high molecular weight polyvinyl alcohol; the low molecular weight polyvinyl alcohol has an average molecular weight of 13,000 to 50,000, and the high molecular weight polyvinyl alcohol has an average molecular weight of 50,000 to 150,000.

[0007] Furthermore, the ratio of the added amount of the low molecular weight polyvinyl alcohol to the high molecular weight polyvinyl alcohol is 1 to 5:1.

[0008] Furthermore, the solvent includes at least one of ethylene glycol monomethyl ether, propylene glycol methyl ether, ethylene glycol, diethylene glycol and ethylene glycol butyl ether.

[0009] Furthermore, the solvent is ethylene glycol monomethyl ether and diethylene glycol; the ratio of the added amount of ethylene glycol monomethyl ether to the added amount of diethylene glycol is 2 to 8:1.

[0010] Furthermore, the surfactant includes at least one of sodium dodecylbenzenesulfonate and sodium dodecyl sulfate.

[0011] Furthermore, the cosolvent is 2-pyrrolidone.

[0012] In a second aspect, the present application further provides a preparation method for use in any of the above-mentioned 3D printing binders, the preparation method comprising the following steps:

[0013] Preparation of solution A: stirring the low molecular weight polyvinyl alcohol and the solvent to obtain solution A;

[0014] Preparation of solution B: stirring the high molecular weight polyvinyl alcohol and the solvent to obtain solution B;

[0015] Preparation of a mixed solution: mixing the solution A and the solution B and stirring them uniformly to obtain the mixed solution;

[0016] To prepare the binder, a cosolvent and a surfactant are added to the mixed solution, and the mixture is stirred evenly to obtain the binder for 3D printing.

[0017] Furthermore, in the step of preparing solution A, the solvent is first mixed and stirred evenly, and then the low molecular weight polyvinyl alcohol is added and mixed and stirred.

[0018] Furthermore, in the step of preparing the solution B, the solvent is first mixed and stirred evenly, and then the high molecular weight polyvinyl alcohol is added and mixed and stirred.

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

[0020] Specifically, the metal binder jet 3D printing includes the following steps:

[0021] S1. Add the 3D printing binder into the inkjet device of the 3D printer, and add the metal powder into the paving device of the 3D printer;

[0022] S2, import the printing model, set the printing parameters, and start the 3D printer;

[0023] S3, the powder spreading device spreads powder to form a powder layer, the print head sprays the 3D printing binder onto the powder layer, and the working box descends by one layer thickness;

[0024] S4, repeating step S3 until printing is completed;

[0025] S5, after solidification and powder removal, a green body of the component is obtained;

[0026] S6. Degreasing and sintering the component green body to obtain a finished component.

[0027] Compared with the prior art, the method of the present invention has the following beneficial effects:

[0028] The 3D printing binder disclosed in this invention uses polyvinyl alcohol as a base material to consolidate metal powder. The ratio of high-molecular-weight polyvinyl alcohol to low-molecular-weight polyvinyl alcohol ensures the strength of the printed green body while effectively reducing the sintering residual carbon content and improving sintering performance. The solvent in the 3D printing binder disclosed in this invention improves the binder's wettability on the metal powder surface and ensures that the binder's viscosity and fluidity are within an appropriate range. The addition of a cosolvent and a surfactant effectively improves the bonding uniformity of the binder system. DETAILED DESCRIPTION

[0029] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the relevant examples. Preferred embodiments of the present invention are provided in the examples. 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 provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] One of the purposes of the present invention is to disclose a binder for 3D printing, which comprises, by weight, 15 to 60 parts of polyvinyl alcohol, 80 to 160 parts of a solvent, 0.5 to 2 parts of a cosolvent, and 0.2 to 2 parts of a surfactant.

[0032] The polyvinyl alcohol (PVA) comprises low-molecular-weight and high-molecular-weight polyvinyl alcohols. The average molecular weight of the low-molecular-weight polyvinyl alcohol is 13,000 to 50,000, while the average molecular weight of the high-molecular-weight polyvinyl alcohol is 50,000 to 150,000. The ratio of low-molecular-weight polyvinyl alcohol to high-molecular-weight polyvinyl alcohol is 1 to 5:1. The low-molecular-weight polyvinyl alcohol quickly spreads on the metal powder surface during the initial binder spraying process and provides initial bonding, while the high-molecular-weight polyvinyl alcohol strengthens the bonding network during the subsequent curing process, improving the green body's strength. The synergistic effect of the low-molecular-weight and high-molecular-weight polyvinyl alcohols ensures excellent bonding performance while helping to reduce carbon residue. This is because the low-molecular-weight polyvinyl alcohol decomposes and volatilizes relatively easily during pyrolysis, reducing carbon residue formation. The addition of a small amount of high-molecular-weight polyvinyl alcohol inhibits the formation of carbonaceous residues to a certain extent, while forming a stable structure that ensures green body strength.

[0033] The solvent is one or more of ethylene glycol monomethyl ether, propylene glycol methyl ether, ethylene glycol, diethylene glycol and ethylene glycol butyl ether. The solvent selected in the present invention has good solubility, which can fully dissolve polyvinyl alcohol to form a uniform and stable solution. The solvent of the present invention has a suitable proportion in the binder system, ensuring that the viscosity and fluidity of the binder are within an appropriate range, facilitating precise spraying through the nozzle during the binder jet additive manufacturing process, and also facilitating the volatilization and removal of the solvent during the subsequent drying and curing process, thereby reducing residual impurities. Preferably, the solvent is ethylene glycol monomethyl ether and diethylene glycol, and the ratio of the added amounts of the two is ethylene glycol monomethyl ether: diethylene glycol = 2 to 8:1. Ethylene glycol monomethyl ether and diethylene glycol can effectively improve the wetting properties of the binder on the surface of the metal powder, and ethylene glycol monomethyl ether as a solvent can also significantly reduce the surface tension of the binder.

[0034] Surfactant selects one or more of sodium dodecylbenzene sulfonate and sodium lauryl sulfate, can reduce the surface tension of binder solution, make binder better wet and spread on metal powder surface, improve bonding uniformity.Simultaneously, surfactant can also regulate the rheological properties of binder, prevent binder from agglomerating, precipitation and other phenomena during storage and use, ensure stable ejection from shower nozzle.Surfactant of the present invention has suitable proportion in binder system, can play surfactant effect, and can not have negative impact on other properties of binder.Solubility promoter can be 2-pyrrolidone, can improve the solubility of solute in solvent, improve bonding uniformity, and prevent binder from agglomerating, precipitation and other phenomena during storage and use, ensure stable ejection from shower nozzle.

[0035] A second object of the present invention is to provide a preparation method for the 3D printing adhesive described in any of the above embodiments. Specifically, the preparation method may include the following steps:

[0036] S110, slowly adding low molecular weight polyvinyl alcohol to the solvent, under stirring conditions, making the low molecular weight polyvinyl alcohol fully dissolved to prepare solution A. This step requires sufficient stirring to ensure that the low molecular weight polyvinyl alcohol is completely dissolved and the solution is uniform and particle-free. Preferably, magnetic stirring or mechanical stirring is adopted, and the stirring speed should be controlled within an appropriate range to avoid generating too many bubbles that affect the solution quality. The dissolution process can be carried out at room temperature or appropriately heated, but the temperature should not be too high to avoid affecting the performance of the polyvinyl alcohol.

[0037] S120, high molecular weight polyvinyl alcohol is slowly added to the solvent, and under stirring, the high molecular weight polyvinyl alcohol is fully dissolved to obtain solution B. This step requires sufficient stirring to ensure that the high molecular weight polyvinyl alcohol is completely dissolved and the solution is uniform and particle-free. Preferably, magnetic stirring or mechanical stirring is used, and the stirring speed should be controlled within an appropriate range to avoid generating too many bubbles that affect the solution quality. The dissolution process can be carried out at room temperature or can be appropriately heated, but the temperature should not be too high to avoid affecting the performance of the polyvinyl alcohol.

[0038] For both solution A and solution B, the concentration of polyvinyl alcohol is preferably 15 to 35 wt.%.

[0039] Furthermore, in step S110 and / or S120, if two or more solvents are used, preferably, the solvents are first mixed and stirred evenly, and then polyvinyl alcohol is slowly added and stirred to dissolve.

[0040] S130: Slowly mix solution A and solution B to obtain a mixed solution. During this mixing step, the two solutions need to be fully stirred to uniformly mix. Preferably, magnetic stirring or mechanical stirring is used, and the stirring time is generally not less than 30 minutes.

[0041] S140. Add a co-solvent to the mixed solution and continue stirring for 10 to 20 minutes to allow the co-solvent to fully diffuse into the solution.

[0042] S150: Slowly add the surfactant to the mixed solution and continue stirring for at least 10 minutes until the surfactant is completely dissolved and evenly dispersed in the solution, thereby producing the 3D printing binder of the present invention. In this step, the stirring speed may be appropriately increased to promote rapid and even dispersion of the surfactant.

[0043] A third object of the present invention is to provide a method of use, which is applied to the 3D printing binder described in any of the above embodiments, that is, using the 3D printing binder for metal binder jet 3D printing.

[0044] Specifically, the method of use may include the following steps:

[0045] S210, measure the properties of the metal powder, dry the powder in a vacuum oven, and then sieve the powder. Place the powder into the powder hopper of the binder jet 3D printer.

[0046] S220 , cleaning the print head to ensure that there are no impurities or residues, adding the adhesive for 3D printing of the present invention into the print head, performing an inkjet test on the print head, and checking the frame loss condition of the print head.

[0047] S230. Import the model to be printed into the software, set the powder layer thickness to 20-80 μm, and determine and set key parameters during the printing process, such as the powder feeding speed, powder spreading speed, roller speed, and heating lamp temperature. Start the printer.

[0048] S240, the powder spreading device spreads powder to form a powder layer, the print head sprays the binder onto the powder layer, and the working box descends by one layer thickness.

[0049] S250: Repeat step S240 until printing is completed.

[0050] S260, placing the working box in a curing device for curing, the curing temperature can be 150-200° C., and the curing time can be 180-600 minutes.

[0051] S270, placing the work box on a powder cleaning table to remove excess powder to obtain a green body of the printed component;

[0052] S280: Place the printed component green body on a ceramic plate and place it in a degreasing furnace for vacuum degreasing at a temperature of 500-800°C for 120-300 minutes.

[0053] S290, placing the degreased green body into a sintering furnace for sintering to obtain a finished component, wherein the sintering temperature is 1200-1400° C. and the sintering time is 120-240 minutes.

[0054] Example 1

[0055] A 3D printing binder comprises, by weight, 18 parts polyvinyl alcohol, 98.4 parts solvent, 1.5 parts 2-pyrrolidone, and 1 part sodium dodecylbenzenesulfonate. The polyvinyl alcohol comprises 15 parts low-molecular-weight polyvinyl alcohol (with an average molecular weight of 15,000) and 3 parts high-molecular-weight polyvinyl alcohol (with an average molecular weight of 100,000). The solvent comprises 26.4 parts diethylene glycol and 72 parts ethylene glycol monomethyl ether.

[0056] The preparation method of the 3D printing adhesive of this embodiment may specifically include the following steps:

[0057] S110, at room temperature, mix 26.4 parts of diethylene glycol and 72 parts of ethylene glycol monomethyl ether, and mechanically stir for 10 minutes to prepare a uniform mixed solvent.

[0058] 15 parts of low molecular weight polyvinyl alcohol were slowly added to the mixed solvent prepared in steps S120 and S110 at a volume of 5 / 6, and mechanically stirred for 30 minutes to fully dissolve the low molecular weight polyvinyl alcohol, thereby preparing solution A.

[0059] 1 / 6 of the mixed solvent prepared in steps S130 and S110 was measured, and 3 parts of high molecular weight polyvinyl alcohol was slowly added thereto, and mechanically stirred for 30 minutes to fully dissolve the high molecular weight polyvinyl alcohol to prepare solution B.

[0060] S140. Slowly mix solution A and solution B, and mechanically stir for 30 minutes to obtain a mixed solution.

[0061] S150: Add 1.5 parts of 2-pyrrolidone to the mixed solution and continue mechanical stirring for 10 minutes.

[0062] S160, slowly add 1 part of sodium dodecylbenzenesulfonate to the mixed solution, and continue mechanically stirring for 10 minutes to obtain the binder for 3D printing of this embodiment.

[0063] The metal components were 3D printed by spraying the binder for 3D printing of this embodiment and the aerosolized 316L metal powder binder. The green strength was tested to be 6.5 MPa, the finished product density was 98.25%, the finished product tensile strength was 512 MPa, the finished product elongation was 50%, and the finished product C content was 0.018%.

[0064] Example 2

[0065] A 3D printing binder comprises, by weight, 30 parts polyvinyl alcohol, 120 parts solvent, 1 part 2-pyrrolidone, and 1 part sodium dodecylbenzenesulfonate. The polyvinyl alcohol comprises 20 parts low-molecular-weight polyvinyl alcohol (with an average molecular weight of 20,000) and 10 parts high-molecular-weight polyvinyl alcohol (with an average molecular weight of 80,000). The solvent comprises 15 parts diethylene glycol and 105 parts ethylene glycol monomethyl ether.

[0066] The preparation method of the 3D printing adhesive of this embodiment may specifically include the following steps:

[0067] S110, at room temperature, mix 15 parts of diethylene glycol and 105 parts of ethylene glycol monomethyl ether, and mechanically stir for 10 minutes to prepare a uniform mixed solvent.

[0068] 2 / 3 of the mixed solvent prepared in steps S120 and S110 was measured, and 20 parts of low molecular weight polyvinyl alcohol was slowly added thereto. The mixture was mechanically stirred for 30 minutes to fully dissolve the low molecular weight polyvinyl alcohol, thereby preparing solution A.

[0069] 1 / 3 of the mixed solvent prepared in steps S130 and S110 was measured, and 10 parts of high molecular weight polyvinyl alcohol was slowly added thereto. The mixture was mechanically stirred for 30 minutes to fully dissolve the high molecular weight polyvinyl alcohol, thereby preparing solution B.

[0070] S140. Slowly mix solution A and solution B, and mechanically stir for 30 minutes to obtain a mixed solution.

[0071] S150: Add 1 part of 2-pyrrolidone to the mixed solution and continue mechanical stirring for 10 minutes.

[0072] S160, slowly add 1 part of sodium dodecylbenzenesulfonate to the mixed solution, and continue mechanically stirring for 10 minutes to obtain the binder for 3D printing of this embodiment.

[0073] The 3D printing binder of this embodiment and the aerosolized 316L metal powder binder were used to spray 3D printed metal components. The green strength was tested to be 7.5 MPa, the finished product density was 99.24%, the finished product tensile strength was 565 MPa, the finished product elongation was 45%, and the finished product C content was 0.023%.

[0074] Example 3

[0075] A 3D printing binder comprises, by weight, 50 parts polyvinyl alcohol, 148 parts solvent, 0.5 parts 2-pyrrolidone, and 0.5 parts sodium lauryl sulfate. The polyvinyl alcohol comprises 25 parts low-molecular-weight polyvinyl alcohol (with an average molecular weight of 30,000) and 25 parts high-molecular-weight polyvinyl alcohol (with an average molecular weight of 130,000). The solvent comprises 28 parts ethylene glycol and 120 parts propylene glycol methyl ether.

[0076] The preparation method of the 3D printing adhesive of this embodiment may specifically include the following steps:

[0077] S110, at room temperature, mix 28 parts of ethylene glycol and 120 parts of propylene glycol methyl ether, and mechanically stir for 10 minutes to prepare a uniform mixed solvent.

[0078] 1 / 2 of the mixed solvent prepared in steps S120 and S110 was measured, and 25 parts of low molecular weight polyvinyl alcohol was slowly added thereto. The mixture was mechanically stirred for 30 minutes to fully dissolve the low molecular weight polyvinyl alcohol, thereby preparing solution A.

[0079] 1 / 2 of the mixed solvent prepared in steps S130 and S110 was measured, and 25 parts of high molecular weight polyvinyl alcohol was slowly added thereto, and mechanically stirred for 30 minutes to fully dissolve the high molecular weight polyvinyl alcohol to prepare solution B.

[0080] S140. Slowly mix solution A and solution B, and mechanically stir for 30 minutes to obtain a mixed solution.

[0081] S150: Add 0.5 parts of 2-pyrrolidone to the mixed solution and continue mechanical stirring for 10 minutes.

[0082] S160: Slowly add 0.5 parts of sodium lauryl sulfate to the mixed solution, and continue mechanically stirring for 10 minutes to obtain the binder for 3D printing of this embodiment.

[0083] The metal components were 3D printed by spraying the binder for 3D printing in this embodiment and the aerosolized 316L metal powder binder. The green strength was tested to be 5.2 MPa, the finished product density was 98.31%, the finished product tensile strength was 524 MPa, the finished product elongation was 48%, and the finished product C content was 0.030%.

[0084] It should be noted that the metal components 3D-printed by binder jetting in Examples 1 to 3 are components of the same structure and model, and the printing parameters and curing, degreasing, and sintering processes are all the same.

[0085] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A 3D printing adhesive, characterized in that: The composition comprises, by weight, 15 to 60 parts of polyvinyl alcohol, 80 to 160 parts of solvent, 0.5 to 2 parts of cosolvent and 0.2 to 2 parts of surfactant; The polyvinyl alcohol is low molecular weight polyvinyl alcohol and high molecular weight polyvinyl alcohol; The average molecular weight of the low molecular weight polyvinyl alcohol is 13,000 to 50,000, and the average molecular weight of the high molecular weight polyvinyl alcohol is 50,000 to 150,000.

2. The 3D printing adhesive according to claim 1, characterized in that: The ratio of the added amounts of the low molecular weight polyvinyl alcohol to the high molecular weight polyvinyl alcohol is 1 to 5:

1.

3. The 3D printing adhesive according to claim 1, wherein The solvent includes at least one of ethylene glycol monomethyl ether, propylene glycol methyl ether, ethylene glycol, diethylene glycol and ethylene glycol butyl ether.

4. The 3D printing adhesive according to claim 2, characterized in that: The solvent is ethylene glycol monomethyl ether and diethylene glycol; The ratio of the added amounts of the ethylene glycol monomethyl ether to the diethylene glycol is 2 to 8:

1.

5. The 3D printing adhesive according to claim 1, characterized in that: The surfactant includes at least one of sodium dodecylbenzenesulfonate and sodium lauryl sulfate.

6. The 3D printing adhesive according to claim 1, characterized in that: The cosolvent is 2-pyrrolidone.

7. A preparation method for the 3D printing binder according to any one of claims 1 to 6, characterized in that: The steps include: Preparation of solution A: stirring the low molecular weight polyvinyl alcohol and the solvent to obtain solution A; Preparation of solution B: stirring the high molecular weight polyvinyl alcohol and the solvent to obtain solution B; Preparation of a mixed solution: mixing the solution A and the solution B and stirring them uniformly to obtain the mixed solution; To prepare the binder, a cosolvent and a surfactant are added to the mixed solution, and the mixture is stirred evenly to obtain the binder for 3D printing.

8. The preparation method according to claim 7, characterized in that In the step of preparing solution A and / or the step of preparing solution B, the solvents are first mixed and stirred uniformly, and then the low molecular weight polyvinyl alcohol or the high molecular weight polyvinyl alcohol is added and mixed and stirred.

9. A method of use, applied to the 3D printing adhesive according to any one of claims 1 to 6, characterized in that: The 3D printing binder is used for metal binder jetting 3D printing.

10. The method of use according to claim 9, characterized in that: The steps include: S1. Add the 3D printing binder into the inkjet device of the 3D printer, and add the metal powder into the paving device of the 3D printer; S2, import the printing model, set the printing parameters, and start the 3D printer; S3, the powder spreading device spreads powder to form a powder layer, the print head sprays the 3D printing binder onto the powder layer, and the working box descends by one layer thickness; S4, repeating step S3 until printing is completed; S5, after solidification and powder removal, a green body of the component is obtained; S6. Degreasing and sintering the component green body to obtain a finished component.