Water-based binder solutions for use in additive manufacturing processes

Abstract

To provide an alternative binder solution, a method of monitoring a print head in an additive manufacturing process, and an additive manufacturing method, which enable shortened wick time and allow print head checks using thermal paper.SOLUTION: The water-based binder solution comprises a thermoplastic binder, 4 wt.% or more and 20 wt.% or less of a non-aqueous solvent having a boiling point of 100°C or more and 175°C or less, and water. The thermoplastic binder includes a first polymer strand having a weight average molecular weight (Mw) of 5,000 g / mol to 15,000 g / mol, and at least one of a second polymer strand having a weight average molecular weight (Mw) of 10,000 g / mol to 50,000 g / mol and a third polymer strand having a weight average molecular weight (Mw) of 1,000 g / mol to 5,000 g / mol. A method of monitoring a print head in an additive manufacturing process includes applying the water-based binder solution onto thermal paper.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to additive manufacturing, and more particularly, to binders used in additive manufacturing processes.

Background Art

[0002] Additive manufacturing, also known as 3D printing, is a process of forming three-dimensional parts by stacking materials layer by layer. Binder jetting is an additive manufacturing technique based on using a binder to bind particles of powder to form three-dimensional parts. In particular, the binder is jetted from a print head onto successive layers of powder within a build volume, where the layer of powder and the binder adhere to each other to form a green body part. In some applications, the green body part is suitable for the end use. In other applications, subsequent processing such as binder removal and powder sintering may be required to convert the green body part into a finished three-dimensional part.

Summary of the Invention

[0003] Conventional binder solutions may require a relatively long time to wick into the layer of powder, which can increase the time required before subsequent layers of powder can be deposited into the build volume. An increased wicking time reduces the throughput of the additive manufacturing apparatus and thus productivity. However, some binder solutions that achieve improved wicking times may not form a pattern on thermal paper during print head checks.

[0004] Accordingly, there is a need for alternative binder solutions that shorten the wicking time and enable print head checks using thermal paper.

[0005] Various aspects disclosed herein meet these needs by providing an aqueous binder solution that includes a thermoplastic binder, a non-aqueous solvent having a boiling point of 100 °C or more and 175 °C or less, and water. The thermoplastic binder includes a first polymer strand and at least one of a second polymer strand and a third polymer strand. In various aspects, the first polymer strand has a weight average molecular weight (Mw) of 5,000 g / mol or more and 15,000 g / mol or less, the second polymer strand has a weight average molecular weight of 10,000 g / mol or more and 50,000 g / mol or less, and the third polymer strand has a weight average molecular weight of 1,000 g / mol or more and 5,000 g / mol or less. The first polymer strand is different from each of the second polymer strand and the third polymer strand, and the second polymer strand is different from the third polymer strand. This formulation rapidly penetrates into the powder layer while also having a balance of a shorter curing time compared to conventional binder solutions and the ability to pattern thermal paper during print head checks. Other features and advantages are described in more detail below.

[0006] According to a first aspect A1, an aqueous binder solution for use in additive manufacturing includes a first polymer strand having a weight average molecular weight (Mw) of 5,000 g / mol or more and 15,000 g / mol or less, and at least one of a second polymer strand having a weight average molecular weight (Mw) of 10,000 g / mol or more and 50,000 g / mol or less and a third polymer strand having a weight average molecular weight (Mw) of 1,000 g / mol or more and 5,000 g / mol or less, where the first polymer strand is different from each of the second polymer strand and the third polymer strand, and the second polymer strand is different from the third polymer strand, a non-aqueous solvent having a boiling point of 100 °C or more and 175 °C or less in an amount of 4 weight percent (wt%) or more and 20 wt% or less based on the total weight of the non-aqueous binder solution, and water.

[0007] A second aspect A2 includes the aqueous binder solution according to the first aspect A1, and the non-aqueous solvent is present in the aqueous binder solution in an amount of 6 wt% or more and less than 18 wt% based on the total weight of the aqueous binder solution.

[0008] The third aspect A3 includes the aqueous binder solution according to the first aspect A1, and the non-aqueous solvent includes at least one of 2-methoxyethanol, butanol, 2-butanol, tert-butanol, 1-methoxy-2-propanol, 2-butoxyethanol, isoamyl alcohol, isobutyl alcohol, 2-butoxyethanol, and di(propylene glycol) dimethyl ether.

[0009] The fourth aspect A4 includes the aqueous binder solution according to the first aspect A1, and the first polymer chain includes at least one of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA).

[0010] The fifth aspect A5 includes the aqueous binder solution according to the fourth aspect A4, and the first polymer chain is present in an amount of 5% by weight or more and 20% by weight or less based on the total weight of the aqueous binder solution.

[0011] The sixth aspect A6 includes the aqueous binder solution according to the first aspect A1, and the thermoplastic binder includes the second polymer chain in an amount of 0.5% by weight or more and 7% by weight or less based on the total weight of the aqueous binder solution.

[0012] The seventh aspect A7 includes the aqueous binder solution according to the sixth aspect A6, and the thermoplastic binder includes the third polymer chain in an amount of 0.1% by weight or more and 5 % by weight or less.

[0013] The eighth aspect A8 includes the aqueous binder solution according to the first aspect A1, and the second polymer chain includes at least one of polyvinyl alcohol (PVA), polyacrylamide (PAAm), polyvinyl methyl ether maleic anhydride (PVME-MA), and derivatives thereof.

[0014] Aspect A9 is the ninth aspect, which includes the aqueous binder solution according to Aspect A1, and the third polymer chain includes at least one of polyacrylic acid (PAA), polymethyl methacrylate (PMMA), polyacrylamide (PAAm), and their derivatives.

[0015] Aspect A10 is the tenth aspect, which includes the aqueous binder solution according to Aspect A1, and the aqueous binder solution further includes a surfactant in an amount of 0.1 wt% or more and 2 wt% or less based on the total weight of the aqueous binder solution.

[0016] Aspect A11 is the eleventh aspect, which includes the aqueous binder solution according to Aspect A1, and the total weight of the polymer present in the aqueous binder solution is 5 wt% or more and 20 wt% or less based on the total weight of the aqueous binder solution.

[0017] According to Aspect A12, the twelfth aspect, a method for monitoring a print head of an additive manufacturing process can include placing thermal paper on a working surface and applying an aqueous binder solution on the thermal paper. The aqueous binder solution includes a non-aqueous solvent that is 4 wt% or more and 20 wt% or less based on the total weight of the aqueous binder solution and has a boiling point of 100°C or more and 175°C or less, and a thermoplastic binder. The thermoplastic binder includes a first polymer chain having a weight average molecular weight (Mw) of 5,000 g / mol or more and 15,000 g / mol or less, and at least one of a second polymer chain having a weight average molecular weight (Mw) of 10,000 g / mol or more and 50,000 g / mol or less and a third polymer chain having a weight average molecular weight (Mw) of 1,000 g / mol or more and 5,000 g / mol or less. The first polymer chain is different from each of the second and third polymer chains, and the second polymer chain is different from the third polymer chain.

[0018] Aspect A13 is the thirteenth aspect, which includes the method according to Aspect A12, and the non-aqueous solvent is present in the aqueous binder solution in an amount of 6 wt% or more and less than 18 wt% based on the total weight of the aqueous binder solution.

[0019] Aspect A14 of the 14th includes the method according to Aspect A12 of the 12th, and the non-aqueous solvent includes at least one of 2-methoxyethanol, butanol, 2-butanol, tert-butanol, 1-methoxy-2-propanol, 2-butoxyethanol, isoamyl alcohol, isobutyl alcohol, 2-butoxyethanol, and di(propylene glycol) dimethyl ether.

[0020] Aspect A15 of the 15th includes the method according to Aspect A12 of the 12th, and the first polymer chain includes at least one of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA).

[0021] Aspect A16 of the 16th includes the method according to Aspect A15 of the 15th, and the first polymer chain is present in an amount of 5% by weight or more and 20% by weight or less based on the total weight of the aqueous binder solution.

[0022] Aspect A17 of the 17th includes the method according to Aspect A12 of the 12th, and the thermoplastic binder includes the second polymer chain in an amount of 0.5% by weight or more and 7% by weight or less based on the total weight of the aqueous binder solution.

[0023] Aspect A18 of the 18th includes the method according to Aspect A17 of the 17th, and the thermoplastic binder includes the third polymer chain in an amount of 0.1% by weight or more and 5% by weight or less based on the total weight of the aqueous binder solution.

[0024] Aspect A19 of the 19th includes the method according to Aspect A12 of the 12th, and the total weight of the polymers present in the aqueous binder solution is 5% by weight or more and 20% by weight or less based on the total weight of the aqueous binder solution.

[0025] According to the 20th aspect A20, the additive manufacturing method comprises depositing a layer of powder on a working surface, and selectively depositing an aqueous binder solution containing a thermoplastic binder and a non-aqueous solvent having a boiling point of 100 °C or higher and 175 °C or lower and being 4% by weight or more and 20% by weight or less based on the total weight of the aqueous binder solution on the layer of powder in a pattern representing the structure of the part, wherein the thermoplastic binder comprises a first polymer chain having a weight average molecular weight (Mw) of 5,000 g / mol or more and 15,000 g / mol or less, and at least one of a second polymer chain having a weight average molecular weight (Mw) of 10,000 g / mol or more and 50,000 g / mol or less and a third polymer chain having a weight average molecular weight (Mw) of 1,000 g / mol or more and 5,000 g / mol or less, the first polymer chain being different from each of the second polymer chain and the third polymer chain, the second polymer chain being different from the third polymer chain, selectively applying the aqueous binder solution, and bonding the first polymer chain to at least one of the second polymer chain and the third polymer chain to form a green body part.

[0026] Further features and advantages of the aspects disclosed herein are described in the following detailed description, some of which will be readily apparent to those skilled in the art from the detailed description, or will be understood by practicing the aspects described and disclosed in this specification, including the detailed description, the claims, and the accompanying drawings.

[0027] It should be understood that both the foregoing general description and the following detailed description present aspects intended to provide an overview or framework for understanding the nature and characteristics of the claimed aspects. The accompanying drawings are included to provide further understanding and are incorporated herein and constitute a part of this specification. The drawings illustrate various aspects of the present disclosure and serve to explain the principles and operations together with this specification.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, various embodiments of the aqueous binder solution for use in an additive manufacturing process will be described in detail. In particular, various embodiments of the aqueous binder solution include a thermoplastic binder, a non-aqueous solvent (having a boiling point of 100°C or higher and 175°C or lower) of 4 wt% or more and 20 wt% or less, and water. In this specification, various embodiments of the aqueous binder solution will be described with specific reference to the accompanying drawings.

[0030] In this specification, a range can be expressed as from “about” one particular value or to “about” another particular value. When such a range is expressed, in another embodiment, it includes from one particular value or to another particular value. Similarly, for example, when a value is expressed as an approximate value by use of the antecedent “about”, it will be understood that the particular value forms another embodiment. It will be understood that each end point (upper end and lower end) of each range is important both in relation to the other end point and in its meaning independent of the other end point.

[0031] The directional terms used in this specification (e.g., up, down, right, left, front, back, top, bottom) are used only with reference to the drawn figures and are not intended to mean absolute directions.

[0032] As used in this specification, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus , for example, a reference to a component with “a” includes embodiments having two or more of such components unless the context clearly dictates otherwise.

[0033] The term “weight percent” or “wt%” described in this specification refers to the weight fraction of the components of the aqueous binder solution based on the total amount (i.e., weight) of the aqueous binder solution, unless otherwise specified.

[0034] Unless otherwise specified, the term "boiling point" as used in this specification refers to the boiling point of a component at 1 atmosphere of pressure.

[0035] As used herein, "non-covalent bond" means that a first functional group and a second functional group interact with each other via a weak non-covalent bonding force such as interaction or bonding, link the thermoplastic polymer chains, or bond in other ways. When used herein, the term "weak non-covalent bonding force" is intended to indicate hydrogen bonds, ionic bonds, van der Waals forces, and the like.

[0036] As used herein, the phrases "green body metal part" and "green body part" refer to parts that have not been subjected to heat treatment for removing chemical binders. As used herein, the phrases "brown body metal part" and "brown body part" refer to parts that have been subjected to heat treatment for removing chemical binders. As used herein, "metal part" means a part having a metal material. Although various aspects are described in the context of metal parts, the binder solutions described herein are applicable to a wide variety of parts including, but not limited to, polymer parts and ceramic parts.

[0037] As used herein, the phrase "water-based" includes mixtures, solutions, suspensions, dispersions, etc. that contain water as the main liquid by volume ratio, but may also contain one or more other liquids. Thus, the solvents used in various binder solutions are mostly water. In some aspects, water is present at a concentration of at least about 50% by volume of the binder solution, and in certain aspects, water is present at a concentration of at least about 75% by volume. As used herein, the term "water" includes deionized water, distilled water, and tap water unless otherwise specified. In some aspects, the water is of a grade of type IV or higher according to ASTM D1193.

[0038] In many additive manufacturing processes by binder jetting methods, a chemical binder (e.g., a polymeric adhesive) is used to bond layers of powder together to form a three-dimensional object. The chemical binder may be, for example, a polymeric adhesive that is selectively applied onto a powder bed in a pattern representing a layer of the part to be manufactured.

[0039] Conventional binder solutions containing a relatively large amount (e.g., more than 20 wt%) of a non-aqueous solvent may require a relatively long time to penetrate into the layer of powder, which can increase the time required until subsequent layers of powder can be deposited within the build volume. An increase in the penetration time results in a decrease in the throughput of the additive manufacturing apparatus and, consequently, a decrease in productivity.

[0040] To shorten the penetration time, a portion of the non-aqueous solvent can be replaced with water. However, reducing the amount of the non-aqueous solvent to a relatively small amount (e.g., less than 4 wt%) may result in a solution that does not form a pattern on thermal paper.

[0041] As described above, the aqueous binder solution described herein contains a thermoplastic binder, a non-aqueous solvent (having a boiling point of 100°C or more and 175°C or less) of 4 wt% or more and 20 wt% or less, and water. By setting the non-aqueous solvent to 20 wt% or less, it is ensured that the aqueous binder solution has a relatively short penetration time compared to conventional binder solutions. By setting the non-aqueous solvent to 4 wt% or more, it is ensured that the aqueous binder solution forms a pattern on thermal paper, which is important for monitoring the integrity of the print head since sporadic jetting can lead to a decrease in part quality. These and additional advantages will be described in more detail below.

[0042] In various aspects, the thermoplastic binder can include a first polymer chain and at least one of a second polymer chain and a third polymer chain. As used herein, the term "polymer chain" includes a polymer backbone (main chain) and functional groups grafted thereon. In some aspects, the thermoplastic binder is a thermoplastic binder that decomposes with a generally very low char yield without the need for the presence of oxygen (O2) (e.g., in a vacuum, inert, or reducing atmosphere). Thus, in some aspects, the thermoplastic binder can be cleanly and easily removed from the part during sintering, and a consolidated part that is substantially free of the thermoplastic binder and decomposition products (including, but not limited to, metal oxides and carbides) that can be generated during heat treatment of the printed metal part can be produced.

[0043] The first polymer chain can include at least a first functional group. The functional groups of the first thermoplastic polymer chain can include, by way of example and not limitation, at least one of a hydrogen bond donor, a hydrogen bond acceptor, a negatively charged group, and a positively charged group. For example, in various aspects, the first functional group can be incorporated into the backbone of the polymer chain (e.g., a vinyl backbone, an amide backbone, an acrylic backbone, etc.) or grafted onto the backbone, and the first functional group can be selected from a hydroxyl group, a carboxylate group, an amine, a thiol, an amide, or other suitable functional groups that enable a weak non-covalent bond (e.g., a hydrogen bond) between the first polymer chain and the second or third polymer chain.

[0044] In various embodiments, the first polymer chain may include, but is not limited to, polymers such as at least one of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and derivatives thereof. In some embodiments, the first polymer chain may have a weight average molecular weight (Mw or weight average) of 5,000 g / mol or more and 15,000 g / mol or less. For example, the first polymer chain may have a weight average molecular weight (Mw) of 5,000 g / mol or more and 15,000 g / mol or less, 5,000 g / mol or more and 12,500 g / mol or less, 7,000 g / mol or more and 15,000 g / mol or less, 7,000 g / mol or more and 12,500 g / mol or less, 9,000 g / mol or more and 15,000 g / mol or less, or 9,000 g / mol or more and 12,500 g / mol or less, and may include any range and sub-range therebetween.

[0045] The first polymer chain may be included in the binder solution in an amount of 5 wt% or more and 20 wt% or less, 5 wt% or more and 18 wt% or less, 5 wt% or more and 16 wt% or less, 5 wt% or more and 14 wt% or less, 5 wt% or more and 12 wt% or less, 7 wt% or more and 20 wt% or less, 7 wt% or more and 18 wt% or less, 7 wt% or more and 16 wt% or less, 7 wt% or more and 14 wt% or less, 7 wt% or more and 12 wt% or less, 9 wt% or more and 20 wt% or less, 9 wt% or more and 18 wt% or less, 9 wt% or more and 16 wt% or less, 9 wt% or more and 14 wt% or less, 9 wt% or more and 12 wt% or less, based on the total weight of the aqueous binder solution, and may include any range and sub-range therebetween.

[0046] The thermoplastic binder can include, in addition to the first polymer chain, a second polymer chain, a third polymer chain, or both the second polymer chain and the third polymer chain. The second polymer chain can include at least a second functional group. The functional group of the second thermoplastic polymer chain can include, by way of example but not limited to, at least one of a hydrogen bond donor, a hydrogen bond acceptor, a negatively charged group, and a positively charged group. In some embodiments, the second functional group of the second polymer chain can complement the functional group of the first polymer chain of the thermoplastic binder to facilitate a non-covalent bond between the first polymer chain and the second polymer chain. For example, in various embodiments, the second functional group can be incorporated into the backbone of the polymer chain (e.g., vinyl backbone, amide backbone, acrylic backbone, etc.) or grafted onto the backbone, and the second functional group can be selected from a hydroxyl group, a carboxylate group, an amine, a thiol, an amide, or other suitable functional groups that allow for a weak non-covalent bond (e.g., hydrogen bond) between the first polymer chain and the second polymer chain.

[0047] In various embodiments, the second polymer chain may include, but is not limited to, polymers such as polyvinyl alcohol (PVA), polyamide, polyacrylamide (PAAm), polyvinyl methyl ether maleic anhydride (PVME-MA), and at least one of their derivatives. In some embodiments, the second polymer chain may have a weight average molecular weight (Mw or weight average) of 10,000 g / mol or more and 50,000 g / mol or less. For example, the second polymer chain may have a weight average molecular weight (Mw) of 10,000 g / mol or more and 50,000 g / mol or less, 10,000 g / mol or more and 30,000 g / mol or less, 10,000 g / mol or more and 25,000 g / mol or less, 10,000 g / mol or more and 23,000 g / mol or less, 13,000 g / mol or more and 50,000 g / mol or less, 13,000 g / mol or more and 30,000 g / mol or less, 13,000 g / mol or more and 25,000 g / mol or less, 13,000 g / mol or more and 23,000 g / mol or less, 23,000 g / mol or more and 50,000 g / mol or less, 23,000 g / mol or more and 30,000 g / mol or less, 23,000 g / mol or more and 25,000 g / mol or less, and may include any range and sub-range therebetween.

[0048] When present, the second polymer chain may be included in the binder solution in an amount of 0.5 wt% or more and 7 wt% or less, 0.5 wt% or more and 6 wt% or less, 0.5 wt% or more and 5 wt% or less, 1 wt% or more and 7 wt% or less, 1 wt% or more and 6 wt% or less, 1 wt% or more and 5 wt% or less, 2 wt% or more and 7 wt% or less, 2 wt% or more and 6 wt% or less, 2 wt% or more and 5 wt% or less, 3 wt% or more and 7 wt% or less, 3 wt% or more and 6 wt% or less, or 3 wt% or more and 5 wt% or less, based on the total weight of the aqueous binder solution, and may include any range and sub-range therebetween.

[0049] The third polymer chain may include at least a third functional group different from the first functional group of the first polymer chain and the second functional group of the second polymer chain. The functional group of the third thermoplastic polymer chain may include, by way of example and not limitation, at least one of a hydrogen bond donor, a hydrogen bond acceptor, a negatively charged group, and a positively charged group. In some embodiments, the second functional group of the second polymer chain and the third functional group of the third polymer chain each complement the first functional group of the first polymer chain of the thermoplastic binder to facilitate non-covalent bonding between the first polymer chain, the second polymer chain, and the third polymer chain. For example, in various embodiments, the third functional group may be selected from a hydroxyl group, a carboxylate group, an amine, a thiol, an amide, or other suitable functional groups that allow for weak non-covalent bonding between the first polymer chain and the third polymer chain.

[0050] In various embodiments, the third polymer chain may include, but is not limited to, polymers such as at least one of polyacrylic acid (PAA), polymethacrylic acid (PMAA), polyacrylamide (PAAm), and derivatives thereof. In some embodiments, the third polymer chain may have a weight average molecular weight (Mw or weight average) of 1,000 g / mol or more and 5,000 g / mol or less. For example, the second polymer chain may have a weight average molecular weight (Mw) of 1,000 g / mol or more and 5,000 g / mol or less, 1,500 g / mol or more and 3,000 g / mol or less, or 1,500 g / mol or more and 2,000 g / mol or less, and may include any range and sub-range therebetween.

[0051] In some embodiments, the specific polymer selected as the third polymer chain can be different depending on the specific polymer selected as the first polymer chain and, if present, the specific polymer selected as the second polymer chain. For example, the first polymer chain can be PVP, the second polymer chain can be PVA, and the third polymer chain can be PAA. Combinations of other polymers may be used if their functional groups can form non-covalent bonds with each other. For example, in some embodiments, one of the functional groups is a hydrogen donor and the other functional group is a hydrogen acceptor.

[0052] If present, the third polymer chain can be included in the binder solution in an amount of 0.1 wt% or more and 5 wt% or less, 0.1 wt% or more and 3 wt% or less, 0.1 wt% or more and 2 wt% or less, 0.5 wt% or more and 5 wt% or less, 0.5 wt% or more and 3 wt% or less, 0.5 wt% or more and 2 wt% or less, 1 wt% or more and 5 wt% or less, 1 wt% or more and 3 wt% or less, 1 wt% or more and 2 wt% or less, based on the total weight of the aqueous binder solution, and can include any range and sub-range therebetween.

[0053] As described above, in some embodiments, one or both of the second polymer chain and the third polymer chain may be included in the binder solution. For example, the binder solution may include the first polymer chain and the second polymer chain, may include the first polymer chain and the third polymer chain, or may include the first polymer chain, the second polymer chain, and the third polymer chain. Further, in various embodiments, it should be understood that the first polymer chain is different from each of the second polymer chain and the third polymer chain, and the second polymer chain is different from the third polymer chain. The specific polymer selected as each polymer chain may vary depending on the specific polymer(s) selected as the other polymer chain(s). In some embodiments, the binder solution may include PVP as the first polymer chain and PVA as the second polymer chain. In some embodiments, the binder solution may include PVP as the first polymer chain and PAA as the third polymer chain. In some embodiments, the binder solution may include PVP as the first polymer chain, PVA as the second polymer chain, and PAA as the third polymer chain. Other combinations of polymer chains are possible and contemplated.

[0054] In some embodiments, the polymer of the thermoplastic binder (e.g., the first polymer chain, the second polymer chain, or the third polymer chain) may be included in a total weight of 5 wt% or more and 20 wt% or less, based on the total weight of the aqueous binder solution. For example, the total weight of the polymer may be 5 wt% or more and 20 wt% or less, 5 wt% or more and 19 wt% or less, 5 wt% or more and 18 wt% or less, 10 wt% or more and 20 wt% or less, 10 wt% or more and 19 wt% or less, 10 wt% or more and 18 wt% or less, 12 wt% or more and 20 wt% or less, 12 wt% or more and 19 wt% or less, 12 wt% or more and 18 wt% or less, based on the total weight of the aqueous binder solution.

[0055] The first polymer chain and the second polymer chain or the third polymer chain may be contained in the binder solution in an amount that allows for an appropriate degree of bonding between the first polymer chain and the second polymer chain or the third polymer chain, resulting in a green body part having a green body strength suitable for handling during post-print processing. Additionally, the polymer chains may be contained in an amount such that the binder solution has a viscosity (viscosity by rheometer) of from about 1 centipoise (cP) to about 40 cP. In some embodiments, the binder solution may have a viscosity of from 2 cP to 40 cP, from 2 cP to 35 cP, from 2 cP to 30 cP, from 2 cP to 25 cP, from 2 cP to 20 cP, from 2 cP to 15 cP, from 2 cP to 12 cP, from 4 cP to 40 cP, from 4 cP to 35 cP, from 4 cP to 30 cP, from 4 cP to 25 cP, from 4 cP to 20 cP, from 4 cP to 15 cP, from 4 cP to 12 cP, from 6 cP to 40 cP, from 6 cP to 35 cP, from 6 cP to 30 cP, from 6 cP to 25 cP, from 6 cP to 20 cP, from 6 cP to 15 cP, from 6 cP to 12 cP, from 8 cP to 40 cP, from 8 cP to 35 cP, from 8 cP to 30 cP, from 8 cP to 25 cP, from 8 cP to 20 cP, from 8 cP to 15 cP, from 8 cP to 12 cP, and may include any range and sub-range therebetween.

[0056] The binder solution includes a binder medium in addition to the thermoplastic binder. The binder medium can include, for example, at least one kind of water and one or more non-aqueous solvents. In some embodiments, the aqueous binder solution can include a non-aqueous solvent having a boiling point higher than 100 °C and lower than or equal to 175 °C at 1 atm. The non-aqueous solvent can generally be non-reactive (e.g., inert) so as not to react with the powder material, the thermoplastic binder, or other additives that may be included in the aqueous binder solution. In some embodiments, in addition to being a solvent for the polymer chains, the non-aqueous solvent can act as a wetting agent, delay the evaporation of water in the binder medium, and as a result, maintain the reliability of the deposition and reduce the risk of flash curing during printing. The non-aqueous solvent can be, by way of example but not limited to, at least one of 2-methoxyethanol, butanol, 2-butanol, tert-butanol, 1-methoxy-2-propanol, 2-butoxyethanol, isoamyl alcohol, isobutyl alcohol, 2-butoxyethanol, and di(propylene glycol) dimethyl ether. In various embodiments, the non-aqueous solvent can be at least one of 2-butoxyethanol and di(propylene glycol) dimethyl ether. The specific non-aqueous solvent can be selected based at least in part on the polymer chains of the thermoplastic binder and any other additives that may be included in the aqueous binder solution.

[0057] By restricting the use of non-aqueous solvents having a boiling point exceeding 100 °C, it is considered possible to increase the vapor pressure of the aqueous binder solution while maintaining the viscosity and penetration characteristics of the aqueous binder solution and reducing the necessary curing energy. However, it has been found that solvents having a boiling point exceeding 175 °C generally increase the post-curing time by up to 50%. Thus, in various embodiments, the non-aqueous solvent can have a boiling point higher than 100 °C and lower than or equal to 175 °C, higher than 125 °C and lower than or equal to 175 °C, higher than 150 °C and lower than or equal to 175 °C, or higher than 165 °C and lower than or equal to 175 °C, and can include any range and sub-range therebetween. Further, in some embodiments, the aqueous binder solution does not include a solvent having a boiling point higher than 200 °C, higher than 195 °C, higher than 190 °C, higher than 185 °C, higher than 180 °C, or higher than 175 °C at 1 atmosphere.

[0058] By restricting the amount of the non-aqueous solvent (e.g., to 20 wt% or less), it is ensured that the aqueous binder solution has a relatively short penetration time compared to conventional binder solutions. However, the non-aqueous solvent should be included in an amount (e.g., 4 wt% or more) that forms a pattern on the thermal paper and enables monitoring of the integrity of the print head. Thus, in some embodiments, the non-aqueous solvent can be included in the aqueous binder solution in an amount of 4 wt% or more and 20 wt% or less based on the total weight of the aqueous binder solution. For example, the non-aqueous solvent can be in the aqueous binder solution in an amount of 4 wt% or more and 20 wt% or less, 4 wt% or more and 18 wt% or less, 4 wt% or more and 16 wt% or less, 4 wt% or more and 14 wt% or less, 4 wt% or more and 12 wt% or less, 6 wt% or more and 20 wt% or less, 6 wt% or more and 18 wt% or less, 6 wt% or more and 16 wt% or less, 6 wt% or more and 14 wt% or less, 6 wt% or more and 12 wt% or less, 8 wt% or more and 20 wt% or less, 8 wt% or more and 18 wt% or less, 8 wt% or more and 16 wt% or less, 8 wt% or more and 1 It can be included in an amount of 4% by weight or less, 8% by weight or more and 12% by weight or less, 10% by weight or more and 20% by weight or less, 10% by weight or more and 18% by weight or less, 10% by weight or more and 16% by weight or less, 10% by weight or more and 14% by weight or less, 10% by weight or more and 12% by weight or less, and can include any range and sub-range therebetween.

[0059] In some embodiments, the non-aqueous solvent can include at least one of 2-butoxyethanol and di(propylene glycol) dimethyl ether, and the non-aqueous solvent can be included in the aqueous binder solution in an amount of 4% by weight or more and 20% by weight or less, 4% by weight or more and 18% by weight or less, 4% by weight or more and 16% by weight or less, 4% by weight or more and 14% by weight or less, or 4% by weight or more and less than 12% by weight, based on the total weight of the aqueous binder solution.

[0060] In some embodiments, the non-aqueous solvent can include at least one of 2-methoxyethanol and 2-ethoxyethanol, and the non-aqueous solvent can be included in the aqueous binder solution in an amount of 10% by weight or more and 20% by weight or less, 10% by weight or more and 18% by weight or less, 10% by weight or more and 16% by weight or less, 10% by weight or more and 14% by weight or less, or 10% by weight or more and 12% by weight or less, based on the total weight of the aqueous binder solution.

[0061] In some embodiments, the aqueous binder solution can optionally include one or more additives such as additives that can promote the coating of the powder material of the thermoplastic binder, improve the wettability of the powder material, and improve the surface tension of the aqueous binder solution. Optional additives include surfactants, diluents, viscosity modifiers, dispersants, stabilizers, dyes or other colorants, or other additives known and used in the art. In some embodiments, the aqueous binder solution includes at least one surfactant.

[0062] In some embodiments, the surfactant improves the wetting rate and mediates the interaction between the thermoplastic binder and the powder. Surfactants suitable for use in aqueous binder solutions can include ionic (e.g., zwitterionic, cationic, or anionic) surfactants or non-ionic surfactants, depending on the properties of the thermoplastic binder or powder material. In various embodiments, the surfactant is 2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethanol (e.g., "TRITON® X-100" available from The Dow Chemical Company), polyoxyethylene (80) sorbitan monooleate (e.g., "TWEEN® 80" available from Croda America, Inc.), polyoxyethylene-23-lauryl ether (e.g., "BRIJ® L23" available from Croda America, Inc.), an alkylene oxide copolymer (e.g., "HYPERMER® KD2" available from Croda Advanced Materials), sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and dodecyltrimethylammonium bromide (DTAB), a polypropoxylated quaternary ammonium chloride (e.g., "VARIQUAT® CC42NS" available from Evonik Industries AG), and can be at least one of them.

[0063] By including a surfactant in the binder solution, it is considered possible that the surface tension of the binder solution is reduced, thereby improving the wettability of the powder material by the binder solution. Thus, in some embodiments, the surfactant can be included in the binder solution in an amount of 0.1 wt% or more and 2 wt% or less, 0.1 wt% or more and 1 wt% or less, 0.25 wt% or more and 2 wt% or less, or 0.25 wt% or more and 1 wt% or less, based on the total weight of the binder solution, and can include any range and sub-range included therein.

[0064] In various aspects, the binder medium may contain water, and water may constitute the balance of the solution in various aspects. In various aspects, water may be present in an amount of 70 wt% or more, 75 wt% or more, 80 wt% or more, or 85 wt% or more based on the total weight of the binder solution.

[0065] Furthermore, in various aspects, the green body parts formed using the aqueous binder solution described herein may exhibit a green body strength of 10 MPa or more in each printing direction in the x and y directions. As used herein, the "x direction" refers to the portion having the largest dimension (e.g., length) along the x-axis, and the "y direction" refers to the portion having the largest dimension (e.g., length) along the y-axis. As used herein, the "x-axis" is, unless otherwise specified, the direction in which the print head moves with respect to the shaping plate on which the green body part is manufactured, as shown in FIG. 2. As used herein, the "y-axis" is the direction perpendicular to the x-axis (shown in FIG. 2) such that each layer of the green body part is located in the x-y plane. The "z-axis" is, as shown in FIG. 2, the axis perpendicular to the x-y plane, and the layers are stacked on top of each other along the z-axis. For example, the green body part may exhibit a green body strength of 10 MPa or more and 25 MPa or less, 10 MPa or more and 20 MPa or less, 12 MPa or more and 25 MPa or less, or 12 MPa or more and 20 MPa or less as measured according to a three-point bending test.

[0066] FIG. 1 is a block diagram showing one aspect of a method 100 for manufacturing an article by additive manufacturing using the aqueous binder solution described herein. Refer to FIG. 2, which is a block diagram showing one aspect of an additive manufacturing apparatus 200 that may be used to perform method 100 to facilitate the description of the aspects of method 100.

[0067] As shown in FIG. 1, method 100 begins by depositing a layer of powder material 202 used to manufacture a part (block 102). In various embodiments, the layer of powder material 202 is deposited on the working surface 204 of an additive manufacturing apparatus. The powder material can be a metal powder such as a nickel alloy, cobalt alloy, cobalt-chromium alloy, casting alloy, titanium alloy, aluminum-based material, tungsten, stainless steel, etc. Other powder materials may be used depending on the particular embodiment.

[0068] Next, method 100 continues by selectively applying an aqueous binder solution 206 to the layer of powder material 202 in a pattern representing the structure of the part (block 104). The binder solution 206 can be, for example, any one of the various embodiments of the binder solution described herein. In various embodiments, the binder solution 206 may be selectively printed using a print head 208 operated by a controller 210 based on a CAD design that includes a representation of the layer of the part to be printed.

[0069] In various embodiments, the controller 210 for controlling the print head 208 can include a distributed control system, or any suitable device employing a general-purpose computer or a device specific to a particular application. The controller 210 generally can include a memory 212 that stores one or more instructions for controlling the operation of the print head 208. In some embodiments, the memory 212 can store a CAD design representing the structure of the part to be manufactured. In some embodiments, the CAD design may include distortion compensation and thus may not exactly match the geometric shape of the final desired part. Further, the controller 210 can include at least one processor 214 (e.g., a microprocessor), and the memory 212 can include one or more tangible, non-transitory, machine-readable media that collectively store instructions executable by the processor 214 for controlling the operations described herein.

[0070] After the binder solution 206 is selectively applied to the layer of powder material 202, the thermoplastic binder 216 in the binder solution 206 at least partially coats the outer surfaces of the powder particles, thereby producing binder-coated particles 218. As will be described below, the thermoplastic binder 216 binds the binder-coated particles 218 according to the pattern of the binder solution 206 printed on the layer of powder material 202 to form a layer of a green body part.

[0071] Method 100 can repeat the step of depositing a layer of powder material (block 102) and the step of selectively applying the binder solution 206 to the layer of powder material (block 104) until a desired number of layers are printed, thereby continuing to shape the part layer by layer. The thermoplastic binder 216 of the binder solution 206 binds the successive layers and provides a certain degree of strength (e.g., green body strength) to the green body part so that the integrity of the structure of the green body part is maintained during post-printing processing (e.g., conveying, inspecting, or depowdering). That is, the green body strength provided by the thermoplastic binder 216 of the binder solution 206 maintains the bond between the particles of the powder material 202 within the layer and prevents (e.g., resists or prevents) layer delamination during processing of the green body part and during post-printing processing.

[0072] In various embodiments, method 100 continues to cure the thermoplastic binder (block 106). For example, as described above, the binder solution 206 may be a mixture of the thermoplastic binder 216 and at least one solvent. In various embodiments, the first polymer chain 220 and the second polymer chain 222 of the thermoplastic binder 216 may be bonded to each other via the interaction between the first functional group of the first polymer chain and the second functional group of the second polymer chain. The embodiment shown in FIG. 1 refers to the first polymer chain 220 and the second polymer chain 222, but other polymer chains (e.g., a third polymer chain), if present, can also interact with other polymer chains in the thermoplastic binder 216.

[0073] Some of the solvent in the binder solution 206 can be evaporated during the application (e.g., printing) of the binder solution 206, but a certain amount of the solvent may remain within the layer of the powder material 202. Thus, in some embodiments, the binder solution 206 can be thermally cured at a temperature suitable to evaporate the solvent and enable efficient binding of the printed layer, thereby forming a green body part. Heat may be applied to the green body part using an infrared (IR) lamp or a heating plate, or by placing the green body part within an oven.

[0074] Unbound particles (e.g., powder material not bound by the binder solution 206) are removed from the powder layer before or after the curing step of block 106 to produce a green body part for post-processing steps such as debinding and sintering.

[0075] In the embodiment shown in FIG. 1, method 100 includes removing (e.g., debinding) a portion of the thermoplastic binder from the green body part to produce a brown body part (block 108). In various embodiments, only a portion (i.e., less than the whole) of the thermoplastic binder is removed during debinding of the green body part to provide strength (e.g., green body strength) to the green body part and improve the handling strength of the brown body part obtained prior to sintering.

[0076] During binder removal in block 108, the green body part is heated to sever some of the polymer chains of the thermoplastic binder 216. For example, the green body part may be heated to a temperature of about 600 °C or less, or about 450 °C or less. In some embodiments, the green body part is heated to a temperature of 250 °C to 450 °C. The heating can be carried out, for example, in an oxygen-free environment (e.g., vacuum, inert atmosphere, or a combination of both), or in air in the case of sintering of ceramic parts. In embodiments where binder removal is carried out in an inert atmosphere, argon, nitrogen, or another substantially inert gas can be used. In some embodiments, the binder removal step may be combined with the sintering step to produce the final densified part.

[0077] According to various embodiments, the binder removal step of block 108 can be effective to remove more than about 95% of the thermoplastic binder 216. For example, 95% or more, 96% or more, 97% or more, 98% or more, or 99% or more of the total amount of the thermoplastic binder is removed during binder removal. In some embodiments, the portion of the thermoplastic binder 216 remaining in the brown body part is 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less of the amount of the thermoplastic binder that was present prior to the binder removal step. In some embodiments, the portion of the thermoplastic binder 216 remaining in the brown body part is in the range of 0.05% to 2%, or 0.1% to 1% of the amount of the thermoplastic binder that was present prior to the binder removal step and is removed at a later stage after sintering treatment (e.g., exceeding 600 °C and reaching a higher sintering temperature as described for block 110 for stainless steel, nickel alloy, etc.).

[0078] Following the removal of the binder in block 108, method 100 continues by sintering the green body part to form a consolidated part (block 110). During sintering, the remaining portion of the thermoplastic binder (e.g., the oligomers formed during binder removal) may be removed from the green body part, and the particles of the metal powder can be consolidated to form a consolidated part. After cooling, strength and integrity are imparted to the green body part by sintering so that the consolidated part can be suitable for, for example, mechanical use.

[0079] In some embodiments, sintering may be performed according to a two-step process that includes a pre-sintering step in which the remainder of the thermoplastic binder is removed and a sintering step in which the metal powder particles are consolidated. In some embodiments, sintering may be performed as a single step. During sintering, the green body part may be heated to a temperature higher than 500 °C, higher than 800 °C, or higher than 1000 °C. In some embodiments, heat may be applied by placing the green body part in a furnace or by exposing the green body part to a concentrated energy source such as a laser beam, an electron beam, or another suitable energy source, depending on the particular embodiment.

[0080] As described herein, it is important to monitor the integrity of the printhead because sporadic jetting can lead to a decrease in part quality. FIG. 3 is a block diagram showing an embodiment of method 300 for monitoring a printhead of an additive manufacturing process using the aqueous binder solution described herein. To facilitate the description of the embodiment of method 300, reference is made to FIG. 4, which is a block diagram showing the additive manufacturing apparatus 200 shown in FIG. 1 that can be used to execute method 300.

[0081] As shown in FIG. 3, method 300 begins by placing thermal paper 400 on the working surface 204 of the additive manufacturing apparatus 200 (block 302). The thermal paper 400 is coated with a material containing a developer compound that changes color when contacted with a specific solution. Commercially available examples of suitable thermal paper that can be used in method 300 include Gorilla Supply® thermal paper, POS thermal paper, Methdic thermal paper, and Alliance Supply thermal paper.

[0082] Next, method 300 continues, in block 304, by applying an aqueous binder solution 206 onto the thermal paper 400. The binder solution 206 can be, for example, any one of the various embodiments of the binder solution described herein. In some embodiments, the binder solution 206 may be selectively printed using a print head 208 operated by a controller 410 based on a design that enables an assessment of the print head's integrity (e.g., nozzle cleanliness).

[0083] Method 300 continues, in block 306, by drying the binder solution 206 on the thermal paper 400 at room temperature for a certain period of time (e.g., 10 minutes).

[0084] Method 300 continues, in block 308, by evaluating the thermal paper to determine the integrity of the print head 208. For example, a sporadic pattern, or a pattern that does not match the intended design, may indicate a print head problem (e.g., nozzle clogging) that may need further evaluation. Generally, the print head is given several cleaning cycles to enable robust jetting and proper pattern formation.

[0085] Although the various embodiments described herein are described with reference to methods 100 and 300, it should be understood that the embodiments of the aqueous binder solution described herein can be used with the various methods known and used by those of ordinary skill in the art. In particular, curing and sintering can be achieved in a number of different ways, a number of different processes, and a number of different locations.

Examples

[0086] The following examples are provided to illustrate various aspects and are not intended to limit the claims. Unless otherwise specified, all parts and percentages are by weight. Approximate physical properties, characteristics, parameters, etc. are provided below for the materials used in the various examples, comparative examples, and examples and comparative examples.

[0087] Six aqueous binder solutions (Samples 1 - 6) of the examples and two aqueous binder solutions (Comparative Samples A and B) of the comparative examples were prepared by mixing a thermoplastic binder in the form of one or more polymer chains in water and at least one additional co - solvent. All formulations (Comparative Samples A and B and Samples 1 - 6) contained water as the main solvent. Comparative Sample A and Samples 1 - 3 contained 2 - butoxyethanol, a non - aqueous solvent, which has a boiling point of 171 °C at 1 atm and a vapor pressure of 0.8 mmHg. Comparative Sample B and Samples 4 - 6 contained di(propylene glycol) dimethyl ether (DPGDME), a non - aqueous solvent, which has a boiling point of 175 °C at 1 atm and a vapor pressure of 0.6 mmHg. All formulations (Comparative Samples A and B and Samples 1 - 6) contained polyvinylpyrrolidone (PVP) as the first polymer chain, poly(vinyl alcohol) (PVA) as the second polymer chain, and poly(acrylic acid) (PAA) as the third polymer chain. Also, all formulations (Comparative Samples A and B and Samples 1 - 6) contained the surfactant Triton - X and KD - 2. The formulations for each of Comparative Samples A and B and Samples 1 - 6 are shown in Table 1 below.

[0088]

Table 1

[0089] Green body samples were prepared by filling a circular silicone mold (4 cm × 0.45 cm) with metal powder and adding a binder to make a wet block. The samples were cured in a normal oven at 200 °C or 170 °C for 1 hour. After cooling, the sample blocks were removed from the mold and used for further study. The green body strength was measured using an Instron 3-point tester. The green body strength was reported in Table 1.

[0090] As shown in Table 1, Samples 1 - 3 containing 4 wt%, 6 wt%, and 8 wt% of 2-butoxyethanol respectively had infiltration times comparable to that of Comparative Sample A containing 2 wt% of 2-butoxyethanol. Samples 4 - 6 containing 4 wt%, 6 wt%, and 8 wt% of DPGDME respectively had infiltration times comparable to that of Comparative Sample B containing 2 wt% of DPGDME.

[0091] Here, referring to FIGS. 5 - 12, 40 μL of Comparative Samples A and B (shown as CA and CB) and Samples 1 - 6 (shown as S1 - S6) were drawn into a capillary and applied onto thermal paper in an "X" pattern and dried for 10 minutes. As shown, the formulations of Samples 1 - 6 with 4 wt%, 6 wt%, or 8 wt% of non-aqueous solvent respectively formed a pattern on the thermal pattern. Comparative Samples A and B only wetted the thermal paper and did not form a pattern on the thermal paper.

[0092] As illustrated by Table 1 and FIGS. 5-12, an aqueous binder solution containing 4 wt% to 20 wt% of a non-aqueous solvent has an equivalent penetration time compared to an aqueous binder solution containing less than 4 wt% of the non-aqueous solvent and forms a pattern on thermal paper.

[0093] Additional aspects of the present disclosure are provided by the subject matter of the following appendices.

[0094] (Appendix 1) An aqueous binder solution for use in additive manufacturing, a first polymer chain having a weight average molecular weight (Mw) of 5,000 g / mol or more and 15,000 g / mol or less, at least one of a second polymer chain having a weight average molecular weight (Mw) of 10,000 g / mol or more and 50,000 g / mol or less and a third polymer chain having a weight average molecular weight (Mw) of 1,000 g / mol or more and 5,000 g / mol or less, a non-aqueous solvent having a boiling point of 100° or more and 175° C. or less and being 4 wt% or more and 20 wt% or less based on the total weight of the aqueous binder solution, and water, wherein the first polymer chain is different from each of the second polymer chain and the third polymer chain, and the second polymer chain is different from the third polymer chain, aqueous binder solution.

[0095] (Appendix 2) The aqueous binder solution according to Appendix 1, wherein the non-aqueous solvent is present in the aqueous binder solution in an amount of 6 wt% or more and less than 18 wt% based on the total weight of the aqueous binder solution.

[0096] (Appendix 3) The aqueous binder solution according to Appendix 1 or Appendix 2, wherein the non-aqueous solvent contains at least one of 2-methoxyethanol, butanol, 2-butanol, tert-butanol, 1-methoxy-2-propanol, 2-butoxyethanol, isoamyl alcohol, isobutyl alcohol, 2-butoxyethanol, and di(propylene glycol) dimethyl ether.

[0097] (Appendix 4) The aqueous binder solution according to any one of Appendices 1 to 3, wherein the first polymer chain contains at least one of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA).

[0098] (Appendix 5) The aqueous binder solution according to any one of Appendices 1 to 4, wherein the first polymer chain is present in an amount of 5% by weight or more and 20% by weight or less based on the total weight of the aqueous binder solution.

[0099] (Appendix 6) The aqueous binder solution according to any one of Appendices 1 to 5, wherein the thermoplastic binder contains the second polymer chain in an amount of 0.5% by weight or more and 7% by weight or less based on the total weight of the aqueous binder solution.

[0100] (Appendix 7) The aqueous binder solution according to any one of Appendices 1 to 6, wherein the thermoplastic binder contains the third polymer chain in an amount of 0.1% by weight or more and 5% by weight or less based on the total weight of the aqueous binder solution.

[0101] (Appendix 8) The aqueous binder solution according to any one of Appendices 1 to 7, wherein the second polymer chain contains at least one of polyvinyl alcohol (PVA), polyacrylamide (PAAm), polyvinyl methyl ether maleic anhydride (PVME-MA), and derivatives thereof.

[0102] (Appendix 9) The third polymer chain is an aqueous binder solution according to any one of Appendices 1 to 8, including polyacrylic acid (PAA), polymethyl methacrylate (PMMA), polyacrylamide (PAAm), and derivatives thereof.

[0103] (Appendix 10) The aqueous binder solution according to any one of Appendices 1 to 9, further comprising a surfactant in an amount of 0.1% by weight or more and 2% by weight or less based on the total weight of the aqueous binder solution.

[0104] (Appendix 11) The aqueous binder solution according to any one of Appendices 1 to 10, wherein the total weight of the polymer present in the aqueous binder solution is 5% by weight or more and 20% by weight or less based on the total weight of the aqueous binder solution.

[0105] (Appendix 12) A method for monitoring a print head of an additive manufacturing process, comprising: placing thermal paper on a working surface; coating an aqueous binder solution on the thermal paper, wherein the aqueous binder solution has a boiling point of 100° or higher and 175° C. or lower, and comprises a non-aqueous solvent in an amount of 4% by weight or more and 20% by weight or less based on the total weight of the aqueous binder solution, and a thermoplastic binder; the thermoplastic binder comprises: a first polymer chain having a weight average molecular weight (Mw) of 5,000 g / mol or more and 15,000 g / mol or less; at least one of a second polymer chain having a weight average molecular weight (Mw) of 10,000 g / mol or more and 50,000 g / mol or less and a third polymer chain having a weight average molecular weight (Mw) of 1,000 g / mol or more and 5,000 g / mol or less; the first polymer chain is different from each of the second polymer chain and the third polymer chain, and the second polymer chain is different from the third polymer chain; Method.

[0106] (Appendix 13) The method according to Appendix 12, wherein the non-aqueous solvent is present in the aqueous binder solution in an amount of 6% by weight or more and less than 18% by weight based on the total weight of the aqueous binder solution.

[0107] (Appendix 14) The method according to Appendix 12 or Appendix 13, wherein the non-aqueous solvent contains at least one of 2-methoxyethanol, butanol, 2-butanol, tert-butanol, 1-methoxy-2-propanol, 2-butoxyethanol, isoamyl alcohol, isobutyl alcohol, 2-butoxyethanol, and di(propylene glycol) dimethyl ether.

[0108] (Appendix 15) The method according to any one of Appendices 12 to 14, wherein the first polymer chain contains at least one of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA).

[0109] (Appendix 16) The method according to any one of Appendices 12 to 15, wherein the first polymer chain is present in an amount of 5% by weight or more and 20% by weight or less based on the total weight of the aqueous binder solution.

[0110] (Appendix 17) The method according to any one of Appendices 12 to 16, wherein the thermoplastic binder contains the second polymer chain in an amount of 0.5% by weight or more and 7% by weight or less based on the total weight of the aqueous binder solution.

[0111] (Appendix 18) The method according to any one of Appendices 12 to 17, wherein the thermoplastic binder contains the third polymer chain in an amount of 0.1% by weight or more and 5% by weight or less based on the total weight of the aqueous binder solution.

[0112] (Appendix 19) The method according to any one of Appendices 12 to 18, wherein the total weight of the polymer present in the aqueous binder solution is 5% by weight or more and 20% by weight or less based on the total weight of the aqueous binder solution.

[0113] (Appendix 20) A method of additive manufacturing, depositing a layer of powder on a working surface, selectively applying an aqueous binder solution containing a thermoplastic binder and a non-aqueous solvent having a boiling point of 100°C or higher and 175°C or lower and being 4% by weight or more and 20% by weight or less based on the total weight of the aqueous binder solution, in a pattern representing the structure of a part, wherein the thermoplastic binder has a first polymer chain having a weight average molecular weight (Mw) of 5,000 g / mol or more and 15,000 g / mol or less, has at least one of a second polymer chain having a weight average molecular weight (Mw) of 10,000 g / mol or more and 50,000 g / mol or less and a third polymer chain having a weight average molecular weight (Mw) of 1,000 g / mol or more and 5,000 g / mol or less, has a boiling point of 100°C or higher and 175°C or lower and is a non-aqueous solvent that is 4% by weight or more and 20% by weight or less based on the total weight of the aqueous binder solution, contains water, wherein the first polymer chain is different from each of the second polymer chain and the third polymer chain, and the second polymer chain is different from the third polymer chain, and selectively applying the aqueous binder solution, and bonding the first polymer chain to at least one of the second polymer chain and the third polymer chain to form a green body part.

[0114] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. Accordingly, the present disclosure is intended to embrace such modifications and variations, provided they fall within the scope of the appended claims and their equivalents.

Claims

**Claim 1** An aqueous binder solution (206) for use in additive manufacturing, a thermoplastic binder (216), a first polymer chain (220) having a weight average molecular weight (Mw) of 5,000 g / mol or more and 15,000 g / mol or less, at least one of a second polymer chain (222) having a weight average molecular weight (Mw) of 10,000 g / mol or more and 50,000 g / mol or less and a third polymer chain having a weight average molecular weight (Mw) of 1,000 g / mol or more and 5,000 g / mol or less, comprising, wherein the first polymer chain (220) is different from each of the second polymer chain (222) and the third polymer chain, and the second polymer chain (222) is different from the third polymer chain, a thermoplastic binder (216), having a boiling point of 100°C or more and 200°C or less, and a non-aqueous solvent of 6% by weight or more and 18% by weight or less based on the total weight of the aqueous binder solution (206), water, an aqueous binder solution (206). **Claim 2** The aqueous binder solution (206) according to claim 1, wherein the non-aqueous solvent comprises at least one of 2-methoxyethanol, butanol, 2-butanol, tert-butanol, 1-methoxy-2-propanol, 2-butoxyethanol, isoamyl alcohol, isobutyl alcohol, 2-butoxyethanol, and di(propylene glycol) dimethyl ether. **Claim 3** The aqueous binder solution (206) according to claim 1, wherein the first polymer chain (220) comprises at least one of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA). **Claim 4** The aqueous binder solution (206) according to claim 3, wherein the first polymer chain (220) is present in an amount of 5% by weight or more and 20% by weight or less based on the total weight of the aqueous binder solution (206). **Claim 5** The aqueous binder solution (206) according to claim 1, wherein the thermoplastic binder (216) comprises the second polymer chain (222) in an amount of 0.5% by weight or more and 7% by weight or less based on the total weight of the aqueous binder solution (206). **Claim 6** The aqueous binder solution (206) according to claim 5, wherein the thermoplastic binder (216) comprises the third polymer chain in an amount of 0.1% by weight or more and 5% by weight or less based on the total weight of the aqueous binder solution (206). **Claim 7** A method (300) for monitoring a print head (208) of an additive manufacturing process, comprising: placing thermal paper (400) on a working surface (204); applying an aqueous binder solution (206) onto the thermal paper (400); wherein the aqueous binder solution (206) has a boiling point of 100°C or higher and 200°C or lower, and comprises a non-aqueous solvent of 6% by weight or more and 18% by weight or less based on the total weight of the aqueous binder solution, and a thermoplastic binder (216); the thermoplastic binder (216) comprises a first polymer chain (220) having a weight average molecular weight (Mw) of 5,000 g / mol or more and 15,000 g / mol or less; at least one of a second polymer chain (222) having a weight average molecular weight (Mw) of 10,000 g / mol or more and 50,000 g / mol or less and a third polymer chain having a weight average molecular weight (Mw) of 1,000 g / mol or more and 5,000 g / mol or less; the first polymer chain (220) is different from each of the second polymer chain (222) and the third polymer chain; the second polymer chain (222) is different from the third polymer chain; the method (300). **Claim 8** The method (300) according to claim 7, wherein the non-aqueous solvent comprises at least one of 2-methoxyethanol, butanol, 2-butanol, tert-butanol, 1-methoxy-2-propanol, 2-butoxyethanol, isoamyl alcohol, isobutyl alcohol, 2-butoxyethanol, and di(propylene glycol) dimethyl ether. **Claim 9** The method (300) according to claim 7 or claim 8, wherein the first polymer chain (220) comprises at least one of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA). **Claim 10** An additive manufacturing method (100), comprising: depositing a layer of powder (202) on a working surface (204); selectively applying an aqueous binder solution (206) comprising a thermoplastic binder (216) and a non-aqueous solvent having a boiling point of 100°C or higher and 200°C or lower and being 6% by weight or more and 18% by weight or less based on the total weight of the aqueous binder solution, in a pattern representing the structure of a part, onto the layer of the powder (202), wherein the thermoplastic binder (216) comprises a first polymer chain (220) having a weight average molecular weight (Mw) of 5,000 g / mol or more and 15,000 g / mol or less; at least one of a second polymer chain (222) having a weight average molecular weight (Mw) of 10,000 g / mol or more and 50,000 g / mol or less and a third polymer chain having a weight average molecular weight (Mw) of 1,000 g / mol or more and 5,000 g / mol or less; comprising; selectively applying the aqueous binder solution, wherein the first polymer chain is different from each of the second polymer chain and the third polymer chain, and the second polymer chain is different from the third polymer chain; combining the first polymer chain with at least one of the second polymer chain and the third polymer chain to form a green body part; A method comprising.

Images