Build material composition with metal powder and freeze-dried heteropolymer

A three-dimensional (3D) printing kit, comprising:

• a build material composition, including:
• a host metal powder present in an amount ranging from about 95.00 weight percent to about 99.99 weight percent, based on a total weight of the build material composition, the host metal powder including host metal particles having an average particle size of less than 20 micrometers and the host metal powder having a sintering temperature of from about 500° C. to about 1800° C.;
• and
• a flow additive present in an amount ranging from about 0.01 weight percent to about 5.00 weight percent, based on the total weight of the build material composition, wherein the flow additive consists of particles of a freeze-dried organic material that is pyrolyzable at a pyrolysis temperature less than the sintering temperature of the host metal powder, and wherein the particles of the freeze-dried organic material include a heteropolymer having a hydrophobic component that makes up from about 65% by weight to about 99.9% by weight of the heteropolymer and a hydrophilic component that makes up from about 0.1 by weight to about 35% by weight of the heteropolymer with the hydrophobic component having a lower glass transition temperature compared to the hydrophilic component, wherein:
• the hydrophobic component is formed from a monomer selected from the group consisting of ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, hydroxyethyl acrylate, octadecyl methacrylate, tetrahydrofurfuryl acrylate, alkoxylated tetrahydrofurfuryl acrylate, 2-phenoxyethyl methacrylate, benzyl acrylate, ethoxylated nonyl phenol methacrylate, cyclohexyl methacrylate, trimethyl cyclohexyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, tridecyl methacrylate, isodecyl acrylate, dimethyl maleate, dioctyl maleate, acetoacetoxyethyl methacrylate, diacetone acrylamide, vinyl chloride, vinylidene chloride, N-vinyl imidazole, N-vinylcarbazole, N-vinyl-caprolactam, and combinations thereof;
• and
• the hydrophilic component is formed from an acidic monomer from the group consisting of ethacrylic acid, dimethylacrylic acid, maleic anhydride, maleic acid, vinylsulfonate, cyanoacrylic acid, vinylacetic acid, allylacetic acid, ethylidineacetic acid, propylidineacetic acid, crotonoic acid, fumaric acid, itaconic acid, sorbic acid, angelic acid, cinnamic acid, styrylacrylic acid, citraconic acid, glutaconic acid, aconitic acid, phenylacrylic acid, acryloxypropionic acid, aconitic acid, phenylacrylic acid, acryloxypropionic acid, vinylbenzoic acid, N-vinylsuccinamidic acid, mesaconic acid, methacroylalanine, acryloylhydroxyglycine, sulfoethyl methacrylic acid, sulfopropyl acrylic acid, styrene sulfonic acid, sulfoethylacrylic acid, 2-methacryloyloxymethane-1-sulfonic acid, 3-methacryoyloxypropane-1-sulfonic acid, 3-(vinyloxy)propane-1-sulfonic acid, ethylenesulfonic acid, vinyl sulfuric acid, 4-vinylphenyl sulfuric acid, ethylene phosphonic acid, vinyl phosphoric acid, vinyl benzoic acid, 2 acrylamido-2-methyl-1-propanesulfonic acid, and combinations thereof, and
• wherein the build material composition is spreadable, having a Hausner Ratio less than 1.25;
• and
• a binder agent to be applied to at least a portion of a layer of the build material composition via an inkjet printhead to pattern a cross-section of an intermediate part.

A method for making a three-dimensional printing build material composition, comprising:

• combining a host metal powder and a flow additive to form a build material mixture, the host metal powder being present in an amount ranging from about 95.00 weight percent to about 99.99 weight percent based on a total weight of the build material mixture and the flow additive being present in an amount ranging from about 0.01 weight percent to about 5.00 weight percent based on the total weight of the build material mixture, wherein the host metal powder has a sintering temperature of from about 500° C. to about 1800° C. and includes host metal particles having an average particle size of less than 20 micrometers, and the flow additive consists of particles of a freeze-dried organic material that is pyrolyzable at a pyrolysis temperature that is less than the sintering temperature of the host metal powder with the particles of the freeze-dried organic material including a heteropolymer having a hydrophobic component that makes up from about 65% by weight to about 99.9% by weight of the heteropolymer and a hydrophilic component that makes up from about 0.1% by weight to about 35% by weight of the heteropolymer with the hydrophobic component having a lower glass transition temperature compared to the hydrophilic component, wherein:
• the hydrophobic component is formed from a monomer selected from the group consisting of ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, hydroxyethyl acrylate, octadecyl methacrylate, tetrahydrofurfuryl acrylate, alkoxylated tetrahydrofurfuryl acrylate, 2-phenoxyethyl methacrylate, benzyl acrylate, ethoxylated nonyl phenol methacrylate, cyclohexyl methacrylate, trimethyl cyclohexyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, tridecyl methacrylate, isodecyl acrylate, dimethyl maleate, dioctyl maleate, acetoacetoxyethyl methacrylate, diacetone acrylamide, vinyl chloride, vinylidene chloride, N-vinyl imidazole, N-vinylcarbazole, N-vinyl-caprolactam, and combinations thereof;
• and
• the hydrophilic component is formed from an acidic monomer selected from the group consisting of ethacrylic acid, dimethylacrylic acid, maleic anhydride, maleic acid, vinylsulfonate, cyanoacrylic acid, vinylacetic acid, allylacetic acid, ethylidineacetic acid, propylidineacetic acid, crotonoic acid, fumaric acid, itaconic acid, sorbic acid, angelic acid, cinnamic acid, styrylacrylic acid, citraconic acid, glutaconic acid, aconitic acid, phenylacrylic acid, acryloxypropionic acid, aconitic acid, phenylacrylic acid, acryloxypropionic acid, vinylbenzoic acid, N-vinylsuccinamidic acid, mesaconic acid, methacroylalanine, acryloylhydroxyglycine, sulfoethyl methacrylic acid, sulfopropyl acrylic acid, styrene sulfonic acid, sulfoethylacrylic acid, 2-methacryloyloxymethane-1-sulfonic acid, 3-methacryoyloxypropane-1-sulfonic acid, 3-(vinyloxy)propane-1-sulfonic acid, ethylenesulfonic acid, vinyl sulfuric acid, 4-vinylphenyl sulfuric acid, ethylene phosphonic acid, vinyl phosphoric acid, vinyl benzoic acid, 2 acrylamido-2-methyl-1-propanesulfonic acid, and combinations thereof;
• and
• mixing the build material mixture until a build material composition having a Hausner Ratio less than 1.25 is formed.