Thermoplastic binders for use in binder jetting additive manufacturing

Abstract

A method of binder jet printing a part including depositing a layer of a powder on a working surface of a binder jet printer and selectively printing a binder solution having a linkable thermoplastic binder into the layer of the powder in a pattern to generate a printed layer. The pattern is representative of a structure of a layer of the part. The linkable thermoplastic binder includes a first polymer strand and a second polymer strand, the first polymer strand includes a first functional group and the second polymer strand includes a second functional group, and the first and second functional groups non-covalently couple the first polymer strand with the second polymer strand. The method of binder jet printing a part also includes curing the linkable thermoplastic binder in the printed layer to generate a layer of a green body part, heating the green body part above a first temperature to remove at least a portion of the linkable thermoplastic binder and generate a brown body part, and heating the brown body part above a second temperature to sinter the powder to generate the part. The part is substantially free of char residue.

1 . A method of binder jet printing a part comprising:
 depositing a layer of a powder on a working surface of a binder jet printer;   selectively printing a binder solution comprising a linkable thermoplastic binder into the layer of powder in a pattern to the generate a printed layer, wherein the pattern is representative of a structure of a layer of the part, wherein the linkable thermoplastic binder comprises a first polymer strand and a second polymer strand, wherein the first polymer strand comprises a first functional group and the second polymer strand comprises a second functional group different from the first functional group, and wherein the first and second functional groups are configured to non-covalently couple the first polymer strand with the second polymer strand;   curing the linkable thermoplastic binder in the printed layer to generate a layer of a green body part;   heating the green body part above a first temperature to remove at least a portion of the linkable thermoplastic binder and generate a brown body part; and   heating the brown body part above a second temperature to sinter the metal powder to generate the part, wherein the part is substantially free of char residue.   
     
     
         2 . The method of binder jet printing the part of  claim 1 , wherein the binder solution comprises a mixture of the linkable thermoplastic binder and a solvent without a surfactant, and wherein curing the printed layer comprises evaporating the solvent. 
     
     
         3 . The method of binder jet printing the part of  claim 1 , wherein the binder solution comprises a mixture of the linkable thermoplastic binder, a solvent, and a surfactant, and wherein curing the printed layer comprises evaporating the solvent. 
     
     
         4 . The method of binder jet printing the part of  claim 1 , wherein a molecular weight of the first polymer strand is between approximately 5K and 150K. 
     
     
         5 . The method of binder jet printing the part of  claim 1 , wherein the molecular weight of the second polymer strand is between approximately 1.5K and 160K. 
     
     
         6 . The method of binder jet printing the part of  claim 1 , wherein the first functional group is a hydrogen bonding acceptor or negatively charged, and the second functional group is a hydrogen bonding donor or positively charged. 
     
     
         7 . The method of binder jet printing the part of  claim 1 , wherein the first and second functional groups comprise a carboxylate group, a hydroxyl group, amine, amide, thiol, or a combination thereof. 
     
     
         8 . The method of binder jet printing the part of  claim 1 , wherein the first polymer strand is polyvinyl alcohol (PVA), polyamides, polyacryl amide, derivatives thereof, and combinations thereof, and wherein the second polymer strand is polyacrylic acid (PAA), polyvinyl pyrrolidone (PVP), polymethyl methacrylate (PMMA), polyvinyl methyl ether-maleic anhydride (PVME-MA), derivatives thereof, and combinations thereof. 
     
     
         9 . The method of binder jet printing the part of  claim 1 , wherein the first polymer strand is a first thermoplastic polymer and the second polymer strand is a second thermoplastic polymer, and wherein the first thermoplastic polymer is different from the second thermoplastic polymer. 
     
     
         10 . The method of binder jet printing the part of  claim 9 , wherein a ratio of the first thermoplastic polymer to the second thermoplastic polymer is 5:1. 
     
     
         11 . The method of binder jet printing the part of  claim 1 , wherein the powder comprises a nickel alloy, titanium alloy, cobalt alloy, aluminum-based material, tungsten, stainless steel, ceramic, or a combination thereof. 
     
     
         12 . The method of binder jet printing the part of  claim 1 , wherein the layer of metal powder has a thickness of between approximately 10 microns and approximately 200 microns. 
     
     
         13 . The method of binder jet printing the part of  claim 1 , wherein selectively printing comprises selectively printing the binder solution with a print head of the binder jet printer. 
     
     
         14 . The method of binder jet printing the part of  claim 1 , comprising drying the green body part before heating the green body part to the first temperature to remove residual solvent used in the binder solution from the green body part. 
     
     
         15 . A part manufactured via a binder jet printing process comprising the steps of:
 depositing a layer of a powder on a working surface of a binder jet printer;   selectively printing a binder solution comprising a linkable thermoplastic binder into the layer of powder in a pattern to generate a printed layer, wherein the pattern is representative of a structure of a layer of the part, wherein the linkable thermoplastic binder comprises a first polymer strand and a second polymer strand, wherein the first polymer strand comprises a first functional group and the second polymer strand comprises a second functional group, and wherein the first and second functional groups are configured to non-covalently couple the first polymer strand with the second polymer strand;   curing the linkable thermoplastic binder in the printed layer to generate a layer of a green body part;   heating the green body part above a first temperature to remove at least a portion of the linkable thermoplastic binder and generate a brown body part; and   heating the brown body part above a second temperature to sinter the powder to generate the part, wherein the part is substantially free of char residue.   
     
     
         16 . The part of  claim 15 , wherein the green body part comprises a strength of between approximately 40 and approximately 118 pounds force (lbF). 
     
     
         17 . The part of  claim 15 , wherein a carbon content of the part is substantially the same or less than a carbon content of the metal powder. 
     
     
         18 . The part of  claim 15 , wherein an oxygen content of the part is substantially the same or less than an oxygen content of the metal powder. 
     
     
         19 . A binder solution configured for use in binder jet printing, comprising:
 a binder solution comprising a linkable thermoplastic binder comprising a first polymer strand and a second polymer strand, wherein the first polymer strand comprises a first functional group and the second thermoplastic polymer strand comprises a second functional group, and wherein the first and second functional groups are configured to non-covalently couple at least a portion of the second polymer strand with at least a portion of the first polymer strand, wherein the binder solution is substantially free of a surfactant.   
     
     
         20 . The binder solution of  claim 19 , wherein the first polymer strand is polyvinyl alcohol (PVA), polyamides, polyacryl amide, derivatives thereof, and combinations thereof, and wherein the second polymer strand is polyacrylic acid (PAA), polyvinyl pyrrolidone (PVP), polymethyl methacrylate (PMMA), polyvinyl methyl ether-maleic anhydride (PVME-MA), derivatives thereof, and combinations thereof. 
     
     
         21 . The binder solution of  claim 19 , wherein a molecular weight of the first polymer strand is between approximately 5K and approximately 150K. 
     
     
         22 . The binder solution of  claim 19 , wherein the molecular weight of the second polymer strand is between approximately 1.5K and approximately 160K. 
     
     
         23 . The binder solution of  claim 19 , wherein the first functional group is a hydrogen bonding acceptor or negatively charged, and the second functional group is a hydrogen bonding donor or positively charged. 
     
     
         24 . The binder solution of  claim 19 , wherein the first and second functional groups comprise a carboxylate group, a hydroxyl group, amide, amine, thiol, or a combination thereof. 
     
     
         25 . The binder solution of  claim 19 , wherein the first polymer strand is a first thermoplastic polymer and the second polymer strand is a second thermoplastic polymer, and wherein the first thermoplastic polymer is different from the second thermoplastic polymer. 
     
     
         26 . The binder solution of  claim 25 , wherein a ratio of the first thermoplastic polymer to the second thermoplastic polymer is approximately 5:1. 
     
     
         27 . The binder solution of  claim 19 , wherein the first polymer strand and the second polymer strand are both polymer strands of the same thermoplastic polymer, and wherein the first polymer strand further comprises the second functional group and the second polymer strand further comprises the first functional group. 
     
     
         28 . The binder solution of  claim 19 , wherein a viscosity of the binder solution is between approximately 2 centipoise (cP) and 200 cP.