THERMALLY CROSSLINKABLE COMPOSITION FOR USE AS A BINDER IN A BINDER JETTING PROCESS

Abstract

The present invention relates to the use of a liquid composition comprising one or more monomers for the production of a polyester, of a polyamide or of a polyesteramide, where at least one monomer is at least trifunctional, as binder in the binder-jetting process. The invention further relates to a process for the production of a shaped body by binder jetting.

Claims

1-7. (canceled)

8: A process for the production of a shaped body by binder jetting, comprising: (i) applying a powder layer on a construction platform or on a previously applied powder layer, (ii) printing a liquid composition on defined areas of the powder layer which has been applied in step (i), the liquid composition comprising one or more monomers for the preparation of a polyester, polyamide or polyesteramide, where at least one monomer is at least trifunctional, and a solvent, (iii) applying a further powder layer on the powder layer which has been subjected to the printing step (ii) and printing a liquid composition on defined areas of the further powder layer, the liquid composition comprising: one or more monomers for the preparation of a polyester, polyamide or polyesteramide, where at least one monomer is at least trifunctional, and a solvent, (iv) optionally applying further powder layers required for the production of the shaped body and printing a liquid composition on defined areas of each of the further powder layers, the liquid composition comprising one or more monomers for the preparation of a polyester, polyamide or polyesteramide, where at least one monomer is at least trifunctional, and a solvent, (v) thermally treating the liquid composition applied by printing, thereby forming a polyester, a polyamide or a polyesteramide and obtaining a shaped body wherein the powder within the shaped body is bonded by the polyester, polyamide or polyesteramide.

9: The process of claim 8, wherein the powder is a metal powder, a ceramic powder, a quartz sand powder or a plastics powder or a mixture of at least two of these powders.

10: The process of claim 8, wherein the thermal treatment in step (v) takes place at a temperature of at least 130° C.

11: The process of claim 8, wherein, after step (v), one or more further thermal treatment step(s) are carried out in order to remove the polyester, the polyamide or the polyesteramide from the shaped body by thermal decomposition and to sinter the powder.

12. (canceled)

13: The process of claim 8, wherein the polyester, polyamide or polyesteramide is prepared by polycondensation.

14: The process of claim 8, wherein the at least trifunctional monomer is a compound having at least three functional groups A.sup.1, A.sup.2 and A.sup.3, where the functional groups A.sup.1, A.sup.2 and A.sup.3 are, independently from each other, a hydroxy group, an amino group, a carboxylic acid group or salt of said carboxylic acid group, a carboxylic ester group or an acyl halide group.

15: The process of claim 8, wherein the at least trifunctional monomer is a compound having at least three functional groups A.sup.1, A.sup.2 and A.sup.3, where two of the functional groups A.sup.1-A.sup.3 together form a carboxylic anhydride group or a cyclic ether group and the third functional group is a hydroxy group, an amino group, a carboxylic acid group or salt of said carboxylic acid group, a carboxylic ester group or an acyl halide group.

16: The process of claim 8, wherein the at least trifunctional monomer is a polyol having at least 3 hydroxy groups; an aromatic trihydroxy compound; a polyamine having at least 3 amine groups; a hydroxycarboxylic acid in which the sum total of the hydroxy groups and the carboxylic acid groups is at least 3; an amino acid in which the sum total of the amino groups and the carboxylic acid groups is at least 3; a hydroxyamino acid; a polycarboxylic acid having at least 3 carboxylic acid groups; or a mixture of at least two of the abovementioned compounds.

17: The process of claim 8, wherein the liquid composition comprises, as at least trifunctional monomers, (a) a polyol having at least 3 hydroxy groups or a polyamine having at least 3 amine groups or a mixture thereof; and (b) at least one of the following compounds: (b1) a hydroxycarboxylic acid in which the sum total of the hydroxy groups and the carboxylic acid groups is at least 3, (b2) an amino acid in which the sum total of the amino groups and the carboxylic acid groups is at least 3, (b3) a hydroxyamino acid, (b4) a polycarboxylic acid containing at least 3 carboxylic acid groups or an anhydride of said polycarboxylic acid.

18: The process of claim 8, wherein the liquid composition comprises one or more bifunctional monomers.

19: The process of claim 18, wherein the bifunctional monomer is one of the following compounds (i)-(iii) or a mixture of at least two of these compounds: (i) a compound having a functional group A and a functional group B, where, the functional group A is an amino group or a hydroxy group, and the functional group B is a carboxylic acid group or salt of said carboxylic acid group, a carboxylic ester group or an acyl halide group; (ii) a compound having a functional group A and a functional group A′, where the functional groups A and A′ are, independently from each other, a carboxylic acid group or salt of said carboxylic acid group, a carboxylic ester group or an acyl halide group, or where the functional groups A and A′ together form a carboxylic anhydride group; (iii) a compound having a functional group B and a functional group B′, where the functional groups B and B′ are, independently from each other, a hydroxy group or an amino group, or where the functional groups B and B′ together form a cyclic ether group.

Description

EXAMPLES

[0157] A liquid binder of the following composition was used:

[0158] 6.9% by weight of glycerol, 16.1% by weight of citric acid, 2.0% by weight of glycine, 75% by weight of isopropanol. In the polyester synthesis that takes place during curing, glycerol and citric acid served as monomers having a functionality of at least 3 (glycerol: trifunctional monomer; citric acid: tetrafunctional monomer).

[0159] The powder used was a stainless steel powder.

[0160] The stainless steel powder was applied layer-by-layer to a construction platform in a construction chamber for binder jetting, and each of the powder layers applied was printed with the liquid binder in the predefined areas. After application of all of the powder layers required for the production of the shaped body, curing was carried out at a temperature of 180° C. for 3 hours.

[0161] The curing gave a green body of high mechanical strength.

[0162] The liquid binder composition enables long residence times in the printing system without blockage of nozzles in the print head and—after the printing of the powder layer—rapid drying and also rapid curing at relatively low temperature, resulting in a green body of high strength (i.e. high green strength). The binder moreover has good thermal removability after curing, which means that after sintering it is possible to obtain a shaped body which contains no problematic residues of the cured binder.