Method for producing shaped bodies
A generative process for the manufacture of three-dimensional mouldings is characterized by constructing the moulding stepwise by site-specific delivery of a structure-forming material in liquid form, where a second material is additionally delivered as a supportive material into regions which are intended to remain free from the structure-forming material, and is removed once the structure-forming material has been solidified. The supportive material exhibits low shrinkage upon cooling and is particularly stable in the cooled state and further exhibits low surface roughness.
1. A process for the additive manufacturing of mouldings by site-specific delivery of a structure-forming material (“sfm”) comprising:
delivering simultaneously or at staggered intervals at least one supportive material (“sm”) into regions which are to remain free from sfm,
where the delivery of the sm is achieved by a device which has at least one delivery unit for the sm positionable in x-, y- and z-directions with a precision of at least ±100 μm which delivers sm in a site-specific manner in an x, y-operating plane and also in the z-direction, successively constructs a supportive structure made of sm for the mouldings,
with the proviso that the sm, at 70° C. is a pseudoplastic, viscoelastic composition comprising
(A) a polyether composition comprising
(A1) at least one first polyether having a melting point lower than 35° C. and
(A2) at least one second polyether having a melting point of 35° C. or higher,
wherein the second polyether (A2) is present in an amount of 5% by weight or more to 70% by weight or less based on the total weight of the polyether composition (A),
(B) at least one particulate rheological additive, and
(C) optionally other additional substances,
the polyether composition (A) having a shear viscosity of at most 10 Pas measured at 70° C. with shear rate 100 s −1 using a rheometer with plate-on-plate geometry with a diameter of 25 mm at a gap width of 300 μm,
has a storage modulus G′ of at least 100 Pa, measured at 70° C., and a solidification temperature of from 20° C. or more up to 60° C. or less,
and once the manufacturing of the moulding has been concluded, removing the sm from the moulding, wherein the melting points are determined by DSC according to DIN EN ISO 11357-3, and the solidification temperature is obtained from a temperature sweep measurement of a sample under dynamic shear stress on a rheometer with plate-on-plate geometry, diameter 25 mm and gap width of 300 μm, wherein the sample is cooled in a stepwise manner from 70° C. to 20° C. at a cooling rate of 1.5 K/min and the sample is stressed with a constant deformation of 0.1% at a constant frequency of 10 Hz.
2. The process of claim 1 , wherein the first polyether (A1) and the second polyether (A2) are independently of one another selected from the group consisting of polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymers, and monoethers thereof.
3. The process of claim 1 , wherein the first polyether (A1) is selected from the group consisting of
polyethylene glycols and/or monoethers thereof having a number-average molar mass Mn of less than 1000 g/mol,
polypropylene glycols and/or monoethers thereof having a number-average molar mass Mn of less than 2000 g/mol and
polyethylene glycol-polypropylene glycol copolymers and/or monoethers thereof having a number-average molar mass Mn of less than 2000 g/mol, wherein the number-average molar mass Mn is determined by size exclusion chromatography.
4. The process of claim 1 , wherein the second polyether (A2) is selected from the group consisting of
polyethylene glycols and/or monoethers thereof having a number-average molar mass Mn of 1000 g/mol or more and
polyethylene glycol-polypropylene glycol copolymers or monoethers thereof having a number-average molar mass Mn of 2000 g/mol or more,
wherein the number-average molar mass Mn is determined by size exclusion chromatography.
5. The process of claim 3 , wherein the second polyether (A2) is selected from the group consisting of
polyethylene glycols and/or monoethers thereof having a number-average molar mass Mn of 1000 g/mol or more and
polyethylene glycol-polypropylene glycol copolymers or monoethers thereof having a number-average molar mass Mn of 2000 g/mol or more,
wherein the number-average molar mass Mn is determined by size exclusion chromatography.
6. The process of claim 1 , wherein the first polyether (A1) is a polyethylene glycol having a number-average molar mass Mn of less than 1000 g/mol, wherein the number-average molar mass Mn is determined by size exclusion chromatography.
7. The process of claim 1 , wherein the second polyether (A2) is a polyethylene glycol having a number-average molar mass Mn of 1000 g/mol or more, wherein the number-average molar mass Mn is determined by size exclusion chromatography.
8. The process of claim 6 , wherein the second polyether (A2) is a polyethylene glycol having a number-average molar mass Mn of 1000 g/mol or more, wherein the number-average molar mass Mn is determined by size exclusion chromatography.
9. The process of claim 1 , wherein the first polyether (A1) is a polyethylene glycol having a number-average molar mass Mn of less than 800 g/mol, wherein the number-average molar mass Mn is determined by size exclusion chromatography.
10. The process of claim 1 , wherein the second polyether (A2) is a polyethylene glycol having a number-average molar mass Mn of 2000 g/mol or more, wherein the number-average molar mass Mn is determined by size exclusion chromatography.
11. The process of claim 9 , wherein the second polyether (A2) is a polyethylene glycol having a number-average molar mass Mn of 2000 g/mol or more, wherein the number-average molar mass Mn is determined by size exclusion chromatography.
12. The process of claim 1 , wherein the proportion of the second polyether (A2) based on the total weight of the polyether composition (A) is 10% by weight or more to 65% by weight or less.
13. The process of claim 1 , wherein the proportion of the second polyether (A2) based on the total weight of the polyether composition (A) is 15% by weight or more to 60% by weight or less.
14. The process of claim 1 , wherein component (B) comprises at least one hydrophobic silica having a silanol group density of less than 1.8 silanol groups per nm 2 determined by acid-base titration.
15. The process of claim 1 , wherein component (B) comprises at least one hydrophobic silica having a methanol number of at least 30, wherein the methanol number is the percentage proportion of methanol which must be added to a water phase to achieve complete wetting of the silica, wherein complete wetting means a complete sinking of the silica in the water-methanol test liquid.
16. The process of claim 1 , wherein the sm of the moulding is removed mechanically or by dissolution in a solvent.