METHOD FOR TREATMENT OF ELEMENTS OBTAINED BY AN ADDITIVE MANUFACTURING PROCESS

Abstract

A method for treatment of elements obtained by an additive manufacturing process comprises applying on the element a treating agent in liquid or gaseous form.

Claims

1. A method for treatment of polymer elements obtained by a powder-based additive manufacturing process comprising applying on the element a treating agent in liquid and/or gaseous form comprising at least one monovalent or polyvalent alcohol, and thereafter removing the treating agent and optionally recovering at least part of the treating agent.

2. The method according to claim 1, wherein the treating agent comprises at least one substituted or unsubstituted aliphatic C.sub.1-C.sub.10 alcohol or substituted or unsubstituted aromatic C.sub.6-C.sub.12 alcohol or a mixture thereof.

3. The method of claim 1, wherein the alcohol is ethanol, propanol, isopropanol, butanol, glycol, glycerol, benzyl alcohol, chloro benzene, trsiethylene glycol, 2,2,2-trifluoroethanol, hexafluoroisopropanol or a mixture thereof

4. The method of claim 1, wherein the treating agent comprises at least one additional solvent and/or at least one plasticizer.

5. The method of claim 4, wherein the additional solvent is esters, ethers, ketones, lactones, or DMSO and/or wherein the plasticizer is aromatic esters, aliphatic esters, cycloaliphatic esters, or bio-based compounds, wherein optionally the solvent is DMSO or γ-butyrolactone, and/or wherein optionally the plasticizer is at least one of phthalates, benzoates, citrates, adipates, sebacates, cyclohexane dicarboxylic acid alkyl esters, fatty oils, or essential oils.

6. The method of claim 1, wherein the treating agent is applied for a period of about 1 second to about 60 minutes.

7. The method of claim 1, wherein the treating agent comprises hexafluoroisopropanol and is applied in liquid form, optionally at a temperature in the range from about −3° C. up to the boiling point of the solvent used for a period of about 1 second to about 35 minutes; or is applied in vapor form, optionally for a time period of about 2 minutes to about 45 minutes.

8. The method of claim 1, wherein the treating agent comprises at least ethanol and is applied at a temperature in the range of about 100° C. to about 165° C. for a period of about 5 seconds to about 40 minutes.

9. The method of claim 1, wherein the treating agent is removed by extracting the vapor and/or drying the elements in an oven for a period of about 5 minutes to about 48 hours.

10. The method of claim 1, wherein the treating agent is removed by contacting treated elements with an aqueous composition and thereafter by drying the elements.

11. The method of claim 1, wherein the treating agent comprises HFIP and the treating agent is applied under a pressure of about 0.01 to about 0.9 bar.

12. The method of claim 1 further additionally comprising a functionalizing step, which comprises applying at least one functionalizing agent on the element during or after treatment with the treating agent.

13. The method of claim 1 wherein in addition to the application step at least one further application step and/or at least one functionalising step, which comprises applying at least one functionalizing agent on the element during or after treatment with the treating agent, are carried out.

14. The method of claim 1 wherein during at least one of the application steps and/or functionalising steps distribution means are used, wherein the distribution means optionally is a microwave, a fan propeller, and/or an ultrasound unit.

15. The method of claim 1 wherein a post-processing step is carried out after application of the treating agent and optionally a functionalising step, wherein the post-processing step comprises treating the elements with a post-processing composition.

16. The method of claim 1, wherein the functionalizing agent comprises at least one agent a colorant, a dye, a pigment, a fiber, a hardening agent, a metal powder, an inorganic pigment or powder, an electrostatic discharge agent, a filler, a base, a finishing agent, and/or a plasticizer.

17. The method of claim 1, wherein a colorant or dye solution is applied having a temperature in the range of about 50 to about 95° C., wherein the temperature is maintained over the treatment period or is increased or decreased continuously or incrementally.

18. The method of claim 1, wherein the element has been obtained by a sintering/melting process, such as selected from the group consisting of a multi jet fusion process (MJF), a selective laser sintering process (SLS), a high-speed sintering process (HSS), a binder-jetting process, and a light induced process.

19. The method of claim 1, wherein the polymer is polyamide selected from the group consisting of polyamide 6 (PA6), polyamide 6.6 (PA6.6), polyamide 11 (PA11), polyamide 12 (PA12), PA 4.6 (PA4.6), polyamide 612 (PA612), polyphthalamide (PPA); a thermoplastic polyamide or co-polyamide, and a blended or filled polyamide, or a copolymer, blend, or mixture thereof, polymethyl methacrylate (PMMA), polyoxy methylene (POM), polyethylene terephthalate (PET), polyether block amide (PEBA), poly carbonate (PC), polyethylene furanoate (PEF), polylactide (PLA), polyvinylchloride (PVC), thermoplastic polyurethane (TPU), thermoplastic polyamides (TPA), thermoplastic copolyester compounds (TPC), polyurethane, polysulfone, polyetherimide (PEI), styrene polymer or copolymer, or a thermoplastic polymer comprising polyetherimide and polycarbonate, or copolymers, blends, or mixtures of these polymers.

20. (canceled)

21. The method of claim 1, wherein a treatment agent recovery step is carried out by removing treating agent with a filtration unit with absorbed solvent and desorbing the solvent.

22. The method of claim 1, wherein the treating agent is applied until the surface roughness has been reduced by 2 to 20 μm and the resultant element surface roughness Ra is from 0.3 to 10 μm.

23. (canceled)

24. A device for treatment of an element obtained by an additive manufacturing process comprising a chamber with a lid, at least one element contact area, a dosing unit for treating agent comprising a solvent feed line for feeding solvent into chamber from a solvent container, and a dosing means, optionally at least one distributor, a fan propeller, a withdrawal unit comprising a pump, and/or at least one recovery unit comprising at least one filter unit or a recovery trap.

25. The device of claim 24, wherein the chamber is a vacuum unit or chamber comprising a microwave and/or ultrasound unit.

Description

EXAMPLE 1

[0160] A vacuum device as shown in FIG. 2 was used to treat polyamide elements: (having a grey color) obtained by an MJF process. The elements had a surface roughness of R.sub.a=9; R.sub.z=50. Elements 106 were laid on an element contact area 105 of vacuum unit 101 and the unit was closed with vacuum lid 102. Engine 103 driving fan propeller 104 was switched on to provide for circulation of air. Then vacuum pump 112 was switched on and air was withdrawn until pressure gauge 108 showed a pressure of 0.1 bar (absolute). Then vacuum pump 112 was switched off. 5 ml of HFIP as treating agent 114 were injected into vacuum chamber 101 via solvent feed line 109. The solvent vaporized and the HFIP vapor was circulated in the vacuum chamber for 10 minutes. The vacuum unit was neither cooled nor heated. After 10 minutes circulation vacuum pump 112 was switched on again and venting valve 119 was opened, whereby solvent was withdrawn from the vacuum chamber and fed into filter element 110. Venting valve 119 was adapted such that about the same volume of air was introduced as volume of solvent was withdrawn. In other words, the pressure remained in about the same range during this step. The withdrawing step was carried out for about 30 minutes. After 30 minutes vacuum pump 112 was switched off. Engine 103 and thereby also fan propeller 104 was also switched off. Then vacuum lid 102 was opened and elements 106 were removed and dried for 4 hours in a convection oven at 70° C.

[0161] The elements obtained were black and smooth and had clear contours. The edges were sharp, not rounded, the surface area was smooth without grooves and elevations, and mechanically strong. The roughness could be reduced significantly:

[0162] Roughness of the element after treatment: R.sub.a=1.1; R.sub.z=7

EXAMPLE 2

[0163] A vacuum device as shown in FIG. 2 was used to treat polyamide elements obtained by an SLS process. The elements had a surface roughness of R.sub.a=12; R.sub.z=64. Elements 106 were laid on an element contact area 105 of vacuum unit 101 and the unit was closed with vacuum lid 102. Engine 103 driving fan propeller 104 was switched on to provide for circulation of air. Then vacuum pump 112 was switched on and air was withdrawn until pressure gauge 108 showed a pressure of 0.1 bar (absolute). Then vacuum pump 112 was switched off. 5 ml of HFIP as treating agent 114 were injected into vacuum chamber 101 via solvent feed line 109. HFIP was vaporized and the HFIP vapor was circulated in the vacuum chamber for 15 minutes. The vacuum unit was neither cooled nor heated. After 15 minutes circulation vacuum pump 112 was switched on again and venting valve 119 was opened, whereby solvent was withdrawn from the vacuum chamber and fed into filter element 110. Venting valve 119 was adapted such that about the same volume of air was introduced as volume of solvent was withdrawn. In other words, the pressure remained in about the same range during this step. The withdrawing step was carried out for about 45 minutes. After 45 minutes vacuum pump 112 was switched off. Engine 103 and thereby also fan propeller 104 was also switched off. Then vacuum lid 102 was opened and elements 106 were removed and were dried for 12 hours under an exhaust hood and thereafter were dried in a convection oven at 70° C. for 4 hours. The elements obtained after this treatment had clear contours, minimal rounding of edges, no grooves or elevations. The surface was smooth.

[0164] Roughness after treatment: R.sub.a=1.7; R.sub.z=10

EXAMPLE 3

[0165] 3D elements are treated with aliphatic alcohol. For this process 3D elements are placed on an element contact area in the form of a platform that can be lowered. A pressure vessel is filled to about half of it with ethanol. The same process is carried out with other alcohols containing 3-6 carbon atoms and with a mixture of one of these alcohols with at least one other solvent. The elements are first deposited on a tray or platform without contact to the treating agent. The vessel is pressurized with compressed air or another process gas, such as a protective gas, up to a pressure of about 20 bar. The liquid treating agent optionally with process gas is heated to a temperature of about 135° C. The heating can be carried out in any manner known to the skilled person in a vessel suitable for heating of alcohols, for example a heating chamber with a double wall. Once the required process temperature has been reached, the lowerable platform with elements is lowered into the alcoholic liquid for about 5 minutes. During this time the surface of the elements is softened and begins to smoothen. After 5 minutes the platform with the elements is lifted up, thereby the elements are contacted with cooler air. By cooling the smoothening process is stopped and the surface becomes strong and smooth. After post-processing elements are removed.

[0166] Once the desired surface quality is achieved, the temperature is lowered to about 50° C. before the elements can be removed.

[0167] The process is carried out again as described above, however, the pressure in the vessel is decreased by evacuating the vessel, the pressure is lowered to about 1 mbar. In this embodiment the treating agent is introduced into the process vessel only after a vacuum is reached, e.g. by opening a valve. The further process steps is carried out as described above, wherein, however, the platform is not lowered.

[0168] In an alternative process, the smoothening process can be stopped slower so that the surface of the elements is in a transition phase where the surface is still soft. This is useful if a functionalizing step is carried out following the smoothening step or when a second smotthening step follows. This improves finishing of the surface while maintaining the exact geometric contours. Another way to stop the smoothening process is to introduce liquid nitrogen into the pressure vessel. This can be advantageous when the inlet pressure is kept as low as possible by introducing compressed air and/or process gas, preferably if the pressure vessel is evacuated before the smoothening phase is initiated.

EXAMPLE 4

[0169] In this example elements prepared from thermoplastic polyetheramide (e.g. available as PEBA 2301 from EOS GmbH Electro Optical Systems, Germany) (TPA or TPE-A) were treated.

[0170] Treating agent: Monovalent alcohol in liquid form, preferably ethanol, at a temperature of about 50° C. to about 120° C., preferably at a temperature of about 60° C. to about 78° C., ambient pressure.

[0171] The elements were immersed individually or as bulk material in ethanol having a temperature of about 60 to about 70° C. for a time of about 15 seconds to about 5 minutes.

[0172] In a second step, the elements were dried either in the air for about 12 hours or in an oven at a temperature of about 70° C. for a period of about 30 minutes. It is also possible to use vacuum drying. The elements were stored separately, to avoid damage of the surface while it was still soft.

[0173] Alternatively, the elements can be contacted with water or an aqueous solution immediately or at most up to 5 minutes after treatment and removal. The contact with water or an aqueous solution provides for a fast solidification of the surface and, thus, avoids sticking together of elements and damage of the surface. Suitable as aqueous solution is for example a mixture of about 1 Vol.-% to about 25 Vol.-% of diethylene glycol in distilled water. It has been found that the result can be improved by using water or an aqueous solution of a temperature in the range of about 0° C. to about 8° C.

[0174] Post-processing of elements obtained after the smoothening step by drying in an oven or by using vacuum for drying can further improve the result.

EXAMPLE 5

[0175] Elements prepared from TPU (TPE-U), for example TPU as commercially available from Rowak AG, Zurich, Switzerland under the tradename Rolaserit° were dyed by using the process of example 4 The treating agent in this example comprised ethanol, for smoothening, a dye and diethylphthalate (DEP) as plasticizer. Elements were obtained that had a smooth coloured surface.

[0176] In a further approach elements obtained with the process of example 4 were functionalized, i.e. the surface was treated with a treating agent comprising ethanol, DEP, and metal powder. For the smoothening step metal powder was dispersed in ethanol comprising DEP and heated. During the smoothening step the composition was agitated to prepare a treating composition with metal powder homogeneously distributed in ethanol. The elements were added to the warm treating composition. When the surface of the components was softened by the warm ethanol, metal powder adhered to the surface of the elements and remained permanently on the surface of the elements after removing the elements from the treatment composition and drying. The same method can be applied for providing a coating of nanotubes or graphene.

EXAMPLE 6

[0177] Elements prepared from TPU, commercially available under the tradename ESTANE® from Lubrizol, Cleveland, Ohio, US, were treated with treating agents comprising ethanol and DMSO, as mixtures with 75% DMSO, 66% DMSO, 50% DMSO, and 33% DMSO.

[0178] The elements were dipped, sprayed or brushed with the treating agent. The elements then were dried at room temperature for up to about 24 hours, or at increased temperature of 78° C., such as up to about 60° C. or in an oven for about 10 to about 60 minutes. The elements after treatment had a smooth surface, where elements before (a) and after treatment (b) are shown.

[0179] This method can also be used for colouring and/or functionalising the surface by adding a colorant or functionalizing agent to DMSO or a DMSO/ethanol mixture and using this composition of treatment.