METHOD FOR TREATMENT OF ELEMENTS OBTAINED BY AN ADDITIVE MANUFACTURING PROCESS

Abstract

A method for preparing an element for use in or as a medical device using an additive manufacturing process comprises applying on the element a treating agent in liquid or gaseous form.

Claims

1. A method for preparing an element for use in or as a medical device comprising the steps: a. preparing an element with an additive manufacturing process, b. applying on the element obtained in step a) at least one treating agent in liquid and/or gaseous form, wherein the treating agent comprises at least one monovalent or polyvalent alcohol, c. removing the element from an application unit and/or removing the treating agent from the element and/or the application unit, and d. storing an element obtained in step c) for a predetermined time period to evaporate remaining treating agent.

2. The method of claim 1, wherein the method additionally comprises at least one of the following steps e) recovering solvent, f) combining elements obtained by steps a) to c), g) packaging an element or a combination of elements and/or h) sterilizing the element or combination of elements.

3. 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.

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

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

6. The method of claim 5, 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.

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

8. 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.

9. 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.

10. The method of claim 1, wherein in step c) after finishing treatment of the element in step b) the treating agent is removed by releasing and/or aspirating and/or withdrawing treating agent in vapor or liquid form.

11. The method of claim 1, wherein in step d) treating agent is evaporated by drying the elements in an oven for a period of about 5 minutes to about 48 hours.

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

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

14. The method of claim 1 further additionally comprising a functionalising step, which comprises applying at least one functionalizing agent on the element during step b) or after treatment with the treating agent in an additional step b′).

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

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

17. The method of claim 1, wherein the functionalizing agent comprises at least one agent of 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.

18. 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.

19. The method of claim 1, wherein the additive manufacturing process is a powder-based additive manufacturing process.

20. The method of claim 1, wherein the element has been obtained by a sintering/melting process, 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, fused filament fabrication (FFF), and a light induced process.

21. 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), polyetherketone (PEK), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyurethane, polysulfone, polyetherimide (PEI), styrene polymer or copolymer, or a thermoplastic polymer comprising polyetherimide and polycarbonate, or copolymers, blends, or mixtures of these polymers.

22. (canceled)

23. 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.

24. 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.

25. The method of claim 1, wherein step d) is carried out for a time period of about 5 minutes to about 48 hours, optionally by drying the elements in an oven for a period of about 5 minutes to about 48 hours.

26. The method of claim 1, wherein step d) is carried out at a temperature between ambient temperature and softening temperature of the element, optionally at a temperature of about 15 to about 40° C.

27. The method of claim 1, wherein a solvent recovery step e) is carried out by removing solvent with a filtration unit wherein solvent released from the chamber is absorbed and thereafter solvent is recovered from the filtration unit by desorbing the solvent.

28. (canceled)

29. A medical device comprising at least one element obtained by the method of claim 1.

30. 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.

31. The device of claim 30, wherein the chamber is a vacuum unit or chamber comprising a microwave and/or ultrasound unit.

32. (canceled)

Description

[0171] When vapor is used, a device that provides for vaporization of the solvent is used, such as a device comprising a chamber, for example a device of the present invention as described in detail below. These embodiments are exemplary and shall not limit the scope of the present invention.

[0172] FIGS. 1 and 2 show application units that can be used to apply a treating agent in a method of the present invention.

[0173] As an example, FIG. 1 shows an application unit that can be used for different embodiments. The following reference numbers are used: [0174] 1 Process chamber [0175] 2 Thermal barrier [0176] 3 Treating agent (liquid or gas) [0177] 4 Elements [0178] 5 Platform [0179] 6 Container [0180] 7 Heating means [0181] 8 Feed pump(s) [0182] 9 Process gas [0183] 10 Body [0184] 11 Venting valve [0185] 12 Heating means [0186] 13 Container [0187] 14 Stirrer

[0188] As can be seen the device comprises a process chamber or application unit (1) for contacting elements (4) with a treatment agent (3). In a preferred embodiment the lower part of process chamber (1) is thermally separated from the upper part of the process chamber (1), for example by one or more thermal barriers (2). The position of the thermal barrier (2) is not critical as long as thermal separation occurs, Thus, the one or more thermal barriers (2) can be arranged at different positions. Elements (4) in a first design can be placed, laid, suspended, or clamped on or at a lowerable platform (5), for example at the upper end of the platform. When elements (4) shall be treated as bulk material, they can be accommodated by accommodating means (10). A treatment agent (3) is preferably stored in a separate container (6) and can be heated to the process temperature by heating elements (7). The treating agent can be heated to the treatment temperature before introduction into the process chamber and/or can be heated within the chamber. For example, the treating agent (3) can be heated outside chamber (1) and can be introduced as soon as it has reached the process temperature. Introduction of treatment agent (3) can be done as known in the art, for example by means of a feed pump (8) and/or by applying a suitable process gas (9) by gas pressure and/or by other methods known to the skilled person.

[0189] In order to achieve a uniform pressure between vessel (6) and process chamber (1), pressure within the process chamber (1) can be adjusted accordingly before, during or after the introduction of the treatment agent (3) into the process chamber (1), for example by feeding process gas (9) into the process chamber (1). The skilled person can identify optimal conditions by routine experiments.

[0190] Alternatively, compressed air can be used as process gas (9). In those cases where elements (4) shall be dipped into the treatment agent (3) sufficient treatment agent (3) will be provided in process chamber (1), so that when lowering platform (5) with the elements (4), they are in contact with the treating agent (3). After a suitable time period, platform (5) is returned to its upper end position, and the elements are removed from contact with the treating agent. This slows down or stops the smoothening process.

[0191] To control the smoothening process, it is possible to feed process gas (9), such as nitrogen, and/or additional treating agent and/or an additional solvent from container (13) to process chamber (1). Feeding of gas can be done simultaneously or after lifting off the platform (5) in order to control the process and to decelerate and/or stop the smoothening process.

[0192] Treatment agent (3) can be recovered, for example by pumping it back into container (6) after treatment. The treatment agent can be fed back into the storage container and can be stored or can be kept at process temperature and recycled for a next smoothening step, or treatment agent can be processed and for a next smoothening process.

[0193] To save energy it is convenient to recycle treatment agent (3) to tank (6) or another container (not shown) and maintain the temperature at or close to the process temperature.

[0194] Process chamber (1) can be equipped with additional heating means (12) which can be provided internally or externally. In addition, process chamber (1) can be provided with agitating means for agitating or circulating liquid and/or gas in the chamber. Many suitable agitating means (14) like stirrer, impeller, turbulator, jet etc. are known to the skilled person. This allows achieving as uniform a smoothening and/or colouring and/or functionalizing process of elements (4) as possible.

[0195] In another embodiment the device shown in FIG. 1 has a central body (10) for receiving, supporting, or holding elements (4), In this embodiment neither a movable platform (5) nor a thermal barrier (2) is necessary. Elements (4) can either be introduced directly into the process chamber (1) as bulk material and/or can be suspended using suspension means. In this embodiment elements can be distributed within and over the entire height/space of process chamber (1). Once elements (4) have been introduced into the process chamber, the chamber and the elements, respectively can be heated by one or more heating elements (12) as required. It is also possible to use heated gas, such as a heated gas stream. The heating element (12) can be any type of heating means as known to the skilled person and can be used as is known to the skilled person.

[0196] When the treatment is carried out at elevated temperature, heating can be obtained either by heating means that are present internally or externally, by introducing heated gas and/or by preheating elements. Once elements (4) have been introduced into the process chamber, the chamber (19 can be heated as required with the heating element (12). The temperature in the chamber can be controlled as is known to the skilled person. When the process chamber (1) and/or elements (4) have the predetermined temperature, process gas (9) may be introduced at a pressure as required. This can also be done during or before the heating of the process chamber (1) and the elements (4). In a next step, treatment agent (3) can be introduced into the process chamber (1). After the smoothening step has been finished, treatment agent (3) can be pumped back into container (6) or another container (not shown). Alternatively, a process-inhibiting liquid and/or a process-inhibiting gas at a predetermined temperature can also be fed from the container (13) or from one or more further containers (not shown) into the process chamber (1) while the treatment agent (3) is still present. A mixture of treatment agent (3) and process-inhibiting liquid and/or process-inhibiting gas can be formed and this mixture can be fed back into container (6) and/or one or more further containers (not shown) after a predetermined time. Elements (4) can then be removed either immediately or after a cooling time.

[0197] In a third embodiment of a device according to FIG. 1, elements (4) are smoothened with a treating agent (3) in gas form instead of a liquid. For this embodiment no thermal barrier (2) is necessary. The difference between this embodiment and the second embodiment is that either treatment agent gas (3) is introduced into the process chamber (1) and/or treatment agent gas (3) is formed at least partially within the process chamber (1). The smoothening process does not differ essentially from the process as carried out and described for a device shown in FIG. 2. The main difference is with regard to the pressure used within chamber (1), which can be above atmospheric pressure. With this embodiment, the gaseous treating agent (3) can preferably be circulated during the process by suitable means such as propellers or impellers (not shown, see FIG. 2). Furthermore, this variant offers the possibility of introducing a process-inhibiting liquid and/or a process-inhibiting gas during and/or after the smoothening step, whereby the smoothening process can be controlled, for example decelerated and/or stopped and/or a functionalizing process can be included, such as generating textures on the component surface. Alternatively, instead of a process-inhibiting liquid, another liquid that positively influences the smoothening process, a corresponding gas or corresponding solids such as powder or fibers can be introduced into the process chamber (1). In all three embodiments, when using a device as shown in FIG. 1, it is possible with a suitable discharge valve (11) and optionally solvent storage and recovery means, for example, activated carbon filter, residual pressure and any residues of the treating agent (3) can be safely discharged from process chamber (1).

[0198] In particular for treating elements that are used in the medical field it is useful to remove s much treating agent (3) and/or additional solvent, if present, as possible. This can be done with a vacuum pump and recovery means (not shown), like filter means or recovery trap, as shown below for the device of FIG. 2. Any treating agent (3) remaining in the process chamber (1) after the pressure has been released can be safely removed and optionally can be recovered.

[0199] All embodiments described above with regard to a device as shown in FIG. 1 can be combined with an additional dyeing and/or functionalization step by introducing suitable substances into the process chamber (1) either during the smoothening step and/or thereafter, for example in a time window after smoothening as described before.

[0200] As a further example, an application unit can be as shown in FIG. 2, and comprises a chamber (101) for contacting elements with vapor, at least one element contact area (105), a dosing unit for solvent, which is the treating agent, comprising a solvent feed line for feeding treating agent into chamber (101) from a treating agent container (113), and a dosing means, and optionally comprises at least one distributor, a withdrawal unit comprising a pump (112), and/or a recovery unit comprising at least one filter unit or a trap. One embodiment of the device of the present invention is shown in FIG. 2 and comprises a vacuum unit as chamber (101). This device uses vacuum for vaporizing the treating agent to be applied to elements and comprises a vacuum unit 1 as shown in FIG. 2 with [0201] 101 vacuum unit [0202] 102 vacuum lid [0203] 103 engine Motor [0204] 104 fan propeller [0205] 105 element contact area [0206] 106 element [0207] 107 vacuum tube [0208] 108 pressure gauge [0209] 109 solvent feed line [0210] 110 activated carbon filter [0211] 111 activated carbon [0212] 112 vacuum pump [0213] 113 treating agent container [0214] 114 treating agent [0215] 115 stop valve [0216] 116 feed pump [0217] 117 flow element [0218] 118 vacuum rotary transmission [0219] 119 venting valve [0220] 120 treating agent

[0221] In the following explanation of the device the term “solvent” is used for any type of treating agent and “solvent mixture” comprises mixtures of treating agent and additional solvent as well as mixtures of treating agent and other liquids. Another embodiment of a device of the present invention is a microwave or ultrasound device, wherein vaporization of the solvent or solvent mixture is obtained by using microwaves and/or ultrasonic waves. In this case, microwaves or ultrasonic waves are applied to the chamber by a microwave unit or a ultrasound unit, respectively. The microwave or ultrasound unit can be applied internally or externally. It is preferred that microwaves and/or ultrasonic waves are applied from outside to the chamber. The amount and wave length of the microwaves and/or ultrasonic waves can be adapted as is known to the skilled person such that solvent in the chamber is vaporized. Vaporization with microwaves and/or ultrasonic waves can be carried out at any convenient temperature, such as ambient temperature, and at any convenient pressure, such as ambient pressure, as long as the solvent is vaporized. It is also possible to use negative or positive pressure.

[0222] After treatment of elements the solvent is withdrawn from the chamber and can be passed to a recovery unit which comprises at least one filter unit and/or a recovery trap. By passing the solvent through the recovery unit, solvent is adsorbed by the at least one filter unit and/or is condensed in a recovery trap. The recovered solvent can then be used again for the method of the present invention. Therefore, the use of a recovery unit contributes to an efficient and environmentally friendly process.

[0223] It has been found that activated carbon is useful as filter means as it is abundantly available and is active in absorbing the solvent or solvent mixture used for the process of the present invention efficiently and also efficiently desorbs the solvent.

[0224] The number of cycles or runs for the filter unit before exchange and the number of units used in a specific process can be determined easily by a person skilled in the art.

[0225] The solvent can be regenerated by desorption from the filter unit. For desorption, the filter unit, for example an activated carbon unit, can be heated to desorb the solvent. In another embodiment, an air stream having a temperature beyond the boiling temperature of the solvent is passed through the filter unit. Thereafter, the air stream enriched with desorbed solvent is passed to a unit for recovery of the solvent by condensation.

[0226] It is also possible to heat the air used for desorption and/or the filtration unit by microwaves and/or ultrasonic waves, either alone or in addition to heating the air stream. For condensation, any trap that is known from distillation processes can be used. In one embodiment, a cold trap, such as a metal tube or a glass vessel can be used. The metal tube can be a tube made from any metal that is inert with regard to the solvent, such as copper or aluminum or any other metal or alloy. The tube can be straight, bent, curved, crooked, or can be in the form of a spiral. Moreover, the tube can be cooled by a heat exchange unit and/or a fluid bath or any other known means. By cooling the solvent, the solvent such as HFIP or a solvent mixture can be condensed and drops into a collecting vessel, such as a collecting jar or a collecting bottle. HFIP has a relatively high density (1.6 kg/L) which provides for fast running down of the condensed solvent. The air, separated from solvent vapor, such as HFIP vapor, having a high temperature, can be passed again into the filtration unit to start a new desorption/condensing cycle.

[0227] The device of the present invention can be used to treat elements with solvent vapor. The solvent to be vaporized can be a a treating agent or a mixture of treating agent and solvents, such as one or more alcohols, for example one or more halogen containing alcohols like HFIP, organic solvents like acetone or other solvents that preferably have a boiling point in the range of about 40° C. to about 100° C., or mixtures of these solvents. One example for a treating agent is HFIP or a mixture comprising HFIP. In the following description of the device HFIP is mentioned, but any other treating agent could be used instead as long as the boiling point is in a suitable range.

[0228] The element to be treated can be any element that should be treated with a vapor or a solvent in gaseous form, respectively. An example for an element to be treated is an element obtained by an additive manufacturing process, in particular an element as described above.

[0229] The device comprises a chamber for treating an element with a solvent in gaseous form, wherein a solvent is vaporized and is in contact with at least one element and wherein the solvent is recovered by a recovery means, such as a filter unit or a cold trap. For example, after treatment solvent is withdrawn from the chamber and solvent is recovered by passing it through a filter unit with at least one filter element. The filter element can be made of any material that is used for solvent recovery such as activated carbon. The filter material can be in the form of a membrane, a powder, particles, granules or any other form known to the skilled person. It is also possible to recover solvent by using known solvent recovery means such as cold traps.

[0230] FIG. 2 shows an embodiment of the device for treatment of elements of the present invention. The vacuum device comprises a vacuum unit 101 with a lid 102 for closing the vacuum unit. Elements 106 to be treated are positioned on element contact area 105. Treating agent 114 to be used for treatment of the surface of elements 106 is introduced into the vacuum unit 101 from solvent container 113 via solvent feed line 109. Treating agent 114 is introduced into the vacuum unit 101 by a feed pump 116 and introduction is controlled via stop valve 115. To improve contact between gaseous solvent and element at least one fan propeller 104 can be provided which is driven by an engine 103 connected to the fan propeller 104 via a vacuum-tight rotary transmission 118. To vaporize treating agent 114, vacuum unit 101 is evaporated by a vacuum pump 112 via vacuum tube 107. After evaporation the vacuum unit 101 comprises a solvent 120. The pressure inside the vacuum unit is monitored by a pressure gauge 108. Element(s) 106 are in contact with the solvent vapor for a predetermined time period. Thereafter, pressure is released via venting valve 119 and solvent is removed via vacuum tube 107. The solvent 120 is withdrawn from the vacuum unit 101 by vacuum pump 112 and is passed through at least one filter 110 comprising activated carbon 111. By passing through the filter the solvent is absorbed by activated carbon and can be recovered and reused.

[0231] The method of the present invention provides for elements with smooth surface that can be used for many purposes. The elements obtained with the method of the present invention are particularly useful for in the medicinal and food industry. For medicinal devices as well as for devices that are used in food technology, smooth surfaces are important not only for esthetical reasons but also for hygienic reasons. Furthermore, the treatment is carried out with a solvent that does not change the elements chemically so that no toxic side products are created. Moreover, elements obtained by additive manufacturing using powder as building material or that have been treated by mechanical grinding or milling have powder on the surface that could be contaminating, i.e. could be taken up by the body when it is on a medicinal product that is inserted in the body or could be taken up by food that is in contact with such an element. This is avoided when using the treatment of the present invention where any powder remaining on the surface after the manufacturing process is “melted in” by treatment with the solvent. Thus, the elements obtained by the method of the present invention are particularly useful for medicinal and food processing devices. Moreover, the elements obtained with the method of the present invention are also useful in the field of aeronautics and astronautics, as powder and solvent residues are undesirable and can be detrimental.

[0232] Because of the favourable properties of the elements obtained with the method of the present invention, the elements can be used in the medical, therapeutic and pharmaceutical field. Examples for uses are

Drilling and cutting templates in, for example, orthopaedics and maxillofacial surgery
Surgical templates, e.g. for vascular surgery, cardiac surgery, visceral surgery
Handles, adapters or attachments for standard instruments, e.g. laparoscopic, endoscopic instruments, ENT instruments, instruments for interventional radiology
Instruments for gastroenterology and visceral surgery such as retractor systems, manipulators, gripping instruments, trocars
Implants in e.g. orthopedics, dentistry and oral and maxillofacial surgery
Instruments in dentistry with contact with mucous membranes, e.g. bite splints
Individualized orthoses and prostheses
Disposable medical instruments
Individualized medical instruments (gripping instruments, holding arms, holding instruments, access systems)
Bioreactor systems and material for cell culture
Scaffolds for tissue engineering

[0233] The invention is further explained by the following examples which are not deemed to be restrictive.

EXAMPLE 1

[0234] 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.

[0235] 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:

[0236] Roughness of the element after treatment: R.sub.a=1.1; R.sub.z=7

EXAMPLE 2

[0237] 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.

[0238] Roughness after treatment: R.sub.a=1.7; R.sub.z=10

EXAMPLE 3

[0239] 3D printed elements are treated with aliphatic alcohol. For this process 3D printed 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.

[0240] Once the desired surface quality is achieved, the temperature is lowered to about 50° C. before the elements can be removed.

[0241] 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.

[0242] 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 smoothening 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

[0243] 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.

[0244] 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.

[0245] 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.

[0246] 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.

[0247] 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.

[0248] 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

[0249] 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.

[0250] 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, diethyl phthalate (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

[0251] Elements prepared from TPU (TPE-U), for example 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.

[0252] 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.

[0253] 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.

EXAMPLE 7

[0254] Cytotoxicity and cytocompatibility were determined for elements obtained by the method of the present invention.

[0255] Elements were prepared with SLS (using an EOS Formiga P100 with EOS PA2200 on basis of PA12 (EOS, Krailing, Germany)) and were treated with a solvent (HFIP) to smoothen the surface. After releasing the solvent, the elements were taken out of the application unit and stored in an oven for 120 minutes. The elements obtained were tested for cytotoxicity and sterility.

EXAMPLE 8

[0256] End Point Test

[0257] The end point test is a method to determine if sterilization was successful. In a first step elements are vaccinated with bacteria, in the present case with E. coli. The elements are then dried for 10 min and then are filled in Falcon tubes containing 10 mL LB-medium. Three contaminated test pieces were transferred into a Falcon tube as positive control. The remaining test pieces were contacted with a solvent for less than 5 sec, 30 sec, or 60 sec, respectively. Thereafter these elements also were transferred to a Falcon tube.

[0258] All Falcon tubes then were stored for 72 hours and tested after 24 h/48 h/72 h via visual inspection. If the Falcon tube contains living microorganisms, these will be amplified in the feed medium and result in a hazy or turbid solution. If no living organisms are in the Falcon tube, the solution will not become hazy or turbid. Thus, the level of turbidity in the tubes is a measure for the presence of living microorganisms.

[0259] It was found that the three test pieces which were contaminated and which were contacted with solvent for some time, did not show any turbidity so that it can be deduced that no living bacteria can be found in the tube. Thus, contacting a surface obtained by the method of the present invention with a solvent results in a surface that is free of living microorganisms.

[0260] A comparison of test pieces is shown in FIG. 3. The first three tubes comprise elements which have been contaminated with E. coli but have not been treated with solvent. These are used as positive control.

[0261] The remaining tubes comprise elements which have been contaminated with E. coli for a predetermined time period (less than 5 sec, 30 sec, and 60 sec) and afterwards were treated with solvent.

[0262] As can be seen the first three tubes show a hazy fluid, whereas the remaining tubes all have clear solutions. This shows that treating with solvent results in sterile surfaces of the elements and prevents growth of microorganisms.

EXAMPLE 9

[0263] Test of Cytotoxicity

[0264] A cytotoxicity tests also know as eluate test was used to analyze whether toxic substances or substances in toxic concentrations are released from elements treated with the method of the present invention, and whether cells die on contact with these substances.

[0265] For the production of eluates, specimens are stored in cell culture medium according to DIN EN ISO 10993-5 and incubated at a defined temperature (usually 36° C.) for a defined period of time. According to the standard, the extraction ratio should be 3 cm2/ml. Eluates with copper are prepared as a positive control. Pure cell culture medium serves as negative control.

[0266] In parallel to the incubation of the eluates, adherent cells together with the cell culture medium are removed into well plates and incubated. The cell culture medium is then aspirated and the cells are brought into contact with the eluate. After a defined incubation period, the eluate is aspirated and a WST-8 assay (Water Soluble Tetrazolium) is performed. For this purpose, water soluble tetrazolium salt (2-(2-methoxy-4-nitrophenyl-)-3-(4-nitrophenyl(-5-(2,4-disulfophenyl)-2H-tetratolium (WST-8 solution) together with cell culture medium is added to the cells. If the metabolism of the cells is active, the pink WST-8 solution changes colour to an orange WST-8 formazan solution. The amount of formazan product correlates with the metabolism of living cells, and thus with cell vitality.

[0267] The color change is detected with a photometer and then evaluated.

[0268] Elements that have been treated with the method of the present invention have been sterilized with hot steam. For this purpose, they are packed in sterilization bags PMS Steripack (PMS Europe GmbH, Germany) and steam sterilized with the autoclave Hospiklav 25-Type B (SHP Steriltechnik AG, Germany) at 121° C. for 15 minutes.

[0269] Production of the Eluates

[0270] To prepare the eluates, the sterilized specimens are transferred under one into Falcon tubes and filled with 11.2 ml cell culture medium. Elution is carried out in an incubator at 37° C., 10% CO2 content and 99% humidity. Eluates can be prepared over different periods of time for the examination. Recommended extraction times are 3 and 7 days.

[0271] WST Test

[0272] A WST test is performed to determine the cytotoxic properties of the eluates. Fibroblasts are seeded in a 96-well microtiter plate with a cell density of 5000 cells/cm.sup.2 and covered with 100 ml cell culture medium. After an incubation period of 24 hours, the cell culture medium is aspirated and the cells are inoculated with 100 ml of the eluate solutions. After a further incubation of 72 hours, the eluate solutions are aspirated and the WST test solution is added to the wells (mixture of WST solution and cell culture medium in a ratio of 1:10). After an incubation period of 1 hour, the absorption values 620 nm and 450 nm are measured with a photometer and referenced to the negative control.