PROCESS

Abstract

The present invention relates to additive layer manufacture methods for producing a cured three-dimensional polymerized object, or an object comprising cured polymer on, in and/or around the object, or part thereof. A bittering agent is distributed within the cured polymer.

Claims

1. An additive layer manufacture method for producing a three-dimensional object, the method comprising the steps of: (i) forming a feedstock comprising a polymerizable liquid resin and a bittering agent; (ii) exposing the feedstock to a curing beam according to a predetermined pattern to form a layer of cured polymer; and (iii) repeating step (ii) layer upon layer to form a cured three-dimensional polymerized object.

2. A method according to claim 1, wherein the additive layer manufacture method is electron beam curing or vat photopolymerization additive layer manufacture.

3. A method according to claim 2, wherein additive layer manufacture method is vat photopolymerization additive layer manufacture and the polymerizable liquid resin is a photocurable liquid resin.

4. A method according to claim 3, wherein the photocurable liquid resin further comprises a photoinitiator.

5. A method according to claim 4, wherein the photoinitiator has an absorption wavelength ≥about 200 nm to ≤about 700 nm.

6. A method according to claim 1, wherein the polymerizable liquid resin comprises a mixture of multifunctional monomers and oligomers functionalized by an acrylate.

7. A method according to claim 1, wherein the bittering agent is selected from the group consisting of denatonium benzoate, denatonium saccharide, quinine hydrochloride, naringin, sucrose octaacetate and mixtures thereof.

8. A method according to claim 7, wherein the bittering agent is denatonium benzoate.

9. A method according to claim 8, wherein the concentration of bittering agent in the feedstock is from about 100 ppm to about 10,000 ppm, such as about 100 ppm to about 5000 ppm.

10. A method according to claim 9, wherein the concentration of bittering agent in the feedstock is from ≥about 500 ppm to ≤1100 ppm.

11. A method according to claim 1, wherein the curing beam is electromagnetic radiation having a wavelength ≥about 200 nm to ≤about 700 nm.

12. A method according to claim 11, wherein the electromagnetic radiation has a wavelength of about 365 nm, about 405 nm, or about 460 nm.

13. A method according to claim 11, wherein the exposure time for the curing beam is about 1 second to about 60 seconds.

14. An additive layer manufacture method for producing an object comprising cured polymer on, in and/or around the object, or part thereof, the method comprising the steps of: (i) forming a feedstock comprising a polymerizable liquid resin and a bittering agent; (ii) immersing an object, or part thereof, into the feedstock; (iii) exposing the feedstock to a curing beam according to a predetermined pattern to form a layer of cured polymer on, in and/or around the object, or part thereof; and (iv) optionally repeating step (iii) layer upon layer to form an object comprising cured polymer on, in and/or around the object, or part thereof.

15. An additive layer manufacture method for producing an object comprising cured polymer on, in and/or around the object, or part thereof, the method comprising the steps of: (i) forming a feedstock comprising a polymerizable liquid resin and a bittering agent; (ii) depositing the feedstock onto, in and/or around an object, or part thereof according to a predetermined pattern; (iii) exposing the feedstock to a curing beam to form a layer of cured polymer on, in and/or around the object, or part thereof; and (iv) optionally repeating step (iii) layer upon layer to form an object comprising cured polymer on, in and/or around the object, or part thereof.

16. (canceled)

17. A cured 3D polymerized object produced according to the method according to claim 1, wherein the cured 3D polymerized object comprises a bittering agent distributed within the cured polymer.

18. A cured 3D polymerized object, wherein the object comprises a cured polymer and a bittering agent, the object comprising multiple layers of individually cured polymer, and the bittering agent is distributed within the individually cured polymer layers.

19. A cured 3D polymerized object according to claim 17, wherein the bittering agent is distributed substantially homogeneously within the individually cured polymer layers.

20. A cured 3D polymerized object according to claim 19, wherein the object is a shell for an in-ear hearing aid.

21. An object, or part thereof, comprising multiple layers of individually cured polymer on, in and/or around the object, or part thereof, wherein a bittering agent is distributed within the individually cured polymer layers.

22. An object according to claim 21, wherein the bittering agent is distributed substantially homogeneously within the individually cured polymer layers.

23. A feedstock comprising a polymerizable liquid resin and a bittering agent.

24. (canceled)

Description

[0065] The invention will now be described further by reference to the following examples, which are intended to illustrate but not limit, the scope of the invention and with reference to the following figures in which:

[0066] FIG. 1 shows a representative 3D file setup in the print software “Rayware”™.

[0067] FIG. 2 shows a representative experimental set-up for curing the samples.

[0068] FIG. 3 shows a representative 3D object having recessed features.

[0069] FIG. 4 shows the representative 3D object of FIG. 3 in which the recessed features contain a cured polymer containing a bittering agent. The cured polymer containing the bittering agent are identifiable as the dark areas within the “JM” and “BITREX” logos.

[0070] FIG. 5 shows a representative series of photographs for the stages of pre-loading, loading, saturation, removal of excess formulation, and result of Example 2, Experiment C.

[0071] FIG. 6 shows a representative example in which the joined end of a pair of tweezers was immersed into a feedstock containing a bittering agent. The layer of feedstock was subsequently cured.

EXAMPLES

Example 1

[0072] General

[0073] The materials used in this experiment are sensitive to 405 nm light. To ensure that the ambient conditions did not affect the results the experiments were performed with limited light sources or the containers for preparation of the materials were shielded such that ambient light could not penetrate. The ambient light power of the laboratory has been measured to ensure that the effect of the ambient light power should be minimal but the additional measures are used to reduce the possibility.

[0074] Three representative resins were selected for initial samples. The selected resins were chosen as they possess distinct properties with respect to each other. All resins include photoinitiators tuned to 405 nm (the working wavelength of the light source on the Moonray S 3D printer) and polymeric precursors i.e. monomers/oligomers possessing acrylic functional groups. The resins are designated as follows: [0075] CPS2030—CPS2030 is a formulated commercially available product that contains a photoinitiator and polymer precursors. This resin is available from Colorado Photopolymer Solutions. [0076] Genesis—Moderate viscosity resin with photoinitiator, dispersant, and monomers/oligomers/cross-linkers. Supplied by Tethon 3D. [0077] ENG1—Moderate viscosity resin with FT1—photoinitiator (2% wt), LB1—light blocker (0.2%), black pigment (0.02%), resin base (97.78%—consisting of oligomers and blue pigment). Supplied by Resyner Technologies Ltd.

[0078] CPS2030 and Genesis are resins that are incomplete formulations i.e. they are intended to have other materials added to complete them. These have been selected to determine the feasibility of incorporating denatonium benzoate into the most basic component of these formulations. ENG1 can be considered a complete formulation that represents a feedstock material from which a potential product could be constructed.

[0079] Denatonium benzoate was supplied as Bitrex™ from Johnson Matthey PLC.

[0080] Three forms of denatonium benzoate were provided: [0081] Solid—anhydrous crystals of pure denatonium benzoate which was ground to a fine powder for incorporation into the resins; [0082] 25% solution of denatonium benzoate in monoethylene glycol and was used as received; [0083] 25% solution of denatonium benzoate in propylene glycol and was used as received.

[0084] Equipment

[0085] Moonray™ S vat photopolymerisation additive layer manufacturing (VP-ALM) machine. *3D Printer.—This printer produces 3D parts by photocuring a liquid resin layer-by-layer. The part is introduced to the machine by a 3D file that has been sliced by the Rayware™ software to correspond with a defined layer thickness (for this machine 20 μm, 50 μm, or 100 μm). Other parameters for the build process are the exposure time for “attachment” or “base” layers, number of “attachment” layers, and normal layer exposure time. The base layers typically require a longer exposure time to ensure adhesion of the part to the build platform (if it is used). It is important to limit the number of base layers to the part of the geometry that is being printed that is not critical i.e. the support structure as these settings are usually not optimized for geometric accuracy. The printer has a light power of 2.8 mW.Math.cm.sup.−2.

[0086] The exposure time/energy flux required for curing any given material can be determined by exposing the resin at multiple energies/times and measuring the thickness of the film.

[0087] XYZ UV Curing chamber—Interlocked enclosure for post-printing curing of parts produced by 3D Printer by irradiation with 16 W 405 nm LED light array. The post-printing curing process is important as the resin is not 100% cured during the printing process as the cured film can stick to the window, or the part can warp due to shrinkage and affect subsequent layers.

[0088] Speedmixer™—is a laboratory mixing system for the rapid mixing, dispersal or pulverizing of different substances and/or chemicals, within particularly short times and with reproducible results.

[0089] Sample Preparation:

[0090] Formulations were prepared where the total mass was approximately 20 g. This was approx. 19.99 g of each resin and 0.01 g denatonium benzoate for 500 ppm and approx. 19.98 g of each resin and 0.02 g denatonium benzoate for 1000 ppm from the solid source. Prior to weighing out the solid denatonium benzoate it was ground down to a fine powder using a mortar and pestle. The crystals were soft and did not require significant energy/time to grind down. For the solutions the amount added was adjusted to ensure the same final concentration of denatonium benzoate in the formulation i.e. 19.96 g,19.92 g resin (500 ppm, 1000 ppm respectively) and 0.04 g, 0.08 g (500 ppm, 1000 ppm respectively) denatonium benzoate solution. The samples prepared with final proportions listed as determined by actual mass added to each are presented in the table below:

TABLE-US-00001 Denatonium Denatonium Benzoate Denatonium Resin Benzoate Ethylene Propylene Concentration Resin Benzoate Form mass (%) mass (%) Glycol (%) Glycol (%) (ppm) Genesis — 100.000 0.000 — — 0 CPS2030 — 100.000 0.000 — — 0 ENG1 — 100.000 0.000 — — 0 Genesis Solid 99.946 0.054 — — 539 CPS2030 Solid 99.951 0.049 — — 490 ENG1 Solid 99.951 0.049 — — 493 Genesis Ethylene Glycol 99.788 0.053 0.159 — 530 solution CPS2030 Ethylene Glycol 99.800 0.050 0.150 — 500 solution ENG1 Ethylene Glycol 99.799 0.050 0.151 — 503 solution Genesis Propylene 99.805 0.049 — 0.146 487 Glycol solution CPS2030 Propylene 99.801 0.050 — 0.149 498 Glycol solution ENG1 Propylene 99.802 0.049 — 0.148 494 Glycol solution Genesis Solid 99.900 0.100 — — 1004 CPS2030 Solid 99.900 0.100 — — 998 ENG1 Solid 99.900 0.100 — — 1004 Genesis Ethylene Glycol 99.605 0.099 0.296 — 987 solution CPS2030 Ethylene Glycol 99.580 0.105 0.315 — 1050 solution ENG1 Ethylene Glycol 99.604 0.099 0.297 — 991 solution Genesis Propylene 99.598 0.100 — 0.301 1005 Glycol solution CPS2030 Propylene 99.584 0.104 — 0.312 1039 Glycol solution ENG1 Propylene 99.599 0.100 — 0.300 1001 Glycol solution

[0091] Sample Mixing

[0092] After weighing out the components were mixed in a small Speedmixer™ pot. Each pot/formulation was mixed in the Speedmixer™ for 60 seconds at 2000 rpm. The Speedmixer™ has a capacity of >110-<150 g. Along with the sample this includes the mass of the pot, lid, and holder (approx. 110 g).

[0093] After mixing under these conditions there were no obvious signs that the materials were not thoroughly mixed i.e. no cloudiness to the clear resins or settling of the denatonium benzoate solid could be observed.

[0094] Sample Curing

[0095] For this experiment the light source of the Moonray™ 3D printer was being used to expose the resins with 405 nm light without the build platform of the printer in place. This was done as the volume of the formulations was not sufficient to 3D print whole parts from the formulations.

[0096] To initiate the print run on the printer a 3D file was loaded into the software. The software sliced the 3D file into slices that correspond to the layer thickness which was defined in the setup of the print run. In this experiment the 3D file was prepared such that it corresponded to a single layer thickness i.e. single exposure of the suitable time determined for each resin.

[0097] The 3D file and duplication of the file was setup in the print software as can be seen in FIG. 1.

[0098] As mentioned previously the volume of each formulation was not sufficient to operate the printer in full automatic mode to produce 3D parts. For this experiment the resin tank reservoir was removed from the base plate (which consists of a glass window) and a fluorinated ethylene polymer (FEP) sheet was placed on top. The polymer sheet is part of the construction of the resin tank to prevent adherence of the cured resin on the window surface.

[0099] The liquid resin was poured on top of the FEP/glass to cover the area of exposure as illustrated in FIG. 2.

[0100] The unmodified resins were used to determine a suitable exposure time for each resin where the time of exposure was controlled through the Rayware™ software. The exposure time to produce a sufficiently thick layer of each resin was:

[0101] CPS2030=7 seconds

[0102] Genesis=10 seconds

[0103] ENG1=10 seconds.

[0104] After curing the excess resin was recovered by pouring back into the Speedmixer™ pot.

[0105] The cured samples were solid enough to handle comfortably without much risk of damage. The samples were cleaned with isopropyl alcohol (2-propanol) and blotted dry with absorbent paper.

[0106] After cleaning the samples were placed between 2 glass slides and placed in the curing chamber. The glass slides were used as the samples would curl due to shrinkage of the polymer as it goes through additional cross-linking reactions under irradiation.

[0107] The samples were all cured for an additional 60 seconds inside the curing chamber. The samples were then placed in labeled zip-lock™ sample bags for storage.

[0108] Before sending, the samples were removed from their zip-lock™ bags and placed on clean, fresh aluminum foil (to prevent contamination) and subjected to another 60 second curing cycle. This was done to ensure any uncured resin was substantially reacted.

[0109] Taste Test

[0110] The samples were taste tested by four people and the denatonium benzoate-containing samples were confirmed to have a bitter taste.

Example 2

[0111] General

[0112] The materials used in this experiment are sensitive to 405 nm light. To ensure that the ambient conditions did not affect the results the experiments were performed with limited light sources or the containers for preparation of the materials were shielded such that ambient light could not penetrate. The ambient light power of the laboratory has been measured to ensure that the effect of the ambient light power should be minimal but the additional measures are used to reduce the possibility.

[0113] Three representative resins were selected for further samples. The selected resins were chosen as they possess distinct properties with respect to each other. All resins include photoinitiators tuned to 405 nm (the working wavelength of the light source on the 3D Systems FIG. 4 Standalone 3D printer) and polymeric precursors i.e. monomers/oligomers possessing acrylic functional groups. The resins are designated as follows: [0114] MED-WHT10—MED-WHT10 is a formulated commercially available product that contains a photoinitiator and polymer precursors. This resin is available from 3D Systems Europe Ltd. [0115] F blue—Moderate viscosity resin with FT1—photoinitiator (2.48% wt), resin base (97.52%—consisting of oligomers and blue pigment). Supplied by Resyner Technologies Ltd. [0116] HDT1—Moderate viscosity resin with FT1—photoinitiator (2.5% wt), LB1—light blocker (1.75%), resin base (96.5%—consisting of oligomers). Supplied by Resyner Technologies Ltd.

[0117] MED-WHT10 is a commercially available resin that is fully formulated to operate with preset conditions on 3D Systems FIG. 4 line of vat photopolymerization additive layer manufacturing (VP-ALM) equipment. 3Dresyn. F blue is provided as components (e.g. resin base, FT1, LB1—light blocker) in order to add components such as FT1 in proportions suited to the vat photopolymerization additive manufacturing equipment to be employed. The formulation prepared here did not include LB1 as with previous mixtures as it was being applied as a single layer in proof of concept experiments. HDT1 was formulated as a full VP-ALM formulation without bittering agent to produce 3D substrates for layering with bittering agent loaded resin.

[0118] Denatonium benzoate was supplied as Bitrex™ from Johnson Matthey PLC.

[0119] Two forms of denatonium benzoate were used: [0120] Solid—anhydrous crystals of pure denatonium benzoate which was ground to a fine powder for incorporation into the resins; [0121] 25% solution of denatonium benzoate in monoethylene glycol and was used as received;

[0122] Equipment

[0123] FIG. 4™ Standalone vat photopolymerization additive layer manufacturing (VP-ALM) machine. *3D Printer.—This printer produces 3D parts by photocuring a liquid resin layer-by-layer. The part is introduced to the machine by a 3D file that has been sliced by the 3DSprint™ software to correspond with a defined layer thickness (for this machine 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, or 100 μm). Other parameters for the build process are the exposure time for “base” or “attachment” layers, number of “base” layers, and normal layer exposure time. The base layers typically require a longer exposure time to ensure adhesion of the part to the build platform (if it is used). It is often important to limit the number of base layers to the part of the geometry that is being printed that is not critical i.e. the support structure as these settings are usually not optimized for geometric accuracy.

[0124] The exposure time required for curing the commercially sourced material is pre-determined by 3DSystems and included within the 3DSprint software as material profiles. Selecting a profile and layer thickness allows production of components for that material.

[0125] XYZ UV Curing chamber—Interlocked enclosure for post-printing curing of parts produced by 3D Printer by irradiation with 16 W 405 nm LED light array. The post-printing curing process may important as the resin may not 100% cured during the printing process as the cured film can stick to the window, or the part can warp due to shrinkage and affect subsequent layers.

[0126] 3D Systems NextDent LC—3DPrint Box UV Curing chamber—Interlocked enclosure for post-printing curing of parts produced by VP-ALM by irradiation with 12×18 W UVA lamps. The post-printing curing process may be important as the resin may not 100% cured during the printing process as the cured film can stick to the window, or the part can warp due to shrinkage and affect subsequent layers.

[0127] Speedmixer™—is a laboratory mixing system for the rapid mixing, dispersal or pulverizing of different substances and/or chemicals, within particularly short times and with reproducible results.

[0128] Sample Preparation:

[0129] Formulations were prepared in three different approaches.

[0130] MED-WHT10 was used as received and combined with solid denatonium benzoate in the following procedure. 191.2 g of MED-WHT10 was added to a speedmixer pot with 0.96 g solid denatonium benzoate crystals. 499.6 g of 1 mm diameter yttria stabilized zirconia (YSZ) milling beads were added to the pot to break down the crystals and disperse them through the resin.

[0131] A stock solution of F blue was prepared where the total mass was approximately 20 g. This was 19.62 g of base resin, mentioned above, and 0.40 g of 25% denatonium benzoate in monoethylene glycol solution for 5000 ppm and approx. 20.02 g of total resin/denatonium benzoate mixture.

[0132] HDT1 VP-ALM resin formulation was prepared by combining the component ingredients as received in the following proportions. 6.53 g FT1, 4.53 g LB1, 250 g clear resin base.

[0133] The samples prepared with final proportions listed as determined by actual mass added to each are presented in the table below:

TABLE-US-00002 Denatonium Denatonium Denatonium Resin Benzoate Ethylene Benzoate Benzoate mass mass Glycol Concentration Resin Form (%) (%) (%) (ppm) HDT1 — 100.0 0.0 — 0 MED- Solid 99.5 0.5 — 5000 WHT10 F blue Mono- 98.0 0.5 1.5 5000 ethylene Glycol solution

[0134] Sample Mixing

[0135] For F blue and HDT1 formulations: After weighing out the components were mixed in a Speedmixer™ pot. Each pot/formulation was mixed in the Speedmixer™ for 60 seconds at 2000 rpm and 120 seconds at 1200 rpm for HDT1, respectively.

[0136] After mixing under these conditions there were no obvious signs that the materials were not thoroughly mixed i.e. no cloudiness to the clear resins or settling of the denatonium benzoate solid could be observed.

[0137] The speedmixing procedure for the MED-WHT10/denatonium benzoate mixture was carried out gradually to ensure the mixture did not overheat and damage the resin as follows:

TABLE-US-00003 Time RPM (s) Iterations Additional Actions 800 30 1 N/A 800 60 1 N/A 1200 60 2 Placed in refrigerator for approx. 15 min 1200 60 3 Placed in refrigerator for approx. 120 min 1200 120 1 Passed through 0.355 mm sieve to remove YSZ beads

[0138] The dispersion of the solid denatonium benzoate was assessed by use of a 0-50 μm Hegman gauge. No visible sign of particulates was observed.

[0139] Sample Preparation

[0140] Each of the aforementioned formulations were prepared to test different applications of the bittering agent modified VP-ALM resins.

[0141] Experiment A—Processability of Modified Commercially Available Formulation

[0142] To initiate the print run on the printer, a 3D file was loaded into the 3D Sprint™ software. The software sliced the 3D file into slices that correspond to the layer thickness which was defined in the setup of the print run. After the VP-ALM process, excess resin was removed with compressed air. Following removal of the excess resin the 3D part was placed in the NextDent LC-3DPrint Box UV Curing chamber for 2×20 min to ensure completion of the photocuring reaction. The successful output can be seen in FIG. 3.

[0143] Experiment B—Application of Photocurable Bittering Agent Formulation to Designed Features

[0144] For this experiment the Moonray™ S 3D printer was employed to create a 3D structure from the HDT1 formulation (20 second exposure for 20 base layers (50 microns per layer) and 6 second exposure for bulk layers (50 microns per layer)). To initiate the print run on the printer a 3D file with features designed to facilitate controlled coating was loaded into the Rayware™ software. The software sliced the 3D file into slices that correspond to the layer thickness which was defined in the setup of the print run.

[0145] After successful reproduction of the 3D file with the Moonray™ S 3D printer, the 5000 ppm denatonium benzoate loaded f blue formulation was applied by pipette to the recessed features of the 3D part to control the surface areas of the part that contained the bitter, photocurable formulation. As the f blue was still liquid the recessed features were kept facing up as it was placed into the XYZ curing chamber. The coated 3D part was placed in the XYZ curing chamber for 10 minutes on full power. The successful output can be seen in FIG. 4.

[0146] Experiment C—Application of Photocurable Bittering Agent Formulation to a Surface

[0147] For this experiment the f blue formulation was deposited by dipping and/or dropping formulation to demonstrate an additive process does not need to be performed on flat surfaces or in a mask/embossed feature.

[0148] When depositing the formulation by dropping, the f blue formulation was added drop-wise to a 3D part using a disposable syringe. The surface was saturated with f blue formulation. The excess formulation was removed by gentle application of compressed air leaving a layer of liquid formulation on the inside of the part. The stages of pre-loading, loading, saturation, removal of excess formulation, and result can be seen in FIG. 5.

[0149] Depositing the formulation by dipping was demonstrated by simply dipping an item into the f blue formulation and curing in the XYZ chamber for 10 minutes on full power. The result of this can be seen in FIG. 6.

[0150] After each experiment the excess resin was recovered by pouring back into the Speedmixer™ pot.

[0151] Taste Test

[0152] The samples were taste tested by four people and the denatonium benzoate-containing samples were confirmed to have a bitter taste.