LAYERED SORBENT STRUCTURES

Abstract

A shaped sorbent is described comprising a plurality of layers of photopolymerised resin containing particles of a sorbent material. The shaped sorbent may be used as a getter for use in gettering one or more contaminants in a sealed enclosure.

Claims

1-19. (canceled)

20. A shaped sorbent comprising a plurality of layers of photopolymerised resin containing particles of a sorbent material.

21. The shaped sorbent according to claim 20 wherein the sorbent material comprises alumina, silica, carbon or a molecular sieve.

22. The shaped sorbent according to claim 20 wherein the sorbent material comprises a reactive sorbent material.

23. The shaped sorbent according to claim 20 comprising a molecular sieve sorbent material and a reactive sorbent material.

24. The shaped sorbent according to claim 20 wherein the maximum particle size (Dv100) of the sorbent material in the shaped sorbent is less than the layer thickness.

25. The shaped sorbent according to claim 20 wherein the photopolymerised resin is derived from a photopolymer comprising a mixture of multifunctional monomers and oligomers functionalized by an acrylate.

26. The shaped sorbent according to claim 20 comprising from 1 to 70% by volume of sorbent material.

27. The shaped sorbent according to claim 20 comprising 5 to 5000 layers.

28. The shaped sorbent according to claim 20 wherein each layer has a thickness in the range of from 10 to 300 mm.

29. The shaped sorbent according to claim 20 wherein the shaped sorbent has a cross-sectional length width or height, in the range of from 0.3 mm to 100 mm.

30. The shaped sorbent according to claim 20 wherein the shaped sorbent is in the form of an open-ended cylinder containing a lattice structure or layers of spaced parallel struts or meshes.

31. A method for making a shaped sorbent unit comprising the steps of (i) combining a sorbent material with a photopolymer to form a sorbent mixture, and (ii) using photopolymerisation to form a shaped sorbent comprising a plurality of layers of photopolymerised resin containing particles of the sorbent material.

32. The method according to claim 31 wherein the photopolymerisation comprises additive layer photopolymerisation.

33. The method according to claim 31 wherein the method comprises the steps of: (i) forming a sorbent mixture comprising a photopolymer and a sorbent material; (ii) exposing the sorbent mixture to electromagnetic radiation according to a predetermined pattern to form a layer of cured polymer; and (iii) repeating step (ii) layer upon layer to form the shaped sorbent.

34. The method according to claim 31 wherein the photopolymer has a viscosity in the range of from 1 to 500 mPa.Math.s. at 20° C.

35. The method according to claim 31 wherein the sorbent mixture comprises from 1 to 70% by volume of the sorbent material.

36. The method according to claim 31 wherein the sorbent mixture comprises a dispersant.

37. The process for gettering using of a shaped sorbent comprising a plurality of layers of photopolymerised resin containing particles of a sorbent material according to claim 20.

38. The process according to claim 37 wherein the getter is placed in a sealed enclosure.

39. The shaped sorbent according to claim 20 wherein the sorbent material comprises a zeolite material.

40. The method according to claim 31 wherein the photopolymerisation comprises digital light processing or continuous liquid interface production.

Description

[0042] The invention will now be further described by reference to the following examples and figures in which:

[0043] FIG. 1 is a depiction of vat photopolymerisation additive-layer manufacture (VP-ALM) equipment used to prepare shaped sorbents.

[0044] FIG. 2 is a side-view of a shaped getter prepared using the equipment,

[0045] FIG. 3 is a top view of the same shaped sorbent, and

[0046] FIG. 4 is an enlarged portion of FIG. 1 depicting the layers in the shaped sorbent.

EXAMPLE 1. PREPARATION OF SHAPED ZEOLITE SORBENTS BY DIGITAL LIGHT PROCESSING

[0047] Materials and Equipment.

[0048] Sorbent materials: 3A Zeolite powder and PdO powder (both commercially available).

[0049] Photopolymer: CPS2030. CPS2030 is a formulated commercially available product that contains a photoinitiator and polymer precursors. The photopolymer viscosity at 20° C. was 30 mPa.Math.s. This photopolymer is available from Colorado Photopolymer Solutions.

[0050] Dispersant: Hypermer™ KD1 is a cationic polymeric dispersant. This material is available from Croda™.

[0051] Computer-aided design equipment: A desktop computer running “Blender” open-source software followed by refinement of the structure using “Element” software available from nTopology.

[0052] DLP printer equipment: Moonray™ S available from Sprintray Inc. The equipment is depicted in FIG. 1. The equipment comprises a computer control unit (not shown) that controls the equipment, a vat or reservoir 10 for the sorbent mixture comprising a wall 12 and a glass window 14 at its base to allow light from a computer-controlled digital light processor 16 to be projected using a mirror 18 onto the underside of the glass window 14. The reservoir-side of the glass window has a non-stick polymer film 20 placed on it to permit detachment of cured material. A build platform 22 is placed in the liquid sorbent mixture 24 such that there is a layer of liquid between the lower face of the build platform 22 and the non-stick polymer film 20. Once a cured layer 26 has been formed, the platform 22 and vat 10 are separated by a layer thickness and the process repeated. The Moonray™ S is able to produce a layer thickness of 20, 50, or 100 μm.

[0053] Sorbent mixture preparation: 65% by weight Zeolite 3A in CPS2030/Hypermer™ KD1.

[0054] 98 g of CPS2030 was weighed out and warmed to 50° C. Hypermer™ KD1 was warmed to 50° C. to ensure that it was liquid before adding to the warmed CPS2030 resin. 2 g of Hypermer™ KD1 was added to 98 g of CPS2030 and mixed in a Hauschild Speedmixer™ at 2000 rpm for 180 s. 153.29 g of 3A zeolite was weighed and placed into a Speedmixer™ pot. 88.2 g of the previously prepared 2% Hypermer™ KD1 in CPS2030 resin solution was warmed to 50° C. and weighed into the Speedmixer™ pot with the powder. The mixture was then placed into the Speedmixer™ and mixed at 1200 rpm for 180 s. After mixing any residue of powder was returned from the sides of the container and mixed into the bulk mixture. The mixture was then mixed again at 1200 rpm for 180 s in the Speedmixer™. Following this mixing procedure, the sorbent mixture was poured into the resin tank of the Moonray™ S DLP equipment ready to produce shaped parts.

[0055] The zeolite 3A was not pre-dried and so contained adsorbed water. For these examples, the moisture content (determined by measuring mass loss on heating to 300° C. for 8 hours) was 18.4% by weight.

[0056] DLP Printer Preparation.

[0057] Methods and software are available commercially from the DLP printer providers or open-source. The method used here was as follows: [0058] 1. Draw/Create a structure design using computer-aided design (CAD) software. [0059] 2. Import the structure design into the DLP printer equipment software for positioning on the virtual build platform and generation of automatic support structures. [0060] 3. Generate a slice file in which the design is divided up into a plurality of layers. [0061] 4. Send the slice file to the DLP printer equipment (it is necessary to ensure at this point that there is sorbent material mixture in the vat and the build platform is fixed if required).

[0062] The CPS2030 photopolymer solidifies upon exposure to 405 nm wavelength light. The power output of the Moonray™ S at the curing surface was 2.8 mWcm.sup.−2 and was calibrated for a peak wavelength of 405 nm. Prior to forming the shaped sorbents, a working curve was determined to identify the exposure to the light source required to produce the desired resolution by exposing the photopolymer to a known amount of energy and then measuring the thickness of the solidified polymer. A description of photopolymerisation including how to determine the working curve may be found in “Additive Manufacturing Technologies—Rapid Prototyping to Direct Digital Manufacturing” by Ian Gibson, David W. Rosen and Brent Stucker, Spring (2010), pages 61-102.

[0063] Shaped Sorbent Production.

[0064] Referring again to FIG. 1, the reservoir 10 was loaded with the sorbent mixture 24 and the build platform 22 securely fastened. A non-stick FEP polymer film 20 was placed on the glass window 14. The pre-prepared slice file was then processed using the DLP equipment. Light 28 at a peak wavelength of 405 nm from the digital light processor 16 was projected through the glass window 14 into the layer of liquid in a pattern according to the first layer of the shaped sorbent, thereby causing it to solidify. The light projected is depicted in FIG. 1 by the dotted lines. The reservoir 10 was then lowered or the build platform 22 raised to allow the liquid to flow in between the cured solidified layer and the non-stick polymer film 20 and then their position adjusted to one layer thickness and the process repeated using a pattern according to a second layer of the shaped sorbent, and so on, building up the layers 26 until the fully-formed shaped sorbent was realised. The layer thickness in this example was 100 μm.

[0065] Sample Cleaning and After-Treatment.

[0066] The shaped sorbent was removed from the build platform and washed with isopropanol to remove unreacted material. The washed shaped sorbent was then placed in a UV curing chamber and post-treated at 375-405 nm to fully cure the polymer.

[0067] The shaped sorbent is depicted in FIGS. 2, 3 and 4.

[0068] The shaped sorbent depicted in FIGS. 2 and 3 comprises and open cylinder structure 30 comprising an internal lattice structure 32 comprising parallel struts. Three equally-spaced lugs 34 were provided on the periphery of the cylinder at one end to enable attachment of the shaped sorbent within a device or sealed enclosure. The cylinder had a diameter of 20 mm. The height of the cylinder was 5 mm (and so L/D was 0.25). The lugs 34 were 2.75 mm wide with a height of 1.25 mm. The strut thickness in the lattice structure was 0.8 mm. FIG. 4 depicts an enlarged section of FIG. 2 showing the lattice structure 32 to comprise multiple layers 36. The number of layers in this shaped sorbent was 50.

EXAMPLE 2. TESTING BY DYNAMIC VAPOUR SORPTION (DVS)

[0069] Tests were performed on a cured sorbent mixture comprising 65% wt Zeolite 3A in 2% wt Hypermer™ KD1/CPS2030 photopolymer as prepared in Example 1. Samples for testing were prepared by casting the liquid sorbent mixture onto a FEP-covered glass slide and exposing the resulting layer to a 405 nm light source. Cured shaped sorbent samples having thicknesses in the range of 0.3 to 1 mm were prepared. The cured samples were then broken up to form flakes of material to fit the 9 mm sample holder for the DVS testing.

[0070] Moisture adsorption was determined using the following procedure using Surface Measurement Systems DVS Advantage™ apparatus. Each sample was pre-heated at 120° C. for 6 hours to record the dehydrated sample mass. Adsorption of moisture was then measured by mass change of the sample exposed to a nitrogen flow of 200 cm.sup.3/minute containing 40% relative humidity at 20° C. for 480 minutes. The results were as follows:

TABLE-US-00001 Thickness Moisture adsorption Sample (mm) (% wt) CPS2030 Polymer no zeolite 1.00 0.94 Cured Sorbent—2 s Exposure 0.30 10.64 Cured Sorbent—5 s Exposure 0.75 4.41 Cured sorbent—10 s Exposure 0.89 3.38

[0071] The results indicate that the thin photopolymerised samples containing the zeolite are more able to capture water vapour.

[0072] It should be noted that the photopolymerised samples are not saturated at the end of the test period (8 hours). A further measurement performed to 16 hours showed a sample to continue to adsorb moisture at a steady rate, achieving a pick-up of 14.3 wt. %.

EXAMPLE 3. PREPARATION OF SHAPED PDO/ZEOLITE SORBENTS BY DIGITAL LIGHT PROCESSING

[0073] Samples of a shaped sorbent were prepared using the casting method of Example 2 to test whether a hydrogen-gettering shaped sorbent could be produced. Sorbent mixtures were prepared by mixing 5% wt or 10% wt PdO powder (sieved to <45 μm) into the 65% wt Zeolite 3A in 2% wt Hypermer™ KD1/CPS2030 photopolymer sorbent mixture as prepared in Example 1, before shaping.

[0074] Hydrogen uptake of samples was then measured using a Chemisorb 2480 volumetric chemisorption analyser. Accurately weighed aliquots of approximately 0.5-1 g of material were used. Activation of the sample was achieved by flowing compressed air through the sample at 50 cm.sup.3 per minute and heating from ambient to 120° C. at 10° C. per minute followed by holding at this temperature for 2 hours. At the end of this period, the compressed air was switched off and the sample opened to vacuum whilst cooling to the analysis temperature of 35° C. and a pressure of less than 10 μmHg. When these conditions were met, the sample was held under vacuum for a further 60 minutes. The uptake of pure hydrogen was measured at 100, 150, 200, 300, 400, 500, 600, 700 and 760 mmHg using an equilibration time of 10 seconds to generate an equilibrium isotherm. Using the post measurement sample weight, the total gas uptake was reported as cm.sup.3/g at 760 mmHg. The results were as follows:

TABLE-US-00002 PdO 3A Zeolite Hydrogen Loading Loading Capacity Thickness (% wt) (% wt) (cm.sup.3 .Math. g.sup.−1) (μm) 5 65 1.8 150 10 65 3.9 150

[0075] The shaped sorbents were able to adsorb hydrogen in the test.

EXAMPLE 4. PREPARATION OF SHAPED ZEOLITE SORBENTS BY DIGITAL LIGHT PROCESSING

[0076] Materials and Equipment.

[0077] Sorbent materials: 3A Zeolite powder.

[0078] Photo-polymer: Genesis Flexible Development Base Resin is a commercially available photocurable resin that is composed of acrylated monomers/oligomers (urethane acrylate resin and urethane acrylate), dispersant, and photoinitiator. The photo-polymer viscosity at 20° C. is 45 mPa.Math.s. This photo-polymer was supplied and used as received from Tethon Corporation Inc.

[0079] Computer-aided design equipment: A desktop computer running “Blender” open-source software followed by refinement of the structure using “Element” software available from nTopology.

[0080] Vat photo-polymerisation additive-layer manufacture (VP-ALM) equipment: Bison 1000 DLP available from Tethon Corporation Inc. The equipment is similar to that depicted in FIG. 1. The equipment comprises a computer control unit that controls the equipment, a vat or reservoir for liquid photo-polymer or adsorbent mixture having a thin, transparent polymer window at its base to allow light from a computer-controlled digital light processor light source to be projected using a mirror onto the liquid layer at the bottom of the reservoir. The transparent polymer window is non-stick to permit detachment of the layers of cured material. A build platform is placed in the liquid photo-polymer or adsorbent mixture such that there is a layer of liquid between the lower face of the build platform and the non-stick polymer film.

[0081] Sorbent mixture preparation: 65% by weight Zeolite 3A in Genesis Flexible Development Base Resin. 50.67 g of 3A zeolite was weighed out and placed into a Hauschild Speedmixer™ pot. 27.28 g of the Genesis Flexible Development Base Resin was weighed into the Speedmixer pot with the 3A zeolite. The mixture was then placed into the Hauschild Speedmixer™ and mixed at 2000 rpm for 60 s. After mixing any residue of powder was returned from the sides of the container and mixed into the bulk mixture. The mixture was then mixed a further three times at 3000 rpm for 60 s in the Speedmixer™.

[0082] The zeolite 3A was not pre-dried and so contained adsorbed water. For this example, the moisture content (determined by measuring mass loss on heating to 300° C. for 8 hours) was 18.4% by weight.

[0083] Following this mixing procedure, the sorbent mixture was poured into the resin tank of the Bison 1000 DLP equipment ready to produce shaped parts.

[0084] DLP Printer Preparation.

[0085] Methods and software are available commercially from the DLP printer providers or open-source. The method used here was as follows: [0086] 1. Draw/Create a structure design using computer-aided design (CAD) software. [0087] 2. Import the structure design into the DLP printer equipment software for positioning on the virtual build platform and generation of automatic support structures. [0088] 3. Generate a slice file in which the design is divided up into a plurality of layers. [0089] 4. Send the slice file to the DLP printer equipment (it is necessary to ensure at this point that there is sorbent material mixture in the vat and the build platform is fixed if required).

[0090] The Genesis Flexible Development photopolymer solidifies upon exposure to 405 nm wavelength light. The Bison 1000 has a variable power light source. At the curing surface the power output is a minimum of 2.24 mW.Math.cm.sup.−2 and a maximum of 9.05 mW.Math.cm.sup.−2. This was calibrated for a peak wavelength of 405 nm.

[0091] Shaped Adsorbent Production.

[0092] The fully assembled reservoir was loaded with adsorbent mixture without the build platform. The pre-prepared slice file was then processed using the DLP equipment. Light was projected through the windows into the layer of liquid from the digital light processor in a pattern according to the first layer of the shaped adsorbent, thereby causing it to solidify. The light switched off after a set exposure time and the process repeated using a pattern according to a second layer of the shaped adsorbent, and so on, building up the layers until the fully-formed shaped adsorbent was realized.

[0093] The number of exposures was determined by designing an input file that, when processed by the software into slices, gave shaped adsorbents of increasing thickness depending on the corresponding number of exposures. Each exposure was 5 s at the respective power setting.

[0094] The layer thickness for each exposure was determined by the material properties of the formulation and output power of the light projector.

[0095] Sample Cleaning and After-treatment.

[0096] The shaped adsorbent was removed from the base of the reservoir and washed with isopropanol to remove unreacted adsorbent material. The washed shaped adsorbent was then placed in a UV curing chamber and post-treated at 375-405 nm to fully cure the polymer.

[0097] Squares of 1 cm×1 cm with thicknesses ranging between 1.0 and 1.5 mm were prepared by this method.

EXAMPLE 5. TESTING BY DYNAMIC VAPOUR SORPTION (DVS)

[0098] Tests were performed on sorbents comprising 65% wt Zeolite A in Genesis Flexible Development photo-polymer prepared by curing several thin films of the adsorbent mixture according to the procedure of Example 4. Cured shaped sorbent samples having thicknesses of 1.11 (5 layers) and 1.40 mm (10 layers) were used. The cured samples were then broken up to form flakes of material to fit the 9 mm sample holder for the DVS testing.

[0099] Moisture adsorption was determined using the following procedure using Surface Measurement Systems DVS Endeavour™ apparatus. Each sample was pre-heated at 120° C. for 6 hours to record the dehydrated sample mass. Adsorption of moisture was then measured by mass change of the sample exposed to a nitrogen flow of 40 cm.sup.3/minute containing 40% relative humidity at 20° C. for 360 minutes. The results were as follows:

TABLE-US-00003 Moisture adsorption Thickness Sample (%) (mm) Cured Sorbent—5 × 5 s exposure 5.66 1.11 (9.05 mW .Math. cm.sup.−2) Cured Sorbent—10 × 5 s exposure 4.09 1.40 (9.05 mW .Math. cm.sup.−2)

[0100] The results indicate that the thin photopolymerised samples prepared using this photo-polymer are able to capture water vapour. The samples were able to pick up water more effectively than those of example 2, despite exposure to 40% RH being for a shorter period of time, and at a lower flow on the DVS equipment, and samples being thicker. This polymer is also flexible, which offers benefits in installation and use.