DRYING CONTAINER

Abstract

The invention relates to containers for the drying, especially the freeze-drying, of material. In particular, the invention relates to a lid of a drying container, said lid enabling to close the container body of the drying container so as to avoid i) contamination of the material to be dried inside the container and ii) spills of airborne solid particles of said material from the container to the environment. The lid comprises a lower and an upper frame with a vapor permeable sheet positioned in between. The invention further provides methods for the drying, especially the freeze-drying, of material.

Claims

1-15. (canceled)

16. A lid assembly for a drying container, comprising: a lower frame F1, an upper frame F2, a vapor permeable sheet positioned between the two frames, and fastening means, wherein the lower frame F1 and the upper frame F2 are each shaped as an open box having a base area and at least one side wall, the lower frame F1 and upper frame F2 being arranged such that a circumferential channel is formed, an outer side wall of the channel being formed by the side walls of the upper frame F2, an inner side wall of the channel being formed by the side walls of the lower frame F1 and a top wall of the channel being formed by a rim of the upper frame F2, wherein a width of the channel is chosen such that a mouth of a container body of a drying container can engage in the channel, the lower frame F1 and the upper frame F2 each comprise at least one opening in their respective base area, wherein the at least one opening in the lower frame F1 at least partially overlaps with the at least one opening in the upper frame F2, the sheet covers the at least one opening in the lower frame F1 and the sheet further covers at least a part of the top wall of the channel, and the lower frame F1, the sheet, and the upper frame F2 are aligned and held together by the fastening means, the fastening means providing a releasable connection between the lower frame F1 and the upper frame F2.

17. The lid assembly according to claim 16, wherein the lower frame F1 and/or the upper frame F2 is/are a folded plate wherein the side walls are folded with respect to the base area.

18. The lid assembly according to claim 16, wherein the fastening means comprise threaded rods attached to the lower frame F1, which extend through holes in the sheet and holes in the upper frame F2, and screw nuts screwed onto the threaded rods so as to press the upper frame F2 and the sheet onto the lower frame F1.

19. The lid assembly according to claim 16, wherein the lid assembly is flexible such that the lid assembly fits tightly on top of the mouth of the drying container when a pressing force is applied to the lid assembly.

20. The lid assembly according claim 16, wherein the lower frame F1 comprises a rim and the at least one opening in the base area of the lower frame F1 is formed as a single opening enclosed by the rim, or a plurality of openings, the rim enclosing the plurality of openings, or a plurality of holes, wherein the rim is free of holes.

21. The lid assembly according to claim 16, wherein the at least one opening in the base area of the upper frame F2 is formed as a single opening enclosed by the rim, or a plurality of openings, the rim enclosing the plurality of openings.

22. The lid assembly according to claim 16, wherein the lower frame F1 and/or the upper frame F2 is/are made from a metal.

23. The lid assembly according to claim 16, wherein the sheet is selected from a) a microporous membrane, b) a nonporous, moisture permeable film, and c) a filter paper.

24. The lid assembly according to claim 16, wherein the sheet is arranged such that the edges are folded back to form a double layer of the sheet within the circumferential channel.

25. The lid assembly according to claim 16, wherein the lid assembly further comprises at least one port, the port being a mobile port having a port opening in the lower frame F1 and/or a port opening in the upper frame F2, the port openings being aligned and covered by the sheet prior to the use of the port or a fixed port having a port opening in the lower frame F1 and/or a port opening in the upper frame F2, and an opening in the sheet, the port openings and the opening in the sheet being aligned and surrounded by a connector arranged on the lower frame F1 or the upper frame F2.

26. A drying container, comprising: a container body having a bottom and at least one side wall, the side walls defining a mouth of the container body, the mouth having a contact surface enclosing the mouth, and a lid assembly according to claim 16, wherein the contact surface engages the circumferential channel of the lid assembly.

27. The drying container according to claim 26, the drying container further comprising one or more fastening means to reversibly attach the container body to the lid assembly.

28. The drying container according to claim 27, wherein the fastening means are selected from clamps, screws, and magnetic fastening means.

29. The drying container according to claim 26, wherein the container body is made from a metal.

30. A method for drying, preferably freeze-drying, of material, comprising the following steps: a) introducing the material to be dried into a container body, b) closing the container body by means of a lid assembly according to claim 16, and c) exposing the closed drying container to conditions suitable to effect drying, wherein steps a) and b) can be carried out in any order.

31. The method of claim 30, wherein the drying is freeze-drying.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0062] FIG. 1a shows an exploded view of one embodiment of the drying container of the present invention with a first embodiment of the lid assembly,

[0063] FIG. 1b shows a cross sectional view of the drying container,

[0064] FIG. 1c shows a cross sectional view of the drying container with a folded sheet,

[0065] FIGS. 2a to 2h show different embodiments of upper and/or lower frame,

[0066] FIG. 3a shows a top view of a second embodiment of the lid assembly,

[0067] FIG. 3b shows a cross sectional view of the second embodiment of the lid assembly

[0068] FIG. 4a shows a top view of a third embodiment of the lid assembly,

[0069] FIG. 4b shows a cross sectional view of the third embodiment of the lid assembly with the sheet resting on the lower frame F1,

[0070] FIG. 4c shows a cross sectional view of the third embodiment of the lid assembly during the drying process,

[0071] FIG. 5a shows an embodiment of a mobile port arranged on the lower frame F1,

[0072] FIG. 5b shows an embodiment of a mobile port arranged on the upper frame F2,

[0073] FIG. 5c shows an embodiment of a fixed port arranged on the lower frame F1,

[0074] FIG. 5d shows an embodiment of a fixed port arranged on the upper frame F2,

[0075] FIG. 6 shows the measurement of the pressure difference between both sides of the sheet of the drying container,

[0076] FIG. 7 shows the temperature measurement inside the drying container,

[0077] FIG. 8 depicts a material transfer though a port of the lid assembly,

[0078] FIG. 9 shows the transfer of liquid through a port of the lid assembly,

[0079] FIGS. 10a to 10c show a first embodiment of fastening means to fix the lid assembly to a container body,

[0080] FIGS. 10d to 10e show a second embodiment of fastening means to fix the lid assembly to a container body,

[0081] FIG. 10f shows a third embodiment of fastening means to fix the lid assembly to a container body,

[0082] FIGS. 11a and 11b show a fourth embodiment of fastening means to fix the lid assembly to a container body,

[0083] FIGS. 12a and 12b show a fifth embodiment of fastening means to fix the lid assembly to a container body,

[0084] FIGS. 13a and 13b show a sixth embodiment of fastening means to fix the lid assembly to a container body, and

[0085] FIG. 14 shows an exploded view of a second embodiment of the drying container.

[0086] The following figures, claims and examples, including the experiments conducted and the results achieved, are provided for illustrative purposes only and are not to be construed as limiting the scope of the claims. Container bodies and lid assemblies of any shape are possible and are not limited to the relative dimensions or the rectangular shape shown in drawings.

[0087] FIG. 1a shows an exploded view of one embodiment of the drying container 10 of the present invention with a first embodiment of the lid assembly 5. The drying container 10 comprises a container body 1 having a bottom wall 20 and four side walls 21 defining a mouth 19 of the container body 1.

[0088] The lid assembly 5 comprises a lower frame F1 2, a vapor permeable sheet 3, and an upper frame F2 4, which are stacked in this order. The frames 2, 4 are each shaped like an open box with four side walls 17, 18. Each of the frames 2, 4 has a rim 11 surrounding an opening 16. The width of the rim 11 of the lower frame F1 2 is marked with the reference numeral 6 and the width of the rim 11 of the upper frame F2 4 is marked with the reference numeral 7. The sheet 3 is positioned between the two frames 2, 4 such that it is clamped between the rims 11 of the two frames 2, 4.

[0089] The lid assembly 5 is held together by means of threaded rods 12 attached to the lower frame F1 2. These threaded rods 12 extend through holes 14 in the sheet 3 and the upper frame 4. After assembly of the lid assembly 5, screw nuts (not shown) are put onto the threaded rods 12 to secure the lid assembly 5.

[0090] FIG. 1b shows a cross sectional view of the drying container 10 as described in FIG. 1a.

[0091] The lid assembly 5 is shown in an assembled state with the sheet 3 securely held between the lower frame F1 2 and the upper frame F2 4. The two frames 2, 4 define a circumferential channel 9 having a channel width 8. The rim 11 of the upper frame F2 4 defines a top wall of the channel 9, the side walls 18 of the upper frame F2 4 define outer walls of the channel 9 and the side walls 17 of the lower frame F1 2 define inner walls of the channel 9. The container body 1 has a bottom wall 20 and side walls 21 which define a mouth 19 of the container body 1. The mouth 19 has a contact surface 13 with a width which is chosen such that the mouth 19 may engage in the channel 9 when the lid assembly 5 closes the drying container 10. The sheet 3 extends into the channel 9 and at least partially covers the top wall of the channel 9. When the drying container 10 is closed, the part of the sheet 3 which is located inside the channel 9 serves as a gasket to seal the drying container 10.

[0092] FIG. 1c shows a variation of the lid assembly 5 of the drying container 10 as described in FIGS. 1a and 1b. The sheet 3 of the lid assembly 5 is arranged in the channel 9 such that the edges of the sheet 3 are folded back to form a double layer of the sheet 3 within the circumferential channel 9. By folding the sheet 3 to form a double layer the gasket-like effect of the sheet is enhanced.

[0093] FIGS. 2a to 2g show several embodiments of plates which may be folded into a lower frame F1 or an upper frame F2 by folding the flaps 22 by 90°. The fold lines are shown as dashed lines in FIGS. 2a to 2g. It should be noted that similar shapes of the lower and upper frames F1 and F2 can be obtained by other techniques such as deep drawing.

[0094] If the plate is used as lower frame F1, rods, e.g. threaded rods, may be attached to the plate. If the plate is used as upper frame F2, through holes may be drilled for attachment onto the rods of a lower frame F1.

[0095] In FIG. 2a the plate has one single opening 16 which is surrounded by a rim 11. Both the opening 16 and the rim 11 have a rectangular shape. Four flaps 22 abut the four sides of the rim 11 and may be folded by 90° to form side walls 17, 18 of the frames.

[0096] FIG. 2b shows an embodiment of the plate having six openings 16 arranged in three columns and two rows. The six openings 16 are surrounded by the rim 11. The material of the plate between the openings 16 forms a support grid 24.

[0097] FIG. 2c shows an embodiment of the plate having four openings 16 arranged in four columns and one row. The four openings 16 are surrounded by the rim 11. The material of the plate between the openings 16 forms support braces 25.

[0098] FIG. 2d shows an embodiment of the plate having a plurality of holes 15 which serve as openings 16. The holes 15 are arranged in a regular pattern inside an area surrounded by the rim 11. The rim 11 is free of holes 15.

[0099] FIG. 2e shows an embodiment of the plate having support braces 25 with included port openings 26. The port openings 26 may be used to attach a mobile port to the frame, and their shape may be chosen depending on the shape of the mobile port, e.g. from square, round, or oval. The width of the support brace 25 is larger in the area surrounding the port opening 26 in order to provide sufficient stability. Alternatively, a support grid 24 with included port openings 26 may be used. Another alternative is arranging a port opening 26 on a tab 29 which projects from the rim 11 into the space of the opening 16.

[0100] The number and arrangement of port openings 26 on the plate may be varied. Further, the shape of the port openings 26 may be chosen as required. Examples for suitable shapes of a port opening 26 include circles, ovals and polygonal shapes such as squares or rectangles.

[0101] FIG. 2f shows a variant of the plate of FIG. 2e wherein the port openings 26 are configured for welding of a connector to the port opening 26. Cuts 31 are provided to compensate for warping due to the welding.

[0102] FIG. 2g shows a plate having six openings 16 and a support grid 24 similar to the embodiment of FIG. 2b. Further, two port openings 26 are provided wherein one of the port openings is provided with cuts 31 to compensate for warping when a connector is welded to the port opening 26.

[0103] FIG. 2h, panel (i) shows a plate having six openings 16 and a support grid 24 similar to the embodiment of FIG. 2b. Further, a port opening 26 is provided wherein the port opening is located in a cup-like recess of the support grid, such that the port opening and the bottom 23 of the cup-like recess are lowered relative to the level of the rim 11. Because the walls 27 of the cup-like recess limit warping, no cuts 31 are needed when a connector is welded to the port opening 26. Panel (ii) shows a blow-up of the part of the support grid, which comprises the port opening. Panel (iii) shows a cross-section of this area in an embodiment where the port is configured as a fixed port with a welded connector 38.

[0104] FIG. 3a shows a top view of a second embodiment of the lid assembly 5.

[0105] The upper frame F2 4 is configured with three support braces 25 as described with respect to FIG. 2c and has four openings 16. The lower frame F1 2 is configured with four support braces 25. The support braces 25 of the lower frame F1 2 do not overlap with the support braces 25 of the upper frame F2 4. Thus, the lower frame F1 has five openings 16 which partially overlap with the four openings 16 of the upper frame F2.

[0106] FIG. 3b shows a cross sectional view of the second embodiment of the lid assembly 5.

[0107] In the situation shown in FIG. 3b a freeze-drying operation is in progress. The sheet 3, which is held between the lower frame F1 2 and the upper frame F2 4, bulges outward due to a pressure difference. The outward bulging is limited by the support braces 25 of the upper frame F2. When there is no pressure difference, the sheet 3 rests on the support braces 25 of the lower frame F1.

[0108] By the alternating arrangement of the support braces 25 of the two frames 2, 4 most of the area of the sheet 3 is exposed during the freeze-drying process. Only the area covered by the support braces 25 of the upper frame F2 4 is covered up.

[0109] FIG. 4a shows a top view of a third embodiment of the lid assembly 5.

[0110] The lower frame F1 2 is configured as described with respect to FIG. 2d and the upper frame F2 4 is configured as described with respect to FIG. 2a. The sheet 3 is held between the two frames 2, 4 and rests on the lower frame F1 2 when there is no pressure difference.

[0111] FIG. 4b shows a cross sectional view of the third embodiment of the lid assembly 5 with the sheet 3 resting on the lower frame F1 2. In the situation shown in FIG. 4b there is no pressure difference between the inside of the drying container 10 and the outside. Thus, the sheet resets on the lower frame F1 2 and the exposed area of the sheet is small, thereby limiting evaporation of the solvent. If a non-conductive sheet material is used, electrostatic charges may discharge over the material of the lower frame F1 2 which is in close contact with the sheet 3.

[0112] FIG. 4c shows a cross sectional view of the third embodiment of the lid assembly 5 when in use in a freeze-drying process. In the situation shown in FIG. 4c there is a pressure difference between the inside of the drying container and the outside so that the sheet 3 bulges outwards. The sheet 3 is held between the rims of the two frames 2, 4 but does not rest on the lower frame F1. As can be seen in FIG. 4c, nearly the entire area of the sheet 3 is exposed and may effectively be used in the freeze-drying process.

[0113] FIGS. 5a to 5d show different embodiments of ports 28, all of which are drawn in a cross sectional view.

[0114] FIG. 5a shows an example of a mobile port arranged on a lower frame F1 2.

[0115] A threaded nipple 30 with a through hole and a projecting rim 37 at the lower end is inserted through the port opening 26 in the lower frame F1 2. The projecting rim 37, which is not necessarily circumferential, keeps the threaded nipple 30 from slipping through the port opening 26 and/or provides a counter surface for an optional washer 32. The sheet 3 rests on the lower frame F1 2 under an optional second washer 32. A seal 34 surrounds the nipple 30 and the threaded nipple 30 is secured using a screw cap or a screw nut (not shown). The cap may be closed or have a through hole. It should be noted that the outer circumference of the threaded nipple's lower end is not necessarily circular, but may be adjusted depending on the shape of the opening 26.

[0116] In further embodiments a threaded nipple 30 with a lower section having a polygonal or oval shaped outer circumference may be used to provide a mobile port. Likewise, the port opening 26 has a matching polygonal or oval shape. When the lower section of the threaded nipple 30 is inserted in the corresponding port opening 26, the threaded nipple 30 is secured against rotation.

[0117] FIG. 5b shows an example of a mobile port arranged on the upper frame F2 4.

[0118] A threaded nipple 30 with a through hole and a and a projecting rim 37 at the lower end is inserted through an opening in the sheet 3 and the port opening 26 in the upper frame F2 4. A washer 32 is placed between the projecting rim 37 and the sheet 3. The sheet 3 rests on the washer 32. A second washer 32 can be used to support the seal 34. The seal 34 surrounds the nipple 30 and the threaded nipple 30 is secured using a screw cap or a screw nut (not shown). The cap may be closed or have a through hole.

[0119] FIG. 5c shows an example of a fixed port arranged on the lower frame F1 2.

[0120] A connector 38 having a thread is attached to the port opening 26 in the lower frame F2 2 by welding. The sheet 3 has an opening through which the connector 38 extends. The sheet 3 rests on the lower frame F1 2. In order to close the port 28, a seal 34 is placed over the connector 38 and a cap (not shown) is screwed onto the connector 38. The cap may be closed or have a through hole.

[0121] FIG. 5d shows an example of a fixed port arranged on the upper frame F2 4.

[0122] The connector 38 is inserted through the port opening 26 in the upper frame F2 4 and is fixed to the upper frame F2 4 by welding. The upper frame F2 4 is placed over the sheet 3, wherein the connector 38 is inserted through an opening in the sheet 3. A seal 34 which is secured with a screw nut 36 seals the side facing towards the inside of the container.

[0123] In order to close the port 28, a seal 34 is placed over the connector 38 and a cap (not shown) is screwed onto the connector 38. The cap may be closed or have a through hole.

[0124] FIG. 6 shows the measurement of pressure inside the drying container 10. A differential pressure measurement device 42 is provided with a first tube 44 which is inserted through the port 28 into the drying container 10. The drying container 10 is filled with material 58 to be dried and rests on a shelf 65 of the drying chamber 40. A second tube 46 opens into the inside of the drying chamber 40. In this arrangement, the pressure difference between the inside of the drying container 10 and the inside of the drying chamber 40 may be measured. The pressure measurement device 42 may be placed inside or outside the drying chamber 40.

[0125] FIG. 7 shows the measurement of temperature inside the drying container 10. A guide tube 47 with a narrower lower part and a closed, thin bottom is inserted into the port 28 of a drying container 10. Preferably, the guide tube 47 is made from a material with good thermal conductivity. In order to provide a tight seal, a screw cap 50 with a through hole having a sealing lip 52 is arranged on the port 28, which is shown in this example as a fixed port with a connector 38. However, mobile ports may likewise be used. The sealing lip 52 forms a tight seal around the broader upper part of the guide tube 47. A temperature probe 48 is inserted into the guide tube, such that its sensor contacts the guide tube's bottom. In order to measure the temperature, the guide tube 47 is pushed down, until its bottom contacts the bottom 20 of the container body. In this way, the temperature in the immediate vicinity of the drying material 58 can be monitored without contaminating the temperature probe or the content of the drying container.

[0126] FIG. 8 depicts a secure transfer of a sample of material 58 out of the drying container 10 through a port 28 of the lid assembly 5. A bag 56 is secured to the port 28 by clamping the bag 56 between the sheet 3 and the seal 34 by means of a cap nut 57. Material 58 may then transferred from the drying 10 container into the bag 56 without the danger of contamination of the surroundings. The bag 56 may then be safely removed, e.g., by applying commercially available safe seal clamps prior to separation with a cutting tool. The clamps will seal both the bag 56 itself and the reminder of the bag 56, which is left at the port 28 after separation of the bag. The place where the clamps are to be applied is schematically indicated by a dot-and-dash line.

[0127] FIGS. 9a and 9b show two different embodiments enabling the transfer of liquid 59 through a port 28 of the lid assembly 5 into the drying container 10. A hose 66 is attached to the port 28 and allows the transfer of liquid 59 onto the material 58 inside the drying container 10 without the danger of contamination of the surroundings.

[0128] FIG. 9a shows an example of a mobile port comprising a (treaded) nipple inserted in an opening of a lower frame 2, a (screw) nut 57, and seal 34.

[0129] FIG. 9b shows an example of a fixed port comprising a connector 38 welded to the lower frame, seal 34, and a screw cap 50 with a through hole having a sealing lip 52. These configurations may either be used to dissolve or suspend the material 58 in the liquid 59 after completion of the drying process. Alternatively, the setup may be used to introduce the liquid material to be dried into the container 10, i.e. the material 58 and the liquid 59 may be the same.

[0130] FIGS. 10a to 10c depict a first embodiment of fastening means to fix the lid assembly 5 to a container body 1. The fastening means is constructed as a clamp 54 made out of a spring steel plate. FIG. 10a depicts the clamp 54 after cutting the plate and before folding. The dashed lines mark the folds. FIG. 10b depicts the clamp 54 after folding in a top view and FIG. 10c depicts the clamp 54 after folding in a side view.

[0131] FIGS. 10d to 10e depict a second embodiment of fastening means to fix the lid assembly 5 to a container body 1. The fastening means is constructed as a clamp 54 made out of a spring steel plate. FIG. 10d depicts the clamp 54 after cutting the plate and before folding. The dashed lines mark the folds. FIG. 10e depicts the clamp 54 after folding in a side view.

[0132] FIG. 10f depicts a third embodiment of fastening means to fix the lid assembly 5 to a container body 1. The fastening means is constructed as a clamp 54 made out of a spring steel plate. FIG. 10f depicts the clamp 54 after cutting the plate and before folding. The dashed lines mark the folds and the fold angles are indicated.

[0133] FIGS. 11a and 11b show a fourth embodiment of fastening means to fix the lid assembly 5 to a container body 1. The fastening means is constructed as a clamp 54 made out of a spring steel plate. FIG. 11a depicts the clamp 54 after cutting the plate and before folding. The dashed lines mark the folds. FIG. 11b depicts the clamp 54 after folding in a in a side view.

[0134] FIGS. 12a and 12b depict a fifth embodiment of fastening means to fix the lid assembly to a container body 1. The fastening means are constructed as a clamp 54 and a locking block 55. FIG. 12a depicts the clamp 54 in a perspective view. The clamp 54 has through holes 53 for insertion of a screw bolt (not shown). FIG. 12b depicts the locking block 55, which is likewise provided with a through hole 53 for insertion of a screw bolt, in a perspective view.

[0135] FIGS. 13a and 13b show a sixth embodiment of fastening means to fix the lid assembly 5 to a container body 1. The fastening means are constructed as magnetic fastening means having a flexible sheet 64 with two attached magnets 60. The magnets 60 are not movable along the flexible sheet 64. The magnetic fastening means are folded along fold lines 62 to secure the lid assembly 5 to the container body as shown in FIG. 13b. The end if the flexible sheet 64 forms a little latch facilitating the separation of the magnets in order to open the container

[0136] FIG. 14 shows an exploded view of a second embodiment of the drying container 10.

[0137] The drying container 10 comprises a container body 1 having a bottom wall 20 and four side walls 21 defining a mouth 19 of the container body 1.

[0138] The lid assembly 5 comprises a lower frame F1 2, a vapor permeable sheet, and an upper frame F2 4, all of which are stacked in this order.

[0139] The lower frame F1 2 is configured as shown in FIG. 2g and has two ports 28. One of the ports 28 is configured as a fixed port with a connector 38 welded to the lower frame F1 2. The upper frame F2 4 is configured as shown in FIG. 2a and has an opening 16 which overlaps with the six opening 16 in the lower frame F2 2.

[0140] The lid assembly 5 is held together by means of threaded rods 12 attached to the lower frame F1 2. These threaded rods 12 extend through holes 14 in the sheet 3 and the upper frame F2 4.

[0141] After assembly of the lid assembly 5, screw nuts (not shown) are put onto the threaded rods 12 to secure the lid assembly 5.

[0142] The lid assembly 5 is secured to the container body 1 by means of eight clamps 54 as described with respect to FIGS. 11a and 11b.

EXAMPLES

Example 1

[0143] To investigate the need for an elastomeric seal, 20 drying containers as depicted in FIG. 14 were assembled with an additional silicone flat seal inserted between the sheet and frame F2 of the lid. The container body, lower frame F1, upper frame F2 and spring clamps were made from stainless steel, a PTFE (polytetrafluoroethylene) membrane with 1-2 μm pore size served as the sheet. The port incorporated into F1 was closed by a screw cap. The drying containers were placed onto the shelfs of a lyophilization chamber.

[0144] Each drying container was filled with about 5 l of an aqueous paracetamol solution (10 g/l) using a peristaltic pump, whose outlet tube was connected to the drying container's port. After removal of the tube, a temperature sensor was inserted into the port, the lyophilization chamber was closed, and the lyophilization program started.

[0145] After the end of the lyophilization program and venting of the lyophilization chamber, swab tests were taken on the surface of the drying containers and inside the lyophilization chamber. The surface concentration of paracetamol ranged from below the detection limit of <0.01 μg/dm2 to a maximum of 0.02 μg/dm.sup.2. The concentration of paracetamol in the room air as well as on the testing probes worn by the operator was likewise below the detection limit.

[0146] The experiment was repeated with 10 drying containers, which differed from the previously used containers only by omission of the silicone flat seal.

[0147] After the end of the lyophilization program and venting of the lyophilization chamber, swab tests were taken on the surface of the drying containers and inside the lyophilization chamber. The surface concentration of paracetamol was below the detection limit of <0.01 μg/dm.sup.2 in most samples and reached a maximum of 0.03 μg/dm.sup.2. The concentration of paracetamol in the room air as well as on the testing probes worn by the operator was likewise below the detection limit of <0.01 μg/m.sup.3. It was therefore concluded that the design of the present drying container enables safe use without the need for an elastomeric seal.

Example 2

[0148] 10 drying containers as depicted in FIG. 14 were assembled and placed onto the shelfs of a lyophilization chamber. The container body, lower frame F1, upper frame F2 and spring clamps were made from stainless steel, a PET (Polyethylenterephthalate) membrane with 7 μm pore size served as the sheet, and was folded back to form a double layer within the lid assembly's circumferential channel (cf. FIG. 1c). The port incorporated into F1 was closed by a screw cap.

[0149] Each drying container was filled with about 5 l of an aqueous paracetamol solution (10 g/l) using a peristaltic pump, whose outlet tube was connected to the drying container's port. After removal of the tube, a temperature sensor was inserted into the port, the lyophilization chamber was closed, and the lyophilization program started.

[0150] After the end of the lyophilization program and venting of the lyophilization chamber, swab tests were taken on the surface of the drying containers and inside the lyophilization chamber. The surface concentration of paracetamol was below the detection limit of <0.01 μg/dm.sup.2 in most samples and reached a maximum of 0.02 μg/dm.sup.2. The concentration of paracetamol in the room air as well as on the testing probes worn by the operator was likewise below the detection limit of <0.01 μg/m.sup.3.

TABLE-US-00001 1 container body 2 lower frame F1 3 sheet 4 upper frame F2 5 lid assembly 6 rim width F1 7 rim width F2 8 channel width 9 channel 10 drying container 11 rim 12 threaded rod 13 contact surface 14 hole 15 holes 16 opening 17 side wall F1 18 side wall F2 19 mouth (container body) 20 bottom (container body) 21 side wall (container body) 22 flap 23 bottom (cup-like recess) 24 support grid 25 support braces 26 port opening 27 side wall (cup-like recess) 28 port 29 tab 30 nipple 31 cut 32 washer 34 seal 36 screw nut 37 projecting rim 38 connector 40 drying chamber 42 pressure measurement device 44 first tube 46 second tube 47 guide tube 48 temperature probe 50 screw cap with through hole 52 sealing lip 53 through hole 54 clamp 55 locking block 56 bag 57 screw nut 58 material 59 liquid 60 magnet 62 fold 64 flexible sheet 65 shelf 66 hose