Process for producing a filter cartridge having a gas filter membrane

Abstract

The present invention relates to a production process for a filter cartridge from a group of hollow fibres for gas separation according to Claim 1 of this application.

Description

[0001] 202400091 Foreign Filing 1

[0002] Process for producing a filter cartridge having a gas filter membrane

[0003] The invention relates to a production process for a filter cartridge having a potted section, which is produced from or by means of a potting mixture, wherein the filter cartridge thus produced or a filter module with such a filter cartridge are used in particular for use of depletions of 02 in aviation, in particular what are called OBIGGS (On-Board Inert Gas Generating Systems).

[0004] There are two main techniques known in industry for gas separation and liquid filtration with hollow fibre membranes. There are firstly membrane modules which contain hollow fibre membranes and in which the filter cartridge tube in which the fibres are potted simultaneously also constitutes the pressure-bearing shell. There are secondly systems in which filter cartridges are installed in a pressure-bearing housing and in which the filter cartridge tube does not itself constitute the pressure-bearing shell.

[0005] In the aerospace sector, for example in OBIGGS applications, preferred membrane modules are typically those in which the fibres are potted directly into a pressure-bearing tube since this is associated with a weight saving compared to a cartridge solution in a separate pressure tube. These filter cartridge tubes that also work as a pressure vessel are also called "shells" in the OBIGGS sector.

[0006] In this case, the filter modules or filter cartridges may be used for various applications, especially in gas separation, for example biogas processing, helium or H2 recovery / processing, for recovery of N2 from air, for recovery of 02 from air, for gas drying, etc.

[0007] The separation-active membranes and accompanying cartridges or modules for fluid separation have a limited lifetime and are typically exchanged repeatedly over the lifetime of a membrane plant. Examples of membrane modules can be found in US 2012 / 0304856 A1 , US 2010 / 0072124 A1 , US 2003 / 0102264 A1 and WO 2002 / 04100 A1 . In the case of what are called cartridge systems, the separation-active membrane area consists of a bundle of several hundred to several hundred thousand individual hollow fibres disposed in a cartridge tube, generally a metallic cartridge tube made of a stainless steel or aluminium, although plastic tubes are also usable. This filter cartridge with the bundle of the separationactive hollow fibre membrane can be found, for example, in US 2012 / 0304856 A1 , EP 1005896 A1 , JP 1 1028341 A, US 4480683, US 5470469 A, US 2011 / 036764 A1 , WO 01 / 66231 A1 , WO 2011 / 022380 A1 and WO 2012 / 170956 A1 .

[0008] It is known here that the bundle of hollow fibres typically has to be potted at both ends with a resin in the cartridge tube in order to delimit the feed / retentate space from the permeate space. These potted sections made of resin, for example epoxy resins, must withstand the process conditions necessary for the gas separation over the product lifetime, especially temperature, pressure and influences of feed components that constitute a chemical burden, such as oxygen, water or VOCs. Particularly in OBIGGS applications, the filter cartridges must withstand many temperature and pressure changes owing to the many takeoff and landing cycles, where cracking can occur in the potted sections (tube sheets) under many changes of load in particular, which can lead to gas leakage or fraction of the potted section. 202400091 Foreign Filing 2

[0009] This problem is described, for example, by WO 2014 / 143336 A1 for the step of assembly and curing or cooling of the potted section, also referred to as tube sheet therein. EP 2 762 222 A1 addresses the problem of cracking, especially for what are called OBIGGS (On-Board Inert Gas Generating Systems), and proposes that different material stretching processes between the filter cartridge and the actual pressure housing should be attenuated by providing suitable O-ring arrangements. In order to improve this solution by means of O-rings, WO 2014 / 143336 A1 proposes providing end caps made of a polymer material that stick to the cartridge element in the inlet of the potting mixture. Finally, for prevention of stress cracks in the potted section, EP 3 007 807 B1 proposes providing a multilayer bonding structure between the potted section and the cartridge tube and / or the pressure housing.

[0010] JPS58-166902A discloses a hollow fibre module having a potting material composed of epoxy resin, a curing agent composed of an aliphatic amine and 2-ethyl-4-methylimidazole, where the modules are proposed for gas separation. The curing agent may be an aliphatic-aromatic amine meta-xylenediamine, which is to be present in a weight ratio of 100:16:1 . A temperature guide for the curing proposed in that document is first storage at 15-35°C and then curing at preferably 75-125°C. This temperature regime requires very long curing times.

[0011] In OBIGGS applications in aerospace, flying devices and all relevant components are subject to temperature changes of in some cases plus 50°C (desert climate, summer) down to an outside temperature of minus 50°C at great flying heights, as well as very rapid thermal changes in some cases as a result of corresponding operations of the flying device. With regard to the extreme changes in load as occur in OBIGGS applications, it has been found that damage still occurs to the membrane fibres, the potted sections and / or the transitions between filter cartridge, filter module (housing) or the filter cartridge (also called "shell") that typically forms the module housing in OBIGGS applications.

[0012] It is therefore an object of the present invention to provide an improved or at least alternative production process and potting mixture (potting material) for a filter cartridge. A further object is that of providing a production process for a filter cartridge with a potting section which, through improved material selection and processing, provides a filter module which is leakproof and intact over its lifetime and which shows no cracks and no leakage, in spite of many cycles of great changes in temperature and pressure in OBIGGS applications (On-board Inert Gas Generating Systems).

[0013] In this context, it has been found that, surprisingly, the step of curing the potting mixture in the production of the potted section is of major significance for the quality and load-bearing capacity of the filter cartridge, in particular the durability of the potted section to mechanical and thermal cycling stresses.

[0014] The object is achieved by the present invention production process for a filter cartridge from a group of hollow fibres (fibre group) suitable as membrane for gas separation, comprising the steps of: grouping step, providing and / or grouping a number of individual fibres to a fibre bundle; 202400091 Foreign Filing 3 bonding step, introducing the fibre bundle into a cartridge tube and aligning and optionally fixing the cartridge tube for the potting and / or filling step; filling step, storing / charging a defined amount of the liquid potting mixture for the potting step, where the potting mixture comprises or is formed from at least a resin component A and a curing agent B as components, where resin component A of the potting mixture is an epoxy resin or epoxy resin mixture composed of two or more constituents; potting step, feeding in a potting mixture at at least one end of the fibre bundle into the cartridge tube to form at least one potted section (500), where the proportion by volume of the individual fibres in the respective potted section is in the range of 50% to 70% by volume, ideally 50% to 60% by volume, based on the cavity volume of the potted section in the cartridge tube; curing step, heating the filter cartridge for a period of time greater than at least one hour, where the potting mixture comprises or is formed from at least a resin component A and a curing agent B as components, where the filter cartridge is subjected to at least the following phases in the curing step:

[0015] - a preheating phase (410) within a first temperature range (T1) of 25 to 85°C, ideally 30 to 80°C, for a preheating time of 2 to 12 h, ideally 3 to 10 h;

[0016] - a heating phase (460) in which the oven temperature of the first temperature range (T1) is raised to an end temperature T2 in the range of 100 to 180°C, ideally 120 to 160°C, where the positive temperature gradient is 10 to 30°C / h, ideally 15 to 25°C / h;

[0017] - a hold phase (470) at the end temperature (T2) for a hold time of 2 to 24 h, ideally 4 to 18 h, and

[0018] - a cooling phase (480) at falling temperature, where the negative temperature gradient is 20 to 60°C / h, ideally 25 to 50°C / h, where and comprises or is formed from at least the following curing agent components (B1 , B2): a) amines (B1), as an amine mixture of aliphatic amines and aromatic amines and b) imidazoles (B2) as catalyst in the range of 0.1 % to 5% by weight, based on the resin component A, where

[0019] • a proportion of aliphatic amines is in the range from less than 40% to at least 5% by weight, based on curing agent B; and

[0020] • a proportion of aromatic amines in the amine mixture is not more than 98 mol%, ideally not more than 95 mol%, based on the amine groups of curing agent B, where the preheating phase comprises at least two subphases, where the temperature range (T1) of the first subphase is 50 to 90°C, ideally 60 to 80°C, and in a subsequent calming or cooling phase (second subphase) the temperature range (TK) is 5 to 50°C lower than the temperature range (T1), ideally 10 to 40°C lower, and where the second subphase is followed by

[0021] - a third subphase of the preheating phase in which the temperature range (T1) is 50 to 90°C, or the heating phase is executed.

[0022] What is meant here by "potting" is the step of producing the potted section by the casting and curing of the hollow fibres or the hollow fibre bundle by means of the potting material, such that a tube sheet is formed from the cured potting material, which fixes the fibres in position in the (filter) cartridge. The word 202400091 Foreign Filing 4

[0023] "potting" is also used in the same way as in the specialist field to a certain degree, for example "potting mixture", "potting material" and "potted section".

[0024] The grouping step includes all substeps that are necessary and / or advantageous in order to select the required number of individual fibres as required after production, and to collate them, cut them to the desired length, align them, fix them to one another as a bundle, for example by lacing, wrapping the free ends of the bundle with netting or hose at a part-length, etc. The grouping step should not be understood in a restrictive manner and serves overall to implement all the necessary substeps in order to then introduce the fibre bundle into the cartridge tube in the bonding step and subsequently to be able to pot it therein.

[0025] The bonding step means and encompasses the introducing of the fibre bundle created in the grouping step into the respective cartridge tube and aligning and optionally fixing the cartridge tube for the potting and / or filling step. The bonding step thus also comprises the arranging and optionally securing of the cartridge tube with the fibre bundle introduced at the site of curing, as for example in a centrifuge, a heat treatment oven for stationary potting, in which each potting element is cured in a static, vertically aligned filter cartridge.

[0026] The filling step means and encompasses the producing of the potting mixture, storing and charging of a defined amount of the liquid potting mixture in at least one reservoir vessel for the potting step, where the potting mixture comprises or is formed from at least a resin component A and a curing agent B as components. The filling step further comprises the connection of the at least one reservoir vessel to at least one conduit that directly or indirectly leads to the section of the cartridge tube in which the potted section is to be generated. Thus, the filling step may also comprise a mixing step by combining and / or mixing of the components of the potting mixture for a defined duration. This mixing time may be at least 1 s up to 180 s, although longer mixing times are also advantageous where required, depending in particular on the mixing properties of resin component A and curing agent B. A stirrer or agitator system may be used as an advantageous mixing unit, although the potting mixture is also producible by means of a static mixer. It may be advantageous in particular to implement the mixing step under an inert atmosphere in order to rule out any oxidizing 02 effect and influences of moisture.

[0027] The aforementioned sequence of grouping, bonding and filling steps is a very preferred, advantageous sequence, although this should not be understood in a limiting manner, and substeps of grouping, bonding and filling steps can also be effected in parallel, as far as technically feasible.

[0028] The potting step means and encompasses the feeding of the free-flowing potting mixture provided to at least one end of the fibre bundle in the cartridge tube for subsequent formation of at least one potted section. In this case, a preliminary potted section is produced in the potting step and in the subsequent curing step, which constitutes the final, intended and usable potted section of the corresponding cartridge tube only after final processing that follows after the curing step. This final processing is generally a mechanical final processing operation, where the preliminary potted section with the potted and hence at 202400091 Foreign Filing 5 least partly sealed fibre ends is cut and / or removed to such an extent that the fibre ends are exposed; preferably all fibre ends in an area for inflow or outflow of gas are exposed. In the present context, no distinction is intended between a "preliminary" and a "final" potted section without explicit reference.

[0029] The curing step means and encompasses all substeps after (complete) feeding of the free-flowing potting mixture that are required to produce a "preliminary" potted section after the potting step, which can subsequently be processed in a final processing step as explained to produce the "final" potted section.

[0030] The preheating phase, heating phase, hold phase and cooling phase of the curing step are run successively, in the absence of any different or supplementary statement.

[0031] The term "positive temperature gradient" means the degree of a rise in temperature over a period of time, also called heating rate. Analogously, a "negative temperature gradient" means the degree of the fall in temperature over a period of time, also called cooling rate.

[0032] A filter cartridge produced by means of the production process, also referred to herein as "cartridge", has an elongated extent along a longitudinal axis (L). It comprises a cartridge tube, a fibre group composed of hollow individual fibres as gas separation membrane, where the fibre group has a potted section at each end in which the fibre ends in the cartridge tube are cast so as to be open to flow, where the potted section is formed from a potting mixture comprising at least the following (material) components:

[0033] - a resin component A, especially an epoxy resin,

[0034] - a curing agent B.

[0035] The term "potting mixture" means the respective mixture of the individual substances, where the terms "potting mixture" and "potting material" are used synonymously to a certain degree. What is meant here by "outer surface" of the potted section is that surface that faces outward with regard to the cartridge tube, where the "inner surface" is the respective other surface or the surface that faces into the interior of the cartridge tube. The (inlet / outlet) openings of the fibres are often in the outer surface.

[0036] The term "fibre group" in the present context is intended to mean the number of individual fibres that collectively form the separation-active membrane and are collectively potted in the potted section with the potting mixture. It is possible here for the individual fibres of a fibre group to be aligned parallel or essentially parallel to one another. In an alternative embodiment, these may be twisted together around the longitudinal axis (L). The terms “fibre group”, “hollow fibre group”, “hollow fibre bundle” and “fibre bundle” are used synonymously hereinafter to a certain degree.

[0037] The potted section functions as a tube sheet, as it is also frequently called in the prior art. What is thus meant in the present connection by the expression "cast so as to be open to flow" is a connection between adjacent hollow single fibres (hollow fibres) that may especially be arranged essentially parallel to one another, where the flow faces at the top ends of the fibre ends are not covered by the potting mixture and hence the inner cavity is open to fluid introduction and / or fluid draining. 202400091 Foreign Filing 6

[0038] The cartridge tube may in principle be formed from any suitable material, but is advantageously a metal tube, especially a stainless steel tube, preferably an aluminium tube. Plastic tubes are possible in principle, but are not usually used in the OBIGGS sector owing to generally unsuitable mechanical properties, for example relatively low temperature stability, inadequate mechanical strength, tendency to creep and tendency to cold deformation, and regulatory constraints. The cross section of the cartridge tube at right angles to the longitudinal axis is advantageously round for many reasons, especially manufacturing reasons, although the cross section is not limited thereto and may have any suitable oval or polygonal shape.

[0039] For passage of fluids, especially draining of permeate from the cartridge tube of the filter cartridge, it has one or more openings over the circumference. The filter cartridge forms the separation-active element and saleable product, which can be inserted into a pressure vessel, the filter module, and operated therewith. For this purpose, a filter module has and / or is connectable to corresponding fluid inlets, fluid drains, connecting elements, closure elements, securing elements, sealing elements, etc. For reduction of weight, it is also known that the filter module has a central filter cartridge that simultaneously also constitutes the outer casing and pressure vessel, also called shell. This outer casing has at least one permeate outlet and a corresponding permeate connection. For introduction of raw gas (feed) and draining of the retentate, closure elements, called caps, are disposed at both ends, each of which has at least one gas connection. The closure elements may, for example, be clamped or flanged onto the cartridge tube (shell).

[0040] What is meant by "filter cartridge" in the present context is

[0041] - a cartridge, especially exchangeable cartridge, that can be placed and / or inserted into an outer pressure vessel and

[0042] - a cartridge designed simultaneously as outer casing and pressure vessel of the membrane module (shell), in the absence of any different or specific statement relating to the design of the cartridge.

[0043] The following ratios and dependences are among the characteristics described herein:

[0044] Ratio Via, which describes the weight ratio as a percentage of the overall curing agent B with all curing agent components to the overall resin component A, where weight ratio V1 a is defined by the general formula Via = B / A.

[0045] Ratio V2, which describes the weight ratio of the adhesion promoter (AP) to the liquid components, where the liquid components are the resin component A, the curing agent B and the adhesion promoter, where the weight ratio V2 is defined by the general formula V2 = AP / (A + B + AP). The filler C and elastomer D components are solids and are not among the liquid components. 202400091 Foreign Filing 7

[0046] Ratio V3, which describes the weight ratio of the (proportion by) weight of resin component B1 to the (proportion by) weight of curing agent component B2, where the ratio V3 is defined by the general formula V3 = B1 / B2.

[0047] Ratio V4, which describes the percentage by weight of the aromatic amines as curing agent component (B1 b) based on the weight of the overall amine curing agent component B1 , where the ratio V4 is expressed by the general formula V4 = B1 b / B.

[0048] In an advantageous embodiment of the production process, it may be the case that the proportion of curing agent B is in the range of 10% to 35% by weight, in particular 15% to 35% by weight, based on the potting mixture.

[0049] In a further-improved advantageous embodiment of the production process, it may be the case that the proportion of aliphatic amines is in the range of less than 30% to at least 5% by weight, based on the overall curing agent B.

[0050] Surprisingly, in the case of a mixture of aliphatic and aromatic amines, it has been found that a higher starting temperature (T1) can be chosen because aromatic amines have lower exothermicity. After the start of curing, recognizable by the very large positive temperature gradient in the centre of the potted section, it has been found to be very advantageous to lower the oven temperature temporarily in order to avoid unwanted side reactions in the potting mixture, to avoid stress in the gradually curing potted section and to continue to save energy, by maximizing the exothermic evolution of heat.

[0051] In a further-improved advantageous embodiment of the production process, it may be the case that the calming and cooling phase and lowering of the oven temperature to the temperature range (TK) after the first subphase starts when the rising core temperature (P3) in the potted section is in the range of 0 to 20°C below the temperature range (T1) of the oven temperature, ideally 10 to 15°C below.

[0052] "Core temperature" hereinafter shall mean the recording of the temperature in the centre of the volume of the potting mixture or potted section, where the core temperature is also a material temperature. "Material temperature" in the present context means any temperature measured within the potting mixture or potted section.

[0053] It may be advantageous to record more than one material temperature and hence realistically estimate the energy flows in the volume of the potted section and / or quantitatively estimate the core temperature as the hottest point / location in the potted section from material temperatures that are not the core temperature.

[0054] The "core temperature" in the centre of the potted section may in the present context be recorded, i.e. measured, directly at the centre, estimated and / or extrapolated indirectly, in situ by means of decentralized thermocouples, and / or 202400091 Foreign Filing 8 ascertained empirically and estimated by means of characteristic curves, in particular as a function of oven temperature, dimensions, material properties, such as reactivity, exothermicity, thermal conductivity of the potting material, in particular the thermal conductivity of the fibres, and the duration of thermal exposure (time) to the oven temperaturee.

[0055] In a further advantageous configuration of the production process, the curing agent B may comprise a catalyst as a component, where the catalyst has a proportion of 0.1 % to 0.6% by weight, in particular 0.15% to 0.55% by weight, based on the weight of the potting mixture. In this case, the catalyst is a substance from one of the following groups: i) imidazole, for example 2-methylimidazole (2MI), 2-ethyl-4(5)-methylimidazole (2E4MI), 1- methylimidazole (1 Ml), 2-ethylimidazole (2EI), 2-phenylimidazole (2Phl), 1-(2-cyanoethyl)-2-ethyl- 4(5)-methylimidazole (2E4MCNI) or a mixture thereof; ii) tertiary amine, for example (dimethylaminomethyl)phenol, diazabicycloundecene, triethylamine or a mixture thereof; iii) polyamines, for example

[0056] - propane-1 ,3-diamine, N,N-dimethyl-, reaction products with 5-amino-1 ,3,3- trimethylcyclohexanemethanamine-5-isocyanato-1-(isocyanatomethyl)-1 ,3,3- trimethylcyclohexane-N-(2-methylphenyl)-N-(2-oxiranylmethyl)-2-oxiranemethanamine;

[0057] - propane-1 ,3-diamine, N,N-dimethyl-, reaction products with benzenemethanamine (Ancamine 2441 :

[0058] CAS No. 912342-92-8);

[0059] - propane-1 ,3-diamine, N,N-dimethyl-, polymers or a mixture thereof; or a mixture of i), ii) and / or iii).

[0060] It has been found that the presence of the catalyst in aforementioned low percentages by weight leads only to a slightly greater exothermicity, and so the calming and cooling phase can advantageously be initiated by lowering the oven temperature to the temperature range (TK) when the rising core temperature in the potted section is in the range of 15 to 20°C below the temperature range (T1) of the oven temperature. Furthermore, it was observed that it is beneficial for acceleration and startup of the catalytic reaction when the preheating temperature in such potting mixtures with a catalyst is in the range of 65 to 100°C, in particular in the range of 70 to 100°C, preferably in the range of 75 to 100°C.

[0061] In this case, the duration for the preheating phase is 1 .0 to 2 h before the start of the cooling phase, advantageously 1 .25 to 1 .75 h. In the cooling phase, the oven temperature is lowered by 10 to 30°C, preferably by 15 to 25 K. 202400091 Foreign Filing 9

[0062] In a further advantageous embodiment of the production process, it may be the case that the calming and cooling phase i) has a duration of 1 to 3 h, ideally 1 .5 to 2.5 h, and / or ii) is ended when the core temperature (P3) in the potting section does not rise by more than 1 .5°C / h in a defined period of time, in particular when it rises by less than 0.1 to 0.5°C / h, has reached a constant value for a defined period of time or falls, in particular at more than 0.1 to 0.5°C / h.

[0063] In order to conduct the curing step in the shortest possible time, it has been found to be particularly advantageous when the rise in the material temperature and in particular the core temperature in the potted section still has at least a small positive gradient, of 0.1 to 0.5°C / h, when the oven temperature is raised again and in particular the heating phase is started. In this way, the heat input imparted from the outside reaches the centre of the potted section when the exothermic processes are largely complete therein.

[0064] In a further advantageous embodiment of the production process, it may be the case that the changeover from the temperature range (T1) of the first subphase to the lower temperature range (TK) of the calming and cooling phase is conducted as a single lowering stage and / or active cooling is effected by means of a cooling medium, for example the introduction of a gas into the space surrounding the cartridge, in particular an inert gas.

[0065] In order to effectively introduce the cooling and slowing effect compared to the exothermic evolution of heat, it is advantageous to implement the lower temperature range (TK) as quickly as possible in a single lowering step.

[0066] In the present context, reference is frequently made to temperature ranges, not to absolute temperatures, such as, in particular, the temperature range (T1) of the first subphase, the lower temperature range (TK) in the calming or cooling phase. This means, and conveys linguistically, that the oven temperature is regulated at least temporarily to a fixed control value, but the potted sections to some extent constitute a significant heat source or heat sink, because of the chemical processes that proceed therein. As a result, there is not just a single (real) oven temperature in the interior surrounding the filter cartridge, such as the oven interior or the interior of the centrifuges, but instead there are at least temporarily significant temperature gradients in the oven. The "oven temperature" thus in particular also means an average of the temperatures in the interior of the oven or centrifuge.

[0067] In a further advantageous embodiment of the production process, it may be the case that the heating phase (460) comprises at least two subphases with two end temperatures (T2a, T2b) and / or the hold phase (470) comprises at least two subphases, where the end temperatures (T2a, T2a) of the two subphases are different or equal.

[0068] This process regime is advantageous especially when a filter cartridge in the preheating phase is within a centrifuge and subsequently, after partial curing of the potted sections, is transferred to a (curing) oven. It 202400091 Foreign Filing 10 has not been found to be disadvantageous when the heating phase is conducted in two parts, i.e. partly in the centrifuge and finally in a (curing) oven after transfer of the filter cartridge thereto.

[0069] In this context, in a further improved advantageous embodiment of the production process, it may be the case that i) the first subphase of the heating phase is effected in a centrifuge with an at least intermittently rotating filter cartridge, and at least one further subphase is effected in an oven, in particular in the case of an at least intermittently stationary filter cartridge, and / or ii) the first subphase of the hold phase is effected in a centrifuge with an at least intermittently rotating filter cartridge, and at least one further subphase is effected in an oven, in particular in the case of an at least intermittently stationary filter cartridge.

[0070] Even though, in principle, the step of curing the potted section of the filter cartridge can be effected entirely in a centrifuge, it is economically advantageous to use this machine that rotates at high speed only for the maximum required time, namely until the fibres are securely fixed in the at least partially cured potted sections. For organisational reasons, it may be advantageous to treat the potted sections of the filter cartridge on the centrifuge for as long as possible under optimum conditions therein, and to initiate all (sub)steps before the centrifuge can be stopped, depending on the availability of operators and / or other operational structure, and the filter cartridge can be transferred to a (curing) oven.

[0071] In addition, it may be an advantage or improvement that the end temperature (T2a) in the first subphase of the hold phase is in the range of 80 to 100°C and the at least one further end temperature (T2b) in the at least one further subphase of the hold phase is in the range of 100 to 200°C, advantageously in the range of 100 to 190°C, ideally in the range of 160 to 190°C.

[0072] As stated above, it has not been found to be disadvantageous when the heating phase and / or the hold phase is conducted in two parts, i.e. partly in the centrifuge and finally in a (curing) oven after transfer of the filter cartridge thereto. In the case of structural limitation of the centrifuge in which, for example, the maximum temperature is lower than the optimum end temperature (T2) for curing, a hold phase in at least two parts at possibly different end temperatures (T2a, T2b) is not detrimental to the potted section. As a result of an intermittently insufficiently high end temperature (T2), the hold phase has to be extended appropriately. In particular, it has been found that, especially in a very well-controlled preheating phase in which the differential between core temperature and edge temperature of the potting section or the core temperature to the furnace temperature is small, i.e. less than 50°C, ideally lies in the range of 20°C to 40°C. A very homogeneous glass softening temperature / point Tg can be achieved in all sections of the potting section when the end temperature (T2b) is in the range of 170-185°C, especially in the range of 155-180°C, with hold times as detailed above.

[0073] In addition, an advantage or improvement may be that the hold phase comprises at least two subphases, where the end temperatures (T2a, T2a) of the two subphases are different or equal. 202400091 Foreign Filing 11

[0074] In an advantageous embodiment, component A may be an epoxy resin or epoxy resin mixture composed of multiple constituents, for example

[0075] - bisphenol A diglycidyl ether (BADGE, CAS 1675-54-3),

[0076] - bisphenol F diglycidyl ether (BFDGE, CAS 2095-03-6),

[0077] - N,N-diglycidyl-4-glycidyloxyaniline or triglycidyl ether of para-aminophenol (TGPAP, CAS 5026-74-4), which is commercially available under the Araldite MY0500 or Araldite MY0510 product name, where Araldite MY0510 has higher purity compared to Araldite MY0500,

[0078] - N,N-diglycidyl-3-glycidyloxyaniline or triglycidyl ether of meta-aminophenol (TGMAP, CAS 71604-74-5), which is commercially available under the Araldite MY0600 or Araldite MY0610 product name, where Araldite MY0610 has higher purity compared to Araldite MY0600,

[0079] - tris(4-hydroxyphenyl)methane triglycidyl ether (TGTPM, CAS 66072-38-6), which is commercially available under the TACTIX® 742 product name,

[0080] - 4,4'-methylenebis(N,N-diglycidylaniline) or tetraglycidyl ether of 4,4'-diaminodiphenylmethane (TGDDM,

[0081] CAS 28768-32-3), which is commercially available under the ARALDITE® MY 721 and ARALDITE® MY 9512 product names.

[0082] The purer monomers have lower viscosity compared to the oligomers. For example, Araldite MY0510 has a viscosity of 550-850 mPa s and Araldite MY0500 a viscosity of 2000-6000 mPa s, measured in a suitable capillary, rotary or quartz viscometer.

[0083] In a further advantageous embodiment of the production process, it may be the case that the potting mixture comprises an inert filler C and / or an elastomer, wherein

[0084] - the inert filler C has an average particle diameter of less than 100 nm, and wherein

[0085] - the elastomer D has an average (particle) diameter of 4 to 15 pm.

[0086] The term "inert" or "inert component" with regard to components C means that this substance does not change its state of matter under the existing conditions of the potting mixture. The initially solid consistency in particular is not altered in the potting mixture, but merely incorporated into the resin. What this means is more particularly that the inert component does not undergo any chemical reaction or chemical transformation with the resin component A and / or the curing agent B. In this context, however, the term "inert" or "inert component" includes at least partial oxidation of the inert component (substance) and / or oxidation of a portion of the inert components under the influence of oxygen, for example. Oxidation of inert components can especially proceed at transition faces / regions of the potting mixture to individual fibres and / or edge regions of the potted section.

[0087] It has been found that, surprisingly, in a particularly advantageous embodiment of the production process and of the potted section, and also of the filter cartridge, the filler C has a particle size in the range from 50 nm to 5 nm, preferably 40 nm to 10 nm, ideally 35 nm to 15 nm. It has been found to be very advantageous that a particle size of 25 to 15 nm is preferable in particular because, with this very small average particle size, sedimentation, because of the nanoscale size, even under the influence of centrifugal forces, is largely suppressed in spite of the higher density of the nanoparticles. 202400091 Foreign Filing 12

[0088] In addition, it has been found that, surprisingly, in the presence of inert filler C, temperature maxima during the curing step which are generated by exothermic processes in the epoxy resin are lowered in terms of the absolute temperature level, and the peak takes a flatter line overall.

[0089] In a further advantageous embodiment of the production process and of the filter cartridge, one improvement may be that the inert filler C has a proportion by weight of 3.0% to 35% by weight, preferably 10% to 35% by weight, ideally 15% to 35% by weight. Without any intention to be restricted to a single interpretation, it is thought that high proportions by weight of filler C are thus particularly advantageous because the high local presence of nanoparticles causes any microcracks to immediately undergo distribution of energy in the tip of the crack, hence particularly efficiently preventing propagation of all microcracks.

[0090] Finally, it was observed overall that, in particular, the temperature progression within the potted section or the initially liquid potting mixture is of central importance for the production process and a high-quality filter cartridge, and so an advantageous embodiment of the production process consists in detecting the temperature in the potted section (material temperature) at least intermittently in situ by means of at least one thermocouple. For this purpose, it has been found to be advantageous to position the one thermocouple, in particular in the form of a rod, in the interior of the potted section and to control and regulate the oven temperature not only according to fixed programs. Such a thermocouple typically has a detection end and a connection end, where the detection end constitutes the actual measuring tip or sensor element for detecting the ambient temperature (material temperature), the potting mixture here, and the connection end serves to connect at least one data cable and / or a transmitter unit, in order to transmit analogue measured values or digital measurement data that has been derived from them and processed if necessary.

[0091] The transmission is effected in particular to a data storage unit, from which the measured values or digital measured data can be read and processed immediately and / or at a later juncture. Alternatively or additionally, the transmission is effected to a display unit, such as a plant operator's monitor and / or to an associated open-loop or closed-loop control unit, in particular an associated open-loop and / or closed-loop control unit which is relevant in respect of the oven temperature during the curing step.

[0092] In a particularly advantageous embodiment of the production process, the oven temperature is controlled at least intermittently on the basis of the measured values detected by the at least one thermostat and / or digital measurement data from which the material temperature can be inferred. Advantageously, the oven temperature is controlled on the basis of the difference of the oven temperature from the (material) temperature measured by at least one thermostat and / or the size of the gradient of the (material) temperature measured by the at least one thermostat, in particular the core temperature. In this case, it is particularly advantageous when the difference between the oven temperature and the material temperature in the centre (core temperature) does not exceed 80°C, preferably 60°C and more preferably 40°C. 202400091 Foreign Filing 13

[0093] In an advantageous variant, it may be the case that a subphase initiated in the preheating phase is a lowering of temperature (cooling phase) as soon as the positive gradient measured by the at least one thermostat is greater than 10°C / h, in particular greater than 15°C / h, and the difference between the oven temperature and the material temperature, in particular the core temperature, is not more than 10°C, preferably not more than 15°C, preferably not more than 20°C. It has been found to be advantageous to initiate the cooling phase at an early stage, as soon as the progress of the exothermic reaction in the potting material is apparent from the temperature gradient of at least 10°C / h. In this way, it is also possible to save heating energy in addition to the avoidance of stresses and unwanted side reactions in the potting mixture.

[0094] It has been found that, surprisingly, the thermocouple can remain at least partly in the potted section as an inert foreign body after curing, since this has no adverse effect at all on the use of the filter cartridge. The connection end or any data cables used are removed in the mechanical post-processing of the filter cartridge and the potted section.

[0095] The thermocouple is advantageously placed within the potted section in such a way that the detection end is positioned in the centre or centre of gravity. What is meant here by "centre" or "centre of gravity" is the core or geometric centre of the potted section, with the greatest average distance from all outer surfaces of the potted section. The term "centre" or "centre of gravity" or core should not be understood here in the strict mathematical sense, but merely describes the approximate position with a variance of up to 20% in x, y and / or z direction from the theoretical centre. This is because it has been found that the highest insulation by the inserted fibres exists in the centre of the potted section, such that exothermic energy formed can flow away only much less efficiently, if at all, than is the case in, for example, a position near edge faces or surfaces.

[0096] The step of placing the thermocouple in the region of the later potted section or the volume that the potting mixture is to occupy, in particular in the centre of this volume, can advantageously be a substep of the grouping step, the bonding step and / or the filling step.

[0097] What is meant in the present context by "thermocouple" is any sensor, temperature probe, thermometer, etc. that is suitable for in situ temperature measurement. In particular, the thermocouple may be formed from at least one pair of electrical conductors which have a connection point (measurement tip) and, by means of a thermoelectric effect, detect the temperature or display a voltage value (measured value) analogous to the temperature.

[0098] Advantageously, the portion of the detection end remaining in the potted section after the curing step, in terms of its geometric dimensions, is no larger, or not significantly larger, than a single fibre. In particular, in the case of a rod-shaped detection end, the diameter is at most 5 times a single fibre, ideally at most twice a single fibre. 202400091 Foreign Filing 14

[0099] In an advantageous embodiment of the production process, a substep of the grouping step, the bonding step and / or the filling step may comprise mounting one potting ring on and / or at least partly within the cartridge tube at least at one end, in particular at each end.

[0100] The potted ring here forms

[0101] - a guide element in which the ends of the fibre group are disposed,

[0102] - a spacer ring, which forms a ring space radially between the fibre group and the inner surface of the cartridge tube, and

[0103] - can assume part of the sealing function at at least one end of the cartridge tube.

[0104] In an advantageous embodiment of the process for producing the filter cartridge, at least one potted ring is provided, which consists in particular of a polymer material or plastic as principal or main component, for example is manufactured from a high-performance plastic, for example polysulfones, for example polyphenylsulfone (PPSU), polyethersulfone (PESU), polysulfone (PSU), polyetherimide (PEI) or polyaryletherketone (PAEK), for example polyetheretherketone (PEEK), polyetherketoneketone (PEKK) or polyetheretherketoneketone (PEEKK).

[0105] One improvement here may be that the potted ring has improved shrinkage properties, especially when heated in the curing step, in that it has been glass fibre-reinforced, for which the proportion of glass fibre in the material of the potted ring is 10% to 30% by weight, ideally 15% to 25% by weight. This glass fibre proportion, as well as elevated mechanical stability, has the effect that the CTE (coefficient of thermal expansion) of the potted ring material can be lowered and hence matched to the CTE of the potting of the cartridge tube. Advantageously, the proportion of fibres in the potted ring and the resin mixture are chosen such that the coefficients of thermal expansion (CTE) of the potted ring and of the potting present thereon, after curing, differ from one another by less than 20 ppm / K, preferably by less than 10 ppm / K, more preferably by less than 5 ppm / K (difference).

[0106] It is possible here for the arrangement of the potted ring, in axial direction of the longitudinal axis (L), to be entirely within the cartridge tube or to project beyond it by at least one section at at least one end in the direction of the longitudinal axis (L). The potted ring or spacer ring may advantageously be potted with the cartridge tube by means of the same potting mixture as individual fibres of the fibre group, or may alternatively be in a gas-tight arrangement in the cartridge tube by means of a different adhesive or sealant.

[0107] The term "potted section" hereinafter is always also intended to include an at least partly integrated potted ring as an option, unless explicitly stated otherwise. Each potted section here has a width (B) in the direction of the longitudinal axis (L) and a diameter (D) in the radial direction; in the present context, a diameter means the average diameter even for non-round cross sections, unless stated otherwise. The two potted sections advantageously take the form of a disk or sheet having multiple interruptions by the individual fibres in the longitudinal direction in the form of a tube sheet. Depending on the feed section for the potting mixture and / or the aftertreatment step after curing, at least one surface may not be even or 202400091 Foreign Filing 15 flat; in particular, the inner surface may be slightly concave by virtue of active centrifugal forces in the course of curing, which is secondary in respect of the present invention and no further distinction will thus be made.

[0108] It has likewise been found that, surprisingly, in a particularly advantageous embodiment of the filter cartridge, the potting mixture is chosen such that the sedimentation rate of the inert filler C or of the various individual components of the inert filler C during processing under centrifugal force is less than 10 mm / h, preferably less than 1 mm / h, more preferably less than 0.1 mm / h. Sedimentation rates can be estimated via an analogous application of the Stokes equation for slow sedimentation: where vPis the sedimentation rate, r is the radius of the sinking article (i.e. of the filler C), VPis the volume of the sinking article, g is the respective applied centrifugal force, pPis the density of the particle, pt is the density of the fluid (i.e. of the mixture of A and B) and p the dynamic viscosity of the fluid.

[0109] For example, in the case of particles having a relatively high difference in density from the fluid (pP. pt), the particle diameter may be correspondingly smaller in order to achieve a sufficiently slow sedimentation rate in the potting mixture at the same centrifugal force, whereas a greater particle diameter can be tolerated in the case of a small difference in density.

[0110] After the viscosity was initially relatively high directly after mixing of the components, the potting mixture then passes through a viscosity minimum owing to heating by the enthalpy of reaction released during the curing process. The sedimentation rate is thus at its highest at this viscosity minimum.

[0111] The sedimentation rate under centrifugal forces can be analysed using the LUMiSizer dispersion analyser from LUM GmbH. It is possible thereby to achieve experimental inline measurement of speed distributions in particle separation and sedimentation under the influence of centrifugal forces, based on the primary principle and without assumptions regarding dispersion properties, models or algorithms. Details of the test method and use of the LUMiSizer are also described by H. Chen, X. Jia, M. Fairweather et al.; Title: Characterising the sedimentation of bidisperse colloidal silica using analytical centrifugation; Advanced Powder Technology 34 (2023) 103950 (https: / / doi.Org / 10.1016 / j.apt.2023.103950).

[0112] The particles of filler C advantageously have a very narrow particle size distribution. In particular, what are called monodisperse nanoparticles are advantageous for the prevention of macrocracking. In the present context, a "microcrack" shall mean a crack length of up to 1 pm. In addition, a "macrocrack" shall mean a single-sided opening or through-opening in a potted section that has a crack length of more than 1 pm and / or a crack depth in the direction of the longitudinal axis of more than 1 pm. In particular, a macrocrack is a crack through which a gas or gas component can flow through the potted section outside the envisaged gas pathways and / or is apparent to the eye or by light microscopy. 202400091 Foreign Filing 16

[0113] Without any intention to be limited to a single interpretation, it is thought that, at these small particle sizes of less than 100 nm, especially less than 50 nm, further crack propagation in the case of microcracks at the tip of the crack toward macrocracks was reliably prevented in the potted section. It is further observed that, surprisingly, particle sizes of 40 to 10 nm in particular are particularly advantageous within a very narrow particle size distribution in order to effectively prevent extension of microcracks at the tip of the crack, because a sufficient amount of the sufficiently small inert particles will be locally available in each resultant microcrack to dissipate the energy at the tip of the respective crack. Particle size distribution can likewise be measured with the aforementioned LUMiSizer dispersion analyser from LUM GmbH.

[0114] In a further advantageous embodiment of the filter cartridge, an improvement may be that the filler C is a silicon dioxide (SiO2), an aluminium dioxide (AI2O3) or a mixture thereof. Advantageously, the filler C is silica, where the silica particles are also available commercially, for example under the Nanopox® product name from the applicant, and are formulated and sold in dispersion in an epoxy resin, especially BFDGE, up to a concentration of about 40-45% by weight. Because of the relatively small difference in density of SiO2 (density about 2.2 g / cm3) (silica) from resin component A (density about 1 .1-1 .12 g / cm3) by comparison with AI2O3 (density 3.9 g / cm3), it is more advantageous to provide a pure silica as filler C in order to reduce sedimentation under centrifugal force.

[0115] According to the invention, the amines are an amine mixture of aliphatic and aromatic amines, where the proportion of aromatic amines may be more than 70 mol%, ideally more than 80 mol%, based on the amine groups, where the proportion of aromatic amines in the amine mixture is not more than 98 mol%, ideally not more than 95 mol%.

[0116] Depending on the respective resin components, catalytic imidazoles as curing agents from the following group may be present:

[0117] Imicure AMI, 2, 2-methylimidazole, CAS No. 693-98-1 ;

[0118] Curezol 2E4MZ, 2-ethyl-4-methylimidazole, CAS No.: 931-36-2;

[0119] Curezol 1 B2MZ, 1-benzyl-2-methyl-1 H-imidazole, CAS No.: 13750-62-4;

[0120] Curezol 2PZ, 2-phenylimidazole, CAS No.: 670-96-2;

[0121] Curezol 2P4MZ, 4-methyl-2-phenyl-1 H-imidazole, CAS No.: 827-43-0;

[0122] Curezol C17Z, 2-heptadecyl-1 H-imidazole, CAS No.: 23328-87-2;

[0123] Curezol 2MZ Azine, 6-[2-(2-methyl-1 H-imidazol-1-yl)ethyl]-1 ,3,5-triazine-2,4-diamine, CAS No.: 38668- 46-1 ;

[0124] Curezol 2PHZ-PW, 4, 5-bis(hydroxymethyl)-2-phenyl-1 H-imidazole, CAS No.: 61698-32-6;

[0125] Curezol 2MA-OK, 1 , 3, 5-triazinane-2, 4, 6-trione, 6-[2-(2-methyl-1 H-imidazol-1-yl)ethyl]-1 ,3,5-triazine-2,4- diamine, CAS No.: 68490-66-4.

[0126] In this case, the catalyst has the function and character of a chemical catalyst with regard to the reaction of resin component A and curing agent B. The customary understanding in the art is that a catalyst does not participate in a reaction as a reactant and is recoverable, which is not the case here. In the present 202400091 Foreign Filing 17 process of curing the potted section and the chosen temperatures, the imidazoles in the potting mixture are effective in essentially two ways with respect to the resin component A (epoxides), in that imidazoles: i) coordinate with the epoxide and hence catalytically facilitate nucleophilic attack of curing agent B on the epoxide, where the imidazole molecule subsequently moves to another epoxide molecule or bond. This primarily catalytic effect of imidazole proceeds particularly up to a temperature of about 100-110°C. ii) at temperatures above about 100°C, attack the epoxide, in particular open the epoxy ring, where the rate of reaction of this attack increases with rising temperature. A chemical reaction takes place here, and so the imidazole is chemically fixed and consumed, which is fundamentally no longer a catalysis.

[0127] Ideally, the weight ratio of the catalyst is 0.1% to 5% by weight, preferably 0.1% to 4% by weight, ideally 0.1% to 3% by weight. The positive effect of the catalyst is that the required curing temperature is lowered and hence the curing is accelerated and made more energetically advantageous. The weight ratio of the catalyst is defined here as the weight of the catalyst relative to the total weight of curing agent B and catalyst.

[0128] In the process of the invention for production of the filter cartridge, the resin component A comprises or is formed from at least one of the following substances:

[0129] • 4,4'-methylene diphenyl diglycidyl ether (A1), also called bisphenol A diglycidyl ether (BADGE), with CAS No. 55818-57-0;

[0130] • bis(4-hydroxyphenyl)methane diglycidyl ether (A2), also called bisphenol F diglycidyl ether (BFDGE), with CAS No. 9003-36-5;

[0131] • p-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl)aniline (A3), also called Araldite MY0510, with CAS No. 5026-74-4;

[0132] • tris(4-hydroxyphenyl)methane triglycidyl ether (TGTPM, CAS 66072-38-6 (A4));

[0133] • 4,4'-methylenebis(N,N-diglycidylaniline) (TGDDM, CAS 28768-32-3 (A5)); and

[0134] • oligomers as reaction products.

[0135] In this case, p-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl)aniline (A3), also called Araldite MY0510, serves as a highly functional crosslinker for increasing the thermal stability of the potted section. What is also meant by "oligomers as reaction products" is in particular polymeric products as oligomers formed from the monomers A1 , A2 and / or A3 mentioned.

[0136] In a further advantageous embodiment, in an improvement or advantageous variant, the resin component A may be an epoxy resin mixture comprising at least two of the following resin components: resin component A1 , resin component A2 or resin component A3.

[0137] Such a mixture of resin component A may be provided advantageously especially when the filler C is already suspended on the production side in high concentration, for example in the resin component A2, and the second resin component A1 is used to establish the desired other concentration and / or physical property of the potting mixture and / or resin component A. 202400091 Foreign Filing 18

[0138] In a further advantageous embodiment of the process for producing the filter cartridge, an improvement may be that the resin component A is formed as a mixture of at least two resin components A1 and A2, where:

[0139] - resin components A1 (BADGE) make up 0.5% to 50% by weight and

[0140] - resin components A2 (BFDGE) make up 5% to 50% by weight, or resin component A2 makes up the remaining proportion. It is advantageously resin component A2 (BFDGE) that forms the greater proportion in the potting mixture.

[0141] It is advantageous here for the introduction of potting mixture when the more extensive resin component is BFDGE because BFDGE has a lower viscosity than BADGE and hence there is an overall drop in viscosity in the mixture as well. This is advantageous for the supply of the potting mixture.

[0142] In a further advantageous embodiment of the filter cartridge, an improvement may be that the resin component A is formed as a mixture of at least three resin components A1 , A2 and A3, where:

[0143] - resin components A1 (BADGE) make up 0.5% to 50% by weight,

[0144] - resin components A2 (BFDGE) make up 5% to 50% by weight and

[0145] - resin component A3 makes up the remaining proportion.

[0146] The aforementioned ratios of resin components A1 , A2, A3 do not take account of other ingredients, such as inert fillers C and / or elastomers D.

[0147] With regard to the mixing ratios of resin component A to curing agent B, it may be advantageous when, in the relationship of curing agent B to resin component A, the curing agent B is a) an amine (B1), where resin component A is in the range from 65% to 85% by weight, preferably 70% to 80% by weight, especially 75% to 78% by weight, and amine as curing agent B is in the range from 15% to 35% by weight, preferably 20% to 30% by weight, especially 20% to 25% by weight, based on the total mass of the potting mixture, and b) an imidazole (B2), where imidazole as a curing agent is in the range from 0.1% to 10% by weight, preferably 0.1% to 5% by weight, ideally 0.1% to 2% by weight, based on resin component A, where resin component A in each case forms the remaining proportion by weight.

[0148] With regard to the mixing ratio or weight ratio Via of the curing agent B to the resin component A, it may be advantageous when the ratio Vi a is in the range of 5% to 35% by weight, preferably 10% to 25% by weight, in particular 15% to 22% by weight. .

[0149] As described in the literature, with the aid of the two equivalent weights AEW and EEW, the theoretically required equivalent amount of curing agent component B1 (amine curing agent) for a given amount of resin component A can be calculated: 202400091 Foreign Filing 19

[0150] PHR (amine curing agent) = AEW*100 / EEW, where:

[0151] PHR: parts per hundred of resin component B1 (amine curing agent), where PHR indicates how many parts by weight of curing agent component B1 (amine curing agent) have to be introduced per 100 parts by weight of resin component A in order to cause each functional epoxy group of the resin component A to chemically react with an amine-functional group of curing agent component B1 ;

[0152] AEW: amine equivalent weight, determined in accordance with DIN ISO 9702:1998;

[0153] EEW: epoxy equivalent weight, determined in accordance with DIN ISO 3001 :1999.

[0154] Based on PHR (amine curing agent), the equivalent weight of amine curing agent component B1 (AEW) is mixed stoichiometrically with the equivalent weight of resin component A (EEW). Analogously, the ratio V1 b denotes the quotient of the equivalent weights used for the amine curing agent component B1 (AEW) and the resin component A (EEW):

[0155] V1 b = PHR * FS / 100, where FS is a stoichiometry factor. V1 b = PHR * 1 / 100 is also referred to hereinafter as "eq." as a short form of equivalence. At an equivalent dose, FS = 1 , and so the equivalent ratio of V1 b = PHR / 100. However, it has been found to be particularly advantageous when the proportion by weight B1 used is lower than the theoretically calculated (equivalent) weight fraction B1 , i.e. FS < 1 (substoichiometric) and greater than zero, wherein the stoichiometry factor FS is preferably in the range of 0.95-0.65, more preferably in the range of 0.85 to 0.7, especially preferably 0.75.

[0156] Advantages have been found to be that, with a substoichiometric mixture of the potting material with FS in the range of 0.95 to 0.65, the cured potted section generally has higher thermal stability, and an improvement in stability to thermooxidative degradation is also expected. Furthermore, advantages in curing were observed in that, during curing, especially during the first 2 to 6 hours, lower reactivity and evolution of heat occurred in the potting mixture.

[0157] Limited exothermicity, i.e. a minimum difference between the oven temperature and the hotter core temperature in the centre of the potted section / material and / or a flat peak (maximum core temperature of the potted section / material above the oven temperature), is advantageous for the establishment of a uniform Tg throughout the potted section and for achieving a maximum Tg as close as possible to the maximum Tg of the system intrinsically possible. A cured potting material that has suffered a very large increase in core temperature above the oven temperature and / or boundary temperature (thermal runaway in the core) also typically has a lower Tg in the core than in the outer region. 202400091 Foreign Filing 20

[0158] It is presumed, without any intention to wish to be tied to a single interpretation, that the substoichiometric amount of the amine makes it possible for the imidazole to function as a catalyst for a longer period of time, and hence for more complete chemical bond formation to occur between molecules of the resin component. It is assumed that, because of a milder progression of the reaction, i.e. small differences in temperature between core and outside temperatures, more structured crosslinking is made chemically possible, which, as set out above, is accompanied by higher Tg values or Tg values closer to the maximum intrinsically possible Tg of the system and a more homogeneous distribution of the Tg values at all positions within the potted section.

[0159] The advantage of catalytic curing agents, such as imidazole, is that the need for relatively small amounts of curing agent B results in an economic benefit, and the imidazole-cured resin components are also more thermally stable and / or more stable to thermooxidative degradation. Thermal stability is manifested in an elevated glass softening point Tg by comparison with amine or anhydride curing agents. What is meant here by "thermooxidative degradation" is the oxidation and loss of material of the cured potting material at elevated temperature under the influence of 02. In addition, potting mixtures comprising imidazoles are slightly latent systems, meaning that they require a certain elevated activation temperature, below which they remain essentially chemically stable, i.e. liquid, and hence permit a longer processing time.

[0160] The glass softening temperature / point Tg was determined by DSC (Differential Scanning Calorimetry) using PerkinElmer Diamond DSC (PED-DSC).

[0161] The dynamic differential calorimeter (DSC) for determining the glass softening temperature was conducted as follows; the methods of the DIN EN ISO 11357 standards group were additionally consulted and may be used in extended form:

[0162] The disk-shaped compacts were used to produce (potted) sample material (cured in each case) by using an HM Z7 cross-tooth machining burr from Hoffmann GmbH to grind off sample material for DSC as a fine powder. The aforementioned PED-DSC consists of 2 ovens, with an empty reference boat introduced into one oven, and the other (sample) oven occupied by a crucible and compressed sample material. The sample material was weighed out by means of a Mettler-Toledo balance. Test conditions:

[0163] • measurement temperature 200°C, with initial temperature of 50°C

[0164] • starting weight: 20 mg + / - 0.01 mg of the sample material

[0165] • heating rate: 20°C / min under nitrogen atmosphere (purge gas) in cycles and hold times; cooling rate: 20°C / min under nitrogen atmosphere (purge gas)

[0166] • triple (heating) cycle (1-3): 50°C to 200°C back to 50°C; hold time 1 min at 200°C; cycle 4: 50°C to 200°C (end). 202400091 Foreign Filing 21

[0167] It has been found that very good crack avoidance as a result of the addition of aforementioned inert particles in the particle size mentioned and the respective proportions by weight (% by weight) leads to extremely hard potted sections and hence filter cartridges that are resistant to changes of load, but some degree of embrittlement was also observed, and a tendency to flaking. Such potted sections are not very suitable for compensating for high internal stresses owing to material expansion in the joining structure.

[0168] Thus, a further advantageous embodiment of the process for producing the filter cartridge may be that at least one elastomer D is included as a further component in a proportion by weight of less than 10% by weight with an average (particle) diameter of less than 30 pm. What is meant here by "one" elastomer D is always an amount or mass of individual particles with the physical properties described.

[0169] This proportion of elastomer D in the potting mixture counters the aforementioned problem of excessive embrittlement and leads to improved elasticity, especially lower damage under flexural stress on the potted section.

[0170] In the present context, resin component A, curing agent B, the catalyst, inert filler C and elastomer D are individually or collectively also called "component(s)" or "component(s) of the potting mixture".

[0171] In an advantageous embodiment of the production process, the elastomer D may also already have been introduced in dispersion with BADGE on the production side, such that the mixing step is significantly facilitated because only liquid components have to be combined and mixed. The elastomer D is advantageously what is called a core-shell rubber particle as sold by the applicant, for example, under the Albidur® product name in dispersion with a BADGE.

[0172] These core-shell rubber particles have a comparatively elastic core composed, for example, of polybutadiene or polydimethylsiloxanes (silicone). The shell serves as adhesion promoter for at least one of the resin components A, including A1 , A2 and / or A3, and is composed, for example, of poly(methyl)methacrylate (PMMA), reaction products of epoxy-functional siloxane such as (3- glycidyloxypropyl)trimethoxysilane (GLYMO, CAS 2530-83-8) or 3-glycidyloxypropyltriethoxysilane (GLYEO, CAS 2602-34-8).

[0173] In a further advantageous embodiment of the process for producing the filter cartridge, an improvement may be that the at least one elastomer D has an average (particle) diameter of 4 pm to 15 pm, especially 5 pm to 10 pm, preferably 6 pm to 8 pm. Preferred method to determine particle sizes are the following: Dynamic Light Scattering (DLS), wherein this method measures the Brownian motion of particles in a liquid and relates it to particle size using the Stokes-Einstein equation. It is suitable for particle sizes in the range of approximately 1 nm to 1 pm. The relevant standard is ISO 22412 (Dynamic light scattering for particle size distribution). Laser Diffraction (LD), wherein Laser diffraction measures the angular distribution of scattered light from a particle ensemble to calculate the size distribution. It works for particle sizes ranging from about 100 nm to 3 mm. The corresponding standard is ISO 13320 (Particle size analysis - Laser diffraction methods). 202400091 Foreign Filing 22

[0174] Further methods are known, such as Scanning Electron Microscopy (SEM), using a focused electron beam to image particles and measure their size directly. It can analyze particle sizes ranging from approximately 1 nm to 1 mm. Transmission Electron Microscopy (TEM) is also suitable, being similar to SEM but uses transmitted electrons to image particles at an even higher resolution. It is suitable for particle sizes in the range of approximately 0.1 nm to 500 nm.

[0175] In a further advantageous embodiment of the process for producing the filter cartridge, an improvement may be that the at least one elastomer D is included in a proportion of 1 .0% to 8.5% by weight, especially 2.0% to 7.0% by weight, preferably 3% to 6.0% by weight.

[0176] In a further advantageous embodiment of the process for producing the filter cartridge, an improvement may be that the at least one elastomer D is taken from the group of the following substances or a mixture thereof: core-shell rubber particles, surface-functionalized silicone, silicone rubber, bisphenol A diglycidyl ether (DGEBA), cyclic-aliphatic epoxy resin, polypropylene glycol triol (PPG triol), vinyl ester resin, O- phthalic unsaturated polyester resin, silane-modified polyurethane prepolymer, trimethoxyvinylsilane.

[0177] These elastomers D advantageously have an average density of density 1 .1 g / cm3at 23°C, where these elastomers D are sold as products by the applicant under the Albidur® product name. It has been found to be particularly advantageous when the sedimentation rate of the elastomer D or of the various individual components of the elastomer D during processing under centrifugal force is less than 10 mm / h, preferably less than 1 mm / h, more preferably less than 0.1 mm / h.

[0178] In a further advantageous embodiment of the process for producing the filter cartridge, an improvement may be that the potting mixture from which the potted section is formed comprises, as further components, at least one adhesion promoter taken from the group of the following substances or a mixture thereof: amino Dynasylan® AMEO, 3-aminopropyltriethoxysilane (CAS No. 919-30-2);

[0179] Dynasylan® 1122, bis(3-triethoxysilylpropyl)amine (CAS No. 13497-18-2);

[0180] Dynasylan® 1124, bis(3-trimethoxysilylpropyl)amine (CAS No.: 82985-35-1);

[0181] Dynasylan® 1505, 3-aminopropylmethyldiethoxysilane (CAS No.: 70240-34-5);

[0182] Dynasylan® AMMO, 3-aminopropyltrimethoxysilane (CAS No.: 13822-56-5);

[0183] Dynasylan® SIVO® 210, proprietary aminosilane composition (mixture);

[0184] Dynasylan® SIVO® 214, proprietary aminosilane composition (mixture);

[0185] Dynasylan® TRIAMO, triamino-functional propyltrimethoxysilane (CAS No.: 35141-30-1);

[0186] Dynasylan® 1189, N-(n-butyl)-3-aminopropyltrimethoxysilane (CAS No.: 31024-56-3);

[0187] Dynasylan® SIVO® 203, functional oligosiloxane (CAS No. 13822-56-5);

[0188] Dynasylan® 9165, phenyltrimethoxysilane (CAS No.: 2996-92-1);

[0189] Dynasylan® 9265, phenyltriethoxysilane (CAS No.: 780-69-8);

[0190] Dynasylan® 1411 , 2-aminoethyl-3-aminopropylmethyldimethoxysilane (CAS No.: 3069-29-2);

[0191] Dynasylan® DAMO, 2-aminoethyl-3-aminopropyltrimethoxysilane (CAS No.: 1760-24-3). 202400091 Foreign Filing 23

[0192] In one variant, it may be advantageous when the curing agent B in the potting mixture from which the potted section is formed is a (curing agent) mixture comprising at least one of the above adhesion promoters from the aforementioned group. It has surprisingly been found to be particularly advantageous in the production of the filter cartridges and / or the filter module when the curing agent B has been mixed with at least one of the above-mentioned adhesion promoters or is in the form of a B-AP mixture in preparation for the making-up of the potting mixture.

[0193] The weight ratio V2 is advantageously in the range of 0.002 to 0.012, advantageously 0.003 to 0.09, ideally 0.04 to 0.03.

[0194] The invention also encompasses a filter module for gas separation which at least one filter cartridge, at least one inlet connection for a raw gas and at least two outlet connections, wherein at least one outlet connection is provided for the retentate and at least one further outlet connection for a permeate, wherein the filter cartridge has been produced and designed according to any of the aforementioned embodiments or variants of the production process. All aspects or advantages that have been mentioned for the filter cartridge are intended to be applicable identically or analogously to the filter module as well.

[0195] Advantageously, the production process for the filter module includes mounting of at least one cap or closure element that enables introduction and / or closure of the filter cartridge. The filter module additionally includes at least one feed (connection), at least one retentate connection (element), at least one permeate connection (element). The interior of the filter module also advantageously has receptacles, stops and sealing surfaces or sealing elements in order firstly to fix the filter cartridge and also to guide the different interiors for the feed gas (feed), the retentate fluid (retentate) and the permeate fluid (permeate) in a procedurally reliable, gas-tight and separate manner.

[0196] In addition, it may be advantageous when the filter module has at least one outer holding and fixing element in order to connect the filter module itself to a bearing and holding structure in the grouping, bonding or filling step.

[0197] Advantageously, two basic embodiments of a filter module are proposed.

[0198] A) In the first embodiment of a filter module, the filter cartridge is disposed in an outer pressure vessel, where the at least one outlet connection for the permeate is disposed on the pressure vessel. In this case, a ring space within which the permeate can flow is formed over part of the length between the cartridge tube and the pressure vessel. In addition, connecting elements and closure elements in particular, for example end caps, are provided. The filter cartridge is advantageously fully enclosed by the pressure vessel, such that the filter cartridge can be exchanged rapidly and inexpensively as required. 202400091 Foreign Filing 24

[0199] B) In an alternative advantageous embodiment which can especially have a lower weight and is therefore advantageously preferable for OBIGGS applications, the filter cartridge itself constitutes a pressure vessel and accordingly has the construction and / or dimensions of a pressure vessel. There is thus no provision of an at least partly surrounding outer pressure vessel. The at least one outlet connection for the permeate is disposed directly on the filter cartridge designed as a pressure vessel. The terminal connecting elements and / or closure elements in the longitudinal direction, for example end caps, are advantageously likewise connected directly to the filter cartridge in a form- and / or force-fitting manner. Advantageously, in such an embodiment, the cartridge tube is not protruded by a potted ring in the axial direction.

[0200] In the present context, the phrase "no at least partly surrounding outer pressure vessel" should be interpreted broadly and means that no completely surrounding or essentially surrounding pressure vessel is provided, with embodiment B) especially including enclosure in sections or partial enclosure of, for example, a terminal connecting or closure element in a flange section or securing section.

[0201] The invention additionally also encompasses a production process for a filter cartridge from a group of hollow fibres (fibre group) suitable as membrane for gas separation, comprising the following the steps:

[0202] - at least one grouping step comprising providing and / or grouping a number of individual fibres to a fibre bundle;

[0203] - at least one bonding step comprising placing the fibre bundle into a cartridge tube;

[0204] - at least one fixing step comprising securing the cartridge tube in a holding device;

[0205] - at least one filling step comprising storing or charging of a defined amount of a liquid or free-flowing potting mixture;

[0206] - at least one potting step comprising feeding in a potting mixture at at least one end of the fibre bundle, wherein the potting mixture comprises at least the following components:

[0207] - a resin component A, especially is an epoxy resin,

[0208] - a curing agent B, wherein

[0209] - the resin component A is in the range from 65% to 85% by weight, preferably 70% to 80% by weight, especially 75% to 78% by weight;

[0210] - the curing agent B is in the range from 15% to 35% by weight, preferably 20% to 30% by weight, especially 20% to 25% by weight, and where the potting mixture comprises, as a further component, at least one inert filler C having an average particle diameter of below 100 nm.

[0211] In the present context, all aspects, advantages, embodiments and variants of the process for producing the filter cartridge, identically or in an analogous manner, shall be applicable as such to the filter cartridge and / or the filter module, where appropriate. In particular, the above production process for producing a filter cartridge or a filter module is to serve for use in aviation for gas separation during flying operations. 202400091 Foreign Filing 25

[0212] In particular, the bonding step and / or filling step may comprise the mounting of a potting cap for improved feeding and curing of the potting mixture, as described, for example, in WO 2014 / 143336 A1 in EP 3 007 807 B1.

[0213] In addition, the invention also encompasses a gas separation process with a filter module and a filter cartridge having a fibre group as separation-active membrane, comprising at least one potted section, especially two potted sections, wherein the filter cartridge has been produced by a production process of the embodiments or variants mentioned herein.

[0214] The gas separation process is advantageously a process in which air is fed in as feed, where the discharged permeate or retentate have different partial pressures of 02 and / or N2. Advantageously, the gas separation process is operated in a flying device in that 02 is depleted and N2 is enriched in air (feed) in an aircraft, where the N2-rich gas stream is directed into at least one fuel tank, especially into the vertically higher gas space of the at least one fuel tank. The terms "flying device" or "aircraft" should not be considered to be limiting here.

[0215] Figures 1 to 5 and 7 to 9 show the results of the experiments, and figure 6 shows the measuring arrangement for a specimen. In the figures:

[0216] Figure 1 shows the temperature progression in the course of curing with different amine contents of the curing agent (B) on a 100 g scale using a filled resin component A.

[0217] Figure 2 shows the temperature progression in the course of curing with different aliphatic-aromatic amine mixtures of the curing agent B using a filled resin component A.

[0218] Figure 3 shows the temperature progression in the course of curing with different aliphatic-aromatic amine mixtures using an unfilled resin component A.

[0219] Figure 4 shows the temperature progression in the course of curing with different amine-imidazole ratios of curing agent B.

[0220] Figure 5 shows the temperature progression in the course of curing of further different amine-imidazole ratios of curing agent B.

[0221] Figure 6 shows a specimen from figure 5 inter alia, and the arrangement of thermocouples in this specimen (potted section).

[0222] Figure 7 shows the temperature progression in the course of the curing of filled and unfilled Araldite with different substoichiometric proportions of XB3473 curing agent. 202400091 Foreign Filing 26

[0223] Figure 8 shows the temperature progression in the course of curing of an unfilled potting mixture with different progressions of the oven temperature.

[0224] Experiment 1 - "Effect of the ratio of resin component A to curing agent B in a filled epoxy resin"

[0225] This experiment was a small-scale preliminary test of a total of 100 g of a (filled) potting mixture and served in particular for screening of the curing agent B and the effect of the curing agent components B1 , B2 (ratio V3), using amine (H418H) as curing agent component B1 and 2,4-ethylmethylimidazole (Imicure 2,4 EMI) as curing agent component B2.

[0226] The curing agent B used (H418H, FDW Handelsges. mbH) is a mixture of the following components: 4,4'- methylenebis(cyclohexylamine) 45-50% by weight (CAS No. 1761-71-3, aliphatic amine), diethylmethylbenzenediamine 45-50% by weight (CAS No. 68479-98-1 , aromatic amine) and the adhesion promoter 3-aminopropyltriethoxysilane 1-5% by weight (CAS No. 919-30-2). The proportions of aliphatic and aromatic amines are 50:50 (V4 = 0.5), with a standard 3% by weight of adhesion promoter in H418H (based on curing agent B) unless stated otherwise.

[0227] The proportion by weight of imidazole B2 was constant at 0.65% by weight, based on the total proportion of resin components A with a (theoretically) stoichiometric proportion of curing agent B. Different proportions of amine curing agent B1 were used. The curing agent components B1 of the curing agent B were a mixture of aliphatic amines and aromatic amines, in a ratio of 50 / 50 (V4 = 0.5). The curing agent B1 was added in different proportions in 0.1 equivalence steps, starting with 0.2 eq. up to 0.8 eq. The epoxy resin mixture used is 50% by weight of Nanopox F520 (with inert filler C), 10% by weight of Albidur EP2240A (with elastomer D), 30% by weight of Araldite MY 0510 (resin component A) and 10% by weight of LH5000 (resin component A).

[0228] LH5000 here is a bisphenol A diglycidyl ether (BADGE, CAS 1675-54-3).

[0229] The components of the potting mixture were intimately mixed in a plastic vessel and with an electric stirrer. The initially liquid potting mixture was then cured in an oven under temperature control.

[0230] Figure 1 shows, in a graph, the temperature progression (y axis) over time (x axis) during the 1st CP. The progression of the oven temperature 400 shows that a heat-up phase 410 has been run at a fixed temperature level (40°C, about 120 minutes), followed by a (first) heating phase 450, likewise at a fixed temperature level (60°C; 350 minutes). The reference numerals P1.1 ... P1.7 show the temperature progressions of the respective test specimens in Fig. 1 . A total of 7 individual samples were made up, each with substoichiometric proportions of curing agent B, with variation of the substoichiometry solely by the curing agent component B1 (amine). The individual curves are assigned to the following proportions of amine: P1.1 : 20%, P1.2: 30%, P1.3: 40%, P1.4: 50%, P1.5: 60%, P1.6: 70% and P1.7: 80%. The imidazole curing agent component (B2) was constant at 0.65% by weight, based on the total proportion of resin components A with a (theoretically) stoichiometric proportion of curing agent B. 202400091 Foreign Filing 27

[0231] The oven temperature 400 shown in the graphs of the figures overall shows the respective oven temperature, while what is shown in Figures 2 and 3 is not a real measured interior temperature of the respective curing oven but the defined (controlled) oven temperature. Figures 1 , 4 and 5 show the real measured interior temperature of the oven in the curve 400.

[0232] As shown in Figure 1 , it was observed that the (material) temperature on commencement of the curing phase rises with increasing amine content (B1) and the temperature maximum was at its highest at an amine content of 80%, i.e. the exothermic reaction increases with rising amine content (B1). It was thus found to be advantageous that lower amine fractions (B1) or higher imidazole fractions (B2) in the amineimidazole mixture reduce the evolution of temperature in the potted section, resulting in lower thermal stress overall. As a result, only relatively low stresses occurred. The aim of achieving a most substantially homogeneous temperature distribution possible between outer regions that follow the oven temperature 400 more quickly and the core region in the potted section can be controlled at least partly via the ratio V3.

[0233] Experiment 2 - "Effect of the ratio of aliphatic curing agent to aromatic curing agent in a filled epoxy resin".

[0234] This experiment was used to examine the effect of different fractions of the curing agent components. These were the aromatic curing agent component to the aliphatic curing agent component and curing agent component B2, an imidazole. This was done using a (filled) mixture analogous to Experiment 1 : epoxy resin mixture of 50% by weight of Nanopox F520 (with inert filler C), 10% by weight of Albidur EP2240A (with elastomer D), 30% by weight of Araldite MY 0510 (resin component A) and 10% by weight of LH5000 (resin component A).

[0235] This experiment was a small-scale preliminary test of a total of 100 g of potting mixture and served in particular for screening of curing agent B, consisting of an aliphatic-aromatic amine curing agent mixture as curing agent component B1 and 2,4-ethylmethylimidazole (Imicure 2,4 EMI, curing agent component B2) 0.5% by weight, based on the total proportion of resin components A with a (theoretically) stoichiometric proportion of curing agent B, where the amine curing agent mixture was 1 eq. (equivalent). The amine curing agent mixture B1 consisted of the aforementioned H418H and XB3473. The curing agent XB3473 is itself a mixture of substances and consisted of:

[0236] 1) 90% diethylmethylbenzenediamine (CAS 68479-98-1 , aromatic fraction) and

[0237] 2) 10% cyclohex-1 ,2-ylenediamine (CAS 694-83-7, aliphatic fraction).

[0238] The composition of the two curing agents H418H (as described for Experiment 1) and XB3473 was varied between 0% by weight and 100% by weight, based on curing agent B).

[0239] Figure 2 shows, in a graph, the temperature progression (y axis) over time (x axis). The progression of the oven temperature 400 shows that a heat-up phase 410 has been run at a fixed temperature level (70°C, about 120 minutes), followed by a calming phase 430 at a fixed temperature level (40°C, about 202400091 Foreign Filing 28

[0240] 120 minutes) and a subsequent (first) heating phase 450 (70°C, about 200 minutes) was carried out. The (first) heating phase 450 was stopped prematurely, because the temperature progressions were observed to be largely constant. The reference numerals P2.1 ... P2.6 indicate the temperature progressions of the respective test specimens in Fig. 2. The individual curves are the proportions of H418H to XB3473 listed as follows, with XB3473 constituting the respective remainder to 100%: P2.1 : H418H 0%, P2.2: H418H 20%, P2.3: H418H 40%, P2.4: H418H 60%, P2.5: H418H 80% and P2.6: H418H 100%. This leads to the following ratios V4 (proportions) of the aromatic amine components: P2.1 : 90%, P2.2: 82%, P2.3: 74%, P2.4: 66%, P2.5: 58% and P2.6: 50%.

[0241] The test results are shown in Figure 2, and it was observed that an elevated oven temperature in the heat-up phase 410 leads overall to homogenization of the curves (P1.7 in Fig. 1 to P2.6 in Fig. 2). It was also observed that the initial exothermic reaction increases with increasing aliphatic amine content (curing agent component), whereas the second exothermic reaction increases after the calming phase 430 at a low oven temperature (minus 30°C) with increasing aromatic amine content (curing agent component).

[0242] Overall, it has been found to be very advantageous to provide a calming phase 430 of at least 1 h to 3 h which follows on from the (first) heat-up phase 410 and has a temperature level 20 K to 40°C below that of the heat-up phase 410.

[0243] Experiment 3 - "Effect of the ratio of aliphatic curing agent to aromatic curing agent in an unfilled epoxy resin".

[0244] This experiment was used to examine the effect of different fractions of the curing agent components. These were the aromatic curing agent component to the aliphatic curing agent component and the curing agent component B2, an imidazole, in an unfilled potting mixture. In contrast to Experiments 1 and 2, the epoxy resin LH 5000 was used as an unfilled resin component (100% by weight); this screening was carried out on a 100 g scale.

[0245] The curing agent B used was the following mixture: 2,4-ethylmethylmidazole (Imicure 2,4 EMI; curing agent component B2) with 0.5% by weight, based on the total proportion of resin components A with a (theoretically) stoichiometric proportion of curing agent B, in combination with 1 eq. (equivalent) of aliphatic-aromatic amine curing agent mixture, where the composition of aliphatic and aromatic fractions was varied in 20% steps by addition of H418H.

[0246] Figure 3 shows, in a graph, the temperature progression (y axis) in the individual samples over time (x axis) in the 1st CP. The progression of the oven temperature 400 shows that a heat-up phase 410 has been run at a fixed temperature level (70°C, about 120 minutes), followed by a calming phase 430 at a fixed temperature level (40°C, about 120 minutes) and a subsequent heating phase (70°C, about 200 minutes) was carried out. The reference numerals P3.1 ... P3.6 indicate the temperature progressions of the respective test specimens in Fig. 3. The individual curves are the proportions of H418H to XB3473 listed as follows, with XB3473 constituting the respective remainder to 100%: P3.1 : H418H 0%, P3.2: 202400091 Foreign Filing 29

[0247] H418H 20%, P3.3: H418H 40%, P3.4: H418H 60%, P3.5: H418H 80% and P3.6: H418H 100%. This leads to the following ratios V4 (based here on the percentages by weight of the aromatic amine components): P3.1 : 90%, P3.2: 82%, P3.3: 74%, P3.4: 66%, P3.5: 58% and P3.6: 50%.

[0248] It was observed that the initial exothermic reaction, commencing in the heat-up phase 410, increases with increasing content of aliphatic amine as curing agent component, whereas the second exothermic reaction, following the calming phase 430, increases with increasing content of the aromatic curing agent component. Without being bound to a single interpretation, because of the more uniform temperature progression, it is assumed that the intended crosslinking is more uniform and complete at higher aromatic amine contents than at high aliphatic amine contents in the curing agent B because very high exothermic reaction temperatures generally also lead to a higher proportion of (undesirable) side reactions.

[0249] In addition, much stronger exothermic reactions were observed with the unfilled epoxy resin LH5000 and the respective curing agent B, compared to the previous experiments with filled epoxy resin in Fig. 1 or 2.

[0250] It was thus found that, surprisingly, the inert fraction of fillers (components C, D) has a homogenizing and lowering effect (temperature) on the exothermicity of the curing process in the 1st CP.

[0251] Experiment 4 - Effect of the ratio of the curing agent components amine (B1) to imidazole (B2) with an adhesion promoter.

[0252] This experiment was used to examine the effect of different fractions of the curing agent components, here the ratio V3. This screening was effected with a potting mixture on a 1000 g scale to produce a potted section in a size of 6 inches (6”) with inlaid fibres (121 200 single fibres) in a centrifuge (1st CP) and a curing oven (2nd CP).

[0253] The potting material used here was the following (filled) mixture: epoxy resin mixture of 50% by weight of Nanopox F520 (with inert filler C), 10% by weight of Albidur EP2240A (with elastomer D), 30% by weight of Araldite MY 0510 (resin component A) and 10% by weight of LH5000 (resin component A).

[0254] The curing agent B used was the following curing agent mixture: curing agent component B2: 2,4-ethylmethylimidazole (Imicure 2,4 EMI) at 0.5% and 0.55% by weight based on resin component A.

[0255] Amine curing agent H418H consisting of:

[0256] - curing agent component B1 : 97% amine curing agent mixture (B1) with

[0257] - adhesion promoter: 3% by weight of Dynasylan AMEO, where the amount of the amine curing agent H418H used was 9.71% by weight, based on the total mass of the potting mixture.

[0258] Figure 4 shows, in a graph, the temperature progression (y axis) over time (x axis), with a 1st CP performed dynamically (410 to 450) in the centrifuge under rotation and a 2nd CP in an oven that was run 202400091 Foreign Filing 30 statically (460 to 480). In the case of Figure 4, the curve of the oven temperature 400 shows the temperature measured by temperature sensor in the oven interior. For this purpose, the filter module was manually removed from the centrifuge and inserted directly into an oven. The reference numerals P4.1 ... P4.4 indicate the temperature progressions of the respective test specimens in Fig. 4. The progression of the oven temperature 400 shows that a first heat-up phase 410 has been run at a fixed temperature level (70°C, about 120 minutes), followed by a calming phase 430 with constantly falling oven temperature 430 down to 50°C over a period of about 120 minutes and a subsequent first heating phase 450 at a constant 70°C for about 200 minutes. This first part of the curing step (1st CP) was performed in the centrifuge. The negative peak at minute 420 occurred when the centrifuge was switched off and opened, and when the individual samples (filter modules) were transferred to a (static) curing oven. The second heat-up phase 460 took place with a temperature gradient of 20°C / h and, on attainment of 170°C in a second heating phase 470, was kept at that temperature level for about 6 hours. The subsequent cooling phase 480 was not carried out in a controlled manner; instead, the samples were cooled with outside air in the switched-off oven under gas exchange (ventilation). Overall, it has been found to be advantageous in avoiding oxidative processes to provide an inert atmosphere in the oven at temperatures in the heating phase above 120°C, in particular above 140°C. The heat-up phase 460 involved heating with a gradient of about 20°C / h, with a cooling gradient in the cooling phase 480 of 50°C / h to 60°C / h.

[0259] The two curves P4.2 and P4.4 that run close to the oven temperature 400 relate to external measuring points in the test specimen (potted section) which correspond to positions P1 or P5 according to Fig. 6. The two curves P4.1 and P4.3 that are remote from the oven temperature 400 relate to inner (central) measurement points in the test specimen (potted section) which correspond to position P3 of Fig. 6.

[0260] It was observed that a higher content of imidazole (curing agent component B2) leads to increased exothermic characteristics in the initial reaction and hence to higher stresses in the potted section. The temperature difference in the potted section (test specimen) AT = Toutside - Tinside serves here as a quality criterion for homogeneous curing. It has been found that, surprisingly, it is still the case that, in the 2nd CP too, AT was greater with higher imidazole content (curing agent component B2) than with the lower proportion of curing agent components B2. Without committing to a specific interpretation, it is assumed that the very high material temperature in the 1st CP, in the sample with the higher imidazole content, resulted in an increase in non-specific reactions and subsequent premature "freezing" of the molecular structures, which cause high disadvantageous stresses within the potted section (test specimen).

[0261] Experiment 5 - Effect of the ratio of the curing agent components amine (B1) to imidazole (B2) with an adhesion promoter AP.

[0262] Analogously to Experiment 4, this experiment likewise served to examine the effect of different proportions of the curing agent components (V3), the amine curing agent component (B1) to imidazole (B2). This screening was effected with a potting mixture on a 1000 g scale to produce a potted section in a size of 6 inches (6”) with inlaid fibres (121 200 single fibres) in what is called a “stationary potting” (1st CP), with the fibres or the fibre bundle randomized in the potting mixture. 202400091 Foreign Filing 31

[0263] The potting material used here was the following (filled) mixture: epoxy resin mixture of 50% by weight of Nanopox F520 (with inert filler C), 10% by weight of Albidur EP2240A (with elastomer D), 30% by weight of Araldite MY 0510 (resin component A) and 10% by weight of LH5000 (resin component A).

[0264] The curing agent mixture used was the following mixture of curing agent B and adhesion promoter: curing agent component B2: 2,4-ethylmethylimidazole (Imicure 2,4 EMI) at 0% and 0.25% by weight based on the total mass of resin component A; curing agent component B1 : 96% by weight and 95.75% by weight of XB3473;

[0265] Adhesion promoter: 4% by weight of Dynasylan AMEO based on curing agent B. The amount of XB3473 used was 14.7% by weight, based on the total mass of the potting mixture.

[0266] Figure 5 shows, in a graph, the temperature progression (y axis) over time (x axis). The reference numerals P5.1 ... P5.4 indicate the temperature progressions of the respective test specimens in Fig. 5. The progression of oven temperature 400 in the 1st CP shows that a heat-up phase 410 has been run at a fixed temperature level (70°C, about 3 hours), followed by a calming phase 430 with constant oven temperature of 40°C over a period of about 2 hours and a subsequent (first) curing phase 450 at 70°C for about 4 hours. At the time of about 9 hours after the start, the oven was switched off and the oven temperature dropped to ambient temperature (25°C) over a period of about 2 hours. The individual curves are assigned to the following proportions of curing agent component B2 (imidazole): P5.1 : 0.25% (inside), P5.2: 0.25% (outside), P5.3: 0% (inside), P5.4: 0% outside.

[0267] It was observed that the presence of imidazole (curing agent component B2) leads to an increase in exothermic characteristics even in the calming phase and in the 1st heating phase. It has been observed that, surprisingly, the high proportions of aromatic amine lead to smaller temperature differences (AT) and overall to lower temperature maxima in absolute terms, which additionally occurred later on, compared to the results of Fig. 4.

[0268] On comparison of the resin / fibre composites produced in Experiment 5 and Experiment 6, it could additionally be visually observed that the adhesion of the epoxy resin potting on the fibres and on the potting ring was improved.

[0269] Figure 6 shows a test specimen 500 in 6" size, as also produced and used in Experiment 5. This has a flat, cylindrical shape, analogously to the real potted sections of a filter module for a filter cartridge, and the measurement sites of the thermocouples used for temperature measurement (thermocouples not shown). The left-hand side of the image, I., shows a schematic of a test specimen that was produced solely with the curing agent component B1 (XB3473) and did not include imidazole as curing agent component B2. The right-hand side of the image, II., likewise shows a schematic test specimen, where the curing agent B had a proportion of the curing agent component B2 (imidazole "Imicure") of 0.25%. The absolute temperature values shown are the Tg values taken from material samples at the respective positions (P1 , P2, P3). 202400091 Foreign Filing 32

[0270] The material temperature was recorded in all previous experiments in the centre of the test specimen 500 (core temperature), which corresponds to position P3 according to Fig. 6 (analogously) at the intersection of vertical axis A1 and transverse axis A2. The textual mention and reference to gravity or view according to Figure 6 should not be construed in a limiting manner and serves merely for easier illustration, since the test specimen 500 can assume any alignment, and can in particular also be moved under centrifugal forces. The reference numerals P1 to P7 relate to the measurement points / positions in the test specimen 500. The vertical axis A1 is guided perpendicularly through the cylindrical test specimen 500 and constitutes an axis of symmetry. The transverse axis A2 is pivoted by 90° to the vertical axis A1 and intersects it in the centre of the test specimen 500. The transverse axis A2 constitutes a further axis of symmetry of the test specimen 500.

[0271] As can be inferred from the absolute values of the glass transition temperatures (Tg) determined, which were determined by DSC (dynamic scanning calorimetry), the AT of the glass transition temperatures (Tg) in the test specimen in the presence of the curing agent component B2 (imidazole, see Experiment 5) was less than 1 °C. In addition, the level of the glass transition temperatures determined was about 15°C above the level of the glass transition temperatures that were generated in the absence of curing agent component B2 (partial image I.). Glass transition temperatures were determined by sampling at the positions (P1 ... P7) of the potted section shown in Figure 6 with the aid of a drill or a knife, followed by an analysis of the Tg by DSC.

[0272] Experiment 7 - Effect of the curing agent components XB and an inert filler C.

[0273] This experiment, analogously to Experiment 1 , likewise served to examine the effect of different proportions of the curing agent XB3473 and an inert component C. This screening was effected with a potting mixture on a 1000 g scale to produce a potted section in a size of 6 inches (6”) with inlaid fibres (121 200 single fibres) in what is called a “stationary potting” (1st CP), with the fibres or the fibre bundle randomized in the potting mixture. The resin component was Araldite MY 0510.

[0274] The potting material used here was the following (filled) mixture:

[0275] P7.1 : Epoxy resin mixture of Araldite 40% by weight, inert filler C 19.5% by weight, curing agent B XB3473 (substoichiometric) 0.7 eq.

[0276] P7.2: Epoxy resin mixture of Araldite 30% by weight, inert filler C 20.3% by weight, curing agent B XB3473 (substoichiometric) 0.7 eq.

[0277] P7.3: Epoxy resin mixture of Araldite 40% by weight, inert filler C 20.0% by weight, curing agent B XB3473 (substoichiometric) 0.7 eq.

[0278] P7.4: Epoxy resin mixture Araldite 40% by weight, inert filler C 19.4% by weight; curing agent B XB3473 (substoichiometric) 0.85 eq.

[0279] Figure 7 shows, in a graph, the temperature progression in degrees Celsius (y axis) over time (x axis) in hours. The reference numerals P7.1 ... P7.4 indicate the temperature progressions of the respective test 202400091 Foreign Filing 33 specimens in Fig. 7. The progression of the oven temperature 400 only affects the heat-up phase 410, which has been run at a fixed temperature level (80°C, up to max. 9 hours).

[0280] It was observed that

[0281] P7.1 runs through a maximum after about 5.5 h in the process, exceeding the oven temperature by about 40°C.

[0282] P7.2 runs through a much lower and flatter maximum after about 4.5 h, exceeding the oven temperature in the peak only by about 15°C and subsequently falling slightly and then slowly rising again.

[0283] P7.3 runs through a quasi-constant phase from hour 3.5 to 5, in which the core temperature corresponds essentially to the oven temperature of 80°C. The core temperature then rises further at about 12°C / h. The run was stopped after 7 h because the surface of the potted section still had a viscous consistency.

[0284] P7.4 similarly to V15, a plateau forms after hour 4 to hour 5, but at about 93°C. From hour 5, the core temperature likewise rises further at about 12-13°C / h. The run was stopped after about 7 h because the surface of the potted section had a viscous, partly gelated consistency.

[0285] It was thus surprisingly observed from the comparison of Experiment V11 (P7.1) and V15 (P7.2) that the inert filler reduces the exothermicity peak in the test specimen, such that curing is more homogeneous and calmer overall.

[0286] Thus, in the case of an epoxy resin mixture with filled Araldite, it was subsequently possible to increase the oven temperature in the heat-up phase to 90 to 95°C, with a simultaneously stable, controlled progression of the core temperature during the heat-up phase 410 in the potted section. This subsequently led to shortening of the heat-up phase 410 and hence the occupancy time of the centrifuge by about 20%.

[0287] Experiment 8 - "Effect of different temperature control methods in an unfilled potting mixture with an amine as curing agent B.”

[0288] In this experiment, a 6” potted section without hollow fibres was produced, as described above in association with Figure 6 in particular. The potting mixture consisted of an intimately stirred resin component LH5000 (bisphenol A diglycidyl ether; BADGE, CAS 1675-54-3) and amine mixture H418H as curing agent B, as described above in particular in connection with Experiment 1 . The ratio of resin component A to curing agent B by weight was 80:20.

[0289] The components of the potting mixture were intimately mixed in a plastic vessel and with an electric stirrer. The initially liquid potting mixture was then cured in a temperature-controlled oven under closed- loop temperature control. 202400091 Foreign Filing 34

[0290] Figure 8 shows the temperature progressions (y axis) over the time (x axis) of two compared test runs with different temperature management. The two oven temperatures here are shown as dashed lines and the core temperatures in the potted section are shown as dotted lines. The progression of the first run with the oven temperature 400.1 shows stepped temperature control in the heating phase 460. Furthermore, in the initial preheating phase 410.1 , a fixed temperature level of 50°C is established for about 6.5 h, followed by two increments, namely of 30°C in the 1st stage (duration 6 h) and ~40°C in the 2nd stage (duration ~ 6.5 h), where the temperature in the hold phase 470.1 was ~ 120°C. The temperature progression of the second run shows continuous heating in the heating phase 460. In addition, the fixed temperature level in the preheating phase 410.2 is regulated at 30°C.

[0291] It was observed that the progression of the core temperature in the potted section in the first run goes through a strongly pronounced peak and the temperature difference AT between the oven temperature and the core temperature was up to about 135°C. In the subsequent heating phase 460, the core temperature follows the oven temperature 460.1 under stepwise control without abnormalities, in particular no conspicuous maxima or minima.

[0292] The test specimen produced after the first test run did not exhibit any outward visual abnormalities after curing. However, the sample material collected in the core section and the PED-DSC analysis showed a Tg value of only 130°C.

[0293] In the second test run with the same potting mixture, the temperature level in the preheating phase 410.2 was set 30° lower than in the first test run and was 30°C. As a result, it was observed that the progression of the core temperature in the potted section went through only a distinctly less pronounced peak and the temperature difference AT between the oven temperature and the core temperature was only about 40°C and the maximum was only about 70°C.

[0294] The test specimen produced after the second test run likewise did not exhibit any outward visual abnormalities after curing. However, the sample material collected in the core section and PED-DSC analysis showed a very high Tg value of 165°C, indicating a very homogeneous, complete reaction between the resin component A and the curing agent B.

[0295] Without wishing to be committed to a specific interpretation, it is assumed that, in the first test run, during the severe overheating in the preheating phase 400.1 , freezing of the molecular structure takes place, by predominantly unwanted side reactions, varying from the desired reaction steps between the resin component A and the curing agent B.

[0296] Furthermore, it was observed that, in the second test run, the core temperature in the heating phase 460 has very good ability to track a gradient of the oven temperature of - 8.7 K / h, such that, even in this phase, internal stresses are largely avoided with such continuous heating. 202400091 Foreign Filing 35

[0297] Furthermore, it was surprisingly observed that, with temperature management according to the second test run, commencement was possible immediately after the maximum in the preheating phase 410.2 because the absolute level is so low. For instance, commencement of the heating phase 416 would be possible with steady or stepped heating even after 4 h, for example, and so the overall duration of the heating could be shortened accordingly.

[0298] Overall, it was thus shown that a curing agent B with a high proportion of aromatic amines, relatively small proportions of aliphatic amine and a small amount of catalytic imidazole in assocation with improved temperature control in the curing process of the potting mixture leads to an improved, high-quality filter cartridge for OBIGGS applications.

Claims

202400091 Foreign Filing 36Claims1 . Production process for a filter cartridge from a group of hollow fibres (fibre group) suitable as membrane for gas separation, comprising the steps of:Grouping step: providing and / or grouping a number of individual fibres to a fibre bundle;Bonding step: introducing the fibre bundle into a cartridge tube and aligning and optionally fixing the cartridge tube for the potting and / or filling step;Filling step: storing / charging a defined amount of the liquid potting mixture for the potting step, where the potting mixture comprises or is formed from at least a resin component A and a curing agent B as components, where resin component A of the potting mixture is epoxy resin or epoxy resin mixture composed of two or more constituents;Potting step: feeding in a potting mixture at at least one end of the fibre bundle into the cartridge tube to form at least one potted section (500), where the proportion by volume of the individual fibres in the respective potted section is in the range of 50% to 70% by volume, ideally 50% to 60% by volume, based on the cavity volume of the potted section in the cartridge tube;Curing step: heating the filter cartridge for a period of time greater than at least one hour, where the potting mixture comprises or is formed from at least a resin component A and a curing agent B as components, where the filter cartridge is subjected to at least the following phases in the curing step:- a preheating phase (410) within a first temperature range (T1) of 25 to 85°C, ideally 30 to 80°C, for a preheating time of 2 to 12 h, ideally 3 to 10 h;- a heating phase (460) in which the oven temperature of the first temperature range (T1) is raised to an end temperature T2 in the range of 100 to 180°C, ideally 120 to 160°C, where the positive temperature gradient is 10 to 30°C / h, ideally 15 to 25°C / h;- a hold phase (470) at the end temperature (T2) for a hold time of 2 to 24 h, ideally 4 to 18 h, and- a cooling phase (480) at falling temperature, where the negative temperature gradient is 20 to 60°C / h, ideally 25 to 50°C / h, characterized in that the weight ratio V1 a of curing agent B to resin component A is in the range of 5% to 35% by weight and comprises or is formed from at least the following curing agent components (B1 , B2): a) amines (B1), aliphatic amines and aromatic amines; and b) imidazoles (B2) as catalyst in the range of 0.1% to 5% by weight, based on the resin component A; where• a proportion of aliphatic amines is in the range from less than 40% to at least 5% by weight, based on curing agent B; and• a proportion of aromatic amines in the mixture is not more than 98 mol%, ideally not more than 95 mol%, based on the amine groups of curing agent B, where the preheating phase (410) comprises at least two subphases, where the temperature range202400091 Foreign Filing 37 cooling phase (430) (second subphase) the temperature range (TK) is 5 to 50°C lower than the temperature range (T1), ideally 10 to 40°C lower, and where the second subphase is followed by - a third subphase (414) of the preheating phase (410) in which the temperature range (T1) is 50 to 90°C, or the heating phase (460) is executed.

2. Production process according to Claim 1 , characterized in that the weight ratio V1 a is in the range of 10% to 35% by weight, in particular 15% to 35% by weight.

3. Production process according to either of the preceding claims, characterized in that the proportion of aliphatic amines is in the range of less than 30% to at least 5% by weight, based on the overall curing agent B.

4. Production process according to any of the preceding claims, characterized in that the calming and cooling phase (430) and lowering of the oven temperature to the temperature range (TK) after the first subphase (412) starts when the rising core temperature (P3) in the potted section (500) is in the range of 0 to 20°C below the temperature range (T1) of the oven temperature, ideally 10 to 15°C below.

5. Production process according to any of the preceding claims, characterized in that curing agent B comprises a catalyst as a component, where the proportion of the catalyst is 0.1% to 0.6% by weight, in particular 0.15% to 0.55% by weight, based on the weight of the potting mixture, and where the catalyst is a substance from one of the following groups: a. imidazole, for example 2-methylimidazole (2MI), 2-ethyl-4(5)-methylimidazole (2E4MI), 1- methylimidazole (1 Ml), 2-ethylimidazole (2EI), 2-phenylimidazole (2Phl), 1-(2-cyanoethyl)-2- ethyl-4(5)-methylimidazole (2E4MCNI) or a mixture thereof; b. tertiary amine, for example (dimethylaminomethyl)phenol, diazabicycloundecene, triethylamine or a mixture thereof; c. polyamines, for example- propane-1 ,3-diamine, N,N-dimethyl-, reaction products with 5-amino-1 ,3,3- trimethylcyclohexanemethanamine-5-isocyanato-1-(isocyanatomethyl)-1 ,3,3- trimethylcyclohexane-N-(2-methylphenyl)-N-(2-oxiranylmethyl)-2-oxiranemethanamine;- propane-1 ,3-diamine, N,N-dimethyl-, reaction products with benzenemethanamine (Ancamine2441 : CAS No. 912342-92-8);- propane-1 ,3-diamine, N,N-dimethyl-, polymers or a mixture thereof; or a mixture of a), b) and / or c).202400091 Foreign Filing 386. Production process according to any of the preceding claims, characterized in that the calming and cooling phase (430)- has a duration of 1 to 3 h, ideally 1 .5 to 2.5 h, and / or- is ended when the core temperature (P3) in the potted section (500) does not rise by more than 1.5°C / h in a defined period of time, in particular rises by less than 0.1 to 0.5°C / h, has reached a constant value for a defined period of time or falls, in particular at more than 0.1 to 0.5°C / h.

7. Production process according to any of the preceding claims, characterized in that the changeover from the temperature range (T1) of the first subphase to the lower temperature range (TK) of the calming and cooling phase (430) is conducted as a single lowering stage and / or active cooling is effected by means of a cooling medium, for example the introduction of a gas into the space surrounding the cartridge, in particular an inert gas.

8. Production process according to any of the preceding claims, characterized in that the heating phase (460) comprises at least two subphases with two end temperatures (T2a, T2b), where the end temperatures (T2a, T2a) of the two subphases are different or equal.

9. Production process according to Claim 8, characterized in that i) the first subphase of the heating phase (460) is effected in a centrifuge with an at least intermittently rotating filter cartridge, and at least one further subphase is effected in an oven, in particular in the case of an at least intermittently stationary filter cartridge, and / or ii) the second subphase of the hold phase (470) is effected in a centrifuge with an at least intermittently rotating filter cartridge, and at least one further subphase is effected in an oven, in particular in the case of an at least intermittently stationary filter cartridge.

10. Production process according to Claim 8 or 9, characterized in that the end temperature (T2a) in the first subphase of the hold phase (470) is in the range of 80 to 100°C and the at least one further end temperature (T2b) in the at least one further subphase of the hold phase (470) is in the range of 100 to 200°C, ideally in the range of 100 to 190°C.11 . Production process according to any of Claims 8 to 10, characterized in that the hold phase (470) comprises at least two subphases (472, 474), where the end temperatures (T2a, T2a) of the two subphases are different or equal.

12. Production process according to any of the preceding claims, characterized in that resin component A is an epoxy resin or epoxy resin mixture of several components, for example:- bisphenol A diglycidyl ether,- bisphenol F diglycidyl ether,- N,N-diglycidyl-4-glycidyloxyaniline or triglycidyl ether of para-aminophenol,- N,N-diglycidyl-3-glycidyloxyaniline or triglycidyl ether of meta-aminophenol,202400091 Foreign Filing 39- tris(4-hydroxyphenyl)methane triglycidyl ether,- 4,4'-methylenebis(N,N-diglycidylaniline) or tetraglycidyl ether of 4.4'- diaminodiphenylmethane, and - oligomers as reaction products thereof.

13. Production process according to any of the preceding claims, characterized in that the potting mixture comprises an inert filler C and / or an elastomer, where- the inert filler C has an average particle diameter of less than 100 nm, and wherein - the elastomer D has an average (particle) diameter of 4 to 15 pm.

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