Method for producing a precious metal mesh on a flat knitting machine

Abstract

The invention relates to a method for producing a double-layered precious metal mesh on a flat-bed knitting machine having a first needle bed and a second needle bed. The method comprises providing at least one precious metal-containing thread and knitting the precious metal mesh. A first layer and a second layer of the precious metal mesh are knitted simultaneously on the first needle bed and the second needle bed, the two parts being at least partially connected at their two adjoining edges by a connecting stitch.

Description

Technical Field

[0001] This invention relates to a method for producing a double-layer precious metal mesh on a flat knitting machine including a first needle bed and a second needle bed. The method includes providing at least one filament containing precious metal and knitting the precious metal mesh. The first and second layers of the precious metal mesh are knitted simultaneously on the first and second needle beds, and the two portions are at least partially connected at their two respective adjacent edges. Background Technology

[0002] The heterogeneous noble metal catalytic oxidation of ammonia (NH3) to nitric acid (HNO3) (Ostwald process) or the production of hydrogen cyanide (HCN) (Andrussow process) is extremely important due to the central relevance of the products to the chemical industry. Catalyst systems for this purpose are typically introduced into the reaction zone of a flow reactor in the form of a breathable fabric in a plane perpendicular to the flow direction of the fresh gas. Collection or trapping systems for recovering the catalytically active components from evaporation are also often based on this mesh structure. Typically, multiple meshes are advantageously arranged one after another and combined to form a catalyst mesh stack. Individual meshes consist of fine noble metal wires primarily containing platinum (Pt), palladium (Pd), rhodium (Rh), or alloys of these metals. Specifically, trapping meshes may also contain additional components, such as nickel.

[0003] Several methods are known for producing this type of knitted fabric, such as machine weaving, warp knitting, and weft knitting. Machine weaving and warp knitting are particularly suitable for producing rectangular webs with a homogeneous material distribution and structure. They offer little flexibility in terms of the shape and material variability of the product to be manufactured. In an additional process step, the web must be cut from the manufactured web to fit the size and shape of the reactor, resulting in edge material containing precious metal components. Furthermore, the machines used require long setup times and high material input.

[0004] In contrast, weft knitting offers greater flexibility: the knitting pattern, the yarn (e.g., in terms of thickness and material), the needles, and the yarn tension can all be used to change the weight per unit area, as well as the available knitted fabric's structure, elasticity, and strength. Another advantage is a significantly shorter machine setup time. It is also possible to use different materials in a single knitted fabric; in so-called intarsia knitting, for example, different areas can be made from different yarns or silks. In principle, the length of a knitted fabric is unlimited; however, in the case of a flat knitting machine, the maximum width is determined by the width of the needle bed.

[0005] Knitting can be performed using either flat knitting machines or circular knitting machines. In a circular knitting machine, needles are arranged in a circular needle bed, and the yarn or filament is supplied in a circular motion. These machines are primarily used for the production of tubular knitted fabrics. However, on a flat knitting machine, the shape and size of the knitted fabric can be varied. Flat knitting machines may also include more than one needle bed, with yarn or filament being guided back and forth between the needle beds during production using a guide wire.

[0006] The use of two needle beds allows for the production of single-layer or double-layer knitted fabrics. In principle, single-layer knitted fabrics can be produced in two ways: in one way, only one needle bed is in operation, i.e., stitches are formed and knitted together only on one needle bed. In another way, stitches produced on the first needle bed can be knitted together with stitches produced on the second needle bed, i.e., the yarn is guided back and forth between the two needle beds in the right and / or wrong rows. Therefore, when knitting is performed in parallel on two needle beds, a double-layer knitted fabric is produced, and the stitches produced on the first needle row are not knitted or are selectively knitted together with the stitches produced on the second needle bed only via edge stitches. In this production method, two single-layer knitted fabrics or knitted layers can also be produced in parallel on the first and second needle beds.

[0007] Knitting of precious metal mesh is described in EP 0544710 A1. For this purpose, EP 3795728 A1 uses a flat knitting machine. It is described that individual layers produced on different needle beds can be interconnected on one side of two knitted surfaces by means of connecting stitches. This allows the production of knitted fabric surfaces with a greater width than previously possible.

[0008] However, it has been shown that such unilateral bonding can lead to warping of knitted fabrics and thus instability in the production process. This instability can manifest itself as yarn breakage and irregularities in structural and mechanical properties during the knitting process, resulting in products of poor quality.

[0009] Therefore, the problem solved by the present invention is to provide a method with high process stability for producing precious metal mesh on a flat knitting machine. Summary of the Invention

[0010] The problem is addressed by a method for producing a double-layer precious metal mesh on a flat knitting machine, the flat knitting machine comprising a first needle bed and a second needle bed, the method comprising the following steps:

[0011] - Provide at least one wire containing a precious metal.

[0012] - Knit the precious metal mesh

[0013] The first layer of the precious metal mesh is knitted on the first needle bed, and the second layer of the precious metal mesh is knitted simultaneously on the second needle bed.

[0014] Each of the two layers includes at least two adjacent edges.

[0015] The first and second layers of the precious metal mesh are at least partially connected at their two respective adjacent edges by at least one connecting knitted stitch.

[0016] Within the scope of this invention, it has been found that the stability of the knitting process can be improved by at least partially connecting the two sides of a knitted fabric portion made of precious metal wire on different needle beds. This produces a dimensionally stable knitted fabric having at least partially an open tubular structure. By stabilizing the knitting process, the entire combined width of the two needle beds of a flat knitting machine can also be utilized.

[0017] The method according to the invention relates to knitting on a flat knitting machine comprising a first needle bed and a second needle bed.

[0018] Knitting is characterized by the row-by-row production of the resulting knitted fabric, in which interlocking stitches are formed. During the knitting process on a flat knitting machine comprising two needle beds, a knitted row is first formed on at least one of the needle beds. Then, the next knitted row is formed in the knitting direction, wherein the portion of the knitted fabric containing the first knitted row is referred to hereinafter as the "bottom". Thread or yarn is guided from one side of one or more needle beds to the other and back. If "thread" is referred to hereinafter, the relevant description is also intended to apply to the corresponding "yarn". Thus, a knitted row comprises a right-side row and a wrong-side row, which is produced by a guide wire. In this case, the thread can be guided in the knitted row on only one needle bed or on two needle beds. Typically, the thread for the entire knitted row can be guided first on the first needle bed (right-side row) and then guided in the opposite direction on the same needle bed or the second needle bed (wrong-side row). However, the thread can also be guided alternately on both needle beds in the right-side row and / or the wrong-side row, wherein a connection is created between the stitches within a knitted row on the two needle beds. Guide lines can be drawn across the entire width of one or more needle beds, but it is also possible to knit only a portion of the width of the needle bed. The width and shape of the knitted fabric can be determined depending on the width of the needle bed used for knitting.

[0019] The method involves providing at least one wire containing a precious metal.

[0020] The term "precious metal-containing wire" is understood to mean a wire composed of or containing a significant proportion (>50% by weight) of at least one precious metal. In the context of this invention, "precious metal" is understood to mean a metal selected from platinum, gold, and silver. Platinum should be understood to mean the so-called platinum group metals, namely platinum (Pt), palladium (Pd), iridium (Ir), rhodium (Rh), osmium (Os), and ruthenium (Ru).

[0021] At least one wire containing a precious metal is preferably composed of platinum, a platinum alloy, palladium, or a palladium alloy. The platinum-based alloy contains more than 50% by weight of platinum, and other alloying components particularly include palladium, rhodium, and ruthenium. The palladium-based alloy contains more than 50% by weight of palladium.

[0022] Preferably, at least one of the precious metal-containing wires is composed of an alloy selected from platinum with 1 to 15 wt% rhodium, platinum with 1 to 15 wt% rhodium and 0.1 to 20 wt% palladium, platinum with 1 to 15 wt% rhodium, 0.1 to 20 wt% palladium and 0.1 to 5 wt% ruthenium, platinum with 1 to 15 wt% rhodium, 0.1 to 40 wt% palladium and 0.001 to 5 wt% iridium, platinum with 1 to 15 wt% rhodium, 0.1 to 20 wt% palladium and 0.001 to 5 wt% iridium, and platinum with 1 to 15 wt% rhodium, 0.1 to 20 wt% palladium and 0.001 to 5 wt% iridium. % tantalum, platinum and 1% to 15% rhodium, 0.001% to 5% iridium and 0.001% to 5% tantalum, palladium and 1% to 25% platinum, palladium and 1% to 20% platinum and 1% to 15% rhodium, palladium and 1% to 25% tungsten, palladium and 1% to 15% nickel, palladium and 0.001% to 5% rhodium, palladium and 1% to 15% copper, palladium and 1% to 15% copper and 1% to 15% nickel, and palladium and 1% to 30% cobalt.

[0023] Preferably, a precious metal-containing wire with a diameter of 40µm to 150µm, more preferably 50µm to 130µm, is used.

[0024] At least one wire containing a precious metal may be designed as a round wire, i.e., having a circular cross-section. In another embodiment, the wire may be designed as a flat round wire or as a wire with a different cross-section.

[0025] At least one precious metal-containing wire may comprise multiple wires, also referred to in this case as filaments, which are preferably twisted together. The filaments may all be composed of the same material, i.e., all containing precious metals, or they may be composed of different materials, and the different materials need not all contain precious metals.

[0026] In many cases, it may be advantageous to knit two or more precious metal-containing filaments together. In other words, multiple precious metal-containing filaments can be guided together when forming a stitch. When knitting with multiple filaments, in one embodiment, the precious metal-containing filaments are composed of the same material, and in another embodiment, precious metal-containing filaments composed of at least two different materials can be used. The multiple filaments may have the same or different diameters.

[0027] In the method according to the invention, a first layer of the double-layer precious metal mesh is knitted on a first needle bed while a second layer of the double-layer precious metal mesh is simultaneously knitted on a second needle bed. In other words, during the knitting process, the two portions of the double-layer precious metal mesh to be produced are each knitted simultaneously on a separate needle bed, so the two layers are not produced one after the other.

[0028] In the context of this invention, "double-layer precious metal mesh" is understood to mean those precious metal meshes comprising two layers, wherein these layers are typically interconnected via one or more adjacent edges of their respective adjacent edges, or may not be connected at their adjacent edges. The two layers lie on top of each other, i.e., they at least partially overlap in a region of their surface area. As in the case of this invention, a precious metal mesh interconnected on one side via adjacent edges of two layers is also referred to as a double-layer precious metal mesh. A single-layer precious metal mesh can be obtained by folding along a common adjacent edge.

[0029] The first and second layers of the double-layer precious metal mesh each include at least two adjacent edges; that is, each layer includes one adjacent edge on one side and another adjacent edge on the other side. The sides of the precious metal layers should be understood in relation to the positions of the adjacent edges perpendicular to the knitting direction on both needle beds. Depending on the shape of the relevant layers, the adjacent edges of the layers may not intersect, as in the case of rectangular layers, or they may intersect, as in the case of semi-circular layers. The adjacent edges are formed from bottom to top in the knitting direction during the knitting process. The two precious metal layers may also include upper or adjacent edges and / or lower or adjacent edges; the presence of these edges depends on the shape of the relevant layers. For example, a rectangular layer includes a lower or adjacent edge and an upper or adjacent edge in addition to the two lateral adjacent edges, while a semi-circular layer does not include any additional edges or adjacent edges.

[0030] The lower edge or adjacent edge is the edge or adjacent edge that is formed first in the knitting direction, that is, located at the bottom of the knitted fabric. Therefore, the upper edge or adjacent edge is the edge that is formed later in the knitting direction. The reference for the height of the knitted fabric, as will be mentioned below, is the bottom knit row of the knitted fabric. Even if the knitting of layers begins in different knit rows, the overall height of the knitted fabric remains the same; in other words, layers of knitted fabric can include different numbers of knit rows at different heights.

[0031] The first and second layers of the double-layer precious metal mesh are at least partially connected at their two respective adjacent edges by at least one connecting knitted stitch. This means that the two layers are interconnected via stitches formed from at least one precious metal-containing filament. These connections produce a knitted fabric that is at least partially tubular.

[0032] The two precious metal mesh layers are partially joined on both sides at least via their respective adjacent edges, and these partial joins can be made at the same height (i.e., in one or more identical knit rows) or at different heights. Partial joins can be made on both sides over the same length, i.e., over the same number of knit rows. However, partial joins can also be made on both sides over different lengths.

[0033] In a preferred embodiment, partial connections are made at least partially within the same knitted rows. In this embodiment, the knitting is thus completed at least partially in a circle, i.e., circular knitting; in other words, a loop structure is created via these knitted rows. It has been shown that knitting such a partially loop structure can have a positive impact on the stability of the knitting process.

[0034] The first and second layers of the double-layer precious metal mesh can preferably be knitted from a single precious metal filament or multiple precious metal filaments having the same composition. However, the two layers can also be knitted from a single precious metal filament or multiple precious metal filaments with different compositions.

[0035] Precious metal-containing filaments of the same or different diameters can be used to knit the first and second layers of a double-layer precious metal mesh. It has been shown that it is advantageous for the first and second layers of the double-layer precious metal mesh to be knitted from one or more precious metal-containing filaments of the same diameter.

[0036] The first and second layers of the double-layer precious metal mesh can be knitted with the same or different knitting patterns. For example, different knitting patterns can be produced from different stitch lengths, floats, or pleats. In a preferred embodiment, the first and second layers of the double-layer precious metal mesh are knitted with the same knitting pattern.

[0037] The first and second layers of the double-layer precious metal mesh may have the same or different lengths in the knitting direction and / or the same or different widths perpendicular to the knitting direction. Preferably, the first and second layers of the precious metal mesh have the same length and the same width.

[0038] The first and second layers of the double-layer precious metal mesh may have the same shape or different shapes. Particularly preferably, the first and second layers of the double-layer precious metal mesh have the same shape. It may be advantageous that the first and second layers of the double-layer precious metal mesh have a semi-circular shape that is flat on one side. It may be particularly advantageous that these two semi-circles have the same width and the same length.

[0039] In a preferred embodiment, the first and second layers of the double-layer precious metal mesh are congruent; in other words, the two layers may have the same length, the same width, and the same shape.

[0040] The additional use of support threads in the method according to the invention may be advantageous. Such support threads can be used to stabilize the resulting knitted fabric or method, for example, to prevent the precious metal-containing threads from breaking. Suitable support threads can be selected through routine testing and taking into account the final intended use of the double-layer precious metal mesh and any additional steps in the manufacturing process. Preferred support threads can be removed after the double-layer precious metal mesh has been produced, for example by dissolving them in an acidic or alkaline medium, cutting them off, melting them, or burning them. Such support threads can have natural or synthetic organic or inorganic properties. Examples of suitable materials are polyamides, polyesters, cellulose fibers, cotton, acrylic-styrene polymers, nylon, PVA and other vinyl polymers, alginates, copper, silver, aluminum, or even metals with low melting points such as tin alloys and lead alloys.

[0041] This method may include simultaneously using support yarns to knit a support web. In other words, the support web can be knitted simultaneously with the two layers of the double-layer precious metal mesh to be produced, so that the two layers and the support web are not produced one after the other. It may be preferred that the support web be knitted at least partially on the first and second needle beds.

[0042] The term "support mesh" refers to an area of ​​a knitted fabric that is at least partially knitted using support yarns. The knitted fabric includes all knit rows formed during the method. The knitted fabric comprises at least a first and a second layer of a double-layered precious metal mesh. However, the knitted fabric may also include additional portions or areas, such as the support mesh.

[0043] The support net may also include additional wires or filaments.

[0044] The support yarn can be knitted in parallel with at least one precious metal-containing filament, meaning that a stitch including both the precious metal-containing filament and the support yarn can be formed during knitting. In these cases, the relevant portion of the resulting knitted fabric contains both the precious metal and the support yarn material. In other embodiments, the support yarn can also be used in portions or areas of the knitted fabric that do not contain the precious metal-containing filament; that is, in these cases, the resulting knitted fabric contains portions with and without the precious metal-containing filament. These embodiments can also be combined with each other.

[0045] Therefore, the support web can include multiple regions. For example, the support web can also include knitted rows in which no precious metal-containing yarns are used, i.e., where only support yarns are used for knitting. In other words, the knitted fabric can include regions that do not contain precious metal-containing yarns. The knitted fabric can also include knitted rows formed solely by regions of the support web.

[0046] The shape of the support mesh is not further restricted. However, it has proven advantageous to design the support mesh in a way that makes the overall shape of the knitted fabric rectangular. In other words, the support mesh can complement the layers of the precious metal mesh in a way that makes the overall shape of the knitted fabric, which includes one or more precious metal layers and the support mesh, rectangular.

[0047] It may be preferable for the support mesh to be knitted into two layers in areas that do not contain precious metal-containing threads. In other words, the support mesh in these knitted rows cannot be knitted using connecting stitches between the first and second needle beds. The two layers can be connected at the edge stitches via connecting stitches; therefore, it may be advantageous for the support mesh to have a tubular structure in these areas. It may also be preferable for the support mesh to be knitted into a single layer in areas that do not contain precious metal-containing threads.

[0048] In a preferred embodiment, the support mesh includes a single-layer knitted area and a double-layer knitted area excluding the precious metal-containing yarn.

[0049] It may be advantageous for the support mesh to surround both layers of the double-layer precious metal mesh on more than one side. In a preferred embodiment, the support mesh surrounds at least 50% of both layers of the double-layer precious metal mesh. This means that at least 50%, preferably at least 60%, and even more preferably at least 80% of the perimeter of both layers of the double-layer precious metal mesh is surrounded by the support mesh. It may be particularly preferred that the support mesh completely surrounds both layers of the double-layer precious metal mesh.

[0050] Preferably, all areas of the support net can be knitted from support yarns with the same composition. However, different areas can also be knitted from support yarns with different compositions. Different areas of the support net can be knitted with the same or different knitting patterns.

[0051] It may be advantageous to remove the support network in an additional process step (e.g., by decomposing, dissolving, melting, burning, or cutting it).

[0052] The method according to the invention may include additional steps.

[0053] The method may include providing at least one additional filament or thread. The appropriate additional filament or thread may be selected depending on its intended use and / or function in the manufacturing process or for subsequent applications to the precious metal mesh. For example, the additional filament may be made of a non-precious metal suitable for stabilizing the precious metal mesh when used in a reactor. For example, it may be steel or stainless steel wire. In these cases, the method includes using at least one additional filament or thread to simultaneously knit various areas of the knitted fabric. In this case, the knitted fabric may include portions or areas containing only the additional filament or thread, or portions or areas containing both the additional filament or thread and precious metal-containing filaments and / or support threads.

[0054] In a further step, one or more connecting stitches between the first and second layers of the double-layer precious metal mesh can be removed on one side; in other words, the two layers are separated on one side. This produces a precious metal mesh that is at least partially connected only on one side of the two layers, i.e., only via an adjacent edge of the two layers. In other words, a single-layer precious metal mesh can be produced in this manner. Attached Figure Description

[0055] The invention will be explained in more detail below with reference to the accompanying drawings and examples. However, the invention is not limited to these embodiments.

[0056] Figure 1 This is a schematic diagram of a flow reactor used for heterogeneous catalytic combustion of ammonia.

[0057] Figure 2 An embodiment of a precious metal mesh that can be produced using the method according to the present invention is shown.

[0058] Figure 2 A and Figure 2 B shows a double-layer precious metal mesh 20' consisting of two rectangular layers 21' and 22', which are connected on both sides and along the entire length of the precious metal mesh 20' in the knitting direction S.

[0059] Figure 2 C shows a structure consisting of two semi-circular layers 21'' and 22'' (the second layer 22'' is in...). Figure 2 The front view of the precious metal mesh 20'' formed (not visible in the perspective view of C).

[0060] Figure 2D shows a perspective view of the precious metal mesh 20'' that is actually unfolded along the adjacent edge 24'' and three exemplary knitted rows M1'', M2'', and M3'' at different heights along the knitting direction S.

[0061] Figure 2 E and Figure 2 F shows a precious metal mesh 20''' formed by two semi-circular layers 21''' and 22''', which are connected to each other on both sides only for a portion of the length of the precious metal mesh 27'''.

[0062] Figure 2 G and Figure 2 H shows a structure consisting of a first semi-circular layer 21'''' and a second rectangular layer 22'''' (in... Figure 2 The precious metal mesh 20'''' is formed (shown in shaded area G). Detailed Implementation

[0063] Figure 1 This is a schematic diagram of a vertically positioned flow reactor 1 used for the heterogeneous catalytic combustion of ammonia. A catalyst system 2 forms the actual reaction zone of the flow reactor 1. This catalyst system includes catalyst packing 3 and a downstream trapping mesh 4. The catalyst packing 3 includes multiple catalyst meshes 6 arranged one after another in the direction of fresh gas flow 5.

[0064] Typically, the catalyst mesh 6 is a knitted mesh, which is produced, for example, from various platinum-rhodium alloys by knitting filaments with a diameter of 76µm. A trapping mesh 4 may also be provided.

[0065] Figure 2 An embodiment of a precious metal mesh that can be produced using the method according to the invention is illustrated schematically.

[0066] Figure 2 A and Figure 2 B shows a double-layered precious metal mesh 20' consisting of two rectangular layers 21' and 22', which are connected on both sides and along the entire length of the precious metal mesh 20' in the knitting direction S. Figure 2 In the front view of A, only the first layer 21' is visible. Figure 2 B shows a view of a precious metal mesh 20' with a slit along the adjacent edge 24' of the first layer 21'. The term "slit" will indeed be understood at this point and used to provide a better understanding of the invention. If, after producing the double-layer precious metal mesh 20', an additional process step is performed in which two adjacent edges 23' and 26' are separated from each other, the corresponding single-layer precious metal mesh will have Figure 2The shape shown in B is also illustrated. The positions of exemplary knitted rows M1', M2', and M3' at different heights along the knitting direction S of the precious metal mesh 20' are also shown, their positions within the precious metal mesh 20' indicated by dashed lines. The length portion 27' of the precious metal mesh shows areas or knitted rows where two layers are joined to each other at their adjacent edges (23' and 24' of the first layer 21' and 25' and 26' of the second layer 22'). The precious metal mesh 20' has a tubular structure open at the bottom and top. According to… Figure 2 A and Figure 2 In the embodiment of the precious metal mesh B, a right-side row (M1'-H, M2'-H, M3'-H) is knitted on the first needle bed, and a wrong-side row (M1'-R, M2'-R, M3'-R) is knitted on the second needle bed. On both sides, the right-side and wrong-side rows (M1'-H-M1'-R, M2'-H-M2'-R, M3'-H-M3'-R) are connected using connecting stitches (M1'-VH, M2'-VH, M3'-VH, M1'-VR, M2'-VR, M3'-VR). These two sides correspond to the respective adjacent edges of the two layers (21', 22') of the precious metal mesh 20'.

[0067] Figure 2 C shows a structure consisting of two semi-circular layers 21'' and 22'' (the second layer 22'' is in...). Figure 2 The front view of the precious metal mesh 20'' formed (not visible in the perspective view of C). Figure 2 D again shows a perspective view of the precious metal mesh 20'' actually unfolded along the adjacent edge 24'' and three exemplary knitted rows M1'', M2'', and M3'' at different heights along the knitting direction S. The outward and return rows of the lower knitted rows M1''-H and M1''-R and the upper knitted rows M3''-H and M3''-R are shorter than the outward and return rows of the middle knitted rows (M2''-H, M2''-R), i.e., they contain fewer stitches. Therefore, the number of stitches per knitted row can be used to determine the shape of the precious metal mesh or the shape of the layers. Layers 21'' and 22'' are joined on both sides over the entire length 27''. When the connection between the two layers 21'' and 22'' of the precious metal mesh 20'' is separated between the adjacent edges 23'' and 26'', a precious metal mesh with a circular cross-section is obtained.

[0068] Figure 2 E and Figure 2F shows a precious metal mesh 20''' formed by two semicircular layers 21''' and 22''', which are connected to each other on both sides only for a portion of the length of the precious metal mesh 27'''. Therefore, the outward and return rows of the lower knit rows M1'''-H and M1'''-R and the upper knit rows M3'''-H and M3'''-R are connected to each other only on one side (M1'''-VH, M3'''-VH). Adjacent edges 23''' and 25''' may be connected to each other over their entire length.

[0069] Figure 2 G and Figure 2 H shows a structure consisting of a first semi-circular layer 21'''' and a second rectangular layer 22'''' (in... Figure 2 The precious metal mesh 20'''' (shown in shaded area G) is formed. The two layers 21'''' and 22'''' are connected to each other only on the portion with a length of 27''''.

[0070] Examples and Comparative Examples

[0071] On a flat knitting machine comprising two needle beds, PtRh5 yarn (76µm diameter) is used to knit rectangular layers (100cm wide, 200cm long) on ​​each needle bed. In a comparative example, the two layers are connected to each other only on one side by suitable yarn guides, and in an embodiment according to the invention, they are connected to each other on both sides by suitable yarn guides (according to...). Figure 2 A and Figure 2 B). In the latter case, one of the connecting sides is not unraveled after the knitting process. In both cases, a precious metal mesh with a width of 200cm and a length of 200cm is obtained.

[0072] Although the products produced according to the present invention involve additional working steps, the method has proven to be faster and more reliable. During the knitting process in the comparative example, repeated yarn breaks occurred, leading to production interruptions. In addition to the necessary repairs to the yarns, the knitted fabric also had an uneven, twisted structure. Such irregularities in the knitted fabric represent potential mechanical weaknesses that have a negative effect when the web is used in the reactor.

[0073] Definition of the symbols used in the illustrations

[0074]

Claims

1. A method for producing a double-layer precious metal mesh on a flat knitting machine, the flat knitting machine comprising a first needle bed and a second needle bed, the method comprising the following steps: - Provide at least one wire containing a precious metal. - Knit the precious metal mesh. A first layer of the precious metal mesh is knitted on the first needle bed, and a second layer of the precious metal mesh is knitted simultaneously on the second needle bed. Each of the two layers includes at least two adjacent edges. Its features are, The first and second layers of the precious metal mesh are at least partially connected at their two respective adjacent edges by at least one connecting knitted stitch, producing a knitted fabric that is at least partially tubular.

2. The method of claim 1, wherein the connection is at least partially formed in the same knit row.

3. The method according to claim 1, wherein the at least one precious metal-containing wire is composed of platinum, a platinum alloy, palladium, or a palladium alloy.

4. The method according to claim 2, wherein the at least one precious metal-containing wire is composed of platinum, a platinum alloy, palladium, or a palladium alloy.

5. The method according to any one of claims 1-4, wherein the first layer and the second layer of the precious metal mesh are knitted from one or more precious metal filaments having the same composition.

6. The method according to any one of claims 1-4, wherein the first layer and the second layer of the double-layer precious metal mesh are knitted from one or more precious metal filaments having the same diameter.

7. The method according to claim 5, wherein the first layer and the second layer of the double-layer precious metal mesh are knitted from one or more precious metal filaments having the same diameter.

8. The method according to any one of claims 1-4, wherein the first layer and the second layer of the double-layer precious metal mesh are knitted with the same knitting pattern.

9. The method of claim 7, wherein the first layer and the second layer of the double-layer precious metal mesh are knitted with the same knitting pattern.

10. The method according to any one of claims 1-4, wherein the first layer and the second layer of the double-layer precious metal mesh are identical.

11. The method of claim 9, wherein the first layer and the second layer of the double-layer precious metal mesh are identical.

12. The method according to any one of claims 1-4, wherein the method includes simultaneously using support yarns to knit a support web.

13. The method of claim 11, wherein the method includes simultaneously using support yarns to knit a support web.

14. The method of claim 12, wherein the support mesh is removed in an additional method step.

15. The method of claim 13, wherein the support mesh is removed in an additional method step.

16. The method according to any one of claims 1-4, wherein in a further step, one or more of the connecting knitting stitches between the first and second layers of the double-layer precious metal mesh are removed on one side.

17. The method of claim 15, wherein in a further step, one or more of the connecting knitting stitches between the first and second layers of the double-layer precious metal mesh are removed on one side.

Images