Fiber material with manganese oxide coating

Abstract

In summary, the invention relates to a method for coating a fiber material (10), in particular a nonwoven, with manganese oxide, a method for producing an antiviral and antibacterial layer, and a fiber material having manganese oxide. In order to increase the proportion of manganese(IV) oxide on the fiber material (10), the following steps are proposed: - applying a manganese oxide precipitate to the fiber material; - drying the manganese oxide precipitate; - oxidizing the manganese oxide precipitate by oxygen plasma at a temperature below 200° C., in particular below 160° C., so that a manganese(IV) oxide layer is formed with at least 70% by weight relative to the manganese oxide precipitate.

Description

[0001] The invention relates to a method for coating fiber materials, in particular nonwovens, with manganese oxide, a method for producing an antiviral and antibacterial layer, and a fiber material comprising manganese oxide.

[0002] Fiber materials, in particular nonwoven materials, made of plastics such as polypropylene fibers or polyamide fibers or also of cellulose-based materials are provided with an antibacterial or antiviral layer for use in respiratory protection masks. This is known from the unpublished application DE 10 2020 203 783.3. There, a fiber material for antibacterial and / or antiviral use is produced, which has fibers with a coating of metallic silver and manganese (IV) oxide.

[0003] The component of the antibacterial and antiviral layer is manganese oxide, which is precipitated on the nonwoven fabric in particular wet-chemically from potassium permanganate and manganese(II) salts by a redox reaction. 2 After precipitation, hydroxyl groups and water molecules remain in the MnO 2 Apparently, these hydroxyl groups and water molecules can affect the antibacterial and antiviral effects of the layer. It is noted that the resulting manganese oxide precipitate after heat treatment at 110 °C consists of approximately:

[0004] -60% Manganese(IV) oxide -MnO 2 ;

[0005] -25% manganese(III) oxide - Mn 2 O 3 ;and

[0006] - 15% manganese(II) oxide - MnO.

[0007] The proportion of manganese(IV) oxide can be increased to 80% by an annealing process under oxygen at over 400° C. Such high temperatures are not feasible in particular for synthetic fiber materials, such as nonwoven materials, since the synthetic fiber materials would be damaged by the heat or even decompose.

[0008] The technical problem to be solved by the present invention is to provide a method which makes it possible to increase the proportion of manganese (IV) oxide without damaging the fiber material. The technical problem of the present invention is also to provide a fiber material with an increased proportion of manganese (IV) oxide.

[0009] To this end, the method for coating a fiber material with manganese oxide has the following steps:

[0010] - applying the manganese oxide precipitate to the fibrous material;

[0011] - drying the manganese oxide precipitate;

[0012] - oxidizing the manganese oxide precipitate by oxygen plasma at a temperature below 200° C., in particular below 160° C., so that a manganese(IV) oxide layer having at least 70% by weight (percentage by weight) relative to the manganese oxide precipitate is formed.

[0013] The method is particularly gentle with respect to the fiber material and allows a greatly increased material selection of fibers that otherwise could not be provided with an improved manganese oxide coating. Manganese oxide precipitates usually have manganese oxides in different oxidation states, which are oxidized to a high-quality manganese (IV) oxide layer using the method. For this purpose, the annealing methods known from the prior art at temperatures of 400° C. or above are replaced by different energy-transferring processes.

[0014] In a further embodiment, the manganese oxide precipitate is applied wet-chemically, in particular from potassium permanganate and manganese(II) salts. This has the advantage that a spraying process can be used, which is particularly well suited to webs. The manganese oxide precipitate can be sprayed onto the fiber material, for example, via a nozzle as a potassium permanganate solution and a manganese(II) salt solution (nitrates or acetates are suitable salts here). If the two solutions meet, a mixture of manganese oxides in different oxidation states is precipitated. The precipitate is preferably dried by a heating device in order to remove water in particular. 110° C. has proven to be advantageous in this regard.

[0015] According to the invention, the manganese oxide precipitate is oxidized by oxygen plasma. The advantage of oxidation by oxygen plasma is that oxidation of different manganese oxides to manganese (IV) oxide can be achieved at relatively low temperatures, in particular temperatures below 200° C., with a high oxidation rate. This further improves the properties of the fiber material. Thus, after drying, the fiber material can be brought to a vacuum device and treated with oxygen plasma, for example by means of a hollow cathode plasma source, in order to convert the undesirable manganese oxides (in particular manganese (II) and manganese (III) oxides) into dimanganese oxides (manganese (IV) oxides) which have a bactericidal and virucidal effect.

[0016] In another embodiment, the method includes removing hydroxyl groups from the manganese (IV) oxide layer. A possible reaction equation is:

[0017] 2Mn(OH) 2 +ΔEnergy+O 2 =2MnO 2 +2H 2 O

[0018] The removal of hydroxyl groups can be particularly advantageously carried out in one step together with the oxidation in oxygen plasma. These negative oxygen ions react with manganese (II) oxide and manganese (III) oxide to form manganese (IV) oxide, which has a bactericidal effect, and at the same time, the hydroxyl groups and water molecules adhering to the manganese oxide mixture are removed as water vapor by a turbo pump at the vacuum chamber. By removing the hydroxyl groups and water molecules that still adhere to the manganese oxide precipitate with atomic layer thickness after the direct production of the manganese oxide precipitate, a chemically closer contact between silver and manganese (IV) oxide can be advantageously established during the deposition of silver.

[0019] In a further embodiment, the method comprises applying silver to the fiber material which has been provided with manganese (IV) oxide according to the method of the invention. This step is advantageously carried out after the application of manganese (IV) oxide. Thus, a very effective antibacterial and antiviral layer is produced.

[0020] In another embodiment, the silver is applied as a silver nitrate solution and reduced to silver by a reducing agent. This can be implemented with a silver nitrate solution applied through a nozzle and hypophosphorous acid as a reducing agent for the silver nitrate.

[0021] In a further embodiment, the fiber material is dried under an inert gas atmosphere. After the silver precipitation, the nonwoven is dried under an inert gas atmosphere (nitrogen or argon). 110° C. has proven to be advantageous for drying in order to remove residual water. An inert gas atmosphere is advantageous so that the silver does not oxidize. This sequence of deposition of the bactericidal active substance is also advantageous in this method, because due to the risk of oxidation of the silver, the manganese (IV) oxide is applied first and the silver is applied subsequently. This leads to an improved chemical contact between the silver and the manganese oxide.

[0022] The technical problem is also solved by a fiber material having a manganese oxide coating, which has at least 70% by weight of manganese (IV) oxide relative to the manganese oxide coating. Here, the weight percentage relative to the manganese oxide coating is determined without the fiber weight. Advantageously, at least 75% by weight relative to the manganese oxide coating. By the method according to the invention, 80% by weight or more weight percentages relative to the manganese oxide coating are also possible. Here, the fiber material has a particularly high concentration of manganese (IV) oxide.

[0023] In a further embodiment, the manganese oxide coating has less than 5% by weight, in particular less than 1% by weight, of manganese(II) oxide, in each case relative to the total weight of the manganese oxide coating. The lower the proportion of manganese(II) oxide, the higher the quality of the coating on the fiber material. It has been shown that the proportion of manganese(II) oxide can be advantageously reduced by using the method according to the invention, in particular by a plasma method.

[0024] According to the invention, the fiber material has a melting temperature below 200° C. Advantageously, fibers can also be selected whose melting temperature is below 180° C. or even below 160° C. This expands the material selection, in particular for nonwoven materials suitable for the skin, such as polypropylene. In addition, fiber materials that do not have a melting point but decompose thermally can also be processed. The temperature range in the case of the decomposition temperature is similar to the melting temperature, below 200° C., below 180° C. or even below 160° C. The fiber material can advantageously be produced by the method according to the invention.

[0025] In a further embodiment, the fiber material comprises silver. To achieve an improved antibacterial and antiviral effect, the fiber material comprises silver.

[0026] The fiber material can also include plastic fibers, in particular polypropylene fibers. The fiber material can be composed completely of plastic fibers coated with a manganese oxide layer.

[0027] The technical problem is also solved by a mouth-nose protection device, which has a fiber material according to the invention. The fiber material can also be used in personal protective equipment.

[0028] The present invention will be described and explained in more detail below with reference to the embodiments shown in the accompanying drawings. In the accompanying drawings:

[0029] Figure 1 An example of an apparatus for carrying out the method according to the invention is shown.

[0030] Figure 1 The device 100 is shown, which can process a fiber material 10 and provide it with a manganese oxide coating. For example, a nonwoven made of plastic used in respiratory protection masks, such as polypropylene or polyamide fibers, can be used as the fiber material 10. For this purpose, the device 100 has a first roller 101, to which the fiber material 10 is supplied and which provides the fiber material 10 for transport through the device 100. In addition, the device has a second roller 102, onto which the finished fiber material is rolled. The rollers 101, 102 can be designed as transportable transport rollers.

[0031] The device 100 also has a first nozzle 121, which applies a potassium permanganate solution to the fiber material 10, and a second nozzle 122, which applies a manganese (II) salt solution or a manganese (II) acetate solution to the fiber material. Thus, a nonwoven made of plastic can be sprayed with a potassium permanganate solution and a manganese (II) salt solution via the nozzles 121, 122, wherein nitrates or acetates can be used as salts. The first heating device 130 dries the manganese oxide precipitate thus produced, in particular at 110°C.

[0032] Fiber materials 10 made of plastics can usually withstand temperatures up to a maximum of 160° C., in special cases up to 200° C., before these plastics melt and decompose at higher temperatures. Therefore, in the device 100, a possible annealing process at 400° C. is replaced by a different energy-transmitting process.

[0033] For this purpose, the device 100 has a plasma generator 110, which can apply an oxygen plasma 112 to the fiber material 10 provided with the dried manganese oxide precipitate. Oxygen molecules and oxygen atoms can be ionized by means of a plasma method (for example, hollow cathode plasma, inductively coupled plasma, capacitively coupled plasma or microwave plasma). In this process, atomic oxygen and oxygen ions O － , O 2－ , O 3－ , which react with the manganese oxide surface produced just before in the device and oxidize it to the corresponding manganese (IV) oxide.

[0034] It is preferred to use a hollow cathode plasma source as the plasma generator 110, because the hollow cathode can enclose oxygen ions and electrons in its cavity due to its design and thus provide a higher plasma density (electron density). In addition, after the plasma is ignited, the voltage drops, but a further increase in the current intensity does not produce a larger voltage slope. In contrast, for a capacitively or inductively coupled plasma source, the voltage continues to rise with the current. The high potential accelerates the ions, and the ions obtain such a high excess energy that the substrate surface may be damaged. In the case of a hollow cathode, the plasma potential remains low, so that the ions absorb less energy and do not damage the substrate surface.

[0035] A fiber material 10, such as a plastic nonwoven, coated with a manganese oxide precipitate (a mixture of manganese oxides in different oxidation states of manganese) can be introduced into a vacuum chamber. In order to convert manganese 2+ and manganese 3+ into a higher oxidation state, oxygen is introduced into the hollow cathode plasma source.

[0036] In the plasma generator 110 designed as a hollow cathode plasma source, a high voltage (100 to 300 volts) is generated between the anode and the cathode by a radio frequency plasma generator, and the impedance difference (AC resistance) that occurs here is minimized and adjusted in a matching box. Oxygen molecules can be ionized at 12.06 eV, and oxygen atoms at 13.62 eV. The discharge of oxygen molecules is mainly carried out by direct electron impact dissociation and by attachment of dissociated electrons. Unstable excited O 2－ *, which then decays into atomic oxygen and oxygen ions. The oxygen discharge is weakly negative, meaning that a small portion of the negative charge is made up of ions rather than electrons. These negative ions are O －, O 2－ and even O 3 － These negative oxygen ions react with manganese (II) oxide and manganese (III) oxide to form manganese (IV) oxide which has a bactericidal effect, and at the same time the hydroxyl groups and water molecules attached to the manganese oxide mixture are removed as water vapor. This can be implemented by the turbo pump 114 at the vacuum chamber. Therefore, nonwoven fabrics mainly composed of plastic and cellulose-based materials can be coated simply in a roll-to-roll process.

[0037] Subsequently, a silver nitrate solution is sprayed onto the fiber material 10 coated / adhered with manganese (IV) oxide through a third nozzle 123, and a reducing agent for silver nitrate (e.g. hypophosphorous acid) is sprayed onto the fiber material coated / adhered with manganese (IV) oxide through a fourth nozzle 124. After the silver is precipitated, the fiber material 10 is preferably dried in an inert gas environment (nitrogen or argon) at preferably 110° C. in a second heating device 140. Here, the drying removes excess water. An inert gas environment is advantageous so that the silver does not oxidize. The order of deposition of the bactericidal active substances is also advantageous in this method. Due to the risk of oxidation of silver, it has proven to be advantageous to apply manganese (IV) oxide first and then silver. The nonwoven fabric can be automatically moved by transport rollers 101, 102. The device 100 can be controlled computer-aided by an electronic control device.

[0038] In summary, the invention relates to a method for coating a fiber material (10), in particular a nonwoven, with manganese oxide, a method for producing an antiviral and antibacterial layer, and a fiber material having manganese oxide. In order to increase the proportion of manganese (IV) oxide on the fiber material (10), the following steps are proposed:

[0039] - applying the manganese oxide precipitate to the fibrous material;

[0040] - drying the manganese oxide precipitate;

[0041] The manganese oxide precipitate is oxidized at a temperature below 200° C., in particular below 160° C., so that a manganese(IV) oxide layer is formed having at least 70% by weight, relative to the manganese oxide precipitate.

[0042] Reference numerals list

[0043] 10Fiber Materials

[0044] 100 Installations

[0045] 101 First Roller

[0046] 102 Second roller

[0047] 110 Plasma Source

[0048] 112 Plasma

[0049] 114 Turbine Pump

[0050] 121 First Nozzle

[0051] 122 Second Nozzle

[0052] 123 Third Nozzle

[0053] 124 Fourth Nozzle

[0054] 130 first heating device

[0055] 140 Second heating device

Claims

1. A method for coating a fiber material (10) with manganese oxide, comprising the steps of: - applying the manganese oxide precipitate to the fibrous material; - drying the manganese oxide precipitate; - oxidizing the manganese oxide precipitate by oxygen plasma at a temperature below 200° C., thereby forming a manganese (IV) oxide layer having at least 70% by weight relative to the manganese oxide precipitate.

2. The method according to claim 1, wherein: The manganese oxide precipitate is oxidized at a temperature below 160°C.

3. The method according to claim 1, wherein: The manganese oxide precipitate is applied wet-chemically.

4. The method according to claim 3, wherein: The manganese oxide precipitate is applied from potassium permanganate and manganese (II) salts.

5. A method according to any one of the preceding claims, comprising: The hydroxyl groups are removed from the manganese (IV) oxide layer.

6. A method for producing an antiviral and / or antibacterial fiber material, comprising coating a fiber material (10) with manganese (IV) oxide by a method according to any one of the preceding claims and coating silver on the fiber material (10).

7. The method according to claim 6, wherein: The silver is applied as a silver nitrate solution and reduced to silver by a reducing agent.

8. A method according to claim 6 or 7, comprising the step of drying the fibrous material under an inert gas environment.

9. A fiber material (10) having a melting temperature and / or a decomposition temperature of below 200°C, further comprising a manganese oxide coating having at least 70% by weight of manganese (IV) oxide, relative to the manganese oxide coating.

10. The fiber material according to claim 9, wherein The manganese oxide coating has at least 75 wt % manganese (IV) oxide relative to the manganese oxide coating.

11. The fiber material according to claim 9, wherein The manganese oxide coating has less than 5 wt % manganese (II) oxide relative to the manganese oxide coating.

12. The fiber material according to claim 11, wherein The manganese oxide coating has less than 1 wt % manganese (II) oxide relative to the manganese oxide coating. 13 . The fiber material according to claim 9 , comprising silver. 14 . The fiber material according to claim 9 , comprising plastic fibers.

15. The fiber material according to claim 14, wherein The plastic fibers are polypropylene fibers.

16. A mouth and nose protection device comprising the fiber material according to any one of claims 9 to 15.

17. Personal protective equipment comprising the fiber material according to any one of claims 9 to 15.

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