WO1993025745A1 - Non-woven with electrically conducting coating - Google Patents

Abstract

Described is a non-woven (1) with a coating (2) applied at least in contiguous zones and consisting of an electrically conducting compound containing a binder plus conducting particles. The coating (2) is applied to one or both sides of the non-woven (1) in such a way that a conducting layer (2a, 2b, 2c) is produced at least over parts of both surfaces (3, 4) of the non-woven and an electrical connection formed between the conducting zones on the two surfaces of the non-woven.

Description

 Nonwoven fabric with a conductive coating

The invention relates to a nonwoven fabric with a coating made of a conductive mass containing a binder and conductive particles, at least in contiguous areas.

A material suitable for protective clothing with a conductive coating made in some areas in the form of a pattern from a paste of conductive particles and binder is known for example from DE 32 11 322 C2. In this known fabric, which is preferably a woven or knitted fabric, the conductive paste is applied to only one side, e.g. by printing two liren patterns on top of each other, a network of conductive material on one side of the

Fabric arises. A corresponding conductive pattern can also be provided on the other fabric surface. However, this known substance cannot be used for all types of protective suits, in particular not for protective suits to be used in mines, where very strict requirements apply in order to reliably avoid firedamp weather caused by electrostatic charging and corresponding sparking, while at the same time being sufficiently watertight and having good breathability. In the case of materials for protective suits to be used in mines, it is stipulated that electrostatic charging of the protective suit is reliably avoided in every respect.

The invention is therefore based on the object to provide a material for protective suits, in particular for those for use in mines or for other areas of application with very high requirements for avoiding electrostatic charging, which is easy and inexpensive to manufacture, but which is also suitable for the material fulfilling the requirements in every way.

To achieve this object, it is proposed to equip a nonwoven of the type mentioned at the outset in such a way that the conductive coating is applied to the nonwoven on one or both sides in such a way that a conductive coating is present on both surfaces of the nonwoven, at least in some areas, and a conductive connection between the conductive Areas on both surfaces of the nonwoven fabric is made.

The nonwoven fabric according to the invention is thus distinguished on the one hand by the fact that its two surfaces are at least partially provided with a conductive coating, and on the other hand by the conductive coatings on both surfaces of the nonwoven fabric are conductively connected to each other. This design reliably prevents electrostatic charging and, above all, reliably ensures that any electrical charges that may arise are removed from the nonwoven fabric. Despite this, compared to known materials, excellent

Properties with regard to the avoidance of electrostatic charge, the nonwoven fabric according to the invention has the advantage that it is relatively easy to manufacture. The application of the electrically conductive coating is indeed possible in a simple manner by means of processes known per se for the application of pastes composed of binder and particles. Such equipment can be accomplished without difficulty in a continuous process and consequently at correspondingly high speeds.

The nonwoven can be finished in various ways. If a very good surface and continuity conductivity is to be achieved, i.e. Both surface resistance and volume resistance of the nonwoven are to be very low, it is particularly expedient if the conductive coating is applied to both surfaces of the nonwoven and bridges between the coating forming mass between the coating on one surface of the nonwoven and the coating on the same other surface are formed. With such a design, it is possible to apply comparatively small amounts of the conductive mass to the two surfaces, but nevertheless to achieve the desired low surface resistance and a sufficiently low volume resistance.

However, it can also be favorable if the mass forming the conductive coating only on one surface of the Nonwoven fabric is applied in such an amount that conductive mass passes through to the other nonwoven fabric surface at least in some areas. With such a configuration of the nonwoven fabric according to the invention, the production can possibly be further simplified, although satisfactory properties with regard to the surface and volume resistance can nevertheless be achieved.

The best conduction properties can be achieved if the conductive coating is applied over the entire surface but is made permeable to air, for example by appropriate foaming of the coating.

In general, however, it is sufficient if, as after the

According to the invention, the conductive coating is applied in the form of a pattern covering only part of the respective surface. The pattern can advantageously be formed in a point, strip and / or diamond shape in such a way that there is a conductive connection between individual sections of the pattern over the entire surface of the nonwoven fabric.

There are various options for applying the pattern of the conductive coating. Appropriately, the procedure is such that the mass forming the pattern is printed on the nonwoven fabric using a screen printing stencil.

With regard to the composition of the conductive composition, it has proven particularly favorable if the conductive composition contains graphite or carbon black as conductive particles. If, as is also possible according to the invention, the conductive composition contains a hydrophobizing agent, the electrical properties of the conductive coating are largely prevented from changing as a result of different moisture or different water contents.

For similar considerations, it can be favorable if the conductive mass is set to be oleophobic.

To further improve the performance properties of the nonwoven fabric according to the invention, it is also possible to use a conductive composition which has flame-retardant properties.

It has also proven to be particularly advantageous if the conductive coating is applied to the nonwoven in an amount of 0.5 to 600 g / m ² and / or the nonwoven has a basis weight of 10 to 1,000 g / m ² .

Particularly favorable wearing properties in connection with high strength and correspondingly low weight can be achieved if the nonwoven fabric comprises several fiber layers, at least one layer of the nonwoven fabric being a staple fiber nonwoven, a spunbonded nonwoven or a layer of so-called "melt-blown" fibers.

The fibers forming the nonwoven fabric can advantageously consist of polyethylene, polypropylene, polyester and / or polyamide.

Finally, it is within the scope of the invention that the nonwoven or at least one layer of a multi-layer nonwoven is thermally bonded, whereby the mechanical strength of the nonwoven is further improved.

Further features, details and advantages of the invention result from the following description of preferred exemplary embodiments with reference to the drawing.

Show here -:

Figure 1 is a plan view of a section of a

Nonwoven fabric according to the invention with a mesh-shaped, conductive pattern; Figure 2 shows a section through a first

Embodiment of a nonwoven according to the invention and Figure 3 shows a section corresponding to Figure 2 through a second embodiment.

The nonwoven fabric according to the invention comprises a single or multi-layer carrier layer 1. The carrier layer 1 consists of a non-woven fabric which can be constructed and composed differently, the fibers preferably consisting of polyethylene, polypropylene, polyester or polyamide. Possibly. it is also conceivable to produce one or more of the layers of woven or knitted fabric if certain mechanical properties are to be achieved. The number of individual layers of the carrier layer 1 can also be selected according to the needs. For example, the nonwoven fabric according to FIG. 2 consists of three layers la, lb and lc, while the nonwoven fabric of the exemplary embodiment in FIG. 3 comprises only one backing layer 1. In the exemplary embodiments shown, a conductive network pattern formed by intersecting line groups 2 of a conductive coating composition is arranged on both surfaces of the carrier layer 1. The coating composition forming the mesh pattern 2 consists of a binder known per se for such coatings, for example a corresponding synthetic resin or adhesive, and conductive particles, preferably graphite or carbon black, arranged in this binder. The binder can be a reaction adhesive, a hot melt adhesive or a dispersion adhesive, depending on the application of the nonwoven according to the invention.

It is important that the mesh pattern of the conductive coating 2 is present on both surfaces 3, 4 of the carrier layer 1.

The net-like coating pattern 2 can be applied in different ways.

According to FIG. 2, an essentially identical coating pattern consisting of lines 2a (on surface 3) and 2b (on surface 4) is applied to both surfaces 3, 4 of carrier layer 1. The amount of coating composition applied must be chosen so large that the coating composition penetrates inwards from the surface 3 or 4 of the carrier layer 1 to such an extent that it penetrates with the coating composition 2b penetrating from the respective other surface 4, 3 of the carrier layer 1 or 2a comes into contact in order to produce a conductive connection between the conductive coatings 2a on the surface 3 and 2b on the surface 4 of the carrier layer 1. It is thus when producing a nonwoven according to the figure

2 requires that both surfaces 3, 4 of the carrier layer 1 are provided with the conductive coating in essentially the same way, i.e. for example, a corresponding pattern of coating composition is printed on both surfaces 3, 4 of the carrier layer 1.

In the nonwoven fabric of the exemplary embodiment in FIG. 3, on the other hand, the design is such that only on the surface

3, a coating pattern 2c is applied, although coating composition 2c is applied in such a large amount that it passes through the carrier layer 1, for example as a result of the capillarity of the carrier layer 1, and emerges from the carrier layer 1 in the region of the other surface 4, so that the surface 4 is also provided with a correspondingly conductive coating which extends over the entire surface 4, all areas being conductively connected to one another in accordance with the basic idea of the invention.

For example, a mass of the following composition can be used as the conductive coating:

Rush

10 - 90 Uzin PE 260 L (conductive

Component made of carbon black and binder) sold by Uzin-Werk, Ulm

0 - 5 Nofo e SF (defoamer) distributed by Tanatex / Krefeld 0.5 - 15 Sandofluor NF fl.

(Water repellent) commercially available fluorocarbon hydrophobizing agent from Sandoz AG, Basel

0 - 20 Miraplast NVP (pressure aids) distributed by Dr. Th. Böhme / Geretsried 0 - 20 Acryloon A300 (thickener) sold by Protex / Lörrach

69 water

A recipe for the conductive coating that has been tried and tested in practice is the following:

Parts by weight

70 Uzin PE 260 L.

1.2 Nofome SF

2.5 Sandofluor NF fl.

6.0 Miraplast NVP 3.0 Acryloon A 300

17.5 water

This conductive coating composition is applied to the nonwoven carrier layer 1 on one or both sides, preferably by means of an anilox roller in the screen printing process, the basis weight of the conductive coating then being approximately 0.5 to 500 g / m ² .

If the conductive coating composition is applied in a pattern, it can be punctiform, strip-shaped, in the form of diamonds or diamonds. It is only essential that there is an electrically conductive connection between the individual areas or sections of the coating over the entire surface of the nonwoven.

For certain areas of application, the conductive paste can also be made hydrophobic and / or oleophobic and / or flame-retardant. The coating composition according to the above embodiment is already hydrophobic due to the addition of Sandofluor NF fl.

When using such coating compositions, the surface and volume resistance can be reduced from less than 10 ohms. When choosing suitable printing patterns for the coating material or corresponding foaming or the like. with full-surface coating, the air permeability, water resistance and water vapor permeability desired for a material for protective clothing can be achieved, for example an air permeability of up to 3,000 1 / m ² at 10 mm water column pressure difference can be achieved. The water vapor permeability can be higher than 500 1 / m ² x day. The longitudinal and transverse strength is not affected by the equipment with the conductive coating.

In this context it should be mentioned that for the purposes of testing nonwovens according to the invention surface and volume resistance, water column, strength and air permeability according to the corresponding DIN

Regulations 53.345 Part 1, 53.886, 53.857 Part 2 and 53.887 should be measured. The nonwoven backing layer can be constructed as follows:

example 1

First layer: spunbonded nonwoven with a basis weight of approx. 5 - 200 g / m ² second layer: melt-blown nonwoven with a basis weight of approx. 3 - 200 g / m ² third layer: staple fiber fleece with a basis weight of approx. 5 - 100 g / m ² m ²

A nonwoven fabric constructed in this way as a backing layer has particularly good clothing physiological properties, because on the one hand it has sufficient air permeability, but on the other hand it also has sufficient watertightness. In addition, it also has the required mechanical strength.

Example 2

First layer: S Sttaappeellffaasseerrvvlliieess eeiinneess basis weight of approx. 5 - 100 g / m ²

Second layer: spunbonded fabric with a basis weight of approx. 5 - 200 g / m ²

Such a nonwoven fabric as the backing layer differs from that of Example 1 by the absence of the melt-blown layer, which means that the water resistance is reduced. However, the mechanical properties are quite comparable. is reduced. However, the mechanical properties are quite comparable.

Example 3

Single-layer spunbonded fabric with a basis weight of approx. 10 to 400 g / m '

Such a fleece can be produced easily and cheaply and is still useful for a large number of applications.

The nonwovens according to the above examples advantageously consist of polypropylene, polyester, polyethylene or polyamide fibers or mixtures thereof. The individual layers are expediently thermally bonded to increase the mechanical strength.

The conductive coating, which has been dealt with in detail above, is then applied over the entire surface or in a pattern to the prepared carrier layer made of nonwoven, and a corresponding one is carried out after the application

Consolidation of the coating, e.g. in a drying oven, whereby the thermal bonding of the fleece can sometimes only take place together with the drying of the coating.

Claims

Expectations -: 1. Nonwoven fabric with a coating provided at least in contiguous areas of a conductive material containing a binder and conductive particles, characterized in that the coating (2) is applied to the nonwoven fabric (1) on one or both sides in such a way that on both surfaces ( 3, 4) of the nonwoven fabric, at least in some areas there is a conductive coating (2a, 2b, 2c) and a conductive connection is made between the conductive areas on the two surfaces of the nonwoven fabric. 2. Nonwoven fabric according to claim 1, characterized in that the conductive coating (2a, 2b) is applied to both surfaces (3, 4) of the nonwoven fabric (1) and bridges between the coating (2a) on the one from the mass forming the coating Surface (3) of the nonwoven and the coating (2b) on the other surface (4) are formed. 3. Nonwoven according to claim 1, characterized in that the mass forming the conductive coating (2c) is applied only to one surface (3) of the nonwoven (1) in such an amount that the conductive mass at least in regions to the other nonwoven surface ( 4) passes through. 4. Nonwoven fabric according to one of the preceding claims, that the conductive coating is applied over the entire surface, but is air-permeable. 5. Nonwoven fabric according to one of claims 1 to 3, so that the conductive coating (2) is applied in the form of a pattern covering only part of the respective surface (3, 4). 6. Nonwoven fabric according to claim 5, characterized in that the pattern (2) is point, stripe and / or diamond-shaped in such a way that over the entire surface (3, 4) of the nonwoven fabric (1) a conductive connection between individual sections of the Pattern exists. Nonwoven fabric according to claim 5 or 6, characterized that the mass forming the pattern (2) is printed on the nonwoven fabric (1) using a screen printing stencil. 8. Nonwoven fabric according to one of the preceding claims, that the conductive mass contains graphite or carbon black as conductive particles. 9. Nonwoven fabric according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the conductive composition contains a hydrophobizing agent. 10. Nonwoven fabric according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the conductive mass is set oleophobic. 11. Nonwoven fabric according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the conductive mass has flame retardant properties. 12. Nonwoven fabric according to one of the preceding claims, characterized in that the conductive coating (2) is applied in an amount of 0.5 to 600 g / m ² on the nonwoven fabric (1). 13. Nonwoven fabric according to one of the preceding claims, characterized in that the nonwoven fabric (1) has a basis weight of 10 to 1,000 g / m ² . 14. The nonwoven fabric according to one of the preceding claims, that the nonwoven fabric (1) comprises a plurality of fiber layers (la, lb, lc). 15. Nonwoven fabric according to one of the preceding claims, that a at least one layer of the nonwoven fabric (1) is a staple fiber nonwoven. 16. Nonwoven fabric according to one of the preceding claims, that a at least one layer of the nonwoven fabric (1) is a spunbonded nonwoven. 17. Nonwoven fabric according to one of the preceding claims, so that at least one layer of the nonwoven fabric (1) is a layer of so-called "melt-blown" fibers. 18. Nonwoven fabric according to one of the preceding claims, so that the fibers forming the nonwoven fabric (1) consist of polyethylene, polypropylene, polyester and / or polyamide. 19. The nonwoven fabric according to one of the preceding claims, that the nonwoven fabric (1) or at least one layer (la, lb, lc) of a multi-layer nonwoven fabric is thermally bonded.