WO2015004072A1

WO2015004072A1 - Electrically conductive conveyor belt having filler objects having a nanostructure and method for production

Info

Publication number: WO2015004072A1
Application number: PCT/EP2014/064479
Authority: WO
Inventors: Peter Blankenhorn
Original assignee: Maschinenfabrik Rieter Ag
Priority date: 2013-07-11
Filing date: 2014-07-07
Publication date: 2015-01-15
Also published as: DE102013107353A1; CN105358747A; EP3019649A1

Abstract

The invention relates to a conveyor belt (8) for transporting a fiber material to be pneumatically compressed which is composed, at least in a region that conducts fiber material, of an air-permeable sheet material, in particular a woven fabric (5), made of plastic filaments. The plastic filaments (15) are at least partially electrically conductive. The electrically conductive plastic filaments (15) contain electrically conductive filler objects, which have a nanostructure and are made of a ductile material. In a method for producing a conveyor belt (8) for transporting a fiber material to be pneumatically compressed, plastic filaments (15) are extruded from a plastic mass, which plastic filaments are at least partially electrically conductive and are processed furthered to form the sheet material. Before the extrusion, electrically conductive filler objects are added to the plastic mass, which filler objects have a nanostructure and are made of a ductile material.

Description

Electrically conductive conveyor belt with a nanostructure filler fabric and method of manufacture

The present invention relates to a conveyor belt for transporting a fibrous material to be compressed pneumatically, wherein the

Conveyor belt at least in a fiber material-carrying region of an air-permeable sheet, in particular a fabric, consists of plastic filaments and wherein the plastic filaments are at least partially formed electrically conductive and a method for its preparation.

In the spinning of fibers in a spinning machine, for example a ring spinning machine or air spinning machine, with a

Compression device, the fiber material is first stretched in a arranged on the spinning frame drafting. Before the stretched fiber material is subsequently spun in the spinning unit of the spinning machine, the fiber material is passed through the

Conducted compression device in which the stretched fiber structure is compressed and is reduced in width, so that the fibers lying in the edge region of the fiber strand are well integrated into the resulting thread. As a result, high-quality yarns with a low hairiness can be produced.

In pneumatic compression devices is doing a

air-permeable conveyor belt passed over a suction slot. The

The conveyor belt is driven and thereby transports the fiber structure through the compression zone arranged after the drafting equipment outlet. In such compression devices with an air-permeable

Conveyor belt often encounters the problem that the conveyor belt, which is usually made of synthetic fibers, electrostatically charges, causing undesirable adhesion of fibers and contaminants to the Conveyor belt can come. As a result, the air permeability of the conveyor belt and thus the compaction effect of

Compaction device reduced. To solve this problem has already been proposed to form the fabric of the conveyor belt electrically conductive so far that electrostatic charges can be avoided.

From DE 20 2007 013 020 U1 it has become known, for example, to provide a part of the threads from which the fabric of the conveyor belt is constructed with a metal coating and thereby to form it in an electrically conductive manner. The disadvantage here is that the fibers or threads of the fabric must be subjected to a comparatively complex coating process after their production and also there is a risk of damage to the coating under mechanical stress on the conveyor belt.

DE 10 2004 005 953 A1 proposes to add to the fabric electrostatic charging-preventing materials. For example, metal fibers or carbon fibers can be used as electrically conductive fibrils in a multifilament. According to another embodiment, it is provided that the plastic filaments are monofilaments interspersed with cut carbon fibers. As a result, although conveyor belts can be produced, which can reduce electrostatic charges. However, there is a risk that the properties of the conveyor belt are lost in terms of its flexibility and strength, so that it can come in operation to damage the conveyor belts. In addition, in the further processing of such filaments in certain manufacturing processes damage to the incorporated fibers may occur, which impair the conductivity of the filament or of the conveyor belt. Object of the present invention is therefore to propose a conveyor belt which can be produced in a simple manner and a

electrostatic charges having decreasing electrical conductivity. Furthermore, a corresponding method for producing such a conveyor belt to be proposed.

The object is solved with the features of the independent claims.

A conveyor belt for transporting a fibrous material to be compacted pneumatically is made of plastic filaments at least in a fiber material-guiding region from an air-permeable fabric, in particular a fabric. The plastic filaments are at least partially electrically conductive. According to the invention, the electrically conductive plastic filaments are conductive in that they contain electrically conductive filling material objects, wherein the filling material objects have a nanostructure and consist of a ductile material.

In a method for producing a conveyor belt for

Transporting a fibrous material to be compressed pneumatically plastic filaments are extruded from a plastic mass, which are at least partially formed electrically conductive and further processed to the fabric of the conveyor belt. The plastic mass to be extruded is admixed with electrically conductive filler objects which have a nanostructure and consist of a ductile material.

In the context of the present invention, a ductile material is understood as meaning a material which has an elongation at break of at least 10%, the value of the elongation at break relating to a conventional solid-state sample. The fact that electrically conductive nanofillers are used, which are already buried before the extrusion of the plastic material, it is possible, the electrically conductive

Plastic filaments in a conventional manner by melt spinning but still fine filaments can be produced. The fact that the fillers are made of a ductile material, there is little risk that the fillers are damaged during the manufacture of the filaments or in subsequent processing steps. Plastic filaments containing such filler objects can therefore be produced without special measures in conventional spinning devices in any subtleties and processed easily. Due to the ductility of the filler objects, a conveyor belt produced in this way can also withstand high mechanical loads during operation without losing its conductivity and flexibility, as may occur, for example, when using conventional fillers and, in particular, carbonaceous fillers. The ductile fillers in the filament can be plastically deformed very well without breaking. Thus, if they themselves are conductive, they can produce a conductive filament by more or less touching each other in the filament.

It is particularly advantageous if the plastic filaments after the

Be stretched, in particular stretched to 2 to 10 times the length of their original length. As a result, a considerable increase in the strength of the filaments can be achieved in a manner known per se, so that the drawn filaments have, for example, a 6 times higher tensile strength than the un-drawn filaments.

In particular, a draw by a factor between 2 and 7 is advantageous. Due to the fact that the plastic filaments contain nano-objects made of a ductile material, the plastic filaments advantageously still have a very high conductivity even after stretching, which is necessary to increase the strength, because the nano-objects, due to their ductility, either overstretch or overshoot

survive, or in the case of a crack have such a small distance from each other that the conductivity is still given by the plastic of the filament. Particularly advantageous in use of nano-objects in such plastic filaments is that the

Nano-objects often have in comparison to solids made of the same material again improved properties and can have a particularly high ductility.

It is furthermore advantageous if the electrically conductive plastic filaments are designed as monofilaments, since they can be produced and drawn in a particularly simple manner.

According to an advantageous embodiment of the invention, the

Filler objects an aspect ratio, ie a ratio of the length of the filler objects to their smallest lateral extent (width or

Diameter), of at least 10, preferably of at least 100 and more preferably of at least 1000. By means of longer nanoobjects, a particularly good conductivity of the plastic filament and thus of the conveyor belt can be achieved since, with longer structures, fewer contact bridges between the individual objects are required in order to produce a conductivity.

It is furthermore advantageous if the ductile material has an elongation at break of at least 10%, preferably of at least 30% and particularly preferably of at least 40%. The elongation at break figures again refer to conventionally determined values for tensile specimens from a solid. In particular come into question

Filler objects containing or consisting of gold, silver, copper, nickel, aluminum, zinc, tin or even lead. It is particularly advantageous if the ductile material is silver and / or contains silver, since this can reach an elongation at break of about 60%. It can therefore be used for the filaments also materials that are higher factors, eg. B. 2 to 7 times their original length, are stretched, for example, polyamides. For fibers that are stretched only by a smaller factor, for example POY fibers (Partially Oriented Yarn) made of polybutylene terephthalate, but also filler objects made of a material with a lower elongation at break, for example steel and iron materials, can be used.

After a particularly advantageous development are the

Filler objects designed as silver nanorods. These can be made with a particularly high aspect ratio of about 2000 and are also suitable for filaments drawn by a larger factor. On the other hand, with less ductile materials and / or with shorter structures there is a risk that the individual filler objects will tear as a result of stretching or that the contact bridges between the filler objects will be torn apart.

Furthermore, it is advantageous if the plastic filaments contain less than 10% filler objects, preferably less than 5% filler objects, since the mechanical properties of the filaments are then only slightly changed and the filaments are still a good one

Have abrasion resistance. If nano-filler objects with a particularly high aspect ratio are used, a very good conductivity can still be achieved due to the small number of required contact bridges.

In the production of the conveyor belt, it is also advantageous if the filler objects are simply added to the plastic mass to be extruded, without aligning them in a certain way. A parallelization and longitudinal alignment of the filler objects then takes place in the production process through the spinneret and possibly the later

Stretching. Filler objects with a high aspect ratio are therefore again particularly advantageous because of the great length and the

Longitudinal alignment only a few contact bridges between the individual filler objects are required. Likewise, it is advantageous if the filler objects have a smallest distance to a surface of the plastic filaments of at most 10 μm in order to achieve a charge dissipation through the material of the plastic filament.

A high-quality conveyor belt with high strength values can be achieved if the plastic filaments are made of a synthetic polymer, in particular a polyamide, wherein preferably the filaments have been drawn before being further processed into the fabric. However, there are also plastic filaments

various polyester materials in question. Also polyethylene,

Polyetheretherketone or polyoxymethylene are conceivable.

Particularly advantageous in the embodiment of the invention

Conveyor belt, are embedded in the ductile nano-objects in plastic filaments, it is further that even after prolonged operation of the conveyor belt with respect to the conductivity and thus the dissipation of electrostatic charges no deterioration can be expected. While, for example, in coated fibers due to abrasion over time to a deterioration of conductivity, can be ensured by the randomly distributed nano-objects, even with a wear of the conveyor belt, the conductivity.

It is particularly advantageous if the plastic filaments after the

Extruding be stretched. It has proved to be particularly advantageous if the filaments are stretched to two to ten times the length of their original length. Stretching is advantageous for giving the filament the strength needed for subsequent weaving of a wire mesh and subsequent use. When using, for example, rigid carbon nanotubes, the contact bridges between the individual carbon nanotubes would be destroyed during stretching. The filament would have been stretched no more conductivity. For example, because silver is much more ductile than carbon, the conductivity of the filament remains.

The invention will become more apparent from the following figures

described. Show it:

1 shows a pneumatic compression device in a

Spinning machine in a schematic overview and

Figure 2 is a schematic plan view of the compression zone of

Compression device with a conveyor belt.

Figure 1 shows a schematic cross-sectional view of a

pneumatic compression device 3 for compression spinning on a spinning machine 1. The spinning machine 1 has a drafting system 2 with presently three pairs of rollers, between which a fiber structure 9 is drawn in a conventional manner and then a spinning unit 4, in this case a ring spindle, is supplied. In order to reduce the width of the fiber composite to be spun 9 and thereby a

To be able to produce high quality compact yarn, a pneumatic compression device 3 is arranged after the defined by the pair of output rollers 6 drafting.

This includes in a conventional manner an air-permeable

Conveyor belt 8, which is guided over a suction slot 10. Of the

Suction slot 10 is in the present representation directly in a

Suction channel 12 is provided. The suction channel 12 is connected to a vacuum source and can also be several spinning units 4th

extend. The conveyor belt 8 is guided by means of a clamping device 13 tensioned around the suction channel 12 and is driven to the fiber structure in the direction of arrow P1 through the compression zone 7 to transport. In the present case is used to drive the conveyor belt 8, a pinch roller 1 1, which is connected to the output roller pair 6 of the drafting system 2 transmission technology, for example by means of a belt drive or a gear transmission. In the compression zone 7, the fiber structure 9 is finally exposed to the compression effect of the suction flow. The pinch roller 1 1 also forms a nip 14, which limits the compression zone 7 and after which the

Fiber assembly 9 of the spinning unit 4 is supplied where it receives its spin twist.

The compression device shown here is to be understood merely as an example. Thus, the conveyor belt 8 instead of the drive by the pinch roller 1 1 may also be driven in another way or be guided over a self-driven drum. Furthermore, there are numerous modifications to the arrangement of the individual

Components of the compacting device possible. Likewise, many other slot shapes may be used instead of the suction slot 10 shown in FIG. The conveyor belt 8 according to the invention can be used in all compaction devices 3, in which an air-permeable conveyor belt 8 is required.

FIG. 2 now shows a schematic plan view of the compression zone 7 of a compression device 3 with a device according to the invention

Conveyor belt 8. For reasons of clarity are the

Drafting rollers 6 and the pinch roller 1 1 not shown. The conveyor belt 8 consists in the present case of a fabric 5, which is woven from individual plastic filaments 15 and thereby has a high strength. The execution of the conveyor belt 8 is also meant to be exemplary only. Thus, the conveyor belt 8 can also be embodied as air-permeable fabric only in its central region, which is guided over the suction slot 10 and be woven more firmly in the edge regions or consist of a different material. Farther the conveyor belt 8 can also be made of a multiply perforated

Sheet of plastic filaments 15 exist, for example, a knitted fabric.

To now electrostatic charges of the conveyor belt 8, which consists of plastic filaments 15 and which often synthetic fibers

transported, to reduce, at least part of the plastic filaments 15 is electrically conductive, in which the plastic filaments are added electrically conductive filler objects, which have a nanostructure and consist of a ductile material. With a filler made of a ductile material, the corresponding plastic filaments can be produced particularly easily, since these are only the one to be extruded

Plastic mass must be buried and because of their ductility in the processing process, for example, when peeling off the

Melt nozzles and in particular in a subsequent

Drawing process will not be damaged. Due to the nanostructure, finer plastic filaments 15 are also conventional

Melt spinning can be produced. Due to the ductility of the buried

Filler objects is the flexibility and strength of such

Plastic filament produced conveyor belt is not affected, so that it is not due to stress during operation to a tearing of contact bridges between the plastic filaments and thus a

Reduction of conductivity comes. Such manufactured

Plastic filaments 15 can also be easily after the

Melt spiders are stretched to increase their strength. Again, a fraction of the added ductile fillers or the contact bridges is not to be feared, so that the conductivity of the filament can be almost completely preserved. On the other hand, in the case of filaments which have been buried with carbon fibers, even slight strains can lead to rupture of contact bridges of adjoining fibers and thus to a reduction in the conductivity. Similarly, filaments offset with carbon fibers may not or only by one Otherwise, both cracking of the fiber pieces and breakage of contact bridges between individual embedded fibers is to be feared.

Particularly advantageous in the conveyor according to the invention is further that this retains its electrical conductivity even after many hours of operation and even with heavy wear of the conveyor belt 8. Thus, especially in the region of the nip 14, at which the pinch roller 1 1 limits the compression zone 7, causes a particularly high wear of the conveyor belt 8, which can lead to a strong reduction in conductivity in conveyor belts 8 of coated filaments 15 over time.

In order to produce a conveyor belt 8 according to a particularly advantageous embodiment of the invention, objects having a nanostructure are added to a plastic melt, in particular a polyamide melt, a filler or filling material. Silver nanorods which have a particularly high aspect ratio of 2000 have proved to be particularly advantageous. For example, silver nanorods with a diameter of 50 nm and a length of 100 μm may be added. Due to the length of such silver nanorods sufficient electrical conductivity can be achieved even with the addition of a comparatively small amount of filler objects. At the same time

Silver nanorods have a particularly high ductility. For example, fine silver as a solid already has an elongation at break of up to 60%. Due to the particularly high ductility of the buried

Silver nanorod is therefore also a stretching of the produced

Filaments 15 by a larger factor possible, without there being a cracking or breakage of contact bridges between individual, adjacent silver nanorods. But it can also be used nanorods made of gold, which usually have a lower aspect ratio. Also gold as well

Gold alloys have a high elongation at break. Unless the

Plastic filaments are stretched after their preparation only by a very small factor, in principle, nanofibers of an iron or steel material in question, by means of which still

Elongation at break of up to 30% relative to a conventional one

Sample rod are possible.

Due to the high elongation at fracture of the filler objects used, the distances between the individual filler objects can be so small even after a breakage of individual objects or a rupture of individual contact bridges that still a conductivity can be ensured.

A conditioned polyamide may, for example, a

Have breakdown voltage of up to 20 volts per μιτι. Lie in the individual filaments or in the tissue, the filler objects

For example, at a maximum distance of 10 μιτι each other or to the surface of the plastic filaments, a discharge can be achieved even at a voltage of 200 volts. In particular, when using filler objects with a very high aspect ratio, these values can be easily achieved even with simple random arrangement in the plastic filaments, so with a simple addition to the plastic melt due to the length of the individual filler.

The invention is not limited to the illustrated embodiments

limited. Further modifications and combinations within the scope of the claims also fall under the invention. LIST OF REFERENCES

spinning machine

drafting system

compacting device

spinning unit

tissue

Output roller pair of the drafting system

compression zone

conveyor belt

fiber structure

suction slot

pinch roller

suction

Clamping device of the conveyor belt

nip

filament

Transport direction of the fiber composite

Claims

Patent claims

1 . Conveyor belt for transporting a pneumatic to

wherein the conveyor belt (8) at least in a fiber material leading portion of an air-permeable sheet, in particular a fabric of plastic filaments (15) and wherein the plastic filaments (15) are at least partially electrically conductive, characterized in that the electrically conductive trained

Plastic filaments (15) contain electrically conductive filler objects, wherein the filler objects have a nanostructure and consist of a ductile material.

2. Transport belt according to the preceding claim, characterized

characterized in that the electrically conductive formed

Plastic filaments (15) are stretched, in particular by two to ten times their original length are stretched.

3. Conveyor belt according to the preceding claim, characterized

characterized in that the electrically conductive formed

Plastic filaments (15) are formed as monofilaments.

4. Conveyor belt according to one of the preceding claims, characterized in that the filler objects have an aspect ratio of at least 10, preferably of at least 100 and more preferably of at least 1000.

5. Conveyor belt according to one of the preceding claims, characterized in that the ductile material has an elongation at break of at least 10%, preferably of at least 30%, more preferably of at least 40%.

6. Conveyor belt according to one of the preceding claims, characterized in that the ductile material is a metal, in particular silver or gold and / or contains such a metal.

7. Conveyor belt according to one of the preceding claims, characterized in that the filling material objects metal nanorods, in particular silver or gold nanorods, in particular with an aspect ratio of about 2000, are.

8. Conveyor belt according to one of the preceding claims, characterized in that the plastic filaments (15) contain less than 10% filler objects, preferably less than 5% filler objects.

9. Conveyor belt according to one of the preceding claims, characterized in that the filler objects have a smallest distance to a surface of the plastic filaments (15) of at most 10 μιτι.

10. Conveyor belt according to one of the preceding claims, characterized in that the plastic filaments (15) are made of a synthetic polymer, in particular a polyester or a polyamide.

1 1. Method for producing a conveyor belt (8) for

Transporting a fibrous material to be compacted pneumatically, wherein the conveyor belt (8) is at least partially made of an air-permeable fabric, in particular a fabric (5), being extruded from a plastic mass plastic filaments (15) which are at least partially electrically conductive, and wherein the plastic filaments (15) to the Fabrics are further processed, characterized in that the plastic material are mixed prior to extrusion electrically conductive filler objects, which have a nanostructure and consist of a ductile material.

12. The method according to the preceding claim, characterized

in that the plastic filaments (15) after the

Extruded be stretched, in particular to be stretched to two to ten times the length of its original length.