GB2190927A

GB2190927A - Electrostatic sizing of textile threads

Info

Publication number: GB2190927A
Application number: GB08705007A
Authority: GB
Inventors: Claus Wehrmann
Original assignee: Sucker & Franz Mueller GmbH
Current assignee: Sucker & Franz Mueller GmbH
Priority date: 1986-05-27
Filing date: 1987-03-04
Publication date: 1987-12-02
Also published as: IT1216876B; NL8700232A; DE3617795A1; GB8705007D0; FR2599397A1; JPS62282058A; DE3617795C2; BE1002397A4; IT8719272A0

Abstract

For sizing a textile thread or thread bundle (1), the moving thread, made electrically conducting in its longitudinal direction, is subjected to an electrostatic field orientated generally radially to the thread longitudinal direction. Into this field are fed electrically charged atomised size particles (5) of opposite polarity to the thread to be sized. When the individual threads (6) have fine hairs (7), these hairs may subsequently be wrapped around the thread by a magnetic rotating field. <IMAGE>

Description

SPECIFICATION Method of sizing textile threads and apparatus for carrying out the method.

This invention relates to a method for sizing a textile thread, wherein the size is applied onto the individual thread or threads combined as a thread bundle, to be moved continuously in the thread longitudinal direction. It relates also to an apparatus for carrying out the method.

The term "textile thread" is to be understood to mean linear structures, especially of staple fibres or filaments on a textile basis and also of, or mixed with, metal, glass or the like fibres, which are suitable for the manufacture of textile flat structures, for example woven or mesh fabrics.

In sizing, a thread bundle prepared, for example, for weaving, is treated with sizing agents in order to make it resistant to working in the loom or enable it to operate with low friction as the warp thread. During sizing the thread runs - generally as part of a thread bundle or set - through a size bath, it is then squeezed and conducted through a wet section field. Thereupon the coated thread is dried and wound on a beam.

The quality of the conventional wet size depends upon the uniformity with which the sizing agent is finally distributed in and on the individual thread. To enable the size to be applied uniformly and deep into the thread bundle, the sizing agent is first applied in great excess by dipping the thread into a trough of size and is then again partly expelled in a squeezing device and made uniform. Even if level and concentration control devices are provided in the size trough, the amount of size on the individual threads can be reproduced with only comparative inaccuracy. For reasons of security, therefore, a stronger size coating is frequently provided in practice than is necessary for the weaving itself.

A further disadvantage of conventional sizing by dipping lies in the fact that the sizing agent has to be applied onto the thread in a liquid vehicle or as a solution, for example in water. This liquid vehicle or solvent must afterwards be removed in an expensive process, usually requiring consumption of heat, before the thread can be wound up ready for weaving.

Finally, the size must in general be removed again after the woven structure is completed.

The removal of size is of course less expensive the smaller the quantity of size that previously has been applied onto the individual thread.

For the production of flock yarn it is proposed, in DE-OS 34 01 581, first to coat a moving synthetic carrier thread with thermoplastics adhesive by dipping and then to conduct the electically earthed thread between high-voltage electrodes of opposite polarity in such a manner that flock fibres brought in by a conveyor belt fly under the influence of the electrostatic field in a radially orientated form onto the thread and remain adhering there to the adhesive coating. The thread covered in this manner with fibres is dried under longitudinal tension and, after a thermal shrinkage treatment, is reeled up. If, in this process, the flock fibres were to be replaced by dry size particles, a useful sizing could not be achieved because the previously applied adhesive coating would prevent penetration and therefore uniform sizing of the thread.A merely superficial sizing of a thread does not usually, however, lead to the desired result of the sizing process. Moreover, the application of the adhesive coating is substantially accompanied by the same problems as the application of the sizing agent in conventional wet sizing.

The task underlying the present invention is to limit the size consumption and application onto the particular thread measurably and reproducibly to the amount absolutely necessary during weaving, and to reduce energy consumption in the treayment of the sized thread for weaving as compared with the case of dip-sizing. The solution according to this invention consists, for the process of the initially named type for the sizing of threads or thread bundles, in that the relevant thread is made electrically conducting and is subjected to an electrical field which is radial relative to the thread longitudinal direction, and that the size is fed into the electrical field from an atomizer which is at the opposite potential to the thread.According to further aspects of the invention, a magnetic rotating field orientated generally radially through the thread is superimposed upon the electrical field.

By the invention the result is achieved that the size is applied onto the individual thread by atomizing, without or with only a very small moisture component. As a consequence, a minimal size consumption results, which can be accurately measured and adjusted reprodu- cibly by regulating the electrical field, the size atomizer and the velocity of the thread. Due to the minimal application of size and the small quantity of moisture contained therein, energy is saved in the subsequent drying. The minimal size application also leads to reduced expense in the subsequent size removal after manufacture of a sheet structure, for example by weaving.

In the process according to this invention, the threads to be treated are first rendered electrically conducting to a defined extent, preferably by applying a liquid. This process step can be carried out either separately or in common with the intended application of size.

For example, a thread which is itself intrinsically electrically non-cobnducting can be made electrically conducting in a defined manner in the sizing process by the addition of a conducting liquid into the atomized size.

According to the method of this invention, the individual threads are subjected to an electrical field which is radial in respect of the thread longitudinal direction. For example, the threads may be negatively charged and an electrical cylindrical electrode surrounding them positively charged as anode. A device for atomizing the size is preferably incorporated into the cylindical electrode or the other means for producing an electrostatic field. In particular thermal, mechanical and pneumatic atomizers may be considered; for example, piezoelectric oscillators are suitable as atomizers. The electrical cylindrical electrode and the atomizer can be at the same electrical potential.

In practice, smooth threads may be sized which, like filament yarns, may possess fibrils or capillaries, but threads having a surface covered with fine hairs may also be treated with advantage according to this invention. In the former case, a sticking together of the fibrils is achieved by the invention, so that fibril breakages during weaving are avoided.

This stabilization is promoted by the capillary action of the size inside the thread. In the other case, the individual small hairs of each of the threads may become orientated in the direction of the electrical field, that is radially to the thread longitudinal direction. The atomized size also moves in the direction of the radial electrical field lines and, due to the higher field strength at the tips of the hairs, is accelerated especially onto the upraised fine hairs.

In this connection it may be advantageous, according to a further aspect of the invention, in addition to the electrostatic field to provide also a magnetic rotating field oriented approximately radially onto the individual thread or thread bundle or to pull the thread through such a magnetic rotating field following the electrostatic sizing. By the action of the magnetic rotating field upon the electrical charges moving with the individual thread, it becomes possible to wind the small hairs sized at their tips around the individual thread and to distribute the applied size uniformly onto the thread.

When the magnetic rotating field is used, the fine hairs which may be seated on the individual thread wrap themselves around the thread with a wrap angle which is dependent upon the frequency of the magnetic rotating field and the transport velocity of the thread.

By predetermining the frequency of the magnetic rotating field and/or the thread velocity, therefore, the angle of wrap can therefore be reproducibly adjusted.

For producing the magnetic rotating field, magnetic single poles may be disposed in the manner of a cylindrical electrode around the thread or thread bundle. The magnetic single poles should, of course, be magnetically insulated from one another but they can lie at the same electrical potential, in such a manner that they also constitute a pole, for example as a cylindrical electrode, of the electrostatic field.

According to a further aspect of the invention it may also be advantageous to dispose the means for producing the magnetic rotating field behind the atomizer in the thread conveying direction. As a result, the effect is achieved that each thread element is first acted upon by the atomized size in the electrostatic field for filling up fibrils or capillaries and/or where radially upstanding hairiness still exists, and only then are the sized small hairs wound around the associated individual thread in the magnetic rotating field.

The result of the sizing according to this invention depends upon parameters that can be electrically controlled, namely upon the thread conveying velocity, the electrical vol- tage difference between thread and electrode, upon the intensity and rotational frequency of the magnetic rotational field and upon the kind and operation of the size atomizing device. All these parameters can be so regulated or kept constant in a manner familiar to the skilled person by means of electrical control circuits, such that an accurately measurably and reproducibly sized thread with the minimum size coating required for use in weaving or the like can be produced.

Details of the invention are now explained with reference to the schematic representation of examples of embodiment thereof. The figures in the drawing show: Figure 1 a section transversely to the thread longitudinal direction through an apparatus for the electrostatic sizing of a thread bundle; Figure 2 a longitudinal section through an apparatus for the electrostatic sizing of a thread bundle in a magnetic rotating field for wrapping a hairiness around the individual thread; Figure 3 A section transversely to the thread longitudinal direction through an apparatus for producing a magnetic rotating field in the region of a sized thread bundle; and Figure 4 A diagram in which the dependence of the angle of wrap of the hairiness upon the thread velocity is illustrated.

In the apparatus according to Fig. 1, a thread bundle composed of individual threads and referenced generally 1 is conducted in a direction perpendicularly to the plane of the drawing through an electrical cylindrical electrode 2. Between the thread bundle 1 and the cylindrical electrode 2, a voltage U1 is applied.

At least one size atomizer 3, for example a piezoelectric oscillator supplied from a highfrequency source 4, is integrated into the cylindrical electrode 2.

The size particles 5 issuing from the atomizer 4 move along the radial electrical field lines extending between cylindrical electrode 2 and individual threads 6 of the thread bundle 1 towards the individual threads 6, because the size particles 5 coming from the atomizer 4, like the atomizer, carry the opposite charge to the thread bundle 1. In this manner, each individual thread 6 of the thread bundle 1 can be uniformly sized utilizing an electrostatic field.

When a thread of the type of a staple yarn, having a surface possessing a hairiness 7, is to be electrostatically sized according to Fig.

1, it must be noted that, due to the action of the electrostatic field corresponding to the voltage U1 between the cylindrical electrode 2 and the individual thread 6, a hairiness 7 present on the thread is orientated generally parallel to the electrical field lines. The individual small hairs of the hairiness therefore stand up substantially radially from the thread 6 and the size particles 5 issuing from the atomizer 4 first meet the tips of the upstanding hairiness 7 as they travel along the field lines, because the higher peak field strength exists there.

According to Fig. 2, in addition to the electrostatic field of the cylindrical electrode 2, a magnetic rotating field, for example according to Fig 3, is provided. The magnetic rotating field is advantageous if threads having a surface which possesses a hairiness orientated in the electrical field parallel to the field lines are to be sized. In the sizing of threads having a smooth surface, in contrast, the magnetic rotating field is not absolutely essential. Indeed, electrostatically sized threads having a smooth surface can be fed directly after sizing into the next treatment step, for example drying, winding up etc.

The following applies particularly to the electrostatic sizing of threads, for example of staple yarn, which possess a surface having a hairiness.

Fig. 2 shows a cylindrical electrode 2 may be electrically and mechanically connected and equipped with means for atomizing size. A thread bundle or set 1, made electrically conducting to a defined extent in some manner, is introduced through a roll pair 8 acting also as electrical contact at a velocity v into the cylindrical electrode 2 and, after passing through a second roll pair 9, serving also as an electrical contact, is conducted onwards to a succeeding treatment operation. Between the first roll pair 8 and the cylindrical electrode 2 there is a voltage U1 + U2, while between the second roll pair 9 and the cylindrical electrode 2 there is only the voltage U1.At the entry E of the thread bundle 1 into the cylindrical electrode 2, a higher electrical field strength therefore acts upon the thread bundle 1 than at the outlet A, in such a way that the electrical field between inlet E and outlet A of the cylindrical electrode 2 has a gradient falling from E to A. Such a construction is advantageous if the size atomizer 4 is disposed in the region of the larger electrical field.

In the direction of the conveying velocity v of the thread bundle 1, after the atomizer 4, a magnetic rotating field device referenced generally 10 may be provided, which for example may possess magnetic poles 12 generating electrical alternating fields 11 as in a polyphase motor. An example of embodiment of a magnetic rotating field device of this type is illustrated in Fig. 3 in section perpendicular to the longitudinal direction of the thread bundle 1. Three magnetic pole pairs 12 are provided, which may be connected to the three phases R, S, T of a frequency-regulated alternating current supply network.

If the moving thread bundle 1 according to Fig. 1, with the hairiness 7 standing up perpendicularly, is first electrostatically charged with atomized sizing agent in an apparatus according to Fig. 2 and then is conducted at its conveying velocity through a magnetic rotating field device 10, the individual small hairs of the hairiness 7 are wrapped around each individual thread 6 of the thread bundle 1 in such a manner that a smooth thread of high strength is obtained.

From the basic diagram according to Fig. 4, it is apparent that the angle of wrap a which a small hair 13 makes with the thread longitudinal axis 14 in projection, is dependent - not only upon the magnetic field B itself - but also upon the frequency of the magnetic rotating field and upon the conveying velocity v of the thread 6. If the frequency f is doubled and the speed v kept constant, or the frequency f kept constant and the speed v is halved, the angle of wrap a will be increased by the same amount.

Claims

CLAIMS:

1. Method of sizing a textile thread (6), wherein the size is applied onto the individual thread or threads (6) in a thread bundle (1) to be moved continuously in the longitudinal direction of the thread, characterized in that the thread (6) is made electrically conducting and is subjected to an electrical field approximately radial to the thread longitudinal direction, and that the size is fed into the electrical field from an atomizer (4) at a potential opposite to that of the thread.

2. Method according to Claim 1, characterized in that, in the sizing of a thread (6) possessing hairiness (7), the hairiness (7) is wound around each individual thread by means of a magnetic field orientated generally radially through the moving thread (6).

3. Method according to Claim 2, characterized in that the angle of wrap (w) of the wound hairiness (7) is determined by regulating the frequency of the magnetic rotating field and/or the transport velocity of the thread (6).

4. Method according to one or more of claims 1 to 3, characterized in that the individual thread element is first sized in the electrical field and then the sized hairiness is wound around the moving thread (6) in the magnetic rotating field.

5. Method according to one or more Claims 1 to 4, characterized in that the thread (6) is made electrically conducting to a defined extent during sizing by the addition of a conducting liquid.

6. Apparatus for carrying out the method according to one or more of Claims 1 to 5, characterized by a cylindrical electrode (2) constituting the one pole of the electrical field for the passing through of the thread (6) constituting the other pole of the electrical field and by a size atomizer (3) having the same potential as the cylindrical electrode (2).

7. Apparatus according to Claim 6, characterized in that a cylindrical electrode (2), positively charged as anode with respect to the thread (6), is provided.

8. Apparatus according to Claim 6 or 7, characterized in that an apparatus (10) for producing a magnetic rotating field, especially in the manner of a polyphase motor is disposed around the thread (to).

9. Apparatus according to Claim 8, characterized in that the apparatus (10) for producing a magnetic rotating field possesses magnetic individual poles (12), which are electrically at the same potential and constitute the cylindrical electrode (2) associated with the thread (6).

10. Apparatus according to one or more of Claims 6 to 8, characterized in that the apparatus (10) for producing the magnetic rotating field is disposed behind the atomizer (4) in the conveying direction of the thread (6).

11. Method of sizing a textile thread as claimed in Claim 1, substantially as disclosed herein.

12. Apparatus as claimed in Claim 6, substantially as described with reference to Figure 1, Figure 2 or Figure 3 of the accompanying drawing.