US2977475A - Method of and apparatus for processing textile fibre materials - Google Patents

Description

March 28, 1961 Filed April 24, 1959 METHOD OF P. KASSE ECK APPARA TEX E FIBRE MATERI FOR OCESSING 5 Sheets-Sheet 1 law March 28, 1961 P. KASSENBECK 2,977,475

METHOD OF AND APPARATUS FOR PROCESSING TEXTILE FIBRE MATERIALS March 28, 1961 P. KASSE ECK 2,977,475

METHOD OF D APP FOR PROCESSING TE LE FI MATERIALS Filed April 24, 1959 FIG-4 FIGS 3 Sheets-Sheet 3 FIG.

ted State METHOD OF AND APPARATUS FOR PROCESSING TEXTILE FIBRE MATERIALS Paul Kasseubeck, Ville DAvray, France, assignor to Inilfiflut Textile de France, Paris, France, a French estabs ment This invention relates to a novel method of processing fibre materials for improving the textile characteristics thereof. The invention is broadly applicable to all classes of fibre, whether natural or synthetic, and to all forms of fibre-base materials including raw fibre, spun yarn and thread, woven, matted and knitted fabrics, and so on.

The process of the invention comprises exposing the fibre material to the action of a high voltage ionizing discharge for a predetermined period of time. It is found that the fibre material thus treated displays greatly improved physical and chemical characteristics, including tensile and wear-taking strength. Hence, it is an object of the invention to improve the characteristics of fibre base materials, whereby to produce finished articles of superior quality.

An electric ionizing discharge occurs when a voltage in excess of a definite value is applied across the plates of a condenser placed in a rarefied atomsphere. When analyzed with cathode oscilloscope techniques it is found that the discharge comprises a series of short pulses of,

very high current intensity superimposed over the lowfrequency energizing alternating current. The discharge may be stabilized by inserting a solid dielectric between the plates of the capacity.

' It has generally been held heretofore that such ionizing discharge exerted adverse elfects on textile materials exposed thereto, the fibre being damaged and ultimately destroyed. The applicant has now made the surprising discovery that when fibre material is exposed to ionizing discharge under controlled conditions and for a predetermined time, such exposure results in extremely and unexpectedly beneficial effects on the physical and mechanical characteristics of the fibre, in direct contrast with the conventional teachings. This improvement in the characteristics is not limited to the time of exposure of the material to the discharge, but continues to unfold and develop for a certain time after the material has been removed from the action of the discharge, and only achieves its final maximum value at the end of a certain period on the order of several weeks. This evidently means that the limited exposure to the ionizing bombar-dment from the discharge has initiated reactions that continue to progress with time. The beneficial effects achieved by the exposure have been found to be very lasting in character. They have been found to be present in fibre materials of all nature, including both natural and synthetic fibres.

Another object of this invention is to provide improved apparatus for processing fibre materials in accordance with the above method, which will be conveniently and simply applicable to fibre materials in various of their commercial forms. Thus in one important aspect apparatus of the invention may comprise means for continuously feeding a web of textile fabric through the space between electrodes across which a discharge is established, at a rate such that the time of exposure of each particle of the web will achieve the desired beneficial efiects of the invention.

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The invention will now be described is greater detail with reference to the accompanying drawings, wherein:

Fig. 1 illustrates a typical oscillogram of a discharge usable for the purposes of the invention;

Fig. 2 is a simplified and partly schematic showing of apparatus for practicing the invention;

Fig. 3 is a perspective view of one practical construction of apparatus for processing textile webs according to the invention;

Fig. 4 is a graph in which the tensile strength of treated woolen yarn is plotted against time after exposure to a discharge according to the invention;

Fig. 5 is a similar plot relating to the bursting strength of wool fabric;

Fig. 6 is a graph showing the increase in wear resistance of wool fabric, both treated and untreated;

Fig. 7 is a graph illustrating the increase in kink-resistance of polyacrylonitrile knitted wear, treated and untreated;

Figs. 8 and 9 are illustrative of the results indicated by the graph of Fig. 7; and

Figs. 10 and 11 are typical electron micrographs of the surface condition of fibre before and after treatment respectively.

Referring first to Fig. l, a typical oscillogram is shown of a discharge at 500 c.p.s. under 4,000 volts in an atmosphere at 10 cm. mercury. The oscillogram clearly shows the high-frequency current pulses that occur.

Apparatus for carrying out a treatment according to the invention is illustrated in an exemplary manner in Fig. 2 as broadly comprising a discharge receptacle, a high voltage generator and a vacuum pump.

The discharge receptacle comprises a sealed enclosure 1 in which a pair of electrodes 2 in the form of aluminum discs 2 mm. thick and 180 mm. diameter are mounted. Between the electrodes'is a stabilizer device 3 which may comprise one or more glass discs 3 mm. in thickness and 260 mm. in diameter. The electrodes and stabilizing layers are mounted in alternating relation and are spaced from one another by 5 mm. gaps with suitable insulating spacers e.g. of Bakelite, Connected with the base of the enclosure is a pipe 4 for the discharge of gas, and two electric terminals 5 on insulating mounts adapted to withstand 10,000 volts and respectively connected with the electrodes 2. Connected with the top of the enclosure is a pressure gauge 6 for indication of the adjusted internal pressure, and an inlet pipe for air and/or gas including a control valve 7, e.g. a needle valve. A relief valve 8 enables the internal pressure to be released at the end of a treating operation.

The voltage generator used in this form of the invention comprises a suitable motor 9 driving an alternator 10 having a 500 c.p.s. output. Excitation voltage for the alternator is provided by way of a control transformer 15 adjustable by means of a manual knob 11. The alternator is able to deliver an output of from to 250 volts A.-C. at its output terminals, and this is applied by way of a step-up transformer 12 which yields at its secondary a voltage of from 2 to S kilovolts connected with the terminals 5 of the discharge device. A voltmeter 13 connected across the transformer secondary serves to indicate the adjusted voltage.

The vacuum pump 14 here used is a rotary vane pump connected with the relief valve 3 and capable of creating within the container 1 a vacuum of about 7 to 10 cm. mercury absolute.

In use, the material to be treated, such as a loose mass of fibre or a piece of fabric, is placed between the electrodes 2 of the discharge device, e.g. upon one of the glass discs therein, or directly upon the lower electrode. The container is then sealed, the vane pump is operated and the control valve adjusted to maintain a asraa'ra '3 l pressure of about 10 cm. Hg within the container. Then the high voltage from generator 10 is applied to the electrodes by meansof a switch notshown, for a period of about from 3 to minutes or more, whereupon the treatment is discontinued.

Apparatus for continuously treating a web of fabric according to the invention is shown in Fig. 3 as comprising a pair of vertical horizontally spaced electrodes E of large area supported within a pressure enclosure C mounted on a suitable frame. A glass plate P is supported between the electrodes for stabilizing the discharge. Suitable roller meansincluding a reel-off roller R anda reel-up roller'R are provided together with ancillary sealing, guiding and drawing means of generallyconventional character, for feeding a web of material T continuously through the space between the electrodes E. In one practical embodiment the electrodes E were 150 by 150 centimeters in size and the rate of feed of the web was 60 centimeters per minute.

Results of tests will now be described that were performed on various types of fiber materials in order to ascertain the changes in characteristics thereof resulting from exposure to treatment according to the invention.

1. Tensile tests on wool fibre Wool fibre having a'tensile yield point of 4.09 grams and elongation 62.5% at yield was exposed liminutes to the treatment described above. At the end of the test the tensile limit was raised to 4.88 grams while the elongation at yield was very slightly reduced to 62.0%.

As previously noted the full benefits of the process only appear some time after the end of the treatment. Woollen yarn treated in the manner described was therefore subjected to repeated tensile tests over a' period of several weeks after treatment. The graph of Fig. 4 shows the results of these tests ploted against time. As shownby the graph the tensile strength increased steadily from a value of 166 grams to a final value of above 211 grams after about two weeks and levelled oif at that value, The elongation at yield first rose paridly from about 37% to about 42% in the first 24 hours and the slowly increased to its final value about 43%.

It is found that the tensile and elongation values thus finally attained are lasting.

Bursting strength Woollen twill fabric was subjected to bursting tests over a period of two weeks following five minutes treatment according to the invention. The graph of Fig. 5 summarizes the results of these tests. The bursting pressure is seen to rise from 9.9 kg. to 11.1 kg. within the first 24 hours after treatment, then increases more slowly to about 11.5 kg. in a week and finally levels off at a slightly higher value. The sag at bursting point similarly increases from about 14 millimeters to something above 17 mm., thus indicating that both the toughness and flexibility of the cloth have increased and confirming the results of the tensile tests.

Wear-taking tests The wear-taking characteristic is probably among the over-all properties to'derive greatest benefit from the novel process of the invention. Woollen twill cloth was tested on a wear testing machine of the type known as Abrasimeter ITF-M, the test results being given as milligrams loss in weight sustained by the material at the end of a given number of revolutions of themacnine. Fig. 6 indicates the losses of material occurring up to 6000 revolutions in the case of untreated fabric (curve I) and samples treated according to the invention under varying discharge conditions (curves II, III and IV).

It will be seen that Whereas the untreated sample lost about 700 milligrams of its weight after being subjected to 5000 revolutions on the abrasion-testing machine, each of the treated samples had at that time only suffered Kinking tests 7 v A further and highly desirable improvement in the characteristics of fibre material treated by the process of the invention is that involving its kinking properties, which are found to be greatly reduced. A jumper knitted from untreated Orlon fibre (acryl fibre) was worn for 15 consecutive days (about 210 hours wear) whereupon it displaced a considerable number of kinks as Will appear from Fig. 8 which shows a part of the garment. An identical jumper when treated according to 'the'invention and worn for the same period of time and under similar conditions was entirely free from kinks as indicated by the view of Fig. 9. Laboratory tests on a testing machine show the results summarized on-the graph of Fig. 7, where the number of kinks persquare centimeter are plotted against number of revolutions of the machine. The curve NT relates to the non-treated fibre, the curve T to the treated fibre. The marked reduction in the kinking rate is immediately apparent.

The above and other'beneficial results'of the process may be ascribed to the particular modification in surface condition of the fibre brought about by the ionic bombardmenttreatmcnt occurring in the process of the invention, as revealed by photomicrographs. Thus, Figs. 10 and 11 show micrographs at 10,000 magnification of the surface of wool fibre, respectively before treatment and after treatment. It will be noted that the treated fibre shows a great number of submicroscopic surface asperities which must result in a greatly'increased adherence bond between the fibres and, among other favourable results, minimizes the tendency to the formation of kinks. a

The process of the invention is of considerable simplicity in its application on an industrial scale. Discharge treating apparatus, only one exemplary industrial form of which was described herein with reference to Fig; 3, can readily be embodied in any of a variety of forms to suit particular production requirements depending on the type of fibre being treated and the particular form, i.e. raw fibre, spun yarn, fabric or woven or knitted article, of the material at the time at which it is treated. The entire process can simply and conveniently be reduced to semi-automatic or fully automatic continuous operation with an automatic control of such factors as feed rate, gas pressure, voltage etc.

The process is inexpensive to operate, the operating costs being determined almost exclusively by the power consumption of the apparatus. By way of indication, about 1 kilowatt power is required for a treating rate of about 50 sq. meters fabric (about 20 to 40 kilograms depending on the type of fabric) per hour.

It will be apparent that various refinements of the process, as for example modifying the gaseous atmosphere' in the treating enclosure,'and various modifications in theelectrical circuitry and treating apparatus to suit practical needs, may be introduced on the basis of the teachings of this invention.

What I claim is:

1. The method of processing fibre material comprising exposing the material to an electric discharge of from about 2 to about 5K volts at a frequency of about from to about 1000 cycles per second for a time of from about. Ito about 10 minutes and at a gas pressure ofnot more than about 10 cm. mercury absolute.

2. Apparatus for processing fibre material, comprising means defining a vacuum enclosure, spaced electrodes therein, means for applying high-voltage alternating power across said electrodes, and means for supporting fibretween and spaced from said electrodes at a controllable rate to be exposed to the electric discharge therein.

References Cited in the file of this patent UNITED STATES PATENTS Smith Oct. 20, 1925 Bierwirth Aug. 3, 1943 Kline et al May 27, 1947 Magruder et al July 7, 1959

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