US3440418A - Method and apparatus for treating fibrous materials by exposure to an electrical discharge through a moving dielectric - Google Patents

Description

,440,4l8 IALS LECTRLCAL mscmmss THROUGH A MOVING DIELECTRIC April 22, 1969 c. PIAZZA METHGD AND APPARATUS FOR TREATING FIBROUS MAT'ER BY EXPOSURE TO AN E Sheet Filed July 26, 1965 INVENTOR.

A Z Z A P O L R A C ATTORNEY April 22, 1969 c. PIAZZA 3,440,418

METHOD AND APPARATUS FOR TREATING FIBROUS MATERIALS BY EXPOSURE TO AN ELECTRICAL DISCHARGE THROUGH A MOVING mmsc'mc Filed July 26, 1965 Sheet 3 of 2 CYCLES -WOOL CONTROL WOOL CORONA DISCHARGE WOOL CONTROL WOOL CORONA DISCHARGHWASHED) WOOL CORONA DISCHARGEWIASHED) INVENTOR. CA R LO P l AZZA ATTORNEY WOOL CORONA DISCHARGE(DRY CLEANED" United States Patent METHOD AND APPARATUS FOR TREATING FIBROUS MATERIALS BY EXPOSURE TO AN ELECTRICAL DISCHARGE THROUGH A MOVING DIELECTRIC Carlo Piazza, Spartanburg, S.C'., as'ignor to Deering Milliken Research Corporation, Spartanburg, S.C., a corporation of Delaware Filed July 26, 1965, Ser. No. 474,878 Int. Cl. H01j 37/26 US. Cl. 250-495 10 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for treating fibrous materials comprising exposing the materials, while shielded by a relatively moving dielectric, to an electrical discharge of about to 30 kilovolts at positive pressures.

This invention relates to a process for treating fibrous materials for purposes of improving textile properties and more specifically an electrical process for treating fibrous materials in order to improve the coefiicient of friction of the fibrous materials.

Subjecting fibrous materials to the action of a high voltage ionizing discharge for a predetermined period of time is a treatment which is known to the textile industry. High voltage textile treatments which have been previously carried out are textile treatments such as those set forth in US. Patent No. 1,557,730 which deals with the curing of a resinous impregnant contained within a textile yarn, by passing a resin impregnated yarn through an electric current of high tension. More recently, high voltage treatments have been employed to produce beneficial effects upon textile materails themselves rather than upon resinous impregnants. US. Patent No. 2,997,475 deals with a process for improving the physical characteristics of a textile material by subjecting the textile material to the high ionizing discharge which takes place when a voltage in excess of a definite value is applied across the plates of a condenser placed in a rare atmosphere. More specifically, the conditions required for improving the physical characteristics of the textile material are exposure to an electric discharge of from about 2 to 5 kilovolts at a frequency of from about 100 to about 1000 cycles per second at a gas pressure of not more than about centimeters of mercury absolute. These conditions are presumed to produce a change in the surface characteristics of the treated fibers which thereby result in improved physical characteristics in the finished textile product. Apparently, the foregoing conditions have been selected, that is to say vacuum conditions have been selected so as to allow the utilization of a low voltage glow discharge which results in a uniform discharge between the electrodes, high voltage corona discharges having =been heretofore considered as being unacceptable due to arcing or so-called point discharge which results in severe burning of the fibrous materials.

It is readily apparent that the elimination of vacuum conditions would result in a less expensive and more manageable process as well as a process which would lend itself to continuous operation. Operating under atmospheric conditions, however, requires the use of higher voltages in order to produce an electric discharge, the high voltages, of course, producing the previously mentioned corona discharge and accompanying arcing which results in destruction of the fiber.

It is therefore an object of this invention to provide an electric ionizing discharge process for fibrous materials ICC which is carried out at atmospheric pressures utilizing a corona discharge without destructive arcing.

It is an additional object of this invention to provide a continuous electric ionizing discharge process for fibrous materials which is carried out at atmospheric conditions utilizing a corona discharge without destructive arcing.

Another object of this invention is to provide keratinous fiber materials having enhanced surface friction characteristics.

Still another object of this invention is to provide apparatus for processing fibrous materials with corona discharge.

In accordance with this invention, it has now been discovered that the textile characteristics of fibrous materials may be enhanced by subjecting the fibrous materials to a corona discharge at positive pressures, i.e., at or above atmospheric pressure, employing voltages in excess of 5 kilovolts and frequencies of at least 20 cycles per second, the fibrous materials being contained within a composite dielectric envelope while being subjected to the corona discharge. The composite dielectric envelope serves to distribute the corona discharge and prevent localized arcing and accompanying burning of the fibrous material. Apparatus for carrying out the process of this invention comprises spaced electrodes, means for applying high-voltage alternating power across said electrodes, means for supporting fibre material between said electrodes, but spaced therefrom and dielectric means disposed between said electrodes and said fibre material. The dielectric means are preferably in motion.

A better understanding of the invention may be had from a description of the drawings wherein:

FIGURE 1 is a schematic illustration of apparatus suitable for carrying out the process of this invention.

FIGURE 2 is a graph illustrating the improvements obtained in pilling resistance of corona discharge treated wool as compared with non-treated wool.

Turning to FIGURE 1, a current source 1 consisting of low voltage alternating current volts, 60 cycles per second) is fed to an audio oscillator 2. The current emanating from audio oscillator 2 is preferably maintained in the range of from 40 to volts at a frequency of 20 to 1000 cycles per second, the voltage being con veniently measured by means of voltmeter 3. After feeding the current from audio oscillator 2 into the secondary circuit of transformer 4, the voltage is increased to a range in excess of 5 kilovolts and preferably from 5 to 30 kilovolts at a frequency of 20 to 1000 cycles per second at an amperage of 1 to 20 milliam-ps (per 100 square inches), the voltage being conveniently measured by means of voltmeter 5 and the amperage being conveniently measured by means of ammeter 6. Upper electrode 7 and lower electrode 8 which are preferably stainless steel or anodized aluminium are placed in circuit with the high voltage current emanating from transformer 4. The top portion of continuous belt member 9 is then caused to pass between upper electrode member 7 and lower electrode member 8, continuous conveyer belt member 9 being supported by means of idler roll 10 and drive roll 11. A dielectric shield member 12 is disposed on either inner face of upper electrode member 7 and lower electrode member 8 and positioned so as to cause the upper portion of continuous conveyer belt member 9 to pass intermediate the upper and lower segments of dielectric shield 12. It is preferred that dielectric shield member 12 continuously progress about the upper portion of continuous conveyer belt member 9. Top or roving (or yarn or fabric as the case may be) is then fed onto continuous conveyer belt member 9 and caused to be passed between dielectric shielded upper electrode member 7 and dielectric shielded lower electrode member 8, at which point the top or roving is subjected to the corona discharge generated by the application of high voltage current to the electrode members. The residence time of the fibre material in the corona discharge is from about seconds to about minutes. Upon emerging from the corona discharge treating area, the top or roving is found to have enhanced surface friction characteristics which may be detected by improved pilling resistance in the final product. It should be understood that the dielectric shield member 12 is a composite dielectric, the unitary structure being shown in the drawing for ease of illustration. The composite dielectric is composed of two or more materials one of which is preferably an air layer.

In order to evaluate the improvements obtained by the process of this invention, pilling tests were carried out, pilling being the tendency of fibers to ball or roll up, especially where fabric is exposed to rubbing. Results of these tests are represented by FIGURE 2 of the drawing. FIGURE 2 presents results graphically by plotting vs. cycles. The ordinate gives the pilling ratio average between set a and b which are being matched against each other, a and b being defined in each case by appropriate legend in the graph. The abscissa describes the number of cycles which the samples have undergone. Each cycle represents a standard randomized amount of rubbing of a vs. 12 and includes the pills cutting operation. The ordinate, actually, is the summation, E, of the pill weight aver age ratio throughout the three or four cycles of the experiment. In FIGURE 2, four different sets of conditions are being matched against each other. All the samples are 100% wool, jersey stitch and the four conditions are: (1) Control (2) Corona discharge treated (3) Corona discharge treated and dry cleaned in trichloroethylene at 140 F. for 1 hour (4) Corona discharge treated and washed in water containing cold water wool detergent for three minutes at 120 F.

FIGURE 2 shows that 100% wool control samples pill at least three times more than 100% wool samples silent discharge treated, that the dry cleaning of the treated wool samples does not affect the corona discharge treatment and that the lukewarm water washing of the treated wool samples lowers the increase in the pilling resistance of the samples by one third. After the lukewarm water washing, the treated samples pill 2 /2 times less, or better, than the 100% wool control samples.

The process of this invention is, of course, suitable for obtaining improvements on a variety of fibrous textile materials. In addition to top or roving, yarn and fabric both woven and nonwoven may be treated. The following table designated as Table I is illustrative of the improvements obtained when treating a wool cloth for 4 minutes with a 15 kilovolt corona discharge, the wool cloth being contained in a dielectric envelope when undergoing the corona discharge treatment. The fabric was a fabric having a construction of 36 ends per inch and 27 picks per inch composed of warp yarns having 12.6 turns per inch of S twist and a woolen run count of 4.59 and fill yarns having 13.3 turns per inch of S twist and a woolen run count of 4.68.

TABLE I Breaking Strength 1 inch strip (lbs) Percent Elongation Warp 9 Fill Warp Fill Untreated 13. 7 I2. 9 32. 23 32. 88 Treated 18. 5 17. l 36. 41 34. 64

% wool worsted two ply 20s yarn, the results being given in the following table designated as Table II:

The terms elongation and breaking strength which are employed in designating certain physical characteristics in the foregoing tables may be defined as follows:

Elongation is deformation caused by a tensile force expressed in terms of the original length Breaking strength is the ability of yarns to resist rupture by means of tension.

The breaking strength is determined by using a single strand of each yarn being tested or a single one inch strip (warp cut and fill cut) of each fabric being tested in the jaws of an Instron machine. The Instron machine, which is a constant-rate-of-traverse machine, applies an increasing load to the test strand until the breakage point is reached. The average single strand breaking load is an arithmetic mean of a plurality of breaking tests.

The breaking elongation of the test strand is determined by measuring the specimen at zero load and at break and by applying the following formula:

Breaking elongation, percent:

The average breaking elongation percent is again an arithmetic mean of a plurality of breaking tests.

It should be understood that the use of a composite dielectric member is a critical feature of the apparatus of the process of this invention. If an attempt is made to carry out the process in the absence of a dielectric shield, severe arcing and burning of the fibrous materials results. The dielectric shield may be either an inorganic or an organic dielectric. Inorganic dielectric materials such a glass which are slightly conductive appear to have the greatest resistance to corona discharge. The majority of inorganic dielectrics will generally crack and fail, however, after being subjected to corona discharge for several hours. It is preferred that an organic dielectric be employed and still more preferably an organic dielectric selected from the molecularly oriented film category such as, for instance, polyethylene terephthalate and Teflon (fluoronated polymer marketed :by E. I. du Pont de Nemours and Company). Still more preferably, the dielectric is composed of alternating layers of different types Of dielectric materials. If the dielectric material is a molecularly oriented film, it is prepared so as to be composed of a plurality of layers of film having an intermediate air space of substantially lesser thickness than the film thickness. The preferred composite dielectric for purposes of this invention is composed of polyethylene terephthalate and Teflon films arranged so as to produce a stack about 50 mills high with a plurality of air spaces disposed between successive layers of film. The inner face of each electrode then has a composite dielectric disposed thereon. It is also preferred that the composite dielectric have exposed faces which are perfectly smooth and are in continuous motion so as to prevent the possibility of arcing due to a breakdown of the dielectric caused by local superheating.

While the process of this invention is suitable for processing a wide variety of fibrous textile material whether natural or synthetic, it should be understood that the process of this invention has its prime utility in the treatment of keratinous fiber textile materials. Apparently the keratinous fiber upon being subjected to a corona discharge undergoes a change in either surface characteristics or in crimp energy which thereby enhances the frictional characteristics of the fibers, a characteristic which is readily detected by improvements in pilling resistance of the finished fabrics produced from such fibers.

Having thus disclosed the invention, what is claimed is:

1. A method of processing fibrous materials comprising exposing the materials to an electrical discharge of about 5 to 30 kilovolts at positive pressures, while shielding the materials by dielectric moving relative to the fibrous materials and to the source of electrical discharge.

2. The product produced by the process of claim 1.

3. The process of claim 1 wherein said electrical discharge is an alternating current discharge having a frequency of from about 20 to 1,000 cycles per second.

4. The process of claim 1 wherein said electrical discharge has an amperage of from about 1 to 20 milliamps per 100 square inches.

5. The method of claim 1 wherein said dielectric is a composite dielectric composed of at least two different materials.

6. The method of claim 1 wherein said dielectric is a composite dielectric composed of air layers and layers of solid dielectric material.

7. A method as defined in claim 1 including the step of continuously moving the fibrous materials relative to the source of electrical discharge, and wherein the dielectric is moved continuously and transversely to the direction of movement of the fibrous materials.

8. Apparatus for processing fibrous material comprising spaced electrodes, means for applying high voltage alternating power across said electrodes, means for supporting and continuously moving fibrous material between said electrodes, dielectric means disposed between said electrodes and said fibrous materials, 'and means for moving the dielectric means relative to the fibrous materials and to the electrodes during processing.

9. Appratus as defined in claim 8 wherein said dielectric moving means includes means for continuously moving the dielectric means transversely to the direction of movement of the fibrous material.

10. Appratus as defined in claim 8 wherein said dielectric means comprises layers of solid dielectric material separated by intermediate air space.

References Cited UNITED STATES PATENTS 1,557,730 10/1925 Smith 204- X 2,683,689 7/ 1954 Nicholls 250-495 X 2,810,933 10/ 1957 Pierce et a1 204-312 X 2,977,475 3/1961 Kassenbeck 250-495 3,179,482 4/1965 Kassenbeck 250-495 X FOREIGN PATENTS 674,718 11/ 1963 Canada.

WILLIAM F. LINDQUIST, Primary Examiner.

US. Cl. X.R.

- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3, 440, 41s Dated April 22, 1969 Patent No.

Inventor(s) Carlo iazza,

It is certified that error appears in the ab ove-idexitifie d patent and that said Letters Patent are hereby corrected as shown below:

r- In the specification, Column 1, Line 37, "mitten-ails should read-- ma.terials--; Column 1, Line 38, "2, 997, 475'" should read --2, 977, 475--.

tmw Mu mm H. mm, II. I

Atteating Officer L SGHUYLER, m

. Commissioner of Patients

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