US2456650A - Method of coating filaments - Google Patents

Description

Dec. 21, 1948. A, O, RYAN 2,456,650

METHOD OF COATING FILAMENTS Filed 001,. 20, 1944 .a4 500750 INVENToR.

v as awire.

Patented Dec. 21, A1948 UNITED STATES PATENT ort-'Ica na'rnop or cosmo mamas Com Ins. Norwalk, Conn., a corporation of Application October 2o. 1044, Serial No. 550,497

and improved methods for forming a continuous coating, such as insulation, about a filament, such Another object of this invention is .to provide a method for coating wire, which assures a true centering of the wire within the coating so formed.

More speciiically, my invention is directed to methods whereby a stream of coating material is; discharged about .the filament to be coated, into a second confining stream, which in some cases may function as a solidifying or coagulative material, moving with viscous flow in a restricted passage, so that as the filament, coating material, and confining material move along. the coating material gradually becomes solidied or coagulated and coats the enclosed illament.

Other objects and advantages of the present invention will appear from .the following description of and examples thereof, illustrated in the accompanying drawings, lin which:l

Fig. 1 is a vertical cross-sectional diagrammatic view of a portion of apparatus adapted for use in carrying out my improved method, with other apparatus indicated diagrammatically. of a Preferred form of arrangement in'accordance with the present invention.

Fig. 2 is an enlarged vertical cross-sectional 35 view of a portion of the apparatus illustrated in Fig. l.

The apparatus for carrying out my method and 'shown by way of example in the drawings may consist of a hollow cylindrical tube II having a 40 relatively long section of small internal diameter, and a short section on one end of relatively greater internal diameter. In the form of invention shown, this tube is preferably mounted vertically.

with the larger section on top. Within the larger 45 section of the tube il is mounted a second hollow 'tube l2 having 4a discharge nozzle Il arranged at 4that portion of the tube il `where the latter is changing to a'v smaller diameter.- In actual practice the position of this nozzle may be at any point (Claims. e (C1. 117-115) l! through the smaller diameter section of the tube Il, and may be guided therefrom by means such as rollers Il. The liquid carrier Il for the coating material is fed into the top of the. tube Il, as from a source 2l, and flows downwardly 'through .the tube. The coating material!! is fed into the inner tube l2 and passes downwardly, outwardly through the nozzle I4 about the filament il. A source of coating material Il will be connected to the tube i2. I

The carrier liquid i8, after passing through 'the lower end of the tube III, may be collected in a sump 2l for re-use. A pump 28 may be used to return this material to the source 20 and, if the action to be described in more detail later involves the use of a heated carrier liquid, a heater may la): interposed between the pump 28 and the source While the filament Il, to be coated, may be generally kept under suitable tension over the rollers. if this filament is awire it is necessary that it be maintained free of bends or kinks, and it must be suitably centered. Within the tube l2 there may, therefore, be provided centering spiders 32 to effect this result.

The actual method followed in carrying out the present invention is substantially the saine as that used and described in my co-pending application, previously identified. For example, if it is desired to coat the iilament l0 witha coagulable material such as latex, liquid latex will be used as the coating material while heated slycerine may be used inside the smaller capillary tube, so long as the l conditions suitable for viscous flow are attained.

A filament to be coated passes through' an opening in thetop of the smaller tube i2, passes outl wax-diy through the nozzle Ilandthen downwardlineal vspeed of the filament must be by as the conilning and carrying fluid. Both the latex and glycerine are fed into their respective tubes at such pressures that the discharge speed of the latex from the nomle I4 is identical with the speed of flow of the glycerine in contact with the latex at this'discharge point, and Vthe speed of both .of the materials at their interface is preferably identical with the speed of movement of the iliament to be covered when .the flow results from the hydraulic pressure above. The speeds are all so related to the vlscoslties of the materialsusedand the size of the filament; outer diameter of the latex andthe inside diameter of the capillary tube il to bring about a condition known as streamline or viscous ilow. Under all conditions the glycerine surrounding the latex will drag along the inner surface of the tube while at the interface of the glycerine and the latex the speed of each will be identical. When the speedvof the lilament is greater than the maximum speed in the latex due to hydraulic pressure, it produces a drag on the latex whichwill increase the rate of flow. The

`atives, waxes, or any other mixtures.

catasto conditions to insure that viscous flow results. Under ail the above conditions the glycerine will support and confine the latex to a definite size andl shape by acting as a lubricating, mobile, confining wall and on moving downward through the tube i.. the' latex will gradually become coagulated about the filament, forming the coating 22' indicated in Fig. 2. 'I'he coated lament is then drawn of! over the rollers M and subjected to any further necessary treatment, while the glycerine, discharged into the sump 28, may be pumped back i'or re-use.

Instead of using glycerine to coagulate the latex bythe combined action of temperature and dehydration, the latex may be coagulated chemically by discharging a stream of alkaline-stabilized latex into a stream of an aqueous external fluid of low pH. The external stream could be a solution containing buffer salts such as magnesium sulphate, zinc-ammonium sulphate, and the like, or'an acid solution such as acetic acid, formic acid, and the like. In all cases, however, the shape of the coating to be formed is maintained by the equilibrium forces of the viscous flow.

It is to be pointed out that the invention is applicable to the coating of a wide variety of filaments with a wide variety of' material. For example, the filament may be a single or multiple strand of metallic wire, a single or multiple thread of any suitable textile material, a single or multiple thread of natural or synthetic rubber, resins, plastics or fiberglas, or, in fact, any i'llamentary substance which can be used with a minimum of tension.

If, for example. the invention is used to coat a solid or stranded copper wire, the-coagulable or solidifiable coating material may be emulsions or dispersions of plasticized vinyl-acetate-vinyl chloride copolymers, plasticized polystyrene, polyethylene or other mixtures. The confining liquid carrier in such cases will be material used to dewhich comprises causing a stream of a confining and supporting liquid to flow through a confining space at such a speed that the liquidfiows throughl said space under conditions of viscous flow. discharging under pressure 'a continuous annular stream oi a soiidinable liquid coating material about a continuous axially moving filament, introducing the moving diament and surrounding liquid coating. material into the center of said viscously owing confining liquid stream at substantially the same speed and in` the same direction as the center of said stream, continuing the movement of said filament and surrounding coating liquid along with said stream oi' viscously flow'- ing confining liquid at substantially the same speed while causing the coating material to solidify, whereby said stream of viscously fiowlng confining liquid supports and holds the liquid coating material in shape during movement thereof through said space, and then withdrawing the filament and the surrounding solidified coating material from said confining liquid in the form of a coated filament. y

2. The method offorming a coated filament which comprises causing a stream of a solidifying liquid to flow through a relatively small tube at such a speed that the liquid flows through the tube I under the conditions of viscous fiow, discharging under pressure a continuous annular liquid stream of a solidifiable coating material about a continuous axially moving filament, introducing the moving filament and surrounding liquid coating material into the center of said stream of solidifying viscously iiowing liquid-at substantistabilize the emulsion, or to changethe liquid coating into a solid coating by any suitable chemical or physical change required.

The invention is equally applicable to the coating of threads or cords with natural or synthetic rubber, natural or synthetic resin,` cellulose deriv- Likewise, the original filament may be a copper wire which may then be coated with suitable asphaltic materials, waxes, paints or lacquers.

Another use for the present invention, involving the principles outlined above, is in the forma tion of small hollow filaments. This merely involves the coating, by the aforedescribedy method, of a central filament with, however, a material which does not adhere to this filament. the coating has been applied in any one of the manners described above, the core may then ybe removed, leaving ahollow fllamentarystructure.

Accordingly, while I have, for the purposes of illustration, described one particular form of ap paratus for carrying out my invention, I have indicated several examples of the manner in which the principles according to this invention After ally the same speed and in the same direction as the center of said stream of solidifying liquid, continuing the movement of said filament and surrounding coating liquid along with said stream of viscously flowing confining liquid at substan- `tially the same speed while causing the coating material to solidify, whereby said stream of viscously flowing confining liquid supports and holds the coating material in shape during solidifying thereof, and then withdrawing the filament and the surrounding solidified coating material from said solidifying liquid in the form of a coated filament.

3. 'Ihe method of forming a coated filament which comprises causing a-stream of a solidifying liquid to flow through a relatively small tube at such a speed that the liquid ows through thetube under the conditions of viscous flow, creating a temperature difference between said solidifying liquid and a temperature-solidifiable liquid coating material, discharging a continuous annular liquid stream of said coating material about a continuousaxially moving filament, introducing the moving filament and surrounding coating material into the center of said stream of solidifying viscously flowing liquid at substantially the same speed and in the same direction as the center of said stream of solidifying liquid, continuing the movement of said filament and surrounding coating material along with said stream of viscously flowing confining liquid at substantially the same speed while said coating material solidifies, whereby said stream of viscously flowing confining liquid supports and holds the coating material in shape during solidifying thereof', and then withdrawing the filament and the surrounding solidified coating material from said solidifying liquid in the form of a coated filament.

4. The method of forming a coated filament which comprises causing a stream of a solidifying liquid heated to a temperature sufficient to solidiiya coating material to now through a relatively small tube at such a speed that the liquid iiows in the vtube with viscous ilow, discharging y a continuous annular liquid stream oi a thermosetting coating material about a continuous axially moving iilament. introducing the moving iliament and surrounding coating material into the center oi the stream of heated solidiiying liquid at substantially the same speed and in the same direction as said soliditying liquid, whereby said stream of solidifying liquid supports and holds said coating material in shape during movement thereof through said tube, and said coated material is hardened while supported by the heated solidifying liquid and then' withdrawing the lila? ter of the stream ol glycerine and at substantially the same speed and in the same direction as the center, of said stream ot glycerine. whereby said stream oi glycerine supports and holds the coating of liquid latex in shape during movement thereof through said tube. and the latex is coagulated while so supported. and then withdrawing the illament and the surrounding coating ot coagulated latex from the glycerine in the form o! a coated iilament.

s. The nieuwe of forming a latex como mny ment which comprises causing a stream of a buter solution having a pH sumciently low to agglomerate latex to iiow through a relatively small tube at such a speed that the solution iiows in the tube with viscous i'iow, discharging a continuous annular stream oialkaline liquid latex about a continuous axially moving filament, introducing the moving mament and surrounding liquid latex into the center of the stream of buii'er solution and at substantially the same speed and in the same direction of iiow as the center of said stream, whereby said stream" of buffer solution supports and holds the latex coating material in shape during movement thereof through said tube and said latex is agglomerated by the buffer solution while so supported. and then withdrawing the filament and the surrounding agglomerated latex from said builer solution in the form of a coated filament.

v ALBERT 0. RYAN.

REFERENCES CITED The following references oi record in the tile oi' this patent:

, UNITED STATES PATENTS Number Name .Date 827,434 Friedrich July 31, 1906 1,590,008 Taylor -i June 29, 1920 1,654,253 Henderson Dec. 27, 1927 2,082,309 Bleibler Dec.- 1. 1936 2,127,413 Leguillon Aug. 10, 1938 2.155.403 (look Apr. 35. 1989 2,288,821 Arber Hay 19, 1942 2.208.982 Waterman et al. July '1, 1943 2,327,638 Harrison Aug. 24. 1943 '2,330,370 Miller Sept. 28, 1943 Ryan June 25,. i946

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