US2140498A - Flotation coating process - Google Patents

Description

Dec. 2,0, 1938. J. F. DREYER FLOTTION COATING PROCES S Filed oct. 1,. 1934 wmmm SS @ml @QZ/Mu@ mental Dee. zo, 193s- FLOTATION COATING PROCESS John F.I Dreyer, Cincinnati, Ohio, assignor to The Formica Insulation Company, Cincinnati, Ohio, a corporation of Ohio lApplication october 1, 1934, serial No. 746,449

4 Claims.

This invention relates particularly to an improved method for treating a strip of fabric, such as, paper, with suitable resins so that the strip may later be incorporated in a laminated sheet,

if desired. The primary object of the invention is to provide an improved method of producing a decorative coating on a strip of fabric by means of a flotation process. f

A further object of the invention is to enable the flotation process to be practiced on strips which have been previously treated with a watermiscible resin, or are to receive subsequent coatings of such a resin.

Heretofore, in practicing the flotation process to decorate a strip, a binder such as gum, soap, wax, oxidizable oil, resin, or other adhesive, has been used to hold the pigments on the surface of the body of water. These binders have been found to be incompatible with water-miscible resins, such as the urea resins. Another diiculty was in the fact that the binder could not be removed, and subsequent heat treatments precluded the use of certain pigments and, in some cases, produced an undesirable color due to the voxidationof the binder.

In the present invention, a binder is not used, but the pigments are suspended in a vehicle Asuch as a solvent, and the water-vimmiscible portions of the vehicle are volatile so that the vehicle may be removed, leaving the pigment to be picked up by the fabric from the lm on top of the water. After the strip has been dried to remove the Water and volatile portions of the vehicle, the strip may be dipped in any desirable resin, such as ureaing treatment, it is ready to be consolidated with other sheets under heat and pressure in the Wellknown manner.

In many cases it is desirable to size the fabric, or strip of paper, with a resin prior to its being dipped in the water in the flotation tank. The resin sizing greatly increases the strength of the paper which otherwise would be so weak as a resuit of wetting that itmight pull apart or tear. It is desirable to use a urea-formaldehyde for this purpose, in some cases, but due to the watermiscibility of such a resin, it has been found to absorb too much water and not suinciently increase the strength of the strip while wet. This diillculty has been overcome by adding to the paper saturating varnish or sizing a small portion, that is, about 1% by-weight, of the resin, of

a water-repelling material, such as stearic acid.

Other possible materials are oleic acid, calcium stearate, or capryl alcohol. This material lowers formaldehyde, and after undergoing another drythe surface tension and on treating the paper, concentrates at the surface. It may be incorporated in the impregnating varnish by dissolving it in a mutual solvent, such as ethyl cellosolve. .While the water-repelling surface thus acquired is obtained by the use of a small impurity, the amount is so small that the impurity does not effect subsequent treatments. InA the Aotation process, paper so treated has good adhesion for 4pigment and repels the water. `It is not critical to vibration in the tank and makes an excellent material for subsequent laminating treatment.

An apparatus for practicing the present invention is illustrated diagrammatically in the accompanying drawing, in which A designates an inclined flotation tank; B, a strip of fabric being dipped in the tank to pick up a color film; and C, a drying oven in which the water and volatile portions of the paint film are driven off.

Water is admitted to the flotation tank A from a water storage tank IU through a valve II. The Water flows to the left, as indicated by the arrow, and over a dam I2 where it is pumped back to the storage tank by means of a centrifugal pump I3. 'I'he pigment-laden vehicle or solvent is spread onto the water surface by means lof a color distributor I4 and the lm floats down through a comb disturber I5 which may be movable and serves to break up islands of the paint and cause a swirling of the colors. If desired, a submerged disturber I6, which may be stationary or power driven, is provided to agitate the water surface as it approaches the paper strip. Thus, it will be understood that the film on the surface of the Water is brought in contact with the strip which picks it up as it passes on to the drying oven C. After the water passes the paper strip, it is acted upon by a concentrator skimmer I'l which .brushes the paint on the surface of the water, which was not picked up by the strip, into the skimmer I8. By employing the skimmer, the water may be used over and over.

If desired, the paper Istrip may pass directlyv from the sizing bath to the iiotation tank, but preferably it is stored in a roll I9 from which it is led down under a dipping roller and up over guide rollers 2| to a storage roll 23.

It is not necessary that the strip travel in the same direction as the water nor is it necessary that it travel at the same speed. However, it has v been found that a satisfactory rate of flow for the water may be about 11 feet per minute and a good design is obtained when the paper travels about 5% slower than the water surface. As stated above, thewater may be pure or treated,

untreated water being commonly used, If the Water be heated, the evaporation of the volatile portions of the pigment vehicle is speeded up and when the strip has been treated with a ureaformaldehyde resin, the adhesion of the pigment is improved. When vinylite resin has been used,

it was found that its viscosity was lowered when passed through warm water.

In practicing the present invention, tangential contact of the strip and the frame is unnecessary and preferably the initial contact is perpendicu-y lar to the surface of the water. Usually the paper is passed about an inch and a half below the surface of the Water.

'I'he solvent or combination of solvents which form the vehicle for the pigments should be such that they will wet the pigment and also be waterrepelling. In some cases it is desirable `to keep the pigment wet with solvent for a long time and in that case, of course, a slow evaporating solvent mixture may be used. In general, it is desirable to remove most of the -solvent before the film is picked up off the water by the strip.: The pigment film can be crowded into a tenacious film which can be broken into cracks, veins, or islands with sharp edges, in this manner. Several colors can be used and they may be blended together by throwing them al1 on the same place on the wa,- ter atthe same time or mixing them before they are deposited on the water.

It has been found that the specific gravity of the solvent pigment mix may be even greater than that of the water due to the water repulsion or surface tension effect and the color will remain on the surface if the drops are not too large.

'Various solvents having different spreading characteristics may be used, depending on the character of the design desired. Solvents of the hydrocarbon type such as petroleum hydrocarbons, coal tar hydrocarbons, water-repelling acetates, as ethyl acetate and butyl acetate, butanol, diethyl phthalate, furfural, ethylene dichloride,

`dibutyl phthalate, carbon tetrachloride, butyl lactate, amyl alcohol, etc., can be used alone or in combination. l

When the colors are to be blended or shaded into one another, it is desirable to use slow evaporating solvents, such as toluol or xylol. Ii. round drops are required, naphtha may be used alone, or if more spreading is desired, ethyl cellosolve may be added or benzol substituted.

Many pigments may be used in the present fiotation process which have heretofore not been considered possible. Metallic powders can be used in place of pigments and pigments of the sulde or'oxide type will work very well.

With any given mix, twelve or so distinctly different configurations can be obtained, depending only on how much color is used, how the color is placed on the water, and how it is subsequently removed. An example of a good mix is zinc sulfide pigment, 30 parts; ethyl acetate, 30 parts; and petro benzol, 15 parts.;

The term solventx it is not intended to be understood as meaning that the pigments are necessarily dissolved in the solvents, as more often they are insoluble and suspended in the vehicle by a grinding or mixinglprocess. 'The term binder-free is meant to imply that the pigment-supporting vehicle does not contain color binders such as gum, wax, oxidizable oil, resin or other adhesives. y

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims shouldbe construed as "broadly as permissible, in view of the prior art. e

` What Iclaim as new, and desire to secure by Letters Patent, is:

1. A process of decorating fabric which comprises: supporting insoluble metallic pigments on an aqueous body through the medium of a film consisting essentially of a volatile liquid which will wet'said pigments and make them waterrepellent and causing the fabric to contact with and pick up the pigment.v f

2. A process of decorating fabric which comprises: supporting lon an aqueous body a illm comprising about 30 parts of zinc sulfide pigmentl l 30 parts of ethyl acetate, and 15 parts of petro benzol; and causing the fabric to contact with and pick up portions of said lm.

,3. A'process of decorating fabric which compriseszisupporting a lm of insoluble pigment on an aqueous body through the medium of a film consisting essentially of a volatile liquid which will wet the pigment and make it water-repellent; and causing the fabric to contact with and pickup the pigment. 4. A process as specified in claim 3, in which the volatile film is a solvent selected from a group consisting of: butanol, benzine, dieth'yl, phthalate, furfural, ethylenedichloride, dibutyl phthalate, carbon tetrachloride, butyl lactate, amyl alcohol, naphtha, toluol, xylol, ethyl acetate, and butyl-acetate.

JOHN F. DREYER.

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