US2378598A - Method of coating - Google Patents

Description

June 19, 1945 H. J. THIELKER METHOD OF COATING Filed Sept. 16, 1942 &

INVENTOR 'H. J. TH/ELKER vuonav.

ATTORNEY Patented June 19, 1945 \PATENT OFFICE 2.378.598 METHOD or COATING I Henry J. Thielker, New York, N. Y., assignor to Western Electric Company, Incorporated, New

York, N. Y., a corporation of New York Application September 18, 1942, Serial No. 458.505

3 Claims. Cl. 117-103) This'invention relates to a'method of coating, and more particularly to a method of coating non-metallic articles having a rough surface, to create or restore a smooth surface thereon.

In the operation and maintenance of tele- '5 phone apparatus it is found that those receiver and handset casings, for example, which are molded shells of phenol-formaldehyde condensation resins, may under certain conditions in time come to have their smooth outer surfaces etched into dull roughness by the natural exudations of the hands of the users. The original polish of the surface of such an article derives from its having been molded against the highly polished surface of a hot metal mold. When paint or enamel does not, in most cases at least, 0

have sumcient adhesion to the artificial resins, of which not only some telephone receiver and handset housings are made but also other articles of innumerable variety, and subject also to abrasive or corrosive wear.

'An object of the invention is to provide a method of coating articles and especially nonmetallic articles of molded artificial resin with a coating to provide originally or to restore a ployed for the restoring of a polished outer surface to the phenol-formaldehyde resin molded ,casings or housings of telephone receivers which havebecome matt or even pitted by abrasion, corrosion or both, in use. It will be remembered, however, that there is only one specific illustrative case of use of the invention among aninnumerable number of analogous cases, as will be hereinafter indicated.

- In carrying out the invention, as herein illustratively disclosed, there is employed a particular composition of matter. The particular telephone parts in question are moldings of a mixture comprising primarily a phenol-formaldehyde condensation resin, e. g. Bakelite, "Catalin or the like commercially named material, in fully and irreversibly condensed solid form. To coat these abraded or corroded articles, there is employed a commercially avail material. This is a clear, substantially colorless,

sirupy liquid primarily intended for molding by casting in hot molds without pressure, and which will stay in. storage at ordinary temperatures (say not over F.) substantially unchanged for a considerable length of time (say six months) but which when heated to about -180 R, will become completely condensed into a solid, irreversible resin. In practise, the time required smooth surface to such articles having a matt, so for this final condensation is shortened if a suitroughened or even indented or pitted surface.

With the above and other objects in view, the invention may be embodied in particular steps-of suitably cleaning the surface of an article to be treated, preparing a solution of a partially condensed artificial resin condensation product in a volatile solvent, coating the cleaned article with the coating material so prepared, and heating the coated article to both drive off the solvent and complete the condensation of the resin on the surface.

Other objects and features will appear from the following detailed description of one embodiment of the invention taken in connection with the accompanying drawing, in which the same reference numerals are applied to identical parts in the several figures and in which Fig. l is a diagrammatic view in perspective of the essentials of a tumbling barrel employable in carrying out the method of the invention;

Fig. 2 is a partial sectional view of a modified form thereof taken on the line 2-2 of Fig. 1; and

Fig. 3 is a perspective view of one of the tumbling pegs employed in the barrel.

The invention will be herein disclosed as emable proportion of an accelerator such as hydrochloric acid is added thereto.

One such product is commercially known as Catabond 200 CZ and is manufactured for sale 35 by the Catalin Corporation of New York City.

For applicant's, present purpose a mixture is made up substantially as follows:

Coating mixture I Catabond 200 CZ a; grams 170 Alcohol (ethyl, 95%) cubic centimeters 96 Hydrochloric acid (35%) do 9 This mixture is rendered. sufficiently thin and 4 flowableat ordinary temperatures by the alcohereinafter described for from thirty to ninety minutes at a temperature preferably about F. at first and rising to about F. toward the v I end of the heating period, when the alcohol and water will have been wholly driven off together with the hydrogen chloride gas or the ammonium 55 chloride formed, and the coating will have set panying drawing, only those elements being shown which are essential for an understanding of the particular procedure involved. In this preferred procedure, the articles are (1) Washed thoroughly, e. g. in soap and water, and rinsed,

(2) Degreased, e. g with carbon tetrachloride liquid or vapor,

(3) Charged into a tumbling barrel with a suitable amount of the above described mixture of Catabond 200 CZ, alcohol and hydrochloric acid and with a suitable volume of waxed tumbling pegs, and the charging apertures of the barrel closed with impervious doors,

(4) Tumbled at room temperature for ten to fifteen minutes,

(5) Tumbled at about 140 F. for. about thirty minutes, and V v (6) Tumbled for about sixty minutes with the heat supply cut off and with multiperforate doors substituted for the impervious doors.

Articles of almost any artificial resin, of vulcanized hard rubber, of hard fiber, of wood, or of other generally analogous, not principally metallic material, after being subjected to the above procedure, are found to have a complete, remarkably strongly adherent and highly polished coating.

During th fifth step above, of tumbling at 140 F. with the barrel loading apertures closed with impervious doors, the further condensation of the partially condensed resin in the raw coating begins, but proceeds slowly enough so that the volatil solvent may be driven off without producing permanent pits r bubbles in the gradually hardening material, whose liquidity and surface tension remain sufiicient to keep the surface of the coating smooth until the major portion, perhaps substantially all of the solvent has been driven out. With the impervious doors, the solvent vapors remain in the barrel and increase in density, so that the rapidity with which the solvent leaves the coating and hence the tendency to produce bubbles diminish as the material of the coating thickens and becomes'more liable to bubble damage. By the end of the thirty minutes of this step there is not enough solvent left in the partially hard ened coating to do any damage by its evaporation. The temperature is raised then for the sixth step to hasten the final setting of the coating, and the impervious doors are replaced by the easily pervious screen doors to allow the solvent vapors to escape and thus lower the vapor pressure of the solvent in the barrel to let the last traces of solvent be driven out of the coating freely.

As indicated in the drawing, the tumbling barrel, generally indicated at Ill, may be a hollow, horizontal, polygonal prism of wood or other suitable material, journalled as indicated at H to be rotatably driven by means (not shown) about its horizontal axis. One side, l2, or two opposite sides I2. and I3 have suitable loading apertures l4, ll, which may be closed by removable solid doors IE or by doors H (Fig. 2) having large apertures therein covered with amount.

woven wire screens It. The pegs ll, of which one of suitable form is shown on an enlarged scale in Fig. 3, are preferably of hard wood, e. g. maple, having the form shown in Fig. 3, although the particular form and material are not critical, so long as the pegs are somewhat porous and can be impregnated with waxy material, e. g. paraffin, to prevent the coating material from adhering to them in any .substantial For providing heat, the barrel may also be furnished with one or more longitudinally disposed elements 18 which may be heated by' any suitable means (not shown), e. g. electrically or by circulation of hot liquid or vapor through them.

If a less highly polished but smooth surface be desired, a commercial product consisting essentially of the same sirupy, partially condensed phenol-formaldehyde compound, but containing about thirty per cent (30%) by weight of a mineral filler in highly divided form, may be employed to make a suitable coating mixture. A satisfactorily partially condensed resin plus mineral filler is the product manufactured by the Catalin Corporation for sale under the commercial name of Catabond 3C," which is the same material above described and designated Catabond 200 CZ with about thirty percent (30%) of mineral filler added. A suitable coating mixture may be as follows:

Coating mixture 11 Catabond 3C grams 1'70 Alcohol (as above) oubic centimeters 19 Hydrochloric acid (as above) do 9 This mixture applied in a tumbling barrel as above described, produces a hard, smooth, remarkably strongly adherent coating, similar to that produced by the first mixture described,

but distinctly less shiny although by no means dully matt.

By adding two grams of aluminum stearate to the last mixture above, the coatings obtained will be definitely flat or matt. The mixture will then be Coating mixture III Catabond 3C grams 170 Alcohol (as above) cubic centimeters l9 Hydrochloric acid (as above) do 9 Aluminum stearate grams 2 Any of the coating compositions above definal coating is to have the remarkably firm adhesion to an under body of artificial resin, hard rubber, hard fiber, Wood or the like materials. which is characteristic of the coatings of the invention. The mixtures and procedures described do not, however, produce satisfactorily adherent coatings on metallic surfaces unless these are pre-coated in such a way as to be no longer characteristically metallic. The invention has been described and illustrated particularly in connection with articles of phenol-formaldehyde resin. It has not been tried out on all the vast variety of new thermosetting molding plastics which have been and are right along appearing in use. It will not, in general, be

applicable in the case of articles made of the, thermoplastic resins such as the polymerization products of vinylidene, butylene and the like. However, it is believed tobe applicable to articles made of any of the thermosetting compositions based on condensation products of phenol, cresol, and the like with formaldehyde, acetaldehyde, urea, furfural, glyptal and the like. Other volatile solvents besides ethyl alcohol, e. g. acetone, may be used in appropriate cases and other accel erators than hydrochloric acid, e. g. phosphoric acid or a suitable acid salt, although hydrochloric acid is preferable.

What is claimed is:

1. The method of coating the entire suitably clean outer non-metallic surface of articles which comprises steps of charging into a tumbling bar-. rel provided with means to render a wall portion thereof pervious or impervious at will, the articles to be coated and a supply of waxed tumbling pegs together with a proportion of a raw coating composition containing a partially condensed condensation resin in liquid form and a volatile solvent therefor and an accelerator, tumbling the contents of the barrel therein at room temperature to coat the outer surface of the articles completely with the composition, continuing the tumbling of the contents of the barrel therein while heating the interior thereof to a temperature at which the volatile solvent is removed in major part before the condensation of the partially condensed resin has progressed materially, the walls of the barrel being wholly impervious during this step to prevent escape of the vapors of the evaporated solvent from the neighborhood of the coated surfaces of the articles to thereby aid in slackening the rate of escape of the solvent from the coated surfaces of the articles, rendering a wall portion of the barrel pervious, and continuing the tumbling of the contents of the barrel therein while heating the interior thereof to a higher temperature to complete the condensation of the resin and to remove substantially all of the solvent, the barrel being provided with a pervious wall portion during this step to release the entrapped vapors of the evaporated solvent from the neighborhood of the coated surfaces of the article to thereby promote the escape of the last traces of solvent from the heated coatings.

2. The method of coating the entire suitably clean outer non-metallic surface of articles which comprises steps of charging into a. tumbling barrel provided with means to render a wall portion thereof pervious orimpervious at will; the articles to be coated and a supply of waxed tumbling pegs together with a proportion of a raw coating com-' position containing a partially condensed phenolformaldehyde resin in liquid form and alcohol and-hydrochloric acid, tumbling the contents of the barrel therein at room temperature to coat the outer. surface of the articles completely with the composition, continuing the tumbling of the contents of the barrel therein while heating the interior thereof to a temperature at which the alcohol is removed in major part before the condensation of the partially condensed resin has progressed materially, the walls of the barrel being wholly impervious during this step to prevent escape of the vapors of the evaporated alcohol from the'neighborhood of the coated surfaces of the articles to thereby aid in slackening the rate of escape of the alcohol from the coated surfaces of the articles, rendering a wall portion of the barrel pervious, and continuing the tumbling of the contents of the barrel therein while heating the interiorthereof to a higher temperature to complete the condensation of the resin and to "remove substantially all of the alcohol, the barrel being provided with a pervious wall portion during this step to release the entrapped vapors of the evaporated alcohol from the neighborhood of the coated surfaces of the articles to thereby promote the escape of the last traces of alcohol, from the heated coatings.

3. The method of coating the entire suitably clean outer non-metallic surface of articles which comprises steps of charging into a tumbling 'barrel provided with means to render a wall portion thereof pervious or impervious at will, the articles to be coated and a supply of waxed tumbling pegs together with a proportion of a raw coating composition containing a partially condensed phenolformaldehyde resin in liquid form and alcohol and hydrochloric acid, tumbling the contents of the barrel therein at room temperature to coat the outer surface of the articles completely with the composition, continuing the tumbling of the contents of the barrel therein while heating the interior thereof to a temperature of about I".

higher temperature of about 1'10 F. to complete the condensation of the resin and to remove substantially all of the alcohol, the barrel being provided with a pervious wall portion during this step. to release the entrapped vapors of the evaporated alcohol from the neighborhood of the coated surfaces of the articles to thereby promote the escape of the last traces of alcoholfrom the heated coatings.

HENRY J, :Ilm zen-

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