US1037469A - Process of metallizing electrotype-molds. - Google Patents

Description

- HYMAN ELI GOLDBERG, OF CHICAGO, ILLINOIS.

PROCESS METALLIZING ELECTROTYPE-MOLDS.

No Drawing,

Specification of Letters Patent. Application filed August 2, 1911. Serial No. 642,082.

Patented Sept. 3, 1912.

To all whom it may aoncem:

Be it known f that I, HYMAN ELI GOLD- BERG, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain'new and useful Process ofMetallizing Electrotype- Molds, of which the following is a specificati n,

My invention relates to 'the process of metallizing or preparing electrotype molds to make them conductive in order of the application of fine flake graphite in dry state to said mold. This process is very objectionable because the graphite fiies about in all directions to the great inconvenience of the workmen. This has been overcome by the construction of special machines which brush the graphite onto the mold, but it nevertheless remains a lengthy and delicate operation. Another method consists in the application of metallic powder, for instance, bronze, to the mold and then applying a solution like silver nitrate or some other metallic salt in order to cause it to take. This process is not used much in practice on account of its inconveniences. There are other processes, namely, the treatment with silver nitrate and phosphorous, and the treatment'with silver nitrate and sulfureted hydrogen. These methods are inconvenient and laborious and require considerable time, and frequently unless the work is very carefully done the results are imperfect and unsatisfactory.

The object of my invention is to simplify, cheapen and improve the so-called process of metallizing and is accomplished in the following manner I first prepare a solution of a conductive solid in colloidal form in a volatile liquid, then apply this solution to the non conductive mold and finally dry the mold, thereby evaporating the solvent and causing the conductive substance to be deposited on the non conductive mold. Among the properties of colloidal metals is the one that upon evaporation of their solvent they become non colloidal orinsoluble. In process the metal is, therefore, deposited uponthe mold in a coherent, continuous, insoluble, electrically,

conductive layer. Among the conducting solids which I employ for the preparation of the colloidal solution maybe-gold, silver, or graphite, et cetera, but I prefer copper. Among the solvents for the solids are water, alcohol, ether, glycerin, acetone, etcetera.

One method of obtaining cop er and other metals in colloidal form is to orm a direct current arc under waterbetween terminals consisting of the metal to be rendered colloidal. Other methods are explained by Theo. Svedberg in his published book upon the subject, entitled H erstellung Kolloz'der Loesungen Anorgam'scher Stojfe, 1909 edition, published by Theodore Steinkopff, Dresden, Germany. He describes methods applicable to organic solvents such as alcohol, ether, glycerin and acetone and the method consists in forming an alternating current are in the liquid andintroducing the metal, for example, silver or copper, in finely divided form, for example, small pieces of foil or thin sheets. The various processes are listed in the index at the end of the book, for instance, those relating. to copper are'listed on page 506.

It is the common practice to employ wax asthe substance for making the electrotype mold. It will be found generally that a water colloidal solution will not wet wax readily. This objection may be avoided by treating the mold previously to the application of the colloidal solution, with alcohol or similar liquid. I greatly prefer, however,

to avoid the necessity for this alcohol pretreatment by employing as the solvent one which has a greater attraction for wax than water, and as such solvent I- prefer ether. Another advantage in employing other as a solvent is that whereas a colloidal solution of copper in water spoils very readily by the oxidation of the copper such oxidation occurs very slowly in ether. Copper, of course, is an excellent conductor, and furthermore, copper is the metal usually employed in electrotyping and consequently by employing copper for the metallizing substance I -avoid mixing metals. Therefore, for all of these reasons I greatly prefer on the whole to use a colloidal solution of copper dissolved in ether.

' Of course electrotype molds areordinarily prepared from wax, but it is well known that galvano plastic molds are made from other substances also, for instance, gutta percha, plaster of Paris, et cetera. The liquid that I use for a solvent depends upon the composition of the mold. For a mold of gutta ercha I employ benzol as a solvent, for I find that a solution prepared from this as'la solvent readily'wets a gutta percha m0 d.

I find that in practice in using ether as a solvent'the operator has to be ve rapid in his work on account of the rapidity of evaporation of the ether. Moreover, the ether if too thickly applied makes the wax rather soft. For both of these reasons I sometimes use. a mixture of ether and alcohol instead of ether alone.

In practicing my method I sometimes pour the colloidal solution onto the mold and thus form a layer upon it or again sometimes apply it with a brush or sometimes di the mold completely in the coll'oidal so ution.

Having thus described my invention,

what v I claim as new, and desire to secur by Letters Patent, is:

1. The herein described process of producing an electrically conductive layer upon ting the said solvent to evaporate.

. 2. The herein described process of producmg an electrically conductive layer upon a surface, such as a mold, which consists in first applying to the mold surface a colloidal solution of a metal in-a volatilesolvent and then permitting the said solvent to evaporate.

In witness whereof, I have hereunto subscribed my name in the presence of two witnessesl HOWARD M. Cox, MARGARET D. R033.