US2236118A - Method of coating molds and product thereof - Google Patents

Description

Patented Mar. 25, 1941 PATENT" OFFICE METHOD or COATING MOLDS AND rnonoc'r 'rnnnnor Charles W. Swartout, Kenmore, N. Y., assignor to The Linde Air Products Company, a. corporation of Ohio No Drawing. Application September 30, 1939, Serial No. 297,363

16 Claims. (01. 22-192) The invention relates to mold coating, and more specifically to the formation of carbonaceous films on mold surfaces. It is particularly concerned with improved carbon film coatings for molds, and a new method of applying or depositing such films from a smoky'fiame of acetylene or other hydrocarbon materials.

The need for, and the advantages of, a protective coating over a mold surface in contact.

with a cast material has long been recognized in the metal and other arts employing casting and molding processes, and a great variety of substances and compositions have been proposed forthis purpose. Carbon in various forms, either alone or in admixture with other materials, has been of prominent use for mold coating purposes, and deposition of carbon films by applying smoky flames of acetylene or other hydrocarbons has produced very satisfactory results in many industries. The finely divided soot particles so deposited form a dense and uniform film which produces a better finish on the molded article, and the improved heat insulating characteristics of such coating maintain a better fluid flow of molten material to all parts of the mold, with improvement in the casting form and detail. These and other. advantages known to the art have established substantial value and importance in mold coatings formed by acetylene smoking. I

It is an object of the present invention to provide further improvements in mold coatings formed by smoking, which will promote and increase the value and use of such coatings in the casting art. A further object is to provide improvements in the method of depositing a carbon.

film coating by incomplete combustion of acetylene or other smoke producing gases, whereby the coating has greater adhesion to the mold surface with increased permanency and durability. Another object is to improve the toughness and permanency of the carbon film, thereby economically providing a more uniformly satisfactory finish on casting surfaces.

In accordance with this invention it is proposed to use in conjunction with the carbon depositing flame a material adapted to supply an increased binding action or adhesion of the carbon film to the mold surface. I have found that the vapors of certain organic liquids intimately mixed with acetylene or other smoke producing gases, will upon partial combustion in the flame impart to the deposited carbon particles a greater binding action, productive of a tougher and more durable coating. Suitable chemicals for this purpose should be of volatile nature, or have a fairly high vapor pressure at ordina y room temperatures, in order that they may be readily mixed .in vapor phase with the smoke producing gas. A wide selection of materials is thus presented which will provide the required binding action when burned in a flame. Of many compounds found suitable by test, certain aldehydes and ketones have proven especially effective. Representative of these are compounds such as octylaldehyde, crotonaldehyde, dicrotonaldehyde and di-isobutyl ketone.

Acetylene is preferred for producing the sooty deposit and no special technique is required over that shown in the prior art to accomplish satisfactory smoking. Acetylene burned in the atmosphere froma hand torch or other apparatus under pressures varying from about 3 to 15 pounds per square inch, is usually employed for n this purpose, with the flame adjusted so that the luminous part strikes the mold. In this manner the incandescent carbon particles are chilled and condensed on the mold surface, forming the carbon deposit without noticeable escape of smoke into the air. The vapor binding medium may be mixed with, or intimately dispersed in, the acetylene gas in any suitable manner, and a ready means of accomplishing this is to conduct the acetylene, in its passage to the flame, through the volatile liquid binder in a container having a vapor space above the liquid. The acetylene thus becomes saturated with the binder vapor and any entrained liquid can be removed by passing subsequently through a simple trap. With this manner of dispensing, the actual amount of vapor in the gas-vapor mixture led to the flame will vary with the vapor pressure of the binding liquid selected, but usually the acetylene will contain not over a maximum of about 5% of the chemical vapor, which is suflicient to provide the required binding action in the deposited carbon films. The resulting carbon coat is of a toughness and durability impossible to obtain with acetylene alone.

' With but slight variation the process is applicable to provideimproved coatings on almost any type of mold, and a wider field of use of smoke-formed coatings is indicated by the present invention. Satisfactory coatings can be produced 0n permanen or chill" molds of either I metals including lead, aluminum and brass, and in glass molding, the coating will serveits required function. The vulcanizing and curing of rubber goods, and the molding of plastics are other fields in which the invention has substantial merit. By many tests the heat insulating and mold surface protecting properties of this coating have proven to be substantially better than the carbon film formed by acetylene alone, and this provides improved casting surfaces, particularly in those of intricate form. The durability and toughness of the coating is represented by its ability to withstand several casting operations, whereas acetylene soot alone often requires renewal after each use.

Numerous modifications in the procedure described will be evident to those skilled in the art. As a binder the vapor of many organic liquids will be suitable, which have suflicient atmospheric vapor pressure to provide ready mixing. The binder decomposition to an adhesive residue isattributed above'to a partial combustion, but within these terms any associated reactions are intended to be included, as a partial oxidation, polymerization, or some other action also quite probably occurs under the conditions of carbon film deposition. Suitable smoking may be ac complished with gases other than acetylene, and the invention should not be limited other than as defined by the appended claims.

I claim:

1. A method of coating molds which comprises intimately mixing with a smoke producing gas a vapor of a compound of the group consistin of volatile aldehydes and ketones and applying a carbon deposit to the surface of the mold with a flame oi said gas-vapor 2. A method of coating molds which comprises intimately mixingwith a smoke-producing 8 a vapor of the compound octyl-aldehyde, and app y g a carbon deposit to the surface of the moldwith a flame of said gas-vapor mixture.

3. A method of coating molds which comprises intimately with a smoke-producing gas a vapor of the compound crotonaldehyde, and applying a carbon deposit to the surface of the mold with a flame of said gas-vapor mixture.

4. A method of coating molds which comprises intimately mixing with a smoke-producing gas a vapor of the compound di-isobutyl ketone, and applying a carbon deposit to the surface of the mold with a flame of said gas-vapor mixture.

5. A method of coating molds which comprises intimately mixing with acetylene in an amount less than about 5% a vapor of a compound of the group consisting of volatile aldehydes and ketones and applying a carbon deposit to the surface of the mold with a flame of said acetylene-vapor mixture.

6. A method of coating molds which comprises intimately mixing with acetylene in an amount less than about 5% a vapor of the compound octylaldehyde, and applying a carbon deposit to the surface of the mold with a flame of said acetylene-vapor mixture.

7. A method of coating molds which comprises intimately mixing withacetylene in an amount less than ,about 5% a. vapor of the compound crotonaldehyde, and applying a carbon deposit to the surface of the mold with a flame of said acetylene-vapor mixture.

8. A method of coating molds which comprises intimately mixing with acetylene in anamount less than about 5% a vapor of the compound di-is-obutyl ketone, and applying a carbon deposit to the surface of the mold with a flame 5 of said acetylene-vapor mixture.

9. Ina process of coating molds by carbon film deposition from an acetylene flame, the steps which compriseintimately mixing with the acetylen-e a vapor of a compound of the group con- 10 sisting of volatile aldehydes and ketones, said vapor being present in about 5% by volume, and depositing the coating with a flame of said acety-lene-vapor mixture.

10. In a process of coating molds by carbon film deposition from an acetylene flame, the steps which comprise intimately mixing with the acetylene about 5% by volume of a vapor of the compound octylaldehyde, and depositing the coating with a flame of said acetylene-vapor'mixture. if)

11. In a process of coating molds by carbon film deposition from an acetylene flame, the steps which comprise intimately mixing with the acetylene about. 5% by volume of a vapor of the compound ci'otonaldehyde, and depositing the 25 coating with a flame of said acetylene-vapor mixture.

12. In a process of coating molds by carbon film deposition from an acetylene flame, the steps which comprise intimately mixing with the acet- 30 ylene about 5% by volumeof a vapor of the compound di-isobutyl ketone, and depositing the coating with a flame of said acetylene-vapor mixture.

13. A mold having a tough, durable coating 35 thereon, said coating comprising a carbon film deposited by a smoke-producing flame of acetylene, and an adhesive binding said film, said adhesiveconstituting the decomposition residue formed by the burning in intimate admixture 4 with the acetylene of said smoke-producing flame of a vapor of a compound of the group consisting of volatile aldehydes and ketones.

14. A mold having a tough durable coating thereon, said coating comprising a carbon film deposited by a smoke-producing flame of acetye lene, and an adhesive binding said film, said adhesive constituting the decomposition residue formed by the burning in intimate admixture with the acetylene of said smoke-producing flame less than 5% by volume of a vapor of .the compound octylaldehyde.

15. A mold having a tough durable coating thereon, said coating comprising a carbon film deposited by a smoke-producing flame of acetylene, and an adhesive binding said film, said adhesive constituting the decomposition residue formed by the burning in intimate admixture with the acetylene of said smoke-producing flame less than 5% by volume of a vapor of the comco pound orotonaldehyde.

16. A mold having a tough durable coating thereon, said coating comprising a carbon film deposited by a smoke-producing flame of acetylene, and an adhesive binding said film, said ad- 5 hesive constituting the decomposition residue formed by the burning in intimate admixture with the acetylene of said smoke-producing flame less than 5% by volume of a vapor or the compound di-isobutyl ketone.

a CHARLES W. SWARTOUT.