Parting compositions

BACKGROUND OF THE INVENTION

This invention relates to a composition comprising a mixture of a castor oil and an alkyl ester of an acetylated hydroxy fatty acid. 25

Brief description of the prior art

It is well known that castor oil possesses certain properties which has rendered it useful as a mold lubricant and parting agent in the casting of aluminum and its al- 30 loys. Although castor oil has been generally satisfactory in its ability to carry relative high loads without rupture of the lubricant film, polymerization has been found to occur leading to the deposit of a varnish-like film on aluminum ingots which results in welding, seizing and galling. This 35 condition is undesirable and has become more pronounced as the aluminum industry shifts over to continuous casting of long billets versus the earlier practice of casting individual ingots.

Another problem encountered during the continuous 40 casting process is that considerable amount of cooling water is used. Therefore, it is most desirable that if the parting material mixes with the cooling water, it be of a type which separates readily to avoid contamination of discharged water. In this regard castor oil is not com- 45 pletely satisfactory because its separation from the cooling water is not sufficiently rapid to avoid some contamination of discharged water.

It has now been discovered that an outstanding parting composition can be obtained by mixing about 60% to 50 80% by weight of a castor oil with about 40% to about 20% by weight of a lower alkyl ester of an acetylated hydroxy fatty acid.

In the context of the present invention the expression “parting material” is also used to describe a composition 55 which has lubricating properties.

DETAILED DESCRIPTION OF THE INVENTION

The compositions of this invention has been found highly effective as a parting material in either the batch 60 or continuous casting of aluminum and its alloys. The success of the composition is based on the combination of about 20 to 40% by weight of a lower alkyl ester of an acetylated hydroxy fatty acid having eight to twentytwo carbon atoms with about 80 to 60% by weight of a 65 castor oil. The preferred composition is one comprising a mixture of about 75% by weight castor oil and about 25% by weight butyl acetyl ricinoleate.

The lower alkyl ester of an acetylated hydroxy fatty acid used in the composition may be prepared by trans- 70 esterification of a hydroxy fatty acid having eight to twenty-two carbon atoms with a lower alkyl alcohol, e.g.

methyl, ethyl, n-butyl, isobutyl and 2-ethyl n-hexyl alcohols, in the presence of sulfuric acid as a catalyst. Illustrative of hydroxy fatty acids are ricinoleic acid, 12-hydroxy stearic acid, hydroxy palmitic acid, hydroxy pentadecanoic acid, hydroxy myristic acid, hydroxy cerotic acid, etc. After the ester interchange is complete, the unreacted alcohol is distilled off, the lower alkyl hydroxy fatty acid is converted to a lower alkyl ester of an acetylated hydroxy fatty acid by reacting it with acetic anhydride.

The lower alkyl ester of an acetylated hydroxy fatty acid is then combined with a castor oil in the proportions heretofor described by simply blending the two components together at ambient temperature until a homogeneous mixture is obtained.

The following example is illustrative of the preparation of the parting composition of this invention.

EXAMPLE

100 pounds of castor oil is reacted with 46 pounds of n-butanol in the presence 0.4% by weight sulfuric acid. A gentle reflux of these components accomplishes the ester interchange. After distilling off unreacted n-butanol and washing out the by-product glycerine, the butyl ricinoleate is converted to butyl acetyl ricinoleate by reacting it with 31 pounds of acetic anhydride per 100 pounds of butyl ricinoleate. The unreacted acetic anhydride plus by-product acetic acid are then distilled off to yield butyl acetyl ricinoleate.

Twenty-five parts by weight of the butyl acetyl ricinoleate is blended at ambient temperature with seventyfive parts by weight of a castor oil, mixing being continued until a homogeneous mixture is obtained.

Other compositions falling within the scope of this invention are prepared in the same manner as described in the above example.

The compositions herein described are outstanding parting materials for molds used in the casting of aluminum and its alloys in that they have a reduced viscosity in comparison to castor oil alone so that application to the mold by conventional techniques is more uniform and formation of a varnish deposit or film is minimixed or eliminated. In addition, the compositions described herein also possess outstanding heat stability and the acetylation of some of the hydroxyl groups in the composition reduces water sensitivity so that any material carried into the cooling water during the casting operation is more readily separated from the cooling water than when castor oil is used as the parting material.

It is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims.