US1845156A - Moldable cellulosic-derivative composition - Google Patents

Description

Patented Feb. 1 1932 UNITED STATES PATENT OFFICE RICHARD L. KRAMER, OF WILMINGTON, DELAWARE, ASSIGNOB TO E. I. DU PONT DE NEMOURS & COMPANY, OF WILMINGTON,

WARE

No Drawing.

This invention relates to compositions adapted to be mass-molded into desired articles, the base of such compositions being a cellulosic derivative, such as a cellulose ether or a cellulose ester, such as cellulose acetate or cellulose nitrate. Particularly, the invention relates to compositions of the char-- acter indicated which compositions when being molded will not adhere to the mold, and which will come from the mold with a Ins-- trous surface.

Heretofore, in the mass-molding of cellulosic derivative compositions difiiculty has been experienced because of the composition adhering to the mold; and, furthermore, the compositions, on being removed from the mold, did not have a properly lustrous surface, which necessitated mechanical polishing of the article. I have devised a composition which overcomes the indicated, and other, difliculties. It is a major object of the invention to provide a composition having the advantages indicated. To this end, and also to improve generally upon compositions of the general character indicated, my invention consists of the following matters hereinafter described and claimed.

In general accordance with the present invention, there is embodied in the composition, prior to the molding thereof, a suitable lubricant. This lubricant prevents adherence of the composition to the mold; and, assuming,

of course, a smooth surface upon the interior of the mold, provides that the article when taken from the mold will have a high polish equal to thatof the mold itself. As distinguished from applying a lubricant to the surface of the mold, the embodying of the lubricant in the composition avoids many difliculties due to non-uniform or incomplete application of lubricant to the mold, which faulty application would be likely to cause local adhesions and even failures. Also, 'flow marks, due to uneven distribution of the lubricant, are avoided.

As a specific illustration of practice in ac-' cordance with the invention, but without restriction of the invention thereto, a composition may be as follows:v

DELAWARE, A conromrxon or DELA- MOLDAIBLE CELLULOSIC-DEB-IVATIVE COMPOSITION Application filed October 21, 1928. Serial No. 148,800.

QParts'by weight Nitrocel1ulose11% nitrogen 20 Plasticizer-diethyl phthalate 16 Fillerchina clay 62 Coloring materialnigrosine 1 Lubr1cant-carnauba wax to 4 (preterred 1) In the above composition, although either hydrous or dehydrated nitrocellulose may be employed, it is to be understood that the 20 parts of nitrocellulose is to be taken as dry weight. It is to be particularly noted that compositions having, as indicated by the above formula, but a moderate amount of lubricant have the great advantage that, despite the fact that they do not adhere to the -mold, give articles of such hardness thatthey will not show finger printing and will have, and take, a high polish.

In the composition there may, of course, be J incorporation with a nitrocellulose plastic 7 mass, but the choice is not limited to these materials since similar results will be obtained v in some cases with the metallic salts of the higher saturated aliphatic acids (e. g. aluminum palmitate), paraflin, beeswax, etc., de-

pending on the filler employed, as will be understood by those skilled in the art. With regard to the filler it is pointed out that the purpose of this is to toughen the composition and to reduce shrinkage, and-filler materials of all kinds can be employed depending upon the properties desired in the resulting composition, as will also be understood by those skilled in the art. So far as the particular feature of the invention is concerned, that is the incorporation of the lubricant in the composition, filler materials might be omitted from the composition but, so far as I am aware, such compositions would be less valuable in application than those containing In making the composition a desirable procedure may consist in mixing together the various ingredients in a mixer, either with or without a volatile solvent, followed by a period of rolling on hot rolls to complete the distribution and incorporation of all ina gredients, insure a uniform intimate mixture,

and eliminate all volatile matter. The resulting product is then sheeted from the rolls and ground in a suitable grinderto reduce it to a powder. When thus powdered, the composi-' tion is in proper form for molding. As will be understood by those familiar with massmolding, the composition is introduced into the (metal) mold and molded under heat and pressure in the usual way, the presence of the lubricant in'the composition introducing no complications into the molding operations.

While, for the sake of definiteness of description, more particular reference has been made to nitrocellulose, it is to be understood that other cellulosic derivatives, such as cellulose acetate and cellulose ether mayform the base of compositions containing lubricant in general accordance with the invention.

I claim:

As a mass-molding powder, a granulated intimate mixture comprising a cellulose derivative, a meltable mold lubricant of the class consisting of carnauba wax, candelilla, or ceresine wax, aluminum palmitate, paraffin and beeswax, in quantity insufficient to substantially efl'ect the hardness of the surface of the molded article, and a filler in quantity suflicient to substantially counteract shrinkage of the mass during molding.

In testimony whereof I aflix my signature.

RICHARD L. KRAMER.