US2088764A - Stencil sheet - Google Patents

Description

Patented Aug. 3, 1937 2,088,764 STENCIL SHEET Otto Schenck, Dessau- Anhalt, and Kurt Stickdorn, Rosslau-Anhalt, Germany No Drawing. Application March 23, 1934, Serial No. 717,086

Claims.

This invention relates to the art of reproducing or duplicating written or typewritten matter as in mimeograph machines and more specifically to novel compositions for coating thin fibrous pa- 5 per for use in the making of stencil sheets and similar products.

Many compositions have heretofore been proposed and used for such purposes but none of them has been completely satisfactory because of rapid deterioration, susceptibility to moisture, or temperature changes, cracking or other of a number of reasons. Paraffinic compositions have not been successful because of their fragile nature due to unavoidable brittleness in cold weather, or their softness and stickiness in warm weather. As an improvement over sheets containing coatings of this nature it has been proposed that sheets coated with a gelatine be employed. Whereas, such sheets were an improvement in many ways other objectionable features arose, including their instability in retaining moisture necessitating a wetting operation prior to use which besides involving annoyance and a loss of time, caused deterioration 5 of the cutting or typewriting machines employed,

due to gumming and rusting. More recently cell lulose ester base compositions have been proposed and used containing oils and fatty acid tempering agents. The duplicating paper produced therefrom has been an improvement in some ways, but is objectionable to the trade particularly because of the deterioration of the rubber rolls of the typewriters employed, resulting from its acid properties.

The object of the present invention is to provide coating compositions for the purposes described which overcome the above mentioned objectionable properties and in addition procure many new desirable qualities, including a more favorable consistency enabling the typewriter to cut better defined letters resulting in clearer and blacker reproduction, and also including a greater capacity as to the number of reproductions produceable from a single stencil. The new compositions also are free of. acid, are unaffected by normal changes in temperature and moisture conditions and do not dry out upon storage for an extended period of time.

The excellent qualities of the compositions or the sheets produced therefrom are due principally to the incorporation in a nitrocellulose base, of a i vegetal alcohol of high molecular weight, i. e.

one having at least 6 carbon atoms. Among the 55 alcohols found suitable are dodecyl alcohol obtained from cocoanut oil and a mixture of hexadecyl and octadecyl alcohol obtained from palm oil. There also may be used hydroxy unsaturated alcohols such as ricinoleyl alcohol obtained from castor oil; monounsaturated alcohols such as octodecenol obtained from castor oil by hardening and splitting oif a molecule of water or by hydrogenation of colza oil by the Blanc and Bouveault process or alcohols obtained by the hydrogenation of olive oil; polyunsaturated alcohols, such as linoleyl alcohol obtained from linseed oil or alcohols obtainable by hydrogenation of soya bean oil or of. colza (rape) oil, and polyhydroxy alcohols such as octadecandiol or octadecendiol obtained as by hardening or hydrogenation of castor oil. In general, it may be said that higher aliphatic alcohols derived from vegetable oils or fats, are suitable in the process.

In the compounding the composition a cellulose ester, preferably cellulose nitrate is dissolved in the usual mixture of solvents and softening agents and is then mixed with octadecandiol or other vegetal higher molecular alcohol. One litre of the composition may contain satisfactorily about 34 g. cellulose nitrate and about 200 g. of the alcohol. Other proportions may be employed depending upon the nature of the alcohol, such as its melting point, dispersing properties, etc.

The sheets of paper or other fibrous materials forming the base of the stencil sheets are coated or impregnated with the coating composition or the composition may be added to the paper stock during the process of manufacture and before it is formed into sheets.

The present invention is independent of. the solvent mixture employed in dissolving the cellulose ester or of the plasticizing or softening oil, for many satisfactory combinations are known to the trade. It is also independent of the manipulative method of making the composition.

The alcohol serves as a plasticizer, though its effect is somewhat different from that of other plasticizers in that the nitrocellulose is not dissolved in the alcohol, as it is in other plasticizers. Surprisingly the alcohol does not sweat-out but remains absorbed throughout the film.

It should be understood that the instant invention is not limited by the specific details hereinbefore set out but that it includes all modifications coming within the tenor of the disclosure and within the scope of the appended claims.

We claim:

1. A base of fibrous material for the production of stencils having an acid free coating, contain- PATENT- OFFlC'Ef I oil having the entire oxygen content of the alcohol present in hydroxyl groups.

4. The composition of the type described in claim 3, in which the alcohol is ricinoleyl alcohol.

5. A coating composition for stencil sheets and 5 the like comprising a cellulose ester and higher molecular alcohol from the group consisting of dodecyl, octadecendiol, octadecandiol, ricinoleyl and linoleyl alcohols, said alcohols being free of odor imparting impurities found in marine animal 10 and fish oils.

O'I'IO SCHENCK. KURT STICKDORN.