US2191731A - Stencil sheet - Google Patents

Description

hmwnumm I 2,191,731

umTE-ofsrnrss PATENT OFFICE Walter Op Smiling, Allentown, Pa., assignor to' Trojan .Powder Company, Allentown, Pa.

' No Drawing. Application July 2, 1m, 'Serial No. 211.302; Y

3 Claims. (Cl. 41-3843) My invention relates 'to improvements in stenlution. This increased friability of the nitrostarch 011 sheets, and more particularly relates to imassists in the ready pulverization or disintegraproved stencil sheets of the so-called indestruc tion of the'film from the impact of the type key,- tibleltype, for .use in the preparation of large and the lack of tensile strength of the nitrostarch 5 numbers of copies closely simulating typewritfilm enables the'coating on the porous backing 5 ten matter. paper to be more readily perforated and removed Stencil sheets for use on a typewriter or for use by the action of the impact of the type key than with a stylus for purposes of reduplication of typeis possible when .nitrocellulose is used in the coatwritten matter or other desired symbols have ing composition, while the brittleness of the nitrobeen used for many years. The earliest stencil starch film facilitates the-complete breaking up 10 sheets adapted to use with a typewriter were of of the film at the point of impact, and-the nona wax .base, and these were followed by stencil adherence of the disintegrated particles of the sheets of a protein base, but the discovery of the nitrostarch film greatly assists in promoting the cellulose ester type of stencil sheet, as described openness and porosity of the prepared stencil at in U. S. Patent 1,526,982 of February-17th, 1925, the points through which the duplicating'ink is 15 to Edward H. Hill, represented a great improveto be, forced, in the subsequent operation of the ment in the art of stencil sheetmanuta'cture, and stencil. m my present invention represents an improvement I have discovered that although nitrostarch has in stencil sheets of this generaltype. all the advantages or nitrocellulose in affording a.

30 I have discovered that the substitution of 'nitrofl m on'p u 'l that is normally p e 20 cellulose by nitrostarch in the preparation 'of ble-to greasy inks at points where the coherence stencils of the celluloseester type leads to 'greatand continuity of the film has not been interly improved results, and aifords the means of rul'ited by impact with a type key or attrition orpreparing stencil sheets that represent a marked pressu f styiils the like, it has great 1 improvement over any of the typescof stencil advantages over corresponding films of a'cellulose 25 sheets known up to this time. ester base because of the much clearer nature of In rd r t explain why the b titution of the prints that it produces, this greater clearness nitrocellulose by nitrostarch leadsto such marked of the prints being due to the fact that the low improvement in stencil sheets, and in order to tensile strength of the nitrostarch film, and its explain the greatly improved results that are decided friability under the influence of impact 30 obtained with nitrostarch stencilsheets as comorpressure, and the almost entire lack of coherpared with nitrocellulose stencil sheets, it is necesence of the finely comminuted material that is sary to describe some of the physical characterp duc When the film is broken by p frieistics of nitrocellulose or cellulose. nitrate. Celtion, at r on 0 p e u all lead to the D d lulose nitrate is a material characterized by relation of incre sed op nness and cleanness" of the 35 tively great tensile strength and extreme toughwork of the finished stencil. ness, and when cellulose nitrate is dissolved in Th s incre ed Openness 0f the Po of e a solvent, and the solvent is evaporated to leave stenci s bj d to impact 0f the y is not a film of residual cellulose nitrate, the cellugained at the 00st of greater P y Of e 40 lose nitrate film thus formed is normally very Ori i sh et, and Ihave found that the original 40 strong and very tough. It may be loaded" with nitrostarch coating before impact or preparation considerable amounts of oils, waxes, resins and wi a ylu r the li i just as n -p r inert diluents,. while still retaining a considerto the duplic t ink as a similar stencil sheet able measure of its normal strength and toughf nitrocelluiosebaso It is only after p p 11935, tion by impact or the like that the friable and 45 I have discovered that when nitrostarch is readi y disi te ated nat of t ep s d substituted for nitrocellulose in this type of coat- I nitrostarch film shows the characteristic of high ing compositions which is used for stencil sheets, p il y to h d pl n ink, nd accordusing the identical formulas used with the nitroinsly e original p s sheet c ated with nitrocellulose compositions, the film of nitrostarch in starch stencil Composition is not any more p 50 admixture with the tempering agents that is left u to an y greasy duplicating ink t an is on the porous paper is relatively weak and fria nitrocellulose sheet of corresponding composiable (type-rupturable),as compared with the cortion, but after preparation in a typewriter, the responding film left after the evaporation ofnitrostarch sheet shows much better printing or u solvents from a corresponding nitrocellulose soduplicating properties than a nitrocellulose sheet.

of its increased solid content,

The advantages which my porous stencil sheets coated with nitrostarch coating compositions have over sheets of exactly similar porous paper coated with corresponding nitrocellulose coating compositions as shown in the earlier art, are not alone to be found in the increased clearness of the duplicated matter. I have found that because of the greater openness or permeability of those portions of my nitrostarch stencil sheets which have been subjected to impact for the purpose of rendering them permeable to the ink, I am able to use inks of higher solid content than is possible with the duplicating inks used with nitrocellulose sheets, and I have further found that I can secure satisfactory impressions from my stencil sheet, with less, pressure on the roller. Accordingly, by the use of my new stencil sheets of a nitrostarch base I am not only able to make use of inks containing less volatile solvent than the inks of the prior art, but I am able to x'nake longer runs of duplicated matter before the stencil sheet becomes unusable, because of the reduced pressure that can be used on the roller in forcing the duplicating inkv through the more open structure of the images produced in the preparation of my stencil sheets coated with nitrostarch composition.

The stencil sheets made in accordance with my present invention are accordingly superior to the nitrocellulose stencil sheets of the prior art in clearness of the reproduced matter, in the effective life of the stencil sheet, and in the ability to use not only a cheaper duplicating ink, but also an ink that shows quicker setting and reduced evaporation on the roller because Notwithstanding all of these advantages, I find that my nitrostarch coatings are just as impermeable to the duplicating inks at points where the stencil effect has not been intentionally produced, as the cellulose nitrate coated stencil sheets of the prior art.

I do not wish to be understood as claiming to obtain simultaneously under all conditions of use, all of the advantages of increased clearness of image, increased cheapness of ink and increased number of copies prepared from a stencil sheet before it becomes unusable, although under some conditions I do simultaneously obtain all of theseadvantages. In general, however, increased clearness of image is a characteristic that is always obtained with my new stencil sheets, as a result of the inherent characteristics of the relatively friable or disintegratable nitrostarch film as compared with the much tougher and much less-friable cellulose nitrate coating of the prior art. If I employ with my nitrostarch stencil sheet the same ink that is employed with a nitrocellulose stencil sheet, I can use much lower pressure on my roller, and can accordingly obtain a much greater number of copies before thestencil sheet becomes weakened, marred, and no longer usable for high grade work. If, however, I increase the solid content of my ink, for the purpose of obtaining an ink which will not lose solvent as fast from the exposed portions of the roller, I find it desirable to use about the same pressure that is used on-the roller of duplicating machines using nitrocellulose stencil sheets, and in this case I do not claim increased length of run with] a stencil sheet of my new type, since the advantage of the use of the new sheet has been ,taken out in the use of a heavier ink, and this requires about the same roller pressurebeing used with my more permeable stencil openings that would be used with a lighter ink and the vantages and the improvements herein described. In general, I follow closely the teachings of the prior art, particularly as described in U. S. Patent 1,526,982 of February 17th, 1925, to

' Edward W. Hill, and I find that it is only necessary to substitute nitrostarch for nitrocellulose in any of the'Hill or similar stencil compositions, to obtain the greatly improved results of increased openness and clearness of image, decreased roller pressure and the possibility of utilizing inks of less fluid nature than are required with the nitrocellulose sheets known up to the time of my present invention.

I do not find that the nitrogen content of the nitrostarch which I use is of any particular significance, and I have used nitrostarch ranging from 11.0% nitrogen to 13.0% nitrogen in conjunction with my present invention, with substantially similar results. .I find nitrostarch of 13.0% nitrogen content is well adapted to use with the other components of stencil compositions, and is compatible with all of the other materials normally used in stencil manufacture, and is readily soluble in all of the solvents normally used in the preparation of nitrocellulose stencil sheets.

It will of course be understood that in the practice of my invention I use with nitrostarch any of the customary solvents (such as amyl acetate, for example), any of the customary pigments (such as carbonv black, for example) any of the customary tempering agents (such as castor oil, for example), any of the customary setting agents (such as hydrogenated cottonseed oil, for example) and any of the customary Waxes (such as camauba wax, for example) and in general I employ the same components, and in the same proportions, that are used in thepreparation of the nitrocellulose class of stencil coating compositions of the prior art.

agent on the weight of carbohydrate ester solution (in this case nitrostarch solution), a setting agent such as soya bean oil in amount to aid in setting the composition without making it sticky, and a limited proportion, say,5 to 10% Following the said patent to Hill, I may 'use, for instance, about 50% of the tempering of a fatty or'tallow-like material such as lard,

cottolene, or Chinese vegetable tallow. F'orlbest results the combined weight of the tempering and setting agents andv tallow-like or waxy material is not more than the weight of the original nitrostarch solution to which theseingredients are added.

I have discovered that the substitution of nitrostarch for nitrocellulose in the nitrocellulose stencil compositions of the prior art, leads to the very useful but unexpected result of proused up to the time of my invention. e

- invention as herein disclosed, and accordingly no limitations'should be placed upon my invention, except such as are indicated in the appended claims.

I claim:

1. A stencil sheet, adapted to be converted into a stencil by the impact of type and the like thereon, comprising a fibrous base and a coating thereon, the coating including a type-impressible, type-rupturable stencil composition of the carbohydrate ester class containing nitrostarch and a tempering agent. r I

2.A stencil sheet, adapted to be converted into a stencil by the impact of type and the like thereon, comprising a fibrous base and a coating thereon, the coating including a type-imstarch, a tempering agent, and a setting agent.

3. A stencil sheet, adapted to be converted-into sible, type-rupturable stencil composition of the" pressible, type-rupturable stencil composition of the carbohydrate ester class containingnitrocarbohydrate ester class containing nitrostarch,

a tempering agent, and a waxymaterial,