US2566754A - Composition for a pencil lead - Google Patents

Description

Patented Sept. 4, 1951 2,566,754 COMPOSITION FOR A PENCIL LEAD Charles H. Van Dusen, Jr., Willoughby, Ohio and Oscar E. Weissenborn, Verona, N. J., assignors to Addressograph-Multigraph Corporation, Wilmington, Del., a corporation of Delaware No Drawing. Application September 9, 1948, Serial No. 48,534

This invention relates to a planographic imageforming pencil and to a so-called lead or writing rod therefor for use in forming planographic images upon master planographic printing plates including aluminum and paper or like cellulose base master planographic printing plates.

A number of problems are encountered in the manufacture of planographic image-forming writing rods or so-called leads and pencils embodying the same which are peculiar to such planographic image-forming pencils and which are not encountered in the manufacture of common so-called lead pencils. Among these problems are: A planographic image-forming pencil must be capable of forming an inscription or image which will produce a satisfactory number of copies from the master plate upon which 1 Claim. (Cl. 106-19),

the image is written; it must be capable of making uniform lines, that is to say, lines which are of substantially uniform width throughout their entire length upon the master plate; the writing instrument, that is to say, the substantially cylindrical writing rod or so-called lead which is embodied in such a planographic pencil must be neither too soft so that the inscription or image formed thereby will wash off the plate readily or so that it will produce lines Which will vary in width as the pencil moves across a master aluminum or paper or like planographic plate on which it is being used to write an image, and it must not be sufliciently hard to scratch such a master planographic printing plate; and it must have good ink-respective and ink-retentive properties so that it will be receptive to and will retain the lithographic inks used in making reproductions from the master plate.

Accordingly, an object of the present invention isto provide a new and improved imageforming planographic pencil embodying a writing instrument or so-called lead which has good image-forming properties and which will produce images having good ink-receptive and inkretentive properties for planographic or lithographic inks; which is sufficiently hard to enable it to make lines of uniform width upon a paper or other planographic printing plate and to prevent the image made thereby from washing off the plate; and which is otherwise a satisfactory image-forming planographic pencil.

Another object of the invention is to provide a novel composition for making the substantially cylindrical writing rods or so-called leads of the new planographic pencil.

A further object of the invention is to provide a a new and improved planographic image-forming lead or writing instrument for use in a planographic image-forming pencil which may be employed in a planographic image-forming pencil 2 of any suitable character including those of the mechanically propelled type.

Other and further objects of the present invention will be apparent from the following description and claims which describe preferred embodiments of the invention and the principles thereof and what we now consider to be the best mode in which we have contemplated applying those principles. Other embodiments of the invention embodying the same or equivalent principles may be used and changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.

A typical formula which may be employed in preparing the so-called lead or the substantially cylindrical writing rod or writing instrument which may be embodied in a planographic imageforming-pencil, in the practice of the present invention, may be that which is shown in the following example:

v Example No. 1 Parts by weight Nigrosine 35 Japan-wax 2 Aluminum stearate 40 Methyl cellulose solution( one part dissolved in six parts of water, by weight) 27.6

In the manufacture of the new planog raphic image-forming pencil, and the new planographic image-forming lead or writing rod therefor, the nigrosine and aluminum stearate referred to in the foregoing Example No. 1 may be mixed together in the dry state and the methyl cellulose may be dissolved in approximately six times its weight of Water, whereupon the nigrosine-aluminum stearate mixture and the aqueous methyl cellulose binder solution may be thoroughly mixed for a period of two or three hours, in a suitable mixer. The Japan wax may then be melted to liquid form and added to the aforesaid mixture of nigrosine, aluminum stearate and methyl cellulose binder and the resulting mixture further thoroughly mixed for a period of two hours. The resulting base mixture is of doughy consistency and may be rolled and extruded in the form of substantially cylindrical rods and out to suitable lengths to form the new planographic image-forming leads or substantially cylindrical planographic image-forming writing rods and the new planographic image-forming pencils embodying the same, whereupon the said leads or rods may then be forced dried until their moisture content is approximately three (3) per cent, by weight.

The thus prepared planographic image-forming leads or substantially cylindrical rods may then be encased or enclosed in grooved wooden formed in one of two complementary SBCtiOIIS'Of. a wood or like pencil casing, adhesively securing the two complementary halves or sections of the pencil casing together with. the substantiallycylindrical writing rod or so -called lead therebetween; suitably shaping the. outer-surfaceof.

the pencilcasing as by forminghexagonalfaces thereon; and then suitably finishing the pencil casing as by sanding and painting the. same.

In addition to being encased in a grooved wooden casing the new planographic imageforming leads'or writing rods may, if desired; be employed in pencils of .the mechanical type.

- It will thus be seen that the new planographlc image-forming writing rods or: so-calledleads which are prepared according. to the foregoing Example No. l, are'comprised-of; the. dried. reaction productof an intimate mixture'ofi an 7 aqueous solution of a binder, namely, a'so'lution oisi methyl cellulose in water, and. the; balance a mixture. of the solidmaterials referred'to' in the foregoing Example. No. 1. namely,., nigrosinej. Japanjwax' and; aluminum stearate..-

.In'; placev of the Japan specified in the foregoing Example-No. 1 we. may: employ suitable equivalent quantities'of one of the following sub stances or mixtures thereof, namely, tallow, stearici-acid, carnauba wax, bee's wax; paraffin wax; and spermaceti.

The aqueous solution of methyl cellulose (binder) specified in the foregoing Example No. lma'y be employed... within a. rather wide range oflfrom approximately 10 per cent to'approximately per cent, by weight, of. the complete pencil base mixture. However, it has been found that: the. resulting planographic image-forming pencil. or. writing rod becomes tooweak 'if: the percentage of theaqueous.methyl-cellulose binder is r'educed below the minimum of lo 'pencent', as:

specified; whereas if? the percentage of the aqueous'methyl. cellulose binder is increased'substantially. in excess of the maximum of 50 per cent specified the writing or. planographicv imageforming qualities of the. resulting pencil or writ-- ingrod are unsatisfactory.

, In place oftheaqueous solution'of methyl cellulosespecified in theforegoing Example No.1. suitable equivalent quantities of the following;

materials, or. mixtures thereof, maybe employed as-the. binder, namely, ethyl cellulose, carboxy methyl cellulose,. gum tragacanth, polyvinyl a1- cohol and clay. v

Indulin' may be employed in place. of the, nigrosine.specified in the foregoing, Example No. land in'place of. the aluminum stearate specified we also employv suitable equivalent quantities of calcium stearate or zinc stearate, or mixturesof these materials.

Another composition which may be employed 7 in. preparing the base for the new substantially cylindrical planographic image-forming pencils or: writing rods is illustrated in the following example in which all parts indicated are by weight:

Example No. 2

Methyl cellulose solution (one part dissolved in six parts of water, by weight) 27.6;

tics of vthe present invention.

creased as much asten per cent of the quantities specified while still aifording a planographic image-forming lead or writing rod having the novel and desirable properties and characteris- The Japan wax, or other material substituted therefor, embodied in the substantially cylindricalplanographic image-forming Writing rod or instrument ?for the new planographic imageforming pencil enables a planographic imageforming pencil embodying the new planographic image-forming pencil or writing rod to slide or move easily over the surface of a planographic printing plate during the writing or image-formingoperation; the nigrosine- (or indulinsubstituted therefor) is an image-forming material and. imparts necessary color to the substantially cylindrical. planographic image-forming writing; rod or'instrum-ent, namely, a black'color; thBfi-lll: minumstearate, or-v other material substituted therefor, is also an image forming material; and thesmethyl cellulose, with or without clayiserves as. a binder to bind the various ingredients to;- gether.

' It has been found that the new planographie image-forming so-called leads or writing rods prepared according to the present invention'have' good image-forming properties, and thatiim ages formed thereby have'good ink receptive proper ties for lithographic inks; that they are sufficient-v ly-hard to enable it to form goodimagesgincluda ing lines of. uniform width, on paper and like. planographic. printing plates; that they. provide. images which will. not readily wash on such.

plates; and that they provide imageswhichzwilh and that the invention has. the desirable. ad-- rod material consisting essentially of the dried-r product of. an intimate mixture of the: following: materials within the range of the'quantities specified; all parts being by weight:

Nigrosine 31.5 to, 38.5.- Japanwax 1.8 to 22- Aluminum stearate 36. to 44' Methyl cellulose (one part dissolved in six parts of water, by weight) 24.84; to 301361 CHARLES H. VAN DUSEN, JR. OSCAR, E. WEISSENBORN.

(References l on. following page REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 7,907 Walpuski Oct. 9, 1877 376,456 Walpuski Jan. 17, 1888 1,937,105 Thomsen Nov. 28, 1933 Number 5 Number