US2281261A - Hectograph composition and blanket and method of preparing same - Google Patents

Description

Patented Apr. 28, 1942 nnc'rocnarn- COMPOSITION AND BLAN- xer AND Mc'rnon or rnnranmc SAME Johan Biorksten, Chicago, and William J. Chan-- pion, Riverside, Ill., assignorl to Ditto, Incorporated, Chicago, Ill., a corporation of West Virginia No Drawing.

10 Claims.

The invention relates to hectograph composi-- tions and blankets, and methods of preparing same.

The ordinary hectograph composition is composed mainly of a gelatin-containing substance such as glue, combined with glycerin and water. The proportions are chosen so as to give maximum strength with flexibility and good copying characteristics. A suitable composition may contain glue or gelatin 35 parts by weight, water 45 parts, and glycerin 300 parts. The glue or gelatin is dissolved in the water and glycerin by heat and agitation to form a sol, a tanning agent is admixed in the sol and the composition is then poured on to a flexible backing and allowed to cooland form a gel. This gives a hectograph blanket comprising a backing having a layer of a gel copy m-ass. However, the copy mass when first made is not of satisfactory hardness and I toughness for use in commercial hectograph machines. The composition is therefore stored or aged for several weeks, during which time the tanning agent reacts with the gelatin and causes the necessary increase in the melting point and mechanical resistance. It wouldbe highly desirable to arrest the action of the tanning agent at this point. However, this has heretofore not been possible and the tanning action has continued, resulting in ever increasing melting point and hardness, so that within a year or so the hectograph composition becomes so hard and brittle that it is practically useless. e

The principal object .of this invention is to provide methods and means whereby the tanning action can be arrested as soon as the desired amount of tanning has been attained.

In accordance with this invention, a tanning combination is employed in the hectograph com- Application January23, 1941, Serial No. 375,616

(Cl. til-31.6)

The first class of substances are exemplified by tanning glucosides whichare subject to hydrolysis, by the tanning compound sodium hypochlorite which decomposes to the non-tanning compound sodium chloride, and by tervalent molybdenum salt in acid'solution which on standing become oxidized to non-tanning higher manner reacts with aldehydes to form oxynitriles.

These oxynitriles in themselves have no tannin action and on further decomposition give acids and ammonia or ammonium salts of organic acids which have no tanning efiect whatever.

Class 3 is exemplified by unsaturated aldehydes in alkaline media. An alkali such as sodiumhydroxide is added to the hectograph composition in such quantities as to give a pH value to the composition of above '7 and up to about 9. An

unsaturated aldehyde such'as acrolein or croton aldehyde is added to the alkaline hectograph composition and the composition poured on a backing and allowed to' gel in the usual manner. As the tanning action of the aldehyde takes place, the aldehyde also undergoes a gradual aldol condensation which leads to the formation of high molecular derivatives which have no tanning action. Thus after a period of time, depending position which becomes inactive within a given period. This period may vary from a few days to a few months, depending on the particular tanning compound employed.

' Suitable tanning combinations may be classlfied in the following groups:

(1) The tanning agent itself may be unstable and decompose so as to lose its tanning efllciency within the desired period of time: v

(2) The tanning agent may be intermixed with another chemical-which over a predetermined period of time'reacts with the tanning agent so as to destroy or inactivate the same;

(3) The tanning agent may be a substance which polymerizes within a few days or months and during this process loses much or all of its tanning eillclency.-

; upon the amount of aldehyde and alkalinity of densation, and in the caseof these compounds which have a low solubility in the hectograph composition, it is advisable to use the water soluble bisulphite derivatives of these aldehydesrather than the free aldehydes.

The quantities of tanning agents used in our 'hectograph compositions may vary from the amounts customarily used in hectograph compov 'sltions to considerably larger amounts than are ordinarily used. The sodium hypochlorite, for

hectograph composition. The aldehyde tanning agents may be used in proportions of, for exam-- pic, .05% to .5%. The thiocyanides or other agents which react with the taming agent to destroy its tanning action may be used, for example, in equimolar amount with the aldehyde; or may be used in larger or smaller amounts, depending upon the period in which it is desired to arrest the tanning action of the aldehyde.

To more clearly set forth the practice in accordance with the invention and to more specifically point out the nature of the product and process contemplated thereby, several specific, illustrative'examples are hereinafter set forth, it being understood that these examples illustrate several embodiment which have given satisfactory results and are not intended to restrict the invention thereto.

Example of group I 50 grams of 225 bloom glue is allowed to swell one hour with 75 grams water.

500 grams'glycerine containing 20 cc. of sodium hypochlorite is heated to 50 C. and slowly mixed with the gelatin, after the latter has been brought into solution by warming on a water bath at 50 C. The entire mass is then poured on a suitable backing and allowed to age several weeks, or until nov chlorine can be detected in the mass by treatment with a metallic iodide and starch.

Example of group II Instead of using a composition which slowly changes on standing into a non-tanning composition, we may use a stable tanning composition in the hectograph composition, allow the tanning to take place to the desired degree, and then arrest the tanning and stabilize the composition against further tanning by diifusing into the composition a reagent which converts the tanning compound into a non-tanning material. For example, we may incorporate bromine into the hectograph composition, allow the bromine to tan the hectograph mass to the desired degree, and then wash the mass with sodium thiosulphate which oxidizes the bromine and stops all tanning action.

While there have been shown and described certain embodiments of the invention, it is to be understood that it is capable of many modifications. Changes, therefore, may be made withinherent in the invention as broadly as possible in view-of the prior art.

We claim:

1. A hectograph copy mass which has substantially no tendency toward increased hardness over an extended period or time, said mass comprising tanned gelatin and a conversion product, other than the tanned gelatin, of a tanning compound which has substantially no tanning action.

2. A hectograph copy mass which-has substantially no tendency toward increased hardness over an extended period of time, said mass comprising tanned gelatin and an aldol condensation product.

3. A hectograph copy mass which has substantially no tendency toward increased hardness over an extended period of time, said mass comprising tanned gelatin and a. reaction product of a I tanning compound and a substance other than gelatin adapted to convert the tanning compound to a non-tanning compound.

4. A hectograph copy mass which has substantially no tendency toward increased hardness over an extended period of time, said mass comprising tanned gelatin and decomposition products of sodium hypochlorite.

5. The method of forming stabilizedhectograph copy surfaces which comprises incorporating a tanning agent into a hectograph composition comprising gelatin, allowing the tanning agent to tan the gelatin to a predetermined degree and such that efiective tanning agent remains in the composition, and converting said efl'ective tanning agent to a non-tanning compound in said hectograph composition.

- fective tanning agent with a reagent other than gelatin adapted to convert the tanning agent to a non-tanning compound.

7. The method of forming stabilized hectograph copying surfaces which comprises incorporating in a hectograph composition a tanning compound and an agent other than gelatin adapted to gradually convert the tanning compound into a substantially non-tanning compound.

8. The method of forming stabilized hectograph copy surfaces which comprises incorporating in a hectograph composition comprising gelatin,water and glycerin, a tanning compoundwhich is subject to decomposition into a non-tanning compound in the presence of glycerin and water.

9. The method of forming stabilized hectograph copy surfaces which comprises incorporating in a hectograph composition comprising gelatin, water and glycerin, a tanning compound subject to polymerization into a non-tanning compound, and a catalyst for inducing said polymerizat on.

10. The method of forming stabilized hectograph copy surfaces which comprises incorporating bromine into a hectograph composition comprising gelatin, allowing the bromine to tan the gelatin to a predetermined degree, and then wash-- ing the composition with a solution of sodium thiosulphate to arrest the tanning action.

JOHAN BJORKSTEN. WILLIAM J. CHAMPION.