US1996858A - Translucent paper - Google Patents

Description

Patented Apr. 9, 1935 UNITED STATES .TRANSLUCENT PAPER Paul Ballinger Davidson, Pittsburgh, Pa.

' No Drawing. 1 Application November 2, 1933, Serial No. 696,411

- 3 Claims. (01. 91-68) This invention relates to paper-making, and consists both in method and in product. In the practice of the method the paper is rendered translucent and rendered serviceable in new fields of use.

Paper in the ordinary meaning of the word is a thin and coherent sheet of cellulose fiber. Vegetable parchment is produced by the long-known process of treating paper with sulphuric acid. The effect of the acid is to swell the fibers of cellulose to the point of producing a gelatinous mass. The process is arrested by washing with water; the gelatinous cellulose, precipitated in the still remaining fibers of the body, acts as a cementing material; the substance of the sheet is rendered more nearly continuous; and, in consequence, the sheet manifests the properties of translucence, waterproofness, and grease-proofness which are characteristic of parchment.

The method of the present invention, unlike the sulphuric-acid method whose essential character has been indicated, does not involve chemical change nor reaction. It is, essentially, a method of impregnation.

In an application for Letters Patent of the United States, filed April 30, 1932, Serial No. 608,- have described a treatment of paper by impregnation, and I have described the impregnating substance to consist typically of a solution of ethyl or methyl abietate and sucrose octoacetate in a volatile solvent, and as a volatile solvent I named preferably ethylene dichloride.

My further discovery is thatsucrose octoacetate alone, not associated with abietate, may be carried in a volatile solvent such as ethylene dichloride, and that when so carried may be caused to impregnate paper, and that, the solvent driven off, the paper will be found to be rendered translucent and adequate for many purposes-for example, as tracing paper.

Other available solvents are acetone, toluene, and rosin spirits. V

softness in greater degree may be imparted to the product by adding to the solution a fatty acid, preferably a normally solid acid, stearic acid, for instance, or palmitic, in an amount of 5% or less the sucrose octoacetate.

No particular type of apparatus is necessary for the application-of this process to the paper; any equipment that will impregnate paper with this combination of materials and then drive off the excess of solution from the treated paper is.

satisfactory. In the practice of the invention the paper may be fioated onthe solution and the solution allowed to penetrate the paper; and, after this has been accomplished, the excess solution may be removed from the paper by means of a scraper bar or the paper may be run between squeeze rolls. The paper then is dried. Again, the invention may be practised by spraying the solution upon the paper, or by completely immersing the paper in the solution, as is done in tub-sizing of paper. In any case the excess of solution is removed and the paper is dried. Again, the invention may be practised by passing the untreated paper between two rolls, one of which at least carries upon its surface a layer of the solution. Satisfactory applications have been made by passing the untreated paper between two large steel rolls, one of which revolves in a pan containing the solution and carries a layer of the solution on-its surface. The paper, coming in contact with this layer of solution, is immediately impregnated and as it. passes between the rolls the excess of the solution is 20 squeezed out of the paper. In some cases it may be found advisable to spread a layer of the solution on the upper roll as well as upon the lower, andin this way the paper may by the two rolls be impregnated from both sides. the parchmentizing ofthe paper may in thiscase be regulated by the degree to which the solution is diluted with the solvent and, to some extent, by the pressure applied to the rolls. The drying of the treated paper can be governed to a large 30 extent by the proper selection of solvents.

A certain stickiness or tackiness, which otherwise may characterize the paper, may be eliminated by treating the paper, after impregnation and drying, by immersion in water. The water.v will dissolve certain incidental impurities, and, these being removed, it will be found that the stickiness or tackiness is overcome.

The fiber of paper that has been subjected to the method of the invention is not altered chemically, and the strength of the paper is not impaired. Paper that has been subjected to the method of the invention is receptive of ink, and

may, ashes been said, be used as tracing paper.

It is available, generally, where a translucent paper of relatively great strength is desired.

I have further discovered, both with respect to procedure as herein disclosed and procedure as disclosed in my prior application Serial No. 608,;

563, alluded to above, that translucence in greater degree or closer approach to transparency may be efieqte'd inthis way: Instead of preparing the SOIlit'Ol'l, whether of octoacetate'alone as is here contemplated, or of abietate and octoacetate to- The extent of 25 gether as is in the earlier application disclosed, in

full strength for the purposes in view, a solution of less strength, of approximately half full strength, may be Prepared, and with this solution of half strength the paper may be twice impregnated, allowing it to dry after the first impregnatiom-- If the impregnation be effected in such two-step manner, it will be found, as I have intimated, that the quality of translucence will be heightened.

I claim as my invention: 7

1. The method herein described of preparing translucent paper whih consists in impregnating the paper with a solution of sucrose octoacetate with or without an addition to as much as 5% of a normally solid fatty acid but otherwise of sucrose octoacetate alone in a volatfle solvent, and driving oil. the solvent.

2. A translucent paper consisting of a paper impregnated with sucrose octoacetate with or without an addition to as much as 5% oi a normally solid fatty acid but otherwise of sucrose octoacetate alone.

method herein described of treating pa s to render it translucent which consists in impregnating it with a solution of sucrose octoacetate with or without an addition to as much as 5% of a normally solid fatty acid but otherwise of sucrose octoacetate alone in a volatile solvent, driving ofl the solvent, immersing the paper in water, and finally PAUL B; DAVIDSON.