US2018875A - Manufacture of sized papers - Google Patents

Description

Patented Oct. 29, 1935 PATENT OFFICE MANUFACTURE OF SIZED PAPEBS George A. Richter, Berlin, N. H., assignor to Brown Company, Berlin, N. IL, a corporation of Maine No Drawing. Application January 12, 1932,

Serial No. 586,233

4 Claims. (CI. 91-68) This invention relates to the sizing of fibrous articles, and more especially papers, with a view toward imparting improved physical qualities, including receptibility of printing and writing inks to the finished product.

In accordance with the present invention, I associate with more or less porous fibrous articles regenerated cellulose, while preserving most, if not multifold increase in the wet strength of the paper, but it does so without appreciably detracting from the printing and writing qualities subsequently imparted by the glue size. Besides, the regenerated cellulose phase vastly enhances the folding endurance of the paper. ing endurance of papers containing the regenerated cellulose in amount as low as about 1%, in addition to the glue size, may be four or more times as great as a paper similarly sized with glue and otherwise similarly fabricated but lacking the regenerated cellulose, An important advantage attending the association of the regeneratedcellulose with the paper as a primary impregnant, is that the wet strength of the paper is so vastly increased that there is little danger of breaking the paper web when it undergoes the stress of being drawn as a continuous sheet through a bath of aqueous glue solution and then being dried.

Theregenerated cellulose can be derived from any suitable cellulose derivative, such as a euprammonium cellulose solution, but I prefer to use a xanthate or viscose solution as the derivative, because of its comparatively low cost and the ease of regenerating cellulose therefrom. The viscose may be added to the paper pulp in the beater engine, to the web of paper at any suitable stage of its travel on the papermaking machine, or to the prefabricated paper web. So, too, the regeneration of the cellulose from the viscose can be accomplished during or after the papermaking process, through the use of suitable acid or acid salt solutions, and/or through the application of heat. Assuming that the viscose solution is applied to a prefabricated waterleaf web of paper, the viscose.

While not re- In fact, the foldtreated papers can be redried under temperature conditions designed to decompose the viscose and to cause the regeneration of cellulose in the paper. The addition of acids like boric and acetic to the viscose solution before it is applied to the paper & promotes the regeneration of the cellulose in the paper during the drying operation. These acids are preferably used in such amount as to give us a partial neutralization of the alkali content of the viscose solution without causing appreciable 10 gelling; It is, of course, possible to adjust the strength of the viscose solution 'so that when a paper web is impregnated therewith and then dried, the porosity of the web will be largely, if not substantially entirely, preserved. In making a paper product embodying the present invention, I may use any suitable cellulose fiber or mixture of fibers as raw material. For example, I may use kraft pulp, bleached sulphite pulp and/or higher grade stocks, such as refined wood pulps of high alpha cellulose content or those prepared from new rags and/or long-fibered stocks, such as those prepared from ropes. The stock can be beaten in water in the usual hollander or beater engine to any desired degree. Ordinarily, it is desirable that the stock be well beaten or hydrated, and thus conduce to paper of high Mullen strength, even as a waterleaf (i. e., an unsized and unfilled) sheet. The beaten stock may be run off on a papermaking machine to produce a waterleaf sheet which, of course, is unsuitable for writing or printing purposes, on account of the absence therefrom of a size for preventing the spread of ink. The sheet, however, lendsitself to being impregnated readily and uniformly with a viscose solution of the proper strength. Such impregnation may be had by passing the sheet progressively as it issues from the papermaking machine through a bath of viscose solution containing, say, about 1% to 5% of dissolved cellulose in the form of the xanthate. The cellulose added to the sheet in the form of the xanthate can be adjusted to the desired value, say, about 1% to 5%, by passing the freshly impregnated sheet over a suction box and/or through squeeze rolls which remove from the sheet the excess viscose solution. The wet, viscose-impregnated sheet may then be redried at elevated temperature to regenerate the cellulose, although this step is not necessary when acids or acid salts, rather than heat, are relied upon for regenerating the cellulose. The sheet coming from the redrying drums or other drying instrumentality can then be passed progressively through a bath of aqueous glue solution, e. g., one containing, say, about 6% to 8% "glue and, if desired, some alum or other tanning agent for the glue. The presence of alum or other tanning agent in the glue fosters the setting of v the viscose and serves to insolubilize or tan the glue. It is possible to substitute for the alum sodium acid sulphate or other acidic reagents which promote the setting of .the. viscose. The wet, glue-sized sheet may be reduced to the desired glue content, say about 2% to 8%, as by pacity to take sharp or distinct imprints, that is, with no blurring or feathering.

As already indicated, the procedure hereinbefore outlined is subject to variation. Thus, the wet, viscose-impregnated paper may be treated with suitable acids or acid salts for the purpose of effecting a regeneration of the cellulose. To this end, the paper web may be immersed in a solution of sulphuric acid and/or sodium acid sul- 'phate, or other cellulose-regenerator. The solution of cellulose-regenerator may be sprayed onto the paper web, if desired. Or the paper web may be passed through an atmosphere of acetic acid fumes, sulphur dioxide gas, or equivalent volatilized cellulose-regenerator. The web' may then be washed free of excess cellulose-regenerator and reaction products, although this step is not necessary, especially when an atmosphere of cellulose regenerator is used and the web absorbs substantially only enough cellulose-regenerator to cause the desired reaction. The use of a cellulose-regenerator for efi'ecting the regeneration of the cellulose neutralizes such alkali as is introduced into the paper web by the viscose solution, which effect is not had when heat is relied upon to bring about the decomposition of the cellulose xanthate into regenerated cellulose. In such latter instance, the alkali can either be washed from the paper web or neutralized, if desired. Indeed, neutralization of the alkali can be secured in the bath of glue sizing solution, which may contain sufficient alum or other acid tanning agent not only to tan the glue but to neutralize the alkali deposited in the paper. In some instances, I might go so far as to dispense with regeneration of the cellulose in the paper until it strikes the glue sizing solution, which might be made sufliciently acid to accomplish the desired regeneration of the cellulose from the viscose simultaneously with the deposition of glue solution on the regenerated cellulose phase. Ordinarily, however, it is preferable to carry out the regeneration of the cellulose in the paper as a distinct step, and then to incorporate the glue size into the paper as a distinct phase enveloping the regenerated cellulose phase. If desired, the bath of glue sizing solution may contain a suitable amount of glycerine, which improves the pliability and folding endurance of the resulting paper without appreciably altering the other characteristics sought therein. The prefabricated web of paper to which the viscose solution is applied need not necessarily be waterproof. It may be presizedwith a small percentage of rosin or glue, say about 1% or less, which, while it does diminish the absorptivity of the web, nevertheless does not preclude the application of the principles of my in- 5 vention to the web. In other words, the web when properlypresized canstill undergo independent successive impregnations with viscose and glue solutions of appropriate strength. The presizing of the web may be accomplished as usual, for instance, by adding rosin size to the paper stock in the beater engine and then precipitating the size on the stock by the use of alum or equivalent precipitant before the stock is run off on a papermaking machine.

So far as I am now aware, the greatest utility of my invention resides in the field of paper manufacture, although my invention might be applied to moulded pulp articles and to threads, yarns, and fabrics of various descriptions.

As already indicated, the regenerated cellulose in the products of the present invention may be derived from solutions of cellulose derivatives other than the xanthate, for instance, from a .cuprammonium cellulose solution. The cuprammonium cellulose solution may be formed in :situ in a paper or fabric composed of cellulose fiber through the use of a suitable cuprammonium solution, rather than treating the paper or fabric with a prepared solution of cuprammonium cellulose. ,When a viscose or similar alkaline solution of a cellulose derivative is employed; it may contain nant, the dissolved soap, oil, resin, or the like 40 will be precipitated in the article. 7

t I claim:

- 1. A method which comprises treating afibrous article first with a viscose solution and then with an acidified glue solution, thereby regenerating cellulose from the viscose and producing an exposed glue surface.

2. A method which comprises treating a fibrous article first with a viscose solution containing a soap dissolved therein, and then with an acidified glue solution, thereby regenerating cellulose from the viscose, liberating the base of the soap, and producing an exposed glue surface.

3. A method which comprises treating a paper web first with a viscose solution and then with a glue solution containing an agent for regenerating cellulose from said viscose, thereby regenerating cellulose from the viscose and producing an exposed glue surface.

4. A printingor writing paper containing both regenerated cellulose and glue, said glue existing primarily as exposedsurface films on said paper to exercise a sizing effect and to impart thereto receptibility of printing and writing inks without blurring or feathering, and said regenerated cellulose existing as subsurface films to impart high wet strength and folding endurance to said paper.

GEORGE A. RICHTER.