US2048293A - Manufacture of absorbent clothlike paper - Google Patents

Description

Patented July 21, 1936 OFFiCE 2.048.293 manuracrnns or ansonnnn'r CLOTH- mm PAPER George A. Richter and Milton 0. Schur', Berlin,

assignors to Brown Company, Berlin,

N. H., a corporation of Maine NoDrawing. Application October 20,1932,

Serial No. 638,774

9 Claims. (CL 92-40) This invention relates to the manufacture of absorbent, cloth-like papers having an advantageous combination of characteristics such that they can be used in place of absorbent cloth or 51. cotton rags or waste for various purposes, some of which will hereinafter be mentioned. It relates more particularly to papers containing glycerine as an ingredient imparting such characteristics as softness, pliancy, and smoothness of 1c :feel thereto.

The use of glycerine in ordinary paper is accompanied by a, serious impairment of such important mechanical properties as the strength and tear resistance of the paper. The action of the :glycerine on paper is evidently like that of water,

which, upon the wetting of ordinary paper there-' which is remarkably tough'and resistant to rupture or tearing and is characterized by its lack of fuzz or lint, its ability to be folded and flexed repeatedly and otherwise handled like a cloth or rag without cracking or tearing, and the smoothness with which it can be wiped over all kinds of surfaces without abrading or scratching them in the slightest degree. The regenerated cellulose evidently not only serves to strengthen or toughen the paper, but to keep the paper strong and tough, even after it has been glycerinated to a high degree. Indeed, a. paper containing regenerated cellulose can be glycerinated to such an extent, in accordance with our invention, as to possess a softness, limpness, and smoothness of feel approaching that of a cloth handkerchief, and yet be able to withstand considerable rough handling without rupturing or tearing. The paper of the present invention, therefore, has many spheres of utility where cloth has heretofore served. For instance, it is highly satisfactory for dusting or 4of-cleaning furniture, glass, machinery, etc., being an excellent mopping material for non-aqueous liquids, such as oils, grease, and inks, as well as for aqueous liquids. It is also highly satisfactory as toweling, for itis characterized not only by a 5 wet strength vastly higher than that of paper lacking regenrated cellulose, butalso by a smoothness of feel such as is highly desired when it is used for wiping wet hands or drying the skin of other parts of the body. In fact, paper towels 55 made in accordance with the present invention of the papermaking machine.

leave the skin smooth and soft'by virtue of the softening action of its glycerine component on the skin.

While it is possible to produce, in accordance with our invention, papers containing various 5 amounts of regenerated cellulose and glycerine, it is preferable to stay within certain limits, depending upon the use to which the papers are to be put. Thus, we prefer to associate not more than about 1% of regenerated cellulose, based on the weight of fiber, with the paper, for as-little 'as $5 of regenerated cellulose is all that is necessary to impart to the paper the desired qualities hereinbefore mentioned. Such a small amount of regenerated cellulose does not detract appreci- 15 ably from the absorbency of the paper. When the paper is appropriately made and. contains besides the fibrous material only a small amount of regenerated cellulose and a. limited amount of glycerine; it is highly absorbent. While for some 20 purposes the regenerated cellulose and'glycerine may exist in the papers of the present invention prepared from fibrous material and other agents, such as sizes and/or fillers, we prefer not to use such other agents, which impair the absorbency 5 of the papers, particularly when they are to be used as dusting, cleaning, or toweling material. The want of glycerine introduced into the papers of the present invention is subject to considerable variation. For instance, a paper to be 30 used as toweling may advantageously contain,

besides the regenerated cellulose, up to about 12% of glycerine, based on the weight-of fiber, whereas a paper to be used for dusting or general cleaning purposes may advantageously contain, besides the 5 regenerated cellulose, as high as about 30% or more of glycerine. These amounts of'glycerlne, however, leave a properly made paper in a highly absorbent condition.

In producing papers falling within the purview of the present invention, various modes of pro= cedure may be adopted. Thus, the regenerated cellulose and/or the glycerine may be associated with a prefabricated, dried paper or with a paper while it is in its course of manufacture. In other words, his possible to associate either or both these ingredients with the papermaking stock all the way from the beater engine to, and including, the dried sheet delivered from the dry end For instance, suitable cellulose derivatives serving as the source of the cellulose derivative may then be combined with the papermaking stock, and regenerated cellulose may then be formed in situ in and throughout the stock by the addition of suitable agents capable of regenerating cellulose from the cellulose derivatives. While various cellulose derivatives, including cuprammonium cellulose, may serve as the source of the regenerated cellulose, we prefer to use cellulose xanthate or viscose as the cellulose derivative, not only-because it is a comparatively inexpensive derivative, but further because cellulose may be readily regenerated from this derivative by heat and/or by the use of various acids or acid salts, which, too, are inexpensive. So, too, the glycerine may be combined with the papermaking stock simultaneously with, before, or after the combination of viscose or regenerated cellulose with the stock. Inasmuch as glycerine is soluble in water and, unless the white-water system of the papermaking machine was a closed one, would be lost in considerable amount in the white water removed from the stock during the papermaking operation, we prefer to apply the glycerine to the stock after it has been formed into a paper web and the web is in a partially or completely dried condition. It is preferable, also, to apply the viscose solution to the paper web in a partially or completely dried condition and before the glycerine is added, for glycerine is soluble to only a limited extent in a viscose solution without precipitating thesolution. In the case of the usual viscose solution, it is possible to admixonly' about 1% to 2% of glycerine without causing precipitation. It is for this reason that we prefer not to mix the viscose solution and the glycerine in treating the partially or completely dried paper web and not to apply the glycerine to the web before treating it with the viscose solution. The paper web in a partially or completely dried condition may be impregnated with a viscose solution and may then be treated with a reagent capable of regenerating the cellulose in situ in the web. Or

the viscose solution may-contain a celluloseregenerating agent which, although it does not, precipitate the solution or regenerate cellulose therefrom to begin with, nevertheless promotes regeneration of the cellulose in the paper when the drying of the paper is performed as ordinarily at elevated temperature. The impregnations.

tion of the partially or completely dried paper web with a viscose solution is highly practical and satisfactory, particularly when less than about 1% of regenerated cellulose is to be incorporated into the web, as the viscose solution to be used for impregnation in such case may be so dilute and, accordingly, have such low viscosity as to cause prompt and uniform impregnation of the web even while' the web is traveling at the high rate of speed incident to usual papermaking opera- In such case, moreover, practically no loss of viscose solution need be experienced, as impregnation with the viscose solution as well as with glycerine may be performed while the paper is passing over a suction box, through squeeze rolls, or is being acted upon by similar instrumentalities which permit the recovery of the excess impregnants in a condition sufiiciently concentrated to be reused.

Cellulose fibers of various origins may be employed as raw material for producing a waterleaf paper web to be treated in accordance with our invention. Thus, mechanical wood pulp or various kinds of chemical wood pulp may be employed as raw material. We prefer to use kraft pulp because of its comparatively high strength, but a more or less refined and/or bleached kraft pulp orsulphite pulp or a mixture of pulps may serve as the; papermaking stock. The waterleaf web may be formed from pulp which has not been unduly beaten or otherwise gelatinized and which hence conduces .to a web of an absorbent character. On the other hand, the pulp may be more or less beaten and/or sized, but, for the articles hereinbefore described, it is preferable that beating and/or sizing of the pulp be performed in such a way as not to affect unduly the absorbency of the paper.

The waterleaf paper web may have the viscose and glycerine sequentially associated therewith. The strength of the viscose solution to be used in getting say, 0.5%, of regenerated cellulose into the web depends on various factors. It depends, for instance, upon whether the web is dry or wet when subjected to impregnation with the solution; whether the solution is applied above a sucgtion box over which the web travels, or by means be passed through a pair of press rolls, the lower i one of which is rotated partially submerged in a trough of an aqueous glycerine solution of, say, about 25% to 50% strength. The glycerine solution is thus applied to the web and squeezed thereinto and therethrough. The amount of glycerine 1 thereby associated with the web will depend upon the rate of travel of the web and the pressure applied thereto. ,When paper toweling is in view; it is preferable to associate about 12% of glycerine with the paper, but when a dusting or cleaning paper is in view, it is preferable to associate about 28% to 30% of glycerine with the paper. The glycerinated paper may then be redried by passage over a bank ofsteam-heated drier drums.

A preferred procedure is to apply both the viscose solution and the glycerine to the freshlyformed, wet paper web while it is traversing the wet end of the papermaking machine and thereby to avoid the necessity of redrying the paper. In

such case, the viscose solution, containing, if desired, boric acid or other suitable chemical, which promotes the regeneration of the cellulose from the viscose during subsequent drying of the paper at elevated temperature, may be applied to the freshly-formed, wet paper web while it is passing over a suction box or through a pair of press rolls at the wet end of the papermaking machine. The glycerine solution may then be applied to the viscose-impregnated paper, say, at one of the later pairs of press rolls, the lower roll rdtating partially submergedinthe glycerine solution. Or, if desired, the glycerine may be showered or spread on the upper press roll, rather than being supplied to the lower press roll.

Another preferred procedure is to start with a prefabricated, dried paper web containing the regenerated cellulose and to impregnate it to the desired extent with concentrated glycerine, say, glycerine of substantially strength. In such case, the paper web may be drawn from a parent roll and passed into the nip of a pair of press rolls, the lower one of which may be caused to rotate, preferably independently of the upper one, par. tially submerged in a bath of substantially 100% glycerine. The upper roll is preferably a soft, i

yielding one, for instances roll whose periphery consists of soft rubber. This latter roll may be run at a speed and under a pressure designed to cause an influx of the glycerine in desired amount into and throughout the paper sheet. "The glycerinated sheet-issuing from the nip of thepress rolls is preferably passed over a steam shower or through a steaming atmospherebeforeit is slit into wem of the desired width and the webs wound into rolls. The function of the steam is to dilute the glycerine moderately and also to distribute it through the sheet more uniformly. In a typical ,case, starting with a paper whose basis weight is about 28 pounds, the basis weight of the glycerlnated sheet may be about 39 pounds and that of the sheet leaving the steam shower about 40 pounds. (The basis weight of a paper sheet is the weight in'pounds of 480 sheets whose dimenthe wet end of the papermaking machine is that.

such malodorsas exist in the ordinary commercial grades of glycerine tend to disappear during the drying operation, that is, while the glycerinated sheet is passing over the bank of steamheateddrier drums constituting the. dry end of the papermaking machine. The malodorous substances present in the glycerine evidently undergo steam distillation from'the paper under the influence of the high temperature prevailing on the drier drums. A similar result is had when a prefabricated paper sheet is treated with a viscose solution and is then redried in accordance" with our invention; The same holds true when a prefabricated paper sheet associated with re generated cellulose undergoes glycerination with an aqueous solution of glycerine and is then redried in accordance with our invention. When, however, glycerine is applied to a prefabricated paper sheet in such concentration that the sheet does not require redrying but, in fact, may be steamed to a slightly higher moisture content, it is desirable and usually necessary to u e lycerine ofa chemically pure grade in order toavoid evil odors in the paper, as the short steaming treatment empl yed to dilute and distribute the glycerine more uniformly throughout-the sheet is not sufllcientlydestructive of th odors inheringin the'ordinary'commer 'gradesof glycerine. Y

. when the paper of the present invention is to serve as toweling, it maybe crinkled as usual. It

may, moreover, be advantageously embossed to "resemble a sheet of cloth, especially when the pulp used as are-w materialisawhite one ofhigh.

strength and tear resistance, for' the, high wet strength,'li mpness, smoothness of feel, and other properties of paper towels produced in accordance 1 with our invention are suggestiveto the user of of paper to serve for dusting or cleaning purposes,

for instance, for the absorption and removal of oil from machines, or. of ink from printing or engraving plates or rolls. Accordingly, the glycerine. content of such latter paper may be as high as 30% or even higher.

While we have indicated various modes of procedure which may be adopted in accordance with .of the papermakin our invention and have pointed out those which we regard as preferable, we wish again to stress the fact that the viscose and/ or the glycerine may be associated with the papermaking stock at any suitable stage of paper manufacture, including 5 the bulk papermaking stock and the dried sheet of paper. While it is preferable that the regeneration of the cellulose from the viscose be effected or promoted by suitable chemicals, as hereinbefore described, it is possibly to rely upon heat alone as the agency for regenerating the cellulose in the viscose-treated paper, for instance, the heat treatment to which such paper is subjected when it is dried or redried by passage over 1 steam-heated drums. We have already cited those procedures wherein the paper is prefab 'cated so as to contain regenerated cellulose and r is then glycerinated; wherein paper is treated with viscose, and glycerine sequentially while traversing the wet end'of the papermaking machine; and wherein paper is treated with viscose and glycerine sequentially after delivery from the dry end of the papermaking machine and is then redried. There are other procedures which we might cite, such as the association of the viscose and glycerine with the bulk papermaking stock; the glycerination of the freshly-formed, wet paper web while it is traversing the wet end g machine followed by the treatment of the glycerinated paper before or 80 after drying with viscose; the glycerination of the dried web followed by the treatment of the glycerinated web with viscose; but all of these last-mentioned procedures, while included within the ambitof our invention, are not considered 85 by us as being as adaptable to factory practice or as yielding as good results as the adore-mentioned procedures. The principles of the present invention may be applied to felted cellulose fiber articles of various kinds, as the presence of regenerated cellulose and glycerine in such articles makes possible an advantageous combination of characteristics. It is possible to use glycols, e. g., ethylene glycol, glucose, or other cellulose-softening liquids in lieu of, or together with, glycerine. All of these liquids are alcohols in the sense that they have hydroxyl groupings in their chemical constitution. The alcohols, and more especially the polyhydric alcohols, like glycerine, ethylene glycol, and glucose, are high- -ly effective as cellulose-softening agents. They also possess the advantage of low volatility and so are not lost in appreciable amount from the articles through evaporation at prevailing atmospheric temperature conditions. We prefer to use glycerine by reason of its high efiectiveness as a cellulose-softeningagent and its'comparatively 'lowcost. I

The articles of the present invention may, in some instances, advantageously contain perfumes, anti oxidants, and flreproofing compoimds. Should there be any odor or odor-gencrating tendencies in the articles attributable, say, to the viscose and/or the glycerine, the odor would be masked by. the perfume. An antioxidant tends to prevent oxidation of the glycerine. As examples of anti-oxidants, we may mention any of the naphthylamines. The articlesof the present invention may also advantageously contain flreprooflng compounds, such as the phosphates and/or tungstates, e. g.,ammonium phosphate and sodium tungstate. The anti-oxidant diminishes the rate of spontaneous heating of the articles; and the fireprooflng compound tends to prevent actual combustion. The use at as &

anti-oxidants and/or flreprooflng compounds is,

for instance, highly desired in papers made in accordance with the present invention and intended for use in mopping up printing inks,

paints, or other liquids containing linseed oil or other spontaneously oxidlzable material which gives rise to the danger of spontaneous combustion.

So far as concerns subject matter, this application is a continuation in part of our applica-:

tion Serial No. 462,927, filed June 21, 1930.

We claim:

1. A process which comprises adding viscose to substantially'ungelatinized papermaking stock at any'stage of paper manufacture, including the bulk papermaking stock and the dried sheet of paper, and glycerinating the paper with glycerine of substantially 100% strength.

2. A process which comprises adding viscose to substantially ungelatinized papermaking stock at any stage of paper manufacture up to the drying operation, drying the paper, and glycerinating the dried paper with glycerine ofsubstantially 100% strength.

3. A process which comprises adding viscose to substantially ungelatinized papermaking stock at lose, and steaming the glycerinated paper.

6. A step which comprises glycerinating substantially uniformly throughout to the desired glycerine content with substantially odorless 100% glycerine, a porous paper web associated .with regenerated cellulose.

7. Steps which comprise glycerinating a prefabricated, dried, porous paper web associated. with regenerated cellulose, with glycerine of substantially 100% strength and free from malodors, and steaming the glycerinated paper. 5 8. A soft, porous, absorptive paper sheet made. from substantially ungelatinized cellulose pulp, and containing distributed substantially uni-. formly therethrough a small amount of regenerated cellulose and a distinctly larger amount of 0- glycerine, the amount of glycerine in said sheet being about 12 to 30%, based on the "dry weight, of pulp, and the amount of regenerated cellulose. in said sheet being so controlled that the absorb-. ency of said sheet is not substantially less than 5 that of a similar sheet made from only the substantially ungelatinized cellulose pulp but said amount of regenerated cellulose imparting sufficient strength to said sheet substantially to offset the-weakening effect thereon when said glycerine exists therein in the absence of'regenerated cellulose.

9. A soft, porous, absorptive paper sheet made from substantially ungelatinized cellulose pulp and' containing distributed substantially uniformly therethrough a small amount of regenerated cellulose and a distinctly larger amount of a cellulose-softeningagent of the group consisting of glycerine, .ethylene glycol, and glucose, the amount of cellulose-softening agent in said sheet being about 12 to 30%, based on the dry weight of pulp, and the amount of regenerated cellulose in said sheet being so controlled that theabsorbency of said sheet is. not substantially less than that of a similar sheet made from only the substantially ungelatinized amount of regenerated cellulose imparting suflicient' strength to' said sheet substantially to offset the weakening efiect