US2046763A - Paper product and method of making - Google Patents

Description

July 7, 1936. B. AsNEs PAPER PRODUCT AND METHOD OF MAKING Filed Dec. 28, 1931 Patented July 7, i936 UNITED STATES PATENT OFFICE PAPER PRODUCT AND METHOD OF MAKING Application December 28, 1931, Serial No. 583,487

2 Claim.

This invention relates to soft paper sheet material which shall be strong when wet and suitable for toilet and nursery purposes, and to the resulting product.

In various applications of sheet materials for personal use, it is prerequisite that they shall be soft. It is also usually desirable that they shall be freely absorbent and retain a relatively large volume of moisture-either before becoming sensibly wet or upon complete saturation of the sheet. Another important property is the mechanical strength of the sheet and the retention of such strength, at least temporarily, after it has been wet or thoroughly saturated with Water.

To meet these requirements, textile fabrics are customarily employed. A woven structure in such materials is necessary in order to provide adequate strength, but such woven materials are expensive, are not readily disposed of, and require laundering.

On the other hand, loose, unwoven textile materials such as loose cotton wool or sheets of cotton batting are both too bulky for most purposes and substantially lacking in mechanical strength and integrity.

Paper has been used to replace cloth for a few purposes such as for paper towels, handkerchiefs, facial tissue, etc., where its absorptive properties are utilized, and it is convenient on account of its low cost and the readiness with which disposal may be made of the used sheets. But papers, generally, either are not sufiiciently soft or, if soft, do not have suflicient mechanical strength to permit of anything but the most transitory use, as above indicated. Furthermore, when wet with water, those papers which are soft enough to be considered for toilet or nursery purposes are immediately disintegrated, presenting no measurable strength whatsoever.

Accordingly, it is an object of the present invention to provide a sheet material which shall be extremely soft and freely flexible, absorbent, porous,-suitable for toilet and nursery purposes,--of uniform quality, hygienic, and temporarily resistant to the weakening effects of water so that it shall be strong when wet, and yet preferably susceptible of ultimate disintegration to permit of convenient disposal. It is a further object to provide a method of making such sheet material of paper stock so that the product may be relatively inexpensive and hence discarded after a single use or application,thus eliminating any necessity of laundering. Other objects will appear from the following disclosure.

The invention includes the preliminary preparation-of a sheet of paper characterized by being of open formation and composed of loosely disposed fibers consisting substantially of alpha cellulose, and substantially free from matrix or bonding materials such as degenerated cellulose, sizing, fillers, coating, and like materials which tend to make ordinary papers dense and impervious and to form a relatively stiff, continuous matrix between the fibers. A typical sheet of such paper may be that known as handkerchief stock or facial tissue, in which the mechanical strength which it possesses may be attributed primarily to the entangled heterogeneous arrangement of the fibers, rather than to bonding or adhesion or cohesion therebetween. The sheet may be derived from purified wood pulp consisting largely or entirely of alpha cellulose fibers, or may contain 'a small amount of cotton fibers or ragstock to impart additional strength thereto, or may be composed almost or completely of cotton fibers. In any event, it is characterized by an open fibrous formation, even though the sheet be initially of relatively low mechanical strength in consequence. It is further characterized by presenting (upon close inspection as through a microscope at 10 diameters) continuous pores or spaces passing completely through the sheet, especially in single thicknesses or when thin sheets are observed.

Briefly stated, the method of the invention includes the treatment of a soft, flexible sheet of paper of open fibrous formation, as above described, with a solution of a gel-forming albuminous adhesive, such as gelatin or glue, in such manner as to bond the fibers of the sheet firmly together at their'points of contact without appreciable filling of the interstices, and rendering the bonding material at such points of contact resistant to disintegration by water and substantially insoluble in water, and at the same time tougher so as to increase the'strength of the sheet. The treated sheet, upon drying, is soft and freely flexible, of open, porous formation, freely wetted by water and of high absorbent capacity, and yet is stronger than the untreated sheet both when dry and when wet. It may, accordingly, be used generally for toilet and nursery purposes, as above set forth, very much in the same manner and for the same purposes that soft cloth has heretofore been considered necessary. Among such uses may be especially mentioned its application as diapers or as liners therefor.

The adhesive solution is preferably in a high state of dispersion (or dilution) more effectively to promote the wetting and penetrating action of the same between the fibers of the paper sheet,

and, to such extent as it may occur, surface adsorption by the individual fibers. Such dispersion or dilution is also important to control the thickness of the colloid deposit to be formed upon and between the fibers and to avoid filling of the small interstices and capillaries of the paper sheet. This may also be promoted by heating the solution slightly or to a preferred temperature at the time of treatment. Relative purity of the reagent is also desirable, not only in respect of the effects of impurities in the finished product treated therewith. but also in permitting of more uniform control of the treatment procedure. In this connection, the viscosity and jelly strength of the gelatin are important, both from the standpoint of the working characteristics of the composition in the treating or creping apparatus and in the strength, insolubility, etc., of the gelatin in the treated sheet. For example, a gelatin having a viscosity of to millipoises (containing 12 grams of gelatin in 105 grams of water at 60 C.) is representative of a suitable consistency. although glues and gelatins of lower viscosity can be used.

Accordingly, a relatively pure gelatin solution, which is relatively colorless, is generally to be preferred, but more or less impure gelatin or glue may be employed, if desired, with satisfactory results if the desired viscosity and jelly strength are provided and appropriate precautions are exercised. For example, extremes of acidity which would be detrimental in the product, or which might interfere with the process, are to be avoided, and the presence of harmful or irritating substances is also to be prevented.

It is accordingly to be understood that the practice of the invention is not limited to the use of gelatin as the gel-forming or gel-precipitating colloid, but that glue and gelatinous compositions of similarly corresponding properties are included within the scope of the invention.

The gelatin content of the treated sheet is freely absorptive of moisture from the atmosphere, but in dry weather a part of such moisture may be lost, with consequent hardening. To prevent this and also to insure a greater degree of softness in the sheet, softening agents may be applied to the sheet either in the course of the treatment outlined above, or before or after such treatment. The softening agents may be water soluble and hygroscopic, such as glycerine, diethylene-glycol, etc. Soften ng agents may also be used which effect their softening action in a somewhat different manner, as by imparting their own specific properties to those of the sheet,such as olive oil, cold cream, talcum, etc. Deodorants or masking odors, such as perfumes, may be added, as Well as antiseptics, either in solid or liquid form:e. g., vanillin, boric acid. talcum powder, aluminum-stearate, zinc oxide, hexyl resorcinol (S. T. 37) and the like. But preferably such additions are made in appropriate quantities and in sufficiently dispersed condition to avoid any appreciable interference with the porosity and absorbency of the sheet where these properties are a desideratum. Moreover, they may be incorporated with the treating solution above described or may be applied separately. If required in appreciable quantity, the softening agent may be applied to one surface of the sheet, and the sheet either folded with this side inward or covered with a second sheet of paper without a softening agent. Various combinations of sheets (treated or treated and untreated) may be made in order to make them more effectively serve the purposes for which they are intended, and to increase or emphasize their relative properties accordingly.

A typical instance of the invention will be described with reference to its application for the manufacture of diaper cloth or lining material, reference being made to the accompanying drawing, in which:

Fig. 1 is a. diagrammatic side elevation of ap- 10 paratus suitable for preparing a plain sheet of paper in accordance with the invention;

Fig. 2 is a diagrammatic side elevation of apparatus suitable for preparing a creped sheet of paper in accordance with the invention; and 15 Fig. 3 is a diagrammatic side elevation of apparatus suitable for treating and creping a sheet of paper in substantially the same operation.

Referring to Fig. 1, a sheet of light-weight tissue I of open formation, such as a handkerchief stock of 9 to 11 pounds per ream (20" x 30"480 sheets) and composed primarily of fibers having a high alpha cellulose composition. may be drawn from the roll 2 and passed over guide roller 3 to the treating tank 4, which is 25 suitably jacketed and heated to a temperature of 95 to 150 but conveniently about to F. at which gelatin solutions, for example, manifest low viscosity. If complete saturation of the sheet is desired, the sheet may be submerged in the treating tank by means of guide rolls 5, 5 which are mounted below the level of the solution 6. Alternatively, the lower roller 5 only may dip into the treating solution.

The treating solution may be prepared of the following composition:

Gelatin 8 lbs. (or less) Water 100 lbs.

Upon leaving the treating tank 4 the sheet is 40 preferably passed between squeeze rolls 1 and thence to a conveyor belt 8. At this stage, the sheet may be transferred directly without further treatment to the hardening or insolubilizing reagent in tank 9, or may be given an intermediate drying by means of a blast of hot air from the blowers l2, as desired. Suction may also be applied to the sheet, while wet and/or during the drying operation, by means of the suction box I 0.

The sheet is then passed into tank 9 containing an insolubilizing solution of suitable composition and concentration, as for example:

Glycerine 30 Formaldehyde 4 (40% solution) Water (q. s.) 50-100 parts in which the formaldehyde renders the gelatin insoluble and the glycerine makes the sheet soft and also preserves it in this condition. [The glycerine, or like softening agents, etc., may or may not be added at this stage, as indicated above.]

The sheet may be submerged in the formaldehyde solution by passing under rollers 13, I3, or the lower roll only may dip into the solution and transfer the solution to the sheet, as in the gelatin impregnating tank. Upon leaving the tank, the sheet may again have excess of the reagent solution expelled by passing between squeeze rolls l4 and is then received upon conveyor belt l5 where it may be partially dried by hot air blowers I8 and suction box 20 and then passed to the heated drum dryer l9 around which it is carried by a continuous belt 2| supported by rollers 22,

23, 24. The dried sheet falls in a free loop 25 75 from which it is drawn over guides 26, 21 to take up roll 23. In the apparatus above described and illustrated in the drawing, a single treating tank, spray, suction box, hot air blast, drum drier, etc.,

is shown, but it is to be understood that such pieces of equipment may be omitted or duplicated, or supplemented, as the case may be, to provide for the various conditions of operation.

In a similar manner a sheet of creped paper may be prepared on apparatus as shown in Fig. 2, corresponding to that of Fig. 1 and in which like numerals indicate like parts. The sheet I, as before, is first treated with the impregnating solution of gelatin in tank 4, and then dried, if desired, then treated with the formaldehyde solution in tank 3, and then, if desired, passed to creping roll 30. The sheet may already be sufficiently wet to adhere to the creping roll, but if not, it may be wet with creping solution from tank 30'. Against the upper part of the creping roll is affixed a creping knife or doctor blade 30", which crepes the sheet. The finished sheet is gathered and rolled up as before on roll 28.

An alternative mode of procedure in which the gelatin and insolubilizing reagents may be applied and the sheet creped in substantially a single step may be carried out on the apparatus shown in Fig. 3. In this apparatus a single composite solution may be prepared in accordance with either of the following formulae:

In this procedure the sheet 3| is drawn from roll 32, passed over guide roll 33, and then between roller 35 and creping roll 36. The lower roller 35 dips into tank 31 containing the treating (and creping) solution 33 and applies it to the sheet so that the latter is uniformly saturated therewith. Means may be provided, such as a supplemental roller (not shown), to express any excess of the solution from the sheet, or roll 35 may bear against the creping roll 36 sufiiciently to serve this purpose. The creping roll is preferably cold and may be kept chilled by internal circulation of water. In this way, the impregnant solution is cooled and may or may not be to some extent gelatinized in the paper sheet immediately after the saturating and squeezing steps. On the other hand, the creping roll may be internally heated, thereby partially drying the sheet and likewise causing gelatinization of the impregnant.

As the creping roll is rotated in the direction of the arrow, the adherent paper sheet strikes the doctor blade 39 which crepes and removes the sheet from the creping roll. The sheet then passes onto the conveyor belt 4| which carries the same beneath spray 42, which may apply additional softening or other reagents thereto, and/or a series of driers or hot air blowers 43 and thence around the heated drying drum 44. The carrier belt is supported by guide rolls 46, 41, 48. The dried, creped sheet is then passed over and under guide rollers 49, 50 to take up roller 5| upon which it is gathered into the form of a roll of finished paper. The sheet may be slit into required widths in usual and known ways.

In this procedure the addition of ammonia retards the hardening (insolubilizing) of the gelatin solution by the formaldehyde until after the sheet has been creped. But, upon heating and drying, a large part of the ammonia is expelled and the hardening action of the formaldehyde takes place.

The porous fibrous sheet when treated by the former of the foregoing processes is first intimately permeated by the solution of the colloid, which is preferably highly dispersed, and which not only thoroughly wets the free surfaces, but

' also penetrates between and wets' the contacting surfaces between adjacent fibers. By employing appropriate concentrations and temperatures in the solutions, such dispersion and penetration is readily promoted. Usually more dilute concentrations and/or increased temperatures effect this result. At the same'time, the amount of gelatin brought into contact with such surfaces may be effectively controlled. The excess of solution, if any, may then be expelled as by squeezing, etc., or by suction, as above described. This avoids filling of the interstices or pore spaces between the fibers. In such cases, it may be desirable to employ a solution which is subject to subsequent gelatinlzation without appreciable reduction in volume. Likewise, the amount of gelatin penetrating between the contacting surface of the fibers (and subsequently forming a bond therebetween) may be regulated by the concentration as well as by the absolute amount of solution applied.

Upon subjecting the treated sheet to compression, a part of the solution (or solvent) may be expressed, as indicated in the drawing. In some cases, however, this may tend to compact the sheet and render it less porous. Accordingly, it is sometimes preferable to remove the solution in other ways, as by the application of suction, as indicated. In any event, upon subsequently drying the treated sheet the colloid is gelatinized (if this has not already been effected), and then contracts appreciably with further drying. This leaves the pores or interstices substantially unfilled and of open formation, and also serves appreciably to strengthen the gel formation upon and between the fibers and thus render it more resistant to subsequent handling and treatment.

The bonding deposit thus formed is then preferably rendered insoluble, in situ: As shown, the insolubilizing reagent may 'be applied in solution,--but formaldehyde, for example, may be applied to the sheet in gaseous condition.

The insolubilizing agent in either case is capable of thoroughly penetrating the gelatinized bond and not only renders it insoluble but also toughens and strengthens it, so that the sheet of bonded fibers thus produced is not only stronger than before but is resistant to the weakening action of water and hence retains considerable strength even when saturated. The sheet is nevertheless of open formation, and the surfaces of the gelatinized bond (upon and between the fibers) are freely wettable with water so that the treated sheet is readily wetted and rapidly absorptive and, owing 'to its porosity, permits the free passage of liquids therethrough. Since the pore spaces are relatively small, however, it opposes the free passage of solids and semi-solids, even though they are in a relatively fine state of subdivision. Moreover, on account of the absorptive structure of the insolubilized gel, the deposit may absorb water appreciably and be caused to swell, either upon immediate or prolonged wetting with water, so as thereafter not only to retain a larger proportion of absorbed water (in addition to that physically retained in its pore spaces) within the gel structure itself, but also to close up the open pore spaces to some extent and thus more completely obstruct the free passage of solids. Hence, while the gelatine bond may be made almost permanently insoluble and resistant to water, such resistance may be reduced by applying a less drastic treatment (or when a. gelatin of high viscosity and/or gel strength is used) insolubilizing or toughening, so that the paper is temporarily water resistant but ultimately penetrated by water and similar liquids, and the sheet thus rendered subject to disintegration. The latter may be promoted by bacterial action (though the formaldehyde, for example, is sufficient to prevent it in the dry sheet) and also by mechanical attrition,--which are ordinarily encountered in drainage disposal systems.

The softening agent, as indicated above, may be applied with the gelatinizing and/or insolubilizing reagents. However, it may be applied before or after such treatments. If applied before, it should of course be of such a nature or in such quantity as not to interfere with the subsequent treatments, and, if applied to crepe paper, in such manner as not to reduce the crepe deleteriously. In some cases, however, reduction of the crepe ratio may be desirable. While glycerine, which is liquid and water soluble, is cited as an example, the softening agent may be insoluble in water, and may also contain or consist of solids. Thus, an effective softness may be promoted by applying finely divided solids such as talcum powder, aluminum stearate, etc., and also by applying insoluble oils such as olive oil, oil emulsions, etc., or semi-solids such as cold cream, and the like. Water soluble antiseptics may also be applied, so that after use, and when the paper has been disposed of, the water of the drainage will dissolve and remove such antiseptics, thus permitting the bactericidal attack upon the gelatin bond, with resulting disintegration of the sheet which is (especially when used for toilet and nursery purposes) highly desirable.

While the product of this invention will, as pointed out above, recommend itself for numerous convenient applications, it is especially adaptable for use in place of diaper cloth, or as a liner when cloth diapers are still employed. For this purpose the treated sheet will be cut out of the desired size and shape, and may in some instances, particularly in multiple layers, serve alone as a complete and adequate substitute for the cloth diapers usually employed. Ordinarily, however, a plurality of treated sheets, or the combination of one or more of such sheets with other absorbent material (enclosed by the treated sheet or sheets) will be preferred in order more fully to insure adequate strength. The absorbent material used may be of low or substantially no wet strength,such as one or more sheets of untreat ed crepe tissue, or loose cellulose pulp, such as cotton or wood pulp in the form of a pad, or socalled, loose-textured, fibrous wadding. Again a single sheet of treated paper may be used as a liner with the usual cloth diaper. In this case the wet strength of the treated sheet is effective to hold the liner in position upon the cloth, without tearing and also to permit of its subsequent removal from the cloth for disposal, thus permitting the more ready laundering of the cloth diaper for re-use.

It is also to be understood that, in accordance with the present invention, the treatment of the sheet with the solution may be effected otherwise than by complete impregnation. While impregnation or saturation of the sheet will normally im- 5 part the greatest degree of strength to the sheet so treated, it may be desirable for special purposes to forego a part of such increased strength. In such cases, the solution may be applied to the sheet in a continuous open pattern, such as a 10 cross-bar system of lines, or a discontinuous, open pattern, such as spaced dots. Such patterns may be provided for by using an application roller having corresponding patterns thereon instead of plain surfaces. Again, the solution may be 15 applied in the form of a fine mist or spray, so that the sheet is closely, but not continuously, saturated. Such treatment may be more effective with relatively thick sheets where a uniform application of the solution is desired but penetration 20 of the same to a limited depth only; so that the treated surface will protect the untreated portion or layer of the sheet. Such a sheet may be adaptable for use in surgical dressings, for example, where it is desirable to keep the surface 5 fibers from disintegrating or linting while permitting the easy separation and removal of the main portion of the dressing material. Of course, both exterior surfaces of the sheet may be treated in this manner, leaving the interior fibers sub- 30 stantially unbonded.

In the several treatments above described, the points of contact between the individual fibers may be preserved. For example, when more concentrated solutions of gelatin are used, which 35 have appreciable viscosity, they may not penetrate between the fibers but tend rather to surround the fibers at their points of contact. More dilute solutions, on the other hand, may penetrate between and wet the fibers at such points, and thus form a film between the contacting points or surfaces, which is subsequently rendered insoluble. In either case, the fibers are considered as forming "points of contact with each other at such points, in the finished sheet, as well as in the sheet material treated. Accordingly, to promote both effects, the sheet material may be first treated with a dilute solution of the gelforming colloid, to promote penetration between the fibers, and then with a more concentrated soso lution to surround and reinforce the union effected between the fibers by the penetrating film of colloid material.

Other modifications of the process and other adaptations and uses for the product of the in- 55 vention will readily occur to those who have need of sheet materials exhibiting such properties. Such modifications and adaptations, however, are to be considered as contemplated by the above disclosure and included by the following claims. 60

I claim:

1. A sheet of creped tissue paper for use as diaper linings and the like characterized by alpha cellulose fibers in open formation, the fibers throughout the sheet being bonded together at 5 their junctions with a thin film of albuminous adhesive which is temporarily water-resistant for several hours, the sheet containing a softening agent in amount at least of the order of three times the amount of albuminous adhesive. and 7 the interstices between the fibers being open, whereby the article is characterized by thinness. softness, flexibility, porosity, and high wet strength.

2. A thin sheet paper product characterized by 75 alpha cellulose fibers in open formation. the fibers throughout the sheet being bonded together at their junctions with a thin mm of albuminous adhesive which is temporarily water-resistant for several hours, the sheet containing a softening agent in amount 0! approximately three to six times the amount of albuminous adhesive, and the interstices between the fibers being open, whereby the article is characterized by thinness, softness, flexibility, porosity, and high wet strength.

BENJAMIN ASNES.

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