US 2018244 A
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Description (OCR text may contain errors)
Oct. 22, 1935. A. v. ALM
PAPER PRODUCT AND METHOD OF MAKING 2 Sheets-Sheet 1 Filed Oct. '7, 1931 \MHX mw W .N\ 0 M Q 0 00000000000 ww Q fl w 00000000000000 RN .0 Y 1 5 h QQ a Away/702' pij/ICJLM Oct. 22, 1935. A. v. ALM
PAPER PRODUCT AND METHOD OF MAKING '2 Sheets-Sheet 2 Filed Oct. '7, 1931 Away/70,8
Aim/ 52 41/14 I 4 Ll (V Patented Oct. 22, 1935 UNITED STATES PATENT OFFICE PAPER rnonuc'r AND METHOD OF MAKING Application October 7, 1931, Serial No. 567,419
' od of preparing the same.
In the manufacture of various sheet materials and like products which are designed for personal use it is essential that they shall be freely flexible and shall 1 also present an extremely smooth and soft surface. For this reason cotton cloth or worn linen has ordinarily been employed. But in general'woven textiles are expensive, and they further more present serious difficulties of disposal or laundering. n the other hand, unwoven materials 'such as cotton batting possess little or no mechanical strength and consequently are too readily'disintegrated to serve as a sheet material and withstand any appreciable wear. I
Paper has been resorted to as a substitute for cotton cloth in many instances, such as for paper towels, paper handkerchiefs, etc., on account of cheapness and the fact that they may be thrown away after using. But the inherent physical characteristics of papers, generally, limit their suitability for such purposes. Among such characteristics may be especially noted the stiifness of the sheet and also of the individual fibers, the continuity and density of the matrix of hydrated cellulose, sizing, or fillers, in which the fibers are embedded, the stiffening and hardening effect of the same, the insufficiency or lack of permeability and absorptivity of such sheets in respect of gases and liquids, want of strength, loss of strength and ready disintegration by friction or by wetting, or both,- want of flexibility (especially when folded or twisted) and wantiof frictional wear resistance generally. Consequently, while paper has been employed to some extent (as for paper toweling, etc., above mentioned) it ordinarily does not possess sufficient strength for anything but brief temporary use,-- or, if it possesses suificient strength, its usefulness is limited to those purposes in which extreme softness of texture is not a desideratum.
It is accordingly an object of the present invention to provide a relatively thin, soft, flexible sheet material of paper which shall possess sufficient strength, particularly when wet, not only to approach a light weight cloth or gauze in tensile strength but to possess appreciable resistance to wear and surface disintegration by friction. It is also an object that such a sheet shall be freely permeable or porous to air and water or other liquids, but preferably relatively impervious to solids, semi-solids, or colloidal suspensions. An..
other object is to produce such a sheet having a substantially open, randomly reticulate structure, in contrast to the closely formed matrix of papers generally. A further object is that the sheet material produced may be ultimately disintegrated by water or at least by the chemical, mechanical or bacteriological action of ordinary drainage. Other objects will appear from the following disclosure.
In accordance with the present invention, a thin, light weight tissue ,paper is'first prepared, preferably from purified wood pulp, which consists of fibers substantially of alpha cellulose and which is substantially free of cellulosic matrix, bonding matter, sizing, fillers, and the like, to form a sheet of open formation-in which the fibers are in a heterogeneous dispersed arrangement or tangle, as shown upon microscopic examination; A sheet of paper thus formed has substantially no strength when wet and comparatively little strength when dry, the dry strength depending upon the tangled arrangement of the fibers rather than adhesion or bonding therebe-' tween. The lack or loss of mechanical strength upon wetting may be due to two causes: first, that the individual fibers quickly absorb water and are thereby rendered limp; and second, that the wetted fibers are permitted to slide freely upon one another, on account ,of their wetted surfaces, so that they are readily separated under tension. Probably both conditions obtain in the wetted sheet.
More dense or thicker sheets may in some cases be employed, but in order to provide and preserve an open formation the sheet in such instances will be either perforated with minute holes or subjected to tension to disrupt the close arrangement of the fibers. Again, the sheet may be very loosely formed on the paper making machine.
In the practice of the present invention, a sheet 40 of paper of open formation, as above described,- which is either thin and of light weight such as tissue paper or if of slightly heavier weight is purposely prepared in such manner as to give it a comparable degree of flexibility, softness and free permeability or porosity as already indicated,is treated with a toughening (or converting) agent which is adapted to render the alpha cellulose fibers gelatinous and hence mutually adhesive and cohesive. Subsequently the sheet is treated to remove the reagent and to make the thus bonded fiber surfaces substantially insoluble in water. The toughening agent characteristically bonds the fibers together so that, upon subsequent wetting, the treated sheet (although of ap- 55 acts upon the alpha cellulosic fibers per se and sequently, it presents the anomaly of a sheet of thin, open, porous paper which is relatively strong while wet as well as when dry.
Typically,-the toughening reagent is one which converts the surface portions thereof -into cohesive films (without the addition'of supplemental cellulosic material thereto)whereupon the superficial cellulosic films thus formed of the fibers merge or fuse at their points or areas of contact upon conversion or removal of the reagent the bonded fibers have more or less water permeable but strong, water insoluble surfaces and bonding films between adjacent fibers. Thus, the unwoven, unbonded, reticulated cellulose fibers are transformed into a firmly bonded but open structured, freely porous sheet. sulting sheet, which is also characteristically freely flexible, may be used for purposes similar to those for which sheets of soft cloth have heretofore been required, and not only are readily and completely saturated by water but permit the free penetration of water therehrough. At the same time the sheet retains substantially all of its dry tensile strength or, in some instances, may be of somewhat greater tearing strengQh when wet than when dry. The latter appears to be due to the orientation of the fibers in the direction of strain.
lose fibers superficially to render them mutually adhesive or cohesive and the integrated sheet thus obtained is found to be rendered appreciably resistant to subsequent disintegration by water. In any event, the toughening agent maybe applied continuously in the form of a liquid treating bath, or discontinuously as a finely dissemihated mist or coarse spray, when appropriate. or it may be applied in the form of a positive, continuous or discontinuous open-spaced pattern, as by printing, or by other well known modes of application. The residue of the toughening agent, if any, is promptly removed or otherwise controlled in its action upon the fibers, and the treated sheet, upon drying, may be regarded and used as the finished product, or may be given other treatments, as desired. A
In this treatment, the open, randomly reticulated'struc ure of the fibrous sheet is preserved in respect of the relationship of its fibers, so that the treated sheet is, for example, substantially as permeable to liquids as it was before the treatment. It nevertheless manifests greatly increased tensile strength when dry, and, even after complete and continued saturation with liquids such as water, its strength is only slightly less or substantially equivalent to its dry s rength. Consequently. this property renders the treated paper applicable to many uses for which cloth has heretofore been regarded as indispensable, and not only is the product thus obtained capable-in many ins ances of replacing cloth but it is in many Hence the rea These conditions do. not obtain with cloth and the like since-such materials, in order to be fab,-
' ricated or woven, must contain a relatively large proportion of long fibers. Moreover, the long fibers which are thus applicable for cloth, such 5 as cotton, are not only firmly united in the yarn or thread from which the cloth is woven but the threads are permanently woven together in the fabric, and strongly resist disintegration. On the other hand, paper which has been treated as 10 above described not only absorbs water readily but is ul'imately substantially disintegrated and hence easily and safely disposed of, without danget of clogging drains or other receptacles.
The application of the invention will be de- 15 I scribed with reference to specific instances of treatment of paper tissue, in sheet or web form.
with the reagents above defined by means of apparaius illustrated in the accompanying drawings, in which: Fig. 1 is a diagrammatic illustration of apparatus for treating plain tissue;
Fig. 2 is a similar illustration of appartus for making creped paper stock;
Fig. 3 is an illustration of apparatus for print 35' ing the paper with a toughening agent; and 4 Fig. 4 is an illus'ration of apparatus for both printing and creping the sheet material.
For example, in carrying out the invention as indicated in Fig. 1, a sheet or ,web I of tissue paper 30 of high alpha cellulose content (typically of light weight,-e. g., having a weight of 9 to 15 lbs. per ream on the basis 20" 30"-480, or tissue commonly designated as "facial tissue" or handkerchief stock) may serve as the raw material. This 35 is characterized by consisting substantially entirely of fine, bleached, or unbleached alpha cellulose fibers (with or without a small amount of cotton fibers) which form an open, tangled, heterogeneous arrangement, substantially without 40 bonding material, cellulosic matrix. sizing, filling, etc., as above stated, and typically has a sumciently open formation to permit the free passage of water and to present definite apertures therethrough when viewed under the microscope, (e. g. 45 at 10 diameters).
Referring to the drawings, a sheet of such tissue paper I is drawn from the roll 2, passed over roll 3 and thence through the treating bath contained in tank 4, in which it is submerged by a 50 guide roll 5.
The treating or'toughening solution in the instant case, may be composed of sulfuric acid, in which case it is preferably relatively concentrated (of the order of 66%) and the treatment is of 55 relatively short duration so as to avoid appreciable hydration of the paper with consequent swelling of the fibers and closing of the interstices or pore spaces therebetween. Nevertheless the sheet is uniformly wetted by the reagent which 60- is effective upon the alpha cellulose fibers, superficially to soften the same enough to promote adhesion between the crossed and contacting fibers. Profound degeneration or gelatinizatlon of the fibers, with consequent swelling of the 65 fibers and closing of the interstices is specifically avoided. To this end (and also to facilitate subsequent handling and preserve the integrity of the sheet) the wetted sheet is promptly with-, drawn and passed between squeeze rolls 6 and thence to the horizontal apron l where it is supported and washed as by sprays of water from the perforated pipes 8, 8. The acid in the sheet is then preferably neutralized by passing through a suitable reagent in tank II, in which it is submerged by guide rolls l2, l3, l4, ii. For this purpose, a solution of caustic soda or sodium bicarbonate or ammonia may be employed, (or
any suitable alkaline neutralizing agent) of sufficient; concentration to neutralize the residual acid left upon the sheet and to check its fur ther action. Additional neutralizing tanks may be used, if required. The sheet is then again washed by sprays of water. (or other volatile liquid) as indicated at l6. It may also be treated with a non-volatile liquid or softening agent, such as glycerine, and the like, as by spray I! or equivalent apparatus, suitable therefor. It is then passed over a heated dryiugdrum l8, by means of guide roll l9 and conveyor belt 2| which is carried by rollers 22, 23, 24. Additional treating and washing means and drying drums may be added to those indicated if desired. The sheet I, as it comes from the drying drum i8, and conveyor belt 2|, is allowed to hang freely in a loop 25 and is then passed over and under tensioning roll's26, 21, 28, 29, and finally gathered upon the roll 3|.
In such treatment of the tissue there is but little tendency for the fibers to felt together and consequently, since the fibers are given such brief treatment as not to cause them to swell appreciably, the structural relationship and arrangement of the same is preserved substantially as in the original paper sheet and without filling or closing of the interstices. The individual fibers, however, acquire a. relatively continuous sheath which upon subsequent washing, neutralization and drying, is more resistant to the weakening action of water than the untreated fiber but is not thereby rendered unduly stiff or brittle, or water-repellant, so that water for example may wet and pass freely through openings between such treated fibers almost as readily as before but does not penetrate between their points of contact enough to weaken the paper sheet. Consequently, the tensile strenth of the sheet is not appreciably decreased even though 'it be thoroughly wet with water.
As a modification of the procedure above described, it may be desired to impart slight elasticity or stretchability to the sheet. This may be effected upon the paper treated as above by creping the sheet, which is preferably carried out in a continuous operation with the treating step, or by embossing, etc.
For example, the sheet I may be led through similar apparatus (as shown diagrammatically in Fig. 2, in which like numerals indicate corresponding parts in Fig. 1) comprising the treating tank 4, washing device 8, neutralizing tank H,
and washing spray l6, and thence over guide roll 9 and between creping rolls in and 20. The lower creping roll may dip into a creping bath 30 if desired, but frequently the sheet, when wet with water is per se sufliciently adhesive to thecreping roll. The upper creping roll is provided improved dry strength and upon wetting preserved approximately 42% of its dry strength in sheet, but it is usually preferable to form a relatively coarse and low crepe ratio for those purposes in which a thin sheet and very soft texture is required. The crepe ratio may be controlled by suitably regulating the tension upon 5 the creped'sheet, an increase of tension tending to stretch out and reduce the crepe ratio or practically to remove the' creped appearance and increased thickness of the sheet, if desired.
- In order to effect further softening and flexibility of the sheets, whether prepared with or without creping, a softening agent such as a neutral or physiologically harmless non-volatile liquid, typically glycerine, di-ethylene glycol, etc., may be applied, before creping, as at H, or by adding the 15 same to the creping bath or by appropriate subsequent treatment of the sheet therewith, not shown.
A sample of paper which before treatment would permit the passage of 40 cc. or more of 2 water per unit area per minute therethrough, was, found to be pervious to substantially the same extent after being treated in themanner above described. At the same time it manifested the machine direction of the sheet and 38% of its dry strength transversely of the sheet. It nevertheless wetted freely with water and showed substantially no tendency to swell or disintegrate for several hours. Upon ingestion with acids or alkalis and particularly with ferments which are commonly encountered in drainage, disintegration is activated, and water alone may be eventually efiective to separate and disperse the fibers. 35 The creping also renders the sheet effectively thicker in some respects without decreasing its porosity or permeability to liquids, or other qualities. Thus, for example, a plurality of creped sheets placed face to face will have greater 40 absorbency than a like pad formed of uncreped sheets.'
- As a further modification of the invention the toughening or converting agent may be applied to the fibrous sheet in predetermined areas or patterns instead of by uniform wetting or saturation throughout. This may be effected, for example, with suitable apparatus as diagrammatically, illustrated in Fig. '3. The paper sheet H is drawn from roll 42, passed over guide roller 43 to print- 50 ing cylinder 44 which is preferably covered by a conveyor belt 45 and carries the sheet 4| around the cylinder and then a short distance away from the cylinder, by passing over ofiset guide rolls 46, 41,. In its passage on the cylinder 44, the sheet 41 isimprinted by means of a printing roll 48 which is "inked with one or another of the toughening agents or parchmentizing soluti'ons above described, contained in tank 49, by means of a fountain roller 5| and web .52 carried by roll- 60 ers 53, 53. The printing cylinder may carry any appropriate design,--e. g., to produce a continuous pattern of the composition with untreated areas spaced apart thereby or may have a discontinuous pattern of the composition with a 65 continuous untreated area therebetween. Of these types, the former will be stronger, the latter somewhat more porous or open.
The parchmentizing solution is preferably washed out, the sheet being passed, on supporting o belt 50, beneath a series of showers 60, which may also contain neutralizing solutions more quickly to check the gelatinizing and bonding action of the parchmentizing reagent.
The printed sheet is then passed successively 75 over and under rows of guide rollers 54, ll, forming a series of vertical festoons, in the course of which the sheet is .dried, usually with the application of artificial heat by means of hot air ducts (not shown). At this stage the sheet may also be treated with a softening agent, such as glycerine, etc., as before. The sheet is then passed over drying drum 56, by meansof'a belt I! carried onrollers 58, I9 and 6|. The sheet then falls in a loose fold 62 from which it passes over and under tensioning rolls 63, 64 to rewinder or take-up roll 65 upon which it is firmlyheld by guide roll it,
may dip directly into the parchmentizing solution contained in tank ll-or it may be wetted by a supplementary roll (not shown) which dips into' the parchmentizing bath. If the pattern is relatively coarse or open supplementary wetting of the sheet may be desired. The sheet or web I I may conveniently be passed between the printing roll 15 and creping roll 10,,the two being closely spaced or held tightly together as the case may be. In either event, the 'paper sheet is suitably treated with the reagent, which may also serve, in conjunction with the adhesiveness of the softened cellulose fibers, adheslvely to retain the sheet upon the creping roll. volved, the sheet becomes more firmly adherent to the creping roll (facilitated by heating the roller internally, usually by steam) and is then removed from the roll by contact with a doctor blade ll, mounted against the surface at a suitable angle. The paper is not only removed from the roll, but also creped. The creped sheet is received by a conveyor belt 19, carried by rollers upon which it may be washed and/or neutralized by sprays Cl and thence passes to belt 82, supported by rolls .3 to 86, which carries the sheet into contact with thedrying drum 81. The latter is rotated and delivers the dried or partially dried sheet into a free loop or festoon 88 from-which it is drawn over and under guide rolls 89 to 9| (which may be driven to prevent stretching of the creped paper) and gathered onto roll and firmly held thereon by roller 96. r
The printed or saturated sheet may be washed either before or upon the creping roll It, so that,
upon being creped by the doctor blade it may be simply dried and rolled up. Again it may be found desirable in the above mode of procedure, to
by making obvious changes in the arrangement of the apparatus, accordingly. Other treatments may be combined with those described, or other sequences of operation, to impart special properties to the treated sheet, such as the application of softening agents, as above mentioned, the addition of medicaments, deodorants, powders, and the like. 7
It is to be noted that in each of the several modifications of the invention above described, while As the creping roll It is recommonly referred to as rag'fibers in the art. Buch fibers, by intermingling with the others and frictional engagement .therewith,'mav in fact be employed to impart appreciable strength and toughness to the sheet.
The product of the invention is characterized by having a soft, fneely pliable texture, is per- I temporarily retains such strength in large part, even when. thoroughly wetted with water, al-
though it may be eventually completely disintegrated under the ordinary conditons encountered in sewage or drainage. Consequently it lends itself to the fabrication of many toilet and nursery accessories where soft cotton or other textile materials have heretofore been regarded as essential; and in some respects, such 20 as cost, lightness of weight, disposability, etc.,'it is to be preferred.
For example, such sheet materials, and especially creped paper, made in accordance with the invention, is eminen ly suitable for use as 25 diaper cloth or as a lining for cloth diapers-of the usual type. The material may be cut to suitable size and shape and used in single sheets (as liners" so-called) or in a number of superposed sheets, which may be either plain or creped, or 30 both. Various combinations and arrangements will suggest themselves to users of the material, as well as other purpom for which the properties of the sheet material thus provided recommend it 35 as particularly applicable.
It is to be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalentswhich-fall within the scope of of a sheet of tissue paper of open formation to 45 bind the fibers-togetherwith a water resistant bond without substantially filling the interstices of the paper.
2. The method of treating a soft flexible porous sheet of tissue paper, composed substantially of 5 alpha cellulose fibers in open formation, which comprises parchmentizing only the surfaces of the fibers to bind them together with a water resistant bond which. does not substantially affect the openness of saidformation. 55
3. An article of the character described comprising, a soft flexible sheet of tissue paper of open formation, characterized in that the surfaces of the paper fibers are converted into a water resistant bond which binds the fibers together