US 2771363 A
Description (OCR text may contain errors)
Nov. 20, 1956 J, FlsH PAPER WEB WITH A SIMULATED WOVEN TEXTURE Filed March 5. 1949 United States Patent PAPER WEB WITH A SIMULATED WOVEN TEXTURE .lames Fish, Erving, Mass., assignor to The `Paterson Parchment Paper Company, Bristol, Pa., a corporatie of Pennsylvania Application March 3, 1949, Serial No. 79,457
Claims. (Cl. 92-3) This invention relates to foraminous papers.
For many ltering operations, and others Where solids must be retained on one side of a barrier which permits the more or less ready through-flow of liquids, woven fabrics are often more satisfactory, albeit more expensive,v
textured minor areas alternating with thicker more closely l textured major areas.
As well understood inthe art, the paper maker usually strives to achieve the maximum possible uniformity of distribution of the randomly matted fibers constituting the paper web. Excepting possibly in the case of certain thin tissues, every effort is usually made to maintain a uniform 4fiber` distribution throughout the paper web such that pinholes or macroscopically visible foramens areavoided. lt is recognized that certain very tenuous tissues have been made so open textured as to be visibly macroporous.` These open textured paper webs have heretofore been characterized by very light weight and a purely random and uncontrollable distribution of their discontinuities, or pinholes.
Because of their light weight and correspondingly low strength-even when reinforced with Wet-strength imparting resins-these open textured tissues can substitute for cloth, in leaching, dyeing and other processes, where a relatively free ow `of liquid through the septum of a solids container is required, only in cases wherethe contained material is in very small amount and the container is subjected to little 0r no agitation or other disruptive strains. For example,such high wet-strength tissues substitute moderately well for cloth in containers for individual portions of tea, the so-called tea balls. the other hand they are insufficiently strong to give adequate assurance against disruptive failure when used where agitation or stirring is involved as obtains in the use of spice bags for instance.
When greater strength is obtained by increasing the thickness of the paper web the liquid transmission rate is correspondingly `cut down.
This is- Well understood in the art of making chemical filter papers Where the avoidance of all macropores is desired. yA so-called fast filter paper is one having the highest liquid transmission rate obtainable without macropores. These papers are usually made with long fibers subjected to little preparatory beating and just thick enough to avoid visible pinholes or macropores. Slower papers are made either in heavier weights from the same furnish or in the same weight but of greater density from shorter more heavily beaten `fibers.
There has heretofore been no wayof making a paper web `having the :strength characteristics of a sheet of 2,771,363 Patented Nov. 20, 19,56
twenty to thirty pounds basis Weight and the ultrafast liquid transmission rate of an open textured tissue' of ten pounds or less.
The method and product of this invention provide a utilitarian answer to the problem of producing ultrafast liquid transmission through a sheet of paper of greater than tissue basis weight.
The products of this invention are characterized by the simulated appearance of a Woven fabric. It has been common practice to impart to paper a simulated woven texture. However this has heretofore been accomplished, the effect was obtained by local compression, as in laid, watermarked or embossed paper, which compression did not disturb, to any appreciable extent, if at all, the lateral substantially uniform disposition of the bers. Where microporosity in paper is a desirable feature, as in lter paper for instance, impressed designs especially of the watermark type diminish the effective porosity because such designs represent local increases in compactness or density yand the liquid transmission rate is in some varying measure inversely as the density for any given paper web of uniform formation.
Lack of uniform formation or wildness in paper as customarily made results from randomly uneven deposition `of the fiber on the wire of the paper making machine. Except in the making of some art papers and cheap wrappings the paper maker seeks to avoid wildness because the adventitious and random local concentrations of fiber do not impart optimum physical characteristics to the sheet. As heretofore made the ideal sheet of paper is characterized by uniform formation and uniform compactness or density excepting only when the density was locally increased by compression to produce a design.
All paper` is made by the deposition of fibers, generally cellulose, from a water suspension upon a wire screen. The choice of size of the Wire mesh depends upon'many factors such as the quality of the paper being made, the speed of the wire and others well understood in the art, but the range of mesh size as heretofore used lies between 10() and 50 mesh. When the coarser mesh wires are used it is possible to tell the wire side from the opposite or felt side by visual inspection when viewed in light of grazing incidence. In no case does the residual wire mark on papers heretofore made have any appreciably advantageous effect on the utilitarian properties of the sheet.
Contrarily it is an object of the present invention to use a heavy wire large mesh screen sometimes though not always or necessarily backed with a ne mesh screen to the end that the fibers may be deposited within the meshes of the coarse screen to a height substantially equal to or slightly greater than that of the screen at the wire knuckles whereby to produce a sheet simulating in appearance a woven fabric.
lt is another object of this invention to produce a paper web of substantially uniform compactness characterized by substantial differences in thickness of which the thicker portions predominate and further characterized by a regular sequential arrangement of thick and thin portions forming a weave-like pattern.
It is another object to produce paper webs in weights, say for example 18 pounds or more on the basis of 500 sheets 24 inches by 36 inches, substantially greater than that of those papers classed as tissues which paper webs are characterized by a regularly recurring sequence of small areas of tissue-like thinness and sometimes though not always or necessarily exhibiting a macro-foraminous texture in the alternate thinner portions of said small areas.
A further object is to produce a simulated woven texture in a paper web characterized by maximum thickness where the pattern simulates thread crossings and minimum thickness in the areas between diagonally adjacent simulated thread crossings.
A still further object is to produce a paper web having macroscopic foraminous areas in substantially regular sequential arrangement in the range of from 12 to 6 to the inch both with and across the grain of the web preferably though not always or necessarily of the same number in each of the two directions.
A further object is to provide a method of forming long fibered pulp into a foraminous web of paper which comprises clothing the cylinder mold of a single cylinder paper machine with a facing wire of ten to twenty-four mash such as has heretofore been used only for the backing wire and sometimes but not always of necessarily reversing the customary cylinder clothing whereby the normally fine facing wire is used as a backing for the coarse wire in the stated range heretofore commonly used as backing wire, and it further comprises the steps of causing fiber to be deposited within the meshes of the coarse wire facing to a height only slightly greater than that of the high knuckles of said wire and thereafter couching and removing from the wire the so-formed web of fibers in the customary manner.
Other objects and advantages will hereinafter appear.
Reference is had to the drawings, in which:
Fig. 1 is a magnied plan view of a small area of a paper made according to the method of this invention;
Fig. 2 is a cross section taken along the line 2 2 in Fig. l;
Fig. 3 is a magnified View in cross section of a coarse wire screen in which the warp wires are shown in section and the shute wire is shown in elevation;
Fig. 4 is a magnified plan view of a combination cable and wire coarse screen;
Fig. 5 is a cross section taken along the lines 5 5 in Fig. 4;
Fig. 6 is a magnified plan view of a twill woven coarse wire screen having cable-laid warp wires and plain shute wires;
Fig. 7 is a cross section taken along the lines 7 7 of Fig. 6;
Fig. 8 is a magnified plan view of a small area of paper made on a coarse twill screen such as is shown in Figs. 6 and 7;
Figs. 9 and 9a are magnified views in cross section taken along the lines 9 9 and 9a 9a in Fig. 8;
Fig. l() is a magnified plan View of a course corduroy screen; and
Fig. ll is a cross section of Fig. 10 taken along the line 11 11 of the latter figure.
As is well understood in the art, the sheet forming elements of a cylinder machine comprise a wire-clothed cylinder mold which revolves horizontally in a vat to which is fed a dilute suspension of fiber in water. The outlet of the vat, from within the cylinder mold, is adjusted so that a desired head, between the outside and the inside of the cylinder mold, is maintained according to the weight of the iinished sheet to be made.
As the water iiows through the wire covering of the cylinder mold the water-borne fibers are caught thereon and the cylinder mold is revolved to progressively bring new wire surface into the zone of liber deposition. At or near the highest point of its periphery a felt is brought into tangential pressure Contact with the accumulation of fiber on the wire, and the fiber web is removed from the wire or couched by the felt which carries it on to be pressed and thereafter transferred to the drying section of the machine.
In ordinary practice the fibers bridge across the fine openings of the wire screen and cover the wires to a depth corresponding to the thickness being made, so that after couching to the felt and subsequent removal of the residual water by pressing and drying the wire marks are,
4 as stated, to a great extent if not always entirely obliterated.
When, according to the method of the present invention, the facing wire is heavy and of coarse mesh the greater part of the deposited fiber is retained below the level of the high knuckles of the wire and only a minor part of the fiber lies over the knuckles. As the wire is ordinarily woven the warp knuckles are higher than the shute knuckles, and when the cylinder mold is clothed with the warp running circumferentially and the fiber deposition, according to the method of this invention, is carried to a height very slightly greater than that of the warp knuckles, the resulting paper web is characterized by a varying thickness corresponding to the varying distances between the top of the warp wire at the inside of the bottom knuckle and the top of the warp wire at the high knuckle. Thus, with reference to Figs. 1, 2 and 3, the sheet may exhibit small foramens or discontinuities 1 corresponding to the top of the high warp knuckles 4. These small foraminous areas may be crossed by a few fibers or none depending mainly upon the precision of the weave and the various adjustments within the operators control.
When the sheet has been formed to leave foraminous areas corresponding to the high warp knuckles of wire as ordinarily woven, the said foraminous areas will be found to alternate, both laterally and longitudinally, with areas 2 of tissue-like thinness corresponding to the top knuckles 5 of the shute wire which are ordinarily slightly below the level of the high warp wire knuckles. The difference in the amount of fiber overlying the top of the knuckles of circumferentially disposed warp and of laterally disposed shute wire is generally greater than would be indicated by the actual difference in level between the two sets of knuckles. This is thought to be due to the rotary motion of the cylinder in the direction of the warp wires. The remainder of the web surrounding the local areas 1 and 2 exhibits thickness in excess of the latter areas. This portion of the web, designated generally by the reference numeral 3, is continuous throughout the web and is the primary strength-conferring portion.
As is well understood in the art, the higher the rotary speed of the cylinder mold the greater the tendency of the fibers to lie in the general direction of rotation, in consequence of which cylinder-made paper is more apt than not to exhibit greater strength longitudinally, i. e., in the grain direction, than it does laterally or across the grain. With the warp wire disposed circumferentially of the cylinder mold, as is customary, the foraminous areas 1 have their long axis in the grain direction. This disposition tends to weaken the sheet somewhat laterally. Slightly better lateral strength can be obtained, everything else being equal, by clothing the cylinder with the warp wire running laterally rather than circumferentially. Another and preferred expedient is to use a clothing composed of cable-laid warp wire 6, see Figs. 4 and 5, and single strand shute wires 7 in which the six fine wire strands composing the cable-laid warp wire flatten out somewhat at the knuckle and do not extend above the level of the single strand shute wire. Rolled wire in which the knuckles are flattened by passing the woven wire between pressure rolls may be used, but the combination of cable-laid warp and single strand shute wire is preferred as stated.
When, as may sometimes be the case, it is desired to so distribute the thin and thicker areas of the sheet as to more nearly equalize its strength with and across the grain, and more particularly when it is desired to increase the area of the thin portions over that obtaining from the use of wire as hereinbefore described, the cylinder mold may be clothed with twill woven wire of the character, for example, shown in Figs. 6 and 7. It is characteristic of a twill weave that on one side the warp wire has a long knuckle and on the other side the shute wire knuckle iS long. When the use of twill woven wire is indicated best results are obtained with wire composed of cable-laid warp and single strand shute wire, and for the stated purposes the wire clothing should be so applied to the cylinder that short cable-laid warp knuckles 8, Figs. 6 and 7, and the long shute knuckles 9 are on the outside or working surface. The twill weave gives best results when the sheet is to be characterized by fairly Well closed tissue-thin areas 10, as shown in Fig. 8, with their long axis normal to the grain of the sheet, alternating with relatively short thin areas 11 which may be macroforaminous or closed as desired, but are in any case disposed at right angles to the longer transverse thin areas.
Having described the method of this invention and how it may be practiced, it will be obvious to those skilled in the art of cylinder paper making that other modifications of the wire will produce corresponding tnodications in the pattern of the thick and thin portions of the sheet as long as the thickness of the wire is of a higher order than that of the sheet produced upon it so that the residual wire mark is almost if not quite as deep as the overall thickness of the sheet. Thus, a sheet characterized in the main by alternating thick and thin lateral bands may be produced on wire of a corduroy or Dutch weave as illustrated in Figs. and 11. When a corduroy Weave is used the shute wires 12 should be, for best results, substantially thicker than the warp wires 13 and ,the said shute wires should extend longitudinally of the cylinder mold.
Both in .the practice of the method of this invention and in the use of the product for the purposes for which it is particularly adapted best results are obtained when the furnish comprises in preponderant amount what the paper maker terms long free bers.
With facing wires between 18 and 24 mesh there is little or no advantage in using a finer backing wire unless the furnish comprises comminuted bers which are not recommended for best results either as to process or particular utility of the product. When, as for the heavier weights, the chosen facing wire lies in the range of 10 to 18 mesh there is sometimes advantage in using a finer backing wire. The factors determining whether or not there is advantage in using a iner backing wire are the length of ber and the required peripheral velocity of the cylinder mold.
The common use of a heavy backing wire is dictated solely by the need for support for the usual ne facing wire. According to the method of this invention the facing wire is necessarily heavy and there is generally no need for a back support other than that afforded by the ribs of the cylinder mold.
Among the advantages ofthe products of this invention, the most important one grows out of the novel combination, in a substantial sheet of paper, of good strength and ultra fast through-flow. Inasmuch as the throughflow characteristic has advantageous utility mainly in the presence of fluids and most particularly aqueous fluids it is obvious that its good dry strength feature must be made to persist in the wet state. High wet strength may be imparted in known manner either by the inclusion in the furnish of the suitable resins or by subsequent treatment such as parchmentizing.
l. As a new article of manufacture, a paper web wherein the interfelted relation of the component bers is continuous throughout said web being of basis weight materially exceeding that of tissue and having a substantially uniform pattern of small areas of tissue-like thinness, said areas constituting collectively a minor part of the total area of that portion of the web in which they occur and each being entirely surrounded by an area of greater thickness, and the said thicker areas being interconnected and constituting the continuous strength conferring portion of the web,
2. A paper web according to claim l wherein the areas of tissue-like thinness and the surrounding areas of greater thickness are of substantially the same density.
3. A paper web according to claim 1 wherein the occurrence of the areas of tissue-like thinness is in the order approximately of from 144 to 36 to the square inch.
4. A paper web according to claim 1 whereof the basis weight is not materially less than 18 pounds.
5. As a new article of manufacture, a paper web of basis weight not materially less than 18 pounds and of substantially uniform density throughout whereof the component matted fibres are in continuously interfelted relation and substantially random arrangement, said fibres having a systematic secondary disposition affording in sequence minor areas of tissue-like thinness alternating with substantially thicker and more closely textured major areas, said major areas having continuity throughout the web so as to constitute the strength conferring portion of the latter, and said minor areas being distributed in substantially uniform pattern approximately in the order of frequency of 144 to 36 to the square inch of web surface.
References Cited in the le of this patent UNITED STATES PATENTS 550,353 Parker Nov. 26, 1895 847,352 Meincke Mar. 19, 1907 995,602 Hawes June 20, 1911 1,224,650 Kitchen May l, 1917 1,616,211 Armstrong Feb. 1, 1927 1,616,222 Harrigan Feb. 1, 1927 1,699,760 Sherman Ian. 22, 1929 1,883,526 Bryan Oct. 18, 1932 2,154,201 Frost Apr. 1l, 1939 2,225,585 Devereux Dec. 17, 1940 OTHER REFERENCES Papermaking Through Eighteen Centuries, by Hunter, published in 1930 by William Edwin Rudge (New York), pages through 194; copy in Division 5.6.