US2045096A - Porous long fibered nonhydrated paper - Google Patents

Description

Patented June 23,, 1936 UNITED STATES PATENT OFFICE Fay H. Osborne, Windsor Locks, Conm, assignor to C. H. Dexter & Sons, Incorporated, Windsor Locks, C'onm, a corporation of Connecticut No Drawing.

Application November 22, 1934, Serial No. 754,307

I '8 Claims. (cl. 92,-3)

This invention relates to paper. My improved paper finds a variety of uses such, for example, as a base for stencils where strength and durability, uniformity in fiber lengths, and uniformity 5 in the distribution of the fibers and the interstices therebetween are important considerations; for packing and cleaning lenses, it being soft and pliable, lintless, and free of abrasive materials; as a wrapping for glassware and polished l0 metals where flexibility and strength, soft texture, and freedom from abrasives are important factors; in the electrical field where its high rate of absorption and its total absorptive capacity (when unsized) is made use of to absorb electrical solutions, thus making a dielectric for condensers, wire covering and similar products; and to cover the wings of model airplanes where its lightness (when made thin) and ability to absorb the dope are factors. The paper may be of any desired weight depending on its intended use,

and it may be sized if desired.

Heretofore, as far as I am aware, paper of this general sort (but lacking some of the desirable characteristics of, and inferior in many respects to, my improved paper) has been excluseively made by hand and only in small sheets. Such hand-made paper (known as Japanese yoshino paper as it is principally made in Japan where labor is very cheap) leaves much to be desired in the Way of strength and durability, uniformity of thickness, distribution of fibers and the interstices therebetween, the absence of lint, et cetera. A sheet of Japanese yoshino paper is made up of fibers varying greatly in length from one another, some of the fibers being relatively minute, and others being crushed or frayed, resulting in a paper which to a noticeable degree is linty and which has thin or weak spots,

rendering it not entirely satisfactory for certain uses such, for example, as a base for stencils. Japanese yoshino paper is procurable only in small sheets which, in the same lot, vary greatly from one another in thickness. The cost of coating or impregnating these small sheets is considerably higher than would be the case if the paper were produced in rolls of unlimited lengths.

An aim of the present invention is to provide an improved, long fibered, soft and pliable paper which is characterized by its strength and durability; by its uniformity in texture, weight, and thickness; and by its high absorptive characteristics when unsized; which is substantially free of weak spots and clots; which is very soft and pliable when unsized; and which, for all practical purposes, is lintless.

A further object of the invention is to provide a paper, having the above and other characteristics, in the form of long webs of unlimited 5 lengths (as distinguished from separate small sheets) in order to effect economy in manufacture of the paper and economies in the subsequent processes of coating the paper or impregnating it.

In accordance with the present invention, I form my paper from the vegetable fiber of the Musa family or genus and, especially, fibers of the banana species. More particularly, and by preference, I form my paper from the fibers of Musa temtz'lis. Musa textz'lis, in the raw stock, is composed of structural fibers of pure cellulose encrusted with ligno material and held together by gums and waxes. The structural fibers from such stock are more or less uniform in length, the fibers of such stock varying from four to seven millimeters and there being nominute fibers which will produce lint in the finished paper. These fibers are relatively cylindrical and have tapered or pointed ends and have little or no tendency to curl or twist so that they do not become entangled or matted but, on the other hand, they will remain separated from one an other when suspended in a largevolume of water. I have found, by experimentation, that ordinary fibers are not suitable for this type of paper. Fibers like linen or cotton tend to twist together in the process of forming the paper, thereby forming bundles which give a clotty effect in the finished paper. Fibers like wood (as bleached 35 sulphite) are too short and, therefore, give a lint to the finished paper which is undesirable.

The structural fibers of pure cellulose forming my improved paper have their original physical and chemical characteristics; that is to say, the 40 fibers are not in any way hydrated during the process of making the paper, and they are not' crushed, shredded, flattened, or frayed. The paper is entirely devoid of all the natural waxes, gums, and ligno or encrusting constituents pres- 5 cut in the original raw stock. The fibers 'comprising my improved paper are substantially uniform in length as before stated and are distributed with such uniformity that they leave substantially uniformly spaced openings through- 50 out the area of the web and avoid clots or bunches of fiber such as occur in yoshino paper. The webs, which are of unlimited lengths, are uniform in thickness and in weight throughout, the variation between various portions of a web not 55 amounting in any instance to more than five per cent. The fibers extend in all directions so that the paper has no grain and, therefore, it is of equal strength and equal absorbency in all directions. Yoshino paper, on the other hand, contains some narrow areas in which the fibers are definitely oriented and other areas in which they are differently oriented, so that the strength of the paper is not equal in all directions. It is observed that, since the fibers are of more or less uniform length and the original physical and chemical characteristics of the cellulose fibers are retained, the fibers being non-hydrated and uncrushed, the original strength of the fibers is taken full advantage of to produce a paperwhich is strong and durable. Also, the paper is very soft and pliable and, for all practical purposes, lintless; further, it will not appreciably expand when wetted with water, nor appreciably contract when dried.

The fibers are not hydrated in the process of forming the prepared stock and all of the natural gums and waxes are eliminated and, therefore, the paper has a very high rate of absorption and a high degree of total absorption, factors of the utmost importance. The high rate of absorption of the paper permits of economy in the process of coating or impregnating it, it being clear that the paper web may be run during these processes at a greater speed than would be the case if the paper had a lesser rate of absorption.

The high total absorptive capacity of the paper is of importance where a high degree of impregnation is desirable as, for example, in the case of dielectric sheets for condensers where it is preferred that the dielectric sheet be relatively thin but have relatively high dielectric properties. The rate of absorption will, of course, vary in accordance with the thickness of the paper and the impregnating material. The following test is given, however, to illustrate the superior absorptive qualities of my improved paper: the test is made by taking a strip of unsized paper-one inch wide from a ten-pound sheet (that is, on the basis of 24"x36"=480 sheets) and suspending the strip vertically with its lower end dipping one-eighth inch below the surface of a body of distilled water 72 F. The distilled water will rise vertically in the strip two and one-half inches in ninety-two seconds. This rate of absorption is at least three times that of the best Japanese yoshino paper of like weight. The rate of absorption of the paper may be controlled by controlling the amount of size in the paper. The total absorption of the paper is the ratio of the weight of the impregnating material which will just saturate the paper to the weight of the dry paper itself. I have found in my tests that a sheet of my improved paper on a ten-pound basis will absorb seven times its own weight of distilled water at 72 F., whereas the best Japanese yoshina paper which I have been able to procure will absorb less than four or five times its own weight, all factors in the comparative tests being similar.

My improved paper may be formed by carrying out the process described in my copending application Serial No. 736,302 filed July 21, 1,934. In accordance with the process therein described, fibers of the banana species, and preferably fibers of Musa textilis, are separated by chemically digesting the stock and then stirring the same without mechanical pressure so as to avoid hydration of the structural fibers or change in the physical characteristics of the structural fibers, there being substantially no shredding, flattening, fraying, or breaking of the individual fibers. By

preference, during the digesting operation, the

stock is subjected to a chemical action which is very drastic in order to dissolve and remove prac- 5 tically all of the gummy and resinous substances and the encrusting ligno material from the fibers so that the fibers may be then completely separated by a mere stirring action in solution and without pressure or hydration. The raw stock may be placed in a rotating boiler and cooked in a very strong alkaline solution, such as caustic soda, for a long duration of time and under high pressure and at a temperatureof about 320 F. The caustic ratio of one pound of sodium hydroxide to two and one-half pounds of dry stock is found very satisfactory as it is strong enough to dissolve the gummy, resinous, and ligno materials and still not too strong to affect or destroy the characteristics of the fibers. Preferably, the caustic ratio for the cook isapproximately 7% sodium hydroxide. The pressure for the cock is preferably at least one hundred pounds per square inch above atmosphere, and the duration of the cock is preferably twenty-four hours, at least. 25

After the digesting operation has been completed, the stock is drained, and then, the drained, cooked stock is thoroughly washed and the fibers are separated by subjecting them to a mere stirring action in solution in such manner that the fibers 30 are not subjected to any mechanical pressure and, therefore, hydration thereof is avoided. After the fibers have been completely separated, and the stock has been thoroughly washed free of all foreign matter and impurities, the fibers 35 are suspended in an extremely large proportion of water, and the dilute suspension thus formed is made to flow freely and rapidly through a transversely moving screen, leaving the fibers deposited on the screen. As explained in my said application, to which reference may be had, the dilute suspension most desirable contains about one pound of dry fiber to twenty-five tons of water; that is, it has a consistency expressed as .002%. This highly diluted, non-hydrated stock is supplied to a traveling, upwardly inclined portion of a wire or screen. The water flows freely and rapidly with an avoidance of eddy currents through the screenand through the web of fibers deposited on the wire. The fibers are deposited evenly and in all directions on the wire in a web without any whirling or rippling effect, whereby is had a paper web of unlimited length many times greater than its width, of uniform texture and free from clots throughout, and of equal strength in all directions and free from areas of differently oriented fibers.

I claim as my invention:

1. A porous, long fibered paper consisting of uncrushed, cylindrical, soft, non-hydrated fibers go of substantially uniform'length uniformly distributed to leave substantially uniformly spaced openings throughout the area of the paper.

2. A porous, long fibered paper consisting of uncrushed, cylindrical, soft, non-hydrated fibers 65 of the Musa genus entirely devoid of natural gums' and waxes and uniformly distributed to leave substantially uniformly spaced openings throughout the area of the paper.

3. A porous, long fibered paper consisting of the 70 structural fibers of the banana species, said fibers being uncrushed and non-hydrated and retaining their original physical and chemical characteristics and being devoid of natural gums and waxes, the fibers being uniformly distributed to leave 75 substantially uniformly spaced openings throughout the area of the paper.

4. A strong, porous, open-texture paper for use as a stencil base and for other purposes consisting of uncrushed structural fibers of Musa teztilis retaining their original physical and chemical characteristics and free. from natural gums and waxes.

5. A porous, long fibered paper consisting of the structural fibers of Muse textilis, said fibers being uncrushed, cylindrical, and non-hydrated and 'being of substantially uniform length, the fibers being uniformly distributed to leave substantially uniformly spaced openings throughout the area of the paper. I

6. A porous, long fibered paper consisting of cylindrical tapered ended fibers of the Musa genus and varying in length from substantially four to seven millimeters, the fibers being uncrushed and non-hydrated and being lmiformly distributed in all directions to leave substantially uniformly spaced openings throughout the area of the paper.

7. A porous, long fibered paper consisting of uncrushed, cylindrical, soft, non-hydrated fibers of substantially uniform length uniformly distributed to leave substantially uniformly spaced openings throughout the area of the paper, the paper being uniform in texture, weight, and thickness throughout, soft and pliable, practically lint- 1 less, and highly absorbent.

8. A porous, long fibered paper for use as a stencil base and for other purposes consisting of a long web of indefinite length of uncrushed,

cylindrical, soft, non-hydrated fibers of substan- 15 tially uniform length, uniformly distributed to leave substantially uniformly spaced openings throughout the area of the web.

FAY H. OSBORNE.