US2339562A - Fibrous absorbent body and method of making same - Google Patents

Description

m 1m 8 19- 1 2,339,562 the Parasite-mat.

-T- N STATESVVPATENTV FFIcEJ 2,339,562 FiBRoUS ansonnan'r nonr AND METHOD v OFMAKING'SAME.

Warner Eustis, Newton, Mass assliznor to The Kendall Company, Wal tion of Massachusetts I v NoDraw ing. Application'June 17,1940,

.' Serial No..34 0,940f

and others.

surgical sponges, dressings, bandages, and the like, all of which absorbency is a highly im-' portant property, but the invention is equally,

useful'a's applied toother fibrous-bodies in which this characteristic is not important. In the manufacture of the various surgical absorbent materials'ia'bove mentioned, gauze is.

extensively used. For example, in making sur gical sponges as much as a square yard of gauze often folded to make a single sponge. The. chief reasonfor' 'using gauzeis to avoid the presence of loose fibers and to obviate the l abllity' of these fine particlesgetting into. the incisionor the wound and remaining there; Whilc;

pole, Mass., at corporaof the surface of ;said body, as desired, toa

treatment which will bind the surface fibers t'ogather and thereby produce a superficial weblike "or net-like structure having a highdegree 'of'porosity and permeability to the passage of air and water, but which will confine the under- "lying fibers and keep them under control. Whether such'a surface treatment completely encloses the fibrous body, or covers only a portion of it, I depends entirely upon the use for which the fibrous body is intended.v A typical procedure consists in making-a fibrousybat, as

' Y for example, by the methods heretofore used in it has been proposed to'combine gauzewith loose 1 cotton or other loose absorbent fibers and thus to reduce the proportion of the gauze usedin a sponge or dressing'and such a product has been" 1 used to a limited extent, it is necessary in such other equivalent fibrous material, may be cases to completely'enclose the cotton and to adopt measures to prevent the presence of fibers so short that .theycannot'be controlled by the gauze. The more common practice still is tofl use gauze exclusively for surgicalpurposes.

It. is evident, however, that cotton or-other absorbent fibers, when once spun, arenot in a" form suitable for producing maximum absorbency. In other words, the ability offibrous bodies to absorb liquids .is chiefly a surface phenomenon, the liquid being held between the fibers largely by capillarity. The spinning of the fibers into threadsand the subsequent weavinc of these threads into a fabric therefore reatly reduces. the water-holding or absorbing capacity of a given amount of fiber. Or, to state the matter differently the same weight of identical fiber in a loose. free, and T fluffy.

condition could hold a much greater quantity of water. I

The present invention aims to devise a fibrous structure in which the necessity for spinning, weaving, and other fabricating processes will oe eliminated. As applied to surgical materials,

it aimsto utilize the greater absorbency of the fiber ina locseand unwoven or unorganized conditionan'd thus to produce surgicalspohges.

dressings, and the like, in which the benefit of this more eiiicient ut lization ofthe' fiber will making cotton batting, dividing such a bat into pads, sponges; or'dressings of the desired size and shape, and then'surface treating them.

sprayed, or superficially wetted in. any convenient manner, with a liquid binder such as ethylcellulose, cellulose acetate, or some of the other I cellulosederivatives dispersed in a suitable solvent, or with rubber latex, either vulcanized or unvulcanized. Ifsuch a spray is made rather fine, the spraying period is brief, the viscosity and surface tension of the binder material. is properly controlled, and the fibrous mass has a density suitable for use as asurgical sponge, no substantial penetration of the spray. into the" body. of the fiber willbe produced, but the par- 'fticles of binder will becaught and held by the surface fibers. Upon" the evaporation of the solvent, or other dispersing liquid, it will be found that-the-surface fibers are bonded toef ,g'ether, forming a strong foraminous surface structure which effectually preventsthe interior fibers from sifting through when. the body is either wet or dry. At the same time the absorbency of the entire mass is not .-.materially aifected. The same treatment may be used on sheeted fibrous bodies and. in somecases one face only of, the sheet material need be so treatedto unite the fibers together.

While a wide variety of binders canbe used in this process, it is desirable in making products designed for surgicalfuse, to employ a be obtained, while at'the same time making I such a body equally as safe as the gauze sponges and dressings heretofore used.

binder that is notdissolved or adversely affected for the purposes ofthis invention by the presence-of water orblood, it being understoodthat the terms dissolved, soluble, and the like. are herein used in their common meanings, instead of in accordance with their strictly scientific definitions. In some cases, also, binders which would be substantially afiected by alcohol ether, or chloroform should be avoided. Bakelite binders are satisfactory for th s purpose. Some of the cellulose derivatives, such as cellulose acetate, answer these requirements as to water or blood, as do also resins of the ureaformaldehyde type, glyptols (glycerol-phthallc anhydride), and the condensation products of formaldehyde with aromatic sulfonamides.

The last mentioned materials are known in the trade as "Santolites.

As above indicated, an important requirement for the conditions here dealt with is that the binder shall not be continuous but that the saucelike or net-like surface structure produced by the treatment shall be of an open mesh, foraminous and highly porous character. This result is readily obtainable by properly controlling the viscosity or the surface tension of the dispersion sprayed upon the fibers. If the binder is used in forms having a high surface tension, the spraying operation may be so performed that the binder will strike the fibrous body in the form of tiny droplets r globules that will not spread easily even on a highly absorbent material, thus depositing the binder in a discontinuous form. Such binders as vulcanized latex and cellulose acetate and others lend themselves readily to control in this manner. A solution of cellulose acetate in acetone, for example, will have the outlined properties. When droplets of such a binder having a high surface tension strike the fibers, they tend strongly to hold their globular form. It sucha droplet happen to contact two or more fibers converging toa common point of intersection, it will try to shift to that point because of the tendency just mentioned. This is a well known phenomenon of high surface tension liquids. Such points of convergence and intersection are present at closely spaced intervals throughout the entire body of fiber. Consequently, this phenomenon is useful in the present process because it tends to positionthe discrete particles of binder at the intersections oi the fibers where their binding action is most effective, with the object of leaving the remainder of the surfaces of the fibers uncovered by a binder so that they may be free, when desired. to exert their absorbent properties.

A further factor demanding attention in the selection of a vbinder is the wettability of the treated surface with water, blood or other aque ous fluids. In other words, it is important not only to have a foraminous surface structure or layer, but also desirable to make the unified surface layer easily wettable. The untreated fiber used in these products naturally has a high chi-- gree of wettability. If the treatment tends to destroy this property. such a resultcan be avoid-cl in two ways, first. by including in the hinder or unifying material a water soluble plasticizcr or wetting agent that willsuitably change the properties of this material. Such agents as t;i ecetin or dimethyl and diethyl phthalates may be used for this purpose with such binders as cellulose acetate or ethyl cellulose. If a binder oi the phthalic glycerol type is used, then suitable plasticizlng and wettability agents as succinic. malic or tartaric acids may be employed. An other method is to apply to the unified surface, after the treatment above described has been completed, a molecular layer of a wetting agent such as one of the sulphonated oils, or very small quantities of such substances as nekal or "neomurpin." The latter are understood to be forms of sodium alkyl naphthaline .sulphonate. Also, the glycols and fatty alcohols may be used for these purposes, either in combination with the binder as initially applied, or as subsequent surface treating agents.

In making relatively thick fibrous bodies of this nature, the surface treatment alone may not give the desired stability to the structure. Accordingly, another phase of this invention involves .the bonding 0r unification of a fibrous body substantially throughout its mass, while still preserving its porosity, and without substantially altering the nature of its fibrous structure except to bond the fibers together where they come in contact-with each other at points so spaced and distributed throughout the mass as to give the entire structure the desired degree of stability. Such a process thus produces a unification of the entire mass. For some purposes it is desirable to use both treatments jointly, or, in other words, to unify the entire mass of the fibrous body in addition to unifying part or all of its surface, as above described. When such unification of the entire mass i desired, it can be produced in the manner disclosed in my copendin-g application referred to below.

A considerable variety of thermoplastic and polymerizable binders are available which are suitable for use in the processes hereinbefore described, including vinyl compounds, such as vinyl chloride, vinyl acetate and copolymer of the same, polymers of styrene, and various esters and ethers of cellulose, such as cellulose acetate. cellulose formats, ethyl cellulose, and others. Also, phenol-formaldehyde, urea-formaldehyde, glyptol, and the like.

Also, the plasticity of these products can be varied by incorporating in their composition suitable plasticizers well known to those skilled in this art. In making surgical sponges, bandages, and the like, it is desirable to use plasticizers which are insoluble in water, or only sparingly soluble, and which are substantially non-toxic and non-corrosive to human tissue. With certain binders thatclass of plasticizers known as Santicizers are particularly valuable for these purposes. Of this group ethyl-phthalyl-ethylglycolate is especially useful where physiologicalefiects are important. By way of illustration, if cellulose acetate is the binder employed, its

thermoplastic properties may be enhanced by adding this plasticizer to the binding material in the proportion of one part of plasticizer to two parts of cellulose acetate. Other members of this group which are also useful are the corresponding methyl or butyl compounds.

Where it is desirable to modify the water wettability of such binding materials, this result may be produced by the addition, either to the binder itself or to the finished product, of any of the wetting agents above mentioned, or such others as ,triet-hanolaminc and sulphonated fatty alcohols.

In making all of these products it is preferable to use textile fibers, partly for the reason that theseflbers can behandled by the common commercial textile machines, and partly also because their length is such that they can be better controlled ln the manufacture of surgical sponges and other articles where such control is especially important, and for the further reason that the more common of these textile fibers, especially cotton, is admirably adapted for use in these products. Other fibers, however, such as viscose, also are useful in. the manufacture of some of these products.

It will be noted that this invention produces a fibrous structure from a body of unorganized, heterogeneously disposed fibers intermingled with each other loosely and without spinning, weaving, or other fabricating processes. Consequently, substantially the maximum efliciency of the fiber as an absorbing mediumis utilized. In

addition, the manufacturing steps involved in making this product are relatively inexpensive.

Furthermore, the surface unification affords a control or restrain of the free :fibers below the unified surface, which makes such a product fully desire to claim as new is:

1. An article of the character described, comprising an absorbent body of intermingled, unorganized, textile fibers easily waterwettable. those fibers of at least a substantial area of the surface of said body beingwater-insolubly united by discrete particles of a waterproof synthetic resinous binder toproduce anet-like surface structure'which is highly'perm'eable to air and 2. An article of. the character described, comprising an absorbent body of intermingled, un-' organized, textile fibers easily water-wettable, those fibers of at least a substantial area of the surface of said body being water-insolubly united by discrete particles of a cellulose ester binder to produce a net-like surface structure which is' highly permeable to air and water, said binder containing a plasticizer of the Santicizer type. I

3. An article of the character described, comprising a body of intermingled, unorganized, absorbent, textile cellulose fibers united by discrete particles of a water-insoluble, freely water wettable bonding agent, and the fibers of at least'a substantial area of the surface of said body being united to produce a net-like surface structure, highly permeable to air and water, insoluble in in water, but of easy wettability, whereby, when in contact with an aqueous material, the material may be freely absorbed into the passages between said absorbent cellulose fibers.

4. An article of the character described, comprising a body of intermingled, unorganized, cellulose fibers united to each other by discrete particlcs of a water-insoluble bonding agent, and a portion of said body of cellulose fibers at the surface thereof being united to form a water-indestructible net-like film highly permeable to air, and the surface of the whole structure of said I 5. An article of the character described comprising a thick, fiuffy, flexible, softv layer of intermingled, unorganized, absorbent, textile fibers,

said layer being bounded on at least one of its surfaces by a thin, water-indestructible, highly as safe to use on wounds, incisions, and the like, v.

porous, web-like film serving to confine the underlying fibers and keep them under control during the use of said article, said film comprising textile fibers attached to each other at their points of crossing by discrete bodies of cellulosic binder.

6. An article of the character describerLcomprising an absorbent body of heterogeneously intermingled textile fibers, those fibers of at least .a substantial area of the surface of said body fibers of said body to .keep them under control during the .use of said article, saidunderlying fibers being more loosely associated than 'th fibers of said web.

7. An article of the character described, comprising an absorbent bodyof heterogeneously intermingled fibers, a substantial; part at least'of water, said binder containing a non-toxic plasti- I cizer. I

the surface area of said body being bounded by a water-indestructible net-like. web, highlypernewbie to air and water and composed of textile fibers at the surface of said body and forming a underlying it and serving to restrain underlying.

part thereof but united to each other by a waterdifferent character from that of the body of fibers fibers of said body.

8. An article of'the character described, cornprising an absorbent body of heterogeneously intermingled textile fibers, those fibers of at least a substantial area of the surface of said body being water-inseparably bonded together into a foraminous web or net-like structure by a waterins'oluble synthetic resinous binder, said web being of an open mesh and highly porous character serving to restrain underlying loosely associated fibers of said body, whereby when said body is in contact with an aqueous material, such material may be freely absorbed into the passages between said fibers.

WARNER EUSTIS.

Patent No. 2,539,562.

CERTIFICATE OF CORRECTION.

January 18, 191411.. WARNER EUSTIS.

It is hereby certified that error appears in the printedspeeification of the above numbered patent requiring correction as follows: Page l, first column, line 6; before the vyord "all" insert --in--; page 2, first column, line 6, after the syllable "hoI" insert soommu; and that the said Letters Patent should be read with this correeti on therein that the same may eonform to the record of the ease in the Patent Office.

Signed and sealed this 28th day of March, A. D 191414..

Leslie Frazer (Seal) Acting Commissioner of Patents.