US2626214A - Paper from long synthetic fibers and partially water soluble sodium carboxymethylcellulose and method - Google Patents

Description

Patented Jan. 20, 1953 PAPER FROM LONG SYNTHETIC FIBERS AND PARTIALLY WATER SOLUBLE SO- DIUM CARBOXYMETHYLCELLULOSE AND METHOD Fay H. Osborne, Windsor Locks, Conn., assignor to C. H. Dexter & Sons, Incorporated, Windsor Locks, Conn., a corporation of Connecticut No Drawing. Application June 14, 1949, Serial No. 99,113

13 Claims.

The present invention relates to a novel web material and method of making same. More particularly, the invention relates to a web product and method of making same wherein the product is a highly porous, absorbent, soft, lowdensity web of unique appearance and good tensile strength composed of uniformly intermingled unwoven synthetic fibers bonded together at intersections of the fibers by small discrete deposits of insoluble sodium carboxymethylcellulose, the latter being chemically unaltered and being present in relatively small amount and distributed in minute spots substantially uniformly throughout the web.

The web material of the present invention has particular usefulness in situations where high porosity and good absorbency are essential. On the other hand, the unique and pleasing appearance of the material and its softness render it desirable for many uses regardless of porosity and absorbency requirements. In many cases, the combination of all of these characteristics has been long sought for in the art. In many of the uses of the new material of the present invention which have been carried out successfully results are obtained which greatly surpass in degree and kind the results which have been obtainable with the best materials available heretofore for such purposes. In this connection, it is a feature of the invention that the web product produced may be varied in many particulars such as weight and strength to fit the particular needs of a contemplated use, and the cost of the web material is sufiiciently low so that it may be used economically in products of relatively inexpensive types. Among the many uses of the web product of the invention wherein the novel characteristics of the web enhance the utility and desirability of the product may be mentioned infusors, such as teabags: decorative material, such as draperies and curtains; surgical materials, such as catamenial bandages; filtering materials, such as milk filters; packaging material including materials for packing and cleaning lenses; stencil sheets and the like.

A principal aim of the invention is to produce a web by a wet deposit method on paper-making machinery utilizing fibers to form the web which are made up entirely of synthetic fibers and are at least six millimeters in length and preferably longer up to and including fibers of textile length; wherein despite the great length of the fibers and their tendency to fiocculate or ball up when suspended in water, a uniform controlled distribution and dispersion of the fibers is obtained; and wherein despite the lack of bonding action of the 2 fibers themselves, a coherent web of good strength is produced even in very thin or light weight webs without materially altering the physical characteristics of the web such as its porosity, softness and unique appearance.

As mentioned above, the fibers which are selected for use in accordance with the present invention are composed entirely of synthetic fibers by which is meant fibers formed commercially by spinning or extruding fiber forming materials into continuous fine filaments or threads. Among them may be mentioned particularly the fibers formed from cellulose esters such as viscose rayon and acetate rayon; cellulose ethers such as ethyl and benzyl cellulose; vinyl compounds including vinyl chloride, vinyl acetate, and the copolymers of the same; polymers of styrene; polyamides, i. e. nylon; and proteinaceous materials such as casein and soybean proten. In dealing with fibers of the length of six millimeters or more in paper-making machinery, it is essential that the fibers be uniform in length and thickness and such control can be attained only by the use of fibers which are formed synthetically as men-- tioned above. Synthetic fibers are conventional- 1y formed, by spinning or extruding, into continuous uniform filaments of any desired denier and may be cut accurately thereafter to any desired length. Furthermore, such synthetic fibers are characterized by a natural sheen or silk-like appearance which is carried over substantially undiminished into the finished web of the invention thereby giving the web a distinctive and pleasing appearance not attainable heretofore in the products formed on paper-making machinery. Furthermore, within the field of synthetic fibers there may be selected fibers of varying absorbency, wet strength, chemical stability, thermoplasticity, etc., to meet the particular requirements desired in the final product. In addition, the synthetic fibers do not hydrate or degenerate to any appreciable extent when handled in aqueous solutions whereby the original fiber structure and characteristics are retained. Moreover, the domestic fabricators of synthetic fibers are able to provide substantially unlimited quantities of uniform fibers from materials of domestic origin and at low cost.

In order to form webs of long length fibers as utilized in the present invention on paper making machinery, it is necessary to disperse and suspend the fibers in copious quantities of water without entangling and fiocculating the fibers. Prior to the present invention, such dispersions of fibers of the length herein defined have been regarded as impracticable due to the tendency of the fibers, which is greatly pronounced in the case of long fibers, to flocculate and ball up when suspended in water. A dispersion of fibers of the orderof about 1 partf fibers'to 5,000 parts bf Water is believed "to be essential 5 in order to carry out the invention and preferably is of the order of about 1 part of fibers to 10,000 parts of water (approXimately- -1-- lb. of fiber to 5 tons of water).

It is therefore essential in ci-d'er zfto practice the invention to provide a material in the suspension which will cause a free dispersion of the fibers therein. It also is essential to provide a" ,1 material which will be effective-whemthe"web. is formed to lock the fibers in the position in which they are deposited to give -the web suit able strength and coherency without at the same time detracting from the desired physical proper;-

ties of the web such as porosity, absorbency, and appearance.- syntheticwfibers, of course, have little bonding properties by .theinselves" 'and; will notiorni; a self-sustaining web, let alone'a web of su fiicient -streng-th to have utility I have found that the aboverequirements'can be met-by-a= single agentwhich. may be added' to the suspension of fibers-in water and which willcarryoutto sir remarkably successful degree both the function of;producing" anon-fiocculating 'uni-form -distribution anddispersion of the fibers for web-formingpurposes and the. ifun'c- 3O tion'-offixing-the fibers as deposited-in theweb to -==produce-acoherent-structure::of adequate J strengths all :without adversely afiecting the de-IY sired 'pr'operties :of the web and-resulting in the; l production 'of' a; unique and 'novel Web=-lil man 3 terial having unusual: advantages and utility: as above mentioned: This agent is'a partioular type or'fo'rm of sodium'carboxymethylcellulose,- sometimes referredto as "sodiuml celluloseglycolate; whidh' is "derived 'by the reaction- 0f alkali .cellulo's'e 'an'd monochloracetic acid-: Variations in the properties of sodium carboxymethylcellulose; mayoccili'ffor 'example by reason of'variations a in the de'gree'or substit'ution' of carboXymet-hy-lr groups peranh'yd'roglucose unit J of the cellulose '45 moleculek as well "as by variations-win the: uni-:- formity bf substitution and the exact place or places-of substitution in thecellulbsahrolecule; all "of which 'factors'areexceedinglymdifilcult to control.- Th'e typepf sodium carboxymethylcel lulbs product whichis 'ess'ential -foli' use in ace w cordan' c'e with 'the pres'ent invention 'fls one in which some-portions are completely solubleand-=- th othehporti'ons are-not so1ub1e":butrhave: the chairacteris'ticbf forming minute ormicroscop size disrete gel particles when dispersedz: in 2 water I have 'i'ou'ndtha't at the present time theselec- 7- tion'of a suitable sodium'-carb'oxyniethylcellulose:I product 'for'u'se in accordance'with' the present 5 0 invention "cannot be preclicated on A any known variations'in themanufacturing procedure, or by relianceuponany of 'theu'sual tests now employedin g'ra'ding'or differentiating sodium carboiiymethylcellulose'products. For" example, it is 5 conventional in the commercialproduction of sodium carboxymethylcellulose to grade the produc'ffon thebasisof the degree'of 'sub'stitution' oi carbcllymethy'l'grcups per glucose unit this belngfin'g'eneraiya measure of the solubility or the product. However, I havefound that some lots of a'particular'grade willnot be satisfactory for th'purposeof the'present invention'while other lots" cf "thesame' grade produced by "the "same 1 manufacturer will be entirely satisfactory, thisdespite the fact that the lots are believed to be made up by employment of identical techniques and under identical conditions. In general, however, TLhaVe found'the most likely sources of lots of sodium carboxymethylcellulose which can be used in accordance with the invention to be the commercially available grades having a substitution.value,in the range of 0.3 to 0.75.

A testawhichlzhave devised for selection of 'a: sodium carboxymethylcellulose product which is suitable forrusein accordance with the present invention is to disperse a sample of the product in waterqand then pass the dispersion through a fine" screen-czhaving, openings of the order of 105,625 bpenings 'p'ersquare inch, If the sodiumcarboxymethylcellulose product being tested is:

suitable) for use in accordance with the inven-- tionnthere will be deposited on the screen a multitude or very small microscopic gel particles which when dried to constant weight and weighed will be'foun'd' to be equal' to about 2'to 25%of the-weight of the briginal sample.izAp a:, parently'the" portion- 0f the sodium; carboxy' methylcellulose which "is deposited on the screen is a water insoluble'form thereof while the por- 1 tion which passes through the screenwith the Water is a water 'solubleform;

When a sodium carboxymethylcellulo'se product selected as described above is employedwith theselected fiber's'of long length which" are uti lize'd' in accordance 'with-thepresent' inventiom" there results'a rlon-flocculati ng uniformidis-" persi'on 'of the "fibers permitting the wet laying of a controlled and uniformwebpf unique appearanc'e and in addition -the-fibers wheniormed into a web are bonded-together by very minute discrete particles 'of the sodium carboxymethylcellulose which gives the webcoherency-and pro-- duces a useful product having" the unexpecteda' advantagesherein' described; The sodium car-"- boxymethylcelhllose' utilized-is not chemically f; altered in any vvay duringthe operation of the" method of my invention and the portion present in the final product. is exactly the same chemicall y as at theoutsetof the process.-

It is believed-as alresult of the discovery of the present invention that the completely soluble" portions of a sodium carboxymethylcellulose: product are probably'responsible for the dis- ,persing-properties thereof, and that'the in.-

soluble gel-forming portions,are'responsible for thebonding properties thereof. .It is conternplated that in the future additionalknowledge may be gained as to thelpr duc-tion of sodium acarboxymethylcellulosel which i will permit the' complete.epredetermination l, of the .;properties thereoito' permit. the preselectionrof a. particular; grade-for use. in accordance withthis invention, or conceivablylther-e may resultltheproduction of gradesconsisting entirelyof soluble material andinsoluble gel-forming material which may, be subsequently. admixed-...in., desired proportions, for use in thislprocessmUntil: such time,-whowlever, the invention may==-be-practiced-success= fully and satisfactorily in accordance-with the 7 teaching -herein.-

In order to carry out the web'forming-operations "of the process of the present-=-invention-, a first step'is to 'form'a relatively "thick s'lurry'of the'selected syntheticfiber in water-with the selected sodium carboxymethylcellulose product. i The manner in which thisis done is not critical; For example, I have found it convenient to introduce thesodium carboxymethylcellulose in dry powder form directlyto a slurryrof rfibeltin wateriin a mixing device such as a conventional beater. When utilizing a heater as a mixing device for this purpose, it is advisable to adjust the beater roll well above the bed plate of the machine so that no beating of the fiber takes place and with the result that the beater roll acts merely as an agitating and mixing device. On the other hand, it may be preferred to premix the powdered sodium carboxymethylcellulose in water prior to adding it to the fiber slurry. Premixing can readily be accomplished in any convenient mixing device such as a tank provided with means for slow agitation As mentioned above, the synthetic filaments or threads selected are cut to provide fibers of not less than 6 millimeters in fiber length and up to and including textile fiber lengths. In general, I prefer to utilize a synthetic fiber having a denier in the range of 1 /2 to 5.

By way of example, a preferred concentration of the slurry at the above stage of the process may be about 1 parts of fiber to about 50 parts v of water, although, of course, this may be varied over a wide range as may be found to be convenient. Prior to forming a web, of course, the

slurry is greatly diluted to the extent referred to hereinbefore.

The amount of sodium carboxymethylcellulose which is added to the slurry is dependent in part upon the proportion of insoluble gel-forming portions and soluble portions of the selected product as well as upon the desired properties of the web, it is intended to produce. In general, this amount may vary from as little as one part of the selected sodium carboxymethyl cellulose to twenty-five parts of fiber to as high as one part thereof to five parts of fiber.

- Inasmuch as the completely soluble portion of the selected sodium carboxymethylcellulose apparently is responsible for its dispersing qualities while the insoluble gel-forming portion apparently is responsible for its bonding properties, it will be apparent that a selected product which is high in content of the former will provide good dispersions but weak bonding when present in small amount, while a selected product which is high in content of the latter will tend to give good bonding but will be less eifective as a dispersing agent when present in small amount. In general, it is necessary to have a minimum of 3% parts of the completely soluble portion of the sodium carboxymethylcellulose product to 100 parts of fiber in order to obtain adequate dispersion of the fibers and a minimum of 1% parts of the insoluble gel-forming portion to 100 parts of fiber in order to produce a selfsustaining web. In most instances, it will be preferred to operate well above these lower limits although it generally is not desirable to exceed a concentration of the order of about one part of the insoluble gel-forming portion to ten parts of fiber for at this concentration and above, the formed web becomes too stiff for most purposes. By way of specific example which is given to assist in the understanding of the invention and not by way of limitation, I have found that 100 parts of fiber to about five parts of a sodium carboxymethylcellulose having a gel-forming content will give good web formation and will produce a very soft and flexible web of moderate tensile strength; when the sodium carboxymethylcellulose content is increased to about 12 parts, good web formation continues and there is a very noticeable increase in web strength with some loss of softness and flexibility; and upon increase of the sodium carboxymethylcellulose to 20 parts a very strong and stiffer web is produced with good web formation.

After a slurry has been formed of the desired proportion of fiber and sodium carboxyrnethylcellulose, the formation of a web may then be carried out. To form the web, the slurry of fibre containing the sodium carboxymethylcellulose is introduced into the headbox of a paper forming machine in proportion to the amount of water separately introduced therein to form the highly diluted fibre dispersion hereinbefore mentioned. It is preferred to carry out this portion of the method of the present invention by utilizing an apparatus of the type described in my prior Patent No. 2,045,095, issued June 23, 1936, to which reference may be made for details of construction and operation. An important feature of apparatus of this type is the use of a headbox for receiving the dilute fibre dispersion which cooperates with a Fourdrinier wire mounted for travel in an inclined plane adjacent the front of the box. By such novel arrangement of the head box and Fourdrinier wire, it is possible to form a uniform deposit of intermingled fibres on the wire to produce the desired web formation of the present invention from the highly dilute fibre dispersion herein described.

As described in my prior Patent No. 2,045,095, the major portion of the water is separated from the fibres during the deposit of the fibres on the inclined portion of the Fourclrinier wire and flows freely into a collecting tray or save-all from which it may be recovered for reuse. Partial additional drying of the web while on the Fourdrinier wire may be accomplished by the use of suitable suction boxes over which the wire travels. Finally the web is diverted from the Fourdrinier wire through a conventional battery of drying rolls some or all of which may be steamheated to facilitate drying and then'wound up on a reel.

I have found that it is particularly important in the practice of my invention to utilize pumps, feeding apparatus, etc. for handling the fibre dispersion which are free of sharp edges and rough surfaces. Because of the exceedingly great length of the fibres utilized in accordance with the invention as distinct from fibres of ordinary paper making lengths, they have a tendency to snag on any sharp projections with which they come in contact. Very frequently small deposits of fibres will build up on such projections until of sufficient weight to break loose and then will deposit on the web without becoming redispersed, thus forming undesirable clots or lumps in the finished web.

. It is a particular advantage of my invention that the weight or thickness of the'webs produced may be varied over a wide range without affecting their uniform and integral structure and by simple control of the process. I have found that by increasing the dilution of the fibres in the headbox and/or decreasing the area of contact between the headbox and the Fourdrinier wire, webs of decreasing thickness can be made. By my method, webs of a very thin gossamer type having somewhat the appearance of a cobweb and running as light as 50 grains per square yard can be produced. On the other hand, by increasing the fibre concentration in the headbox and/or increasing the area of contact between the headbox and Fourdrinier wire, the weight of the webs may be increased to as high as /2 pound per square yard.

Forrmost-iusespit will. be -desired to'iorin a web* composed of ;fibres whic'h:are deposited; without any distinctive orientation'.'-An' advantageofsuch-.webs: is. a substantiallyfuniform tensile trength either lengthwise or transverselyof the web.--:It is an advantage ofmy invention that by carefiilrcontrol of the-flower dilute fibre dispelrsion in theheadbox relative to the'speed of' travelof' the Fourdrinier'wire, such anunoriented uniform deposit can'be accomplished; Ingen erai, the fibres 'willdeposit on the wire'in general relationship to the fiow of the fibre dispersion in the" headbox at. the area of contact with the Fourdrinier-wire.- When the rate of flow of the fibre dispersion? is properly ccordinatedwith the rate offtravel of:.thei-Fourdrinier wire, the fibres maybe deposited-inthe. form of small swirls 'giv ing:.thei webia uniform texture and a very. distinctiverand appealing. appearance. In some instances,-it maybe preferred to=form a web hay-'- inga pronounced fibreiorientation'either across orlengthwiseiof the web. This may be readily accomplished'in accordance with the invention byafiecting the direction of fiow of the dispersion in-ithe headbox.- For example, when the Fourdrinier wire is run at a lower rate of speed, the fibres will tend to deposit'transversely of the machine and, when it is run at higher speeds, the fibres'tend to deposit extending generally inthe machine direction.

Bytheemployment of paper making machinery, it is possible, of course, to form webs of con tinuous length and any suitable width depending upon the capacity of the machines available. Web widths up to 200inches, for example, are readily possible on present day paper machinery. Asa result, the unique andnovel web material of the present invention may be produced in largequantities and ata relatively low cost.

Ingeneral; it will be preferred to form the webs of thepresent invention entirely from a specific selected fibre such as viscose rayon fibre,'for example, but in somecasesas where the Web is to be. utilized'for making heat scalable teabags, it maybe preferred'to utilize'more than one kind offibre andto deposit different concentrations of'the'resp'ective fibres in opposite faces of the web. Such a modification'of my present invention is readily possible by following the procedure disclosed in my prior Patent No. 2,414,833, issued January .28, 1947. .Inthis'modification, the web is formed as .before:except that a second fibre dispersion containingsga difierent selected fibre such as Vinyon fibre is floated :on top of the first fibre dispersion in .the headboxthus causing a deposit of the second. fibre predominantly in the upper face of the web.

The-web-like materialproduced in accordance with the present invention has a unique and distinctive appearance and structure which clearly distinguishes it from any products heretofore made. The fibres are thoroughly and uniformly dispersediandbecause of their great-length are plainlyyisible in the finished sheet. The web is of very lowdensity, being of the order of 0.2 to OAgram-per cubic centimeter. The interstices between the intermingled fibres are also plainly visible and in thin sheets are so pronounced that it is possible --to look through the sheet' without difficulty. The openness of the structure is particularly brought out by standard porosity tests. For example, when a sheet of the new web-like material weighing xof an ounce per sq. yd. is subjectedto a vacuum equivalent to a inch of water, air will flow through the sheet=atarate such as softness and absorptiveness.

0f 772 cubic feet-persquare'foot per minute: This i :nea-rly eight times the =porosity of the mostporous'sheetsof equal weight which have-beenproduced heretofore on-paper makingmachinery.

The fibres themselves appear to be entirely unchanged'by the web forming method of my invention'andretain all oftheir original characteristics ofappearance such-as sheen, translucency and uniformity and'their original physical properties;

sheet is held so as to reflect light, it has a very-- silkyor silvery appearance but,-on the other hand,

when held in close contact'with another surface, it is as translucent as glassine.

The fibres in-the web-like -material-have no means of support Visibleto the naked eye and by reason of the openness and low density of the structure, it comes as'a distinctsurpriseto-thecasual observer that the material has any -tensile strength.-

By -the--use of-selective dyes and microscopic examination, I have determined that'thefibres of the web are held' together by very small deposits or particles of sodium carboxymethylcellulose-- gum which appears to have an 'afiinity for depositing mainly'at the intersections of the fibresand in general will not span across the interstices between the fibres. These spots or deposits of sodium carboxymethylcelluloseare very small,- being of the order of only to' fl square millimeters in area. In eiiectythey appear to form a kind of spot weld between the fibres which efiec tively locks them in deposited position. Inas-" the present invention, it is an advantage that the number of deposits and amount of the sodium carboxymethylcellulose gum 'in the web may be Varied over a wide'range depending 'upo'nthe amount andcharacter of the sodium carboxymethylcellulose mixed with the fibres, and it also is 'an'advanta'ge that adequate'tensilestrength for most purposes'can be obtained with very' small amounts of the gum. Forexampleyl have formed a web in accordance with the invention having a weight of 130 grains per square yard inwhich' the average number or -spots of sodiumcarboxymethylcellulose was only about 7 per square millimeter and yet the'web had a tensilestrength of 1000 gram'sper inch; In-general I prefer to keep the'percentage of sodium carbonymethylcellulose in the finished web within the range of 1 to 5% by weight as this gives adequate strength without adversely affecting thedesir'ed softness and porosity of the web.

The small amount and character of the deposits of sodium carboxymethylcellulose in the web takentogether with the great length of the fibres apparently explains the surprising porosity,- softness and translucency'of the final product. Furthermore, the sodium carboXymethylcellulos'e itself is practically transparent and, being in Such" small and'widely separated deposits, is virtually invisible in the'finished web, thus accountingfor the unique appearance of the web.

The'unique structure of the web-like material of the present inventioncan befurther demonstrated by tearing a sheet "of the material in any directionz Separationtakes place by an unlacing of the fibres producing-a deckle-edge of 'distinc When -thetive appearance with the'long loose ends of the separated fibres clearly visible.

The material as described above is eminently suitable for all desired uses under dry conditions, but possesses low wet strength. This deficiency can be readily overcome, however, by utilizing wet-strengthening treatments of the paper art. For example, I have found it desirable to Wetstrengthen the web-like material produced as described above by running it through a viscose solution bath. This forms a very thin unnoticeable transparent coating over the fibres and particularly the sodium carboxymethylcellulose gum deposits which effectively prevents the weakening action of water, all without any deleterious effects upon the desired properties of the material such as softness, absorbency, and porosity.

It thus will be seen that there has been described a novel web-like material and method of making same, having great utility and usefulness in the art. It will also be apparent that the invention will be subject to considerable variation by one skilled in the art in the light of the disclosure herein, and all such variations are intended to be included within the scope of the invention.

I claim as my invention:

1. A thin, soft, absorbent, extremely porous and light weight web material of substantial strength consisting essentially of synthetic artificiallyformed fibers having a fiber length within the range of from 6 millimeters up to and including textile fiber lengths and uniformly distributed and intermingled in the form of a web with the fibers intersecting but spaced apart to form numerous interstices, said fibers being in their original, non-binding, fibrous, unbeaten, ungelatinized and uncoalesced form but being firmly bonded together at their intersections by small, discrete, water-laid deposits of Water-insoluble chemically-unaltered sodium carboxymethylcellulose having a substitution value of from 0.3 to 0.75 and present uniformly throughout the web in an amount of from 1 to 5% of the weight of the finished web.

2. A thin, soft, absorbent, extremely porous and low density web material consisting essentially of synthetic artificially-formed fibers in original, non-binding, fibrous, unbeaten, ungelatinized and. uncoalesced form and having a fiber length within the range of from 6 millimeters up to and including textile fiber lengths, loosely deposited in uniformly distributed intersecting relationship with relatively large interstices therebetween but firmly bonded together by a small amount of from 1 to 5% based on the weight of the web of water-insoluble chemically-unaltered sodium carboxymethylcellulose having a substitution value of from 0.3 to 0.75 and occurring principally as small discrete, water-laid deposits of from to square millimeters in area at the intersections of the fibers and uniformly distributed throughout the web.

3. A thin, soft, absorbent, extremely porous web material of substantial strength having a maximum density of 0.4 gram per cubic centimeter and a maximum weight of /2 lb. per sq. yd. consisting essentially of synthetic artificiallyformed fibers having a fiber length within the range of from 6 millimeters up to and including textile fiber lengths and uniformly distributed and intermingled in the form of a web with the fibers intersecting but spaced apart to form numerous interstices, said fibers being in their original non-bonding, fibrous, unbeaten, ungelatinized and uncoalesced form but being firmly bonded together at their intersections by small discrete, water-laid deposits of Water-insoluble chemically-unaltered sodium carboxymethylcellulose having a substitution value of from 0.3 to 0.75 and present uniformly throughout the web in an amount of from 1 to 5% of the weight of the finished web.

4. A thin, soft, absorbent, extremely porous and low density web material consisting essentially of synthetic artificially-formed fibers in original fibrous, unbeaten, ungelatinized and uncoalesced form and having a fiber length within the range of from 6 millimeters up to and including textile fiber lengths loosely deposited in uniformly distributed intersecting relationship with relatively large interstices therebetween but firmly bonded together at their intersections by small discrete, water-laid deposits of water-insoluble chemically-unaltered sodium carboxymethylcellulose, having a substitution value of from 0.3 to 0.75, said deposits ranging in area from to A; square millimeters and the number thereof being of the order of 7 per square millimeter of web.

5. A thin, soft, absorbent, extremely porous and light weight web material of substantial strength consisting essentially of synthetic artificially-formed fibers having a fiber length within the range of from 6 millimeters up to and including textile fiber lengths and uniformly distributed and. intermingled in the form of a web with the fibers intersecting but spaced apart to form numerous interstices, said fibers being in their original non-binding, fibrous, unbeaten, ungelatinized and uncoalesced form but being firmly bonded together at their intersections by small discrete, water-laid deposits of water-insoluble chemically-unaltered sodium carboxymethylcellulos having a substitution value of from 0.3 to 0.75 and present uniformly throughout the web in an amount of from 1 to 5% of the weight of the finished web.

6. A thin, soft, absorbent, extremely porous and light weight web material of substantial strength consisting essentially of synthetic artificially-formed viscose rayon fibers having a fiber length Within the range of from 6 millimeters up to and including textile fiber lengths and uniformly distributed and intermingled in the form of a web with the fibers intersecting but spaced apart to form numerous interstices, said fibers being in their original non-binding, fibrous, unbeaten, ungelatinized and uncoalesced form but being firmly bonded together at their intersections by small discrete, water-laid deposits of water insoluble chemically unaltered sodium carboxymethylcellulose having a substitution value of from 0.3 to 0.75 and present uniformly throughout the web in an amount of from 1 to 5% of the weight of the finished web.

7. thin, soft, absorbent, extremely porous and 11ght weight web material of substantial strength cOnsisting essentially of synthetic artificially formed viscose rayon fibers having a fiber length within the range of from 6 millimeters up to and ncluding textile fiber length deposited in intermingled web form in admixture with synthetic artificially formed fibers of a copolymer of vinyl acetate and vinyl chloride, the latter being more concentrated in one surface of the web than the other, said fibers being in their original, non-binding, fibrous, unbeaten, ungelatinized and uncoalesced form and being deposited in intersecting but spaced relationship to provide numerous interstices, said web .being glheld Lto- ,gether'by minute, water-laid particles of water- .insoluble chemically-unaltered sodium .carboxy- .methylcellulose having a substitution value of from 0.3 to 0.75 and occurring as discontinuous 'deposits at the interstices .of the fibers'uniformly throughout the web and in an amount of from -1 to-5% of the Weight ofthe finished web.

8. A method of preparing a thin, soft, highly absorbent and porous web material of lowdensity which comprises forming a highly diluted aqueous slurry of unbeaten, synthetic, artificially- .formed fibers having a lfiber length Within the range -of from 6 millimeters up to and including textile fiber lengths with the addition of. a small quantity of water-dispersible sodium .carboxymethylcellulose having a substitution value of from 0.3 to 0.75 and containing from 2 to 25% by weight of water-insoluble gel-forming ,par-

ticles, said sodium carboxymethylcellulose being added inan'amount of one part by Weight to .from 5 to 25 parts of fiber by weight and having a dual .function in that the water-soluble content disperses and defiocculates the fiber in the suspensionand the Water-insoluble particles bind the fibers at their intersections .in the finished sheet, forming a web by .fiowing the dispersion ontoa travelingmeshed sheet-forming screento cause the fibers and gel particles of sodium carboxymethylcellulose adhering to theintersections of the fiber to deposit uniformly thereon while permitting the remainder of the slurry to flow rapidlyand freelythrough the screen, and dryingthe webto causethe water-insoluble sodium carboxymethylcellulosecontained therein to bind the fibers in deposited web form, and maintaining saidsodium carboxymethylcellulose in chemically-unaltered formthroughout.

9. .Amethod of preparing a thin, soft,.highly absorbent and porous web material of low density which comprises forming alhighly diluted aqueous slurry containing from 5000 to 10000 parts of waterto .1 part by weight of "unbeaten, synthetic, artificially-formed fibers having a fiber length within therangeof from .6 millimeters up to and including-textile fiber lengths with the addition of a small quantity of waterdispersible sodium carboxymethylcellulose containing from 2 to,25% by weight of water-insoluble gel-forming particles, said sodium carboxymethylcellulose having:a substitution value of from 0.3 to 0.75 .and beingadded in an amount of .onepart by weight to from 5 to 25 parts of fiber by weight and having a dualfunctionin that the water-soluble contentdisperses and defiocculates thefiberin the suspension and the water-insoluble particles bind the fibers at their intersections :in the 1mished sheet, forming a web 'byfiowing the .dispersion onto a traveling meshed sheet-forming screen to cause the fibers and gel particles of sodium carboxymethylcellulose adhering to .the intersections of the fiber to deposit uniformly thereon whilepermitting the remainder of the slurry to flow rapidly and freely through the screen, and drying the Web to cause the Waterinsoluble sodium carboxymethylcellulose .contained therein tobind the fibers in deposited Web form, .and maintaining said sodium carboxymethylcellulose in chemically-unaltered form throughout.

110. A method-of preparing'a thin,-soft, highly absorbent and porous Web material of lowdensity which comprises forming ahighlydiluted aqueous slurry containing from 5000 to 10000 ;parts of Water'to 1 part by weight of unheated, synthetic,

artificially-formed fibers having a fiber length in therange of 6 millimeters up to and including textile fiber lengths'with'the addition of 'a small quantity of Water dispersible sodium 'carboxymethylcellulose containing from 2 to 25% by Weight of water-insoluble gel-forming particles, said sodium carboxymethylcellulose having .a substitution value v.of from 0.3 to 0.75 and being added in an amount of .one part by Weight to from 5 to 25 parts .of fiber by weightand having a dual function in that the water-soluble content dispersesand defiocculates thefiber in the suspension and the watereinsoluble particles bind the fibers at their intersectionsin the finished sheet, forminga web .byfiowing the .dispersion onto a traveling meshed sheet-forming screen to .cause the fibers and-gel particles'of sodium carboxymethylcellulose adhering to the intersections of the fiber to deposit uniformly thereon while permitting the remainder of .the slurry to flow rapidly and .freely through the screen, and drying the webto cause the Waterinsoluble sodium .carboxymethylcellulose contained therein to bind the ,fibers in deposited web form, and maintaining said sodium carboxymethylcellulose in chemically-unaltered form throughout.

11. A method of preparing. a thin, soft, highly absorbent and porous-web material of lowdensity which comprises forming .a highly diluted aqueous slurry of unbeaten,-synthetic, artificially-formed fibers having a fiber length awithin therange-of from 6 millimeters up to and including textile fiber lengths with the addition'of a small quantity of water dispersible sodium carboxymethylcellulose containing from .2 to 25% by weight of water-insoluble gel-forming particles, .said sodium carboxymethylcellulose :having a .substitution value of from 0.3 to 0.75 and being addedinan amountsuificient to providea minimum of 3% parts of completely soluble sodium carboxymethylcellulose'and from v1 to .10 -.parts of Water-insoluble gel-formingparticles to 100 parts of fiber by Weight, said completely soluble portion beinglefiectiveto uniformly disperse and defiocculate the said fibers, forming a Web by flowing the dispersion onto a traveling meshed sheet-forming screen to cause the fibers and gel particles of sodium carboxymethylcellulose adhering to the intersections of the fiber to deposit uniformly thereon uwhile permitting the ,remainderof :the .siurryto fiowrapidly and freely through the screen, .and drying the web to cause the water-insoluble sodium icarboxymethylcellulose contained therein to bind the fibers .in .deposited Web form, and maintaining said sodium carboxymethylcellulose in chemically-unaltered form throughout.

12. A.-metnod of preparing a thin, soft, highly absorbent and, porous Web material of low density which comprises forming a highly diluted aqueous slurry of unbeaten, synthetic, artificially-formed fibers having a fiber length within the range of from ,6 millimeters up to and including textile fiber lengths with the addition of: a small quantity of water-dispersible sodium carboxymethylcellulose containing from 2to.25% by weight of waterinsoluble gel-forming particles, said sodium carboxymethylcellulose having a substitution value of from 0.3 to 0.75and being added in an amount-of one part by Weight to from 5 to 25 parts of fiber by weight and having a dual function in that the water-soluble content disperses and=defiocculates-the fiber in the suspension and the water-insoluble particles bind the fibers at their intersections in the finished sheet, forming a web by flowing the dispersion onto a traveling meshed sheet-forming screen to cause the fibers and gel particles of sodium carboxymethylcellulose adhering to the intersections of the fiber to deposit uniformly thereon while permitting the remainder of the slurry to flow rapidly and freely through the screen, and drying the Web to cause the water-insoluble sodium carboxymethylcellulose contained therein to bind the fibers in deposited web form, and maintaining said sodium carboxymethylcellulose in chemically-unaltered form throughout.

13. A method of preparing a thin, soft, highly absorbent and porous Web material of low density which comprises providing a sodium carboxymethylcellulose compound having a carboxymethyl substitution value of from 0.3 to 0.75 which when dispersed in water and passed through a screen having approximately 105,625 openings per inch will yield from 2 to 25% (by dry weight) of microscopic gel-forming particles, said carboxymethylcellulose having a dual function in that the water-soluble content disperses and deflocculates the fiber in the suspension and the water-insoluble particles bind the fibers at their intersections in the finished sheet, forming a highly diluted aqueous slurry of unbeaten, synthetic, artificially-formed fibers having a fiber length within the range of from 6 millimeters up to and including textile fiber lengths with the addition of one part of said sodium carboxymethylcellulose to from 5 to 25 parts of fiber by weight, forming a web by flowing the dispersion onto an inclined traveling meshed sheet-forming screen to cause the fibers and gel particles of sodium carboxymethylcellulose adhering to the intersections of the fiber to deposit uniformly thereon while permitting the remainder of the slurry to flow rapidly and freely through the screen, and drying the web to cause the waterinsoluble sodium carboxymethylcellulose contained therein to bind the fibers in deposited web form, and maintaining said sodium carboxymethylcellulose in chemically-unaltered form through-out.

FAY H. OSBORNE.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 2,236,545 Maxwell et al. Apr. 1, 1941 2,277,049 Reed Mar. 24, 1942 2,306,781 Francis Dec. 29, 1942 2,402,469 Toland et al June 18, 1946 2,414,833 Osborne Jan. 28, 1947 2,459,803 Francis Jan. 25, 1949 2,477,000 Osborne July 26, 1949 2,526,125 Francis Oct. 17, 1950 2,572,932 Horsey et a1 Oct. 30, 1951 FOREIGN PATENTS Number Country Date 450,902 Belgium July 31, 1943 679,334 Germany Aug. 3, 1939 301,807 Great Britain Jan. 30, 1930 505,200 Great Britain May 8, 1939 OTHER REFERENCES Paper Industry and Paper World, June 1943, pp. 263-269.

Paper Trade Journal, Dec. 24, 1942, pages 40 and 41.

gaper Trade Journal, July 24, 1947, pages 52 to 6.

Chemical Abstracts, vol. 41, page 7115 (1947).

Mathews Textile Fibers, 5th edition, published by John Wiley (1947), pages 23 and 27.

Sherman and Sherman, The New Fibers, published by D. Van Nostrand 00., Inc. (1946), page 257.

Ott, Cellulose and Cellulose Derivatives, published by Interscience Publishers, Inc. (1943), page 378.

Claims (1)

1. A THIN, SOFT, ABSORBENT, EXTREMELY POROUS AND LIGHT WEIGHT WEB MATERIAL OF SUBSTANTIAL STRENGTH CONSISTING ESSENTIALLY OF SYNTHETIC ARTIFICIALLYFORMED FIBERS HAVING A FIBER LENGTH WITHIN THE RANGE OF FROM 6 MILLIMETERS UP TO AND INCLUDING TEXTILE FIBER LENGTHS AND UNIFORMLY DISTRIBUTED AND INTERMINGLED IN THE FORM OF A WEB WITH THE FIBERS INTERSECTING BUT SPACED APART TO FORM NUMEROUS INTERSTICES, SAID FIBERS BEING IN THEIR ORIGINAL, NON-BINDING, FIBROUS, UNBEATEN, UNGELATINIZED AND UNCOALESCED FORM BUT BEING FIRMLY BONDED TOGETHER AT THEIR INTERSECTIONS BY SMALL, DISCRETE, WATER-LAID DEPOSITS OF WATER-INSOLUBLE CHEMICALLY-UNALTERED SODIUM CARBOXYMETHYLCELLULOSE HAVING A SUBSTITUTION VALUE OF FROM 0.3 TO 0.75 AND PRESENT UNIFORMLY THROUGHOUT THE WEB IN AN AMOUNT OF FROM 1 TO 5% OF THE WEIGHT OF THE FINISHED WEB.