US2418282A

US2418282A - Abrasive manufacture

Info

Publication number: US2418282A
Application number: US461140A
Authority: US
Inventors: John A Williamson
Original assignee: Carborundum Co
Current assignee: Unifrax 1 LLC
Priority date: 1942-10-07
Filing date: 1942-10-07
Publication date: 1947-04-01
Anticipated expiration: 1964-04-01

Description

J.- A. WILLIAMSON m1" ,WACTURB A ril 1, 1947.

find Oct. 7, 1942 2 sheets-sheet 1 April 1947- J. A. WILLIAMSON 2,418,282

I ABRASIVE mumcms Filed 091:. 7, 1942 2 Sheets-Sheet 2 .Z-hveniog Mr! 4. WALL/Judo Patented Apr. 1, 1947 S PATENT OFFICE ABRASIVE MANUFACTURE John A. Williamson, Niagara Falls, N. Y., as-

signor to The Carborundum Company, Niagara Falls, N. Y., a corporation of Delaware Application October '7, 1942, Serial No. 461,140

12 Claims. 1

This invention relates to the manufacture of flexible abrasive products, and more particularly to the manufacture of felted fibrous web material containing abrasive grains dispersed throughout the body of the web structure to provide a product suitable for use as an abrasive polishing or grinding medium. So-called coated abrasive articles, such as abrasive paper and cloth, discs and the like, are old and well known in the art, but the present invention should not be confused with such articles since it deals with a product which differs therefrom by the absence of the conventional backing. The present product represents an improvement over such articles by reason of the elimination of the backing and may be used for many purposes for which abrasive coated paper is adapted as well as in applications for which the conventional abrasive paper is not suited. In addition, its fibrous structure lends a strength and durability to the final product not to be expected in a backless product.

Recently it has been proposed to form felted abrasive webs, employing a plurality of carding machines to form a number of membranes which are interlocked and into whichabrasive grains are projected. Firstly, such methods are limited to those fibers which by reason of their length and strength are easily cardable, such as cotton, ramie and the like. Moreover, dry methodsof formation are hampered by certain difficulties of incorporating the abrasive internally of the web structure and keeping it in position therein until the web has been compacted by the application of pressure and the introduction of adhesive. The process herein disclosed avoids these difiiculties and has the further advantag that it employs fibers which are cheap and available in quantity, thus providing a new and inexpensive fibrous abrasive material possessing a soft grinding or polishing action.

The present invention provides a method of making felted fibrous abrasive webs of paper fibers and other relatively short-staple fibers which cannot be readily, if at all, carded, and

which are not adaptable to being satisfactorily felted by any of the known dry methods.

In accordance with the present invention felted fibrous webs having abrasive grain incorporated internally of the web are made by forming a thin liquid suspension of a mixture of abrasive grain and fibers, collecting the fibers and abrasive particles of the suspension on a suitable support, extracting water or other suspending liquid from the resulting web, and further drying and compacting the web to the desired density. A particular feature of the present invention is the provision of a fluid mixture in which the abrasive particles remain uniformly in suspension and which is of such a consistency that it can be flowed onto a support .to form sheets or webs of uniform thickness in which the abrasive content is substantially uniform throughout.

In order to provide a wet felted web made of short-staple fibers which will have satisfactory strength and uniformity of distribution, it is essential that the stock or furnish, i. e., the fluid suspension from which the sheets or web are to be formed, be of a relatively thin or highly aqueous consistency, having a fiber content of individually separated fibers amounting to not more than about 5.0%, and preferably for purposes of the present invention approximately 3%, by weight of the suspension. Otherwise, the fibers tend to mat together prematurely so as to retard or prevent the extraction of water therefrom, resulting in an inferior product having thin spots, streaks and other forms of non-uniformity and weakness. On the other hand, unless th suspension contains suflicient fibers, the minimum of which I have found to be about 0.5%, it is extremely difficult, if not impossible. to keep the abrasive grainsfsuspended in the fluid mass. In view of this need for the use of a relatively thin aqueous stock, the suspension therein of granu lar material of high density, such as abrasive grain, presents an extremely diflicult problem. I Q

have discovered a method of making such a wet mixture of fibrous material in which granular abrasive material is uniformly maintained in suspension and which provides an abrasive-ineluded stock suitable for making abrasive webs and sheets having a high abrasive content and an effective cutting action.

Accordingly, in carrying out the present invention an aqueous suspensionof around 3:% fiber over 40%, and preferably -70% by weight of l the final product after the water has been extracted. The agitation of the fibrous suspension previous to and/or during the addition of abrasive grain is very important in preparing a liquid in which the abrasive particles will remain unition or beating of the fibrous suspension necessary to provide a suitable stable mixture of abrasive and fiber of the proper consistency depends upon the size of the abrasive particles. For example, a very slight agitation serves the purpose when the finest abrasive polishing powders are used whereas with the use of 60 or 80 grit abrasive grains, it is desirable to subject the suspension to a much longer and/or more vigorous agitation. Suspension of the abrasive particles may be assisted by incorporating an adhesive in the fiuid mass, either in the form of a preliminary coating of the abrasive particles or by the addition of the adhesive to the liquid. In either case, the adhesive should preferably be soluble in the liquid medium of the suspension or at least -ftenable or soluble in a component thereof.

After a fiber-abrasive suspension of suitable consistency has been prepared as above outlined, it is flowed or otherwise deposited on a suitable foraminous support in the form of a continuous, highly aqueous layer from which the water or other liquid suspending medium is extracted, and the resulting film is further dried and compacted to the desired density. These operations may be performed by flowing the suspension onto a moving endless wire screen or by collecting a plurality of thin/membranes onto cylinder molds and transferring them to a suitable felt blanket in superimposed relation to form a web of the desired thickness. While it is usually desirable to carry out the invention in the described manner of forming continuous fibrous webs, the invention likewise can be practiced in modified form by using the same thin suspension of fibers and abrasive to form individual abrasive coated sheets by a series of discontinuous steps. Adhesive binders can be incorporated in the fibrous web, regardless of the procedure used, at various stages in the process, such as by inclusion in the fibrous suspension, introduction during dewatering of the web, as a coating on the abrasive grains, or after the web has been substantially dewatered and prior to the final'compacting and drying of the web.

Moreover, modifying agents such as waterproofing compounds, anti-friction agents, flexibilizers, plasticizers and other fillers may be incorporated in the web at the time of making in order to render the web resistant to water or impart other specific desirable properties to all or certain controlled portions of the web.

In order that the invention may be more clearly understood, reference is made to the accompanying drawings, in which,

Figure 1 shows a vertical diagrammatic crosssection of an apparatus for making flexible, abrasive-included fibrous webs in accordance with the teachings of the present invention;

Figure 2 shows a vertical diagrammatic crosssection of a modified form of apparatus which may be employed in place of that part of the apparatus shown by A of Figure 1 for collecting and forming the web from the suspension;

Figure 3 shows a highly enlarged fragmentary section through an aqueous suspension, showing the manner in which the fibers become partially gelatinized by agitation and in their gelatinized condition envelop or attach the abrasive particles and hold them in suspension; and

Figure 4 shows a greatly enlarged vertical cross-section through a portion of a fibrous abrasive web made in accordance with the present invention.

Referring further to the drawings, in Figure 1 is illustrated one form of apparatus which may be employed in manufacturing abrasive webs comprised of a felted fibrous material having abrasive grains incorporated therein and bonded with a suitable adhesive binder. The apparatus in the upper portion of Figure 1 comprises the equipment for making the aqueous suspension of fibers and abrasive required later to form the final sheets or web of abrasive material. The particular source of fibrous material depicted in Figure l is a number of laps 5 of paper pulp stock ready for disintegration in the beater 6 which comprises a large oval tank 1 in which is cradled a rotating beater roll 8 equipped with a plurality of bars or blades 9 which cooperate with a bed plate ID to individually separate the fibers of the stock which is fed to the beater after the beater has been half filled with water. The length of time in the beater depends upon the nature and condition of the fibrous material fed into the beater. The fiber lap stock may be previously fed through a shredder for a preliminary disintegration, if desired, although a shredder is not shown in the drawing. The beater serves to some extent to cut the fibers, but its prime purpose in the present process is usually the disintegration of the fiber bundles into individually separated fibers with an accompanying hydration of the fibers.

Any of the common cellulosic tree fibers used in paper making may be satisfactorily used in the present process. Other cellulosic fibrous materials which may be used include seed hairs, of which cotton and bombax wool are examples, stem-fibers, such as linen, jute, manila, etc., leaf fibers, such as straw, esparto, palm and the like and fruit fibers such as cccoanut. Also any of the new synthetic resin or synthetic elastic fibers can be used providing they have sufiicient strength and are of a fineness such that they can be "suspended in a thin solution similar to that formed with wood fibers. The inclusion of a softening agent in the suspension to assist in maintaining the abrasive uniformly suspended may be desirable in cases where various synthetic fibers are used. For example, when cellulose acetate fibers are used, it is advantageous to incorporate an alcohol or the like solvent for the fibers in an amount sufiicient to soften or render the fibers tacky so as to entrap and hold the abrasive in suspension therewith.

After the material has been properly disintegrated into individually separated fibers in the beater 6, the watery mass is transferred by pipe line H to a storage tank l2 which is equipped with paddles l3 which are driven through the shaft M at a speed sufiicient to keep the mass uniformly in suspension. The material is drawn from the storage tank l2 by opening valve H and forcing the material by means of pump l6 through pipe l5 to a refiner [8 which is used to homogenize the fibrous material by breaking up any lumps or slivers of fibers which may not have been previously disintegrated. The refiner may be any one of the well known types, such as the Jordan refiner, used by paper manufacturers. From the refiner ill the aqueous fiber suspension is fed through pipe l9 into an agitating tank 20 where the fibers are subjected to a vigorous agitation by means of paddles 2| which are driven through the shaft 22. It has been found to give most satisfactory results to fill the agitation tank 20 with an aqueous suspension of fibers and subject them to a period of agitation during which time the fibers are rendered gelatinous and the highly aqueous suspension assumes a certain degree of body or consistency, much higher than that possessed when it is introduced into the tank. This increase in consistency is due to a partial gelatinization of the fibers, as will be explained later. At this point, if desired, a small amount of glue, or other suitable adhesive can be added to the fibrous suspension. A controlled amount of abrasive grain is introduced into the gelatinized fibrous mass from grain hopper 23, followed by further agitation of the tank contents to disperse the abrasive particles uniformly throughout the mass and intimately engage the gelatinized fibers with the abrasive grain.

Specific examples of the type and composition of fiber-abrasive mixtures which go to make up satisfactory suspensions for the purposes of the present invention are as follows:

Example I Pounds 80 grit alumina abrasive grain 200 Unbleached sulfite pulp fibers 30 Dried hide glue 30 Water 1,000

In processing the above illustrative mixture the fibers and water first are agitated for a period of 2 hours, after which the glue in the form of a solution of the 30 parts of dried glue dissolved in 60 parts by Weight of the water is admixed thoroughly with the fibrous suspension. The fibers are sufiiciently gelatinized by this time to give a satisfactory body or consistency to the suspension whereupon the abrasive grain is added with continued agitation. After about 2-3 hours further agitation the fiber-abrasive suspension is ready to be removed from the tank through pipe 24 by means of pump 25 to the fiowor stock-box 28.

Example II Pounds 80 grit alumina abrasive grain 120 Unbleached sulfite pulp fibers 20 Dried hide glue 20 Latex (24% solids) 30 Water 1,000

The above mixture is processed in the same manner as that set forth for Example I. If desired, in place of all or part of the latex, 20 parts of a plasticizer such as that sold under the trade name of Flexalyn (a reaction product of rosin and diethylene glycol) or other equivalent plasticizing material can be incorporated in the suspension.

It is desired to point out here that various paper stock and other cellulosic fibrous materials can be obtained which by reason of their easily disintegrable nature, do not require extensive proc-- essing to break them down to individual fibers, in

beater ID for a sufficient length of time to gelatin ize them partially or entirely to the desired degree, followed by removal of the fiber stock, adjustment to the proper consistency by the addition of water thereto, and the addition of the abrasive grain (and adhesive when desired) with further mixing made in the storage tank 20.

The gelantinized fibrous suspension or stock 27 containing abrasive grain is maintained at a constant head inthe flow. or head-box 28 from which it is forced by its own weight out through the slice 29 onto the endless wire screen 30. The rate of flow of the fiber-abrasive stock is governed by the consistency of the stock, the extent of head maintained, and also by valve regulators 3| and. 32 which control the degree of opening of the slice 29. The wire screen 30 isdriven by the couch roll 33 and supported by the breast roll 34, table rolls 35 and wire rolls 36. The water content of the web is being removed continually, first by the series of table rolls'35, and then by th suction boxes 31, suction couch roll 33 and coactin top presure roll 38. As the water is extracted from the web the fibers seem to lose most of their gelatinized character and revert substantially to their original ungelatinized form. Meanwhile as they pass through this tranformation they become felted about the individual abrasive grains which so far have been held in the gelatinized bodied suspension, and also the fibers become interlocked one with the other to provide a strongly felted body having abrasive grain securely held therein. Suitable adhesive can be applied, as by means of a series of spray nozzles 39 posi-' tioned above the wire screen, to provide an additional strength and to assist in maintaining the web in its final compacted form.

The fibrous abrasive-included Web is transferred from the wire screen 30 to a pressing felt 4|, which is usually an endless woolen blanket, and is passed between the top and bottom pressure rolls 42, 43 where more water is removed and the sheet is further compacted. If desired, the bottom roll may be provided with a suction box to promote the extraction of Water. The felt 4| is supported and maintained taut by the felt rolls 44 and stretch roll 45. Additional pressing felts may be provided, if desired; also a top felt may be used to operate in conjunction with the bottom felt so as to retain the fibrous web between two felts a it is being pressed and to provide additionalsupport in its earlier stages, although such top felts are not shown in the various figures of the drawing as their application and use when essential should be clear and understandable and their presence in the drawing would lead to confusion. After the fibrous abrasive web leaves the pressing felts it still contains a large amount of water and is passed over a series of steam-heated dryer rolls 46 which remove additional water, following which the web is rolled onto a reel 4'! for storage or conveyance to machines for cutting into sheets, strips, discs and the like suitable for use.

Figure 2 shows in schematic cross-section an alternative apparatus which may be used for processing the fiber-abrasive suspension as it is taken from the agitating tank 20 of Figure 1 and replaces that part of the apparatus of Figure 1 shown in the sequence following the tank 20. In carrying out the invention with the apparatus of Figure 2, the suspension prepared in tank 2|] is used as a source of raw material for filling the cylinder vats 50 of Figure 2. Referring further to Figure 2, the apparatus depicted comless ,felt 56.

. prises a plurality of cylinder machines, suitably spaced apart and consisting of cylinder vats 50,

cylinder molds and couch rolls 52 adapted to form and deliver a numberof abrasive-included fibrous membranes or labs 53, 54 and 55 to a common carrier support such as the moving end- The stock or furnish 57 is maintained at aconstant head in each one of the cylinder vats. I a i I The cylinder molds 5| are large hollow drums with the cylindricalareas covered with a wire screen, usually of to 60 mesh, partially imabrasive web. The wet felted web containing I in Figure 2, additional top felts so that as the mersed in the fiber abrasive suspension contained in the vat and. revolving in the direction shown by the arrows. The water level within the cylinder mold is lower than. it is in the vatoutside the mold and as a result as the mold revolves; through the suspension it picks up a thin'film of the gelatim'zed fibrous material containing abrasive, which material clings to the foraminousisurface of the cylinder mold and is carried up out of thesuspension. This partially formed, highly aqueous fiber-abrasive membrane is transferred to the moving carrier support 56 by means of a couch roll52 which serves to press the carrier belt 56against the cylinder mold 5| The carrier support is ordinarily a wet woolen felt or blanket. and is supported by rolls 59, 60, GI, 62, 63 and 64, which may be driven by any suitable means (not shown). Roll 65 serves as a stretch roll to remove slack and keep the belt .tight.

The felt 56 picks the highly aqueous fiberabrasive membrane off the wire mesh of the ylinder mold, the membrane adhering to the underside of the felt with sufficient force to withstand the pull of gravity. As the moving felt passes over the remaining cylinder molds it similarly picks up additional abrasive-containing membranes, which are superimposed on the initially deposited membrane until a layer of fibrous material of the desired thickness has been built up on the belt. The thickness of the individual membranes can be controlled by the speed of rowet fibrous web passes through the various rolls it is held between two felts whichhold the web in position and, due to the absorbency of the felt carriers, assist in removing the large amount of water necessarily initially present. Additional press rolls to those shown may be included, after which the fibrous web, which still contains a large percentage of water, is passed over guide roll M to a series of steam-heated dryerrolls 15, from which the web is conducted to a wind-up reel 16.

Figure 3 shows a fragmentary View in greatly enlarged formv of a gelatinized fiber-abrasive grain suspension as it exists in tank 20 when tation of thecylinder mold and also by the consistency of the fiber-abrasive stock or furnish in The rate of feed of the various mem-' 'branes must be synchronized with the speed of 1 the moving felt so as to prevent any appreciable the vat.

strain or pull on the flimsy fibrous membranes I during their deposition and while they are in a highly aqueous, gelatinous condition.

As stated above the initial operations performed on the first membrane are repeated by the transfer of additional abrasive-fiber mem-' branes, such as 54 and 55 of Figure 2, to the carvat may contain a special fibrous stock, the fibers of which are featured by their strength or some other physical property but which used alone would be unsuited for. making satisfactory abrasive web material.

After the web has been built up to the desired thickness on the carrier belt 56 it is passed through a pair of squeeze rolls 63 and 66 which serve to extract additional water from the fibrous it is ready fortransfer to the stockor head-box.

for forming webs or sheets and shows the ma terial picturized as it appears under magnification by a microscope. The abrasive grains 80 are held in the suspension by reason of the gelatinized portion 8| of the fibers 82. The fibers 82, under the agitation to which they are subjectedin tank 20, become gelatinized to the extent that the aqueous medium between the fibers seems to be filled with a gelatinous material and the apparently ungelatinized portions of the fibers themselves become much smaller in size. The entire suspension acquires a body or consistency which is sufliciently viscous to support the abrasive grains 80, which are relatively dense and heavy, uniformly in suspension over rela= tively long periods of time. that, upon the extraction of water from thefiberabrasive suspension the gelatinous matter which has disseminated throughout the suspending medium appears not tohave lost its association with the fibers which constituted its source, since it reverts to the fibers which return to substantially their original size. However, in the procedure the fibers become feltedaround the abrasive grains in such a way as to hold them securely in position within the web.

Figure 4 shows a greatly enlarged cross-section through a portion of a finished web made in accordance with the present invention and shows 1 how the abrasive grains 8!! are included internally throughout the web structure and are held in place securely by the felted fibers 82. In the particular embodiment shown the abrasive is distributed uniformly throughout the entire web, whereas the web can be made, as is evident from consideration of the methods given above, so that the abrasive grain is concentrated in any desired portions of the web where it will be most effective, depending upon the use to which the final product is to be put.

The present process provides a product in which the abrasive grain content amounts to such proportion of the final product that the polishing.

and cutting action of the abrasive is effective and at the same time the fibrous structure provides a softness of abrasive action and freedom from harshness not otherwise found. It also provides a strength-adequate to cope with the stresses and However, it'is notedstrains to which the material will be subjected in use and also exhibits a pliant flexibility much to be desired in such products. The amount of abrasive grain included in the web can be readily controlled, and in cases where the entire structure of the web is charged with abrasive, it has been found that a satisfactory product results when the abrasive material constitutes at least 40%, and preferably around 60 to 70% by weight of the finished web.

\ The adhesive binder used to permeate and assist in maintaining the consolidated condition of the web is preferably one of a flexible or resilient intimately therewith whereby the abrasive particles are substantially all retained uniformly in suspension, continuously collecting said suspension upon a suitable foraminous support and applying a suitable adhesive to the fibrous web, extracting water therefrom, and drying and compacting the web to the desired density.

nature, such as latex, fiexibilized animal or vegetable glue, plasticized vinyl resin, plasticized urea aldehyde resins, and the like. Such flexible adhesives permit the retention of the natural pliable character of the interlocked felted fibrous structure. Also the adhesive binder may be included at any stage in the production of the web depending upon the specific procedure employed and the type of web material being made. For example, the adhesive may be incorporated in the aqueous suspension before it is'fiowed into web form, it may be deposited or applied with the abrasive grains or at any stage during the building up of the fibrous web or during the dewatering operations, or after the web has been dewatered and prior or subsequent to the pressing and compacting of the web.

Also, in practicing the invention any of the abrasive materials in common use may be employed, such as silicon carbide, fused aluminum oxide, flint, corundum, emery, rouge and similar substances, either singly or in combination. The size of the abrasive particles may vary from the finest polishing or buffing powders to the coarser grit sizes used in grinding.

While the preferred embodiments of the invention have been specifically illustrated and described, it is to be understood that the invention may be otherwise embodied and practiced within the scope of the appended claims.

I claim:

1. The method of making flexible fibrous abrasive web material which comprises forming a fluid aqueous suspension of cellulosic fibers and abrasive grains, agitating said suspension to gelatinize said fibers by the mechanical hydration thereof and incorporate the abrasive particles intimately therewith whereby the abrasive particles are substantially all retained uniformly in suspension, continuously collecting said suspension upon a suitable foraminous support, extracting water therefrom, and drying and compacting the web to the desired density.

2. The method of making flexible fibrous abrasive web material which comprises forming -a fluid, aqueous suspension of cellulosic fibers, abrasive grain and a suitable adhesive, agitating said suspension to gelatinize said fibersby the mechanical hydration thereof and incorporate, the abrasive particles all retained uniformly in suspension, continuously collecting said suspension upon a suitable foraminous support, extracting water therefrom, and drying and compacting the web to the desired density.

3. The method of making flexible fibrous abrasive web material which comprises forming a fluid, aqueous suspension of cellulosic fibers and abrasive grains, agitating said suspension to thereof and incorporate the abrasive particles 75 upon a foraminous support and extracting water 4. The method of making a flexible fibrous abrasive web material which comprises forming a 0.5 to 5% aqueous suspension of individually separated cellulosic fibers, incorporating over by weight of abrasive particles in said suspension based on the weight of the fibers, agitating said suspension to gelatinize said fibers by the mechanical hydration thereof and incorporate the abrasive particles more intimately therewith whereby the abrasive particles are substantially all retained uniformly in suspension, continuously collecting said suspension upon a suitable foraminous support, extracting water therefrom, and drying and compacting the web to the desired density.

5. A method of making flexible fibrous abrasive webs which comprises forming a fluid, aqueous suspension of fibrous material, introducing a granular abrasive material together with a suitable adhesive binder into said suspension, agitating the mixture to render the fibers sufilciently gelatinized by the mechanical hydration thereof to render and maintain the ingredients uniformly in suspension, continuously flowing the suspension upon a suitable foraminous support and extracting the liqu d medium to leave as a deposit thereon a relatively thin web of felted fibrous material containing abrasive grains and-- a binder therefor, and drying and compacting the thin fibrous web.

6. A method of making flexible fibrous abrasive Webs which comprises forming a fluid, aqueous suspension of fibrous material, introducing a granular abrasive material to ether with a suitable adhesive binder into said suspension, agitating the mixture to render the fibers sumciently gelatinized by the mechanical hydration thereof to render and maintain the ingredients uniformly in suspension, continuously collecting the suspension upon a suitable foraminous support and extrac-nng the liquid medium to leave as a deposit thereon a relatively thin web of felted fibrous material containing abrasive grains and a binder therefor, drying and compacting the thin fibrous web, and heating to set the adhesive binder.

7. The method of making flexible fibrous abrasive webs which comprises forming as a fluid. aqueous suspension a uniform mixture of fibers. abrasive particles and adhesive binder, agitating the mixture to render the fibers sufliciently gelatinzed by the mechanical hydration thereof .120 maintain the ingredients in suspension, sprayintimately therewith whereby the abrasive particles are substantially gelatinize said fibers by the mechanical hydration I ing the suspension onto a foraminous support and extracting liquid therefrom to leave as a deposit thereon a web of felted fibrous material containing abrasive particles and a binder therefor, drying and compacting the fibrous web to the desired density, and heating toset the binder.

8. The method of making flexible fibrous abrasive webs which comprises forming a fluid aqueous suspension of fibrous cellulosic material, treating said suspension to gelatlnize the fibers thereof, including abrasive particles within the suspension and agitating the mixture to maintain the abrasive particles uniformly suspended with the gelatinized fibers, collecting the suspension auaasa v to leave as a deposit thereon a web of felted fibrous material containing abrasive particles.-

and compacting the web to the desired density.

9. A method of making flexible flbrousabrasive webs which comprises forming a loose dry granular mass of adhesive-coated abrasive grains,

forming a fluid, aqueous suspension of fibrous material which suspension contains a solvent for the adhesive applied to the abrasive grains, introducing the adhesive-coated abrasive material into said fibrous suspension, agitating the mixture to render and maintain the ingredients uniformly in suspension by reason of the gelatinization of the fibers by a mechanical hydration caused by the agitation together with the softening action 12 ized by the mechanical hydration thereof to maintain the ingredients in suspension, collecting the suspension on a foraminous support and extracting water'therefrom to leave as a deposit thereon a web of felted fibrous material containing abrasive particles, and drying and compactin: the fibrous web.

of the solvent on the adhesive, continuously collecting the suspension upon a foraminous support and extractingliquid medium to leave as a deposit thereon a web of felted fibrous material containing adhesive-coated abrasive grains, and

drying and compacting the fibrous web.

10. A method of making flexible fibrous abrasive web. which comprises forming a loose dry granular mass of glue-coated abrasive grains, forming, a; fluid, aqueous suspension of fibrous material, introducing the glue-coated abrasive' material into said fibrous suspension, agitating the mixture to render the fibers sufflciently gelatinized by the mechanical hydration thereof to render and maintain the ingredients uniformly in suspension, continuously collecting the suspensien-upon a foraminous support and extracting water to leave as a deposit thereon a web of felted fibrous material containing glue-coated abrasive grains, and drying and compacting the web to the desired density.

11. The method of making flexible fibrous abrasive webs which comprises forming as a fluid aqueous suspension a uniform mixture compris ing fibers and abrasive particles. agitating the mixture to render the fibers sumciently gelatin- 12. The method of making flexible fibrous abrasive webs which comprises forming a fluid aqueous suspension of cellulosic fibers, agitating said suspension to render the fibers gelatinized by the mechanical hydration thereof, adding abrasive particles to the suspension and mixing therewith, collecting the abrasive-containing suspension on a foraminous support and extracting water therefrom to leave as a deposit thereon a web of felted fibrous material containing abrasive particles, and drying and compacting the fibrous web.

1 JOHN A. WILLIAMSON.

REFERENCES CITED The following references are of record in the file of this patent:

German Oct. 10, 1907