US2057167A - Manufacture of impregnated sheet products - Google Patents

Description

oct. 13, 193e.

J. c. SHERMAN MANUFACTURE OF IMPREGNATED SHEET PRODUCTS Filed Jan. l1, 1933 3 SheetSSheet 1 s sheets-seet 2 Oct. 13, 1936. J, c. SHERMAN MANUFACTURE OF' IMPREGNATED SHEET PRODUCTS Filed Jan. ll, 1933 Oct. 13, 1936. J. c. SHERMAN MANUFACTURE 0F IMPREGNATED SHEET PRODUCTS Filed Jan. 11, 1933 3 Sheets-Sheet 3 Patented Och 13, 1936 PATENT OFFICE MANUFACTURE F IMPREGNATED SHEET PRODUCTS John C. Sherman, Gorham. Main@ assigner to Brown Company. Berlin, N. H., a corporation oi' Maine Application January 11, 1933, Serial No. 651,106

8 Claims.

The subiect of this invention is the manufacture of impregnated sheet products more particularly of the kind comprising a foundation of fibrous material laden throughout with an impregnating binder of a suitable character imparting such qualities as strength, tear-resistance, water repellency. liliancy, fold-endurance, moldability, stretchability, etc.,- to the product. While various' fibrous materials may constitute the 1c fibrous foundation of the present invention, including mineral fibers, such as asbestos, and animal bers, such as wool. cattle hair, or the like, the foundation of the present invention shall be described more specicaliy as embodying cellulose` fiber, such as chemical wood pulp, cotton, rag pulp, or the like, as the raw material. These various cellulosic fibrous materials may be used as a blend to constitute the entire furnish for the fibrous foundation, .or they may be supplemented by the desired amount of mineral and/or animal fibers. The impregnants introduced as the binding media into the fibrous foundation to impart the various qualities hereinbefore mentioned to the :finished product' may be selected from a Wide class including asphalt lor other bitumens, latex, natural resins, artificial resinsv of the so-called phenol or vinyl condensate type,

cellulose ester compositions of the nature of pyroxylin and cellulose acetate, and the so-called drying oils as typied by linseed, tung, and other unsaturated oils preferably carrying metallic salts orA other catalysts of drying.

In preparing fibrous foundations for impregnation purposes. using bulk fibers as the starting material, there' are two established modes of fabrication which may be adopted. Thus, it is possible to prepare so-called water-laid felts on machinery of the paper-making type. To this end, the fibrous material is suspended, after suit- 40 able conditioning treatment, in water and the resulting aqueous ber suspension is delivered to the felt-making machine, whereon the fibers are interfelted into a sheet of uniform texture which is passed over a drier usually consisting of a bank of drier drums. A serious disadvantage inhering in this practice is the limitation as to the thickness of felt which may thus be made, as it is extremely diiiicult to build up a felt beyond a certain thickness at the wet end of the machine or to dry such a web on the dry end of the machine. While it might be possible to exceed the thicknessof water-laid felts now being commercially fabricated by re-designing the wet end of the felt-making machine and extending the dry end, this would make for excessive cost of manufacture. A second, but less familiar, way of preparing a felt is to segregate the bulk iibrous material in substantially dry condition into its individual fiber units and then to deposit the individualized fibers from suspension in air on 5 a foraminous carrier, such as a wire cloth, and

to compress the mat or layer of fibers thus deposited into a felt oi appropriate density. Such latter practice is free from the objection ofjthickness limitation, as it is possible to deposit the l0 .dry fibers to any desired thickness as well as to dispense` with the need of a drying operation. One of. the faults with this practice, however, is that it conduces to a web or feitwhich is comparatively weak from a mechanical standl5 point. This weakness is ascribable to various causes, principal of which are that the web must undergo enormous pressures in order to arrive at the compactness of water-laid felts and that the web is lacking in the hydrated or gelat- 20 inized cellulose usually associated 'with an aqueous suspension of cellulose fibers and which serves to bond together the fibers of a water-laid felt and thereby to strengthen such felt. .Consequently, iibrous webs formed in a dry way are apt to be tender and deficient in tensile strength. The webs formed in a dry way, which shall hereinafter be designated air-laid Webs in contradistinction to water-laid felts, take on surprisingly good characteristics when impregnated 30 with the various binders hereinbefore enumerated. Thus, they are strengthened enormously during impregnation and when the impregnating binder has set therein, the finished product possesses characteristics approaching or excelling 35 those of similarly impregnated water-laid felts. In this connection, it might be remarked that air-laid webs can be impregnated with greater facility and uniformity at all thicknesses than water-laid felts, irrespective of whether the im- 40 pregnating medium consists of water-dispersed material, molten thermoplastic material, or dissolved material. These advantages are imputable to the absence from the air-laid web of hydrated or gelatinized cellulose which, in the case 45 of water-laid felts. tends to obstruct the pores and interstices of the4 felt and thereby to impede free influx of the impregnant into and throughout the felt. Again, the random arrangement and felting of the fibers in the air-laid web is 50 consonant with uniformity of strength throughout the impregnated product, whereas water-laid feits, particularly when built up tc substantial thickness, are apt to exhibit stratification and also greater strength in the machinedirection 55 Y impregnating binder, e. g., the asphalt or rubber, may undergo deterioration and loss of valuable physical properties in the presence of oxygen, moisture, and sunlight, in consequence of which the impregnated product as a whole may become markedly depreciated. This depreciation is not only traceable to the degradation which ther binder has undergone, but to the flimsy structure of the air-laid web constituting the foundation, for, as already indicated, the airlaid web in the absence of binder is weak and deficient in tensile strength.

In accordance with one phase of the present invention', I produce more particularly for im pregnation purposes, a composite sheet made up,

oi both an air-laid web and a water-laid felt in superposed relationship, the water-laid felt preferably existing as the outer ply on either or both faces of the air-laid web. This means that I am enabled to combine in the impregnated composite sheet the values inhering 'in both the air-laid and in the water-laid felt. In other words,v the various advantageous qualities arising from the use of an air-laid web may be part and parcel of the body of the impregnated composite sheet and the advantageous qualities emanating from the water-laid felt may obtain at either or both faces of the sheet where it is exposed to deteriorating influences and where. it is hence desired to provide maximum resistance against tearing and disintegration of the sheet after the binder has lost its best qualities. While the prin'- ,K

ciples .of the. present invention may be availed oi' in preparing all sorts of impregnated products, using the various binding media hereinbefore enumerated, I `shall deal specifically with the value of my invention in the manufacture of a bituminized sheet such as may serve in the roofing, nooring, and other industries. As is well known, in these industries, a bituminized fibrous sheet serves as the base carrying suitable ornamentation the ornamentation in the roofing industry usually being colored crushed slate vor similar mineral granular material embedded in s. coating of vhigh melting-point, asphalt, e. g., blown asphalt, applied to a face of the sheet.

and that in theilooring industry being linseed.

oli-paint or similar pigmented coating applied to s face oi the sheet. I

with the fioregoins and other features and objects in view.. the present invention will now be described in further'l detail in conjunction with the accompanying drawings, wherein,-

ll'igure 1 represents diagrammaticslly and conventionally a longitudinalI largely sectional view of a machine such as may serve for the producuon er saumimzed sheet material embodyingthe invention.

Figure 1a represents a continuation of Figure l.

ligure 2 shows in perspective one of the rolls for the air-laid web of fiber.

ligure 3 illustrates in perspective a fragment of the bituminised product.

ll'igureeisaplanviewofamachinedesigned.

more particularly for the production' of roofing' shingles embodyim the invention.,

ligure 5 represents a longitudinal. largely sectionsl view of. themachine of Figure-4.

- Figures 6, .'I and 8 show in perspective various l A 2,057,1e7 than inany other by virtue of the pronounced forms of shingles such as may be prepared on a shingle-making machine.

Referring now in detail to Figure l ofthe drawings, IU represents a hammer 'mill whereinto sheeted chemical wood pulp or similar bulk iibrous material may be introduced in regulated quantities for the purpose of becoming segregated into substantially individualized fiber units. The wood pulp employed as raw material may, for example, be such commercial chemical pulp as sulphlte or kraft pulp orbe wood pulp which has been refined to higher alpha cellulose content than that of the usual commercial chemical wood pulp. The pulp may bein the'iorm of so-called drier sheets as it commonly appears on the market. In such form, the pulp is associated with comparatively little moisture and lends itself well to the individualizing action of a hammer mill. The light, fluffy mass of individualized fiber Aunits discharged from the hammer mill may be received by a blower I I of the rotary type, whose intake end communicates with the discharge of the hammer mill, and whose exit end consists of a nozzle feeding into a flared conduit I2. The flared conduit I2 has its end opening in close proximity to a roll I3 which is stationed above l -As 'shown in Figure 2. the roll I2 is equipped with- .end flanges I5 which engage the carrier I4 and which determine the clearance between the roll I3 and the carrier I4, and, accordingly, the height to which the iiber can be deposited on the carrier. In order to promote the deposition of the iibers from the air current aswell as to' assist their interfelting into a coherent mat or layer, a suction box IC is preferably arrangedunder the carrier Il at that region corresponding to the fiberdepositing chamber. ,The carriermoves circuitously about end rolls I1, one roll being arranged immediately in front of' the fiber-depositing chamber, and the other being spaced sumciently therefrom to permit successive compacting4 operations to be performed on the mat of fibers while it rests on the carrier I4. While the mat may undergo any desired number of stages of compacting designed to reduce it to the desired density and thickness, I have shown two press rolls Il and I l which, like the roll II, are equipped with end nanges 20 and 2|, respectively, riding on the carrier I4. Suitable rolls 22 may be placed directly under the carrier Il to receive and react Il and the carrier Il is smaller than that be.

tween the roll Il and the carrier, and the clearance between the roll Il and the. carrier'is' in turn smaller than that between the roll II and the carrier, wherefore,.themat is gradually compacted as itpasses under the rolls Il and I9. The

rolls Il. `Il and Il are preferably spaced apart sufficiently to permit the matto rebound and to recover as much of its thickness as it can after each compacting step and before it undergoes a succeeding greater compacting pressure. While it is possible to bring the web to the desired density and thickness in asingle composting operation',"it is preferable to reducethe mat-'gradually by the application of progressively increasing pressure, as this largely does away with the otherplanes of cleavage or lamination.l Either one or both rolls I1 may be positively rotated so as to produce'the desired circuitous travel of the carrier I4 and, so too, the rolls I3, I8 and I3 may be positively rotated. It is, of course, possible to have the rolls I3,y I8 and I9 induce by friction a travel of the carrier I4. although it is preferable to propel the carrier by a variable speed-driving mechanism by which its speed may be adjusted so as to ensure the deposition of fiber to the desired thickness thereupon. The peripheral speed of the rolls I3, I8 and I 9 should be equal to the linear speed of the carrier I4 so as to avoid any disrupting action on the mat.

The compacted mat or web M delivered by the carrier I4 preferably proceeds onto a conveyor belt 23 moving endlessly about end rolls 24. As itcross'es the gap between the adjacent rolls I1 and 24, a water-laid felt may be brought thereover and/or thereunder to form the composite sheet which is to undergo impregnation. As illustrated, a water-laid felt F is progressively unwound from a parent roll 25 and is led over the roll 24 under the mat and, similarly, a waterlaid felt F is progressively unwound from a parent roll 26 and is brought under a roll 2l above the mat, thereby forming a composite sheet whose interior consists of air-laid web and whose surface portions consist of water-laid felt. It is preferable that the superposed plies beunited against displacement while undergoing the subsequent impregnating operation. Accordingly, the face of leach of the felts F which comes in contact with the air-laid web M may be coated while on its way to the web with'a suitable adhesive, such as an aqueous paste of raw potato starch. The adhesive may be applied by any suitable means, for instance, as from spray nozzles 28 arranged to spray the adhesive uniformly over the appropriate face of each Water-laid lfelt F. The rolls 21 and 24 may coact under ,suiiicient pressure to ensure perfect bondage between the superposed plies and to keep the surfaces of the composite sheet smooth and free from wrinkles. The adhesive existing at the interface of the plies may be dried or set as the composite sheet C is carried by theconveyor belt 23, to which end it may pass through a hot-air drying `chamber 29 stationed in front of the rear conveyor roll 24.

The composite sheet is then impregnated as by introduction into a bath of molten asphalt 30 while being guided through the bath by a series of rolls 3l. The asphalt may be of the usual variety used in making bituminized rooiing felt. say, one having a melting point of about 130 F. (ball and ring test) and at a temperature of about 385 to 400 F. in the bath. The bituminized sheet coming from the impregnating bath may then be cooled to permit the congelation of the asphalt therein, as by passing over a set of looping rolls 32 which afford an adequate time of exposure of the sheet to the cooling eiIect of the atmosphere. It is, of course, possible to cool the bituminized sheet in any other approved way, as by passing over cooling drums through which cold water is circulated as the cooling medium. The bituminized sheet may then be accumulated into so-called roll roofing 33, or, when roofing shingles are in view, the bituminized sheet may be coated' with blown asphalt or its' equivalent and be surfaced with ornamental, wcather-resisting material, such as crushed colored slate or the like.

Another phase of the present invention is the manufacture of rooting shingles, each of which simulates a' numberof overlapping, individual, tapered roofing shingles. The manufacture of the bituminized base sheet, from which such shingles are cut transversely of the sheet, may be accomplished on the machine illustrated in Figures 4 and 5. This machine is in general similar to that already described, but the deposition of the fibers on the'foraminous carrier I 471s governed by a roll 40 whose peripheral configuration is generally complemental to the exposed or surface profile of a number of individual tapered roofing shingles assembled in overlapping relationship as on a roof. The roll 40-may be considered as ybeing made up of a plurality of similar truncated cones laid end to end, the planes of truncation lying substantially at right angles tothe axis -of the roll. The depth to which the fibers are deposited from suspension in air on the carrier I4 is determined by the periphery of --the roll 40, wherefore, the resulting mat of iibers is made up of adjacent longitudinal zones, all of which zones progressively vary in thickness of fibrous substance or structure transversely of the'mat, all of the zones being more particularly of progressively decreasing thickness (or, of progressively increasing thickness). toward a common side edge of the mat. It will, of course, be understood that by the term zone, I mean the width of mat subtended by each of the frusta-conical vsections of the roll 40. The mat is subjected to one or more compacting operations while still on I have shown rolls 4I and 42 whose peripheries are generally similar to that of the roll 40 but whose frusto-conical sections are defined by sides of more gradual slope, assuming the axis of each roll as the base line of slope. The sides of the truste-conical sections of the roll 4I bear a deinite angular relationship to those of the frusta-V conical sections of the roll 40 such that a uniform density is reached in the compactedV web. In other words,' the web undergoes the same proportional diminution in thickness of brous substance at the longitudinal zone-boundary lines of maximum thickness as at the longitudinal zone-boundary lines of minimum thickness. The same relationship holds true between the rolls42 4and 4I as that between the rolls 4I and 40. As a specific illustration of what these rolls may accomplish, I may take as a concrete example a web which emerges from under the roll 4U with a maximum thickness of fibrous substance of 4-inches and a minimum thickness of fibrous substance of l-inch. The web coming from the press roll 4I may have a maximum thickness of l-inch and a minimum thickness of onequarter inch, and, correspondingly, the web coming from the press roll 42 may have a maximum thickness of fibrous susbtance of one-quarter inch and a minimum thickness Vof fibrous sub stance of one-sixteenth inch.

Once the air-laid web has undergone the desired compacting treatment, it may be handled essentially like the flat-faced, air-laid web, as illustrated in Figure l. As shown in Figure 5, the

under face of the air-laid web may receive a backing of water-laid felt F while it is passing Vto the conveyor belt 23` exactly in the same Way include a surface coating with blown asphalt and an embedding of crushed, colored slate or its equivalent in the coating.

The bitummlzed and, if desired, annee-rm-` ished sheet is cut transversely into shingles which, by virtue of its surface configuration or exposed profile, simulates a number of individual tapered shingles 'laid in overlapping courses. Such shingies are illustrated in Figures 6, 7 and 8, all of which are shown as having a stepped surface configuration. Each zone corresponding to a shingle course is made up of a thick butt portion B and a thin top portion T, the diminution in thickness from the butt to the top portion being gradual. The shingle in Figure 6 has a composite base, including a backing of water-laid felt F and air-laid web M, and is shown with a coating of asphalt C having embedded therein exposed granular material G of the nature of crushed slate; that shown in Figure 'I includes an airlaid web M confined between a backing offwaterlaid feit F and a similar facing of water-laid felt exposed to weathering; that shown in Figure 8 includes an air-laid web M only faced with waterlaid felt F exposed to weathering. While in all cases, the water-laid felt is a highly valuable addition to the air-laid web, nevertheless it is preferable that the water-laid felt be combined with the air-laid web as shown in Figures Tand 8,

where, by virtue of its better age resistance, itA

can afford the desired reinforcement of the less enduring air-laid web. It will be appreciated that the shingles of my invention are characterized by homogeneity in density and structure throughout and that their tapered, -shinglesimulating parts of fibrous substance are integral with one another and do not present easily iiexing edge portions or flaps which, on a roof, are liable to be raised by wind and other forces.

Y That part of my invention which relates to the production of an air-laid web whose surface con- Vguration comports with the fabrication of roofing shingles having the' exposed profile shown in Figures 6, 7 and 8 is, so far as I am aware, novel perse. It is hence my intention to claim this phase of my invention withoutregard to the feature of reinforcing such an air-laid web on either or both faces with water-laid felt, even though, as has been stressed, this featureenhances the utility of the air-laid web. In other words, the air-laid web, prepared as illustrated in Figure 5, may by itself, after receiving the-appropriate compacting treatment, undergo bituminization and, ifV desired, surface-finishing, and

' nally be cut transversely into what may be termed shingle strips. v

It is possible to modify and to amplify the practices hereinbefore described. For instance, the various plies of the composite base sheet need not be adhesively united prior to impregnation when provision ismade to maintain their superposed relationship as they are fed into and are passing through the bath of molten asphalt or other lmpregnant. In auch case, the lmpregnant .impregnating phase.

itself will, upon setting, afford adequate bonding of the various plies. In those instances when an adhesive film serves to unite the plies of the cornposite base sheet, it should be applied in such a way as not to interfere with rapid and uniform penetration of all the plies. By using a comparatively dilute aqueous paste or solution of raw starch vorother suitable adhesive, such` as a spray of adhesive, preferably a thin mist, may

be delivered onto the fibers while they are suspended in the air current -and are flocking to the carrier. The resulting air-laid web will thus have greater strength and integrity by virtue, of the bond existing between contiguous fibers, the amount of adhesive present` in the web being, however. comparatively small and so well distributed throughout the web as not to detract appreciably from the penetrability of the web by impregnating media. If desired, rather than preforming the air-laid web and uniting water-laid felt therewith, it may be formed directly on a water-laid felt backing fed progressively under -the 'ber shower from which the air-laid web is built up. The surface of the water-laid felt able adhesive and thus have the air-laid web deposited thereon become locked thereto.

There are other materials which may advantageously b added to the fiber shower from which the air-laid web is formed. Thus, various fusible or thermoplastic materials, such as comminuted formly scattered throughout the fiber shower for the purpose of yielding an air-laid web which may be compressed under heat, as between hot press rolls, sufiicient to cause the fusion and coalescence of the fusible particles into a continuous material with the fiber may well be effected in the fan or blower which delivers .the individualized fibers together with such material in wellmixed condition to the carrier on which the airlaid web is deposited. The fusible material thereby incorporated into the web and fused therethroughout may constitute the sole impregnating binder for the web, but it may be desirable to effect impregnation of the web with additional binder. For instance, an air-laid web containing powdered asphalt having a melting point of, say,v 130 F. (ball and ring test) may be passed directly through a bath of similar molten asphalt at a temperature of about 385 to 400 F. 'Ihe powdered asphalt particles will thus become fused in situ and caused to iiow throughout the4 sheet along with the-asphalt of the bath, thereby promoting a rapid and uniform impregnation ofthe sheet. In some instances, the asphalt of the impregnating bath may differ in quality or grade from the powdered asphalt associated with the web. Thus, the asphalt of the 'bath may be a asphalt, powdered rosin, or the like, may be uni- 'I'he commingling of such ensure quick and uniform penetration of the web by virtue of the fluxing action of the molten, higher melting-point asphalt,e. g., a blown asphalt, on the lower melting-point asphalt.

When the air-laid web is to undergo impregnation with aqueous dispersions, such as latex, emulsied asphalt, or the like, there are other materials which may advantageously supplement the liber to be formed into the air-laid web. For instance, acids or salts, such as can break down the dispersions and render the dispersed mate-A rial a continuous phase, may be uniformly disseminated throughout the fiber shower and the air-laid web formed therefrom may be immersed in the aqueous dispersion, which upon entering into the web has its dispersed component converted immediately in situ in the web into a continuous phase before the impregnated web is dried. This serves to inhibit the migration of dispersed particles to the surface of the impregnated web such as tends to take place when drying alone isreiied upon tol break down the disy persion as well as to eliminate water from the web. When latex or similar aqueous rubber dispersions are the impregnants, dry magnesium chloride, ammonium fluoride, alum, or similar coagulants, may form part of the air-laid web as it enters the impregnating bath. When wateremulsined asphalt stabilized as by soaps serves as the impregnating medium, the soap or other stabilizing coilcid may be decomposed by virtue of acids or acid salts associated with. the web. Buch rubber-compounding agents as lamp black, sulphur, zinc oxide, accelerators of vulcanization, or the like. which might tend to filter out on the surface of the web when added as part of a lateximpregnating composition, may constitute part of the dry, web-forming furnish.- 'I'he lamp black orother rubber-compounding agent can thus be compounded with the latex in situ in the web during drying and/or vulcanization of the lateximpregnated web. Webs to be impregnated with water-emulsiiied asphalt or other aqueous dispersions may have as an ingredient therein drystarch or similar water-soluble adhesive whose adhesiveness can come into play in the presence of water but which remain unaffected under temperature conditions which may affect the asphalt or other main binder.

While, as already indicated, the air-laid web may be formed from various dry fiber furnishes, for the sake of economy, nnely shredded rags,

, such as are available at exceedingly low cost, may

be employed as raw material. The shredded rags alone may be used as the web-making furnish or in combinationwith chemical wood pulps or the like. In some instances, a composite air-laid web comprising one layer of finely shredded rags and another layer of chemical wood pulp or similar fibrous material may be made .on web-making machine equipped with two fiber-depositing chambers, one chamber receiving the finely shredded rags directly from a shredder and theother chamber receiving the chemical wood pulp or the like from a hammer mill.y One of the virtues of a hammer mill is that large quantities of .chemical wood pulp can be handled thereby at low cost with satisfactory individualization of the fibers for most practical requirements. 'On

the other hand, there are other machines available for individualizing fibers, such as pickers or cards, which, while they are comparatively expensive, nevertheless are capable of carrying the iiber-individualizing y treatment more nearly to completion, that is, with a minimum content of clumped fibers in the product received therefrom.

Buch latter machines may, therefore, be used in lieu of a hammer millespecially in the formation of air-laid webs which are to go into comparativelylexpensive products, likeartiiicial leather. j As in the case of the air-laid web, the waterlaid felt may be made from various fiber furnishes. Thus the usual water-laid rag felt of lcommerce may serve the purposes of the present invention; or, the water-laid felt may be made from chemical ywood pulp, refined Aor otherwise, or from fiber furnishes containing asbestos' and/.or wool ilber. In the case lof a water-laid felt which is to be placed as the exposed layer on an air-laid feltvand to be bituminized for the manufacture of roonngs, roofing shingles, or the like, the water-laid felt may be made from a furnish containing suflicient asbestos or similar incombustible fiber to render the felt nre-resistant.

The present invention is centered primarily about the use of water-laid felts in combination with air-laid feltsvas a composite base sheetfor impregnation purposes, but another phase of my invention embraces the use of textile fabric, such entirely of nbers interfeltedthrough air-laying or water-laying.

Irrespective of whether a water-laid feit and/or a textile fabric, woven or otherwise, acts as the reinforcement for the air-laid' web, ysuch reinforcement preferably occurs on either or both faces or the air-1am web. It is pessime, however, to have the reinforcing phase located centrally or otherwise within the air-laid web as by interposing the water-laid felt or textile fabric between two independently formed layers of airlaid web or by leading the water-laid feit or textile fabric onto a partially formed air-laid felt and then completing the formation of the air-laid i felt by depositing nbers from suspension in air onto the water-laid felt or textile fabric.

In using the expression ,water-laid felt I mean to include not only sheets formed on papermaking machinery of sumcient thickness to fall within the-generally accepted classification of felts, but similarly formed sheets of such caliper to be termed papers. Such papers should have qualities similarto those of water-laid felts, that iis, they should be porous, bibulous. and, preferably aiso, waterleaf, that is, free from any signincant amount of sizing and/or loading agents. In using the expression "textile fabric, I mean to include also wire cloth or perforated metal sheeting of a nexibility and reticulation comparable to that of ber cloth. Because of the lack oi' a generic expression covering these various'forms of reinforcements for the air-laid web. I shall denominate all of them in the appended lclaims by sheet.

I claimzg i. A binder-impregnated composite sheet product whose base consists of a compressed. airiaid web of fibers existing in random interfeited condition combined with a water-laid felt, the b nder impregnant occurring in a state of continuity throughout said product and on its surthe expression porous reinforcing M faces and bonding together said web and felt and the fibers in the bodies thereof.

2. A bituminized composite sheet vproduct whose base consists of a compressed, air-laid web of cellulose fibers existing in random interfelted condition and a. surface ply of water-laid felt containing sumcient asbestos to be fire-resistant, the bitumen occurring in a state of con' tinuity throughout said sheet and on its surfaces and bonding together said web and felt and the bers in the bodies thereof.

3. A bituminized, compressed, air-laid web of bers existing in random interfelted condition and of substantial homogeneity in structure and density throughout, said web having a substantially flat back face and a front face whose profile of fibrous substance simulates that of tapered 4shingles laid in overlapping courses.

random interfelted condition and a surface ply of water-laid felt, said sheet having a substantially flat back face and a front face whose pronle of nbrous substance simulates that at tapered shingles laid in overlapping courses.

6. A method which comprises progressively depositing fibers from suspension in air into a web of substantially uniform density throughout made up of adjacent longitudinaizones, all of which progressively decrease in thickness of nbrous A substance transversely of the web toward a common side edge of the web, compressing said web while maintaining it at substantially uniform density, and bituminizing the compressed web.

'7. A method which comprises progressively depositing fiber from suspension in air into a web -of substantially uniform density throughout made up of adjacent longitudinal zones, all of which progressively vary in thickness of bx'ous substance transversely of the web toward a common side edge of the web, compressing said web while maintaining it at substantially uniform density, adhesively uniting the web with a waterlaid felt, and bituminizing the composite sheet;

8. A method which comprises progressively depositing fiber from suspension in air into a web, compressing the web, uniting the compressed web with a water-laid felt, and impresnating the ecmposite sheet throughout with a binder.

JOHN c. am. 30

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