US2057166A - Manufacture of sheeted fiberbinder products - Google Patents

Description

M. o. scHuR 2,057,166

MANUFACTURE OF SHEETED FIBER BINDER PRODUCTS Filedv F'eb i 27. 1931 Patented Oct. 13, 1936 -k UNITED STATES MANUFACTURE OF SHEETED FIBER- BINDER PRODUCTS Milton o. schuf, nerim, N. nQmignor to Brown Company, Maine Berlin, N. H., a. corporation of Application February 27, l1931, serial No. 518,112

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and to runv oif the suspension on machinery ofl the papermaking type. The usual types of paper machines, e. g.. a cylinder or Fourdrinier machine, deliver a more or less compact web or felt, especially when the pulp has been beaten or hydrated to a substantial degree prior to its sheeting. It

has been a matter of difficulty and considerable expense to depart from standard papermaking practice in the direction of producing on machineryv of the paper making type a web of loosely interfelted, substantially unpressed bers. For

instance, when a lightly beaten pulp is used as a raw material and such pulp is deposited from aqueous suspension on an endless foraminous carrier`or wire gauze as a layer or web to be dewatered to dry condition without undergoing much compacting, it is found necessary to evaporate large quantities of water from the web, and sometimes to support the web on the carrier during the drying operation., This means either slow running of the machine or equipping it with exceedingly long driers. In either case'. drying of the web is expensive and its handling diflicult.-`

increasing with the iiuiness or looseness of structure of the nished web. Again, one cannot, under the best conditions, avoid the action of surface tension during the drying of the web in drawing together the fibers.

In accordance with the present invention, I can produce at low expense an exceedingly loose and fluffy web by using dry cellulose ber and forming a web directly therefrom. More especially, it is within the contemplation of my invention to be able to use comparatively inexpensive short fibers, such as wood pulp, as the raw material. In this connection, it should be mentioned that when wet wood pulp is dried, the fibers tend to aggregate into hard clumps. Ordinarily, the manufacturer of wood pulp stores and markets his product as so-called drier sheet, which is made by forming the pulp and drying it as sheet material on large-capacity pulp driers. Such drier sheet is not unlike heavypaper board in. its density or compactness, but may be readily disintegrated into small pieces. Ordinarily, the drier sheets are broken up and slushed with water in a beater engine, wherein beating or hydration of 5 the fibers is eected as previously described, prior to the delivery of the aqueous pulp suspension to a machine of the paper-making type. The initial step of my process, on the other hand, is the conversion of the fiber, whatever be its origin or. form, l0 into a fiu'y, dry mass from which iindividual bers or docks of fibers may be lifted and blown readily by a gaseous medium, such as air, to a web-forming machine. In the case of wood pulp, dense aggregates of fiber, such as pieces of drier l5 sheet, may be readily and inexpensively converted into the desired kind of uiy mass by -passage through a hammer mill. I have found that fiber may be lifted from the hammered mass by a blast of air, and then deposited on a foraminous back- 20 ing or wire gauze, against which the blast is directed, as a uniform layer or web of interfeited fibers. Such a web is characterized by a random arrangement of fibers, by which I mean that there is no marked lay of the fibers in any one direc- 25 tion. So, toc, its structure is far more loose and iiufl'y than a waterlaid web produced under conditions conducive to maximum looseness and vlufilness. The process of the present invention comprehends the foregoing practice of forming a 30 loose and fluffy web whose compactness and strength may be increased at will by mere pressing. It is thus seen that I am enabled to realize webs of a wide variety of compactnesses or densities and strengths. A web formed by what may be 35 termed a dry deposition of fluffed bers may be impregnated with media such as asphalt, latex, and the like, to produce products useful in many arts. I'hese impregnated products are characterized by uniformity and strength, because 'of the 4o random entanglement of the fibers as opposed to the marked lay or predominance of direction given the fibers on carding or other textile machines, and thev appreciable lay effected even on paper machines. In some cases, liquid binding 45 media, such as asphalt or latex, may be sprayed onto the fibers while they are suspended in air and immediately before their deposition as a layer, although, as indicated,the preformed web may be treated with such media for the rst time. Such 50 4treatment may be performed while the web is being supported by4 a suitable foraminous backing, for instance by the same backing on which it was formed, especially when the web is weak and is to undergo the stress of 55 `the gate rotates, uniform addition of stock isbeing drawn continuously through a bath ofthe impregnating medium, under which conditions it is apt to be ruptured, if ,permitted to sustain it self. The web produced by my process may be a composite one in the sense that it is made up of layers of different classes of fibers possessing different characteristics. For instance, the foraminous backing or carrier on which the web is formed may initially receive a blast of air carrying chemical wood pulp bers of high alpha cellulose content, then a blast of air carrying unrened chemical wood pulp bers such as kraft or sulphite pulp fibers, and nally a blast of air again carrying chemical wood pulp fibers of high With the foregoing and other features and objects in view, I shall now describe my invention in conjunction with the accompanying drawing, wherein Figure 1 represents diagrammatically and conventionally a machine for producingsheet fiber products embodying the principles of my invention.

Figure 2 is a plan view of one portion of'the machine.

Figure 3 is a front view of another portion of the machine.

Before describing the machine illustrated, the steps or operations to be performed thereby will be briefly described. Sheeted pulp, for instance refined wood pulp of high alpha cellulose content, is chopped into pieces and fed into a hammer mill which iiuffs the pulp into a mass of flbers or fiber flocks capable of being lifted and kept in suspension in a blast or current'of air impinging against the mass. The air current is caused to pass through a circuitously moving `wire screen on which the fibers deposit or separate out as a layer of loosely entangled bers, which, after suitable compacting, if desired, may be progressively removed from the screen and Wound into a roll, or first put through an impregnating treatment and then accumulated.

Referring to the drawing in detail, l indicates a rolled drier sheet of wood pulp which may be progressively unwound. passed over a guide roll 2, then between feed rolls 3, and then between pairs of rotary slitters 4. The series of longitudinal strips coming from the slitters (best shown in Figure 3) pass between a pair of rotary cutters or choppers 5, which serve to divide the strips into relatively small pieces falling into a hopper 6 having a rotating gate 1 at its exit. As

made by way of the chute 8 to a hammer mill of the usual type indicated conventionally at 9, with its casing partly broken away to show a series of hammers I mounted radially therein. The hammers act to break up the closely compacted fibers of the sheeted stock into a uiy mass of fibers or fiber flocks which -can be sucked from the bottom of the mill through coarse screens (not shown) by a fan or blower I I. The fiber or fiber flocks become suspended in the blast of air acting upon the fluffed fibers; and this blast of air discharges through a gradually expanding nozzle I2 into a chamber I3, which,A as shown,.is partly above and partly below a stretch of an endless wire gauze I4 moving circuitously between end rolls I5 and I6, which may be driven by suitable means (not shown) The chamber I 3 is defined or enclosed by a sloping top partition I1 and upper side walls I8 terminating just short of the wire gauze, and a sloping bottom 4partition I9 and side walls 20 also just clearing the wire gauze. As the current of air passes through the traveling wire gauze, the ber or ber :docks are deposited or retained thereon as a uniform, coherent layer of loosely entangled fibers. The deposition and entanglement of the fibers on the gauze may be promoted by suction fans 2| communicating through each of the lower side walls 20 of the chamber with the interior of the chamber, and thus creating a suction on the under side of the gauze. The fans 2I may, as shown, exhaust into a pipe 22 leading to the chute 8 so as to effect a recovery and reuse of such fiber or fiber dust as may work its way through the Wire gauze. At the entrance into the chamber I3 is shown a pair of gates or dampers 23, whose extent of opening or closing may be controlled by hand-wheels 24. 'I'he gates may thus be positioned to deect the air and fibers carried thereby to certain areas of the gauze when such deflection is necessary to the maintenance of uniform thickness of the web across the' gauze. The web is carriedfrom the chamber I3 under a roll 25 pressing down on the web against the end roll I6 and thus serving to compact it. The pressure applied to the web may be determined by counterbalancing the roll as at 26. The web issuing from between the rolls 25 and I6 may be removed from the gauze and accumulated as a roll, before, as shown, it undergoes further treatment as a continuous, self-sustaining sheet in a bath of impregnating medium or binder of the character hereinafter described. The gauze, before completing its cycle to the webforming station, may undergo the cleaning action of air jets issuing from one or more manifolds 21, which, as shown, are arranged above and transversely of the lower horizontal stretch of gauze.

The treatment of the continuous web may involve guiding it through a bath or pool 32 of suitable impregnating medium, such as latex, sups plied from a tank 28. When latex is the impregnating medium, the impregnated web may then be guided through a bath-29 of suitable coagulant, such as acetic acid, to. set the rubber in the sheet, whereupon the sheet may be led over a bank of drier drums 30, and the dried sheet finally accumulated as a -roll 3 I. The lateximpregnated sheet may, of course, be dried directly, that is, without undergoing the action of the coagulant, but the use of a coagulant does away w'ith the otherwise prevalent tendency for rubber particles to migrate to the surface of the sheet during the drying operation.

A rubber-impregnated sheet material made pursuant to my invention possesses many important leather-like qualities, including toughness, body, feel, resistance to tear, flexibility, etc. The foundation of the product may be made so fluffy and absorbent that it is capable of absorbing rubber in amount many timesrits own weight to form a substantially 'continuous phase of rubber binder in which the foundation is embedded. The rubber coats the fibers and bonds them together without necessarily destroying the porosity possessed by the foundation. In fact, the iinished product may be possessed of suilicient residual porosity to permit it to be breathed through likel natural 'leather'. As already indicated, the foundation may be impregnated with the other media hereinbefore mentioned, which impart thereto characteristics similar to or diilerent from those furnished by rubber. Thus, the imdividualized. dry cellulose bers oi' the nature of wood pulp in a gaseous vehicle, progressively depositing the bers from said suspension as a coherent. continuous web, wherein the bers exist in loose, random state, progressively cornpacting the web to a self-sustaining condition, progressively passing the compacted web in selisustaining condition through a bath ot liquid im-= pregnant while permitting said impregnant to contact substantially unobstructedly with substantially all oi both surfaces oi' the web and thus to enter the body oi the web substantially f3 uniformly and to embed the web in a substantially continuous phase of said impregnant, and

causing said impregnant to set in said web.

2. In the production of ber-'reinforced rubber products, a method which comprises suspending short-bered, substantiallyindividualized, dry cellulose iibers of the nature of wood pulp ina gaseous vehicle, progressively depositing the bers from said suspension as a coherent, continuous web, wherein the ilbers exist in a loose. random. substantially unbonded state, progressively compacting the web to a self-sustaining condition, progressively passing the compacted `web in self-sustaining condition through a bath oi' rubber latex while permitting said latex to contact substantially unobstructedly with substantially all of both surfaces of the web and thus to enter the body of the web substantially uniformly and to impregnate the web with a substantially continuous phase of said latex, and 20 drying the latex-impregnated web.

MILTON O. SCHUR.

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