US1631173A

US1631173A - Aware

Info

Publication number: US1631173A
Authority: US
Publication date: 1927-06-07
Anticipated expiration: 1944-06-07

Description

. June 7, 1927.

H. F. WEISS WALL BOARD AND PROCESS OF MAKING THE SAME Filed Aug. :22. 1921 R v Q Q0 w lNlE/YTO Howard Fit B Patented june 7, 1927.

UNITED STATES PATENT OFFICE.

HOWARD I. WEISS, OI MADISON, WISCONSIN, ASSIGNOR, BY MESNEgASSIGNHENTB, TO WOOD CONVERSION COMPANY, OF CLOQ'UE'I, MINNESOTA, A CORPORATION OF DEL- AWARE.

WALL BOARD AND rnocnss or MAKING THE sum.

Application flee August 22, 1921. semi No. 494,150.

There are now on'the market three general pes of wall board made from wood. "The st type is made as follows: Round wood is ground into a mechanical pulp on "grinding equipment such as is used in making ordinary ground wood pulp for. paper manufacture. To this ground wood pulp is added a certain amount of chemical pul to give added strength to the finished pro uct,

then the mixture is flowed over an ordinary board machine into a sheet of paper having the thickness of ordinary card-board.

At the end of the paper ma ing machine the sheets are wound into rolls of a size convenient for transportation. The wall board is made from them by un-rolling five rolls or more simultaneously and gluing or cementing the various sheets of paper together, usually with an adhesive such as sodium silicate. The sheets of paper or card-board thus glued together are then out to the desired size and dried and in this form are commercial wall board. Some manufacturers use waste pa ers in whole or in part instead of groun round wood, but without change'in the essentials of the process as above outlined. Wall boards of this type are sold in the United States in greater tonnage than those of any other type.

A second type of wall board now on the market is made by grinding the wood to a pulp and then beating the pulp in standard paper makin heaters and finally flowing it into trays; t ese trays are then put into a hydraulic press and the mass is compressed into a dense product which is then removed from the press, dried, trimmed, and surfaced. Chemical pulp can be substituted in whole or in part for ground wood pulp in this type of oard. 'This board consists of but one layer, and usually is denser and has a more compact surface than wall board made from paper sheets.

A third type of wall board is made by gluing or cementing between two heavy sheets of paper, slats of wood placed side by side. This board is expensive because of the cost of the wood slats and because of the relatively large quantity of sodium silicate or other adhesive that must be used in holding the slats together and in fasteningthe covering sheets firmly to the wood.- The covering sheets are relatively tough and thick and have the characteristic appearance and surface texture of paper.

These three types include all of the various varieties of wood wall board now on the market in a large way. They all involve the of good size and qualit which, if not used in the manufacture 0 wall board, could 'well be used in the manufacture of newsprint paper and even more expensive papers,

aside from the standard pulp-making equipment used in these processes, the boards themselves are made on large and expensive machines requiring large floor area; the single exception being the one dply board made on a press as above outline All of the wall boards above described rely mainly for their strength upon the interlacing and interlocking o the fibers and, there fore, their rocesses of manufacture aim to make a pu p havin fibers as long as possible. In general, or best results, this requires the use of round wood of good quality and of grinding equipment well designed and carefully maintained. But. around everysaw mill there accumulates large quantities of what may be termed saw mill offal or wood waste, such as slabs, edgings, trimmings, sawdust, shavings, and bark. Some of this material such as the slabs and edgings, is marketable, under favorable shipping conditions, to "aper mills, but though the quality of fiber 1n the slabs and edgings is as good or better than the general run of fiber from round wood, the pieces of wood are in such physical condition that they are not readily reduced to a pulp,v with the result that the yield of fiber is low, the quality of the pulp is poor, and the practical difilculties of operation are enormous.

Also. around every saw mill there accumulates large quantities of deca ed wood. Some of this is usually saw mill offal or wood waste such as slabs, edgings and trimmings for which there has been no market and, continued exposure of which to the elements has resulted in decay of the wood. Some of the rotted wood is usually from the hearts of overripe trees or from lumber piles not properly protected. In general, the rotting or decay of wood is the result of the action of fungi which attack the lignin components of the wood by a process of oxidation whereby the lignin is largely converted into a gas and so passes off into the atmosphere. The usual fungi do not attack the cellulose constituent of the wood and do not attack the resin components to any appreciable extent.

There is .a small market for decayed boards, not for building purposes, but as a facing for the surface of the ground when ore is to be piled up; but in accordance with my present invention, such inferior lumber can be put to better use and I can even use wood that has so far decayed as to have substantially no mechanical strength. For instance, I can make use of the hearts of logs that are so far oxidized by the fungi that the wood falls apart and has to be swept up with a broom. Such material is not as good for my purpose as sound wood, but there are some advantages resulting from its relatively high cellulose content and its relatively high resin content. The power consumption necessary for putting this rotted Wood into proper-condition for use in accordance with the present invention is of course relatively low because of the physical weakness of the material.

Any wall board process that depends for its raw material on grinding'round wood on a stone requires the expenditure of large quantities of power. For example, a ton of ground wood pulp, suitable for making the plies of a wall board, requires 1200 to 2400 orsepower hours for grinding alone. This great quantity of power is consumed, partly in the mechanical work of tearing the fibers one from another, but more largely in frictional loss at the surface of the stone where it rubs with heavy pressure on the log of wood andwhere the log acts as a brake on the stone. This frictional loss is dissipated in the form of heat and the heat is carried away in the cooling water and thus is lost. The cooling water, after separation of the fibers, is ordinarily run to waste.

It is an object of the present invention to provide a ready market for saw mill offal or wood waste, including decayed wood.

It is a further object of the present invention to produce a wall board consisting essentially of a single ply. this board prefer- .ably being free from sodium silicate and being uniform throughout. The board may have a surface that is dense and capable of taking a good finish and even a high polish, and if desired can be ornamented by graining and painting *uethods now well developed in the decoration of sheet material such, for instance, as sheet metal.

It is a further object of the present invention to produce a wall board of acceptable character from saw mill offal such as slabs, trimmings, edgings, sawdust, shavings and even bark and decayed wood, and to do this with .a power consumption far below that ordinarily needed and in machinery and buildings less expensive than those now needed for the production of wall board from ground Wood or from chemical pulp. Other objects and advantages of the present invention will become clear from the following description which is to be taken in conjunction with the accompanying drawings, wherein:

Figure 1 is a diagrammatic representation,

in elevation, of a complete plant for making wall board by the present process, and Fig. 2 is a diagrammatic plan view of the same.

The wall board of the present invention comprises a binder and a filler and the novelty in the product lies particularly in the binder and in its combination with a filler of special character. There is also novelty in the process of making and using the binder, particularly for the manufacture of a wall board such as that hereinafter described.

The binder consists essentially of lignocellulose gelatinized by mechanical disintegration preferably in the presence of water and preferably with the aid of a gelatinizing chemical such as caustic soda. This binder per se when dried is a hard and horny mass having good binding qualities and yet offering no impediments to usual wood working operations such as sawing, planing, chiseling. and the like. The binder can be 'made from sawdust or somewhat larger particles of raw wood and preferably is made bycrushing or rolling thewood particles between relatively rotating discs whereby the fibers are torn apart and subjected'to pres-' sure in the presence of water and ultimately are converted in part at least into a gelatinized mass. If wood particles other than sawdust are used as the raw material for the binder. they are preferably obtained by chipping, hogging or shredding mill waste or offal or decayed wood, and not. by grinding solid wood on a stone as in pulp making.- As

a step in the gelatinization or partial gelatinization "of the sawdust or similar wood particles. a water-logging procedure is applied to the particles to facilitate their mechanical disintegration and conversion into gelatinous material. Preferably this waterlogging operation is applied to the wood after it has been reduced to a fineness cons parable to that of sawdust, or even finer than this.

The filler need not be separate fibers, as

excellent results are had by using bundles of fibers such as sawdust preferably screened to take out the finest and the coarsest particles. Incompletely gelatinized wood par- T he binder.

Starting with saw mill offal or waste, such as slabs, edgings, trimmings, shavings, and

barker, I pass the waste through a hog such as is used at saw mills for cnttin up waste wood to make it suitable for fue or through a chipper, such as is\ used in preparing wood for the soda, sulfite or sulfate process, or through a coarse shredder; such as is sometimes used at saw mills in place of a hog to reduce wood to small chips or fragments. If desired, a hog and a shredder may be used .in conjunction, the hog cutting the wood into fragments say two inches long, and the shredder beating these fragments into smaller pieces. Good sound round wood can of course be used as raw material but mill waste is much cheaper and is entirely satisfactory. All of these operations which, for lack of a better name, I will hereinafter designate as chipping, are carried out by a cutting action which requires very much less power than if the waste were reduced to a pulp by holding solid blocks of it against a rapidly rotating stone as in grinding wood for ground wood pulp. Also, the product resulting from chipping is entirely different from ground wood, pulp.

Thus. by chipping, the saw mill or paper mill ofi'al is reduced to a mass of chips or wood particles of a size aboutone-half inch in length by one-eighth inch in diameter, or less. If the mill waste is all in the form of sawdust, or other like small particles, the

chipping and shredding steps can be omitted.

These small wood particles (which. as above explained, may benothing more than sawdust or may be larger particles), are

' next passed into hopper 2 (Fig. 1) preparatory to delivery into a machine 3' whereby they are torn apart and reduced in part, but preferably not' entirely to separate fibers. The machine 8 for separating'the fibers may be constructed in many ways but best results have been obtained by me in an apparatus having two discs of metal, one of which is rotatable with respect to the other and between which the sawdust orother relatively small wood particles are subjected to a rolling action to tear, or more strictl speaking crush the fibers one from anot ier. Goot results have been obtained by the use of disc grinders commonly known as corn crackers of which the 36 single disc mill of Bauer Bros. Company, Springfield, Ohio, U. S. A., is a good illustration. Thedetails of such a disc grinder or'corn cracker are well illustrated in U. S. Patents Nos. 565,696"

and 817,610. In such a machine the action of tearing the wood fibers apart resembles somewhat the disintegrating effect of rolling a wooden match under foot on the floor, excepting, however, that because of the relative rotative movement of the discs, each piece of wood or bundle of fibers has a gyroscopic motion about the axis of the rotating disc so that not onlyare the fibers and bundles of fibers subjected to a crushing action, but they are subjected to a twisting effect. As one disc rotates with respect to the other, the small wood particles or bundles of fibers will naturally take up positions along radii of the rotating disc and.- since their outer ends travel through a greater distance than their-inner ends, there will be a decided tendency for the fibers to slip longitudinally with a twisting movement. That is to say, there is not only a crushin g pressure perpendicular to the axes of the individual fibers, but there is a strain,

-in shear, superimposed on the crushing strain and parallel to the axes of the fibers, or more strictly speaking, radial to the rotating plate of the machine; It will be understood that the two plates of themachine between which the particles are rolled have slightly concavedfaces and can be roughened or surfaced toaccelerate the disintegrating action or fiber liberation. Both plates may rotate in opposite directions, or

grinding action that gives best results in the manufacture of the products hereinafter described. Too much of the grinding for tearing the fibers apart on an ordinary paper mill grindstone; for not only has the chipping and shredding cut the fibers from the solid wood, but the disintegrating or fiber liberating power has been applied to the particles in compression and in shear, and therefore along their lines of least resistance. Also, in this process, friction and 'frictional losses have been reduced to a minimum. The bundles of fibers act as rollers between the moving surfaces while rolling one upon the other. No water need be added at this stage.

To reduce the wood to the desired condition, it may be passed repeatedly through the same fiber liberating machine. Or, if desired, a series of fiber liberating machines may be used in each succeeding one of which the relatively moving surfaces are so adjusted as to give best disintegrating action on the partially reduced wood with which it is supplied. The latter procedure is pref-- erable and passage through three of the grinders will disintegrate the sawdust or similar wood particles to the extent desired at this stage of the process.

A suitable arrangement of the three grinders is indicated diagrammatically in Fig. 2 of the drawing. where the material delivered from disc grinder 3 to box 4 is carried by an elevator 5 to a hopper 6 adapted to deliver to a disc grinder 7. \Vhen delivered from the latter to box 8, the mass can be lifted by either of conveyors 9 or 10 and delivered to the hopper of grinders 11 or 12, which in turn deliver to tank 13 from which the mass ultimately can be conveyed to other disc grinders of the series.

The next step consists in conveying the finely divided wood from storage tank 13 to a tank 14 where a water-logging procedure :is initiated. This water-logging -is used because wood that is wet is very much weaker and can be torn apart with less expenditure of energy than wood that is drythe fibers separate from one another more easily. For xample, wet wood has, in compression, about one-half to one-third of the strength of dry wood; Thiswater-logging can he done conveniently by first submerging the fiber aggregates in water heated nearly or preferably to the boiling point, and then, while the wood particles are submerged in a closed tank, subjecting the mass to pressure, such as steam pressure, to force the hot water into the fiber aggregates.

As an alternative procedure, the fiber aggregates can be thoroughly .heated in the traction of the expanded air and gases, as

above described. Under some circumstances it is more economical merely to let the hot water and the submerged wood particles cool by radiation, for by so doing. large quantities of water will be drawn into the pores and voids of the wood.

By such a treatment fiber aggregates (such as sawdust or chips that have been mechanically disintegrated in the three grinders) can be so thoroughly saturated with water that they will sink in water in an hour or less. If they were merely submerged in water, it would take months and, in the case of resistant woods, years. before the fiber aggregates soaked up enough wa- 3 ter to sink. The heating in hot water is not intended to be a cooking operation and there need be no chemical present to effect cooking. Nevertheless, the hot water dissolves out some or perhaps all of the highly soluble constituents of the wood. lVhen western larch is used as the wood, this is a. valuable feature of the process because'of the possibility of recovering valuable sugar making ingredients from the liquor.

As an alternative and the preferred procedure, the water is hot and contains 1% of caustic soda (NaOH) by weight. and the fiber aggregates are soaked in this liquor at boiling temperature and at atmospheric pressure for about one hour. after which the fiber aggregates are dumped into a second tank containing caustic soda solution of the same strength but at room temperature. These operations can be carried out in

tanks

14 and 15 where 14 is the hot soda tank and 15 is the cold soda tank. The presence of soda facilitates the penetration of moisture into the fiber aggregates and in addition is a component useful in subsequent steps of the process.

From tank 15 the cold and water-logged fiber aggro ates, together with the soda liqnor, are de ivered to a. press 16 for the removal and recovery of the caustic soda liq.- uor. This recovered liquor is returned to one of the soda tanks and is used over again. This press may be of the roller type such as was commonly used for squeezing the liquor from malt sprouts in the beer industry. This moist mass of water-logged fiber aggregates, impregnated with a small quantity of caustic soda. is next delivered to a hopper 17, and from there passes into a second serics of grinders similar in structure to those above described, but with their platescloser feet may not be very great in grmder 18 together. The soda content will then be about 40 lbs. per ton of fiber ag regates,

gregates. This water can besupplied con-- veniently, by means of a pipe 19 which delivers a steady stream into the top of hopper 17. The use of water in the mill is to acilitate the flow or flushing out of the material and not because of the cooling action of the water. In fact hot water can best be used for this purpose, because of its effect in lowering the resistance of the wood to the crushing action and similar disintegrating stresses. No caustic soda or other chemical need be added to the water for the fiber aggregates have already been charged with enough of the caustic soda to insure the results desired.

The ulpy mass delivered by grinder 18 is lifted by a pump 20 to a second grinder 21 where the disinte rating treatment is repeated. Ordinarily time of these grinders are sufficient to produce the effect desired, though more than that number can be used when more complete chemical and physical changes of the wood are deemed advisable.

As the wood proceeds through this series of grinders the particles or fiber aggregates are torn apart to yield separated individual fibers and, furthermore, these fibers undergo a chemical change and ultimately are delivered from the last grinder of the series into storage tank 22 in a gelatinous structureless form well adapted for use as a binder in the wall board of m resent invention. But with the individua ers so separated and gelatinized, there is mixed a relatively high percentage of fiber aggregates that have resisted complete physical disintegration and are gelatinized only on the surface.

It is well recognized in the literature that the hydration qualities of lignocellulose or wood are not very great and that mechanical wood pulp suflers little alteration by beating in a paper maker s beater. But I have found that when lignocellulose or wood is crushed or rolled under pressure in a corn cracker and in the presence of water, h dration will begin even with the first mill of the series and the hydration will rogressively increase as the wood is re need to fiber and the fibers are broken and crumbled under pressure. The water-loggingtreatment to which the wood has been subjected and the addition to it of a small quantity of caustic soda both facilitate hydration. However, it is entirely possible to produce a elatinized liguocellulose without giving it t e water-logging treatment and by merely rolling and breaking the fibers in cold water.

by dry weight, Caustic potash can e used'as a.

out, crush, and gelatinize the fiber While the hydration or gelatinizing ef- (Fig. 2), the other and particularl the last grinders of the series in which t e plates are set close together, so completely comb gregates that the'fibrous structure of a arge proportion of the separated fibers disappears entirely. I

As above explained, the resultant product is a slimy mass of lignocellulose consisting in part of gelatinized fibers and in part of undisintegrated and superficially elatinized fiber. aggregates. The galatinize lignocellulose might perhaps be called hydrated lignocellulose, though I know of no method for determining how many water molecules have attached themselves to the cellulose molecule, or if indeed any such water molecules have been added. I know that the chemical structure of the gelatinized material must be different from that of lignocellulose, and as appears below, the physical structure is likewise radically different. Therefore, for lack of a better name, I have herein designated this material, which. is to be the binder or binding element of the wall board, as gelatinized lignocellulose. Gelatinized lignocellulose, as the term is herein used, means wood fibers (lignocellulose) that have been so treated mechanically as to be completely torn and broken so that their len th is but a fractional part of their original ength, say, for instance,- one-tenth or less;, furthermore, the original wood cellulose has been changed chemically and perhaps to the extent of adding to it an un known number of water molecules. The gelatinous com onent of the material delivered from the ast grinder, when wet, is a slimy mass which on drying. shrinks enormously and is inclined to warp and forms a dense, hard, bone-like massof considerable strength and without appreciable fibrous structure, but inclined to split or flake and of a color usually somewhat darker than that 'of the wood from which it was made. Made from pine, spruce or hemlock the material is cream colored, and made from fir, tamarack or larch it is somewhat darker in color. It can be made readily from any of these woods and others, but with cedar the rob lem is more difiicult because of diflicult es in chemically changing the water-reslstant fibers of such gymnosperms.

Both physically and chemically, gelatinized lignocellulose is readily distinguishable from wood flour,.though according to my experiments, wood flour often results from prolonged mechanical treatment of wood fiber, as, for instance, when the fiber is passed repeatedly through a Jordan. The ulpy mass of partially elatinized lignocel ulose delivered by the ast grinder of this series 'is the material used by me for ans the production of wall board in accordance with the present invention. The gelatinized component of this lignocellulose mass not only constitutes an appreciable percentage of the total material used, but acts as a binder to unite with and hold in place the other and more inert material or materials with which it is associated. These other materials properly may be designated as the filler.

A. feature which readily may be incorporated in the above described process of making gelatinized lignocellulose is the recirculation of the water in some, at least, of the fiber-liberating machines which, with the soluble material in the wood, can be recovered in a manner similar to that described in my- U. S. Patent No. 1,339,489, issued May 11, 1920. Furthermore, whenever a plurality of fiber-liberating machines are used in series to progressively reduce the wood particles to pulp, and then to gelatinize the pulp, the circulation of the water to take out soluble material (as from western larch), can be on the counter-current principle, that is to say, the water used in the last machine or grinder of the series can be filtered ofi from the pulpy material delivered therefrom and can be introduced as the flushing water of the machine next preceding, and so on throughout the series, the strongest solution of soluble constituents being drawn ofl from the partially disintegrated shredded wood particles of the machine into which these particles initially were delivered.

When the pulpy mass is delivered from the last grinder it consists, as above explained, of gelatinous lignocellulose, adapted to serve as the binder of the wall board, and other material somewhat like sawdust but more finely divided, and with the component particles gelatinized on the surface. I have called these small wood particles fiber aggregates and by fiber aggregates I mean five or more wood fibers still 'oined together as in the living tree. The bers need not, however, be of full length and ordinarily are not.

The relative proportions of the two ingredients of the mixture may be varied throu h relatively wide limits. Up to a certaln point the larger thepercentage of gelatinized lignocellulose the stronger s the resultant board. The board should contain 25% or more by dry wood weight of the gelatinized lignocellulose and 30% or more by dry wood weight of fiber aggregates. Amixture composed of 60% gelatinized lignocellulose and 40% fiber aggregates by dry wood weight to which enough water has been added to makethe mass flow readily gives a very strong, stifi and satisfactory wall board. pr'uce or pine give a stronger board than cedar but any one of these woods or mixtures of. any of them are suitable.

The sizing.

While the pulpy mass is being mechanically disintegrated in

grinders

18, 21 and succeeding grinders, there preferably is added to it a solution of sodium resinate in water, and after this has been thoroughly mixed with the mass and ground into it, a water solution of alum is introduced (as at the last grinder) to convert the soluble sodium resinate into an insoluble resinate. This treatment sizes the fiber. aggregates, and also sizes the gelatinized lignocellulose, and makes them and the finished board highly resistant to moisture. The sizing is uniform throughout the entire board. These sizing materials may be omitted entirely when waterproofing is not desired without injuring the' strength or other characteristics of. the board, excepting that of its resistance to water. Normally the percentage of sodium resinate may be from two to eight per cent of the dry weights of the other components, depending on the amount of wood used and particularly its resinous content and the degree of waterproofing desired in the finished product. When decayed wood is bein used in appreciable quantity, this wood, i of a coniferous variety, may be abnormally high in its percentage of resin, and under these con-- ditions due allowance must be made in the percentage of resinate added to the pulp. The quantity of alum is in proportion to the sodium resinate, due allowance being made for the amount of water present etc.

If a fireproof board is desired. the requisite amount of ammonium sulfate or analogous fire retardant can be added to the batch and uniformly ground into it while it is assing through this series of grinders.

non-mineral coloring, such as an aniline dye, can also be added if a colored board is desired. This is particularly advantageous when the board is to be finished in imitation of mahogany.

Pressing.

The now thoroughly mixed mass of sized gelatinized lignoce lulose and wood fiber aggregates is next delivered to a flow box 23 (Fig. 2) like those in ordinary paper making machines, and so constructed as to maintain a constant head in the box with an overflow through pipe 24 into the underground storage tank 22 (Fig. 1). A constant stream of the pulpy mass flows out of a horizontal slot in the side of the box under a gate 25. This gate is provided with a rack and pinion 26 by which it ma be raised or lowered to vary the size 0 the stream. As the thick mixture 'flows through the slot it is delivered in a uniformly thick layer on a traveling wire screen or conveyor 27 which is mounted on. cylinders 28 and onto the w1re conveyor is approximately the length of layer.

The width .of the wire screen conveyor or belt corresponds with the length of the board or panel to be made, and the cellulosic mass is prevented from flowing ofi the sides of the conveyor by means of two stationary baffles 31 (Fig. 2). These baflles are adjustable laterally toaccommodate several widths of cellulosic mass to accord with changes in "the boards to be made. In eneral, a board length of 16 feet is suitable or ordinary trade demands. Converging boards 32 smooth off the top of the pulp Thus the cellulosic mass in a relatively thick and uniform layer 16 feet wide and 2 inches thick on the wire screen conveyor is carried forward between the stationary baflles 31 and ultimately passes between the platens of a powerful press. wire screen conveyor moves forward with an intermittent movement and as soon as the proper amount of the mass is between the platens a rectangular die 33, having inside dimensions corresponding to the size of the board to be made, is'lowered into the mass until it rests on the wire screen conveyor. The cellulosic mass is so fluid that it readily moves aside to permit this lowerin of the die. Then the upperlaten, which ts within the die with a su stantially water-tight joint, is lowered into the dieand compresses the cellulosic mass, while simultaneously squeezing its excess water both upward and downward through suitable slots in the platens. It is advantageous to appl suction to these openings in the top an bottom platens to facilitate prompt removal of the water. Much of the water drips out of the mass while it is on the wire screen and before it reaches the press, but the proportion remaining should be reduced by pressure and suction to about of the total weight of the compressed board. A pressure of 200 lbs. per square inch applied aduall over a period of half a minute and sit on or a period of five to ten seconds will, when su plemented by adequate suction, efiect t a desired extraction. The liquor thus drawn from the pulpy mass is not thrown awa but, on the contrary, is fed back into t e last series of grinders, thereby economizing in water and conserving whatever binding agents and other soluble'eomponents of value mayhave passed into the water. As soon as the compressing is completed. the suction is cut off and air under pressure is applied in place of the suc- Th removes tion. The platens then separate, the compressed air releases the board from the platens, the die lifts, and'the wire screen conveyor moves forward rmtil a fresh amount of material has passed between the platens when the operation just "described is repeated. This operation is done mechanically and takes less time than a minute to press each sheet.

Drying.

of a damp, fairly stiff, compressed sheet.

Suction plate 34'is adjustable vertically in supports 35 totransfer the compressed sheet vertically and sidewise into a dry kiln 36. This kiln may be of the tunnel type heated by steam coils and provided with well known means for regulating'the circulation of air, its humidity, temperature, etc., to secure most effective and uniform drying action, and to lessen such tendenc as there may be for warp-age of the boar s. The dry kiln the water from the boards so that they emerge from the kiln dry, hard.

Finis hing.

The boards are next run through saws and stiff and a cut to desired size or shape and in that form,

are marketable in place of wall board made by usual processes. The boards may be nailed directly to the studdin of a building to serve in place of lath and p aster, and like wall board now on the market, may be sawed and similarly cut to meet the needs of the builder. But unlike wall boards of more usual manufacture, the contain no sodium silicate or other minera harmful to the saws and other edge tools of the carpenter. On the contrary, they consist throughout of nothing but woody material through which a saw or chisel will work as readily as through solidwood and with no more injury to the edge of the tool. The resin size and the ammonium sulfate, if present, are not harmful to edge tools.

Such small amount of caustic soda as remains with the cellulosic material after squeezing of the mass at press 16 is neutralized by the alum and gives to the product no objectionable characteristics.

In many respects this new roduct is different from wall board m e from paper sheets cemented together, for, if desired, the wall board of the present invention may be passed through an ordinary wood planer tofinish the surface, or through a sand machine to dress its surface, or between steel rolls to give the surface either a high polish or to' impress in or on the surface patterns or designs or to give a finish similar to burlap -it the appearance of grained mahogany or other woods. The surface can be painted and decorated much as can be done with solid wood, excepting that it has not the characteristic grain of wood, but on the contrary, if made with fiber aggregates, has a uniform and pleasing mottled appearance not unlike the so-called oatmeal wall papers.

As above indicated, the process by which 'this novel and valuable product is made,

may vary in many of its details, both as to the origin ofthe raw materials and as to the procedure by which these materials are treated to bring them into proper physical and chemical condition to unite under pressure and kiln drying into the product described in detail above. It is of particular importance, however, that no chemical need be used in the process and that water alone, together with suitable mechanical manipulations, such as cutting, rolling, and twisting, properly repeated, is suflicient to convert saw mill offal such as slabs, edgings, trimmings, sawdust, shavings and even ba-rk, into a readily marketable product and with relatively low power consumption.

Theap aratus whereby the process is carried out o viously may vary in details without fundamentally altering either the process or the product claimed herein. Novel features of the apparatus will be claimed in a. separate application. The present application describes further developments in the invention described and claimed in my copending application, Serial No. 470,967, filed May 19, 1921.

I claim 1. The method of preparing a wall board binder, which consists in chipping saw mill oflal, crushing and rolling the chips until reduced to small particles and then waterlogging said particles, and mechanically disintegrating the water-logged particles while wet until at least 25% of themass by dry wood weight has been reduced to a structureless, gelatinous mass, substantially as described.

2. The method of preparing a wall board binder, which consists in chipping saw mill ofl'al, repeatedly crushing and rolling the chips until reduced to small particles, then water-logging sa'id particles, and repeatedly crushing and rolling the water-logged.par ticles between relativelyrotating discs, substantially as described.

-- 3. The method of preparing gelatinous;

lignocellulose, which consists in chippingsaw mill ofl'al, repeatedly crushing and rolling the chips while dry until reduced to small particles, water-logging said particles, and then repeatedly crushing and rolling said water-logged particles between relatively r0- tating discs until'converted into gelatinous lign'ocellulose to the extent desired, substantially as described.

4:. The method of preparing a wall board binder, which comprises chipping saw mill oflal, reducing the chips to small Wood particles by repeatedly crushing and rolling the chips while dry, water-logging said small particles and mechanically disintegrating the water-logged particles in water until at least 25% of the fibers have been crushed and broken and converted into a structureless gelatinous mass.

5. The method of making wall board, which consists in mechanically disintegrating small wood particles to form a mass consisting of about 50% gelatinous lignocellulose and 50% of fiber aggregates by dry wood, weight, shaping and pressing into a board and drying and finishing the board, substantially as described.

6. The method of making Wall board, which consists in water-logging small wood particles, crushing and rolling said particles while wet until converted into gelatinous ligno-cellulose to the extent of more than 25% and less than by dry wood weight, shaping and pressing into a board and drying and finishing the board, substantially as described.

7. The method of making wall board, which consists in reducing saw mill oflal to small particles, water-logging said particles by heating in water and then cooling, then mechanically disintegrating said. waterlogged particles until converted into gelatinous ligno-cellulose to the extent of more than 25% and less than 70% by dry wood weight, flowing the mixture into a layer, pressing said layer into a board and drying and finishing the board, substantially as described.

8. The method of making wall board, which consists in chipping saw mill ofl'al, repeatedly crushing and rolling the chips until reduced to small particles, water-loggin-g said particles, then mechanically disintegrating said particles in water uutil'converted into gelatinous ligno-cellulose to the extent of more than 25% and less than 70% by dry wood weight, flowing the mixture into a layer, pressing said layer into a board and drying and finishing the board, substan-. tially as described.

9. The method of making wall board, which consists in reducing saw mill ofl'al to small particles, water-logging said particles, repeatedly crushing and rolling said waterlogged particles while wet until converted into gelatinous ligno-cellulose to the extent of more than 25% and less than 70% by dr wood weight, sizing the mixture during said conversion, flowing the mixture into a layer, pressing said layer into a board and drying and finishing the board, substantially as described. I

10. The method of making wall board, which consists in reducing saw mill ofial to small particles, water-logging said particles by heating in water and then cooling, repeatedly crushing and rolling said waterlogged particles until converted into gelatinous ligno-cellulose to the extent of more than 25% and less than by dry wood weight, flowing the mixture into a layer, compressing said layer into a board, and drying and finishing the board, substantially as described.

11. The method of making wall board, which consists in/reducing saw mill offal to small particles, water-logging said particles by heating in water containing caustic soda and then cooling, pressing to remove and recover the alkaline liquor, then repeatedly crushing and rolling said water-logged particles in water until converted into gelatinous ligno-cellulose to the extent of more than 25% and less than 70% by dry wood weight, flowing the mixture into a layer, compressing said layer into a board, and drying and finishing the board, substantially as described.

12. The method of making wall board, which consists in reducing saw mill oflt'al to small particles, water-logging said particles by heating in water containing about 1% of caustic soda and then cooling, pressing to remove and recover the alkaline liquor, then repeatedly crushing and rollin said water-logged particles in water unti converted into gelatinous ligno-cellulose to the extent of more than 25% and less than 70% by dry wood weight, flowing the mixture into a layer, compressing. the layer into a board with simultaneous sucking of moisture therefrom, and drying and finishing the board, substantially as described.

13. The method of making wall board, which consists in reducing saw mill ofi'al to small particles, water-logging said particles by boiling them about an hour at atmospheric pressure in water containing about 1% of caustic soda and then cooling, pressing to remove and recover the alkaline liquor, then repeatedly crushing and rolling said water-logged particles in water until converted into gelatinous ligno-cellulose to the extent of more than 25% and less than 70% by dry wood weight, sizing. and fireproofing the mixture during said conversion, flowing the mixture into a layer, compressing said layer into a board with simultaneous sucking of moisture therefrom, and drying and finishing the board, substantially as described. Y

14. The method of making wall board, which consists in chipping saw mill ofi'al, repeatedl crushing and rolling the chips while ry until reduced to small particles, water-logging said particles, repeatedly crushing and rolling said water-logged particles in water between relatively rotating discs until converted into gelatinous lignocellulose to the extent of more than 25% and less than 70% by dry wood weight, flowing the mixture into a layer, compressing said layer into a board, and drying and finishing the board, substantially as described.

15. The method of making wall board, which consists in chipping saw mill offal, repeatedly crushing and rolling the chips while dry between relatively rotating discs until reduced to small particles, water-logging said particles by heating to about boiling temperature in water containing an alkali and then cooling, pressing to. remove and recover the alkaline liquor, then repeatedly crushing and rolling said water-logged particles in water until converted into gelatinous ligno-cellulose to the extent of more than 25% and less than 70% by dry wood weight, flowing the mixture into a layer, compressing said layer into a board, and drying and finishing the board, substantially as described.

16. The method of making wall board, which consists in chipping saw mill ofi'al, repeatedly crushing and rolling the chips while dry until reduced to small particles, water-logging said particles by heating in water containing caustic soda and then cooling, pressing to remove and recover the alkaline liquor, then repeatedly crushing and rolling said water-loggedparticlesin water until converted into gelatinous lignocellulose to the extent of more than 25% and less than 70% by dry wood weight, flowing the mixture into a layer, pressing said layer into a board, and drying and finishing the board, substantially as described.

17. The method of making wall board, which consists in chipping saw mill ofl'al, repeatedly crushing and rolling the chips while dry until reduced to small particles, waterlogging said particles by heating in water containing about 1% of caustic soda and then cooling, pressing to remove and recover the alkaline liquor, then repeatedly crushing and rolling said water-logged particles in water until converted into gelatinous lignocellulose to the extent of more than 25% and less than 70% by dry wood weight, flowing the mixture into a la er, pressin said layer into a board, and rying and ishing the board, substantially as described.

18. The method of making wall board, which consists in chipping saw mill offal, repeatedly. crushin and rolling the chips while dry until reduced to small particles, water-logging said particles by heating in water containing about 1% of caustic soda and then cooling, pressing to remove and recover the alkaline liquor, then repeatedly crushing and rolling said water-logged particles in water until converted into gelatinous lignocellulose to the extent of more than 25% and than 70% by dry wood weight, sizing and fireproofing the mixture repeatedly? crushing and rolling the chipswhile dry until reduced to small particles, water-logging said particles by boiling them about an hour at atmospheric pressure in water containing about 1% of caustic soda and then cooling, pressing to remove and recover the alkaline liquor,' then repeatedly crushing and rolling said waterlogged particles in water until converted into gelatinous lignocellulose to the extent of more than 25% and-less than 70% by dry wood weight, sizing and fireproofing the mixture during said conversion, flowing the mixture into a layer, vcompressing said layer into a board, with simultaneous sucking of moisture therefrom, and drying and finishing the board, substantially as described. I

20. Artificial lumber consisting essentially of a dried gelatinous mass of mechanicall disintegrated lignocellulose intermixed wit fiber gelatinized on the surface.

21. Artificial lumber consisting essentially of a dried gelatinous mass of mechanicall disintegrated li ocellulose intermixed wit fiber gelatinize on the surface, a dried gelatinous mass constituting 25% to 70% of the lumber by dry wood weight.

22. Artificial lumber consisting essentially "of a dried gelatinous massof mechanically disintegrated lignocellulose intermixed with fibergelatinized on the surface, the, dried gelatinous mass comprising about 40% of the lumber by dry wood weight.

' 23. Artificial lumber comprising a dried gelatinous mass of mechanically disintegrated lignocellulose'intermixed with fiber aggregates gelatinized onthe surface.

24. Artificial lumber comprising a dried gelatinous mass of mechanically disintegrated lignocellulose intermixed with fiber aggregates gelatinized on the surface, the,

fiber aggregates constituting about 50% 0f the lumber by dry wood welght.

25. Artificial lumber consisting essentially of a dried gelatinous mass of mechanicall disintegratedlignocellulose intermixed wit '55 I the residue of mechanically disintegrated and partially gelatinized fiber aggregates.

26. Artificlal lumber comprising a dried gelatinous mass of mechanically disintegrated lignocellulose intermixed with a resi due of partially gelatinized fiber aggregates,

said mass'being waterproofed throughout.

-27. Artificial lumber comprising a dried gelatinous unass of mechanically disintegrated lignocellulose intermixed with a rest-- 5 due of partially gelatinized fiber aggregates, said mass being fireproofed uniformly. throughout.

28. Artificial lumber consisting essentially of a dried gelatinous mass of mechanically 7 disintegrated lignocellulose intermixed with while wet to form a mass of about 50% ge-r latinous lignocellulose and 50% of fiber ag- 80 gregates by dry wood weight, shapin and pressing into a board and drying and nishing the board, substantially as described.

30. The'method of making wall board which consists in mechanically disintegrat- 85.

ing small'wood particles until converted into gelatinous lignocellulose to the extent of more than 25% and less than by dry wood weight, shaping and pressing intoa making wall board board and dryin and finishing the board at substantially as escribed. v In testimony whereof I aflix my signature.

:HOWARD F. wnrss. f