US1631171A - Utilizing wood waste - Google Patents

Description

H, F. WEHSS UTILIZNG WOOD WASTE @riginal Filed May 19 1923 @kwam/hoz 331g: if@ @Vio/wwwa Patented .lune 7, 1927.

UNITED STATES.A

PATENT OFFICE.

HOWARD F. WEIS'OF MADISON, WISCONSIN, ASSIGNOB, BiY MEBNE ASSIGNIBNTB, TO WOOD CONVERSION COMPANY, OI CLOQUET, MINNESOTA, A CORPORATION OF DELA- WARE.

UTILIZING WOOD WASTE.

application nea ny 1s, 1921, smal mi. 410,961. Renewed apra 1e, 11m.

There are now on the market three general types of wall board made from wood. The first type is made as follows: Round wood is ground into a mechanical pulp on grinding equipment such as is used 1n making ordinary ground Wood pulp for paper manufacture. To this ground wood pulp 1s added a certain amount of chemical pulp to give added strength .to the finished product,

"l 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 making machine the sheets are wound into rolls of a size conlf venient for transportation. The wall board is made from them by unrolling tive Irolls or more simultaneously and gluing or cementing the various sheets of paper together, usually with an adhesive such as sodlum 1' silicate. The sheets of paper or card-board thus glued to ether are then cut to the desired size an dried and in this form are commercial wall board. Some manufacturers use waste papers in whole or in art 3" instead of ground round wood, but wit out change in the essentials of the process as above outlined. falls boards of this type are sold in the United States in greater tonnage than those of any other tpe. t

A second type of wall boar now on the market is made by grinding the wood to a pulp and then beating the Eulp in standard paper making beaters and nally flowing it into trays; these 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 iu part for ground wood pulp in this type of board. 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 '45 gluing or cemeuting between two heavy sheets of paper, slats of wood placed side by side. This board is expensive because of.

thel cost of the WoodV slats and because of' the relatively large quantity of sodium sili- :lo cate or other adhesive that must be used in holding the slats together and in fastening the 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 t pes include all of the various varieties o wood wall board now on the market in a large way. They all involve the step of first preparing a wood pulp either mechanically or chemicall in standard pulp making equipment. uch equipment is, from its very character, expensive to install and expensive to operate, and requires large floor area, particularly for the driers of the pa er making machine. Furthermore, the manu acture of all of these types starts with logs `of good size and quality, which, if not used in the manufaeture of wall board, could well be used in the manufacture of newsprint paper and even more expensive pa ers. And aside from the standard pulp-ma ing equipment vused in these processes, the boards themselves are made on large and expensive machines requiring large floor area; the single exception being the one ply board made on a press as above outlined.

All of the wall boards above described rely mainly for their strength upon the interlacing and interlocking of the libers and, therefore, their processes of manufacture aim to make a pulp having fibers as long as possible.' In general, for best results, this requires the use of round wood of good quality and of grinding equipment well desi ned and carefully maintained. But aroun every saw mill there accumulates large quant-ities of what may be termed saw mi such as slabs, edgings trimmings, sawdust, shavings, and bark. ome of this material such as the slabs and'edgings, is marketable, under favorable shipping conditions, to paper mills, but though the quality of-fiber in 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, with the result that the yield of fiber is low, the quality of the pulp 1s poor, and the practical .difficulties of operation are enormous.

Any Wall board process that de ends for its raw material on grinding roun wood on a stone requires the expenditure of large quantities of power. For example, a ton ofl ground wood pulp, suitable for making the lies of a wall board, requires 1200 to 2400 oursepower hours for grmding alone. This great quantity of power is consumed, partly in the mechanical work of tearing the fibers l olal or wood waste,

one from another, but more largely in frietional loss at the surface of the stone Where it rubs with heav pressure on the log of wood and where 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 separatlon of the fibers, is ordinarily run to waste.

It is an object ol' the present invention to produce a Wall board consisting essentially of a single ply, this board 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 land even a high polish, and if desired, can be ornamented by graining and painting methods now well developed in the decoration of sheet material, such for instance as sheet metal.

It is a further object ot the present invention to produce a wall board of acceptable character from saw mill offal such as slabs, trimmings, edgings, sawdust, shav ings, and even bark 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 thelaccompanying drawings. wherein: v

Figure 1 is a diagrammatic representation, in elevation, of a complete plant for making wall board bv the present process,

andF ig. 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 lignoeellulose gelatinized by mechanical disintegration preferably in the presence of water and without the use of any gelatinizing chemical. This binder, when dry, is a hard, horny mass having good binding qualities. and yet offering no impediment to usual woodworking operations, such as sawing,

laning, chiseling. and the like. The binder 1s preferably made from sawdust or somewhat larger particles of raw wood as by crushing or rolling the wood particles between relatively rotating discs whereby the fibers are torn apart and subjected to pressure in the presence of water, and ultimately are convertedsubstantially entirely into a than sawdust are used as the raw material for the binder, they are preferably obtained by chipping, hogging or shredding mili waste or oal, and not by grinding solid wood on a stone as in pulp making. These chips or particles advantageously can. be water-logged to facilitate theirv mechanical disintegration and their conversion into gelatinous material.

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 eoarsest particles. Incompletely gelatinized wood particles can constitute the filler, and it is possible to use ground wood pulp or cooked wood pulp or old newspapers beaten to a pulp as the filler. but as hereinafter pointed out at length, there are many practical advantages in using sawdust or equivalent unground and unbeaten fibers grouped together or aggregated as in the living tree.

The details of the process and of the product in their preferred embodiments will be better understood from the following disclosure.

The binder.

Starting with saw mill oti'al or waste, such as slabs. edgings, trimmings, shavings, and even bark or with mixtures of these, or starting with paper mill offal or waste such as crooked bolts, or limbs or branches such as are commonly left in the forest. either with or without preliminary removal of the bark by usual methods. as in the .so-called drum barker, I pass the waste through a hog such as is used at saw mills for-eutting up waste wood to make it suitable for fuel, or through a chipper, such as is used in preparing wood forthe 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 ot' course be used as raw material but millwaste is much cheaper and is entirely satisfactory.

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 ehipping,'the saw mill or paper mill ofal is reduced to a mass of chips or Au of these l operations which, for lack of a better name,

wood particles of a size about one-half inch in length by one-eighth inch in diameter, or less. This material is then passed over a series of screens and the. very fine particles, which for want ot' a better name I will hereina fier designate as liber aggregates, are collected and stored in a bin. These fiber aggregates may be as fine as ordinary sawdust and in fact by starting with sawdust, such as is obtainable at any saw mill I can dispense with the chipping procedure described above,.i'or the material is already fine enough to be called fiber aggregates and to be used as such. lIn the drawing, the bin for holding the sawdust of other fiber aggregates is marked with reference character l.

The next coarser grade from the screens, which I prefer to. call small wood particles, goes ultimately to a storage bin 2, and the coarsest particles are returned from the screen to the shredder for retrcatment and ultimate conversion into small wood particles and into the smaller fiber aggregates. lf the saw mill waste is all in the forni of sawdust, or other like small particles, the. chipping and shredding steps can be omitted for the material that is to go into bin 2, the same as for that supplied to bin 1.

The small wood particles that are to be supplied to bin 2 can with advantage be given a water-logging treatment after being taken from the screen and before being delivered into the bin. If sawdust is to be used as a raw material, the procedure is the` same. This water-logging 1s used because wood that is wet is very much weaker and can be torn apartwith less expenditure of energy than wood that is dry-the fibers separate from one another more easily. For example, wet wood has, in compression, about one-halt1 to one-third of the strength of dry wood. This water-logging can be done conveniently by first submerging the small wood particles in water heated near or preferably to the boiling point, and then, while the wood particles are subn'icrged 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 small wood particles can he thoroughly heated in the hot water and then, while the temperature of the water is near or at the' boiling' point, cold water can be added to cause contraction of the expanded air and gases of the wood particles, thereby drawing water into the pores or voids of the "particles,

As another procedure, the small wood particles while hot from the exposure to hot water, can be dumped into cold water to cause contraction 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 b so doing arge quantites of water will be rawn intol the pores and voids of the wood.

By such a treatment, small wood particles (and sawdust) can be so thorou hly saturated with water that they will sin in water in an hour or less. It they were merely submerged in water it would take months and, in the case of resistant'- woods, years, before the wood soaked up enough water tosink. '.lhe heating in hot water is not intended to be al 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.y \Vlien 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.

The small wood particles (which, as above explained, may be nothing more 'than sawdust or may be larger particles), now thoroughly saturated with water and consequently in a very weak condition, are passed into hopper 2 (Fig. 1) preparatory to delivery iiito a machine 3 whereby they are torn apart and reduced to separated fibers. Since wood is weaker hot than cold, l prefer to pass the .small wood particles into this machine while they are stillhot from the water-logging procedure.` the chilling with cold water has completely cooled the Wood pai'ticles,'it is sometimes advisable to again heat them up before delivery into inachine 3. The machine 3, for separating the fibers, may be constructed in many ways, but

best results have been obtained by me in aii apparatus having two large discs of metal, one of which is rotatable with respect to the other, and between which the hot and water-` logged wood is subjected to a rolling action to tear, or more strictly speaking, crush the .fibers one from another. Good results have been obtained by use of disc grinders commonly known as corn crackers, of which thc .36 inch single disc mill of Bauer Bros. Co., Springfield, Ohio, U. S. A., 'is a good illustration. The details of such a disc grinder or corn cra-cker are well illustrated in U.'S. Letters Patent Nos. 565,690, issued August 11, 1896, 817,610, issued April 1U, 1906.

In such a machine, the action of tearing the 'wood fibers apart resembles somewhat the disintegrating effect of rolling a match under foot on the fiooi', excepting, however, that because of theY relative yrotative movement of the discs, each pieceof wood or bundle of fibers has a gyroscopic motion about the axis of the rotating disc so that not only are 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 he a decided tendency vI'or the fibers to slip longitudinally with a twisting movement. That is to say, there is not only a crushing 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 vthe fibers, or more strictlv speaking, radial to the rotating plate of the. machine. lt will be understood that the two plates of the machine between which the particles are rolled have slightly concaved faces and can be roughencd or surfaced to accelerate the disintegrating action or fiber liberation. Both plates maj` rotate in opposite directions, or one may be stationary and the other rotatable. The. working faces of the discs are preferably of metal; but of whatever material. the surfaces are adjusted in such manner that they do not touch. It is also important that means be provided for adjusting the distances between the plates in accordance with the size, character and origin of the wood particles under treatment. and the character of the product desired. It .is a rolling and twisting act-ion rather than a grinding` action that gives best results in the manufacture of the products hereinafter described. Too much of the grinding action produces too large a percentage of wood flour, as distinguished from fiber pulp.

Thepower consumed for reducing wood to pulp by first chipping, then shredding and then rolling the small wood particles between two relatively moving dises as above described, is much less than that required for tearing the fibers apart on an ordinary l paper niill grindstone; for not only has the (Sil chipping and shredding cut the fibers from the solid wood` but theresistance or strength of the particles has been reduced by waterlogging and by heating, and, furthermore, the disintegrating or fiber-liberating power is' applied to the particles in compression and in shear, and there fore along their lines of least resistance. Also, in this process, friction and frietional losses have been reduced to a minimum. The bundles of fibers act as rollers between the moving surfaces while rolling` one upon the other'. If desired, water may be passed through the mill with the particles, but this is to facilitate the flow or flushing out of the material and not because of the cooling action of the water. ln fact hot water can best be used for this purpose because of its effect in lowering the resistance of the wood to crushing action and similar disintegrating stresses. When water is used, or even without the water, it is well not to rotate the mill too fast, for not only is there a power loss due to the inertia of the water and the material being ground, but also there is apt to be a bad effect on the product because of too great breakage of individual fibers and too high a production of wood flour. machine 3 can be screened and the wood particle-sof proper size to be called fiber aggregates can be separated out and deliveredto bin 1 as a substitute for, or an a-dmixture to, the sawdust therein.

To reduce the wood to individual fibers, it may be passed repeatedly through the same fiber liberating machine, screens being used t0 separate out those fibers that have been sufficiently reduced and returning to the machine for further treatment only the coarser bundles or shives. 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 preferable.

Such an arrangement is indicated diagrammatically in Fig. 2 of the drawings, where the material delivered from disc grinder 3 is carried by an elevator 4 to a hopper 5 adapted to deliver to a dise grinder 6. When delivered from the latter to tank 7, the mass can be lifted by pump 8 and delivered through pipes 9 or 10 to grinders 11 or 12, which, in turn, deliver to tank 13 from which the mass can similarly be pumped to other disc grinders of the series. Asthe wood proceeds through the series of grinders, the particles are torn apart into sepa ate individual fibers and furthermore these fibers undergo a chemical change and ultimately are delivered from the last grinder of the series into storage tank 14 as a gelatinous, structureless mass free from chemicals of any sort and well adapted for use as a binder in the wall boa rd of my present invention. Y

It is well recognized in the literature that the hydration qualities of lignocellulose or wood are not very great, and that mechanical wood pulp suffers little alteration by beating in a paper-makers beater. But. l have found that when li gnocellulose or wood is crushed or rolled under pressure in a corn cracker. hydration will begin even in the first mill of the series, and the hydration will progressively increase as the wood is reduced to fiber and the fibers are broken and crumbled under pressure. The waterlogging treatment to which the wood has been subjected facilitates hydration. Furthermore, the wood hydrates and approaches gelatinization more easily while it is warm or hot. However, it is entirely possible to produce gelatinized lignocellulose without giving it the water-logging treatment and by rolling and breaking the fibers in cold water instead of hot.

The material delivered from i titl While the hydration or gelatinizin eiect may not be very great in grinder 3 ig. 2),

. the other, and particularly thel last grinders of the series, in which the plates are set close to ether so completely c`omb out, crush and ige atinize the wood fibers, that their fibrous and as appears below, Athe 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 bindingelement 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 thattheir length is but a fractional part of their origina] length, say for instance, one-tenth or less; furthermore, the original wood cellulose has been changed chemlcally, though only by mechanical treatment in the presence of water, and perhaps to the..extent of adding to it an unknown number of water molecules. The material, when wet, is a slime which on drying shrinks enormously and is inclined to warp and forms a dense hard bone-like mass of 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 lir, 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 problem is more diilijcult because of difficulties in chemically changing the water-resistant fibers of such a gymnosperm. To gelatinize water-resistant fibers, such as cedar, I lind it expedient to supply the grinders, not with water, but with an aqueous solution of sodium silicate. This is not so cheap as water alone and yields a final product that may not be entirely free from chemical additions, and therefore more likely to change in color, or otherwise, while in use as on the wall of a building.

Vhen properly made, the gelatinized lignocellulose contains no spindle shaped .fibers of their original length, nor bundles of cut fibers, such as is found in wood Hour. Both physically and chemically, gelatinized lignocellulose is readily distinguishable from Wood Ilour, though according to my experirated in the above describedv process of making gelatinized lignocellulose is the recirculation of thc water in some, at least, of the liber-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 ll, 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 0n the counter-current principle, that is to say, the water used in the last machine or grinder of the series can be filtered off 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 lstrongest solution of soluble constituents being drawn off from the partially disintegrated shredded wood particles of the machine into which these particles initially were delivered.`

The filler.

Stored in bin 1 is the filler for the board. As above explained, this material may be sawdust or may be the finer particles obtained by screening material from the shredder, or may have been obtained by screening thei material delivered from. one of the grinders. I have called these smallest wood particles ber aggregates, and by fiber aggregates I mean fiveormore wood fibers still joined together as inA the living tree. The. fibers need .no t,. however, .be of full length, and in the caseof sawdust, often are not. Shingle sawdust is veryl good lraw material for use as a-fillcr after the very fine and the very coarse particles have been screened out. This sawdust is slivery in character, light in weight, and durable, and has the further characteristic, particularly if made from cedar, that it does not hydrate during mixing nor while in use.

Instead of using a. dry filler, such as sawdust, the filler may be obtained from other sources. For instance` it may consist of a part of the output of one or more of the grinders or gelatinizers above described, or of coarse particles screened fromthe output of one or more of those elatinizers, and may be in the wet condition 1n which it came from the elatinizers. Such incompletely gelatinized ignocellulose is in-fact a mixture of completely gelatinized and structureless wood with wood fibers and aggregates that have been gelatinized on the surface. Such a material blends well with the completely gelatinized and structureless binder and of course is cheap, for it can be made of saw mill offal with the expenditure of but little power.

But instead of using fiber aggre ates in whole or in part, as above describe I can use a more expensive filler, such as ground wood pulp, or cooked wood pulp, or mixtures of these; or I can beat up newspapers and other paper waste in a beater and use the resultant pulp, but none of these substitute fillers is as satisfactory for m purpose as fiber aggregates, such as saw ust or the incompletely disintegrated product of one of the early grinders of the series, and none of them givesa wall board that is as easy to dry, is as free from shrinkage, has as beautiful a surface, nor is as good a sound and heat insulator, as when ber agigregates are used as the filler of the boar The The next step in the production of the wall board consists in mixlng the gelatinized lignocellulose with the filler. The latter, as above explained, may consist wholly, or in large part, of wood fiber aggregates of the 4same kind of wood, and even of the same origin as that which went into the gelatinizers. Or the ller may be a different wood, as for instance, one not easily gelatinized by grinding in water such as cedar or aspen. To bring the gelatinized lignocellulose and the wood ber aggregates into intimate contact and to insure a mass uniform throughout, I pump the slimy gelatinized lignocellulose into a mechnical mixer 15, consisting of a metal trough, set at a slight incline, and provided wtih a power driven stirrer, comprising a central shaft on which are mounted a series of inclined stirring blades or paddles. The liber aggregates are fed to this from hopper l, and water may be added to thin the mix.

The relative proportions of the several ingredients of the mixture may be varied through relatively vide limits. Up to a certain point, the larger the percentage of gelatinized lignocellulose, the stronger is the resultant board. The board should contain 25% or more by dry wood weightl of the gelatinized lignocellulose and 30% or more by dry wood weight of fiber aggregates. A mixture composed of gelatinized lignocellulose and 40% fiber aggregates, by dry 'wood wei ht, to which enough water has been adde to make the mass flow readily,

gives a very strong, stili' and satisfactory wall board. Cedar sawdust is satisfactory as a filler, though not readily adapted to the manufacture of the binder. Spruce or pine give a stronger board than cedar.

The

These materials may be omitted entirelyy when water-proofing is not desired, Without lmpalrmg the strength or other characteristics of the board excepting that of its resistance to water. Normally, the percentae of sodium resinate may be from two to eiglit per cent of the dry weights of the other components, depending on the kind of wood used and particularly its resinous content, and the degree of waterproofing desired in the iimshe product. The quantity of alum is 1n proportion to the sodium resinate, due allowance being made for the amount of water present, etc.

If a ireproof board is desired, the requisite amount of ammonium sulfate can be added to the batch while in the mixer.

A 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. u I

Another treatment consists in coloring the gelatlnized lignocellulose one colo'r` and the filler a different shade or color. This gives a. very pleasing product.

Pressing.

tain a constant head in the box with an over` A iow into an underground storage tank 18- (Fig. l). A constant stream of the pulpy mass flows out of a horizontal slot in the side of the box under a gate 19. This gate is provided with a ra'ck and pinion 20, 'by which it may be raised or lowered to vary the size of the stream. As the thick mixture y Hows through the slot it is delivered in a uniformly thick layer on a traveling canvas belt or conveyor 2l which is mounted on cylinders 22 and 23 and is reinforced along its upper stretch by underlying and power driven endlesstraveling screens 24 and 25 suitably supported on drums and rollers` This prevents sagging of the canvas belt while its load of material is being ldelivered to :md from the ress. To make a board about ,36 thick, t ie thickness of this layer as it flows onto the canvas'belt is approximately 213- inches.

The width of the canvas belt corresponds with the length of the board or panelto be made, and the cellulosie mass is prevented from iowing oi the sides of the belt by means of two stationary baiiles 26 and 27 (Fig. 2). These baiiies are adjustablelaterally to accommodate various widths of cellulosic mass,y to accord with changes in the len th ofthe boards to be made. In genera a board length of sixteen feet is suitable for ordinary trade delnands. Thus the cellulosic mass in a relativel thick and uni form layer sixteen feet wi e and one inch thick on the canvas belt is carried forward between the stationary side barriers 26 and 27 and ultimately passes between the platens of a hydraulic press. Thel canvas belt moves forward with an intermittent movement and as soon as the roper amount of the mass is between the p atens, a rectangular die 28 having inside dimensions corresponding to the size of the board to be made, is lowered into the mass until it rests on the canvas sheet. lThe cellulosic mass is so fluid that it readily movesaside to permit this lowering of the die. Then the upper platen, which fits within the die with a substantially water tight joint, is lowered into the die and compresses the cellulosic mass,`

whilef simultaneously squeezing its excess water both upward and downward through suitable slots in the platens. The platens then separate, the die lifts, and thebelt moves forward until a fresh amount of material has passed between the platens, when the operation just described is repeated. This entire operation is done mechanically and less time than a minute is needed to press each sheet.

In order to prevent that part of the cellulosic mass which has not been pressed from flowing onto the compressed mass after the platens have been released, there are provided a `series of cross baffles or' partitions 31, adjustably attached between t'wo sprocket chains 32 which are driven by a power driven sprocket and pass over guide wheels 34, 35 and 36 as shown. These baffles or partitions, which may be made of Wood, press down into the soft watery nia-ss before it reaches the press and block it off into rectangles of approximately the size needed at lthe press. Because of these cross baiiies 31 and the side barriers 26 and 27 there is no necessity for using trays in which to form and press the boards.

I Drying.

Thecompressed cellulosic mass-is carried forward from the press on the canvas belt and\when picked up from this belt by an endless conveyor 37 is in the form of a damp but. fairly stiff compressed sheet. Conveyor 37 1s adjustable vertically in sup rts 38 to `transfer the compressed sheet sic ewise into a dry kiln 39. This kiln may be oit'. the tunnel type heated by steam coils and provided wlth well known means for regulating the circulation of air, its humidity, temperature, etc., to secure most effective and uniform drylng action and to lessen such tendency as there may be for warpage of the boards.

The dry kiln removes the water from the boards so that they emerge from the kiln, dry, stiff and hard. 'i

Finishing.

The boards are nextrun through saws and 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 nalled directly to the Astudding of abuild- .lng to serve in place of lath and plaster, and like wall board now on the market, may be sawed and similarly cutto meet the needs of the builder.. But unlike wall boards of more usual manufacture, they do not contain enough sodium silicate or other mineral to be harmful to the .saws andother edge tools of the carpenter. On the contrary, the t consist throughout of substantiall not ing but woody material through which a saw or chisel will work as lreadily as through solid wood and with no more in- ]ury to the edge of the tool. The rosin size `and the ammonium sulfate, if present, are

not harmfulv to edge tools.-

.But in many respects this new 4product is different from wall board made from paper sheets cemented together, for, if desired, the

wall board of the present invention maygbe' passed through an ordinary wood planer tov fimsh the surface, or through a sandma chine to dress its surface, or betweenA steel. rolls to glve the surface either a high polish l or to impress 1n or on the surface patterns.

or designs or to give a finish similarvto burlap or canvas. Likewise, the finished and even polished face of vthe board may be treated much as sheet steel is now treated to give it the appearance of grained mahogan 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 ber aggregates, has

a uniform and pleasin mottled appearance not unlike the so-calledD oatmeal Wall pa ers. AS above indicated. the process by W iich this novel and valuable product is made, may vary in many of its details, both as 'to the origin of the raw materials and as to the, procedure by which those 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, rollin", and twisting, properly repeated, is lsufficient to convert saw mill oi'al such as slabs. edgings, trimmings, sawdust, shavings, and even bark, into a readily marketable product and with relatively low power consumption. As a permissible variation from the preferred method above described, I may proceed by chipping saw mill oii'al such as slabs, edgings, trimmings, shavings, or bark. orf/paper makers waste, such as crooked bolts, sa-plings, and the limbs and branches ordinarily left in the forest, and then mechanically disintegrating the chipped wood by grinding or, more strictly speaking, crushing, in a disc grinder in the presence of water, preferably hot. water, as above described, and with or without the preliminary water-logging, and stopping this Inechanical disintegration before the fiber aggregates are completely reduced to a structureless gelatinized mass. For instance`I l can carry the wood through less than six grindings and obtain a mixture consisting in part, say 60%, of completely gelatinized material and in part, sav 40%, of wood fibers and fiber aggregates which have been gelatinized on the surface but are of woody character at the core. The exact number of grindings requisite for the desired result depends on many factors, such as the character of' the wood and whether it is highly resistant to water, Whether it has been water-logged before grinding, how close together the grinding plates have been set and whether hot water has been used in the grinders` etc. But roughly stated, three or .four water grindings as above described will yield a product approximately half of which is in a gelatinized condition, and the other half' of which consists of fibers and fiber aggreates with but a surface gelatinization. uch a mixture, when delivered from the grinders, can be pumped into mixer l5 and thereafter can be sized, fireproofed, and then flowed out in a sheet for pressing, drying and finishing in much the same way as il' sawdust or equivalent dry fiber aggregates were used as a filler with a completely gelatinized binder. This alternative procedure, though permissible, is in my present opinion not so good as that first described,

and yields a product having the disadvantages that it is not so cheap, not so attraetive, not so good as a heat or sound insulator (because of the relative absence of voids and air pockets), more inclined to shrink and warp on drying, not so easy to dry, and not so light in weight. Also, a board so made has a monotonous appearance quite in contrast with the beautiful mottled or composite appearance resulting from the'use of fiber aggregates that have not been broken up by passage through a disc grinder.

As a still further permissible variation, an incompletely gelatinized mass of fiber aggregates mechanically disintegrated by grinding or crushing in the presence of water, as above described. can be used as a binder for a filler consisting essentiall of unground fiber aggregates such as sawcust,

due care being taken to keep the proportionl of binder to filler within the ranges dictated by the requirements of strength, freedom rIpm warping, undue shrinkage and the Preferably, the mass as it reaches the press, should comprise at least by dry wood weight of mechanically gelatinized lignocellulose, and preferably as much as 4057 to 60%. Likewise, the mass should contain as much as or more by dry weight of fiber aggregates and preferably as much as to 40%.

The apparatus whereby the process is carried out. obviously ma vary in details without fundamentally a tering either the process or the product claimed herein'.

ovel features of the apparatus will be claimed in a separate application.

I claim 1. The method of making wall board which consists in mechanically disintegrab,

ing small wood fibers to form a gelatinous mass, incorporating therewith a fibrous filler and then pressing and drying the mass.

2. The method of making` wall board which consists in mechanically disintegrating a cellulose containing material to form a gelatinous mass, incorporating therein fiber aggregates to the extent of 30% to 60% by dry Weight, and then pressing and drying the mass.

3. The method of making Wall board which consists in mechanically disintegrating small `wood particles to form a'gelatinous mass, mixing fiber aggregates therewith to the extent of about 50% by dry Wood Weight, and then pressing and drying, substantially as described.

4. The method of making- Wall board, which consists in water-logging small wood particles, crushing and rolling said particles While Wet between relatively rotating discs until substantially converted into gelatinous llo lignocellulose, mixing fiber aggregates theref with, shaping and pressing into a board, and drying and finishing the board, substantially as described.

'drying and finishing the board, substantially as described.

6. The method of making wall board, which consists lin chipping saw mill ofi'al, forming small wood particles therefrom, water-logging said particles, crushing and rolling said particles while wet between relatively rotating discs until converted into gelatinous lignocellulose, mixing therewith an approximately equal amount by dry weight of ber aggregates, sizing and fireproofing the mixture, shaping and pressing the mixture into a board, and drying and finishing the board, substantially as described.

7. The method of making wall board, which consists in chipping saw mill oial, forming small wood particles therefrom,

water-logging said particles, repeatedly Y, crushing and rolling said particles in hot water between relatively rotating discs until converted into gelatinous lignocellulose, mixing therewith an ap roximately equal amount by dry weight ci) sizing and fireproofing the mixture, diluting with water, flowing into a layer, pressing the layer into a board, and drying and f finishing the board, substantially as described.

8..A wall board consistin essentially of a binder and a filler, the ginder being ,a dried gelatinous ymass of mechanically disintegrated lignocellulose.

' 9. A wall board consisting essentially of a binder and a filler, the binder being a dried gelatinous mass of mechanically disintegrated lignocelluloseand the filler being essentially fibrous.

10. A wall board consisting essentially oly a binder and a filler, 'the binder being a dried gelatinousmass of mechanically disintegrated li ocellulose and the filler consisting essentially of fiber aggregates.

fiber aggregates,I

11'. A wall. boardV consisting essentially of a binder and a ller, the binder being a dried gelatinous mass of mechanically disintegrated lignocellulose, and the filler consisting of untreated sawdus't.l

12. A wallboard consisting essentiall of a binder and a filler, the binder being a ried gelatinous mass of mechanically disintegrated lignocellulose, and the filler consisting essentially of fiber aggregates, said board being sized uniformly throughout, substantially as described.

13. A wall board consisting essentially of a binder anda filler, the binder being a dried gelatinous mass of mechanically disintegrated lignocellulose, and the filler consisting essentially of fiber aggregates, said board being fireproofed uniformly throughout, substantially as described.

414. A`wall board consisting essentiall of a binder and a filler, the binder being a ried gelatinous mass of mechanically disintegrated lignocellulose, and the filler consisting essentially of fiber aggregates, said board being dyed, substantially as described.

15. A/wall board consisting essentially of a binder and a filler, the binder being a dried gelatinous mass of mechanically disintegrated lignocellulose and the filler consisting essentially of fiber aggregates, said y binder being dyed one color and said filler being of a different color.

16. A wall board consisting essentially of -a binder and a filler, the binder being a dried gelatinized4 mass of mechanically disintegrated lignocellulose and the filler consisting essentiall of fiber aggregates, said binder ybeing yed one shade and said filler being Adyed a different shade.

17. A .wall board consisting essentialflly of a binder and a filler, the b inder being a' ried gelatinized mass of mechanicall disintegrated lignocellulose from saw mi oial.

18. A wall board consisting essentially of a Ybinder and a filler, the binder being a dried gelatinized mass of mechanically disintegrated li nocellulose prepared from saw mill oi'al an the filler consisting essentially of fiber aggre ates.

19. A wa l board consisting essentiall of a binder and a filler, the binder being a ried gelatinous mass of mechanically disinte ated li ocellulose from saw mill oial an the fille consisting of untreated sawdust.

. In testimony whereof I aix my si ature.

HOWARD F. W ISS.

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