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Main Mill Buildings, Masonite Corporation, Laurel, Miss.
The Masonite Process' Robert M. Boehm MASONITB CORPORATION, LAUREL,MIS.
I
N RECEXT years public attention has been directed as
never before to the elimination of waste and the profitable utilization of by-products. All wastes today-agricultural, industrial, and thc like-are undergoing cloze scrutiny. As a result many materials which were considered worthless, or practically so, are now being converted into commodities of great economic value. This has been particularly noticeable in the insulation-board industry, where bagasse, cornstalks, eel grass, and wood waste are raw materials. From an economic point of view, what could be more praiseworthy than to take these materials, of little or no real value, and convert them into a product which serves as a buffer between mankind and nature, keeping him cool during the summer's heat, warm during the freezing months of winter, and shutting out noises which disturb his rest. History of Process The Masonite Corporation is now slightly over three years old. In that time it has progressed from a small experimental station operating two guns and turning out about 40,000 feet of board daily, to the present plant, equipped with nine guns and turning out over 130 million feet annually. It is one of the few developments in the industry which can boast of an entirely new process. Instead of reducing the wood structure by chemical means or by grinding, the chips are exploded under a steam pressure of 1000 pounds per square inch, thus preserving the fiber structure without loss through chemical action. The originator of this process is W. H. Mason, and he has brought it through the experimental stage to its present position in the insulation field. Mr. Mason was formerly with Thomas Edison and for seventeen years worked with that great inventor on problems of many types. He first thought of exploding wood structures while investigating the removal of naval stores from sawed lumber. Khen this Received March 3, 1930. Presented before the Division of Cellulose Chemistry at the 79th Meeting of the American Chemical Society, Atlanta, Ga., April 7 to 11, 1930.
development was successfully established, he turned his attention to the explosion process. The first experiment in the production of Masonite was rather crude. A gun was made by drilling a hole in a large piece of shafting. It was filled with chips, a small amount of water was added, and a tapered steel plug was fastened in the end. The gun was then placed in a vise and heated with blow torches until it was assumed that a pressure of about 1000 pounds per square inch had been reached. The steel plug was then struck with a long bar and the fibers were blown out of the gun with a terrific report. Enough of the fibers were gathered up to demonstrate the possibility of securing a suitable fiber structure in this manner. The tapered steel plug could not be found; it had apparently been blown several hundred yards. The fiber was formed into a board on a small hand frame, run through a wash wringer to remove a portion of the water, and then pressed and dried t o form insulation board. The method of making Presdwood was discovered by accident. The idea had been conceived of manufacturing a very hard, dense board, but efforts t o produce it by first pressing the wet lap and then drying the board in an oven were unsuccessful. I n a neighboring paper mill a small letter press equipped with steam-heated platens was used to obtain the moisture content of pulp samples. This was used in some of the preliminary experiments. One day the steam on the press was carefully turned off and a portion of wet lap was placed in the press. For some reason hlr. hlason forgot about the board in the press for about 2 hours. When he went back, he discovered a leaking steam valve on the press and found that the wet lap had been under pressure and a relatively high temperature for 2 hours. When the press was opened, much to everyone's surprise, a very hard, dense board had been formed. This was the first piece of Presdwood. Since the day when the first piece of Masonite was run through a wash wringer the process has steadily grown. A pilot mill was first established, consisting of three guns,
May, 1930
INDUSPBIAL A N D BNGINEBfiIA’G CHBMISTRY h ~ d n u f ~ C t u r hProcesses &
Wood is received at tlie plant in throe classes-roundwood, or small logs with thc bark on: trimnii~igxand edgings from saw mills; and wood waste, wdiieh contains shavings, bark, splinters, sawdust, etc., and forms the hulk of our raw ma-
terial. All the woad except tliu %roodwade is run Uirougii chippers which reduce it to chips approximately 3//p inch long. These chips, together with the wood waste, pass through chip screens, which separate tlicm into fine, medium, and coarse fractions. The fines, which arc practically all sawdiist, are sent to the boilers to be iised as fuel. The medium-sized chips ( I / # to 1 inch in length) are sent to t.be chip bins. The long chips are run through hogs or chip crushers and then returned to the screens. No effort i~ made to separate barks or knots, as these are taken care of in the explosion process. Exrmiofi-The guns used in the explosion process are 20 inches in diameter and 5 feet high, and have a capacity of 10 cubic feet. They are equipped with quick-opening hydraulic valves a t the bottom for the release of the load and with both low-pressure and high-pressure steam inlets at the top. Our “low-prcssure steam” is at 350 pounds per square inch which hardly coincides with the customary use of the term. The high-pressure steam is 1000 pounds per square inch. The gun is loaded with chips through a port in the top, which is then tightly closed. Immediately the low-pressure steam is admitted, hrinirine t,he chins to a temDeratore of approximately 375; F. ;?he condensate formed in’tliis way is cont,inuouslyremoved from tlie bottom of the gun by an automatic trap system. The chips are left at this temperature for 30 to 40 seconds during which time they are softened and the moisture content equalized. No chemicals are added. The high-pressure steam is then admitted and the gun brought up to a pressure of loo0 pounds per square inch in 2 to 3 seconds. This is equivalent to a t.emperature of about .540” I?. After remaining at this pressure for about 5 seconds, the hydraulic discharge valve is opened, and the cliils pass through a small port in the hottom of the gun, where they explode immediately owing to the high internal pressure. This completely ruptures the chip and produces a mass of long fiber bundles. The exploded fibers pass into a cyclone, where the steam is separated and the fibers fall into a storego chest. The stock at this point in the process is known a8 “grin fiber.” IIot water, %>-hichhas been clarified of all suspended solids, is added to the stock and the entire mass is maintained at approximately 160” F. tbroiighout the refining. This teinperature s e r n s a double purpose--it a in tlic penetration of ihe sizing enlulsions, as explained Mer, snd it also facilit,ates the refining of the fiber. l301~~1ks-Thehiah-pressure boilers supply saturated steam to the nine guns. T h y were boik by t.he 13abcock R: Wilcox Company and have a total lieating aniface of 3880 sqirarc feet. They hare a single cross drum 4‘/r inches thick at the front, tlic main tubes being 6/ia inch thick and 3l//, i n d m in diameter and tlic circulnting tubes inch thick. The peak load is 400 per cent rating, the average load beiiig 250 per ccnt.. Both coal arid wood refuse are burned under tliese boilers, t i s well a8 kinder the Ion,-pressure boilem The feed Tvater ifi slightly acid, ranging from a pH of 6.0 to 6.5, and is obtained from the condensate of the low-pressure boilers. The fliic gas nomially has a carbon dioxide content of 16 per cent when operating on wood refuse a l o n e p d approximately 15 per cent when both wood and coal are being used. REFINING-The gun fiber is refined by passing through rod mills containing rods 3 inches in diameter. The consistency
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of the stack is maiiitaimed bv a consistericy renilator. which functions by measuring ttie-resistaxe to kiecilanicai action of the mixture and adds water to maintain a uniform ratio of stock bo water. Three rod mills arc in operation on the
Presdwood unit and one of the Insirlation unit. TIS stock is screened t o remove all fiber wliich has not been sufficiently refined for the next operation, and again returned to tlre rod mills. The accepted stock from the rod mills now passes through a battery of refiners. A refiner consists of a cone-shaped plug rotating in a sliell. nofh shell and plug are equipped with bars, tho clearance of which is adjusted by a horizontal motion of the plug. The stock enters at the large end and leaves a t the small end, rcrersing the usiral procedure of Jordans, Claflins, ani1 tlie likr.
Rod Mills Weed in Refinink the Fiber aftor If Is Exploded from the Steam Guns
After leaving the refiners, the stock is again screened to remove all fibers which have been sufficientlyrefined to enter the accepted stock. The remainder of the fibers pass through two more batterim of refiners a i d then enter the machine stock chest, ready to be felted into board. ~ ~ A T E R P R O O F 1 , Y ~ W a t e r p r o O f i nCOnSiSkS g Of Sizing emulsion having a paraffin base. It is heated and added to tlie stock through a regidator which continuously delivers it at the desired rate. This emulsion penetrates well into i.he fibers and imparts an extremely high water resistance to the product. rH CoNT~ol.-During the refiniiig the tcmperatore of the stock is carefully controlled to secure tlie greatest possible efficiency. The plI must also be held constant at tlie optimum point for greatest efliciciicy. Since the explosion process produces free tannic, acetic, and formic acids, a.s well as other products, the pH of the stock leaving &heguns is about 4.5. In order to secure correct refining ~ t swell as to lessen corrosion of eqiripment, it is desirable to maintain a plI of about 6.5. In this case Nature has been very geiieroor;. We hare a well which has been sunk to a dnpt,li of 1050 feet and which tapped a rich vein of soda water. This coni.ains approximately 650 p. p. m. of sodium carbonate and sodium bicarbonate, and by tho judicious use of this soiln well 1T.e are enabled to maintain almost. any desired PIS. Incidentally, the entire platit is operated on w e l l n-ater. The other three wells are only 400 feet deep and deliver a very pure water, almost neutral, and with very low hardness. ?mssmo--The machines on which the fibers are felted together to produce the “wet lap” have been devcloped by this company. They are similar to the ordinary Fourdrinier paper machine, except that they produce a wet, lap about
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"4 inch thick rather than inch thick or less as on a FourAfter leaving the humidifier the boards are again inspected drinier. They are slightly over 4 feet in width and the wet and graded and are piled in storage to allow complete equaliend is approximately 40 feet long. zation of moisture. After a week or more in storage, they The fibers pass through a head box, where the consistency are ready to be shipped in any size. is carefully adjusted by another regulator. The stock then CHRoMIvi+PLATIivc+ PLmT-In connection with the manupasses to the machine, where it is formed on an endless wire facture of Presdwood, it has been found necessary to install 57 inches wide. At this point the wet lap is about 2 inches a chromium-plating plant to plate and polish the 41/2by thick. It then passes over suction boxes and through press 121/2foot plates. A great deal of original work was necessary rolls, emerging, still hot, as a wet lap "4 inch thick, containing in this installation, since we are practically pioneers in about 65 per cent water. An automatic cut-off knife cuts the chromium plating of obiects of larne size. The Dlant has t h e w e t - l a p i n t o 121/2-foot " been in iperation abbut nine lengths. These pass along table m o n t h s a n d , although many rolls until they reach an autocomplications were found, on the matic tipple, which feeds them whole it is operating extremely into large movable racks, each well. of w h i c h holds twenty panels Process Control and consists of an endless screen, mounted on driven rollers, The control of the entire procFrom the racks, the boards are ess must be v e r y c a r e f u l l y fed into the presses. Each press watched. The wood is tested t a k e s t w e n t y boards and is periodically for moisture, bark, a c t u a t e d by three large hyand imperfections. While wood draulic rams 50 inches in diis not rejected unless it is proved ameter. Between each board is to be extremely poor, a differa steam-heated platen covered by ence in treatment is necessary a wire screen fastened to rollers, for different types. For examwhich are driven to insert or reple, very dry wood will not remove the boards. On top of quire so much time in the guns e a c h P r e s d w o o d board is a d u r i n g the preheating period. polished chrome plate which imSoft wood will not require the parts a smooth finish and a hard, same degree of refining as harder glossy surface. wood. F o r p r e s s i n g Insulation or The control of the guns must Quartrboard, the presses a r e be watched very closely since, equipped with stops which hold when dealing with pressures of the boards a t the desired thickthis magnitude, a few seconds ness. The boards are dried in one way or the other may result t h e p r e s s , requiring about 30 in a raw or burned shot. Howminutes. I n making Presdwood ever, by means of pressure reguCompleted American Storaee Company Building Los no stops are used, and the full lators and recorders and a close Angeles. Presdwood Used for Concrete Forms oh All Flat Surfaces wessure of 300 to 400 Dounds examination of each shot, it is per square inch is placed b n the possible to obtain very uniform board. This pressure may be varied to suit different condi- results, even though the wood used varies in moisture, bark tions of fiber, but it must be great enough t o cause a coa- content, and size of chips. lescence or welding of the fibers a t the press temperature. The The refining is watched by men who have been trained to drying time for Presdwood is about 15 minutes. During this recognize proper fiber length instinctively. Their judgment time the board is converted from a soft, spongy mass of fibers is checked up continually by freeness tests and by analyses to the extremely hard, dense product which is known as Presd- of the fiber by separatory screens or fiber counts or both. wood. The fibers lose many of their original characteristics These are referred to standards which have been set up, and and become hard and glassy. It is believed that the lignins by comparing the run of any refiner with the corresponding present in the original wood, separated by the explosion process, sample, both enlarged ten diameters on a balopticon, very become reunited or welded together to produce this product, small differences can be recognized and corrected. HUMIDIFICATION-when the press is opened, the boards The addition of the waterproofing is automatically conare again placed in the movable racks and, after being in- trolled, but must be checked periodically, both by extraction spected, tested, and graded, are run through a humidifier, of the finished product to determine the retention of the size in which there is a moisture regain of about 7 per cent. This and by tests for water absorption. These tests are made operation is carefully controlled so that the moisture content every40 minutes and give a running check on the producof each piece of Presdwood shipped will correspond to the tion. average humidity of the district where it is to be used. The operation of the felting machines is under the control of Although Masonite products are very well waterproofed, if skilled men and is checked regularly by the control laboratory, exposed to damp conditions, a certain amount of moisture by means of tests for consistency, temperature, and freeness will be absorbed and some expansion will follow. While this of stock, and caliper, weight, and moisture content of the wet amount is small, it may cause a warping of the surface under lap. Machine operation is also closely watched. extreme conditions if the board is not humidified. Application of pressure and temperature in the presses is The humidifier is 18 feet wide by 180 feet long and has a carefully controlled, since slight differences here may greatly capacity of seven hundred 4 by 12 foot panels. The panels change the character of the product. Recording gages mainremain in the humidifier about 10 hours a t 80" F. and 100 tain a complete record, while periodical examinations disper cent relative humidity. This insures a moisture uptake close any variations. After the boards have been removed from the presses, they of about 7 per cent.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
are sampled, and physical tests, including tensile strength, deflection, and bursting strength, are made. The weight and caliper are taken and a portion of the sample is tested for moisture absorption. I n addition, each type of board has certain tests n-hich are made periodically to determine its value for specific applications. Any boards which do not meet the rather rigid specifications are graded out. Furthermore, these tests, since they are made a t short intervals, afford a running check on production and any variations from the standards of operation can be immediately corrected. The moisture regain in the humidifier is carefully checked, not only by spot tests and inspections, but by weighing entire truck loads of boards to determine the moisture regain. A control of the water used in the process is very important, particularly since m‘e have a neutral water, an alkaline water, and white water which has already passed through the process and which is re-used to take advantage of its heat content and the soluble materials it contains. Correct proportions of each of these must be combined to give the optimum pH for refining and to reduce corrosion. Furthermore, the water usage must be carefully controlled to prevent overloading of the system. Since our white water is clarified and re-used, an excessive supply of fresh water will throw a burden on our clarifying units. Since the bark enters the guns with the wood, during the explosion it is completely pulverized and, together with some water-soluble portions of the wood, is in suspension in the white water. This white water was formerly discharged into a small stream near the plant which was useless for any purpose. Owing to the quantity of eflluent and its sludge, the stream turned a deep brown and was relatively unsightly, although it was no menace to public health. It was found,
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however, that the re-use of the white water without the bark would pay for the removal of this sludge, due to the heat and the dissolved solids in the effluent. This is now being done, thus, partially a t least, solving the problem of stream pollution as well as saving money by the re-use of the white mater. Research Activities
Undoubtedly the most fascinating part of our research activities is the attempt t o follow chemically the changes which occur in the process and to investigate the possibilities of various by-products. The dream of every manufacturer of insulation board is to have many gradations of fiber length, each in its separate bin, from which he may combine a certain amount of one length with some of another, securing the optimum results so far as strength, rigidity, and density are concerned. While this is not feasible in practice, we are striving to accomplish this by systematic studies of the effect of various fiber lengths on the physical properties of the board, both by studies of the individual fiber and by semi-commercial experiments. The photomicrograph and the balopticon have greatly aided us in this study and, although definite results come slowly, we are gradually gaining an insight into the private lives of these fibers and their reactions. An entirely different line of research is the investigation of the uses of different types of machinery and modifications of our existing machines. This calls for an investigation of the design and uses of many kinds of equipment. Chippers, screens, guns, rod mills, refiners, machines, presses, and so onall come under close scrutiny and we try to be always on the alert for possible changes or modifications which will tend to improve operation or reduce cost.
Semi-Commercial Production of Xylose’,’ W. T. Schreiber, N. V. Geib, B. Wingfield, and S. F. Acree BUREAUOF STANDARDS, WASHINGTON. D. C .
BOUT two years ago the Bureau of Standards was authorized by Congress to investigate and tto develop uses for the so-called waste products from the land. “Waste products from the land” are understood to be those parts of the farmers’ crops which have no commercial value. Cottonseed kernels, before the advent of the cottonseed-oil industry, were in this category. Now there is a market for cotton fibers, linters, and seed kernels; while the bulk of the c r o p t h e leaves, burrs, hulls, roots, etc.-has no value. If it were possible then to develop uses for these products, either as such or after chemical treatment, the farmer, as well as the rest of the country, would undoubtedly profit. The Bureau divided its work on waste products from the land into three more or less correlated parts.
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(1) The laboratory research on many of these products is being done in Washington. ( 2 ) A cooperative research with Iowa State College is being carried out on the production of wall board from cornstalks a t Ames, Iowa. (3) An experimental semi-commercial plant for the production of xylose from cottonseed-hull bran has been in operation a t the Anniston plant of the Swann Corporation for the past year. 1 Received March 27, 1930. Presented by W. T. Schreiber hefore the Division of Industrial and Engineering Chemistry a t the 79th Meeting of the American Chemical Society, Atlanta, Ga., April 7 to 11, 1930. * Publication approved by the Director of the Bureau of Standards of the United States Department of Commerce.
This development has been a cooperative project of the Alabama Polytechnic Institute, the University of Alabama, the Swann Corporation, and the Bureau of Standards. It is the purpose of this paper to discuss xylose and the operations of the xylose plant a t ilnniston, Ala. Previous Work on Xylose
Xylose is a dextrorotatory five-carbon sugar. It is not new to the scientific world, although until recently it sold a t the exorbitant price of $100 per pound. This was true despite the fact that xylan, the condensation product from which it is obtained, is, next to cellulose and lignin, probably the most widely distributed organic compound found in nature. Koch (S),its discoverer, isolated xylan from wood in 1886. Since then it has been obtained from innumerable plant materials. It has been found in various grains, straws, gums, woods, parts of the corn plant, and other plant substances. Koch prepared xylose by extracting wood with a caustic solution, precipitating the xylan from the extract with alcohol, and hydrolyzing the xylan to xylose. I n 1899 Bertrand (1) showed that xylose could be prepared by direct hydrolysis of oat straw and therefore that the isolation of xylan before hydrolysis was unnecessary. Interest in xylose seemed to lapse from that time until the World War. Then, because of the greatly increased demand for acetic acid, research on xylose was resumed. The reason
