US1946953A - Process for producing synthetic lumber that is not attacked by molds - Google Patents

Description

Patented Feb. 13, 1934 UNITED STATES PATENT OFFICE PROCESS FOR PRODUCING SYNTHETIC LUMBER THAT IS NOT ATTACKED BY MOLDS No Drawing. Original application June 27, 1929,

Serial No. 374,274. Divided and this application April 16, 1931. Serial No. 530,736

3 Claims. (01. 92-40) This invention relates to the process or method of treating synthetic lumber, paper or the like against attacks from molds. For purposes of illustration I will specifically consider and herein 5 discuss the treating of synthetic lumber made from cornstalks against such attacks by molds and the like. To this end the invention may consist of: first, cooking the unshredded corn plant under pressure; second, allowing it to stand for a certain length of time without washing it; third, passing it through a rod mill or like; fourth, suitably washing the same; fifth, passing the washed product through a refining machine; sixth, treating said material with a suitable amount of water; seventh, adding to said mass 2. sizing material such as rosin or alum; eighth, forming it into a board; ninth, drying it on a suitable machine; and tenth, spraying the formed board with a copper sulphate solution. When such a board is formed it will be economical in manufacture, durable and strong in use, and will be free from the possibility of its deterioration by molds. The step by step procedure may be varied as will hereinafter be explained.

Heretofore, a great deal of experimenting has been done in attempting to make suitable synthetic lumber from cornstalks and from this standpoint I might state that my UnitedStates Letters Patent on a Process relating to the production of synthetic lumber from cornstalks, Patent No. 1,803,737, under date of May 5, 1931, and of which this invention is a division, goes into great detail to explain.

Suffice it to say that the examination of the cornstalk shows that it is composed of a hard outer shall called the cortex. This cortex surrounds a soft pulpy material known as pith or parenchyma, and this pith surrounds elongated cell fibers called vascular bundles. Any processing of this material is difficult because of the different physical properties. For example, if the grinding machinery is not especially adapted to the purpose, the pith will be beat to a jelly long before pieces of the outside fibers are reduced to a suitable pulp.

This causes the mat forming machine to become clogged and produce an unsatisfactory product. Likewise in the digesting of the cornstalks with chemicals, no wholly satisfactory process has been worked out because the pith and vascular bundles are completely hydrolyzed and disintegrated before the cortex is properly cooked.

In the standard practice it is the custom to shred or otherwise comminute the cornstalks before subjecting them to cooking or chemical treatment.

I have found that if the cornstalks be unshredded and then fed into the digester as they come in bales or directly from the field, before they have been given any serious mutilation, and that if the digestion be carried out using approximately pure water, or in other words water whose pH value does not vary greatly from 7.0, and that if these whole unmutilated stalks are subjected to a pressure of from thirty to one hundred pounds in contact with hot water, that there results a product which when properly macerated gives a board of great strength and of highly desirable properties for use in the parts.

I have also found that it is advisable after cooking the cornstalks for from one to three hours under such a pressure with hot water, that the fibers will be made tougher and that the pith cells will draw into fiber better and be removed more completely from the fibrous cortex cells if I allow the cooked stalks to stand for from four to twenty-four hours before they are further handled in the processes. This standing has a double advantage in that it allows the fibers to absorb from the cook liquors ligneous or pentosic materials which probably partly oxidize and at the same time the greater amount of the cooking liquors drain away thus reducing the necessity for excessive washing of the material.

In order to get the best results from the water digested fibers or cornstalks as prepared in the foregoing manner, I next pass the cornstalks through a heavy rod mill. This rod mill is of the usual construction consisting of a large drum mounted for rotation and having a plurality of heavy rods therein.

As the drum revolves on its axis the rods naturally either tumble over each other or rise upon the side of the drum and slide down continuously. It is obvious that if the rods tumble from the top portion of the drum downwardly, a pounding action will result, whereas if the rods slide down the side they will give a rubbing action to the material inside the drum.

For my purposes I prefer the rubbingaction as it draws the pith cells into long fibers which do not jell up and which work better when commingled with the tough, strong cortex fibers. The obtaining of this result will vary with the 105 different types of rod mills, but any skilled workman can easily determine the speed the drum should rotate for realizing this rubbing action. Results will also depend on the rate the cornstalks are fed into the mill. Obviously the larger 110 the rods and rod mill the greater the feed must be in order to produce satisfactory fiber.

I have found that it is best to run the comstalks through at such a rate as to cause the cortex fibers at the discharge end to vary in lengths from very short fibers to fibers of about one-half inch in length. Best results are not generally obtained by attempting to completely reduce the pulp in the rod mill. By passing the cornstalks through at a rate to give fibers of the above-mentioned dimensions, the pith is not excessively jelled, but is drawn into fibers. There will also be produced a small percentage of thread-like fibers several inches in length which is very desirable.

It is necessary to feed into the rod mill at the same time that the stalks are going through, an amount of water such as to make the cornstalk fiber come from the discharge freely. The amount of this water will be at least five hundred per cent of the weight of the cornstalks fed into the mill.

After the pulp has come through the mill it is now coarse enough to be free on a screen which is so positioned as to receive the pulp. It is upon this screen that the cornstalk pulp is washed with water to remove a certain amount of the pentosans and lignins produced during the water cooking. This washing must not be too thorough because the adhesive properties of these before-mentioned materials are desirable. If, however, none of the lignins or pentosans are washed out, the board will not be free enough on the machines used to make up the same. The screen should be of approximately forty mesh and may be either of the inclined sheet type or the rotating cylinder type. As the pulp travels down and across the screen it is washed by the water sprayed on it which can be controlled by a valve in the water line.

If a very refined board is desired, the pulp from the washing screen should be passed through a refiner in order to take out the small pieces of material which are sometimes termed shiners or chives. After the pulp is washed, a suitable amount of water is added to the same and to this mass usually is added a sizing material such as rosin or alum. The mass is then conveyed to the board forming machine as is well known in the art.

The above discussion will give a general idea of one way of making and forming a synthetic lumber and will form a basis upon which I may discuss the treating of the same against molds. Therefore, generally I would state that this invention consists of spraying a substance onto the board that eliminates molds.

When the pulp is placed on the board forming machine it is pressed in the usual manner by rollers or the like and the water removed from the same. The water thus removed is generally called white waters and I have found that for economy of water consumption it is desirable to use this water by returning it to the process. I use it direct for washing the pulp and for diluting the pulp in the refining machine.

After the board mat is formed it is then pressed and dried in the usual manner by suitable pressing and drying machinery which delivers the formed board in a hot condition. It is at this point that I spray a solution of copper sulphate, which is an excellent poison for successfully combating molds onto the heated boards, which due to their below normal dryness will readily absorb the solution of copper sulphate, thereby making the board mold-proof. The copper sulphate will more fully impregnate the boards if they are stacked one on top of the other and allowed to stand in such condition for a certain length of time.

Another method of treating the board is to spray the copper sulphate on the board mass before it reaches the pressing and drying machinery. However, in either case the board will be successfully treated against molds.

I claim as my invention:

1. The process of manufacturing and producing a synthetic lumber from cornstalks consisting of the breaking up of the cornstalks into comparatively fine pieces, commingling the pieces with water, forming the mass into lumber by pressing and heat drying, and lastly spraying said lumber with a solution of copper sulphate, while said lumber is still warm from said heat drying.

2. The process of manufacturing and producing a synthetic lumber from cornstalks consisting of the cooking of the cornstalks in water under pressure, discharging the material from the cooker, breaking the material into particles by a suitable machine, adding liquid to the particles, forming the mass into lumber by pressing and heat drying, and last spraying said lumber with a copper sulphate solution, while said lumber is still warm from said heat drying.

3. The process of manufacturing and produc ing synthetic items from cornstalks consisting in the cooking of the unshredded corn plant in water under pressure, discharging the material from the cooker, rubbing and breaking the cornstalks into elongated particles by a suitable machine, treating the particles with water, forming the mass into items by pressing and heat drying, and last spraying said items with a copper sulphate solution, while said lumber is still warm from said heat drying.

ORLAND R. SWEENEY.