US1891732A - Building board - Google Patents

Description

' 1 No Drawing.

Patented Dec. 20, 1932 UNITED STATES PATENT oFncE EDWARD S. SHEPERD, DECEASED, LATE 0F. VINCENNES, INDIANA, BY .LELA E. SHEPERD, ADMINISTRATRIX, OF VINCENNES, INDIANA, ASSIGNOR TO ALBERT D.

STEWART, OF ST. JOSEPH, MISSOURI r BUILDING BOARD This is a continuation in part of the copending application Serial No. 391,111, filed Sept. 7, 1929, and relates to a building board composed of cereal straw fibres such as the fibrous residue from wheat, oats, rye, barley and analogous cereal straw stock, and in one specific embodiment relates to a relatively thick light weight board possessing high porosity and physical characteristics suitable for structural purposes, thus producing a board eminently suitable as a substitute for lumber or in conjunction with lumber or similar building material, characterized by be-' ing self-sustaining and possessing heat insulatingand sound deadening qualities to a marked degree. By relatively thick, is meant a sheet approximately one-fourth to one inch-in thickness. To satisfy commercial requirements, a building board which can be used as a substitute for lumber, must possesscertain properties among which may be listed stiffness, tensile strength, transverse strength, structural strength, and penetration resistance.

This invention proposes to utilize what is now practically a waste product of little or no value, most of which is beingb urned to facilitate its disposal, namely the residue from the threshing of grain comprising" the fibrous constituents of said grain as a base for a commercial product of high value.

It is known that heretofore attempts have been made to utilize a small portion of this. enormous quantity of cereal straw fibre for 5 facture of a relatively thick board, but products made from straws of this character do not possess the physical properties required in a board which is to be used as a substitute for lumber, which properties have hereinbefore been pointed out. It is also known that there is manufactured relatively thick boards Application filed January 25, 1932. Serial No. 588,842.

for insulating and structural use, utilizing cane and wood fibre.

Board of the present invention comprises relatively long slim cereal straw fibres interlaced and felted into a fibrous structure, said fibres having been relieved of the natural gummy components contained in the raw cereal straw, and the fibrous structure made therefrom being consequently devoid of such gummy components; said fibres being further binder, and yet lends itself to economical commercial manufacture, as will be herein- 7 after more particularly pointed out.

Other objects and advantages of the in vention will be more apparent from the following description.

To understand the contribution which is being made hereby in this field, it will probably be helpful to describe themethod of preparing the raw cereal straw and the reasons therefor, which will logically lead to the reasons for certain characteristics of the final product, which constitutes the basis of this invention. v 1

In the preparation of the stock the cereal straw, which generally is in bale form, is broken up and subjected to a cutting action for the purpose of separating'the mass of straw into individual straws'and also for the purpose of shortening the length of the individual straws in order that in the cooking operation the straws may be more quickly and thoroughly agitated due to such shortness and be thereby more quickly, evenly and thoroughly cooked in order that the gums, or gum-like material naturally associated with the straw, may be loosened and readily removed. In this cutting operation the straw is individualized and the individual straws cut to a length of from three to five inches, more or less.

' It should be noted at this point that, as a feature of the present invention, it has been superior board relative to those found to be more or less essential in the preparation of cereal straw fibre for the purpose described to separate and remove all of the gums and gum-like materials naturally associated with and contained in the straw prior to the operation which produces the board.

Subsequent to the cutting operation the individualized straw is subjected to a cookingaction. Prior to being charged to the cooker the straw may be subjected to a shower of water to remove foreign matter such as dirt, dust, etc, which also facilitates charging of the cooker by wetting down the straw.

As another feature of the present invention, the amount of water added to the cooker is carefully controlled and regulated for purposes to be hereinafter more particularly described. The water introduced may oe at atmospheric temperature or may be at an elevated temperature. In practice about eight barrels of water is used to each ton of straw charged to the cooker. Only such an amount of water is introduced as can be absorbed by the straw, that is care should be taken not to put too much water into the straw as it tends to injure natural strength and resiliency of the straw fibres. After being charged, the cooker may be connected with a source of live steam of, say from 25 to 55 pounds pressure, more or less, at a temperature of approximately 275 to 300 degrees F. The stock is agitated for from three to five hours more or less, the time of cooking being regulated relative to the temperature and amount of water used to that necessary to loosen said gums and gum-like materials without excessive softening of the straw itself.

It is important at this point to note that in the cooking operation of the present inven tion no chemical is used for the purpose of softening the fibres, as is usual in the ordinary processing of straw fibre for the manufacture of thin paper. It also is important to note that too high a temperature carbonizes the natural gums and gum-like materials present in said straw and prevents separation of said gums from the straw fibres during subsequent processing, while too low a temperature merely prolongs the cooking time with danger of excessive softening ot the fibres.

Straw cooked as above described would not be practical for regular paper making purposes for the reason that in the manufacture of a relatively thick building board, it is necessary that the fibres be of such character that they will not be soft and moisture absorbent; rather they should be relatively hard and tough (resilient). By careful regulation of the amountof water used, the temperature and duration of cooking, one is enabled to secure a fibre which is tougher, more resilient and harder than if the stock was cooked for a longer length of time under such conditions and in the presence of the usual chemicals employed in the ordinary processing of st aw for paper work. In the ordinary paper mill practice a very fine soft fibre is the desired product of the cooking operation, because of the fact that it is desired to manufacture a relatively thin sheet having a very high density, and the extraction of the water is not such a problem, because of the thinness of the sheet, as is the case in the manufacture of a building board with a thickness of from one-quarter to one inch. The longer the length of time the fibre is cooked under the above noted conditions and the more the fibres are subjected to the action of any chemicals usually employed in cooking this fibre the softer the fibres will be, making them more susceptible to the holding of water. Vhercas, in this process, it is essential that one have a fibre which is not soft, which will absorb the minimum amount of moisture and will have great resiliency.

The formation of a sheet from a straw stock is dependent upon the draining ability of the fibres, and stock is classed either as slow or free, referring to the draining characteristics. Example, sand would be slow while pebbles would be free. In the ordinary practice of cooking straw, chemicals such a lime caustics and sulphur, are used which assist in disintegrating and softening the fibres. Such a process will produce fibres of a slimy gelatinous and glue-like nature which would be undesirable for use in the product that is intended to be manufactured After the straw has been cooked for the proper length of time and under the desired conditions it is dried to eliminate substmn tially all water, which may be accomplished by air drying or aerating in order to separate and dehydrate the straw. This drying step is important, since it is desirable that the straw be as dry as possible in the next step of the process. In the process of drying and dehydrating, the liquid is thoroughly drainedofl the fibres, carrying with it the greater part of the gums and gum-like materials loosened in the cooking operation.

As the next step in the process, these dried cooked fibres may be conveyed to a hammer mill shredder, or the like, especially designed to preserve the greatest possible length of fibre while reducing such fibres to the smallest cross section which can be obtained, it being desired to use long slim fibres in the manufacture of the building board heretofore described.

From the hammer mill shredder the dry stock may be passed over a magnetic device where all metal, such as pieces of baling wire, tie wires, etc., may be extracted. If such metal was not extracted it might very serious- 1y impair the apparatus through which the straw subsequently passes.

The straw fibres may be then subjected to a tearing action by being passed through 5 and between two metal disks, the faces of which may be corrugated or ridged, said disksbeing rotated at a speed of approximately 1200 R. P. M.', each disk revolving in an opposite direction. The action effected by these metal disks is a tearing action rather than a grinding or cutting action, the object being to further reduce the cross sectional width of the individual fibres while preserving their greatest length.

passes through these disks, it may be subjected to the action of steam introduced under about 100 pounds pressure for the purpose of aiding in the uniform reduction of the fibres and facilitating'their feed through this mill. The steam in effect tends to blow the individual straw fibres through this mill.

This part of the process may also be accomplished in a specially designed beating engine, if desirable.

From this latter mill, the straw maybe conveyed to a vat where water is introduced,

either heated or unheated, in sufficient quantity to make a stock of such consistency that it can be pumped to the washing and beating machines. The stock may be then subjected to the action of a beater preferably provided with a special type ofbeater adapted to give the greatest possible brushing action to the fibres to preserve their length, avoiding a cutting action which would shorten the length of said fibres and be injurious to the finished product. This beating further tends to break up and loosen any gum or gum-like materials remaining associated with the fibres.

As a final step'in the preparation of the stock, it is then subjected to a very severe washing treatment carried on until the fibres are thoroughly cleansed, i. e., until the water in which the fibres are held in suspension is clear, or substantially clear, or, in other words, free or substantially free from color, which color would result from any gums or gum-like materials still remaining in the stock.

Subsequent to the cleansing operation, the stock may be transferred to the usual stuff chests and conventional Jordan, or any other usual refining engine, where the fibres may be subjected to another brushing action and are made ready for the felting machine which produces the board.

The stock in aqueous. suspension of the proper consistency is then felted into a coni tinuous fibrous sheet from approximately one-quarter to one-half inch in thickness. The water is removed, the sheet dried and severed into strips of desired length and width. 1

WVhile the invention has been described in As the straw terms of successive steps, it is tube understood that the tearing and grinding steps may be combined if desired. The final cleansing operation to remove any gum or gum-like materials still in the stock may be interposed before the beater operation in some instances.

From the foregoing, it will be apparent that a board has been produced" composed of cereal straw fibres which have been relieved of all or substantially all of the naturally gummy or gum-like materials contained in the raw stock, and characterized in that the fibres are of great, length and small cross section, that is, the process of preparing the fibres is so designedthat the fibres are long and slim. In addition, the board'is characterized by being non-moisture absorbent, and the fibres instead of being soft are relatively hard and tough, i. e., resilient.

Since no chemical is used in the preparation of the straw stock, it follows that the final product is not gelatinous or slimy as is the case .where chemicals are used in the preparation of the stock.

In removing the gummy component, the density of the resulting product is lowered with a corresponding decrease in thermal conductivity. It is essential in the manufacture of an insulating material to maintain the lowest possible density which has been acfoot, the product having a maximum thermal conductivity of approximately .34 B. t. u.

per square foot, per hour, per inch of thickness, for each degree F. difference in temperature.

What is claimed as the invention is:

Asa new article of manufacture, relatively long cereal straw fibres interlaced and felted into a rigid self-sustainingfibrous structure having a maximum thermal conductivity of about .34 B. t. 11. per square foot per hour, per inch of thickness for each degree F.

difference in temperature, the fibres having been relieved of the gummy components naturally associated with the raw cereal straw from which the structure is made by water whereby the fibres are characterized by being resillent and non-moisture absorbent.

In testimony whereof I afiiX my signature.

LELA E. SHEPERD, Admz'm s tratriw 0f the Estate of the Late Edward S. Shepard.