US1772502A - Method of making hard-lumber substitute - Google Patents

Description

Patented Aug. 12,

; UNITED STATES PATENT OFFICE ORLAND R. SWEENEY, 0]? AMES, IOWA, ASSIGNOR TO IOWA STATE COLLEGE OF AGRI- OF AMES, IOWA, A CORPORATION OF IOWA CULTURE AND MECHANIC ARTS,

METHOD OF MAKING HARD-LUMBER SUBSTITUTE No Drawing.

The object of my invention is to provide a substitute for hard lumbermade from agricultural waste products, such as corn stalks.

A further object is to provide a lumber substitute of this character which will remain permanently in the shape in which it is pressed or moulded, and not be likely to warp; and also to provide a lumber substitute of this character which is highly resistant to the action of moulds of common varieties met with in nature;

A further object is to provide an improved and simplified method of producing hard lumber substitute from agricultural waste materials such as corn stalks. v

My invention consists in the arrangement and combination of the various steps of the process bywhich my improved hard lumber substitute is produced, and in the hard lumber substitute produced by my improved process.

I have discovered that among the agricultural waste products, corn stalks have high pentosan content, which is desirable in connection withmy improved process.

The corn stalks are first reduced to a pulp by grinding with machinery similar to that used at the present time in the paper industry, or the more recently developed machinery for grinding wood pulp. This may be done in the presence of water, or-water may be added later.

The pulp is then formed into a mat, and this may be done with either a revolving perforated cylinder, which will pick up the pulp and form it into a mat as the cylinder revolves in the vessel in which the pulp is contained. I have'also successfully produced mats of this' pulp by placing it in a box with a perforated screen bottom and then applying suction below the perforated screen to remove the water from the pulp, leaving the mat in the form of a sheet.

Having formed themat in the manner be-' fore described, I then place it in a. hydraulic press and subject it to heavy pressure between platens.- vThese platens are so designed that steam may be introduced into them to heat them. After pressure has been applied to the hydraulic press, and the platens have Application filed October 2, 1928. Serial No. 809,900.

come to a stop, and a large proportion of the water has been squeezed out of the mats, then heat is applied to the platens.

1 have discovered thatthe application to said mat of pressure of a suflicient amount and heat to a certain degree at the same time the temperatures withinthe mat are elevated rather rapidly and since we have high pressure on the mat, the steam from the mat escapes slowly and in so doing it hydrates peutosans in said material and these materials then polymerize or otherwise congeal to bind the cellulosic parts and fibers of the mat into a strong, tough and durable material, which is a marketable product.

In practice I have produced satisfactory results with a hydraulic press havin hollow plates into which steam is admitted for heat ing purposes, and pressure applied at the same time to the amount of from one hundred pounds to two thousand pounds to the square inch. The higher the pressure, the stronger and harder will be the board produced. The heat and pressure are applied from twenty minutes to two hours.

Before the mat is formed, I have obtained advantageous results by giving the shredded material a treatment in an autoclave under steam pressure of from twenty to ninety pounds, and when so treated, I findthat 1t speeds the disintegration of, the material, and

thereby aids in its subsequent mechanical treatment. v I

I have also demonstrated that if, during this cooking in an autoclave, from two to fifteen per centof soda ash, or a mixture of soda ash and lime, is employed, it will speed the disintegration.

I have also had satisfactory results by adding to the material in its pulp form certain sizing materials, such as rosin size, casein, starch or extracted soy bean meal, in such a manner as to cause this material to adhere to the particles of the pulp. This part of the process is similar to the one now used in the paper industry, and I find that theuse of size in this manner gives'a denser surface and somewhat stronger lumber.

During the time that the mats are in the ing of the material from the outer circumferenceis progressively slower as it approaches the center of the material, and in some instancesi't has taken several hours to evaporate the la st'traces of moisture from the center ofthe material. I have satisfactorily demonstrat'ed that scoring the surface of the platen provides channels which facilitate the removal of the steam generated by the heat and results in carrying out the drying process much faster. Then after the material has been formed, it presents a surface on the side of the material to which it had been applied which is somewhat roughened, and which is desirable for certain purposes.

Corn stalks being of high pentosan content, have the peculiar property of hydrolizing at elevated temperatures in the presence of moisture to pentosie compounds, intermediate between xylose and the pentosans. I am not yet clearly aware of the exact nature of the products, but it is known that they resemble to some extent starch, dextrin and other materialsof that type which. are hydrolized from cellulose. The pentosan content of corn stalks is differentiated from starch and dextrin in being a better adhesive and far more stable towards the action of bacteria or moulds 0f the common varieties met with in nature and of being less soluble in water.

I have discovered that straw, eanut shells, cotton seed hulls and oat hulls have substantiallythe same properties as corn stalks, so far as its use in this connection is concerned, and hence throughout this application I .wish to include these as the equivalent of corn stalks.

I claim as my invention:

1. The method of making hard, tough material which can be used as a substitute for hard lumber and the like, and which consists in first pulping corn stalks, then forming a mat of the pulped corn stalk, then subjecting the mat to pressure between heated latens in the manner and to the extent speciiied, to thereby liberate pentosic compounds and cause them to polymerize or otherwise con alto bind the cellulosic parts and fibers of t e material.

2. The method of making hard, tough material which can be used as a substitute for hard lumber and the like, and which consists in first pulping corn stalks, then sizin said pulp, then forming a mat of the pn ped corn stalks, and then subjecting the mat to pressure between heated platens in the manner and to the extent specified, to thereby liberate pentosie compounds and cause them to polymerize or otherwise conalto bind the cellulosic parts and fibers of t a material. 3. The method of making hard, tough material which can be used as a substitute for hard lumber and the like, and which consists in first pulping corn stalks, then applying a sizing material to the pulp and precipitating it on the fibers of the pulp, then formin a mat of the pulped corn stalks, and

then subjecting the mat to pressure between heated platens in themanner and to the ex:- tent specified, to thereby liberate pentosic compounds and cause them to polymerize or otherwise congeal to bind the cellulosic parts and fibers of the material.

4. The method of making hard, tough material which can be used as a substitute for hard lumber and the like, and which consists in first pulping corn stalks, then forming a mat of the pulped corn stalks, then subjecting the mat to pressure between heated platens, the heat being in excess of 180 F., and the pressure being in excess of eighty pounds to the square inch, to thereby liberate pentosic compounds and cause them to polymerize or otherwise congeal to bind the cellulosic parts and fibers of the material.

5. The method of making hard, toua'h material which can be used as a substitute for hard lumber and the like, and which consists in first ulping corn stalks, then forming a. mat of t 1e pulped corn stalks, then subjecting the mat to pressure between heated platens in the manner and t0 the extent specified, to thereby liberate pentosic compounds and cause them to polymerize or otherwise congeal to bind the cellulosic parts and fibers of the material, and providing channels or passages on one side of the pulp While it is being pressed and heated to facilitate the escape of steam.

Des Moines, Iowa, Sept. 26, 1928.

ORLAND R. SWEENEY.