US1819152A - Method of treating cellulosic material - Google Patents

Description

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and other Patented Aug. 18, 1931 PATENT OFFICE BELL DORNER, OF BUDAPEST, HUNGARY,

ASSIGNOR, BY MESNE ASSIGNMENTS, TO

CORNSTALK PRODUCTS COMPANY METHOD OF TREATING QELLULOSIG MATERIAL This invention relates to methods of treating cellulosic material, and particularly to methods of treating cornstalks and analogous straws for the purpose of obtaining cellulosic roducts therefrom.

Cornsta s are for the most part encased with layers of leaves which adhere tightly to the stalks, and which form pockets to catch dirt. Various processes for producing paper pulp from cornstalks and similar materials have been proposed in the past. In my copending application, Serial No. 161,713, filed January 17, 1927, I describe and claim-a method of producing pulp from cornstalks and other straws, which process includes leaching out water-soluble materials, disintegrating the leached material in a beater, and subjecting the disintegrated material to two successive alkaline cooks, the first for the purpose of removing silica, and the second for removing the other non-cellulosic constituents. This process produces excellent pulp, but it does not produce a pulp which is suflicientl white for some purposes. This is due to the act that the leaching process does not remove the dirt which is retained under the leaves of the cornstalk and in its cellular structure, and this dirt is carried on through the cooking process, contaminating the pulp produced and affecting its color. The cornstalks contain besides leaves, parts of the cobs and even a certain quantity of grains, which are not suitable for the production of cellulose. Some of these constltuents, however, have considerable food value for stock, and it is one of the objects of the present invention to remove dirt and finely di vided material unsuitable for pulpin before the cooking processes are begun, an at the same time to recover a considerable portion of the material which is unsuitable for pulping in a form in which it can be used for stock food, particularly when combined with the syrupy residues which are obtained from the waste liquors of the cooking process, as described in my prior application above mentioned.

According to the present invention, the cornstalks or similar material, after having been chopped or shredded, are sieved dry in Application filed February 28, 1927. Serial No. 171,732.

order to remove finely divided material such as leaf rubbish, corn cob rubbish, corn grains and the like, which are, for the most part, not suitable for transforming into pulp, either because they lack the proper cellulose content or because of shortness of fibres. This waste material while unsuitable for the production of pulp, has considerable value as a stock food, particularly when it. contalns considerable amounts of corn grains or seeds of other plants. After the dry-sieving process, the cornstalks are subjected to a washlng process combined with sufiicient disintegration (for example, in a beater), so that wash water can penetrate into the cells and remove the dirt from inaccessible spots, such as the pockets formed by the leaves.

The washing process of the present invention will be described in connection with the pulping process described in my prlor application, above referred to, and is particularly suitable for use in such a process. It should be understood, however, that the utility of the invention is not limited to a process possessing all of the features of that described in my prior application, and the washing may be used in connection with any other pulping process. The following specific example of the invention is therefore intended to be 11- lustrative of one method of carryingout the invention, and is not intended to l1m1t 1ts sco e.

(l ornstalks as received from a mach ne, such as, for example, a McCormick machine,

are subjected to dry-sieving to remove nonpulpable constituents in a form usable for stock food and subjected to an extraction process with Water, which may be cold or warm. Preferably, the extraction process is effected in the manner described in my prior application by moving the shredded stalks very slowly counter to a slowly moving current of Water. This may advantageously take place, for example, in a. large vat, through which the stalks are moved slowly, and in which a slow current of Water is maintained. The

leaching process may, for example, take sevoral-days. This process removes a large proportion of the water-soluble materials, such assugars, mineral salts and the like, and some of the superficial dirt. Most of the dirt which is retained under the leaves is not re moved by the leaching. I

The leached material is then placed in a beater and beaten with water until the material has become sufficiently disintegrated to enable the water to thoroughly wash out the dirt. The water can then advantageously be removed from the material by sieving. The sieving may be effected, for example, by a rotary sieve of the type which is common in beaters. Not only does the washing and sieving of the partly disintegrated cornstalks remove the dirt, but at the same time, some of the finely divided leaf rubbish, moldy or rot-- ten cells or portions of cornstalks and the like are mechanically removed in the form of a finely divided sludge or mud. These materials, which are mechanically removed, are for the most part unsuitable for the production of pulp. In some cases, they do not contain good cellulose and in other cases, even where the cellulose is of fair quality, the fibres are too short to be satisfactory for paper pulp. While the beating, or equivalent defibration, is necessary to the satisfactory washing of the cornstalks, the beating should not be carried too far, as, if too fine a pulp is formed, it will tend to retain the dirty water, which cannot be removed without excessive washing, and such a fine pulp also tends to clog the sieves or to pass through them. Clogging of the sieve not only renders the removal of the dirty water difiicult, but likewise prevents the mechanical removal of finely divided material, referred to above. It IS lmportant to remove as much as possible of the materials which are not suitable for pulping, as the more material there is removed by washing processes, the smaller will be the consumption of cooking and bleaching chemicals which must be used at a later stage in the process. The beating, therefore, should be carried only to the point where the dirty water and fine rubbish can be removed by s eving. No definite period of time can be given, as it will depend on the beater and method of operating it, and particularly on the nature of the material treated.

After washing, the material is further beaten, and is then cooked with an amount of caustic soda just suflicient to combine with the silica present. This cook method may advantageously take place at a moderate temperature. The waste liquor, which con talns practically all of the silica together with some organic material, such as, for example, carbohydrate material, is removed from the pulp, or paste, and acidified to precipitate the organlc material, which can then be recovered for stock food and may be mixed with the concentrate obtained from the leaching process, which also contains largev amounts of sugars and somevaluable mineral constituents.

The partiall cooked pulp is then subjected to a second coo ing with caustic soda at moderate temperatures, which should bekept sufficiently low to prevent caramelizatlon of the pentosans and other sugars present. Pressures around two atmospheres of steam are suitable for this step, as described 1n my prior application. The amount and concentration of caustic soda used should in general be considerably in excess of that used in the first cook, where the caustic soda was intended only for removing the silica present. After the cook is completed, the waste liquor is drawn off and treated with carbon dioxide to precipitate the organic materials, the caustic soda being then recovered in the usual manner. This treatment may advantageously be carried out according to the process in my co-pendin application, Serial No. 171,783, filed Feb. 28, 1927. The pulp produced is of a remarkably light color and easily bleached to a high grade product.

The present process which is, of course, applicable to all cornstalk pulping processes, not only removes the dirt and many of the non pulpable constituents, such as, for example, seeds, leaf rubbish, rotten or unpulpable portions of the stalks, and the like, but a very marked saving in chemicals is effected, due to the fact that part of the non-cellulosic and non-pulpable material is removed before cooking, and also due to the fact that the waste liquors are not contaminated with dirt, which sometimes reduces the recovery of the chemicals to a considerable extent.

It should be clearly understood that the present invention, in which the washing in the beater takes place before pulping, does not have anything to do with the ordinary washing processes, in which pulp, which has already been cooked, is beaten in a beater with water, in order to still further defibrinate it and remove the chemicals introduced from the cooking liquor. Such a washing does not accomplish the purpose of the present invention, because, in the first place all of the impurities removable by the washing have been carried through the cooking process, increasing the consumption of chemicals and contaminating the waste liquors; and in the second place, the washing takes place with a pulp so fine as to render the sieving, which is so important a feature of the present process, difficult or impossible.

In the claims, the expression straw-like material is used to cover not only straw, but also cornstalks, bagasse and similar material.

What is claimed is:

1. The method of preliminary treating straw-like materials for fiber-liberation therefrom, which comprises shredding the same to a state of disintegration suflicient to permit access of wash-water and removal of insoluble adherent dirt, and washing said disintegrated material while agitating the same in a rotary sieve fine enough to retain the shredded material but coarse enough to permit passage of suspended dirt, the shredding of the material being insuflicient to allow the same to mat and form a pulp.

2. In a method of producing pulp or pulplike products from straw-like material, steps 'which comprise shredding the material, subjecting it to dry-sieving, and then subjecting the sieved material to a Washing and disintegrating process, the disintegration being carried to the point where the cell structure is sufliciently opened up to permit access of the wash water, but insuflicient to produce a pulp which substantially retains dirty water.

3. The method of treating straw-like materials prior: to chemical action for fiber-liberation, which comprises coarsely shredding the material, dry-sieving the loose non-adherent dirt therefrom, lightly beating the sieved material in water to loosen adherent dirt therefrom, and thereupon passing the water and beaten material over a rotating sieve having a mesh fine enough to retain the fibers but coarse enough to permit passage of the loosened dirt.

4. In the process of washing dirt from cornstalks prior to paper-pulp manufacture therefrom, the steps of dry-sieving the shred- (led stalks, lightly beating them in water to loosen adherent dirt, and thereupon passing said water and beaten stalk material over a sieve fine enough to retain the material but coarse enough to pass the loosened dirt.

Signed at New York, New York, this 25th day of February, 1927.

' BELA DORNER.