US1991499A - Method of making paper - Google Patents

Description

P. DREWSEN INVENTOR Pzerra fir ws fl METHOD OF MAKING PAPER Original Filed Jan. 8, 1932 Feb. 19, 1935.

ATTORNEYS Patented Feb. 19, 1935 UNITED STATES METHOD or MAKING PAPER Pierre Drewsen, Sandusky, Ohio, assignor to Hinde 8; Dauch Paper Company, Sandusky, Ohio; a corporation of Ohio Application January 8, 1932, Serial No. 585,603

Renewed July 17, 1934 2 Claims.

This invention relates to paper manufacture and more particularly to the methods of chemically and mechanically treating and hydrating the raw material and separating it into fibres. Specifically, the invention relates to .the manufacture of straw paper but in its broader aspects it has application also to other materials.

In the present state of the art the method most generally used in the manufacture of straw paper is first, to cook the straw with alkali chemicals in rotary digesters under elevated pressures and temperatures, and then to subject it to a mechanical beating with or without washing. Another process which has been used to some extent is to simultaneously treat the straw with alkali liquor and to mechanically defibre the same. The first of these processes is one requiring a considerable period of time for its completion, the cycle for the digester treatment being approximately twenty-four hours. Also the manual operations incident to this process require a relatively large number of workmen. The second process necessitates the use of a large quantity of the chemical and although a part of this may be recovered and re-used, the actual consumption in proporticn to the product obtained is high. One reason for this high consumption is that with apparatus that has heretofore been used for beating or defibering the straw, it is necessary to have a fairly large quantity of water so that to maintain the desired strength of chemical in the solution a large quantity is required.

My improved process is one having many advantages over either or both of the processes above described including First, a very material reduction in the quantity of chemical required for producing a given quantity of the finished paper; 1

Second, in materially reducing the time required for the operations;

Third, in materially reducing the labor costs by dispensing with the service of a number of workmen required for the other processes;

Fourth, in efi'ecting other economies such as reducing the heat and power consumption;

Fifth, in obtaining increased production of the paper in proportion to the raw materials;

Sixth, in obtaining a better product having a greater resistance to crushing stress so as to particularly adapt the paper for use in the manufacture of corrugated board.

Generally described, my improved process is one in which the chemical treatment and mechanical defibering are simultaneously accomplished. l have, however, departed from the usual practice of beating and defibering the straw, using a different type of apparatus by which I am enabled to dispense with a large quantity of water relative to the straw heretofore necessary. Thus in place of the usual Holland or paper mill heaters I employ an apparatus which kneads and shreds the stock-in the presence of a small quantity of liquid. By thus reducing the quantity of liquid required in the mechanical treatment, I am enabled to-greatly increase the strength of chemical in solution and at the same time to reduce the total quantity of chemical required per given weight of straw. This increased strength of solution greatly intensifies the reaction so that the defibering of the straw may be accomplished in very much less time than heretofore possible.

In the drawing I have diagrammatically illustrated my improved process,

Figure 1 representing the sequence of operations from the introduction of the straw to the delivery of the material to the paper machine;

Figure 2 is a cross section through an apparatus in which the chemical treatment and the mechanical defibering are carried out;

Figure -3 is a longitudinal section therethrough.

As illustrated in Figure 2, the apparatus employed differs from that generally used in paper manufacture. It consists essentially of a casing A containing one or more kneaders B which engage the stock and press it against a cylindrical segment 0. The kneaders B as shown are in the form of separately curved bars B which at their opposite ends are connected by arms or heads B with trunnions or stub shafts D passing outward through bearings in the casing A. Preferably there are two of these kneaders arranged adjacent to each other in the same casing and driven to rotate at different speeds. The bars B are also preferably provided with detachable and renewable blades B having serrated outer edges which have a tendency to tear or shred the stock. If desired the segments C may also be roughened or serrated. The casing A is preferably surrounded by a steam jacket E by means of which the liquid within the casing may be kept at approximately the boiling point.

In carrying out the treatment the proportions are approximately as follows: For pounds of straw, 300 pounds of water, 6 to 10 pounds of caustic soda or 5 to 8 pounds of calcium oxide or any other equivalent alkali or alkali mixture. Either the water and straw are first introduced into the casing and then the alkali or vice versa. By the action of the kneaders the straw is kneaded or beaten while in contact with hot alkali solutlon maintained at a temperature substantially of 100 C. The time of treatment is one hour or less, depending somewhat upon the speed of operation and power applied, but particularly upon the initial chemical concentration. The chemical reaction rate or the speed of hydration of the fibre is initially very rapid, being substantially proportional to the strength of alkali in the solution, and as the alkali is consumed or enters into chemical combination, reaction is progressively retarded. As soon as the stock is sufliciently softened it is removed from the casing A and can then pass directly to the Jordans or equivalent apparatus from which it is passed on, with or without screening, to the paper machines.

As diagrammatically represented in Figure 1, the straw is, if desired, first introduced into a cutter F which reduces it to short lengths. It is then carried by a conveyor G preferably provided with a magnetic or other separating device at the point Hwhich will remove any bolts, scraps of iron or other similar foreign material. It is then deposited on a conveyor I which introduces it into the casing A. The chemical from a tank J and the hot water from a tank K in suitable proportions are also introduced into the casing A, and after treatment the mixture is dumped into a hopper L from which it is carried by a. screw conveyor M to a receiving hopper N of a Jordan 0. From the latter it passes directly to the paper machine.

The apparatus for carrying out the process requires considerably less space than necessary for the apparatus usually employed. It also requires less power and less steam for heating. As before stated, the amount of chemical required for a given quantity of straw is considerably less than usual and an increase of approximately 10% in the quantity of the product relative to the raw material is also obtained. The saving in labor cost is a very considerable item so that the total cost of production is largedly decreased.

As there is always some unexhausted alkali present in the stock after this chemical and mechanical treatment it may be necessary to neucontrol within very narrow tolerances.

' What I claim as my invention is:

1. In a process of manufacturing paper, the step of mechanically deflbering the stock in the presence of alkali solution and with a stock density during treatment of between 10% and 50%.

2. In a process of manufacturing straw paper, the steps of mechanically kneading the straw in the presence of a relatively small quantity of alkali solution at high concentration and-the neutralization of the residual alkali while still subjected to the mechanical treatment.

PIERRE DREWSEN.

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