US1816457A - Method of making straw pulp for straw board - Google Patents

Description

45 process.

60 presence of water and steam,

Patented July 28, 1931 PATENT OFFICE MAX ZIMMERMAN, OF LOGKPORT, NEW YORK METHOD OF MAKING- STRAW PULP FOR STRAW BOARD No Drawing.

-This invention relates, generally, to pulp and paper board making; and the invention has reference, more particularly, to anovel method of preparing straw pulp for the manufacture of straw board, such as used in making corrugated paper board and for other uses.

Heretofore, it has been common practice to employ the lime process in cooking straw to m be used in producing straw board. The straw board produced by the limeprocess is not en- I tirely satisfactory for many uses owing to the relative softness of the fibres composing the same, and the consequent tendency of such board to disrupt or tear, when subjected to forming operations, for example, when using straw board for forming corrugated sheets or boards. Soft fiber boards, produced by use of the lime process, while passing through present day high speed corrugating machines are frequently disrupted or injured, resulting in an inferior and ofttimes useless product. Also, when using the lime process the knots of the straw are frequently either partially or wholly undigested so that it is,necessary to I remove these knots from the cook after the same has been discharged from the rotary. To remove such knots, the washing and beating processes, following the cooking of the straw, are rendered more lengthy, difiicult and expensive, and frequently more or less of the knots are not removed so that they subsequently appear as blotches or spots in the finished paper product, thereby detracting from the appearance of the product and lowerlng its value.

In my copending application, Ser. No.

442,463, filed April 7, 1930, I have disclosed a method whereby straw is treated with lime,

4o soda ash and sulphur in a rotary or other digester, to produce a pulp having strong, tough fibres and adapted to e fabricated into a board of far greater strength and reliability than that produced by the old lime The present invention discloses another novel method by means of which straw is treated with lime and salt cake with or without the addition of a small quantity of soda ash in a rotary or other diglesterin the w ereby pulp Application filed N ovember 10, 1930. Serial No. 494,697.

so produced has exceedingly strong fibres and which is especially adapted for manufacturing board to be used for corrugating purposes.

The principal object of the present invention is to provide 'a novel method of making straw pulp suitable for the manufacture of straw board, which method will cause the resulting board product to be composed of hardened, tough and strong fibres, so that a straw board made by the method possesses ample strength, elasticity and tenacity to enable the same to be subject to normal operations, such as its passage through high speed corrugating operations without disruption or other injury, the said board product being free from blotches or disfiguring marks.

Another object of the present invention lies in the provision of a method for making straw pulp for the manufacture of straw board, which method will materially increase the pulp yield over that of lime process, the said method serving to-thoroughly digest knots and other hard fibre portions of the straw to Still another object of the present invention is to provide a method for making straw pulp suitable for the manufacture of straw board, which method consists in treating straw with chemicals in a rotary or other digester or container to' produce straw pulp which may be manufactured into straw board with but littlewashing, thereby reducing the washing period considerably and also reducin the loss of pulp 'and of chemicals, and re ucing the amount of slime and waste products, whereby a reduction in the depreciation of cylinders and felts is obtained resulting in a substantial "saving in cost.

Other objects of this invention, not at this time more particularly enumerated, will be' whereupon the head of the rotary is closed approximately 15,000 pounds.

and the rotary is then revolved for about a half hour, during which period steam is admitted which acts to wilt or break down the straw somewhat, thereby rendering the same more compact. The head of the rotary is then opened and more straw is added, whereupon the head is again closed and the charge again steamed or wilted as before. This operation is repeated a number of times until the full amount of straw which the rotary is capable of taking has been added. When the rotary has been filled with its entire quota of straw, salt cake is introduced thereinto, whereupon the rotary head is again closed and the rotary revolved while the steam pressure therein is increased for the cooking operation. The whole batch is cooked for about eight hours, more or less, whereupon the liquor is drained off, the charge is cooled, the head removed and the charge dumped. The charge is then washed and proceeded with in the usual way to produce pulp suitable for making paper board.

Without restricting the invention to details, the following is given as an example of the method of the present invention. The rotary, digester or other suitable container is charged with 400 pounds of dry straw, such as wheat, rye or oat straw. lVater is then added to the extent of 2,000 gallons, whereupon 450 pounds of slaked lime is added. The rotary head is now closed and steam is admitted thereinto and the rotary revolved for about thirty minutes. The head of the rotary is then opened and about 2,000 additional pounds of straware added, whereupon the rotary is again closed and the charged steamed down or wiltedflfor another thirty minutes while revolving the rotary. The rotary is then opened and more straw'added, whereupon the charge is again steamed down while rotating the rotary. This cycle of operations is continued until the rotary has received its full quota or batch of straw, which in the presant instance is Dry salt cake to the approximate amount of 450 pounds is then introduced into the rotary.

The rotary is now closed and the batch is cooked for about eight hours under a steam pressure of from thirty to forty pounds per square inch, depending upon. the softness of the straw, the rotary being rotated all the while. During the cooking process, the lime functions to loosen and separate the incrust edmatters, such as starches, gums and silicates from the cellulose of the straw, while the salt cake acts as a digesting agent to aid in loosening and separating the straw fibres and in breaking down the knots of the strawinto fibres. The salt cake at the same time acts to greatly toughen and harden the straw fibres and render them particularly valuable for use in making paper board for corrugating purposes, the said board being well capa ble of withstanding the desired high speed forming operations, such e. g. as corrugating operations. The lime and salt cake combine with the lignin and foreign matter of the straw to form various soluble or semi-soluble compounds, the said compounds being ofa liquid nature and consequently easily washed from the straw fibres. Very little slime is produced by this process which is an advantage over the process of applicants copending application, wherein an appreciable quantity of slime is produced, necessitating more thorough washing. After cooking the batch, the liquid and steam are blown off, the rotary is opened and the stock dumped to be thereupon washed, beaten and proceeded with in the usual way to produce straw board.

When using, the pulp formed by the process of this invention, the washing and heating steps are greatly simplified and shortened, because of the absence of slime in the pulp and also because of the absence of knots or other undigested matter. Also, the absence of knots and such foreign matter facilitates the formation of the paper web and greatly reduces the depreciation of cylinders and felts. The paper so produced is of strong, even texture, of high quality and capable of being put through any type of high speed machine. No foul odors are present when the rotary is blown ofl.

Owing to the use of salt cake in the combination with the lime during the cooking process, the cellulose straw fibres are rendered more pure, are better separated and are far stronger and tougher than the fibres produced by other methods. In some instances, a small amount of soda ash may be usedtogether with the salt cake in the treatment of the straw, for example, when using the above proportions, 50 pounds of soda ash together with 400 pounds of salt cake may be used in lieu of 450 pounds of salt cake. However, the use of soda ash is not essential though the same may be used to advantage when it is desired to produce a somewhat softer fiber than that produced by the present process.

It is not intended to limit the invention to the relative proportions of straw, salt cake and lime mentioned, inasmuch as variations from these proportions may be made, de-

pending upon the physical characteristics of the straw used. Also, additional quantities of lime and salt cake may be added during the cooking process in some instances.

and texture and is free of blotches or other disfiguring marks.

It is to be understood that the steps above recited are given for the purpose of illustrating the invention and are not to be considered in a limiting sense. Modifications will occur to those skilled in the art, such for example, as the addition of an increased quantity of soda ash. It is intended to cover all such modifications that fall within the scope of the appended claims.

What is claimed is 1. A process of disintegrating' straw which consists in first treating a minor quantity of straw with slaked lime and steam While agitating in a rotary, adding additional uantities of straw at intervals until a full atch is loaded into the rotary, and then adding salt cake to the batch and then cooking the batch.

2. A process of disintegrating straw which consists in first treating a minor quantity of straw with slaked lime and steam while agitating in a rotary, adding additional quantities of straw at intervals until a full batch is loaded into a rotary and then adding salt cake and a relatively small quantity of soda ash to the batch and then cooking the batch under steam pressure for about eight hours.

3. A cooking process for disintegrating straw, consisting in first partially disintegrating an initial quantity of straw b the application of slaked'lime and steam, a ding additional quantities of straw and similarly disintegrating the same until a total batch of straw is obtained, adding salt cake to this batch of straw, and then finally cooking the batch by the use of steam under pressure while agitating the batch.

In testimony, that I claim the invention set forth above I have hereunto set my hand this 20th day of October 1930.

MAX ZIMMERMAN.