US1924660A - Pulp making process - Google Patents

Description

A'g. 29, 1933. i M. SKOLNIK 1,924,660

PULP MAKING PROCES S Filed Nov. so, 1951 2 sheets-sheet 1 Patented Aug. 29, 1933 l UNITED STATES PULP MAKING PROCESS Max skoluik, chicago, n1., as signor to skolnik:

Patents Corporation, Chicago, Ill., a corporation of Indiana Application November 30, 1931 Serial No. 577,968

4 Claims.

This invention relates to an improved method of producing paper pulp from straw and the like, as distinguished from the manufacture of paper from the pulp.

By my invention I am able to overcome the difficulties now encountered in the common long digestion process with Weak caustic soda, which process requires expensive containers of large capacity, coupled with agitation and beating in an attempt to secure a uniform product. The long digestion often softens the ber until it becomes weak, and the manipulation breaks the iibers into short lengths. By my improved process the time is reduced from hours to min,

l5 utes, and the material is removed from the chemical bath at the critical stage where the fibers are set free before they are softened, and the sur-l plus chemicals are immediately removed by efcient washing.

2 From the time the ties are removed from the bale to the delivery of the product to the moisture extractor, the fibers are not subjected to any force tending to break them. Further, by this quick process, substantially the only part of the o straw removed with the liquor is the resinous portion, thus leaving over 75% of the weight of the straw as good, strong, long length pulp, capable of making paper of unusual strength.

The main object of my invention is to provide a method for rapidly producing paper pulp from straw with inexpensive equipment; and further to provide apparatus for handling the straw in quantity without breaking the natural fibers; to provide a methodof obtaining the natural bers wherein only a portion of the glutinous material therein is removed; to provide a timed chemical treatment that will not soften or weaken the natural fibers; to provide an eflicient and rapid washer; to provide a method of moisture and chemical extraction that will not crush the natural fibers; to provide means for the recovery of the surplus chemicals; and to provide a process by which the losses of material in the pulping process is reduced to a minimum.

A specific arrangement of apparatus for attaining the objects of my invention is shown in the accompanying drawings, in which:

Figure 1 is a sectional View through a straw pulp producingl plant showing the arrangement of equipment and the treating and washing tanks in section.

Fig. 2 is a vsectional view taken on line 2-2 of Fig. l, and showing the relation of the straw carrier to the washing tank.

Fig. 3 is a sectional plan view of the straw carrier taken on 3--3 of Fig. 4. f

Fig. 4 is a side view of the straw carrier.

The main constituent in the structure of all plants is theliber or cellulose which forms the casing or walls of the different cells; it is the woody portion of the plant freed from all foreign substances, and forms the skeleton of the vegetable ber to the amount of to 78% It is generally the object of the paper maker to elimi nate the glutinous, resinous, siliceous, and other inter-cellular matters fromthe raw plant material, and to produce a fiber as pure and as strong as possible. y

However, in the usual pulp making process, the 70 material is subjected to a prolonged caustic treatment to soften the resinous material and to free or loosen the iibers, and the usual result is that all the glutinous material is completely dissolved, and while the fiber produced is quite pure, it is at the same time considerably weakened. Furthermore, the usual pulp making process includes passing the pulp through a series of beaters in order to completely separate the fibers, and this process has the undesirable feature that the bers are generally broken or crushed so that they are only a fraction of their original length and therefore will not produce as strong a paper product as might be possible.

The purpose of my invention is to treat the straw material in such a manner that the fibers are obtained in their natural length and strength, and so that they willretain a portion of their original glutinous material content.

The first step in the process of carrying out my improved method for producing paper pulp, is to subject the straw `to a very limited period of hot strong caustic treatment, such period being definitely predetermined so that the resinous material binding the natural bers together will be softened suiliciently to be washed away, but also such that the glutinous material in the natural fibers will be only partially attacked. K

After the straw has been subjected to a limited strong caustic treatment period, it is then thoroughly washed to remove the softened, resinous material and any siliceous material that might be present. After the washing operation the excess entrained moisture is removed and the straw is 105 passed to a mixer where the fibers are gently and thoroughly separated and mixed with fresh water so that the mixture of iiber and water may be pumped directly to a pulp storage tank, where it awaits passage to a paper making machine, or 110 the mixture of fiber and water may be pumped directly to the paper making machine.

The total time involved in this method of straw treatment for making paper pulp is merely a matter of` minutes; whereas, the ordinary method of producing pulp from straw requires a time period of from eight to ten hours.

By my improved process, costly and time consuming digesters can be eliminated, and beaters are entirely unnecessary. The straw can be carried in baskets or containers through the caustic treatment process and the washing operation, and need only be handled or removed from the baskets during the excess moisture removing process, and lthe process of mixing the fibers with fresh water for passage to the paper making machines. By reducing the handling to a minimum, the straw bers are kept intact and are less likely to'be broken. Also the loss of material is greatly reduced.

In large scale paper pulp production, the straw is preferably handled in its baled form, as received at the pulp mill. Several bales of straw, having their ties cut or removed, may be handled in one single container which carries the straw material, without further handling, through the strong caustic treatment, which may be either by bath in a hot strong caustic chemical solution, or by saturation with a hot caustic chemical vapor, and then through the washing process, which is preferably carried out by subjecting the baskets of straw material to strong sprays of water which, striking the basket from all sides, penetrates into the interior of the bale of straw. After the washing process the containers are emptied of their straw load and returned to the starting point where they are again loaded with fresh material.

As shown in Figure 1 of the accompanying drawings, a typical apparatus for carrying out my improved method of producing paper pulp from straw comprises a basket 1 into which bales of straw 2 are loaded and conveyed by means of a monorail conveyor 3 to the entrance'chamber 4 of the caustic treatment tank 5. The baskets or carriers 1 are successsively loaded into the caustic treatment tank 5, and each succeeding carrier serves to push the preceding carrier along Y in the tank towards the leaving chamber 6.

The time that the carriers 1 remain in the hot caustic treatment tank 5 is definitely predetermined so that only the resinous material in the straw bers is attacked by the caustic chemical.

-At the precise moment that the resinous material has been softened sufficiently so that it may be Washed away from the straw, and while a minimum amount of the glutinous material in the straw has been attacked by the caustic, the carriers 1 are emitted from the treatment tank 5 into the leaving chamber 6, from which they are removed and conveyed to the washing tank 7.

The baskets or carriers travel through the washing tank 7 and are thoroughly sprayed with warm water in order to wash away any entrained caustic chemical and all softened resinous material. After the baskets 1 have reached the leaving end of the washing tank 7, and have been thoroughly sprayed and washed with warm water, they are removed from the washing tank and conveyed to a hopper 8, Where the baskets or carriers are dumped, and the straw mate-- rial conveyed therein is fed into the hopper. The hopper 8 is arranged to continuously feed the'straw material into a revolving worm 9, which serves to squeeze out any excess moisture or chemical solution that might remain `in the straw material, and pass the straw material into a separator 10, which serves to stir the straw material and nally separate the fibers, at the same time continuously feeding the bers into a mixing tank 11. As the straw fibers are fed into the mixing tank 11, fresh water is added thereto in order to producea mixture of fibers and water that can be readily pumped through a pipe 12 -to either a paper making machine or a nished into a closed position, as shown by dotted lines- 15, when the basket has reached the bottom of the entrance chamber; The movable gate 13 is then opened to .admit the basket or carrier 1 into the caustic treatment tank 5. As the basket 1 reaches the end of the caustic treatment tank 5, the gate 14 is opened, and one carrier is admitted into the leaving chamber 6, which is also provided with a self closing trapV door arrangement at its top. y

The purpose of the sliding gates 13 and 14 is to prevent steam or vapor from escaping from the caustic treatment tank 5, as the carriers 1 are dropped into the entrance chamber 4, or removed from the leaving chamber 6, and slnce the caustic treatment process may be either by complete immersion of the carrier and its contents in a caustic bath, or by saturation of the straw material with a caustic'vapor, the trap doors 15 and 16 at either end of the caustic tank are necessary to serve as a double seal.

The caustic tank 5 is furnished with a hot caustic solution or vapor, as the case may be, through the pipes 17, which extend through the oor of the caustic tank. The pipes 17 lead from a heater or boiler 18, which is supplied with caustic solution from the tank 19, by means of a pump 20 and a pipe 21. The tank 19 is also connected by means ofA a pipe and valve 22 to the bottom of the leaving chamber 16, in order that a constant circulation of the caustic uid may be had from the treatment tank 5 to the boiler 18. .l During the course of treatment in the caustic tank, the solution is being continuously depleted because of the caustic chemical being entrained in the treated straw, and it is therefore necessary to occasionally replenish the supply of caustic chemical from 'a chemical reservoir 23, through a supply pipe 24. v

The washing tank 7 is constructed so that a chamber 25 will extend halfway up the sides of 135 and water is forced from the tank 25 through.

the standing spray pipes 26, by means'of steam, air, or water pressure, which is furnished through the pipe 27. I

When the water in the tank 25 becomes sat# urated with caustic chemical that is washed from the treated straw by means of the spray, the same can be pumped or drained into the caustic tank 19 through the pipe 28, and thereby caustic chemical can be recovered that would otherwise be lost. Also as excess moisture and entrained caustic chemical is squeezed from the straw pulp by the moisture remover 9, the same will drain through holes 29 onto a shelf 30, where it can drain through suitable openings l finto the entrance chamber 4 of the caustic treatment tank 5.

As shown in Figs.`3 and 4 of the accompanying drawings, the basket or carrier 1 is preferably made square so as to hold four bales of straw, each bale usually weighing approximately '75 pounds. In this way, the basket is evenly balanced around the supporting pintles 31, to'

which the conveyer hooks are attached. The basket 1 is made with an open grill bottom 32, through which liquid can readily drain, and to which are attached at each corner of the basket bottom, casters or wheels 33, which serve to guide and carry the basket through the causticl treatment tank and the washing tank. The basket 1 is provided with sides made of perforated sheets of metal, or metallic wire mesh, in order that the water from the standing sprays 26 can penetrate into the interior of the basket.

The herein described method requires a time period of only approximately thirty minutes to produce finished paper from the bale of straw as originally received and the cost of the equipment involved in the process is approximately one tenth of the usual cost of an ordinary pulp making plant, principally because of the elimination of the usual digesters. Because of the high speed and short process period of my improved pulping process, the loss in raw material is approximately only 15%, instead of the usual 35 to 40% loss which is involved in the present day pulp making process, and since my method produces the straw fibers without weakening them or mateterially reducing their natural length, the paper that is made fromsuch pulp is of a strength that is approximately two times greater than paper of the same thickness made according to the usual present day methods.

It has beenfound that the glutinous material contained in the original straw fibers lends considerable strength and body to the straw fibers, and it is the primary purpose of this invention to provide such a process of obtaining free plant fibers that will not weaken the fibers because of removal of an excessive amount of the glutinous material involved in their natural structure. This is accomplished by the limited treatment with a strong caustic chemical which softens the resinous material in the plant structure with such rapidity that the straw may be removed from such treatment before the fibers have been softened and while an appreciable amount of the glutinous material is still retained.

Although but one specific embodiment of this invention has been herein shown and described, it will be understood that certain details of the construction shown may be altered or omitted without departing from the spirit of this invention as defined by the following claims.

I claim:-

1. The method of producing vpaper pulp from straw which consists in loading a bale of straw into a carrier, removing the ties from said bale, passing said carrier and straw through a caustic treatment tank at a definite rate predetermined to loosen the straw fibres and effect a minimum amount of the glutinous material in the straw, passing said carrier and straw through a washing tank to wash the entrained caustic chemical from the straw, dumping the straw from said carrier and mixing the straw with fresh water, and passing the mixture to finished pulp storage.

2. In the manufacture of paper pulp from straw, the method of treating the straw in its baled form to remove the resinousmaterial therefrom while keeping the straw fibres intact, which consists in subjecting untied bales of straw to a predetermined period of caustic treatment while carried in mesh containers, Washing said straw after said caustic treatment and while held in said containers, and removing the straw from said containers after such treatment to separate the fibres and mix the same with fresh water for passage to a paper-making machine.

3. In the manufacture of paper pulp from straw, the method of treating the straw to produce pulp comprising straw fibers of substantially natural length, which consists in placing the straw in mesh containers, subjecting the straw to successive chemical and washing treatments to loosen the straw fibers and while said straw is carried in said mesh containers, and removing the straw from said containers only aftersuch treatment is completed.

4. In the manufacture of paper pulp vfrom straw, the method of treating the straw to produce pulp comprising straw fibers of substantially natural length, which consists in placing the straw in mesh containers, subjecting the straw to successive chemical and washing treatments to loosen the straw fibers and while said straw is carried in said mesh containers, removing the straw from said containers only after such treatment is completed, and mixing the treated straw with fresh water to separate the loosened fibers.

MAX SKOLNIK.

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