US40728A - Improvement in the manufacture of paper-pulp - Google Patents

Description

employed.

UNITED STATES f XUGUSTUS H. TA IT, OF JERSEY CITY, NEW JERSEY, AND WILLIAM H. HOL- ATENT Orrlce.

BROOKE, OF NEW YORK, N. Y.

IMPROVEMENT IN THE MANUFACTURE OF PAPER-PULP.

Specification forming part of Letters Patent No. 40,728, dated November 24, 1863.

To all whom it may concern:

Be it known that we, AUGUSTUS H. TAIT, ofJersey (lily, county ofHudson, State of New Jersey, and WILLIAM H. HOLBROOKE, of the city, county, and State of New York, have invented a new and useful Improvement in the Manufacture of Paper-Pulp from Straw; and we do hereby declare that the following is a full and exact description thereof.

The nature of our invention consists in subjecting the straw to grinding process while in the dry state, and also in duplicating weak alkaline, weak acid, and weak chlorine treatment.

To enable others skilled in the art to use our invention, we will proceed to describe its operation.

1. We pass the straw through a cutting-machine, cutting it into lengths of about threefourths of an inch.

2. We next subject the straw'to the action of a burr-stone or other mill, the advantage of which is to economize the use of chemicals and shorten the period of boiling by reducing to powder, ornearly so, a large percentage of silica and other matters which it would be necessary otherwise to dissolve out by such dividing and splitting up the straw lengthwise, by grinding of the knots and separating in the form of dust the earthy matter contained in them, and when such foreign substances are not capable of being removed by the next-described process of screening they are brought into a finely-divided state, and are readily acted upon by the chemicals. We do not confine ourselves to use of burr-millstones but any variety of millstone may be It should not, however, be too coarse.

8. We next pass the ground straw through a winnowing-machine, or through sieves or screens, in order to separate from it the fine ground particles of silica and other earthy matters. v

4. We next place the straw in a vessel containing cold water, provided with fire or steam heat, (the latter being preferred,) and gradually raise the heat to a boiling-point, the object of this operation being to discharge so much of the coloring-matter of the straw as is soluble in water. Care should be taken not to raise the heat of the mass too rapidly.

5 We next drain oft the colored water and add a solution of caustic soda of the strength of 15 Baum, or caustic potash of equivalent strength, in the proportion of seventy gallons of the solution to one hundred pounds of the dry straw, and boil the whole for from five to six hours. After the boiling is complete we wash the stock thoroughly with hot water to remove as much as possible of the alkali.

6. We next cover the stock with a weak solution of muriatic or sulphuric acid of the strength of one gallon of commercial acid with thirty gallons of water. We boil for two hours. We then drain off the liquor without washing.

7. We next pour into the stock a solution of .the chloride of lime (consisting of the spent solution used in a previous final bleach) and let it remain for from twelve to eighteen hours, 4

setting free the chlorine from time to time by the addition of portions of the acid solution above described, taking care that sufficient acid has been used during the operation to set free all the chlorine gas. Then we run off the liquor and wash it well with hot water.

8. We next boil the stock in a second solution of caustic soda of the strength of l Baum, seventy gallons to one hundred pounds of straw, for four hours, run off the liquor, and wash well with hot water.

9. We next repeat the operation described in subdivision 6 above.

10. We next bleach the stock by the use of chloride of lime in the ordinary manner.

The advantages we claim by the adoption of the useof our patent are as follows:

First. The thorough separation lengthwise and disintegration of. the straw, the breaking up of the knots, and the abrasion of a large portion of the outer coating of silica by the process of grinding instead of the old method of merely crushing the straw between rollers. By this process of grinding, not only is the action of the chemicals subsequently used facilitated and the time required for such action shortened in consequence of the minute division of the fibers of the straw, but the quantity of chemicals required is reduced in proportion to the quantity of silica and the earthy matters contained in the interior of the knots got rid of in the shape of dust by the subsequent operation of screening.

Second. The only process of thepresenttime in successful operation for making paper from straw is by means of a strong solution of caustic alkali in close vessels of iron at high pressures and temperatures, which, after a tedious manipulation of eight or ten hours, leaves the fiber weak, short, and broken-a fact in the treatment of vegetable fiber well known to the bleachers of cotton goods, who are particularly careful to avoid high temperatures and strong chemicals. The examination of the quality of our straw pulp will show the Value of our process in which all such high pressures and temperatures are guardedagainst.

Third. By our method of working out the whole process of making pulp in one vessel without change we save nearly one-half ot the labor at present expended.

Fourth. The highest grade of paper which the makers have been able to produce by the present methods of working is only adapted for newspapers, being full of black spots visible to the naked eye, principally due to the earthy matters and other impurities contained in the interior of the knots of the straw, which the strong outer coat of silica has preserved from being attacked by the chemicals used, but from which the pulp made from our improved process will be found entirely free, even when examined under the microscope, provided attention is paidin the mill to exclude extraneous dust, &c. We are consequently enabled to produce a higher grade of paper, suitable for book or writinglpaper, at a trifle over the present cost of common printing-paper.

Fifth. It is also a well-known fact to bleachers of cotten fabrics that all the matters other than pure fiber or cellulose,which it is their object to get rid of previous to bleachingsueh as silica,resin, albumen, dextrine, &c.--cannot be dissolved out by a single operation of strong caustic alkali without injuring the fiber. It requires a double application of the alkali ata reduced strength with the useof a weak treatment of chloride of lime or gas between the two applications of alkali in order to dehydrogenate the coloring-matter in the vegetable fiber, after which the action of the second alkali is rendered effective, the first alkali being necessary to dissolve out a portion of the foreign matters preparatory to the action of the chlorine.

Sixth. Another decided advantage in the practical working of our process will be found in the increased percentage of pulp independent of the superior length, tenacity, and firm;-

ness of the fiber,whieh latter are absolutely essential to give to the pulp the property of felting, without which the paper will be deficient in strength.

It is also well known to the cotton and linen bleachers that vegetable fiber cannot be rendered a pure white by one application of strong chlorine without serious injury to the fiber itself; hence the obvious necessity of that part of our process of dividingthe bleach. In fact, we have briefly to say that the two processes of making paper and bleached fabrics from vegetable fiber are identical, the whole science in bothinstances being redueedto the process of dissolving out the foreign matters and producing, as nearly as possible, i a pure white cellulose without injury to its felting property and tenacity.

We do not claim the crushing of straw as is already known and practiced 5 nor do we claim the use of alkali acids, nor of chlorine, nor the strengths of their respective solutions, nor the order of their application; but

What we do claim as our invention, and desire to secure by Letters Patent, is-

1. The passing of straw between grindingsurfaces in the manufacture of paper-pul p, substantially in the manner and for the purpose hereinbefore described.

2. Treating the stock after it has passed through a weak alkaline andchlorine treatment, with or without acid, to a second application of weak alkali and chlorine, with or without acid, substantiali y as above described, for the purpose of making paper-pulp.

A. H. TAIT. WM. H. HOLBROOKE.

Witnesses:

EMMET WELLS, En. BARTLETT.