US1112887A - Process for the recovery of pulp from waste papers. - Google Patents

Description

UNITED STATES r a rnnr OFFICE,

JOHN M. BURBY, 0F ASTORIA, NEW YORK, ASSIGNOR TO THE PEMBEE COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PROCESS FOR THE RECOVERY OF PULP FROM WASTE PAPERS.

No Drawing.

To all whom it may concern Be it known that'I, J OHN M. BURBY, a citizen of the United States, and a resident of Astoria, Long Island, county of Queens,

and State of New York, have invented a cer- ,art, solvents are employed to dissolve or saponii'y the oily constituents of the printers ink, and in some of them directions are iven to boil such Waste papers in the stated solvents, or to subject them to the action of such solvents heated by steam under pressure, to reduce or destroy the adhesity of the ink, sizing, etc., to facilitate the separating of the pulp fibers therefrom. The grades of paper, known collectively as print or news print papers and some grades of book papers are made partlysome of them largelyof wood fibers, produced by grinding of raw wood. This material, known as the mechanical wood pulp, difi'ers from the chemical or sulfite pulp in that the fibers of this mechanical pulp, not having been subjected to the chemical process di 'estingretain the nature of raw wood. When waste papers, made partly of this mechanical wood pulp, are subjected to the action of such, or as strong solvents as are to be used in the processes heretofore known, or of such solvents heated, or under steam pressure, the raw wood fibers are discolored. This discoloration is very similar to that produced by exposing such papers to strong sunlight and cannot be obliterated, because the fibers of mechanical wood pulp are detrimentally affected by bleaching, and liable to be rendered thereby wholly unfit to be used again, except probably as a filler. The more concentrated, or the hotter the solvent is employed, the more intensive is its discoloring efieot, and the larger the proportion of the mechanical wood pulp is contained in the waste papers, the more pro- Specification of Letters Patent.

Application filed June 15, 1911.

Patented Oct. 6, 1914.

Serial No. 633,417.

nounced is the discoloring effect upon all the pulp recovered. The fibers of the so-called chemical pulp are not so discolored by these solvents, or by subjecting them to the action of such solvents in highly heated state, but as it is not practically feasible, to separate the fibers of this chemical pulp from those of the mechanical pulp, the processes, heretofore known, cannot be employed for the recovery of pulp from waste papers containing a percentage of the mechanical wood pulp, because the pulp thus recovered is reduced in quality to such an extent that it is no longer suitable for the manufacture oi? the same grade of paper for which it was originally used.

The object of this invention is to devise a process to recover also the fibers of this socalled mechanical wood pulp, without their being discolored or their suitability for use in the manufacture of the same grade of paper otherwise impaired.

Alkalis are most suitable for use as solvents in processes for the recovery of pulp from printed waste papers, but if used in solutions containing more than the equivalent of two parts of caustic soda to one thousand parts of water, or if weaker solutions are employed at a temperature of about 150 F., or more, they produce the explained discoloring effect upon the mechanical wood pulp which may be contained in such Waste papers. I found, by an extended course of experiments, that a solution of one, or even less than one, part of caustic soda, measured by weight, in one thousand parts of water, if employed in proportionate quantities, is, in

"most instances, sutticient to so diminish the adhesity of the oily medium of printers ink, and of the sizing, that the pulp fibers can be readily separated therefrom, and that a solution containing less than two parts of caustic soda, or its equivalent of other alkali, does not discolor the fibers of this mechanical pulp, unless heated to more than 150 F. Heating increases the intensity of the action of such a weak solution and causes it to produce, to a degree, the stated thereto, so proportioned that, taking in condiscoloring effect upon the fibers of the me: chanical wood pulp.

In place of caustic .soda, caustic potash may be used, and it should be noted, that line solutions or compounds, as for instance, carbonates of soda andof potash, or ammonia, are. effective in dissolving or saponifying the oily ingredients of printers ink and of the sizing, but they also have. a similar discoloring efiect uponthe fibers of the mechanical wood pulp, if used in solutions containing more than the equivalent of two parts of caustic soda to one thousand parts of water, or if a weaker solution of any of these alkalis is used hotter than 150 F. Also ammonia is not as efiective in discoloring the fibers of mechanical wood pulp when used diluted proportionately to the stated standard of two parts of caustic soda toone thousand parts of water. It is, however, not as certain in its effect upon the oily adhesive ingredients of printers ink as the equivalent solutions of caustic potash .or soda, or of their carbonates, and if? usedin a stronger solution, is apt to produce a yet darker brown discoloration of the fibers of the mechanical wood pulp.

The process of recovering pulp from printed waste papers, is best carried on, according to my invention, as follows: The waste papers are pulped in a beating engine and then conveyed to chests, provided with mechanical agitators. There a quantity of the caustic soda solution is added sideration the quantity of water contained in the beaten stock, and which averages about twenty-nine thousand pounds to each ton of such waste papers, there should be not more than two pounds of caustic soda, or its equivalent of some of the other alkalis, to one thousand pounds of water. It is necessary to explain, that in the course of the process, a part of the alkali, contained in the solution, is consumed in saponifying the oily and adhesive ingredients of the ink and sizing. Taking, as a' standard, a solution, containing one part of caustic soda (or its equivalent of other alkali), to one thousand parts of water, this consumption ofthe alkali amounts to from thirty-three to forty-one per cent, if a quantity (weight) of the solution, equal to fifteen times the weight of the paper stock treated, is used.

The percentage of the consumption will be l greater, if the solution is used in a smaller proportion, quantitatively, to the dry weight of the paper stock treated. Consequently,

a somewhat stronger or more concentrated solution may be employed at the start of the process, provided that it be used in a I,

suflicient quantitynot less than fifteen times the dry weight of the paper stockas the strength of the solution is quite rapidly diminished by the consumption of the, ,alkali contained therein. "When determin ing the initial strength of the solution, also the proportionate quantity of water, contamed in the pulped material, when it is run out from the beating engine, on the average of about fourteen and a half timesits weight, must be taken in consideration as diminishing the strength of the solution added thereto. The pulped material is thoroughly mixed and agitated in the solution and then the liquid is drained 0E, the pulped material conveyed upon movable screens and there washed with fresh clean water, whereby the carbon or other pi ments, and other impurities, are remove all traces of the alkali eliminated therefrom and the clean pulp fibers recovered. To-

be soaked in fresh water and drained, be-

fore being conveyed upon the screens. The pulp recovered from waste papers thus treated, may be conveyed to the paper making machine, or stored for future use; the fibers of the mechanical pulp contained therein are then and remain in such physical condition and color that the pulp can beused again as it was recovered, without any further treatment, in the manufacture of new paper of such a grade.

I claim as my invention:

'1. The process of recovering the pulp fro-m printed waste papers made in part of mechanical wood pulp, the process consisting of the following steps: (1? pulping waste papers; (2) steeping the pu ped material in a solution, made of not more than two parts by weight of caustic soda, or its equivalent of other alkali, to one thousand parts of water at a temperature of not more than about 150 F. and agitating it therein; washing the pulped material in fresh water; and (4') separating the pulp fibers from all impurities, and collecting the cleaned pulp, substantially as herein set forth.

2. The process of recovering the pulp from 'printed waste papers made in part of mechanical wood pulp, the process consisting of the following steps: (1) pulping the waste news print papers in a soluseparating the pulp from all impurities and tion, made of not more than two parts by collecting it; substantially as herein set Weight of caustic soda, or its equivalent of forth.

other alkali, to one thousand parts of water J OHN. M. BURBY. 5 at a temperature of not more than about Witnesses:

150 F.; (2) soaking and washin the I R. A. PIPER,

ipulped material in fresh water; all (3) VERONICA BRAUN.