US2673798A - Deinking - Google Patents

Description

Patented Mar. 30, 1954 OFFICE DEINKING Jean Ernest Ziindel, Kayserberg, France, and Robert S. Aries, Brooklyn, N. Y.

N Drawing. Application July 20, 1949, Serial No. 105,913

3 Claims. (Cl. 92-'-1.5)

This invention relates to deinking of waste paper and more particularly to deinking of newsprint.

Many processes and compositions are found in the prior art that have as their object the recovery of newsprint in re-useable form. In order to be re-useable the recovered pulp should possess a whiteness equal to or approaching that of the original unprinted sheet. This desired result is very difficult to attain with newsprint, because newsprint is generally composed of about 75 per cent ground wood pulp and about 25 per cent sulfite pulp, i. e. wood pulp obtained by the chemical sulfite process for dissolving out the lignin constituents. As is commonly known ground wood consists of small slivers of wood rubbed from a pulp wood log by means of frictional pressure between the log and a pulp-stone. The slivers have'jagged sawtooth ends and there by afford excellent crevices for trapping the carbon particles of the printers ink used in printing newsprint. Because of this trapping effect of ground wood for carbon particles substantially all prior art newsprint recovery processes failed to produce a re-useable pulp of a high quality of whiteness, but instead produced a dull greyish sheet.

In order to obtain a high quality white pulp we have found it desirable to attack the problem in a threefold manner, viz. (a) a chemical agent to partially disintegrate the binder and facilitate carbon removal, (b) a mechanical aid whichremoves the pigment by friction and (c) a physicalchemical agent to emulsify the insoluble sub.- stances in a colloidal form thereby rendering the colloidal particles to be freely dispersed and substantially non-retainable in the web of the recovered stock.

In performing our process the newsprint is shredded and then mixed with a solution of alkaline agent substantially of the following composition:

Per cent Alkali extract of coniferous bark 0.25 Detergent (such as sodium silicate, sodium carbonate, trisodium phosphate, etc.) 0.5 Caustic soda 0.1

A method for obtaining bark extract suitable for our purposes is to steam the coniferous bark for about 2 hours at a pressure of about 6 atmos pheres whereupon the bark is ground to a powder by any suitable means. About 100 grams of ground bark are extracted with about 400 cc. of about 10 per cent caustic soda, and while a continuous system of extraction is preferred, intermittent extraction methods are also within the contemplation of this invention. If continuous extraction is used, the alkali solution may be continuously allowed to flow by means of gravity through a tall column containing the bark until substantially all the extractives have been extracted. The extracted bark is then washed with water and the solution plus wash waters is brought up to a total volume of 8,000 cc.

This extraction procedure can be done hot or cold, but hot solutions are preferred because greater amounts of emulsificants are extracted thereby.

The degree of dilution of the 400 cc. of 10 per cent caustic soda extract varies with the species of conifer used in the extraction process. The dilution to 8,000 cc. being a good average concentration for effective deinking purposes, but a dilution of the 400 cc. of extract from 100 grams of pine bark to 12,000 cc. is feasible. Furthermore the 400 cc. alkaline extract from spruce may be effectively diluted to 24,000 cc. thereby producing an effective deinking concentration, while 400 cc. of alkaline extract of fir may be diluted to 35,000 cc. and yield an equally effective emulsificant.

The newsprint to be pulped is added to the diluted emulsificant .mentioned above to give a pulp concentration of from 5 to '7 per cent; thus about 400 to 500 grams of newspaper are added to 8,000 cc. of emulsificant. This mixture of newspaper and emulsificant is then disintegrated by any suitable means as for example a beater, hydrapulper or the like. The pulp is then dewatered to a concentration of about per cent in a screw press, vacuum filter or other means and then washed free from carbon particles. The washed pulp has substantially the whiteness of the original newspaper pulp. If there be a slight yellowing due to caustic soda, it may be corrected by the addition of a small amount of sodium acid sulfite solution.

The waste liquor obtained after the extraction process may be regenerated for re-use by first diluting about 300 00., with fresh 10 per cent caustic soda to a total volume of 400 cc. One hundred grams of steamed, ground coniferous bark is then extracted with this regenerated solution and the extract with its wash waters are diluted as previously noted to about 8,000 cc. In this regeneration process the carbon black particles are retained by the ground bark. When using the regenerated process, the average fresh bark consumption amounts to about 6.2 per cent of the weight of newsprint deinkedand the caustic soda consumption amounts to about 3.25 per cent of the weight of the newsprint deinked. Repeated use of the regenerated solution tends to concentrate the coniferous emulsificants, so that the amount of fresh bark required may be substantially less than the 6.2 per cent mentioned above. The bark extract may be obtained from wood pulp operations wherein coniferous logs are steamed in order to assist in the debarking of the logs, yielding a waste bark ideally suitable for deinking purposes. Steaming of coniferous bark at pressures from substantially zero to 10 atmospheres for periods of 1 to 4 hours is practical but bark steamed at about 6 atmospheres and for about 2 hours is preferred.

If non-steamed bark is used, the caustic extract has a marked reddish brown color which is imparted to the recovered newsprint. Steamed bark on the other hand gives a substantially colorless extract of greater efficiency and stability. Furthermore the steaming process facilitates the rapid extraction with the 10 per cent caustic soda since the steaming makes the ground bark more porous.

Bark as normally obtained in the air dry condition is used. Moreover, the steaming and extraction procedures may be conducted in the same extraction apparatus. Furthermore, while we prefer caustic soda as our source of alkalinity for the extraction process and admix therewith such alkaline detergents as sodium silicate, trisodium phosphate, sodium carbonate, etc., we have found that use of said alkaline detergents, without addition of excess caustic soda, but admixed with coniferous bark extract will also remove carbon particles, though not quite as effectively a when added caustic is present.

Thus bark extracted with, for example, a solution of trisodium phosphate yields a solution effective in the removal of carbon particles from newsprint.

This invention has been illustrated by means 51 of embodiments thereof but it is to be understood that the scope of the invention is not limited to the illustrative embodiments herein presented.

We claim: I 1. The process of de-inking newspaper slurry comprising emulsifying the ink particles in said slurry with an emulsifyin solution consisting 01' a caustic soda extract of steamed resinous coniferous bark.

2. The process of de-inking newspaper slurry comprising emulsifying the ink particles in said slurry with an emulsifying solution consisting of a caustic soda extract of steamed resinous coniferous bark, separating said emulsifying solution from said slurry, and regenerating said emulsifying solution by passing it through a column of steamed comminuted resinous coniferous bark.

3. The process of deinking newspaper consisting essentially of shredding the newspaper, emulsifying the ink binder of said newspaper with an 0.25% alkaline aqueous extract of steamed resinous coniferous bark, beating the shredded particles to separate the wood fibers and also the emulsified ink particles, dewatering the disintegrated stock to remove the emulsified solution containing ink particles, and washing said dewatered stock to float away any residual ink particles. I

JEAN ERNEST ZiiNDEL. ROBERT S. ARIES.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 228,955 Terne June 15, 1830 354,855 Friede Dec. 21, 1886 1,281,670 Schmid Oct. 15, 1918 1,572,478 Hammond Feb. 9, 1926 1,601,193 Welsh Sept. 28, 1926 1,925,372 Darling Sept. 5, 1933 1,933,227 Snyder et a1. Oct. 31, 1933 1,933,228 Snyder et a1. Oct. 31, 1938 2,018,938 Wells Oct. 29, 1935 2,116,511 Earle May 10, 1938 2,220,950 Bird Nov. 12, 1940 2,346,909 Dahl-Rode Apr. 18, 1944 2,403,143 Tutt July 2, 1946 2,505,818 Williams May 2, 1950 OTHER REFERENCES Printing Inks, by Ellis, published by Reinhold, New York (1940) pages 480, 481.

Whittaker and Bates: Chemical Utilization of Southern Pine Waste, The Journal of Industrial and Engineering Chemistry, vol. 6, No. 4, April 1914, pp. 289298 (of which pp. 297-298 are relied upon).

Claims (1)

1. THE PROCES OF DE-INKING NEWSPAPER SLURRY COMPRISING EMULSIFYING THE INK PARTICLES IN SAID SLURRY WITH AN EMULSIFYING SOLUTION CONSISTING OF A CAUSTIC SODA EXTRACT OF STEAMED RESINOUS CONIFEROUS BARK.