US1572840A

US1572840A - Production of pulp

Info

Publication number: US1572840A
Application number: US705711A
Authority: US
Inventors: Bradley Linn; Edward P Mckeefe
Original assignee: Individual
Current assignee: Individual
Priority date: 1921-03-28
Filing date: 1924-04-10
Publication date: 1926-02-09
Anticipated expiration: 1943-02-09

Description

Patented Feb. 9, 1926.

UNITED STATES PATENT OFFICE.

LINN BRADLEY, E MONTGLAIR, NEW JERSEY, Aim DWARD P. McKEEFE, or PLATTS- BURG, NEW YORK.

PRonuo'rroN 0E PULP.

No Drawing. Original application filed March 28, 1921, Serial No.'456,187. Divided and this application filed April 10, 19-24. Serial No.'7 05,711.

respectively, have invented certain new and useful Improvements in the Production of Pulp; and we do hereby declare the following to be a full, clear, and exact descrlptlon of the invention, such as will enable others skilled in the art to which it make and use the same.

This invention relates to improvements in processes of cogking wood chips and similar material for the production of Wood cellu lose products or pulp.

The present invention includes a new method of cookin or digesting Wood chips in'ivhich the cooking liquor is an alkaline liquor containing a thiosulfate of an alkali, or both a sulfite and a thiosulfate of an alkali. This method is distinguished by the fact that caustic soda is present in sufficient amounts to give an alkaline cooking liquor of appropriate strength, while sodium thioappertains, to

sulfate,'or both sodium sulfite and sodium thiosulfate, is or are also present in substantial amounts. The composite cooking "liquor, containing caustic soda and sodium thiosulfate, or containing caustic soda together with sodium sufite and sodium thiosulfate,' can vary somewhat in, its composi tion and in the proportions of caustic soda and of sodium thiosulfate, or of sodium thiosulfate and sodium sulfite. Ordinarily a preponderating proportion of caustic soda will be used, forexample, so that from 50 to 90% of the total sodium of the cooking 40 liquor will be present as caustic soda and the remainder mainly as sodium thiosulfate, or

as sodium sulfite and sodium thiosulfate.

- A cooking liquor may thus be used containing at least 40 gr. of sodium per liter, pf which at least40% is present as sodium hydroxide and at least 5% as sodium thiosulfate, or as sodium sulfite and sodium thio sulfate, with the articular amounts of caustic soda and so ium thiosulfate, or of sodium thiosulfate and sodium sulfite, varying somewhat above these percentages. The amount of cooking liquor ma be about 700 to 1100 gallons or a cord 0 wood (measured before chipping), the liquor containing the higher percentages of caustic soda being used in smaller amount, and those containing the smaller percentages of caustic soda being used in larger amount. By the use of such an alkaline cooking liquor containing thiosulfate, or thiosulfate and sulfite, it is possible to produce satisfactory pulp or cellulose material from forest prod nets and other cellulose-bearing materials which, due to their inherent composition and properties, have been unsuited to the production of high grade cellulose material by the processes heretofore commonly practiced. Materials such as woods and other forest material of inferior value (for treatment according to common methods) as well as materials such as bagasse, reeds, grasses, bamboo co'rnstalks, straw, etc., can advantageously be subjected to digestion with such a'lkaline thiosulfate, or sulfite and thiosulfate, cooking liquor and high grade pulp or cellulose material produced therefrom.

This method, therefore, increases the available supply of raw materials for the ductlon of high grade pulp or cellulose products.

In carrying outthe digestion with such an alkaline thiosulfate liquor, or with such an alkaline sulfite and thiosulfate liquor, the time of treatment and the temperature, pressure, etc.', can be varied depending upon the particular wood or other material un dergoing digestion; but the process can becarried out under similar conditions of temperature and pressure to those commonly used in the soda process, e. g., by heating the digester by direct steam at a pressure which may vary for about 90 to 140 lbs, and with circulation of the liquor within the digester by the steam duringthe digestion. The digestion will, however, be modified by the action of the composite cooking liquor so "that less injury to the cellulose material will take place and so that a superior pulp or cellulose material will be produced.

According. to the present invention, accordingly, the alkaline cooking liquor may be composed of caustic soda and sodium thioslufate, or it may be composed of three ingredients, namely, caustic -soda, sodium sulfite and sodium thiosulfate. The liquor may also contain other compounds than 4 prothose mentioned, such, for example, as sodium sulfate, sodium carbonate, or sodium sulfide.

Our investigations have shown that if some untreated black liquor is mixed with new cooking liquor containing caustic soda,

a portion of the caustic soda is used up in the formation of other sodium compounds by reaction either directly or indirectly between the caustic soda. and soluble organic compounds, so that the total content of caustic soda is not available for cooking the wood chips in the same way that it would be if no such soluble organic constituents were present. Sodium sulfite and sodiumthiosulfate exert a retarding influence upon the reaction between the caustic soda and the soluble organic compounds, and likewise upon the cellulose, so that the caustic soda can act more efiectively, and so that the destructive action for the same total amount of caustic soda is minimized.

The present application is a division of our 'r1or application, Serial No. 456187, filed arch 28, 1921.

We claim:

1. The improvement in the production of pulp, which comprises subjecting the wood chips in the digester to the action of a cookliquor containing caustic soda and,

m sodium thiosulfate, thecaustic soda being present in preponderating amount.

2. In the preparation of chemical pulp, the use of a cooking li uor comprising sodium hydroxide and so ium thiosulfate, the sodium hydroxide being used materially in excess of the amount, required to decompose silicates and aluminates. in the material treated.

3. In the preparation of chemicaljpulp,

the use of a cooking liquor comprising a hydroxide and a thiosulfate,-the hydroxide being used materially in excess of the amount required to decompose silicates and aluminates in the material treated.

4. In the preparation of chemical pulp,

the use of a cooking liquor comprising a 7. The improvement in the production of pulp, which comprises subjecting wood chips to digestion with a-cooking liquor containing caustic soda and sodium thiosulfate, the cooking liquor containing at least 40 grams of sodium per liter, of which at least 40 per cent is present as sodium hydroxide and at least 5 per cent as sodium thiosulfate.

8.' The method of minimizing the destruc live action of caustic soda upon the soluble organic compounds of wood in the cooking of wood chips, which comprises cooking the chips with a caustic soda cooking liquor con taining sodium thiosulfate in amount less than that ofthe caustic soda.

In testimony whereof we hereunto afiix our signatures.

LINN BRADLEY. EDWARD P. MoKEEFE.