US1579525A - Process for treating pulp - Google Patents

Description

Patented A r. 6, 1926.

UNITED STATES PA WILLIAM :0. camera WESLEY M. OSBQRNE, AND ALEX J. KEMZURA, OF NE WTON FALLS, NEW YORK.

PROCESS FOR TREATING PULZ.

No Drawing.

To all whom it may concern:

Be it known that we, WILLIAM D. Gnnoon, WESLEY M. OSBORNE, and ALnx J. KEMZURA, citizens of the United States, residing at Newton Falls, in the county of St. Lawrence, State of New York, and Newton Falls, in the county'of St. Lawrence and State of New York, and Newton Falls, in the county of St. Lawrence and State of New York, respectively, have invented certain new and useful Improvements in Processes-for Treating Pulp, of which the following is a specification. 5 Y

The present invention relates to processes for treating pulps ofvarious kinds used in the manufacture of paper, papier-mach and like materials, to aid the bleaching quality thereof.

More particularly the invention relates to processes for treating pulps prior to bleaching'thereof which have been roduced in any well known manner, such or example,

- as by the sulphite process, the soda process and the sulphate process, or other processes which leave the pulp with an excess of acid or alkali, in a mannerto neutralizet-he excess acid or alkali, and at the same time to set up reactions .with'the foreign coloring and other undesirable substances, such for example, as the lignine contained therein. These reactions form soluble compounds, and loosen and free-the foreign substances I from the fiber so that they may to a large extent, be removed by washing rather than depending upon bleaching to remove these impurities. The results attained. have been marked in reducing the amount of bleaching chemicals necessary, in the'ftime required to effect bleaching, and in the higher quality and greater strength of the fiberproduced, when the pulp is treated in accordance with the present invention beforebeing subjected to any 'of the well known bleachingproc esses.

The special treatments hereinafter setforth either soluble in certain dilute acids or alkalie's, or are converted into water soluble actions referred to predominate, and probably all three are present to produce the stock chest, the pulp is passed to the bleach 85 are based upon the facts that the vari-. ous' coloring matters contained therein are of the ad *hausted, and the pulpgis, pumped; from the" Application filed July 14, 1924. Serial No. 725,981.

highly beneficial results which have been attained in practice. In addition to the actions above referred to, if an excess of acids are present in the pulp, advantage is taken of the neutralizing effect by utilizing an alkali in the special treatment, while if an excess of alkalies are present, dilute acids are utilized.

Objects of the invention are to provide processes for treatin pulps in a manner to remove foreign su stances and produce higher grade stock; to' specially treat pulp prior to the bleaching thereof in a manner. to" reduce the amount of bleaching chemicals used; to specially treat pulp prior to bleachingin a manner to produce hi her rade and stronger bleached fibers than ave een heretofore produced, and such other objects as may be attained by utilization of the various steps hereinafter set forth and claimed.

In practice, after the stock is reduced to pulp in the digestors, it is passed into blow pits and the blow liquors are washed out in well known manner. After the blow liquors have been washed out, it is common practice to pump to a stock or storage chest, and fro-m the ing apparatus as needed. In the preferre embodiments of the present invention, the special treatment. is applied between the blow pit washing system and the bleaching system. A storage vat is (preferably provided into 'which the washe pulp from the blow pit is flowed, and from which the pump feeding the stock chest is supplied. After the washed pulp from the blow pits the cooking liquors are washed from the pulp, a dilute solution of acidor alkali in accordance with the alkali or acid nature of the pulp, is slowly and continuously supplied to and mixed with the pulp either in the blow pit, or as it flows to the storage vat. Because of the greater concentration of pulp in the blow pit after washing, the

solution is preferably added at this point.

In this manner the solution is more active for a short time, and becomes more diluteas the stock passes through the system. Thevarious' actions and reactions above referred to, due to the addition of the solution. then roceed until the chemical action ed solution-is substantially 'ex-' storage vat to the stoe chest.

In the treatment of sulphite pulps, a solution in the proportion of one pound of sodium carbonate to three gallons of water has been found to give excellent results, when applied to the pulp at the rate of eighteen gallons for each ton of air dry fiber. This solution is preferably heated to the boiling point before being mixed with the pulp. It is to be noted that this amount of heated solution added to the pulp in the amount given above will not heat the mass appreciably above normal temperatures. It has been found that above a certain strength of solution, no beneficial results are attained as the main actions and reactions are produced with a small percentage of alkali. Excellent results are also attained with sulphite and acid pulp by the use of potassium carbonate, caustic soda, caustic potash, and by various combinations of these alkalies, but sodium carbonate and potassium carbonate are preferably used. Although a proportion of six pounds of alkali dissolved in eighteen gallons of water, to each ton of air dry sulphite pulp has been given, it will be understood that these quantities may be varied within Wide limits for different pulps, and the best proportions for each kind of pulp and each kind of alkali are most conveniently determined by trial, because of the Wide Variations in acidity, in impurities, and in quality of commercial alkalies.

A similar treatment is carried out using dilute acids at this stage, for alkaline pulps, such as are produced by the soda and sulphate processes. In this case dilute acids are applied to the pulp. Sulphurous acid with calcium as a base, such as the well known bisulphite cooking acid, or dilute solutions of acids formed from sulphur dioxide, trioxide, or the salts compounded therefrom, such as bisulphite of calcium, bisulphite of soda, and the sulphites of sodium and calcium, are effectively used.

An effective solution for the treatment of soda and sulphate pulps has been found to consist of three tenths of a pound of sodium carbonate for each gallon of water, treated with S0 gas to a point where the solution still shows a slight alkaline reaction. It has also been found that beneficial results are attained by treating the stock directly with SO gas, but the solution is most effective and most convenient.

In the stock chest the reactions are completed. As the material passes through the system, properly treated material shows increasingly faint reactions, and'the stock is tures with an alkaline so diluted by water as to have no harmful effect on the strength of the fiber. As the pulp is drawn from the stock chest and passed to the bleaching apparatus, the alkali or acid together with the free and soluble coloring matter and foreign substances formed in the reactions are washed out, the pulp is thickened and screened, and then is ready to be bleached by anv of the known processes. Any well known form of washing and thickening apparatus may be employed.

Actual mill tests on sulphite pulp have shown a saving of 23.2 per cent in bleach on spruce pulp, 31.9 per cent on hemlock, 14.8 per cent on poplar, and 17.4 per cent on hardwood pulps when treated in accordance with the present invention over the amount of bleach used in bleaching like pulps by the same method, but not treated in accordance with the present invention.

Having described preferred embodiments of the invention, what is desired to be sccured by Letters Patent and claimed as new is:

1. In the process of preparing digested paper pulp for bleaching, the step which comprises treating the pulp at about normal temperatures with an agent capable of converting impurities contained in said pulp into water soluble compounds.

2. In the process of preparing sulphite pulp for bleaching, the step which comprises treating the pulp at about normal temperamaterial to convert impurities contained in said pulp into water soluble compounds.

3. The process of preparing digested paper pulp for bleaching, which comprises treating the pulp at about normal temperatures With an agent capable of converting impurities contained in said pulp into water soluble compounds, and washing the thus treated pulp to remove the impurities therefrom.

4. The process of preparing sulphite pulp for bleaching which comprises treating the pulp at about normal temperatures, W1th a solution containing an alkaline material capable of converting impurities contained 1n said pulp into water soluble compounds, and Washing the thus treated pulp to remove the impurities therefrom.

In testimony whereof, I afiix my signature.

V. D. GREGOR. In testimony whereof, I affix my signature. 7 \V. M. OSBORNE. In testimony whereof, I aflix my signature.

ALEX I. KEMZURA.

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