US1910613A - Preliminary boiling or cooking process for cellulose - Google Patents

Description

Patented May 23, 1933 KARL an; or nnnsmcrrons, rm'nann PRELIMINARY BQILING OR COOKING- PROCESS EQR, CELLUL OSE No Drawing. Gontinuatlon at application Serial Ito. 259,921, filed march 7, 1928, and in Finland March 17, 1927. This application filed June 2? 1932. Serial No. 619,612.

- The present application is a continuation of my co-pending application Serial No. 259, 921, filed March 7, 1928, and relates to the production of cellulose sulphite. More particularly, the present invention relatesto the provision of a shorter cooking period, a greater yieldof cellulose, and a lower loss of fibers in the waste lyes than is possible according to any of the reviously known proc esses. At the same time, the quality of the cellulose is maintained substantially unimpaired, g

To the end of carrying out the invention, it is contemplated that the chips be impregnated either with gases, such for instance as ammonia gases, sulphurdioxide gas, nitrous acid gas, and acetic acid gas, or liquids containing acetic acid or salts such as acetates or phosphates, or a mixture of the acids and 21D salts, so that the resinous and fatty materials are dissolved. This action taking place prior to the main cooking process. The liq-' uids employed for the preliminary treatment do not materially afiect the chips, being 25 adapted primarily for dissolving the resinous and fatty substances contained therein.

After such impregnation, the pro-cooking liquid is pressed into the pores of the chips in any desired manner, as by pneumatic, gas, or steam pressure, and then cooked. During this pre-cooking treatment, the liquids, depending upon the kinds of wood undergoing treatment, are either slightly alkaline, neutral, or slightly acid.

It is also possible for the impregnation to take place by pressure in the absence of boiling, so that heat is used only during the subsequent or main cooking, in order to accelerate the main boiling ppocess.

After a thorough lmpregnation of the chips in the preliminary treatment, the pressure in the cooker is preferably returned to the atmospheric value, whereupon the chips, remaining in the cooker without subsequent 5 washing, are filled up, dependent upon the type of cellulose to be made, with either alkaline or acid cooking-lyes, whereupon subsequent cooking takes place.

When either the Mitscherlich or indirect process, or the Ritter-Kellner or direct cooking process, the two processes previously used in commercial practice, is employed, a working pressure of approximately 4: to 6 atmospheres, and a temperature ranging sary with the prior, direct process. In addition, the yield of cellulose is increased to approximately 48 to 52%, the loss of fibers in the waste lye is no more than from 2 to 3%, and the tearing length varies between 8 and 9000 meters.

With my process the novel advantage is obtained that if the boiling lye employed in the preliminary treatment is replenished by a quantity of gas or liquid corresponding to that absorbed by the chips during the impregnation treatment, this boiling lye can be employed several times, merely by circulation from one cooking to another.

llt is to be distinctly understood that it is desired to dissolve the resins and fats in the fibers in order that the fibers can then be lined with the acetic acid, acetates, phosphates orother materials contained in the preliminary treatment. It is not sufiicient to place this treating material in the ultimate or final bath, for then, the hydrogen or hydroxyl ions in the lye penetrate more rapidly than do the ions of the protective material, so that undesirable charring can not be avoided at the elevated temperatures and pressures that I desire to'employ.

However, when the pre-treatment accordmg to my invention is employed, for example, with the addition of natron lye, phosphates, acetic acid, or acetates, then the temperature in the subsequent or main cooking treatment, with for example, calcium-magnesium, or sodium-sulphite, may be raised without danger to say 170 (1, while the pressure can be elevated to as high as 8 atmospheres. With such raise in the temperatures and pressures, the cooking is greatly accelerated, without deterioration of the quality of the cellulose,

an accomplishment unobtainable in the previous process, not employing my preliminary treatment; and any attempt at such accelerated cooking was always accompanied by black boiling. One of the greatest advantages of my invention is that despite the raised temperatures and pressures employed, and consequent acceleration of the process, the quality of the cellulose nevertheless remains extremely high.

Especially when phosphates are employed in the pre-cooking, this pre-cooking material remains in the fibers to protect them during the high temperaturesmaintained in the main boiling process, it of course being necessary to observe the precaution that the material undergoing treatment is not washed between the preliminary and the main cooking processes.

Merely by way of example, the following three examples of my invention are given.

Example 1 1000 kg of chips are impregnated for from 1 to 3 hours at a temperature above 100 C. and at a pressure of 4 to 8 atmospheres with solutions of the acetates of calcium, magnesium, sodium or other compositions which act in the same way and manner. The hot lye is then introduced into the next following cooker, which is filled anew, and the chips are impregnated in the same manner pointed out above. The impregnation is followed, without subsequent washing, by a main cooking with bisulphite of calcium, sodium or magneslum.

' The cooking period in accordance with the direct rocess is 7 to 8 hours, including the pre-coo mg.

Example 2 positions acting in a similar way or manner.

The hot lye is then introduced into the succeedmg cooker, and without subsequent washs ing, an acid or alkaline cookingmethod fOlfi/ lows.

The process may also be carried out by introducting acetates and phosphates into the pores of the chips by means of gas, air, or hydraulic pressure, whereupon a slightly alkaline, neutral or acid cooking process follows.

Example 3 1000 kg chips are impregnated for 1 to 3 hours at a temperature above 100 C. and a pressure of 2-8 atmospheres with soda solutions, which have been neutralized or made slightly acid by organic gases or liquids (for instance acetic acid or acetic acid gas) where'- upon a cooking with bisulphite of magnesium takes place, accomplished by means of comminuted magnesite, without subsequent washing.

It is of course obvious that the foregoing examples are by no means exhaustive of the various possible ways of carrying my invention into practice, and that numerous variations of the process, within the scope of the invention, will readily occur to those skilled in the art upon perusal of my disclosure. Accordingly, it is contemplated that the invention be limited only by the scope of the appended claims.

I claim:

1. The process comprising saturating cellulosic material with a liquid containing at least one substance selected from the group comprising acetic acid, natron lye, acetates, and phosphates, and thenboiling the material without previous washing in'a bisulphite digesting liquor at a temperature materially higher than 130 C. and a pressure of materially higher than 4 to 6 atmospheres.

2. The process comprising saturating cellulosic material with a liquid containing at least one substance selected from the group comprising acetic acid, natron lye, acetates, and phosphates, and then boiling the material without previous washing in a bisulphite digesting liquor ata temperature 1n excess of 130 to 145 C. and pressure in excess of 4 to 6 atmospheres, and not materially greater than 170 C. and a pressure of approximately 8 atmospheres.

3. The process comprising saturating ce1 lulosic material with a liquid containing at least one substance selected from the group comprising acetic acid, natron lye, acetate, and phosphates, and then boiling the material without previous washing in a bisulphite digesting liquor at a temperature of approzimately 17 0 C. and a pressure of approximately 8 atmospheres.

4. The process comprising saturating cellulosic material with a liquid containing acetic acid, and then boiling the material without previous washing in a bisulphlte digesting liquor at a temperature of approximately 170 C. and a pressure of approximately 8 atmospheres.

5. The process comprising saturating cellulosic material with a liquid containing acetates, andthen boiling the material without previous washing in a bisulphite digesting liquor at a temperature of approximately 170 C. and a pressure of approximately 8 atmospheres.

6. The process comprising saturating cel lulosic material with a liquid containing phosphates, and then boiling the material without previous washing in a bisulphite dige'sting liquor at a temperature of approximately 170 C. and a pressure of approximately 8 atmospheres.

7. The process comprising saturating'celacetates and phosphates, and then boiling the material without previous washing in a bisulphite digesting liquor at a temperature of approximately 17 0 C. and a pressure of aproximately 8 atmospheres.

8. The process comprising saturating cellulosic material with a liquid containing acetic acid and phosphates, and then boiling the material without previous washing in a bisulphite digesting liquor at a temperature of approximately 17 0 C. and a pressure of approximately 8 atmospheres. r

9. The process comprising saturating cellulosic material with aliquid containing acetic acid and acetates, and then boiling the material without previous washing in a bisulphite digesting liquor at a temperature of approximately 170 G. and a pressure of approximately 8 atmospheres. v

10. The process of preparing cellulose, comprising saturating cellulosic material in. a liquid containing a mixture of substances selected from the group comprising acetic acid, acetates, natron lye, and phosphates, and then boiling the material without previous washing in a hisulphite digesting liquor at a temperature of approximately 170 C. and a pressure of approximately 8 atmospheres.

11. The process of producing cellulose, comprising saturating .cellulosic material with a liquid containing phosphates, to dissolve the resinous and fatty materials therein and to form a protective lining on the interior of the fibers, and then boiling the material, without previous washing, in a loisulphite digesting liquor at temperatures and pressures materially in excess of those employed in the previously known processes In testimony whereof I have signed my name to this specification KARL YRJU KYLANDER.