US2407909A

US2407909A - Purification of crude cellulosic material

Info

Publication number: US2407909A
Application number: US357281A
Authority: US
Inventors: George P Vincent; Archie L Dubeau
Original assignee: Mathieson Alkali Works Inc
Current assignee: Mathieson Alkali Works Inc
Priority date: 1940-09-18
Filing date: 1940-09-18
Publication date: 1946-09-17
Anticipated expiration: 1963-09-17

Description

Patented Sept. 17, 1946 PURIFICATION OF CRUDE CELLULOSIC MATERIAL George P, Vincent, Poughkeepsie, N. Y.-, and ArchieL. Dubeau, Rumfcrd, R. I., assignors to The Mathieson Alkaii VJorks, Inc., New York, N. Y, a corporation of Virginia,

No Drawing. Application September 18, 1940-, Serial No. 357,281

4 Claims. 1

This invention relates to the purification of crude cellulosic vegetable material, such as ground wood, cotton linters and carding waste, which contain large proportions of natural noncellulosic impurities such, for example, as lignin. The invention contemplates the production from such materials of relatively pure cellulose suitable for acetylation, nitration and other uses, including paper manufacture. In one of its aspects, the invention contemplates improvements for controlling the viscositycharacteristic of the. celluloss product.- l I In accordance with our invention, the crude cellulosic vegetable material to be purified, for example ground wood, cotton linters, carding Waste, bagasse and the like, is subjected to a twostage steaming while impregnated'with hot aque-' ous liquors. In the first of said stages the material is exposed to the action of steam while impregnated with a decidedly alkaline aqueous solution ofcaustic soda, that is, one containing at least about 4% of caustic soda. in the second steaming operation the material, arteran intermediate water washing, is exposed to the action of steam while impregnated with an acid aque-. ous solution sediuin chlo'rite, in amount effective to eliminate a substantial part of the non-cellulose impurities remaining in the material; These steaming operations are carried out in a steam chamber and are of considerable duration, gen-* erally of the order of a half-hour or more. With cotton linters, carding waste and similar lowgrade cotton plant Icy-products, the preferred preliminary treatment involves exposure in the presence of steam'to the action of a hot alkaline aqueous solution containing a detergent.

Control of the viscosity characteristic of-the cellulose product may be accomplishedadvantageously by treating the cellulosic material, prefera-bly at an intermediate stage, with an aqueous hypochlorite solution pre'ferably in a cold state. Thus, sodium hypochlorite solutions tend to reduce the viscosity characteristic of the cellulose and also aid in impurity removal. When control of the viscosity characteristic important, as when the purified cellulose is to be converted into nitrate, acetate or other esters, hypochlorite treatment is especially recommended, for by regulating the contact of the material with the hypochldrite through control of the time of treatment or the concentration of the hypochlorite, Viscosity characteristics maybe altered at will.

To consider in somewhat greater detail the purification of linters and similar low-grade byproducts of cotton ginning, carding and similar cotton-cleaning processes, our preferred preliminary treatment involves stearning the material while it is impregnated with a decidedly'alkaline solution, containing at least 4% caustic soda, and also containing a suitable detergent, i. e., one that is active in alkaline solution. A wide variety of detergents may be employedsince common soaps and numerous synthetic detergents are activ in alkaline solution. If hypochlo'rite treatment is employed, this should follow the alkali-steaming stage. In any case, thelater treatment involves the exposure of the material, in the presence. of steam, to the action of a hot acid solution containing sodium chlorite and, preferably, also containing a detergent that is active in acid-solution,

, such,.for example, as sodium ocenol sulfates, boro iii) cetyl alcohol and sodium alkyl sulionate benzene.

Certain synthetic organic detergents, for example, .Modinalfl which is a completely sulfated sodium ocenol sulfate, are active in acid and a1- kaline solutions and may be employed in the preliminary alkaline stage and in the acid-chlorite stage.

Alkalinity may be imparted to the preliminary treatment liquors with various reagents, but so dium hydroxide is preferred.

. A- Variety of acids may be employed to acidify Example A.-Two-stage' treatment for raw cotton linters A quantity of linters is immersed in a solution containing 12% sodium hydroxide, and .5% of a detergent, say, Modinal/i After immersion, the linters are squeezed to drive out excess solution and leave a ratioot two parts by Weight of solution to one part by Weight of solid. The resulting Wet linters is then introduced into a steam chamber and held at 100 C. for about onehalf hour in the presence of the steam. "Thereafter, the partially purified linters is Washed with hot water.

- The washed linters is immersed in a solution containing 1% available chlorine (C12) as sodium chlorite, 5% of a suitable detergent, say Modinal, and 3% by weight of acetic acid (56% strength). The linters is then squeezed to remove excess solution and leave a ratio of two parts by Weight of solution to one part by weight of solid. The wet linters is then held at a tem- Example B.-Three-staqe treatment of raw cot-- ton linters In this instance, a mass of dry raw linters was immersed in a solution containing 8% sodium hydroxide and .5% Modinal. It was then squeezed to leave two parts by weight of solution to one part by weight of solid and the resulting wet pulp was held for one-half hour at 100 C. in a steam chamber. It was then washed in hot water.

The washed mass was immersed in a 1% by weight aqueous solution of sodium hvpochlorite and then squeezed to leave a 2:1 liquor to solid ratio therein. The squeezed mass was left at room temperature (approximately 30 C.) for about half an hour and then washed in cold water.

The washed mass from the second-stage was immersed in the solution containing .5% available chlorine as sodium chlorite, .5% Modinal and 1% acetic acid (56%). After immersion, the mass/Was squeezed to remove excess liquor and leave a ratio of 2:1 liquor to solids. Thereafter, the mass was held at 100 C. for about half an hour in a steam chamber and finally washed with hot water.

The resulting product was satisfactory for use in acetylation, nitration and the like, and was fully as white asv standard purified linters employed heretofore in such processes.

Very low-grade linters (cotton seed hull fiber) containing an especially high proportion of impurities may also be treated advantageously in accordance with the process of our invention in two or three stages.

Example. C,--Two-stage treatment of low-grade linters A mass of dry linters (cotton seed hull fiber) was immersed in an aqueous solution containing 12% sodium hydroxide and .5% Modinal and squeezed to remove excess liquor and leave a 2:1 liquor. to solid ratio. The mass was then held at 100 C. for about half an hour in a stem chamber and thereafter washed in hot water.

The washed mass was immersed in an aqueous liquor containing 1% available chlorine as sodium chlorite, .5% Modinal and 3% acetic acid (56%). After immersion,'the mass was squeezed to remove excess liquor and leave a 2:1 liquor to solid ratio. The mass was then steamed in a chamber for one-half an hour at 100 C. and finally washed with hot water.

The resulting cellulose was suitable for acetylation and compared favorably in whiteness with that produced according to Examples A and B from ordinary raw linters.

Example D.Three-stage treatment of loin-grade raw linters mersed in a sodium hypochlorite solution containing 1% available chlorine and, as in the previous cases, thereafter squeezed to leave a ratio of 2:1 liquor to solids. The squeezed mass was then held at room temperature for half an hour and thereafter washed with hot water. 1

In the third stage, the mass from the previous treatments was immersed in a solution containing .5% available chlorine as sodium chlorite, .5% Modinal and 1% acetic acid (56%). After immersion, the mass was squeezed to leave two parts by weight of liquor to one part by weight of solids and the mass was then held at 100 C. for about one-halfhour in the steam chamber. hot water.

The resulting cellulose had a whiteness of and was at least as good as that heretofore customarily employed in acetylation.

Linters which have been cooked in the usual way and so partially cleansed may also. be treated with advantage in accordance With our invention. Such treatment, however, need not employ such strong solutions as those employed in the treatment of raw and low-grade linters. Treatment of cooked linters in accordance with ourinvention is illustrated by the following example:

Example E.--Two-stage treatment of cooked linters The washed linters was immersed in a solution containing 25% available chlorine as sodiumchlorite, .5% Modinal and .5%" acetic acid (56%). After immersion, the mass was squeezed to leave two partsby weight of liquor' to one part by weight of solids and thereafter held for about one-half hour at C. in a steam chamber. After heating, the material was washed with hot water.

As in the previous cases, the resulting product was comparable with'cotton linters heretofore employed for acetylation purposes and was of standard whiteness.

' In the treatment of low-grade cotton byproducts, such as carding waste, the process of the invention also offers advantages. Applica- Y tion of the process to carding waste with a very high percentage of impurities and which contained whole seeds is illustrated by the following example:

Example F.T'wo-stage treatment of carding waste The dry carding waste (card strip waste) was immersed in a solution containing 8% sodium hydroxide and .5% Modinal, squeezed to leave a 2:1 liquor to solid ratio and held at 100 C. for about one-half an hour in a steam chamber. It was then washed with hot water.

The washed material was immersed in a solution containing 1% availablechlorine as sodium chlorite, .5% Modinal and 2% acetic acid (56%). After immersion, material was squeezed to leave a 2:1 liquor to solid ratio, held at 100 C. for about one-half hour in a steam chamber and thereafter washed with hot water.

Finally, the mass was washed with The resulting material was bleached to a color as good as that obtained in the foregoing examples and in general all non-:cellulosic impurities were removed. The product contained a few partially bleached hulls.

We claim:

1. A process for purifying crude cellulosic vegetable materials which comprises impregnating said material with an alkaline aqueous solution containing about 4 to 12% of caustic soda, discharging solution from the material until the ratio by weight of solution remaining in the mat rial to the material is about 2:1, exposing the said material while wet with the solution to the action of steam for a period of at least about one-half hour in a steam chamber, thereafter washing the material with water, impregnating it with an acid aqueous solution containing sodium chlorite in amount efiective to eliminate a substantial part of the non-cellulose impurities remaining in the material, discharging solution therefrom until the ratio by weight of solution remaining in the material to the material is about 2:1, and exposing the said material while wet with the second said solution to'the action of steam for a period of at least about one-half hour in a steam chamber.

2. A rocess for purifying crude cellulosic vegetable materials which comprises impregnating said material with an alkaline aqueous solution containing about 4 to 12% of caustic soda and a detergent, discharging solution from the material until the ratio by weight of solution remaining in the material to the material is about 2:1,

exposing the said material while wet with the I solution to the action of steam for a period of at least about one-half hour in a steam chamber, thereafter washing the material with water, impregnating it with an acid aqueous solution containing sodium chlorite in amount effective to eliminate a substantial part of the non-cellulose impurities remaining in the material, discharging solution therefrom until the ratio by weight of solution remaining in the material to the material is about 2: 1, and exposing the said material while wet with the second said solution to the action of steam for a period of at least about onehalf hour in a steam chamber.

3. A process for purifying crude cellulosic vegetable materials which comprises impregnating said material with an alkaline aqueous solution containing about 4 to 12% of caustic soda, discharging solution from the material until the ratio by weight of solution remaining in the material to the material is about 2:1, exposing the said material while wet with the solution to the action of steam for a period of at least about onehalf hour in a steam chamber, thereafter washing the material with water, impregnating it with an acid aqueous solution containing a detergent and sodium chlorite, discharging solution. therefrom until the ratio by weight of solution remaining in the material to the material is about 2:1, and exposing the said material while wet with the second said solution to the action of steam for a period of at least about one-half hour in a steam chamber.

4. A process for purifying crude cellulosic vegetable materials which comprises impregnating said material with an alkaline aqueous solution containing about 4 to 12% of caustic soda, discharging solution from the material until the ratio by weight of solution remaining in the material to the material is about 2:1, exposing the material while wet with the'solution to the action of steam for a period of at least about onehalf hour in a steam chamber, thereafter washing the material with water, subjecting the washed cellulosic material to the action of an aqueous solution containing sodium hypochlorite in amount effective to eliminate a substantial part of the non-cellulose impurities remaining in the material, regulating the contact of the cellulosic material with the hypochlorite solution to control the viscosity characteristic of the final cellulosic product, thereafter washing the material with water, impregnating it with an acid aqueous solution of sodium chlorite, discharging solution therefrom until the ratio by weight of solution remaining in the material to the material is about 221, and exposing the said material while wet with the last said solution to the action of steam for a period of at least about onehalf hour in a steam chamber.

GEORGE P. VINCENT. ARCHIE L. DUBEAU.