US2469764A - Manufacture of hydroxy alkyl cellulose - Google Patents

Description

y 10, 1949- D; R. ERICKSON ,7

MANUFACTURE OF HYDROXY ALKYL CELLULOSE Filed Jan. 16, 1946 x w INVENTOR.

flan 4m Paa /Pf [Hm 50m Patented May 10, 1949 UNITED STATES PATENT OFFlCE I Donald Robert Erickson, Kalamazoo, Mich.

Application January 1c, 1946, Serial No. 841,653 2 Claims. ((31. 260-231) l This invention relates to the manufacture of hydroxy alkyl cellulose, and particularly .of hydroxy ethyl cellulose.

Heretofore, the manufacture has been carried taminated with beta and gamma cellulose before it is all used and then must be purified, which is a diflicult and expensive procedure, or thrown away. carbonation takes place during the process .and this deleteriously aflects the later reaction. The ageing reducesthe percentage of alpha cellulose and the desired yield of the final product. V

This invention does away with the objectionable features of the prior art process.

One of its objects is to provide a new and improved process for making hydroxy alkyl cellulose and particularly hydroxy ethyl cellulose Another object is to provide such a process in which the final product is obtained with a minimum of material and with a minimum of time and handling of the material. Y

Another object is to provide such. a process that can be carried out in a single piece of equipment. Another object is to provide sucha process in which carbonation due to carbon dioxide in the air is reduced to a minimum.

' Another object is to provide a process in which the cellulose is used most efliciently without losses of the alpha cellulose.

Other objects and advantages of the invention will appear from the description which follows.

Dry cellulose pulp is first flocked to a small particle size. which will pass through a 50-80 mesh screen.

The flocked fibres are then placed in a gas tight container which is provided with an agitator which continuously tosses and mixes the fibres so as to present new surfaces of the flocked fibre at every turn of the agitator.

When the flocked pulp is placed in the gas tight container substantially all air is exhausted therefrom. I preferhaving a vacuum of about 29 inches, but this may vary somewhat. The exhausting of the air from the container serves the purpose of eliminating substantially 'all carbon dioxide from the container and thus eliminates any significant carbonation of the sodium hydroxide which is next used in the process. It also exhausts substantially all air from the fibres and assists inthe wetting of themwith the sodium hydroxide, but its main function is to eliminate any material amounts of gas such as the carbon dioxide which might react to any material extent with the materials and give a. less desirable reaction or final product.

After the air is exhausted from the container, the flocked cellulose fibres are sprayed slowly with a filtered solution of sodium hydroxide in water to thoroughly wet them and to add the requisite amount of sodium hydroxide to carry out the desired reaction. The aqueous sodium hydroxide is impigned in a very fine spray by means of pressure through a small orlflce and is not atomized by means of mixing with air. In this way carbonation of the sodium hydroxide is avoided. The sprays are directed over the entire exposed surface of the flocked cellulose fibres which are continuously agitated and tossed to present new surfaces to the sprays.

In carrying out the process, 100 parts by weight of the flocked cellulose fibres are placed in the gastight container. About 200 parts by weight or about thirty per cent by weight sodium hydroxide aqueous solution are used and after the spraying is completed, agitation of the flocked fibres is continued until even wetting of the fibres is obtained, .as well as complete absorption of the calculated amount of the sodium hydroxide.

This treatment of the flocked cellulose flbres makes them highly reactive for the next step of the process which consists in introducing an alkalene oxide gas such as ethylene oxide or propylene oxide. This gas is introduced into the same container without admitting any air and thus excluding any undesirable gas such as car- I prefer to break it up to a size bon dioxide.

The fibres having become very reactive from the sodium hydroxide treatment react with the gas to form the hydroxy alkyl cellulose corresponding to the alkaline oxide introduced. In the case of ethylene oxide, it is hydroxy ethyl cellulose, and in the case of propylene oxide it is the hydroxy propyl cellulose.

About ten parts by weight of the gas are admitted and best results are obtained if the temperature of the reaction is kept below F.

This can be controlled by using a cooling water jacket on the container or by controlling the rate of introduction of the gas or by using both methods.

I prefer exhausting the container to 29 inches of vacuum before introducing the gas, although this is not absolutely necessary.

When the reaction is completed, the hydroxy alkyl cellulose may be dissolved in water by the addition of small amounts of sodium hydroxide to it. It may be desirable to freeze the solution and then thaw it to aid in dissolving the hydroxy alkyl cellulose and also to adjust the pH of the solution if it tends to Jell,

The product which is obtained is very pure and after filtering may be used for various coatings, extrusions and as a binder for various pigments.

The process is most economical both of time and material. I have found that the cellulose can be depolymerized at the pulp mill in the step of bleaching the pulp and my process can then be used on this material or the depolymerization can take place after modification of the cellulose.

The drawing illustrates apparatus suitable for carrying out the process. Medium alpha pulp is supplied in sheet form from a roll I which is mounted on a suitable support 2. The sheet 3 goes to the flocker l where the material is flocked into its fiuify finely divided form. A blower 5 connected by a suitable duct 8 to the flocker is used to convey the fluffy flocked cellulose to the reaction chamber. A suitable duct 1 conveys the material to a cyclone collector 8 which discharges through a duct 9 into the reaction chamber ID.

The reaction chamber i0 is cylindrical in form and is air-tight. Mounted in suitable bearings il therein and driven by a motor I! in the shaft l3 of an agitator on which are mounted agitating arms I! which agitate and tumble the iluil'y flocked cellulose during the carrying out of the process. The arms 14 are straight cross'mem bers and sumcient of them are mounted on the shaft to give the tumbling a itating effect. I

have only illustrated a few of these arms and there may be more if desired.

The sodium hydroxide solution is supplied from a tank I! which is connected by a pipe I6 to spray heads IT. The sodium hydroxide is sprayed, without the admission of air, preferably by the application of pressure to the top of the liquid in the tank IS.

A suitable vacuum pump i8 is provided to exhaust the reaction chamber Ill through a pipe IS.

The ethylene oxide is supplied from a cylinder 20 where'it is maintained under pressure. A pipe 2i connects the tank to the reaction chamber Iii. Suitable scales 22 are provided for weighingthe amount of ethylene oxide.

The various openings into the reaction chamber it are provided with air-tight seals which are illustrated in detail since they are conventional.

On the completion of the reaction, the material from the reaction chamber is withdrawn parts by weight of solution through the opening 23. It is then dissolved in the dissolver 24 which is provided with a suitable agitator 25 driven by a motor 26. A pump 21 withdraws the dissolved material through pipe 28 from the dissolver 24 and conveys it through a pipe 29 to a suitable filter 30.

I have described my invention in its preferred form, but it will be understood that there can be departures from this form without departing from my invention and I do not intend to be limited to the specific form of invention described except as set forth in the claims.

What I claim as my invention and desire to secure by Letters Patent is:

1. In the process of producing alkali cellulose in which cellulose is reacted with sodium hydroxide to produce alkali cellulose, the steps of creating dry flocked cellulose fibers for reaction with the sodium hydroxide by flocking dry cellulose to a particle size which will pass a screen of approximately 50 to 80 mesh, and spraying aqueous sodium hydroxide solution on the dry flocked cellulose fibers in the ratio of about two parts by weight of solution to one part by weight of flocked cellulose fibers. and maintaining the fibers in flocked condition throughout the spraying and reaction to produce flocked alkali cellulose fibers by tossing and mixing the flocked fibers to present new surfaces to the spraying and maintaining the material in a substantial vacuum throughout the process of alkalizing the cellulose. 2. In the process of producing hydroxy ethyl cellulose in which cellulose is reacted with sodium hydroxide and the resulting alkali cellulose is reacted with gaseousethylene oxide, the steps of creating dry flocked cellulose fibers for reaction with the sodium hydroxide by flocking dry cellulose to a particle size which will pass a screen of approximately 50 to 80 mesh. and spraying aqueous sodium hydroxide solution on the dry flocked cellulosefibers in the ratio of about two to one part of weight of flocked cellulose fibers, and maintaining the fibers in flocked condition throughout the spray ing and reaction to produce flocked alkali cellulose fibers by tossing and mixing the flocked fibers to present new surfaces to the spraying, and thereafter introducing gaseous ethylene oxide into the flocked alkali cellulose fibers, and maintaining the material in a substantial vacuum throughout the process of alkalizing and reacting it with the ethylene oxide.

DONALD ROBERT ERICKSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 6 5 Certificate of Correction Patent No. 2,469,764. May 10, 1949.

DONALD ROBERT ERICKSON It is hereby certified that errors appear in thegprinted specification of the above numbered patent requiring correction as follows:

Column 3, line 62, for the words which are read which are not; column 4, I

line 42, for of before Weight read by;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed andsealed this 4th day of October, A. D. 1949.

THOMAS F. MURPHY,

Assistant Uommz'saidner ofPateMa. v

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