US2957797A

US2957797A - Preparation of reactive cellulosic material

Info

Publication number: US2957797A
Application number: US637862A
Authority: US
Inventors: Nakayama Masatoshi
Original assignee: Asahi Chemical Industry Co Ltd
Current assignee: Asahi Kasei Corp; Asahi Chemical Industry Co Ltd
Priority date: 1954-05-24
Filing date: 1957-02-04
Publication date: 1960-10-25
Anticipated expiration: 1977-10-25

Description

Oc 2 1960 MASATOSHI NAKAYAMA ,9

PREPARATION OF REACTIVE CELLULOSIC MATERIAL Filed Feb. 4, 1957 INVENTOR. MASATOSHI NAKAYAMA United States Ratent PREPARATION OF REACT IV E CELLULOSIC MATERIAL Filed [Eeb. '4, 1957,Ser..No. 637,862 Claims priority, application Japan May '24, 19 54 4 Claims. (Cl. 1162-458) This application is a continuation-in-gpart application of US. Serial No. 490,156, now abandoned, filed on Feb. 23, 1955.

This invention relates to a method of preparing a cellulosic material adapted for further uniform chemical reaction. The cellulosic material according to the present invention has improved reactability of the cellulose itself of wood pulp or linters and is most suitable for preparing cellulose ester, cellulose ether or other chemical industrial materials.

In the chemical industry for the manufacture of cellulose ester such as nitrocellulose, cellulose ether such as ethyl cellulose or other cellulose derivatives, commercial wood pulp sheets and linters were used as they were. Sometimes, if desired, cotton linterrs were loosed by means of a beater, and pulp sheets were transformed into the form of tissue paper, loose l inters or chips. However, even thus treated materials were poor in reactivity for chemical reagents. It is because of the fact that a number of small blocks of cellulose remain even after beating and that the cellulose is chemically and internally combined to form a block which prevents reactivity with chemical agents. In fact, the cellulosic materials are simply dispersed in water to form a dispersion thereof in which each fiber may be separated, but once the water is drained off with the result that cellulosic materials agglomerate, interlace and are rather chemically combined due to occluded water. -If the materials are subjected to extremely violent beating, the fibers of the cellulose are cut into shorter pieces which result in loss of the raw materials.

In order to improve reactivity of the cellulosic mate rials, the cellulose fiber each, even after drying, should preferably be separated and clearances exist as much as possible between cellulosic fibers as in sanitary cotton. A primary object of the present invention is to produce such cellulosic materials, each fiber of which is separated from each other and not interlaced. The product cellulosic materials are feathery.

Many researches have been made to manufacture such reactive cellulosic materials. Many unsatisfactory proposals have been made. In one such process cellulosic materials are dispersed in water while carbon dioxide is bubbled therein. Said process, however, fails to obtain satisfactory reactive and bulky materials.

According to the present invention, the raw cellulosic materials are floated in foam of a surface active agent in a rotating drum and the materials are washed not so as to destroy the clearances between the cellulosic fibers.

A rotating drum with blades is fed with a small amount of an aqueous solution surface active agent, preferably in concentration of O.l-l%, and the agent is foamed therein. Loosed cellulosic materials, such for example as loosed pulp sheet, are dipped into water, dewatered and fed to the drum. The pretreatment with water may be omitted. While the surface active agent is foamed, the

cellulosic materials are further loosed and dispersed in the foam until each fiber cellulose is uniformly lfloated in 2,957,797 Patented Oct. 25, 196.0

2 is aside view ,(with a part broken away) of said drum typeagitator.

In the drawings, 1 is a drum and 2 is an agitating bar which agistates the starting cellulosic materials, such as pulp, with a surface active agent to foam the surface active agentsolution until the cellulosic materials are incorporated into the foam. The agitation is stopped and an aqueous solution is separated from the cellulosic material-incorporated foam. The aqueous solution is removed through-discharge 3. 4 is a rotating axis which connects to the agitating bar. 5 is a pulley which connects to rotating means, such as an electric motor, and makes the axis 4 and bar 2 rotate. 6 is a rack for the drum type agitator. 7 is .a hopper from which the startingmaterials are fed. '8 is a door which prevents the contents from spinning out during agitation.

The blades are driven in a definite direction anddriving force F defined by the formula When F is lower than 20, satisfactorily pieces of cellulose cannot be obtained, while when F is higher than 50, pieces of cellulose are further dispersed to single fibers, but the present purpose cannot be attained.

Number of revolutions of the blade, n, is calculated as below for the above range of F, taking the amount of cellulosic material as 60 g., with k=l.3 and r=0.l8.

When k-n-r=20, n= r.p.m.

The ratio of the amount of an aqueous surface active agent solution fed to the drum to the amount of feed (dry) of cellulosic materials is from 16:1 to 25:1 parts by weight. The foam volume produced from employment of such amount of surface acitve agent solution and the above range of driving force of the blades is 80 to liters per kilogram of cellulosic materials. When the foam volume is lower than 80' liters 1 kg. or higher than 130 liters, single fibers will interlace one another. Therefore the above foam volume is critical.

An aqueous surface active agent is used in concentration of (Ll-1%, preferably 0.2%. The surface active agent may be an anionic active agent selected from the group consisting of alkyl naphthalene sulfonate, fatty acid salts such as potassium oleate, fatty acid amide sulfonate such as methyl taurine oleate, higher alcohol sulfates such as fatty alcohol sulfate and petroleum alkyl sulfates, alkyl sulfonate and the like; a cationic active agent selected from a group consisting of alkyl amine such as polyalkyl polyamine, acylated diamine, quaternary alkyl ammonium, alkyl pyridinium, sulfonium salts and the like; a nonionic active agent selected from a group consisting of polyethylene glycol, polyoxyethylene alkyl esters, polyox-yethylene alkyl ethers, polyhydric alcohol alkyl esters and ethylene oxide derivatives thereof such as polyoxyethylene sor-bitane fatty acid esters, ethylene oxide derivatives of alkyl phenol, ethylene oxide from foam is removed off the drum, whereby volume of foam is reduced to 9 to 13 times as much as the weight of the cellulosic materials. The flotation operation is repeated as in the first one.

In the first flotation step a highly voluminous foam is used against the cellulosic materials and the situation is like the case wherein the materials are dispersed in a great volume of liquid. In order to prevent such defect, the volume of foam in the second flotation step is reduced as far as possible, by removing excess liquid in the foam after the first flotation operation. By the second flotation step, the resultant foam is more suitable to the object of the present invention. The final length of fibers can be controlled by size of foam. It is not practical to initially employ a small amount of foaming solution in the first flotation operation a in the second operation because, in order to obtain effective flotation action on original cellulosic material blocks, quite a large amount of solution is required, at least as high as 16 times the amount of raw material fibers, as mentioned above.

When the requirement is severe for the uniformity of chemical reaction, separation among the cellulose pieces should be extremely clear, and in addition, the pieces should be slender. Twice-repeated flotation steps under the defined conditions are thus preferable according to the present process.

The foaming mass is then centrifuged, washed with spray of steam or water and dried. In centrifuge, the foam is separated in the form of a dilute aqueous solution resulting in reduction of the foaming agent adhered to the fibers to within the range of 40-70%. The residual foaming agent is washed off by steam or water spraying while the centrifuge is operated. At that time water is preferably supplied in the form of mist. If a large amount of water is applied at a time for the washing, clearances occupied by the residual foaming agent are spoiled, resulting in adhering of the fibers with one another. The object of the present invention is favorably achieved by washing off only the remaining foaming agent while the clearances occupied by the agent remain as they are.

The present process is carried out at room temperature. Some higher or lower temperature gives no significant effects on the operation.

Now examples of the present invention are shown in the following. However, the present invention should not be limited by these examples.

Example 1 50 g. of refined linters were dispersed in 5 liters of water while stirring for 10 to 20 minutes. The water was separated. 1 liter of 0.5% soap solution (sodium oleate) was added to the linters. When the mixture was stirred at 20 C. at r.p.m. 136 for 10 minutes in a drum (r=0.18 m., volume=8 l, 8 blades), the soap solution foamed and the linter fibers floated in the foam. Then, the foam was separated by .the centrifuge. While the centrifuge was being rotated, the adhering ageiii was washed with steam spray. Lastly, the washed linters were dried. Thus, linters in the form of absorbent cotton were obtained. Such linters were favorable as raw materials of nitrocellulose for lacquer.

Example 2 water, 1 g. of soap (sodium oleate) was added thereto.

Apparatus and operating conditions were all the same with those in Example 1. After foaming, when the mixture was filtered by meansof a centrifuge, was washed with sprays at 1000 revolutions per minute and was dried, pulp in the form of absorbent cotton was obtained. Nitrocellulose for celluloid was manufactured from the above obtained pulp and was found to have uniformity equal to or better than that of nitrocellulose manufactured from tissue paper under the same conditions with nitration mixed acid.

Example 3 g. of pulp were stirred together with 4 liters of water. After the pulp was thus dispersed in water, the water was separated. 1.6 liters of 1% soap (sodium oleate) solution were added to the pulp and the mixture was stirred and foamed for about 10 minutes. Apparatus and other operating conditions were same as those in Example 1. The foamy mass in the state wherein the fibers remain or are floated in the foam was separated by means of a centrifuge at about 1000 revolutions per minute. A small amount of soap adhering to the fibers was washed with sprays while the centrifuge was rotated. When the fibers were dried, pulp in the form of uniform linters was obtained. In order to obtain nitrocellulose for gun cotton containing, for eX- ample, 13.4% nitrogen, linters hitherto used and the pulp of the present invention were compared. As a result, it was found that the nitrogen content of the nitrocellulose of the present invention wa equal to or a little higher than that of the conventional product.

Example 4 60 g. of refined pulp were stirred together with 4 liters of water. After the pulp was thus dispersed in water, the water was separated. While the water content of the pulp then was kept at 40 to 50%, 1.2 liters of a mixed solution of 0.15% alkyl aryl sulphonate and 0.15% polyoxyethylene alkyl ether were added to the pulp. The mixture of the pulp was stirred and foamed for about 20 minutes and was left for 10 minutes. Apparatus and other operating conditions were same with those in Example 1. Then 0.6 liter of the treating solution was separated.

After the separation, the mixture was further stirred for 10 minutes and the fibers were floated in the foam. Then while the fibers remained (dispersed) in the foam, the treating foam was separated by means of a centrifuge. A small amount of the foaming agent adhering to the fibers was then washed with sprays during the operation of the centrifuge. Then the fibers were dried. The pulp obtained here was in the form of cut line threads due to the cooperative action of the mixed active agents and was very suitable for chemical reactions. In the case of a nitrating reaction to obtain nitrocellulose of any amount of nitrogen, the penetration by the mixed acid was so favorable that uniform nitration was possible.

I claim:

1. A method of producing cellulose material whose fibers are separated from each other, which consists of floating a refined cellulosic material with stirring in foam of a dilute aqueous solution of a surface active agent in the condition that the amount of the solution of the surface active agent per amount of cellulosic material is from 16:1 to 25:1 parts by weight, the foam volume is from 80 to liters to each kg. of cellulosic material, stirring is always in a definite direction, and the driving force for stirring defined by the formula r=radius of stirrer in metres is within the range of 20 to 50 removing excessive liquid as much as possible from the foam in which the cellulose material has been floated;

'floating again the cellulose material in the foaming floated, by centrifuging, washing out residual foaming agent remaining in the cellulose by water spray while maintaining the water content of the cellulose at 40 to 70%; and drying the same.

2. A method according to claim 1 wherein concentration of the aqueous solution of surface active agent is 0.1 to 1% by weight.

3. A method according to claim 1 wherein water spraying is substituted by steaming.

4. A flulfy, distended and purified cellulose which is obtained by a process as defined in claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 1,062,187 Roberts May 20, 1913 1,740,280 Bryant Dec. 17, 1929 1,821,856 Spafiord Sept. 1, 1931 1,966,437 Bryant July 17, 1934 2,332,369 Burton Oct. 19, 1943

Claims

1. A METHOD OF PRODUCING CELLULOSE MATERIAL WHOSE FIBERS ARE SEPARATED FROM EACH OTHER, WHICH CONSISTS OF FLOATING A REFINED CELLULOSIC MATERIAL WITH STIRRING IN FOAM OF A DILUTE AQUEOUS SOLUTION OF A SURFACE ACTIVE AGENT IN THE CONDITION THAT THE AMOUNT OF THE SOLUTION OF THE SURFACE ACTIVE AGENT PER AMOUNT OF CELLULOSIC MATERIAL IS FROM 16:1 TO 25:1 PARTS BY WEIGHT, THE FOAM VOLUME IS FROM 80 TO 130 LITERS TO EACH KG. OF CELLULOSIC MATERIAL, STIRRING IS ALWAYS IN A DEFINITE DIRECTION, AND THE DRIVING FORCE FOR STIRRING DEFINED BY THE FORMULA