US2553725A - Process of preparing cellulose derivatives - Google Patents

Description

May 22, 1951 L. N. ROGERS ET AL PROCESS OF PREPARING CELLULOSE DERIVATIVES Filed Sept. 10. 1948 Sr@ Mm. view/wm @Mlm/@m MH@ d m. .M @m6 [In f WB@ Patented May 22, 1951 UNITED srarss PROCESS F PREPARING CELLULOSE DERIVATIVES Application September 10, 1948, Serial No. 48,732

, 16 Claims. l

This invention relates to an improved process for the preparation from cellulose pulp of salts of acidic ether derivatives of cellulose, and more particularly to a process for the preparation of salts of an acidic ether derivative of cellulose of the group consisting of cellulose ether derivatives of aliphatic carboxylic and alkyl sulfonic acids having not more than 4 carbon atoms, as for example water-soluble salts of carboxymethyl cellulose and of cellulose ethane sulfonic acid.

Cellulose .derivatives of the character indicated are highly useful in laundry operations, in which they enhance the action of the detergent, apparently by retaining in suspension the dirt particles removed from the fabrics, whereby graying of the fabric on repeated washing with the detergent composition is reduced. This ability of a detergent composition to maintain the whiteness cf white fabrics on repeated Washing is sometimes referred to as whiteness maintenance. Furthermore, these cellulose derivatives tend to prevent the deposition on the fabric of insoluuble salts, and thus tend to reduce the harsh feel so imparted to the fabrics, especially when the detergent is of low grade. For this and related purposes, thesolubility of the cellulose derivatives in water is quite important to effective results, and clarity is desirable. When, as is often the case, the derivative is to be mixed with the detergent While fluid, derivatives having low Viscosity, adapted for use in conventional mixing equipment such as crutchers and the like, are preferable. Moreover, there has been some indication that those cellulose derivatives, which give low-viscosity aqueous solutions, have greater efficiency in improving `the whiteness maintenance of detergent compositions.

It is accordingly an object of the invention to provide a novel process for the eiiicient low-cost production of salts of acidic ether derivatives of cellulose, which salts form clear solutions in water, are highly elective, and which have a viscosity suiciently low to facilitate handling with convenient detergent making equipment.

It is a feature of the instant process that the cellulose derivatives may be produced continuously; in the preferred process the cellulose pulp is conveyed through each of the treatment zones in the form of a continuous sheet, emerging in sheet form after conversion to the ether salt for delivery to crushing and grinding equipment. It is` particularly important to pass the material through the etherifying zone in the form cf a continuous sheet in order that the final product may have the desired properties, as hereinafter more fully explained.

It is a further object of the invention to provide a method cf forming cellulose derivatives of the character described which includes the step of etherifying a sheet of cellulose bythe application to the sheet of liquid reagents in amount which is at no time greater than the amount of liquid which the sheet is capable of absorbing.

It is a further object of the invention to pro--` vide a process of etherifying cellulose which includes the steps of applying thereto in succession, and in the order named, an alkaline agent,v a halogenated lower fatty acid, or halogenated lower alkyl sulfonic acid, and an alkaline agent, in total amount not greater than that which the sheet is capable of absorbing.

More specifically, it is an object of the invention to provide a new and improved process for the manufacture of carboxymethyl cellulose which involves feeding the pulp continuously in, sheet form in succession, and in the order named. through a hydrolyzing zone, a Washing zone, a drying zone, an etherifying zone, a ripening Zona..

cosity, water soluble carboxymethyl cellulose. It will be understood, however, that the process isn readily applicable to the preparation of cellulose ethers of other aliphatic carboxylic acids having,

not more than 4 carbon atoms per molecule and of lower alkyl sulphonic acids having not more than 4 carbon atoms per molecule by appropriate substitution of reagents, and that the use of speciiic language describing the preferred embodiment of the invention is not intended to limit SCOpe.

The following specific examples are illustrative: of preferred methods of processing cotton linters, in sheet form to produce the acidic ethers of cel-` lulose.

Example I A lil-pound roll of cotton linters sheet, l0 inches wide and 0.040 inch thick, and a viscosity of 1l seconds when 2.5 grams are dissolved in cuprammonium according to the A. C. S. Standard Method, was passed continuously through a hydrochloric acid bath at 70 C. and containing 15% hydrogen chloride.

The speed was so regulated that the contact time of the paper with the acid Was 60 seconds. During this time the vis cosity was reduced to 20 seconds, as measured by the A. C. S. method, using a -gram sample, but other characteristics of the paper such as strength and absorbency remained practically unchanged. The sheet was then passed through squeeze rolls to remove the excess acid, and then alternately through three successive Water Washes and squeeze rolls to remove the remaining acid, and finally through a roll dryer and partially dried to about 20% moisture.

The dried sheet was passed through a series of saturating rolls (coating rolls) to spread uniformly over both sides of the sheet 10 pounds of 35% aqueous sodium hydroxide. The resultant sheet, showing very little shrinkage, Was immedi ately passed through a second set of saturating rolls to coat onto the paper 8.9 pounds of an aqueous solution prepared by adding to 19 pounds of 80% chloracetic acid solution 1.8 pounds of dry soda ash, and finally through a third set of saturating rolls to coat 7 pounds of 35% sodium hydroxide.

The sheet Was then passed (a) through a nondrying oven at 190 C. for a period of 4 minutes of ripening, (b) through a tank containing carbon dioxide gas (15 seconds), (c) over a second roll dryer to dry to 3% moisture and, (d) into crushing and grinding equipment.

The product dissolved readily in water to form a free flowing 2% solution which, when adjusted to pH 7, Was substantially water clear.

Example II The procedure was the same as Example I except that the sheet was coated first with l2 pounds of 35% aqueous sodium hydroxide then 8 pounds of 80% chloracetic acid, and nally 8 pounds of sodium hydroxide. The product was similar to that of Example I.

Example III The procedure was the same as Example I except that the hydrolysis, washing, and partial drying Were omitted. The product formed a gel when prepared into 0.5 solution.

Example IV A l-pound roll of absorbent cellulose sheet, l inches wide and 0.040 inch thick, was passed continuously through a hydrochloric acid bath at 67 C. and containing 20% hydrogen chloride. The speed was so regulated that the contact time 0f the paper with the acid was 45 seconds. During this time the viscosity was reduced to 25 seconds, as measured by A. C. S. method using a gram sample, but other characteristics of the paper such as strength and absorbency remained practically unchanged. l The sheet was then passed through squeeze rolls to remove the excess acid, and then alternately through three successive Water Washes and squeeze rolls to remove the remaining acid, and Iinally through a roll dryer and partially dried to about 32 moisture.

The dried sheet was passed through a series of coating rolls to spread uniformly over both sides of the sheet 7.2 pounds of 29% aqueous sodium hydroxide. The resultant sheet, showing very little shrinkage, was immediately passed through a second set of saturating rolls to coat onto the paper 7.3 pounds of a solution prepared by adding 2.0 pounds oi sodium carbonate to 19 pounds of a 70% aqueous solution of mono` Cir chloracetic acid, and nally through a third set of saturating rolls to coat 8.4 pounds of 29% sodium hydroxide.

The sheet was then passed (a) through a non drying oven at 120 C. for a period of 3 minutes of ripening, (b) 'through a tank containing carbon dioxide gas (ll seconds), (c) over a second roll dryer to dry to 3% moisture and, (d) into crushing and grinding equipment.

Over 97% of the product was soluble in Water when dissolved to make a 2% solution and adjusted to pI-I 7. This solubility was less than that of Example I, but the product Was eminently suitable as a detergent aid.

Eample V A -pound roll of absorbent cellulose sheet, l0 inches Wide and 0.622 inch thick, was passed continuousiy through a hydrochloric acid bath at 70n C. and containing hydrogen chloride. The speed was so regulated that the contact time of the paper with the acid was 90 seconds. During this time the viscosity was reduced to l5 seconds as measured by A. C. S. method using a -gram sample, but other characteristics of the paperA such as strength and absorbency remained prac tically unchanged. The sheet was then passed through squeeze rolls to remove the excess acid, and then alternately through three successive Water Washes and squeeze rolls to remove the remaining acid, and nally through a roll dryer and partially dried to about 9.0% moisture.

The dried sheet was passed through a series of two or more saturating (coating) rolls to spread uniformly over both sides of the sheet l2 pounds of 34% aqueous sodium hydroxide. r.The resultant sheet, showing very little shrinkage, Was immediately passed through a second set of saturating rolls to coat onto the paper 12 pounds of a solution prepared by adding 1.8 pounds of sodium carbonate to l0 pounds of 80% aqueous solution of monochloracetic acid, and nally through a third set of saturating rolls to coat 7.1 pounds of 34% sodium hydroxide.

The sheet was then passed (a) through a non-` drying oven at 90 C. for a period of 6 minutes of ripening, (b) through a tank containing carbon dioxide gas (22 seconds), (c) over a second roll dryer to dry to 3% moisture, and (d) into crushing and grinding equipment.

The product was readily and completely soluble in water when dissolved to make a 2% solution, and when adjusted to pI-I of 7 this solution was water clear.

Example VI The procedure was the same as Example I except that the paper was coated rst with 9.5 pounds of sodium hydroxide, then with 11.5 pounds of an aqueous solution containing 75% alpha chloro propionic acid which was neutralized with soda ash, and nally with 8.6 pounds of 35% sodium hydroxide.

Example VII The procedure Was the same as Example VI except that the acid used in the second coating step was 10.2 pounds of chloro-ethane sulfonic acid. The product was very similar to carboxymethyl cellulose, and had excellent properties as a detergent added.

Other halogenated acids which may be employed to form acidic ether derivatives of cellulose are chlorobutyric acid, chloropropane sulfonic acid, bromobutane sulfonic acid and chlorohydroxy propane sulfonic acid.

The apparatus 'shown in the drawing may be used to carry outv the lprocesses justA described. r17h-us Athe fibrous sheetv which is designated throughout by the reference character I0, initially constituted by absorbent cellulose sheet having the characteristics set forthv in the eX- ample, is drawn continuouslyl from a roll I2 by draw rolls I3 and passed through hydrochloric acid in tray i5, being supported therein yby rollers 1.6. Following depolymerization lor hydrolysis in the acid bath and consequent reduction of viscosity, the sheet is led between squeeze rolls I1 and is washed with water, to remove the acid.

Itv is then led over heated drying rolls i8, or

through any conventional roll dryer, where it is dried to the specied moisture content.

The partly dried sheet of depolymerized cellulose vis then passed through a series of two-or more sets of saturating or coacting rolls, two sets being shown in the drawings, to apply caustic 'to the sheet. Each set of coating rolls may comprise three superposed rolls J, the sheetV being fedbetween the several rolls so as to absorb the caustic which is fed onto the rolls from-troughs on side of rolls similar to those used in the paper industry for saturating paper. It will be noted that the sheet is not submerged in the solution. By suitable selection of the number of sets ofrolls and their diameters, the amount of caustic supplied can be determined with exactness.

From the causticl rolls the sheet is fed directly to coating rolls 25, of which several sets are similarly provided, whereby the halogenated acid is supplied to the sheet from troughs, on side of rolls same as above. From these rolls thesheet is passed directly to one or more sets of rolls 28, functioning similarly to 'the coating rolls hereinbefore described, by which the final application of caustic from troughs are effected.

The sheet is then fedvinto a ripening cabinet 3U in which it is supported on a series o'superposed continuous conveyors 3l, alternate conveyors being driven in opposite directions, whereby the sheet is passed along each conveyor :from the uppermost to the lowest of the series. Cabinet is heated from steam coils 32 in bottom of cabinet. High humidity is maintained.

Upon leaving the ripening cabinet, the sheet is fed into a neutralizing chamber which isr supplied with carbon dioxide gas, the sheet being supported on rolls 36. from a chamber38 in which chloracetic acid to be supplied rolls 25 is partially neutralized with sodium carbonate, as described more fully hereinafter.

The Vsheet is then passed between screen conveyors L30, 4i which are entrained over'drying rolls 43, and is then fed by positively driven rolls to a conventional grinding or pulverizing mill The type of pulp used may vary widely, the processing conditions beingv altered to treat effectively the selected' pulp. Cotton linters is the preferred material, but wood, straw, bagasseor other cellulosic material may be employed. The viscosity of the initialr pulp obviouslyaffects materially the selection or processing condi-tions for the production of a derivative having specified characteristics.

The strength of the pulp sheet should, o1" course, be sufcient to ensure against breakage as the sheet is passed through the various treatment zones, but the mullen (tear) value should below, for ready penetration. Values of Vthe order of 25 The gas may be derived 48, thev ground material being delivered to Va 'hinV to "40 mullen, measured on a sheet 0.040'in`ch" thick, aresatisf'actory, lthis being the'optimum thickness of sheet'. However, the sheet thickness may vary substantially, cotton linters sheets ofi As has been pointed out, processing conditions. may be varied rather widely depending upon the' initial pulp and the nature of the nal product.`

The following more vdetailed discussion of the several steps of the process are indicative of the variations in processing conditions which are possible.

Acid hydro-lysis The hydrolysis or ldepolyn'ierization of the 'cellulose may be effected with a wide variety of' acids, inorganic mineral acids such asy hydrochloric, sulfuric, nitric, and 'phosphoric 'being commonly used. Hydrcchloric acid is preferred,

and the limits and conditions specified herein relate to this acid.

In order to produce carboxymethyl cellulose having a viscosity vin a 2% aqueous solution (pH '7) of less than 100 centipoises, for example. 2.5, to centipoises, the hydrolyzed sheet should' have a' viscosity of' 12 to 36 seconds, when measured by the standard method of the American Chemical Society, using a 5gram sample. When pulp such as described in the foregoing specicexample, having a viscosity of 11 seconds (Z5-gram sample) is employed, the concentration of hydrochloric acidshould be from about 5% to aboutV 30% by weight, preferably betweenV 13% and 17%. If the acid concentration is 15%, the time of contact between acid and pulp may vary from 30 to 90 seconds. If the acid concentration is held at 15% and the contact,Y time to seconds', the temperature of the bath may vary between 60 and 80 C. It is the primary purpose in conducting this stepto hydrolyze the ber without reducing the liber strength materially and without substantial swelling of the sheet, and temperatures from about 50 C. to about 100 C. and time from aboutr l5 to about 200 seconds andother'processing conditions are selected with this end in View. Excellent results are achieved, using the pulp of Example I, by the use ofY 15% hydrochloric acid at a temperature of to 80 C., the sheet being immersed for a period of 60 seconds. `v

` Washing and. drying Itis an important feature of the invention that etheri'c'ation of the cellulose is effected by absorption of the reagents in the brous sheet, no

excess of reagent being applied at any time. It isth'erefore necessary to remove the hydrolyzing acid and at least partially dry the sheet'V prior tok weight of the sheet when dry.

Etherifcatz'on A significant feature of. the instant invention is the application of the alkaline agent, for in- Preferably drying is continued until the moisture of the sheet is .from 10% to V25% by' stance caustic soda, in two steps which respectively precede and follow the application of the esterifying agent, such as chloracetic acid, bromacetic acid or other halogenated aliphatic carboxylic acid or alkyl sulfonic acid having not more than 4 carbon atoms, chloracetic acid being most generally applicable, however, The chief effects of the double causticization are to ensure more uniform penetration, less swelling of the pulp, and less heating and therefore less decomposition of the chloracetic acid, for example, and to eifect corresponding improvements in solubility and clarity of the product. The caustic serves to further the reaction between chloracetic acid and cellulose, either by combining with the halogen of the chloracetate and causing the resultant free radical to combine with the hydroxyl of the cellulose, or by combining with the hydrogen chloride formed in the reaction. Mercerization (i. e. conversion of all of the cellulose to alkali cellulose) is undesirable in the instant process, and is eiectively avoided by the absorption of ail of the caustic in the cellulose sheet, there being no unabsorbed solution in contact with the cellulose at any time. For instance, the contraction of the sheet (a measure of the amount of swelling) when processed by the present invention is less than 3%, Whereas a similar sheet dipped in caustic of the same strength contracts from 15 to 20%. `Since swelling tends to close the interstices of the sheet, the initial application of caustic as proposed herein results in a sheet which is quite porous and absorptive, and which therefore can absorb and distribute uniformly a relatively viscous solution of halogenated acid of high concentration. It is therefore desirable to limit the amount of caustic initially applied so as to eliminate swelling before application of halogenated acid, and to add thereafter an additional amount of caustic. In the case of the use of caustic soda and ohloracetic acid this additional amount is preferably suincient to bring the total weight of NaOH to substantially the weight of actual chloracetic acid introduced.

While any alkaline agent of adequate strength may be employed, alkali metal hydroxides function most satisfactorily, and caustic soda is preferred.A When using caustic soda, the concentration may vary from 25% to 40% and the temperature from 15 to 40 C. In the initial causticization step, We prefer to add slightly over half of the total amount of caustic required, for instance 60%, or about 1.2 to about 2.2 mols per glucose unit, the balance of about 1.0 to about 1.4 mols being added in the second causticizing step. By applying the caustic on a plurality of sets of rolls, more uniform distribution is obtained and the product correspondingly improved. A higher concentration of caustic can be used if the temperature of the solution is raised sumciently to avoid viscosity difficulties; a concentration of less than 25% should be avoided, however, because introduction of too much water retards subsequent reaction by formation of a gel, mercerization or swelling.

The acid preferably used in the preparation of carboxymethyl cellulose is an aqueous solution of monochlcracetic acid (ClCmCOOH), the acid concentration ranging from 60% to 80% and the temperature from 15 to 40 C. An 80% solution of chloraceticacid corresponds to the solubility of the acid at room temperature, and at higher temperatures the acid tends to hydrolyzed. Lower concentrations than 60% introduce sufficient water to result in gellation of the product and'reduce the workability` of the sheet. The amount of actual chloracetic acid used may vary between about 50% and 100% by Weight of the pulp being treated. Preferably we employ from about 0.8 to about 1.5 mols of acid per glucose unit or from about 0.45 lb. to about 0.88 lb. of actual chloracetio acid per pound of hydrolyzed cellulose, the ratio selected depending upon the degree of substitution and the clarity of the product desired.

The acid may be partially neutralized with an alkaline agent, before application to the sheet to decrease the heat of neutralization liberated in the sheet and to reduce corrosion of equipment. As hereinbefore indicated, the employment of sodium carbonate for this purpose is helpful since the carbon dioxide gas which is liberated may be used in the nal neutralization step, as indicated hereinbefore.

Complete neutralization of the chloracetic acid at this point isundesirable, and there are a number of factors to consider in determining4 the most desirable extent of neutralization. Thus when large quantities of salt are formed, much of the salt fails to go into solution, the viscosity of the solution is increased, and there is a greater tendency toward foaming. On the other hand, as the extent of neutralization is decreased, the aforementioned advantages of neu-Y tralizing are realized in less degree. We prefer to neutralize from 30% to 50% of the chloracetic acid, neutralization of about 40% giving optimum results.

In order to produce carboxymethyl cellulose which is readily soluble in water, the final product should contain as an average at least 0.4 and preferably 0.6 to 1.0 glycolic acid groups per glucose unit, and the reagents and conditions should be selected accordingly.

Following -halogenated acid impregnation, caustic is again applied to the sheet in amounts sufficient to make up the total required. It should be noted, however, that when the halogenated acid has been partially neutralized before application to the cellulose, the amountof caustic required for each application may be reduced proportionately. At no time is there excess caustic in the sheet to allow conditions of steeping required for the formation of alkali cellulose.

It is important to the effective practice of this step of etheriiication that the total amount of reagents supplied to the sheet is always less than that which the sheet is capable of absorbing.`

Consequently the final caustic application results in prompt absorption and uniform distribution of reagent.

The reagents used in the etheriiication step may be applied in immediate sequence, and the time required for the material to pass through the entire set of coating rolls is usually only about one minute, rapid application of caustic and acid being essential to prevent swelling and other difculties.

In describing the application of the reagents as a coating step, it will be appreciated that the term coating is not intended in a limited sense; the cellulose is promptly impregnated with the reagent by absorption, for the reason stated above.

Ripening It is a feature of the invention that the etherication reaction is completed in a non-drying `the gas.

crushing occurs in the dryer.

or humid atmosphere, and to this end the impregnated sheet may be conveyed through a ripening cabinet which may be humidiiied by the introduction of steam. This is desirable in order to eliminate any substantial drying with resultant lack of control of the degree of substitution. A relative humidity or" 90 is found to be entirely adequate for the purpose.

The conveyors in the ripening chamber are de signed to retain the sheet in the chamber for a period of time which varies with the temperau ture selected. If a temperature of 100 C. is established in the chamber, a period of 4 minutes is satisfactory, and the ripening time may be decreased to 3 minutes at a temperature of '120 C. As the temperature is lowered, the time in creases rapidly, l minutes being required at 80 C. The time and temperature may vary considerably, periods of ripening of from one to 20 minutes Aand temperatures of from 60 to 130 C.

being satisfactorily employed. Only very slightv color in the product on drying, it is desirable to neutralize the etheriiied product. Carbon dioxide gas, preferably derived from partial neutralization of the halogenated acid, with sodium carbonate or other alkali metal carbonate for example, may be employed, or Dry Ice may be introduced in the neutralizing chamber to supply Hydrogen chloride gas, aqueous hydrogen chloride, or other acidic gas such as sulphur dioxide may also be used. The gas penetrates the sheet rapidly and only a loop dip is required. This step may, of course, be omitted, where neutrality is not desired, and color control is not needed, or where the product is not to be dried.

Drying- Any type of dryer, such as an ordinary open or closed roll dryer may be employed to dry the neutralized sheet. The dry product is flexible when hot, and `brittle when cold, so that no However, the sheet is easily crushed in any conventional grinder to the desired particle size.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

l. In the process of preparing salts of acidic ether derivatives of cellulose from cellulose pulp, the steps which comprise (l) contacting the pulp in the form of a continuous sheet, while feeding the vsheet through a hydrolyzing zone, With a mineral acid at elevated temperature for a period of time sufficient to effect substantial depolymerization of the pulp, (2) Washing and drying the sheet while feeding the sheet through an acid removal zone, and (3) impregnating the sheet, while feeding the sheet through an etherifying zone, with an aqueous solution of a halogenated acid of the group consisting of halogenated alim phatic carboxylic and halogenated alkyl sulfonic acids having not more than 4 carbon atoms in the molecule and an alkaline agent in total amount not greater than that which the sheet is capable of absorbing.

2. In the process of preparing salts of cellulose ether carboxylic acids from cellulose pulp, the steps which comprise (l) contacting the pulp in the form of a continuous sheet, while feeding the sheet through a hydrolyzing zone, with amineral acid at elevated temperature for a period of time suflici'ent to effect substantia1 depolymerization of the pulp, (2) washing and drying the sheetlcellulose, the steps which comprise (l) `contacting Acellulose pulp in the form of a continuous sheet, whilevfeeding the sheet through a hydro- 'lyzing zone, with a-mineral'acid atelevated temperature for a period ofA time sufficient to effect substantial depolymerization of` the pulp, (2,)

'washing and drying the sheet while feeding the sheety through 'an acid removal zone, and (3) impregnating the sheet, while feeding the sheet through an etherifying zone, with caustic soda and an `aqueous solution of chloracetic acid, the amounts by weight of actualv chloracetic acid and caustic being substantially equal, and Ythe molar ratio of Vchloracetic acid to glucose unit being in the range of about 0.8:1 to about 1.75,:1.

4. In the process of preparing a wateresoluble carboxymethyl cellulose, having a viscosity of less than c p. in a 2%aqueous solution of pI-I 7, the steps which comprise (l) contacting cellulose -pulp in a continuous sheet of thickness 00125-006 inch, Awhile feeding the sheet `through a hydrolyzing zone, with an` aqueous solution of hydrochloric acid of concentration of 5-30% by weight; maintaining within the zoneV a vtempera,-

seconds, (2)V alternately washingand pressingjthe sheets, adding after each pressing an amount-of water equal in weight to the weight of the pulp while feeding through a washing zone, (3) drying at elevated temperatures until the moisture content of the pulp is from lil-25% by weight while feeding through a drying zone, (4) impregnating the sheet while feeding through an etherifying zone, first with an aqueous solution of caustic soda of concentration 254-,40% by weight in quan. tity of about 1.2 to about 2.2 mols of caustic alkali per glucose unit, then with an aqueous solution of chloracetic acid of concentration of 60-80% by weight in quantity of 0.8 to 1.5 mols of acid per glucose unit, and finally with an aqueous solution of caustic soda of concentration of 2540% by weight in quantity sufficient to yield with the caustic soda added previously an amount of sodium hydroxide equal in weight to the weight of ClCHzCOOH employed in the etherication, and maintaining throughoutthe etheriflcation process a temperature of 15 to 40 C.

5. In a process for the manufacture of salts of cellulose ether carboxylic acids, the steps which comprise continuously feeding a cellulose sheet while applying to the sheet, in succession and inthe order named, an alkaline agent, a halo-k` genated lower fatty acid having not more than 4 carbon atoms, and an alkaline agent, in total amount not greater than that which the sheet is 11 being supplied in substantially equal quantity by Weight and the acid being in the molar proportion of about 0.8 `to about 1.5 mols acid per glucose unit.

'7. In a process for the manufacture of carboxymethyl cellulose, the steps which comprise continuously feeding a cellulose sheet while applying to the sheet, in succession and in the order named, aqueous solutions of caustic soda, chloracetic acid, and caustic soda, the acid and caustic being supplied in substantially equal quantity by weight and the acid being in the molar proportion of about 0.8 to about 1.5 mols acid per glucose unit, approximately 60% of the total caustic being supplied in the initial application.

8. In a process for the manufacture of carboxymethyl cellulose having a degree of substitution of 0.4-1.0 glycolic acid groups per glucose unit, the steps which comprise feeding a cellulose sheet While applying to the sheet in succession and in the order named, an aqueous solution of caustic soda of concentration of -40% by weight in quantity of about 1.2 to about 2.2 mols of caustic per glucose unit, an aqueous solution of chloracetic acid of concentration of E-80% by weight in quantity of about 0.8-1.5 mols of acid per glucose unit, and caustic soda of concentration of 25-40% by weight in quantity of about 1.0-1.4 mols of caustic per glucose unit.

9. In a process for the manufacture of salts of cellulose ether carboxylic acids, the steps which comprise continuously feeding a cellulose sheet through an etherifying zone and a ripening zone, impregnating the sheet While in said etherifying zone with aqueous solutions of a halogenated lower fatty acid and an alkali metal hydroxide, and maintaining in said ripening zone a temperature of from about 60 C. to about 130 C. and a humid atmosphere, the rate of feed in said ripening zone being such that the period of ripening is from about one to about 20 minutes.

10. In aprocess for the manufacture of salts of cellulose ether carboxylic acids, the steps which comprise continuously feeding through an etherifying zone a cellulose sheet while applying to the sheet, irl-succession and in the order named, aqueous solutions of an alkaline agent, a halogenated lower fatty acid, having not more than e carbon atoms, and an alkaline agent, in total amount not greater than that which the sheet is capable of absorbing, and thereafter feeding the sheet through a ripening zone While maintaining in said zone a temperature of from about 60" C. to about 130 C. and a humid atmosphere, the rate of feed in said zone being such that the ripening is completed in from about one to about 2G minutes.

1l. In a process for the manufacture of salts of cellulose ether carboxylic acids, the steps which comprise continuously feeding a cellulose sheet through an etherifying zone and a ripening zone, impregnating the sheet While in said etherifying zone with aqueous solutions of a halogenated lower fatty acid having not more than 4 carbon atoms and an alkali metal hydroxide, and maintaining in said ripening zone a temperature of from about 60 C. to about 130 C. and a humid atmosphere, the rate of feed in said ripening zone being such that the period of ripening is from one to about 20 minutes.

12. In a process for the manufacture of carboxymethyl cellulose, the steps which comprise continuously feeding a cellulose sheet through an etherifying zone and a ripening zone, impregnating the sheet While in said etherifying zone with a partially neutralized aqueous solution of chloracetic acid and an aqueous solution of an alkali metal hydroxide, and maintaining in said ripening zone a temperature of from about C. to about 130 C. and a humid atmosphere, the rate of feed in said ripening zone being such that the period of ripening is from about one to about 20 minutes.

13. In a process for the manufacture of carboxymethyl cellulose, the steps which comprise continuously feeding a cellulose sheet in succession through an etherifying zone and a neutralizing zone, reacting chloracetic acid with an alkali metal carbonate to effect partial neutralization of the acid with liberation of carbon dioxide gas, contacting the sheet while in said etherifying zone with the partially neutralized acid and an aqueous alkali metal hydroxide, and passing the liberated gas into said neutralizing zone to effect neutralization of unreacted hydroxide in the cellulose.

14. In a process for the manufacture of carboxymethyl cellulose, the steps which comprise continuously feeding a cellulose sheet in succession through an etherifying zone and a neutralizing zone, reacting chloracetic acid with an alkali metal carbonate to eiect neutralization of about 40% of the acid with liberation of carbon dioxide gas, and contacting the sheet while in said etherifying zone with the partially neutralized acid and an aqueous alkali metal hydroxide.

15. In a process for the manufacture of carboxymethyl cellulose from cellulose pulp, the steps which comprise continuously feeding cellulose pulp in the form of a continuous sheet through a hydrolyzing zone, an acid acid removing zone, an etherifying zone, a ripening zone, and a neutralizing zone, contacting said sheet While in said hydrolyzing zone with a strong mineral acid to partially degrade the cellulose, Washing the sheet with an aqueous liquid and heating the Washed sheet to effect removal of washing liquid, applying to the sheet in said etherifying zone aqueous solutions of a halogenated lower fattyacid having not more than 4 carbon atoms and an alkaline agent and maintaining an elevated temperature in said etherifying zone to effect substitution of glycoiic acid groups on the cellulose chain, and contacting the sheet in said neutralizing zone with a neutralizing agent for the unreacted remainder of the alkaline agent.

16. In a process of preparing Water soluble salts of cellulose ether alkyl sulfonic acids Where the alkyl radical contains no more than 4 carbon atoms the steps which comprise continuously feeding the cellulose in the form of a continuous sheet, through a hydrolyzing zone, an acid removal zone, a drying zone, and then impregnating the sheet while feeding through an etherifying zone successively and in the order named (l) with an aqueous solution of caustic alkali of concentration of :Z5-40% by weight in quantity of about 1.2 to 2.2 mols sodium hydroxide per glucose unit of cellulose, (2) with an aqueous solution of a halogenated alkane sulfonic acid having not more than 4 carbon atoms in concentration of about 60% to about 80% by Weight in quantity of about 0.8 to 1.5 mols of acid per mol of glucose unit, (3) with an aqueous solution of caustic alkali of concentration of 25-40% by weight in quantity of 1.0 to 1.4 mols sodium hydroxide per mol glucose unit, maintaining throughout the etherifying zone a temperature of 15 to 40 C., then continuing the process while feeding the sheet continuously through a ripening zone, a

fle of this patent:

14 UNITED STATES PATENTS Name Date Seel Aug. 5, 1924 Reid June 28, 1932 Ellsworth Nov. 10, 1936 Maxwell Dec. 7, 1937 Freeman et al May 23, 1939 Collings et a1 Apr. 7, 1942

Claims (1)

1. IN THE PROCESS OF PREPARING SALTS OF ACIDIC ETHER DERIVATIVES OF CELLULOSE FROM CELLULOSE PULP, THE STEPS WHICH COMPRISE (1) CONTACTING THE PULP IN THE FORM OF A CONTINUOUS SHEET, WHILE FEEDING THE SHEET, THROUGH A HYDROLYZING ZONE, WITH A MINERAL ACID AT ELEVATED TEMPERATURE FOR A PERIOD OF TIME SUFFICIENT TO EFFECT SUBSTANTIAL DEPOLYMERIZATION OF THE PULP, (2) WASHING AND DRYING THE SHEET WHILE FEEDING THE SHEET THROUGH AN ACID REMOVAL ZONE, AND (3) IMPREGNATING THE SHEET, ZONE, WITH AN AQUEOUS SOLUTION OF A HALOGENATED WHILE FEEDING THE SHEET THROUGH AN ETHERIFYING ACID OF THE GROUP CONSISTING OF HALOGENATED ALIPHATIC CARBOXYLIC AND HALOGENATED ALKYL SULFONIC ACIDS HAVING NOT MORE THAN 4 CARBON ATOMS IN THE MOLECULE AND AN ALKALINE AGENT IN TOTAL AMOUNT NOT GREATER THAN THAT WHICH THE SHEET IS CAPABLE OF ABSORBING.

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