A Staff-Industry Collaborative Report

A Staff-Industry. Collaborative Report. RODNEY N. HADER. Associate Editor in eollrboration with. W. F. WALDECK AND F. W. SMITH. Wymadotte Chemieob ...
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A Staff-Industry Collaborative Report RODNEY N. HADER Associate Editor

in eollrboration w i t h

W. F. WALDECK AND F. W. SMITH Wymadotte Chemieob Corp.. wyindotte, Mieh.

c

ARBOXYMETHYLCELLUL08, a chemical of demonstrated Usefuhem in scoren of applications and of Suggested applicability in hundrede, nevertheless repuired eeveral decadcs to attain genuine industrial status. The product wae &st developed in Germnny toward the end of World War I by Jansen (7), but it wan not until the late 193o’s, and particularly during and since World War 11, that large male wea began to emerge and commercial production appeared justified. In 1945,a literature Survey by Hollabaugh, Burt,and Walah (6) summarized the many w s to which carboxymethylcellulose, particularly in the form of ita sodium salt, had by then been directed: Hollabaugh cited numerous applications in the textile, paper, and food industries and in the manufacture of dmgs and ccemetics, deramios. leather d. . Oaints _ and laeauers. . . filmsand filaments.

Following the appesnrnoe of the Hoyt report, the deterwIcYimproving chsraeteristicn of ncdium carbo?qmethyldIulme were confirmed in laboratory teste in the United States (9). Extensive inmatigations were undertaken by r-h p u p of the Wyandotte Chemimb Corp., with a view t o d develop ing a carboxymethyleelldase with high detergency-promoting Pmpertiee for use with the high @amps and synthetic detergente slready available on the American market. Ab the came time, @reduction methode were subjected to m t i n y . CarhmrJc meth~leelldosehad reoeived the impetus neceimry for the lahching of a new industrid chemical, and a atart had been made toward thedevelopment ofapmcesaforitsmanufaoture.

snd adh&vea.

Stabilizer, ahd Detergency-Improver

-

no sinale lawe scale demand Dpsoite this arest diversits of then ,&e ai least in the-United States.- In the m e month that the Hollabaugh survey appeared, however, a report written by Hoyt (6),a Quartermaster Corpa consultant, revealed that &xymethylceUdose had been extensively used in Germany duringthe warns adetergency promoter. The abilityof carboxymethyloelldose to improve d e t e m y had been diemered in Germanfabout 1935, and in 1940 the Kalle plant of I. G. Farbenindustrie w88 recommending its Tyloee HBR for use with fatty acid m p products and synthetic detergent mixtures. Hoyt, who interview& German techniciane and inspected production facilities after the war, found that the cellulose derivative had been widely wed 88 an extender for low grade synthetic detergents, with demand awgnented by the extreme Shortage of fatty acida in wartime Germmy, ,The pwnibdity of using carboxymethylcellulose with high grade synthetics apparently had not been investigated and definitely had not been exploited.

CMC Is VduqJde as ThioLenu,

The production data in Table I indicate the w i d gmwth reejsteredby csrboxymethylcellulase (CMC) in the United Stsbea since 1947. Because of the great variety of forms in which it can now be made and the wide range of physical pmprtien it can be given through variations in pmwsdmg ‘ techniquee, the msrket poseibditiea of carboxymethfidlulase m extensive. In its various technical grades, o a r b o ~ e t h y l e e U d mhss pmved its value in adhesive compositions such 88 watewmluble glw; in stabilization of laties such an plsstics, rubber, and the new latex paints; and in ceramic#, where it serve4 88 a dispenjng agent to help keep the oernmlo glaze in suspension. Table I1 ihdicates the approximate d i s t r i k t i w pattern for 1960 productim of c a r b e q m e t h y l e l l ~in the United States, according to major abuse da~sific~~tions. The paper induntry offers a large and continually w h g markct. On jute liners, earboxWethyldldase increaw burnt-

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TABLE I. CARBOXYRIETHYLCELLULOSE PRODUCTION (Tariff Commission figures)

1947

1948

1949 1950 1951

Thous. Lb.a 2,260b 5,7728 7,1498

a Believed t o be on a n "as-is" basis, except 1951, which is based on 100% active CMC. 8 Does not include production f o r Buckeye Cotton Oil Co.

FOR

Thous. Lb.a Detergents Drilling muds Foods and pharnmceiiticals Paint Paper Textiles Miscellaneous a

Other markets, such as the development of specialty films for unique packaging applications, are still in the suggestion stage; as yet no more than a surface scratch-let alone a real denthas been made in markets of this kind. Solubility of CMC Depends on Degree of Substitution of Hjdroxyl Units

15,691 16,733

TABLE11. ESTIMATED 1950 C O N S E V P T I O N PATTERN CARBOXYMETHYLCELLULOSE

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10,000 2,000 1,000 500 500

500 1,000 15.500

An extensive discussion of the chemistry of sodium carboxymethylcellulose is given by Hoppler (4). The conventional process for the production of sodium carboxymethylcellulose, as first conceived by Jansen, and later improved by Chowdhury ( a ) and Hoppler ( 4 ) , consists essentially of steeping bleached sulfite pulp sheets in caustic soda solution, pressing out the excess liquor, shredding the alkali cellulose, and allowing it to react with dry sodium monochloroacetate to form sodium carbouymethylcellulose and sodium chloride. The reactions that occur may be represented as follows:

"As-is'' basis.

OH

OH I

ing strength; on coated boxboard, it increases gloss and gives printed characters a brighter appearance; in de-inking systems, it helps to suspend ink for subsequent removal. The European textile industry has employed carboxymethylcellulose for warp sizing. This application has not yet been too successful in the United States, but further development work will undoubtedly improve this market. In textile printing paste, the compound thickens dyes to prevent their running during the printing operation. As a finishing agent, it improves the "hand" or feel of cloth. The petroleum industry has recently proved the outlet for increasing amounts of carboxymethylcellulose. Less than 1 % of the product added to oil well drilling mud improves mud viscosity control and helps to plug porous formations in the bore, preventing loss of water from the mud. In this application, carboxymethylcellulose in many cases cuts water loss by as much as 95%. Perhaps the material's greatest potential still lies in the laundry field, where detergency improvement demands larger and larger quantitiea of carboxymethylcellulose each year. In addition, the product has been found effective as a laundry sizing, where it may be used with starch to aid in suspension, or may even replace starch entirely as a stiffening agent. Since carboxymethylcellulose is currently more expensive than starch, its widespread use aa a starch replacement is not considered likely for the immediate future. Nevertheless, this use is becoming more important, and one carboxymethylcellulose producer considers it one of the biggest potential markets. A new possibility has come to light with the rapid emergence of soil-conditioning agents for use in home gardening or full scale farming. Although evaluation has not been extensive, there are indications that carboxymethylcellulose may improve the physical characteristics of soil in somewhat the same manner as the acrylic-type soil conditioners do. By mid-1952, one soilconditioning formulation with carboxymethylcellnlose as its principal ingredient had already reached the home-consumer market via New York department stores. Considerable expansion of carboxymethylcellulose markets is expected for purified grades which can be added to food, cosmetic, and pharmaceutical preparations. The ice cream market alone could prove amajor outlet; 0.1 to 0.2% by weight of carboxymethylcellulose, replacing natural gums, is an excellent stabilizer for this favorite American dessert. Besides inhibiting the formation of ice crystals, it decreases the amount of beating required for the incorporation of minute air bubbles t o improve the consistency and decrease the density of packaged ice cream.

1

+ NaOEI HC--OH I H

r

OH

OH

I

1

/c-c\

I

HC-OIia

OH

OH

,

H&-ONa

H OH I

OH I

+ SaCl I

//

HC-OCH2C-0Na

I

H

+

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Much of Wyandotte’s Development Work Was Conducted in a &Foot Drum Segment 16 Inches i n Length Using batches of about 60 pounds, operating variables were studied on a semicontinuous hasis which permitted easy collection of data pertinent to a design of a production unit

Theoretically, all three hydroxyl groups in each anhydroglucose unit of the cellulose chain may be substituted, with the sodium carboxymethyl group replacing hydrogen. In most commercial samples, however, an average of less than one hydroxyl unit is affected, with 0.4 t o 0.8 hydroxyl per cellulose unit the most common substitution range. The fraction of a hydroxyl unit which is substituted in this way is termed the degree of sub.stitution. Thus, replacement of an average of one hydroxyl per anhydroglucose unit is considered one degree of substitution; three degrees of substitution are theoretically possible. As a cellulose derivative, sodium carboxymethylcellulose can undergo the reactions characteristic of cellulose. The unsubstituted hydroxyl groups, for example, may behave as the hydroxyls of aliphatic alcohols, forming addition compounds with alkalies and certain complex salts. Esters and ethers also can be formed, and oxidation can convert the hydroxyls to aldehyde or acid groups. Carboxymethylcellulose (not the sodium sal@) with 0.3 degree of substitution is a moderately strong acid, with a n ionization constant of the same order of magnitude as that of acetic acid. As an acid, the product will form compounds with alkalies and other metal hydroxides. The sodium derivative, a s a salt of this acid, reacts with metal salts in aqueous solution by double decomposition, whenever the metal carboxymethylcellulose thus formed is insoluble. Solutions of sodium carboxymethylcellulose are compatible with alkalies and alkali salts, but the addition of either inorganic or moderately strong organic acids, in amounts sufficient to give a p H of about 3, causes precipitation of the carboxymethylcellulose. Strong oxidizing agents which attack the free hydroxyl groups also cause cleavages between the glucosidic linkages of the cellu-

lose chain, lowering the molecular weight and markedly altering most of the characteristic properties of sodium carboxymethylcellulose. Pure sodium carboxymethylcellulose is a white powder, soluble or dispersible in water or alkaline solutions. I t s degree of water solubility and its rate of solution vary considerably with the degree of substitution, as do many of its other physical and chemical properties. In general, the greater its degree of substitution, the greater is its solubility. Water solutions of the sodium salt are highly viscous and for this reason are useful for their thickening, suspending, and stabilizing properties. I n pure form, the powdered product is odorless and tasteless; toxicological tests have shown it t o be physiologically inert (1). The technical form of sodium carboxymethylcellulose, which is supplied for most uses outside the food, drug, and cosmetics fields, is generally a cream t o light-tan colored solid. It is substantially odorless, but because of the possible presence of mildly toxic sodium glycolate i t is not suited for ingestion. Both technical and purified grades usually retain the general physical appearance of the cellulose from which they are prepared. Dry Sodium Monochloroacetate Reacts with Alkali Cellulose in German Batch Process In the manufacture of Tylose HBR as practiced by Kalle and Co., A.G., Wiesbaden-Biebrich, Germany, a subsidiary of I.G. Farbenindustrie, the two principal steps are the reaction between bleached sulfite pulp and caustic soda t o form alkali cellulose, and reaction of the latter intermediate with dry sodium monochloroacetate t o form sodium carboxymethylcellulose and sodium chloride. Excess caustic is neutralized with sodium bicarbonate, and the product is ground and packaged. Previously the mate-

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risl was aold without drying,but now moat of t h w production is dded in a drum dryer. An abbreviated flow aheet for the German proceea is given

Vol. 44, No. 12

d u m bicarbonate and d u m carbonate formed by the rew tion of the bicarbonate with w x m s cauatic in the alkali cellulose. The German process is entirely a batch process, requiring the uee of a conaider.de amount of heavy equipment, which in turn n d t a t e s a 1srg.v inlreetment to d m only moder8t.s production ram. In addition, the steps involved in the process m of a typw whiah do not lend thermselves to ooutmuoun automatic operatiou, BO that the &bility.of outlabor costs with this proosss is quite mnsll. Findly, the requir6ment of dry d u m mend-te for the process d t a t e s preliminary praparation of the salt through reaction of monochlomacetic aoid with sodium hydroxide. Continuous Proceds Una MMoebloroacelic Acid

when the Wyandotte Chemic& Corp. undertmk ita inveatigsr tion of carboxymwthyldulcen manufactum, ita firat aim was to develop a pmcess which could be handled on a continuous basis and w d d elimihste m e of the maeaiw equipment and clumsy operations inherent in the batch pmopes. -tion of the steeping and prwing steps in the pmprahn ofalkali cellulose was a primary goal, to be followed if &bh by aircumventing the shredding operation Findly, it ' ~ . deaired 8 to simplify the chemistrg of the pmcese wbrmver ppdble, awreasing the number of separate opmntions, and hence e h t i n g asin building and equipment inv&mmta, operatiq mSy and storuge Bpace for cbeanimlk Fkgbing with the German process, and h k l h g ita d v o r a ble faturea one by one, the Wyandotte m e a d and develop ment dwpartmemt evolved a much simpli6ed pmceea whiah fasturw Continuous operation with a minimum of heavy equip ment. It offm a decided e ~ of~ operation e in mntrsat to the older proceea, and an easily expandable pmduction capacity. Wyandotte completed ita pilot plant investigations in 1947, and late in that ywar entered the market with Carbose, the Wyan-

.

Figure 1. Abbreviated Flow Sheet Indicating Principal Step in Geman Batch P m c e s n for CarboxymethylceUulose Manufacture Polpismppliedinahewts80 x 1OOcm.; amixturwofpinesnd beech sulfitepulp is used,with the proportions varied from batch to batoh as required, in order to maintain a atandud vhcaity for t h w &d pmduet. About la00 pounds of cellulose is duwged h aach batch and steeped in 18% caustic for 1% to 2 hours at to 2W C. The~xoesscaustic is then w e e d fmm the alksli Quulose by means of a hydraulic ram, yielding a maiat pmduct wdghing about 2.5 to 2.7 times as much as the original cellulode

cQs%e. The moist sheets a m put tbrough toothed roll mills, a OOBLBB .bredder, a$d a horisontd disk shredder mill, from wbich the alkali cellulose emerges as a h e crumb. About 13B pounds of the SlLali cellulcen a o m b in admitted to a janketad kneader, and d u m monochlomacetate is added in the form of the dry sdt. Theae ingediemts m mixed at a W p e r a t m of 36' C.; excess beat fmm the exothermic reaetion is mmoved by cooling watez circulating in the jacket. A t the end of about a bours,the reaction is about Bo to 70% ~ o m p l e +and ~ , the kdcb is dumped to make mom for a new chqe. The dumped batch mtem a large rotating drum, jacketed to maintain the correct reaction temperature; and &w material+atumbM until is essentially cdmplete. With the batch &ill tmbling'in th6 drum. aodium bicarbonate is added to neutralize the ex8Wi; From &.drum the batch is dischaned to mills wbich further b r d x down the product to a h w , gr&ular form. I n this form it is packsged f a shipment. Ita composition is approximately 85 to 36% d u m cnrboxymwthylcellulose and 85% moistUrei the Manes ooosiatsod&, chiefly sodium ohloride formed during the r e s d i n , a d l m o u n t of sodium glycolate, aome &dud

,-ti-

P o w d d csllulose, Purchased in %Pound Bags, Is Fed ManUdiy into Hopper of Bucket Elevator for Transfer to Rotary Reactor

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INDUSTRIAL AND ENGINEERING CHEMISTRY

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dotte trade name for its commercial grade of sodium carboxymethylcellulose. The patented Wyandotte process (IO) has since been made available for licensing. Qther Producers Manufacture Special-Purpose CMC

Other U. S. producers of sodium carboxymethylcelluloseinclude E. I. du Pont de Nemours & Co., Inc., Hercules Powder Co., and Buckeye Cotton Oil Co., a subsidiary of Procter & Gamble Co. Du Pont manufactures only technical grades, the principal use being in synthetic detergents. Little information is available outside the company concerning the manufacturing process used, but it is believed to be a batch process based on the use of powdered wood cellulose. Hercules, too, is thought to use a batch process, described by the company as “a novel and efficient” process which improves considerably on the German steeping and pressing methods. The Hercules plant is located a t Hopewell, Va.; although a relatively new plant, it has been expanded several times during the past few years. Hercules is the sole commercial producer of purified sodium carboxymethylcellulose in the United States. This grade contains carboxymethylcellulose of better than 99% purity and is suitable for use in foods, such as ice cream. The patented continuous process used by Buckeye (8) is based on the use of cotton linters in continuous sheet form. In this process the cellulose sheet is carried by rolls through successive chemical reaction steps, and finally is ground to powdered form after all chemical modification of the sheet has been accomplished. Sheet thickness is important in determining penetration of chemical reactants; the optimum thickness is about 0.040 inch, although sheets ranging from 0.0125 to 0.06 inch can be handled. I n commercial operation, sheet width is about 40 inches. From the feed roll, the cellulose sheet is fed through a hydrolysis bath containing 15% hydrochloric acid solution a t 70” t o 80” C. Immersion lasts for about 60 seconds. As the sheet leaves the bath, it passes through squeeze rolls which remove excess acid. The hydrolyzed, partially depolymerized sheet is given three water washes, each followed by water removal on squeeze rolls. With the acid removed, the sheet is passed over a roll dryer where moisture content is reduced to 10 to 25% of the dried weight of the sheet. Sodium hydroxide solution is spread over both sides of the hydrolyzed cellulose by means of coating rolls; this is followed immediately by treatment with monochloroacetic acid solution on a second set of coating rolls. A final treatment with sodium hydroxide brings the concentration of alkali up to the stoichiometric proportion. The treated sheet is passed through a “ripening” cabinet, where it is aged in a nondrying atmosphere at about 100” C. for 4 minutes. It next passes through a tank where gaseous carbon dioxide neutralizes the alkaline product to prevent yellowing on subsequent drying. From the gas chamber, the sheet passes over a roll dryer where its moisture content is reduced to about 301,. The dried product is transferred to conventional crushing and grinding equipment and thence to bins for packing and shipping. Buckeye’s entire output is used within the Procter & Gamble organization, primarily in industrial and household detergents; none is currently sold on the outside market. Wyandotte Produces Technical Grade CMC from Bleached Sulfite Pulp

Figure 2 is a flow sheet for the Wyandotte continuous process for manufacture of sodium carboxymethylcellulose. The process consists of spraying powdered cellulose first with caustic solution and then with chloroacetic acid as the solid cellulose is tumbled in a rotary drum. The two major reactions involved in the process

Monochloroacetic Acid Shoveled through Opening Drops into Dissolving Tank on Floor Below Note safety shield; no one is permitted t o enter manufacturing area without safety glasses or shield

occur successively within the drum as the cellulose slowly progresses from entrance to exit. The cellulose employed is a bleached sulfite pulp, purchased in powdered form in paper bags of 50 pounds net weight. The bags are manually emptied into the hopper of a bucket elevator which transfers the cellulose to a ribbon mixer. Here the compacted cellulose from the bags is broken up. The fluffed material is discharged through a slide valve and into a feed hopper equipped with a rotating scraper; from this point it moves by screw conveyor into the feed end of the rotating reactor. The feed screw is provided with a variable speed drive, normally set to deliver 160 pounds of cellulose per hour t o the reactor. Processing Is Continuous i n a Three-Zone Rotary Reactor

The reactor is 20 feet long and 4 feet in diameter; it is driven at 16 r.p.m. by a 7l/2-hp. motor. Average residence time for a given particle of cellulose in the reactor is about 3 hours, or 1 hour in each of three “zones.” The reactor contains no baffles or flights, but it is equipped with a longitudinal scraper bar which prevents the moist solid from caking on the wall. The reactor is normally about one third full; mixing action is provided entirely by tumbling. Figure 3 is a schematic end view of the rotary reactor used by Wyandotte. Caustic soda for converting the cellulose to alkali cellulose is received as 50% liquor and is diluted with water to a concentration of about 35%. Caustic from the dilution tank is metered into the reactor by means of a positive displacement pump with adjustable stroke ( I E ) . I n normal operation, the caustic feed pump is regulated to deliver the solution a t the rate of 225 pounds per hour. This rate is checked by use of a rotameter and by observing levels on a graduated measuring tank. The solution is sprayed onto the tumbling cellulose at the feed end or

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Vol. 44, No. 12

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INDUSTRIAL A N D ENGINEERING CHEMISTRY

my center shaft of the reactor. The thermometer bulb dmgs in the rest+ tion maas in the region of maximum temperature, just downstream fmm the acid feed. I n order to m o v e the beat of reaction and prevent temperature build-up, an air stream is drawn through the reactor bv a blower. Air flow is r&dated by adjustment of dmpern in the reactor inlet and discharge ducts. During the summer, air is drawn from the outside atmw phem; in bot, humid weather it bae been found neoessary to pull sa much 88 700 cubic feet of air per minute thmugh the reactor to maintain the desired temperature range. In cooler, leas humid weather, the demand is much lees; room air is used during the winter months. The cooling air eEluent from the reactor carries with it a small amount of celluloee and carboxymethylcelluloee "dust," amounting to 1% or lass oftheductstream. Anrmdliarv stream ;d hinted sir joins the & u e k -g* &&'- e .and driea the d&t, to prevent ita in &,e.k&&? is Teatsd on S1 Setup More InwNon into Rm&r sticking to the duct walls. The dust is moved from the air etby means of a cyclow' aepemtor, and is normally discarded. The air leaving the top of the cyclone 6mt sone of the mtor,through four pneumatic atomizing nodes psases through a Multiclone dust collector (.LE), where the re(JIG). Small solid particlesin the caustic solution B I ' ~moved by maining trace of dust is m o v e d . a IoO-meSh ~cm ahead of the feed pump and a 2oomeah BcTeen shead of the aimmizing nozzles. Complete Reaction Requires about 3 €IoPneu-tic Atomizers D i n During the average holdup time of about 3 hours in the rotary MOn&-etic Acid i n E c t o r drum,reaction bsa been virtually completed. The moist carboxy"ha alkali __. __ cellulase formed bv reaction with the caustic wlu- methvloellulhse arriving- at the discharm - end of the drum is m o v e d by a variablegpeed mrew conveyor, with the vertical tion pmgmsms slowly throughthe drum and is next sprayed with positioning of the s a w providing a rough control on the level mondorcmetic acid. The four pneumatic atomizing noszlee wbcb disperse the acid are located in the central zone of the lpao of the tumbling reaction maas; the reactor is kept about one third full. tor. The acid solution, with the camtic, is metered into the system The ncraw discharge the wet d u c t , containing about 40% by a proportioning p i t i v e displacement pump (le), with atroke moisture, into fiber drums, where it is allowed to "age" for several adjust& to deliver 114 pounds per hour of 78% acid solution. The acidandcaustic pumparedriven byacommonmotor but h o w . This allows the &ion to go to completion. The are independently adjustable to change flow ratio or rates. temperatureof the d i w h a r d wet product, about85"C. whenthe material leaven the reactor, rises Mondoroacetic acid for the to 50°ta 55'C. duringthe 6 r a t process is purchases as a solid SuPPoRT 'INQ 6 to 8 h o w of the aging cycle. in fiber drums of aM) pounds By this time reaction is e e a net; the solid is dissolved in tially complete, and the conwater in stainleas steel tanks to provide the 78% solution d* . t e n t s of t h e a g i n g d r u m s sired. T h e s o l u t i o n pasaes CENTER SPRAY &Tadually cool. S"PPoRT thmugh a clarifying filter W E ) en route to the reactor; any Flash Drying Yields remaining minute particlea of Desirable M u c t foreign matter are trapped by For most industrial um, a IoO-meah screen ahend of the a dried form of sodium carboxyfeed pump and a 2oomeah methylcelluloee, containing 6 to Bcreen ahead of the atomizing noszlea 8% moisture, is produced. Hence, the wet carboxymethylhe optimum temperature tor cellulose from the reactor, after the tumbling reaction maae'has aging for 8 t o 10 hours, must been determined as 35' to 40' C. be dried. Drying may be 80 A constant check is maintained by D m m S Of an indkSting ~i~~~~ 3. Schematic End view of continuous complished by Of Several Rotary Reactor for Ca~box~metbyleellulose metbcds, such sa wen drying thermometer, the bulb of which is supported from the stationManufacture or flaeh drying. Wyandotte "

~

i

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Vol. 44, No. 12

Over-all View of Production Unit Which Continuously Produces Carboxymethylcellulose Dry powdered cellulose i s transferred from feed hopper a t left into rotary reactor. A s it tumbles i n reactor, cellulose is sprayed successively with solutions of caustic soda and monochloroacetic acid, which convert i t to moist sodium carboxymethylcellulose. The moist product is discharged into drums ( r i g h t ) , and after aging for several hours is flash dried and packed for shipment

has found that flash drying yields the product in its most desirable physical form. I n preparing the dry product, wet carboxymethylcellulose from the aging drums is fed into a preliminary mill which breaks up the compacted moist material and discharges it to an agitated hopper; a screw with variable speed drive transfers the wet particles from the hopper to the flash dryer, where hot combustion products from a gas burner instantly reduce the moisture content to the desired level. The dried, pulverized carboxymethylcellulose is carried upward in the stream of air and combustion gases and into a product cyclone. Here the carboxymethylcellulose is separated from the gas stream and is discharged through a star valve to a cooling duct. The effluent gas stream, containing some fine dust, passes from the cyclone to a secondary separator. In the second cyclone, the remaining recoverable product is separated from the air and returned tothe flash dryer, while the air is diverted through the Multiclone for eventual discharge to the atmosphere. The dried carboxymethylcellulose from the primary collecting cyclone is air-cooled to about room temperature as it passes through the cooling duct en route to a final cyclone. This unit collects the final product and discharges it through a star valve to a packing hopper. The dried product is then sampled and packed for shipment. Waterproof fiber containers are used, since dry sodium carboxymethylcellulose is hygroscopic and is subject to caking if exposed to moist air. Type 316 Stainless Steel Is Major Material of Construction

Carbon steel and Type 316 stainless steel are the principal materials of construction throughout the TTyandotte installation. Small amounts of Monel metal, Durichlor, saran-lined pipe, and chemical stonen-are are in use in the system, but tests

indicate that Type 316 stainless could be used to replace all these materials without adversely affecting the corrosion resistance of the units involved. In general, Type 316 is suitable throughout the system where corrosion or contamination is a problem; carbon steel, because of its lower cost, is indicated wherever inert streams are handled. The one exception to the use of Type 316 in corrosive service is in the preparation of the concentrated monochloroacetic acid solution. Here it has been found that stainless is not suitable a t temperatures much above 25" C.; a stainless steel steam sparger in the acid dissolving tank was found to corrode very rapidly. Substitution of Hastelloy C in this application halted the corrosive attack. Type 316 stainless is in use in the rotary reactor lining, the angle-iron scraper and its support chains, the reactor's center support pipe, and the pipelines for air, caustic, and acid which enter a t the feed end. Stainless steel nozzles are used for the acid spray, while either stainless or None1 is satisfactory for the caustic soda nozzles. The metering tank for the acid is of stainless steel, as are all acid pipelines and the main acid storage tanks. A Durichlor pump is used to transfer the acid solution from the dissolving tank to the storage tanks. The clarifying filter is of htonel but is to be replaced with one of stainless steel; saran filter cloth has been found satisfactory in this application. Mild steel has proved entirely suitable for the storage, dilution, and metering tanks in caustic soda service, and cast-iron transfer pumps are used between the tanks. Mild steel also is used for the handling of the powdered cellulose used as ram material. At the take-off end of the reactor, the screw conveyor, flash dryer, cyclones, star valves, cooling ducts, blowers, and packing hopper are all of mild steel construction, and all are satisfactory.

December 1952

INDUSTRIAL AND ENGINEERING CHEMISTRY

2811

Performance Tests Check Product Quality

TABLE 111. PROPERTIES OF TECHNICAL SODIUM Analytical procedures for the evaluation of carboxymethylCARBOXYMETHYLCELLULOSE cellulose still are not very clearly defined. Specificationsfor the Typical Acceptable Production final product are therefore based on performance tests rather than Limits Sample on chemical analyses. Work is in progress on analytical procedures, however, and some of these are already adequate to provide data useful in correlating chemical composition with performance. ....._ ...-The determination of active agent present in a sample of carstandard lot Sodium chloride content, % .... 16 boxymethylcelluloseisbased on measurement of alcohol insolubles. Low-molecular wei h t sodium carboxymethylcellulose plus s o f i u ~ glycolate, % .... 6 The method consists of stirring the sample in hot 80% (by volume) ethanol, filtering, and washing, first with 80% and finally with a p H of commercial product can be oontrolled t o specifications dictated b y consumer’s requirements. 95y0 ethanol. I n this manner the sodium chloride, sodium glycolate, and other salts are dissolved and removed while the sodium carboxymethylcellulose, essentially insoluble, remains as a residue. The latter is dried and weighed, and the active agent Among the other properties measured for carboxymethylcontent is calculated. cellulose are alkalinity, chlorides content, pH, volatiles (moisture) The determination of the degree of substitution is based on the a t 110’ C., carbon soil removal capacity, and whiteness retenmethod of Eyler et al. (3). It consists of acidifying the sample with tion capacity. The two latter properties are most significant a nitric acid-methanol solution, removing excess acid with a methin establishing the product’s usefulness in detergency promotion. anol-water solution, adding a known amount of standard sodium Table I11 indicates the acceptable limits for several of the hydroxide solution in excess of the amount required for neutralizchemical and physical properties of “dry” sodium carboxying the acid carboxymethylcellulose, and titrating the excess methylcellulose. I n the final column are values for a typical sodium hydroxide with standard hydrochloric acid solution. From the data obtained in p r o d u c t i o n sample. The this way, it is possible to values in Table I11 are caldetermine the degree of subculated on a moisture-free stitution. The accuracy of basis; the actual moisture the method is only fair, and content of this product is Wyandotte’s research diviordinarily about 5%, and its sion is developing a new active agent content on an method which is expected to “as-is” basis is usually about improve the accuracy of the 68%. W y a n d o t t e m a k e s determination. products of both higher and The presence of sodium lower viscosity, by modifying glycolate in sodium carboxyproduction techniques. methylcellulose cannot be tolerated if the material is to Wyandotte Unit Produces be used for food, pharma3l/t Tons of CMC per ceutical, or cosmetic uses, 24-Hour Day since sodium glycolate is Virtually 100% of the mildly toxic. The analytical materials entering t h e test for this impurity is not Wyandotte process show up considered entirely satisfacin the final product, sincetory. It is based on a a t least for the technical colorimetric comparison of grades-it is not necessary a diluted alcohol extract from to remove the coproduct the carboxymethylcellulose sodium chloride nor all the sample with solutions of water entering the system. known sodium glycolate conWith the exception of a tent. The method was devery small loss of cellulose veloped by Eyler (3). as dust, the only material Among the most important which leaves the main of the chemical and physical Moist Carboxymethylcellulose Discharges from Rotary product stream is moisture. properties of carboxymethylReactor into Fiher Drums, i n Which It Is Stored for Aging Under normal conditions, cellulose is its viscosity bethe unit produces 3 1 / 2 tons havior in aqueous solution. of carboxymethylcellulose U n f o r t u n a t e l y , the exact per 24-hour day. Table IV is a summary of the materials conmeasurement of this property is quite difficult, since the product sumed in production of a ton of technical carboxymethylcellulose forms a colloidal suspension-not actually a solution. The suscontaining 5% moisture. It is apparent that the total weight pension is thixotropic, adding to the difficulty of obtaining of the raw materials (exclusive of dilution water) entering the true viscosity measurements. Furthermore, it has been found reaction is only slightly over 1 ton, most of the excess being that the viscosity of a given sample dispersed in water is deeliminated as water in the conversion of cellulose to alkali cellupendent on the sample’s history, particularly with regard to lose as indicated in Equation 1. temperature changes. The American Society for Testing MateService requirements for producing a ton of carboxymethylrials has organized a committee to study development of a more cellulose are given in Table V. The raw materials costs a t the satisfactory procedure for measuring carboxymethylcellulose Wyandotte plant may be broken down as follows: solution viscosities as well as other properties.

INDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y

2812

Vol. 44, No. 12

TABLEIT’. RAW hI.4TERIAL REQUIREMESTS FOR PRODUCIKG SODICM CARBOXYLIETRYLCELLULOSE R a w Material Powdered cellulose (5% moisture) Monochloroacetic acid, technical (anhydrous basis) Caustic soda (dry NaOH basis) Dilution v a t e r Filter aid Total

TABLEJ7.

T o n l t o n 6870 C M C (570 Moisture) 0.578 0,290 0.256 0.412 0,0003 1.536

REQUIREVESTS FOR P R O D U C I V G S O D I U M CARBOXY\IETHYLCELLULOSE

SERT. I C E

Coke-oren gas (500 R.t.u./cri. f t . ) . CII. f t . / t o n 68% C M C Electric power, kw.-hr./ton 68% C N C Cooling mater ffor bearings of hammer mill), gal./ton 68% CLIC Steam (for heating acid in dissolving t a n k ) , Ib./ton 68% C N C

9000

622 1050 52

Wyandotte’s current production is concentrated primarily on its Carbose D for detergency promotion and Carbose I for general industrial uses. The company’s line also includes Carbose IM, a product of higher viscosity; TP, used primarily in textile printing pastes; MX, for oil well drilling muds; LS, a low pH product designed for laundry sizing; and SIL, a new grade boasting a viscosity as lorn as that of any sodium carboxymethylcellulose on the market. In May of this year, the company put into operation a new unit of greater capacity than the unit described in this report. The added capacity and flexibility permit commercial manufacture of some of the newer forms which up t o now have been made only in experimental or interim-production quantities. Because of its great versatility, carboxgmethylcellulose can look for continued rapid expansion throughout the foreseeable future. Dry Sodium Carboxymethylcellulose, Ready for Use as Detergency Promoter, Is Packed i n Moistureproof Fiber Drums for Shipment

Literature Cited (1)

Brown, C. J., and Houghton, A. A , , J . Soc. Chem. I n d . ( L o n d o n ) ,

(2) (3)

Chowdhury, J. K., Biochem. Z., 148, 76-97 (1924). Eyler, R. W.,Klug, E. D., and Diephius, F., Anal. Chem., 19,

(4) (5)

Hcppler, F., Chem.-Ztg., 66, 132-5 (Apiil 1942). Hollabaugh, C . R., Burt, L. H., and Walsh, a.P., IND.ENG.

60, 254-8 (1941).

Per Cent Chloroacetic acid Caustic soda Powdered cellulose

44.0 4 8 51.2

Processing costs are broken down as follows: Direct labor Operating and supervisory Analytical Amortization Maintenance

Per Cent 68 2 9 8 13.8 8.2

Versatility of CMC Assures Its Future

With an economical process for producing a versatile chemical and with a production capacity that can be easily and rapidly expanded, Wyandotte’s concern for the immediate future is naturally the extension of markets. By modifying processing conditions only slightly, it is possible to turn out a broad series of carboxymethylcellulose types differing in viscosity, pH, solubility, or active agent content. More than a half dozen different types are already in production on a commercial or semicommercial scale, and others ran be added to the roster as demands are established.

24-7 (1947).

CHEM.,37, 943-7 (1945). (6) Hoyt, L. F., “German Chemical Developments in Tylose HER,” APO 757, U. S. Dept. Commerce, Vaashington 25, D. C., PB Rept. 3865 (1945).

Jansen (to Deutsche Celluloid Fabrik), German Patent 332,203 (Jan. 10. 1918). (8) Rogers, L. N., Mueller, W. A , , and Hembree, E. E., U. S. Patent, 2,553,725 (May 22, 1951). (9) Vaughn, T. H., and Tremain, H. E., Soap S a n k Chemicals, 24, (7)

37-9, 98 (1948).

(10) Waldeck, W. F., U. S. Patent 2,510,355 (June 6, 1950).

Processing Equipment

(1E)Hills-McCanna Co., Chicago, Ill., dual proportioning positive

(2E) (3E) (4E)

displacement pump; Type 316 stainless steel bodies: Hastelloy C plungers: 15.6 gal./hr. max. capacity on acid side; 27.9 gal./hr. max. capacity on caustic soda side. Sparkler Mfg. Co., Nundelein, Ill., horizontal leaf filter, Monel metal with saran cloth. Spraying Systems, Inc., Bellwood, Ill., pneumatic atomizing nozzles for spraying caustic and monochloroacetic acid solutions. Western Precipitation Corp., Los .4ngeles, Calif., hlulticlone dust collector.