Physicaland

ChemicalProperties

AQUALON®

Sodium

Carboxymethylcellulose

CM

CMC

CMC

CMC

CMC

CMC

CMC

CMC

CMC

CMC

CMC

CMC

CMC

CMC

CMC

CMC

CMC

CMC

CMC

MC

1

AQUALON® CMCAn Anionic Water-Soluble Polymer

CONTENTS PAGE

AQUALON CMC — AN ANIONICWATER-SOLUBLE POLYMER . . . . . . . . . . . . . . 2APPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . 3CHEMISTRY . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5GRADES AND TYPES . . . . . . . . . . . . . . . . . . . . 6

Grades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Degree of Substitution . . . . . . . . . . . . . . . . . . . 6Viscosity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Particle Size . . . . . . . . . . . . . . . . . . . . . . . . . . 7Product Coding . . . . . . . . . . . . . . . . . . . . . . . . 7

PROPERTIES . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Moisture Absorption . . . . . . . . . . . . . . . . . . . . . 8Physiological Properties . . . . . . . . . . . . . . . . . . 8

DISPERSION AND DISSOLUTION OF CMC . . . . 9Solvent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Type of CMC . . . . . . . . . . . . . . . . . . . . . . . . . . 9Shear Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Dispersion Methods . . . . . . . . . . . . . . . . . . . . . 9Theory of Polymer Dissolution . . . . . . . . . . . . . 11

PROPERTIES OF CMC SOLUTIONS . . . . . . . . . 13Viscosity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Effect of Concentration . . . . . . . . . . . . . . . . 13Effect of Blending . . . . . . . . . . . . . . . . . . . . 13Blending Chart . . . . . . . . . . . . . . . . . . . . . . 13Effect of Shear . . . . . . . . . . . . . . . . . . . . . . 16

Pseudoplasticity . . . . . . . . . . . . . . . . . . . 16Thixotropy . . . . . . . . . . . . . . . . . . . . . . . . 17

Effect of Temperature . . . . . . . . . . . . . . . . . 20Effect of pH . . . . . . . . . . . . . . . . . . . . . . . . . 20Effect of Mixed Solvents . . . . . . . . . . . . . . . 20

Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Microbiological Attack . . . . . . . . . . . . . . . . . 21Chemical Degradation . . . . . . . . . . . . . . . . . 21

Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . 22Effect With Salts . . . . . . . . . . . . . . . . . . . . . 22

Monovalent Cations . . . . . . . . . . . . . . . . . 22Polyvalent Cations . . . . . . . . . . . . . . . . . . 23

Gelation of Solutions . . . . . . . . . . . . . . . . . . . . 23Effect With Water-Soluble Nonionic Gums . . . . 23

PROPERTIES OF CMC FILMS . . . . . . . . . . . . . . 24PACKAGING AND SHIPPING . . . . . . . . . . . . . . . 25MICROBIOLOGICAL INFORMATION AND REGULATORY STATUS FOR USE IN FOODS, DRUGS, COSMETICS, AND TOILETRIES . . . . . 25

Microbiological Information . . . . . . . . . . . . . . . 25Food Status . . . . . . . . . . . . . . . . . . . . . . . . . . 25Food Labeling . . . . . . . . . . . . . . . . . . . . . . . . . 26Pharmaceutical Use . . . . . . . . . . . . . . . . . . . . 26Cosmetics and Toiletries . . . . . . . . . . . . . . . . . 26

APPENDIX—METHODS OF ANALYSIS . . . . . . . 27Viscosity of Solution . . . . . . . . . . . . . . . . . . . . 27

Moisture Determination . . . . . . . . . . . . . . . . 27Solution Preparation . . . . . . . . . . . . . . . . . . 27Viscosity Measurement . . . . . . . . . . . . . . . . 28

© Hercules Incorporated, 1999.

Aqualon® sodium carboxymethylcellulose (CMC) has a minimum purity of 99.5%. An anionic water-soluble polymerderived from cellulose, it has the following functions and properties:

• It acts as a thickener, binder, stabilizer, protective colloid,suspending agent, and rheology, or flow control agent.

• It forms films that are resistant to oils, greases, andorganic solvents.

• It dissolves rapidly in cold or hot water.

• It is suitable for use in food systems.

• It is physiologically inert.

• It is an anionic polyelectrolyte.

These properties and functions make it suitable for use in a broad range of applications in the food, pharmaceutical,cosmetic, paper, and other industries. To serve these diverseindustries, the polymer is available in three grades: food,pharmaceutical, and standard, and in many types based on carboxymethyl substitution, viscosity, particle size, andother parameters.

This booklet describes basic chemical and physical propertiesof Aqualon CMC in all its forms. The wide variety of typesproduced and the typical uses for this versatile polymer arealso discussed. The contents page will guide the reader tosubjects of special interest.

Technical or semi-refined grades of sodium carboxymethyl-cellulose are also available and are described in Booklet250-3, available from Aqualon by request.

2

AQUALON® CMCAN ANIONIC WATER-SOLUBLE POLYMER

Since its commercial introduction in the United States byHercules Incorporated in 1946, sodium carboxymethyl-cellulose has found use in an ever-increasing number ofapplications. The many important functions provided by this polymer make it a preferred thickener, suspending aid,stabilizer, binder, and film-former in a wide variety of uses.

The wide range of viscosity and substitution types availablefrom Aqualon for the highly purified grades and the lesshighly purified technical grades of CMC continues to expandthe uses for this product line.

A representative listing of the many applications for sodiumcarboxymethylcellulose is given below and on the followingpage. Many of these applications do not require the use ofthe highly purified grade, and a technical grade of CMC isavailable for certain applications. Aqualon’s chemists andengineers continue to tailor-make various grades and typesto meet the needs of specific customers and industriesrequiring water-soluble polymers.

3

APPLICATIONS

APPLICATIONS FOR PURIFIED CMC(1)

Types of Uses Specific Applications Properties Utilized

Cosmetics Toothpaste Thickener; flavor stabilizer; suspending aid; binder

Shampoos; foamed products Suspending aid; thickener; foam stabilizer;high water-binding capacity

Creams; lotions Emulsion stabilizer; film-former; thickener

Gelled products Thickener; gelling agent; film-former

Denture adhesives Wet tack; long-lasting adhesion

Foods Frozen desserts; soft-serve Controls ice crystal growth; improves mouthfeel, body, and texture

Pet food Water binder; gravy thickener; extrusion aid; binder of fines

Protein foods Retains water; improves mouthfeel

Baked goods Batter viscosifier; improves moisture retention and texture

Beverages Suspending aid; rapid viscosifier; improves mouthfeel and body; protein stabilizer in acidified drinks

Desserts; icings; toppings Odorless and tasteless; thickens; controls sugar crystal size; improves texture; inhibits syneresis

Low-calorie foods No caloric value(2); thickens; imparts body and mouthfeel

Syrups Clear; thickens; imparts favorable mouthfeel and body

Dressings; sauces Thickener and suspending aid; imparts mouthfeel

Animal feed; Lubricant; binder; film-former extrusion products

Pharmaceuticals Ointments; creams; lotions Stabilizer; thickener; film-former

Jellies; salves Thickener; gelling agent; protective colloid, film-former

Tablet binder; granulation aid High-strength binder

Bulk laxatives Physiologically inert; high water-binding capacity

Syrups Thickener

Suspensions Thickener; suspending aid

(1)For these applications, food grades (designated “F”) or pharmaceutical grades (designated “PH”) are used.These types may be referred to as “cellulose gum.”

(2)Depends on test method.

4

APPLICATIONS FOR STANDARD GRADE OF CMC

Types of Uses Specific Applications Properties Utilized

Adhesives Wallpaper paste Water-binding aid; adhesion; good open time;nonstaining

Starch-corrugating adhesive Thickener; water-binding and -suspending aid

Latex adhesives Thickener; water-binding aid

Aerial-drop fluids Insecticides Thickener; binder; suspending aid

Drift-control agent Thickener

Ceramics Glazes Binder for green strength; thickener; suspending aid Porcelain slips Vitreous enamels Refractory mortars

Welding rod coatings Binder; thickener; lubricant

Coatings Foundry core wash Binder; thickener; suspending aid

Latex paints; paper coatings Rheology control; suspending aid; protective colloid

Detergents Laundry Whiteness retention through soil suspension

Lithography Fountain and gumming Hydrophilic protective film solutions

Water-based inks Binder; rheology control; suspending aid

Paper and paper Internal addition High-strength binder; improves dry strength of paper products

Surface addition High-strength binder; oil-resistant film-former; provides control of curl and porosity and resistance to oils and greases

Pigmented coatings Thickener; rheology control; water-retention aid

Textiles Laundry and fabric sizes Film-former

Latex adhesives; backing Rheology control; thickener; water binding and holdout compounds

Printing pastes and dyes

Warp sizing High film strength; good adhesion to fiber; low BOD value

Tobacco Cigar and cigarette adhesive Good wet tack; high film strength

Reconstituted sheet High-strength binder and suspending aid

5

CHEMISTRY

CMC is a cellulose ether, produced by reacting alkali cellulose with sodium monochloroacetate under rigidly controlled conditions.

Figure 1 shows the structure of the cellulose molecule; it isvisualized as a polymer chain composed of repeating cello-biose units (in brackets). These, in turn, are composed of two anhydroglucose units (β-glucopyranose residues). In this structure, n is the number of anhydroglucose units(which are joined through 1,4 glucosidic linkages), or thedegree of polymerization, of cellulose.

Each anhydroglucose unit contains three hydroxyl groups,shown in white. By substituting carboxymethyl groups forsome of the hydrogens of these hydroxyls, as shown inFigure 2, sodium carboxymethylcellulose is obtained. Theaverage number of hydroxyl groups substituted per anhy-droglucose unit is known as the “degree of substitution,” orDS. If all three hydroxyls are replaced, the maximum theo-retical DS of 3.0 (impossible in practice) results.

CASRN: 9004-32-4 CAS Name: Cellulose, carboxymethyl ether,

sodium salt

Optimum water solubility and other desirable physical prop-erties of CMC are obtained at a much lower degree of sub-stitution than 3. The most widely used types of Aqualon®

CMC have a DS of 0.7, or an average of 7 carboxymethylgroups per 10 anhydroglucose units. Higher degrees of substitution result in CMC products having improved compatibility with other soluble components.

Cellulose ethers, such as CMC, are long-chain polymers.Their solution characteristics depend on the average chainlength or degree of polymerization (DP) as well as the degreeof substitution. Average chain length and degree of substi-tution determine molecular weight of the polymer. As molecular weight increases, the viscosity of CMC solutionsincreases rapidly. Approximate values (weight averages) forthe degree of polymerization and molecular weight of sev-eral viscosity types of Aqualon CMC are given in Table I.

The degree of neutralization of carboxymethyl groups alsoimpacts viscosity. In solution, the degree of neutralization iscontrolled by the pH.

At the end of the carboxymethylation, the reaction mixturecontains a slight excess of sodium hydroxide, which is usu-ally neutralized. Although the neutral point of CMC is pH8.25, the pH is generally adjusted to about 7-7.5. If the pH to which the CMC is neutralized is 6.0 or less, the driedproduct does not have good solubility in water; solutions are hazy and contain insoluble gel particles. If the pH is 4 or below, the dried product is insoluble in water.

HO

HH OH H

OH

OH

H

HHHH H

H OH

OH H H H H OH H H H H

H OHCH2OH CH2OH

O

OO

O O

CH2OHCH2OH

OH

OHH

OO

n-22

Figure 1 Structure of Cellulose

HH

OH

OH

OH

H H H H

H

O

OH

H

O

H

H

O

O

CH2OCH2COONa

CH2OCH2COONa

Figure 2 Idealized Unit Structure of CMC, With a DS of 1.0

Table I — Typical Molecular Weights for RepresentativeViscosity Types of Aqualon CMC (DS = 0.7 in All Cases)

Viscosity Degree of MolecularType Polymerization Weight

High 3,200 700,000Medium 1,100 250,000Low 400 90,000

6

GRADES AND TYPES

To serve its diverse markets, Aqualon produces CMC in several grades and in a wide variety of types, based on the degree of substitution, viscosity, particle size, and other parameters.

GRADESAqualon® CMC is available in the three grades outlined below.

Grade Designation Intended Use

Food F Food, cosmetic,P* pharmaceutical

Pharmaceutical PH** Cosmetic, pharmaceutical

Standard None Industrial

*P (1.2 D.S. types and CMC 7L2P)**PH (0.7 and 0.9 D.S. types)

DEGREE OF SUBSTITUTION Aqualon CMC is produced with the following degrees of substitution:

Substitution SodiumType Range(a) Content, %

7 0.65-0.90(b) 7.0-8.99 0.80-0.95 8.1-9.2

12 1.15-1.45 10.5-12.0

(a)Ranges shown in this table are not necessarily current specifications.

(b)ln 7S types, the upper limit of substitution is 0.95.

Higher degrees of substitution give improved compatibilitywith other soluble components such as salts and nonsol-vents. Generally, the number given in the product desig-nation is approximately 10 times the DS.

Table II — Some Types of Aqualon CMC

Viscosity Range at 25°C,(c) cps (mPas) Designations for Indicated Substitution Types7 9 12

High—at 1% Concentration 2,500-6,000 7H4 9H41,000-2,800 7H3S, 7HOF1,500-3,000 7H

Medium—at 2% Concentration 800-3,100 12M31

1,500-3,100 9M31400-800 7M 9M8 12M8200-800 7M8S100-200 7M2

Low(d)—at 2% Concentration25-50 7L

—at 4% Concentration50-200 7L2

(c)Ranges shown in this table are not necessarily current specifications.(d)Some even lower viscosity types are available. Contact your technical representative for additional information.

7

VISCOSITYCMC is manufactured in a wide range of viscosities. High-viscosity types are prepared from high viscosity cotton lin-ters. Medium-viscosity types are prepared from wood pulp of specified viscosity. Low-viscosity types are prepared byaging the shredded alkali cellulose and by using chemicaloxidants. The foregoing methods of regulating the viscosityare based on controlling the DP. It is also possible to attainhigh viscosity by decreasing the solubility so that the productis highly swollen but not completely dispersed. This can beaccomplished by decreasing the uniformity of the reactionand lowering the DS. For example, products at DS 1.2 do not have solution viscosities as high as products of DS 0.7prepared in substantially the same way. However, the solu-tions of the higher-substituted products are much smoother.

The viscosity ranges of some types are listed in Table II.Others are available to meet specific needs. Regular viscos-ity types with a DS of 0.7 meet most needs and are desig-nated by the number 7, followed by the letter H (high), M(medium), or L (low). All other types are designated by anadditional number following the letter which, when multipliedby a factor, gives the approximate upper viscosity limit. Thefactor and applicable concentration appear below.

Viscosity Type Factor Concentration, %

High 1,000 1Medium 100 2Low 10 2

Solutions of all CMC types display pseudoplastic behavior.(See page 16.) Some types, particularly those of higher molecular weight and lower substitution, also show thixo-tropic behavior in solution. (See page 17.) These thixotropicsolutions will possess varying amounts of gel strength andare used where suspension of solids is required. The “S,” 9,and 12 types produce solutions with little or no thixotropy,and are utilized where smooth solutions without structure are required.

Specific properties are available in certain other types. Forexample, the “O” type, 7HOF, provides the best solubility and storage stability in acid media.

PARTICLE SIZE Aqualon® CMC is available in several different particle sizesto facilitate handling and use in processing operations suchas solution preparation and dry-blending. Screen analysis isgiven here for three of the types. Other types are available.

Designation Description Particle Size(e)

None Regular On U.S. 30, %, max 1 On U.S. 40, %, max 5

C Coarse On U.S. 20, %, max 1Through U.S. 40,

%, max 55Through U.S. 80,

%, max 5

X Fine On U.S. 60, %, max 0.5 Through U.S. 200,

%, min 80

(e)AII screens are U.S. Bureau of Standards sieve series.

PRODUCT CODING An example of the coding used for ordering Aqualon CMCfollows:

For cellulose gum Type 7H3SCF:7 means that the typical degree of substitution is

approximately 0.7.H means high viscosity.3 means that the viscosity of a 1% solution is in the

range of 3,000 cps.S means smooth solution characteristics.C means coarse particle size.F means food grade.

Aqualon can tailor the chemical and physical properties ofCMC to meet special requirements. Users are encouraged to discuss their needs with their technical representative, or to call the 800 number shown on the back cover for product information.

8

PROPERTIES

Typical properties of Aqualon® CMC polymer and in solutionand film form are shown in Table III. These are not necessar-ily specifications.

Table III—Typical Properties of Aqualon CMC

Polymer Sodium carboxymethylcellulose—

dry basis, %, min . . . . . . . . . . . . . . . . . . . . 99.5Moisture content (as packed), %, max . . . . . . . 8.0 Browning temperature, °C . . . . . . . . . . . . . . . . 227 Charring temperature, °C . . . . . . . . . . . . . . . . . 252 Bulk density, g/ml . . . . . . . . . . . . . . . . . . . . . .0.75 Biological oxygen demand (BOD)(f), ppm

7H type . . . . . . . . . . . . . . . . . . . . . . . . . 11,000 7L type . . . . . . . . . . . . . . . . . . . . . . . . . . 17,300

Solutions pH, 2% solution . . . . . . . . . . . . . . . . . . . . . . . . 7.5Surface tension, 1% solution,

dynes/cm at 25°C. . . . . . . . . . . . . . . . . . . . . . 71 Specific gravity, 2% solution . . . . . . . . . . . . 1.0068Refractive index, 2% solution . . . . . . . . . . . . 1.336

Typical Films (Air-Dried) Density, g/ml . . . . . . . . . . . . . . . . . . . . . . . . . 1.59 Refractive index . . . . . . . . . . . . . . . . . . . . . . 1.515 Thermal conductivity, W/mK. . . . . . . . . . . . . . 0.238

(f)After 5 days’ incubation. Under these conditions, cornstarch hasa BOD of over 800,000 ppm.

MOISTURE ABSORPTION CMC absorbs moisture from the air. The amount absorbedand the rate of absorption depend on the initial moisturecontent and on the relative humidity and temperature of the surrounding air. Figure 3 shows the effect of relativehumidity on equilibrium moisture content of three types of Aqualon CMC.

As Aqualon CMC is packed, its moisture content does notexceed 8% by weight. Because of varying storage and ship-ping conditions, there is a possibility of some moisturepickup from the “as-packed” value.

Figure 3Effect of Relative Humidity on Equilibrium MoistureContent of Aqualon CMC at 25°C

40

30

20

10

0 0 20 40 60 80

Equ

ilibr

ium

Moi

stur

e C

onte

nt, %

Relative Humidity, %

7HF

12M31P

PHYSIOLOGICAL PROPERTIES Dermatological and toxicological studies by independent laboratories demonstrate conclusively that sodium carboxy-methylcellulose shows no evidence of being toxic to whiterats, dogs, guinea pigs, or human beings. Feeding, metabo-lism, and topical use studies also show that CMC is physio-logically inert. Patch tests on human skin demonstrated thatsodium carboxymethylcellulose was neither a primary irritantnor a sensitizing agent. Additional information is availablefrom Hercules Incorporated.

9

DISPERSION AND DISSOLUTIONOF CMC

A number of factors such as solvent, choice of polymer, andshear rate affect dispersion and dissolution of CMC.

SOLVENT Aqualon® CMC is soluble in either hot or cold water. The gum is insoluble in organic solvents, but dissolves in suit-able mixtures of water and water-miscible solvents, such asethanol or acetone. Solutions of low concentration can bemade with up to 50% ethanol or 40% acetone. Aqueoussolutions of CMC tolerate addition of even higher propor-tions of acetone or ethanol, the low-viscosity types beingconsiderably more tolerant than the high-viscosity types, as shown below.

Tolerance of Aqualon CMC Solutions for Ethanol

Volume Ratio of Ethanolto CMC Solution, 1%

CMC First Evident First DistinctType Haze Precipitate

7L 2.4 to 1 3.6 to 17M 2.1 to 1 2.7 to 17H 1.6 to 1 1.6 to 1

Note: In these tests, ethanol (95%) was added slowly at roomtemperature to the vigorously stirred 1% CMC solution.

TYPE OF CMC The higher the degree of substitution, the more rapidly CMC dissolves. The lower the molecular weight, the fasterthe rate of solution.

Particle size has a pronounced effect on the ease of dis-persing and dissolving CMC. “C,” or coarse, types weredeveloped to improve dispersibility of the granules when agitation is inadequate to produce a vortex on the liquid surface. Solution time, on the other hand, is extended considerably with a coarse material.

For applications requiring a rapid solution time, CMC of fine particle size (X grind) is best. However, special dis-solving techniques, such as prewetting the powder with anonswelling liquid, mixing it with other dry materials, or using an eductor-type mixing device, are necessary to obtain dispersion.

SHEAR RATE Preparing solutions by extremely low shear agitation, suchas shaking by hand, is generally not recommended. Prop-erties of the resulting solution are quite different from thoseprepared by higher shear methods. The effect of shear onsolution properties is discussed in more detail on pages 11and 16.

DISPERSION METHODS CMC particles have a tendency to agglomerate, or lump,when first added to water. To obtain good solutions easily,the dissolving process should be considered a two-stepoperation:

1. Dispersing the dry powder in water. Individual par-ticles should be wet and the dispersion should notcontain lumps.

2. Dissolving the wetted particles.

When the proper technique is used, good dispersion is obtained, and CMC goes into solution rapidly. To preparelumpfree, clear solutions, a variety of methods can be used:

Method 1Add CMC to the vortex of vigorously agitated water. The rateof addition must be slow enough to permit the particles toseparate and their surfaces to become individually wetted,but it should be fast enough to minimize viscosity buildup ofthe aqueous phase while the gum is being added.

Method 2Prior to addition to water, wet the powder with a water-miscible liquid such as alcohol, glycol, or glycerol that willnot cause CMC to swell. Two to three parts of liquid per partof CMC should be sufficient.

Method 3Dry-blend the CMC with any dry, nonpolymeric material used in the formulation. Preferably, the CMC should be less than 20% of the total blend.

Method 4Use a water eductor (Figure 4) to wet out the polymer par-ticles rapidly. The polymer is fed into a water-jet eductor,where a high-velocity waterflow instantly wets out each particle, thus preventing lumping. This procedure speedssolution preparation and is particularly useful where largevolumes of solutions are required. For users wishing the convenience of an automatic system, a polymer solutionpreparation system (PSP), which is used in conjunction with a water eductor, is shown in Figure 5.

Special, fast-dissolving fluidized polymer suspensions ofCMC are available to give very rapid dissolution where it isrequired or where agitation is substandard.

Users are encouraged to contact their technical representa-tive for information on PSP units or fluidized suspensions of CMC.

10

Air Bleed-Holes

WaterInlet

Discharge

Special Mixing DeviceThis inexpensive equipment ismost effective for quickly pre-paring uniform solutions of CMC.

Eductor

Mix TankFunnel

Lightnin Mixer Polymer Feed

Mixing Device

Makeup Water

WorkmanPlatform

Figure 4Typical Installation of Eductor-Type Mixing Device

DustCollector

Polymer Hopper

ScrewDriveMotor

Helical Screw Feeder

Air

PSP UnitEductor

PolymerEductor

Water

Preparation Tank

Figure 5Automated Polymer Solution Preparation (PSP) System

11

THEORY OF POLYMER DISSOLUTION When a polymer is dispersed in a solvent, the degree of disaggregation—i.e., separation of polymer molecules—is affected by the:

• Chemical composition of the polymer.• Solvating power of the solvent.• Shear history of the resulting solution.

Figure 6 shows how these states of disaggregation may affect viscosity of the liquid. If CMC is added to a liquid and its degree of disaggregation reaches equilibrium, thepolymer may:

• Remain as a suspended powder, neither swelling nor dissolving (1).

• Swell to a point of maximum viscosity without com-pletely dissolving (2).

• Reach maximum disaggregation (3).• Exist in an intermediate state (1a, 1b, 2a).

Depending on choice of polymer, solvent, and mechanicalmeans of preparing the solution, the user of CMC can alterits state of disaggregation to suit his needs. Table IV showsthe effect of these factors on the disaggregation of CMC asmeasured by solution viscosity.

Increasing DS makes CMC more hydrophilic, or “water-loving”; hence, types having high DS are more readily dis-aggregated in water. Plotting solution viscosity at constantshear against increasing DS (Types 7 through 12) producesa curve similar in shape to that shown in Figure 6.

Increasing electrolyte concentration reduces disaggre-gation, as evidenced by the lower viscosity in saltwater ofType 7. The viscosities listed in Table IV were measuredunder quality control conditions—that is, two hours aftersolution was complete. At this point, CMC dissolved in anelectrolyte solution is probably in the Stage 1 section of thedisaggregation curve. CMC dissolved in distilled water under quality control conditions is at Stage 3 of the curve.Viscosities of CMC/salt solutions measured at this point willbe lower than the viscosities of corresponding CMC solu-tions prepared in distilled water. Since disaggregation is a

time-dependent phenomenon, if CMC/salt solutions areallowed to stand, it is very possible that the final stage of disaggregation will be Stage 2 and the equilibrated viscositywill be higher than that of CMC in distilled water. Hence, onecannot assume that addition of salt will lower equilibratedsolution viscosity, only that it will inhibit polymer disaggre-gation. With Types 9 and 12, the slight viscosity increase insaturated salt is caused by the “viscosity bonus effect” dis-cussed on page 20.

Figure 6 Idealized Curve Showing Effect of Degree of Disaggregation on Viscosity of Polymer Solution

Table IV — Factors Affecting Disaggregation of Aqualon® CMC (This table shows the effect of polymer composition, solvent strength, and mechanical shear on disaggregation, asmeasured by solution viscosity. All data are at 25°C. Cellulose gum was added dry to the solvents listed.)

Viscosity, cps (mPas)

Anchor Stirrer Waring Blendor

Cellulose Distilled Saturated Distilled SaturatedGum Type Water 4% NaCl NaCl Water 4% NaCl NaCl

7HF 1,680 140 45 760 1,040 2,440

7H3SF 1,680 570 165 760 750 1,720

9M31F 215 160 225 125 95 235

12M31P 175 80 180 100 55 140

Degree of Disaggregation

2

2a

3

1b

1a

1

Vis

cosi

ty

12

In many cases, the high shear imparted by the Waring blendorcan enhance viscosity development or disaggregation.

The effect of solvent strength (polarity in binary solvent mix-tures) on the disaggregation of CMC is shown in Figure 7.Note the similarity of these curves to the curve in Figure 6.The data in Figure 7 and in Table IV show that an increasein solvating power or an increase in mechanical shearbreaks internal associations of gel centers and promotesdisaggregation.

The effect of solutes such as salts or polar nonsolvents onthe viscosity of CMC solutions also depends on the order ofaddition of the gum and solute. This is shown in Figure 8. IfCMC is thoroughly dissolved in water and the solute is thenadded, it has only a small effect on viscosity. However, if thesolute is dissolved before the CMC is added (as is the casewith Table IV data), it inhibits breaking up of crystallineareas, and lower viscosities are obtained. This effect ofsolutes is less apparent with more uniformly substitutedmaterial containing fewer crystalline areas.

Figure 7Effect of Solvent Strength on Disaggregationof Aqualon® CMC(1.75% CMC in Glycerin-Water)

100,000

10,000

1,000

300

0 20 40 60 80 100Water in Solvent, weight %

Vis

cosi

ty, c

ps

12M8P

9M8F 7MF

Figure 8Effect of Solutes on Viscosity of CMC Solutions

Solutes Used:App

aren

t Vis

cosi

ty, c

ps

Solute Added After CMC

Solute Added Before CMC

NaClNaCl + NaOH (pH 10.1)Na2So4

Na4P2O7 • 10H2O (pH 9.5-9.8)KCl or LiCl

10

20

30

40

60

80

100

200

300

0.02 0.04 0.08 0.1 0.2 0.4 0.8 1.0Molal Concentration of Cation, moles/1,000 g solvent

13

PROPERTIES OF CMC SOLUTIONS

Viscosity is the single most important property of CMC solu-tions. Aqualon has acquired considerable information on factors affecting viscosity, and these data are given here.Stability of CMC solutions to microbiological attack andchemical deterioration is also discussed in this section.

VISCOSITYSolutions of CMC can be prepared in a wide range of vis-cosities. Such solutions are non-Newtonian because theychange in viscosity with change in shear rate. Consequently,it is essential to standardize viscosity determination methods.This standardization must include the type and extent of agitation used to dissolve the CMC, as well as precise con-trol of temperature, conditions of shear, and method of vis-cosity measurement. The procedure used in the Aqualoncontrol laboratory is described in detail in the Appendix,page 27.

Effect of Concentration The viscosity of aqueous CMC solutions increases rapidlywith concentration. This is shown in Figure 10. The bandsshow the range of viscosity obtainable with standard viscosity types.

Effect of Blending Two viscosity types of CMC can be blended to obtain an in-termediate viscosity. Because viscosity is an exponentialfunction, the viscosity resulting from blending is not an arithmetic mean.

A blending chart (VC-440), available from Aqualon, can beused to determine the result of blending various amounts oftwo viscosity types of CMC. It can also be used to determinethe amount of CMC required to achieve a desired viscositywhen blending two types of known viscosity.

Blending ChartThe blending technique outlined in this bulletin can be used eqully well for Aqualon® cellulose gum (sodium carboxymethylcellulose), Natrosol® hydroxyethylcellulose,Culminal® methylcellulose and methyl hydroxypropylcelluloseand Klucel® hydroxypropylcellulose. This technique is usefulwhen it is desirable to blend two viscosity types of the samewater-soluble polymer in order to obtain a solution having apredetermined viscosity and solids concentration.

Blends can be calculated directly from the equation that fol-lows; or, more conveniently, the blending chart in Figure 9can be used. From this chart, one can determine, withoutcalculations, the percentage of any two viscosities that mustbe blended to secure a desired intermediate viscosity.Likewise, it is possible to determine the viscosity that willresult from utilizing any blend.

Equation: Because the viscosity-concentration relationship isan exponential function, the viscosity resulting from blendingis not an arithmetic mean. The viscosity of a blend can, how-ever, be approximated by use of the equation below, whichis derived from the Arrhenius equation that relates viscositywith polymer concentration.

n log V1 + (100-n) log V2

Log Vs = 100where Vs = Viscosity sought

n = Percent (by weight) of the first component of theblend having a viscosity of V1

V2 = Viscosity of the second component of the blend

Note: All viscosities must be expressed at the same polymerconcentration and in the same units.

Use of the chart itself is simple. For example, suppose onewishes to obtain a solution with a viscosity of 900 cps at 3%concentration. The water-soluble polymer is available asMaterial A with a viscosity of 1,800 cps at 3% concentration,and Material B with a viscosity of 700 cps at 3% concentra-tion. A line is drawn connecting these two viscosities on thechart. The point at which this line intersects the desired vis-cosity line is then determined, and the percentage it repre-sents is read from the bottom of the chart. Thus, in thisexample, 28% of Material A and 72% of Material B areneeded to yield the desired viscosity of 900 cps at a totalpolymer concentration of 3%.

Limitations of Blending: The relationship between viscosityand concentration can vary significantly, depending on thechemical composition as well as the molecular weight (vis-cosity type) of the polymers involved. The greatest accuracyis obtained from use of the equation or the blending chart ofFigure 9 if the following conditions are met. Departure fromthese conditions can result in deviation from the predictedvalue of viscosity.

• The chemical composition of the polymers must be similar—i.e., the type and level of chemical substitution must be the same.

• The solution viscosities of the polymers should be asclose together as possible.

14

100 90 80 70 60 50 40 30 20 10 0

0 10 20 30 40 50 60 70 80 90 100

Material A, %

Material B, %

20

30

40

50

60

708090

100

200

300

400

500

600700800900

1,000

2,000

3,000

4,000

5,000

Sol

utio

n V

isco

sity

at 2

5˚C

, cps

DesiredViscosityin Example

Blend Neededfor DesiredViscosity

Viscosity of AvailableMaterial B

Viscosity of AvailableMaterial A

Figure 9Chart for Blending Aqualon Water-Soluble Polymers

15

Figure 10Effect of Concentration on Viscosity of Aqueous Solutions of Aqualon® CMC(Bands approximate the viscosity range for the types shown.)

CMC, weight %

0 1 2 3 4 5 6 7 8 9 10

30,000

20,000

7M2

7M, 9M8, 12M8

7H4, 9H47H

7H3S, 7HOF

9M31, 12M317L

7L2

10,000

Sol

utio

n V

isco

sity

at 2

5˚C

, cps

1,000

100

10

5

16

Effect of Shear CMC is often used to thicken, suspend, stabilize, gel, or otherwise modify the flow characteristics of aqueous solu-tions or suspensions. Preparation and use of its solutionsinvolve a wide range of shearing conditions. It is thereforeimportant that the user understand how rheological behaviorcan affect the system.

Pseudoplasticity—Small amounts of CMC dissolved inwater greatly modify its properties. The most obvious imme-diate change is an increase in viscosity. Interestingly, a singleCMC solution will appear to have a different viscosity whendifferent physical forces are imposed on it.

These physical forces may be conveniently referred to ashigh, intermediate, or low shear stress. For example, rollingor spreading a liquid as if it were an ointment or lotion wouldbe high shear stress. After the liquid has been applied, grav-ity and surface tension control flow. These forces are condi-tions of low stress. Intermediate stress is typified by pouringa liquid out of a bottle.

If a solution of high-viscosity CMC appears to be a viscoussyrup as it is poured from a bottle, it will behave as a thinliquid when applied as a lotion, and yet when high shearstress is removed it will instantly revert to its original highlyviscous state. This type of flow behavior is referred to aspseudoplasticity or time-independent shear-thinning—a formof non-Newtonian flow. It differs from the time-dependent viscosity change called thixotropy.

If shear stress is plotted vs. shear rate, as in Figure 11, aNewtonian fluid will produce a straight line passing throughthe origin. A pseudoplastic liquid, such as a CMC solution,will give a curved line. Plotting apparent viscosity againstshear rate, as in Figure 12, produces a horizontal straightline for a Newtonian fluid and a curved line for a pseudo-plastic liquid.

Solutions of some medium- and high-viscosity types of CMC exhibit pseudoplastic behavior because their long-chain molecules tend to orient themselves in the direction of flow; as the applied force (shear stress) is increased, theresistance to flow (viscosity) is decreased. When a lowerstress is imposed on the same solution, the apparent viscosity is higher because random orientation of mole-cules presents increased resistance to flow.

Figure 11 Shear Stress vs. Shear Rate for Newtonian and Pseudoplastic Liquids

Shear Rate

She

ar S

tres

s

Pseudoplastic

Newtonian

Figure 12 Viscosity vs. Shear Rate

When viscosity (shear stress divided by shear rate) is plotted against shear rate, a Newtonian system gives a horizontal line. If viscosity decreases as shear rate isincreased, the flow is pseudoplastic.

App

aren

t Vis

cosi

ty

Shear Rate

Newtonian

Pseudoplastic

17

Generally, solutions of the medium- and high-viscosity types with a high DS (i.e., 0.9 and 1.2) and “S” types arepseudoplastic rather than thixotropic. In contrast to this,regular high- and medium-viscosity gums of DS 0.7 (slightlyless uniformly substituted) show thixotropic behavior in solution. (See Thixotropy, below.)

Solutions of low-molecular-weight CMC – i.e., low-viscositytypes—are less pseudoplastic than those of high-molecular-weight gum. However, at very low shear rate, all CMC solutions approach Newtonian flow. Figure 13 shows these relationships.

Figure 13Effect of Shear Rate on Apparent Viscosity of Aqualon® CMC Solutions

Rheograms are helpful to illustrate the effect of thixotropy.A thixotropic solution will form a hysteresis loop when shearstress is plotted against shear rate, as shown in Figure 14A.The increased shear stress required to break the thixotropicstructure has reduced the resistance to flow, or viscosity. If a solution has gel strength, a spur forms in the hysteresisloop; this is shown in Figure 14B. It is an indication of thestress necessary to break the gel structure and cause thesolution to revert to its normal apparent viscosity.

Figure 14AThixotropic Flow

Film

Sag

Und

erG

ravi

ty

Bro

okfie

ldV

isco

met

er

Tum

blin

gor

Pou

ring

Hom

e M

ixer

War

ing

Ble

ndor

App

aren

t Vis

cosi

ty, c

ps

Shear Rate (Reciprocal sec)

10,000

1,000

100

100.01 0.1 1 10 100 1,000 10,000

1% 7H3S

7.3% 7L

Thixotropy—If long-chain polymers have a considerableamount of interaction, they will tend to develop a three-dimensional structure and exhibit a phenomenon known as thixotropy.

Thixotropy is a time-dependent viscosity change. It is char-acterized by an increase in apparent viscosity when a solu-tion remains at rest for a period of time after shearing. Incertain cases, the solution may develop some gel strength,or even set to an almost solid gel. If sufficient force (shearstress) is exerted on a thixotropic solution, the structure can be broken and the apparent viscosity reduced.

Shear Rate

She

ar S

tres

s

Figure 14BExtremely Thixotropic Flow With Gel Strength

Shear Rate

She

ar S

tres

s

18

Figure 15 illustrates thixotropy in another manner. At a constant shear rate (D = K), viscosity decreases with time.When shear is removed (D = zero), viscosity increases sig-nificantly with time.

Thixotropic solutions are desirable, or even essential, forcertain uses of CMC, such as suspension of solids. High-and medium-viscosity types of regular Aqualon® CMC (0.7 DS) generally exhibit thixotropic behavior. “S” types and high-DS types in medium and high viscosity have beendeveloped for uses requiring clear, smooth solutions of little or no thixotropy. Figure 16 illustrates the difference in appearance between solutions of regular and “S”-typeAqualon CMC. “S” and high-DS types show the typicalpseudoplasticity of long-chain molecules.

Figure 15Thixotropic Flow Is a Time-DependentChange in Viscosity

t

App

aren

t Vis

cosi

ty

D = K

D = Zero

Figure 16Thixotropic and Nonthixotropic Solutions of CMC

The solution of regular Aqualon CMC, left, is thixotropic; “S”-type Aqualon CMC, right, is essentially nonthixotropic.

19

Figure 17Effect of Temperature on Viscosity of Aqualon® CMC Solutions

Temperature, ˚C

Vis

cosi

ty, c

ps

10,000

1,000

100

100 10 20 30 40 50 60 70 80

1% 7H

2% 9M8

2% 7M

1% 9M311% 12M31

2% 7L

20

Effect of TemperatureViscosity of CMC solutions depends on temperature, asshown in Figure 17. Under normal conditions, the effect oftemperature is reversible, so temperature variation has nopermanent effect on viscosity. However, long periods of heat-ing at high temperatures will degrade CMC and permanentlyreduce viscosity. For example, a 7L type held for 48 hours at180°F lost 64% of its original viscosity.

Effect of pHCMC solutions maintain their normal viscosity over a widepH range. In general, solutions exhibit their maximum vis-cosity and best stability at pH 7 to 9. Above pH 10, a slightdecrease in viscosity is observed. Below pH 4.0, the lesssoluble free acid carboxymethylcellulose predominates and viscosity may increase significantly. Figure 18 shows the effect of pH on the viscosity of typical Aqualon®

CMC grades.

Figure 18Effect of pH on Viscosity of Aqualon CMC Solutions

2 4 6 8 10 12

1.0% 7H

2.0% 7H

2.0% 9M315,000

1,000

500

100

Bro

okfie

ld V

isco

sity

, cps

pH

Tests with Aqualon CMC Type 7M have shown that very littlepolymer degradation takes place if solutions are allowed tostand overnight at room temperature at a pH as low as 2.However, at pH values of 4-5 and temperatures of 150°F,most of the viscosity is lost in 24 hrs.

In acidic systems, the order in which CMC is added to thesolvent is also important. If a CMC solution is prepared priorto the addition of acid, a higher viscosity is obtained thanwhen dry CMC is dissolved in an acidic solution.

Aqualon cellulose gum Type 7HOF is a particularly efficientthickener for acidic systems. Clear, viscous solutions areobtained when it is dissolved in water and then acidified. Itsstability in several organic acids, typical of those used inlow-pH foods, is shown in Figure 19.

Figure 19Stability of Aqualon Cellulose Gum in Organic Acids—1% Solution of Type 7HOF

10,000

1,0000.3% Fumaric Acid

5.0% Acetic Acid

1.0% Lactic Acid

1.0% Citric Acid

Storage Time at 25˚C, months

Vis

cosi

ty a

t 25˚

C, c

ps

1001 2 3 4 5

Effect of Mixed Solvents The behavior of highly substituted CMC in mixed-solventsystems, such as glycerin-water, is similar to its effect inwater alone. In mixed systems, however, viscosity of the sol-vent affects viscosity of the solution. For example, if a 60:40mixture of glycerin and water (which is 10 times as viscousas water alone) is used as the solvent, the resulting solutionof well-dispersed CMC will be 10 times as viscous as thecomparable solution in water alone. This behavior is shownin Figure 19 and is commonly referred to as the “viscositybonus effect.”

Figure 20Effect of Mixed Solvents on Viscosity of Aqualon CMC Solutions—1% Type 12M31

10,000

1% CMC in Glycerin-Water

1% CMC in Water

Glycerin in Water

Water

10 100 1,000 10,000

Shear Rate, sec

App

aren

t Vis

cosi

ty, c

ps

1,000

100

10

1

-1

-1

10

STABILITYCMC is subject to microbiological attack and chemicaldegradation. However, corrective measures can be taken to prevent both from occurring.

Microbiological Attack Although CMC is more resistant to microbiological attackthan many other water-soluble gums, its solutions are notimmune. Heat treatment can be used to destroy manymicroorganisms while having little effect on CMC prop-erties. Heating for 30 min at 80°C, or for 1 min at 100°C, is generally sufficient.

When solutions are stored, a preservative should be addedto prevent viscosity degradation. If cellulases (hydrolytic, viscosity-destroying enzymes) have been introduced bymicrobial action, even in trace amounts, addition of mostpreservatives will not prevent degradation; therefore, it is important to preserve solutions as soon as possible after preparation.

The preservatives shown below have proved effective forsolutions of Aqualon® CMC. The preservative manufac-turer should be consulted regarding the kind and amount to be added.

Chemical Degradation Under certain conditions, solutions of CMC are susceptibleto chemical degradation. Permanent loss of viscosity canoccur resulting from scission of the long-chain molecules.Such viscosity loss is accelerated by increasing the temper-ature and/or lowering the pH. Aqualon cellulose gum Type7HOF provides improved resistance to viscosity degradationand precipitation in low-pH systems.

An oxidative type of degradation occurs under alkaline con-ditions in the presence of oxygen. The rate of viscosity lossis also increased by heat and/or ultraviolet light. Inclusion ofan antioxidant, exclusion of oxygen, and avoidance of highlyalkaline conditions are obvious preventive measures.

To obtain the best stability during prolonged storage of CMCsolutions, users should:

• Protect against microbiological attack.

• Maintain solution pH as nearly neutral as possible (7.0 to 9.0).

• Avoid prolonged exposure to elevated temperatures.

• Exclude oxygen and sunlight.

21

Preservatives for Aqualon CMC

Busan 11M1, 85(g) PhenolDowicide A(h) Proxel GXL(j)

Dowicil 75, 200(h) Sodium benzoate(i)

Formaldehyde Sodium propionate(i)

Methyl- and propylparabens(i) Sorbates (Na and K salts)(i)

(g)Buckman Laboratories International, Inc.(h)Dow Chemical Co.(i)Preservatives cleared by the Food and Drug Administration for food, cosmetic, and pharmaceutical products. Pertinent regulations indicate

maximum use levels (tolerances) in some cases.(j)Zeneca Biocides

22

COMPATIBILITYAqualon® CMC is compatible in solution with most water-soluble nonionic and anionic polymers and gums. Its compatibility with salts depends on factors discussed in this section.

Effect With SaltsCompatibility of CMC with inorganic salt solutions dependslargely on the ability of the added cation to form a solublesalt of carboxymethylcellulose. For example, the potassiumsalt of carboxymethylcellulose is as soluble in water as thesodium salt; consequently, if potassium ion is added in mod-erate amounts to a CMC solution, it has little effect on solu-tion viscosity, clarity, or other properties. On the other hand,the zirconium salt of carboxymethylcellulose is insoluble inwater; therefore, if zirconium ion is added to a CMC solution,precipitation results.

As a general rule, monovalent cations from soluble salts ofcarboxymethylcellulose, divalent cations are borderline, andtrivalent cations form insoluble salts. Some exceptions to thisrule are given in the following pages.

The effect of salts varies with the particular salt, its concen-tration, pH of the solution, degree of substitution of the CMC,and manner in which the salt and CMC come in contact.Highly substituted CMC (i.e., DS 0.9 and 1.2) has a greatertolerance for most salts. Increased salt tolerance can also be obtained by dissolving the CMC before adding the salt.Adding dry CMC to a salt solution or dissolving the salt andgum simultaneously will reduce compatibility.

Compatibility of Aqualon CMC with some inorganic salt solu-tions is shown in Table V. Solutions of 1% CMC Type 7Hwere prepared in distilled water. Aqueous solutions of saltswere prepared at concentrations of 10% and either 50% orsaturated. Then, 1 g of gum solution was added to 15 g ofeach salt solution, and the effect was observed.

Monovalent Cations—As previously stated, monovalentcations usually interact with carboxymethylcellulose to formsoluble salts. In aqueous systems containing these cations,viscosity depends primarily on the order of addition of gumand salt. If CMC is thoroughly dissolved in water prior toaddition of such a salt, the latter has little effect on solutionviscosity. However, the viscosity imparted by CMC will bedepressed if the gum is added dry to a salt solution. (SeeFigure 8, page 12.) The effect of polymer composition, saltconcentration, and shear history is shown in Table IV, page11. Viscosity developed by “S” types of Aqualon CMC is lessaffected by salts of monovalent cations than that developedby other types, regardless of the order of addition.

Table V — Compatibility of Aqualon CMC WithInorganic Salt Solutions

50% or10% Saturated

Salt Solution Solution

Aluminum nitrate P PAluminum sulfate P PAmmonium chloride C CAmmonium nitrate C CAmmonium sulfate C PCalcium chloride C PCalcium nitrate C PChromic nitrate P PDisodium phosphate C CFerric chloride P PFerric sulfate P PFerrous chloride P PMagnesium chloride C CMagnesium nitrate C CMagnesium sulfate C CPotassium ferricyanide C CPotassium ferrocyanide C CSilver nitrate P PSodium carbonate C CSodium chloride C CSodium dichromate C CSodium metaborate C CSodium nitrate C CSodium perborate C CSodium sulfate C PSodium sulfite C CSodium thiosulfate C CStannic chloride P PZinc chloride P PZinc nitrate P PZinc sulfate P P

C = Compatible P = PrecipitateNote: 1 g of a 1% solution of CMC Type 7H was added to 15 g of salt solution.

23

Polyvalent Cations—Generally, divalent cations will notform crosslinked gels with CMC. Viscosity reduction occurs,however, when divalent cations are added to a CMC solu-tion, and it may be accompanied by the formation of a haze.Calcium, barium, cobalt, magnesium, ferrous, and manga-nous cations will perform this way. “S” types of Aqualon®

CMC are only slightly affected by moderate concentrationsof divalent cations if the cation is added to the CMC solution.

Trivalent salts form insoluble precipitates with CMC. Traceamounts of heavy metal cations of lesser valence also formprecipitates. Precipitation occurs by crosslinking, ionic bond-ing, or complex formation. Included in this classification arecuprous, cupric, silver, ferrous, uranium, chromous, stan-nous, plumbous, and zirconium cations.

GELATION OF SOLUTIONS The effect of trivalent cations on CMC solutions can be controlled and used to advantage where gelation is desired.Gels of varying texture can be produced by careful additionof certain salts of trivalent metals, such as aluminum.Gradual release of aluminum ions to a CMC solution willresult in uniform crosslinking of the polymer moleculesbetween carboxymethyl groups. Gradual release of alumi-num ions can be accomplished by using a slowly solublealuminum salt such as monobasic aluminum acetate, AIOH (C2H3O2)2; soluble salts such as aluminum sulfate, Al2(SO4)3, in combination with appropriate chelating agents; orinsoluble salts such as dihydroxyaluminum sodium carbon-ate (DASC), Al(OH)2OCOONa, followed by in situ formationof the soluble acid form of DASC.

Properties of CMC gels depend on many factors. In general,the stiffness of a CMC gel increases with:

• An increase in CMC concentration.• An increase in CMC molecular weight.• An increase in the concentration of trivalent metal ion.• A decrease in solution pH.

Techniques for producing CMC gels by crosslinking withtrivalent metals are discussed in more detail in AqualonBulletin VC-521 and Bulletin VC-522.

EFFECT WITH WATER-SOLUBLE NONIONIC GUMS CMC is compatible with most water-soluble nonionic gumsover a wide range of concentrations. In many instances, thelow-viscosity types are compatible over a broader range thanthe high-viscosity types.

When a solution of anionic CMC is blended with a solutionof nonionic polymer such as NATROSOL® hydroxyethylcellu-lose or KLUCEL® hydroxypropylcellulose, a synergistic effecton viscosity is observed. Such a polymer mixture producessolution viscosities considerably higher than would ordinarilybe expected, as shown in Table Vl. The polymers can beblended dry, then dissolved; or solutions can be preparedfirst, then blended. If other electrolytes are present in thesystem, the effect is reduced.

Table Vl – Synergistic Effect on Viscosity When a Nonionic Polymer Is Blended WithAqualon CMC

Viscosity Viscosity of a Blendof a 1% of Equal Parts

Solution at at 25°C, cps (mPas)25°C, cps

Polymer (mPas) Expected(k) Actual

Cellulose gum,Type 7H3SF 1,500 1,650 3,200

Natrosol 250 HR 1,800

Cellulose gum,Type 7H3SF 1,500 1,570 3,280

Klucel H 1,640

(k)From blending chart, VC-440.

24

CMC is seldom used to prepare free or unsupported films.However, its ability to form strong, oil-resistant films is ofgreat importance in many applications.

Clear films can be obtained by evaporating the water fromCMC solutions. These fairly flexible films are unaffected byoils, greases, or organic solvents. Their typical properties are given in Table Vll. The films were 2 mils thick and con-tained about 18% moisture.

Where improved flexibility and elongation are desired, plas-ticizer is added to the casting solution. By including 10 to30% glycerol in a formulation, elongation can be improvedby 40 to 50%, and folding endurance can be increased to10,000 MIT double folds. Plasticizers that have proved effective with CMC are:

• Ethanolamines • 1,5-pentanediol• Ethylene glycol • Polyethylene glycol • Glycerol (mol wt 600 or less)• 1,2,6-hexanetriol • Propylene glycol• Mono-, di-, and triacetin • Trimethylolpropane

Table Vll—Typical Properties of Films Prepared From Aqualon® CMC

CMC

Property Type 7L Type 7M Type 7H

Tensile strength, psi (kg/cm2) 8,000 (563) 13,000 (915) 15,000 (1,056)

Elongation at break, % 8.3 14.3 14.3

Flexibility, MIT double folds 93 131 513

Electrostatic charge Negative Negative Negative

Refractive index 1.515 1.515 1.515

Specific gravity 1.59 1.59 1.59

PROPERTIES OF CMC FILMS

25

PACKAGING AND SHIPPING

Aqualon® CMC is packed at a moisture content no higherthan 8%. Because of varying storage and shipping condi-tions, there is a possibility of some moisture pickup from the “as-packed” value. The standard package is a 50-lb-net,3-ply, polyethylene-lined multiwall kraft paper bag. The type,lot number, and bag number are stenciled on the bottom ofeach bag.

Truckload shipments originate from Hopewell, Virginia.Less-than-truckload quantities are also available fromHopewell or from warehouse stocks conveniently locatednear industrial centers.

Read and understand the Material Safety Data Sheet(MSDS) before using this product.

MICROBIOLOGICAL INFORMATION ANDREGULATORY STATUS FOR USE IN FOODS,DRUGS, COSMETICS, AND TOILETRIES

MICROBIOLOGICAL INFORMATIONAqualon production facilities for carboxymethylcellulose(CMC) are operated in compliance with Current GoodManufacturing Practice Regulations (CGMPRs) as promul-gated in the U.S. Code of Federal Regulations. Whileextreme care is exercised at every process step and theproduct is of excellent microbiological quality, CMC is notmarketed as a sterile material.

Aqualon CMC is routinely sampled and subjected to microbi-ological testing by an independent laboratory and data aretabulated to provide an ongoing indicator of control in pro-duction. The data generated are not intended to be used toprovide product specifications, but typical results using ourstandard protocol, are shown below.

Aerobic plate count, cfu/g . . . . . . . . . . . . . . . . . . . . . . <100Mold, cfu/g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <100Yeast, cfu/g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <100Coliforms, MPN/g . . . . . . . . . . . . . . . . . . . . . . . . . . . . <30E. coli/10 g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . negativeStaphylococcus aureus/10 g . . . . . . . . . . . . . . . . . negativeSalmonella/25 g . . . . . . . . . . . . . . . . . . . . . . . . . . negativePseudomonas/10 g . . . . . . . . . . . . . . . . . . . . . . . . negative

Aqualon utilizes officially approved methods to determine the above microbial parameters, but recommends that usersof Aqualon CMC assure themselves of compliance with anymicrobiological criterion by testing each lot.

The typical values above allow for the fact that somemicroorganisms may be present in CMC. We therefore recommend that our customers control the microbiologicalquality of their finished product through appropriate processand formulation expertise.

Certain types of purified sodium carboxymethylcellulose (cel-

lulose gum) meet standards set by the U.S. Code of FederalRegulations, Title 21, Section 182.1745—Substances thatare generally recognized as safe (GRAS). The FDA definesthis GRAS substance as the sodium salt of carboxymethyl-cellulose, not less than 99.5% on a dry-weight basis, withmaximum substitution of 0.95 carboxymethyl groups peranhydroglucose unit, and with a minimum viscosity of 25 cpsfor 2% (by weight) aqueous solution at 25°C. Aqualon food-grade (F) cellulose gum meets these requirements. Aqualoncellulose gum is also certified to be kosher.

Both the Food Chemicals Codex and the Food andAgriculture Organization of the United Nations World HealthOrganization (FAO/WHO) have established specifications foridentity and purity of sodium carboxymethylcellulose, whichare also met by Aqualon food-grade cellulose gum.

FOOD STATUS Title 9, Chapter III, of the Code of Federal Regulations listsingredients acceptable by the U.S. Department of Agriculturefor use in meat and poultry food products, subject to labelingrequirements, under the following Sections:

318.7 Binder, extender, or stabilizer for meat typebaked pies when used in an amount suffi-cient for the purpose in accordance with21CFR172.5

381.147 Binder, extender, or stabilizer in variouspoultry products when used in an amountsufficient for the purpose

FDA Definitions and Standards for FoodCellulose gum may be used in a wide variety of standardizedfoods, subject to Title 21 of the Code of Federal Regulations.Within each of the following parts of Subchapter B—Food

26

and Food Products are several definitions and standardspermitting use of cellulose gum. Further details on individ-ual sections of the standards are available by request.

131 Milk and cream products 133 Cheese and related cheese products 135 Frozen desserts 150 Fruit butters, jellies, and preserves 169 Food dressings and flavorings

In addition, the use of cellulose gum is permitted under thefollowing Sections:

146.121 Frozen concentrate for artificially sweet-ened lemonade

152.126(a) Frozen cherry pie165.175 Soda water168.180 Table syrup

Cellulose gum, including CMC standard grades, is permittedfor use in boiler water additives and food-packaging applica-tions under the following Sections:

173.310 Boiler water additives174.5 General provisions applicable to indirect

food additives175.105 Adhesives175.300 Resinous and polymeric coatings176.170 Components of paper and paperboard in

contact with aqueous and fatty foods 176.180 Components of paper and paperboard in

contact with dry food177.1210 Closures with sealing gaskets for food

containers182.70 Substances migrating to food from

cotton and cotton fabrics used in dry food packaging

Note: A communication from the Food and Drug Adminis-tration to Hercules Incorporated, Aqualon Division, definesas suitable for use in packaging materials sodium carboxy-methylcellulose of purity not less than 90% on a dry-weight basis.

FOOD LABELING “Cellulose gum,” accepted as a common, or usual, name forAqualon® purified sodium carboxymethylcellulose, may beused in food-label ingredient statements. The food manufac-turer or processor is permitted to use either “sodium car-boxymethylcellulose” or the shorter and more common term, “cellulose gum.” The Food Chemicals Codex, whichdescribes in detail the standards required of food-gradeadditive materials uses “cellulose gum” as the primary name, in addition to the more technical term, “sodiumcarboxymethylcellulose.”

Establishment of “cellulose gum” as an accepted commonname for sodium carboxymethylcellulose resulted from anAqualon petition granted by order of the Deputy Commis-sioner of Food and Drugs, effective June 26, 1963.

PHARMACEUTICAL USE Sodium carboxymethylcellulose is listed in the current U.S.Pharmacopoeia. Its applications may be both therapeuticand excipient. Therapeutic uses include bulk-forming laxa-tives in which sodium carboxymethylcellulose may be theprimary ingredient. Excipient uses include those of suspend-ing, tablet binding, or viscosity increasing.

Sodium carboxymethylcellulose 12 (degree of substitution1.15-1.45 min) is listed in the National Formulary for use as a pharmaceutic aid. The same excipient uses just givenare applicable.

Aqualon CMC meeting the requirements of the U.S.Pharmacopoeia or the National Formulary can be suppliedby request.

COSMETICS AND TOILETRIES “Cellulose gum” is the accepted term used by the Cosmetic,Toiletry and Fragrance Association, Inc., for sodium car-boxymethylcellulose. The product is so listed in the Associ-ation’s CTFA International Cosmetic Ingredient Dictionaryand Handbook.

27

APPENDIX —METHODS OF ANALYSIS

General principles for analysis of CMC and details of severalprocedures are contained in Aqualon Bulletin VC-472,“Analytical Procedures for Assay of CMC and Its Determi-nation in Formulations.” Copies may be obtained by request.

Several analytical procedures are contained in ASTM D1439,“Standard Test Methods for Sodium Carboxymethylcellulose.”Copies are available directly from ASTM, 100 Barr HarborDrive, West Conshohocken, PA 19428.

VISCOSITY OF SOLUTION An accurate determination of the viscosity of a CMC solutionis frequently needed. As explained on page 13, the apparentviscosity of such a solution depends on a number of factors,and if reproducible results are to be obtained, a closely stan-dardized method of solution preparation and viscosity deter-mination must be followed.

The standardized Aqualon method for determining viscosityof CMC solutions specifies the Brookfield viscometer(3). Thespindle guard supplied with this instrument should be usedfor all determinations.

Solution volumes specified should not be less or they maynot cover the appropriate Brookfield spindle.

Preparation of the solution is critical, in that the CMC mustbe completely dissolved to obtain a significant measure-ment. To determine the proper amount of gum, a moisturecorrection must be included to place the viscosity measure-ment on a dry CMC basis.

The viscosity-measurement test must be rigidly standard-ized because the viscosity reading obtained depends on rateof shear, temperature, amount of agitation prior to measure-ment, and elapsed time between agitation and measure-ment. The method used in Aqualon laboratories is givenhere in detail.

Moisture Determination1. Weigh duplicate samples of 5 g, to the nearest 0.001 g,

into previously dried and weighed moisture cans withcovers. The samples for solution preparation (see nextsection) should be weighed right after these moisturesamples.

2. Place the samples in a gravity convection oven main-tained at 105 6 0.5°C and heat for three hours. Cool in a desiccator and weigh.

(3)Brookfield Synchro-Lectric Model LVF, 4 speeds, 4 spindles, range 0 to 100,000 cps, Brookfield Engineering Laboratories, Middleboro,Massachusetts.

3. Return the samples to the oven for 45 minutes; cool andweigh as before. If the second dried weight is not within0.005 g of the first, repeat the 45-minute oven periodsuntil two subsequent weighings are in agreement. Then,using the lowest dried weight obtained, calculate percentmoisture as follows:

Original sample wt – dry sample wt × 100 = % moisture.Original sample wt

Solution PreparationImmediately after weighing CMC samples for moisture deter-mination, the same undried gum should be weighed for solu-tion preparation. Moisture and solution sample weighingsshould be made closely together to ensure that the moisturecontent of both is the same at time of weighings.

1. Quickly weigh the required amounts of CMC (see TableVlII), to the nearest 0.005 g, into clean weighing dishes.

2. From the determined percent moisture, calculate theweight of distilled water to be added as follows:a. For 1% viscosity solution:

Weight of undried CMC × (99 – percent moisture)= Weight of water.

b. For 2% viscosity solution:Weight of undried CMC ×(98 – Percent moisture) = Weight of water.

2

c. For 4% viscosity solution:Weight of undried CMC ×(96 – Percent moisture) = Weight of water.

4

3. Add the calculated amount of distilled water to therespective 12-oz. bottles. Use 12-oz. bottles with an ID of 21⁄2 in.

4. Stir the water with a mechanical agitator to create a vor-tex. An anchor-shaped stirrer turned by compressed air is satisfactory. Carefully sift the sample into the water,avoiding the center of the vortex, and be sure that all thematerial is transferred. Lower the bottle into a constant-temperature bath (25 6 0.5°C).

5. Increase stirring speed and stir vigorously until solution is complete. (Usually 1 to 3 hrs is required.) When solu-tion is complete, measure viscosity as described in thenext section.

28

If the solution cannot be kept at constant temperatureduring preparation, follow Steps 6 and 7.

6. When the solution is complete, remove the stirrer, place a sheet of cellophane over the mouth of the bottle, andcap it.

7. Place the bottle in a constant-temperature bath for at least30 minutes, but no more than two hours. (If the samplestands longer than two hours, return it to the stirrer for 10 minutes.)

Table VllI – Approximate Undried CMC Weightsfor Solution Preparation

Add Distilled WaterAqualon® to Give This Exact

CMC Sample Percent SolidsViscosity Type Weight, g Content

L2 10.5 4.0L & M 5.2 2.0

H 2.3 1.0

Viscosity Measurement 1. Select from Table IX, below, the Brookfield spindle-

speed combination for the viscosity type of gum beingtested. Attach the selected spindle to the instrument, then set the instrument for the corresponding speed.

2. If the solution was prepared in a constant-temperaturebath, immediately insert the spindle (with the guardattached) into the solution. Start the spindle rotating and allow it to rotate for three minutes before taking the reading.

3. If Steps 6 and 7 of the solution preparation procedurewere followed, remove the bottle from the constant-temperature bath and shake it vigorously for 10 seconds.Then remove the cap and proceed with Steps 1 and 2 of the viscosity measurement.

4. Stop the instrument, read the dial, and multiply the dialreading by the factor shown in Table IX. The result is thesolution viscosity in centipoises (mPas).

Table IX — Brookfield Spindle-Speed Combinations for Determination of Solution Viscosity

SpindleConcentration, Spindle Speed, Maximum Reading,

Aqualon CMC Type % Number rpm Factor cps (mPas)

7L2 4 2 60 5 5007L 2 1 60 1 1007M2 2 2 60 5 5007M, 7M8S, 9M8, 12M8 2 2 30 10 1,0009M31, 12M31 2 3 30 40 4,0007H, 7H3S, 7HOF 1 3 30 40 4,0007H4, 9H4 1 4 30 200 20,000

HERCULES INCORPORATEDAqualon DivisionHercules Plaza

1313 North Market StreetWilmington, DE 19894-0001

(800) 345-0447www.aqualon.com

The products and related information provided by Hercules are for manufacturing use only. Hercules makes no express, implied, or other represen-tation, warranty, or guarantee concerning (i) the handling, use, or application of such products, whether alone, in combination with other products, orotherwise, (ii) the completeness, definitiveness, or adequacy of such information for user’s or other purposes, (iii) the quality of such products, exceptthat such products are of Hercules’ standard quality. Users are advised to make their own tests to determine the safety and suitability of each productor product combination for their own purposes. Read and understand the Material Safety Data Sheet (MSDS) before using this product. Hercules doesnot recommend any use of its products that would violate any patent or other rights.

250-10H REV. 4-02 Supersedes all previous editions. PRINTED IN U.S.A.

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