IndianJournalofFibre& TextileResearchVol.16, December1991, pp.263-269

Preparation and characterization of carboxymethyl cellulose fromjute wastes

A Ragheb,I Abd EI-Thalouth,H Elsayed& A HebeishTextileResearchDivision,NationalResearchCentre,Dokki,Cairo, Egypt

Received29 October 1990; revisedreceived\0 January 1991; accepted16 January 1991

Jute waste fibreshave been used as the starting material for the preparation of carboxymethyl cellulose(CMC) and the dependence of the properties of CMC on the purity of starting material as well as on theconcentration ofetherifyingagents has been investigated.It isobservedthat the degreeof substitution (DS) ofCMC increaseswith the increase in the degreeof purity of the starting cellulosicmaterial; it followsthe order:n-cellulose> holocellulose> dewaxedand pectin-freejute> dewaxedjute. DS also increaseswith increase inthe concentration of etherifying agents (monochloroacetic acid and sodium hydroxide). On the other hand,the solubility of CMC is governed not only by DS and the purity of the starting material but also by theconcentration of the etherifyingagents used. It is further observed that the rheologicalproperties ofCMC arecharacterized by non-Newtonian pseudoplastic behaviour, with the exception of very fewsamples whichexhibit thixotropic behaviour. The purity of the starting material as well as the DS ofCMC determine therheological properties. The measuring temperature as wellas storing of the CMC pastes before commencingthe measurements have no significant effecton the rheological properties. The apparent viscosity has beenfound to be dependent on the degree of purity ofthe cellulosic samples, DS and duration of storing beforemeasurement.

IKeywords: Apparent viscosity,Carboxymethyl cellulose, Jute waste fibre

1 IntroductionCarboxymethyl cellulose (CMC) is a water-soluble

cellulose derivative which has found wide-spreadapplications in different industries such as textile 1- 6

and paper 7 - 12industries. It is prepared by reactingcellulose with monochloroacetic acid in presence ofsodium hydroxide. Cellulose of different plantsources and different degrees of purification are usedfor manufacturing CMC13 -16. The quality of rawmaterials used in carboxymethylation varies with theprocess used, the degree of purification of product andthe intended end use.

The present work was undertaken with a view tofind out the most appropriate conditions for thepreparation of CMC using jute waste fibres. Toachieve this goal, the latter were used at differentdegrees of purity and the carboxymethylation wascarried out under different conditions. The mainreaction product, i.e. CMC, was monitored for degreeof substitution and rheological properties.

2 Materials and Methods

1.1 MaterialsJute waste fibres supplied by the Jute

Manufacturing Co., Belbis, Egypt, were used. The

sample was provided as a blend of short rope cutt'ngsand thread wastes. These jute waste fibres were treatedwith water at boil for 2 h using a material-to-liquorratio I :30. This treatment was repeated 3 times toremove the water-soluble matter. The material soobtained was subjected to various treatments toprepare the following samples.

2.1.1 Sample No. I (Dewaxed)Boiling water treated jute sample was extracted in a

soxhlet with alcohol/benzene (l :2) mixture for 12 h toremove wax. The extracted material was washedsuccessively with alcohol and water and air dried.

2.1.2 Sample No. II (Dewaxed and Peetie-free)The dewaxed jute sample was extracted at 85°C for

24 h with ammonium oxalate solution (0.5%) using amaterial-to-liquor ratio 1:50 to remove pectin. Thetreated sample was then washed with the ammoniumoxalate solution followed by several washings withdistilled water and dried at room temperature.

2.1.3 Sample No. III (Dewaxed, Pectin-free and Delignified i.e.Holocellulose )

The pectin-free jute material was treated withsodium chlorite solution (0.7% active chlorite) of pH

263

--INDIAN J. FIBRE TEXT. RES., DECEMBER 1991

4 at 98 ± 1°C for 2 h using a material-to-liquor ratioI:50 to remove lignin. The pH of the chlorite solutionwas adjusted by the addition of requisite amount ofsodium acetate-acetic acid mixture. The sample wasthen washed with water followed by treatment withsodium chlorite as described above. Afterdecantation, the sample was washed with water andthen treated with sodium bisulphite solution (2%) atroom temperature for 10 min using a material-to-liquor ratio I:20. At the end, the sample was washedwith distilled water and dried at 105°C.

2.1.4 Sample No. IV (Pure ex-C('lIulose)The delignified sample was treated with 17.5% aq.

sodium hydroxide solution for 4:5 min at 25°C using amaterial-to-liquor ratio I:25 to remove thehemicelluloses. The solution containing the samplewas then diluted with an equal volume of water andallowed to stand for 5 min prior to decantation. Theresultant substance was washed with water, followedby neutralization with 10% acetic acid for 15min andwashing with distilled water. The sample was thendried at 105°C in an oven.

2.2 Methods

2.2.1 CarboxymethylationCarboxymethylation was carried out according to

the non-aqueous method described by Paddison andSommers!". The following experimental techniquewas adopted: 100g of cellulose was added to a mixtureof ethyl alcohol (630 ml) and toluene (554 ml)followedby the addition of a calculated amount of aq. sodiumhydroxide solution (44.8%) in 1 min. The reactionmixture was mixed well, steeped at 30°C for 30 min anda calculated amount of monochloroacetic acid wasadded to it gradually with agitation. The reactionmixture was left overnight and then kept at 65°C for 70min. The excess caustic soda was neutralized withglacial acetic acid using phenolphthalin and theproduct was filtered. Finally, the product was purifiedby extraction in soxhlet with 80% ethyl alcohol till freefrom salts.

To investigate the effect of etherifying agents on theproperties of the produced CMC samples, the amountof monochloroacetic acid was changed in eachexperiment (40,60,80 and 100g/lOOg cellulose). Theamount of sodium hydroxide was 2 mol/mol ofmonochloroacetic acid.

2.2.2 PurificationThe produced CMC samples were purified by

extraction in a soxhlet with 80% ethyl alcohol.

2.2.3 Analysis and MeasurementsThe OS, expressed as carboxyl groups, was

264

estimated iodometrically according to a methoddescribed by Finkel 'Shtein et al.',

The rheological properties of the pastes of CMCdissolved in distilled water in a concentration of 5%were measured using a coaxial viscometer'Rheomat-15' (Zurich, Switzerland) according to aprocedure detailed elsewhere 18.

3 Results and Discussion

3.1 Degree of Substitution

3.1.1 Effect of Degree of Purity of CelluloseTable I shows the OS of CMC obtained on

carboxymethylation of samples I-IV under identicalconditions. As is evident, the OS ofCMC increases asthe degree of purity of the starting cellulosic materialincreases. For instance, sample Iwhich is only freefrom water-soluble matters and wax exhibits a OS of0.29 when 40 g monochloroacetic acid/lOO g jute isused. This is against a OS of 0.4 for sample IV which ispure ex-cellulose. This implies that the presence ofnon-cellulosic and foreign impurities in the startingmaterials impedes the reaction of mono chi oro aceticacid with the cellulose. Most probably, thenon-cellulosic impurities mask the cellulosehydroxyls via intimate association and/or act asdiffusion barrier.

Table I-DependenceofDS and solubility ofCMCon the degreeof purity of cellulosic source

Sample Cone. of DS Solubility in water"No. CICHzCOOH

g/IOO gjute

II

40 0.29 Partially soluble60 0.35 Soluble80 0.51 Highly soluble

100 0.60 Highly soluble

40 0.35 Partially soluble60 0.45 Soluble80 0.54 Highly soluble

100 0.66 Highly soluble

40 0.38 Partially soluble60 0.46 Soluble80 0.57 Highly soluble

100 0.69 Highly soluble

III

IV 40 0.40 Partially soluble60 0.51 SolubleSO 0.64 Highly soluble

100 0.70 Highly soluble

"The term soluble indicates that the sample undergoes swelling,dispersion and dissolution within 5 min. whereas the term highlysoluble indicates immediate swelling, dispersion and dissolution.

RAGHEB et al.: CARBOXYMETHYL CELLULOSE FROM JUTE WASTES

It is also observed from Table I that the OS values ofCMC derived from holocellulose (sample III) arelower than those found with ex-cellulose (sample IV).Since the difference between the two samples lies in thepresence of hemicellulose in sample III, current datasuggest that the carboxymethylation products of thehemicarboxymethyl celluloses dissolve in thereaction medium by virtue of their shorter chains andlarger amounts of carboxymethyl groups.

3.1.2 Effect of Concentration of Etherifying AgentsTable I shows the effect of concentrations of

monochloroacetic acid and sodium hydroxide on OS.While the concentrations of monochloroacetic acidare indicated in the table, sodium hydroxideconcentrations were based on these concentrations,i.e. 2 mol alkali/mol monochloroacetic acid. It isseen that the OS value increases by increasing theconcentration of etherifying agents. This could beinterpreted in terms of greater availability ofmonochloroacetic acid and sodium hydroxidemolecules in the vicinity of the cellulose hydroxyls athigher concentrations of the etherifying agents. It isunderstandable that the cellulose hydroxyls areimmobile and their reactivity relies on the availabilityof the etherifying agent molecules in their vicinity.

,~l

3.1.3 OS I'S SolubilityTable I shows that the solubilityufCMCdepends

largely on DS, which, in turn, depends on theconcentration of etherifying agents, i.e.monochloroacetic acid and sodium hydroxide. Forexample, samples prepared using 40 gCI.CH2COOH/IOO g jute are not highly soluble inwater whereas the samples prepared usingmonochloroacetic acid concentrations higher than60 g/l 00 g jute are highly soluble in water.

A noticeable feature in Table I is that despite thehigh OS values of 0.38 and 0.4 for CMC samplesderived from holocellulose (sample III) andex-cellulose (sample IV) respectively usingmonochloroacetic acid at a concentration of 40 g/ I00g jute, these samples are not completely soluble inwater. On the other hand, the CMC sample of OS 0.35,which was derived from dewaxedjute (sample I) usingmonochloroacetic acid at a concentration of 60 g/ I00gjute, is completely soluble in water. Hence, it can beconcluded that it is not only the OS of CMC whichdetermines its solubility. Factors associated with thecarboxymethylation environment, such as concen-tration of monochloroacetic acid and sodiumhydroxide, should also be taken into consideration.Besides deciding the magnitude of OS, thecarboxymethylation environment induces changes in

the physical fine structure of cellulose. That is, duringcarboxymethylation, cellulose undergoes changes inthe physical and chemical structure and such changesplaya key role in the properties ofCMC, particularlythe solubility.

3.2 Rheological PropertiesIt has been reported that sodium carboxymethyl

cellulose solutions are non-Newtonian, i.e. theirshearing stress is not directly proportional to the rateof shear. Butts et al. 19 studied the flow properties ofaqueous solutions of CMC and classified them aspseudoplastic, thixotropic or forming a gel structure.Schurz et al.20 discussed the flow curves offive CMCsamples in 6% sodium hydroxide solutions withdegree of polymerization varying from 115 to 510 andfound that they are pseudoplastic.

Taking the above results into consideration, itappears of interest to investigate the rheologicalproperties of the aforementioned CMC samplesderived from jute wastes. Owing to their incompletesolubility, CMC samples prepared usingmonochloroacetic acid at a concentration of 40 gj I00gjute were excluded. Hence, pastes ofCMC derivedfrom the four cellulosic samples using 60-100 gmonochloroacetic acid/ I00 gjute were prepared at aconcentration of 5% in distilled water. Therheological properties of these pastes before and afterstoring were then measured at 25°C using aRheomat-15. The results obtained are shown inFigs 1-6.

3.2.1 Effect of DS and Degree of PurityThe effect of OS and the degree of purity of

cellulosic material on the rheological properties ofCMC is shown in Figs I-4. The rheograms reveal thatmost of the CMC samples are characterized by anon-Newtonian pseudoplastic behaviour since theup and down flow curves are coincident. Only a fewCMC samples show thixotropic behaviour where theup and down flow curves are not coincident.

CMC samples with thixotropic behaviour arethose of relatively lower OS and derived fromcellulosic material of relatively low degree of purity orthose derived from ex-cellulose regardless of their OSvalues. However, the degree of thixotropy, i.e. thearea between the up and down flow curves, is small andrenders these samples nearer to the pseudoplasticbehaviour.

With respect to CMC samples derived frompartially purified jute and/or with relatively low OSvalues, it seems that the OS, the molecular weight ofcellulose and the presence of impurities have aremarkable effect on the rheological properties of

265

INDIAN J. FIBRE TEXT. RES., DECEMBER 1991

~oa:

120

100

oil<,

L.. 80o'"s:oil

B

o 60

40 II

)(

20 fIO~~-L~ __ L--L~ __L-~-L~~~~o 4 B 12 16 20 24

Shearong stressXlO~ dynes/em2

Fig. I-Rheograms of CMC derived from dewaxed jute fibres'[DS:(A) 0.35, (B) 0.51, and (C) 0.60)

160

140

120

100

'" 80'<,L..

2.s:'" 60'0~0

40a:

20

00

C a

2812 16 2 20 24St)l'<lring stress X10 ,dyn~ Ie m2

Fig. 2-Rheograms of CMC derived from dewaxed andpectin-free jute fibres [OS: (A) 0.45, (8) 0.54, and(C) 0.66)

CMC. Presence of impurities such as waxes, pectinand lignin with CMC of relatively low DS values helpsthe formation of gel structure. The latter ischaracterized by the thixotropic behaviour. This stateof affairs is diminished as the DS increases. It is logicalthat increase in DS is accompanied by increased solu-bility which compensates for the effect of impuritiesacting in favour of formation of gel structure. In other

266

oil-0 8'"s:oil

'0~ 60a:

4

2

IC r A

/0

I •

! /I

e •

/ I0 e

ji JIIOe- 0

I0 e •

0 /I

//cP .: /

0 I /e /-. /- e""'-

0~~/

I I

.. \Ii

160

140

120

100

o 8 12 16 20 244

Shearing stress X102,dynes/em 2

Fig. 3-Rheograrns ofCMC derived from holocellulose preparedfrom jute fibres [OS: (A) 0.46, (8) 0.57, and (C) 0.69]

110r-----------------------------------,

90IC'"- , A~

700~-Si ~ ~'0 50 ~ ~B~ .1' ~::7.CJa:

30

8 12 16 20 24 28Shearing stres s Xl02,dynes / c m2

Fig. 4-Rheograms ofCMC derived from u-cellulose preparedfrom jute fibres [OS: (A) 0.51, (8) 0.64, and (C) 0.70)

words, the possibility of gel structure formation forCMC samples derived from partially purified jutesubstrates is eliminated or at least reduced byincreasing the solubility of these CMC samples viaincreasing their DS. Similar observation wasreported>' where cooked insoluble starch forms a gelstructure. The latter was characterized by highlythixotropic behaviour but when starch was modifiedin such a way that it became water soluble, thethixotropic behaviour diminished.

The tendency of CMC samples derived fromo-cellulose to exhibit thixotropic behaviour could be

RAGHEB et af.: CARBOXYMETHYL CELLULOSE FROM JUTE WASTES

associated with its higher molecular weight. The longchains of cellulose when subjected to a high rate ofshear orient themselves parallel to the rate of shearaxis. On removing the rate of shear, it needs time toretain its original state and viscosity, i.e.characterized by thixotropicbehaviour. That is, theCM C is deformed under the action of shearing and no

140

120

100

III

-- 80o"s:III"0 60

se

cr 40

o 4 8 12 16 20 245ht'oring stre-ss Xl0

2.dynt's/cm2

Fig. 5-Rheograms ofCMC derived from ex-cellulose preparedfrom jute fibres after storing for 24 h [DS: (A) 0.51, (8) 0.64, and (C)

0.70]

160

I /40oC

f~700CJ·550C •

Aooc

i i / I/ij 1·;7. .. / ,yII.! .~

.. 1I .//.;:/x'.; • ./ ~

20 i 1./ ./ ...•..;.

V? •..•/~.•..••...-=',.:::.....--'

O~~~-L~~~~L-~-L~~-.~~~~o 4 8 12 16 20 24 28Sht'oring stress Xl02,dynt's/cm2

Fig. 6---Effect of measuring temperature on the rheologicalproperties of CMC derived from holocellulose of DS 0.46

140

120

100

III 80..••..~o'".J:.'" 60's'""0cr 40

immediate rebuilding ofCMC structure occurs. As aresult, a certain time is required for the occurrence ofthis rebuilding and, therefore, the thixotropicbehaviour.

The rheograms of the four samples were alsoexamined after these samples were stored for 24 handcompared with their corresponding rheogramsbefore storing. The comparison revealed that storingthe CMC pastes for 24 h has no significant effect on therheological properties of most, if not all, CMC pastesunder investigation. Nevertheless, the rheogramschanged to some extent on storing as evidenced bycomparing Figs 4 and 5 as typical example of theresults obtained. This is due to change in apparentviscosity on storing as will be discussed later.

A

3.2.2 Effect of Temperature of MeasurementThe effect of measuring temperature on the

rheological properties of CMC samples preparedfrom samples I-IV using 60 g CI-CH:-COOH/IOO gcellulose was examined. CMC pastes were preparedat a concentration of 5% in distilled water and therheological properties measured at a temperaturerange of 10-70°C. The results obtained are shown inFig. 6. It is observed that as the measuringtemperature increases, the location of the rheogram isshifted nearer to the rate of shear axis. The implicationof this is that the apparent viscosity decreases byraising the measuring temperature.

It is also observed that all the samples measured at40°C or above are characterized by a non-Newtonianpseudoplastic behaviour. This indicates that thesmall degree of thixotropy observed with somesamples at lower temperature is temporary andconverted into pseudoplasticity by increasing themeasuring temperature, a point which could beascribed to the enhanced solubility via breaking of thephysical forces, particularly the hydrogen bonding,and the increased mobility of the molecules as well ascompatibility and uniformity of the entire structure ofCMC as the temperature increases.

28

3.3 Apparent Viscosity

3.3.1 Dependence of Apparent Viscosity 011 DS and Degree ofPurity

Table 2 shows that the apparent viscosity ofCMCdecreases with increase in DS in case of samples I-IIIboth before and after storing CMC pastes for 24 h. Onthe other hand, in case of sample IV (o-cellulose), theapparent viscosity exhibits maximum value at DS0.64. This maximum is pertained even after storing theCMC for 24 h before commencing the viscositymeasurements. Nevertheless, the apparent viscosityof the CMC pastes derived from this particular sample

267

INDIAN J. FffiRE TEXT. RES., DECEMBER 1991

decreases with increase in DS when the storing time isprolonged to 4 days (Table 3).

Since the increment in DS values was broughtabout by increasing the severity of thecarboxymethylation reaction, current data suggestthat besides carboxymethylation, celluloseundergoes certain chemical degradation via chainscission under the influence of atmospheric andoccluded oxygen in the strongly alkaline medium.That is why the apparent viscosity decreases as the DSincreases.

It is further observed that for a given equal rate ofshear, the apparent viscosities ofCMC pastes derived

from sample II(dewaxed and pectin-free) are higherthan those of the corresponding CMC pastes derivedfrom sample I(only dewaxed fibre). Homogeneity inthe distribution of the carboxymethyl groups inabsence of pectin may account for this. It seems thatthe presence of pectin not only inhibits thecarboxymethylation reaction but also adverselyaffects the distribution of carboxymethyl groupsalong the cellulose chains through masking some ofthe cellulose hydroxy Is.

Table 2 also reveals that the apparent viscosities ofCMC pastes derived from sample IV (purecx-cellulose) are higher than those of the

Table 2-Effect of DS and degree of purity of CMC on its apparentviscosity at different shear rates before and after storing for 24 h

Sample DS Apparent viscosity (POise) at different shear rates (s -1)No.

2.18 5.139 13.12 23.03 44.10 103.9

0.35 94.19 71.92 52.17 42.75 32.28 21.21(100.47) (79.91 ) (57.38) (41.45) (34.76) (22.79)

0.51 11.46 10.50 8.00 7.72 6.23 5.3a(17.43) (13.62) (11.81) (9.63) (-) (-)

0.60 9.17 8.56 7.01 6.86 5.85 4.04(13.67) (11.01) (10.00) (8.00) (-) (-)

II 0.45 175.89 122.54 79.30 60.63 43.14 26.08(lSO.71) (106.55) (73.04) (55.87) (40.35) (25.03)

0.54 113.03 90.57 66.78 52.31 39.11 ~4.SO(113.03) (90.57) (66.78) (52.31) (39.11) (24. SO)

0.66 22.95 20.21 16.45 11.72(-) (-) (22.95) (20.21) (16.45) (11.72)

III 0.46 75.35 61.27 49.95 39.23 29.80 19.63(81.63) (63.93) (47.99) (39.04) (29.18) (18.84)

0.57 29.36 26.08 23.18 18.93 13.57(-) (34.63) (29.21) (24.96) (19.86) (14.23)

0.69 9.39 8.32 7.13 5.79(-) (-) (-) (-) (-) (-)

IV 0.51 200.59 146.51 95.99 71.92 SO.60(288.87) (197.13) (123.12) (89.16) (61.46) (-)

0.64 251.19 181.14 114.77 86.78 61.15(439.58) (282.37) (164.86) (-) (-) (-)

0.70 SO.28 47.95 37.56 27.48 23.59 15.81(106.75) (75.91) (52.79) . (42.79) (31.66) (20.55)

Values in parentheses indicate the apparent viscosity of same sample after being stored for 24 h

Table 3-Effect ofDS of CMC prepared froma-cellulose (sample IV) on its apparent viscosity at different shear rates after storing for 4days

DS Apparent viscosity (POise) at different shear rates (S-I)

2.18 2.92 3.85 5.13 6.77 9.77 13.12 17.26 23.03 30.38

0.51 288.87 252.56 227.51 199.79 175.69 145.71 124.16 107.87 93.32 80.210.64 263.75 233.85 213.29 186.47 163.57 137.30 116.86 103.11 87.97 77. SO0.70 113.03 159.02 149.30 133.19 121.16 89.66 88.69 77.73 65.98 58.58

268

44.10 59.22

49.04 42.07

RAGHEB et al.: CARBOXYMETHYL CELLULOSE FROM JUTE WASTES

Table 4-Variation of apparent viscosity of CMC pastes with temperature of measurement at different shear rates

Temperature Apparent viscosity (POise) at different shear rates (S-I)

·C 2.18 13.12 44.10 2.18 13.12 44.10

Sample I Sample n10 125.59 73.04 44.08 213.51 110.61 58.9825 94.19 52.17 32.28 175.83 79.30 43.1540 22.96 15.52 87.92 42.78 26.0855 16.69 11.49 62.79 31.30 19.2370 13.56 8.07 18.78 13.04

Sample III Sample IV

10 138.15 82.43 43.46 263.75 137.7325 75.36 49.96 29.80 200.95 95.99 50.6040 25.04 17.38 125.59 59.48 32.9155 16.69 12.42 75.36 42.78 25·4670 10.43 7.76 50.24 29.22 17.38

corresponding CMC pastes derived from sample III(holocellulose). Presence of hemicellulose with itsshort chains and, therefore, low viscosity in sample IIIaccounts for this.

3.3.2 Effect of StoringIt isobserved from Tables 2 and 3 that storing is

accompanied either by an increment in the apparentviscosity or the latter remains unimpaired afterstoring. Storing time seems to allow for betterswelling, compatibility and uniformity of the CMCpaste molecules. thereby increasing the apparentviscosity. However, the formation of hemiacetallinkages cannot be ruled out. Concurrently with itsfavourable effect, storing may adversely affect theapparent viscosity. It is likely that CMC undergoeshydrolytic scission during storing, leading todecrement in apparent viscosity. The findings that theapparent viscosity remains unaltered with someCMC pastes suggest that the said favourable effect ofstoring is counterbalanced by hydrolytic scission ofthe cellulose chains.

3.3.3 Effect of Temperature of MeasurementTable 4 shows the variation of the apparent

viscosity of CMC pastes with the temperature ofmeasurement. The apparent viscosity was measuredwithin a temperature range of 1O-70°C. As evidentfrom Table 4 the apparent viscosity decreases onincreasing the temperature from 10°C to 70°C at aconstant rate of shear. This has been pointed out anddiscussed before.

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