Indian Journal of Textile ResearchVoL 6. September 1981, pp. 120-123

Water Soluble Cellulose Acetate and Its Application

A K MUKHERJEE, R K AGARWAL, H K CHATURVEDI & B D GUPTADepartment of Textile Technology, Indian Institute of Technology, New Delhi 110016

Received 5 February 1981; accepted 28 May 1981

Qualitative filter grade cellulose was acetylated using acetic anhydride and suiphuric acid, and the product was hydrolysedwith dilute acetic acid using sulphuric acid or sodium acetate as the catalyst for hydrolysis. The acetyl content decreasedcontinuously on increasing the duration of hydrolysis with sulphuric acid as the catalyst. The product was initially soluble inacetone, the solubility decreasing with decrease in acetyl content, and the product finally becoming insoluble. However, withacetyl content in the range 18-20%. the product became water soluble. On increasing the temperature of hydrolysis, the rate ofhydrolysis increased. The system with sodium acetate as the catalyst for hydrolysis showed the same trend. However, the watersoluble product could not be obtained with sodium acetate as the catalyst. The water soluble product was evaluated forapplication as a size for cotton yarns and the results were compared with those for starch and polyvinyl alcohoL In general,water-soluble cellulose acetate had tensile and flex abrasion properties intermediate between those of starch and polyvinylalcohoL However, its ease of removal by water treatment is highest of the three sizes.

The reaction of acetic anhydride with cellulosichydroxyl groups in the presence of acetic acid, usingsulphuric acid as the catalyst, gives rise to cellulosetriacetate. In the initial stages, the product is nearlycompletely substituted cellulose acetate. Throughjudicious use of water (in the form of dilute acetic acid),the degree of substitution (DS) can be lowered. Thehydrolysis, depending upon DS, gives a wide range ofsubstituted products. The hydrolysis is influenced bythe duration and temperature of reaction, rate ofaddition of water 1 and the presence and quantity of thehydrolytic catalyst (sulphuric acid)", The aim of thepresent study was to study the effect of sulphuric acidand sodium acetate as hydrolytic catalysts on theproduction of cellulose acetate. The solubility ofdifferent products has also been evaluated. A water-soluble product synthesized can be used as a cheapsizing materiaL

Materials and MethodsFilter paper having DP of about 600 (determined by

cuprammonium viscosity method) was used. Aceticanhydride, acetic acid, sulphuric acid, acetone and 2-methoxyethanol (AR grade) were used as such. Starchand PYA were purified before use.

Preparationof celluloseacetate-To 50 g filter papertaken in a 500 ml beaker, 300 ml acetylating mixture(acetic anhydride - acetic acid - sulphuric acid) wasadded at 30°C under vigorous stirring. Within 2 hr, ahomogeneous product was obtained. A small amountof the product was taken out from time to time to testits solubility in chloroform. Within 4 hr, a chloroform-soluble product was obtained:'.

Acetic acid (60% soln vol.zvol.; 100 ml) was then

120

added to the flask and the hydrolysis was allowed totake place at the same temperature. When an acetone-soluble product had been formed, the heating wasstopped. The acetone soluble secondary cellulose wasthen precipitated through the addition of a largeamount of water under continuous stirring. Thereaction was over within 8 hr. The product was driedunder vacuum.

Hydrolysis--Cellulose acetate formed as above wasused for hydrolysis". The sample (50 g) was dissolved in200 ml acetic acid (85%) containing sulphuric acid orsodium acetate by continuous stirring for 4 hr at roomtemperature. This dissolved material was transferredto a three-necked flask equipped with a stirrer, and thetemperature was raised to 60°C, The material wastaken out from time to time and tested for its solubility;its acetyl content was also determined. The reactionwas stopped as soon as a water-soluble and acetone-insoluble product was obtained.

To isolate the above product, excess of acetone wasadded to precipitate the water-soluble celluloseacetate; it was washed to remove traces of acetic acid.The acetyl content of the products at various stages ofthe reaction was determined by the method reportedearlier".

Preparation of sizing solutions- Three sizmgmaterials-starch, polyvinylalcohol and water-solublecellulose acetate-were used for preparing sizingsolutions. Starch and polyvinyl alcohol solutions of 2and 4% concentrations were prepared. A 4% solutionof cellulose acetate in water was also prepared.

Hank preparation-A hank of 120 rounds wasprepared for carrying out various tests. The hank waskept in all the five solutions for 5 min. It was kept

--------------~~-_.... -_.- -.-.--,------- .------.-....,,-------------~---~~====--------------~~~~~~~~...,...,...,...,...,...,...,...,---

VERMA: A TEST METHOD FOR STUDYING THE SETTING BEHAVIOUR OF COTTON YARNS

Table I-Variation of Acetyl Content with Duration ofHydrolysis at Different Temperatures in Acetic Acid

(Material, Secondary cellulose acetate of 41.4% acetyl content; water

in the hydrolysing mixture, 15%; sulphuric acid in the hydrolysingmixture, 3% (by wt); material-liquor ratio, 1:4)

more irregular structure of the cellulose derivative tothat of pure cellulose or cellulose triacetate. It isobvious from Table 1 that the product remains solublein acetone up to about 40% acetyl content and beyondthis it becomes insoluble in acetone. However, withincrease in temperature, insolubility appears at aslightly lower acetyl content. The acetone-insolubleproduct becomes soluble in 2-methoxyethanol up to anacetyl content of 30% with hydrolysis temperature50°C and up to 27% with hydrolysis temperature 60°C.The acetone-insoluble product obtained at ,O°Cis, however, not soluble in 2-methoxyethanol. Onfurther hydrolysis, the product remains insoluble untilit attains an acetyl content of 18-19% (irrespective ofthe temperature of hydrolysis), when the productbecomes water soluble. A patent mentions a similarproduct without giving details 7.

The water-soluble product must be quicklyprecipitated out with acetone to stop the hydrolysis atthis stage; otherwise, further hydrolysis will render theproduct again insoluble in hydrophilic solvents likewater.

Effect of duration and temperature of reaction onhydrolysis of cellulose acetate with sodium acetate as

catalyst-Sulphuric acid acts not only as a catalyst forthe hydrolysis reaction of cellulose acetate, but also asa degrading agent. If the reaction is carried out in theabsence of a catalyst, completion of hydrolysis takes a

long time. As mentioned earlier, a temperature of 30Tis more suitable than higher temperatures. A longduration is also favourable. Therefore, a mild catalyst,

1,

rotating using rods as is done in laboratory hankdyeing. Finally, it was passed through rollers of thepadding mangle at a constant pressure. The squeezewas found to be 50%. The products were then dried.

Tests-The characteristics of cotton yarn sized withdifferent sizing materials (cellulose acetate, PV A andstarch) were evaluated.

Mechanical properties were determined using an

Instron-ModeIII12, with the following setting: Gaugelength, 5 cm; jaw speed, 5 cm/min; and chart speed, 5cm/min.

Flex abrasion tester was used to determine flex

abrasion. The head load was kept at 15lb and a tensionload of 4 Ib was applied. The yarn samples wereprepared using 15 threads for each test. The 15 threads

were laid straight and parallel to one another, giving anappearance of a narrow strip of fabric.

Ubbelhode viscometer was used to determine the

viscosities of various sizing materials. The flow timefor the solution and the appropriate solvent wasdetermined.

The properly sized and weighed samples werecompared for the ease of removal of the sizingmaterial. Each of the five samples was washed in 200·ml distilled water in a 500 ml beaker heated to 60°C.

Washing was done for 10 min. The washed sampleswere dried and reweighed to find out the loss in weight.The percentage removal of the size was calculated.

Results and Discussion

Cellulose acetate prepared by the method describedshowed an acetyl content of 41.4% (equivalent to DS=2.8). This cellulose acetate was used for furtherstudies.

Effect of duration and temperature of reaction on thehydrolysis of cellulose acetate with sulphuric acid ascatalyst-Cellulose acetate of 41.4% acetyl contentwas hydrolyzed in a mixture containing glacial acetic

. acid and water (15% of the volume of the hydrolysingmixture), in the presence of 3% sulphuric acid, withmaterial-liquor ratio 1:4 at three different tempera­tures for different durations. The results are presentedin Table I. It is seen that on increasing the duration of

hydrolysis, the acetyl content decreases continuously.Increase in the rate of hydrolysis with increase intemperature has been reported by earlier workersals03. However, the cellulose acetate becomes moresusceptible to degradation with decrease in acetyl

content6. For this reason, a lower temper~ture and alonger duration will ensure chances of less degradationand will also give rise to a more uniform product.Keeping this in view, a temperatur:~ of 30°C ispreferable to a higher temperature.

There is a continuous decrease in solubility with

decreaseinacetyl content. ThiS can be ascribed to the

Temp.°C

30

50

60

Duration AcetylSolubilityhr

content

0

41.4Acetone soluble

30

40.3Acetone soluble60

40.2Acetone soluble

80

34.0Insoluble100

22.1Insoluble130

19.6Partially water soluble175

18.0Water soluble

0

41.4Acetone soluble

3039.5Acetone soluble

60

30.22-Methoxyethanol soluble80

20.5Insoluble100

17.8Water soluble0

41.4Acetone soluble30

38.6Acetone soluble40

27.42-Methoxyethanol soluble60

20.0Partially water soluble _80

18.5Water soluble

121

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INDIAN J TEXT RES. VOL 6. SEPTEMBER 1981

Table 3+-:-ComparisoiJ of Viscosity and % Add-on ofDifferent Sizes

(Material, Cotton hank; count of yarn, 18; and duration of

steeping, 5 min)

Table 2- Variation of Acetyl Content of Cellulose Acetatewith the Duration of Hydrolysis at Different Concentrations

of Sodium Acetate

(Material, Secondary cellulose acetate of 41.4% acetyl content;

temperature, 30°C; water in hydrolysing mixture, IS%; material,liquor ratio, 1:4)

sodium acetate (AcONa), has been used at threedifferent concentrations. for the hydrolysis reaction.The results are presented in Table 2.

On increasing sodium acetate concentration, therate of hydrolysis increases, but the rate is always lowerthan that in the case of sulphuric acid-catalyzedreaction.

Though sodium acetate is capable of giving rise todecreased acetyl content, resulting in lower solubilityin acetone followed by solubility in 2-methoxyethanoland ultimately an insoluble product (Table 3), it isincapable of giving rise to a water-soluble product.Sodium acetate, being a mild catalyst, lowers the rateof hydrolysis, and probably is not efficient enough tor,educe the acetyl content to the level necessary for awater-soluble product (18-19%) under the experimen­tal conditions.

I~

Table 4-Mechanical Properties of Sized Cotton Yarns

(Count of yarn, 18)

Size Breaking ElongationInitialFlex abrl,lsionload

at breakmoduluscycle to breakg

%glin 2' x 10-6

Unsized

463.709.5029.613.252% Starch

648.909.1637.019.504% Cell. Ac.

592.809.4024.423.75

2% PYA590.509.2037.025.00

4% PYA*

-- 25.75

4% Starch"-

-- 20.75

Comparison of viscosity values 'and % add-on ofdifferent sizes-To evaluate the properties of water­soluble cellulose acetate (18-19% acetyl content), it wasdissolved in water and used for sizing cotton hank.Similar experiments were conducted with starch andpolyvinyl alcohol solutions. The results are presentediriTable 3. It is seen that 2% starch and PVA solutionshave higher viscosities than 4% cellulose acetatesolution. However, these three solutions are capable ofgiving rise to more or less the same % add-on on theyarns. The evaluation (reported later) of the sized yarncan be compared only with that of yarn having similar% add-on. It is evident that cellulose acetate gives amuch less viscous solution than other materials. It is

important that the higherthe viscosity, the lower is therate of penetration into the yarn.

Properties of sized cotton yarns with various sizes­The mechanical properties of the sized yarns withvarious sizes have been evaluated and the results arepresented in Table 4. It is seen that the tensile,properties of the yarns sized with 4% cellulose acetateare comparable to those of yarns sized with 2% PVA.The'starch-sized material shows a higher tensilestrength.

In respect of flex abrasion again, the behaviour ofcellulose acetate-sized material is intermediatebetween that of the other two sizes. However, thecellulose acetate-sized sample can withstand a highernumber of cycles than starch solution.

Ease of removal-Size is necessary for impartingstiffness and reducing the yarn to yarn friction, duringthe weaving operation. However, these sizes beingsuperfluous materials as such need to be removed priorto any chemical treatment necessary after w«aving.

The ease of removal of the three sizes, namely starch,cellulose acetate and PVA, has been evaluated inboiling water and the results are presented in Table 5.It is seen that 4% water-soluble cellulose acetate is

*Only 2~~ solutions of starch and PV A gave approximately the same% add-on as in the case of 4% cellulose acetate solution. Therefore,

the mechanical properties of only these three sized yarns (having

similar ,%" add-on) have been determined for comparative study.

6.312.8

6.1

12.3

6.9

Add-on

%

*

1.69

4.901.39

Specific viscosity

(fls.le) of solndl/g2.80

Duration AcetylSolubilityhr

content

%60

40.2'Acetone soluble80

38.1Acetone soluble100

34.4Acetone soluble130

26.62-Methoxyethanol soluble60

40.2Acetone soluble80

39.3Acetone soluble100

35.9Insoluble130

29.32-Methoxyethanol soluble150

26.4Insoluble60

40.2Acetone soluble80

39.6Acetone soluble100

38.9Acetone soluble

130

37.3Acetone soluble'150

35.0Insoluble

Sample

15

50

NaOAc

cone.

gllitre

5

2% Starch

4% Starch

2% PVA4% 'PYA

) 4% Cellulose acetate

*Non-measurable in an Ubbelhode viscometer.

122

'VERMA: A TEST METHOD FOR STUDYING THE SETTING BEHA VIOUR OF COTTON YARNS

Table 5 -Ease of Removal of Various Sizes

(Washing liquor used. water; temp. of washing liquor. 60 C and

duration of washing. 10 min)

removed easily as compared to the other sizes. In fact,about twice the amount of size is removed in the case of

cellulose acetate-sized yarns compared to the other

Add-on Size

(on the parent yarn) removed

~/O %

\

/

t-

Sample

2~0 Starch

4~0 Starch4'10 Water soluble CeIL Ac.

2'10 PYA

4% PYA

6.34

12.7676.94

6.077

12.26

55.769

40.78

84.327

40.536.74

sized material treated under similar conditions. Hence,

this material has an advantage over other sizematerials.

References

I MaIm C J. Tanghe L J & Lair-d B C. J Arn chern Soc. 72 (1950)2674.

2 Ost H, Z angew Chern. 32 (1919) 66.

3 Maim C J, Tanghe LJ & Laird BC,lnd Engng Chern, 38(1946) 77.

4 Whistler R L, GreenJ W & Be Miller J N, Methods in carbohydrate

chernistry (Academic Press!nc., London) 1963.

5 Interlaboratory study on determination of acetyl in celluloseacetate, Analyt Chern, 24 (1952) 400.

6 Maim C J & Fletcher C L, US Pat. 2. 013, 830, (to Eastman Kodak

Co.) 10 Sept. 1935; Chern Abstr, 29 (1935) 7074.

7 Fordyce CR. Chern Abstr, 32 (1938) 8777.

123