Indian Journal of Textile Research

Vol. 6, December 1981, pp. 151-153

Preparation and Application of Sodium Percarbonate as Bleaching Agent forCotton Fabric

EM ABDEL-BARY, M M MOSTAFA* & S EL-BAZZA

Chemistry Department, Faculty of Science, Mansoura University, Egypt

Received 30 July \979; accepted 24 July \98\

A new method has been developed for the preparation of sodium percarbonate for use as a bleaching agent for colouredand white textiles. The maximum stabilization of sodium percarbonate is obtained with 2.2% crystalline magnesium sulphateand 1.2% sodium silicate.

Fig. \- Variation of stabilized hydrogen peroxide in sodiumpercarbonate with the amount of sodium silicate and magnesium

sulphate added

Results and Discussion

The main parameters which can affect thestabilization of hydrogen peroxide in sodiumpercarbonate are: (1) type and amount of stabilizer, (2)amount of water, and (3) amount of sodiumpercarbonate. While studying the effect of both thetype and amount of stabilizer, all other parameterswere kept constant. It was found that increase in thequantity of sodium silicate or magnesium sulphateused up to 0.14 and 0.12 g respectively increases theamount of hydrogen peroxide which reacts with 109sodium carbonate. Further increase in the quantity ofsodium silicate has no effect, while increase in thequantity of magnesium sulphate decreases the amountof combined hydrogen peroxide. Better results wereobtained by using a mixture of 0.325 g magnesiumsulphate and 0.175 g sodium silicate (Fig. 1). Sodium

Sodium percarbonate is an important bleaching agentfor coloured and white textiles1 -3. Methods of

preparation and the conditions for getting maximumbleaching efficiency with this compound are coveredby patents4 -7 which do not give full informationabout its preparation and application conditions. Inthe present paper, a new method for preparing sodiumpercarbonate and the conditions for its application as ableaching agent for cotton fabrics have been described.

Experimental ProcedurePreparation of sodium percarbonate - Sodium

percarbonate was prepared by mixing sodiumcarbonate (10 g)and sodium silicate (0.175 g) in 17.5mlbidistilled water. To the cold mixture, 20 ml hydrogenperoxide (30% wt/vol) containing '0.325 g magnesiumsulphate heptahydrate was added and the slurry ofsodium percarbonate formed was dried in an oven at60-65°C for 20 min.

Evaluation-Copper numbers, fluidity9 andwettability10 of cotton fabric were determined by thestandard methods. The percentage of hydrogenperoxide stabilized in sodium percarbonate at roomtemperature as well as after boiling for 2 hr wasdetermined by the potassium permanganatemethod11.

The degree of whiteness was measured using aHunterlab reflectometer (Model D 40).

Bleaching process-A bleaching solution of pH10.7-10.9 was prepared by dissolving sodiumpercarbonate (1-6 g/litre) in the required amount ofwater. The cotton fabric specimen was placed in thebleaching solution for 1.5 hr at 95°C. The specimenwas then removed from the bleaching solution, rinsedwith water, squeezed and finally dried at 60°C.

*To whom all correspondence may be addressed.

408

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151

INDIAN J. TEXT. RES., VOL. 6, DECEMBER 1981

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Fig. 3-ElTect of concentration of sodium percarbonateon fabric characteristics

matters in the fabric without scission of the cellulosicchains. The rate of decomposition of hydrogenperoxide increases with increase in temperature and itreaches its maximum value at 90°C. The wettability ofthe fabric also improves.

Both the fluidity and copper number remainunaffected after bleaching for 2 hr. However, theincrease in bleaching period in alkaline medium at95°C causes partial hydrolysis of the cellulosic chains.Also, the degree of whiteness improves and it is notdependent on the bleaching period.

The relationships between copper number (NcJ,fluidity (F) and the concentration of sodiumpercarbonate (Cpc) are shown in Fig. 3 and can beexpressed as follows:

Ncu m Cpc+ KF = m Cpc+ k

E 0 C B

The values of m, m, K and k are found to be 0.19,0.76, 0.003 and 2.1 respectively. This illustrates thatboth copper number and fluidity increase with increasein the concentration of sodium percarbonate. Thedegree of whiteness and wettability improve withincrease in sodium percarbonate concentration. Itfollows that in contrast to the conventional bleachingagents, sodium percarbonate is relatively stable duringstorage at room temperature up to 5months in an openvessel. However, the content of hydrogen peroxidedecreases from 30.8 to 26.0%.

ReferencesI Takashi S, Yoshio M & Mashairo M, Japan Pat 7,107, 371 (to

100 Japan Peroxide Co. Ltd), 24 Feb. 1971; Chem Abstr, 75(1971) 38564 Y.

2 Riyouichi M & Takashi F, Germ Offen 2,420,561 (to Kao SoapCo. Ltd) 30 Oct 1975; Chem Abstr, 84 (1976) 19570 s.

E 0CBArr

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AVERAGE WETTA8lUTY824 FlUDITY

7

21 CCPPER NUMBER

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B515

4

1276 ".•.A C

~...

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2

I [3 64OL

OLOL 0 6075

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TEMPERATURE, ·C

Fig. 2-ElTect of temperature on fabric properties152

percarbonate so obtained contained 30.8% stabilizedhydrogen peroxide at room temperature. Theformation of colloids by silicate hydrolysis inhibits thecatalytic effect of metal ions present in sodiumcarbonate and maintains the pH value at 10-11. Thisindicates the importance of adding sodium silicate as astabilizer. Also, magnesium hydroxide (obtained bythe hydrolysis of magnesium sulphate) assists theprecipitation of heavy metal ions, res~lting inimproved stability of sodium percarbonate.

Effect of water-Only a small amount of bidistilledwater should be used in the preparation of sodiumpercarbonate. Excess water accelerates the decom­position of hydrogen peroxide 12. If the amount ofwater is less than that required, a part of sodiumcarbonate remains suspended without reacting withhydrogen peroxide. The maximum stabilization isobtained by using 17.5 ml bidistilled water.

Effect of sodium carbonate-The optimum ratio ofthe quantities of hydrogen peroxide and sodiumcarbonate is 5: II; about 4.7 g hydrogen peroxidereacts with 10 g sodium carbonate. The optimumquantity of sodium carbonate is 109.

Bleaching of cotton fabric with sodiumpercarbonate-Sodium percarbonate which contains65.8% sodium carbonate, 30.8% stabilized hydrogenperox.ide, 1.16% crystalline magnesium sulphate and1.1% sodium silicate can be used as a bleaching agent.The main parameters which govern the bleachingprocess, such as temperature, period of bleaching andthe concentration of sodium percarbonate, have alsobeen studied.

The effect of temperature on the characteristics ofthe bleached cotton fabric is shown in Fig. 2. Thedegree of whiteness improves and reaches itsmaximum value of 86.5 (in comparison to 62.5 for greyfabric) at 100°C without any change in fluidity andcopper number. This means that the oxygen releasedfrom sodium percarbonate destroys the coloured

ABDEL-BARY et al.: SODIUM PERCARBONATE AS A BLEACHING AGENT FOR COTTON FABRIC

} Fumikatsu T & Takehiko K, Japan Pat 7,592,870 (to Kao SoapCo. Ltd) 22 July 1975; Chern Abstr, 84 (1976) 137624 k.

4 Madhusudan J, Gerrn Offen 2,344,017 (to du pont de nemours,E.I., and Co.) 7 March 1974; Chern Abstr, 81 (1974) 65749 t.

5 Milton S, US Pat 3,801,706 (to Allied ChemiCal Corp) 2 April1974; Chern Abstr, 81 (1974) 65750 m.

6 Richard E H & Suchilk B, US Pat 3,870,783 (to FMC Corp) IIMarch 1975; Chern Abstr, 83 (1975) 30439 f.

7 Yoshiki N, Kyoichi H, Takashi S & Terashi M, Japan Pat

6,734,899 (to Toyo Soda Manufacturing Co. Ltd) 24 March1976; Chern Abstr, 85 (1976) 145328 c.

8 Clibbens D A & Geaka A, J Text Inst, 15 (1924) 27.9 Farrow F W & Neak S M, J Text Inst, 15 (1924) 157.

10 Egyptian Standard: 121 (l96\).II Vogel A I, Quantitative inorganic analysis (Longmans Ltd,

London) 1961.12 Etienne A & Zumbrunn J P, Fr Pat 1,367,499,24 July 1974;Chern

Abstr, 62 (1965) 3687 c.