The Extraction and Classification of Dyes from Cellulose Acetate Fibres

J. Forens. Sci. SOC.,(1981), 21, 233

Received 2 May 1980

The Extraction and Classification of Dyes from Cellulose Acetate Fibres BERYL BEATTIE, HELEN ROBERTS and R. J . DUDLEY* Home Oflice Central Research Establishment, Aldermaston, Reading, Berkshire, England, RG7 4PN

A simple scheme is described for the extraction and classzfication of dyestuffsfrom l c m to 2cm length5 of sec-cellulose acetate and cellulose triacetate fibres. Introduction Efficient extraction and classification schemes have already been described for the dyes on wool fibres (Macrae and Smalldon, 1979) and on polyamide, polyacrylonitrile and polyester fibre, (Beattie et al., 1979). This paper extends these studies on extraction and classification to the dyes found on secondary cellulose acetate and cellulose triacetate. Dyes Used on Cellulose Acetate Fibres The majority of sec-cellulose acetate and cellulose triacetate fibres are dyed with disperse dyes, with a notable quantity being mass pigmented (Venkataraman, 1977). Diazotisable dyes are also used but mainly for blacks or sometimes navy blues. Venkataraman (1977) also reports that acidic, basic and vat dyes are used, but these are not very common. Experimental Samples of sec-cellulose acetate and cellulose triacetate dyed with disperse and diazotised dyes were collected and various extraction procedures were studied. Samples Dyed fibres were taken from pattern cards supplied by dye manufacturers. The samples used in this study are listed in Tables 1 and 2. General Assessment of Dye Extraction A single fibre approximately lcm to 2cm in length was placed in a capillary tube, 5p1 of the appropriate solvent were added and the tube sealed. The various solvents used are shown in Table 3. One fibre from each sample was also placed in a separate capillary tube and 5p1 of distilled water were added. After each solvent extraction at room temperature for 30 mins the fibre and solvent were compared with the appropriate aqueous standard under a low power microscope ( x 16). The intensity of the extracted colour and the amount of dye extracted was assessed on the ordinal scale 0-5, 0 corresponding to no extraction and 5 to complete extraction.

Results and Discussion Dye Extraction The degree of extraction obtained for the various solvents employed is shown in Table 4 for sec-cellulose acetate and Table 5 for cellulose triacetate. As

" Present address: Home Office Forensic Science Laboratory, Priory House, Gooch Street North, Birmingham B5 6QQ.

expected, solvent V I dissolved the sec-cellulose acetate fibres while solvent V dissolved the cellulose triacetate fibres. O n examining Table 4 it is clear that only one solvent, namely I V (aqueous pyridine), cleanly extracted the disperse dyes from ~ec-celluloseacetate fibres. Solvents 111 and V also offered fairly good extraction, but were found to swell the fibres to the point of dissolution. No solvent fully extracted the diazotisable

TABLE 1 DYED sec-CEL1,ULOSE ACETATE SAMPLES Code* Disperse A(d) B(d) C (d) D(d) E (d) F(d) G(d) H(d) I (d) J (dl K(d) L (4) React~veDisperse A(rd) B(rd) C(rd) Diazotisable A(dz) B(dz) C(dz) *d

= disperse

Dye

Ma~litjacturer

Dispersal Fast Crimson B1 50 Uuranol Brilliant Blue B300 Artisil Rubine GFI. Artisil Blue ERP Celliton Scarlet B Palanil Scarlet G Palanil Blue R T Supracet Fast Scarlet R Supracet Fast Red G Supracet Fast Crimson B Supracet Fast Blue 2G Supraret Fast Violet B

ICI 1C1 Sandoz Sandoz BASF BASF BASF L. B. Holliday L. B. IIolliday L. B. Holliday I,. B. Holliday I,. R. Holliday

Procinyl Red GS Procinyl Blue R S Procinyl Scarlet GS

ICI ICI ICI

Dispersol Diazo Black 2BN Brentacet Black BC Artisil Diazo Black GPN

ICI ICI Sandoz

rd

=

reactive disperse

dz

= diazotisable

TABLE 2 DYED CELLULOSE TRIACETATE SAMPLES Code* Disperse

DYE

A(d) B(d) C(d) D(d) E(d) F(d)

Dispersol Fast Rubine BT Duranol Blue T R Artisil Rubine GFL Artisil Blue E R P Celliton Blue Green B Palanil G Scarlet Palanil Blue R T Celliton Scarlet B Artisil Rubine G P Artisil Blue BSQ Dispersol Fast Scarlet I3 Duranol Red GN

ICI ICI Sandoz Sandoz BASF BASF BASF BASF Sandoz Sandoz ICI ICI

Prorinyl Red GS Procinyl Blue RS Procinyl Scarlet GS

ICI ICI ICI

Artisil Diazo Black Dispersol Diazo Black B Dispersal Diazo Black 2BN

Sandoz ICI ICI

$3 I(d)

J (dl

K (d) L(d) React~veDisperse A(rd) B(rd) C(rd) Diazot~sable A(dz) B(dz) C(dz)

*d

=

disperse

rd

=

rractive disperse

Manujacturer

dz

=

diazotisable

EXTRACTING SOLVENTS USED

component^

Ni~rnbt-r

C,'omposztion

(~~14 Chlorobenzene Toluene I-Methyl-2-pyrrolidone/watrr Pyridinelwater R4ethylene Chloride Acetonelwater Ethanol

1 I1 111 1\' V \'I \'I 1

-.

-

113 413 -

911

ASSESSMENT O F DYE EXTRACTION FROM see-CELLUI.OSE ACETATE FIBRES AT R O O M TERfPERATURE Solvent

I

I1

III

IV

v

1 1 1 0 0 1 0 0 0 1

0 0 1 0 0 0 0 1 0 0

1,

5a

5 5 5 5 5 5 5 5 5 5

5" 5" 5a 4 5a 4% 5" 5" 5" 58

0 0 0

0 0 0

0a 4" 4"

5 5 5

5" 5" 5"

0 0 0

0 0 0

0 0

0 1 1

4&

VI"

VII

Disperse

;/:I

C(d) D(d) E(d) F(d) G(d) H(d) l(d) .J(d) K(d) 1.(d) React~veDisperse X(rd) B(rd) C(rd) Diazot~sable 4(dz) B(dz) C(dz) a

5 5a 5a 0 4" 1 0" 4a

2

1" 3"

d disperse rd = reactive disperse dz = diazotisable Fibres swelled to a gel, partial dissolutio '1 = Fibres dissolvrd

:

The intensity of the extracted colour and the amount of dye extracted was assessed or. the ordinal scale 0-5, 0 corresponding to no extraction and 5 to complete extraction.

dyestuffs, although solvent V yielded good extractions probably due to partial dissolution of the fibre. Table 5 shows that solvent IV was the only solvent that offered any significant extraction of disperse dyes from cellulose triacetate fibres, without swelling and dissolution. Again no solvent was found to extract the diazotisable dyestuffs. Further studies of solvent IV showed that complete extraction of the disperse dyes on sec-cellulose acetate was achieved after only 5 minutes, while heating in a n oven for 20 mins a t 100°C was sufficient to extract fully disperse dyes from cellulose triacetate fibres. Reactive disperse dyes examined on both fibre types behave as disperse dyes since there are no reactive sites on the cellulose acetate fibres. Class~ficationProcedure O n the basis of the results given in this paper a simple classification scheme 235

TABLE 5 ASSESSMENT O F IIYE EXTRACTION F R O M CEL1,ULOSE TRIACE'I'KTE FIBRES A T R O O M TEMPERATURE

-?ye Disperse A(d) B(d) C(d) D(d) E(d) F (4

'34

H (d) I (d) J (dl K(d) L(d) Reactive llispersr A(rd) B(rd) C(rd) Diazotisable A(dz) B(dz) ~(dz) a =

I

II

III

1 1 1 1 1 I 1 1 I 1 1

1 1 1 1 1 1 I

5 4" 1 5" 1

za

Solvent

I

VII

1 5 5 5 2 1 4 0 5 5 5 5

5 5 5" 5" 5 5 5 5 5 5" 5r

1 1 0 0 0 1 0

5 5" 5

0 0 1

0Q OQ 3"

0 0

1

0 0 1 1

1 I 5" 5 58 1

0 0 0

0 0 0

0 2a 0

J

0 0

0 0

0" 08 4a

1 1

o

0

n

V"

IV

5 5

o

d = disperse rd = reactive disperse dz Fibres swelled to a gel, partial dissolution

0

0 0 0

0

o

diazotisable = Fibres dissolved

=

"

'The intensity of the extracted colour and the amount of dye extracted was assessed on tlic ordinal scale 0-5, 0 corresponding to no extraction and 5 to complete extraction.

can be proposed for dyes found on cellulose acetates based on their extraction characteristics with aqueous pyridine (Figure 1). This scheme correctly classified all the dyes examined in this study.

General Discussion This paper describes a simple procedure for the extraction and classification of dyes most usually found on both sec-cellulose acetate and cellulose triacetate. A problem arises with this approach for cellulose acetate fibres which are mass-coloured, and which presumably will show little or no extraction. The extent of this problem is as yet unknown, but mass-coloured fibres should be recognised by microscopy. As mentioned above, diazo dyes are generally used only for black or navy-blue colouration and therefore if the dye from a different coloured fibre is not extracted it is probably mass-coloured. The discussion has ignored other lesser used dyes which would be misclassified by the proposed scheme, but the available information suggests that dyes such as vat, acid and basic are extremely rare. Where large samples are available Haigh (1964) has described a multiple step procedure for the identification of these dyes on sec-cellulose acetate. Previous reports have used elution properties on thin-layer plates for classification purposes (Macrae and Smalldon, 1979; Beattie et a]., 1979). I n the present work this procedure is not necessary, but the thin-layer chromatographic (TLC) examination of dye extracts is of great importance and will be reported later. As part of thc present study, fibres dyed with diazo dyes were dissolved, the solution spotted onto T L C platcs and eluted for 2mm with methanol. The

Aqueous Pyridine a)sec-Cellulose

acetate

Room temp( l 5 m i n ) b)Cellulose

triacetate

100~~(20min)

Good extn

I DISPERSE

(score33)

Poor extn

(scoreb2)

I DIAZO

Figure 1 . The extraction and classification of dyes from cellulose acetate fibres.

dyes moved up with the solvent front and produced numerous spots when developed in toluene/cyclohexane/aceticacid (5 :5 :2 v/v) mixture. Thus the extraction and classification of dyestuffs from single fibres has been extended to cellulose acetate fibres. As before, data are required to measure the frequency of the dye classes on these fibres, and are probably best collected from casework samples. References BEATTIE,I. B., DUDLEY, K. J. and SMALLDON, K. W., 1979, 3. Soc. Dyers and Colourists, 95, 295. HAIGH,D., 1964, J. Soc. Dyers and Colourists, 80, 479. R. and SMALLDON, K. W., 1979, J . Forens. Sci., 24, 109. MACRAE, K. (ED), 1977, The Analytical Chernistr3, of Synthetic Dyes, .John VENKATARAMAN, Wiley & Sons, New York.