Polymer International 41 (1996) 391-394

Synthesis of Polycondensable Anthraquinone Dyes and Coloured

Nylon Fibres: I

Zhenguo Liu, Weixiao Cao*

Department of Chemistry, Peking University, Beijing 100871, People's Republic of China

Yanhui Sun, Aaron C. L. Su

Experimental Station, Du Pont Company, Wilmington, DE 19980, USA

al

Charles L. Liotta

School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA

(Received 1 May 1996; accepted 4 July 1996)

Abstract: The reaction of dihydroxyanthraquinone (DHA) and amines in the presence of catalyst has been reported. We found that DHA reacted easily with hexamethylenediamine in chloroform or toluene without addition of any cata- lyst, and mono- or dihexamethylenediamine-substituted anthraquinone, a violet green colourant, was formed. Using the colourant as a comonomer in the poly- condensation of caprolactam or nylon-6,6 salt, coloured nylon-6 and nylon-6,6 fibres were prepared.

K e y words: polycondensation, anthraquinone dye, coloured nylon fibre.

IN TR 0 D U CTI 0 N

Amination of dihydro~yanthraquinone,'-~ the replace- ment of hydroxy groups attached to the aromatic nucleus by amines, is a synthetic reaction of commercial importance. In principle, the amination is usually carried out in the presence of but we found that the direct amination of anthraquinone with hexa- methylenediamine took place easily in chloroform or in toluene, and it should be a useful method for the prep-

lution problems. To resolve this, we obtained coloured nylon directly by the addition of polycondensable dyes to the nylon melt, followed by spinning the coloured nylon into fibres.

Polycondensable dyes, which contain -NH2 or -COOH groups, can condense with caprolactam or nylon-6,6 salt to form coloured nylon-6 or nylon-6,6. In this paper, we report the synthesis of 1,4-bis(6- aminohexylamino-)anthraquinone and use it to prepare coloured nylon fibres.

* *

EXPERIMENTAL

Materials and instruments

aration of amino-substituted anthraquinone derivatives. Nylon fibre is one of the largest artificial commercial

products in the world. The dyeing of nylon fibre is usually carried out in aqueous solutions of acid dyes.'** The large amount Of waste water Severe Pol- 1,6-Hexamethylenediamine, 1,4-dihydroxyanthraquin-

one, adipic acid and 6-aminocaproic acid were pur- chased from Aldrich Company and used as received. * To whom all correspondence should be addressed.

Polymer International 0959-8103/96/$09.00 0 1996 SCI. Printed in Great Britain 39 1

392

TABLE 1. Polycondensation of caprolactam and polycondensable dyes

2. Liu et al.

Composition of feed Polymer obtained

CL (9) ACA (9) Dye (9) Colour Viscosity (dl g-') MW x

9.5 0.5 0.0 colourless 0.824 2.21 9.0 0.5 0.5 dark yellow 0.856 2.31 9-5 0.5 0.05 golden yellow 0.542 1.63 9.5 0.5 0.1 yellow 0.656 1.67

CL, caprolactam; ACA, 6-aminocaproic acid. Conditions: 8 h at 260°C under N,, viscosity was determined using 85% formic acid as solvent.

Caprolactam (from Polysciences Inc.) was recrystallized before use. Dimethyl sulphone (DMSO) was distilled after drying over CaH, under reduced pressure, and all other chemicals were analytical grade.

The UV spectra were recorded on a Shimadzu-210 spectrophotometer and the nuclear magnetic resonance (NMR) spectra on an ARX-400 spectrometer.

Synthetic experiments

Synthesis of 1,4-bis(6-aminohexylamino-)anthraquinone (BAHA). (a) Chloroform as solvent. A 500ml three- necked flask was charged with 23-28 (0.2mol) of hexa- methylenediamine. 1,4-Dihydroxyanthraquinone (DHA) (4.8 g, 0.02 mol) in 50ml chloroform was added drop- wise at 60°C over about 30min and refluxed for 3 h. The reaction mixture was then evaporated under reduced pressure to dryness and washed with water to remove unreacted hexamethylenediamine. The residue was dissolved in 1 : 4 (vol.) acetic acid/water mixture and precipitated by addition of 3~ NaOH to pH > 8. The BAHA was obtained as a deep violet green powder (4-8g, yield 55%); A,,, (in CH,COOH) 264nm; 'H

NMR (in CH,COOD, ppm) 1.63-3.7 (m, 23 -(CH2)6-); 7-70-8.51 (m, 6 H, nuclear aromatic).

I

(b) Toluene as solvent. Using toluene instead of chloro- form in procedure (a), 5.5g of violet green colourant was obtained (yield 63%); A,,, (in CH,COOH) 264nm; 'H NMR (in CH,COOD, ppm) 1.54-3.89 (m, 24H, -(CH&-); 7-90-8-79 (m, 6 H, nuclear aromatic).

(c) Water as dispersant. The reaction of DHA with alkyl primary amine in water as dispersant has been r e p ~ r t e d . ~ Using a similar procedure, we have prepared the hexamethylenediamine-substituted anthraquinone as follows. Into a mixture of 12g (0-05mol) of DHA (dispersed in 100 ml water), 1-9 g of Na,CO, , 0.69 g of NaHCO, , 15 g (0-10 mol) of hexamethylenediamine was added with stirring under nitrogen and reacted at 70- 80°C for 6h and 95-100°C for 3h. The mixture was then oxidized by aerating at 95-100°C for 2h. After cooling, 2.5g of sodium perborate were added and the mixture was poured into 100ml of water and filtered. The precipitate was washed with water and dried. A violet green colourant was obtained (15.0 g, yield 66%). The values of A,,, and 'H NMR were similar to those of the product obtained from CHCl, .

TABLE 2. Polycondensation of nylon-6.6 salt with polycondensable dye

Composition of feed Polymer obtained

NS (9) AA (9) Dye (9) Colour Viscosity (dl g-')8,9 MW x 1 0-4

5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0

0.0 0.0 0.0 0.0 0.01 0.01 0.01 0.0 0.0

0.0 0.025 A 0.025 B 0.025 C 0.025 A 0.025 B 0.025 C 0.075 B 0.125 C

colourless yellow

golden yellow golden yellow golden yellow golden yellow golden yellow

yellow dark yellow

0.626 0.759 0.675 0.497 0.659 0.636 0.606 0.683 0.499

1.34 1.74 1.50 1.01 1.45 1.38 1.31 1.52 1.02

Nylon-6.6 salt (NS) and polycondensable dye in the presence or absence of adipic acid (AA) were heated at 270-280°C for 6-8 h under protection of nitrogen. Dyes A, B and C represent the products obtained from the procedures (a), (b), (c), respectively (see Experi- mental section). The viscosity was determined using 85% formic acid as solvent.

POLYMER INTERNATIONAL VOL. 41, NO. 4, 1996

Synthesis of polycondensable dyes

Synthesis of coloured nylon fibres. Caprolactam (9.0- 9.5 g), 0.5 g of 6-aminocaproic acid and 0.05-0.5 g of polycondensable dye were added into a Pyrex tube (diameter = 25 mm, length = 200 mm) with a rubber stopper into which were inserted two syringe needles, one as entrance for nitrogen gas and the other as exit. The test tube was immersed in a silicone oil bath and heated at 260-270°C for 6-8 h. The protection of inert gas is necessary during the polycondensation, otherwise the molecular weight of the polymer is too low. After the polycondensation the stopper was opened and the nylon melt was taken out with the tip of a rough glass rod and drawn smoothly with a drawing machine, which was made from a laboratory stirrer, in order to obtain as long a fibre as possible. If the molec- ular weight is high enough (usually > lo4 g mol- l), the drawing process is easy and a fibre more than 10 m long can be obtained. The results of the polycondensation are summarized in Table 1 for nylon-6 and in Table 2 for nylon-6,6.

RESULTS AND DISCUSSION

Mono- or dihexamethylenediamine-substituted DHA were formed in the reaction of DHA and hexa- methylenediamine. A tentative mechanism involving the formation of an intermediate A, for the disubstituted derivative was proposed as follows :

,H

0, O H

A

where R represents -(CH&-. The next step is elimination of water:

A * @T+ \ / 2H20

OH " H 2

B

POLYMER INTERNATIONAL VOL. 41, NO. 4, 1996

393

Then stable product C is formed through intramolecu- lar hydrogen transfer:

8 H W N H 2

Htmnsfer ~ B

C

When the disubstituted derivative is used as poly- condensable dye, the dye molecule will link in the chain of the polymer as follows :

0 II C- NH o + (CYh

Caprolactam 0 HNRNH2

BAHA

ACA I

where ACA represents 6-aminocaproic acid. If the monosubstituted derivative, which was

obtained by a similar method to the disubstituted deriv- ative, was used, a coloured nylon was also obtained. In this case the monosubstituted derivative was incorpor- ated into the nylon molecules as an end-capping reagent as follows :

ACA I

394 Z . Liu et al.

That the polycondensable dye is linked into the 3 Gosei, y., Kagaku K o b a s k 482 (1990) 157. polymer chain can be verified by the fact that the cO1- oured nylon fibres, prepared from caprolactam or 32. nylon-6,6 salt and the polycondensable dye gave a yellow polyamide and a colourless solved in 85% formic acid then precipitated with addi- tion of acetic acid aqueous solution, in which the dye is soluble.

4 Yoshida, K., et a?., Chem. Lett., (1978) 765. 5 Lord, W. M., & Peters, A. T., J. Appl. Chem. Biotechnol., 27 (1977)

6 Matsuokal M.9 Dyes and Pigments, 1 (1980) 27. 7 Gechele, G. B. & Mattiussi, A., Eur. Polym. J., 1 (1965) 46. 8 Burke, J. J. & Orofine, T. A., J . Polym. Sci., A-2 (1969) 71. 9 Wyn, A. &James, G., British Patent, (1978) 1504 137.

when dis-

REFERENCES

1 Takei, T., Bull. Chem. SOC. Japan, 54:9 (1981) 2735. 2 Melpolder, J. B., Europe Patent, (1990) 396 376.

POLYMER INTERNATIONAL VOL. 41, NO. 4. 1996