GB611662A - Improvements in dyeing - Google Patents

Abstract

Acrylonitrile polymer filaments, films and the like are made from a polymer having a molecular weight within the range 15,000 to 250,000 (Staudinger equation), prepared, for example, by polymerizing a 5 per cent aqueous solution of the monomer at 3 DEG to 5 DEG C. in the presence of 4 per cent of ammonium persulphate catalyst. Yarns may be prepared by spinning a solution in dimethyl formamide of polyacrylonitrile, having a molecular weight of 120,000, into glycerol at 140 DEG C. and subjecting the yarn to a tension of 1.2 grams per denier. The yarn is washed to remove the glycerol and dyed whilst still in the gel state. Specification 404,504 is referred to.ALSO:Filaments, films and the like composed of acrylonitrile polymer are dyed by treating them, preferably in a gel state, with a Naphtol first component, subjecting them to treatment with an aqueous acid solution, and thereafter applying a coupling component. The acid used in the aqueous acid solution preferably has an ionisation constant of not less than 2X10-5 and the concentration of acid is between 1N and 2N. In an example: (1) polyacrylonitrile yarn in the gel state is immersed in Naphthanil AS, dissolved in aqueous caustic soda in the presence of the sodium salt of triisopropyl naphthalene - sulphonic acid and diluted with water, squeezed, immersed in 10 per cent aqueous sulphuric acid solution, rinsed, and immersed in a solution of Naphthanil diazo Scarlet G.G. In examples (2), (3) and (4), the sulphuric acid solution is replaced by 2N hydrochloric acid, 2N acetic acid, and 0.5N acetic acid, respectively. In example (5), instead of Naphthanil AS and Naphthanil diazo Scarlet GG the following are used: (a) Naphthanil ASD and Naphthanil diazo Orange GC, (b) Nephthanil AS-BG and Naphthanil diazo Scarlet GG, (c) Naphthanil AS-BO and Fast Red Salt B, and (d) -naphthol and Naphthanil diazo Scarlet GG. In example (6) the same yarn in the gel state is treated with a solution containing hydrogen peroxide and sodium hydroxide in order to bleach the yarn and partially to hydrolyse the nitrile groups, and then dyed as in (1), (7) the first example is repeated, but coupling is carried out at 50-60 DEG C., (8) the acid treatment in (1) is carried out with 10 per cent sulphuric acid at 35 DEG C., and (9) the first example is repeated, using 0.5N and 2.0N aqueous boric acid solutions at 25 DEG and 50 DEG C., respectively, whereby lighter shades are obtained. The acrylonitrile polymer preferably has a molecular weight within the range 15,000 to 250,000 (Staudinger equation) and may be prepared for example by polymerizing a 5 per cent aqueous solution of the monomer at 3 DEG to 5 DEG C. in the presence of 4 per cent of ammonium persulphate catalyst.