Patent GB-863207-A (GB)
Title: Colouring acetone-soluble cellulose acetate textile materials
Inventor: MANN RALPH JAMES
IPC: D06P1/92
Filed: 1956-08-23
Abstract: The acetone-soluble cellulose acetate content of textile materials consisting of or containing fibres thereof is coloured by contacting the material for from 5 to 120 seconds with a solution of an acid wool dye or a metallized azo or azo-methine dye in an aqueous liquid containing per litre 100-250 grams of lower fatty alcohol, 150-250 grams of lower fatty acid, and 2-8 grams of sulphuric acid, and thereafter washing the material with water.  By "lower fatty alcohol" is meant methyl, ethyl or n- or iso-propyl alcohol, and by "lower fatty acid" is meant formic or acetic acid.  In a modification of the process the alcohol content of the dye solution is replaced by acetone in amount less than 167 grams per litre.  The aqueous liquid may contain per litre 120-160 grams of lower fatty alcohol, 170-220 grams of lower fatty acid of which 100-160 grams is formic acid, and 2-6 grams of sulphuric acid.  In a preferred method the material is contacted for 10-30 seconds at 25 DEG -35 DEG C. with a solution of an acid wool dye or a metallized azo or azo-methine dye in an aqueous liquid containing per litre about 138 grams of isopropyl alcohol, about 122 grams of formic acid, about 83 grams of acetic acid, and about 4.4 grams of sulphuric acid, and the material is thereafter washed with water. Preferred metallized dyes include products obtained by metallizing, with one atomic proportion of chromium or cobalt, two molecular proportions of an unsulphonated monoazo dye in which the azo group unites two carbon atoms each of which is directly attached to a carbon atom carrying a hydroxyl group.  A number of dyes of this and other types, as defined above, are specified. The aqueous liquid may also contain a wetting agent, e.g. isopropyl naphthalene sulphonic acid or an acid sulphate of a fatty alcohol containing 8 or more carbon atoms, especially the acid sulphate mixture made by the action of sulphuric acid on a mixture of aliphatic monounsaturated hydrocarbons containing from about 8 to about 14 carbon atoms in the molecule.  Fabrics may be passed continuously through a succession of baths of the dye solution with intervening passes through air, the baths being continuously replenished by feeding dye solution to the last bath and permitting each of the preceding baths to receive dye solution by overflow from the next succeeding bath.  Thus, in Fig. 1, fabric 38 passes between the series of rollers shown, receiving dye liquor from the troughs 17, 18, 19, which are separated from the lower rollers 14, 15 16 by the minimum clearance desirable for easy passage of the fabric, and is squeezed between rollers 13 and 22.  Dye liquor fed to trough 19 overflows to troughs 18 and 17, the feed to trough 19 being controlled by the liquid level in trough 17, by means of the floatoperated valve 23 placed in the feed line 24 from supply tank 25.  The feed to trough 19 is via a small trough 26, overflowing into trough 19 and extending along the length thereof, parallel to the width of the fabric. Water-washing is conveniently effected in a washer in which the fabric is carried vertically downwards into a body of water by the flow of water over two weirs, one on each side of the fabric. Thus in Fig. 2, fabric passes from roller 30 between weirs 32 of trough 31, which is fed with water through perforated pipes 34. Below trough 31 baffles 35 extend vertically downwards into tank 29 towards roller 36, and the fabric is led away over roller 37. The fabric may be sprayed with water by means of spray pipes 39. Fig. 3 shows suitable apparatus for processing a heavy pile fabric, e.g. a carpet.  Fabric enters the casing at 56 and is carried by drum 50 through dye liquor in casing 51 and thence to squeeze rolls 52, 53, so placed that squeezed-out liquor is returned to the casing 51. Fresh dye liquor is supplied by pipe 54 to trough 55, from which it overflows into the casing 51 at a point near to that at which the fabric leaves the drum.  The Provisional Specification also discloses the use of direct cotton dyes and cellulose acetate disperse dyes, and the use of hydrochloric or other strong mineral acid in place of sulphuric acid.  A modification of the process is also disclosed in which the alcohol is replaced by another neutral, water-miscible organic liquid which, in admixture with water, constitutes a swelling agent for the cellulose acetate.  Specified liquids include, in addition to acetone, diacetone alcohol, ethyl lactate, and water-miscible ethers, esters, or ether-esters of glycol, glycerol and diethylene glycol, especially compounds in which the etherifying group is a C1-C3 alkyl group or the esterifying group is that of formic or acetic acid.  Examples include glycol monomethyl ether, glycol monoethyl ether, glycol monoethyl ether acetate, glycol monoacetate and diethylene glycol mono- or di-acetate.  Where the liquid is a solvent for acetone-soluble cellulose acetate, e.g. diacetone alcohol, it should be used in a lower proportion than that specified for the alcohol, e.g. 1/2 -\ba2/3 of that proportion, and the content of the liquid and fatty acid together should preferably not exceed 300-350 grams per litre.  Specification 632,938 is referred to.