Dyestuff Reporter

AMERICAN DYESTUFF REPORTER Volume 47 January 27, 1958 Number 2 FAST DYES ON CELLULOSIC FIBERS T \ICKERSTAFF Imperial Chemical Industries Ltd Manchester 9, England INTRODUCTION in their brightness and range of fiber, and are therefore suitable for shades. Furthermore, large molecules cold dyeing and continuous process NE of the main preoccupations diffuse into cellulose very slowly so ing. To the dye molecule is attached Oof the dyer always has been the that if a direct dye molecule is made the reactive group, which contains ichievement of fast dyeings, but the larger to increase its affinity and wet one or two reactive chlorine atoms. )resent paper is concerned mainly fastness, it becomes increasingly dif In alkaline solution, reaction between vith the problem of wetfastness on ficult to level, and dyeing temper the dye and the hydroxyl groups in :ellulosic fibers. From the theoretical atures near the boil must be used in cellulose can occur to link the dye )oint of view, wetfastness can be ob- order to obtain penetration of the to the fiber by a definite chemical ained in two ways, namely: fiber in a reasonable time. Finally, bond. These dyes do therefore com 1) The introduction into the fiber direct dyeing must remain funda bine the simplicity of application of |.f insoluble coloring matters. Wet- mentally a reversible adsorption proc water-soluble dyes with high wet astness is then attained by the me- ess, and since the adsorbed dye re fastness properties to an extent which hanical retention of the pigment par- mains unchanged and water-soluble, has not hitherto been attainable. icles within the fiber, coupled with the highest degree of wetfastness Ile insolubility of the pigment in soap must remain unattainable. Solutions. Typical examples of this THEORY OF DYEING aethod are the mass pigmentation of APPLICATION OF WITH REACTIVE DYES ayons and the use of vat, azoic, The evidence for the existence of hthalogen and Alcian dyes. REACTIVE DYES chemical linkages within Procion- t2) The use of soluble dyes, which The recent introduction of chem ically reactive dyes opens an entirely dyed fibers has been reviewed else re designed to have an appreciable where (I) and the practical methods ffinity for the fiber. The classical ex- new approach to this problem. The principle involved is very simple and of dyeing have also been described mple of this method is the direct (2). Consequently attention will be consists merely of attaching to a yes, where the molecular structure directed in this paper towards the water-soluble dye molecule a reac f the dye is selected so that physical theoretical aspects of the application tive group which is capable of enter bsorption forces of considerable of reactive dyes and the implications ing into chemical combination with rength are built up between dye in terms of practical dyeing methods. cellulose. With such a system it is id fiber. In the first place, the use of reac t possible to use dyes which have little The simplicity of application of tive dyes introduces a new charac or no affinity for cellulose. Conse ^ater-soluble dyes has always been teristic into the dyeing operation. quently, simple dye molecules can be ttractive, but in order to achieve any Dyeing behavior is no longer con employed and theoretically any shape ignificant wetfastness, the soluble trolled solely by rate of diffusion of chromophoric system. The dye yes must have a high affinity for and affinity but also involves reaction molecule can be small and thus able ellulose. Simple acid wool dyes have rates. Any dye which will react with to diffuse within the fiber quickly to egligible affinity and are completely cellulose will almost certainly react give rapid penetration and good emoved by washing, and the higher with water so that in any dyeing op leveling. Once within the fiber, how ffinity of direct dyes is obtained by eration two competing reactions must ever, the reactive group will combine uilding up long, flat molecules, be taking place, namely 'hese molecules must be linear and with cellulose and will anchor the lust be large, which means in effect dyestuff to give a high degree of wet (1) NaSOs-D-Cl -t-HO-cellulose—►NaSO-D- lat polyazo structures must be used, fastness. O-cellulose+HC1. (21 N aSO,-D-a+H O H-^N aSO:-D-O H r onsequently, many attractive chrom- These principles are employed in phoric systems, such as anthra- the Procion dyes. The dyes at pres HCl. ent available are simple mono-azo, uinone dyes and triphenyl methane Reaction (1) is the desired reaction anthraquinone, or phthalocyanine de yes, are ruled out, while the com- with the fiber. Reaction (2) is a side rivatives, which are polysulfonated lexity of a polyazo system almost reaction leading to inactivation of to give high solubility. With the ex levitably introduces dullness. Direct the dye, since the hydroxyl deriva ception of the phthalocyanine deiiv- yes are therefore somewhat limited tive formed will not react with cellu ative, they are of small moleculai lose. The relative speeds of these ’resented before the American Chemical Society size, diffuse very rapidly within the New York, N Y. 33 AMERICAN DYESTUFF REPORTER januory 27, 1958 two reactions are obviously ol' vital 0-0 importance, and reaction (1) must be much taster than (2) if the dyes are to be of practical value. O>. RELATIVE RATES OF REAC O TION WITH CELLULOSE AND WA TER---------Attempts to determine quantitatively the rates of reaction of Piocion Brilliant Red 2BS with cellulose have so far failed com pletely, except in so far as they es tablish that the reaction is very a '10 rapid. Pieces of viscose film (Dio- phane PT 300) were dyed to equilib rium in a neutral solution of Procion Brilliant Red 2BS (0.33 g/1) and common salt (30 g/1) at 30°C. Un der these conditions no reaction with the fiber occurred and all the dye XO could be removed by treatment in Time (minutes) boiling Lissapol NC solution. The Figure 1 pieces of dyed film were immersed for short times ranging from 15 sec Rate ot hydrolysis of Procion Brilliant Red 2BS at 25 C onds to 12 minutes in a cold solution [jitiiess 01 of sodium carbonate (10 g/1) and I'ealeJ, Ho salt (30 g/1) and then transferred immediately diluted and buffered to immediately to boiling Lissapol NC pH 6.4 to stop the reaction, and then TABLE III processes IS solution (2 ml/1) and boiled for 10 measured on a spectrophotometer Eff ect of pH on hydrolysis of minutes. The film was then squeezed without delay. It was found that the Procion Brilliant Red 2BS on to a glass plate and its optical absorption spectra of the initial re in water at 25°C density measured at 538 m/x. The re active dye and the inactivated hy (Dye concentration — 0.33 g/lj sults in Table I show no significant droxy derivative differed sufficiently change in density with time so that to enable the proportions of the two M eas Velocity’ reaction must be complete in less forms to be measured, although the ured Constant' C onditions pH K than 15 seconds. accuracy is not high owing to the volved or if small differences in optical density 4 g/1 NazCO.,, 0.91 g/1 HCl 10.1 o .o o s 1 in till A similar experiment was carried 5 g/1 Na2COj 11.1 0.030 out by air drying the dyed film and which are involved. In all the experi 4.5 g/1 N a 2C 03, 0.5 g/1 NaOH 11.8 o.os< eralkoursor 12.7 0.175 then suspending the film in ammonia ments it was found that the kinetics 2 g/1 N aO H liliere more vapor for short times before washing of decomposition were those of a iemperatiire i off. The results are shown in Table II. first order reaction in that a straight T Again the results show no increase line was obtained by plotting the in fixation beyond the shortest prac logarithm of the concentration of re TABLE IV ticable time of treatment so that active dye remaining in solution at Effect of electrolyte concentration separate solu again the reaction of the absorbed any time against the time. An ex on hydrolysis of Procion Brilliant reactive dye with cellulose when the ample is shown in Figure 1. From Red 2BS in water environment is made alkaline must the slope of the line, the velocity con ( Dye concentration = 0.33 g I) be extremely rapid. stant K of this hydrolysis reaction The rate of reaction of these dyes may be calculated. Results obtained with water is more easily measured. at different hydrogen ion concentra To stirred solutions of the dyes, al tions, electrolyte concentrations, and T em p C onditions kali was added and samples removed temperatures are summarized in Ta 25°C 5 g/1 Na2COi 25°C 10 g T NaoCOi, at various times. The samples were bles III, IV and V. 30 g 1 NaCl 25®C 20 g/1 Na2C03, 60 g/1 NaCl TABLE I Rate of reaction of Procion Brilliant Red 2BS with cellulose in soda ash solution TABLE V Effect of temperature on the Time of Treatment 15 secs 30 secs 45 secs 1 min 4 min 12 min hy<lrolysis of Procions Brilliant Optical Density 0.175 0 169 0.165 0.169 0.174 0.174 Red 2B S and Blue 3GS fifaloutii (Dye concentration — 0.33 ISa.,CA); = lOg/l-, ISaCl = 30 g I) ta TABLE II Rate of reaction of Procion Brilliant Red 2BS Procion Brilliant can with cellulose in ammonia vapor Red 2BS Procion Blue 3C: H'ater T em p pH K pH K n 1 0 5 secs r»-nTime of Treatment 10 secs 15 secs 1 min 16 min 25® C 11 1 0.048 11.1 0.015 '"111: 30® C 11 1 0.10 10 95 o.ou Optical Density 0 020 0 093 0.090 0-091 0.091 0 084 35® C 11 1 0 14 10.85 0.051 34 AMERICAN DYESTUFF REPORTER January 21, 1^® These results show clearly that the rate of hydrolysis increases rapidly with increasing pH and with increas ing temperature and to a lesser de gree increases with increasing elec trolyte concentration.

Load more