Textile dyes belong to Bronze Age. If we compare this to the 21st-century, these constitute an important segment of the whole business of specialty chemicals. Dyes that are used by the textile industry are now mostly synthetic. They are mostly derived from two sources namely, coal tar and petroleum-based intermediates. These dyes are marketed as powders, granules, pastes or liquid dispersions. The concentrations of active ingredients typically range from 20 to 80 percent. These are now characterized as new dyes and are regularly developed for meeting the demands of new technology, new kinds of fabrics, detergents, advances in dyeing machineries, along with overcoming the serious environmental concerns posed by some existing dyes. Another important factor is the fact that almost all the products are subjected to seasonal demand and variation. Industrial textiles Dyes must rise up to meet all these new and specific technical requirements.
With the fast changing of the product profile of the textile industry, from high-cost cotton textiles to the durable and versatile synthetic fibers, the pattern of consumption of these dyes is also going through rapid changes. Now a days, Polyesters account for a major part of dye consumption. Accordingly, disperse dyes that are used in Polyesters, are also projected to grow at a faster rate.
The dyeing of cotton, modified previously by reaction with benzoyl chloride, has been carried out using disperse dyes in supercritical carbon dioxide at 100°C and 300 bar and compared with the dyeing of polyester under the same conditions. The color yields of fibers are assessed by measurements before and after washing to investigate the quality of dyeing in this medium. Good color intensity and wash fastness were obtained.
The dyeing machines are equipped with maximally 3 dyeing vessels and are connected to a CO2 recovery and supply unit. These 3 dyeing vessels are able to dye textile simultaneously, but sequentially pressurized or depressurized.
A dyeing cycle is divided into 5 steps
Step 0: Atmospheric: the dyeing vessel is not under pressure
Step 1: Pressurization: the dyeing vessel will be filled with CO2
Step 2: Dyeing and levelling: the textile will be dyed
Step 3: Rinsing: the dyeing vessel and the textile will be rinsed
Step 4: Depressurization: the dyeing vessel will be depressurized
The operator has to choose which dyeing vessel should start with pressurization (step 1) and select the dyeing time. Then the control system takes it over and executes automatically the remaining steps (2, 3, 4, 0) for the activated dyeing vessel(s).
The cotton fabrics were pretreated by sodium 2-(2,3-dibromopropionylamino)-5-(4,6-dichloro-1,3,5-triazinylamino)-benzenesulfonate (DBDCBS) at alkaline condition of room temperature and then dyed with four disperse dyes having amino groups (C.I. Disperse Yellow 9, C.I. Disperse Red 11, C.I. Disperse Blue 56 and C.I. Disperse Violet 1) at acidic condition of high temperature.
A novel hetero-bi functional bridge compound, DBDCBS, has two reactive groups such as dichloro-s-triazinyl group and α,β-dibromopropionyl amido group. The first has reactivity towards hydroxy group of cellulosic fiber and the second shows reactivity towards amino groups of disperse dye containing amino groups. The results indicate that it is possible to dye polyester/cotton blend at one-bath dyeing using one kind of disperse dye containing amino groups.
Therefore, two kinds of dyeing methods such as two-bath process one-bath dyeing and one-bath process one-bath dyeing are investigated and their dye abilities are compared. The differences between these two methods were negligibly small so that perfect one-bath one-step dyeing of polyester/cotton blend by one kind of disperse dye is achieved.
Modified cotton fabric disperse dye transfer printing
Printed cotton fabric has comfortable, good air permeability, suitable for personal wear. Copy number of traditional craft production of cotton printed fabric color, pattern contours are not clear enough, and the production process is long and complex, dyes and low utilization rate of environmental pollution. In order to solve the above problems, dyeing workers conducted a number of studies, such as the use of the polymer on the cotton fiber surface modification, then disperse dye thermal transfer printing, but this method affects the moisture permeability of the printed fabric.
In this study, low cost, low toxicity and good biocompatibility benzoyl thio glycolate as modifier, modification of cotton fabric, and then using the tradition disperse heat transfer printing, examines the printed fabric color yield, mechanical properties and color fastness indicators in order to achieve an optimal cotton fabric disperse dye transfer printing process.
Cotton Modification process
Benzoyl chloride molecule, a carbonyl oxygen atom and a chlorine atom having a strong electron-withdrawing carbonyl carbon atom shows a strong positive charge. Under alkaline conditions, the group with electron-rich structure is very easy to attack the carbonyl carbon atom, chlorine atom is easy to leave, benzoyl chloride prone nucleophilic substitution reaction, access to a variety of reactive benzyl acyloxy derivatives. The reaction process is as follows:
92 g of thioglycolic acid was added 440 mL of cold aqueous sodium hydroxide solution (40 to 80 g), a solution of sodium thioglycolate, temperature of the reaction system was maintained at -5 ° C or below. 70.25 ~ 210.75 g of benzoyl chloride was added dropwise with stirring to a mixed solution of pH value 5-6, the end of the reaction. 1 mol / L hydrochloric acid solution was gradually added the above mixed solution, a white precipitate, namely benzoyl thioglycolate. Vacuum filtration the precipitate was collected, washed with water and dried under reduced pressure, and finally recrystallized from toluene, in a fume hood to remove residual toluene to give the product of colorless flaky crystals.
Cotton fabric modified and the modification rate determination
Cotton fabric in full no foam soap lotion soap, hot water, cold water and drying pre-treatment process to remove the fabric surface stains and impurities. Take a certain amount of benzoyl chloride, sodium carbonate and an anionic softener added to water and heated until all dissolved, the modifier solution. Pretreated cotton fabric the modified solution immersed rolled (dip-rolling, rolling over 80%) → pre-drying (80 ℃ × 60 s) → hot air curing → cooling → hot water (70 ~ 80 ℃, washed many times) → drying (80 ° C X60 ~ 90 s), set aside.
The modified fiber modified according to the formula (1) the degree of substitution (DS):
Since the graft reaction takes place in three hydroxyl groups, so in the calculation of the modified degree of substitution to be multiplied by 3. Before weighing the fabric is placed in a constant temperature and humidity for 24 h and multiple parallel test.
Printing Process
With different molecular weight of polyethylene glycol (PEG 200, PEG 400 and PEG 1000) the preparation of solutions of different concentrations spare as printing pretreatment solution; then modified cotton fabric pretreatment liquid immersed rolling (two dip rolling, rolling over 80%), then dried (80 ° C × 60 - 90 S); silicone trademark machine work table, placed in a bottom-up order the interlining, modified cotton and printing paper, and thereafter transfer printing (pressure of 121.59 kPa); Latest hot water (60 ° C X2 times), drying (80 ° C × 60.90 s).
