Preparation And Application Of Disperse Dye Microcapsules

The volume of water consumed by human beings has increased dramatically in recentyears while water supply remains constant. Both of population growth and the expansion ofindustrial activity require more water consumption. It is well known that the dyeing andprinting processes in textile industry produce large amounts of waste water which causesserious problem to water quality and the environment. The main challenge that textileindustries faces is to keep the balance between solving the environmental problems andinsuring the product quality while keeping general cost low.In this study, microencapsulation technique was applied by using melamine prepolymeras wall material in order to achieve the clean dyeing of disperse dye onto PET or Nylon fabrics.Melamine resin microcapsules containing pure disperse dye were prepared by in situpolymerization. Differential scanning calorimetry (DSC), scanning electron microcopy(SEM)and particle size analyzer were used to obtain information about the characters of themicrocapsules on structure, morphologies, a mean particle size and size distribution. Thedyeing behaviors of microencapsulated disperse dyes were evaluated on polyamide fabrics inabsence of auxiliaries. A series of microencapsulated disperse dyes in different color wereprepared for super-micro polyester fabrics dyeing without dispersant addition. The possibilityof recycling microencapsulated disperse dyes bath effluent for secondary dyeing and scouringafter simple filtration was assessed, and the results were compared to those using distilledwater. The spectral reflectance value and relative levelness of each sample were collectedusing a Datacolor Spectraflash 600. Dyeing kinetics of PET membrane were studied withdisperse dye C.I. Disperse Red 60, disperse dye C.I. Disperse Yellow 54 and disperse dye C.I.Disperse Blue 56.The main results are summarized as following:(1) Microcapsules were prepared by in situ with pure disperse dye as the core material andmelamine prepolymer as the wall-former. The influence of core-to-wall ratio, the stirring rate,pH value of the solution,the dosage of emulsifier and dropping time of wall material werediscussed. The results showed that the optimum conditions for preparing microencapsulateddisperse dye were defined as sheafing rate higher than 10000rpm, suitable pH value 3-5,dropping time over 2 hours and the dosage of emulsifier 2%-3%.(2) According to the dyeing of polyamide fabric with microcapsule disperse dyes(C:W=1:1), it was found that dyeing with microcapsule disperse dyes should be carried out at a little bithigher temperature, so that the same depth of dyeing as that of the corresponding commercialdisperse dyes can be achieved. For example, dyeing polyamide fabric with microcapsuledisperse dye at 100℃can not only enhance the high temperature levelness and migration, butalso reduce its dependence on pH value. So, it can be surely used as a substitute for thecommercial dye in polyamide fabric dyeing, and has such advantages as no need of addingdyeing assistants, and recyclable use of dyeing effluent after simply filtered. In addition, thedyeings after only treated in the dye-bath containing no microcapsules for a certain timefeatured good color fastness without rinsing or washing.(3) Dyeing processes were carried out with microencapsuled dyestuffs of C.I. disperse red 60,C.I. disperse yellow 54 and C.I. disperse blue 56 with the ratio of core to wall 1:3,whichshowed that three dyeing Curves had good compatibility. The combination of three dyestuffswith the ratio, of core to wall 1:3 and 1:1 were used to dye polyester or polyamide fabrics andthe dyeings all featured good color fastness to washing.(4) Diffusion behaviors of microcapsules containing disperse dyestuffs, such asmicroencapsuled dyestuffs of C.I. disperse red 60, microencapsuled dyestuffs of C.I. disperseyellow 54 and microencapsuled dyestuffs of C.I. disperse blue 56 in polyester film werestudied, and the results were compared with those of commercial disperse dyestuffs and theirpure types. It was shown that for all the disperse dyes, the diffusion coefficient D wouldincrease along with the increase of temperature. The diffusion activation energy E calculatedfrom D under different temperatures showed that the existence of surfactants would lead to thedecrease in diffusion activation energy.(5) Microcapsules were prepared with C.I. disperse blue 291, C.I. disperse violet 93 and C.I.orange 288 individually, and these three microcapsules were combined in a certain proportionto dye supermicro polyester fabric in conventional high-temperature dyeing machine. Thedyeing effluent treated by simple filtration was recycled for dyeing and scouring. Acceptablechanges in color and dark-white difference were assessed. All the dyeings featured goodlevelness and fastness to washing, rubbing and light fastness. Microencapsuled disperse dyescan be surely used in dyeing super-micro polyester fabrics without surfactants, and theeffluents can be recycled. Being thoroughly auxiliary free, using microencapsuled dispersedyes dyeing method costs much less in eliminating pollution than using traditional method. It can be surely used as a substitute for the commercial dye in dyeing polyester andpolyamide fabric and has such advantages as no need of adding dyeing assistants, andrecyclable use of the effluent only after simple filtration. In addition, the dyeings treated in thedye-bath containing no microcapsules for a certain time, possessed good color fastnesswithout rinsing or washing, which was beneficial for environmental protection.