| Organic pigments(OPs)are widely used in textile coating,ink printing,rubber and plastic products due to bright and various colors.However,there are the common problems for OPs in the process of being used,such as easy agglomeration,poor water-dispersion stability,poor color grade and conceal the underlying substrate,and so on.On the other hand,the process of industrial-production for OPs usually includes a complicated removing the impurities from industrial-grade pigment crystal,consumed a lot of labor costs and energy.Therefore,the polymer encapsulated pigment with high-content pigment was prepared herein by miniemulsion polymerization,using the industrial-grade pigment crystal as raw OPs.The aims of this work not only to improve the dispersion stability of OPs,but achieve high opacity and hiding power.The study firstly the industrial-grade pigment red 170 crystal dispersion had been washed by water for removing salts beforehand,because the present of salts would cause the deterioration of stability of the polymerization system.The polyacrylate and styrene-acrylic resin encapsulated pigment with high pigment content were respectively prepared by miniemulsion polymerization,using methyl methacrylate(MMA)and styrene(St)as hard monomers,and n-butyl acrylate(BA)as soft monomers.The influences of encapsulated pigment on suspension stability,coverage rate,colloidal size was investigated by the mass ratio of monomer to Pigment Red 170,ratio of soft and hard monomer,ratio of anionic emulsifier and nonionic emulsifier.The results show that the composite of pigment and polymer was effectively improved,the average particle size of pigment in aqueous medium was significantly reduced,and the suspension stability of the emulsion system was improved,after adjusting the amount of non-ionic emulsifier OP-10,the proportion of hard and soft monomer and the amount of pigment input.Secondly,the morphology,thermal stability and actual content of organic pigments of polymer encapsulated pigments with high pigment content were characterized by transmission electron microscopy(TEM)and thermogravimetric analysis(TGA).The results show that the polymer is uniformly encapsulated on the surface of Pigment Red 170 particles,which significantly improves the thermal stability of the organic pigment.Notably,it was found that the actual pigment content of the polyacrylate-coated pigment was as high as 77.6%,which agreed with the theoretical calculation.Thirdly,the dynamic light scattering(DLS)and UV-visible spectrophotometer(UV-vis)were used to investigate the dispersion of stability of the encapsulated pigments under the treatment of light,ultrasound,storage and freeze-thaw in aqueous media.It was found that the dispersion of unencapsulated pigment is extremely unstable in the aqueous medium due to the serious agglomeration.Excitingly,a very small amount of polymer can dramatically improve the dispersion stability of the pigment towards light,ultrasound,storage and freeze-thaw.Finally,the cotton,polyester and silk fabrics were respectively printed by using the obtained polymer encapsulated pigments with high pigment content.It is found that,by comparing the unencapsulated pigment,the opacity and hiding power of encapsulated pigments improved by 2-3 times,as well as the dry and wet rubbing friction enhanced by 1-2 grade in the same pigment content,resulting from a small particle size,uniform dispersion and better stability of the obtained pigment.Though this research,the above results are favorable for achieving the development of OPs with easily dispersed in aqueous media,high opacity and hiding power.The pigment encapsulated polymer with high pigment content has good industrial application value in the area of waterborne coatings. |
PDF Full Text Request