| Bentonite, which is rich in resources and wide application, is a inorganic mineral material. The using range of it has been extended into many fields, including building, chemical, oil, rubber, plastics, soil, textile, coating, environment industry.But the development of bentonite has still been primary stage.The scope of using bentonite does not open. In order to open new application and reduce the cost of color ink jet paper, the efforts were taken to modification of bentonite and using it in the coating of color ink-jet paper in this paper. Firstly, the modification and dispersion process of bentonite were investigated. Secondly, the effect of modified bentonite on the coating rheological behavior and paper properties were systematically studied, simultaneously.According to the characteristics of pigment used in color ink-jet paper coating, combining the structure and properties of bentonite, Na-bentonite was modified with sulfuric and dially dimethy ammonium chloride,respectively. The results showed that the specific surface ares of acid- bentonite enhanced sharply and organic bentonite is oleophilic. The study on dispersion characteristics of modified bentonite showed that acid-bentonite had better dispersion and stabilization. After modified bentonite dispersed in water, the particles size distribution of acid bentonite was mainly between 0.43μm and 2.09μm, the organic bentonite was 0.43-2.5μm, while gel level of organic bentonite dispersed in organic phases was 7.8%.The modified and unmodified bentonite were characterized by SEM, XRD, analysis of chemical composition, FTIR and TGA-SDTA techniques. Through XRD, it was found that the layer space of acid bentonite increased, which was the result that the cation in the layer was exchanged. The layer space of organic bentonite increased, too. It showed that chemical agent was inserted in the layer. The modified bentonite keeped the same structure as Na-bentonite. FTIR analysis also confirmed the same result. The themeral and FTIR analysis of organic bentontie showed the organic agent coveded the surface and inserted layer of bentonite. It meant that the modification raction succeed. SEM image showed the specific surface ares of acid bentonite enhanced sharply, this was explained by change of chemical composition. Through determining contact angle and calculating surface energy, it showed surface energy and polar components of organic bentonite decreased.The rheological behavior of pigment diapersion have important infulance on the characteristics of coating. The effect of dispersion concentration, diapersant dosage, pH and salt concentration on rheological behavior of acid bentonite were studied. At low shear rate, all of dispersion system exhibited the behavior that changed form pseudoplastic to dilatant fluid except the dispersion containing 0.4% polyacrylate sodium. The dispersion containing 0.4% polyacrylate sodium lasted the behavior of dilatant fluid, characterized as shear thickening, and exhibited the lowest apparence viscosity and yield stress, which showed that this system had good dispersing result. At high shear rate, most of dispersion exhibited the same rheological behavior as it at low shear rate. But the dispersion containing 0.4% polyacrylate sodium showed the behavior changing from pseudoplastic to dilatant fluid unlike the rheological behavior at low shear rate. All of curves of dispersion well fitted the Herschel–Bulkle model.Color ink-jet paper coatings containing various amount of modified bentonite were prepared and the coating rheological behavior were discussed. The steady rheological results showed, at low shear rate, the paper coatings cotaining modified bentonite exhibited the behavior of pseudoplastic fluid, characterized as shear thinning. The flow properties of paper coating at high shear rate was similar to flow behavior at low shear rate. It was obviously increased the solid content of coating by additiving acid bentonie. The bentonite modified with DADMAC could promote the rheological behavior of coating. The results obtained from dynamic viscoelasticity experiment revealed that the critical strain of paper coatings not containing acid bentonite was about 1.2%, while the critical strain of paper coatings containing acid bentonite was less than 0.1%. Comparatively, the dynamic elastic storage modulus and viscid loss modulus of paper coatings decreased with increasing acid bentonite content. The phase angle (δ) of paper coating containing acid bentonite were below 45°, and value of tanδwere not over 1. In brief, all of paper coatings belonged to a viscoelastic solid. The paper coating containing organic bentonite, which the tanδwas less than 0.6, showed the property of strong viscoelastic solid.The color ink-jet paper coating containing acid-bentonite, which substituted for parts of SiO2 as pigment, could improve the glossy and smoothness, but lower whiteness, opacity, ink absorption and surface strength of coated paper. The ink density and Lab value of ink-jet paper containing 20% acid-bentonite were higher than the sample containing pure SiO2,both of ink density and Lab decreased in case the coating containing over 20% acid-bentonite . So the content of acid-bentonite in coating must to be adjusted to impeove the properities of paper. The color ink-jer paper containing acid-bentonite showed the minimizing bleeding and wicking.The color ink-jet paper coating containing bentonite modified with DADMAC, could lower the whiteness, opacity and ink absorption of coated paper, but improved the glossy, smoothness and surface strength. The ink density and Lab value of ink-jet paper were improved with bentonite modified with DADMAC.
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