Preparation Of Modified Guar Gum And Its Application In Reactive Dyeing Of Cotton Fabric

Guar gum（GG）is an excellent natural thickener with good pasting property.The viscosity of 1 wt % GG solution reaches 4000 6000 mPa ×s.However,The structure guar gum can not be used in reactive dye printing due to many active hydroxyl groups of its structure.Therefore the modification of GG is neccessary.In this paper,the active-group substitution method of GG was creatively proposed with difference from the traditional etherification substitution method.The active hydroxyl groups of GG were substituted by the monochlorotriazine active group modifier（T₁S₂）and the negative sulfonic groups were also introduced in the structure of GG.The modified guar gums with different degree of substitution were prepared.The rheological properties of the modified guar gums with different degree of substitution were studied by the rheological tests.The relationships between the rheology and the printability were discussed.Furthermore,the modified guar gums were used as thickeners in reactive printing of cotton fabric.The availability and applicable potential of GG in place of sodium alginate（SA）were explored.T₁S₂ was synthesized by cyanuric chloride and p-aminobenzenesulfonic acid.The modification of GG was carried out.The effects of sodium carbonate concentration,reaction temperature and reaction time on the substitution degree of modified guar gum were investigated by single factor experiments.The synthesis condition of modified guar gum was optimized by orthogonal test.The results showed that when n（T₁S₂）: n（GG）=1: 1,the maximum degree of substitution（DS= 0.213）was obtained at 1.1g/L sodium carbonate solution at 90℃ for 45 min.Under the optimal condition,a series of modified guar gums with different degree of substitution were prepared by controlling the ratio of n（T₁S₂）: n（GG）（the sequences of DS from small to large were as TSGG1,TSGG2,TSGG3,TSGG4,TSGG5,TSGG6,TSGG7）.The flowability,viscoelasticity and thixotropy of modified guar gums with different degree of substitution were studied by steady-shear,dynamic oscillatory and transient tests.The results showed that the modified guar gum had the shear thinning characteristics.The flowability of the modified guar gum was better than that of GG,and the flowability of the modified guar gum increased with the degree of substitution increasing.The guar gum showed the obvious elastic behaviors while the modified guar gum exhibited the weaker elastic behaviors and the more viscous behaviors.The flow property and viscous behavior of the modified guar gum were more favorable for the transfer of the printing paste through the mesh to the fabric and the uniform penetration into the fabric.The recoverability of apparent viscosity of the modified guar gum was better than that of GG after the removal of the shears,preventing the flushing out.The printing performances and the basic properties of the modified guar gum were studied in the reactive dyeing of cotton fabrics with flat screen.The results showed that the printing performances of guar gum modified with different degrees of substitution were significantly improved in comparison with GG,especially those of TSGG3.The paste add-on,color yield and penetration of TSGG3 increased by 52%,48.3%,33.8%.Moreover,TSGG3 had good outlines,levelness,handle and color fastness.In comparison with GG,the pasting property and the reactivity with active black KN-B of TSGG3 had a little decrease and the storage stability,chemical compatibility and water holding capacity were improved remarkably.Compared to SA,TSGG3 has little lower chemical reactivity with reactive black KN-B and the little higher water holding capacity,pasting and storage stability.The overall performances of TSGG3 were close to those of SA.