Method for measuring diffusion performance of acid dye in color paste

A method for measuring the diffusion performance of an acid dye in a color paste, comprising the steps of:

• A) preparing a primary paste with a solid content of 3-35% by adding a suitable amount of a paste into a suitable amount of water under stirring, and placing the primary paste into a transparent cylindrical container and standing the primary paste to remove residual bubbles therein, so that an upper surface of the primary paste in the cylindrical container is flat, wherein the cylindrical container has an inner cross-sectional area S;
• B) formulating a color paste by adding a dye to be measured into the primary paste obtained in the step A, and flatly and uniformly paving a layer of the color paste with a volume of V0 on the upper surface of the primary paste in the cylindrical container of the step A;
• C) placing the cylindrical container with the paved color paste of the step B in an automatic temperature control device, and performing constant-temperature treatment at a temperature of 60° C.-95° C. so that the dye in the color paste on the top of the blank primary paste in the cylindrical container diffuses downwards to the bottom of the cylinder, and determining the time t of downward diffusion of the dye in the color paste to the bottom of the cylinder;
• D) sampling 0.1-1.0 g of the color paste with the dye being diffused from the bottom of the cylindrical container, and diluting the sampled color paste to 10-100 mL with deionized water, and determining the absorbance A of the dye in the solution at a characteristic wavelength by an ultraviolet-visible spectrophotometer;
• E) formulating a series of color pastes with a concentration Ci (i=1, 2, 3 . . . , n) by respectively adding the dissolved dye to be measured into a suitable amount of the primary paste prepared in the step A, and measuring the absorbance A1 (i=1, 2, 3 . . . , n) corresponding to the series of dye concentrations using the same method as the step D, and obtaining a standard working curve equation Y=c×X+d for the concentration of the dye to be measured in the color paste and its absorbance by fitting;
• wherein Y is the absorbance value for the fitted working curve, X is the concentration of the dye in the color paste for the fitted working curve, and c and d are constants, obtainable by fitting the working curve;
• F) determining the concentration b of the dye to be measured in the sampled color paste of the step D according to the standard working curve equation obtained in the step E;
• and
• G) calculating the number of moles of the diffused dye in the color paste per unit area and per unit time, i.e. diffusion rate v, from the color paste volume V0, the diffusion area S, the diffusion time t, and the concentration b of the dye in the sampled color paste obtained in the previous steps, by the formula:
• v
• =
• b
• ×
• V
• 0
• M
• ×
• S
• ×
• t
• ,
• wherein, the diffusion rate v is expressed in mol/(m2 s), the concentration b of the dye to be measured in the color paste is expressed in g L−1, the volume V0 of the applied color paste is expressed in L, the diffusion area S is the inner cross-sectional area of the transparent cylindrical container, expressed in m2, the diffusion time t is expressed in sec (s), and M is the molar mass of the dye to be measured, expressed in g mol−1.