Synthesis Of Polyether Waterborne Polyurethane And Its Application In Preparation Of Liquid Indigo

With the implementation of the national strategic goal of"peak carbon dioxide emissions and carbon neutralization",the textile printing and dyeing industry is also actively transforming and upgrading.The traditional powdered indigo dye used in denim dyeing has many problems,such as large dye particles,difficult dye reduction,large consumption of reductant and caustic soda,long dyeing cycle,serious pollution of wastewater and dust in dyeing process,which obviously does not conform to the basic concept of national energy conservation and emission reduction and"dual carbon"requirements.Based on this,this paper designed and synthesized polyether waterborne polyurethane dispersant,and prepared liquid indigo dispersion by mechanical grinding.By relying on the hydrogen bond between urethane bond(C=O,N-H)of polyurethane structure and C=O,N-H of indigo structure,as well as the anchoring effect between benzene ring structure and-COO~-and dye.The prepared liquid indigo dispersion has the advantages of small particle size,good stability,high dye utilization and dye uptake,short dyeing cycle,and low consumption of reductant and caustic soda,which provides a theoretical basis for environmental friendly transportation of dyes,convenient weighing and green production process of dyeing and finishing.In order to improve the defects of traditional dispersants(lignin 85A,dispersant MF),such as small content of anchoring group,dark color and poor stability of dispersion system.A polyether and linear waterborne polyurethane dispersant WPU is designed and synthesized from isophorone diisocyanate,PEG400,DMPA,1-phenyl-1,2-ethanediol and methyl ethyl ketone oxime.The infrared spectrum shows that it is successfully synthesized,and Tg and DSC can show that it has good thermal stability,which is sufficient to withstand the temperature when grinding and dispersing.WPU,lignin 85A and dispersant MF are applied to prepare liquid indigo dispersion.The particle size D90 of the prepared dispersion is 306.4nm,373.9 nm and 350.8 nm respectively.The centrifugal stability and storage stability of the liquid indigo dispersion prepared by WPU dispersant are higher than those of the other two traditional dispersants.The dye diffusion grade is 4-5 grade,the K/S of dyed fabric is 9.283,the K/S of powdered dye dyed fabric is 5.591,The soaping fastness of dyed fabric is 4-5grade,dry rubbing fastness is 3-4 grade,and wet rubbing fastness is 1-2 grade,which conforms to the requirements of FZ/T 81006-2017《Jeans》.At the same time,WPU dispersant itself is colorless,so it will not affect the color of dyeing fabric.In order to further improve the stability of liquid indigo dispersion and reduce its viscosity.Waterborne polyurethane prepolymer is synthesized with isophorone diisocyanate,PEG400 and DMBA as raw materials.Two dispersants,branched BWPU and linear LWPU,are designed and synthesized by using trimethylolpropane as branching chain extender,1-phenyl-1,2-ethylene glycol as linear chain extender and 2,4-dihydroxybenzophenone as blocking agent.The branched waterborne polyurethane dispersant contains more anchoring groups than the linear structure and the three-dimensional structure makes it have the advantages of weak intermolecular force,low viscosity and strong adsorption with dyes and good dispersion stability.The structure and thermal stability of the two dispersants are characterized by FTIR,NMR,TG and DSC and the performance of liquid indigo dispersion prepared with two dispersants are evaluated by particle size,viscosity and stability.The results showed that the particle diameter D90 of liquid indigo dispersion prepared with BWPU and LWPU as dispersant is 317.8 nm and 398.0 nm,respectively,and the viscosity is10.08 m Pa·s and 33.1 m Pa·s.Under the centrifugal condition of 1000 r/min,the centrifugal stability is 82.97%and 81.61%respectively,and the particle diameter D90 is 458.7 nm and492.1 nm respectively after storage at 50℃for 7 d.The results of the acid-base and salt stability test also show that the properties of liquid indigo dispersion prepared by BWPU as dispersant is better than that of LWPU.From SEM and TEM,it can be seen that the dye particles in the liquid indigo dispersion prepared by branched structure dispersant are small in size,evenly distributed,and there is no obvious large particles or particle aggregation.In order to explore the advantages of liquid indigo dispersion with nanometer particle size in practical application.The liquid indigo dispersion prepared with BWPU as dispersant is used for fabric dyeing.By comparing with powdered indigo dye dyeing,the dye diffusion,the dye reduction uniformity,the consumption of reductant and caustic soda and the K/S and SEM of the dyed fabric,the soaping and rubbing properties are analyzed in detail.The results show that the dye diffusion grade of liquid indigo dispersion is 4-5 grade,and that of powdered dye is 1-2 grade;The K/S of dyed fabric is 11.16 and that of powdered dye is 5.56;Under the same reduction conditions,the dye particles in the liquid indigo dispersion are almost completely reduced,and there are no large particles.But there are a large number of unreduced large particles at the bottom of the powdered dye reducing solution,and only part of them are reduced.The SEM surface of the fabric dyed with liquid indigo dispersion has no obvious aggregation of large particles of dye and the dye particles are small.Compared with powdered indigo,the dyeing process of liquid indigo dispersion can save about 57.52%caustic soda and 51.27%reductant.The soaping fastness of the dyed fabric is 4-5 grade,and the dry rubbing fastness is 3-4 grade,which meets the requirements of FZ/T 81006-2017《Jeans》.The wet rubbing fastness is 2 grade,which is half grade higher than that of the powdered dye dyed fabric.