Preparation And Performance Of Biomass Modified Waterborne Polyurethane Leather Finishing Agent

The rapid economic development and the improvement of environmental protection laws and regulations have promoted environmentally friendly coatings to penetrate people's daily lives.As an environmentally friendly coating,water-based polyurethane coatings have far-reaching significance for promoting the transformation of coating products and the development of the coating industry.The use of renewable resources and synthetic materials to reduce the dependence on non-renewable resources has become a development trend.This topic uses biomass materials to modify water-based polyurethanes in order to synthesize a new type of water-based polyurethane coating agent,from synthetic processes,molecular structure design,etc.In this aspect,the preparation and performance of the finishing agent are discussed.(1)Phenolic modification of sodium lignin sulfonate(SLS)under acidic environment,convert methoxy group to phenolic hydroxyl group,improve reactivity and preserve sulfonate group,and add epoxy in alkaline environment The lignin-based epoxy resin(LBER)was prepared from chloropropane.The FT-IR characterization test showed that the modifier LBER had been synthesized and used to modify the water-based polyurethane(WPU)to successfully prepare the lignin-based epoxy resin-Water-based polyurethane emulsion(LBER-WPU).Based on the synthesis conditions of the emulsion and the appearance of the synthesized emulsion,storage stability,and water resistance of the film,the optimum reaction time was 3 hours,the reaction temperature was 80?,and the hydrophilic chain extender 2,2-dimethylol was determined.The amount of propionic acid(DMPA)was 5%.The effects of the amount of modifier LBER on the properties of dispersions,films,and coatings were investigated.The results showed that when the LBER mass fraction was 0.3%to 0.4%,the dispersion had a good appearance and a small particle size.The above storage stability period is good at 60? high temperature stability and-20? low temperature stability,the acid and alkali resistance have been improved;the tensile strength of the film can reach up to 22MPa,which is improved compared with pure water-based polyurethane(WPU-0)It is about 2 times,the water resistance and solvent resistance of the film are enhanced,and the thermal stability is also significantly improved.With the increasing amount of LBER,the water vapor permeability of the coating is continuously reduced,the wear resistance is continuously improved,and the gloss and The resistance to dry and wet rubbing is improved.When the modifier LBER mass fraction is 0.3%,the abrasion resistance of the coating is 0,the gloss is 6.8 Gu,the dry rub resistance is 5.0,and the wet rub resistance is 4.5.(2)Polycaprolactone diol(PCL-1000),hexamethylene diisocyanate(HDI)as the basic raw materials,DMPA as the hydrophilic chain extender,and sodium alginate(SA)as the crosslinking agent,successfully A sodium alginate modified waterborne polyurethane emulsion(SAWPU)was synthesized.In the film-forming process,a second-cross linked aqueous polyurethane film was prepared by chelating reaction between-COOH on the SA molecular structure and metal Ca2+ ions.The effects of reaction temperature,R value(n(-NCO):n(-OH))and DMPA content on the appearance and performance of the emulsion were discussed.The optimal reaction temperature was 80?,R value was 1.4,and DMPA content was 5%.FT-IR characterization results show that SA has been successfully introduced into the molecular structure of WPU as a cross-linking agent.The relationship between the amount of SA and the properties of emulsions,films,and coatings was studied.The results showed that the experimentally synthesized SAWPU emulsion was uniform and had a storage stability period of 6 months and above.As the amount of SA added increased,the particle size of the emulsion increased first.It decreases afterwards,and has excellent acid and alkali resistance,high and low temperature resistance;the minimum water absorption of the film is 7.2%,the maximum contact angle is 84.3°,the solvent resistance is improved,the tensile strength is up to 76.55 Mpa,and the elongation at break is 1253.95%Compared with SAWPU-0,it has increased by 163%and 52%,respectively.The addition of SA reduces the thermal stability of WPU in the low temperature region(before 300?),but at the same time improves the thermal stability of the high temperature region.The performance test of the coating shows that with the increase of the amount of S A added,the water vapor permeability of the coating weakens and then increases,and the abrasion resistance,gloss,and wet and dry resistance are improved.0.2%to 0.3%.