Preparation Of Castor Oil-Based Aqueous Polyurethane And Its Application In Pigment Printing

Coating printing is an energy and water-saving printing and dyeing technology with a wide range of applications and many advantages,representing the future development direction of textile coloring.Water-based polyurethane/acrylic resin(WPUA)is widely used in the field of high-performance adhesives because of its low content of volatile organic compounds(VOCs),water resistance,solvent resistance and excellent mechanical properties.However,most WPUA are mainly made by reacting short and medium chain petroleum-based diols with isocyanates.Although the cost is low and the process is mature,the petroleum resources are not renewable and the main chains of polyurethane monomers made by short and medium chain diols are mostly linear and polar,so there are still some shortcomings in their performance such as water resistance and strength in special environments.To address the above problems,this paper uses renewable bio-polyol castor oil(CO)to replace the traditional petroleum-based short-chain diol for the synthesis of aqueous polyurethane macromolecules,and copolymerizes and modifies with isobornyl methacrylate(IBOMA)containing rigid side groups to produce WPUA binder for coating printing,optimizing the performance of the binder,and thus improving the performance of coating printed fabrics and improving their coloration.This paper will focus on the preparation of aqueous polyurethanes.In this paper,we focus on the preparation of aqueous polyurethane,copolymerization modification of emulsions,and microphase structure control of WPUA adhesive films.Firstly,a series of self-emulsifying castor oil-based waterborne polyurethanes with different CO doses were prepared in the waterborne polyurethane system using CO as polyol,isophorone diisocyanate(IPDI),2,2-dihydroxymethylbutyrate(DMBA),pentaerythritol triacrylate(PETA)as raw materials,dibutyltin dilaurate(DBTDL)as catalyst and triethylamine(TEA)as neutraliser.The series of self-emulsifying castor oilbased aqueous polyurethanes with different CO It was found that the particle size of the WPU emulsion gradually increased with the increase of CO When the CO mass fraction was 49.87%,the water absorption rate of the WPU film was 3.69%,the water contact angle was 67.09 °,and the glass transition temperature of the film was 6.9 °C.The WPU emulsion could form a continuous and uniform film on the fabric surface by spraying.Secondly,a series of IBOMA-modified WPUA emulsions were prepared by emulsion polymerization and various properties such as particle size,viscosity,and stability were investigated.After drying,the water contact angle,water absorption,X-ray diffraction(XRD),mechanical properties,atomic force microscopy(AFM),and thermal properties such as differential scanning calorimetry(DSC)and thermal weight loss analysis(TGA)were carried out to systematically study and analyze the water resistance,mechanical properties and thermal properties of the films.The results showed that with the increase of IBOMA,the water resistance of the films improved,the breaking strength increased and the elongation at break decreased.When the mass fraction of IBOMA was8%,the water contact angle of IBOMA-WPU film increased by 26.97 ° compared with that of WPU,the breaking strength increased by 15.81 MPa and the elongation at break decreased by 241.61%.Finally,the prepared castor oil-based WPU and IBOMA-WPUA were used as binders to compound with nanopigments to produce pigment inks that were sprayed onto polyester fabrics for coating printing.The optimum printing process was determined by varying the baking conditions and the amount of organic pigments.The properties of the printed fabrics such as K/S value,rub fastness,stiffness and air permeability were then investigated.The results showed that with the increase of IBOMA mass fraction,the dry and wet rub fastness of the printed fabrics were improved,but the stiffness of the printed fabrics increased and the air permeability slightly decreased due to the structural properties of IBOMA.Based on the comparative study of WPU and IBOMA-WPU,it was found that the introduction of IBOMA improved the cross-linking of WPU,which resulted in the limitation of the relative motion of the macromolecular chain segments within the adhesive film,which led to an increase in the fastness of the adhesive covering the organic pigments on the fabric surface,which in turn improved the friction fastness of the printed fabric.Through the research in this thesis,the synthesis mechanism of castor oil-based WPUA was revealed,the regulatory system of its structural components was further constructed,and a series of WPUA emulsions with different particle size and chemical composition were designed and fabricated,which significantly improved the mechanical strength and water resistance of the adhesive film.On this basis,the strong and thin adhesion of the pigment/adhesive film to fabric fibers was achieved by spraying,which has implications for the development and application of functional bio-based WPUA coating printing adhesives.