Preparation Of Waterborne Polyurethane/Acrylate Core-shell Emulsion And Its Application In Photoresist

The photoresist is a hybrid material where chemical reactions occur to produce cross-linking or photolysis when irradiated with a specific wavelength of light,and its solubility changes accordingly.Conventional photoresist is mostly composed of photosensitive resin,reactive diluent,solvent and photoinitiator.The photoresist invariably creats environmental pollution and waste of resources because it is mostly solvent-based.More importantly,Photoresist soft film has poor film formation at room temperature,requiring refrigerated storage and transportation.In order to solve the problems above,a hydrophilic photoresist was prepared in this paper.Firstly,a waterborne polyurethane resin was prepared,and it served as the host resin to coat the acrylate monomer,obtaining the waterborne polyurethane-acrylate core-shell emulsion--photoresist precursor.Secondly,the soft photoresist film was prepared by adding an appropriate amount of photoinitiator to the core-shell emulsion obtained.And it can respond quickly to form a cross-linked network structure under ultraviolet light.Detailed research contents are as following:(1)The linear waterborne polyurethane was prepared using polytetrahydrofuran diol,toluene diisocyanate,1,4-butanediol and dimethylolpropionic acid as the main raw materials.And the structure of polyurethane resin was designed by adjusting three parameters: chain extension parameter,hard segment content and hydrophilic monomer content.The results show that when the chain extension parameters,hard segment content and hydrophilic monomer content of the resin are 0.98,40% and 6%,the resin exhibits the best film-forming properties and comprehensive properties;When the solid content is 100% and 30%,the emulsion shows the best stability.Based on the parameters above,the introduction of double bonds in the resin can effectively improve the mechanical properties of the material.While,the double bond content is inversely related to the molecular weight of the resin;The cross-linked waterborne polyurethane was prepared based on the gel point theory.The results showed that as cross-linking density of the resin increased from 0mmol/g to 0.6 mmol/g,the tensile strength of the resin increased from 12.26 MPa to24.08 MPa,and the elongation at break decreased from 1563% to 225%.(2)A water-based polyurethane-shell/acrylate-core core-shell emulsion was prepared by self-emulsifying coating method.Compared with the swelling method,the emulsion obtained by this method is more stable and is under a higher coverage rate of acrylate monomers.The effect of acrylate monomer content on the properties of WPUA was explored.The results showed that,as the mass ratio of acrylate monomer to waterborne polyurethane increases from 0 to 1.2,the particle size of the emulsion increases from 24.65 nm to 543.61 nm,and the viscosity increases from31.4 c P to 2571.2 c P,the tensile strength decreased from 12.16 MPa to 6.73 MPa and then increased to 16.38 MPa,the elongation at break of the cured film deceased from1771.4% to 63.8%,and the water resistance and heat resistance are also improved;The effects of acrylate types on the cured film were studied,and the results showed that the increase in the number of double bonds of acrylate monomer resulted in an increase in the tensile strength and a decrease in the elongation at break of the cured film.The influence of the shell layer waterborne polyurethane structure on the mechanical properties was explored.The results showed that the tensile strength of the linear resin cured film was less than that of the cross-linked type,but the elongation at break was higher than that of the cross-linked type.The tensile strength and elongation at break of the linear resin cured film was 7.25 MPa,325%,and that of the cross-linked resin cured film was 13.94 MPa,139.2%.(3)A photoresist film was prepared by adding an appropriate amount of photoinitiator to the aqueous polyurethane acrylate core-shell emulsion.The effects of the molecular weight and acidity of the host resin on the properties of the photoresist film were studied.And the results showed that the alkali solubility of the soft film and the hard film became better as the increase of the molecular weight of the resin or the increase of the acidity;The effect of active diluent on the properties of photoresist film is explored.The results show that with the increase of active diluent content,the tensile strength of the soft film deceased from 14.02 MPa to 0.98 MPa,elongation at break increased from 924.5% to 1398%,and glass transition temperature of photoresist soft film decreased from-8°C to-33°C,while the tensile strength of photoresist hard film deceased from 6.77 MPa to 15.21 MPa,elongation at break deceased from 700.8% to 70.4%,and glass transition temperature of photoresist soft film increased from 49°C to 77°C;The effects of reactive diluent types on the properties of photoresist films were investigated.The results show that the type of reactive diluent has negligible effect on the mechanical properties and glass transition temperature of the photoresist soft film.However,for photoresist hard film,the increased functionality of the reactive diluent is beneficial for the tensile strength and glass transition temperature of the material,while detrimental to elongation at break.