Water-based Polyacrylate Composite Emulsion With High Hydroxyl Content Prepared By Self-emulsification

With the strengthening of people's environmental awareness,the state has introduced a series of laws and regulations,and solvent-based coatings with high volatile organic compound(VOC)content have gradually been replaced by environmental friendly coatings.Water-based coatings are a kind of environmental friendly coatings.They have the characteristics of safety,reliability and no pollution with water as the solvent.Water-based resin has an important effect on the properties of water-based coatings.Among them,water-based polyacrylic resin has been widely used in many fields such as construction,automobile,wood,metal coating and so on because of its good gloss and color retention,weather resistance,corrosion resistance and anti-pollution ability.But it also inevitably has some disadvantages,mainly reflecting its heat-adhesiveness and cold brittleness after resin drying.In order to overcome these limitations,functional monomers or other resins need to be introduced into the acrylate resin for modification.The introduction of hydroxyl monomer can increase the content of hydroxyl in the polyacrylate molecular chain,which is beneficial to improve the crosslinking density of the film.Due to the separation of hard and soft segments on the molecular chain,polyurethane film has the advantages of good mechanical properties,strong adhesion,good abrasion resistance,good temperature resistance,easy modification,etc.,which can make up for the defects of acrylate.In addition,polyester structure determines that it has good wear resistance,good gloss,fullness,good weather resistance,high mechanical strength characteristics,it can also be modified acrylate for prepared the excellent properties of composite resin.Therefore,in this paper,polyurethane and polyester were respectively used to modify acrylate.The specific work is as follows:The first chapter introduced the basic situation of waterborne acrylate,waterborne polyurethane,and listed the research progress of waterborne polyurethane acrylate and waterborne polyester propylene resin.In the second chapter,hydroxy-functionalized waterborne polyurethane acrylate was prepared by adding emulsifier.The choice of monomer,the dosage of initiator,the reaction temperature and the ratio of emulsifier were studied in the preparation of waterborne urethane acrylate.Through a series of experiments,it was determined that IPDI and PCDL were selected as the soft and hard segments of PU,and ammonium persulfate with a total monomer mass of 2%was selected.APS as an initiator,using SDS/OP-10 in an amount of 2/3 as an emulsifier at 80°C,with AA,MAA,BA,BMA,St,HEMA for emulsion free radicals The hydroxyl functionalized aqueous urethane acrylate composite emulsion was prepared by polymerization.DLS,DSC,and TG have proved that the emulsion has good stability and excellent performance,but after drying into a film,Due to the migration of the small molecule emulsifier,the gloss of the film is poor,and the water resistance is not good.In the third chapter,in order to solve the problem of small molecule emulsifier residue in emulsion,the amphiphilic polyurethane macromolecule is supplemented with a small amount of SE-10 as the reaction emulsifier instead of SDS/OP-10 for pre-emulsification of acrylic monomer.AA and MAA as carboxyl monomers,HEMA as hydroxyl monomer,the waterborne polyurethane-hydroxy acrylate composite emulsion with the core-shell structure synthesized by pre-emulsification and seeded semi-continuous emulsion polymerization method.The polyurethane prepolymer capping group,the ratio of PU/PA,the way of adding water-soluble monomer,the amount of emulsifier and the amount of DMPA were discussed.The effect of emulsion properties.Through a series of experiments,it was determined that the terminal carboxyl group unsaturated polyurethane prepolymer was prepared by adding DMPA in an amount of7%of the total mass of the polyurethane,and the ratio of PU/PA was 1/3,and the total mass of the monomer was 1%.The emulsifier is added to the bottom solution by adding AA and the MMA is added to the emulsion to prepare a hydroxyl functionalized water-based polyurethane acrylate composite emulsion with a core-shell structure.The core-shell structure of the latex particles can be clearly seen by TEM.After various tests,it was proved that the prepared emulsion has small particle size,narrow distribution,high solid content,good stability and excellent film performance.At the same time,the problem of residual small molecule emulsifier in the emulsion is also solved.In the fourth chapter,based on the previous chapter,the polyurethane prepolymer was dispersed by using acrylic monomer instead of acetone,so that no organic solvent was added during the whole reaction process.In order to increase the crosslinking density of the composite emulsion coating film,the content of HEMA is further increased.Maintain the PU/PA ratio,the ratio of AA/MAA/BA/St is unchanged,reduce the content of BMA,increase the amount of HEMA,and adjust the ratio of BA/St to ensure that the T_g of the film after drying of the composite emulsion will not Too high to maintain its flexibility.At the same time,the effect of changing the amount of chain transfer agent on the properties of the emulsion was studied,so that the composite emulsion with different properties was prepared to be applied to different needs.Through a series of experiments,under the premise of keeping the emulsion stable,the amount of HEMA is increased to 30%of the total mass of the monomer,the ratio of BA/St is set to 1/1,and the amount of chain transfer agent is 1-3%,a composite emulsion suitable for different needs can be prepared.Through testing,it was found that the film has better water resistance,solvent resistance and adhesion after the HEMA content is increased.In the fifth chapter,poly(ethylene glycol adipate)is modified to prepare a carboxyl terminated unsaturated polyester(UPE),which is then used for emulsion copolymerization with acrylic monomers.The amount of HEMA added,the ratio of UPE/AC,the ratio of BA/St,and the amount of chain transfer agent were investigated.Through a series of experiments,we determined that the amount of HEMA added is35%of the total mass of the monomer,the ratio of UPE/AC is 1/5,and the ratio of BA/St is 1/3.By changing the amount of chain transfer agent,water-based polyester acrylate composite emulsion with high hydroxyl content which viscosity in the range of 3000-15000 and 450-1400 mPa·s can be prepared.Through testing,the resin has the advantages of high solid content,good stability,good impact resistance and good mechanical properties.The coating prepared by using the composite emulsion as a raw material has good coating film properties and can be used in the automobile industry.The sixth chapter summarizes the full paper.Environmentally-friendly high-performance polyacrylate composite emulsions will widely used in the coatings industry and replace traditional solvent-based coatings.