| As people’s environmental awareness and their demand on life quality improve,using polymer emulsion as the base of coatings and adhesives has become a trend.Whereas, more and more importance has been attached to the water-based acrylic estercoating which has great potential in the market, due to its little pollution, low cost, highperformance, wide application, convenient and safe use and its free from heating.However, there are still some disadvantages in the practical use of the water-basedacrylic ester coating because of the defect in its own structure, for instance its formingspeed, mechanical strength and water tolerance are not satisfactory, inferior to thesolvent-based coating. Therefore, the study of water-based acrylic ester coating wouldaim at the introduction of self-crosslink technology. The cross-linking agent dealed withthe defect of stickiness when heated and brittleness when cooled, and improved thecoating’s mechanical strength, forming speed and water tolerance.The paper makes styrene (St), butyl acrylate (BA), acrylic acid (AA) and diacetoneacrylamide (DAAM) as the reactive monomers, and the potassium sulfate (KPS) as theinitiator. The SN-10and SE-10anionic and non-ionic composition type of reactiveemulsifier has been selected to prepare the core-shell structured emulsion whichcontains the active ketone group; then through the reaction between the ketone groupand the hydrazide group, the coating which is self-cross-linkable under the roomtemperature is obtained, with adipic dihydrazide (ADH) as the cross-liking agent.Meanwhile, elements, such as the initiator, emulsifier, functional monomer,cross-linking agent and the proportion of soft-hard monomers, have been observed tofind out their influence on the stability of emulsion, monomer conversion rate, dryingtime of coating film and water resistance and so on. The Fourier transform infraredspectrometer (FTIR), the gel permeation chromatograph (GPC), the transmissionelectron microscopy (TEM)and the differential scanning calorimeter (DSC) and so onhave been applied to test the structural composition, molecular weight distribution, latexparticle morphology and film-formation properties and so on. It is found that theperformance of emulsion is the best when the dosage of KPS is0.5wt%, dosage ofemulsifier4wt%, and the proportion of SN-10and SE-10is1:2; and the stability ofemulsion is reach the optimum condition when the dosage of functional monomer is4wt%, the proportion of ADH/DAAM is n(ADH):n(DAAM)=0.5:1, the proportion of soft andhard monomers is m(soft monomer):m(hard monomer)=25:25. The degree of crosslinkingemulsion can reach more than90%. Film can reach surface dry in6hours andcompletely dry in14hours at room temperature. The pencil hardness reached2H andthe adsorption reached the level of2.The absorption can be controlled at3%.The paper also makes styrene (St), butyl acrylate (BA), acrylic acid (AA) as thereactive monomers. The initiators and emulsifiers same with that of the DAAM/ADHsystem have been selected to prepare the acrylate emulsion; then coating film which is self-cross-linkable under room temperature has been obtained with the zinc acetatedehydrate (C4H6O4Zn·2H2O) as the cross-linking agent to cross-link with carboxyl.Using the same method as above, studied the factors that affect the performance. Whenthe polymerization temperature reaches80℃, the dosage of KPS (initiator) is0.4wt%,the dosage of emulsifier is2.5wt%, and SN-10:SE-10=1:2, the emulsion obtained has ahigher conversion rate, less gelating, smaller particle size and narrower size distribution.When the content of AA is8wt%, the proportion of Zn2+/AA is n(Zn2+):n(AA)=0.4:1, andthe proportion of soft and hard monomers is60:40, the performance of coating filmreaches the best condition. The degree of crosslinking emulsion can reach more than90%. Film can reach surface dry in10hours and completely dry in15hours at roomtemperature. The pencil hardness reached2H and the adsorption reached the level of2.The absorption can be controlled at5%. |
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