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Preparation And Modification Of Redispersible Polymer Latex Powder And Powdered Coatings

Posted on:2015-01-05Degree:MasterType:Thesis
Country:ChinaCandidate:L N WangFull Text:PDF
GTID:2181330422982294Subject:Chemical Engineering
Abstract/Summary:PDF Full Text Request
The powdered paints were prepared by mixing the redispersible latex powder and otherfillers and additives. It could be used directly after adding water under stirring. The redispersiblelatex powder as the binder of powdered coatings was prepared from polyacrylate emulsion byspray drying, which has the similar properties as the original emulsion after redispersing in thewater. The latex was modified by adipic dihydrazide (ADH) to lower the minimum film-forming temperature (MFFT) of redispersible latex, and the mechanism was discussed. Thensilica-sol was used as anti-caking agent during spray drying. The re-dispersible polymerpowders as the main film-forming materials, combining with other fillers were used to preparethe powdered latex coatings. The crack resistance and scrub resistance were investigated.Firstly, the film-forming of original emulsion was discussed. We introduced ADH to thepolyacrylate latex system. It was found that the ADH lowered the minimum film formingtemperature (MFFT) of the re-dispersible latex. The optimum amount of ADH by mass was0.33%of the monomer. The reason was that as a long chain molecule, ADH could react withcarboxyl and thus enhance flexibility of shell of emulsion.The emulsion should be pretreated before spray drying. The silica sol could be introducedto the polyacrylate latex system as a drying agent after the system was alkalified. The silicaparticles distributed around the latex particles from the TEM pictures. These silica particlesexisted on the surface of polymer during spray drying and prevented the latex particlescoalescence or aggregation, which also testified by SEM-EDX and XPS. And we found theoptimum amount of silica sol was25%. On the other hand, the silica sol was benefit to the film-forming of redispersible latex.The self-made redispersible polymer latex powder was used as basic film-formingsubstance. The kaolin was replaced by mica and the talc was replaced by ground calciumcarbonate (GCC). When Natrosol plus330PA5075as the cellulose was used, the coatingresistance of construction was the least and the crack resistance was enhanced. However, the scrub resistance was still needed to improve.When the silane coupling agent A-187was loaded by GCC under spraying directly andthe amount was0.5%, the scrub resistance was significantly increased. The scrub resistance ofcoatings was up to1950, which more than the standard requirement and satisfied forapplications.
Keywords/Search Tags:redispersible polymer latex powder, adipic acid dihydrazide (ADH), silica sol, powdered coating, silane coupling agent
PDF Full Text Request
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