Research Of Organosilicone-Modified Acrylates Composite Latexes And Latex Paints Based On These Silylated Polymer Emulsion For Architectural Exterior Wall Applications

This paper aims at developing a friendly-environment architectural paint with high performance. The polymerizing kinetics of conventional emulsion and soap-free emulsion are discussed on the base of acrylic emulsion, namely three-unit system composed by methyl methacrylate, butyl acrylate and methacrylic acid. And the influence of these factors, including polymerizing technologies, reaction conditions, initiator systems, on emulsion synthesis and material properties are also investigated. The experiments results show that soap-free emulsion has better performance compared with traditional emulsion in water resistance, adhesion capacity and surface properties. The fundamental reaction conditions are as follows:1. All co-monomers are pre-emulsified; In order to balance the reactivity of co-monomers, acrylic latexes are prepared by a semi-continuous batch process.2. Firstly initiated in heating-discomposed initiator system, at last stage added to peroxide and complex redox initiator to post-disposed so as to increase monomers conversion and minimize non-reaction monomers contents in polymer latexes. Although paints based on all-acrylic latexes have some good properties, waterresistance, weather durability and high-low temperature endurance of coatings couldn't satisfy for the performance requirements of the exterior decoration of high-storied construction. Therefore, silanes are involved in acrylic systems, owing to Si-O covalent bond with rather high dissociation energy (452kJ/mol), silylated polymer resin coatings shows perfect superiority in weather durability. Furthermore, these silylated resins can resist dirt pickup successfully because of low surface energy. Along with same importance, these resins can "breathe" and allow water to leave the wall substrates as vapor but they provide a barrier to bulk water.In review of some requirements that architectural coatings usually should be dried and cured at ambient conditions and with moderate prices, vinyl silanes are incorporated into these systems via emulsion co-polymerization in our work. Thus silanes are incorporated with acrylic resins in the forms of chemical bonds. The reaction-storage stable latexes with high silanes contents can be attained by twontechniques that are hindered-hydrolyde and post-cured with easily hydrolyzed silylated emulsion and hindered, slow-to-hydrolyze alkoxy silanes are catalyzed when paints latexes are cured, respectively. The structures and properties of silane-acrylate copolymer have been characterized by means of DSCU TG^ TEM> SEM, and the properties of latexes paints have been determined according to GB/T9755-1995 (Standards for Testing Exterior Latex House Paints). The test results indicate that the silylated emulsions have no gel over a year period of ambient storage. The compositions have greatly improved properties including water resistance, weather durability and adhesion, and some properties have greatly surpassed the performance requirements in GB/T9755-1995 and amount to ASTM.