Improving Hiding Power Obtained by Variation of Fillers for Interior Emulsion Paints
Petruta Dumitru, Ioana Jitaru, Polizu Str · 2010
To obtain a quality and stable paint is necessary to establish the optimal technological parameters. Although, the basic principles can be found in the literature of World War period when Schou describes the possibility of obtaining emulsified paint binders based on triglycerides, emulsified paints are relatively new [1]. An emulsified paint systems development occurred only after the Second World War, when become available quantities of butadiene and styrene plants manufacturing synthetic rubber. These materials combined to form butadiene-styrene latex, became able to make paint diluted with water. There are today three main types of latex used as binders for paints, namely: styrene-butadiene copolymers, poly-vinyl-acetate and acrylic polymers and copolymers. The term of latex based paint was given initially to emulsified styrenebutadiene paints, but now it defines all polymer systems made with emulsified [2-3]. Close correlation that exists between the rheological behavior of a system and the structure of some non-newtonian mixture was analyzed and explained in many works, showing its importance and its influence on other elements of the system [4]. Materials and devices The Base – it was used a base that includes the main components of paint: copolymer and ethylene vinyl acetate (EVA), cellulose-ether thickener, filler, preservative (biocide), water and ammonia solution. The Base’s characteristics are presented in table 1. Water based paint is a nano dispersion of a solid component called Base and fillers in an aqueous medium [5]. To give a stability and other properties than hiding power, white and yellow index it is need to add foaming agent, dispersing agent, coalescent agent and fillers. The fillers used were: natural calcium carbonate (CCN), precipitated calcium carbonate (PCC), titanium dioxide, opaque polymers, sodium aluminum silicate, 14.5 SiO 2 * 1.4 Na 2 O * Al 2 O 3 , mica, talc, kaolin, micronized barite, diatomite, BaSO 4 , silica. Optical properties of pigments and fillers are determined by the refractive index difference between air and pigment or filler. The higher the diference the bigger the hiding power [6]. The substances with a refractive index higher than 1.7 are generally called white pigments. Bigger differences occur between air and fillers with the effect that everywhere there is an interface between pigment and air or between filler and air there is a distinct increase of hiding power. All raw materials used in this study were chosen so as to meet European Union legislation on the environment [7]. It assumes that the original recipe has 60% in weight fillers. This percentage will be distributed to each type of fillers depending on the composition, role and its ratio relative to the resin from Base.