Acrylic Emulsions for Paints
We are leading manufacturers of Acrylic Polymer Emulsions intended for manufacture of Interior / Exterior Water based Paints. Our range of products include Styrene-Acrylic Emulsions & Pure Acrylic Emulsions for the Paint Industry.
Our range of products for the Paint industry include Kamicryl-295 (50% Solids Styrene-Acrylic Copolymer for Interior/Exterior Paints), Kamicryl-3045 (46% Solids Styrene-Acrylic copolymer for Putty/Distemper Paints), Pure Acrylic Emulsion Kamicryl-61 (For High Gloss/Sheen Exterior Paints), among others.
TYPES OF EMULSION POLYMERS
Continuous advancements in emulsion technology have lead to availability of polymers with improved performance capability. It is important for the paint manufacturer to know the different types of polymers available for paint applications to enable a proper selection for the specific application. The different types of polymers are as under:
1. Vinyl Acetate homopolymers: These produce hard and brittle films which need plasticisation.They cannot be used on exterior, alkaline surfaces as vinyl acetate has a tendency to hydrolyse and ultimately disintegrate in the presence of water. These are, therefore, no longer in use.
2. Vinyl acetate – Acrylic copolymers: These are internally plasticised and hence, have better flexibility than pure vinyl acetate homopolymers but these are still not recommended for highly alkaline surfaces.
3. Vinyl acetate – Veova copolymers: When adequate proportion of Veova is used in these polymers, they produce a tough film which has excellent water and alkali resistance. But such a polymer can be prohibitively expensive as Veova is a costly monomer which has to be imported into the country.
4. Pure Acrylic copolymers: Paints based on pure acrylic emulsions are a standard in performance as they have very good pigment binding capacity, excellent water and alkali resistance and form a tough clear film which gives gloss as well as abrasion resistance. These too, are quite expensive and can only be justified in better quality paints.
5. Styrene- Acrylic copolymers: These combine performance with economy due to their high pigment loading properties, good water and alkali resistance and find application in a wide range of paints for both interior and exterior applications. Polymers of this kind represent more than half of the total consumption of polymers used by the developed world.
Important Properties Of Emulsion Polymers
After knowing the different kinds of polymers, it is also important to differentiate the various polymers by their properties so that it is possible to identify the most appropriate emulsion for the desired end application. The important properties are listed below:
1. SOLIDS: The solids or polymer content of an emulsion should not be viewed in isolation as the performance is governed not just by solids, but also by its chemical composition as well as particle size.
2. pH: The pH of emulsion can be either acidic or alkaline.
3. VISCOSITY: In emulsion paints, there is no direct co relation between the viscosity of the emulsion and the viscosity of the final paint. This is so because the paint viscosity is also largely influenced by the thickener and extender combinations as well as particle size and chemical composition of the emulsion.
4. PARTICLE SIZE: Particle size of emulsions for paint applications ranges from 0.1 to 1.5 microns. The particle size has a direct influence on pigment binding, gloss, coalescence and the flow properties of the final paint. Finer particle size emulsions import better pigment binding, gloss and coalescence to the final paint. The flow properties of such emulsions need to be improved by a proper formulation to take full advantage of their other good properties.
5. GLASS TRANSITION TEMPERATURE (Tg): The minimum film forming temperature (MFFT) of a polymer is closely related to its Tg. This temperature is derived from the combination of monomers used in the polymer. This is the minimum temperature at which the paint emulsion will form a continuous film. The flexibility, adhesion, and mechanical resistance of the final paint will be depend upon the Tg of the monomers used.
6. CHEMICAL COMPOSITION: The chemical composition is determined by the monomers used in its production and this composition, influences the resistance properties of a paint. As vinyl acetate monomer is susceptible to hydrolysis in the presence of water and alkali, all copolymers of vinyl acetate monomer are water sensitive. Vam -Veova emulsions, too will remain susceptible to hydrolysis, unless they contain at least 20-25% Veova, which will make them unviable in price. Pure acrylic and styrene acrylic are the most resistant to hydrolysis, due to the hydrophobicity of side chains of acrylic esters and the styrene ring.
7. From the foregoing, it is clear that for interior applications, the particle size and glass transition temperature need to be considered, while for exterior paints, the chemical composition also needs to be taken into account.
Thus, for interior high PVC paints, the styrene acrylic emulsions are the best and most economical, while pure acrylics may be used for interior sheen/semi-gloss paints. For high PVC exterior paints, good quality styrene acrylics can be safely used, and for lower PVC exterior paints, pure acrylic or Vam-Veova emulsions with at least 20-25% Veova content should be used.
Popular Types Of Water Based Paints
Architectural water based paints can be broadly classified into interior and paints which are further categorised as under on the basis of their PVC (Pigment volume concentration)
PVC and CPVC
PVC is the ratio of the pigment to the total composition by volume, where pigment also includes the extenders.
The CPVC is the PVC level at which there is just enough binder in the paint to wet the pigments and extenders completely and fill in the inter spaces. Above the CPVC, there is an inadequate amount of binder to completely cover all the pigments and extenders and there are air gaps which make the paint film a porous one. Below CPVC, there is an excess of binder and the extenders are fully immersed in the binder.
CPVC is not a constant but is determined by the nature of raw materials used as well as the formulation of the paint. While formulating a paint, the CPVC should be adjusted to the highest possible value to ensure good performance and economy as all film properties undergo a distinct change when CPVC is extended.
Basic Ingredients Of An Emulsion Paint
Paint mainly consists of a continuous phase, which is the binder and a discontinuous phase, that consists of the pigments and extenders and additives.
The different emulsions that constitute the continuous phase of a paint have been discussed in detail earlier. One should keep in mind that a finer particle size emulsion will increase the CPVC of a paint.
The discontinuous phase consisting of pigments and extenders should also be carefully chosen to optimize the paint formulation in terms of performance, efficiency and economy. It should be noted that lameller extenders like talc increase CPVC, but very fine particle size extenders reduce CPVC.
Conclusion
Form the foregoing one can conclude that:
Pure acrylic emulsions are unsurpassed in performance due to their very good pigment binding capacity, excellent water and alkali resistance and UV stability. However, their high cost makes them uneconomical except in high priced paints.
Styrene acrylic emulsions are the work horses of the paint industry the world over, as they give excellent performance in high PVC paints for both interior and exterior applications. Their finer particle size enables high pigment loading without sacrificing performance and their chemical composition gives them excellent water resistance. Truly, they can be said to combine performance with economy in a broad range of paint applications.
