Resin Supported: The Superior Emulsion For Your Formulations

July 7, 2015 02:00 PM
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Formulators looking for ways to give their coatings a competitive edge might take a look at the graphics arts industry. Printers like working with inks and coatings that use resin supported rather than latex emulsions. These advanced polymer resin formulations are easier to work with and give the end product a host of desirable qualities not otherwise achievable.

Replacing the Surfactant

In conventional water-based emulsions a surfactant is an essential part of the mix. Part hydrophilic and part hydrophobic, this performs the essential dual roles of controlling polymer growth and preventing separation of the latex particles.

In a resin supported emulsion a resin is processed so it can take the place of the surfactant. This entails first solubilizing a hard styrene acrylic with ammonia before adding it to the monomer. During polymerization some of the resin grafts onto the backbone of the polymer, creating a core shell type of structure, while the rest stays in the aqueous phase. Polymer growth and separation are controlled as before, but the resin confers additional beneficial characteristics.

Special Characteristics of Resin Supported Emulsions

The acrylic resin has a lower molecular weight, (7,000 to 8.500 dalton,) and a higher glass transition temperature (Tg) – typically around 120 deg C – than the polymer. This lets the emulsion take on characteristics of each. Additionally, rheology is near-Newtonian so there’s virtually no change in viscosity due to sheer, and the more resin that’s used, the higher the acid number, signifying superior polymer functionality.

Benefits in Use

Coatings made with resin supported emulsion polymers have advantages in terms of both application ease and final product quality. Printers value the good ‘runnability’ and ‘re-wet’ performance of inks and overprint varnishes (OPV's) made with resin supported emulsion polymers. They get good ink transfer from the roller, which reduces waste, and the absence of thickening makes it easier to get a uniform, repeatable application. Film formation takes place at a lower temperature than the Tg would suggest, and clean-up is easier too, reducing press downtime and increasing capacity.

Another benefit: resin remaining in the aqueous phase, (rather than bonding to the polymer,) blooms to the surface of the coating as it dries. There its high Tg imparts a hard, tack-free feel and provides a high-gloss finish. As a result, resin supported emulsion-based coatings have a high quality look and feel when dry.

Beyond the Graphics Arts

If you’re not already using resin supported emulsions in your coatings, take a look at what they have to offer. Printers already know how they help create durable, high quality finishes, but possible applications extend right across the spectrum of paints and other coatings.

 

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