Phosphate Esters in Emulsion Polymerization
Surfactants used as primary or co-emulsifiers in the polymerization of acrylic and/or vinyl monomers must have carefully controlled properties if the final emulsions are to have good stability and low coagulum. Dexter Chemical has developed a group of phosphate ester surfactants designed to provide maximum effectiveness in emulsion polymerization processes.
The DEXTROL OC products are phosphate esters of nonionic and polyoxytheylene adducts. They are usually mixtures of the mono-and-diesters, as illustrated below:
R = Hydrophobe n = Number of moles ethylene oxide
In addition, some unreacted nonionic will be present in the product. Control of these materials, plus the proper ratio of mono to diester, are critical to efficiency and reproducibility of the polymerization.
Phosphate esters offer many advantages in the finished latex, including good mechanical and storage stability. In addition, the cast films have anti-rusting properties, as well as excellent clarity and improved resistance to degradation by light and heat.
Phosphate esters used as emulsifiers also promote color acceptance by the resin, especially in the acrylics. If dispersed pigments are introduced into the latex, the danger of reflocculation due to excess dispersant is minimized or eliminated because of the flat dispersant demand curve produced by the organic phosphates.
Neutralized Products
The DEXTROL OC® phosphate ester products are normally supplied in the free acid form. The user thus has the option of neutralizing to any desired degree, using his choice of inorganic or organic alkalis.
Two partial salts are currently produced by Dexter Chemical:
DEXTROL OC-50 is the partial sodium salt of DEXTROL OC-15
DEXTROL OC-180 is the potassium salt of DEXTROL OC-60
We also produce three fully neutralized salts:
DEXTROL OC-45N is the sodium salt of DEXTROL OC-40
DEXTROL OC-65K is the potassium salt of DEXTROL OC-60
DEXTROL OC-78N is the sodium salt of DEXTROL OC-70
Product Selector Charts
Phosphate Esters of Tridecyl Alcohol Ethoxylate (Free Acid)