Ametech is a distributor of Solvay Novecare and other Principals for specialty chemicals for Emulsion Polymerisation in Italy, Spain, France, Switzerland, Hungary, Romania, Greece, Slovenia, Croatia, Serbia and Turkey offering a wide variety of Surfactants and Specialty Monomers:
to produce latexes used mainly in paints, adhesives, paper, textile coating, industrial coatings, automotive, construction and plastics.
to improve solutions associated with adhesion, emulsification, dispersion and rheology control
Emulsion polymerization methods can be defined according to the mode of catalysis used.
- Batch Process
- Delayed Monomer Addition
- Delayed Monomer and Surfactant Addition
- Pre-emulsion of Monomer
- Seeding Techniques
In general, a surfactant molecule contains both polar (hydrophilic) and non-polar (hydrophobic or lipophilic) groups which enable the surfactant to form stable emulsions of monomers in water. Both anionics and
nonionics surfactants are widely used in emulsion polymerization systems; dosages typically range from 3-6% for nonionics and 2% or less for anionics (both based on monomer content).
Combinations of anionics and nonionics are used to take advantage of properties conferred by each type.
Surfactants, although used at relatively small levels, are important and critical components to provide:
reduction of interfacial tension between monomers and the aqueous phase to yield a stable dispersion or emulsification thus facilitating diffusion of monomer into the reaction sites.
the micelle formation for polymerization to form the sites for particle nucleation.
stabilization of the emulsion of unreacted monomer.
control of the particle size.
growth of polymer particles to obtain the proper latex emulsion.
freeze/thaw, mechanical, shear and multivalent cation stability.
and to impart particular properties to the latex properties such as reaction rate, molecular weight, particle size, viscosity, surface tension, wetting, water sensitivity / resistance, heat sensitivity, weatherability, stability (salt, mechanical, shelf) and film properties (gloss, clarity, tack).
Particle size plays a key role in both the preparation and utilization of emulsion polymer products governing viscosity, surface tension and mechanical stability and in finished latex the particle size plays an important role in coating rheology, gloss, pigment binding, water resistance and porosity.
Some of the major factors affecting the particle size are:
Quantity of Surfactant: it will generally be observed that, according to the micellar theory of polymerization, particle size decreases with increasing levels of surfactant.
Nature of Surfactant: high CMC surfactants typically initiate fewer particles than the low CMC types thus forming a coarser particle size latex.
Method of Polymerization:
- to obtain small particle size: charge all of the surfactant initially
- to reduces the number of micelles and hence particles produced in the initiation stage: charge only a
portion of the surfactant
- pre-emulsion techniques also restrict the number of micelles formed, by maintaining a low level of
surfactant relative to monomer and
polymer throughout the polymerization, and tends to produce emulsions containing coarser particles.
Reaction Temperatures: increasing temperature causes a reduction in surfactants stabilizing efficiency.
Electrolytes: small addition (with care because of potential excessive coagulation loss) of electrolytes can be an effective way of increasing latex particle size.
Monomers: typically less water soluble monomers will produce smaller particle size emulsions than more water soluble monomers.
Also a small amount of a highly water soluble monomer such as acrylic acid or acrylamide can significantly reduce latex particle size.
Specialty Monomers and Copolymerisable Surfactants
Specialty Monomers and Copolymerisable / Functional Surfactants provide better water resistance and enhanced adhesion properties in adhesives, paints, architectural, industrial coatings, automotive coatings, textile coatings and finishes.
Rhodia’s specialty monomers Sipomer® range provides to the polymer systems:
exceptionally high adhesive power,
enhanced mechanical properties,
mproved chemical and water resistance.
Rhodia has now expanded its specialty monomer line (Sipomer® PAM series) to include phosphate functional monomers. Working in latex- or solvent-based formulations, these monomers promote adhesion of polymer resins to metal, glass, concrete and other inorganic substrates in many applications, including industrial, maintenance, automotive and architectural.
Specialty Monomers selection according their performance:
- Sipomer WAM and Sipomer WAM II
- Sipomer PAM series
- Sipomer ß-CEA
- Sipomer COPS 1
- Sipomer BEM
- Sipomer SEM 25