PVC and Latex Applications for Dow Industrial Specialty Polymers

PVC suspension polymerization with METHOCEL Cellulose Ethers
Emulsion and Suspension Latex Polymerization with CELLOSIZE Hydroxyethyl Cellulose

PVC suspension polymerization with METHOCEL Cellulose Ethers

METHOCEL™ cellulose ethers are used in PVC polymerization as primary and secondary suspension agents. They provide excellent particle size control, good porosity for improved plasticizer absorption, low reactor scaling, and high bulk densities.

IFT-lowering and thermal gelling abilities – Aqueous solutions of METHOCEL Cellulose Ethers reduce the interfacial tension (IFT) of the vinyl chloride monomer, facilitating dispersion and yielding smaller droplets. METHOCEL Cellulose Ethers form a skin at the interface, preventing the droplets from coalescing. Upon heating, cellulose ethers dehydrate, forming a gel that further strengthens the protective film. The gelling temperature determines the application temperature of the cellulose ether. Typical gel temperatures of METHOCEL Cellulose Ethers range from 48 to 70°C, allowing reactor operations in the range of 50 to 85°C.

Generally, low-viscosity grades of METHOCEL Hydroxypropyl Methylcellulose Polymers are used for PVC suspension processing. These include METHOCEL E15 PVC, E50 PVC, F50 PVC, K35 PVC, and K100 PVC. These high-quality METHOCEL Products are available worldwide to customers’ current production needs and planned expansions.

Gel Temperatures of METHOCEL Cellulose Ethers for Suspension Polymerization

METHOCEL Product	Gel Temperature (°C)	Recommended Reactor Temperature (°C)
K100 PVC	70	70-85
F50 PVC	56	60-70
E50 PVC	57	60-70
181 (E15 PVC)	57	60-70
A15 LV PVC	48	50-60
E15 PVC	(Need data)	(Need data)

Compatible with other suspending agents – although the use of METHOCEL Cellulose Ethers alone for vinyl chloride monomer polymerization allows the production of many PVC resin grades of various grain sizes, porosities, and morphologies, PVC producers often prefer combinations of several suspending agents to optimize their resin properties. Combinations with polyvinyl alcohols yield recipes with excellent grain size control over a wide range of shear profiles. METHOCEL Cellulose Ethers can be successfully combined with secondary suspending agents such as hydroxypropyl cellulose or polyvinyl alcohols with low hydrolysis levels to increase grain porosity.

Emulsion and Suspension Latex Polymerization with CELLOSIZE Hydroxyethyl Cellulose

CELLOSIZE™ Hydroxyethyl Cellulose Products are used as protective colloids in both emulsion and suspension polymerization. Processes for vinyl, vinyl-acrylic, and all-acrylic polymer systems employ CELLOSIZE HEC Products. CELLOSIZE HEC Products are also use in manufacturing expandable polystyrene beads. A typical use level in suspension polymerization is 0.4%, based on total monomer charge. CELLOSIZE HEC Polymers are also used to control latex viscosity after polymerization.

CELLOSIZE EP09 HEC is custom-designed for use as a protective colloid in emulsion polymerization processes. Solutions of this product show high clarity and the absence of gels reduces the risk of the possible formation of grits in the polymerization process. The substitution pattern of CELLOSIZE EP 09 HEC is especially designed to promote its grafting on the emulsion polymer particles, enhancing emulsion stability and improving latex rheology.

The molar substitution of the protective colloid grades of CELLOSIZE HEC was chosen to optimize its role in the initiation of catalyst-protective colloid polymerization sites, in the stabilization of the growing polymer particles, and in the stabilization of the finished latex to freeze-thaw and mechanical shear.

The concentration of protective colloid in the polymerization charge is a critical variable in the control of latex viscosity, polymer particle size, and freedom of the emulsion from coagulum and grit.