Continuous process for preparing polymers

Abstract

A continuous process for preparing polymers, preferably emulsion polymers, with minimal fouling of the reactor is provided. The process is effected in a reactor which does not contain a gas phase, optionally by reducing the gas content of the reaction mixture.

Description

[0001] This invention relates to a continuous process for preparing polymers and a method for the reduction of polymer fouling on reactor surfaces, especially in a continuous process for preparing emulsion polymers.[0002] Polymers are typically prepared in batch, semi-continuous, or continuous processes. Such processes are susceptible to various degrees to polymer build-up or fouling on the reactor surfaces. Polymer fouling results in the need to shut the reactors down and clean the reactor surfaces which reduces available production time and may, for certain reactor geometries such as tubular reactors, be highly inconvenient.[0003] European Patent Application 926 161 A discloses a continuous process for preparing polymers in a reactor having a non-cylindrical channel which provides low levels of fouling. Even lower levels of fouling are desired.[0004] "Effects of Dissolved Gas on Emulsions, Emulsion Polymerization, and Surfactant Aggregation" by M. E. Karaman, et al. J. Phys. Chem,...

AI Technical Summary

Benefits of technology

[0007] According to a second aspect of the present invention there is provided a method for reducing polymer fouling during a continuous process for preparing a polymer including continuously feeding at least one reaction mixture containing at least one monomer to a reactor wherein the reactor does not contain a gas phase; polymerizing the monomer in the reactor; and continuously removing the polymer from said reactor.

[0021] In another embodiment the reactor consists of non-cylindrical channels and alternating channels for the temperature control medium which may be, for example, certain types of heat exchangers such as plate-frame, plate-fin, and spiral-plate heat exchangers. The plate-frame heat exchanger consists of standard plates which may be flat or corrugated. Corrugated plates are preferred due to improved mixing of the monomer with the other reactants. The plates serve as heat exchange surfaces and may be made of stainless-steel types 304 and 316; titanium, Monel, Incoloy 825, Hastelloy C, phosphor bronze, and cupronickel. The plates may be coated with materials such as graphite or polytetrafluoroethylene. The plates form alternating non-cylindrical channels for the reaction mixture containing at least one monomer and the temperature control medium to flow through. The plates are supported by a frame. Gaskets prevent leakage where the plate and frame meet. The frame may be made of clad stainless steel and enamel-coated mild steel.

Problems solved by technology

Such processes are susceptible to various degrees to polymer build-up or fouling on the reactor surfaces.

Polymer fouling results in the need to shut the reactors down and clean the reactor surfaces which reduces available production time and may, for certain reactor geometries such as tubular reactors, be highly inconvenient.