Emulsion Polymerization Technology

These substances include ethylene carboxylates, water-soluble initiator fragments, monomers containing hydrophilic groups, etc.

Because of the absence of emulsifiers, the polymerization does not exist in micelles. The nucleation of particles is in aqueous phase with slow polymerization rate and poor stability of the system.

However, pure latex particles with good water resistance and good monodispersity can be prepared.

On the contrary, the emulsion polymerization system is an oil in water system (W/O), that is, the aqueous solution of dispersed phase is a hydrophilic monomer, and the continuous phase is a hydrocarbon solution dissolved with oil soluble emulsifier.

The polymerization system has poor stability, but the higher polymerization rate is similar to traditional emulsion polymerization, and the product has large molecular weight, so the colloid is easily redispersed in water.

Such polymerization has been widely used in the preparation of acrylamide, acrylic acid and other hydrophilic monomers for the preparation of super absorbent polymers and thickeners.

In the polymerization process, external conditions such as temperature, stirring, electrolytes and other factors can easily break down or produce condensate.

Compared with traditional emulsion polymerization, microemulsion polymerization increased the co emulsifier (long chain fatty alcohol or long chain alkanes), and two, the system had to be strongly emulsified by ultrasonic or homogenizer to further disperse the droplets of the monomers into a single submicro droplet (less than 0.4 microns).

There is hardly any monomer droplet and monomer solubilized micelles in the system, and the nucleation of particles is in monomer submicron droplets.

The miniemulsion system is more stable than the traditional emulsion system. It is metastable in thermodynamics, and the emulsion is not layered for several months.

Compared with traditional emulsion polymerization, the system contains a large number of emulsifiers and a medium chain long fatty alcohol co emulsifier, with a relatively small monomer content, which can spontaneously form pparent or plucent thermodynamically stable emulsion systems. There are no monomer droplets and submicron droplets, but only droplets similar to monomer solubilized micelles.

The nucleation of latex particles is in micro droplets, and the prepared polymer latex particles are less than 50 nm.

If the hydrophilic monomer, lipophilic emulsifier and co emulsifier are used, the oil in water (W/O) reverse microemulsion can be prepared.

The dispersed droplet has been deformed into a polyhedron separated by a thin liquid membrane containing a continuous phase.

The initiating and polymerizing reactions are carried out in the liquid cell and the polymer latex particles are formed.

There are three important characteristics of super concentrated emulsion polymerization. One is that the monomer migration in the cell is very small, and the gel effect is delayed throughout the process.

Therefore, the polymerization rate and average molecular weight are larger than bulk polymerization. Two, the size of polymer latex particles can be controlled by adjusting the variety, concentration and other conditions of the emulsifier; three, it is possible to directly prepare polymer latex particles with low water content and easy to dry powder polymerized resin.

The "super concentrated emulsion" is called "Concentrated emulsion" in English. It is literally plated as "concentrated emulsion". In order to make the plation express its meaning in essence and the characteristics of the emulsion, we think it is more appropriate to plate it into "super concentrated emulsion".

Dispersive polymerization is usually made of nonaqueous solvent. The monomer is dissolved in medium before polymerization, and the system is homogeneous.

As polymerization proceeds, the resulting polymer chain is precipitated from the solution and stabilized by the existing or "in-situ" dispersant into polymer particles.

The polymer emulsion system can be directly used to prepare paint or paint with good performance, especially for direct polymerization of special monodisperse, large particle size, functional and cross-linked polymer microspheres.

The monomers of the continuous phase diffuse into the suspended large water droplets and form small swelling micelles in the water droplets under the action of water-based emulsifiers, and initiate polymerization in the swelling micelles to form primary polymer particles and grow and aggregate. Finally, the size of the polymer particles is close to the size of the suspended droplets.

A large polymer particle is composed of many small latex particles. The diameter of the large particles is about 100 microns, which is similar to the polymer particles prepared by suspension method.

If the PVC particles obtained by this method have special structures inside the particles, they will have a good effect on the absorption of plasticizers.