CZ106894A3 - Process for preparing nacreous polymers and copolymers of unsaturated monomers - Google Patents

Abstract

This method is based on the uniform dosing of the monomeric phase, consisting of monomers, mixture of monomers, or an aqueous solution of monomers, into a liquid polymerising medium, immiscible with the monomeric phase, maintained in quiet and equilibrated to the temperature of the polymerisation, while forming the small drops of the monomeric phase which are left to pass spontaneously through the layer of the polymerising medium due to the different density of both the liquid phases. During this passage they polymerise by the influence of the temperature of the polymerising medium to a gel-like up to solid particles which are concentrated at the level or on the bottom of the layer of the polymerising medium from where they are periodically or continually removed.

Description

Process for preparing bead polymers and copolymers of unsaturated monomers

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Area, techniques

The invention relates to a process for the free-radical suspension polymerization and copolymerization of unsaturated monomers.

BACKGROUND OF THE INVENTION

A set of polymers and copolymers is conventionally prepared by suspension or bead polymerization techniques. The technology consists first of converting monomers or their aqueous solutions containing polymerization initiators into small droplets in a non-reactive liquid medium with stirring, with which the monomer or its solution does not mix, the resulting heterogeneous dispersion stabilizing against coalescence of dispersed monomer phase particles by various stabilizers dispersion system. Due to the polymerization temperatures and the initiator, the dispersed monomer phase particles are polymerized so that the product is tiny polymer beads, the size of which is dependent on a number of variables, including, in particular, the mixing rate of the heterogeneous mixture, concentration = and type of stabilizer. and polymerization temperature. Keeping all these factors in equilibrium is very difficult, and any breach of the slurry polymerization technology regime causes a number of difficulties. Even with careful observance of all technological parameters, the suspension type polymerization is usually accompanied by larger labels of the polymer component on the agitator and on the internal surface of the reactor, which requires relatively frequent cleaning of the production equipment. In addition, bead polymers and copolymers of unsatisfactory and mainly broad particle size distribution are formed, which must then be sorted for different purposes before being reused. The polymer particles are also usually contaminated with the monomer phase suspension stabilizer in the polymerization medium and therefore cannot be used for applications requiring high purity.

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SUMMARY OF THE INVENTION

The present invention is directed to a process for preparing pearl polymers and copolymers of unsaturated monomers by suspension polymerization in the presence of polymerization initiators. SUMMARY OF THE INVENTION The monomer base consisting of monomers, a mixture of monomers or an aqueous monomer solution and containing a polymerization initiator is uniformly metered into a monomer phase-immiscible liquid polymerization medium, maintained at rest and tempered to the polymerization temperature to form tiny droplets of monomer phase in a polymerization medium. These are spontaneously passed through the polymerization medium layer due to the different density of the two liquid phases, during which time they are polymerized by the temperature of the polymerization medium to form gel-to-solid polymer particles which concentrate at the surface or bottom of the polymerization medium layer. subscribe.

The polymer particles prepared by this process have a uniform size which can be influenced by the droplet size selection of the monomer phase entering the polymerization medium and therefore need not be screened. Since the heterogeneous suspension stabilizer of both immiscible liquids does not need to be used in the proposed process, the resulting polymer or copolymer is not contaminated with this substance. In addition, the problems of sticking the polymeric component to the inner surface of the production equipment and thus cleaning it are completely eliminated.

The process for preparing the bead polymers or copolymers of the present invention requires a vertical cylindrical reactor that can be tempered to a polymerization temperature. Reactor

K 3 may have several zones with different polymerization temperatures, but generally these are two zones: the first, polymerization, is usually longer, the second, dopolymerization, is shorter. The reactor must be in a vertical position so that the falling or rising monomer phase droplets are not hampered by contact with its wall. The diameter of the reactor is determined primarily by the manner of dispersing the monomer phase into the polymerization medium. Spraying this phase in the upper part of the reactor above the level of the polymerization medium requires a larger space, i.e. a larger reactor diameter, since the monomer phase droplets must not fall on the reactor wall. Conversely, when injecting monomer base below the level of the polymerization medium through a narrow nozzle, where a continuous stream of injected liquid oscillates and disintegrates into separate droplets at a relatively short distance from the nozzle orifice, the diameter of the cylindrical reactor may be relatively small. The internal orifice of the nozzles β 'and the injection rate of the monomer base depend on the particular

In cases a, it must be chosen according to the physical properties of the injected liquid so that the size distribution of the droplets formed and later of the polymer beads is as narrow as possible.

If the monomer phase is dropped into the reactor, the reactor having a diameter of several centimeters is also suitable.

The height of the reactor must be selected such that the monomer phase droplets will reliably dopolymerize during their fall or rise with the polymeric medium. Generally, the height of the reactor is inversely proportional to the polymerization rate of the monomers used and directly proportional to the rate of movement of the monomer phase droplets through the polymer medium. Therefore, for example, in the polymerization of styrene, which is relatively slow, it is necessary to use much higher reactors than in the case of acrylic monomers which polymerize much faster.

The rate of passage of individual droplets of monomeric phase through the polymerization medium can be controlled by the density of the polymerization medium, since the speed of this movement is proportional to the magnitude of the difference between the density of the two immiscible liquids. A no less important factor affecting the rate of movement of the monomer base phase droplets through the polymerization medium is its viscosity. The more viscous liquids impart a much greater resistance to the passageway, thereby extending the time of droplet movement through the reactor and substantially reducing its height. As the polymerization medium, for example, water can be used in which the viscosity can be increased by adding high molecular weight polyelectrolytes, starch, water-soluble cellulose derivatives, polyvinyl alcohol and the like. These additives can also act as stabilizers of the monomer phase suspension formed in the polymerization medium. For the polymerization of water-soluble monomers, various water-immiscible inert liquids can be applied, such as pentane, hexane, cyclohexane, C10-13- or C14-18-alkane naphtha, aromatic hydrocarbons, mineral oils.

Examples

Example 1

Preparation of superabsorbent

100 wt. parts of acrylic acid in which 0.2 wt. % of N, N-methylenebisacrylamide. The acid is neutralized with a 50 wt. parts of sodium hydroxide in 150 wt. parts of distilled water. The free space in the boiler is then first evacuated and then filled with a nitrogen atmosphere. A solution of 1 wt. % of ammonium persulfate in 9 wt. parts of distilled water.

The monomer mixture and the initiator solution are passed through a static mixer in which they are continuously mixed in mutual mass. ratio of 20: 1, and the initiated mixture of monomers with an inlet-injected gear pump having a diameter of 072 mm ^- Immediately below the para-arginic oil level (a 14-18 alkane alkane), which is charged with a 5-meter cylindrical internal diameter reactor 150 mm. It is tempered to 60 ° C up to 2 m, the remaining 3 m are tempered to 40 ° C. The injection rate is adjusted so that droplets of a uniform size monomer mixture «/ approximately 500 μπι are formed in the paraffin oil. They pass freely through a column of paraffin oil, gradually polymerize and transform into solid gel beads, which are sodium polyacrylate crosslinked with N, N-methylenebisacrylamide and swollen with water. After the monomer mixture with the initiator has been consumed, the copolymer beads are removed from the reservoir at the bottom of the reactor, freed of residual paraionic oil on the sieve, washed with cyclohexane and finally dried at 130 ° C.

In this way, superabsorbent beads having a size of 300 to 400 µm are obtained. The superabsorbent exhibits a sorption capacity of 500 < = r of distilled water per 1 g of copolymer at high gel strength. It is suitable for sanitary purposes.

Example 2

Preparation of acrylate flocculant

40 wt. parts of acrylamide in 100 wt. parts of distilled water. Evacuate to remove air from the space above the solution and replace it with a nitrogen atmosphere. A 0.5 wt. % of ammonium persulfate in 4.5 wt. parts of distilled water.

The monomer solution and the initiator solution are fed through a static mixer in which they mix with each other in mass. ratio 28: 1, to the top of the reactor, where the initiated mono-monomer mixture is sprayed onto the level of cyclohexane to fill a 1 m diameter and 6 m high cylindrical reactor and tempered to 50 ° C. Cyclohexane contains, as stabilizer, the suspension of monomer mixture sorbitan monooleate in an amount of 1 wt. part per 100 wt. parts of cyclohexane. The monomer mixture droplets falling on the level of cyclohexane are freely carried to the bottom of the reactor and gradually polymerized to water-swollen polyacrylamide beads having a size ranging from 100 to 200 µm. After the monomer mixture and the initiator are consumed, they are removed from the reservoir below the reactor.

the sieves are freed of cyclohexane residues and dried at 105 ° C. The product is 50 to 150 µm polyacrylamide beads. The polymer is completely linear and has a high molecular weight of about 7,000,000. It is useful as an effective acrylate flocculant with high flocculation rate and good sediment resistance of the sediment.

Example 3

Continuous preparation of bead monodisperse polystyrene

From a container containing a solution of dibenzoyl peroxide as an initiator in styrene and another container containing a 0.1% solution of ferrocene as a polymerization accelerator also in styrene, these solutions are fed through a static mixer where they are mixed together in a mass. ratio of 1: 1 to the bottom of a 1 m diameter and 20 m high reactor filled with 90 ° C tempered water. Monomem! the mixture is injected into the center of the reactor through several nozzles with a diameter of 0.1 mm at a rate such that droplets of uniform size of about 400 µm are formed in the water, which then gradually rise through the reactor and polymerize during the rise. No more sticky pearls of polystyrene are continuously removed from the top of the reactor.

Example 4

Preparation of a bead styrene-divinylbenzene copolymer

In the container in 95 wt. parts of styrene dissolve 1 wt. 0.1 part by weight of dibenzoyl peroxide as polymerization initiator; % of ferrocene as polymerization accelerator in 8 wt. parts of divinylbenzene. The contents of both containers are passed through a static mixer where the solutions are mixed together in mass. ratio of 12: 1 to the bottom of a 1 m diameter and 20 m high reactor filled with 90 ° C tempered water containing 1.5 wt. ammonium polyacrylate. The monomer mixture is injected into the center of the bottom of the reactor through several nozzles having a diameter of 0.2 mm at such a rate that droplets of monomer mixture of uniform size of about 1 mm are formed which slowly rise upwards and polymerize during the rise. From the top of the reactor, the non-sticky beads of the styrene-divinylbenzene copolymer, which is the starting material in the ion exchange process, are continuously removed.

Claims (1)

PATENT OFFERS Process for the preparation of bead polymers and copolymers of unsaturated monomers by suspension polymerization in the presence of polymerization initiators, characterized in that the monomer phase consisting of monomers, monomer mixture or aqueous monomer solution and containing the polymerization initiator is uniformly metered into the monomer phase immiscible liquid polymerization medium at rest and tempered to the polymerization temperature, forming tiny droplets of monomeric phase which are spontaneously passed through a layer of polymerization medium due to the different density of the two liquid phases, during which they pass through the polymerization medium temperature to form gel-to-solid particles which concentrate at the surface or at the bottom of the polymerization layer, from where they are taken periodically or continuously.