Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1981-09-18
1984-01-03
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
526 64, C08F 220
Patent
active
044243189
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the production of polymer beads and more particularly to the continuous production of spherical polymer beads of controlled size within a restricted size range.
BACKGROUND ART
Polymer beads of substantially uniform size and shape are required for various industrial applications such as the production of ion-exchange resins, or manufacturing processes involving molding or extrusion.
However, known processes which comprise polymerizing monomer droplets in suspension generally provide non-uniform polymer beads in a relatively broad size range, for example from about 0.1 mm to about 1.3 mm.
Subsequent screening steps are thus necessary in order to provide beads in several more restricted size ranges, which entails significant screening and storage costs, as well as the rejection of commercially unusable beads produced.
Uniform droplets may be produced by various known devices comprising for example calibrated tubes or vibrating nozzles which must be adapted to the droplet size required in each case, and are not particularly suitable for industrial manufacturing processes.
An investigation of the phenomenon of "limited coalescence" of oil droplets in water is discussed in an article by R. M. Wiley, published in the Journal of Colloid Science, Vol. 9, No 5, October 1954, p. 427-437, and incorporated by reference herein. This article shows more particularly that a colloid or finely divided, dispersable solid agent, which will be called hereinafter a surface protective agent, is essential for coalescence up to a limiting droplet size which is directly proportional to the product of the dispersed (coalescing) phase volume and the solid particle size (colloid), and inversely proportional to the weight of solid colloid dispersed in the water.
It is nevertheless particularly difficult to produce uniform polymer beads since the monomer droplets in suspension should be kept as free as possible from collisions while they are slowly solidified in the course of polymerization. On the other hand, if the monomer droplets are suspended in an agitated liquid polymerizing medium, monomer droplets which undergo collisions while they are still liquid or in an intermediate gelled state may either break up into smaller droplets, or stick together to form larger droplets. U.S. Pat. No. 2,934,530 may be cited in this connection.
In addition, French Pat. Nos. 1,485,547 and 1,469,922, German Democratic Republic Patents No. 99386 and No. 61099, German Federal Republic published patent application No. DE-OS 2,402,674 may be cited to further illustrate the state of the art relating to suspension polymerization.
As may be seen from the above explanations and from the cited prior art, the continuous production of polymer beads of controlled size is particularly difficult to achieve on an industrial scale.
DISCLOSURE OF THE INVENTION
An object of this invention is to provide spherical polymer beads of substantially uniform controlled diameter in a restricted size range.
Another object of the invention is to provide a process for the continuous production of such uniform polymer beads of adjustable size in a reproducible manner, on an industrial scale.
A further object of the invention is to provide a simple apparatus for carrying out said process.
These objects are met by the process and apparatus in accordance with the invention as set forth in the claims.
Polymer beads are produced in accordance with the invention by a special combination of three successive but distinct stages which may each be carried out under optimum conditions, namely:
(a) In a first stage, uniform monomer droplets are continuously produced by controlled coalescence in a laminar liquid stream, while their size is essentially controlled via the proportion of dispersed surface protective agent added to the stream.
(b) In a second stage, these uniform monomer droplets are continuously converted into hardened beads by suspension polymerization in a laminar liquid stream for a relatively short period, for example of t
REFERENCES:
patent: 2618626 (1952-11-01), Van Dijk
patent: 3922255 (1975-11-01), Koestler et al.
patent: 4360651 (1982-11-01), Dinbergs
Chemical Abstracts, vol. 85, No. 14 (Oct. 4, 1976), p. 17, Abstract 94902a.
Carbonel Jack
Desnoyers Michel R. L.
Firsov Vladimir I.
Grammont Paul D. A.
Grigoriev Vladimir A.
Michl Paul R.
Skinner William A.
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