Coating processes – Particles – flakes – or granules coated or encapsulated – Solid encapsulation process utilizing an emulsion or...
Patent
1980-12-03
1984-05-08
Lovering, Richard D.
Coating processes
Particles, flakes, or granules coated or encapsulated
Solid encapsulation process utilizing an emulsion or...
252 6254, 42721334, 428402, 428900, 524459, B01J 1302, B05D 716
Patent
active
044474750
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to polymeric composites which are useful for the separation of small quantities of material from solution. In particular it relates to processes for the manufacture of polymeric material containing non-polymeric particulate matter.
The incorporation of particulate matter, such as for example magnetic particles, into polymeric resin beads to facilitate the handling and uses of these resins in ion exchange processes is well known. The particle-containing resins utilize the discovery that when finely divided ferromagnetic-containing ion exchange adsorbents are flocculated by magnetic forces of a suitable strength and agitated in the liquid to be treated, they still exhibit the high rates of adsorption appropriate to the original resin bead size but have the mechanical characteristics normally associated with larger resin beads. In another application ferromagnetic-containing resin beads may be used in mixed beds with other nonferromagnetic beads and conveniently separated as desired, by the application of a magnetic field.
In addition to these ion exchange resin applications, magnetic particles have also been incorporated in composite adsorbents containing common adsorbing materials such as activated carbon which is used extensively throughout the chemical and process industries. It is typically used in the form of carbon black, graphite, or charcoals. Other materials with suitable adsorbing properties are the various naturally-occurring clays, for example, fuller's earth, and other mineral powders. Examples of the latter include quartz, silica gel, titanium dioxide, bauxite, zeolite and many metallic oxides.
In this approach the composite adsorbent material typically comprises adsorbent particles and magnetic particles embedded in a porous matrix of organic polymeric material, the porosity of the matrix being such as to allow small molecules of molecular weight up to several hundred to enter freely into the interstitial structure of the matrix but to exclude large molecules of higher molecular weight whereby the composite material functions selectively to adsorb dissolved materials from solution. The inclusion of magnetic particles enables the composite adsorbents to be easily and rapidly separated from the solutions being treated even when those solutions contain other suspended particulate matter.
BACKGROUND ART
Conventional ion-exchange resins and composite adsorbents have suffered from a number of disadvantages.
First, there has been the risk of interaction between the magnetic particles and the components of the system in which the ion exchange resins or composite adsorbents have been employed. This is a particularly serious problem with the porous composite adsorbents referred to above. Many of the common magnetic materials, such as ferrites, cannot be readily used at a pH below 7 and are rapidly degraded at a low pH.
Secondly, it has been very difficult to avoid "flushing" of the particulate matter during the preparation of the resin or composite adsorbent bead. "Flushing" refers to the tendency of the particle to leave the polymer during the formation of the bead. The particles frequently are competely excluded from the forming bead or concentrate and protrude from the outer surfaces of the bead. Where attempts have been made to encapsulate magnetic particles in a protective coating prior to incorporation in a resin or composite adsorbent, flushing has also been a problem.
A further problem relates to the processes of manufacturing ion exchange resins. Frequently it is desired to prepare polymeric beads and by subsequent reaction schemes to introduce onto these beads functional groups which will provide the desired ion exchange function. When magnetic particles are incorporated into the beads the range of possible subsequent chemical reactions of the polymeric bead matrix can be severely limited by the susceptibility of the magnetic material to attack. For example, for the important class of cross-linked styrene based resins key processes such as chloromethy
REFERENCES:
patent: 3884871 (1975-05-01), Herman et al.
patent: 4133774 (1979-01-01), Brynko et al.
patent: 4211664 (1980-07-01), Dixon et al.
Eldridge Robert J.
Lubbock Frederick J.
Mok Christopher C. K.
Commonwealth Scientific and Industries Research Organization
ICI Australia Limited
Lovering Richard D.
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