Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Patent
1983-12-23
1987-03-31
Schofer, Joseph L.
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
428900, 252 6254, 521 55, 5253282, 5253304, 5253305, 5253322, 5253335, 5253336, 525344, 525374, H01F 120, B32B 1508
Patent
active
046542671
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to magnetic polymer particles and a process for the preparation thereof. It has been tried to use magnetic polymer particles within several fields of biochemistry and medicine. They have been tried as carriers for pharmaceutical preparations since they, due to their magnetic properties, are capable of transporting the preparations to the desired location in the body. Magnetic particles also have other practical applications and have been used within diagnostics since it is possible to replace separation of particles by means of centrifugation by the much simpler method of magnetic extraction. Further, magnetic particles have been used for cell separation and as carriers for enzymes. Of more technical applications may be mentioned toners for copying purposes.
Previous processes for preparing particles containing for instance magnetic iron oxide (magnetite) have started from magnetite Fe.sub.3 O.sub.4. In several ways it has been tried to coat the magnetite particles with polymeric material to obtain polymer particles containing magnetite.
A commonly used method employs magnetite powder which is mixed mechanically with molten polymer. After this treatment the polymeric material containing magnetite is finely divided. This provides particles having an uneven shape and being of different size. Particles prepared in this manner are often used as toner, but the uneven shape is undesired since it will result in uneven and unsharp edges on the characters.
Another method employs finely divided magnetite to which vinyl monomer and initiator are added in water to form polymer around the magnetite grains. This will also provide magnetic particles having an undefined and highly variable size and shape. Further, only some of the particles will be magnetic, and the content of magnetite in the particles is usually very unequal. Other methods employ the admixture of albumin and other proteins with magnetite and vigorous stirring in water with emulsifier to form drops which contain magnetite and protein. Another method comprises treatment of swelling polymer particles with finely divided magnetite to obtain magnetite on and possibly some inside the particles.
The fact that magnetite is used will, even if it is employed in very finely divided form, represent great limitations with respect to the type and the size of the particles. A real diffusion of molecular material into the particles or into pores of the particles will not take place. With solid, porous particles, very large pores would be necessary, and accordingly, large particles, so that magnetite grains are deposited not only on the surface of the particles. With highly swelling particles it is possible to get some magnetite into the particles mechanically, but the magnetite will essentially be deposited on the surface and result in a very uneven surface.
According to the process of the present invention iron is introduced into the particles in the form of salts and is then converted to magnetic iron oxide which to a great extent will be magnetite (Fe.sub.3 O.sub.4) or oxides having corresponding magnetism.
For many of the above purposes, the particles prepared according to the invention will be advantageous since they are spherical and have an even concentration of magnetic material which may be varied as desired within wide limits. In particular, the process provides the possibility for preparing monodisperse particles of desired size, compact as well as porous.
The process according to the present invention is suitable for compact as well as porous polymer particles and may be used for the preparation of magnetic polymer particles of all sizes. In particular the process is suitable for the preparation of particles in the range 0.5-20 .mu.m, but it may also be used for the preparation of particles smaller than 0.5 .mu.m and larger than 20 .mu.m in diameter. A great advantage of the process is that it allows all of the particles to have the same concentration of magnetic iron oxide. When monodisperse polymer particles are used as start
REFERENCES:
patent: 4001288 (1977-01-01), Gable et al.
patent: 4018691 (1977-04-01), Neal
patent: 4123396 (1978-10-01), Rembaum et al.
patent: 4339337 (1982-07-01), Tricot et al.
patent: 4438179 (1984-03-01), Solc
Hackh's Chemical Dictionary, J. Grand (ed.), McGraw-Hill Inc., p. 457 (1969).
Berge Arvid
Ellingsen Turid
Helgee Oskar B.
Ugelstad John
Schofer Joseph L.
Sintef
Teskin F. M.
LandOfFree
Magnetic polymer particles and process for the preparation there does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic polymer particles and process for the preparation there, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic polymer particles and process for the preparation there will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2212504