Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1998-11-12
1999-11-16
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
106122, C08J 9224
Patent
active
059859431
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to expandable polystyrene (EPS) beads containing blowing agent, from which moldings having a reduced water absorption capacity and/or reduced water permeability can be produced.
In many applications of polystyrene foams, for example for roof insulation materials, perimeter insulation or fish crates, the foam moldings come into contact with water, with the risk of moisture penetrating into the interior of the foam, resulting in a reduction in the insulation action.
Hitherto, the water absorption of the boards and moldings made from polystyrene foam has usually been prevented or reduced by applying a plastic film or surface coating to the finished moldings. However, this requires an additional step, and in addition this covering is not uniform everywhere in the case of complex shapes.
Another way of minimizing the ingress of water into moldings made from polystyrene foam is to keep the spaces between the EPS beads as small as possible. This can be achieved by increasing the pressure and temperature of the steam used for the expansion. However, this has the disadvantage of increasing the molding production time and, if the temperature is raised, the energy consumption.
It is an object of the present invention to provide molded polystyrene foams of reduced water absorption capacity which can be produced simply and without additional steps.
We have found that this object is achieved by EPS beads which contain blowing agent and are coated with a hydrophobicizing agent. The present invention accordingly provides expandable polystyrene (EPS) beads which contain blowing agent and are coated with from 0.01 to 0.5% by weight of a hydrophobicizing agent which melts above 10.degree. C. and has a mean particle size of less than 100 .mu.m. The present invention further provides correspondingly coated expanded polystyrene beads. It is usual to coat EPS beads with stearates, for example glycerol monostearate or zinc stearate, as agents for shortening the cooling time. However, these stearates do not act as hydrophobicizing agents. It is also known to apply liquid paraffin oils to EPS beads during molding production in order to shorten the cooling time, but this results in reduced expandability.
EPS beads are produced by known and conventional processes. To this end, the monomeric styrene, if desired mixed with other olefinically unsaturated comonomers, catalysts, auxiliaries and additives, is suspended in water and polymerized, usually in the presence of suspension stabilizers. The resultant polystyrene beads are separated off, washed and dried. The blowing agent can be added during the polymerization or introduced into the polystyrene beads in a subsequent step. Suitable blowing agents are C.sub.4 -C.sub.8 -hydrocarbons, preferably pentane.
The EPS beads are coated in accordance with the invention with from 0.01 to 0.5% by weight, preferably from 0.1 to 0.3% by weight, in each case based on the solids content, of a hydrophobicizing agent which melts above 10.degree. C. and has a particle size of less than 100 .mu.m, preferably less than 10 .mu.m. If the particle size is too great, it is difficult to prepare a stable emulsion.
Preferred hydrophobicizing agents are paraffin waxes having 10 to 30 carbon atoms in the carbon chain, preferably those having a melting point of from 10 to 70.degree. C., in particular from 25 to 60.degree. C. Such paraffin waxes are present, for example, in the BASF commercial products RAMASIT KGT, PERSISTOL E and PERSISTOL HP and in AVERSIN HY-N from Henkel and CEROL ZN from Sandoz.
Another class of suitable hydrophobicizing agents comprises resinous products of the reaction of an N-methylolamine with a fatty acid derivative, for example a fatty acid amide, amine or alcohol, as are described, for example, in U.S. Pat. No. 2,927,090 or GB-A 475,170. Their melting points are generally from 50 to 90.degree. C. Resins of this type are present, for example, in the BASF commercial product PERSISTOL HP and in ARCOPHOB EFM from Hoechst.
Finally, polyfluoroalkyl (meth)acrylate
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patent: 5110835 (1992-05-01), Walter
Gurtler Manfred
Hahn Klaus
Loffler Achim
Naegele Dieter
Reichert Jurgen
BASF - Aktiengesellschaft
Foelak Morton
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