Thermoplastic expandable microsphere process and product
AssigneeThe Dow Chemical Company
InventorsWilliam E. Cohrs, Roland E. Gunderman
Life of this patent
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Abstract
Expandable synthetic resinous microspheres are expanded in a matrix by heating under pressure to at least a foaming temperature and permitting the microspheres to expand at a lower pressure.
Claims7
A process for the incorporation of expandable thermoplastic synthetic resinous monocellular microspheres having a thermoplastic resinous shell, a volatile liquid foaming agent therein within a heat plastifiable matrix material which, at its heat plastification temperature does not act as a rapid solvent for the microspheres to cause the destruction thereof by solvent action or heat plastify at a temperature sufficiently high that the microspheres are destroyed by thermal degradation, the steps of the method comprising
- admixing the microspheres and matrix forming material,
- heat plastifying the matrix material and
- mechanically working the mixture to form a matrix about the microspheres without causing expansion thereof, subsequently
- passing the mixture into a zone of lower pressure wherein the microspheres expand to form a plurality of hollow, generally monocellular particles within the matrix, and
- cooling the mixture below the heat plastifying temperature.
A method of preparing a heat expandable product, the steps of the method comprising
- providing a mixture of heat expandable synthetic resinous microspheres capable of expanding on heating to form monocellular hollow gas-filled spheres within a thermoplastic synthetic resin,
- heating the mixture to a temperature sufficient to heat plastify the resin under pressure sufficient to prevent expansion of the microspheres,
- shaping the mixture to a desired configuration, and
- cooling the mixture below the heat plastifying temperature of the resin.
Dependencies are inferred from the claim text.