Method and apparatus for the preparation of foamed thermoplastic articles
AssigneeThe Dow Chemical Company
InventorsLouis C. Rubens, Willard E. Alexander, Carl A. Raeck
Life of this patent
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Abstract
Expandible synthetic resinous particles are molded by injecting heated air generally centrally into the mold cavity by means of a probe, withdrawing the probe and heating the surface of the mold. Low densities and rapid cycle times are obtained.
Claims15
A method for the molding of expanded synthetic resinous thermoplastic articles from a plurality of synthetic resinous particles, the steps of the method comprising providing a plurality of foamed synthetic resinous particles, introducing into the said foamed particles an expanding agent in a quantity sufficient that on heating said particles to a foaming temperature their volume will increase by a factor of at least 1.7;
- disposing said particles within a mold having an inner molding surface;
- introducing a heated gas substantially devoid of steam, which is a nonsolvent for the particles at at least one location generally remote from the inner surface of the mold, the heated gas being at a temperature sufficient to cause the particles to expand and adhere to one another, permitting said heated gas to escape from the mold;
- heating at least a major portion of an internal surface of the mold to a temperature to cause expandable particles adjacent thereto to expand and thereby provide a unitary synthetic resinous foam article.
A foam molding apparatus, the foam molding apparatus comprising in cooperative combination a metal mold having defined therein a molding cavity and means to introduce foamed particulate material into the cavity;
- the mold having an inner surface and an outer surface, the mold defining gas escape means extending between the inner surface and the outer surface of the mold;
- means to heat the mold disposed on at least a major portion of the outer surface thereof;
- means to cool the mold disposed on at least the major portion of the outer surface thereof;
- means to introduce a heated gas substantially devoid of steam, within the mold at a location remote from the inner surface, said means introducing the gas at a location generally remote from the inner surface of the mold;
- means to withdraw the means to introduce gas from the cavity of the mold.
Dependencies are inferred from the claim text.