Formation of hollow spherical articles
AssigneeCanadian Patents and Development Limited
InventorsJoseph Redmond Farnand, Ira Edwin Puddington
Life of this patent
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Abstract
Hollow articles, in particular microballoons, hollow fibers and other shapes, are prepared by dispersing or dissolving a soluble film-forming solid in a core solvent which is normally solid but transformable slowly to gas, shaping the blend while molten, cooling to solidify and slowly removing the solid core material as a gas. The film-forming solid migrates to form a shell having the original core shape and a non-uniform cross-section of an outer skin and an inner sponge lining.
Claims13
A method of forming hollow substantially spherical particles or balls of non-uniform wall cross-section comprising:
- a. uniformly dispersing a soluble film-forming solid into a core solvent material which is a solid transformable directly into gas while the solvent material is in liquid form, the film-forming solid being present in a migratable amount of from about 0.5 to about 20% by wt. of the core solvent,
- b. shaping the mixture comprising said two materials in at least about 62.5% of the total mixture, into substantially spherical particles or balls of a diameter not more than about 10mm. while the solvent is molten,
- c. rapidly cooling said particles or balls to solidify the same,
- d. slowly transforming the solid core material directly into a gas and removing the gas from said particles or balls without deformation thereof to cause migration of the film-forming material to the surface, the time for core removal being not less than about 0.5 hour, and sufficient to allow the migration to occur, and
- e. recovering hollow substantially spherical particles or balls of said film-forming solid having a wall cross-section consisting of an outer skin and an inner sponge lining, the wall thickness being less than about 15% of the diameter.
Dependencies are inferred from the claim text.