Abstract A method and apparatus are disclosed for the manufacture of foamed polystyrene particles of moderately great density, such as 3 to 25 lbs. per cubic foot (50 to 400 milligrams per cubic centimeter). Beads are fed by a constant-displacement auger to an expander vessel having the form of, in its lowest part, a cylinder with a vertical axis, and thereabove, of a frustrum of an inverted cone having a base angle of about 83° to 70°. Steam is supplied to the vessel in an appropriate, controlled manner. The vessel also contains stator bars, to break lumps and retard the rotation of the material in the vessel, and rotating bars, to provide the necessary agitation. Desirably, the equipment includes a discharge chute of adjustable location, to facilitate adjustment of the residence time and consequently of the density of the expanded beads being produced. With apparatus according to the invention, it is possible to obtain beads substantially uniformly expanded to a desired density within the range indicated above. Such higher-density expanded polystyrene particles find use in various applications, such as shoe soles, or as a substitute for wood.
Apparatus for producing a quantity of small particles of expanded polymer substantially uniformly expanded to a desnity on the order of one-half to one-thirteenth of its average density as unexpanded, said apparatus comprising, in combination, a vessel having a first, lower, small-diameter portion in the form of a right cylinder and thereabove a second frustroconical portion having thereabove a top shell and having an interior in the form of a frustrum of an inverted cone having a base angle of 70° to 83°, said first portion having therein a feed opening and said second portion having therein a discharge opening, the effective height of said vessel from its bottom to said discharge opening being related to the diameter of the midsection of said frustroconical portion such that said midsection diameter is 0.5 to 1.1 times said effective height, said first portion having a diameter one-fifth to one-tenth that of said top shell, means for feeding unexpanded particles of polymer and steam to said first portion of said vessel, a central vertically extending shaft within said vessel and journaled for rotation about a vertical axis, said shaft having affixed to it a plurality of blade members extending outwardly therefrom towards and into close proximity to the walls of said vessel, a plurality of stationary bar members mounted within said vessel in non-interfering relationship with said plurality of blade members affixed to said shaft, and means for rotating said shaft at a velocity adequate to provide suitable agitation of said particles of polymer when said vessel is used to heat and expand said particles.
Claim 2
Dependent Claim
262 words
Apparatus for producing a quantity of small particles of expanded polymer substantially uniformly expanded to a desnity on the order of one-half to one-thirteenth of its average density as unexpanded, said apparatus comprising, in combination, a vessel having a first, lower, small-diameter portion in the form of a right cylinder and thereabove a second frustroconical portion having thereabove a top shell and having an interior in the form of a frustrum of an inverted cone having a base angle of 70° to 83°, said first portion having therein a feed opening and said second portion having therein a discharge opening, the effective height of said vessel from its bottom to said discharge opening being related to the diameter of the midsection of said frustroconical portion such that said midsection diameter is 0.5 to 1.1 times said effective height, said first portion having a diameter one-fifth to one-tenth that of said top shell, means for feeding unexpanded particles of polymer and steam to said first portion of said vessel, a central vertically extending shaft within said vessel and journaled for rotation about a vertical axis, said shaft having affixed to it a plurality of blade members extending outwardly therefrom towards and into close proximity to the walls of said vessel, a plurality of stationary bar members mounted within said vessel in non-interfering relationship with said plurality of blade members affixed to said shaft, and means for rotating said shaft at a velocity adequate to provide suitable agitation of said particles of polymer when said vessel is used to heat and expand said particles.
Claim 3
Dependent Claim
51 words
Apparatus as defined in claim 1, where said means for supplying steam supplies steam at 2 to 30 pounds per square inch gage and a temperature of 95° to 102°C and at a rate of 0.5 to 1 pound of steam per pound of unexpanded particles fed to said first portion.