There are provided methods for making heat-resistant, foamed, crystalline plastic materials. For example, polyethylene terephthalate may be foamed with a polycarbonate, extruded into a foamed sheet and this foamed sheet may be thermoformed by being subjected to crystallization annealing. The thermof
There are provided methods for making heat-resistant, foamed, crystalline plastic materials. For example, polyethylene terephthalate may be foamed with a polycarbonate, extruded into a foamed sheet and this foamed sheet may be thermoformed by being subjected to crystallization annealing. The thermoformed, foamed, crystalline plastic sheets prepared by this process are particularly useful for forming light weight, ovenable food containers.
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A process for preparing a thermoformed, foamed, crystalline, plastic sheet, said sheet being essentially composed of the foamed reaction product of a polyester and a polycarbonate, said process comprising the steps of: (i) introducing into an extruder a mixture consisting of: (a) a high molecular we
A process for preparing a thermoformed, foamed, crystalline, plastic sheet, said sheet being essentially composed of the foamed reaction product of a polyester and a polycarbonate, said process comprising the steps of: (i) introducing into an extruder a mixture consisting of: (a) a high molecular weight linear polyester, which is a polycondensation product of an aromatic dicarboxylic acid and a glycol; and (b) a high molecular weight linear aromatic polycarbonate represented by the repeating structural unit of the formula: [Figure] wherein X is a divalent hydrocarbon radical with a total of from 2 up to about 9 carbon atoms selected from the group consisting of [Figure] in which R1 represents a member selected from the group consisting of hydrogen and lower alkyl and R2 represents a member selected from the group consisting of phenyl and alkyl of 1 to 7 carbon atoms, in a weight ratio of (a):(b) of about 20:1 to 1:20; (ii) reacting said blend of step (i) inside said extruder by providing sufficient mixing and heating to homogeneously react said polyester (a) and polycarbonate (b), thereby releasing carbon dioxide from said polycarbonate into the reacted polyester/polycarbonate mass; (iii) passing said reacted polyester/polycarbonate mass of step (ii) through the die section of said extruder, said die section being adapted to cast said polyester/polycarbonate mass therefrom in the form of a sheet, thereby causing said released carbon dioxide to expand in said mass and reduce the density of the extruded sheet, the temperature of the extruded sheet being sufficient to cause rapid crystallization of said sheet; (iv) passing the foamed, extruded sheet of step (iii) through one or more chill rolls, to reduce the tempeature of said sheet, thereby preventing substantial crystallization of said sheet, whereby said sheet can be thermoformed, pursuant to steps (v-vii) recited hereinafter, without substantial shrinkage, the temperature of the thusly cooled sheet being substantially insufficient to cause crystallization of said sheet; (v) heating said sheet of step (iv), said sheet not being in contact with a mold, said sheet not being subjected to forces comprising a differential in applied pressure to said sheet, said sheet being heated to a temperature sufficient to cause slow crystallization of said sheet, thereby forming a preheated sheet; (vi) contacting said preheated sheet of step (v) with a mold by applying forces comprising a differential in applied pressure to said sheet so as to make said sheet conform to said mold, said mold being maintained at a temperature higher than that of said preheated sheet sufficient to further heat said sheet to a temperature sufficient to rapidly crystallize said sheet; (vii) allowing said sheet of step (vi) to remain in contact with said mold for a time sufficient to provide sufficient crystallization of said sheet so as to enable the molded sheet to essentially retain its shape without substantial deformation when the, thusly, thermoformed sheet is subsequently cooled to room temperature and is then heated to 400°F. and is maintained at 400°F. for one hour; and (viii) removing said thermoformed sheet of step (vii) from said mold.
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이 특허에 인용된 특허 (1)
Dempsey ; Robert E. ; Throne ; James L., Thermoforming process for polyalkylene terephthalate polyester resins.
Snell Tung Deborah Ann ; Rollick Kevin ; Scoarste John Michael ; Johnston Walter Francis, Compositions of polycondensed branched polyester polymers and aromatic polycarbonates, and the closed cell polymer foams made therefrom.
Tung Deborah Ann Snell ; Rollick Kevin ; Scoarste John Michael ; Johnston Walter Francis, Compositions of polycondensed branched polyester polymers and aromatic polycarbonates, and the closed cell polymer foams made therefrom.
Tung Deborah Ann Snell ; Rollick Kevin ; Scoarste John Michael ; Johnston Walter Francis, Compositions of polycondensed branched polyester polymers and aromatic polycarbonates, and the closed cell polymer foams made therefrom.
Tung Deborah Ann Snell ; Rollick Kevin ; Scoarste John Michael ; Johnston Walter Francis, Compositions of polycondensed branched polyester polymers and aromatic polycarbonates, and the closed cell polymer foams made therefrom.
Joseph M. DeSimone ; Saad A. Khan ; Joseph R. Royer ; Richard J. Spontak ; Teri Anne Walker, Method of making foamed materials using surfactants and carbon dioxide.
DeSimone, Joseph M.; Khan, Saad A.; Royer, Joseph R.; Spontak, Richard J.; Walker, Teri Anne; Gay, Yvon J.; Siripurapu, Srinivas, Methods of making foamed materials of blended thermoplastic polymers using carbon dioxide.
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