Thermoplastic containers having high dimensional stability

Abstract

Thermoplastic compositions comprising a bulk polymer, an additive, and a compatibilizer/emulsifier/surfactant (CES) are described. The bulk polymer comprises an alkylene terephthalate or naphthalate polyester such as polyethylene terephthalate. The additive comprises an amorphous or substantially amorphous co-polymer of ethylene and a co-monomer that forms polar portions, such as methylacrylate, butylacrylate, ethylacrylate, or ethylhexyl methacrylate. The CES comprises a co-polymer or ter-polymer of ethylene and a glycidyl acrylate or maleic anhydride, and optionally an acrylate such as methylacrylate, ethylacrylate, propylacrylate, butylacrylate, ethylhexyl acrylate, or mixtures thereof. The thermoplastic compositions of the present invention exhibit improved molding properties, high dimensional stability, high temperature resistance, and are particularly useful in food-grade applications such as dual-ovenable containers.

What is claimed is:  
     
         1 . A food-grade container made by thermal crystallization of a substantially non-oriented composition comprising an alkylene terephthalate or naphthalate bulk polymer having an intrinsic viscosity of less than 0.95, wherein said bulk polymer is present in a concentration of at least about 30 wt %, based on a total weight of the composition.  
     
     
         2 . The food-grade container of  claim 1  wherein said intrinsic viscosity is less than about 0.90.  
     
     
         3 . The food-grade container of  claim 2  wherein said intrinsic viscosity is less than about 0.85.  
     
     
         4 . The food-grade container of  claim 3  wherein said intrinsic viscosity is less than about 0.80.  
     
     
         5 . The food-grade container of  claim 1  wherein said bulk polymer comprises one or more linear or branched homo-polymers, co-polymers, recycled polyesters, or a mixture thereof, selected from the group consisting of PET, PEN, PETG, PCT, PCTA, PBT, PTT, and mixtures thereof.  
     
     
         6 . The food-grade container of  claim 1  further comprising an additive in a concentration from about 4 wt % to about 40 wt %, based on the total weight of the composition, wherein said additive comprises a substantially amorphous co-polymer of ethylene and an acrylate.  
     
     
         7 . The food-grade container of  claim 1  further comprising a compatibilizer/ emulsifier/surfactant (CES) in a concentration from about 0.1 wt % to about 8 wt %, based on the total weight of the composition, wherein said CES comprises a grafted or backbone co-polymer or ter-polymer of ethylene and a glycidyl acrylate or maleic anhydride, and optionally an acrylate selected from the group consisting of methylacrylate, ethylacrylate, propylacrylate, butylacrylate, ethylhexylacrylate, and mixtures thereof.