Method of forming multilayer container with polyethylene naphthalalte (pen)

A method of forming a container having a substantially transparent multilayer sidewall comprising;

• forming at an elevated temperature a preform having a substantially amorphous and transparent multilayer sidewall-forming portion including first and third layers of a first polymeric material and a second core layer between the first and third layers of a second polymeric material;
• wherein the first polymeric material comprises on the order 80-100% PEN and and 0-20% PET by total weight of the layer, and the second polymeric material is substantially nonstrain-crystallizable polyester which remains substantially transparent when stretched within an orientation, temperature range of the first polymeric material;
• cooling below the glass transition temperature of the first polymeric material and then reheating the preform from the exterior such that heat is transferred across the core layer, wherein the reheating and expanding is performed at an orientation temperature which is on the order of 11.degree. to 36.degree. C. above the glass transition temperature of the first polymeric material;
• and
• expanding the sidewall-forming portion within the orientation temperature range of the first polymeric material to form a container having a substantially transparent multilayer sidewall with strain-crystallized layers of the first polymeric material.

A method of forming a container having a substantially transparent multilayer sidewall, including forming at an elevated temperature a preform having a substantially amorphous and transparent multilayer sidewall-forming portion including a first layer of a first polymeric material and a second layer of a second polymeric material, cooling and then reheating and expanding the preform to form the container, characterized in that:

• the first polymeric material is a copolymer or blend which is substantially non-crystallizable and contains both polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), and the second polymeric material is strain-hardened and remains substantially transparent when stretched at a temperature within the orientation temperature range of the first polymeric material;
• cooling is performed below the glass transition temperature of the first polymeric material and then reheating of the first and second layers is performed within the orientation temperature range of the first polymeric material which is on the order of 11.degree. to 36.degree. C. above the glass transition temperature of the first polymeric material;
• and
• expanding of the preform is performed within the orientation temperature range of the first polymeric material to form a container having a substantially transparent multilayer sidewall with a substantially amorphous first polymeric material layer and a strain-hardened second polymeric material layer.