Plastic Technologies Inc. has developed a way to make foamed PET bottles and jars that fit existing recycling programs.
The process relies on injection molding of a foamed parison followed by blow molding of the parison into the finished shape. Nitrogen gas is currently the preferred foaming agent but carbon dioxide also can be used, according to PTI Vice President Frank Semersky.
The oPTI bottle technology produces a white or silver bottle wall without using pigments that can contaminate a recycling stream, Semersky said in a recent telephone interview.
Instead of being a contaminant to the clear recycling stream, white foamed bottles will mold into a transparent bottle after remelting and subsequent processing, Semersky said.
Foamed PET bottles meet existing barrier-property specifications and their stiffness allows downgauging of up to 5 percent without losing performance, according to a PTI news release. PTI has mainly worked with bottle-grade PET but it envisions uses for polylactic acid and polyethylene naphthalate.
We can make monolithic foam bottles or overmold foam over a PET inner layer, Semersky said.
Besides recycling benefits, the oPTI bottle promises shelf appeal and product differentiation, he said. Swirls and streaks on the bottle exterior can be controlled in the injection process and can improve the bottle's grip.
PTI claims the bottle is the first of its kind and has applied for patents. At high gas levels, foam containers can withstand hot filling without excessive shrinkage, Semersky said. Gas levels vary from 2-8 percent of the foam wall. Barrier additives can be used to meet long shelf-life concerns.
The oPTI bottle includes MuCell microcellular foam injection molding technology licensed from Trexel Inc. In the first stage, nitrogen is injected into the polymer melt in a modified injection press. Foam is produced as cavity fill pressure drops during the injection cycle. Processing conditions are used to control cell growth. Preforms are blow molded on conventional, unmodified blow molding machines, according to PTI.
Semersky said PTI has lined up a technology agreement with an undisclosed company. It plans to grant licenses on a sector-by-sector basis.
PTI of Holland, Ohio, designs and develops packages, does rapid prototyping and evaluates material engineering.