Treatments to accelerate degradation of plastics
Apparatus, systems (including solvent or enzyme), and methods of degrading plastic are described. Plastic waste is stretched in the presence of solvent. The surface may be further treated to increase hydrophilicity. The resulting plastics can be treated with plastic-degrading enzyme either with microorganisms or direct application of enzyme.
1 . A plastics degrading system, comprising:
a shredder;
a plastic feed passing through the shredder;
a solvent contacting the plastic feed;
wherein the plastic feed is in the form of a film or sheet;
wherein the shredder comprises a pair of rollers disposed below, in the direction of gravity, a hinged trap door, wherein the trap door has a first edge opposite to a side having a hinge, and the first edge is adjacent a fixed surface, and a cam wheel positioned against the trap door such that rotation of the cam wheel periodically cycles the trap door between an open position and a closed position in which the first edge is pressed toward the fixed surface such that the plastic feed is held between the first edge and the fixed surface; and
wherein the shredder optionally further comprises one or any combination of the following:
a serrated or knurled cutting blade adapted to indent the plastic feed as it goes through the shredder;
blades that are angled or with a spacing to form cutters configured to increase tension on the plastic feed as it passes through the blades;
a spring loaded pair of blades;
at least two pairs of rollers that are adapted to stretch pieces of the plastic feed held between the pairs of rollers;
a serrated die and a movable blade tooth configured such that pieces of the plastic feed contacts and is held by a surface of the serrated die and the movable blade tooth engages and pulls the feed to generate tension in the feed.
2 . The system of claim 1 further comprising one or more spray nozzles configured to spray the solvent at the plastic feed as it passes through the system.
3 . The system of claim 1 wherein the solvent comprises ethanol or butanol.
4 . The plastics degrading system of claim 1 wherein the shredder comprises the at least two pairs of rollers that are adapted to stretch pieces of the plastic feed held between the pairs of rollers.
5 . The plastics degrading system of claim 4 wherein the at least two pairs of rollers have projections on roller surfaces that engage the plastic feed.
6 . The plastics degrading system of claim 1 wherein the shredder comprises the serrated die and the movable blade tooth configured such that pieces of the plastic feed contacts and is held by the die surface of the serrated die and the movable blade tooth engages and pulls the plastic feed to generate tension in the plastic feed.
7 . The plastics degrading system of claim 1 wherein the solvent is an organic solvent.
8 . The plastics degrading system of claim 7 wherein the solvent comprises ethylene glycol, isopropanol, anisole, toluene, dichloromethane, ethyl acetate, heptane, acetonitrile, t-butyl methyl ether, acetone, methanol, ethanol, propanol, butanol, or combinations thereof.
9 . The plastics degrading system of claim 8 having a mass ratio of the plastic feed to the solvent in a range of 100 to 0.01.
10 . The plastics degrading system of claim 8 having a mass ratio of the plastic feed to the solvent in a range of 10 to 0.1.
11 . A plastics degrading system, comprising:
a shredder;
a plastic feed passing through the shredder;
an organic solvent contacting the plastic feed as the plastic feed passes through the shredder;
wherein the shredder comprises one or any combination of the following:
blades that are misaligned to form cutters configured to increase tension on the plastic feed as it passes through the blades;
at least two pairs of rollers that are configured to stretch pieces of the plastic feed held between the pairs of rollers; or
a serrated die and a movable blade tooth configured such that pieces of the plastic feed contacts and is held by the die surface and the movable blade tooth engages and pulls the plastic feed to generate tension in the plastic feed.
12 . The plastics degrading system of claim 11 wherein the shredder comprises the blades that are misaligned.
13 . The plastics degrading system of claim 12 wherein the misaligned blades comprise opposing blade tips that are farther apart than 3 mm.
14 . The plastics degrading system of claim 13 wherein the misaligned blades comprise opposing blade tips that are farther apart than 5 mm.