Method for processing and analyzing contaminated mixed waste plastics to produce reformulated, blended feed materials having a target density
View Patent ↗A method for reformulating reclaimed, contaminated mixed waste plastics into useful articles wherein a plurality of batches of the mixed waste plastics are preprocessed to produce substantially homogeneous mixtures of a desired particle size range that are characterized according to their respective apparent densities, and are thereafter blended to produce a mixed plastic feed material having a target density predetermined to be desirable for reprocessing into at least one of such useful articles.
1. A method for preparing a reformulated feed material from a plurality of batches of reclaimed mixed waste plastic, the reformulated feed material having a target density that is suitable for use in manufacturing a desired product, the method comprising:
preprocessing a plurality of different batches of contaminated, reclaimed mixed waste plastic by removing gross contaminants, shredding the resultant product, densifying the shredded mixed waste plastic to a bulk density of at least about 16 pounds per cubic foot, and pulverizing the densified mixed waste plastic to a predetermined maximum particle size;
selecting a sample from each of the plurality of batches of preprocessed mixed waste plastic;
further reducing the particle size of the sample to obtain a more uniform particle size distribution;
injection molding a substantially homogeneous composition from the mixed waste plastic within each sample;
analyzing at least a portion of each injection molded composition to determine an apparent density for that sample;
selecting a target density suitable for use in making the desired product;
calculating a reformulated blend including mixed waste plastic from at least some of the plurality of batches of mixed waste plastic based upon the apparent densities of the injection molded compositions; and
blending a quantity of mixed waste plastic from the at least some of the plurality of batches of mixed waste plastic according to the calculated reformulated blend to produce a reformulated feed material having a density falling within a predetermined range of the selected target density.
2. The method of claim 1 wherein the predetermined maximum particle size is about −10 mesh.
3. The method of claim 1 wherein each selected sample is milled prior to injection molding.
4. The method of claim 1 wherein the particle size of the sample is further reduced to a size that will pass through a 2 mm screen.
5. The method of claim 1 wherein the apparent density of each injection molded composition is determined from measurement of the heat flux required to melt a test sample taken from the injection molded composition as a function of temperature.
6. The method of claim 5 wherein the test sample is analyzed using a differential scanning calorimeter.
7. The method of claim 1 wherein a portion of the injection molded composition is analyzed to determine a plastic content of the mixed waste plastic.
8. The method of claim 1 wherein a portion of the injection molded composition is analyzed to determine a level of contaminants.
9. The method of claim 1 wherein a portion of the injection molded composition is analyzed to determine a level of color.
10. The method of claim 1 wherein the blending is done under conditions that promote thorough mixing.
11. The method of claim 1 wherein the reformulated blend is calculated using an algorithm.