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Recycle coex PP barrier bottles in blends with post-consumer HDPE.

Recycle Coex PP Barrier Bottles In Blends With Post-Consumer HDPE

Six-layer PP ketchup bottles don't necessarily have to be separated form either post-consumer HDPE milk jugs or mixed HDPE bottle collections, concludes a recent technical report by SPI's Plastic Bottle Institute. The report says that up to 6% multilayer ketchup-bottle material can be blended with post-consumer homopolymer milkjug resin without hurting its basic bottle properties.

The study also concludes that the hygroscopic EVOH barrier material, constituting up to 5% of a coextruded ketchup bottle, doesn't necessitate special drying stages or equipment. The study gives results of a production run by Owens-Brockway, Toledo, Ohio of 90,000 commercial three-layer, 64-oz, handled HDPE bottles for fabric softener, containing 3% ketchup-bottle scrap, 22% post-consumer HDPE, as well as virgin HDPE and regrind from the same run. Owens-Brockway is also a big producer of multilayer PP ketchup bottles. The company says it continues to include ketchup-bottle material with milk-jug recycle and has by now made some 350,000 commercial bottles with it.

The SPI study had three goals: first, to determine basic physical properties of a blend of ketchup bottles with HDPE; second, to determine whether special processing equipment was necessary to work with such a blend; and third, to make commercial bottles containing ketchup bottle material.

Ketchup-bottle scrap for the test came from Beatrice/Hunt-Wesson's ketchup filling plant in Rossford, Ohio. It consisted of 89.5% PP copolymer, 5% EVOH and 5.5% olefin-based tie layer. About 60% of the scrap bottles were filled and capped; 40% were unfilled. Foil-lined caps were removed and bottles water-rinsed before being shipped to United Resource Recovery in Findlay, Ohio, for granulating, washing and drying under standard production conditions.

Granulated material was then blended at 3%, 6%, 9% and 12% levels with virgin HDPE homopolymer. Blends of the multi-material bottle scrap and HDPE were then processed on a single-screw, non-vented extruder into bars for testing. Physical-properties were tested by United Resource Recovery.

CAN USE UP TO 6%

Tests showed (see graphs I-IV) that up to 6% multi-material PP bottle material can be added to HDPE without seriously hurting density, melt index, flex modulus or notched Izod impact. At over 6% loading, however, the notched Izod drops sharply. Density also decreases when multilayer PP content goes over 6%, since PP is inherently lighter than HDPE.

Flex-modulus results were somewhat contradictory - modulus drops at 3%, 6% and 9%, then rises again sharply at 12%. The study suggests that "experimental variation" explains this apparent anomaly and that the effect on bottle properties "is expected to be slight."

SPECIAL DRYING NOT NEEDED

Four different drying procedures were then studied to determine their effectiveness. A blend of 12% ketchup-bottle resin and 88% post-consumer HDPE was used to form 48-oz monolayer bottles for testing. The four options were:

1) Ketchup-bottle and milk-jug flake were blended, pelletized and molded into bottles without extra drying.

2) Ketchup-bottle flake was dried in a dehumidifying dryer, then blended with milk-bottle flake, pelletized and molded into bottles.

3) Ketchup- and milk-bottle flake were blended and pelletized. Pellets were then dried in a dehumidifying dryer and molded into bottles.

4) Ketchup-bottle flake was dried in a dehumidifying dryer, then blended with milk-bottle flake and pelletized. Pellets were then dried in a dehumidifying dryer and molded into bottles.

Pellet samples from the four methods were then measured for moisture content or volatiles by vacuum-oven drying at 212 F for 6 hr, then measuring weight loss. The results were these:

*Method 1 - 0.048% moisture content.

*Method 2 - 0.040% moisture.

*Method 3 - 0.030%.

*Method 4 - 0.025%.

*Virgin HDPE - 0.028% moisture.

"As expected, the volatiles content is lower for those samples that were specially dried in the dehumidifying dryer," the study notes. The blend without extra drying had 71% more moisture than the virgin HDPE sample, but the study concludes that differences in moisture levels for all of the cases are small. The report also notes that no molding problems or bubbles were encountered in making any of the samples.

COMMERCIAL PRODUCTION

As a final test before commercial production, Owens-Brockway made three sample sets of 64-oz, three-layer handleware bottles: with 3% ketchup bottle/22% recycled HDPE; with 6% ketchup bottle/19% recycled HDPE material; and no ketchup bottle/25% recycled HDPE as a control (see table).

TABLE : PROPERTIES OF 3-LAYER 64-OZ HOPE BOTTLES
 3% 6%
 Ketchup Ketchup
 Bottle Bottle
Property Control Content Content


Test Run:
 Bottle Weight, g 95.64 95.97 96.62
 Top Load, lb 148.0 142.7 149.3


Drop Impact,

Bruceton

in. to Fail 66.8 73.0 58.2

ESCR @ 140 F,

7 days, Fabric

Softener No fail No fail No fail

Production Run:

Drop Impact,

Bruceton

in. to Fail 66.8 63.5 -

Overall weights were the same for the 3%, 6% and control bottles. Top-load strength, measured on empty non-vented bottles, was lowest for the 3% sample, but acceptable in all three cases. Drop impact, measured using the Bruceton staircase technique (up-and-down method) with 12-in. drop-height intervals at 68% F, was acceptable with all three samples. Estimated mean failure height (EMFH) was slightly lower for the 6% bottle. And environmental stress-crack resistance (ESCR), tested by filling bottles with fabric softener at 140 F for seven days, showed no bottle failures in any samples.

Owens-Brockway then made 90,000 commercial bottles using 3% ketchup-bottle content, 22% post-consumer homopolymer HDPE, plus virgin and regrind in a three-layer construction. Bottles were made under normal production conditions and machine settings.

The only anomaly observed in comparing actual production bottles with the previous test bottles, was that drop impact strength was lower in the production bottles - though still within acceptable levels. Bruceton drop impact for the production bottle with 3% ketchup-bottle content was only 63.5 in. EMFH, vs. 73.0 in. for the 3% test bottle. Lot-to-lot variability could partly account for this difference, says James Herman, materials supervisor at Owens-Brockway, who supervised technical aspects of the project.

Sonoco Graham Co., in York, Pa., the country's largest maker of recycled-content HDPE bottles, has also tested recycle with up to 6% PP ketchup bottles and is "pleased with the results," says Gerry Claes, director of environmental programs at Sonoco Graham. It doesn't have a measurable effect on the quality of the bottles. For some time we've been letting the ketchup bottles and bottle caps go right through," he says.

PHOTO : Tests show multilayer PP ketchup bottles containing EVOH and tie layer can blend at up to 6% level with HDPE without hurting basic bottle properties. This means recycling centers no longer have to pick up their

ketchup and syrup bottles, but can let them go through with the HDPE.
COPYRIGHT 1991 Gardner Publications, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
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Title Annotation:coextruded polypropylene material mixed with high density polyethylene
Author:Schut, Jan H.
Publication:Plastics Technology
Date:Feb 1, 1991
Words:1114
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