Method and system for sampling and determining the presence of contaminants in recyclable plastic materials

• US 5,688,693 A
• Filed: 04/29/1996
• Issued: 11/18/1997
• Est. Priority Date: 06/01/1992
• Status: Expired due to Term

• Current Assignee: The Coca-Cola Company
• Original Assignee: The Coca-Cola Company
• Inventors: Myers, Dirck vanBuren, Fine, David H., Fraim, Freeman W., MacDonald, Stephen J., Malaspina, Alex, Bayer, Forrest Lee
• Primary Examiner(s): Le, Long V.
• Application Number:
  US08/639,757
• Time in Patent Office: 568 Days
• Field of Search: 436/43, 436/47, 436/53, 436/106, 436/172, 436/165, 436/50, 436/55, 422/80, 422/83, 422/82.05, 422/82.08, 422/50, 422/62, 422/105, 422/119, 209/3, 209/523, 209/3.1, 241/19, 241/24.1, 241/76, 241/79, 241/99, 241/DIG. 38, 73/23.35, 73/23.41
• US Class Current: 436/43
• CPC Class Codes: B07C 5/34 Sorting according to other particular properties material testing per se G01N; quality control G07C3/14
• CPC Class Codes: B08B 2203/005 the liquid being ozonated
• CPC Class Codes: B08B 9/46 Inspecting cleaned containers for cleanliness
• CPC Class Codes: B29B 17/00 Recovery of plastics or other constituents of waste material containing plastics; volume reduction of waste plastics, e.g. by mechanical compacting or melting disposal of solid waste B09B; chemical recovery C08J11/00
• CPC Class Codes: B29B 17/02 Separating plastics from other materials
• CPC Class Codes: B29B 2017/0203 Separating plastics from plastics
• CPC Class Codes: B29B 2017/0275 using chemical sensors, e.g. analysing gasified constituents
• CPC Class Codes: B29K 2067/00 Use of polyesters or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2105/065 containing impurities
• CPC Class Codes: B29L 2031/7158 Bottles
• CPC Class Codes: G01N 1/2202 involving separation of sample components during sampling
• CPC Class Codes: G01N 1/2226 Sampling from a closed space, e.g. food package, head space
• CPC Class Codes: G01N 1/24 Suction devices G01N1/22 - G01N1/2294 take precedence
• CPC Class Codes: G01N 2001/2223 aerosol sampling devices
• CPC Class Codes: G01N 2001/2229 Headspace sampling, i.e. vapour over liquid
• CPC Class Codes: G01N 2033/0081 containers; packages; bottles
• CPC Class Codes: G01N 21/64 Fluorescence; Phosphorescence
• CPC Class Codes: G01N 21/76 Chemiluminescence; Bioluminescence
• CPC Class Codes: G01N 21/766 of gases
• CPC Class Codes: G01N 21/9018 Dirt detection in containers
• CPC Class Codes: G01N 21/9081 : Inspection especially designed for plastic containers, e.g. preforms
• CPC Class Codes: G01N 33/442 : Resins, plastics
• CPC Class Codes: Y02W 30/62 : Plastics recycling; Rubber recycling
• CPC Class Codes: Y10S 241/38 : Solid waste disposal
• CPC Class Codes: Y10T 436/11 : Automated chemical analysis
• CPC Class Codes: Y10T 436/115831 : Condition or time responsive
• CPC Class Codes: Y10T 436/25375 : Liberation or purification of sample or separation of material from a sample [e.g., filtering, centrifuging, etc.]
• CPC Class Codes: Y10T 436/25875 : Gaseous sample or with change of physical state

Abstract

An inspection system for sampling and determining the presence of residues of contaminants within plastic materials to be recycled from used plastic materials such as plastic beverage bottles or plastic food containers includes a chemical sniffing apparatus, or alternatively an optical scanner, for detecting the contaminants as the plastic materials are rapidly moved along a conveyor past a series of stations. Recycled food or beverage bottles are fed through a shredder in-line with the conveyor and the shredded plastic material from the bottles is fed to a washer. The bottles and shredded material may be tested for contaminants at any location in an in-line process. In one exemplary system first the bottles are tested prior to entry into the shredder in order to remove bottles containing gross contaminants. Second the shredded material emerging from the shredder is immediately tested for contaminants at an elevated temperature caused by the shredding process and contaminated materials are separated or sorted out from the uncontaminated material. Third, the materials are again tested for contaminants as they emerge from the washer once again taking advantage of the elevated temperature of the materials which is conducive to the emission of vapors of the contaminants. Contaminated materials are again sorted from the uncontaminated supply of materials to be used for the fabrication of new plastic food or beverage bottles.

Claims

1. A method of determining whether plastic material moving along a conveyor obtained from used containers is free of volatiles of contaminants and sorting that material so that the material can be recycled to produce new containers, comprising the steps of:

providing a supply of used containers to the conveyor;

testing each used container for volatiles of contaminants therein;

separating and removing contaminated containers from the conveyor;

breaking each remaining container into pieces of said material, said breaking causing said pieces to be heated to temperatures sufficient to vaporize the contaminants and emit volatiles thereof;

testing said volatiles to determine the presence or absence of said contaminants in said materials;

separating and removing pieces of material containing contaminants from the conveyor;

washing the pieces of materials remaining on the conveyor in a heated fluid to remove a portion of contaminants and to emit detectable levels of volatiles of the contaminants therein;

testing the volatiles of the contaminants from pieces which have been washed to determine the presence or absence of contaminants in the materials; and

separating pieces containing contaminants from those not containing contaminants.

2. The method of claim 1, wherein each step of testing comprises the steps of:

directing fluid at said container or pieces of materials in order to displace at least a portion of volatiles therein to positions spaced from the materials to form a sample cloud at a region spaced from the materials;

evacuating a sample of said portion of the volatiles so displaced by applying suction to the sample cloud at said region spaced from said materials; and

analyzing the sample evacuated to determine the presence or absence of said contaminants in the materials.

3. The method of claim 2 including the additional step of:

maintaining the temperature of washed material below a level that would emit detectable levels of vapors derived from the plastic material itself.

4. The method of claim 3 wherein the plastic material is PET and the temperature is maintained below about 650°

F.

5. The method of claim 1 including the additional step of:

maintaining the temperature of washed material below a level that would emit detectable levels of vapors derived from the plastic material itself.

6. The method of claim 5 wherein the plastic material is PET and the temperature is maintained below about 650°

F.

7. A system for determining whether plastic material moving along a conveyor obtained from used containers is free of volatiles of contaminants and sorting that material so that the material can be recycled to produce new containers, comprising:

a supply of used containers on the conveyor;

first means for testing each used container for volatiles of contaminants therein;

first means for separating and removing contaminated containers from the conveyor;

means for breaking each remaining container into pieces of said material, said breaking causing said pieces to be heated to temperatures sufficient to vaporize the contaminants and emit volatiles thereof;

second means for testing said volatiles to determine the presence or absence of said contaminants in said materials;

second means for separating and removing pieces of material containing contaminants from the conveyor;

means for washing the pieces of materials remaining on the conveyor in a heated fluid to remove a portion of contaminants and to emit detectable levels of volatiles of the contaminants therein;

third means for testing the volatiles of the contaminants of pieces which have been washed to determine the presence or absence of contaminants in the materials; and

third means for separating pieces containing contaminants from those not containing contaminants.

8. The system of claim 7 wherein each means for testing comprises:

means for directing fluid at said container or pieces of materials in order to displace at least a portion of volatiles therein to positions spaced from the materials to form a sample cloud at a region spaced from the materials;

means for evacuating a sample of said portion of the volatiles so displaced by applying suction to the sample cloud at said region spaced from said materials; and

means for analyzing the sample evacuated to determine the presence or absence of said contaminants in the materials.

9. The system of claim 8 further including:

means for maintaining the temperature of washed material below a level that would emit detectable levels of vapors derived from the plastic material itself.

10. The system of claim 9 wherein the plastic material is PET and the temperature is maintained below about 650°

F.

11. The system of claim 7 further including:

means for maintaining the temperature of washed material below a level that would emit detectable levels of vapors derived from the plastic material itself.

12. The system of claim 11 wherein the plastic material is PET and the temperature is maintained below about 650°

F.