Plastic flake processing

• US 20040140248A1
• Filed: 01/17/2003
• Published: 07/22/2004
• Est. Priority Date: 01/17/2003
• Status: Abandoned Application

• Current Assignee: Constar International Incorporated (Plastipak Holdings Incorporated)
• Original Assignee: Constar International Incorporated (Plastipak Holdings Incorporated)
• Inventors: Schmidt, Frank J., Dauzvardis, Matthew J.
• Application Number:
  US10/347,081
• Publication Number:
  US 20040140248A1
• Time in Patent Office: Days
• US Class Current: 209/3.3
• CPC Class Codes: B07C 5/3427 by changing or intensifying the optical properties prior to scanning, e.g. by inducing fluorescence under UV or x-radiation, subjecting the material to a chemical reaction
• CPC Class Codes: B29B 17/02 Separating plastics from other materials
• CPC Class Codes: B29B 2017/0015 Washing, rinsing
• CPC Class Codes: B29B 2017/0203 Separating plastics from plastics
• CPC Class Codes: B29B 2017/0279 Optical identification, e.g. cameras or spectroscopy
• CPC Class Codes: B29K 2023/06 PE, i.e. polyethylene
• CPC Class Codes: B29K 2023/086 EVOH, i.e. ethylene vinyl alcohol copolymer
• CPC Class Codes: B29K 2023/12 PP, i.e. polypropylene
• CPC Class Codes: B29K 2029/04 PVOH, i.e. polyvinyl alcohol B29K2031/04 takes precedence
• CPC Class Codes: B29K 2033/04 Polymers of esters
• CPC Class Codes: B29K 2067/00 Use of polyesters or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2069/00 Use of PC, i.e. polycarbonates or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2077/00 Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2105/065 containing impurities
• CPC Class Codes: B29K 2995/0092 hydrophilic
• CPC Class Codes: B29K 2995/0093 hydrophobic
• CPC Class Codes: B29L 2007/008 Wide strips, e.g. films, webs
• CPC Class Codes: B29L 2009/00 Layered products
• CPC Class Codes: B29L 2031/7158 Bottles
• CPC Class Codes: Y02W 30/62 Plastics recycling; Rubber recycling

Abstract

A method for identifying and separating hydrophilic plastic from hydrophobic plastic includes tagging the hydrophilic plastic with a tagging agent, such as a fluorescent dye. Upon exposure to a water bath or other processing fluid, the hydrophilic plastic incorporates, such as by absorption, the tagging agent. The plastic containing the tagging agent is then detected and separated from the remainder of the plastic material.

Claims

1. A method of separating hydrophilic plastic from hydrophobic plastic, comprising the steps of:

a) providing plastic flake that includes hydrophilic plastic and hydrophobic plastic;

b) contacting the plastic flake with a fluid comprising a tagging agent, the hydrophilic plastic incorporating a quantity of the agent, the hydrophobic plastic not incorporating the agent;

c) illuminating the plastic flake;

d) detecting the illuminated hydrophilic plastic; and

e) separating the detected hydrophilic plastic from the hydrophobic plastic.

2. The method of claim 1 wherein the contacting step b) includes washing the plastic flake.

3. The method of claim 1 wherein the contacting step b) includes introducing the plastic flake into a water bath.

4. The method of claim 3 wherein the tagging agent is mixed into the water bath, and the hydrophilic plastic incorporating the tagging agent in the water bath.

5. The method of claim 4 wherein the hydrophilic plastic absorbs the tagging agent, thereby incorporating the tagging agent.

6. The method of claim 5 wherein the tagging agent becomes illuminated during the illuminating step c), whereby the tagging agent is detected during the detection step d).

7. The method of claim 6 wherein the tagging agent is a dye.

8. The method of claim 7 wherein the tagging agent is a fluorescent dye.

9. The method of claim 7 wherein the tagging agent is a fluorophore.

10. The method of claim 7 wherein the tagging agent is a chromophore.

11. The method of claim 7 wherein the tagging agent is fluorescein.

12. The method of claim 11 wherein the fluorescein is at a concentration of less than approximately 200 parts per million.

13. The method of claim 11 wherein the fluorescein is at a concentration of between 5 and 50 parts per million.

14. The method of claim 5 wherein the water bath is alkaline and at an elevated temperature.

15. The method of claim 5 wherein the hydrophobic plastic comprises at least one of a polyethylene terephthalate, a polyethylene, a polypropylene, a polycarbonate, an acrylonitrile, and a copolymers.

16. The method of claim 5 wherein the hydrophobic plastic is polyethylene terephthalate.

17. The method of claim 16 wherein the hydrophilic plastic is absorptive such that the hydrophilic plastic absorbs water and the tagging agent upon the contacting step b).

18. The method of claim 16 wherein the hydrophilic plastic comprises at least one of a nylon and an EVOH.

19. The method of claim 16 wherein the hydrophilic plastic comprises an oxygen scavenger.

20. The method of claim 16 wherein the hydrophilic plastic comprises an oxidizable organic component and a metal catalyst for the oxidation of the oxidizable organic component.

21. The method of claim 20 wherein the oxidizable organic component is a condensation polymer of m-xylylenediamine and adipic acid and metal catalyst includes one of cobalt, copper, and rhodium.

22. The method of claim 14 wherein the water bath includes a surfactant.

23. The method of claim 1 wherein the separating step e) includes separating the detected hydrophilic plastic by air means.

24. The method of claim 1 wherein the separating step e) includes separating the detected hydrophilic plastic by directing a jet of compressed air at said detected hydrophilic plastic.

25. The method of claim 1 wherein the providing step a) includes providing the ground plastic flake from plastic containers.

26. The method of claim 1 wherein the providing step a) includes grinding plastic containers.

27. The method of claim 26 wherein at least some of the plastic containers include polyethylene terephthalate and an oxygen scavenger.

28. The method of claim 26 wherein at least some of the plastic containers include polyethylene terephthalate and an oxygen barrier.

29. The method of claim 1 wherein the providing step a) includes grinding containers formed of both the hydrophilic plastic and the hydrophobic plastic.

30. The method of claim 29 wherein the containers include multiple layers.

31. The method of claim 1 wherein the illuminating step c) includes subjecting the flake to ultraviolet light.

32. The method of claim 1 further comprising the step of viewing the separated hydrophobic plastic to determine efficacy of the separation step.

33. The method of claim 32 wherein the viewing step includes illuminating the hydrophobic plastic.

34. A method for detecting and, if found, separating impurity plastics from a plastic stream, comprising the steps of:

a) providing ground plastic flake at least partially from plastics comprising multiple layers, at least one of the layers comprising a first material for oxygen protection and at least an other one of the layers comprising a second material;

b) contacting the plastic flake with a fluid comprising a tagging agent, the first material incorporating a quantity of the agent, the second material not incorporating the agent;

c) illuminating the plastic flake;

d) detecting the illuminated first material; and

e) separating the detected first material from the second material, whereby separating the first material removes impurities from the remaining plastic stream.

35. The method of claim 34 wherein the first material comprises an oxygen scavenger that takes up the fluid and thereby incorporates the tagging agent.

36. The method of claim 35 wherein the oxygen scavenger comprises an oxidizable organic component and a metal catalyst for the oxidation of the oxidizable organic component.

37. The method of claim 35 wherein second material comprises polyethylene terephthalate.

38. The method of claim 34 wherein the first material comprises an oxygen barrier that takes up the fluid, and thereby incorporates the tagging agent.

39. The method of claim 38 wherein the first material comprises EVOH.

40. The method of claim 38 wherein second material comprises polyethylene terephthalate.

41. The method of claim 34 wherein the contacting step b) includes washing the plastic flake.

42. The method of claim 34 wherein the contacting step b) includes introducing the plastic flake into a water bath.

43. The method of claim 34 wherein the illuminating step c) and the detecting step d) employ ultraviolet light.

44. The method of claim 34 wherein the tagging agent comprises a fluorescent dye.

45. The method of claim 34 wherein the tagging agent comprises fluorescein.

46. The method of claim 45 wherein the fluorescein is at a concentration of less than approximately 200 parts per million.

47. The method of claim 45 wherein the fluorescein is at a concentration of between 5 and 50 parts per million.

48. The method of claim 34 further comprising the step of viewing the separated hydrophobic plastic to determine efficacy of the separation step.

49. The method of claim 48 wherein the viewing step includes illuminating the hydrophobic plastic.

50. A method of preparing plastic flake for processing, comprising the steps of:

a) providing plastic flake that includes hydrophobic plastic and, possibly, hydrophilic plastic; and

b) tagging the hydrophilic plastic, if any, to enhance detection thereof by contacting the plastic flake with a fluid comprising a tagging agent, the hydrophilic plastic incorporating a detectable quantity of the tagging agent, the hydrophobic plastic not incorporating the agent;

whereby the tagging agent incorporated in the hydrophilic plastic is capable of being detected and thereby identified.

51. The method of claim 50 further comprising the step of detecting the hydrophilic plastic after said hydrophilic plastic incorporates the tagging agent.

52. The method of claim 51 wherein the detected plastic provides an indication of an amount of hydrophilic plastic in the plastic flake.

53. The method of claim 50 wherein the hydrophilic plastic comprises at least one of a barrier material and a scavenger material.

54. The method of claim 50 wherein the hydrophilic plastic comprises material for oxygen protection.

55. The method of claim 54 wherein the material for oxygen protection comprises an oxygen scavenger that takes up the fluid and thereby incorporates the tagging agent.

56. The method of claim 55 wherein the oxygen scavenger comprises an oxidizable organic component and a metal catalyst for the oxidation of the oxidizable organic component.

57. The method of claim 54 wherein the material for oxygen protection comprises an oxygen barrier that takes up the fluid and thereby incorporates the tagging agent.

58. The method of claim 57 wherein the oxygen barrier comprises EVOH.

59. The method of claim 54 wherein the hydrophobic plastic comprises polyethylene terephthalate.

60. The method of claim 54 wherein the tagging step b) includes washing the plastic flake.

61. The method of claim 54 wherein the tagging step b) includes introducing the plastic flake into a water bath.

62. The method of claim 61 wherein the tagging agent is disposed in the water bath.

63. The method of claim 54 wherein the tagging agent is a fluorescent dye.

64. The method of claim 54 wherein the tagging agent is fluorescein.

65. The method of claim 64 wherein the fluorescein is at a concentration of less than approximately 200 parts per million.

66. The method of claim 64 wherein the fluorescein is at a concentration of between 5 and 50 parts per million.

67. The method of claim 64 wherein the fluorescein is at a concentration of between 10 and 25 parts per million.

68. The method of claim 50 wherein said plastic flake contains a negligible amount of hydrophilic plastic such that said method is employed to verify purity of said plastic flake.

69. A system for detecting and separating impurity plastics from a plastic stream, comprising the steps of:

c) a grinding system for receiving and reducing size of plastic products to produce a plastic flake, the grinding system including metallic grinding elements;

d) a bath including a fluid for receiving the plastic flake, the fluid comprising a tagging agent that is capable of being incorporated into a hydrophilic component of the plastic flake; and

e) detection means for detecting said tagging agent incorporated into the hydrophilic component of the plastic flake; and

f) separation means for removing the detected hydrophilic component from a remainder of the plastic flake.