Title of Invention

A METHOD FOR DECREASING THE CONTENT OF GLUE AND PVC CONTAMINATIONS IN RECYCLED PET FLAKES TO MAKE IT SUITABLE FOR BOTTLE TO BOTTLE RECYCLING

Abstract

A method for decreasing the content of glue and PVC contaminations in recycled PET flakes comprising the steps of : washing the flakes in a bath of caustic soda with some detergent; heating an alkaline solution to a temperature of 75-95°C; subjecting the flakes and solution to agitation; treating the flakes with a solution of n-butyl pentane and subjecting the flakes thus obtained to agitation to remove the glue; washing the flakes and dipping it in a solution of n-optyl Butane; adding a dye to the said solution to identify PVC from PET flakes; subjecting the flakes thus obtained to the step of manual sorting to remove the PVC.

Full Text

FIELD OF INVENTION: This invention relates to a method for decreasing the content of glue and PVC contaminations in recycled PET flakes to make it suitable for bottle to bottle recycling. BACKGROUND OF THE INVENTION: The level of glue and PVC contamination becomes more and more critical as the recycled PET goes into more high end application. Previously a simple dip and stir in a hot caustic solution sufficiently removed the glue for the required end applications, the process becomes quite ineffective when the required level of glue is less practice of using non-water soluble glues, which simply could not be removed in the previous processes. The present process could overcome the dual requirement of handling both water insoluble glues and bringing down the glue content to below 10 ppm levels. Similarly, in the case of PVC removal, the earlier process of positive sorting was sufficient to remove PVC to the then desired requirement. But, now when level below 30 ppm is required the convensional method can at the most be the process of primary separation of PVC. Whereas, the present application efficiently treats the flakes for positive indentification and also removes PVC to give flakes with a PVC contamination of less than 30 ppm. OBJECT OF THE INVENTION: An object of this invention is to propose a method for decreasing the content of glue and PVC contamination in recycled PET flakes; Another object of this invention is to propose a method for decreasing the content of glue and PVC contamination in recycled PET flakes to make it suitable for bottle to bottle recycling process; Further object of this invention to propose a method for decreasing the content of glue and PVC contamination in recycled PET flakes to produce recycled PET with the glue content below 10 ppm levels; Still further object of this invention is to propose a method for decreasing the content of glue and PVC contamination in recycled PET flakes to produce recycle PET with the PVC contamination less than 30 ppm. DESCRIPTION OF THE INVENTION: The process relates to the effective removal of glue, both water soluble and otherwise that find use in packaging bottle application. The glue is an inherent contaminant in all packaging bottle applications in as much as it forms the basis of manufacturer identity in all bottles used for packaging. Removal of the glue is an integral part of the washing process and the efficacy of its removal defines the effectiveness of the washing process. PVC contamination is an external contamination in the PET waste bottle stream. It arises from the continued unregulated use of PVC bottles in the packaging of certain commodities. Also, in the present waste stream, a lot of labels pasted on the bottles for identification is made of PVC film. Being of similar Specific Gravity as PET, the process of cyclonic separation and/or separation by sink float methods are not effective in the present separation. Owing to the different structures of PET and PVC, the two are inherently non-compatible and the removal of PVC for any bottle to bottle application is mandatory. For glue removal, the process application entails addition of intermediate washer and/or additional chemical wash in the manufacture of PET flakes from bottle waste. A primary wash is given to the flakes in a bath of caustic soda with some detergent. An Alkaline Medium is prepared to a concentration level of 2% to 5% along with detergent soap to a concentration level of 0.5%. The bath is heated to a temperature of 75°C to 95°C. The solution is kept in circulation with a pump and is continuously filtered through bucket filters. Flakes and solution in the ratio of 1:5 is subjected to high agitation at about 600 to 1000 rpm in a vessel. A residence time of about 6 mins to 12 mins is maintained in the vessel. The flakes are then transferred to another vessel containing a solution of a derivative of n-butyl pentane at a concentration level of about 3% to 8%. A flake concentration in solution in the ratio of 1:8 with high agitation at 600-1000 rpm with a residence time of 3 mins to 6 mins at ambient temperature ensures that all glue is removed from the surface of the flakes and the resultant flakes have a glue content of the required concentration of less than 10 ppm. For removal of PVC, the protocol followed entailed a two stage process, viz. identification and then separation. For the purpose of identification the washed flakes are dipped in a concentrated solution of a derivative of n-Optyl Butane in the presence of an inhibitor. The chemical has a selective action on PVC to the exclusion of PET. Thus, when a dye was added to the solution and the washed flakes were dipped in it, the PVC absorbed the colour of the dye. There being no effect on PET flakes, it remained unchanged. The process is established at ambient temperature, wherein the flakes are slowly agitated at about 10 rpm to 20 rpm in a vessel, maintaining a residence time of 10 mins to 15 mins for complete identification. The flakes so treated are then transferred to a sorting conveyor, wherein the PVC, being in the form of dyed flakes, are easily identifiable and are picked out from the material stream. The level of PVC contamination can easily be controlled to the desired level of less than 30 ppm. EXAMPLE: Process: High agitation wash for removal of glue. 1) Reactor-1 Flakes quantity : 30 Kgs. Solution quantity : 150 Kgs Concentration of alkaline medium: 3.2% Concentration of detergent : 0.5% Temperature : 82°C Agitator speed : 600 rpm Residence time : 10 mins 2) Reactor-2 Flakes quantity : 30 Kgs. (from Reactor-1) Solution quantity : 240 Kgs Concentration of : 5% Agitator speed : 600 rpm Residence time : 4 mins Material checked for Glue Content Content of Glue : Separation of PVC 3) Reactor Flakes quantity : 20 Kgs. Solution quantity : 100 Kgs Agitator speed : 20 rpm Residence time : 15 mins The resultant material is examined visually. The PVC has a deep purple colour, which is then manually sorted out. Material checked for PVC Content Content of PVC : We Claim: 1. A method for decreasing the content of glue and PVC contaminations in recycled PET flakes comprising the steps of: washing the flakes in a bath of caustic soda with some detergent; heating an alkaline solution to a temperature of 75-95°C; subjecting the flakes and solution to agitation; treating the flakes with a solution of n-butyl pentane and subjecting the flakes thus obtained to agitation to remove the glue; washing the flakes and dipping it in a solution of n-optyl Butane; adding a dye to the said solution to identify PVC from PET flakes; Subjecting the flakes thus obtained to the step of manual sorting to remove the PVC. 2. The method as claimed in claim 1, wherein the alkaline Medium is prepared to a concentration level of 2% to 5% along with detergent soap to a concentration level of 0.5%. 3. The method as claimed in claim 1, wherein the ratio of flakes and the alkaline solution is 1:5. 4. The method as claimed in claim 1, wherein the speed of agitation is 600 to 1000 rpm and the residence time is about 6 min to 12 minutes. 5. The method as claimed in claim 1, wherein the concentration of n-butyl pentane is not definitive 3 to 8%. 6. The method as claimed in claim 5, wherein the concentration of the flake and the solution is in the ratio of 1:8. 7. The method as claimed in claim 5, wherein the speed of agitator is 600 to 1000 rpm and the residence time is 3 to 6 min. 8. The method as claimed in claim 1, wherein the flakes for the removal of PVC is slowly agitated at around 10 rpm to 20 rpm and the residence time is 10 to 15 minutes. ABSTRACT Tile: "A METHOD FOR DECREASING THE CONTENT OF GLUE AND PVC CONTAMINATIONS IN RECYCLED PET FLAKES." A method for decreasing the content of glue and PVC contaminations in recycled PET flakes comprising the steps of : washing the flakes in a bath of caustic soda with some detergent; heating an alkaline solution to a temperature of 75-95°C; subjecting the flakes and solution to agitation; treating the flakes with a solution of n-butyl pentane and subjecting the flakes thus obtained to agitation to remove the glue; washing the flakes and dipping it in a solution of n-optyl Butane; adding a dye to the said solution to identify PVC from PET flakes; subjecting the flakes thus obtained to the step of manual sorting to remove the PVC.

Documents:

01186-kol-2007-correspondence others.pdf

01186-kol-2007-description provisional.pdf

01186-kol-2007-form 1.pdf

01186-kol-2007-form 2.pdf

01186-kol-2007-form 3.pdf

1186-KOL-2007-(23-03-2012)-CORRESPONDENCE.pdf

1186-KOL-2007-CORRESPONDENCE 1.1.pdf

1186-KOL-2007-CORRESPONDENCE.pdf

1186-KOL-2007-EXAMINATION REPORT.pdf

1186-KOL-2007-FORM 18 1.1.pdf

1186-kol-2007-form 18.pdf

1186-KOL-2007-FORM 26.pdf

1186-KOL-2007-FORM 3 1.1.pdf

1186-KOL-2007-FORM 5.pdf

1186-KOL-2007-FORM 9.pdf

1186-KOL-2007-GRANTED-ABSTRACT.pdf

1186-KOL-2007-GRANTED-CLAIMS.pdf

1186-KOL-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

1186-KOL-2007-GRANTED-FORM 1.pdf

1186-KOL-2007-GRANTED-FORM 2.pdf

1186-KOL-2007-GRANTED-SPECIFICATION.pdf

1186-KOL-2007-OTHERS.pdf

1186-KOL-2007-REPLY TO EXAMINATION REPORT.pdf