Title of Invention

A PROCESS FOR RECYCLING CONSUMED POLYETHYLENE TEREPHTHALATE (PET) AND PREPARING AN UNSATURATED POLYESTERIMIDE COMPOSITE THEREOF

Abstract

A process for recycling consumed polyethylene terephthalate (PET). Used PET is water washed, dried, depolymerised using tris-2-hydroxyethyl isocyanurate (THEIC) and then repolymerised using propylene glycol, ethylene glycol, maleic anhydride or fumaric acid or combinations thereof to obtain unsaturated polyester resins. If desired, the unsaturated polyester resins are further blended with a filler, reactive diluent and compatibilizing agent and optionally, additives, to form a viscous mass which is cured in the presence of methyl ethyl ketone peroxide(MEKP) at room temperature to obtain an unsaturated polyesterimide composite for electrical encapsulation or insulation.

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 OF 1970) As amended by the Patents (Amendment) Act, 2005 & The Patents Rules, 2003 As amended by the Patents (Amendment) Rules, 2006 COMPLETE SPECIFICATION (See section 10 and rule 13) TITLE OF THE INVENTION A process for recycling consumed polyethylene terephthalate (PET) and preparing an unsaturated polyesterimide composite thereof APPLICANTS Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company INVENTORS Jaiswal Rajendra and Lokesh Kisan Chaudhari, both of Crompton Greaves Ltd, Advanced Materia! & Process Technology Centre, CG Global R&D Centre, Kanjur Marg (East), Mumbai 400042, Maharashtra, India, both Indian nationals PREAMBLE TO THE DESCRIPTION The following specification particularly describes the nature of this invention and the manner in which it is to be performed: FIELD OF THE INVENTION The invention relates to a process for recycling consumed polyethylene terephthalate (PET) and preparing an unsaturated polyesterimide composite thereof. BACKGROUND OF THE INVENTION Polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) have a wide range of applications in single use and multiple use products such as containers like food and beverage containers, and especially carbonated drink containers, photographic films, magnetic tapes or packaging materials. They are capable of being thermoformed or blow molded. They are also used for encapsulation of electrical equipment like dry type transformers, current transformers or other electrical devices. In an effort to conserve resources, several methods are being used for recycling polyesters. Some of the methods involve blending virgin polyester with consumed polyesters. However, a major drawback of these methods is that many constituents, such as colorants and catalyst metals present in post-consumer polyesters, remain unremoved. Hence desired levels of purity of the recycled polyester may not be achieved. Also the use of virgin polyesters makes these methods expensive. Other methods of recycling consumed polyesters involve depolymerization of the polyester, i.e. breaking the ester bond and reducing the polyester polymer to its monomer components and re-polymerising these monomers to obtain polyesters. US5413681 discloses a process for the neutral hydrolysis of polyethylene terephthalate and the purification of its major constituent monomers, as well as methods for the isolation of ethylene glycol and 2 3 1 MAR 2009 terephthalic acid. US5051528 discloses a method of recovering ethylene glycol and dimethyl terephthalate from scrap polyethylene terephthalate resins by dissolving the scrap in oligomers of the same monomers and passing methanol through the solution. Depolymerization of post-consumer PET into its monomeric components offers more promise since the monomers can be purified by techniques well known in the art such as distillation, crystallization and filtration after which the monomers can be fed into a polymer production process to yield an electrical grade polymer after curing the polymer at high temperatures. However, the cost involved in purification of the recycled monomers may make them more expensive than virgin raw materials. Also, curing the polymer at high temperatures is expensive and energy-consuming. OBJECTS OF THE INVENTION An object of the invention is to provide an economical process for recycling consumed polyethylene terephthalate (PET) and preparing thereof an unsaturated polyesterimide composite for electrical encapsulation or impregnation. Another object of the invention is to provide a process for recycling consumed polyethylene terephthalate (PET) and preparing thereof an unsaturated polyesterimide composite which is easy to carry out and does not require virgin raw materials/polyesters. Another object of the invention is to provide an unsaturated polyesterimide composite for electrical encapsulation or impregnation which is curable at room temperature. 3 31 MAR 2009 Another object of the invention is to provide electrical equipments encapsulated or impregnated with the unsaturated polyesterimide composite. DETAILED DESCRIPTION OF THE INVENTION According to the invention there is provided a process for recycling consumed polyethylene terephthalate (PET) to obtain unsaturated polyesterimide resin, the process comprising: (a) water washing the consumed PET and drying the same at 100 to 120°C; (b) depolymerising the dried PET by reacting it with tris-2-hydroxyethyl isocyanurate (THEIC) in the presence of a catalyst at 150 to 200°C to form a viscous liquid comprising monomers of the depolymerised PET; and (c) repolymerising the monomers in the viscous liquid by reacting them with tetrahydrophthalic anhydride (THPA) or maleic anhydride or fumaric acid or combinations thereof in the presence of a catalyst at 150 to 210°C. According to the invention there is also provided an unsaturated polyesterimide resin prepared by the above process. According to the invention there is also provided a process for preparing an unsaturated polyesterimide composite for electrical encapsulation or impregnation, the process comprising: 4 3 1 MAR 2009 (a) water washing the consumed PET and drying the same at 100 to 120°C; (b) depolymerising the dried PET by reacting it with tris-2-hydroxyethyl isocyanurate (THEIC) in the presence of a catalyst at 150 to 200°C to form a viscous liquid comprising monomers of the depolymerised PET; (c) repolymerising the monomers in the viscous liquid by reacting them with tetrahydrophthalic anhydride (THPA) or maleic anhydride or fumaric acid or combinations thereof in the presence of a catalyst at 150 to 210°C to obtain unsaturated polyesterimide resin; (d) blending the unsaturated polyesterimide resin with a filler, reactive diluent and compatibilizing agent and, optionally, additives to yield a polyesterimide composite; and (e) curing the polyesterimide composite in the presence of methyl ethyl ketone peroxide (MEKP) at room temperature. The used PET may be cut into smaller pieces before water washing it but this is optional and depends upon the size and source of the used PET article. Preferably the filler used in step (d) is silica powder. Preferably the reactive diluent used in step (d) is styrene. Preferably, the compatibilizing agent used in step (d) is silane. Preferably, the additives used in step (d) include coloring agents like titanium dioxide, flame retardants like aluminium trihydrate or fillers like silica or combinations thereof. The catalyst used in the above processes may be dibutyl tin oxide or zinc acetate. 3 1 MAR 2009 According to the invention there is also provided an unsaturated polyesterimide composite for electrical encapsulation or impregnation prepared by the above process. The invention also provides electrical equipments encapsulated or impregnated with the above unsaturated polyesterimide composite. The above process for recycling consumed PET to obtain a modified unsaturated polyester namely polyesterimide involves depolymerization of the consumed PET by alcoholysis. As the above process does not involve the use of virgin polyesters, it is far more economical. Also, as curing of the polyesterimide composite is carried out at room temperature, the above process is energy-saving, involves simple molding and is therefore less expensive as compared to conventional processes for curing requiring high temperatures. Also, the polyesterimide composite obtained by the above process is freed from contaminants during the water washing step and is fairly pure without requiring the use of sophisticated and expensive equipment for purification. It shows good electrical resistance and heat resistance and can be used as an insulating material and even for encapsulation of electrical equipment like dry type transformers, current transformers or other electrical devices. The polyesterimide composite of this invention also shows excellent resistance to heat shock. This invention thus provides an economical process of recycling consumed PET to obtain unsaturated polyesterimide resin and preparing an electrical grade polyesterimide composite thereof The following example is illustrative of the invention: 6 31 MAR 2009 Example 1; 68.47gm of consumed polyethylene terephthalate (PET) was cut into small pieces. The consumed PET was then water washed and dried in an air oven at 120°C for 30 minutes. The dried PET was depolymerised by reacting with 90.07gm tris-2-hydroxyethyl isocyanurate (THEIC) and 0.15gm zinc acetate catalyst at 150 to 200°C for 1 to 3 hours to yield a viscous fluid comprising monomers of the depolymerised PET which was further repolymerised by reacting with 38.46gm maleic anhydride at 150 to 210°C to give unsaturated polyestenmide resin. Then, 1.2% by weight of styrene, 0.24% by weight of silane and 17.5% by weight of the unsaturated polyesterimide resin were blended with 68.35% by weight of silica powder, 1.6% by weight of coloring agent titanium dioxide and 10.4% by weight of flame retardant aluminium trihydrate to yield a viscous mass comprising the polyesterimide composite. 2.1% by weight of methyl ethyl ketone peroxide (MEKP) was then added to the viscous mass which was ultimately poured into a mold for casting. Curing was carried out for 3 to 4 hours at room temperature followed by de-molding. The composite was then kept for 24 hours at room temperature. After the polyesterimide composite was cured, it displayed excellent electrical resistance and heat resistance. The above example is illustrative only and is not limiting. The present invention is defined by the claims which follow. 31 MAR 2009 We claim: 1. A process for recycling consumed polyethylene terephthalate (PET) to obtain unsaturated polyesterimide resin, the process comprising: (a) water washing the consumed PET and drying the same at 100 to 120°C; (b) depolymerising the dried PET by reacting it with tris-2-hydroxyethyl isocyanurate (THEIC) in the presence of a catalyst at 150 to 200°C to form a viscous liquid comprising monomers of the depolymerised PET; and (c) repolymerising the monomers in the viscous liquid by reacting them with tetrahydrophthalic anhydride (THPA) or maleic anhydride or fumaric acid or combinations thereof in the presence of a catalyst at 150 to 210°C. 2. Unsaturated polyesterimide resin prepared by the process as claimed in claim 1. 3. A process for preparing an unsaturated polyesterimide composite for electrical encapsulation or impregnation, the process comprising: (a) water washing the consumed PET and drying the same at 100 to 120°C; (b) depolymerising the dried PET by reacting it with tris-2-hydroxyethyl isocyanurate (THEIC) in the presence of a catalyst at 150 to 200°C to form a viscous liquid comprising monomers of the depolymerised PET; (c) repolymerising the monomers in the viscous liquid by reacting them with tetrahydrophthalic anhydride (THPA) or maleic anhydride or fumaric acid 8 31 MAR 2009 or combinations thereof in the presence of a catalyst at 150 to 210°C to obtain unsaturated polyesterimide resin; (d) blending the unsaturated polyesterimide resin with a filler, reactive diluent and compatibilizing agent and, optionally, additives to yield a polyesterimide composite; and (e) curing the polyesterimide composite in the presence of methyl ethyl ketone peroxide (MEKP) at room temperature. 4. The process as claimed in claim 3 wherein, the filler used in step (d) is silica powder. 5. The process as claimed in claim 3 or 4 wherein, the reactive diluent used in step (d) is styrene. 6. The process as claimed in any one of claims 3 to 5 wherein, the compatibilizing agent used in step (d) is silane. 7. The process as claimed in any one of claims 3 to 6 wherein, the additives include flame retardants like aluminium trihydrate, coloring agents like titanium dioxide and combinations thereof. 8. An unsaturated polyesterimide composite for electrical encapsulation or impregnation prepared by the process as claimed in any one of claims 3 to 7. 9 31 MAR 2009 9. Electrical equipments encapsulated or impregnated with the unsaturated polyesterimide composite as claimed in claim 8. Dated this 31st day of March 2009 (Ivan Bernard Fuller) ofKhaitan&Co Agent for the Applicants 3 1 MAR 2009 10

Documents:

851-mum-2009-abstract.doc

851-mum-2009-abstract.pdf

851-MUM-2009-CLAIMS(AMENDED)-(26-12-2013).pdf

851-MUM-2009-CLAIMS(MARKED COPY)-(26-12-2013).pdf

851-mum-2009-claims.doc

851-mum-2009-claims.pdf

851-MUM-2009-CORRESPONDENCE(11-10-2010).pdf

851-MUM-2009-CORRESPONDENCE(22-6-2009).pdf

851-MUM-2009-CORRESPONDENCE(28-12-2010).pdf

851-MUM-2009-CORRESPONDENCE(IPO)-(10-9-2009).pdf

851-mum-2009-correspondence.pdf

851-mum-2009-description(complete).doc

851-mum-2009-description(complete).pdf

851-MUM-2009-FORM 1(22-6-2009).pdf

851-mum-2009-form 1.pdf

851-mum-2009-form 13(11-10-2010).pdf

851-MUM-2009-FORM 18(11-10-2010).pdf

851-mum-2009-form 2(title page).pdf

851-mum-2009-form 2.doc

851-mum-2009-form 2.pdf

851-MUM-2009-FORM 26(11-10-2010).pdf

851-mum-2009-form 26.pdf

851-mum-2009-form 3.pdf

851-MUM-2009-REPLY TO EXAMINATION REPORT(26-12-2013).pdf