A PROCESS AND AN APPARATUS FOR MANUFACTURING BI-AXIALLY ORIENTED POLYESTER FILM FROM RPET

Abstract

The present disclosure relates to a process for producing bi-axially oriented polyester (BOPET) film from the recycled polyethylene terephthalate (RPET) granules. The process involves preparing recycled PET (RPET) granules form post-consumer recycled PET (PCR PET) by depolymerization and polycondensation followed by preparing the biaxially oriented polyethylene terephthalate (BOPET) film having recycled polyethylene terephthalate (RPET) up to 100%. The bi-axially oriented polyester film has good elongation, mechanical and/or thermal properties and are similar in quality to virgin PET films useful in high end food and pharma packaging and industrial applications.

Claims

1. A process for preparing a biaxially oriented polyethylene terephthalate (BOPET) film comprising, the steps of preparing a recycled polyethylene terephthalate (RPET) granules, comprises depolymerization by glycolysis of a pre cleaned PET products to produce monomers, polycondensation of monomers in a polycondensation reactor or an autoclave to produce recycled PET (RPET) granules. preparing the biaxially oriented polyethylene terephthalate film, comprises charging the RPET granules along with a virgin PET granules, to an extruder to obtain a molten polyethylene terephthalate, extruding the molten polyethylene terephthalate through a die, quenching the extruded polyethylene terephthalate on chilled rollers and stretching to obtain biaxially oriented polyethylene terephthalate film. characterized in that, the glycolysis reaction is conducted in an esterification reactor by addition of glycol, at a temperature of 245-255° C. and at a pressure of 0.5-1 bar, and the RPET granules are up to 100% in the mixture of the RPET and virgin PET granules, charged to the extruder.

2. The process as claimed in claim 1, wherein the biaxially oriented polyethylene terephthalate obtained has at least three layers.

3. The process as claimed in claim 1, wherein the biaxially oriented polyethylene terephthalate is an A/B/A or A/B/C configuration, the B layer comprises biaxially oriented polyethylene terephthalate film made from the recycled PET (RPET) and cap layers A and/or C, comprises biaxially oriented polyethylene terephthalate film, made from virgin PET granules, along with inorganic filler.

4. The process as claimed in claim 1, wherein the step of film preparation comprises up to 95% of the recycled PET granules.

5. The process as claimed in claim 1, wherein the step of film preparation comprises up to 90% of the recycled PET granules.

6. The process as claimed in claim 1, wherein the step of pre cleaning of PET products comprises the followings steps, primary washing of PET products by solvent to remove contamination, non PET materials such as poly propylene, poly ethylene, poly vinyl chloride. de brushing the washed PET product for removal of dust and unwanted materials, de-stoning of the PET product for removal of the stones to obtain cleaned PET products.

7. The process as claimed in claim 1, wherein the step of preparing the recycled polyethylene terephthalate (RPET) is followed by filtration for foreign particles removal and de-coloration, before the film preparation step.

8. The process as claimed in claim 1, wherein the PET products are selected from one or more films, sheets, laminate, bottles and flakes, amorphous PET (A-PET), crystalline PET (C-PET), polyester film and post-consumer recycled PET (PCR PCT).

9. The process as claimed in claim 1, wherein the autoclave temperature is 275-295° C. and the batch time is of 3-4 hrs.

10. The process as claimed in claim 1, wherein the autoclave reactor is maintained at vacuum and catalyst is added.

11. The process as claimed in claim 1, wherein the stretching involves machine direction stretching with stretch ratio of 3-3.5, and transverse direction stretching with stretch ratio of 3.8-4.2.

12. The process as claimed in claim 1, wherein the autoclave reactor is added with additives.

13. The process as claimed in claim 1, wherein the biaxially oriented polyethylene terephthalate (BOPET) is a food grade packaging film or pharma products packaging film.

14. An apparatus for producing biaxially oriented polyethylene terephthalate (BOPET) film comprises, cleaning device for pre cleaning PET products to be recycled, esterification reactor for converting a pre cleaned PET product to a monomer, autoclave reactor operated at temperature of 275-295° C. and at vacuum pressure, for polycondensation of the monomers to obtain a recycled PET granules, extruders for extruding the recycled PET granules and optionally a virgin PET granules to obtain the molten polyethylene terephthalate (PET), chilled rollers for quenching the molten PET and stretching to obtain biaxially oriented polyethylene terephthalate, characterized in that, the esterification reactor involves glycolysis reaction by addition of glycol, at a temperature of 245-255° C. and at a pressure of 0.5-1 bar, and the RPET granules are up to 100% in the mixture of the RPET and virgin PET charged to the extruder.

15. The apparatus as claimed in claim 14, wherein the cleaning apparatus comprises pre cleaning machine for washing, removing contamination and non-PET materials such as poly propylene, poly ethylene, poly vinyl chloride from the PET flakes, de brushing apparatus for removal of dust and unwanted materials, de stoning apparatus for the removal of the stones to obtain cleaned PET products. magnetic separator for removal of iron and other metal particles.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1—Illustrates a flow chart of the process according to the invention. The drawings referred to in this description are not to be understood as being drawn to scale except if specifically noted, and such drawings are only exemplary in nature.

DETAILED DESCRIPTION

[0028] While the invention is susceptible to various modifications and alternative forms, an embodiment thereof has been shown by way of example in the drawings and will be described here below. It should be understood, however that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the invention.

[0029] The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, structure or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or structure or method. In other words, one or more elements in a system or apparatus proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.

[0030] For the better understanding of this invention, reference would now be made to the embodiment illustrated in the accompanying Figures and description here below.

[0031] Furthermore, it is to be understood that the invention is not limited to the details of construction or process steps set forth in the following description. The invention is capable of other embodiments and of being practiced or being carried out in various ways.

[0032] Expressions “a”, “an”, “the”, when used to define a term, include both the plural and singular forms of the term.

[0033] One embodiment of the invention relates to a process for preparing a biaxially oriented polyethylene terephthalate (BOPET) film comprising, the steps of [0034] preparing a recycled polyethylene terephthalate (RPET) granules, comprises [0035] depolymerization by glycolysis of a pre cleaned PET products to produce monomers, [0036] polycondensation of monomers in a polycondensation reactor or an autoclave to produce recycled PET (RPET) granules. [0037] preparing the biaxially oriented polyethylene terephthalate film, comprises [0038] charging the RPET granules optionally along with a virgin PET—granules, to an extruder to obtain a molten polyethylene terephthalate, [0039] extruding the molten polyethylene terephthalate through a die, [0040] quenching the extruded polyethylene terephthalate on chilled rollers and stretching to obtain biaxially oriented polyethylene terephthalate film.
characterized in that, the glycolysis reaction is conducted in an esterification reactor by addition of glycol, at a temperature of 245-255° C. and at a pressure of 0.5-1 bar, and
the RPET granules are up to 100% in the mixture of the RPET and virgin PET granules, charged to the extruder.

[0041] Another embodiment of the invention relates to the process, wherein the biaxially oriented polyethylene terephthalate obtained has at least three layers.

[0042] Yet another embodiment of the invention relates to the process, wherein the biaxially oriented polyethylene terephthalate is an A/B/A or A/B/C configuration, the B layer comprises biaxially oriented polyethylene terephthalate film made from the recycled PET (RPET) and cap layers A and/or C, comprises contains biaxially oriented polyethylene terephthalate film, made from virgin PET granules, along with inorganic filler.

[0043] Yet another embodiment of the invention relates to the process, wherein the step of film preparation comprises up to 95% of the recycled PET granules.

[0044] Yet another embodiment of the invention relates to the process, wherein the step of film preparation comprises up to 90% of the recycled PET granules.

[0045] Yet another embodiment of the invention relates to the process, wherein the step of pre cleaning of PET products comprises the followings steps, [0046] primary washing of PET products by solvent to remove contamination, non PET metals such as poly propylene, poly ethylene, poly vinyl chloride. [0047] de brushing the washing the PET product for removal of dust and unwanted materials, [0048] de-stoning of the PET product for removal of the stones to obtain cleaned PET products.

[0049] Yet another embodiment of the invention relates to the process, wherein the step of preparing the recycled polyethylene terephthalate (RPET) is followed by filtration for foreign particles removal and di-coloration, before the film preparation step.

[0050] Yet another embodiment of the invention relates to the process, wherein the PET products are selected from one or more films, sheets, laminate, bottles and flakes, amorphous PET (A-PET), crystalline PET (C-PET), polyester film and post-consumer recycled PET (PCR PCT).

[0051] Yet another embodiment of the invention relates to the process, wherein the autoclave temperature is 275-295° C. and the batch time is of 3-4 hrs.

[0052] Yet another embodiment of the invention relates to the process, wherein the autoclave reactor is maintained at vacuum and catalyst is added.

[0053] Yet another embodiment of the invention relates to the process, wherein the stretching involves [0054] machine direction stretching with stretch ratio of 3-3.5, and [0055] transverse direction stretching with stretch ratio of 3.8-4.2.

[0056] Yet another embodiment of the invention relates to the process, wherein the autoclave reactor is added with additives.

[0057] Yet another embodiment of the invention relates to the process, wherein the biaxially oriented polyethylene terephthalate (BOPET) is a food grade packaging film or pharma products packaging film.

[0058] Another embodiment of the invention relates to an apparatus for producing biaxially oriented polyethylene terephthalate (BOPET) film comprises, [0059] cleaning device for pre cleaning PET products to be recycled, [0060] esterification reactor for converting a pre cleaned PET product to a monomer, [0061] autoclave reactor operated at temperature of 275-295° C. and at vacuum pressure, for polycondensation of the monomers to obtain a recycled PET granules, [0062] extruders for extruding the recycled PET granules and optionally a virgin PET granules to obtain the molten polyethylene terephthalate (PET), [0063] chilled rollers for quenching the molten PET and stretching to obtain biaxially oriented polyethylene terephthalate,
characterized in that, the esterification reactor involves glycolysis reaction by addition of glycol, at a temperature of 245-255° C. and at a pressure of 0.5-1 bar, and
the RPET granules are up to 100% in the mixture of the RPET and virgin PET charged to the extruder.

[0064] Yet another embodiment of the invention relates to the apparatus, wherein the cleaning apparatus comprises [0065] pre cleaning machine for washing, removing contamination and non-PET metals such as poly propylene, poly ethylene, poly vinyl chloride from the PET flakes, [0066] de brushing apparatus for removal of dust and unwanted materials, [0067] de stoning apparatus for the removal of the stones to obtain cleaned PET products. [0068] magnetic separator for removal of iron and other metal particles.

[0069] The dust is removed from RPET granules by filtration and decolourisation by using clay beds. The migration of the RPET on the film surface is prevented by filtration and de-colourisation.

[0070] The use of recycled PET in place of virgin/fresh resin results environmental impact and carbon footprint.

[0071] The present disclosure relates to a process of manufacturing bi-axially oriented polyester (BOPET) film from the Recycled Polyethylene Terephthalate (RPET) granules. Particularly, the disclosure relates to the RPET granules produced by depolymerisation of the PET bottle flakes/granules, PET film. The BOPET is manufactured with RPET as a raw material. The BOPET film of the present invention has recycled PET granules (RPET). The RPET may be up to 90% in the BOPET for food and pharma packaging application and up to 100% RPET granules applicable for industrial applications such as insulation.

[0072] The BOPET film of the present disclosure overcomes the problem of migration, on the film surface and manufactured film applicable for food packaging application, produced from up to 90% RPET granules. The RPET granules are produced by depolymerization of flakes in monomer in presence of ethylene glycol in esterified-glycolysis process and produce the granules after polycondensation. Further, the properties of granules are improved by filtration and decolourisation which prevent from the migration of the chemicals and contaminants/foreign particles.

[0073] Extruding the said molten polyester through a die and quenching the same on chilled rollers in order to obtain transparent polyester film.

[0074] PET bottle flakes charge in esterification reactor through feeding tank, under heating and in presence of Ethylene Glycol (EG) get depolymerised, form the 100% monomer batch in reactor and with time, pressure and temperature, additives are added get polymerised and produce the granules after polycondensation.

[0075] These granules go under filtration for dust removal and di-colouration for colour improvements.

RPET Granules Preparation:

[0076] PET bottled flake collected through vendors is fed into a tank through a jumbo bag. The flake then passes into feeding tank through which the flake passes to an esterification reactor maintained the pressure and temperature i.e. the PET bottle flakes are charged in esterification reactor through feeding tank, under heating.

[0077] Purified terephthalic acid (PTA) is added to flake in the esterification reactor. The reactor has an agitator that runs at high rpm during the process. The process condition for the esterification reactor is disclosed in Table 1. This reaction leads to depolymerised of PET bottle flakes and produce 100% monomer batch in the reactor. From the esterification reactor, the batch (monomer) passes to an autoclave reactor, in which polycondensation reaction takes place. The autoclave reactor is maintained at vacuum and additives is added to it. Additives are added to autoclave to prevent the colour of melt from turning yellow, under stirring of agitator. As the polycondensation reaction progresses the RPM of agitator is reduced, and the autoclave is pressurized with nitrogen to take out polymer melt. The polymer melt (RPET) is sent to cutting and drying. The RPET granules thus formed is tested for various properties namely ash content, IV, end group and haze which were found to be comparable with virgin PET.

TABLE-US-00001 TABLE 1 Process Parameter of Esterification Reactor Esterification Reactor Parameter Virgin PET R PET Temperature (° C.) 245-255 245-255 Pressure (bar) 0.5-1   0.5-1   RPM  800-1200  800-1200 Autoclave reactor temperature (° C.) 275-295 275-295 Batch time (hrs) 3-4 3-4

TABLE-US-00002 TABLE 2 PET flakes properties S No. Parameter Unit Values/Results 1 Intrinsic viscosity dl/gm 0.7-1.0 2 Melting point ° C. 240-255 3 PVC ppm <50 4 Moisture %  <1 5 Bulk density Kg/m3 250-350 6 Wrong colors ppm <50 7 Other contamination ppm <20 8 Al/metal ppm <25 9 Paper/lable/floatable/PE/PP ppm <20

Filtration and De-Coloration:

[0078] A filter used on the process to remove any impurities and ensure consistently high quality RPET granules. It improves the granules quality and improved the productivity.

[0079] Clay is used extensively for decolourisation purposes in the production of RPET granules. Clay used in a granular form in a fixed bed adsorber. The RPET granules are passed through the clay in the fixed bed absorber, which absorbs the colourants from the RPET granules. Surface area and good porosity of clay material make them useful adsorbent. The clay used in the process is Mineral clay like Bentonite which has good surface area and porosity.

BOPET Film Preparation:

[0080] The present disclosure relates to a process for preparing the bi-axially oriented polyester film, said process comprising the steps of charging of RPET granules produced, in main extruder and virgin granules in side extruder to obtain molten polyester, extruding, quenching and stretching the film to obtain the BOPET film. The film comprises three layers (e.g. an A/B/A or A/B/C) configuration. One and/or two layers in films comprise the silica.

[0081] The bi-axially oriented polyester film in particular include a multilayer structure such as A/B/A and/or A/B/C wherein the B-layer (core-layer) comprises polyethylene terephthalate layers of the film and contains recycled PET (RPET) and cap layers (A and/or C) comprises polyethylene terephthalate layers of the film and contains virgin PET granules with inorganic filler.

[0082] In the present disclosure, up to 90% RPET or even 100% uses to manufacturer the film applicable for food and pharma packaging application.

[0083] Presently disclosed bi-axially oriented polyester film is made of using 100% RPET granules i.e. core as well as cap layer made of RPET granules, applicable for the industrial applications.

TABLE-US-00003 TABLE 3 Film Processing Parameter MDO TDO TDO Stretching MDO stretching crystallizing TDO Temperature Draw Temperature Temperature Draw Film Grade (° C.) Ratio (° C.) (° C.) Ratio RPET Film 80-85 3-3.5 90-100 225-240 3.8-4.2 (A/B/A Layer)

[0084] In one embodiment of the invention the film comprises three layers (e.g. an A/B/A or A/B/C) configuration. One and/or two layers in films comprise the silica.

[0085] The bi-axially oriented polyester film in particular include a multilayer structure such as A/B/A and/or A/B/C wherein the B-layer (core-layer) comprises polyethylene terephthalate layers of the film and contains recycled PET (RPET) and cap layers (A and/or C) comprises polyethylene terephthalate layers of the film and contains virgin PET granules with inorganic filler.

[0086] In the present invention, up to 90% RPET is used to manufacturer the film applicable for food and pharma packaging application.

[0087] Presently disclosed bi-axially oriented polyester film is made of using 100% RPET granules i.e. core as well as cap layer made of RPET granules, applicable for the industrial applications.

Environmental Benefits from Producing RPET

[0088] Producing the RPET film from the PET post consumer waste has the various environment benefits compare to virgin PET film. It reducing the carbon footprint and reducing the energy consumption in manufacturing of film, also reducing the usage of fossil feedstocks. It has the Life cycle analysis (LCA) advantage over virgin PET film, recycling 1 tons of plastic bottles saves 1.5 tonnes of CO.sub.2 in reference to landfill or incineration. It also reduces the green house gases (GHG) and energy use compare to virgin PET film. Land and ocean pollution

[0089] The said bi-axially oriented polyester film has good elongation, mechanical and thermal properties and useful in high end food and pharma packaging and industrial applications.

[0090] The invention itself, together with further features and attended advantages, will become apparent from consideration of the following detailed description, taken in conjunction with the accompanying drawings. One or more embodiments of the present invention are now described, by way of example.

EXAMPLES

Examples 1

[0091] Various batches of RPET produced by the method of the present disclosure are analyzed for the properties like IV, COOH, Ash and DEG. The properties of RPET are comparable to the virgin PET. Hence, up to 90% RPET can be used to manufacture the film applicable for food or pharma packaging application.

TABLE-US-00004 TABLE 4 Test Results Virgin RPET IV COOH ASH DEG PET IV COOH ASH DEG 1 0.643 23.64 0.057 1.691 1 0.631 27.6 0.006 1.094 2 0.643 25.5 0.022 1.924 2 0.64 26.5 0.016 1.16 3 0.646 24.74 0.021 1.172 3 0.628 31.6 0.024 1.04 4 0.642 23.93 0.014 1.72 4 0.623 28.31 0.01 1.208 5 0.639 23.5 0.018 1.827 5 0.626 32.58 0.022 1.036 Average 0.6426 24.262 0.0264 1.6668 Average 0.6296 29.318 0.0156 1.1076

Example 2

[0092] Comparison between virgin and RPET film properties:

[0093] The biaxially oriented PET film produced by the process of the invention (involving recycled PET) is compared with the biaxially oriented PET film produced from the virgin PET. Mechanical properties like tensile strength, elongation at break of rPET films are similar to virgin PET film. Similarly optical, surface properties and performances are also comparable with virgin PET film. The results are summarized in the below table.

TABLE-US-00005 TABLE 5 Result Comparation Test Standard Properties Method Unit PET 70% rPET 90% rPET Nominal Standard Micron   12 + 0.5   12 + 0.5   12 + 0.5 Thickness Method Gauge 48 + 2 48 + 2 48 + 2 Yield Standard m2/kg 60 + 5 60 + 5 60 + 5 Method in2/lb 42000 42000 42000 Tensile ASTM D- kg/cm2 2200 + 500 2200 + 500 2200 + 500 Strength-MD 882 kpsi 31.3 31.2 31.2 Tensile ASTM D- kg/cm2 2300 + 500 2300 + 500 2300 + 500 Strength-TD 882 kpsi 32.7 32.5 32.5 Elongation at ASTM D- % 130 + 25 130 + 25 130 + 25 Break-MD 882 Elongation at ASTM D- % 125 + 25 125 + 25 125 + 25 Break-TD 882 Heat Shrinkage (At 150 Degree C. for 30 mins) MD ASTM D- %    2 + 0.5    2 + 0.5    2 + 0.5 1204 TD ASTM D- %  0.2 + 0.5  0.2 + 0.5  0.2 + 0.5 1204 Co-efficient of Friction, A/B Static ASTM D- 0.52 + 0.5 0.52 + 0.5 0.52 + 0.5 1894 Dynamic ASTM D- 0.42 + 0.5 0.42 + 0.5 0.42 + 0.5 1894 Surface Tension Plain Side ASTM D- 44 + 4 44 + 4 44 + 4 2578 Corona Side ASTM D- 56 + 4 56 + 4 56 + 4 2578 Optical Properties Haze ASTM D- %  2.3 + 0.5  2.3 + 0.5  2.3 + 0.5 1003

[0094] Mechanical properties like tensile strength, elongation at break of RPET films are similar to virgin PET film. Similarly, optical, surface properties and performances are also comparable with virgin PET film. Hence, the process of the present invention makes the usage of RPET up to 90% to produce a food grade biaxially oriented PET.

Advantages:

[0095] The BOPET disclosed in the present disclosure provide the following advantages: [0096] The BOPET film of present disclosure meets the requirement of various food packaging compliance/standards like food and drug administration (FDA) and European food safety authority (EFSA). [0097] Upto 100% RPET may be used in the film manufacturing. [0098] No issue of the migration of the contaminants/dust on the film surface. [0099] Remove the impurities by filtration and de-colouration by clay beds. [0100] Uses more recycled PET and less or no virgin PET. [0101] Environment friendly. [0102] Economical process.