|Title of Invention||
A POLYMERIC COMPOSITION SUITABLE FOR MANUFACTURING PASTEURIZABLE CONTAINERS
|Abstract||A polymeric composition suitable for manufacturing pasteurizable containers comprising, polyethylene terephthalate (PET) in the ratio of about 80 to about 95 mass % by mass of the total composition; polyethylene naphthalate (PEN) in the ratio of about 20 to about 5 mass % by mass of the total composition; tungsten trioxide in the range of 10 to 100 ppm by mass of the composition and particle size of 2 to 20 microns; and optionally a nucleating agent and a polycondensation catalyst.|
THE PATENTS ACT, 1970
(39 of 1970)
THE PATENTS RULES, 2003
(See section 10 and rule 13)
PET AND PEN/PTN CO POLYESTERS AND THEIR ALLOY/BLENDS
RESIN SUITABLE FOR MANUFACTURING PASTEURIZABLE CONTAINERS FOR PACKING JUICES, BEVERAGES, KETCHUP AND
FUTURA POLYESTERS LIMITED
an Indian Company of Paragon Condominium, 3rd floor, Pandurang Budhkar Marg, Mumbai 400 013,
THE FOLLOWING SPEC IFICATION DESCRIBES THE INVENTION.
Field of Invention:
The present invention relates to the development of a composition of a PET and PEN/PTN co polyesters and their alloy/blends resin suitable for manufacturing pasteurizable containers for packing juices, beverages, ketchup and the like.
Juices are well known in the beverage industry, such as apple, grape, tomato, and mango. Juices are typically packaged in single serving cans, in multiple serving cans, bottles, tetra packs etc. Juices are subject to spoilage and discoloration from various bacteria, fermentation by yeast, and the breakdown of cellular products, enzymes and vitamins of the fruit. While preservatives are available to slow or stop such spoilage and discoloration, they can cause a detectable change in the taste of the juice. Likewise, the consumer is more aware than ever of food additives and prefers natural preservation versus chemical preservation. Various natural ways of extending the shelf life of juices without using preservatives have been tried as described below.
Hot Filled - The finished beverage is heated to ~ 88°C and the container filled and cappet' and the contents cooled. Commonly this is applicable for beverages with pH Pasteurization - The beverage is filled into the container, capped and then pasteurized by passing through a tunnel with hot water (70 to 90°C) spray and holding at the required temperature of 60-75°C for a specified time followed by a cooling gradually to ambient temperature in a tunnel. A typical example is beer.
Aseptic Filling - The beverage particularly those with pH > 4.5 is sterilized to high temperature (120 to 140°C) for a short period of time and then rapidly cooled without the introduction of microorganisms. The process requires a "clean room" and is a more expensive process with expensive machineries.
Retort Processing - It is common for unpreserved beverages with a pH > 4.0. The already filled container is subjected to ~ 120 - 140°Cfor a specific time and cooled.
Depending on the contents and the container each one has its own merits and demerits. But it is always advisable to have a shorter heat history while filling the beverage like in pasteurization and aseptic filling. Compared to hot filling, in these two methods the thermal history is shorter as the product is immediately cooled down after pasteurization or aseptic filling and as a result these drinks lose less of their original content and taste. Also the Polyethylene Terephthalate (PET) bottles have to be heat set to withstand the high temperatures of around 85°C and also have to be specially designed with panels to prevent the distortions which happens when the hot filled bottles are cooled. A standard PET bottle cannot withstand the temperature, pressure, shrinkage and vacuum during the hot fill process. The special resins and the heat setting process of the bottles with a special design increases the price of hot fill bottles when compared to bottles made for pasteurization or aseptic filling.
Although PET is a very common material for packaging applications it will not meet the need for juice and beverage filling applications due to its low glass transition temperature Tg (75 - 78°C) limiting its usage for non hot filing and not having adequate gas barrier property.
Compared to PET, Polyethylene Naphthalate (PEN) has a higher Tg (119-124°C) ~ 40°C higher than PET, and superior barrier properties e.g., lower permeability to oxygen, 4-5 times lesser than PET, has a higher U.V. Absorption cut off and chemical resistance. PEN would be a very useful polymer for bottling applications, including hot filling of juices, but unfortunately it is not price competitive.
In order to incorporate the performance advantages of PEN without over engineering the container, blends, alloys and copolymers of PEN and PET have been made to provide a material that is cheaper than PEN but has a higher Tg and better barrier properties than PET. Copolymers of PET and PEN are designated as PETN5, PETN10 or PETN20 where 5, 10 or
20 is the % (w/w) naphthalate in the polymer. PET and PEN/PTN co-polymers are produced either with DMT or PTA as the raw material along with NDC partially substituting DMT or PTA to the required level of naphthalate in the PET and PEN/PTN co-polyester. . The co polyester can also be produced by the direct addition of PEN oligomer or polymer in the form of chips / powder or melt either after esterification or during polycondensation or just before the end of polycondensation. As PEN has a higher melting point it is recommended to add it in the form of its powder to take advantage of its faster melting and quicker reaction. Though the blends of PET and PEN are more versatile than copolymers since their melts are immiscible the blends needs to be processed under conditions of adequate transesterifications to achieve miscibility. Lack of miscibility leads to non transparent hazy molded products.
On the other hand excessive transesterification promotes randomization of PET and PEN components resulting in the material losing its blend characteristics yielding a corresponding co polymer composition product. PET and PEN co polymer compositions with ~ 85 mole% naphthalate content will undergo strain induced crystallization giving a crystalline melting point. PET and PEN compositions where the naphthalate content lies ~ between 15 and 85 mole% remain amorphous. Since our interest of the PET/PEN or PET/PTN copolyester or its alloy/blend material is in its application in transparent rigid packaging we have chosen PET - PEN/PTN copolymer with naphthalate content of 5, 10 and 20% for our studies and not the PET - PEN/PTN blends/alloys due to their time bound tranesterification phenomenon.
US 6586558, 6395865, 6194536 and 5902539 disclose processes for making PET/PEN blends for transparent articles by controlling the intrinsic viscosity (I.V.) and tranesterification by the addition of an ethylene glycol (EG) compound.
US 6414063 discloses nucleated PET/PEN blends/co polymers with PEN at > 20 mole%.
US 6031065 discloses a process of producing a copolymer of PET and PEN with emphasis on unit operations.
US 5695710 discloses a process for making transparent blow molded product made of PET and PEN copolymer of 80/20 (w/w) by transesterifying via melt extrusion with varying % transesterifications.
US 5688874 describes a process for preparing blends of PET and PEN.
US 5612423, 5594092, and 5539078 disclose processes for manufacturing PET/PEN co polyesters with naphthalate content ranging between 2 and 10 mole%.
US 5628957 describes a method of forming multilayer container consisting of a layer of PEN, copolymer or blend of PET/PEN with the PEN ratio maintained at 1 to 20% or 80 to 100%
KR 100351374, 20020012966 and 100325120 disclose PET/PEN co polyesters with 1-15 mole% or 1 -50 mole% PEN and their containers for hot fill applications.
KR 20030057797 describes PET/PEN resin composition containing 1-40 parts PEN for bottles with excellent UV light blocking.
Objects of the Present Invention:
The primary object of the present invention is to provide a co polyester resin composition with enhanced thermal stability, gas barrier property and U.V.absorption cut off.
Another object of the present invention is to provide a process for the preparation the co polyester resin composition in accordance with this invention .
Another object of the present invention is to provide a co polyester resin composition
suitable for non heat set juice and beverage containers.
One more object of the present invention is to provide a co polyester resin composition suitable for pasteurizable and aseptic filling containers.
Another object of the present invention is to provide a co polyester resin composition with enhanced barrier properties and reduce permeation of gases like oxygen, carbon dioxide and the like.and water vapor as well as retention of flavor.
Another object of the present invention is to provide a co polyester resin composition with suitable additives for extended U.V. Light stability of the contents in the containers.
Another object of the present invention is to provide a co polyester resin composition containing non heavy metals as catalysts.
Another object of the present invention is to provide a co polyester resin composition containing clear fast reheat additives to help in fast reheating of the preforms prior to stretch blow molding and getting clear, transparent and non hazy containers.
Yet another object of the present invention is to provide a co polyester resin composition containing nucleating agents like nano silica to enhance the crystallinity of the containers.
Summary of the Invention:
The present invention envisages a thermally stable co polyester resin composition with enhanced gas barrier and U.V.light stability properties. The co polyester resin composition -comprises a co polymer of Polyethylene Terephthalate (PET) and Polyethylene Naphthalate (PEN) / Polytrimethylene Naphthalte (PTN) wherein the naphthalate content varies between 1 and 20 %.
The present invention also provides a process for modification of the co polyester resin composition with appropriate additives to form amorphous PET - PEN/PTN co polyester pellets by melt polymerization. The PET - PEN/PTN co polyester resin with the desired mole% of PEN or PTN is subjected to Solid State Polymerization (SSP) to increase the I.V. and injection molded to preforms which are further stretch blown into containers having the extended gas barrier properties and U.V. light stability suitable for juice and beverage filling and fit for pasteurization and aseptic filling.
Description of the Invention:
Accordingly, the present invention provides a co polyester resin composition of PET-PEN/PTN along with heavy metal or non heavy metal catalysts, gas barrier additives, nucleating agents, U.V. light stabilizing additives and clear fast reheat additives. The additives of the present invention can be added to the co polyester during melt polymerization at different stages like esterification, prepolymerization or polycondensation. The present invention also provides a process for making the co polyester resin composition of PET with PEN/PTN either by adding the appropriate quantity of Naphthalene Dicarboxylate (NDC) or the PEN polymer along with the raw materials viz. PTA and EG or 1,3-Propylene Diol (PDO) or after the esterification. NDC addition after esterification is preferred as it retains the melt charateristics.
The PET-PEN/PTN co polyester containing the additives of the present invention can be converted into preforms by injection molding of the resin and subsequently to bottles by stretch blow molding with enhanced thermal stability, improved gas barrier properties, U.V. light stability and flavor retention.
In the present invention the co polyester resin PET with PEN/PTN is modified with nucleating agents typically but not limited to sodium acetate, sodium salicylate, sodium sorbitol, micronized sodium benzoate, potassium benzoate, talc and the like, catalysts typically but not limited to antimony trioxide, antimony acetate, manganese acetate, potassium titanium oxide oxalate, germanium dioxide and the like, and clear fast reheat
additives typically but not limited to tungsten, tungsten trioxide, tungsten carbide, molybdenum oxide and the like.
In the process of the present invention, the selected additives are added to the paste of pure terephthalic acid (PTA) and mono ethylene glycol (MEG) in the ratio of about 70:30 and the paste is charged into an esterifier. The paste also comprises a polycondensation catalyst, preferably antimony (Sb) and Titanium (Ti) based, and germanium compounds along with suitable clear fast reheat (CFRH) additives like oxides and carbides of transition metals like tungsten and molybdenum.
The paste also comprises colorants like cobalt acetate and organic toners like 8,9,10,11-tetrachloro-12H-phthaloperin-12-one (Red Toner) and l,4-bis(mesitylamino)anthraquinone (Blue Toner). Appropriate quantities of NDC along with the required quantity of manganese catalyst or the PEN or PTN polymer (PEN / PTN polymer can also be added after the PET polymerization to the melt. PEN or PTN can also be added as their corresponding monomer, prepared separately, to the PET monomer after esterification) are added either initially or after the esterification process, the product is pre-polymerized in a pre-polymerization reactor and transferred to the polycondensation reactor.
Prior to the transfer, heat stabilizers like phosphorous acid or phosphoric acid or triethyl phosphonoacetate are preferably and advatnageeously added to the prepolymer melt. After reaching the required intrinsic viscosity (I.V.) the amorphous PET-PEN/PTN chips are subjected to solid state polymerization (SSP) to increase the I.V.
In a similar manner, Polyethylene naphthalate resins (PEN), if added instead of NDC, are made by reacting NDC with monoethylene glycol (MEG), 1,3-Propylene diol (PDO). Before reaching the required IV, say 20-40 minutes before completion of polycondensation, PEN chips are added (if PEN is added instead of NDC) to the PET melt and further polymerized. After reaching the required intrinsic viscosity (I.V.) the molten polymer is extruded into amorphous PET-PEN/PTN co polyester chips and subjected to solid state polymerization
(SSP) to increase the IV. The PET-PEN/PTN co polyester SSP resin can be used for injection molding of the preforms and are then stretch blow molded to make bottles. These bottles are then characterized for their clarity, thermal stability, crystallinity, gas barrier properties, U.V. stability and the like.
In an embodiment of the present invention the PET- PEN/PTN co polyester resin composition having heavy metal or non heavy metal catalysts, nucleating agents, clear fast reheat additives, U.V.light stabilizers and the %mole ratio PEN/PTN to PET varies between 1 and 20.
In yet another embodiment of the present invention, the PET resin wherein PEN is used in place of PTN at about 0-20 % levels.
In accordance with another preferred embodiment of the present invention, in the PET-PEN/PTN co polyester resin, the nucleating agents are selected from sodium stearate, sodium benzoate, potassium stearate and benzoate, silica sol, nano clays, sorbitol based chemicals and micronized sodium or potassium benzoates and stearates and talc.
In yet another preferred embodiment of the present invention, in the PET-PEN/PTN co polyester resin the clear fast reheat additives (CFRH) are selected from oxides and carbides of transition metals like tungsten and molybdenum.
In a further preferred embodiment of the present invention, in the PET-PEN/PTN co polyester resin the base PET-PEN/PTN co polyester resin's I.V. is in the range of 0.70 -0.86 dL/g.
The invention is further explained in the form of following non limiting example, typically for a PET-PEN co polyester preparation at PET to PEN ratio of 95:5 (PETN5). However, this example should not be considered as limiting the ambit and the scope of the present invention.
9.85 kg of pure terephthalic acid and 4.23 kg of monoethylene glycol are taken in an esterification vessel, in 1:1.15 molar ratio. To this, nucleating agent, sodium salicylate 2C ppm (O.g) is added. Polymerization catalyst antimony trioxide 300 ppm as Sb (g), colorants cobalt acetate 20 ppm as Co (1.01 g), red toner 1.5 ppm (0.018 g) and blue toner 1.2 ppm (0.014 g) are further added to the above mixture. 5 % of NDC (0.50 g) is also added for insitu PEN formation. The esterification reaction is carried out at 240 - 265 °C temperature for 190 minutes. The esterified pre-polymer is transferred to the polycondensation reactor.
' Before commencing polymerization, triethyl phosphonoacetate 50 ppm as P (TEPA, 4.34 g) and CFRH additive viz. oxide of transition metal 10 ppm (0.12 g) are added. The polymerization is conducted at a temperature of 265 - 287/292°C (the former is the the final poly temperature and the latter is the peak poly temperature) under 5-15 mbar for 180 minutes. After the required torque is reached, the molten amorphous polymer PETN5 is extruded under nitrogen pressure and collected as pellets. The resulting amorphous polymer PETN5 with I.V. ~ 0.6 dL/g is solid state polymerized to I.V.~ >0.77 dL/g, made into a preform by injection molding and analyzed for their characteristics.
The quality parameters of the amorphous PETN5 chips are given in Table - 1 and SSP chips • in Table - 2 from different trials.
TABLE - 1 : PETN5 Amorphous Co Polyester Chips Properties
Properties Pilot Trial 1® Pilot Trial 2 Plant Trial 1 Plant Trial 2
I.V. dl/g 0.64 0.57 0.57 0.58
L* - as such 73.3 69.9 73.3 73.9
a *- as such -0.5 -1.4 -1.1 -1.8
b *- as such -5.7 -4.0 -5.4 -5.2
COOH No. meq/kg 23 18 24 12
DEG,wt.% 1.6 1.38 1.22 1.17
Haze, NTU 1.7 1.5 - 7.3
Tg°C 80.6 79.9 80.8 81.4
Tch°C 158.2 153.8 148 149.1
Tm°C 241.2 242.1 244.2 244.3
@- In Pilot Trial 1 PEN chips are added instead of NDC addition. The I.V.of PEN chips can be in the range of 0.40 to 0.60. The lower range is better as it disperses and mixes well in the prepolymer formed and reacts faster. Addition of PEN as a powder instead of the chips also helps in hastening the reaction.
Tg = Glass transition temperature
Teh = Exothermic crystallization temperature in the heatingcycle of DSC
Tm = Melting point in the 2nd heating cycle of DSC
TABLE - 2 : PETN SSP Co Polyester Chips Properties - From a typical Plant Trial
Properties Plant Trial Values
I.V. dl/g 0.76
COOH No. meq/kg 9
DEG, wt.% 1.20
Teh, oC 153.7
Tm, oC 242
Salient Features of this Invention:
1 The present invention deals with the PET-PEN/PTN co polyester preparation preferably through a melt polymerization route instead of the chips blending route. It has been observed that to get the same properties of the co polyester more PEN or PTN have to be used in the dry blending route in comparison with the melt polymerization route.
2 Compared to the dry blending route reaction cycle times are less in melt polymerization method.
3 The quality of the co polyester is also superior and consistent in the case of melt polymerization procedure. Dry blending of PET/PEN requires excessive heat input to melt the PEN and this results in increase of acetaldehyde and haze as well as yellowing of the co polyester resin.
4 PET-PEN/PTN co polyester preparation by melt polymerization is more economical than by the dry blending process.
5 By melt polymerization method of co polyester preparation any proportion of PET and PEN/PTN ratio can be easily achieved.
6 In contrast to dry blending lower I.V. (~ 0.4) chips can be used in melt polymerization due to its easy misicibility.
7 Due to the addition of clear FRH additive thicker wall containers are possible without losing the clarity.
8 The addition of FRH additive helps in uniform blowing of the preform to containers.
9 The presence of clear FRH additive prevents the blackish/greyish tinge normally seen with the conventional FRH additives.
10 Due to the higher melt viscosity of the present melt co polymerized PET-PEN/PTN the resin composition can also be used for containers having intricate contours by the EBM process. 10. Containers made from the co polyester resin composition of PET-PEN with 5 mole% PEN withstood tunnel pasteurization at 75°C for ten minutes.
While considerable emphasis has been placed herein on the specific structure of the preferred embodiment, it will be appreciated that many alterations can be made and that many modifications can be made in the preferred embodiment without departing from the principles of the invention. These and other changes in the preferred embodiment as well as other embodiments of the invention will be apparent to those skilled in the art from the
disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.
|Indian Patent Application Number||1457/MUM/2007|
|PG Journal Number||44/2012|
|Date of Filing||31-Jul-2007|
|Name of Patentee||FUTURA POLYESTERS LIMITED|
|Applicant Address||PARAGON CONDOMINIUM,3RD FLOOR, PANDURANG BUDHKAR MARG, MUMBAI|
|PCT International Classification Number||B32B27/36|
|PCT International Application Number||N/A|
|PCT International Filing date|