WO2025188873A1

WO2025188873A1 - Polyester composition for extrusion blow molded containers containing post-consumer polyester and process for its preparation

Info

Publication number: WO2025188873A1
Application number: PCT/US2025/018539
Authority: WO
Inventors: Xinfei YU
Original assignee: Auriga Polymers Inc
Current assignee: Auriga Polymers Inc
Priority date: 2024-03-06
Filing date: 2025-03-05
Publication date: 2025-09-12
Anticipated expiration: 2026-09-06
Also published as: WO2025188873A8

Abstract

A copolyester for an extrusion blow molded container that includes from about 60 wt.% to about 90 wt.% copolyester, including:(i) a diacid component comprising 95 to 100 mole % of dicarboxylic acid residues based on the total mole % of dicarboxylic acid residues in the polyester compositions; (ii) a glycol component comprising 90 to 100 mole % of glycol residues based on the total mole percent of glycol residues in the polyester compositions; (iii) optionally a branching comonomer; and (iv)from about 10 wt% to about 40 wt. % recycled polyethylene terephthalate (rPET). The container has a drop height of more than 160 cm when tested according to ASTM D 2463-95, procedure B, Bruceton Staircase Method, after two weeks a % haze of less than 3%.

Description

POLYESTER COMPOSITION FOR EXTRUSION BLOW MOLDED CONTAINERS CONTAINING POST-CONSUMER POLYESTER AND PROCESS FOR ITS PREPARATION

FIELD OF THE INVENTION

This invention relates to polyester polymers, and more particular to polyethylene terephthalate copolyesters for transparent extrusion blow molded containers that contain post-consumer polyester.

BACKGROUND OF THE INVENTION

Aromatic polyesters generally are semi-crystalline and have low melt strength. Containers made from polyethylene terephthalate (PET), with minor amounts of a modifying comonomer, by the injection stretch molding process (ISBM) are the most common transparent container on the market. However, the ISBM process is limited to uniform shapes and cannot produce bottles with a handle. Handles are a desirable feature for larger bottles and containers to facilitate handling by the consumer. Large bottles and containers with handles can be produced by the extrusion blow molding (EBM) process.

A typical EBM process involves: a) melting the resin in an extruder b) extruding the molten resin through a die to form a tube of molten polymer (a parison) c) clamping a mold having the desired finished shape around the parison d) blowing air into the parison, causing the extrudate to stretch and expand to fill the mold e) cooling the molded container f) ejecting the container from the mold and g) removing excess plastic (flash / flashing) from the container.

The hot parison that is extruded in this process often must hang for several seconds under its own weight prior to the mold being clamped around it. During this time, the extrudate must possess high melt strength — a feature that enables the material to resist stretching, flowing, and sagging that would cause uneven distribution in the parison and thinning of the parison walls. The sag of the extruded parison is directly related to the weight of the parison, whereby larger and heavier parisons will have a greater tendency to sag. Melt strength is directly related to the polyester resin's viscosity, under zero shear rate, and temperature when the molten extrudate exits the die. However, a resin with high melt strength, or high melt viscosity at zero shear rate, is too viscous to be extruded in the extruder and pumped through the die without using high temperatures which cause the polymer to degrade and lose its melt viscosity. Therefore, an optimal-polyester resin, tailored for EBM end uses, must have a rheology such that the viscosity at the shear rates associated with the extrusion process, generally 100 to 1000 s’¹, is lower than the viscosity at zero shear rate (i.e. it exhibits shear thinning).

During the EBM process, the molten polyester cannot thermally crystallize on cooling; otherwise, a cloudy container is produced. Unlike the ISBM process, the EBM process produces waste from the flash that has to be cut off the molded container (e.g. clamped sites). This waste (or recycled material) from the EBM process must be ground and blended with virgin resin and dried prior to re-extrusion. This waste (regrind) usually comprises about 40-50% of the feedstock in the EBM manufacturing process.

Prior art has met these requirements for extrusion blow molding by using comonomers such as isophthalic acid (IPA) and 1 ,4-cyclohexanedimethanol (CHDM) in order to reduce the thermal crystallization rate (Modern Polyesters: Chemistry’ and Technology of Polyesters and Copolyesters 2003, 246-247). Amorphous copolyesters using CHDM as a comonomer for EBM have been disclosed, for example in US 4,983,711 ; 6,740,377; 7,025,925; 7,026,027; 7,915,374; 8,431,068; 8,890,398; and 2011/0081510. Amorphous copolyesters using IPA as a comonomer have been disclosed, for example in US 4,182,841.

Alternatively high melt strength copolyester resins with an ultra-high molecular weight (IV > 1.1 dl/g) that contain a low amount of IPA or CHDM can be used to provide the necessary melt strength as they exhibit some degree of shear thinning (US 9,399,700). These ultra-high IV polyester resins have to be processed at higher temperatures which cause the resin to thermally degrade giving not only an increased yellowness in the container but a narrower EBM processing window. Decreasing the temperature leads to melt fracture and a marked increase in the pressure required from the extruder to feed molten polymer to the die. In addition these tough resins are more difficult to cut and to cleanly remove flash from the finished container.

Higher melt strengths at a zero shear rate with shear thinning that reduce the melt viscosity at higher shear rates have been achieved by the use of branching comonomers in copolyesters containing CHDM or IPA as modifying comonomers. Typical branching comonomers such as trimellitic anhydride (TMA) and pentaerythritol (PENTA) were disclosed in US 4,132,707 and 4,999,388. To date, the majority of copolyester formulations designed for EBM containers have been essentially amorphous, with the use of branching comonomers in order to achieve the proper balance of both processing as well as good container appearance and performance. Recent legislation in Europe and the USA requires single use articles such as bottles and other containers to contain at least 25% of post-consumer polyester resin (PCR), increasing over time to at least 50% PCR. Typically used polyester bottles, made from an ISBM process, are collected granulated, washed, and sorted into clean clear polyester flakes (rPET). This rPET has a low IV in the range of 0.7 to 0.8 dL/g. The rPET flake can be melted, filtered and extruded into pellets that are subsequently solid state polymerized to the IV range of 0.74 to 0.85 dL/g required for new ISBM bottles and containers. This range is too low to be used as a feedstock for EBM bottles.

W02023/017038 discloses a process in which the rPET flakes are solid state polymerized to the high TV range of 0.9 to 1.4 dL/g required for EBM processes. US2023/0182365 discloses a process in which the rPET flakes are reactively extruded with chain extenders or chain branchers to increase the molecular weight prior to a final solid state polymerization process. US 11,254,797 discloses a process in which the rPET is extruded in the presence of water to reduce its molecular weight prior to solid state polymerization.

These processes to convert rPET flakes to the IV range required for the EBM process, which are subsequently mixed with virgin EBM PET resins, add an additional melt step to the rPET which increases the thermal degradation and color of the resultant product. They also cannot adjust the resin manufacturing process to accommodate the variability in the various types of rPET in the market. There is a need for a process in which rPET can be directly polymerized with virgin PET to produce EBM resins containing PCR content of varying types.

SUMMARY OF INVENTION

In the broadest sense, the present invention relates to a process to manufacture polyester resin for extrusion blow molded bottles comprising at least 25% of PCR content.

In the broadest sense, the present invention relates to the process of preparing EBM bottles from this composition.

In the broadest sense, the present invention relates to the EBM containers made from this composition. DESCRIPTION OF THE INVENTION

The ranges set forth herein include both numbers at the end of each range and any conceivable number there between, as that is the very definition of a range.

Polyester EBM resins are generally prepared by the addition of comonomers to retard the crystallization rate of the polyester resin together with a multifunctional branching comonomer to increase the melt strength and provide the resin with a shear thinning rheological behavior.

The polyester compositions suitable for use in this invention typically comprise:

(a) from about 40 wt.% to about 90 wt.% copolyester comprising

(i) a diacid component comprising 95 to 100 mole % of di carboxylic acid residues based on the total mole % of dicarboxylic acid residues in the polyester compositions, and

(ii) a glycol component comprising 90 to 100 mole % of glycol residues based on the total mole percent of glycol residues in the polyester compositions, and

(iii) optionally a branching comonomer and

(b) from about 10 wt% to about 60 wt. % recycled polyethylene terephthalate (rPET).

The di carboxylic acid residues may comprise terephthalic acid, naphthalene dicarboxylic acids or mixtures thereof. The glycol residues comprise ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol, branched aliphatic glycols or mixtures thereof. The copolyester contains from about 20 wt. % to about 50 wt. % recycled polyethylene terephthalate (rPET) and an intrinsic viscosity of at least 0.9 dL/g. The di carboxylic acid component may comprise up to 5 mole % of one or more modifying aromatic dicarboxylic acids chosen from 4,4'-biphenyldicarboxylic acid, 1,4- naphthalene dicarboxylic acid, 1,5- naphthalene dicarboxylic acid, 2,6- naphthalene dicarboxylic acid, 2,7-naphthalenedicarboxylic acid, trans-4,4'-stilbenedicarboxylic acid, heterocyclic dicarboxylic acid and esters thereof. At least one additive can be added to the copolyester chosen from colorants, toners, dyes, mold release agents, flame retardants, plasticizers, stabilizers, impact modifiers, or a mixture thereof. The copolyester may also comprise up to 5 mole % of one or more aliphatic dicarboxylic acids chosen from malonic, succinic, glutaric, adipic, pimelic, suberic, octanoic, azelaic, sebacic, dodecanedioic-dicarboxylic acids, diethyl-di-n-propyl malonate, dimethyl benzylmalonate, 2,2-dimethyl-malonic acid and 2,3-dimethyl glutaric acid.

An extrusion blow molded process for forming a container may typically comprise:

(1) melting a resin, comprising:

(i) from about 40 wt.% to about 90 wt.% copolyester, comprising

(a) a diacid component comprising 95 to 100 mole % of dicarboxylic acid residues based on the total mole % of dicarboxylic acid residues in the polyester compositions, and

(b) a glycol component comprising 90 to 100 mole % of glycol residues based on the total mole percent of glycol residues in the polyester compositions, and

(c) optionally a branching comonomer, and

(ii) from about 10 wt. % to about 60 wt. % recycled polyethylene terephthalate (rPET);

(2) forming a parison;

(3) blowing the parison into the shape of the container; and

(4) removing scrap from the container.

The process may further comprise grinding the scrap from the container and then mixing with the resin in step (a). The container may include, but is not limited to, bottles, bags, vials, tubes, and jars. The melting point of the resin is between 235°C to 255°C. The dicarboxylic acid residues comprise terephthalic acid, naphthalene dicarboxylic acids or mixtures thereof, and the glycol residues comprise ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol, branched aliphatic glycols or mixtures thereof. The copolyester contains from about 20 wt. % to about 50 wt. % recycled polyethylene terephthalate (rPET), and an intrinsic viscosity of at least 0.9 dL/g. The dicarboxylic acid component may comprise up to 5 mole % of one or more modifying aromatic di carboxylic acids chosen from 4,4'-biphenyldicarboxylic acid, 1,4- naphthalene dicarboxylic acid, 1,5- naphthalene dicarboxylic acid, 2,6- naphthalene dicarboxylic acid, 2,7-naphthalenedicarboxylic acid, trans-4,4'-stilbenedicarboxylic acid, heterocyclic dicarboxylic acid and esters thereof. At least one additive can be added to the copolyester chosen from colorants, toners, dyes, mold release agents, flame retardants, plasticizers, stabilizers, impact modifiers, or a mixture thereof. The copolyester may also comprise up to 5 mole % of one or more aliphatic dicarboxylic acids chosen from malonic, succinic, glutaric, adipic, pimelic, suberic, octanoic, azelaic, sebacic, dodecanedioic-dicarboxylic acids, diethyl-di-n-propyl malonate, dimethyl benzylmalonate, 2,2-dimethyl-malonic acid and 2,3-dimethyl glutaric acid. The container color is provided in Table 2, and the bottle drop performance is provided in Table 3.

An extrusion blow molded container comprising a copolyester may comprise:

(a) from about 40 wt.% to about 90 wt.% copolyester comprising

(iii) optionally a branching comonomer, and

(b) from about 10 wt. % to about 60 wt. % recycled polyethylene terephthalate (rPET).

The dicarboxylic acid residues may comprise terephthalic acid, naphthalene dicarboxylic acids or mixtures thereof. The glycol residues comprise ethylene glycol, di ethylene glycol, 1,4-cyclohexanedimethanol, branched aliphatic glycols or mixtures thereof. The copolyester contains from about 20 wt. % to about 50 wt. % recycled polyethylene terephthalate (rPET) and an intrinsic viscosity of at least 0.9 dL/g. The di carboxylic acid component may comprise up to 5 mole % of one or more modifying aromatic dicarboxylic acids chosen from 4,4'-biphenyldicarboxylic acid, 1,4- naphthalene di carboxylic acid, 1,5- naphthalene dicarboxylic acid, 2,6- naphthalene dicarboxylic acid, 2,7-naphthalenedicarboxylic acid, trans-4,4'-stilbenedicarboxylic acid, heterocyclic dicarboxylic acid and esters thereof. At least one additive can be added to the copolyester chosen from colorants, toners, dyes, mold release agents, flame retardants, plasticizers, stabilizers, impact modifiers, or a mixture thereof. The copolyester may also comprise up to 5 mole % of one or more aliphatic dicarboxylic acids chosen from malonic, succinic, glutaric, adipic, pimelic, suberic, octanoic, azelaic, sebacic, dodecanedioic-dicarboxylic acids, diethyl-di-n-propyl malonate, dimethyl benzylmalonate, 2,2-dimethyl-malonic acid and 2,3-dimethyl glutaric acid.

The container has a drop height of more than 160 cm when tested according to ASTM D 2463-95, procedure B, Bruceton Staircase Method, after two weeks, and has a % haze of less than 3%. The container may include, but is not limited to, bottles, bags, vials, tubes, and jars. The container color is provided in Table 2, and the bottle drop performance is provided in Table 3.

A method for manufacturing copolyester polymer for extrusion blow molded containers containing recycled polyethylene terephthalate (rPET) in a continuous polymerization unit comprising the following steps: a) feeding said rPET to an extruder, and b) melting said rPET in said extruder, and c) extruding said molten rPET into a molten stream containing oligomers from said continuous polymerization unit creating a prepolymer, and d) polymerizing said prepolymer thereby producing copolyester containing rPET, and wherein the color of the said copolyester containing rPET is adjusted during said polymerization step (d) to match the color of the copolyester manufactured without said rPET.

The container may include, but is not limited to, bottles, bags, vials, tubes, and jars. The container color is provided in Table 2, and the bottle drop performance is provided in Table 3. The term "polyester", as used herein, is intended to include "copolyesters" and is understood to mean a synthetic polymer prepared by the reaction of one or more difunctional carboxylic acids and/or multifunctional carboxylic acids with one or more difunctional hydroxyl compounds and/or multifunctional hydroxyl compounds, for example, branching comonomers. Typically, the difunctional carboxylic acid can be a dicarboxylic acid and the difunctional hydroxyl compound can be a dihydric alcohol such as, for example, glycols and diols. The term "glycol" as used herein includes, but is not limited to, diols, glycols, and/or multifunctional hydroxyl compounds, for example, branching comonomers. Alternatively, the difunctional carboxylic acid may be a hydroxy carboxylic acid such as, for example, p-hydroxybenzoic acid, and the difunctional hydroxyl compound may be an aromatic nucleus bearing 2 hydroxyl substituents such as, for example, hydroquinone, resorcinol or other heterocyclic diols, and isosorbide, for example.

The term "residue", as used herein, means any organic structure incorporated into a polymer through a polycondensation and/or an esterification reaction from the corresponding monomer. The term "repeating unit", as used herein, means an organic structure having a dicarboxylic acid residue and a diol residue bonded through a carbonyloxy group. Thus, for example, the dicarboxylic acid residues may be derived from a dicarboxylic acid monomer or its associated acid halides, esters, salts, anhydrides, and/or mixtures thereof. As used herein, therefore, the term "dicarboxylic acid" is intended to include dicarboxylic acids and any derivative of a dicarboxylic acid, including its associated acid halides, esters, half-esters, salts, half-salts, anhydrides, mixed anhydrides, and/or mixtures thereof, useful in a reaction process with a diol to make polyester. As used herein, the term "terephthalic acid" is intended to include terephthalic acid itself and residues thereof as well as any derivative of terephthalic acid, including its associated acid halides, esters, half-esters, salts, half-salts, anhydrides, mixed anhydrides, and/or mixtures thereof or residues thereof useful in a reaction process with a diol to make polyester.

The polyesters used in the present invention typically can be prepared from dicarboxylic acids and diols which react in substantially equal proportions and are incorporated into the polyester polymer as their corresponding residues. The polyesters of the present invention, therefore, can contain substantially equal molar proportions of acid residues (100 mole %) and glycol (and/or multifunctional hydroxyl compound) residues (100 mole %) such that the total moles of repeating units is equal to 100 mole %. The mole percentages provided in the present disclosure, therefore, may be based on the total moles of acid residues, the total moles of diol residues, or the total moles of repeating units. For example, a polyester containing 1 mole % isophthalic acid, based on the total acid residues, means the polyester contains 1 mole % isophthalic acid residues out of a total of 100 mole % acid residues. Thus, there is 1 mole of isophthalic acid residues among every 100 moles of acid residues. In another example, polyester containing 1.5 mole % di ethylene glycol out of a total of 100 mole % glycol residues has 1.5 moles of di ethylene glycol residues among every 100 moles of glycol residues.

In other polyesters of the invention, the glycol component employed in making the polyesters useful in the invention can comprise, consist essentially of, or consist of ethylene glycol and one or more difunctional glycols chosen from diethylene glycol, 1,2- propanediol, 1,5 -pentanediol, 1,6-hexanediol, branched aliphatic glycols such as 2- methyl-1, 3 -propane diol, 2-ethyl- 1,3 -propane diol, 2-butyl- 1,3 -propane diol, 2,2'-dimethyl- 1,3-propanediol, 2-methyl-l,4-butanediol, 2-ethyl- 1,4-butanediol, 2-butyl- 1,4-butanediol, 3-methyl-l,5-pentanediol, 2,4-dimethyl-l,5-pentanediol and mixtures thereof. The preferred glycol is ethylene glycol.

In addition to terephthalic acid and/or dimethyl terephthalate, the dicarboxylic acid component of the polyesters useful in the invention can comprise up to 5 mole %, or up to 1 mole % of one or more modifying aromatic dicarboxylic acids. Examples of modifying aromatic dicarboxylic acids which may be used in this invention include, but are not limited to, 4,4'-biphenyldicarboxylic acid, 1,4-, 1,5-, 2,6-, 2,7- naphthalenedicarboxylic acid, and trans-4,4'-stilbenedicarboxylic acid, and esters thereof. Heterocyclic dicarboxylic acid, for example 2,5-furan dicarboxylic acid may also be used. The preferred modifying aromatic dicarboxylic acid is 2,6-naphthalene dicarboxylic acid.

The dicarboxylic acid component of the polyesters useful in the invention can be further modified with up to 5 mole % or up to 1 mole % of one or more aliphatic dicarboxylic acids containing 2 to 16 carbon atoms, such as, for example malonic, succinic, glutaric, adipic, pimelic, suberic, octanoic, azelaic, sebacic, dodecanedioic- dicarboxylic acids, diethyl-di-n-propyl malonate, dimethyl benzylmalonate, 2,2- dimethyl-malonic acid and 2,3 -dimethyl glutaric acid. The preferred aliphatic dicarboxylic acid is adipic acid.

The polyesters of the invention can also comprise at least one chain extender. Suitable chain extenders include, but are not limited to, multifunctional (including, but not limited to, bifunctional) isocyanates, multifunctional epoxides, including for example, epoxylated novolacs, and phenoxy resins. In certain embodiments, chain extenders may be added at the end of the polymerization process or after the polymerization process. If added after the polymerization process, chain extenders can be incorporated by compounding or by addition during conversion processes such as injection molding or extrusion. The amount of chain extender used can vary depending on the specific monomer composition used and the physical properties desired but is generally about 0.1 to about 5 % by weight, or about 0. 1 to about 2 % by weight, based on the total weight of the polyester.

In addition, the polyester compositions and the polymer blend compositions useful in the invention may also contain any amount of at least one additive, for example, from 0.01 to 2.5% by weight of the overall composition common additives such as colorants, dyes, mold release agents, flame retardants, plasticizers, stabilizers, including but not limited to, UV stabilizers, thermal stabilizers and/or reaction products thereof, and impact modifiers. Examples of typical commercially available impact modifiers well known in the art and useful in this invention include, but are not limited to, ethylene/propylene terpolymers, functionalized polyolefins such as those containing methyl acrylate and/or glycidyl methacrylate, styrene-based block copolymeric impact modifiers, and various acrylic core/shell type impact modifiers. For transparent EBM containers the refractive index of these additives must closely match the refractive index of the polyester composition to prevent a hazy container. Residues of such additives are also contemplated as part of the polyester composition.

In addition, certain agents which tone the polymer can be added to the melt. A bluing toner can be used to reduce the yellowness of the resulting polyester polymer melt phase product. Such bluing agents include cobalt salts, blue inorganic and organic toner(s) and the like. In addition, red toner(s) can also be used to adjust the redness. Organic toner(s), e.g., blue and red organic toner(s) can be used. The organic toner(s) can be fed as a premix composition. The premix composition may be a neat blend of the red and blue compounds or the composition may be pre-dissolved or slurried in one of the polyester's raw materials, e.g., ethylene glycol.

The total amount of added toner components depends on the amount of inherent yellow color in the base polyester and the efficacy of the toner. Generally, a concentration of up to about 15 ppm of combined organic toner components and a minimum concentration of about 0.5 ppm are used, with the total amount of bluing additive typically ranging from about 0.5 ppm to about 10 ppm. Conventional production of polyesters can be achieved by a batch, semi-continuous, or continuous process. A typical polyesterification process is comprised of multiple stages and commercially carried out in one of two common pathways. For a process which employs Direct Esterification, the initial stage of the process reacts the dicarboxylic acids with one or more diols at a temperature of about 200° C to about 250° C to form macro-monomeric structures and a small condensate molecule, water. Because the reaction is reversible, the water is continuously removed to drive the reaction to the desired first stage product. The branching comonomer is normally added at this stage of the process. In a like manner, when using diesters (versus diacids), an Ester Interchange process is used to react the ester groups of the diesters and diols with certain well known catalysts, as manganese acetate, zinc acetate, or cobalt acetate. After completing the ester interchange reaction these catalysts are sequestered with a phosphorus compound, such as phosphoric acid, to prevent degradation during the polycondensation process.

Next, in the second stage of the reaction, either macro-monomeric structures (Direct Esterification Products) or interchanged moieties (Ester Interchange Products) undergo a polycondensation reaction to form the polymer. In this process, the temperature of the molten mass is increased to a final temperature in the range of about 280° to 300° C and a vacuum (about 150 Pa) applied to remove excess diols and water. This polymerization is stopped when the required / targeted molecular weight is achieved and/or the maximum molecular weight of the design of the equipment is reached. The polyester is extruded through a die into strands which are quenched and cut into pellets. The catalysts generally used for the polycondensation reaction are compounds containing antimony, germanium, aluminum, titanium or other catalysts known to those skilled in the art, or mixtures thereof. The specific additives used and the point of introduction during the reaction is known in the art and does not form a part of the present invention. Any conventional system may be employed and those skilled in the art can select among various commercially-available systems for the introduction of additives so as to achieve an optimal result. The polyester pellets can be further polymerized to a higher molecular weight by well-known solid state polymerization processing techniques.

The terephthalic acid and/or ethylene glycol are preferably derived from a biomass feedstock rather than a petroleum based feedstock. In addition, the use of chemically recycled terephthalic acid (or dimethyl terephthalate) and ethylene glycol from post-consumer polyester waste is also preferred for the polyesters of this invention. Another preferred method of manufacturing the polyester resins of this invention utilizes bis-(hydroxyethyl)-terephthalate, purified from the reaction product of glycolysis of postconsumer polyester waste — this monomer can be added to the polymerization process, preferably prior to the polycondensation stages.

The polyester compositions suitable for use in this invention include those having an intrinsic viscosity of at least about 0.90 dl/g, preferably at least about 1.0 dl/g, and more preferably between about 0.9 and about 1.2 dl/g. Lower intrinsic viscosity resins have insufficient melt strength for an EBM process, whereas higher intrinsic viscosity resins have too high a melt viscosity at the extrusion temperatures above which there is thermal degradation and a loss of molecular weight.

Branching Comonomer

The optional branching comonomer present in the composition has 3, or more, carboxyl substituents, hydroxyl substituents, or a combination thereof. Examples of branching monomers include, but are not limited to, multifunctional acids or multifunctional alcohols such as trimellitic acid, trimellitic anhydride, pyromellitic dianhydride, benzene-l,3,5-tncarboxylic acid, trimethylolpropane, glycerol, sorbitol, 1,2,6-hexanetriol, pentaerythritol, citric acid, tartaric acid, 3 -hydroxy glutaric acid, trimesic acid and the like. Ethoxylated or oxypropylated triols can also be used. In the preferred embodiment, the branching monomer residues are chosen from at least one of the following: pentaerythritol, trimethylolpropane, trimethylolethane, trimellitic acid, trimellitic anhydride and/or benzene- 1, 3, 5 -tricarboxylic acid. The branching comonomer can be present in an amount ranging from 50 to 2000 pmol based on the copolyester.

Addition of rPET

One method to add the rPET flake to the process is disclosed in US 20030134915 in which the rPET is added to the esterification step of a continuous polyester process. This process depolymerizes the rPET and allows for any residual contaminants in the rPET to be removed during the extrusion of the rPET or its subsequent polymerization.

Another method of mixing the rPET with the esterification product of a continuous polyester process is disclosed in W02022040434 in which the rPET is melted and added to a stream of monomer using a centrifugal mixer. Extrusion Blow Molding

In another aspect, this invention relates to a process for preparing extrusion blow molded containers. The extrusion blow molding process can be accomplished via any EBM manufacturing process known in the art. Although not limited thereto, a typical description of extrusion blow molding manufacturing process involves: 1) melting the resin in an extruder 2) extruding the molten resin through a die to form a tube of molten polymer (i.e. a parison) 3) clamping a mold having the desired finished shape around the parison 4) blowing air into the parison, causing the extrudate to stretch and expand to fill the mold 5) cooling the molded container 6) ejecting the container from the mold and 7) removing excess plastic (commonly referred to as fl ash/fl ashing) from the container. The term "container" as used herein is understood to mean a receptacle in which material is held or stored. Containers include, but are not limited to, bottles, bags, vials, tubes, and jars. Applications in the industry for these types of containers include, but are not limited to, food, beverage, cosmetics, household or chemical containers, and personal care applications. The term "bottle", as used herein, is understood to mean a receptacle containing resin which is capable of storing or holding liquid.

The exact resin formulation must provide a melt such that when extruded has a high melt strength capable of resisting stretching and flowing, sagging, or other undesirably aspects that would lead to uneven material distribution in the parison and thinning of the parison walls. Melt strength is directly related to the polyester resin's viscosity, under zero shear rate, and temperature when the molten extrudate exits the die. However, a resin with high melt strength, or high melt viscosity at zero shear rate, is too viscous to be extruded in the extruder and pumped through the die without using high temperatures which cause the polymer to degrade and lose its melt viscosity. Therefore an optimal polyester resin, designed for EBM end uses, must have a rheology such that the viscosity at the shear rates associated with the extrusion process, generally 100 to 1000 s’ is lower than the viscosity at zero shear rate (i.e. exhibits shear thinning).

In addition, during the EBM process, the molten polyester should not thermally crystallize; otherwise, a cloudy container is produced. The EBM process produces waste from the flash that has to be cut from the molded container where, for instance, it has been clamped. This waste from the EBM process must be ground and mixed with the virgin resin and dried prior to re-extrusion. Therefore, the designed resin of interest has to possess and maintain a low level of crystallinity such that it does not agglomerate during drying.

In order to pass the APR Critical Guidance protocol for use in the postconsumer clear polyester recycle stream, the polyester resins of this invention must be semicrystalline (i.e. exhibit a melting endotherm as detected by Differential Scanning Calorimetry). In this regard, the melting point for an EBM resin should be in the range of 225-255° C.

Another parameter that must be met by the resin relates to the drop resistance of an EBM container filled with liquid when dropped from a height of 4 feet (122 cm). After such a drop test, it is expected that no more than one out of ten containers break, split or leak. As copolyesters age with time, it is important that the drop resistance is measured after several weeks, e.g. 2 to 4 weeks, from manufacture.

TEST AND PREPARATIVE METHODS

1. TEST METHODS a. The Intrinsic Viscosity of the polyesters are measured according to ASTM D 460396, and reported in units of dL/g. b. Hie haze of the bottle walls was measured with a Hunter Lab ColorQuest II instrument. D65 illuminant was used with a CIE 1964 10° standard observer. The haze is defined as the percent of tire CIE Y diffuse transmittance to the CIE Y total transmission. The color of the preform and bottle walls was measured with the same instrument and is reported using the CIELAB color scale. L* is a measure of brightness, a* is a measure of redness (+) or greenness (-) and b* is a measure of yellowness (+) or blueness (-). c. The drop resistance of the containers was measured according to ASTM D 2463- 95, procedure B, Bruceton Staircase Method. The containers were filed with 2.6 liter of water (23 °C) prior to dropping. The containers were stored at 23 °C and 50% Relative Humidity for aging (1 day, 1 week, 2 weeks, 3 weeks, 4 weeks, etc.). d. The content of the diacids and diols, including DEG (diethylene glycol), in the polymer was determined from proton nuclear magnetic spectra (1H MNR), using a JOEL ECX-300, 300 MHz instrument. e. General sample preparation was as follows:

20 mg of polyester is placed in a suitable 2 mL glass reaction vessel or vial with 1 mL of 10: 1 chloro form-d:TFA-d [Cambridge Isotope Laboratories, Inc. Chloroform-d (d, 98.9%)+0.05% V/V TMS: Cambridge Isotope Laboratories, Inc. Tri fluoro acetic acid-d (d, 99.5%)] and capped. The reaction vessel / vial is placed on a heating block at a temperature of 100°C for approximately 10 minutes, or until sample is fully solvated. The sample is then removed from the heat block and placed in the hood to equilibrate to RT. The solvated sample is then transferred to a standard NMR tube and analyzed via a pre-defined NMR experimental protocol. Resultant spectral integrations were worked-up via Excel macros in order to determine the reported monomer contents.

2. PREPARATIVE METHODS

Extrusion Blow Molded (EBM) Bottles

A 90 mm Bekum H-155 Continuous EBM Machine fitted with a barrier screw was used to produce model EBM containers. These containers were standard 2.63 liter, rectangular handleware containers weighing 105 g. The extrusion temperature was adjusted between 245 and 260° C to obtain an even polymer distribution in the containers. The polyesters were dried to a moisture level of less than 50 ppm prior to extrusion.

EXAMPLES

Example 1 (Control)

The control EBM resin was made on a commercial continuous polymerization (CP) PET unit manufacturing. The target amorphous IV of this copolyester is 0.72 dL/g, with 5.3 mole % isophthalic acid (IP A) and 2.1 mol % diethylene glycol (DEG); antimony trioxide is used as the polycondensation catalyst with process conditions typical of standard operating procedures known in the art. The amorphous copolyester was further polymerized in the solid state to achieve the target IV of 1.25 dL/g. The EBM extrusion conditions used to produce bottles are summarized in Table 1, the bottle color provided in Table 2, and the bottle drop performance provided in Table 3.

Example 2 (Inventive)

The same process as used in Example 1 was changed with 25% rPET (EcoMex) flake melted in an extruder and metered into the secondary esterifier through a 20- micron filter. This rPET flake replaced 25% of the monomer, made in the primary esterifier, to maintain a constant throughput in the CP unit. The IPA, DEG and color of the rPET was measured and the amount of IPA, DEG and toners adjusted in the CP unit to meet the target values of these parameters (IPA, DEG and color) as the 100% virgin PET product. The EBM bottle extrusion conditions are summarized in Table 1, the bottle color provided in Table 2, and the bottle drop performance provided in Table 3.

Example 3 (Comparative)

EcoMex rPET having an IV of 0.81 dL/g was dried, but not solid state polymerized, and mixed with the EBM resin made in Example 1, dried and extruded into EBM bottles. The EBM extrusion conditions are summarized in Table 1, and the bottle color provided in Table 2.

Example 4 (Comparative)

EcoMex rPET was solid state polymerized to 1.25 dL/g and 25 % mixed with 75 % the EBM resin made in Example 1, dried and extruded into EBM bottles. The EBM extrusion conditions are summarized in Table 1, and the bottle color provided in Table 2, and the initial bottle drop performance provided in Table 3.

Example 5 (Comparative)

EcoMex rPET flake, 25 %, was compounded with the EBM resin made in Example 1. This polymer was solid state polymerized to 1.25 dL/g, dried and extruded into EBM bottles. The EBM extrusion conditions are summarized in Table 1, and the bottle color provided in Table 2, and the bottle drop performance provided in Table 3.

Table 1

EBM Extrusion Conditions

Example 1, Control 2, Inventive 3, Comp. 4, Comp. 5, Comp.

Bottle Wall IV, dL/g L09 L09 07 L 13 1.09

Melt Pressure (MPa) 11.7 10.0 8.0 12.3 12.0 Motor Load (%) 60 49 39 62 46

Melt Temp (° C) 248 245 236 245 248

Zone 1 (° C) 282 282 271 282 282

Zone 2 (° C) 288 288 277 388 288

Zone 3 (° C) 277 277 271 271 277

Zone 4 (° C) 260 260 266 254 260

Zone 5 (° C) 254 254 238 254 254

Zone 6 (° C) 254 254 238 254 254

Zone 7-9 (° C) 254 254 238 254 254

Mold temperature (° C) 22 22 13 13 11

Table 2

Color Indices

Example 1, Control 2, Inventive 3, Comp. 4, Comp. 5, Comp.

L* 95.0 93.6 93.8 94.6 93.9 a* -0.2 -0.8 -0.4 -0.3 -0.6 b* 0.5 1.8 1.3 1.1 3.3

% haze 1.5 2.5 5.4 5.2 8.3

Table 3

Mean drop heights (cm)

Example 1, Control 2, Inventive 3, Comp. 4, Comp. 5, Comp.

1 day 193 196 n.m. 187 202

1 week 193 180 n.m. n.m. n.m.

2 weeks 145 165 n.m. n.m. 145

4 weeks 193 171 n.m. n.m. 175

Description of Examples

Inventive Example 2 produced resin with 25% rPET made EBM bottles comparable to the control virgin type 5507 resins (Example 1). The slight increase in yellowness can be adjusted by the addition of toners in the polymerization process. Example 3, in which the rPET was not solid state polymerized to the same IV as the virgin EBM resin had low melt strength, such that EBM bottles could not be made. Example 4, in which the rPET was solid stated to the same IV as the virgin EBM resin had high haze and exhibited black specks in the bottle walls. Example 5, in which the rPET was compounded with the virgin EBM resin, had unacceptable color (yellowness).

While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.

Claims

What is claimed is

1. A copolyester for an extrusion blow molded container comprising:

(a) from about 40 wt.% to about 90 wt.% copolyester comprising

(i) a diacid component comprising 95 to 100 mole % of dicarboxylic acid residues based on the total mole % of dicarboxylic acid residues in the polyester compositions, and

(iii) optionally a branching comonomer, and

2. The copolyester for an extrusion blow molded container of claim 1, wherein the di carboxylic acid residues comprise terephthalic acid, naphthalene di carboxylic acids or mixtures thereof.

3. The copolyester for an extrusion blow molded container of claims 1 or 2, wherein the glycol residues comprise ethylene glycol, di ethylene glycol, 1,4- cyclohexanedimethanol, branched aliphatic glycols or mixtures thereof

4. The copolyester for an extrusion blow molded container according to at least one of claims 1 to 3, wherein the copolyester contains from about 20 wt. % to about 50 wt. % recycled polyethylene terephthalate (rPET).

5. The copolyester for an extrusion blow molded container according to at least one of claims 1 to 4, wherein the copolyester contains about 25 wt. % recycled polyethylene terephthalate (rPET).

6. The copolyester for an extrusion blow molded container according to at least one of claims 1 to 5, further comprising an intrinsic viscosity of at least 0.9 dL/g.

7. The copolyester for an extrusion blow molded container according to at least one of claims 1 to 6, wherein the aromatic dicarboxylic acid component further comprises up to 5 mole % of one or more modifying aromatic dicarboxylic acids chosen from 4, d'biphenyldicarboxylic acid, 1,4- naphthalene di carboxylic acid, 1,5- naphthalene di carboxylic acid, 2,6- naphthalene dicarboxylic acid, 2,7-naphthalenedicarboxylic acid, trans-4,4'-stilbenedicarboxylic acid, heterocyclic dicarboxylic acid and esters thereof.

8. The copolyester for an extrusion blow molded container according to at least one of claims 1 to 7, further comprising at least one additive chosen from colorants, toners, dyes, mold release agents, flame retardants, plasticizers, stabilizers, impact modifiers, or a mixture thereof.

9. The copolyester for an extrusion blow molded container according to at least one of claims 1 to 8, further comprising up to 5 mole % of one or more aliphatic dicarboxylic acids chosen from malonic, succinic, glutaric, adipic, pimelic, suberic, octanoic, azelaic, sebacic, dodecanedioic-dicarboxylic acids, diethyl-di-n-propyl mal onate, dimethyl benzylmal onate, 2,2-dimethyl-malonic acid and 2,3 -dimethyl glutaric acid.

10. An extrusion blow molded process for forming a container, comprising:

(1) melting a resin, comprising:

(i) from about 40 wt.% to about 90 wt.% copolyester, comprising

(c) optionally a branching comonomer, and

(2) forming a parison;

(3) blowing the parison into the shape of the container; and

(4) removing scrap from the container.

11. The extrusion blow molded process for forming a container according to claim 10, wherein the container is a bottle.

12. The extrusion blow molded process for forming a container according to claims 10 or 11, further comprising grinding the scrap from the container and then mixing with the resin in step (a).

13. The extrusion blow molded process for forming a container according to at least one of claims 10 to 12, wherein the melting point of the resin is between 235°C to 255°C.

14. The extrusion blow molded process for forming a container according to at least one of claims 10 to 13, wherein the dicarboxylic acid residues comprise terephthalic acid, naphthalene dicarboxylic acids or mixtures thereof.

15. The extrusion blow molded process for forming a container according to at least one of claims 10 to 14, wherein the glycol residues comprise ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol, branched aliphatic glycols or mixtures thereof.

16. The extrusion blow molded process for forming a container according to at least one of claims 10 to 15, wherein the copolyester contains from about 20 wt. % to about 50 wt. % recycled polyethylene terephthalate (rPET).

17. The extrusion blow molded process for forming a container according to at least one of claims 10 to 16, wherein the copolyester contains about 25 wt. % recycled polyethylene terephthalate (rPET).

18. An extrusion blow molded container comprising a copolyester comprising:

(a) from about 40 wt.% to about 90 wt.% copolyester comprising

(iii) optionally a branching comonomer, and

19. The extrusion blow molded container comprising a copolyester according to claim 18, wherein the container has a drop height of more than 160 cm when tested according to ASTM D 2463-95, procedure B, Bruceton Staircase Method, after two weeks.

20. The extrusion blow molded container comprising a copolyester according to claims 18 or 19, wherein the container is a bottle.

21. The extrusion blow molded container comprising a copolyester according to at least one of claims 18 to 20, wherein said container has a % haze of less than 3%.

22. The extrusion blow molded container comprising a copolyester according to at least one of claims 18 to 21, wherein the dicarboxylic acid residues comprise terephthalic acid, naphthalene dicarboxylic acids or mixtures thereof.

23. The extrusion blow molded container comprising a copolyester according to at least one of claims 18 to 22, wherein the glycol residues comprise ethylene glycol, di ethylene glycol, 1,4-cyclohexanedimethanol, branched aliphatic glycols or mixtures thereof.

24. The extrusion blow molded container comprising a copolyester according to at least one of claims 18 to 23, wherein the copolyester contains from about 20 wt. % to about 50 wt. % recycled polyethylene terephthalate (rPET).

25. The extrusion blow molded container comprising a copolyester according to at least one of claims 18 to 24, wherein the copolyester contains about 25 wt. % recycled polyethylene terephthalate (rPET).

26. A method for manufacturing copolyester polymer for extrusion blow molded containers containing recycled polyethylene terephthalate (rPET) in a continuous polymerization unit comprising the following steps: e) feeding said rPET to an extruder, and f) melting said rPET in said extruder, and g) extruding said molten rPET into a molten stream containing oligomers from said continuous polymerization unit creating a prepolymer, and h) polymerizing said prepolymer thereby producing copolyester containing rPET, and wherein the color of the said copolyester containing rPET is adjusted during said polymerization step (d) to match the color of the copolyester manufactured without said rPET.