WO2006079044A2 - Melanges polymeres ameliores de polyamide-polyester et leurs procedes de production - Google Patents

Melanges polymeres ameliores de polyamide-polyester et leurs procedes de production Download PDF

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Publication number
WO2006079044A2
WO2006079044A2 PCT/US2006/002385 US2006002385W WO2006079044A2 WO 2006079044 A2 WO2006079044 A2 WO 2006079044A2 US 2006002385 W US2006002385 W US 2006002385W WO 2006079044 A2 WO2006079044 A2 WO 2006079044A2
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Prior art keywords
polyamide
polyethylene terephthalate
polymers
compatible
precursors
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PCT/US2006/002385
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English (en)
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WO2006079044A3 (fr
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Daniel Allen Huenefeld
Carl Steven Nichols
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Wellman, Inc.
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Publication of WO2006079044A2 publication Critical patent/WO2006079044A2/fr
Publication of WO2006079044A3 publication Critical patent/WO2006079044A3/fr
Priority to US11/780,926 priority Critical patent/US20080009574A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/005—Processes for mixing polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
    • C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
    • C08L77/06—Polyamides derived from polyamines and polycarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds

Definitions

  • PCT/US04/39726 for Methods of Making Titanium-Catalyzed Polyethylene Terephthalate Resins, filed November 24, 2004 (and published November 3, 2005, as WO 2005/103110); and International Patent Application No. PCT/US05/03149 for Imide- Modified Polyester Resins and Methods of Making the Same, filed January 28, 2005 (and published August 11, 2005, as WO 2005/073272).
  • the present invention relates to polyamide-compatible polyethylene terephthalate resins, which are useful in forming polyamide-polyester barrier blends that possess improved gas barrier, clarity, and organoleptic properties.
  • the invention also relates to methods of forming both polyamide-compatible polyethylene terephthalate polymers and polyamide- polyester barrier blends.
  • polyester containers, films, sheets, and fibers are an integral component in numerous consumer products manufactured worldwide.
  • polyester used for polyester containers, films, sheets, and fibers is polyethylene terephthalate polyester.
  • Polyester resins, especially polyethylene terephthalate and its copolyesters, are also widely used to produce rigid packaging, such as 16-ounce (-0.5 liter) and two-liter soft drink containers.
  • polyester packages produced by stretch-blow molding possess outstanding strength, clarity, and shatter resistance.
  • polyester possesses satisfactory — if not excellent — gas barrier and organoleptic properties, too. Consequently, lightweight plastics have virtually replaced glass in packaging numerous consumer products ⁇ e.g., carbonated soft drinks, fruit juices, and peanut butter). For other consumer products ⁇ e.g., beer), glass and aluminum continue to be the favored packaging materials.
  • polyester packaging provides inadequate shelf life.
  • polyester packaging provides satisfactory shelf life. Even so, suppliers and retailers would benefit from improved performance in this regard. Accordingly, there is a desire to further enhance the gas barrier properties of polyester resins that are used to package food products, such as carbonated soft drinks and beer.
  • polyesters i.e., nylons
  • polyamides i.e., nylons
  • polyamides and polyesters have a poor affinity for one another.
  • polyamides have been blended with various polyesters, including polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polypropylene terephthalate (PPT), polyethylene naphthalate (PEN), polybutylene naphthanoate (PBN), polypropylene naphthanoate (PPN), polycyclohexane dimethanol terephthalate (PCT), polycyclohexylene dimethylene terephthalate, glycol (PCTG), and polycyclohexylene dimethylene terephthalate acid (PCTA).
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PPT polypropylene terephthalate
  • PEN polyethylene naphthalate
  • PBN polybutylene naphthanoate
  • PPN polypropylene naphthanoate
  • PCT polycyclohexane dimethanol terephthalate
  • PCTG polycyclohexylene dimethylene terephthalate acid
  • U.S. Patent Application Publication No. 2004/0013833 discloses the use of isophthalic acid (IPA) derivatives as polyamide-polyester compatibilizers.
  • IPA isophthalic acid
  • U.S. Patent No. 5,300,572 discloses adding various classes of aromatic carboxylic monomers at charge to improve the compatibility of polyamides with various kinds of polyesters.
  • U.S. Patent No. 5,300,572 discloses generic formulas for a broad range of possible compatibilizers.
  • the aromatic may be represented by a benzene ring or a naphthalene ring.
  • Figure 1 depicts the chemical structure and chemical abstract service (CAS) number of dimethyl sulfoisophthalate sodium salt (DMSIP-Na).
  • Figure 2 depicts the chemical structure and chemical abstract service (CAS) number of sulfoisophthalic acid sodium salt (sIP A-Na).
  • Figure 3 depicts theoretical carbonation loss for carbonated soft drink (CSD) bottles.
  • Figure 4 depicts the shelf-life improvement of polyester carbonated soft drink bottles enhanced with nylon-MXD6 polyamide polymers.
  • Figure 5 depicts the bottle sidewall haze, as measured on 16-ounce ( ⁇ 500-milliliter) bottles, for various blends of polyethylene terephthalate polymers and nylon- MXD6 polyamide polymers.
  • Figure 6 depicts L* values, as measured on 16-ounce ( ⁇ 500-milliliter) bottles, for the polyamide-compatible polyethylene terephthalate polymers of the present invention as blended with various weight fractions of nylon-MXD6 polyamide polymers.
  • Figure 7 depicts b* values, as measured on 16-ounce ( ⁇ 500-milliliter) bottles, for the polyamide-compatible polyethylene terephthalate polymers of the present invention as blended with various weight fractions of nylon-MXD6 polyamide polymers.
  • Figure 8 depicts the oligomer distribution in various polyethylene terephthalate polymers as measured by high performance liquid chromatography (HPLC).
  • the invention embraces polyamide-compatible polyethylene terephthalate resins that are useful in forming polyamide-polyester barrier blends possessing improved gas barrier, clarity, and organoleptic properties.
  • the polyamide-compatible polyethylene terephthalate resins of the present invention are composed of about a 1:1 molar ratio of a terephthalate component and a diol component (i.e., a terephthalate moiety and a diol moiety).
  • the terephthalate component is typically either a diacid component, which includes mostly terephthalic acid, or a diester component, which includes mostly dimethyl terephthalate.
  • the diol component comprises mostly ethylene glycol.
  • the terephthalate component typically includes between about 0.1 and 2.0 mole percent sulfonated organic compound (e.g., between about 0.2 and 1.5 mole percent, such as 0.5 and 1.5 mole percent). In some circumstances, such as where the polyamide-compatible polyethylene terephthalate polymers are to be blended with higher fractions of polyamide polymers, higher concentrations of the sulfonated organic compound may be desirable (e.g., between about 1.0 and 2.0 mole percent). More typically, the terephthalate component includes between about 0.2 and 1.0 mole percent sulfonated organic compound (e.g., between about 0.25 and 0.75 mole percent or between about 0.5 and 1.0 mole percent).
  • the sulfonated organic compound may be employed in both aromatic and aliphatic forms.
  • Organic sulfonic acids are especially suitable. Such organic sulfonic acids are typically available in less reactive salt form (i.e., neutralized). In this regard, those having ordinary skill in the art will appreciate that neutralized organic sulfonic acids (e.g., those including, without limitation, sodium, lithium, potassium, or magnesium atoms), are more stable.
  • Sulfonated isophthalate derivatives particularly dimethyl sulfoisophthalate (DMSIP) and sulfoisophthalic acid (sIPA) — are especially effective sulfonated organic compounds.
  • DMSIP dimethyl sulfoisophthalate
  • sIPA sulfoisophthalic acid
  • exemplary sulfonated isophthalate derivatives according to the present invention may be represented by the structure (below), wherein R 1 and R 2 independently include hydrogen, alkyl radicals, or radicals of the formula C n H 2n OH:
  • such polyethylene terephthalate copolymers are composed of about a 1:1 molar ratio of a diacid component and a diol component, wherein the diacid component includes a sulfonated organic compound, but mostly terephthalic acid (e.g., 90-98 mole percent).
  • such polyethylene terephthalate copolymers are composed of about a 1 :1 molar ratio of a diester component and a diol component, wherein the diester component includes a sulfonated organic compound, but mostly dimethyl terephthalate (e.g., 90-98 mole percent).
  • the diol component includes mostly ethylene glycol (e.g., 90 mole percent or more).
  • the invention embraces improved barrier blends formed from polyamide polymers and the aforementioned polyamide-compatible polyethylene terephthalate resins.
  • the polyamide-polyester barrier blends of the present invention possess excellent barrier, clarity, and organoleptic properties, and are especially useful for packaging (e.g., containers, sheets, and films).
  • polyamide-polyester barrier blends are achieved by compounding polyamide polymers with the polyamide-compatible polyethylene terephthalate polymers of the present invention.
  • the polyamide-polyester barrier blends of the present invention can include up to 30 weight percent polyamide polymers.
  • the polyamide-polyester barrier blends typically include one or more kinds of polyamide polymers compounded with polyester polymers consisting essentially of the polyamide-compatible polyethylene terephthalate polymers. That is, the polyamide-polyester barrier blends of the present invention do not require — but certainly can include — more than one kind of polyester to achieve a compatibilized blend of polyamide and polyester polymers.
  • the polyamide-polyester barrier blends should include at least about 5 or 10 weight percent polyamide polymers. Indeed, for some uses the polyamide-polyester barrier blends may include at least about 15 weight percent polyamide polymers.
  • the polyamide-polyester barrier blends of the present invention typically include less than about 10 weight percent polyamide polymers (e.g., between about 3 and 10 weight percent), more typically between about 1 and 5 weight percent polyamide polymers (e.g., less than about 5 weight percent, such as between about 2 and 4 weight percent polyamide polymers or between about 1.5 and 3 weight percent polyamide polymers).
  • the polyamide-polyester barrier blends may include between about 0.5 and 1.5 weight percent polyamide polymers and at least about 95 weight percent polyamide-compatible polyethylene terephthalate polymers.
  • Exemplary polyamides for use in the present polyamide-polyester barrier blends include, without limitation, nylon-66, nylon-6, nylon-612, nylon- 11, nylon- 12 and nylon-46, and nylon-MXD6.
  • Nylon-MXD6 which is available from Mitsubishi Gas Chemical Company, Inc. (New York, New York), is especially suitable.
  • Nylon-MXD6 is a semi- crystalline polyamide that possesses thermal and physical properties similar to polyethylene terephthalate. Nylon-MXD6 also exhibits excellent gas barrier properties.
  • Figure 3 depicts the theoretical carbonation loss of a carbonated soft drink (CSD) bottle over time. Carbonation loss is directly related to shelf life. Figure 3 shows that percent carbonation loss occurs faster with smaller containers. This is a function of the increased surface area to volume ratio in the smaller container.
  • CSD carbonated soft drink
  • Figure 4 depicts the improvement in shelf life (as measured by CO2 permeability) of 20-ounce ( ⁇ 600-milliliter) carbonated soft drink bottles. These CSD bottles are made from polyethylene terephthalate resins blended with 0 (i.e., control polyester), 2, or 4 weight percent nylon-MXD6 polyamide polymers. The improvement in gas barrier properties over the control, as measured by product shelf life, are more than two weeks with a 2 weight percent blend of nylon-MXD6 polyamide polymers, and over a month with a 4 weight percent blend of nylon-MXD6 polyamide polymers.
  • the polyamide-polyester barrier blends include between about 1 and 5 weight percent nylon-MXD6 polyamide polymers (i.e., nylon-MXD6) and between about 99 and 95 weight percent polyamide-compatible polyethylene terephthalate polymers that have sulfoisophthalate modification in an amount between about 0.1 and 2.0 mole percent (e.g., between about 0.2 and 1.5 mole percent of ionomeric sulfonated isophthalate derivatives).
  • the polyamide-polyester barrier blends include between about 2 and 4 weight percent nylon-MXD6 polyamide polymers and between about 98 and 95 weight percent polyamide-compatible polyethylene terephthalate polymers that have sulfoisophthalate modification in an amount between about 0.2 and 1.0 mole percent (e.g., 0.5 mole percent of ionomeric sulfonated isophthalate derivatives).
  • the polyamide-polyester containers of the present invention can substantially extend shelf life typically provided by conventional polyester containers (i.e., about ten weeks or so). As compared with an otherwise identical container formed from conventional homopolymer polyester, the present polyamide-polyester containers provide superior barrier properties, yet possess comparable clarity and organoleptic properties.
  • conventional homopolymer polyester is intended to embrace not only pure homopolyesters but also copolyesters that include low amounts of comonomer substitution (e.g., less than about 5 mole percent modification).
  • polyamide-polyester containers of the present invention possess at least about 15 percent better oxygen and carbon dioxide barrier properties as compared with otherwise identical containers formed from conventional polyethylene terephthalate, typically between about 20 and 75 percent better oxygen and carbon dioxide barrier properties (e.g., more than about a 50 percent improvement).
  • the barrier properties of the resulting polyamide- polyester containers demonstrate increasing oxygen and carbon dioxide barrier properties.
  • the polyamide-polyester containers of the present invention can possess at least about 100 percent better oxygen and carbon dioxide barrier properties as compared with otherwise identical containers formed from homopolymer polyethylene terephthalate — and with some polyamide-polyester blends, more than 200 percent better barrier.
  • barrier resins must yield containers exhibiting low haze.
  • modifying polyethylene terephthalate polymers with a sulfonated organic compound, such as DMSIP or sIPA substantially reduces sidewall haze.
  • a sulfonated organic compound such as DMSIP or sIPA
  • Sidewalls for 16-ounce ( ⁇ 500-milliliter) and 20-ounce ( ⁇ 600-milliliter) carbonated soft drink bottles are, for example, about 0.010-0.012 inch (about 0.25-0.30 mm). Likewise, sidewalls for two-liter carbonated soft drink bottles are typically less than 0.014 inch (0.35 mm).
  • the polyamide-polyester containers according to the present invention possess at least about 10 percent less sidewall haze — more typically at least about 20 or 30 percent less sidewall haze — as compared with otherwise identical containers formed from the same relative weight fractions of polyamide and homopolymer polyethylene terephthalate (i.e., including only low amounts of comonomer substitution, if any).
  • the polyamide-polyester containers according to the present invention may possess at least about 40 or 50 percent less sidewall haze as compared with otherwise identical containers formed from the same relative weight fractions of polyamide and homopolymer polyethylene terephthalate.
  • FIG. 5 depicts the bottle sidewall haze measurements after blending both conventional and DMSIP-modified polyethylene terephthalate resins with 0 (i.e., control polyester), 2, or 4 weight percent of nylon-MXD6 polyamide polymers.
  • Bottle sidewall haze was measured in 16-ounce ( ⁇ 500-milliliter) carbonated soft drink bottles formed from the resin blends and having a sidewall thickness of 0.010-0.012 inch (about 0.25-0.30 mm).
  • bottle sidewall haze increased 6 percent in the bottles blended with 2 weight percent nylon-MXD6 polyamide polymers as compared with the control polyester; bottle sidewall haze increased more than 12 percent in the bottles blended with 4 weight percent nylon-MXD6 polyamide polymers as compared with the control polyester.
  • the DMSIP-modified polyethylene terephthalate resins possessed 5 percent less bottle sidewall haze as compared with the conventional polyethylene terephthalate resins; at 4 weight percent nylon-MXD6 polyamide polymers, the DMSIP-modified polyethylene terephthalate resins possessed over 10 percent less bottle sidewall haze as compared with the conventional polyethylene terephthalate resins.
  • barrier resins must yield containers possessing excellent color (i.e., not too dark or yellow). In contrast to prior polyamide-polyester blends, which tend to be excessively yellow, the polyamide- polyester barrier blends of the present invention possess excellent color characteristics.
  • L*a*b* color space of the Commission Internationale PEclairage (CIE).
  • CIE Commission Internationale PEclairage
  • L* which describes luminosity on a scale of 0-100 ⁇ i.e., 0 is black and 100 is white
  • a* which describes the red-green axis ⁇ i.e., positive values are red and negative values are green
  • b* which describes the yellow-blue axis ⁇ i.e., positive values are yellow and negative values are blue
  • L* and b* values are of particular interest.
  • the polyamide-polyester barrier blends of the present invention can be injection molded or otherwise formed into articles, such as preforms.
  • Polyamide-polyester preforms containing between about 2 and 4 weight percent nylon-MXD6 can possess L* values of 75 or more and b* color values of 5 or less (as measured directly on the preforms).
  • polyamide-polyester bottles stretch-blow molded from such preforms can possess L* values of 90 or more and b* color values of 4 or less ⁇ e.g., 2 or less) as measured directly on the sidewalls of such bottles.
  • 16-ounce ( ⁇ 500-milliliter), 20-ounce ( ⁇ 600-milliliter), and two-liter carbonated soft drink bottles typically possess sidewalls thicknesses of about 0.010-0.014 inch (about 0.25-0.35 mm).
  • increasing polyamide fractions in the polyamide-polyester barrier blends lowers L* values and raises b* color values. See Figures 6 and 7.
  • preforms and bottles can be formed into standard test plaques to facilitate comparative color measurements.
  • polyamide-polyester articles according to the present invention ⁇ e.g., preforms and bottles
  • preforms and bottles may be ground, melted at 280°C, and then injected into a cold mold to form standard, three- millimeter (3 mm) non-crystalline polyester test plaques. Color values for such articles may then be conveniently measured on these standard test plaques, which are about the same thickness as CSD bottle preforms ⁇ e.g., 20-oz. bottle preforms are about 3.5 millimeters thick and two-liter preforms are about 4.0 millimeters thick).
  • CIE L*a*b* color space values for polyamide-polyester articles of the present invention may be reported based on color measurements taken upon these standard test plaques. Such articles may include, without limitation, films, sheets, fibers, preforms, bottles, and even pellets.
  • CIE L*a*b* color space values for the three-millimeter, non- crystalline polyamide-polyester test plaques may be determined using a HunterLab LabScan XE spectrophotometer (illuminant/observer: D65/10 0 ; diffuse 8° standard; transmittance port).
  • Those having ordinary skill in the art will appreciate that non-crystalline polyamide- polyester plaques are essentially transparent and so are typically measured by transmittance.
  • polyamide-polyester articles of the present invention e.g., films, sheets, preforms, bottles, and crystalline pellets
  • a L* value of more than about 55 e.g., more than about 60
  • a b* color value of less than about 6 e.g., less than about 5
  • polyamide-polyester articles of the present invention possess a L* value of more than about 70 (e.g., more than about 75 or 80) and/or a b* color value of less than about 3 (e.g., less than about 2) as classified by the CIE L*a*b* color space and as measured upon standard three-millimeter test plaques.
  • CIE L*a*b* color space values that are based upon color measurements taken upon these three-millimeter non-crystalline test plaques will be so identified
  • polyamide-polyester articles of the present invention preferably possess b* color values of less than about 4 (e.g., between about -3 and 2) as classified by the CIE L*a*b* color space and as measured directly upon such polyamide-polyester articles.
  • CIE L*a*b* color space values that are based upon color measurements taken directly from articles formed from the polymer blend will be so identified.
  • the CIE L*a*b* color space is also of interest in characterizing the polyamide-compatible polyethylene terephthalate polymers of the present invention.
  • the present polyamide-compatible polyethylene terephthalate polymers possess an amorphous L* value (i.e., luminosity) of more than about 50 and an amorphous b* color value of less than about 5.
  • the polyamide-compatible polyethylene terephthalate polymers typically possess an amorphous L* value of more than about 60 (e.g., more than about 65).
  • the polyamide-compatible polyethylene terephthalate polymers typically possess an amorphous b* color value of less than about 4 (e.g., less than about 2).
  • the amorphous b* color value is evaluated for uncolored resins (i.e., not including colorants).
  • polyester processing often affects color.
  • the luminosity of polyethylene terephthalate typically increases upon crystallization and solid state polymerization (i.e., the L* color value increases slightly).
  • Polyester bottles formed only from the polyamide-compatible polyethylene terephthalate polymers of the present invention possess L* values of 94 or more and b* color values of 1 or less as measured directly on the polyester bottles.
  • the terms "amorphous L* value” and “amorphous b* color value” refer to measurements based on uncolored, amorphous pellets.
  • crystalline L* value and "crystalline b* color value” refer to measurements based on uncolored, crystalline pellets.
  • the CIE L*a*b* color space values for such amorphous and crystalline polyethylene terephthalate resins may be determined using a HunterLab LabScan XE spectrophotometer.
  • the CIE L*a*b* color space values reported herein for the polyamide-compatible polyethylene terephthalate polymers of the present invention relate to amorphous pellets (i.e., "amorphous L* value” and "amorphous b* color value”). It will be noted, however, that polyethylene terephthalate bottle resins are most often commercially available in the form of crystalline pellets. Thus, color measurements of crystallized polyethylene terephthalate pellets are sometimes more convenient.
  • Test procedures e.g., standards and calibrations
  • amorphous pellets, crystalline pellets, noncrystalline test plaques, preforms, and bottles are readily available to and within the understanding of those having ordinary skill in the art.
  • pellets is used generally to refer to chips, pellets, and the like.
  • the invention embraces methods of making improved polyamide-compatible polyethylene terephthalate resins.
  • the invention likewise embraces methods of making improved polyamide-polyester barrier blends.
  • the step of reacting a terephthalate component and a diol component typically means reacting either a diacid component (e.g., mostly terephthalic acid) or a diester component (e.g., mostly dimethyl terephthalate) with ethylene glycol to form polyethylene terephthalate precursors.
  • these polyethylene terephthalate precursors Prior to the introduction of the sulfonated organic compound, these polyethylene terephthalate precursors typically include less than about 10 mole percent comonomer substitution (e.g., between about 3 and 8 mole percent comonomer), typically less than about 5 mole percent comonomer substitution (e.g., about 3 or 4 mole percent comonomer). Modification of the terephthalate and diol components via selective comonomer substitution is further discussed herein.
  • the sulfonated organic compound is introduced into the polyethylene terephthalate precursors rather than at charge.
  • the sulfonated organic compound reacts with the polyethylene terephthalate precursors to yield modified polyethylene terephthalate precursors. Thereafter, the modified polyethylene terephthalate precursors are polymerized via melt phase polycondensation to form polyamide-compatible polyethylene terephthalate polymers.
  • the melt phase polymerization typically continues until the polyamide-compatible polyethylene terephthalate polymers achieve an intrinsic viscosity of at least about 0.45 dL/g (e.g., between about 0.45 and 0.75 dL/g) and typically between about 0.5 and 0.8 dL/g (e.g., between about 0.55 and 0.70 dL/g).
  • the method typically includes subsequent solid state polymerization of the polyamide-compatible polyethylene terephthalate polymers to an intrinsic viscosity of at least about 0.60 dL/g (e.g., between about 0.65 and 1.0 dL/g) and typically between about 0.7 and 0.85 dL/g (e.g., about 0.75 dL/g). Solid state polymerization typically proceeds at temperatures above about 190 0 C (e.g., about 200 0 C or more).
  • the polyamide-compatible polyethylene terephthalate polymers may polymerized via melt-phase polycondensation (without solid state polymerization) to achieve an intrinsic viscosity greater than about 0.8 dL/g. Thereafter, the polyamide-compatible polyethylene terephthalate polymers may be subjected to crystallization.
  • the polyamide-compatible polyethylene terephthalate polymers are, in fact, modified polyethylene terephthalate polyesters.
  • the polyamide-compatible polyethylene terephthalate resins described herein are typically modified polyethylene terephthalate polyesters.
  • the modifiers in the terephthalate component and the diol component are typically randomly substituted in the resulting polyester composition.
  • additives include, without limitation, preform heat-up rate enhancers, friction-reducing additives, UV absorbers, inert particulate additives (e.g., clays or silicas), colorants, antioxidants, branching agents, oxygen barrier agents, carbon dioxide barrier agents, oxygen scavengers, flame retardants, crystallization control agents, acetaldehyde reducing agents, impact modifiers, catalyst deactivators, melt strength enhancers, anti-static agents, lubricants, chain extenders, nucleating agents, solvents, fillers, and plasticizers.
  • preform heat-up rate enhancers e.g., friction-reducing additives, UV absorbers, inert particulate additives (e.g., clays or silicas), colorants, antioxidants, branching agents, oxygen barrier agents, carbon dioxide barrier agents, oxygen scavengers, flame retardants, crystallization control agents, acetaldehyde reducing agents, impact modifiers, catalyst deactivators, melt strength enhancers, anti
  • the term "comonomer” is intended to include monomeric and oligomeric modifiers (e.g., polyethylene glycol).
  • diol component refers primarily to ethylene glycol, although other diols may be used as well.
  • terephthalate component broadly refers to diacids and diesters that can be used to prepare polyethylene terephthalate.
  • the terephthalate component mostly includes either terephthalic acid or its dialkyl ester (i.e., dimethyl terephthalate), but can include diacid and diester comonomers as well.
  • the "terephthalate component” is either a “diacid component” or a "diester component.”
  • diacid component refers somewhat more specifically to diacids (e.g., terephthalic acid) that can be used to prepare polyethylene terephthalate via direct esterification.
  • diacid component is intended to embrace relatively minor amounts of diester comonomer (e.g., mostly terephthalic acid and one or more diacid modifiers, but optionally with some diester modifiers, too).
  • diester component refers somewhat more specifically to diesters (e.g., dimethyl terephthalate) that can be used to prepare polyethylene terephthalate via ester exchange.
  • diester component is intended to embrace relatively minor amounts of diacid comonomer ⁇ e.g., mostly dimethyl terephthalate and one or more diester modifiers, but optionally with some diacid modifiers, too).
  • the diol component can include diols besides ethylene glycol; polyalkylene glycols such as polyethylene glycol; 1,3-propane diol; 1,4-butane diol; 1,5-pentanediol; 1,6- hexanediol; propylene glycol; 1,4-cyclohexane dimethanol; neopentyl glycol; 2-methyl-l,3- propanediol; 2,2,4,4-tetramethyl-l,3-cyclobutanediol; adamantane- 1,3 -diol, 3,9-bis(l,l- dimethyl-2-hydroxyethyl)-2,4,8, 10-tetraoxaspiro[5.5]undecane; and isosorbide).
  • polyalkylene glycols such as polyethylene glycol; 1,3-propane diol; 1,4-butane diol; 1,5-pentanediol; 1,6-
  • the terephthalate component in addition to terephthalic acid or its dialkyl ester ⁇ i.e., dimethyl terephthalate, can include modifiers such as isophthalic acid or its dialkyl ester ⁇ i.e., dimethyl isophthalate); 2,6-naphthalene dicarboxylic acid or its dialkyl ester ⁇ i.e., dimethyl 2,6 naphthalene dicarboxylate); adipic acid or its dialkyl ester ⁇ i.e., dimethyl adipate); succinic acid, its dialkyl ester ⁇ i.e., dimethyl succinate), or its anhydride ⁇ i.e., succinic anhydride); or one or more functional derivatives of terephthalic acid.
  • modifiers such as isophthalic acid or its dialkyl ester ⁇ i.e., dimethyl isophthalate); 2,6-naphthalene dicarboxylic acid or its dialkyl ester ⁇ i.
  • exemplary diacid or diester comonomers modifiers include phthalic acid, phthalic anhydride, biphenyl dicarboxylic acid, cyclohexane dicarboxylic acid, anthracene dicarboxylic acid, adamantane 1,3-dicarboxylic acid, glutaric acid, sebacic acid, and azelaic acid.
  • diacid comonomer should be employed when the terephthalate component is mostly terephthalic acid ⁇ i.e., a diacid component
  • diester comonomer should be employed when the terephthalate component is mostly dimethyl terephthalate ⁇ i.e., a diester component).
  • the molar ratio of the diacid component and the diol component is typically between about 1.0:1.0 and 1.0:1.6.
  • the diacid component typically includes at least 90 mole percent terephthalic acid, and more typically at least 95 mole percent terephthalic acid ⁇ e.g., between about 96 and 98 mole percent terephthalic acid);
  • the diol component typically includes at least 90 mole percent ethylene glycol, and more typically at least 95 mole percent ethylene glycol ⁇ e.g., between about 96 and 98 mole percent ethylene glycol).
  • the molar ratio of the diester component and the diol component may exceed 1.0:2.0 but is typically between about 1.0:1.6 and 1.0:2.0.
  • the diester component typically includes at least 90 mole percent dimethyl terephthalate, and more typically at least 95 mole percent dimethyl terephthalate ⁇ e.g., between about 96 and 98 mole percent dimethyl terephthalate);
  • the diol component typically includes at least 90 mole percent ethylene glycol, and more typically at least 95 mole percent ethylene glycol ⁇ e.g., between about 96 and 98 mole percent ethylene glycol).
  • the diol component usually forms the majority of terminal ends of the polymer chains and so is present in the resulting polyester composition in slightly greater fractions. This is what is meant by the phrases "about a 1:1 molar ratio of a terephthalate component and a diol component,” “about a 1:1 molar ratio of a diacid component and a diol component,” and “about a 1:1 molar ratio of a diester component and a diol component,” each of which is used herein to describe the polyester compositions of the present invention.
  • Intrinsic viscosity is the ratio of the specific viscosity of a polymer solution of known concentration to the concentration of solute, extrapolated to zero concentration. Intrinsic viscosity, which is widely recognized as standard measurements of polymer characteristics, is directly proportional to average polymer molecular weight. See, e.g., Dictionary of Fiber and Textile Technology, Hoechst Celanese Corporation (1990); Tortora & Merkel, Fairchild's Dictionary of Textiles (7 th Edition 1996).
  • Intrinsic viscosity can be measured and determined without undue experimentation by those of ordinary skill in this art.
  • the intrinsic viscosity is determined by dissolving the polyester in orthochlorophenol (OCP), measuring the relative viscosity of the solution using a Schott Autoviscometer (AVS Schott and AVS 500 Viscosystem), and then calculating the intrinsic viscosity based on the relative viscosity. See, e.g., Dictionary of Fiber and Textile Technology (“intrinsic viscosity").
  • a 0.6-gram sample (+/- 0.005 g) of dried polymer sample is dissolved in about 50 ml (61.0 - 63.5 grams) of orthochlorophenol at a temperature of about 105 0 C. Fibrous samples are typically cut into small pieces, whereas chip samples are ground. After cooling to room temperature, the solution is placed in the viscometer at a controlled, constant temperature, ⁇ e.g., between about 20° and 25 0 C), and the relative viscosity is measured. As noted, intrinsic viscosity is calculated from relative viscosity. [0095] Those having ordinary skill in the art will know that there are two conventional methods for forming polyethylene terephthalate. These methods are well known to those skilled in the art.
  • One method employs a direct esterification reaction using terephthalic acid and excess ethylene glycol.
  • the aforementioned step of reacting a terephthalate component and a diol component includes reacting terephthalic acid and ethylene glycol in a heated esterification reaction to form monomers and oligomers of (i) terephthalic acid and, optionally, diacid modifiers, and (//) ethylene glycol and, optionally, diol modifiers. Water, as well, is formed as a byproduct.
  • the water must be continuously removed as it is formed.
  • the monomers and oligomers are catalytically polymerized via polycondensation (i.e., melt phase and/or solid state polymerization) to form polyethylene terephthalate polyester.
  • polycondensation i.e., melt phase and/or solid state polymerization
  • ethylene glycol is continuously removed to create favorable reaction kinetics.
  • the other method involves a two-step ester exchange reaction and polymerization using dimethyl terephthalate and excess ethylene glycol.
  • the aforementioned step of reacting a terephthalate component and a diol component includes reacting dimethyl terephthalate and ethylene glycol in a heated, catalyzed ester interchange reaction (i.e., transesterification) to form monomers of (0 dimethyl terephthalate and, optionally, diester modifiers, and (ii) ethylene glycol and, optionally, diol modifiers.
  • Methanol, as well is formed as a byproduct.
  • dimethyl terephthalate and ethylene glycol yield bis(2-hydroxyethyl)-terephthalate monomers.
  • Polyethylene terephthalate polyester may be produced in a batch process, where the product of the esterification or ester interchange reaction is formed in one vessel and then transferred to a second vessel for polymerization.
  • the second vessel is agitated.
  • the polymerization reaction is continued until the power used by the agitator reaches a level indicating that the polyester melt has achieved the desired intrinsic viscosity and, thus, the desired molecular weight.
  • the continuous production of polyethylene terephthalate results in greater throughput, and so is more typical in large-scale manufacturing facilities.
  • catalysts increases the rates of esterification and polycondensation and, hence, the production of the polyethylene terephthalate resins.
  • Catalysts will eventually degrade the polyethylene terephthalate polymer.
  • degradation may include polymer discoloration (e.g., yellowing), acetaldehyde formation, or molecular weight reduction.
  • stabilizing compounds can be employed to sequester ("cool") the catalysts.
  • the most commonly used stabilizers contain phosphorus, typically in the form of phosphates and phosphites.
  • the aforementioned U.S. Patent No. 6,599,596 for Methods of Post- Polymerization Injection in Continuous Polyethylene Terephthalate Production discloses a process for the production of high quality polyethylene terephthalate polyester that improves upon the stabilizer-addition techniques disclosed by commonly-assigned U.S. Patent No. 5,898,058.
  • the method for making polyamide-compatible polyethylene terephthalate polymers employs the aforementioned direct esterification reaction using terephthalic acid and excess ethylene glycol.
  • This method includes reacting (i) a diacid component comprising terephthalic acid and (H) a diol component comprising ethylene glycol to form polyethylene terephthalate precursors.
  • This latter reaction achieves polyethylene terephthalate precursors having an average degree of polymerization between about 2 and 10, typically between about 3 and 6.
  • the polyethylene terephthalate precursors are reacted with a sulfonated organic compound to yield modified polyethylene terephthalate precursors.
  • the modified polyethylene terephthalate precursors are then polymerized via melt phase polycondensation to form polyamide-compatible polyethylene terephthalate polymers.
  • excess diethylene glycol causes a number of problems.
  • high diethylene glycol content e.g., more than about 8 mole percent
  • can adversely narrow the blow molding temperature range i.e., shrinks the resin processing window
  • (if) can disrupt bottle weight distribution (i.e., crystallization in the base)
  • (Hi) can suppress glass transition (T G ) temperature, thereby diminishing thermal stability
  • (Zv) can promote the formation of acetaldehyde, which degrades favorable organoleptic properties.
  • the introduction of the sulfonated organic compound into the polyethylene terephthalate precursors be delayed until the polyethylene terephthalate precursors have a carboxyl end group concentration of less than about 1000 microequivalents per gram, typically less than about 900 microequivalents per gram (e.g., between about 300 and 900 microequivalents per gram), and more typically less than about 800 microequivalents per gram (e.g., between about 400 and 800 microequivalents per gram).
  • the carboxyl end group concentration of the esterification reaction is less than about 1000 microequivalents per gram (e.g., about 500 microequivalents per gram).
  • a buffer e.g., sodium acetate may be introduced to the esterification reaction in an amount sufficient to control the acidity of the sulfonated organic compound.
  • the polyamide-compatible polyethylene terephthalate polymers include DMSIP substitution
  • sodium acetate may be introduced to the esterification reaction at 10 mole percent of the DMSIP mole fraction to control diethylene glycol formation.
  • the buffer is introduced to the esterification reaction prior to or concurrently with the initiation of the reaction between the sulfonated organic compound and the polyethylene terephthalate precursors.
  • the method according to the present invention provides polyamide-compatible polyethylene terephthalate polymers having less than about 6 mole percent diethylene glycol content — typically less than about 3 or 4 mole percent diethylene glycol content.
  • these polyamide- compatible polyethylene terephthalate polymers facilitate the manufacture of polyamide- polyester bottles that, as compared to conventional polyamide-polyester bottles, possess reduced diethylene glycol content and superior clarity while maintaining excellent barrier properties.
  • the two-step ester exchange reaction between dimethyl terephthalate and excess ethylene glycol is less acidic than the direct esterification reaction between terephthalic acid and excess ethylene glycol.
  • the sulfonated organic compound is introduced to the polyethylene terephthalate precursors after the initiation of the transesterification reaction to reduce the formation of unwanted byproducts, such as diethylene glycol.
  • the sulfonated organic compound can be introduced to the polyethylene terephthalate precursors after the completion of the transesterification reaction, such as just prior to the initiation of melt phase polycondensation.
  • the reaction between the sulfonated organic compound and the polyethylene terephthalate precursors typically proceeds at less than about 27O 0 C (e.g., between about 255°C and 265°C).
  • the sulfonated organic compound is typically introduced into polyethylene terephthalate precursors during esterification, though it can be introduced after esterification as well (e.g., just prior to the initiation of melt phase polycondensation).
  • the sulfonated organic compound is usually introduced into polyethylene terephthalate precursors after esterification or transesterification.
  • the continuous feed enters a direct esterification vessel that is operated at a temperature of between about 240 0 C and 290 0 C and at a pressure of between about 5 and 85 psia (30-590 kPa) for between about one and five hours.
  • the esterification reaction forms polyethylene terephthalate precursors having an average degree of polymerization of between about 4 and 6, as well as water. The water is removed as the reaction proceeds to drive favorable reaction equilibrium.
  • the polyethylene terephthalate precursors are then reacted with a sulfonated organic compound, typically a sulfonated isophthalate derivative such as dimethyl sulfoisophthalate sodium salt, at between about 255°C and 265°C to yield modified polyethylene terephthalate precursors.
  • a sulfonated organic compound typically a sulfonated isophthalate derivative such as dimethyl sulfoisophthalate sodium salt
  • the introduction of the sulfonated organic compound is delayed until the carboxyl end group concentration of the esterification reaction is less than about 1000 microequivalents per gram (e.g., between about 400 and 800 microequivalents per gram).
  • the modified polyethylene terephthalate precursors are polymerized via melt phase polycondensation to form polyamide-compatible polyethylene terephthalate polymers.
  • This polycondensation stage generally employs a series of two or more vessels and is operated at a temperature of between about 250 0 C and 305 0 C for between about one and four hours.
  • the polycondensation reaction usually begins in a first vessel called the low polymerizer.
  • the low polymerizer is operated at a pressure range of between about 0 and 70 torr (0-9.3 kPa).
  • the modified polyethylene terephthalate precursors polycondense to form polyamide-compatible polyethylene terephthalate polymers and ethylene glycol.
  • the ethylene glycol is removed from the polymer melt using an applied vacuum to drive the reaction to completion.
  • the polymer melt is typically agitated to promote the escape of the ethylene glycol from the polymer melt and to assist the highly viscous polymer melt in moving through the polymerization vessel.
  • the molecular weight and thus the intrinsic viscosity of the polymer melt increases. The temperature of each vessel is generally increased and the pressure decreased to allow greater polymerization in each successive vessel.
  • the final vessel typically referred to as the "high polymerizer,” is operated at a pressure of between about 0 and 40 torr (0-5.3 kPa).
  • each of the polymerization vessels is connected to a vacuum system having a condenser, and each is typically agitated to facilitate the removal of ethylene glycol.
  • the residence time in the polymerization vessels and the feed rate of the ethylene glycol and terephthalic acid into the continuous process is determined, in part, based on the target molecular weight of the polyamide-compatible polyethylene terephthalate polymers.
  • the intrinsic viscosity of the polymer melt is generally used to determine polymerization conditions, such as temperature, pressure, the feed rate of the reactants, and the residence time within the polymerization vessels.
  • the melt phase polymerization generally continues until the polyethylene terephthalate possesses an intrinsic viscosity of at least about 0.45 dL/g (e.g., between about 0.55 and 0.65 dL/g).
  • the polymer melt After exiting the polycondensation stage, usually from the high polymerizer, the polymer melt is generally filtered and extruded. After extrusion, the polyamide-compatible polyethylene terephthalate polymers are quenched and solidified, typically by spraying with water. The solidified polyamide-compatible polyethylene terephthalate polymers are cut into chips or pellets for storage and handling purposes. The polyester pellets typically have an average mass of about 15-20 mg. As noted previously, the term "pellets" is used generally to refer to chips, pellets, and the like. [00124] Usually, the pellets formed from the polyamide-compatible polyethylene terephthalate polymers can be subjected to crystallization.
  • the polyamide- compatible polyethylene terephthalate polymers can be further polymerized in the solid state to increase molecular weight, typically to an intrinsic viscosity of at least about 0.6 dL/g (e.g., between about 0.65 and 0.85 dL/g).
  • these subsequent steps are constrained by the degree of polyester modification.
  • high levels of comonomer substitution preclude subsequent crystallization and solid state polymerization.
  • polyethylene terephthalate copolyesters may lose intrinsic viscosity.
  • the polyamide-compatible polyethylene terephthalate polymers of the present invention are no different in this regard. From chip to preform such intrinsic viscosity loss is typically between about 0.02 dL/g and 0.06 dL/g.
  • the polyamide-compatible polyethylene terephthalate polymers typically include less than about 10 mole percent comonomer substitution, including less than about 2 mole percent sulfonated organic compound substitution.
  • the polyamide-compatible polyethylene terephthalate polymers may be blended with up to 30 weight percent polyamide polymers to thereby form a polyamide-polyester barrier blend.
  • exemplary polyester resin pellets that are suitable for compounding with polyamide polymers are mostly polyamide-compatible polyethylene terephthalate polymers.
  • These polyamide-compatible polyethylene terephthalate polymers are composed of (z) a terephthalate moiety that includes at least about 95 mole percent terephthalic acid (or its dialkyl ester, dimethyl terephthalate) and between about 0.1 and 2.0 mole percent sulfonated organic compound and (if) a diol moiety that includes ethylene glycol and less than about 6 mole percent diethylene glycol.
  • such polyamide-compatible polyethylene terephthalate polymers when intended for packaging applications, further possess an intrinsic viscosity of at least about 0.80 dL/g and a b* color value of less than about 4 as classified by the CIE L*a*b* color space as measured on either amorphous pellets or crystalline pellets.
  • exemplary polyamide-polyester polymer blends typically include at least about 70 weight percent polyamide-compatible polyethylene terephthalate polymers and less than about 30 weight percent polyamide polymers (e.g., between about 0.5 and 15 weight percent polyamide polymers).
  • the polyamide-compatible polyethylene terephthalate polymers are typically composed of (i) a terephthalate moiety that includes at least about 95 mole percent terephthalic acid (or its dialkyl ester, dimethyl terephthalate) and between about 0.1 and 2.0 mole percent sulfonated organic compound and (ii) a diol moiety that includes ethylene glycol and less than about 6 mole percent diethylene glycol.
  • the polyamide-polyester barrier blends are formed into preforms, which can thereafter be formed into polyester containers (e.g., beverage bottles).
  • the container is a high-clarity, carbonated soft drink bottle.
  • the carbonated soft drink bottle according to the present invention is capable of withstanding internal pressures of about 60 psig (400 kPa).
  • the container is a high-clarity, hot-fill bottle.
  • heat-setting performance diminishes at higher intrinsic viscosity levels and mechanical properties (e.g., stress cracking, drop impact, and creep) decrease at lower intrinsic viscosity levels.
  • the polyamide-compatible polyethylene terephthalate polymers can include additional comonomer substitution (i.e., modification in addition to the sulfonated organic compound modification).
  • isophthalic acid is an effective modifier (e.g., between about 1 and 4 mole percent isophthalic acid substitution).
  • the polyamide-compatible polyester resins may include a heat-up rate additive, which promotes the absorption of energy during preform reheating processes. See, e.g., commonly assigned U.S. Patent Applications Ser. No. 10/850,918, for Slow-Crystallizing Polyester Resins, filed May 21, 2004, and Ser. No. 10/996,789, for Polyester Preforms Useful for Enhanced Heat- Set Bottles, filed November 24, 2004.
  • Polyethylene terephthalate is typically converted into a container via a two-step process.
  • an amorphous bottle preform (e.g., less than about 4 percent crystallinity) is produced by melting bottle resin in an extruder and injection molding the molten polyester into a preform.
  • Such a preform usually has an outside surface area that is at least an order of magnitude smaller than the outside surface of the final container.
  • the preform is reheated by passing the preforms through a reheat oven of a blow molding machine.
  • the reheat oven may consist of a bank of quartz lamps (3,000 and 2,500 watt lamps) that emits radiation mostly in the infrared range.
  • the reheated preform is then placed into a bottle blow mold and, by stretching and inflating with high-pressure air, formed into a heated bottle.
  • the blow mold is maintained at a temperature between about 115 0 C and 200°C, usually between about 12O 0 C and 160°C.
  • the introduction of compressed air into the heated preform effects formation of the heated bottle.
  • the compressed air is turbulently released from the bottle by the balayage technique to facilitate cooling of the heated bottle.
  • Preform reheat temperature is important for optimal bottle performance. Though it varies depending on the application ⁇ e.g., hot-filled beverage bottle or carbonated soft drink bottles), reheat temperature is typically in the range of 30-50 0 C above the glass transition temperature (T G ).
  • the rate at which a preform can be reheated to the orientation temperature is important for optimal bottle performance in high-speed, polyethylene terephthalate blow-molding machines, such as those manufactured by Sidel, Inc. (LeHavre, France). This is especially true for heat-set bottles that are intended for filling with hot liquids in excess of 185°F (85°C).
  • the preform is reheated rapidly to as high a temperature as possible. This maximizes crystallization upon blow molding and avoids thermal crystallization in the preform.
  • thermal crystallization can cause unacceptable haze as a result of spherulitic crystallization.
  • polyamide-polyester barrier blends are formed into unoriented films.
  • the polyamide-polyester barrier blends are formed into either uniaxially oriented film or biaxially oriented film.
  • polyamide-polyester barrier blends are formed into sheets (e.g., 1+ millimeter sheets), either unoriented or oriented. When modified with UV blockers, such sheets are especially durable despite prolonged exposure to sunlight.
  • polyamide-polyester barrier blends are formed into articles, such as by injection molding.
  • polyamide- polyester barrier blends can be modified with fillers (e.g., glass or minerals) to provide an engineering resin.
  • fillers e.g., glass or minerals
  • polyamide-polyester barrier blends are suitable for use as unfilled engineering resin.
  • polyamide-polyester barrier blends are formed into fibers. Such fibers may be further formed into textile materials and products, such as yarns and fabrics.
  • the polyamide- compatible polyester polymers are usually polymerized only in the melt phase (i.e., the resins usually do not undergo solid state polymerization). Moreover, when used for fibers, the polyamide-compatible polyester polymers do not require additional comonomer substitution.
  • the polyamide-compatible polyester polymers of the present invention may be directly compounded with polyamide polymers.
  • the present invention requires that the polyamide-polyester polymer blend be subjected to the melt phase just once to effect compounding and forming of an article (e.g., a preform, a container, a sheet, or a film).
  • an article e.g., a preform, a container, a sheet, or a film.
  • the polyamide-polyester polymer blend does not acquire unfavorable heat histories, which cause polymer yellowing.
  • initial blending of the polyamide-compatible polyethylene terephthalate polymers and the polyamide polymers usually includes melt blending, which is followed by forming operations while the polyamide-polyester polymer blend is already in the melt phase.
  • the polyamide-compatible polyethylene terephthalate polymers and the polyamide polymers may be mixed as solids to form premixed polyamide-polyester polymer blends.
  • premixed polyamide-polyester polymer blends may be convenient for users that prefer to have polymer suppliers control the polyamide-polyester polymer formulations (i.e., QA/QC). Accordingly, both dry blending and melt blending of the polyamide-compatible polyethylene terephthalate polymers and the polyamide polymers are within the scope of the invention.
  • Polyamide-compatible polyethylene terephthalate polymers were prepared using a slurry of terephthalic acid, isophthalic acid, ethylene glycol (to facilitate polymerization, a nominal 15 percent molar excess of ethylene glycol is used), antimony trioxide, and cobalt acetate. This is the batch charge (“BC").
  • the slurry was esterified for approximately two hours at 260 0 C and a pressure of 40 psi (280 kPa). Under these conditions, the acids esterify to approximately 90 percent completion and diethylene glycol begins to form. Next, the pressure is reduced to atmospheric. At this point, DMSIP may be added as an ethylene glycol slurry.
  • Esterification is continued at atmospheric pressure ⁇ i.e., atmospheric esterification, or "AE" for approximately one hour at 265 0 C, followed by the addition of a phosphoric acid/ethylene glycol solution as a stabilizer.
  • the reaction temperature is increased to 285° to 290 0 C and the pressure is gradually reduced to about 1 torr (0.1 kPa).
  • polymer molecular weight and melt viscosity increase.
  • the polymer reaches a melt viscosity indicative of 18,000 to 20,000 g/mole the polymerization is terminated, the polymer discharged from the reactor, and formed into chips.
  • Higher molecular weight polymers e.g., intrinsic viscosity in excess of 0.70 dL/g
  • VLD vacuum let down
  • Table 1 shows the results of varying the timing of addition and the amount of sodium salt sulfoisophthalate derivatives into polyethylene terephthalate polymers prepared as described. The results are measured with respect to polymer quality and mole percent of diethylene glycol.
  • DMSIP produced the most favorable results when added at a concentration of 0.5 percent during atmospheric esterification ("AE").
  • AE atmospheric esterification
  • the DMSIP dissolved completely into the polymer and the diethylene glycol level was 3.1 mole percent.
  • Higher DMSIP levels added during atmospheric esterification yielded a slightly higher mole percentage of diethylene glycol.
  • DMSIP added during the batch charge yielded undesirably higher diethylene glycol levels ⁇ i.e., 8.0 mole percent).
  • 2.0 percent DMSIP added during the batch charge resulted in small precipitates in the polymer.
  • polyethylene terephthalate bottles made from the above process were evaluated for sidewall haze and carbon dioxide (CO 2 ) barrier property.
  • Polymers lacking or containing from 0.2, 0.50, or 1.0 mole percent DMSIP were produced as described above, with DMSIP added during atmospheric esterification.
  • the polymers were then dry blended with 2 weight percent of the nylon-MXD6 polyamide.
  • the control polymer lacked nylon-MXD6 and DMSIP. Thereafter, bottles were formed and evaluated. Table 2 shows a more than two week increase in shelf life between the control bottle compared with the same bottle blended with 2 weight percent nylon-MXD6.
  • shelf life is defined by a 17.5 percent loss in product carbonation ⁇ i.e., CO 2 loss).
  • the bottle sidewall haze is much greater.
  • DMSIP-containing polyester bottles reduced the sidewall haze (as compared with the blended, non-DMSIP-containing bottle) at all levels tested. Furthermore, there is no decrease in shelf life with the DMSIP-containing polyester bottles.
  • DMSIP-modified copolyesters were analyzed for unreacted (i.e., residual) DMSIP.
  • the analysis involved two steps. The first step is separating the low molecular weight species (oligomers) from the polymer by gel permeation chromatography (GPC). The second step is analyzing the oligomers isolated by GPC for unreacted DMSIP using high pressure liquid chromatography (HPLC). This method will resolve (but not specifically identify) oligomers up to hexamers. Given a nominal polyethylene terephthalate molecular weight of 192, this HPLC analysis covers oligomers up to roughly 1000 molecular weight.
  • HPLC will quantify terephthalic acid (TA), 2- hydroxyethylterephthalate (MHET), bis-(2-hydroxyethyl)-terephthalate (BHET), and cyclic trimer.
  • TA terephthalic acid
  • MHET 2- hydroxyethylterephthalate
  • BHET bis-(2-hydroxyethyl)-terephthalate
  • concentrations of other oligomers can be closely approximated based on the HPLC response factor for cyclic trimer.
  • Table 3 details the polymer formulations for this experiment, including mole percentages of 0.0, 0.5, and 1.0 mole percent for DMSIP.
  • Table 4 shows the unreacted
  • DMSIP measured by HPLC in parts per million (ppm) for polymer containing 0.0, 0.5, or 1.0 mole percent DMSIP. Each sample was performed in duplicate. Table 5 shows the tabulated data for oligomers present at concentrations over 100 ppm. Table 5 further shows unreacted terephthalic acid (TA), unreacted 2-hydroxyethylterephthalate (MHET), unreacted bis-(2- hydroxyethyl)-terephthalate (BHET), and unreacted DMSIP, measured in ppm. In the data shown in Table 5, one oligomer was found unique to DMSIP polymers. This oligomer possesses a HPLC retention time of approximately 14.27 minutes. Figure 8 depicts Table 5, with HPLC retention time shown on the x-axis and ppm shown on a logarithmic y-axis.
  • Table 6 shows the comparison, by percentage, of oligomers present at greater than 100 ppm compared with the total ppm of oligomers for polymer lacking or containing 0.5 or 1.0 mole percent DMSIP.
  • the data show that the presence of DMSIP does not contribute to the percentage of oligomers present in an amount greater than 100 ppm.

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Abstract

L'invention concerne des mélanges barrière de polyamide-polyester possédant des propriétés améliorées de barrière aux gaz, de clarté et des propriétés organoleptiques, ainsi que des récipients (par exemple, des bouteilles), des feuilles et des films formés à partir de ces résines barrière. L'invention concerne également des résines de polyéthylène téréphthalate compatibles avec un polyamide utilisées pour former les mélanges polymères améliorés de polyamide-polyester.
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