HK1000322B - Naphthalenedicarboxylic acid containing polymers having reduced fluorescence - Google Patents

Description

FIELD OF THE INVENTION

This invention relates to naphthalenedicarboxylic acid containing polymers having reduced fluorescence. More specifically, the polymers contain at least 0.1 mole percent of 2,6-naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylate ester, with 0.1 to 5 mole percent of a copolymerizable aromatic ketone. These polymers are useful for packaging applications where clarity and/or aesthetic appeal are of concern.

BACKGROUND OF THE INVENTION

Naphthalenedicarboxylic acid is used to make extrusion and injection-molding resins because of the good heat resistance, high glass transition temperature, and gas barrier properties of naphthalenedicarboxylic acid based polymers. Polymers containing naphthalenedicarboxylic acid are used in the fabrication of various articles for household or industrial use, including appliance parts, containers, and auto parts. One major drawback of naphthalenedicarboxylic acid containing polymers, however, is their inherent bluish fluorescence. Thus, objects prepared with naphthalenedicarboxylic acid containing polymers have a hazy and bluish appearance. This phenomenon is especially of concern in the packaging of foods and beverages wherein the food or beverage inside a container made from a naphthalenedicarboxylic acid containing polymer appears unnatural.

The fluorescence of homopolymers of poly(ethylene 2,6-naphthalenedicarboxylate), referred to as PEN, is known in the art. Because of the improved properties of naphthalenedicarboxylic acid containing polymers, it is desirable to incorporate small amounts of naphthalenedicarboxylic acid in polymers such as poly(ethylene terephthalate) (PET). However, copolymers containing very small amounts of naphthalenedicarboxylic acid fluoresce with intensity similar to, or in some cases greater than PEN homopolymers. Surprisingly, PET modified by copolymerizing in less than 1 mole percent naphthalenedicarboxylic acid has significant visible fluorescence.

Fluorescence is a type of luminescence in which an atom or molecule emits radiation in passing from a higher to a lower electronic state. The term is restricted to phenomena in which the time interval between absorption and emission of energy is extremely short (10^-10 to 10^-6 second). Fluorescence in a polymer or small molecule, occurs when a photon is emitted from an excited singlet state. Quenching of fluorescence eliminates or reduces the ability for photon emission by providing an alternative pathway for the excited state energy such as vibronic or heat loss, or intersystem crossing to the excited triplet state.

Methods to quench fluorescence in PEN have been disclosed by Chen Shangxian et al. in an article entitled, "Fluorescence Spectra Of Poly(Ethylene-2,6-Naphthalene Dicarboxylate)" which appeared in SCIENTIA SINICA, Vol. XXIV, No. 5, May 1981, and by CAO Ti et al. in an article entitled, "Intermolecular Excimer Interaction In Poly(Polytetramethylene Ether Glycol Aryl Dicarboxylate)" which appeared in ACTA CHIMICA SINICA, Vol. 42, No. 1, 1984. Both of the references disclose the use of o-chlorophenol to quench PEN fluorescence in a chloroform solution. Dissolving the PEN in a chloroform solution to disperse the fluorescence quencher therein, however, is not practical on an industrial scale because only very dilute PEN solutions can be prepared. In addition, the PEN must have a low molecular weight to dissolve in the chloroform solution.

In contrast, the present inventors have unexpectedly determined that the incorporation of 0.1 to 5 mole percent of a copolymerizable aromatic ketone in polymers containing naphthalenedicarboxylic acid significantly reduces fluorescence without deleteriously affecting the physical properties of the polymer.

SUMMARY OF THE INVENTION

Accordingly, it is one object of the present invention to provide naphthalenedicarboxylic acid containing polymers with reduced fluorescence.

Accordingly, it is another object of the invention to provide naphthalenedicarboxylic acid containing polymers which have reduced fluorescence and are useful in applications where good heat resistance, high glass transition temperature and gas barrier properties are required.

These and other objects are accomplished herein by a naphthalenedicarboxylic acid containing polymer with reduced fluorescence comprising repeat units from:

• (a) a dicarboxylic acid component which comprises at least 0.1 mole percent of 2,6-naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylate esters;
• (b) a diol or diamine component; and
• (c) 0.1 to 5 mole percent, based on 100 mole percent dicarboxylic acid and 100 mole percent diol or diamine, of a copolymerizable aromatic ketone which has at least one acyl group directly attached to the aromatic ring.

DESCRIPTION OF THE INVENTION

The polymers of the present invention contain naphthalenedicarboxylic acid and a fluorescence quenching compound. The polymers contain repeat units from a dicarboxylic acid, a diol or a diamine, and a copolymerizable aromatic ketone. The dicarboxylic acid, component (a), consists of at least 0.1 mole percent 2,6-naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylate ester. The diol or diamine, component (b), may be any diol or diamine. The copolymerizable aromatic ketone, component (c), consists of 0.1 to 5 mole percent, based on 100 mole percent dicarboxylic acid and 100 mole percent diol or diamine, of a copolymerizable aromatic ketone diacid, diester, or diol. Preferably, the polymer is a polyester containing repeat units from 0.1 to 100 mole percent of 2,6-naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylate ester, and 0 to 99.9 mole percent of terephthalic acid or dimethyl terephthalate, and at least 90 mole percent ethylene glycol.

The dicarboxylic acid component of the polymer may optionally include one or more different monomers other than 2,6-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylate ester, terephthalic acid, and dimethyl terephthalate. Such additional dicarboxylic acids include aromatic dicarboxylic acids preferably having 8 to 14 carbon atoms, aliphatic dicarboxylic acids preferably having 4 to 12 carbon atoms, or cycloaliphatic dicarboxylic acids preferably having 8 to 12 carbon atoms. Examples of dicarboxylic acids to be included with 2,6-naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylate ester are: phthalic acid, isophthalic acid, cyclohexanediacetic acid, diphenyl-4,4'-dicarboxylic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, azelaic acid, sebacic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, resorcinoldiacetic acid, diglycolic acid, 4,4'-oxybis(benzoic) acid, biphenyldicarboxylic acid, 1,12-dodecanedicarboxylic acid, 4,4'-sulfonyldibenzoic acid, 4,4'-methylenedibenzoic acid, trans-4,4'-stilbenedicarboxylic acid, and the like. It should be understood that use of the corresponding acid anhydrides, esters, and acid chlorides of these acids is included in the term "dicarboxylic acid". The polyester may be prepared from one or more of the above dicarboxylic acids or esters.

Component (b) of the present invention is a diol or diamine. Suitable diols include cycloaliphatic diols preferably having 6 to 20 carbon atoms or aliphatic diols preferably having 3 to 20 carbon atoms. Specific examples of diols are: ethylene glycol, diethylene glycol, triethylene glycol, 1,4-cyclohexanedimethanol, propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, 2,2-dimethyl-1,3-propanediol, 1,10-decanediol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 3-methylpentanediol-(2,4), 2-methylpentanediol-(1,4), 2,2,4-trimethylpentane-diol(1,3), 2-ethylhexanediol-(1,3), 2,2-diethylpropane-diol-(1,3), hexanediol-(1,3), 1,4-di-(hydroxyethoxy)-benzene, 2,2-bis-(4-hydroxycyclohexyl)-propane, 2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane, 2,2-bis-(3-hydroxyethoxyphenyl)-propane, and 2,2-bis-(4-hydroxypropoxyphenyl)-propane.

The polyester may also contain small amounts of trifunctional or tetrafunctional comonomers such as trimellitic anhydride, trimethylolpropane, pyromellitic dianhydride, pentaerythritol, and other polyester forming polyacids or diols generally known in the art.

Naphthalenedicarboxylic acid containing polyamides can be formed from adipic acid, isophthalic acid, terephthalic acid, 1,3- or 1,4-cyclohexanedicarboxylic acid, aliphatic diacids containing 6 to 12 carbon atoms, aliphatic amino acids or lactams with 6 to 12 carbon atoms, 1,6-hexanediamine, meta- or para-xylylenediamine, 1,3- or 1,4-cyclohexane(bis)methylamine, aliphatic diamines with 4 to 12 carbon atoms, and other polyamide forming diacids and diamines. The polymer may be prepared from one or more of the above diols or diamines.

The polymer may also contain polycarbonate repeat units formed from the reaction of a carbonic acid derivative with a diol such as bisphenol A. The polymer may be a blend of the above-described polyesters, polyamides, polycarbonates, or polyesteramides.

Component (c) of the present invention is 0.1 to 5 mole percent, preferably 0.5 to 2 mole percent of a fluorescence quenching compound. Using more than 5 mole percent of the fluorescence quenching compound hinders the crystallization of the polyester and results in inferior physical properties. The fluorescence quenching compound is a copolymerized aromatic ketone which is copolymerized in the polymer backbone. The copolymerized aromatic ketone contains an aromatic ring selected from benzene, naphthalene and biphenyl.

At least two polymerizable groups are attached to the aromatic ring. Preferably, two polymerizable groups are attached to the aromatic ring. The polymerizable groups are carboxylic acids or esters and/or aliphatic hydroxyl groups. The carboxylic ester has the formula: wherein R₃ is selected from a substituted and unsubstituted C₁-C₆ alkyl group and a substituted and unsubstituted phenyl group. C₁-C₆ unsubstituted and substituted alkyl groups represented by R₃ include straight or branched chain fully saturated hydrocarbon radicals and these substituted with one or more of the following: C₅-C₇ cycloalkyl, and C₅-C₇ cycloalkyl substituted with one or two of C₁-C₆ alkyl, C₁-C₆ alkoxy or halogen. The substituted phenyl groups represent such phenyl groups substituted by one or two of C₁-C₆ alkyl. Preferably R₃ is methyl.

The aliphatic hydroxyl group has the formula:         (CH₂)_nOH wherein n is an integer from 1 to 6, preferably n is 2. Preferred aromatic ring compounds containing polymerizable groups are terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid. The most preferred is 2,6-naphthalenedicarboxylic acid.

In addition to the copolymerizable groups, the aromatic ring contains at least one acyl group which has the structure wherein R₄ is selected from unsubstituted and substituted C₁-C₁₀ alkyl, unsubstituted and substituted phenyl, and unsubstituted and substituted naphthyl groups. C₁-C₁₀ unsubstituted and substituted alkyl groups represented by R₄ include straight or branched chain fully saturated hydrocarbon radicals and these substituted with one or more of the following: C₅-C₇ cycloalkyl, and C₅-C₇ cycloalkyl substituted with one or two of C₁-C₆ alkyl, C₁-C₆ alkoxy or halogen. The substituted phenyl groups mentioned above, unless otherwise specified, represent such phenyl groups substituted by one or two of C₁-C₆ alkyl. The alkyl, phenyl and naphthyl groups of R₄ may contain any substituent thereon as long as such substituents do not deleteriously effect the fluorescence quenching of the copolymerized aromatic ketone. Examples of acyl groups include acetyl, benzoyl, 1- or 2-naphthoyl, and propionyl. Preferred acyl groups are benzoyl and 1- or 2-naphthoyl. The most preferred acyl group is the benzoyl group (C₆H₅CO-).

The acyl groups can be attached to any of the unsubstituted positions on the aromatic rings. Preferred copolymerizable aromatic ketones include dimethyl benzoylterephthalate (or benzoyl terephthalic acid), dimethyl 1-benzoyl 2,6-naphthalenedicarboxylate, dimethyl 3-benzoyl 2,6-naphthalenedicarboxylate, dimethyl 4-benzoyl 2,6-naphthalenedicarboxylate, dimethyl 1-(2-naphthoyl) 2,6-naphthalenedicarboxylate, dimethyl dibenzoyl-2,6-naphthalene dicarboxylate, and dimethyl benzoylisophthalate. The most preferred copolymerizable aromatic ketones are dimethyl benzoylterephthalate, dimethyl benzoyl-2,6-naphthalenedicarboxylate, and dimethyl dibenzoyl-2,6-naphthalenedicarboxylate.

Many other ingredients can be added to the compositions of the present invention to enhance the performance properties of the polyester. For example, surface lubricants, denesting agents, stabilizers, antioxidants, ultraviolet light absorbing agents, mold release agents, metal deactivators, colorants such as black iron oxide and carbon black, nucleating agents, phosphate stabilizers, zeolites, fillers, and the like, can be included herein. All of these additives and the use thereof are well known in the art. Any of these compounds can be used so long as they do not hinder the present invention from accomplishing its objects.

The naphthalenedicarboxylic acid containing polymer with the fluorescence quenching compound is prepared by conventional polycondensation procedures well-known in the art which generally include a combination of melt phase and solid state polymerization. Melt phase describes the molten state of the naphthalenedicarboxylic acid containing polymer during the initial polymerization process. The initial polymerization process includes direct condensation of the naphthalenedicarboxylic acid with the diol or diamine or by ester interchange using naphthalenedicarboxylic ester. For example, dimethyl-2,6-naphthalenedicarboxylate is ester interchanged with ethylene glycol at elevated temperatures in the presence of the copolymerizable aromatic ketone and a catalyst. The melt phase is concluded by extruding the naphthalenedicarboxylic acid polymer into strands and pelletizing. Optionally, the copolymerizable aromatic ketone can be melt blended with the naphthalenedicarboxylic acid containing polymer.

The naphthalenedicarboxylic acid containing polymer with the fluorescence quenching compound may optionally be solid state polymerized. Solid state polymerization involves heating the polymer pellets to a temperature in excess of 200°C, but well below the crystalline melt point, either in the presence of an inert gas stream or in a vacuum to remove a diol. Several hours are generally required in the solid state polymerized unit to build the molecular weight.

Typical catalysts which may be used include titanium alkoxides, dibutyl tin dilaurate, combinations of zinc, manganese, or magnesium acetates or benzoates with antimony oxide or antimony triacetate.

The inherent viscosity of the naphthalenedicarboxylic acid containing polymer should be 0.3 to 1.5 dL/g. However, inherent viscosities of from 0.5 to 0.9 are preferred, as measured at 25°C using 0.50 grams of polymer per 100 ml of a solvent consisting of 60% by weight phenol and 40% by weight tetrachloroethane.

The naphthalenedicarboxylic acid containing polymers serve as excellent starting materials for the production of moldings of all types. The naphthalenedicarboxylic acid containing polymers may also be blended with other polymers. Specific applications include food packaging such as bottles, trays, lids and films, medical parts, appliance parts, automotive parts, tool housings, recreational and utility parts. The molding compositions of the present invention are especially useful in applications that require transparent molded parts. Additionally, the polymers can be used to prepare extruded sheets for thermoforming applications. The polymers are readily extruded into films or processed into monolayer or multilayer food and beverage containers. Potential methods for producing containers include: (1) injection stretch blow molding using either one or two stage technology, (2) injection blow molding, (3) extrusion blow molding, (4) pipe extrusion, and (5) co-injection or coextrusion where the polymers can serve as either the structural layer or barrier layer depending upon end use requirements. Fibers, melt-blown webs, extruded sheets, vacuum-drawn trays/parts, Injection molded parts, and extrusion coated wires may also be made from these polymers.

The materials and testing procedures used for the results shown herein are as follows:

Fluorescence Intensity was determined using a Perkin-Elmer LS5B Luminescence Spectrometer which measured relative fluorescence intensity at peak maxima.

The composition of the polymers was determined using H-NMR spectroscopy (JEOL 270 Mhz). Solutions (2.5% weight/volume) in 70/30 CDCl₃/CF₃COOD were scanned 256 times. A delay of 10 seconds was used with a pulse width of 3.4 microseconds (5.0 microseconds, 90°).

Glass transition temperature (Tg), melting temperature (Tm) and crystallization half-time (t_1/2) were determined by differential scanning calorimetry (DSC) using a Perkin-Elmer DSC II instrument. The Tg and Tm were determined using a 20°C/minute scan rate after the samples had been heated above the Tm and quenched below the Tg. The t_1/2 was determined by the following method: The sample was heated to 300°C under a nitrogen atmosphere and held for two minutes. The sample was removed from the DSC and immediately cooled to -20°C. The DSC was cooled to 50°C and the sample was returned to the DSC. The temperature of the DSC was increased at a rate of 320°C/minute to a test temperature of 190°C, 210°C or 230°C. Samples were isothermally crystallized at each of the test temperatures. The crystallization half-time (t_1/2) is the time required to reach the peak on the crystallization exotherm.

Inherent viscosity (I.V.) was measured at 25°C using 0.50 grams of polymer per 100 ml of a solvent consisting of 60% by weight phenol and 40% by weight tetrachloroethane.

Sample preparation for determining fluorescence intensity involved grinding the polyester samples to 3-4 mm. The samples were micropulverized in an analytical grinding mill and passed through a 120 mesh screen. The powders were dried for 24 hours at 140°C. Approximately 0.5 grams of the powder was packed into a sample holder and measurements were taken by reflectance. The excitation wavelength was 350 nm and the emission maximum was 428-432 nm unless listed otherwise. The values are reported as normalized to poly(ethylene-2,6-naphthalenedicarboxylate) (fluorescence intensity 100). The fluorescence intensity of poly(ethylene-2,6-naphthalenedicarboxylate) was repeated 10 times with a standard deviation of 5.0. Two measurements were taken of all other samples and the averages are reported in Table I.

The present invention will be further illustrated by a consideration of the following examples, which are intended to be exemplary of the invention. All parts and percentages in the examples are on a weight basis unless otherwise stated.

EXAMPLE 1 Poly(ethylene 2,6-naphthalene dicarboxylate) was prepared by the following procedure.

Dimethyl 2,6-naphthalene dicarboxylate (0.5 moles, 122 grams), ethylene glycol (1.0 moles, 62 grams), and catalyst metals were placed in a 500 mL polymerization reactor under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 2 hours. The temperature was increased to 220°C and maintained for 1 hour. The temperature was increased to 290°C which took approximately 20 minutes. When the temperature reached 290°C, the nitrogen flow was stopped and vacuum was applied. The polymer was stirred under vacuum 0.01-0.04 kPa (0.1-0.3 mmHg) for 50 minutes. The polymer was cooled and ground. The fluorescence intensity and I.V. of the polymer are summarized in Table I, and Tg, Tm and t_1/2 are listed in Table II.

EXAMPLE 2 Poly(ethylene 2,6-naphthalene dicarboxylate) with 0.5 mole percent copolymerized dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate was prepared by the following procedure.

Dimethyl 2,6-naphthalene dicarboxylate (0.124 moles, 30.35 grams), dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate (0.00063 moles, 0.22 grams), ethylene glycol (0.25 moles, 15.5 grams), and catalyst metals were placed in a 100 mL polymerization reactor under a nitrogen atmosphere. The polymer was prepared according to the procedure as set forth in Example 1. The fluorescence intensity and I.V. of the polymer are summarized in Table I, and t_1/2 are listed in Table II.

EXAMPLE 3 Poly(ethylene 2,6-naphthalene dicarboxylate) with 1.0 mole percent copolymerized dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate was prepared by the following procedure.

Dimethyl 1,6-naphthalene dicarboxylate (0.124 moles, 30.35 grams), dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate (0.00125 moles, 0.44 grams), ethylene glycol (0.25 moles, 15.5 grams), and catalyst metals were placed in a 100 mL polymerization reactor under a nitrogen atmosphere. The polymer was prepared according to the procedure as set forth in Example 1. The fluorescence intensity and I.V. of the polymer are summarized in Table I, and t_1/2 are listed in Table II.

EXAMPLE 4 Poly(ethylene 2,6-naphthalene dicarboxylate) with 2.0 mole percent copolymerized dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate was prepared by the following procedure.

Dimethyl 2,6-naphthalene dicarboxylate (0.123 moles, 29.98 grams), dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate (0.0025 moles, 0.87 grams), ethylene glycol (0.25 moles, 15.5 grams), and catalyst metals were placed in a 100 mL polymerization reactor under a nitrogen atmosphere. The polymer was prepared according to the procedure as set forth in Example 1. The fluorescence intensity and I.V. of the polymer are summarized in Table I, and Tg, Tm are listed in Table II.

EXAMPLE 5 Poly(ethylene 2,6-naphthalene dicarboxylate) with 5.0 mole percent copolymerized dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate was prepared by the following procedure.

Dimethyl 2,6-naphthalene dicarboxylate (0.119 moles, 28.98 grams), dimethyl l-benzoyl-2,6-naphthalene dicarboxylate (0.00625 moles, 2.18 grams), ethylene glycol (0.25 moles, 15.5 grams), and catalyst metals were placed in a 100 mL polymerization reactor under a nitrogen atmosphere. The polymer was prepared according to the procedure as set forth in Example 1. The fluorescence intensity and I.V. of the polymer are summarized in Table I, and Tg are listed in Table II.

EXAMPLE 6 Poly(ethylene 2,6-naphthalene dicarboxylate) with 1.2 mole percent copolymerized dimethyl benzoylterephthalate was prepared by the following procedure.

Dimethyl 2,6-naphthalene dicarboxylate (0.495 moles, 120.78 grams), dimethyl benzoylterephthalate (0.0058 moles, 1.74 grams), ethylene glycol (1.0 mole, 62.0 grams), and catalyst metals were placed in a 500 mL polymerization reactor under a nitrogen atmosphere. The polymer was prepared according to the procedure as set forth in Example 1. The fluorescence intensity and I.V. of the polymer are summarized in Table I, and t_1/2 are listed in Table II.

EXAMPLE 7 Poly(ethylene 2,6-naphthalene dicarboxylate) with 2.0 mole percent copolymerized dimethyl benzoylterephthalate was prepared by the following procedure.

Dimethyl 2,6-naphthalene dicarboxylate (0.49 moles, 119.56 grams), dimethyl benzoylterephthalate (0.010 moles, 2.98 grams), ethylene glycol (1.0 mole, 62.0 grams), and catalyst metals were placed in a 500 mL polymerization reactor under a nitrogen atmosphere. The polymer was prepared according to the procedure as set forth in Example 1. The fluorescence intensity and I.V. of the polymer are summarized in Table I, and t_1/2 are listed in Table II.

EXAMPLE 8 Poly(ethylene 2,6-naphthalene dicarboxylate) with 3.5 mole percent copolymerized dimethyl benzoylterephthalate was prepared by the following procedure.

Dimethyl 2,6-naphthalene dicarboxylate (0.483 moles, 117.7 grams), dimethyl benzoylterephthalate (0.018 moles, 5.22 grams), ethylene glycol (1.00 mole, 62.0 grams), and catalyst metals were placed in a 500 mL polymerization reactor under a nitrogen atmosphere. The polymer was prepared according to the procedure as set forth in Example 1. The fluorescence intensity and I.V. of the polymer are summarized in Table I, and t_1/2 are listed in Table II.

EXAMPLE 9 Poly(ethylene 2,6-naphthalene dicarboxylate) with 5.0 mole percent copolymerized dimethyl benzoylterephthalate was prepared by the following procedure.

Dimethyl 2,6-naphthalene dicarboxylate (0.475 moles, 115.90 grams), dimethyl benzoylterephthalate (0.025 moles, 7.45 grams), ethylene glycol (1.00 mole, 62.0 grams), and catalyst metals were placed in a 500 mL polymerization reactor under a nitrogen atmosphere. The polymer was prepared according to the procedure as set forth in Example 1. The fluorescence intensity and I.V. of the polymer are summarized in Table I, and t_1/2 are listed in Table II.

EXAMPLE 10 Poly(ethylene 2,6-naphthalene dicarboxylate) with 0.5 mole percent copolymerized dimethyl 1-(2-naphthoyl)-2,6-naphthalene dicarboxylate was prepared by the following procedure.

Dimethyl-2,6-naphthalene dicarboxylate (0.124 moles, 30.35 grams), dimethyl 1-(2-naphthoyl)-2,6-naphthalene dicarboxylate (0.00063 moles, 0.25 grams), ethylene glycol (0.25 mole, 15.5 grams), and catalyst metals were placed in a 100 mL polymerization reactor under a nitrogen atmosphere. The polymer was prepared according to the procedure as set forth in Example 1. The fluorescence intensity and I.V. of the polymer are summarized in Table I, and Tg and Tm are listed in Table II.

EXAMPLE 11 Poly(ethylene 2,6-naphthalene dicarboxylate) with 1.0 mole percent copolymerized dimethyl 1-(2-naphthoyl)-2,6-naphthalene dicarboxylate was prepared by the following procedure.

Dimethyl-2,6-naphthalene dicarboxylate (0.124 moles, 30.20 grams), dimethyl 1-(2-naphthoyl)-2,6-naphthalene dicarboxylate (0.00125 moles, 0.50 grams), ethylene glycol (0.25 mole, 15.5 grams), and catalyst metals were placed in a 100 mL polymerization reactor under a nitrogen atmosphere. The polymer was prepared according to the procedure as set forth in Example 1. The fluorescence intensity and I.V. of the polymer are summarized in Table I, and Tg and Tm are listed in Table II. TABLE I

EXAMPLE	AROMATIC KETONE (mole%)	I.V. (dL/g)	FLUORESCENCE INTENSITY (at 430 nm)
1 PEN control		0.42	100
2 PEN + 0.5%		0.48	47
3 PEN + 1.0%		0.47	33
4 PEN + 2.0%		0.43	26
5 PEN + 5.0%		0.45	13
6 PEN + 1.2%		0.38	79
7 PEN + 2.0%		0.42	62
8 PEN + 3.5%		0.44	62
9 PEN + 5.0%		0.39	43
10 PEN + 0.5%		0.35	40
11 PEN + 1.0%		0.39	28

TABLE I

The results in Table I clearly indicate that the poly(ethylene-2,6-naphthalene dicarboxylate) compositions containing a critical range of an aromatic ketone as a fluorescence quencher, which is copolymerized in the PEN backbone, exhibit significantly less fluorescence than PEN compositions without the fluorescence quencher. In addition, the data in Table I also indicates that the use of the fluorescence quencher in a critical amount does not deleteriously effect the inherent viscosity of the polyester. TABLE II

EXAMPLE	AROMATIC KETONE (mole%)	Tg (°C)	Tm (°C)
				190°C	210°C	230°C
1 PEN control		123	268	2.5	1.5	2.5
2 PEN+0.5%		-	-	5.7	3.7	5.8
3 PEN+1.0%		-	-	6.0	4.2	7.9
4 PEN+2.0%		123	262	-	-	-
5 PEN+5.0%		126	-	-	-	-
6 PEN+1.2%		-	-	3.0	1.9	3.1
7 PEN+2.0%		-	-	3.9	2.6	4.9
8 PEN+3.5%		-	-	3.8	2.8	6.3
9 PEN+5.0%		-	-	4.0	3.3	8.8
10 PEN+0.5%		122	266	-	-	-
11 PEN+1.0%		124	266	-	-	-

TABLE II

The results in Table II establish the critical range for the aromatic ketones as fluorescence quenchers which are copolymerized in the poly(ethylene-2,6-naphthalene dicarboxylate) backbone. The data indicates that 0.1 to 5 mole percent of the aromatic ketones reduce fluorescence without deleteriously effecting the physical properties of the polyester. In contrast, greater than 5 mole percent of the aromatic ketones in the compositions slows down the crystallization rate to an unacceptable level.

EXAMPLE 12 Preparation of industrial scale poly(ethylene 2,6-naphthalene dicarboxylate) with 1.0 mole percent copolymerized dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate was prepared by the following procedure.

Dimethyl 2,6-naphthalene dicarboxylate (28.1 moles, 6.86 kilograms), dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate (0.28 moles, 96.6 grams), ethylene glycol (56.3 moles, 3.49 kilograms), and catalyst metals were placed in a 10 gallon steel polymerization reactor equipped with a twin-blade helical agitator under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 2 hours. The temperature was increased to 220°C and maintained for 2 hours. The temperature was increased to 285°C. When the temperature reached 285°C, the nitrogen flow was stopped and vacuum was applied. The polymer was stirred under vacuum 0.067 kPa (0.5 mmHg) for 50 minutes. The polymer was extruded into a water bath and pelletized. The amorphous polymer was transferred to a vacuum oven and dried for three hours at 80°C. Crystallization was accomplished in a tumbler crystallizer for three hours at 180°C. The I.V. of the polymer at this stage was 0.59 dL/g.

To increase the molecular weight of the polymer, solid-state polymerization was utilized. The crystalline polymer was charged to a stationary bed solid-state unit equipped with nitrogen flow. The polymer was heated to 230°C. The temperature was maintained for 24 hours in the presence of a nitrogen purge. The I.V. of the polymer at this stage was 0.71 dL/g. The fluorescence intensity of the polymer was 50 as compared to 135 for similarly prepared PEN containing no fluorescence quencher.

EXAMPLE 13

A two-stage stretch blow molding process was utilized to make 2-liter bottles. Preforms were made on a Cincinnati Milacron injection molding machine at a molding temperature of 310°C. The preforms were stored for 24 hours before the bottle blowing step. Bottles were blown by reheating preforms using a quartz lamp by stretch blow molding or reheat blow molding. The preforms were heated slightly above the Tg of the polymer and pressurized to blow them into bottle shaped molds.

Visual inspection indicated that bottles prepared from PEN without a fluorescence quencher exhibited more bluish fluorescence than bottles prepared using PEN with 1.0 mole percent copolymerized dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate.

EXAMPLE 14 Dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate was prepared by the following procedure.

2,6-dimethyl naphthalene (100 grams, 0.64 moles), aluminum chloride (89.3 grams, 0.67 moles), carbon disulfide (600 mL), and methylene chloride (200 mL) were introduced into a 3-neck 2L flask fitted with a mechanical stirrer and cooled to 0-5°C. Benzoyl chloride (94.2 grams, 0.67 moles) was added dropwise over a period of about 1 hour. The temperature was kept below 10°C during this addition and throughout the reaction. The reaction mixture was stirred for 6 hours and then decomposed by pouring into ice/HCl. The organic layer was washed 5 times with water and then dried for 12 hours over sodium sulfate. The organic layer was concentrated to a viscous oil and treated with methanol, precipitating 1-benzoyl-2,6-dimethylnaphthalene as an off-white solid. The 1-benzoyl-2,6-dimethylnaphthalene was collected and dried (105 grams, 63%). The 1-benzoyl-2,6-dimethylnaphthalene was determined to be pure by gas chromatography with a melting point of 81-82°C (literature mp 84°C). A molecular weight of 260 was confirmed by Field Desorption Mass Spectroscopy (FDMS).

The 1-benzoyl-2,6-dimethylnaphthalene was oxidized to 1-benzoyl-2,6-naphthalenedicarboxylic acid by the following procedure.

The 1-benzoyl-2,6-dimethylnaphthalene (60 grams, 0.23 moles), sodium dichromate (185 grams, 0.621 moles), and 500 mL water were added to a 1 liter high pressure autoclave. The high pressure oxidation was carried out for 6 hours at 250°C with stirring. Chromium oxide was filtered off. Filtrate acidification with HCl resulting in precipitation of a light yellow material (67 g, 90%) which was used on the next step without further purification. The 1-benzoyl-2,6-naphthalenedicarboxylic acid had a melting point over 315°C and FDMS confirmed molecular weight of 320.

The 1-benzoyl-2,6-naphthalenedicarboxylic acid was converted to its dimethyl ester by the following procedure.

The 1-benzoyl-2,6-naphthalenedicarboxylic acid (100 grams, 0.313 moles) and methanol (600 mL) were placed in a 1 liter high pressure autoclave fitted with a magnetic stirrer. High pressure esterification was carried out for 2 hours at 250°C with stirring. The reaction mixture was concentrated to dryness. A light brown solid was the result. Recrystallization from methanol followed with treatment with activated carbon in acetone which was repeated three times afforded (upon concentration) 75 grams (69%) of almost white dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate. The dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate was gas chromatography pure with a melting point of 135-137°C. FDMS confirmed a molecular weight of 348 and a H-NMR spectrum consistent with the stated structure.

EXAMPLE 15 Poly(ethylene terephthalate) containing 5 mole percent copolymerized dimethyl 2,6-naphthalenedicarboxylate was prepared by the following procedure.

Dimethyl terephthalate (0.713 mol, 138.2 g), dimethyl 2,6-naphthalenedicarboxylate (0.0375 mol, 9.15 g), ethylene glycol (1.5 mol, 93.0 g), and catalyst metals were placed in a 0.5 L polymerization reactor under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 90 min. The temperature was increased to 220°C and maintained for 90 min. The temperature was increased to 285°C, the nitrogen flow was stopped and vacuum was applied. The polymer was stirred under vacuum 0.04 kPa (0.3 mmHg) for 30 minutes. The polymer was cooled and ground. The polymer had 0.43 dL/g I.V. Fluorescence data are summarized in Table III.

EXAMPLE 16 Poly(ethylene terephthalate) containing 5 mole percent copolymerized dimethyl 2,6-naphthalenedicarboxylate and 1.0 mole percent copolymerized dimethyl 1-benzoyl-2,6-naphthalenedicarboxylate was prepared by the following procedure.

Dimethyl terephthalate (0.705 mol, 136.7 g), dimethyl 2,6-naphthalenedicarboxylate (0.0375 mol. 9.15 g), ethylene glycol (1.5 mol, 93.0 g), dimethyl 1-benzoyl-2,6-naphthalenedicarboxylate (0.0075 mol, 2.40 g), and catalyst metals were placed in a 0.5 L polymerization reactor under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 90 min. The temperature was increased to 220°C and maintained for 90 min. The temperature was increased to 2850C, the nitrogen flow was stopped and vacuum was applied. The polymer was stirred under vacuum (0.04 kPa) for 25 minutes. The polymer was cooled and ground. The polymer had 0.40 dL/g I.V. fluorescence data are summarized in Table III.

EXAMPLE 17 Poly(ethylene terephthalate) containing 25 mole percent copolymerized dimethyl 2,6-naphthalenedicarboxylate was prepared by the following procedure.

Dimethyl terephthalate (0.563 mol, 109.1 g), dimethyl 2,6-naphthalenedicarboxylate (0.187 mol, 45.7 g), ethylene glycol (1.5 mol, 93.0 g), and catalyst metals were placed in a 0.5 L polymerization reactor under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 90 min. The temperature was increased to 220°C and maintained for 90 min. The temperature was increased to 285°C, the nitrogen flow was stopped and vacuun was applied. The polymer was stirred under vacuum 0.04 kPa (0.3 mmHg) for 24 minutes. The polymer was cooled and ground. The polymer had 0.36 dL/g I.V. Fluorescence data are summarized in Table III.

EXAMPLE 18 Poly(ethylene terephthalate) containing 25 mole percent copolymerized dimethyl 2,6-naphthalenedicarboxylate and 1.0 mole percent copolymerized dimethyl 1-benzoyl-2,6-naphthalenedicarboxylate was prepared by the following procedure.

Dimethyl terephthalate (0.555 mol, 107.6 g), dimethyl 2,6-naphthalenedicarboxylate (0.187 mol. 45.7 g), ethylene glycol (1.3 mol, 93.0 g), dimethyl 1-benzoyl-2,6-naphthalenedicarboxylate (0.0075 mol, 2.40 g), and catalyst metals were placed in a 0.5 L polymerization reactor under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 90 min. The temperature was increased to 220°C and maintained for 90 min. The temperature was increased to 285°C, the nitrogen flow was stopped and vacuum was applied. The polymer was stirred under vacuum (0.04 kPa) for 28 minutes. The polymer was cooled and ground. The polymer had 0.45 dL/g I.V. Fluorescence data are summarized in Table III.

EXAMPLE 19 Poly (butylene 2,6-naphthalenedicarboxylate) containing 30 mole percent copolymerized 1,4-cyclohexanedimethanol was prepared by the following procedure.

Dimethyl 2,6-naphthalenedicarboxylate (0.5 mol, 122.0 g), 1,4-butanediol (0.7 mol, 63.0 g), 1,4-cyclohexanedimethanol (0.15 mol, 21.6 g) and catalyst metals were placed in a 0.5 L polymerization reactor under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 90 min. The temperature was increased to 220°C and maintained for 90 min. The temperature was increased to 260°C, the nitrogen flow was stopped and vacuum was applied. The polymer was stirred under vacuum 0.04-0.067 kPa (0.3-0.5 mmHg) for 8 minutes. The polymer was cooled and ground. The polymer had 0.41 dL/g I.V. Fluorescence data are summarized in Table III.

EXAMPLE 20 Poly (butylene 2,6-naphthalenedicarboxylate) containing 30 mole percent copolymerized 1,4-cyclohexanedimethanol and 1.0 mole percent copolymerized dimethyl 1-benzoyl-2,6-naphthalenedicarboxylate was prepared by the following procedure.

Dimethyl 2,6-naphthalenedicarboxylate (0.495 mol, 120.8 g), 1,4-butanediol (0.7 mol, 63.0 g), 1,4-cyclohexanedimethanol (0.15 mol, 21.6 g), dimethyl 1-benzoyl-2,6-naphthalenedicarboxylate (0.005 mol, 1.60 g) and catalyst metals were placed in a 0.5 L polymerization reactor under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 90 min. The temperature was increased to 220°C and maintained for 90 min. The temperature was increased to 260°C, the nitrogen flow was stopped and vacuum was applied. The polymer was stirred under vacuum (0.04-0.067 kPa) for 8 minutes. The polymer was cooled and ground. The polymer had 0.42 dL/g I.V. Fluorescence data are summarized in Table III.

EXAMPLE 21 Poly(butylene 2,6-naphthalenedicarboxylate) was prepared by the following procedure.

Dimethyl 2,6-naphthalenedicarboxylate (0.5 mol, 122.0 g), 1,4-butanediol (1.0 mol, 90.1 g), and catalyst metals were placed in a 0.5 L polymerization reactor under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 90 min. The temperature was increased to 220°C and maintained for 90 min. The temperature was increased to 285°C, the nitrogen flow was stopped and vacuum was applied. The polymer was stirred under vacuum 0.04 kPa (0.3 mmHg) for 5 minutes. The polymer was cooled and ground. The polymer had 0.62 dL/g I.V. Fluorescence data are summarized in Table III.

EXAMPLE 22 Poly(ethylene 2,6-naphthalenedicarboxylate) containing 25 mole percent copolymerized dimethyl terephthalate was prepared by the following procedure.

Dimethyl 2,6-naphthalenedicarboxylate (0.563 mol, 137.3 g), dimethyl terephthalate (0.187 mol, 36.4 g), ethylene glycol (1.5 mol, 93.0 g), and catalyst metals were placed in a 0.5 L polymerization reactor under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 90 min. The temperature was increased to 220°C and maintained for 90 min. The temperature was increased to 285°C, the nitrogen flow was stopped and vacuum was applied. The polymer was stirred under vacuum (0.04 kPa) for 25 minutes. The polymer was cooled and ground. The polymer had 0.38 dL/g I.V. Fluorescence data are summarized in Table III.

EXAMPLE 23 Poly(ethylene 2,6-naphthalenedicarboxylate) containing 50 mole percent copolymerized dimethyl terephthalate was prepared by the following procedure.

Dimethyl 2,6-naphthalenedicarboxylate (0.375 mol, 91.5 g), dimethyl terephthalate (0.375 mol, 72.7g), ethylene glycol (1.5 mol, 93.0 g), and catalyst metals were placed in a 0.5 L polymerization reactor under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 90 min. The temperature was increased to 220°C and maintained for 90 min. The temperature was increased to 285°C, the nitrogen flow was stopped and vacuum was applied. The polymer was stirred under vacuum 0.04 kPa (0.3 mmHg) for 30 minutes. The polymer was cooled and ground. The polymer had 0.39 dL/g I.V. Fluorescence data are summarized in Table III.

EXAMPLE 24 Poly(ethylene terephthalate) was prepared by the following procedure.

Dimethyl terephthalate (0.75 mol, 145.5 g), ethylene glycol (1.5 mol, 93.0 g), and catalyst metals were placed in a 0.5 L polymerization reactor under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 60 min. The temperature was increased to 215°C and maintained for 60 min. The temperature was increased to 285°C, the nitrogen flow was stopped and vacuum was applied. The polymer was stirred under vacuum 0.04-0.067 kPa (0.3-0.5 mmHg) for 30 minutes. The polymer was cooled and ground. The polymer had 0.35 dL/g I.V. Fluorescence data are summarized in Table III.

EXAMPLE 25 Poly(ethylene terephthalate) containing 1 mole percent copolymerized dimethyl 2,6-naphthalenedicarboxylate was prepared by the following procedure.

Dimethyl terephthalate (0.743 mol, 144.1 g), dimethyl 2,6-naphthalenedicarboxylate (0.0075 mol, 1.83 ), ethylene glycol (1.5 mol, 93.0 g), and catalyst metals were placed in a 0.5 L polymerization reactor under a nitrogen atmosphere. The mixture was heated with stirring at 200°C for 90 min. The temperature was increased to 220°C and maintained for 90 min. The temperature was increased to 285°C, the nitrogen flow was stopped and vacuum was applied. The polymer was stirred under vacuum 0.40 kPa (0.3 mmHg) for 40 minutes. The polymer was cooled and ground. The polymer had an I.V. of 0.51dL/g. Fluorescence data are summarized in Table III. TABLE III

EX.	Polymer Composition	Aromatic Ketone (mole%)	Relative Fluorescence Intensity	Maximum Wavelength (nm)
15	PET + 5% DMN	None	181	383
16	PET + 5% DMN	1% BzN	26	385
17	PET + 25% DMN	None	85	418
18	PET + 25% DMN	1% BzN	26	419
19	PBN + 30% CHDM	None	64	421
20	PBN + 30% CHDM	1% BzN	29	431
21	PBN	None	74	428
22	PEN + 25% DMT	None	110	429
23	PEN + 50% DMT	None	102	431
24	PET	None	21	388
25	PET + 1% DMN	None	241	380
DMN = dimethyl 2,6-naphthalenedicarboxylate
BzN = dimethyl 1-benzoyl-2,6-naphthalenedicarboxylate
PBN = poly(butylene 2,6-naphthalenedicarboxylate)
CHDM = 1,4-cyclohexanedimethanol
PET = poly(ethylene terephthalate)

The results in Table III clearly indicate that naphthalenedicarboxylic acid containing polymers have a significant fluorescence intensity even when naphthalenedicarboxylic acid is a minor component. Unexpectedly, PET copolymerized with as little as 1 mole percent naphthalenedicarboxylate has a greater fluorescence intensity than PEN homopolymer. The results also indicate that the aromatic ketone additives of this invention effectively reduce fluorescence intensity in a broad composition range of naphthalenedicarboxylic acid containing polymers.

Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious modifications are within the full intended scope of the appended claims.

Claims (19)

1. A naphthalenedicarboxylic acid containing polymer with reduced fluorescence comprising repeat units from:

   (a) a dicarboxylic acid component which comprises at least 0.1 mole percent of 2,6-naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylate esters;

   (b) a diol or diamine component; and

   (c) 0.1 to 5 mole percent, based on 100 mole percent dicarboxylic acid and 100 mole percent diol or diamine, of a copolymerizable aromatic ketone which has at least one acyl group directly attached to the aromatic ring.
2. A naphthalenedicarboxylic acid containing polymer with reduced fluorescence comprising repeat units from:

   (a) a dicarboxylic acid component which comprises at least 85 mole percent of 2,6-naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylate esters;

   (b) a diol component which comprises at least 85 mole percent of ethylene glycol; and

   (c) 0.1 to 5 mole percent, based on 100 mole percent dicarboxylic acid and 100 mole percent diol or diamine, of a copolymerizable aromatic ketone which has at least one acyl group directly attached to the aromatic ring.
3. A naphthalenedicarboxylic acid containing polymer with reduced fluorescence comprising repeat units from:

   (a) a dicarboxylic acid component which comprises 0.1 to 50 mole percent of 2,6-naphthalenedicarboxylic acid or esters thereof, and 50 to 99.9 mole percent of terephthalic acid or esters thereof; and

   (b) a diol component; and

   (c) 0.1 to 5.0 mole percent, based on 100 mole percent dicarboxylic acid and 100 mole percent diol, of a copolymerizable aromatic ketone which has at least one acyl group directly attached to the aromatic ring.
4. The polymer of Claim 3 wherein the diol component, component (b), is at least 95 mole percent ethylene glycol.
5. The polymer of Claim 1 wherein the copolymerized aromatic ketone has an aromatic ring selected from the group consisting of benzene, naphthalene and biphenyl.
6. The polymer of Claim 5 wherein the aromatic ring contains at least two polymerizable groups selected from the group consisting of carboxylic esters, aliphatic hydroxyl groups and combinations thereof.
7. The polymer of Claim 6 wherein the carboxylic ester has the formula: wherein R₃ is selected from the group consisting of a C₁-C₆ alkyl group and a phenyl group.
8. The polymer of Claim 7 wherein the carboxylic ester is
9. The polymer of Claim 6 wherein the aliphatic hydroxyl group has the formula:         (CH₂)_nOH wherein n is an integer from 1 to 6.
10. The polymer of Claim 8 wherein the aliphatic hydroxyl group is (CH₂)₂OH.
11. The polymer of Claim 6 wherein the aromatic ring compound containing polymerizable groups is selected from the group consisting of terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid and the ester derivatives thereof.
12. The polymer of Claim 11 wherein the aromatic ring compound containing polymerizable groups is 2,6-naphthalenedicarboxylic acid.
13. The polymer of Claim 5 wherein the aromatic ring contains at least one acyl group of the formula wherein R₄ is selected from the group consisting of C₁-C₁₀ alkyl, phenyl, and naphthyl group.
14. The polymer of Claim 13 wherein the acyl group is selected from the group consisting of acetyl, benzoyl, 1- or 2-naphthoyl, and propionyl.
15. The polymer of Claim 14 wherein the acyl group is C₆H₅CO-.
16. The polymer of Claim 1 wherein the copolymerizable aromatic ketone is selected from the group consisting of dimethyl benzoylterephthalate, dimethyl 1-benzoyl 2,6-naphthalenedicarboxylate, dimethyl 3-benzoyl 2,6-naphthalenedicarboxylate, dimethyl 4-benzoyl 2,6-naphthalenedicarboxylate, dimethyl 1-(2-naphthoyl) 2,6-naphthalenedicarboxylate, dimethyl benzoylisophthalate, dimethyl dibenzoyl-2,6-naphthalenedicarboxylate, and combinations thereof.
17. The polymer of Claim 16 wherein the copolymerizable aromatic ketone is dimethyl benzoylterephthalate.
18. The polymer of Claim 16 wherein the copolymerizable aromatic ketone is dimethyl 1-benzoyl-2,6-naphthalene dicarboxylate.
19. The polymer of Claim 16 wherein the copolymerizable aromatic ketone is 1-(2-naphthoyl)-2,6-naphthalene dicarboxylate.