WO1998034981A1 - Method for preventing photodegradation of polymers containing naphthalenedicarboxylic acid residues - Google Patents

Abstract

The present invention relates to an article formed from a polyester derived from an acid component comprising 2,6-napththalene dicarboxylate and attached to at least one surface of said article a coating layer having a cutoff wavelength between about 380 nm and about 410 nm and an absorbance of greater than about 2 at all wavelengths between 300 nm and 365 nm. The coating layers comprise at least one absorbing compound selected from benzylidene compounds, benzoxazinone compounds, triazine compounds, benzophenone compounds and benzotriazole compounds.

Description

Method for Preventing Photodegradation of Polymers Containing Naphthalenedicarboxylic Acid Residues

RELATED APPLICATION

This application claims the benefit of provisional application U.S. Serial No. 60/037,324 filed February 7, 1997.

FIELD OF THE INVENTION This invention relates to novel films which prevent the photodegradation and yellowing of polymers containing residues of naphthalenedicarboxylic acid resulting from exposure to ultaviolet light. The prevention of photodegradation is accomplished by coating formed articles of naphthalenedicarboxylic acid containing polymers with coating resins containing ultraviolet absorbers. These polymer compositions are useful for applications such as fibers an films where exposure to ultraviolet light is prominent.

BACKGROUND OF 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 residues are used in the fabrication of various articles for household or industrial use, including appliance parts, containers, fibers and auto parts. One major drawback of polymers containing residues of naphthalenedicarboxylic acid, however, is yellowing that occurs when they are exposed to ultraviolet light. Thus, objects prepared with polymers containing residues of naphthalenedicarboxylic acid will discolor when exposed to ultraviolet light.

Photodegradation which leads to yellowing results when the polymers containing residues of naphthalenedicarboxylic acid absorb ultraviolet light.

Poly(ethylene-2,6-naphthalate) intensely absorbs ultraviolet light with wavelengths ranging from 300nm to 390nm. Ultraviolet light of these wavelengths are found in sunlight and indoor lighting. For example, Ouchi, et. al., Photodegradation of Polyethylene 2,6-Naphthalate) Films, J. APPL. POLYM. SCI. Vol. 20, pg. 1983- 87, 1976 discloses that poly(ethylene-2,6-naphthalate) discolors most intensely when exposed to light with a wavelength around 380nm and is less discolored when exposed to light with wavelengths less than 375nm.

Allen and McKellar, Photochemical Reactions in Commercial Poly(ethylene- 2,6-naphthalate), J. APPL. POLYM. SCI. Vol. 22, pgs 2085-2092, 1978 discloses that irradiating poly(ethylene-2,6-naphthalate) in a Xenotest-150 weatherometer results in marked changes of the mechanical properties of poly(ethylene-2,6- naphthalate) but does not significantly discolor poly(ethylene-2,6-naphthalate). John Scheirs and Jean-Luc Gardette, Photo-oxidation and Photolysis of Poly(Ethylene Naphthalate), Polymer Degradation and Stability, vol. 56, pp. 339- 350, 1997, and Photo-oxidation of Poly(Butylene Naphthalate), Polymer Degradation and Stability, vol. 56, pp. 351-356, 1997, disclose that the UV-light induced yellowing of polymers containing naphthalenedicarboxylic acid residues occurs mainly in a very thin surface layer and disclose some information about the dependence of the yellowing rate on the wavelength of irradiation. UV absorbers capable of protecting various polymers from photodegradation resulting in discoloration or deterioration of physical properties are known. However, polymers containing residues of naphthalenedicarboxylic acid, such as poly(ethylene-2,6-naphthalate) (PEN), exhibit strong absorptions up to 390nm. Generally, UV absorbers that have strong absorptions at 380nm to 390nm also absorb significantly beyond 400nm causing the UV absorbers to be yellow. Unfortunately incorporating these UV absorbers in polymers containing residues of naphthalenedicarboxylic acid produces an undesirable yellow color.

EP 711,803 and JP 8225672 disclose the use of coatings containing UV absorbers to reduce the fluorescence emission of PEN. The coating compositions disclosed in EP 711,803 and JP 8225672 are designed for fluorescence reduction and not for protection against photodegradation resulting from exposure to ultraviolet light. EP 711803 discloses the use of cyclic imino esters and quinoxalines which have been blended into PEN in combination with a UV absorber containing coating to reduce fluorescence in PEN. Unfortunately, high concentrations (3 to 10 weight %) of the cyclic imino esters and quinoxalines are needed to significantly improve the light stability of the PEN which can deleteriously affect the physical properties and be prohibitively expensive. In addition, US 5,310,857, US 5,39_. 1,330, US 5,391,701, US 5,393,862, US

5,418,318, US 5,391,702 and US 5,352,761 disclose how compounds such as aroyl substituted naphthalene dicarboxylic esters, halogen containing aromatic compounds, aromatic ketones, naphthol compounds can be blended or copolymerized into polymers containing residues of naphthalenedicarboxylic acid to reduce fluorescence. None of these patents disclose or suggest how to protect polymers containing residues of naphthalenedicarboxylic acid against photodegradation resulting from exposure to ultraviolet light.

DECRIPTION OF THE FIGURES FIGURE 1 is a graph showing b* value over time for poly(ethylene-2,6- naphthalenedicarboxylate) with and without filters, exposed to a xenon arc lamp with intensity of 0.15W/m² at 340 nm and at a temperature of 90°C to 95°C.

FIGURE 2 is a graph showing b* value over time for poly(ethylene-2,6- naphthalenedicarboxylate) with and without filters, exposed to a xenon arc lamp with intensity of 0. lOW/m at 340 nm and at a temperature of 75°C.

FIGURE 3 is a graph showing b* value over time for poly(ethylene-2,6- naphthalenedicarboxylate) plaques with and without UV absorbing coatings exposed to a xenon arc lamp with intensity 0. lOW/m at 340nm and at a temperature of

75°C. FIGURE 4 is a graph showing the rate of yellowing under xenon arc lamp as a function of cutoff wavelength for poly(ethylene-2,6-naphthalenedicarboxylate) plaques covered with UV absorbing filters or coatings

FIGURE 5 is graph showing b* values over time for poly(ethylene-2,6- naphthalenedicarboxylate) plaques with and without filters, exposed to fluorescent lights FIGURE 6 isa graph showing b* value over time for poly(ethylene-2,6- naphthalenedicarboxylate) plaque and a poly(ethylene-2,6-naphthalenedicarboxylate) coated with poly(methyl methacrylate) containing methyl 4-hydroxybenzylidene cyanoacetate exposed to fluorescent lights.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to polymers comprising residues of naphthalenedicarboxylic acid articles coated with a resin comprising at least one ultraviolet absorber which provides resistance to discoloration upon exposure to ultraviolet light.

More specifcally, the present invention relates to an article formed from a polyester derived from an acid component comprising 2,6-naphthalene dicarboxylate and in contact with at least one surface of said article a coating layer having a cutoff wavelength between about 380 nm and about 410 nm and an absorbance of greater than about 2 for all wavelengths between 300 nm and 365 nm.

The present invention also relates to a method of inhibiting photodegradation or yellowing of polymers comprising coating polymers comprising residues of naphthalenedicarboxylic acid with a resin comprising at least one ultraviolet absorber. The coated polymers of the present invention are useful in articles such as extruded films (both oriented and non-oriented) sheets, molded objects, fibers, fabrics and filaments.

The polyester of the present invention is any polyester containing residues of naphthalenedicarboxylic acid or a blend containing said polyester as one of the components. Thus, the polyester component of the present invention comprises repeat units from a dicarboxylic acid and a diol. The dicarboxylic acid, component (1), comprises naphthalene-2,6-dicarboxylic acid, ester or acyl chloride. Preferably the dicarboxylic acid comprises at least 5 mole% naphthalene-2,6-dicarboxylic acid and alternatively at least about 50 mole % naphthalene-2,6-dicarboxylic acid. The diol, component (2), consists of at least 50 mole percent of a diol selected from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, propanediol, based on 100 mole percent dicarboxylic acid and 100 mole percent diol. Preferably, the polyester contains repeat units from naphthalene-2,6-dicarboxylic acid or naphthalene-2,6-dicarboxylate ester, and at least 90 mole percent of a diol selected from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, propanediol, based on 100 mole percent dicarboxylic acid and 100 mole percent diol. More preferably, the polyester contains at least 85 and more preferably 95 mole percent naphthalene-2,6-dicarboxylic acid or naphthalene-2,6-dicarboxylate ester, and at least 95 mole percent ethylene glycol.

Modifying dicarboxylic acid and/or glycol components may be included. The dicarboxylic acid component of the polyester may optionally be modified with up to as much as 95, but more preferably 15 mole percent of one or more dicarboxylic acids other than naphthalene-2,6-dicarboxylic acid. 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 naphthalene-2,6-dicarboxylic acid or naphthalene-2,6-dicarboxylate ester are: terephthalic acid, phthalic acid, isophthalic acid, cyclohexanediacetic acid, diphenyM^'-dicarboxylic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, azelaic acid, sebacic acid, 2,7- naphthalene-dicarboxylic 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.

In addition, the polyester may optionally be modified with up to 15 mole percent, of one or more different diols other than ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, propanediol. Such additional diols include cycloaliphatic diols preferably having 6 to 20 carbon atoms or aliphatic diols preferably having 3 to 20 carbon atoms. Examples of such diols to be included with are: diethylene glycol, triethylene glycol, pentane-l,5-diol, hexane-l,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-(l,3), 2,2-diethylpropane-diol-(l,3), hexanediol-(l,3), 1,4- di-(hydroxyethoxy)-benzene, 2,2-bis-(4-hydroxycyclohexyl)-propane, 2,4- dihydroxy-l,l,3,3-tetramethyl-cyclobutane, 2,2-bis-(3-hydroxyethoxyphenyl)- propane, and 2,2-bis-(4-hydroxypropoxyphenyl)-propane. The polyester may be prepared from one or more of the above diols.

Polyester blends within the scope of this invention comprise about 1 mole% or more PEN homopolymer or copolymer described above with a second polymer. Suitable second polymers are well known in the art and include homo and copolyesters of poly(ethylene)terephthalate, poly(cyclohexane)terephthalate, poly(butylene)terephthalate and polycarbonate.

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.

The PEN 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 PEN during the initial polymerization process. The initial polymerization process includes direct condensation of the naphthalene-2,6-dicarboxylic acid with the diol(s) or by ester interchange using naphthalene-2,6-dicarboxylic ester. For example, dimethyl-2,6- naphthalenedicarboxylate is ester interchanged with the diol(s) at elevated temperatures in the presence of a catalyst. The melt phase polymerization is concluded by extruding the PEN polymer into strands and pelletizing. The PEN polymer may optionally be solid state polymerized. Solid state polymerization involves heating the PEN 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 polymerization unit to build the molecular weight to the target level. Typical polyesterification 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, as well as variuos germanium salts. At least one layer or surface of the articles of the present invention is in contact or covered with at least one coating resin comprising at least one ultraviolet light absorbing compound having an ultraviolet cutoff between about 380 nm and about 410nm. For this invention the ultraviolet cutoff is the wavelength at which the transmittance is 50%. Functionally, this means that the UV absorbing compounds which are useful in the present invention are efficient absorbers below wavelengths of about 380 nm to about 410 nm.

Absorbance, A, of a given film or coating can be measured using the following expression (I),

A = -log[I/Io] = -logT

wherein I is the intensity of the light transmitted through the film or coating, Io is the intensity of light incident on the film or coating and T is transmittance.

The surface layer of this invention must absorb a sufficient amount of ultraviolet light of wavelengths shorter than about 380nm to significantly reduce the rate of yellowing caused by such light. The amount of ultraviolet light that must be absorbed is significantly greater than the amount of UV light that must be absorbed to achieve the objective of JP 8225672 and EP 711,803, which is only to reduce the fluorescence of polymers containing naphthalenedicarboxylic acid residue. JP 8225672 teaches coating layers with a thickness of 30μm or less. To achieve the amount of light absorption of the current invention in a layer of 30μm or less would require the addition of UV absorbers to the coating resin at concentrations of more than about 5% to 10% by weight, which is not practical in most applications. The problems that may be encountered by additions of such high concentrations of UV absorbers are insolubility of the UV absorber, formation of haze in the coating resin, embrittlement of the coating resin, poor processibility of the coating resin and significant reduction in other desirable mechanical and/or optical properties. Suitable ultraviolet absorbers include substituted or unsubstituted benzotriazoles, benzylidenes, benzophenones, benzoxazinones, triazines and oxanilides.

In one embodiment the ultraviolet absorber is selected from substituted or unsubstituted benzylidenes.

Preferred UV absorbers are selected from substituted or unsubstituted benzotriazoles, benzoxazinones and benzylidene compounds with absorption maximums in the range of about 330nm to about 375nm.

Benzylidene compounds useful for the practice of the invention are disclosed in US 4,845,187, US 4,826,903, US 4,749,774, US 4,749,773, US 4,707,537, US 4,617,374, US 4,338,247, US 5,057,594, US 4,950,732, and US 4,845,188, the disclosures of which are incorporated herein by reference. An example of a suitable benzylidene compound is methyl 4-hydroxybenzylidene cyanoacetate.

Benzylidene whch are useful in the practice of the invention have the following formulae:

R C=HC-A-OR R₂

I

R₁-C=HC-A-0-L-θ-A,-CH=C-R R, R 2

in

IV

wherein R is selected from the group consisting of hydrogen; Cι-Cι₂ alkyl; aryl; C₃-C₈ cycloalkyl; C₃-C₈ alkenyl; C₃-C₈ alkynyl; and Cι-Cι₂ substituted 1-3 times with a group selected from the group consisting of hydroxy, halo, carboxy, cyano, Cι-Cι₂ alkoxy, aryl, arylthio, aryloxy, Cι-C₄ alkoxycarbonyl, Cι-C₄ alkoxycarbonyl, C₃-C₈ cycloalkyloxy, carbamoyl, sulfamyl, hydroxy-Cι-C₄ alkoxy, hydroxy-d-Q alkylthio,Cι- C₄ alkanoylamino, aroylamino, C1-C12 alkylsulfonamido, arylsulfonamido, succirninido and phthalimido;

Ri is selected from the group consisting of cyano; C₃-C₈ alkenyloxycarbonyl; Ci- C12 alkoxycarbonyl; C₃-C₈ cycloalkoxycarbonyl; and aryloxy carbonyl;

R₂ is as defined for Ri or is selected from the group consisting of carbamoyl; Ci- C₄ alkanoyl, C₃-Cs cycloalkanoyl, aroyl; C1-C12 alkylsulfonyl; C₃-Cβ cycloalkylsulfonyl; arylsulfonyl, aryl, and heteroaryl;

L and Li are divalent organic linking groups bonded by non-oxo carbon atoms; A and Ai are independently 1, 4-phenylene and 1,4-phenylene substituted with a group selected from the group consisting of hydroxy, halo, and Cι-C₄ alkoxy; and n is one or two.

The preferred UV absorbers contain a 4-oxybenzylidene moiety and correspond to the following formulae:

and

wherein R3 is selected from hydrogen, CI-CA alkyl, C₃-C₈ cycloalkyl, aryl and Cι-C₄ alkyl substitited with aryl, aryloxy, hydroxy, Cι-C₄ alkanoyloxy and Cι-C₄ alkoxycarbonyl; R₄ is selected from hydrogen, hydroxy and Cι-C₄ alkoxy; Ri- is selected from the group consisting of Cι-C alkyl and Cι-C₄ alkyl substituted with 1-2 groups selected from hydroxy, Cι-C₄ alkoxy, halogen, cyano and aryl; L₂ is a C₂- C₈ alkylene radical or a C₂-C₈ alkylene radical substituted with a group selected from hydroxy, halogen and Cι-C₄ alkanoyloxy.

The terms "Ci-Gt alkyl" and "Cι-Cι₂ alkyl" are used herin to denote straight or branched-chain monovalent hydrocarbon moieties containing one to four and one to twelve carbon atoms, respectively.

The terms "C₃-C₈ alkenyl" and "C₃-C₈ alkynyl" refer to C₃-C hydrocarbon groups containing at least one double or triple bond, respectively.

In the terms "C1-C12 alkylthio", "C1-C12 alkylsulfonyl", "C1-C12 alkoxy", "C1-C12 alkoxycarbonyl", and "C1-C12 alkylsulfonamido", the alkyl portion of the group contains one to twelve carbon atoms and is straight or branched chain.

In the terms "Cι-C₄ alkanoyloxy", "Cι-C alkoxycarbonyl", "Cι-C₄ alkoxy", "Ci- C₄ alkylthio", "Cι-C₄ alkanoyl" and "Cι-C₄ alkanoylamino" the alkyl portion of the group contains one to four carbon atoms and is straight or branched chain. In the terms "C₃-Cs cycloalkyl", "C₃-C« cycloalkoxy" and "C₃-C₈ cycloalkanoyl" the cycloalkyl portion of the group contains three to eight carbon atoms and may be substituted with one or more Cι-C alkyl groups.

The terms "carbamoyl" and "sulfamoyl" are used to denote groups the formulae -CON(R6)R7 and -SO2N(R-s)R₇, respectively, wherein Re and R7 are independently selected from the group consisting of hydrogen; C1-C12 alkyl; C3-C8 alkenyl; C3-C8 alkynyl; aryl; heteroaryl; and C1-C12 alkyl substituted 1-3 times with a group selected from the group consisting of hydroxy, halo, carboxy, cyano, Cι-C₄ alkoxy, aryl, Cι-C₄ alkylthio, phenylthio, phenyloxy, Cι-C₄ alkoxycarbonyl, Cι-C₄ alkanoyloxy, C₃-C₈ cycloalkyloxy carbamoyl, sulfamyl, hydroxy-Cι-C₄ alkoxy, hydroxy-Cι-C₄ alkylthio, Ci- C12 alkylthio, Cι-C₄ alkanoylamino, aroylamino, C1-C12 alkylsulfonamido, aroylsulfonamido, succinimido and phthalimido.

The term "halo" refers to fluoro, chloro, bromo and iodo.

The term "alkylene" refers to a divalent C1-C12 aliphatic hydrocarbon moiety, either straight or branched-chain and such alkylene moieties substituted with groups such as hydroxy, halogen, Cι-C₄ alkoxy, aryl, Cι-C₄ alkanoyloxy and Cι-C₄ alkoxycarbonyl. The terms "C₃-C₈ alkenylene" and "C₃-C₈ alkynylene" are used to describe divalent straight or branched-chain hydrocarbon moieties containing at least on double bond and triple bond, respectively, and having from three to eight carbon atoms.

The terms "aryl" and "aroyl" as used herein preferably denotes a group wherein the aromatic portion is a phenyl or naphthyl group, optionally substituted one to three times with a group selected from the group consisting of Ci-Cπ alkyl, C1-C12 alkoxy, halo, trifluromethyl, Cι-C₄ alkoxycarbonyl, Cι-C alkanoyloxy, hydroxy, carbamoyl, sulfamyl, nitro, cyano, C1-C12 alkylsulfonylamino, and phenylsulfonylamino.

The term "heteroaryl" is used herein to represent mono or bicyclic hetero aromatic radicals containing at least one "hetero" atom selected from oxygen, sulfur and nitrogen, or a combination of these atoms, in combination with carbon atoms to complete the aromatic ring. Examples of suitable heteroaryl groups include: thiazolyl, benzothiazolyl, pyrazolyl, pyrrolyl, thienyl, furyl, thiadiazolyl, oxadiazolyl, benzoxazolyl, benzimidazolyl, pyridyl, pyrimidinyl and triazolyl and such groups substituted 1-3 times with a group selected from the group consisting of hydroxy, halo, carboxy, cyano, Cι-C₄ alkoxy, phenyl, Cι-C₄ alkylthio, phenylthio, phenyloxy, Cι-C₄ alkoxycarbonyl, Cι-C₄ alkanoyloxy, C3-C8 cycloalkyloxy carbamoyl, sulfamyl, hydroxy-Cι-C₄ alkoxy, hydroxy- Q-C₄ alkylthio, C1-C12 alkylthio, Cι-C₄ alkanoylamino, benzoylamino, C1-G2 alkylsulfonamido, phenylsulfonamido, succiminido and phthalimido. The term "arylene" as used herein preferably denotes a divalent phenylene and naphthylene, optionally substituted by a group selected from the group consisting of Cι- C₄ alkyl, Cι-C₄ alkoxy, hydroxy, and halo.

The above divalent linking groups L and Li can be selected from a wide variety of C1-C12 alkylene, C₃-C₈ alkynylene, C3-C8 cycloalkylene, carbocyclic and heterocyclic arylene and combinations of such divalent groups. The alkylene linking groups may contain within their main chain hetero atoms, e.g., oxygen, sulfur, sulfonyl, nitrogen, substituted nitrogen, and/or cyclic groups such as C₃-C₈ cycloalkylene, carbocyclic arylene, divalent aromatic heterocyclic groups or ester moieties such as: o o o o o 9

— O ICIO — — O ICI — O ICI— alkylene I CIO — OC π arylerte \ C\O-

° ° o o

— O ICINH alkylene — NH !θ- and — OCNH — arylene NHCO —

Examples of alkylene linking groups containing a cyclic moiety in the linking chain include:

alkylene — [- -jj — alkylene, alkylene-O— V - -O-alkylene,

^\ — N alkylene — [- -j — alkylene, alkylene— ^ Jl— alkylene,

alkylene— 11 l— alkylene, alkylene— _c L- alkylene,

O o

aanndd

The arylene groups are typically 1,2-, 1,3- and 1,4-phenylene and 1,4-, 1,5, 2,6 and 2,7-naphthylene.

Examples of the divalent heterocyclic groups include unsubstituted and substituted triazines such as l,3,5-triazin-2,4-diyl, 6-methoxy-l,3,5-triazin-2,4-diyl and the group having the structure:

wherein Ri and R₂ are defined hereinabove; diazines such as 2,4-pyrimidindiyl, 6- methyl-2, 4-pyrimidindiyl, 6-phenyl-2,4-pyrimidindiyl, 3,6-pyridazindiyl and 2-methyl-3- oxo-4, 5-pyridazindiyl; dicyanopyridines such as 3,5-dicyano-2,6-pyridindiyl; quinolines and isoquinolines such as 2,4-quinolindiyl and 2,8-isoquinolinediyl; quinoxalines such as 2,3-quinoxalindiyl; and azoles such as 2,5-thiazoldiyl, 5-methylene-2-thiazolyl, 3,5- isothiazoldiyl, 5-methylene-3-isothiazolyl, l,3,4-thiadiazol-2,5-diyl, l,2,4-thiadiazol-3,5- diyl, 2,6-benzothiazoldiyl, 2,5-benzoxazoldiyl, 2,6-benzimidazoldiyl, 6-methylene-2- benzothiazolyl and the group having the structure:

and maleimides such as l-methyl-3, 4-maleimidediyl and l-phenyl-3, 4-maleimidediyl. The acyclic moieties of the linking group represented by L and Li also may be substituted, for example, with hydroxy, Cι-C₄ alkoxy, halogen, Cι-C alkanoyloxy, cyano, Cι-C alkoxycarbonyl, aryl, aryloxy,, and C3-C8 cycloalkyl. The cyclic moieties of linking group L and Li may be substituted with C1-C4 alkyl as well as with the substituents already mentioned. In addition to the possible substitution described above, the nitrogen atom of the nitrogen containing alkylene groups may be substituted, for example, with Cι-C₄ alkyl, aryl, Cι-C₄ alkanoyl, aroyl, Cι-C₄ alkylsulfonyl, or carbamoyl, e.g.,

CO aryl Sθ₂ aryl alkylene N alkylene, alkylene— — alkylene ,

NH aryl aryl 1 c=o alkylene N 1 alkylene, alkylene- N-alkylene i

NH alkyl NH cycloalkyl

1 c=o C=-=:0 alkylene N alkylene, alkylene N alkylene, or

alkyl alkylene I alkylene-

Benzoxazinone compounds found to be useful in the practice of the invention are disclosed in US 5,480,926 and US 4,446,262, the disclosures of which are incorporated herein by reference. Representative benzoxazinones include:

2,2'-bis(3 , 1 -benzoxazin-4-one),

2,2'-ethylenebis(3,l-benzoxazin-4-one),

2,2'-tetramethylenebis(3,l-benzoxazin-4-one),

2,2'-hexamethylenebis(3,l-benzoxazin-4-one), 2,2' -decamethylenebis(3 , 1 -benzoxazin-4-one),

2,2'-p-phenylenebis(3,l-benzoxazin-4-one),

2,2'-m-phenylenebis(3,l-benzoxazin-4-one),

2,2'-(4,4'-diphenylene)bis(3,l-benzoxazin-4-one),

2,2'-(2,6- or l,5-naphthalene)bis(3,l-benzoxazin-4-one), 2,2'-(2-methyl-p-phenylene)bis(3, l-benzoxazin-4-one),

2,2' -(2-nitro-p-phenylene)bis(3 , 1 -benzoxazin-4-one),

2,2'-(2-chloro-p-phenylene)bis(3,l-benzoxazin-4-one),

2,2' -( 1 ,4-cyclohexylene)bis(3 , 1 -benzoxazin-4-one), N-p-(3, l-benzoxazin-4-on-2-yl)phenyl, 4-(3, l-benzoxazin-4-on-2-yl) phthalimide, and N-p-(3, l-benzoxazin-4-on-2-yl)benzoyl, 4-(3, l-benzoxazin-4-on-2-yl)aniline.

Triazine compounds found to be useful in the practice of the invention are disclosed in US 4,619,956 and Eur. Pat. Appl. EP444,323, the disclosures of which are incorporated herein by reference. Typical triazine compounds useful for the practice of the invention include 2,4-di-(2,4-dimethlyphenyl)-6-(2-hydroxy-4- O(mixed octoxy)-l,3,5-triazine, 2,4-di-(2,4-dimethlyphenyl)-6-(2-hydroxy-4-O- normal-octoxy)- 1 ,3 ,5-triazine and 2-(4,6-diphenyl- 1 ,3 ,5-triazin-2-yl)-5- hexyloxyphenol.

Benzophenone compounds useful for the practice of the invention are available from companies such as Cyanamid who sells them under the general tradename of Cyasorb. The benzophenone can be, for example, 2-hydroxy-4- octoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy- 4,4'dimethoxybenzophenone, 2,2',4,4'-tetrahdroxybenzophenone, 2,4-dihydroxy benzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid and the like.

Benzotriazole compounds useful for the practice of the invention are disclosed inDE2.853,631 Al, CH432,842, and US 3,308,095 (the disclosures of which are incorporated herein by reference) and are available from companies such Ciba, who sells them under the general tradename of Tinuvin. Typical bezotriazoles are 2-(2H-benzotriazol-2-yl)-4,6-bis(l-methyl-l-phenylethyl)-phenol, 2-(2H- benzotriazol-2-yl)-4-( 1 , 1 ,3 ,3 -tetramethylbutyl)-phenol, 2-(2H-benzotriazol-2-yl)-4- methyl-phenol, 2-(2H-benzotriazol-2-yl)-4,6-di-t-butyl-phenol, 2-(2H-benzotriazol- 2-yl)-4,6-di-t-amyl-phenol, 2-(2H-benzotriazol-2-yl)-4-t-butyl-phenol, 2-(2' - hydroxy-3'-t-butyl-5'-methlyphenyl)-5-chloro-2H-benzotriazole, and 2-(2'-hydroxy- 3 ' , 5 ' -di-t-butylphenyl)-5 -chloro-2H-benzotriazole.

The coating resin may contain ultraviolet absorbers at concentrations of 0.1 to 10 weight %, and preferably from about 0.1 to about 5 weight % of the total resin composition. The coating resin may be comprised of a thermoplastic resin or a thermosetting resin. The thermoplastic resins may include thermoplastic acrylics, polyesters, polyurethanes and the like. Suitable coating resins include those formed from polyesters such as PET homo and copolyester, water dissipatible polymers such as those sold by Eastman Chemical Company under the AQ designation. Suitable thermo setting resins may include heat or UV curable acrylic resins, silicon resins, urethane resins, unsaturated polyester resins, epoxy resins, cyanoacrylate resins and the like. An example of a suitable coating resin is poly(methyl methacrylate).

The coating layer containing an ultraviolet absorber is formed on the surface of an article made from polymers containing residues of naphthalenedicarboxylic acid. To form the coating layer on the surface of the article, a method which comprises preparing a solution obtained by dissolving at least one of the ultraviolet absorbers as described above and a coating resin in a solvent, applying the solution to the article and then drying the coated article. Suitable solvents may be polar or non-polar. Examples of suitable solvents include, but are not limited to, water and ethyl acetate, actetone, methyl ethyl ketone, chlorinated solvents, toluene, xylene or ethers. Methods for applying the coating solution are generally known in the art and include immersion, flow coating, spray coating, spin coating, brushing, rolling and curtain flow coating may be used.

The coating may be comprised of a thermoplastic or thermosetting resin containing an ultaviolet absorber which has been compounded or reacted into the thermoplastic resin. In other words, the ultraviolet absorber may be dissolved in the thermoplastic or thermosetting resin or it may be a copolymer of the resin. A coating layer may then be formed on articles of a polymer containing residues of naphthalenedicarboxylic acid by coextruding the thermoplastic resin containing an ultaviolet absorber with the polymer containing residues of naphthalenedicarboxylic acid. The coating layer may also be formed by laminating a preformed film of the thermoplastic resin containing an ultaviolet absorber onto an article of a polymer containing residues of naphthalenedicarboxylic acid.

The thickness of the coating resin containing ultraviolet absorbers useful in the present invention are generally greater than about 10 μm, preferably in the range of lOμm to 5000μm and more preferably between about 20 μ_m to about 1000 μm on the finished article. The coating may be applied at the desired thickness or it may be applied in a thicker coating on an article which will be stretched after coating. For example the coating can be applied to a film either before or after orientation or may be applied to a bottle or a preform or parison which will be subsequently stretched into a bottle.

Many other ingredients can be added to the compositions of the present invention to enhance the performance properties of the polymer containing residues of naphthalenedicarboxylic acid and the resin containing an ultaviolet absorber. For examples, surface lubricants, denesting agents, stabilizers, antioxidants, mold release agents, metal activators, 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 can be used so long as they do not hinder the present invention from accomplishing its objects.

EXAMPLES

Comparative Example 1

Molded plaques of poly(ethylene-2,6-naphthalenedicarboxylate) with thicknesses of ~1850μm were exposed to ultraviolet light in an Atlas Sunchex Weatherometer. The Atlas Sunchex Weatherometer contains a Xenon Arc lamp which emits light in the range of 300nm to well above 400nm. The samples contained no coatings or filters. The samples were placed in the weatherometer and were exposed to the light at an intensity of 0.15 W/m at 340nm and at a temperature of 90°C - 95°C. The discoloration of the poly(ethylene-2,6- naphthalenedicarboxylate) plaques was determined by measuring b* as an estimate of yellowing. A Hunter Lab Ultrascan spectrocolorimeter was used to determine the color of the plaques in CIE color units of b*. Higher values of b* mean that the polymer is more yellow. The results are shown in Figure 1. Example 2

Molded poly(ethylene-2,6-naphthalenedicarboxylate) plaques with thicknesses of ~1850μm were covered with ultraviolet light cutoff filters to determine the wavelengths of light which resulted in the most discoloration of the poly(ethylene-2,6-naphthalenedicarboxylate). The filters used in this study are the Schott glass type WG305 (cutoff wavelength = 305nm; absorbance A = 2.0 or greater below 285nm), WG320 (cutoff wavelength = 320nm; A = 2.0 or greater below 302nm), WG335 (cutoff wavelength = 335nm; A = 2.0 or greater below 320nm), WG360 (cutoff wavelength = 360nm; A = 2.0 or greater below 352nm), GG375 (cutoff wavelength = 375nm; A = 2.0 or greater below 357nm), GG420 (cutoff wavelength = 420nm; A = 2.0 or greater below 408nm). The covered, molded plaques of poly(ethylene-2,6-naphthalenedicarboxylate) were exposed to ultraviolet light in an Atlas Sunchex Weatherometer as described in Comparative Example 1. The discoloration of the poly(ethylene-2,6-naphthalenedicarboxylate) plaques was determined by measuring b* as described in Comparative Example 1. The change in b* as a function of exposure time is summarized in Figure 1. The results show that when nearly all of the ultraviolet light below 320nm is blocked the poly(ethylene-2,6-naphthalenedicarboxylate) plaque yellows almost as much as the control plaque that is exposed to all of the light. When nearly all of the ultraviolet light below 357 nm is blocked, the b* changes much less in the poly(ethylene-2,6- naphthalenedicarboxylate) plaques compared to the control plaque that is exposed to all of the light, however the change in b* is still significant Yellowing is only substantially reduced by the filter that blocks essentially all light below 408nm.

Comparative Example 3

Molded poly(ethylene-2,6-naphthalenedicarboxylate) plaques with a thickness of ~1850μm were exposed to ultraviolet light in an Atlas Sunchex

Weatherometer as in Comparative Example 1, except that the intensity was 0. lW/m at 340 nm and the temperature was 75°C. The discoloration of the poly(ethylene-2,6-naphthalenedicarboxylate) was determined by measuring b* as described in Comparative Example 1. The results are shown in Figure 2.

Example 4 Molded poly(ethylene-2,6-naphthalenedicarboxylate) plaques with thickness of ~1850μm were covered with ultraviolet light cutoff filters to determine the wavelengths of light which resulted in the most discoloration of the poly(ethylene-

2,6-naphthalenedicarboxylate). The filters used in this study were the Schott glass type WG335, WG345, WG360, GG375, GG395 (cutoff wavelength 395nm). The covered, molded plaques were exposed in an Atlas Sunchex Weatherometer as in Comparative Example 3. The discoloration of the poly(ethylene-2,6- naphthalenedicarboxylate) was determined by measuring b* as described in Comparative Example 3. The change in b* as a function of exposure time is shown in Figure 2. Figure 4 shows the rate of yellowing as a function of the cutoff wavelength for these samples. These results along with the results from

Comparative Examples 1 and 3 and Example 2 clearly demonstrate that filters or coatings with a cutoff wavelength longer than about 375nm are needed to adequately protect poly(ethylene-2,6-naphthalenedicarboxylate) from discoloration due to ultraviolet light.

Example 5.

Several samples of Poly(ethylene-2,6-naphthalenedicarboxylate) were coated with poly(methyl methacrylate) containing 3% by weight of an ultraviloet light absorbing compound selected from methyl 4-hydroxybenzylidene cyanoacetate (MHBC), ethylhexyl-2-cyano-3,3-diphenylacrylate (EHCD), ethyl-2-cyano-3,3- diphenylacrylate (ECD), 2-(2-hydroxy-3-t-butyl-5-methylphenyl)-5-chloro-2H- benzotriazole (Ciba Specialty Chemicals Tinuvin 326) or 2-[2-hydroxy-3,5-di(l,l- dimethylbenzyl)phenyl]-2H-benzotriazole (Ciba Specialty Chemicals Tinuvin 234). The coating resin solution was made by dissolving 0.44 grams of the UV absorbing compound and 15 grams of poly(methyl methacrylate) in 85 grams of ethyl acetate. A 1850μm thick poly(ethylene-2,6-naphthalenedicarboxylate) plaque was placed in a Buchner funnel. The Buchner funnel was covered with a plastic wrap and purged with ethyl acetate rich nitrogen. This allowed for the slow evaporation of ethyl acetate from the coated plaques. The coating resin solution was then applied to the surface of the poly(ethylene-2,6-naphthalenedicarboxylate) plaque with a syringe through the covering. The funnel was then covered with additional plastic wrap. The samples were left in the apparatus for 16 to 20 hours, during which time the ethyl acetate evaporated. The coated plaques were then placed in a vacuum oven at 50°C for at least six hours. Plaques with a coating of poly(methyl methacrylate) containing no UV absorber were prepared in the same manner. The coating containing methyl 4-hydroxybenzylidene cyanoacetate had an absorbance of greater than 2.0 at wavelengths between 300nm and 378nm. These samples as well as uncoated plaques of the same thickness were placed in the Atlas Sunchex Weatherometer as described in Comparative Example 3. The discoloration of the coated and uncoated poly(ethylene-2,6-naphthalenedicarboxylate) plaques was determined by measuring b* as described in Comparative Example 1. The change in b* as a function of exposure time is summarized in Figure 3. Figure 4 shows the rate of yellowing of these samples as a function of the UV cutoff wavelength along with data for the yellowing rates measured in Example 4. The UV cutoff wavelength of the UV absorbing compounds was measured for a separate set of films prepared in the same manner as those on the exposed plaques. For this measurement, the films were peeled off the plaques and absorption spectra were measured in a spectrophotometer. Table 1 gives the UV cutoff wavelengths for these samples. The thickness of the coatings for which the cutoff wavelengths were measured differed somewhat from the thickness of the coating on the plaques that were exposed to UV light in the weatherometer. The thickness for both sets of films is also given in Table 1. The difference in the cutoff wavelength due to the difference in thickness of the coatings may be on the order of 5nm. Tablel:

Comparative Example 6

Molded plaques of poly(ethylene-2,6-naphthalenedicarboxylate) with thicknesses of ~1850μm were exposed to ultraviolet light emitted from Sylvania cool white fluorescenct light bulbs . The samples were placed under the fluorescent lights at a distance of one inch from the bulb. The temperature was 26°C. The discoloration of the poly(ethylene-2,6-naphthalenedicarboxylate) plaques was determined by measuring b* as an estimate of yellowing. A Hunter Lab Ultrascan spectrocolorimeter was used to determine the color of the plaques in CIE color units of b*. Higher values of b* mean that the polymer is more yellow. The results are shown in Figures 5 and 6 .

Example 7.

Molded plaques of poly(ethylene-2,6-naphthalenedicarboxylate) plaques were covered with ultraviolet light cutoff filters to determine the wavelengths of light which resulted in the most discoloration of the poly(ethylene-2,6- naphthalenedicarboxylate). The filters used in this study are the Schott glass type WG305 (cutoff wavelength = 305nm; absorbance, A = 2.0 or greater below 285nm), WG320 (cutoff wavelength = 320nm; A = 2.0 or greater below 302nm), WG335 (cutoff wavelength = 335nm; A = 2.0 or greater below 320nm), WG360 (cutoff wavelength = 360nm; A = 2.0 or greater below 352nm), GG375 (cutoff wavelength = 375nm; A = 2.0 or greater below 357nm), GG420 (cutoff wavelength = 420nm; A = 2.0 or greater below 408nm). The covered, molded plaques of poly(ethylene-2,6-naphthalenedicarboxylate) were exposed to ultraviolet light from a fluorescent bulb as described in Comparative Example 6. The discoloration of the poly(ethylene-2,6-naphthalenedicarboxylate) plaques was determined by measuring b* as described in Comparative Example 4. The change in b* as a function of exposure time is summarized in Figure 5. The results show that when nearly all of the ultraviolet light below 320nm is blocked the poly(ethylene-2,6- naphthalenedicarboxylate) plague yellows as much as the control plaque that is exposed to all of the light. When nearly all of the ultraviolet light below 352nm is blocked, the poly(ethylene-2,6-naphthalenedicarboxylate) plaques yellow much less compared to the control plaque that is exposed to all of the light.

Example 8

Several poly(ethylene-2,6-naphthalenedicarboxylate) plaques were coated with poly(methyl methacrylate) containing methyl 4-hydroxybenzylidene cyanoacetate (MHBC). The coating resin solution was made by dissolving 0.048 grams of methyl 4-hydroxybenzylidene cyanoacetate and 15 grams of poly(methyl methacrylate) in 85 grams ethyl acetate. The ~1850mm poly(ethylene-2,6- naphthalenedicarboxylate) plaques were placed in a Buchner funnel. The Buchner funnel was covered with a plastic wrap and purged with ethyl acetate rich nitrogen.

This allowed for the slow evaporation of the ethyl acetate from the plaques after coating. The coating resin solution was applied to the surface of the poly(ethylene- 2,6-naphthalenedicarboxylate) plaques with a syringe through the covering. The funnel was then covered with additional plastic wrap. After 2 hours, most of the ethyl acetate had evaporated from the coating. The coated plaques were then removed and allowed to air dry. The coating containing methyl 4- hydroxybenzylidene cyanoacetate had an absorbance of greater than 2.0 at wavelengths between 300nm and 378nm. The coated plaque along with an uncoated poly(ethylene-2,6-naphthalenedicarboxylate) plaque were exposed to ultraviolet light from a fluorescent bulb as described in Comparative Example 6. The samples were placed under the fluorescent lights at a distance of one inch from the bulb. The discoloration of the poly(ethylene-2,6-naphthalenedicarboxylate) plagues was determined by measuring b* as described in Comparative Example 6. The change in b* as a function of exposure time is summarized in Figure 6. The results show that the coating of poly(methyl methacrylate) containing methyl 4- hydroxybenzylidene cyanoacetate significantly inhibits yellowing of the poly(ethylene-2,6-naphthalenedicarboxylate) plaque. After 4000 hours exposure to the fluorescenct light, the uncoated poly(ethylene-2,6-naphthalenedicarboxylate) plaque has a b* of 1.9 and the coated poly(ethylene-2,6-naphthalenedicarboxylate) plaque has a b* of 0.5.

Claims

WE CLAIM

1. An article formed from a polyester derived from an acid component comprising 2,6-naphthalene dicarboxylate and attached to at least one surface of said article a coating layer having a cutoff wavelength between about 380 nm and about 410 nm and an absorbance of greater than about 2 at all wavelengths between 300 nm and 365 nm.

2. The article of claim 1 wherein said coating layer further comprises a transmittance greater than about 80% for all wavelengths between 420 nm and 680 nm.

3. The article of claim 1 wherein said coating layer (film) comprises at least one absorbing compound selected from the group consisting of benzylidene compounds, benzoxazinone compounds, triazine compounds, benzophenone compounds and benzotriazole compounds.

4. The article of claim 3 wherein the benzylide compounds have the formulae:

R_rC=HC-A-OR R₂

I

R₁-C=HC-A-0-L-0-A₁-CH=C-R R R₂

II

R-0-A-CH=C-C0₂-L,-0₂C-C=HC-A-0-R

R R2

m

IV wherein R is selected from the group consisting of hydrogen; C1-C12 alkyl; aryl; C₃-C₈ cycloalkyl; C₃-C₈ alkenyl; C₃-C₈ alkynyl; and C1-C12 substituted 1-3 times with a group selected from the group consisting of hydroxy, halo, carboxy, cyano, C1-G2 alkoxy, aryl, arylthio, aryloxy, C╬╣-C₄ alkoxycarbonyl, C╬╣-C₄ alkoxycarbonyl, C₃-C cycloalkyloxy, carbamoyl, sulfamyl, hydroxy-C╬╣-C₄ alkoxy, hydroxy-C╬╣-C₄ alkylthio,C╬╣-C₄ alkanoylamino, aroylamino, C╬╣-C╬╣₂ alkylsulfonamido, arylsulfonamido, succiminido and phthalimido;

Ri is selected from the group consisting of cyano; C₃-Cs alkenyloxycarbonyl; Ci- C12 alkoxycarbonyl; C₃-C₈ cycloalkoxycarbonyl; and aryloxycarbonyl; R2 is as defined for Ri or is selected from the group consisting of carbamoyl; Ci-

C₄ alkanoyl, C₃-C₈ cycloalkanoyl, aroyl; C1-C12 alkylsulfonyl; C₃-C₈ cycloalkylsulfonyl; arylsulfonyl, aryl, and heteroaryl;

L and Li are divalent organic linking groups bonded by non-oxo carbon atoms; A and Ai are independently 1, 4-phenylene and 1,4-phenylene substituted with a group selected from the group consisting of hydroxy, halo, and C╬╣-C₄ alkoxy; and n is one or two.

5. The article of claim 4 wherein the benzylidene compounds have the formulae:

and

wherein R3 is selected from hydrogen, C╬╣-C₄ alkyl, C₃-C₈ cycloalkyl, aryl and C╬╣-C₄ alkyl substitited with aryl, aryloxy, hydroxy, C╬╣-C alkanoyloxy and C╬╣-C₄ alkoxycarbonyl; R₄ is selected from hydrogen, hydroxy and C╬╣-C₄ alkoxy; R5 is selected from the group consisting of C╬╣-C₄ alkyl and d-C₄ alkyl substituted with 1-2 groups selected from hydroxy, C╬╣-C₄ alkoxy, halogen, cyano and aryl; L2 is a C2-C₈ alkylene radical or a C2-Cg alkylene radical substituted with a group selected from hydroxy, halogen and C╬╣-C alkanoyloxy.

6. The article of claim 3 wherein said at least one absorbing compound is present in a concentration of less than about 10 wt%.

7. The article of claim 3 wherein said at least one absorbing compound is present in a concentration of less than about 5 wt%.

8. The article of claim 1 wherein said film has a thickness between about 30um and 5000um.

9. The article of claim 1 wherein said article is selected from the group consisting of film, sheet, fibers and woven and non- woven articles.

10. The article of claim 1 wherein said article is selected from the group consisting of fibers and woven and non-woven articles.

11. The article of claim 7 wherein said article is an oriented film.

12. An article formed from a polyester derived from an acid component comprising 2,6-naphthalene dicarboxylate and attached to at least one surface of said article a coating layer comprising at least one benzylidene absorbing compound.

13. The article of claim 12 wherein said at least one benzylidene absorbing compound is present in a concentration of less than about 10 wt%.

14. The article of claim 12 wherein said at least one benzylidene absorbing compound is present in a concentration of less than about 5 wt%.

15. The article of claim 12 wherein said film has a thickness between about 30um and 5000um.

16. The article of claim 12 wherein said article is selected from the group consisting of film, sheet, fibers and woven and non- woven articles.

17. The article of claim 4 wherein said article is selected from the group consisting of fibers and woven and non-woven articles.

18. The article of claim 4 wherein said article is an oriented film.