Thermoplastic polyester resin composition and molded articles produced therefrom

Abstract: A thermoplastic polyester resin composition comprising a thermoplastic polyester and an effective amount for ultraviolet screening of at least one diimide compound selected from formulae (I) and (II): wherein: m and m′ each independently represents an integer of from 0 to 4; A and A′ each independently represents a halogen atom, -COOH or an ester thereof, -OH, -O-C(=O)CH₃, -NH₂, -CN, -NO₂, -SO₃H or a metal salt thereof, an unsubstituted or substituted alkoxyl group, an unsubstituted or substituted aliphatic group or an unsubstituted or substituted aromatic group, such that when m and/or m′ are/is from 2 to 4, A and A′ are the same or different from each other; X represents wherein Y represents SO₂, -S-, C=O, -O-, -CH₂-, -CH₂CH₂-, -CH=CH-, wherein any aromatic group in X is unsubstituted or substituted with a substituent as defined for A or A′ above; and Z represents wherein Y, which is the same or different from Y above, is as defined above, and any aromatic group in Z is unsubstituted or substituted with a substituent as defined for A or A′ above.

Description: The present invention relates to a thermoplastic polyester resin composition and molded articles thereof and to the use of a compound as an ultraviolet screening agent in such a composition. The composition is suited for producing, for example, films and containers having excellent ultraviolet screening properties, and such molded articles. Polyesters, a most typical example of which is polyethylene terephthalate, have been widely used as materials for, for example, fibers and films, owing to their excellent mechanical and chemical properties. Recently, attention has focused on their good adaptability to containers for, for example, a carbonated beverage, fruit juice, liquid seasoning, edible oil, liquor and wine because of the excellent transparency, gas barrier properties and hygienic safety of polyesters. Also, use of polyester film as a window-stuck film for energy saving, screening of heat rays and prevention of scatterring of broken glass pieces as a safety measure against earthquakes is rapidly spreading in recent years as new applications of polyester film. In the field of agriculture and horticulture, a strong request is heard for a transparent film which can selectively screen ultraviolet rays in a specific wavelength region to promote growth of farm products and increase their harvests (see, for example, JP-A-53-98242 (1978)). These conventional polyester containers and films have excellent ultraviolet screening in the short wavelength region of up to about 320 nm, but they are almost transparent to ultraviolet rays in the longer wavelength region and visible light rays. When edible oil or a liquid seasoning such as sweetened cooking sake (Japanese mirin) or a dressing is filled in such a polyester container and kept therein for several months, the quality of the contents tends to degrade, for example, a delicate change tends to take place in colour, taste and flavor, although the degree of such degradation or change depends on the type of food contained and the storage conditions. Such deterioration of the contents is caused by external factors such as oxygen, heat, light and especially ultraviolet rays and microorganisms. Therefore, in the case of polyester containers, since they have relatively excellent oxygen barrier properties, it would become possible to prevent the degradation of the quality of the contents even though stored for a long time if the ultraviolet screening properties of the polyester is further improved. On the other hand, in the case of window-stuck film, if it allows passage of, for example, ultraviolet rays in the sunrays, such ultraviolet rays may cause discoloration or fading of various types of furniture, books and other interior household stuff, so that it is necessary to minimize or perfectly prevent transmission of such ultraviolet rays. In agriculture and horticulture, by means of mulching with a transparent covering material capable of substantially preventing transmission of ultraviolet rays of wavelengths not greater than 370 nm, it is possible to promote growth of many useful plants and to have a high and early harvest of high-quality crops (see, for example, JP-A-53-124556 (1978). Currently, in the art, it is a common practice to add ultraviolet absorbers to polyesters for said purpose. These ultraviolet absorbers, however, are generally expensive and difficulties are involved in their addition. Also, these compounds usually have a high subliming tendency and most of them are poor in thermal stability, so that trouble tends to occur in the adding and molding steps. Furthermore, in the case of using a polyester film containing an ultraviolet absorber for food containers or packages, the ultraviolet absorber is liable to contaminate the contents. Various types of ultraviolet absorbers (such as those described in EP-A-263,705 and International Publication No. W086/04903) have been disclosed for solving the problems, but none of these known ultraviolet absorbers is capable of screening ultraviolet rays in the longer wavelength region. The present invention seeks to provide a polyester resin composition which is suitable for producing molded articles having excellent ultraviolet screening properties, which is capable of screening ultraviolet rays even in the longer wavelength region, and which also has high thermal and dispersion stability and has no possibility of causing problems such as deposition of extraneous matter on the molded articles through the molding process, and to provide molded articles obtained by using the polyester resin composition. The inventors have found that a thermoplastic polyester resin composition comprising a thermoplastic polyester resin and a specific diimide compound(s) is capable of sufficiently screening ultraviolet rays in both short wavelength and long wavelength regions. The present invention provides a thermoplastic polyester resin composition comprising a thermoplastic polyester, the dicarboxylic acid component thereof containing at least 80% terephthalic acid units and the glycol component thereof containing at least 80% ethylene glycol units, and an effective amount of ultraviolet screening of at least one diimide compound selected from formulae (I) and (II): wherein m and m' each independently represents an integer from 0 to 4; A and A' each independently represents a halogen atom, -COOH or an ester thereof, -OH, -O-C(=O)CH₃, -NH₂, -CN, -NO₂, -SO₃H or a metal salt thereof, an unsubstituted or substituted alkoxyl group, an unsubstituted or substituted aliphatic group or an unsubstituted or substituted aromatic group, such that when m and/or m' are/is 2 to 4, A and A' are the same or different from each other; X represents wherein Y represents SO₂, -S-, C=0, -O-, -CH₂-, -CH₂CH₂-, -CH=CH-, wherein any aromatic group in X is unsubstituted or substituted with a substituent as defined for A or A' above; and Z represents wherein Y, which is the same or different from Y above, is as defined above, and any aromatic group in X is unsubstituted or substituted with a substituent as defined for A or A' above. The present invention also provides a moulded article comprising a composition as defined above. The present invention additionally provides a process for producing a thermoplastic polyester resin composition as defined above which comprises dry blending the thermoplastic polyester and the diimide compound selected from formulae (I) and (II), or adding the diimide compound of formula (I) or (II) to a reaction mixture for preparing the thermoplastic resin before or during a polycondensation reaction, and then carrying out the polycondensation reaction. The present invention further provides the use of at least one diimide compound selected from formulae (I) and (II) as an ultraviolet screening agent in a thermoplastic polyester resin composition. FIG. 1 and FIG. 2 are graphs showing the light transmittance of the polyester resin compositions obtained in Examples 1, 3, 8 and 9 and Comparative Examples 1 and 2. In the graphs, transmittance is plotted as ordinate and wavelength as abscissa. In formulae (I) and (II), A and A' each independently represents a halogen atom, -OH, -O-C(=0)CH₃, -COOH or an ester thereof, -NH₂, -CN, -NO₂, -SO₃H or a metal salt thereof, an unsubstituted or substituted alkoxyl group, an unsubstituted or substituted aliphatic group or an unsubstituted or substituted atomatic group. Among them, -COOH or an ester thereof is preferred. Halogens include, for example, chlorine and bromine. A typical example of an ester of -COOH is a C₁ to C₂₀ alkyl ester. The sodium salt is an example of a metal salt of -SO₃H. The alkoxyl groups include, for example, those having from 1 to 13 carbon atoms. Examples of the aliphatic group are alkyl or alkenyl groups having from 1 to 13 carbon atoms, and an example of the aromatic group is phenyl. The alkoxyl, aliphatic and aromatic groups may be substituted with, for example, a carboxyl group, hydroxyl group, halogen or alkyl group. In formula (I), m and m' each independently represents an integer of from 0 to 4, preferably from 1 to 4. The diimide compounds of formulae (I) and (II) can be produced by a conventional method, for example, by the following process (Bull. Soc. Chim. France, 727-732, 1951). Into a flask provided with a stirrer and a nitrogen gas feed pipe, is added a compound of formula (V): NH₂-X-NH₂ (V) wherein X is as defined above, and an aprotonic polar solvent such as dimethylacetamide. The contents are sufficiently stirred at a temperature of equal to or less than the boiling point of the solvent, preferably at 100°C or less, to form a slurry-like mixed liquid. A phthalic acid compound selected from those of formulae (VI): wherein A, A', m and m' are as defined above and a solvent are then added, and the mixture is reacted while passing nitrogen gas into the reaction system at a temperature of 100°C or less, preferably 50°C or less for from one to 24 hours to obtain an amide acid solution. To this amide acid solution are added dimethylaminopyridine as catalyst and acetic anhydride as dehydrating agent, and the mixture is reacted at from room temperature to 150°C for from one to 24 hours. The thus obtained reaction solution is supplied into a large amount of methanol and filtered to obtain a powdery diimide compound of formula (I). Examples of compounds of formula (V) include 3,3'-dihydroxy-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, diaminodiphenylsulfone diaminodiphenyl sulfide diaminodiphenylether diaminodiphenyl ketone diaminodiphenylmethane diaminodiphenylethane diaminostilbene bis(aminophenoxy)benzene 9,9-bis(aminophenyl)fluorene 9,9-bis(aminophenyl)anthracene 2.2-bis(aminophenoxyphenyl)propane 9,10-bis(aminophenyl)anthracene bis(aminophenyl)-3,4-diphenylthiophene bis(aminophenyl)benzobisthiazole and diaminobenzobisthiazole The aromatic nucleus in these diamino compounds may be substituted with any of the substituents mentioned in the definitions of A and A'. Among these diamino compounds, 3,3'-dimethyl-4,4'-diaminobiphenyl, 9,10-bis(4-aminophenyl)anthracene, bis(3-aminophenyl)benzobisthiazole, bis(4-aminophenyl)benzobisthiazole and bis(4-aminophenyl)-3,4-diphenylthiophene are most preferably used. Examples of the phthalic acid compounds of formula (VI) functioning as the terminal group of the diimide compounds of formulae (I) and (II), are phthalic acid, trimellitic acid, 4-carboxyphthalic acid, 4-chlorophthalic acid, 4-hydroxyphthalic acid, 4-acetoxyphthalic acid, 4-nitrophthalic acid, 4-methoxyphthalic acid, 4-ethoxyphthalic acid, 4-methylphthalic acid, 4-ethylphthalic acid, 4-aminophthalic acid, 4-sulfophthalic acid and the sodium sulfonate thereof, 4-phenylphthalic acid, and the 5-, 6- or 3-substituted isomers of any of the above compounds. Phthalic acid derivatives substituted with COOH, OH or its ester forming group are preferred. Diimide compounds of formula (II) can be synthesized, for example, as follows. A compound of the formula (V): NH₂-X-NH₂ (V) wherein X is as defined above, is added with an aprotonic polar solvent such as dimethylacetamide and the mixture is sufficiently stirred at a temperature of equal to or less than the boiling point of the solvent, preferably at 100°C or less, to prepare a slurry-like mixed solution. To this solution are added a tetracarboxylic acid of formula (VII): wherein Z is as defined above, or a mono- or dianhydride thereof, in a molar amount of half the amount of the compound of formula (V) and the solvent, and the mixture is reacted while passing nitrogen gas into the reaction system at a temperature of 100°C or less, preferably 50°C or less, for from one to 72 hours. This is followed by further addition of twice the molar quantity, based on said reaction product, of a compound selected from those of formulae (VI) as defined above, and a solvent. The mixture is reacted while passing nitrogen gas into the reaction system at a temperature of 100°C or less, preferably 50°C or less, for from one to 24 hours to obtain an amide acid solution. This amide acid solution is then added with dimethylaminopyridine as catalyst and acetic anhydride as dehydrating agent and stirred for reaction at from room temperature to 150°C for from one to 24 hours. The resulting reaction solution is supplied into a large amount of methanol and filtered to provide a powdery diimide compound of formula (II). The tetracarboxylic acids of formula (VII) or their mono- or dianhydrides include various tetracarboxylic acids such as pyromellitic acid, biphenyl tetracarboxylic acid, diphenyl sulfone tetracarboxylic acid, diphenyl sulfide tetracarboxylic acid, diphenyl ether tetracarboxylic acid, diphenyl ketone tetracarboxylic acid and diphenylethane-tetracarboxylic acid, their mono- and di-anhydrides and their structural isomers. It is preferred that the carboxyl groups on the same phenyl nucleus are situated in adjacent positions, such as 2,3,2',3'- or 3,4,3',4'-. The phenyl nucleus of these tetracarboxylic acids may be substituted with the groups referred to in the definitions of A and A'. Among these tetracarboxylic acids, pyromellitic acid, 3,4,3',4'-biphenyltetracarboxylic acid and their mono- or dianhydrides are preferably used. The amount of the diimide compound of formula (I) or (II) is preferably from 0.001 parts by weight or more, more preferably from 0.001 to 70 parts by weight, even more preferably from 0.001 to 50 parts by weight, further preferably from 0.001 to 30 parts by weight, and most preferably from 0.01 to 10 parts by weight, per 100 parts by weight of the thermoplastic polyester resin. When the amount is less than 0.001 parts by weight, no envisaged ultraviolet screening effect can be obtained. In the present invention, in order to enhance the ultraviolet screening effect, it is recommended to additionally use at least one naphthalenedicarboxylic acid compound of formula (III) or (IV): In formula (III), R¹ and R² each independently represents a hydrogen atom, an unsubstituted or substituted alkyl group or an unsubstituted or substituted aryl group. Examples of the alkyl group are methyl, ethyl, propyl and butyl. An example of the aryl group is phenyl. A tolyl group is an example of a substituted alkyl group; D and E each independently represents a halogen atom, -COOH or an ester thereof, -OH, -O-C(=O)CH₃, -NH₂, -CN, -NO₂, -SO₃H or a metal salt thereof, an unsubstituted or substituted alkoxyl group, an unsubstituted or substituted aliphatic group or an unsubstituted or substituted aromatic group. Halogens include, for example, chlorine and bromine. Examples of esters of -COOH are C₁ to C₂₀ alkyl esters. The sodium salt is a typical example of a metal salt of -SO₃H. The alkoxyl group may have, for example, from 1 to 13 carbon atoms. Alkyl groups having from 1 to 13 carbon atoms or alkenyl group having from 1 to 13 carbon atoms may be mentioned as examples of the aliphatic group. A phenyl group is an example of the aromatic group. The alkoxyl groups, aliphatic groups and aromatic groups may be substituted with, for example, a carboxyl group, hydroxyl group, halogen atom or alkyl group. Also, in formula (III), ℓ and n each independently represents an integer of from 0 to 3. In formula (IV), D, E, ℓ and n are as defined above, and B represents -0- or N-R³ wherein R³ is a hydrogen atom, an unsubstituted aliphatic group such as methyl, ethyl, propyl or butyl, a substituted aliphatic group such as carboxymethyl, carboxyethyl or carboxypropyl, an unsubstituted aromatic group such as phenyl or a substituted aromatic group such as carboxyphenyl or tolyl. Also, in formula (IV), the acid anhydride or imide group represented by -C(=0)-B-C(=0)- is bonded to the 1 and 2 positions, 1 and 8 positions or 2 and 3 positions of the naphthalene ring. Examples of compounds of formula (III) or (IV) include dicarboxylic acid structural isomers such as 1,4-, 2,6-, 2,7-, 1,8-, 1,5- or 2,3-naphthalenedicarboxylic acids, esters or anhydrides thereof, and imides produced from the reactions of the naphthalenedicarboxylic acids and, for example, ammonia, amines, aminocarboxylic acid and amino-alcohols. The naphthalene ring of these naphthalenedicarboxylic acids and esters, acid anhydrides or imides thereof may, for example, be substituted with halogen, -OH, -O-C(=0)CH₃, -NO₂, -NH₂, -CN, -SO₃H or a metal salt thereof, -COOH or an ester thereof, an unsubstituted or substituted alkoxyl group, an unsubstituted or substituted aliphatic group or an unsubstituted or substituted aromatic group. Examples of the compounds of formula (III) and (IV) are naphthalene-2,3-dicarboxylic acid and its dimethyl, diethyl, dipropyl, dibutyl and diphenyl esters, naphthalene-2,3-dicarboxylic acid anhydride, naphthalene-2,3-dicarboxyimide, N-(carboxymethyl)naphthalene-2,3-dicarboximide, N-(β-carboxyethyl)naphthalene-2,3-dicarboximide, N-(o-(m- or p-)carboxyphenyl)naphthalene-2,3-dicarboximide, N-(boromomethyl)naphthalene-2,3-dicarboximide, N-(hydroxymethyl)naphthalene-2,3-dicarboximide and their 1,4-, 1,5-, 1,8-, 2,6- and 2,7- structural isomers. The above dicarboxylic acids and esters, anhydrides or imides thereof may be substituted with from 1 to 6 substituents selected from -OH, -O-C(=0)CH₃, a halogen, -NO₂, -NH₂, -CN, -SO₃H or a metal salt thereof, -COOH or an ester thereof, an unsubstituted or substituted alkoxy group, an unsubstituted or substituted aliphatic group or an unsubstituted or substituted aromatic group. It is important to have a naphthalenedicarboxylic acid skeleton to attain an effect in combined use. Especially preferred naphthalenedicarboxylic acid compounds are naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, naphthalene-2,3-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid or esters, preferably lower alkyl esters, thereof. When using a naphthalenedicarboxylic acid of formula (III) or (IV) in combination with a diimide compound of the formula (I) or (II), the amount thereof added is preferably 0.001 parts by weight or more, more preferably from 0.001 to 70 parts by weight, even more preferably from 0.001 to 50 parts by weight, further preferably from 0.001 to 30 parts by weight, and most preferably from 0.01 to 10 parts by weight based on 100 parts by weight of the thermoplastic polyester resin. When the amount of the compounds of formulae (III) or (IV) added is less than 0.001 parts by weight, no notable effect in combined used is obtainable. Conventional methods for producing polyester compositions can be employed to obtain the thermoplastic polyester composition, by adding a compound of formula (I) or (II) to a polyester and mixing them, if necessary, with a compound of formula (III) or (IV). The diimide compounds of formulae (I) and (II) or the naphthalenedicarboxylic acid compounds of formulae (III) and (IV) can be used either in the form as they are or in the form of oligomers after reacting the compounds with a suitable substance such as a glycol. Such compounds may be added at any stage in the polyester preparation process or may be added at any stage before a molding process in order to provide the same ultraviolet screening effect. In this invention, the diimide compounds and the naphthalenedicarboxylic acids may be added at any desired stage in the process before molding of the polyester composition is completed. For example, these compounds may be added before the start of, during or after the end of the polycondensation reaction, or in the course of a molding process after pulverization. Particularly when using a compound of formula (I) or (II) in which A and A' both represent a polymerizable group such as -OH, -COOH or an ester thereof or -SO₃H or a metal salt thereof, it is recommended to add the compound just before the start of or during the polycondensation reaction for producing a polyester because this facilitates bonding of the compound to the polyester chains. The thermoplastic polyester used in this invention has a dicarboxylic acid component of at least one dicarboxylic acid selected from aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid and diphenyl sulfone dicarboxylic acid, and esters thereof, alicyclic dicarboxylic acids, which are the nuclear hydrogenated compounds of the aromatic dicarboxylic acids, such as hexahydroterephthalic acid, and esters thereof, aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelaic acid, and esters thereof, and unsaturated dicarboxylic acids such as fumaric acid, 4-carboxycinnamic acid, and esters thereof, and a glycol component primarily comprising ethylene glycol. Polyethylene terephthalate units are preferably the main constitutional repeating units of the polyester. However, the polyester may, for example, contain dicarboxylic acids other than terephthalic acid in an amount of 20% or less based on the dicarboxylic acid component. The glycol component of the polyester may, for example, contain, beside ethylene glycol, an aliphatic glycol such as diethylene glycol, trimethylene glycol, tetramethylene glycol and neopentyl glycol, alicyclic glycol such as cyclohexane-dimethanol, bisphenol derivatives such as 2,2-bis(4'-β-hydroxyethoxyphenyl)propane and bis-(4'-β-hydroxyethoxyphenyl)sulfone, polyethylene glycols or polytetramethylene glycol represented by the formula: wherein n is an integer of from 1 to 6, and m is an integer of 4 or greater, in an amount of 20% or less based on the total amount of the glycol component. The polyesters used in this invention may also be obtained by copolymerizing an oxyacid such as glycolic acid and hydroxybenzoic acid. Furthermore, as far as the polyester is substantially linear, it may be copolymerized with a polyfunctional (tri- or higher- functional) compound such as pentaerythritol, trimethylolpropane, trimellitic acid, trimesic acid or pyromellitic acid, or a monofunctional compound such as o-benzoylbenzoic acid. Still further, said polyester may be blended with other thermoplastic resins such as polybutylene terephthalate, polyethylene naphthalate, polyester elastomer or polycarbonate, in an amount usually used in polyester compositions. The polyester used in this invention preferably has an intrinsic viscosity of from 0.5 to 2.5, more preferably from 0.6 to 1.2. The range of polyester viscosity is important especially in relation to the molding method in case of producing, for instance, hollow articles. Particularly when obtaining substantially non-oriented hollow articles by extrusion blow molding, it is necessary to maintain the fluidity of the molten polyester above a certain level for preventing drawdown, although the required fluidity level depends on the volume of the blow molded article. Thus, usually, a polyester having an intrinsic viscosity of 0.7 or above, preferably from 0.8 to 1.2, is used. In the case of stretch hollow molding, extrusion molding for obtaining mono- or biaxially stretched films from sheets and injection molding for obtaining various forms of molded articles, it is possible to use a polymer with a relatively low viscosity in comparison with the case of the extrusion blow molding, viz. a polymer having an intrinsic viscosity usually of 0.5 or above, preferably from 0.6 to 1.2. A polyester with a notably high viscosity may be also used depending on the required properties of the molded articles. Known additives used in polyester compositions, such as a stabilizer, releasing agent, antistatic agent, dispersing agent or coloring matter such as a dye or pigment may be added at any stage in the polyester preparation process, or they may be added by a so-called masterbatch formulation before molding. Preferred dyes and pigments are titanium oxide, carbon black, phthalocyanine blue, phthalocyanine green, ultramarine, cobalt blue, titanium yellow, red iron oxide, calcined amber, yellow oxide, and heat-resistant oil-soluble dyes, which are mostly polycyclic, such as oil-soluble dyes having a perinone, quinophthalone, anthtrapyridone or anthraquinone type skeleton. Among them, those having a group which is able to react with the functional groups in a polyester to attach to the polyester chain are especially preferred. It is also preferred to use those dyes or pigments which have good compatibility with polyesters, show satisfactory heat resistance and color stability in the production and molding of a polyester and also cause no hygienic problem in application to packages or containers of foods. The dye or pigment is added into the polyester composition by, for example, the following way. First, a masterbatch containing the dye or pigment in a concentration as high as several to 100 times, preferably up to about 50 times, a predetermined concentration is prepared. This masterbatch is diluted with a non-colored polyester or a polyester tinted to another color tone to develop new color tone, thereby obtaining a polyester composition of a desired color tone. The polyester resin composition may be molded in the form as it is, or if necessary it may be molded after being subjected to a solid-phase polymerization under a high-degree vacuum or in a stream of an inert gas to effect high-degree polymerization in order to reduce the content of aldehyde and oligomer. An aftertreatment such as solvent extraction with xylene or chloroform may be also employed before molding. The polyester resin composition having the excellent ultraviolet screening properties may be subjected to melt molding to obtain molded articles. For melt molding, all known types of methods generally used for polyester molding are appliable. Typical examples are a usual blow molding method such as extrusion-blow molding method, injection-blow molding method and cold parsion method in which a preform is reheated and then biaxially stretched. According to these methods, it is possible to obtain hollow molded articles having excellent ultraviolet screening properties, gas barrier properties, toughness and chemical resistance as well as glass-like transparency that adds to a high quality impression of the molded article. These molded articles are particularly suited for use as containers of, for example, seasonings such as soy bean sauce (Japanese shoyu), sauce, sweetened cooking sake (Japanese mirin), dressings, edible oil, carbonated drinks, fruit juice, sake, wine, cosmetics and chemicals. Mono or biaxially stretched films obtained from the extrusion molded sheets, or laminate films with other resin films find particularly useful application to packages of ordinary foods, chemicals, cosmetics, window-stuck film and agricultural and horticultural mulches. It is possible to obtain other forms of molded articles by injection molding. The molded articles obtained from the polyester resin composition can substantially screen ultraviolet rays with wavelengths of up to 400 nm although the screening ability depends on thickness of the molded articles, amount of diimide compound added and other factors. The present invention is now further described in the following Examples. All "parts" are by weight unless otherwise noted. Shown below are the various methods for measurement used in the Examples. Intrinsic viscosity Measured in a 50/50 (by weight) mixture of phenol and tetrachloroethane at a concentration of 1.0 g/dl and 30°C. Ultraviolet transmittance Measured in the usual way by using HITACHI SPECTROPHOTOMETER Model 340. Amount of acetaldehyde Determined by high-sensitivity gas chromatography after a two hour water extraction at 160°C. Inert gas flow rate The volume of the inert gas that passed through a unit amount of resin (kg) per unit time (hr) was measured and the volume (ℓ) obtained by converting it to a 1 atm (101 kPa) and 25°C basis was employed. Synthesis Example 1 (diimide compounds of formula (I)) Synthesis of a diimide compound of formula (1) obtained from 9,10-bis(4-aminophenyl)anthracene and trimellitic acid anhydride: Precisely weighed 7.21 g of 9,10-bis(4-aminophenyl)anthracene was supplied into a 300 ml four-necked flask equipped with a stirrer and nitrogen gas feed pipe, followed by addition of 50 ml of dimethylacetamide and sufficient stirring of the mixture to form a slurry-like mixed solution. To this solution were further added 7.77 g of trimellitic acid anhydride and 50 ml of dimethylacetamide to adjust the concentration to 15 wt/vol% and the contents were subjected to a reaction at 30°C for 5 hours while passing nitrogen gas into the reaction system to obtain an amide acid solution. To this amide acid solution were added dimethylaminopyridine in an amount of 0.03 times the molar amount of trimellitic acid as catalyst and acetic anhydride in an amount of 1.5 times the molar amount of trimellitic acid as dehydrating agent, and the mixture was heated to 80°C under stirring and kept at this condition for 3 hours. The thus obtained reaction solution was supplied into a large quantity of methanol and filtered to obtain a powdery diimide compound of formula (1). Synthesis Example 2 (diimide compounds of formula (II)) Synthesis of a diimide compound of formula (2) obtained from 9,10-bis(4-aminophenyl)anthracene, pyromellitic acid anhydride and trimellitic acid: Into a 300 ml four-necked flask provided with a stirrer and a nitrogen gas feed pipe, were added 12.98 g of 9,10-bis(4-aminophenyl)anthracene and 50 ml of dimethylacetamide and the mixture was stirred well to form a slurry-like mixed solution. To this solution were further added 3.93 g of pyromellitic acid anhydride and 40 ml of dimethylacetamide, and the mixture was stirred at 30°C for 3 hours while passing nitrogen gas into the reaction system and reacted at 80°C for 5 hours to obtain a green slurry-like solution. Then 6.99 g of trimellitic acid anhydride and 69 ml of dimethylacetamide were further added to adjust the concentration to 15 wt/vol%, stirred at 30°C for 3 hours while passing nitrogen gas into the reaction system and reacted at 80°C for 5 hours. To the thus obtained green amide acid slurry-like solution were added dimethylaminopyridine and acetic anhydride in amounts of 0.06 mole and 3 moles, respectively, per one mole of trimellitic acid, and the mixture was heated to 80°C under stirring and kept at this state for 3 hours. The resulting reaction mixture was fed into a large quantity of methanol, filtered and dried to obtain a brown powdery diimide compound of formula (2). Example 1 Into a polymerizer were added 4,000 parts of bis(β-hydroxyethyl) terephthalate, 0.4 part of germanium dioxide, 0.4 part of orthophosphoric acid and 15 parts of diimide compound of formula (1) synthesized in Synthsis Example 1. The mixture in the polymerizer was heated gradually from 260°C while the inner pressure of the polymerizer was reduced little by little from normal pressure, and after a total time of polymerization of 3.0 hours under a pressure of 1 Torr and at 280°C, there was obtained a polyester having an intrinsic viscosity of 0.71. This polyester, after usual drying in vacuo, was molded into a 350 µm thick sheet using a 30 mm⊘ extruder having its cylinder and nozzle portions adjusted to a temperature of 275°C, screw speed of 40 r.p.m. and an extrusion rate of 80 g/min. The sheet showed light transmittances of 0.2%, 0% and 0% at wavelengths of 370 nm, 380 nm and 400 nm, respectively. A light transmittance chart is shown in FIG. 1. Furthermore, this dry resin was continuously injection molded into 100 mm x 100 mm x 2 mm thick boards using an Injection Molder IS-60B (Toshiba Kikai Co. Ltd.) arranged to have a temperature of 275°C at the cylinder portions and nozzle and set at screw speed of 100 r.p.m., injection time of 10 seconds and mold cooling water temperature of 10°C. None of the obtained boards had any deposit such as a white powder even after injection molding of 500 boards. Examples 2 - 6 Various types of polyesters were obtained by following the same procedure as in Example 1 except that 15 parts of various types of diimide compounds represented by formula (I)' were used in place of the diimide compound of the formula (1). The ultraviolet transmittances measured are shown in Table 1. Example 7 A transparent pale green polyester having an intrinsic viscosity of 0.60 was obtained by carrying out the same operations as in Example 1 except for the addition of 0.005 parts of copper phthalocyanine. The polyester chip surfaces were crystallized at a resin temperature of 165°C in a SOLID AIRE® stirring crystallizer (mfd. by Bepex Corp., U.S.A.), transferred into a stationary solid phase polymerization tower and, after 3-hour drying at 120-160°C, subjected to solid phase polymerization at a resin temperature of 210°C for 10 hours by passing nitrogen gas through at a rate of 30 ℓ/kg.hr. The solid polymerization product had an intrinsic viscosity of 0.75 and contained 3.0 ppm of acetaldehyde in chips. A preform was molded from this polyester by using an injection molder IS-60B (Toshiba Kiki Co., Ltd.) having its cylinder portions and nozzle adjusted to 275°C and set at screw speed of 100 r.p.m., injection time of 10 seconds and mold cooling water temperature of 10°C. This preform was blow molded by a blow molder BMB-3 (CORPOPLAST COPP.) set at a preheating oven temperature of 90°C, blow pressure of 20 kg/cm² and molding cycle of 10 seconds to obtain a bottle having a capacity of 1 litre. The ultraviolet transmittances at the 350 µm thick portion of this bottle was 0.2%, 0% and 0% at wavelengths of 370 nm, 380 nm and 400 nm, respectively. Example 8 A polyester with an intrinsic viscosity of 0.70 was obtained in the same way as Example 1 except for using of 15 parts of the diimide compound (2) synthesized in Synthesis Example 2. After ordinary drying in vacuo, the polyester was molded into a 350 µm thick sheet by using a 30 mm⊘ extruder having its cylinder and nozzle portions set at a temperature of 275°C and operated at a screw speed of 40 r.p.m. and an extrusion rate of 80 g/min. The sheet showed light transmittance of 0.5%, 0% and 0% at wavelengths of 370 nm, 380 nm and 400 nm, respectively. A light transmittance chart of the sheet is shown in FIG. 2. Furthermore, this dry resin was continuously injection molded into 100 mm x 100 mm x 2 mm thick boards using an injection molder IS-60B (Toshiba Kiki Co., Ltd.) having its cylinder and nozzle portions set at a temperature of 275°C and operated at a screw speed of 100 r.p.m., injection time of 10 seconds and mold cooling water temperature of 10°C. None of the molded boards had any contaminant deposition such as a white powder even after 500 successive runs of injection molding. Example 9 A polyester with an intrinsic viscosity of 0.70 was obtained by conducting the same operations as Example 8 except that the amount of the diimide compound (2) synthesized in Synthesis Example 2 was changed to 6 parts. A 345 µm thick sheet was obtained from this polyester according to the same process as Example 1. This sheet showed light transmittances of 12.6%, 2.7%, 0.6% and 0.2% at wavelengths of 330 nm, 370 nm, 380 nm and 400 nm, respectively. A light transmittance chart of the sheet is shown in FIG. 2. Example 10 A polyester with an intrinsic viscosity of 0.71 was prepared by following the same procedure as Example 9 except for the addition of 12 parts of 2,6-naphthalene-dicarboxylic acid. A 350 µm thick sheet molded from this polyester showed light transmittances of 0%, 2.2%, 0.5% and 0.2% at wavelengths of 330 nm, 370 nm, 380 nm, and 400 nm, respectively. Example 11 A polyester with an intrinsic viscosity of 0.70 was obtained from the same process as Example 9 except for the addition of 12 parts of N-carboxymethyl-4-chloro-1,8-naphthalenedicarboximide, and a 355 µm thick sheet was molded from this polyester in the manner described above. The sheet showed light transmittances of 0%, 0.9%, 0.2% and 0.2% at wavelengths of 330 nm, 370 nm, 380 nm and 400 nm, respectively. Examples 12 - 15 Various types of polyester were obtained in the same manner as in Example 1 by adding 15 parts of various types of diimide compound of formula (II)' in place of the diimide compound of the formula (2). The ultraviolet transmittances measured are shown in Table 2. Example 16 A transparent polyester colored pale green and having an intrinsic viscosity of 0.60 was obtained by following the same procedure as Example 8 except that 0.005 parts of copper phthalocyanine was added, and this polyester was subjected to solid-phase polymerization according to Example 7. The solid-phase polymerization product had an intrinsic viscosity of 0.74 and contained 3.3 ppm of acetaldehyde in its chipped material. A preform was molded from the polyester by using an injection molder IS-60B (Toshiba Kiki Co., Ltd.) having its cylinder and nozzle portions set at 275°C and operated under screw speed of 100 r.p.m., injection time of 10 seconds and mold cooling water temperature of 10°C. This preform was then blow molded by a blow molder Model BMB-3 (CORPOPLAST CORP.) set at a preheating oven temperature of 90°C, blow pressure of 20 kg/cm² and molding cycle of 10 seconds to obtain a bottle having a capacity of 1 litre. The ultraviolet transmittances of this bottle at its 350 µm thick portion were 0.4%, 0% and 0% at wavelengths of 370 nm, 380 nm and 400 nm, respectively. Comparative Example 1 A polyester with an intrinsic viscosity of 0.70 was obtained under the same operating conditions as in Example 1 except that diimide compound of formula (1) was not used. A 350 µm thick sheet molded from this polyester in the same manner as Example 1 showed ultraviolet transmittances of 68% at 370 nm and 69% at 380 nm. A light transmittance chart of the sheet is shown in FIG. 1. Comparative Example 2 A 350 µm thick sheet was obtained by dry blending 5,000 parts of polyethylene terephthalate (RT-543C®, available from NIPPON UNIPET Co., Ltd.) with an intrinsic viscosity of 0.78 with 5.5 parts of Tinuvin 326® (2(2'-hydroxy-3'-t-butyl-5'-methylphenyl)benzotriazole), a typical commercially available UV absorber, and by molding this blend into a sheet according to the method of Example 1. A light transmittance chart of this sheet is shown in FIG. 1. The light transmittances of this sheet were 2.8% at 370 nm and 8.0% at 380 nm. When the blend was continuously injection molded into 2 mm thick boards according to the process of Example 1, a yellow powdery substance deposited at the nozzle end of the molder, and a yellow contaminant had begun to be clearly noticed on the surfaces of about the 200th and succeeding boards. Example 17 A 350 µm thick transparent sheet was obtained by adding 0.4 parts of diimide compound of formula (1) to 100 parts of the same polyethylene terephthalate resin as used in Comparative Example 2 (RT-543 C®, available from NIPPON UNIPET Co., Ltd.), and by mixing well by a V type blender and drying in vacuo, then, treating similarly as in Example 1. This sheet showed light transmittances of 0.3%, 0% and 0% at wavelengths of 370 nm, 380 nm and 400 nm, respectively. Example 18 A blend of 0.2 parts of diimide compound of formula (2) and 100 parts of the same polyethylene terephthalate as used in Comparative Example 2 (RT-543C®, NIPPON UNIPET Co., Ltd.) was mixed well by a V type blender, dried in vacuo and subjected to similar treatments as in Example 1 to obtain a 350 µm thick transparent sheet. This sheet showed light transmittances of 12.6%, 2.7%, 0.6% and 0.2% at wavelengths of 330 nm, 370 nm, 380 nm and 400 nm, respectively.

Claims: A thermoplastic polyester resin composition comprising a thermoplastic polyester, the dicarboxylic acid component thereof containing at least 80% terephthalic acid units and the glycol component thereof containing at least 80% ethylene glycol units, and an effective amount for ultraviolet screening of at least one diimide compound selected from formulae (I) and (II): wherein: m and m' each independently represents an integer of from 0 to 4; A and A' each independently represents a halogen atom, -COOH or an ester thereof, -OH, -O-C(=O)CH₃, -NH₂, -CN, -NO₂, -SO₃H or a metal salt thereof, an unsubstituted or substituted alkoxyl group, an unsubstituted or substituted aliphatic group or an unsubstituted or substituted aromatic group, such that when m and/or m' are/is from 2 to 4, A and A' are the same or different from each other; X represents wherein Y represents SO₂, -S-, C=O, -O-, -CH₂-, -CH₂CH₂-, -CH=CH-, wherein any aromatic group in X is unsubstituted or substituted with a substituent as defined for A or A' above; and Z represents wherein Y, which is the same or different from Y above, is as defined above, and any aromatic group in Z is unsubstituted or substituted with a substituent as defined for A or A' above. A composition according to claim 1 which comprises at least one naphthalene dicarboxylic acid compound of formula (III): wherein: R¹ and R² each independently represents a hydrogen atom, an unsubstituted or substituted alkyl group or an unsubstituted or substituted aryl group; D and E each independently represents a halogen atom, -COOH or an ester thereof, -OH, -O-C(=O)CH₃, -NH₂, -CN, -NO₂, -SO₃H or a metal salt thereof, an unsubstituted or substituted alkoxyl group, an unsubstituted or substituted aliphatic group or an unsubstituted or substituted aromatic group; and ℓ and n each represents an integer of from 0 to 3; or at least one compound of formula (IV): (IV): wherein: E, D, ℓ and n are as defined above; and B represents -O- or N-R³ wherein R³ represents a hydrogen atom, an unsubstituted or substituted aliphatic group or an unsubstituted or substituted aromatic group, and the group represented by -C(=O)-B-C(=O)- is bonded to the 1 and 2 positions, 1 and 8 positions or 2 and 3 positions of the naphthalene ring. A composition according to claim 1 or 2 wherein the diimide compound of formula (I) is A composition according to any one of the preceding claims wherein the diimide compound of formula (II) is A composition according to any one of the preceding claims wherein the diimide compound of formula (I) or (II) is present in an amount of at least 0.001 parts by weight per 100 parts by weight of the thermoplastic polyester. A composition according to claim 5 wherein the diimide compound of formula (I) or (II) is present in an amount of from 0.001 to 10 parts by weight per 100 parts by weight of the thermoplastic polyester. A moulded article comprising a composition as defined in any one of the preceding claims. A process for producing a composition as defined in any one of claims 1 to 6 which comprises dry blending the thermoplastic polyester and the diimide compound selected from formulae (I) and (II), or adding the diimide compound of formula (I) or (II) to a reaction mixture for preparing the thermoplastic resin before or during a polycondensation reaction, and then carrying out the polycondensation reaction. A process according to claim 8 wherein at least one naphthalene dicarboxylic acid compound of formula (III) or (IV) as defined in claim 2 is added during the dry blending or before or during the polycondensation reaction. Use of at least one diimide compound selected from formulae (I) and (II) as defined in claim 1 as an ultraviolet screening agent in a thermoplastic polyester resin composition. Use according to claim 10 wherein the composition comprises at least one compound of formula (III) or (IV) as defined in claim 2. Use according to claim 10 or 11 wherein the diimide compound is of formula (1) or (2) as defined in claim 3 or 4. Use according to any one of claims 10 to 12 wherein the diimide compound of formula (I) or (II) is used in an amount as defined in claim 5 or 6.

Inventors: HIRAHARA TAKUJI, KASAI TETSUO, KUMENO YOSHIKO, NAKAMURA TAKASHI, OHTA TAKAYUKI, HIRAHARA, TAKUJI, KASAI, TETSUO, KUMENO, YOSHIKO, NAKAMURA, TAKASHI, OHTA, TAKAYUKI
Applicants: MITSUBISHI CHEM IND, MITSUBISHI KASEI CORPORATION
Application year: 1989
Main classification: C08K5
IPC codes: C08K5