JP2008111076A - Copolyester and coated polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high quality copolyester which inhibits oligomers, foreign substances and the like and has a sodium 5-sulfoisophthalate residue as a constituting component, and a coated polyester film whose surface is coated with the copolyester. <P>SOLUTION: In the copolyester having 45.5-49.5 mol% TPA residue, 44-48 mol% IPA residue, and 4.5-8.5 mol% sodium 5-sulfoisophthalate totaling 100 mol% as acid components and 43-47 mol% EG residue, 50-54 mol% NPG component, and 2.5-4.5 mol% DEG residue totaling 100 mol% as glycol components, the amount of the oligomers whose constituting component is sodium 5-sulfoisophthalate in the copolyester is 1,000 ppm or less in terms of dimethyl 5-sodium sulfoisophthalate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to copolyesters and coated polyester films. More specifically, the present invention relates to a copolymerized polyester comprising a sodium 5-sulfoisophthalate residue in which the content of an oligomer having a specific structure and the amount of foreign matter are suppressed, and a coated polyester film formed by coating the copolymerized polyester.

  Polyester, especially polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate or poly-1,4-cyclohexanedimethylene terephthalate and polyesters based on these are excellent in physical and chemical properties. It has characteristics and is widely used as a fiber, film, sheet or molded product.

  In particular, polyester film has excellent properties in heat resistance, chemical resistance, and mechanical properties, so it is used in many applications such as magnetic recording materials, various photographic materials, packaging materials, electrical insulating materials, and general industrial materials. ing.

  However, since the polyester itself is generally inert and has poor adhesion, various coatings such as magnetic paints, chemical matte paints, diazo photosensitive paints, gelatin compositions, heat-adhesive resin compositions, inks, etc. are applied to the film surface. When applying or printing, a method of coating an easily adhesive resin on the film surface is known in order to improve the adhesion to the coating.

The method of coating the easy-adhesive resin can be carried out in the production process of the polyester film, is advantageous in terms of cost, and is easy to handle various polyester films and workability in film production. In view of this, various water-dispersible or water-soluble copolyesters have been proposed as easily adhesive resins. In particular, a polyester resin containing a sulfonic acid metal base-containing compound has excellent recovery and reusability of the polyester film coated with the easily adhesive resin, that is, recyclability, in addition to the above characteristics. A water-dispersible or water-soluble copolyester having the following composition has been proposed (see, for example, Patent Documents 1 to 7).
Japanese Examined Patent Publication No. 47-40873 Japanese Patent Laid-Open No. 50-83497 JP 60-1414525 A Japanese Patent Laid-Open No. 5-86175 Japanese Patent Laid-Open No. 5-140277 JP-A-6-56779 JP 2004-331830 A

  As the above easy-adhesive resin, the use of water-dispersible resin (resin with excellent dispersibility in aqueous solvent) is superior to water-soluble resin in terms of water resistance of the film formed on the surface of the polyester film. Particular attention has been paid.

  In recent years, the use amount of a polyester film as a base material of an optical functional film used as a member of a large flat display represented by a liquid crystal or a plasma display has been increasing. The polyester film used in this field has extremely strict market demand for optical defects caused by foreign matters and scratches, and the demand for reducing the amount of foreign matter contained in the copolymerized polyester resin is increasing.

  For example, in Patent Document 7, the amount of foreign matter is reduced by optimizing the type and amount of a phosphorus compound used for blocking the metal compound and the metal compound used as a transesterification catalyst or a polycondensation catalyst. A method is disclosed.

  The copolymerized polyester contains an oligomer containing a sodium 5-sulfoisophthalate residue. When the copolymer polyester is made into an aqueous dispersion when the oligomer content increases, if the aqueous dispersion is stored for a long period of time, the oligomer becomes a nucleus and precipitates due to aggregates such as polyester components are generated. For example, when used as a coating agent for a film, there may be cases where defects on the film surface increase due to the precipitate, and appearance defects may occur. A method for improving such defects and appearance defects is not described.

  An object of the present invention is to provide a copolymer polyester containing a high-quality sodium 5-sulfoisophthalate residue containing a 5-sulfoisophthalate residue-containing oligomer or foreign matter as a constituent component, and a film of the copolymer polyester. The object is to provide a coated polyester film coated on the surface.

  In order to solve the above-mentioned problems, the present invention has finally been completed as a result of intensive studies. That is, according to the present invention, the acid component contains 45.5 to 49.5 mol% of terephthalic acid residues, 44 to 48 mol% of isophthalic acid residues and 4.5 to 8.5 mol of sodium 5-sulfoisophthalate residues. % And total 100 mol%, glycol component 43-47 mol% ethylene glycol residue, neopentyl glycol component 50-54 mol%, diethylene glycol residue 2.5-4.5 mol%, and total 100 mol %, The oligomer containing sodium 5-sulfoisophthalate in the water-dispersible copolymer polyester is 1000 ppm or less in terms of 5-sodium sulfoisophthalic acid dimethyl ester. It is a copolyester.

In this case, the number of foreign matters having a maximum diameter of 3 μm or more in the copolyester is preferably 200 / 3.2 mm ² or less.

  The present invention also provides a coated polyester film obtained by dispersing the above-described copolymer polyester in an aqueous solvent and coating the surface of the polyester film.

  The copolyester of the present invention is excellent in dispersibility in an aqueous solvent (hereinafter sometimes referred to simply as dispersibility). For this reason, for example, while maintaining the properties that should be originally provided, such as the effect of improving adhesiveness when used as a coating layer of a polyester film, foreign matters and residual sodium 5-sulfoisophthalate remain in the copolymerized polyester. The amount of the group-containing oligomer can be reduced. Therefore, for example, it is suitable as a constituent material of the coating layer for surface modification that improves the easy adhesion of the polyester film. In particular, since the amount of foreign substances and oligomers containing sodium 5-sulfoisophthalate residue is reduced, it is useful as a surface modifier for films that are highly demanded for defects caused by foreign substances such as optical applications. is there.

  In addition, the coated polyester film formed by dispersing the copolymerized polyester in an aqueous solvent and coating the surface of the polyester film is excellent in adhesiveness with, for example, printing ink and the like, and has little surface foreign matter. In this case, it is possible to suppress the occurrence of fogging phenomenon of the film that occurs due to the storage. Therefore, for example, it is suitable as a base material for an optical functional film.

  The composition of the copolymerized polyester in the present invention is not limited as long as it has a 5-sulfoisophthalic acid sodium residue as a constituent component, but the acid component is 45.5 to 49.5 mol% of terephthalic acid residue, and the isophthalic acid residue. 44-48 mol% and sodium 5-sulfoisophthalate residues are 4.5-8.5 mol% and total 100 mol%, glycol component is 43-47 mol% ethylene glycol residue, neopentylglycol component 50 It is preferable that it consists of -54 mol%, diethylene glycol residue 2.5-4.5 mol%, and total 100 mol%. By satisfying the composition ratio, various properties to be possessed when used, for example, as a film surface modifier, such as dispersibility, transparency, film strength, adhesion improvement effect, recoverability and water resistance of the film, etc. Therefore, it is preferable because the total balance can be achieved.

  If the above copolyester is 6 mol% or less of the total dicarboxylic acid component, (1) oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid Acid, dodecanedicarboxylic acid, tetradecanedicarboxylic acid, hexadecanedicarboxylic acid, 1,3-cyclobutanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4 -Saturated aliphatic dicarboxylic acids exemplified by cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, dimer acid, etc., or ester-forming derivatives thereof, (2) exemplified by fumaric acid, maleic acid, itaconic acid, etc. Unsaturated aliphatic dicarboxylic acids or their esters Synthetic derivatives, (3) orthophthalic acid, diphenic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalene Dicarboxylic acid, 4,4′-biphenyldicarboxylic acid, 4,4′-biphenylsulfone dicarboxylic acid, 4,4′-biphenyl ether dicarboxylic acid, 1,2-bis (phenoxy) ethane-p, p′-dicarboxylic acid, Other dicarboxylic acids such as pamoic acid and anthracene dicarboxylic acid may be used in combination.

  In addition to these dicarboxylic acids, a polyvalent carboxylic acid may be used in combination if the amount is small. Examples of the polyvalent carboxylic acid include ethanetricarboxylic acid, propanetricarboxylic acid, butanetetracarboxylic acid, pyromellitic acid, trimellitic acid, trimesic acid, 3,4,3 ′, 4′-biphenyltetracarboxylic acid, and these Examples thereof include ester-forming derivatives.

  Further, if it is 4.5 mol% or less of the total glycol component, (a) an aliphatic glycol (for example, 1,2-propylene glycol, 1,3-propylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1 , 4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediethanol, 1,10-decamethylene glycol, 1,12-dodecane Diol, polyethylene glycol, polytrime Lenglycol, polytetramethylene glycol, etc.), (2) aromatic glycol (eg, hydroquinone, 4,4′-dihydroxybisphenol, 1,4-bis (β-hydroxyethoxy) benzene, 1,4-bis (β- Hydroxyethoxyphenyl) sulfone, bis (p-hydroxyphenyl) ether, bis (p-hydroxyphenyl) sulfone, bis (p-hydroxyphenyl) methane, 1,2-bis (p-hydroxyphenyl) ethane, bisphenol A, bisphenol C, 2,5-naphthalenediol, glycols obtained by adding ethylene oxide to these glycols, etc.).

  In addition to these glycols, polyhydric alcohols may be used in combination in small amounts. Examples of the polyhydric alcohol include trimethylolmethane, trimethylolethane, trimethylolpropane, pentaerythritol, glycerol, hexanetriol, and the like.

  The reduced viscosity of the copolymerized polyester of the present invention is preferably 0.38 to 0.50. For example, the reduced viscosity of the copolyester is preferably 0.38 or more from the viewpoint of adhesiveness when used as a coating layer material for film surface modification. The reduced viscosity of the copolyester is preferably 0.50 or less from the viewpoint of handling properties such as dispersibility and economical efficiency. Moreover, even if the reduced viscosity of copolymerized polyester exceeds 0.50, the adhesive improvement effect is saturated.

  In addition, the copolymer polyester used in the present invention preferably has an acid value of 10 to 30 eq / ton. The acid value of the copolyester is preferably 10 eq / ton or more from the viewpoint of adhesiveness when used as a coating layer material for surface modification of a film, for example. The acid value of the copolyester is preferably 30 eq / ton or less from the viewpoint of water resistance stability.

  Moreover, it is preferable from the point of long-term storage stability that the oligomer amount containing the sodium 5-sulfoisophthalate residue in copolymerized polyester is 1000 ppm or less. The oligomer is quantified using the following method.

[Quantitative determination method of oligomer amount comprising sodium 5-sulfoisophthalate residue in copolymer polyester]
After freezing and pulverizing the sample, 500 mg is accurately weighed and extracted with about 5 ml of methanol three times at room temperature. The resulting methanol extract is filtered through a polytetrafluoroethylene membrane filter (0.45 μm), then made up to 25 ml, and subjected to HPLC analysis and LC / MS analysis under the following conditions.

[Measurement condition]
(A) LC device: Agilent 1100
(B) Column: Imtakt Cadenza CD-C18 2 × 150 mm
(C) Mobile phase: (A) 0.1% formic acid, (B) acetonitrile / 0.1% formic acid
0 min (20% B) -40 (98) -55 (98)
(D) Flow rate: 0.2 ml / min
(E) Column temperature: 40 ° C
(F) Injection volume: 5 μl
(G) Detection: UV258nm
(H) MS device: BRUKER DALTONICS esquire 3000 Plus
(I) Ionization method: ESI negative ion mode In the LC / MS analysis described above, only oligomers containing sodium 5-sulfoisophthalate as a constituent component are selectively detected. With respect to all the peaks of the oligomer having sodium 5-sulfoisophthalate as a constituent component detected by this method, the area ratio of 5-sodium sulfoisophthalic acid dimethyl ester to the peak of a standard solution of 5-sodium sulfoisophthalic acid dimethyl ester measured separately was determined. The equivalent amount of dimethyl ester of isophthalic acid is obtained and displayed as the total equivalent amount of all detected components.

  From the viewpoint of long-term storage stability, the oligomer amount is more preferably 900 ppm or less, and further preferably 800 ppm or less. When the copolymerized polyester is used as an aqueous solvent dispersion, if the aqueous solvent dispersion is inferior in long-term storage stability, precipitation of aggregates in which the oligomers become nuclei and the polyester components and the like are aggregated occurs. When used as a coating agent, surface precipitates may increase due to the precipitates or appearance defects may occur.

  As a method for imparting long-term storage stability to the aqueous solvent dispersion of the copolymerized polyester, for example, a method in which a sodium 5-sulfoisophthalate component is added as a dihydroxyethyl ester before the esterification reaction is started as described below.

The copolymer polyester used in the present invention preferably has 200 / 3.2 mm ² or less of foreign matter having a maximum diameter of 3 μm or more (hereinafter simply referred to as foreign matter). The amount of foreign matter is evaluated by observing the number of foreign matters contained in the copolyester with a microscope. That is, a piece of copolymer polyester is sandwiched between two cover glasses, melt-pressed at 280 ° C., rapidly cooled, and then observed in 20 fields of view with a 100 × phase-contrast microscope, and the number of particles of 3 μm or more is measured with an image analyzer. It is counted and evaluated.

The number of foreign matters is more preferably 150 /3.2Mm ² or less, more preferably 100 or /3.2Mm ² below. By setting the number of foreign substances to 200 / 3.2 mm ² or less, for example, when used as a coating layer material for surface modification of a film, defects of the coating layer can be suppressed. It can also be used in applications where the demand for surface defects is severe.

In order to reduce the foreign matter in the copolymerized polyester to 200 pieces / 3.2 mm ² or less, for example, as described later, sodium 5-sulfoisophthalic acid dihydroxyethyl ester is an ester of sodium 5-sulfoisophthalic acid dimethyl ester and ethylene glycol. It is a preferred embodiment to prepare by an exchange reaction and to carry out the transesterification reaction in the presence of 2 to 10 equivalent% of a sodium compound with respect to 5-sulfoisophthalic acid sodium dimethyl ester.

  In the present invention, the properties of the copolyester can be effectively utilized by dispersing the copolyester in an aqueous solvent and then coating the surface of the polyester film.

  The production method of the copolyester in the present invention is preferably produced by a direct esterification method from the viewpoint of economy.

  A preferred production method for imparting the above properties to the copolyester using the direct esterification reaction method is described below.

  In this method, it is preferable to add a sodium 5-sulfoisophthalate component as dihydroxyethyl ester before starting the esterification reaction. When sodium 5-sulfoisophthalate is added as dicarboxylic acid instead of dihydroxyethyl ester, or when added as dihydroxyethyl ester, sodium 5-sulfoisophthalate is added before the esterification reaction is completed. This is preferable because generation of oligomers having residues as constituent components (hereinafter simply referred to as GCM-containing oligomers) can be suppressed. In addition, when the production | generation of a GCM containing oligomer increases, the long-term storage stability at the time of making this copolyester into an aqueous solvent dispersion will fall.

  The sodium 5-sulfoisophthalic acid sodium dihydroxyethyl ester is preferably prepared by a transesterification reaction between sodium 5-sulfoisophthalic acid dimethyl ester and ethylene glycol. Furthermore, when preparing 5-sulfoisophthalic acid sodium dihydroxyethyl ester, the transesterification reaction may be carried out in the presence of 2 to 10 equivalent% of a sodium compound with respect to 5-sulfoisophthalic acid sodium dimethyl ester. This is preferable from the viewpoint of suppressing the generation of foreign matters insoluble in polyester.

  The amount of the sodium compound present is more preferably 3-9 equivalent mol%, and still more preferably 3-8 equivalent mol%, relative to 5-sulfoisophthalic acid sodium dimethyl ester. By making the amount of the sodium compound present at 2 equivalent% or more, it is possible to suppress the formation of foreign substances insoluble in the copolymerized polyester. For example, when the transesterification is carried out using 1 equivalent% sodium acetate disclosed in Japanese Patent Application Laid-Open No. 58-157761, the effect of suppressing the formation of foreign substances is insufficient.

  Moreover, the production | generation of the foreign material resulting from a sodium compound and coloring of a copolyester can be suppressed by making the abundance of a sodium compound into 10 equivalent% or less. Even if the amount of the sodium compound exceeds 10 equivalent%, the effect of suppressing the formation of foreign matters insoluble in the copolymerized polyester is saturated.

  Examples of the sodium compound include saturated aliphatic carboxylates such as sodium metal formic acid, acetic acid, propionic acid, butyric acid, and succinic acid, unsaturated aliphatic carboxylates such as acrylic acid and methacrylic acid, and aromatics such as benzoic acid. Group carboxylates, halogen-containing carboxylates such as trichloroacetic acid, hydroxycarboxylates such as lactic acid, citric acid, salicylic acid, carbonic acid, sulfuric acid, nitric acid, phosphoric acid, phosphonic acid, hydrogen carbonate, hydrogen phosphate, hydrogen sulfide, Inorganic acid salts such as sulfurous acid, thiosulfuric acid, hydrochloric acid, hydrobromic acid, chloric acid and bromic acid, organic sulfonic acid salts such as 1-propanesulfonic acid, 1-pentanesulfonic acid and naphthalenesulfonic acid, organic such as lauryl sulfuric acid Sulfate, methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, tert-butoxy and the like Kokisaido, chelate compounds and the like acetylacetonate, hydrides, oxides, hydroxides, and the like.

  Among these sodium compounds, when using strongly alkaline compounds such as hydroxides, they tend to be difficult to dissolve in diols such as ethylene glycol or organic solvents such as alcohols, so they must be added to the polymerization system in an aqueous solution. It may be a problem in the polymerization process. Furthermore, when a strongly alkaline material such as a hydroxide is used, the copolymerized polyester is liable to undergo side reactions such as hydrolysis during polymerization, and the polymerized polyester tends to be easily colored and is resistant to hydrolysis. There is also a tendency to decrease.

Therefore, the preferred sodium compounds used in the present invention are sodium metal saturated aliphatic carboxylate, unsaturated aliphatic carboxylate, aromatic carboxylate, halogen-containing carboxylate, hydroxycarboxylate, sulfuric acid, Inorganic acid salt, organic sulfonate, organic sulfate, chelate compound selected from nitric acid, phosphoric acid, phosphonic acid, hydrogen phosphate, hydrogen sulfide, sulfurous acid, thiosulfuric acid, hydrochloric acid, hydrobromic acid, chloric acid, bromic acid , And oxides.
Among these, sodium metal saturated aliphatic carboxylates, particularly acetates are preferred from the viewpoint of ease of handling and availability.

  The manufacturing method of said 5-sulfoisophthalic-acid sodium dihydroxyethyl ester can be performed according to a conventional method so that the said requirements may be met.

  Although the mechanism by which the above-described effect is manifested by the above production method is unknown, the esterification reaction or transesterification reaction of sodium 5-sulfoisophthalic acid dihydroxyethyl ester is caused by a specific amount of sodium compound used as a transesterification reaction catalyst. It is presumed that it was manifested by subtle changes.

  The copolymerized polyester of the present invention is preferably produced batch-wise using one pressure esterification reaction tank attached with a distillation column and two polycondensation reaction tanks attached with a vacuum generator. Furthermore, from the above-mentioned esterification reaction vessel, ethylene glycol solution of terephthalic acid, isophthalic acid, sodium 5-sulfoisophthalic acid sodium dihydroxyethyl ester, neopentyl glycol melted at 130-150 ° C. in a nitrogen atmosphere, and copolymer polyester production equipment Prepare a mixed solution of ethylene glycol and neopentyl glycol purified by distillation and distilling the distilled glycol. Add the ethylene glycol solution of triethylamine and antimony trioxide with stirring, pressurize with nitrogen and heat with a heating medium. While the temperature of the reaction vessel was raised, the glycol was refluxed into the reaction vessel while controlling the tower top temperature at 140 to 160 ° C., and at 230 to 240 ° C. under a pressure (gauge pressure) of 0.2 to 0.5 MPa. It is more preferable to perform an esterification reaction.

  Moreover, it is preferable that the addition amount of said antimony trioxide is 0.02-0.06 mol% as an amount of antimony trioxide with respect to an acid component, More preferably, it is 0.03-0.05 mol%. It is. The amount of antimony trioxide is preferably 0.02 mol% or more from the viewpoint of polycondensation activity. In addition, the amount of antimony trioxide is preferably 0.06 mol% or less from the viewpoint of suppressing the generation of foreign substances caused by antimony metal. Even if antimony trioxide in an amount exceeding 0.06 mol% is added, the polycondensation catalytic activity is saturated and no improvement effect is observed. In addition to antimony trioxide, a polycondensation catalyst composed of a titanium compound, a germanium compound, an aluminum compound, or the like may be used.

  Moreover, it is preferable to filter novel neopentyl glycol in a molten state or after preparing a mixed solution with ethylene glycol. Since neopentyl glycol is solid at room temperature, it is usually packaged and distributed in paper bags. When this solid neopentyl glycol is used as a raw material of the slurry, foreign matters are mixed in the resulting copolymerized polyester, and the clarity thereof is lowered. By performing the above-mentioned filtration treatment, foreign matter can be prevented from being mixed and the clarity of the copolyester is improved.

  For the filtration, it is preferable to use a filter having an average pore size of 20 μm or less, more preferably a filter having an average pore size of 15 μm or less, and further preferably 10 μm or less. On the other hand, the lower limit of the average pore diameter is about 1 μm from the viewpoint of the degree of clarity and the operability of filtration. The type and capacity of the filter are not limited, and may be appropriately selected in consideration of the clarity and operability of the copolyester.

What is necessary is just to install a filtration means in the arbitrary places between the supply tank of neopentyl glycol and the manufacturing apparatus of copolyester, for example.
In addition, it is preferable to handle neopentyl glycol in a molten state or a solution state from the viewpoint of improving the accuracy of the supplied amount of neopentyl glycol. The melting of neopentyl glycol may be carried out by installing a melting tank in the production equipment for copolymerized polyester, or a commercially available product in a molten state may be purchased.

  In the production described above, as a part of the glycol component, it is possible to use a mixed solution of ethylene glycol and neopentyl glycol, which is obtained by purifying the distillate glycol distilled from the production apparatus of the copolymer polyester of the present invention by distillation. preferable.

  The distillation glycol may be purified by distillation using a distillation column installed in the above-mentioned copolymerized polyester production apparatus or using a distillation column installed outside the production apparatus. May be. The form and performance of the distillation column are not limited. For example, a low-boiling fraction mainly composed of water and a high-boiling fraction containing diethylene glycol, oligomers, and the like using a 20 to 40-stage distillation column in a bubble column method. It is preferable to carry out the removal method.

  In the above production method, amines such as triethylamine may be added in order to suppress side reactions such as by-production of diethylene glycol.

  In the above production method, it is preferable that the entire amount of glycol evaporated by heating is refluxed into the reaction vessel. By the correspondence, the composition variation of the copolyester is suppressed and the esterification reaction can be smoothly advanced.

  It is preferable that the esterification reaction product is transferred to the first polycondensation reaction tank to perform an initial condensation reaction. It is preferable to carry out the pressure reduction rate in the initial condensation reaction step in at least two stages and gradually decrease the pressure reduction rate. By this countermeasure, bumping of the reaction liquid due to reduced pressure is suppressed, and blockage of the exhaust system due to entrainment caused by the bumping is suppressed, and stable operation is possible.

  That is, with stirring, the pressure is reduced to 40 KPa at a pressure reduction rate of 3 to 7 KPa / min, and then to 0.3 KPa at a pressure reduction rate of 0.6 to 1.0 KPa / min, and initial condensation is performed at 250 to 260 ° C. It is preferred to obtain a polymer. In addition, the prepolymer of the above copolyester was transferred to a second polycondensation reaction tank in which a helical stirring blade was rotated under a vacuum of 0.10 to 0.16 KPa, and at a temperature of 260 to 270 ° C. It is preferable to carry out the latter condensation, introduce nitrogen gas into the reaction tank when the predetermined rotational torque is reached, return to normal pressure, take out the copolymerized ester in a sheet form with a gear pump, and crush it with a sheet cutter while cooling with water.

  The late condensation reaction temperature is preferably 260 to 270 ° C, more preferably 262 to 268 ° C. When the reaction temperature exceeds 270 ° C., the deterioration of the copolymerized polyester is increased, which causes a deterioration in the color tone of the obtained copolymerized polyester and an increase in carboxyl end groups, which is not preferable. On the other hand, if it is less than 260 ° C., the polycondensation reaction rate is lowered, the productivity is deteriorated, and this is economically disadvantageous.

  By the above measures, the above-described high-quality copolyester can be stably and efficiently produced. For example, when the depressurization rate exceeds the above range, entrainment of reactants may increase, clogging of the depressurization system may occur, and the polycondensation reaction may become unstable. Moreover, it leads to increase in foreign matter generation. On the contrary, when the pressure reduction rate is less than the above range, the progress of the polycondensation reaction is slow, which is not preferable.

  Since the copolymerized polyester of the present invention is stiff and brittle, it is difficult to stably operate chips by a pelletizer system that is usually used for producing polyester. Moreover, in the method of extruding into a sheet shape and cutting with a dicer cutter, slab cracks may occur at the feed roller portion of the dicer. Therefore, it is preferable to crush with a sheet cutter while cooling with water.

  In the present invention, it is preferable to disperse the copolyester obtained by the above method in an aqueous solvent and coat the surface of the polyester film. As a method for dispersing the copolymerized polyester in an aqueous solvent, for example, a method in which the copolymerized polyester is dispersed in water together with a water-soluble organic compound is suitable.

  Specifically, a method in which the copolymerized polyester and a water-soluble organic compound are mixed in advance at 50 to 200 ° C., and water is added to the mixture and stirred, or, conversely, the method in which the mixture is added to water and dispersed. Alternatively, a typical method is a method in which a copolyester, a water-soluble organic compound, and water are coexistent and stirred at 40 to 120 ° C.

  As the water-soluble organic compound, a water-soluble organic compound having a solubility in 1 L of water at 20 ° C. of 20 g or more is suitable. For example, aliphatic and alicyclic alcohols, ethers, esters and ketone compounds, for example, monohydric alcohols such as methanol, ethanol, isopropanol and n-butanol, glycols such as ethylene glycol and propylene glycol, methyl Examples thereof include glycol derivatives such as cellosolve, ethyl cellosolve and butyl cellosolve, ethers such as dioxane and tetrahydrofuran, esters such as ethyl acetate, and ketones such as methyl ethyl ketone. These water-soluble organic compounds can be used alone or in combination of two or more. Of these compounds, butyl cellosolve and ethyl cellosolve are preferred from the viewpoint of dispersibility in water and applicability to films.

In the aqueous solvent dispersion, the blending ratio of the copolyester (A), the water-soluble organic compound (B) and water (C) is preferably in the following range.
(A) / (B) = 100/5000 to 100/20
(B) / (C) = 100/10000 to 100/50

  From the viewpoint of dispersibility of the aqueous solvent dispersion, (A) / (B) is preferably 100/20 or less. Further, even when (A) / (B) exceeds 100/20, dispersibility can be assisted by adding a surfactant. However, it should be noted that if the amount of the surfactant is too large, adhesiveness, water resistance and the like are lowered.

  Moreover, it is preferable that (A) / (B) is 100/5000 or more or (B) / (C) is 100/50 or less from the viewpoint of suppression of environmental pollution by water-soluble organic compounds and cost.

  Moreover, when (B) / (C) is less than 100/10000, the surface tension of the aqueous solvent dispersion liquid is increased, the wettability to the film is lowered, and coating spots may occur. In this case as well, the wettability can be improved by adding a surfactant. However, if the amount of the surfactant is too large, adhesiveness, water resistance, etc. are reduced as described above, so care should be taken. It is.

  The preparation of the aqueous solvent dispersion may be carried out within the production process of the copolymer polyester or may be carried out in a separate process.

  Various particles and the like may be added to the aqueous solvent dispersion for the purpose of imparting slipperiness to the coating film.

  As a method for producing a coated polyester film by applying the aqueous solvent dispersion to a polyester film, for example, after applying the polyester aqueous dispersion to an unstretched film or a uniaxially stretched film, heating and drying may be followed by further stretching. A method of applying to a biaxially stretched film and drying is preferable, and a method of applying to a uniaxially stretched film is more preferable.

  As a coating method, for example, kiss coating, reverse coating, gravure coating, and die coating are suitable. The final thickness of the coating layer (after drying) is preferably from 0.01 to 5 μm, more preferably from 0.01 to 2 μm.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, these Examples illustrate this invention and are not limited. Moreover, the moisture content in the polyester chip | tip in the following Example was measured by the following method.

(1) Reduced viscosity 0.05 g of copolyester was dissolved in 25 mL of a mixed solvent (phenol / tetrachloroethane = 60/40) and measured at 30 ° C. using an Ostwald viscometer.

(2) Polymer acid value 15 mg of a sample was dissolved in 0.13 ml of a hexafluoroisopropanol (HFIP) / CDCl ₃ = 1/1 mixed solvent, diluted with 0.52 ml of CDCl ₃ , and further 0.2 M triethylamine solution (HFIP / CDCl ₃ 1/9) was added and 22 μl of the solution was used for quantification by H-NMR measurement at 500 MHz. The quantitative value was measured three times and the average value was used.

(3) Amount of oligomer containing GCM in copolymerized polyester After freezing and grinding the sample, 500 mg was precisely weighed and extracted with about 5 ml of methanol three times at room temperature. The obtained methanol extract was filtered through a polytetrafluoroethylene membrane filter (0.45 μm), then made up to 25 ml, and subjected to HPLC analysis and LC / MS analysis under the following conditions.

[Measurement condition]
(A) LC device: Agilent 1100
(B) Column: Imtakt Cadenza CD-C18 2 × 150 mm
(C) Mobile phase: (A) 0.1% formic acid, (B) acetonitrile / 0.1% formic acid
0 min (20% B) -40 (98) -55 (98)
(D) Flow rate: 0.2 ml / min
(E) Column temperature: 40 ° C
(F) Injection volume: 5 μl
(G) Detection: UV258nm
(H) MS device: BRUKER DALTONICS esquire 3000 Plus
(I) Ionization method: ESI negative ion mode

  In the LC / MS analysis, only oligomers containing sodium 5-sulfoisophthalate as a constituent component are selectively detected. With respect to all the peaks of the oligomer having sodium 5-sulfoisophthalate as a constituent component detected by this method, the area ratio of 5-sodium sulfoisophthalic acid dimethyl ester to the peak of a standard solution of 5-sodium sulfoisophthalic acid dimethyl ester measured separately was determined. The equivalent amount of isophthalic acid dimethyl ester was determined and displayed as the total equivalent amount of all the detected components.

(4) Amount of foreign matter in copolymerized polyester A piece of copolymerized polyester is sandwiched between two cover glasses, melt-pressed at 280 ° C, rapidly cooled, and then observed in 20 fields of view with a 100 × phase contrast microscope. The number of particles of 3 μm or more was counted. Displayed in terms of 3.2 mm ² .

(5) Long-term storage stability 300 parts by weight of copolyester and 200 parts by weight of n-butyl cellosolve were charged in a container and stirred at 110 to 120 ° C. for about 1 hour to obtain a uniform and viscous solution. Thereafter, 500 parts by weight of water was gradually added with vigorous stirring, and a uniform aqueous dispersion was obtained after about 1 hour.
The dispersion was placed in a glass container and stored at room temperature for 3 months, and the presence or absence of a sediment component in the dispersion was evaluated by visual observation. A case where no sediment was observed at the bottom of the container due to the storage was judged as good, and a product where sediment was produced was judged as bad.

Example 1
[Preparation of 5-sodiumsulfoisophthalic acid di (hydroxyethyl) ester]
In a reaction vessel equipped with a distillation tower, 320 kg of 5-sodiumsulfoisophthalic acid dimethyl ester (manufactured by Nippon Hydrazine Kogyo Co., Ltd.), 880 kg of ethylene glycol, and sodium acetate (20 mass% ethylene glycol solution) It was charged at a ratio of 5 mol% with respect to sodium isophthalic acid dimethyl ester, transesterified for 4 hours while refluxing ethylene glycol at a reaction temperature of 180 ° C, cooled to 60 ° C, and cooled with 5-sodium sulfoisophthalic acid diester. (Hydroxyethyl) ester (hereinafter simply referred to as dihydroxyethyl ester) was taken out.

[Production of copolyester]
A copolyester was synthesized in a batchwise manner using one pressure esterification reaction vessel with a distillation column and two polycondensation reaction vessels with a vacuum generator.
First, 229 kg of terephthalic acid, 222 kg of isophthalic acid in an esterification reactor, 191 kg of dihydroxyethyl ester (ethylene glycol solution containing 34% by mass) synthesized with 1, 213 kg of neopentyl glycol melted at 140 ° C. in a nitrogen atmosphere, and further recovery and purification 87 kg of a mixed solution of ethylene glycol and neopentyl glycol (= 45/55; mass ratio) was added, and 39 kg of an ethylene glycol solution of antimony trioxide (antimony trioxide concentration: 1.3% by mass) was added while stirring. (0.05 mol% as antimony trioxide with respect to the acid component) and then pressurizing with nitrogen, raising the temperature of the reaction vessel with a heat medium, while controlling the tower top temperature at 150 ° C, glycol in the reaction vessel At 235 ° C. under a pressure of 0.3 MPa (gauge pressure). To obtain an oligomer of copolyester performs minutes esterification reaction.

  Next, the oligomer was transferred to the first polycondensation reaction tank, and while stirring, the pressure was reduced to 40 KPa at a pressure reduction rate of 5 KPa / min, and then to 0.3 KPa at a pressure reduction rate of 0.8 KPa / min, and initial condensation was carried out at 255 ° C. for 160 minutes. And a prepolymer of copolyester was obtained. Thereafter, the prepolymer was transferred to a second polycondensation reaction tank in which a spiral stirring blade was rotated under a vacuum of 0.13 KPa, and subjected to late condensation at a temperature of 265 ° C. for 120 minutes to obtain a reduced viscosity of 0.41. A copolymerized ester polymer was obtained. Nitrogen was introduced into the second polycondensation reaction tank, and the copolymerized ester polymer was taken out as a 7 mm thick sheet with a gear pump, and crushed with a sheet cutter while cooling with water to obtain a crushed copolymerized polyester.

The obtained copolymer polyester has an acid value of 20 eq / ton, a specific gravity of 1.281, a glass transition point of 67 ° C., a neopentyl glycol content of 50 mol% with respect to all glycol components, and a diethylene glycol content of 3.6. The sulfur content in the polymer was 10100 ppm, the sodium content was 7700 ppm, and the molar ratio of sodium to sulfur was 1.06. Moreover, the amount of oligomers containing sodium 5-sulfoisophthalate in the copolyester as a constituent component was 582 ppm, and the amount of foreign matter was 10 / 3.2 mm ² . Further, the molar ratio of ethylene glycol terminal to neopentyl glycol terminal is 1.4, the ratio of mass average molecular weight to number average molecular weight (Mw / Mn) is 2.6, and cyclic 2 of terephthalic acid and neopentyl glycol. The content of the monomer was 0.23% by mass of the whole.
As shown in Table 1, the copolymerized polyester obtained in this example was high in quality with low foreign matter amount and GCM-containing oligomer amount.

  In the GCM-containing oligomer quantification method described above, a total of 15 peaks were detected. Table 2 shows the composition of the oligomer of each peak identified by MS analysis and the converted content of each component with respect to the copolyester.

(Preparation of coating solution)
Using the aqueous dispersion of the copolymerized polyester prepared according to the method described in the above-mentioned storage stability evaluation method, the copolymerized polyester and sodium dodecyldiphenyloxide disulfonate (manufactured by Matsumoto Yushi Co., Ltd.) as the sulfonic acid metal salt , Anionic antistatic agent), polyethylene emulsion wax (manufactured by Toho Chemical Co., Ltd.) as a polymer wax agent, styrene-benzoguanamine-based spherical organic particles (manufactured by Nippon Shokubai Kogyo Co., Ltd.) having an average particle size of 2.2 μm, average Colloidal silica (manufactured by Nissan Chemical Co., Ltd.) having a particle size of 0.04 μm is mixed so that the weight ratio of solids is 50 / 2.5 / 2.5 / 0.5 / 5, respectively, and ion-exchanged water and isopru Use a mixed solvent of pill alcohol (= 60/40: mass ratio) to dilute the total solid concentration to 5% by mass to obtain the coating solution. It was manufactured.

(Preparation of coated polyester film)
After the polyethylene terephthalate having an intrinsic viscosity of 0.60 that does not substantially contain lubricant particles is sufficiently dried, it is supplied to an extruder and melted at 290 ° C., extruded into a sheet form from a T-type die, and cooled with a cooling drum at 30 ° C. An unstretched film was obtained by cooling and solidification. Next, the unstretched film was heated to 95 ° C. and stretched 3.4 times in the longitudinal direction to obtain a uniaxially stretched film. Furthermore, the coating solution obtained above was applied to one side of this uniaxially stretched film by a gravure coating method so that the coating thickness became 0.1 μm after biaxial stretching. Subsequently, it was heated to 100 ° C. and stretched 3.5 times in the transverse direction, and heat treated at 200 ° C. to obtain a 125 μm thick polyester film having an adhesive layer.

  Solvent-based ink (TSP-400G, manufactured by Toyo Ink Co., Ltd.) was printed on the coated surface of the coated polyester film obtained by the above method and then allowed to dry for 24 hours, in accordance with the cross-cut evaluation described in JIS-K5400. After making 100 1 mm squares with a cutter blade using a cross-cut guide, the ink adhesion of the squares was evaluated using an adhesive tape (manufactured by Nichiban Co., Ltd., cellophane tape). All 100 printing inks remained and the adhesion was good.

  In addition, using the following optical defect detection apparatus, for the 10 coated polyester film pieces obtained by the above method of 100 mm × 100 mm, the coated surface is observed, and the defects that are optically recognized as 20 μm or larger are observed. As a result of detection, coarse particles on the coated surface were not observed.

  As a projector, a 20 W × 2 fluorescent lamp is arranged 400 mm below the XY table, and a mask having a slit width of 10 mm is provided. When light is incident so that the angle formed between the line connecting the projector and the light receiver and the vertical direction of the film to be measured is 12 °, if there is a scratch on the test piece at the incident position, that portion shines. The amount of light in that portion is converted into an electrical signal by a CCD image sensor camera placed 500 mm above the XY table, the electrical signal is amplified, differentiated, and compared with a threshold hole level and a comparator, and an optical defect detection signal is output. did. Also, the video signal input from the CCD image sensor camera was automatically analyzed to measure the size of the optical defect, and the position of the defect having the set size was displayed and counted.

  Furthermore, even after the coated polyester film obtained by the above method was produced and left at room temperature for 3 months, the coated polyester film was observed to be cloudy even if it was observed by hanging in front of a three-wavelength fluorescent lamp. Was not.

Comparative Example 1
A copolymer polyester of Comparative Example 1 was obtained in the same manner as in Example 1 except that the addition of dihydroxyethyl ester was changed after the esterification reaction in the method of Example 1. Table 1 shows the evaluation results of the obtained copolyester.
The copolymerized polyester obtained in this example had a higher amount of GCM-containing oligomer than the copolymerized polyester obtained in Example 1, was poor in storage stability and was of low quality.

  Moreover, the coating film was obtained by the method similar to Example 1 using the coating liquid prepared by the same method as Example 1, and preserve | saved for four months. As a result of evaluating the obtained coated film by the method described in Example 1, fogging was observed in the three-wavelength emission fluorescent lamp observation, and it was unsuitable for optical use, for example.

Comparative Example 2
In the method of Comparative Example 1, the same procedure as in Comparative Example 1 was used except that the transesterification catalyst was switched from sodium acetate to manganese acetate (0.48 mol% added to 5-sodiumsulfoisophthalic acid dimethyl ester). A polymerized polyester was obtained.
Table 1 shows the evaluation results of the obtained copolyester.
The copolymer polyester obtained in this comparative example had a large amount of foreign matter in addition to the problems of the copolymer polyester obtained in comparative example 1, and was of low quality.

Moreover, the coating film was obtained by the same method as the comparative example 1. As a result of evaluating the number of coarse particles on the surface of the coated film by the same method as described in Example 1, 3 / m ² coarse particles were present on the surface. Even lower quality than the coated polyester film.

Comparative Example 3
In the method of Example 1, a coated polyester film was obtained in the same manner as in Example 1 except that the application of the coating solution was stopped. The adhesiveness of the solvent-based ink of the obtained coated polyester was evaluated in the same manner as in Example 1. The remaining number of inks was 0, and the adhesion of the solvent-type ink was inferior.

ここで、ＧＣＭは５−スルホイソフタル酸ナトリウム残基、ＰＡはテレフタル酸あるいはイソフタル酸残基、ＮＰＧはネオペンチルグリコール残基、ＥＧはエチレングリコール残基を示す。

Here, GCM represents a sodium 5-sulfoisophthalate residue, PA represents a terephthalic acid or isophthalic acid residue, NPG represents a neopentyl glycol residue, and EG represents an ethylene glycol residue.

  The copolyester of the present invention is excellent in dispersibility in an aqueous solvent (hereinafter sometimes simply referred to as dispersibility) and, for example, an effect of improving adhesiveness when used as a coating layer of a polyester film. Since the amount of foreign matter and oligomers containing sodium 5-sulfoisophthalate residue in the copolyester is reduced while maintaining the properties that should be originally provided, such as easy adhesion of polyester film, etc. It is suitable as a constituent material of the coating layer for surface modification to be improved. In particular, since the amount of foreign substances and oligomers containing sodium 5-sulfoisophthalate residue is reduced, it is useful as a surface modifier for films that are highly demanded for defects caused by foreign substances such as optical applications. is there.

  In addition, the coated polyester film formed by dispersing the copolymerized polyester in an aqueous solvent and coating the surface of the polyester film is excellent in adhesiveness with, for example, printing ink and the like, and has little surface foreign matter. In this case, since the occurrence of the clouding phenomenon of the film generated by the storage is suppressed, it can be suitably used as a film for optical applications, for example. Therefore, it is important to contribute to the industry.

Claims (3)

  The acid component is 45.5 to 49.5 mol% of terephthalic acid residue, 44 to 48 mol% of isophthalic acid residue and 4.5 to 8.5 mol% of sodium 5-sulfoisophthalate residue, and a total of 100 Copolyester having a mol%, glycol component 43 to 47 mol%, ethylene pentyl glycol component 50 to 54 mol%, diethylene glycol residue 2.5 to 4.5 mol%, and a total of 100 mol% The copolymer polyester according to claim 1, wherein the oligomer containing sodium 5-sulfoisophthalate in the copolymer polyester is 1000 ppm or less in terms of dimethyl ester of 5-sodium sulfoisophthalate. The copolymer polyester according to claim 1, wherein the number of foreign matters having a maximum diameter of 3 µm or more in the copolymer polyester is 200 pieces / 3.2 mm ² or less.   A coated polyester film obtained by dispersing the copolymerized polyester according to claim 1 or 2 in an aqueous solvent and coating the surface of the polyester film.