JPH0586965B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing polyester, and more particularly to a method for producing polyester for use in films, which is transparent and suitable for electrostatic casting, by a direct polymerization method. [Prior Art] Because polyethylene terephthalate has excellent physical and chemical properties, it is widely used not only for fibers but also for films such as packaging films, photographic films, capacitor films, and magnetic tapes. The manufacturing method for polyethylene terephthalate is as follows:
A transesterification method using dimethyl terephthalate and ethylene glycol as starting materials and a direct polymerization method using terephthalic acid and ethylene glycol as starting materials are well known. For polyester films, polyester produced by transesterification has traditionally been used, but in recent years polyester produced by direct polymerization has also been used. Polyester film is usually made by melt-extruding polyester into a sheet using an extruder and then biaxially stretching it in the longitudinal and lateral directions.In order to improve the thickness and transparency of the film, an extrusion die and a rotating cooling drum are used to improve the thickness and transparency of the film. A method is used in which an electrode is provided between the two and a high voltage is applied to apply an electrostatic charge to the upper surface of the uncured film, thereby bringing the film into close contact with the surface of the cooling drum. However, in such a method, when the film forming speed is increased, the electrostatic charge per unit area on the surface of the film adhered to the cooling drum surface decreases, the adhesion between the film and the cooling drum surface decreases, and the film thickness becomes insufficient. It becomes uniform and pin-like defects occur on the surface. If the applied voltage is increased to increase the amount of static charge in order to avoid this, discharge may occur between the electrode and the surface of the cooling drum and the film may be destroyed. In order to solve these problems, we added a metal compound with electrical conductivity to polyester to lower its specific resistance, thereby making it possible to produce polyester films with excellent thickness uniformity at high speed. JP-A-51-70269 describes that polyester contains alkali metals and alkaline earth metals in order to form a film.
Japanese Patent Application Laid-Open No. 1983-1989 discloses that a compound of cobalt, manganese and/or magnesium is added to polyester.
It is described in Publication No. 67392. In addition, in the direct polymerization method, a technique of adding a metal compound and a phosphorus compound to impart electrical conductivity to polyester has been proposed in Japanese Patent Publication No. 15730/1982; The reaction between the metal and the phosphorus compound produces undesirable metal phosphorus compound particles, which tends to cause turbidity.
In addition, filtration performance tends to deteriorate. Furthermore, when the material has sufficient electrical conductivity to impart electrostatic castability, there is a problem in terms of transparency, which has not yet been satisfactory. Polyesters containing small amounts of metal compounds have been widely produced industrially using dimethyl terephthalate (DMT) as a starting material. In the case of this method, the raw materials for polyester: their reaction products at each stage, including intermediate products and products, are:
For example, since it is composed of hydroxyl groups and ester groups related to EG and DMT and essentially does not contain carboxyl groups, even the addition of a small amount of metal compounds will have no effect on the quality of the polyester, especially its transparency. is not necessarily a major hindrance. In the production of polyester by direct polymerization from EG and TPA, the products of the esterification reaction, which is carried out at elevated or normal pressure, are usually easily processed by the polycondensation reaction, which is carried out in the presence of a polycondensation catalyst. However, if a small amount of metal compound, especially calcium compound, is added at this stage, the transparency of the resulting polyester will be reduced.
known to be extremely bad. Conventionally, when applying polyester to photographic supports, polyethylene terephthalate, which is a polyester that is advantageous due to its physical and chemical properties, has been commonly used. Among the various properties required as a support for photographic film, there has recently been a high demand for polyester film that is highly transparent, has no defects on its surface, and does not have a yellowish or blackish tone. It is worshiped. For example, in the case of X-ray photography, the high transparency of the film makes it possible to identify more subtle shadows and discover affected areas when evaluating the photograph. Also, from an ergonomic point of view, it is colored blue to alleviate eye fatigue and make it easier to judge, but normally the coloring is applied to the polyester film that is the film support. A clear blue color with no yellow or red tinges is required. Furthermore, for printed photographs,
Because photographic films are layered and photographed to create an original plate, and minute imperfections are emphasized in black and white, the polyester film used as the support is increasingly required to be transparent and free from surface imperfections. It's coming. When trying to apply polyester obtained by the above-mentioned conventional technique to photographic applications in particular, the present inventors found that its transparency and color tone were not in a situation that fully satisfied the above requirements, and the film It was determined that it was necessary to develop a polyester that not only increased productivity but also improved transparency and color tone. According to the present inventors, the transparency and color tone of polyester film are affected by the conditions when extruding polyester and forming a film using a biaxial stretching film forming apparatus, but mainly the transparency of polyester (solution It is highly correlated with the haze (evaluated as haze) and color tone (L value and b value measured by a color difference meter), and it is clear that when applied to photographic film, it greatly affects the transparency and color tone. Generally, in photographic films, the lower the polyester solution haze, the higher the transparency of the unexposed areas after development, which is preferable. In addition, the higher the L value of the polyester color,
The weaker the darkening of the unexposed areas after development and the closer the b value is to 0, the less yellowish or bluish the photographic film can be obtained. [Problems to be Solved by the Invention] The present inventors have developed a transparent film that is free from filtration pressure increase and turbidity caused by metal phosphorus compound particles, etc., and has excellent electrostatic casting properties. As a result of intensive study on a method for producing polyester by direct polymerization, a means to solve the above-mentioned problems was found. [Means for Solving the Problems] That is, in the method of the present invention, when producing polyester from dicarboxylic acid and glycols, 0.03 × 10 ^-3 to 2.0 × 10 ^-3 mol per 1 mol of dicarboxylic acid. A slurry of dicarboxylic acid containing a phosphorus compound corresponding to a phosphorus atom and glycols is mixed with bis(β-
Hydroxylethyl) terephthalate (hereinafter referred to as
(abbreviated as BHET) and/or its low polymer continuously or intermittently to carry out the esterification reaction, and after substantially completing the esterification reaction, the presence of a catalyst at a pressure below atmospheric pressure. At the stage where polycondensation is carried out and the reaction product satisfies the following formula, a divalent metal compound corresponding to 0.08×10 ^-3 to 2.0×10 ^-3 mol of metal atoms is added to 1 mol of dicarboxylic acid.
It is characterized in that it is added in a mixture with BHET and/or its low polymer to continue polycondensation. 0.3 (%) ≦Acid value/Saponification value It may be produced from a slurry of dicarboxylic acid containing a phosphorus compound and glycols. A preferred polyester obtained by the present invention is polyethylene terephthalate.
i.e. 80% or more of its constituent units, preferably 90%
The above is composed of ethylene terephthalate units obtained using terephthalic acid and ethylene glycol as starting materials, and may contain other copolymerized components within a range of less than 20%. Copolymerization components include aromatic dicarboxylic acids such as isophthalic acid; aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid; alicyclic carboxylic acids such as adipic acid and sebacic acid; diethylene glycol, propylene glycol, 1,4-butanediol,
Examples include glycols such as cyclohexane-1,4-dimethanol. The most suitable polyester for the present invention is polyethylene terephthalate. Hereinafter, dicarboxylic acid is terephthalic acid (hereinafter abbreviated as TPA), and glycol is ethylene glycol (hereinafter abbreviated as TPA).
(abbreviated as EG). The slurry applied to the present invention contains a phosphorus compound,
It is a mixture of EG and TPA, and TPA and
The ratio (molar ratio) of EG is usually 1:1.05 to 1.50, preferably 1:1.05 to 1.25. Examples of the phosphorus compounds applicable to the present invention include phosphoric acid, phosphorous acid, their monoesters, diesters, triesters, phosphonic acids, and phosphonic acid esters, including phosphoric acid, phosphorous acid, and trimethyl phosphate. and triethyl phosphate are preferred. These phosphorus compounds may be used alone or in combination of two or more. The phosphorus compound is preferably added to TPA or EG to form a uniform slurry, or added to a mixture of TPA and EG to be used as a uniform slurry. In addition, the phosphorus compound is pre-contained in EG and TPA, made into a slurry, and mixed in advance with EG and TPA in order to obtain the same effect as when it is continuously added to BHET and/or its low polymer. Alternatively, it can be dissolved in ethylene glycol and added continuously to BHET and/or its low polymer in parallel with the slurry of EG and TPA. or,
Either a small amount of phosphorus compound is added to BHET and/or its oligomer beforehand and then a slurry containing phosphorus compound is added as described above, or a slurry of EG and TPA and ethylene glycol without phosphorus compound is added. It is also possible to add a solution of a phosphorus compound dissolved in . The amount of the phosphorus compound added is preferably in a range corresponding to 0.03 x 10 ^-3 to 2.0 x 10 ^-3 mol of phosphorus atoms, preferably 0.1 x 10 ^-3 to 0.6 x 1 mol of dicarboxylic acid.
This amount corresponds to 10 ^-3 moles of phosphorus atoms. 2.0×
If the amount exceeds 10 ^-3 mol, it is not preferable because some kind of reaction occurs with the metal compound added after the esterification reaction is substantially completed, producing metal phosphorus compound particles. On the other hand, if it is less than 0.03×10 ⁻³ mol, the resulting polyester tends to have lower heat resistance and coloration, which is not preferable. Esterification reaction is carried out by continuously or intermittently adding slurry to BHET and/or its low polymer, but when polycondensation is carried out batchwise.
The amount of BHET and/or its low polymer is usually determined when the total weight after the esterification reaction is 100 parts.
It is 20 parts to 50 parts, preferably 30 parts to 50 parts. In this case, the esterification reaction temperature is usually 230℃ at normal pressure.
Above, preferably 240 to 260°C. The reaction time varies depending on the temperature, etc., but if the above value of BHET is 50 parts at normal pressure and the reaction temperature is 250°C, it is usually 4 parts.
If the above value is 33 copies, it will take about 6 hours. When under pressure, the pressure condition is 0.3 to 3.0Kg/
cm ² , preferably 1.0 to 2.0 Kg/cm ² , especially when the esterification rate in continuous esterification is up to about 85%. At this time, the esterification reaction temperature is usually
The temperature is 240°C to 280°C, preferably 250°C to 270°C, and can be selected regardless of the pressure of the esterification reaction. The reaction time for esterification varies depending on the pressure and temperature; for example, in the case of continuous esterification, the reaction time
270℃, pressurized condition of 1.5Kg/ ^cm2 (pressure 2.5Kg/cm2)
cm ² ), the esterification rate is 80 with a reaction time of about 1 hour and 30 minutes.
%, and then at a reaction temperature of 260℃ and under normal pressure.
The esterification reaction is completed after a reaction time of about 1 hour and 30 minutes. Therefore, in the case of continuous esterification, the temperature is 260℃~
3 at a temperature of 270℃ and a pressure of normal pressure to 2.5Kg/ ^cm2 .
The esterification reaction takes place in a reaction time of about 1 hour. After the esterification reaction is substantially completed, a polycondensation reaction is carried out in the presence of a catalyst at a pressure below atmospheric pressure.
Here, "the esterification reaction has been substantially completed" refers to a state in which a high molecular weight polycondensate can be reliably obtained by a normal method in the presence of a polycondensation catalyst.
The conversion rate to BHET and/or its low polymer (hereinafter also referred to as esterification reaction product), that is, the esterification rate is 90 to 98%, preferably 95% to 98%.
It is. The esterification rate can be determined by measuring the saponification value and acid value of the sample using a conventional analytical method, and using the following formula. Esterification rate = saponification value - acid value / saponification value x 100 (%) Generally, the esterification rate varies depending on the esterification reaction conditions such as the molar ratio of EG and TPA, esterification temperature, pressure, and time. To set the esterification reaction conditions to obtain the desired esterification rate,
The final esterification reaction conditions can be obtained by adjusting the esterification reaction conditions and checking the esterification rate of the sample at that time. In the method of the present invention, a phosphorus compound is usually added.
The esterification reaction is carried out while supplying a slurry of TPA and EG under normal pressure or increased pressure. After the supply is finished, the esterification reaction is carried out under normal pressure until the esterification rate is 90% to 98%, preferably 95%.
When it reaches ~98%, it is sent to the polycondensation step. The divalent metal compound is added at a stage when the esterification reaction is substantially completed and then polycondensation is carried out in the presence of a catalyst at a pressure below atmospheric pressure so that the reaction product satisfies the following formula. 0.3 (%) ≦ (acid value / saponification value) × 100 (%) ≦ 1.2 (%) If the value of the above formula is less than 0.3%, the melt viscosity of the polycondensation reaction product will be large, making it difficult to uniformly add the metal compound. This is difficult and tends to generate foreign matter in the resulting polyester, and if it exceeds 1.2%, undesirable particles of dicarboxylic acid and metal compounds are likely to be generated. For example, when esterification and polycondensation are carried out in a continuous manner, the range between the complete mixing tank of the polycondensation step and the polycondensation finishing machine may be within a range that satisfies the value of the above formula. The divalent metal compounds used in the present invention include zinc,
Examples include organic acid salts such as acetate, oxalate, benzoate, and stearate of magnesium, manganese, calcium, and lead, and halides. For example, zinc acetate, magnesium acetate, lead acetate, zinc oxalate, magnesium benzoate, calcium stearate, magnesium oleate,
Zinc chloride, calcium chloride, etc. are used, but
It is not limited to those shown here, and these can be used alone or in combination of two or more. These divalent metal compounds have, for example, a melting point of
A predetermined amount of divalent metal compound is added to high-purity BHET at 110℃, BHET with a polymerization degree of about 1.5 obtained by transesterification using DMT and EG as the main starting materials, at a concentration of about 2 to 8% by weight. Can be added by mixing with The amount of divalent metal compound added is 1 dicarboxylic acid
The amount corresponds to 0.08 to 10 ^-3 to 2.0 x 10 ^-3 mol of metal atoms per mole, preferably 0.15 x 10 -3 to 2.0 x 10 ^{-3 mol} .
This amount corresponds to 1.2×10 ^-3 moles of metal atoms.
If it is less than 0.08 x 10 ^-3 mol, the electrostatic application castability during film formation will be poor, while if it exceeds 2.0 x 10 ^-3 mol, insoluble particles and by-products generated by some reaction with the metal will increase. . The polycondensation of the esterification reaction product may be carried out by either a conventional batchwise or continuous method, and the polycondensation catalyst may be, for example, antimony trioxide or germanium dioxide. When polycondensing the esterification reaction product by a batch method, the precondensation reaction is generally carried out at a temperature of 260°C to 280°C for 30 to 60 minutes and at a pressure of 10 mmHg/cm ² from normal pressure. After that, 280℃~290℃, 0.1~0.5mmH
Polycondensation is carried out at a pressure of g/cm ² for usually 3 to 6 hours to produce a polyester with an intrinsic viscosity of 0.6 to 0.7. In addition, when polycondensing the esterification reaction product by continuous method, generally 270℃~280℃, 10~100mm
After the precondensation reaction in a precondensation machine with a residence time of 30-45 minutes at a pressure of Hg/ ^cm2 , a residence time of 60-75 minutes at a temperature of 280℃-290℃ and a pressure of 0.1-0.5mmHg/ ^cm2 . Polycondensation is carried out using a time polymerization finishing machine to produce polyester with an intrinsic viscosity of 0.6-0.7. Therefore, polycondensation of the esterification reaction product takes 3 to 6 hours in the batch method, whereas it takes 1.5 to 6 hours in the continuous method.
It will be held in a short time of 2 hours. In addition, in the present invention, silicon dioxide,
Various additives such as lubricants mainly composed of metal oxides such as aluminum trioxide, magnesium dioxide, and calcium carbonate, matting agents such as titanium dioxide, and pigments can be used. (Effects) According to the method for producing polyester of the present invention, in order to carry out the esterification reaction of glycol represented by ethylene glycol and dicarboxylic acid represented by terephthalic acid in the presence of a phosphorus compound, the phosphorus compound is converted into BHET. This reaction is reliably carried out, and the resulting polyester can stably and uniformly contain a predetermined amount of phosphorus. When a phosphorus compound is added before the start of polycondensation as in the conventional technology,
The phosphorus content of the obtained polyester tends to vary, which poses a problem in quality control of the polyester. This is considered to be due to the difficulty in controlling the reaction rate with BHET when a phosphorus compound is added at the start of polycondensation. It is common knowledge in the industry that the phosphorus content greatly affects the quality of polyester. Further, according to the method for producing polyester of the present invention, a divalent metal compound is added to a polycondensation product that already contains phosphorus, and polyester is produced by continuing polycondensation. The mutual reaction between the metal compound and the polycondensation product works very mildly, making it possible to efficiently ensure the various functions required when forming a polyester film. According to the conventional method, since the phosphorus compound is added about 10 minutes after the metal compound is added to the esterification reaction product, the reaction between the two becomes radical, and undesirable metal compounds are removed. Particles are generated, which hinders polyester film formation. Furthermore, according to the production method of the present invention, esterification is carried out not only under normal pressure as in the prior art, but also under pressure, thereby making it possible to significantly shorten the esterification reaction time and improve productivity. Not only can it contribute to the rationalization of equipment as the technology improves, but also
The original effects of the present invention can be fully obtained. The effects of the present invention are particularly exhibited in so-called direct continuous polymerization of polyester, in which esterification and polycondensation are carried out continuously. In this case, if the esterification reaction is carried out under pressure until the esterification rate reaches about 85%, the reaction time can be significantly shortened. Among polymer compounds, polyester is generally manufactured through a reaction at relatively high temperatures and over a relatively long period of time, so it is thought that the quality is degraded during manufacture. This is an essential issue in improving the quality of polyester.
Furthermore, in our experience, the contribution to improving the quality of polyester by reducing the time required for esterification and polycondensation is approximately equal. As already explained, if the polycondensation reaction of the esterification reaction product is carried out in a continuous manner, the polycondensation reaction time can be significantly shortened.
This task can be achieved more advantageously. Therefore, by carrying out the method for producing polyester of the present invention based on the direct continuous polymerization method of polyester, it is possible not only to achieve a higher standard in terms of the usual quality of polyester, but also to achieve a higher standard for film use than conventional techniques. The technology level of polyester, which was previously unattainable, can be achieved, especially transparency, color tone, and processability. Furthermore, according to the method for producing polyester of the present invention, compared to the conventional direct polymerization method, a smaller amount of metal compound is required to impart the same electrostatic application castability, and therefore a polyester having excellent transparency can be produced. can be obtained. Furthermore, according to the method for producing polyester of the present invention, calcium compounds, which are difficult to apply using conventional methods, can be used as the metal compound for imparting electrostatic castability, so there is a great degree of freedom in selection. There is. Therefore, especially when applied to a photographic support, it is easy to stably obtain a film that is less likely to have surface defects due to coarse particles and less likely to be colored due to metal compounds. As mentioned above, the polyester obtained by the method of the present invention has stable quality, has excellent transparency and color tone, and has little increase in filtration pressure during film formation, so that films can be produced over a long period of time. Moreover, since it has excellent electrostatic application castability, high-speed operation is possible, and therefore, high-quality films can be manufactured with good productivity. The polyester film produced from the polyester obtained by the polyester production method of the present invention, which has excellent transparency, a uniform film thickness without surface defects, and good color tone, can be used as a support for photography, especially for X-ray photography. When applied to film, polyester film produced from polyester obtained by conventional methods has a yellowish tinge and unsatisfactory transparency, making it difficult to obtain clear blue coloring. Since it has a small taste and is transparent, it is possible to obtain an ultra-transparent, high-quality X-ray photographic film with a clear blue color. Furthermore, when applied to a photographic film for printing, whereas polyester films produced from conventionally obtained polyesters were unsatisfactory due to lack of transparency and occurrence of surface defects, the method for producing polyesters of the present invention By applying a polyester that is highly transparent, it is possible to obtain a polyester film that is ultra-transparent and has no surface defects with high productivity. Of course, the polyester obtained in the present invention can be used for purposes other than films, and other additives, lubricants, matting agents, dyes, and pigments can also be used to impart performance as necessary. (Example) The present invention will be described in detail with reference to Examples below. The methods for measuring each characteristic value in the Examples are as follows. Note that parts are parts by weight. [Intrinsic viscosity] Phenol/ethane tetrachloride = 6/4 (weight ratio)
Dissolve in a mixed solvent and measure with an Ubbelohde viscometer at 25°C. [DEG content] After polyester is decomposed with alkali, it is quantified using gas chromatography (manufactured by Shimadzu Corporation). [Solution haze] 5.4 g of polyester was added to 40 ml of a mixed solvent of phenol/tetrachloroethane = 6/4 (weight ratio) at 100°C.
After dissolving for 2 hours, haze is measured using a 10 mm cell with a digital turbidity meter (manufactured by Tokyo Denshokusha). [Color tone of polyester and film] L value, b by fully automatic color difference meter (manufactured by Tokyo Denshokusha)
Displayed as a value. The larger the L value, the stronger the brightness, and the b value indicates the degree of yellow and blue, and the larger it is on the (+) side, the stronger the yellow. [Polyester melt specific resistance value] Two copper plate electrodes are placed in polyester melted at 290℃, and when a high voltage of 1KV is applied, the current value is read and the specific resistance value (Ω cm) is determined by calculation. . [Electrostatic application casting properties] 10KV is applied between the electrode at the top of the extruded film and the casting drum at the mouth of the extruder.
The film was formed at a casting speed of 30 m/min, and the resulting film was visually judged for its flatness and the presence or absence of pin-like defects. The judgment criteria are shown in the table below.

[Table] Example 1 The esterification process consists of a complete mixing tank and a horizontal multi-stage tank, each equipped with a rectification column, and the polycondensation process consists of a complete mixing tank and a horizontal polymerization finishing machine that are operated at below atmospheric pressure. Trimethyl phosphate (TMP) 0.0422 parts (0.3 x 10 ^-3 mol) in a continuous polyester polymerization equipment
and 68.2 parts (1.10 moles) of ethylene glycol (EG),
and 166 parts (1.00 mol) of terephthalic acid (TPA) into the first reactor (complete mixing tank) of the esterification process, and 0.05 part of antimony trioxide into the final section of the horizontal multi-stage tank of the esterification process. 0.128 parts (0.6 x 10 ^-3 mol) of magnesium acetate mixed with 2.5 parts of BHET having a melting point of 110°C were continuously supplied to the middle of the complete mixing tank and the horizontal polymerization finishing machine in the polycondensation process, as shown in Table 1. Polyester was obtained under the conditions shown in Table 3. The results are shown in Table 5. color, transparency,
The polyester had excellent electrostatic casting properties and was suitable for photographic use with no film failure.

[Table] Example 2 ^205.0 parts of BHET with an esterification rate of 97.0% (TPA1. (equivalent to 0 mol) is stored in a reactor at 250℃, and this
The esterification reaction is carried out at 250℃ under normal pressure while continuously adding a slurry consisting of 0.0294 parts of TMP, 74.4 parts of EG, and 166 parts of TPA, and the resulting water is continuously distilled out of the system from the rectification column. I let it happen. The addition of the slurry consisting of TMP, EG and TPA was completed in 3 hours and 30 minutes, and the esterification reaction was further continued, and the esterification reaction was substantially completed in a total of 4 hours. Obtained esterification reaction product 205.0
A portion was left in the reactor and the esterification reaction was carried out again in the same manner as above, and these operations were repeated three times in total to finally obtain an esterification reaction product with an esterification rate of 97.0%. 205.0 parts of this was taken into a reactor for the polycondensation process, 0.058 parts of antimony trioxide was added, and polycondensation was carried out under reduced pressure in a conventional manner. Adding 0.129 parts of magnesium (0.6 x 10 ^-3 mol),
Polycondensation was further continued for 2 hours and 30 minutes, and the final temperature was 283
℃, a vacuum degree of 0.5 mmHg/cm, and a polymerization time of 4 hours and 45 minutes to obtain polyester. The results are shown in Table 4. The properties of the obtained polyester and its film were such that they had little coloring and devitrification and were suitable for photographic use without any problems. Example 3 and Comparative Example 1 Example 2 except that the timing of adding magnesium acetate was changed as shown in Table 2.
Polycondensation was carried out in a batch manner in the same manner as above to obtain polyester. The results are shown in Table 4. The properties of the polyester and film obtained in Example 3 were excellent in color tone and transparency suitable for photography, whereas the properties of the polyester and film obtained in Comparative Example 1 were as good as those in Example 2. , 3 had a yellowish tinge and inferior transparency, and were somewhat unsatisfactory for photographic use. Note that Comparative Example 1 has preferable properties compared to the conventional method (Comparative Example 2) due to the effect of adding a phosphorus compound to the slurry.

[Table] Comparative Example 2 A polyester was obtained in the same manner as in Example 2, except that TMP was not included in the slurry and added after the esterification reaction and before the start of polycondensation. The results are shown in Table 4. The properties of the obtained polyester and film thereof were yellowish and had poor transparency, making them unsuitable for photographic use. This shows that the conventional direct polymerization method is unsatisfactory in terms of quality because it cannot achieve the effect of containing the phosphorus compound of the present invention in the slurry and the effect of specifying the timing of addition of the divalent metal compound. Comparative Example 3 In Example 1, the same number of moles of magnesium acetate was used as calcium stearate with a melting point of 179°C.
Example 1, except for the change in which the polycondensation process was completed (after the horizontal polymerization finishing machine).
Polyester was obtained in the same manner as above. The results are shown in Table 4. The obtained polyester had difficulty in uniformly adding calcium stearate, had extremely poor transparency, and had foreign matter observed in the film, making it unsuitable for photographic use. This is to ensure that the metal compound to be added is evenly mixed into the polyester.
This shows that it is advantageous that the melt viscosity is not too high, and also shows that the range of (acid value/saponification value) x 100 value of the present invention is preferable in view of equipment difficulties. Examples 4 and 5 TMP and magnesium acetate in Example 1 were
tertiary to other phosphorus compounds and divalent metal compounds, respectively.
Polyester was obtained in the same manner as in Example 1 with the changes shown in the table. The results are shown in Table 4. The obtained polyesters of Examples 4 and 5 and their films were both excellent in color tone, transparency, and electrostatic castability, and were suitable for photographic use. Comparative Examples 4 and 5 A polyester was obtained in the same manner as in Example 1, except that the amounts of TMP and magnesium acetate added were changed to amounts outside the range of the present invention shown in Table 3. The results are shown in Table 4. The properties of the obtained polyester and its film are both problematic for photographic use, and in Comparative Example 4, in which the amount of metal compound added is small, the melt specific resistance value is extremely poor, making it unsuitable for high-speed film formation; In Comparative Example 5, which had a large amount of color, the transparency was significantly poor, and the color tone was problematic due to a strong yellowish tinge. Examples - Suitability for photographic film Biaxially stretched films with a thickness of 100 μm were prepared from the polyesters obtained in each of Examples 1 to 5 and Comparative Examples 1 to 5 using a conventional electrostatic casting method. A printed photographic film was prepared by coating and drying a photosensitive emulsion for printed photographs. These were evaluated as described below, and their suitability as photographic films was determined comprehensively. The results are shown in Table 4. The properties of each of the photographic films obtained showed that the films using the polyesters of Examples 1 to 5 all showed good suitability, exhibited the effects of the present invention, and produced high-quality photographic films. On the other hand, the polyesters of Comparative Examples 1 to 5 obtained without using the method of the present invention had some defects in photographic film properties and were unsatisfactory as photographic films. The evaluation method for photographic film is shown below. [Color tone of photographic film] Samples of unexposed photographic film developed in a conventional manner were visually evaluated under white light. The color tone evaluation criteria of the present invention were determined and displayed as follows.

[Table] [Transparency of Photographic Film] Five samples of unexposed photographic film developed in a conventional manner were layered, exposed to white light, and evaluated and displayed using the following criteria.

[Table] [Photographic film failures] Among photographic film failures, failures that are considered to be caused by the film support include uneven coating due to surface irregularities, sensitization or desensitization due to foreign matter, scratches, and crystallization. The number and severity of failures per unit area (m ² ) were comparatively determined and displayed based on the following criteria.

[Table] Photographic film suitability The suitability of each of the above-mentioned photographic film supports was comprehensively evaluated, judged based on the following criteria, and displayed.

【table】

【table】

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Claims (1)

[Scope of Claims] 1. When producing polyester from dicarboxylic acid and glycols, dicarboxylic acid containing a phosphorus compound corresponding to 0.03×10 ^-3 to 2.0×10 ^-3 mol of phosphorus atoms per 1 mol of dicarboxylic acid. A slurry of acid and glycols is continuously or intermittently supplied to bis(β-hydroxyethyl) terephthalate and/or its low polymer to carry out an esterification reaction, and the esterification reaction is substantially completed. After that, polycondensation is carried out in the presence of a catalyst at a pressure below atmospheric pressure, and at the stage where the reaction product satisfies the following formula, 0.08×10 ^-3 to 2.0×10 ^-3 mol of metal is added to 1 mol of dicarboxylic acid. The divalent metal compound corresponding to the atom is bis(β-hydroxyethyl) terephthalate and/or
A method for producing polyester, which comprises adding the polyester by mixing it with a low polymer thereof to continue polycondensation. 0.3(%) ≦Acid value/Saponification value×100(%) ≦1.2(%)