JPH0371970B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing polyester having excellent heat resistance and color tone, and improved electrostatic castability. Polyester, which is used industrially today,
In particular, polyethylene terephthalate has a high degree of crystallinity, high softening point, strength, chemical resistance, heat resistance,
It exhibits excellent properties such as weather resistance and electrical edge resistance.
It is widely used industrially for fibers, films, and various molded products. When polyester is used in various industrial fields, it usually has a high operability in forming processes such as spacing extrusion, drawing, stretching, and heat treatment, in weaving, dyeing, and processed yarn processing processes, or in the case of film production. In addition to magnetic layer coating and metal vapor deposition, heat resistance and operability during various coatings, operability in secondary processing processes such as cutting and finishing in the case of molded products, and even in the final product. It is required to have excellent slipperiness, transparency, and color tone, and a desirable surface morphology. In addition, particularly in film applications, it is required that the film has excellent electrostatic application castability as described below. In other words, polyester film is usually obtained by extruding polyester into a sheet using a melt extruder and then biaxially stretching it in both the vertical and horizontal directions simultaneously or sequentially. In order to prevent loss, the sheet-like material melt-extruded from the extrusion nozzle is usually cooled on the surface of a rotating cooling drum. At this time, a high voltage is applied to the sheet-like material between the extrusion nozzle and the rotating cooling drum, A method is employed in which electrostatic charges are deposited on the surface of an unsolidified sheet material and the sheet is rapidly cooled while being brought into close contact with the surface of a grounded cooling drum (hereinafter referred to as electrostatic application casting method). When the film thickness is constant, the productivity of polyester film is determined by the casting speed, and in order to improve productivity, it is extremely important to increase the casting speed. In this way, the properties required for polyester for film can be roughly divided into (a) slipperiness and heat resistance to improve workability, and (b) electrostatic castability to improve productivity. Currently, great efforts are being made to improve and improve these points. First, regarding the improvement of slipperiness, as disclosed in Japanese Patent Application No. 57-174832 previously filed by the present inventors, when the esterification reaction rate reaches 90% or more, phosphoric acid A method in which fine particles are precipitated in polyester by adding an ethylene glycol solution and then adding a lithium compound and a calcium compound to cause polycondensation (hereinafter referred to as the internal particle method), or inorganic inert materials such as silica and alumina. A method in which particles are finely dispersed in polyester (hereinafter referred to as the external particle method) is known, and although it is somewhat effective in terms of slipperiness, it is difficult to form a film due to poor electrostatic casting properties. In particular, when the internal particle method is used, the concentration of diethylene glycol bonds (hereinafter referred to as DEG) in the polyester tends to increase, which impairs heat resistance. On the other hand, in order to improve the castability by electrostatic application, for example, Japanese Patent Publication No. 56-15730 and Japanese Unexamined Patent Publication No. 55
As disclosed in Publication No. 84322, by adding appropriate amounts of magnesium or manganese compounds and alkali metal compounds or phosphorus compounds to cause polycondensation, the resistivity of molten polyester is lowered and electrostatically applied cast Methods for improving sexual performance are well known. In this case, although some results have been achieved in terms of improving the castability by electrostatic application, the slipperiness is poor and the operability during the process is low. The disadvantage was that the resulting film was colored yellow, reducing the color tone, and the DEG concentration increased, resulting in a decrease in heat resistance. By the way, it can be easily inferred that improvements in slipperiness and improvements in electrostatic castability can be simply combined. However, a method that is just a collection of both improvement techniques, for example, simply combining the internal particle method and the method for improving castability by electrostatic application, will only result in a mere combination effect, although it will slightly improve the physical properties of both. However, not only no special synergistic effect is produced, but also magnesium, manganese, or even alkali metals are precipitated as internal particles, the particles become coarse and the surface morphology is deteriorated, and the castability by electrostatic application is not improved. Also,
The drawbacks of the obtained film, such as a decrease in color tone and a deterioration in heat resistance due to an increase in DEG concentration, are not improved at all. In this way, conventionally, heat resistance, slipperiness, transparency,
It has been said that it is extremely difficult to produce polyester for film that has excellent color tone and electrostatic castability and has a desirable surface morphology. As a result of intensive research into a method for producing a polyester film free from such drawbacks, the present inventors found that a specific mixture of a polyester containing a specific amount of a magnesium compound, a phosphorus compound, and an alkali metal compound, and a polyester containing only a specific amount of a phosphorus compound. By mixing in the ratio and forming into a film,
The present invention was completed based on the discovery that it is possible to produce a polyester film that has excellent heat resistance, slipperiness, transparency, color tone, and electrostatic castability, and has a desirable surface morphology. That is, in the present invention, the magnesium compound is added in an amount of 3x per mole of the total acid components constituting the polyester
10 ⁻⁴ mol or more of a phosphorus compound, 0.15 to 1.0 mol per mol of the magnesium compound, and 0.05 to 7.50 mol of an alkali metal compound per mol of the magnesium compound, and a phosphorus compound; Polyester C after mixing with polyester B that does not contain
The magnesium content in polyester C is 0.3×10 ^-4 to 1.5× per mole of all acid components constituting polyester C.
After mixing to give 10 ^-4 mol and melt-extruding it into a sheet, electrostatic charge is deposited on the sheet from the upper or lower surface, and the resulting unstretched material is cooled and solidified on the surface of a rotary cooling body. The gist of this invention is a method for producing a polyester film, which is characterized by biaxially stretching a sheet. The polyester referred to in the present invention mainly refers to polyethylene terephthalate produced from terephthalic acid and ethylene glycol, but part of the terephthalic acid (hereinafter referred to as TPA) contains isophthalic acid and
Dicarboxylic acids such as naphthalenedicarboxylic acid, diphenylsulfonedicarboxylic acid, adipic acid, sebacic acid, and 5-sodium sulfoisophthalic acid
It may be contained at about 30 mol%, and if ethylene glycol (hereinafter referred to as EG) contains glycols such as tetramerylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, etc. at about 30 mol%. May be included. The magnesium compound referred to in the present invention refers to a magnesium carboxylate, and specific examples include magnesium acetate, magnesium propionate, magnesium stearate, and magnesium benzoate, with magnesium acetate being particularly preferred. Further, the amount of the magnesium compound added to the polyester A needs to be 3 x 10 ^-4 mol or more per 1 mol of the total acid components constituting the polyester, and if it is less than this amount, the specific resistance will substantially decrease. There is no effect of reducing the amount. The phosphorus compound referred to in the present invention refers to phosphoric acid, phosphorous acid, and derivatives thereof, and specifically refers to phosphoric acid, phosphorous acid, mono-n-butyl phosphate, and di-n-butyl phosphate. , mono-i-propyl phosphate,
di-i-propyl phosphate, monooctyl phosphate,
Examples include dioctyl phosphate, trimethyl phosphate, triethyl phosphate, dibutylhydrodiene phosphite, triphenyl phosphite, and phosphoric triesters are preferred, with triethyl phosphate being particularly preferred. The amount added to the polyester A needs to be 0.15 to 1.0 mol per 1 mol of the magnesium compound added. If the amount added is more than this range, it will impair electrostatic casting properties and transparency, which is undesirable, while if it is less than this range, the color tone will be deteriorated, which is not preferable. On the other hand, the phosphorus compound added to the polyester B is usually suppressed to 20 x 10 ^-4 mol or less, preferably 5 x 10 ^-4 mol or less, per 1 mol of the total acid components constituting the polyester. is preferable. If the amount of the phosphorus compound added to polyester B is greater than the above amount, the electrostatic casting properties will not be improved, which is not preferred. In this case, the phosphorus compound added to polyester A and the phosphorus compound added to polyester B do not necessarily have to be the same, but it is preferable to use the same compounds. The alkali metal compound referred to in the present invention refers to an alkali metal carboxylate, and specifically includes lithium acetate, sodium acetate, potassium acetate, lithium propionate, lithium stearate, lithium benzoate, etc. Lithium acetate is preferred. Further, the amount of the alkali metal compound added needs to be 0.05 to 7.50 moles relative to the number of moles of the magnesium compound added to polyester A. If the amount of the alkali metal compound added is less than the lower limit of the above range, the DEG concentration in the polyester A produced will increase, which is undesirable.On the other hand, if the amount of the alkali metal compound added is more than the upper limit of the range, the DEG suppressing effect will no longer be saturated. This is not only meaningless, but also causes deterioration of electrostatic application castability and surface morphology, both of which are undesirable. Next, regarding the mixing ratio of polyester A and polyester B, which is one of the main points of the present invention, the magnesium content in polyester C after mixing is based on 1 mole of the total acid components constituting polyester C.
It is necessary to mix so that the amount is 0.3×10 ^-4 to 1.5×10 ^-4 mol. The magnesium content is 0.3×
If it is less than 10 ^-4 mol, the electrostatic castability will not be improved, while if it is more than 1.5 x 10 ^-4 mol, the DEG concentration,
This is not preferable because it increases the b value (described later) and deteriorates the surface morphology. In particular, the DEG concentration must be 0.1 mol% in order to maintain the heat resistance of the film.
However, it would be advantageous if it could be lowered. As mentioned above, the purpose of the present invention is to produce a polyester film that (a) has excellent heat resistance and slipperiness, and (b) has excellent electrostatic charge castability. It is already known that in order to improve the applied castability, it is sufficient to reduce the resistivity of the molten polyester. Figure 1 shows the relationship between the magnesium content in a polyester film and the specific resistance. They discovered the surprising fact that when a film is formed by mixing two types of polyester raw materials with different properties, the specific resistance value differs greatly even if the magnesium content in the film is the same. Figure 2 shows the amount of magnesium added during polyester production and DEG in the produced polyester.
This shows the relationship between concentration and b value of polyester, and it can be seen that as the amount of magnesium added increases, the DEG concentration and b value tend to increase. It is generally known that when the specific resistance of polyester is 1×10 ⁸ Ωcm or less, the electrostatic casting property is good, but as is clear from Figure 1, in the conventional method, the amount of magnesium compound added is It is necessary to add about 4×10 ^-4 mol or more per mol of the total acid components constituting the polyester. However, the second
As is clear from the figure, the DEG concentration in this case is approximately
It was 1.75 mol% and the b value was about 8, which was a problem from the viewpoint of heat resistance and color tone. However, according to the present invention, as described above, polyester A containing specific amounts of a magnesium compound, a phosphorus compound, and an alkali metal compound
By mixing polyester B containing a specific amount of phosphorus compound, polyester C after mixing
Even if the magnesium content is significantly lower than the above-mentioned 4×10 ^-4 mol/acid component, it shows excellent resistivity (1×10 ⁸ Ωcm or less) in electrostatic application castability, so it has a high resistivity. DEG concentration and b value are reduced, making it possible to create films with excellent heat resistance and color tone. In other words, the above-mentioned features of the present invention are that, when the amount of magnesium is the same, it is possible to extremely reduce the specific resistance of polyester compared to the conventional technology, and the castability by electrostatic application is significantly improved. It also means Although the reason for the above effects brought about by the method of the present invention has not been fully elucidated at present, it is thought that this is due to the difference in the properties of the phosphorus compounds contained in the polyesters A and B. That is,
When producing polyester A referred to in the present invention,
Although the molar ratio of the phosphorus compound to the magnesium compound cannot exceed 1, the number of moles of the phosphorus compound in polyester B referred to in the present invention is determined from the above limit because polyester B does not contain magnesium. Can be added in large quantities.
Therefore, it is presumed that this is because the amounts of the magnesium compound and phosphorus compound at the time of forming the polyester C referred to in the present invention can be selected. In order to impart slipperiness to polyester in the present invention, for example, as described above, inorganic inert particles may be added to polyester A or B, but it is preferable to add them to polyester A. Hereinafter, the present invention will be explained in more detail using examples. In the examples, "parts" represent "parts by weight" unless otherwise specified, and each characteristic value in the examples was determined by the following method. . (1) Intrinsic viscosity of polymer [η] It was determined from the solution viscosity measured at 20°C using a mixed solvent of equal weight of phenol and tetrachloroethane. (2) DEG concentration The polymer was subjected to alcoholysis under methanol reflux for 2 hours, and the produced ethylene glycol and diethylene glycol were analyzed and quantified by gas chromatography to determine the DEG concentration. (3) Color tone The color tone of the obtained polyester changes after molding into granules.
Evaluation was made by determining the b value using a color difference meter. The b value is a yellow-blue tone (+ means yellowish, - means blueish)
represents. As for the color tone of polyester, the smaller the b value, the better, as long as it does not become extremely small. (4) Film haze The obtained polymer was formed into a film with a thickness of 12 microns, and the film was measured using a Tokyo Denshoku haze meter. (5) Surface morphology The obtained polymer was formed into a film with a thickness of 12 microns, and its surface roughness was measured using a surface roughness meter manufactured by Kosaka Research Institute, and the results were classified into the following four ranks, with rank A being considered good. . Rank A: Many irregularities of about 0.1 micron can be seen. Rank B: Overall close to rank A, but in some places
Rough irregularities of about 0.3 microns can be seen. Rank C: Overall, close to rank B, but in some places
Rough irregularities of about 0.5 microns can be seen. Rank D: There are many irregularities exceeding 0.5 microns, and the surface is not uniform. (6) Specific resistance of molten polymer The specific resistance of molten polymer was measured using the apparatus shown in FIG. In FIG. 3, 1 is a DC high voltage generator, 2 is an electrometer, 3 is a high voltage voltmeter, 4 is a heating medium, 5 is a polymer to be measured, 6 is a cylindrical electrode, 7 is a grounded main body electrode, 8 is an insulator. The specific resistance R of the polymer is determined by reading the voltage V and the current I, respectively, and using the following formula. R=V·S/I· (Here, the distance between the electrodes (cm), and S is the electrode surface area (cm ² ).) This specific resistance was used as a measure of the quality of the electrostatic casting property. (7) Electrostatic application casting property A voltage of 6KV is applied between the casting drum and the electrode installed on the top of the extruded film in the extruder nozzle, and the casting speed is controlled.
Judgment was made based on whether or not a film could be formed satisfactorily at 43 m/min. The specific resistance of molten polyester is 1×10 ⁸ (Ω・cm)
When the following conditions were met, the electrostatic application castability was generally good. Reference Example 1 A slurry of terephthalic acid and ethylene glycol (the molar ratio of terephthalic acid/ethylene glycol is 1.6) was supplied and reacted at 250°C and a pressure of 0.05 Kg/cm ² G, and the residence time was 8 hours. The esterification reaction rate was 95.
% BHET was obtained continuously. Reference Example 2 100 parts of BHET obtained in Reference Example 1 was transferred to a polymerization tank and heated to 280°C. Magnesium acetate, lithium acetate, and triethyl phosphate were each added at 16 ^-4 mol, 8 x 10 ^-4 mol, 8 x 10 ^-4 mol, and 2 x 10 ^-4 mol of antimony trioxide as a catalyst per 1 mol of the total acid components constituting the polyester. Silica with an average diameter of about 2.5 microns
Added 0.008 parts, started reducing pressure, and caused a polycondensation reaction. As a result, [η] = 0.68 (dl/g), DEG = 2.14 (mol%),
A polyester with a b value of 2.17 was obtained. Reference Example 3 The amounts of magnesium acetate, lithium acetate, and triethyl phosphate to be added are 8 x 10 ^-4 mol and 4 mol, respectively, per 1 mol of the total acid components constituting the polyester.
× 10 ^-4 mol, 4 × 10 ^-4 mol, and the reaction was carried out in the same manner as in Reference Example 2 except that the amount of silica added was 0.004 part. [η] = 0.66 (dl/g), DEG
= 1.83 (mol%), b value = 8.2 polyester was obtained. Reference Example 4 The reaction was carried out in the same manner as in Reference Example 3, except that the amount of triethyl phosphate added was 9.5 × 10 ^-4 mol per 1 mol of the total acid components constituting the polyester. [η] = 0.67 (dl /g), DEG=2.06 (mol%),
A polyester with a b value of 11.7 was obtained. Reference Example 5 The reaction was carried out in the same manner as in Reference Example 3, except that the amount of triethyl phosphate added was 1 x 10 ^-4 mol per 1 mol of the total acid components constituting the polyester. [η] = 0.65 (dl /g), DEG=2.22 (mol%), b
A polyester with a value of 14.1 was obtained. Reference example 6 Reference example 3 except that lithium acetate is not added
When the reaction was carried out in the same way, [η] = 0.67 (dl/
g), DEG=1.92 (mol%), b value=8.1 polyester was obtained. Reference Example 7 The reaction was carried out in the same manner as in Reference Example 3, except that lithium acetate was added in an amount of 80 × 10 ^-4 mol per 1 mol of the total acid components constituting the polyester, and [η] = 0.68 (dl/g), DEG=1.79 (mol
%), a polyester with a b value of 7.9 was obtained. Reference Example 8 The amounts of magnesium acetate, lithium acetate, and triethyl phosphate to be added are 2 x 10 ^-4 mol and 1 mol, respectively, per 1 mol of the total acid components constituting the polyester.
×10 ^-4 mol, 1 × 10 ^-4 mol, and the reaction was carried out in the same manner as in Reference Example 2 except that the amount of silica added was 0.001 part [η] = 0.70 (dl/g), DEG
= 1.65 (mol%), b value = 5.9 polyester was obtained. Reference Example 9 The amount of magnesium acetate, lithium acetate, and triethyl phosphate to be added is 1 x 10 ^-4 mol, respectively, per 1 mol of the total acid components constituting the polyester.
The reaction was carried out in the same manner as in Reference Example 2, except that the amounts were 0.5×10 ^-4 mol and 3.31×10 ^-4 mol, and the amount of silica added was 0.0005 parts. [η] = 0.68 (dl/g),
A polyester with DEG=1.63 (mol%) and b value=6.1 was obtained. Reference Example 10 100 parts of BHET obtained in Reference Example 1 was transferred to a polymerization tank, heated to 280°C, and triethyl phosphate and antimony trioxide were each added at 3 x 10 ^-4 for 1 mole of the total acid components constituting the polyester. mol, DEG ⁼ 1.55 (mol).
%), a polyester with a b value of 5.8 was obtained. Reference Example 11 The reaction was carried out in the same manner as in Reference Example 10, except that the amount of triethyl phosphate added was 8 x 10 ^-4 mol per 1 mol of the total acid components constituting the polyester. [η] = 0.68 (dl/g), DEG=1.56 (mol%),
A polyester with a b value of 5.6 was obtained. Reference Examples 12 to 14 The reaction was carried out in the same manner as in Reference Example 2, except that the various additive compounds used were magnesium stearate, lithium benzoate, and di-n-butyl phosphate, respectively. In Reference Example 12, [η] =0.68
(dl/g), DEG = 2.13 (mol%), b value = 12.5, [η] = 0.68 (dl/g), DEG = 2.13 in reference example 13
(mol%), b value = 12.8, and in Reference Example 14 [η]
= 0.67 (dl/g), DEG = 2.11 (mol%), b value =
A polyester of 12.4 was obtained. Reference Examples 15, 16 The amounts of magnesium acetate, lithium acetate, and triethyl phosphate to be added are 1.5 x 10 ^-4 mol, respectively, per 1 mol of the total acid components constituting the polyester.
0.8 × 10 ^-4 mol, 1.5 × 10 ^-4 mol, (Reference Example 15), and 4 × 10 ^-4 mol, 2 × 10 ^-4 mol, 4 × 10 ^-4 mol (Reference Example 16), and add. When the reaction was carried out in the same manner as in Reference Example 2 except that silica was changed to 0.0005 parts, Reference Example 15 had [η] = 0.68 (dl/g), DEG = 1.67 (mol
%), b value = 6.7, [η] = 0.67 (dl/
g), DEG=1.87 (mol%), b value=6.9 polyester was obtained. Example 1 After drying polyester A obtained in Reference Example 2 and polyester B obtained in Reference Example 10, the weight ratio of A/B=
The mixture was mixed to a ratio of 1/15, extruded into a sheet using a melt extruder, and formed into an unstretched film using an electrostatic casting method. Then 3.3x vertically, 3.1x horizontally, 2x at the same time
A stretched film with a thickness of 12 μm was obtained by axial stretching. The properties of this film are shown in Table 1, and it was found to have excellent transparency and electrostatic castability, and a desirable surface morphology. Example 2 After drying polyester A obtained in Reference Example 3 and polyester B obtained in Reference Example 10, the weight ratio of A/B=
Example 1 except that the ratio was 1/7.
Film molding was performed in the same manner as above, and the results shown in Table 1 were obtained. Examples 3-5 Polyester A obtained in Reference Examples 12-14 and Reference Example 10
After drying the polyester B obtained in the above, the weight ratio is A/
A film was formed in the same manner as in Example 1, except that the mixture was mixed so that B=1/15, and the results shown in Table 1 were obtained. Example 6 After drying polyester A obtained in Reference Example 2 and polyester B obtained in Reference Example 10, the weight ratio of A/B=
Example 1 except that the ratio was 1/23.
Film molding was performed in the same manner as above, and the results shown in Table 1 were obtained. Example 7 After drying polyester A obtained in Reference Example 1 and polyester B obtained in Reference Example 10, the weight ratio of A/B=
Example 1 except that the mixture was 1/10.
Film molding was performed in the same manner as above, and the results shown in Table 1 were obtained. Comparative Example 1 After drying polyester A obtained in Reference Example 8 and polyester B obtained in Reference Example 10, the weight ratio of A/B=
Example 1 except that the ratio was 1/1.
A film was formed in the same manner as above, and the results shown in Table 1 were obtained. At this time, the electrostatic application castability is not good,
Operability was poor, with discharge phenomena occurring once every few hours. Comparative Examples 2 and 3 Example 2 except that the polyesters obtained in Reference Examples 4 and 5 were used as polyester A, respectively.
A film was formed in the same manner as above, and the results shown in Table 1 were obtained, but the electrostatic casting properties were poor. Comparative Examples 4 and 5 Example 2 except that the polyesters obtained in Reference Examples 6 and 7 were used as polyester A, respectively.
A film was formed in the same manner as above, and the results shown in Table 1 were obtained, but the DEG concentration was high, the surface morphology was poor, and the electrostatic casting properties were poor. Comparative Example 6 A film was formed in the same manner as in Example 1 except that only the polyester obtained in Reference Example 9 was dried and then melt-extruded, and the results shown in Table 1 were obtained, but the electrostatic castability was extremely poor. It was. Comparative Example 7 A film was formed in the same manner as in Example 1 except that the polyester obtained in Reference Example 11 was used as polyester B, and the results shown in Table 1 were obtained, but the electrostatic casting properties were extremely poor. . Comparative Examples 8 and 9 Film molding was performed in the same manner as in Example 2 except that the mixing ratio of polyester A and polyester B was 1/39 or 1/3, respectively, and the results shown in Table 1 were obtained, but the DEG concentration It was not preferable because the b value was high and the castability by electrostatic application was poor. Comparative Examples 10, 11 Example 1 except that only the polyester obtained in Reference Example 15 (Comparative Example 10) or the polyester obtained in Reference Example 16 (Comparative Example 11) was melt-extruded after drying.
Film molding was performed in the same manner as above, and the results shown in Table 1 were obtained. In Comparative Example 10, the magnesium compound in polyester C contained the amount (upper limit) of the present invention, but 2
Since the conventional method does not mix seed polymers, the specific resistance is large and the electrostatic casting properties are poor. Further, although Comparative Example 11 was able to lower the specific resistance, since the content of the magnesium compound was high, the DEG concentration in the polyester was high and the surface morphology was poor.

【table】

【table】

【table】 [Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the magnesium content in the film and the specific resistance of molten polyester, and Figure 2 is a diagram showing the relationship between the magnesium content in the polyester, the DEG concentration in the polyester, and the b value of the polyester chip. It is. Moreover, FIG. 3 shows a schematic diagram of a polymer specific resistance measuring apparatus according to the present invention.

Claims (1)

[Claims] 1 Magnesium compound, 3 x 10 ^-4 mol or more per 1 mol of the total acid components constituting the polyester, phosphorus compound per 1 mol of the magnesium compound
0.15 to 1.0 mol, and 0.05 to 7.50 mol of the alkali metal compound per mol of the magnesium compound.
Polyester A containing mol of polyester A and polyester B containing a phosphorus compound but not containing a magnesium compound are mixed in such a manner that the magnesium content in polyester C after mixing is 0.3×10 per mol of the total acid components constituting polyester C. ^-4 to 1.5 x 10 ^-4 mol and melt-extruded into a sheet, electrostatic charges are deposited on the sheet from the top or bottom and the sheet is cooled and solidified on the surface of a rotary cooling body. A method for producing a polyester film, which comprises biaxially stretching the unstretched sheet.