JPH021173B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing film-forming polyesters. Biaxially oriented polyester films, especially polyethylene terephthalate, used industrially today have a high degree of crystallinity and a high softening point, and have excellent elongation, bending strength, chemical resistance, weather resistance, heat resistance, etc. It has excellent properties and is widely used in industry. Although the required properties of polyester film differ depending on its use, the universally desired properties are excellent workability when handling the film and no loss of transparency. Conventionally, there are two main methods known for improving the slipperiness of polyester films.
One is a method called an addition method, in which fine particles of an inorganic compound, such as kaolin, talc, calcium carbonate, calcium phosphate, etc., are blended particularly at the initial stage of the polycondensation reaction or during the melt extrusion process to obtain a film. This method of adding inert fine particles to polyester has a relatively excellent slipperiness imparting effect, but coarse particles often get mixed in. In order to remove these coarse particles, a classification operation is necessarily required, and if necessary, a crushing operation is required as a pretreatment thereof, which makes the operation complicated. Moreover, even if such an operation is performed, the contamination of coarse particles is still unavoidable. Furthermore, it is generally difficult to uniformly disperse inorganic compounds in polyester, which is an organic compound, and aggregate particles often exist due to poor dispersion. The presence of these coarse particles or agglomerated particles significantly impairs the appearance of the film and causes quality problems. For example, in magnetic tape applications, it causes dropouts, and in capacitor applications, it causes poor withstand voltage. Another method that is contrasted with the addition method is a method called a precipitation method, in which fine particles are formed and precipitated in a polyester in a reaction system. Previously, the present inventors disclosed a method for improving slipperiness without significantly impairing transparency in JP-A-53-
Proposed in No. 113868. That is, a film obtained from a polyester containing a specific amount of particles containing lithium and phosphorus elements precipitated during the production of the polyester is
The conventionally widely used method of adding inert fine particles,
The relationship between slipperiness and transparency is so excellent that it cannot be achieved by a method in which an alkali metal compound or an alkaline earth metal compound is precipitated as a metal salt of a polyester oligomer, and in particular, particles containing lithium and phosphorus elements, Furthermore, it was revealed that more excellent effects can be exhibited when calcium element is included. This precipitation method has the advantage that it can be easily implemented industrially since it does not require special equipment or complicated operations, and therefore, if it can be adopted, its utility value is extremely large. By the way, in the current production of polyester, unlike the case for fibers, production of a wide variety of products in small quantities is common, so a so-called batch method is often adopted. Therefore, it is an industrial necessity to efficiently produce polyester of stable quality by a batch method. In addition, in recent years, stricter film quality has been required than ever before, especially for various film uses.
There has been a strong demand for slipperiness, transparency, and stability of surface roughness for each count. However, according to the experience of the present inventors, when attempting to produce polyester containing a specific amount of particles containing lithium, calcium, and phosphorus elements by a batch method, slight variations in operating conditions from batch to batch may cause problems. The amount and diameter of the precipitated particles often change, making it difficult to maintain constant quality of the final film. That is, in such a batch method, two reaction vessels, an esterification or transesterification reaction vessel and a polycondensation vessel, are usually used and operations are repeated in each.
In this case, since the polyester obtained in the polycondensation tank has a high viscosity, an indeterminate amount of polyester from the previous batch remains for each batch on the walls, bottom or stirring blades. Washing this remaining polyester after each batch and extracting it from the bottom of the polycondensation tank is extremely economically disadvantageous in terms of workability and polyester yield, so the polymerization of the next batch is usually started with the remaining polyester remaining. Ru. In this case, according to the findings of the present inventors, if the next polymerization is carried out in the presence of residual polyester, even though the amounts of metal compounds and phosphorus compounds are constant, that is, the same as the previous polymerization, Since the amount and particle size of precipitated particles in the remaining polyester, which are considered to influence the generation and growth of nuclei of precipitated particles, are not necessarily constant, stable precipitated particles cannot be obtained. The present inventors have conducted intensive studies to eliminate such drawbacks and produce polyester with excellent slipperiness and transparency industrially advantageously by a batch method. If a specific amount of two types of phosphorus compounds consisting of a trialkyl phosphate and a trialkyl phosphite are added to the total amount of a lithium compound and a calcium compound, a polyester containing specific precipitated particles can be produced in an extremely stable manner. This is what we discovered and arrived at the present invention. That is, the gist of the present invention is that the main component is ethylene terephthalate units, which are precipitated in the reaction system.
In a method for producing polyester containing fine particles containing lithium, calcium, and phosphorus elements in a polycondensation tank by a batch method after transesterification or esterification reaction, polymerization is performed with the polyester from the previous batch remaining in the polymerization tank. Before the start of the condensation reaction, a trialkyl phosphide is added to the transesterification or esterification reaction product containing a lithium compound and a calcium compound so that the total amount of the phosphorus compound is 1 to 2 times equivalent to the total amount of the lithium compound and calcium compound. The present invention relates to a method for producing polyester, which comprises adding an ester and a trialkyl phosphite. The present invention will be explained in more detail below. The polyester containing ethylene terephthalate units as a main component of the present invention is obtained from a dicarboxylic acid whose main component is terephthalic acid or its lower alkyl ester and a glycol whose main component is ethylene glycol, and a part of the dicarboxylic acid is acid components, such as dicarboxylic or oxycarboxylic acids other than terephthalic acid, such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, p-hydroxyethoxybenzoic acid, adipic acid, sebacic acid and ester-forming derivatives thereof You can also replace it with The glycol component of the polyester raw material is mainly ethylene glycol, but a portion thereof may be replaced with other glycol components such as trimethylene glycol, tetramethylene glycol, hexamethylene glycol, etc. In any case, the polyester containing ethylene terephthalate as a main component as used in the present invention refers to a polyester in which 80 mol% or more of the polyester is, for example, ethylene terephthalate units. Note that the polyester of the present invention may contain various modifiers such as flame retardants, anti-coloring agents, antistatic agents, heat resistant agents, and weathering agents within the range that satisfies the requirements of the present invention. Next, in the present invention, a specific amount of a lithium compound and a calcium compound must be added before adding a phosphorus compound, and for example, the following method can be adopted. A transesterification reaction is carried out using a lithium compound and a calcium compound. A transesterification reaction is carried out using either a lithium compound or a calcium compound, and the calcium compound or lithium compound is added before adding the phosphorus compound. The lithium compound used in this case may be one that is soluble in ethylene glycol, such as salts of aliphatic carboxylic acids such as acetic acid, propionic acid, butyric acid, salts of aromatic carboxylic acids such as benzoic acid and p-methylbenzoic acid, Furthermore, ethylene glycol
Mention may be made of lithium glycolates such as propylene glycol. Among these, lithium aliphatic carboxylates, particularly lithium acetate, are preferred. The amount used is preferably 0.03 to 0.3 mol%, particularly 0.05 to 0.2 mol%, based on the dicarboxylic acid component. There are no particular restrictions on the calcium compound as long as it dissolves in ethylene glycol, such as salts of aliphatic carboxylic acids such as acetic acid, propionic acid, and butyric acid, and aromatic carboxylic acids such as benzoic acid and p-methylbenzoic acid. and calcium glycolates such as ethylene glycol and propylene glycol. Among these, calcium aliphatic carboxylates, particularly calcium acetate, are preferably used. In addition, the amount of the calcium compound is 0.05 to 0.3 relative to the aromatic carboxylic acid component.
Mol %, especially 0.08 to 0.15 mol %, is preferably used. In any case, in the present invention, a specific amount of lithium compound and calcium compound must be contained before adding the phosphorus compound. The present inventors investigated the effects of various phosphorus compounds on systems in which these lithium compounds and calcium compounds coexist, and as a result, it was completely unexpected that one particular phosphorus compound was selected from among many phosphorus compounds. It was discovered that when different types of phosphorus compounds, namely trialkyl phosphates and trialkyl phosphites, were used in combination, it was possible to obtain a polymer containing a certain amount of precipitated particles with good reproducibility even when repeated batch polymerizations were carried out. I found it. Examples of the trialkyl phosphate used in the present invention include trimethyl phosphate,
Examples include triethyl phosphate and tributyl phosphate. Further, as the trialkyl phosphite, trimethyl phosphite, triethyl phosphite, tributyl phosphite, etc. are preferably used. In the present invention, the total amount of these two types of phosphorus compounds must be 1 to 2 times equivalent to the total amount of the lithium compound and the calcium compound. If the phosphorus compound is used in an amount less than the equivalent amount to the lithium compound and calcium compound, the lithium or calcium salt of the polyester oligomer remains, and this salt is not compatible with the polyester, so it is not mixed around the particles during stretching. Many voids occur in the film, impairing transparency. Further, the obtained polymer has a strong yellowish tinge, and when made into a film, the color tone is significantly inferior. On the other hand, when the phosphorus compound is used in an amount exceeding 2 times the equivalent, the polymerization rate during polyester production becomes slow, which is extremely disadvantageous industrially. Here, the equivalent ratio of the phosphorus compound to the total amount of the lithium compound and the calcium compound is expressed by the following formula: P/Ca+1/2Li (wherein, P, Ca, and Li are each of the phosphorus compound, calcium compound, and lithium compound, respectively). (indicates the number of moles of the element). The most important feature of the present invention is that a combination of trialkyl phosphate and trialkyl phosphate is used as the phosphorus compound. Trialkyl phosphate is the most preferred phosphorus compound for use in the present invention because it yields a large amount of precipitated particles, has a uniform particle size, and has high solubility in ethylene glycol and is easy to use. However, it has become clear that when polymerization is repeatedly carried out in a batch method using only the trialkyl phosphate, the amount and particle size of the precipitated particles often fluctuate. However, the present inventors have discovered that if the same reaction is carried out in the coexistence of a trialkyl phosphite, uniform precipitated particles can be obtained with good reproducibility. Although the reason for this phenomenon is not clear, it is probably because a trivalent phosphorus compound is incorporated into the precipitated particles, thereby inactivating the particles. Therefore, even if a new polymerization reaction is carried out in the presence of the residual polymer from the previous batch containing the particles, it is considered that there will be little effect. Even if the same trivalent phosphorus compound is used, if an acidic phosphorus compound such as phosphorous acid or its partially esterified phosphorus compound is used, some of the lithium compounds and calcium compounds will immediately react with these phosphorus compounds. Extremely small particles may be partially formed or coarse particles may be formed.
It is not preferred as a phosphorus compound for use in the present invention because it deteriorates the physical properties of the resulting film. In addition, in the present invention, the trialkyl phosphite is 0.01 to 0.5 to the trialkyl phosphate.
It is best to use double the molar ratio. This value is 0.01
If the value is less than 0.5, the stabilizing effect will be insufficient, and if this value exceeds 0.5, the particle size of the particles obtained will be non-uniform, and if an antimony compound is used as a polymerization catalyst, the polymer will tend to darken. . The timing of adding the trialkyl phosphate is not particularly limited, but it is preferably at the same time as the trialkyl phosphate or after the trialkyl phosphate. These phosphorus compounds used in the present invention are usually 2 to 30
It is added as a w/w % strength ethylene glycol solution. Of course, two or more phosphorus compounds may be used as the trialkyl phosphate or the trialkyl phosphite. As detailed above, when producing polyester by the batch method, if a specific amount of trialkyl phosphate and trialkyl phosphite are added to a system containing a lithium compound and a calcium compound and the polymerization reaction is subsequently carried out, it is possible to Regardless of slight variations in the conditions of the transesterification, such as the final stages of transesterification, especially the average degree of polymerization of the reaction product, the concentration of the phosphorus compound, the addition rate, the temperature and pressure during the polymerization reaction, the amount of polymerization catalyst, and the amount of residual polymer, etc. We have discovered a revolutionary effect in that stable results can be obtained. In the present invention, ordinary reaction conditions can be used for the transesterification reaction and the polycondensation reaction. The particles precipitated in the polymer obtained by the present invention contain 1% by weight or more of lithium, calcium, and phosphorus elements each, and the film obtained using the polyester has excellent slip properties, so it can be used for magnetic tables. It can be used for many purposes including. Furthermore, since there is little decrease in transparency when made into a film, it is suitably used in fields where the relationship between slipperiness and transparency is important, such as plate making, transfer marks, gold and silver thread, and microfilm. In either case, a polyester film having a uniform and fine surface structure free of coarse particles can be obtained with good reproducibility, and therefore has great industrial value. The present invention will be explained in more detail below based on Examples. In the Examples and Comparative Examples, "parts" indicate "parts by weight." The measurement method used is shown below. 1 Solution haze Add 2.7 g of polyester to 20 ml of a 4/6 (weight ratio) mixed solution of tetrachloroethane/phenol, and add approx.
After heating and melting at 110°C for 1 hour, the solution was cooled, and a portion of the solution was placed in a 10 mm thick quartz glass cell, and measured at a wavelength of 550 nm using an integrating sphere hazemeter (SR type, manufactured by Nippon Seimitsu Kogaku Co., Ltd.). Measure. Generally, the larger the particle size of the precipitated particles and the greater the amount of precipitated particles, the higher this value becomes. 2 Measurement of amount of precipitated particles Add o-chlorophenol to 100g of polyester
1.0 and heated at 120°C for 3 hours, centrifuged at 30,000 rpm for 40 minutes using a Beckman ultracentrifuge L3-50, and the resulting particles were vacuum dried at 100°C. When the particles are measured using a scanning differential calorimeter, if a melting peak corresponding to the polymer is observed, o-chlorophenol is added to the particles, and after heating and cooling, centrifugation is performed again. When the melting peak is no longer observed, the particles are defined as precipitated particles. Normally, two centrifugation operations are sufficient. 3 Measurement of the amounts of lithium, calcium, and phosphorus elements in precipitated particles Elemental phosphorus: Add sulfuric acid to the sample of precipitated particles separated from the polymer by the method described above, dissolve in hydrochloric acid solution after wet ashing, and quantify by atomic absorption method. Calcium element: After incinerating the precipitated particle sample, dissolve it in a hydrochloric acid solution and quantify by atomic absorption method. Elemental phosphorus: After wet-ashing the precipitated particle sample in the presence of sulfuric acid and perchloric acid, color was developed with ammonium molybdate in an acidic solution of sulfuric acid.
Measure the absorbance at 845 nm and quantify using a calibration curve prepared in advance. 4 Measurement of Precipitated Particle Size The average particle size was observed using a microscope after melting the polymer between prepared slides. Because particles are difficult to observe, we recommend using large (1-2μ), medium (about 1μ), and small (0.3~2μ) particles.
1μ) and displayed in three ranks. 5 Friction coefficient This is an improved method based on the method of ASTM D 1894-63 so that it can be measured using a tape-shaped sample.Measurements are performed in an atmosphere with a temperature of 21 ± 2 °C and a humidity of 65 ± 5%, and the measurement conditions are tension speed 40
mm/min, and the chart speed was 120 mm/min, and the sample size used was 15 mm in width and 150 mm in length. The slipperiness was indicated by the magnitude of the friction coefficient. 6 Film Haze The transparency of the film was measured according to the method of ASTM D 1003-61 using a Nippon Denshoku turbidimeter model NDH-2A. Example 1 (Manufacture of polyester) 100 parts of dimethyl terephthalate, 75 parts of ethylene glycol, 0.19 parts of lithium acetate dihydrate, and 0.08 parts of calcium acetate hydrate were placed in a transesterification reactor, heated to raise the temperature, and methanol was distilled off. A transesterification reaction was carried out. The reaction initiation temperature was 150°C, and it took 4 hours from the start of the reaction to reach 227°C to substantially complete the transesterification reaction. Next, this transesterification product was transferred to a polycondensation tank, and then 0.30 part of triethyl phosphate was added thereto, and after 5 minutes, 0.03 part of triethyl phosphite was added thereto. In this case, the total amount of phosphorus compounds relative to the total amount of metal compounds is 1.3 times equivalent. After another 10 minutes, antimony trioxide was added as a polycondensation catalyst.
After adding 0.04 part, polymerization was carried out according to a conventional method. That is, 100 minutes after the addition of antimony trioxide, the temperature in the system was brought to 280° C. and the pressure was brought to 15 mmHg, and thereafter the pressure was gradually reduced until it finally reached 1 mmHg or less.
After 4 hours, the pressure inside the system was returned to normal and the polymer was discharged. The intrinsic viscosity of the polymer at this time was 0.67, and due to its high viscosity, 6% of the polymer produced in the second reaction remained in the polycondensation tank. Next, a second polymerization was carried out. That is, a polymer was obtained by carrying out the same operations as the first polymerization, except that the second polymerization was carried out in the presence of 6% of the remaining polymer from the first polymerization. This polymerization reaction was repeated four times in total, leaving 3-7% of the polymer remaining in each batch. (Precipitated particles in polyester) The solution haze of the polyester obtained and the average particle diameter and particle amount of the precipitated particles in the polyester were measured and the results are shown in Table 1, but there was no substantial change after the second measurement. Nakatsuta. Next, as a representative example, the amounts of lithium, calcium, and phosphorus elements contained in the precipitated particles in the polyester polymerized for the third time were measured, and they were 2.0, 2.9, and 6.8% by weight, respectively, based on the precipitated particles. (Manufacture of polyester film) The obtained polymer was extruded into a sheet form from an extruder at 290°C, rapidly cooled to form an amorphous sheet, and then
A film having a thickness of 12 μm was obtained by stretching and heat treating the film at 95° C. by 3.6 times in both the longitudinal and transverse directions. The results of measuring the coefficient of friction and film haze of the obtained film are shown in Table 1, and there was virtually no change after the second test. Comparative Example 1 Polymerization was repeated a total of 4 times in the same manner as in Example 1, except that triethyl phosphate was not added in Example 1 and only triethyl phosphate was added in an equivalent amount of 1.3 times the total amount of metal compounds. Ta. Table 1 shows the solution haze, average particle diameter, and amount of precipitated particles of the polyester obtained at this time.
Further, a biaxially stretched polyester film was obtained from the polyester in the same manner as in Example 1, and the measurement results of the friction coefficient and film haze of this film are shown in Table 1. In this case, the physical properties of the polymer change due to uncontrollable differences in operating conditions between batches. In addition, the slipperiness and transparency of the films obtained from the polyester differed from batch to batch, and the average particle size of the precipitated particles also varied from batch to batch. That is, the precipitated particles of a film obtained from a polyester having a high solution haze are larger, and the surface of the film is therefore roughened, making it impossible to obtain a film having certain properties. Comparative Example 2 A polyester was obtained in the same manner as in Example 1, except that instead of the two types of phosphorus compounds in Example 1, only triethyl phosphite was added in an equivalent amount of 1.3 times the total amount of metal compounds. The polymer obtained at this time had an extremely strong black color and was difficult to put to practical use. That is, when the L value was measured using a color difference meter (TC-5D type) manufactured by Tokyo Denshoku, it was 42.8. On the other hand, the lightness of the first polymer of Example 1 was 47.1, which was high. This is thought to be due to the fact that the antimony compound is significantly reduced when only the trivalent phosphorus compound is used, and metallic antimony is precipitated. Also, the obtained particles are average
Large particles of about 2μ were observed, and many irregular particles of about 0.5μ and 3μ were also observed. Next, polymerization was carried out repeatedly in the same manner as in Example 1. The results are shown in Table 1. In addition to the large variation between batches, the product had a strong black color and was of little industrial value. 【table】

Claims (1)

[Scope of Claims] 1 Polyester containing ethylene terephthalate units as a main component and containing fine particles containing lithium, calcium, and phosphorus elements precipitated in a reaction system is polycondensed by a batch method after transesterification or esterification reaction. In the method of manufacturing in a tank, the total amount of phosphorus compounds is added to the transesterification or esterification reaction product containing a lithium compound and a calcium compound before the start of the polycondensation reaction with the polyester of the previous batch remaining in the polymerization tank. A method for producing polyester, which comprises adding trialkyl phosphate and trialkyl phosphite in an amount of 1 to 2 times the total amount of the lithium compound and the calcium compound. [The equivalent ratio of the phosphorus compound to the total amount of the lithium compound and the calcium compound is determined by the following formula: P/Ca+1/2Li (wherein, P, Ca, and Li are the respective amounts of each element in the phosphorus compound, calcium compound, and lithium compound. (indicates the number of moles). 2. The method for producing polyester according to claim 1, wherein the amount of the lithium compound added is 0.03 to 0.3 mol % based on the dicarboxylic acid component that is the polyester raw material. 3 The amount of calcium compound added is 0.05 to 0.3 with respect to the dicarboxylic acid component that is the raw material for polyester.
A method for producing polyester according to claim 1 or 2, which is mol%. 4 Claims 1 and 2, characterized in that the amount of trialkyl phosphite is 0.01 to 0.5 times the mole of trialkyl phosphate.
A method for producing polyester according to item 1 or 3.