JPS5937012B2 - Polyester manufacturing method - 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 industrial fields.

However, the properties required for polyester films differ depending on their uses, and for example, for so-called medium-thickness films of about 20 to 150 microns, it is particularly desirable to have excellent workability when handling the film and not impair transparency. It is well known that in order to improve workability, inorganic or organic fine particles may be present in polyester to improve slipperiness.

However, a decrease in transparency is unavoidable due to the difference in refractive index between the particles and polyester and the voids created around the particles during stretching. As a method for improving this antinomy phenomenon of slipperiness and transparency, many methods have been proposed, particularly in which an alkaline earth metal compound and a phosphorus compound are used in combination.

For example, Japanese Patent Publication No. 34-5144 describes a method of adjusting the frictional properties of a film by adding phosphorous acid or its esters to an alkaline earth metal compound.

Furthermore, although the purposes and effects of using phosphorus compounds are not necessarily the same, for example, US Patent No. 769.220 and British Patent No. 2,921,051 disclose phosphoric acid and Phosphorous acid and these anoVrere, F/L/:. It is stated that one or more phosphorus compounds selected from the group consisting of alkylphenyl, hydroxyalkyl ester, etc. can be used. Furthermore, special public service 1973-3319
Publication No. 8 describes an example of the combination of a trivalent phosphorus compound and a pentavalent phosphorus compound, and Japanese Patent Publication No. 48-41712 describes the use of a phosphorus acid and a phosphorus ester in combination. .

In this way, the entire surface of the alkaline earth metal compound or... Converting a portion of the metal into a phosphorus-containing compound, and the phosphorus compound is a trivalent or pentavalent phosphorus compound, or a phosphorus acid (including condensed phosphoric acid and acidic phosphoric acid ester).
Alternatively, it is well known that esters of phosphorus can be used.

However, according to the findings of the present inventors, not all of the combinations selected from all these phosphorus compounds uniquely satisfy the characteristics required for medium-weight films, and certain limited specific requirements are met. It became clear that a high-grade medium-count film could be obtained only when the conditions were met. In other words, in recent years, polyester films in general have been required to have higher film quality than ever before, and among them, medium-thickness films have not only improved the relationship between slipperiness and transparency, but also improved uniformity without coarse protrusions. As a result, materials with fine surface structures have become desirable.

The advantages of a film with such a surface structure are that, for example, fish eyes do not occur at all, and when metal is vapor-deposited, it is possible to achieve a uniform, even, high-quality finish.Furthermore, the uniformity of the film product is excellent, making it suitable for use in photography and plate making. For example, it can be effectively used for mold release. Specifically, a uniform and fine surface structure that does not contain coarse protrusions is one in which the number of third-order interferences measured by multiple interferometry that shows coarse protrusions is 2/1 or less, and which is measured by a stylus-type surface roughness measuring device. Number of surface protrusions larger than 0.05μ: 6/? It refers to something that is greater than or equal to ItWt.

On the other hand, from the viewpoint of manufacturing polymer ten, in addition to containing particles that have an excellent relationship between slipperiness and transparency and providing an excellent surface structure, the polymerization rate and color tone of the polymer should not be impaired;
It is particularly required that the content of diethylene glycol produced by side reactions be low. Naturally, the properties must also be achieved by a process suitable for implementation on an industrial scale. As a result of intensive research into the reaction between calcium compounds and various phosphorus compounds and the properties of films containing particles produced by the reaction, the present inventors found that trimethyl phosphate or triethyl phosphate and a certain trialkyl phosphite By adding these in a specific ratio and in a specific amount to the calcium compound, it is possible to industrially easily obtain a polymer that does not impair the polymerization rate or color tone and has a small amount of diethylene glycol by-product. The present inventors have discovered that it is possible to obtain a polyester film that has an excellent relationship between slipperiness and transparency, and has a uniform and fine surface structure free of coarse particles when formed using a polyester film, leading to the completion of the present invention.

That is, the present invention is a method for producing a polyester containing easily 80 moles or more of ethylene terephthalate units by using a lower alkyl ester of terephthalic acid as the main acid component and ethylene glycol as the main glycol component, and performing a transesterification reaction followed by a polycondensation reaction. In, 1
A soluble calcium compound is added to the reaction system at any time before the start of polycondensation, and 2. After the transesterification reaction is substantially completed, the following two types of phosphorus compounds are added at any time before the start of polycondensation. (1) Trimethyl phosphate and/or triethyl phosphate (11) P(0P)3 (R represents an alkyl group having 1 to 4 carbon atoms.

) at least one trialkyl phosphite represented by
The molar ratio of the phosphorus compound of (1) to the phosphorus compound of (11) is 1 to 20, and the total amount of the phosphorus compounds of (1) and (11) is 1 to 3 times the mole of the calcium compound. Add as follows.

A method for producing polyester is provided.

The present invention will be explained in more detail below.

In the present invention, the lower alkyl ester of terephthalic acid as the acid component of the polyester raw material mainly refers to the alkyl ester of terephthalic acid having 1 to 4 carbon atoms, especially dimethyl terephthalate, but some of it is also used as the acid component of other acid components,
For example, dicarboxylic or oxycarboxylic acids other than terephthalic acid, such as lower alkyl esters such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, P-hydroxyethoxybenzoic acid, adipic acid, and sebacic acid, may be substituted.

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 film-forming polyester as used in the present invention refers to a polyester in which 80 mol% or more is 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 a range that satisfies the requirements of the present invention.

In addition, the calcium compound soluble in the reaction system as used in the present invention includes, for example, calcium salts of aliphatic carboxylic acids such as acetic acid, propionic acid, and butyric acid, and calcium salts of aromatic carboxylic acids such as benzoic acid and P-methylbenzoic acid. , and furthermore, calcium compounds such as calcium glycolates such as ethylene glycol and propylene glycol, and inorganic calcium compounds such as calcium hydride.

These calcium compounds are used when one or more types of calcium compounds are used to carry out the transesterification reaction, or when the transesterification reaction is carried out with or without using these calcium compounds. In some cases, a calcium compound is added afterwards.

When transesterification is carried out using the above calcium compounds, these calcium compounds turn into calcium salts of polyester oligomers at the end of the reaction, but calcium compounds soluble in the reaction system in the present invention are There is no problem even if the form of the calcium compound changes in the reaction system as long as it is dissolved in the calcium compound. In the present invention, the amount of the calcium compound soluble in these reaction systems is preferably 0.05 to 0.3 mol % based on the total acid component of the polyester raw material. If the amount of the calcium compound added is too small, the precipitated particles of the present invention cannot be obtained, and if the amount added is too large, excess calcium tends to precipitate during the reaction, resulting in the formation of coarse particles. As a result of systematic research by the present inventors on the effects of various phosphorus compounds on calcium compounds, we found that: 1. When phosphorus compounds are used in an amount less than the equivalent mole of calcium compounds, the calcium salt of the polyester oligomer remains, and coarse particles are formed. To generate.

Further, when the phosphorus compound is used in an amount exceeding 3 times the mole, the polymerization rate during polyester production becomes slow, which is extremely disadvantageous industrially. 2 Even if the amount of the phosphorus compound is in the range of 1 to 3 times the mole of the calcium compound, the phosphorus compound may be phosphoric acid, phosphorous acid, pyrophosphoric acid, condensed phosphoric acid such as polyphosphoric acid, or acidic phosphoric acid ester. When a partially esterified phosphorus compound is used, coarse particles are not generated, but only extremely fine particles that hardly contribute to improving slipperiness are generated.

Furthermore, the amount of by-product diethyrezoglycol in the polymer increases compared to trisubstituted phosphorus compounds such as trialkyl esters. 3. In addition, when only a trivalent phosphorus compound is used, although the slipperiness is improved, there are many coarse particles, the polymer becomes dark, and the color tone is significantly inferior.

4. On the other hand, when only a Ξ-substituted phosphorus compound among pentavalent phosphorus compounds is used, although it is excellent in terms of transparency and color tone, almost no improvement in slipperiness is observed.

etc. were discovered.

As a result of detailed analysis of these results and further consideration,
A trivalent phosphorus compound and a pentavalent phosphorus compound are combined, and in this combination, a trialkyl phosphate, especially trimethyl phosphate or triethyl phosphate is used as the pentavalent phosphorus compound, and a trialkyl phosphite is used as the trivalent phosphorus compound. In particular, a combination in which a trialkyl phosphite having a carbon number of 1 to 4 is used and the molar ratio of a pentavalent phosphorus compound to a trivalent phosphorus compound is 1 to 20 is comprehensive for the various properties required for polymers and films. It was found that this is the most preferable combination. In the present invention, triethyl phosphate is particularly preferred among the pentavalent phosphorus compounds trimethyl phosphate and triethyl phosphate.

This is because trimethyl phosphate is extremely reactive with alcoholic hydroxyl groups and, in turn, with lucium compounds, and tends to give particles that are often too fine. In addition, pentavalent phosphoric acid esters having an alkyl group with 3 or more carbon atoms have a too slow reaction rate with alcoholic hydroxyl groups, so a considerable portion of them is distilled out of the system unreacted after being added to the reaction system. The residual rate in the polymer becomes small, the amount of haze particles tends to fluctuate, and the particle diameter also tends to fluctuate. Furthermore, aromatic substituted phosphorus compounds such as triphenyl phosphate are difficult to dissolve in ethylene glycol and are difficult to handle industrially. Only extremely fine particles, which have little effect on improving slipperiness, are produced. On the other hand, among the combinations of phosphorus compounds in the present invention, trialkyl phosphites are preferred as trivalent phosphorus compounds, but among them, trialkyl phosphites having 1 to 4 carbon atoms are preferred from the viewpoint of easy solubility in ethylene glycol. Particularly preferred.

When a phosphorous acid such as phosphorous acid is used as a trivalent phosphorus compound, the amount of by-product diethylene glycol increases,
Further, aromatic substituted phosphorus compounds such as triphenyl phosphite are difficult to dissolve in ethylene glycol, making them difficult to handle industrially.

Furthermore, in the present invention, the molar ratio of the pentavalent phosphorus compound to the trivalent phosphorus compound is 1 to 20), preferably 2 to 10.
must be within the range of In this case, when a plurality of phosphorus compounds are used as the trivalent phosphorus compound or the pentavalent phosphorus compound, the above molar ratio is based on the total amount of each phosphorus compound. When this value is less than 1, the blackness of the polymer becomes extremely strong;
When the size is larger, the amount of precipitated particles becomes extremely small, and neither of them satisfy the characteristics required for a medium-count film.

The total amount of trivalent and pentavalent phosphorus compounds used is determined by the relationship with the amount of calcium compound added, as described below.
If too large a quantity is added, it will have a negative effect on the polymer properties, so it is generally added from 0.05 to 0.05 to the total acid component of the polyester raw material.
It is selected between 0.9 mol%, preferably between 0.05 and 0.6 mol%.

In the present invention, it is also necessary to satisfy the condition that two types of phosphorus compounds that meet such specific requirements are added so that the total amount thereof is 1 to 3 times the mole of the added calcium compound. . If the total amount of the two types of phosphorus compounds to be added is less than equimolar to the calcium compound, sometimes the calcium salt of the polyester oligomer will remain and coarse particles will be formed, and if more than 3 times the molar amount is used, it will be difficult to produce polyester. The polymerization rate slows down when the phosphorus compound is added, which is extremely disadvantageous industrially.A particularly preferable range is a range exceeding 2 times the mole.The addition temperature of the phosphorus compound is 23
Preferably, the temperature is between 5 and 255°C. When the temperature is 220 to 230°C, at which the transesterification reaction is usually completed, it is difficult to obtain the desired uniform and fine particles even if other conditions are satisfied, and coarse particles are likely to be produced. Furthermore, if it is added at a temperature of 260° C. or higher, the resulting particles will contain a large number of acicular particles, and the relationship between slipperiness and transparency tends to be insufficient. Therefore, the addition temperature of these two types of phosphorus compounds is 235~
The temperature is preferably 255°C, particularly 240-250°C.
Note that the two types of phosphorus compounds and calcium compounds may be added in any order, but more preferable results can be obtained by adding the phosphorus compound to a system in which the calcium compound is present.

Further, the two types of phosphorus compounds may be added at the same time, or one of them may be added first. These phosphorus compounds are usually added as an ethylene glycol solution at a concentration of 2 to 30% by weight/volume. In this way, by adding triethyl phosphate or trimethyl phosphate and a specific trialkyl phosphite in a specific ratio and in a specific amount to the calcium compound, it is possible for the first time to maintain the polymerization rate and color tone without impairing the polymerization rate and to reduce the amount of diethylene glycol by-product. To obtain a polyester film which can be easily obtained industrially and which has an excellent relationship between slipperiness and transparency and has a uniform and fine surface structure free of coarse particles when formed using the polymer. be able to.

In order to obtain such a film, a known film forming method is used, for example, usually 50° C. after melt extrusion into a film at 270 to 295° C.
After being cooled and solidified at ~70°C to form an amorphous sheet, it is biaxially stretched vertically and horizontally or simultaneously biaxially to 160 to 240°C.
Methods such as heat treatment at ℃ (for example, Japanese Patent Publication No. 30-5639
method described) can be used.

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. Film Hezny AST
According to the method of MDlOO3-61, Nippon Denshoku Turbidity Meter N
Measurement was performed using DH-2A model.

Coefficient of friction: Based on the method of ASTM D1894-63, it has been improved so that it can be measured using a tape-shaped sample.The measurement is carried out in an atmosphere with a temperature of 21 ± 2 °C and a humidity of 65 ± 5%, and the measurement conditions are as follows: Tension speed 40mm/Min) Chart speed 120mm/Mm. The size of the sample used was 15 mm in width and 150 mm in length.

The slipperiness was indicated by the magnitude of the friction coefficient. Intrinsic viscosity: Polymer 1.0y was mixed with phenol/tetrachloroethane (50
/50 weight ratio) was dissolved in 100ml and measured at 30.0°C.

Polymer color tone: The color tone of the obtained polymer was measured using a Tokyo Denshoku color difference meter (TC-5D type).

Polymer color tone is expressed by the L value, and the larger the value, the higher the lightness.

Diethylene glycol content: Quantitate the polymer and Na
After hydrolysis by adding an OH/CH3OH solution and heating, the amounts of ethylene glycol and diethylene glycol were determined by gas chromatography.

The amount of diethylene glycol (mol%) relative to the sum of ethylene glycol and diethylene glycol was defined as the diethylene glycol content.

Quantification of coarse particles by multiple interference method: Measurement was carried out using a Nippon Kogaku Surfing System Finitus and an attached multiple interference device.

The number of third-order interferences per unit surface (m9) was measured and determined as the number of coarse particles.

This value is preferably 2/1 or less.

Number of surface protrusions: The number of surface protrusions of 0.05 μ or more per unit length (Mm) on the surface of the biaxially stretched film was measured using a stylus-type surface roughness measuring device manufactured by Taylor Hopson.

This value is preferably 6 pieces/Mm or more.

Example 1 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.09 parts of calcium acetate hydrate were placed in a reactor, heated to raise the temperature, and methanol was distilled off to perform a transesterification reaction. In short 2
The temperature was reached to 40°C, and the transesterification reaction was substantially completed.

At this point the reaction mixture was clear and the calcium compound was in solution. Next, a solution prepared by dissolving 0.175 parts of triethyl phosphate and 0.040 parts of trimethyl phosphite in 2.2 parts of ethylene glycol was added to the product after the transesterification reaction.

Next, 0.04 part of antimony trioxide was added as a polymerization catalyst, and then polymerization was carried out according to a conventional method.

That is, 100 minutes after adding antimony trioxide, the temperature in the system decreased to 2.
The temperature was raised to 80° C. and the pressure reached 15 mmHg, and thereafter the pressure was gradually reduced to 0.3 mmHg. After 4 hours, the pressure in the system was returned to normal and the polymer was discharged.

Next, the obtained polymer was extruded into a sheet form from an extruder at 290°C, rapidly cooled to form an amorphous sheet, stretched at 95°C to 3.5 times in the longitudinal and transverse directions, and heat-treated at 230°C for 3 seconds. A film with a thickness of 25 μm was obtained. Table 1 shows the measurement results of the intrinsic viscosity, color tone, and amount of by-product diethylene glycol of the polymer, as well as the slipperiness and transparency of the stretched film, the number of coarse particles on the film surface, and the number of surface protrusions.

Examples 2 to 5 and Comparative Examples 1 to 6 Products of two types of phosphorus compounds added in Example 1,
A polyester was obtained in the same manner as in Example 1, except that the molar ratio of both and the molar ratio of the sum of both to the calcium compound was changed, and a film with a thickness of 25 μm was obtained in the same manner as in Example 1 using the polyester.

Table 1 shows the measurement results for this polyester and film.

While the Examples satisfy all the properties, when the sum of the phosphorus compounds is less than the equivalent molar amount to the calcium compounds as in Comparative Example 1, the relationship between the slipperiness and transparency of the obtained film is irrelevant. However, the number of coarse particles was large, making it unsuitable for use as a medium-grid film.

Furthermore, Comparative Example 2 shows that when the sum of phosphorus compounds exceeds 3.0 times the mole of calcium compounds, the polymerization rate slows down and the amount of by-product diethylene glycol increases.

Comparative Examples 3 and 4 show the results when the proportion of triethyl phosphate is too low and when it is too high,
In the former case, the color tone of the polymer deteriorates significantly, and in the latter case, the number of surface protrusions decreases significantly and the slipperiness becomes extremely poor.

Comparative Example 5 uses phosphoric acid instead of triethyl phosphate, but the number of effective surface protrusions is small and the slipperiness is extremely poor.

Furthermore, the amount of by-product diethylene glycol also increases. Comparative Example 6 is a case in which phosphorous acid is used instead of trialkyl phosphite having 1 to 4 carbon atoms, but in this case, the color tone of the polymer deteriorates and the amount of by-product diethylene glycol increases.

Claims (1)

[Claims] 1. A polyester having 80 mol% or more of ethylene terephthalate units is produced by carrying out a transesterification reaction followed by a polycondensation reaction using a lower alkyl ester of terephthalic acid as the main acid component and ethylene glycol as the main glycol component. In the manufacturing method, (1) a soluble calcium compound is added to the reaction system at any time before the start of polycondensation, and (2) after the transesterification reaction is substantially completed, at any time before the start of the polycondensation reaction. At this point, the following two types of phosphorus compounds (i) trimethyl phosphate and/or triethyl phosphate (ii) P(OR)_3 (R is 1 carbon number
~4 alkyl group is shown. ) at least one trialkyl phosphite represented by
The molar ratio of the phosphorus compound (i) to the phosphorus compound (ii) is 1 to 20, and the total amount of the phosphorus compounds (i) and (ii) is 1 to 3 times the mole of the calcium compound. A method for producing polyester, characterized by adding the following: