JPH0375566B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a polyester film, and more particularly, to a method for producing a polyester film having improved surface condition and slipperiness. In general, polyester, especially polyethylene terephthalate, has excellent mechanical properties, heat resistance, weather resistance, electrical insulation, and chemical resistance, so it is used as textiles for clothing and industrial use, as well as magnetic tape films, photographic films, electric insulation films, and capacitor films. Widely used in film fields such as When polyester is used in the film field, it has to be passed through the molding processes of melt extrusion, stretching, and heat treatment, or in film molding, it has to be rolled up, cut, surface coated with magnetic layers, etc., and incorporated into electrical parts. In order to improve the workability of film products and the quality of final products such as slippage, we created a polyester composition containing fine particles, which gave the surface an appropriate level of roughness to give it smoothness. It is usually done. Polyester compositions containing such fine particles include polyesters obtained by adding and blending inert insoluble inorganic particles such as silicon oxide, titanium dioxide, calcium carbonate, talc, and clay, and catalyst components used during polyester synthesis. Polyesters obtained by precipitating part or all of the above as fine particles during the polymerization reaction process are known. However, such known fine particle-containing polyesters have the following problems, and especially when molded into a film, their slipperiness, surface condition, film formability, etc. are not satisfactory. That is, in the above-mentioned so-called external particle-containing polyester composition, it is difficult to make the additive particles fine, coarse particles are mixed due to agglomeration of particles, and the particle size is uneven, and the affinity between the particles and the polyester is There are drawbacks such as falling off due to insufficient film formation, tearing occurs during film formation, and when made into a film, coarse protrusions due to coarse particles are mixed, causing problems such as sticking eyes and dropouts, and electrical insulation These polyesters have many disadvantages, such as a decrease in properties, and furthermore, dispersants added to prevent particles from agglomerating often decrease the heat resistance and electrical insulation properties of these polyesters. On the other hand, polyester obtained by the so-called internal particle method described above tends to produce coarse particles, it is difficult to control the particle size of the precipitated particles, and the amount of precipitated particles varies greatly between polymerization batches. When molded, not only is it not possible to obtain satisfactory slipperiness, but there are also undesirable drawbacks such as the occurrence of fish eyes and dropouts, making it difficult to obtain satisfactory surface properties. Especially in recent years, the magnetic tape field of audio tapes, video tapes, and memory tapes has become smaller.
In order to achieve higher density, there is an increasing demand for making the film surface irregularities more uniform and fine. However, when the additive particles are made finer in the above method in order to make the film surface unevenness more uniform, the formation of coarse particles due to agglomeration of particles becomes noticeable, and in the above method,
For example, JP-A-50-101494, JP-A-54-
Catalyst components as described in Publication No. 90294, etc.
In the past, it has been possible to make internal particles finer depending on the amount of addition, but this method is sufficient in the magnetic tape field mentioned earlier, especially in the so-called "high-grade type" used for high magnetic density video tapes, metal tapes, and vapor-deposited tapes. A film having fine and uniform surface irregularities could not be obtained. In view of the above-mentioned circumstances, the inventors of the present invention have made extensive studies to obtain a polyester film in which fine particles are uniformly present and have fine and uniform surface irregularities.
The present invention was achieved by discovering that a polyester synthesized by adding a specific metal-containing phosphorus compound and an alkaline earth metal compound to a polyester reaction system without reacting them in advance can be melt-formed into a film. That is, the present invention comprises a first step reaction in which an ester-forming derivative of a dicarboxylic acid, mainly terephthalic acid, and at least one glycol are reacted to produce a glycol ester of a dicarboxylic acid and/or a low polymer thereof; In producing a film made of polyester synthesized by the second stage reaction of polycondensing the reaction product,
At any stage until the synthesis of the polyester is completed, (a) the following general formula (In the formula, R ¹ and R ² are hydrogen atoms or monovalent organic groups, and R ¹ and R ² may be the same or different,
M is an alkali metal or an alkaline earth metal, and m is 1 when M is an alkali metal and 1/2 when M is an alkaline earth metal. ) and (b) an alkaline earth metal compound other than the metallized phosphorus compound in an amount of 0.5 to 1.2 times the mole of the metallized phosphorus compound. This method of producing a polyester film is characterized in that the polyester is added without reacting, the synthesis of the polyester is then completed, and the obtained polyester is melt-formed into a film. The polyester in the present invention is a polyester having terephthalic acid as the main acid component and at least one type of glycol, preferably at least one alkylene glycol selected from ethylene glycol, trimethylene glycol, and tetramethylene glycol as the main glycol component. The main target is It may also be a polyester in which a part of the terephthalic acid component is replaced with another difunctional carboxylic acid component, and/or a part of the glycol component is replaced with the above-mentioned glycol other than the main component or other diol component. It may also be polyester. Examples of difunctional carboxylic acids other than terephthalic acid used here include isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid,
Diphenoxyethanedicarboxylic acid, β-hydroxyethoxybenzoic acid, p-oxybenzoic acid, 5-
Examples include aromatic, aliphatic, and alicyclic difunctional carboxylic acids such as sodium sulfoisophthalic acid, adipic acid, sebacic acid, and 1,4-cyclohexanedicarboxylic acid. In addition, examples of diol compounds other than the above-mentioned glycols include cyclohexane-1,4-dimethanol, neopentyl glycol, bisphenol A, and bisphenol S.
Examples include aliphatic, alicyclic, and aromatic diol compounds such as, and polyoxyalkylene glycols. Such polyesters may be synthesized by any method. For example, in the case of polyethylene terephthalate, the first step is usually a transesterification reaction between a lower alkyl ester of terephthalic acid such as dimethyl terephthalate and ethylene glycol to produce a glycol ester of terephthalic acid and/or a low polymer thereof. reaction and
It is produced by the second stage reaction in which the reaction product of the first stage is heated under reduced pressure and subjected to a polycondensation reaction until a desired degree of polymerization is achieved. The metal-containing phosphorus compound used in the present invention has the following general formula: It is a phosphorus compound represented by the formula, where R ¹ and
R ² is a hydrogen atom or a monovalent organic group. This monovalent organic group is specifically an alkyl group, an aryl group, an aralkyl group, or [-(CH ₂ )O] _k R ³ (however,
R ³ is preferably a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group; k is an integer of 1 or more; and R ¹ and R ² may be the same or different. M is an alkali metal or alkaline earth metal, including Li, Na, K, Mg, Ca, Sr, Ba
are preferred, and Ca, Sr, and Ba are particularly preferred. m is 1 when M is an alkali metal, and 1/2 when M is an alkaline earth metal. R ¹ and/or in place of the above metal-containing phosphorus compound
If you use a phosphorus compound in which R ² is replaced with a metal (especially an alkali metal or alkaline earth metal),
The obtained polyester film has large surface irregularities, and phosphorus compounds tend to aggregate, resulting in poor quality. The above metal-containing phosphorus compounds are usually produced by heating orthophosphoric acid or the corresponding orthophosphoric acid ester (mono, di, or tri) and a predetermined amount of the corresponding metal compound in the presence of a solvent. It is easily obtained. In this case, it is most preferable to use glycol, which is used as a raw material for the target polyester, as the solvent. The alkaline earth metal compound to be used in combination with the metal-containing phosphorus compound is not particularly limited as long as it reacts with the metal-containing phosphorus compound to form a salt insoluble in polyester, and alkaline earth metal acetates, alkaline earth metal acetates, Organic carboxylates such as oxalates, benzoates, phthalates, stearates, inorganic salts such as borates, sulfates, silicates, carbonates, bicarbonates, chlorides etc. Examples include halides, chelate compounds such as ethylenediaminetetraacetic acid complex, hydroxides, oxides, alcoholates such as methylates, ethylates, and glycolates, and phenolates. organic carboxylates, halides, especially soluble in ethylene glycol;
Chelate compounds and alcoholates are preferred, and organic carboxylates are particularly preferred. The above alkaline earth metal compounds may be used alone or in combination of two or more. When adding the above-mentioned metal-containing phosphorus compound and alkaline earth metal compound, in order to give the final polyester film fine irregularities and slipperiness, it is necessary to It is necessary to specify the ratio of the amount of metal compound used within the range of 0.5 to 1.2 times the mole. If the amount of the alkaline earth metal compound added is less than 0.5 times the amount of the metal-containing phosphorus compound added, the number of protrusions in the obtained polyester film will not be sufficient.
In addition, the polycondensation rate decreases, making it difficult to obtain a polyester with a high degree of polymerization, and the softening point of the resulting polyester decreases significantly. On the other hand, if the alkaline earth metal compound is used in an amount exceeding 1.2 times the mole of the metal-containing phosphorus compound, the particles will not become fine but coarse particles will be formed, resulting in coarse surface irregularities of the film. Therefore, the amount of alkaline earth metal added to the metal-containing phosphorus compound should be in the range of 0.5 to 1.2 times the mole, and particularly preferably 0.5 to 1.0 times the mole. On the other hand, if the amount of the metal-containing phosphorus compound used in the present invention is too small, the resulting polyester film will have a small number of surface protrusions, resulting in a decrease in slipperiness; if it is too large, there will be many surface protrusions, resulting in surface irregularities. tends to become substantially rough. Therefore, the amount of the metal-containing phosphorus compound added is preferably in the range of 0.02 to 3 mol%, particularly preferably 0.05 to 1 mol%, based on the acid component constituting the polyester. It is necessary to add the metal-containing phosphorus compound and the alkaline earth metal compound to the polyester reaction system without reacting them in advance. By doing so, the insoluble particles can be produced in the polyester in the form of uniform ultrafine particles.
If the above-mentioned metal-containing phosphorus compound and alkaline earth metal compound are reacted externally in advance to form insoluble particles and then added to the polyester reaction system, the dispersibility of the insoluble particles in the polyester becomes poor and coarse agglomerated particles are formed. is contained, so that the effect of improving the surface properties of the polyester film finally obtained is no longer recognized, which is not preferable. The metal-containing phosphorus compound and the alkaline earth metal compound can be added in any order at any stage until the synthesis of the polyester is completed. However, if only the metal-containing phosphorus compound is added before the first stage reaction is completed, the completion of the first stage reaction may be inhibited, and if only the alkaline earth metal compound is added to the first stage reaction. If it is added before the end of the reaction, the transesterification reaction may proceed more quickly and cause bumping, so in this case it is preferably about 20% by weight or less. It is preferable that at least 80% by weight of the alkaline earth metal compound and the total amount of the metal-containing phosphorus compound be added after the first stage reaction of polyester synthesis is substantially completed. In addition, if the metal-containing phosphorus compound and the alkaline earth metal compound are added at a stage when the second stage reaction has progressed too much, particles tend to aggregate and coarsen, resulting in poor surface properties of the final polyester film. Since this tends to be sufficient, it is preferable that the reaction mixture in the second stage reaction reach an intrinsic viscosity of 0.3. The above-mentioned metal-containing phosphorus compound and alkaline earth metal compound may be added all at once, added in two or more divided portions, or added continuously. In the present invention, any catalyst can be used for the first stage reaction, but some of the alkaline earth metal compounds mentioned above have the ability to catalyze the first stage reaction, that is, the transesterification reaction. When a compound is used, there is no need to use a separate catalyst, and the alkaline earth metal compound can be added before or during the first stage reaction to serve as a catalyst as well. Since bumping may occur as described above, the amount used is preferably kept to less than 20% by weight of the total amount of the alkaline earth metal compound added. In addition, in the conventional internal particle method, it was necessary to independently add one or more types of phosphorus compounds selected from phosphoric acid, phosphorous acid, and ester compounds thereof, but in the present invention, it is not necessary to add these phosphorus compounds. do not have. When these phosphorus compounds are added, the number of protrusions in the obtained polyester film is not sufficient, and in addition, the polycondensation reaction rate decreases, making it difficult to obtain polyester with a high degree of polymerization, and the softening point of the polyester decreases significantly. This is not desirable. As explained above, the metal-containing phosphorus compound and the alkaline earth metal compound in a specific ratio to the phosphorus compound are added to the polyester reaction system without reacting in advance, and then the synthesis of the polyester is completed. As a result, it is possible to obtain a polyester film which has a high degree of polymerization, a high softening point, good passability through the film forming process, and has excellent film surface properties. In order to melt and form a film from the polyester obtained in this way, it is not necessary to employ any special method, and an ordinary method for melting and forming a polyester film can be used. The polyester film obtained according to the present invention has uniform and fine surface characteristics free of coarse particles and is therefore preferably used for magnetic tapes, particularly video tapes. Hereinafter, it will be explained in more detail based on examples. Note that "parts" in the Examples and Comparative Examples indicate "parts by weight." The measurement method used is shown below. a Observation of coarse particles 10 mg of polymer was sandwiched between two cover glasses, melt-pressed at 280°C, rapidly cooled, and then observed under a microscope. Observation Results Particles with a size of 5μ or more were considered coarse particles and were judged as follows. Grade 1: 0 to 10 particles/mg of coarse particles exceeding 5μ
exist. Grade 2: 11-20 particles/mg of coarse particles exceeding 5μ
exist. Grade 3: Coarse particles exceeding 5 μ are present at 30 particles/mg or more. Note that only the first grade is used for practical use. b Intrinsic viscosity of polymer Measured at 25°C using o-chlorophenol as a solvent. c Polymer Softening Point A polymer chip was placed in a heating bath and heated at a rate of 6°C/5 minutes, and the temperature at which the tip penetrated into the chip by 5 mm or more under load was measured. d Film friction coefficient according to slip tester ASTM-O-1894
Measured according to the law. The coefficient of static friction was used as a measure of slipperiness. e Roughness of film surface irregularities CLA [Center line average (Center
Line Average/center line average roughness) According to JISB0601, using a stylus type surface roughness meter (SURFCOM 3B) manufactured by Tokyo Seimitsu Co., Ltd., the needle radius is 2 μm,
Place the chart under the condition of a load of 0.07 g, and extract a portion of measurement length L from the film surface roughness curve in the direction of its center line.The center line of this sampled portion is the X axis, and the direction of vertical magnification is the Y axis. When the roughness curve is expressed as Y=(x), the value given by the following equation is expressed in μm. R _CLA = 1/L∫ ^L _p ｜(x)｜dx In this measurement, the reference length was 0.25 mm, and 8 pieces were measured.
It is expressed as the average value of 5 values excluding 3 from the largest value. R _CLA is 0.01 for high magnetic density applications in videotape.
The following will be put to practical use. f Number of protrusions on film surface The number of protrusions of 0.1 or more in 1 mm ² is counted using a surface roughness meter (stylus type) and expressed in units of protrusions/mm ² . Example 1 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol, and 0.06 parts of calcium acetate monohydrate (0.066 mol% relative to dimethyl terephthalate) were charged into a transesterification tank, and heated from 140°C over 4 hours under a nitrogen gas atmosphere. The transesterification reaction was carried out while raising the temperature to 230°C and distilling the generated methanol out of the system. Subsequently, 0.51 part of trimethyl phosphate (relative to dimethyl terephthalate) was added to the resulting reaction product.
0.70 mol%) and 0.32 parts of calcium acetate monohydrate (1/2 mole relative to trimethyl phosphate) at 8.5%
At room temperature, 9.31 parts of a clear solution of phosphoric acid diester calcium salt prepared by reacting 1 part of ethylene glycol at a temperature of 120°C for 60 minutes under total reflux was added.
9.88 parts of a mixed transparent solution of diester calcium phosphate and calcium acetate obtained by dissolving 0.57 parts of calcium acetate monohydrate (0.9 times the mole relative to trimethyl phosphate) were added, and then 0.04 parts of antimony trioxide was added. was added and transferred to a polymerization can. Next, the pressure was reduced from 760 mmHg to 1 mmHg over 1 hour.
At the same time, the temperature was raised from 230°C to 285°C over 1 hour and 30 minutes. Polymerize for an additional 3 hours at a polymerization temperature of 285℃ under a reduced pressure of 1 mmHg or less, for a total of 4 hours and 30 minutes, to reduce the intrinsic viscosity.
A polymer with a softening point of 0.641 and a softening point of 259°C was obtained. After the reaction was completed, the polymer was made into chips according to a conventional method. This chip was melt-extruded at 290°C in a conventional manner to form a sheet, stretched with a biaxial stretching machine at a longitudinal stretch ratio of 3.3 times and a transverse stretch ratio of 3.5 times, and then heat-treated at 210°C to obtain a film with a thickness of 15 μm. . Work stability during film formation was good, and there were no problems such as film breakage. The measurement results of the obtained film are shown in Table 1, and the surface roughness and number of protrusions were fine and dense, and the number of coarse particles was small, making it sufficiently satisfactory as a magnetic tape for videotape. Ta. Examples 2 to 5, Comparative Examples 1 to 2 In the polymer synthesis reaction of Example 1, except for changing the amounts of the additives phosphoric acid diester calcium salt and calcium acetate monohydrate to the amounts shown in Table 1. was carried out in the same manner as in Example 1. The measurement results of the obtained films are also shown in Table 1, and Examples 2 to 2 which satisfy the scope of the claims of this patent
No. 5 had excellent surface properties, and Examples 2 to 3 in particular had excellent balance of each property value and were suitable for magnetic tapes for video tapes. On the other hand, in Comparative Example 1, there were many coarse particles, making it undesirable as a magnetic tape. In Comparative Example 2, the degree of polymerization did not increase sufficiently during polymerization, and a polymer that could be formed into a film could not be obtained.

[Table] Example 6 In the polymer synthesis reaction of Example 1, 0.5 part of trimethyl phosphate (0.693 mol% based on dimethyl terephthalate) and 0.49 part of acetic acid were used instead of the additive calcium diester phosphate. Sodium trihydrate (equal mole to trimethyl phosphate)
Example 1 was carried out in the same manner as in Example 1, except that phosphoric acid diester sodium salt was used. The measurement results of the obtained film are shown in Table 2, and it showed good characteristics similar to Example 1. Example 7 760 mmHg in the polymer synthesis reaction of Example 1
Time required to reduce pressure from to 1mmHg (1 hour)
The same procedure as in Example 1 was carried out except that the time period was shortened to 30 minutes. The obtained polymer had an intrinsic viscosity of 0.641 and a softening point of 260.1°C. The measurement results of the obtained film are shown in Table 2, and as in Example 1, it exhibited good surface properties and was suitable for use as a magnetic tape for videotape. Comparative Example 3 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol, and 0.06 parts of calcium acetate monohydrate (0.066 mol% relative to dimethyl terephthalate) were charged into a transesterification tank, and heated from 140°C over 4 hours under a nitrogen gas atmosphere. The transesterification reaction was carried out while raising the temperature to 230°C and distilling the generated methanol out of the system. Subsequently, calcium acetate was applied to the resulting reaction product.
1.07 parts of trimethyl phosphate and 0.5 parts of trimethyl phosphate were added thereto, followed by 0.04 parts of antimony trioxide, and the mixture was transferred to a polymerization pot. Thereafter, polymerization reaction and film formation were carried out in the same manner as in Example 1 to obtain a polyester film. As shown in Table 2, the particle dispersibility and surface properties were poor and undesirable. Comparative example 4 High-speed stirring disperser (stirring blade outer diameter 28 mm, outer cylinder ring inner diameter
29mm, using a laboratory mixer emulsion fire manufactured by Silverson Machine Co., Ltd. in the UK.
At a rotation speed of 5000 rpm, silicon oxide and ethylene glycol with an average temporary particle size of 30 mμ are mixed in a weight ratio of 5:95.
The mixture was dispersed for 60 minutes to obtain a slurry. This slurry was added as silicon oxide in an amount of 0.5% based on the resulting polyester instead of the mixed transparent solution of diester calcium phosphate and calcium acetate monohydrate that was added after the transesterification reaction in Example 1. The same procedure as in Example 1 was carried out except for the following. The results are shown in Table 2. There were many coarse particles and the surface properties of the film were also unfavorable.

[Table] Comparative Example 5 In the polymer synthesis reaction of Example 1, 0.5 parts of trimethyl phosphate (0.693 mol% based on dimethyl terephthalate) and 0.49 parts of acetic acid were used instead of the additive calcium diester phosphate. Sodium trihydrate (equal mole to trimethyl phosphate)
Example 1 was carried out in the same manner as in Example 1, except that phosphoric acid diester sodium salt reacted with phosphoric acid diester sodium salt and 0.66 parts of triethyl phosphate (0.9 mol % based on dimethyl terephthalate) were used. The properties of the obtained film are as follows. Amount of coarse particles [ke/mg]: 2 (grade 1) Surface roughness [μ]: 0.004 Number of protrusions [ke/ ^mm2 ]: 20 Coefficient of friction: 1.0 or more In this example, the degree of polymerization increases slowly and is not easily obtained. The film had a small number of protrusions and had insufficient slipperiness.

Claims (1)

[Claims] 1. A first step in which an ester-forming derivative of a dicarboxylic acid, mainly terephthalic acid, is reacted with at least one glycol to produce a glycol ester of a dicarboxylic acid and/or a low polymer thereof. In producing a film made of a polyester synthesized by the reaction and the second stage reaction of polycondensing the reaction product, at any stage until the synthesis of the polyester is completed, (a) the following general formula (In the formula, R ¹ and R ² are hydrogen atoms or monovalent organic groups, and R ¹ and R ² may be the same or different,
M is an alkali metal or an alkaline earth metal, and m is 1 when M is an alkali metal and 1/2 when M is an alkaline earth metal. ) and (b) an alkaline earth metal compound other than the metallized phosphorus compound in an amount of 0.5 to 1.2 times the mole of the metallized phosphorus compound. A method for producing a polyester film, which comprises adding the polyester without reacting it, then completing the synthesis of the polyester, and melting the obtained polyester into a film. 2. The method for producing a polyester film according to claim 1, wherein the amount of the metal-containing phosphorus compound added is 0.02 to 3 mol% based on the acid component constituting the polyester.