JPS6042255B2 - Method for manufacturing biaxially stretched polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a biaxially oriented polyester film containing polyethylene terephthalate as a main component and having excellent color tone, transparency, and surface smoothness.

Polyesters, especially polyesters mainly composed of polyethylene terephthalate, have a high softening point and good mechanical properties such as hardness, tensile strength, elastic modulus, and impact strength, and chemical properties such as oil resistance, alkali resistance, and acid resistance. Therefore, it is widely manufactured industrially as fiber or film.

When such polyester is used as a photographic film base for black and white, color, X-ray, microfilm, etc., it is essential that the film be transparent and not cloudy in order to obtain clear images. be.

For example, when adding a blue tint to an X-ray film, the polyester film itself is required to have a good color tone, especially since yellowing deteriorates the blue tint of the final product. However, even if polyester pellets with good color tone and excellent transparency are obtained, oxidative decomposition and thermal decomposition easily occur during melt film formation at high temperatures, producing colored substances, which usually give an undesirable color tone to the final product. . For example, polyethylene terephthalate is produced by esterifying or transesterifying terephthalic acid or its dimethyl ester with ethylene glycol to produce bis(2-hydroxyethyl).
It is produced by a first step reaction to obtain terephthalate or its low polymer, and a second step reaction in which this is polycondensed under high temperature and reduced pressure.

In both the first and second steps, by using an appropriate catalyst, the reaction can proceed smoothly even in large-scale equipment, but the residue of these catalysts can cause coloring or cloudiness in the final product. Become. Furthermore, in the third step of forming the film, that is, the step of melt extrusion at high temperature, the degree of polymerization decreases during high temperature melting, the amount of carboxy end groups increases, and the color tone changes due to the generation of aldehyde compounds, resulting in the final product. have a huge impact on In addition, the reasons for inhibiting the transparency of the film obtained from the polyester are: (1) an increase in internal haze due to foreign substances with different refractive indexes and voids generated around the foreign substances during stretching, and (2) an increase in surface haze due to the formation of irregularities on the film surface. There is one.

The present inventors have investigated the problems in obtaining a transparent polyester film with excellent surface smoothness, especially the coloring in the raw polyester melting process, the electrostatic casting process, and the process of forming the film through the biaxial stretching process. The present invention was developed through extensive research aimed at solving the problems of internal haze caused by catalyst residue and surface haze caused by unevenness on the film surface. The object of the present invention is to produce a polyester whose main repeating unit is ethylene terephthalate, by adding 1 glycol-soluble cobalt compound, 2 glycol A polyester composition obtained by adding a soluble magnesium compound, at least one manganese compound, and a 35-valent phosphorus compound in a range that satisfies the following general formulas 1, (■), and (2) is formed into a sheet shape and subjected to stretching heat. This can be achieved by a method for producing a biaxially stretched polyester film in which the surface roughness of the film obtained by fixation [Hma phantom] is 0.1μ or less. (The formula discharged CO is the amount of metallic cobalt, M
e represents the total amount of metallic magnesium and metallic manganese, respectively Ppm relative to the polyester CO+Me stellate, and P indicates the molar ratio.

) The most distinctive feature of the present invention is the use of a polyester constituting the film that contains a specific catalyst and phosphorus that satisfies the general formula described above.

The use of cobalt metal, manganese metal or magnesium metal as catalyst for obtaining polyethylene terephthalate is known from US Pat. No. 24,653m.

In addition, manganese salt and magnesium salt (Special public interest
No. 897, No. 33-5746, etc.), cobalt salt (Special Publication No. 33-5746), combination of cobalt salt and manganese salt (
Special Publication No. 31-4146, No. 32-679? , 36-
12797, etc.), and the combination of cobalt salt and magnesium salt (Japanese Patent Publication No. 33-5746, Japanese Patent Publication No. 34-4844, etc.) are also known. It is also known that phosphorus compounds are mainly added as stabilizers and color preventive agents for polyesters, especially polyethylene terephthalate; for example, British Patent No. 76922
吋, British Patent No. 588834, Special Publication No. 32-2398
It is known to use phosphoric acid and phosphoric acid alkyl esters.

However, none of these known methods can achieve the object of the present invention. That is, l manganese salt,
When a magnesium salt is used alone, the resulting polymer is colored yellow by adding an appropriate amount of catalyst, and the coloring is particularly noticeable when a high molecular weight polymer is produced in large quantities. There is also the problem that coloring increases during melt extrusion in the third step described above. The use of cobalt salts has the effect of suppressing coloration caused by manganese and magnesium salts, but especially when producing high molecular weight polymers in large quantities, the softening point decreases, heat resistance deteriorates, and the amount of aldehyde compounds generated increases. . Furthermore, as the amount of cobalt salt increases, the internal haze increases, which impairs transparency. The inventors of the present invention have conducted intensive studies on these interrelationships, and have found that 1-cobalt compounds, 2-manganese compounds, and at least one or more compounds selected from magnesium compounds are used in combination, and the amount of each added is controlled to a specific level. It has been found that by defining the range, the defects in hue and transparency after thermal history can be solved all at once.

In other words, by using a small amount of manganese or magnesium compound in combination with a cobalt compound, the dullness of the polymer can be significantly reduced or eliminated;
The effect is that the transesterification time is shortened and the heat resistance is improved.

This effect is remarkable when a pentavalent phosphorus compound is used in combination, and furthermore, it becomes possible to prevent the generation of an appropriate amount of the pentavalent coarse protrusions and increase in film surface haze. The polyester constituting the polyester film obtained in the present invention has 80 mol% or more of its repeating units consisting of ethylene terephthalate. The copolymerization components include isophthalic acid, p-β-oxyethoxybenzoic acid, diphenyl ether-4,4''-dicarboxylic acid, diphenoxyethane-4,4''-dicarboxylic acid, adipic acid, sebacic acid, - Dicarboxylic acid components such as sodium sulfoisophthalic acid or their alkyl ester derivatives; glycols such as propylene glycol, butanediol, neopentyl glycol, cyclohexanedimethanol, and the ethylene oxide adduct of bisphenol A; Examples of the cobalt compound added to the polyester reaction system include glycol-soluble cobalt such as cobalt chloride, cobalt acetate, cobalt benzoate, cobalt chromate, and cobalt acetylacetonate (■, ■), and the amount added is equal to the cobalt metal. 10-200 in converted amount
ppm (relative to polyester). Addition amount is 10ppm
If it is less than 200 ppm, the effect of improving the color tone of the polyester disappears, while if it exceeds 200 ppm, the transparency of the polyester decreases, and the amount of diethylene glycol generated increases, resulting in a decrease in heat resistance, which is not preferable. As magnesium compounds and manganese compounds, glycol-soluble compounds such as inorganic salts such as halides, nitrates, and sulfates, organic acid salts and oxides such as acetates, oxalates, and benzoates, and oxides can be used. Two or more types selected from the group may be used in combination.

The amount of the magnesium compound and manganese compound to be added is determined in relation to the cobalt compound used in combination, and the appropriate amount falls within the range of general formula (2) above.

In this case, generally speaking, the higher the amount added, the lower the softening point of the polymer will be suppressed, but if the total amount of magnesium and manganese compounds in terms of metal exceeds 1000 ppm (relative to polyester), the softening point will drop and the color tone will deteriorate, so use this method. Quantities are limited. If the amount is less than 25 ppm, the softening point will be lowered and the transesterification reaction rate will be lowered, resulting in an increase in the number of alkoxy groups, making it impossible to obtain a polyester with a high degree of polymerization. Examples of pentavalent phosphorus compounds used in combination with the catalyst include phosphoric acid and trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate,
Triesters such as tricresyl phosphate, partially esterified phosphoric acid compounds such as monomethyl phosphate, dimethyl phosphate, monoethyl phosphate, diethyl phosphate, monobutyl phosphate, dibutyl phosphate, or Examples include ethylene glycol esters of the above compounds.

The amount of the pentavalent phosphorus compound to be blended is limited in terms of electrostatic castability during film molding and transparency of the resulting film, and must satisfy the general formula (2).
The molar ratio of and in the general formula (2) for CO+Me is based on the assumption that manganese hydrogen phosphate [MrlHPO4] and magnesium hydrogen phosphate [MgHPO4] are produced from a manganese or magnesium compound and phosphoric acid, for example.
The value is expressed as CO+Me.

If the molar ratio of , is less than 1, partial discharge occurs during electrostatic application casting in the film forming process, resulting in craters and pinholes. On the other hand, when the molar ratio of CO+Me exceeds 4, the color tone deteriorates during melting.
Favorable as the drawback of increased surface haze is recognized CO+M
eCO+Me doesn't look good.

In addition, the values of 1 and 2 are more preferably in the range of 1≦ and ≦2 from the viewpoint of color tone and transparency. When a trivalent phosphorus compound such as a phosphite is added as a phosphorus compound, it is not preferable because it reduces a commonly used polymerization catalyst, such as antimony trioxide, and gives a blackish color to the polyester. If a pentavalent phosphorus compound is not used in combination, protrusions with a height of 0.1 μm or more appear on the surface of the biaxially stretched film, increasing the surface haze and inducing uneven coating of the photosensitive layer of the film. The polyester constituting the polyester film obtained in the present invention can be obtained by either method ♦, which involves 1 direct esterification followed by polycondensation or 2 transesterification followed by polycondensation.

When producing the polyester, the timing of adding cobalt compounds, magnesium compounds, and manganese compounds to the reaction system is preferably after the completion of esterification in method 1;
In the method described above, it is preferable to add the compound before the transesterification reaction, and a portion may be added after the transesterification reaction is completed. Further, the order in which each compound is added may be simultaneous, separate, or whichever is added first. The pentavalent phosphorus compound may be added to the reaction system at any time from the end of the esterification or transesterification reaction to before the end of the polycondensation reaction, but it is preferably immediately after the esterification or transesterification reaction. The method for producing a polyester film of the present invention comprises adding polyester chips containing a specific amount of the catalyst obtained above to 270 to 3
This method involves melt extrusion at 20°C, forming a sheet by electrostatic casting, and then subjecting it to longitudinal stretching, transverse stretching, and a heating process to form a biaxially stretched film.

In this case, electrostatic application casting is effective in maximizing the effects of the present invention. The electrostatic application casting referred to in the present invention is a method known in Japanese Patent Publication No. 37-61, etc., in which a sheet material extruded from an extrusion die is rapidly cooled on the surface of a rotating cooling body such as a rotating drum. A wire or knife-shaped electrode is provided between the extrusion die and the surface of the rotary cooling body to deposit an electrostatic charge on the top surface of the unsolidified sheet, and the sheet is brought into close contact with the surface of the cooling body for rapid cooling. This is the way to do it. A subbing layer is applied to the resulting biaxially stretched polyester film to improve adhesion to the gelatin emulsion layer.

Furthermore, in the case of black-and-white panchromatic film and X-ray film, a photographic light-sensitive layer in which light-sensitive silver salt particles are dispersed in gelatin is coated.

In the case of a color film for movies, a red-sensitive layer, a green-sensitive layer, and a blue-sensitive layer are laminated in this order. In addition to silver salt-based photosensitive layers, photosensitive layers containing diazonium salts dispersed therein, photosensitive layers containing photochromic compounds such as spiropyran, or palladium, copper,
A non-silver salt based photosensitive layer, such as a photosensitive layer containing a photoconductive substance in a vapor deposited layer such as tin oxide, is also preferably coated.

Furthermore, a protective layer may be applied on the above-mentioned photosensitive layer, or an antihalation layer may be applied on the back side of the base film.

The features of the present invention are summarized as follows.

1. Even after the high-temperature melt extrusion step, there is almost no decrease in molecular weight or change in color tone, and a biaxially stretched film with extremely good color tone can be obtained.

2. A biaxial film with excellent transparency that passes through the electrostatic application casting process and stretching process during film forming, has excellent planar smoothness and does not cause an increase in surface haze, and does not increase internal haze during stretching. A stretched film is obtained.

3. Catalyst residues in the polyester constituting the film are inert to the photosensitive layer of the film and do not cause staining or corrosion.

Further, even when these photosensitive layers are laminated on a film, a photographic film with excellent optical properties can be obtained without being colored or with a decrease in visible light transmittance. The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto.

In addition, the average particle size may be 0 within a range that does not impede the objectives and effects of the present invention.
．． It is also possible to add inert inorganic particles such as silicon dioxide, calcium carbonate, and titanium dioxide of 0.01 to 3 μm, antistatic agents, oxidative deterioration inhibitors, pigments, and the like. In addition, the measurement method of each characteristic in an Example is as follows.

(Polymer color tone) Polyester is indicated by the hander value (L, a, b) measured with a color machine (manufactured by Toyo Rika), where L is the lightness (the larger the value, the brighter), a is the red-green hue (+ is b indicates a yellow-blue hue (+ indicates yellow, - indicates bluish).

(Metal compounds) Quantitative analysis of cobalt, manganese, and magnesium metals is
Polyester 2y was accurately weighed, ignited at 700°C for 2 hours to incinerate it, and then subjected to atomic absorption spectrometry using a hydrochloric acid solution in a conventional manner.The values are expressed in Ppm.

(Quantification of phosphorus) A sample was wet-ashed in the presence of sulfuric acid and perchloric acid, and the ashed product was colored with ammonium molybdate in an acidic sulfuric acid solution, and the absorbance at 845 mμ was measured. It was compared and quantified.

(Film haze, light transmittance) Measured according to ASTM-DlOO3-52.

(Film surface roughness [Hmax] μ) The difference between the highest and lowest portions of the irregularities on the film surface observed using a microscopic light wave interferometer is expressed as μ.

(Surface haze) The surface haze [Hs] is the straight transmittance of 1 film [T1], the total transmittance of 2 films [T2], the straight transmittance of 3 films mounted with tetralin [T3], and 4 total transmittance. It was calculated from the rate [T4] using the following formula. Example 1 1.80 mole amount of ethylene glycol was added to 1 (1) part of dimethyl terephthalate, and further 4 parts of magnesium acetate was added.
Water salt [(CH3COO)2Mg・4H20') 0.04
and cobalt acetate tetrahydrate [(CH3COO)2C0-4
0.01 part of H20] was added as a catalyst, and the mixture was heated to 150 to 220°C under a nitrogen atmosphere to carry out a transesterification reaction, and the generated methanol was continuously distilled out of the system.

The transesterification reaction was completed 3 hours and 10 minutes after the start of the reaction. Subsequently, 0.03 parts of antimony trioxide and 0.03 parts of a 1:1 mixture of monoethyl phosphate and diethyl phosphate were added to the obtained product, and the system was gradually reduced in pressure, and finally 2
Polycondensation was carried out at 85°C for 2 hours and under reduced pressure of 1T1rmHg. The properties of the obtained polymer are that the intrinsic viscosity is 0.65,
L value 44. The b-value was 0.8, and it was an extremely transparent polymer with no coloration and excellent gloss.

Elemental analysis of this polymer revealed that it contained 24 ppm of cobalt, 42 ppm of magnesium, and a molar ratio of (metal/phosphorus) of 1.
It was 32. This polymer was dried under reduced pressure at 180'C for 3 hours, then formed into a sheet using an extruder set at 295°C, and then heated to 18°C.
Applied voltage 850 on the casting drum cooled to
Casting was carried out by applying an electrostatic charge of 0 volts.

Subsequently, longitudinal roll stretching was performed at 95°C to 3.3 times, and 13
3. at 0°C. The film was horizontally stretched and heat treated at 210'C for 2 cycles to obtain a 60μ biaxially stretched film. The total haze of the obtained film was 0.3, and the light transmittance was 8.
It was 8.8%. In addition, the surface haze is 0.2 in the Mauwat method using a tetralin solution, and the surface roughness [Hma
x] 0.1μ or less, and the surface smoothness was excellent.

Furthermore, the film had excellent transparency and was free from coloration, and by applying an undercoat layer and a blue tinting layer to the film, an excellent film for X-ray photography was obtained. Example 2 To 10 parts of dimethyl terephthalate was added 1.80 molar amount of ethylene glycol, and further, manganese acetate tetrahydrate [(CH3C
OO)2MnI. 4H20') 0.03 parts by weight, cobalt acetate tetrahydrate [(CH3COO)2C0.. 4H20)
0.01 parts by weight was added as a catalyst, and 1 part by weight was added under nitrogen atmosphere.
The transesterification reaction was carried out by heating to 50 to 220'C, and the methanol produced was continuously distilled out of the system.

The transesterification reaction was completed after 3 hours from the start of the reaction, and then 0.03 parts by weight of antimony trioxide, 0.005 parts by weight of germanium dioxide, and 0 parts by weight of phosphoric acid were added to the obtained product.
．． 005 parts by weight and 0.015 parts by weight of trimethyl phosphate were added, and the system was gradually reduced in pressure, finally at 285°C and 1T.
Polycondensation was carried out for 2 hours and 30 minutes under reduced pressure of WLHg. The obtained polymer had an intrinsic viscosity of 0.655, an L value of 43.1, b
The polymer had a value of 0.3, and was an extremely transparent, uncolored polymer with excellent gloss.

Elemental analysis of this polymer revealed that cobalt was 24 ppm, manganese was 67 ppm, and the molar ratio (metal/phosphorus) was 1.04.
It was hot. From this polymer, 60 μm was prepared in the same manner as in Example 1.
A biaxially stretched film was obtained.

The resulting film had a total haze of 0.2 and a surface haze of 0.2, and a light transmittance of 89.3%, making it extremely transparent. There was no change in color tone after film formation or coloring of the end face of the film roll, and the surface roughness [Hmax] was 0.1 μm or less, indicating excellent planar smoothness. Example 3 86.5 parts by weight of terephthalic acid was added to bis-(β-hydroxyethyl) terephthalate and its low polymer at a molar ratio of ethylene glycol/terephthalic acid of 1.15, melted and stored in an esterification reactor at 245 to 250'C. 3. A slurry obtained by kneading 37.1 parts by weight of ethylene glycol (mole ratio 1.15). The esterification reaction was carried out by continuous pumping over a period of time, and the resulting water was distilled out from the top of the rectification column.

After the supply of the slurry was completed, the esterification reaction was continued for another 1.5 hours to complete the esterification reaction. During this time, the reaction temperature was raised to 255°C. The reaction rate determined from the acid value and saponification value was 99.2%. Then, 105 parts by weight of the obtained reaction mixture (equivalent to 10 parts by weight of polyester) was transferred to a polycondensation reactor, and trimethyl phosphate was added to 0.
．． 0 parts of heel was added.

After 5 minutes, 0.04 parts by weight of magnesium acetate tetrahydrate and 0.00 parts by weight of cobalt acetate tetrahydrate were added.
After a few minutes, 0.025 parts by weight of antimony trioxide was added, and the reaction system was then heated under reduced pressure to carry out a polycondensation reaction for 3 hours.

The properties of the obtained polymer were that the intrinsic viscosity was 0.64 and the L value was 47.
2. The b value was 0.5, and it was an extremely transparent polymer with no coloration and excellent gloss.

This polymer was added with 45 ppm of magnesium (metal/phosphorus).
The molar ratio of was 1.86. After drying this polymer under reduced pressure at 180°C for 3 hours, it was formed into a sheet using an extruder set at 295°C, and electrostatic casting was carried out at an applied voltage of 8500 volts on a lower casting lume cooled to 18°C.
Subsequently, longitudinal roll stretching was performed at 95°C to 3.3 times, and 1
3 at 30'C. The film was horizontally stretched and heat treated at 210°C for 2 cycles to obtain a 60μ biaxially stretched film. The resulting film had a total haze of 0.2 and a light transmittance of 88.8%. Furthermore, in the mounting method using a tetralin solution, the surface haze was 0.15, and the surface roughness [H
max') 0.1μ or less, and the surface smoothness was excellent.

Comparative Example 1 In Example 1, manganese acetate tetrahydrate [(CH3COO)2Mn-4H20') 0.0
The polymer obtained by adding only 6 parts by weight and 0.03 parts by weight of antimony trioxide as a polymerization catalyst had a b value of 6.2 and was colored yellow.

The resulting biaxially stretched film coated with a blue tinting layer turned yellowish-green and was not suitable as an X-ray film. Comparative Example 2 In Example 1, cobalt acetate tetrahydrate [(CH3COO)2C0-4H20] 0.08 was used as the transesterification catalyst.
The polymer obtained by adding only 0.03 parts by weight of antimony trioxide as a polymerization catalyst had a b value of 2.0 and a relatively good color tone, but the biaxially stretched film obtained from this polymer The total haze was 2.1, and the transparency was poor.

Furthermore, the surface texture (JcHmaX) was between 0.1 and 0.2 microns, and the surface haze was 0.8, which was not desirable as a photographic film.

Comparative Example 3 In Example 1, cobalt acetate tetrahydrate [(CH3COO)2C0.4H20] 0.02 was used as the transesterification catalyst.
Parts by weight, manganese acetate tetrahydrate [(CH3COO)2Mn
・4H20] The polymer obtained by adding only 0.0 part of weight and 0.0 part of antimony trioxide as a polymerization catalyst and without adding any phosphorus compound has a b value of 2.0 and a relatively good color tone. However, the surface roughness [Hmax] of the biaxially stretched film obtained from this polymer was 0.1 to 0.2 microns, the total haze was 1.2, the surface haze was 0.7, and the transparency was insufficient.

Comparative Example 4 A polymer was obtained in exactly the same manner as in Example 2, except that the amount of phosphoric acid was increased to 0.04 parts by weight.

Claims (1)

[Claims] 1. When producing a polyester whose main repeating unit is ethylene terephthalate, (1) a glycol-soluble cobalt compound, ( 2) A polyester composition obtained by adding a glycol-soluble magnesium compound, at least one manganese compound, and (3) a pentavalent phosphorus compound in a range that satisfies the following general formulas I, II, and III is sheeted. Formed into a shape and stretched,
The surface roughness [Hmax] of the film obtained by heat setting is 0.
．． A method for producing a biaxially stretched polyester film, characterized in that the film has a thickness of 1μ or less. 10≦Co≦200...I 25≦Co+Me≦1000...IICo+M
e1≦(Co+Me)/P≦4...III (in the formula, Co is the amount of metal cobalt, and Me is the total amount of metal magnesium and metal manganese, respectively pp to polyester)
m, and (Co+Me)/P shows the molar ratio. )