JP3303569B2 - Polyethylene-2,6-naphthalate film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene naphthalate film. More specifically, the present invention relates to a polyethylene naphthalate film that has a low amount of low molecular weight precipitates on the film surface when heated.

[0002]

2. Description of the Related Art Polyesters are widely used in applications such as films and molded products because of their excellent physical and chemical properties. In particular, a polyethylene terephthalate film is suitably used as a support for a magnetic recording medium, a capacitor, an electric insulating material, a photographic material, a card and a label material, and the like.

[0003] However, with recent advances in miniaturization, weight reduction and high performance of electric and electronic equipment, the characteristics required for base films are becoming increasingly sophisticated. For example, in the magnetic recording field, it is necessary to make the base film thinner in order to achieve long-time recording, miniaturization, and weight reduction, but at the same time, maintaining a higher elastic modulus and maintaining the stiffness of the film. is important. For this reason, when the thickness of the base film is very thin, there have been cases where the elastic modulus of the conventional base film made of polyethylene terephthalate is insufficient.

[0004] Polyethylene-2,6-naphthalate is
It is known to exhibit properties superior to polyethylene terephthalate in terms of heat resistance, mechanical properties, chemical properties, and the like, and their utilization is being studied. For example, Japanese Patent Application Laid-Open No. 62-260822 (polymerization is completed, the pressure is reduced after reducing the pressure, and then the polymer is discharged), Japanese Patent Application Laid-Open No. 64-155 (containing spherical silica by the alkoxide method),
No. 112411 (limited to catalytic metal compounds and phosphorus compounds), such as those relating to polyethylene naphthalate compositions or production methods, or JP-A No. 62-113529 (relation between polymer specific resistance, center line roughness, thickness) ), JP-A-2-120329 (limited the hardness of the particles to be used, the mechanical strength of the film, and the amount of the oligomer),
JP-A-2-202925 (Limiting the Young's modulus in the vertical and horizontal directions of the film and the number of projections on the surface)
Many proposals regarding 2,6-naphthalate film have been made. Especially in recent years, in the field of magnetic tapes, especially for high-grade magnetic tapes, the quality of final products, especially electromagnetic conversion characteristics, is degraded even by a small amount of foreign matter contained in the film. Surface conditions have been required. On the other hand, for example, Japanese Patent Application Laid-Open No. 62-290722 proposes a method for producing a high-quality polyester by suppressing fine particles contained in a polyester raw material to a specific amount or less. This method has not yet met the current requirements. The reason for this is that, in addition to the above impurities, low molecular weight polyethylene-2,6-naphthalate, which precipitates on the film surface from inside the polymer itself when heated, significantly lowers the film surface characteristics. . In general, it is known that polyethylene-2,6-naphthalate has a smaller amount of precipitated low molecular weight substances than, for example, polyethylene terephthalate or the like. The mere use of naphthalate is a cause of deteriorating the electromagnetic conversion characteristics, and among the precipitated low molecular weight substances, especially crystalline low molecular weight substances have the same adverse effect as coarse projections.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved polyethylene-2,6-naphthalate film which does not cause deterioration in the performance of the product due to the precipitation of low-molecular-weight substances.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a 2,6-polyethylene naphthalate film in which the amount of low molecular weight substances deposited on the surface when heated at 170 ° C. is 0.7 mg / m ² or less. Can be achieved by:

The polyester in the present invention has a repeating unit substantially composed of an ethylene-2,6-naphthalenedicarboxylate unit. Also,
The polyethylene-2,6-naphthalate of the present invention contains a copolymer in which 10% or less, preferably 5% or less, of the number of repeating units is replaced by another component, or 10% or less, preferably 5% or less of the total weight. Mixtures that are other polymers are included. Here, as other components, compounds having a divalent ester-forming functional group, for example, 2,7,1,4,1,1,2
5 isomers of naphthalenedicarboxylic acid, such as terephthalic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, dichlorophenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, anthracene dicarboxylic acid , Or alkylene glycols such as trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, alicyclic diols such as cyclohexane dimethanol, and polyalkylene glycols such as polyethylene glycol and polypropylene glycol. And long-chain diols. Further, as compounds having a trivalent or higher ester-forming functional group, hemi-mellitic acid, trimesic acid, trimellitic acid, prenitic acid, melophanic acid, pyromellitic acid, biphenyl-3,3 ', 4,4'-tetracarboxylic acid Polyfunctional carboxylic acids such as benzophenone-3,3 ', 4,4'-tetracarboxylic acid and glycerin;
Trimethylolethane, trimethylolpropane, trimethylolbutane, 1,3,5-trimethylolbenzene, 1,3,5-triethylolbenzene, 1,3,5
-Tributyrolbenzene, 1,2,6-hexanetriol, pentaerythritol, sorbitol, 2,
Polyhydric alcohols such as 2,6,6-tetramethylolcyclohexanol can be mentioned.

[0008] The polyester film of the present invention can be produced, for example, by the following method.

The compound can be produced by either the esterification method or the transesterification method. The transesterification method will be described as an example. After feeding the ester-forming derivative of 2,6-naphthalenedicarboxylic acid and ethylene glycol to a transesterification reactor, the esterification reaction is carried out to about 220 to 250 ° C. in the presence of a transesterification catalyst.
It takes ８8 hours to gradually raise the temperature to distill out excess ethylene glycol to obtain a low polymer. Subsequently, the low polymer was transferred to a polycondensation reactor, and then the reaction system was gradually heated and decompressed to perform a polycondensation reaction.
A polyethylene naphthalate having an intrinsic viscosity of 0.45 to 0.75 is obtained by setting the pressure at -350 ° C and the degree of reduced pressure at 5 Torr or less. After completion of the reaction, the mixture is discharged from the reaction vessel and cut into chips according to a conventional method.

A conventionally known esterification or transesterification catalyst can be used arbitrarily. Such catalysts include, for example, alkali metals, alkaline earth metals, zinc, lead, manganese, aluminum, silicon, phosphorus and other acetates and chlorides, and the like. As the polycondensation catalyst, any conventionally known polycondensation catalyst can be used.
Examples of such a catalyst include antimony trioxide, germanium dioxide, and tetraalkoxytitanate. Germanium dioxide is particularly preferred. The addition amount of the esterification or transesterification catalyst and the polycondensation catalyst may be any as long as the reactivity and heat resistance of the polyester are not impaired.

The chip-like polyethylene naphthalate obtained above is subjected to a pressure of 10 kgf / cm ² for 0.01 T
Suppressing deposition of low-molecular-weight substances during film heating by performing heat treatment at a temperature of 150 ° C. to the melting point of the polymer, preferably 10 to 50 ° C. lower than the melting point, under an arbitrary pressure under a reduced pressure of orr. Can be. The low-molecular-weight product referred to in the present invention is a low-molecular-weight product such as a trimer, a tetramer, or a pentamer mainly containing linear or cyclic ethylene naphthalate as a structural unit.

In the present invention, the heat treatment may be carried out, if desired, in an atmosphere of an inert gas such as nitrogen or under a flow. If it is not desirable that the intrinsic viscosity of the polymer changes during the heat treatment, the heat treatment is performed under a non-circulating inert gas atmosphere under normal pressure or under pressure, preferably under normal pressure. If it is acceptable to increase the intrinsic viscosity,
The heat treatment is performed under reduced pressure or under a flow of an inert gas. From the viewpoint of avoiding an increase in the melt viscosity in the film forming step, a method that does not involve an increase in the intrinsic viscosity is preferable, and a particularly preferable method is a heat treatment at normal pressure in a non-circulating atmosphere of an inert gas.

Another example of obtaining the film of the present invention is as follows.

That is, in the above-mentioned optional step of obtaining polyethylene naphthalate by melt polycondensation or in the optional step of obtaining a film by melt film formation, the melting point is 20.
By adding a wax at a temperature of up to 250 ° C., precipitation of low molecular weight substances during film heating can be suppressed. It is not clear why the addition of wax to polyethylene naphthalate suppresses the deposition of low molecular weight substances when the film is heated, but the low molecular weight substances are dissolved or adsorbed in the wax dissolved or finely dispersed in the polymer. It is estimated that precipitation is suppressed. The amount of the wax contained in the film is preferably 0.01 to 3% by weight, more preferably 0.05 to 2% by weight, particularly preferably 0.1 to 1% by weight. Examples of the wax to be added to the polymer include, for example, rice wax, vegetable wax such as carnauba wax, mineral wax such as montanic acid wax,
Polyolefin, stearic acid or its ester,
Synthetic waxes such as amides, hardened tallow oil, beans wax, animal waxes such as lanolin, and the like,
One or more of these waxes can be added.

The thus obtained chip-like polyethylene naphthalate can be formed into a film by a melt biaxial stretching film forming method to obtain a film of the present invention.

After the chip-shaped polyethylene naphthalate is dried as required, it is supplied to an extruder of a known melt biaxial stretching film forming machine, extruded into a sheet shape from a slit die, and cooled on a casting roll. It is solidified to make an unstretched film. In the case of a laminated film, the polyester in a molten state is laminated using two or three extruders, two or three layers of a manifold or a merging block. Next, the unstretched film is biaxially stretched and biaxially oriented. When using the sequential biaxial stretching method in which stretching is performed first in the longitudinal direction and then in the width direction, the longitudinal stretching temperature is 70 ° C to 17 ° C.
The range of 0 ° C. and the total longitudinal stretching ratio of 3.0 to 8.0 is preferable. As a stretching method in the width direction, a method using a stenter is preferable, and a stretching temperature is preferably in a range of 70 to 160 ° C.

Next, the stretched film is heat-treated. The heat treatment temperature in this case is 190 to 250 ° C. and the time is 0.5 to
A range of 60 seconds is preferred.

When the film of the present invention is heated at 170 ° C. for 3 hours, the deposition amount of low molecular weight substances is 0.7 mg / m ² or less, more preferably 0.4 mg / m ² or less, and particularly preferably 0.1 mg / m ² or less.
It is preferably at most ² mg / m ² .

The film of the present invention may be blended with various particles for the purpose of improving the processability in the film forming process, the handling property in processing or using the film, the workability, and the commercial value. Specifically, crushing natural products
Classification or various particles produced by a synthetic method can be used. Specifically, silicon dioxide, titanium dioxide,
Constituents include at least one of inorganic particles such as aluminum oxide, zirconium oxide, calcium carbonate, cerium dioxide, molybdenum oxide, tungsten oxide, calcium phosphate, barium sulfate, iron oxide, kaolin, carbon, and at least one of alkali metals and alkaline earth metals, and phosphorus. Particles precipitated in the polyester polymerization reaction system to be part of,
That is, internal particles, and further, crosslinked polymer particles such as various vinyl-based particles such as silicone resin particles, epoxy resin particles, polyimide particles, crosslinked polystyrene particles, and alkyd particles, and the like are included.

The film of the present invention may contain various ultraviolet absorbers, antistatic agents and the like.

As a method for producing a film containing inorganic particles, internal particles or crosslinked polymer particles, for example, a method of adding both of them to a polyester reaction system may be used, or a master chip separately mixed with a polymer may be used. May be chip-blended or melt-kneaded before film formation.

The film of the present invention may be a single layer or a laminate of two or more layers. In the case of a laminated film, a layer having a function of suppressing deposition of low molecular weight substances is provided on one or both outermost layers. When forming a layer having a function of suppressing precipitation of low molecular weight substances as an inner layer, the thickness is preferably 60% or more of the total thickness.

[0023]

The present invention will be described in more detail with reference to the following examples. The characteristic values in the examples were measured according to the following methods.

A. Intrinsic viscosity It was measured at 25 ° C. using orthochlorophenol as a solvent.

B. Amount of Precipitation A film sample was heat-treated at 170 ° C. for 3 hours in the air, and one side of the 20 cm ² film was immersed in chloroform at 22 ° C. for 5 minutes, and the absorbance of the chloroform around 240 nm was measured with an ultraviolet spectrophotometer. From the calibration curve, the weight of the precipitated low molecular weight product was determined. This value is converted to a unit of mg / m ² .

Example 1 65.8 parts of dimethyl 2,6-naphthalenedicarboxylate and 33.5 parts of ethylene glycol, manganese acetate tetrahydrate were added to a transesterification reactor equipped with a stirrer, a rectification column and a condenser. After supplying 0.08 parts, the temperature was gradually increased from 170 ° C. to 240 ° C., and simultaneously produced methanol was subjected to transesterification while continuously distilled out of the reaction system. To the reaction product thus obtained, 0.04 parts of trimethyl phosphate was added and reacted for 15 minutes.
03 parts were added, and the mixture was further reacted for 5 minutes. 280 ° C. while continuously distilling ethylene glycol continuously
And simultaneously reduced the pressure to 0.2 mmHg to carry out a polycondensation reaction to obtain a polymer having an intrinsic viscosity of 0.65.

After the polymer was formed into chips having a surface area of 1200 m ² / m ³ , it was supplied to a rotary evaporator and crystallized at 150 ° C. for 5 hours in a nitrogen stream. Thereafter, the temperature in the apparatus was raised to 240 ° C. under a non-circulating nitrogen atmosphere at normal pressure. In this state, heat treatment was performed for 20 hours.

After drying this chip-shaped polymer, it is supplied to an extruder set at 290 ° C. of a usual biaxial stretching film forming machine.
After melting and high-precision filtration, discharge from the base
And cooled and solidified to obtain an unstretched film. This unstretched film is stretched 5.0 times in the longitudinal direction at 90 ° C. and 6.0 times in the width direction at 95 ° C., 2
Heat treatment was performed at 10 ° C. to obtain a biaxially oriented film having a thickness of 15 μm.

The film obtained above was heat-treated in an oven set at 170 ° C. for 3 hours, and the precipitated low molecular weight product was measured. As a result, it was 0.1 mg / m ² .

COMPARATIVE EXAMPLE 1 In Example 1, a chip-shaped polymer was prepared at 240 ° C. for 20 minutes.
In the same manner except that no heat treatment is performed for
A μm film was obtained.

The obtained film was used in the same manner as in Example 1 for 17 times.
The mixture was heat-treated in an oven set at 0 ° C. for 3 hours, and the precipitated low molecular weight product was measured. As a result, it was 0.9 mg / m ² .

EXAMPLE 2 65.8 parts of dimethyl 2,6-naphthalenedicarboxylate and 33.5 parts of ethylene glycol, manganese acetate tetrahydrate were added to a transesterification reactor equipped with a stirrer, a rectification column and a condenser. After supplying 0.08 parts, the temperature was gradually increased from 170 ° C. to 240 ° C., and simultaneously produced methanol was subjected to transesterification while continuously distilled out of the reaction system. To the reaction product thus obtained, 0.04 part of trimethyl phosphate was added and reacted for 15 minutes. Then, 0.02 part of germanium dioxide was added, and the mixture was further reacted for 5 minutes. Thereafter, 1.0 part of carnauba wax was added. Was added. Subsequently, the temperature was raised to 280 ° C. while continuously distilling ethylene glycol, and simultaneously the pressure was reduced to 0.2 mmHg to carry out a polycondensation reaction, thereby obtaining a polymer having an intrinsic viscosity of 0.65 in the form of chips. The chip-shaped polymer obtained above was formed into a film in the same manner as in Example 1 to obtain a film having a thickness of 15 μm.

The obtained film was used in the same manner as in Example 1 for 17 times.
Heat treatment was performed in an oven set at 0 ° C. for 3 hours, and the precipitated low molecular weight product was measured. As a result, it was 0.2 mg / m ² .

Example 3 In Example 2, 1.0 part of carnauba wax was added after the transesterification reaction, and then the average diameter was 0.4 μm.
In the same manner as above, except that 4 parts of an ethyne glycol slurry of calcium carbonate containing 10% by weight of calcium carbonate particles was added, a polymer was obtained in the form of chips.

The obtained film was used in the same manner as in Example 1 to obtain a film.
Heat treatment was performed in an oven set at 0 ° C. for 3 hours, and the precipitated low molecular weight product was measured. As a result, it was 0.2 mg / m ² .

Example 4 Example 2 was carried out using two extruders, an extruder 1 and an extruder 2, and a film-forming machine equipped with a three-layer melt composite film-forming die having a polymer merging section and a distributor. After drying the wax-containing polymer (Polymer (I)) and the ordinary polymer (Polymer (II)) obtained in Comparative Example 1, the extruder 1 and the extruder 2 respectively feed the polymer (I), (II) respectively,
Melted and discharged from the die to form a three-layer laminate (lamination configuration:
Polymer (I) / polymer (II) / polymer (I)). This was wound around a casting drum under the same conditions as in Example 1 and cooled and solidified to produce an unstretched film. The unstretched film is stretched 5.5 times in the longitudinal direction and 5.5 times in the width direction and heat-treated, and the polymer (I) has a front and back surface of 2 μm each, a middle layer of the polymer (II) of 11 μm, and a total thickness of 15 μm. An axially-oriented laminated film was obtained.

The obtained film was used in the same manner as in Example 1 to obtain a film.
The mixture was heat-treated in an oven set at 0 ° C. for 3 hours, and the precipitated low molecular weight product was measured. As a result, it was 0.3 mg / m ² .

Example 5 The procedure of Example 4 was repeated, except that the wax-containing polymer (polymer (I)) obtained in Example 2 was replaced with the wax obtained in Example 3 and the polymer (polymer (III) containing calcium carbonate particles. )), Except that the polymer (III) is supplied to the extruder 1 in the same manner as above, except that the front and back sides of the polymer (III) are 2 μm each, the middle layer of the polymer (II) is 11 μm, and the total thickness is 15 μm. I got

The obtained film was used in the same manner as in Example 1 for 17 times.
The mixture was heat-treated in an oven set at 0 ° C. for 3 hours, and the precipitated low molecular weight product was measured. As a result, it was 0.3 mg / m ² .

[0040]

The film of the present invention has almost no precipitation of low molecular weight substances from the inside of the film even when used under normal temperature as well as at high temperature. Does not cause pollution. Therefore, it is particularly suitable for a support film of a high-performance magnetic recording medium which requires formation of fine and uniform surface projections.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08G 63/00-63/91 C08J 5/18

Claims (4)

(57) [Claims] 1. A polyethylene-2,6-naphthalate film wherein a low molecular weight substance precipitated on the surface when heated at 170 ° C. for 3 hours is 0.7 mg / m ² or less. 2. The polyethylene-2,6-naphthalate film according to claim 1, further comprising a wax having a melting point of 20 to 250 ° C. 3. The polyethylene-2,6-polyethylene according to claim 1, wherein the polyethylene-2,6-naphthalate is obtained by forming a film of granular polyethylene-2,6-naphthalate heat-treated at a temperature of 150 to 250 ° C. Naphthalate film. 4. The polyethylene-2,6 according to claim 3, obtained by forming a film of granular polyethylene-2,6-naphthalate heat-treated at normal pressure under a non-circulating gas atmosphere. -Naphthalate film.