JPH07100757B2 - Polyester film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyester composition, and more specifically, it has excellent particle dispersibility, very few coarse projections on the surface, and excellent slipperiness. The present invention relates to a polyester film containing ethylene-2,6-naphthalate as a main repeating unit, which has good winding properties and abrasion resistance.

[Problems to be Solved by Prior Art and Invention]

Biaxially stretched films of polyester and sometimes polyethylene terephthalate have excellent physical and chemical properties, and are therefore used as substrates in extremely wide industrial fields such as magnetic tapes, capacitors, packaging, and plate making. .

By the way, in recent years, there has been a strong demand for miniaturization, weight reduction, and high performance of electric and electronic devices, and accordingly, the required characteristics of films used have become severe. For example, improvements in mechanical strength and heat resistance associated with thinner counts are applicable. Even in the case of polyethylene terephthalate, some improvement in mechanical properties can be expected by changing the stretching formula, for example, by applying a re-stretching method, but it is impossible to make a significant improvement. I have to say that it is extremely difficult to come.

Under these circumstances, a polyethylene-2,6-naphthalate biaxially stretched film has been drawing attention, and it has been clarified that its mechanical strength and heat resistance are superior to those of a polyethylene terephthalate biaxially stretched film. ing.

As with the polyethylene terephthalate film,
In the case of polyethylene-2,6-naphthalate biaxially stretched film, also improve slipperiness so as not to hinder process passability and winding characteristics in the film manufacturing process, and handleability in post-processing processes such as coating and vapor deposition. There is a need. To this end, in the case of polyethylene terephthalate, fine particles are contained in the polymer to give appropriate irregularities to the film surface, and a method of improving the slipperiness of the film is performed. It can also be applied to a 6-naphthalate film.

As one of the methods of incorporating fine particles into polyester, there is a method of adding particles during the polyester polycondensation reaction to complete the polycondensation, and the particles used here are talc, kaolin, silica, calcium carbonate. Inorganic compound particles that are substantially insoluble and inactive in polyesters such as titanium dioxide and lithium fluoride are well known. However, although these inorganic particles are usually obtained by crushing or synthesizing natural minerals, it is extremely difficult to avoid mixing coarse particles and agglomerated particles.

When coarse particles and agglomerated particles are contained in the polyester, the filter is severely clogged in the film forming reaction step, and the film is broken in the stretching step. Further, from the viewpoint of the quality of the film, minute defects called fish eyes are generated in the film, which causes problems such as dropout in magnetic tape and defective withstand voltage in capacitors.

On the other hand, the dispersibility of the particles in the polyester is also important, and when the particles agglomerate, the above-mentioned problems also occur, but in the case of polyethylene-2,6-naphthalate, the dispersion of the particles is better than that of polyethylene terephthalate. I know that is difficult.

In order to solve the above problems, crushing, classifying and filtering inorganic compound particles to remove coarse particles and agglomerated particles contained therein, and to improve dispersibility in polyester, various Method is used,
The result is not always satisfactory.

The recent trend toward miniaturization and high performance of electric and electronic devices requires that the surface of the polyester film has almost no fish eyes and that the unevenness of the surface is more uniform or fine. , It is difficult to achieve with conventional technology.

By the way, various products having different average particle diameters of silica particles are commercially available. However, even if the silica particles are contained in polyester to form a film, the above-mentioned strict requirements are not satisfied. That is, the activity of the particle surface such as silica particles is relatively high, and fine particles easily form secondary agglomerated particles, and it is difficult to completely disperse the particles in the dispersion medium. Agglomeration of particles occurs even after addition to the reaction system, and as a result, coarse agglomerated particles are contained in the polyester, causing troubles during film formation and deterioration of film quality as described above. It was.

[Means for solving problems]

The present inventors have focused on silica particles as particles to be added and contained in polyester, and regarding silica particles which do not contain coarse / aggregated particles and have good dispersibility in polyester, especially polyethylene-2,6-naphthalate. Diligently studied. As a result, the fine particles of amorphous silica obtained by hydrolyzing and condensing the alkoxysilane using a specific catalyst have an extremely sharp particle size distribution, do not contain coarse / aggregated particles, and use a medium such as ethylene glycol. It has been found that it has excellent dispersibility in polyesters and polyesters, and when formed into a film, it gives a surface with very few fine and uniform surface roughness, and also has excellent slipperiness, good winding properties, and good abrasion resistance.
The present invention has been completed.

That is, the gist of the present invention is a polyester film containing ethylene-2,6-naphthalate as a main repeating unit, which is obtained by a hydrolysis reaction and a condensation reaction of an alkoxysilane and is substantially amorphous and has an average particle size of 0.01.
To 3.0 μm and 0.001 to 5% by weight of spherical silica fine particles having a particle size distribution defined in the text that satisfies the following formula (I), and 0.3 to 0.9 of the metal contained in the polyester.
It is characterized by the addition of twice the molar amount of phosphorus compound, the specific resistance during melting is 5 × 10 ⁸ Ω · cm or less, and the number of coarse projections defined in the text is 7/25 cm ² or less. It exists in the polyester film.

1.1 ≦ [d10 / d90] ≦ 2.7 (I) (In the above formula, [d10 / d90] represents the ratio of the particle size when the cumulative number of particles is 90% to the particle size when the cumulative number is 10%. ) Hereinafter, the present invention will be described in detail.

The polyester in the present invention means naphthalene-2,6-
Dicarboxylic acid or its alkyl ester as the main acid component, ethylene glycol as the main glycol component, after esterification or transesterification, refers to the polyester obtained by carrying out the polycondensation reaction, part of which is the other component May be replaced with. For example, a part of the acid component is naphthalene-2,7-dicarboxylic acid,
Terephthalic acid, isophthalic acid, phthalic acid, adipic acid,
It may be replaced with sebacic acid, p-hydroxybenzoic acid or a lower alkyl ester thereof, or a part of the glycol component may be trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol. You may replace with. In any case, the polyester referred to in the present invention refers to a polyester in which 80 mol% or more, preferably 90 mol% or more is an ethylene-2,6-naphthalate unit.

In the present invention, the additive particles contained in the polyester to improve the surface properties and the slipperiness of the film are silica particles having an average particle diameter of 0.01 to 3 μm. Is obtained by a hydrolysis reaction and a condensation reaction.

As the alkoxysilane compound, (C _n H _{2n + 1} O) ₄ Si (n
= 1 to 8), and specifically, compounds such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane are preferably used. As a catalyst for the hydrolysis reaction and the condensation reaction, ammonia, trimethylamine, tetraethylammonium aqueous solution, urea or the like can be used, but an ammonia aqueous solution is preferable.

The silica particles are synthesized, for example, as follows. That is, a solution (referred to as solution A) in which tetramethoxysilane is dissolved in a methanol solvent is prepared, and a solution (referred to as solution B) in which water and an aqueous ammonia solution are dissolved in methanol is separately prepared. After keeping both solutions at a prescribed temperature, for example 20-30 ° C, add solution A while vigorously stirring solution B,
Then, after holding at a predetermined temperature for several hours, centrifugation, washing with alcohol as a solvent, drying, and then dispersing in ethylene glycol, or adding ethylene glycol to the suspension of silica particles after the reaction is completed, and then distilled. Then, excess ammonia, alcohol and water are removed to obtain silica particles. In any case, it is preferable that the spherical silica of the present invention is finally prepared as a slurry of ethylene glycol. At this time, the water content in the ethylene glycol slurry must be 0.1% or less.

The concentration of spherical silica particles in the ethylene glycol thus prepared is less than 20% by weight, preferably less than 10% by weight, particularly preferably 0.5 to 5% by weight. If it exceeds 20% by weight, aggregation is likely to occur when it is added to the polycondensation reaction system, which is not preferable. If it is less than 0.5% by weight, the amount of ethylene glycol used becomes too large, which is economically disadvantageous.

The silica particles obtained by the hydrolysis reaction and condensation reaction of the alkoxysilane according to the present invention are characterized in that their shape is spherical and the particle diameter is extremely uniform. That is, the value of the ratio [d10 / d90] of the particle size when the cumulative number of particles is 90% to the particle size when the cumulative number is 90% must be in the range of 1.1 to 2.7. When it exceeds 2.7, it means that the particle size distribution is wide, which makes it difficult to control the surface roughness of the film and increases the number of coarse particles, which is not preferable because the characteristics of the silica particles in the present invention are lost.

The spherical silica particles used in the present invention have a particle size of 0.01 to 3.
It is necessary to be 0 μm, preferably 0.01 to 2 μm
m, and more preferably 0.01 to 1 μm. If it is less than 0.01 μm, the effect of improving the surface properties and the slipperiness of the film is not sufficient. If it exceeds 3.0 μm, the surface roughness of the film becomes too large, and coarse particles are mixed, which is not good because the quality of the film is deteriorated.

In the present invention, the content of spherical silica particles in the polyester film needs to be 0.001 to 5% by weight, preferably 0.001 to 2% by weight, and more preferably 0.0.
01 to 1% by weight is preferable. If it is less than 0.001% by weight, the effect of improving the slipperiness of the film is insufficient, and if it exceeds 5% by weight, the surface roughness of the film becomes too large or agglomeration occurs, which is not preferable.

The spherical silica particles used in the present invention have a very sharp particle size distribution and also have excellent dispersibility in ethylene glycol, so that special dispersion treatment or classification treatment is not required, and the slurry filter is also extremely excellent in filterability. There is.

In the production of the polyester film of the present invention, the spherical silica particles are preferably added as an ethylene glycol slurry during the polyester synthesis reaction, but it is particularly preferable to add the spherical silica particles at any time before the initiation of the polycondensation reaction.

The polyester obtained in the present invention may be used in combination with fine particles of silica particles, calcium carbonate, amorphous zeolite, titanium dioxide, kaolin, talc, lithium fluoride, etc., within a range not impairing the gist of the present invention, Further, it may be used in combination with fine particles deposited by the reaction of the catalyst residue and the phosphorus compound in the polyester polycondensation reaction system, for example, those comprising calcium, lithium and phosphorus compounds, or those comprising calcium and phosphorus compounds.

The preferred intrinsic viscosity of the polyethylene-2,6-naphthalate film is 0.5 to 1.0, more preferably 0.55 to 0.9.
Is. However, since the melt viscosity of polyethylene-2,6-naphthalate is much higher than that of polyethylene terephthalate, polyethylene-2, which has an intrinsic viscosity of 0.5 to 1.0, can be obtained using the batch reactor used in the production of polyethylene terephthalate. There are great difficulties in producing 6-naphthalate. Therefore, the solid phase polymerization method is used to produce polyethylene-2,6-naphthalate having a preferable intrinsic viscosity without any problem. That is, a melt polymerization method is carried out in a batch reactor to obtain a prepolymer having an intrinsic viscosity of 0.4 to 0.5. This is pre-crystallized at 160-180 ° C, then dried at 170-190 ° C, and then solid-state polymerized at 210-250 ° C for a predetermined time under reduced pressure or under a nitrogen stream to give polyethylene-2,6 with an intrinsic viscosity of 0.5-1.0. -Naphthalate can be obtained and can be suitably used as a film raw material.

The specific resistance of the obtained polyester at the time of melting is also important (hereinafter, the specific resistance simply means the specific resistance at the time of melting).
In the case of polyethylene terephthalate, when the sheet-like material melt-extruded from the extrusion die at the time of film formation is rapidly cooled by a rotating cooling drum, an electrostatic charge is applied to the surface of the sheet-like material to bring the sheet-like material into close contact with the cooling surface The so-called electrostatic applied cooling method is widely adopted, and it is well known that the lower the specific resistance of polyester, the stronger the adhesion force, which is also the case with polyethylene-2,6-naphthalate. For example, when applying a polyethylene-2,6-naphthalate film to a magnetic tape, it is necessary to strictly control the thickness accuracy, and the electrostatic applied cooling method must be applied effectively. The specific resistance is 5 × 10 ⁸
Ω · cm or less, preferably 1 × 10 ⁸ Ω · cm or less. To lower the specific resistance, solubilize the metal compound in the polyester and remove the metal contained in the polyester.
It has been found that it is sufficient to add 0.3-0.9 times the molar amount of the phosphorus compound. It is particularly preferable to add these metal compounds and phosphorus compounds as an ethylene glycol solution before the start of polycondensation. Thus, a polyester having a low specific resistance and to which the electrostatic cooling method can be effectively applied can be obtained.

The polyester mainly composed of polyethylene-2,6-naphthalate obtained as described above can be formed into a biaxially stretched film by the following method.

That is, the polyester composition is usually extruded in a sheet form from an extruder at 280 to 320 ° C. and rapidly cooled to 80 ° C. or less to form a substantially amorphous sheet, and then the sheet form is longitudinally and laterally at least at an area magnification. To obtain a biaxially stretched film, which is then stretched to 4 times at a temperature of 120 to 250 ° C.
It can be obtained by heat treatment at a temperature in the range. The thickness of the film is 0.2 to 300 μm, preferably 0.3 to 200 μm.

The biaxially stretched film obtained by the polyester composition of the present invention has higher mechanical strength and heat resistance than the polyethylene terephthalate film, and thus can be used in a wider range of fields than the polyethylene terephthalate film, and is industrially used. It is extremely useful for

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded. "Parts" in Examples and Comparative Examples indicate "parts by weight". The measuring method used is shown below.

(1) Average particle size (d50) About spherical silica particles are photographed by an electron microscope.
1000 particles were measured, and the particle size when the cumulative number of particles was 50% was used. Other particles were determined by a Shimadzu centrifugal sedimentation type particle size distribution analyzer SA-CP3.

(2) Particle size distribution (d10 / d90) Similar to the case of the average particle size, spherical silica particles are photographed by an electron microscope, and other particles are measured with a Shimadzu centrifugal sedimentation particle size distribution analyzer SA-CP3. The number was counted from the particle side and the ratio of the particle size at 10% to the particle size at 90% was used with respect to the total number.

(3) Intrinsic viscosity [η] 1.0 g of polymer is phenol / tetrachloroethane = 50/5
It was dissolved in 100 ml of 0 (weight ratio) mixed solvent and measured at 30 ° C.

(4) Specific resistance during melting [British Journal of Applied Physics (Brit.J.Appl.Phys.) 17 , 1149-1154, 1966]
According to the method described in. However, in this case, the melting temperature of the polymer was 295 ° C., and the value immediately after applying a DC voltage of 1000 V was taken as the specific resistance during melting.

(5) Surface roughness of film Measured by the method described in JIS B0601-1976. For the measurement, a surface roughness measuring device model SE-3F manufactured by Kosaka Laboratory was used, and the center line average roughness (measured with a stylus diameter of 2 μm, a stylus load of 30 mg, a cutoff value of 0.08 mm, and a measured length of 2.5 mm ( Ra).

(6) Sliding property of film The friction coefficient is represented by μd, and the friction coefficient was measured by a method improved according to ASTM D-1894 so that it can be measured with a tape-shaped sample. At the time of measurement, the sample has a width of 15 mm, a length of 150 mm, a pulling speed of 20 mm / min, a measuring temperature of 21 ± 2 ° C, and a humidity of 65 ± 5.
% Atmosphere.

(7) Dispersibility of Particles in Film The dispersed state of particles in the biaxially stretched film was determined by observing the inside of the film with a microscope.

(8) Number of Coarse Protrusions Aluminum was vapor-deposited on the film surface, and the number was measured by the two-beam method using an interference microscope. Determine the number of projections (projection height of 0.81 μm or more) that show interference fringes of the third order or higher at the measurement wavelength of 540 nm.
It is shown in terms of conversion per 25 cm ² .

(9) Winding characteristics The appearance of the roll surface and the roll end surface when the film was wound into a roll was judged as follows.

◯: The roll surface has almost no wrinkles or bump-like defects and the roll end faces are aligned.

Δ: Almost no wrinkles were formed on the roll surface, but some bump-like defects were generated, and the roll end surface was slightly uneven.

X: Wrinkles are generated on the roll surface, or the end faces of the roll are uneven.

(10) Friction (Evaluation of White Powder) The film was run for 500 m in the running system shown in FIG. 1 and the amount of worn white powder attached to the hard chrome fixing pin shown in (I) was visually evaluated.

⊚: No adhesion ○: Slight adhesion Δ: Small amount (more than ○) adhered ×: Total adhesion Example 1 <Synthesis of spherical silica particles> 30.4 g of tetramethylsilane was dissolved in 400 g of methanol 2
The temperature was maintained at 0 ° C (solution A). On the other hand, 900 g of methanol and 110 g of water
Was added and 243 g of 28% aqueous ammonia solution was mixed and maintained at 20 ° C (solution B). Then, a stirring device was attached to the liquid B, and the liquid A was added while stirring. Immediately after the addition, a hydrolysis reaction and a condensation reaction occurred and the inside of the reaction system became cloudy. After adding solution A and stirring for another hour, hold 288 g of ethylene glycol.
Was added and heated under reduced pressure to distill off excess water, methanol and ammonia to obtain an ethylene glycol slurry containing 4% concentration of spherical silica. After the ethylene glycol slurry was dried, a photograph was taken with an electron microscope to determine the average particle size d ₅₀ and the particle size distribution d 10 / d 90. d ₅₀ is 0.30 μm, d
10 / d90 was 1.5. The obtained silica particles were uniform spherical particles having a uniform size. The slurry was filtered through a filter having a filtration accuracy of 3 μm cut, and the filter passability was good. The water content was 0.07%.

<Production of Polyester Composition> 100 parts of 2,6-naphthalenedicarboxylic acid dimethyl ester,
60 parts ethylene glycol and magnesium acetate tetrahydrate 0.
09 parts were placed in a reactor and heated to raise the temperature, and transesterification was carried out while distilling off methanol. After about 4 hours from the start of the reaction, the temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Then ethyl acid phosphate 0.04
Part was added, and then the spherical silica particle slurry having the average particle diameter of 0.30 μm was added so that the content of the spherical silica particles was 0.3% with respect to the polyester, and 0.04 parts of antimony trioxide was further added, and then the temperature was changed. Gradually increase and finally 28
Allow the temperature to reach 5 ℃ and gradually reduce the pressure from normal pressure to 1mmHg.
Was reached.

After 3 hours from the start of the reaction, the reaction was stopped and polyethylene-2,6-naphthalate was discharged under nitrogen pressure.
The obtained polyethylene-2,6-naphthalate had an intrinsic viscosity of 0.46 and a specific resistance when melted of 1.4 × 10 ⁸ Ω · cm.

This polymer was pre-crystallized under nitrogen at 170 ° C for 2 hours, further dried at 0.3mmHg and 180 ° C for 4 hours, then 0.3mmH
Solid state polymerization was performed at 240 ° C. for 11 hours. The intrinsic viscosity of the obtained polyester was 0.61.

<Production of Polyester Film> Polyethylene-2,6-naphthalate containing spherical silica particles obtained by solid-phase polymerization was extruded into a sheet at 295 ° C. from an extruder, and 110 μm thick using an electrostatic cooling method. An amorphous sheet was obtained. Then, it was stretched 4.0 times in the machine direction and 4.0 times in the cross direction and heat-set at 220 ° C. for 5 seconds to obtain a biaxially stretched film having a thickness of 7 μm.

These results are shown in the first example together with the following examples and comparative examples.
Shown in the table.

Examples 2 to 4 Spherical silica particles having various average particles and particle size distributions were synthesized in the same manner as in Example 1 except that the mixing ratio of methanol, water and aqueous ammonia solution in the liquid B was changed. The same examination as in Example 1 was performed. In addition, Example 4
Then, the amount of particles added to the polyester is also changed.

Example 5 The same examination as in Example 1 was conducted except that the amount of particles added was 0.6%.

Example 6 Ethyl acid phosphate after completion of transesterification reaction
The same examination as in Example 1 was conducted except that 08 parts and 0.09 parts of magnesium acetate tetrahydrate were added. The specific resistance at the time of melting was lower than that of Example 1, and was 5.1 × 10 ⁷ Ω · cm.

Comparative Example 1 Silica particles (primary particle size 0.04 μm) obtained by the dry method were dispersed in ethylene glycol at 10000 rpm for 1 hour using a homomixer manufactured by Tokushu Kika Kogyo. The obtained 5% concentration slurry was filtered with a 7 μm cut filter, but it was difficult to filter. The average particle size d ₅₀ of this slurry by the centrifugal sedimentation method was 0.11 μm, and the particle size distribution d 10 / d 90 was 2.9. The same examination as in Example 1 was conducted except that the slurry was used.

Comparative Example 2 Silica particles (primary particle size: 0.05 μm) obtained by a wet method were dispersed in ethylene glycol using a homomixer manufactured by Tokushu Kika Kogyo at 10,000 rpm for 1 hour. The obtained 5% concentration slurry was filtered with a 10 μm cut filter, but it was difficult to filter. The average particle size d ₅₀ of this slurry by the centrifugal sedimentation method was 0.21 μm, and the particle size distribution d 10 / d 90 was 3.5. The same examination as in Example 1 was conducted except that the slurry was used.

Comparative Example 3 Silica particles obtained by gelation of silicic acid were placed in ethylene glycol using a homomixer manufactured by Tokushu Kika Kogyo Co., Ltd.
The dispersion treatment was performed at 000 rpm for 1 hour. The obtained slurry having a concentration of 5% was filtered with a filter of 20 μm cut, but the filtration was difficult. The average particle size d ₅₀ of this slurry by the centrifugal sedimentation method was 1.85 μm, and the particle size distribution d 10 / d 90 was 2.9. Using the slurry, the same examination as in Example 1 was conducted except that the amount of particles added was 0.2%.

In all of the above comparative examples, the dispersibility is poor and the number of coarse projections is large, which is not preferable.

Comparative Example 4 The same examination as in Example 1 was carried out except that 0.3% of spherical silica particles having an average particle size d50 of 0.70 μm and a particle size distribution d10 / d90 of 2.9 were added to the polyester.

[Effect of the Invention] As described above, according to the present invention, the dispersibility of particles is excellent, the number of coarse projections on the surface is extremely small, the slipperiness is excellent, and the winding property and the wear resistance are good. Ethylene-2,6
-A polyester film containing naphthalate as a main repeating unit is obtained, which is extremely significant industrially.

[Brief description of drawings]

FIG. 1 is a diagram showing a running system for evaluating wear resistance,
(I) is a 6 mmφ hard chrome fixing pin, (II) is a tension meter, and θ is 130 °.

Claims (1)

[Claims] 1. A polyester film containing ethylene-2,6-naphthalate as a main repeating unit, which is obtained by a hydrolysis reaction and a condensation reaction of an alkoxysilane and is substantially amorphous and has an average particle size of 0.01 to 3.0 μm. And containing 0.001 to 5% by weight of spherical silica fine particles whose particle size distribution defined in the text satisfies the following formula (I), and adding 0.3 to 0.9 times mol of the phosphorus compound of the metal contained in the polyester. The specific resistance when melted is 5 × 10 ⁸ Ω ・ c
A polyester film having a size of m or less and a number of coarse projections defined in the text of 7/25 cm ² or less. 1.1 ≦ [d10 / d90] ≦ 2.7 (I) ([d10 / d90] in the above formula represents the ratio of the particle size when the cumulative number of particles is 90% to the particle size when the cumulative number is 10%. )]