JP2000007798A - Biaxially oriented polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide films having uniform surfaces, excellent in traveling properties, abrasion resistance and clarity and applicable to various uses such as graphic arts, displays, packaging, transfer marks, magnetic recording media and electrical parts such as condensers. SOLUTION: Desired biaxially oriented films are obtained by biaxially orienting a polyester containing 0.001-3.0 wt.% porous spherical silica particles having an average particle diameter of 0.3-15 μm, a spherical ratio, defined by equation I: spherical ratio = projected area of particle/area corresponding to circle of maximum diameter at projected plane of particle, of 0.90-1.0 and a particle size distribution value, defined by equation II: particle size distribution value = d10/d90 (wherein d10 and d90 are particle diameters (μm) corresponding to 10% and 90% of the entire volume of particles by measuring the integrated volume of particle groups from the side of greater particles, respectively, of 1.2-2.5, and the degree of deformation of the porous spherical silica particle is 1.2-5.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester film having a relatively uniform surface with few coarse projections and excellent in transparency, flatness, running properties and abrasion resistance.

[0002]

2. Description of the Related Art Polyester films typified by polyethylene terephthalate have excellent physical and chemical properties and, due to their excellent transparency, have been awarded for use in graphic arts, displays and packaging. It is also widely used in fields such as base films for magnetic recording media and capacitor derivatives.

However, in order to produce a film that makes full use of its transparency, runnability and abrasion resistance, it is necessary to improve the processability in the production process, the post-processing steps such as coating and vapor deposition, or the production of the product itself. Although the running property of the film is particularly required in terms of handleability, this has not always been sufficiently achieved in the past. This is because
In many cases, this was caused by friction and abrasion caused by the high-speed contact between the film and the substrate.

In general, it has been found that in order to improve the running properties and abrasion characteristics of a film, it is only necessary to roughen the film surface appropriately. In order to achieve this, a method in which fine particles are present in the raw polyester has been adopted, and some of them have been put to practical use.However, it has not always been successful to satisfy these characteristics to a high degree. Absent.
For example, when so-called precipitated particles from a catalyst residue or the like at the time of polyester production are used as the fine particles, the fine particles are easily broken by stretching, so that the running property and abrasion resistance are inferior, and it is difficult to recycle. In addition, when inactive inorganic compound particles are added to polyester such as kaolin, silicon oxide, titanium dioxide, calcium phosphate, etc., the particles are not broken or deformed by stretching, and give relatively steep projections, so that running is performed. Although the properties are improved, such particles have poor affinity for polyester, so voids are generated around the particles at the time of stretching, the transparency is remarkably reduced, the particles are easily detached from the film surface, and the white powdery substance is removed. Phenomenon such as generation occurs.

As one of the addition methods, a method using silica particles having a relatively good affinity for polyester (for example, a method described in JP-A-56-42629) is known. The film is easily deformed and it is difficult to form steep protrusions on the film surface, so that the running property may not be sufficiently satisfied. Further, the silica particles are massive and have a very wide particle size distribution, and when formed into a film, many coarse projections are present on the film surface, and the flatness and transparency of the film are reduced.

In order to overcome this trade-off phenomenon, it has recently been proposed to use inorganic particles having a sharp particle size distribution. For example, JP-A-62-207356 discloses monodispersed spherical silicon oxide particles. However, since the particles have poor affinity for polyester, voids may be generated around the particles depending on the stretching conditions, which may cause a decrease in transparency or dropping of the particles.
As described above, a polyester film having a high degree of transparency, flatness, running property and abrasion resistance and having other necessary properties has not been obtained so far.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to solve the problems which have a uniform surface, excellent running properties, abrasion resistance and transparency, graphic arts and displays. , For packaging, for transfer marks,
Photoengraving, magnetic recording media, electrical use for capacitors, etc.
It is to provide a film applicable to various uses.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above problems, and as a result, have found that a film containing specific silica particles in a specific amount can easily solve the above problems. Thus, the present invention has been completed.
That is, the gist of the present invention is that the average particle size is 0.3 to 15 μm.
m, 0.001-3.0 weight of porous spherical silica particles having a spherical ratio defined by the following formula of 0.90-1.0 and a particle size distribution defined by the following formula of 1.2-2.5. % Containing polyester biaxially stretched film,
The biaxially oriented polyester film is characterized in that the degree of deformation of the porous spherical silica particles in the film is 1.2 to 5.0.

[0009]

## EQU2 ## Spherical ratio = Projected area of particle / Equivalent area of circle of maximum diameter on particle projected plane Particle size distribution value = d ₁₀ / d ₉₀ (where d ₁₀ and d ₉₀ are integrated of particle group) The volume is measured from the large particle side, and the particle size (μm) corresponding to 10% and 90% of the total volume is shown, respectively)

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polyester in the present invention refers to a polyester obtained using terephthalic acid or an ester thereof and ethylene glycol as main starting materials, but may contain other third components.

In this case, as the dicarboxylic acid component, for example, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, terephthalic acid, adipic acid, sebacic acid, and oxycarboxylic acid component such as p-oxyethoxybenzoic acid One or more types can be used. As the glycol component, one or more of ethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like can be used.

In any case, the polyester used in the present invention is preferably a polyester having an ethylene terephthalate unit in which at least 80% of the repeating structural units are present. Further, the polyester used in the present invention may contain optional additives such as a heat stabilizer, an antiblocking agent, an antioxidant, a coloring agent, an antistatic agent, and an ultraviolet absorber.

The biaxially oriented polyester film of the present invention refers to a polyester film using such a polyester as a starting material, and any known method can be used for producing the polyester film, which satisfies the constitutional requirements of the present invention. As long as it is not particularly limited to the following examples. In obtaining the film of the present invention, the polyester is supplied to a known melt extruder represented by an extruder, and is heated to a temperature equal to or higher than the melting point of the polyester to be melted. Next, the melted polyester is extruded from a slit-shaped die and rapidly cooled and solidified on a rotary cooling drum so as to have a temperature equal to or lower than a glass transition temperature, thereby obtaining a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed.

Preferably, the unstretched sheet is stretched in the longitudinal direction by 7 mm.
Stretching 2 to 6 times at 0 to 145 ° C to make a longitudinally uniaxially stretched film, then stretching at 90 to 160 ° C in the transverse direction 2 to 6 times, and performing heat treatment at 150 to 250 ° C for 1 to 600 seconds Is preferred. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the outlet of the heat treatment is preferable. Further, re-longitudinal stretching and re-lateral stretching can be added as necessary.

The greatest feature of the present invention resides in the use of porous spherical silica particles which can be appropriately deformed by stretching. Inorganic particles that are commonly used as additives for polyester do not deform themselves even if a strong stress is applied during stretching, and voids are formed around the particles. When the voids are formed, when the film surface is worn, the particles are easily separated from the film starting from there.

However, the present inventor has found that when porous spherical silica particles which are relatively familiar with polyester, have stretch following properties, and have a specific degree of deformation in a film are used. It was found that the film had little voids around the particles, and was extremely excellent in running property and abrasion resistance of the film. In addition, the deformation degree of the particles referred to in the present invention refers to a ratio between the maximum diameter and the minimum diameter of the particles existing in the film (detailed definition will be described later).

In order to obtain particles having a specific degree of deformation in a film from, for example, spherical particles before stretching,
It requires an appropriate combination of the ease of deformation of the particles themselves and the stretching conditions. That is, in the case of particles that are relatively easily deformable, the degree of deformation becomes large even under a relatively high temperature, low magnification and gentle stretching condition. Conversely, in the case of particles that are relatively difficult to deform, it is necessary to apply a strong stretching stress in order to obtain the specific deformation degree of the present invention.

As a method for producing such particles, a method called a wet method, for example, a reaction between sodium silicate and a calcium salt such as calcium chloride is first performed to form calcium silicate and then decomposed with a mineral acid or carbon dioxide gas. Is the way. Silica particles obtained by the wet method are usually 100 to 7
Although it is a porous silica particle having a specific surface area of about 00 m ² / g, its shape is indefinite and its particle size distribution is extremely wide and cannot reach a desired particle size distribution.

The inventors of the present invention select the production conditions such as the coexisting ions of the system and the reaction temperature in the method of synthesizing the wet-processed silica, so that the spherical particles have a sharp particle size distribution. It has been found that porous silica particles which are easily deformable can be produced. In any case, in the present invention, the particle size ratio before stretching is 0.9 to 1.0.
By applying a stretching stress to the porous spherical silica particles having a degree of deformation of 1.2 to 5.0, preferably 1.3.
To 4.0, more preferably 1.3 to 3.0. If the degree of deformation is less than 1.2, voids are generated around the particles, and the particles easily fall off the film, which is not preferable. On the other hand, when the degree of deformation exceeds 5.0, the ability to form protrusions becomes poor, and the runnability becomes poor.

The average particle size of the porous spherical silica particles used in the present invention is 0.3 to 15 μm, preferably 0.5 to 10 μm.
m. If the average particle size is less than 0.3 μm, the running property and abrasion resistance of the film become insufficient, which is not preferable. On the other hand, if the average particle size exceeds 15 μm, the surface roughness of the film becomes too large, and the flatness is impaired, which is not preferable.

The amount of the porous spherical silica particles used in the present invention is 0.001 to 3% by weight, preferably 0.005 to 5% by weight.
2% by weight. If the amount is less than 0.001% by weight,
It is not preferable because the running property and abrasion resistance of the film become insufficient. On the other hand, if the amount is more than 5% by weight, the surface roughness becomes too large and the flatness is impaired, which is not preferable.

The particle shape of the porous spherical silica particles used in the present invention is preferably as close to spherical as possible from the viewpoint of film running properties, and the spherical ratio is 0.90 to 1.0, preferably 0.9 to 1.0.
It is 3 to 1.0, more preferably 0.96 to 1.0. If the sphere ratio is less than 0.9, the running property becomes inferior, which is not preferable. The particle size distribution value of the porous spherical silica particles used in the present invention is 1.2 to 2.5, preferably 1.5 to 2.5.
2.3, more preferably 1.6 to 2.0. If the particle size distribution value is less than 1.2, it is not preferable because the film may be disturbed when wound up into a roll at the time of film production or grain marks may be generated. On the other hand, if the particle size distribution value exceeds 2.5, coarse particles are mixed and planarity is impaired, which is not preferable.

Further, the porous spherical silica used in the present invention
The specific surface area of the particles is 100-600m ^Two / G, preferably
300-600m^Two / G, more preferably 400 to 6
00m^Two / G. Specific surface area is 100m^Two / G
Loses the porosity of the particles and increases the affinity for polyester
And voids are formed around the particles during stretching,
It is not preferable because the particles easily fall or the particles fall off. Ma
The specific surface area is 600m ^Two / G is more than polyester
Agglomeration of particles occurs during the manufacturing process of
It is not preferable because the flatness is impaired.

As described above, in the present invention, the desired effect can be obtained only by using certain silica particles. However, within the range not impairing the gist of the present invention, the purpose of further improving the film properties is as follows. For example, one or more other particles may be used in combination.

As one of such particles, precipitated particles can be mentioned. The term “precipitated particles” as used herein refers to, for example, those that precipitate in a reaction system by polymerizing a system using an alkali metal or alkaline earth metal compound as a transesterification catalyst by a conventional method. Further, precipitation may be carried out by adding terephthalic acid during the transesterification reaction or the polycondensation reaction. In these cases, one or more phosphorus compounds such as phosphoric acid, trimethyl phosphate, triethyl phosphate, tributyl phosphate, acidic ethyl phosphate, phosphorous acid, trimethyl phosphite, triethyl phosphite, tributyl phosphite, etc. It may be present. In addition, even in the case of undergoing an esterification step, the inert substance particles can be precipitated by these methods. For example, an alkali metal or alkaline earth metal compound is present before or after the end of the esterification reaction, and the polymerization reaction is performed in the presence or absence of a phosphorus compound. In any case, the fine precipitate compound formed during the polyester formation reaction in the present invention contains one or more elements such as calcium, lithium, antimony, and phosphorus.

As another example of the particles, so-called additive particles can be mentioned. The term “added particles” refers to particles added from the outside in the polyester production process. Specifically, kaolin, talc, carbon, molybdenum sulfide, gypsum, rock salt, aluminum oxide, barium sulfate, lithium fluoride, calcium fluoride, zeolite , Calcium phosphate, silicon dioxide, titanium dioxide and the like.

When the average particle size of the particles used in the present invention is larger than that of the porous spherical silica particles used in the present invention, the weight is equal to or less than the weight of the silica particles, preferably 0.005 to 0.05 times. , More preferably 0.01
Select from the range of ~ 0.3 times the weight. Conversely, when the particle size of the particles used together is smaller, the weight may be equal to or more than the weight of the silica particles, for example, 1 to 100 times the weight.

In the present invention, two porous spherical silica particles having different average particle sizes satisfying the above-mentioned particle characteristics are used.
More than one species may be used. The method for blending the porous spherical silica particles used in the present invention with the polyester as a film-forming raw material is not particularly limited, and a known method can be employed. For example, the particles and the polyester chips can be directly blended, but in particular, as an ethylene glycol slurry dispersed in ethylene glycol as a raw material of the polyester, at any stage of the polyester production process, preferably an esterification or transesterification reaction. After the completion, it is preferable to add the polycondensation at a stage before the start of the polycondensation reaction to perform the polycondensation reaction.

The dispersion slurry of the porous spherical silica particles used in the present invention can be prepared by a known method. For example, the dispersion can be adjusted using a high-speed stirrer having a plurality of shearing blades in which particles and ethylene glycol are arranged in parallel with the rotation direction of the stirring blades, a homomixer, an ultrasonic disperser, or the like. The dispersion slurry is desirably filtered with a filter of 1000 mesh or more in order to remove coarse particles and undispersed aggregated particles in the slurry.

[0030]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the invention. The methods for measuring physical properties used in the present invention are shown below. In the examples, “parts” and “%” are “parts by weight” and “% by weight”, respectively.
Means

(1) Average Particle Size and Particle Size Distribution Values The particle size was measured by a photographic method using an electron microscope before the particles were added to the polyester and converted into equivalent spheres. Particle size distribution is about 1
The particle size of 000 particles was measured, and the volume was integrated from the large particle side. Relative to the total volume, and the particle size of the time 10% and d _10, 9
The particle size of the time 0% exhibited a sharp particle size distribution by the value of the ratio (d ₁₀ / d ₉₀₎ as d _90. The closer this value is to 1, the sharper the image. The average particle size is represented by d ₅₀ (μm). (2) Spherical ratio The projected area of about 1000 particles before addition to the polyester and the area equivalent to the circle of the largest diameter on the projected surface were determined by a photographic method using an electron microscope, and the spherical ratio was calculated by the following equation.

[0032]

## EQU3 ## Spherical ratio = projected area of particle / area equivalent to circle of maximum diameter on particle projected surface

(3) Specific surface area The particles before addition to the polyester were measured by a nitrogen adsorption / desorption method using a fully automatic surface measuring device (manufactured by Carlo Elba). (4) Deformation A small piece of film was fixed and molded with an epoxy resin, then cut with a microtome, and a cross section in the longitudinal direction of the film was observed. For about 100 particles existing within 5 μm from the cross section of the film, the maximum diameter and the minimum diameter were determined for each particle, and the degree of deformation was calculated by the following equation.

[0034]

Degree of deformation = maximum diameter of particle / minimum diameter of particle

(5) Intrinsic viscosity 1 g of the polymer was mixed with phenol / tetrachloroethane = 50.
30/50 (weight ratio) in 100 ml of a mixed solvent.
It was measured at 0 ° C. (6) Transparency In accordance with JIS-K61714, the film haze was measured with a spectroscopic turbidimeter NDH-20D manufactured by Nippon Denshoku Industries. (7) Runnability On a smooth glass plate, two films cut to a width of 15 mm and a length of 150 mm are overlapped with each other, and a rubber plate is placed thereon, and the contact pressure of the two films is set to 2 g / cm ² , and 20 m is set.
Measure the frictional force by sliding the films at m / min.
The coefficient of friction at the point of sliding by m was determined as the dynamic friction coefficient.
The measurement was performed in an atmosphere at a temperature of 23 ° C. ± 1 ° C. and a humidity of 50% ± 5%.

(8) Winding Characteristics A film manufactured at a line speed of about 170 m / min on a paper tube having a diameter of 15 cm was observed at a winding end of 6000 m and classified into the following three ranks.

[0037]

[Table 1] Ａ A: The end faces are all aligned B: The end faces are almost aligned and practically usable C: Some of the end faces are not aligned Yes D: A considerable part of the end face is irregular.

(9) Wear Characteristics Wear characteristics were evaluated based on the amount of white powder generated. That is, the film was run over 1000 m while being in contact with a hard chrome fixing pin having a diameter of 6 mm, and the amount of abrasion white powder adhering to the fixing pin was visually evaluated and evaluated according to the following criteria. The film speed was 13 m / min and the tension was about 200
g, the winding angle around the fixing pin was 135 °.

[0039]

[Table 2] Rank A: No adhesion at all Rank B: Small amount of adhesion Rank C: Small amount (more than rank B) ) Adhesion Rank D: Extremely large adhesion 多 く

(10) Number of Coarse Protrusions 10 mg of a sample was weighed, sandwiched between 18 × 18 mm cover glasses, and pressed at 280 to 290 ° C. to obtain a diameter of about 10 mm.
Was prepared, and this film was prepared using a phase contrast microscope (1).
(× 00)), particles having a maximum length of 10 μm or more were counted, and the number of coarse projections was determined. (11) Comprehensive evaluation

[0041]

[Table 3] ───────────────────────────────── ○: Excellent, high industrial value △: Poor industrial value due to some defects in manufacturing and film properties. ×: Low industrial value due to large defects in manufacturing and film properties. ──────────────────

Example 1 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were placed in a reactor, heated and heated, and methanol was distilled off to carry out a transesterification reaction. The temperature was raised to 230 ° C. over 4 hours, and the transesterification reaction was substantially completed. Next, the average particle size is 2.05 μm, and the spherical ratio is 0.9.
8, 0.1 part of porous spherical silica particles having a particle size distribution of 1.83 and a specific surface area of 520 m ² / g are added as an ethylene glycol slurry, and 0.04 part of ethylene acid phosphate and 0.04 part of antimony trioxide are further added. Was added and a polycondensation reaction was performed for 4 hours to obtain polyethylene terephthalate.

The intrinsic viscosity of the obtained polyester is 0.6.
3. Observation of the inside with a microscope confirmed that the particles were uniformly dispersed. Next, a biaxially oriented polyester film was produced using the obtained polyester. That is, the polyester is extruded into a sheet from an extruder at a temperature of 295 ° C.
A 73 μm amorphous sheet was obtained. Next, the obtained amorphous sheet is stretched 3.6 times at 90 ° C. in the sheet flow direction, and then 4.0 ° at 110 ° C. in a direction orthogonal to the sheet flow.
Stretched twice and heat-treated at 230 ° C for 3 seconds to a thickness of 12μ.
m was obtained.

Example 2 In Example 1, the thickness of the amorphous sheet was 123 μm, and the amorphous sheet was subjected to 3.2 at 90 ° C. in the sheet flow direction.
After stretching twice, 110 ° C in the direction perpendicular to the sheet flow
A biaxially stretched film was obtained in the same manner as in Example 1 except that the film was stretched 3.2 times in Step 1.

Comparative Examples 1 to 8 and Examples 3 to 4 Biaxially stretched films were obtained in the same manner as in Example 1 except that the particles to be incorporated in the film were changed as shown in Tables 1 to 3 below. The aluminum oxide used in Example 2 had a delta-type crystal form obtained by a pyrolysis method, and the precipitated particles of Example 3 contained 1 element of calcium, lithium, and phosphorus, respectively. It is a particle containing at least% by weight. As described above, the obtained results are summarized in Tables 1 to 5 below.
3 is shown.

[0046]

[Table 4]

[0047]

[Table 5]

[0048]

[Table 6]

[0049]

The film of the present invention has a uniform surface,
Excellent in runnability, abrasion resistance and transparency, and can be applied to various uses such as graphic arts, display, packaging, transfer mark, photoengraving, magnetic recording media, capacitors, etc., and its industrial value is high. .

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) B29K 67:00 B29L 7:00 F term (Reference) 4F071 AA43 AB26 AD02 AD03 AD06 AF22 AF27 AF28 AF30 AH14 BA01 BB06 BB08 BC01 4F210 AA24 AB17 AB26 AC01 AC04 AG01 AH38 QA02 QA03 QC06 QD13 QG01 QG18 4J002 CF031 CF051 CF081 DJ016 FD010 FD016

Claims (1)

[Claims] 1. A porous material having an average particle size of 0.3 to 15 μm, a sphericity ratio defined by the following formula of 0.90 to 1.0, and a particle size distribution defined by the following formula of 1.2 to 2.5. Is a film obtained by biaxially stretching a polyester containing 0.001 to 3.0% by weight of porous spherical silica particles, wherein the degree of deformation of the porous spherical silica particles in the film is 1.2 to 5.0.
A biaxially oriented polyester film, characterized in that: ## EQU1 ## Spherical ratio = projected area of particle / equivalent area of circle of maximum diameter on particle projected plane Particle size distribution value = d ₁₀ / d ₉₀ (where d ₁₀ and d ₉₀ are integrated of particle groups) The volume is measured from the large particle side, and the particle size (μm) corresponding to 10% and 90% of the total volume is shown, respectively)