JPH03234523A - Oriented polyester film - Google Patents

Abstract

PURPOSE:To obtain an oriented polyester film which is smooth and superior in wear resistance and slidability, by a method wherein inactive inorganic particles obtained by modifying the surfaces of the inactive inorganic particles, whose mean particle diameter is specified, with a specific multifunctional silane coupling agent are contained at a specific ratio. CONSTITUTION:Inactive inorganic particles obtained by modifying the surfaces of the inactive inorganic particles, whose mean particle diameter is 0.1-2.0mum, by a multifunctional silane coupling agent shown by a formula I are contained at the ratio of 0.01-0.50wt.%. In the formula I, X and Y show an organic group possessing a functional group capable of performing cavalent bonding with polyester oligomer which can form polyester and kinds of them may be the same as each other or different from each other. Hereupon, an area ratio (%)of the inactive inorganic particles to a circumscribed circle defined by a formula II is at least 60% and it is preferable that a degree of dispersion of a particle diameter defined by a formula III is 30% or less. With this construction, a polyester film which is smooth, superior in slidability and wear resistance and extremely free from generation of white powder or coarse particles which are the cause of generation of defects such as dropouts can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an oriented polyester film, and particularly to an oriented polyester film that is smooth and has excellent abrasion resistance and slipperiness.

(Prior Art) Polyesters represented by polyethylene terephthalate generally have excellent physical and chemical properties. Therefore, in addition to being used in various fibers and molded products, polyester is also used in a wide variety of applications, including magnetic tape, floppy disks, photography, condensers, packaging, X-ray film, microfilm, and other films. . When polyester is used in these films, the slipperiness and abrasion resistance of the polyester depend on the workability of the film manufacturing process and processing process in each application, as well as the quality of the products in which these films are used. This is a major factor that determines whether quality is good or bad.

In particular, when used as a magnetic tape in which a magnetic material is coated on the surface of a polyester film, the following problems will occur if the slipperiness and abrasion resistance of polyester are insufficient.

Since the friction between the coating roll used for applying the magnetic material and the film surface increases, the film is extremely abraded, and wrinkles and scratches are likely to occur on the film surface. Furthermore, if the film feeding speed in the coating and calendering processes is increased in order to increase productivity, the film surface is more likely to be scraped, and when the resulting magnetic tape is used, magnetic recording signal dropouts, or dropouts, are more likely to occur. Become. In addition, if the film's slipperiness and abrasion resistance are insufficient, the film can be slit (cut vertically) to
Inconveniences occur even after processing into video or computer tapes. In other words, if you use a processed tape to pull it out from a reel, cassette, etc., wind it up, or perform other operations, the tape may be worn out, scratched, or distorted due to friction between the guide and the playback head. This may occur. Furthermore, resin powder generated due to tape abrasion, scraping, etc. adheres to the film surface, making dropouts more likely to occur.

Various methods have been proposed to improve the slip properties and abrasion resistance of films. For example, a method is conventionally known in which the contact area between the film and a guide roll or the like is reduced by providing unevenness to the film surface. For example, an internal particle precipitation method (Japanese Patent Publication No. 49-1323
4 and Japanese Patent Publication No. 50-6493, etc.), and an external particle addition method (JP-A-51-1999) in which inorganic particles insoluble in the polymer used for the film are added during polymerization or before melt extrusion of the polymer. Publication No. 34272, Japanese Patent Application Publication No. 1978-78953, Japanese Patent Publication No. 55-2
225 Publication and Special Publication No. 55-41648, etc.)
It has been known.

The above internal particle precipitation method has the advantage that the particles to be precipitated have good affinity with the polyester, but it is difficult to control the amount and particle size of the particles used. Therefore, it is not possible to precisely adjust the surface morphology of the film,
It had the disadvantage of insufficient slipperiness. on the other hand,
In the external particle addition method, designing the surface morphology of the film is easier than in the internal particle precipitation method. However, it is difficult to satisfy all of the requirements of surface smoothness, slipperiness, abrasion resistance, and running durability due to the inclusion of coarse particles, secondary agglomeration of particles, poor affinity with polyester, etc. Ta.

Generally, the larger the particle size of the particles in the raw material polymer, the better the slipperiness. However, when used in precision applications such as magnetic tapes, if large particles are mixed in, the particles themselves can cause dropouts and the like.

The occurrence of dropout leads to deterioration of electromagnetic conversion characteristics. Therefore, when used for precision applications, the unevenness on the film surface needs to be as fine as possible.

Thus, when used as a film for precision applications, it is necessary to satisfy two contradictory characteristics.

As a means to satisfy these two characteristics, that is, to improve the slipperiness and to make the surface unevenness finer, inert inorganic particles of different particle sizes (large particle size particles and small particle size particles) are used. ) has been proposed.
-78953, Japanese Patent Publication No. 55-40929, USP 3821156, USP 38848
No. 70, etc.). However, since the large particles used in these methods have a relatively large particle size, the surface smoothness is insufficient and coarse protrusions are likely to be formed on the film surface. The formed coarse protrusions cause dropouts, and furthermore, since inert inorganic particles generally have poor affinity with polyester, when blended with polyester, the polyester polymer becomes poorly dispersed in the matrix. Therefore, agglomerates with large particle sizes are formed, which causes dropouts and the like. Even polymer polymer) I
Even if inorganic particles with excellent dispersibility are used in J-socks, the affinity of inorganic particles for polyester is weak, so polyester to which inorganic particles are added is difficult to use when biaxially orienting an unstretched film of the polyester. When an external force is applied to the film, it has the disadvantage that voids are formed, resulting in a decrease in transparency and a decrease in the abrasion resistance of the film surface.

In order to improve the affinity between inert inorganic particles and polyester, in Japanese Patent Publication No. 58-23414, etc., inert inorganic particles are produced by a coupling reaction between a silane compound or a titanate compound, etc., and inert inorganic particles. A method of surface treatment has been proposed.

However, the adhesion of the interface between the inorganic particles and the polymer surface-treated by this method is still not sufficient, and no satisfactory effect has been achieved in terms of improving the abrasion resistance of the film.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems, and its purpose is to provide a smooth, wear-resistant and The purpose of the present invention is to provide a high-quality oriented polyester film with excellent slip properties.

(Means for Solving the Problems) The oriented polyester film of the present invention has an average particle size of 0.
The surface of inert inorganic particles with a diameter of 1 to 2.0 microns is modified with a polyfunctional silane coupling agent whose general formula is represented by the following formula (1). Contained in a proportion of 50% by weight: X N (CH2)3-3l-(OC)+3)-...
” (1) (In the formula, X and Y represent an organic group having a functional group capable of covalent bonding with the polyester oligomer capable of forming the polyester, and the types may be the same or different.) Preferred implementation In the embodiment, the inert inorganic particles have an area ratio (%) of 60% or more with respect to a circumscribed circle defined by the following formula (2), and have a particle size variation degree defined by the following formula (2). is 30% or less.

The polyester used in the present invention is a crystalline polyester whose main repeating unit is ethylene terephthalate. The content of ethylene terephthalate is not particularly limited, but is preferably 80 mol% or more. Other copolymer components contained in the polyester of the present invention include:
The following dicarboxylic acid components and glycol components are mentioned. As the dicarboxylic acid component, isophthalic acid, p-β
Oxyethoxybenzoic acid, 2,6-naphthalene dicarboxylic acid, 4.4°-dicarboxyldiphenyl, 4,4°dicarboxylbenzophenone, bis(4-carboxylphenyl)ethas, adipic acid, sebacic acid, 5-sodium sulfoisophthal acid, cyclohexane-1,4
-Dicarboxylic acids, etc. Glycol components include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexane dimetatool, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like. In addition, oxycarboxylic acid components such as p-oxybenzoic acid may also be used. Further, as other copolymer components, compounds containing small amounts of amide bonds, urethane bonds, ether bonds, carbonate bonds, etc. may be included.

As methods for producing such polyesters, either the so-called transesterification method in which dimethyl ester of aromatic dicarboxylic acid and glycol are transesterified, or the direct polymerization method in which aromatic dicarboxylic acid and glycol are directly reacted can be applied. You can. Further, both batch-type and continuous-type production methods can be applied. In the above transesterification method, the transesterification catalyst is not particularly limited. Conventionally known transesterification catalysts can be used. In the direct polymerization method, amines and quaternary polymers are used as inhibitors to suppress the by-product of diethylene glycol
Grade ammonium salts and the like may also be used.

The average particle size of the inert inorganic particles used in the present invention is 0.1 to 2.
．． It is 0 μm. Preferably it is 0.2 to 1.5 μm, more preferably 0.3 to 1.2 μm.

If the average particle size is less than 0.1 μm, the resulting film will have insufficient slipperiness. When the average particle size exceeds 2.0 μm, surface smoothness becomes insufficient. Particularly when used for magnetic tape, the particles cause dropouts and the like. The content of such inert inorganic particles is 0.01 to 0.50% by weight based on the total weight of the film. Preferably 0.05 to 0.40% by weight, particularly preferably 0.1
It is 0 to 0.30% by weight. If it is less than 0.01% by weight, slipperiness is insufficient. If it exceeds 0.50% by weight, the surface smoothness will be insufficient. In particular, when used for magnetic tape, the number of coarse particles that cause dropouts and the like increases.

There are no particular limitations on the degree of uniformity of the particle shape and particle size of the inert inorganic particles. However, uniformity of particle shape and particle size can be one of the factors for improving slipperiness, surface smoothness, etc. Therefore, regarding the particle shape, considering the necessity of precisely adjusting the surface morphology of the film, evaluation using the conventionally used volume shape coefficient alone is insufficient. In the present invention, in order to quantitatively understand the particle shape, the particle shape is defined as the ratio of the projected cross-sectional area of the particle to the area of a circle circumscribing the projected diagram of the particle, that is, the area ratio (%) to the circumscribed circle. (Equation (2)).

The area ratio with respect to the circumscribed circle defined by formula (2) is 100%
The closer it gets to , the more spherical the particle shape becomes. The area ratio of the inert inorganic particles used in the present invention to the circumscribed circle is preferably 60% or more, more preferably 65% or more, particularly preferably 70% or more. The area ratio to the circumscribed circle is 60
A film using less than % of inert inorganic particles is not preferable because the slipperiness becomes insufficient. In addition, regarding the uniformity of particle size, the inventors have found through studies that the closer the particle size distribution is to monodisperse, the more uniform the height and shape of the protrusions formed on the film surface will be. . Based on this knowledge, the uniformity of particle size is defined by the ratio of the standard deviation of individual particle sizes to the average particle size, that is, the degree of variation in particle size (Equation (3)).

The degree of variation in particle size of the inert inorganic particles defined by formula (3) is preferably 30% or less, more preferably 25% or less.
% or less, particularly preferably 20% or less.

When the degree of variation in particle size exceeds 30%, the shape of the protrusions on the film surface becomes irregular.

As described above, by using inorganic particles whose particle shape is close to spherical and whose particle size is relatively uniform, the shape and height of the protrusions can be precisely adjusted. Therefore, it is possible to satisfy the contradictory characteristics of being smooth and having excellent slipperiness.

In the present invention, the general formula is (1) so that such inert inorganic particles have excellent adhesion to polyester.
The surface of the inert inorganic particles is modified with a polyfunctional silane coupling agent represented by the formula: X-N-(CH2), -5
i-(OCH3)3"" (1) In the formula, X and Y represent an organic group having a functional group capable of covalent bonding with a polyester oligomer capable of forming a polyester. Specifically, organic groups having an epoxy group, carboxyl group, alkoxycarbonyl group, amino group, etc. at the end can be mentioned.

The types of X and Y may be the same or different. The polyfunctional silane coupling agent of formula (1) has an atomic group (hydroxyl group) that chemically reacts with inert inorganic particles through hydrolysis. As described above, the silane coupling agent used in the present invention has two functional groups (X and Y) in one molecule that can bond to polyester or its oligomer. Therefore, the number of bonding sites between the coupling agent and the polyester increases compared to when a conventional silane coupling agent having only one such functional group in one molecule is used. This improves the adhesion at the interface between the inert inorganic particles and the polyester via the coupling agent. As a result, the abrasion resistance of the resulting film is highly improved.

The amount of the polyfunctional silane coupling agent added is preferably 0.01 to 5% by weight, more preferably 0.5 to 2% by weight, based on the weight of the inert inorganic particles.

Methods for modifying the surface of inert inorganic particles with a polyfunctional silane coupling agent include a wet treatment method and a dry treatment method. Wet processing methods include a method in which inert inorganic particles are sufficiently dispersed in a dispersion medium such as water or ethylene glyol, the polyfunctional silane coupling agent is added and mixed, and then the dispersion medium is evaporated. The dry processing method includes spraying a solution of the polyfunctional silane coupling agent onto a fine powder of inert inorganic particles under high-speed stirring using a spray nozzle, and then drying the solution.
There is a so-called spray drying method. In the present invention, the modification method is not particularly limited.

If the inert inorganic particles meet the above conditions,
The type is not particularly limited. Inert inorganic particles having functional groups (for example, hydroxyl groups) such as spherical silica are preferred.

Inert inorganic particles that do not have functional groups on their particle surfaces, such as calcium carbonate particles and barium sulfate particles, can also be used. In this case, prior to surface treatment with a polyfunctional silane coupling agent, a known method (for example, JP-A-63
-258958 publication and JP-A-63-30403
8) If the pretreatment is performed, the effect will be noticeable. The above pretreatment is to treat the surface of the inert inorganic particles with a silane compound and/or a titanium compound to form a strong coating layer with a network structure.

Methods for adding inert inorganic particles whose surface has been modified with a polyfunctional silane coupling agent to polyester include adding the modified particles in the form of a slurry during polyester polymerization, and adding the modified particles to the polymer before extrusion. There is a way to knead it. As the solvent for the slurry of inert inorganic particles, it is preferable to use ethylene glycol alone, but other solvents such as water and alcohols may be mixed as long as the amount is 50% by weight or less. When dispersing inert inorganic particles into a slurry, the inert inorganic particles are uniformly dispersed so that they remain as original primary particles as much as possible without agglomeration. In particular, it is particularly preferable to substantially eliminate particles of 5 μm or more in the slurry from the viewpoint of reducing coarse protrusions. The method of dispersing the inert inorganic particles when preparing the slurry is not particularly limited. Any method such as a rotary high-speed stirring method, a high-pressure homogeneous dispersion method, an ultrasonic dispersion method, or a combination of these methods may be employed.

In addition, in order to obtain particles with a predetermined average particle size, crushing treatment,
Treatments such as classification treatment and filtration may be employed.

An unstretched film is produced by a suitable method such as an extrusion method using the polyester containing inert inorganic particles whose surface has been modified as described above. This is stretched appropriately depending on the purpose to obtain a -axially oriented film or a biaxially oriented film. Biaxially oriented films are particularly preferred.

(Example) Examples of the present invention will be described below. In Examples and Comparative Examples, all parts are by weight unless otherwise specified. The average particle diameter, area ratio and degree of dispersion with respect to the circumscribed circle of the fine particles used in the present invention are determined as follows (a) to (
It was determined by method C). Furthermore, the obtained films were evaluated using methods (d) to (odor).

(a) Average particle size of fine particles Inert inorganic particles are sufficiently dispersed in a slurry using ethylene glycol as a solvent. The particle size distribution in the obtained slurry was measured using a light transmission type centrifugal sedimentation type particle size distribution analyzer (S
^-CPa model manufactured by Shimadzu Corporation). The value at which the integrated value is 50% is defined as the average particle diameter.

(b) Area ratio with respect to the circumscribed circle The inert inorganic particles are observed and photographed using a scanning electron microscope (Hitachi Model S-510), and the images are enlarged and copied. Further tracing is performed and images corresponding to 200 particles are randomly filled in black.

From this trace image, the projected cross-sectional area of each particle is
The image analysis device is Luzex 500 manufactured by Reco Co., Ltd.)
Measure using. The area of a circle circumscribing those particles is calculated, and the area ratio is determined using equation (2).

(C) Grain size dispersion degree (b) Using the trace image obtained in (b) as an image analysis device (Luzex Model 500 manufactured by Reco Co., Ltd.), the horizontal direction Feere diameter is measured. Let the average value of the Feer diameter be the average particle diameter in equation (3). The degree of variation in particle diameter is calculated using the following formula.

(Space below) (d) Surface smoothness (TAR) of the film The film surface was measured using a stylus-type three-dimensional surface roughness meter (manufactured by Koita Research Institute, 5E-3).
AK) under the following measurement conditions over a measurement length of 1.

Needle radius: 2 μm Load: 30 mg Cutoff value: 0.25 Random measurement direction: Measurement data in the height direction is measured every 2 μm in the longitudinal direction of the film, with a quantization width of 0.00
It is imported into an external storage device at 312 μm.

A series of such measurements are carried out 150 times continuously at intervals of 2 μm in the transverse direction of the film, that is, over a width of 0.3 mm in the transverse direction of the film.

The measurement data in the height direction at each position (longitudinal direction, transverse direction) is h (i, J) Ci = 1 ~ 500, j =
1 to 150], the value obtained by calculating the following formula is μ
The value expressed in m units is TAR (Three Dimensional Average Roughness).

(e) Slip properties of films According to ASTM-D-1894-63, the coefficient of static friction between films is measured using a thread type slip tester under environmental conditions of 23° C. and 65% RH.

(f) Abrasion resistance A film slit to a width of 12.5 mm is brought into contact with a commercially available razor and run at a speed of 60 m/min. After running for 10 m, the amount of white powder adhering to the razor is evaluated by ranking it in three stages as follows.

○...There is almost no white powder generation.△...There is a lot of white powder generation.X...There is a lot of white powder generation. 28 between cover glasses
After melt pressing at 0°C and quenching, observation was made using a phase contrast microscope. Next, the image analysis device Luzex 500
(manufactured by Nippon Regulator), and in the obtained particle image, the number of particles with a maximum length of 5 μm or more (number per measurement area of 4.8 mm) is counted, and depending on the number of particles, the following Evaluate by ranking.

X ----- 51 pieces or more / 4.8mm "X~△・
...21-50 pieces/4.8mm ”△ ...1
1~20 pieces/4.8mm 2Δ~○---4~10
pcs/4.8mm 20...0~3 pcs/4.8
mm 2 Example 1 Using a continuous esterification reactor consisting of a two-stage complete mixing tank equipped with a stirring device, a condenser, a raw material inlet, and a product outlet, esterification was carried out in the first esterification reactor of the device. An ethylene glycol slurry of TPA with a molar ratio of ethylene glycol to terephthalic acid (TPA) in the iron system of 1.7 and containing 289 ppm of antimony trioxide per TP unit as an antimony atom is added to the system where the reaction product is present. Supplied continuously.

At the same time, an ethylene glycol solution of magnesium acetate tetrahydrate was supplied from a supply port different from the TPA ethylene glycol slurry supply port, with 1100 Mg atoms per polyester unit in the reaction product passing through the reaction vessel.
pp, and the reaction was carried out at normal pressure for an average residence time of 4.5 hours and at a temperature of 255°C.

This reaction product was continuously taken out of the system and supplied to the second esterification reactor. 0.5 parts by weight of ethylene glycol and an ethylene glycol solution of trimethyl phosphate based on the polyester unit in the reaction product passing through the second esterification reactor are 64 P atoms.
ppm, the ethylene glycol solution of sodium acetate is 10 ppm % as Na atoms, the area ratio with respect to the circumscribed circle is 95%, and the average particle size is 0.7 μm, the degree of variation in particle size is 10%, as shown in Table 1. Ethylene glycol slurry of spherical silica fine particles whose surface has been modified with a functional silane coupling agent (processing amount: 1.0% by weight based on the fine particles) becomes 0.10 weight% (as 5102 with respect to the produced polyester). They were continuously supplied from separate supply ports. Thereafter, the reaction was carried out at normal pressure for an average residence time of 5.0 hours and at a temperature of 260°C.

The obtained esterification reaction product is continuously supplied to a two-stage continuous polycondensation reactor equipped with a stirrer, a condenser, a raw material inlet, and a product outlet for polycondensation, and the intrinsic viscosity is 0. 620 polyester was obtained. The obtained polyester was melt-extruded at 290°C, stretched 3.5 times in the machine direction at 90°C and 3.5 times in the transverse direction at 130°C, and then heat-treated at 220°C to obtain a film with a thickness of 15 μm. Ta. The properties of this film are shown in Table 1.

The film obtained in this example was smooth, had excellent slipperiness and abrasion resistance, and contained extremely few coarse particles.

Comparative Examples 1 to 4 Comparative Examples 1 to 4 were carried out in the same manner as Example 1 except that the requirements shown below were outside the scope of the claims of the present invention.

Requirements outside the scope of claims of the present invention Comparative example 1: No surface modification of inert inorganic particles Comparative example 2 Types of functional groups of Nijiran coupling agent Comparative example 3 Comparative example of number of functional groups of Nijiran coupling agent 4: Degree of variation in particle size of inert inorganic particles The properties of the obtained film are shown in Table 1.

From Table 1, it can be seen that these films cannot satisfy all the characteristics of being smooth, having excellent slipperiness and abrasion resistance, and having a complementary and small number of coarse particles in the film.

Example 2 Synthetic calcium carbonate fine particles that had been tightly coated in advance with a network structure (reticular structure) mainly composed of polysiloxane bonds and then surface-modified with a polyfunctional silane coupling agent shown in Table 1 were placed in ethylene glycol. It was dispersed, classified and filtered. After the treatment, the area ratio of the synthetic calcium carbonate to the circumscribed circle was 77%, the degree of variation in particle size was 18%, and the average particle size was 0.86 μm. The same procedure as in Example 1 was carried out except that 0.25% by weight of the surface-treated synthetic calcium carbonate was used. Table 1 shows the film properties of the obtained film.

From Table 1, it can be seen that the film obtained in Example 2 has a smooth surface, good slipperiness, abrasion resistance, and the number of coarse particles, and is of high quality.

(Margin below) (Effects of the invention) The oriented polyester film of the present invention has a specific amount of inert inorganic particles added to the polyester film, and these inert inorganic particles are within a specific particle size range close to spherical monodisperse. The surface is modified with a specific polyfunctional silane coupling agent that has multiple functional groups capable of chemically bonding to the polyester matrix. As a result, it is possible to obtain a polyester film that is smooth, has excellent slipperiness and abrasion resistance, and has very little generation of white powder or coarse particles that cause defects such as dropouts.

that's all

Claims (1)

[Claims] 1. The surface of inert inorganic particles having an average particle size of 0.1 to 2.0 μm is modified with a polyfunctional silane coupling agent whose general formula is represented by the following formula (1). Inert inorganic modified particles from 0.1 to
An oriented polyester film containing 0.50% by weight. ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・(1) (In the formula, X and Y represent an organic group having a functional group capable of covalent bonding with a polyester oligomer capable of forming a polyester, and the types are They may be the same or different. 2. The inert inorganic particles have an area ratio (%) of 60% or more with respect to the circumscribed circle defined by the following formula (2), and are defined by the following formula (3). The oriented polyester film according to claim 1, wherein the degree of variation in particle size is 30% or less. Area ratio (%) with respect to a circumscribed circle = (projected cross-sectional area of particles / area of circle circumscribed to particles) x 100. ...(2) Degree of variation in particle size (%) = (standard deviation of particle size/average particle size) x 100... (3)