JPH08100110A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE: To prepare a biaxially oriented polyester film suitable for package, lithography, laminate and substrate for photography because of its excellence in transparency and slippage. CONSTITUTION: A polyester having ethylene terephthalate as a major structural units is blended with crused silica particles of 0.1-1.0μm average diameter in an amount of 0.001-0.1% to give a biaxially oriented polyester film of 25-300μm thickness, where the diameters of dispered silica particles therein are from 0.01 to 5.0μm and the proportion of the particles having than 1.0μm diameters is less than 20%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a biaxially stretched polyester film having excellent transparency and slipperiness. More specifically, it relates to a biaxially stretched polyester film whose main constituent unit is ethylene terephthalate, which is suitable for applications such as packaging, plate-making printing, laminating, and photographic support.

[0002]

2. Description of the Related Art Polyester, particularly polyethylene terephthalate (hereinafter referred to as PET), which has ethylene terephthalate as a main constituent unit, is used for molding fibers, films, sheets, etc. due to its excellent mechanical properties, thermal properties, chemical stability and the like. Widely used as a material.

A film obtained by biaxially stretching this polyester is excellent in various properties such as strength, but due to its good smoothness, squeaks occur when the films are stacked and are difficult to handle. Therefore, a method has been adopted in which fine particles are mainly mixed into the film to form irregularities on the surface to impart slipperiness. As such fine particles, inorganic compounds insoluble in polyester such as talc, silica, aluminum oxide, calcium carbonate, and carbon, and organic compounds such as crosslinked polymers are used, and for example, highly slippery is required. Many proposals have been made regarding the type of particles to be present, the particle size and the amount thereof, mainly for the use of the magnetic recording medium fill. However, when such particles are blended in the film, there is a problem that the transparency of the film is impaired due to voids generated around the particles directly or biaxially stretching the particles themselves. Especially in applications such as packaging, plate-making printing, laminating, and photographic support, the transparency of the film is a very important characteristic, and it is at a level where the trade-off characteristics of slipperiness and transparency can be sufficiently satisfied. It hasn't arrived yet.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a biaxially stretched polyester film having the above-mentioned problems, that is, high transparency and good sliding properties.

[0005]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors to solve the above-mentioned problems, a biaxially stretched film containing crushed silica having a specific particle size distribution in a specific amount of PET was found. The inventors have found that these characteristics are highly satisfied and have reached the present invention.

[0006] That is, the gist of the present invention is that a crushed silica particle having an average particle diameter of 0.1 to 1.0 µm is added to a polyester whose main constituent unit is ethylene terephthalate.
A biaxially stretched polyester film having a thickness of 25 to 300 μm, which is obtained by blending 01 to 0.1%, wherein the silica particles have a particle diameter distributed in a range of 0.01 to 5.0 μm, and have a particle size of 1.0 μm.
The biaxially stretched polyester film is characterized in that the proportion of particles of m or more is 20% or less of all silica particles. Further, the silica particles are preferably crushed quartz glass or crystalline crushed silica.

The polyester referred to in the present invention is a polyester whose main constituent unit is ethylene terephthalate, but components other than ethylene terephthalate may be copolymerized in the range of 10 mol% or less. Examples of the bifunctional carboxylic acid component that can be a copolymerization component include 2,6-naphthalenedicarboxylic acid, isophthalic acid, 5-
In addition to aromatic dicarboxylic acids such as sodium sulfoisophthalic acid, aliphatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, adipic acid, and sebacic acid and their ester-forming derivatives, trimellitic acid and pyromellitic acid are also included. Examples thereof include functional carboxylic acids or their ester-forming derivatives. Similarly, examples of the glycol component include diethylene glycol, butanediol, polyalkylene glycol having a molecular weight of 150 to 20,000, 1,4-cyclohexanedimethanol, and an ethylene oxide adduct of bisphenol A. Further, as the esterification reaction catalyst, transesterification reaction catalyst, and polycondensation reaction catalyst used in the production of polyester, titanium compounds, manganese compounds, zinc compounds, antimony compounds, germanium compounds, etc., which have been conventionally known, may be appropriately used. Depending on the purpose, other metal compounds, nitrogen-containing basic compounds, antioxidants,
Antistatic agents, ultraviolet absorbers, optical brighteners, dyes and the like may be used. Further, in the present invention, it can be carried out by a conventionally known ordinary method, and any of a batch type, a semi-batch type and a continuous type may be used, and a transesterification method or a direct esterification reaction method may be used.

The polyester film of the present invention means a biaxially oriented film using such polyester as a starting material. A known method can be used as a method for producing the film. For example, polyester is preliminarily dried and melt-extruded into a sheet at 270 ° C to 310 ° C, and then cooled and solidified at 40 to 70 ° C to form an amorphous sheet. It is obtained by stretching twice and then heat treating at 160 to 250 ° C. In addition, it may be annealed at a temperature not higher than the glass transition temperature of polyester. The thickness of the polyester film in the present invention is 25 μm to 300 μm.
μm, and particularly preferably 40 μm to 200 μm.

In the method of the present invention, crushable silica is used as a slipperiness-imparting agent for forming a film. However,
The particle size of this silica should be distributed within the range of 0.01 to 5.0 μm, and the average particle size should be 0.1 to 1.0 μm. In addition, in the particle size distribution, the proportion of particles having a particle size of 1.0 μm or more needs to be 20% or less of all silica particles. In order to make the crushed silica particles have the above-mentioned particle size distribution, a method of classifying crushed silica having a wide particle size distribution or mixing two or more kinds of crushed silica having a narrow particle size distribution may be adopted. .

The particle size of silica referred to in the present invention is an individual value obtained by expressing the particle size distribution obtained by the method described in Examples in terms of area, and the average particle size is the median size, that is, 50% of cumulative distribution curve of particle size expressed by area standard
The particle size corresponding to In the present invention, the particle size is 1.0
The proportion of particles having a size of μm or more needs to be 20% or less of the total silica particles, which means that the cumulative distribution curve expressed by area is 20% or less of 1.0 μm sieve particles.

Silica having a particle size of less than 0.01 μm has substantially no effect as a slipperiness-imparting agent when formed into a film, and merely causes haze. Although the effect is great from the viewpoint of imparting slipperiness, when a particle having such a large particle diameter is used, a large void is likely to be generated around the particle in the biaxially stretched film, resulting in high haze and impaired transparency. It becomes a thing. Further, if such silica having a large particle size is aggregated and exists in the film, it becomes a serious defect.

If particles having an average particle size of less than 0.1 μm are used, a large amount is required to secure the slip property, and as a result, the transparency of the film deteriorates. On the other hand, if the average particle size exceeds 1.0 μm or if the ratio of particles having a particle size of 1.0 μm or more exceeds 20%, haze due to the occurrence of voids is likely to occur, and the film is This may cause clogging of the filter used during melt film formation.

In the present invention, the above-mentioned silica particles are blended in a biaxially stretched polyester film in an amount of 0.001 to 0.1%. If the amount is less than 0.001%, the required slipperiness cannot be secured, and if the amount is more than 0.1%, the slipperiness becomes excessive and the transparency is impaired in the use of the present invention. The particle diameter of the crushable silica and the conditions for use as described above are for optimally balancing both the slip property and the transparency within the film thickness range of 25 to 300 μm in the present invention. The crushable silica in the present invention may be surface-treated as long as the average particle size, particle size distribution and the like are within the above range. Examples of the surface treatment agent include silane coupling agents, sulfonic acid compounds and phosphoric acid compounds.

The silica having the above-mentioned characteristics can be directly blended at the time of melt extrusion of polyester, but in order to obtain a film having good flatness and less haze without agglomerated coarse particles, it is particularly preferable in the production process of polyester. It is preferable to mix and add at the stage until the polycondensation reaction is started. At that time, silica was added to the polyester in an amount of 0.00
The obtained polyester may be formed into a film as it is with an addition amount of 1 to 0.1%, or a polyester is produced with an addition amount of 0.1 to 20%, and the polyester and the silica-free polyester are added. You may employ | adopt what is called a masterbatch system which mixes and forms a film. In any of the methods, when silica is added in the polyester production step, it is preferable to sufficiently disperse silica in ethylene glycol and add it in a uniform slurry state.

[0015]

The biaxially stretched polyester film obtained by the method of the present invention has a low haze, high transparency, and good slipperiness. Such films are for packaging, plate-making printing,
Most suitable for laminating and photographic supports.

[0016]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In addition, "parts" in the examples mean parts by weight, and the measuring method of each property is as follows. (1) Particle Size of Silica Silica was uniformly dispersed in ethylene glycol by ultrasonic treatment, and the dispersion was measured using a Horiba ultracentrifuge automatic particle size distribution analyzer (CAPA-700). The average particle diameter and the particle diameter distribution are the area-based standard values of spherical conversion measured by the above method, and the average particle diameter is the median diameter. (2) Transparency The polyester film was measured with a haze meter (NDH-1001DP manufactured by Nippon Denshoku Industries Co., Ltd.) and shown as a haze value. (3) Friction coefficient Static friction coefficient measuring device (HEIDON-10 manufactured by Shinto Kagaku)
Was used to measure the coefficient of static friction between the two films. A coefficient of static friction of 0.7 or less was passed.

Reference Example 1 (Synthesis of silica-containing polyester) 100 parts of terephthalic acid and 50 parts of ethylene glycol were placed in an esterification reaction tank.
Parts, 0.1 part of magnesium acetate tetrahydrate and 0.035 part of antimony trioxide were charged, and the contents were gradually heated by pressurizing with 3.5 kg / cm 2 of nitrogen while stirring. While removing the water produced by the reaction from the rectification column, the theoretical production amount of 9
The reaction was carried out until 3.4 L of water corresponding to 0% was distilled.
After that, the reaction product was transferred to a polycondensation tank, and the average particle size was 0.5μ.
m 20% ethylene glycol slurry of 1 part of crystalline crushable silica having a ratio of particles of 1 μm or more of 6%, and 0.035 parts of trimethyl phosphate dissolved in 0.5 part of ethylene glycol. Was added. After the addition was completed, the mixture was left stirring for 10 minutes, and then the pressure inside the system was gradually reduced to carry out a polycondensation reaction at 280 to 300 ° C. for about 2 hours to obtain a silica-containing polyester.

Example 1 3 parts of the polyester obtained in Reference Example 1 was thoroughly mixed with 97 parts of a silica-free polyester synthesized in the same manner as in Reference Example 1 except that silica was not added, to obtain 16 parts.
After drying at 0 ° C for 8 hours, it was extruded at 280 ° C into a molten sheet. This was stretched 3.5 times in the machine direction at 85 ° C,
Then, the film was stretched 4.5 times in the transverse direction at 125 ° C. and heat-set at 240 ° C. to obtain a biaxially stretched film having a thickness of 100 μm.
As shown in the properties shown in Table 1, this polyester film had a low haze and was excellent in transparency and slipperiness.

Example 2 By the same operation as in Example 1, a biaxially stretched film having a thickness of 50 μm was obtained. As shown in Table 1, this film had good properties.

Examples 3 to 4 and Comparative Examples 1 to 5 Table 1 shows the types of silica compounded in Reference Example 1 and the mixing ratios of the silica-containing polyester and the silica-free polyester in Example 1 respectively. A 100 μm-thick polyester film was obtained by performing the same operation except that the above was changed to. The characteristic values of these polyester films are shown in Table 1.

As can be seen from Table 1, the polyester film obtained by the present invention can sufficiently satisfy both the characteristics of transparency and slipperiness.

[0022]

[Table 1]

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Claims (3)

[Claims] 1. A polyester whose main constituent unit is ethylene terephthalate has an average particle diameter of 0.1 to 1.0 μm.
It is a biaxially stretched polyester film having a thickness of 25 to 300 μm, which is obtained by blending 0.001 to 0.1% of crushable silica particles having a particle diameter of 0.01 to 5.
A biaxially stretched polyester film, wherein the proportion of particles having a particle size of 0 μm and 1.0 μm or more is 20% or less of all silica particles. 2. The biaxially stretched polyester film according to claim 1, wherein the silica particles are crushed quartz glass. 3. The biaxially stretched polyester film according to claim 1, wherein the silica particles are crystalline crush type silica.