JPH0718163A - Polyester film - Google Patents

Abstract

PURPOSE:To prepare a biaxially oriented polyester film which contains inner particles containing calcium element and phosphorus element and silicas of specific average particle sizes prepared by bOth wet and dry methods, thus can be used in a variety of packaging materials with excellent slip characteristics and transparency. CONSTITUTION:Terephthalic acid and ethylene glycol are charged in a reactor and heated up to 260 deg.C under stirring to effect esterification into bis(beta- hydroxyethyl)terephthalate. The esterification product is mixed with (A) 150 to 450ppm of wet-process silica of 1.0 to 5.0mum average particle size, (B) 50 to 100ppm of dry-process silica of 0.1 to 1.0mum average particle size, (C) 100 to 450ppm of calcium acetate in terms of the calcium element, and (D) 0.6 to 1.5P/Ca atomic ratio of trimethyl phosphate in terms of the Ca element in (C), and subjected to polycondensation reaction in the presence of a polymerization catalyst up to 290 deg.C under reduced pressure to prepare polyethylene terephthalate, which is melt-extruded and biaxially oriented to give the objective polyester film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film used for various packaging materials, and more particularly to a biaxially oriented polyester film for packaging which is excellent in slipperiness and transparency.

[0002]

2. Description of the Related Art Biaxially stretched films of polyester, typified by polyethylene terephthalate, have physical properties such as transparency, mechanical strength and dimensional stability, and chemical properties such as chemical resistance. It is widely used for magnetic tapes, capacitors, food packaging, etc. due to its excellent properties. In particular, in magnetic tape applications, high slipperiness is required on the film surface in terms of running stability and wear resistance, and if sufficient slipperiness is not obtained, running troubles and wear reduce tape life. In addition, the surface is likely to be scratched, resulting in deterioration of quality.

Also, in general packaging applications such as food packaging, it is essential that the slipperiness is above a certain level in the manufacturing process and the processing process, and if it does not reach a certain level, wrinkles in the winding process occur. Not only the occurrence and defective winding shape,
In some cases, the value as a product is significantly reduced.

From the above, the polyester film has excellent physical and chemical properties as described above, but has a high friction coefficient due to its resin property, and therefore has a slip property. Was not enough in terms of.

Therefore, in order to improve the slipperiness of the polyester film, a method of roughening the surface of the film is generally performed. As a roughening method, an external particle method in which inorganic fine particles having a refractive index close to that of polyester are added during the polymerization step, and an internal particle method in which particles are precipitated in the polymer in the condensation process of polyester have been proposed.

In the external particle method, inert inorganic compound particles are added to polyester such as calcium carbonate, titanium dioxide, calcium phosphate, etc. In such a method, the film is not broken or deformed by stretching, and the film is formed. A sharp projection is formed on the surface, and high slipperiness is obtained. However, since the inorganic compound particles have a poor affinity with polyester, there is a problem that particles are likely to fall off due to the generation of voids in the periphery of the particles during stretching, and a white powdery substance is formed on the film surface. is doing. Further, the inorganic compound particles also have an unfavorable property of significantly impairing the transparency of the film even when added in a small amount. Therefore, silica particles having a relatively good affinity with polyester are generally used. However, since silica particles have extremely poor dispersibility in polyester and easily aggregate during the production of polyester, and many coarse particles are generated on the film surface, the use of silica particles cannot prevent a decrease in transparency of the film. .

On the other hand, the internal particle method is an application of a catalyst residue or the like deposited during the production of polyester. But,
When the internal particle method is used, it is extremely difficult to control the amount of precipitated particles and particle size, and coarse particles are easily generated, which causes a rapid increase in filtration pressure in the film-forming process and induces product defects. Have the problem of. Furthermore, since the internal particles are easily broken by the deformation during stretching, running stability and wear resistance are poor, and recycling is also difficult. Therefore,
In the biaxially stretched polyester film roughened by the internal particle method, slipperiness can be imparted without impairing the transparency of the film, and although it has good slippery in the region where the friction coefficient is relatively small, after film formation When a high contact pressure is applied as in the slitter process of No. 1, there is a problem that the effect of improving the slipperiness by the internal particles is hardly exhibited. Therefore, when such a high contact pressure is applied, it has been carried out by using external particles such as silica particles together with the internal particles to give sufficient slipperiness. It was unavoidable that there was a dropout and a decrease in transparency. It is an object of the present invention to provide a polyester film having sufficient slipperiness and transparency that can be used as a general packaging film that requires high transparency.

[0008]

Means for Solving the Problems The present inventors have completed the present invention as a result of earnestly researching a polyester film satisfying both a sufficient sliding property and a high transparency.
That is, according to the present invention, internal particles containing an element of calcium and an element of phosphorus, 150 to 450 ppm of wet process silica (A) having an average particle size of 1.0 to 5.0 μm and an average particle size of 0.
1 to 1.0 μm dry process silica (B) 50 to 100 pp
It is a polyester film containing m.

The polyester resin used in the polyester film of the present invention comprises a dicarboxylic acid component containing at least one aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid or an ester-forming derivative thereof as a main component, and ethylene. It is composed of a diol component containing at least one of glycol, butanediol, cyclohexanedimethanol, diethylene glycol, propylene glycol, triethylene glycol, neopentyl glycol, an ethylene oxide adduct of a bisphenol compound or its derivative as a main component. It is a polyester resin in which 80% or more of the repeating units are ethylene terephthalate. Examples of ester-forming derivatives of aromatic dicarboxylic acids include dialkyl esters and diaryl esters of aromatic dicarboxylic acids. Further, in the present invention, a third component other than the above, such as an aliphatic dicarboxylic acid such as glutaric acid, adipic acid, sebacic acid, oxalic acid or succinic acid, may be contained.

These polyester resins can be produced by a known direct polymerization method, transesterification method or the like, and the degree of polymerization thereof is not particularly limited, but the intrinsic viscosity (phenol / Measured in a mixed solution of tetrachloroethane and the like at 25 ° C) is 0.5 to
It is preferably about 1.2 dl / g.

The polyester film of the present invention is a polyester film made from the polyester resin having the above-mentioned constitution, and contains internal particles containing calcium element and phosphorus element, wet process silica and dry process silica. is there.

The first feature of the present invention resides in that the polyester film is made to contain two kinds of wet process silica (A) and dry process silica (B) which are different in the production method and the particle size in combination. That is, the wet process silica (A) having a particle size of 1.0 to 5.0 μm and the particle size of 0.1 to 1.0 μm.
It was found that by using a specific amount of the dry process silica (B) within the range, sufficient slip property can be obtained even under a high load without impairing transparency.

In the wet process silica (A) used in the present invention, the primary particles form a three-dimensional matrix structure due to the siloxane bond, the surface is made porous, and the internal surface area is very large. Have
The silica produced by such a wet method has a large surface area because of its porous surface and a large contact area with the resin, which causes large friction, resulting in high adhesion with the resin. Even under severe conditions during use, it does not fall off and the effect of slipperiness is not reduced. In addition, since the wet process silica has a large internal surface area because its structure is a three-dimensional matrix, it can be deformed when subjected to a strong external force, and is deformed in the direction of the stress due to the deformation in the stretching process. A gap is unlikely to form between the resin and it does not fall off. Therefore, it does not fall off even when it is rubbed with a strong force in the winding step in the film forming step, and particularly in the slit step after winding, and it is possible to exhibit sufficient slipperiness even under a high load. is there.

The average particle size of the wet process silica used in the present invention is in the range of 1.0 to 5.0 μm,
If it is less than 1.0 μm, the effect on the slipperiness is small, and if it exceeds 5.0 μm, the height of the protrusions is large. It also develops defects such as eye.

The content of the wet process silica in the polyester film is in the range of 150 to 450 ppm. 150
If it is less than ppm, the slipperiness is insufficient, and if it exceeds 450 ppm, the haze becomes large and the transparency is lowered.

Further, in the present invention, by using the dry process silica (B) in combination with the wet process silica, the haze increase due to the addition of the wet process silica is suppressed and sufficient slipperiness is imparted. Is something that can be done.

The dry process silica used in the present invention does not have an internal surface area as compared with the wet process silica, has a very dense structure, has a small specific surface area, and has a form relatively close to a true sphere. ing. Therefore, since the particle surface is smoother than that of a porous surface such as wet-process silica, slippage of the particles themselves is high. Therefore, the slipperiness obtained with respect to the added amount is high, and it becomes possible to exhibit the high slipperiness with an added amount smaller than that of the wet process silica. Therefore, the haze of the film can be reduced.

Since the dry process silica has a surface smoothness and a morphology close to a true sphere, it reduces the adhesiveness with the resin forming the film and increases the dropout during stretching deformation and during use. Therefore, when considering the adhesiveness with resin,
It is particularly necessary to increase the specific surface area of the dry process silica particles, and for that purpose, it is effective to reduce the particle size of the dry process silica particles. From this, the average particle size of the dry process silica used in the present invention is 0.1 to 1.
It must be in the range of 0 μm. This is because when the average particle diameter of the dry process silica is less than 0.1 μm, the effect formed on the surface of the film is too small to have an effect on the slipperiness, and when it exceeds 1.0 μm. Because the height of the protrusion formed on the surface of the film approaches the protrusion of wet silica used together, it is easy to receive an external force,
The dry process silica, which has low adhesiveness to the resin, is preferentially removed, and the effect of adding the dry process silica is reduced.

The content of dry process silica in the polyester film is in the range of 50 to 100 ppm and is 50 pp.
When it is less than m, the slipperiness is not sufficient, and when it exceeds 100 ppm, the haze becomes high and the transparency is lowered.

In the present invention, in addition to the above-mentioned wet process silica (A) and dry process silica (B), internal particles containing calcium element (C) and phosphorus element (D) in the polyester are contained. The internal particles containing the element and the phosphorus element are particles precipitated by adding a calcium compound and a phosphorus compound to the reaction system during the production of polyester. As the calcium compound added to the reaction system, inorganic compounds such as hydroxides, oxides, carbonates and hydrogen carbonates, organic acid salts such as acetates, propionates, butyrates and stearates can be used. . These compounds can be used alone or in combination of two or more kinds.

Here, the calcium content has a great influence on the slidability, and as the calcium content increases, the slidability of the obtained film tends to gradually improve. However, an excessive amount of calcium element causes the aggregation of calcium in the system and induces the formation of coarse particles, so that it is preferable to set it in a range that provides the minimum slipperiness required for the film. Therefore, the calcium compound, the amount of calcium element contained in the film,
It is preferable to add it in the range of 100 ppm to 450 ppm. The content of calcium element is 100
When it is less than ppm, the slipperiness of the film tends to decrease, and when it exceeds 450 ppm, the slipperiness becomes excessive and coarse particles are easily generated in the film, impairing the process passability and the film surface morphology. This is because there is a tendency.

The phosphorus compound used in the present invention includes
Phosphoric acid, phosphorous acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite and the like, these may be used alone or in combination of two or more. Can be used.

Since the internal particles are formed through the reaction between calcium and phosphorus, addition of a phosphorus compound in a certain amount or more with respect to the amount of calcium element requires addition of excess phosphorus as a condensation polymerization catalyst. Since it also reacts with a substance to inhibit polymerization, the phosphorus compound is preferably added so that the amount of the phosphorus element is 0.6 to 1.5 in terms of the element amount ratio to the calcium element. This is because when the element amount ratio to the calcium element is less than 0.6, the internal particles corresponding to the added calcium element are not formed, and the unreacted calcium element easily causes thermal decomposition of the polymer, resulting in a degree of polymerization. This is because there is a tendency that a polymer having a high viscosity cannot be obtained and the polymer may be colored. Further, the element amount ratio of phosphorus element to calcium element is 1.
When it exceeds 5, the excess phosphorus tends to react with the metal oxide added as the polycondensation catalyst, which tends to inhibit the polymerization and a polymer having a high degree of polymerization cannot be obtained, resulting in an extremely long polymerization time. This is because it promotes oxidative decomposition and thermal decomposition of the polymer, which may lead to deterioration in quality.

The method for producing the polyester film of the present invention is as follows:
Although not particularly limited, for example, it can be obtained by producing the above-described wet process silica, dry process silica, a polyester resin containing calcium element and phosphorus element by a melt condensation method and orienting them biaxially. As its manufacturing method, a known manufacturing method, for example, resin 270-300
After melt-extruding at 40 ° C. and then cooling and solidifying at 40 to 80 ° C., a substantially non-oriented sheet obtained at 80 to 120 ° C. is stretched biaxially in the longitudinal and transverse directions at the same time, or in the longitudinal direction, and then in a tenter. In general, or in a multi-stage transverse stretching, a so-called sequential stretching method is used. Further, after the transverse stretching is substantially finished, heat treatment is performed in a tenter at 200 to 240 ° C. for crystallization. The orientation can be fixed by using the method described above to improve the dimensional stability, and the like.

The thickness of the polyester film of the present invention is
Although not particularly limited, it is in the range of 6 to 380 μm.

[0026]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. Evaluations in Examples and Comparative Examples were performed by the following methods.

1. Haze The haze of the film was measured with a Tokyo Denshoku Co., Ltd. (MODEL TC-HIII) haze meter.

2. Dynamic friction coefficient Using a surface tester manufactured by Shinto Kagaku Co., Ltd., the same film was attached to both fixed and movable parts to measure the dynamic friction coefficient.

3. The falling film of the particles was attached to the movable part and the fixed part of the above surface property tester, and the load was 300 g and the scratching speed was 100 (mm / mi).
After repeating the scratch test 100 times in n), the film surface was evaluated by observing it with a scanning electron microscope at a magnification of 3500. A: Almost no dropout of particles was observed. B: Particle loss is less than 20% C: Particle loss is 20% or more

Example 1 100 parts of terephthalic acid and 140 parts of ethylene glycol were charged into a reaction vessel equipped with a rectification column and a stirrer, the temperature was gradually raised to 260 ° C. with stirring, and the water flowing out was discharged from the system. BHT (bis (β-hydroxyethyl) terephthalate) with a reaction rate of 93% by esterification while discharging
Got The obtained BHT was transferred to a polycondensation reactor, and separately prepared calcium hydrate monohydrate of 300 ppm was added as a calcium element amount and trimethyl phosphate was added as a phosphorus element amount of 258 ppm. 200ppm of average particle size 1.5μm, 75pp of dry process silica with average particle size 0.3μm
m was added. Furthermore, 2 parts of a 2% ethylene glycol solution of antimony trioxide was added as a polymerization catalyst. After 15 minutes, decompression was started, the degree of vacuum was reduced to 1 mmHg or less in 30 minutes, the temperature was raised to 290 ° C, and polycondensation was performed for 3 hours to obtain an intrinsic viscosity (measured in a mixed solution of phenol / tetrachloroethane and the like at 25 ° C). ) 0.67 (dl / g) polyethylene terephthalate chips were obtained. This chip 12
After vacuum drying at 0 ° C. for 10 hours, the film was formed by an ordinary extruder used for polyester film to obtain a 150 μm original fabric. Further, by a stretching machine connected to the extruder, 90
After stretching 3.5 times in the machine direction at 90 ℃, 90 ℃ in a tenter
Was laterally stretched 3.5 times to obtain a film having a thickness of 12 μm. Table 1 shows the evaluation results of the obtained film.

Example 2 400 ppm of wet-process silica having an average particle size of 1.5 μm,
A film having a thickness of 12 μm was produced in the same manner as in Example 1 except that the dry method silica having an average particle size of 0.3 μm was changed to 55 ppm. The evaluation results are shown in Table 1.

Example 3 A film having a thickness of 12 μm was produced in the same manner as in Example 1 except that the content of wet process silica was 300 ppm. The evaluation results are shown in Table 1.

Comparative Examples 1 to 10 The particle size and addition amount of wet process silica and dry process silica were changed as shown in Table 1, and the method of Example 1 was repeated to prepare films having a thickness of 12 μm. did. The evaluation results are shown in Table 1.

[0034]

[Table 1]

[0035]

As described above, since the polyester film of the present invention contains the wet process silica, the dry process silica, the calcium element and the phosphorus element having the above-mentioned constitutions,
It has good slipperiness and high transparency, and is extremely useful as a film for general packaging.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area C08K 3/36 // B29K 67:00

Claims (2)

[Claims] 1. Internal particles containing elemental calcium and elemental phosphorus, 150 to 450 ppm of wet process silica (A) having an average particle size of 1.0 to 5.0 μm, and an average particle size of 0.1 to 0.1.
A polyester film comprising 50 to 100 ppm of 1.0 μm dry process silica (B). 2. The content of calcium element (C) is 100.
The polyester film according to claim 1, wherein the content of elemental elements is 450 ppm and the content of phosphorus element (D) is 0.6 to 1.5 with respect to the calcium element (C).