JPH0670166B2 - Polyester film - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyester film containing wet process silica particles containing elemental calcium.

[0002]

2. Description of the Related Art Polyester films represented by polyethylene terephthalate have excellent physical and chemical properties and are widely used as graphic arts, displays and packaging materials. It is also widely used in the fields of magnetic recording media such as base films and capacitor derivatives. However, a film particularly required to have transparency is required to have excellent processability in the manufacturing process, post-processing steps such as coating and vapor deposition, or handleability of the product itself,
Specifically, it is necessary for the film to have excellent running properties and abrasion resistance, but conventionally, this has not always been sufficiently achieved.

It has been found that in order to improve the running property and abrasion resistance of the polyester film, the surface of the film should be appropriately roughened. Then, in order to achieve this, a method in which fine particles are present in the raw material polyester has been proposed, and partly put into practical use,
A high degree of satisfaction with these properties has not always been successful.

For example, when so-called precipitated particles, which are generated as catalyst particles from a catalyst residue during the production of polyester, are used, the particles are likely to be broken in the stretching process, so that the effect of improving the running property and abrasion resistance is poor, Further, it is difficult to recycle the polyester. When inert inorganic compound particles are added to polyesters such as silica, calcium carbonate, titanium dioxide, and calcium phosphate, the particles are not broken or deformed by stretching, and a relatively sharp projection is given to the film. However, since the particles have poor affinity with polyester, voids are generated around the particles during the stretching process, the transparency is significantly reduced, and particles are detached from the film surface. A white powdery substance was generated, and a film having both good running property and transparency could not be obtained.

[0005]

Means for Solving the Problems The inventors of the present invention have made earnest studies to provide an excellent film that satisfies both traveling property and transparency at the same time and sufficiently satisfies various properties required as a film. As a result of overlapping, it was found that such characteristics can be imparted to the film by blending certain specific silica particles, and the present invention has been completed. That is, the gist of the present invention is characterized in that the average particle size is 0.1 to 5 μm and that the wet method silica particles containing 5 to 40% by weight of calcium element are contained in an amount of 0.001 to 5% by weight. It exists in polyester film.

The present invention will be described in more detail below. The polyester in the present invention means terephthalic acid, 2,6-
An aromatic dicarboxylic acid such as naphthalenedicarboxylic acid or an ester thereof and a polyester obtained by using ethylene glycol as a main starting material are mentioned, but other third component may be contained. In this case, examples of the dicarboxylic acid component include isophthalic acid, terephthalic acid,
2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid and the like can be used. As the glycol component, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol or the like can be used. In any case, the polyester referred to in the present invention is a polyester in which 80% or more of the repeating structural units have ethylene terephthalate units or ethylene-2,6-naphthalate units.

Further, the polyester film of the present invention is
At least a uniaxially oriented polyester film using such a polyester as a starting material is referred to, and a known method can be adopted as a manufacturing method thereof. For example, after melt extruding into a sheet at 270 to 320 ° C.,
After cooling and solidifying at 40-80 ° C to form an amorphous sheet, 8
Sequential biaxial stretching or simultaneous biaxial stretching at an area ratio of 4 to 20 in the longitudinal and transverse directions at 0 to 130 ° C., 160 to
Method of heat treatment at 250 ° C. (for example, Japanese Examined Patent Publication Sho 30-563)
The method described in Japanese Patent Publication No. 9) can be used. The stretching in the machine direction and the transverse direction may be performed in each one stage, and if necessary, it may be performed in multiple stages, or a heat treatment section for relaxing orientation may be provided between the multiple stages. Further, after biaxial stretching, it may be stretched again before being subjected to the heat treatment step of the next step. This re-stretching can be carried out in any of longitudinal and transverse directions.

The polyester film of the present invention is characterized in that it contains wet process silica particles containing a calcium element. As a method for producing such particles, a method using a medium mainly containing water, that is, a wet method is adopted. The wet method is a method in which, for example, sodium silicate and calcium salts such as calcium chloride are reacted to first generate calcium silicate, and then decomposed with mineral acid or carbon dioxide gas. According to this method, particles having a particle size and composition suitable for use in the present invention can be efficiently obtained.

The content of the calcium element in the wet process silica particles containing the calcium element in the present invention is from 5 to 5.
It is 40% by weight, preferably 10 to 30% by weight. When the content of the calcium element in the wet-process silica particles is less than 5% by weight, the transparency of the film is lowered. On the other hand, when the amount of calcium element exceeds 40% by weight, particles are aggregated during blending with polyester, the number of coarse particles increases, the surface roughness of the film becomes too large, and the transparency decreases.

The average particle size of the silica particles used in the present invention is
The thickness is 0.1 to 5 μm, preferably 0.5 to 2 μm. When the average particle size is less than 0.1 μm, the running property and abrasion resistance of the film are insufficient. On the other hand, when the average particle size exceeds 5 μm, the surface roughness of the film becomes too large and the transparency is lowered. The amount of silica particles used in the present invention is 0.001 to 5% by weight, preferably 0.01 to 1% by weight. If the blending amount is less than 0.001% by weight, the running property and abrasion resistance of the film are insufficient. Further, if the blending amount exceeds 5% by weight, the surface roughness becomes too large, which is not preferable.

The method of blending the wet process silica particles containing calcium element used in the present invention with the polyester as the film-forming raw material is not particularly limited, and a known method can be adopted. For example, the particles and the polyester chips can be directly blended, but in particular, they are dispersed in ethylene glycol, which is a raw material for polyester, to obtain ethylene glycol slurry at any stage of the polyester production process, preferably after completion of the esterification or transesterification reaction. It is preferable to add the polycondensation reaction at a stage before the start of the polycondensation reaction to carry out the polycondensation reaction.

The silica particle dispersion slurry used in the present invention can be prepared by a known method. For example, the particles and ethylene glycol can be dispersed and adjusted using a high-speed stirrer having a plurality of shearing blades arranged in parallel with the rotating direction of the stirring blade, a homomixer, an ultrasonic disperser, or the like. The dispersed slurry is preferably filtered with a filter of 1000 mesh or more for the purpose of removing coarse particles and undispersed aggregated particles in the slurry.

If desired, other particles such as kaolin, talc, calcium carbonate and aluminum oxide may be used in combination.

[0014]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples without departing from the gist thereof. The measuring methods and definitions of various physical properties and characteristics in the present invention are as follows. In the examples and comparative examples, "part" means "part by weight". (1) Content of Calcium Element in Silica Particles Hydrofluoric acid was added to silica particles to dissolve them, and excess hydrofluoric acid was removed by heating. Then, a hydrochloric acid solution was added and quantitatively determined by an atomic absorption method.

(2) Average particle size and particle size distribution Centrifugal sedimentation type particle size distribution analyzer (SA-CP) manufactured by Shimadzu Corporation
Equivalent spherical distribution measured by type 3) 5
The particle size (diameter) of 0% was taken as the average particle size. (3) Travelability Two films cut into a width of 15 mm and a length of 150 mm are stacked on a smooth glass plate, a rubber plate is placed on the two films, and the film contact pressure of the two films is set to 2 g / cm ² , and then 20 m.
Measure the frictional force by sliding the films at m / min,
The coefficient of friction at the point of sliding by 5 mm was determined as the coefficient of dynamic friction. The measurement was performed at a temperature of 23 ° C ± 1 ° C and a humidity of 50% ± 5
% Under an atmosphere.

(4) Wear characteristics Wear characteristics were evaluated by the amount of white powder generated. That is, the film was run for 1000 m while being in contact with a 6 mmΦ fixed pin made of hard chrome, and the amount of worn white powder adhering to the fixed pin was visually evaluated and evaluated according to the following criteria. The film speed was 13 m / min and the tension was about 20.
0 g, and the winding angle around the fixed pin was 135 °.

Rank A: No adhesion Rank B: Small quantity adhesion Rank C: Small quantity (more than rank B) adhesion Rank D: Very large quantity of adhesion (5) Number of coarse projections Weigh 10 mg of sample and measure 18 × 18 mm Scissors on cover glass, press at 280-290 ℃, diameter of about 10mm
Of the phase difference microscope (1
(00 times), particles having a maximum length of 10 μm or more were counted and defined as the number of coarse protrusions. (6) Transparency According to JIS-K61714, the film haze was measured by a Nippon Denshoku Industries Co., Ltd. sphere-type turbidimeter NDH-20D.

Example 1 [Preparation of slurry] 10 parts of wet process silica particles containing 15% by weight of calcium and having an average particle size of 0.95 μm were dispersed in 90 parts of ethylene glycol. Then, use a homomixer (TK homomixer manufactured by Tokushu Kika Kogyo) to 1000
The mixture was dispersed at 0 rpm for 60 minutes and filtered through a 1000-mesh wire net filter to obtain an ethylene glycol slurry.

[Production of Polyester] 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate are heated and heated, and methanol is distilled off to carry out a transesterification reaction, and 4 hours from the start of the reaction. The temperature was raised to 230 ° C., and the transesterification reaction was substantially completed. Then add the above slurry to 3
After adding 1 part, ethyl acid phosphate 0.04
Part was added, and further 0.04 part of antimony trioxide was added and polycondensation reaction was carried out for 5 hours to obtain polyethylene terephthalate having an intrinsic viscosity of 0.65.

The resulting polyester is dried and melt-extruded at 290 ° C. to form an amorphous sheet, which is then stretched 3.5 times at 90 ° C. in the longitudinal direction and 3.7 times at 110 ° C. in the transverse direction, and 21 ° C.
Heat treatment for 3 seconds to obtain a film with a thickness of 15 μm,
Its characteristics were evaluated.

Example 2 The same as Example 1 except that the average particle size of the wet process silica particles containing 15% by weight of calcium element was 1.35 μm and the addition amount of ethylene glycol slurry was 1 part. The characteristics were evaluated.

Example 3 As in Example 1, except that the average particle size of the wet process silica particles containing 15% by weight of calcium element was 1.35 μm and the amount of ethylene glycol slurry added was tripled. The characteristics were evaluated.

Comparative Example 1 The characteristics were evaluated in the same manner as in Example 1 except that wet-process silica particles containing no calcium element were used.

Comparative Example 2 The characteristics of Example 1 were the same as in Example 1 except that 3 parts of an ethylene glycol slurry of wet-process silicon oxide particles containing 3% by weight of calcium and having an average particle size of 1.35 μm was added. Was evaluated.

Comparative Example 3 The characteristics of Example 1 were the same as in Example 1 except that 3 parts of an ethylene glycol slurry of wet-process silica particles containing 50% by weight of calcium and having an average particle size of 1.35 μm was added. evaluated. The results obtained above are summarized in Table 1 below.

[0026]

[Table 1]

As shown in Table 1, all of the films of Examples 1 to 3 which are the scope of the present invention have excellent transparency, running property and abrasion resistance.
While it is extremely useful as a base film for displays and packaging, it is inferior in transparency when calcium particles in the wet process silica particles are small or not contained at all as in Comparative Examples 1 and 2. Further, when the content of the calcium element in the wet process silicon oxide particles is too large as in Comparative Example 3, the dispersibility of the particles is inferior and coarse projections frequently occur.

[0028]

The film of the present invention has a uniform surface,
It has excellent runnability, abrasion resistance and transparency, and can be applied to various applications such as graphic arts, displays, packaging, transfer marks, photolithography, magnetic recording media, and electrical applications such as capacitors, and its industrial value is high. .

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Claims (1)

[Claims] 1. A polyester film having an average particle size of 0.1 to 5 μm and containing 0.001 to 5% by weight of wet process silica particles containing 5 to 40% by weight of calcium element. .