JPH075764B2 - White polyester film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a white biaxially stretched polyester film having highly improved light resistance.

(Problems to be Solved by Conventional Techniques and Inventions) Polyester typified by polyethylene terephthalate is used for information recording materials because of its excellent mechanical properties, electrical properties, chemical resistance, and dimensional stability. For capacitors,
It is used as a base material in many fields such as packaging, plate making, electricity loss, and photographic film applications.

Taking advantage of the excellent properties of such polyester films in recent years, whiteboards for electronic white boards and, for example, credit cards, telephone cards, are widely used for financial cards such as Japanese National Railways cards, communications, transportation institutions, etc. The range of use is expanding.

However, in such applications, the polyester film used as the base material turns yellow over a long period of time because it is used while being affected by the sunlight outside or the ultraviolet rays from indoor fluorescent lamps. Or, there is a problem that the mechanical strength is likely to decrease.

In particular, the former is a serious problem, but it is known that this is a phenomenon based on deterioration yellowing of titanium dioxide contained as a white masking agent in the white polyester film due to ultraviolet rays. In order to improve these properties required of the white polyester film, a UV absorber is generally contained in the white polyester film. This makes it possible to prevent deterioration of the white polyester film to some extent.

However, conventionally used ultraviolet absorbers are organic ultraviolet absorbers such as benzophenone type, benzotriazole type, and hydroquinone type, and these organic ultraviolet absorbers are generally easily decomposed by heat or oxidatively. Moreover, some sublime at high temperatures.

On the other hand, a polyester film, such as polyethylene terephthalate, is formed at 270 to 300 ° C. Therefore, even if such an organic ultraviolet absorber is added at the time of film formation, the ultraviolet absorber undergoes thermal decomposition or sublimation and its ultraviolet absorption ability is increased. Is significantly reduced.

Further, if the amount of the ultraviolet absorber added is increased to compensate for the decrease in the ultraviolet absorbing ability, the hue of the obtained film may be reduced or accumulated in the film forming machine, which causes various troubles.

Furthermore, some of such organic UV absorbers have a harmful effect on the human body.

As described above, at present, it is very difficult to maintain sufficient light resistance and whiteness even if the organic ultraviolet absorber is blended with the white polyester film.

(Means for Solving Problems) The present inventors have made earnest studies in order to achieve such an object in view of a situation in which the demand for improving the light resistance to ultraviolet rays of the white polyester film and the maintenance of whiteness is becoming strict. As a result of overlapping, it was found that the light resistance to ultraviolet rays and the maintenance of whiteness of the white polyester film can be achieved for the first time by using the anatase type titanium dioxide fine particles containing an aluminum compound and, if necessary, silicon dioxide, and reached the present invention. It was done.

That is, the gist of the present invention is that anatase titanium dioxide containing 0.01% by weight or more and 2.0% by weight or less of an aluminum compound in terms of aluminum element and 1.0% by weight or less of silicon dioxide in terms of silicon element is 2.0 to 30% by weight with respect to polyester. % White biaxially stretched polyester film.

The present invention will be described in detail below.

The polyester referred to in the present invention means an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, or its ester and ethylene glycol, diethylene glycol, tetramethylene glycol, neopentyl glycol, etc. It is a polyester that can be obtained by polycondensing such a glycol.

This polyester can be obtained by directly polycondensing an aromatic dicarboxylic acid and a glycol, or by subjecting an aromatic dicarboxylic acid dialkyl ester and a glycol to an ester exchange reaction and then polycondensation, or by diluting an aromatic dicarboxylic acid diester. It can also be obtained by a method such as polycondensation.

Typical examples of such polymers include polyethylene terephthalate and polyethylene-2,6 naphthalate. This polymer may be a homopolymer or may be a copolymer of a third component. In any case, in the present invention, the ethylene terephthalate unit and / or the ethylene-2,6 naphthalate unit is 80 mol%.
The polyester containing above is preferable.

In the present invention, a specific amount of anatase titanium dioxide containing a specific amount of an aluminum compound and silicon dioxide is blended with the polyester.

Examples of the aluminum compound contained in anatase type titanium dioxide include aluminum acetate, aluminum sulfate,
Examples include aluminum oxide, aluminum carbonate, aluminum chloride, aluminum hydroxide, aluminum lactate, aluminum phosphate, aluminum formate, aluminum nitrate, aluminum stearate, aluminum monostearate, aluminum laurate, and aluminum zinc sulfate. Of course, it is not limited to these. Among these, an aluminum compound having particularly good heat resistance is preferable.

The average particle size of the aluminum compound and silicon dioxide-containing anatase type titanium dioxide used in the present invention is preferably 0.1 to 1.0 μm, and more preferably 0.2 to 0.5 μm. If the average particle size is less than 0.1 μm, the light transmittance becomes large and the white hiding effect becomes insufficient, which is not preferable.
On the contrary, if the average particle size exceeds 1.0 μm, the original whiteness of the anatase type titanium dioxide decreases, which is not preferable.

Further, the amount of the aluminum compound contained in the anatase-type titanium dioxide needs to be 0.01 to 2.0% by weight in terms of aluminum element, preferably 0.1 to 1.0% by weight. The amount of aluminum compound contained in anatase titanium dioxide is 0 in terms of aluminum element.
If it is less than 01% by weight, the light resistance improving effect becomes insufficient, which is not preferable. Conversely, the amount of aluminum compound contained in the anatase type titanium dioxide is 2.
If it exceeds 0% by weight, the thermal stability of the polyester is lowered and problems such as film breakage during film formation are likely to occur, such being undesirable.

Further, the amount of silicon dioxide contained in the anatase-type titanium dioxide needs to be 1.0% by weight or less in terms of silicon element, and preferably 0.1 to 0.5% by weight.
When anatase-type titanium dioxide contains silicon dioxide in an amount of 1.0% by weight or less in terms of silicon element, the dispersibility of the titanium dioxide in the polyester can be improved. On the other hand, if the amount of silicon dioxide contained in the anatase type titanium dioxide exceeds 1.0% by weight in terms of silicon element, the effect of improving dispersibility becomes insufficient, which is not preferable.

In addition, the compounding amount of anatase type titanium dioxide containing an aluminum compound and silicon dioxide is based on that of polyester.
It is necessary to be 2.0 to 30% by weight, preferably 5.0 to 20% by weight.

If the blending amount is less than 2.0% by weight, the light transmittance becomes large and the white hiding effect becomes insufficient, which is not preferable. On the other hand, if this amount exceeds 30% by weight, the mechanical strength of the polyester is lowered and problems such as breakage of the film during film formation occur, which is not preferable.

The manufacturing method of the anatase type titanium dioxide containing an aluminum compound and silicon dioxide used in the present invention is not limited as long as the conditions defined above are satisfied. As a method for incorporating such an aluminum compound and silicon dioxide into anatase titanium dioxide, a predetermined amount of aluminum compound such as aluminum oxide, aluminum hydroxide, aluminum carbonate, aluminum chloride and silicon dioxide are added and blended during the production of anatase titanium dioxide. Alternatively, commercially available anatase type titanium dioxide may be surface-treated with an aluminum compound such as aluminum oxide, aluminum hydroxide, aluminum carbonate or aluminum chloride and silicon dioxide.

The aluminum compound and silicon dioxide may be contained inside the anatase type titanium dioxide or may be present on the surface, but in order to improve the light resistance and the initial whiteness, it is preferable that they are present on the surface. preferable.

In the present invention, the anatase type titanium dioxide containing an aluminum compound and silicon dioxide can be compounded at any stage of the production process of the polyester film. For example, anatase type titanium dioxide containing an aluminum compound and silicon dioxide may be blended, for example, as a glycol slurry or as a powder at any stage before the polycondensation start, during the polycondensation reaction, and after the polycondensation reaction. not useable. Alternatively, a polyester resin, an anatase type titanium dioxide containing an aluminum compound and silicon dioxide may be melt mixed in an extruder to form a chip. A so-called master batch containing anatase titanium dioxide containing an aluminum compound and silicon dioxide in a high concentration is produced, and this master batch is, if necessary, anatase titanium dioxide containing an aluminum compound and silicon dioxide. It is also possible to produce a polyester film having a predetermined blending amount by mixing with a polyester containing no or a small amount.

In the present invention, the initial whiteness, if necessary, does not adversely affect the light resistance, does not increase the number of coarse particles, and is a compounding amount that does not adversely affect the smoothness of the polyester film surface, the aluminum compound Further, inert particles other than anatase type titanium dioxide containing silicon dioxide may be used in combination. In addition to the above-mentioned inert particles, so-called precipitation type fine particles precipitated by the reaction of the catalyst residue and the phosphorus compound in the reaction system may be used together.

In any case, the eye of the present invention is to obtain a biaxially stretched polyester film in which a specific amount of anatase type titanium dioxide containing a specific amount of an aluminum compound and silicon dioxide is blended.

A publicly known method can be adopted for the polycondensation of the polyester film in the present invention. For example, one or more antimony compounds, germanium compounds, titanium compounds and the like are used as a catalyst for the polycondensation reaction, heated to about 230 to 300 ° C., and the reaction is advanced by distilling glycol under reduced pressure. A known method can be adopted for forming the chip and the master batch. For example, the raw material polyester chips and particles are melt-mixed by an extruder at 270 to 300 ° C., cooled, and then made into chips. Further, a known film forming method can be adopted for forming the film. For example, after melt extruding a raw material polyester chip containing an anatase type titanium dioxide containing an aluminum compound and silicon dioxide at 270 to 300 ° C. into a film,
After cooling at 40 to 70 ° C and solidifying to form an amorphous sheet,
5 to 3.5 times) Horizontal (2.5 to 3.5 times) sequential biaxial stretching, or simultaneous biaxial stretching and heat treatment at 160 to 270 ° C (for example, the method described in Japanese Patent Publication No. 30-5639) can do.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Various physical properties and characteristics are measured or defined as follows. In the examples and comparative examples, "part" means "part by weight" and "%" means "% by weight".

(1) Average particle size Centrifugal sedimentation type particle size distribution measuring device (SA-CP3 manufactured by Shimadzu Corporation
The value of the integrated (weight basis) 50% in the equivalent spherical distribution measured by (type) is used.

(2) Thermal stability 7 g of polymer was put into a test tube, vacuum dried at 160 ° C-1 mmHg for 2 hours, then recompressed to 100 mmHg with nitrogen gas, and then 290 ° C2.
The heat-melting heat treatment was carried out for an hour, and the degree of retention of the degree of polymerization was evaluated from the retention rate of the intrinsic viscosity [η] of the polymer before and after the treatment, which was measured by the method (3) below.

(3) Intrinsic viscosity [η] 1 g of polymer is phenol / tetrachloroethane = 50/50
It was dissolved in 100 ml of a mixed solvent (weight ratio) and measured at 30 ° C.

(4) Dispersibility in polymer 8.5 Kg / h using 1000 mesh filter with filtration area of 30 cm ^2.
When the molten polymer is extruded at r, the extrusion rate until the pressure at the inlet of the filter reaches 150 kg / cm ² (converted to ton / m ² )
Expressed as The larger this value, the better the filterability of the filter, and the better the dispersibility of the polymer. The dispersibility in the polymer at that time was judged as follows.

＞ 80 (ton / m ² ) …… ◎ 40 to 80 (ton / m ² ) …… ○ 20 to 40 (ton / m ² ) …… △ <20 (ton / m ² ) …… × (5) Film Film-forming property of 40-70 after melt extruding into film at 270-300 ℃
After cooling and solidifying at ℃ to make an amorphous sheet, lengthwise (3.0 times),
Biaxial stretching was sequentially carried out horizontally (3.0 times), and the frequency of breakage at that time was judged as follows.

Not broken at all …… ○ Sometimes broken …… △ Frequently broken …… × (6) Initial whiteness of the film Measured using a Tokyo Denshoku color difference meter (TC-5D type).
The whiteness of the film is represented by the b value, and the smaller the value, the higher the whiteness. Further, the larger the b value, the stronger the yellowish color and the yellowing.

(7) Concealment Degree The density of transmitted light under a G filter was measured using a Macbeth densitometer (TD-904 type). The larger this value is, the higher the hiding power is.

(8) Evaluation of light resistance UV long life fade meter (FA
L-3 type) was used, and after irradiating with ultraviolet rays at 63 ° C. ± 3 ° C. for 300 hours, the b value was measured using the color difference meter (TC-5D type) of the above (6). The smaller the change (Δb value) between the initial b value and the b value after 300 hours, the better the light resistance.

<Example 1> (Production method of polyester chip) 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol
Parts and 0.07 parts of calcium acetate monohydrate are heated in a reactor and heated, and methanol is distilled off to carry out a transesterification reaction. It takes about 4 and a half hours after the reaction is started to reach 230 ° C. The transesterification reaction was completed.

Next, 0.04 part of phosphoric acid and 0.035 part of antimony trioxide were added, and polymerization was carried out according to a conventional method. That is, the reaction temperature was gradually increased to finally 280 ° C., while the pressure was gradually reduced to finally 0.5 mmHg. After 4 hours, the reaction was completed,
A polyester (A) was obtained by chipping according to a conventional method. At that time, the intrinsic viscosity was 0.702.

(Manufacturing method of master batch) 60 parts of the obtained polyester (A) and aluminum hydroxide manufactured according to a conventional method (0.3% of aluminum element conversion)
And 40 parts of anatase type titanium dioxide containing silicon dioxide (0.3% in terms of silicon element) and having an average particle size of 0.3 μm were melt-mixed in an extruder at 290 ° C. according to a conventional method to obtain a master batch chip (B).

(Film Forming Method) The polyester (A) and the polyester (B) were blended at 62.5: 37.5 so that the blending amount of the titanium dioxide was 15%, followed by drying at 180 ° C. for 5 hours and at 290 ° C. according to a conventional method. The film was melt-extruded, cooled at 50 ° C. and solidified to form an amorphous sheet, which was sequentially biaxially stretched lengthwise and widthwise and heat-treated at 230 ° C. to obtain a white biaxially stretched film having a thickness of 250 μm.

The characteristics of the obtained white polyester film are shown in Table 1. As shown in Table 1, the initial whiteness and light resistance of the obtained white polyester film are very good and have very satisfactory characteristics.

<Example 2> Aluminum hydroxide (aluminum element conversion 0.3%) and silicon dioxide (silicon element conversion 0.3%) used in Example 1
Example 1 except that anatase-type titanium dioxide containing aluminum oxide (0.3% aluminum element conversion) and silicon dioxide (0.3% silicon element conversion) and having an average particle size of 0.3 μm was used in place of the anatase-type titanium dioxide containing C. A white biaxially stretched film was obtained by the same method as described above. The characteristics of the obtained white polyester film are shown in Table 1. The white polyester film thus obtained has very satisfactory properties as in Example 1.

(Example 3) A method similar to that of Example 1 except that anatase type titanium dioxide containing aluminum hydroxide (aluminum element conversion 0.6%) and silicon dioxide (silicon element conversion 0.3%) having an average particle diameter of 0.3 µm was used. To obtain a white biaxially stretched film. The characteristics of the obtained white polyester film are shown in Table 1. The white polyester film obtained was obtained from Example 1.
Similar to the above, it has extremely satisfactory characteristics.

(Example 4) Example 1 except that the anatase type titanium dioxide containing aluminum hydroxide (aluminum element conversion 0.6%) and having an average particle size of 0.3 µm was compounded in an amount of 20% with respect to the polyester. A white biaxially stretched film was obtained by the same method as described above. The characteristics of the obtained white polyester film are shown in Table 1. The obtained white polyester film has satisfactory properties except that the dispersibility is slightly inferior to those of Examples 1 to 3.

Comparative Example 1 A white biaxially stretched film was obtained in the same manner as in Example 1 except that anatase type titanium dioxide having an average particle size of 0.3 μm was used. The characteristics of the obtained white polyester film are shown in Table 1. As shown in Table 1, since it does not contain an aluminum compound and silicon dioxide, it is inferior in light resistance and is inadequate as a characteristic of the white polyester film.

(Comparative example 2) Aluminum hydroxide (aluminum element conversion 0.005%)
A white biaxially stretched film was obtained in the same manner as in Example 1 except that anatase type titanium dioxide containing was used.
The characteristics of the obtained white polyester film are shown in Table 1. As shown in Table 1, since the content of aluminum hydroxide is less than 0.01% in terms of aluminum element, the light resistance is poor and the properties of the white polyester film are insufficient.

(Comparative Example 3) A method similar to that of Example 1 except that anatase-type titanium dioxide containing aluminum hydroxide (2.5% aluminum element conversion) and silicon dioxide (0.3% silicon element conversion) and having an average particle size of 0.3 µm was used. Although it was tried to obtain a white biaxially stretched film, the dispersibility in the polymer and the thermal stability of the polymer were poor and a white polyester film could not be obtained smoothly.

(Comparative Example 4) Anatase-type titanium dioxide containing aluminum hydroxide (aluminum element conversion 0.6%) and silicon dioxide (silicon element conversion 0.3%) and having an average particle diameter of 0.3 μm was added to the polyester in an amount of 1%. A white biaxially stretched film was obtained in the same manner as in Example 1 except that the components were blended. The characteristics of the obtained white polyester film are shown in Table 1. As shown in Table 1, the hiding power is inferior and the properties of the white polyester film are insufficient.

(Comparative Example 5) Anatase type titanium dioxide containing aluminum hydroxide (aluminum element conversion 0.6%) and silicon dioxide (silicon element conversion 0.3%) and having an average particle diameter of 0.3 μm was adjusted to 35% with respect to polyester. An attempt was made to form a film by the same method as in Example 1 except that the polyester film was blended in an excessively large amount, but the mechanical strength of the polyester film was lowered due to the excessive content of the titanium dioxide and the film-forming property was poor, resulting in a smooth white polyester film. I couldn't get it.

(Comparative Example 6) A method similar to that of Example 1 except that rutile titanium dioxide having an average particle size of 0.4 μm and containing aluminum hydroxide (aluminum element conversion 0.6%) and silicon dioxide (silicon element conversion 0.3%) was used. To obtain a white biaxially stretched film. The characteristics of the obtained white polyester film are shown in Table 1. As shown in Table 1, the initial whiteness is inferior and the characteristics of the white polyester film are insufficient.

(Effect of the Invention) As described in detail above, the white biaxially stretched polyester film of the present invention contains a specific amount of anatase titanium dioxide containing a specific amount of an aluminum compound and silicon dioxide, and is a whiteboard for electronic whiteboard. In addition to having excellent light resistance required for magnetic cards, the initial whiteness was also improved.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area B29L 7:00

Claims (2)

[Claims] 1. Anatase type titanium dioxide containing 0.01 to 2.0% by weight of aluminum compound in terms of aluminum element and 1.0% or less of silicon dioxide in terms of element of silicon is blended in an amount of 2.0 to 30% by weight with respect to polyester. A white biaxially stretched polyester film. 2. The average particle size of anatase titanium dioxide is 0.
Claim 1 characterized in that it is 1 to 1.0 μm.
The white biaxially stretched polyester film described in the item.