JPS63193934A - White polyester film - Google Patents

Abstract

PURPOSE:To obtain the titled biaxially oriented white film having remarkably improved light-resistance and suitable as a base for electronic white board or magnetic card, by using a specific amount of anatase titanium oxide containing a specific amount of a zinc compound. CONSTITUTION:The objective film contains anatase titanium dioxide (preferably having an average particle diameter of 0.1-1.0mum) containing 0.1-2.0wt.% Zn compound in terms of Zn based on titanium dioxide. The amount of the titanium dioxide is 2.0-3.0% based on the polyester. The polyester is preferably those containing >=80mol.% ethylene terephthalate unit and/or ethylene 2,6- naphthalate unit.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a white biaxially oriented polyester film with highly improved light resistance.

<Prior art and problems to be solved by the invention> Polyesters, represented by polyethylene terephthalate, are used for information recording materials, due to their excellent mechanical properties, electrical properties, chemical resistance, and dimensional stability. It is used as a base material in many fields such as capacitors, packaging, plate making, electrical disconnection, and photographic film applications.

In recent years, taking advantage of the excellent properties of such polyester films, they have been widely used in finance, communications, transportation, etc. for electronic whiteboards and magnetic cards such as credit cards, telephone cards, and Japanese National Railways cards. They lie in an attempt to expand the range of use.

However, in such applications, the polyester film used as the base material may turn yellow over a long period of time because it is exposed to sunlight outdoors or ultraviolet rays from indoor fluorescent lights. There is a problem that the mechanical strength tends to decrease.

The former is a serious problem, and it is known that this is a phenomenon caused by yellowing of titanium dioxide, which is contained as a white masking agent in the white polyester film, due to deterioration due to ultraviolet #iIK. In order to improve these properties required of a white polyester film, a UV absorber is generally included in the white polyester film.

This makes it possible to prevent the white polyester film from deteriorating to some extent.

However, the UV absorbers conventionally used are organic UV absorbers such as benzophenone, benzotriazole, or hydroquinone, and these organic UV absorbers are generally susceptible to thermal decomposition or oxidative decomposition. , and some sublimate at high temperatures.

On the other hand, polyester films such as polyethylene terephthalate are formed at temperatures between -7θ and 300°C, so even if such an organic ultraviolet absorber is added during film formation, the ultraviolet absorber undergoes thermal decomposition or sublimation and its ultraviolet rays are absorbed. Absorption capacity is significantly reduced.

Furthermore, if the amount of ultraviolet absorber added is increased to compensate for the decrease in ultraviolet absorbing ability, the hue of the resulting film may be reduced or the ultraviolet absorber may accumulate in the film forming machine, causing various troubles.

Moreover, among such organic ultraviolet absorbers, some K has harmful effects on the human body.

As mentioned above, even if an organic ultraviolet absorber is blended into a white polyester film, it is currently very difficult to maintain sufficient light resistance and whiteness.

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to achieve the above objectives, in view of the growing demand for improvements in the light resistance of white polyester films to ultraviolet rays and the maintenance of whiteness. As a result of repeated efforts, it was discovered that the light resistance to ultraviolet rays and the maintenance of whiteness of a white polyester film could only be achieved by circulating fine particles of anatase-type titanium dioxide containing a zinc compound, and the present invention was achieved.

A white di@stretched polyester film is characterized in that it contains anatase-type titanium dioxide in an amount of θ to 30% by weight based on polyester.

The valve assembly VciI52 of the present invention will be explained below.

The polyester referred to in the present invention refers to aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, or esters thereof, and ethylene glycol, diethylene glycol, tetramethylene glycol, neopentyl glycol, etc. It is a polyester that can be obtained by polycondensation with glycols such as

This polyester can be obtained by direct polycondensation of aromatic dicarboxylic acid and glycol, or can be obtained by transesterifying aromatic dicarboxylic acid dialkyl ester and glycol, or by combining aromatic dicarboxylic acid dialkyl ester and glycol. It can also be obtained by methods such as diester polycondensation.

Typical examples of such polymers include polyethylene terephthalate, polyethylene-2, and inaphthalate. This polymer may be a homopolymer or may be a copolymer with a third component.
However, in the present invention, polyesters having ethylene terephthalate units and/or ethylene co-naphthalate units in an amount of θ mole or more are preferred.

In the present invention, a specific amount of anatase titanium dioxide containing a specific amount of a zinc compound is blended into polyester.

Zinc anatase contained in titanium dioxide,
Examples include zinc sulfate and zinc nitrate, but are not limited to these.

Among these, zinc compounds having good heat resistance are preferred.

The average particle diameter of the zinc compound-containing anatase titanium dioxide incorporated in the present invention is preferably 0.7 to 1.0 μm, particularly 0.7 μm to 1.0 μm. -~0. ! Preferably it is μm. If the average particle size is less than 0.7 μm, the light transmittance will increase and the white hiding effect will be insufficient, so it is preferable.On the other hand, if the average particle size exceeds 80 μm, the original whiteness of 7-nataze titanium dioxide will decrease. This is not preferable because it reduces the

Also, the amount of zinc compounds contained in anatase world titanium dioxide Kfi is the zinc element'! 0.1 to 2.0% by weight of An, especially θ,! It is preferable that the weight of the zinc compound contained in the anatase-type titanium dioxide is θ in terms of zinc element, and if it is less than 7 weight, the light resistance improvement effect will be insufficient. On the other hand, if the amount of zinc compound contained in the anatase titanium dioxide exceeds 2.0% by weight in terms of zinc element, the thermal stability of the polyester will decrease, leading to problems such as film breakage during film formation. This is not recommended as it tends to occur.

The amount of zinc compound-containing anatase titanium dioxide is 2.0 to 30% by weight, especially 1.0 to 10! It is preferable that the amount of anatase titanium dioxide containing a b0 zinc compound is less than 4.0% by weight, which is not preferable because the light transmittance increases and the white hiding effect becomes insufficient. Also, this amount is 30 weight -
Exceeding this is not preferable because the mechanical strength of the polyester decreases, leading to problems such as breakage of the film during film formation.

The manufacturing method of the zinc compound-containing anatase titanium dioxide used in the present invention is not limited in any way as long as it satisfies the conditions specified above.

As a method for incorporating such zinc compounds into anatase-type titanium dioxide, a predetermined amount of zinc compounds such as zinc oxide, zinc hydroxide, zinc carbonate, zinc chloride, etc. may be added and blended during the production of anatase-type titanium dioxide. Zinc compounds such as commercially available anatase-type titanium dioxide, zinc chloride, water-catalyzed zinc, zinc carbonate, and zinc chloride may be used for surface treatment.

There is no problem even if the zinc compound is washed inside the anatase type titanium dioxide or exists on the surface, but it is better to exist on the surface in order to improve the initial whiteness. preferable.

In the present invention, the zinc compound-containing anatase titanium dioxide can be blended at any stage up to the production of the polyester film. That is, the zinc compound-containing anatase titanium dioxide may be blended, for example, as a glycol slurry or as a powder at any stage before the start of the polycondensation reaction, during the polycondensation reaction, or after the end of the polycondensation reaction. Alternatively, a polyester resin and anatase-type titanium dioxide containing a zinc compound may be melt-mixed in an extruder to form chips. In addition, a so-called master patch chip containing a high concentration of anatase-type titanium dioxide containing a zinc compound is manufactured, and if necessary, a master patch chip is made of polyester that does not contain anatase-type titanium dioxide containing a zinc compound or contains a small amount of anatase-type titanium dioxide. A polyester film having a predetermined blending amount can also be produced by mixing with.

In the present invention, as necessary, the average particle size is set to a level that does not adversely affect initial whiteness and light resistance, does not increase the number of coarse particles, and has a smooth polyester film surface. Inert particles other than anatase-type titanium dioxide containing a zinc compound may be used in combination if the content is as follows. In addition to the above-mentioned inert particles, it is also possible to use so-called precipitation-type fine particles that are precipitated by reaction with catalyst residue and a phosphorus compound in the reaction system.

Even with the fluctuation K, a biaxially oriented polyester film containing a specific amount of anatase type titanium dioxide containing a specific amount of a zinc compound satisfies the initial whiteness and light resistance that are the objectives of the present invention.

Known methods can be used for polycondensation of polyester in the present invention. For example, as a catalyst for the polycondensation reaction, one or more of antimony compounds, germanium compounds, titanium compounds, etc. is used, heated to about 230 to 300°C, and the reaction is allowed to proceed by distilling off glycol under reduced pressure.

Note that a known method can be adopted for forming chips and master patch chips. For example, raw polyester chips and particles are melt-mixed in an extruder at 270 to 300°C, and after cooling, they are formed into chips.

In addition, a known film forming method can be employed when forming a film. For example, raw polyester chips containing anatase-type titanium dioxide containing zinc compounds are melt-extruded into a film at -70 to 300°C, cooled at 4tO to 20°C, solidified to form an amorphous sheet, and then vertically (2,1 301 times), lateral (-0! to 3.1 times) sequential biaxial stretching, or simultaneous biaxial stretching and heat treatment at 760 to 7θ°C (for example, as described in Japanese Patent Publication No. 30-1632) method) can be adopted.

<Examples> The present invention will be explained in more detail by Examples below, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. In addition, various physical properties and characteristics were measured or defined as follows. In the examples, “part” is “
``parts by weight'', and ``chi'' means ``% by weight''.

(1) Average particle size Centrifugal sedimentation type particle size distribution analyzer manufactured by Takasugi Seisakusho (SA-OP
The value of the integrated (weight-based) jθ% in the uniform spherical distribution measured with J-type is used.

(2) Take 7g of thermostable polymer in a test tube, /Otsu0℃-/vaHJi
After vacuum drying for one hour, the pressure was restored to 100 H9 using nitrogen gas, and then the pressure was increased to 100 H9. Melting heat treatment was carried out at Q°C for 1 hour, and the degree of retention of the degree of polymerization was evaluated from the retention 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] Polymer/l is phenol/tetrachloroethane-60
Dissolved in a mixed solvent of 710 (weight ratio) 1ootxt,
Measured at 30°C.

(4) Dispersibility in polymer When extruding molten polymer at J', j kg/hr using a 1000 mesh filter with an opening area of JOaA, the pressure of the filter population reaches /j Ojc97d. It was expressed in the amount of extrusion (converted to tons/-). The larger this value is, the better the filter mouthability is, and the better the dispersibility of the polymer. The dispersibility in the polymer at that time was judged as follows.

〉 4t Q (ton/,,?')
−・−・・・−○so Ngu θ (ton/
, /) ・・−1・・ △ku−20 (ton/−
) ......-× (5) After forming a film formable sheet, it was sequentially biaxially stretched vertically (3,0 times) and horizontally (3,0 times), and the frequency of breakage at that time was The judgment was as follows.

Does not break at all ・－・・・・・・・・・・－〇 Breaks sometimes ・・・・・・・・・・・・・・・Δ Frequently breaks ・・・・・・・・・・・・-x measurement.

The whiteness of the film is expressed by the b value, and the smaller this value, the higher the whiteness.

The thicker the value, the stronger the yellowish tinge, indicating quantification.

(Power Hiding power Macbeth densitometer (model TD-204) was used to measure the transmitted light density under the G filter. The larger the value, the higher the hiding power.

(8) Evaluation of light resistance using Suga Test Instruments UV Long Life Fade Meter (F
After irradiating with ultraviolet rays for 300 hours at ≦3℃±3℃ using the color difference meter (To-, tD) of (6) above,
The b value was measured using A small change in b value (Δb value) between the initial value and after 300 hours indicates good light resistance.

<Example/> (Method for manufacturing polyester chips) 700 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.07 parts of calcium acetate hydrate are placed in a reactor and heated to raise the temperature to distill off co-trapped methanol and carry out a transesterification reaction. was carried out, and it took about Z hours and a half after the start of the reaction,
The temperature was reached to 230°C, and the transesterification reaction was substantially completed.

Next, phosphoric acid O, O4 parts and antimony dioxide 0, Oj
7 parts were added and 1 cup was added in the usual manner.

That is, the reaction temperature is gradually raised until it finally reaches ♂Q°C, while the pressure is gradually decreased and finally reaches 0. jtrrs
It was called H9. After 1 hour, the reaction was completed and the mixture was made into chips according to a conventional method to obtain a polyester product. Viscosity at that time [η)
-0,70! Met.

(Production method for masterbatch chips) The obtained polyester (1,) tO parts and zinc oxide (converted to zinc elemental o,
4 tO parts of anatase-type titanium dioxide containing 3q6) were melt-mixed in an extruder at -20°C according to a conventional method to obtain a masterbatch chip (B).

(!A layer film method) The above polyester (A) and polyester (B) are mixed so that the amount of titanium dioxide is /42.1: j
1. After tK blending, 1tro℃-! After drying for an hour and melt-extruding it into a film at λ 0℃ according to a conventional method,
After cooling and solidifying at .degree. C. to form an amorphous sheet, it was sequentially biaxially stretched vertically and horizontally, and heat treated at 23.theta..degree. C. to obtain a white biaxially stretched film with a thickness of 2j.theta..mu.m.

The properties of the obtained white polyester film are shown in Table 1. As shown in Table 7, the initial whiteness, light resistance, etc. of the obtained white polyester film were very good and had extremely satisfactory properties.

Example/Except that anatase-type titanium dioxide containing zinc hydroxide (0.3% in terms of zinc element) with an average particle size of 0.3 μm was used instead of anatase-type titanium dioxide containing (0.3% in terms of zinc element). A white biaxially stretched film was obtained in the same manner. The properties of the obtained white polyester film are shown in Table 1.

The white polyester film obtained has very satisfactory properties as in Example/.

<Example 3> Zinc oxide with an average particle size of 0.3 μm (converted to zinc element o, t
e16) A white biaxially stretched film was obtained in the same manner as in Example except that anatase-type titanium dioxide containing e16) was used. The resulting white polyester body has characteristics.

<Example DA> Zinc oxide with an average particle size of 0.3 μm (converted to zinc element o, t
%) Containing anatase type titanium dioxide, its blending amount is -
A white biaxially stretched film was obtained in the same manner as in Example except that the composition was blended so as to have a composition of 0.04. The properties of the obtained white polyester film are shown in Table 1. The white polyester film obtained has, like Example 1, very satisfactory properties.

Comparative Example 1> A white biaxially stretched film was obtained using anatase titanium dioxide having an average particle size of 0.3 μm in the same manner as in Example except for the round plate. The properties of the obtained white polyester film are shown in Table 1. As shown in Table 1, since it does not contain a zinc compound, the light resistance is poor and the properties of a white polyester film are insufficient.

Comparative Example> Zinc oxide with an average particle size of 0.3 μm (Zinc element equivalent: 0.07
A white biaxially stretched film was obtained in the same manner as in Example except that anatase-type titanium dioxide containing (%) was used. Table 7 shows the properties of the white polyester film obtained. As shown in Table 1, the content of zinc oxide is
Since it is less than r1-, the light resistance is poor and the properties of a white polyester film are insufficient.

Comparative Example 3> Zinc oxide with an average particle size of 0.3 μm (zinc element equivalent -z, -
I tried to obtain a white biaxially stretched film using the same method as in Example except that titanium dioxide with anatase plate was used, but the dispersibility in the polymer and the thermal stability of the polymer were poor, resulting in a white polyester film. Couldn't get the film.

Comparative Example> Zinc oxide with an average particle size of 0.3 μm (0.6% in terms of zinc element)
A white biaxially stretched film was obtained in the same manner as in Example 1, except that the amount of anatase titanium dioxide contained in Example 1 was blended in an amount of 0. The properties of the obtained white polyester film are shown in Table 1. As shown in Table 1, the hiding degree is poor and the properties of a white polyester film are insufficient.

Great comparison example! 〉 Zinc oxide with an average particle size of 0.3 μm (Zinc element equivalent: 0, l
The amount of anatase type titanium dioxide contained is 3! An attempt was made to obtain a white biaxially stretched film in the same manner as in Example except that the content of titanium dioxide was too high, and the mechanical strength of the polyester film decreased. Film forming properties were poor and a white polyester film could not be obtained.

Comparative Example A> Zinc oxide with an average particle size of 3 μm (0.6% in terms of zinc element)
A white biaxially stretched film was obtained in the same manner as in Example except that the containing rutile titanium dioxide was used. Table 1 shows the properties of the white polyester film obtained. As shown in Table 1, since rutile titanium dioxide was used, the initial whiteness was poor and the properties of a white polyester film were insufficient.

<Effects of the Invention> As detailed above, the white biaxially stretched polyester film of the present invention contains a specific amount of anatase-type titanium dioxide containing a specific amount of zinc compound, and is suitable for whiteboards for electronic whiteboards and hunting cards. It has excellent light resistance as required.

Further, by using anatase titanium dioxide containing a zinc compound, the initial whiteness is also improved.

Sender: Diafoil Co., Ltd. Representative Patent Attorney Hase - 1 other person

Claims (2)

[Claims] (1) 0.1 to 2 in terms of zinc element relative to titanium dioxide
．． Anatase type titanium dioxide containing 0% by weight of zinc compound on polyester A white biaxially stretched polyester film characterized by containing 2.0 to 30% by weight. (2) Average particle size of anatase titanium dioxide is 0.1~
The white biaxially stretched polyester film according to claim 1, characterized in that the film has a thickness in the range of 1.0 μm.