JPH02185532A - White polyester film - Google Patents

Abstract

PURPOSE:To get rid of occurrence of marks and nonuniformity of quality and to improve producibility, luster and heat-resistant dimensional stability by adding inorg. particles with a specified mean particle diameter coated with a polyolefin resin in a polyester and making it into a film. CONSTITUTION:An inorg. particle comprising a compd. of an element selected from among those of groups IIa, IIb, IIIb, IVa, IVb, Vb, VIa and VIIa of the periodical table with a mean particle diameter of 0.2-10mum, pref. 0.3-7mum (e.g. BaSO4) is coated with 0.5-50wt.% polyolefin resin (e.g. PP). A polyester (e.g. polyethylene terephthalate) is mixed with 3-50wt.%, pref. 5-40wt.% resin-coated inorg. particles and the mixture is made into a film at about 285 deg.C. The film is cooled at about 20 deg.C and solidified. The film is then drawn 2.5 to 7-fold in the longitudinal direction at 75-120 deg.C, 2.5 to 5-fold in the transverse direction at 80-110 deg.C and then heat-treated at 160-230 deg.C to obtain a biaxially oriented title film.

Description

[Detailed description of the invention] U industrial application field The present invention relates to card labels, display boards, and photographic paper.

The present invention relates to a white polyester film used for substrates such as X-ray intensifier paper, printing substrates for thermal transfer printers, information recording paper for FA, OA, and other applications in various paper fields.

[Prior Art] It has been well known to add a large amount of white inorganic particles to polyester in order to obtain a white polyester film.

For example, Japanese Patent Publication No. 4901/1983, in which large amounts of titanium oxide and barium sulfate are added, and Japanese Patent Publication No. 12013/1987, in which calcium carbonate is added, are disclosed.

Further, a polyester film to which a polyolefin is added is also disclosed in JP-A-63-172740.

[Problems to be Solved by the Invention] However, as described above, polyester films to which a large amount of inorganic particles are added or polyester films to which polyolefins are added have the following problems.

) In a system in which a large amount of inorganic particles are added, (1) convex lines in the longitudinal direction of the film that occur at the die (hereinafter referred to as die lines) appear, resulting in poor productivity.

■The film surface is easily scratched.

ii) In polyolefin-added systems, (1) uneven dispersion of polyolefin occurs, resulting in uneven film quality;

■The gloss level is not sufficient.

■Lack of heat resistance and dimensional stability.

The present invention provides a polyester film that solves these problems.

[Means for Solving the Problems] The present invention provides a white polyester film in which 3 to 50 wt% of polyolefin-coated inorganic particles, which are inorganic particles having an average particle diameter of 0.2 to 10 μm coated with a polyolefin resin, are added to polyester. This is a characteristic feature.

The polyester of the present invention is a polymer having an ester bond consisting of a dicarboxylic acid and a diol in its main chain,
Typical dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenic acid, diphenyldicarboxylic acid, adipic acid, sepatic acid, dodecanedicarboxylic acid, and derivatives thereof. Typical examples include ethylene glycol, butylene glycol, hexylene glycol, diethylene glycol, polyethylene glycol, polytetramethylene glycol, cyclohexane dimetatool, and derivatives thereof, and polymers from oxycarboxylic acids.

Particularly preferred polynitsels of the present invention include:
These include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and their derivatives.

Of course, different polyesters can be used depending on the application, and if heat resistance and mechanical properties are important, a homopolymer with a heat of crystal fusion ΔHU of gcal/g or more and a glass transition temperature Tg of 70°C or more is used. On the other hand, when softness and flexibility are important, a copolymerized polyester and elastomer with a heat of crystal fusion ΔHu of 8 Ca1/g or less is preferable.

Moreover, the inorganic particles as used in the present invention are particles made of inorganic compounds, and are particles of IIa, nb, and ub of the periodic table.

A compound consisting of at least one element selected from IVa, IVb, Vb, VIa, and ■a, for example,
Examples include magnesium oxide, aluminum oxide, silicon oxide, titanium oxide, calcium carbonate, barium sulfate, magnesium carbonate, calcium silicate, talc, and mixtures thereof.

The average particle diameter of the inorganic particles is preferably 0.2 to 10 μm, preferably 0.3 to 7 μm.

If it is less than 0.2 μm, it tends to aggregate, creating film surface defects. On the other hand, if the thickness exceeds 10 μm, there will be drawbacks such as tearing of the film during stretching and clogging of the filter.

The polyolefin as used in the present invention refers to olefin polymers such as polyethylene, polypropylene, poly4-methyl-pentene 1, and polystyrene, or copolymers thereof, wax-like materials, and the like.

This polyolefin needs to be mixed with the above-mentioned inorganic particles and coated on the surfaces of the inorganic particles.

The method may be any method. For example, there is a method in which a dilute solution is prepared with the solvent of each polyolefin and inorganic particles are immersed in it, or a method in which powder is scattered and the dilute solution is sprayed with a spray gun.

The amount of the polyolefin-coated inorganic particles thus produced is preferably 3 to 50 wt% based on the polyester.
It is preferable to add up to 40 wt%, and if it is less than 3 wt%, the optical density, whiteness, etc. will decrease, which is not preferable. Also, 5
If it exceeds 0 wt%, the stretchability will be poor and the productivity will be reduced.

The polyolefin-coated inorganic particles may be added immediately after the polyester is polymerized, once kneaded with the polyester resin, melt-extruded, and then pelletized, or even when melt-extruded into a sheet.

In addition, the polyolefin-coated inorganic particles have a polyolefin content of 0.0% relative to the weight of the inorganic particles. 5-50 wt
%, more preferably 1 to 40 wt%.

When the amount added is less than 0.5 wt%, there is almost no coating effect, and when it exceeds 50 wt%, the thermal dimensional stability deteriorates, the cushioning ratio decreases, and the void ratio decreases, resulting in a decrease in film thickness and dimensional problems. Stability deteriorates.

In addition, the total amount of uncoated inorganic particles or polyolefins that do not contain inorganic particles is 50 area % or less, preferably 40 area % or less, more preferably 30 area % or less of the total amount added including coated inorganic particles. That's fine.

If it exceeds 50 area %, problems similar to those described above, such as coating effect and thermal dimensional stability, will occur.

In addition, if the inorganic particles are calcium carbonate, phosphorus compounds may be added to polyester or polyolefin in order to suppress air bubbles generated in the film, prevent yellowing of polyester, or obtain white discoloration. Good.

Further, it is more preferable to use a fluorescent brightener in combination to further improve the whitening of the film.

Furthermore, a surfactant may be added to impart antistatic properties, and in this case, it is preferable to add a surfactant to the polyolefin polymer to improve dispersibility.

The polyester film of the present invention must be biaxially oriented, and the area magnification is 7 to 35 times, preferably 9 to 20 times.
Double is better. If the area magnification is less than 7 times, the whiteness, glossiness,
The optical density and cushioning properties deteriorate, making it unusable as a white film. Moreover, if it is about 22 times or more, the stretchability decreases, and if it exceeds 35 times, the stretchability decreases further, which is not preferable.

Next, the method for manufacturing the polyester film of the present invention will be explained. Note that this method is an example and is not limited thereto.

Blend 3 to 50 wt% of inorganic particles of a specific particle size coated with polyolefin to polyester, and heat at 285°C.
It is extruded through a T-die in an extruder heated to A white polyester film is obtained by stretching, then stretching 2.5 to 5 times in the width direction at 80 to 110°C, followed by heat treatment at 160 to 230°C to obtain a biaxially stretched film, and winding it up. .

In addition, this film may be subjected to surface activation treatment such as N2, CO
Corona discharge treatment or plasma treatment under various gases such as No. 2 may be performed.

[Effects of the Invention] Even if the white polyester film of the present invention is a system in which a large amount of inorganic particles is added, by using polyolefin-coated inorganic particles, a film having the following excellent effects can be obtained.

■No die streaks occur, allowing stable film formation for long periods of time, greatly improving productivity.

■No more scratches on the film surface.

■Dispersibility becomes uniform, eliminating unevenness in film quality.

■Sufficient gloss can be obtained.

■Products with good heat resistance and dimensional stability can be obtained.

[Measuring method] The measurement method used in the present invention is shown below.

(1) Stretchability Films were formed under various conditions and the time taken until the film broke was shown as follows.

When it breaks within 4 hours: × (poor productivity) When it breaks after 4 to 8 hours: △ When it breaks after 8 hours or more: 20 (good productivity) (2) Scrapability Daiei Kagaku Seiki Seisakusho (manufactured by Gakushin), a dry cloth was applied at a load of 216 g/20 mm using a dyed material abrasion fastness tester of 50
Evaluation was made based on the presence or absence of scratches after rubbing twice, and those with scratches were marked with an X, and those with no scratches were marked with an O.

(3) Agglomerated foreign matter Those where foreign matter was clearly visible to the naked eye were marked with an x mark, and those where no foreign matter was observed were marked as good and marked with an ○ mark. In addition, those that had a slight amount of foreign matter but were still usable were marked with a △ mark.

(4) Whiteness Whiteness is determined by method B (2) of J I 5-L1015-1981.
Measured by wavelength method).

(5) Optical density OD Measurement is performed using a Macbeth densitometer model TD504.

The transmission density is 01 and the amount of human radiation is ■. , where I is the amount of transmitted light, it is defined as D-log (I/Io).

(6) Cushion rate Attach a 10g pedestal to the top of the spindle of the Mitoyo dial gauge. Lift the spindle and lower it onto the sample set on the measurement stand. Place a 50g weight on the pedestal,
The thickness after 5 seconds was read, the value at this time was set as 5 μm, and the cushioning ratio C was calculated using the following formula.

C=100x (a-b)/a (%) Note) Dial gauge type: No, 2109-10 Measuring element: 3mmφ hard ball (7) Glossiness Obtained by measuring method 2 of JIS-28741-1962 .

(8) Average particle size The inorganic particles were dispersed in ethanol and measured using a centrifugal sedimentation type particle size distribution analyzer (manufactured by Horiba, CAPA500) to calculate the volume average diameter, which was defined as the average particle size.

(9) Method for measuring the amount of uncoated inorganic particles and polyolefin containing no inorganic particles A cross section of the film was observed using an optical microscope or a scanning electron microscope, and each state was separated, and the area ratio was determined.

[Example] Hereinafter, a more detailed explanation will be given by showing examples.

Example 1, Comparative Example I Polyethylene terephthalate with an IV of 0.6 was added with 20 wt% of barium sulfate with an average particle size of 0.8 μm, and the same particles were added with 5 wt% of polypropylene based on the particle weight. % coating (the former Comparative Example 1, the latter Example 1), and 20 wt % of this was added.

This raw material is melt extruded from an extruder heated to 285°C,
The material discharged from the T-die was molded in a cooling drum kept at 20°C. This film was heated at 95°C by 3.2 cm in the longitudinal direction.
After stretching, the film was stretched 3.8 times in the width direction at 90° C. using a tenter, and then heat-treated at 2300° C. for 5% relaxation. The discharge amount was adjusted so that the film thickness after this stretching heat treatment was 150 μm.

At this time, the time until the appearance of die streaks and the film properties were as shown in Table 1.

As is clear from this table, the use of polyolefin-coated inorganic particles eliminates the occurrence of die streaks and improves the abrasion resistance of the film.

Examples 2 to 5, Comparative Examples 2 to 3 Polyethylene terephthalate with an IV of 0.65 was
4 pieces of calcium carbonate each having the average particle size shown in the table.
- Methyl-pentene-1 coated with 7% by weight of particles
wt% of 4-methyl-pentene-1), which was added to 20 wt.
% added. Other conditions were the same as in Example 1.

The results show that if the particle size is not within a specific range, the homogeneous white polyester film of the present invention cannot be obtained because agglomerated foreign matter is generated or stretchability is deteriorated.

Examples 6 to 8, Comparative Examples 4 to 5 Polyethylene terephthalate with an IV of 0.8 and calcium carbonate with an average particle size of 1.0 μm were coated with polypropylene at 5 wt% based on the particle weight as shown in Table 3. Added. Other conditions were the same as in Example 1, but the stretching in the longitudinal direction was at 100° C. and 4.0 times the stretching.

As a result, it can be seen that if it is added in excess of necessary, the stretchability deteriorates and productivity decreases, while if it is added in too little, the whiteness, optical density and cushioning rate decrease, making it unusable as a white polyester film.

Table 1 ]5

Claims (1)

[Claims] A white polyester film characterized in that 3 to 50 wt% of polyolefin-coated inorganic particles, which are inorganic particles having an average particle diameter of 0.2 to 10 μm coated with a polyolefin resin, are added to polyester.