JP2001011210A - White polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a white polyester film improved in hiding power, stability during film formation, and processability, wherein the average concentration of titanium dioxide in the film is specified, and the crystallization index of the polyester around the titanium dioxide particles is specified. SOLUTION: In this white polyester film, the average concentration of titanium dioxide particles in the film is 10-50 wt.%, and the crystallization index of the polyester around the titanium dioxide particles is at most 45, and the intrinsic viscosity of the film is 0.58-0.7 dl/g. It is desirable that the melting point of the film is 180-270 deg.C, and the film is desirably a biaxially oriented one though it is not limited to a uniaxially oriented one or a biaxially oriented one. It is desirable that the polyester constituting the film comprises at least 75 mol% polyester mainly consisting of ethylene phthalate units and/or ethylene naphthalate units, and it is desirable that the entire thickness of the film is 3-50 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white polyester film. More specifically, the present invention relates to a white polyester film suitable for processing such that the film becomes an outer surface of a container or the like after being bonded to a metal plate or the like.

[0002]

2. Description of the Related Art Conventionally, for the purpose of preventing corrosion, the inner and outer surfaces of a metal can are coated with various kinds of thermosetting resins such as epoxy and phenol melted or dispersed in a solvent.
Coating metal surfaces has been widely practiced. However, such a coating method using a thermosetting resin has unfavorable problems such as a decrease in productivity due to a long time required for drying and environmental pollution due to a large amount of an organic solvent.

Recently, as a method for solving these problems,
Attempts have been made to coat (laminate) a film on a steel plate, an aluminum plate, or a metal plate obtained by subjecting the metal plate to various surface treatments, such as plating, as the material of the metal can. When a metal can is manufactured by drawing or ironing a film laminated metal plate, the film is required to have the following characteristics. (1) The lamination property to the metal plate is excellent. (2) Excellent adhesion to a metal plate. (3) It has excellent moldability and does not cause defects such as pinholes after molding. (4) The polyester film does not peel off, crack or pinhole due to impact on the metal can.

[0004] In addition, a film used for the outer surface of a metal can requires the following characteristics in addition to the above in order to omit the undercoating of a conventionally used white paint. (5) It is excellent in whiteness and metal concealing property, has a beautiful appearance, and is suitable for printing.

[0005] In recent years, with the increase in laminating and canning speeds,
It is desired to further improve laminating properties, moldability, and adhesion between the film and the steel sheet. Particularly in white films used for outer surfaces of cans, higher whiteness, higher concealment, and use in severe molding processes There is a need for a film for external surfaces that can be made. However, for example, in order to improve the degree of concealment, in a white film in which white pigment particles are simply added at a high concentration, although the degree of concealment is improved, the film itself becomes brittle, many breaks occur during stretching, and the film forming stability is greatly reduced. In addition, for example, when processing a laminate or a can, the film cannot withstand the molding, and problems such as cracks and cracks become a problem.

[0006] In addition to the use for cans, concealability as a packaging material that can be laminated and processed on other films,
Laminating properties, processability of white film with excellent thin film properties,
Improving formability has been an important issue.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and has a high concealing property as a white polyester film, especially a white polyester film for the outer surface of a container, and has a high film-forming stability. Another object of the present invention is to provide a white polyester film excellent in processability.

[0008]

It is an object of the present invention that the average concentration of titanium oxide in the film is 10 to 50% by weight and the crystallization index of the polyester around the titanium oxide particles is 45 or less. This is achieved by a white polyester film characterized by:

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester in the present invention is a generic term for high molecular weight compounds constituted by ester bonds. Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenyl Aromatic dicarboxylic acids such as sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, 5-sodium sulfoisophthalic acid and phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, and aliphatic such as dimer acid, maleic acid and fumaric acid Alicyclic dicarboxylic acids such as dicarboxylic acid and cyclohexanedicarboxylic acid, p
And oxycarboxylic acids such as oxybenzoic acid. On the other hand, as the glycol component, for example, ethylene glycol, propanediol, butanediol,
Examples include aliphatic glycols such as pentanediol, hexanediol and neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, aromatic glycols such as bisphenol A and bisphenol S, and diethylene glycol. In addition, two or more of these dicarboxylic acid components and glycol components may be used in combination.

Further, in the present invention, the above polyester is
More than one kind may be blended and used.

As long as the effects of the present invention are not impaired, trimellitic acid, trimesic acid,
A polyfunctional compound such as trimethylolpropane may be copolymerized.

From the viewpoint of heat resistance, the polyester of the present invention
It is preferable that 75 mol% or more of the polyester constituting the film is a polyester having an ethylene terephthalate unit and / or ethylene naphthalate unit as a main component, more preferably 80 mol% or more, and still more preferably 85 mol% or more. is there.

The melting point of the polyester film in the present invention is preferably from 180 to 270 ° C., more preferably from 200 to 265 ° C., particularly preferably from 210 to 260 ° C. from the viewpoint of heat resistance and moldability. Here, the melting point of the polyester film means a main melting peak temperature detected when the film is subjected to differential scanning calorimetry (DSC).

The polyester film of the present invention is not limited to any of an unstretched film, a uniaxially stretched film and a biaxially stretched film, but is preferably a biaxially stretched film from the viewpoint of heat resistance and dimensional stability. The method of biaxial stretching may be either simultaneous biaxial stretching or sequential biaxial stretching.

In the present invention, the white polyester film needs to have an average concentration of titanium oxide in the film of 10 to 50% by weight, preferably 20 to 45% by weight, in view of concealing properties and processability. Preferably 25 to 40
% By weight. The average concentration of titanium oxide in the film is 10
When the amount is less than the weight%, the whiteness and the concealing property are reduced, and in order to obtain the desired concealing property, it is necessary to increase the film thickness. , Workability deteriorates. On the other hand, when the average concentration of titanium oxide in the film exceeds 50% by weight,
There is a problem that the film is greatly embrittled and the film formability and workability are deteriorated.

In the present invention, it is necessary that the crystallization index of the polyester around the titanium oxide particles is 45 or less, and preferably 40 or less. From the viewpoint of heat resistance, the crystallization index of the polyester around the titanium oxide particles is 1
It is preferably 0 or more, and more preferably 15 or more. By setting the crystallization index of the polyester around the titanium oxide particles to 45 or less, film formability and workability can be drastically improved. We investigated in detail the phenomenon that the film is easily torn or cut at the time of film formation and processing under the application of external force, and revealed that the main cause is the occurrence of cracks around the titanium oxide particles. Further investigations have found that this is caused by excessive crystallization of the polymer around the particles. As a result of diligent studies, they have found that by setting the crystallization index of the polyester around the titanium oxide within the above range, the occurrence of cracks can be suppressed and the film formation stability and workability can be improved. That is, when the crystallization index of the polyester around the titanium oxide particles exceeds 45,
The film is easily broken or cut during film formation or processing. Here, the crystallization index of the polyester around the titanium oxide is determined by dissolving the film before or after the processing and then centrifuging the polyester to obtain the polyester around the titanium oxide by infrared spectroscopy.

In the present invention, the intrinsic viscosity (IV) of the film is 0.58 to 0.5 to improve the adhesion and the mechanical properties.
It is preferably 0.7 dl / g. IV is 0.58
If it is less than dl / g, not only the adhesion to the metal plate is reduced, but also the mechanical properties such as elongation are reduced, and the film-forming stability and workability are undesirably deteriorated. On the other hand, IV is 0.7 dl
If the amount exceeds / g, problems such as an increase in the amount of decomposed products and unmelted products during melt extrusion of the raw material polymer occur.

In the present invention, the polyester around the titanium oxide particles is not particularly limited as long as the crystallization index around the particles is 45 or less, but from the viewpoint of further improving film forming properties and processability. It is very effective that the molar copolymerization amount of the polyester around the titanium oxide particles is higher than the molar copolymerization amount of the polyester constituting the bulk,
Further, the polyester around the titanium oxide particles is preferably a copolymer polyester of 10 to 50 mol%, more preferably a copolymer polyester of 13 to 40 mol%. When the content is 10 mol% or more, the effect of lowering the crystallization of the polyester is enhanced. On the other hand, if it exceeds 50 mol%, the crystallinity may be too low, the heat resistance may be poor, or the production efficiency may be low. It is preferably 13 to 40 mol% in the sense that both are compatible. In addition, isophthalic acid 10 from the viewpoint of productivity, handleability, and low crystallization
A copolymer polyester of 50 mol is preferable, and a copolymer polyester of 15 to 40 mol of isophthalic acid is more preferable. If it is less than 10 mol%, the effect of low crystallization may be insufficient, and if it is more than 50 mol%, productivity and handleability may decrease. 15 to mean both
Preferably it is 40 mol%.

In the present invention, a layer having a titanium oxide concentration of 1 to 10% by weight is preferably laminated on at least one side, more preferably a titanium oxide concentration of 3 to 7%, from the viewpoint of reducing abrasion of a roll or the like. %. The polyester around the titanium oxide particles contained in the layer to be laminated,
The crystallization index is preferably 45 or less, particularly preferably 40 or less, but is not particularly limited. The laminated structure is two layers of A / B, B / A / B, B / A / C
Are exemplified, but are not particularly limited. The lamination thickness is preferably 0.2 to 5 from the viewpoint of abrasion.
μm, more preferably 0.5 to 3 μm, may be on one side or both sides, or may be laminated on the lamination surface.

In the present invention, the titanium oxide added to the polyester has an average particle size of 0.1 to 0.5 μm, preferably 0.2 to 0.35 μm. If the average particle size is less than 0.1 μm, the dispersibility in the polyester is reduced, causing problems such as the occurrence of spots. Titanium oxide preferably has a purity of 95% or more, and if less than 95%, dispersibility is poor. The titanium oxide is not limited to anatase type or rutile type, but rutile type titanium oxide is preferable from the viewpoint of improving concealing properties.

In the present invention, the titanium oxide inorganic surface treating agent is not particularly limited, but a surface treating agent containing an aluminum component is preferable, and the amount of addition is 0.01 to 1.5% by weight. Is more preferable, more preferably 0.05 to 1% by weight, particularly preferably 0.1 to 1% by weight.
0.5% by weight. Here, the ratio (% by weight) of the aluminum component is a weight ratio with respect to titanium oxide, and can be quantified by fluorescent X-ray analysis or the like. Other examples of the inorganic surface treatment agent for titanium oxide include a silica compound and a titania compound. In particular, when titanium oxide is added to polyester, it is preferable to contain an aluminum component from the viewpoint of dispersibility. The aluminum component is preferably treated as an aluminum oxide compound or an aluminum hydroxide compound as a titanium oxide surface treating agent. In terms of the amount of aluminum, the aluminum component contained in the aluminum oxide or aluminum hydroxide is preferably 0.1%.
By being present in an amount of from 0.01 to 1.5% by weight, dispersibility and affinity with polyester are improved, and whiteness and hiding properties are excellent.
In addition, since it is uniformly dispersed in the polyester, white spots and the like are drastically reduced, and the beauty is improved. Further, since the coarse particles are also reduced, roll abrasion during film-forming stretching and trouble during lamination and can-making are eliminated.

Examples of the organic surface treating agent for titanium oxide in the present invention include amine compounds, polyhydric alcohol compounds, and silicone compounds.
Polyhydric alcohol compounds and silicone compounds are preferred from the viewpoint of dispersibility, and silicone compounds are more preferred, particularly from the standpoint of further improving dispersibility in combination with heat resistance and a surface treatment agent containing an aluminum component. The content of the silicon-based compound is preferably 0.02 to 2% by weight, more preferably 0.05 to 1% by weight, based on the weight of titanium oxide. In the case of the polyhydric alcohol compound, the content is preferably 0.01 to 1.5% by weight, more preferably 0.05 to 0.8% by weight based on the weight of titanium oxide. By using the above compound as a surface treatment agent, it is possible to significantly suppress the generation of foreign substances during melt extrusion due to deterioration of dispersibility and aggregation of titanium oxide. Here, the amount of the silicon-based compound and the amount of the polyhydric alcohol-based compound are represented by weight ratio (% by weight) to the weight of titanium oxide. The amount of the silicon-based compound is determined by thermogravimetric-mass spectrometry and thermogravimetric-gas chromatography /
From room temperature to 50 ° C under helium flow using mass spectrometry
/% Of the total amount of the gas generated attributable to the silicone compound when heated to 300 ° C. for 60 minutes after heating at 300 ° C./min to titanium oxide. For example, the gas generated attributable to the silicone compound is , (CH ₃ ) ₃ Si ⁺ ,
Examples include [(CH ₃ ) ₂ SiO] ₃ , [(CH ₃ ) ₂ SiO] _{4 and the} like. . The amount of the polyhydric alcohol-based compound was measured using a thermogravimetric / mass simultaneous analysis method and a thermogravimetric / gas chromatography / mass simultaneous analysis method under a helium flow at a heating rate of 50 ° C./min from room temperature.
After heating to 00 ° C., the total amount of generated gas attributed to the polyhydric alcohol when held for 60 minutes relative to titanium oxide is% by weight. For example, the generated gas attributed to the polyhydric alcohol is Butanal, Methylpropenal, or Methyldihydropyran. For example, when a gas belonging to a polyhydric alcohol compound is detected in addition to the above at the time of measurement, it is also assumed to be combined.

In the present invention, in order to further improve the dispersibility, it is preferable to pass the molten polymer through a filter during extrusion, and it is particularly preferable to use a multi-stage filter. As the filtration characteristics of the filter, those capable of removing insoluble matters and foreign substances of 30 μm or more are preferable, and particularly preferably 10 μm.
m or more of insolubles and foreign substances are removed.

In the present invention, in addition to the titanium oxide particles, known internal particles having an average particle diameter of 0.01 to 10 μm,
Particles arbitrarily selected from external particles such as inorganic particles and / or organic particles, and a whitening agent can be contained. It is not preferable to use particles having an average particle diameter of more than 10 μm because defects in the film are likely to occur. As the particles, for example, wet and dry silica, colloidal silica, aluminum silicate, calcium carbonate, calcium phosphate, barium sulfate, zinc sulfide, calcium silicate,
Examples include inorganic particles such as magnesium carbonate, zinc carbonate, mica, kaolin, and clay, and organic particles containing styrene, silicone, acrylic acid, and the like as constituents. From the viewpoint, the content of the aggregated inorganic particles is preferably 0.01 to 5% by weight, more preferably 0.105 to 1% by weight. Further, among the agglomerated inorganic particles, agglomerated silica particles having an average particle size of 0.5 to 5 μm are preferred, and wet agglomerated silica is particularly preferred, and the addition amount is particularly preferably 0.105 to 0.5% by weight. In the case of lamination, these aggregated inorganic particles are more effective when added to each layer. The particles may be used in combination of two or more kinds as long as the properties are not impaired.

The polyester film of the present invention preferably has an average elongation at break of 80% or more, more preferably 100% or more, particularly preferably 100% or more, from the viewpoint of laminating properties and moldability. Is 120% or more. If the titanium concentration is increased to improve the whiteness, the elongation tends to decrease. If the elongation at break is less than 80%, the film may break at the time of lamination, or may have irregularities in the molding process, or the film may be peeled off after making the can. May cause problems.

In producing the polyester of the present invention,
Conventionally known reaction catalysts and coloring inhibitors can be used. Examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, Germanium compounds, titanium compounds, etc.
Examples of the coloring inhibitor include a phosphorus compound. It is desirable to add an antimony compound, a germanium compound, or a titanium compound as a polymerization catalyst at any stage before the production of the polyester is completed. As such a method, for example, when a germanium compound is taken as an example, a method of adding a germanium compound powder as it is, or as described in JP-B-54-22234, a glycol component which is a starting material of a polyester, A method in which a germanium compound is dissolved and added therein can be used. As the germanium compound, for example, germanium dioxide, germanium hydroxide containing crystal water, or germanium alkoxide compounds such as germanium tetramethoxide, germanium tetraethoxide, germanium tetrabutoxide, germanium ethylene glycoloxide, germanium phenolate, germanium β-naphtholate and the like A germanium phenoxide compound, germanium phosphate,
Examples include phosphorus-containing germanium compounds such as germanium phosphite, and germanium acetate. Among them, germanium dioxide is preferable. Examples of the antimony compound include, but are not particularly limited to, antimony oxides such as antimony trioxide, and antimony acetate. The titanium compound is not particularly limited, but an alkyl titanate compound such as tetraethyl titanate and tetrabutyl titanate is preferably used.

For example, a case where germanium dioxide is added as a germanium compound when producing polyethylene terephthalate will be described. The terephthalic acid component and ethylene glycol are subjected to a transesterification or esterification reaction, and then germanium dioxide and a phosphorus compound are added.Then, the polycondensation reaction is continued under a high temperature and a reduced pressure until a constant diethylene glycol content is obtained, and a germanium element-containing polymer is obtained. obtain. Furthermore, preferably, the obtained polymer is subjected to a solid-phase polymerization reaction under reduced pressure or an inert gas atmosphere at a temperature equal to or lower than its melting point, to reduce the content of acetoadheride, and obtain a predetermined intrinsic viscosity and a carboxyl end group. Methods and the like can be mentioned.

In order to make the polyester contain titanium oxide, for example, a method of adding titanium oxide at the time of synthesis of the polyester, a method of adding titanium oxide to the polyester and melting and kneading the same, or a method of adding a large amount of titanium oxide to the polyester is used. There is a method in which a master pellet is produced, kneaded with a polyester containing no titanium oxide, and a predetermined amount of titanium oxide is contained. Also in the present invention, the method of adding titanium oxide particles to the polyester is not particularly limited, but a high-concentration titanium oxide-containing master pellet of 45 to 70% by weight is once produced, and is made of a polyester not containing titanium oxide. A method of uniformly mixing the pellets for dilution with an appropriate ratio and supplying the mixture to the extruder can be preferably used from the viewpoint of improving the dispersibility of the particles in the polyester.

In the present invention, from the viewpoint of improving the adhesion between the film and the steel sheet, the amount of carboxyl terminal groups of the polyester A constituting the steel sheet side layer is preferably 25 to 60 equivalents / ton, and particularly preferably 30 to 60 equivalents / ton. ５５55 equivalents / ton.

The total thickness of the polyester film of the present invention is preferably from 3 to 50 μm, more preferably from 5 to 35 μm, from the viewpoint of moldability after lamination on metal, coatability to metal, and impact resistance. And particularly preferably 10 to 30 μm.

The method for producing the polyester film in the present invention is not particularly limited. For example, after drying each polyester as required, it is supplied to a known melt extruder, passed through a desired filter, and then slit. It is extruded into a sheet form from a die, and is brought into close contact with a casting drum by a method such as electrostatic application to be cooled and solidified to obtain an unoriented film. The unstretched film is stretched and heat-treated in the longitudinal and width directions of the film to obtain a film having a desired degree of orientation. As the stretching method, a tenter method is preferable in terms of film quality.After stretching in the longitudinal direction, a sequential biaxial stretching method in which the film is stretched in the width direction, and the longitudinal direction and the width direction are stretched almost simultaneously. A simultaneous biaxial stretching method is desirable. The stretching ratio is 1.2 to 4.5 times, preferably 1.5 to 4.0 times in each direction. When a film is obtained by sequential biaxial stretching, the stretching in the longitudinal direction is preferably multi-stage stretching, but is not particularly limited. Either the stretching ratio in the longitudinal direction or the stretching ratio in the width direction may be increased, and may be the same. The stretching speed is 10
The stretching temperature is desirably from 00% / minute to 200,000% / minute, and the stretching temperature can be any temperature as long as it is equal to or higher than the glass transition temperature of the polyester and equal to or lower than the glass transition temperature + 100 ° C. Is preferred. After the stretching, the film is subjected to a heat treatment. This heat treatment can be carried out by any conventionally known method such as in an oven or on a heated roll. Heat treatment temperature is 120-24
Any temperature of 5 ° C can be used, but preferably 1 ° C.
20-240 ° C. The heat treatment time can be arbitrarily set, but it is usually preferable to perform the heat treatment for 1 to 60 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction. Furthermore, re-stretching may be performed once or more in each direction, and then heat treatment may be performed.

It is also possible to improve the adhesiveness by subjecting the film to a surface treatment such as a corona discharge treatment.
It is preferable for further improving the characteristics.

Various coatings may be applied on the film of the present invention, and the coating compound, method and thickness are not particularly limited as long as the effects of the present invention are not impaired.

Although the container of the present invention is not particularly limited, for example, a metal plate made of iron, aluminum, or the like is preferable in terms of moldability. Further, in the case of a metal plate made of iron, an inorganic oxide coating layer on the surface thereof for improving adhesion and corrosion resistance, for example, chromic acid treatment, phosphoric acid treatment, chromic acid / phosphoric acid treatment, electrolytic chromic acid treatment A chemical conversion treatment coating layer represented by, for example, a chromate treatment or a chromium chromate treatment may be provided. In particular, a chromium hydrated oxide having a chromium equivalent of 6.5 to 150 mg / m ² in terms of chromium is preferable, and further provided with a spreadable metal plating layer such as nickel, tin, zinc, aluminum, gunmetal, brass and the like. Is also good. 0.5 to 15 mg / m for tin plating
² , 1.8 to 20 g for nickel or aluminum
/ M ² is preferable.

The white film for forming the outer surface of the container according to the present invention is a beverage can or a food can manufactured by drawing or ironing after laminating to a metal plate or the like by heat laminating or coating the film with an adhesive. It can be suitably used for coating the outer surface of a two-piece metal can. Also, it can be preferably used for covering the lid portion of a two-piece can or the body, lid, and bottom of a three-piece can because of its good metal adhesion and moldability.

[0036]

The present invention will be described below in detail with reference to examples. The characteristics were measured and evaluated by the following methods.

(1) Film-forming property The film-forming property of the film was evaluated according to the following criteria. ：: Stable film formation is possible with almost no occurrence of film breakage. ×: Many film breaks occurred, resulting in low film formation stability.

(2) Workability The elongation of the film was measured (a tensile speed of 300 mm / min, a width of 10 mm, and a sample length of 10 using a tensile tester).
The elongation at break was measured at 0 mm), and the average elongation in the longitudinal and width directions was evaluated according to the following criteria. ：: 150% or more ：: 120% or more and less than 150% Δ: 80% or more and less than 120% ×: less than 80% (◎ ○ △ is accepted).

(3) Intrinsic Viscosity of Polyester (IV) The polyester was dissolved in orthochlorophenol, and the titanium oxide particles were removed by centrifugation.

(4) Melting point The film was treated in a vacuum at 40 ° C. for 60 hours to sufficiently remove water, sampled at 5 mg, and measured with a differential scanning calorimeter (DSC2, Perkin-Elmer Co.).
The peak temperature of the main melting was measured as the melting point at a heating rate of ° C./min. The melting point of each layer of the laminated film was determined by scraping each layer with a single blade and measuring the melting point by the same measuring method as described above.

(5) Crystallization Index of Polyester Around Titanium Oxide Particles The films obtained in Examples and Comparative Examples were prepared at a temperature of 6 at a ratio of 10% by weight to orthochlorophenol (OCP).
Dissolve at 0 ° C for 4 hours. After filtration, the solution was subjected to centrifugation to remove the polymer, washed and vacuum-dried at 40 ° C. for 10 hours. The obtained titanium oxide and the titanium oxide-adhered polyester mixture were measured by infrared spectroscopy, and the crystallization index was measured. did. The weight of the polyester adhering to the titanium oxide obtained at this time was 3% by weight of the polyester in the film.
In the case where the above is satisfied, a solution which has been newly treated so that the dissolution time is extended to less than 3% by weight is used.

Infrared spectroscopy measurement: A transmission absorption spectrum is measured with a microscopic infrared spectrometer (apparatus: IR μs (SPECTRA to TE
CH company), total number of times: up to 1024, resolution: 4 cm ^-1 ), 1389
The absorption intensity attributable to the trans form near cm ^-1 was determined to be 1410
The absorbance ratio Abs (1389 cm ^-1 / 1410 cm ^-1 ) was normalized by the intensity of the absorption attributed to the benzene ring near cm ^-1 , and Ab was determined.
s × 100 was taken as the crystallization index.

(6) Polyester Composition Around Titanium Oxide Particles The polyester composition of the above separated titanium oxide and titanium oxide-adhered polyester mixture was determined by FT-IR measurement, DSC measurement, NMR, liquid chromatography measurement by Na methylate pretreatment, and the like. .

(7) Optical Density The optical density of the film was measured with an optical densitometer (Macbeth TR-927). Although the optical density depends on the thickness, the optical density of the film alone (based on 13 μm) is preferably 0.4 or more, more preferably 0.45 or more,
More preferably, it is 0.5 or more from the viewpoint of concealment efficiency.

(8) Formability A tin-free ftir steel plate having a thickness of 0.22 mm heated to 260 ° C. was laminated and cooled with water. The laminated steel sheet is formed by an ironing forming machine and a drawing forming machine (forming ratio (maximum thickness / minimum thickness) = 3.2, forming in a formable temperature range),
I got a can. The laminate film of this can was visually evaluated according to the following criteria. ：: No minute crack or breakage is observed. X: Fine cracks and breaks are observed. (○: passed, ×: failed).

Example 1 As shown in Table 1, as a polyester, isophthalic acid copolymerized polyethylene containing 60% by weight of rutile type titanium oxide particles (surface treatment: aluminum compound, silicone compound, average particle size: 0.21 μm) Each of terephthalate pellets (copolymerization amount 16.5 mol%) and isophthalic acid copolymerized polyethylene terephthalate pellets containing no titanium oxide particles (copolymerization amount 10.5 mol%) was 160
After vacuum drying at 5 ° C for 5 hours, they were mixed at a weight ratio of 4.2: 5.8 and supplied to an extruder. The polyester melt-extruded from the extruder was filtered through a multi-stage filter, discharged from a die, cooled and solidified with a mirror-surface cooling drum while applying static electricity, to obtain an unstretched film. This unstretched film is stretched 3.1 times in the longitudinal direction at a temperature of 101 ° C., stretched 3.2 times in the width direction at a preheating temperature of 95 ° C. and a stretching temperature of 120 ° C., and then relaxed at 168 ° C. by 5%, Heat treatment was performed for 5 seconds to obtain a 13-μm-thick biaxially stretched white polyester film shown in Table 3. The film properties were good as shown in Table 3.

Example 2 Films shown in Table 3 were obtained from polyester, titanium oxide and inorganic particles shown in Tables 1 and 2 under the same conditions as in Example 1. The film properties were good as shown in Table 3.

Example 3 The polyester, titanium oxide, and inorganic particles shown in Tables 1 and 2 were separately dried, mixed, melted, and filtered by a multi-stage filter in the same procedure as in Example 1 to obtain a mixture from a die adjacent to each other. The polymers of the layers A and B were co-extruded, laminated and fused, and cooled and solidified with a mirror-surface cooling drum while applying static electricity to obtain an unstretched film. This unstretched film was stretched 3.1 times in the longitudinal direction and 3.15 times in the transverse direction at a temperature of 106 ° C. by a simultaneous biaxial method, relaxed at 170 ° C. for 5%, and heat-treated for 5 seconds. A biaxially stretched white polyester film having a thickness of 15 μm was obtained. As shown in Table 3, the film properties were excellent.

Example 4 Biaxial stretching with a thickness of 15 μm shown in Table 3 was carried out in the same manner as in Example 3 by using the polyester, titanium oxide and inorganic particles shown in Tables 1 and 2 to make the stretching ratio in the width direction 3.2 times. A white polyester film was obtained. The film properties are shown in Table 3,
It was good.

Example 5 The polyester, titanium oxide, and inorganic particles shown in Tables 1 and 2 were used to increase the longitudinal stretching ratio to 3.2 times.
As in the above, a biaxially stretched white polyester film having a thickness of 15 μm shown in Table 3 was obtained. The film properties were good as shown in Table 3.

Comparative Example 1 Films shown in Table 3 were obtained from polyester, titanium oxide and inorganic particles shown in Tables 1 and 2 under the same conditions as in Example 1. As shown in Table 3, the film properties were inferior.

Comparative Example 2 With the polyester and titanium oxide shown in Tables 1 and 2, the stretching ratio was set to 3.2 times in the longitudinal direction and 3.3 times in the width direction.
The films shown in Table 3 were obtained in the same manner as in Comparative Example 1. The film properties were quite poor, as shown in Table 3.

The abbreviations in the table are as follows. PET / I: isophthalic acid copolymerized polyethylene terephthalate

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

[Table 3]

[0057]

According to the present invention, by controlling the average concentration of titanium oxide in the film and the crystallization index around the titanium oxide particles, high concealing properties, film forming stability, and workability are achieved.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/22 C08L 67/02 C08L 67/02 B65D 1/00 B F-term (Reference) 3E033 AA06 BA07 BA13 BA17 BA18 BB04 BB08 CA03 CA07 EA10 4F071 AA44 AA88 AA89 AB18 AH05 BA01 BB06 BB07 BB08 BC01 4F100 AA21H AB01C AK41A AK41B AL01A BA02 BA03 BA07 BA10A BA10C DE01H EH17 EH172 EJ10A1J8JJ1J8J18J38A

Claims (7)

[Claims] An average concentration of titanium oxide in a film is 10 to 10.
50% by weight, wherein the crystallization index of the polyester around the titanium oxide particles is 45 or less. 2. The film has an intrinsic viscosity of 0.58 to 0.7 d.
The white polyester film according to claim 1, which is 1 / g. 3. The white polyester film according to claim 1, wherein the molar copolymerization amount of the polyester around the titanium oxide particles is higher than the molar copolymerization amount of the polyester constituting the bulk. 4. The polyester around the titanium oxide particles is 10
4 to 50 mol% of a copolyester.
The white polyester film according to any one of the above. 5. The white polyester film according to claim 1, wherein the polyester around the titanium oxide particles is a copolymer polyester of 10 to 50 mol% of isophthalic acid. 6. A titanium oxide concentration of at least 1 on one side is 1 to 1.
The white polyester film according to any one of claims 1 to 5, wherein a layer of 0% by weight is laminated. 7. The white polyester film according to claim 1, which is molded into a container after laminating to a metal plate.