JP3087573B2 - Biaxially stretched polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a biaxially oriented polyester
It relates films, specifically, the present invention is biaxially comprising a polyester resin modifier for consisting the surface treated calcium carbonate with a specific phosphorus compound in a high concentration
Are those concerning the stretched polyester Ruch I le-time, more specifically, printing paper, X-rays intensifying screens, card, label, display board, a suitable biaxially oriented polyester <br/> fill beam as a base material, such as whiteboard it relates to.

[0002]

2. Description of the Related Art Polyesters represented by polyethylene terephthalate have excellent physical and chemical properties and are widely used as fibers, films and other molded products. In particular, among these uses, white films are used as substrates for cards, labels, display boards, white boards, and the like.

Hitherto, it has been well known that a large amount of white inorganic particles is added to polyethylene terephthalate to obtain a white film. For example, Japanese Patent Publication No. 59-490
In Japanese Patent Publication No. 1 (JP-A-60-30930), a large amount of titanium oxide and barium sulfate is added, in Japanese Patent Publication No. Sho 60-30930, a large amount of barium sulfate is added, and in Japanese Patent Publication No. Sho 60-30930 and Japanese Patent Publication No. 43-122013. It is necessary to add a large amount of calcium carbonate in JP-A-51-2814.
No. 1, JP-A-61-209260 discloses a method of kneading an inorganic filler powder and a white inorganic pigment at a high concentration. However, in the above prior art, those containing barium sulfate are inferior in dispersibility of particles, and when formed into a film using the obtained polyester, a film having sufficient whiteness, hiding power, and gloss is obtained. I can't. On the other hand, the titanium oxide-added one has an excellent hiding power due to the high refractive index of the particles.
m, a decrease in spectral reflectance in a low wavelength region of less than
A film having sufficient whiteness cannot be obtained.

Further, as disclosed in JP-B-43-122013, polyesters containing only a high concentration of calcium carbonate and JP-A-51-28141 and JP-A-61-209260 are disclosed. In the method as disclosed, when calcium carbonate is simply kneaded with polyester at a high concentration, it is not preferable because agglomeration of particles occurs or a polyester having a strong yellow tint is obtained,
If the polymer stays at a high temperature, it foams or generates foreign matter. Further, it is difficult for the film obtained from the polyester to have sufficient whiteness and hiding power.

In order to solve the above-mentioned drawbacks, Japanese Patent Application Laid-Open No. Sho 62-207337 discloses a method in which a mixture of polyester, calcium carbonate and a phosphorus compound is simply melt-extruded and then a film is produced. 6622
No. 2 discloses a method of adding calcium carbonate and a phosphorus compound to a polyester reaction system. However, even in these methods, it is difficult to efficiently contain calcium carbonate in the polyester at a high concentration, the dispersibility of the particles is not sufficient, and when the polymer stays at a high temperature, foaming or foreign matter occurs. Or occur. Further, it is difficult for the resulting film to have sufficient whiteness, hiding power and gloss.

[0006] On the other hand, studies have been actively conducted on the addition of small amounts of various inorganic particles for the purpose of imparting the slipperiness, abrasion resistance, transparency and the like of a polyester film. Among them, a typical one is calcium carbonate. For example, JP-A-62-224331 discloses a method in which calcium carbonate containing phosphorus element is added to a polyester reaction system, and JP-A-62-235353. The gazette discloses that a polyester contains calcium carbonate treated with a specific phosphorus compound. However, these small amounts of calcium carbonate make it difficult for the film to have sufficient whiteness and hiding power. Further, Japanese Unexamined Patent Publication No. Sho 62
Japanese Patent Application Laid-Open No. Sho 62-2353 discloses a method of adding calcium carbonate to a polyester reaction system as disclosed in JP-A-2-23243.
With calcium carbonate surface-treated with a phosphorus compound as disclosed in JP-A-53-53, it is difficult to efficiently contain calcium carbonate in a polyester at a high concentration, the dispersibility of particles is not sufficient, When it stays, foaming or foreign matter is generated. Further, it is difficult for the film to have sufficient whiteness and hiding power.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyester containing a large amount of white inorganic particles and to perform surface treatment with a specific phosphorus compound in order to obtain a molded article excellent in whiteness, hiding properties and glossiness. An object of the present invention is to solve the above-mentioned conventional disadvantages by using a polyester resin modifier comprising calcium carbonate and a polyester composition and a film containing the modifier at a high concentration.

[0008]

The object of the present invention is as follows: (1) selected from the group consisting of phosphoric acid, phosphorous acid, phosphinic acid, phosphonic acid and their alkyl ester compounds having 3 or less carbon atoms. Stretching containing calcium carbonate powder surface-treated with at least one phosphorus compound
Polyester film .

(2) The surface treatment amount of the phosphorus compound is calcium carbonate
0.1% by weight or more based on calcium
The biaxially stretched polyester film according to the above (1) .

(3) 100 to 30000 pp of phosphorus element
(1) or (2).
Biaxially stretched polyester film. (4) phosphoric acid, phosphorous acid, phosphinic acid, phosphonic acid,
And their alkyl ester compounds having 3 or less carbon atoms.
At least one phosphorus compound selected from the group consisting of
(1) to (3), wherein a polyester-based resin modifier made of calcium carbonate powder surface-treated with a polyester and a polyester are kneaded with a vent-type extruder.
A biaxially stretched polyester film as described in any of the above .

(5) The filler according to the above (1) to (4)
Biaxially oriented polyester characterized in that the film is white
Film, which can be achieved.

The polyester of the present invention is produced by an esterification or transesterification reaction of a dicarboxylic acid or an ester-forming derivative with diol and a subsequent polycondensation reaction. The type of polyester is not particularly limited as long as it can be formed into fibers, films, and other molded products. Fibers, films, suitable polyesters that can be molded into other molded articles are those using aromatic dicarboxylic acid as the dicarboxylic acid component,
For example, polyethylene terephthalate, polyethylene-
p-oxybenzoate, polyethylene-1,2-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate, polyethylene-1,2-bis (phenoxy) ethane-4,4′-dicarboxylate, Polyethylene-2,6-naphthalene carboxylate, polybutylene terephthalate, polycyclohexane dimethylene terephthalate and the like can be mentioned, among which polyethylene terephthalate is preferable. Of course, these polyesters may be homopolyesters or copolyesters, and the components to be copolymerized include, for example, adipic acid, sebacic acid, dimer acid, phthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid Acid, 5-sodium sulfoisophthalic acid, diphenyldicarboxylic acid, 4,4
Dicarboxylic acids such as' -sulfonyldibenzoic acid or its ester-forming derivatives, polyfunctional carboxylic acids such as trimellitic acid and pyromellitic acid or its ester-forming derivatives, oxycarboxylic acids such as p-oxyethoxybenzoic acid or the like Ester-forming derivatives and the like, and further, ethylene glycol, butanediol, propylene glycol, diethylene glycol, neopentyl glycol,
Examples thereof include p-xylylene glycol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and polyalkylene glycol having an average molecular weight of 200 to 20,000.

[0013] The modifier of the present invention is surface-treated with at least one phosphorus compound selected from the group consisting of phosphoric acid, phosphorous acid, phosphinic acid, phosphonic acid and alkyl ester compounds having 3 or less carbon atoms. Calcium carbonate powder must be used. Examples of phosphoric acid, phosphorous acid, phosphinic acid, phosphonic acid and their alkyl ester compounds having 3 or less carbon atoms include phosphoric acid, phosphorous acid, trimethyl phosphate, tripropyl phosphate, phosphoric acid Mono or dimethyl ester, phenylphosphonic acid dimethyl ester, phenylphosphonic acid diethyl ester and the like can be mentioned. Two or more of these phosphorus compounds may be used in combination. Of these phosphorus compounds, phosphoric acid, phosphorous acid and phosphoric acid mono-, di- or trialkyl esters are preferred.

The amount of the phosphorus compound used for the surface treatment of the calcium carbonate of the present invention is not particularly limited.
When the modifier of the present invention is added to the polyester and blended,
From the viewpoints of particle dispersibility of calcium carbonate in polyester, generation of foreign matter during high-temperature residence of polyester, and foaming, the content is preferably 0.1% by weight or more, more preferably 0.5 to 20% by weight, based on calcium carbonate. 2.0-15% by weight is preferred. If the amount is less than 0.1% by weight based on calcium carbonate, the dispersibility of calcium carbonate particles in the polyester may be poor, or foreign matter may be generated or foamed when the polyester stays at a high temperature, which may be undesirable.

The amount of the phosphorus element contained in the modifier of the present invention is not particularly limited, but the amount of the phosphorus element is preferably 100 to 100%.
It is preferably contained at 30,000 ppm, more preferably from 300 to 20,000 ppm, further preferably from 500 to 15000 ppm, particularly preferably from 1,000 to 1,000 ppm.
10,000 ppm. When the phosphorus element content is less than 100 ppm, when added and blended with polyester, there may be problems such as poor dispersibility of calcium carbonate particles in the polyester, generation of foreign matter and foaming when the polyester stays at high temperature. On the other hand, if it exceeds 30,000 ppm, there is a disadvantage that a polyester having a high degree of polymerization cannot be obtained, which is not preferable in some cases.

The method of surface treatment of calcium carbonate with a phosphorus compound to obtain the modifier of the present invention is not particularly limited, but it is preferable to employ a method of physically mixing the phosphorus compound with calcium carbonate. . The physical mixing method is not particularly limited, and various types of pulverizers, for example, a roll rolling mill, a high-speed rotary pulverizer, a ball mill, a jet mill, etc., are used to pulverize calcium carbonate. A method of surface treating with a phosphorus compound while rotating, or a container rotating type mixer in which the container itself rotates,
Examples of the method include a surface treatment using a fixed container-type mixer having a rotating blade in a fixed container or blowing an air current. Specifically, mixers such as a Nauta mixer, a ribbon mixer, and a Henschel mixer are preferable.
The processing conditions at that time are not particularly limited,
When the modifier of the present invention is added to the polyester and blended,
The processing temperature is preferably 30 ° C. or higher, more preferably 50 ° C. or higher, particularly preferably 90 ° C. or higher, from the viewpoints of the particle dispersibility of calcium carbonate in the polyester, the generation of foreign matters when the polyester stays at a high temperature, and the foaming. The treatment time is preferably within 5 hours, more preferably within 3 hours, particularly preferably within 2 hours. Further, the phosphorus compound may be mixed simultaneously with the calcium carbonate, or the phosphorus compound may be added after the calcium carbonate is charged in advance. At this time, the phosphorus compound may be dropped or sprayed, or may be dissolved or dispersed in water, alcohol, or the like. As described above, the modifier of the present invention can be obtained by physically mixing a phosphorus compound and calcium carbonate.

The calcium carbonate in the present invention is a natural product,
Any of synthetic products may be used, and examples of the crystal form include calcite, anagorite and vaterite, but are not particularly limited. Also other metal compounds, for example,
Magnesium oxide, aluminum oxide, silicon dioxide and the like may be contained.

The particle size and specific surface area of the calcium carbonate of the present invention are not particularly limited, but the particle size is 0.01 to 20 μm in average particle size, more preferably 0.1 to 10 μm.
In particular, 0.2 to 5 μm is preferable in terms of whiteness, hiding properties, and glossiness. The specific surface area is preferably 0.5 to 100 m ² / g, more preferably 1 to 70 m ² / g, and particularly preferably 3 to 60 m ² / g in terms of whiteness, hiding power, and gloss. When the particle diameter exceeds 20 μm in average particle diameter or the specific surface area is less than 0.5 m ² / g, the particle dispersibility in the polyester is good, but when the obtained polyester composition is formed into a film, In some cases, the whiteness, the hiding property, and the glossiness are poor, which is not preferable. On the other hand, if the particle diameter is less than 0.01 μm in average particle diameter or the specific surface area exceeds 100 m ² / g,
Particle dispersibility in polyester is remarkably inferior, coarse foreign matter is generated when polyester stays in a high temperature field, or foaming, and further, it is not preferable because polyester having a high degree of polymerization cannot be obtained. .

In producing the modifier of the present invention, polyester, another thermoplastic resin such as polyethylene,
Polypropylene, polystyrene, etc., and various additives,
For example, ultraviolet absorbers, antioxidants, antistatic agents, surfactants, pigments, optical brighteners, and other inorganic particles, organic particles such as titanium dioxide, barium sulfate, clay, talc, kaolin, alumina, and wet type In addition, inorganic particles such as dry and spherical silica, and organic particles containing acrylic acid, styrene, and the like as constituents may be appropriately mixed as necessary.

The polyester composition of the present invention contains a modifier composed of calcium carbonate. The preferred content is more than 5% by weight and not more than 80% by weight, more preferably 7 to 78% by weight, particularly preferably 10 to 75% by weight.
%, More preferably 26 to 70% by weight. When the content is 5% by weight or less, when the obtained polyester composition is formed into a film, the whiteness and hiding properties of the film may be insufficient. If the content exceeds 80% by weight, the particle dispersibility of calcium carbonate in the polyester is inferior, foreign matters are generated or foamed when the polyester stays at a high temperature, and the polyester having a high degree of polymerization cannot be obtained. May not be enough.

The amount of phosphorus element in the polyester composition of the present invention is not particularly limited.
0 to 10000 ppm is preferable, and more preferably 20 to 10000 ppm.
0-9000 ppm, more preferably 300-800 ppm
0 ppm, particularly preferably 500 to 7000 ppm. If the phosphorus element content is less than 100 ppm, the dispersibility of calcium carbonate particles in the polyester may be poor, or foreign matter may be generated or foamed when the polyester stays at a high temperature, which may be undesirable. On the other hand, if it exceeds 10,000 ppm, a polyester having a high degree of polymerization cannot be obtained, which may be undesirable.

Examples of the method for obtaining the polyester composition of the present invention include a method of adding the modifier of the present invention in the polyester production step, and a method of dry blending with the polyester. In the method of adding the modifier of the present invention in the polyester production process, the modifier of the present invention can be added at any stage of the polyester production process, and the reactivity and the dispersibility of the calcium carbonate particles are reduced. It is preferably from before the esterification or transesterification reaction in the polyester production step to the beginning of the polycondensation reaction, and more preferably from after the esterification or transesterification reaction to the beginning of the polycondensation reaction. The method for adding the modifying agent of the present invention to the polyester reaction system is not particularly limited, but it is preferable to add the modifying agent in a slurry form appropriately mixed with an organic solvent such as glycol.

In the method of dry-blending the modifier of the present invention into polyester, it is preferable to use a conventional single-screw or twin-screw extruder or a vented single-screw or twin-screw extruder. In particular, it is preferable to use a vent type single or twin screw extruder. Extrusion conditions are not less than the melting point of the polyester, and the residence time is preferably within 2 hours, more preferably within 1 hour. The vent is set to a vacuum of 100 torr as much as possible to remove decomposed gas components and low volatile components and to suppress decomposition of polyester. Or less, more preferably 10 torr or less, and more preferably 2 to
rr or less is preferable. The method of supplying the modifier and the polyester to the extruder is not particularly limited, but the modifier and the polyester may be mixed in advance or may be supplied separately. At this time, the modifier may be supplied in a slurry form appropriately mixed with a solvent such as water or alcohol. Further, a mixture obtained by mixing the polyester at the time of producing the modifier of the present invention may be supplied to the extruder at a time. Among these methods for obtaining the polyester composition of the present invention, a method of dry blending with polyester is preferable from the viewpoint of adding and blending a high concentration of a modifier, and further using a vent-type single-screw or twin-screw extruder. Is particularly preferred.

In preparing the polyester composition of the present invention, polyester, other thermoplastic resins such as polyethylene, polypropylene, polystyrene and the like, and various additives such as ultraviolet absorbers, antioxidants, antistatics Agents, surfactants, pigments, optical brighteners, etc., and other inorganic particles, organic particles such as inorganic particles such as titanium dioxide, barium sulfate, clay, talc, kaolin, alumina, wet and dry, spherical silica, acrylic. Organic particles containing an acid, styrene, or the like as a component may be appropriately mixed as necessary.

[0025] From the polyester composition of the present invention, by a sheet-like or after stretching by melting extrusion
Biaxially oriented polyester films can be produced. The resulting biaxially stretched polyester film is slippery,
It is excellent in gloss, whiteness, concealing properties, and the like.

A specific method for producing a film comprising the polyester composition of the present invention will be described. The polyester composition is dried, melt-extruded to form an unstretched sheet, and then biaxially stretched and heat-treated to form a film. . The biaxial stretching may be any of longitudinal and transverse sequential stretching or simultaneous biaxial stretching, and the stretching ratio is not particularly limited, but usually 2.0 to 5.0 times each in the longitudinal and transverse directions. Also,
After biaxial stretching, the film may be further stretched in either the longitudinal or transverse direction. At this time, the content of the modifier composed of calcium carbonate by mixing the polyester composition of the present invention with various polyesters can be appropriately changed according to the purpose. Further, various polyesters to be mixed may be the same as or different from the polyester used as the base of the polyester composition of the present invention.

The film of the present invention can be obtained from the polyester composition by the method described above. Although the film of the present invention is not particularly limited, in order to obtain a biaxially stretched film having excellent whiteness, gloss, and hiding properties, the content of the modifying agent composed of calcium carbonate in the film exceeds 5% by weight. , 4
0% by weight or less, more preferably 7 to 30% by weight.
% By weight, particularly preferably 10 to 20% by weight. When the content of the modifier is 5% by weight or less, the whiteness and the hiding property are inferior, which may not be preferable. If the content of the modifier exceeds 40% by weight, the mechanical properties of the film may be inferior and may not be preferable. The density of the film is 0.80
1.38 g / cm ³ is preferred. 0.80g / c density
If less than m ³ poor in productivity and mechanical properties of the film,
When the density exceeds 1.38 g / cm ³ , the whiteness and the hiding property are inferior and may not be preferable.

When producing a biaxially oriented polyester film comprising the polyester composition of the present invention, polyester, other thermoplastic resins such as polyethylene, polypropylene, polystyrene and the like, and various additives such as an ultraviolet absorber , Antioxidants, antistatic agents, surfactants, pigments, optical brighteners, and other inorganic particles, organic particles such as titanium dioxide, barium sulfate, clay, talc, kaolin, alumina, wet and dry, spherical Inorganic particles such as silica, and organic particles containing acrylic acid, styrene and the like as constituent components may be appropriately blended and added as necessary.

The film of the present invention may be a composite film comprising a layer comprising the polyester composition of the present invention and another polyester layer. The lamination structure at this time is not particularly limited as long as it is two or more layers.

[0030]

The present invention will be described in more detail with reference to the following examples. The characteristics in the examples were measured as follows.

A. Specific surface area and particle size of calcium carbonate The specific surface area was measured by a BET surface area measuring device, and the particle size was measured by an ultracentrifugal particle size distribution measuring device.

B. Amount of phosphorus element contained in modifier The modifier was decomposed with an acid and measured by a colorimetric method.

C. Intrinsic viscosity of polyester Measured at 25 ° C. using an o-chlorophenol solvent.

D. Particle dispersibility in polyester 20 mg of polymer sandwiched between two cover glasses 280
After cooling with a melt press at a temperature of 0 ° C., it was determined by microscopic observation. ；: No aggregated particles or coarse particles were observed. Δ: Aggregated particles or coarse particles are slightly observed. X: Many aggregated particles or coarse particles are observed.

F. Film concealing property The visible light transmitting density of a 50 μm-thick film was measured with a Macbeth transmission densitometer TD-504, and the concealing property was determined.
The transmission density here was calculated by the following equation. O · D = −log (T / 100) where O · D; transmission density [−] T; visible light transmittance [%]

G. Whiteness of film 450 μm and 550 nm thick 50 μm measured with a tungsten light source using Hitachi Automated Spectrophotometer EPE-2
It was calculated from the reflectance R ₄₅₀ and R _{550 of} each film of m by the following formula. Whiteness (%) = 4R ₄₅₀ -3R ₅₅₀

H. Gloss of Film According to JIS Z84741, 60-degree specular gloss was measured, and the gloss of the film was measured.

Example 1 Calcium carbonate powder having an average particle diameter of 1.2 μm and a specific surface area of 8.0 m ² / g was charged into a Henschel mixer as a fixed container mixer, and stirred at a rotation speed of a rotary blade of 1500 rpm. When the temperature in the can reached 90 ° C., trimethyl phosphate as a phosphorus compound was added while spraying so as to be 5% by weight with respect to calcium carbonate. Thereafter, the mixture was mixed for 10 minutes to perform a surface treatment. When the phosphorus element content of the obtained modifier was measured by a colorimetric method, it was 77.
It was contained at 00 ppm.

[0039] 30 parts by weight of the resulting modifier and an intrinsic viscosity of 0.
After mixing with 70 parts by weight of 65 dl / g of polyethylene terephthalate, the mixture was supplied to a vented twin-screw extruder, kneaded at a temperature of 290 ° C. and a residence time of 5 minutes, and the modifier was added at 30% by weight.
Polyethylene terephthalate was obtained. No foreign matter was generated during kneading, and no foaming was observed. Also,
The particle dispersibility of calcium carbonate in the obtained composition was also good. Further, the amount of phosphorus element in the composition was 1350 ppm as measured by a colorimetric method.

The obtained polyethylene terephthalate containing 30% by weight of the modifier and polyethylene terephthalate having an intrinsic viscosity of 0.65 dl / g were mixed so that the modifier became 15% by weight, and further added to 100 parts by weight of the total polyester. On the other hand, optical brightener "OB-1" (manufactured by Eastman)
After 0.02 parts by weight were mixed and sufficiently dried, the mixture was supplied to an extruder, melted at 290 ° C., extruded into a sheet shape from a T-type die, cooled and solidified with a cooling drum at 30 ° C. to obtain an unstretched film. Next, the unstretched film is heated to 95 ° C., stretched 3.3 times in the machine direction, further heated to 100 ° C., stretched 3.3 times in the transverse direction, and heat-treated at 200 ° C. to have a thickness of 50 μm. A film was obtained. Table 1 shows the characteristic results of the obtained film. The density is 1.25 g / cm ³ , whiteness,
Both hiding and gloss were excellent.

Comparative Example 1 A polyethylene terephthalate containing 30% by weight of calcium carbonate and a film were obtained using a vented twin-screw extruder in the same manner as in Example 1, except that the calcium carbonate was not surface-treated with a phosphorus compound. . When a polyethylene terephthalate containing 30% by weight of calcium carbonate was produced using a vented twin-screw extruder, foaming occurred in the polymer, and the dispersibility of calcium carbonate particles was poor. Further, tearing due to foaming during the production of the film was severe, and the resulting film was poor in whiteness, hiding properties, and gloss.

Examples 2 to 11 As described in Tables 1 and 2, the type of calcium carbonate and the type and amount of the phosphorus compound were changed in the same manner as in Example 1 to modify the modifying agent. Used to obtain a polyester composition and a film. Tables 1 and 2 show the results of various characteristics.

Examples 2 to 11 fall within the scope of the present invention, in which the obtained polyester had good dispersibility of calcium carbonate particles, and the film was excellent in both whiteness and hiding power.

[0044]

[Table 1]

[Table 2] Example 12 70 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol were subjected to a transesterification reaction using 0.09 part by weight of calcium acetate as a catalyst according to a conventional method, and then the modifier produced in Example 1 was subjected to 50% by weight. 60 parts by weight of the ethylene glycol slurry contained was added, and then 0.04 parts by weight of antimony trioxide was added as a polymerization catalyst.

Thereafter, a polycondensation reaction was carried out at a high temperature under reduced pressure according to a conventional method to obtain a polyester composition. The amount of phosphorus element in the polyester composition was 1850 ppm. As a result of observing the dispersed state of calcium carbonate particles, neither aggregated particles nor coarse particles were observed.

The obtained polyethylene terephthalate containing 30% by weight of the modifier and polyethylene terephthalate having an intrinsic viscosity of 0.65 dl / g were mixed so that the modifier became 15% by weight. On the other hand, optical brightener "OB-1" (manufactured by Eastman)
After 0.02 parts by weight were mixed and sufficiently dried, the mixture was supplied to an extruder, melted at 290 ° C., extruded into a sheet shape from a T-type die, cooled and solidified with a cooling drum at 30 ° C. to obtain an unstretched film. Next, the unstretched film is heated to 95 ° C., stretched 3.3 times in the machine direction, further heated to 100 ° C., stretched 3.3 times in the transverse direction, and heat-treated at 200 ° C. to have a thickness of 50 μm. A film was obtained. The characteristics of the obtained film are as follows: density 1.23 g / cm ³ , whiteness 97%, O · D 0.
9, the glossiness was 28%, and the whiteness, hiding power and glossiness were all excellent.

[0047]

According to the present invention, as described above, the dispersibility of calcium carbonate particles is improved by blending and adding a polyester resin modifier consisting of calcium carbonate surface-treated with a specific phosphorus compound to polyester at a high concentration. , A polyester composition having excellent heat resistance can be obtained, and from the polyester composition, biaxial rolling excellent in whiteness, hiding properties, and glossiness can be obtained.
A stretched polyester film is obtained. In particular, when a polyester composition is formed into a film, a white film having excellent whiteness, hiding power, and glossiness can be produced, and a photographic paper, an X-ray intensifying screen, a card, a label, a display board, a white board, etc. It is preferably used as a substrate.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 5/00 C08J 5/18 C08L 67/00-67/04

Claims (5)

(57) [Claims] 1. A calcium carbonate powder surface-treated with at least one phosphorus compound selected from the group consisting of phosphoric acid, phosphorous acid, phosphinic acid, phosphonic acid and their alkyl ester compounds having 3 or less carbon atoms. Contains
Biaxially stretched polyester film. 2. The biaxially stretched polyester film according to claim 1, wherein the surface treatment amount of the phosphorus compound is 0.1% by weight or more based on calcium carbonate . 3. The biaxially stretched polish according to claim 1, wherein the biaxially stretched polish contains 100 to 30,000 ppm of a phosphorus element.
Ester film. 4. Phosphoric acid, phosphorous acid, phosphinic acid, phos
Honic acid and their alkyl esters having 3 or less carbon atoms
At least one species selected from the group consisting of
Claim, characterized by comprising kneading consisting of calcium carbonate powder surface treated with emissions compounds port <br/> Riesuteru resin modifier for a polyester in a vented extruder 1-3
The biaxially stretched polyester film according to any one of the above. 5. A biaxially stretched polyester film, wherein the film according to claim 1 is white .