JPH11152325A - Aromatic polyester and biaxially oriented polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aromatic polyester whose number of foreign matters and color are well controlled and, from which a molding of less surface defects and better color than conventional one can be made, and a biaxially oriented polyester film of less surface defects and better color than conventional one using the polyester. SOLUTION: This is an aromatic polyester polymerized with an Sb compd. as a polymerization catalyst and adding P compd., particularly, a polyester with ethylene terephthalate as a main repeating unit, and its number of contaminant not smaller than 10 μm in 1 g polymer is not more than 50, and L value and b value of the color measured by Lab method satisfy the following formulae I and II, and this biaxially oriented film is manufactured therewith. Formula I:75<=L-b. Formula II:b<=3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aromatic polyester film and a biaxially stretched polyester film, and more particularly to a biaxially stretched film having a small amount of foreign matter in the polymer and a small amount of coloring, excellent in moldability and quality of molded products. The present invention relates to an aromatic polyester suitable for production and a biaxially stretched film comprising the same.

[0002]

2. Description of the Related Art Aromatic polyesters represented by polyethylene terephthalate have excellent mechanical properties, heat resistance, weather resistance, electric insulation resistance, and chemical resistance, and are widely used as films, fibers, bottles, and other molded products. I have.

[0003] Such polyesters have different required properties in each application, but in the production thereof, a polymerization catalyst is used in order to make the polymerization reaction proceed smoothly. Various metal compounds are known as the polymerization catalyst, and among them, an antimony (Sb) compound such as antimony trioxide is widely used as a catalyst having low polymerization activity and high polymerization activity.

[0004] However, these catalysts also have problems. For example, a part of the Sb compound is reduced during the reaction to generate metal Sb and other foreign substances, which darkens the color of the polymer, deteriorates the process condition, and deteriorates the quality of the molded product.

Conventionally, various studies have been made on the reduction of foreign matter in polymers using an Sb compound as a polymerization catalyst. For example, Japanese Patent Application Laid-Open Nos.
No. -3420 proposes to add an Sb compound at the early stage of the EI reaction in the transesterification (EI) method and use it as a catalyst for both the EI and the polycondensation reaction, without adding another EI catalyst. It is described that foreign matters in the polymer are reduced by the amount. However, according to the study of the present inventors, the polymer obtained by such a polymerization method is less effective in reducing the number of foreign substances and preventing coloring caused by the Sb compound used as a polymerization catalyst, and a polymer of good quality is obtained. It turned out to be difficult to get. Also,
JP-A-61-231025 proposes a technique of using a Sb compound as a polymerization catalyst and adding a small amount of terephthalic acid in the latter half of the polycondensation reaction to reduce foreign substances deposited on a spinneret during spinning. I have. However, even if this technique is used, foreign matter in the polymer is not sufficiently reduced, and it is difficult to obtain good polymer quality. Furthermore, Japanese Patent Application Laid-Open No. 54-39490
Japanese Patent Application Laid-Open No. 60-67529 discloses the use of, as a polycondensation catalyst, a mixture obtained by heating and mixing an Sb compound and a phosphorus compound in advance under suitable conditions. The effect of reducing foreign matter in the polymer cannot be expected.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to control the number of foreign matters and the hue in polyester to a satisfactory level.
It is an object of the present invention to provide an aromatic polyester capable of forming a molded product having less surface defects and good hue than ever before. It is another object of the present invention to provide a biaxially stretched polyester film using the polyester, which has less surface defects than ever before and has good hue.

[0007]

An object of the present invention is to provide an aromatic polyester obtained by polymerizing an Sb compound as a polymerization catalyst and adding a P compound according to the present invention. 50 foreign substances with a size of 10 μm or more
This is achieved by an aromatic polyester which is less than or equal to and whose color L value and b value measured by the Lab method satisfy the following formulas (1) and (2).

[0008]

[Expression 2] 75 ≦ L−b (1) b ≦ 3 (2)

The dicarboxylic acid component of the aromatic polyester in the present invention includes, for example, aromatic dicarboxylic acids such as terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, phthalic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, and diphenoxyethanedicarboxylic acid. Can be mentioned. Of these, terephthalic acid and 2,6-naphthalenedicarboxylic acid are particularly preferred,
These are 80 mol% in the dicarboxylic acid component.
It is preferable that it is above. In this case, the aromatic dicarboxylic acid other than terephthalic acid or 2,6-naphthalenedicarboxylic acid, the aliphatic dicarboxylic acid such as adipic acid and sebacic acid, and the alicyclic dicarboxylic acid such as 1,4-cyclohexanedicarboxylic acid are copolymerized. can do. Also,
As the glycol component, for example, ethylene glycol,
Trimethylene glycol, 1,4-butanediol, diethylene glycol, 1,4-cyclohexanedimethanol, neopentylene glycol, bisphenol A,
Examples thereof include aliphatic, alicyclic, and aromatic glycols such as bisphenol S, and polyoxyalkylene glycols. Of these, ethylene glycol and 1,4-butanediol are particularly preferred, and the proportion of these in the glycol component is preferably at least 80 mol%.

Specific examples of the aromatic polyester include polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polyester containing polybutylene-2,6-naphthalate as a substantial constituent, or polyesters containing these. The main component is, for example, a copolymerized polyester containing the dicarboxylic acid component and / or the glycol component as a copolymerization component.

These aromatic polyesters are usually prepared by a method of subjecting a dicarboxylic acid and a glycol to an esterification reaction,
A dicarboxylic acid glycol ester and / or a low polymer thereof is formed by a method of transesterifying a dicarboxylic acid dialkyl ester and glycol, or a method of performing an esterification reaction of dicarboxylic acid and alkylene oxide. It is obtained by heating under reduced pressure to polymerize until a predetermined polymerization degree is reached.

As the polymerization catalyst used in the above polymerization reaction, it is necessary to use an antimony compound from the viewpoint of high catalytic activity and cost. The antimony compound is not particularly limited, and any Sb compound having a polymerization catalytic ability can be used. For example, oxides such as antimony trioxide, antimony tetroxide, and antimony pentoxide, halides such as antimony trichloride and antimony tribromide, carboxylate salts such as antimony acetate, and alcoholates such as antimony glycolate can be given. . Among them, oxides are preferable, and antimony trioxide is particularly preferable. The addition amount of the antimony compound is 50 to 400 pp in terms of antimony atomic weight.
m, more preferably 100 to 350 ppm.

The P compound used as an additive is S
This has the effect of suppressing the b-based polymerization catalyst from being reduced during the polymerization reaction and being deposited as foreign matter in the polymer as metal Sb.
The additive is not particularly limited as long as it is a P compound, but a compound containing phosphorus (P), hydrogen, and oxygen as constituent elements is preferable, and orthophosphoric acid and phosphorous acid are particularly preferable. These compounds may be used in combination of two or more.

The phosphorus compound can be added at any stage as long as the polymerization reaction is substantially completed. At this time, the P compound used as an additive preferably has a logarithmic pKa of the reciprocal of the dissociation constant in an aqueous solution at 25 ° C. of 0.9 or more. If the pKa is less than 0.9, the acidity in the polymerization reaction system is too high, and the amount of diethylene glycol by-produced increases, making it difficult to control the polymer quality. The amounts of the Sb compound and the P compound added are the same as those of the Sb compound in the polyester.
The ratio (Sb / P) of the amount of Sb atoms in the compound to the amount of P atoms in the P compound (Sb / P) is preferably from 5 to 250, more preferably from 50 to 200, and particularly preferably from 90 to 18.
0. If this ratio (Sb / P) is less than 5, the acidity in the system is too high, and the amount of diethylene glycol by-produced increases, making it difficult to control the quality of the polymer. On the other hand, this ratio (Sb /
When P) exceeds 250, the amount of P with respect to Sb is insufficient, so that not only a sufficient effect of suppressing foreign substances is not obtained, but also the hue of the polymer deteriorates.

After the completion of the melt polycondensation, the polymer is melt-extruded, cooled in a suitable cooling medium such as water, cut into a suitable size, and formed into chips. The tip may be a rectangular parallelepiped, a cylinder, a die, or a sphere. Further, if necessary, solid-state polymerization may be performed to obtain a predetermined intrinsic viscosity.

In the production of the aromatic polyester, other additives such as a tinting agent, an antioxidant, an ultraviolet absorber, an antistatic agent and a flame retardant may be used, if necessary.

In the aromatic polyester of the present invention, the number of foreign substances having a size of 10 μm or more
It is necessary to be less than 30 pieces, preferably 30 pieces or less,
Particularly preferably, the number is 10 or less. When the number of foreign substances having a size of 10 μ or more exceeds 50, for example, when forming a biaxially stretched film or the like, voids (voids) are generated around the foreign substances because the peripheral parts of the foreign substances are also stretched, and a large film is formed. The probability of causing surface defects increases.

Means for reducing the number of foreign substances having a size of 10 μm or more in 1 g of polyester to 50 or less is not particularly limited. For example, the logarithm p of the reciprocal of the dissociation constant in an aqueous solution at 25 ° C.
It is effective to use a P compound having a Ka of 0.9 or more as an additive.

The aromatic polyester in the present invention is La
The L value and b value of the color measured by the b method must satisfy the following expressions (1) and (2).

[0020]

[Equation 3] 75 ≦ L−b (1) b ≦ 3 (2)

In the above formula, the value of Lb needs to be 75 or more, more preferably 80 or more. Further, the b value needs to be 3 or less, but is more preferably 2 or less. The larger the value of L, the better the whiteness, and the larger the value of b, the more yellowish the color. If the aromatic polyester does not satisfy the conditions of the above formula, it is further colored yellow due to the heat history at the time of melt extrusion molding into a film or the like. It is not preferable because the willingness to purchase is reduced. Means for controlling the hue of the aromatic polyester so as to satisfy the above formula is not particularly limited. For example, the ratio of the Sb compound and the P compound in the polyester in terms of Sb atoms and the residual amount ratio in terms of P atoms (Sb / P) Can be achieved by appropriately adjusting the polymerization temperature and the polymerization time.

The limiting viscosity number of the aromatic polyester is not particularly limited.
Preferably it is in the range of 0.4 to 1.5.

Further, the second object of the present invention is achieved by a biaxially stretched film made of the polyester.

In the biaxially stretched film, the aromatic polyester is melt-extruded from a die, quenched on a cooling drum to obtain an unstretched film, and then the unstretched film is heated in a longitudinal direction (for example, Tg-10 to 10). Tg + 70 ° C, T
g: glass transition temperature of polyester), stretched to a uniaxially stretched film, and subsequently heated in the transverse direction (for example, Tg
~ Tg + 70 ° C), stretched, heat-set and / or thermally relaxed. The thickness of the biaxially stretched film is preferably 1 to 300 μm, particularly preferably 1 to 150 μm. When the thickness is less than 1 μm, the thickness is too small to stabilize the film forming process, and in extreme cases, the film is cut. On the other hand, if the thickness exceeds 300 μm, the quality becomes excessive and uneconomical. Although the stretching ratio varies depending on the application, it is preferable that both the longitudinal stretching and the transverse stretching ratio be in the range of 2 to 6 times. If the stretching ratio is less than 2 times, the orientation of the film is insufficient and mechanical strength is not provided. On the other hand, if the stretching ratio exceeds 6 times, the stretching ratio becomes too high, so that film formation becomes difficult and the quality becomes excessive. Known means and conditions can be used for the heat setting and / or the thermal relaxation depending on the use of the film.

The biaxially stretched polyester film of the present invention is preferably provided with lubricity as required. Means for imparting lubricity are not particularly limited, for example, a method of dispersing a lubricant such as SiO ₂ , BaSO ₄ , CaCO ₃ , alumina, alumina silicate, crosslinked organic particles in a resin composition, A method of providing a layer having lubricity on the surface is exemplified.

[0026]

The present invention will be described below in detail with reference to examples. In the examples, “parts” means parts by weight. The method for measuring the characteristics used in the examples is shown below.

1) Intrinsic viscosity phenol / tetrechloroethane (weight ratio 60/40)
Calculated from the solution year measured at 35 ° C. using the mixed solvent of

2) Sb, P content in polymer The amount of metal (unit: ppm) in the polymer is measured by X-ray fluorescence (Rigaku Denki Kogyo Co., Ltd. X-ray fluorescence type 3270) by a predetermined method.

3) Amount of diethylene glycol (DEG) 200 g of the polymer is decomposed with hydrazine, and the solution is determined by gas chromatography. The gas chromatography used was a gas chroma 263 manufactured by Hitachi, Ltd.

4) Hue The polymer was heat-treated at 1400 ° C. for 60 minutes in a dryer and dried, and then a color difference meter Z-1001 manufactured by Nippon Denshoku Industries Co., Ltd.
Measure with DP.

5) Measurement of size of foreign matter 1 g of the polymer chip was thoroughly washed with acetone and then with chloroform, dissolved in a solution of hexafluoroisopropanol (HFIP) / chloroform = 1/1, and opened.
Filtration is carried out with a 1 μm membrane filter, and the collected matter is observed with an optical microscope (× 200) to count the number of foreign substances having a major axis of 10 μm or more.

6) Evaluation of Surface Defects of Biaxially Stretched Film 1 g of the film is observed with a deflection microscope, and those having a major axis of surface defects exceeding 50 μm are evaluated according to the following criteria. No number of foreign substances whose major axis exceeds 50 μm per 1 g of biaxially stretched film ....... ◎ 1 to 5 foreign substances whose major axis exceeds 50 μm per 1 g of biaxially oriented film. 6 to 10 foreign substances having a major axis of more than 50 μm... Δ 10 or more foreign substances having a major axis of more than 50 μm per 1 g of the biaxially stretched film.

7) Hue of the film The film is cut into a size of 10 cm in length and 10 cm in width, and ten pieces of the pieces are placed on a white drawing paper. This is visually observed by a 30 person under an incandescent lamp of 100 W, and the sensory evaluation of the hue of the film is performed. 3 or less people who feel yellow or darkness in the color of the film …… ◎ 4 to 6 people who feel yellow or darkness in the color of the film …… ○ 6 people who feel yellow or darkness in the color of the film 10 to 10 people more than 10 people feel yellow or darkening in the color of the film.

[Examples 1 to 3, Comparative Example 1] 3600 parts of terephthalic acid and 2750 parts of ethylene glycol were slurried at room temperature, and charged in an autoclave equipped with a stirrer.
The reaction was performed at 270 ° C. under a pressure of g / cm ² . When the volume of distillate reaches 600 parts, the pressure is released, and the pressure is reduced to 270 at normal pressure.
The reaction was carried out at ℃. Further, a transparent solution of antimony trioxide / ethylene glycol was added as a polymerization catalyst and a P compound was added as an additive so that Sb / P in the produced polyester was as shown in Table 1. Subsequently, the polymerization temperature was 295.
Polymerization was performed at 0.1 mmHg under reduced pressure under high vacuum gradually at ℃ to obtain polyethylene terephthalate having an intrinsic viscosity of 0.642. The quality of this polymer was as shown in Table 1.

Further, the dried chips of the polyester were continuously supplied at a rate of 10 tons / day to a biaxial ruder, and the melted polymer was filtered through a stainless steel sintering type filter (Eugin 15G manufactured by Eugene Carbon Co., Ltd.). Thereafter, an unstretched film was extruded into a sheet on a casting drum cooled from the slit. Subsequently, the unstretched film was stretched 3.3 times in the longitudinal direction by a heating roll, and then stretched 3.6 times in the transverse direction by a stenter to obtain a biaxially stretched film having a thickness of 30 μm. Table 2 shows the evaluation results of surface defects and hue of the obtained biaxially stretched film.

Comparative Example 2 A predetermined polyethylene terephthalate was obtained in the same manner as in Example 1 except that the polymerization temperature after adding a transparent solution of antimony trioxide / ethylene glycol as a polymerization catalyst was 305 ° C. . The quality of this polymer was as shown in Table 1. The obtained polymer was molded in the same manner as in Example 1 to form a biaxially stretched film. Table 2 shows the evaluation results of surface defects and hue of the obtained biaxially stretched film.

Examples 4 and 5, Comparative Example 3 The same procedure as in Example 1 was carried out except that Sb / P in the polyester was changed to obtain a predetermined polyethylene terephthalate. The quality of this polymer was as shown in Table 1. The obtained polymer was molded in the same manner as in Example 1 to form a biaxially stretched film. Table 2 shows the evaluation results of surface defects and hue of the obtained biaxially stretched film.

[0038]

[Table 1]

[0039]

[Table 2]

As is clear from the results shown in Tables 1 and 2, the aromatic polyester of the present invention has very few foreign substances due to the Sb catalyst, and the biaxially stretched polyester film using the polyester has few surface defects and a low hue. In particular, it is excellent as a packaging material film.

[0041]

According to the present invention, an aromatic polyester in which the number of foreign substances in the polyester and the hue are controlled to a satisfactory level, a molded article having less surface defects and a good hue than ever before can be formed, and It is possible to provide a biaxially stretched polyester film using the polyester, which has less surface defects than before and has a good hue.

[Procedure amendment]

[Submission date] July 17, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 4

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction contents]

[0038]

[Table 1]

Claims (5)

[Claims] 1. An aromatic polyester obtained by polymerizing an Sb compound as a polymerization catalyst and adding a P compound, wherein the number of foreign matters having a size of 10 μm or more in 1 g of the polyester is 50 or less, and is obtained by a Lab method. L of the measured color
An aromatic polyester, wherein the value and the value b satisfy the following formulas (1) and (2). [Expression 1] 75 ≦ L−b (1) b ≦ 3 (2) 2. The aromatic polyester according to claim 1, wherein the logarithm pKa of the reciprocal of the dissociation constant of the P compound in an aqueous solution at 25 ° C. is 0.9 or more. 3. The ratio (Sb / P) of the amount of the Sb compound in the polyester in terms of Sb atoms to the amount of the P compound in terms of P atoms is 5:
The aromatic polyester according to claim 1 or 2, which has a molecular weight of from 250 to 250. 4. The aromatic polyester according to claim 1, wherein the aromatic polyester is a polyether having ethylene terephthalate as a main repeating unit. 5. A biaxially stretched polyester film comprising the aromatic polyester according to claim 1.