JPH11269257A - Production of copolyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a copolyester which is excellent in gas barrier properties, resistances to heat and impact, color tone, clarity, etc., and has a low cyclic oligomer content by adding specified amts. of isophthalic acid and ethylene glycol to a polyethylene terephthalate oligomer and subjecting the resultant mixture to esterification and then to polycondensation. SOLUTION: Isophthalic acid in a molar ratio of isophthalic acid component to terephthalic acid component of (95/5)-(15/85), ethylene glycol, and phosphoric acid or its ester in an amt. of 1×10<-4> -200×10<-4> mol per mol of the acid component are added to a polyethylene terephthalate oligomer having a number average mol.wt. of 2,000 or lower. The resultant mixture is subjected to esterification for at least 0.5 hr and then to polycondensation in the presence of a polycondensation catalyst under such conditions that the temp. X ( deg.C) and degree of vacuum Y (hPa) in the polycondensation satisfy the relation expressed by formulas I and II, until the number average mol.wt. reaches 10,000 or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas barrier,
The present invention relates to a method for producing a high molecular weight poly (ethylene isophthalate / ethylene terephthalate) -based copolymerized polyester having excellent heat resistance, impact resistance, color tone, transparency, and the like, and having a small amount of cyclic oligomers generated.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
Because of its excellent mechanical properties, chemical stability, transparency, etc., and because it is lightweight and inexpensive, it is widely used as a packaging material for various containers, films and sheets.

[0003] However, PET has better gas barrier properties than other thermoplastic resins such as polyolefins, but has insufficient gas barrier properties depending on applications. For example, carbonated drinks, containers for beverages such as wine, containers for medical products, and the like require particularly strict gas barrier properties from the viewpoint of preserving the contents.
This requirement could not be sufficiently satisfied with a container made of T.

As a polyester container having improved gas barrier properties, JP-A-59-64624 discloses a container made of a copolymerized polyester such as polyethylene isophthalate or poly (ethylene isophthalate / ethylene terephthalate). ing. Of these, polyethylene isophthalate contains a cyclic oligomer having a high melting point, and therefore has a problem that it is mixed as a foreign substance into a molded product. Copolymerized polyester is more preferable for containers.

A poly (ethylene isophthalate / ethylene terephthalate) copolymerized polyester (hereinafter referred to as “PEI”)
T ". ) Has been known for a long time (for example, Japanese Patent Publication No. 34-3238). However, in PEIT,
When the proportion of the ethylene isophthalate component is increased, when an antimony catalyst or a germanium catalyst is used, a large amount of cyclic oligomers are formed during the polycondensation reaction, and these are sublimated, so that they are submerged in the polymerization vessel or in the distilling system. Adheres to
There is a problem that the vacuum path and the distilling path are closed. There is also a problem that these are mixed into the molded product as foreign matter.

On the other hand, JP-A-59-64625 discloses a method using a proton acid catalyst as a method for suppressing the amount of cyclic oligomers generated. In this method, PE
The diethylene glycol component in IT increased, and PEIT
However, since the glass transition point of the resin pellet decreases, it is necessary to dry the resin pellets at a low temperature for a long time, and there is a problem that productivity is poor. Another problem is that sufficient heat resistance cannot be obtained when a molded article is formed.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a high molecular weight, high heat resistance, impact resistance, color tone, transparency, etc., which is suitable for use as a gas barrier container, etc. It is intended to provide a method for producing a molecular weight PEIT.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and its gist is as follows. (1) In a polyethylene terephthalate oligomer having a number average molecular weight of 2000 or less, isophthalic acid and ethylene glycol are mixed at a molar ratio of an isophthalic acid component to a terephthalic acid component.
95/5 to 15/85, and phosphoric acid or an ester thereof are added in an amount of 1 × 10 ^-4 to 200 × 10 ^-4 mol per 1 mol of the acid component, and the esterification reaction is carried out for 0.5 hour or more. After going,
A polycondensation catalyst is added, and the polycondensation temperature and the degree of polycondensation pressure reduction satisfy the following formula and the number average molecular weight is 10,000.
A method for producing a copolymerized polyester, wherein a polycondensation reaction is carried out until the above. 270 ° C. ≦ X ≦ 290 ° C. 0.0266X−6.916 ≦ Y ≦ 0.0225X ² −11.993X + 1605.1 where X is the polycondensation temperature (° C.), and Y is the polycondensation depressurization degree (hP
represents a). (2) Poly (ethylene isophthalate / ethylene terephthalate) having a number average molecular weight of 2,000 or less and a molar ratio of isophthalic acid component to terephthalic acid component of 95/5 to 15/85.
Phosphoric acid or an ester thereof is added to the copolymerized oligomer in an amount of 1 × 10 ⁻⁴ to 200 × 10 ⁻⁴ mol per 1 mol of the acid component, and the esterification reaction is carried out for 0.5 hours or more. A process for producing a copolymerized polyester, comprising adding a catalyst and conducting a polycondensation reaction under conditions in which the polycondensation temperature and the degree of polycondensation pressure satisfy the above formulas and until the number average molecular weight becomes 10,000 or more.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The PEIT in the present invention is a random copolymerized polyester having a molar ratio of ethylene isophthalate unit to ethylene terephthalate unit of 95/5 to 15/85. If the proportion of ethylene isophthalate units is too large,
When a large amount of cyclic oligomers are generated during the polycondensation reaction, the operability deteriorates, the amount of foreign substances in the molded article increases, and when the molded article is blended with PET to obtain a molded article,
The compatibility with T deteriorates. On the other hand, when the proportion of the ethylene isophthalate unit is too small, the gas barrier property is reduced.

The PEIT may contain other copolymer components as long as its properties are not impaired.
Specific examples of the copolymer component include phthalic acid, 2,6-naphthalenedicarboxylic acid, diphenylsulfonedicarboxylic acid,
4'-biphenyldicarboxylic acid, succinic acid, adipic acid,
Examples include 1,5-pentamethylene glycol, 1,6-hexamethylene glycol, neopentyl glycol, diethylene glycol, 1,4-cyclohexanedimethanol, and ethylene oxide adducts of bisphenol A and bisphenol S.

Next, a method of manufacturing the PEIT of the present invention will be described. In the first method, first, terephthalic acid and ethylene glycol are esterified by a conventional method to obtain a polyethylene terephthalate oligomer having a number average molecular weight of 2000 or less (hereinafter referred to as “PET oligomer”). Next, isophthalic acid and ethylene glycol are added to the PET oligomer in such an amount that the molar ratio between the isophthalic acid component and the terephthalic acid component is 95/5 to 15/85,
And phosphoric acid or its ester in an amount of 1 to 1 mol of the acid component.
× 10 ^-4 to 200 × 10 ^-4 mol, and the esterification reaction was carried out for 0.5 hours or more while removing by-product water from the system at a temperature of 200 to 250 ° C under normal pressure to slight pressure. Do. The molar ratio of isophthalic acid and ethylene glycol to be added to the PET oligomer is suitably about 1 / 1.2 to 1 / 3.5. These may be added separately, but it is preferable in terms of operation that they are added in the form of a slurry of the two or a solution in which the two have partially reacted.

In the second method, first, isophthalic acid, terephthalic acid and ethylene glycol are esterified by a conventional method to have a number average molecular weight of 2,000 or less and a molar ratio of isophthalic acid component to terephthalic acid component of 95. / 5
~ 15/85 poly (ethylene isophthalate / ethylene terephthalate) oligomer (hereinafter referred to as "PEIT oligomer"). Next, to the PEIT oligomer, phosphoric acid or an ester thereof is added in an amount of 1 × 10 ⁻⁴ to 200 × 10 ⁻⁴ mol per 1 mol of the acid component, and 0.5% under the same conditions as in the first method. Perform the esterification reaction for more than an hour.

As the phosphoric acid or its ester in the present invention, phosphoric acid, phosphoric acid (mono, di, tri) alkyl ester, phosphoric acid (mono, di, tri) alkyl ester aryl ester, phosphoric acid (mono, Di, tri) hydroxyalkyl esters are used, and specific examples thereof include phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, and tris-2-hydroxyethyl phosphate.

When adding phosphoric acid or an ester thereof,
The ET oligomer or PEIT oligomer needs to have a number average molecular weight of 2000 or less. If an oligomer having a higher molecular weight than the above is used, the amount of terminal carboxyl groups is small and the reaction with phosphoric acid or its ester does not proceed sufficiently, so that phosphoric acid or its ester is scattered out of the system, which is not preferable.

The esterification reaction time after the addition is 0.5
It must be longer than an hour. The reaction time is 0.5
If it is less than the time, the PET oligomer or PEIT
The reaction between the oligomer and phosphoric acid or its ester becomes insufficient. However, if the time is too long, the transparency of the reactant deteriorates. Therefore, it is not preferable.

The amount of phosphoric acid or its ester is required to be ^{1 × 10 -4 ~ 200 × 10} -4 mol of the acid component to 1 ^{mol, 5 × 10 -4 ~ 100 ×} 10 - Preferably, it is ⁴ mol. When the amount is less than 1 × 10 ^-4 mol, PEIT having good color tone cannot be obtained. On the other hand, when the amount exceeds 200 × 10 ^-4 mol, the effect of improving color tone and transparency does not change. Is not preferred because PEIT may gel.

After the above esterification reaction, a polycondensation catalyst is added, and the polycondensation reaction is carried out under conditions that the polycondensation temperature and the degree of polycondensation pressure satisfy the above formulas and the number average molecular weight becomes 10,000 or more.

The polycondensation catalyst is not particularly restricted but includes, for example, antimony compounds such as antimony trioxide and antimony acetate; germanium compounds such as germanium dioxide and germanium tetraethoxide; cobalt compounds such as cobalt acetate and cobalt chloride; Examples thereof include titanium compounds such as tetra-n-butyl titanate and tetraethyl titanate. These compounds may be used alone or in combination.

The amount of the polycondensation catalyst varies depending on the type of the catalyst to be used, but is usually in the range of 0.5 × 10 ^{-4 to} 20 × 10 ^-4 mol per mol of the acid component constituting PEIT. Is desirable.

Normally, in the polycondensation of PEIT, the pressure is gradually reduced from the start of the polycondensation, and the pressure is reduced to 0.9 hPa or less.
A method of performing a polycondensation reaction at a temperature of 0 to 300 ° C. is used. In this method, it is necessary that the polycondensation temperature (X) and the degree of polycondensation decompression (Y) satisfy the following formulas. 270 ° C ≦ X ≦ 290 ° C 0.0266X−6.916 ≦ Y ≦ 0.0225X ² −11.993X + 1605.1

When the polycondensation temperature (X) is lower than 270 ° C., the activity of the polycondensation catalyst is not sufficiently exhibited, so that the high molecular weight P
EIT is difficult to obtain. On the other hand, the polycondensation temperature (X) is 290
When the temperature exceeds ℃, the thermal decomposition reaction proceeds simultaneously, so that not only high molecular weight PEIT cannot be obtained but also the color tone is inferior.

When the polycondensation temperature (X) is set to 270 ° C., the degree of polycondensation decompression (Y) must be in the range of 0.27 to 7.24 hPa, and the polycondensation temperature (X) is set to 290 ° C. When the temperature is set to ° C., the degree of polycondensation pressure reduction (Y) must be in the range of 0.80 to 19.4 hPa. Polycondensation decompression degree (Y)
Is smaller than the lower limit of the formula, it is difficult to suppress the cyclic oligomer generated during the polycondensation reaction. On the other hand, if the degree of polycondensation pressure reduction (Y) is larger than the upper limit of the formula, a high molecular weight PEIT cannot be obtained.

Furthermore, the polycondensation reaction has a number average molecular weight of 100
It is necessary to perform the process until a PEIT of 00 or more, preferably 12000 or more is obtained. When the number average molecular weight is small, sufficient strength as a molded product cannot be obtained, and mechanical strength such as impact resistance decreases.

The PEIT may contain additives such as a lubricant, a pigment, an antioxidant, and an ultraviolet absorber, if necessary.

The PEIT obtained by the method of the present invention is
Various molded articles can be formed by various molding methods, can be used alone, or can be used as a mixture with PET or the like.

[0027]

The reason why the method of the present invention suppresses the formation of cyclic oligomers during the polycondensation reaction is not clear,
It is presumed that phosphoric acid or an ester compound thereof is randomly copolymerized with the T oligomer or PEIT oligomer, thereby suppressing the cyclization of the ethylene isophthalate unit at the latter stage of the polycondensation reaction.

[0028]

Next, the present invention will be described specifically with reference to examples. The method for measuring and evaluating the characteristic values and the like is as follows. (a) Number average molecular weight According to gel permeation chromatography manufactured by Waters, weight ratio of hexafluoroisopropanol to chloroform was 5/95.
Was used as a solvent to obtain a molecular weight distribution curve, and the number average molecular weight was calculated. (b) Copolymerization ratio PEIT was dissolved in a mixed solvent of deuterated hexafluoroisopropanol and deuterated chloroform at a volume ratio of 1/25, and ¹ HN was applied with a JEOL LA-400 type NMR apparatus.
The MR was measured, and the copolymerization ratio was determined from the integrated intensity of the proton peak of each copolymer component in the obtained chart. (c) Color Tone The color tone was measured using a color difference meter ND- # 80 manufactured by Nippon Denshoku Industries Co., Ltd. The color tone was determined using a Hunter Lab colorimeter.
The L value is lightness (the larger the value, the brighter), the a value is a red-green hue (+ is reddish,-is greenish), and the b value is a yellow-blue hue (+ is yellowish,-is Blue). The color tone is better as the L value is larger, the a value is closer to 0, and the b value is smaller unless the value is extremely reduced. (d) Solution haze (transparency) 2 g of PEIT was dissolved in 20 ml of chloroform, and the haze of the resulting solution was measured with a turbidimeter MODEL 1001DP manufactured by JEOL Ltd. (haze of chloroform: 0%). The smaller the haze value, the better the transparency (10% or less passes). (e) Sublimate of cyclic oligomer After the completion of the polycondensation reaction, 50 kg of ethylene glycol was charged into the polycondensation reaction vessel, the temperature was raised to 200 ° C., and the circulation washing between the polycondensation reaction vessel, the separator and the condenser was performed for 2 hours. . Thereafter, ethylene glycol was extracted, and the whole amount was subjected to filtration under reduced pressure to collect a cyclic oligomer. This circulation washing operation was performed twice, and the collected cyclic oligomer was finally washed with methanol and dried, and then the amount of sublimate of the cyclic oligomer was determined. (f) Oxygen permeation (gas barrier property) For a section of a film molded to a thickness of 100 μm,
Using OX-TRAN 100A manufactured by CON, it was determined from the volume of permeated oxygen at 23 ° C., 60% RH and 1 atm. (The unit is “ml / m ² · 24 hrs · atm”.) The smaller this value is, the better the gas barrier property is (22 or less is acceptable). (g) Heat Resistance of Bottle The bottle obtained by stretch blow molding was filled with hot water at 70 ° C., and the presence or absence of a volume change after standing for 30 minutes was visually examined. ：: No change in volume (pass). X: Volume change (fail). (h) Bottle strength (impact resistance) The bottle obtained by stretch blow molding is
The sample was dropped on a concrete plate at a temperature of 5 ° C. from a position having a height of 3 m and examined for the occurrence of cracks and dents. ：: No crack or dent (pass). ×: Cracks and dents occurred (fail).

Example 1 [Production of PEIT] A molar ratio of terephthalic acid to ethylene glycol was set to 1 in an esterification reactor in which bis (β-hydroxyethyl) terephthalate and its low polymer were present.
/1.6 slurry continuously, temperature 250 ℃, pressure 50
The reaction was carried out under the conditions of hPaG, PET oligomer having a esterification reaction rate of 95% and a number average molecular weight of 1400 as a residence time of 8 hours
(A) was obtained continuously. PET to another esterification reactor
A slurry composed of 5.2 kg of oligomer (A), 38.8 kg of isophthalic acid and 23 kg of ethylene glycol (isophthalic acid /
The molar ratio of ethylene glycol was 1 / 1.6), and the concentration was 3
A solution of 10% by weight of triethyl phosphate in ethylene glycol was mixed with 10 × 10 ^{-4 of} triethyl phosphate per mole of acid component.
After the addition in a molar amount, the esterification reaction was carried out under normal pressure at a temperature of 200 ° C. for 3 hours. The obtained esterification reaction product is charged into a polycondensation reactor, and 5 × 10 ⁻⁴ mol of antimony trioxide and 3 × 10 ⁻⁴ mol of cobalt acetate are added to 1 mol of the acid component. Finally, a polycondensation reaction was performed at a pressure of 1.4 hPa and a temperature of 270 ° C. for 4 hours. PEI obtained
T had a copolymerization ratio of isophthalic acid (IPA) of 89.9 mol% and a number average molecular weight of 13,500. The sublimate content of the cyclic oligomer was measured to be 780 g. [Production of PET] 60 kg of PET oligomer (A) and 2.5 × 10 ^-4 mol of germanium dioxide with respect to 1 mol of an acid component were charged into a polycondensation reactor, and the pressure was gradually reduced.
A polycondensation reaction was performed at 0.9 hPa and a temperature of 280 ° C. for 2 hours to obtain a PET prepolymer having a number average molecular weight of 16,500. This PET
The prepolymer was charged into a rotary solid-state polymerization apparatus, pre-dried at 70 ° C. for 2 hours, and then dried at 130 ° C. for 4 hours.
Solid phase polymerization was carried out at a temperature of 220 ° C. and a pressure of 0.9 hPa for 10 hours to obtain PET having a number average molecular weight of 21,000. [Production of film] 30 parts by weight of PEIT and PET70
The composition consisting of parts by weight, using a melt extruder,
It was melt-extruded from a T-die at a temperature of 285 ° C., quenched and solidified to produce a film having an average thickness of 100 μm. [Preparation of bottle] Using the same composition as the film, the temperature of each part of the cylinder and the nozzle was 280 ° C, and the screw rotation speed was 10
Injection molding machine (ASB-50HT, manufactured by Nissei ASB Inc.) set to 0 rpm, injection time 8 seconds, cooling time 10 seconds, and mold temperature 20 ° C.
The preform was molded with a mold. Next, this preform is stretch-blow molded at a blowing pressure of 2 MPa in an atmosphere of 110 ° C. to form a bottle having an average body pressure of 250 μm and an inner volume of 1 L. Subsequently, the bottle is compression-tensified in a mold set at 160 ° C. Heat set for 10 seconds to make a bottle.

Example 2 40.2 kg of a PEIT oligomer having a number average molecular weight of 1500 obtained by an esterification reaction of isophthalic acid, terephthalic acid and ethylene glycol (prepared molar ratio: 90/10/100)
Was charged into an esterification reactor, and a 3% by weight solution of triethyl phosphate in ethylene glycol was added in an amount of 10 × 10 ⁻⁴ mol of phosphoric acid to 1 mol of the acid component.
The sterilization reaction was performed at 00 ° C. for 3 hours. The obtained esterification reaction product was charged into a polycondensation reactor, and 4 × 10 ⁻⁴ mol of antimony trioxide and 3 mol of cobalt acetate were added to 1 mol of the acid component.
× 10 ^-4 mol, gradually reduce the pressure, finally pressure 3 hP
a) A polycondensation reaction was performed at a temperature of 275 ° C. for 4 hours. The obtained PEIT had a copolymerization ratio of isophthalic acid (IPA) of 89.9.
Mole%, number average molecular weight was 13,500. The sublimate amount of the cyclic oligomer was measured to be 790 g. Using the above PEIT and the PET of Example 1, films and bottles were produced in the same manner as in Example 1, and the characteristics thereof were evaluated.

Examples 3 to 8 and Comparative Examples 1 to 6
Was performed in the same manner as described above. However, in Example 6 and Comparative Example 3, phosphoric acid was used instead of triethyl phosphate.

The production conditions, the characteristic values of PEIT, the amount of cyclic oligomer sublimate in Examples 1 to 8 and Comparative Examples 1 to 6,
Table 1 summarizes the oxygen permeation amount of the film and the evaluation results of the bottle.

[0033]

[Table 1]

The PEITs obtained in Examples 1 to 8 all showed good characteristics, but the comparative examples had the following problems.

In Comparative Example 1, since the polycondensation degree of vacuum (Y) was larger than the upper limit of the equation, a PEIT having a number average molecular weight of 10,000 or more was not obtained, and the strength (impact resistance) of the bottle was not sufficient. In Comparative Examples 2 to 4, since the degree of polycondensation pressure reduction (Y) was smaller than the lower limit of the formula, a large amount of cyclic oligomer sublimate was generated. In Comparative Example 5, since the polycondensation temperature was lower than the lower limit of the formula, PE having a number average molecular weight of 10,000 or more was used.
IT could not be obtained, and the strength (impact resistance) of the bottle was not sufficient. In Comparative Example 6, since the polycondensation temperature was higher than the upper limit of the formula, not only a large amount of cyclic oligomer sublimate was generated, but also a PEIT having a number average molecular weight of 10,000 or more was not obtained, and the strength (impact resistance) of the bottle was low. Was not enough.

[0036]

According to the present invention, a high molecular weight PEIT which is suitable for use as a gas barrier container, has a high molecular weight, is excellent in heat resistance, impact resistance, color tone, transparency, etc. and has a small amount of cyclic oligomers generated. Can be manufactured.

Claims (2)

[Claims] 1. A polyethylene terephthalate oligomer having a number average molecular weight of 2,000 or less, isophthalic acid and ethylene glycol in an amount such that a molar ratio of an isophthalic acid component to a terephthalic acid component is 95/5 to 15/85, and phosphoric acid. Or its ester is used in an amount of 1 × 10 ⁻⁴ to 200 × 10 ⁻⁴ per mole of the acid component
The esterification reaction was performed for 0.5 hours or more, and then a polycondensation catalyst was added.The polycondensation temperature and the polycondensation pressure reduction degree satisfied the following formula and the number average molecular weight was 10,000 or more. A method for producing a copolymerized polyester, wherein a polycondensation reaction is carried out until the following conditions are satisfied. 270 ° C. ≦ X ≦ 290 ° C. 0.0266X−6.916 ≦ Y ≦ 0.0225X ² −11.993X + 1605.1 where X is the polycondensation temperature (° C.), and Y is the polycondensation depressurization degree (hP
represents a). (2) a number average molecular weight of 2,000 or less, and a molar ratio of an isophthalic acid component to a terephthalic acid component is 95/5 to 15/85.
Phosphoric acid or an ester thereof is added to the poly (ethylene isophthalate / ethylene terephthalate) copolymer oligomer in an amount of 1 × 10 ^-4 to 200 × 10 ^-4 mol per 1 mol of the acid component, and the ^mixture is added for 0.5 hour. After performing the above esterification reaction, a polycondensation catalyst is added, and the polycondensation temperature and the degree of polycondensation pressure reduction satisfy the above formula and the number average molecular weight is 10
A method for producing a copolymerized polyester, comprising performing a polycondensation reaction until the molecular weight reaches 000 or more.