DE2338824A1 - IMPROVED PROCESS FOR MANUFACTURING POLYESTERS - Google Patents

Description

24 292 n / wa

Toyo Boseki Kabushiki Kaisha, Osaka-shi Osaka-fu / Japan

Improved Process for Making Polyesters

The invention relates to the manufacture of polyesters. The invention particularly relates to a Improvement in the production of polyesters by direct esterification of a dicarboxylic acid component with

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a glycol component and polycondensation of the resulting Product.

Various processes have already become known for the production of polyethylene terephthalate. At a The process involves transesterification or ester exchange of dialkyl terephthalate (e.g. dimethyl terephthalate) and Ethylene glycol (hereinafter referred to as the "ester interchange process" designated). Another method involves direct esterification of terephthalic acid and ethylene glycol (hereinafter referred to as the "direct esterification process").

Since terephthalic acid is currently of high purity, it suffers from low Cost is available, it appears that the direct esterification process has a greater application than that Ester interchange process found in the industry. The advantages of the availability of the cheaper ones also contribute to this Raw materials and operational simplification. In particular, the direct esterification process is suitable for the production of such polyesters, which are required as industrial materials with a high level of demand Heat stability can be used, since here a metal salt catalyst for carrying out the ester exchange process, which has an unfavorable lowering of heat stability and poor processability of the produced Polyester can effect is not required.

However, compared to the ester interchange method, the direct esterification method has some disadvantages. For example, the direct esterification process is usually carried out at a higher temperature under a higher one Pressure for a longer period of time than the ester expression

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Exchange process carried out so that diethylene glycol and colored materials necessarily as by-products appear. The produced, contaminated with such by-products Polyester has a relatively low melting point and is used in the manufacture of fibers, films and not sufficiently suitable for other processed materials. Thus the direct esterification process is the ester interchange process somewhat inferior in terms of productivity and product quality.

The invention has therefore set itself the task of providing an improved process for the production of polyesters by direct esterification of a dicarboxylic acid component and a glycol component and through polycondensation of the resulting product. Another job The invention resides in the provision of a process for the production of polyesters which have high heat stability and have a high melting point. The invention is further directed to providing a method for Production of polyesters directed in a short operating time. These and other tasks result from the following description.

According to the invention, the production of polyesters carried out by having a dicarboxylic acid component and a glycol component of direct esterification to a partial degree of esterification and then the resulting product of a polycondensation, if appropriate after eliminating the unreacted glycol from the esterification product at a temperature lower than that required for esterification

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a reduced pressure below atmospheric pressure,

subject.

The term "dicarboxylic acid component" is intended to mean terephthalic acid or a mixture thereof with one or more polyfunctional carboxylic acids, in which the content of Terephthalic acid is not less than 50 mol. #. Examples for polyfunctional carboxylic acids are isophthalic acid, 1,5-naphthalene dicarboxylic acid, sodium sulfoisophthalic acid, p-hydroxybenzoic acid, adipic acid, glutaric acid, suberic acid, azelaic acid, sebacic acid, 1,10-decanedicarboxylic acid, Succinic acid, trimethylic acid, pyromellitic acid etc.

The term "glycol component" refers to any alkanediol or its mixture with one or more polyfunctional alcohols. Examples of the alkanediol are ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,6-hexamethylene diol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, etc. Examples of polyfunctional alcohols are p- (ß-hydroxy-ethoxy) phenol, diethylene glycol, triethylene glycol, tetramethylene glycol, trimethylolpropane _T pentaerythritol, etc.

The esterification is usually carried out at a temperature of about 220 to 280 C under above atmospheric pressure lying pressure, preferably a pressure which is higher than the vapor pressure of the glycol component at the temperature, carried out.

The amount of the glycol component can be from 1.1 to 10 moles, preferably from 1.3 to 3.0 moles, versus 1 mole of the dicarboxylic acid component be.

409831/0952

In order to suppress the formation of by-products of diethylene glycol, any additive can be added to the reaction system be introduced. Examples of a suitable additive are an alkali metal or alkaline earth metal salt (e.g. sodium acetate, potassium acetate, potassium terephthalate, magnesium acetate, calcium acetate), an alkylamine (e.g. diethylamine, Triethylamine, diisopropylamine, tri-n-propylamine, tri-n-butylamine), a phosphine (e.g. triethy! Phosphine, Triphenylphosphine) a tetraalkylammonium salt (e.g. tetraethylammonium hydroxide, tetraalkylammonium terephthalate,) a phosphonium salt (e.g. tetraethylphosphonium hydroxide, Methyl triphenylphosphonium hydroxide), an N, N-dialkyl amide (e.g. dimethylformamide, di-ethylformamide, dimethylacetamide, Diethylacetamide), etc. These additives can be used in a Amount from 0.001 to 5 mol. #, Preferably from 0.01 to 1 mol. $, Based on the amount of the dicarboxylic acid component, can be applied.

The esterification can be carried out up to 70-95 #, in particular 75-90 #, of the acid groups of the acid being esterified. If the degree of esterification is less than $ 70, the esterification reaction time is shortened and the time for carrying out the polycondensation is considerably increased. In addition, the polyester produced has a larger acid value such that it is not necessarily suitable for the production of fibers, films and the like. If the degree of esterification is more than 95 % , not only the esterification but also the polycondensation may require longer reaction times. Furthermore, the polyester produced can contain a relatively large amount of diethylene glycol.

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The reaction product of the esterification is then subjected to a polycondensation under a pressure lying below atmospheric pressure, at which the ester exchange between the 2-Hydrox3 ^r -ethyl ester groups with elimination of ethylene glycol as the main reaction and the reaction between a 2-hydroxy-ethyl ester group and a carboxylic acid group under E] imination of water partially takes place.

Before and / or during this polycondensation, the pressure of the reaction system increases gradually or continuously and then the reaction system is kept under a reduced pressure.

For example, the pressure of the reaction system at an un » The temperature used for the esterification is n ± n temperature e.g. from 150 to 220 C, to eliminate the unreacted Ethylene glycol and the diethylene glycol formed as a by-product, which contaminates the reactant product, decreased. The rate of reduction of the pressure can be controlled such that the distillation of the esterification product, in particular of bis-2-hydroxyethyl terephthalate is prevented and the final pressure is brought to about 1 mmHg or less. When the .reduction is effected at a temperature above the reaction temperature used for the esterification, can the diethylene glycol present here with the dicarboxylic acid component are reacted to remain in the final product polyester.

409831/0952

After the elimination of the unreacted ethylene glycol or upon substantial completion of the by-product formation of diethylene glycol, the temperature is reduced below Pressure increased. Alternatively, the vacuum can be achieved once by purging with an inert gas Production of atmospheric pressure must be turned off, after which the temperature is gradually decreasing the pressure is increased. During these processes or working methods, polycondensation takes place at an early stage Stage (early stage polycondensation).

The polycondensation in late stage (late stage polycondensation) is then at a higher temperature (for example, the final temperature is 2 ² K) to j5OO ° C) under a more reduced pressure, thereby producing a polyester having a high degree of polymerization and a high melting point .

The polyester is of good quality in that it has a low diethylene glycol content. In addition, the reaction time of the polycondensation is considerably reduced, since the esterification is stopped at a degree of esterification of 70 to 95% and the free form of the glycol component is eliminated beforehand.

Any polycondensation catalyst can be introduced into the reaction system prior to initiation of the polycondensation will. Examples of such catalysts are antimony trioxide, Antimony triacetate, TelQurdioxid, germanium dioxide, tetrabutyl titanate, ammonium titanyl oxalate, sodium titanyl oxalate, Potassium titanyl oxalate, calcium titanyl oxalate, tungsten

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acid, sodium tungstate, etc. The amount of the catalyst can be from 0.0001 to 0.1 Mol.Ji, preferably from 0.0005 to 0.05 mol. $, against the amount of the dicarboxylic acid component be. These catalysts can be added to the reaction system either after or before the esterification.

The reactions according to the invention can be either batchwise or be effected continuously.

Any conventional additives such as a pigment (e.g. titanium oxide, ultramarine, cobalt blue, carbon black) can also be used Stabilizer (e.g. a phosphorus-containing compound, an alkylphenol, an amine) or a modifier in the reaction system can be introduced at any stage of esterification and polycondensation.

The following examples, in which parts are by weight, set forth practical and presently preferred embodiments of the invention. The intrinsic viscosity (intrinsic viscosity) / \ _ 7 is in a solution in a mixture of phenol and tetrachloroethane: determined (4: 6 in weight) at 30 ⁰ G. The dietary glycol content is determined by subjecting the polymer (0.5 g) to methanolysis with methanol (10 ml) at 250 ° C. for 6 hours and analyzing the resulting product by gas chromatography, and is given in mol. # In the glycol unit. The melting point is given by the temperature at which the polarized light of the stretched polymer thread disappears when heated on a hot plate. The degree of esterification (ES %) gives those of

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Terephthalic acid, which according to the following equation is calculated:

SV - AV
ES =

SV

herein, AV means an acid value and SV means a saponification value of the esterification reaction product, both of which are measured by conventional methods. The b-value of the Hunter scale is determined with the polymer as a pellet and indicates the extent of the yellow color. The acid value of the polymer represents the concentration of the terminal carboxyl group in the polymer which permeates! Equivalent / 10 is reproduced.

example 1

In an autoclave equipped with a stirrer, a distillation column and a pressure regulator Terephthalic acid (166 parts), ethylene glycol (155 parts)

and triethylamine (o.l Mol. $) entered, and the esterification

o P

tion is at 240 C under 4 kg / cm G for 75 minutes

carried out, during which the water generated as a by-product and corresponding to an 87/6 esterification is distilled off. The reaction product is converted to polycondensation in a reactor and the unreacted Sthylenglykol is distilled off at 205 ⁰ C, while

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printing at a rate of 20 mmHg / min. for 20 minutes and then at a rate of 40 mmHg / min. is decreased. Thereafter, the reaction mixture is kept under a pressure of 1 mmHg or less for 15 minutes, whereby the distillation of the ethylene glycol is terminated. To produce atmospheric pressure, nitrogen gas is introduced into the reactor and antimony trioxide (0.03 mol. ^) Is added. The temperature is raised to 265 ⁰ C and the pressure to 5 mmHg in 20 minutes decreases and causes the polycondensation in the early stage under these conditions for 30 minutes, then carried out the polycondensation in the late stage at 275 ° C under 0.1 mmHg for 55 minutes .

The polyester produced in this way has a good color. The basic viscosity / I ₁ J is 0.631. The diethylene glycol content is 1.23 mol, #. Melting point 267.2 ⁰ C.

Control example 1

Esterification, early stage polycondensation and polycondensation in the late stage are carried out in the manner described in Example 1, except that the procedure the elimination of the unreacted ethylene glycol in one temperature below the esterification temperature is omitted. The late stage polycondensation requires 80 minutes.

The polyester produced in this way has a basic viscosity

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233882A

from / j \ J = O.627 to. The diethylene glycol content is 2.37 mol. #. Melting point 263.8 ⁰ C.

Since the melting point is relatively low, this polyester proves itself for the production of industrial fiber materials, e.g. tire cord, as unsuitable.

Examples 2 to 10 and Control Examples 2 to 5

As in Example 1 or Control Example 1, the esterification, the elimination of the unreacted glycol component and carrying out the polycondensation under various conditions to produce a polyester. the Results are summarized in Table 1.

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Tabel

O CD OO U)

example
No. Tereph
thalsäu
re (parts) Ethylene
glycol
(Parts) additive
(Mol .56) Esterification Tempe
temperature ( ⁰ C) Time
(min) Vereste
degree of efficiency
d) Elimination of the inevitable
set ethylene glycol
kols Time
(min) .
I. 2 166 93 sodium
acetate
(0.05) Pressure ₀
(kg / cnTG) 240 190 89.2 temperature 30th 3 166 124 Tr i -Xi-
butylamine
(0.3) 3.5 240 95 87.3 205 45 po 4th 166 150 Triethyl
amine
(0.2) 4th 240 80 89.3 195 40 LO
X)
X)
Ό 5 166 200 Dimethyl
formamide
(0.3) 4th 230 75 86.2 200 45 6th 166 190 Tetraethyl
ammonium
hydroxide
(0.05) 2.5 235 55 89.8 210 50! - 3.5 200

example
No. Polycondensation
sationska-
catalyst
(Mol .Ji) Polycondensation
sation time
the early
Level (min) Polycondensation
sation time
the late
Level (min) total
reaction
Time
(min) Produced polymer _; Diethylene glycol
content (Mol .Ji) Enamel
point ( ⁰ C) 2 Antimony-
trioxide
(0.03) 50 75 3 ^ 5 Basic viscosity
sity l \ 7 1.53 266.3 3 Germanium
dioxide
(0.02) 50 67 257 0.621 I.31 267.I
I. 40983 antimony
trioxide
(0.03) 50 85 235 0.627 1.27 267.2 I. 1 / 0-952 5 Tetra-n-
butyl
titanate
(0.005) 50 75 245 0.632 1.13 267.5 i
i 6th Antimony-
trioxide
(0.02) 50 95 0.625 250 0.617 '. 1.37
I.
! 266.8

CO GO CDO OO

Port setting table

O CO QO GO

example
No. Tereph
thalsäu
re (parts) Ethylene
glycol
(Parts) additive
(Mol. Fo) Esterification Tempe ~
temperature (° C) Time
(min) Remodeling
rungsfrad Elimination of the inevitable
set ethylene glycol
kols Time
(min) 23388 ■ 7 166 124 Dimethyl
formamide
(0.05) Print _{or similar}
(kg / cm ^ G) 230 115 86.3 temperature 41 ro 8th 166 124 Triethyl
amine
(O.30) 2.5 24o 86 8I.3 205 35 9 166 124 Dimethyl
formamide
(0.30 4th 230 95 77.5 205 30th 10 166 150 Triethyl
amine
(0.50) 3 235 79 82.3 205 35 control
2 166 93 sodium
acetate
(0.05) 4th 240 190 88.7 205 3.5 -

example
No. Polycondensation
sationska-
catalyst
(Mol %) Polycondensation
sation time
the early
Level (min) Polycondensation
sation time
the late
Level (min) Total-
responsive ■
Time
(min) Produced polymer Basic viscosity
sity / tw Diethylene glycol
content (Mol. 58) Enamel
point ( ⁰ C P-
O
CD
rift 7th Antimony-
trioxide
(0.025) 50 80 286 0.623 1.31 267.O 131/0952 8th Antimony-
trioxide
(0.025) 50 72 243 0.624 I.I8 267.2 ORJGlNAL INSPECTED 9 Antimony-
trioxide
(0.030) 50 77 252 0.632 1.12 267.6 10 Antimony-
trioxide
(0.030) 50 75 239 O.623 1.08 267.9 [ontroll
2 Antimony-
trioxide
(0.030) 50 85 325 O.618 2.25 264.5 ^
CO
OO
OO
tU—

Port setting table

CD CD CO

I.
'■. example
No. Tereph
thalsa
re (parts) Ethylene
glycol
(Parts) additive
faol.jS) Esterification Tempe
temperature ( ⁰ C) Time
(min) Vereste
degree of efficiency
H) Elimination d
ten ethylene glycol it must be implemented
lrr \ ~ \ «3 control
3 166 200 Triethyl
amine
(0.2) Pressure ο
(kg / crrTG) 240 50 86.8 ^Temp ! ^s cT control
4th 166 124 Triethyl
amine
(0.50) - 4th 240 115 96.7 - Time
(min) control
5 166 124 Triethyl
amine
(0.30) - 4th 240 103 91.3 205 - - 4th - 30th -

Ca> Cv »OO OO

example
No.

Polycondensation catalyst (Mol. 56)

Polycondensation time of the early stage (min)

Polycondensation time
the late
Level (min)

Total reaction time (min)

Produced polymer

Basic viscosity / * η7

Diethylene glycol content (mol.%)

Melting point ( ⁰ C)

O CO OO CJ

control
3

Antimony trioxide (O.030)

control
4th

Antimony-

trioxide

(0.025)

50

90

190

50

107

302

0.612

0.611

2.53

2.16

263.5

2 61 ;. 7th

control
5

Antimony-

trioxide

(0.025)

50

113

266

0.624

2.93

26 ^ .2

SK

CO
CO

CO
OD

! 5

Example 11

Terephthalic acid (1000 parts), ethylene glycol (7 ^ 5 parts), potassium acetate (0.211 parts) and antimony trioxide (0.262 parts) are introduced into an autoclave equipped with a stirrer, a distillation column and a pressure regulator, and nitrogen gas is introduced to set a pressure of 3 kg / cm G introduced. While this pressure is maintained, the temperature is increased to 235 ° C., as a result of which esterification takes place. After a 80 $> - appropriate weight esterification water is distilled off in 103 minutes, the Autoklac is brought to atmospheric pressure. The reaction product is transferred to a reactor to carry out the polycondensation and the pressure is increased at a rate of 25 mmHg / min. at 265 C for 30 minutes, and after reaching a pressure of 10 mmHg. , at a rate of 1 mmHg / min while increasing the temperature up to 280 ° C for 10 minutes to set a final pressure of 0.1 mmHg. The stirring is carried out under these final conditions until the stirring torque shows a basic viscosity of / \ 7 = 0.62. The time required to complete the polycondensation after reaching the final temperature of 280 ° C. and the final pressure of 0.1 mmHg is 87 minutes. The total time from the start of the esterification to the end of the polycondensation is 230 minutes.

The quality of the polyester produced in this way is as follows:

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409831 / 09B2

Intrinsic viscosity C ¹ TfJ = 0.627; Acid value 14 equivalent / 10 g; Diethylene glycol content 1.89 Mol.Ji; b-value of the Hunter scale 3.2.

Example 12

As in example 1 will be

Terephthalic acid (1000 parts), ethylene glycol (745 parts) and triethylamine (0.150 parts) subjected to esterification. After the water corresponding to a 77% esterification has been distilled off in 95 minutes, the autoclave is brought to atmospheric pressure. The polycondensation is then carried out in the manner described in Example 11. Up to display an intrinsic viscosity of a / *) 7 = O.62 corresponding Rührungsdrehmomentes after reaching a temperature of 280 ⁰ C and a pressure of 0.1 mmHg required time is 85 minutes. The total time from the beginning of the esterification to the end of the polycondensation is 220 minutes.

The quality of the polyester produced in this way is as follows: basic viscosity l \ Z = O.63I; Acid value I3 equivalents / 10 g; Diethylene glycol content I.79 Mol.Ji; Hunter scale b value 2.7.

Control example 6

Terephthalic acid (1000 parts), ethylene glycol (745 parts) and calcium acetate (0.211 parts) are used in the example

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409831/0952

233R824

11 described manner subjected to an esterification. After the water corresponding to a 95% esterification has been distilled off in 145 minutes, the autoclave is brought to atmospheric pressure. The polycondensation is then carried out as in Example 11. The to display a Rührungsdrehmomentes which corresponds to an intrinsic viscosity of // <\ 7 = 0.62, time required to reach a temperature of 280 ⁰ C and a pressure of 0.1 mm Hg is 127 minutes. The total time from the start of the esterification to the end of the polycondensation is 312 minutes.

The quality of the polyester produced in this way is as follows: basic viscosity / \ J = O.618; Acid value 8 equivalents / 10 g, diethylene glycol content 2.37 mol. Ji; Hunter scale b value 4.1.

Control example 7

Terephthalic acid (1000 parts), ethylene glycol (745 parts) and triethylamine (0.150 parts) are esterified as in Example 11. After the water corresponding to 81% esterification has been distilled off in 105 minutes, the pressure is reduced further to 1 kg / cm G. After the water corresponding to a degree of esterification of $ 97 has been removed over the course of 20 minutes, the autoclave is brought to atmospheric pressure. The polycondensation is then carried out as in Example 11. The time required for a stirring torque corresponding to a basic viscosity of £ \ 7 = O.62 after reaching a temperature of 280 ° C. and a pressure of 0.1 mm of mercury is 118 minutes. The total time from

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409831/0952

The beginning of the esterification until the end of the polycondensation is 283 minutes.

The quality of the polyester produced in this way is as follows: basic viscosity £ i \ J = 0.627; Acid value 6 equivalents / 10 ⁶ g; Diethylene glycol content 2.38 Mol.Ji; b-value of the Hunter scale 3.8.

Examples Ij5-18 and Control Examples 8-11

The esterification and polycondensation to produce a polyester is as described in Example 11, however carried out using approximately different reaction conditions. The results are in Table 2 summarized.

409831/0952

Table 2

CD CD OO CO

CD CO cn

example
No. Terephthal
acid (parts) ι
Ethylene additive
glycol ^! (Wlol.fi)
(Parts) Esterification esterification
time (min) \ degree (%)
1
i 80.3 Polycondensation ca-
catalyst (MoI. #) / 1000 558 I triethyl
amine
j (Ο.6Ο6) 136! 75.0
I.
j 87.0 Antimony trioxide
(Ο.262) 14th 1000 558 triethyl
amine
(Ο.6Ο6) 162 84.6 Antimony trioxide
(Ο.262) 15th 1000 558 , dimethyl , 9Ι
formamide ■
(Ο.439)
¹ I. Kaliumt it any1-oxalate
(0.043) 16 1000 632; Triethyl 130
amine
(0.303) Antimony trioxide
(O.262) 17 1000 745 dimethyl 78 77.5 ί potassium titanyl oxalate
formamide i (0.043)
(Ο.439)

(O CO 00 K)

σ co cn

example
No. Polycondensation
tion time in
later
Stadiura (min) Total-
reaction
time (min) Produced polymer Basic viscosity
sity / JrJ Acid value
Xq / 10g Diethylene glycol
content (Mol.Si) b value of
Hunter scale 13th 47 223 0.631 13th 2.15 2.8 14th 51 253 0.627 11 1.93 3.1 15th 59 290 Ο.623 8th I.83 4.1 16 50 220 0.618 12th 2.52 2.7 17th 49 167 0.625 10 I.76 4.3

GO CO CO

Table 2 continued

example
No. Terephthal
acid (parts) Ethylene glycol
kol (parts) additive
(Mol. #) ■ esterification
time (min.) Esterification
degree (? o) Polycondensation T.
catalyst (mol. $) O
CD
OO
CO 18th 1000 745 Dimethyl
formamide
(O.439) 87 83.2 Antimony trioxide
(O.262) O
CD
cn
ΝΪ control
8th 1000 6 ^ 2 Triethyl
amine
(0.606) 90 64.7 Antimony trioxide
(O.262) control
9 1000 632 Triethyl
amine
(O.6O6) 172 94.I Antimony trioxide
(O.262) control
10 100 745 Dimethyl
formamide
(O.439) 63 65.7 Potassium titanyl oxalate
(0.043) control
11 1000 745 Dimethyl
formamide
(O.439) 160 96.8 Antimony trioxide
(O.262)

example
No. Polycondensation
tion time in
later
Stage (min) total
reaction
time (min) Produced polymer Basic viscosity
sity l \ 7 Acid value
Eq / 10g Diethylene glycol
content (mol. %) b value of
Hunter scale 18th 53 180 0.619 11 1.95 3.4 control
8th 128 258 0.627 67 I.78 4.8 control
9 72 284 0.605 9 2.86 4.3 control
10 117 220 0.619 58 I.87 6.2 control
11 81 28I 0.626 11 3.15 5.1 I.

- 2β -

Example 19

In the autoclave of Example 11 are terephthalic acid (1000 parts) and 1,4-but-andiol (811 parts) to esterification in the presence of K ₀ TiO (C _o 0 ,,) ". 2H _o 0 (0.425 parts) at 230 ° C

p d. egg. ^{1 part} C.

subjected to below 2 kg / cm G for 73 minutes. After the autoclave has been switched off, it is determined by analyzing the reaction product that an esterification of 76.1% has occurred. The reaction product is immediately subjected to polycondensation at 255 ° C, while the pressure at a rate of 25 mmHg / min. is decreased. After the pressure reaches 10mm / Hg in 30 minutes, the rate of decrease is reduced to 1 mmHg / min so that a pressure of mmHg is reached in 10 minutes. The polycondensation is then carried out while the pressure and temperature are kept constant until a stirring torque is obtained which corresponds to a basic viscosity of pr \ J = 0.83. The total time from the start of the esterification to the end of the polycondensation is 178 minutes.

The quality of the polyester produced in this way is as follows:

Intrinsic viscosity / I] J = 0.827; Acid value 11 equivalents / 10 g; Melting point 224 ° C; b-value of the Hunter scale 1.8.

Examples 20 and 21 and Control Example 12

Terephthalic acid, ethylene glycol, dimethylformamide or triethylamine and antimony trioxide are placed in a slurry making tank to form a uniform slurry

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entered. The slurry is introduced into a series of three autoclaves connected in series, each autoclave being equipped with a distillation column and a stirrer and esterification at a temperature of 232 to 241 ^° C. under a pressure of 3.0 to 4.5 kg / cm G subject. The reaction product is flushed from the last autoclave into a flush can at almost the same temperature that is used for esterification under atmospheric pressure to remove the unreacted ethylene glycol. The reaction product is removed from the outlet of the built-in can and the degree of esterification is measured. The reaction product is placed in a reactor in which an early stage polycondensation is carried out at 265 ° C. under 5 mm Hg. The reaction mixture is then introduced into a further reactor in which the polycondensation of the late stage is carried out at 272 to 275 ° C. under 0.1 mm Hg to produce polyethylene terephthalate. The residence times in the esterification reactors are set in such a way that they are almost the same for the spray stage polycondensation and for the late stage polycondensation. The results are summarized in Table 3.

Λ09831 / 0952

Table 3

example
No. Tereph
thalsäu
re (kg / h) Ethylene
glycol
(kg / h) additive
(g / h) Polycon
densations
catalyst
(g / h) Esterification Tempe
temperature ( ⁰ C) ■ Vereste
degree of efficiency
{%) Polycondensation
the early stage tempera
tur ( ⁰ C) 20th 20.0 14.9 Triethyl
amine
(12.12) Antimony-
trioxide
(3-48) Pressure "
(kg / crn G) 232 81.3 pressure
(mmHg) 265 21 20.0 11.2 Dimethyl
formamide
(8.78) Antimony-
trioxide
(5.24) 3.0 241 78.2 5 control
12th 20.0 14.9 Triethyl
amine
(12.12) Antimony-
trioxide
(3.48) 4.5 240 96.5 5 265 4.5 5

A09831 / 0952

GO OO CO OO

example
No. Polycondensation
the late stage tempera
tur ( ⁰ C) Produced polymer yield
(kg / h) Basic vis
kosity
ί \ 7 Acid value
(Eq / 10 ⁵ g) Diethylene glycol
content (mol. %) b value of
Hunter scale 20th pressure
(mtriHg) 275 23.0 0.637 2.03 2.6 21 0.1 272 23.1 0.652 16 i
2.31 I 2.8 409831 control
12th 0.1 0.1 275 22.8 0.562 9 3-lS '■■ 3.9 / 0952

CO CO CO OO K)

Claims (6)

Claims t-3r. Process for the production of polyesters by direct esterification of a bicarboxylic acid component which contains at least 50 UoI.fo terephthalic acid and a glycol component, and subsequent polycondensation of the resulting product, characterized in that the direct esterification of the dicarboxylic acid component with the glycol component is partially carried out at a Carries out pressure exceeding atmospheric pressure and then effected the polycondensation of the resulting product at an elevated temperature at a reduced pressure below atmospheric pressure to obtain a polyester having a high melting point and excellent heat stability. 2. The method according to claim 1, characterized in that the unreacted glycol before the polycondensation essentially of the esterification product at a temperature below that required for direct esterification is, be: a below atmospheric pressure removed reduced pressure. 3. The method according to claim 1, characterized in that the direct esterification at a temperature between 220 to 28O C carried out. - 51 - 409831/0952 4. The method according to any one of the preceding claims, characterized in that the direct esterification is carried out up to a degree of esterification of 70 to 95 % . 5. The method according to any one of the preceding claims, characterized in that the unreacted glycol at a temperature between 150 to 22O ⁰ C removed. 6. The method according to any one of the preceding claims, characterized in that one used as the dicarboxylic acid component terephthalic acid and as the glycol component A '^ ethylene glycol. 409831/0952