DE2120092A1 - Process for the production of fiber-forming polytetramethylene terephthalate - Google Patents

Description

PAT Ξ N TANW JUT F

DR.-ING. BY KFiEiSLER DR.-ING. SCHÖNWALD DK.-ING. TH. MGYER DR. FUES DiPL-CHEM. ALEK VON KREISLER DIPL-Cri £ M. CAROLA KELLER DR.-ING. KLOPSCH Dipl.-Ing.Selting

KOLNI ₇ DEICHMANNHAUs 2

Cologne, April 22nd, 1971

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Charlotts, V ^ -rth Carolina (USA ) .

Process for the production of fiber-forming polytetramethylene terephthalate

The invention relates to an improved process for the production of fiber-forming polytetramethylene terephthalate.

Polytetramethylene terephthalate is a very useful one Starting material for the production of molded parts, foils, clothing, bridges, carpets, etc. Fiber-forming Polytetramethylene terephthalate is particularly advantageous as a starting material for the manufacture of carpets ,, Die Carpets made with it have excellent properties.

Processes for the production of polytetramethylene terephthalate are known. For example, it is known that 1,4-butanediol and dimethyl terephthalate are converted to Bi3 - (<£ ^ ydroxybutyl) terephthalate "monomers" at elevated temperatures can and the "monomer" then at even higher Temperatures and can be heated under reduced pressure to form polytetramethylene terephthalate. This Process is known as the "ester exchange process". It leads to suitable polymers, but has the disadvantage that the terephthalic acid is first converted into dimethyl terephthalate.

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must be converted before the above-mentioned "monomer" can be produced via this ester.

The invention relates to the production of fiber-forming Polytetramethylene terephthalate by a process in which the '.Terephthalic acid is not converted into another chemical Compound must be converted before using 1,4-butanediol is implemented »Oas method according to the invention for Manufacture of fiber-forming polytetramethylene terephthalate is characterized in that one

a) a mixture of terephthalic acid and 1,4-butanediol in a molar ratio of 1,4-butanediol to terephthalic acid of at least 3.4: 1.0 for about 2 to 8 hours at a temperature of about 200 to 300 ^° C. below one Overpressure of at least 2 atmospheres and heated to at least the partial vapor pressure of 1,4-butanediol at the reaction temperature,

b) the reaction mixture is then subjected to a polycondensation temperature from about 200 to 275 0 while holding it under a vacuum of about 0.05 to 15 mm Hg and.

c) the reaction mixture at a temperature of about 200 to 275 ° C and under a vacuum of about 0.05 to 15 mm Hg holds up a polymer with a relative viscosity of was formed around 13 to 75 »

The closest prior art known to the applicant is USAo Patent 3,050,533, which relates to the esterification of terephthalic acid with 1,4-butanediol by a process in which one essentially consists of terephthalic acid and 1 to 3 molar fractions of the glycols existing mixture heated to a temperature between the normal boiling point of the glycol and 300 ⁰ C under an overpressure which corresponds at least approximately to the partial vapor pressure of the glycol, but is not higher than the sum of the partial vapor pressures of the glycol and that formed during the reaction V / assers. (Claim 1).

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In this patent it is taught that in the case of the one described therein Process with a possible low molar ratio of moles to acid is to be used. Ea means:

In addition, the esterification according to the invention is carried out at the lowest possible diol / acid molar ratio. Using a diol / acid molar ratio of 1: 1 is the theoretical goal pursued, but in practice this can only be achieved if a complete separation of the water from all other reactants is achieved.This is not easily achievable, 30 that a diol / acid molar ratio in the range of 1.1i1.0 to 1.3: 1.0 is more appropriate , 5: .1, O appropriate to the easy formation of tetrahydrofuran . compensate. If the process according to the invention is carried out continuously or semi-continuously using any diol, it is sometimes expedient to work with higher diol / prop.re molar ratios of, for example, up to 3.0: 1.0. Generally speaking, the invention can be carried out at diol / acid molar ratios between 1.0: 1.0 and 3 »0: 1.0. (Column 3) <>"

Although the process of the above-mentioned patent is suitable for the production of an acceptable fiber-forming polyethylene terephthalate, however, it has been found that those proposed there for the production of polytetramethylene terephthalate ! conditions not for the formation of fan education Polytetramethylene terephthalate can be used. if is worked under these conditions, a polytetramethylene terephthalate formed that for manufacturing for example suitable for pollen, but not fiber-forming.

It has now been found that suitable fiber-forming polytetramethylene torephthalates obtained if the method described in the above-mentioned patent specification

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is modified so that at least 3.4 moles of 1,4-butanedioi are used per mole of terephthalic acid in the mixture and the direct esterification of 1,4-butanediol and terephthalic acid is carried out for at least 2 hours. For the purposes of the invention, fiber-forming polytetramethylene terephthalate has one relative viscosity of about 13 "to 75, although in the preferred embodiment it has a relative viscosity of about 18 to 45, while the relative viscosity of the particularly preferred polymer made in accordance with the invention is about 22 to 36." Relative viscosity "is a measure of the Degree of polymerisation of the polymer and represents the ratio of the viscosity of a perpetual solution (8 g of polymer in 100 ml of freshly distilled o-chlorobenzene at a temperature of 100 ⁰ O) to the viscosity of freshly distilled o-chlorophenol, measured in the same units at 25 ⁰ C , dar.

In the process according to the invention, the abovementioned reaction mixture must _{contain at least about 3-4 moles of 1 S} 4-butanediol per mole of the terephthalic acid present before the start of the esterification. 1.0 to 4.0: In the preferred embodiment, this molar ratio is about 3.5 _o 1.0

The process according to the invention comprises three stages: direct esterification, application of vacuum and polycondensation. These stages are described in detail below.

The direct esterification of terephthalic acid with 1,4-butanediol is carried out by heating a mixture which contains at least 3.4 mol of 1,4-butanediol per mole of terephthalic acid to a temperature of about 200 "to 300 ^° C. for 2 to 8 hours atü a Überdruok of at least 2 and at least the partial vapor pressure of 1,4-butanediol at the reaction temperature "While dieeer reaction, a part of the used 1,4-Butandiola lost (it is converted into by-produced tetrahydrofuran) · the for the

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Process according to the invention prescribed molar ratios of 1,4-butanediol to terephthalic acid thus apply for the concentrations of the diol and the acid before the point in time at which the direct esterification takes place »

During the direct esterification is preferably the mixture is heated to a temperature of 210 to 26O ⁰ C and kept at this temperature, wherein a reaction temperature is preferably from about 220 to 245 ⁰ C. The direct esterification is preferably carried out under a pressure of about 2 to 10 atmospheres. A pressure of about 3 to 5 atmospheres is particularly preferred. When operating at the preferred molar ratio, preferred temperature and preferred pressure, the direct esterification step according to the invention will require about 2 to 6 hours to carry out. A time of only about 2 to 4 hours may be required for the direct esterification reaction if the particularly preferred conditions are used in accordance with the invention.

After the direct esterification, the application of the vacuum is started. In a continuous process, the vacuum can be generated instantaneously, since the reaction mixture can be transferred to a vessel in which the required vacuum conditions exist. In the batch process, however, the vacuum must be applied over a certain period of time. In both methods, the reaction mixture after reaching atmospheric pressure to a temperature of about 200 is brought to 275 ⁰ C while a vacuum is applied from etv / a 0.05 to 15 mm Hg. Preferably, the reaction mixture is maintained at a vacuum of about 0.1 to 2 ram Hg and a temperature of about 240 to 260 ⁰ C. In the particularly preferred embodiment, the Reaktionagemisch to a temperature of about 250 is brought to 255 ⁰ C while a vacuum is applied of approximately 0.1 to 0.4 mm Hg "In the batch method, the above-mentioned vacuum should slowly over a period of about 10 to 120 minutes, preferably about 10 to 95 Mi min

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tea can be placed on the reaction mixture. Especially "before- • A time for the application of the vacuum of about 35 "to 60 minutes, in particular about 50 minutes, is given.

The application of the vacuum to the reaction mixture in the manner described above can take place in the same reaction vessel. in which the direct esterification was carried out. Preferably, however, the "monomer" (i.e. the reaction mixture) is transferred to a vessel designed for the high vacuum and the high temperatures usually required for polycondensation is suitable. This overpass usually occurs before the time when the ™ "monomer" is under the vacuum of about 0.05 to 15 mm Hg stands. Before this vacuum is reached, various additives, e.g. heat stabilizers, Dyes, matting agents and polycondensation catalysts, added to the "monomer".

When the reaction mixture is subjected to the desired vacuum, it can be held at about that vacuum and at about the temperature it was at when the vacuum was applied until a polymer of the desired relative viscosity has been formed. For example, a reaction mixture that was at a temperature of 250 ⁰ G while a vacuum of 0.3 mm Hg was applied for a time of 50 minutes, then under the vacuum of about 0.3 mm Hg and at a temperature of about 250 ⁰ C are maintained, has been formed until a polymer having the desired relative viscosity ₀ In general, the polycondensation reaction is interrupted when da3 reaction mixture has a relative viscosity of about 13 to 75 miles. The polycondensation reaction is preferably terminated when a polymer with a relative viscosity of about 18 to 45, in particular with a relative viscosity of about 22 to 36, has been formed ο

Some preferred embodiments according to the invention are described in the following examples-

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are all parts as parts by weight "

example 1

In one equipped with a thermocouple, stirrer motor and rectifying column. The stainless steel reactor was charged with 17 kg of 1,4-butanediol and 5-67 kg of terephthalic acid, thereby forming a reaction mixture in which the molar ratio of 1,4-butanediol to terephthalic acid was 5.5: 1.0 " reaction mixture, the distillate was contacted with nitrogen under a pressure of 5.5 atm and stirred while the temperature was raised within 2.5 hours of 210 ⁰ C (start of reaction) to 235 ° C. during this time were collected, and the mixture was stirred mixture was then depressurized to atmospheric pressure "After the addition of 10.0 g of a Polykond'ensationskatalysators to the reaction mixture, the temperature of the reaction at 25O ⁰ O was increased after reaching a temperature of 250 C daa reaction mixture over 60 minutes under a. absolute pressure of 0.2 mm Hg brought «the reaction mixture was then held for an additional 2.25 hours at this temperature of 25O ⁰ C and at the pressure of 0.2 ram Hg, whereby a polymer was formed, d as had a relative viscosity of 30, a melting point of 223 ⁰ C (determined by thermal differential analysis) and a concentration of terminal carboxyl groups of 22 equivalents per 10 g.

The expression "Consentration at terminal" used here Carboxyl group η "denotes both the non-ionized Acid group (-COOH) as well as the ionized group (-COO ^). The concentration of terminal carboxyl groups is determined by the method described by Maurice and Huizinga in "Analytica Chemica Acta", Volume 22, pages 363-368 (1960) and is expressed in equivalents per million grams.

109846/1836

Example 2

The experiment described in Example 1 was repeated with the difference that the esterification time was 5.75 hours, the molar ratio of 1,4-butanediol to terephthalic acid was 4.5: 1.0, 0.10 & ew .- ^ (based on the Weight of the polymer) zinc oxide were used as the polycondensation catalyst and the polycondensation time 2.25 hours and the polycondensation temperature 255 C was ₀ A polymer with a relative viscosity of 20, a melting point of 217 ° 0 and a concentration of terminal carboxyl groups of 89 equivalents per Million grams was received "

This example illustrates that long esterification times are not necessary.

Examples 3 and 4

The experiments were carried out in the manner described in Example 1, with the difference that the ¹ 1,4-butanediol / terephthalic acid molar ratio was 2.0: 1.0, the duration of the direct esterification was 3.2 hours and the polycondensation stone temperature was 250.degree . In the case of example 3, an esterification ^{temperature of 215 to 235 °} C., a concentration of the polycondensation catalyst of 0.10% by weight (based on the weight of the polymer), and a polycondensation time of 3.75 hours were used. In the case of Example 4, the esterification temperature was 220 to 245 ° C., the concentration of the polycondensation catalyst was 0.20% by weight and the polycondensation time was 2.6 hours. In both cases, no fiber-forming polytetramethylene terephthalate was formed as a result of the use of the low molar ratio of butanediol to terephthalic acid.

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Examples 5 and 6

According to the process described in Examples 6 and 7 of U.S. Patent 3,050,533, 42 parts (per million ropes of polymer) sodium hydroxide were added to the reaction mixture, in which the molar ratio of 1,4-butanediol to terephthalic acid 3, 5: 1.0 (example 5) and 5.5: 1.0 (example 6) was "the Veresterungsteraperaturen amounted to 240-260 ⁰ C, the Veresterungsdrücke 4.2 atm, the 'esterification 75 minutes and 135 minutes polycondensation time. In both cases, no fiber-forming polytetramethylene terephthalate was formed as a result of the short esterification time.

Example 7

Continuous polymerization was carried out according to the method according to the invention. A primary esterification reactor was fed terephthalic acid in an amount of 13.61 kg / hour and 1,4-butanediol in an amount of? .8.12 kg / hour. Thus, about 3.8 moles of 1,4-butanediol per mole of terephthalic acid were introduced into the primary esterification reactor. The primary esterification reactor was kept at a temperature of about 240 ^° C. and a pressure of 3.5 atmospheres. The mean residence time of the butanediol and the terephthalic acid which were fed to the primary esterification reactor was about 3 hours , 17 wt .- ^ e of a polycondensation catalyst had been introduced. The mean residence time of the reaction mixture in the secondary esterification reactor was 1.5 hours. The reaction mixture was then fed to a “low” polymerization reactor which was kept at a temperature of about 250 ^° C. and a vacuum of 25 mm Hg. The mean residence time in this reactor was 0.7 hours. The reaction mixture was then fed to a "high" polymerization reactor, the mm at a temperature of about 27O ⁰ C and a vacuum of about 3 Hg absolute

109846/1836 bad original

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was held. The middle residence tent in this reactor was 2.0 hours. The polymer was from the "Hoch" -Polymerisat.tonsreaktor deducted in an amount of 18.14 kg / hour »

The properties of the monomer and the polymer were continuously measured during the polymerization .the total concentration of terminal carboxyl groups (CEG) and the degree of esterification determine "the total concentration, at terminal carboxyl groups (CEG) excluded the terminal carboxyl groups from the unreacted Terephthalic acid. The degree of esterification (VG) of the Tereph ™ Thalic acid in a sample was determined according to the following formula:

VG = 100 100 ( total CEG of the sample?)

Total CEG of the starting mixture

The primary monomer had an average total CEG value of about 1800 and an average degree of esterification of about 67 $. The secondary monomer had an average total CEG value of about 750 and an average degree of esterification of about 85. That Low polymers showed an overall CEG averaging about 60 and an average degree of esterification of 9Sj- '. The high polymer exhibited an overall CEG value averaging et v / a '$ b * The average polymer formed had a relative viscosity of 20 and a melting point of 224 Co

For the preparation of high molecular weight polymers is a maximum esterification of the dicarboxylic acid used, d _o h ₀ of the terephthalic acid is desired. A continuous reduction in the concentration of terminal carboxyl groups from an initial value of 12043 for pure terephthalic acid to a minimum value during the entire polymerization process is therefore necessary. Since the degree of esterification (VG) for the concentration of terminal carboxyl groups (CEG) according to the above formula in

109846/1836

In relation to the relationship 3, an increase in the degree of esterification to a maximum during the entire process is the consequence of the reduction in the concentration of terminal carboxyl groups to a minimum ^ -PolymeriGP.tionareaktor, necessary to achieve a functioning process «These minimum degrees of esterification are about 60 / J for the primary monomer, about ^r Jbp for the secondary monomer and about 95 $ for the low polymer.

Polytetramethylene has Assuming a theoretical melting point of 23O ⁰ C, that the molecular weight of the polymer is above about 2000, the melting points of the polymers can serve as a criterion for the purity: the lower the melting point depression of 2'5O ⁰ C out, the higher is the purity of the polymer.

Example 8

The experiment was carried out essentially in the same way as described in Example 7, with the difference that the molar ratio of 1,4-butanediol to terephthalic acid 4 * 5: 1.0. The total CEG of the primary monomer averaged about 1500 and the degree of esterification an average of 68 ^.

Example 9

The experiment was carried out essentially in the same way as described in Example 7, with the difference that the ratio of 1,4-butanediol to terephthalic acid was 3.4: 1.0. The total CEG value of the primary monomers averaged around 2100 and the degree of esterification averaged $ 68. The total CEG of the secondary polymer averaged about 1000 and its esterification rate averaged 15 °

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Example 10

The experiment described in "Example 7" was essentially repeated with the difference that the molar ratio of 1,4-butanediol to terephthalic acid was 3.3 and a degree of esterification of an average of 58 / o _& The average high polymers showed a total CEG value of 85, a relative viscosity of 15 and a melting point of 224 ° 0th

Example 11

* The experiment was carried out essentially in the manner described in Example 7 with the difference that the molar ratio of 1,4-butanediol to terephthalic acid was 2.6: 1.0 = the total CEG-V / ert of the primary monomer an average of about 3300 and the average Veresterungßgrad 54 / £ <> the secondary monomers showed a G-tal-CEG value of an average of about 2500 and an average degree of esterification of 60fo _e In the "low" - or "high" polymerization reactor polymerization did not statti

Example 12

The properties of staple fibers made of polytetramethylene terephthalate, produced by the process according to the invention have the properties of staple fibers compared made by the ester interchange process. The results are in the following Called table.

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Inventiveness
moderately
put Sta
fiber fibers Through Esteraus
exchange herge
put stacks
fibers Limiting viscosity (I ₀ V ₀ ) der
dry schnitzel, dl / g 0.740 0.800 Properties of the woven
Yarn: I ₀ V ₀ , dl / g 0.736 0.792 Single titre per thread 62.5 62.4 Birefringence 17.6 χ 10 ~ ³ 6.1 χ 10 ~ ⁵ Properties of the stretch
ten yarn: Single titre per thread 21.4 20.5 Tear strength, g / den 2.23 2.58 Elongation, ^ 74.6 76.4 10 ^ module, g / den .0.66 0.67 Krä us e 1 ung e n / m 417 433 Ripple,? O 21.8 21.1 Finish, ° /> 0.14 0.23 Hot air shrinkage, ^c / o 5.2 4.9 Springback from bending *, $ 77 80 Cutting length 6.10 6.16

* At $ 20 surface deformation

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Claims (1)

Claims 1.) Process for the production of fiber-forming polytetramethylene terephthalate, characterized in that one a) a mixture of 1,4-butanediol and terephthalic acid im Molar ratio of 1,4-butanediol to terephthalic acid of "At least 3 * 4: 1 about 2 to 8 hours at a temperature of about 200 ° to JOO ⁰ C under an overpressure of at least 2 atmospheres and at least untsr the partial vapor pressure of 1 .4-butanediol heated at Reaktionsternperatur, b) the reaction mixture then under a vacuum of about 0.05 to 15 mm Hg of a polycondensation temperature exposing from about 200 ° to 275 ° C and c) the reaction mixture under these conditions until a polymer with a relative viscosity of about 13 until 75 has been formed. 2.) The method according to claim 1, characterized in that one vorzu in the molar ratio of about 3> 4: 1 to 5: Ij _; - :; v? ei: e from 3.5: 1 to 4: 1 present mixture of 1,4-butanediol and terephthalic acid, about 2 to 6 hours, preferably 2 to 4 hours, at 210 ° to 26O ⁰ C, preferably heated to 220 ° to 245 ° C and the reaction mixture then under a vacuum of about 0.1 to 2 mm Hg, preferably up to about 0.4 mm Hg and temperatures between about 240 and 260 ° C, preferably between 250 'and 255 ° C vieiterbehar.de! t until a polymer with a relative viscosity of about 18 to 45, preferably 22 to 36, has been formed. 3.) Process according to claim 1 or 2, characterized in that the polycondensation temperature is allowed to act at a vacuum between 0.05 and 15 mm Hg over a period of about 10 to 12 minutes . BAD ORlQtNAL 109846/1836 H.) Process according to claim 1 or 2, characterized in that the polycondensation temperature is allowed to act at a vacuum between about 0.1 and 2 mm Hg over a period of up to about 95 minutes. 5.) Method according to claim 1 to 4, characterized in that that the polycondensation temperature at a vacuum between about 0.1 and 0.4 mm Hg over a period of Let it act for about 35 to 60 minutes. 10984 6/1836 BATH ORIGINAL