Process for producing liquid crystal polymer

• US 5,616,680 A
• Filed: 11/22/1995
• Issued: 04/01/1997
• Est. Priority Date: 10/04/1994
• Status: Expired due to Term

• Current Assignee: CNA Holdings Incorporated (Celanese Corporation)
• Original Assignee: Hoechst Celanese Corporation (Sanofi )
• Inventors: Linstid, H. Clay III
• Primary Examiner(s): Acquah, Samuel A.
• Application Number:
  US08/563,910
• Time in Patent Office: 496 Days
• Field of Search: 528/176, 528/183, 528/185, 528/190, 528/194, 528/206, 528/219, 528/272, 528/275, 528/288, 528/298, 528/302, 528/308, 528/308.6, 524/779
• US Class Current: 528/183
• CPC Class Codes: C08G 63/605 the hydroxy and carboxylic groups being bound to aromatic rings
• CPC Class Codes: C08G 63/78 Preparation processes
• CPC Class Codes: C08G 69/44 Polyester-amides

Abstract

A process for producing an anisotropic melt-phase forming polymer involving separate acetylation and polymerization steps, which utilizes controlled vapor phase reflux to reduce reactant loss and assist in maintaining the stoichiometry of the process.

Claims

1. A process for producing an anisotropic melt-forming polymer consisting essentially of repeating units of the formula:

##STR5## wherein for each repeating unit represented by formula (II) Y is oxygen or nitrogen and wherein for each repeating unit represented by formula (II) or (III) Ar¹ and Ar² independently represent a divalent radical comprising at least one aromatic ring,

which comprises the steps of;

(a) combining, in a first reactor equipped for controlled vapor phase reflux the p-hydroxybenzoic acid, aromatic diol, and 6-hydroxy-2-naphthoic acid reactants from which repeating units (I), (II) and, when present, (IV) are derived with an excess of from about 1 to about 10 mole percent of acetic anhydride, based on the total moles of reactive hydroxyl and, if present, amine groups present on said reactants, to form an acetylation mixture;

(b) heating the acetylation mixture to a temperature at which acetylation of the hydroxyl groups is initiated;

(c) maintaining the resulting acetates in a molten state for a period of time sufficient to substantially complete the acetylation reaction and remove substantially all acetic acid byproducts generated by the acetylation reaction without causing significant polymerization or loss of the acetates;

(d) introducing the molten acetates into a second reactor equipped for controlled vapor phase reflux and preheated to a temperature sufficient to maintain the acetates in the melt without causing significant polymerization;

(e) heating the polymerization mixture, in the presence of a polycondensation catalyst and a stoichiometric amount of the aromatic dicarboxylic acid from which repeating unit (III) is derived, to a temperature sufficient to induce polymerization at a rate which avoids sublimation of the acetates or the oligomeric products initially produced;

(f) maintaining the melt at polymerization temperature under vacuum for a period of time sufficient to produce a polymer of desired melt viscosity; and

(g) discharging the resultant polymer from the second reactor.

2. A process as described in claim 1 wherein in the first reactor, controlled reflux during the initial stage of the acetylation maintains vapor phase temperature below a temperature at which acetic acid and acetic anhydride begin to distill.

3. A process as described in claim 2 wherein controlled reflux during completion of the acetylation allows the vapor phase temperature to exceed the boiling point of acetic acid, but to remain low enough to retain residual acetic anhydride in the first reactor.

4. A process as described in claim 3 wherein vapor phase temperature during completion of the acetylation is held at about 120°

to about 130°

C.

5. A process as described in claim 4 wherein in the second reactor, vapor phase temperature is held at about 120°

to about 130°

C. by controlled reflux until a temperature of about 300°

to 350°

C. is reached.

6. A process as described in claim 5 wherein the final melt temperature of the molten acetates in the first reactor is from about 150°

to about 220°

C.

7. A process as described in claim 1 wherein discharged polymer has an inherent viscosity (I.V.) of at least about 1.0 dl/g at 60°

C. in pentafluorophenol at a concentration of 0.1 wt %.

8. A process as described in claim 1 wherein an excess of from about 1 to about 3 mole percent of acetic anhydride is utilized.

9. A process as described in claim 4 wherein the molten acetates are filtered to remove any solid impurities present prior to their combination with the aromatic diacid precursor of recurring unit (III).

10. A process as described in claim 5 wherein after reaching a temperature of about 300°

to about 350°

C. the vapor phase temperature of the second reactor is allowed to increase to remove volatile byproducts.

11. A process as described in claim 5 wherein the polycondensation catalyst is at least one compound selected from the group consisting of alkali and alkaline earth metal salts of carboxylic acids.

12. A process as described in claim 11 which contains from about 50 to about 500 parts per million of catalyst, based on the total weight of the reactants from which the above-described repeating units are derived, excluding the acetic anhydride.

13. A process as described in claim 11 wherein the catalyst is potassium acetate and is present in amount of from about 100 to about 300 parts per million by weight, based on the total weight of the reactants from which the above-described repeating units are derived, excluding the acetic anhydride.

14. A process as described in claim 10 wherein the catalyst is present in the first reactor.

15. A process as described in claim 5 wherein the final melt temperature of the molten acetates is from about 180°

to about 200°

C.

16. A process as described in claim 5 wherein said anisotropic melt-forming polymer consists essentially of from about 20 to about 80 mole percent of repeating unit (I), from about 40 to about 10 mole percent of repeating unit (II), from about 40 to about 10 mole percent of repeating unit (III), and from about 0 to about 20 mole percent or repeating unit (IV), which when present replaces an equivalent amount of repeating unit (I).

17. A process as described in claim 16 wherein Y is oxygen;

Ar¹ is selected from the group consisting of ##STR6## and mixtures thereof; and

Ar² is selected from the group consisting of ##STR7## and mixtures thereof.

18. A process as described in claim 17 wherein Ar¹ is ##STR8## and Ar² is ##STR9##

19. A process as described in claim 18 wherein Ar¹ is ##STR10## and Ar² is a mixture of ##STR11##

20. A process for producing an anisotropic melt-forming polymer consisting essentially of repeating units of the formula:

##STR12## wherein for each repeating unit represented by formula (II) Y is oxygen or nitrogen and wherein for each repeating unit represented by formula (II) or (III) Ar¹ and Ar² independently represent a divalent radical comprising at least one aromatic ring,

which comprises the steps of;

(a) combining, in a first reactor equipped for controlled vapor phase reflux the p-hydroxybenzoic acid, aromatic diol, and 6-hydroxy-2-naphthoic acid reactants from which repeating units (I), (II) and, when present, (IV) are derived with an excess of from about 1 to about 10 mole percent of acetic anhydride, based on the total moles of reactive hydroxyl and, if present, amine groups present on said reactants, to form an acetylation mixture;

(b) heating the acetylation mixture to a temperature at which acetylation of the hydroxyl groups is initiated;

(c) maintaining the resulting acetates in a molten state for a period of time sufficient to substantially complete the acetylation reaction and remove substantially all acetic acid byproducts generated by the acetylation reaction without causing significant polymerization or loss of the acetates;

(d) introducing the molten acetates into a second reactor equipped for controlled vapor phase reflux and preheated to a temperature sufficient to maintain the acetates in the melt without causing significant polymerization, into which is also introduced a stoichiometric amount of the aromatic dicarboxylic acid from which repeating unit (III) is derived, to produce a polymerization mixture;

(e) heating the polymerization mixture, in the presence of a polycondensation catalyst to a temperature sufficient to induce polymerization at a rate which avoids sublimation of the acetates or the oligomeric products initially produced;

(f) maintaining the polymerization mixture at polymerization temperature under vacuum for a period of time sufficient to produce a polymer of desired melt viscosity; and

(g) discharging the resultant polymer from the second reactor.

25. A process as described in claim 20 wherein in the first reactor, controlled reflux during the initial stage of the acetylation maintains vapor phase temperature below a temperature at which acetic acid and acetic anhydride begin to distill.

26. A process as described in claim 25 wherein controlled reflux during completion of the acetylation allows the vapor phase temperature to exceed the boiling point of acetic acid, but to remain low enough to retain residual acetic anhydride in the first reactor.

27. A process as described in claim 26 wherein vapor phase temperature during completion of the acetylation is held at about 120°

to about 130°

C.

28. A process as described in claim 27 wherein in the second reactor, vapor phase temperature is held at about 120°

to about 130°

C. by controlled reflux until a temperature of about 300°

to 350°

C. is reached.

21. A process for producing an anisotropic melt-forming polymer consisting essentially of repeating units of the formula:

##STR13## which comprises the steps of;

(a) combining, in a first reactor equipped for controlled vapor phase reflux the p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid reactants from which repeating units (I) and (IV) are derived with an excess of from about 1 to about 10 mole percent of acetic anhydride, based on the total moles of reactive hydroxyl groups present on said reactants, to form an acetylation mixture;

(b) heating the acetylation mixture to a temperature at which acetylation of the hydroxyl groups is initiated;

(c) maintaining the resulting acetates in a molten state for a period of time sufficient to substantially complete the acetylation reaction and remove substantially all acetic acid byproduct generated by the acetylation reaction without causing significant polymerization or loss of the acetates;

(d) introducing the molten acetates into a second reactor equipped for controlled vapor phase reflux and preheated to a temperature sufficient to maintain the acetates in the melt without causing significant polymerization;

(e) heating the melt, in the presence of a polycondensation catalyst, to a temperature sufficient to induce polymerization at a rate which avoids sublimination of the acetates or the oligomeric products initially produced;

(f) maintaining the melt at polymerization temperature under vacuum for a period of time sufficient to produce a polymer of desired melt viscosity; and

(g) discharging the resultant polymer from the second reactor.

22. A process as described in claim 21 wherein said anisotropic melt-forming polymer consists essentially of from about 20 to about 80 mole percent of repeating unit 1 and from about 80 to about 20 mole percent of repeating unit IV.

23. A process as described in claim 22 wherein the polycondensation catalyst is at least one compound selected from the group consisting of alkali and alkaline earth metal salts of carboxylic acids.

24. A process as described in claim 23 which contains from about 50 to about 500 parts per million of catalyst, based on the total weight of the reactants from which the above-described repeating units are derived, excluding the acetic anhydride.

29. A process as described in claim 21 wherein in the first reactor, controlled reflux during the initial stage of the acetylation maintains vapor phase temperature below a temperature at which acetic acid and acetic anhydride begin to distill.

30. A process as described in claim 29 wherein controlled reflux during completion of the acetylation allows the vapor phase temperature to exceed the boiling point of acetic acid, but to remain low enough to retain residual acetic anhydride in the first reactor.

31. A process as described in claim 30 wherein vapor phase temperature during completion of the acetylation is held at about 120°

to about 130°

C.

32. A process as described in claim 31 wherein in the second reactor, vapor phase temperature is held at about 120°

to about 130°

C. by controlled reflux until a temperature of about 300°

to 350°

C. is reached.