SEMI-AROMATIC POLYAMIDE PREPARATION METHOD

Abstract

An industrial method for preparing a semi-aromatic copolyamide having a general formula A/10.T, wherein: A denotes a unit obtained by polycondensing a lactam or a C.sub.9-C.sub.12 amino acid; and 10.T denotes a unit obtained by polycondensing 1.10-decanediamine and terephtalic acid. The method includes a step for polycondensing the comonomers, the amino acid or the lactam, 1.10-decanediamine and terephtalic acid in the presence of at least one C.sub.1-C.sub.7 linear aliphatic acid. The level of foaming in a reactor is substantially reduced, during the polycondensation step, in relation to the level observed without C.sub.1-C.sub.7 linear aliphatic acid.

Claims

1. An industrial process for preparing a semiaromatic copolyamide of general formula A/10.T in which A denotes a unit obtained from the polycondensation of a lactam or of a C.sub.9-C.sub.12 amino acid, 10.T denotes a unit obtained from the polycondensation of 1,10-decanediamine and terephthalic acid, wherein the process comprises a step of polycondensation of the comonomers: the amino acid or the lactam, 1,10-decanediamine and terephthalic acid, in the presence of at least one linear C.sub.1-C.sub.7 aliphatic acid in a reactor, the level of foaming in the reactor being substantially reduced during the polycondensation step relative to the level observed without the linear C.sub.1-C.sub.7 aliphatic acid.

2. The industrial preparation process as claimed in claim 1, in which the polycondensation step is performed in the absence of antifoam.

3. The process as claimed in claim 1, in which the level of foaming is reduced by at least 10% relative to the level observed without the linear C.sub.1-C.sub.7 aliphatic acid.

4. The process as claimed in claim 1, in which the polycondensation step is performed in a single step in the same reactor at a temperature from 200 to 300° C., at a pressure which may rise up to 30 bar, and gradually reduced down to a pressure less than or equal to atmospheric pressure so as to complete the polymerization.

5. The process as claimed in claim 1, in which the polycondensation step is performed in three steps and comprises the following steps: a. a first step of pre-polymerization in a concentrator by heating the comonomers in the presence of said at least aliphatic acid, at a temperature of from 200° C. to 300° C., at a pressure of from 20 to 30 bar to obtain a prepolymer, said temperature being a temperature above the melting point of the prepolymer; b. a second step of transfer of the prepolymer from the concentrator to a polymerizer at a temperature of from 220 to 280° C. at a pressure from 10 to 20 bar; c. a third step of polymerization by heating at a temperature of from 200 to 300° C. at a pressure which may range up to 30 bar, then reduced down to a pressure less than or equal to atmospheric pressure so as to complete the polymerization to obtain said copolyamide, said temperature being a temperature above the melting point of said copolyamide.

6. The process as claimed in claim 5, in which the reduction in the level of foaming takes place at least during the first step, in the concentrator.

7. The industrial preparation process as claimed in claim 1, in which the linear aliphatic acid is chosen from propanoic acid and acetic acid.

8. The industrial preparation process as claimed in claim 1, in which said semiaromatic copolyamide is 11/10.T.

9. A semiaromatic copolyamide which may be obtained via the process as defined in claim 1.

10. The semiaromatic copolyamide as claimed in claim 9, in which said copolyamide is 11/10.T.

11. A method for substantially reducing the level of foaming in a reactor during the step of polycondensation of the comonomers of a semiaromatic copolyamide as defined in claim 1, relative to the level observed without the linear C.sub.1-C.sub.7 aliphatic acid.

12. The method as claimed in claim 11, in which the polycondensation step is performed in the absence of antifoam.

13. The method as claimed in claim 11, in which the level of foaming is reduced by at least 10% relative to the level observed without the linear C.sub.1-C.sub.7 aliphatic acid.

14. The method as claimed in claim 11, in which the linear aliphatic acid is acetic acid.

15. The method as claimed in claim 11, in which said semiaromatic copolyamide is 11/10.T.

Description

EXAMPLES

[0056] Comparison of the level of foaming during the preparation of a PA 11/10T (0.7/1 mol %) in the presence of stearic acid or acetic acid in a process comprising a polycondensation step in three steps.

[0057] The comonomers comprising stearic acid or acetic acid, sodium hypophosphite, Silikonol 1000 and water in proportions as defined in Table I below are introduced into the concentrator and heated at a temperature from 200 to 300° C. at a pressure from 20 to 30 bar to form a prepolymer, and the prepolymer is then transferred into a polymerizer and the prepolymer is then heated in the polymerizer at a temperature from 200° C. to 300° C. at a pressure of 20 to 30 bar, and the pressure is then gradually reduced to atmospheric pressure.

TABLE-US-00001 Comparative example: Example 1 With stearic acid With acetic acid Components Mass (kg) Mass (kg) 1,10-Decanediamine 129.7 129.7 11-Aminoundecanoic 100 100 acid Terephthalic acid 120.8 120.8 Acetic acid — 2.5 Stearic acid 8.3 — 60% NaH.sub.2PO.sub.2 1.4 1.4 Silikonol ® 1000 0.07 0.07 Water 73 73

[0058] The level of foaming is determined by means of a detector for measuring the maximum level of the reaction medium in the concentrator and in the polymerizer for each compound (Example 1 and comparative example).

TABLE-US-00002 Level in the Level in the concentrator polymerizer (% of the maximum (% of the maximum level of the reactor) level of the reactor) Comparative example: 70.02 71.03 With stearic acid (n = 20) (n = 24) Example 1 54.17 57.16 With acetic acid (n = 6)  (n = 6)  % of decrease 22.64% 19.5% in foaming

[0059] The same type of result was observed with a one-step process in a single reactor.