Process for preparing PA-4X, and PA-410 obtainable by the process
A process for preparation of a polyamide PA-4X containing monomer units of 1,4-diaminobutane and an aliphatic linear dicarboxylic acid X with at least 8 carbon atoms, which contains the following steps: 1) making a solution comprising a salt of 1,4-diaminobutane and the aliphatic linear dicarboxylic acid and water, at a temperature at which the salt dissolves; 2) concentrating the solution of the salt at a temperature above the crystallization temperature of the salt, at a pressure of at most 7 barA to a water content of between 0 and 30 wt % based on the total amount of solution, 3) producing a polymer from the solution obtained by step 2, while keeping the polymer in a melt and at a pressure of less than 18 barA, 4) depressurizing the polymer obtained at step 3 while keeping the polymer in the melt to further polymerize the polymer. In an preferred embodiment the aliphatic linear dicarboxylic acid is 1,10-decanedioic acid. Also claimed is a polyamide 410 having a viscosity number (VN) of at least 100 ml/gram.
1. A process for preparation of a polyamide PA-4X containing monomer units of 1,4-diaminobutane and an aliphatic linear dicarboxylic acid X with at least 8 carbon atoms, wherein the process comprises the following steps:
(1) making an aqueous solution comprising a salt of 1,4-diaminobutane and the aliphatic linear dicarboxylic acid and water, at a temperature at which the salt dissolves;
(2) concentrating the solution of the salt at a temperature above the crystallization temperature of the salt, at a pressure of at most 7 barA to a water content of between 0 and 30 wt % based on the total amount of aqueous solution,
(3) producing a polymer from the aqueous solution obtained by step (2), while keeping the polymer in a melt by controlling escape of water from the aqueous solution and by maintaining an increased pressure of at least 8 barA to less than 18 barA and an increased temperature which are sufficient to thereby obtain polymerization conditions above a liquid freezing point of the polymer to achieve a viscosity number (VN) of the polymer as measured according to ISO307, fifth edition 2007 May 15 in formic acid (c=0.005 g/mL) at 25° C. which is at least 100 ml/gram,
(4) depressurizing the polymer having a VN of at least 100 ml/gram obtained in step (3) while keeping the polymer in the melt to further polymerize the polymer; and
(5) without an intervening step immediately following step (4), subjecting the polymer to strand or under-water granulating.
2. The process according to claim 1 , in which the aliphatic linear dicarboxylic acid is chosen from the group of 1,8-octanedioic acid, 1,9-nonanedioic acid, 1,10-decanedioic acid, 1,11-undecandioic acid, 1,12-dodecanedioic acid, 1,13-tridecanedioic acid, 1,14-tetradecanedioic acid, 1,15-pentadecanedioic acid, 1,16-hexadecanedioic acid, 1,17-heptadecanedioic acid and 1,18-octadecanedioic acid.
3. The process according to claim 1 , in which X is 1,10-decanedioic acid.
4. The process according to claim 1 , wherein the water content in step (2) is less than 15 wt %, based on the total amount of the solution.
5. The process according to claim 1 , wherein the water content in step (2) is less than 10 wt %, based on the total amount of the solution.
6. The process according to claim 1 , wherein the pressure in step (3) is less than 24-X barA, in which X has a value of the number of carbon atoms in the aliphatic linear dicarboxylic acid.
7. The process according to claim 1 , wherein the pressure in step (3) is between 22-X barA and 24-X barA, in which X has a value of the number of carbon atoms in the aliphatic linear dicarboxylic acid.
8. The process according to claim 1 , wherein the temperature in step (4) is at least 233° C. and the aliphatic linear dicarboxylic acid is 1,10-decanedioic acid.
9. A polyamide 410 obtained by the process according to claim 1 , wherein the polyamide 410 has a viscosity number (VN) as measured according to ISO307, fifth edition 2007 May 15 in formic acid (c=0.005 g/mL) at 25° C., of at least 105 ml/gram.
10. The polyamide 410 according to claim 9 , wherein the viscosity number (VN) is at least 110 ml/gram.
11. The polyamide 410 according to claim 9 , wherein the polyamide 410 satisfies formulae (I):
([acid end groups]+[amine end groups])> b−a·VN (I),
wherein:
[acid end groups] is the concentration of acid end groups in the polyamide 410 in meq/kg,
[amine end groups] is the concentration of amine end groups in the polyamide 410 in meq/kg,
a is equal to 0.77,
b is equal to 160, and
VN is the viscosity number in ml/gram.
12. The polyamide 410 according to claim 11 , wherein b is equal to 165.
13. The polyamide 410 according to claim 11 , wherein formulae I is applicable with the proviso that:
[acid end groups]+[amine end groups]>20 meq/kg.
14. The polyamide 410 according to claim 9 , wherein the viscosity number (VN) is at least 120 ml/gram.
15. The polyamide 410 according to claim 9 , wherein the viscosity number (VN) is at least 130 ml/gram.
16. The polyamide 410 according to claim 9 , wherein the viscosity number (VN) is 105 ml/gram up to 260 ml/gram.
17. The polyamide 410 according to claim 9 , wherein the viscosity number (VN) is 105 ml/gram up to 240 ml/gram.
18. A shaped article, comprising the polyamide 410 according to claim 9 .