Process for preparing copolyamide without encrustation in autoclave
A technology of copolyamide and polyamide, applied in the field of preparation of copolyamide, which can solve the problems of high cost, lower product yield, unsatisfactory solution, etc.
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example 1
[0090] Example 1 (invention)
[0091] Preparation of copolyamide 66 / 6T in an industrial-scale batch plant comprising an evaporator of the external recirculation type and an agitated autoclave, both equipped to supply heat by suitable means and under pressure-controlled conditions Evaporated process steam is discharged below. The following manufacturing processes are used:
[0092] - 52% by weight of an aqueous solution of the N-salt (a stoichiometric aqueous solution of hexamethylenediamine and adipic acid) was charged together with 40% by weight of an aqueous solution of the 6T salt (a stoichiometric aqueous solution of hexamethylenediamine and terephthalic acid) to evaporate In the container, the ratio of the two solutions is selected to obtain a composition (mixed salt) containing 6T salt with a molar fraction equal to 35% in the resulting mixed salt. Some additives were also added to the salt mixture: acetic acid (1.65 mol per 100 mol of mixed salt), hexamethylenediamine...
example 2
[0101] Example 2 (comparative example)
[0102] The process of Example 1 was repeated with the main difference that the pressure release phase in the autoclave started when the mass temperature reached 268°C instead of 288°C. Some other process parameters were modified accordingly:
[0103] - Stress Polymerization has a duration of 61 minutes instead of 85 minutes
[0104] - Mass temperature at the end of the 35 minute pressure release phase is 288°C instead of 293°C
[0105] - The refining stage at atmospheric pressure lasted 14 minutes instead of 7 minutes, the polymer mass temperature at the end of this stage was 291 °C. This longer refining stage is offset by a slightly lower refining temperature and shorter pressure polymerization time, resulting in a final polymer with the same molecular mass as in Example 1.
[0106] All other process features remained unchanged compared to Example 1.
[0107] Thus, a polymerization cycle of 8 consecutive batches was carried out in ...
example 3
[0109] Example 3 (comparative example)
[0110] The process of Example 1 was repeated with the main difference that the pressure release phase in the autoclave started when the mass temperature reached 277°C instead of 288°C. Some other process parameters were modified accordingly:
[0111] - Stress Polymerization has a duration of 70 minutes instead of 85 minutes
[0112] - Mass temperature at the end of the 35 minute pressure release phase is 290°C instead of 293°C
[0113] - The refining stage at atmospheric pressure lasted 12 minutes instead of 7 minutes, the polymer mass temperature at the end of this stage was 292°C. This longer refining stage is offset by a slightly lower refining temperature and shorter pressure polymerization time, resulting in a final polymer with the same molecular mass as in Example 1.
[0114] All other process features remained unchanged compared to Example 1.
[0115] Thus, polymerization cycles of 10 consecutive batches were carried out in ...
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Abstract
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