Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
  • C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
  • C08G69/26—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from polyamines and polycarboxylic acids
  • C08G69/28—Preparatory processes

Definitions

• the invention relates to a process for the preparation of polyamides by heating aqueous solutions of salts from dicarboxylic acids and diamines to polyamide-forming temperatures under increased pressure and removal of water.
• aqueous solutions of such salts are generally used.
• aqueous solutions of such salts are usually 45 to 70 weight percent aqueous salt solutions.
• the excess water must be largely removed from such solutions by a pre-evaporator stage, e.g. except for a remainder of 30 to 10 weight percent water. This means that the aqueous salt solutions used must first be heated and excess water must be evaporated, which requires considerable amounts of energy, and only then can the actual condensation be carried out.
• the technical task was therefore to avoid the evaporation of large amounts of water in the production of polyamides and, on the other hand, to avoid the metering difficulties of molten liquid starting materials.
• This object is achieved in a process for the preparation of polyamides by heating aqueous solutions of salts from alkanedicarboxylic acids with 6 to 12 carbon atoms and diamines of the formula NH 2 RNH 2 , in which R denotes an alkylene radical with 6 to 12 carbon atoms to elevated temperatures at polyamide-forming temperatures Pressure and removal of water, starting from 75 to 90 weight percent aqueous solutions of salts of dicarboxylic acids and diamines, by neutralization of 40 to 65 wt .-% saline solutions at a temperature of 60 to 110 ° C, the corresponding amount of each Contained dicarboxylic acid dissolved in excess, were obtained with the corresponding diamines under increased pressure while maintaining end temperatures of 140 to 210 ° C.
• the new process has the advantage that much less water has to be evaporated during the polycondensation, which includes the advantage of smaller devices.
• a concentrated solution of such salts is easier to handle compared to molten starting materials.
• Alkane dicarboxylic acids with 6 to 12 carbon atoms are used as starting materials.
• ⁇ , ⁇ -straight-chain alkanedicarboxylic acids of the stated carbon number are particularly suitable.
• Suitable dicarboxylic acids are, for example, adipic acid, suberic acid, azelaic acid, decanedioic acid or dodecanedioic acid. Adipic acid, sebacic acid and dodecanedioic acid have acquired particular technical importance.
• Alkane diamines of the formula NH 2 RNH 2 in which R is an alkylene radical having 6 to 12 carbon atoms, in particular ⁇ , ,- straight-chain alkane diamines, are used as diamines.
• Suitable diamines are, for example, hexamethylene diamine, octamethylene diamine, decamethylene diamine and dodecamethylene diamine. Hexamethylenediamine has gained particular technical importance.
• dicarboxylic acid is additionally dissolved in such a salt solution in an amount which is necessary to achieve the desired final concentration of salt.
• the dicarboxylic acid is dissolved at temperatures of 60 to 110 ° C.
• the salt solution thus obtained, containing free dicarboxylic acids, is then neutralized with the corresponding diamine, advantageously in molten form.
• crystalline dicarboxylic acid is mixed with an aqueous solution of diamine, but using the dicarboxylic acid in excess.
• the neutralization takes place e.g. in mixing sections which contain internals for rapid mixing, it being advantageous not to initially add the entire amount of diamine required for neutralization, and only after a first mixing operation and determination of the pH value is the final adjustment carried out with a further addition of diamine.
• neutralization means reaching the equivalence point for the respective salts of diamines and dicarboxylic acids.
• This is, for example, pH 7.62 for hexamethylene diammonium adipate and pH 7.5 for hexamethylene diammonium sebazate (measured after dilution in 10% by weight aqueous solution at 25 ° C.).
• amounts of diamines equivalent to the amounts of dicarboxylic acid optionally in a slight excess, e.g. up to 1 mole percent to compensate for diamine losses in the condensation.
• the neutralization is expediently carried out with the exclusion of molecular oxygen, e.g. under inert gas, by.
• reaction mixture heats up due to the heat released during neutralization.
• Final temperatures during the neutralization 140 to 210 ° C., in particular 170 to 200 ° C., are maintained.
• neutralization is carried out under increased pressure, e.g. 2 to 15 bar.
• the salt solutions obtained from dicarboxylic acids and diamines should have a content of 75 to 90 percent by weight. A content of 80 to 85 percent by weight of the respective salts is particularly preferred. Salt solutions of hexamethylene diammonium adipate of the concentration mentioned have become particularly important.
• the highly concentrated salt solutions of dicarboxylic acids and diamines thus produced are condensed to polyamides in a manner known per se.
• the condensation usually takes place at temperatures of 240 to 300 ° C. Temperatures of 260 to 290 ° C. are particularly preferably used. In general, pressures of up to 100 bar are used, in particular pressures of 20 to 80 bar have proven successful.
• the water still introduced with the salt solution and the water formed during the condensation are removed. This can e.g. happen so that the water is gradually separated during the condensation.
• regulators such as lower fatty acids, stabilizers, antistatic agents and matting agents can be added before, during or after the condensation.
• the condensation process can be carried out batchwise. However, it is advantageous to use continuous working methods. Suitable procedures are described for example in DT-AS 1495087, GB-PS 11 95 151, DT-PS 1060139 and GB-PS 674 or DT-OS 2417 003.
• Polyamides which are produced by the process of the invention are suitable for producing shaped structures from the melt, such as threads, fibers, moldings, plates or coatings.
• AH salt hexamethylene diammonium adipate
• AH salt hexamethylene diammonium adipate
• 8025 g of solid adipic acid were gradually added with stirring at 90-95 ° C. and dissolved.
• the autoclave was flushed with nitrogen and sealed.
• the contents were heated to 100 ° C, which resulted in a pressure of 2 bar (all pressure values are absolute values).
• 6375 g of molten hexamethylenediamine at 100 ° C were from an inlet vessel with nitrogen pressure within 2 minutes while running. Stirrer pressed into the autoclave.
• the Ah salt solution was polycondensed without prior cooling. It was heated to 275 ° C. in the course of 31/2 hours, the pressure being kept at 19 bar by blowing off steam. After reaching 275 ° C., the pressure was released to atmospheric pressure within 1 hour and the condensation was continued at 275 ° C. for 1 hour.
• the product was removed from the autoclave with nitrogen pressure. pressed out, the melt strand was cooled in a water bath and granulated.
• the polyamide 6.6 obtained had one. relative viscosity of 2.54, measured in 1 percent solution in 96 percent sulfuric acid, and a content of acidic groups of 54 mAq / kg and basic groups of 76 meq / kg.
• Polyamide 6.9 and polyamide 10.6 are obtained in an analogous manner.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polyamides (AREA)

Applications Claiming Priority (2)

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• 1977
  • 1977-06-27 DE DE19772728931 patent/DE2728931A1/de not_active Withdrawn
• 1978
  • 1978-06-08 US US05/913,748 patent/US4251653A/en not_active Expired - Lifetime
  • 1978-06-14 EP EP78100150A patent/EP0000142B1/de not_active Expired
  • 1978-06-14 DE DE7878100150T patent/DE2860225D1/de not_active Expired
  • 1978-06-20 IT IT24768/78A patent/IT1096578B/it active
  • 1978-06-26 JP JP7659078A patent/JPS5411999A/ja active Granted

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