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
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/41—Preparation of salts of carboxylic acids
  • C07C51/412—Preparation of salts of carboxylic acids by conversion of the acids, their salts, esters or anhydrides with the same carboxylic acid part

Definitions

• the invention relates to a process for the preparation of 70 to 90% by weight aqueous solutions of salts from dicarboxylic acids and diamines and polyamide precondensates by reacting alkanedicarboxylic acids with 6 to 12 carbon atoms and alkanediamines with 6 to 12 carbon atoms in water.
• the technical task was to provide starting solutions for the production of polyamides from dicarboxylic acids and diamines that are easy to handle and contain as little water as possible and that the thermal energy contained in the starting solutions can be used.
• This object is achieved in a process for the preparation of 70 to 90% by weight aqueous solutions of salts from dicarboxylic acids and diamines and polyamide precondensates by reacting alkanedicarboxylic acids with 6 to 12 carbon atoms and alkanediamines with 6 to 12 carbon atoms in water, characterized in that 40 to 65% by weight aqueous salt solutions of dicarboxylic acids and diamines from 60 to 110 ° C., which contain a corresponding amount of the respective dicarboxylic acid in excess, with the respective molten diamine in equivalent amounts based on dissolved dicarboxylic acid in a manner known per se implemented, with the proviso that the reaction is carried out under increased pressure and a final temperature of 160 to 200 ° C is maintained during the reaction.
• the new process has the advantage that it immediately leads to highly concentrated aqueous starting solutions for polyamide production, which no longer need to be concentrated.
• the new process also has the advantage that starting solutions are obtained in which the heat of neutralization contained is used for the polycondensation.
• the new process has the advantage that the starting materials can be metered and mixed easily.
• alkane dicarboxylic acids with 6 to 12 carbon atoms are used.
• Straight-chain a-w dicarboxylic acids of the stated carbon number are preferably used.
• Suitable dicarboxylic acids are, for example, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid and dodecanedioic acid. Adipic acid and sebacic acid have acquired particular technical importance.
• alkane diamines with 6 to 12 carbon atoms are used.
• Straight-chain a-w-alkanediamines having 6 to 12 carbon atoms are particularly preferably used.
• Suitable diamines are, for example, hexamethylene diamine. Octamethylene diamine, decamethylene diamine or dodecamethylene diamine.
• the starting point is an aqueous salt solution of dicarboxylic acids and diamines of 40 to 65 percent by weight, which contains a corresponding amount of the respective dicarbon contains acid dissolved in excess. Solutions which contain 50 to 65 percent by weight of the respective salts, based on the sum of salt and water, are advantageously used. The amount of dissolved dicarboxylic acid depends on the desired final concentration of the highly concentrated aqueous solutions to be prepared.
• solid dicarboxylic acid is dissolved in a salt solution of lower concentration. Temperatures of 60 to 110 ° C are observed. Salt solution thus obtained containing free dicarboxylic acid is then reacted with molten diamine in equivalent amounts based on the dissolved dicarboxylic acid. It is advantageous to ensure that the pH value for the equivalence point of the salt to be produced is observed.
• the equivalence point for hexamethylene diammonium adipate is pH 7.62 and for hexamethylene diammonium sebacate pH 7.5 measured in 10 percent aqueous solution at 25 ° C.
• the reaction is advantageously carried out in a mixing section, first adding a small deficit of molten diamine and then carrying out the precise adjustment by adding molten diamine again.
• diamines are generally used in excess, e.g. 1.5 mole percent.
• Solve according to another preferred embodiment first solid dicarboxylic acid in an aqueous solution of diamine in deficit. This gives a salt solution of dicarboxylic acid and diamine, which contains an excess amount of dicarboxylic acid in solution. It is understood that the proportions are chosen so that a salt solution of the aforementioned concentration is obtained and the excess amount of dicarboxylic acid corresponds to the desired final concentration of the aqueous solution.
• the diearbonic acid is dissolved at temperatures of 60 to 110 ° C, usually keeping atmospheric pressure.
• the salt solution thus obtained containing free dicarboxylic acid is then reacted with molten diamine in equivalent amounts based on the dissolved dicarboxylic acid. This implementation is advantageously carried out as described in the aforementioned procedure.
• reaction of the dissolved dicarboxylic acid with molten diamine is carried out under increased pressure. Pressures of 2 to 15 bar are advantageously obtained. A corresponding pressure arises automatically due to the autogenous pressure and can be increased by adding a small amount of nitrogen to prevent the solution from boiling. It is also an essential feature of the invention that a final temperature of 160 to 200 ° C is maintained during neutralization.
• Aqueous solutions thus obtained contain salts of dicarboxylic acids and diamines. Due to the beginning of polycondensation, they can also contain polyamide precondensates. The conversion of the amino and carboxyl groups can be up to 50% e.g. 20 to 45%.
• the aqueous solutions produced have a content of 70 to 90 percent by weight, in particular 80 to 90 percent by weight, of salts from dicarboxylic acids and diamines and polyamide precondensates.
• Highly concentrated aqueous solutions of salts and polyamide precondensates prepared according to the invention, which are derived from dicarboxylic acids and diamines, are outstandingly suitable for the production of polyamides by condensation.
• the condensation can be carried out batchwise or continuously. Suitable condensation processes are described, for example, in DT-AS 14 95 087, GB-PS 1 159 151, GB-PS 674 954 or DT-PS 1 060 139 and DT-OS 24 17 003. It is particularly advantageous to use the aqueous solution according to the invention Use solutions for condensation without first removing the heat of neutralization. In this context, heat losses caused by the device are irrelevant.
• Polyamides which are produced from the solutions according to the invention are suitable for the production of masses shaped 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 to 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 pressed into the autoclave from a feed vessel with nitrogen pressure within 2 minutes with the stirrer running.
• the example shows the use of part of the heat of neutralization to dissolve the dicarboxylic acid.
• the flask was immersed in a water bath at 75 ° C acting as a protective heater; immediately thereafter, a solution of 75 g of hexamethylenediamine in 92 g of water, kept in the dropping funnel at 90 ° C., was added with stirring within 20 seconds. After 2 minutes a clear solution had formed, the temperature of which was 69 ° C.
• the composition of the solution was 37% AH salt, 43% adipic acid and 20% water.
• the further implementation was carried out analogously to Example 1.
• the AH salt solution obtained in Example 1 was polycondensed without cooling the solution. It was heated to 275 ° C. in the course of 3 1/2 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 to 275 ° C. for 1 hour. The product was pressed out of the autoclave under nitrogen pressure, the melt strand being cooled in a water bath and granulated.
• the polyamide 66 obtained had a relative viscosity of 2.54, measured in 1 percent solution in 96 percent sulfuric acid, and a content of acidic groups of 54 meq / kg and of basic groups of 76 meq / kg.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Engineering & Computer Science (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Polyamides (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 1977
  • 1977-06-27 DE DE19772728817 patent/DE2728817A1/de not_active Withdrawn
• 1978
  • 1978-06-08 US US05/913,641 patent/US4213884A/en not_active Expired - Lifetime
  • 1978-06-16 DE DE7878100175T patent/DE2860572D1/de not_active Expired
  • 1978-06-16 EP EP78100175A patent/EP0000157B1/de not_active Expired
  • 1978-06-20 IT IT24766/78A patent/IT1096586B/it active
  • 1978-06-26 JP JP7659178A patent/JPS5412316A/ja active Granted

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