Batch process for preparing polyamides

Abstract

Polyamides based on dicarboxylic acids and on diamines are produced in a batch process by 1) feeding the entire amount of monomer composed of dicarboxylic acids, of diamines, and, if appropriate, of further polyamide-forming monomers, in the desired stoichiometry, in a closed stirred-tank reactor, 2) heating the monomer mixture in the stirred-tank reactor, with stirring, and with setting of a certain pressure, to a desired reaction temperature for the production of a prepolymer, 3) if appropriate, completely or partially depressurizing the reaction mixture from stage 2), 4) if appropriate, carrying out further thermal treatment of the reaction mixture from stage 2) or 3), and 5) reacting the reaction mixture from stage 2), 3), or 4) in the melt in a vented extruder for further increase of the molecular weight, with discharge of water vapor, and without use of additional polyamide-forming monomers or of polyamides.

Claims

1. A batch process for the production of copolyamides, the copolyamides being the reaction products of monomers consisting of a) at least one aliphatic dicarboxylic acid having from 4 to 18 carbon atoms; and b) at least one aliphatic diamine having from 4 to 16 carbon atoms, said process comprising 1) feeding the entire amount of the at least one aliphatic dicarboxylic acid and the at least one aliphatic diamine, in the desired stoichiometry, in a closed stirred-tank reactor to provide a reaction mixture, 2) heating the monomer mixture in the stirred-tank reactor, with stirring, and with setting of a certain pressure, to a desired reaction temperature for the production of a prepolymer, wherein the reaction in stage 2) is carried out at a temperature in the range from 120 to 320 C. and at a maximum pressure in the range from 3 to 100 bar and the reaction in the stirred-tank reactor is terminated once the conversion reached is in the range from 50 to 97%, based on the amino groups and carboxy groups, wherein the intrinsic viscosity of the prepolymer is in the range from 3 to 200 ml/g, determined by solution viscometry, and 5) reacting the reaction mixture from stage 2) in the melt in a vented extruder for further increase of the molecular weight, with discharge of water vapor, and without use of additional polyamide-forming monomers or of polyamides, at a temperature in the range from 120 to 370 C. and at a pressure in the range from 0.01 to 20 bar, the copolyamide produced in stage 5) having a crystallinity of at least 20%, wherein the reaction mixture from stage 2) is passed directly into the vented extruder in stage 5) and two or more stirred-tank reactors installed in parallel are operated alternately, and their reaction products are introduced alternately to the vented extruder.

2. The process according to claim 1, wherein, prior to the reaction in the stirred-tank reactor, no separate stage is undergone for the formation of monomer salts.

3. The process according to claim 2, wherein no water is fed into the stirred-tank reactor.

4. The process according to claim 1, wherein, in the vented extruder, not only water vapor but also unconverted monomers are discharged, these being returned to the process.

5. The process according to claim 1, wherein the melting point of the resultant copolyamides is from 110 to 350 C.

6. The process according to claim 1, wherein the at least one aliphatic diamine is selected from the group consisting of butanediamine, hexamethylenediamine, octanediamine, decanediamine and any one mixture thereof.

7. The process according to claim 1, wherein the at least one aliphatic dicarboxylic acid is selected from the group consisting of adipic acid, sebacic acid, dodecanedoic acid, tetradecandoic acid, and any one mixture thereof.

8. A batch process for the production of copolyamides, the copolyamides being the reaction products of monomers consisting of a) at least one aliphatic dicarboxylic acid having from 4 to 18 carbon atoms; and b) at least one aliphatic diamine having from 4 to 16 carbon atoms, said process comprising 1) feeding the entire amount of the at least one aliphatic dicarboxylic acid and the at least one aliphatic diamine, in the desired stoichiometry, in a closed stirred-tank reactor, and wherein no water is fed into the stirred-tank reactor to provide a reaction mixture, 2) heating the monomer mixture in the stirred-tank reactor, with stirring, and with setting of a certain pressure, to a desired reaction temperature for the production of a prepolymer, wherein the reaction in stage 2) is carried out at a temperature in the range from 120 to 320 C. and at a maximum pressure in the range from 3 to 100 bar and the reaction in the stirred-tank reactor is terminated once the conversion reached is in the range from 50 to 97%, based on the amino groups and carboxy groups, wherein the intrinsic viscosity of the prepolymer is in the range from 3 to 200 ml/g, determined by solution viscometry, and 5) reacting the reaction mixture from stage 2) in the melt in a vented extruder for further increase of the molecular weight, with discharge of water vapor, and without use of additional polyamide-forming monomers or of polyamides, at a temperature in the range from 120 to 370 C. and at a pressure in the range from 0.01 to 20 bar, the copolyamide produced in stage 5) having a crystallinity of at least 20%, wherein the reaction mixture from stage 2) is passed directly into the vented extruder in stage 5) and two or more stirred-tank reactors installed in parallel are operated alternately, and their reaction products are introduced alternately to the vented extruder.

Description

EXAMPLE 1: PRODUCTION OF A COPOLYAMIDE CONSTITUTED AS FOLLOWS

(1) TABLE-US-00001 Component Weight Hexamethylenediamine (HMD) 7.75 kg Dicyclohexylmethyldiamine (dicycan) 10.54 kg Adipic acid 17.22 kg Caprolactam 15.15 kg
Polycondensation:

(2) HMD and dicycan were weighed into the feed vessel and inertized by flushing with nitrogen. The temperature was raised to 75, with stirring, in order to melt these components. Adipic acid and caprolactam were weighed directly into the tank reactor and inertized before the diamine components were added to these. The temperature of the tank reactor was then raised to 220 C. These components reacted together in the reactor with elimination of water as condensate by-product. The reaction pressure increased with time, and reached 16 bar after 2 h. Once the pressure was constant, the reaction mixture was heated for a further two hours, using the same temperature, and then discharge was begun, using a ZDSK-30 twin-screw extruder and a feed rate of from 1 to 3 kg/h.

(3) The product emerging from the extruder die was taken off in the form of extrudate, cooled in a waterbath, and pelletized to give cylindrical pellets. The viscosity of the products was analyzed by solution viscometry, and the value was displayed in the form of intrinsic viscosity. The polyamide specimens were dissolved in 960.1% sulfuric acid in order to prepare a 0.5% strength by weight polymer solution. The flow time of the solvent and of the polymer solution was determined at 250.05 C. waterbath temperature in an Ubbelohde viscometer.

(4) Results:

(5) TABLE-US-00002 Specimen number Feed rate into extruder Intrinsic viscosity 1 1 kg/h 77 ml/g 2 1.5 kg/h 66 ml/g 3 2 kg/h 62 ml/g 4 3 kg/h 51 ml/g

(6) Example 1, which comprises hexamethylenediamine/dicycan/adipic acid/caprolactam in a ratio by weight of 1/1.36/2.22/1.95, was reproduced using a different monomer ratio:

(7) Example 1a: 1/1.36/2.22/1

(8) Example 1b: 2/1.36/4.44/1.95

(9) The results were as follows:

(10) TABLE-US-00003 Specimen number Feed rate into extruder Intrinsic viscosity 1a: 1 1 kg/h 62 ml/g 1a: 2 1.5 kg/h 55 ml/g 1a: 3 2 kg/h 51 ml/g 1a: 4 3 kg/h 47 ml/g 1b: 1 1 kg/h 82 ml/g 1b: 2 1.5 kg/h 73 ml/g 1b: 3 2 kg/h 68 ml/g 1b: 4 3 kg/h 56 ml/g

EXAMPLE 2: PRODUCTION OF A COPOLYAMIDE CONSTITUTED AS FOLLOWS

(11) TABLE-US-00004 Component Weight Hexamethylenediamine (HMD) 7.75 kg Dicyclohexylmethyldiamine (dicycan) 10.54 kg Adipic acid 17.22 kg Caprolactam 15.15 kg
Polycondensation:

(12) HMD and dicycan were weighed into the feed vessel and inertized by flushing with nitrogen. The temperature was raised to 75, with stirring, in order to melt these components. Adipic acid and caprolactam were weighed directly into the tank reactor and inertized before the diamine components were added to these. The temperature of the tank reactor was then raised to 220 C. These components reacted together in the reactor with elimination of water as condensate by-product. The reaction pressure increased with time, and reached 16 bar after 2 h. The reaction mixture was then heated using an external temperature of 280 C. until the pressure was 18 bar. Once the pressure was constant, the reaction mixture was heated using the same external temperature for a further two hours, and was then depressurized to 1 bar. The reaction mixture was further heated, for 1 hour at 1 bar, using the same external temperature.

(13) The resultant prepolymer was finally discharged by using a ZDSK-30 twin-screw extruder and a feed rate of from 10 to 30 kg/h.

(14) The product emerging from the extruder die was taken off in the form of extrudate, cooled in a waterbath, and pelletized to give cylindrical pellets. The viscosity of the products was analyzed by solution viscometry, and the value was displayed in the form of intrinsic viscosity. The polyamide specimens were dissolved in 960.1% sulfuric acid in order to prepare a 0.5% strength by weight polymer solution. The flow time of the solvent and of the polymer solution was determined at 250.05 C. waterbath temperature in an Ubbelohde viscometer.

(15) Results:

(16) TABLE-US-00005 Specimen number Feed rate into extruder Intrinsic viscosity 1 10 kg/h 134 ml/g 2 20 kg/h 123 ml/g 3 30 kg/h 108 ml/g

EXAMPLE 3: PRODUCTION OF A COPOLYAMIDE CONSTITUTED AS FOLLOWS

(17) TABLE-US-00006 Component Weight Hexamethylenediamine (HMD) 7.75 kg Dicyclohexylmethyldiamine (dicycan) 10.54 kg Adipic acid 17.22 kg Caprolactam 15.15 kg
Polycondensation:

(18) HMD, dicycan, adipic acid, and caprolactam were dissolved at 20% by weight in water at 95 C. Once the stoichiometry had been set, the tank reactor was heated using an external temperature of 280 C. until the total pressure reached was 18 bar. Once pressure was constant, the reaction mixture was heated using the same external temperature for a further two hours, and then was depressurized to 1 bar. The reaction mixture was further heated for one hour at 1 bar, using the same external temperature.

(19) The resultant prepolymer was finally discharged by using a ZDSK-30 twin-screw extruder and a feed rate of from 25 kg/h.

(20) The product emerging from the extruder die was taken off in the form of extrudate, cooled in a waterbath, and pelletized to give cylindrical pellets. The viscosity of the products was analyzed by solution viscometry, and the value was displayed in the form of intrinsic viscosity. The polyamide specimens were dissolved in 960.1% sulfuric acid in order to prepare a 0.5% strength by weight polymer solution. The flow time of the solvent and of the polymer solution was determined at 250.05 C. waterbath temperature in an Ubbelohde viscometer.

(21) Results:

(22) TABLE-US-00007 Specimen number Feed rate into extruder Intrinsic viscosity 1 25 kg/h 124 ml/g

EXAMPLE 4: PRODUCTION OF POLYAMIDE CONSTITUTED AS FOLLOWS

(23) TABLE-US-00008 Component Weight HMD 36.378 kg Sebacic acid 63.315 kg
Polycondensation:

(24) HMD was weighed into the feed vessel and inertized by flushing with nitrogen. The temperature was raised to 75 C., with stirring, in order to melt these components. Sebacic acid was weighed directly into the tank reactor, and inertized with nitrogen, before the HMD was added to the reactor. The temperature of the tank reactor was then raised to 220 C. The diamine and the diacid reacted together with elimination of water as condensate by-product. The reaction pressure increased with time, and reached 17.5 bar after 2.5 h. Once the pressure was constant, the reaction mixture was heated for a further two hours, using the same temperature, and then discharge was begun, using a ZDSK-30 twin-screw extruder and a feed rate of from 1 to 3 kg/h.

(25) The product emerging from the extruder die was taken off in the form of extrudate, cooled in a waterbath, and pelletized to give cylindrical pellets. The viscosity of the products was analyzed by solution viscometry, as described at an earlier stage above.

(26) Results:

(27) TABLE-US-00009 Specimen Feed rate into extruder Intrinsic viscosity 1 2.2 kg/h 71 ml/g

EXAMPLE 5: POLYAMIDE BASED ON CAPROLACTAM, HEXAMETHYLENEDIAMINE, ADIPIC ACID, AND DICYCAN

(28) In this process, the monomers were dissolved in water at 90 C. Water was charged to a stirred tank which served as feed tank for the stirred tank reactor that followed. The liquid monomers (hexamethylenediamine and dicycan) were then added, and this was followed by addition of the solid monomers. Heating to 90 C. and mixing gave an aqueous solution of the monomers with the following composition:

(29) TABLE-US-00010 Component Weight Water 20 kg Caprolactam 24.2 kg Adipic acid 11.8 kg Dicycan 17 kg AH salt 26.7 kg

(30) After homogenization of the monomers, a specimen was taken in order to determine pH. pH was then corrected by adding small amounts of the missing monomer. After pH measurement and correction, the monomer solution was transferred to a stirred tank reactor of capacity 150 l. Using a jacket temperature of 280 C., the reactor was heated to give an internal pressure of 18 bar/abs. The pressure was held constant via a pressure-control valve, until most of the water had been removed from the reactor. The pressure was then slowly discharged to give atmospheric pressure within a period of 60 minutes. Once atmospheric pressure had been reached, the reactor was flushed with a stream of nitrogen at 300 l/h for 30 minutes. The reactor was then closed and the mixture was stirred for a further 30 minutes. The reactor was then pressurized with nitrogen at 16 bar/abs, in order to discharge the product from the reactor.

(31) The prepolymer produced in the stirred tank reactor was discharged via a corotating vented twin-screw extruder. The discharge rate was controlled by a pump located directly above the extruder. The prepolymer was postcondensed in the extruder until the desired molecular weight had been reached, with devolatilization to remove the water of reaction. The temperature in the extruder was 220 C., and the rotation rate was 200 revolutions per minute. The discharge rate was 25 kg/h.

(32) The polymer strands emerging from the extruder were cooled in a water bath and pelletized.

(33) The properties obtained were as follows:

(34) TABLE-US-00011 Intrinsic viscosity: 125 ml/g Carboxy end groups: 64 mmol/kg Amino end groups: 65 mmol/kg.

EXAMPLE 6: PRODUCTION OF NYLON-6,10

(35) In this process, the monomers were dissolved in water at 90 C. Water was charged to a stirred tank which served as feed tank for the stirred tank reactor that followed. Hexamethylenediamine was then added, and this was followed by addition of sebacic acid. Heating to 90 C. and mixing gave an aqueous solution of the monomer salt with the following composition:

(36) TABLE-US-00012 Component Amount Water 35 kg Hexamethylenediamine 42.1 kg Sebacic acid 23.8 kg

(37) After homogenization of the monomers, a specimen was taken in order to determine pH. pH was then corrected by adding small amounts of the missing monomer.

(38) After pH measurement and correction, the monomer solution was transferred to a stirred tank reactor of capacity 150 l.

(39) Using a jacket temperature of 290 C., the reactor was heated to give an internal pressure of 18 bar/abs. The pressure was held constant via a pressure-control valve, until most of the water had been removed from the reactor. The pressure was then slowly discharged to give atmospheric pressure within a period of 80 minutes. As soon as atmospheric pressure had been reached, the reactor was closed and pressurized with nitrogen at 16 bar/abs. and the mixture was stirred for a further 60 minutes.

(40) The resultant prepolymer was then passed directly from the stirred tank reactor into a corotating vented twin-screw extruder. The discharge rate was controlled by a pump arranged directly above the extruder. The prepolymer was postcondensed in the extruder until the desired molecular weight had been reached, with devolatilization to remove the water of reaction. The temperature in the extruder was 230 C., and the rotation rate was 180 revolutions per minute. The discharge rate was 20 kg/h. The polymer strands from the extruder were cooled in a water bath and pelletized.

(41) The properties obtained were as follows:

(42) TABLE-US-00013 Intrinsic viscosity: 147 ml/g Carboxy end groups: 66 mmol/kg Amino end groups: 53 mmol/kg.

EXAMPLE 7: PRODUCTION OF NYLON-6,10

(43) The monomers were treated as described in example 6, using a composition as in that example. The remainder of the production process follows the process according to example 6, except that the pressure in the stirred tank reactor was reduced to 3 bar/abs. within a period of 80 minutes. The reactor was then closed and pressurized with nitrogen at 17 bar/abs., and the mixture was stirred for a further 60 minutes.

(44) The rotation rate in the extruder that followed was 240 revolutions per minute, with a discharge rate of 32 kg/h.

(45) The properties of the polyamide obtained were as follows:

(46) TABLE-US-00014 Intrinsic viscosity: 112 ml/g Carboxy end groups: 85 mmol/kg Amino end groups: 70 mmol/kg

EXAMPLE 8: PRODUCTION OF NYLON-6,10

(47) The starting monomers were treated as described in example 6. The remainder of the production process was also as described in example 6, except that the pressure in the stirred tank reactor was reduced slowly to 1.3 bar/abs. within a period of 80 minutes. The reactor was then closed and pressurized with nitrogen at 17 bar/abs., and the mixture was stirred for a further 60 minutes. The rotation rate in the extruder that followed was 240 revolutions per minute with a discharge rate of 30 kg/h.

(48) The properties of the polyamide obtained were as follows:

(49) TABLE-US-00015 Intrinsic viscosity: 129 ml/g Carboxy end groups: 70 mmol/kg Amino end groups: 54 mmol/kg

EXAMPLE 9: PRODUCTION OF NYLON-6,10

(50) The preparation of the monomers and the production process were as in example 6. The pressure was reduced as described in example 6 to atmospheric pressure within a period of 80 minutes. Once atmospheric pressure had been reached, the reactor was flushed for 15 minutes with a stream of nitrogen at 300 l/h. The reactor was then closed and pressurized with nitrogen at 17 bar/abs., in order to discharge the product from the reactor. The remainder of the production process was as described in example 6, the discharge rate from the extruder being 14 kg/h.

(51) The properties of the polyamide obtained were as follows:

(52) TABLE-US-00016 Intrinsic viscosity: 171 ml/g Carboxy end groups: 54 mmol/kg Amino end groups: 42 mmol/kg

EXAMPLE 10: PRODUCTION OF NYLON-6,6

(53) In this process, 85 kg of AH salt and 15 kg of water were charged to a stirred tank reactor of capacity 150 l. The reactor was then heated to a jacket temperature of 300 C. in order to obtain an internal pressure of 15.5 bar/abs. The pressure was held constant via a pressure-control valve until most of the water had been removed from the reactor. The pressure was then slowly reduced to atmospheric pressure within a period of one hour. As soon as atmospheric pressure had been reached, the reactor was flushed for 15 minutes with a stream of nitrogen at 3001/h. The reactor was then closed and pressurized with nitrogen at 16 bar/abs., in order to discharge the product from the reactor.

(54) The reaction in the extruder was operated as in example 6, the temperature being 270 C., the rotation rate being 240 revolutions per minute, and the discharge rate being 30 kg/h.

(55) The properties of the polyamide obtained were as follows:

(56) TABLE-US-00017 Intrinsic viscosity: 157 ml/g Carboxy end groups: 46 mmol/kg Amino end groups: 72 mmol/kg

EXAMPLE 11: POLYAMIDE BASED ON HEXAMETHYLENEDIAMINE, TEREPHTHALIC ACID, ISOPHTHALIC ACID, AND META-XYLYLENEDIAMINE

(57) In this process, the monomers were dissolved in water at 95 C. Water was charged to a stirred tank, which served as feed tank for the stirred tank reactor that followed. The liquid monomers (hexamethylenediamine and meta-xylylenediamine) were then added, followed by the acid monomers. Heating to 95 C. and mixing gave an aqueous solution of the monomers with the following composition:

(58) TABLE-US-00018 Component Amount Water 66 kg Isophthalic acid 11.12 kg Terephthalic acid 20.54 kg Hexamethylenediamine 21.11 kg meta-Xylylenediamine 1.21 kg

(59) The remainder of the production process was as described in example 6. The reactor was heated to a jacket temperature of 280 C. in order to achieve an internal pressure of 25 bar/abs. The pressure was held constant via a pressure-control valve until most of the water had been removed from the reactor. The resultant prepolymer was then passed from the stirred tank reactor into the corotating vented twin-screw extruder. The discharge rate was controlled by a discharge valve arranged directly above the extruder. This valve was heated to a temperature of 340 C. The prepolymer was postcondensed in the extruder until the desired molecular weight had been reached, with devolatilization of water. The temperature in the extruder was 320 C., and the rotation rate was 160 revolutions per minute. The discharge rate was 30 kg/h.

(60) The strands discharged from the extruder were cooled in a water bath and pelletized. The properties obtained were as follows:

(61) Intrinsic viscosity of 113 ml/g at throughput 5 kg/h, 91 ml/g at 10 kg/h, 78 ml/g at 15 kg/h, 65 ml/g at 20 kg/h, 55 ml/g at 30 kg/h.