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
  • C08G69/46—Post-polymerisation treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B9/00—Making granules
  • B29B9/10—Making granules by moulding the material, i.e. treating it in the molten state
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B9/00—Making granules
  • B29B9/16—Auxiliary treatment of granules
• • 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
  • C08G69/04—Preparatory processes
• • 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
  • C08G69/08—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from amino-carboxylic acids
  • C08G69/14—Lactams
  • C08G69/16—Preparatory processes
• • 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
  • C08G69/08—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from amino-carboxylic acids
  • C08G69/14—Lactams
  • C08G69/16—Preparatory processes
  • C08G69/18—Anionic polymerisation
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/12—Powdering or granulating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B9/00—Making granules
  • B29B9/16—Auxiliary treatment of granules
  • B29B2009/165—Crystallizing granules
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2077/00—Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material

Definitions

• the present invention relates to a process for the continuous production of polyamide granules comprising the steps:
• polyamides are well known, see e.g. L. Bottenbruch and R. Binsack, "Polyamide", Carl Hanser Verlag, Kunststoff, 1998.
• the standard process comprises several process stages in order to obtain a sufficient degree of polymerization and a virtually monomer-free polymer.
• VK tubes vertical reaction tubes
• the pressure is 1.0 - 1.2 bar absolute and the residence time is 18 - 22 h.
• the desired degree of polymerization with a correspondingly high molecular weight is achieved in the second stage.
• Granulation of the resulting polyamide melt with a relative viscosity of 2.3-3.0 (measured in 1% strength by weight solution in sulfuric acid), for example by underwater granulation at a pressure of 1 bar.
• Concentration of the extract water e.g. by evaporation, and recycling of the extract in the polymerization.
• Particularly economical is the direct recycling of the extract into the polymerization, i. the extract is not subjected to further purification steps such as distillation.
• additional purification steps may be required if e.g. In film or spinning applications special demands are placed on the quality of the recycled extract.
• Disadvantages of the established process are, in general, the long residence times, inter alia, during the hydrolytic polymerization and the high temperatures which are involved, which can lead to thermal damage to the polymer.
• a process with a polymerization of caprolactam in two stages is described in WO 95/01389 A1, wherein in the first stage under a pressure of 5 to 30 bar, a caprolactam conversion of 85% is achieved over a residence time of 2 to 4 hours becomes. In the second stage, adiabatic expansion and further polymerisation takes place. During this phase, foaming of the polymer may occur. The further processing takes place either by hot water extraction and subsequent solid phase postcondensation or by
• a polyamide melt is discharged at a pressure of at least 3 bar from a pressure reactor into a cooling liquid and granulated therein by the mentioned underwater granulation.
• This form of granulation requires a not too low relative viscosity of the polymer material of at least 1.6.
• lower viscosity polyamides can be granulated by dripping under vibration.
• Direct dropletization is understood to mean a process in which droplets directly from the molten liquid product, i. without the use of cutting or striking tools.
• WO 01/81450 A1 and DE 100 19 508 A1 which were carried out with drip devices from Rieter Automatik GmbH, D-63762 Grossostheim. These dripping devices are known under the type designation "DROPPO".
• a similar process for polyamide resins which are liquid at room temperature is described in DE 100 50 463 A1.
• the object of the invention is to specify a gentle process for the continuous production of polyamide granules, which manages with comparatively low residence times and which are run at comparatively low temperatures can.
• hydrolytic polymerization of a mixture of at least one lactam and water to a low-viscosity polyamide melt is carried out under a pressure of at least 5 bar
• the granulation of the low-viscosity polyamide melt is carried out by direct dripping while maintaining a pressure which at least corresponds to the vapor pressure of the water contained in the polyamide melt.
• the applied during the hydrolytic polymerization pressure is limited upwards by the strength of the pressure vessels used, but could be up to amount to 20 bar.
• a pressure vessel is suitable as in the prior art, a so-called. VK tube.
• the procedure according to the invention presupposes that it is possible to granulate the preferably low-viscosity polyamide melt prepared by the hydrolytic polymerization under pressure.
• granulation methods such as Underwater granulation, a certain minimum viscosity of the melt ahead, which is not achieved in the inventive method.
• Conventional granulation methods are therefore not usable in the context of the invention.
• the above-mentioned dropletizing methods are fundamentally more suitable at low melt viscosities.
• these methods and the apparatus developed for them have hitherto been used or operated only under ambient pressure. In the present case, however, the melt is under a pressure of at least 5 bar.
• the granulation of the preferably low-viscosity polyamide melt is carried out by dripping, but while maintaining a pressure which at least equal to the vapor pressure of the water contained in the polyamide melt. As a result, the foaming is effectively prevented.
• the minimum pressure required during the dripping is, depending on the steam pressure of the water contained in the polyamide melt, depending on the temperature traveled. In practice, it should not be below 3 bar. It should also be no more than 2 bar lower than the pressure under which the hydrolytic polymerization is carried out. However, in order to be on the safe side, one will choose a higher than the minimum required pressure and, if necessary, set it even higher than the pressure under which the hydrolytic polymerization is carried out.
• lactone e.g. ⁇ -caprolactam and / or lauryl lactam can be used.
• the mixture of at least one lactam and water may advantageously contain further polyamide-forming components, in particular a dicarboxylic acid, such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acid,
• a dicarboxylic acid such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acid
• Terephthalic acid or isophthalic acid and a diamine such as hexamethylenediamine, decanediamine, dodecanediamine or m-xylylenediamine.
• the mixture additionally contains chain regulators, such as mono- or dicarboxylic acids.
• the water content of the polymerization supplied lactam / water mixture should be at least the saturation pressure at polymerization conditions correspond, for example in caprolactam> 10% at a temperature of 240 0 C and a pressure of 15 bar.
• caprolactam In the case of caprolactam, a residence time of 0.5-5 h, in particular 1-3 h, is sufficient for hydrolytic polymerization under pressures> 5 bar.
• the hydrolytic polymerization of caprolactam can be carried out at a temperature of 200-250 0 C. Compared to the hydrolytic polymerization of the above-mentioned standard method in which the
• the temperature is greater than 240 0 C, thus lower temperatures are possible in the inventive method in this phase.
• melt viscosity 0.2 - 2.0 Pa's, in particular from 0.5 to 1.5 Pas. This corresponds to a relative viscosity of 1.3 - 1.5 for PA6.
• the hydrolytic polymerization can be carried out efficiently in a single stage in a pipe reactor suitable for overpressure, e.g. a so-called VK pipe.
• the dripping can take place in a dripping apparatus under the influence of vibration in a gas atmosphere. Suitable as a gas is eg nitrogen.
• a gas eg nitrogen.
• the melt is forced through a nozzle or a casting head and excited to vibrate.
• the granules obtained by the dropping in the form of substantially spherical melt droplets can then, as also already provided in the known Vertropfungsvon, after falling through a drop distance in the gas atmosphere in a cooling liquid are collected.
• the drop distance should be sufficiently long so that the melt drops have sufficient time for at least partial solidification.
• suitable as cooling liquid are ser, caprolactam or a mixture of both.
• a pressure of at least 3 bar must be maintained, which also requires the use of a special pressure vessel for dripping.
• the granules are discharged together with the cooling liquid, with at least partial pressure relief from the pressure region of the dropletization and then separated from the cooling liquid.
• the separation of the cooling liquid can be carried out by means of a centrifuge, through a sieve or in a hydrocyclone.
• the relative viscosity of a PA6 is preferably increased to a value of 2.4 - 4.2.
• the post-treatment of a low-viscosity PA6 is more preferably carried out with superheated steam at a temperature of 140-180 0 C, as is already known from WO 95/01389 Al or EP 0 284 968 Bl for other starting viscosities.
• the water vapor itself should have a temperature of 170-210 0 C for this purpose.
• the temperature of the granules during this post-treatment phase below the melting point of the granules and thus at PA6 in any case substantially lower than 220 0 C.
• the aftertreatment of a PA6 with the superheated steam results with particular advantage, as is also known from WO 95/01389 A1 or EP 0 284 968 B1, in addition to the increase in molecular weight simultaneously an extraction of unreacted monomer and of cyclic dimer the granules.
• the content of these components can be reduced to values of 0.1 to 1.0 wt .-%.
• the water content in the granules is reduced to values which require a considerably lower expenditure for the subsequent drying than is the case with the standard method described at the outset (example: 10 - 12% H 2 O in the standard method, 0.4 - 1%). in the method according to the invention).
• the aftertreatment of the granules can be carried out in the context of the process according to the invention in an extractor in countercurrent to the superheated steam.
• a residence time of 5 to 50 hours is expediently selected. Together with the residence time during the hydrolytic polymerization, this results in a total residence time of only 25-54 h for the process according to the invention compared to a total residence time of at least 60 h in the standard process mentioned in the introduction.
• the monomer is preferably recovered and introduced into the polymerization stage, dhzB in the aforementioned tubular reactor, returned.
• a particular advantage results from the way in which the unreacted caprolactone is separated off: While in conventional hot-water extraction the lactam is separated off in the liquid state, this is carried out in gaseous form during the extraction with steam. This includes a cleaning step for the reusable extract, without the need for additional equipment.
• water-soluble fractions of inorganic additives such as matting agents are co-extracted during hot water extraction and accumulate over time in polymerization and extraction. This accumulation of by-products leads to problems, which are, inter alia, in deficient
• the granules coming from the post-treatment is more preferably with nitrogen, for example, in a silo, even to a temperature of 40 - 50 0 C cooled. A residence time of 4 - 6 h is sufficient for this purpose. Through the nitrogen, the granules are dried and the remaining water vapor is still displaced from the cavities of granules. A residual water content of 0.04 to 0.06 wt .-% is achievable here.
• Fig. 2 shows the process steps of a process according to the invention for polyamide 6 using
• Granulation of the resulting polyamide melt by direct dripping at a pressure of 3 - 25 bar.
• tubular heat exchanger By means of a tubular heat exchanger were 30 kg / h of a mixture of 85% caprolactam and 15% water to 150 0 C and placed in a heated tubular reactor (VK tube). In the tubular reactor, a temperature of 242 0 C and a pressure of 6.8 bar was set. This resulted in a polyamide melt with a relative viscosity of 1.3, measured in sulfuric acid, and a melt viscosity of 0.5 Pas during a residence time of about 2.5 h.
• the low-viscosity polyamide melt was treated with a
• the granules were collected in the lower part of the container in water and cooled to 65 0 C.
• the granulate-water mixture was removed from the withdrawn and dosed with a volumetric pump in a centrifuge, in which the granules were separated from the liquid.
• the pressure was reduced to 3 bar to the centrifuge. After the centrifuge, a pressure of 1 bar prevailed.
• the granules were fed into an extractor. There it was conducted in countercurrent to 88 kg / h of superheated steam, with a temperature of 190 0 C, and brought to a temperature of 170 0 C. The residence time of the granules in the extractor was about 32 hours. By solid phase condensation, the relative viscosity of the granules increased to 2.8. At the same time, the content of caprolactam in the granules was reduced from 7.9 to 0.2% by weight and the content of cyclic dimer from 0.5 to 0.05% by weight. The water content dropped to 0.3 wt .-%.
• Example 1 was repeated, but a pressure of 3 bar was set in the dropletizer.
• the polymer formed a foam mass that could not be granulated.
• Example 1 was repeated, but with a different setting in the extractor.
• the supplied steam had a temperature of 160 0 C and the granules were heated to 140 0 C.
• the residual content of caprolactam in the granules was 0.6% by weight and the content of cyclic dimer 0.1% by weight.
• the water content reached 1.2 wt.%. With these values, the polyamide granules could not meet the usual requirements in terms of further processing (production of moldings, films, fibers or filaments).
• Example 1 was repeated, but instead of water, a solution of 30% by weight of caprolactam in water was used as a dropping agent. As a result, the content of cyclic dimer in the granules after extraction to 0.02 wt .-% could be reduced.
• the caprolactam content of the granules after extraction was 0.3% by weight and the water content was 0.3% by weight. At the outlet of the cooling silo, the water content was even only 0.04 wt .-%.

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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)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Polyamides (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

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• 2007
  • 2007-05-04 KR KR1020087027445A patent/KR20090009231A/ko not_active Application Discontinuation
  • 2007-05-04 EP EP07724885A patent/EP2046863A2/de not_active Withdrawn
  • 2007-05-04 WO PCT/EP2007/003960 patent/WO2007128521A2/de active Application Filing
  • 2007-05-04 CN CNA2007800160244A patent/CN101437870A/zh active Pending
  • 2007-05-04 JP JP2009508220A patent/JP2009535468A/ja active Pending

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