Classifications

• • 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
  • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
  • C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
  • C08J3/07—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media from polymer solutions
• • 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
  • C08G69/04—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
• • 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
• • 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
  • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
  • C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
• • 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
  • C08J3/14—Powdering or granulating by precipitation from solutions
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
  • C08L77/02—Polyamides derived from omega-amino carboxylic acids or from lactams thereof
• • 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
  • C08J2377/00—Characterised by the use of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Derivatives of such polymers
  • C08J2377/02—Polyamides derived from omega-amino carboxylic acids or from lactams thereof

Definitions

• the present invention relates to a process for the production of polyamide powders and the polyamide powder obtainable by this process.
• Polyamides are characterized by high chemical resistance and very good mechanical properties. It is known to use powdered coating compositions based on polyamides for producing paint-like coatings of metals. The coating takes place here, for example, by vortex sintering process, flame spraying or by electrostatic coating process. In this case, preference is given to polyamide powders which have a narrow particle size distribution, a round shape and a smooth surface. Polyamide powders which fulfill the abovementioned properties are readily fluidisable and therefore particularly suitable for coating processes. The polyamide powders described above are usually prepared by precipitation processes.
• DE 29 06 647 describes a process for the preparation of coating powders based on polyamides having at least 10 aliphatically bonded carbon atoms per Carboamid devis.
• the polyamides are dissolved under pressure at temperatures in the range of 130 to 150 ° C in ethanol. Subsequently, this solution is cooled to temperatures in the range of 100 to 125 ° C, wherein the polyamide precipitates in powder form. The polyamide powder is subsequently filtered off and dried.
• the polyamide powders obtainable by the process according to DE 29 06 647 have a relatively broad particle size distribution in the range from 40 to 250 ⁇ m.
• DE 1 494 563 describes a process for the preparation of polyamide powders dyed with pigments.
• the polyamides described in DE 1 494 563 are polyamides of ⁇ -caprolactam, of ⁇ -aminoundecanoic acid and of polyamides of hexamethylenediamine and adipic acid.
• To prepare the colored polyamide powder the polyamide is dissolved together with a pigment dispersion in an organic solvent. The mixture is heated to temperatures of> 100 ° C for this purpose. Subsequently, the solution thus obtained is cooled, wherein the polyamide precipitates together with the pigment as a powder.
• the dyed polyamide powder is subsequently filtered off and dried.
• EP 0 863 174 likewise describes a process for the preparation of polyamide powders by precipitation processes.
• the polyamide component used are polyamides of lactams or ⁇ -aminocarboxylic acids containing at least 10 carbon atoms. These polyamides are dissolved in an aliphatic alcohol having 1 to 3 carbon atoms under pressure. For this purpose, the solution is heated under pressure to 130 to 165 ° C. Subsequently, this solution is first cooled to a so-called nucleation temperature and held at this temperature for 10 minutes to 2 hours. Subsequently, the solution is further cooled, wherein the polyamide powder precipitates.
• the polyamide powder is subsequently filtered off and dried.
• EP 0 863 174 polyamide powders having a relatively narrow particle size distribution are obtained.
• One disadvantage of the process according to EP 0 863 174 is that very high pressures are necessary to achieve temperatures in the range from 130 to 165 ° C. when using alcohols as solvents. As a result, the process according to EP 0 863 174 is complicated and therefore expensive.
• CH 549 622 describes a process for the preparation of polymer powders, in which a polymer, for example polyamide, is melted in a solid at 25 ° C organic solvent. The resulting melt is subsequently poured out, whereby the melt solidifies. The resulting solid is subsequently ground and the resulting powder is spotted. From this powder, the solid at 25 ° C organic solvent is extracted in a further process step, whereby the polymer powder is obtained.
• the process according to CH 549 622 is very complicated since a large number of process steps are required for the preparation of the polymer powders, including melting, solidification, production of a powder by a grinding process, screening of the powder, subsequent extraction of the solid at 25 ° C. organic solvent and drying. The method described in CH 549 622 is therefore technically extremely complex and expensive.
• DE 1 089 929 describes a process for the preparation of polyamide powders for use in cosmetic and medical powders.
• Polyamides used are preferably polycaprolactams.
• the polyamides are subsequently heated in a carbamyl compound to give a clear solution of the polyamide in the carbamyl compound.
• Preferred carbamyl compounds are aliphatic compounds which are substituted on the nitrogen atom by alkyl groups. Particularly preferred are dimethylformamide, dimethylacetamide, diethylacetamide and acetamide.
• pyrrolidone is described as the cyclic carbamyl compound.
• DE 1 089 929 describes two alternatives.
• the polyamide powder by cooling the clear solution.
• the addition of water to the clear solution whereby the polyamide powder precipitates.
• the polyamide powders according to DE 1 089 929 are particularly suitable for use in cosmetic and medical powders.
• the polyamide powders obtained have a particle size distribution in the range from 1 to 25 ⁇ m.
• the US 3,446,782 also describes a process for the preparation of polyamide powders.
• an aqueous solution of a lactam is initially charged and subsequently the polyamide is added.
• the resulting mixture is subsequently heated in an autoclave with stirring.
• the temperature is chosen to be above the softening point of the polyamide and below the melting point of the polyamide.
• the concentration of the lactam in the aqueous solution is in the range of 10 to 95 wt .-%, based on the total weight of the aqueous solution.
• a dispersion of the polyamide in the aqueous solution is obtained by stirring and heating.
• the present invention is therefore based on the object to provide a process for the preparation of polyamide powders, which does not have the disadvantages of the prior art described above or only to a reduced extent.
• the process should be simple and inexpensive to carry out and provide polyamide powder having a narrow particle size distribution and a spherical geometry.
• the process should also reduce the formation of fines or coarse fraction compared to the process described in the prior art.
• This object is achieved by a process for the preparation of polyamide powder comprising the process steps a) heating a mixture containing a polyamide and a lactam to a temperature greater than a turbidity temperature (T T ) above which the polyamide is completely dissolved in the lactam, to obtain a melt , the the process steps a) heating a mixture containing a polyamide and a lactam to a temperature greater than a turbidity temperature (T T ) above which the polyamide is completely dissolved in the lactam, to obtain a melt , the the process steps
• the process according to the invention gives polyamide powders which have a narrow particle size distribution.
• the particles of polyamide powder also have a round shape (sphericity).
• the inventive method significantly reduces the formation of fine and coarse particles in the polyamide powder in comparison with the process described in the prior art.
• Polyamide As polyamide, exactly one polyamide can be used. It is also possible to use mixtures of two or more polyamides. Preferably, exactly one polyamide is used.
• Suitable polyamides generally have a viscosity number of from 70 to 350, preferably from 70 to 240 ml / g.
• the determination of the viscosity number is carried out according to the invention from a 0.5 wt .-% solution of the polyamide in 96 wt .-% sulfuric acid at 25 ° C according to ISO 307th
• polyamides semicrystalline or amorphous polyamides are preferred.
• Suitable polyamides have a weight-average molecular weight (M w ) in the range from 500 to 2,000,000 g / mol, preferably in the range from 5,000 to 500,000 g / mol and particularly preferably in the range from 10,000 to 100,000 g / mol ,
• M w weight average molecular weight
• polyamides for example, polyamides are suitable, which are derived from lactams with 7 to 13 ring members. Further suitable polyamides are polyamides which are obtained by reacting dicarboxylic acids with diamines.
• polyamides derived from lactams include polyamides derived from polycaprolactam, polycapryl lactam and / or polylaurolactam.
• co-aminoalkyl nitriles are obtainable from co-aminoalkyl nitriles.
• Preferred co-aminoalkylnitrile is aminocapronitrile, which leads to polyamide 6.
• dinitriles can be reacted with diamine.
• Adiponitrile and hexamethylenediamine are preferred, the polymerization of which leads to polyamide 66.
• the polymerization of nitriles takes place in the presence of water and is also referred to as direct polymerization.
• dicarboxylic acid alkanes aliphatic dicarboxylic acids having 6 to 36 carbon atoms, preferably 6 to 12 carbon atoms, and especially preferably 6 to 10 carbon atoms are used.
• aromatic dicarboxylic acids are suitable.
• adipic acid, azelaic acid, sebacic acid, dodecanedioic acid and also terephthalic acid and / or isophthalic acid may be mentioned here as dicarboxylic acids.
• Suitable diamines are, for example, alkanediamines having 4 to 36 carbon atoms, preferably alkanediamines having 6 to 12 carbon atoms, in particular alkanediamines having 6 to 8 carbon atoms and aromatic diamines, for example m-xylylenediamine, di (4-aminophenyl) methane, di- (4 -aminocyclohexyl) methane, 2,2-di- (4-aminophenyl) -propane and 2,2-di- (4-aminocyclohexyl) -propane and 1, 5-diamino-2-methyl-pentane.
• alkanediamines having 4 to 36 carbon atoms preferably alkanediamines having 6 to 12 carbon atoms, in particular alkanediamines having 6 to 8 carbon atoms and aromatic diamines, for example m-xylylenediamine, di (4-aminophenyl) methane, di- (4 -aminocycl
• Preferred polyamides are polyhexamethylene adipamide, polyhexamethylene sebacamide and polycaprolactam and also copolyamide 6/66, in particular with a content of 5 to 95% by weight of caprolactam units.
• polyamides which are obtainable by copolymerization of two or more of the monomers mentioned above and below, or mixtures of several polyamides, the mixing ratio being arbitrary. Mixtures of polyamide 66 with other polyamides, in particular copolyamide 6/66, are particularly preferred as mixtures.
• Suitable polyamides are thus aliphatic, partially aromatic or aromatic polyamides.
• aliphatic polyamides means that the polyamides are exclusively composed of aliphatic monomers
• partially aromatic polyamides means that the polyamides are composed of both aliphatic and aromatic monomers.
• aromatic polyamides means that the polyamides are composed exclusively of aromatic monomers.
• PA 9 9-aminopelargonic acid PA 1 1 1 1 -aminoundecanoic acid
• PA 46 tetramethylenediamine, adipic acid
• PA 66 hexamethylenediamine, adipic acid
• PA 69 hexamethylene diamine, azelaic acid
• PA 610 hexamethylenediamine, sebacic acid
• PA 612 hexamethylenediamine, decanedicarboxylic acid
• PA 613 hexamethylenediamine, undecanedicarboxylic acid
• PA 1212 1, 12-dodecanediamine, decanedicarboxylic acid
• PA 1313 1, 13-diaminotridecane, undecanedicarboxylic acid
• PA 6T hexamethylenediamine, terephthalic acid
• PA MXD6 m-xylyenediamine, adipic acid
• PA 61 hexamethylenediamine, isophthalic acid
• PA 6-3-T trimethylhexamethylenediamine, terephthalic acid
• PA 6 / 6T (see PA 6 and PA 6T)
• PA 6/66 (see PA 6 and PA 66)
• PA 6/12 see PA 6 and PA 12
• PA 66/6/610 see PA 66, PA 6 and PA 610)
• PA 6I / 6T see PA 61 and PA 6T
• PA PA PACM 12 diaminodicyclohexylmethane, laurolactam
• PA 6I / 6T / PACM such as PA 6I / 6T and diaminodicyclohexylmethane
• the present invention thus also provides a process in which the polyamide is at least one polyamide selected from the group consisting of PA 4, PA 6, PA 7, PA 8, PA 9, PA 1 1, PA 12, PA 46, PA 66, PA 69, PA 610, PA 612, PA 613, PA 1212, PA 1313, PA 6T, PA MXD6, PA 61, PA 6-3-T, PA 6 / 6T, PA 6/66, PA 6/12 , PA 66/6/610, PA 6I / 6T, PA PACM 12, PA 6I / 6T / PACM, PA 12 / MACMI, PA 12 / MACMT, PA PDA-T and copolyamides of two or more of the aforementioned polyamides.
• the polyamide is at least one polyamide selected from the group consisting of PA 4, PA 6, PA 7, PA 8, PA 9, PA 1 1, PA 12, PA 46, PA 66, PA 69, PA 610, PA 612, PA 613, PA 1212, PA 1313, PA 6T, PA MXD6, PA
• the polyamide is at least one polyamide selected from the group consisting of polyamide 6 (PA 6), polyamide 66 (PA 66), polyamide 610 (PA 610) and polyamide 6 / 6T (PA 6 / 6T).
• Particularly preferred polyamides are polyamide 6 (PA 6) and / or polyamide 66 (PA 66), with polyamide 6 (PA 6) being particularly preferred.
• lactam is understood to mean cyclic amides which contain 3 to 12 carbon atoms, preferably 4 to 6 carbon atoms, in the ring.
• Suitable lactams are, for example, selected from the group consisting of 3-aminopropanoic acid lactam ( ⁇ -lactam, ⁇ -propionlactam), 4-aminobutanoic acid lactam ( ⁇ -lactam, ⁇ -butyrolactam), 5-aminopentanoic acid lactam ( ⁇ -lactam, ⁇ -valerolactam), 6 Aminohexanoic acid lactam ( ⁇ -lactam; ⁇ -caprolactam), 7-aminoheptanoic acid lactam ( ⁇ -lactam; ⁇ -heptanolactam), 8-aminooctanoic acid lactam ( ⁇ -lactam; ⁇ -octanolactam), 9-nonanoic acid lactam ( ⁇ -lactam
• the present invention thus also provides a process in which the lactam is selected from the group consisting of 3-aminopropanoic acid lactam, 4-aminobutanoic acid lactam, 5-aminopentanoic acid lactam, 6-aminohexanoic acid lactam, 7-aminoheptanoic acid lactam, 8-aminooctanoic acid lactam, 9-nonanoic acid lactam, 10 Decanoic acid lactam, 1-undecanoic acid lactam and 12-dodecanoic acid lactam.
• the lactam is selected from the group consisting of 3-aminopropanoic acid lactam, 4-aminobutanoic acid lactam, 5-aminopentanoic acid lactam, 6-aminohexanoic acid lactam, 7-aminoheptanoic acid lactam, 8-aminooctanoic acid lactam, 9-non
• the lactams may be unsubstituted or at least monosubstituted. In the event that at least monosubstituted lactams are used, these may carry on the nitrogen atom and / or on the carbon atoms of the ring one, two or more substituents which are independently selected from the group consisting of C to C 10 alkyl, C 5 - to C 6 -cycloalkyl and C 5 - to C 10 -aryl.
• Suitable C 1 to C 10 -alkyl substituents are methane, ethane, propyl, isopropyl, n-butyl, sec-butyl and tert-butyl.
• Suitable C 5 to C 6 cycloalkyl substituents are cyclohexyl.
• Preferred C 5 to Cio-aryl substituents are phenyl and antranyl.
• Unsubstituted lactams are preferably used, preference being given to ⁇ -lactam ( ⁇ -butyrolactam), ⁇ -lactam ( ⁇ -valerolactam) and ⁇ -lactam ( ⁇ -caprolactam). Particularly preferred are ⁇ -lactam ( ⁇ -valerolactam) and ⁇ -lactam ( ⁇ -caprolactam), with ⁇ -caprolactam being particularly preferred.
• process step a) is a mixture containing a polyamide and a lactam, heated to temperatures above a cloud point temperature (T T), above which the Polyamide completely dissolved in the lactam is present.
• T T cloud point temperature
• the polyamide Above the clouding temperature (T T ), the polyamide is completely dissolved in the molten lactam. In other words, this means that an optically clear solution of the polyamide is obtained in the molten lactam.
• the melt of the lactam forms the solvency in this solution, the polyamide forms the solvate.
• the polyamide molecules are homogeneously and statistically distributed above the turbidity temperature (T T ) in the molten lactam and can not be separated by filtration. Above the clouding temperature (T T ), polyamide and lactam are thus present as an optically clear solution, the polyamide molecules being distributed homogeneously and statistically in the lactam.
• the turbidity temperature (T T ) in the process according to the invention depends on the type of lactam, the type of polyamide and the concentration of the polyamide in the melt produced in process step a).
• the mixture containing the polyamide and the lactam is generally at temperatures in the range of 170 ° C to 250 ° C, preferably at temperatures in the range of 170 ° C to 230 ° C, particularly preferably at temperatures of 170 ° C to 210 ° C and in particular heated to temperatures in the range of 180 ° C to 200 ° C.
• the mixture is heated in process step a) to a temperature which is at least 10 ° C below the melting temperature of the polyamide used.
• the mixture is particularly preferably in process step a) to a temperature in the range of 10 to 50 ° C below the melting temperature of the polyamide used, more preferably to a temperature in the range of 10 to 35 ° C below the melting temperature of the polyamide used and in particular to a Temperature in the range of 10 to 20 ° C below the melting temperature of the polyamide used, heated.
• the melting temperature of the polyamide used in process step a) is defined as the temperature at which the polyamide in the pure substance of the solid state of aggregation at least partially passes into the liquid state.
• the melting temperature of the polyamide is determined by differential scanning colorimetry.
• the present invention thus also provides a process in which the mixture is heated in step a) to obtain the melt to a temperature in the range of 170 ° C to 250 ° C. As a result, the lactam contained in the mixture melts and the polyamide completely dissolves in the molten lactam.
• the melt produced in process step a), which contains the polyamide completely dissolved in the lactam generally contains less than 5% by weight of water, preferably less than 4% by weight of water, more preferably less than 2% by weight of water and in particular preferably less than 1% by weight of water, in each case based on the total weight of the melt obtained in process step a), which contains the polyamide completely dissolved in the lactam.
• the lower limit of the water content of the melt obtained in process step a) is generally in the range from 0 to 0.5% by weight, preferably in the range from 0 to 0.3% by weight, particularly preferably in the range from 0 to 0, 1 wt .-%, each based on the total weight of the melt obtained in step a).
• the present invention thus also provides a process in which the water content of the melt obtained in process step a) is in the range from 0 to less than 5% by weight, based on the total weight of the melt obtained in process step a).
• the water content of the melt obtained in process step a) is decisively determined by the water content of the polyamide used and by the water content of the lactam used.
• the water content of the polyamide used is generally in the range of 0 to ⁇ 2.5 wt .-%, preferably in the range of 0 to 2 wt .-% and particularly preferably in the range of 0 to 1 wt .-%, each based on the total weight of the polyamide used in process step a).
• the lower limit of the water content of the polyamide used in process step a) is generally in the range from 0 to 0.5 wt .-%, preferably in the range of 0 to 0.2 wt .-%.
• the water content of the lactam used in process step a) is generally in the range from 0 to ⁇ 5 wt .-%, preferably in the range of 0 to ⁇ 4 wt .-%, particularly preferably in the range of 0 to 2 wt .-%, and particularly preferably in the range from 0 to 1 wt .-%, each based on the total weight of the lactam used in step a).
• the lower limit of the water content of the lactam used in process step a) is generally in the range from 0 to 0.5 wt .-%, preferably in the range of 0 to 0.2 wt .-%, each based on the total weight of the process step a ) used lactams.
• the water content of the polyamide used in process step a) and the water content of the lactam used in process step a) is generally selected so that the melt obtained in process step a) has the above-described water content, for which the above statements and preferences apply accordingly.
• the mixture of lactam and polyamide used in process step a) and the melt obtained in process step a) are thus essentially anhydrous.
• This has the advantage that the melt formed in process step a) represents a true solution of the polyamide in the lactam.
• the formation of a dispersion or emulsion of the polyamide in the lactam is thereby prevented in process step a).
• the polyamide is used in process step a) in amounts such that the melt obtained in process step a) contains the polyamide in amounts ranging from 5 to 60% by weight, preferably in the range from 8 to 50% by weight, and particularly preferably in the range of 10 to 30 wt .-%, in each case based on the total weight of the melt obtained in process step a), which contains the polyamide completely dissolved in the lactam.
• the present invention thus also provides a process in which the melt obtained in process step a) contains the polyamide in amounts ranging from 5 to 60% by weight, based on the total weight of the melt obtained in process step a).
• additives are antinucleating agents.
• Preferred antinucleating agents are selected from the group consisting of lithium chloride, nigrosine, methylene blue and neutral red.
• Preferred antinucleating agent is nigrosine.
• Nigrosine is one synthetic black dye, also known as "Solvent Black 5" (Color Index 50415) Nigrosine can be prepared, for example, by heating nitrobenzene and aniline and aniline hydrochloride in the presence of copper or iron.
• Methylene blue is a dye which is also referred to as ⁇ /, ⁇ /, ⁇ / ', ⁇ /' - tetramethylenethionine chloride or Basic Blue 9 (Color Index 52015, CAS numbers 61-73-4 and 122965-43-9, respectively) becomes.
• Neutral red is a dye, also referred to as 3-amino-7-dimethylamino-2-methylphenazine hydrochloride or toluene red (Color Index 50040: CAS number 553-24-2).
• the additives are generally added in process step a) in amounts such that the polyamide powder obtained after process step c) has an additive content in the range from 0 to 3% by weight, preferably in the range from 0, 5 to 2.5 wt .-%, particularly preferably in the range of 0.5 to 2 wt .-%, in particular in the range of 1 to 2 wt .-%, each based on the total weight of the polyamide powder obtained according to process step c) ,
• the present invention thus also provides a process in which the melt contained in process step a) contains at least one antinucleating agent selected from the group consisting of lithium chloride, nigrosine, methylene blue and neutral red.
• the present invention furthermore relates to a process in which the antinucleating agent is added in process step a) in amounts such that the polyamide powder obtained after process step c) contains the antinucleating agent in amounts in the range from 0.1 to 3% by weight , based on the total weight of the polyamide obtained according to process step c).
• Process step a) is carried out in a preferred embodiment under a protective gas atmosphere.
• a protective gas in this case, for example, nitrogen can be used.
• Process step a) can be carried out under atmospheric pressure, but process step a) is preferably carried out under pressure.
• the pressure during process step a) is generally in the range of 0.5 to 10 bar abs.
• Process step a) is preferably carried out under agitation.
• Suitable devices for carrying out the process step a) to obtain the melt which contains the polyamide completely dissolved in the lactam are known to the person skilled in the art.
• Suitable devices are, for example, reactors, the Have stirring unit and can be pressurized.
• Suitable stirrers are, for example, anchor stirrers.
• the melt obtained in process step a) is cooled to a temperature ⁇ the turbidity temperature (T T ).
• the melt contained in process step a) is cooled to a temperature which is at least 0.5 ° C, preferably at least 1 ° C below the turbidity temperature (T T ).
• T T the clouding temperature
• the melt melts that is, it is no longer visually clear.
• the clouding can be perceived purely visually with the naked eye.
• the reference value used here is the transmission of the melt produced in process step a), which contains the polyamide completely dissolved in the lactam.
• the transmission of the melt obtained in process step a) is hereby set to 100% and subsequently used as the reference value.
• the transmission decreases.
• the transmittance of the melt during cooling in process step b) when reaching or falling below the turbidity temperature (T T ) decreases by at least 5%, preferably by at least 20%, particularly preferably by at least 30%, based on the transmission in the process step a) obtained melt containing the polyamide completely dissolved in the lactam (transmission 100%).
• melt in process step b) ie when reaching or falling below the turbidity temperature (T T ) and before adding the water, when reaching or falling below the turbidity temperature (T T ) has a maximum transmission of 95%, preferably of not more than 80% and more preferably of not more than 70%, based on the transmission of the melt obtained in process step a) (transmission 100%).
• process step b) in addition to water, further solvents such as, for example, alcohol may be added. Suitable further solvents are for example, methanol, ethanol, n-propanol or isopropanol. In the event that further solvents are added in process step b), these can be added before or after the addition of water. In addition, it is possible in process step b) to add a mixture which contains water and at least one further solvent. It is according to the invention only necessary that in step b) water is added. In a preferred embodiment, only water is added in process step b).
• the addition of water can be added according to the invention before or after solidification of the melt 10.
• the water dissolves the lactam, whereby the suspension of the polyamide powder is obtained.
• the addition of water in step b) before the solidification of the melt is added according to the invention before or after solidification of the melt 10.
• the clouding temperature (T T ) thus forms the upper temperature limit at which water can be added in process step b).
• the lower temperature limit up to which water can be added in process step b) generally represents the melting temperature (T s ) (melting point) of the lactam used in the process according to the invention.
• T s melting temperature
• the melting point is at a pressure according to the invention
• the melting temperature (T s ) is equal to the melting point of the lactam.
• the present invention thus also provides a process in which the lactam has a melting temperature (T s ) and the melt obtained in process step a) in process step b) to a temperature in the range of equal to the clouding temperature (T T ) to greater than Melting temperature (T s ) of the lactam is cooled and then water is added.
• T s melting temperature
• T s clouding temperature
• the lower limit, 30 must be added before the water, thus 68 ° C.
• the lower limit above which water must be added in process step b) is thus 40 ° C.
• the turbidity temperature (T T ) depends, as stated above, on the properties of the polyamide and the lactam and on the concentration of the polyamide in the melt. Suitable temperature ranges within which the addition of water according to process step b) can be carried out are generally in the range of 80 to ⁇ 170 ° C, preferably in the range of 90 to 160 ° C, more preferably in the range of 100 to 150 ° C and in particular Range of 120 to 40 145 ° C, wherein the addition of water takes place only after reaching or falling below the turbidity temperature (T T ).
• step b) the addition of water in step b) in a temperature range whose upper limit is equal to the turbidity temperature (T T ) and its lower limit by a temperature which is not more than 20 ° C below the crystallization temperature (T K ) of the polyamide used lies, is defined.
• the present invention thus also relates to a process in which the polyamide has a crystallization temperature (T K ) and the melt obtained in process step a) in process step b) to a temperature in the range of equal to the turbidity temperature (T T ) to a maximum of 20 ° C is cooled below the crystallization temperature (T K ) of the polyamide and then water is added.
• T K crystallization temperature
• Polyamides are generally semicrystalline.
• the degree of crystallinity of polyamides is generally in the range of 20 to 50%.
• the degree of crystallinity is also referred to as crystallinity or degree of crystallinity.
• a melt is formed which contains the polyamide completely dissolved in the lactam.
• the crystalline regions of the polyamide dissolve.
• the polyamide goes from the form of a solid in the state of matter of a solution.
• the polyamide absorbs heat (energy). This heat is also called latent heat.
• the latent heat is composed of the enthalpy that must be used to dissolve crystalline areas and the enthalpy required for the transition from the solid to the solution.
• the two enthalpies are also referred to as enthalpy of crystallization or enthalpy of solution.
• the clouding temperature (T T ) is first reached in process step b).
• the turbidity temperature (T T ) is different from the crystallization temperature (T K ).
• the crystallization temperature (T K ) is generally below the turbidity temperature (T T ).
• the polyamide Upon reaching the crystallization temperature (T K ), the polyamide is completely from the solution in the solid state, wherein the crystalline regions form again.
• the heat (latent heat) absorbed by the polyamide in process step a) is released here again in process step b).
• the onset of crystallization that is, the achievement of the crystallization temperature (T K ), can therefore be detected by a temperature rise.
• crystallization temperature (T K ) is thus understood to mean the temperature at which the polyamide releases the latent heat received in process step a), that is to say the sum of solution enthalpy and crystallization enthalpy to the environment.
• the crystallization temperature (T K ) can be determined, for example, by a resistance thermometer (PT100) or a thermocouple in combination with a torque measurement.
• the torque shows a marked change in slope at the crystallization temperature (T K ), the torque increases significantly, while it increases only slightly in the cooling phase due to the viscosity increase of the continuous phase.
• the crystallization temperature (T K ) is determined by a temperature sensor, which is located in the reactor and measures the temperature of the melt in process step b).
• the crystallization temperature (T K ) can therefore be detected by a temperature rise of the melt in process step b).
• the addition of water in process step b) takes place above a temperature of not more than 20 ° C., preferably not more than 10 ° C., more preferably not more than 5 ° C. and more preferably not more than 2 ° C. below the crystallization temperature (T K ). of the polyamide used.
• the crystallization temperature (T K ) also depends on the properties of the polyamide and the lactam and on the concentration of the polyamide in the melt.
• the amount of water added in process step b) can vary within wide limits.
• at least one part by weight of water preferably at least 2 parts by weight of water, more preferably at least 3 parts by weight of water and in particular at least 5 parts by weight of water are added in step b) based on one part by weight of the melt contained in the melt or at least partially solidified melt.
• a maximum of 20 parts by weight of water preferably not more than 15 parts by weight of water, more preferably not more than 10 parts by weight of water and in particular not more than 8 parts by weight of water are added, based in each case on one part by weight of the polyamide contained in the melt or the at least partially solidified melt.
• this is not associated with an advantageous effect, since larger amounts of water have to be separated in the subsequent process steps, which makes the process according to the invention more expensive.
• the present invention thus also provides a process in which the amount of water added in process step b) is from 1 to 100 parts by weight of water, based on one part by weight of the polyamide contained in the melt.
• the temperature of the water added in process step b) can vary within wide limits. In general, the temperature of the water added in process step b) is in the range from 20 to ⁇ 170 ° C., preferably in the range from 20 to 160 ° C., more preferably in the range from 50 to 150 ° C. and especially preferably in the range from 60 to 145 ° C, wherein the addition of water takes place only after reaching or falling below the turbidity temperature (T T ).
• the present invention thus also provides a process in which the addition of water in process step b) takes place at a temperature in the range from 20 to ⁇ 170 ° C. and after reaching or falling below the turbidity temperature (T T ).
• process step b) is carried out under pressure in a preferred embodiment.
• a closed reactor such as an autoclave
• Process step b) is also carried out under agitation in a preferred embodiment. Since process steps a) and b) are preferably carried out in the same reactor, the statements and preferences given for process step a) apply correspondingly to the reactors.
• the present invention thus also relates to a process in which process steps a) and b) are carried out in the same reactor. After addition of water, a suspension is obtained in process step b) which contains the polyamide powder suspended in a solution of water and the lactam.
• Process Step c) The polyamide powder obtained in process step b) in the form of a suspension can be separated off in process step c).
• the separation of the polyamide powder is carried out by the skilled person known methods such as filtration or centrifugation.
• the polyamide powder is thus separated from the solution containing water and the lactam.
• the polyamide powder thus obtained may optionally be worked up further.
• the polyamide powder is washed with water in order to separate any residues of the lactam contained from the polyamide powder.
• the polyamide powder is washed after the separation according to process step c) with water and subsequently dried.
• the drying can take place thermally.
• Preferred thermal drying methods are, for example, drying in one with hot air pressurized fluidized bed or drying under a nitrogen atmosphere in vacuo at elevated temperatures, for example in the range of 50 to 100 ° C.
• the polyamide powders obtainable by the process according to the invention have a narrow particle size distribution (particle size distribution) and a substantially round shape.
• SPHT value S Georgrizticians value
• the sphericity value of the polyamide particles indicates the ratio of the surface of the polyamide particles to the surface of ideal spheres of equal volume.
• the sphericity value can be determined by image analysis using, for example, a camsizer.
• the polyamide powders obtainable by the process according to the invention generally have a sphericity value in the range from 0.4 to 1.0.
• the polyamide powders obtainable by the process according to the invention have a narrow particle size distribution.
• the polyamide powder In general, the polyamide powder
• the polyamide powder in a preferred embodiment, the polyamide powder
• the present invention thus also provides a process in which the polyamide powder obtained after process step c)
• D10 value in this context means the particle size at which 10% by volume of the particles, based on the total volume of the particles, is less than or equal to the D10 value and 90% by volume of the particles based on the total volume of the particles greater than the D10 value are.
• the D50 value is understood to mean the particle size at which 50% by volume of the particles, based on the total volume of the particles, is less than or equal to the D50 value and 50% by volume of the particles, based on the total volume of the particles are greater than the D50 value.
• the D90 value is understood to be the particle size at which 90% by volume of the particles, based on the total volume of the particles, is less than or equal to the D90 value and 10% by volume of the particles, based on the total volume of the particles greater than the D90 value.
• the polyamide powder obtained in process step b) is measured in the form of the suspension obtained in process step b).
• the D10, D50 and D90 values are determined by means of laser diffraction using a Mastersizer 3000 from Malvern. The evaluation is carried out by means of Oberhofer diffraction.
• a measure of the width of the particle size distribution is the difference between the D90 and D10 values (D90 value minus D10 value). The closer these two values are together, that is, the smaller the difference, the narrower the particle size distribution.
• the polyamide powders obtainable by the process according to the invention generally have values in the range from 25 to 110 ⁇ m, preferably in the range from 10 to 50 ⁇ m, for the difference between the D90 and D10 values.
• the chip is defined as (D90-D10) / D50.
• the particle size of the polyamide powder obtainable by the process according to the invention is generally in the range from 0.5 to 2.5, preferably in the range from 0.6 to 1.2.
• the polyamide powders obtainable by the process according to the invention have small amounts of fines and small amounts of coarse fraction.
• fine fraction is understood to mean polyamide particles which have a particle size of less than 10 ⁇ m.
• coarse fraction is understood according to the invention to mean polyamide particles which have a particle size of greater than 130 ⁇ m.
• the polyamide powders obtainable by the process according to the invention contain less than 5% by weight, preferably less than 4% by weight and particularly preferably less than 2% by weight, based in each case on the total weight of the polyamide powder.
• the polyamide powders obtainable by the process according to the invention contain less than 5% by weight, preferably less than 4% by weight and more preferably less than 2 wt .-% coarse fraction, each based on the total weight of the polyamide powder.
• the polyamide powder obtained by the process according to the invention can be further processed without further classification. Separation of coarse or fines by sieving or screening is not required in some cases. As a result, consuming and costly classification steps can be saved in the inventive method.
• the present invention thus also provides the polyamide powder obtainable by the process according to the invention.
• the present invention thus also relates to the use of the polyamide powder according to the invention in coating processes, preferably powder coating processes.
• the present invention furthermore relates to the use of the polyamide powders according to the invention in processes for sintering, preferably in processes for laser sintering.
• the present invention thus also relates to the use of the polymamide powder obtainable by the process according to the invention as a sintering powder in a process for the production of moldings by selective laser sintering.
• the polyamide powder had a D 10 value of 24.0 ⁇ , a D50 value of 62.7 ⁇ and a D90 value of 129 ⁇ .
• the particle size distribution was determined by means of laser diffraction with a Mastersizer 30005 from Malvern. The evaluation was carried out by means of Fraunhofer diffraction.
• the internal temperature of the pressure reactor slightly increased. This is due to the onset of crystallization of the polyamide 6.
• the water preheated in the second pressure cylinder was supplied to the pressure reactor with stirring. The resulting suspension was stirred for 30 minutes. Subsequently, it was cooled to room temperature (20 ° C) and the resulting polyamide powder was separated as described above for Example 1, worked up and measured.
• the polyamide powder thus obtained had a D10 value of 22 ⁇ , a D50 value of 38 ⁇ and a D90 value of 60 ⁇ .
• Example 3 The particle size distribution was determined by means of laser diffraction with a Mastersizer 30000 from Malvern. The evaluation was carried out by means of Fraunhofer diffraction. Example 3
• ⁇ -caprolactam 166.5 g was placed in a pressure reactor with internal thermometer and rendered inert with nitrogen. Subsequently, the ⁇ -caprolactam was melted by heating to 5 120 ° C. 18.5 g of polyamide 6 having a viscosity number of 120 ml / g and 0.69 g Ultrabatch (40% nigrosine, 60% polyamide 6) were added with stirring to the ⁇ -caprolactam melt and subsequently heated to 190 ° within 5 hours C (internal temperature) heated, whereby a melt was obtained which contained the polyamide 6 completely dissolved in the ⁇ -caprolactam.
• the polyamide powder thus obtained had a D10 value of 37.2 ⁇ , a D50 value of 63.2 ⁇ and a D90 value of 104.5 ⁇ .
• the particle size distribution was determined by means of laser diffraction with a Mastersizer 3000 from Malvern. The evaluation was carried out by means of Fraunhofer diffraction.
• ⁇ -caprolactam 166.5 g was placed in a pressure reactor with internal thermometer and rendered inert with nitrogen. Subsequently, the ⁇ -caprolactam was melted by heating to 120 ° C. To the ⁇ -caprolactam melt was added 18.5 g of polyamide 6 having a viscosity number of 120 ml / g and 0.69 g Ultrabatch (40% nigrosine, 60% polyamide 6) with stirring and then with stirring within 5 hours heated to 190 ° C (internal temperature), whereby a melt was obtained, which contained the polyamide 6 completely dissolved in the ⁇ -caprolactam.
• the polyamide powder thus obtained had a D10 value of 19.4 ⁇ , a D50 value of 33.2 ⁇ and a D90 value of 49.2 ⁇ .
• the particle size distribution was determined by means of laser diffraction with a Mastersizer 3000 from Malvern. The evaluation was carried out by means of Fraunhofer diffraction.
• the polyamide powder thus obtained had a D10 value of 30.2 ⁇ , a D50 value of 57.6 ⁇ and a D90 value of 100.4 ⁇ .
• the particle size distribution was determined by means of laser diffraction with a Mastersizer 3000 from Malvern. The evaluation was carried out by means of Fraunhofer diffraction.

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