Polymer powder comprising polyamide use thereof in a moulding method and moulded body made from said polymer powder

European).

OK II-12 / P24445PL00

EP 1 742 986 B1

Polymeric polyamide powder, use in a method of shaping and shaped article made from this polymeric powder

The rapid and continuous preparation of prototypes has recently been a frequently asked task. Particularly useful are processes that operate on the basis of powder materials and in which the desired structures are produced in layers by selective melting and solidification. It is possible to dispense with supporting structures for hanging and cutting, since the powder layer surrounding the molten areas ensures sufficient supporting action. Additional work on removing supports is also out of the question. These methods are also suitable for making small runs.

The invention relates to a polymer powder based on XY type polyamide, preferably polyamide XY type produced by polycondensation of diamines with dicarboxylic acids, the use of this powder in shaping methods and shaped products produced using this powder with a layered method by which the layers of the layer are selectively melted powder. After cooling and solidifying the previously melted areas layer by layer, the shaped article can be removed from the powder bed.

The selectivity of the layered process can take place, e.g., through susceptors, absorbers, inhibitors, masks, or by introducing focused energy, such as e.g. a laser beam, or through glass fibers. The introduction of energy is achieved by electromagnetic radiation.

The following text discusses several methods by which shaped products can be made from the powder of the invention without being limited to this invention.

Selective laser sintering is a method that is particularly well suited for rapid prototype production. In this method, the plastic powder is briefly irradiated in the chamber with a laser beam, whereby the powder particles that have encountered the laser beam melt. The molten particles move inside and solidify quickly again into a solid mass. By repeated exposure of new layers applied, it is possible to produce three-dimensional solids simply and quickly.

The method of laser sintering (rapid prototype production) to show molded products made of powder polymers is comprehensively described in US 6136948 and WO 96/06881 (both DTM Corporation). A large number of polymers and copolymers such as polyacetate, polypropylene, polyethylene, ionomers and polyamide are claimed in this application.

Other well-suited methods are the SIV method, described in WO 01/38061, or the method described in EP 1015214. Both methods work with flat infrared heating to melt the powder. The melting selectivity is achieved in the first method by applying an inhibitor, and in the second method by means of a mask. A further method is described in DE 103 11 438. In this method, the energy necessary for melting is introduced by means of a microwave generator, and selectivity is obtained by applying a susceptor.

For the described methods for rapid prototype production or rapid production (RP or RM process), powder substrates can be used, in particular polymers selected preferably from polyesters, polyvinyl chloride, polyacetal, polypropylene, polyethylene, polystyrene, polycarbonate, poly (N-methylmethacrylimide) ( PMMI), polymethyl methacrylate (PMMA), ionomer, polyamide or mixtures thereof.

WO 95/11006 describes a polymer powder suitable for laser sintering, which, when determining the melting behavior by differential scanning calorimetry at a scanning speed of 10-20 ° C / min, does not show any overlap of melting and recrystallization maxima, it is also marked by DSC degree of crystallinity

10-90%, has a number average molecular weight Mn 30000500000 and its MW / Mn ratio is in the range of 1-5.

Document DE 197 47 309 describes the use of polyamide 12 powder with a higher melting maximum and higher melting enthalpy, which is obtained by precipitation of a polyamide previously formed by ring opening followed by polycondensation of lauric lactam, with type X polyamide.

When processing with one of the methods of shaping described above, it is disadvantageous that in order to avoid the so-called "delay", the temperature in the structure space should be kept as evenly as possible at a level barely below the melting point of the polymeric material. "Delay" means the delay of an already molten area that causes at least partial projection from the plane of structure construction. Hence, there is a risk that when laying the next layer of powder, the protruding areas will move and even tear completely. This has the effect on the process that the temperature of the structure's construction space must generally be kept at a relatively high level. Hence, for there to be a sharp separation of the areas into which electromagnetic energy was introduced from those that should not be fused, the highest possible melting enthalpy is required, which occurs as a sharp maximum in DCS (differential scanning calorimetry according to DIN 53765). Also, the thermal conductivity and heat radiation of the molten area, which, however, cannot be prevented, have the effect that the shaped article deviates more or less from the given outline. The possibly high enthalpy of powder melting prevents the powder layer from burning to the molten area.

Hence, it was the object of the present invention to provide a polymer powder that enables the production of a possible faithful shape product with the highest possible surface quality. The processing method is a layered process in which the areas of the respective powder layer melt selectively by means of electromagnetic energy and after cooling bind to the desired shaped article.

In accordance with the claims, it has now surprisingly been found that thanks to the use of special polyamides, polymeric powders can be produced by precipitation crystallization, from which a layered process in which selectively melting areas of a given powder layer can produce shaped products that are advantageous in terms of quality surface and shape fidelity, and at the same time have comparatively good processing properties and mechanical parameters, such as from the polymer powder according to the prior art, e.g. according to DE 197 47 309.

Therefore, the present invention relates to a polymer powder for processing by a layered process in which the regions of each layer are selectively melted, which is characterized in that the powder contains at least one XY type polyamide obtained by polycondensation of diamines and dicarboxylic acids, preferably XY type polyamide PA610, PA612, PA613, PA1010, PA1012 groups,

PA1212. XY type polyamide PA1010, PA1012 or PA1212 is particularly preferably used. The polymer powder has a melting enthalpy of DSC of at least 125 J / g and a maximum recrystallization of at least 148 ° C, preferably a melting enthalpy of at least 130 J / g and a maximum recrystallization of at least 150 ° C, in particular a melting enthalpy of at least 130 J / g and a maximum recrystallization of at least 155 ° C.

In addition, the present invention relates to shaped articles made by a layered process in which the regions of each layer are selectively melted, which are characterized in that they contain at least one polyamide XY prepared by polycondensation of diamines and dicarboxylic acids, preferably polyamide XY PA610, PA612, PA613, PA1010, PA1012, PA1212. The shaped article particularly preferably comprises an XY type polyamide from the PA1010, PA1012 or PA1212 group.

The polymer powder according to the invention has the advantage that shaped products made by a layered process in which the areas of each layer are selectively melted have better shape fidelity and better surface quality compared to shaped products from traditional polyamide powders.

Shaping products made from the powder according to the invention have similarly good mechanical properties, as do shaped products made from conventional powders.

Also, the processability of the powder according to the invention is comparable to the processability of traditional polyamide powders.

The polymer powder according to the invention is discussed below without limiting the invention to this.

The polymer powder according to the invention for processing by a layered process in which the areas of each layer are selectively melted is characterized by the fact that the powder contains at least one polyamide-XY, homopolymers of the general formula:

- (NH- (CH2) x-NH-CO- (CH2) y-CO) n / 2.

The nomenclature of polyamides is regulated in ISO 1874-1 and in particular Appendix A describes the determination and labeling of linear aliphatic polyamides. XY type polyamides, the use of which according to the invention, are obtained by polycondensation of diamines with dicarboxylic acids. By x is meant the number of C atoms in the diamine, and by y is meant the number of C atoms in the dicarboxylic acid. In the preferred powder, both diamines and dicarboxylic acids have an aliphatic (linear) nature, with diamines from the following group being used as monomeric bricks: butanediamine, hexamethylenediamine, decanediamine, 1,12-diaminododecane. Monomers for dicarboxylic acids are e.g. adipic acid (hexanoic diacid, b = 4), azelaic acid (nonanoic diacid, b = 7), sebacic acid (decanoic diacid, b = 8), dodecanoic diacid (b = 10), brasylic acid (b = 11), diacid tetradecanoic acid (b = 14), pentadecanoic acid (b = 15), octadecanoic acid (b = 18).

The powder according to the invention is obtained, for example, by the process of DE 29 06 647 B1 or DE 197 08 146, however, polyamide of the type

XY. The polyamide is dissolved in methanol and crystallized under certain conditions, optionally accompanied by screening and further classification or cold milling. The skilled person can easily determine the conditions by way of preliminary preliminary tests.

It has surprisingly been found that the advantageous properties of the polyamide powder described in DE 197 47 309, namely high melting enthalpy, can be set more advantageously when type XY is used instead of type X polyamide. The difference lies in the possibility of producing hydrogen bonds. Eg. in the case of PA66, the XY type polyamide according to the invention, the carbonamide groups of adjacent molecules are always arranged in such a way that each functional group can form a hydrogen bridge without distortion. Compared with this, this is possible with PA 6, which is an example of type X polyamide, only with additional energy input through deformation of the molecules, which leads, among other things, to the fact that the maximum melting and enthalpy of melting are in the case of PA 66 (about 260 ° C) clearly higher than for PA 6 (about 220 ° C).

Unlike DE 197 47 309 A1, the high recrystallization temperature is also advantageous, because on the one hand the processing window is not narrowed, because other factors play a greater role, and on the other hand, the recyclability of the material is clearly improved. The powder, which in the process of building the structure was not melted, can be reused with a more favorable refresh rate, without adversely affecting the surface properties when the recrystallization temperature is high. Therefore, the polymer powder according to the invention has a melting enthalpy, determined by DSC, at least 125 J / g and a maximum recrystallization of at least 148 ° C, preferably a melting enthalpy of at least 130

J / g and a maximum recrystallization of at least 150 °, in particular a melting enthalpy of at least 130 J / g and a maximum recrystallization of at least 155 ° C. Different parameters were determined by DSC (differential scanning calorimetry) according to DIN

53765 or according to AN-SAA 0663. Measurements were carried out using a Perkin Elmer DSC 7 instrument with nitrogen as purge gas and a cooling rate of 20 K / min. The measuring range was from -90 to + 250 ° C.

The dissolution viscosity of the polyamide powders according to the invention in a 0.5% m-cresol solution is according to DIN 53727 preferably 1.4-2.1, even more preferably 1.5-1.9, especially 1.6-1.7.

The polymer powder according to the invention preferably contains XY type polyamide powder with an average particle size of 10-250 μπι, preferably 45-150 μπι, and especially 50-125 μπι.

Starting granules for processing into powders according to the invention are commercially available e.g. from Degussa, Marl, Germany (Polyamid 612, trade name Vestamid series D), or from EMS Chemie, Donat, Switzerland (Technyl D, Polyamid 610).

The polymer powder according to the invention may furthermore contain auxiliaries and / or fillers and / or further organic or inorganic pigments. Such excipients may be e.g. sprinkling aids, e.g. precipitated and / or pyrogenic silicas. Precipitated silicas are offered, for example, by Degussa AG under the Aerosol product name, with various specifications. The polymer powder according to the invention preferably contains less than 3% by weight, even more preferably 0.0012% by weight and particularly preferably 0.05-1% by weight of such excipients, based on the sum of existing polymers. The fillers can be e.g. glass, metal or ceramic particles, such as glass beads, steel beads or metal shot, or foreign pigments, such as e.g. transition metal oxides. Pigments can be e.g. titanium dioxide particles based on rutile or anatase, or soot particles.

Preferably, the filler particles have a smaller or approximately the same average particle size as the polyamide particles. The average particle size d50 of fillers should not exceed the average particle size d50 of polyamides by more than 20%, preferably not more than 15% and especially not more than 5%. Particle size is limited, in particular, by the allowable structure height or layer thickness in the rapid prototyping / rapid production device.

The polymer powder according to the invention preferably contains less than 75% by weight, even more preferably 0.001-70% by weight, particularly preferably 0.05-50% by weight and especially 0.5-25% by weight of such fillers with respect to the total existing polyamides.

Depending on the fillers or auxiliaries used, the maximum mechanical limits of shaped articles which have been produced with such polymeric powders can be exceeded when the maximum limits given for the auxiliary substances and / or fillers are exceeded.

It is also possible to mix traditional polymer powders with the polymer powders according to the invention. In this way, polymer powders can be produced with a further combination of surface properties. The method of producing such mixtures can be found, for example, in DE 34 71 708.

In order to improve the melting behavior in the production of shaped articles, a leveling agent can be added to the precipitated polyamide powder, such as, for example, metal soaps, preferably the alkali or alkaline earth metal salts underlying alkane monocarboxylic or dimeric acids. Metallic soap particles may be incorporated into the polymer particles, but mixtures of fine metallic soap particles and polymer particles may also be present.

Metal soaps are preferably used in amounts of 0.01-30% by weight, preferably 0.5-15% by weight, based on the sum of the polyamides contained in the powder. The metal soaps used were preferably the sodium or calcium salts of the underlying alkane monocarboxylic or dimeric acids. Examples of commercially available products are Licomont NaV 101 or Licomont CaV 102 from the company

Clariant.

In order to improve processability or to further modify the polymer powder, inorganic foreign pigments such as, for example, transition metal oxides, stabilizers such as phenols, and in particular phenols with a spatial obstacle, leveling agents and spraying aids, such as e.g. pyrogenic silicas, and filler particles. Preferably, so many substances are added to the polymers, based on the total weight of the polymers in the polymer powder, that the filler and / or excipient concentrations given for the polymer powder according to the invention are maintained.

The present invention also relates to methods for producing shaped articles by layered processes in which the areas in which the polymer powders according to the invention are characterized by containing at least one polyamide XY prepared by polycondensation of diamines and dicarboxylic acids, preferably polyamide, are selectively melted. XY from the group consisting of PA66, PA610, PA612, PA1010, PA1012, PA1212, PA613. The shaped articles of the invention preferably have a polyamide XY type PA1010, PA1012 or PA1212. The XY type polyamide whose use is according to the invention is obtained by polycondensation of diamines with dicarboxylic acids. By x is meant the number of C atoms in the diamine, and by y is meant the number of C atoms in the dicarboxylic acid. The preferred powder has both diamines and aliphatic (linear) dicarboxylic acids, e.g. as monomeric bricks, diamines from the following group are used: butanediamine, hexamethylene diamine, decanediamine, 1,12-diaminododecane. Monomers for dicarboxylic acids are e.g. adipic acid (hexane diacid, b = 4), azelaic acid (nonanoic diacid, b = 7), sebacic acid (decanoic diacid, b = 8), dodecanoic diacid (b = 10), brasylic acid (b = 11), tetradecanoic acid (b = 14), pentadecanoic acid (b = 15), octadecanoic acid (b = 18).

Energy is introduced by means of electromagnetic radiation, while selectivity is introduced, e.g. by masking, applying inhibitors, absorbers, susceptors, as well as by focusing radiation. After all layers have cooled down, shape products according to the invention can be removed.

The following examples of such methods are for illustrative purposes and are not intended to be limiting to this invention.

The methods of laser sintering are sufficiently known and rely on the selective sintering of polymer particles, wherein the layers of polymer particles are briefly exposed to laser light, and thus the polymer particles that have been exposed to laser light bind to each other. Consecutive sintering of layers of polymer particles produces three-dimensional objects. Details of the selective laser sintering method can be found, e.g. from documents US6136948 and WO

96/06881.

Other well-suited methods are the SIV method described in WO 01/38061 or the method described in EP 1 015 214.

In both methods, flat infrared heating is used to melt the powder. The melt selectivity is obtained in the first method by applying an inhibitor and in the second method by masking. A further method is described in DE 103 11 438. In this method, the energy necessary for melting is introduced by means of a microwave generator, and selectivity is obtained by applying a susceptor.

Shaped products according to the invention, which are produced by a layered process in which the areas are selectively melted, are characterized in that they contain at least one XY type polyamide produced by polycondensation of diamines and dicarboxylic acids, preferably XY type polyamide from the group consisting of PA66, PA610, PA612,

PA613, PA1012. Particularly preferably, shaped articles according to the invention contain XY type PA1010, PA1012 or PA1212 polyamide. XY type polyamides, the use of which according to the invention, are obtained by polycondensation of diamines with dicarboxylic acids. By x is meant the number of C atoms in the diamine and by y the number of C atoms in the dicarboxylic acid. The preferred powder has both diamine and dicarboxylic acid, of an aliphatic (linear) nature, with diamines from the following group being used as monomeric bricks:

butanediamine, hexamethylenediamine, decanediamine, 1,12-diaminododecane. Monomers for dicarboxylic acids are e.g. adipic acid (hexane diacid, b = 4), azelaic acid (nonanoic diacid, b = 7), sebacic acid (decanoic diacid, b = 8), dodecanoic diacid (b = 10), brasylic acid (b = 11), tetradecanoic acid (b = 14), pentadecanoic acid (b = 15), octadecanoic acid (b = 18).

The shaped articles may further contain fillers and / or auxiliaries, such as e.g. heat stabilizers, such as e.g. phenolic derivatives with spatial obstacle. Fillers can be e.g. glass particles, ceramics, as well as metal particles, e.g. iron spheres, or suitable hollow spheres. Preferably, the shaped articles of the invention contain glass particles, particularly preferably glass beads.

The shaped articles according to the invention preferably contain less than 3% by weight, even more preferably 0.001-2% by weight and especially 0.05-1% by weight of such excipients, based on the sum of existing polymers. The shape products according to the invention also preferably contain less than 75% by weight, more preferably 0.001-70% by weight, particularly preferably 0.05-50% by weight and especially 0.5-25% by weight of such fillers with respect to the sum of existing polymers.

The examples below should describe the polymer powder of the invention and its use without limiting the invention to these examples.

The measurement values ​​of the deflection of the laser rays were obtained with the Malvern Mastersizer S, version

1.18.

Example 1: Precipitation of polyamide 12 (PA 12) (not according to the invention)

400 kg of irregular PA 12 obtained by hydrolytic polymerization, with a relative solution viscosity of 1.62 and a content of end groups of 75 mmol / kg COOH or 69 mmol / kg NH2, with 2500 l ethanol contaminated with 2-butanone and 1% water content, fed in 5 hours in 3 m³ a vessel with a stirrer (a = 160 cm) to 145^°C and stirring (paddle stirrer, x = 80 cm, revolutions 49 per minute) leaves at this temperature for 1 hour. The jacket temperature is then lowered to 124 ° C and, with continuous distillation of ethanol at a cooling rate of 25 K / h at the same speed of the stirrer, the internal temperature is brought to 125 ° C. From this moment, at the same cooling rate, the jacket temperature is maintained at 2-3K below the internal temperature. The internal temperature at the same cooling rate is brought to 117 ° C and then kept constant for 60 minutes. Then the distillation is continued at a cooling rate of 40K / h and the internal temperature is adjusted to 111 ° C in this way. At this temperature, precipitation occurs which is recognized by the evolution of heat. The distillation rate increases in such a way that the internal temperature does not rise above 111.3 ° C. After 25 minutes, the internal temperature drops, indicating the end of precipitation. By further distilling and cooling through the jacket, the temperature of the suspension is brought to 45 ° C, and then the suspension is transferred to a scraper dryer. Ethanol is distilled off at 70 ° C / 400 mbar, and the residue is then dried in 3 hours at 20 mbar / / 86 ° C.

Precipitated PA 12 with an average grain diameter of 55 μπι is obtained. The bulk density was 435 g / l.

By analogy with the procedure described in example 1 or according to DE 197 08 146, a powder from PA1012, PA1010, PA 612, PA613 is prepared.

Example 2: One-stage precipitation of PA1010 (according to the invention)

According to example 1, a 400 kg sample of PA1010 obtained by polycondensation of 1,10-decane diamine and sebacic acid is precipitated, with the following parameters: η_Γβ1= 1.84, [COOH] = 62 mmol / kg, [NH2] = 55 mmol / kg.

The precipitation conditions are changed in relation to example 1 as follows:

Precipitation temperature: 120 ° C, precipitation time: 2 hours, stirrer speed: 90 rpm

<td colspan="3">Bulk density:</td><td colspan="2">417 g / l</td>

<td>Analysis</td><td>sieve:</td><td> &lt;</td><td> 32</td><td>μχι: 6.0% by weight</td>

<td></td><td></td><td> &lt;</td><td> 45</td><td>μχι: 8.5% by weight</td>

<td></td><td></td><td> &lt;</td><td> 63</td><td>μχι: 23.5% by weight</td>

<td></td><td></td><td> &lt;</td><td> 100</td><td>μχ: 96.1% by weight</td>

<td></td><td></td><td> &lt;</td><td> 160</td><td>μχ: 99.7% by weight</td>

<td></td><td></td><td> &lt;</td><td> 200</td><td>μχ: 99.9% by weight</td>

<td></td><td></td><td> &lt;</td><td> 250</td><td>μχ: 100.0% by weight.</td>

Example 3: One-stage precipitation of PA1012 (according to the invention)

According to example 1, a 400 kg sample of PA1012 granulate is precipitated obtained by polycondensation of 1,10-decanediamine and dodecane diacid, with the following parameters: n_rel= 1.7 6, [COOH] = 4.6 mmol / kg, [NH₂] = 65 mmol / kg.

The precipitation conditions are changed in relation to example 1 as follows:

Dissolution temperature: 155 ° C, precipitation temperature: 123 ° C, precipitation time: 40 minutes, stirrer speed: 110 rpm

Bulk density: 510 g / l

Sieve analysis: &lt;32 μχ: 0.2% by weight &lt;100 μχ: 44.0% by weight &lt;250 μχ: 99.8% by weight.

Example 4: One-stage precipitation of PA1012 (according to the invention)

Example 3 is repeated with the following changes: Precipitation temperature: 125 ° C, precipitation time: 60 minutes Bulk density: 480 g / l

Sieve analysis: &lt;32 μχ: 0.1% by weight &lt;100 μχ: 72.8% by weight &lt;250 μχ: 99.7% by weight.

Example 5: One-stage precipitation of PA1012 (according to the invention)

Example 4 is repeated with the following changes:

Precipitation temperature: 128 ° C, precipitation time: 90 minutes

Bulk density: 320 g / l

Sieve analysis: &lt;32 μιη: 0.5% by weight &lt;100 μη: 98.5% by weight &lt;250 pm: 99.6% by weight.

Example 6: One-stage precipitation of PA1212 (according to the invention)

According to example 1, 400 kg of a PA1212 granulate sample obtained by polycondensation of 1,10-decanediamine and 1,12-dodecane diacid is precipitated, with the following data: r_rel= 1.80, [COOH] = 3 mmol / kg, [NH₂] = 107 mmol / kg.

The precipitation conditions are changed in relation to example 1 as follows:

Dissolution temperature: 155 ° C, precipitation temperature: 117 ° C, precipitation time: 60 minutes, stirrer speed: 110 rpm

Bulk density: 450 g / l

Sieve analysis: &lt;32 pm: 0.5% by weight &lt;100 pm: 54.0% by weight &lt;250 pm: 99.7% by weight

Example 7: Two-stage precipitation of PA1010 (according to the invention)

400 kg of irregular sample PA1010, obtained by polycondensation of 1,10-decanediamine and sebacic acid, with the following parameters: rrel = 1.84, [COOH] = 62 mmol / kg, [NH2] = 55 mmol / kg, with 2,500 ethanol contaminated with 2-butanone and with a 1% water content, fed over 5 hours in 3 m³ a vessel with a stirrer (a = 160 cm) to 155^°C and stirring (paddle stirrer, d = 80 cm, number of revolutions: 90 rpm) leaves at this temperature for 1 hour. The jacket temperature is then reduced to 135 ° C and the internal temperature is brought to 138 ° C with continuous distillation of ethanol at a cooling rate of 25 K / h at the same stirrer speed. From this moment, at the same cooling rate, the jacket temperature is maintained at 2-3K below the internal temperature. The internal temperature at the same cooling rate is brought to 128 ° C and then kept constant for 60 minutes. Then the distillation is continued at a cooling rate of 40K / h and in this way the internal temperature is brought to 120 ° C. At this temperature, precipitation occurs which is recognized by the evolution of heat. The distillation rate increases in such a way that the internal temperature does not rise above 121.3 ° C. After 25 minutes, the internal temperature drops, indicating the end of precipitation. The internal temperature is left for a further 35 minutes at 120 ° C. By further distilling off and cooling through the jacket, the temperature of the suspension is brought to 75 ° C, and then the suspension is transferred to a scraper dryer. Ethanol is distilled off at 70 ° C / 400 mbar, and the residue is then dried in 3 hours at 20 mbar / 86 ° C.

<td>Density</td><td colspan="2">bulk:</td><td> 440</td><td>g / l</td>

<td>Analysis</td><td>sieve:</td><td> &lt;</td><td> 32</td><td>μπ: 4.2% by weight</td>

<td></td><td></td><td> &lt;</td><td> 63</td><td>μπ: 28.6 by weight</td>

<td></td><td></td><td> &lt;</td><td> 100</td><td>μπ: 86.1% by weight</td>

<td></td><td></td><td> &lt;</td><td> 160</td><td>μπ: 99.7% by weight</td>

<td></td><td></td><td> &lt;</td><td> 250</td><td>μπ: 100.0% by weight</td>

Example 8: Two-stage precipitation of PA1012 (according to the invention)

According to example 7, 400 kg of a PA1012 granulate sample obtained by polycondensation of 1,10-decanediamine and dodecane diacid is precipitated, with the following data:

n_rel = 1.76, [COOH] = 46 mmol / kg, [NH₂] = 65 mmol / kg (as in example 3).

The precipitation conditions are changed in relation to example 7 as follows:

Dissolution temperature: 155 ° C, nucleation temperature: 141 ° C, precipitation temperature:

123 ° C, precipitation time: 40 minutes, stirrer speed: 110 rpm

Bulk density: 530 g / l

Sieve analysis: &lt;32 μπ: 1.3% by weight &lt;100 μπ: 34.1% by weight &lt;250 μπ: 99.7% by weight.

Example 9: Two-stage precipitation of PA1012 (according to the invention)

Example 7 is repeated with the following changes:

Crystallization time: 90 minutes

Bulk density: 530 g / l

Sieve analysis: &lt;32 pm: 0.8% by weight &lt;100 μπ: 32.2% by weight &lt;250 μπ: 99.8% by weight.

Example 10: Two-stage precipitation of PA1012

Example 7 is repeated with the following changes:

Crystallization time: 120 minutes

Bulk density: 530 g / l

Sieve analysis: &lt;32 pm: 0.3% by weight &lt;100 pm: 28.4% by weight &lt;250 pm: 99.8% by weight.

Example 11: Two-stage precipitation of PA1212 (according to the invention)

According to example 7, 400 kg of a sample of granules PA1212 obtained by polycondensation of 1,10-decanediamine and 1,12-dodecane diacid is precipitated, with the following data: n_rei = 1.80, [COOH] = 3 mmol / kg, [NH₂] = 107 mmol / kg.

The precipitation conditions are changed in relation to example 1 as follows:

Dissolution temperature: 155 ° C, nucleation time: 60 minutes, precipitation temperature: 117 ° C, precipitation time: 60 minutes, stirrer speed: 110 rpm

Bulk density: 480 g / l

Sieve analysis: &lt;32 pm: 1.3% by weight &lt;100 pm: 56.6% by weight &lt;250 pm: 99.8% by weight.

Example 12: Two-stage precipitation of PA613 (according to the invention)

Example 7 is repeated using PA613 obtained by polycondensation of hexamethylenediamine and brasylic acid - solution viscosity n_rel = 1.83, [COOH] = 17 mmol / kg, [NH2] = 95 mmol / kg, with the following changes: Dissolution temperature: 152 ° C, nucleation temperature: 125 ° C, nucleation time: 45 minutes, precipitation temperature: 114 ° C, precipitation time: 120 minutes, stirrer speed: 110 rpm

Bulk density: 380 g / l, BET = 11.19 m²/ g

Laser beam deflection: D10 55 pm

D50 78 pm

D90 109 μπ.

Example 13: One-stage precipitation of PA613 (according to the invention)

Example 1 is repeated using PA613 obtained by polycondensation of hexamethylenediamine and brasylic acid - solution viscosity n_rei = 1.65, [COOH] = 33 mmol / kg, [NH2] = 130 mmol / kg, with the following changes: Dissolution temperature: 152 ° C, precipitation temperature: 119 ° C, precipitation time: 150 minutes, number of revolutions stirrers: 110 rpm

Bulk density: 426 g / l, BET = 7.63 m²/ g

<td>Laser beam deflection:</td><td>D10</td><td>50 pm</td>

<td></td><td>D50</td><td>89 pm</td>

<td></td><td>D90</td><td>132 pm.</td>

<td></td><td>Enthalpy m.p. [J / g]</td><td>Maximum recrystallization [° C]</td>

<td>PA 12 of Example 1 not according to the invention (precipitation crystallization)</td><td> 112</td><td> 141</td>

<td>Hydrolytically polymerized PA 12 (Vestamid from Degussa), not according to the invention</td><td> 71</td><td> 141</td>

<td>Hydrolytically polymerized PA 11 (Rilsan from ELF Atochem SA), not according to the invention</td><td> 87</td><td> 157</td>

<td>PA1012 manufactured according to DE 29 06 647 B1, according to the invention</td><td> 152</td><td> 155</td>

<td>PA613 manufactured according to DE 29 06 647 B1, according to the invention</td><td> 130</td><td> 172</td>

<td>PA1010 manufactured according to DE 29 06 647 B1, according to the invention</td><td> 146</td><td> 165</td>

<td>PA612 produced according to DE 29 06 647 B1, according to the invention</td><td> 131</td><td> 185</td>

<td></td><td> 132</td><td> 150</td>

From the examples it can be easily recognized that the polyamide powders according to the invention have a clearly higher melting enthalpy as well as a higher recrystallization temperature than traditional polymeric powders. Accordingly, structural parts with better surface quality can be produced because less powder adheres to the molten areas. The recyclability of the powder according to the invention is therefore also better compared to conventional polyamide powders.

Evonik Degussa GmbH

Deputy:

OK II-12 / P24445PL00

EP 1 742 986 B1