EP3491066A1

EP3491066A1 - Polyamide blends for laser sintered powder

Info

Publication number: EP3491066A1
Application number: EP17740407.6A
Authority: EP
Inventors: Claus Gabriel; Florian Richter; Philipp KLOKE; Thomas Meier; Klaus Stoll
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2016-07-29
Filing date: 2017-07-21
Publication date: 2019-06-05
Also published as: IL264444A; AU2017303415A1; TW201817812A; CN109642076A; WO2018019727A1; JP2019524939A; KR20190039147A; JP7055788B2; MX2019001264A; SG11201900390XA; KR102383704B1; US20190177537A1; CA3032219A1; CN109642076B

Abstract

The present invention relates to a method for producing a moulded body by the selective laser sintering of a sintered powder (SP). The sintered powder (SP) contains at least a partially crystalline polyamide and at least one polyamide 6I/6T. The invention also relates to a moulded body obtained according to the claimed method and to the use of polyamide 6I/6T in a sintered powder (SP) for broadening the sintering window (WSp) of the sintered powder (SP).

Description

The present invention relates to a method for producing a shaped body by selective laser sintering of a sintered powder (SP). The sintering powder (SP) contains at least one partially crystalline polyamide and at least one polyamide 6I / 6T. Moreover, the present invention relates to a molded article obtainable by the process according to the invention and the use of polyamide 6I / 6T in a sintering powder (SP) for widening the sintering window (W _S p) of the sintering powder (SP).

Rapid deployment of prototypes is a common task in recent times. One method that is particularly suitable for this so-called "rapid prototyping" is selective laser sintering (SLS). In this case, a plastic powder is selectively exposed in a chamber with a laser beam. The powder melts, the molten particles run into each other and solidify again. Repeated application of plastic powder and subsequent exposure with a laser allows the modeling of three-dimensional moldings. The process of selective laser sintering for the production of molded articles from pulverulent polymers is described in detail in US Pat. Nos. 6,136,948 and WO 96/06881.

Of particular importance in selective laser sintering is the sintering window of the sintering powder. This should be as wide as possible to reduce distortion of components during laser sintering. In addition, the recyclability of the sintered powder is of particular importance. The prior art describes various sintering powders for use in selective laser sintering. WO 2009/1 14715 describes a sintering powder for selective laser sintering which contains at least 20% by weight of polyamide polymer. This polyamide polymer contains a branched polyamide, wherein the branched polyamide is prepared starting from a polycarboxylic acid having three or more carboxylic acid groups. WO 201 1/124278 describes sintering powders which contain coprecipitates of PA 1 1 with PA 1010, PA 1 1 with PA 1012, PA 12 with PA 1012, PA 12 with PA 1212 or PA 12 with PA 1013.

EP 1 443 073 describes sintering powder for a selective laser sintering process. These sintering powders contain a polyamide 12, polyamide 1 1, polyamide 6.10, polyamide 6.12, polyamide 10.12, polyamide 6 or polyamide 6.6 and a flow aid. US 2015/0259530 describes a partially crystalline polymer and a secondary material which can be used in a sintering powder for selective laser sintering. Polyetheretherketone or polyetherketone ketone are preferably used as partially crystalline polymer and polyetherimide as secondary material.

US 2014/0141666 describes a polyamide blend that can be used as a filament in a 3D printing process. This polyamide blend contains, as partially crystalline polyamide, for example polyamide 6, polyamide 66, polyamide 69, polyamide 610, polyamide 7, polyamide 1 1, polyamide 12 or mixtures thereof and as polyamide 6 / 3T as amorphous polyamide, wherein in the range from 30 to 70 Wt .-% of the amorphous polyamide are contained in the polyamide blend.

A disadvantage of the sintering powders described in the prior art for the production of moldings by selective laser sintering is that the sintering window of the sintering powder is often reduced compared to the sintered window of the pure polyamide or of the pure semicrystalline polymer. A reduction of the sintering window is disadvantageous, as this often warp the moldings during production by selective laser sintering. By this delay, a use or further processing of the molded body is almost impossible. The delay can already be so strong during the production of the moldings that a further layer application is not possible and therefore the production process must be terminated.

The object underlying the present invention was therefore to provide a process for the production of moldings by selective laser sintering, which does not or only to a lesser extent have the aforementioned disadvantages of the processes described in the prior art. The process should be simple and inexpensive to carry out. This object is achieved by a method for producing a shaped body by selective laser sintering of a sintered powder (SP), wherein the sintered powder (SP), the components

(A) at least one partially crystalline polyamide containing at least one unit selected from the group consisting of -NH- (CH ₂ ) _m -NH- units, where m

4, 5, 6, 7 or 8 means -CO- (CH ₂ ) _n -NH- units, where n is 3, 4, 5, 6 or 7, and -CO- (CH ₂ ) ₀ -CO- units where o is 2, 3, 4, 5 or 6,

(B) at least one polyamide 6I / 6T, wherein the sintering powder (SP) in the range of 75 to 90 wt .-% of component (A) and in the range of 10 to 25 wt .-% of component (B) contains, in each case based on the sum of the weight percent of components (A) and (B).

The present invention furthermore relates to a process for the production of a shaped body by selective laser sintering of a sintering powder (SP), wherein the sintering powder (SP) comprises the components

(A) at least one partially crystalline polyamide containing at least one unit selected from the group consisting of -NH- (CH ₂ ) _m -NH- units, where m is 4, 5, 6, 7 or 8, -CO- (CH ₂ ) _{n is} -NH units, where n is 3, 4, 5, 6 or 7, and -CO- (CH ₂ ) ₀ -CO- units, where o is 2, 3, 4, 5 or 6,

(B) contains at least one polyamide 6I / 6T.

It has surprisingly been found that the sintering powder (SP) used in the process according to the invention has a widened sintering window W _S p) such that the shaped body produced by selective laser sintering of the sintering powder (SP) has no or significantly reduced distortion. In addition, the recyclability of the sintering powder (SP) used in the process according to the invention is high even after thermal aging. This means that unmelted sintered powder (SP) can be reused in the production of the molded article. The sintering powder (SP) has similar advantageous sintering properties after several laser sintering cycles as in the first sintering cycle.

In addition, the shaped bodies produced by the process according to the invention have surfaces smoother than those produced by processes described in the prior art and in particular by shaped bodies produced by sintering powders described in the prior art.

The method according to the invention will be explained in more detail below.

Selective laser sintering

The method of selective laser sintering is known per se to the person skilled in the art, for example, from US Pat. No. 6,136,948 and WO 96/06881.

In laser sintering, a first layer of a sinterable powder is arranged in a powder bed and exposed locally and briefly with a laser beam. In this case, only the part of the sinterable powder which has been exposed by the laser beam, selectively melted (selective laser sintering). The molten sinterable Powder flows into each other, forming a homogeneous melt in the exposed area. Subsequently, the area cools down again and the homogeneous melt solidifies again. Then, the powder bed is lowered by the layer thickness of the first layer, a second layer of the sinterable powder applied, selectively exposed to the laser and melted. As a result, on the one hand, the upper second layer of the sinterable powder connects to the lower first layer, and in addition the particles of the sinterable powder within the second layer combine with one another by melting. By repeating the lowering of the powder bed, the application of the sinterable powder and the melting of the sinterable powder, three-dimensional molded bodies can be produced. By the selective exposure of certain points with the laser beam, it is possible to produce molded bodies which, for example, also have cavities. An additional support material is not necessary because the unfused sinterable powder itself acts as a support material.

Suitable sinterable powders in selective laser sintering are all powders known to those skilled in the art which can be melted by exposure to a laser. According to the invention, the sintering powder (SP) is used as the sinterable powder in selective laser sintering.

In the context of the present invention, therefore, the terms "sinterable powder" and "sintered powder (SP)" can be used synonymously, they then have the same meaning. Suitable lasers for selective laser sintering are known to the person skilled in the art and, for example, fiber lasers, Nd: YAG lasers (neodymium-doped yttrium aluminum garnet lasers) and carbon dioxide lasers.

Of particular importance in the case of the selective laser sintering process is the melting range of the sinterable powder, the so-called "sintering window (W)." If the sinterable powder is the sintering powder (SP) according to the invention, the sintering window (W) is used as "sintered window" in the context of the present invention (W _SP ) "of the sintering powder (SP). If the sinterable powder is the component (A) contained in the sintering powder (SP), the sintering window (W) is referred to as "sintering window (W _A )" of component (A) in the context of the present invention.

The sintering window (W) of a sinterable powder can be determined, for example, by differential scanning calorimetry (DSC).

In the dynamic differential calorimetry, the temperature of a sample, in this case a sample of sinterable powder, and the temperature of a Reference changed linearly with time. For this purpose, the sample and the reference are supplied with heat or removed therefrom. It determines the amount of heat Q necessary to keep the sample at the same temperature as the reference. The reference value used is the quantity of heat Q _R supplied or discharged to the reference.

If the sample undergoes endothermic phase transformation, an additional amount of heat, Q, must be supplied to keep the sample at the same temperature as the reference. If an exothermic phase transformation takes place, a quantity of heat Q has to be removed in order to keep the sample at the same temperature as the reference. The measurement provides a DSC diagram in which the amount of heat Q, which is supplied to the sample and discharged from it, is plotted as a function of the temperature T. Usually, a heating run (H) is first carried out during the measurement, that is, the sample and the reference are heated linearly. During the melting of the sample (solid-liquid phase transformation), an additional amount of heat Q must be supplied to keep the sample at the same temperature as the reference. In the DSC diagram, a peak is then observed, the so-called melting peak.

Following the heating run (H), a cooling run (K) is usually measured. The sample and the reference are cooled linearly, so heat is dissipated from the sample and the reference. During the crystallization or solidification of the sample (liquid-solid phase transformation), a larger amount of heat Q must be dissipated to keep the sample at the same temperature as the reference, since heat is released during crystallization or solidification. In the DSC diagram of the cooling run (K), a peak, the so-called crystallization peak, is then observed in the opposite direction to the melting peak.

In the context of the present invention, the heating during the heating run usually takes place at a heating rate of 20 K / min. The cooling during the cooling is usually carried out in the context of the present invention with a cooling rate of 20 K / min.

A DSC diagram with a heating run (H) and a cooling run (K) is shown by way of example in FIG. On the basis of the DSC diagram, the onset temperature of the melting (T _M ^onset ) and the onset temperature of the crystallization (T _c ^onset ) can be determined. To determine the onset temperature of the reflow (T _M ^onset ), a tangent is applied to the baseline of the heating run (H), which runs at the temperatures below the melting peak. A second tangent is applied to the first inflection point of the reflow peak, which at temperatures below the temperature is at the maximum of the reflow peak. The two tangents are extrapolated to intersect. The vertical extrapolation of the point of intersection to the temperature axis indicates the onset temperature of the melting (T _M ^onset ). To determine the onset temperature of the crystallization (T _c ^onset ), a tangent is applied to the baseline of the cooling run (K), which runs at the temperatures above the crystallization peak. A second tangent is applied to the inflection point of the crystallization peak, which at temperatures above the temperature is at the minimum of the crystallization peak. The two tangents are extrapolated to intersect. The vertical extrapolation of the point of intersection to the temperature axis indicates the onset temperature of the crystallization (T _c ^onset ).

The sintering window (W) results from the difference between the onset temperature of the melting (T _M ^onset ) and the onset temperature of the crystallization (T _c ^onset ). The following applies: onset onset

= I M - I C

In the context of the present invention, the terms "sintering window (W)", "size of the sintering window (W)" and "difference between the onset temperature of the melting (T _M ^onset ) and the onset temperature of the crystallization (T _c ^onset ) "the same meaning and are used synonymously.

The determination of the sintering window (W _S p) of the sintering powder (SP) and the determination of the sintering window (W _A ) of component (A) are carried out as described above. The sintering powder (SP) is then used as the sample for determining the sintering window (W _S p) of the sintering powder (SP); component (A) is used as a sample to determine the sintering window (W _A ) of component (A). Sintered powder (SP)

According to the invention, the sintering powder (SP) contains at least one partially crystalline polyamide as component (A) and at least one polyamide 6I / 6T as component (B). In the context of the present invention, the terms "component (A)" and "at least one partially crystalline polyamide" are used synonymously and therefore have the same meaning. The same applies to the terms "component (B)" and "at least one polyamide 6I / 6T". These terms are also used synonymously in the context of the present invention and therefore have the same meaning.

The sintering powder (SP) may contain components (A) and (B) in any amount. For example, the sintering powder (SP) in the range of 60 to 95 wt .-% of component (A) and in the range of 5 to 40 wt .-% of component (B), in each case based on the sum of the weight percent of the components (A ) and (B), preferably based on the total weight of the sintering powder (SP).

Preferably, the sintering powder (SP) in the range of 60 to 85 wt .-% of component (A) and in the range of 15 to 40 wt .-% of component (B), in each case based on the sum of the weight percent of components (A ) and (B), preferably based on the total weight of the sintering powder (SP).

The sintering powder (SP) particularly preferably contains in the range from 75 to 85% by weight of component (A) and in the range from 15 to 25% by weight of component (B), in each case based on the sum of the percentages by weight of the components ( A) and (B), preferably based on the total weight of the sintering powder (SP).

The present invention therefore also relates to processes in which the sintering powder (SP) contains in the range from 60 to 85% by weight of component (A) and in the range from 15 to 40% by weight of component (B), respectively based on the sum of the weight percent of components (A) and (B).

In a further preferred embodiment, the sintering powder (SP) contains in the range from 75 to 90% by weight of component (A) and in the range from 10 to 25% by weight of component (B), in each case based on the sum of the percentages by weight the components (A) and (B), preferably based on the total weight of the sintering powder (SP).

The sintering powder (SP) may additionally contain at least one additive selected from the group consisting of antinucleating agents, stabilizers, end group functionalizers and dyes.

The present invention therefore also provides processes in which the sintering powder (SP) additionally comprises at least one additive selected from the group consisting of antinucleating agents, stabilizers, end group functionalizers and dyes. A suitable antinucleating agent is, for example, lithium chloride. Suitable stabilizers are, for example, phenols, phosphites and copper stabilizers. Suitable end group functionalizers are, for example, terephthalic acid, adipic acid and propionic acid. Preferred dyes are, for example, selected from the group consisting of carbon black, neutral red, inorganic black dyes and organic black dyes.

With particular preference, the at least one additive is selected from the group consisting of stabilizers and dyes.

As a stabilizer, phenols are particularly preferred.

Therefore, the at least one additive is particularly preferably selected from the group consisting of phenols, carbon black, inorganic black dyes and organic black dyes.

The present invention therefore also provides a process in which the sintered powder (SP) additionally comprises at least one additive selected from the group consisting of phenols, carbon black, inorganic black dyes and organic black dyes.

Carbon black is known to the person skilled in the art and is available, for example, under the trade name Special Black 4 from Evonik, under the trade name Printex U from Evonik, under the trade name Printex 140 from Evonik, under the trade name Special Black 350 from Evonik or under the trade name Special Black 100 from Evonik.

A preferred inorganic black dye is available, for example, under the trade name Sicopal Black K0090 from BASF SE or under the trade name Sicopal Black K0095 from BASF SE.

A preferred organic black dye is, for example, nigrosine.

The sintering powder (SP) may, for example, in the range of 0.1 to 10 wt .-% of the at least one additive, preferably in the range of 0.2 to 5 wt .-% and particularly preferably in the range of 0.3 to 2, 5 wt .-%, each based on the total weight of the sintering powder (SP).

The sum of the percentages by weight of components (A), (B) and, if appropriate, of the at least one additive usually add up to 100% by weight. The sintering powder (SP) has particles. These particles have, for example, a size in the range of 10 to 250 μm, preferably in the range of 15 to 200 μm, particularly preferably in the range of 20 to 120 μm, and particularly preferably in the range of 20 to 110 μm.

The sintered powder (SP) according to the invention has, for example, a D10 value in the range from 10 to 30 μm,

a D50 value in the range of 25 to 70 μηι and

a D90 value in the range of 50 to 150 μηι on.

The sintering powder (SP) according to the invention preferably has a D10 value in the range from 20 to 30 μm,

a D50 value in the range of 40 to 60 μηι and

a D90 value in the range of 80 to 1 10 μηι on.

The present invention therefore also relates to a process in which the sintering powder (SP) has a D10 value in the range from 10 to 30 μm,

a D50 value in the range of 25 to 70 μηι and

has a D90 value in the range of 50 to 150 μηι.

In the context of the present invention, the "D10 value" is understood as meaning 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 are greater than the D10 value. By analogy, 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 the particles are greater than the D50 value. Accordingly, the "D90 value" is understood to mean 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.

To determine the particle sizes, the sintered powder (SP) is suspended by means of compressed air or in a solvent, such as water or ethanol, and measured this suspension. The determination of the D10, D50 and D90 value takes place using laser diffraction using a Master Sizers 3000 from Malvern. The evaluation is carried out by means of Fraunhofer diffraction.

The sintered powder (SP) usually has a melting temperature (T _M ) in the range of 180 to 270 ° C. Preferably, the melting temperature (T _M ) of the sintering powder (SP) is in the range of 185 to 260 ° C, and more preferably in the range of 190 to 245 ° C.

The present invention therefore also relates to a process in which the sintering powder (SP) has a melting temperature (T _M ) in the range from 180 to 270 ° C.

The melting temperature (T _M ) is determined within the scope of the present invention by means of Differential Scanning Calorimetry (DSC). As described above, a heating run (H) and a cooling run (K) are usually measured. In this case, a DSC diagram as shown by way of example in FIG. 1 is obtained. The melting temperature (T _M ) is then understood to be the temperature at which the melting peak of the heating run (H) of the DSC diagram has a maximum. The melting temperature (T _M ) is therefore different from the onset temperature of the melting (T _M ^onset ). The melting temperature (T _M ) is usually above the onset temperature of the melting (T _M ^onset ).

The sintered powder (SP) also usually has a crystallization temperature (T _c ) in the range of 120 to 190 ° C. The crystallization temperature (T _c ) of the sintering powder (SP) is preferably in the range from 130 to 180 ° C. and particularly preferably in the range from 140 to 180 ° C.

The present invention therefore also provides a process in which the sintering powder (SP) has a crystallization temperature (T _c ) in the range from 120 to 190 ° C.

The crystallization temperature (T _c ) is determined in the context of the present invention by means of differential scanning calorimetry (DSC). As described above, a heating run (H) and a cooling run (K) are usually measured. In this case, a DSC diagram as shown by way of example in FIG. 1 is obtained. The crystallization temperature (T _c ) is then the temperature at the minimum of the crystallization peak of the DSC curve. The crystallization temperture (T _c ) is thus different from the onset temperature of the crystallization (T _c ^onset ). The crystallization temperature (T _c ) is usually below the onset temperature of the crystallization (T _c ^onset ).

The sintered powder (SP) also usually has a sintering window (W _S p). The sintering window (W _S p) is, as described above, the difference between the onset Melting temperature (T _M ^onset ) and crystallization onset temperature (T _c ^onset ). The onset temperature of the reflow (T _M ^onset ) and the onset temperature of the crystallization (T _c ^onset ) are determined as described above. The sintering window (W _S p) of the sintering powder (SP) is preferably in the range of 15 to 40 K (Kelvin), particularly preferably in the range of 20 to 35 K and particularly preferably in the range of 20 to 33 K.

The subject matter of the present invention is therefore also a method in which the sintering powder (SP) has a sintering window (W _S p), the sintering window (W _S p) representing the difference between the onset temperature of the melting (T _M ^onset ) and the Onset temperature of the crystallization (T _c ^onset ) is and wherein the sintering window (W _S p) is in the range of 15 to 40 K. The sintering powder (SP) can be prepared by all methods known to those skilled in the art. Preferably, the sintering powder (SP) is prepared by grinding the components (A) and (B) and optionally of the at least one additive.

The preparation of the sintering powder (SP) by grinding can be carried out by all methods known to those skilled in the art. For example, component (A) and component (B), and optionally the at least one additive, are added to a mill and ground.

Suitable mills are all mills known to the person skilled in the art, for example classifier mills, counter-jet mills, hammer mills, ball mills, vibrating mills or rotor mills.

Milling in the mill can also be carried out by all methods known to those skilled in the art. For example, the grinding may take place under inert gas and / or under cooling with liquid nitrogen. Cooling with liquid nitrogen is preferred.

The temperature during grinding is arbitrary. The grinding is preferably carried out at temperatures of liquid nitrogen, for example at a temperature in the range -210 to -195 ° C.

The present invention therefore also provides a process in which the sintered powder (SP) is prepared by grinding the components (A) and (B) at a temperature in the range from -210 to -195 ° C.

The component (A), the component (B) and, if appropriate, the at least one additive can be introduced into the mill by all methods known to the person skilled in the art be introduced. For example, the component (A) and the component (B) as well as optionally the at least one additive may be added separately to the mill and ground therein and thus mixed together. Moreover, it is possible and preferred according to the invention that the component (A) and the component (B) and optionally the at least one additive are compounded together and then added to the mill.

Processes for compounding are known to those skilled in the art. For example, component (A) and component (B) and optionally the at least one additive may be compounded in an extruder, then extruded therefrom and then added to the mill.

Component (A) Component (A) is at least one partially crystalline polyamide.

"At least one partially crystalline polyamide" according to the invention means both exactly one partially crystalline polyamide and one mixture of two or more partially crystalline polyamides.

"Partially crystalline" in the context of the present invention means that the polyamide has a melting enthalpy Δ H2 _(A) of greater than 45 J / g, preferably greater than 50 J / g and particularly preferably greater than 55 J / g, in each case measured using differential scanning calorimetry (DSC) according to ISO 1 1357-4: 2014.

The component (A) according to the invention also preferably has a melting enthalpy Δ H2 _(A) of less than 200 J / g, more preferably less than 150 J / g and particularly preferably less than 100 J / g, measured by differential scanning calorimetry (differential scanning calorimetry, DSC) according to ISO 1 1357-4: 2014.

According to the invention, component (A) contains at least one unit selected from the group consisting of -NH- (CH ₂ ) _m -NH- units, where m is 4, 5, 6, 7 or 8, -CO- (CH ₂ ) _{n is} -NH units, where n is 3, 4, 5, 6 or 7 and -CO- (CH ₂ ) ₀ -CO- units, where o is 2, 3, 4, 5 or 6.

Component (A) preferably contains at least one unit selected from the group consisting of -NH- (CH ₂ ) _m -NH- units, where m is 5, 6 or 7, - CO- (CH ₂ ) _n - NH units, where n is 4, 5 or 6 and -CO- (CH ₂ ) ₀ -CO- units, where o is 3, 4 or 5. More preferably, component (A) contains at least one unit selected from the group consisting of -NH- (CH ₂ ) ₆ -NH- units, -CO- (CH ₂ ) ₅ -NH- units and -CO- (CH ₂ ) ₄ -CO units. If component (A) contains at least one unit selected from the group consisting of -CO- (CH ₂ ) _n -NH units, then these units derive from lactams having 5 to 9 ring members, preferably from lactams having 6 to 8 ring members , particularly preferably from lactams with 7 ring members. Lactams are known to the person skilled in the art. According to the invention, lactams are generally understood to mean cyclic amides. These have in the ring according to the invention 4 to 8 carbon atoms, preferably 5 to 7 carbon atoms and more preferably 6 carbon atoms. For example, the lactams are selected from the group consisting of butyro-4-lactam (γ-lactam, γ-butyrolactam), 2-piperidinone (δ-lactam, δ-valerolactam), hexano-6-lactam (ε-lactam, ε- Caprolactam), heptano-7-lactam (ζ-lactam, ζ-heptanolactam) and octano-8-lactam (η-lactam; η-octanolactam). The lactams are preferably selected from the group consisting of 2-piperidinone (δ-lactam; δ-valerolactam), hexano-6-lactam (ε-lactam, ε-caprolactam) and heptano-7-lactam (ζ-lactam; ζ- Heptanolactam). Especially preferred is ε-caprolactam.

If component (A) contains at least one unit selected from the group consisting of -NH- (CH ₂ ) _m -NH- units, these units are derived from diamines. The component (A) is then obtained by reaction of diamines, preferably by reaction of diamines with dicarboxylic acids.

Suitable diamines contain from 4 to 8 carbon atoms, preferably from 5 to 7 carbon atoms and most preferably 6 carbon atoms.

Such diamines are for example selected from the group consisting of

1, 4-diaminobutane (butane-1, 4-diamine, tetramethylenediamine, putrescine),

1, 5-diaminopentane (pentamethylenediamine, pentane-1, 5-diamine, cadaverine), 1,6-diaminohexane (hexamethylenediamine, hexane-1,6-diamine), 1,7-diaminoheptane and

1, 8-diaminooctane. Preferably, the diamines are selected from the group consisting of 1, 5-diaminopentane, 1, 6-diaminohexane and 1, 7-diaminoheptane. Particular preference is given to 1,6-diaminohexane. If component (A) contains at least one unit selected from the group consisting of -CO- (CH ₂ ) ₀ -CO- units, these units are usually derived from dicarboxylic acids. The component (A) was then so by Reaction of dicarboxylic acids, preferably by reacting dicarboxylic acids with diamines obtained.

The dicarboxylic acids then contain 4 to 8 carbon atoms, preferably 5 to 7 carbon atoms and most preferably 6 carbon atoms.

These dicarboxylic acids are, for example, selected from the group consisting of butanedioic acid (succinic acid), pentanedioic acid (glutaric acid), hexanedioic acid (adipic acid), heptanedioic acid (pimelic acid) and octanedioic acid (suberic acid, suberic acid). Preferably, the dicarboxylic acids are selected from the group consisting of pentanedioic acid, hexanedioic acid and heptanedioic acid, particularly preferred is hexanedioic acid.

Component (A) may also contain other units. For example, units derived from lactams with 10 to 13 ring members, such as capryllactam and / or laurolactam.

In addition, the component (A) may contain units derived from dicarboxylic acid alkanes (aliphatic dicarboxylic acids) having 9 to 36 carbon atoms, preferably 9 to 12 carbon atoms, and more preferably 9 to 10 carbon atoms. In addition, aromatic dicarboxylic acids are suitable.

By way of example, azelaic acid, sebacic acid, dodecanedioic acid and also terephthalic acid and / or isophthalic acid may be mentioned as dicarboxylic acids.

In addition, component (A) may contain, for example, units derived from m-xylylenediamine, di- (4-aminophenyl) methane, di (4-aminocyclohexyl) methane, 2,2-di- (4-aminophenyl) - Propane and 2,2-di- (4-aminocyclohexyl) propane and / or 1, 5-diamino-2-methyl-pentane.

The following, non-exhaustive list contains the preferred components (A) for use in the sintering powder (SP) according to the invention and the monomers contained.

AB-polymers:

PA 4 pyrrolidone

PA 6 ε-caprolactam

PA 7 enantholactam

PA 8 capryllactam AA / BB-polymers:

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 6T hexamethylenediamine, terephthalic acid

PA MXD6 m-xylyenediamine, adipic acid

PA 6 / 6I (see PA 6), hexamethylenediamine, isophthalic 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), lauryl lactam

PA 66/6/610 (see PA 66, PA 6 and PA 610)

PA 6I / 6T / PACM such as PA 6I / 6T and diaminodicyclohexylmethane

PA 6 / 6I6T (see PA 6 and PA 6T), hexamethylenediamine, isophthalic acid. Component (A) is therefore preferably selected from the group consisting of PA 6, PA 6.6, PA 6.10, PA 6.12, PA 6.36, PA 6 / 6.6, PA 6 / 6I6T, PA 6 / 6T and PA 6 / 6I.

In particular, component (A) is preferably selected from the group consisting of PA 6, PA 6.10, PA 6.6 / 6, PA 6 / 6T and PA 6.6. More preferably, component (A) is selected from the group consisting of PA 6 and PA 6 / 6.6. Most preferably, component (A) is PA 6.

The present invention therefore also provides a process in which component (A) is selected from the group consisting of PA 6, PA 6.6, PA 6.10, PA 6.12, PA 6.36, PA 6 / 6.6, PA 6 / 6I6T, PA 6 / 6T and PA 6 / 6I.

Component (A) generally has a viscosity number of from 70 to 350 ml / g, 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 component (A) and in 96 wt .-% sulfuric acid at 25 ° C according to ISO 307th

The component (A) preferably has a weight-average molecular weight (M _w ) in the range of 500 to 2,000,000 g / mol, more preferably in the range of 5,000 to 500,000 g / mol, and particularly preferably in the range of 10,000 to 100,000 g / mol, up. The weight average molecular weight (M _w ) is determined according to ASTM D4001. The component (A) usually has a melting temperature (T _M ). The melting temperature (T _M ) of the component (A) is, for example, in the range of 70 to 300 ° C, and preferably in the range of 220 to 295 ° C. The melting temperature (T _M ) of component (A) is determined as described above for the melting temperature (T _M ) of the sintering powder (SP) by means of differential scanning calorimetry.

The component (A) also usually has one

Glass transition temperature (T _G ). The glass transition temperature (T _G ) of

Component (A) is, for example, in the range of 0 to 10 ° C, and preferably in the range of 40 to 105 ° C.

The glass transition temperature (T _G ) of component (A) is determined by differential scanning calorimetry. For the determination according to the invention, first a first heating run (H1), then a cooling run (K) and then a second heating run (H2) of a sample of the component (A) (weighing approx. 8.5 g) are measured. The heating rate for the first heating (H1) and the second heating (H2) is 20 K / min, the cooling rate for the cooling (K) is also 20 K / min. In the area of the glass transition of component (A), a step is obtained in the second heating run (H2) of the DSC diagram. The glass transition temperature (T _G ) of component (A) corresponds to the temperature at half the step height in the DSC diagram.

Component (B)

According to the invention, component (B) is at least one polyamide 6I / 6T.

"At least one polyamide 6I / 6T" in the context of the present invention means both exactly one polyamide 6I / 6T and one mixture of two or more polyamides 6I / 6T Polyamide 6I / 6T is a copolymer of nylon-6D and nylon-6T.

Preferably, component (B) consists of units derived from hexamethylenediamine, terephthalic acid and isophthalic acid. In other words, component (B) is thus a copolymer prepared from hexamethylenediamine, terephthalic acid and isophthalic acid.

The component (B) is preferably a random copolymer. The at least one polyamide 6I / 6T used as component (B) may contain any proportions of 6I and 6T units. Preferably, the molar ratio of 6I units to 6T units is in the range of 1 to 1 to 3 to 1, especially preferably in the range of 1.5 to 1 to 2.5 to 1, and more preferably in the range of 1.8 to 1 to 2.3 to 1.

Component (B) is an amorphous copolyamide.

In the context of the present invention, "amorphous" means that the pure component (B) has no melting point in differential scanning calorimetry (DSC) measured according to ISO 1 1357. Component (B) has a glass transition temperature (T _G ) The glass transition temperature (T _G ) of the component (B) is usually in the range of 100 to 150 ° C, preferably in the range of 15 to 135 ° C, and more preferably in the range of 120 to 130 ° C. The determination of the glass transition temperature (T _G ) of component (B) is carried out by means of differential scanning calorimetry as described above for the determination of the glass transition temperature (T _G ) of component (A).

The MVR (275 ° C / 5 kg) (melt volume-flow rate, MVR) is preferably in the range of 50 ml / 10 min to 150 ml / 10 min, more preferably in the range of 95 ml / 10 min to 105 ml / 10 min.

The zero viscosity rate η ₀ (zero shear rate viscosity) of component (B) is, for example, in the range from 770 to 3250 Pas. Zero shear rate viscosity (η ₀ ) is determined using a TA Instruments "DHR-1" rotational viscometer and a 25 mm diameter plate-and-plate geometry with a gap distance of 1 mm to form unannealed samples of the component (B) dried for 7 days at 80 ° C under vacuum and then measured with time-dependent frequency sweep (sequence test) with an angular frequency range of 500 to 0.5 rad / s The following additional measurement parameters were used: deformation: 1, 0%, Measuring temperature: 240 ° C, measuring time: 20 min, preheating time after sample preparation: 1, 5 min.

The component (B) has an amino end group concentration (AEG) which is preferably in the range of 30 to 45 mmol / kg, and more preferably in the range of 35 to 42 mmol / kg.

To determine the amino end group concentration (AEG), 1 g of component (B) is dissolved in 30 ml of a phenol / methanol mixture (phenol: methanol 75:25 by volume) and then titrated potentiometrically with 0.2 N hydrochloric acid in water. The component (B) has a carboxyl end group concentration (CEG) which is preferably in the range of 60 to 155 mmol / kg, and more preferably in the range of 80 to 135 mmol / kg. To determine the carboxyl end group concentration (CEG), 1 g of component (B) is dissolved in 30 ml of benzyl alcohol. It is then titrated visually at 120 ° C with 0.05 N potassium hydroxide in water.

moldings

According to the invention, a shaped body is obtained by the method of selective laser sintering described above. The sintered powder (SP) melted in the selective exposure with the laser solidifies again after the exposure and thus forms the shaped body according to the invention. The shaped body can be removed from the powder bed immediately after the solidification of the melted sintering powder (SP). It is also possible to cool the shaped body first and then remove it from the powder bed. Optionally adhering particles of the sintering powder (SP), which has not been melted, can be mechanically removed from the surface by known methods. Methods of surface treatment of the molded article include, for example, tumbling or sliding cutting, and sandblasting, glass bead blasting or microblasting.

It is also possible to further process the resulting shaped articles or, for example, to treat the surfaces.

The shaped article according to the invention contains, for example, in the range from 60 to 95% by weight of component (A) and in the range from 5 to 40% by weight of component (B), in each case based on the total weight of the shaped article. Preferably, the molding according to the invention in the range of 60 to 85 wt .-% of component (A) and in the range of 15 to 40 wt .-% of component (B), in each case based on the total weight of the molding.

The molding according to the invention particularly preferably contains in the range from 75 to 85% by weight of component (A) and in the range from 15 to 25% by weight of component (B), in each case based on the total weight of the molding.

In a further preferred embodiment, the shaped body according to the invention contains in the range from 75 to 90% by weight of component (A) and in the range from 10 to 25% by weight of component (B), in each case based on the total weight of the shaped body. In the present invention, the component (A) is the component (A) contained in the sintered powder (SP), and the component (B) is the component (B) contained in the sintered powder (SP) was. If the sintering powder (SP) contains the at least one additive, the shaped body obtained according to the invention also contains the at least one additive.

It is clear to the person skilled in the art that the exposure of the sintering powder (SP) to the laser, the component (A), the component (B) and, if appropriate, the at least one additive can lead to a chemical reaction and can thereby change. Such reactions are known in the art.

Preferably, the component (A), the component (B) and optionally the at least one additive, by the exposure of the sintering powder (SP) with the laser, no chemical reaction, but the sintered powder (SP) melts only on.

The present invention therefore also relates to a shaped article obtainable by the process according to the invention. By using a polyamide 6I / 6T in the sintering powder (SP) according to the invention, the sintering window (W _SP ) of the sintering powder (SP) is widened with respect to the sintering window (W _A ) of the component (A).

The present invention therefore also relates to the use of a polyamide 6I / 6T in a sintering powder (SP) comprising the components

(B) at least one polyamide 6I / 6T, for broadening the sintering window (W _SP ) of the sintering powder (SP) relative to the sintering window (W _A ) of the component (A), wherein the sintering window (W _s p, W _A ) respectively Difference between the onset temperature of melting (T _M ^onset ) and the onset temperature of crystallization (T _c ^onset ).

For example, the sintering window (W _A ) of component (A) is in the range of 5 to 30 K (Kelvin), preferably in the range of 9 to 25 K, and more preferably in the range of 15 to 21 K. The sintering window (W _SP ) of the sintering powder (SP) widened with respect to the sintering window (W _A ) of component (A), for example by 2 to 20 ° C, preferably by 2.5 to 18 ° C and particularly preferably by 4 to 12 ° C. It goes without saying that the sintering window (W _SP ) of the sintering powder (SP) is wider than the sintering window (W _A ) of the component (A) contained in the sintering powder (SP).

The invention will be explained in more detail below by means of examples, without limiting it thereto.

Examples:

The following components are used: Partially crystalline polyamide (component (A)):

(Pi a) Polyamide 6 (Ultramid® B27, BASF SE)

(P1b) Polyamide 6 (Ultramid® B24, BASF SE)

(P1c) Polyamide 6 (Ultramid® B22, BASF SE)

(P2) Polyamide 6.10 (Ultramid® S3K Balance, BASF SE)

(P3) Polyamide 6.6 / 6 (Copolymer, BASF SE)

(P4) Polyamide 6.6 (Ultramid® A27, BASF SE)

(P5) Polyamide PA6 / 6I6T (copolymer, prepared as described below, BASF SE)

Polyamide PA6 / 66 (Ultramid® C33, BASF SE) Polyamide 6.36 (experimental product from

Hexamethylenediamine and Pripol, Croda, BASF SE)

(P8) polyamide PA6 / 6I6T (copolymer, prepared as described below, BASF SE)

(P9) polyamide PA6 / 6I6T (copolymer, prepared as described below, BASF SE)

(P10) Polyamide PA6 / 6I6T (copolymer, prepared as described below, BASF SE)

(P1 1) Polyamide PA12 (Grilamid L16, EMS)

(P12) Polyamide PA6T / 6 (Ultramid® T, BASF SE)

(P13) Polyamide 6 / 6.6 (Ultramid® C33, BASF SE)

Amorphous polyamide (AP) (component (B)): (AP1) Polyamide DTDI (from 1,3-benzenedicarboxylic acid, 1, 6)

Hexadiamine and 2-methyl-1, 5

Pentanediamine) (PPA 201, Invista)

(AP2) Polyamide MACM.14 (Rilsan Clear G350, Arkema)

(AP3) polyamide 12 / MACM. I (Grilamid TR55, EMS)

(AP4) Polyamide 12 / MACM.12 (Grilamid TR90, EMS)

(AP5) Polyamide PACM.12 (Trogamid CX 7323, Evonik)

(AP6) Polyamide 6I / 6T (Grivory G16, EMS), with a molar

Ratio of 6I: 6T of 1, 9: 1

(AP7) Polyamide 6I / 6T (Grivory G21, EMS), with a molar

Ratio of 6I: 6T of 2.1: 1

(AP8) Polyamide 6I / 6T (Selar PA3426 R, DuPont), with a molar ratio of 6I: 6T of 2.2: 1 - Additive:

(A1) Irganox 1098 (N, N'-hexane-1,6-diylbis (3- (3,5-di-tert-butyl-4-hydroxyphenylpropionamide)), BASF SE)

Production of polyamide 6 / 6I6T copolymers

To prepare the polyamide 6 / 6l6T copolymers (P5, P8, P9, P10), the monomers given in Table 1 were polymerized in the molar ratios given in Table 1 in the presence of water and sodium hypophosphite. 90% by weight of monomers, 0.1% by weight of sodium hypophosphite and 10% by weight of water were used, based on the sum of the percentages by weight of the monomers, sodium hypophosphite and water. The polymerization took place at a nominal temperature of 280 ° C. (actual temperature in the reactor 270 ° C.) in water over a period of 95 minutes. It was heated for 15 min, then the pressure of 14 bar was kept constant for 30 min and finally relaxed over 45 min at a constant temperature. Table 1

Hexamethylene terephthalic isophthalic

caprolactam

diamine acid

[Mol%]

[mol%] [mol%] [mol%]

P5 82.4 8.8 2.6 6.1

P8 86.8 6.6 1, 98 4.62 P9 91, 2 4.4 1, 3 3.1

P10 95.6 2.2 0.66 1.54

Table 2 shows essential parameters of the semicrystalline polyamides used (component (A)). Table 3 shows the essential parameters for the amorphous polyamides used (component (B)).

Table 2

Table 3

Type AEG CEG T _G Zero viscosity η ₀

[mmol / kg] [mmol / kg] at 240 ° C

[° C]

[Pas]

AP1 PA DTDI 46 43 143 2550

AP2 PA MACM.14 49 51 141 4650

AP3 PA 12 / MACM. I 62 71 159 10800

AP4 PA 12 / MACM.12 60 63 149 5000

AP5 PA PACM 12 57 56 135 2220 (at 260 ° C)

AP6 PA 6I6T 37 86 125 770 AP7 PA 6I6T 41 90 126 3250

AP8 PA 6I6T 41 132 128 2070

AEG indicates the amino end group concentration. This is determined by means of titration. To determine the amino end group concentration (AEG), 1 g of the component (semicrystalline polyamide or amorphous polyamide) was dissolved in 30 ml of a phenol / methanol mixture (phenol: methanol 75:25 by volume) and then titrated potentiometrically with 0.2 N hydrochloric acid in water ,

The CEG indicates the carboxyl end group concentration. This is determined by means of titration. To determine the carboxyl end group concentration (CEG), 1 g of the component (semicrystalline polyamide or amorphous polyamide) was dissolved in 30 ml of benzyl alcohol. It was then titrated visually at 120 ° C with 0.05 N potassium hydroxide in water.

The melting temperature (T _M ) of the partially crystalline polyamides and the glass transition temperatures (T _G ) of the partially crystalline polyamides and of the amorphous polyamides were determined in each case by means of differential scanning calorimetry. To determine the melting temperature (T _M ), as described above, a first heating run (H1) was measured at a heating rate of 20 K / min. The melting temperature (T _M ) then corresponded to the temperature at the maximum of the melting peak of the heating run (H1).

To determine the glass transition temperature (T _G ), a cooling run (K) was subsequently measured after the first heating run (H1), followed by a second heating run (H2). The cooling run was measured at a cooling rate of 20 K / min, the first heating run (H1) and the second heating run (H2) were measured at a heating rate of 20 K / min. The glass transition temperature (T _G ) was then determined halfway up the level of the second heating run (H2) as described above.

Zero shear rate viscosity η ₀ was determined using a TA Instruments "DHR-1" rotational viscometer and a 25 mm diameter plate-and-plate geometry with a gap spacing of 1 mm Days were dried under vacuum at 80 ° C. and then measured with a time-dependent frequency sweep (sequence test) with an angular frequency range of 500 to 0.5 rad / s The following further measuring parameters were used: deformation: 1.0%, measuring temperature: 240 ° C. , Measuring time: 20 min, preheating time after sample preparation: 1, 5 min.

Blends of semi-crystalline polyamides To prepare blends of semicrystalline polyamides, the semicrystalline polyamides were compounded in the proportions given in Table 4 in a twin-screw extruder (ZSK 18) at 260 ° C., a speed of 200 rpm and a throughput of 5 kg / h, followed by strand pelletization ,

The resulting blends were then characterized. The melting temperature (T _M ) was determined as described above. The crystallization temperature (T _c ) was determined by differential scanning calorimetry. For this purpose, first a heating run (H) with a heating rate of 20 K / min and then a cooling run (K) with a cooling rate of 20 K / min were measured. The crystallization temperature (T _c ) is the temperature at the extremum of the crystallization peak.

The amount of complex shear viscosity was determined by a plate-plate rotary rheometer at an angular frequency of 0.5 rad / s and a temperature of 240 ° C. A rotary viscometer "DHR-1" from TA Instruments was used, the diameter being 25 mm and the gap spacing being 1 mm, and unannealed samples were dried for 7 days at 80 ° C. under vacuum and then subjected to a time-dependent frequency sweep (sequence test). measured with a circular frequency range of 500 to 0.5 rad / s The following further measuring parameters were used: deformation: 1, 0%, measuring time: 20 min, preheating time after sample preparation: 1, 5 min.

The sintering window (W) was determined as described above as the difference between the onset temperature of the melting (T _M ^onset ) and the onset temperature of the crystallization (T _c ^onset ).

The results are shown in Table 5.

Table 4

Example (Pia) (P2) (P4) (P6) (P7)

[% By weight] [weight%] [weight%] [weight%] [weight%]

Polyamide PA 6 PA 6.10 PA 66 PA 6/66 PA 6.36

V1 100

V2 80 20

V3 90 10

V4 90 10

V5 80 20

V6 80 20 Table 5

The use of semicrystalline polyamides as a blend with polyamide 6 does not lead to a widening of the sintering window over that of pure PA 6 (V1), but in some cases even to a significant reduction.

Blends of semi-crystalline polyamides with amorphous polyamides

To produce blends of partially crystalline polyamides with amorphous polyamides, the components shown in Table 6 were in the proportions shown in Table 6 in a DSM 15 cm ³ mini extruder (DSM Micro15 microcompounder) at a speed of 80 rev / min (revolutions per minute ) at 260 ° C for 3 min (minutes) mixing time and then extruded. The resulting extrudates were then ground in a mill and screened to a particle size of <200 μηι.

The resulting blends were characterized as described above. The sintering window broadening with respect to PA 6 corresponds to the difference between the sintering window (W _SP ) of the blend (the sintering powder (SP)) and the sintering window (W _A ) of PA 6 (component (A)). The results are shown in Table 7.

Table 6

Example (Pia) (AP1) (AP2) (AP3) (AP4) (AP5) (AP6)

[% By weight] [% by weight] [% by weight] [% by weight] [% by weight]

%]%]%]

Polyamide PA 6 PA PA PA 12 / PA 12 / PA PA 6I6T

DTDI MACM.14 MACM.I MACM.12 PACM.12

V7 100

V8 79 21 V9 79 21

V10 79 21

V1 1 79 21

V12 79 21

B13 79 21

Table 7

It can be clearly seen that only when using polyamide 6I / 6T as the amorphous polyamide (component (B)), a significant broadening of the sintering window (W) over that of pure polyamide 6 (comparative example V7) is achieved (example B13).

Blends of polyamide 6 with polyamide 6I / 6T

To prepare blends of polyamide 6 with polyamide 6I / 6T, the components listed in Table 8 were in the proportions shown in Table 8 in a DSM 15 cm ³ mini extruder (DSM Micro15 microcompounder) with a speed of 80 rev / min (revolutions per minute) at 260 ° C for a mixing time of 3 minutes (minutes) and then extruded. The resulting extrudates were then ground in a mill and screened to a particle size of <200 μηι.

The resulting blends were characterized as described above. The results are shown in Table 9.

Table 8

Example (Pia) (P1b) (P1c) (AP6) (AP7) (AP8)

[Weight%] [Weight%] [Weight%] [Weight%] [Weight%] [Weight%]

Polyamide PA 6 PA 6 PA 6 PA 6I6T PA 6I6T PA 6I6T V14 100

B15 79 21

B16 79 21

B17 79 21

B18 79 21

B19 79 21

Table 9

All PA 6I6T used cause a significant broadening of the sintering window and a significant increase in the glass transition temperature (T _G ) of the sintering powder (SP). These effects are independent of the PA 6 base polymer used.

Comparison of PA 6-PA 6I6T Blends with PA 6 / 6I6T Copolymers To prepare blends of polyamide 6 with polyamide 6I / 6T, the components shown in Table 10 were blended in the proportions shown in Table 10 in a DSM 15 cm ³ mini extruder ( DSM Micro15 microcompounder) at a speed of 80 rpm (revolutions per minute) at 260 ° C for a mixing time of 3 min (minutes) compounded and then extruded. The resulting extrudates were then ground in a mill and screened to a particle size of <200 μηι.

The resulting blends as well as the copolyamides (P5), (P8), (P9) and (P10) were characterized as described above. To determine the thermooxidative stability of the blends, the complex shear viscosity of freshly prepared blends and of blends after furnace storage at 0.5% oxygen was determined for 16 hours and 195 ° C. The ratio of the viscosity after storage (after aging) to the viscosity before storage (before aging) was determined. The viscosity measurement takes place by means of rotational rheology at a measuring frequency of 0.5 rad / s at a temperature of 240 ° C.

The results are shown in Table 1 1. Table 10

Table 1 1

It can be clearly seen that the copolymer from Example V20, despite its identical molar composition as the blend of Inventive Example B25, has a significantly lower melting temperature. In addition, the viscosity of the copolymer is significantly increased. The sintering window of the copolymer V20 is significantly broader than that of the blend of Example B25. However, the copolymer V20 has a significantly lower melting point than PA 6, so that the properties of the copolymer V20 differ significantly from those of the inventively preferred components (A) (in particular of PA 6). The copolymer V20 is therefore not suitable for the production of moldings by means of selective laser sintering.

Sintered powder (SP) for selective laser sintering For the preparation of the sintering powder (SP), the components shown in Table 12 were in the ratio shown in Table 12 in a twin-screw extruder (MC26) with a speed of 300 rev / min (revolutions per minute) and a throughput of 10 kg / h at a Temperature of 270 ° C compounded with a subsequent strand granulation.

The granules thus obtained were ground to a particle size of 10 to 100 μηι.

The properties of the resulting sintered powder (SP) were determined as described above. The results are shown in Table 13.

Table 12

Table 13

V32 1 10 nb 240 208 9.6 nb - -

B33 290 0.64 236 198 16.1 15.7 6.5 -

V34 158 8.5 262 233 14.3 n. B. - -

B35 335 0.72 258 224 18.4 14.1 4.1 -

B45 632 3.4 218.2 172.5 28.3 27.1 1 1, 6 15.9

B46 616 1, 9 218.2 178.4 22.4 22.8 5.7 1 1, 6

B47 682 2.5 217.9 177.7 24.0 n.b. 7.3 n.b.

It can be clearly seen that the sintering powder (SP) according to the invention has a significantly widened sintering window, even after thermooxidative storage (aging). The sintered powder (SP) according to the invention also exhibits a lower degradation of the molecular weight after aging, expressed as the viscosity ratio.

Laser sintering tests

The sintered powder (SP) was introduced with a layer thickness of 0.12 mm into the installation space at the temperature indicated in Table 14. Subsequently, the sintering powder (SP) was exposed to a laser at the laser power indicated in Table 14 and the specified dot pitch, with the speed of the laser over the sample being 5 m / s upon exposure. The dot pitch is also referred to as laser spacing or track pitch. In selective laser sintering, scanning is usually done in stripes. The dot pitch indicates the distance between the centers of the stripes, ie between the two centers of the laser beam of two stripes.

Table 14

Example Temperature Laser power Laser speed Point distance

[° C] [W] [m / s] [mm]

V24 209 18 5 0.2

B27 195 20/25 5 0.2

B28 195 20 5 0.2

B29 200 20/25/30 5 0.2

V30 200 20/25 5 0.2

B31 195 20/25 5 0.2

V32 215 25 5 0.2

B33 215 20/25 5 0.2

V34 240 25 5 0.2

B35 240 20/25 5 0.2

B45 198 25 5 0.2

B46 198 25 5 0.2 B47 198 25 5 0.2

Subsequently, the properties of the obtained tensile bars (sintered bars) were determined. The results are shown in Table 15. The warpage of the resulting sintered bars was determined by placing the sintered bar with the concave side on a planar surface. Subsequently, the distance (a _m ) between the planar surface and the upper edge of the center of the sintering rod was determined. In addition, the thickness (d _m ) in the middle of the sintering bar was determined. The delay in% is then determined according to the following formula:

V = 100 - (a _m -d _m ) / d _m

The dimension of the sintered rods was usually 80 mm in length, 10 mm in width and 4 mm in thickness.

The bending strength corresponds to the maximum stress in the bending test. The bending test is a three-point bending test according to EN ISO 178: 2010 + A1: 2013.

The process capability was assessed qualitatively, where "2" means "good", ie a slight distortion of the component and "5" "poor", ie a strong distortion of the component.

The surface roughness is given as mean roughness Ra and as average roughness Rz.

The average roughness Ra indicates the mean distance of a measuring point on the surface to a center line. This centerline intersects the actual profile of the surface within the datum line so that the sum of the profile deviations with respect to the centerline becomes minimal. The average roughness Ra thus corresponds to the arithmetic mean of the deviation from the centerline.

The average roughness depth Rz is determined as follows: A defined measuring section on the surface of the workpiece is divided into seven individual measuring sections, with the middle five measuring sections being the same size. The evaluation takes place only over these five measuring distances. From each of these individual measuring sections of the profile, the difference between the maximum and minimum values is determined (single roughness), then the mean value, the average roughness depth Rz, is formed from the five individual roughness depths thus obtained. Table 15

For the tensile bars (sintered bars) of Examples B45 to B47 were also determined in a dry state after drying at 80 ° C for 336 hours in vacuo, the tensile strength, tensile modulus and elongation at break according to ISO 527-1: 2012. The grades for the delay and the process capability were determined as above.

Table 15a

It can be seen that the shaped bodies produced from the sintering powders (SP) according to the invention, clearly lower distortion and better processability, have higher strength and a lower surface roughness.

The shaped bodies produced from the sintered powders (SP) according to the invention also have a very good tensile modulus and a good tensile strength. Their elongation at break is in a range suitable for their application. Blend of PA 6T / 6 and PA 6I / 6T, PA6 / 6.6 and PA 6I / 6T as well as PA 12 and PA 6I / 6T

To prepare blends of polyamide 6T / 6 with PA 6I / 6T and PA 12 with PA 6I / 6T, the components listed in Table 16 were in the proportions shown in Table 16 in a DSM 15 cm ³ mini extruder (DSM Micro15 microcompounder ) at a speed of 80 rpm (revolutions per minute) at 260 ° C for a mixing time of 3 minutes (minutes) and then extruded. The resulting extrudates were then ground in a mill and screened to a particle size of <200 μηι.

Examples V36 and V39 were not compounded and extruded but processed directly as received from the manufacturer. The resulting blends were characterized as described above. The results are shown in Table 17.

Table 16

Table 17

Example TG [° C] T _M [° C] Tc [° C] sintering window W

[K]

V36 37 177.2 130.3

V37 37 177.8 152.4 17.4

V38 36 177.2 152.3 17.3

V39 105 291, 1 241, 1 n.d.

V40 104 294.2 253.2 8.6 B41 109 286.9 231, 5 nd

V42 52 195.5 159.2 20.6

B43 56 194.4 153.2 24.6

B44 63 193.3 141, 0 32.5

In the blend of PA 12 with PA 6I / 6T (Comparative Example C38), the crystallization temperature (T _c ) of the blend remains opposite to that of

Crystallization temperature (T _c ) of pure PA 12 (Comparative Example V37) is the same, as does the melting temperature (T _M ) does not change. Thus, PA 6I / 6T does not broaden the sintering window.

In contrast, the crystallization temperature (T _c ) of the blend of PA 6T / 6 with PA 6I / 6T (Example B41) is well below the crystallization temperature (T _c ) of the pure PA 6T / 6. At the same time, although the melting temperature (T _M ) is slightly lowered compared to the melting temperature (T _M ) of pure PA 6T / 6, but the lowering of the melting temperature (T _M ) is lower than the lowering of the crystallization temperature (T _c ), so that a total Broadening of the sintering window is achieved.

In the blend of PA 6 / 6.6 with PA 6I / 6T, a lowering of the crystallization temperature (T _c ) is also observed. Although the melting temperature (T _M ) also decreases slightly compared to pure PA 6 / 6.6, but less than the crystallization temperature (T _c ), so that overall a significantly widened sintering window is achieved.

Claims

claims

Process for producing a shaped body by selective laser sintering of a sintering powder (SP), characterized in that the sintering powder (SP) comprises the components

(B) at least one polyamide 6I / 6T, wherein the sintering powder (SP) contains in the range of 75 to 90 wt .-% of component (A) and in the range of 10 to 25 wt .-% of component (B), in each case based on the sum of the percentages by weight of components (A) and (B).

A method according to claim 1, characterized in that the sintering powder (SP) additionally contains at least one additive selected from the group consisting of phenols, carbon black, inorganic black dyes and organic black dyes.

A method according to claim 1 or 2, characterized in that the sintering powder (SP) in the range of 75 to 85 wt .-% of component (A) and in the range of 15 to 25 wt .-% of component (B) contains, respectively based on the sum of the weight percent of components (A) and (B).

Method according to one of claims 1 to 3, characterized in that the sintering powder (SP) has a D10 value in the range of 10 to 30 μηη,

a D50 value in the range of 25 to 70 μηη and

has a D90 value in the range of 50 to 150 μηη. 5. The method according to any one of claims 1 to 4, characterized in that the sintering powder (SP) has a melting temperature (T _M ) in the range of 180 to 270 ° C.

6. The method according to any one of claims 1 to 5, characterized in that the sintering powder (SP) has a crystallization temperature (T _c ) in the range of 120 to 190 ° C.

5

7. The method according to any one of claims 1 to 6, characterized in that the sintering powder (SP) has a sintering window (W _S p), wherein the sintering window (W _S p), the difference between the onset temperature of the melting (T _M ^onset ) and the onset temperature of crystallization (T _c ^onset )

10 and wherein the sintering window (W _S p) is in the range of 15 to 40 K.

8. The method according to any one of claims 1 to 7, characterized in that the sintering powder (SP) is prepared by grinding the components (A) and (B) at a temperature in the range of -210 to -195 ° C.

15

9. The method according to any one of claims 1 to 8, characterized in that the component (A) is selected from the group consisting of PA 6, PA 6.6, PA 6.10, PA 6.12, PA 6.36, PA 6 / 6.6, PA 6 / 6I6T, PA 6 / 6T and PA 6 / 6I.

20 10. Moldings obtainable by a method according to one of

Claims 1 to 9.

1 1. Use of a polyamide 6I / 6T in a sintering powder (SP) containing the components

25

(A) at least one partially crystalline polyamide containing at least one unit selected from the group consisting of -NH- (CH ₂ ) _m -NH- units, where m is 4, 5, 6, 7 or 8, -CO- (CH ₂ ) _n -NH- units, where n is 3, 4, 5, 6 or 7, and -CO- (CH ₂ ) ₀ -CO-

30 units, where o is 2, 3, 4, 5 or 6,

(B) at least one polyamide 6I / 6T, for broadening the sintering window (W _S p) of the sintering powder (SP) 35 with respect to the sintering window (W _A ) of the component (A), wherein the

Sintering window (W _S p; W _A ) is in each case the difference between the onset temperature of the melting (T _M ^onset ) and the onset temperature of the crystallization (T _c ^onset ).