METHOD FOR PRODUCING A POWDER COMPRISING AT LEAST ONE POLYMER AND SUCH A TYPE OF POWDER

Abstract

A method for producing a powder comprising at least one polymer for use in a method for the additive manufacture of a three-dimensional object is described. The method includes the step of mechanically treating the powder in a mixer with at least one rotating mixing blade, wherein the powder is exposed to a temperature T.sub.B and T.sub.B is at least 30° C. and is below the melting point T.sub.m of the polymer (determined according to DIN EN ISO 11357) if the polymer is a semi-crystalline polymer, or wherein T.sub.B is at least 30° C. and wherein T.sub.B is at most 50° C. above the glass transition temperature T.sub.g of the polymer (determined according to DIN EN ISO 11357) if the polymer is a melt-amorphous polymer. Compared to a time before the start of the treatment, it may be achieved that after the treatment, the bulk density of the powder is increased by at least 10% (or in the case of polymer, copolymer or polymer blend of polyamide at least 2% and more) and the BET surface area is decreased by at least 10%, and optionally also the pourability is improved by at least 10%.

Claims

1. Method for producing a powder comprising at least one polymer for use in a method for the additive manufacture of a three-dimensional object, comprising the step of mechanically treating the powder in a mixer with at least one rotating mixing blade, wherein the powder is exposed to a temperature T.sub.B, wherein T.sub.B is at least 30° C. and wherein T.sub.B is below the melting point T.sub.m of the polymer (determined according to DIN EN ISO 11357) if the polymer is a semi-crystalline polymer, or wherein T.sub.B is at least 30° C. and wherein T.sub.B is at most 50° C. above the glass transition temperature T.sub.g of the polymer (determined according to DIN EN ISO 11357) if the polymer is a melt-amorphous polymer.

2. Method according to claim 1, where T.sub.B is defined by one or more of the following conditions or methods (i) to (vii): (i) T.sub.B is above the heat deflection temperature HDT-A of the polymer (determined according to DIN EN ISO 75; measured in a reference measurement on a test specimen consisting only of the polymer, i.e. without any additives; (ii) T.sub.B is above the heat deflection temperature HDT-A of the polymer (determined according to DIN EN ISO 75; measured in a reference measurement on a test specimen consisting only of the polymer, i.e. without any additives), wherein the polymer is a semi-crystalline polymer; (iii) T.sub.B is at most 100° C. below the glass transition temperature T.sub.g of the polymer (determined according to DIN EN ISO 11357); (iv) T.sub.B is at most 100° C. below the glass transition temperature T.sub.g of the polymer (determined according to DIN EN ISO 11357), wherein the polymer is a semi-crystalline polymer; (v) T.sub.B is at most 100° C. below the glass transition temperature T.sub.g of the polymer (determined according to DIN EN ISO 11357), wherein the polymer is a melt-amorphous polymer; (vi) for a polymer powder to be used, T.sub.B is at most at a temperature T.sub.max determined in a temperature-current consumption measurement of the same polymer in a mixer with a mixing blade rotation in the range of 20 to 50 m/s during the heating process, wherein T.sub.max is determined in the temperature-current consumption measurement by one or both methods (a) or (b) as follows: (a) maximum T.sub.B is determined by a temperature-current consumption diagram, wherein one data point is recorded every minute, wherein [(gradient/min)/current consumption] considered only in the range Tg−20° C. to T.sub.m is at least greater than 5% and at most 30%; or (b) maximum T.sub.B is determined by a temperature-current consumption diagram, wherein the current consumption of the mixer rises disproportionately strongly within a short time to an increased current consumption value Ix, which fulfils at least one condition selected from the group consisting of the conditions: Ix is at least 10% higher than the average value of at least 10 preceding measuring points, recorded at at least one measurement per minute, wherein only current increases in the range Tg−20° C. to Tm are considered, Ix is at most 100%, higher than the average value of at least 10 preceding measuring points, recorded at at least one measurement per minute, wherein only current increases in the range Tg−20° C. to Tm are considered; (vii) T.sub.B is at (±10° C.) or below the temperature T.sub.max at which the bulk density of the powder drops to a value below that of the untreated powder as a result of the use of the mixer, wherein the maximum T.sub.max is determined by a test series with different T.sub.B and otherwise the same mixing conditions.

3. Method according to claim 1, wherein the maximum speed of the mixing blade during a heating time before reaching T.sub.B fulfils at least one condition selected from the group consisting of the condition; the maximum speed is at least 20 m/s if the volume of the mixer is more than 40 litres, the maximum speed of the mixing blade during a heating time before reaching T.sub.B is at most 100 m/s if the volume of the mixer is at most 40 litres.

4. Method according to claim 1, wherein at least part of the powder, starting from an initial temperature which is below T.sub.B, reaches the temperature T.sub.B within a heating time of 20 min.

5. Method according to claim 1, wherein, following to reaching T.sub.B, the temperature is maintained in a range of T.sub.B±20° C. for a holding time.

6. Method according to claim 1, wherein the polymer fulfils at least one condition selected from the group consisting of the conditions: the polymer is a semi-crystalline polymer and T.sub.B is above the heat deflection temperature HDT-A, the polymer is a semi-crystalline polymer and T.sub.B is below the heat deflection temperature HDT-B, the polymer is a semi-crystalline polymer and T.sub.B is at least 20° C. below the melting point T.sub.m, the polymer is a semi-crystalline polymer, copolymer or polymer blend of polyamide and T.sub.B is: at least 50° C. below the melting point T.sub.m, wherein the polymer is a semi-crystalline polymer and wherein T.sub.B is at maximum 250° C., the polymer is a semi-crystalline polymer and wherein T.sub.B is at maximum at maximum 300° C., the polymer is a semi-crystalline polymer and T.sub.B is at most 50° C. below the glass transition temperature T.sub.g of the polymer (determined according to DIN EN ISO 11357), the polymer is a semi-crystalline polymer and T.sub.B is at most 20° C. below the glass transition temperature T.sub.g of the polymer (determined according to DIN EN ISO 11357), the polymer is a semi-crystalline polymer and Tg is at most 10° C. below the glass transition temperature Tg of the polymer (determined according to DIN EN ISO 11357), the polymer is a melt-amorphous polymer and T.sub.B is at most 20° C. above the glass transition temperature T.sub.g and at least 10° C., below the glass transition temperature T.sub.g, the polymer is a melt-amorphous polymer and T.sub.B is at most 20° C. above the glass transition temperature T.sub.g and at least 20° C. below the glass transition temperature T.sub.g, the polymer is a melt-amorphous polymer and T.sub.B is above the heat deflection temperature HDT-A (determined according to DIN EN ISO 75), the polymer is a melt-amorphous polymer and T.sub.B is between the heat deflection temperature HDT-A (determined according to DIN EN ISO 75) and the heat deflection temperature HDT-B (determined according to DIN EN ISO 75).

7. Method according to claim 1, further comprising a further step in which the powder is exposed to a temperature T.sub.N by heating for a period of at least 30 min and/or at most 30 hours.

8. Method according to claim 7, wherein the further step is associated with one or more of the conditions, each compared to the value of the corresponding parameter before the further step, selected from the group consisting of the conditions: increase of the bulk density, improvement of the pourability, reduction of the BET, increase of the onset temperature of the melting point, increase of the melting enthalpy of the treated powder.

9. Method for producing a powder comprising at least one polymer for use in a method for the additive manufacture of a three-dimensional object, comprising the step of mechanically treating the powder in a mixer with at least one rotating mixing blade, wherein the occurring temperature T.sub.B of the powder is adjusted in such a way that, compared to a time before the start of the treatment, after the treatment the bulk density of the powder is increased by at least 10% or, in the case of polymer, copolymer or polymer blend of polyamide, by at least 2%, and the BET surface area of the powder is reduced by at least 10%, optionally also the pourability is improved by at least 10%.

10. Method according to claim 1, wherein the polymer is an amorphous, a pseudo-amorphous, or a semi-crystalline polymer, wherein at least one of the following measures is taken: (a) use of at least two mixing blades in a mixer whose mixing chamber has a volume of at least 5 L and/or at most 100 L; (b) use of at least four mixing blades in a mixer whose mixing chamber has a volume of at least 200 L and/or at most 1000 L; (c) choice of a mixer degree of filling of at least 30% and/or at most 99%; (d) the temperature T.sub.B is set by adjusting the rotation speed of the mixer and the treatment duration; (e) the powder, starting from the initial temperature, reaches the temperature T.sub.B within not more than 25 minutes.

11. Method according to claim 1, wherein the powder comprises at least one polymer selected from the group consisting of the following polymers or a polymer blend of at least two polymers selected from the group consisting of the following polymers: polyetherimides, polycarbonates, polyarylene sulfides, polyphenylene sulfones, polysulfones, polyphenylene oxides, polyether sulfones, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-styrene-acrylate copolymers (ASA), polyvinyl chloride, polyacrylates, polyesters, polyamides, polyaryletherketones, polyethers, polyurethanes, polyimides, polyamide-imides, polysiloxanes, polyolefins, and copolymers which have at least two different repeating units of the above polymers.

12. Method according to claim 1, wherein the powder comprises at least one polymer selected from the group consisting of the following polymers or a polymer blend of at least two polymers selected from the group consisting of the following polymers: polyaryletherketone, wherein the polyaryletherketone has a melting point T.sub.m (determined according to DIN EN ISO 11357) of at most 330° C., polyaryletherketone, wherein the polyaryletherketone has a melting point T.sub.m (determined according to DIN EN ISO 11357) of at most 320° C., polyaryletherketone, wherein the polyaryletherketone has a melting point T.sub.m (determined according to DIN EN ISO 11357) of at most 310° C., polyaryletherketone, wherein the polyaryletherketone has a glass transition temperature T.sub.g (determined according to DIN EN ISO 11357) of at least 120° C., polyaryletherketone, wherein the polyaryletherketone has a glass transition temperature T.sub.g (determined according to DIN EN ISO 11357) of at least 140° C., polyaryletherketone, wherein the polyaryletherketone has a glass transition temperature T.sub.g (determined according to DIN EN ISO 11357) of at least 160° C.; polyether ketone ketone, wherein the polyether ketone ketone has a terephthalic acid/isophthalic acid isomer ratio with a terephthalic acid mole fraction of at most 80%, polyether ketone ketone, wherein the polyether ketone ketone has a terephthalic acid/isophthalic acid isomer ratio with a terephthalic acid mole fraction of at most 70%, polyether ketone ketone, wherein the polyether ketone ketone has a terephthalic acid/isophthalic acid isomer ratio with a terephthalic acid mole fraction of at most 65%, polyether ketone ketone, wherein the polyether ketone ketone has a terephthalic acid/isophthalic acid isomer ratio with a terephthalic acid mole fraction of at least 20%, polyether ketone ketone, wherein the polyether ketone ketone has a terephthalic acid/isophthalic acid isomer ratio with a terephthalic acid mole fraction of at least 40%, polyether ketone ketone, wherein the polyether ketone ketone has a terephthalic acid/isophthalic acid isomer ratio with a terephthalic acid mole fraction of at least 55%, polyether ether ketone or its copolymer with diphenyl ether ketone (PEEK-PEEK); polyetherimide, wherein the polyetherimide comprises repeating units selected from the group of Formulae I to III ##STR00009## polycarbonate, wherein the polycarbonate comprises repeating units according to ##STR00010## polyarylene sulfide, wherein the polyphenylene sulfide that comprises repeating units according to ##STR00011## polyaryletherketone-polyetherimide polymer blend, polyetherketone-polyetherimide-polycarbonate polymer blend, polyphenylene sulfide-polyetherimide polymer blend polyetherimide-polycarbonate polymer blend, polyetherimide-polycarbonate polymer blend, wherein the polyaryletherketone of the polymer blend is a polyether ketone ketone with a terephthalic acid/isophthalic acid isomer ratio between 65/35 and 55/45, polyetherimide-polycarbonate polymer blend, wherein the polyetherimide of the polymer blend comprises the repeating unit according to formula I defined above, polyetherimide-polycarbonate polymer blend, wherein the polycarbonate of the polymer blend comprises the repeating unit according to ##STR00012## polypheylene sulfide polymer blend comprising a repeating unit according to ##STR00013##

13. Method according to claim 1, wherein as polymer, a semi-crystalline polymer is used, wherein in this case T.sub.B is below the crystallisation point Tk (determined according to DIN EN ISO 11357 at a cooling rate of 20° C./min), or wherein a pseudo-amorphous polymer is used, wherein in this case T.sub.B is at most 40° C. above Tg of the polymers, or wherein a melt-amorphous polymer is used, wherein in this case T.sub.B is at most 20° C. above Tg of the polymer.

14. Powder comprising at least one polymer, wherein the powder has been mechanically treated in a mixer with at least one rotating mixing blade, wherein compared to a time before the start of the treatment, after the treatment the bulk density of the powder is increased by at least 10% or, in the case of polymer, copolymer or polymer blend of polyamide, by at least 2%, and the BET surface area of the powder is reduced by at least 10%.

15. Powder according to claim 15, wherein the powder comprises at least one polymer that is selected from the group of polymers and polyblends defined in anyone of claims 11, 12, and 13.

16. Powder comprising at least one polymer, wherein the powder is selected from the group consisting of: (i) the powder comprises polyether ketone ketone, wherein the polyether ketone ketone has a terephthalic acid/isophthalic acid isomeric ratio with a terephthalic acid mole fraction of at most 80% and/or at/least 20%, and wherein the powder has: the d.sub.90 value is at most 150 μm (determined according to ISO 13322-2), the bulk density has a value of at least 0.33 g/cm.sup.3, and/or the BET surface area of the powder is at most 10 m.sup.2/g; (ii) the powder comprises polyether ketone ketone and at least 20% by weight of carbon fibres as filler, wherein the powder has: a bulk density of more than 0.50 g/cm.sup.3, and/or wherein the BET surface area of the powder is at most 10 m.sup.2/g; (iii) the powder comprises polyether ether ketone or polyether ether ketone-polyether diphenyl ether ketone (PEEK-PEDEK), wherein the powder has: the d.sub.90 value of the powder (determined according to ISO 13322-2) is at most 150 μm, and/or the bulk density is at least 0.32 g/cm.sup.3, and/or the BET surface area of the powder is at most 40 m.sup.2/g; (v) the powder comprises polyphenylene sulfide, the d.sub.90 value of the powder is at most 150 μm (determined according to ISO 13322-2), and the bulk density is at least 0.48 g/cm.sup.3, and/or wherein the BET surface area of the powder is at most 10 m.sup.2/g; (v) the powder comprises a polymer blend of polyphenylene sulfide and polyetherimide, wherein the molar fraction polyphenylene sulfide:polyetherimide is at least 40:60, and wherein the d90 value of the powder is at most 150 μm (determined according to ISO 13322-2), and wherein the bulk density is at least 0.32 g/cm.sup.3; (vi) the powder comprises polyamide 12, wherein the d.sub.90 value of the powder is at most 150 μm (determined according to ISO 13322-2), and wherein the bulk density is at least 0.35 g/cm.sup.3, and/or wherein the BET surface area of the powder is at most 10 m.sup.2/g; (vii) the powder comprises polyamide 11, wherein the d.sub.90 value of the powder is at most 150 μm (determined according to ISO 13322-2), and wherein the bulk density is at least 0.35 g/cm.sup.3, and/or wherein the BET surface area of the powder is at most 10 m.sup.2/g; (viii) the powder comprises polypropylene, wherein the d.sub.90 value of the powder is at most 150 μm (determined according to ISO 13322-2), and wherein the bulk density is at least 0.36 g/cm.sup.3, and/or wherein the BET surface area of the powder is at most 10 m.sup.2/g.

17. Method according to claim 1, wherein the powder comprises at least one additive selected from the group consisting of: heat stabilizers, oxidation stabilizers, UV stabilizers, fillers, dyes, plasticizers, reinforcing fibres, dyes, IR absorbers, SiO.sub.2 particles, carbon black particles, carbon fibres, carbon nanotubes, glass fibres, mineral fibres, wollastonite, aramid fibres, Kevlar fibres, glass beads, mineral fillers, inorganic pigments, organic pigments, flame retardants, phosphate-containing flame retardants such as ammonium polyphosphate, brominated flame retardants, other halogenated flame retardants, inorganic flame retardants such as magnesium hydroxide or aluminium hydroxide, flow aids, polysiloxanes, and fumed silica.

18. Method for the additive manufacture of a three-dimensional object, comprising the steps: providing a powder as defined in claim 1, and producing a three-dimensional object by selective layer-by-layer solidification of the powder provided at the positions corresponding to the cross-section of the object in a respective layer by means of exposure to electromagnetic radiation.

19. Method according to claim 1, wherein the powder has been produced by melt spinning including fibre cutting.

20. Powder according to claim 17, wherein the powder selected from the powders according to (i) to (viii) has been obtained by melt spinning which includes fibre cutting.

21. Powder according to claim 15, wherein the powder comprises at least one additive selected from the group consisting of: heat stabilizers, oxidation stabilizers, UV stabilizers, fillers, dyes, plasticizers, reinforcing fibres, dyes, IR absorbers, SiO.sub.2 particles, carbon black particles, carbon fibres, carbon nanotubes, glass fibres, mineral fibres, wollastonite, aramid fibres, Kevlar fibres, glass beads, mineral fillers, inorganic pigments, organic pigments, flame retardants, phosphate-containing flame retardants such as ammonium polyphosphate, brominated flame retardants, other halogenated flame retardants, inorganic flame retardants such as magnesium hydroxide or aluminium hydroxide, flow aids, polysiloxanes, and fumed silica.

Description

[0260] Further features and advantages of the invention can be found in the description of embodiments and examples with reference to the attached drawings.

[0261] FIG. 1 shows a schematic and vertical sectional view of a device with which the method for the additive manufacture of a three-dimensional object can be carried out.

[0262] FIG. 2 shows a mixing blade arrangement which can be used according to the invention.

[0263] FIG. 3 shows a plot of the bulk density vs. the total treatment time for an example of the invention.

[0264] FIG. 4 shows a plot of the bulk density vs. the maximum temperature occurring in the mixer during treatment for a further example of the present invention.

[0265] FIG. 5 shows the relationship between maximum temperature and powder mass for this example, wherein the actually dependent variable is plotted on the abscissa.

[0266] FIG. 6 shows a plot of the bulk density vs. the total treatment time for a further example of the present invention.

[0267] FIG. 7 shows a plot of the bulk density vs. the holding time for this example.

[0268] FIG. 8 shows in a temperature-current consumption diagram the change in current consumption in the mixer over time compared to the increase in temperature in experiment V23 of Example 5.

[0269] FIG. 9 shows in a temperature-current consumption diagram the change in current consumption in the mixer over time compared to the increase in temperature in experiment V3 of Example 10.

[0270] FIG. 10 shows in a temperature-current consumption diagram the change in current consumption in the mixer over time compared to the increase in temperature in experiment V4 of Example 11, during the heating phase.

[0271] FIG. 11 shows in a temperature-current consumption diagram the change in current consumption in the mixer over time compared to the rise in temperature in experiment V2 of Example 12.

[0272] FIG. 12 shows in a temperature-current consumption diagram the change in current consumption in the mixer over time compared to the increase in temperature in experiment V9 of Example 13.

[0273] The device shown in FIG. 1 is a laser sintering or laser melting device 1 for manufacturing an object 2 from a material 15 in powder form. Powder material 15 is also referred to as “building material” in this context. With regard to the choice of the powder material, reference is made to the above description.

[0274] Device 1 comprises a process chamber 3 with a chamber wall 4. In the process chamber 3, a container 5 open at the top is arranged with a container wall 6. A working plane 7 is defined by the upper opening of the container 5, wherein the area of the working plane 7 lying within the opening, which can be used for the construction of the object 2, is called build area 8. In the container 5, there is a support 10 movable in a vertical direction V, to which a base plate 11 is attached, which closes the container 5 at the bottom and thus forms its bottom. The base plate 11 may be a plate formed separately from the support 10 and attached to the support 10, or it may be formed integrally with the support 10. Depending on the powder and process used, the base plate 11 may also have a building platform 12 attached as a building base on which the object 2 is built. However, object 2 can also be built on the base plate 11 itself, which then serves as a building base. In FIG. 1, the object to be built is shown in an intermediate state. It consists of several solidified layers and is surrounded by unsolidified powder material 13.

[0275] Furthermore, the device 1 comprises a storage container 14 for a powder material 15 which can be solidified by electromagnetic radiation and a recoater 16 which can be moved in a horizontal direction H to apply layers of the powder material 15 within the build area 8. Preferably, a radiation heater 17 is arranged in the process chamber 3, which serves to heat the applied powder material 15. For example, an infrared radiator 17 can be provided as radiation heater 17.

[0276] Furthermore, the device 1 comprises an irradiation device 20 with a laser 21 which generates a laser beam 22 which is deflected by a deflecting device 23 and focused by a focusing device 24 to the working plane 7 via a coupling window 25 arranged at the top of the process chamber 3 in the chamber wall 4.

[0277] Furthermore, the device 1 comprises a control device 29, by means of which the individual components of the device 1 are controlled in a coordinated manner to carry out a method for the manufacture of a three-dimensional object 2. The control device 29 may include a CPU, the operation of which is controlled by a computer program (software). The computer program may be stored separately from the device 1 on a storage medium from which it can be loaded into the device 1, particularly into the control device 29.

[0278] The laser sintering devices offered by the applicant under the type designations P110, P396, P500, P770, P800 and P810, for example, have proved to be suitable for the execution of the invention.

[0279] During operation, in order to apply a layer of the powder material 15, the support 10 is lowered by a height which preferably corresponds to the desired thickness of the layer of the powder material 15. The recoater 16 first moves to the storage container 14 and takes from it a quantity of powdered material 15 sufficient to apply a layer. Then the recoater 16 moves over the build area 8 and applies a thin layer of the powder material 15 to the building base 10, 11, 12 or a previously existing powder layer. The application is carried out at least over the entire cross-section of the object to be produced, preferably over the entire build area 8. The powder material 15 is preferably heated to a processing temperature by means of the radiant heater 17. Then the cross-section of the object to be produced 2 is scanned by the laser beam 22 so that this area of the applied layer is solidified. The steps are repeated until the object 2 is finished and can be removed from the container 5.

[0280] The invention is preferably applied to, but not limited to, laser sintering or laser melting. It may be applied to various methods as far as these concern the production of a three-dimensional object by applying and selectively solidifying a powder material layer by layer by means of exposure to electromagnetic radiation.

[0281] The irradiation device 20 may, for example, comprise one or more gas or solid-state lasers or lasers of any other kind, such as laser diodes, in particular line exposure devices using VCSEL (Vertical Cavity Surface Emitting Laser) or VECSEL (Vertical External Cavity Surface Emitting Laser). In general, any radiation source which may be used to apply electromagnetic radiation selectively to a layer of the powder material 15 may be used as an irradiation device. For example, instead of a laser, another light source or any other source of electromagnetic radiation suitable for solidifying the powder material 15 may be used. Instead of deflecting a beam, it is also possible to use exposure with a movable line irradiator. The invention may also be applied to selective mask sintering, in which a light source radiating over an area and a mask are used, or to high-speed sintering (HSS), in which a material is selectively applied to the powder material 15, which increases the radiation absorption at the positions corresponding to the cross section of the three-dimensional object 2 (absorption sintering) or reduces it at the other positions of the build area 8 (inhibition sintering), and is then exposed non-selectively over a large area or with a movable line irradiator.

[0282] According to the invention, it is preferred to preheat the powder material 15 before it is selectively sintered or melted and solidified by the exposure to electromagnetic radiation. in the course of preheating, the powdered material 15 is heated to an elevated processing temperature, so that less energy to be introduced by the electromagnetic radiation serving for selective solidification.

[0283] Within the context of the invention, commercially available mixers may be used.

[0284] For example, a Henschel mixer type FML, machine size 40 from the supplier Zeppelin Systems GmbH, Germany, may be used. This mixer is hereinafter referred to as “Henschel FML”. The mixing chamber, in which the mixing material is located during operation of the mixer, has a usable volume of 13 to 36 litres.

[0285] The degree of filling of the mixer is the quotient of the volume of the powder filled into the mixer and the volume of the mixing chamber of the mixer. The volume of the powder is determined at a time before the method according to the invention is carried out. The degree of filling is hereinafter referred to as F.

[0286] Furthermore, a mixer of the type “Mixaco LAB-CM 6-12 MB/SM” with a container size of 6 litres may also be used, for example.

[0287] However, other mixers may also be used, particularly other commercially available mixers which allow the batch-wise processing of larger powder quantities on a kilogram scale in one batch.

[0288] In FIG. 2, a mixing blade arrangement 100 is shown schematically. Examples 1 to 8 may be realised with such a mixing blade arrangement 100.

[0289] The mixing blade arrangement 100 has a shaft 107 along its length. A bottom scraper 105, three straight mixing blades 101, 102, 103 and an upwardly curved mixing horn 106 are attached to the shaft in this sequence. The mixing blades are often referred to as “mixer blades”. The mixing blades 101, 102, 103 are straight, i.e. neither bent upwards nor downwards. Bottom scraper 105 and mixing horn 106 are therefore examples of mixing blades that are not straight. The mixing blades 101, 102, 103 may preferably be arranged at an inclined angle around the shaft 107. Particularly the distances between the bottom scraper 105, mixing blades 101, 102, 103 and mixing horn 106, which are called y1, y2, y3 and y4, are typically in the range of 10 to 40 mm, preferably in the range of 25 to 35 mm. The maximum lateral extension of the bottom scraper 105, the mixing blades 101, 102, 103 and the mixing horn 106 is designated as x. x corresponds to twice the mixing blade radius r. x is preferably in the range from 100 to 1000 mm, preferably in the range from 200 to 900 mm. In the case of the mixer of the “Henschel FML” type, machine size 40, for which the mixing container inside diameter is 386 mm and the mixing container height is 396 mm, x=350 mm. In case of the mixer type “Henschel FML”, machine size 600, where the inner diameter of the mixing container is 1330 mm and the height of the mixing container is 1370 mm, x=870 mm. In case of the mixer of the type “Mixaco LAB-CM 6-12 CM/SM” with a container size (volume of the mixing container) of 6 litres, x=222.8 mm.

[0290] For the mixer type “Henschel FML”, machine size 40, a mixer with a bottom scraper 105, a mixing horn 106 and a straight mixing blade 101 is preferred. For the mixer type “Henschel FML”, machine size 600, a mixer with a bottom scraper 105, a mixing horn 106 and three straight mixing blades 101, 102, 103 is preferably used. The preferred number of mixing blades 101, 102, 103 is therefore selected depending on the size of the used mixer.

[0291] It is preferred that the mixing blades 101, 102, 103 are arranged in a twisted manner to each other relative to the shaft. For example, based on the situation shown in FIG. 2, mixing blade 102 could be arranged rotated by 90° relative to the other mixing blades 101, 103.

[0292] During operation, the mixing blade assembly 100 is located inside a mixing container (not shown in FIG. 2), inside which the powder (not shown in FIG. 2) to be treated according to the method according to the invention is also located. The bottom scraper 105 is arranged closer to the bottom of the mixing container than the mixing blades 101, 102, 103 and the mixing horn 106.

[0293] During operation, the shaft 107 is rotated around its own axis by means of a motor. The rotation is shown by the arrow 108. The bottom scraper 105, the mixing blades 101, 102, 103 and the mixing horn 106 are preferably arranged rotationally symmetrically in relation to the shaft 107, so that no imbalance occurs when the shaft rotates.

EXAMPLES

[0294] Several examples of the present invention are described below. The examples described below serve to illustrate the present invention and therefore do not limit the scope of the present invention in any way. It is obvious to the person skilled in the art that the examples described below may be altered and modified in the context of the entire disclosure. The features of the individual examples may be combined with each other wherever possible.

Example 1

[0295] In Example 1, polyphenylene sulfide powder was used. Polyphenylene sulfide (also referred to as Poly(thio-p-phenylene) and usually abbreviated as “PPS”) is a high-temperature resistant thermoplastic plastic with the following repeating unit:

##STR00008##

[0296] A commercially available product was used which is offered by Toray Industries, Inc., Japan under the commercial name “Toray 50NNAB”. The quantiles d.sub.10, d.sub.50 and d.sub.90, measured before the method according to the invention was carried out, are given in the first line “Comparison” of table 3.

[0297] A mixer of the type “Henschel FML” was used as a mixer. The casing of the mixer was not cooled.

[0298] Phase 1 refers to the heating phase, i.e. the phase up to the moment when the mixed material (powder) in the mixer reaches the maximum temperature T.sub.max T.sub.max corresponds to the treatment temperature T.sub.B. The casing of the mixer only reaches the less high temperature T.sub.Man. The revolution frequency of the mixer in phase 1 is called D.sub.1. The duration of phase 1 is called t.sub.1. Phase 2 is the holding phase, i.e. the phase during which the temperature reached was maintained. The revolution frequency of the mixer in phase 2 is referred to as D.sub.2. The duration of phase 2 is referred to as t.sub.2.

[0299] The designations T.sub.max, T.sub.Man, D.sub.1, D.sub.2, t.sub.1, t.sub.2 are used in the same manner in the further examples.

[0300] The method according to the invention was carried out three times with independent powder batches (nos. 1 to 3). The values for T.sub.max, T.sub.Man, D.sub.1, D.sub.2, t.sub.1, t.sub.2 and t.sub.1+t.sub.2 for the powder batches nos. 1 to 3 are stated in Table 2.

[0301] The values obtained for the bulk density S, the BET surface area, the fraction of powder particles with a particle size of <10 μm in volume percent (%<10 μm), the quantiles d.sub.10, d.sub.50 and d.sub.90 of the particle size distribution and the pourability determined by means of the 25 mm nozzle are given for nos. 1 to 3 in Table 3. These are the average values from three measurements each. Comparative values for the PPS powder which has not been treated according to the invention are also given in Table 3. If no value is stated in a column and line, this means that the corresponding measurement has not been carried out.

TABLE-US-00002 TABLE 2 T.sub.max T.sub.Man D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [° C.] [m/s] [m/s] [min] [min] [min] 1 175 154 36.0 21.6 14 7 21 2 175.5 158 36.0 21.6 13 6 19 3 175 160 36.0 19.8 9 8 17

TABLE-US-00003 TABLE 3 Pour- S BET % <10 d.sub.10 d.sub.50 d.sub.90 ability No. [g/cm.sup.3] [m.sup.2/g] μm [μm] [μm] [μm] [s] Comparison 0.458 15.69 0.4 38 72 126 no free- flowing 1 0.516 7.762 0.2 41 70 120 5.4 2 0.512 — 0.2 40 71 124 5.8 3 0.512 — 0.3 40 71 123 5.4

[0302] In FIG. 3, the achieved bulk density is plotted vs. the total treatment time t.sub.1+t.sub.2. The data point at t.sub.1+t.sub.2=0 represents the PPS powder that has not been treated in the manner according to the invention. From FIG. 3, it can be clearly seen that a significant increase in the bulk density was achieved by the treatment according to the invention at temperatures above the glass transition temperature T.sub.g (T.sub.g of PPS≈90 to 110° C., or 105° C. for the PPS used here; compare Table 2 for the temperature T.sub.max occurring during treatment). This effect was already achieved at a total treatment time of 17 min. For example at temperatures in the range between 105° C. and 180° C., depending on the production method.

[0303] In addition, the treatment has also significantly improved the pourability. While the ground powder is not free-flowing before the treatment according to the invention, it shows a good flowability of approx. 5 seconds afterwards (test with 25 mm nozzle), see Table 3.

[0304] In addition, the BET surface has been drastically reduced from approx. 16 m.sup.2/g to approx. 8 m.sup.2/g by the treatment according to the invention, cf. Table 3.

[0305] In addition, the fraction of fine powder has been significantly reduced from approx. 0.4% to approx. 0.2% as a result of the treatment according to the invention, cf. Table 3.

Example 2

[0306] In Example 2, a polyblend of 50 wt. % PPS and 50 wt. % polyetherimide (PEI) was used. In Example 2 a total of 1.65 kg of the polyblend powder was used. The powder obtained by cryogenic grinding using a pin mill is fibrous and has a very low bulk density of approx. 0.27 g/cm.sup.3. The quantiles d.sub.10, d.sub.50 and d.sub.90, measured before the method according to the invention was carried out, are given in the first line of Table 5.

[0307] A mixer of the type “Mixaco LAB-CM 6-12 CM/SM” with a container size of 6 litres was used as a mixer. The casing of the mixer was not cooled.

[0308] The values for T.sub.max, T.sub.Man, D.sub.1, D.sub.2, t.sub.1, t.sub.2 and t.sub.1+t.sub.2 are stated in Table 4, wherein the powder batch of Example 2 has the number 4.

[0309] The values obtained for the bulk density S and the quantiles d.sub.10, d.sub.50 and d.sub.90 of the grain size distribution are given in Table 5. They are the average values of three measurements each. Also in Table 5, comparative values are given for the powder of PPS-PEI-Polyblend, which has not been treated in the manner according to the invention. If no value is stated in a column and line, this means that the corresponding measurement has not been carried out.

TABLE-US-00004 TABLE 4 T.sub.max T.sub.Man D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [° C.] [m/s] [m/s] [min] [min] [min] 4 146.2 — 34.42 29.17 15 10 25

TABLE-US-00005 TABLE 5 No. S [g/cm.sup.3] d.sub.10 [μm] d.sub.50 [μm] d.sub.90 [μm] Comparison 0.273 51 99 142 4 0.428 33 85 133

[0310] By the treatment according to the invention above the T.sub.g value of PPS (T.sub.g≈90 to 100° C.), the bulk density could be increased very significantly to 0.428 g/cm3. This corresponds to an increase of 57%.

[0311] The application of temperatures above the T.sub.g value for PEI (approx. 215° C.) and below the melting point of PPS (approx. 275° C.) is optionally possible to achieve an even more significant increase in the bulk density.

Example 3

[0312] In Example 3, a polyether ketone ketone (PEKK) with a copolymerisation ratio of terephthalic acid units to isophthalic acid units of approx. 60:40 was used. This is a PAEK plastic.

[0313] A commercially available product was used, which is commercialised under the trade name “Kepstan 6002PF” by Arkema S.A., France. This coarse powder was ground and screened to the appropriate particle size.

[0314] A mixer of the type “Henschel FML” was used as a mixer. The casing of the mixer was cooled by water cooling.

[0315] The method according to the invention was carried out six times with independent powder batches (nos. 5 to 10). The mass of a powder batch is designated as m. The values for T.sub.max, T.sub.Man, m, F, D.sub.1, D.sub.2, t.sub.1, t.sub.2 and t.sub.1+t.sub.2 are stated in Table 6 for batches nos. 6 to 10. F is the degree of filling of the mixer. This designation is used in the same manner in the further examples.

[0316] The values obtained for the bulk density S, the BET surface area, the fraction of powder particles with a particle size of <10 μm in volume percent (%<10 μm) and the quantiles d.sub.10, d.sub.50 and d.sub.90 of the particle size distribution are given in Table 7. These are the average values from three measurements each. Comparative values for the 60:40 PEKK powder, which has not been treated in the manner according to the invention, are also given in Table 7. If no value is stated in a column and row, this means that the corresponding measurement has not been carried out.

TABLE-US-00006 TABLE 6 T.sub.max T.sub.Man m F D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [° C.] [kg] [%] [m/s] [m/s] [min] [min] [min]  5 120.7 97 9 78.6 46.8 39.6 10 10 20  6 90.2 72 8 69.9 46.8 46.8 8 12 20  7 113 91 9 78.6 46.8 46.8 6 14 20  8 120 97 9 78.6 46.8 46.8 7 13 20  9 129 104 9 78.6 46.8 46.8 8 12 20 10 70.1 57 6.6 57.7 46.8 46.8 10 10 20

TABLE-US-00007 TABLE 7 S BET % <10 d.sub.10 d.sub.50 d.sub.90 No. [g/cm.sup.3] [m.sup.2/g] μm [μm] [μm] [μm] Comparison 0.318 — — — — —  5 0.397 1.243 3.94 20 69 134  6 0.387 1.343 4.08 20 71 138  7 0.393 1.499 4.46 18 67 127  8 0.396 1.369 4.27 19 67 127  9 0.394 1.250 4.05 19 70 138 10 0.376 1.375 4.23 20 71 140

[0317] PEKK powders with a copolymerisation ratio of terephthalic acid units to isophthalic acid units of approx. 70:30 to approx. 10:90, particularly of approx. 60:40, have the following special features: If the powders are obtained by polymerisation and possibly size reduction, they are typically semi-crystalline. However, the polymer typically only crystallises from the melt if the cooling rate is less than 5° C./min, wherein the case is considered that the polymer does not comprises any fillers (unfilled PEKK). In this respect it behaves more like an amorphous polymer and less like a semi-crystalline polymer.

[0318] If the powder shows amorphous behaviour due to rapid cooling, the HDT-A value is 139° C. The HDT-B value is closer to T.sub.g (approx. 155° C.). If the powder shows semi-crystalline behaviour due to slower cooling, the HDT-A value is between T.sub.g and T.sub.m.

[0319] Significant and possibly maximum increases in bulk densities may be achieved during heating up to T.sub.g. But even at T.sub.g+20° C. a significant increase in the bulk density may still be achieved. The 60:40 copolymer has a T.sub.g value of 155° C. and a melting point of about 300° C.

[0320] Significant and possibly maximum increases in the bulk density could already be achieved at treatment times of significantly less than 30 minutes. Herein, the treatment time depends on the initial bulk density of the powder (compare also Examples 4 and 5) and the mass m of the powder in the mixer.

[0321] The bulk density may be increased depending on the treatment temperature. The treatment temperature is preferably between 110 and 155° C. Above T.sub.g, the bulk density decreases again slightly (compare also Examples 4 and 5). Below 90° C. the bulk density does not yet reach a maximum.

[0322] In FIG. 4, the achieved bulk density is plotted vs. the maximum temperature T.sub.max occurring in the mixer during the treatment. The data point at T.sub.max=20° C. (room temperature) represents 60:40 PEKK powder that has not been treated in the manner according to the invention. From FIG. 4, it can be clearly seen that very strongly improved bulk densities are achieved by the treatment according to the invention at temperatures beyond approx. 90° C., and particularly that at approx. 120° C., optimised, i.e. maximum bulk densities are achieved.

[0323] The maximum temperature which may be achieved in the mixer used at the most possible rotation speed of 2600 rpm depends on the degree of filling of the mixer. With the polymer powder used in this Example, sufficient shear energy is only introduced into the mixer for a mass beyond approx. 9 kg, so that the temperature may rise to approx. 110° C. or above when the mixer casing is cooled with water. In FIG. 5, the relationship between powder mass m and T.sub.max is shown, wherein the actually dependent variable T.sub.max is plotted on the abscissa.

[0324] For other types of mixers or other sizes of the mixer, a different powder mass than 9 kg may be more suitable. This must be determined iteratively for each mixer and for each powder. This determination may be based on a series of measurements corresponding to the series of measurements shown in FIG. 5.

Example 4

[0325] In Example 4, the PEKK with a copolymerisation ratio of terephthalic acid units to isophthalic acid units of approx. 60:40 was used, which was also used in Example 3. The product commercialised under the commercial name “Kepstan 6002PL” by Arkema S.A., France was used directly.

[0326] The powder used in Example 4 differed from the powder used in Example 3 with respect to the bulk density that was present before the method according to the invention was carried out (so-called “initial bulk density”). The initial bulk density was much lower in the case of Example 4 (0.271 g/cm.sup.3 compared to 0.318 g/cm.sup.3).

[0327] As a mixer, again a mixer of the type “Henschel FML” was used. The casing of the mixer was not cooled, except for powder batch no. 12. In the case of powder batch no. 12, cooling took place as described in Example 3.

[0328] The method according to the invention was carried out ten times with independent powder batches (nos. 11 to 20). The mass of a powder batch is designated as m. The values for T.sub.max, T.sub.Man, m, D.sub.1, D.sub.2, t.sub.1, t.sub.2 and t.sub.1+t.sub.2 are given in Table 8 for powder batches nos. 11 to 20.

[0329] The obtained values for the bulk density S are given in Table 9. They are the average values of three measurements each. Also in Table 9, the comparative value for the 60:40 PEKK powder that has not been treated according to the invention is given.

TABLE-US-00008 TABLE 8 T.sub.max T.sub.Man m F D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [° C.] [kg] [%] [m/s] [m/s] [min] [min] [min] 11 151 138 9 92.4 46.8 46.8 19 10 29 12 99.8 83 9 92.4 46.8 46.8 30 10 40 13 164 146 9.5 97.5 46.8 32.4 31 9 40 14 158.7 140 9 92.4 46.8 36.0 20 10 30 15 148 118 9 92.4 46.8 46.8 14 0 14 16 146 127 9 92.4 46.8 46.8 16 5 21 17 148 128 9 92.4 46.8 46.8 16 10 26 18 153.4 136 9 92.4 46.8 36.0 18 15 33 19 148.3 130 9 92.4 46.8 34.2 14 10 24 20 153 135 9 92.4 46.8 34.2 16 10 26

TABLE-US-00009 TABLE 9 No. S [g/cm.sup.3] Comparison 0.271 11 0.344 12 0.340 13 0.327 14 0.340 15 0.336 16 0.344 17 0.352 18 0.350 19 0.348 20 0.346

[0330] In FIG. 6, the achieved bulk density is plotted vs. the total treatment time t.sub.1+t.sub.2. The data point at t.sub.1+t.sub.2=0 represents the PEKK-powder which has not been treated in the manner according to the invention. FIG. 6 clearly shows that a significant increase in the bulk density was achieved by the treatment according to the invention. This effect was essentially already achieved with a total treatment time of 14 minutes.

[0331] In FIG. 7, the achieved bulk density is plotted vs. the holding time t.sub.2. Selected data points are shown. The data point at t.sub.2=0 represents the PEKK-powder which was not treated in the manner according to the invention. FIG. 7 shows that a holding time of 10 min leads to optimal results in many cases.

[0332] The PEKK powder used in Example 4 had a lower initial bulk density than the PEKK powder used in Example 3 (0.271 g/cm.sup.3 compared to 0.318 g/cm.sup.3, see line “Comparison” in Tables 7 and 9). With a powder mass m=9 kg in the mixer, the powder used in Example 4 reached at most 99.8° C. in the mixer (temperature of the mixed material) when the casing of the mixer was cooled by water cooling. Furthermore, in this case more time was needed to reach this maximum temperature T.sub.max. Without cooling the mixer casing, higher temperatures could be reached in a shorter time with the powder used in Example 4 in the mixer.

[0333] The required mixing time in the mixer is therefore strongly dependent on the bulk density of the powder. This is taken into account in the invention.

[0334] But even with the powder used in Example 4, a practically maximum increase in the bulk density could be achieved with total treatment times t.sub.1+t.sub.2 of considerably less than 30 minutes. After 26 minutes, a plateau of 0.35 g/cm.sup.3 is achieved, which does not increase even with longer treatment duration. The greatest increase in the bulk density is already achieved after 15-20 minutes of total treatment duration. Afterwards, the bulk density increases only slightly in relative terms.

Example 5

[0335] In Example 5, the PEKK with a copolymerization ratio of terephthalic acid units to isophthalic acid units of approx. 60:40 was used, which was also used in Examples 3 and 4. Again, the product distributed under the trade name “Kepstan 6002PF” by Arkema S.A., France was used. This coarse powder was ground on an impact mill and sieved to the appropriate particle size.

[0336] As a mixer, again a mixer of the type “Henschel FML” was used. With the exception of powder batch no. 23, the casing of the mixer was cooled by means of water cooling. In the case of powder batch no. 23, there was no cooling.

[0337] The method according to the invention was performed three times with independent powder batches (nos. 21 to 23). The mass of a powder batch is designated as m. The values for T.sub.max, m, F, D.sub.1, D.sub.2, t.sub.1, t.sub.2 and t.sub.1+t.sub.2 are given for nos. 21 to 23 in Table 10. If no value is entered in a column and line, this means that the corresponding measurement has not been carried out.

[0338] The values obtained for the bulk density S and the BET surface area are given in Table 11. These are the average values from three measurements each. Table 11 also shows the comparative value for the 60:40 PEKK powder that was not treated in a manner according to the invention.

[0339] The powders of the batches nos. 21, 22 and 23 were mixed to ⅓ mass % each and then exposed to a temperature of 270° C. in a circulating air furnace under a nitrogen atmosphere for a period of 2 hours. 270° C. corresponds approximately to the onset of the melting peak observed in the DSC. The values for the bulk density measured afterwards are also shown in Table 11 (“270° C./2 h”).

TABLE-US-00010 TABLE 10 T.sub.max T.sub.Man m F D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [° C.] [kg] [%] [m/s] [m/s] [min] [min] [min] 21 107 82 8.5 87.3 45.0 46.8 6 14 20 22 94 75 8.5 87.3 46.8 46.8 10 10 20 23 165 — 8.5 87.3 45.0 32.4 23 10 33 to 46.8

TABLE-US-00011 TABLE 11 No. S [g/cm.sup.3] BET [m.sup.2/g] Comparison 0.352 1.618 21 0.410 1.289 22 0.409 1.438 23 0.389 0.775 270° C./2 h 0.370 0.758

[0340] From the values in Table 11, it is clearly visible that the treatment according to the invention resulted in a significant increase in the bulk density and a significant reduction in the BET surface area after considerably less than 30 minutes. At a treatment time of 33 min and a T.sub.max value of 165° C., the bulk density is comparatively much lower. An even lower BET was obtained when the powder, which had been treated according to the invention, was exposed to a temperature of 270° C. for a period of 2 hours.

[0341] FIG. 8 shows in a temperature-current consumption diagram the change in current consumption in the mixer over time compared to the increase in temperature for sample no. 23. It can be seen that the current consumption increases disproportionately by more than 5% at the temperature T.sub.Bmax of 150° C.

[0342] From the following tabular presentation of the temperature-current consumption diagram, it can be seen that T.sub.Bmax presently with PEKK 60/40 may be at least at approx. 150° C. and preferably at 154° C., due to the respective gradient of approx. 7% and approx. 10.5% compared to the respective previous value for current consumption.

TABLE-US-00012 dA (f = ax) gradient/ rotation gradient between current Time T Strom speed the last consumption Δ T [min] [° C.] [A] [rpm] two points [%] [° C.] 2 80 20.0 2500 0.00% 4 100.0 25.0 2500 2.5 10.00% 20.0 7 128.0 18.0 2600 −2.333333333 −12.96% 28.0 10 129.0 19.0 2600 0.333333333 1.75% 1.0 13 141.0 19.0 2600 0 0.00% 12.0 15 146.0 20.0 2600 0.5 2.50% 5.0 16 150.0 21.5 2600 1.5 6.98% 4.0 17 154.0 24.0 2600 2.5 10.42% 4.0 19 159.0 2000 5.0 21 163.0 2000 4.0 23 165.0 2000 2.0

Example 6

[0343] In Example 6, a PEKK with a copolymerization ratio of terephthalic acid units to isophthalic acid units of approx. 60:40 was used. The product distributed under the trade name “Kepstan 6003PF” by Arkema S.A., France was used. This coarse powder was ground on an impact mill and screened to the appropriate particle size.

[0344] As a mixer, again a mixer of the type “Henschel FML” was used. The casing of the mixer was not cooled.

[0345] The method according to the invention was performed with a single powder batch (no. 24). The values for T.sub.max, D.sub.1, D.sub.2, t.sub.1, t.sub.2 and t.sub.1+t.sub.2 are given in Table 12.

[0346] The values obtained for the bulk density S, the BET surface area, the fraction of powder particles with a particle size of <10 μm in volume percent (%<10 μm), the quantiles d.sub.10, d.sub.50 and d.sub.90 of the particle size distribution are given in Table 13. These are the average values from three measurements each. Comparative values for the 60:40 PEKK powder, which has not been treated in the manner according to the invention, are also given in Table 13.

TABLE-US-00013 TABLE 12 T.sub.max D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [m/s] [m/s] [min] [min] [min] 24 155 46.8 21.6 7 10 17 to 27.0

TABLE-US-00014 TABLE 13 S BET d.sub.10 d.sub.50 d.sub.90 No. [g/cm.sup.3] [m.sup.2/g] % <10 μm [μm] [μm] [μm] Comparison 0.307 1.900 5 17 56 109 24 0.359 1.200 4.2 18 52 100

[0347] From the values in Table 13, it is clearly visible that by the treatment according to the invention, a significant increase in the bulk density as well as a significant reduction in the BET surface area and a significant reduction in the ultra-fine powder percentage (%<10 μm) could be achieved already after a treatment time of 17 min.

Example 7

[0348] In Example 7, a PEKK with a copolymerization ratio of terephthalic acid units to isophthalic acid units of approx. 60:40 was used. The product distributed under the trade name “Kepstan 6003PF” by Arkema S.A., France was used as in Example 6. This coarse powder was ground on an impact mill and screened to the appropriate particle size.

[0349] As a mixer, again a mixer of the type “Henschel FML” was used. The casing of the mixer was not cooled.

[0350] The method according to the invention was performed with a single powder batch (no. 25). The mass of a powder batch is designated as m. The values for T.sub.max, m, D.sub.1, D.sub.2, F, t.sub.1, t.sub.2 and t.sub.1+t.sub.2 are given in Table 14.

[0351] The value obtained for the bulk density S is given in Table 15. This is the average value from three measurements. Table 15 also shows the comparative value for the 60:40 PEKK powder that was not treated in a manner according to the invention.

TABLE-US-00015 TABLE 14 T.sub.max m F D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [kg] [%] [m/s] [m/s] [min] [min] [min] 25 160 7 71.9 46.8 32.4 23 2 25

TABLE-US-00016 TABLE 15 No. S [g/cm.sup.3] Comparison 0.284 25 0.354

[0352] From the values in Table 15, it is clearly visible that by the treatment according to the invention, a significant increase in the bulk density could be achieved already after a treatment time of 25 min.

Example 8

[0353] In Example 8, a PEKK with a copolymerization ratio of terephthalic acid units to isophthalic acid units of approx. 60:40 which comprised approx. 36 wt. % carbon fibres as filler (reinforcement material) was used. A PEKK powder with carbon fibres incorporated in the core produced by the company ALM LLC was used.

[0354] As a mixer, again a mixer of the type “Henschel FML” was used. The casing of the mixer was not cooled.

[0355] The method according to the invention was performed with a single powder batch (no. 26). The values for T.sub.max, D.sub.1, D.sub.2, t.sub.1, t.sub.2 and t.sub.1+t.sub.2 are given in Table 16.

[0356] The value obtained for the bulk density S is given in Table 17. This is the average value from three measurements. Table 17 also shows the comparative value for the 60:40 PEKK powder with 36 wt. % carbon fibres that was not treated in a manner according to the invention.

TABLE-US-00017 TABLE 16 T.sub.max D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [m/s] [m/s] [min] [min] [min] 26 166 46.8 27.0 8 8 16

TABLE-US-00018 TABLE 17 No. S [g/cm.sup.3] Comparison 0.464 26 0.512

[0357] From the values in Table 17, it is clearly visible that by the treatment according to the invention, a significant increase in the bulk density of the carbon fibre reinforced PEKK powder could be achieved already after a treatment time of 16 min.

[0358] In this context, the following should be noted, which is not only valid in the context of Example 8 but in general in connection with fibre reinforced plastics: For PEKK without fibres and PEKK with fibres, it was found in the experiments that the increase in bulk density may be carried out at similar temperatures. This means that within the context of the invention the same or at least similar treatment temperatures T.sub.B are preferred for fibre-reinforced polymers and also other composites as for the non-reinforced polymers.

Example 9

[0359] In Example 9, the same polyphenylene sulfide (semi-crystalline) powder as in Example 1 was used (“Toray 50NNAB” from Toray Industries, Inc., Japan). This has a melting point of 293° C. and a T.sub.g of 105° C., determined according to DIN EN ISO11357 and an MVR (melt viscosity) value of 25 cm.sup.3/10 min, determined via ISO1133 at 315° C. and 2.16 kg.

[0360] As a mixer, a mixer of the type “Mixaco LAB-CM 6-12 CM/SM” was used. The casing of the mixer was not cooled.

[0361] The treatment temperature below the T.sub.g was varied between 64 and 87° C. and the holding time was kept constant at 10 minutes in each case. The heating time varied between 1.5 and 4 minutes.

TABLE-US-00019 TABLE 18 T.sub.max D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [m/s] [m/s] [min] [min] [min] Comparison 0 1 64 34.4 8.8 1.5 10 11.5 2 74.8 34.4 12.3 3 10 13 3 86.7 34.4 14.6 4 10 14

TABLE-US-00020 TABLE 19 Pour- S BET % <10 d10 d50 d90 ablility No. [g/cm.sup.3] [m.sup.2/g] μm [μm] [μm] [μm] [s] Compar- 0.459 15.73 0.4 37.98 72 126.13 no free- ison flowing 1 0.505 14.94 0.3 39.9 72.6 128.1 4.367 2 0.512 14.98 0.3 38.9 71.8 119.9 4.567 3 0.515 14.09 0.3 39.8 71.6 125.5 4.300

[0362] An increase in the bulk density could already be achieved at a temperature of T.sub.g−40° C. At a temperature of T.sub.g−30° C. to T.sub.g−19° C. the increase in bulk density is at a maximum.

[0363] Furthermore, the pourability has also improved significantly as a result of the treatment. While the ground powder is not free-flowing before the treatment according to the invention, it shows a good flowability of approx. 4.5 seconds afterwards (test with 25 mm nozzle), cf. table 19.

[0364] The BET decreases only slightly with increasing treatment temperature below T.sub.g, while above T.sub.g (see Example 1, V1−V3, T.sub.B=175° C.), it decreases significantly to about 7.5 m.sup.2/g.

[0365] In addition, the percentage of ultra-fine powder has been significantly reduced from approx. 0.4% to approx. 0.3% as a result of the treatment according to the invention, see also Table 3.

Example 10

[0366] A commercially available semi-crystalline polyether ether ketone (PEEK) of the company Victrex plc (Thornton Cleveleys, Great Britain), of the type PEEK 150PF, with a melting point of 343° C. and a T.sub.g of 143° C. was used.

[0367] As the mixer, a mixer of the type “Mixaco LAB-CM 6-12 CM/SM” was used. The casing of the mixer was not cooled.

[0368] The treatment temperature was varied between 103 and 156° C. and the holding time was kept constant with 10 minutes each.

TABLE-US-00021 TABLE 20 T.sub.max D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [m/s] [m/s] [min] [min] [min] Comparison 0 0 V1 103.1 34.4 24.5 10 10 20 V2 132.2 34.4 28.0 21 10 31 V3 156 34.4 34.4 32 10 42

TABLE-US-00022 TABLE 21 Pour- S BET % <10 d10 d50 d90 ability No. [g/cm.sup.3] [m.sup.2/g] μm [μm] [μm] [μm] [s] Compar- 0.313 43.86 5.1 13.70 40.14 84.67 not ison pourable V1 0.368 35.06 5.6 13.04 41.20 87.20 not pourable V2 0.382 25.77 7.2 11.41 36.37 80.23 not pourable V3 0.399 16.47 5.7 12.59 40.71 90.32 not pourable

[0369] An increase in the bulk density could already be achieved at a temperature of T.sub.g−40° C., a further increase is achieved at T.sub.g−11° C. At a temperature above T.sub.g at T.sub.g+13 and at the same time in the range between HDT-A and HDT-B for PEEK (compare also Table 1) the increase in bulk density is at a maximum.

[0370] The BET decreases with increasing treatment temperature already below T.sub.g; above T.sub.g and in the HDT-A and HDT-B range, it may be significantly further reduced. It must be assumed that the BET may be further reduced at temperatures above HDT-B and below T.sub.m.

[0371] The particle size distribution changes only slightly over the treatment temperature.

[0372] The change in current consumption in the mixer over time in line with the increase in temperature for the experiment V3 (T.sub.B=156° C.) can be seen in FIG. 9 and in Table 22 below. Up to T.sub.g, the current consumption is essentially constant. It can be seen that between T.sub.g and HDT-A value there is a short-term increase in the current consumption from 3.0 A to 3.4 A. Above HDT-A this then drops even to a slightly lower value of 2.8 A than below T.sub.g (2.9-3.0 A), which indicates a better pourability of the powder and thus less shear, which leads to lower current consumption. The temperature no longer rises further due to the improved pourability and remains at around 156° C. despite the same rotation speed. Therefore, the maximum treatment temperature has not yet been reached at 156° C. for PEEK. A higher treatment temperature could not be realised with this setup, because the mixer has already worked at maximum rotation speed during the heating phase and holding phase. By using a PEEK with a higher initial bulk density, a different degree of filling or the use of a mixer with a higher speed, such as the mixer of the type “Henschel FML”, however, this may probably be realised. It is also likely that the time required for the heating phase may be significantly reduced.

[0373] As can be seen in particular from Table 22, T.sub.Bmax may be most effectively defined as at most 150° C. for PEEK 150PF (specifically 149.1° C. due to a gradient of 12.5% compared to the previous value for current consumption).

TABLE-US-00023 TABLE 22 a (f = ax) rotation gradient gradient/current Time T Current speed between 2 consumption Δ T [min] [° C.] [A] [U/min] data points [%] [° C.] 0 46.7 2.9 0.00% 2 65.5 2.9 0.000 0.00% 18.8 4.0 75.4 3.0 0.050 1.67% 9.9 6.0 89.5 3.0 0.000 0.00% 14.1 8.0 98.3 3.0 0.000 0.00% 8.8 10.0 105.2 3.0 0.000 0.00% 6.9 12.0 111.5 3.0 0.000 0.00% 6.3 14.0 117.2 3.0 0.000 0.00% 5.7 16.0 122.0 2.9 −0.050 −1.72% 4.8 18.0 126.7 2.9 0.000 0.00% 4.7 20.0 130.6 2.9 0.000 0.00% 3.9 22.0 134.6 3.0 0.050 1.67% 4.0 24.0 138.5 3.0 0.000 0.00% 3.9 25.0 140.4 2.9 −0.100 −3.45% 1.9 26.0 142.5 2.9 0.000 0.00% 2.1 27.0 144.1 3.0 0.100 3.33% 1.6 29.0 147.9 3.0 0.000 0.00% 3.8 29.5 149.1 3.2 0.400 12.50% 1.2 30.5 152.3 3.4 0.200 5.88% 3.2 32.0 155.6 2.9 −0.333 −11.49% 3.3 34.0 156.3 2.8 −0.050 −1.79% 0.7 36.0 156.0 2.8 0.000 0.00% −0.3 38.0 156.1 2.8 0.000 0.00% 0.1 40.0 156.5 2.8 0.000 0.00% 0.4 42.0 156.8 2.8 0.000 0.00% 0.3

Example 11

[0374] A commercially available semi-crystalline polyether ether ketone (PEEK) from the company EOS GmbH (Krailling, Germany) of the type PEEK-HP3 with a melting point of 372° C. and a Tg of 164° C. was used.

[0375] A mixer of the type “Mixaco LAB-CM 6-12 CM/SM” was used as mixer. The casing of the mixer was not cooled.

[0376] The treatment temperature was varied between 75 and 192° C. and the holding time was kept constant with 10 minutes each. A higher treatment temperature could not be realised with this mixer type, as the at highest possible temperature is 200° C.

TABLE-US-00024 TABLE 23 T.sub.max D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [m/s] [m/s] [min] [min] [min] Comparison 0 V1 75 34.4 9.9 2 10 12 V2 126.6 34.4 16.3 5 10 15 V3 148 34.4 18.1 8 10 18 V4 192 34.4 23.3 15 10 25

TABLE-US-00025 TABLE 24 Pour- S BET % <10 d10 d50 d90 ability No. [g/cm.sup.3] [m.sup.2/g] μm [μm] [μm] [μm] [s] Compar- 0.454 1.37 0.9 27.59 51.03 79.64 not ison pourable V1 0.459 1.16 0.9 27.17 50.39 77.01 not pourable V2 0.486 1.13 0.7 27.66 51.38 78.77 not pourable V3 0.483 1.08 0.9 26.82 50.76 79.74 not pourable V4 0.507 0.8 30.56 53.94 81.21 not pourable

[0377] Only a minimal increase in bulk density of about 1% could be achieved at a temperature of Tg−89° C., a significant increase to approximately the same level of 0.48 is achieved at Tg−39° C. and Tg−17° C. At a temperature above Tg and above the HDT-A value (compare Table 1) at Tg+27 the increase in bulk density is at a maximum.

[0378] The BET decreases with increasing treatment temperature, even already below the Tg.

[0379] The particle size distribution changes only insignificantly over the treatment temperature below Tg. Above Tg, it increases slightly, which also explains the slightly improved pourability.

[0380] The change in current consumption in the mixer over time in line with the increase in temperature for the experiment V3 (Tb=192° C.) can be seen in FIG. 10. Up to 114° C., the current consumption increases by approx. 10%. Afterwards it remains essentially constant. There is no change in the current consumption in the range of the Tg or HDT-A value. Therefore, it can be assumed that an even higher treatment temperature than 192° C. and below Tm is possible, namely up to the temperature at which the current consumption increases significantly and does not drop after the increase.

Example 12

[0381] A commercially available amorphous polystyrene from EOS GmbH (Krailling, Germany), type Primecast 101, with a T.sub.g of 100° C. was used.

[0382] A mixer of the type “Mixaco LAB-CM 6-12 CM/SM” was used. The casing of the mixer was not cooled.

[0383] For the treatment temperature at T.sub.g−2° C., a holding phase of 10 minutes was carried out. For the treatment temperature T.sub.g+16° C., no reasonable holding phase could be carried out, as no reasonable mixing process could be carried out due to extreme agglomeration of the powder in the mixer. The experiment was therefore stopped after 2 minutes of the holding phase.

TABLE-US-00026 TABLE 25 T.sub.max D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [m/s] [m/s] [min] [min] [min] Comparison 0 V1 98.8 34.4 17.5 28 10 38 V2 116.3 34.4 34.4 29 3 32

TABLE-US-00027 TABLE 26 % <10 d10 d50 d90 Pourability No. μm [μm] [μm] [μm] [s] Comparison 0.1 69.00 79.70 85.49 n.d. V1 0.1 68.90 79.82 85.65 1.633

[0384] The change in the current consumption in the mixer over time in line with the increase in temperature for the experiment V2 can be seen in FIG. 11 and Table 27. After a drop in current consumption at the beginning of the treatment, it remains constant up to 111° C. (T.sub.g+11) and only then it rises significantly, which is due to strong agglomerate formation in the mixer.

TABLE-US-00028 TABLE 27 dA (f = ax) Time T Current gradient between gradient/current Δ T [min] [° C.] [A] last 2 points consumption [%] [° C.] 0 22.1 3.4 0.00% 5.0 40.7 2.9 −0.1 −3.45% 18.6 12.0 71.9 2.9 0 0.00% 31.2 15.0 82.2 3.0 0.033333333 1.11% 10.3 18.0 90.5 3.0 0 0.00% 8.3 20.0 95.6 3.0 0 0.00% 5.1 21.0 98.3 3.0 0 0.00% 2.7 22.0 100.5 3.0 0 0.00% 2.2 23.0 103.0 3.0 0 0.00% 2.5 24.0 104.0 3.0 0 0.00% 1.0 25.0 106.4 3.0 0 0.00% 2.4 26.0 108.8 3.1 0.1 3.23% 2.4 27.0 111.0 3.1 0 0.00% 2.2 28.0 113.0 3.3 0.2 6.06% 2.0 29.0 116.3 3.4 0.1 2.94% 3.3 31.0 112.0 3.2 −0.1 −4.3

[0385] As can be seen in particular from Table 27, T.sub.Bmax may be defined for polystyrene as approx. 113° C. in view of the gradient of about 6% compared to the previous current consumption value.

Example 13

[0386] A polyamide 12 precipitation powder produced in a conventional manner according to EP863174 with a melting point of 187° C. and a T.sub.g of approx. 50° C. that did not comprise any flow aid, was used. The powder was produced by a precipitation process from an ethanolic solution. The principle for controlling the particle size distribution and the melting point of the starting powder is known from EP863174.

[0387] As mixer, a mixer of the type “Mixaco LAB-CM 6-12 CM/SM” was used. The casing of the mixer was not cooled, except in experiment V10.

[0388] In V1 to V3, the treatment temperature was varied between 56° C. and 101° C. and the holding phase was left constant for 10 minutes. There occurs an increase of the bulk density with increasing temperature, which is at a maximum at 101.3° C. (about 4%). From a treatment temperature above 75.5° C., a significant reduction of the ultra-fine fraction from 3.6 to 2.7% occurs in V3.

[0389] Increasing the rotation speed during the heating phase (V4 vs. V3) from 23.3 to 34.4 m/s reduces the heating time from 21 to 15 minutes. The bulk density remains the same, but the fine fraction is further reduced from 2.7 to 2.1%.

[0390] In V5-V7, the rotation speed during the heating phase and the treatment temperature were kept constant at about 100° C. The holding time was varied between 0 minutes and 30 minutes. The bulk density increases minimally until 15 minutes, after that it remains almost constant. With no holding time, the reduction of the fine fraction is the most pronounced (3.6>1.9%), whereas it rises again to 2.2% with a longer holding time. The pourability improves most with 0 minutes holding time to 6 seconds (lowest pouring time=best pourability) and increases again up to 9 seconds with increasing holding time. From a holding time of 30 minutes, the melting enthalpy and thus also the crystallinity of the powder is significantly reduced from 118 to 108 J/g. This indicates that the treatment causes crystalline areas on the surface to melt and recrystallize.

[0391] In the experiments V5, V8 and V9, the treatment temperature in the mixer was varied between 95 and 140° C. and the rotation speed in the heating phase was kept constant at 34.4 m/s and the holding time was kept constant at 0 minutes. The bulk density increases by more than 2% at 95° C. and 120° C. and drops back to the level of the reference powder at 140° C. The ultra-fine fraction is reduced with increasing treatment temperature from 2.7 to up to 0.3% for 140° C. treatment temperature.

[0392] In V10, the mixer was cooled, in V11 there was no cooling of the mixer. The treatment temperature was kept constant at about 125° C. for 30 minutes holding time. The rotation speed during the heating phase was 34.4 m/s. Due to the cooling of the mixer, the heating phase was significantly extended from 23 to 48 minutes. The bulk density increases slightly more with mixer cooling than without cooling. Similarly, with mixer cooling, the ultra-fine fraction decreases slightly more to 0.5% and the pourability improves slightly more to around 7 seconds.

[0393] The change in BET depends on temperature. At a treatment temperature of 120° C., it is reduced from 5.4 to 3.5 m.sup.2/g regardless of the holding time (V9+V11). At a treatment temperature of 140° C., this is reduced even further to approx. 2 m.sup.2/g.

[0394] The melting enthalpy and thus the crystallinity re decreased significantly at a holding time of 30 minutes from 100° C. (V7, V10, V11). At 120 and 140° C. the reduction is most pronounced from 118 J/g to 105 J/g.

TABLE-US-00029 TABLE 28 T.sub.max D.sub.1 D.sub.2 t.sub.1 t2 t.sub.1 + t.sub.1 No. [° C.] [m/s] [m/s] [min] [min] [min] Comparison 0 V1 55.8 23.3 9.3 7 10 17 V2 75.5 23.3 11.7 10 10 20 V3 101.2 23.3 15.2 21 10 31 V4 100.2 34.4 15.2 15 10 25 V5 94.9 34.4 0.0 18 0 18 V6 100.6 34.4 15.2 15 15 30 V7 100 34.4 15.8 17 30 47 V8 120 34.4 0.0 28 0 28 V9 140.3 34.4 0.0 35 0 35 V10 126.4 34.4 18.7 48 30 78 V11 123.3 34.4 15.2 23 30 53 V12 146 34.4 16.3 26 7 33

TABLE-US-00030 TABLE 29 melting S BET % <10 d10 d50 d90 Pourability enthalpy No. [g/cm.sup.3] [m.sup.2/g] μm [μm] [μm] [μm] [s] [J/g] Com- 0.429 5.38 3.6 38.75 59.13 77.56 not 119.4 parison pourable V1 0.439 3.6 38.73 58.77 77.40 8.830 120.1 V2 0.441 3.6 35.42 58.31 77.24 6.367 V3 0.445 2.7 39.89 58.91 77.66 10.317 120.8 V4 0.445 2.1 41.13 59.33 79.69 9.027 118.1 V5 0.442 1.9 41.04 58.91 78.30 6.038 118.7 V6 0.448 2.2 40.95 59.22 78.27 8.715 118.4 V7 0.450 2.2 39.60 58.75 79.73 9.520 108.0 V8 0.441 3.58 1.0 41.81 59.26 79.02 5.010 116.0 V9 0.429 2.05 0.3 43.55 60.11 83.53 5.777 114.9 V10 0.455 0.5 42.46 61.51 129.70 7.567 106.7 V11 0.447 3.48 0.8 41.68 59.07 78.83 8.943 105.4 V12 0.378 0.2 46.36 61.12 80.92 4.987 106.7

[0395] The change in current consumption in the mixer over time in line with the rise in temperature is examined in V9 and can be seen in FIG. 12 and Table 30. At the beginning, the current consumption drops slightly until Tg is reached. Until the HDT-A temperature is reached (see Table 1), the current consumption rises only very slowly from 3.3 to 3.9 A. Above 130.5° C., the current consumption then increases disproportionately strongly from 3.9 A to 4.5 A by approx. 11% until it reaches a value of 6.5 A at 140° C.

[0396] If a holding time at 140° C. is subsequently implemented (V12), the temperature continues to rise despite the reduction in rotation speed and after 7 minutes the current consumption is so high that the mixer automatically stops the mixing process by means of a safety shutdown. The bulk density is significantly reduced by approx. 10% compared to the reference material.

[0397] Table 30 shows for polyamide 12 (without flow aids) as an example, the change in current consumption in the mixer over time compared to the increase in temperature in experiment V9 of Example 13.

TABLE-US-00031 TABLE 30 dA (f = ax) rotation gradient gradient/current Time T Current speed between last consumption Δ T [min] [° C.] [A] [U/min] 2 points [%] [° C.] 1 22.3 4 2950 0.00% 2 30.6 3.8 2950 −0.2 −5.26% 8.3 3 38.3 3.7 2950 −0.1 −2.70% 7.7 4 44.5 3.6 2950 −0.1 −2.78% 6.2 5 49.7 3.5 2950 −0.1 −2.86% 5.2 6 54.2 3.4 2950 −0.1 −2.94% 4.5 7 58.2 3.3 2950 −0.1 −3.03% 4.0 8 62.2 3.3 2950 0 0.00% 4.0 9 66.2 3.4 2950 0.1 2.94% 4.0 10 70.0 3.3 2950 −0.1 −3.03% 3.8 11 73.5 3.3 2950 0 0.00% 3.5 12 76.7 3.3 2950 0 0.00% 3.2 13 79.9 3.3 2950 0 0.00% 3.2 14 82.9 3.4 2950 0.1 2.94% 3.0 15 85.6 3.3 2950 −0.1 −3.03% 2.7 16 88.3 3.4 2950 0.1 2.94% 2.7 17 90.9 3.4 2950 0 0.00% 2.6 18 93.3 3.4 2950 0 0.00% 2.4 19 95.8 3.4 2950 0 0.00% 2.5 20 98.3 3.4 2950 0 0.00% 2.5 21 100.6 3.4 2950 0 0.00% 2.3 22 102.7 3.4 2950 0 0.00% 2.1 23 105.0 3.5 2950 0.1 2.86% 2.3 24 107.2 3.5 2950 0 0.00% 2.2 25 109.4 3.5 2950 0 0.00% 2.2 26 111.5 3.5 2950 0 0.00% 2.1 27 113.7 3.5 2950 0 0.00% 2.2 28 115.7 3.6 2950 0.1 2.78% 2.0 29 117.9 3.6 2950 0 0.00% 2.2 30 120.1 3.7 2950 0.1 2.70% 2.2 31 122.5 3.8 2950 0.1 2.63% 2.4 32 124.9 3.9 2950 0.1 2.56% 2.4 33 127.2 3.9 2950 0 0.00% 2.3 34 130.5 4.5 2950 0.6 13.33% 3.3 35 134.8 5.2 2950 0.7 13.46% 4.3 36 140.3 6.5 2950 1.3 20.00% 5.5