COMPOSITE MATERIAL AND ITS USE IN ADDITIVE MANUFACTURING METHODS

Abstract

The present invention relates to a composite material comprising at least one thermoplastic polymer and a particulate inorganic material and its use in additive manufacturing methods.

Claims

1. Composite material comprising (a) at least one thermoplastic polymer and (a) a particulate inorganic material, wherein the composite material is particulate matter.

2. Composite material according to claim 1, wherein the particulate inorganic material has a heat capacity in range of from 100 to 1,000 J/(kg.Math.K), particularly 200 to 900 J/(kg.Math.K), preferably 300 to 800 J/(kg.Math.K), more preferably 400 to 600 J/(kg.Math.K).

3. Composite material according to claim 1 or 2, wherein the inorganic particulate material increases the heat capacity of the composite material by at least 10%, particularly at least 20%, preferably at least 30%, compared to the heat capacity of the thermoplastic polymer.

4. Composite material according to claim 1, wherein the composite material has a particle size in the range of from 5 to 100 m, particularly 10 to 80 m, preferably 15 to 70 m, more preferably 20 to 50 m.

5. Composite material according to claim 1, wherein the composite material has a mean particle size of 10 to 70 m, particularly 20 to 60 m, preferably 30 to 50 m, more preferably 35 to 40 m.

6. Composite material according to claim 1, wherein the particulate inorganic material has particle sizes in the range of from 1 to 20 m, particularly 2 to 15 m, preferably 3 to 12 m, more preferably 4 to 10 m.

7. Composite material according to claim 1, wherein the particulate inorganic material is selected from the group consisting of metals, inorganic oxides and their mixtures.

8. Composite material according to claim 7, wherein the particulate inorganic material is selected from the group consisting of iron, steel, aluminum, titanium dioxide, zinc oxide, iron oxides, alumina, glass and their mixtures.

9. Composite material according to claim 1, wherein the composite material contains the particulate inorganic material in amounts of up to 25% by weight, particularly up to 20% by weight, preferably up to 18% by weight, more preferably up to 17% by weight, based on the weight of the composite material.

10. Composite material according to claim 1, wherein the composite material contains the particulate inorganic material in amounts of 1 to 20% by weight, particularly 2 to 10% by weight, preferably 3 to 7% by weight, more preferably 3 to 4% by weight, based on the weight of the Composite material.

11. Composite material according to claim 1, wherein the composite material has a bulk density in the range of from 0.2 to 1.0 g/cm.sup.3, particularly 0.3 to 0.9 g/cm.sup.3, preferably 0.4 to 0.8 g/cm.sup.3, more preferably 0.5 to 0.7 g/cm.sup.3.

12. Composite material according to claim 1, wherein the polymer is a high-performance polymer.

13. Composite material according to claim 1, wherein the polymer is selected from the group consisting of polyetherketone (PEK), Polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyamid-imide (PAI), polysulfone (PSU), polyether sulfone (PES), polyphenylsulfone (PPSU) or their blends, particularly polyetherketone (PEK), Polyetheretherketone (PEEK), polyphenylene sulfide (PPS) and their blends.

14. Composite material according to claim 1, wherein the composite material comprises the polymer in amounts of up to 99% by weight, particularly up to 95% by weight, preferably up to 90% by weight, more preferably up to 85% by weight, even more preferably up to 70% by weight, based on the weight of the composite material.

15. (canceled)

16. (canceled)

17. Process for preparing a composite material according to claim 1, wherein (i) in a first process step a starting material comprising (a) at least one thermoplastic polymer and (b) a particulate inorganic material is blended at temperatures above the melting temperature of the polymer and (ii) in a subsequent second process step the material obtained in process step (i) is comminuted, particularly by grinding.

18. Process according to claim 17, wherein in the first process step (i) the starting material is extruded, particularly with a screw extruder.

19. Process according to claim 17, wherein in the second process step (ii) the composite material is comminuted by cryogenic grinding.

20. A shaped article obtained by processing the composite material of claim 1 with an additive manufacturing method, particularly an additive layer manufacturing method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 provides an apparatus for selective laser sintering that is suited to carry out the inventive method for obtaining a shaped article; and

[0046] FIG. 2 shows a shaped article consisting of magnetite-modified PPS obtained from the inventive composite material with selective laser sintering (SLS).

DETAILED DESCRIPTION OF THE INVENTION

[0047] Subject-matter of the present inventionaccording to a first aspect of the present inventionis therefore a composite material comprising

[0048] (a) at least one thermoplastic polymer and

[0049] (b) a particulate inorganic material,

[0050] wherein the composite material is particulate matter.

[0051] For, as applicant has surprisingly found, it is possible to compound thermoplastic materials, particularly high-performance thermoplastic materials, such as PEEK, PEK or PPS, with a particulate inorganic material and the resulting composite material has drastically enhanced properties in additive manufacturing processes, particularly in fused bed sintering processes.

[0052] The composite material according to the invention has a much higher bulk density and heat transfer rate in comparison to thermoplastic powders, particularly powders of high-performance polymers, conventionally used for fused bed sintering processes. Thus, the composite material according to the invention allows for a much faster and enhanced fabrication of three-dimensional articles with additive manufacturing methods, particularly sintering methods.

[0053] Compounding a thermoplastic material, particularly a high-performance thermoplastic material, with particulate inorganic material enhances the heat-storing capacity of the resulting composite material in comparison to the unmodified thermoplastic material. The increase in heat capacity makes it possible to comminute even high-performance thermoplastic materials, such as PEEK, PEK or PPS, particularly by cryogenic grinding.

[0054] As applicant surprisingly has found, high-performance thermoplastic materials which are modified with inorganic particulate materials, for example magnetite, show unchanged mechanical characteristics compared to unmodified high-performance thermoplastics, but can be comminuted at much higher process speeds and with higher throughputs.

[0055] Moreover, the particle size distribution of the polymeric powder obtained after the comminution is drastically reduced in comparison to an unmodified high-performance polymer and the particle size distribution can be adjusted to fixed values. Thus, the present invention makes it possible for the first time, to comminute high-performance polymers, such as PEEK, PEK or PPS, at reasonable economic costs.

[0056] The composite material according to the present invention shows its advantages particularly in cryogenic grinding operations. Due to the higher heat capacity of the modified high-performance polymer according to the invention, the inventive composite material retains low temperatures down to 193 C. much longer than unmodified polymers. The cold granules of the inventive composite material are dosed into a mill and hit the pegs of the mill at high velocity which results in a comminution of the granules. The impact of the granules with the pegs usually results in a rapid warming of the granules so that the debris of the granules show viscoelastic properties on their next encounter with the pegs. This results in an incomplete comminution of the granules and a large part of particles with a big particle size in the resulting powder.

[0057] The inventive composite material with its specifically enhanced heat capacity is apparently comminuted much more effectively, since it retains the low temperature much longer. The inventive composite material is brittle for a longer time and can be comminuted by mechanical means much more easily.

[0058] A further advantage of the enhanced heat capacities of the inventive composite material is a homogeneous melting of the polymeric material during laser sintering processes. Particularly, the present invention allows for the first time a full melting of high-performance polymers, such as PPS, PEK or PEEK in selective sintering, particularly selective laser sintering, processes. Thus, the inventive composite material allows for a full melting of the particles and layers during the sintering process and not only for a superficial melting of the particles which results in the particles being adhered to each other only. According to the invention, it is possible to obtain a completely homogeneous object with no particles or layers being detectable on a microscopic scale.

[0059] Without being bound to this theory, the enhanced properties can be attributed to compounding the thermoplastic material with the inorganic particulate material in the inventive composite material, particular magnetite, since the resulting higher heat capacity of the composite material apparently results in a more homogeneous distribution of the energy input by a laser, particularly, if CO.sub.2 lasers with only a short scanning time are used.

[0060] Compared to unmodified thermoplastics, the sintering time of the inventive composite materials is prolonged, and the heat is spread homogeneously and for a prolonged time.

[0061] A complete sintering, i.e. a complete melting, of the thermoplastic material and high density articles with higher tensile strengths are the result, if the inventive composite material is used.

[0062] A further drawback of high-performance polymers with a high melting point is that thermoplastic polymers with a high melting point often show an inferior adsorption of CO.sub.2 laser irradiation, which is the standard laser scanner system used for additive manufacturing, particularly sintering, processes. The inorganic particulate material, in particular magnetite, apparently enhances not only the specific heat capacity of the polymeric material, but also the absorption of radiation energy at 10.6 m wavelengths.

[0063] Moreover, as applicant has surprisingly found, the observed effects as to comminution and processing of the composite material is independent from the polymeric material. However, the observed effects are the more powerful the higher the polymeric material ranks in the materials performance pyramid.

[0064] The composite material according to the invention is most effective, if high-performance polymers are used. High-performance polymers, particularly high-performance engineering polymers, have a high tensile strength, a high melting point and their rheological properties are problematic and, furthermore, their absorption of CO.sub.2 laser energy is very low. This specifically applies for high-performance engineering thermoplastic materials, such as PPS, PEEK, PEK, PEI etc.

[0065] The inventive composite material is furthermore well suited for processing with diodes or fiber lasers which are used in the latest concepts for laser sinter processes.

[0066] Furthermore, the inventive composite material is also suited for new sintering strategies since it allows to laser sinter polymers at much lower temperatures in the sintering chamber, so that the temperature gap between the melting temperature of the polymeric material and the temperature of the powder in the sintering chamber is quiet high. With the inventive composite material multiple scans can be avoided since the energy is much more effectively absorbed and distributed in the powder bed, which results in a dramatic increase in processing speed and a complete melting of the powdered material during the sintering process.

[0067] In general, the particulate inorganic material has a heat capacity of less than 1,000 J(kg.Math.K), particularly less than 900 J/(kgK), preferably less than 800 J/(kgK), more preferably less than 600 J/(kgK).

[0068] Furthermore, it is possible that the particulate inorganic material has a heat capacity in the range of from 100 to 1,000 J/(kgK), particularly 200 to 900 J/(kgK), preferably 300 to 800 J/(kgK), more preferably 400 to 600 J/(kgK).

[0069] If the particulate inorganic material has a heat capacity which corresponds to the abovementioned values or ranges, respectively, the heat capacity of the thermoplastic polymer can be increased with only small amounts of the particulate inorganic material in the resulting composite material. This results in the composite material having the same mechanical characteristics as the unmodified thermoplastic polymer, on the one hand, and a much enhanced processability, both in comminution and sintering processes, on the other hand.

[0070] According to a preferred embodiment of the present invention, the inorganic particulate materials increases the heat capacity of the composite material by at least 10%, particularly at least 20%, preferably at least 30%, based as compared to the heat capacity of the thermoplastic polymer.

[0071] Moreover, it is possible according to the present invention that the inorganic particulate material increases the heat capacity of the composite material by a range of from 10 to 50%, particularly 20 to 45%, preferably 30 to 40%, compared to the heat capacity of the thermoplastic polymer.

[0072] According to the invention, heat capacities of polymers are preferably measured by differential scanning calorimetry (DSC) in accordance with ISO 11357-4:2014.

[0073] According to the invention, the composite material usually has a particle size in the range of from 5 to 100 m, particularly 10 to 80 m, preferably 15 to 70 m, more preferably 20 to 50 m.

[0074] According to the invention, it is also possible that the composite material has a mean particle size of 10 to 70 m, particularly 20 to 60 m, preferably 30 to 50 m, more preferably 35 to 40 m. It is a specific feature of the present invention that a powder of the inventive composite material is obtainable even if high-performance polymers, such as PEEK, PEK or PPS, are used. Usually, it is not possible to comminute high-performance polymers properly so as to obtain a rather homogeneous particle size distribution which results in a powder that can be used for laser sintering processes.

[0075] Particle sizes are preferably measured according to the invention by laser diffraction, e.g. with the aid of a HELOS P laser diffraction device PM 32/03 from Sympatec GmbH. The mean particle size, also known as D50 value, indicates that 50% of the measured particles have a smaller size than the named value.

[0076] According to a preferred embodiment of the present invention, the composite material is obtained by comminuting solid composite material. In this regard, it is preferred, if the composite material is comminuted by grinding, particularly by cryogenic grinding. Particularly in regard to high-performance polymers, the present invention allows for an effective comminution of the compounded composite material by grinding, particularly by cryogenic grinding. Due to the increased heat capacity of the composite material according to the invention, the material remains for a longer period of time at very low temperatures down to 193 C. during the grinding process. At these low temperatures, the high-performance polymers do not show any viscoelastic properties, but are brittle and can be easily grinded.

[0077] The particle size of the particulate inorganic material can vary in wide ranges depending on the application conditions. However, good results are obtained, if the particulate inorganic material has particle sizes in the range of from 1 to 20 m, particularly 2 to 15 m, preferably 3 to 12 m, more preferably 4 to 10 m.

[0078] Moreover, it is possible that the particulate inorganic material has a mean particle size in the range of from 2 to 15 m, particularly 3 to 12 m, preferably 4 to 10 m, more preferably 5 to 8 m.

[0079] Particulate inorganic material with the aforementioned particle sizes is small enough to be homogeneously distributed and blended in a thermoplastic material, particularly without changing the mechanical characteristics of the thermoplastic material, but allows for a significant increase of the heat capacity of the resulting composite material in comparison with the unmodified thermoplastic material.

[0080] The particulate inorganic material is usually selected from the group consisting of metals, inorganic oxides and their mixtures.

[0081] In this regard, very good results are obtained, if the particulate inorganic material is selected from the group consisting of iron, steel, aluminum, titanium dioxide, zinc oxide, iron oxides, alumina, glass and their mixtures.

[0082] Particularly, very good results are obtained, if the particulate inorganic material is selected from the group consisting of iron oxides, particularly magnetite, glass, particularly glass beads, and their mixtures.

[0083] According to a preferred embodiment of the present invention, the particulate inorganic material is magnetite. Magnetite is a mixed oxide of Fe.sup.2+ and Fe.sup.3+ ions with the chemical formula Fe.sub.3O.sub.4. Magnetite is a readily available, low cost iron oxide that can be easily processed.

[0084] In regard to the amount of particulate inorganic material in the inventive composite material, these amounts can vary in very wide ranges depending on the application conditions. However, very good results are obtained, if the composite material contains the particulate inorganic material in amounts of up to 25% by weight, particularly up to 20% by weight, preferably up to 18% by weight, more preferably up to 17 weight %, based on the weight of the composite material.

[0085] Moreover, it is preferred, if the composite material contains the particulate inorganic material in amounts of 1 to 20% by weight, particularly 2 to 10% by weight, preferably 3 to 7% by weight, more preferably 3 to 4% by weight, based on the weight of the composite material. The aforementioned amounts of particulate inorganic material in the inventive composite material do not adversely effect the mechanical characteristics of the thermoplastic material, but decisively enhance the heat capacity of the resulting composite material compared to the unmodified thermoplastic material.

[0086] As already delineated above, the composite material according to the invention is preferably characterized by a high bulk density. Preferably, the composite material has a bulk density in the range of from 0.2 to 1.0 g/cm.sup.3, particularly 0.3 to 0.9 g/cm.sup.3, preferably 0.4 to 0.8 g/cm.sup.3, more preferably 0.5 to 0.7 g/cm.sup.3. Thus, the composite material according to the invention provides a much denser powder bed compared to conventional thermoplastic materials, which results in much better sintering properties and non-porous articles with higher breaking strength. Bulk density, also referred to as pouring density, is defined as the ratio of bulk mass to bulk volume and is preferably measured in accordance with DIN ISO 697 and DIN ISO 60.

[0087] According to a preferred embodiment of the present invention, the polymer is a high-performance polymer, particularly a high-performance engineering polymer.

[0088] According to the invention, it is preferred, if the polymer is selected from the group consisting of polyetherketone (PEK), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyamid-imide (PAI), polysulfone (PSU), polyether sulfone (PES), polyphenylsulfone (PPSU) or their blends. According to the invention, it is preferred, if the polymer selected from the group consisting of polyetherketone (PEK), polyetheretherketone (PEEK), polyphenylene sulfide (PPS) and their blends. The present invention provides composite materials with enhanced thermal and mechanical properties, particularly, if high-performance polymers are used as the thermoplastic polymer for the inventive composite material. High-performance polymers usually have a very high melting point, hardly absorb laser radiation and have problematic rheological properties. All these problems can be overcome with the inventive composite material.

[0089] According to a further preferred embodiment of the invention, the composite material comprises the polymer in amounts of up to 99% by weight, particularly up to 95% by weight, preferably up to 90% by weight, more preferably up to 85% by weight, even more preferably up to 70% by weight, based on the weight of the composite material.

[0090] Moreover, it is possible that the composite material comprises the polymer in amounts of 40 to 99% by weight, particularly 50 to 95% by weight, preferably 55 to 90% by weight, more preferably 60 to 85% by weight, even more preferably 65 to 70% by weight, based on the weight of the composite material.

[0091] Furthermore, it is possible that the composite material comprises at least one filler. Very good results are obtained, if the composite material comprises a filler selected from the group consisting of carbon nanotubes, fibers, preferably carbon fibers, glass fibers, silica, inorganic carbonates, particularly calcium carbonate, inorganic sulfates, particularly barium sulfate, and their mixtures. By adding a further filler or further fillers to the inventive composite material, the mechanical properties of the composite material as well as of objects obtained by additive manufacturing processes can be selectively enhanced. Particularly, the incorporation of carbon nanotubes or fibers enhances the tensile strength of both the composite material as well as objects formed thereof.

[0092] If the composite material comprises a further filler, it is possible that the composite material comprises the filler in amounts of 1 to 30% by weight, particularly 5 to 25% by weight, preferably 7 to 20% by weight, more preferably 10 to 15% by weight, based on the weight of the composite material.

[0093] According to a further embodiment of the present invention, the composite material comprises at least one additive.

[0094] If the composite material comprises an additive, very good results are obtained, when the additive is selected from the group consisting of processing aids, surfactants, pigments, dyes, plasticizers and stabilizers, particularly UV stabilizers, and their mixtures.

[0095] The amount of additives in the inventive composite material can vary in wide ranges. However, very good results are obtained, if the composite material comprises the additive in amounts of 0.1 to 15% by weight, particularly 0.5 to 10% by weight, preferably 1 to 7% by weight, more preferably 2 to 5% by weight, based on the weight of the composite material.

[0096] Usually, the composite material according to the invention is a semi-finished product. Particularly, the composite material according to the invention is not a powder blend, but a composite material. Powder blends of for example thermoplastic polymers with glass beads or metal particles or inorganic oxides are known in the art. However, these powder blends usually contain very high amounts of inorganic material and only very low amounts of the thermoplastic material since the organic material is only used to produce the green body of the finished object. The green body is sintered at high temperaturesusually above 1,000 C.and the organic material is removed during the sintering process. In very contrast to this, according to the invention, a composite material comprising a thermoplastic polymer and a particulate inorganic material is provided.

[0097] In the figures:

[0098] FIG. 1 an apparatus for selective laser sintering that is suited to carry out the inventive method for obtaining a shaped article; and

[0099] FIG. 2 shows a shaped article consisting of magnetite-modified PPS obtained from the inventive composite material with selective laser sintering (SLS).

[0100] According to a second aspect of the present invention, the present invention relates to the use of a composite material as described before in additive manufacturing methods.

[0101] According to a preferred embodiment of the present invention, the additive manufacturing method is selective laser sintering (SLS).

[0102] According to another preferred embodiment of the present invention, the additive manufacturing method is a extrusion based 3D printing method, particularly fused filament fabrication (FFF).

[0103] For further details in regard to the inventive use of a composite material, reference is made to the above description of the further aspects of the present invention which also apply in regard to the inventive use.

[0104] A further aspect of the present inventionaccording to a third aspect of the present inventionis the use of a composite material as described above in the manufacture of an object with additive manufacturing methods.

[0105] For further details in regard to the inventive use of a composite material, reference is made to the above description of the further aspects of the present invention which also apply in regard to the inventive use.

[0106] A further aspect of the present inventionaccording to a fourth aspect of the present inventionis a process for preparing a composite material as described above, wherein

[0107] (i) in a first process step a starting material comprising

[0108] (a) at least one thermoplastic polymer and

[0109] (b) a particulate inorganic material

[0110] is blended at temperatures above the melting temperature of the polymer and

[0111] (ii) in a subsequent second process step the material obtained in process step (i) is comminuted, particularly by grinding.

[0112] According to a preferred embodiment of the present invention, in the first process step (i) the starting material is extruded, particularly with a screw extruder. Very good results are obtained according to the invention, if the starting material is extruded with a twin screw extruder.

[0113] By blending the at least one thermoplastic polymer and the particulate inorganic material, as well as further components listed above, above the melting temperature of the thermoplastic polymer and extruding the obtained material a composite material is obtained. The composite material obtained with the inventive process cannot be compared to a powder blend of for example a thermoplastic polymer and inorganic particles. According to the invention, the particulate inorganic material is embedded in the thermoplastic polymer.

[0114] Furthermore, according to the invention, it is preferred, if in the second process step (ii) the composite material is comminuted by cryogenic grinding.

[0115] In this regard, it is preferred, if the composite material is cooled with liquid nitrogen, particularly prior to the grinding operation.

[0116] Very good results are obtained in the course of the present invention, if the material is cooled to temperatures below the glass transition temperature of the thermoplastic polymer.

[0117] If the composite material is comminuted by cryogenic grinding, the material is usually cooled to temperatures below 50 C., particularly 100 C., preferably 150 C., more preferably 190 C.

[0118] Moreover, it is possible that the composite material is cooled to temperatures in the range of from 50 to 196 C., particularly 100 to 196 C., preferably 150 to 195 C., more preferably 190 to 195 C.

[0119] At low temperatures the thermoplastic polymer, even a high-performance thermoplastic polymer, does not show any viscoelastic properties, but is brittle and can be comminuted easily. Moreover, due to the high heat capacities of the inventive composite material, the inventive composite material warms much slower compared to unmodified thermoplastic materials and thus, can be comminuted much more easily by grinding processes.

[0120] Particularly in regard to high-performance polymers, it is usually not possible to obtain a homogeneous distribution of fine particles from a high-performance polymer, i.e. fine particles with a narrow particle size distribution.

[0121] The particle sizes to which the composite material is comminuted, can vary in wide ranges and strongly depend on the application conditions. However, very good results are obtained, if in the second process step (ii), the composite material is comminuted to obtain a particulate composite material having particle sizes of less than 100 m, particularly less than 80 m, preferably less than 70 m, more preferably less than 50 m.

[0122] Moreover, it is possible and also preferred according to the invention, if in the second process step (ii), the composite material is comminuted to obtain a particulate composite material having particle sizes in the range of 5 to 100 m, particularly 10 to 80 m, preferably 15 to 70 m, more preferably 20 to 50 m.

[0123] Moreover, it is possible that in the second process step (ii), the composite material is comminuted to obtain a particulate composite material having a mean particle size in the range of from 10 to 70 m, particularly 20 to 60 m, preferably 30 to 50 m, more preferably 35 to 40 m.

[0124] For further details in regard to the inventive process, reference is made to the above descriptions of the further aspects of the present invention which also apply in regard to the inventive process.

[0125] A further aspectaccording to a fifth aspect of the present inventionis a shaped article obtained by processing a composite material as described above with an additive manufacturing method, particularly an additive layer manufacturing method.

[0126] According to a preferred embodiment of the present invention, the additive manufacturing method is selective laser sintering (SLS).

[0127] If the shaped article is obtained by selective laser sintering, the shaped article is preferably obtained by a process, wherein [0128] (A) in a first process step, a layer of a particulate polymeric material comprising a composite material as described above in the form of a powder bed is provided, [0129] (B) in a subsequent second process step, the layer of the particulate polymeric material is selectively sintered and [0130] (C) in subsequent third process step, a layer of the particulate polymeric material is deposited on the sintered structure, wherein the second (B) and the third (C) process steps are repeated so as to form a shaped article.

[0131] In this regard it is preferred, that the powder bed in the first process step (A) is provided at a temperature in the range of from 15 to 50 C., particularly 15 to 40 C., preferably 20 to 30 C. Thus, the temperatures of the powder bed and in the construction field are usually kept at room temperature or slightly above.

[0132] In very contrast to the inventive method, the temperature of the powder bed and the construction field in conventional methods for selective laser sintering of thermoplastic materials is only slightly below the melting temperature at the thermoplastic material.

[0133] According to another preferred embodiment of the present invention, the additive manufacturing method is an extrusion based 3D printing method, particularly fused filament fabrication (FFF). The composite material according to the invention is specifically suited for application in extrusion based 3D printing methods since due to the high heat capacity of the inventive composite material subsequent layers of molten composite material form a homogeneous and uniform shaped article. Thus, due to the use of the inventive composite material the layers that form the shaped article of the invention are not visible. The shaped article of the invention consists of a homogeneous material.

[0134] For further details with regard to the inventive shaped article, reference is made to the above descriptions in regard to the other aspect of the present invention, which also apply in regard to the shaped article.

[0135] The subject-matter of the present invention is further illustrated with the aid of the figures and the examples displaying preferred embodiments of the present invention, without limiting the present invention to these embodiments.

[0136] FIG. 1 shows a cross section of an apparatus 1 for creating three-dimensional articles with selective laser sintering in a xz plain.

[0137] For carrying out the inventive process, a thin layer of a composition 3 consisting of the inventive composite material or comprising the inventive composite material is provided on the construction field 2. The composition 3 is sintered by regioselective irradiating the construction field 2 with a laser beam 4 generated in means for generating laser beams 9. The laser beam 4 generated in the means for generating laser beams 9 is deflected with the deflection means 10, so that a pattern of melted thermoplastic material is obtained in the layer of the composition 3.

[0138] Afterwards, the construction field is lowered at least slightly with the motion of the piston 6 and further composition 3 is provided from stocking means 7. The further composition 3 is spread with the spreading means 8, e.g. a roll, in the form of a thin layer on the construction field. Therefore, a new layer of composition 3 is provided, which is irradiated. Excess composition 3 is stored in the opposing stocking means 7. The new layer of composition 3 is regioselectively sintered with laser beams 4, creating a new layer of melted thermoplastic material which due to the high heat-capacity of the inventive composite material forms a one-phase system with the previously formed layer. By repetition of these process steps, a three-dimensional article 5 is created.

EXAMPLES

[0139] A mixture comprising 96% by weight polyphenylene sulfide (PPS) and 4% magnetite is fed into a compounder and extruded to form a homogenous composite material. The extrudates are further processed to pellets which are subjected to cryogenic milling at 196 C. A homogeneous fine powder of dark grey to black color with particle sizes in the range from 8 to 70 m is obtained. Particles sizes are obtained by measurement with a HELOS P laser diffraction device PM 32/03 from Sympatec GmbH.

[0140] To examine the inventive composite material in regard to its use in additive manufacturing methods for obtaining articles from high-performance polymers, test articles with a size of 1007035 mm are produced via selective laser sintering (SLS) with the above described composite material. For this purpose, the inventive composite material is provided in a selective laser sintering device and the test articles are produced layer by layer by exposure to the beam of a CO.sub.2 laser.

[0141] The thickness of each layer of composite material is 0.1 mm and, thus, 350 layers are required for the test objects with a height of 35 mm. The bed temperature of the selective laser sintering device is 230 C. and the feed temperature for the inventive composite material is 140 C. Each layer is subjected to the laser beam with a scan speed of 500 inch/sec and a laser power of 50 W. This laser fill scan spacing is 0.12 mm.

[0142] FIG. 2 depicts one of the test articles. It is obvious from FIG. 2 that a homogenous three-dimensional object has been produced from the magnetite-modified PPS. The article has a rough surface, but is non-porous and no the single layers can be detected in the article. The use of the inventive composite material results in a homogenous and completely sintered three-dimensional article.

REFERENCE SIGNS

[0143] 1 apparatus [0144] 2 construction field [0145] 3 composition [0146] 4 laser beam [0147] 5 article [0148] 6 piston [0149] 7 storing means [0150] 8 spreading means [0151] 9 means for generating laser beams [0152] 10 deflection means