EP3727801A1

EP3727801A1 - Method for producing a treated, 3d printed object

Info

Publication number: EP3727801A1
Application number: EP18816133.5A
Authority: EP
Inventors: Dirk Achten; Thomas BÜSGEN; Roland Wagner; Jonas KÜNZEL; Michael Kessler; Bettina METTMANN
Original assignee: Covestro Deutschland AG
Current assignee: Stratasys Inc
Priority date: 2017-12-19
Filing date: 2018-12-18
Publication date: 2020-10-28
Also published as: US20200306829A1; WO2019121718A1; CN111465482A; US11833749B2

Abstract

The present invention relates to a method for producing a treated object, comprising the steps of: applying a layer of particles to a target area; applying a liquid binder to a selected portion of the layer in accordance with a cross-section of the object, so that the particles in the selected portion are bonded; repeating the steps of applying a layer of particles and applying a binder for a plurality of layers so that the bonded portions of the adjacent layers are bonded to form an object, wherein at least a part of the particles comprises a meltable polymer. A binder which cures by cross-linking is preferably selected as the binder. The obtained object is at least partially contacted with a liquid heated to ≥ T or with a powder bed heated to ≥ T in order to obtain the treated object. T represents a temperature of ≥ 25 °C, the liquid does not represent a solvent or a reaction partner for the binder present in the object and the meltable polymer, and the powder bed is different from the particles of the meltable polymer. The invention also relates to a treated object that can be obtained by the method according to the invention.

Description

Process for preparing a treated. 3D printed object

The present invention relates to a process for the preparation of a treated article comprising the steps of: depositing a layer of particles on a target surface; Applying a liquid binder to a selected portion of the layer corresponding to a cross-section of the article so that the particles are joined in the selected part; Repeating the steps of applying and applying binder to a plurality of layers such that the bonded portions of the adjacent layers combine to obtain an article, wherein at least a portion of the particles comprise a meltable polymer. The invention further relates to a treated article obtainable by the process according to the invention.

Additive manufacturing processes are processes by which objects are built up in layers. They therefore differ significantly from other methods of manufacturing objects such as milling or drilling. In the latter method, an article is processed so that it receives its final geometry by removal of material.

Additive manufacturing processes use different materials and process techniques to build objects in layers. In so-called Fused Deposition Modeling (FDM), for example, a thermoplastic plastic wire is liquefied and laid in layers on a mobile construction platform with the aid of a nozzle. When solidifying, a solid object is created. The control of the nozzle and the build platform is based on a CAD drawing of the object. If the geometry of this object is complex, for example with geometric undercuts, support materials must be printed in addition and removed after completion of the object.

In addition, there exist additive manufacturing processes which use thermoplastic powders to build up objects in layers. In this case, thin powder layers are applied via a so-called coater and then selectively melted by means of an energy source. The surrounding powder supports the component geometry. Complex geometries are thereby more economical to produce than in the previously described FDM process. In addition, various items can be packed or made tightly packed in the so-called powder bed. Because of these advantages, powder-based additive manufacturing processes are among the most economical additive manufacturing processes on the market. They are therefore used predominantly by industrial users. Examples of powder-based additive manufacturing processes are the so-called laser sintering (SLS, Selective Laser Sintering) or high-speed sintering (HSS). They differ from each other in the method to enter the energy for the selective melting in the plastic. In the laser sintering process, the energy input occurs over a steered laser beam. In the so-called high-speed sintering (HSS) method (EP 1648686), the energy is introduced via infrared (IR) emitters in combination with an IR absorber which is selectively printed in the powder bed. Selective heat sintering (SHS) uses the printing unit of a conventional thermal printer to selectively melt thermoplastic powders.

Based on the polymers that are predominantly used today in powder-based additive manufacturing processes, articles are produced whose mechanical properties can fundamentally differ from the characteristics of the materials known in other plastics-processing processes, such as injection molding. During processing by the additive manufacturing processes, the thermoplastic materials used lose their specific characteristics.

Polyamide 12 (PA 12) is currently the most widely used material for powder-based additive manufacturing processes, such as e.g. the laser sinter. PA12 is characterized by high strength and toughness when processed by injection molding or extrusion. For example, a commercially available PA12 exhibits an elongation at break of more than 200% after injection molding. PA 12 articles produced by the laser sintering process, on the other hand, show elongations at break of 15%. The component is brittle and therefore can no longer be regarded as a typical PA12 component. The same applies to polypropylene (PP), which is offered as a powder for laser sintering. This material also embrittles and thus loses the PP-typical tough-elastic properties. Reasons for this can be found in the morphology of the polymers.

During the melting process by means of laser or IR and in particular during cooling, an irregular internal structure of the so-called semi-crystalline polymers (for example PA12 and PP) arises. The internal structure (morphology) of semicrystalline polymers is characterized in part by high order. A certain portion of the polymer chains forms crystalline, tightly packed structures upon cooling. During melting and cooling, these crystallites grow irregularly at the boundaries of the unfused particles as well as at the former grain boundaries of the powder particles and additives contained in the powder. The irregularity of the resulting morphology favors the formation of cracks under mechanical stress. The unavoidable residual porosity in the powder-based additive process promotes crack growth.

Brittle properties of the resulting components are the result. To explain these effects, reference is made to European Polymer Journal 48 (2012), pages 1611-1621. The elastic polymers used in the laser sintering based on block copolymers show a property profile which is atypical of the polymers used, if they are used as powders with additive Manufacturing processes are processed into objects. Laser sintering today uses thermoplastic elastomers (TPE). Articles made from the TPEs available today have high porosity after solidification and the original strength of the TPE material is not measurable in the article made therefrom. In practice, these porous components are therefore subsequently infiltrated with liquid, curing polymers to adjust the required property profile. The strength and elongation remains at a low level despite this additional measure. The additional process complexity leads - in addition to the still inadequate mechanical properties - to a poor economy of these materials.

In laser sintering processes using polymer particles, these are typically processed in a sealed volume or chamber so that the particles can be processed in a heated atmosphere. In this way, the temperature difference, which must be overcome for sintering the particles by the action of the laser, can be reduced. In general, it can be stated that the thermal properties of the polymer influence the possible processing temperatures in laser sintering processes. Therefore, various solutions have been proposed in the art for such polymers and their Verarb eitungs procedures.

US 2005/0080191 A1 relates to a powder system for use in solid freeform production processes, comprising at least one polymer having reactive properties and fusible properties, wherein the at least one polymer is selected to react with a liquid binder and at a temperature above the melting point or the glass transition temperature of the at least one polymer is meltable. The at least one polymer may comprise at least one reactive polymer and at least one fusible polymer, and the at least one fusible polymer may have a melting point or a glass transition temperature in the range of about 50 ° C to about 250 ° C.

There is also a need in the prior art for powder-based additive production processes in which the components obtained have homogeneous material properties.

Therefore, a method according to claim 1 and an article according to claim 14 is proposed. Advantageous further developments are specified in the subclaims. They can be combined as desired, provided the context does not clearly result in the opposite.

A method for producing a treated article comprises the steps of:

- orders of a layer of particles on a target surface; Applying a liquid binder to a selected part of the layer, corresponding to a cross-section of the article, so that the particles are joined in the selected part;

Repeating the steps of applying the particles and applying binder to a plurality of layers such that the bonded portions of the adjacent layers combine to obtain an article; wherein at least a portion of the particles comprise a meltable polymer.

The resulting article is contacted at least partially with a liquid heated to> T or heated to> T to obtain the treated article, where T is a temperature of> 25 ° C, the liquid for the binder present in the article and the fusible polymer is not a solvent or reactant and the powder bed is different from the particles of the fusible polymer.

The contacting of the article with the heated liquid or the heated powder bed is hereinafter also referred to as annealing.

In the method according to the invention, an object is built up in layers. If the number of recoveries for orders and irradiation is sufficiently small, it is also possible to speak of a two-dimensional object that is to be set up. Such a two-dimensional object can also be characterized as a coating. For example, for the construction of> 2 to <20 repetitions for orders and irradiation can be performed.

It is contemplated that at least a portion of the particles comprise a meltable polymer. Preferably, all particles used in the process to a meltable polymer. It is further preferred that at least 90% by weight of the particles have a particle diameter of <0.25 mm, preferably <0.2 mm, particularly preferably <0.15 mm. The particles with the meltable polymer may, for example, be of homogeneous composition, so that there are no further fusible polymers in the particles.

Suitable powders of thermoplastic materials can be prepared by various common processes, such as milling, cryomilling, precipitation, spray drying, and others.

Suitable fusible polymers for the process according to the invention are, for example, all known thermoplastics which can be bonded with an adhesive having an adhesive force of> 0.5 N / mm ² (tensile shear test in accordance with DIN EN 1465). In addition to the meltable polymer, the particles may contain other additives such as fillers, stabilizers and the like, but also other polymers. The total content of additives in the particles may be, for example,> 0.1% by weight to <40% by weight, preferably> 1% by weight to <20% by weight.

Suitable binders are physically setting adhesives and chemically hardening adhesives. The binder may be, for example, an aqueous dispersion adhesive, a solvent-containing wet adhesive, a polymerization adhesive, a polycondensation adhesive or a polyaddition adhesive.

The binder is preferably applied via a digital application method. This can be a drop-on-demand process, a screen printing process (with layer-wise changeable masks), an inkjet process or another easily controllable metering process. Preferably, as the application method for the binder, a digital printing method such as the Inkj etverfahren.

It is provided according to the invention that the liquid for the present in the subject binder and the meltable polymer is not a solvent or reactant. Thus, in the context of the present invention, "binder present in the article" includes compounds derived from the binder formed by physical processes such as evaporation of a solvent or chemical processes such as crosslinking or polymerization reactions, and as Glue the particles together.

"No solvent" means in particular that the solubility of the considered component in the liquid at 20 ° C <10 g / L, preferably <1 g / L, more preferably <0.1 g / L and particularly preferably <0.01 g / L. Furthermore, particularly suitable liquids do not lead to any unwanted discoloration of the article and allow the article to swell only reversibly or preferably not at all.

Particularly suitable liquids are further distinguished by the fact that they can be repeatedly heated to the exten sion temperature of the thermoplastic without showing degradation phenomena.

Preferably, the surface tension of the liquid is at least 10 mN / m less than or greater than the surface tension of the thermoplastic material of the component.

It may be preferred to use low-volatile apolar liquids which can be heated under pressure to the desired temperatures, but then slightly from the obtained, treated object to be removed.

Upon receipt of the article, it can be freed of powder residues by conventional methods such as brushing or compressed air.

Upon receipt of the article, it may further be further strengthened by conventional post-processing techniques such as coating or infusing with suitable coating or infusion agents such as an aqueous polyurethane dispersion followed by drying and curing at temperatures below or below 20 ° C below the softening temperature of the thermoplastic powder before it comes into contact with the inert liquid or the inert powder material. In the method according to the invention, the article obtained after the additive manufacturing process is at least partially contacted by a heated liquid or a heated powder bed. In this case, the resulting article remains fonnstabil by the binder and the bonded powder particles can be sintered to the treated article.

This new inventive method has several advantages over the prior art or conventional selective laser sintering or high speed sintering method. Thus, the installation space temperature may be low, as in a method analogous to binder jetting. The only requirement is that the adhesive hardens sufficiently. The subsequent, but spatially separable sintering processes can be significantly simplified and offered cheaper, since no heated space is necessary. Furthermore, the products of several building processes can be sintered together in a subsequent process, which again increases the flexibility and cost-efficiency of the construction process.

The method according to the invention can produce materials with higher density and hardness than conventional sintering methods, since the binder prevents a part of the porosity which arises in a normal sintering process. The inventive method also allows the processing of almost any thermoplastic powders, since the problems of the installation space process in the SLS and HS process do not occur. With the method according to the invention, according to the knowledge of the inventor for the first time, non-crystalline thermoplastics can also be processed into mechanically high-quality components.

In the inventive method further preferred complex component geometries are realized because the liquid / the powder bed counteract the powder analogous to the powder in the SLS and HS process of gravity.

After sintering, the temperature of the liquid is preferably set to a value of <20 ° C., preferably <50 ° C., particularly preferably <80 ° C., slowly within> 20 min, preferably> 40 min, particularly preferably> 60 min below the softening temperature, and the treated body is obtained. Subsequently, the body can be washed, if desired.

In a preferred embodiment, the temperature of the liquid is preferably after sintering to a value of <20 ° C, preferably <50 ° C, more preferably> 80 ° C within <15 min, preferably <10 min, more preferably <5 Lowered below the supernatant temp eratur and the treated received in body. Subsequently, the body can be washed, if desired. This method is particularly preferred when sintering amorphous materials.

In a preferred embodiment, the binder selected is a binder which cures with crosslinking. Covalent bonds are then formed during curing of the binder, which at least partially lead to a spatial network structure in the cured binder. In a further preferred embodiment, the binder is selected from: radiation-curing binders, binders which cure by radical initiator, binders which increase through exposure to increasing temperature, two-component reactive binders and mixtures of the abovementioned binders and curing variants. Preferred are binders based on (meth) acrylates, isocyanates, polyurethanes, epoxides, or cyanoacrylates or mixtures of at least two thereof.

In a further preferred embodiment, the binder present in the article, for example after crosslinking or film formation, has a softening temperature which is greater than the softening temperature of the meltable polymer, wherein the softening temperature is defined as the intersection of the curves for memory modulus E 'and loss modulus E "in one Temp-dependent dynamic-mechanical analysis.

In a further preferred embodiment, the adhesive present in the article (for example after crosslinking or film formation) in the tensile shear test according to DIN EN 1465 has an adhesive force of> 0.5 N / mm ² (preferably> 1 N / mm ² ) in the bonding of test specimens of the fusible polymer, more preferably> 2 N / mm ² ).

In a further preferred embodiment, during contacting of the article with the heated liquid, the liquid is at least temporarily pressurized. The pressure (relative, ie overpressure) is preferably> 1 bar to <100 bar, preferably> 2 bar to <50 bar, particularly preferably> 3 bar to <20 bar and very particularly preferably> 4 bar to < 10 bar. The pressure impact can be carried out in suitable autoclave made of glass or metal by means of pressing a suitable gas or by mechanical reduction of the autoclave volume. When pressurizing the liquid with overpressure can the temperature of the heated liquid can be lowered compared to process variants without pressurization, for example by> 5 ° C or> 10 ° C.

In a further preferred embodiment, the temperature T, expressed in degrees Celsius, is> 1 ° C, preferably> 2 ° C, more preferably> 5 ° C below the softening temperature of the meltable polymer, wherein the softening temperature is defined as the intersection of the curves for storage modulus E 'and loss modulus E "in a temperature-dependent dynamic-mechanical analysis.

In a further preferred embodiment, the temperature T, expressed in degrees Celsius, further <95% (preferably <90%, more preferably <85%) of the decomposition temperature of the binder after crosslinking, wherein the Z set temperature is defined as the temperature, at a mass loss of> 10% is detected in a thermogravimetric analysis at a heating rate of 5 ° C / min in the air stream.

In a further preferred embodiment, the temperature T is selected so that at this temperature the modulus of elasticity E ', determined by means of dynamic mechanical analysis of the fusible polymer, is> 10 ⁵ Pa to <10 ⁸ Pa, preferably> 5 · 10 ⁵ Pa to <5 × 10 ⁷ Pa, more preferably> 1 × 10 ⁶ Pa to <1 × 10 ⁷ Pa.

In a further preferred embodiment, contacting the resulting article with the liquid or powder bed is carried out for> 5 minutes to <24 hours, preferably> 30 minutes to <18 hours, more preferably> 1 hour to <12 hours.

In a further preferred embodiment, the temperature is T> 40 ° C to <300 ° C, preferably> 50 ° C to <280 ° C and more preferably> 80 ° C to <250 ° C.

In a further preferred embodiment, the meltable polymer is selected from: PEEK, PAEK, PEKK, polyethersulfone, polyimide, polyetherimide, polyester, polyamide, polycarbonate, polyurethane, polyvinyl chloride, polyoxymethylene, polyvinyl acetate, polyacrylate, polymethacrylate, TPE (thermoplastic elastomers), polystyrene, Polyethylene, polypropylene or mixtures of at least two of said polymers.

Preferably, the meltable polymer is a polyurethane which is at least proportionally available from the reaction of aromatic and / or aliphatic polyisocyanates with suitable (poly) alcohols and / or (poly) amines or mixtures thereof. Preference is given, at least in part, to using (poly) alcohols from the group consisting of: linear polyesterpolyols, polyetherpolyols, polycarbonatepolyols, polyacrylatepolyols or a combination of at least two thereof. In a preferred embodiment, these carry (poly) alcohols or (Poly) amine terminal alcohol and / or amine functionalities. In a further preferred embodiment, the (poly) alcohols and / or (poly) amines have a molecular weight of 52 to 10,000 g / mol. Preferably, these (poly) alcohols or (poly) amines as starting materials have a melting point in the range of 5 to 150 ° C. Preferred polyisocyanates which can be used, at least in part, for the preparation of the fusible polyurethanes are TDI, MDI, HDI, PDI, H12MDI, IPDI, TODI, XDI, NDI and decane diisocyanate. Particularly preferred polyisocyanates are HDI, PDI, H12MDI, MDI and TDI.

It is also preferred that the meltable polymer is a bisphenol A and / or bisphenol TMC based polycarbonate.

In a further preferred embodiment, the liquid is selected from: silicone oils, fluorinated hydrocarbons, polyethylene waxes, salt water, molten metals, ionic liquids and mixtures of at least two of said liquids. In the case of salt water, a saturated NaCl solution is preferred.

In a further preferred embodiment, the powder bed contains particles of glass, polytetrafluoroethylene, silicon dioxide, aluminum oxide, metals low and high-melting salts, water-soluble salts, acid-soluble salts, base-soluble salts or mixtures of at least two thereof. Powders having a high heat conductivity of> 0.2 WHT'K ¹ are particularly preferred. The ability to adapt can be determined as described in the publication TK04 Application Note, 2015, TeKa, Berlin, Germany "Testing fragments and powder".

Examples of particularly suitable combinations of meltable polymers and binders in the process according to the invention are listed below. Depending on the dosage form, the binders may be present as aqueous dispersions, solvent adhesives or 100% reactive adhesives. In the context of the invention, reactive adhesives are adhesives which react either by reacting the adhesive components with themselves to form new compounds and / or by reacting the adhesive components with the powders to form new compounds. The reactions may be reacted by contacting the components with themselves and / or the powder and / or by heat and / or by catalyst addition (catalyst activation) and / or by radiation activation and / or by drying the solvent or dispersion to form a film. According to the invention, the effect of an adhesive by film formation due to drying from solution or dispersion, wherein typical physical interactions with the powder for bonding lead. In addition to the use of one-component adhesives, the use of at least two-component adhesives is preferred. Adhesives belong to the meaning of Invention to the binders and are used partly synonymous.

Table 1. Suitable combinations of meltable polymers and preferably solid binders

Examples of particularly suitable combinations of meltable polymers and liquids in the process according to the invention are listed below:

Table 2. Suitable combinations of meltable polymers and liquids

Examples of particularly suitable combinations of binders and liquids in the process according to the invention are listed below:

Table 3. Suitable binders and liquids

Examples of particularly suitable combinations of meltable polymers, binders and liquids in the process according to the invention are listed below:

Table 4. Suitable combinations of meltable polymers, binders and liquids

Examples of particularly suitable combinations of meltable polymers, suitable binders and powders in the process according to the invention are listed below: Table 5. Suitable combinations of meltable polymers, binders and powders

When using Metallpulvem is preferably carried out under inert gas or at least surface-oxidized or oxidation-resistant metal powder are used to exclude metal fires. Examples of particularly suitable combinations of metals and suitable binders and powders in the process according to the invention are listed below. Again, the process is preferably carried out under inert conditions, for example by using inert gas:

Table 6. Suitable combinations of metals, binders and powders

The present invention further relates to a treated article obtainable by a process as described in detail above. Such an article may in particular have improved mechanical properties. The article produced according to the method of the invention preferably has a surface with a mean roughness Ra (DIN EN ISO 4287) of <500 mih, preferably of <200 mih, or preferably of <100 mih or preferably in a range of 10 to 500 mih, or more preferably in a range of 50 to 100 mih.

The article produced by the process according to the invention is distinguished in particular by its particularly high stability and, furthermore, by particularly homogeneous mechanical properties.

With regard to the mechanical properties, in particular the density and the tensile strength are mentioned, which in particular represents the stability of the article in the layer plane.

In this regard, it is particularly preferred that in the tensile test based on DIN EN ISO 527-2, the product of the method according to the invention has a tensile strength which is greater than the tensile strength of the untempered article. In other words, after annealing, the treated articles have a tensile strength that is greater than before annealing. It is preferred that the treated articles, after annealing, have a tensile strength which is greater than the tensile strength of the untreated article, preferably by an amount of> 10%, more preferably by an amount of> 20%, more preferably by one Amount of> 30%, more preferably by an amount of> 50%, more preferably by an amount of> 100%, wherein the values described above relate to the tensile strength of the untreated article or the article before annealing.

It is further preferred that the density of the treated article is greater than the density of the untreated article, or in other words, that the density after annealing is greater in a suitable medium according to the present invention than before annealing. The difference in density is typically expressed by the fact that the tempered product or object has smaller geometrical dimensions than the unannealed object. It is particularly preferred that the density of the treated article is greater than the density of the untreated article, preferably by an amount of> 1%, preferably by an amount of> 2%, more preferably by an amount of> 5%, on preferably by an amount of> 10%, based on the density of the untreated article or based on the density of the article before annealing.

In particular, these mechanical properties can be achieved by the method described here Improve compared to conventional additive produced objects.

In a preferred embodiment, in the tensile shear test based on DIN EN 1465, the layers of the treated body to each other have a shear strength of> 1 N / mm ² (preferably> 1.5 N / mm ² , more preferably> 2 N / mm ² ). With regard to further advantages and technical features of the method according to the invention and of the article according to the invention, reference is made to the following description of the production of an article, and vice versa.

Examples:

In the following, various experiments are shown in which an object produced by binder jetting or a binding method is examined. The article comprising a powder and an adhesive holding the powder together was prepared by an additive layer-forming manufacturing process and examined for its properties before and after annealing in a suitable medium according to the invention.

Test method: Tensile test: According to DIN EN ISO 527-2.

Particle sizes or particle diameters: Unless otherwise specified, particle sizes or particle sizes were determined by means of laser diffraction (HELOS particle size enanaly s e)

Starting Materials:

Silicone oil (silicone oil bath): Oil M 50 El from the company Momentive ™, colorless NaCl: table salt with grain size from 0.1 to 0.9 mm.

Sand (filter sand): quartz sand with grain size from 0.4 to 0.8 mm.

S1 tensile bars based on Polypor C (PPC) prepared by the Binderj ettingverfahren based on PMMA obtained from Voxeljet AG and used as purchased. TPU: Desmopan® 3787A was purchased from Covestro Deutschland AG.

Polycarbonate: Makroion® 2408 was purchased from Covestro Deutschland AG. Polyurethane adhesive: Dispercoll® U54, 50% polyurethane adhesive dispersion was purchased from Covestro Deutschland AG.

Part of the resulting PMMA-based S1 rods were completely enveloped with powdered NaCl, with the rods each being enclosed in the direction of space by at least one 1 cm thick salt layer and heated at 140 ° C. and 160 ° C. for 2 h and 4 h in a circulating air oven. This process is also called annealing. Following annealing, the vessel was removed from the convection oven with NaCl powder and tensile bars and slowly cooled to 23 ° C over 30 minutes before the bars were removed and mechanically separated from the salt.

The resulting S1 rods of PMMA were then tested in the tensile test after storage for 24 h at 23 ° C. according to DIN EN ISO 527-2.

The results are listed in samples 7 to 5 in Table 7. Comparison attempts are marked with *.

The TPU powder used was obtained by cryomilling Desmopan® 3787A, obtained from Covestro Deutschland AG. For this purpose, the TPU was mixed with 0.2% by weight, based on TPU, of hydrophobized pyrogenic silica as flow agent (Aerosil® R972 from Evonik), and the mixture was mechanically converted into powder under cryogenic cryogenization (cryogenic comminution) in a pin mill Screening machine classified. 90% by weight of the composition had a particle diameter of less than 140 μm (measured by means of laser diffraction (HELOS particle size analysis)).

To simulate the Binderj ettingverfahrens the TPU powder with Dispercoll® U54, a polyurethane dispersion, purchased from Covestro Deutschland AG, in a mass ratio of 1: 1 and mixed in 8 * 1 mm layers, with intermediate drying for 20 min at 23 ° C. in a rectangular shape of 8 * 20 cm with Teflon bottom layered with a squeegee. For this purpose, the walls of the mold were each increased by 1 mm with adhesive tape during each coating process. After further drying of the mixture for 24 h at 23 ° C and 1 h at 80 ° C, the plate was cut into 1 cm * 8cm rods and a part of the rods obtained according erfmdungsgemäß coated with powdered NaCl. The bars were in the direction of space in each case surrounded by at least one 1 cm thick salt layer and heated for 1 h at 180 ° C in a convection oven (annealing). Following annealing, the vessel was removed from the convection oven with NaCl powder and sample rods and cooled to 23 ° C over 30 minutes before the bars were removed and mechanically separated from the salt. The rods obtained were then tested after storage for 24 h in accordance with DIN EN ISO 527-2 (the test specimens do not conform to DIN EN ISO 527-2) in the tensile test.

The results of tensile bars made of TPU are listed in samples 7 and 7 in Table 7. P reparation tests are marked with *.

The polycarbonate powder used was obtained by cryomilling Makrolon® 2408, purchased from Covestro Deutschland AG. For this purpose, the polycarbonate with 0.2 wt .-%, based on polycarbonate, hydrophobi erter fumed silica as a superplasticizer (Aerosil® R972 from Evonik) was mixed and the mixture processed mechanically under deep freezing (cryogenic comminution with liquid nitrogen) in a pin mill to powder and then classified by a screening machine. 90% by weight of the composition had a particle diameter of less than 140 μm (measured by means of laser diffraction (HELOS particle size analysis)).

To simulate the Binderj ettingverfahrens the polycarbonate powder with Dispercoll® U54, a polyurethane dispersion, supplied by Covestro Deutschland AG, in a mass ratio of 1: 1 and mixed in 8 * lmm layers, with intermediate drying for 20 min at 23 ° C in a rectangular Shape of 8 * 20cm with Teflon base layered with a squeegee. For this purpose, the walls of the mold were each increased by 1 mm with adhesive tape during each coating process. After further drying of the mixture for 24 h at 23 ° C and lh at 80 ° C, the plate obtained was cut in about learning * 8 cm rods and a part of the rods obtained according to the invention coated with powdered NaCl, the rods in the direction of each of at least a schles thick salt layer were enclosed and heated for lh at 180 ° C in a convection oven. Following annealing, the vessel was removed from the convection oven with NaCl powder and sample rods and cooled to 23 ° C over 30 minutes before the bars were removed and mechanically separated from the salt.

The rods obtained were then tested in the tensile test after storage for 24 h on the basis of DIN EN ISO 527-2 (the test specimens do not conform to DIN EN ISO 527-2).

The results of tensile bars made of polycarbonate are listed in Sample 7 and Sample 9. Comparison attempts are marked with *.

Due to the high stresses, the rods 6 to 9 slid in the clamps of the tensile tester, so that only the tensile moduli were compared. Table 7. Tempering in NaCl

Sample samples

Tensile- Maximum fracture- fracture- body

Module voltage tension expansion height width

MPa MPa MPa% mm mm

PMMA

Sample 1 * reference

untreated 240.1 3.0 2.9 1.4 4.0 10.0

Sample 2 lh 140 ° C 314.6 3.6 3.5 1.2 3.9 10.0

Sample 3 2h 140 ° C 335.1 4.0 4.0 1.3 3.9 9.9

Sample 4 lh 160 ° C 316.3 3.6 3.5 1.1 3.8 9.9

Sample 5 2h 160 ° C 334.2 4.3 4.1 1.4 3.8 9.8

Sample samples

Tensile body

Module height wide

MPa mm mm

TPU

Sample 6 * Reference

untreated 3.7 6.2 10.1

Sample 7 17.0 5.3 9.9

polycarbonate

reference

Sample 8 * untreated 51.9 6.6 10.2

Sample 9 123.2 6.3 10.0

Marked with * means comparative experiment

A portion of the obtained PMMA-based S1 rods were heated according to the invention in silicone oil for 110 ° C. and 130 ° C. for 1 h in a circulating air oven. Following the tempering were the

Removed vessel with silicone oil and tensile rods from the convection oven and slowly cooled to 23 ° C within 30 min before the rods were removed and were largely freed of residues of silicone oil using absorbent paper. The resulting S1 rods of PMMA were then tested in the tensile test after storage for 24 h at 23 ° C. according to DIN EN ISO 527-2. Results for tensile bars made from PMMA and annealed in silicone oil are listed in Tables 8, Sample 10, 11, and 12. Comparison attempts are marked with *.

Table 8. Heat treatment in silicone oil

Sample Sample

Tensile- Maximum fracture- fracture- body

Module voltage tension expansion height width

MPa MPa MPa% mm mm

PMMA

Sample 10 * reference

untreated 240 3.0 2.9 1.4 4.0 10.0

Sample 11 lh 110 ° C 267 3.25 3.24 1.4 3.97 9.95

Sample 12 lh 130 ° C 292 3.49 3.49 1.4 3.89 9.96 The comparison of the results of the tensile bars produced according to the method of the invention compared to the tensile bars not according to the invention shows a significant improvement in the mechanical properties according to the invention Temperature storage compared to the non-annealed samples.

Furthermore, the density of the samples re-tempered according to the invention has increased, which is to be deduced from the lower heights and widths of the sample body after tempering.

Furthermore, significantly improved dimensional stability of the bodies has been achieved by annealing in suitable inert media with higher density than air, in contrast to free-tempered specimens, since they are less effectively exposed to gravity, resulting in the increase of the values of the tensile modulus, the maximum The voltage and the breaking stress of the test specimens reflect. This is an important property improvement, especially for filigree buildings.

Further, the surface roughness of the samples post-annealed according to the present invention tends to be improved toward a lower surface roughness. This was determined by haptic tests on the surfaces. This effect is particularly evident when using non-dissolving and swelling tempering liquids or fine powders.

Claims

claims

A method of making a treated article comprising the steps of:

- orders of a layer of particles on a target surface;

Applying a liquid binder to a selected part of the layer, corresponding to a cross section of the article, so that the particles are joined in the selected part;

Repeating the steps of applying the particles and applying binder to a plurality of layers such that the bonded portions of the adjacent layers combine to obtain an article; wherein at least a portion of the particles comprise a meltable polymer, characterized in that the resulting article is contacted at least partially with a liquid heated to> T or heated to> T to obtain the treated article, wherein T is at a temperature of > 25 ° C, the liquid for the present in the binder and the meltable polymer is not a solvent or reactant and the powder bed is different from the particles of the meltable polymer.

2. The method according to claim 1, characterized in that a binder is selected as the binder, which cures with crosslinking.

A method according to claim 1 or 2, characterized in that the binder present in the article has a softening point which is greater than the softening temperature of the meltable polymer, the softening point being defined as the intersection of the curves for the storage modulus E 'and loss modulus E. "In a temperature-dependent dynamic-mechanical analysis.

4. The method according to any one of claims 1 to 3, characterized in that the present binder in the tensile shear test according to DIN EN 1465 in the bonding of test specimens of the fusible polymer has a bond strength of> 0.5 N / mm ² .

5. The method according to any one of claims 1 to 4, characterized in that during the contacting of the article with the heated liquid, the liquid is at least temporarily pressurized.

6. The method according to any one of claims 1 to 5, characterized in that further the temperature T, expressed in degrees Celsius,> 1 ° C below the softening temperature of the meltable polymer, wherein the softening temperature is defined as the intersection of the curves for memory module E ' and loss modulus E "in a temperature-dependent dynamic-mechanical analysis.

A method according to any one of claims 1 to 6, characterized in that the temperature T, expressed in degrees Celsius, is still <95% of the decomposition temperature of the binder present in the article, the decomposition temperature being defined as the temperature at which a mass loss occurs of> 10% in a thermogravimetric analysis at a heating rate of 5 ° C / min in the air stream.

8. The method according to any one of claims 1 to 7, characterized in that the temperature T is further selected so that at this temperature the modulus of elasticity (determined in a temperature-dependent dynamic mechanical analysis) of the meltable polymer> 10 ⁵ Pa to <10 ⁸ Pa is.

9. The method according to any one of claims 1 to 8, characterized in that the contacting of the obtained article with the liquid or the powder bed is carried out for> 5 minutes to <24 hours.

10. The method according to any one of claims 1 to 9, characterized in that the temperature T> 40 ° C to <300 ° C.

11. The method according to any one of claims 1 to 10, characterized in that the meltable polymer selected from: PEEK, PAEK, PEKK, polyethersulfones, polyimide, polyetherimide, polyesters, polyamides, polycarbonates, polyurethanes, polyvinyl chloride, polyoxymethylene, polyvinyl acetate, polyacrylates, polymethacrylates , TPE (thermoplastic elastomers), polystyrene, polyethylene, polypropylene and blends of said polymers.

12. The method according to any one of claims 1 to 11, characterized in that the liquid is selected from: silicone oils, fluorinated hydrocarbons, polyethylene waxes, salt water, molten metal, ionic liquids and mixtures of said liquids.

13. The method according to any one of claims 1 to 11, characterized in that the powder bed contains particles of glass, polytetrafluoroethylene, silica, alumina, metal or mixtures thereof.

14. A treated article obtainable by a process according to any one of claims 1 to 13.

15. An article according to claim 14, characterized in that the tensile shear test based on DIN EN 1465, the layers of the treated body to each other a shear strength of> 1

N / mm ² .