Process for the production of complex structures from thermoplastic polymers and polymer moldings with complex structures produced in this way

Abstract

A method for producing complex structures from at least one thermoplastic polymer, in which the polymer is plasticized and deposited layer by layer by melt layers by means of at least one nozzle of a controllably movable print head of a 3D printer to form the complex structure, after which the layers of the polymer thus produced are solidified, characterized in that at least one thermoplastic polymer with shape memory properties and / or with thermoresponsive properties is used to produce the complex structure, that the print head of the 3D printer is moved at a speed of at most 20 mm / s during the deposition of the plasticized polymer with shape memory properties and / or with thermoresponsive properties,and that the print head of the 3D printer is moved at least immediately after the deposition of the polymer with shape memory properties and / or with thermoresponsive properties forming part of the complex structure at a speed which is at least 10 times the speed of the print head during the deposition of the plasticized polymer, wherein after generating the complex structure by means of the 3D printer, the at least one polymer with shape memory properties and / or with thermoresponsive properties is programmed by the complex structure, - at a temperature which corresponds at least to the switching temperature of the at least one polymer with shape memory properties and / or with thermoresponsive properties, is at least partially deformed, after which the deformed complex structure is cooled at least to the shape-fixing temperature of the at least one polymer with shape memory properties and / or with thermoresponsive properties; or - is cold-formed at ambient temperature.

Description

The invention relates to a method for producing complex structures from at least one thermoplastic polymer by plasticizing the polymer and depositing it layer by layer by melt layers by means of at least one nozzle of a controlled movable print head of a 3D printer to form the complex structure, after which the layers of the polymer thus produced are solidified. The invention further relates to a polymer moulding made of at least one thermoplastic polymer having at least one complex structure produced in this way.For the production of polymer moldings, the melt-layer process, also referred to as fused deposition modeling (FDM) or fused filament fabrication (FFF), is known, which is used in particular in 3D printers and constitutes a production process in which a thermoplastic polymer or a polymer blend of thermoplastic polymers is plasticized and deposited layer by layer by means of a nozzle usually provided in the print head of the 3D printer, in order to produce the polymer molding ultimately formed from a multiplicity of such layers. This enables, on the one hand, a layer-by-layer production of relatively complex moldings having more or less complex structures, which is also suitable for prototyping or for small series production, and for example moldings with more or less complex structures which are not producible by conventional thermoplastic processing methods, such as injection molding, extrusion, etc., wherein, on the other hand, the melt-layer method is increasingly also used for the series production of polymer moldings having relatively complex structures. For the purposes of the present disclosure, "complex structures" are used to refer to three-dimensional shaped structures with relatively thin structures, including as fine structures as possible.In the melt-coating process by means of 3D printing, also referred to as "additive manufacturing", a three-dimensional model of the molded part to be produced is usually digitally created, which can be done in particular by means of the known methods of computer aided design (CAD). Furthermore, by means of suitable software, such as a so-called slicer program (e.g. Cura™ or the like), the three-dimensional model of the molded part to be produced is broken down into a plurality of thin layers, whereupon the plasticized polymer is deposited layer by layer by means of the nozzle of the correspondingly moved print head in order to build up the molded part layer by layer. Immediately after the application of the polymer plastic discharged from the nozzle of the print head in a more or less strand-shaped or drop-shaped manner, the curing process begins--or more precisely: the solidification process--wherein the deposited plastic solidifies, for example, at ambient temperature or also with active cooling.US 2015 / 0235069 A1 is concerned with 3D printing of objects having complex three-dimensional structures, such as in particular various machine-readable codes, which can be generated by means of various 3D printing methods including fused deposition modeling (FDM). US 2018 / 0086924 A1 describes a process for 3D printing of thermoplastic polymers admixed with additives, wherein, in addition to a large number of "hard" thermoplastics, mention is also made of thermoplastic elastomers, such as thermoplastic polyurethanes, for example, as polymers to be processed.However, despite its increasing spread, the fusible layer method still presents a great technical challenge, in particular in that case, the more complex or the more delicate the structures to be produced therewith are to be designed, with limits being placed on the resolution or the "sharpness" of such structures produced in this way. This is primarily due to the fact that, on the one hand, the diameter of the nozzle which discharges the plasticized polymer in layers cannot be made as small as possible, because the most homogeneous possible plastic flow must be maintained during the deposition or printing process. On the other hand, the separated plastic strand is often twisted in the vicinity of the drive or the nozzle, also referred to as the "coiling effect", which is associated with a deviation from the exactly desired shape of the produced structure.In order to combat the above-mentioned "coiling effect", in particular, attempts have been made, for example, to reduce the pressure in the drive unit of the 3D printer, which, however, leads to a loss of quality of the polymer structure produced. If, instead, the die temperature is increased excessively in order to ensure the lowest possible melt viscosity of the polymer to be deposited, there is the risk of thermal degradation of the polymer used, so that once again only low print quality can be achieved with fiber-like structures of the molded part produced.While in the solid or solidified state relatively stiff or rigid thermoplastic polymers, such as polylactide (PLA), acrylonitrile-butadiene-styrene copolymers (ABS) or the like, can be processed by means of the melt layer method to form polymer molded parts with relatively complex structures, this has not been possible until now with elastic or semi-elastic thermoplastic polymers, such as in particular those from the group of thermoplastic polymers with shape memory properties and / or with thermoresponsive properties, because there occurs in particular a very strong "coiling effect", which places narrow limits on the resolution or "sharpness" of relatively complex structures. For this reason, no complex or delicate structures can be produced hitherto by means of the melt layer method from the polymers mentioned having shape memory properties and / or having thermoresponsive properties. On the other hand, there is a need for production of polymer moldings from such polymers by means of fusible layers, because the fusible layer process basically offers the possibility of producing virtually any desired molding structures.Shape memory polymers are polymers which usually consist of at least two polymer components or, in particular, of a polymer component having different segments. These are, on the one hand, "hard" segments which also function as network points. On the other hand, they are "soft" segments which connect the network points to one another and are also referred to as switching segments and are elastic at high temperatures (they are present in amorphous form in this case), while they are rigid at low temperatures (they are present in partially crystalline or vitrified form in this case). Such polymers can be programmed with regard to their shape by heating them to a temperature which corresponds at least to the so-called switching temperature at which the phase transition (glass transition or melting transition) of the soft or switching segments takes place. At such a temperature, the polymer is then shaped, after which it is cooled to its so-called shape fixing temperature, which corresponds to the crystallization temperature or glass transition temperature of the soft segments or switching segments and can lie in the range of the switching temperature, but is usually at least somewhat lower in contrast. The soft or switching segments are then again present in partially crystalline or vitrified form, so that the shaping is maintained. However, this shaping is only temporary insofar as a shape memory polymer mechanically deformed in this way "programmed" is heated to a specific temperature, namely to its switching temperature, the soft segments (switching segments) are converted back into their amorphous form, so that they can no longer counteract the restoring force induced by the hard component (network points) and the shape memory polymer again assumes its original shape, that is to say the mechanical deformation is "reversed". In addition to such a shape memory, thermoresponsive polymers can also have a temperature memory. This is understood to mean that, when the shape memory effect is triggered, the shape recovery begins approximately at the temperature at which the mechanical deformation has previously been introduced into the material. Such material behavior comprises, for example, polymers having semicrystalline network structures, such as thermoplastic polyurethane polymers (Fritzsch, N., Pretsch in Macromolecules 47, 2014, 5952-5959; Mirtschin, N., Pretsch in RSC Advances 5, 2015, 46307-46315).One field of application for such polymers with shape memory properties and / or with thermoresponsive properties is, for example, in various medical applications including bandages, compresses, insoles and the like, but also in articles of use such as dishes, toys, pacifiers, textiles, mattresses, hoses, spindles and the like. A particularly interesting field of application is in information carriers, for example for tamper-proof identification of goods in order to check their authenticity, wherein it is used, for example, that a code applied to the goods, for example machine-readable and / or otherwise optically unambiguously identifiable, becomes visible or readable only (or until then) when the information carrier made of such polymers is heated to its switching temperature after it has been previously (temporarily) deformed by means of the above-described programming. After processing, such polymer moldings, such as information carriers or else any other moldings, such as, for example, of the type mentioned above, namely have a memory and / or temperature, it being possible, in addition to a thermoresponseity, for example, to provide thermochromic properties, if the polymer molding has been printed or mixed with corresponding thermochromic dyes or pigments. In the case of information carriers, the authenticity can then additionally be detected by means of a color change at the corresponding color change temperature; in the case of any other shaped parts, a special effect is thereby achieved. In addition, such polymer moldings can also be admixed, for example, with magnetoresistive or electroactive additives, in particular in fine-particle form, as a result of which a shape change triggered by inductive heating can be triggered after the polymer has been admixed with shape memory properties and / or with thermoresponsive properties with such additives and has subsequently been programmed.The object of the invention is to improve a method for producing complex structures from at least one thermoplastic polymer of the type mentioned at the beginning in a simple and cost-effective manner to the effect that it makes it possible to produce complex structures from thermoplastic polymers from the group of the polymers having shape memory properties and / or having thermoresponsive properties while at least avoiding the disadvantages mentioned above to the greatest possible extent. It is also directed to a polymer molding of the type mentioned at the beginning produced in this way.In terms of process engineering, this object is achieved according to the invention in a method of the type mentioned at the beginning in that at least one thermoplastic polymer having shape memory properties and / or having thermoresponsive properties is used to produce the complex structure, in that the print head of the 3D printer is moved at a speed of at most 20 mm / s during the deposition of the plasticized polymer having shape memory properties and / or having thermoresponsive properties, and in that the print head of the 3D printer is moved further at a speed which is at least 10 times the speed of the print head during the deposition of the plasticized polymer, at least immediately after the deposition of the polymer forming part of the complex structure and having shape memory properties and / or having thermoresponsive properties, wherein, after generating the complex structure by means of the 3D printer, the at least one polymer having shape memory properties and / or having thermoresponsive properties is programmed by programming the complex structureat a temperature which corresponds at least to the switching temperature of the at least one polymer having shape memory properties and / or having thermoresponsive properties, at least partially deformed, after which the deformed complex structure is cooled at least to the shape fixing temperature of the at least one polymer having shape memory properties and / or having thermoresponsive properties; orcold forming at ambient temperature.To achieve this object, the invention further provides a polymer molding made of at least one thermoplastic polymer having shape memory properties and / or having thermoresponsive properties having at least one complex structure produced by a method of the aforementioned type.Surprisingly, it has been found that the so-called "coiling effect" during the deposition of thin layers of "soft" thermoplastic polymers having shape memory properties and / or having thermoresponsive properties can be prevented to the greatest possible extent by moving the print head equipped with the nozzle for applying the polymer plasticizer, on the one hand, at a speed of at most about 20 mm / s during the deposition of the plasticized polymer. However, it has been found that this measure alone does not yet lead to a high resolution of complex, filigrane structures of the polymer molding to be produced, because the still molten polymer plasticizer threatens to flow locally, in particular when the nozzle of the print head is closed and the print head is moved to another location within the currently produced layer of the molding to be produced. This problem is solved by the invention in that the print head is moved further at a speed which is at least approximately 10 times the speed of the print head during the deposition of the plasticized polymer, at least immediately after the deposition of the polymer forming part of the complex structure, or preferably also always when the print head is moved back and forth within a layer to be produced between different regions in which the plasticized polymer is to be deposited. In this way, a sharp break-off of the polymer plasticate takes place, wherein on the one hand the already deposited polymer is prevented from flowing out, on the other hand the already deposited polymer remains adhering to the nozzle of the print head and is "smeared" in the areas adjacent to the actual structure, which resulted in an only "blurred" structure.Consequently, the invention makes it possible to produce polymer moldings from thermoplastic polymers having shape memory properties and / or having thermoresponsive properties having complex structures by means of melt lamination, so that, owing to the high flexibility of the melt lamination process, virtually any shapes or structures can be produced from the aforementioned polymers, which, owing to the fact that the polymer used has shape memory and / or thermoresponsive properties, can be programmed in a manner known per se in order to bring about a desired change in shape by heating to its switching temperature. In addition, it is also possible, of course, to process thermoplastic elastomers, such as thermoplastic polyurethanes and the like, without shape memory properties. As is illustrated in more detail below with reference to the drawings, the method according to the invention thereby enables the production of very fine, filigrane structures with a line or web thickness of less than about 500 μm, in particular of less than about 400 μm, preferably of less than about 300 μm, for example of less than about 200 μm, from the aforementioned thermoplastic polymers, wherein furthermore the production of layer thicknesses of corresponding dimensions is possible, so that optionally very thin layers or - by multilayer deposition of the plasticized polymer - also layers of greater or lesser thickness can be produced.As already mentioned, the method according to the invention is suitable for producing molded parts having shape memory properties and / or having thermoresponsive properties, wherein at least one thermoplastic polymer having shape memory properties and / or having thermoresponsive properties is used to produce the complex structure, and wherein after production of the complex structure by means of the 3D printer the at least one polymer having shape memory properties and / or having thermoresponsive properties is programmed by at least partially deforming the complex structure at a temperature which corresponds at least to the switching temperature of the at least one polymer having shape memory properties and / or having thermoresponsive properties, after which the deformed complex structure is cooled at least to the shape fixing temperature of the at least one polymer having shape memory properties and / or having thermoresponsive properties. If the deformed complex structure is subsequently heated again at least to the switching temperature of the polymer having shape memory properties and / or having thermoresponsive properties, it is able to restore itself to its original, undeformed state. Instead of such programming, which is customary as such in the case of shape memory polymers, it is also possible in the case of many thermoplastic polymers having shape memory properties and / or having thermoresponsive properties to carry out the programming by means of cold deformation, for example at ambient temperature, it being possible for the complex structure deformed in this way to be restored to its original, undeformed state even in this case when the polymer is heated at least up to its switching temperature.The method according to the invention is suitable virtually for any known thermoplastic polymers having shape memory properties and / or having thermoresponsive properties, it being particularly suitable, for example, for thermoplastic polymers from the group of the polyester urethanes and the polyether urethanes.Examples of thermoplastic polymers found to be suitable having shape memory and / or having thermoresponsive properties include, in particular, linear block copolymers, preferably polyurethanes and polyurethanes having ionic or mesogenic components, block copolymers of polyethylene terephthalate and polyethylene oxide, block copolymers of polystyrene and poly(1,4-butadiene), ABA triblock copolymers of poly(2-methyl-2-oxazoline) (A block) and polytetrahydrofuran (B block), multiblock copolymers of polyurethanes having poly(ε-caprolactone) switching segments, block copolymers of polyethylene terephthalate and polyethylene oxide and block copolymers of polystyrene and poly(1,4-butadiene). Furthermore, thermoplastic polyurethane elastomers have proven suitable whose phase forming the hard segment is composed of a diisocyanate, such as methylene diphenyl diisocyanate (MDI), isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HMDI), toluene 2,4-diisocyanate (TDI) or 1,5-pentane diisocyanate (PDI), and a diol, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol or 1,10-decanediol. Both the diisocyanates mentioned and the polyols can be used individually or else in any desired mixture with one another. The soft segment in such thermoplastic polyurethane elastomers can be, for example, an oligoether, in particular polyethylene oxide, polypropylene oxide, polytetramethylene ether glycol (PTMEG) or a combination of 2,2-bis(4-hydroxyphenyl)propane and propylene oxide. Likewise, the soft segment can be, for example, an oligoester, in particular polyethylene adipate, polypropylene adipate, polybutylene adipate, polypentylene adipate or polyhexamethylene adipate, wherein further oligoesters have also proven to be useful. The oligoesters can be prepared, for example, by reacting ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol or 1,10-decanediol with aliphatic dicarboxylic acids, such as succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid and sebacic acid, or with aromatic dicarboxylic acids, such as phthalic acid, isophthalic acid and terephthalic acid. The dicarboxylic acids can be used individually or as mixtures, for example in the form of a succinic, glutaric and adipic acid mixture. For the preparation of the polyester polyols, it may optionally be advantageous to use, instead of dicarboxylic acids, the corresponding dicarboxylic acid derivatives, for example diesters of carboxylic acids having 1 to 4 carbon atoms in the alcohol radical, anhydrides or chlorides of carboxylic acids. Examples of polyhydric alcohols include glycols having 2 to 10, preferably having 2 to 6, carbon atoms, ethylene glycol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 2,2-dimethyl-1,3-propanediol, 1,3-propanediol and dipropylene glycol. The polyhydric alcohols may be used alone or optionally in admixture with each other. The polyester polyols also advantageously have molecular weights of between about 400 and about 10,000 g / mol, preferably between about 600 and about 5,000 g / mol.In addition, polycarbonate-based polyurethane elastomers are suitable, for example, as thermoplastic polymers having shape memory and / or having thermoresponsive properties. In this case, the diol in a thermoplastic polyurethane elastomer is preferably substantially completely or partly substituted by a polycarbonate having hydroxyl end groups, i.e. by a polycarbonate diol which is obtained from the reaction of a diol, in particular from the group of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol and 1,10-decanediol, with diaryl carbonates, such as, for example, diphenyl carbonate, ditolyl carbonate, dixylyl carbonate, dinaphthyl carbonate, dialkyl carbonates, such as, for example, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, diamyl carbonate, dicyclohexyl carbonate, The following compounds may be used as starting materials: dioxolanes, such as ethylene carbonate and propylene carbonate, hexanediol-1,6-bischlorocarbonic acid ester, phosgene or urea.In addition, especially in thermoplastic polyurethane elastomers having shape memory and / or thermoresponsive properties, for example, the chain extender diol can be partially substituted by a diamine. Exemplary embodiments thereof include isophoronediamine, ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, N-methyl-1,3-propylenediamine, N,N'-dimethylethylenediamine and aromatic diamines, such as, for example, 2,4-tolylenediamine and 2,6-tolylenediamine, 3,5-diethyl-2,4-tolylenediamine and / or 2,6-tolylenediamine, and primary ortho-di-, tri- and / or tetraalkyl-substituted 4,4'-diaminodiphenylmethanes. The diamines mentioned can likewise be used either individually or in any desired mixture with one another.Diamines as sole chain extenders are generally not suitable since the resulting polyureas cannot then be processed thermoplastically or have inadequate shape memory properties.In addition, it is possible, for example, to add an oil component, e.g. silicone oil, and / or other components, such as additives, to a thermoplastic elastomer mixture having shape memory and / or having thermoresponsive properties, which is processed according to the invention. Such auxiliary materials or fillers can have, for example, a graphene structure, as is present, for example, in graphite, carbon nanotubes (CNTs), graphene flakes or expanded graphite. Also, other fine particles having a nano-scale dimension can be used as auxiliary materials or fillers. For example, magnetic nanoparticles, ferromagnetic particles, in particular NiMn particles, iron oxide particles and magnetite particles are suitable for this purpose. So-called nanoclays can likewise be used as fillers. The nanoclays can be formed, for example, on the basis of silicon nitride, silicon carbide, silicon oxide, zirconium oxide and / or aluminum oxide. Other possible fillers include oligomeric silsesquioxanes, graphite particles, graphenes, carbon nanotubes, but also metal fine particles. Combinations of such filling materials can of course also be used. The fillers are suitable for adjusting the mechanical, electrical, magnetic and / or optical properties of the polymer and adapting them to the particular application.Furthermore, polymers with shape memory and / or with thermoresponsive properties in the form of polynorbornene, natural rubber (cis-1,4-polyisoprene), trans-1,4-polyisoprene, graft copolymers of polyethylene / nylon-5, block copolymers with polyhedral oligomeric silsesquioxanes (POSS), including the combinations polyurethane / POSS, epoxy / POSS, polysiloxane / POSS, polymethyl methacrylate / POSS, silicone-based shape memory polymers and materials of poly(cyclooctene), are conceivable for use in the method according to the invention.In polyester urethanes having shape memory and / or having thermoresponsive properties, for example, switching segment blocks can be constructed from poly(ε-caprolactone)diols, inter alia, having number-average molecular weights of between about 1,000 and about 10,000. The switching temperature for the shape memory effect can vary depending on the weight proportion of the switching segment (variation e.g. between about 50% by mass and about 90% by mass) and the molecular weight of the poly(ε-caprolactone) diols e.g. between about 40° C. and about 60° C., in particular between about 44° C. and about 55° C. The crystallization temperatures are, for example, in the order of magnitude between about 20° C. and about 40° C., in particular between about 25° C. and about 30° C. Block copolymers which are composed of trans-polyisoprene and urethanes also exhibit the shape memory effect, wherein the recovery temperature in this case can be in the order of magnitude of about 65° C., while the crystallization temperature depends on the chemical composition and can be set, for example, between about 0° C. and about 30° C. Furthermore, for example, the use of carbon black as filler additive can alter the shape memory properties (i.e., the recovery rate and the recovery temperature) of trans-polyisoprene.Furthermore, polyadipate-based polyester urethanes, for example, are suitable for the process of the invention, the switching temperature of their soft segments being about 37° C., and the crystallization temperature being significantly below about 23° C., in particular below about 10° C. In addition, such a material has very good shape memory properties (shape recoverability, fixability). In addition, an elastomeric polymer, in particular from the group of polyvinyl chloride, ethylene-vinyl acetate copolymers, covalently crosslinked copolymer systems of stearyl acrylate and esters of methacrylic acid, can be used as thermoplastic polymer having shape memory and / or having thermoresponsive properties.It has proven to be particularly advantageous if the print head of the 3D printer is moved during the deposition of the plasticized polymer with shape memory properties and / or with thermoresponsive properties at a speed of at most about 15 mm / s, in particular of at most about 12 mm / s, preferably of at most about 10 mm / s, for example of at most about 9 mm / s, wherein it can be advantageous if the print head is moved during the deposition of the plasticized polymer at a speed of at least about 1 mm / s, in particular of at least about 1.5 mm / s, preferably of at least about 2 mm / s.Furthermore, it has proven to be particularly advantageous if the print head of the 3D printer is moved further at a speed which is at least approximately 200 mm / s, in particular at least approximately 250 mm / s, preferably at least approximately 300 mm / s, for example at least approximately 320 mm / s or at least approximately 340 mm / s, such as at least approximately 370 mm / s or at least approximately 400 mm / s, at least immediately after the deposition of the polymer forming part of the complex structure and having shape memory properties and / or having thermoresponsive properties.In addition, for the purpose of achieving a very low viscosity of the polymer plasticizer discharged from the nozzle of the print head, it may be advantageous if the nozzle temperature of the print head is set, at least during the deposition of the plasticized polymer having shape memory properties and / or having thermoresponsive properties, to a temperature which is at least about 25° C., in particular at least about 32.5° C., preferably at least about 40° C., higher than the melting temperature of the polymer. On the other hand, for the reasons mentioned at the beginning and also to avoid thermal impairment of the polymer plasticizer, the die temperature should not be chosen to be too high, in order in particular to avoid thermal and / or oxidative damage to the polymer.The invention also provides the possibility that at least one additive is added to the polymer having shape memory properties and / or having thermoresponsive properties, it being possible for the additive to comprise, in particular, dyes, pigments and / or fillers, but it being possible, of course, for any other additives, such as lubricants, plasticizers, antioxidants, UV stabilizers, matting agents, reinforcing materials, flame retardants, antistatics, hydrolysis stabilizers, impact modifiers, etc., to be added (cf. also the above explanations in respect of advantageous additives). The use of dyes and / or pigments can serve, for example, in addition to a mere coloring, for better identification or machine-readability of complex structures produced in the form of codes, letters, numbers or the like (see further below in this regard). In addition to a saving in polymer known as such, the use of fillers can be used, for example, in particular to impart certain desired properties to the produced polymer molded part, such as electroactive properties and / or the possibility of resistance heating, wherein such fillers can comprise, in particular, electrically conductive materials, such as graphite, carbon nanotubes (CNTs) or other carbon modifications, metals and metal compounds including their alloys and oxides or the like. As will be explained in more detail further below, this, in conjunction with a produced polymer molding made of polymers having shape memory properties and / or having thermoresponsive properties, opens up the possibility that the molding is heated inductively or convectively to its switching temperature in order to specifically trigger the previously programmed shape change process.In addition, according to an advantageous development of the method according to the invention, it can be provided that for generating the complex structureat least two different thermoplastic polymers having shape memory properties and / or having thermoresponsive properties; and / orat least two thermoplastic polymers having shape memory properties and / or having thermoresponsive properties, at least one of which has been admixed with at least one additive; and / orat least two thermoplastic polymers with shape memory properties and / or with thermoresponsive properties, to which various additives have been addedThese may be used. In this way, it is possible, for example, to produce shaped parts with different properties of the polymers used in each case, or it is possible in particular to produce shaped parts with different colors of the complex structure or else of the same color of the complex structure, but a differently colored and consequently contrasting background, or it is possible to produce shaped parts which, owing to additives present only in regions, can be heated inductively or convectively in regions there in order to trigger a regional shape transition as a result of heating at least up to the region of the switching temperature of the polymer having shape memory properties and / or having thermoresponsive properties. From the technical device point of view, it is possible in this case, for example, to use a print head of a 3D printer having two nozzles or to use two separate print heads each having one nozzle in order to apply the different polymers and / or the polymers with different additives while moving the print head in the speed ranges according to the invention and in the process to build up the at least the complex structure of the molded part in layers.As already indicated, the method according to the invention is suitable, although not necessarily, in particular for producing complex structures from the group of the, in particular machine-readable, codes, such as QR codes, Acetag codes, Data Matrix codes, bar codes and the like, letters, such as Arabic, Kyrillic, Greek characters etc., including characters of the blind texts and / or of the morse alphabet, numbers, symbols and pictograms, which can each be produced three-dimensionally in very high sharpness.A polymer molding according to the invention can have, for example, at least one very fine complex structure, which can have, for example, a height or thickness of at most about 300 μm, for example of at most about 200 μm or else of at most about 150 μm.In addition, a polymer molding of the invention can be used.at least one additive in at least one portion of the complex structure, the additive comprising, in particular, dyes, pigments and / or fillers; and / orat least two different thermoplastic polymers having shape memory properties and / or having thermoresponsive properties.Furthermore, in the case of a polymer molding according to the invention, it may be advantageous if it has at least one complex structure from the group of, in particular machine-readable, codes, such as QR codes, Acetag codes, Data Matrix codes, bar codes and the like, letters, such as arabic, kyrillic, greek characters, etc., including characters of the blind texts and morse characters, numbers, symbols and pictograms.Thus, according to an advantageous embodiment of a polymer molded part according to the invention, it can be provided, for example, that it is an information carrier provided with at least one complex structure in the form of a / one, in particular machine-readable, code, letter, number, symbol and / or pictogram, wherein the information carrier can in turn be produced by means of the melt layer method or else be prefabricated by means of any other known thermoplastic processing method. Furthermore, the information carrier can have, for example, a more or less film-shaped configuration, in order to be able to apply it, for example, in a simple manner to any desired product which is to be marked with the complex structure, or the information carrier can be configured in the manner of any desired three-dimensional shaped part.Alternatively, according to an advantageous embodiment of a polymer molded part according to the invention, it can be provided, for example, that it is a key provided with at least one / one, in particular machine-readable, code, letter, number, symbol and / or pictogram, such as an actuation key provided for electrical and / or electronic devices including keyboards.Furthermore, in the case of a polymer molding according to the invention, it can preferably be provided for the reasons mentioned above that it further has a heating device which is suitable for heating the thermoplastic polymer having shape memory properties and / or having thermoresponsive properties at least to its switching temperature.Further features and advantages of the invention are evident from the following description of two exemplary embodiments with reference to the drawings. The following are shown: FIG. 1 is a schematic perspective view of a QR code as it was generated for the production of an information carrier provided with it by means of melt layers as a CAD model by means of the commercially available slicer program "Cura™"; FIG. 2 shows a schematic view of the QR code produced by melt layers using shape memory polymers on a film-shaped information carrier; FIG. 3 shows a schematic view of the deformed and thus not (more) machine-readable QR code according to FIG. 2 after programming the shape memory polymer; FIG. 4 shows a schematic view of the reset and thus (again) machine-readable QR code according to FIG. 3 after heating the shape memory polymer to a temperature in the range of its switching temperature; FIG. 5 shows various states of the information carrier provided with the QR code according to FIGS. 2 to 4 before and after its deformation on the occasion of programming the shape memory polymer and during its return on the occasion of heating the shape memory polymer to its switching temperature; FIG. 6 is a schematic perspective view of shaped parts made from shape memory polymers produced by means of the melt-coating process, in the form of pushbuttons provided for a computer keyboard, each with a letter applied in the font "Arial" with font size 10; FIG. 7 shows various states of the key with the letter according to FIG. 6 before and after its deformation on the occasion of programming the shape memory polymer and during its return on the occasion of heating the shape memory polymer to its switching temperature; and FIG. 8 shows a schematic enlarged view of a letter applied to a carrier substrate by means of the melt-coating method in the type type "Arial" with type size 4 made of shape memory polymers.Embodiment 1: Production of a film-shaped information carrier provided with a complex structure in the form of a QR code from shape memory polymers.First, the QR code to be generated is generated by means of a generator of an Internet site in such a manner. The QR code can then be processed in a manner which is likewise known per se by means of an AutoCAD program in order to generate an.stl file with the three-dimensional model of the QR code reproduced in FIG. 1. This three-dimensional model can then be processed by means of a slicer program-in this case: "Cura™"-in order to split it into a plurality of individual layers which are to be produced by means of the melt layer method. The set parameters for the slicing process and for the melt lamination by means of a 3D printer are summarized in the following table:Layer height of the complex structure of the QR code including the film-shaped information carrier0,39 mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mmFill density100%Nozzle Temperature232°CNozzle Diameter400 μmPressurized Bed Temperature23° CPrinting Speed of Sheet-Shaped Information Carrier50 mm / sPrinting Speed of Protrusions of QR Code7 mm / sSpeed of Movement of Print Head After or Between Deposition of Polymeric Plastic360 mm / sFilling PatternCubes CubesStandby Temperature100° CMaterial Flow107%Filament Diameters of Raw Polymers2,80 - 2.95 mmTo produce the polymer molding in the form of the QR code applied to an essentially film-shaped information carrier referred to below as a "carrier film", two filaments each made of a thermoplastic polyesterurethane with shape memory properties ("Desmopan™ DP2795 A SMP") with a switching temperature of about 55° C. and a shape fixing temperature of about -15° C. are used as raw polymers, which differ with regard to their coloring for better contrasting the QR code. For this purpose, one of the filaments consists of the same polyester urethane as the other filament, but contains the commercially available dye "Irgazin™ Red DPP BO". On occasion of the melt coating, the non-colored polymer filament is first plasticized by means of the 3D printer to produce the carrier film and deposited and solidified in layers with a layer thickness of a total of 200 μm by means of the print head moved at a speed of approximately 50 mm / s. The dyed polymer filament is then plasticized in a corresponding manner and the QR code is deposited layer by layer on the previously produced carrier film with a layer thickness of in total about 190 μm by means of the print head which is moved at a speed of about 7 mm / s during the deposition of the polymer, wherein the print head of the 3D printer is moved further at a speed of about 360 mm / s immediately after the depositing of the dyed shape memory polymer which in each case forms part of the QR code, which speed is thus about 50 times the speed of the print head during the deposition of this plasticized shape memory polymer. The substantially film-shaped polymer molding in the form of an information carrier provided with the QR code obtained in this way can be seen from FIG. 2, wherein it has been produced in the above manner by means of melt layers within a total time of about 11 min 30 s. In the present exemplary embodiment, the dimensions of the QR code contrasting with the film-shaped carrier are, for example, approximately 25 mm x 25 mm at a height or thickness of approximately 190 μm, while the carrier film serving as substrate has, for example, a volume (length x width x height or thickness) of approximately 40 mm x 30 mm x 200 μm. In the square matrix-like grid of the QR code, the size of each square grid is about 1.5 mm x 1.5 mm.As can be seen from FIG. 3, the polymer with shape memory properties used can now, if desired, be programmed by at least partially deforming - in this case: stretching - the shaped part provided with the complex structure in the form of the QR code at a temperature which corresponds at least to the switching temperature of the polymer with shape memory properties used, so that the QR code is no longer machine-readable, after which the deformed QR code is cooled at least to the shape fixing temperature of the shape memory polymer in order to "freeze" the deformation. If the deformed complex structure is then heated again at least to the switching temperature of the polymer having shape memory properties used, the complex structure deforms back into its original state (cf. FIG. 4 ), whereby properties serving, for example, for anti-forgery purposes can be imparted to the molded part if such an information carrier is applied to a product to be marked.Finally, FIG. 5 shows different degrees of deformation of the polymer molding before and after the programming of the shape memory polymer and during its return to the original shape, wherein the image on the left in FIG. 5 shows the original or permanent shape directly after the above-described printing process, while the second image from the left shows the deformed shape after the likewise above-described programming of the shape memory polymer after the shape fixing thereof. In the following four images (third image from the left to second image from the right), different stages of the recovery can be seen on occasion of the repeated heating of the shape memory polymer to its switching temperature. The right-hand image in FIG. 5 finally shows the fully restored shape of the shape memory polymer, it being evident that this corresponds virtually identically to the original state (left-hand image in FIG. 5 ).Embodiment 2: Production of a key provided with a complex structure in the form of a letter from shape memory polymers.First, the desired shape of the molded part to be produced is generated in the form of a pushbutton by means of an AutoCAD program in a manner known as such and an.stl file is generated therefrom. The shape of the letter to be applied to the key can be imported into the AutoCAD program in the desired font size-here: Arial 10-for example, and can also be exported into an.stl file. Both.stl files of the key on the one hand and of the letter on the other hand are then combined and a G code (according to the standard DIN 66025 / ISO 6983) is generated therefrom. The G-code is further processed by means of a G-code editor (e.g. "Repeat Host™") in order to be able to carry out the layer-by-layer deposition of the plasticized polymer on the occasion of the melt layer in the predetermined sequence. The set parameters of the melt layering by means of a 3D printer are tabulated below:Layer Height of the Complex Structure of the Book-Stable1,71 mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mm mmFill density of the key ("substrate")50%Fill Density of the Letter ("Structure")100%Nozzle Temperature for Key ("Substrate")238°CNozzle Temperature for Letters ("Structure")226° CNozzle Diameter400 μmPressurized Bed Temperature23° CPrint Speed for Key50 mm / sPrinting Speed for Letter Regions7 mm / sSpeed of Movement of Print Head After or Between Deposition of Polymeric Plastic360 mm / sStandby Temperature100° CMaterial Flow107%Filament Diameters of Raw Polymers2,80 - 2.95 mmTo produce the polymer molding in the form of the key provided with a letter, two filaments each made of a thermoplastic polyesterurethane having shape memory properties ("Desmopan™ DP2795 A SMP") are again used as raw polymers, which differ with regard to their coloring for better contrasting the letter. For this purpose, one of the filaments consists of the same polyester urethane as the other filament, but contains the commercially available dye "Irgazin™ Red DPP BO", while the other filament instead contains graphite black powder (fine). On occasion of the melt coating, the red-colored polymer filament is first plasticized by means of the 3D printer to produce the key as such and is deposited and solidified in layers with a layer thickness of a total of 6.26 mm by means of the print head moved at a speed of approximately 50 mm / s. The black-colored polymer filament is then plasticized in a corresponding manner and the letter of the type 10 is deposited in layers on the previously produced key with a layer thickness of in total about 1.71 mm by means of the print head which is moved at a speed of about 7 mm / s during the deposition of the polymer, the print head of the 3D printer being moved further immediately after the deposition of the black-colored shape memory polymer which in each case forms part of the letter at a speed of about 360 mm / s, which is therefore about 50 times the speed of the print head during the deposition of this plasticized shape memory polymer. The polymer molding obtained in this way in the form of a push button provided with the letter--here on the one hand "A" and on the other hand "B"--can be seen from FIG. 6, it having been produced in the above manner by means of melt layers within a total time of about 45 min.As can be seen from FIG. 7, which shows different degrees of deformation of the polymer molded part during the programming of the shape memory polymer and during its return to the original shape, the polymer with shape memory properties used can now, if desired, be programmed again by at least partially deforming - in this case: compressing - the molded part provided with the complex structure in the form of the letter at a temperature of in the present case about 60° C., which corresponds at least to the switching temperature of the polymer with shape memory properties used, which switching temperature in the present case is about 55° C., with a compressive force of, for example, about 250 N, such that the letter no longer projects three-dimensionally from the surface of the key, for example, but is aligned, for example, approximately flush with the key surface, after which the deformed letter is cooled at least to the shape fixing temperature of the shape memory polymer, which switching temperature in the present case is about 15° C., The deformation is therefore "frozen in", the deformation being retained as long as the deformed letter is not heated again up to the range of the switching temperature of the shape memory polymer used. If the deformed complex structure is then heated again at least to the switching temperature of the polymer with shape memory properties used, the structure deforms back into its original state, whereby haptic properties can be imparted to the molded part, for example, as required.The two images on the left in FIG. 5 each show the original or permanent shape directly after the above-described printing process (on the one hand the key provided with the letter "A" and on the other hand the key provided with the letter "B" according to FIG. 6 ), while the third image from the left shows the deformed shape of the key provided with the letter "A" after the likewise above-described programming of the shape memory polymer after shape fixing thereof, it being evident that the elevated complex structure of the letter is aligned practically flush with the key surface. In the following four images (fourth image from the left to second image from the right), different stages of the recovery can be seen on occasion of the repeated heating of the shape memory polymer to its switching temperature. The right-hand image in FIG. 7 finally shows the fully reset shape of the shape memory polymer of the key provided with the letter "A", it being evident that this corresponds virtually identically to the original state (left-hand image in FIG. 7 ).Embodiment 3: Production of a complex structure in the form of a letter from shape memory polymers on a substrate, for example approximately in the form of a film.First, according to the above embodiment 2, the complex structure in the form of the letter to be applied to the substrate, which may be prefabricated or may likewise be produced by means of fusible layers, for example, in the manner described in the above embodiment 1, is imported from a conventional word processor in the desired font size-here: Arial 4-into an AutoCAD program, post-processed and exported into an.stl file. A G code (according to the standard DIN 66025 / ISO 6983) is then generated from the.stl file of the letter. The G-code is further processed by means of a G-code editor (e.g. "Repeat Host™") in order to be able to carry out the layer-by-layer deposition of the plasticized polymer on the occasion of the melt layer. The set parameters of the melt layering by means of a 3D printer are tabulated below:Layer height of the complex structure of the letter100 μmNozzle Temperature for Letters ("Structure")234 °CNozzle Diameter100 μmPressurized Bed Temperature23° CPrinting Speed for Letter Regions5 mm / sMoving Speed of Print Head400 mm / safter or between the deposition of polymer plasticificatesStandby Temperature100° CMaterial Flow107%Filament Diameters of Raw Polymers2,80 - 2.95 mmTo produce the complex structure of the letter, the raw polymers used are again a filament of a thermoplastic polyesterurethane having shape memory properties ("Desmopan™ DP2795 A SMP"). At the time of the melt coating, the polymer filament is plasticized and the letter of type 4 is applied in layers onto the substrate, for example in the form of a film, by means of the print head which is moved during the deposition of the polymer at a speed of about 5 mm / s and the nozzle of which has a diameter of only 100 μm in the present case, the print head of the 3D printer being moved further, immediately after the deposition of the shape memory polymer forming in each case part of the letter, at a speed of about 400 mm / s which is thus about 80 times the speed of the print head during the deposition of the plasticized shape memory polymer. The polymer molding obtained in this way in the form of a substrate provided with the letter--here "A"--can be seen from FIG. 8, it being evident that the complex structure has a very low "line thickness", i.e. a very low thickness of the webs forming the letter, of less than 400 μm, so that consequently the production of complex structures from thermoplastic polymers having shape memory properties and / or having thermoresponsive properties is possible with very high resolution or sharpness by means of melt layers.

Claims

Method for producing complex structures from at least one thermoplastic polymer, in that the polymer is plasticized and deposited layer by layer by means of melt layers by means of at least one nozzle of a printing head of a 3D printer which can be moved in a controlled manner to form the complex structure, after which the layers of the polymer produced in this way are solidified, characterized in that at least one thermoplastic polymer having shape memory properties and / or having thermoresponsive properties is used to produce the complex structure, and in that the printing head of the 3D printer is moved at a speed of at most 20 mm / s during the deposition of the plasticized polymer having shape memory properties and / or having thermoresponsive properties, and in that the print head of the 3D printer is moved further at least immediately after the deposition of the polymer having shape memory properties and / or having thermoresponsive properties, which polymer forms part of the complex structure, at a speed which is at least 10 times the speed of the print head during the deposition of the plasticized polymer, wherein after the production of the complex structure by means of the 3D printer the at least one polymer having shape memory properties and / or having thermoresponsive properties is programmed in that the complex structure is at least partially deformed - at a temperature which corresponds at least to the switching temperature of the at least one polymer having shape memory properties and / or having thermoresponsive properties, after which the deformed complex structure is cooled at least to the shape fixing temperature of the at least one polymer having shape memory properties and / or having thermoresponsive properties; or cold forming at ambient temperature.Method according to claim 1, characterized in that the print head of the 3D printer is moved during the deposition of the plasticized polymer with shape memory properties and / or with thermoresponsive properties at a speed of at most 15 mm / s, in particular of at most 12 mm / s, preferably of at most 10 mm / s.Method according to claim 1 or 2, characterised in that the print head of the 3D printer is moved further at a speed which is at least 200 mm / s, in particular at least 250 mm / s, preferably at least 300 mm / s, at least immediately after deposition of the polymer forming part of the complex structure having shape memory properties and / or having thermoresponsive properties.Method according to any one of claims 1 to 3, characterised in that the nozzle temperature of the print head is set, at least during the deposition of the plasticized polymer with shape memory properties and / or with thermoresponsive properties, to a temperature which is at least 25°C, in particular at least 32.5°C, preferably at least 40°C, higher than the melting temperature of the polymer with shape memory properties and / or with thermoresponsive properties.Method according to one of Claims 1 to 4, characterized in that at least one additive is added to the polymer having shape memory properties and / or having thermoresponsive properties, the additive comprising, in particular, dyes, pigments and / or fillers.Method according to one of Claims 1 to 5, characterized in that, in order to produce the complex structure, - at least two different thermoplastic polymers having shape memory properties and / or having thermoresponsive properties; and / or - at least two thermoplastic polymers having shape memory properties and / or having thermoresponsive properties, of which at least one has been added with at least one additive; and / or - at least two thermoplastic polymers, added with different additives, having shape memory properties and / or having thermoresponsive properties are used.Use of a method according to one of Claims 1 to 6 for producing complex structures from the group of, in particular machine-readable, codes, letters, numbers, symbols and pictograms.Polymer moulding made of at least one thermoplastic polymer with shape memory properties and / or with thermoresponsive properties with at least one complex structure produced by a method according to one of Claims 1 to 7.Polymer moulding according to Claim 8, characterized in that - it contains at least one additive at least in at least one section of the complex structure, the additive in particular comprising dyes, pigments and / or fillers; and / or - it contains at least two different thermoplastic polymers having shape memory properties and / or having thermoresponsive properties.Polymer moulding according to Claim 8 or 9, characterized in that it has at least one complex structure from the group of the codes, letters, numbers, symbols and pictograms, in particular machine-readable codes, letters, numbers, symbols and pictograms.The polymer molding according to any one of claims 8 to 10, characterized in that it is an information carrier provided with at least one / one, in particular machine-readable, code, letter, number, symbol and / or pictogram.Polymer moulding according to one of Claims 8 to 10, characterized in that it is a key provided with at least one / one, in particular machine-readable, code, letter, number, symbol and / or pictogram.Polymer moulding according to one of Claims 8 to 12, characterized in that it has a heating device which is suitable for heating the thermoplastic polymer having shape memory properties and / or having thermoresponsive properties at least to its switching temperature.

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