Polymer compositions for 3D printing and methods of use thereof

Abstract

The present invention relates to a polymer composition in the form of filaments or pellets comprising: (a) from 80% to 97% of at least one PA-6 polyamide; (b) from 3% to 20% of at least one PA-6, 9 / 6 copolymer; the percentages are referred to the total weight of components (a) and (b). The invention also relates to a method for manufacturing a three-dimensional product by a 3D printing process using the above composition.

Description

Technical Field

[0001] The present invention relates to polymer compositions for 3D printing and methods of using the same. In particular, the present invention relates to polymer compositions for 3D printing comprising mixtures of polyamide polymers and their use for manufacturing three-dimensional articles by an extrusion-based 3D printing system. Background Art

[0002] Additive manufacturing (AM) is a technique by which three-dimensional articles are manufactured starting from a digital representation of the article (e.g., CAD / CAM file) by depositing thin layers of material on top of each other.

[0003] One of the most common AM techniques is extrusion-based 3D printing (hereinafter only referred to as "3D printing"). In extrusion-based 3D printing, a filament of a solid thermoplastic material is supplied to a heated nozzle and is thus extruded in a fluid (semi-liquid) form. The extruded material is deposited in the form of thin layers (e.g., 0.03 mm to 0.2 mm) along a predetermined path on the plane x-y of a build substrate, where it cools and solidifies. Then, by moving the build substrate or the nozzle along the z-axis perpendicular to the plane x-y of the build substrate, additional material is extruded onto the previously deposited material, which adheres to the previously deposited material by solidification. Then, additional layers of the extruded material are deposited on top of each other until the final article is completed. This additive manufacturing technique is also known as Fused Deposition Modelling (FDM) or Fused Filament Fabrication (FFF).

[0004] Typically, for manufacturing relatively small-sized products, in the FFF technique, the thermoplastic material is supplied in the form of a filament to a desktop printer. However, the FDM technique can also be used for manufacturing larger-scale articles using a printing device in which the fluid thermoplastic material is deposited via an extruder (to which the thermoplastic material is supplied in the form of pellets).

[0005] The FDM technique has different advantages, such as: a wide variety of available thermoplastic materials, good mechanical properties of the final article, low manufacturing costs, low equipment costs, flexibility in designing products, the possibility of manufacturing articles with complex geometries and being easily customizable. In addition, compared to subtractive manufacturing (SM) in which the final article or parts thereof are obtained from a block of raw material by operations such as cutting, drilling, peeling, etc., the FDM technique has a significantly reduced environmental impact.

[0006] In addition to the manufacturing flexibility and speed, the above advantages have enabled additive manufacturing technologies (especially via FDM) to be applied in several industrial fields, such as prototyping, aerospace, automotive, biomedical, packaging, and jewelry.

[0007] Different thermoplastic materials available for 3D printing with different mechanical properties and technical characteristics are commercially available and known in the prior art. The most commonly used thermoplastic polymers in the form of filaments in FDM technology for hobby applications are polylactic acid (PLA) and acrylonitrile-butadiene-styrene copolymer (ABS). Polyamides, known for their mechanical properties, are more commonly used in industrial applications. In particular, the most common polyamides on the market are PA-11 and PA-12. Among polyamides, PA-6 (polycaprolactam) is considered a very promising polyamide due to its mechanical properties and high recycling potential. In fact, through chemical recycling techniques (e.g., hydrolysis depolymerization), PA-6 can be converted into its starting ε-caprolactam monomer with the same quality as the original monomer and thus can be reused for any type of application.

[0008] However, PA-6 is a thermoplastic polymer with different drawbacks during the 3D printing process. The primary problem with this polyamide is related to its high water absorption capacity in a short time, reaching saturation within minutes if exposed to favorable environmental humidity conditions. The second problem involves the dimensional shrinkage of the polymer. Dimensional shrinkage occurs after extrusion printing due to the presence of residual stresses and the change in the density of the polymer when the temperature changes. In fact, in 3D printing, as the printing process progresses, the temperature of the polymer deposited on the build substrate decreases. Additionally, if the product is large-sized, the printing time may last for many hours. These inherent characteristics of PA6 cause many problems and limitations for products manufactured through the 3D printing process. The most obvious drawbacks are:

[0009] 1. "Warping": It consists of the deformation of the printed product, which may cause it to detach from the build substrate during printing;

[0010] 2. Delamination: A phenomenon that occurs when the adhesion between the deposited polymer layers is not optimal. The layers constituting the product separate, resulting in structural failure of the product;

[0011] 3. Formation of bubbles: A phenomenon that occurs when the PA-6 supplied to the extruder is not dry enough (e.g., the filaments are not stored under humidity-controlled conditions); the water absorbed by the polymer evaporates at high extrusion temperatures (180 °C to 230 °C), leaving gaps in the printed product.

[0012] To address these issues, it is known in the prior art to vary the composition of PA-6 in different ways. For example, adding carbon fibers and glass fibers to the polyamide matrix of the filaments to impart dimensional stability to the printed polymer is known. The fibers also improve the mechanical properties and quality of the printed material.

[0013] Farina et al., “High-Performance Nylon-6 Sustainable Filaments for Additive Manufacturing”, (2019), Materials 12, no. 23: 3955 describes alternative filaments for 3D printing based on PA-6 modified by adding ABS and TiO 2 to improve the printability of the material.

[0014] Jia et al., “Preparation of a new filament based on polyamide-6 for three-dimensional printing”, (2017), Polymer Engineering & Science, 57: 1322-1328 solved the problems of dimensional shrinkage and deformation by adding maleic anhydride-grafted poly(ethylene 1-octene) and possibly polystyrene to the PA-6 matrix to control the crystallization of the polymer.

[0015] To obtain printed products with higher quality than using PA-6 as such, the use of polyamide copolymers such as PA-6 / 6,6 copolymers (e.g., the filament Adline sold by the Radici Group) is also known in the art.

[0016] US2014 / 0141166 A1 describes a thermoplastic material for 3D printing formed from a polyamide mixture (e.g., a PA-6 / 3T mixture) that includes at least one semi-crystalline polyamide and an amorphous polyamide that is substantially miscible with the semi-crystalline polyamide. These mixtures have the advantage of allowing more effective annealing of the printed product to reduce the accumulation of mechanical stress and the resulting dimensional deformation.

[0017] Another commercially available product suitable for 3D printing is the polyamide filament LUVOCOM 3F Filament PAHT (Levhoss). This filament (in the version without added fiber material) has a higher print quality than PA-6 as such.

[0018] However, although the solutions described in the prior art allow obtaining 3D printed products with acceptable quality, they have the drawback of complicating the recycling of polyamide at the end of the life cycle of the printed articles. In fact, the presence of non-negligible amounts of additional fibrous materials such as glass fibers and carbon fibers, as well as polymers other than PA-6, makes the chemical recycling process based on the depolymerization of PA-6 not very efficient or even impossible. Summary of the Invention

[0019] In view of the above prior art, the Applicant has solved the problem of providing a PA-6-based thermoplastic polymer composition for 3D printing that overcomes the drawbacks of the known art.

[0020] In particular, an object of the present invention is to provide a PA-6-based polymer composition for 3D printing and a method of using the same, which method allows manufacturing printed products having a quality equivalent to or higher than that of polyamide-based polymer compositions of the known art.

[0021] Another object of the present invention is to provide a PA-6-based polymer composition for 3D printing and a method of using the same, from which the printed product PA-6 can be easily recycled by known chemical recycling processes.

[0022] Now, unexpectedly, it has been found that the above and other objects, which will be better illustrated in the following description, can be achieved by a polymer composition comprising at least one PA-6 polyamide and at least one PA-6,9 / 6 copolymer. In fact, it has been observed that adding an appropriate amount of the PA-6,9 / 6 copolymer to PA-6 to form a polymer matrix on the basis of the composition allows obtaining a thermoplastic material that can be used in the 3D printing process to obtain products with high printing quality.

[0023] In particular, 3D printed products can be obtained by using different types of printers with the polymer composition according to the present invention, which are characterized by the uniformity of deposition of the molten material, good adhesion between the deposited layers, dimensional accuracy, the possibility of printing without supports, and the substantially absence of dimensional shrinkage and deformation (warpage).

[0024] It has also been observed that, advantageously, crosslinking of the polymer chains of PA-6 and the PA-6,9 / 6 copolymer, which can be obtained by adding a crosslinking agent to the polymer composition, allows effectively controlling the occurrence of deformation phenomena in the printed products.

[0025] The polymer composition according to the invention consists essentially of PA-6 polyamide, and the components other than PA-6 (PA-6,9 / 6 copolymer and additives) are present in relatively low amounts, for example in amounts of less than 20% by weight, preferably as low as 5% to 10% by weight of the polymer composition. The high PA-6 content enables the polymer composition and the products made therefrom to be easily recycled by chemical recycling processes (such as hydrolysis depolymerization processes), which allows the recovery of ε-caprolactam monomers with high performance and quality of the recycled monomers.

[0026] Thus, according to a first aspect, the present invention relates to a method for manufacturing a three-dimensional product by an extrusion-based 3D printing process, which comprises:

[0027] - melting the polymer composition to obtain a molten polymer composition, the polymer composition comprising:

[0028] (a) 80% to 97% of at least one PA-6 polyamide,

[0029] (b) 3% to 20% of at least one PA-6,9 / 6 copolymer,

[0030] the percentages being with reference to the total weight of components (a) and (b);

[0031] - printing the molten polymer composition through an extrusion-based 3D printing system to form the three-dimensional product.

[0032] According to a second aspect, the present invention relates to a polymer composition in the form of filaments or pellets, comprising:

[0033] (a) 80% to 98% of at least one PA-6 polyamide;

[0034] (b) 2% to 20% of at least one PA-6,9 / 6 copolymer,

[0035] the percentages being with reference to the total weight of components (a) and (b).

[0036] According to a third aspect, the present invention relates to the use of the polymer composition according to the second aspect for manufacturing a three-dimensional article by an extrusion-based 3D printing system. Detailed Description

[0037] As described, the polymer composition according to the invention comprises at least: (a) a PA-6 polyamide and (b) at least one PA-6,9 / 6 copolymer. With respect to the total weight of components (a) and (b), the PA-6 polyamide is present in the polymer composition in an amount in the range of 80% to 98% by weight, preferably in the range of 85% to 97% by weight, more preferably in the range of 90% to 97% by weight.

[0038] PA-6 polyamide can be prepared by polymerizing ε-caprolactam according to methods well-known to those skilled in the art. Advantageously, PA-6 can contain ε-caprolactam derived from recycled materials containing PA-6, or can be formed solely from ε-caprolactam derived from recycled materials containing PA-6. ε-Caprolactam (the raw material of PA-6) can be virgin or recycled by chemical recycling. And PA-6 can be virgin or from mechanical recycling.

[0039] Generally, any PA-6 polyamide of the types known in the art can be used for the purposes of the present invention. Preferably, the melting temperature of PA-6 is in the range of 215 °C to 225 °C. Preferably, PA-6 has one or more of the following characteristics:

[0040] - The value of RV (Relative Viscosity - ASTM D789-19) is in the range of 2.2 to 3.3, preferably in the range of 2.4 to 2.7;

[0041] - The value of the color coordinate b* (CIELAB) is in the range of -4 to +5, preferably -2 to +2;

[0042] - The humidity is equal to or lower than 0.5%, preferably equal to or lower than 0.1%.

[0043] Relative to the total weight of components (a) and (b), the PA-6,9 / 6 copolymer is present in the polymer composition in an amount in the range of 2% by weight to 20% by weight, preferably in the range of 3% by weight to 15% by weight, more preferably in the range of 3% by weight to 10% by weight.

[0044] The PA-6,9 / 6 copolymer is a random copolymer of the formula (I) having the following representation, which contains PA-6,9 repeating units and PA-6 repeating units.

[0045]

[0046] Wherein:

[0047] - x is the number of PA-6 repeating units, and 1 - x is the number of PA-6,9 repeating units, and x is a number greater than 0 and less than 1.

[0048] - n (related to the length of the copolymer chain) is a number in the range of 40 to 75, preferably in the range of 50 to 65.

[0049] The PA-6,9 / 6 copolymer can be prepared by synthetic methods known to those skilled in the art, for example, from monomers such as hexamethylenediamine, ε-caprolactam, and azelaic acid. A method for preparing the PA-6,9 / 6 copolymer that can be used for the purposes of the present invention is described in Bertolla, M. et al., “Comparison of the Properties of a Random Copolymer and a Molten Blend PA6 / PA6.9”, Polymers 2022, 14, 4115( https: / / doi.org / 10.3390 / polym14194115 ).

[0050] Preferably, the PA-6,9 / 6 copolymer contains PA-6,9 units and PA-6 units in a weight ratio of PA-6,9:PA-6 in the range of 5:95 to 95:5, more preferably 10:90 to 90:10, and even more preferably 15:85 to 85:15.

[0051] In one embodiment, the polymer composition according to the present invention comprises:

[0052] (a) 90% to 97% of at least one PA-6 polyamide;

[0053] (b) 3% to 10% of at least one PA-6,9 / 6 copolymer;

[0054] wherein the weight ratio of PA-6,9:PA-6 in the PA-6,9 / 6 copolymer is in the range of 5:95 to 95:5, preferably 10:90 to 90:10.

[0055] Preferably, the melting temperature of the PA-6,9 / 6 copolymer is in the range of 215 °C to 220 °C.

[0056] Preferably, the PA-6,9 / 6 copolymer has one or more of the following characteristics:

[0057] - The value of RV (relative viscosity - ASTM D789-19) is in the range of 2.4 to 3.3, preferably in the range of 2.6 to 3.0;

[0058] - The glass transition temperature (Tg) is in the range of 25 °C to 45 °C, as a function of the composition of the monomers used in the steps of manufacturing the copolyamide;

[0059] - The humidity is equal to or lower than 0.5%, preferably equal to or lower than 0.1%.

[0060] In one embodiment, the polymer composition comprises at least one crosslinking agent for chemically bonding the polymer chains of PA-6 to the polymer chains of PA-6,9-6 copolyamide to each other. For this purpose, crosslinking agents of known types in the art can be used to crosslink the polymers obtained by polycondensation.

[0061] Particularly preferred crosslinking agents are (meth)acrylic oligomers or styrene-(meth)acrylic oligomers functionalized with epoxy groups. These compounds (also known as chain extenders) react with the terminal functional groups of the polyamide polymer chains of the polymer composition, coupling them to each other. Preferably, the epoxy equivalent weight (EEW) of the crosslinking agent is in the range of 180 g / mol to 2800 g / mol, more preferably 200 g / mol to 800 g / mol (EN ISO 3001). These crosslinking agents are described, for example, in WO 03 / 066704 and are commercially available, such as the product ADR4400 from BASF. ADR4400.

[0062] Preferably, at least one crosslinking agent (e.g., ADR4400) is present in the polymer composition in an amount in the range of 0.1% by weight to 5% by weight, preferably in the range of 0.5% by weight to 1.5% by weight, relative to the total weight of components (a) and (b).

[0063] The polymer composition may also contain additives of the types commonly used in preparing polymer compositions for 3D printing, such as colorants, compatibilizers, antioxidants, plasticizers, lubricants, flame retardants, impact modifiers, etc.

[0064] Although the use of filler materials (fillers), such as powders or fibers capable of improving mechanical, thermal, and electrical conductivity properties, is not excluded, their presence in the polymer composition is not necessary. In a preferred embodiment, the polymer composition does not contain added fillers, particularly glass fibers or carbon fibers are not added to the polymer composition.

[0065] For use in 3D printing methods, the polymer composition can be formulated in the form of pellets or filaments. Preferably, the pellets and filaments are prepared, for example, by extruding a mixture of the components of the polymer composition through a single-screw extruder or a twin-screw extruder.

[0066] The individual components of the polymer composition (i.e., PA-6, PA-6,9 / 6, and optionally additives such as crosslinking agents) can be supplied to the extruder after pre-mixing, or can be mixed with each other inside the extruder to form a homogeneous polymer composition.

[0067] Based on the type of 3D printing process and apparatus used, the polymer composition in the form of pellets can be used as such for printing three-dimensional products.

[0068] In a preferred embodiment, the polymer composition can be extruded in the form of filaments having a geometry (e.g., cylindrical or bar-shaped) and dimensions (e.g., 1 mm to 3 mm) suitable for an FDM printing process. The filaments can be obtained by directly extruding a mixture of the components of the polymer composition or by converting extruded pellets of the polymer composition.

[0069] In the case of an extrusion-based 3D printing process (FDM), the polymer compositions described herein are suitable for 3D printers of types known to those skilled in the art, even 3D printers with very variable dimensions.

[0070] In the following exemplary embodiments of the invention, other features and advantages of the invention will be apparent, which are provided for illustrative purposes only and are not intended to limit the scope of protection defined by the appended claims.

[0071] In the examples, reference will also be made to the appended Figure 1 , which reports illustrations of three-dimensional products printed with the materials described in the examples.

[0072] Example

[0073] 3D Printing Test

[0074] A set of thermoplastic polymer materials according to the invention and known in the prior art in the form of filaments is used to print three-dimensional products with a 3D printer Ultimaker 2+. The article to be printed is a so-called "All-in-One" product, the digital file (CAD file) of which is available on the website www.thingiverse.com . A selected article to be printed is often used in the field of extrusion-based 3D printing to test the print quality of materials. Illustrations of the product are reported in Figure 1 . The product consists of a plurality of parts, each of which allows the evaluation of different printing characteristics.

[0075] To objectively evaluate the printability (print quality) of the materials tested, the quality of each of the following parts of the product is visually evaluated, the numbering of which refers to Figure 1 : small protrusions (1), large protrusions (2), bridges (3), cones (4), smears (5), dimensional accuracy (6), warping (7).

[0076] The quality of the observed parts 1 to 7 is evaluated using the rating scale reported in Table 1.

[0077] Table 1

[0078]

[0079]

[0080] * Deformation (warpage): the height of the corners of the product relative to the x-y plane.

[0081] The printability (print quality) of the materials tested was evaluated by a total score obtained from the sum of the scores assigned to each of the printed parts 1 to 7.

[0082] Example 1 (Comparison)

[0083] By extruding pellets from a commercial product ECO27 manufactured by Aquafil SpA to obtain PA-6 filaments: the product is a PA-6 polyamide obtained from caprolactam monomers from chemical recycling (RV equal to 2.7, b* equal to -2.5, molecular weight of about 19,500).

[0084] The extrusion was carried out in a single-screw extruder 3Devo under the conditions reported in Table 2 (where T1 to T4 are the temperatures along the extruder from the inlet T1 to the die head T4).

[0085] Table 2

[0086]

[0087] The evaluation of the print quality of the products obtained with this filament is reported in Table 3.

[0088] Table 3 – Example 1: Filament in PA-6 (as received)

[0089]

[0090] Products in PA-6 (without any additives or copolymers) have different critical issues, in particular: the presence of gaps, the non-uniformity of the products, and the need to add support materials to print in the gaps, as well as significant warpage. Therefore, the data and total scores for each part reported are associated with thermoplastic materials not suitable for 3D printing.

[0091] Example 2 (Comparison)

[0092] In contrast, products were printed by using a commercial filament LUVOCOM 3F Filament PAHT (Levhoss) based on PA-6 (exact chemical composition unknown).

[0093] The evaluation of the printing quality of the products obtained with this filament is reported in Table 4.

[0094] Table 4 – Example 2: Commercial Filament LUVOCOM 3F Filament PAHT (Levhoss)

[0095]

[0096] The printing quality of this product is generally higher than that of Example 1. According to the scoring, some improvements related to the possibility of printing without using a support, the absence of warping, and the greater uniformity of the product are highlighted. However, the printed product has key problems related to low dimensional accuracy and the presence of trailing. In addition, after several months of printing, the product begins to show significant deformation, which may be caused by temperature changes in the product and / or by the humidity it absorbs over time. Therefore, the said filament is mainly suitable for printing large-sized products that do not require high detail accuracy.

[0097] Example 3 (Comparison)

[0098] For comparison, products are printed by using a commercial filament NYLFORCE3 based on PA-12 (exact chemical composition unknown).

[0099] The evaluation of the printing quality of the products obtained with this filament is reported in Table 5.

[0100] Table 5 – Example 3: Commercial Filament PA-12

[0101]

[0102] Filaments based on PA-12 are suitable for 3D printing. However, as is known, they cannot be recycled by a depolymerization process to retrieve the monomers that make them up.

[0103] Example 4 (Invention)

[0104] Filaments for 3D printing are prepared from pellets having the following composition:

[0105] - 94% by weight of PA-6,

[0106] - 6% by weight of PA-6,9 / 6 copolymer,

[0107] (Copolymer composition: 80% of PA-6,9 and 20% of PA-6).

[0108] Use the commercial product ECO27 of Aquafil SpA of Example 1 as the PA-6 polyamide.

[0109] The PA-6,9 / 6 copolymer prepared as described by Bertolla, M. et al. in Polymers 2022, 14, 4115 has the following characteristics: RV is equal to about 3.1, b* is equal to -2.5, and the molecular weight is about 24,000.

[0110] The extrusion of the filaments was carried out as described in Example 1. The pellets of the polymer composition for extruding the filaments were prepared by extrusion, i.e., PA-6 and PA-6,9 / 6 were supplied to a twin-screw extruder Twin Screw Extruder 20MM manufactured by LabTech Engineering under the conditions reported in Table 6 (where T1 to T10 are the temperatures along the extruder from the inlet T1 to the extrusion die head T10).

[0111] Table 6

[0112]

[0113] The evaluation of the printing quality of the products obtained with the filaments is reported in Table 7.

[0114] Table 7 - Example 4: Filament PA-6, 6% PA-6, 9 / 6 (80 / 20)

[0115]

[0116] Compared with the as-received PA-6 of Example 1, the filaments of Example 4 have improved printing quality and are comparable to the commercial product of Example 2.

[0117] Example 5 (Invention)

[0118] By the same procedure as in Example 4, filaments according to the present invention were prepared from pellets having the following composition:

[0119] - 93.2 wt% of PA-6,

[0120] - 0.8 wt% of a crosslinking agent, Joncryl ADR4400 from BASF (EEW equal to 485 g / mol),

[0121] - 6 wt% of a PA-6,9 / 6 copolymer,

[0122] (Copolymer composition: 80% of PA-6,9 and 20% of PA-6).

[0123] The pellets of the polymer composition and the filaments were prepared according to the procedure described in Example 4.

[0124] The evaluation of the printing quality of the products obtained with the filaments is reported in Table 8.

[0125] Table 8 - Example 5: Filament PA-6, 6% PA-6, 9 / 6 (80 / 20), 0.8% Crosslinking Agent

[0126]

[0127] With respect to the as-received PA-6 of Example 1, the filaments of Example 5 have improved printing quality and are comparable to the commercial product of Example 2. With respect to Example 4, it can be noted that the addition of a chain extender causes an improvement in the "deformation" test.

[0128] Example 6 (Invention)

[0129] By the same procedure as in Example 4, filaments according to the invention were prepared from pellets having the following composition:

[0130] - 96.2 wt% of PA-6,

[0131] - 0.8 wt% of crosslinking agent Joncryl ADR4400,

[0132] - 3 wt% of PA-6,9 / 6 copolymer,

[0133] (Copolymer composition: 80% of PA-6,9 and 20% of PA-6).

[0134] The evaluation of the printing quality of the products obtained with these filaments is reported in Table 9.

[0135] Table 9 - Example 6: Filament PA-6, 3% PA-6, 9 / 6 (80 / 20), 0.8% Crosslinking Agent

[0136]

[0137] Example 7 (Invention)

[0138] By the same procedure as in Example 4, filaments according to the invention were prepared from pellets having the following composition:

[0139] - 90.2 wt% of PA-6,

[0140] - 0.8 wt% of crosslinking agent Joncryl ADR4400,

[0141] - 9 wt% of PA-6,9 / 6 copolymer,

[0142] (Copolymer composition: 80% of PA-6,9 and 20% of PA-6).

[0143] The evaluation of the printing quality of the products obtained with these filaments is reported in Table 10.

[0144] Table 10 - Example 7: Filament PA-6, 9% PA-6, 9 / 6 (80 / 20), 0.8% Crosslinking Agent

[0145]

[0146] Example 8 (Invention)

[0147] By the same procedure as in Example 4, filaments according to the invention were prepared from pellets having the following composition:

[0148] - 93.2% by weight of PA-6,

[0149] - 0.8% by weight of the crosslinking agent Joncryl ADR4400,

[0150] - 6% by weight of a PA-6,9 / 6 copolymer,

[0151] (Copolymer composition: 20% of PA-6,9 and 80% of PA-6).

[0152] The evaluation of the printing quality of the products obtained with this filament is reported in Table 11.

[0153] Table 11 - Example 8: Filament PA-6, 6% PA-6, 9 / 6 (20 / 80), 0.8% Crosslinking Agent

[0154]

[0155] Example 9 (Invention)

[0156] By the same procedure as in Example 4, filaments according to the invention were prepared from pellets having the following composition:

[0157] - 93.2% by weight of PA-6,

[0158] - 0.8% by weight of the crosslinking agent Joncryl ADR4400,

[0159] - 6% by weight of a PA-6,9 / 6 copolymer,

[0160] (Copolymer composition: 40% of PA-6,9 and 60% of PA-6).

[0161] The evaluation of the printing quality of the products obtained with this filament is reported in Table 12.

[0162] Table 12 - Example 9: Filament PA-6, 6% PA-6, 9 / 6 (40 / 60), 0.8% Crosslinking Agent

[0163]

[0164] Examples 5 to 9 demonstrate the effectiveness of the polymer composition according to the present invention as a thermoplastic polymer material for extrusion 3D printing. The print quality of the thermoplastic material is comparable to or higher than that of the most used commercial products. By comparing Examples 8 and 9, it can be understood that in the case of the same amount of copolymer in the polymer composition, the ratio between PA-6,9 and PA-6 in the copolymer basically does not affect the printability of the thermoplastic material. Using a copolymer containing a lower amount of PA-6,9 polyamide facilitates the chemical recycling of ε-caprolactam monomer from the printed product at the end of its life.

Claims

1. A method for manufacturing a three-dimensional product by an extrusion-based 3D printing process, comprising: - melting a polymer composition to obtain a molten polymer composition, the polymer composition comprising: (a) 80% to 98% of at least one PA-6 polyamide, (b) 2% to 20% of at least one PA-6,9 / 6 copolymer, the percentages being with reference to the total weight of components (a) and (b); - printing the molten polymer composition through an extrusion-based 3D printing system to form the three-dimensional product.

2. The method according to claim 1, wherein the weight ratio of PA-6,9:PA-6 in the PA-6,9 / 6 copolymer is in the range of 5:95 to 95:5, preferably 10:90 to 90:10, more preferably 15:85 to 85:

15.

3. The method according to claim 1 or 2, wherein the polymer composition comprises: (a) 90% to 97% of at least one PA-6 polyamide; (b) 3% to 10% of at least one PA-6,9 / 6 copolymer; wherein the weight ratio of PA-6,9:PA-6 in the PA-6,9 / 6 copolymer is in the range of 5:95 to 95:5, preferably 10:90 to 90:

10.

4. The method according to any one of claims 1 to 3, wherein the polymer composition comprises at least one crosslinking agent, and the at least one crosslinking agent is preferably included in an amount in the range of 0.1% by weight to 5% by weight, preferably 0.5% by weight to 1.5% by weight, with reference to the total weight of components (a) and (b).

5. The method according to any one of claims 1 to 4, wherein the polymer composition is in the form of filaments or pellets.

6. The method according to any one of claims 1 to 5, wherein the printing step is carried out according to the fused deposition modeling (FDM) technique.

7. A polymer composition in the form of filaments or pellets, comprising: (a) 80% to 98% of at least one PA-6 polyamide; (b) 2% to 20% of at least one PA-6,9 / 6 copolymer; the percentages being with reference to the total weight of components (a) and (b).

8. The polymer composition according to claim 7, wherein the weight ratio of PA-6,9:PA-6 in the PA-6,9 / 6 copolymer is in the range of 5:95 to 95:5, preferably 10:90 to 90:10, more preferably 15:85 to 85:

15.

9. The polymer composition according to claim 7 or 8, comprising: a) 90% to 97% of at least one PA-6 polyamide, b) 3% to 10% of at least one PA-6,9 / 6 copolymer, the percentages being with reference to the total weight of components (a) and (b), wherein the weight ratio of PA-6,9:PA-6 in the PA-6,9 / 6 copolymer is in the range of 5:95 to 95:5, preferably 10:90 to 90:

10.

10. The polymer composition according to any one of claims 7 to 9, comprising at least one crosslinking agent, the at least one crosslinking agent preferably being comprised in an amount in the range of 0.1% by weight to 5% by weight, preferably in the range of 0.5% by weight to 1.5% by weight, relative to the total weight of components (a) and (b).

11. Use of the polymer composition according to any one of claims 7 to 10 for manufacturing a three-dimensional article by means of an extrusion-based 3D printing system.

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