Method for preparing a pla material loaded with end-of-life textile for 3D printing

Abstract

The invention relates to the field of materials recycled for 3D printing. More particularly, it relates to a PLA material loaded with whole textile fibres that are heterogeneous in nature for 3D printing and to the method for preparing same.

Description

PROCESS FOR PREPARING A PLA MATERIAL LOADED INTO END-OF-LIFE TEXTILE FOR 3D PRINTING

[0001] The invention relates to the field of recycled materials. More particularly, it relates to a PLA-type material loaded with whole textile fibers and of heterogeneous nature for 3D printing and its preparation method. Field of invention

[0002] The fashion industry is considered the second most polluting industry in the world, after the oil industry. A highly active sector whose CO2 emissions are higher than those of air transport and oil combined.

[0003]

[0004] Given the environmental consequences of this sector, the textile recycling industry is growing rapidly and has been structuring itself for several years for the collection and sorting of textiles. However, to date, only a small portion of textiles is actually recycled.

[0005] Several processes have been developed in recent years to integrate textiles into recycled materials.

[0006] Document WO2022 / 112719 describes a process for manufacturing a composite material in the form of granules from ground textile fibers and polymer in the form of resin grains. This process has the advantage of allowing the processing of any type of textile, including fiber blends, without the need to know the nature of the fibers. This new material filled with textile fibers is developed by the company PLAXTIL®.

[0007] FDM (Fused Deposition Modeling) is a 3D printing technique that involves creating parts by successively depositing thin layers of material. It uses a PLA filament that, once melted, is deposited using a printing nozzle from a 3D model; the melted layers are superimposed until the object is fully produced. The diameter of the printing nozzle of a 3D printer generally varies between 0.2 and 1.2 mm, it defines the precision of the deposition.

[0008] A new generation of 3D printers is emerging on the market; these new printers do not operate using filament but directly from printable material in the form of pellets.

[0009] A flax-filled yarn compatible with 3D printing has been developed by Nanovia. This material is based on PLA, a polymer derived from starch. It has a smooth and uniform appearance. The flax fibers are up to 500 microns in size and are therefore in powder form.

[0010] Document EP 3 922 665 describes a method for preparing a PLA material loaded with textile fibers. The fibers are pulverized in the form of powder in which the fiber size must be less than 0.5 mm to avoid problems during extrusion (see [0065)] and not to affect the properties of the plastic material obtained ([0066)]. The fibers must necessarily be less than 1 mm ([0061)]. Disadvantages of the state of the art

[0011] As it stands, there is no 3D yarn incorporating any type of textile fiber that is not in powder form.

[0012] The textile fibers used in the state of the art for the manufacture of a thread for 3D printing are reduced to powder, that is to say they have a size of less than 1 mm, to avoid problems of nozzle blockage during the extrusion of the material, which constitutes a significant energy expenditure. Document EP 3 922 665 reports that the presence of fibers larger than 1 mm affects the mechanical properties of the composite material. Furthermore, fillers in powder form contribute little to the mechanical strength of the material.

[0013] It is desirable to develop the offer of 3D printing filament loaded with recycled textile, which is compatible with 3D printing.

[0014] The inventors have developed a new process for producing a 3D material, particularly in the form of 3D yarn, loaded with all-purpose textile fibers, which is suitable for use in a 3D printer.

[0015] The present invention thus relates to a method for preparing a PLA material loaded with textile fibers suitable for 3D printing comprising the steps of:Grinding a textileDrying said textile ground material obtainedProviding PLA in the form of granulesProviding a resin that is surfactant with respect to textile fibers and compatible with PLAAdding said resin to the PLAExtruding using a twin-screw extruder assisted by vacuum degassing, a mixture consisting of (i) PLA with the addition of said resin and (ii) textile ground material to obtain granules loaded with between 5 and 25% by total weight of the textile ground material,

[0016] in which:

[0017] - said surfactant resin is added in a quantity equivalent by weight to that of said textile shred

[0018] - said surfactant resin is of the polybutylene adipate terephthalate (PBAT) type

[0019] - said ground material is made up of fibers whose size is between 1 and 10 mm.

[0020] In a particular embodiment, the method comprises an additional step of extruding said textile-filled granules obtained at the end of the first extrusion (compounding), in the form of thread for 3D printing using a single-screw extruder coupled to a pulling unit.

[0021] The invention also relates to a PLA-based material loaded with textile fibers in the form of granules or filament for 3D printing as well as the use of such a material for the manufacture of objects by 3D printing. Advantages of the invention

[0022] In a completely innovative manner, the process according to the invention allows the preparation of material for 3D printing incorporating textile fibers of millimeter size without this preventing extrusion or 3D printing. Its energy cost should be lower than that of a process requiring the reduction of textile fibers into powder. This process is industrializable.

[0023] The preparation process allows the integration of "long" or "whole" fibers (as opposed to fibers ground in powder form), thanks to the presence of a thermal protection additive. The latter coats the fibers and protects them from carbonization. As a result, the fibers do not fold on themselves and therefore do not create excess thickness that could block the passage through the printing nozzles. In addition, remarkably, it is possible to use "random" textile fibers as raw material, i.e., fibers that have not been sorted and whose nature is not controlled at the start of the process. The raw material is therefore heterogeneous and this characteristic differentiates it from prior art processes that use a homogeneous textile material, such as linen.

[0024] The 3D printed material is characterized by a certain flexibility. It retains the original color of the textile. The fibers can be visible to the naked eye.

[0025] The new 3D printing material made from recycled materials has properties comparable to reinforced virgin PLA and can be used as a replacement for the latter in most 3D printers, whether they operate with conventional 3D filament or pellets for the latest generation of 3D printers.

[0026] PLAXTIL® 3D printing material has a fluffy appearance, both visually and to the touch, due to the presence of ground textile fibers in the compound. This appearance is preserved in objects obtained by 3D printing. This characteristic differentiates it from materials currently available on the market, particularly prior art 3D yarns, and helps expand the range of new materials for the manufacture of objects by 3D printing. The 3D material after printing is characterized by a certain flexibility. It retains the original color of the textile. The fibers can be visible to the naked eye. The 3D material can also be used in a similar way to standard plastic.

[0027] FDM 3D printers are now accessible, particularly through their availability in collaborative spaces such as fablabs. Many companies also have 3D printers for their prototyping (Airbus, Thales, Jaguar, Land Rover, Akwel, etc.).

[0028] The new 3D filament developed by PLAXTIL® meets market needs. The 3D printing pellets are suitable for use in next-generation 3D printers.

[0029] 3D PLAXTIL® yarn, like 3D PLAXTIL® granules, is part of an eco-responsible approach, contributing to the reduction of the use of virgin materials, through the use of a material based on the recycling of textile products, preferably combined with recycled PLA. DETAILED DESCRIPTION OF THE INVENTION

[0030] A first subject of the invention relates to a method for preparing a PLA material loaded with textile fibers suitable for 3D printing comprising the steps of:Grinding a textileDrying said obtained textile ground materialProviding PLA in the form of granulesProviding a surfactant resinAdding said resin to the PLAExtruding using a twin-screw extruder assisted by vacuum degassing, a mixture consisting of (i) PLA added with said resin and (ii) textile ground material to obtain granules loaded with between 5 and 25% by total weight of the textile ground material,

[0031] In which:

[0032] - said surfactant resin is added in a quantity equivalent by weight to that of said textile shred

[0033] - said surfactant resin is of the polybutylene adipate terephthalate (PBAT) type.

[0034] - said ground material is made up of fibers whose size is between 1 and 10 mm.

[0035] The textile can be of any type, natural, synthetic but more generally a mixture of all textiles, for example polycotton, cotton, polyester, polyamide, viscose. The textile material used as raw material can therefore be and generally is heterogeneous (it has not been sorted after recovery in recycling points). In the context of the invention which is part of an eco-responsible approach, it is preferably end-of-life textile (damaged, no longer usable) which is thus recycled into material for 3D printing. It is necessary that the fibers are sufficiently finely ground so that the 3D material obtained does not clog the nozzles of 3D printers.

[0036] The textile can be ground by any means, preferably with a grinder using a grid whose sieve has a diameter of less than 10 mm. Preferably, the size of the ground fibers is greater than 1 mm and less than or equal to 10 mm, preferably less than 8 mm, or even less than 5 mm. The fibers have a size between 1 and 10 mm, preferably between 1 and 5 mm. The additive allows the integration of whole fibers – not in powder form – with a size greater than 1 mm in a material for 3D printing.

[0037] The textile shred is then dried before extrusion, by any means known to those skilled in the art, for example in an oven, preferably by a desiccator.

[0038] The textile filler content is between 5% and 25%. In particular embodiments, the filler content may be between 5% and 15%, 5% and 10%, 10% and 15%, 12% and 18%, 15% and 20% depending on the desired effect and mechanical strength. Indeed, the textile fibers provide a fluffy appearance which may be more or less accentuated depending on the filler content. In addition, the rigidity of the material increases with the filler content.

[0039] PLA can be virgin or recycled. It is supplied in the form of granules. These granules are preferably pre-oiled in order to obtain a good quality material after extrusion, which is well known to those skilled in the art. The PLA is added with a thermal protection additive before being injected into the twin-screw extruder with the textile shred.

[0040] The term "surfactant resin" means an aromatic polyester. This aromatic polyester is preferably polybutylene adipate terephthalate (PBAT), a biodegradable random polymer.

[0041] PBAT is represented by formula (I) below.

[0042] (I)

[0043] The role of the surfactant resin is to protect the textile fibers by limiting / preventing their carbonation during extrusion (compounding). It also has the role of forming a sheath around the fiber, which remains flexible without folding back on itself. The resin thus plays the role of surfactant by coming around each fiber and dispersing them in the PLA polymer matrix. The phenomenon can be compared to the formation of micelles in which the interior of the micelle comprises the textile fiber and the exterior the polymer matrix. This explanation being theoretical, it should not be considered as limiting the scope of the invention.

[0044] The presence of the surfactant resin thus allows the extrusion and 3D printing of a material comprising fibers of a size in the millimeter range. This surfactant resin therefore ensures the role of thermal protection and sheathing of the textile fibers. The good dispersion of the fiber also allows the initial color of the textile to be reflected in the matrix. Poor quality dispersion has the effect of darkening the final product. Poorly dispersed fibers limit the propagation of light by forming opaque balls.

[0045] In a preferred embodiment of the invention, the surfactant resin is based on aromatic polyester. The latter can be provided in the form of powder, granules or liquid solution. When present in the form of granules, it is mixed with the PLA before mixing the PLA with the textile shred. The amount of surfactant resin added to the PLA is equivalent by weight to that of the shredded textile mixed with the PLA.

[0046] The first extrusion (compounding) is carried out using a twin-screw extruder in which a mixture consisting of PLA and surfactant resin on the one hand and textile shred on the other. This mixture is extruded at a temperature between 160°C and 200°C. The presence of the surfactant resin greatly reduces / prevents the carbonization of the textile fibers and allows them to be sheathed; this is essential for stable production of material filament suitable for use in a 3D printer. This step allows the production of plastic granules loaded with millimeter-sized textile fibers which constitute a first compound.

[0047] Typically, a vacuum pump is used to degas during compounding (during twin-screw extrusion) to remove moisture and bubbles and achieve good quality material. This creates a bubble-free material. It is also flexible, which is essential if you want to produce 3D filament that can be wound onto spools.

[0048] If the 3D printer accepts the granules as a fusible material, then the granules obtained at the end of the compounding step can be used directly for 3D printing.

[0049] In a particular embodiment of the invention, the method further comprises a step of extruding the textile-filled granules obtained from the compounding in the form of a thread for 3D printing using a single-screw extruder coupled to a pulling unit. After pulling, the filament is preferably wound in the form of a spool suitable for a 3D printer.

[0050] A second subject of the invention relates to a PLA-based material loaded with textile fibers in the form of a material compatible with FDM-type 3D printing (filament / granules), characterized in that the loading rate is between 5% and 25% and in that the PLA contains a surfactant resin in a quantity equivalent by weight to that of the textile fibers.

[0051] In a preferred embodiment of the invention, said resin is polyester-based.

[0052] This material is advantageously obtained by the process according to the invention.

[0053] The 3D material consists of textile fibers ranging in size from 1 mm to 10 mm. These fibers are visible to the naked eye and provide a fluffy feel. The final material is printable, stable, and flexible despite the presence of fibers.

[0054] A third subject of the invention relates to the use of a material as defined above for the manufacture of an object by 3D printing.

[0055] The material can also be used in injection, using conventional processes.

[0056] The present invention will be better understood from the following examples, provided for illustration purposes and in no way to be considered as limiting the scope of the present invention. DESCRIPTION OF FIGURES

[0057] : Illustration of 3D printed specimens from PLA loaded at 15%, 17% and 20% respectively, going from left to right.

[0058] : Example of 3D printed objects from PLA loaded with textile according to the invention EXAMPLES

[0059] EXAMPLE 1: Production of 3D yarn loaded with polycotton

[0060] A used textile made of a fabric blend (not characterized as "all-in" type, which may contain cotton, polyester, polyamide, viscose) is ground using a 4mm screen until a homogeneous ground material is obtained (absence of long fibers or residual squares). It is then steamed to remove moisture. The dried ground material is ready to be introduced into the extruder.

[0061] A PLA-type plastic matrix is ​​steamed and then polyester resin granules are added to act as a surfactant. This resin will coat the fibers during compounding. The amount of surfactant resin added is equivalent to the amount of textile mixed with the PLA, i.e. between 5% and 25% of the weight of the PLA.

[0062] The amount of textile corresponds to 5-25% of the total weight of the final material.

[0063] Below is an example of a thread formulation according to the invention:

[0064] DesignationProportion compoundPLA70%SURFACTANT RESIN15%TEXTILE15%

[0065] Table 1: Example of 3D yarn formulation loaded with textile

[0066] A compound is made from the PLA / resin / textile mixture using a twin-screw extruder at a temperature between 160° and 200°C. The yarn is then extruded and spooled using a single-screw extruder-drawing bench.

[0067] EXAMPLE 2: Characteristics of materials comprising textile fibers

[0068] A material according to the invention was prepared by adding 17% ground textile to PLA and an equivalent quantity by weight of PBAT textile (i.e. 17% textile, 17% PBAT, 66% PLA).

[0069] The material was extruded at temperatures between 160°C and 200°C.

[0070] Extrusion in the form of wire in 3D printing produces a straight, soft (thanks to the presence of textile), smooth rod. The extrusion is stable thanks to the presence of PBAT, which acts as a thermal protection and allows the textile fibers to be shaped by coating. These characteristics are those expected for an extruded wire.

[0071] On the contrary, without PBAT, the rods have a wavy shape, making sinusoids. Such a rod is not desirable for the skilled person for many reasons: irregular cutting, potential stress in the material, process that can drift. In addition, carbonization of the textile is observed within the granules.

Claims

A method for preparing a PLA material loaded with textile fibers for 3D printing comprising the steps of:Grinding a textileDrying said obtained textile ground materialProviding PLA in the form of granulesProviding a surfactant resinAdding said resin to the PLAExtruding using a twin-screw extruder assisted by vacuum degassing, a mixture consisting of (i) PLA added with said additive and (ii) textile ground material, to obtain granules loaded with between 5 and 25% by total weight of the textile ground material, wherein:- said resin is added in an amount equivalent by weight to that of said textile ground material- said resin being polybutylene adipate terephthalate- said ground material consists of fibers whose size is between 1 and 10 mm. Process according to claim 1 in which the temperature of the twin-screw extrusion step is between 160°C and 200°C. Method according to one of claims 1 or 2 further comprising a step of extruding the textile-filled granules in the form of thread for 3D printing using a single-screw extruder coupled to a pulling unit. Method according to one of claims 1 to 3 in which said textile shred is of heterogeneous nature. Method according to one of claims 1 to 3 in which the charge rate is between 10 and 25%. PLA-based material loaded with textile fibers for 3D printing, characterized in that:The textile fibers have a size between 1 and 10 mmthe loading rate is between 5% and 25%the PLA contains a surfactant resin in a quantity equivalent by weight to that of the textile fibers. Material according to claim 6 wherein said resin is of the polybutylene adipate terephthalate (PBAT) type. Material according to one of claims 6 or 7 in the form of a 3D filament. Material according to one of claims 6 or 7 in the form of 3D granules. Use of a material as defined in one of claims 6 to 9 for the manufacture of objects by 3D printing.

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