Method for preparing a filled material from a polycotton and polyolefin mixture

Abstract

The disclosure relates to the field of recycled materials. More particularly, the disclosure relates to a method for preparing a polyolefin-based material filled with polycotton textile fibers. The disclosure also relates to the resulting filled material, which material can be used in industry as a replacement for plastic. The resulting material is referred to as "PLAXTIL" material.

Description

METHOD FOR PREPARING A FILLED MATERIAL FROM A POLYCOTTON AND POLYOLEFIN MIXTURE

[0001] The invention relates to the field of recycled materials. More particularly, the invention relates to a method for preparing a polyolefin-based material filled with polycotton-type textile fibers. The invention also relates to the filled material obtained, a material that can be used in industry as a replacement for plastic. The material obtained is called "PLAXTIL material". 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] Given the environmental consequences of this sector, the textile recycling industry is growing rapidly and has been structuring itself in recent years for the collection and sorting of textiles. However, to date, only a small portion of textiles is actually recycled. This deficit is partly due to the heterogeneity of textile fibers, which makes large-scale recycling complex.

[0004] The prior art processes are generally adapted to particular types of textile fibers and the processes are quite complex. For example, patent FR2998572 may be cited which describes a process for recycling the constituents of a textile product, possibly comprising a pretreatment of the textile product to be recycled and at least the following steps: (i) hydrolysis of animal fibers, (ii) hydrolysis of cellulose fibers, (iii) glycolysis of polyester fibers. The hydrolysis steps carried out in parallel each result in the production of a cake, the different residual textile cakes being mixed and the mixture extruded to produce a recycled plastic material.Another example is patent US2020 / 0262108, which describes a process for recycling a cotton-polyester mixed textile consisting of hydrolyzing the textile in an aqueous solution containing an organic acid catalyst heated to 110-180°C in a high-pressure reactor so as to separate the cotton fibers from the polyester and recover the cotton fibers using a vacuum filtration membrane.

[0005] None of these processes allow for the treatment of all-purpose mixed textiles. The choice of a "custom-made" treatment is explained in particular by the difficulty of mixing and homogenizing two materials whose densities differ significantly, particularly in the case of textiles comprising mixed natural synthetic fibers with a polymer.

[0006] Given the volumes of textile waste generated worldwide, it is desirable to have suitable recycling methods.

[0007] The inventors propose a new filled material obtained from recycled cotton-polyester and polyolefin textiles and a process for preparing such a material.

[0008] Thus the invention relates to a filled material comprising a mixture of polycotton type textile fibers in ground form and polyolefin, characterized in that the polycotton represents between 15% and 50% by weight of said material, the polyolefin is chosen from polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and polybutene-1 (PB-1) and in that it does not contain any chemical agent capable of modifying the structure of the polycotton fibers and the polyolefin.

[0009] The invention also relates to a method for preparing a filled material as defined above in the form of "compound" type granules from polycotton type textile and polyolefin comprising the following steps:Providing polycotton type textile in the form of ground materialsDensifying said ground textile materials by compressing the materialMixing said compressed ground materials obtained in the previous step with said polyolefin, said ground materials representing between 15% and 50% by weight of said mixtureMechanically treating the mixture obtained in the previous step at a temperature of between 150°C and 240°C, said treatment being carried out by extrusion. Advantages of the invention

[0010] The filled material obtained from polycotton and polyolefin is considered an environmentally friendly plastic.

[0011] This filled material has very good mechanical properties, which make it suitable for plastics applications. It can replace plastic materials made from 100% petroleum and is a credible alternative to plastic for industry in general, and for the fashion industry in particular. The fibers improve the properties of the matrix by fulfilling the role of "reinforcement" in a similar way to a conventional composite material.

[0012] The process is characterized by its tolerance. It can be implemented from all-purpose cotton-polyester textiles: textiles made of mixed natural and synthetic fibers, and remarkably, it is not required to know the relative percentage of these two components to implement the process. This allows the processing of large volumes of used textiles, which removes a major obstacle compared to current recycling processes. In addition, the presence of other types of fibers in the textile, in minority quantities compared to cotton-polyester, does not hinder the process.

[0013] The resulting filled material is recyclable for at least 10 reuse cycles and is part of the circular and sustainable economy. However, there is a gradual loss of mechanical performance inherent to the polymers themselves. In particular, the polymer chains break following successive melting cycles. The color of the compound darkens as it is recycled.

[0014] The life cycle of the materials according to the invention responds to a long-term recycling logic. Firstly because the materials are produced from recycled used textile materials (waste), but also because the loaded material can itself be recycled over a large number of cycles. Tests carried out over 10 cycles show a mechanical loss limited to 30% which is comparable to virgin plastic recycled 10 times. DETAILED DESCRIPTION OF THE INVENTION

[0015] A first subject of the invention relates to a polyolefin-based material loaded with polycotton-type textile fibers, characterized in that:the loading rate is between 15 and 50% by weightsaid textile fibers are in ground formsaid polyolefin is chosen from polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and polybutene-1 (PB-1)it does not contain any chemical agent capable of modifying the structure of the polycotton fibers and the polyolefin.

[0016] In other words, it is a loaded material comprising a mixture of polycotton type textile fibers in ground form and polyolefin characterized in that:

[0017] - polycotton represents between 15 and 50% by weight of said material

[0018] - the polyolefin is chosen from polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and polybutene-1 (PB-1)

[0019] - it does not contain any chemical agents that could modify the structure of polycotton and polyolefin fibers.

[0020] Polycotton, also called "cotton-polyester," is a polymer made from natural cotton fibers and synthetic polyester fibers. Textile fibers can be woven or non-woven. The relative percentage between these two types of fibers can vary, which is a barrier to recycling using currently available processes.

[0021] The polycotton fibers are in ground form in the material, that is to say they retain a certain length, typically between 0.1 and 5 mm, preferably between 0.3 and 3 mm. Grinding makes it possible to densify the material and facilitate mixing with the polyolefin matrix, but the size of the ground materials does not need to be homogeneous. It is in no way a powder, which differentiates the material obtained by the process according to the invention from prior art materials in which the textile fibers are previously pulverized in order to obtain a powder. The fact of retaining a fiber length (as opposed to a powder) directly contributes to the mechanical properties of the material (as described below).

[0022] In the context of the present invention, the textiles from which the filled material is prepared are made of polyester and cotton fibers regardless of the ratio between these two materials. The cotton / polyester ratio may in particular be between 50 / 50 and 96 / 4; this ratio applies in both directions, namely that the cotton and the polyester may each represent between 4 and 96% of the polycotton material. For example, conventional polyester compositions may contain the following ratios: 80 / 20, 75 / 25, 50 / 50 and 60 / 40 (in both directions of the mixture: cotton / polyester or polyester / cotton).

[0023] Polycotton can represent up to 50% of the filled material. In other words, the filler rate can be up to 50%, but is generally less than or equal to 50%. Preferably, the filler rate is between 15% and 50% and usually this rate is between 20% and 40%.

[0024] Thus, the filled material comprises at least 50% polyolefin matrix and preferably, the polyolefin matrix represents between 50% and 85% of the material.

[0025] The polyolefin matrix (also called "polyolefin") can be virgin, recycled or derived from waste. The recycled matrix can also come from recycled synthetic fibers (e.g. FFP1 surgical masks) or any other waste source. In addition, it can contain up to 20% mineral filler; the presence of a mineral filler in these proportions does not disrupt its preparation process. The general behavior of the material is affected depending on the type and proportion of mineral filler added. The mineral filler can consist of materials such as talc, mica, wollastonite, kaolin, CaCO3, BaSO4, dolomite, graphite MoS2.

[0026] By "polyolefin" or "polyolefin matrix" is meant thermoplastic polyolefins of the type: polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and polybutene-1 (PB-1). Preferably, the polyolefin matrix comprises PE and / or PP.

[0027] In addition, the polycotton may include other components in addition to polyester and cotton fibers. These other components are preferably thermoplastic textile materials such as polyamide, aramid fibers, modacrylic and viscose. These additional components, present in limited proportions, do not harm the process.

[0028] The polycotton may also include elastane (or other thermosetting fibers for which a proportion limit of up to 50% in the polycotton is acceptable. Beyond this, the polycotton material cannot be recycled by this process. In particular embodiments of the invention, the proportion of elastane in the polycotton is less than or equal to 40%, 30%, 20% or 10% depending on the nature of the textile and the polycotton / polyolefin ratio applied.

[0029] The material does not contain any chemical agents that could alter the structure of its components. The material does not contain any types of fibers other than textile fibers. Polycotton remains the predominant textile in the material. Fibers other than polycotton may be those typically associated with them, such as polyamide, aramid fibers, modacrylic, elastane, or viscose.

[0030] The filled material has good strength properties. It is suitable as a substitute for virgin or filled polyolefin plastic. It can be used in the industrial manufacture of common "plastic" objects, for example: measuring instruments (rulers, school protractors), hangers, supports or containers. The list is almost endless. By optimizing the choices and proportions of textiles / matrices / additives and adapting the design of the part, a very wide range of technical production types in plastics is possible with this material.

[0031] A second subject of the invention relates to a process for preparing a filled material as defined above in the form of granules of thermoplastic material from polycotton type textile and polyolefin comprising the steps of:Providing polycotton type textiles in the form of ground materialsDensifying said ground textile materials by compressing the materialMixing said compressed ground materials obtained in the previous step with said polyolefin, said ground materials representing between 15% and 50% by weight of said mixtureMechanically treating the mixture obtained in the previous step at a temperature of between 150 and 240°C, said treatment being carried out by extrusion

[0032] wherein the polyolefin is selected from polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and polybutene-1 (PB-1).

[0033] The resulting loaded material comes in the form of “compounds” or thermoplastic granules ready to be used in the plastics industry as a replacement for virgin plastics.

[0034] Obtaining a high-quality filled material depends on the "quality" of the materials used in its composition. The inventors have highlighted the importance of the density parameter of the textile fiber shreds in this process and propose densifying the textile fiber shreds before mixing them with the polymer for melting. Densification allows the textile to be correctly dosed for mixing with the polymer and facilitates textile-polymer mixing. Typically, the polycotton shred is compacted until it reaches a density at least 5 times, or even 10 times, higher than that of the starting shred. In a preferred embodiment, the densified shred is in the form of semi-solid and friable granules (also called pellets). This densification step is preferably carried out by compression. The granules obtained after densification are illustrated in Figure 1B, in comparison with the undensified shred shown in Figure 1A.

[0035] Preferably, the ground polycotton textile fibers or "polycotton ground" have a size of approximately 5 mm before densification. The length of the ground fibers is typically between 0.1 and 5 mm, or even between 0.5 and 5 mm or between 1 and 5 mm. The ground material does not need to be homogeneous.

[0036] Optionally, natural additives are added to the polycotton fibers before and / or during the densification step. The amount of these additives represents up to 10% or even 20% of the amount of textile material, generally between 1 and 2% (by weight). These may be process additives that provide stability to the process. This improves the cohesion of the fibers between them and thus facilitates mixing with the polymer and their fusion so that the resulting filled material is homogeneous. These process additives ("process additives") are, for example, conventional lubricants (such as water or glycerin); they do not change the material but stabilize the process.

[0037] Polyolefin is also supplied in the form of granules or shredded material. Recycled polyolefin can be obtained from textile fibers (woven or non-woven) that have been previously shredded and densified.

[0038] After densification, the cotton-polyester textile fibers are mixed with the polyolefin polymer grains in an extruder.

[0039] The treatment temperature of the mixture is between 150°C and 240°C. In a particular embodiment of the invention, it is between 160°C and 220°C, or even between 180°C and 210°C.

[0040] Preferably, the heat treatment for shaping the granules is carried out by extrusion. This extrusion allows compounding to be carried out.

[0041] Compounding is an extrusion-granulation process allowing the melt mixing of a polymer, here polyolefin (thermoplastic resin), with one or more reinforcing / filling additives / additives, here cotton-polyester textile fibers, in order to obtain a plastic material in the form of "compounds" (a type of granule) with specific physical or thermal characteristics.

[0042] Other specific properties such as: antistatic, anti-UV, antioxidant, etc. can be obtained by adding standard additives used to obtain said properties.

[0043] In the context of the invention, compounding consists of extruding granules of standard size similar to virgin granules of thermoplastic material mixtures. In compound form, the loaded material is compatible with all presses used for injectable products and can therefore be used by manufacturers like any other plastic material.

[0044] The method according to the invention aims to avoid, or at least minimize, fiber degradation. Good fusion of the fibers with each other improves fiber dispersion in the compound and can have an aesthetic effect with less visible fibers. The process parameters can be adjusted depending on the desired visual appearance of the filled material.

[0045] Thus, it has been established that the polycotton-polyolefin blend must be treated at a temperature between 150°C and 240°C (preferably between 160°C and 220°C) during the extrusion and injection phase so that the resulting material complies with the expected properties. This temperature range allows for good dispersion of the fibers in the polymer matrix in an industrial process.

[0046] All composite materials according to the invention are recyclable. This interesting property is directly linked to the fact that the process does not induce any structural modification of either the fibers or the polymer. In particular, no chemical agent capable of inducing such a modification of the material is used. However, it is possible to use small quantities of chemical agents to improve certain characteristics of the material, such as chain extenders to improve mechanical performance within the framework of a regeneration loop. In a particular embodiment of the invention, no chemical agent is used, even among the chemical agents not capable of inducing a structural modification of the fibers or the polymer, but which allow an improvement of certain characteristics of the loaded material.

[0047] Dyes and / or pigments can be added to modify the color rendering. Other additives can also be used to functionalize the material, without affecting the structure of the fibers or the polymer. Similarly, the temperatures and forces applied during the process do not cause a change of state (no modification by reactive chemistry is sought). The resulting filled material typically behaves like a thermoplastic material.

[0048] 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

[0049] : Representation of the products obtained at the different stages of the process, here obtained from recycled surgical masks. A: starting textile shred, B: Densified textile shred in the form of semi-solid granules

[0050] : Graphical representation of Young's modulus in bending as a function of the number of recycling cycles

[0051] : Graphical representation of resilience with notches as a function of the number of recycling cycles EXAMPLES

[0052] EXAMPLE 1: Preparation of the charged materials and appearance obtained

[0053] An example of a method for preparing a filled material is described here.

[0054] The polycotton-based textile is first uniformly ground to obtain ground particles with a size of approximately 5 mm. This ground material is then densified by compression until it obtains friable semi-solid granules which are then dried, if necessary, in a steamer or desiccator to remove water. Water is responsible for the hydrolysis of plastics, one of the main reasons for the breakage of polymer chains and which therefore affects the mechanical properties of the materials. These textile granules are then mixed with polyolefin polymer grains in an extruder. The mixture is extruded at a temperature of 200 ° C into the form of standard-sized granules similar to virgin granules of thermoplastic blends; this is the compounding step. The resulting filled material is generically called "PLAXTIL material". EXAMPLE 2: Properties of charged materials

[0055] The tests were carried out according to ISO standards in order to be reproducible (NF EN ISO527-1 for traction for example).

[0056] The characteristics of the obtained charged materials are presented below:

[0057] Charpy impact strength:

[0058] unnotched resilience: 20-40 KJ / m2

[0059] notched resilience: 15-22 KJ / m2

[0060] Bending test at 10 mm for 10 min

[0061] Maximum stress: 30-40 MPa

[0062] Flexural modulus: 1900-2300 MPa

[0063] Tensile test

[0064] Maximum stress: 10-17 MPa

[0065] Elongation at break at 10 mm for 10 min: <5%

[0066] Tensile modulus: 1200-1400 MPa

[0067] Melt flow index

[0068] MFR under 2.6 kg at 230°C: >2 g / 10 min (for example 5 g / 10 min)

[0069] These properties are mechanically comparable to the thermoplastic filled material. The filled material according to the invention is notably more rigid due to the presence of fibers.

[0070] EXAMPLE 3: Study of the environmental impact of the process according to the invention

[0071] The textile recycling process according to the invention differs from incineration treatment processes by its reduced environmental impact: the recycling and injection process leads to CO2 emissions of 1.71 kg / T of recycled material, whereas incineration produces between 1,000 and 1,700 kg of CO2 / T. The environmental impact is therefore divided by 1,000 thanks to the process according to the invention, and the latter makes it possible to produce composite materials of interest as a replacement for plastic, where incineration only destroys.

[0072] Furthermore, the comparative analysis of the life cycle between the same object in virgin PP (origin Asia or Europe) and in PLAXTIL material (1st use or recycled) demonstrates the interest of using PLAXTIL material in terms of resources consumed. Indeed, on average, the impact on resources is divided by 3. EXAMPLE 4: Recyclability of loaded materials

[0073] The mechanical performance of the recycled materials was evaluated using Young's flexural modulus and resilience measurement.

[0074] Lamontre shows that the Young's modulus is impacted by approximately 30% in the first cycles and then remains stable. This result shows good maintenance of mechanical properties for 10 recycling cycles.

[0075] Lamontre shows the impact of the number of recycling cycles on resilience. It should be noted that the material's ability to resist crack propagation decreases over the cycles, but this decrease remains moderate up to 7 cycles, which is already significant. The use of recycled material can also be adapted to the material's life cycle by taking this parameter into account.

[0076] These results can be compared with data on polyethylene terephthalate (PET) recycling. PET is the most widely used plastic in packaging (bottles) and the most recycled in the world, through primary or secondary recycling. PET recycling has reached one of the most advanced levels of maturity among consumer plastics. However, the loss of mechanical properties of PET after each recycling cycle remains problematic. It appears that the breaking stress of "virgin" PET is 42% but that this value drops to 0.7% after the fifth recycling cycle. This substantial loss of mechanical properties thus limits the ultimate number of cycles that can be carried out.

[0077] The material loaded according to the invention can be recycled more than 4 times, without substantial loss of mechanical properties and by an environmentally friendly process.

Claims

Polyolefin-based material loaded with polycotton-type textile fibers, characterized in that:the loading rate is between 15 and 50% by weightsaid textile fibers are in ground formsaid polyolefin is chosen from polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and polybutene-1 (PB-1)it does not contain any chemical agent capable of modifying the structure of the polycotton fibers and the polyolefin. Filled material according to claim 1 wherein the polyester / cotton or polyester / cotton ratio of the polycotton is between 50 / 50 and 4 / 96 by total weight of the textiles. Filled material according to one of the preceding claims in which the filler rate is between 20% and 40% by weight. Filled material according to one of the preceding claims wherein said polyolefin may be virgin, recycled, derived from waste and may contain up to 20% by weight of mineral filler. Filled material according to one of the preceding claims further comprising other thermoplastic textile materials originating from said polycotton type textile such as polyamide, aramid fibers, modacrylic or viscose Filled material according to one of the preceding claims further comprising elastane from said polycotton type textile in a proportion of up to 50% by weight of said textile. A method of preparing a filled material as defined in one of claims 1 to 6 in the form of granules of thermoplastic material from polycotton textile and polyolefin comprising the steps of:Providing polycotton textiles in the form of ground materialsDensifying said ground textile materials by compressing the materialMixing said compressed ground materials obtained in the previous step with said polyolefin, said ground materials representing between 15% and 50% by weight of said mixtureMechanically treating the mixture obtained in the previous step at a temperature between 150 and 240°C, said treatment being carried out by extrusionin which the polyolefin is chosen from polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and polybutene-1 (PB-1). A method according to claim 7 wherein the textile is a densified ground material in the form of semi-solid and friable pellets.

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