Biodegradable biocomposite material and method for preparing same

Abstract

The present invention relates to biodegradable composite materials based on blends of thermoplastic polymeric materials and cellulosic materials that are useful for several industrial and packaging applications, in particular for the production of biodegradable films and articles of complex shape with improved mechanical properties, oxygen barrier properties, biodegradability and heat resistance, and to methods for producing these biodegradable composite materials.

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention relates to the field of composite materials useful for several industrial applications, in particular to a biodegradable composite material obtained by its preparation method, which is also part of the present invention, and its use in several industrial and packaging applications. The composite material of the present invention is particularly useful for preparing biodegradable films and articles of complex shapes, with improved mechanical and oxygen barrier properties, biodegradability, and heat resistance. [Background technology]

[0002] technical level Biodegradable composites derived from renewable resources can be processed by standard industrial methods used for thermoplastics, such as melt extrusion and injection molding, and are commonly emerging as environmentally sustainable alternatives to petroleum-based composites in the automotive, packaging and consumer goods sectors.

[0003] Among suitable materials of natural origin, paper is the cheapest and most ubiquitous, since it can be obtained directly from cellulose obtained from agriculture and forestry, and from cellulose recovered from waste production in the packaging industry and other paper recycling methods. Furthermore, paper is lightweight, mechanically strong and biodegrades quickly.

[0004] Among bio-based thermoplastic polymer matrices, polylactic acid (PLA), a thermoplastic aliphatic polyester, dominates the market of biodegradable bioplastics due to its mechanical strength, versatile processability, high production capacity, biodegradability, and biocompatibility as well as its excellent sustainability in terms of energy consumption, environmental impact, and life cycle compared to polyolefins [1]. The incorporation of paper in a bio-based matrix such as PLA is not only environmentally and commercially attractive, but also adds value to the resulting biocomposite by enhancing important properties such as oxygen impermeability, heat resistance, and biodegradation rate, as observed with other cellulosic fillers [1,2,3].

[0005] Despite such tremendous potential applications, the availability of paper / bio-based thermoplastic blends on the market is limited by the lack of efficient industrially scalable processing methods based on melt compounding, such as extrusion and injection molding. Furthermore, previous studies and patent applications have disclosed innovations on the melt processing of natural fibers, lignocellulosic biomass, and micro / nanocrystalline fillers (German Patent No. 102013208876A1, EP Patent No. 3183288A1, [4]), which require complex methods to separate rather than paper, and less attention has been paid to the promotion of waste paper and cardboard. For example, Huda et al. [3] combined up to 40 wt% of recycled cellulose fibers from newspapers with PLA in a microcompounding device, but this method has not been investigated on a large scale to evaluate its potential applicability in industry. Furthermore, because no compatibilizer was used, the tensile and impact strength of the resulting materials decreased significantly with increasing fiber content due to agglomeration. JP Patent No. 2011152787A features a method for producing PLA / cellulose flexible molded articles from various cellulose raw materials such as cardboard and waste paper by extrusion molding at 170-220°C followed by injection molding. However, the patentee reports that to obtain a formulation suitable for the extrusion process, the cellulose component must be subjected to a long continuous grinding process at 5-250°C for up to 50 hours, and the addition of stabilizers up to a 1:1 ratio with respect to the paper is required.

[0006] US Patent No. 5,964,933 describes an extrusion method for preparing a biodegradable composite starting from polylactic acid and paper powder. International patent application published under WO 2015 / 048589 and European patent application No. EP 0897943 also describe a method for preparing a composite based on polylactic acid and finely divided or, respectively, micronized cellulose.

[0007] The most important challenges so far unsolved with regard to the processing of paper / thermoplastic polymer blends by melt extrusion include: 1) non-uniform dispersion of the paper in the polymer matrix due to agglomeration resulting from poor compatibility with the hydrophobic polymer, 2) non-continuous feeding to the extruder, and 3) the need for effective stabilization of the polymer matrix against thermal and oxidative degradation of the paper at the temperatures used for processing (e.g., about 180-200 °C for PLA [5]). Insufficient interfacial adhesion between the paper and the thermoplastic matrix and the thermal sensitivity of the paper strongly impair the structural and aesthetic properties of the final composite, causing weakening of stiffness and tensile strength, as well as off-odors and burnt coloration.

[0008] Methods have been disclosed in the patent and scientific literature to improve the dispersibility of cellulosic materials and allow them to be fed in extruders by granulation through physical methods such as roll milling and blade cutting [6]. Other conventional methods include mechanical grinding using water, lubricants, surfactants or softeners and subsequent palletization (JP Patent No. 200726094A, US Patent No. 6730249B2) or compaction of wet cellulose fibers by compression molding (JP Patent No. 2005014499A). Yet another widely used approach is premixing with a thermoplastic polymer in the molten state, usually for more than 10 minutes, before extrusion (JP Patent No. 2010089483A, WO Patent No. 2011144441A1). However, cutting / grinding operations significantly reduce the length and reinforcement potential of the fibers, and extensive moistening or hydration-dehydration cycles lead to irreversible aggregation of the fibers upon drying [7]. On the other hand, kneading at high temperatures can result in the degradation of both the polymer matrix and the cellulose component of the fibers.

[0009] Another aspect concerns compatibilization with the polymer matrix by the addition of large amounts of reactive compatibilizers, coupling agents, grafting, etc. These conventional methods require the use of environmentally friendly solvents and processes, and non-biodegradable or harmful additives that release toxic volatile components. At the top, they are effective for high-purity cellulose (i.e., microfibrillated and nanocrystalline cellulose) with a large surface-to-volume ratio, rather than bulk paper materials. To obtain such cellulose, expensive and time-consuming treatments of cellulose pulp, such as enzymatic, acidic or mechanical shearing, are required. In US Patent US6632863B2, cellulosic materials, including paper (35-70% by weight), are treated with synthetic non-biodegradable polyethylene at temperatures ranging from 170-190°C, and with high concentrations of additives, up to 45% by weight of the formulation, which were required for the treatment. Moreover, the additives also contained toxic lead and cadmium metals used as stabilizers.

[0010] US Patent No. 20130331518A1 discloses a method for compatibilizing cellulose fibers with PLA using long-chain organic compounds containing epoxy or anhydride functional groups. In the final material, despite the use of compatibilizers, the amount of cellulose fibers did not exceed 30% by weight of the total composition, but the interfacial adhesion between the matrix and the filler remained poor and in some cases, a 50% drop was reported in tensile strength and elongation at break. Even in more environmentally friendly approaches based on water-soluble coupling agents and copolymers, the high water content resulted in long drying times that were not industrially and energetically sustainable.

[0011] For example, in US Patent No. 6,730,249 B2, cellulose pulp was treated with sodium carboxymethylcellulose and softeners using a moisture content of 60-70 wt.%, followed by drying overnight at 90 °C. According to [8], cellulose fibers were suspended in water at a concentration of 1 wt.% before compatibilization, then spray-dried at 200 °C, and further dried under vacuum overnight at 75 °C. Moreover, the practical effectiveness of the disclosed methods has not been fully demonstrated, since the properties of the obtained composites have hardly been investigated or are inferior compared to the pure polymers.

[0012] Finally, a significant problem especially felt in paper-based composites is the extrusion temperature of the paper thermoplastic blends, which, as reported in the examples above, is usually in the range of 180-240 °C, causing thermal and oxidative degradation resulting in darkening and poor mechanical properties.

[0013] International Patent Application WO2019055921A2 discloses composite materials comprising a thermoplastic polymer matrix in which cellulose pulp and a filler material are dispersed. The composites can be in solid form (pellets) or in molten form. A method of molding a part includes providing a solid composite material comprising a thermoplastic polymer, a filler material, and cellulose pulp fibers to an injection molding system. These composite materials contain a significant proportion of filler.

[0014] Improvements in the formulation and compatibilization of paper-based materials in thermoplastic compositions are still necessary to make them suitable for melt processing, especially melt extrusion. At the same time, an environmentally conscious and sustainable approach needs to be adopted, combined with rigorous validation of proposed manufacturing methods through evaluation of the physicochemical properties of the composites considering their potential applications in food, toys, etc. Summary of the Invention [Means for solving the problem]

[0015] Summary of the Invention Here, we have discovered a continuous and automatable method for the production of biodegradable biocomposites by melt extrusion. These composites include compressed pulp or treated paper, recycled paper from the packaging industry, high-load (high-capacity) paper from waste paper or cardboard, and biodegradable thermoplastic polymers such as PLA, used alone or in combination with other polyesters.

[0016] Yet another scope of the present invention is that the thermoplastic blends can be easily processed at temperatures below 180°C to prevent degradation and discoloration of the paper, producing uniform extruded strands with smooth surface, bright color and rheological properties, which can be subjected to further melt processing to obtain complex shaped items / objects.

[0017] Another subject of the invention is to compatibilize the paper capsules with a hydrophobic polymer matrix and stabilize them against oxidative and thermal degradation by means of an environmentally friendly and sustainable solution using non-toxic and food contact approved additives in limited weight ratios compared to the total weight of the material, all without organic solvents and using limited amounts of water to avoid long drying times before extrusion.

[0018] Another subject of the present invention is to develop a simple method for obtaining compact paper capsules from commercially available paper and cardboard as well as from recycled and waste paper that is appropriately mixed with a thermoplastic polymer material and of a size suitable for feeding into an extruder in dry form without shortening the fiber length.

[0019] It is a further subject of the present invention to produce items (goods) from the extruded biocomposite by injection and compression moulding, which exhibit improved mechanical and oxygen barrier properties, heat resistance and biodegradability and are suitable for many industrial and packaging applications, in particular food packaging.

[0020] The subject of the present invention is therefore a method for the preparation of a biodegradable biocomposite material according to claim 1, which solves the technical problems highlighted above for known methods and provides a homogeneous dispersion of the paper in the polymer matrix, excellent resistance of the paper to oxidative and thermal degradation during processing.

[0021] Further subject matter of the present invention are the biodegradable biocomposite materials obtainable by the above process, as claimed in claims 16-17, their uses and shaped articles, as claimed in claims 18 and 19, respectively.

[0022] Further important features of the subject matter of the invention are defined in the appended claims. [Brief description of the drawings]

[0023] BRIEF DESCRIPTION OF THE DRAWINGS The characteristics and advantages of the biodegradable biocomposite material, as well as its preparation method according to the invention, are also clearly illustrated in the following exemplary and non-limiting description of embodiments thereof, with reference to the accompanying figures, in which:

[0024] [Figure 1] FIG. 1 shows a schematic diagram of a punching machine for producing paper capsules from a paper sheet according to Example 1 below. [Diagram 2] FIG. 2 is a photograph of the paper capsules obtained in Example 1 collected in a tray. [Diagram 3] FIG. 3 shows SEM (scanning electron microscope) micrographs of the paper before (FIG. 3a) and after encapsulation (FIG. 3b), as in Example 1 below. [Figure 4] FIG. 4 shows the FTIR (Fourier Transform Infrared Spectroscopy) spectra of the starting paper sheet and the paper capsule obtained in Example 1. [Diagram 5] FIG. 5 shows the thermogravimetric analysis (TGA) profiles of the starting paper sheet and the capsules obtained in Example 1 (FIG. 5a) and the corresponding first derivatives of the thermogravimetric curves (FIG. 5b). [Figure 6]Figure 6 shows the FTIR spectra of paper capsule (PC), tannic acid (TA), and paper capsule treated with tannic acid (PC / TA). The amount of TA in the final blend is 5 wt% with respect to the total weight of PLA and PC, as described in Example 2 below. [Figure 7] FIG. 7 shows a photograph of extruded pellets obtained by extrusion of the following formulations, as described in Example 3 below: a) PLA6302D-PC, b) PLA6302D-PC-TEC-SOY, c) PLA6302D-PC50-CA-GTA, d) PLA6302D-PC60-CA-GTA, e) PLA-CB-CA-GTA and f) PLA2003D-SIL. [Figure 8] Figure 8 shows pictures of a dog-bone shaped item obtained by injection molding of pellets made of a) PLA6302D-CB-CA-GTA, b) PLA2003D-SIL, and c) red PLA6302D-PC-CA-GTA, d) shows pictures of spoons of different colors obtained by injection molding of pellets made of PLA6302D-PC-CA-GTA, and e) and f) show pictures of cups and cup sealers obtained by injection molding as described in Example 4 below. [Figure 9] FIG. 9 shows SEM micrographs of pellets made from blends of a) PLA6302D-PC and b) PLA6302D-PC-CA-GTA shown in Table 1 below, and fractured dog bone shaped items made from blends of c) PLA3052D-PC and d) PLA3052D-PC / TA shown in Table 1 below. [Figure 10] FIG. 10 shows a) SEM micrographs, b) FTIR spectra, c) TGA curves, and d) first derivatives of the thermogravimetric curves of cellulose extracted as described in Example 5 below from dog-bone shaped items made with formulations PLA3052D-PC40 and PLA3052D-PC / TA as shown in Table 1 below. [Figure 11]FIG. 11 shows a) shear viscosity and b) shear stress of PLA6302D-PC based biocomposites measured as described in Example 7 below. [Figure 12] FIG. 12 shows extruded pellets and injection molded dog bones made with a) PLA2003D-PC-20-GTA-CA-BW (Formulation 1) and b) PLA2003D-PC-30-GTA-CA-BW (Formulation 2) of the present invention prepared as described in Example 11 below. [Figure 13] Figure 13 shows a pre-extrusion blend of Comparative Formulation 3 of PLA-PC-GTA-CA-BW-PVA (Figure 13a) and Comparative Formulation 4 of PLA-PC-GTA-CA-BW-GF (Figure 13b), with reference to Example 11 below. Figure 13c shows extruded pellets from Formulation 3. [Figure 14] FIG. 14 shows extruded pellets and injection molded dog bones of the following comparative formulations described in Example 11 below: a) PLA2003D-PC-20-GTA-CA-BW-CL1 (Formulation 5), b) PLA2003D-PC-20-GTA-CA-CL1 (Formulation 6), c) PLA2003D-PC-20-GTA-CA-CL2 (Formulation 7) and d) PLA6302D-PC-20-GTA-CA-CL1 (Formulation 8). [Figure 15] Figure 15 shows extruded pellets and injection molded dog bones of a formulation of 53.5 wt% PLA2003D + 40 wt% paper capsule + 0.5 wt% citric acid + 3 wt% bio-based wax + 3 wt% glycerol triacetate dried prior to extrusion at 50°C (Figure 15a) and extruded at 4.7 wt% moisture of total material (10 wt% of cellulose) following the experiment described in Example 12 below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Detailed Description of the Invention As mentioned above, the present invention relates to a method for preparing biodegradable biocomposite materials, to these biodegradable biocomposite materials, to their uses, and to molded articles, including articles with complex shapes, obtained by molding the biocomposite materials of the present invention.

[0026] The term "biocomposite" as used herein refers to a composite material in which the major part by weight, if not the entire compound or item, is made of natural components such as cellulose or components such as polylactic acid (PLA) derived from enzymatic treatment of natural materials and subsequent polymerization.

[0027] The term "biodegradable" refers to materials that can be broken down by the action of naturally occurring microorganisms into harmless components such as carbon dioxide and water.

[0028] The biodegradable biocomposite material of the present invention comprises a thermoplastic polymeric material and a cellulosic material, and optionally one or more additives, wherein the thermoplastic polymeric material is a melt-extruded matrix comprising at least 10% by weight of the cellulosic material in finely divided form uniformly dispersed within the matrix.

[0029] The biodegradable biocomposite material of the present invention can be used to prepare molded articles, even of complex shapes, which are biodegradable, preferably by injection or compression molding.

[0030] Most preferably, the thermoplastic polymeric material of the composite is a commercially available polylactic acid (PLA) polymer, such as polylactide sold under the trade name Ingeo by Natureworks. Modified polylactic acids and different configurations, such as poly-D-lactic acid, poly-L-lactic acid, poly-DL-lactic acid, and combinations thereof, can also be used. Polylactic acids with different degrees of crystallinity and amorphous can also be used. Other sustainable polyesters such as succinic acid based polyesters such as polybutylene succinate (PBS), polyhydroxyalkanoates (PHAs), polycaprolactone (PCL), poly(DL-lactide-co-glycolide) (PGLA), poly(dioxanone) (PDO), poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), poly(1,4-butylene adipate) (PBA), poly(butadiene adipate coterephthalate) (PBAT), poly(ethylene carbonate) (PEC), poly(propylene carbonate) (PPC), thermoplastic starch, polyethylene oxide, as well as non-biodegradable polymers such as polyurethanes, polyolefins, and mixtures thereof, can also be used in combination with PLA in the present invention. The content of thermoplastic polymer materials or mixtures thereof in the present invention can range from 35 to 90% by weight, more preferably from 35 to 55% by weight.

[0031] The cellulosic material content of the present invention is at least 10% by weight, such as from 10 to 60% by weight, more preferably from 30 to 60% by weight, even more preferably between 40 and 50% by weight, relative to the total weight of the composition.

[0032] According to the present invention, the term "cellulosic material" means any material based on cellulose, for example selected from pure paper, cellulose pulp, waste paper, recycled paper, cardboard, coated and processed paper, plant leaves, pulp and skin (for example coffee husks or platano bananas, pet food, etc.). According to the present invention, this cellulosic material is in the form of capsules, which are compact capsules of millimeter size. In one embodiment of the present invention, "millimeter size" means that the capsules of the present invention have a size of more than about 850 micrometers and up to a few millimeters, for example about 8 millimeters. Preferably, the capsules of the present invention have a size of about 3 mm in diameter and about 1 mm in height. In one embodiment, as far as the size of the capsules of the present invention is concerned, their diameter is greater than their thickness. The cellulose capsules of the present invention can be obtained by compressing the above-mentioned different types of cellulosic materials in the form of sheets and foils in a punching machine, an example of which is described in detail below. In this method, a paper sheet is inserted between two plates of a punching machine that applies mechanical pressure to the paper sheet so that the capsules are produced. In order to obtain capsules of the above-mentioned preferred size, a punching machine with a number of metal punching cylinders of about 3 mm in diameter should be used. By varying the diameter of the punching cylinders and controlling the pressure exerted by them, different heights and diameters of the capsules can be obtained.

[0033] The inventors have found a surprisingly good performance for the millimeter-sized paper capsules of the present invention with respect to state-of-the-art powder and pulverized materials when subjected to extrusion by fusion, which has a positive impact on both the final composite properties and the process conditions. Firstly, the size of the capsules of the present invention is regular, all capsules having exactly the same size, thickness and shape. This makes the process highly reproducible and the final composite product perfectly homogeneous. Conversely, powders, even when finely ground, do not guarantee the same size uniformity, which affects the final product. Furthermore, without wishing to be bound by theory, the inventors believe that the millimeter-sized paper capsules of the present invention are able to absorb possible liquid additives by impregnation without adversely affecting the extrusion process. Conversely, the addition of liquid additives to powder and pulverized materials tends to form agglomerates that can deposit on the walls of the feeder, thus causing problems for the extrusion process. With regard to the mechanical properties, as also shown in the examples below, the performance of the composites obtained using powders is inferior to that of the composites of the present invention obtained using capsules. This can be explained by the shortening of the length of the cellulose fibres due to crushing relative to the intact fibres of the capsule, which may result in a deterioration of the mechanical properties.

[0034] Moreover, the use of millimeter capsules also has great advantages for the composite preparation process itself, with respect to the use of powdered and pulverized materials, in terms of the safety and efficiency of the process. Indeed, the capsules do not emit fine dust or particles, do not require protective equipment for the operator and can be mixed with the polymer pellets in the hopper without the use of large amounts of material. This is not feasible if powders are added, which also require a dedicated feeder separated from the polymer pellets. Furthermore, the cohesiveness of powders and the heterogeneity of the particles that compose them can cause problems of plant stoppage, which are partially solved by adding a vibrating component in the feeder. Thanks to their higher density in bulk and their homogeneity, the millimeter capsules of the invention do not present such problems. For the same reason, the dispersion of the millimeter capsules of the invention in the polymer pellets before extrusion by fusion is also easier than that obtained with powdered or pulverized materials.

[0035] According to a particular embodiment of the invention, the biodegradable biocomposite material consists of a thermoplastic polymeric material, a cellulosic material in the form of a capsule, optionally treated with one or more additives.

[0036] The biodegradable biocomposite materials of the present invention are typically filler-free, by which is meant polymers having a higher melting point than the thermoplastic polymeric and lignocellulosic materials described above, such as polyvinyl alcohol and nylon, and minerals such as fiberglass, mica, talc, clay, basalt, calcium carbonate, and wollastonite.

[0037] Additives that can be used in the present invention include non-toxic natural and / or food contact approved plasticizers, lubricants, rheology modifiers, stabilizers, colorants, processing aids, gloss agents, antioxidants, and mixtures thereof. As described in detail below, these additives are preferably added to the cellulosic materials as a pretreatment before mixing with the thermoplastic polymeric material. They have been shown to enhance the processability of the cellulosic materials, reduce their aggregation, stabilize them against oxidation at processing temperatures, and compatibilize them with the hydrophobic polymer matrix so that extruded strands exhibit bright colors and smooth surfaces even with more than 40% by weight of cellulosic material. When used, the amount of these additive components ranges from 0.1% to 15% by weight of the composition, more preferably 0.5 to 5% by weight.

[0038] The method for preparing the above-mentioned biodegradable biocomposite material according to the present invention comprises the following steps: i) providing a cellulosic material in the form of a capsule, optionally pretreated with one or more additives, and a thermoplastic polymeric material and drying them to remove moisture; ii) mixing the dry cellulosic material in the form of capsules with a dry thermoplastic polymeric material to form a dry mixture in which the cellulosic material is at least 10% by weight based on the total weight of the mixture; iii) Processing the mixture from step ii) by melt extrusion at a temperature ranging from 130-170° C. to form extruded strands of the biodegradable biocomposite material of the present invention.

[0039] According to an embodiment of the method, it further comprises a step of pelletizing the extruded strands of biodegradable biocomposite material. The strands resulting from the extrusion can, if necessary, be subjected to a cooling step before pelletizing, for example by immersion in a water bath or in air. The pellets thus obtained, preferably about 4 mm in length, of the biocomposite material of the invention can then be used to feed the biocomposite material in the form of moulded articles, even in complex forms, by injection moulding or compression moulding. Starting from the pellets of the biodegradable biocomposite material of the invention, films and objects of different shapes and dimensions, such as cups, boxes, dog bones, cutlery, etc., can be manufactured using conventional thermoplastic processing methods, such as compression moulding or injection moulding. The temperatures used for these moulding methods range from 140 to 170 °C, preferably from 145 to 165 °C. It has been observed by the inventors that pre-treatment of the cellulose capsules with one or more additives improves the processability of the biocomposite material during moulding, prevents the degradation of the cellulosic material and results in a homogeneous material, as observed both in morphology and physical appearance.

[0040] The drying procedure of step i) of the present process may be carried out at a temperature ranging from 40 to 70°C for a period of 8 to 48 hours, preferably at 50°C for 12 hours, in order to remove the moisture in the thermoplastic polymer and the cellulosic material prior to mixing them.

[0041] If additives are present in the biocomposite of the invention, they are added to the cellulosic material capsules in a capsule pretreatment procedure with said additives. These additives can be in liquid phase, molten state, in suspension, or dissolved in water. When water is used, it is preferred to use it in the range of 8-10% by weight relative to the weight of the cellulosic material to be treated. This is an amount of water comparable to the natural moisture content of paper, which is removed from the treated capsules in the subsequent drying step without the need for excessively long drying times and high temperatures. In an alternative preferred embodiment, an aqueous solution of the additives can be sprayed onto the cellulose capsules to further reduce the subsequent drying time. In another embodiment of the method, viscous additives can also be mixed with the capsules without dilution or dissolution methods. In another embodiment of the method, solid additives can be added to the paper capsules and melted by a gentle heating step when their thermal transition temperature is below 70°C. In this case, a heating step of about 3 hours at 60-70°C is preferred to impregnate the cellulose capsules with the molten additives.

[0042] It has been observed by the inventors that pretreatment of cellulose capsules with one or more additives provides a) more effective compatibilization of the molten blend components, b) improved melt viscosity, free flow of the melt, and continuous strand formation during extrusion, c) stabilization of the paper against oxidation and thermal degradation at processing temperatures, d) compatibilization of the cellulose within the paper in a hydrophobic polymer matrix, and e) improved properties of the resulting material. The most important results are reported in the experimental section below.

[0043] Additives that can be used in the biocomposite of the present invention can be selected from the group consisting of polyphenols, phenols, sugar alcohols, terpenes, oils, poly oils, esters, organic acids, waxes, and mixtures thereof. A non-limiting exemplary selection of such additives includes tannic acid, glycerol, carnauba wax, lignite wax, triethyl citrate, glycerol triacetate, corn oil, soybean oil, castor oil, succinic acid, tartaric acid, citric acid, orange terpenes, polyethylene glycol, sorbitol, corn starch, and mixtures thereof.

[0044] According to the preferred embodiment of the method, one or more additives are added to cellulose capsule, more preferably, one or more additives with carboxyl, hydroxyl and ester moieties are added.Without wishing to be bound by theory, it appears that these additives can reduce cellulose aggregation through hydrogen bonding interaction between the above-mentioned functional groups of additives and cellulose hydroxyl groups, thus providing improved melt processability of blends, stabilization of cellulose in hydrophobic polymer matrix in blends, and resistance to radical oxidation and thermal degradation.

[0045] In one embodiment of the process of the present invention, one or more of the additives mentioned above, in particular also colour modifiers such as stanch or food colours, may be added to the mixed material before or after the melt extrusion step iii).

[0046] Once dried, the thermoplastic polymer material and the cellulosic material, possibly pretreated with one or more additives, are then physically mixed in process step ii) and this mixture is then extruded.

[0047] The melt extrusion in step iii) of the process is carried out at a temperature ranging from 130 to 170° C., preferably at a temperature ranging from 135 to 165° C. The extrusion step is carried out in a twin-screw extruder with a screw speed ranging from 200 to 350 rpm, more preferably from 250 to 300 rpm, and a preferred feed rate of the mixture of about 2 kg / h, to obtain the biocomposite of the invention.

[0048] In the extrusion process of the present invention, as a result of the high shear stresses experienced by the paper capsules during pultrusion, they undergo mechanical disintegration, and even at high loads a uniform dispersion is achieved in the melt, and the strands produced are uniform and continuous. Microscopically, the cellulose in the blend is uniformly dispersed and coated by the polymer matrix, with almost no phase separation being observed. After extraction of the polymer matrix with chloroform, which was only carried out within the scope of the characterization, the cellulose in the blend appears as an aggregate of fine particles, which confirms that a micronization process occurs during extrusion. Furthermore, as observed in the molding process, the melt extrusion process iii) also makes use of a pretreatment of the cellulosic material with one or more additives.

[0049] The process of the present invention can be easily scaled up, automated and made continuous, from the production of cellulose capsules, which are fed into a gravimetric feeder containing additives and thermoplastic polymer, to being continuously extruded to obtain biocomposite strands which are then pelletized.

[0050] The biodegradable biocomposite of the present invention is environmentally friendly and commercially attractive. For example, it exhibits faster biodegradation, higher heat resistance, equal or better Young's modulus, and improved oxygen barrier properties compared to pure PLA. It can therefore be used in a variety of applications, including food and cosmetic packaging, manufacturing several types of disposable items, agricultural pipelines and tubing, laminated paper, food trays, cutlery, brushes, combs, toys, and more.

[0051] In addition to being simple and cost-effective in itself, the method of the present invention is economically and environmentally sustainable, since it allows the use of conventional melt processing techniques used for thermoplastics and can be used without solvents, except for possible small amounts of water. The additives that may be used in the method do not exceed 15% by weight of the total composition, more preferably their content is much lower, and include commercially available low-cost FDA approved and commonly used natural additives.

[0052] Moreover, the biocomposites, obtained by blending paper, waste paper, cardboard, and other cellulosic materials with PLA and other biodegradable thermoplastic polyesters, have mechanical, rheological, and oxygen barrier properties comparable or superior to pure polymers and petroleum-based plastics, and have improved biodegradability and heat resistance. They are therefore cost-effective and environmentally friendly alternatives to plastics in several applications, including but not limited to disposable items such as cutlery, glasses, cups, food and cosmetic packaging, toys, furniture, agricultural pipes and tubes, automobiles, and general household items.

[0053] Finally, the market for biodegradable plastics and composites is almost exclusively dominated by polyesters such as PLA, whose prices are still higher than traditional plastics. Incorporating large amounts of paper into PLA, as in the present method, can reduce the cost of the final product. Furthermore, if the paper used is paper or cardboard from industrial or domestic waste, or cellulose-rich waste from agriculture or food, blending with PLA is not only commercially attractive, but also allows for the recycling of waste materials, significantly reducing the disposal costs of those waste materials, consistent with modern principles of the circular economy.

[0054] The present invention will now be described in detail by the following non-limiting examples.

[0055] Example 1 Preparation and characterization of paper capsules The paper sheets obtained from the compression of softwood pulp were cut into rectangular strips of 5 cm x 10 cm and inserted between the metal plates of a punching machine, shown diagrammatically in Figure 1. The lower plate of this machine is equipped with holes of 5 mm diameter, while the upper plate is equipped with a cylindrical metal puncher of 3 mm diameter, which exerts mechanical pressure on the sheet, so that, with a downward movement, paper capsules of 3 mm diameter and 1 mm height are produced. The paper capsules so obtained were then collected in a tray, as shown in Figure 2.

[0056] The morphology of the paper sheets and capsules was characterized by scanning electron microscopy (SEM) using a JEOL JSM-6490LA microscope operating in high vacuum with an accelerating voltage of 10 kV. Prior to imaging, each sample was coated with a 10 nm thick layer of gold using a Cressington 208HR high resolution sputter coater (Cressington Scientific Instrument Ltd., UK). As shown in Figure 3, the paper capsules have a fibrous morphology (Figure 3b) similar to that of the starting paper sheets (Figure 3a).

[0057] To study their chemical structures, a spectrometer (Equinox 70 FT-IR, Bruker) connected to an attenuated total reflectance (ATR) accessory (MIRacle ATR, PIKE Technologies) was used to measure the 4 cm -1 Scan resolution of 4000-600 cm -1 FTIR (Fourier Transform Infrared Spectroscopy) spectra were acquired for both the starting paper sheet and the prepared paper capsules, accumulating 128 scans in the spectral range of 1000 nm and 1000 nm, respectively. The FTIR spectra, which show essentially the same absorption peaks, indicating similar chemical structures, are shown in Figure 4.

[0058] The thermal degradation profile shown in Figure 5 was then obtained by thermogravimetric analysis (TGA) (Q500, TA Instruments). 2 Atmosphere, temperatures ranging from room temperature to 600°C and 10°C min -1 At a heating rate of 50 ml min -1 The weight loss (Figure 5a) and its first derivative (Figure 5b) were simultaneously recorded as a function of time / temperature. Again, very similar thermal degradation profiles were obtained, with T deg was 355°C.

[0059] From the above experiments, it is evident that the resulting capsules have similar fiber morphology, chemical structure, and pyrolysis profile as the starting paper sheet, thus indicating that encapsulation, i.e., capsule formation, does not change the chemical and physical properties of the paper.

[0060] The same encapsulation method as above was also carried out starting with platano, coffee, pet food, and silicone coated paper capsules.

[0061] Example 2 Capsule composition Starting from the capsules obtained as described in Example 1 above, the formulations shown in Table 1 below were prepared by using PLA or a mixture of PLA and PBS as the thermoplastic polymer matrix.

[0062] [Table 1]

[0063] For each formulation in Table 1, at least 500 g was produced as follows: the polymer and capsules were first dried at 50 °C for 12 h to remove the moisture. In formulations 1, 2, 8, 9, 10, 12 and 13 after drying, the components were mixed manually and fed to the extruder. In formulations 3-5, 11 and 14-16, the powder was first dissolved in water and the solution so obtained was distributed to the paper capsules in a ratio such that 0.08-0.16 g of solution per gram of paper was obtained to allow impregnation of the paper with the solution. After drying at 50 °C for 12 h, the treated paper capsules were first mixed manually with the liquid additives, then mixed with the PLA in pellets and the solid additives, and subsequently the blend so obtained was fed to the extruder. In formulations 6 and 7, the additives were added to the dried paper capsules, then such capsules were mixed manually with the PLA and fed to the extruder.

[0064] FTIR spectra were recorded for paper capsules (PC), tannic acid (TA), and formulation No. 3 in Table 1, i.e., paper capsules treated with tannic acid (PC / TA), where the amount of TA in the final formulation was 5 wt% with respect to the total weight of PLA and PC. As shown in Figure 6, the CO stretching band of TA at 1189 to 1180 cm -1 and cellulose (3322 cm -1 ) and TA(3304cm -1 ) The OH stretching band is broader than both bands at 3325 cm -1 The shift towards the center indicates the presence of hydrogen bonding interactions between the two materials, cellulose and TA, and is therefore expected to improve the melt processability of the blends, stabilizing the cellulose in the hydrophobic polymer matrix, and against radical oxidation and thermal degradation.

[0065] Example 3 Extrusion of compounded capsules Extrusion of the blends of Table 1 in Example 2 above was carried out through a 6-zone twin screw extruder (Eurexma, Eurotech Extruders Srl) with a screw length to diameter (L / D) ratio of 14: 1. The extruder was equipped with a hopper for gravimetric feeding of materials.

[0066] For formulations 1, 3, 6, 7, 8, 11, 13, 15, and 16 in Table 1, the following conditions were used: -Feed rate: 2kg / h -Screw speed: 250-300rpm -T 1 =150-160℃, T 2 =155-160℃, T 3 =160-165℃, T 4 =160-165℃, T 5 =165-170℃, T 6 =165-170℃, Die:160-165℃. The following conditions were used for extrusion of formulations 2, 4, 5, 9, 10, 12, and 14 in Table 1: -Feed rate: 2kg / h -Screw speed: 250-300rpm -T 1 =130-135℃, T 2 =130-135℃, T 3 =130-135℃, T 4 =135-140℃, T 5 =140-145℃, T 6 =140-145℃, Die:130-135℃.

[0067] The extruded strands were then cooled in a water bath and introduced into a pelletizer to obtain pellets 4 mm long. Such pellets have a smoother surface and lighter color compared to non-functionalized paper, either in the silicone-coated wastepaper due to the layer of silicone acting as a stabilizer or by treating the paper with antioxidants, oils, waxes, GTA TEC, etc., used alone or in combination. A photograph of the extruded pellets is shown in Figure 7.

[0068] Example 4 Injection and Compression Molding The extruded pellets obtained in Example 3 were dried at 50° C. for 12 hours and then processed in an injection molding machine (Megatech H7 / 18, TecnicaDuebi Srl) equipped with a stainless steel mold to produce prismatic dog-bone shaped items (76×4×2 mm).

[0069] For formulations 1, 3, 6, 7, 8, 11, 13, 15, 16 in Table 1 above, and more generally for blends of PLA3052D and PLA2003D, the following conditions were used: Temperature: 160-170℃ Injection pressure: 140 bar Dose: 14mm For formulations 2, 4, 5, 9, 10, 12, 14 in Table 1 above, and more generally, any blend of PLA6302D, the following conditions were used: Temperature: 145-155℃ Injection pressure: 140 bar Dose: 18mm

[0070] The items so obtained exhibited homogenous color and smooth surfaces. As explained in Example 3 above, materials in which the paper was compatibilized before extrusion exhibited much lighter coloration (see Figure 8a, b, c).

[0071] Food colorants were added to the extruded biocomposite from formulation 5 by physically mixing the colorant powder with the pellets prior to the injection molding process, so that colored dog-bone shaped items and other objects were obtained (see Figure 8d). The amount of food colorant was 1 wt% with respect to the total weight of the pellets. The objects include spoons, rings, cups that can be used as disposable cutlery, packaging materials for food and cosmetics, heat-sealable reinforcements for glass, etc. (see Figure 8e, f).

[0072] Alternatively, the extruded pellets were also processed by compression molding using a hot press (Carver 4386, Carver, Inc.). 7.5 g of extruded pellets were heated as in Example 3 above at 145 °C for PLA6302D-based composites, or at 165-170 °C for PLA3052D- and PLA2003D-based composites for 5 min, followed by 10 tons of pressure for 5 min, and finally cooled at room temperature, resulting in films with thicknesses ranging from 400 to 500 μm.

[0073] Example 5 Morphology of biocomposite materials The morphology of the extruded pellets obtained from Formulations 2 and 5 in Table 1 above, and the fracture surface morphology of the dog-bone shaped samples obtained from Formulations 1 and 3 in Table 1, were characterized by scanning electron microscopy (SEM) performed as described in Example 1 above.

[0074] The cellulose fibers of paper in the biocomposites, both in the pellets and the dog-bone shaped items, are well dispersed and completely coated by the PLA polymer matrix, as shown in Fig. 9. The pellets in which the paper was treated with CA and GTA or TA (formulations 3, 5) showed a more compact and less rough morphology (see Fig. 9b, d) compared to the samples with untreated paper (formulations 1, 2) (see Fig. 9a, c).

[0075] Furthermore, the biocomposite pellets and dog-bone paper obtained from formulations 1 and 3 in Table 1 above were extracted by precipitation in chloroform and purified by filtration under vacuum. The obtained powders were subjected to chemical, morphological and pyrolysis analysis. The SEM micrographs in Figure 10a show that in both materials, the cellulose fibers are micronized upon melt compounding during extrusion and injection molding. Furthermore, since negligible differences were observed in the FTIR spectra and the pyrolysis profile of the cellulose powder compared to the original paper capsules (see Figure 10b, c, d), it can be concluded that cellulose does not undergo substantial thermal or chemical degradation during processing to obtain the biocomposite of the present invention.

[0076] Example 6 mechanical properties The mechanical properties of some representative biocomposites were studied and the results are reported in Table 2 below. Such properties were determined by uniaxial tensile tests on a dual column universal testing machine (Instron 3365) equipped with a 500 N load cell. The measurements were carried out in controlled environmental conditions (T = 21 °C, relative humidity 45%) on prismatic dog-bone shaped specimens (gauge length 35 mm, width 4 mm) obtained by injection molding as described in Example 4 above. The specimens were stretched for 5 mm min until fracture occurred. -1 The specimens were strained at a rate of 0.01 mm. The Young's modulus, ultimate tensile strength (UTS), and elongation at break values ​​were calculated as the average of 10 different samples. All values ​​were normalized by the thickness of the respective sample.

[0077] [Table 2]

[0078] In all tests tested, a significant improvement in Young's modulus was observed with respect to pure PLA, with variations of up to 45%, 31%, and 41% observed for PLA3052D-, PLA6302D-, and PLA2003D-based formulations, respectively.

[0079] The UTS is comparable to the values ​​of pure PLA for most materials. The composites PLA3052D-CP-SA and PLA2003D-PC showed a rather high UTS. In other cases, when using cellulose capsules, such as coffee, banana pulp, and pet food, instead of paper capsules, the UTS decreased from 51 to 34 MPa. However, the aforementioned UTS values ​​are even higher or similar compared to other non-biodegradable polymers used in packaging, such as polyethylene (15 MPa), polypropylene (40 MPa), and polystyrene (40 MPa). In all tested materials of the present invention, the elongation at break was found to be lower than pure PLA, as is generally expected from cellulose composites. However, when cellulose is compatibilized with TA, SA, or presented with a silicone coating, such a decrease is only 25% compared to the 50% variation seen in biocomposites where cellulose is not functionalized.

[0080] Example 7 Rheological properties The rheological curves of the extruded pellets in Table 3 below were obtained at 145°C via a capillary rheometer (CEAST SR20, Instron). Prior to testing, the pellets obtained as above in Example 3 were dried at 50°C for 12 hours. For the measurement of shear viscosity, typically 50 g of pellets were introduced into the barrel of the rheometer (working length = 290 mm) and the piston moved the material from 0 to 4000 s. -1 The mixture was forced into a capillary die (length = 20 mm, diameter = 1 mm) at shear rates in the range of 0.1 to 1.0 mm.

[0081] [Table 3]

[0082] The biocomposites tested ranged from 100 to 1000s -1 It showed higher shear viscosity at low shear rates in the region of 100–4000 s compared to pure PLA. -1 ) showed significantly higher shear stress. These values ​​were observed to increase with the amount of paper in the material, for example from 40 wt% to 50 wt%. The addition of a plasticizer such as GTA reduces the shear viscosity and shear stress to values ​​similar to PLA.

[0083] The melt flow rates (MFR) of the samples in Table 4 below were determined at 210°C according to ASTM D1238 B. 6-8 g pellets extruded as described in Example 3 were typically introduced into the barrel of a melt flow indexing machine (Instron MF-20). A 2.16 kg weight was then added to the piston, forcing the material down a length of 25.4 mm. The weight of the strand collected from the 2.095 mm diameter die was measured to determine the density (d) of the melt and the relative melt flow rate (MFR) from the measured melt volume rate (MVR) according to the following equation 1: MFR = MVR d (1)

[0084] [Table 4]

[0085] The tested biocomposites showed MFR values ​​of 10-20 g / 10 min, much lower than extruded PLA. The MFR was found to decrease with increasing amounts of paper, for example from 30 to 40 wt%. MFR values ​​in this range are versatile and are used especially for extrusion and injection molding. The addition of SA and TA was found to result in a very high MFR compared to formulations using only PLA and PC. The obtained values ​​of 44.86 ± 2.23 g / 10 min and 79.75 ± 3.23 g / min make these materials suitable for melt methods requiring high flow rates, such as fiber melt spinning.

[0086] Example 8 Oxygen Barrier Properties Oxygen permeation tests were performed on the films described in Example 4 above and reported in Table 5, using an Oxysense® 5250i device (Oxysense®, USA) equipped with a film permeation chamber, according to ASTM method F3136-15 (ASTM 1989). The tests were performed under standard laboratory conditions, i.e., a temperature of 23 °C and 50% relative humidity. The permeation chamber consisted of a cylinder divided into two parts (sensing well and driving well). The sensing well was equipped with a fluorescent sensor called Oxydot®, which is sensitive to oxygen concentration. This chamber was purged with nitrogen, while the other chamber (fully driving) was left open to the surrounding air. The film obtained according to Example 5 was cut into rectangular pieces (6 cm x 6 cm) and placed in the chamber. An OxySense® fiber optic pen measures the oxygen readings from the Oxydot® at specific time intervals. The oxygen transmission rate (OTR) of each film was measured by monitoring the oxygen uptake over time. The Oxysense® OTR software used this oxygen evolution to determine the OTR of the film. The minimum coefficient of determination (R 2 ) value was 0.95 and at least five readings were taken for each sample. The oxygen permeability of the films was then calculated according to Equation 2: OP=OTR·Ft (2) Here, OP is oxygen permeability, OTR is oxygen transmission rate, and Ft is membrane thickness.

[0087] [Table 5]

[0088] A 40–80% reduction in oxygen permeability was observed in the biocomposites compared to pure PLA, indicating that the incorporation of paper via the method of the present invention significantly enhances the oxygen barrier properties of the material.

[0089] Example 9 heat resistance Heat resistance was evaluated in terms of deformation of a dog-bone shaped sample after immersion in 90°C water.

[0090] [Table 6]

[0091] The biocomposite of the present invention does not bend or deform when immersed in boiling water, representing a significant improvement over the poor heat resistance of PLA alone.

[0092] Example 10 biodegradable The biodegradability of the biocomposite of the present invention was evaluated by a standard biochemical oxygen demand (BOD) test by measuring the amount of oxygen consumed during biodegradation. 200 mg of each sample pellet was immersed in a 432 mL bottle containing seawater. Oxygen consumption was monitored for 30 days by the sealed OxyTop cap of each bottle. For reference, the BOD of a blank bottle filled with seawater only was also measured.

[0093] [Table 7]

[0094] As shown in Table 7, PLA alone did not undergo biodegradation, but for the inventive composites of the present invention (numbers 2 and 3 in Table 7 above), the BOD values ​​and onset of degradation were similar to those seen for pure paper, indicating that the incorporation of paper results in better biodegradability and faster biodegradation rates.

[0095] Example 11 Comparative study - Evaluation of the effectiveness of fillers In order to achieve comparative data with prior art such as WO2019 / 055921, the effect that fillers may have in formulations such as the present invention is evaluated in the experiments described below, which disclose materials consisting of fillers and cellulose pulp fibers dispersed in a thermoplastic polymer matrix. The term "fillers" refers to fiberglass, minerals (mica, talc, clay, basalt, calcium carbonate, wollastonite, etc.), polymers with a higher melting point than the thermoplastic matrix (such as polyvinyl alcohol and nylon), and lignocellulosic materials.

[0096] According to WO2019 / 055921, if glass fibers are used as a filler, the amount must be at least 2% by weight. For other fillers, no indication of their content is provided. The composite material of WO2019 / 055921 may contain one or more additives selected from the group of lubricants, acid scavengers, compatibilizers, coupling agents and impact modifiers. In certain embodiments, the composite material contains no more than 2% by weight of additives. In others, it contains no more than 20% by weight of additives.

[0097] Starting with the same formulations as in Table 1 above, the formulations in Table 8 below were prepared by physically mixing the indicated materials and subsequently feeding the resulting mixture into a twin-screw extruder. Processing conditions were T=165-170°C, screw speed=300 rpm for formulations 1-7, and T=135-145°C, screw speed=300 rpm for formulation 8. The extruded pellets were further processed by injection molding at 155-160°C to obtain dog-bone shaped specimens. Formulations 1 and 2 in Table 8 are part of the present invention, the others are comparative formulations and are included in the claims of WO2019 / 055921.

[0098] [Table 8]

[0099] Inventive formulations 1 and 2, which lack the presence of fillers, showed good processability by extrusion. The resulting pellets and dog bones are light in color and homogeneous (Figure 12a, b).

[0100] In contrast, Comparative Formulations 3 and 4 were not suitable for extrusion due to agglomeration induced by either the PVA or the glass fiber filler, respectively, as shown in Figure 13a, b. No material could be collected by extrusion of Comparative Formulation 3, while only a few grams of dark pellets could be produced using Formulation 4 (see Figure 13c).

[0101] Comparative formulations 5-8 in Table 8 above containing different amounts of clay filler could be extruded and further processed by injection molding. However, the resulting pellets and dog bones appeared much darker in color than the samples without filler, probably due to degradation (Figure 14a-d). Such effects were observed at relatively low (0.5 wt%) and high (5 wt%) clay (CL) concentrations, with both types of clay, at different processing temperatures (135-145 and 165-170 °C), and when different amounts of additive from 2 to 7 wt% were used.

[0102] Table 9 below summarizes the mechanical properties of injection molded dog-bone shaped specimens for inventive Formulations 1 and 2, and comparative Formulations 5-8 which contain fillers.

[0103] [Table 9]

[0104] As shown in Table 9, the incorporation of clay even at an amount of 0.5 wt% had a dramatic effect on the Young's modulus of the material. The ultimate tensile strength (UTS) and elongation at break did not change significantly with respect to the composites without clay of the invention, but the higher standard deviation of the comparative formulations indicates that the cellulose and fillers are not uniformly distributed. This effect is more evident at a clay content of 5 wt%, where the standard deviation of the elongation at break reaches a value of ±6. Moreover, in said composites, the UTS and Young's modulus are reduced by 15% and about 9%, respectively, compared to the same formulations without clay according to the invention. Moreover, the comparative samples with clay also showed less homogeneity and lower mechanical properties compared to the specimens of the invention with a higher loading of cellulose fibers (30 wt%).

[0105] These results indicate that the incorporation of fillers into PLA / PC composites has a detrimental effect on the melt processing of the material during extrusion, on the dispersion of the components within the thermoplastic blend, and on the color and mechanical properties of the resulting composites.

[0106] Example 12 Comparative study - evaluation of the effect of drying before extrusion Two formulations were prepared containing PLA 2003D, paper capsule (PC), citric acid (CA), glycerol triacetate (GTA), and bio-based wax (BW) in the following ratios of 53.5%, 40%, 0.5%, 3%, and 3% by weight, respectively. These mixtures were dried at 50°C. Prior to extrusion, 4.7% by weight of water was added to only one of the formulations, so that the exact amount of moisture in the sample was known, while the other formulation was kept dry. Extrusion was performed at 165-170°C with a screw speed of 300 rpm. Injection molding was performed at 160°C. Samples that were dried before extrusion appeared lighter in color and the extrusion process was continuous (Figure 15a). Conversely, the darker color of both pellets and dog bones extruded in the presence of moisture (Figure 15b) indicates that a degradation process occurred during extrusion. Furthermore, moisture promoted the formation of air bubbles, which increased the pressure at the die and made the extrusion process non-continuous.

[0107] Table 10 below shows the mechanical properties of injection molded dog bones for samples that were dried prior to extrusion and samples that contained 4.7% moisture (wet) by weight.

[0108] [Table 10]

[0109] The decrease in mechanical properties coupled with the higher standard deviation of the wet samples compared to the dry samples prepared according to the method of the present invention indicates a less uniform distribution of cellulose in the material and a limited reinforcing effect probably due to degradation phenomena occurring in the presence of moisture in the extruder.

[0110] Example 13 Comparative study - Evaluation of the effect of using capsules instead of milled material on the mechanical properties of composites Composites based on PLA3052D and millimeter capsules according to the invention, as well as composites based on PLA4032D and pulverized paper according to what is disclosed in the state of the art (WO2015 / 048589), and composites based on cellulose fibers and PLA from newspapers and kraft paper as described in the state of the art by Huda et al. [3] were prepared. In parallel, the respective pure PLA was also tested. In the following Table 11, the mechanical properties found in the tested products are reported, and the variation of the composites with respect to the pure PLA is also shown.

[0111] The results thus obtained, prepared according to the latest reference WO2015 / 048589, for PLA composites containing 30% pulverized paper, show an improvement of 25% in Young's modulus with respect to the corresponding pure PLA, but a worsening of 9.6% and 60% in ultimate tensile strength (UTS) and elongation at break, respectively. Moreover, always in table 11, the results are reported that for the composites of the state of the art represented by Huda et al. [3] and containing cellulose microfibers TC1004, the ultimate tensile strength is significantly lower for the composites than the corresponding pure PLA, being 24.8% and 37.3%, respectively, and significantly lower than the composites of the invention containing the same amount of cellulose volume in the form of millimeter capsules. For these composites containing cellulose fibers, a very high Young's modulus was also measured, so that materials made of such composites are very stiff and unsuitable as a replacement for plastic materials. Also, the elongation at break measured for these composites with respect to pure PLA is much worse than that measured for the composites of the invention.

[0112] In fact, for composites prepared by the method of the present invention and containing 30% by weight of paper millicapsules, a 30% improvement in Young's modulus, a 1.6% improvement in ultimate tensile strength, and only a 27.6% reduction in elongation at break were observed, relative to pure PLA. These properties are clearly superior to those exhibited by state-of-the-art composites, even at much higher paper loads. For example, composites containing 50% by weight of the paper millicapsules of the present invention have a 44% increase in Young's modulus, a 10% increase in ultimate tensile strength, and a 50% reduction in elongation at break, relative to pure PLA, with much better general mechanical performance.

[0113] [Table 11]

[0114] Example 14 Comparative study - Evaluation of the effect of using capsules instead of pulverized material on the thermal properties of composites Composites based on PLA3052D and millimeter capsules according to the invention, as well as PLA and cellulose fibers derived from newspapers and kraft paper as described in the technical standard by Huda et al. [3], were prepared. In parallel, the respective pure PLA was also tested. In the following Table 12, the results of the thermogravimetric analysis carried out on these tested materials are reported, which, in addition to the values ​​found, also show the variability of the composites with respect to the pure PLA. In particular, in the following Table 12, the T 25 , T 50 , and T 75 are reported, i.e., the temperatures at which 25%, 50%, and 75% weight loss of the tested materials was observed.

[0115] All tested composites of the present invention with millimetric capsule contents of 30 wt%, 40 wt% and 50 wt% show a T 25 , T 50 and T 75The thermal degradation exhibited by composites known in the art containing cellulose microfibers is less than 5% lower than that of composites with 30% of the volume of cellulose fibers. Similar variations are shown for paper capsules not treated with PLA, indicating that the capsules undergo negligible conversion in the process of the present invention. In contrast, the thermal degradation exhibited by composites known in the art containing cellulose microfibers is less than 5% lower than that of composites with 30% of the volume of cellulose fibers. 75 The temperature value variation reaches 14%, which is significantly higher than that of pure PLA. Such high thermal degradation is not observed in starting cellulose fibers that have not been treated with PLA according to the methods described in the art. Without wishing to be bound by theory, the inventors believe that cellulose fibers are adversely affected by the long times and high temperatures of treating the fibers, as taught by the authors of [3].

[0116] [Table 12]

[0117] Although the present invention has been described above with reference to preferred embodiments thereof, there may be further embodiments, all falling within the same inventive core, as defined by the appended claims. In relation to the present invention, the following is further disclosed: [1] 1. A method for preparing a biodegradable composite material comprising a thermoplastic polymeric material and a cellulosic material, and optionally one or more additives, comprising: The method comprising the steps of: i) providing a cellulosic material in the form of millimeter-sized capsules, optionally pretreated with one or more additives, and a thermoplastic polymeric material, and drying them to remove moisture; ii) mixing said dry cellulosic material in the form of millimeter-sized capsules with a dry thermoplastic polymeric material to form a dry mixture in which said cellulosic material is at least 10% by weight based on the total weight of the mixture; iii) processing the mixture resulting from step ii) by melt extrusion at a temperature ranging from 130 to 170° C. to form extruded strands of said biodegradable composite material. [2] The method according to [1], wherein the capsule has a diameter of 3 mm and a height of 1 mm. [3] The method according to [1] or [2], further comprising a step of pelletizing the extruded strands of the biodegradable composite material, and optionally molding the pellets thus obtained by injection or compression molding at a temperature ranging from 140 to 170° C. to obtain the biodegradable composite material in the form of a molded article. [4] The method according to any one of [1] to [3], wherein the drying is carried out at a temperature in the range of 40 to 70° C. for a time in the range of 8 to 48 hours. [5] The method according to [4], wherein the drying is carried out at a temperature of 50° C. for 12 hours. [6] The method according to any of [1] to [5], wherein the amount of dry cellulosic material is comprised between 30 and 60% by weight, preferably between 40 and 50% by weight, relative to the total weight of the mixture. [7] The method according to any of [1] to [6], wherein the amount of the dry thermoplastic polymer material is in the range of 35 to 90% by weight, preferably 35 to 55% by weight, relative to the total weight of the mixture. [8] The method according to any one of [1] to [7], wherein the cellulosic material is selected from pure paper, waste paper, recycled paper, coated paper, cardboard, vegetable leaves, fruit pulp and skins, such as coffee husks and platano banana pulp, and pet food. [9] The method according to any one of [1] to [8], wherein the thermoplastic polymer material is selected from the group consisting of D-polylactic acid, L-polylactic acid, D,L-polylactic acid, meso-polylactic acid, and combinations thereof, optionally in combination with one or more polyesters selected from polybutylene succinate (PBS), polyhydroxyalkanoates (PHAs), polycaprolactone (PCL), poly(DL-lactide-co-glycolide) (PGLA), poly(dioxanone) (PDO), poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), poly(1,4-butylene adipate) (PBA), poly(butadiene adipate coterephthalate) (PBAT), poly(ethylene carbonate) (PEC), poly(propylene carbonate) (PPC), and mixtures thereof, and / or in combination with thermoplastic starch, polyethylene oxide, polyurethane, polyolefin, and mixtures thereof.

[10] The method according to any of [1] to [9], wherein the amount of the one or more dry additives is in the range of 0.1 to 15% by weight, preferably 0.5 to 5% by weight, relative to the total weight of the mixture.

[11] The method according to any of [1] to

[10] , wherein the one or more additives are selected from non-toxic natural and / or food contact approved plasticizers, lubricants, rheology modifiers, stabilizers, colorants, processing aids, gloss agents, antioxidants, and mixtures thereof.

[12] The method of claim 11, wherein the one or more additives are selected from compounds having carboxyl, hydroxyl and ester moieties.

[13] The method according to any of [1] to

[12] , wherein the melt extrusion in step iii) is carried out at a temperature in the range of 135 to 165°C.

[14] The method according to any of [1] to

[13] , wherein the molding is carried out at a temperature in the range of 145 to 165°C.

[15] The method according to any of [1] to

[14] , wherein the cellulosic material in the form of capsules is obtained by compressing the cellulosic material in the form of a sheet or strip between the plates of a punching machine.

[16] A biodegradable biocomposite material obtainable by the method according to any one of [1] to

[15] , comprising a thermoplastic polymer material and a cellulosic material, and optionally one or more additives, wherein the thermoplastic polymer material is a melt extruded matrix with at least 10% by weight of the cellulosic material in finely divided form, optionally comprising one or more additives, and wherein the cellulosic material is uniformly dispersed within the matrix.

[17] 16. The biodegradable biocomposite according to claim 15, wherein the amount of cellulosic material dispersed in the melt extruded matrix in finely divided form is 30-60% by weight, based on the total weight of the composite.

[18] Use of the biodegradable biocomposites described in

[16] -

[17] in the manufacture of food and cosmetic packaging, agricultural disposable items, pipelines and tubes, laminated paper, food trays, cutlery, brushes, combs, and toys.

[19]

[16] ~

[17] Molded articles made from biodegradable biocomposite materials.

[0118] Bibliographic references [Table 0]

Claims

1. 1. A method for preparing a biodegradable composite material comprising a thermoplastic polymeric material and a cellulosic material, and optionally one or more additives, comprising the steps of: The method comprising the steps of: i) providing a cellulosic material in the form of millimeter-sized cylinders, optionally pretreated with one or more additives, and a thermoplastic polymeric material, and drying them to remove moisture; ii) mixing said dry cellulosic material in the form of millimeter-sized cylinders with a dry thermoplastic polymeric material to form a dry mixture in which said cellulosic material is at least 10% by weight based on the total weight of the mixture; iii) processing the mixture resulting from step ii) by melt extrusion at a temperature ranging from 130 to 170° C. to form extruded strands of said biodegradable composite material.

2. 2. The method of claim 1, wherein the cylinder has a diameter of 3 mm and a height of 1 mm.

3. 3. The method according to claim 1 or 2, further comprising a step of pelletizing the extruded strands of the biodegradable composite material, and optionally molding the pellets so obtained by injection or compression molding at a temperature ranging from 140 to 170°C to obtain the biodegradable composite material in the form of a molded article.

4. A method according to any one of claims 1 to 3, wherein the drying is carried out at a temperature of from 40 to 70°C for a time period of from 8 to 48 hours.

5. 5. The method of claim 4, wherein the drying is carried out at a temperature of 50° C. for 12 hours.

6. 6. The method according to any one of claims 1 to 5, wherein the amount of dry cellulosic material is comprised between 30 and 60% by weight with respect to the total weight of the mixture.

7. 6. The method according to any one of claims 1 to 5, wherein the amount of dry thermoplastic polymeric material is in the range of 35 to 90% by weight, based on the total weight of the mixture.

8. 8. The method according to any one of claims 1 to 7, wherein the cellulosic material is selected from pure paper, waste paper, recycled paper, coated paper, cardboard, vegetable leaves, fruit pulp and skins, such as coffee husks and platano banana pulp, and pet food.

9. 9. The method of any one of claims 1 to 8, wherein the thermoplastic polymeric material is selected from the group consisting of D-polylactic acid, L-polylactic acid, D,L-polylactic acid, meso-polylactic acid, and combinations thereof, optionally in combination with one or more polyesters selected from polybutylene succinic acid (PBS), polyhydroxyalkanoates (PHAs), polycaprolactone (PCL), poly(DL-lactide-co-glycolide) (PGLA), poly(dioxanone) (PDO), poly(hydroxybutyrate-cohydroxyvalerate) (PHBV), poly(1,4-butylene adipate) (PBA), poly(butadiene adipate coterephthalate) (PBAT), poly(ethylene carbonate) (PEC), poly(propylene carbonate) (PPC), and mixtures thereof, and / or in combination with thermoplastic starch, polyethylene oxide, polyurethane, polyolefin, and mixtures thereof.

10. 10. The method according to any one of claims 1 to 9, wherein the amount of the one or more dry additives ranges from 0.1 to 15% by weight relative to the total weight of the mixture.

11. 11. The method of any one of claims 1 to 10, wherein the one or more additives are selected from non-toxic natural and / or food contact approved plasticizers, lubricants, rheology modifiers, stabilizers, colorants, processing aids, gloss agents, antioxidants, and mixtures thereof.

12. The method of claim 11 , wherein the one or more additives are selected from compounds having carboxyl, hydroxyl and ester moieties.

13. 13. The method according to any one of claims 1 to 12, wherein the melt extrusion in step iii) is carried out at a temperature in the range of 135 to 165°C.

14. A method according to any one of claims 1 to 13, wherein the forming is carried out at a temperature in the range of 145 to 165°C.

15. 15. The method according to any one of claims 1 to 14, wherein the cellulosic material in the form of a cylinder is obtained by compressing the cellulosic material in the form of a sheet or strip between the plates of a die cutter.

16. A biodegradable biocomposite material obtainable by the method according to any one of claims 1 to 15, comprising a thermoplastic polymeric material and a cellulosic material, and optionally one or more additives, said thermoplastic polymeric material being a melt extruded matrix with at least 10% by weight of cellulosic material in finely divided form, optionally comprising one or more additives, said cellulosic material being homogeneously dispersed within said matrix.

17. 17. The biodegradable biocomposite of claim 16, wherein the amount of cellulosic material dispersed in finely divided form in the melt extruded matrix is ​​30-60 wt. % based on the total weight of the composite.

18. Use of the biodegradable biocomposite material according to any one of claims 16 to 17 in the manufacture of food and cosmetic packaging, agricultural disposable items, pipelines and tubes, laminated paper, food trays, cutlery, brushes, combs and toys.

19. A molded article made from the biodegradable biocomposite material according to any one of claims 16 to 17.

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