Bioplastic offering rapid biodegradation, made from grasses and non-woody green waste, and its manufacturing protocol

Abstract

The field of the invention is that of bio-based polymers and biodegradable bioplastics. The invention relates to the creation of a bioplastic that decomposes in a few days in an uncontrolled natural environment, made in particular from grasses and non-woody green waste, and possessing mechanical characteristics similar to petrochemical-based plastics. The invention also proposes a protocol for manufacturing this bioplastic from natural materials and easily neutralizable chemicals. The protocol consists in particular of several successive solid-liquid extractions of lignocellulosic compounds from biomass in order to obtain the cellulose necessary for manufacturing the bioplastic. The cellulose is used as a filler to reinforce the bioplastic made from a starch matrix and a plasticizer such as glycerin.This patent highlights the ease of disposal of the invention once it is classified as waste. This invention aims to address the problems associated with the overproduction of difficult-to-recycle plastics, particularly through its rapid and environmentally friendly decomposition. The bioplastic according to the invention is specifically designed for use in packaging, as protection for the service industry, or as single-use bags due to its rapid decomposition. The bioplastic according to the invention is also intended for use in the manufacture and protection of consumer goods.

Description

Title of the invention: Bioplastic offering rapid biodegradation, manufactured from grasses and non-woody green waste, and its manufacturing protocol Technical field

[0001] The field of the invention is that of bio-sourced and biodegradable polymers. The invention relates in particular to a bioplastic, offering rapid biodegradation and mechanical characteristics similar to existing petrochemical plastics, manufactured from a protocol employing in particular grasses and green waste. The invention also includes the manufacturing protocol of said bioplastic and different variations of this protocol. Prior art

[0002] The advantages of plastic are unmatched when compared with those of any other material used in areas such as packaging, insulation or the manufacture of objects intended for mass consumption. Plastics are lightweight and do not react when brought into contact with most organic and inorganic solvents. Their manufacturing costs are low, while maintaining good mechanical characteristics.

[0003] The majority of plastics currently used are made from fossil fuels (or hydrocarbons). These have the disadvantage of being difficult to recycle, in addition to causing increased risks of cancer and disease to living beings exposed to them for a long time. Their difficult decomposition combined with imperfect plastic waste management has led to an overabundance of plastic residues in urban areas and in nature, causing significant ecological problems for both fauna and flora. In France, plastic waste management is done through recycling, combustion (with or without energy recovery) and burial in landfills. According to a study carried out in 2020 by PlasticsEurope, recycling only concerns 24.2% of plastic waste in France, 32.5% is sent to landfills, while 43.3% is incinerated.Although the share of recycled waste tends to increase (+6.8% between 2016 and 2018), a very significant share is still not revalued.

[0004] An alternative to this problematic situation is the substitution of plastics made with fossil components with plastics of biological origin, otherwise known as bioplastics. The bioplastic currently in majority in the industry is polylactic acid (PLA), which is a bio-sourced polymer and Compostable made from corn. These bioplastics aim to stand out, in particular, thanks to their improved biodegradability and renewability. However, bioplastics tend to release methane gas during decomposition, particularly when they are disposed of in landfills. Methane emissions occur particularly in anoxia (absence of oxygen), which is most often the case in landfills.

[0005] Bioplastics are materials manufactured by following a generic structure: a polymer or resin (also called a base or matrix) is mixed with one or more fillers (a substance that modifies the mechanical properties of the polymer) and a plasticizer (a substance that causes the polymer to transform into plastic). Many variations of this structure exist, and some of them have already been patented. A first international patent WO 2020115619, for example, chooses a bioplastic made from 4 to 10% agarose, a polymer obtained from algae, silica and sodium lauryl sulfate, a vegetable oil derivative. A second example is international patent WO 2018021980, which proposes a bioplastic made from 60 to 100% of a mixture of PLA and PBS (polybutylene succinate, a thermoplastic resin), and which chooses to integrate an additive derived from coffee cultivation.A third European patent EP 3305855 proposes to use wheat bran, a residue from grinding the cereal, up to 30% of the mass of the bioplastic.

[0006] Scientific research has also focused on bioplastics. A prime example is the article “Isolation, preparation and characterization of cellulose microfibers obtained from bagasse” by Bhattacharya et al. This article focuses on the best method for extracting and preparing cellulose in the form of microfibers obtained from sugarcane residues. These microfibers can be used as reinforcement for composite materials. A second article entitled “Corn and Rice Starch-Based Bio-Plastics as Alternative Packaging Materials” by Marichelvam et al. explains that the authors worked on the production of a bioplastic made from rice and corn starch, and succeeded in obtaining a material with good tensile strength. The article “Current Trends in the Production of Cellulose Nanoparticles and Nanocomposites for Biomedical Applications”, written by Rojas et al.chooses to focus on the different protocols for producing cellulose nanoparticles (fibers with a diameter between two and twenty nanometers) as well as their applications in the biomedical field.

[0007] The field of bioplastics is particularly innovative with regard to the reuse of organic matter as filler or matrix. In addition to offering a certain economic advantage due to the reuse of organic waste (having a low or even zero unit value), bioplastics can create a circle virtuous with individuals and industrialists wishing to get rid of their waste. This organic matter can then be used in the manufacture of bioplastics from which these same individuals and industrialists can thus benefit. Description of the invention

[0008] In order to address the issues mentioned above, the invention aims to achieve at least one of the following goals: • The invention aims to solve the technical problem of overproduction of plastic waste by manufacturing a bioplastic that can biodegrade naturally in a few days without having to be industrially composted. • The invention also aims to propose a material meeting the needs of industry, and in particular the needs for single-use or short-life plastics, with mechanical properties similar to alternatives of petrochemical origin. • The invention also aims to provide a cellulose-based material enabling the manufacture of a varied range of products with adaptable properties. • The invention also aims to propose a protocol allowing the manufacture of the bioplastics mentioned in the previous objectives. Summary of the invention

[0009] This invention is based on the manufacture of a bioplastic having as raw materials grasses and non-woody green waste (the following plants are grouped under this name, within the framework of this invention, among others: dead leaves, grass cuttings, weeds, faded flowers). These act as a filler to reinforce the mechanical characteristics of the manufactured polymer. One of the particularities of this invention is the indifferent use of several plants as a source of cellulose. A second component, glycerin, is also used in order to modify the elasticity of the material. Glycerin is a by-product of the transformation of vegetable oils and fats, and is therefore also of natural origin. According to a preferred possibility, the bioplastic matrix is ​​produced from starch derived from wheat flour.

[0010] Grasses and green waste are not used directly. It is necessary first to extract their various components; cellulose being in particular the substance of interest. Nevertheless, one of the particularities of this invention is to offer the possibility of extraction in several stages, offering the possibility of recovering all the extractables from the grasses and green waste. These extractables, in addition to the cellulose previously mentioned, are lignin and hemicellulose (which in turn three form the lignocellulosic components of green waste). This invention therefore emphasizes the recovery and reuse as raw materials of the main constituents of grasses and green waste. The bioplastic according to the invention therefore allows significant economic gains through the reuse of waste, an inexpensive raw material.

[0011] The bioplastic according to this invention is obtained via molding in order to obtain bioplastic sheets, which can subsequently be machined according to the user's needs. According to one possibility, the bioplastic sheets obtained by following the protocol detailed below can then be thermoformed. The bioplastic according to the invention is semi-transparent, flexible, ductile, smooth, with a thickness of less than 1 millimeter, and a surface mass of between 80 grams per square meter and 200 grams per square meter.

[0012] In addition, the bioplastic according to the invention also has the advantage of being able to biodegrade completely in a few days once buried, while not requiring industrial composting.

[0013] This invention is intended to be innovative, particularly in its consideration of the environmental impacts attributable to the different phases of the life of the manufactured bioplastic. Particular attention has been paid to the use of chemical reagents that can easily be neutralized during manufacturing in order to be safe at the end of life of the bioplastic according to the invention. Due to its composition, the bioplastic according to the invention does not pollute the soil and water in which it decomposes. Incineration of the bioplastic according to the invention can also be considered, since the particles emitted during its combustion contain very few harmful elements, given the sole presence of raw materials of natural origin in the material.The bioplastic according to the invention therefore has the characteristic of not being toxic for the environment at the end of its life (whether during its biodegradation, its incineration or during its recycling).

[0014] This invention is also based on the protocol for manufacturing bioplastic using the components mentioned above. This protocol is broken down into two main stages: the extraction and purification of the components of grasses and green waste on the one hand, and the manufacturing of bioplastic on the other hand. Brief description of the figures

[0015] [Fig-1] Graph describing the evolution of the mass of the bioplastic according to the invention (in percentage) as a function of the duration for which it was buried (in days). The evolution of the mass is described via the percentage of mass lost compared to the initial mass of the bioplastic. The percentage evolves up to 100% loss of mass (which therefore corresponds to the complete degradation of the bioplastic according to the invention) after approximately 10 days.

[0016] [Fig.2] Graph describing the reaction of the bioplastic according to the invention when it is subjected to a tensile test. This curve plots the elongation of the material (dimensionless) as a function of the stress exerted (in megapascals). Also graphically represented on this curve are the value of the elastic resistance of the bioplastic (oE, stress from which the material undergoes irreversible deformation), the tensile strength (oA, highest stress supported by the material), the elongation of the elastic resistance (eE, value of the elongation when the elastic resistance is reached) and the maximum elongation (emax, value of the elongation of the material after rupture).

[0017] [Fig.3] Graph comparing the tensile tests of the bioplastic according to the invention and a bioplastic based on wheat flour starch without added cellulose, and plotting the elongation of the two materials (dimensionless) as a function of the stress exerted (in megapascals). These curves make it possible to highlight the differences in the mechanical characteristics between the two materials, and in particular to present the advantages of the invention.

[0018] [Fig.4] Graph describing the absorption capacities of bioplastic according to the invention after immersion in water. The curve relates the mass gain of the material (in percentage) as a function of the time immersed (in minutes). After a rapid increase in mass (an increase of almost 200% of its initial mass in approximately 5 minutes), the bioplastic according to the invention reaches a water saturation corresponding to a mass gain of 320% after 90 minutes of immersion.

[0019] [Fig.5] Graph describing the mass loss of the bioplastic according to the invention (in percentage) after immersion in water for a variable duration (in minutes). The curve shows a mass loss of almost 20% from the first minutes of immersion, and almost 50% of the mass of the bioplastic is lost after immersion for at least 50 minutes.

[0020] [Fig.6] Graph describing the evolution of the mass of the bioplastic according to the invention (in percentage) when the material is immersed in water (in minutes). [Fig.6] considers both the mass gain due to liquid absorption ([Fig.4]) and the mass loss due to material degradation by water ([Fig.5]). The bioplastic reaches a maximum mass after about 30 minutes of immersion (mass increase of about 150%) before gradually decreasing. Detailed description

[0021] This invention patent proposes a bioplastic that is at least partially biosourced and biodegradable, comprising in particular starch, cellulose and glycerin, and a protocol for its manufacture. Starch is preferably sourced from wheat flour. Alternatively, the starch required for this protocol can be sourced, in part or entirely, from cereals, corn, potatoes, rice, cassava, or any other source, depending on whichever source is most readily available locally. Cellulose comes from biomass, preferably composed of grasses that have been mowed and considered organic waste. Biomass can also be composed, in whole or in part, of non-wood green waste (wood green waste is not considered due to its lower cellulose composition). Glycerin is the preferred plasticizer, but this can be chosen from esters, glycerin esters, esters based on vegetable oils, esters based on polyols of vegetable origin or modified vegetable oils. The present invention provides a generic protocol that can be adapted to different biomass dry mass by proportionally modifying the volumes and masses of the components and reactants.

[0022] Briefly, the manufacturing process is defined as follows: 1. Washing the selected biomass with water, followed by air drying. The washed and dried biomass is then ground to obtain particles with a diameter of approximately 1 millimeter. 2. Successive treatments of the biomass with a sodium hydroxide solution followed by vacuum filtration. The sodium hydroxide solution used in the successive treatments of the biomass has a molar concentration of 0.5 moles per liter and is heated to 60°C for 2 hours under magnetic stirring. 3. Treatment of the biomass with a hydrogen peroxide solution, having a pH close to 11, at room temperature for 24 hours, followed by vacuum filtration 4. Treatment of biomass with hydrochloric acid solution followed by vacuum filtration. The hydrochloric acid solution used in the treatment of biomass is heated for 40 minutes at 80°C under magnetic stirring. 5. Production of a preparation consisting of a homogenization comprising a matrix, a plasticizer and the cellulose from the previously treated biomass. This preparation consists of a homogenization of the matrix and the plasticizer under magnetic stirring, with a temperature minimum of 85°C, for a period of 60 minutes, then the incorporation and homogenization of the cellulose. 6. Molding and drying of the preparation. The mold used is preferably made of silicone, and drying is carried out in the open air or in a desiccator until the mass of the bioplastic no longer varies.

[0023] In more detail, the manufacturing process is defined as follows:

[0024] The first part of the protocol corresponds to the cleaning and preparation of the biomass. This part is necessary in order to eliminate impurities that may be present in or on the biomass before the extraction of the cellulose in order to ensure that a pure final product is obtained. - Step 1: The biomass is first washed with undistilled water to remove any residue left on the surface of the plant when it was cut. - Step 2: The washed biomass is dried for 24 hours at room temperature. - Step 3: The dried biomass is ground to particles with a diameter of approximately 1 millimeter. The biomass is then weighed. The resulting mass will subsequently be referred to as “initial biomass mass” or “grams of initial biomass.”

[0025] The second part of the protocol corresponds to the pretreatment of the biomass and the extraction of the cellulose. - Step 4: The biomass is added to a solution of 50 milliliters of sodium hydroxide (chemical formula NaOH) per gram of initial biomass, diluted to 0.5 moles per liter, and is heated to 60°C for two hours with magnetic stirring. - Step 5: The mixture is then filtered under vacuum, and is washed with distilled water until the filtrate obtained has a neutral pH. - Step 6: The operation is repeated three more times to ensure complete dissolution of the lignin and hemicellulose in the biomass.

[0026] Pretreatment using a sodium hydroxide solution has the effect of causing delignification of the lignocellulosic biomass by breaking the bonds between lignin and hemicellulose, before causing solubilization of the lignin. It is thus at this stage that recovery of the lignin is possible, since it has been solubilized in the solvent during the alkaline pretreatments. The sodium hydroxide solution also has the particularity of causing swelling of the cellulose fibers, thus increasing their availability. - Step 7: The recovered substrate is added to a solution of 25 milliliters of hydrogen peroxide (chemical formula H2O2) per gram of biomass initial, diluted to 6%, while maintaining the pH at a value close to 11 for 24 hours at room temperature in order to bleach the cellulose. - Step 8: The solution is filtered under vacuum and washed thoroughly with distilled water.

[0027] Steps 7 and 8 are repeated until the cellulose turns white. Alternatively, the hydrogen peroxide solution is kept at 100°C for 40 minutes, while maintaining a pH close to 11. - Step 9: Acid hydrolysis is carried out by incorporating the dry matter into a solution containing 0.1 mole of hydrochloric acid (chemical formula HCl) per gram of initial biomass, for 40 minutes at 80°C with magnetic stirring.

[0028] Step 9 allows the degree of polymerization of the cellulose to be reduced, which corresponds to reducing the size of the cellulose chains in order to weaken its crystalline structure. It is also at this step that the hemicellulose is solubilized, and can be recovered. - Step 10: The solution is filtered under vacuum, and the substrate is washed thoroughly with distilled water until a neutral pH is reached. - Step 11: In a preferred case, the substrate is placed in a centrifuge for 10 minutes at 6000 rpm. The cellulose particles are then recovered by separating them from the supernatant.

[0029] The third part of the protocol corresponds to the neutralization of the hydrochloric acid and sodium hydroxide filtrates.

[0030] One of the most important aspects to ensure the viability of this invention from an ecological point of view is the harmfulness of the products used during its manufacture. Two products in particular can pose such problems: hydrochloric acid and sodium hydroxide. However, these two products have the particularity of neutralizing each other, since their reaction leads only to the formation of water, salt and heat. It is partly for this reason that they were selected within the framework of this protocol. To facilitate the management of this waste, it is possible to accurately calculate the amount of material involved during manufacturing. In this way, the manufacturing method can be adapted so that the reagents used reach stoichiometric quantities. The neutralization equation for these two chemical species is as follows: [æ 31 ] NaOH(s) +HCl(aq) NaCl(s) +H2O(l)

[0032] To obtain stoichiometric quantities, the quantity of NaOH material used during the manufacture of the bioplastic must therefore be equal to that of HCl. In steps 4 to 6, a solution containing 200 milliliters of sodium hydroxide, diluted to 0.5 moles per liter, per gram of initial biomass was used for delignification, corresponding to 0.1 moles of NaOH per gram of initial biomass. In steps 9 to 10, also 0.1 moles of HCl was used per gram of initial biomass. Filtrates containing hydrochloric acid and sodium hydroxide can therefore be mixed with each other to completely neutralize their acidity and basicity since they contain the same amount of material respectively. This process thus corresponds to the overall vision of this invention to provide a completely environmentally friendly bioplastic.

[0033] The fourth part of this protocol corresponds to the production of the bioplastic according to the invention. - Step 12: The previously obtained cellulose is weighed and mixed with 10 milliliters of distilled water per gram of initial biomass. In an ideal situation, the mass of cellulose obtained should be equal to approximately 33% of the mass of initial biomass, given that grasses and non-woody green waste are composed on average of one-third of cellulose. - Step 13: Starch (2.5 grams per gram of initial biomass) and glycerin (0.75 grams per gram of initial biomass) are homogenized in 25 milliliters of distilled water per gram of starch. These values ​​were chosen to obtain a bioplastic containing approximately 10% cellulose. The preparation is heated with magnetic stirring for 60 minutes at a minimum temperature of 85°C to cause the starch to gelatinize. - Step 14: The cellulose solution is slowly incorporated into the preparation of starch and gelatinized glycerin placed under magnetic stirring to ensure that a homogeneous mixture is obtained. - Step 15: The preparation is then poured into a suitable mold and left in the open air until it is completely dry (i.e. until the mass no longer varies). The mold is preferably made of silicone to facilitate demolding. Alternatively, the preparation is placed in a desiccator to accelerate its drying.

[0034] The proportions of starch and glycerin relative to the mass of cellulose can vary in order to modify the mechanical properties of the bioplastic according to the invention. Characterization of the invention

[0035] The bioplastic according to this invention was subjected to several tests in order to determine the following characteristics: the biodegradation rate, the Young's modulus, the elastic limit, the breaking point and the absorption capacity. These tests were carried out on a sample of bioplastic manufactured according to the protocol defined in the part “Detailed description” of this patent, with a mass of 4 grams of initial dry biomass.

[0036] In order to characterize the bioplastic according to the invention, an in situ biodegradation test on soil is carried out. The test consists of burying previously weighed samples for a variable period of time before being recovered and weighed again. The variation in mass over time makes it possible to obtain the biodegradation rate.

[0037] The European standard EN 13432 makes it possible to precisely define the concept of biodegradability and therefore the characteristics required for a plastic to be characterized as biodegradable. This standard defines that, to be biodegradable, a plastic must in particular have a biodegradation of 90% of its initial mass in 6 months. This same standard defines that, to be characterized as compostable, a plastic must also, after 3 months of composting with organic waste, see all of its residues greater than 2 millimeters have a mass less than 10% of its initial mass. Several samples of the bioplastic according to the invention with a mass equal to 2.5 grams were thus buried. These samples were then dug up after a variable number of days, then weighed again in order to check the loss of mass. Table 1 represents the biodegradation of the bioplastic according to the invention (in grams) as a function of time (in days).

[0038] [Tableauxl] Time (d) Observed mass (g) 0 2.5 1 2.45 2 2.4 3 2.25 4 1.7 5 1.3 6 0.8 7 0.3 5 0.15 9 ​​0.1 10 0

[0039] Table 1 and [Fig.l] show that the bioplastic according to the invention lost 90% of its initial mass in 8 days after being buried, and almost 100% of its initial mass in 10 days. These results tend to prove that the invention offers a particularly biodegradable material, and this in just a few days.

[0040] In order to characterize the mechanical properties of the bioplastic according to the invention, a tensile test was carried out to determine, among other things, its breaking point, its elastic limit and its longitudinal modulus of elasticity (Young's modulus). The test consists of the progressive elongation of a sample of the tested material until its rupture, during which the applied force as well as its elongation are measured. The test was carried out in accordance with ISO 527-3:2018 given that the sample of bioplastic according to the invention used was 0.15 millimeters thick. Table 2 corresponds to the results of the tensile test of the bioplastic according to the invention, opposing the elongation (dimensionless) to the exerted stress (in megapascals).

[0041] [Tables2] Stress (MPa) Elongation (dimensionless) 0.000 0.000 1.486 0.001 2.973 0.001 4.459 0.003 5.202 0.003 5.945 0.003 7.432 0.003 8.175 0.003 8.918 0.006 9.364 0.007 10.120 0.012 10.804 0.017 11.891 0.022 13.377 0.028 14.269 0.033 15.310 0.039 16.350 0.045 17.242 0.051 17,836 0.058 18.728 0.065 19.769 0.072 20.809 0.078 21.255 0.085 21.701 0.092 22.295 0.099 22.626 0.106 22.956 0.112 23.286 0.119 23.617 0.126 23.947 0.133 24.277 0.140 24.608 0.147 24.938 0.153 25.268 0.161 25.714 0.168 26.160 0.175 26.011 0.182 25.565 0.190 25.268 0.196 24.674 0.204 24.228 0.212 23.782 0.220 22.295 0.228 20.809 0.238

[0042] The tensile test (presented in Table 2 and in [Fig.2]) made it possible to determine the value of the elastic limit of the bioplastic according to the invention ^as being equal to 8.175 megapascals. Beyond this value, the material undergoes plastic deformation, and will no longer regain its initial dimensions.

[0043] The elastic limit aE is necessary to determine the Young's modulus. Graphically, the Young's modulus E can be determined by calculating the slope of the initial straight part of the tensile test curve ([Fig.2]).

[0044] Hooke's Law informs us that:

[0045] [Math.l]

[0046] In equation 1, ge is the stress (in megapascals), E is the Young's modulus (in megapascals) and se is the elongation (unitless). We can deduce that:

[0047] [Math.2] __ (7r E = ^

[0048] The tensile test carried out (^e being the value used, [Fig.2]) and equation 2 stated previously allowed the estimation of the Young's modulus of the bioplastic according to the invention at approximately 2.44 gigapascals.

[0049] The tensile strength of the bioplastic according to the invention could be obtained (^a, [Fig.2]) and is approximately equal to 26.16 megapascals.

[0050] The value of the maximum elongation 8max is calculated as follows:

[0051] [Math.3] T -T

[0052] In equation 3, is the maximum elongation (dimensionless), Linax is the final length of the sample (in millimeters) and Lo is the initial length of the sample (in millimeters).

[0053] The maximum elongation of the bioplastic according to the invention em«x is therefore equal to approximately 0.223.

[0054] To highlight the specificities and relevance of the bioplastic according to the invention, the latter was compared to a similar bioplastic without cellulose. The manufacture of such a bioplastic was carried out by following steps 13 and 15 of the protocol detailed previously in order to manufacture a bioplastic composed solely of starch and glycerin. (The quantities of starch and glycerin used were respectively 10 grams and 3 grams, in order to use the same quantities as those used during the manufacture of the sample of bioplastic according to the invention tested, based on 4 grams of initial biomass).

[0055] In order to be able to compare the mechanical characteristics of the bioplastic according to the invention with those of a bioplastic without cellulose, a tensile test was carried out on the latter.

[0056] In [Fig.3], superimposing the tensile test of the bioplastic according to the invention on that of the bioplastic without cellulose, significant differences are instantly noticed.

[0057] By calculating the Young's modulus, elastic limit, tensile strength and maximum elongation of the cellulose-free bioplastic in the manner mentioned above, it is possible to compare the mechanical properties of the two materials.

[0058] [Tables3] Bioplastic according to the invention Bioplastic without added cellulose Elastic limit (MPa) 8.18 5.3 Young's modulus (MPa) 2438 212 Tensile strength (MPa) 26.16 13.8 Maximum elongation (without dimension) 0.22 0.56

[0059] The bioplastic according to the invention, although having a lower maximum elongation, offers a much greater Young's modulus, elastic limit and tensile strength. The bioplastic according to the invention is therefore truly relevant in that the protocol proposing the introduction of cellulose from grasses and green waste offers a much stronger and more rigid material.

[0060] This invention patent also seeks to demonstrate that the bioplastic according to the invention can be a relevant alternative to LDPE, given that the applications envisaged are currently mainly fulfilled by the latter. It is therefore appropriate to seek that the bioplastic according to the invention has mechanical characteristics similar to those of low density polyethylene.

[0061] The MatWeb database compiles the properties of more than 150,000 materials, including LDPE, and reports the following values:

[0062] [Tables4] Bioplastic according to the invention LDPE (minimum values) LDPE (maximum values) Elastic limit (MPa) 8.18 6.34 28 Young's modulus (MPa) 2438 140 480 Tensile strength (MPa) 26.16 7.00 34.5 Maximum elongation (without dimension) 0.22 0.5 10

[0063] Table 4 informs us that the bioplastic according to the invention has mechanical characteristics at least superior to the minimum values ​​observed for those of LD PE, with the exception of its maximum elongation. Bioplastic is therefore, depending on the applications, a possible alternative to LDPE.

[0064] The values ​​of the mechanical characteristics of the bioplastic according to the invention presented in Table 4 are those observed for a bioplastic comprising approximately 10% of cellulose obtained via the process described above. To determine the minimum and maximum amounts of cellulose from grasses and green waste that can be incorporated into the bioplastic according to the invention, the same tests were carried out on samples containing different quantities of cellulose. For each quantity, the tests were carried out in triplicate, and the averages of the results obtained were included in Table 5.

[0065] [Tables5] Quantity of cellulose incorporated (percentage of total mass) 0% 10% 20% 30% 40% 80% Yield strength (MPa) 5.3 8.18 5.995 4.66 0.38 1.31 Young's modulus (MP a) 212 2438 1237 1191 93 1820 Tensile strength (MPa) 13.8 26.16 16.75 15.8 1.51 2.94 Maximum elongation (s dimensionless) 0.56 0.22 0.40 0.13 0.02 0.01

[0066] Table 5 therefore provides information on the percentages of the mass of cellulose that can be included in the bioplastic according to the invention to obtain a material having capacities at least equal to the minimum values ​​of LDPE. According to Table 5, it is therefore possible to include between 10% and 30% of cellulose in the bioplastic according to the invention. The bioplastic according to the invention does not aim to completely replace the use of LDPE, but to offer an alternative to some of its uses, in particular those where Young's modulus or tensile strength are important criteria. The incorporation of different quantities of cellulose from grasses and green waste thus makes it possible to obtain bioplastics with slightly different characteristics, which can therefore be adapted to several complementary needs.

[0067] In order to determine the hydrophilicity of the bioplastic according to the invention, an immersion test was carried out. This test aims in particular to obtain the absorption curve of the material, as well as to determine to what extent it deteriorates during prolonged contact with water. The test was carried out in accordance with the ASTM D570-98 (2018) standard.

[0068] The test consists of immersing samples, previously dried and then weighed, in a container filled with distilled water for a variable period of time. The samples are then wiped to remove the water remaining on the surface of the material, and are then immediately weighed to determine the change in its mass following the absorption of liquid. Finally, the samples are dried and then weighed a final time to determine the loss of mass caused by prolonged contact with distilled water during immersion.

[0069] When the bioplastic according to the invention is immersed, two phenomena take place simultaneously: the absorption of water by the material will, on the one hand, increase its mass, and the hydrolysis of the material will, on the other hand, cause a loss of mass.

[0070] The initial hypothesis concerning the absorption curve of the material was that it would be composed of two distinct parts: a first linear part and a second part tending towards a maximum value (otherwise called saturation value).

[0071] The water absorption by the material as a function of time is calculated using the following formula:

[0072] [Math.4] M z = ^xl00

[0073] In equation 4, Mt is the mass gain of the bioplastic upon immersion at a given time (in percentage), int is the mass of the wet bioplastic after immersion at a given time (in grams) and is the initial mass of the bioplastic (in grams). The samples were immersed for a duration ranging from 0 to 120 minutes, and the results were compiled in Table 6 and in [Fig.4].

[0074] [Tableauxô] Sample Time immersed (min) Initial mass ms (g) Final mass mt (g) Mass gain Mt (%) 1 0 0.095 0.095 0 2 2 0.088 0.238 170.5 3 5 0.085 0.258 203.5 4 10 0.066 0.198 200.0 5 15 0.057 0.189 231.6 6 30 0.06 0.221 268.3 7 45 0.06 0.241 301.7 8 60 0.052 0.206 296.2 9 90 0.029 0.122 320.7 10 120 0.048 0.201 318.8

[0075] The initial hypothesis is confirmed by the results obtained (see [Fig.4]). In the first part of the curve, the material rapidly and linearly absorbs the water in which it is immersed, before slowly reaching a saturation value. In the case of the bioplastic according to the invention, this saturation value is equivalent to 320% of its dry mass, which confirms its very high hydrophilicity.

[0076] Hydrolysis of the material causing a loss of mass is the second phenomenon involved, and was calculated using the following formula:

[0077] [Math.5] m f-ni: = x 100

[0078] In equation 5, A m is the change in the mass of the bioplastic during its immersion (in percentage), mf is the mass of the dry bioplastic after immersion (in grams) and mi is the initial mass of the dry bioplastic (in grams). The samples were immersed for a duration ranging from 0 to 120 minutes, and the results were compiled in Table 7 and in [Fig.5].

[0079] [Tables7] Sample Time immersed (min) Initial mass m; (g) Final mass mf (g) Mass loss Am (%) 1 0 0.089 0.089 0 2 2 0.104 0.095 8.65 3 5 0.056 0.045 19.64 4 10 0.114 0.085 25.44 5 15 0.098 0.066 32.65 6 30 0.087 0.055 36.78 7 45 0.099 0.60 39.39 8 60 0.120 0.052 56.67 9 90 0.069 0.029 57.97 10 120 0.052 0.031 59.62

[0080] The bioplastic according to the invention deteriorates very quickly when it undergoes hydrolysis ([Fig.5] and Table 7). The material loses nearly 25% of its initial mass after being immersed for 10 minutes, and nearly 60% after immersion for 120 minutes, demonstrating its ability to degrade very quickly if it comes into contact with an aqueous environment at the end of its life.

[0081] Since the gain and loss of mass of the bioplastic according to the invention, when immersed, occur in parallel, it was possible to trace the evolution of the mass of the material as a function of time.

[0082] The bioplastic according to the invention reaches a maximum mass after immersion for a period of 30 minutes before seeing a progressive decrease in its mass ([Fig.6]). Beyond this limit, the absorption capacity of the material is no longer sufficient to compensate for the mass losses caused by the hydrolysis it undergoes and the change in the mass of the bioplastic according to the invention then becomes negative ([Fig.6]). Examples

[0083] Several applications are contemplated for the use of this invention.

[0084] The first application envisaged is to use the bioplastic according to the invention for the manufacture of packaging for consumer goods or goods intended for industry. In their article “Production, use and fate of all plastics ever made”, Geyer, Jambeck and Law state that 44.8% of the plastics produced between 2002 and 2014 were used as packaging, making it the highest-consuming sector. In the same article, the authors also mention that 20% of the plastics produced between 2002 and 2014 were made of low-density polyethylene (LDPE), mainly used to manufacture flexible plastic. LDPE, however, has several drawbacks, starting with its petrochemical origin and the fact that it does not biodegrade easily, two problems solved by the bioplastic proposed by this invention. In addition, LDPE has an average Young's modulus of between 140 and 480 megapascals, much lower than that of the bioplastic according to the invention.

[0085] Consumer goods have the disadvantage of needing to be protected before their sale, but lose this need once purchased. These packages therefore have a very limited lifespan, and their end of life is not always well managed. According to the study carried out in 2020 by PlasticsEurope, 30.7% of plastic packaging waste produced in France was buried in landfills in 2018. Thanks to its rapid decomposition and not requiring a controlled environment, the bioplastic according to the invention is not dangerous, even if it is placed in landfill since it does not pollute the soil and water in which it decomposes. However, the hydrophilicity of the bioplastic according to the invention qualifies it rather for packaging of dry products, such as hardware or certain consumer goods.

[0086] The second application envisaged is to use the bioplastic according to the invention for the manufacture of single-use bags. This application offers a solution to their controversial use, mainly due to their complicated recycling. The bioplastic according to the invention is a possible alternative given its mechanical characteristics and its rapid biodegradation (presented previously). Concerning the difficulties of managing bags at the end of their life, the bioplastic according to the invention proposes to respond to them in particular thanks to its rapid biodegradation. After use, the user can easily compost it, let it biodegrade if it is no longer needed, or throw it away so that it can be recycled or incinerated.

[0087] The third application envisaged is to use the bioplastic according to the invention for the manufacture of products or packaging intended for gardening. The rapid degradation of the bioplastic according to the invention in an uncontrolled environment allows users to easily dispose of it after use. Seed packets that can be buried directly fall into this application, for example. Another possibility would be the direct incorporation of seeds of different annual plants into the plastic during its manufacture. In this way, the bioplastic according to the invention would make it possible to completely get rid of packaging for this type of product; the user would simply have to bury it. The bioplastic according to the invention would decompose quickly, while the seeds, then released, could then grow. List of cited documents

[0088] • PlasticsEurope (Décembre 2020). Plastics - the Facts 2020 An analysis of European plastics production, demand and waste data. Consulté le 07 / 09 / 2021 sur https: / / www.plasticseurope.org / fr / resources / publications / 4312-plastics-facts-2020 • PADMANABHA, B.V. Composition ofa bioplastic andprocessfor préparation ofa bioplastic film. Brevet WO2020115619. 11 Juin 2020. https : / / data.inpi.fr / brevets / W02020115619 • JUNKASEM, J.; KAABBUATHONG, K. ; THAMMONGKOL, V. ; PAIBOOLSUK, J.; HEMMOND, S. A bioplastic composition comprising biomass as a component and a production process. Brevet WO2018021980. 01 Février 2018. https: / / data.inpi.fr / brevets / W02018021980 • PARK, E. J.; CHOI, H. M.; MOON, S. G. Bio-plastic composition containing wheat bran and bio-plastic film using same. Brevet EP3305855A2. 14 Avril 2018. https: / / data.inpi.fr / brevets / EP3305855 Deepanjan Bhattacharya, Louis T. Germinario, William T. Winter, Isolation, préparation and characterization of cellulose microfibers obtained from bagasse, Carbohydrate Polymers, Volume 73, Issue 3, 2008, 371, 377, https: / / doi.org / 10.1016 / j.carbpol.2007.12.005. Marichelvam, M.K.; Jawaid, M.; Asim, M. Corn and Rice Starch-Based Bio-Plastics as Alternative Packaging Materials. Fibers, 2019, 7, 32. https: / / doi.org / 10.3390 / fib7040032 John Rojas, Mauricio Bedoya and Yhors Ciro (9 Décembre 2015). Current Trends in the Production of Cellulose Nanoparticles and Nanocomposites for Biomédical Applications, Cellulose - Fundamental Aspects and Current Trends, Matheus Poletto and Heitor Luiz Ornaghi Junior, IntechOpen, https: / / doi.org / 10.5772 / 61334. International Organization for Standardization. (2018). Plastiques -Détermination des propriétés en traction - Partie 3 : Conditions d’essai pour films et feuilles. (ISO 527-3:2018) ASTM International. (2018). Standard Test Method for Water Absorption of Plastics. (ASTM D570 - 98(2018)) Geyer R, Jambeck JR, Law KL. Production, use, and fate of garlic plastics ever made. Sci Adv. 2017 Jul 19;3(7):el700782. https: / / doi.Org / 10.l 126 / scia dv. 1700782. MatWeb. MatWeb, Material Property Data, [Online] http: / / www.matweb.com / index.aspx (accessed November 25, 2021) AFNOR. (2000). Packaging - Requirements for packaging that can be recovered by composting and biodegradation - Test program and evaluation criteria for final acceptance of packaging. (NF EN 13432)

Claims

1. Claims Process for manufacturing a bioplastic that is at least partially biosourced and biodegradable, characterized in that it is composed of:

1. Cellulose from biomass, mainly composed of grasses and non-wood green waste, in a percentage between 10 and 30% of the total mass of the bioplastic.

2. a plasticizer of natural origin, chosen from glycerin, esters, glycerin esters, esters based on vegetable oils, esters based on polyols of vegetable origin or modified vegetable oils.

3. a naturally occurring matrix of wheat flour starch. The said method comprises the following successive steps:

1. Washing the selected biomass with water, followed by air drying. The washed and dried biomass is then ground to obtain particles with a diameter of approximately 1 millimeter.

2. Successive treatments of the biomass with a sodium hydroxide solution followed by vacuum filtration. The sodium hydroxide solution used in the successive treatments of the biomass has a molar concentration of 0.5 moles per liter and is heated to 60°C for 2 hours under magnetic stirring.

3. Treatment of the biomass with a hydrogen peroxide solution, having a pH close to 11, at room temperature for 24 hours, followed by vacuum filtration 4. Treatment of biomass with hydrochloric acid solution followed by vacuum filtration. The hydrochloric acid solution used in the treatment of biomass is heated for 40 minutes at 80°C under magnetic stirring.

5. Production of a preparation consisting of a homogenization comprising a matrix, a plasticizer and the cellulose from the previously treated biomass. This preparation consists of a homogenization of the matrix and the plasticizer under magnetic stirring, with a minimum temperature of 85°C, for a period of 60 minutes, then the incorporation and homogenization of the cellulose.

6. Molding and drying of the preparation. The mold used is preferably made of silicone, and drying is carried out in the open air or in a desiccator until the mass of the bioplastic no longer varies.

2. A method of manufacturing bioplastic according to claim 1, characterized in that the sodium hydroxide and hydrochloric acid solutions used have an equal quantity of material such that their neutralization with each other is facilitated.

3. Process for manufacturing bioplastic according to any one of claims 1 to 2, characterized in that the biomass from step 4 is placed in a centrifuge rotating at 6000 revolutions per minute for 10 minutes.

4. A method of manufacturing bioplastic according to any one of claims 1 to 2, characterized in that during step 6 the preparation comprising the matrix, the plasticizer and the cellulose is molded and dried using a desiccator.

5. Process for manufacturing bioplastic according to any one of claims 1 to 2, characterized in that the hydrogen peroxide solution is maintained at 100°C for 40 minutes, while maintaining a pH close to 11.

6. At least partially biosourced and biodegradable bioplastic obtained by the process according to any one of claims 1 to 5.

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