Polylactic acid and carbon nanoclusters masterbatch and related preparation method

Abstract

The invention relates to a composition comprising polylactic acid (PLA) and Carbon Nanoclusters, more specifically the invention refers to a masterbatch of polylactic acid (PLA) and Carbon Nanoclusters and related preparation method. The masterbatch of the invention has high antibacterial, anti-algal proliferation and improved structural and mechanical characteristics compared to PLA without Nanoclusters and is also advantageous for its simple production process, for the easily obtainable raw materials and for the low cost. The masterbatch of the invention can be used for all products / artifacts wherein standard PLA is already used, such as for products in the sectors of agriculture, food packaging, tableware, medical instrumentation and the like.

Description

[0001] Polylactic acid and Carbon Nanoclusters masterbatch and related preparation method

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention concerns a composition comprising polylactic acid (PLA) and Carbon Nanoclusters, more in particular the invention refers to a polylactic acid (PLA) and Carbon Nanoclusters masterbatch and the relative method of preparation.

[0004] The masterbatch of the invention has high antibacterial capacities, algal anti-proliferation and improved structural and mechanical characteristics compared to PLA without Nanoclusters. The masterbatch is also advantageous for its simple production process, for the raw materials that can be easily obtained and for the low cost.

[0005] The masterbatch according to the invention can be used for all products / artifacts wherein standard PLA is already used, such as e.g. for products in the agriculture, food packaging, dishes, medical instrumentation and the like sectors.

[0006] KNOWN ART

[0007] In recent years, the prevention of pollution by bacteria harmful for materials has been at the center of research in the fields of biological medicine, food packaging, daily chemical industry and the like. The bacteria adhere to the surface of the material and form a biofilm, causing various related diseases, seriously putting human health at risk and causing huge economic losses.

[0008] The lactic acid-based biopolymer PLA is a biodegradable and biocompatible polymeric material that belongs to the polyester family. This polymer is mainly obtained from the bacterial fermentation of starch or sugar sources, such as corn, sugar cane or potatoes, through a production process that involves the conversion of sugars into lactic acid and subsequent polymerization. PLA is an important biopolymer material that finds wide application in the fields of medical instrumentation, textiles, agricultural mulch films, food packaging and the like thanks above all to its biocompatibility. However, PLA alone does not have an antimicrobial function and cannot inevitably counteract common problems in its fields of application, such as bacterial contaminations, with consequent production losses especially in the agricultural sector, food and medical packaging.

[0009] The insertion of an antibacterial substance in PLA is currently a common method to create some antibacterial function, however, the commonly used filling materials that comprise Ag oxides, Cu oxides, antibiotics, antimicrobial peptides, etc., are often limited by their biocompatibility, from resistance to drugs and, in the case of inorganic particles (Cu-Ag), they cannot be adequately dispersed and therefore, when inorganic particles and the organic matrix in PLA are subjected to composite processing, structures are often created separating microphases that cause a series of stability problems with consequent structural and unstable mechanical properties of materials, which significantly limit the field of application of the material and do not obtain satisfactory results from the point of view of structural resistance.

[0010] Algal proliferation or algal blooming is an environmental phenomenon that occurs when algae grow and multiply quickly in a water body, such as a lake or river. This phenomenon is often caused by the excess of nutrients such as phosphorus and nitrogen, which can be released in water by human activities such as agriculture and wastewater discharge. Algal blooms can have negative effects on the environment and human health. For instance, some algae produce toxins that can contaminate fish and other aquatic organisms, making them dangerous for human consumption. In addition, algal blooms can cause the death of fish and other aquatic animals due to the reduction of oxygen in the water.

[0011] The need to provide a solution to the problems of the known technique is evident. Therefore, considering the problems referred to above, it is believed that a combination of PLA with products named Carbon Nanoclusters can improve the antibacterial properties and anti-algal properties of PLA. Carbon Nanoclusters are known to have antioxidant and / or antimicrobial properties in the dermo-cosmetic preparations sector and are described in the IT 102018000009526 and IT 102022000014722 patents.

[0012] If not specifically excluded in the detailed description that follows, what is described in this chapter is to be considered as an integral part of the detailed description.

[0013] SUMMARY OF THE INVENTION

[0014] The purpose of the invention is to create a masterbatch that allows to overcome the inconveniences of the well-known solutions.

[0015] Another purpose of the invention is to create a masterbatch that has antibacterial and / or antiviral and / or antimicrobial properties.

[0016] Another purpose of the invention is to create a masterbatch that has improved mechanical characteristics compared to the correspondent PLA without the Carbon Nanoclusters.

[0017] Another purpose of the invention is to create a masterbatch that has a physical-chemical stability, and structural characteristics improved compared to the correspondent PLA without the Carbon Nanoclusters.

[0018] Another purpose of the invention is to create a masterbatch that has a simple and economic production.

[0019] Another purpose of the invention is to create a masterbatch that is an alternative and / or improvement compared to known devices.

[0020] The masterbatch according to the invention comprises PLA and Carbon Nanoclusters and the quantities by weight of Carbon Nanoclusters to be added to 1 kg PLA vary between 5 and 50 g.

[0021] All these purposes, both individually and in their any combination, and others that will result from the description that follows are achieved, according to the invention, with a masterbatch with the characteristics indicated in claim 1 and with a method according to claim 8.

[0022] BRIEF DESCRIPTION OF THE FIGURES The present invention is further clarified below in some of its preferred embodiments reported for purely exemplary and not limiting purposes with reference to the attached drawing tables, wherein:

[0023] Figure 1 shows an example of optimal dispersion of the Carbon Nanoclusters in the dissolved PLA matrix,

[0024] Figure 2 shows a SEM image which highlights the homogeneous dispersion of the Carbon Nanoclusters in the matrix of the composite film PLA / PLA / Carbon Nanoclusters masterbatch (A: PLA without Carbon Nanoclusters B: PLA with metal oxides (typically ZnO and CuO) C: PLA with Carbon Nanoclusters),

[0025] Figure 3 shows a SEM image which highlights the homogeneous dispersion of the carbon nanoclusters in the matrix of the profile for packaging composite PLA / masterbatch PLA / Carbon Nanoclusters (A: PLA with macro agglomerates of metal oxides (typically ZnO and CuO) B: PLA with Carbon Nanoclusters)

[0026] Figure 4 shows a detail of Fig. 3 B showing the homogeneous dispersion of the Carbon Nanoclusters in the PLA matrix for packaging profiles,

[0027] Figure 5 shows Raman spectrum (Cora 5001 of Anton Paar) and relative intensity for the Carbon Nanoclusters materials used.

[0028] DETAILED DESCRIPTION OF THE INVENTION

[0029] The wording masterbatch is intended to identify a concentrated mixture of additives that are mixed, processed together and used to give specific characteristics to other materials to which they are added (in general they are mixed with a final plastic product). The general process for the production of masterbatch primarily provides for the identification and weighing of the necessary additives, therefore the mixing of additives with a resin or a support polymer. Finally, the concentrated mixture is generally extruded, cooled and formed in granules or powder.

[0030] The masterbatch subject of the invention, thanks to its completely organic nature, has perfect biocompatibility and can be easily applied in the sectors: agricultural to make, as a non-limiting example, mulch film, packaging to make, as a non-limiting sample, film, shoppers, disposable tableware and food packaging, medical instruments to make, as a not limiting example, tissue scaffolds, aquaculture and the like and in all applications where PLA is used and all those sectors wherein biodegradable plastic materials are used.

[0031] According to the invention, the Carbon Nanoclusters are integrated by dispersion in PLA with consequent formation of a PLA / Carbon Nanoclusters masterbatch with better antibacterial / anti-algal properties and better mechanical and structural qualities.

[0032] The quantities by weight of Carbon Nanoclusters to be added to one kg PLA vary between 5 and 50 g.

[0033] The Carbon Nanoclusters are obtained starting from vegetable material appropriately treated as described in the IT 102018000009526 and 102022000014722 patents and have the following characteristics:

[0034] Dimensions: between 1 and 6 nanometres,

[0035] Composition: carbon between 98.8 and 99.8%, hydrogen between 0.1 % and 0.7%, oxygen between 0.1 % and 0.5%

[0036] Relative humidity: 1 -2%

[0037] Morphology: number of OH hydroxyl groups between 50,000 and 250,000; carbon-based nano-clusters in a number between 200,000 and 500,000 for 1 gr of product they have carbon atoms with sp2hybridization, as can be easily measured by Raman spectroscopy, in particular they have a peak around 1300cm’1(Band D) and a peak around 1600 cm’1(G), and the G band is more intense than the D band

[0038] The present invention concerns a method to prepare a PLA and Carbon Nanocluster masterbatch which comprises the following phases. All percentages are to be understood as % by weight if not indicated differently.

[0039] Phase 1 - Preparation of the masterbatch:

[0040] Required materials (for the preparation of 1kg of masterbatch): - Carbon Nanoclusters: they are used in a quantity between 5 gr and 50 gr (for 1 kg of masterbatch to be produced) having a size between 1 and 6 nm and a composition consisting of carbon between 98 and 99%, hydrogen between 0.4% and 1 %, oxygen between 0.4% and 1 %, relative humidity between 1 % and 2%, a morphology with a number of OH groups between 200,000 and 400,000 per 1 g of Nanocluster; number of Carbon Nanoclusters between 450,000 and 550,000 for 1 g of Nanoclusters,

[0041] - PLA: PLA granules are used in a quantity between 900 gr and 955 gr (per kg of masterbatch to be prepared), 100% composed by PLA having a molecular weight between 100,000 and 200,000 Dalton, a density between 1 .22 g / cm3and 1.25 g / cm3and a relative humidity between 2% and 2.5%,

[0042] - Anti-aggregating agents: they are used in a quantity between 40 gr and 70 gr (for 1 kg of masterbatch to be prepared) and are for instance but not limited to the following materials: coconut wax, rice wax, soy wax, palm wax.

[0043] - solvents: they are used in a quantity between 200 gr and 400 gr (for 1 kg of masterbatch to be prepared) and are for instance but not limited to the following materials: terpinene, terpinolene, myrcene, limonene, dimethyl sulfoxide (DMSO), (the expert in the field is able to choose a more suitable solvent to allow the complete dissolution of PLA and which evaporates completely during the mixing process).

[0044] Mixing procedure:

[0045] PLA dissolution: to be performed preferably in a well-ventilated area or under an aspiring hood or under reduced pressure, dissolving PLA granules in the solvent selected at room temperature. Mixing the mixture until PLA is completely dissolved, forming a clear solution.

[0046] Addition of anti-aggregating agent: incorporating the measured quantity of anti-aggregating agent in the PLA solution. Mixing the mixture to ensure uniform distribution.

[0047] Carbon Nanoclusters dispersion: gradually adding the carbon nanoclusters powder to the PLA / solvent / anti-aggregating agent solution by stirring constantly. Homogenization: preferably using a sonicator with a frequency between 30 and 40 kHz for a period of 30-40 minutes to completely disperse and homogenize the mixture, (see Figure 1 )

[0048] Solvent evaporation: letting the mixture rest and making the solvent evaporate completely, placing the mixture in a rotating evaporator at a temperature between 85 and 95°C until complete evaporation of the solvent, typically for a period between 20 and 60 minutes.

[0049] Material obtained: the resulting material is an injectable paste composed of PLA / Carbon Nanoclusters, with a viscosity between 900 and 1200 PI rotating viscosimeter VEVOR NDJ-9S thermostatically controlled at 65°C for a measurement time of about 10 minutes, which can be used for various polymers processing techniques, comprising extrusion, injection molding or 3D printing.

[0050] The composition thus prepared is a masterbatch that can be mixed with a further quantity of PLA or other biodegradable or poorly biodegradable or totally non-biodegradable polymer or mixture of polymers to form sheets, wires, films or other forms to be used in the sectors wherein plastic materials are used, in particular the biodegradable plastics.

[0051] According to a not limiting embodiment of the invention, the mixing of the masterbatch with the PLA polymer is described below.

[0052] Phase 2 - Use of the masterbatch:

[0053] Mixing, fusion and granulation process of a mixture consisting of a masterbatch of Carbon Nanoclusters and PLA to obtain a biopolymer granulate consisting of the mix of PLA and masterbatch of PLA / Carbon Nanoclusters.

[0054] Materials used: pellets of commercial PLA, for instance PLA marketed with high quality, biodegradable and derived from renewable resources such as corn starch or sugar cane; masterbatch of PLA / Carbon Nanoclusters obtained according to the process described in phase 1.

[0055] Mixing of the material: for 1 kg PLA in pellets, use a quantity of PLA / Carbon Nanoclusters masterbatch between 1 % and 10% by weight, preferably using a mixer at a speed between 50 and 100 rpm, for a period between 1 and 10 minutes. Extrusion process', feed PLA and PLA / Carbon Nanoclusters masterbatch mixture in a commercial extruder, e.g. "Haake Minijet Pro" model of the ALPHA TEST with a drying pre-phase lasting 10-60 minutes at a temperature between 65 and 85°C followed by a melting phase of the mixture of materials at a temperature between 165°C and 210°C for a period of 1 -5 minutes, followed by a cooling phase with liquid system with a cooling temperature between 5 and 15 degrees for a period between 1 and 5 minutes and consequent extrusion of the desired profile (film, thread, pellets etc.).

[0056] Injection molding process: feed the PLA PLA / Carbon Nanoclusters masterbatch mixture in a commercial injection printer, e.g. Fanuc's "a S30 I b" model, with a drying pre-phase lasting 15-50 minutes at a temperature between 70 and 90°C followed by a phase of melting the mixture at a temperature between 170°C and 200°C for a period of 1 -5 minutes followed by an injection molding phase at a temperature between 170 and 200°C; the mixture of PLA and PLA / Carbon Nanoclusters materials are injected into a cavity and are left to cool at a temperature between 5 and 10°C for a period between 1 and 3 minutes to obtain the desired packaging profile consisting of PLA / PLA Carbon Nanoclusters.

[0057] The carbon nanoclusters used in the invention guarantee:

[0058] • Mechanical improvements: thanks to their homogeneous distribution in the PLA matrix, the Carbon Nanoclusters act as a structural reinforcement, increasing the tensile strength, hardness and thermal stability of the material compared to PLA without additives.

[0059] • Antimicrobial properties: the unique chemical composition of the Carbon Nanoclusters, characterized by a predominance of carbon atoms with sp2hybridization and by a high number of hydroxylic groups (-OH), promotes effective interaction with bacteria and algae, preventing their proliferation.

[0060] • Improvement of physical-chemical stability: uniform dispersion and nanometric dimension of the Carbon Nanoclusters contribute to reducing the formation of unstable microphases, typical of other alternative fillers, such as metal oxides or carbon nanotubes, guaranteeing greater structural integrity of the material.

[0061] From the results expressed in the examples is evident, in addition to the improvement in terms of bacterial resistance and algal proliferation, also the considerable improvement of the mechanical performance that the masterbatch according to the invention confers to PLA or other plastic materials to which it is added, thanks to the widespread homogenisation of the Carbon Nanoclusters in the PLA matrix (see Fig. 4).

[0062] Other advantages related to the addition of the Carbon Nanoclusters were observed and verified: the increase in thermal resistance and the increase in the heat deflection point of the biopolymers containing the masterbatch according to the invention. This means that the material can bear higher temperatures without deforming or losing its structural integrity. In the food packaging sector, this is crucial to ensure that packaging is able to resist the high temperatures associated with the sterilization process or the conservation of hot foods, improving the safety and reliability of the packaging. The greater thermal resistance guarantees a longer useful life of the tools that can be used in the food sector; this is particularly important in catering contexts, where tools could be exposed to high temperatures through high temperature washing or during use in catering service, this translates into greater safety of food packaging and in the reduction of the risk of rupture of dishes and cutlery, improving the overall consumer experience.

[0063] Examples

[0064] The present invention will be described with reference to specific examples of realization which are not to be considered limiting of the scope of the invention.

[0065] Measurement of the size of the carbon nanoclusters

[0066] The measurement of the size of the Carbon Nanoclusters is carried out using the scan electronic microscopy technique (SEM), which guarantees precision in the dimensional data shown. The SEM scan electronic microscopy has been used to obtain high resolution images of the Carbon Nanoclusters and to analyse their distribution in the polymer matrix.

[0067] Below, the details of the operating conditions used:

[0068] Sample preparation:

[0069] The PLA / Carbon Nanoclusters masterbatch has been powdered in particles of size lower than 1 mm to facilitate their analysis.

[0070] The samples were covered with a thin layer of gold using sputtering, to ensure uniform electrical conductivity during observation.

[0071] The coating was applied with a thickness of about 5 nm, using an under vacuum sputtering system.

[0072] Tool used:

[0073] Model: Zeiss Evo 50 SEM.

[0074] Acceleration voltage: 5 kV.

[0075] Imaging methods: secondary electrons mode (SE), to highlight the topography and distribution of particles.

[0076] Analysis parameters:

[0077] Space resolution: up to 3 nm at low voltage.

[0078] Magnification range: from 1 ,000x to 50,000x, to analyse both the macroscopic distribution and the size of the particles.

[0079] Slope angle: 0°, with possible 45° rotation for three -dimensional analysis of the dispersion.

[0080] Vacuum conditions: high resolution vacuum chamber, with a pressure lower than 1 x1 O’4Pa.

[0081] Data analysis:

[0082] The images obtained were processed using the Imaged software, to measure the average size of the Carbon Nanoclusters. The dimensional distribution was determined on a representative sample of at least 500 particles, providing statistical data on minimum, maximum and average dimensions, with standard deviation.

[0083] Results obtained:

[0084] The size of the carbon Nanoclusters were between 1 and 6 nm, with a uniform distribution in the PLA matrix, as shown in the images provided (see fig. 1 -3).

[0085] Uniform dispersion was confirmed by the absence of visible agglomerations up to 50,000x magnification.

[0086] Example 1 : Preparation of PLA and PLA / Carbon Nanoclusters masterbatch packaging film

[0087] 1. masterbatch preparation procedure

[0088] Materials for 1 kg of PLA / Carbon Nanoclusters masterbatch to be prepared:

[0089] - Carbon Nanoclusters powder: 5 gr,

[0090] - PLA granules: 955 gr (Luminy LX 175),

[0091] - anti-aggregating agents: 40 gr (coconut wax)

[0092] - solvents: 200 gr (dimethyl sulfoxide DMSO)

[0093] In a well-ventilated area or under an aspiring hood, melt PLA granules in the selected solvent. Mix the mixture until PLA is completely dissolved, forming a clear solution.

[0094] Incorporate the measured quantity of anti-aggregating agent in the PLA solution. Mix the mixture to ensure uniform distribution.

[0095] Gradually add the Carbon Nanoclusters powder to the PLA / Solvent / anti- aggregating agent solution by stirring constantly.

[0096] Homogenize the mixture using a sonicator with a frequency of 30 kHz for a period of 30 minutes to further disperse and homogenize the mixture described above. Leave the mixture to rest and completely evaporate the solvent, placing the mixture in a controlled rotating evaporator at a temperature of 85°C for a period of 30 minutes.

[0097] The resulting material is an injectable paste composed of PLA / PLA Carbon Nanoclusters, with a viscosity of 950 PI, which is used for the production of films with extrusion process. (See Fig. 2)

[0098] 2. Flat extrusion:

[0099] Use 50 gr of PLA / Carbon Nanoclusters masterbatch and 950 gr of PLA in granules to produce packaging films by means of a flat extrusion process through a T-shaped matrix arranged on the head of the extruder,

[0100] Mix the materials in a mixer at a speed of 50 rpm for a period of 5 minutes.

[0101] Feed with the PLA and PLA / Carbon Nanoclusters mixture, the extruder, through a drying pre-phase at a temperature of 65°C for a period of 30 minutes, a subsequent melting and extrusion phase in films at the temperature of 190°C, and final cooling of the film at a temperature of 5°C for a period of 2 minutes.

[0102] 3. Antibacterial performance:

[0103] Prepare a solution of Escherichia coli ATCC N°'8739. Add 50 ml of bacterial broth suspension in a triangular flask containing 2 g of packaging films in standard PLA covered with silver oxides as an anti-bacterial agent (SAG PLA), 2 g of packaging films in PLA / PLA Carbon Nanoclusters (in PLAC) and 2 gr of packaging films consisting only of PLA (Control). Take 1 ml of inoculation liquid respectively from the triangular flask without the sample to be diluted 10 times, considering the number of bacteria without sample as 0 contact time. Fix the other triangular flask on a vibrating table, shaking for 1 hour. Take 200 pl from each flask and cultivate at 37 + / - 2°C for 24 hours. The percentage of antibacterial activity of the different samples (according to ISO 20743: 2013) is listed below:

[0104] 4. Mechanical performance

[0105] Packaging film sections (having similar size of 25x50 cm, 40 micron thickness) in standard PLA with silver oxides as antibacterial agents (SAG PLA), in PLA / PLA Carbon Nanoclusters (IN PLAC) and PLA (CONTROL), are subjected to mechanical properties characterization tests according to the standards defined by ISO 527-1 and ISO 179-1 eA to define the impact resistance and by ISO 75-1 for heat resistance. Below are the results:

[0106] The results show a considerable improvement in the mechanical performance of the film obtained with the masterbatch according to invention, due to the widespread homogenization of the Carbon Nanoclusters in the PLA matrix (see Fig. 3).

[0107] Example 2: Preparation of a food packaging profile based on the use of PLA and PLA / Carbon Nanoclusters masterbatch :

[0108] 1. Preparation procedure

[0109] Materials for 1 kg of PLA / Carbon Nanoclusters masterbatch to be prepared:

[0110] - Carbon Nanoclusters powder: 8 gr,

[0111] - PLA granules: 942 gr (AD-Bio W 721 ), - anti-aggregating agents: 50 gr (palm wax)

[0112] - Solvents: 250 gr (Terpinolene)

[0113] In a well-ventilated area or under an aspiring hood, melt PLA granules in the selected solvent. Mix the mixture until PLA is completely dissolved, forming a clear solution.

[0114] Incorporate the measured quantity of anti-aggregating agent in the PLA solution. Mix the mixture to ensure uniform distribution.

[0115] Gradually add the Carbon Nanoclusters powder to the PLA / Solvent / anti- aggregating agent solution by stirring constantly.

[0116] Homogenize the mixture using a sonicator with a frequency of 35 kHz for a period of 35 minutes to further disperse and homogenize the mixture described above.

[0117] Leave the mixture to rest and completely evaporate the solvent, placing the mixture in a controlled rotating evaporator at a temperature of 90°C for a period of 35 minutes.

[0118] The resulting material is an injectable paste composed of PLA / PLA Carbon Nanoclusters, with a viscosity of 970 PI, which is used for the production of packaging profiles with injection molding techniques.

[0119] 2. Injection molding:

[0120] Use 100 gr of PLA / Carbon Nanoclusters masterbatch and 900 gr of PLA in granules to produce a packaging profile by means of extrusion process with injection molding.

[0121] Mix the materials in a mixer at the speed of 100 rpm for a period of 6 minutes.

[0122] Feed with the PLA and PLA / Carbon Nanoclusters mixture, the extruder, through a drying pre-phase at a temperature of 70°C for a period of 25 minutes, a subsequent fusion and paste extrusion phase at the temperature of 200°C, subsequently, the production process passes to the injection molding phase, the PLA and PLA / Carbon Nanoclusters mixture is injected into a mold cavity and left to cool at a temperature of 7°C for a period of 5 minutes to obtain the packaging profile for food packaging, consisting of PLA / PLA Carbon Nanoclusters.

[0123] 3. Antibacterial performance test:

[0124] Prepare a solution containing a concentration of Escherichia coli ATCC N° 8739. Add 50 ml of bacterial broth suspension in a triangular flask containing 3 g of packaging profile with silver oxides as an antibacterial agent (SAG PLA), 3 g of PLA / PLA Carbon Nanoclusters packaging profile (IN PLAC) and 3 gr of packaging profile consisting only of PLA (CONTROL), taking 1 ml of inoculation liquid respectively from the triangular flask without the sample to be diluted 10 times, considering the number of bacteria without sample as 0 contact time. Fix the other triangular flasks on a vibrating table, shaking for 1 hour. Take 200 pl from each flask and cultivate at 37 + / - 2°C for 24 hours. The percentage of antibacterial activity of the different samples (according to ISO 20743: 2013) is listed below:

[0125] 4. Algal proliferation resistance test:

[0126] Similar sections, having 10x10 cm dimensions, of standard PLA with antibacterial agent represented by silver oxides (SAG PLA), PLA / PLA Carbon Nanoclusters (IN PLAC) and only PLA (CONTROL), are immersed in separate containers containing inoculation liquid containing algae (Oscillatoria Cyanobacteria sp. BG-1 1 Freshwater Sigma-Aldrich); the different containers are placed in an incubator for a period of 14 days at a constant temperature (25°C), with lighting for 12 h per day variable between 2000 and 10000 lx, and 12 hours in the dark and fresh inoculation liquid that comes periodically integrated, the results obtained according to the ASTM G29 standards are those illustrated below. 5. Mechanical performance

[0127] Sections of packaging profiles (having similar size of 25x25 cm thickness 150 microns) in standard PLA with silver oxides as an antibacterial agent (SAG PLA), in PLA / PLA Carbon Nanoclusters (IN PLAC) and PLA (CONTROL), are subjected to mechanical properties characterization tests according to the standards defined by ISO 527-1 by ISO 179-1 eA to define the resistance to impact and by ISO 75-1 for heat resistance. Below are the results:

[0128] The results show a significant improvement in the mechanical performance of the profile obtained with the masterbatch according to invention, due to the widespread homogenization of the Carbon Nanoclusters in the PLA matrix (see Fig. 4).

Claims

CLAIMS1. A masterbatch composition comprising polylactic acid (PLA) and an aliquot of Carbon Nanoclusters wherein the Carbon Nanoclusters have a size between 1 and 6 nm and a composition consisting of Carbon between 98 and 99%, Hydrogen between 0.4% and 1 %, Oxygen between 0.4% and 1 %, relative humidity between 1 % and 2%, a morphology with a number of OH groups between 200,000 and 400,000 for 1 g of Nanocluster, said masterbatch composition having a quantity by weight of Carbon Nanoclusters to be added to one kg of PLA that varies between 5 and 50g.

2. The masterbatch composition according to the previous claim wherein the Carbon Nanoclusters have the following characteristics:- Dimensions: between 1 and 6 nanometers;- Composition: Carbon between 98.8 and 99.8%, Hydrogen between 0.1 % and 0.7%, Oxygen between 0.1 % and 0.5%- Relative Humidity: 1 -2%;- Morphology: number of hydroxyl groups OH in a number between 50,000 and 250,000; carbon-based nano-clusters in a number between 200,000 and 500,000 for 1 g of Nanocluster;- They present carbon atoms with sp2hybridization, as can be easily measured by Raman spectroscopy, in particular they present a peak around 1300 cm-1(D band) and a peak around 1600 cm-1(G band), and the G band is more intense than the D band.

3. The masterbatch composition according to anyone of the previous claims wherein for 1 kg of composition the Carbon Nanoclusters are used in a quantity between 5 g and 50 g and PLA is used in a quantity between 900 g and 955 g.

4. The masterbatch composition according to anyone of the preceding claims further comprising one or more of:- anti-aggregating agents in a quantity between 40 g and 70 g and preferably selected from: Coconut wax, Rice wax, Soy wax, Palm wax.

5. The masterbatch composition according to anyone of the preceding claims which is an injectable paste with a viscosity between 900 and 1200 PI measured with a Rotary Viscometer Model VEVOR NDJ-9S thermostated at a temperature of 65°C for a measurement time of about 10 minutes.

6. A polymer mixture comprising an aliquot of the masterbatch composition according to anyone of claims 1 -5 in combination with a further aliquot of a polymeric material selected from PLA or another biodegradable polymer or a mixture of polymers.

7. The polymer mixture according to the preceding claim wherein the masterbatch composition is added to PLA or other biodegradable polymer or mixture of polymers in an amount of between 1 % and 10% by weight.

8. A method for obtaining the masterbatch composition according to anyone of claims 1 -5 comprising the phases of:- Dissolving an aliquot of PLA at room temperature in a solvent preferably chosen from: Terpinene, Terpinolene, Myrcene, Limonene, Dimethyl sulfoxide and mixing the mixture until PLA is completely dissolved, forming a clear solution;- Adding an aliquot of anti-aggregating agent and mixing the mixture to obtain a uniform distribution;- Adding the Carbon Nanoclusters in powder form to the mixture of PLA, solvent, anti-aggregating agent and mixing;- Homogenizing the mixture of the previous phase by sonication;- Evaporating the solvent, preferably in a rotary evaporator at a temperature between 85 and 95°C until complete evaporation of the solvent to obtain an injectable paste.

9. The method according to the preceding claim which further comprises the phase of processing the injectable paste of the preceding claim to obtain a granulate.

10. The method according to the preceding claim which further comprises the phase of mixing the granulate with a further portion of a polymeric materialselected from PLA or another biodegradable polymer or a mixture of polymers to obtain the polymeric mixture according to anyone of claims 6-7.

11. The method according to the preceding claim which further comprises the phase of processing the polymeric mixture according to anyone of claims 6-7 with a technique selected from: extrusion, preferably flat extrusion, or molding, preferably injection molding.

12. Artifacts obtained with the polymeric mixture according to anyone of claims 6-7.

13. The artifacts according to the preceding claim in the form of a formed body, wire, sheet, film.

14. The artifacts according to anyone of claims 12-13 to be used in the agricultural sector to make, for instance, mulching films; in the packaging and disposable products sector to make, for instance, films, food packaging bags, disposable tableware; in the medical instrumentation sector to produce, for instance, tissue scaffolds; in the aquaculture sector and in all sectors wherein biodegradable plastic materials are used.

15. Use of the masterbatch according to anyone of claims 1 to 5 for the preparation of a polymeric material with antibacterial and anti-algal proliferation properties.

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