HOT-MELT BIOBASED POLYMERIC FORMULATIONS

FOR COATING APPLICATIONS CONTAINING ACTIVE BIOMOLECULES

DESCRIPTION

Technical field

[0001] The present invention relates to the field of hot-melt formulations for coating applications. Specifically, the present invention deals with low molecular weight and low melting point polymeric biobased solid coatings containing active biomolecules with anti-microbial and/or water vapor barrier properties. The application of these solid coatings on polymeric or paper substrates can be used in different fields such as packaging, cosmetic and personal care products.

State of the art

[0002] Polymeric coatings may be applied to modify the surface properties of a substrate, such as adhesion, wettability, corrosion resistance, wear resistance and gas permeability. In particular, coatings can also guarantee new properties that are the features basically desired of a finished product.

[0003] Polymeric coatings can be applied by several different techniques, such as extrusion/dispersion coating and solution application. For example, in packaging industry, the incorporation of anti-microbial agents such as Chitin in coatings has been explored as an attractive option for protecting material from microorganism and environmental effects.

[0004] Hot-melt coatings (HMC), in use since the ‘50s, are solvent-free thermoplastic materials, with molecular weight below 10000 g/mol. At low temperatures, conventional HMC are normally solid, while at higher temperatures, i.e., for instance above 82°C, they become low-viscosity fluids that are able to quickly set upon cooling. When an HMC is in the fluid state, it flows onto the substrate to be coated and, as it solidifies, immediately forms a bond to the latter. [0005] Today, HMCs are used in a variety of manufacturing processes including packaging, bookbinding, product assembly, and box and carton heat- sealing, as well as other pressure-sensitive applications such as disposable products, stamps, and envelopes.

[0006] CN 215592982 (U) discloses a composite film for a water vapor and oxygen high barrier performance package, also including anti-counterfeiting protective layer. Disadvantageously this coating is not renewable

[0007] WO 2015/153226 A1 discloses a biobased hot-melt adhesive including a poly(lactide) homopolymer or copolymer with a molecular weight of about 1000 to about 40000 Dalton and a plasticizer including an ester with about 50% - 99% bio-based content.

[0008] CN 1 13527978 A discloses a bio-based hot-melt marking paint and a preparation method thereof. The formula comprises 15-22 parts of petroleum resin; 3-5 parts of titanium dioxide; 40-60 parts of bone material, where calcium carbonate to quartz sand mass ratio is 2:1 ; 18-22 parts of glass beads; 0.5-3.0 parts of auxiliary agent; and 0.5-3.0 parts of bio-based high polymer material, i.e., a very small amount thereof.

[0009] WO 1999013016 A1 discloses the use of natural oils into fully petro-based hot-melt coatings.

[0010] DE 10016183 A1 relates to a low-viscosity hot-melt adhesive obtained on the basis at least one hydrocarbon resin solid at 20°C and one oil. The invention also discloses a production method for this hot-melt adhesive and describes its use.

[0011] Gigante, et al, “Liquid and Solid Functional Bio-Based Coatings”, Polymers 2021 , 13, 3640, is a review in which only literature is cited dealing with solid formulations for hot melt coating drug tablets and the like, in order to avoid the use of any solvent, for instance, by a spray coating technique. Moreover, polymeric coating materials are known in which such biomolecules as Chitin, Chitosan, Cutin are used to give the coating material anti-microbial, water vapor barrier properties and even gas barrier properties. Among those coating materials, solid HMC and powder coatings are cited. However, the article clarifies that Chitin, Chitosan, Cutin cannot be easily incorporated in solid matrices to obtain solid functional bio-based coatings, in particular, solid functional bio based hot- melt coatings. [0012] CN 105 968 743 A relates to a biodegradable plastic film based on such a biodegradable raw material as polylactic acid and a to method for making said plastic film. More in detail, a raw material blend is disclosed including, beside polylactic acid, hemp fibres to impart mechanical resistance, and cornstarch to contain the costs. In the description of the manufacture method, a step of hot melting the raw material blend is cited in connection with a blow-molding step to obtain the film.

Summary of the invention

[0013] It is therefore an object of the present invention to provide a method for hot-melt coating a product by a layer having anti-microbial and/or hydrophobic properties, said layer obtained from a solid, fully bio-based hot-melt coating formulation useful for application on such thermosensitive substrates as cellulosic paper/board and polymer films and sheets.

[0014] It is also an object of the present invention to provide such a solid, fully bio-based hot-melt coating formulation useful for application on such thermosensitive substrates as cellulosic paper/board and polymer films and sheets. [0015] According to one aspect of the invention, the objects indicated above are achieved by a method for hot-melt coating a product by a layer having anti-microbial and/or hydrophobic properties as defined in claim 1 . Exemplary and advantageous embodiments of the invention are defined in the dependent claims.

[0016] The method of the invention provides the steps of: prearranging an amount of a biobased polymer having a melting temperature lower than 80°C and a number average molecular weight lower than 15000 g/mol; prearranging an amount of an active biomolecule; prearranging an amount of a dispersion aid; wherein the dispersion aid and the biomolecule have a weight ratio set between 1 :2 and 1 :20, in particular between 1 :3 and 1 :15, in particular 1 :8 and 1 :10; forming an emulsion of the active biomolecule in the dispersion aid; feeding the biobased polymer and the emulsion to a compounding extruder, such that a formulation is formed in which the active biomolecules are dispersed into a matrix of the biobased polymer through the dispersion aid; wherein the amount of the biobased polymer is set between 60% wt. and 90% wt. of the formulation; wherein the amount of the active biomolecule is set between 0.2% wt. and 10% wt. of the formulation, in particular the active biomolecule forms 1 % wt. to 5% wt. of the formulation; removing a volatile fraction from the formulation, the volatile fraction mainly formed by moisture present in said biobased polymer and water present in said emulsion; extruding a strand of the formulation from the extruder; cooling the strand and chopping it into pellets; hot-melting the pellets and applying said layer on said product.

[0017] This way, by making an emulsion of the active biomolecule into an appropriate dispersion aid before bringing the active molecule and the biobased polymer into contact with each other in the compounding extruder, the active molecules can be protected and maintained evenly dispersed in the matrix despite the high-shear conditions taking place within the compounding extruder. Thanks to the above effect, upon applying the obtained solid HMC product onto any substrate, it is possible to obtain a coating having uniform anti-microbial and water-repellence properties.

[0018] In order to obtain both anti-microbial and water-repellence properties, different active biomolecules can also be dispersed together in the dispersion aid of a same emulsion, using a combination of the active biomolecules providing the different desired properties. As an alternative, granules containing the individual active biomolecules can be used and a multilayer coating can be performed.

[0019] This way, solid bioplastic formulations are obtained that can be used as coatings on different substrates and that provide the latter with antimicrobial and/or water vapor barrier properties thanks to the active biomolecules embedded in the polymeric matrix.

[0020] The authors have developed formulations of biobased hot-melt solid coatings which, moreover, turned out to be highly compostable and/or biodegradable in soil. In this context, the present invention is an improvement with respect to the state of the art. In fact, significant innovation lies in the addition of active biomolecules, coming from natural resources.

[0021] In particular, the process for the dispersion of these biomolecules, including preliminary emulsification with a dispersion aid and subsequent coextrusion of the obtained emulsion with the biobased polymer of the matrix, provides an advantageous alternative to the use of toxic solvents, so as to guarantee a homogenous dispersion and solubility of the active biomolecules.

[0022] More in detail, such dispersion process prevents the biomolecules from forming agglomerates during the extrusion and during the application of the obtained hot-melt coating formulation, which would drastically degrade the performances of the coating.

[0023] Surprisingly, just biobased low molecular weight plasticizers turned out to be effective enough as dispersing aids to obtain said emulsification. [0024] The melting temperature and number average molecular weight of the biobased polymer are selected so that the formulation has appropriate rheological properties to be effectively applied as a coating on the substrate.

[0025] The above-mentioned biomolecules can be obtained from highly available and low-valorised biomass, such as tomato, legumes, melons, insects, fish, crustaceans, fungi.

[0026] The dispersion aid, basically a low molecular weight oligomer otherwise used as a plasticizer, assists and makes more effective the incorporation of the biomolecules into the biobased polymer of the matrix, fed to the extrusion step as an aqueous mixture and a solid to be molten in situ, respectively. The dispersing aid is also environment-friendly selected among technically appropriate molecules that can be obtained from renewable and/or biodegradable sources.

[0027] The innovative features of the present bio-based coatings copes with the actual requirements of food packaging, cosmetics and personal care products industries. More specifically, the largest part of the bio-based coating research activity is primarily focused upon short-lived bioplastic-based food packaging and paper coating for personal care. Food products, indeed, endure many chemical, physical, and bacterial modifications when stored. For this reason, the development of eco-sustainable coatings for packaging applications can slow down the deterioration rate of the packaged product, and therefore extend the shelf life of food.

[0028] Moreover, the production of bio-based formulations of the invention is an encouraging alternative with respect to the direct application of antimicrobials to the food.

[0029] In particular, the polymeric matrix forms 80% wt. to 90% wt. of the formulation.

[0030] The melting temperature of the biobased polymer and of the formulation can be assessed by conventional means, in particular, by differential scanning calorimetry (DSC), or other well-known calorimetric techniques. In particular step can be provided of checking the biobased polymer and/or the formulation, after the step of chopping the strand into pellets, in order to determine the melting temperature thereof. For instance, the differential scanning calorimetry step can be carried out by heating at 10°C/min from -60°C to 130°C.

[0031] The pellets can have a main dimension set between about 1 and 5 mm. The method can further include a step of grinding such pellets into a powder before the steps of hot-melting the formulation and of applying the layer of the formulation on said product. The powder can be a coarse or fine powder, e.g. with particle size in the range of 5-500 pm.

[0032] In particular, the biobased polymer is selected from the group comprised of: polybutylene sebacate; starch; polyesters and co-polyesters; copolymers based on co-polyesters and polyamides.

[0033] The active biomolecule can be selected from the group comprised of:

Chitin;

Chitosan;

Cutin; beeswax; carrauba wax; pullulan; ulvan; a flavonoid; a thiosulfinate; a glucosinolate; hyaluronic acid; a saponin; a terpene; a combination thereof.

[0034] The dispersion aid can be selected from the group comprised of a citrate; an oligomer selected from the group comprised of: a lactic acid oligomer (OLA); poly(N-(2-Hydroxypropyl)methacrylamide) (PHPMA); an oligo-co-polyester of adipic acid with 1 ,3-butanediol, 1 ,2-propane- diol and 2-ethyl-1 -hexanol, and having a molecular weight lower than 5000 g/mol, in particular lower than 4000 g/mol;

Glycerol;

Sorbitol;

Cardanol;

Soybean Oil;

Sunflower Oil; a combination thereof.

[0035] According to another aspect of the invention, the objects indicated above are achieved by a solid formulation for hot-melt coating a product by a layer having anti-microbial and/or hydrophobic properties as defined in claim 16. Exemplary and advantageous embodiments of the invention are defined in the dependent claims.

[0036] The solid formulation is obtained by coextrusion of:

60% wt. to 90% wt. of a polymeric matrix of a biobased polymer having a melting temperature lower than 80°C and a number average molecular weight lower than 15000 g/mol, wherein the biobased polymer is selected from the group comprised of: polybutylene sebacate; starch; polyamides; polyesters and co-polyesters; copolymers based on co-polyesters and polyamides, and an emulsion including:

0.2% wt. to 10% wt. of an active biomolecule dispersed in the polymeric matrix, the active biomolecule selected from the group comprised of:

Chitin;

Chitosan;

Cutin; beeswax carrauba wax pullulan ulvan; flavonoid; thiosulfinate; glucosinolate; hyaluronic acid; saponin; terpene; a dispersion aid selected from the group comprised of: a citrate;

Glycerol;

Sorbitol;

Cardanol;

Soybean Oil;

Sunflower Oil; an oligomer selected from the group comprised of: a lactic acid oligomer (OLA); poly(N-(2-Hydroxypropyl)methacrylamide) (PHPMA); oligo-co-polyester of adipic acid with 1 ,3-butanediol, 1 ,2- propanediol and 2-ethyl-1 -hexanol and having a molecular weight lower than 5000 g/mol, in particular lower than 4000 g/mol; wherein the dispersion aid and the biomolecule have a weight ratio set between 1 :2 and 1 :20, in particular between 1 :3 and 1 :15, in particular 1 :8 and 1 :10.

[0037] Preferably, the biobased polymer of the matrix is polybutylene sebacate, a totally biodegradable low-molecular weight thermoplastic adhesive copolyester, that has a low melting point of 64 °C, and can easily be applied as a film.

[0038] In one embodiment, the active biomolecule is selected between Chitin and Chitosan, which are materials adapted to provide anti-microbial properties.

[0039] Besides showing anti-microbial properties Chitin and Chitosan are biocompatible, biodegradable and non-toxic.

[0040] The use of Chitin and/or Chitosan is also advantageous in view of the great availability of these biopolymers on Earth, ranging between 1 O ¹⁰ and 10 ²⁰ ton/year. Chitin is present in several materials, e.g., portions of insects, molluscs, crustaceans and fungi. The proper use of this resource may allow recovery of value-added goods into currently expanding fields of activity, such as biomedical, pharmaceutical, food technology, agro-bioscience and cosmetic dermatology industries. Besides showing anti-microbial properties Chitin and Chitosan are biocompatible, biodegradable and non-toxic.

[0041] Preferably, Chitin or Chitosan are in the form of nano-fibres, in particular in the form of partially deacetylated fibrils. More in particular, the partially deacetylated fibrils are obtained by deacetylation of raw Chitin coming from shrimp shells by Masuko technology, for example, by processing them for about 3 hours and at about 1 .5% of concentration in water. In the case of Chitin and Chitosan, the dispersion aid is a biobased lactic acid oligomer with a molecular weight set between 200 and 5000 g/mol, in particular between 500 and 4000 g/mol, an ester content higher than 90-99%, a density set between 0.9 and 1.10 g/cm ³ , a viscosity at 40°C set between 80 and 100 mPa s, a maximum water content of 0.3%.

[0042] More in general, coatings having anti-microbial properties can be obtained by embedding such active biomolecules as Polysaccharides or secondary metabolites possessing anti-microbial activity into the polymeric matrix. Such natural anti-microbials can be obtained from different sources like plants, fruits, vegetables, seeds, herb, and spices; from animals (shrimps, insects), and from such microorganisms as fungi and bacteria. Anti-microbials include chitin; Chitosan; Pullulan; Ulvan; flavonoid; thiosulfinate; glucosinolate; hyaluronic acid; saponin; terpene.

[0043] In another embodiment, the active biomolecule is cutin, which is adapted to provide hydrophobic properties. In this case, the dispersion aid is a hydrophobic dispersion aid, preferably a polyester of adipic acid with 1 ,3-bu- tanediol, 1 ,2-propanediol and 2-ethyl-1 -hexanol, in particular having a density set between 0.88 and 1 .3 g/cm ³ at 25 ^S C, and a low molecular weight set between 2500 and 3500. These are highly biodegradable oligomeric plasticizers, limiting plasticizer losses due to volatility, migration or extraction and are resistant to extraction.

[0044] Unlike Chitin and Chitosan, Cutin is a non-water-soluble crosslinked polyester mainly consisting of condensed, i.e., esterified mono-, bi- and trifunctional polyhydroxylated acid, adapted to provide hydrophobic, i.e. water vapor barrier properties. Similar acids, such as oleic acid, beeswax, carrauba wax also have water repellence properties.

[0045] Cutin is the main constituent of the cuticles of the plant, making up 40-80% of the cuticle's dry mass. Plant cuticles are the outermost membranes covering the epidermis of leaves, stems, flowers, and fruits of many plants, and forming a barrier against leakages from internal tissues, thanks to their water repellency.

[0046] Coatings having water repellence properties can also be obtained by embedding into the polymeric matrix other active biomolecules as fatty acids, as they can be obtained from fruit cuticle by-products.

[0047] In the method, the step of forming the emulsion of the active biomolecule into the dispersing aid dispersion is preferably carried out by a mixer for liquids having a stirrer member configured to rotate at a speed of at least 10000 rpm. The stirrer member is caused to rotate in the presence of the active biomolecule and the dispersing aid during a mixing time of at least 4 minutes.

[0048] The preparation of the mixture serves to guarantee the desired dispersion avoiding residuals and agglomerates. More in detail, the mixing time is selected so that the emulsion, once obtained, it has not to unmix. [0049] Moreover, the emulsion preferably has a viscosity of about 1 Pa s at 25°C, so that it can be conveyed and fed to the extrusion step by such a conventional means as a liquid feeder or a peristaltic pump. If the above viscosity value is not attained, the emulsion can be heated and the designated temperature maintained before being sent to the extrusion step.

[0050] The extrusion step advantageously allows to incorporate the low- molecular weight biomolecules into the polymeric matrix through a solvent-free process, providing biopolymeric formulations in the shape of pellets, or of a powder obtaining by grinding the latter, that are ready to be used in a subsequent melt application process as barrier adhesive coatings for mono or multilayers.

[0051] Polybutylene sebacate stands out for its great versatility, as it is used to make compostable formulations for injection moulding, blown extrusion and strand extrusion. It is also used as carrier polymer for biodegradable masterbatches, as hot-melt adhesive component for the footwear and other industries, in 3D printing, and potentially in any application where biodegradability is required. The polymer is more than 95% bio-based and the content of renewable sources can be increased up to 100% by using bio-1 ,4-butanediol (bioBDO).

[0052] Advantageously, the step of removing a volatile fraction from the mixture being extruded is carried out by a vacuum suction system provided in said compounding extruder and including a vacuum pump and a venting. The suction elements of the vacuum suction are located along the extrusion line and possibly also at the head of the extruder.

[0053] Moreover, the extruder is set in such a way that the residence time of the formulation being extruded is shorter than a maximum residence time. In particular, the maximum residence time is set between 20 and 40 sec, more in particular the maximum residence time is about 30 sec.

[0054] In one embodiment, the active biomolecule is selected between Chitin and Chitosan, which are fully biocompatible, biodegradable and non-toxic materials, adapted to provide anti-microbial properties, with the effects and advantages specified in the above description of the method. Preferably, Chitin or Chitosan are in the form of nano-fibres, in particular in the form of partially deacetylated fibrils. More in particular, the partially deacetylated fibrils are obtained by deacetylation of raw Chitin coming from shrimp shells by Masuko technology. In the case of Chitin and Chitosan, the dispersion aid is preferably a biobased lactic acid oligomer having a molecular weight set between 200 and 5000 g/mol, in particular between 500 and 4000 g/mol.

[0055] In another embodiment, the active biomolecule is cutin, which is adapted to provide hydrophobic properties with the effects and advantages specified in the above description of the method. In this case, the dispersion aid is a hydrophobic dispersion aid, preferably a polyester of adipic acid with 1 ,3- butanediol, 1 ,2-propanediol and 2-ethyl-1 -hexanol. These are highly biodegradable oligomeric plasticizers, limiting plasticizer losses due to volatility, migration or extraction and are resistant to extraction.

[0056] It falls within the scope of the present invention also the use of any formulation made according to the method, or of the above-described solid formulation, on a cellulosic, biopolymeric and polymeric surface of a packaging, the surface selected from the group comprised of: a cellulosic paper or board surface; a film surface; a surface of woven or non-woven sheet; a surface including porosities and/or micro/nanopatterning; the packaging selected from the group comprised of a biomedical packaging; a sanitary packaging; a cosmetics packaging; a textile and personal care packaging by a process selected from the group for granules comprised of: coating roller; lamination; compression moulding; extrusion coating; additive manufacturing; or methods for the application of powders or fibres on surfaces or porous substrates based on vacuum, radiation or electric fields.

[0057] Therefore, the granules obtained from the previous extrusion compounding technique can be applied on any cellulosic or polymeric substrate, or even alternative substrates, so as to improve water repellence and/or anti-microbial properties. The formulations of the invention can be applied by the conventional techniques already in use for petro-based, conventional hot-melt coatings, in particular Hot-melt coater, both in laboratory and industrial scale, and compression Moulding, which do not require the use of solvents and adhesives. No modifications to existing equipment are required for applying the HMC formulations according to the invention.

[0058] Moreover, optional, conventional additives can be added both to the emulsions and during the compounding extrusion process, for instance, to improve processing and/or thermal, and/or mechanical and/or barrier properties.

Brief description of the drawings

[0059] The invention will be now shown with the description of examples and exemplary embodiments thereof, exemplifying but not limitative, with reference to the attached drawings, in which:

Fig. 1 is a diagram showing the relationship between the dynamic viscosity of the matrix itself and of HMC formulations of examples 1 -4 at 70°C and the shear rate applied thereto;

Figs. 2-5 show thermogravimetric analysis thermograms of HMC formulations of examples 1 -4;

Fig. 6 show the DSC thermograms of HMC formulations of examples 1 -4; Fig. 7 shows bacteria contact plates of anti-microbial tests of HMCs applied onto cellulosic substrates.

Fig. 8 shows moulds contact plates of anti-microbial tests of HMCs applied onto cellulosic substrates;

Fig. 9 is a diagram showing how the contact angle of a drop of water deposited on the sample evolves with time;

Fig. 10 is a block diagram of the process according to the invention.

Detailed description of the invention

[0060] Experiments and examples listed below are intended to better illustrate what is reported in the above description, these examples are not in any way to be considered as limitation of the foregoing description and the appended claims.

[0061] In particular, three different active biomolecules derived from natural resources were successfully tested, Chitin and Chitosan providing anti- microbial properties, Chitosan also providing some gas barrier effect, whereas cutin was used to obtain water-repellent HMCs.

EXAMPLES

Example 1 . Method of preparation and characterization of HMC formulation with Chitin from shrimps

[0062] Chitin slightly deacetylated fibrils from shrimps, processed for 3 hours by a Masuko technology at 1 .5 wt.% of concentration in water, as available, for instance, at CELABOR, Chaineux, Belgium, were mixed to a lactic acid oligomer at a Plasticizer/Chitin weight ratio of 9:1 , as shown in Table 1 .

[0063] The liquid oligomer was selected as a dispersing aid so as to promote the dispersion of the active biomolecules of Chitin. Completely biodegradable Lactic Acid Oligomer 2 was used (trade name: Glyplast OLA 2), with an ester content > 99%, a density of 1 .10 g/cm ³ , a viscosity (ASTM D 445) of 90 mPA s at 40°C, a maximum water content (ASTM E 203) of 0.1 %. A homogeneous dispersion was obtained with a disperser at 10000 rpm for 240 s in order to attain a viscosity of about 1 Pa s, which was necessary for the subsequent pumping through forced liquid feeder.

[0064] Subsequently, the emulsion was supplied to a semi-industrial twin- screw extruder compounder being simultaneously fed with Polybutylene Sebacate. The extruder was equipped with a venting system adapted to ensure the complete stripping of the water accompanying, in particular the emulsion of the Chitin and the OLA2. The temperature profile set in the extruder zones is shown in Table 2. The total flow rate was set at 9 kg/h in order to obtain a 1 wt.% Chitin final product, and the screw speed was set at 150 rpm. The strands produced by the extruder were cooled in a water bath and then pelletized into granules that were subsequently dried in a vacuum oven for 24 hours.

[0065] The granules were tested by a Melt Flow Tester in order to evaluate the melt strength and the fluidity of the optimized product. The tests were carried out at 70°C under a constant load of a 2.16 kg weight (ISO 1 133), in nonstandard conditions, in order to take into account the low melting point of the materials. As shown in Table 3, a melt flow rate of 3.4 g/10 min was obtained, which is suitable for subsequent manufacturing coating processes. [0066] Thermogravimetric analysis (TGA) was also carried out as shown by the thermogram of Fig. 2, indicating the percentage mass loss as a function of temperature and the trend of the derivative of mass loss as a function of time as temperature increases. The TGA made it possible to extrapolate the temperature degradation range of the active biomolecules and to check the absence of water in the formulation, i.e., to assess the effectiveness of the extruder venting system provided therefor. The tests were carried out under nitrogen gas flow at a scanning speed of 10 °C/min, from room temperature to 600°C.

[0067] A first degradation peak was observed around 250°C, which is related to shrimp degradation. However, such a temperature is far above the processing temperatures of the invention. A second higher peak was also observed, in connection to OLA and Polybutylene Sebacate degradation.

[0068] Moreover, the thermogram revealed the absence of water in the formulations, thanks to removal efficiency of the vacuum suction system of the extrusion process.

[0069] The viscosity of the obtained formulation was also evaluated as a function of the applied shear rate in a rotational viscometer at a test temperature of 70°C. As shown in Fig. 1 , the introduction of the emulsion of the active biomolecules and the plasticizer into the matrix significantly lowers the viscosity of the formulations, which is useful for a correct application of the formulation as a hot-melt coating. At low shear rates this effect is not so sensitive as at high value. More in detail, as the shear rate increases, the viscosity decreases down to about 5 Pa s at 100 s’ ¹ , which is a value far lower than the raw matrix viscosity, and is an optimum value in view of a subsequent coating application.

[0070] In order to assess whether a typical melting temperature of a hot- melt had been obtained, differential scanning calorimetry (DSC) was carried out heating at 10°C/min from -60°C to 130°C. For Example 1 , the DSC thermograms of Fig. 6 showed a melting peak centred at about 62.7°C. A slight but negligible decrease in melt temperature of the formulations, due to the plasticizer in the formulations, is an effect common to all the examples.

[0071] Anti-microbial properties of the HMC applied onto three different bioplastics substrates (PS) were evaluated employing bacterial concentration stated by ISO 22196:201 1 . The test was performed on three replicates and six specimens of the untreated material as control samples. Three untreated test specimens were used to measure viable cells immediately after inoculation, and three specimens were used to measure viable cells after 24 h-incubation. As bacterial inoculum, 24 hours-old cultures of Escherichia coli and Staphylococcus aureus were used to prepare two solutions (1/500 Nutrient Broth) containing 5 x 105 cells/ml of each bacterial strain. Bacterial suspensions were immediately used for test assessment. After the specimen was inoculated and covered with Parafilm, the lid of the Petri dish was replaced and incubated at a temperature of 35 ± 1 °C and at a relative humidity of not less than 90 % for 24 ± 1 h. Immediately after inoculation, half of the untreated test specimens were processed by adding 10 ml of either SCDLP broth to the Petri dish containing the test specimen. The obtained values were used to determine the recovery rate of the bacteria from the test specimens. Viable bacteria were enumerated by performing 10-fold serial dilutions of the SCDLP in phosphate-buffered physiological saline. 1 ml of each sample and their dilutions was placed into separate sterile Petri dishes and added with 15 ml of plate count agar. All plating was performed in duplicate. Petri dishes were incubated at 35 ± 1 °C for 48 h.

[0072] After incubation, the number of colonies in the Petri dishes was counted and recorded. If no colonies grew in any of the agar plates in the dilution series, the number of colonies was reported as “< 1 For calculation of antibacterial activity, data are expressed as colony forming units (CFU) or viable cells per cm ² . When the test was deemed to be valid, the antibacterial activity was calculated using the following equation, and recording the result to one decimal place.

R = (Ut - U0) - (At - U0) = Ut - At, where R is the antibacterial activity; “U0” is the average of the common (i.e. base 10) logarithm of the number of viable bacteria, in cells/cm ² , recovered from the untreated test specimens immediately after inoculation; “Ut” is the average of the common logarithm of the number of viable bacteria, in cells/cm ² , recovered from the untreated test specimens after 24 h; “At” is the average of the common logarithm of the number of viable bacteria, in cells/cm ² , recovered from the treated test specimens after 24 h. The value of the antibacterial activity can be used to characterize the effectiveness of an antibacterial agent or treatment. ISO 22196:201 1 reports that “the antibacterial-activity values used to define the effectiveness shall be agreed upon by all interested parties”. In other words, criteria for effectiveness assessment must be established with case-specific modalities. As it can be seen in table 4, the results of Examplei hot-melt coating applied on different bioplastic substrates show an evident anti-microbial effect on all the tested substrates.

[0073] As shown in Table 5 and Fig. 7, microbiological examination (bacterial growth on contact plates) of the HMC of Example 1 on cellulosic substrates (CS) was conducted according to the ISO 8784/2 standard. From bacteria contact plate tests it can be noticed the shrimps Chitin anti-microbial. The samples show a very low total number of colony-forming unit (CFU) per 100 cm ² , equal or below 3, measured on 5 repetitions.

[0074] Table 5. Results of anti-microbial tests of HMC examples 1 -3 (Chitin and Chitosan) applied onto cellulosic substrates (CS). Microbiological examinations on treated paper have been conducted following the ISO 8784/2 standard.

[0075] Similarly, total moulds contact plate tests were evaluated according to ISO 8784/2 using SDA Agar. Example 1 show a very good inhibiting effect on growth of mould colonies, as shown in Table 6. More in detail, the samples showed a very low total number of colony-forming unit (CFU) per 100 cm ² , equal or below 3, measured on 5 repetitions.

Example 2. Method of preparation and characterization of HMC formulation with Chitin from Mushrooms.

[0076] Chitin slightly deacetylated fibrils from mushrooms, processed for 3 hours by a Masuko technology at 1 .5 wt.% of concentration in water, as available, for instance, at CELABOR, Chaineux, Belgium, were mixed to a lactic acid oligomer at a Plasticizer/Chitin weight ratio of 9:1 , as shown in Table 1 . The dispersion containing Chitin and OLA2 was obtained by the same procedure as in Example 1 . The parameters of the extruder, also in this case being simultaneously fed with Polybutylene Sebacate, were the same as in Example 1 as well.

[0077] The granules were tested by a Melt Flow Tester as described in Example 1 . As shown in Table 3, a melt flow rate of 3.5 g/10 min was obtained, which suitable for subsequent manufacturing coating processes.

[0078] Thermogravimetric analysis (TGA) was also carried out as shown in Fig. 3, by the same procedure as in Example 2. A first degradation peak was observed around 250°C, which is related to mushroom degradation. However, such a temperature is far above the processing temperatures of the invention. A second higher peak was also observed in connection to OLA and Polybutylene Sebacate degradation.

[0079] The viscosity was also calculated as a function of the applied shear rate, as described in Example 1 . As shown in Fig. 1 , as the shear rate increases, the viscosity decreases down to a value of about 4.5 Pa s at 100 s ^-1 , which is a value far lower than the pure matrix viscosity, and is an optimum value in view of a subsequent coating application.

[0080] In order to assess whether a typical melting temperature of a hot- melt had been obtained, differential scanning calorimetry (DSC) was carried out heating at 10°C/min from -60°C to 130°C. For Example 2, the DSC thermograms of Fig. 6 showed a melting peak centred at about 60.5 °C.

[0081] Anti-microbial tests were carried out on cellulosic substrates by the same procedure as in Example 1. The results show an evident anti-microbial effect of Example 2 on the CS for both bacteria and the mould.

Example 3. Method of preparation and characterization of HMC formulation with Chitin from Shrimps Chitosan.

[0082] Chitosan powder from shrimp source was mixed to a lactic acid oligomer at a Plasticizer/Chitosan weight ratio of 9:1 , as shown in Table 1 . The dispersion containing Chitin and OLA2 was obtained by the same procedure as in Example 1 . The parameters of the extruder, also in this case being simultaneously fed with Polybutylene Sebacate, were the same as in Example 1 as far as concern the temperature profile, while a flow-rate of 16 kg/h and a screw speed of 200 rpm were adopted.

[0083] The granules obtained by pelletizing the strand from the extrusion were then tested with a Melt Flow Tester as described in Example 1 . As shown in Table 3, a melt flow rate of 2.2 g/10 min was obtained, which is suitable for subsequent manufacturing coating processes, nevertheless higher than Example 1 and 2.

[0084] Thermogravimetric analysis (TGA) was also carried out as shown in Fig. 4, with the same procedure as in Example 2. A first degradation peak was observed around 280°C, which is related to Chitosan degradation. However, such a temperature is far above the processing temperatures of the invention. A second higher peak was also observed at about 400°C, in connection to OLA and Polybutylene Sebacate degradation

[0085] The viscosity was also calculated as a function of the applied shear rate, as described in Example 1 . As shown in Fig. 1 as the shear rate increases, the viscosity decreases down to a value of about 4.5 Pa s at 100 s ^-1 , which is a value far lower than the pure matrix viscosity, and is good for the subsequent coating application even higher than Example 1 and Example 2.

[0086] In order to assess whether a typical melting temperature of a hot- melt had been obtained, differential scanning calorimetry (DSC) was carried out heating at 10°C/min from -60°C to 130°C. For Example 3, the DSC thermograms of Fig. 6 showed a melting peak centred at about 60.5 °C.

[0087] Anti-microbial tests were carried out on cellulosic substrates by the same procedure as in Example 1. The results show an evident anti-microbial effect of Example 3 on the CS for both bacteria and the mould.

Example 4. Method of preparation and characterization of HMC formulation with cutin from tomato peel

[0088] Raw cutin extracted from tomato peels was dispersed into a polyester plasticizer used as a dispersing aid. The preparation of the mixture was in such a way to obtain a desired dispersion of cutin into a polyester of adipic acid, for example commercial product Glyplast® 206-3 NL, selected to improve the hydrophobicity of the hot-melt coating. Glyplast® 206-3NL is a polyester of adipic acid with a density of 1 .07 g/cm ³ at 25 ^S C, a low molecular weight polymer obtained from adipic acid and propylene glycol, i.e. 1 ,2 propandiol, MW = 3200 g/mol.

[0089] To facilitate the mixing process, cutin was stored for 24h in oven at 60°C before preparing the mixture. In addition, the mixture of the plasticizer used as a dispersing aid, prepared at a Plasticizer/Chitosan weight ratio of 3:1 as shown in Table 1 , was heated on a hotplate overnight at 60°C. A homogeneous dispersion was then obtained using a disperser at 15000 rpm for 180 s. The parameters of the extruder, also in this case being simultaneously fed with Polybutylene Sebacate, were the same as in Example 1 . [0090] Extrusion parameters were to the same as in Example 1 as far as concern the temperature profile, while a flow-rate of 15 kg/h and a screw speed of 250 rpm were adopted.

[0091] The granules obtained by pelletizing the strand from the extrusion were then tested with a Melt Flow Tester as described in Example 1 . As shown in Table 3, a melt flow rate of 4.6 g/10 min was obtained. This value is higher than de corresponding values of the previous example, but is still suitable for subsequent manufacturing coating processes.

[0092] The viscosity was also calculated as a function of the applied shear rate, as described in Example 1 . As shown in Fig. 1 as the shear rate increases, the viscosity decreases down to a value of about 2.6 Pa s at 100 s ^-1 , which is a value far lower than the raw matrix viscosity, and is an optimum value in view of a subsequent coating application.

[0093] Thermogravimetric analysis (TGA) was also carried out as shown in Fig. 5 with the same procedure as in Example 2. A first degradation peak was observed around 400°C, which is related to Glyplast 206/3NL and Polybutylene Sebacate degradation. A second lower peak was also observed at about 510°C in connection to cutin degradation, which showed a higher stability with respect to the other active biomolecules tested in the previous examples.

[0094] In order to assess whether a typical melting temperature of a hot- melt had been obtained, differential scanning calorimetry (DSC) was carried out heating at 10°C/min from -60°C to 130°C. For Example 4, the DSC thermograms of Fig. 6 showed a melting peak centred at around 61 .5 °C.

[0095] Water repellence tests were conducted to assess the hydro- philic/hydrophobic properties of a cellulosic substrate (CS) coated with the formulation of Example 4 by contact angle analysis, using ultrapure water as a wet liquid. The test was carried out according with EN ISO 19403-2:2020. Measurements were carried out on a total of three specimens from each of two different samples. 5 to 10 drops of ultrapure water were deposed per specimen, as shown in Fig. 9. The average contact angle, shown in Table 7, is slightly below 90°, which is the limit between hydrophobic and hydrophilic property. The samples showed excellent uniformity, and the results were very easy to replicate. Fig. 10 shows a slight decrease with time of the contact angle falling from 84° to 74° during 10 minutes. This contact angle decrease does not correspond to any contact surface increase, but rather to a volume or height decrease.

[0096] Cobb test was also performed to measure the water absorption capacity (expressed in g/m2) of a cellulosic substrate coated with the formulation of Example 4. If the Cobb value is high, the substrate can absorb and retain moisture. On the contrary, if the Cobb value is low, the substrate is able to resist to the penetration and retention of moisture. Cobb test was carried out according to ISO 535:2014, in a 23°C / 50% humidity control environment. Measurements were carried out at 1 min, 30 mins and 12 h. As shown in Table 8, the results indicated very low water absorption, which confirms the high water-repellence of the coated sample. Following this result, the slight decrease of the contact angle and drop volume can be explained by the evaporation of the water drop.

[0097] Water vapour permeability was assessed onto hot-melt coatings applied on polymeric substrates according to DIN 53122-1 : 08/2001 (gravimetric method) at a temperature of 23 °C and at a relative humidity (r.h.) gradient from 85 % -> 0 %. The measurement was performed using 4 specimens of each sample.

[0098] As shown in table 9, the results indicate an evident improvement of water vapour resistance adding Example 4 formulation as a coating to the polymeric substrate.

- Table 1 -

Details of the composition of HMC formulations obtained by extrusion in the examples 1-4.

- Table 2 -

Details of temperature profiles for the 11 zones and extrusion set up of the extruder in HMCs production in the examples 1-4. - Table 3 -

Melt Flow Rate values of HMC formulations of examples 1-4.

- Table 4 - Results of anti-microbial tests of HMC examples 1 and 3 (Chitin and Chitosan) applied onto three different bioplastics substrates (PS). Data shown are average of 5 replicated tests executed for every specimen, each one performed in duplicate count for every bacterial strain.

- Table 5 -

Results of anti-microbial tests (bacterial growth on contact plates) of HMC examples 1-3 (Chitin and Chitosan) applied onto cellulosic substrates (CS).

- Table 6 -

Results of anti-microbial tests (mould growth on contact plates) of HMC examples 1-3 (Chitin and Chitosan) applied onto cellulosic substrates (CS). - Table 7 -

Water repellence test HMC example 4 (cutin) applied onto cellulosic substrates (CS) by contact angle analysis.

- Table 8 -

Cobb test on HMC example 4 (cutin) applied onto cellulosic substrate (CS).

- Table 9 -

Water vapour transmission rate (WVTR) tests performed onto different polymeric substrates (PS) coated with HMC example 4 (cutin).

[0099] The foregoing description of exemplary embodiments and specific examples of the invention will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt such embodiments for various applications without further research and without parting from the invention, and, accordingly, it is to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiment and to the examples. The means and the materials to perform the various functions described herein could have a different nature without, for this reason, departing from the scope of the invention. It is to be understood that the phraseology or terminology that is employed herein is for the purpose of description and not of limitation.