Process for preparing a lacquer usable as a biocoating for coating

Abstract

The present invention relates to a process for preparing a coating lacquer comprising the following steps: a) providing a natural hydrocolloid and a solvent, the solvent comprising or consisting of water, b) introducing, under stirring, the natural hydrocolloid into the solvent to obtain a pre-hydrolysis solution, the natural hydrocolloid having a concentration ≥ 13% by weight of the total weight of the pre-hydrolysis solution, c) reaching a temperature comprised between 40°C and 57°C, d) introducing a hydrocolloid-specific hydrolyzing enzyme to obtain a coating lacquer, wherein the coating lacquer has a natural hydrocolloid concentration ≥ 13% by weight of the total weight of the coating lacquer.

Description

[0001] TITLE: “Process for preparing a lacquer usable as a biocoating for coating”

[0002] DESCRIPTION

[0003] FIELD OF THE INVENTION

[0004] The present patent application relates to the technological field of lacquers, i.e., compositions that can be used in the context of the coating technique for deposition on a suitable substrate.

[0005] In the present case, a process has been developed for the production of a lacquer consisting of a coating lacquer for spreading based on hydrocolloids that is usable as a biocoating for spreading, for example usable in the food packaging sector.

[0006] STATE OF THE ART

[0007] Coating technology is well-established in various sectors, including food packaging. Historically, the deposition of thin polymeric layers has mainly concerned converting operations, such as printing (ink deposition), or lamination (adhesive deposition for the creation of multilayer structures). Subsequently, the deposition of thin layers has concerned "ennoblement" operations of packaging material (with particular reference to plastic materials), including lacquering and metallization processes, to obtain specific functionalities of the finished packaging, including gas and vapor barrier properties, thermal stability, mechanical resistance, or special sealing properties. More recently, coating technology has instead assumed increasing importance for achieving the sustainability targets imposed by European legislation (Directive 94 / 62 / EC of 20 December 1994 on packaging and packaging waste).

[0008] The need to replace heterogeneous multilayer configurations with so-called "monomaterial" configurations has made coating technology a "key enabling technology", i.e., a key technology for achieving this sustainability objective. European legislation defines "monomaterial" as a material consisting of at least 95% by weight of an identical molecule (or polymer), with the remaining part (5%) represented by accessory layers (for example: inks, adhesives, lacquers). Specifically, polyolefinic monomaterials (based on polyethylene - PE or polypropylene - PP) or polyester-based (for example polyethylene terephthalate - PET) or even obtained using bioplastics (for example polylactic acid - PLA) can be produced. In any case, in order to guarantee an adequate shelf-life of the packaged product, it is necessary to impart to the finished material the necessary gas and vapor barrier properties which, in multilayer structures, are usually provided by an aluminum foil (thickness of about 7-8 pm), or by the superposition of different layers that include a barrier polymer (such as, for example, polyamide, otherwise known by the trade name Nylon) having a thickness of about 10 pm. With the introduction of monomaterials, it is essential to guarantee the same performance of multilayer materials, but by reducing the thickness of the functional layers. It is in this context that coating technology assumes considerable importance, allowing the realization of monomaterials capable of performing on par with previous multilayer configurations and, moreover, guaranteeing the environmental sustainability requirements imposed by the legislator. In the specific case of gas and vapor barriers, to date, this objective can be achieved through two main deposition technologies: metallization and coating.

[0009] Metallization is a process of deposition in high vacuum of a metal (solid), such as aluminum, which, at high temperatures and under high vacuum conditions, evaporates. Such vapors are deposited on the surface of the plastic substrate, representing an excellent gas and vapor barrier. This technology, however, has limitations, represented by high plant costs and the fact that metallized materials do not allow the packaged product to be seen. If the oxidized form of aluminum (aluminum oxide, AI2O3) were deposited, transparency would be guaranteed, but at the expense of excessive rigidity of the functional layer which severely limits its application in the food packaging sector.

[0010] Coating technique

[0011] Unlike metallization, coating involves the deposition of a product in liquid (and not solid) state through different deposition techniques, among which the main ones are: gravure, flexo, and semi-flexo techniques.

[0012] These techniques have in common the use of engraved cylinders which, by direct (gravure) or indirect (flexo and semi-flexo - "reverse" gravure) means, deposit a specific quantity of liquid substance on the plastic substrate, which, after solvent removal, results in a solid functional layer, which is, in fact, the coating. The coating deposition techniques are today the most widespread not only for the lower cost of the machinery, but also for the versatility of the plants themselves, being able to be used for the deposition of lacquers, as well as for inking and lamination operations.

[0013] Specifically, gravure technology (in English rotogravure) is a printing and coating process in which the solution (for example, an aqueous solution) of the coating is applied to a substrate using an engraved cylinder. It is a widely used method for applying thin coatings to materials such as paper, plastic, textiles, plastic. It starts with an engraved cylinder (the engravings are defined lines), usually made of steel, more rarely of copper. As the number of lines of the cylinder increases, the quantity of liquid deposited decreases, but its definition increases (in other words, fewer drops of liquid, but more dots). Conversely, a lower number of lines implies a greater quantity deposited, but with less definition (larger drops deposited on the substrate). The cylinder is engraved with small cells or cavities on its surface. The geometry and depth of the cells determine the quantity of material (coating) that will be transferred to the substrate. The engraved cylinder passes, rotating continuously, through the basin containing the liquid (aqueous solution of coating) and its cells are filled with the liquid to be applied to the material (plastic film, for example). A blade, called a "doctor blade", scrapes off excess liquid on the cylinder surface, leaving the coating only inside the engraved cells. This ensures that the quantity of deposited material is exactly that of the cells, without excess. As the cylinder collects the liquid, it comes into direct contact with a second cylinder (more precisely called a pressure roller) that carries the plastic substrate. Through this contact, the cylinder "discharges" the liquid onto the plastic substrate, thanks to the pressure exerted. The transfer is very precise and the applied coating is homogeneous and controlled in terms of thickness. Once the coating has been applied to the substrate, it is dried, i.e., the solvent (for example, water) is removed. This process is carried out with the aid of hot air ovens, sometimes complemented by infrared lamps which, in the case of water solvent, are very useful for promoting water evaporation. At this point, the lacquered plastic film is wound onto a reel ready for subsequent operations.

[0014] Gravure technology is the most suitable for the deposition of thin layers (< 2 pm), its main advantage being its precision and uniformity of process. The process, in fact, allows very precise control of the thickness and distribution of the coating thanks to the adjustment of the dimensions of the cells on the cylinder. Furthermore, gravure technology is suitable for large-scale and high-speed processes (up to 500 m / min), which makes it ideal for continuous production.

[0015] In the field of liquid coating, a particularly important class of lacquers in the food packaging sector are oxygen barrier lacquers.

[0016] Oxygen, in fact, represents one of the primary factors of degradation and qualitative decay for many foods and, for this reason, it is necessary to design packaging solutions with low gas permeability values. In fact, the food packaging sector pushes for the realization of transparent configurations with oxygen permeability values (expressed as Oxygen Transmission Rate (OTR) in cm3 / m224h) below unity (< 1.0 cm3 / m224h).

[0017] Since coating is a deposition technique that starts from liquid solutions, it is necessary that these solutions have viscosity values compatible with "direct roto-gravure" processes, for which the ideal viscosity is -90-130 mPas; for "reverse roto-gravure" processes, for which the ideal viscosity is -50-80 mPas; and for depositions using "flexo" technology, for which the viscosity rises to -180-230 mPa*s (Brookfield, spindle R2, 200 rpm, 23 °C, ISO 2555).

[0018] Problem of the known art

[0019] Despite being of extreme interest and importance for the sector, the oxygen barrier lacquers currently on the market are only of three types: i) vinyl lacquers: these are the most used and, among them, we find the two most used products on the market, namely ethylene-vinyl alcohol (EVOH) and poly-vinyl alcohol (PVOH). These molecules are used as is, meaning that the granules are purchased, dissolved in water, and deposited on the plastic substrate. However, vinyl lacquers are essentially synthetic and do not meet current sustainability and / or biodegradability requirements of finished materials, in addition to usually being characterized by a dry solids content unsuitable for the coating process, as will be explained later; ii) so-called "hybrid" lacquers: these consist of a vinyl base (like the vinyl lacquers in point (i) above) and an inorganic component (usually a metal alkoxide based on silicon), which gives the finished product greater resistance to high humidity values. Being characterized by a certain vinyl base, hybrid lacquers also do not meet current sustainability and / or biodegradability requirements of finished materials;

[0020] Hi) chlorine-based lacquers, with particular reference to polyvinylidene chloride (PVDC), which, however, are today in disuse because, like all chlorine derivatives, their environmental impact and toxicity represent a notable problem, linked to the emission of dioxins when such products are thermally degraded.

[0021] In view of this, it is desirable to achieve coatings from biopolymers (hereinafter also referred to as biocoatings) obtained using biomacromolecules or biopolymers, such as hydrocolloids.

[0022] Biomacromolecules, such as hydrocolloids, are natural molecules predominantly used in the food sector as rheology modifiers, thickeners, texture modifiers, precipitating agents, thickeners, gelling agents, etc. More recently, hydrocolloids have been used in the cosmetic sector (to determine the consistency of creams), pharmaceutical sector (to generate capsules containing the active ingredient) and medical sector (for the production, for example, of hydrocolloid patches). Biomacromolecules are natural molecules also used in the food sector as additives and, in particular, as modifiers of the rheological properties of food matrices (beverages, creams, jams, etc.) in which they are used.

[0023] Hydrocolloids are usually added to food formulations in quantities not exceeding 2%, precisely because, in this case, the objective is to modify the rheological characteristics of food formulations without altering the initial formulation.

[0024] In the state of the art, aqueous compositions usable as coatings are known, which contain proteins, such as animal gelatin, or polysaccharides, such as pectin. Such aqueous compositions may or may not comprise other components, such as plasticizers, lipids, emulsifiers, antifoams. It should be noted that the protein or polysaccharide content is between 3% and 5% and, in any case, does not exceed 10% by weight of the total weight of the aqueous composition; in the absence of the other components mentioned above, the remaining part consists of water solvent.

[0025] Furthermore, in the state of the art and in the field of packaging, polysaccharides are used as an anchoring or sealing agent, but not for imparting coating properties. For example, anchoring agents are used in chemical methods; anchoring agents are substances that are coated before depositing the actual coating.

[0026] In other cases of the state of the art, coatings comprise inorganic substances to obtain a hybrid matrix; however, such solutions do not meet ecological sustainability and / or recyclability requirements.

[0027] Currently, in the context of coating with gravure technology, using aqueous liquid solutions with concentrations < 10%, a cylinder that "discharges" a considerable amount of liquid should be used to achieve the desired thickness of the final coating (i.e., after evaporation of the aqueous solvent). However, the use of such cylinders (i.e., with a low number of lines) is highly counterproductive, as it entails two main problems when working with aqueous solutions:

[0028] 1) the deposition / discharge of large drops makes the wettability of the aqueous liquid on plastic substrates more difficult, especially polyolefinic substrates (polyethylene and polypropylene) which show the lowest surface energy values (about 28-30 mN / m) and, therefore, are thermodynamically less prone to wetting; this wettability is instead favored by smaller and more defined drops;

[0029] 2) the deposition of a larger quantity of aqueous solution implies that a larger quantity of solvent must be removed during the drying process. To overcome this problem, it is necessary to pursue one of three options: use longer ovens to expose the lacquered material to hot air for a longer time; or, for the same oven length, use higher temperatures, which however complicates operations with polyolefinic substrates, such as LDPE and CPP (cast polypropylene), which exhibit considerable temperature sensitivity (around 100°C); or, alternatively, work at lower speeds to have longer residence times of the material in the oven; this, however, has two main consequences: the induction of possible thermal damage to the plastic substrate (as mentioned above); a reduction in speed means a decrease in productivity.

[0030] For these reasons, rather than using low-line cylinders, it is preferred to perform two successive lacquering steps to achieve the final coating thickness. Obviously, this approach also has negative implications, related to the fact that two deposition steps must be performed instead of one, with a consequent effect on overall productivity and system efficiency.

[0031] In addition to the formulation complexity of the known compositions, there is also the need to increase the solids content to values > 12% by weight of the total weight of the initial aqueous solution containing the biomacromolecules. It should be noted that, even in the case of vinyl-based lacquers (for example, EVOH and PVOH), as well as for "hybrid" lacquers, the maximum solids content that can be achieved is 10-12% by weight.

[0032] The fact of achieving highly concentrated aqueous solutions of biomacromolecules impacts several aspects, including:

[0033] - the final thickness of the biocoating on the plastic material (after solvent evaporation), such as to guarantee adequate coverage of the substrate and, therefore, a satisfactory performance (in terms of oxygen barrier). Reducing the thickness of the coating layer aims to reduce the overall finished film, especially in compliance with recent legislation on the use of monomaterials;

[0034] - the drying time of the biocoating. In this sense, the solvent removal process is faster where the biocoating contains more dry matter, i.e., the biopolymer.

[0035] The use of such natural biomacromolecules for the production of solutions useful for the aforementioned applications in coating plants is not, to date, practicable also due to an intrinsic characteristic of such biomacromolecules, namely the high viscosity of the derived aqueous solutions. In fact, for aqueous solutions to be processed and worked on coating plants, they must not have excessively high viscosity, generally between 80 mPas and 500 mPas (Brookfield, spindle R2, 200 rpm, 23 °C, ISO 2555) depending on the type of coating plant and the substrate to be coated (plastic, cellulosic, etc.).

[0036] The obtaining of concentrated hydrocolloid solutions (with high solids content) and with controlled viscosity can occur chemically.

[0037] In fact, it is possible to treat the starting solutions with acid solutions (for example hydrochloric acid or sulfuric acid) at high (IM or 2M) or low (0.01-0.5) concentration and at temperatures between 60°C and 80°C, resulting in chemical hydrolysis of the biomacromolecules (breakage of intramolecular or glycosidic bonds) and decomposition of the polymer chains, obtaining a reduction in molecular weights with consequent reduction in viscosity, since viscosity is a direct function of molecular weight. In this way, it is also possible to increase the solids content of the final solution. For this type of chemical process, however, it is essential to carefully control the reaction time and temperature to avoid excessive degradation.

[0038] Excessive hydrolysis can, in fact, lead to complete depolymerization (with consequent impossibility of using the polymer as it is reduced to monomers), and it is therefore important to accurately monitor the reaction. These aspects negatively impact the operational production procedures, making them more cumbersome and riskier.

[0039] This chemical process presents other disadvantages that make its use difficult and complicated, among which are the following:

[0040] 1) acid hydrolysis is mediated by strong acids that cause deleterious effects on common metallic parts of production plants (such as agitated tanks) and coating machines (lacquering machines), with evident corrosive phenomena that would require protection by appropriate coatings and / or replacement of existing materials with anticorrosion materials;

[0041] 2) the use of strong acids entails the development of vapors, especially when high temperatures are used (for example, pectin is solubilized at 80-90°C); these vapors represent a risk for operators who must take special precautions, such as, for example, the use of appropriate filtering facial masks specific for vapors;

[0042] 3) the use of strong acids entails storage in dedicated areas within the company for safety reasons.

[0043] It should be added that the use of strong acids makes an additional neutralization step (partial or total) of the acid itself necessary, bringing the pH back to sub-acid values (pH ~ 5) or close to neutrality to avoid problems related to acidic pH values (pH < 3). For this purpose, one can proceed with the use of a weak or strong base, or by using specific membranes through a dialysis process.

[0044] Following the first approach, by adding a base, this can be a strong or weak base.

[0045] In case of using a strong base, such as NaOH, a diluted NaOH solution (e.g., 0.1 M or 0.5 M) is slowly added to the biopolymer solution, constantly stirring to promote homogeneous distribution of the base. The exact amount of base to be added will depend on the volume and concentration of the biopolymer solution. During the process, the pH is continuously monitored using a pH meter inserted in the reaction tank. The main advantage of using a strong base is that it rapidly increases the pH. Despite this, the main disadvantage is that, by adding NaOH too quickly, salt formation occurs (for example, sodium chloride if hydrolysis was performed with hydrochloric acid), and these salts will remain in solution. In the case of using a weak base, such as sodium bicarbonate (NaHCCh), it is possible to control the neutralization process more easily, with less possibility of generating salt crystals and a lower risk of exceeding the desired pH compared to NaOH. However, a deleterious secondary effect is the formation of carbon dioxide (CO2) during the reaction, which could cause bubble formation that is best avoided as it is highly probable to negatively impact the subsequent coating process.

[0046] The use of bases (strong or weak) must be very well calibrated depending on the starting biopolymer, as it is very important to stop at the most suitable and specific pH value for each molecule. For example, chitosan is soluble in low pH solutions, but can precipitate or form a gel when the pH approaches neutrality or exceeds pH 6.5-7.

[0047] The second approach involves the use of dialysis membranes.

[0048] Dialysis is a purification technique that separates molecules based on their size through a semi-permeable membrane, allowing small molecules (H+ions, in this case) to pass through, but retaining larger molecules (the biopolymer, in this case). The use of the dialysis membrane is advantageous as it allows pH modification without incurring salt formation and by enabling more accurate pH monitoring. The process consists of immersing the dialysis membrane in distilled water and then inserting the biopolymer solution into the membrane. At this point, it is necessary to wait for the hydrogen ions to migrate towards the distilled water. It is important to change the water frequently to promote the neutralization process. When the solution pH is close to the target value, the dialysis process will be stopped.

[0049] The use of the dialysis membrane is advantageous because, unlike neutralization with strong bases, it does not introduce salts or other by-products into the biopolymer solution. Furthermore, dialysis avoids abrupt pH changes that could destabilize the biopolymer and cause its precipitation. Finally, in addition to bringing the pH back to neutrality, dialysis helps remove any traces of acid used in the hydrolysis.

[0050] However, the dialysis process has a major disadvantage, represented by very long neutralization times. Depending on the volume to be treated and the initial and final pH values of the biopolymer solution, these times can vary from 24 hours to one week. Furthermore, if for small volumes it is possible to proceed with "static" setups (dialysis membranes in tanks filled with distilled water), for large volumes it is necessary to adopt more efficient "dynamic" approaches, especially with the aim of reducing the times involved. In this perspective, it is possible to use industrial dialyzers, which provide faster and more efficient dialysis compared to classic dialysis tubes, as they use membranes with very large surface areas and controlled water flows. Alternatively to industrial dialyzers, continuous flow dialysis systems can be used, in which the external water is continuously replaced and circulated around the membrane. In this way, it is possible to reduce the need to manually change the water, ensuring that the internal solution is always exposed to a favorable concentration gradient. In any case, these systems imply considerable operational complexity as well as considerable investments, aspects that affect the cost of the finished product.

[0051] Furthermore, often, the OTR values achieved by known biocoatings, measured at 23°C and with R.H. of 0%, are well above unity (> 1.0 cm3 / m224h), therefore not in line with the requirements for packaging, especially in the food sector.

[0052] In other cases, biomacromolecules, although used in aqueous compositions, are not used with the aim of obtaining a coating or biocoating but rather act as "anchoring agents". In other words, such biomacromolecules are not included in the oxygen barrier coating.

[0053] Therefore, it is necessary to develop an alternative, ecological / eco-sustainable process, with a low impact on the environment, operators, and production structures / lines involved, and which is, moreover, less expensive and characterized by reduced timings compared to the processes known in the state of the art.

[0054] There is also a felt need to obtain biomacromolecule-based lacquers that can constitute the coating or biocoating after deposition on the substrate to be covered and solvent evaporation, such that they are environmentally friendly but also versatile or adaptable to the industrial machinery used for the lacquering process by coating technique.

[0055] SUMMARY OF THE INVENTION

[0056] The Applicant has developed a process for preparing a coating lacquer for coating comprising the following steps: a) providing a natural hydrocolloid and a solvent, the solvent comprising or consisting of water, b) introducing, under stirring, the natural hydrocolloid into the solvent to obtain a prehydrolysis solution, the natural hydrocolloid having a concentration > 13% by weight of the total weight of the pre-hydrolysis solution, c) reaching a temperature between 40°C and 57°C, d) introducing a hydrocolloid-specific hydrolyzing enzyme and allowing it to act to obtain a coating lacquer, wherein the coating lacquer for spreading has a natural hydrocolloid concentration > 13% by weight of the total weight of the coating lacquer for spreading. Furthermore, the Applicant has also developed a coating lacquer for spreading comprising or consisting of

[0057] - a natural hydrocolloid, preferably chosen from the group consisting of: alginate, starch, carrageenans, cellulose, chitosan, gellan, pectin, pullulan, xanthan, and mixtures thereof, and

[0058] - a solvent comprising or consisting of water, wherein the natural hydrocolloid concentration is > 13% by weight of the total weight of the same coating lacquer for spreading.

[0059] Further objects of the invention are the coating or biocoating obtained following the evaporation of the solvent from the coating lacquer for spreading and the film for packaging comprising said coating.

[0060] Advantages of the invention

[0061] The technology of the invention overcomes the drawbacks hitherto known in the state of the art.

[0062] First, natural hydrocolloids are advantageously used as starting biomacromolecules to obtain concentrated aqueous solutions which, after solvent evaporation, act as an oxygen barrier coating.

[0063] Hydrocolloids, although chemically similar to the molecules currently used for oxygen barrier (for example, EVOH and PVOH), due to the presence of polar functional groups, have a functional advantage related to the absence of the vinyl part that does not contribute to the barrier effect; hydrocolloids, therefore, have a better performance, i.e., they are able to provide higher barrier values for the same thickness, or allow the same performance to be achieved with a lower thickness.

[0064] Being natural molecules, directly extracted from biomass or obtained by fermentation, hydrocolloids possess the attribute of biodegradability; for this reason, the use of such molecules is most relevant in the case of compostable substrates, such as bioplastics and cellulosic substrates; in such cases, in fact, and unlike fossil-derived molecules, the presence of the coating would not alter the nature of the base polymer, potentially affecting (or at least hindering) the composting phases.

[0065] Overall, the invention is advantageous because:

[0066] - the preparation process is more ecological, with low environmental impact, as well as characterized by lower operational complexity and danger, related to the substances used, compared to state-of-the-art technologies. Furthermore, the preparation process is characterized by reduced timings compared to known solutions, for example compared to the chemical hydrolysis process;

[0067] - the coating lacquer for spreading is suitable for being subjected to the coating / spreading technique, both in terms of solids concentration and viscosity; it should be noted that aqueous solutions with solids concentrations < 12% are not suitable for the aforementioned lacquering process by coating. Similarly, aqueous solutions with excessively high viscosity (and in any case above 500 mPa*s) are unusable in the aforementioned lacquering process by coating;

[0068] - the biocoating, which is obtained by evaporating the coating lacquer, meets ecological requirements and complies with the latest legislations that prefer the use of monomaterials for packaging films, especially in the food sector. For example, the biocoating obtained by the invention is characterized by a lower thickness compared to known technologies, achieving performances, such as those related to the oxygen barrier effect, that are better or at least comparable to known solutions;

[0069] - repeated biocoating depositions on the substrate are not necessary; a single deposition (single lacquering) is sufficient to achieve better or comparable performance compared to known solutions.

[0070] From this, the process for preparing the packaging film, including the substrate, possibly primed, and biocoating, benefits from reduced operational complexities and timings, increasing its performance.

[0071] It should also be noted the great versatility of use of the coating lacquer for spreading, as it can be used for the various coating techniques known in the packaging sector.

[0072] DETAILED DESCRIPTION OF THE INVENTION

[0073] Hereinafter, the invention and its preferred embodiments are described in more detail. It should be noted that, although the structure has been organized into paragraphs and sub-paragraphs, the information contained in each paragraph or sub-paragraph is not isolated, and can eventually be combined with that contained in other paragraphs or, more generally, with other information contained in the text of the patent application.

[0074] By "aqueous (concentrated) coating solution for spreading" (hereinafter, for brevity, referred to as "coating lacquer for spreading") is meant an aqueous solution suitable for use as a coating for a substrate (after solvent evaporation), for example a plastic or metallized plastic substrate, by depositing the solution on the substrate using a coating technique, for example direct coating (gravure) or indirect coating (for example, flexo and semi-flexo - "reverse" gravure).

[0075] By lacquer is meant a mixture or a solution that can be deposited, by coating, on a suitable substrate for packaging purposes.

[0076] By hydrocolloid is meant a substance that is in a colloidal state formed by water as the dispersing phase and a dispersed phase.

[0077] By natural hydrocolloid is meant a hydrocolloid in which the dispersed phase is a natural biomacromolecule, meaning that it can be obtained from a natural source. Such biomacromolecules are natural substances that, when brought into contact with water, swell to such an extent as to assume a solid or semi-solid form. An example of a biomacromolecule is a polysaccharide. Preferably, the natural hydrocolloid is a natural polysaccharide, meaning not chemically modified, since it is already present in nature as it is and has not undergone any chemical or physical treatment. For example, the natural hydrocolloid is not a chemically modified cellulose derivative, or it is not chemically modified pectin, for example it is not methylated and / or amidated pectin. Non-natural or chemically modified hydrocolloids have a higher cost. Among the advantages of the invention is therefore that of using natural hydrocolloids and obtaining good results or more satisfactory results compared to coatings already on the market that use non-natural hydrocolloids.

[0078] Preferably, the natural hydrocolloid is selected from the group consisting of: alginate, starch, carrageenans, cellulose, chitosan, gellan, pectin, pullulan, xanthan, and mixtures thereof.

[0079] More preferably, the natural hydrocolloid is selected from: chitosan, cellulose, pectin.

[0080] It should be noted that "solids concentration" refers to the quantity of solid, i.e., of the natural hydrocolloid polymer, contained in the coating lacquer or obtained through the preparation process of the invention.

[0081] For the purposes of the invention, by suitable substrate (hereinafter, for brevity, also referred to as "substrate") is meant a substrate known to those skilled in the art on which it is possible to perform the deposition of a lacquer by spreading or lacquering. Preferably, the suitable substrate can consist of plastic material or metallized plastic material.

[0082] Preferably

[0083] - the plastic substrate is selected from the group consisting of: polyethylene, polypropylene, polyethylene derivatives, propylene derivatives, polyethylene terephthalate (PET), PET derivatives, polyamides (or nylon), polyamide derivatives, and mixtures thereof, or

[0084] - the metallized plastic substrate is selected from the group consisting of: metallized polyethylene, metallized polypropylene, metallized polyethylene derivatives, metallized propylene derivatives, metallized polyethylene terephthalate (PET), metallized PET derivatives, metallized polyamides (or nylon), metallized polyamide derivatives, and mixtures thereof.

[0085] It should be noted that the substrate can be made of virgin and / or recycled material.

[0086] By "OTR" is meant the "Oxygen Transmission Rate" index, measured according to ASTM D3985 (23°C and 0% RH).

[0087] By "WVTR" is meant the "Water Vapor Transmission Rate" index, measured according to ASTM F 1249 (38°C and 90% RH).

[0088] By "U.R.", "UR" or "R.H." is meant relative humidity.

[0089] Process for preparing the coating lacquer

[0090] As mentioned, the process for preparing a coating lacquer for spreading (hereinafter, for brevity, "process" or "preparation process") comprises the following steps: a) providing a natural hydrocolloid and a solvent, the solvent comprising or consisting of water, b) introducing, under stirring, the natural hydrocolloid into the solvent to obtain a prehydrolysis solution, the natural hydrocolloid having a concentration > 13% by weight of the total weight of the pre-hydrolysis solution, c) reaching a temperature between 40°C and 57°C, preferably between 40°C and 55°C, preferably between 45°C and 55°C, preferably of 45°C, d) introducing a hydrocolloid-specific hydrolyzing enzyme and allowing it to act to obtain a coating lacquer for spreading, wherein the coating lacquer for spreading has a natural hydrocolloid concentration > 13%, preferably between 13% and 60% by weight, preferably between 13% and 55% by weight, preferably between 13% and 50% by weight, preferably between 13% and 45% by weight, preferably between 13% and 40% by weight, preferably between 13% and 30% by weight, preferably between 15% and 30% by weight, preferably between 20% and 25% by weight, of the total weight of the coating lacquer. Preferably, at these percentages, the coating lacquer for spreading is called "concentrated". It should be noted that "pre-hydrolysis solution" is used because the natural hydrocolloid is completely dissolved in the solvent.

[0091] Preferably, independently of the first or second embodiment described below, the process of the invention provides for the use of the expressly indicated ingredients; preferably, the process does not contain other ingredients different from those expressly indicated.

[0092] Independently of the first or second embodiment described below, step (d) of hydrolysis may preferably be followed by the step of depositing the lacquer on a substrate, as explained below.

[0093] Preferably, the solvent is an organic solvent, preferably it is water, preferably it is distilled water. Preferably, when the solvent is water, the pre-hydrolysis solution is an aqueous pre-hydrolysis solution.

[0094] According to a first preferred embodiment, the process does not involve the use of organic solvents other than water.

[0095] According to a second preferred embodiment, the solvent is selected from the group consisting of: water, at least one low-boiling (volatile) organic solvent, and mixtures thereof.

[0096] Examples of low-boiling organic solvents are selected from the group consisting of: alcohols, such as ethanol or isopropyl alcohol, ethyl acetate, and mixtures thereof. Preferably, when the solvent is at least one low-boiling organic solvent, this is in an amount between 1% and 20% by weight, preferably 10% by weight, of the total weight of the lacquer.

[0097] It should be noted that the presence of the low-boiling organic solvent is useful when short drying times are required, for example when long ovens are not available for drying.

[0098] By coating lacquer for spreading is meant the aqueous post-hydrolysis solution, i.e., the one obtained following the enzymatic hydrolysis of the natural hydrocolloid.

[0099] Preferably, the initial concentration of the natural hydrocolloid (step (b) - prehydrolysis) is equal to its final concentration, i.e., the post-hydrolysis concentration of the natural hydrocolloid as comprised in the coating lacquer for spreading. The solids concentration in the coating lacquer for spreading depends on the initial concentration of the natural hydrocolloid; this latter concentration preferably does not change during the enzymatic hydrolysis process. By hydrocolloid-hydrolyzing enzyme (hereinafter, for brevity, "enzyme") is meant an enzyme used for a specific natural hydrocolloid, capable, that is, of hydrolyzing or cleaving the intrapolymeric chains of a specific natural hydrocolloid. For example, if the natural hydrocolloid is cellulose, the hydrocolloid-hydrolyzing enzyme will be cellulase.

[0100] Preferably, the enzyme is selected from the group consisting of: alginate lyase; amylase; carrageenase; cellulase; chitosanase; gellan lyase or glucosidase; pectinase; pullulanase; xanthanase; and combinations thereof.

[0101] Preferably, the enzyme is in an amount between 0.001% and 1% by weight, preferably between 0.005% and 1% by weight, preferably between 0.01% and 1% by weight, preferably between 0.02% and 1% by weight, preferably between 0.05% and 1% by weight, preferably between 0.05% and 0.7% by weight, preferably between 0.05% and 0.5% by weight, preferably between 0.1% and 0.5% by weight, preferably between 0.2% and 0.4% by weight, of the total weight of the pre-hydrolysis solution.

[0102] It should be noted that the enzyme concentration can impact the final viscosity of the coating lacquer.

[0103] Preferably, the hydrolyzing agent for the natural hydrocolloid is not an acid, for example inorganic or organic, but an enzyme. In other words, the preparation process is not a chemical hydrolysis, meaning it does not involve the use of acids, for example inorganic or organic, for the hydrolysis of the natural hydrocolloid. The hydrolysis of the natural hydrocolloid occurs enzymatically.

[0104] Preferably, between step (a) of providing and step (b) of introducing, under stirring, the natural hydrocolloid into the solvent, the process may further comprise at least one of the following steps: a’) reducing the pH, preferably to a pH between 4 and 5, preferably of 4.5, and / or a”) increasing the temperature of the solvent to a range between 55°C and 90°C, preferably between 60°C and 90°C, preferably between 60°C and 80°C, said step (a’) of pH reduction and / or said step (a”) of increasing the temperature of the solvent being comprised between step (a) of providing and step (b) of introducing, under stirring, the natural hydrocolloid into the solvent. 1st preferred embodiment o f the preparation process

[0105] According to a first preferred embodiment, the process for preparing a coating lacquer for spreading comprises the following steps: a) providing a natural hydrocolloid and a solvent, the solvent comprising or consisting of water, a’) reducing the pH of the solvent, preferably to a pH between 4 and 5, preferably of 4.5, b) introducing, under stirring, the natural hydrocolloid into the solvent to obtain a prehydrolysis solution, the natural hydrocolloid having a concentration > 13% by weight of the total weight of the pre-hydrolysis solution, c) reaching a temperature between 40°C and 57°C, preferably between 40°C and 55°C, preferably between 45°C and 55°C, preferably of 45°C, d) introducing a hydrocolloid-specific hydrolyzing enzyme and allowing it to act to obtain a coating lacquer, wherein the coating lacquer for spreading has a natural hydrocolloid concentration > 13%, preferably between 13% and 60% by weight, preferably between 13% and 55% by weight, preferably between 13% and 50% by weight, preferably between 13% and 45% by weight, preferably between 13% and 40% by weight, preferably between 13% and 30% by weight, preferably between 15% and 30% by weight, preferably between 20% and 25% by weight, of the total weight of the coating lacquer for spreading.

[0106] According to this first preferred embodiment, the natural hydrocolloid is chitosan. For chitosan, acidification makes it possible to dissolve it in the solvent, for example water. It should be noted that the pH reduction using an organic acid does not mean that acid hydrolysis occurs. The pH reduction is exclusively functional for the solubilization of the natural hydrocolloid chitosan in the aqueous solvent.

[0107] Preferably, step (a’) of reducing the pH of the solvent, preferably to a pH between 4 and 5, preferably of 4.5, occurs by adding an organic acid, preferably acetic acid.

[0108] It should be noted that, at this pH, chemical-acid hydrolysis of the natural hydrocolloid does not occur.

[0109] Preferably, the concentration of the organic acid is between 0.1M and 1 M, preferably between 0.3M and 0.7M, preferably of 0.5M. Preferably, steps (a) of providing a natural hydrocolloid and a solvent, (a’) of reducing the pH of the solvent, and (b) of introducing, under stirring, the natural hydrocolloid into the solvent, occur at ambient temperature.

[0110] Ambient temperature means a temperature between 23°C and 30°C, preferably between 23°C and 28°C, preferably between 25°C and 28°C.

[0111] 2nd preferred embodiment of the preparation process

[0112] According to a second preferred embodiment, the process for preparing a coating lacquer for spreading comprises the following steps: a) providing a natural hydrocolloid and a solvent, the solvent comprising or consisting of water, a”) increasing the temperature of the solvent to a range between 55°C and 90°C, preferably between 60°C and 90°C, preferably between 60°C and 80°C, b) introducing, under stirring, the natural hydrocolloid into the solvent to obtain a prehydrolysis solution, the natural hydrocolloid having an initial concentration > 13% by weight of the total weight of the pre-hydrolysis solution, c) reaching a temperature between 40°C and 57°C, preferably between 40°C and 55°C, preferably between 45°C and 55°C, preferably of 45°C, d) introducing a hydrocolloid-specific hydrolyzing enzyme and allowing it to act to obtain a coating lacquer for spreading, wherein the coating lacquer has a natural hydrocolloid concentration > 13%, preferably between 13% and 60% by weight, preferably between 13% and 55% by weight, preferably between 13% and 50% by weight, preferably between 13% and 45% by weight, preferably between 13% and 40% by weight, preferably between 13% and 30% by weight, preferably between 15% and 30% by weight, preferably between 20% and 25% by weight, of the total weight of the coating lacquer for spreading.

[0113] According to this first preferred embodiment, the natural hydrocolloid is selected from the group consisting of: pectin, cellulose, alginates, starch, xanthan, and mixtures thereof.

[0114] Independently of the first or second embodiment, preferably, the preparation process provides that, once the natural hydrocolloid has been introduced into the solvent (step (b)) under stirring, the stirring is maintained for a time between 15 and 90 minutes, preferably between 30 and 90 minutes, preferably between 30 and 60 minutes, preferably for 60 minutes.

[0115] Independently of the first or second embodiment, preferably, the preparation process provides that, once the natural hydrocolloid has been introduced into the solvent (step (b)), under stirring, the temperature reached in the preceding steps, such as ambient temperature, or the temperature of step (a”) of increasing the temperature, is maintained for the aforementioned period of time.

[0116] Independently of the first or second embodiment, preferably, step (d) of hydrolysis following the introduction of the hydrocolloid-specific hydrolyzing enzyme has a duration between 1 and 4 hours, preferably between 1 and 3 hours.

[0117] It should be noted that the timings and temperatures of the process can impact the final viscosity of the coating lacquer for spreading.

[0118] It should be noted that, independently of the first or second embodiment, following step (d) of hydrolysis of the natural hydrocolloid after the introduction of the hydrocolloid-specific hydrolyzing enzyme, it is possible to reintroduce the hydrocolloid-specific hydrolyzing enzyme (step (d’)). Preferably, the hydrocolloidspecific enzyme is re-added in an amount between 0.01% and 0.05% by weight of the total weight of the lacquer. This minimal addition helps to adjust the final viscosity to the desired value.

[0119] It should be noted that the coating lacquer for spreading, obtained by the process of the invention, is characterized by:

[0120] - a solids concentration > 13% by weight, preferably between 13% and 60% by weight, preferably between 13% and 55% by weight, preferably between 13% and 50% by weight, preferably between 13% and 45% by weight, preferably between 13% and 40% by weight, preferably between 13% and 30% by weight, preferably between 15% and 30% by weight, preferably between 20% and 25% by weight, of the total weight of the coating lacquer for spreading,

[0121] - a viscosity < 500 mPas, preferably between 55 and 500 mPas, preferably between 55 and 225 mPas, preferably between 80 and 180 mPas, preferably between 80 and 130 mPas, preferably between 90 and 130 mPas, so that it is suitable for deposition by coating on a substrate and thus acts as a coating or biocoating after solvent evaporation.

[0122] In this sense, the coating lacquer for spreading constitutes a coating lacquer for spreading for deposition on a packaging substrate. Furthermore, such coating lacquer obtained by the process of preparation described so far acts as an oxygen barrier once converted into a biocoating by solvent evaporation.

[0123] Coating lacquer for spreading

[0124] The coating lacquer for spreading (for brevity "lacquer") comprises or consists of

[0125] - a natural hydrocolloid, preferably chosen from the group consisting of: alginate, starch, carrageenans, cellulose, chitosan, gellan, pectin, pullulan, xanthan, and mixtures thereof, and

[0126] - a solvent comprising or consisting of water, wherein the natural hydrocolloid concentration is > 13% by weight of the total weight of the same coating lacquer for spreading.

[0127] Preferably, the lacquer does not comprise inorganic substances; preferably, the lacquer is not a hybrid matrix.

[0128] Preferably, the coating lacquer does not contain other components besides the natural hydrocolloid and the solvent.

[0129] Preferably, the natural hydrocolloid concentration is comprised between 13% and 60% by weight, preferably between 13% and 55% by weight, preferably between 13% and 50% by weight, preferably between 13% and 45% by weight, preferably between 13% and 40% by weight, preferably between 13% and 30% by weight, preferably between 15% and 30% by weight, preferably between 20% and 25% by weight, of the total weight of the coating lacquer for spreading.

[0130] Preferably, the viscosity of the coating lacquer for spreading is measured by the Brookfield ISO 2555 method (200 rpm, spindle R2, 23 °C).

[0131] Preferably, the viscosity of the coating lacquer for spreading is < 500 mPas, preferably between 55 and 500 mPas, preferably between 55 and 225 mPas, preferably between 80 and 180 mPas, preferably between 80 and 130 mPas, preferably between 90 and 130 mPas.

[0132] Coating or biocoating

[0133] The coating film (also called polymeric biocoating) is obtained following the evaporation of the solvent from the coating lacquer for spreading, preferably the solution obtained through the preparation process of the invention. In other words, the coating lacquer represents the precursor of the biocoating. Preferably, the biocoating can be deposited on the external surface (which "faces" the surrounding environment) of the material / substrate to be coated.

[0134] Preferably, alternatively, the biocoating can be deposited on the internal surface (the biocoating "faces" the contents, for example food) of the material / substrate to be coated.

[0135] According to a further preferred alternative embodiment, the biocoating is deposited "in a sandwich" arrangement, i.e., in an intermediate position between two layers, one of which is the substrate and the other is a material in contact with the external environment, for example of plastic or bioplastic type.

[0136] Preferably, the biocoating is recyclable.

[0137] Preferably, the process for obtaining the coating film comprises the steps described in the preceding paragraphs for preparing the coating lacquer, followed by the following steps:

[0138] - depositing the coating lacquer for spreading on a suitable substrate, followed by

[0139] - evaporating the solvent from the coating lacquer for spreading to obtain the coating or biocoating.

[0140] Preferably, the deposition step occurs using known coating technology, preferably gravure.

[0141] Preferably, the solvent evaporation step occurs using suitable and known means in the state of the art, for example hot air ovens and / or IR lamps.

[0142] Preferably, the Oxygen Transmission Rate (OTR) index is measured under conditions of 1 atm, 23°C and relative humidity of 0%.

[0143] Preferably, the biocoating has an OTR index that is < 1.2 cm3 / m224h, preferably < 1.1 cm3 / m224h, preferably < 1 cm3 / m224h, preferably between 0.01 and 0.9 cm3 / m224h, preferably between 0.01 and 0.7 cm3 / m224h, preferably between 0.05 and 0.7 cm3 / m224h, preferably between 0.1 and 0.7 cm3 / m224h, preferably between 0.1 and 0.6 cm3 / m224h, preferably between 0.1 and 0.55 cm3 / m224h, preferably between 0.2 and 0.55 cm3 / m224h.

[0144] Preferably, the Water Vapor Transmission Rate (WVTR) index is measured at 38°C and relative humidity of 90%, i.e., at a partial water pressure difference of 0.059 atm. Preferably, the biocoating has a WVTR index that is < 3.5 g / m224h, preferably < 3 g / m224h, preferably between 0.05 and 3 g / m224h, preferably between 0.07 and 3 g / m224h, preferably between 0.1 and 3 g / m224h.

[0145] Preferably, the biocoating has a grammage between 0.2 and 2 g / m2, preferably between 0.6 and 2 g / m2, preferably between 0.5 and 2 g / m2, preferably between 1 and 2 g / m2, preferably between 1 and 1.5 g / m2, preferably between 0.8 and 1.5 g / m2.

[0146] It should be noted that grammage and thickness coincide for a biopolymeric solution density value of ~lg / cm3.

[0147] Preferably, the biocoating has a thickness < 1.5 pm, preferably < 1 pm, preferably between 0.2 and 1 pm, preferably between 0.2 and 0.8 pm, preferably between 0.2 and 0.7 pm, preferably between 0.3 and 0.7 pm, preferably between 0.3 and 0.5 pm, preferably between 0.2 and 0.3 pm.

[0148] It should be noted that, for "mono-material" configurations, typical of the food packaging sector, the maximum value of the coating must be 1.5 pm; this is to have "sufficient space" for the other layers, for example glue and / or ink, and to fall within the maximum 5% of components different from the substrate, the latter being the remaining part of the final configuration of the packaging material (film) (95%).

[0149] Preferably, the biocoating is suitable for deposition on plastic materials or substrates; preferably, the biocoating is not suitable for deposition on cellulosic materials.

[0150] Preferably, the biocoating does not contain polymers such as EVOH and / or PVOH.

[0151] Packaging film

[0152] By packaging film is meant a film suitable for use in a packaging technology, for example in the food packaging sector.

[0153] Preferably, such packaging film is a mono-material, meaning that it is substantially composed of a single material, which is the substrate. Preferably, the film comprising the biocoating is recyclable.

[0154] By substantially composed of a single material is meant that the substrate is in an amount > 95% by weight of the film's weight.

[0155] The packaging film comprises or consists of

[0156] - at least one plastic or metallized plastic substrate, the plastic substrate being selected from the group consisting of: polyethylene, polypropylene, polyethylene derivatives, propylene derivatives, polyethylene terephthalate (PET), PET derivatives, polyamides (or nylon), polyamide derivatives, and mixtures thereof, or the metallized plastic substrate being selected from the group consisting of: metallized polyethylene, metallized polypropylene, metallized polyethylene derivatives, metallized propylene derivatives, metallized polyethylene terephthalate (PET), metallized PET derivatives, metallized polyamides (or nylon), metallized polyamide derivatives, and mixtures thereof,

[0157] - a coating or biocoating,

[0158] - preferably, complementary additive substances,

[0159] - preferably, at least one sealing layer, i.e., a layer comprising or consisting of at least one sealant.

[0160] Preferably, the packaging film does not contain polymers such as EVOH and / or PVOH.

[0161] Preferably, the substrate can be primed, meaning that, as is known to a person skilled in the art, the substrate is treated by physical methods ("corona" treatment, flame or atmospheric plasma) or chemical methods (i.e., by coating additive substances that promote subsequent anchoring of the biocoating to the substrate). An example of a priming additive substance is polyethylene imine (PEI).

[0162] The coating or biocoating has already been described above and acts as an oxygen barrier.

[0163] Complementary additive substances are understood to be substances known to those skilled in the art that are useful for completing the subsequent operations after coating / spreading the coating, for example for converting operations. For example, substances useful for the lamination or printing phase, which are usually subsequent to the deposition of the coating on the substrate (lacquering).

[0164] Preferably, the complementary additive substances are chosen from: inks; glues or adhesives; sealants; and mixtures thereof.

[0165] Preferably, by sealant is meant a complementary additive substance that has the function of hermetically sealing the package. Preferably, examples of sealants are: low-density polyethylene (LDPE) and / or cast polypropylene (c-PP); acrylic or polyurethane sealants. Preferably, the quantity of the coating or biocoating is < 5% by weight of the total weight of the material.

[0166] Preferably, the sum of the quantity of the coating or biocoating and the other additive substances, when present, is < 5% by weight of the total weight of the material.

[0167] Preferably, within the film, the biocoating has a thickness < 1.5 pm, preferably < 1 pm, preferably between 0.2 and 1 pm, preferably between 0.2 and 0.8 pm, preferably between 0.2 and 0.7 pm, preferably between 0.3 and 0.7 pm.

[0168] Preferably, the film has a total thickness < 400 pm, preferably between 10 and 300 pm, preferably between 10 and 250 pm, preferably between 10 and 200 pm.

[0169] Preferably, the film can be used for rigid packaging (for example, trays) or for flexible packaging. Examples of rigid packaging are trays; examples of flexible packaging are pouches or sachets.

[0170] Preferably, the film has a total thickness < 150 pm, preferably < 120 pm, preferably between 10 and 120 pm, preferably between 10 and 100 pm, preferably between 10 and 80 pm, preferably between 10 and 60 pm, preferably between 10 and 50 pm, preferably between 10 and 45 pm. Preferably, in these ranges, the film is used for flexible packaging applications.

[0171] Preferably, the film has a total thickness < 400 pm, preferably < 300 pm, preferably between 160 and 300 pm, preferably between 160 and 280 pm, preferably between 160 and 250 pm, preferably between 160 and 220 pm, preferably between 160 and 200 pm. Preferably, in these ranges, the film is used for rigid packaging applications.

[0172] It should be noted that, preferably, the deposition of the biocoating on the substrate advantageously occurs in a single step, i.e., by a single deposition phase using coating, due to the high solids content (dry matter) of the concentrated solution. Repeated depositions of biocoating on the substrate are not necessary.

[0173] Preferably, the deposition of the biocoating on the substrate occurs using a technique chosen from the group consisting of: roll (gravure) (roller engraving), or flexo.

[0174] Preferably, the film can be used for packaging food, for example food that requires oxygen protection because it contains oxidizable matrices in its formulation, such as oils and fats.

[0175] Preferably, food of the aforementioned type is chosen from: rice, coffee, snacks, fresh pasta, cured meats, cheeses. EXAMPLES

[0176] Hereinafter, the Applicant presents examples for illustrative but not limiting purposes.

[0177] Example 1 - Preparation of a concentrated chitosan lacquer for the production of an oxygen barrier biocoating according to the invention.

[0178] An aqueous solution of 15% by weight of chitosan was obtained according to the following procedure:

[0179] - filling a tank equipped with high torque agitation with distilled water to treat high viscosity solutions (85 kg of distilled water);

[0180] - lowering the pH to 4.5 using 0.5 M acetic acid (CH3COOH);

[0181] - introducing chitosan powder (15 kg) into the tank; the addition is performed gradually, specifically 1 kg of powder is added every 10 minutes;

[0182] - stirring the solution at a speed such as to ensure adequate mixing of the powder in water;

[0183] - raising the temperature of the aqueous solution to 45°C;

[0184] - adding chitosanase enzyme to the aqueous chitosan solution, in a concentration of 0.3% by weight;

[0185] - monitoring the viscosity by taking samples at different time intervals;

[0186] - eventual addition (0.015%) of enzyme to adjust the viscosity to the precise desired value.

[0187] The viscosity reduction process can be considered completed after 2 hours.

[0188] The aqueous solution thus obtained has a viscosity of 130 mPa*s measured by the Brookfield ISO 2555 method (200 rpm, spindle R2, 23 °C).

[0189] The solution was used to coat a plastic substrate of oriented polyethylene (MDOPE) having a thickness of 25 pm and previously primed. The deposition was carried out using gravure technology on an industrial coater at double station of General Converting Machines Sri, using a 120-line cylinder with a wet deposition of 6 g / m2and using both hot air ovens and IR lamps for the evaporation of the aqueous solvent.

[0190] The final coating (after drying) has a thickness of 0.8 g / m2. The material thus obtained was subjected to oxygen permeability analysis, expressed as OTR. For this purpose, a Totalperm permeabilimeter from Extrasolution Sri was used. The analysis was conducted at 23°C and 0% R.H. The final result was 0.524 ± 0.03 cm3 / m224h.

[0191] It should be noted that the starting plastic material (MDOPE) has an OTR value immeasurable with the same instrument as it is above the upper detection limit of the instrument (> 3000 cm3 / m224h).

[0192] Example 2 - Preparation of a concentrated pectin lacquer for the production of an oxygen barrier biocoating according to the invention.

[0193] An aqueous solution of 30% by weight of pectin was obtained according to the following procedure:

[0194] - filling a tank equipped with high torque agitation with distilled water to treat high viscosity solutions (70 kg of distilled water);

[0195] - increasing the temperature to 80°C;

[0196] - introducing pectin powder (30 kg) into the tank under strong agitation, in such a way that a vortex is created that prevents the formation of lumps;

[0197] - maintaining agitation and temperature (80°C) of the solution for one hour at a speed sufficient to ensure adequate mixing of the powder in water;

[0198] - lowering the temperature of the aqueous solution to the optimal value for enzymatic activity (50°C);

[0199] - adding pectinase enzyme to the aqueous pectin solution, in a concentration of 0.4% by weight;

[0200] - monitoring the viscosity by taking samples at different time intervals;

[0201] - eventual addition (0.01%) of enzyme to adjust the viscosity to the precise desired value;

[0202] The viscosity reduction process can be considered completed after 3 hours.

[0203] The aqueous solution thus obtained has a viscosity of 110 mPa*s measured by the Brookfield ISO 2555 method (200 rpm, spindle R2, 23 °C).

[0204] The solution was used to coat a plastic substrate of biaxially oriented polypropylene (BOPP) having a thickness of 30 pm and previously primed. The deposition was carried out using gravure technology on an industrial coater at double station of General Converting Machines Sri, using a 140-line cylinder with a wet deposition of 4 g / m2and using both hot air ovens and IR lamps for the evaporation of the aqueous solvent.

[0205] The final coating (after drying) has a thickness of 1.0 g / m2.

[0206] The material thus obtained was subjected to oxygen permeability analysis, expressed as OTR. For this purpose, a Totalperm permeabilimeter from Extrasolution Sri was used. The analysis was conducted at 23°C and 0% R.H. The final result was 0.213 ± 0.01 cm3 / m224h.

[0207] It should be noted that the starting plastic material (BOPP) has an OTR value of 1800 cm3 / m224h.

[0208] Example 3 - Preparation of a concentrated cellulose lacquer for the production of an oxygen barrier biocoating according to the invention.

[0209] An aqueous solution of 20% by weight of cellulose was obtained according to the following procedure:

[0210] - filling a tank equipped with high torque agitation with distilled water to treat high viscosity solutions (80 kg of distilled water);

[0211] - increasing the temperature to 60°C;

[0212] - introducing cellulose powder (20 kg) into the tank under strong agitation, in such a way that a vortex is created that prevents the formation of lumps;

[0213] - maintaining agitation and temperature (60°C) of the solution for one hour at a speed sufficient to ensure adequate mixing of the powder in water;

[0214] - lowering the temperature of the aqueous solution to the optimal value for enzymatic activity (45°C);

[0215] - adding cellulase enzyme to the aqueous cellulose solution, in a concentration of 0.2% by weight;

[0216] - monitoring the viscosity by taking samples at different time intervals;

[0217] - eventual addition (0.018%) of enzyme to adjust the viscosity to the precise desired value;

[0218] The viscosity reduction process can be considered completed after 1 hour. The aqueous solution thus obtained has a viscosity of 90 mPa*s measured by the Brookfield ISO 2555 method (200 rpm, spindle R2, 23 °C).

[0219] The solution was used to coat a plastic substrate of oriented polyethylene (MDOPE) having a thickness of 25 pm and previously primed. The deposition was carried out using gravure technology on an industrial coater at double station of General Converting Machines Sri, using a 120-line cylinder with a wet deposition of 6.0 g / m2and using both hot air ovens and IR lamps for the evaporation of the aqueous solvent.

[0220] The final coating (after drying) has a thickness of 1.5 g / m2. The material thus obtained was subjected to oxygen permeability analysis, expressed as OTR. For this purpose, a Totalperm permeabilimeter from Extrasolution Sri was used. The analysis was conducted at 23°C and 0% R.H. The final result was 0.372 ± 0.03 cm3 / m224h.

[0221] It should be noted that the starting plastic material (MDOPE) has an OTR value immeasurable with the same instrument as it is above the upper detection limit of the instrument (> 3000 cm3 / m224h).

[0222] Example 4 - Table with examples of films in which the oxygen barrier biocoating of the invention is used.

[0223]

[0224] Table 1 Example 5 - Examples of finished materials in which the oxygen barrier biocoating of the invention is used on different substrates.

[0225] 5.1. Polyethylene plastic substrate

[0226] The finished material consists of: machine direction oriented polyethylene (MDOPE) in combination with the biocoating in combination with low-density polyethylene (LDPE). The coating lacquer for spreading precursor of the biocoating consists of pectin at 20% (dry matter by total weight).

[0227] Specifically, the lacquer (i.e., the biopolymeric biocoating) is deposited on MDOPE and then the lacquered MDOPE and LDPE are joined by a lamination process (i.e., using a specific adhesive).

[0228] Where necessary, printing can be carried out over the coating.

[0229] The configuration of the finished material presents:

[0230] . OTR < 1 cm3 / m224h,

[0231] . WVTR < 3 g / m224h.

[0232] This type of product can be conveniently used for packaging coffee and rice.

[0233] For coffee, a typical configuration provides: MDOPE 25 pm / biopolymeric biocoating 1 pm / LDPE 80 pm.

[0234] For rice, a typical configuration provides: MDOPE 30 pm / biopolymeric biocoating 1 pm / LDPE 85 pm.

[0235] 5.2. Polypropylene plastic substrate

[0236] The finished material consists of: OPP polypropylene or biaxially oriented BOPP polypropylene in combination with biocoating in combination with cast polypropylene c-PP (sometimes also coextruded polypropylene coex-PP). The coating lacquer precursor of the biocoating consists of pectin at 15% and cellulose at 5% (dry matter by total weight).

[0237] The final configuration will present

[0238] . OTR < 1 cm3 / m224h,

[0239] . WVTR < 2 g / m224h. This configuration can be used for coffee, rice or for food matrices more sensitive to humidity, such as potato chips snacks.

[0240] For rice packaged in a protective atmosphere, a typical configuration provides: OPP 30 pm / biopolymeric biocoating 1 pm / c-PP 40 pm.

[0241] For potato chips (snacks), a typical configuration provides: BOPP 20 pm / biopolymeric biocoating 1 pm / c-PP 20 pm.

[0242] 5.3. Metallized plastic substrate

[0243] Application for "ultra high-barrier" configurations.

[0244] In this case, the biocoating is used as a coating for a metallized layer to improve the barrier properties of the metallized film.

[0245] A metallized polyethylene or polypropylene (VMPE orVMPP, where VM means "Vacuum-Metallized") is used, onto which the oxygen barrier biocoating is applied. The coating lacquer for spreading precursor of the biocoating consists of chitosan at 20% (dry matter by total weight). The metallized and lacquered substrate is then coupled by lamination to the corresponding sealing layer (LDPE or c-PP).

[0246] In this case, the final configuration will present:

[0247] . OTR of O.l cm3 / m2,

[0248] . WVTR of O.l g / m224h.

[0249] This configuration is desired for food matrices sensitive not only to oxygen, but also to humidity exchanges, such as powdered milk and the finest qualities of coffee.

[0250] Example 6 - Comparative examples.

[0251] It should be noted that, for examples 6.1-6.3, the natural hydrocolloids have not undergone the enzymatic treatment of the invention.

[0252] To achieve a viscosity suitable for coating application (so that it can be handled by coating machines), it is necessary to consider low concentration values for the starting natural hydrocolloids.

[0253] The results of examples 6.1-6.3 show that an untreated solution according to the invention is too dilute to lead to significant thicknesses for obtaining relevant OTR values. 6.1. Preparation of an aqueous chitosan solution for the production of a biocoating

[0254] An aqueous solution of 1.5% by weight of chitosan was obtained according to the following procedure:

[0255] - filling a tank equipped with high torque agitation with distilled water to treat high viscosity solutions (98.5 kg of distilled water);

[0256] - lowering the pH to 4.5 using 0.5 M acetic acid (CH3COOH);

[0257] - introducing chitosan powder (1.5 kg) into the tank in a single solution;

[0258] - stirring the solution at a speed such as to ensure adequate mixing of the powder in water;

[0259] - after 60 minutes the solution is ready for use.

[0260] The aqueous solution thus obtained has a viscosity of 165 mPa*s measured by the Brookfield ISO 2555 method (200 rpm, spindle R2, 23 °C).

[0261] The solution was used to coat a plastic substrate of oriented polyethylene (MDOPE) having a thickness of 25 pm and previously primed. The deposition was carried out using gravure technology on an industrial coater at double station of General Converting Machines Sri, using a 120-line cylinder with a wet deposition of 6 g / m2and using both hot air ovens and IR lamps for the evaporation of the aqueous solvent.

[0262] The final coating (after drying) has a thickness of 0.1 g / m2.

[0263] The material thus obtained was subjected to oxygen permeability analysis, expressed as OTR. For this purpose, a Totalperm permeabilimeter from Extrasolution Sri was used. The analysis was conducted at 23°C and 0% R.H. The final result was 50.20 ± 4.96 cm3 / m224h.

[0264] 6.2. Preparation of an aqueous pectin solution for the production of a biocoatins

[0265] An aqueous solution of 3% by weight of pectin was obtained according to the following procedure:

[0266] - filling a tank equipped with high torque agitation with distilled water to treat high viscosity solutions (97 kg of distilled water);

[0267] - increasing the temperature to 80°C; - introducing pectin powder (3 kg) into the tank under strong agitation, in such a way that a vortex is created that prevents the formation of lumps;

[0268] - maintaining agitation and temperature (80°C) of the solution for one hour at a speed sufficient to ensure adequate mixing of the powder in water;

[0269] - after 90 minutes the solution is ready for use.

[0270] The aqueous solution thus obtained has a viscosity of 150 mPa*s measured by the Brookfield ISO 2555 method (200 rpm, spindle R2, 23 °C).

[0271] The solution was used to coat a plastic substrate of biaxially oriented polypropylene (BOPP) having a thickness of 30 pm and previously primed. The deposition was carried out using gravure technology on an industrial coater at double station of General Converting Machines Sri, using a 140-line cylinder with a wet deposition of 4 g / m2and using both hot air ovens and IR lamps for the evaporation of the aqueous solvent.

[0272] The final coating (after drying) has a thickness of 0.12 g / m2.

[0273] The material thus obtained was subjected to oxygen permeability analysis, expressed as OTR. For this purpose, a Totalperm permeabilimeter from the Extrasolution Sri (Totalperm model) was used. The analysis was conducted at 23°C and 0% R.H. The final result was 45.41 ± 7.12 cm3 / m224h.

[0274] 6.3. Preparation of an aqueous cellulose solution for the production of a biocoatins

[0275] An aqueous solution of 2% by weight of cellulose was obtained according to the following procedure:

[0276] - filling a tank equipped with high torque agitation with distilled water to treat high viscosity solutions (98 kg of distilled water);

[0277] - increasing the temperature to 60°C;

[0278] - introducing cellulose powder (2 kg) into the tank under strong agitation, in such a way that a vortex is created that prevents the formation of lumps;

[0279] - maintaining agitation and temperature (60°C) of the solution for one hour at a speed sufficient to ensure adequate mixing of the powder in water;

[0280] - after 60 minutes the solution is ready for use. The aqueous solution thus obtained has a viscosity of 190 mPa*s measured by the Brookfield ISO 2555 method (200 rpm, spindle R2, 23 °C).

[0281] The solution was used to coat a plastic substrate of oriented polyethylene (MDOPE) having a thickness of 25 pm and previously primed. The deposition was carried out using gravure technology on an industrial coater at double station of General Converting Machines Sri, using a 120-line cylinder with a wet deposition of 6.0 g / m2and using both hot air ovens and IR lamps for the evaporation of the aqueous solvent.

[0282] The final coating (after drying) has a thickness of 0.14 g / m2.

[0283] The material thus obtained was subjected to oxygen permeability analysis, expressed as OTR. For this purpose, a Totalperm permeabilimeter from Extrasolution Sri was used. The analysis was conducted at 23°C and 0% R.H. The final result was 52.63 ± 6.34 cm3 / m224h.

[0284] For examples 6.1-6.3, the fact that the increase in OTR is more than proportional to the decrease in coating thickness is explained by the fact that the coating, being very thin (about 0.1 g / m2), does not sufficiently cover the entire substrate. The surface of the plastic substrate considered (polyolefin) must be imagined, in fact, as "rough", i.e., with peaks and valleys that, if not adequately filled, leave some "spikes" of the uncoated material. Evidently, the thicker the coating, the greater the probability of better covering / coating the entire surface of the plastic substrate.

[0285] It should be added that, compared to PET and Nylon, the materials tested (i.e., MDOPE and PP, which are the most used for the creation of monomaterials) exhibit very high initial OTR values (> 1000 cm3 / m224h).

Claims

CLAIMS1. Process for preparing a coating lacquer for spreading comprising the following steps: a) providing a natural hydrocolloid and a solvent, the solvent comprising or consisting of water; b) introducing, under stirring, the natural hydrocolloid into the solvent to obtain a pre-hydrolysis solution, the natural hydrocolloid having a concentration > 13% by weight of the total weight of the pre-hydrolysis solution; c) reaching a temperature comprised between 40°C and 57°C; d) introducing a hydrocolloid-specific hydrolyzing enzyme to obtain a coating lacquer for spreading, wherein the coating lacquer has a natural hydrocolloid concentration > 13% by weight of the total weight of the coating lacquer.

2. The process according to claim 1, wherein the natural hydrocolloid is selected from the group consisting of: alginate, starch, carrageenans, cellulose, chitosan, gellan, pectin, pullulan, xanthan, and mixtures thereof.

3. The process according to any one of claims 1 to 2, wherein the concentration of the natural hydrocolloid is comprised between 13% and 60% by weight of the total weight of the coating lacquer for spreading.

4. The process according to any one of claims 1 to 3, wherein the enzyme is in an amount comprised between 0.001% and 1% by weight of the total weight of the aqueous solution.

5. The process according to any one of claims 1 to 4, further comprising a step (a’) of reducing the pH of the solvent, preferably to a pH comprised between 4 and 5, said step (a’) of pH reduction being comprised between step (a) of providing and step (b) of introducing, under stirring, the natural hydrocolloid into the solvent.

6. The process according to any one of claims 1 to 4, further comprising a step (a”) of increasing the temperature of the solvent to a range comprised between 55°C and 90°C, said step (a”) of increasing the temperature being comprised between step (a) of providing and step (b) of introducing, under stirring, the natural hydrocolloid into the solvent.

7. A coating lacquer for spreading comprising or consisting of• a natural hydrocolloid, preferably selected from the group consisting of: alginate, starch, carrageenans, cellulose, chitosan, gellan, pectin, pullulan, xanthan, and mixtures thereof, and• a solvent comprising or consisting of water, wherein the natural hydrocolloid concentration is > 13% by weight of the total weight of the same coating lacquer for spreading.

8. Coating lacquer according to claim 7, wherein the viscosity is < 500 mPa*s measured by the Brookfield ISO 2555 method at 200 rpm, spindle R2, 23°C.

9. Coating or biocoating obtained following the evaporation of the solvent from the coating lacquer according to claim 7 or 8 or obtained through the process according to any one of claims 1 to 6, wherein the Oxygen Transmission Rate (OTR) index is < 1.2 cm3 / m224h, measured under conditions of 1 atm, 23°C and relative humidity of 0% according to ASTM D3985.

10. Packaging film comprising or consisting of• at least one plastic or metallized plastic substrate, the plastic substrate being selected from the group consisting of: polyethylene, polypropylene, polyethylene derivatives, propylene derivatives, polyethylene terephthalate (PET), PET derivatives, polyamides (or nylon), polyamide derivatives, and mixtures thereof, or the metallized plastic substrate being selected from the group consisting of: metallized polyethylene, metallized polypropylene, metallized polyethylene derivatives, metallized propylene derivatives, metallized polyethylene terephthalate (PET), metallized PET derivatives, metallized polyamides (or nylon), metallized polyamide derivatives, and mixtures thereof,• the coating according to claim 9.

11. The packaging film according to claim 10, wherein the quantity of the barrier coating is < 5% by weight of the total weight of the film.

12. The packaging film according to claim 10 or 11, wherein the thickness of the coating is < 1.5 pm.

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