Process for polymerizing a cutin-based mixture, and polymers thus obtained

Abstract

A process for preparing a polymer based on a polyhydroxylated fatty acid, comprising the following successive steps: - Supplying or preparing a reaction medium comprising a mixture called the starting mixture, comprising at least 30 wt% of at least one monomer selected from polyhydroxylated fatty acids and esters of a polyhydroxylated fatty acid and alcohols with linear or branched aliphatic chains, said reaction medium being free of catalyst; - Heating said reaction medium at ambient pressure for a period of less than 120 minutes, at a temperature between 100 °C and 160 °C, to obtain an intermediate product that is at least partially polymerized and possibly at least partially crosslinked. Figure for the abstract: [Fig. 1].

Description

Title of the invention: Process for polymerizing a cutin-based mixture, and polymers thus obtained. Technical field of the invention

[0001] The invention relates to the field of polymers, and more particularly to that of elastomers, which are polymers with rubbery elasticity properties. More specifically, the invention relates to a new process for manufacturing a hydrophobic and water-repellent elastomer based on cutin. This process according to the invention can be implemented using a biological resource comprising cutin. This biological resource, which may be a waste product from the food industry, is pretreated so that the cutin is at least partially depolymerized, thus presenting a certain quantity of monomers. This mixture is then repolymerized under controlled conditions.

[0002] The invention also relates to an elastomer that can be obtained by such a process. State of the art

[0003] The industrial use of waste from agriculture and the agri-food sector has become a subject of interest and offers an alternative to fermentation that could potentially valorize the biopolymers it contains. In particular, these biopolymers could be used to produce industrially usable materials that would themselves be biodegradable. An introduction to the subject is given in the publication by C. Maraveas, "Production of Sustainable and Biodegradable Polymers from Agricultural Waste," published in the journal Polymers 2020, 12, 1127 (doi:10.3390 / polyml2051127). Furthermore, it is desirable that the manufacturing processes for these biopolymers not themselves require the use of products that are toxic to humans and animals and / or harmful to the environment.

[0004] The inventors sought a process for manufacturing a hydrophobic and water-repellent coating for textiles that uses biological resources as extensively as possible. This coating would preferably also exhibit elastomeric properties. It would be desirable, for example, to present an alternative to textile coatings based on per- and polyfluoroalkyl substances (PFAS).

[0005] Cutin is a hydrophobic biopolymer that coats the aerial organs (particularly leaves and fruits) of many terrestrial plants. It is a polyester of hydroxylated fatty acids and glycerol (typically C16 or C18). It has It has been considered that this could be used to produce biomaterials, as plant waste constitutes an abundant source of cutin. For example, a dry extract of tomato skins contains approximately 20% to 30% cutin by mass. However, this resource is largely unused due to a lack of applications: cutin is insoluble and cannot be melted without decomposition (see the publication by JA Heredia-Guerrero et al., “Cutin from agri-waste as a raw material for the production of bioplastics,” published in the Journal of Experimental Botany, vol. 698, no. 19, pp. 5401–5410, 2017).

[0006] Processes for extracting cutin from plants are known. They require at least partial depolymerization of the cutin; this depolymerization, as described in WO 2017 / 100636, takes place in water or ethanol in a fairly slow and several-step manner, at high temperature and under pressure.

[0007] A basic process is described in WO 2015 / 028299. More specifically, EP 4 116 352 Al (Tomapaint Srl) describes an optimized process that uses the extraction and partial depolymerization of cutin from tomato peel waste under the action of a strong base and a temperature between 105 °C and 130 °C. After separation of the pulp, an organic acid is added to the liquid phase, resulting in a partially depolymerized suspension of cutin. A solid phase, representing the cutin extract, is separated by centrifugation. This is a mixture that typically comprises between 50% and 80% by mass of 10,16-dihydroxyhexadecanoic acid and its oligomers, water, and an organic solvent (typically an alcohol). This document also describes the application of a cutin layer onto a solid substrate.

[0008] WO 2020 / 260312 describes a process for manufacturing an elastomer from a cutin extract. In this process, the cutin extract, comprising at least 20% of 10,16-dihydroxyhexadecanoic acid monomer, is polymerized in the presence of a polyol other than the monomer at a temperature between 120 °C and 200 °C for a period of at least 4 hours and preferably between 4 and 60 hours. At least during an initial phase, before reaching the gel point of the polymer being formed, the polymerization reaction must take place under reduced pressure. Applying reduced pressure allows the water produced during the polymerization reaction to be removed as it forms, thereby shifting the thermodynamic equilibrium in favor of polymer formation. An elastomer is thus obtained.

[0009] The process described in WO 2020 / 260312 avoids the use of a catalyst, but it nevertheless presents numerous industrial drawbacks: it is slow and must be precisely controlled throughout its duration to obtain a polymer with the desired properties, it requires the application of reduced pressure to extract a reaction gas (in this case, mainly water vapor), and It involves a polyol, in this case glycerol, which represents a cost. From an industrial perspective, the application of reduced pressure is particularly detrimental.

[0010] WO 2323 / 187159 (Lamberti SpA) describes the modification of a crude cutin extract by a heat treatment involving polymerization and crosslinking. The resulting product is a paste. It is then diluted in an aqueous ammonia solution to obtain a liquid that can be used to coat paper. The heat treatment is carried out at a temperature between 80 °C and 100 °C, and its duration is on the order of 2 to 24 hours. Given the high viscosity of the product resulting from the heat treatment, such a duration is difficult to reconcile with the constraints of an industrial process.

[0011] The present inventors sought a simpler and faster process for obtaining a polymer from a cutin extract, which avoids at least some of the disadvantages set out above.

[0012] Objects of the invention

[0013] Based on the technical teaching of document WO 2020 / 260312, the inventors discovered that the polymerization process described therein can be considerably simplified with certain reaction media. In particular, a cutin extract that is at least partially depolymerized and contains monomers of 10,16-dihydroxyhexadecanoic acid can be polymerized and transformed into an elastomer usable in technical applications without the need for reduced pressure during the initial phase of the polymerization reaction. Furthermore, it is not necessary to add polyols. The process can be carried out at a lower temperature, and in particular below 150 °C, and the reaction time can be shorter, and in particular less than 5 hours.

[0014] A first object of the present invention is a process for preparing a polyhydroxylated fatty acid-based polymer, comprising the following successive steps:

[0015] - Supplying or preparing a reaction medium comprising a mixture called initial mixture comprising at least 30% by mass of at least one monomer selected from polyhydroxylated fatty acids and esters of a polyhydroxylated fatty acid and alcohols with linear or branched aliphatic chains,

[0016] said reaction medium being free of catalyst,

[0017] - Heating said reaction medium at ambient pressure and for a duration of less for 120 minutes at a temperature between 100 °C and 160 °C, obtain an intermediate product.

[0018] Said heating makes it possible to obtain an intermediate product that is at least partially polymerized; depending on the duration and temperature chosen, it can be at least partially crosslinked.

[0019] The duration of this heating step is advantageously less than 90 minutes, to avoid obtaining a product that is too viscous and difficult to use at this stage. To obtain a low-viscosity intermediate product, a duration of between approximately 1 and 30 minutes, preferably between approximately 1 and 20 minutes, and even more preferably between approximately 2 and 15 minutes, is sufficient. This intermediate product can be applied to a substrate like a liquid, by painting, printing, impregnation, or spraying techniques; for this application to a substrate, it may optionally be diluted with a suitable solvent (preferably inorganic). The temperature of this heating step is preferably between approximately 100 °C and approximately 150 °C, even more preferably between 120 °C and approximately 150 °C.

[0020] According to one aspect of the invention, said initial mixture also comprises oligomers, and in particular dimers and / or trimers, of said polyhydroxylated fatty acid.

[0021] According to another aspect of the invention, said polyhydroxylated fatty acid is 10,16-dihydroxyhexadecanoic acid.

[0022] Preferably, said initial mixture is a cutin extract at least partially depolymerized, or contains a cutin extract at least partially depolymerized.

[0023] According to advantageous embodiments of the process according to the invention:

[0024] - said polymer is shaped and then subjected to a crosslinking treatment comprising between about 0.5 hours and 10 hours at a temperature between about 100 °C and about 160 °C, preferably between about 100 °C and about 150 °C, even more preferably between about 100 °C and about 140 °C, and even more preferably between 120 °C and 140 °C.

[0025] Monomers or oligomers of polyesters can be added to said reaction mixture.

[0026] Another object of the invention is a polymer based on a natural polyhydroxylated fatty acid, which can be obtained by the process according to the invention. This polymer can be in various stages of polymerization or crosslinking, and can be used in various stages of polymerization or crosslinking. When incompletely polymerized or incompletely crosslinked, it can be in a form diluted by a suitable solvent, which may be ethanol or an inorganic solvent such as ammonia; in this form, it can be used, in particular, to form thin films.

[0027] Yet another object of the invention is the use of a polymer according to the invention for the manufacture of waterproof or water and ethanol resistant layers and coatings.

[0028] Another object is the use of a polymer or intermediate product according to the invention, diluted in a suitable solvent in the form of a liquid or paste phase, for coating solid surfaces, for coating or impregnating textile fabrics based on natural and / or synthetic fibers, or for coating or impregnating natural or synthetic fibers. In these uses, any suitable printing techniques (including screen printing and flexography) or known coating techniques, such as dipping, extrusion, a printing process, preferably inkjet printing or flexographic printing, a coating process, preferably by squeegee, roller, curtain, dip-shrink, or through a slotted die, may be employed.

[0029] A layer is thus formed which can then be crosslinked by heating at a temperature between approximately 100 °C and approximately 150 °C, preferably between 120 °C and 150 °C.

[0030] Said coated surfaces, said coated or impregnated fabrics, and said coated or impregnated fibers each constitute yet another object of the present invention. Brief description of the figures

[0031] [Fig.1] shows a schematic representation of certain processes according to the invention for obtaining certain intermediate products and certain types of products.

[0032] [Fig.2] refers to Example 7 and represents differential scanning calorimetry curves of several MxC samples during temperature rise.

[0033] [Fig.3] also refers to example 7 and represents a second passage of the same samples as those in [Fig.2] during temperature rise, after their cooling. Detailed description

[0034] Unless otherwise specified, all values ​​expressed as percent and describing a chemical composition refer to mass percentages. Unless otherwise specified, all viscosity values ​​refer to ambient temperature (25°C).

[0035] In a highly advantageous embodiment of the invention, the initial mixture is a cutin extract, referred to herein as "MxC", obtained in particular from tomato skins. This extract can be obtained by a process described in EP 4 116 352 A1 and is sold by the company Tomapaint Srl

[0036] This commercial product has the following characteristics: It comprises approximately 60 to 70% polyhydroxylated fatty acid monomers, as well as oligomers with a low degree of polymerization, which are mainly dimers and trimers of this acid. The fatty acid is primarily 10,16-dihydroxyhexadecanoic acid, which is characteristic of cutin extracted from tomatoes. The moisture content of the product is in the range of 20% to 30%, its acid value is approximately 120 mgKOH / g, it contains no sugar or fat, its salt content is less than 1%; this product is very sticky at room temperature, has a modeling clay-like consistency, and a dark orange color.

[0037] This product represents a cutin extract that is at least partially depolymerized. This extract will be referred to below simply as "depolymerized," which includes the possibility of containing oligomers with a low degree of polymerization, such as dimers and / or trimers. Derived from a product of natural origin, it exhibits a characteristic spectrum of impurities compared to pure 10,16-dihydroxyhexadecanoic acid.

[0038] To polymerize it, this MxC product can be heated to a temperature between approximately 100 °C and approximately 160 °C, with stirring, and at atmospheric pressure. Preferably, the temperature does not exceed 150 °C, and more preferably it does not exceed 140 °C. A temperature between 120 °C and 140 °C is particularly suitable.

[0039] After a first heating step of approximately two to five minutes, a first intermediate product is obtained, which is a partially crosslinked polymer still containing water and exhibiting a relatively low viscosity. The water is partly generated during the reaction; it evaporates during this first step, which must therefore be carried out under stirring. The duration of this first step depends on the moisture content of the MxC used; DSC analyses show evaporation of free water at around 100 °C, followed by evaporation of the water resulting from the esterification reaction.

[0040] For preparing small quantities (e.g., up to about 3 kg), this first step can be carried out, for example, in a beaker with magnetic stirring. For larger quantities, a Banbury-type mixer can be used, for example.

[0041] If the heating of this first intermediate product is continued for a second step of approximately 5 to 10 minutes at a temperature between approximately 100 °C and approximately 150 °C, at atmospheric pressure, a second intermediate product is obtained, which is a more strongly cross-linked polymer with very low water content and high viscosity. During this second step, more water evaporates from the reaction mixture.

[0042] If the heating of this second intermediate product is continued, for a second step of about 10 to about 60 minutes at a temperature between about 100 °C and about 150 °C, at atmospheric pressure, a third intermediate product is obtained, which is a highly crosslinked polymer, of pasty and sticky consistency, with high viscosity.

[0043] This third intermediate product can be subjected to a crosslinking treatment at a temperature between approximately 100 °C and approximately 150 °C, for a duration typically between approximately 10 minutes and approximately 120 minutes. This treatment is typically carried out in an oven and can be performed continuously by passing the intermediate product through the oven. A crosslinked product is obtained. This crosslinking treatment is typically carried out after the elastomer has been shaped, because the third intermediate product is so viscous that it would be very difficult to shape it after the crosslinking treatment.At a certain point in this crosslinking treatment, the properties of the product (and in particular, its mass, its colour, its solubility in water and in ethanol, the tackiness of its stabilized surface) no longer change when this crosslinking treatment is prolonged: advantageously, the said crosslinking treatment is stopped at this point.

[0044] It is possible to use said intermediate products directly. In a first embodiment, said first intermediate product can be used in a polyester composition by compounding. This yields a polyester blend.

[0045] In a second embodiment, said first intermediate product may be supplemented with a solvent to obtain a liquid phase of relatively low viscosity, typically between approximately 80 cps and approximately 120 cps (at 25 °C). This solution can be used in several ways. It can be incorporated into polymer formulations as an additive or as a colorant, particularly for the manufacture of colored textiles. It can also be applied as a thin film using techniques such as printing or thin-film deposition techniques like dipping and spray coating. The layer deposited from this solution, or the product made with this solution, must be crosslinked (possibly after evaporation of the solvent) at approximately 100 °C to approximately 150 °C for a period of approximately 10 minutes to approximately 120 minutes.

[0046] Said second intermediate product can be used with a viscosity advantageously between approximately 10,000 cps and approximately 40,000 cps (at 25 °C), and preferably between approximately 14,000 cps and approximately 40,000 cps. To adjust this viscosity, either solvent or the first intermediate product with added solvent can be added, according to the second variant described above. This product can be poured and used in several coating techniques, such as screen printing, the lamination, coating or knife coating. The final product must be cured between approximately 100 °C and approximately 150 °C, for a period of approximately 10 minutes up to approximately 120 minutes, for example in an infrared oven.

[0047] Said third intermediate product has a viscosity of approximately 100,000,000 cps at 25 °C. It can be shaped by pressing in a mold, or between two plates, or by extrusion and / or injection. It can be applied to sheets of paper, cardboard, or textiles, or to metallic surfaces, for example by calendering or laminating. The final product must be cured at approximately 100 °C to approximately 150 °C for a period of approximately 10 minutes to approximately 120 minutes.

[0048] In a highly advantageous embodiment of the invention, no polyol is added to the reaction medium comprising at least principally said depolymerized cutin extract. The intermediate products thus obtained are distinguished from those obtained with the addition of polyol by the absence of polyol units in the polymer chains.

[0049] It is possible to incorporate fillers or other functional additives into the elastomer according to the invention. These fillers and functional additives are preferably of biological or mineral origin. Typically, they can be incorporated within the second intermediate product or within the third intermediate product. These fillers or functional additives can advantageously be selected from the group formed by:

[0050] (i) Cellulose and cellulose derivatives, and in particular: wood cellulose, nanocellulose, cellulose acetate.

[0051] The technical effect of this addition is an effect of improving tensile strength, rigidity and thermal stability.

[0052] In one variant, the cellulose may come from the same plant from which the cutin was extracted.

[0053] Certain cellulosic products exhibit specific technical effects. In this respect, coconut shell powder improves the elastomer's abrasion resistance. This effect is less pronounced than that of carbon black, but it is a product of natural origin.

[0054] (ii) Natural fibers, and in particular: Jute, flax, kenaf, hemp, bamboo, nettle.

[0055] These fibers may be cellulosic fibers.

[0056] The technical effect of this addition is a strengthening effect, an improvement in mechanical properties, and biodegradability.

[0057] (iii) Proteins and polypeptides, and in particular: Soy protein, legume protein, rapeseed protein, gelatin, keratin.

[0058] The technical effect of this addition is a plasticizing effect, increased flexibility, biodegradability.

[0059] (iv) Natural oils and fats, including: soybean oil, linseed oil, castor oil, tomato seed oil, and grapeseed oil. This addition acts as a plasticizer and improves the processability of the elastomer. Compared to synthetic or petroleum-based products, these additions have a reduced environmental impact.

[0060] (v) Resins and gums, and in particular: rosin, gum arabic, Shellac and copal resin. Their technical effect is that of an adhesion promoter, a bonding agent, and / or an improved viscosity.

[0061] (vi) Natural waxes, and in particular: carnauba wax, beeswax, candelilla wax, tomato skin wax. The technical effect of this addition is the improvement of the processability, the improvement of the release properties and / or the surface condition of the product.

[0062] (vii) Mineral fillers, and in particular: Calcium carbonate, silica, clay, ash.

[0063] In general, this addition has the technical effect of strengthening and improving the thermal properties of the product, and also helps to reduce its cost. Certain mineral fillers have specific technical effects.

[0064] Silica can be derived from sand or quartz. It improves abrasion resistance and tensile strength. It can be incorporated after being treated with silane- or siloxane-based coupling agents.

[0065] Calcium carbonate (CaCO3) can be derived, for example, from limestone or chalk of geological origin. The technical effect of this addition is that of a filler to reduce production costs; it also gives the elastomer increased rigidity and improved processing properties.

[0066] Clays can be selected in particular from the group consisting of: montmorillonite, kaolin, talc. The technical effect of this addition is reinforcement, improved thermal stability, and improved barrier properties.

[0067] Usable ash includes, in particular, ash from the combustion of cellulosic products. In this respect, an advantageous addition is rice husk ash, which typically has a high silica content and enhances the mechanical properties of the elastomer.

[0068] Calcium oxide (CaO), also called quicklime, is a mineral filler of a particular type, its technical effect being that of a dehydrating agent or drying agent: it helps to eliminate moisture during the treatment, and in particular the moisture released by the reaction.

[0069] (viii) Carbon, and in particular: carbon black, charcoal (also called biochar), graphene. The technical effect of this addition lies in the improvement of abrasion resistance.

[0070] (ix) Plasticizers of biological origin, and in particular: epoxidized vegetable oils, citric esters. The technical effect of this addition lies in the improvement of the product's flexibility. Compared to synthetic or petroleum-based products, these additions have a reduced environmental impact.

[0071] (x) Natural antioxidants and stabilizers, and in particular: tocopherols, the Lignin, ferulic acid. The technical effect of this addition is protection against oxidation and UV degradation.

[0072] (xi) Biopolymers, and in particular: polylactic acid (PLA), polyhydroxyalkanoates (PHA), polybutylene succinate (PBS), and starch mixtures. The technical effect of this addition is the improvement of biodegradability, the possibility of adapting the mechanical properties of the product to specifications, and the possibility of using bio-based additives.

[0073] (xii) Functional additives of microbial origin, and in particular: bacterial cellulose, fungal mycelium. The technical effect of this addition lies in the specific and particular texture of the product, as well as in the improvement of its biodegradability; this addition promotes sustainable production.

[0074] (xiii) General plasticizers, and in particular phthalates (generally non-bio-based), adipates, bio-based plasticizers such as epoxidized vegetable oil. The technical effect of this addition is increased flexibility, reduced brittleness, and a lower glass transition temperature.

[0075] (xiv) Additives for protection against ultraviolet radiation, and in particular zinc oxide, titanium dioxide, and certain organic compounds. The technical effect of this addition is protection against UV degradation, extension of the product's shelf life, and maintenance of color and mechanical properties.

[0076] (xv) Polysaccharides, and in particular cellulose, starch, pectin, chitin, alginates. The technical effect of this addition is the improvement of the product's biodegradability, the possibility of adapting its mechanical properties to specifications, and the possibility of using bio-based additives.

[0077] Since cutin is a polyester, it can be blended with other polyesters, such as PHA or PBS. This blending can be carried out before crosslinking by adding other polyester monomers or oligomers to MxC. A homogeneous mixture is obtained. For example, it is possible to manufacture solution-dyed polyester yarn (with an orange-yellow color whose shade depends on the concentration of McX), with crosslinking taking place during the production of the textile yarn, for example, during extrusion or melt spinning.

[0078] The elastomer according to the invention can be used in different ways.

[0079] It can be used as a waterproof coating or as a material in place of other polymers, for example in place of rubber or polyurethane. It It can serve as a matrix for composite materials by adding natural (cellulose fibers) or synthetic materials. It can be coated with dyes and / or pigments. It can be used to coat or impregnate textile materials. It can be used as a coating on many products and materials, including paper, cardboard, sheet metal and metal products, and flexible, semi-rigid, or rigid composite materials.

[0080] We now describe in relation to [Fig.1] different ways of using, according to the invention, mixtures of cutin (MxC).

[0081] In step 1000, a reaction mixture, referred to herein as the "cutin mixture" or MxC, is supplied or prepared. It necessarily comprises a cutin extract that is at least partially depolymerized. It may include a polyol, preferably up to about 20% by mass, but the addition of a polyol is not a preferred variant.

[0082] This mixture of cutin is reacted by applying 1-1 conditions. A first intermediate product is obtained in step 1100.

[0083] Said first intermediate product can be transformed, by applying conditions called 1-2, to obtain at step 1150 a product of type 1.

[0084] Alternatively, said first intermediate product can be transformed, by applying so-called 2-1 conditions, to obtain at step 1200 a second intermediate product.

[0085] Said second intermediate product can be transformed, by applying conditions of type 2-1, to obtain at step 1250 a product of type 2.

[0086] Alternatively, said second intermediate product can be transformed, by applying conditions of type 3-1, to obtain at step 1300 a third intermediate product.

[0087] Said third intermediate product can be transformed; by applying conditions called 3-2, to obtain at step 1350 a product of type 3.

[0088] All conditions 1-1, 1-2, 2-1, 2-2 and 3-1 include heating to a temperature between 100 °C and 160 °C (preferably between 100 °C and 150 °C) at atmospheric pressure.

[0089] Conditions 1-1 include a heating step lasting between approximately 2 minutes and approximately 5 minutes. The first intermediate product has a medium viscosity and a low water content. It can be used directly as an additive to manufacture other polyesters by compounding in an extruder.

[0090] Conditions 1-2 include the addition of a solvent. Type 1 products are typically in the form of a liquid (solution) with a typical viscosity of about 80 cps to about 120 cps. They can be used as an additive to manufacture other polyesters, particularly in the form of textile fibers. The process of The manufacture of these fibers includes a heat crosslinking step, the conditions of which are typically close to the 2-2 conditions described below.

[0091] Type 1 products can also be used as inks in printing techniques, in particular screen printing, spray coating, dipping, or doctor blade printing. In this case, these inks, after application, must be processed under conditions of type 2-2.

[0092] Type 1 products can also be used in the application of type 2 products, in particular to adjust their viscosity.

[0093] Conditions 2-1 include a heating step lasting between approximately 5 minutes and approximately 10 minutes. Said second intermediate product has a typical viscosity of between approximately 14,000 cps and approximately 40,000 cps. It can be used as an ink in printing techniques, particularly screen printing and doctor blade printing, but also spray coating and dipping printing.

[0094] Conditions 2-2 include a heating crosslinking step lasting from approximately 10 minutes to approximately 120 minutes.

[0095] Conditions 3-1 include a heating step lasting from approximately 10 minutes to approximately 60 minutes. The third intermediate product is in the form of a thick paste with a viscosity greater than approximately 50,000 mps, which is typically in the range of approximately 100,000 cps. It can be applied to any solid substrate by lamination or to a textile substrate by calendering. It can be used for the manufacture of composite materials (for example, by adding solid phases such as natural fibers, e.g., cellulosic fibers). It can be applied by pressing between two plates or in a mold.

[0096] Conditions 3-2 include crosslinking, the conditions of which are typically close to conditions 2-2 described above.

[0097] Type 2 products include, in particular, textiles colored throughout the fiber mass, sheets coated with cutin polymer (paper, cardboard, metal, plastic), textiles coated with a thin layer of cutin polymer.

[0098] Type 3 products include, in particular, solid rubber products, composite materials comprising solid materials incorporated in the cutin polymer matrix, textiles coated with a thick layer of cutin. Examples

[0099] The following examples are given by way of illustration to enable a person to carry out the invention. They do not in any way limit the scope of the invention.

[0100] Example 1: Polymerization of MxC with the addition of polyol at a temperature of 150 °C, at atmospheric pressure

[0101] A mixture of cutin (hereinafter referred to as MxC) was supplied by Tomapaint Srl; this mixture had been obtained by the cutin extraction process from tomato processing waste described in EP 4 116 352 A1. This mixture comprised monomers and oligomers (mainly dimers and trimers) of hydroxylated fatty acids. The principal fatty acid was 10(9)-16 dihydroxyhexadecanoic acid, which is typical for cutin extracted from tomatoes. The monomer content was approximately 60–70 wt% (determined by NMR and NAT).

[0102] This mixture exhibited the following properties:

[0103] Moisture content approximately 30%; Total Acid Number (TAN) approximately 120 mg KOH / g; no sugars or fats; salt content < 1%; consistency of modeling clay, very sticky at room temperature, dark orange colour.

[0104] MxC was mixed with 10% by mass of sorbitol (which is a polyol). This mixture was heated in a beaker under magnetic stirring at atmospheric pressure. At approximately 70 °C, the MxC began to melt. Heating continued. At approximately 90 °C, a foam formed, which can probably be attributed to the evaporation of water; this water is that initially present in the MxC, and that resulting from the cross-linking of the cutin. Heating continued to a temperature of 150 °C; during this heating, the MxC thickened. After about 10 minutes at this temperature, the mixture became very sticky, with a rubbery consistency. This gel, referred to here as "GMxC," could no longer be poured. It was transferred to a plate using a wooden spatula. It was then pressed using a Carver-type hot press at a temperature of 150 °C for 2 minutes. This process removed most of the gas bubbles.

[0105] This resulted in a thin film that had a slightly sticky feel, with few visible bubbles. This film had low tensile strength and could be easily torn by hand.

[0106] This film was then baked in an oven at 150°C. After one hour of baking, the material changed color, becoming darker, and was less sticky and more resistant to tensile stress. After two hours of baking, the material was black and no longer sticky to the touch. After immersion in water for 48 hours, no swelling was detected. After immersion in ethanol for 12 hours at room temperature, no signs of dissolution were detected.

[0107] The interpretation given to these observations is as follows: upon heating, MxC crosslinks by releasing water molecules. The absence of sticky properties thus The insolubility of crosslinked GMxC in water and ethanol indicates a high degree of crosslinking. It should be noted that bubbles that form at the beginning of polymerization can be removed by pressing the film in a plate press or roller press.

[0108] Example 2: Polymerization of MxC without the addition of polyol at a temperature of 130 °C (according to a preferred embodiment of the invention)

[0109] The same MxC was used as supplied for Example 1. However, no polyol was added, and a lower reaction temperature was used.

[0110] 50 g of MxC was heated in a beaker to a temperature of 130 °C for 1 hour at atmospheric pressure, with the beaker placed in an oven at that temperature. During the heating process, the MxC released fumes and thickened. A gelled mixture of MxC, referred to herein as GMxC, was formed. It contained some air bubbles. After one hour in the oven, the beaker was removed, and the viscous, sticky mixture was poured onto a cotton fabric and spread using a wooden spatula. This fabric was then pressed in a hot press to form a film of uniform thickness on the fabric; during this step, the base and top plates were at a temperature of 150 °C, and the press was held for 10 minutes. This step resulted in the planarization of the GMxC and the removal of air bubbles. After cooling to room temperature, the film thus formed on the textile was still too sticky to the touch.It was then heated on a hot plate (150°C) for an additional 15 minutes.

[0111] A film with a thickness of 1 mm was obtained, which was no longer sticky to the touch, water-repellent (contact angle greater than 90°), insoluble in water and in ethanol.

[0112] Example 3: Tests to explore the crosslinking process

[0113] Three 25 g samples of MxC were placed in aluminum containers and heated at atmospheric pressure in a convection oven heated to a temperature of 100 °C. A sample of the gel thus formed was then spread onto a substrate.

[0114] Test 3-1:

[0115] 1 h at 100 °C. The gel thus obtained was weakly hydrophobic. It is soluble in ethanol at room temperature.

[0116] Test 3-2:

[0117] 2 h at 100 °C: The gel thus obtained swells slightly in cold water, and colors the water cold, after 24 hours.

[0118] Test 3-3:

[0119] 3 h at 100 °C: The gel thus obtained was hydrophobic and insoluble in water and ethanol at room temperature.

[0120] This test shows that MxC crosslinks at a temperature of 100 °C, without the addition of polyol.

[0121] Example 4: Tests to verify the influence of the presence of a polyol and the crosslinking treatment conditions

[0122] Test 4-1:

[0123] With stirring, 80 g of MxC were heated to 150 °C, which took approximately 30 minutes. At this temperature, 7.77 g of sorbitol were added, still with stirring, and the mixture was allowed to react with stirring at 150 °C. The freezing point was reached after 10 minutes. The mass was molded under pressure for 15 minutes at 200 °C. The resulting elastomeric product was not sticky and exhibited high elongation at break.

[0124] Test 4-2:

[0125] The product obtained at the end of test 4-1 was crosslinked in an oven at 150 °C for one hour. The elastomeric product thus obtained was found to have improved tensile strength.

[0126] Test 4-3:

[0127] Test 4-1 was repeated with 40 g of MxC and 3.88 g of sorbitol. An intermediate product, referred to herein as product 4-3A, was obtained. A first quantity of product 4-3A was shaped by pressure molding. A second quantity of product 4-3A was spread with a roller heated to approximately 100 °C to 120 °C, and a certain amount of hemp powder was added as a filler.

[0128] Test 4-4:

[0129] The product obtained from test 4-3 was crosslinked in an oven at 150 °C for one hour. The resulting product was more friable than that obtained from test 4-6.

[0130] Test 4-5:

[0131] Under stirring, 40 g of MxC were heated to a temperature of 150 °C, which took approximately 30 minutes. Heating continued. The gel point was reached at 171 °C after 10 minutes. This example shows that MxC polymerizes on itself, without the addition of a polyol.

[0132] Test 4-6.

[0133] A first part of the product obtained at the end of test 4-5 was pressure molded at 200 °C for 10 minutes.

[0134] Test 4-7

[0135] A second quantity of product 4-4A was spread with a roller heated to approximately 100°C to 120°C, and a certain amount of hemp powder was added as a filler. This product was difficult to work with, very sticky, adhered to the roller, and was difficult to remove from the roller.

[0136] Test 4-8

[0137] The product from test 4-7 was crosslinked in an oven at 150 °C for three hours. The resulting product was rubbery and resistant.

[0138] Test 4-9

[0139] Test 4-1 was repeated with 40 g of MxC and 3.88 g of glycerol. The gel point was reached after 17 minutes.

[0140] Test 4-10

[0141] The product obtained at the end of test 4-9 was pressure molded at 200 °C for 15 minutes.

[0142] Test 4-11

[0143] Test 4-5 was repeated, and the freezing point was reached after 4 minutes at 150 °C.

[0144] Test 4-12

[0145] Test 4-3 was repeated. After the addition of sorbitol, the reaction was allowed to take place at 150 °C with stirring for 2 minutes. The reaction mixture was then transferred to an oven preheated to 150 °C and maintained at that temperature for 3 hours. The mass was then spread with a roller heated to approximately 100 °C to 120 °C, and a certain amount of hemp hurd powder was added as a filler. This product proved to be very brittle and could not be worked.

[0146] Test 4-13

[0147] Test 4-12 was repeated, but after the addition of sorbitol, the mixture was allowed to react at 150 °C with stirring until it reached the gel point after approximately 10 minutes. The mass was then spread with a roller heated to approximately 100 °C to 120 °C, and 12 g of hemp powder was added as a filler. This mass was then cross-linked in an oven at 150 °C for 3 hours. The resulting product proved to be quite hard and brittle, with a rather attractive matte finish.

[0148] Test 4-14

[0149] 40 g of cutin was allowed to gel in an oven at 150 °C, without stirring. The freezing point was observed after one hour. The product thus obtained showed gas bubbles.

[0150] Example 5: Viscosity monitoring

[0151] A quantity of MxC was allowed to polymerize in a container heated in an oil bath, and the bath temperature and the temperature of the reaction mixture were recorded over time. The viscosity of the reaction mixture was also determined, and samples were taken for characterization. The results are summarized in Table 1 and [Fig. 1].

[0152] [Tables 1] Time [min] Oil bath temperature [°C] Reaction medium temperature [°C] Mixture observation Viscosity [10⁻¹ Pa⁻s] Solubility of 99% ethanol at 20°C Solubility of distilled water at 20°C Use 0 167 20 Numerous small bubbles 3 Very large Low 2 169 99 Numerous small bubbles 3 7 172 106 Large but fewer bubbles 7 8 172 114 8 10 173 133 35 13 174 149 More bubbles 40 Moderate None (1) 14 175 153 50 16 175 153 65 17 175 153 70 None None 18 176 153 75 21 174 150 80 (2) 24 173 155 95 28 176 147 100 29 175 141 110 (3) 30 174 136 120 34 174 133 120 (4) 1. Intermediate product that can be dissolved in ethanol to deposit a layer after evaporation of the solvent. 2. Intermediate product that can form a thin layer on a textile substrate. 3. Intermediate product that can form a thick layer on a textile substrate. 4. Rubbery intermediate product that can be molded in a heated mold press.

[0153] A sharp increase in viscosity is clearly seen between approximately 8 minutes and approximately 10 minutes of reaction; thereafter, the viscosity reaches a plateau.

[0154] Example 6: Incorporation of cellulose fibres from tomato plant waste

[0155] A mixture of exhausted tomato peels was supplied, which is a by-product of the cutin extraction process from tomato processing waste described in EP 4 116 352 A1. This mixture, referred to herein as "ExP", comprises approximately 77.6% moisture, approximately 0.27% protein, approximately 0.30% fat, a total fiber content of 11.6% and 550 mg / kg of lycopene.

[0156] 20 g of ExP was heated and 10 g of McX was added under stirring. The mixture was allowed to polymerize for 3 h under stirring at >130 °C, and a fairly hard, slightly brittle and non-sticky elastomer was obtained, which exhibits slight solubility in water.

[0157] Example 7: Characterization of reactions by differential scanning calorimetry (DSC)

[0158] Various MxC samples were characterized by DSC using an instrument from TA Instruments-Waters LLC and Universal Analysis software version 4.5 provided by that manufacturer. The results are shown in [Fig. 2] and [Fig. 3]. The horizontal axis shows the temperature in degrees Celsius. The vertical axis shows the heat flux in W / g. Several curves were superimposed with a vertical offset, so the absolute values ​​of the heat flux are not significant.

[0159] [Fig.2] represents a test with four samples of unpolymerized MxC. The Curve (b) corresponds to a sample of crude MxC containing 20% ​​water. Curve (a) corresponds to a sample of crude MxC that was oven-dried at 60°C for 12 hours prior to testing. Curve (c) corresponds to a sample of crude MxC with the addition of 10% wt. of sorbitol. Curve (d) corresponds to a sample of crude MxC with the addition of 10% wt. of glycerol.

[0160] Curve (a) shows an initial event around 46.5 °C, corresponding to the melting of cutin. Water evaporation is then observed around 92 °C, followed by the onset of endothermic esterification around 110 °C. Curve (a) does not show water evaporation because it represents a pre-dried sample; esterification occurs suddenly around 114 °C. The addition of polyol (curve (c) for sorbitol, curve (d) for glycerol) increases the melting temperature and decreases the esterification onset temperature.

[0161] The oscillation of the curves can be attributed to vibrations of the sample holder during the departure of water bubbles resulting from the esterification reaction.

[0162] [Fig. 3] shows a second test using the same four indexed samples (a), (b), (c), and (d) from [Fig. 2] after cooling in open air. The origin of the event around 12°C is not elucidated; it may be the evaporation of water that had been accidentally condensed. It is observed that the melting point of The material density is higher than in [Fig. 2], indicating that it is a structurally different material. There is also a complete absence of any esterification event. This shows that esterification was complete during the first pass in [Fig. 1].

Claims

1.

2.

3.

4.

5.

6.

7. Demands A process for preparing a polymer based on polyhydroxylated fatty acids, comprising the following successive steps: - Supplying or preparing a reaction medium comprising a mixture called the initial mixture comprising at least 30% by mass of at least one monomer selected from polyhydroxylated fatty acids and esters of a polyhydroxylated fatty acid and alcohols with linear or branched aliphatic chains, said reaction medium being free of catalyst, - Heating said reaction medium at ambient pressure for a period of less than 120 minutes, and preferably less than 90 minutes, at a temperature between 100°C and 160°C, preferably between 100°C and 150°C and even more preferably between 120°C and 150°C, to obtain an intermediate product that is at least partially polymerized and possibly at least partially crosslinked. A process according to claim 1, characterized in that said initial mixture also comprises oligomers, and in particular dimers and / or trimers, of said polyhydroxylated fatty acid. A process according to claim 2, characterized in that said polyhydroxylated fatty acid is 10,16-dihydroxyhexadecanoic acid. A process according to any one of claims 1 to 3, wherein said initial mixture is at least partially depolymerized cutin extract, or contains at least partially depolymerized cutin extract. A process according to any one of claims 1 to 4, wherein said reaction medium does not comprise any added polyol. A method according to any one of claims 1 to 5, wherein the heating step has a duration of between 1 minute and 30 minutes, preferably between 1 minute and 20 minutes, and even more preferably between about 2 minutes and about 15 minutes. A process according to any one of claims 1 to 6, wherein said intermediate product is shaped and then subjected to a crosslinking treatment of between approximately 0.5 hours and 10 hours at a temperature between 100 °C and 160 °C, preferably between 100 °C and 150 °C, and even more preferably between about 100 °C and 140 °C.

8. A process according to any one of claims 1 to 6, wherein polyester monomers or oligomers are added to said reaction mixture.

9. Natural polyhydroxylated fatty acid-based polymer, which can be obtained by the process according to any one of claims 1 to 8.

10. Use of a polymer according to claim 9, for the manufacture of waterproof or water and ethanol resistant layers and coatings.

11. Use of a polymer according to claim 9 in diluted form in a solvent in the form of a liquid or paste phase, for coating solid surfaces, or for coating or impregnating textile fabrics based on natural and / or synthetic fibers, or for coating or impregnating natural or synthetic fibers.