Composition and use thereof for sealing

Abstract

The invention relates to a composition comprising natural latex and a natural or synthetic wax, the proportion of the natural latex to the natural or synthetic wax being 40:60 to 60:40 by weight. The invention also relates to the use of such a composition for sealing a surface.

Description

Composition and its use for waterproofing

[0001] The invention relates to a composition and its use for sealing surfaces, in particular porous surfaces.

[0002] Fibrous substrates, such as paper, cardboard, preformed paper containers, fabric, and other fiber-based materials, are widely used in packaging operations.

[0003] However, fibrous substrates are porous and therefore do not prevent the penetration of water, steam, solvents, etc. into them. To improve their strength and impregnation, fibrous substrates have long been coated with a wide variety of compositions, particularly when the substrates are used for food packaging.

[0004] Many such coatings are known, for example those described in US patent 3632424 which describes the use of a wax or waxes incorporated into a latex and applied to a fibrous substrate as a coating. The latex used is 21 / 76 / 3 ethylene / vinyl chloride / acrylamide latex terpolymer. It therefore requires the transformation of the latex.

[0005] Reference may also be made to application WO2007140009, which again describes a hydrophobic coating suitable for covering fibrous materials such as paper or cardboard, these coated materials being impermeable to steam, the materials however being recyclable after covering. The coating is composed of latex derivatives and crystalline lamellar structures, and above all are free of waxes.

[0006] Indeed, beyond the issue of waterproofing, the question of the recyclability of materials is now taking an important place in the field in question. Therefore, it is important to consider both the waterproofing of packaging materials, but also their recycling and reuse.

[0007] The invention therefore aims to resolve these problems identified in the prior art.

[0008] One of the objects of the invention is to provide a natural and recyclable composition which can be used for packaging.

[0009] Another object of the invention is to provide a method of manufacturing this composition.

[0010] Yet another object of the invention is to provide a method of waterproofing a permeable support which is simple and rapid.

[0011] Also, the invention relates to a composition comprising natural latex and a natural or artificial, or synthetic, wax, or a mixture thereof, the proportion of natural latex and natural or artificial wax being 40:60 to 60:40 by mass relative to the total mass of solid compounds.

[0012] The invention is based on the surprising observation made by the inventors that a mixture of natural latex and a wax, in particular proportions, makes it possible to confer sealing properties to a permeable support, and above all that this type of composition does not alter the recyclability of the support despite its covering.

[0013] Indeed, natural latex is very interesting for forming elastic films. However, it is generally crosslinked by a vulcanization process which creates disulfide bridges at the level of the unsaturations of the polyisoprenes. This crosslinking provides better resistance to external constraints (temperatures, mechanical stresses, ultraviolet rays, oxidizing compounds). However, this crosslinking (which requires a heavy industrial process) does not make the latex recyclable.

[0014] Therefore, the inventors decided to use natural latex which is not transformed, thus respecting the environment.

[0015] In the invention, the composition therefore comprises a natural latex. In the context of the invention, we will speak of “natural latex” to designate any latex composition derived from the rubber tree, and which has not undergone treatment aimed at modifying the properties of the polyterpenoid polymers which it contains, as is the case for the manufacture of rubber.

[0016] Natural latex consists mainly of 1,4 cis polyisoprene, proteins and water, the proteins allowing the stabilization of the polymer dispersion in water. It is a macroscopically homogeneous but thermodynamically unstable binary system. The natural evolution over time leads to the irreversible separation of the two phases. This rupture of the pseudo-equilibrium, called coacervation, is necessary for the production of rubber articles but proves very restrictive during transport or storage of the latex. The dispersed phase is essentially composed of spherical particles (diameter less than 0.5 μm) surrounded by a peripheral layer of proteins adsorbed at the water-polymer interface. It is this protein film that plays a major role in the stability of the latex.

[0017] However, when talking about natural latex, the addition of ammonia will be accepted, in order to protect it from acid coagulation on the one hand, and to avoid contamination by bacteria on the other. The addition of ammonia to the latex serum has the effect of decreasing the detectable protein content. These hydrolysis reactions lead to the formation of ionized long-chain fatty acids which adsorb to the surface of the particles and lead to an increase in the colloidal stability of the latex.

[0018] In the composition according to the invention, the proportion of latex relative to the wax varies from 40:60 to 60:40, which means that the quantity of latex relative to the quantity of wax can be one of the following proportions: 40:60, 40.5:59.5, 41:59, 41.5:58.5, 42:58, 42.5:57.5, 43:57, 43.5:56.5, 44:56, 44.5:55.5, 45:55, 45.5:54.5, 46:54, 46.5:53.5, 47:53, 47.5:52.5, 48:52, 48.5:51.5, 49:53, 50:52, 50:53, 50:54, 50:5 ... 51, 49.5: 50.5, 50: 50, 50.5: 49.5, 51: 49, 51.5: 48.5, 52: 48, 52.5: 47.5, 53: 47, 53.5: 46.5, 54: 46, 54.5: 45.5, 55:45, 55.5:44.5, 56:44, 56.5:43.5, 57:43, 57.5:42.5, 58:42, 58.5:41.5, 59:41, 59.5:40.5 or 60:40.

[0019] It should be noted that if the quantity of latex is too high (greater than 60% by mass), the composition according to the invention will be sticky and will not allow for a uniform covering.

[0020] Conversely, if the latex is in too low a quantity (less than 40% by mass), the composition will be brittle and will lose its film-forming and covering properties.

[0021] Advantageously, the invention relates to the above-mentioned composition, where said natural latex is an aqueous dispersion, in particular colloidal, comprising up to 70% by mass of solid particles relative to the total mass of the natural rubber latex.

[0022] It is advantageous for the latex used to comprise from 30 to 70% by mass of particles or solid matter, preferably from 40 to 60% by mass of solid matter, the percentages being expressed relative to the total mass of the natural latex.

[0023] Among natural latexes, the most widely used grade is latex with a low concentration of ammonia, called "lowammonia", which comprises approximately 0.2% by mass of ammonia compared to the total mass of latex.

[0024] Another grade of natural latex, called "high ammonia", can be used and comprises from about 0.3% to about 0.6% by mass of ammonia relative to the total mass of latex.

[0025] One of the advantages of natural latex in the manufacturing of a coating, particularly for paper, is that this material does not affect the recyclability of the support, particularly a cellulosic or fibrous support. Indeed, the committee for the evaluation of the recyclability of paper and cardboard packaging issued a favorable opinion in 2015 on the recyclability of packaging containing 65% paper and 15% natural latex. This is notably due to its biodegradable nature, which is an asset in the current context of pollution caused by packaging waste.

[0026] The composition according to the invention further comprises a wax. This wax may be of natural or synthetic origin, i.e. derived from artificial synthesis.

[0027] Advantageously, the invention relates to the aforementioned composition, where said natural wax is a fossil or non-fossil wax, in particular chosen from animal or vegetable waxes, and or the synthetic wax is a partially or completely synthetic wax.

[0028] In the invention we will distinguish

[0029] - natural waxes which include fossil waxes (coal or petroleum waxes) and non-fossil waxes (animal or vegetable waxes), and

[0030] - synthetic waxes which include partially (fatty acid amide waxes) and completely (polyolefin waxes, such as polyethylene or polypropylene or Fisher-Tropsch or polar synthetic waxes) synthetic waxes.

[0031] In the context of the invention, it is particularly advantageous for the composition to be composed, in the above-described proportions, of natural wax and natural latex.

[0032] Advantageously, the waxes used in the invention are in the form of a dispersion of waxes in water, in particular in the presence of a surfactant or surfactant. This makes it possible to produce a cold mixture of the dispersed wax and the natural latex and then deposit this mixture on the fibrous substrate.

[0033] The natural waxes advantageous for the composition according to the invention are the following:

[0034] - Carnauba wax (natural vegetable wax): this wax is made up of a mixture of aliphatic esters (40%), 4-hydroxycinnamic acid diester (21%), hydroxycarboxylic acid esters (13%), fatty alcohol (12%), 4-methoxycinnamic acid diesters (7%), aliphatic and aromatic acids (5%), terpenes and other compounds 4.4%, etc. It also contains about 1% hydrocarbons. It is one of the natural waxes with a high hardness and a high dropping point, generally around 83°C. Advantageously, the carnauba wax used has a dropping point of 85°C. It is a dispersion of carnauba wax in water with a particle size mainly between 100 and 200nm. The mass percentage of solids is 30%. The surfactant is anionic and the pH is between 5 and 7;

[0035] - Sugarcane wax (natural vegetable wax): Sugarcane produces a wax representing approximately 0.1 to 0.25% of its mass. Sugarcane wax, the refining of which is necessary, is composed of aliphatic esters and sterol esters (78 to 82%), free fatty acids (14%), fatty alcohol (6-7%) and hydrocarbons (3 to 5%). The melting temperature is generally between 68°C and 81°C. The sugarcane wax to be used in the context of the invention is advantageously a wax dispersed in water with an anionic surfactant. The mass percentage of the dispersion is 35%;

[0036] - Hydrogenated vegetable oil: The hydrogenation of vegetable oils produces almost completely saturated oils with a higher melting point than the non-hydrogenated oil from which they are derived. The hydrogenation reaction is most often carried out between 150 and 200°C, with a pressure between 0.1 and 0.5 MPa and in the presence of a catalyst, often nickel-based. The preferred hydrogenated vegetable oil is an oil, for example rapeseed, palm or soybean, with a dropping point close to 75°C. It has been used in dispersed form. The surfactant used is anionic and the mass percentage of hydrogenated vegetable oil is 40%.

[0037] - Beeswax (natural vegetable wax): beeswax is a particular natural wax secreted by honey bees (Apismelifera) which is obtained in a conventional way in beekeeping. It is composed among other things of hydrocarbons (10 to 20%) having between 23 and 35 carbons. It is often treated with charcoal or aluminum or magnesium silicates to eliminate some of its color and odor;

[0038] - Polyethylene wax (completely synthetic wax): Polyethylene waxes can be considered as polyethylene of very low molar mass. The average molar mass by weight does not exceed 37000g.mol -1 and is generally around 6000g.mol -1 . The kinematic viscosity must not exceed 20000mm 2 .s -1at 120°C. Generally the melting point is between 105°C and 115°C. They are manufactured in the same way as PE by radical polymerization of ethylene and the operating conditions (type of reactor, pressure and temperature of the reactor, type and quantity of radical initiator and regulating agent, type of catalyst) determine the structure and molar mass of synthesized PE waxes. It is possible to manufacture polar PE waxes by oxidation of apolar PE wax, or by radical polymerization of ethylene in the presence of polar co-monomers. These polar PE waxes can then be dispersed in water in the presence of surfactants. The dropping point is between 110°C and 120°C and 98% of the dispersed particles have a size less than 1μm. The mass percentage of PE wax is 35%. The surfactant used is non-ionic and the pH of the dispersion is between 6 and 8.

[0039] - Fischer Tropsch Wax (completely synthetic wax): Fischer-Tropsch waxes are manufactured by the process of the same name which consists of the synthesis of hydrocarbons from synthesis gas or syngas. The latter is a mixture of carbon monoxide (CO) and dihydrogen (H2). The reaction takes place between 220-240°C at 2MPa in the presence of an iron-based catalyst generally. Alkanes and alkenes are formed, of which about 40% are compounds that will form the wax. They are separated by distillation and condensation then purified and the wax obtained at the end is practically only composed of linear alkanes between 20 and 50 carbons. The viscosity is generally lower than macrocrystalline paraffin but their melting point is higher. In the same way as PE waxes, it is possible to manufacture polar Fischer-Tropsch waxes. These waxes can then be dispersed in water using a surfactant.An advantageous wax in the invention has a dropping point between 110°C and 120°C and 98% of its particles have a size less than 1μm. The mass percentage is 35% and the surfactant is non-ionic.

[0040] Hydrogenated vegetable oil is particularly advantageous in the context of the invention. Also advantageously the invention relates to a composition comprising natural latex and hydrogenated oil, the proportion of natural latex and hydrogenated oil being from 40:60 to 60:40 by mass relative to the total mass of solid compounds.

[0041] Even more advantageously, the invention relates to the aforementioned composition, comprising, in addition to a filler, in particular kaolin or calcium carbonate, in particular at most 10% by mass relative to the total mass of the composition.

[0042] As mentioned above, the paper-cardboard packaging recyclability assessment committee has issued a favorable opinion on the recyclability of packaging containing 65% paper, 15% natural latex and 20% mineral fillers. Finally, a final advantage of natural latex is that it is a biodegradable material.

[0043] Mineral fillers are intended to reduce the stickiness of natural latex. The mass percentages of fillers are generally 5% to 10% by mass relative to the mass of the composition. However, it should be noted that interesting results are obtained with the use of 20% kaolin in natural latex. With this formulation, the adhesion strength decreases by 45% compared to natural latex and the contact angle increases by 10% up to 108°C. The film obtained is therefore less sticky and, above all, it remains hydrophobic.

[0044] Even more advantageously, the invention relates to the above-mentioned composition, comprising:

[0045] - at least 90% by mass of a mixture of hydrogenated vegetable oil and natural latex, the proportion of natural latex and hydrogenated vegetable oil being 40:60 to 60:40 by mass, and

[0046] - at most 10% by mass of kaolin relative to the total mass of the composition.

[0047] Advantageously, the invention relates to the aforementioned composition, comprising:

[0048] - at least 90% by mass of a mixture of hydrogenated vegetable oil and natural latex, the proportion of natural latex and hydrogenated vegetable oil being 40:60 to 60:40 by mass, and

[0049] - at most 10% by mass of a mineral filler relative to the total mass of the composition.

[0050] Such a composition is particularly advantageous for covering porous materials such as paper or cardboard.

[0051] The filler, in particular kaolin, must not exceed 10% by mass compared to the total mass of the composition

[0052] Furthermore, the invention relates to a method for manufacturing the above-mentioned composition, comprising a step of homogeneous mixing of natural latex and a natural or artificial wax, and optionally a filler, in particular at room temperature, i.e. at a temperature of 17°C to 40°C.

[0053] The process for preparing the composition according to the invention is particularly simple and consists of a homogeneous mixture of natural latex as defined above, and wax as defined above.

[0054] More specifically, latex, which is a dispersion in water of 1,4 cis polyisoprene polymers, is mixed with a dispersion of wax in water. It is possible for the wax dispersion to be in the form of a dispersion in the presence of one or more surfactants. It is therefore a mixture of two dispersions of polymers in water.

[0055] It is also possible to add to this mixture of the two dispersions a mineral filler, such as calcium carbonate or kaolin, in powder form in proportions as defined above.

[0056] Mixing is carried out in a conventional manner using any suitable mixer known to those skilled in the art, of a size appropriate to the quantity of mixture desired.

[0057] This mixture is made at a conventional ambient temperature varying in particular from 17°C to 40°C, that is to say at a temperature of 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 or 40°C depending on the conditions of the place where the mixture is prepared.

[0058] It is also advantageous not to leave the mixture in the open air for too long (> 1 hour) to avoid surface drying.

[0059] Also described herein is a homogeneous composition as obtained from the above-described process.

[0060] The invention further relates to a method for waterproofing a support allowing aqueous or organic liquids to pass through, for example aqueous solutions having a pH between 4 and 12, and optionally gases, said method comprising the following steps:

[0061] - the homogeneous mixing of natural latex and a natural or artificial wax, and possibly a filler, so as to avoid the formation of bubbles, to obtain a smooth homogeneous mixture, free from bubbles;

[0062] - bringing the smooth homogeneous mixture into contact with the support allowing aqueous or organic liquids to pass through, to obtain a covered support,

[0063] - drying the coated support at a temperature above 40°C to eliminate both the water contained in the homogeneous mixture and the porous support permeable to aqueous solutions having a pH between 4 and 12 and to certain organic / liquid solvents), to obtain a waterproofed coated support.

[0064] The inventors were able to observe, surprisingly, that the covering of a porous material permeable to aqueous solutions, in particular having a pH between 4 and 12 and to certain liquid organic solvents, as well as possibly to gas, can be made impermeable to said aqueous solutions or organic solvent and possibly to gases, by covering it using the above-mentioned composition.

[0065] The aforementioned composition will create a film-forming barrier protecting the material from said liquids and possibly gases.

[0066] In the first step of the above-mentioned process, the natural latex and the wax, and possibly the filler, as previously defined, are mixed homogeneously in order to disperse the particles of the natural latex and the wax so that in the final mixture, macroscopically, it does not allow the different constituents to be distinguished separately and distinctly.

[0067] It is essential that when this homogeneous mixture is produced there are no bubbles. Indeed, the presence of bubbles in the homogeneous mixture can generate interstices which will allow fluids, and possibly gases, to pass through, and which will ultimately cause the composition layer to lose its watertight character.

[0068] To avoid bubbles during mixing, it is recommended to stir slowly to avoid incorporating air that would cause the bubbles. Furthermore, once the mixture is homogeneous, it is recommended to let the mixture rest, possibly by heating its surface, to eliminate the bubbles. However, this resting time should not be too long to prevent the particles in the mixture from coalescing.

[0069] Once the smooth homogeneous mixture is obtained, it is applied, that is to say brought into contact, with the support allowing aqueous or organic liquids to pass through. This contact can be carried out by any means known to those skilled in the art.

[0070] Advantageously, when the support to be sealed is thin and flat, such as sheets of paper or fibrous fabrics, this contact can be achieved by the following techniques:

[0071] - immersion coating: the support to be waterproofed is immersed vertically in a container filled with the smooth homogeneous mixture and then removed vertically, in particular using the so-called elevator technique;

[0072] - curtain coating: the support to be coated is placed on a mobile device under which there is a tank containing the smooth homogeneous mixture. The tank allows, by means of an opening, to let the smooth homogeneous mixture flow at a constant rate under the action of gravity (coating curtain), so that the entire support will be covered with said smooth mixture due to its movement;

[0073] - coating by a sizing press: the support to be coated is passed between two rollers, one of the rollers being immersed in the smooth homogeneous mixture. When the roller is immersed in the smooth homogeneous mixture, the smooth homogeneous mixture is driven and applied to a surface of the support to be coated;

[0074] - coating by coating bar: the smooth homogeneous mixture is applied in a non-uniform manner to the support to be covered, and a bar comes to flatten and distribute the smooth homogeneous mixture over the entire surface of the support to be coated.

[0075] Obviously, other coating techniques well known in the art are applicable by those skilled in the art.

[0076] Once the support is covered with the smooth homogeneous mixture, the support thus covered is dried at a temperature above 40°C, more particularly above 60°C, in particular above 80°C or even 90°C or more. However, it is preferable that this drying is not carried out at a temperature which induces swelling of the film due to drying too quickly; a person skilled in the art is able to determine this temperature. Indeed, if the drying is too rapid, the surface of the film will dry first and the water contained in the substrate and in the incompletely dried film will no longer be able to evaporate. The film will then swell. The maximum drying temperature depends on the quantity of mixture deposited and the ventilation of the oven. For example, a temperature of 160°C in a ventilated oven causes swelling to appear if the mass concentration of the mixture is 40%.Drying conditions should be determined by trial and error to determine the optimal drying time and temperature for the tool used.

[0077] Advantageously, this drying is carried out in an oven with ventilation. The purpose of using ventilation is to better distribute the heat and therefore to lower the temperature. The purpose of ventilation is to evacuate the evaporated water vapor from the film being formed in order to reduce the partial pressure of vapor in the oven and therefore accelerate drying.

[0078] The purpose of this heating step is to remove the water contained in both the substrate and the smooth homogeneous mixture, both of which form the coated substrate. By removing the water, the latex and wax mixture will form a film on the surface of the substrate, which will impermeable the substrate to fluids and possibly gases. The formation of a polymer film on paper from latex is a complex, multi-step phenomenon. Three main steps are generally distinguished:

[0079] - the reduction in the distance between particles following the evaporation of the solvent,

[0080] - the coalescence of polymer particles, and

[0081] - the interdiffusion of polymer chains between adjacent particles. Drying therefore makes it possible to fix the film of the composition according to the invention. As demonstrated in the examples below, the drying temperature plays an important role in the film-forming and sealing properties of the composition according to the invention.

[0082] The invention further relates to the use of a composition as defined below, for waterproofing a support, in particular a porous support, in particular a support permeable to aqueous solutions, and more particularly to aqueous solutions having a pH of between 4 and 12 and to certain organic solvents.

[0083] In another aspect, the invention relates to a waterproofed support covered, on at least one of its surfaces, with a composition as defined in one of the abovementioned ones, in particular capable of being obtained by the process as defined above.

[0084] The composition of the invention is particularly suitable for waterproofing fibrous supports, in particular cellulosic supports, such as paper, cardboard, and more generally materials used in packaging. However, the composition according to the invention can also be used for waterproofing textile fibers.

[0085] The film obtained from the composition according to the invention being sufficiently flexible and supple, it will therefore allow use on stressed supports such as clothing.

[0086] Other porous materials such as granular agglomerates, or construction materials can also be covered, and thus sealed, using the composition according to the invention.

[0087] Other supports are conceivable within the framework of the invention and in particular supports for seals, banknotes, or even food containers such as pots or cups or glasses.

[0088] Advantageously, the invention relates to the aforementioned support where said support is a fibrous and / or porous support, and in particular paper, or one of its derivatives.

[0089] The fibrous supports according to the invention are in particular paper, cardboard, fabrics such as cotton, linen, hemp or wool fabrics, but also synthetic textiles or fabrics obtained by weaving polyamide, polyester, acrylic fibers, etc.

[0090] This list is obviously not exhaustive.

[0091] It is therefore covered by the invention of waterproof textiles, such as raincoats, jackets, trench coats, hats, umbrellas, hats or bonnets, overalls, bibs, towels, tablecloths, mattress protectors, or any other textile likely to be in contact with water.

[0092] The invention will be better understood by reading the figures and examples which follow: Brief description of the figures

[0093] Figure 1 represents a graph showing the quantity (in gm -2 ) of a composition comprising 60% latex and 40% vegetable oil deposited on a paper support depending on the viscosity (in mPa.s)

[0094] Figure 2 shows photos obtained by electron microscopy of paper coated with the following compositions: A = CAR / Latex in proportion 40:60; B = CANN / Latex in proportion 40:60; C = PE / Latex in proportion 40:60 and D = FISHER / Latex in proportion 40:60. The right column has a scale as described by the white bar (50µm) and the right column corresponds to a 5-fold enlargement (bar = 10 µm).

[0095] Figure 3 shows electron microscopic photographs of paper coated with a HVH / Latex composition in a 50:50 ratio (A) or with a 95% by mass HVH / Latex composition in a 50:50 ratio, in the presence of 5% by mass kaolin (B). The right column has a scale as described by the white bar (50µm) and the right column corresponds to a 5-fold enlargement (bar = 10µm).

[0096] Figure 4 shows electron micrographs of paper coated with pure natural latex and dried at 20°C (A) or 90°C (B). The right-hand column has a scale as described by the white bar (50 µm) and the right-hand column corresponds to a 5-fold enlargement (bar = 10 µm).

[0097] Figure 5 shows electron microscopic photographs of paper coated with a HVH / natural latex composition in a 40:60 ratio and dried at 20°C (A) or 90°C (B). The right-hand column has a scale as described by the white bar (50µm) and the right-hand column corresponds to a 5-fold enlargement (bar = 10µm).

[0098] Figure 6 represents a graph showing on the left y-axis the quantity of water absorbed (in gm -2 ) as a function of the immersion time (in h) (A) and on the right ordinate axis the nominal breaking force (in N) as a function of the immersion time (in h) (B), of a paper.

[0099] Figure 7 represents a graph showing the amount of water absorbed (in gm -2 ) as a function of time (in h) of a paper covered with pure natural latex (A) or an HVH / Latex composition in proportion 40:60.

[0100] Figure 8 shows photographs showing the effect of attempting to separate the composition layer according to the invention from the paper on which they were deposited. Examples

[0101] Example 1: Tests performed.

[0102] The inventors carried out a series of experiments on sealing a paper support with compositions according to the definition in the invention. The compositions tested are as follows:

[0103] - Latex + carnauba wax (CAR / latex),

[0104] - Latex + sugarcane wax (CANN / Latex)

[0105] - Latex + hydrogenated vegetable oil (HVH / Latex),

[0106] - Latex + polyethylene wax (PE / Latex), and

[0107] - Latex + Fischer Tropsch wax (FISCHER / Latex).

[0108] The mass percentage of solids in the latex-wax mixture is between 40% and 60%, preferably 50%, relative to the mass of water. This makes it possible to deposit between 100 and 170 gm-2 of the mixture on the reference paper of the examples: Kraft pulp, 150g.m -2 , 0.8% rosin and 4% talc + (cationic starch and aluminum salts), Cobb 60s = 25.

[0109] Example 2: Viscosity test of the composition deposited on paper.

[0110] In this example, the inventors tested the viscosity of the composition according to the invention as a function of the quantity deposited on the reference paper.

[0111] Dynamic viscosity was measured using a cone-plate rheometer. The rheometer is a Thermoscientific HAAKE MARS III model and the plate geometry is TMP60, and the cone geometry is C60 / 1° TiL. This means that the plate diameter is 60 mm and the cone angle is 1°. The shear rate used is 500 s -1 (Newtonian domain). 1 g of wax sample is placed on the plate and after an equilibrium time of 30 s, the dynamic viscosity is measured at 20°C.

[0112] The results for a HVH / Latex composition in proportion 40:60 are presented in Figure 1.

[0113] The increase in the viscosity of the mixture is correlated with the increase in the amount deposited by dipping. Viscosities are between 5 mPa.s and 37 mPa.s and the amount of coating deposited between 40 gm -2 and 180 gm -2This study allows us to predict the amount of coating that will be deposited by dipping by measuring the dynamic viscosity of the mixture.

[0114] Example 3: Characterization of the composition layers according to the invention.

[0115] In this example, the inventors observed by electron microscopy the structure of the layers of composition according to the invention on paper, after drying at 90°C for 90 min in a non-ventilated oven.

[0116] The following compositions were tested:

[0117] - CAR / Latex in proportion 40:60;

[0118] - CANN / Latex in proportion 40:60;

[0119] - PE / Latex in proportion 40:60;

[0120] - FISHER / Latex in proportion 40:60.

[0121] Scanning electron microscopy (SEM), performed on a JEOL JSM-7100F instrument, allows the visualization of a surface at the micrometer scale. An electron beam scans the surface and electron-matter interactions produce different types of emissions. Different detectors are used to collect the emitted electrons to reconstruct an image of the surface. Prior to analysis, the samples dried in a desiccator are covered with a thin film of gold / palladium of approximately 2 to 3 nm. SEM was used to visualize the surface of the coated papers at the micrometer scale in order to highlight possible pores, defects or certain crystalline arrangements.

[0122] Electron microscopy observations are presented in Figure 2.

[0123] The images show non-porous and relatively homogeneous surfaces. This indicates good particle coalescence and therefore suitable drying conditions. An exception may be the PE / Latex coating where phase separation in the form of bands is observed. The bands are potentially PE crystallized in the form of spherulites. It is likely that polyethylene, even if it has a low molar mass in the case of a wax, does not mix with cis-1,4-polyisoprene. Indeed, the mixture of two polymers is most of the time thermodynamically unfavorable.

[0124] Example 4: Characterization of the layers of composition according to the invention, in the presence or absence of mineral filler.

[0125] In order to complete the study of example 3, the inventors observed by electron microscopy the structure of the layers of composition according to the invention on paper, after drying at 90°C for 90 min in a non-ventilated oven.

[0126] The following solid particle mass compositions were tested:

[0127] - HVH / Latex in a proportion of 50:50, and

[0128] - 95% by mass of HVH / Latex in a proportion of 50:50, in the presence of 5% by mass of kaolin.

[0129] Electron microscopy observations are presented in Figure 3. Scanning electron microscopy (SEM), performed on a JEOL JSM-7100F device, allows the visualization of a surface at the micrometric scale. An electron beam scans the surface and electron-matter interactions produce different types of emissions. Different detectors are used to collect the emitted electrons to reconstruct an image of the surface. Prior to analysis, the samples dried in a desiccator are covered with a thin film of gold / palladium of approximately 2 to 3 nm. SEM was used to visualize the surface of the coated papers at the micrometric scale in order to highlight possible pores, defects or certain crystalline arrangements.

[0130] Figure 3 shows SEM images of the surface of the 50%HVH_50%Latex and 50%HVH_50%Latex + 5%Kaolin coatings. In both cases, there are no visible pores. The coating is homogeneous and relatively smooth. For the 50%HVH_50%Latex + 5%Kaolin coating, kaolin grains can be distinguished, dispersed on the surface of the coating. The presence of Kaolin does not visually appear to prevent good film formation.

[0131] Example 5: Influence of temperature on the formation of an impermeable layer.

[0132] In this example, the inventors focused on testing the influence of the drying temperature when applying the composition according to the invention to paper.

[0133] The following compositions were tested:

[0134] - Pure natural latex, and

[0135] - HVH / Latex in a proportion of 40:60.

[0136] The compositions, after mixing, were deposited on paper and dried at 20°C for 24 hours or 90°C for 90 minutes.

[0137] The results obtained for natural latex are presented in Figure 4 and those with the HVH / Latex composition in Figure 5.

[0138] In Figure 4, images of a coating made entirely of natural latex show that when dried at 20°C, the surface of the coating is completely porous. In contrast, the porosity of the latex coating decreases significantly when the coating is dried at 90°C. There are only a few areas where pores are still visible.

[0139] In Figure 5, concerning the 40%HVH_60%Latex coating, with drying at 20°C for 24 hours, the coating obtained is completely porous. On the other hand, there are no more visible pores on the surface of the coating when it is dried at 90°C.

[0140] To explain this apparent difference in porosity as a function of the coating drying temperature, it is necessary to look at the stages of coating formation. Initially, the colloidal particles of the dispersion are far from each other. As the water evaporates, the particles come into contact with each other. Then, the particles deform and finally the polymer chains inter-diffuse. For the film formation stages (particle deformation and chain inter-diffusion) to proceed correctly, it is necessary to reach a minimum drying temperature or, in other words, sufficient energy. This minimum film formation temperature has been defined as the minimum temperature from which the film becomes continuous and translucent. The force that allows the coalescence of two latex particles is the reduction in the surface tension of the surface associated with these two particles.However, the energy required to break the water film between two particles creates a thermodynamic barrier to coalescence. Increasing the drying temperature therefore facilitates the coalescence phenomenon by providing the energy needed to overcome this thermodynamic barrier. This experiment allows us to conclude that drying these coatings at 20°C does not allow the formation of a homogeneous coating and possibly a barrier to gases or liquids.

[0141] Example 6: Waterproofing test: water absorption of paper.

[0142] In order to verify the waterproofing of the paper when it was covered with a composition according to the invention, the inventors tested the water absorption of the paper with or without a covering.

[0143] For uncoated paper, the mass of water absorbed over time and the nominal breaking force are shown in Figure 6. It is found that water absorption in the paper is a very rapid phenomenon (a few minutes) and this is correlated with the almost total loss of the mechanical properties of the paper.

[0144] Figure 7 shows the results for paper coated with latex alone or with an HVH / Latex composition in a 40:60 ratio.

[0145] The HVH / Latex composition in a ratio of 40:60 provides an effective barrier to liquid water and thus preserves most of the mechanical properties of the paper support for approximately 700 hours. The composition composed solely of natural latex is less of a barrier to liquid water than the HVH / Latex composition in a ratio of 40:60. Water absorption in the paper support is approximately two to three times faster.

[0146] Example 7: Recycling: peelability of the composition according to the invention.

[0147] In addition to waterproofing the paper, the inventors sought to verify whether the composition according to the invention, once applied to the paper, was easily removable (peelable) in order to allow recycling of the paper.

[0148] To this end, the inventors carried out experiments according to the method of the invention, with the following compositions:

[0149] - a HVH / Latex composition in a proportion of 70:30, and

[0150] - a HVH / Latex composition in a proportion of 40:60.

[0151] The paper was covered with each of the compositions, dried according to the conditions of the invention (here at 90°C).

[0152] The corner of each sheet was then manipulated in an attempt to separate the composition layer from the paper.

[0153] The results are shown in Figure 8.

[0154] It can be seen that the HVH / Latex composition layer in a proportion of 40:60 seems to detach easily from the paper on which it was deposited, as shown by the untorn part of the paper visible in the photo at the top right of figure 8. Conversely, the HVH / Latex composition in a proportion of 70:30 seems very adherent to the paper so that the peelability test inevitably leads to the tearing of the paper without it being possible to separate it from the composition layer.

[0155] These experiments show that the composition according to the invention, due to its particular proportions, retains peelability properties, which allows it to be removed from the paper for recycling.

[0156] Example 8: Recycling: test under paper recycling conditions.

[0157] The Technical Paper Centre (CTP) carried out recyclability tests on cardboard pots coated with the composition according to the invention. The recyclability test was carried out according to standard EN 13430:

[0158] The first step is to resuspend the fibrous part. This operation is called pulping. It consists of individualizing the cellulose fibers in such a way as to make the fibrous suspension pumpable for classification. The following conditions are used for resuspension in the laboratory pulper:

[0159] -Temperature: 45°C

[0160] -Concentration: 3% (by mass)

[0161] - Duration: 15 min

[0162] -Neutral pH

[0163] These conditions are representative of those applied industrially for the recycling of packaging paper / cardboard. After 15 minutes of pulping, the disintegrated raw material is observed in order to verify two things:

[0164] - complete individualization of the fibers indicating good defibration, corresponding to sufficient pulping time and

[0165] - the color of the pulper water to check for possible bleeding or not of the ink or varnish possibly present.

[0166] The second step involves filtering the fibrous separation to separate the fibrous elements from the non-fibrous elements. This step is called classification. The pulp corresponding to the disintegration of the sample to be tested is collected and then classified on a Somerville-type laboratory classification device equipped with a 10 / 100mm slotted sieve. The accepted pulp passes through the slots while the unwanted ones (e.g., pieces of plastic) remain on the surface of the classification sieve.

[0167] The third stage corresponds to the production of the form using the Rapid-Köthen method (ISO 5269-2:2004 standard). At the end of the pulping and classification stages, sheets (called form) are produced in order to visually check their appearance.

[0168] Visual analysis of the forms allows the presence of non-fibrous elements or stains of glue, ink or wax present on the forms to be detected.

[0169] During a recyclability test according to the EN 13430 standard, three parameters are studied: disintegration in the pulper, the rejection rate and the appearance of the forms. Disintegration corresponds to the separation of cellulosic material from non-cellulosic material. Observation is visual, so the skill of the observer must be taken into account. The rejection rate corresponds to the percentage of material that does not pass through the filters during the classification stage. Ideally, this rate should be close to the percentage of non-cellulosic material because if there has been good disintegration, this would mean that only the cellulosic material passes through the filter. Finally, the appearance of the forms made with the pulp that has passed the classification stage is essential because if it is not correct, the packaging will not be considered recyclable.

[0170] The tests were carried out on a 6-gram paper pot coated with 2.5 g of HVH / Latex composition in a 40:60 ratio. The percentage of non-cellulose material is 30% and the percentage of cellulose material is 70%. The cellulose resuspension is proceeding correctly. There is good individualization of the fibers. The rejection rate at classification is 32.3%. It is therefore close to the percentage of non-cellulose material present at the origin. The appearance of the small sheets made from the pulp resulting from classification has a very good surface condition. The operator specifies that a vortex purification step is not necessary to obtain a pulp quality sufficient to be sent to a paper machine.

[0171] In conclusion, pots made from 40%HVH_60%Latex coatings are considered perfectly recyclable within the meaning of standard EN 13430. They disintegrate easily and the non-cellulosic material is retained during the classification stage which therefore only allows cellulose to pass through.

Claims

A composition comprising natural latex and a natural or artificial, or synthetic, wax, or a mixture thereof, the proportion of natural latex and natural or artificial wax being 40:60 to 60:40 by mass relative to the total mass of solid compounds. The composition of claim 1, wherein said natural latex is an aqueous dispersion comprising up to 70% by mass of solid particles relative to the total mass of the natural rubber latex. Composition according to claim 1 or claim 2, where said natural wax is a fossil or non-fossil wax, in particular chosen from animal or vegetable waxes, and or the synthetic wax is a partially or completely synthetic wax. Composition according to any one of claims 1 to 3, comprising in addition to a filler, in particular kaolin or calcium carbonate, in particular at most 10% by mass relative to the total mass of the composition. Composition according to claim 4, comprising:- at least 90% by mass of a mixture of hydrogenated vegetable oil and natural latex, the proportion of natural latex and hydrogenated vegetable oil being from 40:60 to 60:40 by mass, and- at most 10% by mass of kaolin relative to the total mass of the composition. Process for manufacturing a composition according to any one of claims 1 to 5, comprising a step of homogeneous mixing of natural latex and a natural or artificial wax, and optionally a filler. Method for waterproofing a support allowing aqueous or organic liquids, and possibly gases, to pass through, said method comprising the following steps: - homogeneously mixing natural latex and a natural or artificial wax, and possibly a filler, so as to avoid the formation of bubbles, to obtain a smooth homogeneous mixture, free of bubbles; - bringing the smooth homogeneous mixture into contact with the support allowing aqueous or organic liquids to pass through, to obtain a covered support, - drying the covered support at a temperature above 40°C to remove both the water contained in the homogeneous mixture and the support allowing aqueous or organic liquids to pass through, to obtain a waterproofed covered support. Use of a composition as defined in any one of claims 1 to 6, for waterproofing a porous support. Waterproofed permeable support covered, on at least one of its surfaces, with a composition as defined in any one of claims 1 to 6, in particular capable of being obtained by the process as defined in claim 7. Support according to claim 9, wherein said support is a fibrous and / or porous support.

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