Method for improving airtightness of building using membrane based on biopolymer

Abstract

The present invention relates to a method for improving the airtightness of a building or a room within a building, which comprises applying a vapor barrier membrane to the inner surface of the wall of the building or the wall of the room within the building, wherein the vapor barrier membrane is as follows: a first layer having a thickness of -2 μm to 200 μm, preferably 4 μm to 100 μm, which increases with the average relative humidity and has a water vapor transmission coefficient P of at least 300 barrers when measured at 23 °C and an average relative humidity of 25.5%. 1 The first layer made of a biopolymer having P, and a second layer on only one of the two surfaces of the first layer, preferably in contact with the first layer, having a thickness of -100 nm to 20 μm, preferably 200 nm to 2.5 μm, which has a water vapor transmission coefficient P of at most 250 barrers, preferably 0.05 to 100 barrers, particularly 1.0 to 20 barrers when measured at 23 °C and an average relative humidity of 25.5%. 2 A method, characterized by a humidity control membrane having an active part, which comprises the second layer made of a synthetic organic polymer having P.

Description

Technical Field

[0001] The present invention relates to a method for improving the airtightness of a building or a room in a building using a vapor barrier membrane, which has a hydrophilic layer based on a biopolymer and an adjacent layer that is relatively more hydrophobic than the layer based on the biopolymer.

Background Art

[0002] Humidity-regulating or humidity-adjusting vapor barrier membranes whose water vapor transmission rate changes according to the humidity of the air have been known for many years. For example, for the reasons described in WO 96 / 033321, it is required to obtain a membrane that allows water vapor to easily pass through when the relative humidity (RH) is high (70% - 100% RH) and effectively blocks it when the relative humidity is low (50% RH or less).

[0003] When such a membrane is placed on the inner surface of a heat-insulating material (the surface facing the inside of the building or room), during cold and dry seasons, water vapor is prevented from entering the space between the membrane and the wall from the inside of the building and condensing on the latter (the cold wall) as much as possible. Conversely, during hot seasons, the high permeability of the membrane allows moisture potentially present in the structural elements of the frame to be discharged towards the inside of the building. This property is particularly important, especially in the case of new construction where certain elements may have a very high water content due to their storage conditions during installation, and also when water has penetrated into an existing structure. In any case, it is important to effectively dry the entire structure towards the outside and inside of the building during the summer. This need is extremely important especially when the elements constituting the system promote the growth of microorganisms.

[0004] Such vapor barrier membranes that exhibit different behaviors depending on the ambient relative humidity conditions are often referred to as "smart vapor retarder" (SVR) membranes. In this application, the expressions "humidity adjustability", "humidity adjustment", and "smart" are used as synonyms when they explain the change in the water vapor permeability of the vapor barrier membrane.

[0005] It is common to express the water vapor permeability of the membrane in terms of the "equivalent air layer thickness" (S d ) for the diffusion of water vapor. This thickness is expressed in meters and corresponds to the thickness of the air layer that matches the resistance to the diffusion of water vapor. Therefore, the greater the equivalent air layer thickness, the lower the permeability of the membrane to water vapor. The equivalent air layer thickness (S d ) can be determined according to the standards EN1931 and ENISO12572.

[0006] Humidity-adjusting vapor barrier membranes are generally considered to be more beneficial and effective when the equivalent air layer thickness is large when the relative humidity is low and the equivalent air layer thickness is small when the relative humidity is high.

[0007] Humidity-adjusting vapor barrier membranes that are available on the market and described in state-of-the-art technology are generally based on synthetic organic polymers manufactured from petroleum monomers.

[0008] The most frequently described and used polymers are polyamides, especially polycaprolactam, polyvinyl alcohol (PVOH), and copolymers of ethylene with vinyl acetate and / or vinyl alcohol (EVA and EVOH). The most hydrophilic polymers (PVOH, EVOH) may be combined in a multilayer structure with relatively hydrophobic thin layers, especially those based on polyolefins such as polyethylene, polypropylene, and ethylene and propylene copolymers.

[0009] As examples of documents describing such "smart" vapor barrier membranes, International Publication No. WO 2007 / 010388, International Publication No. WO 2006 / 034381, International Publication No. WO 2005 / 110892, U.S. Patent No. 7,008,890, U.S. Patent No. 6,808,772, and U.S. Patent No. 6,878,455 may be mentioned.

[0010] The object of the research leading to the present invention was generally to replace the prior art humidity regulating vapor barrier membranes based on petroleum-derived polymers, which are generally non-biodegradable, with humidity regulating vapor barrier membranes based on bio-derived polymers and / or biodegradable polymers. Hereinafter, these bio-derived polymers and / or biodegradable polymers are referred to as "biopolymers". Biopolymers are preferably bio-derived, that is, based on biological materials that are renewable in a short period of time. In a particularly preferred embodiment, the biopolymers used in the membranes of the present application are both bio-derived and biodegradable.

[0011] Bio-derived biopolymers include natural organic polymers that exist in biomass in their original form, organic polymers obtained by physical and / or chemical modification of these natural polymers, and synthetic organic polymers obtained by polymerization of bio-derived components.

[0012] Membranes based on such biopolymers, for example based on cellulose, chitosan, or even poly(3-hydroxybutyric acid) (PHB), are known and are used as alternatives to films based on petroleum-derived synthetic polymers, particularly in the field of food packaging where the membrane is required to provide a water vapor permeability that is relatively independent of humidity and temperature conditions. Furthermore, in the field of food packaging, the service life of packaging films is quite limited, generally in the range of several days to several weeks, at most several months. In contrast, in the field of vapor barrier membranes, a long service life of at least several years, or even several decades, is required.

[0013] Membranes based on biopolymers are often rather hydrophilic and have a high permeability to water vapor. The equivalent air layer thickness of these membranes is generally less than 1 m, and its absolute value hardly changes depending on the relative humidity of the atmosphere surrounding them. Therefore, these membranes maintain a very high permeability to water vapor regardless of the ambient conditions.

[0014] Without wishing to be bound by any theory, it is considered possible that the low variation in the water vapor permeability of these relatively hydrophilic membranes is due to the plasticizing effect of water that "dissolves" in the membrane even at low humidity. The higher the ambient humidity, the more the membrane material is plastified by water, and water molecules diffuse relatively easily within the membrane.

[0015] Therefore, the main drawback of these membranes made of biopolymers, which are intended to be used as humidity-regulating vapor barriers, is the fact that their permeability to water vapor is overall too high when the relative humidity is low, and they cannot function satisfactorily during cold and dry seasons. Therefore, membranes made of only cellulose do not form a sufficient barrier against water vapor generated inside a building, and do not effectively prevent water vapor from entering the space between the membrane and the wall and condensing on the inner surface of the thermal insulation material and the outer wall.

[0016] In summary, hydrophilic membranes based on biopolymers used in the field of food packaging are still too permeable to water vapor under low relative humidity (cold period) conditions. Therefore, in the field of building thermal insulation, especially in improving the airtightness and management of water vapor flow inside a building, they are not "smart" enough to function properly as vapor barriers.

[0017] The present invention is based on the surprising discovery that it is possible to very significantly enhance the "smartness" of membranes based on biopolymers by applying a very thin layer of a hydrophobic polymer that is not very permeable to water vapor only on one of the two faces of the membrane, and in this way to adapt them for use as vapor barrier membranes in the construction field.

[0018] This discovery was even more surprising considering the fact that hydrophobic polymers deposited on both sides of the biopolymer membrane have a water vapor permeability that does not depend on the ambient relative humidity. In other words, a membrane consisting only of these hydrophobic polymers does not have humidity regulating properties. Therefore, it was not possible to predict that depositing these same hydrophobic polymers on one of the two faces of a membrane made of one or more hydrophilic biopolymers would significantly improve its "smartness" by enabling it to have a very low permeability to water vapor during dry periods and a high permeability to water vapor during wet periods.

[0019] The applicant recently filed an international application PCT / FR2022 / 050009 claiming French priority of January 7, 2021, which was not yet published at the time of filing of the present application. The subject of this application is a method for improving the airtightness of a building or a room within a building using a humidity regulating vapor barrier membrane having at least three layers, namely an intermediate layer made of a biopolymer having a relatively high permeability coefficient P 1 to water vapor, and on both sides thereof, two outer layers made of an organic polymer having a permeability coefficient to water vapor lower than P 1 SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0020] In the course of advancing research in this field, the applicant has surprisingly discovered in recent years that it is not necessary at all to apply hydrophobic thin layers to both sides of the hydrophilic intermediate layer, and that applying a hydrophobic thin layer to only one of the two sides of the hydrophilic biopolymer membrane is sufficient to dramatically improve its humidity control ability.

Means for Solving the Problems

[0021] Therefore, an object of the present application is a method for improving the airtightness of a building or a room inside a building, which includes using a vapor barrier membrane on the inner surface of the wall of the building or the room inside the building, wherein the vapor barrier membrane is a humidity control membrane having an active part including the following: - A first layer having a thickness of 2 μm to 200 μm, preferably 4 μm to 100 μm, and having a water vapor transmission coefficient P that increases with the average relative humidity and is at least 300 barrer when measured at 23°C and an average relative humidity of 25.5%. 1 The first layer, which is made of a biopolymer having And, on only one of the two surfaces of the first layer, preferably in contact therewith, - A second layer having a thickness of 100 nm to 20 μm, preferably 200 nm to 2.5 μm, and having a water vapor transmission coefficient P that is at most 250 barrer, preferably 0.05 to 100 barrer, particularly 1.0 to 20 barrer when measured at 23°C and an average relative humidity of 25.5%. 2 The second layer, which is made of a synthetic organic polymer having

[0022] The present application also relates to such a humidity control membrane having an active part including the following: - A first layer having a thickness of 2 μm to 200 μm, and having a water vapor transmission coefficient P that increases with the average relative humidity and is at least 300 barrer when measured at 23°C and an average relative humidity of 25.5%. 1 The first layer, which is made of a biopolymer having And, on only one of the two surfaces of the first layer, preferably in contact therewith, - A second layer having a thickness of 100 nm to 20 μm, with a water vapor transmission coefficient P of at most 250 Barrer, preferably 0.05 to 100 Barrer, particularly 1.0 to 20 Barrer, measured at 23 °C and an average relative humidity of 25.5%. 2 The second layer, which consists of a synthetic organic polymer having 2 . The active part of the membrane preferably has a two-layer structure consisting of a first layer of biopolymer and a second layer of synthetic organic polymer, and these layers are defined as above. .

Mode for Carrying Out the Invention

[0023] The first layer of biopolymer and the second layer of synthetic organic polymer are, of course, continuous non-perforated layers. Thus, they are impermeable to fluids, whether liquid or gaseous.

[0024] The second layer consisting of a synthetic organic polymer preferably has the following thickness: 0.8 μm or more, 0.9 μm or more, 1.0 μm or more, and / or 20 μm or less, 10 μm or less, 5 μm or less, 2.5 μm or less.

[0025] The transmission coefficient P 1 and P 2 are the transmission coefficients of the polymers forming the first and second layers, respectively. These correspond to the ratio of the mass flow rate Q of water vapor passing through the area A of the membrane of the test polymer having a predetermined thickness (E) under the influence of the water vapor pressure difference (dP) existing on both sides of the membrane.

Number

[0026] These are determined according to the experimental protocol described in detail below and are expressed in "Barrers", i.e., the mass flow rate Q is in cm per second 3 (standard pressure and temperature), the thickness E is in cm, and the passed area A is in cm 2It is represented by [formula not shown], and the water vapor pressure difference (dP) is represented in cmHg (see in particular S.A. Stern, Journal of Polymer Science: Part A-2, Vol. 6 (1968), pages 1933-1934).

[0027] Therefore, the membrane of the present invention has a relatively thick layer (first layer) based on a hydrophilic biopolymer, and only one of its two surfaces is coated with a continuous layer of a hydrophobic polymer (second layer of a synthetic organic polymer).

[0028] The second layer of the synthetic organic polymer is generally thinner than the first layer of the biopolymer. The ratio of the thickness of the first layer to the thickness of the second layer is advantageously from 1.5 / 1 to 1000 / 1, preferably from 2 / 1 to 500 / 1, in particular from 3 / 1 to 200 / 1.

[0029] The second layer of the synthetic organic polymer is preferably in direct contact with the first biopolymer layer, i.e., the interface between the layers preferably does not contain an adhesive.

[0030] In the case of a lower degree of preference, when the second layer is attached to the first layer by an adhesive, the latter preferably has a permeability coefficient P 1 and P 2 greater than P 3 In other words, the adhesive should not provide a resistance to water vapor diffusion greater than the resistance from each layer constituting the membrane.

[0031] The layers defined above form the "active part" of the membrane of the present invention. This part is preferably a membrane obtained in a known manner by coextrusion of thermoplastic polymers forming different layers, by thermal bonding of a film (second layer of a synthetic organic polymer) onto the biopolymer layer, or by deposition of a coating on only one of the two surfaces of the first layer of the biopolymer.

[0032] The active part, in principle, has the mechanical strength to be used alone, i.e., without a support layer. However, especially in the case of an active layer with a small thickness (less than 50 μm), it is reinforced with a mechanically structured air-permeable structure, and thus, it may be advantageous to make its resistance to water vapor diffusion negligible compared to the resistance of the air-impermeable active layer.

[0033] Thus, in an advantageous embodiment, the vapor barrier membrane further has an air-permeable reinforcing layer or protective layer that is in direct contact with the active part, i.e., in contact with one of the two layers constituting the active part. This support layer may be an air-permeable grid, perforated plate, porous foam, or woven or non-woven fabric. This is preferably an air-permeable fabric, preferably a non-woven fabric. Examples of particularly preferred support layers may include non-woven fabrics made of polypropylene or polyester fibers, or glass fibers. One or more support layers are preferably attached to the active membrane or active layer by bonding using a polyurethane adhesive. The present invention also includes membranes in which a reinforcing structure, such as a grid or non-woven fabric, is incorporated within the active part of the membrane, more particularly within the first layer of the biopolymer or between the first layer of the biopolymer and the second layer of the synthetic organic polymer.

[0034] The water vapor transmission coefficient P of the organic polymer constituting the hydrophobic second layer 2 does not vary significantly with the average relative humidity. P 2湿潤 / P 2乾燥 The ratio is generally 1.0 to 1.10, preferably 1.0 to 1.05.

[0035] As described in the introduction, the biopolymer forming the first layer is a bio-derived and / or biodegradable organic polymer. These are preferably bio-derived.

[0036] Bio-derived biopolymers are preferably selected from the group consisting of: - osides, - proteins, and, - Synthetic polymers obtained from biologically derived monomers.

[0037] Oside includes heterosides, and its hydrolysis produces saccharides and non-carbohydrate compounds, while holoside is a polymer consisting only of saccharides.

[0038] Examples of osides that can be used to form the first layer of the biopolymer of the water vapor barrier of the present invention include those selected from the group consisting of alginic acid, carrageenan, cellulose, particularly regenerated cellulose (cellulose hydrate), chitin, chitosan, pectin, dextrin, starch, curdlan, FucoPol, gellan gum, pullulan, and xanthan.

[0039] Proteins are preferably selected from the group consisting of gluten, soy protein isolate, zein, whey protein, casein, collagen, and gelatin.

[0040] Most of these biologically derived polymers extracted from biomass have a high affinity for water and dissolve or swell in water to form hydrogels.

[0041] Therefore, it may be advantageous or even necessary to chemically modify them to thereby reduce their hydrophilicity, particularly to crosslink them to render them insoluble in water.

[0042] Examples of chemically modified biologically derived biopolymers include cellulose esters, particularly cellulose acetate, cellulose ethers (particularly ethyl cellulose, hydroxyethyl cellulose), nitrocellulose, starch esters, and ethers.

[0043] The third category of biologically derived biopolymers is formed by polymers synthesized from biologically derived monomers.

[0044] These polymers are linear or branched and are thus thermoplastic or thermosetting.

[0045] Examples of synthetic polymers obtained from bio-based monomers include polyhydroxyalkanoates (PHA), in particular polyhydroxybutyrate (PHB) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(lactide-co-glycolide) (PLGA), polymers obtained by polymerization of lipid monomers, and thermosetting polymers obtained by reaction of monosaccharides, disaccharides, oligosaccharides, and / or alditols with polycarboxylic acids and / or polyaldehydes, and may be selected from the group consisting of.

[0046] Thermosetting polymers obtained by reaction of monosaccharides, disaccharides, oligosaccharides, and / or alditols with polycarboxylic acids and / or polyaldehydes are well known in the field of binders for mineral wool and are described in detail, for example, in International Publication No. WO 2009 / 080938, International Publication No. WO 2010 / 029266, International Publication No. WO 2013 / 014399, International Publication No. WO 2013 / 021112, and International Publication No. WO 2015 / 132518 in the name of the applicant.

[0047] As described in the introduction, it is also possible to use petrochemical-derived polymers to form the first layer of the biopolymer of the membrane of the present invention, provided that they have biodegradability within the meaning of the NF EN 13432 standard.

[0048] Biodegradable biopolymers are preferably selected from the group consisting of homopolymer aliphatic polyesters such as polycaprolactone (PCL) and polybutylene succinate (PBS), aliphatic copolyesters such as poly(butylene succinate-co-adipate), aromatic copolyesters such as poly(butylene adipate-co-terephthalate) (PBAT), and polyesteramides.

[0049] All biopolymers constituting the first layer of the biopolymer have a transmission coefficient P that, when determined at 23°C under dry conditions (average relative humidity of about 25%), is 300 barrers or more, preferably 300 to 50,000 barrers, particularly 400 to 30,000 barrers, and ideally 500 to 20,000 barrers. 1 have.

[0050] This transmission coefficient is determined as follows. Five samples of membranes of the same thickness (E) are sealed on a test cup containing a desiccant (CaCl powder that brings the relative humidity in the cup to about 1%) using a sealing product. Before applying the sealing product, a template is placed on the surface of the film, thereby creating an exchange zone of defined area (A) without the sealing product. Various sealing products can be used. The sealing product is, for example, a mixture of 60% microcrystalline wax and 40% purified crystalline paraffin. 2

[0051] The cup thus produced is placed in a temperature-controlled test chamber (23°C) and in a relative humidity (50%).

[0052] Due to the difference in vapor pressure (dP) between the inside of the test cup and the chamber, water vapor moves through the exchange zone of the membrane. Periodic weighing of the cup is performed, thereby determining the steady-state water vapor transmission rate (Q), and then, by calculation, the water vapor transmission coefficient of the above film, expressed in barrers, is obtained. Then, the average value of the transmission rates measured in different assemblies is calculated, corresponding to the above transmission coefficient P. 1 corresponds to.

[0053] The hydrophilic first layer of the vapor barrier membrane of the present invention is covered on only one of its two surfaces with a continuous layer of an organic polymer that is more hydrophobic and has lower water vapor permeability than the first layer of the biopolymer. As used herein, the term "continuous" means that the second layer completely covers the above surface of the first layer of the biopolymer, thereby preventing the surface from contacting the atmosphere. Of course, the opposite side of the first layer of the biopolymer that is not covered by the second layer contacts the surrounding atmosphere.

[0054] The permeability coefficient P of the second layer of the synthetic organic polymer 2 is at most 250 barrers, preferably 0.05 to 100 barrers, particularly 1.0 to 20 barrers. The permeability coefficient is determined in the same manner as the coefficient P 1 is determined.

[0055] The organic polymer constituting the second layer is preferably selected from the group consisting of polypropylene, polyethylene, poly(ethylene-co-propylene), and homopolymers and copolymers of vinyl monomers selected from vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, and acrylonitrile.

[0056] A vapor barrier membrane having a first layer made of cellulose, particularly regenerated cellulose, and a second layer made of polyethylene, polypropylene, ethylene-propylene copolymer, or poly(vinylidene chloride), preferably poly(vinylidene chloride), is a particularly preferred embodiment of the vapor barrier membrane used in the method of the present invention.

[0057] The active part of the vapor barrier membrane used in the method of the present invention preferably has a thickness of 5.0 μm to 240 μm, preferably 10 μm to 120 μm, particularly 15 μm to 80 μm. These values correspond to the active part (two layers) of the membrane and do not include the reinforcing and / or protective structure.

[0058] The vapor barrier membrane is applied in a plurality of strip shapes. The width of the strip is 0.5 m or more, preferably 1 m or more. The length of the strip depends on the height of the wall to be blocked. The length is more than 0.5 m, preferably more than 1.0 m, or more than 2 m. Adjacent membrane strips overlap along their length. This overlap is at least 2 cm, preferably at least 5 cm, or even at least 8 cm or 10 cm.

[0059] Preferably, the overlap, opening, or penetration zone is sealed. This can be done with tape or putty.

[0060] Preferably, the wall of the room or building whose airtightness is to be improved is blocked, i.e., covered, with a heat-insulating material. The vapor barrier membrane is - fixed to the heat-insulating material or incorporated into the heat-insulating material.

[0061] In one embodiment of a method for improving the airtightness of a building or a room within a building, - a blocking material, preferably in the form of juxtaposed blocking elements, is applied to the inner surface of the wall of the above building or the above part of the building, and - a vapor barrier membrane is applied to the inner surface of the wall covered with a heat-insulating material.

[0062] The inner surface is the surface facing the inside of the building or room.

[0063] In this embodiment, the membrane is attached to a blocking material having a plurality of blocking elements. The dimensions of the blocking material elements are different from those of the membrane. Thus, the membrane improves the airtightness of the building.

[0064] The vapor barrier membrane of the present invention is located internally with respect to the heat insulating material and preferably in direct contact therewith. Attachment can be effected by any suitable means that does not significantly reduce the airtightness of the membrane. For example, it can be effected by adhesion, stapling, or a mechanical fastening system using hooks and fabric loops (Velcro®-type surface fasteners).

[0065] In another embodiment of the method of the present invention, the vapor barrier membrane is integrated into the insulating material and attached to the wall of the room or building simultaneously with the insulating material. The membrane is preferably oriented parallel to the two main surfaces of the insulating material and is located relatively closer to the main surface facing the inside of the room or building than to the main surface facing the wall.

[0066] The insulating material can be any insulating material that is permeable to water vapor and particularly includes materials based on foams and fibers. Preferably, it is made of inorganic fibers (mineral wool) or natural organic fibers (lignocellulose fibers, cellulose cotton, animal wool), synthetic fibers (polyester fibers) or artificial fibers. Preferably, it is made of mineral wool.

Examples

[0067] A cellulose / PVDC bilayer membrane was produced by wet laminating PVDC latex (Diofan® B204, Solvay) onto a 23 μm cellulose film (NatureFlex® 23NP, UL Prospector). The latex was deposited using a bar coater with a wet thickness of 4 μm. After drying, the thickness of the PVDC film was approximately 1.5 μm.

[0068] The cellulose / PVDC bilayer structure according to the present invention was subjected to an evaluation of its water vapor permeability under wet and dry conditions in comparison with three membranes of the prior art.

[0069] For this purpose, each membrane was arranged to seal an aluminum cup using molten paraffin wax (a mixture of 60% microcrystalline wax and 40% refined crystalline paraffin) as a bonding product to ensure airtightness. To measure the water vapor transmission rate in the dry state, calcium chloride was introduced into the cup before sealing it with the membrane to bring the relative humidity inside to about 1%. Then, the cup / membrane assembly was introduced into a climate chamber set at a relative humidity of 50% and a temperature of 23 °C, thereby creating a water vapor pressure difference (dP) across the membrane. The flow of water vapor (Q) through zone (A) of the membrane of thickness (E) was determined by measuring the weight of the cup at regular intervals, and the transmission coefficient (expressed in barrers) was calculated using the following formula. [Number]

[0070] The transmission coefficient P calculated in this way 1 corresponds to an average relative humidity of 25.5% ((1% + 50%) / 2).

[0071] To measure the water vapor transmission rate under wet conditions (average relative humidity 90%), the procedure is similar, but liquid water is introduced into the cup, thereby setting the relative humidity to 100% and setting the relative humidity in the climate chamber to 90%.

[0072] Also, the equivalent air layer thickness (S d ) is determined for each membrane in accordance with standard EN ISO12572.

[0073] The first membrane is a vapor barrier membrane according to the present invention. This has a first layer of cellulose with a thickness of 23.5 μm, one side of which is covered with a layer of polyvinylidene chloride (PVDC) with a thickness of 1.5 μm. The transmission coefficient P of the first layer of cellulose 1 is 5600 barrers at a relative humidity of 25.5% (23 °C) and 34600 barrers at a relative humidity of 90% (23 °C); the transmission coefficient P of the PVDC layer2 is 5 bar (23 °C). This does not change with relative humidity.

[0074] For this two-layer membrane according to the invention, the equivalent air thickness is determined for two possible orientations: a first orientation in which the PVDC layer faces and is in contact with dry air, and a second orientation in which the PVDC layer faces and is in contact with humid air.

[0075] The second membrane (comparative membrane) is used for manufacturing the membrane according to the invention. It consists only of cellulose and has the same transmission coefficient P as the first layer of the membrane according to the invention. 1 It has a thickness of 23.5 μm.

[0076] The third membrane (comparative membrane) is a membrane made of a single active layer of polyamide 6 with a thickness of 40 μm attached to a polypropylene nonwoven fabric. It is commercially available under the name Vario KM Duplex (trademark) (Saint-Gobain Isover).

[0077] The fourth membrane (comparative membrane) is a three-layer membrane according to the prior art, the active part of which consists of an intermediate layer of ethylene vinyl alcohol copolymer (EVOH) sandwiched between two layers of polyamide 6 and is attached to a polypropylene nonwoven fabric. This membrane is commercially available under the name Vario Xtra (trademark) (Saint-Gobain Isover).

[0078] The technical characteristics of the four membranes (layer composition, thickness, equivalent air layer thickness under dry and humid conditions, orientation of the asymmetric membrane) are summarized in Table 1 below.

[0079]

Table 1

[0080] The humidity adjustment behavior of the cellulose / PVDC two-layer membrane according to the invention is Sd It is very interesting because a large difference is observed in

[0081] When compared with the performance of the Vario™ KM Duplex membrane, it can be seen that the two-layer membrane assembly studied here shows a much higher Sd value under dry conditions and a much lower value under humid conditions (100 - 80% RH). As a result, the intelligent behavior of this two-layer membrane is much more prominent than that of this commercially available membrane.

[0082] The cellulose / PVDC two-layer membrane according to the invention has a lower Sd value than the Vario™ Xtra membrane in both the dry and wet states. As a result, a membrane is obtained that blocks some water vapor in winter (low relative humidity) but allows more water vapor circulation in summer (high relative humidity), which is particularly useful for ensuring good drying in summer.

[0083] Furthermore, when comparing the active films of these three membranes, it can be seen that the total polymer usage is relatively small in the case of the cellulose / PVDC membrane (the PA6 active film of Vario™ KM Duplex is 40 μm and the PA6 / EVOH / PA6 of Vario™ Xtra is 30 μm, while the cellulose / PVDC membrane is 24.5 μm). Therefore, the environmental impact of this cellulose / PVDC membrane is superior to that of current commercial membrane active films, which furthermore consist only of non-biodegradable organic polymers.

Claims

1. A method for improving the airtightness of a building or a room within a building, comprising using a vapor barrier membrane on the inner surface of the wall of the building or the wall of the room within the building, wherein the vapor barrier membrane is as follows: - A first layer having a thickness of 2 μm to 200 μm, preferably 4 μm to 100 μm, wherein the water vapor transmission coefficient P increases with the average relative humidity and is at least 300 bars when measured at 23°C and an average relative humidity of 25.5%. １ The first layer is made of a biopolymer having the following properties: Furthermore, on only one of the two surfaces of the aforementioned layer, preferably in contact with the aforementioned layer, - A second layer having a thickness of 100 nm to 20 μm, preferably 200 nm to 2.5 μm, wherein the water vapor transmission coefficient P is measured at 23°C and an average relative humidity of 25.5%, with a maximum of 250 bars, preferably 0.05 to 100 bars, and particularly 1.0 to 20 bars. ２ A second layer made of a synthetic organic polymer having A method characterized by a humidity control membrane having an active portion containing a portion.

2. The method according to claim 1, wherein the active portion of the membrane consists of the first layer of biopolymer and the second layer of synthetic organic polymer.

3. The water vapor permeability coefficient P of the synthetic organic polymer constituting the second layer ２ The method according to claim 1 or 2, wherein the average relative humidity does not change significantly.

4. The method according to claim 1 or 2, wherein the biopolymer is a biopolymer selected from the group consisting of osides, proteins, and synthetic polymers obtained from biological monomers.

5. The method according to claim 4, wherein the oside is selected from the group consisting of alginic acid, carrageenan, cellulose, particularly regenerated cellulose, chitin, chitosan, pectin, dextrin, starch, curdlan, FucoPol, gellan gum, pullulan, and xanthan.

6. The method according to claim 4, wherein the protein is selected from the group consisting of gluten, soy protein isolate, zein, whey protein, casein, collagen, and gelatin.

7. The method according to claim 5, wherein the oside and the protein are chemically modified.

8. The method according to claim 4, wherein the synthetic polymer obtained from the aforementioned biological monomers is selected from the group consisting of polyhydroxyalkanoates (PHA), poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(lactide-co-glycolide) (PLGA), polymers obtained by polymerization of lipid monomers, monosaccharides, disaccharides, oligosaccharides and / or algitols, and thermosetting polymers obtained by reaction with polycarboxylic acids and / or polyaldehydes.

9. The method according to claim 1 or 2, wherein the biopolymer is a biodegradable polymer selected from the group consisting of aliphatic polyesters, aliphatic copolyesters, aromatic copolyesters, and polyesteramides.

10. The method according to claim 9, wherein the biodegradable biopolymer is selected from the group consisting of poly(caprolactone) (PCL), poly(butylene succinate) (PBS), poly(butylene succinate-co-adipate), and poly(butylene adipate-co-terephthalate) (PBAT).

11. The method according to claim 1 or 2, wherein the organic synthetic polymer constituting the second layer has a thickness of 0.9 μm to 20 μm.

12. The method according to claim 1 or 2, wherein the synthetic organic polymer constituting the second layer is selected from the group consisting of polypropylene, polyethylene, poly(ethylene-copropylene), and homopolymers and copolymers of vinyl monomers selected from vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, and acrylonitrile.

13. The method according to claim 1 or 2, wherein the first layer is made of cellulose, and the second layer is made of polyethylene, polypropylene, ethylene-propylene copolymer, or poly(vinylidene chloride), preferably poly(vinylidene chloride).

14. The method according to claim 1 or 2, wherein the active portion of the membrane has a thickness of 5.0 μm to 240 μm, preferably 10 μm to 120 μm.

15. The method according to claim 1 or 2, wherein the vapor barrier membrane further comprises a reinforcing layer or a protective layer that contacts the first or second layer of the active portion of the membrane.

16. The method according to claim 1 or 2, wherein the vapor barrier membrane is applied to a wall in the form of a plurality of strips having a width of 0.5 m or more and a length of 0.5 m or more.

17. The method according to claim 16, wherein adjacent membrane strips overlap by at least 2 cm over their respective lengths.

18. The following features: - A thermal barrier material, preferably in the form of juxtaposed barrier elements, is applied to the inner surface of the wall of the building or the part of the building, and - The vapor barrier membrane is applied to the inner surface of the wall covered with the heat-insulating material. The method according to claim 1 or 2, comprising:

19. The method according to claim 18, wherein the heat-insulating material is made of inorganic, organic, natural, synthetic, or artificial fibers.

20. Humidity control membranes, including the following: - A first layer having a thickness of 2 μm to 200 μm, wherein the water vapor transmission coefficient P increases with the average relative humidity and is at least 300 bars when measured at 23°C and an average relative humidity of 25.5%. １ The first layer is made of a biopolymer having the following properties: and, preferably, on only one of the two surfaces of the first layer, and in contact with it. - A second layer having a thickness of 100 nm to 20 μm, preferably 0.9 μm to 20 μm, and having a water vapor transmission coefficient P of a maximum of 250 bars, preferably 0.05 to 100 bars, and particularly 1.0 to 20 bars, as measured at 23°C and an average relative humidity of 25.5%. ２ A second layer made of a synthetic organic polymer having A humidity-regulating membrane having an active portion containing [specific components].