METHOD FOR IMPROVING THE AIRTIGHTNESS OF BUILDINGS USING A BIOPOLYMER-BASED MEMBRANE

Abstract

A method for improving the airtightness of a building or a room, includes providing a vapor barrier membrane on the inner face of the wall or the room, the vapor barrier membrane being a humidity-regulating membrane including an active portion having a middle layer having a thickness of between 2 m and 200 m and made of a biopolymer having a water vapor permeability coefficient P1 which increases with the average relative humidity and which, when it is determined at 23 C. and at an average relative humidity of 25.5%, is at least equal to 600 Barrers, and, on either side of the middle layer two outer layers having a thickness of between 100 nm and 20 m made of, independently of each other, an organic polymer having a water vapor permeability coefficient P2, determined at 23 C. and at an average relative humidity of 25.5%, of between 105 and 550 Barrers.

Claims

1. A method for improving an airtightness of a building or room in a building comprising providing a vapor barrier membrane on an inner face of a walls of the building or the room in the building, wherein the vapor barrier membrane is a humidity-regulating membrane comprising an active portion comprising a middle layer having a thickness of between 2 m and 200 m and consisting of a biopolymer having a water vapor permeability coefficient P.sub.1 which increases with average relative humidity and which, when determined at 23 C. and at an average relative humidity of 25.5%, is at least 600 Barrers, and, on either side of the middle layer, two outer layers with a thickness of between 100 nm and 20 m and consisting, independently of each other, of an organic polymer having both a water vapor permeability coefficient P.sub.2, determined at 23 C. and at an average relative humidity of 25.5%, between 105 and 550 Barrers.

2. The method according to claim 1, wherein the biopolymer forming the middle layer is a biosourced biopolymer selected from the group consisting of osides, proteins and synthetic polymers obtained from biosourced monomers.

3. The method according to claim 2, wherein the osides are selected from the group consisting of alginate, carrageenan, cellulose, in particular regenerated cellulose, chitin, chitosan, pectin, dextrin, starch, curdlan, FucoPol, gellan gum, pullulan and xanthan.

4. The method according to claim 2, wherein the proteins are selected from the group consisting of gluten, soy protein isolate, zein, whey proteins, casein, collagen and gelatin.

5. The method according to claim 3, wherein the osides and proteins are chemically modified.

6. The method according to claim 2, wherein the synthetic polymers obtained from biosourced monomers are selected from the group consisting of polyhydroxyalkanoates (PHA), poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(lactide-co-glycolide) (PLGA), the polymers obtained by polymerization of lipid monomers, the thermoset polymers obtained by reaction of monosaccharides, disaccharides, oligosaccharides and/or alditols with a polycarboxylic acid and/or a polyaldehyde.

7. The method according to claim 1, wherein the biopolymers are biodegradable polymers selected from the group consisting of aliphatic polyesters, aliphatic copolyesters, aromatic copolyesters and polyesteramides.

8. The method according to claim 7, wherein the biodegradable biopolymers are 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).

9. The method according to claim 1, wherein the organic polymer constituting the outer layers is selected from the group consisting of semi-aromatic polyesters obtained by polycondensation of aliphatic polyols and aromatic polyacids.

10. The method according to claim 1, wherein the middle layer is made of cellulose and the two outer layers consist of poly(ethylene terephthalate) (PET).

11. The method according to claim 1, wherein the active portion of the membrane has a thickness comprised between 5.0 m and 240 m.

12. The method according to claim 1, wherein the vapor barrier membrane further comprises a reinforcing or protective layer which is in contact with one of the outer layers of the active portion.

13. The method according to claim 1, wherein the wall of the building or of the room in the building is covered by a thermal insulation material and wherein the vapor barrier membrane is applied in an internal position relative to the thermal insulation material or that the membrane is integrated into the thermal insulation material.

14. The method according to claim 13, wherein the thermal insulation material is made of mineral or organic, natural, synthetic or artificial fibers.

15. A humidity-regulating vapor barrier membrane comprising an active portion comprising aa middle layer having a thickness of between 2 m and 200 m consisting of a biopolymer having a water vapor permeability coefficient P1 which increases with the average relative humidity and which, when it is determined at 23 C. and at an average relative humidity of 25.5%, is at least equal to 600 Barrers, and, on either side of the middle layer, two outer layers with a thickness of between 100 nm and 20 m and consisting, independently of each other, of an organic polymer having both a water vapor permeability coefficient P.sub.2, determined at 23 C. and at an average relative humidity of 25.5%, between 105 and 550 Barrers.

16. The method according to claim 1, wherein the middle layer has a thickness of between 4 m and 100 m.

17. The method according to claim 1, wherein the two outer layers that in contact with the middle layer.

18. The method according to claim 1, wherein the thickness of the two outer layers is between 200 nm and 2.5 m.

19. The method according to claim 1, wherein the water vapor permeability coefficient P2 is between 120 and 500 Barrers.

20. The method according to claim 9, wherein the organic polymer constituting the outer layers is selected from the group consisting of poly(ethylene terephthalate), polybutylene terephthalate, poly(trimethylene terephthalate), and poly(ethylene naphthalate), and corresponding copolyesters.

Description

EXAMPLES

[0066] Four vapor barrier membranes were subjected to an evaluation of their permeability to water vapor under wet and dry conditions.

[0067] For this, each membrane was positioned so as to close an aluminum cup using as a jointing product molten paraffin wax (mixture of 60% microcrystalline wax and 40% refined crystalline paraffin) to ensure sealing. To measure water vapor permeability in dry conditions, calcium chloride is introduced into the cup before sealing it with the membrane to impose relative humidity of about 1% inside. The cup/membrane assembly is then introduced into a climate chamber wherein the relative humidity is set at 50% and the temperature at 23 C., so as to create a water vapor differential pressure (dP) on either side of the membrane. The flow of water vapor (Q) which passes through the zone (A) of the membrane with thickness (E) is determined by weighing the cups over time, and the permeability coefficient (expressed in Barrers) is calculated using the formula

[00002]$P=\left(QE\right)/\left(A\mathrm{dP}\right)$

[0068] The permeability coefficient P.sub.1 thus calculated corresponds to an average relative humidity of 25.5% ((1%+50%)/2).

[0069] To measure the water vapor permeability under wet conditions (90% average relative humidity), the procedure is analogous, except that liquid water is introduced into the cup in order to set the relative humidity to 100%, and the relative humidity in the climate chamber is set at 80%.

[0070] The equivalent air layer thickness (S.sub.d) is also determined for each membrane in accordance with standard EN ISO12572.

[0071] The first membrane is a vapor barrier membrane according to the invention. It consists of a middle layer of cellulose with a thickness of 21.4 m sandwiched between two layers of polyethylene terephthalate (PET) with a thickness of 800 nm each. The permeability coefficient P.sub.1 of the middle layer of cellulose is 5,600 Barrers at a relative humidity of 25.5% (23 C.) and 34,600 Barrers at a relative humidity of 90% (23 C.); the permeability coefficient P.sub.2 of the PET layers is 300 Barrers (23 C.). It varies little depending on relative humidity.

[0072] The second and third membranes consist solely of cellulose and have the same permeability coefficients P.sub.1 as the middle layer of the first membrane.

[0073] The fourth membrane is a membrane made up of a single active layer of polyamide 6 with a thickness of 40 m attached to a polypropylene nonwoven. It is available on the market under the name Vario KM Duplex (Saint-Gobain Isover)

[0074] The technical characteristics of the membranes (composition of the layers, thickness, equivalent air layer thickness under dry and wet conditions) are gathered in Table 1 below.

TABLE-US-00001 TABLE 1 S.sub.d S.sub.d Total (25.5% (90% Membrane thickness RH) RH) 1 (invention) PET-cellulose-PET 23 m 6.6 m 0.8 m 2 (comparative) cellulose 23 m 0.35 m 0.04 m 3 (comparative) cellulose 45 m 0.52 m 0.05 m 4 (comparative) Polyamide (PA6) 40 m 4 m 0.14 m

[0075] It can be seen that the difference between the equivalent air thickness of the three-layer vapor barrier membrane according to the invention (membrane 1) under dry and wet conditions is significantly stronger than that of all the comparative membranes (membranes 2 to 4).

[0076] The two cellulose membranes (membranes 2 and 3) have an equivalent air thickness (S.sub.d) less than 1 m, whether in wet or dry conditions. They are not suitable as vapor barrier membranes since their humidity-regulating power is insufficient. During the dry and cold season, these membranes would let too much water into the space between the membrane and the wall of the building. This insufficiently smart behavior is efficiently corrected by the presence of the two thin PET layers.

[0077] It may also be noted that the membrane according to the invention (membrane 1) has a total thickness (23 m) much lower than that of the active portion of the membrane sold by the Applicant, which is equal to 40 m (Vario KM Duplex). The excellent performance of the membrane according to the invention consequently makes it possible to reduce the raw materials and consequently the costs.