GB2473618A

GB2473618A - Self adherent water vapour permeable membrane comprising an adhesive composition

Info

Publication number: GB2473618A
Application number: GB0916260A
Authority: GB
Inventors: Beatrix Loehner; Martin Butters; Ian Biggin
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2009-09-17
Filing date: 2009-09-17
Publication date: 2011-03-23
Also published as: GB0916260D0

Abstract

A self adherent, water vapour permeable membrane, for use in a building envelope, comprises a water vapour permeable membrane 1 and an adhesive composition 2 on at least one surface of the water vapour permeable membrane, wherein the adhesive composition comprises a hydrophobic adhesive polymer and hydrophilic microparticles. The hydrophobic adhesive polymer may be a pressure sensitive adhesive. Preferably, the hydrophilic particles may be polymeric and can be formed from water soluble ethylenically unsaturated monomer(s). A method for manufacturing a self adherent, water vapour permeable membrane is also claimed. The use of the self adherent water vapour permeable membrane in buildings for preventing the ingress of water and allowing the transmission of water vapour from the interior of the building to the exterior is also claimed. The membrane can be adhered to surfaces within a building envelope, which typically may be sheathing in wall applications, sarking board in roof applications or rafters.

Description

I

Water Vapour Permeable, Self Adherent Building Membrane The present invention relates to a self adherent, water vapour permeable, membrane employed in the building envelope. The self adherent membrane possesses good water vapour transmission properties and can be readily affixed to surfaces within the building envelope. Typically the membrane can be adhered to rafters, insulation between rafters, sarking board in roofing applications, or to sheathing (e.g. plywood, oriented strand board) in wall applications.

The construction of buildings generally takes into account four major performance objectives: structural integrity; moisture control; temperature control; and the control of air pressure boundaries. Usually the separation between the interior and the exterior environments of a building is referred to as a building envelope. Typically, a building envelope serves as the outer shell to protect the indoor environment as well as to facilitate its climate control.

Measures for enhancing the effectiveness of a building envelope include improved thermal insulation and air tightness. Unfortunately this can lead to a greater build up of condensation or moisture within the building envelope. To overcome this problem, water vapour permeable membranes are often installed to enable water vapour to pass from the inside of the building envelope to the outside before it has an opportunity to condense and form condensation or moisture. Frequently these membranes are referred to as breather membranes.

These membranes are also designed to resist the passage of liquid water, for instance rainwater, from the outside to the interior of the building envelope.

When the water vapour permeable membranes are mechanically attached to surfaces, for instance panels, in a factory before installation or installed in roofing and walls, this commonly involves fixing with nails and/or staples.

However, in view of the increased occurrence of extreme weather conditions, employment of these fixing means alone is frequently insufficient to hold the water vapour permeable membrane in place. Furthermore, the use of mechanical fixing by means, such as nails or staples, punctures the membrane and may allow the passage of water from the outside. This is particularly so where tears or rips form around the punctures created by the nails or staples.

Nevertheless the securing of such water vapour permeable membranes can be enhanced by the use of a suitable adhesive which is able to provide extra hold to secure the membrane in place. Frequently such membranes are provided with an adhesive coating applied to one side, typically the underside. The adhesive layer may be applied to essentially all of the underside surface or sometimes part of the underside surface of the membrane. These types of water vapour permeable membranes are known as self adherent membranes.

Sometimes they are also referred to as "self adhered" membranes. Typically a protective cover, such as a release liner, may be applied to the surface of the adhesive layer which is then removed immediately prior to installation. This is often referred to as a "peel and stick" system. Such membranes may also be additionally secured by mechanical means such as nails and/or staples. Whilst this may provide additional securing this can nonetheless give rise to water ingress due to the puncture holes as previously described. Consequently it is preferable not to use such mechanical means in order to avoid this disadvantage.

However, the adhesives employed in these self adherent membranes are usually hydrophobic and water repelling in nature. This can drastically reduce the ability of the water vapour permeable membrane to allow the passage of water vapour which can result in the build up of moisture resulting in the problems usually associated with damp or condensation within buildings.

US published patent application 20050214496 attempts to overcome this problem by applying a non-continuous covering of the adhesive to the membrane. However, although the barrier sheet membrane will allow the passage of water vapour over the regions of the sheet where no adhesive has been applied, large sections of the membrane where adhesive has been applied will still be impermeable to the passage of water vapour and may still give rise to the accumulation of moisture. Furthermore, the non-continuous covering of the adhesive can reduce the bonding capacity resulting in the membrane being less securely fastened.

WO 2004/082932 describes a housewrap for attachment to a building after installation of sheathing and prior to installation of siding/cladding. The housewrap comprises a barrier layer and an adhesive layer. The barrier layer provides a moisture barrier against outside water or moisture but allows a water vapour transmission rate of at least 100 g/m2/day from the interior of the building. The adhesive layer is applied to one of the surfaces and comprises a pressure sensitive adhesive that has a high moisture vapour transmission rate of at least about 100 g/m2/day. However, the pressure sensitive adhesive containing the hydrophilic moieties that will impart some hydrophilicity are expensive to manufacture and may not necessarily have the most effective adhesive properties and therefore may compromise the fixing strength of the self adhered housewrap.

It would be desirable to provide a self adherent, water vapour permeable, but water resistant, membrane for use in a building envelope, which possesses a combination of high water vapour transmission properties and adhering strength. Furthermore, it would be additionally desirable for such a membrane to allow additional mechanical securing means without suffering the disadvantages of water ingress.

According to the present invention we provide a self adherent, water vapour permeable membrane, for use in a building envelope, comprising i) a water vapour permeable membrane, and ii) an adhesive composition on at least one surface of the water vapour permeable membrane, wherein the adhesive composition comprises, a) hydrophobic adhesive polymer and b) hydrophilic microparticles.

The invention also relates to a process for manufacturing a self adherent, water vapour permeable membrane, for use in a building envelope, comprising the steps of i) providing a water vapour permeable membrane, and ii) applying an adhesive composition to at least one surface of the water vapour permeable membrane, wherein the adhesive composition comprises, a) a hydrophobic adhesive polymer and b) hydrophilic microparticles.

The invention further relates to the use of a self adherent, water vapour permeable membrane in buildings for preventing the ingress of liquid water and allowing the transmission of water vapour from the interior of the building to the exterior.

In addition the invention also relates to the use of an adhesive composition in a self adherent, water vapour permeable membrane for providing adhesion to surfaces within a building envelope, wherein the adhesive composition comprises, a) a hydrophobic adhesive polymer and b) hydrophilic microparticles.

Figure 1 represents a vertical cross-section of the self adherent water vapour permeable membrane according to the present invention. A water vapour permeable membrane (1) is coated on the underside by an adhesive composition (2) containing microparticulate hydrophilic polymer distributed in a hydrophobic adhesive polymer and in which the adhesive composition is coated as a continuous layer. A release liner (3) is applied to the surface of the adhesive composition.

Figure 2 represents a vertical cross-section of a self adherent water vapour permeable membrane according to the present invention analogous to figure 1 except that the adhesive composition (4) is applied as a discontinuous layer. In this way the adhesive composition may be applied as islands of adhesive in a regular or random manner.

Preferably a continuous layer of adhesive composition is applied to the underside of the membrane.

The water vapour permeable membrane of the present invention may be referred to as breathable. By breathable we mean that the membrane allows the passage of water vapour, but resists the passage of liquid water. By water vapour we mean water which is in a gaseous state. It is also sometimes referred to as moisture vapour. Nevertheless moisture vapour should not be confused with moisture which is liquid water and may include fine water droplets. Liquid water includes rain water, moisture, or condensation etc. The inventors have found that the presence of the hydrophilic microparticles in the adhesive imparts high water vapour transmission characteristics to the self adherent water vapour permeable membrane, whilst retaining good bonding properties. This means that the membrane can be coated with the adhesive composition and still possess good water vapour permeability. This is particularly advantageous for membranes which are employed in the building envelope where water vapour permeability is essential to prevent condensation occurring whilst not compromising the ability to resist penetration of liquid water from the outside to the inside. Typically the self adherent water vapour permeable membrane of the present invention may exhibit water vapour transmission rates of at least 100 glm2lday, preferably above 340 g/m2/day and more preferably above 900 g/m2/day.

We have also found that the self adherent water vapour permeable membranes are resistant to water ingress where additional mechanical securing means e.g. nails or staples have been used. The inventors found that this self-sealing property is a result of the formation of a seal around nails, staples or other mechanical means which have punctured the adhesive coated membrane or formed small tears or other apertures and which would otherwise have caused water ingress. This sealing effect is achieved by the swelling of the hydrophilic microparticles, and therefore the adhesive layer, in the vicinity of the aperture or tear when contacted by permeating liquid water. The hydrophilic microparticles swell to an extent of forming a seal around the aperture or tear and thereby blocking further penetration of water through the tear or aperture. This swelling of the hydrophilic microparticles to form a seal to the ingress of water is known as gel blocking.

The adhesive composition may coat part or all of at least one surface of the water vapour permeable membrane. Frequently it will only be necessary to coat one surface of the membrane although in some applications it may be desirable to coat both surfaces. Typically it is the underside surface of the water vapour permeable membrane which is coated. This underside surface of the membrane can be affixed to suitable building surfaces within the envelope of the building.

Suitably such building surfaces may include rafters, insulation between rafters, sarking board in roofing applications, or sheathing (for instance plywood, oriented strand board) in wall applications.

The adhesive composition can be coated onto the water vapour permeable membrane using techniques such as rod, roll or slot die coaters, but this should not in anyway be seen as limiting. Coat weights of the adhesive composition on the water vapour permeable membrane can be any conventional amount.

Generally this can be in the range of 10 to 200 g/m2 (dry), but more typically in the range 20 to 80g/m2 (dry).

The self adherent water vapour permeable membrane of the present invention can be secured in roofs and walls of buildings including domestic dwellings, larger municipal and commercial buildings in a conventional manner.

Furthermore, buildings also include those that are constructed using so-called offsite methods, for instance whereby components of the buildings, such as all sections, are fabricated in a factory and fitted together at the building site.

The adhesive composition may be applied to the surface of the membrane which will form the underside just before the membrane is installed thereby forming the self adherent water vapour permeable membrane. Alternatively it may be applied to the membrane in a factory during the manufacture of the self adherent water vapour permeable membrane. In this latter case the adhesive surface is desirably protected with a release liner (such as release paper), which is removed immediately prior to installation of the self adherent water vapour permeable membrane. This type of membrane may be described as a "peel and stick" membrane.

The adhesive composition comprising the hydrophobic adhesive polymer and the hydrophilic microparticles may also comprise other components for instance a tackifying resin, antioxidant, fillers, stabilisers and/or plasticiser.

The adhesive composition may also be referred to as breathable in the sense that it will allow the passage of water vapour but not liquid water.

The hydrophobic adhesive polymer of the adhesive composition may be any hydrophobic polymer which confers adhesive properties to the adhesive composition. In general it may be any adhesive polymer which is substantially water insoluble. By water insoluble we mean that it has a solubility in water of less than 5 g per 100 mIs at 25°C, typically less than 2 g per 100 mIs and usually less than I g per 100 mIs.

Suitably the hydrophobic adhesive polymers may be pressure sensitive adhesives, typically including natural, butyl, isoprene, neoprene, styrene-butadiene rubbers, acrylics (including ultraviolet curable), silicones and polyurethanes; hot melt adhesives, such as ethylene ethyl acrylate, ethylene methyl acrylate and styrene copolymers, (for instance styrene-butadiene-styrene orstyrene-isoprene-styrene), ethylene vinyl acetate copolymers; and solvent types in which the solvent is typically a water immiscible or hydrophobic liquid. The hydrophobic adhesive polymer component suitably may be any conventional hydrophobic adhesive polymer used in conventional self adherent water vapour permeable membranes. Hydrophobic adhesive polymers are well documented in the literature.

Preferably the hydrophobic adhesive polymer is a pressure sensitive adhesive.

More preferably the hydrophobic pressure sensitive adhesive is in the form of a solution in an organic solvent, such that the solvent can facilitate addition of hydrophilic microparticles.

Typically such polymers may be for instance any polymer that possesses pressure sensitive adhesive properties as defined by the Pressure Sensitive Tape Council (Glossary of Terms Used in Pressure Sensitive Tape Industry, PSTC, Glenview, III, 1959). Preferably the adhesive polymer is a polymer formed from hydrophobic acrylic monomers.

More preferably the hydrophobic adhesive polymer is formed from a monomer or blend of monomers comprising at least 70% by weight first monomers selected from C218 alkyl acrylates and C218 alkyl methacrylates and up to 30% by weight further ethylenically unsaturated monomers.

C2-C18 alkyl usually stands for ethyl, n-, i-propyl, n-, i-, sec.-or tert. butyl, n- pentyl, n-hexyl, n-heptyl, n-octyl, 2-ethyl-hexyl, n-nonyl, n-decyl, n-undecyl, n- dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, or n-octadecyl.

Suitably the polymers may be prepared in an organic solvent. Preferably the amount of first monomer is at least 80% by weight, more preferably at least 90% by weight and more preferably still at least 95% by weight particularly between 97% and 100% by weight. The first monomer is generally selected from C218 alkyl acrylates. Usually at least 50% by weight, preferably at least 75% by weight, of the first monomer is 2-ethyl hexyl acrylate. More preferably all of the first monomer is 2-ethyl hexyl acrylate.

Preferably the amount of further ethylenically unsaturated monomer is up to 20 % by weight, more preferably up to 10 % by weight and more preferably still up to 5% by weight particularly between 3% and 0% by weight. The further ethylenically unsaturated monomers may be water soluble monomers, for instance ethylenically unsaturated carboxylic acids such as acrylic acid (or salts thereof), methacrylic acid (or salts thereof), maleic acid (or salts thereof), fumaric acid (or salts thereof) or itaconic acid (or salts thereof); hydroxy alkyl esters of ethylenically unsaturated carboxylic acids, such as 2-hydroxy ethyl acrylate or other water soluble monomers. Where other ethylenically unsaturated monomers are included preferably they are water insoluble monomers such as methyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, styrene and vinyl acetate etc. Suitably the hydrophilic microparticles are distributed throughout a matrix of the hydrophobic adhesive polymer. Preferably the hydrophilic microparticles are substantially uniformly distributed throughout the matrix of the hydrophobic adhesive polymer. Most preferably the hydrophilic microparticles are uniformly distributed throughout the matrix of the hydrophobic adhesive polymer.

The hydrophilic microparticles may be inorganic, for instance a polysilicate such as a water swellable clay. The water swellable clay may for instance be typically a bentonite type clay. The preferred clays are swellable in water and include clays which are naturally water swellable or clays which can be modified, for instance by ion exchange to render them water swellable. Suitable water swellable clays include but are not limited to clays often referred to as hectorite, smectites, montmorillonites, nontronites, saponite, sauconite, hormites, attapulgites and sepiolites. The clay may be in the form of the calcium salt or magnesium salt but is preferably an alkali metal salt such as potassium, lithium or sodium. Preferably the salt is sodium. By salt we are referring to the replaceable cation of the water swellable clay.

Preferably the hydrophilic microparticles are polymeric and formed from water-soluble ethylenically unsaturated monomers. By water-soluble we mean that the monomers have a solubility in water of at least 5 g per 100 mIs at 25°C.

Suitably the monomers may be selected from the group consisting of water- soluble, ethylenically monounsaturated polar non-ionic monomers, water-soluble, ethylenically monounsaturated anionic monomers, water soluble, ethylenically monounsaturated cationic monomers, and mixtures thereof. The polymeric hydrophilic microparticles are preferably cross-linked suitably by polymerising in the presence of a cross-linker.

As water-soluble, ethylenically monounsaturated polar nonionic monomers the following monomers can be chosen: acrylamide, methacrylamide, N,N-di (C1-C8 alkyl) acrylamide such as N,N-dimethylacrylamide, vinyl alcohol, vinyl acetate, allyl alcohol, hydroxyethylmethacrylate, or acrylonitrile.

As water-soluble, ethylenically monounsaturated anionic monomers the following monomers can be chosen: water-soluble, ethylenically monounsaturated anionic monomers containing acidic groups selected from carboxylic group, sulphonic group, phosphonic group, and the corresponding salts, preferably monomers such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, 2-acrylamido-2-methylpropanesulphonic acid, allyl sulphonic acid, vinyl sulphonic acid, allyl phosphonic acid, and vinyl phosphonic acid.

As water-soluble, ethylenically monounsaturated cationic monomers the following monomers can be chosen: N,N-di-C1-C8alkylamino-C1 -C8alkylacrylate such as N,N-dimethyl amino ethyl acrylate, N,N-di-C1-C8alkylamino-C1-C8alkylmethacrylate such as N,N-dimethyl amino ethyl methacrylate, including quaternised forms e.g. methyl chloride quaternised forms, diallyldimethyl ammonium chloride, N,N-di-C1-C8alkylamino-C1-C8alkylacrylamide and the quaternised equivalents such as acrylamidopropyl trimethyl ammonium chloride.

C1-C8alkyl usually stands for methyl, ethyl, n-, i-propyl, n-, i-, sec.-or tert. butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, or 2-ethyl-hexyl.

In general, the amounts of monomers are chosen in the ranges of: (a) 0 to 80% by weight (polar and nonionic), (b) 20 to 100 % by weight (anionic), (c) 20 to 100 % by weight (cationic), wherein the total amount sums up to 100 % by weight.

In a preferred embodiment of the instant invention the total amount of the water-soluble anionic and cationic monomers is chosen in the range of from 40 to 100, preferably from 50 to 100 % by weight and the amount of water-soluble polar nonionic monomers is chosen in the range of 60 to 0, preferably from 50 to 0 % by weight. More preferably the polymer is not amphoteric, i.e. it is formed from either anionic or anionic and polar nonionic monomers, or cationic or cationic and polar non ionic monomers are chosen, or if anionic and cationic monomers are chosen (with or without polar nonionic monomers), then usually either one is in excess of the other one.

In another preferred embodiment the amount of anionic monomers is chosen in the range of from 40 to 100%, preferably from 50 to 100% by weight and the weight of nonionic polar monomers is chosen from 60 to 0, preferably from 50 to 0% by weight. Most preferably the anionic monomer is acrylic acid or a water-soluble salt thereof.

In case the copolymers contain both anionic and cationic groups, with or without polar groups, then the preferred molar ratio of anionic monomers to cationic monomers is chosen in the range of from 3:1 to 20:1, or the molar ratio of cationic monomers to anionic monomers is chosen in the range of from 3:1 to 20:1.

In a preferred embodiment of this invention the acid groups of the polymeric hydrophilic microparticles, which are obtained from the above mentioned monomers, and wherein the amount of anionic monomers is not zero, are partially or fully neutralized. Preferably the degree of neutralization is chosen in the range of from 50 to 100%, more preferably from 75 to 100% (on a molar basis). The neutralization can be carried out by known methods such as applying bases to the corresponding acidic groups carrying hydrophilic polymer microparticles. The usual, most convenient practice is to neutralize the monomers prior to carrying out the polymerization reaction. Such bases suitable for neutralizing the acidic monomers can be e.g. alkali metal hydroxides such as NaOH or KOH as well as ammonia or amines such as mono-, di-or tn-ethanolamine, most preferably NaOH is chosen. In some cases it can be beneficial to neutralize up to 50% of the acid groups (on a molar basis) in the form of di-, tn-or polyvalent cationic salts such as polyamine salt or alkali earth metal salt such as Mg(OH)2, Ca(OH)2 or Ba(OH)2 as a means of controlling the degree and/or rate of swelling.

Preferably the hydrophilic polymer microparticles are crosslinked. Cross-linking can be achieved in a number of ways, which will be clear to those skilled in the art. For example, di-or polyvalent metal ions can be used to confer a degree of cross-linking to polymers containing acid groups, particularly carboxylic acid groups. Other compounds such as di-or polyamines can be used in a similar way. Furthermore, water-soluble organic substances, which are able to react with groups on the hydrophilic polymer microparticle, can also be used, such as polyvalent epoxy compounds. Preferably, cross-linking is achieved through the use of a suitable water-soluble (or monomer phase soluble) di-, tn-or polyunsaturated polymerizable monomer, which usually is present in the aqueous monomer solution. Suitable cross-linking monomers include e.g. methylenebisacrylamide, diacrylamidoacetic acid, polyol(meth)acrylates such as pentaerythritol tri(meth)acrylate or ethyleneglycoldi(meth)acrylate and tetraallyl ammonium chloride. Preferably an amount of cross-linking monomer is chosen to give a polymer, which is water-insoluble, but water-swelling and water vapour transmittable, whilst avoiding excessive structuring, which would restrict the water-absorbency and water vapour transmittance of the hydrophilic polymer microparticle of the inventive composition comprising such polymer microparticles or dispersions thereof.

The desired level of cross-linking monomer usually depends on the chain length (or molecular weight) of the polymer chain segments of the cross-linked polymer. For example it is possible to control the chain length of the hydrophilic polymer microparticle using a chain-transfer reagent, which tends to give shorter chains. The use of certain low reactivity monomers may also give shorter chains. The chain length can also be controlled to some degree by the choice and amount of initiator used for the polymerization. Where conditions are used that would be expected to give shorter chain lengths, higher levels of cross-linking monomer may be used to give the appropriate degree of structuring of the cross-linked hydrophilic microparticle. In general, a suitable level of cross-linking monomer can be chosen in the range of 5 to 2000 ppm, preferably from 5 ppm to 500 ppm and most preferably from 5 to 100 ppm based on weight of the chosen monounsaturated monomers.

The polymeric hydrophilic microparticles will usually have a volume mean diameter of less than 20 microns (as determined by laser diffraction technique using a Sympatec Helos H 1539 with RI lens and Quixcel dispersion system).

Preferably the volume mean diameter is less than 10 microns and more preferably less than 5 microns and more preferably still less than 2 microns.

The volume mean diameter may be as low as 50 nm but in general will be at least 100 nm normally at least 500 nm especially at least 750 nm.

Most preferably the polymeric hydrophilic microparticles of the invention are obtained by reverse-phase polymerisation, a technique that is well known from the prior art, for example as described and discussed in WO 97/34945. This may be either water-in-oil suspension polymerisation or by water-in-oil emulsion polymerisation for example according to a process defined by EP-A-I 50933, EP-A-I 02760 or EP-A-I 26528.

The carrier fluid of the reverse phase dispersion can be removed so that the hydrophilic microparticles are substantially free of carrier fluid and are therefore in a powder, paste, damp cake or granular form, which may contain residues of the carrier fluid.

The adhesive composition of the present invention desirably may comprise a) a hydrophobic adhesive polymer in an amount of between 50% and 99% by weight, preferably between 60% and 95% and most preferably between 65% and 90% and b) hydrophilic microparticles in an amount of between 1% and 50 % (active polymer) by weight, preferably between 5% and 40% (active polymer) and most preferably between 10% and 35% (active polymer).

The hydrophilic microparticles are most preferably provided in the form of a dispersion in a non-aqueous liquid.

These ratios of hydrophobic adhesive polymer and hydrophilic microparticles have been found to provide the optimum balance between adhesive properties, water vapour permeability and gel blocking properties. This is especially so when the hydrophilic microparticles are polymeric hydrophilic microparticles and in particular when the hydrophobic adhesive polymer is a pressure sensitive adhesive.

We have found that the polymeric hydrophilic microparticles may also be used in conjunction with inorganic hydrophilic microparticles, preferably a swellable clay and more preferably sodium bentonite. In this case the polymeric hydrophilic microparticles will usually be greater than 50% (active polymer) by weight, preferably greater than 70% (active polymer) by weight. Nevertheless it is most preferred that the hydrophilic microparticles are entirely polymeric hydrophilic microparticles.

The water vapour permeable membrane may be any conventional building membrane in which water vapour is able to pass through but essentially remains resistant to the passage of liquid water. Typically this will suitably include membranes which have water vapour transmission rates of at least 100 g/m2/day, preferably above 340 g/m2/day and more preferably above 900 g/m2/day.

Suitable water vapour permeable membranes comprise spunbonded polypropylene or spunbonded polypropylene/polyethylene. Typically they may be laminated on one or both sides of a microporous polypropylene and/or polyethylene film. Alternatively the water vapour permeable membranes may include monolithic spunbonded membranes, which are dense, pinhole free polymer films produced by casting or extruding a solid film which is laminated to a fabric.

Without intending to be limiting examples of suitable water vapour permeable membranes include Tyvek® Supro (DuPontTM), Tyvek® Housewrap (DuPontTM), and Roofshield® (A. Proctor Group). Nevertheless any other commercially available water vapour permeable membranes may be used.

Tyvek® Supro (DuPontTM) is manufactured by spinning strands of high density polyethylene (PE-HD) and bonding them together with heat and pressure. To this a polypropylene non-woven sheet is laminated using an adhesive and heat bonding to form a flexible sheet for use in unsupported and fully supported

specifications.

Tyvek® Housewrap (DuPontTM) is a high specification vapour permeable membrane mainly for timber frame wall applications, but it is also suitable for steel frame and concrete structures. It is a non-woven, non-perforated sheet made by spinning extremely fine continuous high-density polyethylene (HDPE) fibres that are fused together to form a strong uniform web.

Roofshield® (A. Proctor Group) is a triple layer spunbonded polypropylene laminate, where the central layer is of fine-fibred meltblown material.

Any of the aforementioned water vapour permeable membranes or other commercially available water vapour permeable membranes may be used in the construction of the self adherent, water vapour permeable membrane, of the present invention by applying to at least one surface of the water vapour permeable membrane the adhesive composition as provided herein.

The following examples are an illustration of the invention without intending to in any way be limiting.

Examples

Example I

A disc of approximately 73mm in diameter is cut from uncoated Roofshield® (supplied by A. Proctor Group), hereafter referred to as Sample A. This is placed over a Payne Permeability Cup (Ref:1003A), from Sheen Instruments Limited, with an open area of 25cm2 (O.0025m2) containing approximately 5m1 deionised water. The disc is then clamped to the cup by means of an inner ring and screw cap to form a vapour tight seal. The cup is weighed (4 decimal places) and then stored in a humidity chamber at a constant relative humidity of 55% ©25°C. It is re-weighed after 24 hours and the water vapour transmission rate (gIm2I24hr.), which indicates how much water vapour can pass through I m in 24 hours is calculated using the readings obtained.

Examle2 The procedure of Example I is repeated using the same size of disc cut from Roofshield®, but coated with 50g/m2 acrylic adhesive. This is placed adhesive side down over the cup and hereafter referred to as Sample B.

Example 3

The procedure of Example I is repeated using the same size of disc cut from Roofshield®, but coated with 50g/m2 acrylic adhesive containing 15% active hydrophilic microparticles. This is placed adhesive side down over the cup and hereafter referred to as Sample C.

Example 4

The procedure of Example I is repeated using the same size of disc cut from Roofshield®, but coated with 50g/m2 acrylic adhesive containing 25% active hydrophilic microparticles. This is placed adhesive side down over the cup and hereafter referred to as Sample D.

Example 5

The procedure of Example I is repeated using the same size of disc cut from Roofshield®, but coated with 50g/m2 acrylic adhesive containing 35% active hydrophilic microparticles. This is placed adhesive side down over the cup and hereafter referred to as Sample E. For Examples 2 to 5 inclusive the coated Roofshield® samples used are supplied by Apollo Chemicals Limited.

The hydrophilic microparticles comprise a 60/40 acrylamide/sodium acrylate copolymer (cross-linked with 40 ppm methylene-bisacrylamide), typically one micron, dispersed in a solvent neutral hydrocarbon oil.

Results for examples I -5 inclusive

Example Sample WVTR

(g/m2/24hr.) 0-24 hours Example I Sample A 1847 Example 2 Sample B 247 Example 3 Sample C 1507 Example 4 Sample D 1625 Example 5 Sample E 1744

Claims

Claims 1. A self adherent, water vapour permeable, membrane, for use in a building envelope, comprising i) a water vapour permeable membrane and ii) an adhesive composition on at least one surface of the water vapour permeable membrane, wherein the adhesive composition comprises, a) a hydrophobic adhesive polymer and b) hydrophilic microparticles.
2. A self adherent, water vapour permeable, membrane according to claim I in which the hydrophobic adhesive polymer is a pressure sensitive adhesive.
3. A self adherent, water vapour permeable, membrane according to claim I or 2 in which the hydrophilic microparticles are polymeric and formed from water-soluble ethylenically unsaturated monomer or blend of monomers comprising, (a) 0 to 80% by weight polar and nonionic water-soluble ethylenically unsaturated monomer, (b) 20 to 100% by weight anionic water-soluble ethylenically unsaturated monomer, (c) 20 to 100 % by weight cationic water-soluble ethylenically unsaturated monomer.
4. A self adherent, water vapour permeable, membrane according to any preceding claim in which the hydrophilic microparticles are polymeric and have a volume mean diameter of less than 20 microns (as determined by laser diffraction technique using a Sympatec Helos H 1539 with RI lens and Quixcel dispersion system).
5. A self adherent, water vapour permeable membrane, according to any preceding claim in which the adhesive composition comprises, a) a hydrophobic adhesive polymer in an amount of between 50% and 99% by weight, and b) hydrophilic microparticles in an amount of between 1% and 50% (active polymer) by weight.
6. A self adherent, water vapour permeable, membrane according to any preceding claim in which the water vapour permeable membrane comprises spunbonded polypropylene, spunbonded polypropylene/polyethylene or monolithic spunbonded.
7. A process for manufacturing a self adherent, water vapour permeable, membrane for use in a building envelope, comprising the steps of i) providing a water vapour permeable membrane, and ii) applying an adhesive composition to at least one surface of the water vapour permeable membrane, wherein the adhesive composition comprises, a) a hydrophobic adhesive polymer and b) hydrophilic microparticles.
8. Use of a self adherent, water vapour permeable, membrane defined according to claim I in buildings for preventing the ingress of liquid water and allowing the transmission of water vapour from the interior of the building to the exterior.
9. Use of an adhesive composition in a self adherent, water vapour permeable membrane for providing adhesion to surfaces within a building envelope, wherein the adhesive composition comprises, a) a hydrophobic adhesive polymer and b) hydrophilic microparticles.