Technical field

The invention relates to the field of waterproofing of above ground building constructions by using waterproofing membranes. In particular, the invention relates to roofing membranes having an improved mechanical properties, flexibility at cold temperatures, and resistance against hail impact.

Background of the invention

In the field of construction polymeric sheets, which are often referred to as membranes, panels, or sheets, are used to protect underground and above ground constructions, such as basements, tunnels, and flat and low-sloped roofs, against penetration water. Waterproofing membranes are applied, for example, to prevent ingress of water through cracks that develop in concrete structures due to building settlement, load deflection, or concrete shrinkage. Roofing membranes used for waterproofing of flat and low-sloped roof structures are typically provided as single-ply or multi-ply membrane systems. In a single-ply system, the roof substrate is covered using a roofing membrane composed of a single polymeric waterproofing layer. Single-ply roofing membranes typically contain one or more reinforcing layers to increase the mechanical stability of the membrane. Multi-ply membranes are composed of multiple polymeric waterproofing layers having similar or different compositions. Single-ply membranes have the advantage of lower production costs compared to the multi-ply membranes, but they are also less resistant to mechanical damages caused by punctures of sharp objects.

Commonly used materials for roofing membranes include plastics, particularly thermoplastics such as plasticized polyvinylchloride (p-PVC), thermoplastic olefins (TPE-O, TPO), and elastomers such as ethylene-propylene diene monomer (EPDM). Roofing membranes are typically delivered to a construction site in form of rolls, transferred to the place of installation, unrolled, and adhered to the substrate to be waterproofed. The substrate on which the roofing membrane is adhered may be comprised of variety of materials. The substrate may, for example, be a concrete, metal, or wood deck, or it may include an insulation board or a cover board and/or an existing membrane.

Roofing membranes must be securely fastened to the roof substrate to provide sufficient mechanical strength to resist the shearing forces applied on it due to high wind loads. Roof systems are typically divided into two categories depending on the means used for fastening the roofing membrane to the roof substrate. In a mechanically attached roof system, the roofing membrane is fastened to the roof substrate by using screws and/or barbed plates. Mechanical fastening enables high strength bonding, but it provides direct attachment to the roof substrate only at locations where a mechanical fastener affixes the membrane to the surface, which makes mechanically attached membranes susceptible to flutter. In fully-adhered roof systems the membrane is typically adhered to the roof substrate indirectly by using an adhesive composition.

Roofing membranes are exposed to various stresses during their lifetime including thermal stresses, prolonged exposure to ozone and ultraviolet irradiation, and mechanical stresses. Mechanically fastened PVC membranes are known to be more susceptible to weathering induced aging compared to fully adhered systems. Furthermore, aged roofing membranes show particularly poor resistance mechanical impacts, such impact of hail stones. Mechanical properties of a roofing membrane can be improved, for example, by using non-woven reinforcing layers, such as polyester fabrics or laid scrims, that are integrated into structure of the membrane. However, the use of such reinforcing layers also brings negative impact on the flexibility of membrane. Due to high stiffness of the yarns of a reinforcing layer, bending of a reinforced multi-ply membrane at low temperatures will cause the scrim to exert a push force that can eventually result in delamination of the membrane layers, especially if a relatively thin membrane top layer is used.

There thus remains a need for a novel type of reinforced roofing membrane that has superior physical properties including tensile strength, tear and puncture resistance, flexibility at low temperature, and hail resistance, and which membrane can be used for providing roof systems with prolonged lifetime and improved security. Summary of the invention

The object of the present invention is to provide a novel improved roofing membrane having improved physical properties, especially in terms of tensile strength, tear, puncture, and hail impact resistance, and flexibility at low temperatures.

The subject of the present invention is a membrane as defined in claim 1.

It was surprisingly found out that a membrane comprising a top layer and a reinforcing scrim, wherein at least a portion of the first major surface of the reinforcing scrim is covered with an adhesive coating material, is able to solve or at least mitigate the problems of the State-of-the-Art reinforced membranes.

One of the advantages of the membrane of the present invention is that the improvements in mechanical properties and aging resistance can be achieved without significantly increasing the production costs of the membrane.

Other aspects of the present invention are presented in other independent claims. Preferred aspects of the invention are presented in the dependent claims.

Brief description of the Drawings

Fig. 1 shows a cross-section of a membrane (1) comprising membrane top layer (2), a reinforcing scrim (3), and an adhesive coating material (5) covering the first major surface of the reinforcing scrim (3).

Fig. 2 shows a cross-section of a membrane (1) comprising membrane top layer (2), a reinforcing scrim (3), a membrane back layer (4), and an adhesive coating material (5) covering the first major surface of the reinforcing scrim (4), wherein the reinforcing scrim (3) is arranged between the membrane top and back layers (2, 4).

Fig. 3 shows a cross-section of a roof system comprising a roof underlayment (6) and a membrane (1 ) of Figure 2 adhered to a surface of the roof underlayment (6). Detailed description of the invention

The subject of the present invention is a membrane (1) comprising: i. A membrane top layer (2), ii. A reinforcing scrim (3) having first and second major surfaces, and iii. Optionally a membrane back layer (4), characterized in that at least a portion of the first major surface of the reinforcing scrim (3) is covered with an adhesive coating material (5) comprising: a) A polyvinylchloride resin, b) At least one polyvinylchloride resin crosslinker, c) Optionally at least one plasticizer, and d) Optionally at least one inorganic filler.

The prefix “poly” in substance designations such as “polyol” or “polyisocyanate” refers to substances which in formal terms contain two or more per molecule of the functional group that occurs in their designation. A polyol, for example, is a compound having two or more hydroxyl groups, and a polyisocyanate is a compound having two or more isocyanate groups.

The term “polymer” designates a collective of chemically uniform macromolecules produced by a polyreaction (polymerization, polyaddition, polycondensation) where the macromolecules differ with respect to their degree of polymerization, molecular weight and chain length. The term also comprises derivatives of said collective of macromolecules resulting from polyreactions, that is, compounds which are obtained by reactions such as, for example, additions or substitutions, of functional groups in predetermined macromolecules and which may be chemically uniform or chemically non-uniform.

The term “glass transition temperature” (T _g ) designates the temperature above which temperature a polymer component becomes soft and pliable, and below which it becomes hard and glassy. The glass transition temperature is preferably determined by dynamical mechanical analysis (DMA) as the peak of the measured loss modulus (G”) curve using an applied frequency of 1 Hz and a strain level of 0.1 %.

The “amount or content of at least one component X” in a composition, for example “the amount of the at least one plasticizer” refers to the sum of the individual amounts of all plasticizers contained in the composition. Furthermore, in case the composition comprises 20 wt.-% of at least one plasticizer, the sum of the amounts of all plasticizers contained in the composition equals 20 wt.-%.

The term “room temperature” designates a temperature of 23 °C.

The membrane of the present invention comprises a membrane top layer, a reinforcing scrim, and optionally a membrane back layer, wherein at least a portion of the first major surface of the reinforcing scrim is covered with an adhesive coating material. The term “layer” refers in the present disclosure to a sheet-like element having first and second major surfaces, i.e. top and bottom surfaces, a width defined between the longitudinally extending edges, and a thickness defined between the first and second major surfaces. Preferably, a layer has a length and width at least 5 times, more preferably at least 15 times, even more preferably at least 25 times greater than the thickness of the layer.

Preferably, the at least one of the membrane top and back layers is a polymeric layer. The term “polymeric layer” refers in the present disclosure to a film comprising a continuous phase composed of one or more polymers. According to one or more embodiments, both membrane back and top layers are polymeric layers. Preferably, the membrane of the present invention is a roofing membrane.

The reinforcing scrim is preferably a non-woven scrim. The term “non-woven scrim” refers in the present disclosure to non-woven products composed of at least two sets of parallel yearns (warp and weft yarns), which lay on top of each other and chemically bonded to each other using one or more binders. Such non-woven scrims are also known as “laid scrims”. The yarns of a non-woven scrim are typically arranged with an angle of 60 - 120°, particularly as 90 ± 5°, towards each other thereby forming interstices, wherein the interstices typically occupy more than 50 % of the entire surface area of the non-woven scrim.

Commonly used materials for non-woven scrims include metal fibers, inorganic fibers, such as glass fibers, aramid fibers, wollastonite fibers, and carbon fibers, and synthetic organic fibers, such as polyester fibers, polypropylene fibers, polyethylene fibers, fibers, polyamide fibers, and polyethylene terephthalate (PET).

Suitable binders for chemically bonding of the yarns to each other include, for example, polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), polyvinyl chloride (PVC), polyacrylates, acrylates, ethylene-vinylacetate copolymers (EVA), polyurethane (PUR), styrene butadiene copolymers (SB) and mixtures thereof. The chemical bonding is typically accomplished such that the warp and weft yarns are impregnated with the binder and then contacted with each other.

According to one or more embodiments, the reinforcing scrim has a single or double warp construction, preferably a single warp construction. In a single warp construction, the first warp yarn (yarn in machine direction) under a weft yarn (yarn in cross direction) is followed by a warp yarn above the weft yarn. This pattern is repeated across the whole width of the scrim. The spacing between the yarns can be regular across the whole width of the scrim. At the intersections, two yarns will always meet each other. In a double warp construction, the upper and lower warp yarns will always be placed one upon the other so that the weft yarns will always be fixed between an upper and a lower warp yarn. At the intersections three yarns will always meet each other.

According to one or more embodiments, the reinforcing scrim has at least 4, preferably at least 5, more preferably at least 5.5, even more preferably at least 6, still more preferably at least 7, warp yarns per cm (in the machine direction of the scrim) and/or at least 4, preferably at least 5, more preferably at least 5.5, even more preferably at least 6, still more preferably at least 7, weft yarns per cm (in the cross direction of the scrim).

According to one or more preferred embodiments, the reinforcing scrim has 4 -15, preferably 5- 12, more preferably 5.5 - 12, even more preferably 6 - 10, still more preferably 7 - 10, warp yarns per cm (in the machine direction of the scrim) and/or 4 - 15, preferably 5 - 12, more preferably 5.5 - 12, even more preferably 6 - 10, still more preferably 7 - 10, weft yarns per cm (in the cross direction of the scrim).

The thickness of the yarns of the reinforcing scrim is not particularly restricted and preferred thickness depends on the materials of the scrim and further on the density of the warp and weft yarns. Preferably, the yarns of the reinforcing scrim have a thickness of not more than 750 pm, more preferably not more than 500 pm, even more preferably not more than 350 pm. According to one or more embodiments, the yarns of the reinforcing scrim have a thickness of 100 - 750 pm, preferably 150 - 500 pm, more preferably 200 - 350 pm.

The mass per unit area of the reinforcing scrim is preferably not more than 500 g/m ² , more preferably not more than 350 g/m ² . According to one or more embodiments, the reinforcing scrim has a mass per unit area of 25 - 250 g/m ² , preferably 50 - 200 g/m ² , even more preferably 100 - 200 g/m ² . The mass per unit area can be determine by measuring the mass of a sample of the scrim and dividing the mass by area of the sample. Preferably, the mass per unit area of the reinforcing scrim is determined as defined according to ISO 9073-18:2007 standard.

Preferably, the scrim has a thickness of not more than 1.0 mm, preferably not more than 0.75 mm. According to one or more embodiments, the reinforcing scrim has a thickness of 0.10 - 1.0 mm, preferably 0.15 - 0.75 mm, more preferably 0.2 - 0.5 mm, even more preferably 0.25 - 0.5 mm.

According to one or more embodiments, the reinforcing scrim has an elongation at break determined according to ISO 20932-1 :2018 standard of 2 - 35 %, preferably 4 - 25 %, more preferably 6 -20 %.

According to one or more preferred embodiments, the yarns of the reinforcing scrim comprise or are composed of synthetic organic polymers, preferably selected from the group consisting of polyester, polypropylene, polyethylene, polyamide, and polyethylene terephthalate, more preferably selected from the group consisting of polyester, polypropylene, and polyethylene, even more preferably polyester. According to one or more embodiments, the membrane comprises a membrane back layer and the reinforcing scrim is arranged between the membrane top and back layers. Such membranes are especially suitable for use as multi-ply roofing membranes.

According to one or more embodiments, the second major surface of the reinforcing scrim is directly connected to the membrane back layer. The expression “directly connected” is understood to mean in the context of the present invention that no further layer or substance is present between the layers and that the opposing surfaces of the layers are directly bonded to each other or adhere to each other. At the transition area between the two layers, the materials of the layers can also be present mixed with each other.

According to the present invention, at least a portion of the first major surface of the reinforcing scrim is covered with an adhesive coating material.

In order to provide sufficient bonding between the reinforcing scrim and the membrane top layer, it is preferred that at least 50 %, more preferably at least 75 %, even more preferably at least 85 %, still more preferably at least 95 %, of the first major surface of the reinforcing scrim is covered with the adhesive coating material. According to one or more embodiments, the first major surface of the reinforcing scrim is essentially completely covered with the adhesive coating material. The expression “essentially completely” is understood to mean that at least 97.5 %, preferably 98.5 %, more preferably 99 %, is of the first major surface of the reinforcing scrim is covered with the adhesive coating material.

It is furthermore preferred that the reinforcing scrim is at least partially impregnated with the adhesive coating material. The term "impregnated" is understood to mean that a substrate contains porosities which have been filled to the saturation point by the respective composition, in this case by the adhesive coating material.

The adhesive coating material comprises: a) A polyvinylchloride resin, b) At least one polyvinylchloride resin crosslinker, c) Optionally at least one plasticizer, and d) Optionally at least one inorganic filler.

According to one or more embodiments, the adhesive coating material comprises: a) 25 - 75 wt.-%, preferably 35 - 65 wt.-%, more preferably 40 - 60 wt.-%, of the polyvinylchloride resin, b) 0.1 - 15 wt.-%, preferably 1 - 10 wt.-%, more preferably 2.5 - 7.5 wt.-%, of the at least one polyvinylchloride resin crosslinker, c) 0 - 55 wt.-%, preferably 5 -50 wt.-%, more preferably 15 -45 wt.-%, of the at least one plasticizer, and d) 0 - 35 wt.-%, preferably 2.5 - 30 wt.-%, more preferably 5 -25 wt.-%, of the at least one inorganic filler. Suitable polyvinylchloride resin for use in the adhesive coating material include polyvinylchloride resins having a K-value determined by using the method as described in ISO 1628-2-1998 standard in the range of 50 - 85, more preferably 65 - 75. The K- value is a measure of the polymerization grade of the polyvinylchloride resin and it is determined from the viscosity values of the polyvinylchloride homopolymer as virgin resin, dissolved in cyclohexanone at 30 °C.

According to one or more embodiments, the at least one polyvinylchloride crosslinker is a polyisocyanate. Suitable polyisocyanates for use as the at least one polyvinylchloride crosslinker include, for example, aliphatic, cyclo-aliphatic, and aromatic polyisocyanates, especially monomeric di- and tri-functional isocyanates. The term “monomer” designates in the present disclosure a molecule having at least one polymerizable group. In the context of polyisocyanates, a monomeric polyisocyanate contains particularly no urethane groups. Non-monomeric polyisocyanates, such as oligomers, polymers, and derivatives of monomeric polyisocyanates, for example adducts of monomeric diisocyanates, are also suitable. According to one or more embodiments, the at least one polyvinylchloride resin crosslinker is a monomeric diisocyanate, preferably selected from the group consisting of 4,4'-diphenylmethane diisocyanate, optionally with proportions of 2,4'- and/or 2,2'- diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate or mixtures with 2,6- tolylene diisocyanate (TDI), 1 ,6-hexamethylene diisocyanate (HDI), and 1-isocyanato- 3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI). Furthermore, a person skilled in the art knows that the technical grade products of diisocyanates may frequently contain isomer mixtures or other isomers as impurities.

Suitable plasticizers for use in the adhesive coating material include, for example, linear or branched phthalates such as di-isononyl phthalate (DINP), di-nonyl phthalate (L9P), diallyl phthalate (DAP), di-2-ethylhexyl-phthalate (DEHP), dioctyl phthalate (DOP), diisodecyl phthalate (DIDP), and mixed linear phthalates (911 P). Other suitable plasticizers include phthalate-free plasticizers, such as trimellitate plasticizers, adipic polyesters, and biochemical plasticizers. Examples of biochemical plasticizers include epoxidized vegetable oils, for example, epoxidized soybean oil and epoxidized linseed oil and acetylated waxes and oils derived from plants, for example, acetylated castor wax and acetylated castor oil.

Particularly suitable phthalate-free plasticizers for use in the adhesive coating material include alkyl esters of benzoic acid, dialkyl esters of aliphatic dicarboxylic acids, polyesters of aliphatic dicarboxylic acids or of aliphatic di-, tri- and tetrols, the end groups of which are unesterified or have been esterified with monofunctional reagents, trialkyl esters of citric acid, acetylated trialkyl esters of citric acid, glycerol esters, benzoic diesters of mono-, di-, tri-, or polyalkylene glycols, trimethylolpropane esters, dialkyl esters of cyclohexanedicarboxylic acids, dialkyl esters of terephthalic acid, trialkyl esters of trimellitic acid, triaryl esters of phosphoric acid, diaryl alkyl esters of phosphoric acid, trialkyl esters of phosphoric acid, and aryl esters of alkanesulphonic acids.

According to one or more embodiments, the at least one plasticizer is selected from the group consisting of phthalates, trimellitate plasticizers, adipic polyesters, and biochemical plasticizers. Especially suitable inorganic fillers for use in the adhesive coating material include inert mineral fillers which, unlike mineral binders, are not reactive with water, i.e. do not undergo a hydration reaction in the presence of water. Suitable inert mineral fillers include, for example, sand, granite, calcium carbonate, clay, expanded clay, diatomaceous earth, pumice, mica, kaolin, talc, dolomite, xonotlite, perlite, vermiculite, Wollastonite, barite, magnesium carbonate, calcium hydroxide, calcium aluminates, silica, fumed silica, fused silica, aerogels, glass beads, hollow glass spheres, ceramic spheres, bauxite, comminuted concrete, and zeolites. The term “calcium carbonate” as inert mineral filler refers in the present document to calcitic fillers produced from chalk, limestone, or marble by grinding and/or precipitation.

The thickness of the adhesive coating material is not particularly restricted. According to one or more embodiments, the adhesive coating material has a thickness of 25 - 350 pm, preferably 50 - 300 pm, more preferably 75 - 200 pm.

According to one or more preferred embodiments, the membrane top and/or back layer is a polyvinylchloride-based layer, preferably comprising: A) 25 - 65 wt.-%, preferably 35 - 55 wt.-%, of a polyvinylchloride resin,

B) 10 - 50 wt.-%, preferably 15 -45 wt.-%, of at least one plasticizer, and

C) 0 - 30 wt.-%, preferably 1 - 30 wt.-%, of at least one inert mineral filler, all proportions being based on the total weight of the membrane back or top layer. Suitable polyvinylchloride resins, plasticizers, and inert mineral fillers include the ones presented above as suitable for use in the adhesive coating material.

Preferably, the composition of the membrane top and/or back layer has a glass transition temperature (T _g ), determined by dynamical mechanical analysis (DMA) using an applied frequency of 1 Hz and a strain level of 0.1 %, of below - 20 °C, more preferably below - 25 °C.

According to one or more embodiments, the at least one inert mineral filler is present in the membrane top and/or back layer in an amount of 5 - 30 wt.-%, preferably 10 - 30 wt.-%, more preferably, 15 - 30 wt.-%, based on the total weight of the membrane back or top layer.

According to one or more embodiments, the membrane top and/or back layer further comprises:

D) 0 - 15 wt.-%, preferably 0.5 - 10 wt.-%, more preferably 0.5 - 7.5 wt.-%, based on the total weight of the membrane top or back layer, of at least one flame retardant.

The at least one flame retardant is preferably selected from the group consisting of magnesium hydroxide, aluminum trihydroxide, antimony trioxide, ammonium polyphosphate, and melamine-, melamine resin-, melamine derivative-, melamine- formaldehyde-, silane-, siloxane-, and polystyrene-coated ammonium polyphosphates.

Other suitable flame retardants for use as the at least one flame retardant include, for example, 1 ,3,5-triazine compounds, such as melamine, melam, melem, melon, ammeline, ammelide, 2-ureidomelamine, acetoguanamine, benzoguanamine, diaminophenyltriazine, melamine salts and adducts, melamine cyanurate, melamine borate, melamine orthophosphate, melamine pyrophosphate, dimelamine pyrophosphate and melamine polyphosphate, oligomeric and polymeric 1 ,3,5-triazine compounds and polyphosphates of 1 ,3,5-triazine compounds, guanine, piperazine phosphate, piperazine polyphosphate, ethylene diamine phosphate, pentaerythritol, borophosphate, 1 ,3,5-trihydroxyethylisocyanaurate, 1 ,3,5-triglycidylisocyanaurate, triallylisocyanurate and derivatives of the aforementioned compounds.

Suitable flame retardants are commercially available, for example, under the trade names of Martinal® and Magnifin® (both from Albemarle) and under the trade names of Exolit® (from Clariant), Phos-Check® (from Phos-Check) and FR CROS® (from Budenheim).

The membrane top and back layer can comprise further auxiliary components, for example, UV- and heat stabilizers, antioxidants, dyes, pigments such as titanium dioxide and carbon black, matting agents, antistatic agents, impact modifiers, biocides, and processing aids such as lubricants, slip agents, antiblock agents, and denest aids. The total amount of these auxiliary components is preferably not more than 45 wt.-%, more preferably not more than 35 wt.-%, even more preferably not more than 25 wt.-%, based on the total weight of the membrane top or back layer.

According to one or more embodiments, the membrane has a thickness determined by using the measurement method as defined in EN 1849-2:2019 standard of 0.5 - 5.0 mm, preferably 0.75 - 3.5 mm, more preferably 0.85 - 3.0 mm.

The membrane of the present invention is typically provided in a form of a prefabricated membrane article, which is delivered to the construction site and unwound from rolls to provide sheets having a width of 1 - 5 m and length of several times the width.

However, the membrane can also be used in the form of narrow strips having a width of typically 1 - 35 cm, preferably 5 - 25 cm, for example to seal joints between two adjacent membranes. Moreover, the membrane can also be provided in the form of planar bodies, which are used for repairing damaged locations in existing adhered roofing systems.

The preferences given above for the membrane top and back layers, the reinforcing scrim, and to the adhesive coating material apply equally to all aspects of the present invention unless otherwise stated.

Another subject of the present invention is a method for producing a membrane according to the present invention, the method comprising steps of:

I) Providing a membrane top layer (2) and a reinforcing scrim (3) having an adhesive coating material (5) covering at least a portion of a first major surface of the reinforcing scrim (3) and

II) Laminating the reinforcing scrim (3) to a second major surface of the membrane top layer (2).

According to one or more embodiments, the method comprises further steps of:

III) Providing a membrane back layer (4) and IV) Laminating the membrane back layer (4) to the membrane top layer (2) such that the reinforcing scrim (3) becomes sandwiched between the membrane top and back layers (2, 4).

The lamination of the individual layers to each other can be conducting using any conventional techniques known to a person skilled in the art, such as heat (hot)- pressing, thermo-laminating, and adhesive lamination. The choice of the suitable lamination technique depend on the embodiments of the membrane.

According to one or more embodiments, the reinforcing layer has been thermally laminated to at least a portion of the second major surface of the membrane top layer in a manner that gives direct bonding between the adhesive coating material and the membrane top layer and/or the membrane back layer has been thermally laminated to at least a portion of the second major surface of the reinforcing scrim in a manner that gives direct bonding between the membrane back layer and the reinforcing scrim.

Another subject of the present invention is a roof system comprising a roof underlayment (6) and a membrane (1) according to the present invention adhered to a surface of the roof underlayment (6) by using mechanical fastening or adhesive bonding means, preferably by using mechanical fastening means.

According to one or more embodiments, the roof underlayment comprises a cover board and/or an insulation board.

Preferably, the insulation board comprises at least one foam panel having a closed cell structure. Suitable foam panels having a closed cell structure include molded expanded polystyrene (EPS) foam panels, extruded expanded polystyrene (XPS) foam panels, polyurethane foam panels (PUR), and polyisocyanurate (PIR) foam panels.

The thickness of the insulation board is not particularly restricted. It may be preferable that the insulation board has a thickness determined by using the measurement method as defined in DIN EN 1849-2 standard of 5 - 500 mm, preferably 10 - 350 mm, even more preferably 25 - 150 mm. According to one or more embodiments, the insulation board comprises at least one foam panel having a closed cell structure selected from the group consisting of molded expanded polystyrene (EPS) foam panel, extruded expanded polystyrene (XPS) foam panel, polyurethane foam panel (PUR), and polyisocyanurate (PIR) foam panel, preferably having a density in the range of 10 - 150 g/l, more preferably 15- 100 g/l, even more preferably 25 - 75 g/l.

The insulation board can be secured to a roof substrate, such as a roof deck, by using any suitable fastening means, such as by using adhesive bonding or mechanical fastening means, preferably by mechanical fastening means.

According to one or more embodiments, the roof underlayment comprises a cover board.

Suitable cover boards include, for example, gypsum boards, fiber-reinforce gypsum boards, wood fiber boards, cementitious boards, high-density (compressed) polyisocyanurate boards, perlite boards, asphaltic boards, mineral fiber boards, and plywood or oriented strand boards. The cover board may be used in addition of instead of the insulation board.

According to one or more embodiments, the roof underlayment comprises the insulation board and the cover board, wherein the cover board is preferably positioned between the membrane and the insulation board. The cover board can be secured to the insulation board by using any suitable fastening means, such as by using adhesive bonding or mechanical fastening means.

According to or more embodiments, the roof system further comprises a vapor control layer arranged on the bottom side of the roof underlayment opposite to the side of the membrane.

The vapor control layer is liquid impermeable but at least partially permeable to moisture vapor. According to one or more embodiments, the vapor control layer has a water vapor diffusion equivalent air layer thickness value (Sd-value) measured according to the method as defined in ISO 1931 standard of not more than 100 m, preferably not more than 50 m.

According to one or more further embodiments, the vapor control layer has a moisture variable diffusion resistance. In these embodiments, the vapor control layer has a lower water vapor diffusion resistance at higher relative humidity of the surroundings and higher water vapor diffusion resistance at lower relative humidity of the surroundings. For example, the Sd-value of the vapor control layer can be in the range of 0.5 - 20 m, preferably 1 - 10 m at relative humidity of 80 %, and in the range of 25 - 100 m, preferably 35 - 65 m at relative humidity of 20 %.

The composition of the vapor control layer is not particularly restricted. Preferably, the vapor control layer comprises at least polymer selected from the group consisting of polyethylene (PE), polypropylene (PP), ethylene - vinyl acetate copolymers (EVA), ethylene - a-olefin co-polymers, ethylene - propylene co-polymers, polyvinylchloride (PVC), ethylene acrylic acid co-polymers, polyurethane, polyesters, co-polyesters, polyether-esters, polystyrene (PS), polyethylene terephthalate (PET), polyamides (PA), co-polyamides, and ionomers. The term “ionomer” refers to a polymer that comprises ionic groups that are carboxylate salts, for example, ammonium carboxylates, alkali metal carboxylates, alkaline earth carboxylates, transition metal carboxylates and/or combinations of such carboxylates. Such polymers are generally produced by partially or fully neutralizing the carboxylic acid groups of precursor or parent polymers that are acid copolymers, for example, by reaction with a base.

Preferably, the vapor control layer has a thickness of 5 - 500 pm, more preferably 25 - 350 pm, even more preferably 50 - 250 pm and/or a mass per unit are of 25 - 500 g/m ² , more preferably 50 - 350 g/m ² , even more preferably 75 - 250 g/m ² . Examples

Preparation of membranes The exemplary membrane was composed of PVC-based membrane top and back layers and an inventive polyester-based reinforcing scrim having an adhesive coating material covering the top surface of the scrim sandwiched between the membrane top and back layers. The membrane was prepared by co-extruding the membrane top and back layers on opposite surfaces of the reinforcing scrim using a laboratory size co extruding apparatus. The inventive polyester-based reinforcing scrim had 7.2 warp yarns per cm of the scrim (warp yearn density) and 7.2 weft yearns per cm of the scrim (weft yearn density). The linear density of the warp and weft yearns was 840 denier.

The membrane top and back layers had a thickness of 1.7 mm, the reinforcing scrim had a thickness of 0.3 mm, and the adhesive coating material covering the top surface of the reinforcing scrim had a thickness of 0.1 mm.

The reference membrane was composed of the membrane back and top layers of the exemplary membrane and a normal polyester reinforcing scrim having a thickness of 0.25 mm sandwiched between the membrane back and top layers.

The membranes were then tested for tensile strength, elongation at break, lamination force, tear resistance, static puncture resistance, and for flexibility at low temperature. The results from these measurements are presented in Table 1.

Tensile strength and elongation at break

The tensile strength and elongation at break were measured for samples cut from the tested membrane in machine (MD) and cross machine direction (CMD). The measurements were conducted according to GB 12952-2011 standard at a temperature of 23 °C. Lamination force

Lamination force was measured for samples having dimensions of 50 x 200 mm cut from the tested membrane in machine direction. The measurements were conducted by peeling the membrane top layer from the reinforcing scrim using a tensile testing machine and a constant speed of 100 mm/min.

Tear resistance

The tear resistance was measured for samples cut from the tested membrane in machine and cross machine direction. The measurements were conducted according to EN 12310-2 standard at a temperature of 23 °C.

Static puncture resistance

The static puncture resistance was measured for samples cut from the tested membrane in machine direction. The measurements were conducted according to EN ISO 12236 standard at a temperature of 23 °C.

The measurements for the low temperature flexibility were conducted according to GB 12952-2011 standard. Sample strips having dimensions of 100 x 25 mm were first cut from the tested membrane in machine direction.

The strips were then stored at the measurement temperature for one hour and then bended and visually analyzed for the presence of cracks in the polymeric layers. In case of no signs of cracks, the measurement was repeated at a lower temperature until the first cracks could be detected.

Hail impact resistance

The hail impact resistance was tested according to the following procedure. Test specimens composed of the tested membrane adhered to an insulation panel were shot targeting the side of the membrane with round ice balls having a different diameter, speed, and impact energy. The insulation panel was a polyisocyanurate insulation panel having a thickness of 38 mm (H-Shield® from Hunter Panels). The membrane was mechanically adhered to the insulation panel via the outer surface of the membrane back layer using an aluminum bar framework.

The test specimens were built into a climatized chamber (fridge) to simulate the conditions in during a hailstorm. The temperature of the climatized chamber was decreased until the surface of the membrane reached a value of 4.4 °C or below. The ice balls were then shot against the outer surface of the roofing membrane.

In case the membrane survived the impact of the ice ball without showing any loss of material integrity, the “damages to the membrane” was evaluated as “pass”. Tables 2 and 3 show the results obtained with inventive membrane (Ex-1 , Ex-2) and with reference membrane (Ref-1, Ref-2).

Table 1 ^a Membrane top layer, ^b Membrane back layer Table 2

Table 3