EP4403718A1

EP4403718A1 - A method for connecting an edge metal flashing to a roofing membrane

Info

Publication number: EP4403718A1
Application number: EP23152949.6A
Authority: EP
Inventors: Xiong JIANG; Wilfried Carl; Michael DARSCH; Sabina HOLDENER; Roger KATHRINER; Johannes PECHER; Dorothee Quinzler; Gary W. Whittemore
Original assignee: Sika Technology AG
Current assignee: Sika Technology AG
Priority date: 2023-01-23
Filing date: 2023-01-23
Publication date: 2024-07-24

Abstract

The invention is directed to a method for installing a cover strip between a roofing membrane and an edge metal flashing positioned over a portion of the roofing membrane, the method comprising using a cover strip or a self-adhering cover strip to bridge a joint formed between the edge metal flashing and the roofing membrane. One end of the cover strip is indirectly or directly bonded to the edge metal flashing by using an adhesive whereas the other end is heat-welded or adhesively bonded to the roofing membrane.

Description

Technical field

The invention relates to the field of roof assemblies used in the field of construction. Particularly, the invention relates to a method for connecting an edge metal flashing to a roofing membrane using a cover strip.

Background of the invention

Outer exterior surfaces of buildings must be protected from environmental forces such as wind and rain. Roofing membranes composed of polymeric materials are used for waterproofing of flat or slightly sloped roofs whereas sloped roofs are typically covered with roof shingles. Commonly used materials for the roofing membranes include plastics, in particular thermoplastics such as plasticized polyvinylchloride (p-PVC), thermoplastic olefins (TPE-O, TPO), and elastomers such as ethylene-propylene diene monomer (EPDM).
Low-slope roof assemblies are typically composed of a roofing membrane, a rigid insulation and/or cover board, and a roof deck. The roofing membrane can be applied directly on the top of the insulation board, which is used to improve the thermal insulation properties of the roof assembly. Alternatively, the roofing membrane can be secured to a cover board, which is applied on top of the insulation board. In ventilated and cold roof designs, the insulation board can also be located below the roof deck.
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. In a mechanically attached roof system, the roofing membrane is fastened to the roof substrate by using screws and/or barbed plates. In fully adhered roof systems, the roofing membrane is adhered to the roof substrate indirectly by using an adhesive composition, such as a solvent- or water-based contact adhesive. In ballasted roof systems, the roofing membrane is not anchored or adhesively adhered to the roof substrate but "ballasted" with a stone material, typically gravel. 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.
To create a continuous waterproofing seal on the surface of a roof substrate, the edges of adjacent membrane sheets are overlapped to form sealable joints. The joints can then be sealed by bonding the opposing surfaces of the edge portions to each other by using an adhesive ("bonded seams") or by heat-welding ("welded seams"). In addition, the outer edges of the membrane sheets adjacent to the roof edge, as well as edges of the membrane surrounding objects on the roof surface, must be sealed
to ensure watertightness of the roof assembly. Cover strips composed of thermoplastic or thermoset materials, which are also known as "flashings", are commonly used for sealing the edges of roofing membranes. Thermoplastic flashings are typically made of materials that enable bonding to roofing membranes by heat-welding. Thermoset flashings are adhered to roofing membranes and other surfaces via pre-applied adhesive layer or by using adhesive agents that are applied at the construction site.
Metal edge flashings, such as drip edge and gravel stop flashings, are used to terminate the roof, and prevent water infiltration. These types of flashings typically direct water away from the roof edge either into a gutter, onto a water-impermeable surface below, or to the ground. A cover strip used for sealing a joint formed between a metal flashing and a roofing membrane must provide a watertight connection, whose long-term durability corresponds to that of the full roof, which is designed for several decades of service. One way to ensure watertightness of the connection is to provide the metal flashing with a polymeric coating that enables bonding of the cover strip to the metal flashing by heat-welding. Polymer coated metal flashings are commercially available, for example, under the trade name of Sarnaclad (from Sika Corporation). Such metal flashings are, however, only available in limited colors and sizes.
EP 3418466 B1 discloses use of a self-adhering cover strip intended to connect a metal edge flashing to a PVC roofing membrane. The cover strip comprises an outer PVC layer, a barrier layer covering a bottom surface of the outer PVC layer to prevent migration of plasticizers, a primer layer covering the barrier layer, and a layer of pressure sensitive adhesive applied on the primer coating. Furthermore, the cover strip is not directly bonded to the roofing membrane, but the surface of membrane is first coated with a strip barrier layer, which is then covered with a second primer layer. The barrier and primer layers are applied as wet films, which are cured by allowing the liquid to evaporate.
Although the system disclosed in EP 3418466 B1 solves the problem of connecting a thermoplastic cover strip to a metal edge flashing, it has several substantial drawbacks. First, two solvent-based primer compositions are applied, and a full evaporation of the wet films is required in each process step. Besides negative effect on the environment and worker safety resulting from VOC emissions, such process is also very sensitive towards applicator errors, particularly if the conditions on a construction site with large temperature variations (summer/winter, morning/afternoon) and humidity, are considered. Secondly, the primer must not be applied on the metal, but only to the roofing membrane, which is an additional source for application errors. Thus, the suggested system is suitable for a controlled environment and highly skilled workforce but does not provide the application safety and robustness required in a typical construction site. Finally, the primer application for the cover strip joints is very time consuming and thus expensive.
It is thus highly desirable to have cover strip system which is easy to apply and provides the required long-term watertightness.

Summary of the invention

The object of the present invention is to provide an edge metal flashing connection system which is easy to apply and provides the required long-term watertightness.
The subject of the present invention is a method for installing a cover strip as defined in claim 1.
The present invention provides two technical solutions to solve or at least mitigate the problems or disadvantages of the techniques of prior art.
It was surprisingly found out that the disadvantages related to the prior art solutions can be solved or at least partially mitigated by using two techniques. According to the first alternative, a first end portion of a cover strip is bonded to a sealing strip covering an edge metal flashing using a reactive adhesive whereas the opposite end portion is bonded to a roofing membrane by heat-welding. According to the second alternative, a self-adhering cover strip is used to directly connect the edge metal flashing to the roofing membrane. The seams formed along the periphery of the cover strip can further be sealed using a suitable sealant mass.
Both techniques provide a durable watertight connection between the edge metal flashing and roofing membrane. Since the methods involve only one adhesive application step and do not require use of liquid primers, potential application errors as well as release of VOCs are avoided. Moreover, the proposed methods have the advantage that they can be conducted fast and efficiently, which reduces the installation costs.
Other aspects of the present invention are presented in other independent claims. Preferred embodiments of the invention are presented in the dependent claims.

Brief description of the Drawings

Fig. 1 shows a cover strip (4, 5) comprising upper and lower major surfaces limited between long and short edges and first (8, 11) and second (8', 11') long edge portions of the lower major surface of the cover strip (4, 5).
Fig. 2 shows a cross-section of a roof system comprising a roof substrate (1), a roofing membrane (2), an edge metal flashing (3), a cover strip (4), and a sealing strip (6), wherein the sealing strip (6) is adhesively bonded via its lower major surface to an upper major surface of the edge metal flashing (3) using a reactive adhesive (7). A first long edge portion (8) of a lower major surface of the cover strip (4) is heat-welded to a portion of an upper major surface of the sealing strip (6) and a second long edge portion (8') of the lower major surface of the cover strip is heat-welded to a portion of an upper major surface of the roofing membrane (2).
Fig. 3 shows a cross-section of a roof system comprising a roof substrate (1), a roofing membrane (2), an edge metal flashing (3), and a self-adhering cover strip (5) comprising a carrier layer (9) and a layer of pressure sensitive adhesive (10), wherein a first long edge portion (11) of the lower major surface of the carrier layer (9) is bonded to a portion of an upper major surface of the metal edge flashing (3) by the adhesive layer (10) and a second long edge portion (11') of the lower major surface of the carrier layer (9) is bonded to a portion of an upper major surface of the roofing membrane (2) by the adhesive layer (10).

Detailed description of the invention

The subject of the present invention is a method for installing a cover strip between an edge metal flashing and a roofing membrane, the method comprising steps of:

i) Providing a roof assembly comprising a roof substrate, an edge metal flashing, and a roofing membrane, wherein a portion of the roofing membrane is trapped between the edge metal flashing and the roof substrate,
ii) Providing a sealing strip having upper and lower major surfaces limited between short and long edges,
iii) Adhesively bonding the sealing strip via its lower major surface to a portion of an upper major surface of the edge metal flashing using a reactive adhesive,
iv) Providing a cover strip having upper and lower major surfaces limited between short and long edges,
v) Heat-welding a first long edge portion of the lower major surface of the cover strip to a portion of an upper major surface of the sealing strip and a second long edge portion of the lower major surface of the cover strip to a portion of an upper major surface of the roofing membrane,

I) Providing a roof assembly comprising a roof substrate, an edge metal flashing, and a roofing membrane, wherein a portion of the roofing membrane is trapped between the edge metal flashing and the roof substrate,
II) Providing a self-adhering cover strip comprising a carrier layer having upper and lower major surfaces limited by short and long edges and a layer of a pressure sensitive adhesive coated directly to and covering at least a portion of the lower major surface of the carrier layer,
III) Positioning the self-adhering cover strip such that the adhesive layer covering a first long edge portion of the lower major surface of the carrier layer is directly connected to a portion of an upper major surface of the edge metal flashing and the adhesive layer covering a second long edge portion of the lower major surface of the carrier layer is directly connected to a portion of an upper major surface of the roofing membrane,
IV) Pressing the carrier layer against the roof substrate to effect adhesive bonding between the opposing surfaces of the carrier layer and the edge metal flashing and between opposing surfaces of the carrier layer and the roofing membrane, and
V) Optionally applying a sealant composition to at least one of the long and/or short edges of the carrier layer.

Substance names beginning with "poly" designate substances which formally contain, per molecule, two or more of the functional groups occurring in their names. For instance, a polyol refers to a compound having at least two hydroxyl groups. A polyether refers to a compound having at least two ether 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 "molecular weight" refers to the molar mass (g/mol) of a molecule or a part of a molecule, also referred to as "moiety". The term "average molecular weight" refers to number average molecular weight (M_n) of an oligomeric or polymeric mixture of molecules or moieties. The molecular weight may be determined by gel permeation chromatography (GPC) using polystyrene as standard, preferably using styrene-divinylbenzene gel with porosity of 100 Angstrom, 1000 Angstrom and 10000 Angstrom as columns and, depending on the molecule, tetrahydrofurane as a solvent, at 35°C, or 1,2,4-trichlorobenzene as a solvent, at 160 °C.
The term "melting temperature" refers to a temperature at which a material undergoes transition from the solid to the liquid state. The melting temperature (T_m) is preferably determined by differential scanning calorimetry (DSC) according to ISO 11357-3 standard using a heating rate of 2 °C/min. The measurements can be performed with a Mettler Toledo DSC 3+ device and the T_m values can be determined from the measured DSC-curve with the help of the DSC-software. In case the measured DSC-curve shows several peak temperatures, the first peak temperature coming from the lower temperature side in the thermogram is taken as the melting temperature (T_m).
The term "glass transition temperature" (T_g) refers to the temperature above which temperature a polymer component becomes soft and pliable, and below which it becomes hard and glassy. The glass transition temperature (T_g) 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 acrylic polymer AP" refers to the sum of the individual amounts of all acrylic polymers AP contained in the composition. Furthermore, in case the composition comprises 20 wt.-% of at least one acrylic polymer AP, the sum of the amounts of all acrylic polymers AP contained in the composition equals 20 wt.-%.
The term "room temperature" designates a temperature of 23 °C.
The cover strip used to bridge the joint formed between the edge metal flashing and the roofing membrane and sealing strip are sheet-like articles having upper and lower major surfaces, i.e., top and bottom surfaces, limited by short and long edges, and a thickness of the strip defined there between.
The lower surface of the cover strip comprises first and second long edge portions and first and second short edge portions. The term "long edge portion" is understood to mean a limited area on a surface of the cover strip extending between the first and second short edges along the long edge of the cover strip. The maximum width of a long edge portion is half of the width of the cover strip. In analogy, the term "short edge portion" refers to a limited area on a surface of the cover strip extending between the first and second long edges along the short edge of the cover strip, wherein the maximum width of a short edge portion is half of the length of the cover strip.
One of the advantages of the claimed method is that it enables connecting a substrate having a non-heat weldable surface with a heat-weldable membrane without the use of primers. This reduces the number of installation steps and potential application errors and enables the use of non-coated edge metal flashings in flat roof systems.
According to one or more preferred embodiments, the upper major surface of the edge metal flashing and/or the upper major surface of the roofing membrane is/are non-primed surface(s).
The term "primer" refers in the present disclosure to a thin layer, typically thinner than 1 mm, particularly 1 - 200 µm, preferably 1 - 100 µm, of a solvent- or water-based composition, which is applied as a underlayer coating to a surface of a substrate, and which leads to an improvement in the adhesion of an adhesive to the surface of the substrate. Accordingly, the term "non-primed" refers to a surface that has not been treated with a primer.
According to one or more embodiments, at least a portion of the lower major surface of the sealing strip has been subjected to pre-treatment to improve bonding to reactive adhesives. Suitable pre-treatments to improve adhesion with reactive adhesives include, for example, surface treatments based on a flame ("flaming"), oxofluorination, plasma, or corona. Such treatments do not add an extra layer to the surface of the sealing strip, i.e., a pre-treated surface is not a "primed surface" according to the definition of the present disclosure.
According to the first embodiment, the sealing strip is adhesively bonded via its lower major surface to a portion of an upper major surface of the edge metal flashing using a reactive adhesive.
Step iii) of the method preferably comprises:

iii1) Applying the reactive adhesive to at least a portion of the lower major surface of the sealing strip and/or to a portion of the upper major surface of the edge metal flashing,
iii2) Covering a portion of the upper major surface of the edge metal flashing with the sealing strip such that the applied reactive adhesive forms and interlayer between the edge metal flashing and the sealing strip such that a portion of the opposing surfaces are directly connected to each other via the interlayer, and
iii3) Curing the reactive adhesive.

The reactive adhesive can be applied to the surface of the sealing strip and/or to the edge metal flashing by using any conventional techniques, for example, by means of a roller, brush, or by pouring-out and further distributed by means, for example, of a roller, a scraper, or a notched trowel. Pressing the cover strip against the surface of the metal edge flashing can be conducted, for example, by using a roller.
The interlayer formed by the reactive adhesive between the edge metal flashing and the sealing strip preferably has a thickness of 0.25 - 5 mm, more preferably 0.5 - 4 mm.
Suitable reactive adhesives include one- and two-component epoxide, acrylic, and polyurethane adhesives. The adhesives can be one-component reactive adhesives, where all constituents are packed in one single component/package or multi-component adhesives, particularly two-component adhesives, where the constituents of the adhesive are provided two or more separately stored packages or compartments of a single package. At the time of use, the components of a multiple-component adhesive are mixed with each other to provide a reactive adhesive composition having a specified open time.
Suitable reactive adhesives are commercially available, for example, under the trade name of SikaDur^® and SikaFast^®, such as SikaDur^® 31 HiMod, and SikaFast^® 3341.
Step iv) of the method can be conducted manually, for example by using a hot air tool, or by using an automatic welding device, such as an automatic hot-air welding device, for example Sarnamatic^® 661 welding device. The temperature to which the contacted portions of the sealing strip, cover strip and roofing membrane are heated depends on the material of the cover strip, sealing strip, and roofing membrane and whether the welding step is conducted manually or by using an automatic welding device. Preferably, the contacted portions are heated to a temperature of at or above 150 °C, more preferably of at or above 200 °C.
According to a second embodiment, the cover strip is a self-adhering cover strip comprising a carrier layer and a layer of a pressure sensitive adhesive, wherein the first long edge portion of the lower major surface of the cover strip is adhered to the edge metal flashing via the adhesive layer and the second long edge portion of the lower major surface of the cover strip is adhered to the roofing membrane via the adhesive layer.
The term "pressure sensitive adhesive (PSA)" designates in the present disclosure viscoelastic materials, which adhere immediately to almost any kind of substrates by application of light pressure, and which are permanently tacky. The tackiness of an adhesive layer can be measured, for example, as a loop tack.
Suitable pressure sensitive adhesives for use in the adhesive layer of the cover strip include, for example, acrylic adhesives and synthetic rubber-, natural rubber-, and bitumen-based pressure sensitive adhesives.
The term "acrylic adhesive" designates in the present disclosure adhesive compositions containing one or more acrylic polymers as the main polymer component, wherein the term "acrylic polymer" designates homopolymers, copolymers and higher inter-polymers of an acrylic monomer with one or more further acrylic monomers and/or with one or more other ethylenically unsaturated monomers.
The term "monomer" refers to a compound that chemically bonds to other molecules, including other monomers, to form a polymer. The term "acrylic monomer" refers to monomers having at least one (meth)acryloyl group in the molecule. The term "(meth)acryloyl" designates methacryloyl or acryloyl. Accordingly, the term "(meth)acrylic" designates methacrylic or acrylic. A (meth)acryloyl group is also known as (meth)acryl group.
Acrylic pressure adhesives are provided as crosslinkable or non-crosslinkable dispersion, syrup, and hot-melt adhesives, wherein the crosslinking reaction can be induced by treating the adhesive layer with UV- or electron beam radiation or by heating.
Suitable rubbers for use in a synthetic rubber-based pressure sensitive adhesive include for example, styrene block copolymers, vinyl ether polymers, styrene-butadiene rubber (SBR), ethylene propylene diene monomer (EPDM), butyl rubber, polyisoprene, polybutadiene, polychloroprene rubber, ethylene-propylene rubber (EPR), nitrile rubber, acrylic rubber, ethylene vinyl acetate rubber, or silicone rubber.
Bitumen-based pressure sensitive adhesives typically comprise one of more different types of bitumen materials mixed with one or more modifying polymers to improve the resistance to UV-radiation, toughness, and flexibility at low temperatures
In addition to the above-mentioned constituents, pressure sensitive adhesives typically comprise one or more additional constituents including, for example, tackifying resins, waxes, and additives, for example, UV-light absorption agents, UV- and heat stabilizers, optical brighteners, pigments, dyes, and desiccants.
According to one or more embodiments, the pressure sensitive adhesive is an acrylic pressure sensitive adhesive, preferably a non-crosslinked acrylic pressure sensitive adhesive.
The advantage of using an acrylic pressure sensitive adhesive layer in the adhesive layer is that acrylic PSAs have been found out to be highly compatible with plasticized polyvinylchloride membranes. For the present invention this means that the plasticizers contained in the cover strip or the roofing membrane do not migrate to the adhesive layer increasing the risk of deterioration of adhesive properties and delamination of the cover strip from the roofing membrane.
According to one or more embodiments, adhesive layer comprises at least 35 wt.-%, preferably at least 50 wt.-%, more preferably at least 75 wt.-%, even more preferably at least 85 wt.-%, of at least one acrylic polymer AP, based on the total weight of the adhesive layer.
Examples of suitable acrylic monomers for use in the at least one acrylic polymer AP include, for example, (meth)acrylates, (meth)acrylic acid or derivatives thereof, for example, amides of (meth)acrylic acid or nitriles of (meth)acrylic acid, and (meth)acrylates with functional groups such as hydroxyl group-containing (meth)acrylates and alkyl (meth)acrylates.
According to one or more embodiments, the acrylic polymer AP has been obtained from a monomer mixture comprising at least 45 wt.-%, preferably at least 55 wt.-%, more preferably at least 65 wt.-%, even more preferably at least 75 wt.-%, still more preferably at least 85 wt.-%, based on the total weight of the monomer mixture, of at least one acrylic monomer AM of formula (I):
where

R₁ represents a hydrogen or a methyl group; and
R₂ represents a branched, unbranched, cyclic, acyclic, or saturated alkyl group having from 2 to 30 carbon atoms.

Examples of suitable acrylic monomers of formula (I) include methyl acrylate, methyl methacrylate, ethyl acrylate, ethoxy ethoxy ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate, and their branched isomers, as for example isobutyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, and also cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate or 3,5-dimethyladamantyl acrylate.
Suitable comonomers to be used with the acrylic monomers of formula (I) include, for example, hydroxyl group containing acrylic monomers, such as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl(meth)acrylate, 4-hydroxybutyl butyl(meth)acrylate, 2-hydroxy-hexyl(meth)acrylate, 6-hydroxy hexyl(meth) acrylate, 8-hydroxyoctyl(meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl(meth)acrylate. Further suitable hydroxyl group containing acrylic monomers include (4-hydroxymethyl cyclohexyl)methyl acrylate, polypropylene glycol mono (meth)acrylate, N- hydroxyethyl (meth)acrylamide, and N- hydroxypropyl (meth)acrylamide, esters of hydroxyethyl(meth)acrylate and phosphoric acid, and trimethoxysilylpropyl methacrylate.
According to one or more embodiments, the monomer mixture used for obtaining the at least one acrylic polymer AP comprises not more than 25 wt.-%, preferably not more than 20 wt.-%, such as 0.01 - 15 wt.-%, preferably 0.1 - 10 wt.-%, based on the total weight of the monomer mixture, of at least one hydroxyl group containing acrylic monomer.
Further suitable comonomers for the synthesis of the at least one acrylic polymer AP include vinyl compounds, such as ethylenically unsaturated hydrocarbons with functional groups, vinyl esters, vinyl halides, vinylidene halides, nitriles of ethylenically unsaturated hydrocarbons, phosphoric acid esters, and zinc salts of (meth)acrylic acid. Examples of especially suitable vinyl compounds include, for example, maleic anhydride, styrene, styrenic compounds, acrylic acid, beta-acryloyloxypropionic acid, vinylacetic acid, fumaric acid, crotonic acid, aconitic acid, trichloroacrylic acid, itaconic acid, vinyl acetate, and acryloyl morpholine.
According to one or more embodiments, the monomer mixture used for obtaining the at least one acrylic polymer AP comprises at least 0.1 wt.-%, preferably at least 0.5 wt.-%, such as 0.1 - 20 wt.-%, preferably 0.5 - 15 wt.%, based on the total weight of the monomer mixture, of at least one vinyl compound, preferably selected from the group consisting of maleic anhydride, styrene, styrenic compounds, (meth)acrylamides, N-substituted (meth)acrylamides, acrylic acid, beta-acryloyloxypropionic acid, vinylacetic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, trichloroacrylic acid, itaconic acid, vinyl acetate, and amino group-containing (meth)acrylates.
According to one or more embodiments, the at least one acrylic polymer AP 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 0 °C, preferably below - 20 °C and/or a number average molecular weight (Mn) determined by gel permeation chromatography using polystyrene as standard of 50'000 - 1'000'000 g/mol, preferably 100'000 - 750'000 g/mol, more preferably 150'000 - 500'000 g/mol.
According to one or more embodiments, the pressure sensitive adhesive is a water- or solvent-based acrylic pressure sensitive adhesive.
The term "water-based pressure sensitive adhesive" designates in the present disclosure pressure sensitive adhesives, which have been formulated as an aqueous dispersion, an aqueous emulsion, or as an aqueous colloidal suspension. The term "aqueous dispersion" or "aqueous emulsion" refers to dispersions or emulsions containing water as the main continuous (carrier) phase. Typically, a water-based pressure sensitive adhesive comprises surfactants to stabilize the hydrophobic polymer particles and to prevent these from coagulating with each other.
The term "solvent-based pressure sensitive adhesive" designates in the present disclosure pressure sensitive adhesives comprising acrylic polymers, which are substantially completely dissolved in the organic solvent(s). Typically, the organic solvent(s) comprise at least 20 wt.-%, preferably at least 30 wt.-%, more preferably at least 40 wt.-%, of the total weight of the solvent-based pressure sensitive adhesive composition. The term "organic solvent" refers in the present document to organic substances that are liquid at a temperature of 25 °C, can dissolve another substance at least partially, and have a standard boiling point of not more than 225 °C, preferably not more than 200 °C. The term "standard boiling point" refers in the present disclosure to boiling point measured at a pressure of 1 bar. The standard boiling point of a substance or composition can be determined, for example, by using an ebulliometer.
Suitable organic solvents for the solvent-based pressure sensitive adhesives include, for example, alcohols, aliphatic and aromatic hydrocarbons, ketones, esters, and mixtures thereof. It is possible to use only a single organic solvent or a mixture of two or more organic solvents. Suitable solvent-based pressure sensitive adhesive compositions are substantially water-free, for example, containing less than 10 wt.-%, preferably less than 5 wt.-%, more preferably less than 1 wt.-% of water, based on the total weight of the solvent-based pressure sensitive adhesive.
According to one or more embodiments, the adhesive layer has a thickness 50 - 500 µm, preferably 100 - 350 µm. Such thicknesses of adhesive layer have been found out to provide sufficiently high peel strengths between the carrier layer of the cover strip and the metal edge flashing and between the carrier layer and the roofing membrane.
According to one or more embodiments, the method comprises a further step V) comprising applying a sealant composition to at least one of the long and/or short edges of the carrier layer. The sealant may be used to improve the watertightness of the seam formed between the self-adhering cover strip and the underlying surface.
Suitable sealants for use in step V) include, for example, one-component polyurethane and silicone sealants. Particularly suitable polyurethane sealants include moisture-curing zero VOC, permanently elastic, super strong, very low permeability, all-in-one hybrid polyurethane sealants. Especially suitable silicone sealants include self-leveling, one-component, ultra-low modulus, elastomeric, and neutral cure silicone sealants.
Suitable polyurethane and silicone sealants are commercially available, for example, under the trade name of Sikabond^® and Sikasil^®, such as Sikabond^® T100 and Sikasil^® 728 SL (all from Sika AG).
According to one or more embodiments, the cover strip or the carrier layer of the self-adhering cover strip comprises at least one polymer P1 selected from polyvinylchloride (PVC), polyolefin, halogenated polyolefin, rubber, and ketone ethyl ester (KEE) and/or the roofing membrane comprises at least one polymer P2 selected from polyvinylchloride (PVC), polyolefin, halogenated polyolefin, rubber, and ketone ethyl ester (KEE).
Suitable PVC resins for use polymers P1 and P2 include ones having a K-value determined by using the method as described in ISO 1628-2-1998 standard in the range of 50 - 85, preferably 65 - 75. The K-value is a measure of the polymerization grade of the PVC-resin and it is determined from the viscosity values of the PVC homopolymer as virgin resin, dissolved in cyclohexanone at 30° C.
Term "polyolefin" refers in the present disclosure to homopolymers and copolymers obtained by polymerization of olefins. Suitable polyolefins for use as the at least one polymer include, for example, thermoplastic polyolefins (TPO, TPO-E).
Especially suitable thermoplastic polyolefins include heterophasic propylene copolymers. These are heterophasic polymer systems comprising a high crystallinity base polyolefin and a low-crystallinity or amorphous polyolefin modifier. The heterophasic phase morphology consists of a matrix phase composed primarily of the base polyolefin and a dispersed phase composed primarily of the polyolefin modifier. Suitable commercially available heterophasic propylene copolymers include reactor blends of the base polyolefin and the polyolefin modifier, also known as "in-situ TPOs" or "reactor TPOs or "impact copolymers (ICP)", which are typically produced in a sequential polymerization process, wherein the components of the matrix phase are produced in a first reactor and transferred to a second reactor, where the components of the dispersed phase are produced and incorporated as domains in the matrix phase. Heterophasic propylene copolymers comprising polypropylene homopolymer as the base polymer are often referred to as "heterophasic propylene copolymers (HECO)" whereas heterophasic propylene copolymers comprising polypropylene random copolymer as the base polymer are often referred to as "heterophasic propylene random copolymers (RAHECO)". The term "heterophasic propylene copolymer" encompasses in the present disclosure both the HECO and RAHECO types of the heterophasic propylene copolymers.
Suitable commercially available heterophasic copolymers include, for example, "reactor TPOs" and "soft TPOs" produced with LyondellBasell's Catalloy process technology, which are available under the trade names of Adflex^®, Adsyl^®, Clyrell^®, Hifax^®, Hiflex^®, and Softell^®, such as Hifax^® CA 10A, Hifax^® CA 12A, and Hifax^® CA 60 A, and Hifax^® CA 212 A. Further suitable heterophasic propylene copolymers are commercially available under the trade name of Borsoft^® (from Borealis Polymers), such as Borsoft^® SD233 CF.
Further suitable polyolefins include propylene homopolymers, for example, isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), and homopolymer polypropylene (hPP), and propylene copolymers, especially propylene-α-olefin copolymers. Ethylene copolymers, for example, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE), and ethylene copolymers, particularly ethylene-α-olefin copolymers, may also be suitable for us as the at least one polymer.
Suitable rubbers for use as the at least one polymer include, for example, styrene-butadiene rubber (SBR), ethylene propylene diene monomer (EPDM) rubber, butyl rubber, polyisoprene, polybutadiene, natural rubber, polychloroprene rubber, ethylene-propylene rubber (EPR), nitrile rubber, acrylic rubber, ethylene vinyl acetate rubber, and silicone rubber, and chemically crosslinked versions of these rubbers.
According to one or more embodiments, the cover strip or the carrier layer of the self-adhering cover strip comprises at least 25 wt.-%, preferably at least 50 wt.-%, more preferably at least 60 wt.-%, based on the total weight of the cover strip or the carrier layer, of the at least one polymer P1.
The thickness of the covering strip and the carrier layer of the self-adhering covering strip may be in the range of 0.1 - 5 mm, preferably 0.3 - 3.5 mm, more preferably 0.5 - 3 mm. The thickness can be determined by using the measurement method as defined in DIN EN 1849-2 standard.
According to one or more embodiments, the cover strip or the carrier layer of the self-adhering cover strip has a width of 10 - 100 cm, preferably 15- 75 cm and/or the first long edge portion of the lower major surface of the cover strip or the carrier layer has a width of 2.5 - 35 cm, preferably 5 - 30 cm.
The edge metal flashing is preferably a L-shaped non-coated metal sheet or a coated metal sheet comprising less than 2.5 wt.-%, preferably less than 1 wt.-%, based on the total weight of the coating, of the at least one polymer P1.
The edge metal flashing can be affixed to the roof substrate by using adhesive bonding or mechanical fastening means, such as nails or screws.
The roofing membrane can be a single- or multi-ply-membrane. The term "single-ply membrane" designates in the present disclosure membranes comprising one single waterproofing layer whereas the term "multi-ply membrane refers to membranes comprising more than one waterproofing layer having same or different compositions.
Single- and multi-ply membranes are known to a person skilled in the art and they may be produced by any conventional means, such as by way of extrusion or co-extrusion, calendaring, or by spread coating.
According to one or more embodiments, the roofing membrane comprises at least one waterproofing layer comprising at least 25 wt.-%, preferably at least 50 wt.-%, more preferably at least 60 wt.-%, of the at least one polymer P2.
According to one or more embodiments, the roofing membrane has a thickness of 0.5 - 5 mm, preferably 0.75 - 3.5 mm, more preferably 1 - 3 mm, even more preferably 1 - 2.5 mm.
According to one or more embodiments, the polymers P1 and P2 are compatible with each other, preferably at least partially miscible with each other.
By the polymers components being "compatible" with each other is understood to mean that the properties of a blend composed of the two polymers are not inferior to those of the individual polymer components. By the polymer components being "miscible" is understood to mean that a polymer blend composed of the two polymers has a negative Gibbs free energy and heat of mixing. Polymer blends composed of entirely miscible polymer components tend to have one single glass transition point, which can be measured using dynamic mechanical thermal analysis (DMTA). The glass transition point can be determined, for example, as the peak of the measured tan delta curve (ratio of storage and loss moduli).
According to one or more preferred embodiments, polymers P1 and P2 selected from polyvinylchloride or polyolefins, preferably from polyvinylchloride or thermoplastic polyolefins (TPO).
The preferences given above for the cover strip, self-adhering cover strip, reactive adhesive, metal edge flashing, and roofing membrane apply for all other subjects of the present invention unless specified otherwise.
Another aspect of the present invention is a roof system comprising:

i. A roof substrate (1),
ii. A roofing membrane (2) covering at least a portion of an upper major surface of the roof substrate (1),
iii. An edge metal flashing (3), wherein a portion of the roofing membrane (2) is trapped between the edge metal flashing (3) and the roof substrate (1), and
iv. A cover strip (4) or a self-adhering cover strip (5),

wherein the roof system further comprises a sealing strip (6) having upper and lower major surfaces limited between short and long edges, wherein the sealing strip (6) is adhesively bonded via its lower major surface to a portion of an upper major surface of the edge metal flashing (3) using a reactive adhesive (7) and wherein the cover strip (4) has upper and lower major surfaces limited between short and long edges and wherein a first long edge portion (8) of the lower major surface of the cover strip (4) is heat-welded to a portion of the upper major surface of the sealing strip (6) and a second long edge portion (8') of the lower major surface of the cover strip is heat-welded to a portion of an upper major surface of the roofing membrane (2),
or wherein the self-adhering cover strip (5) comprises a carrier layer (9) having upper and lower major surfaces limited by short and long edges and an adhesive layer (10) of a pressure sensitive adhesive coated directly to and covering at least a portion of the lower major surface of the carrier layer and wherein a first long edge portion (11) of the lower major surface of the carrier layer (9) is bonded to a portion of an upper major surface of the metal edge flashing (3) by the adhesive layer (10) and a second long edge portion (11') of the lower major surface of the carrier layer (9) is bonded to a portion of an upper major surface of the roofing membrane (2) by the adhesive layer (10).

Preferred embodiments of the roofing membrane, edge metal flashing, cover strip, sealing strip, and the self-adhering cover strip have already been discussed above.
The roof substrate can be any conventional roof substrate, such as a concrete, metal, or wood deck.
According to one or more embodiments, the roof system further comprises:
v. A sealant composition (11) covering at least one of the long and/or short edges of the carrier layer (8), preferably both long and short edges of the carrier layer (8).
The roof system may comprise further elements, such as films, membranes, or boards, such as vapor barriers, vapor breathers, insulation boards, or cover panels. A skilled person is familiar with these types of elements and knows where they are used in a roof system.

Experiments

Example 1

A cover strip was used to cover/seal a joint formed between a Kynar painted metal sheet and a plasticized polyvinylchloride roofing membrane.
A sealing strip having a width of 400 mm was cut from a roll of SikaPlan^® WP Tape-200 and bonded to an upper surface of the metal sheet using a reactive acrylic adhesive (SikaFast^® 3341). One of the long edge portions of the cover strip was then bonded an upper surface of the sealing strip and the other long edge portion was bonded to an upper surface of the roofing membrane by hot air welding. A sample of the plasticized PVC roofing membrane having a width of 400 mm was used as the cover strip.
The strength of the adhesive bond between the sealing strip and the painted metal sheet was determined with a 90° peel strength measurement. According to the results, the peel strength of the sealing strip from the painted metal sheet was > 200 N/50 mm. The test specimens composed of the cover and sealing strips, painted metal sheet, and the roofing membrane were stored for 7 days before measuring of the peel strengths.

Example 2

A strip of a plasticized PVC membrane having a layer of a pressure sensitive adhesive and a width of 400 mm was used to cover/seal a joint formed between a Kynar painted metal sheet and a plasticized PVC roofing membrane. Both long and short edges of the cover strip were sealed with a silicone sealant (Sikasil^® 728 SL).
The strength of the adhesive bonds between the cover strip and the painted metal sheet and between the cover strip and the roofing membrane were determined with a 90° peel strength measurement. According to the results, the peel strength of the cover strip from the painted metal sheet was 20 N/50 mm whereas the peel strength of cover strip from the roofing membrane was20 N/50 mm. The test specimen composed of the cover strip, painted metal sheet, and the roofing membrane was stored for 7 days before measuring the peel strengths.

Claims

A method for installing a cover strip between an edge metal flashing and a roofing membrane, the method comprising steps of:
i) Providing a roof assembly comprising a roof substrate, an edge metal flashing, and a roofing membrane, wherein a portion of the roofing membrane is trapped between the edge metal flashing and the roof substrate,

ii) Providing a sealing strip having upper and lower major surfaces limited between short and long edges,

iii) Adhesively bonding the sealing strip via its lower major surface to a portion of an upper major surface of the edge metal flashing using a reactive adhesive,

iv) Providing a cover strip having upper and lower major surfaces limited between short and long edges,

v) Heat-welding a first long edge portion of the lower major surface of the cover strip to a portion of an upper major surface of the sealing strip and a second long edge portion of the lower major surface of the cover strip to a portion of an upper major surface of the roofing membrane,
or
I) Providing a roof assembly comprising a roof substrate, an edge metal flashing, and a roofing membrane, wherein a portion of the roofing membrane is trapped between the edge metal flashing and the roof substrate,

II) Providing a self-adhering cover strip comprising a carrier layer having upper and lower major surfaces limited by short and long edges and a layer of a pressure sensitive adhesive coated directly to and covering at least a portion of the lower major surface of the carrier layer,

III) Positioning the self-adhering cover strip such that the adhesive layer covering a first long edge portion of the lower major surface of the carrier layer is directly connected to a portion of an upper major surface of the edge metal flashing and the adhesive layer covering a second long edge portion of the lower major surface of the carrier layer is directly connected to a portion of an upper major surface of the roofing membrane,

IV) Pressing the carrier layer against the roof substrate to effect adhesive bonding between the opposing surfaces of the carrier layer and the edge metal flashing and between opposing surfaces of the carrier layer and the roofing membrane, and

V) Optionally applying a sealant composition to at least one of the long and/or short edges of the carrier layer.
The method according to claim 1, wherein the upper major surface of the edge metal flashing and/or the upper major surface of the roofing membrane is/are non-primed surface(s).
The method according to claim 1 or 2, wherein step iii) comprises:
iii1) Applying the reactive adhesive to at least a portion of the lower major surface of the sealing strip and/or to a portion of the upper major surface of the edge metal flashing,

iii2) Covering a portion of the upper major surface of the edge metal flashing with the sealing strip such that the applied reactive adhesive forms and interlayer between the edge metal flashing and the sealing strip, and

iii3) Curing the reactive adhesive.
The method according to any one of previous claims, wherein the reactive adhesive is selected from one- and two-component epoxide, acrylic, and polyurethane adhesives.
The method according to any one of previous claims, wherein the pressure sensitive adhesive is an acrylic pressure sensitive adhesive, preferably a non-crosslinked acrylic pressure sensitive adhesive.
The method according to any one of previous claims, wherein the cover strip or the carrier layer of the self-adhering cover strip comprises at least one polymer P1 selected from polyvinylchloride, polyolefin, halogenated polyolefin, rubber, and ketone ethyl ester.
The method according to claim 6, wherein the cover strip or the carrier layer of the self-adhering cover strip comprises at least 25 wt.-%, preferably at least 50 wt.-%, of the at least one polymer P1.
The method according to any one of previous claims, wherein the roofing membrane comprises at least one polymer P2 selected from polyvinylchloride, polyolefin, halogenated polyolefin, rubber, and ketone ethyl ester.
The method according to claim 8, wherein the roofing membrane comprises at least 25 wt.-%, preferably at least 50 wt.-%, of the at least one polymer P2.
The method according to 8 or 9, wherein polymers P1 and P2 are selected from polyvinylchloride and polyolefin, preferably from polyvinylchloride and thermoplastic polyolefin elastomer (TPO).
The method according to any one of previous claims, wherein the cover strip or the carrier layer of the self-adhering cover strip has a width of 10 - 100 cm, preferably 15- 75 cm.
The method according to any one of previous claims, wherein the first long edge portion of the lower major surface of the cover strip or the carrier layer of the self-adhering cover strip has a width of 2.5 - 35 cm, preferably 5-30 cm.
The method according to any one of claims 6-12, wherein the edge metal flashing is a non-coated metal sheet or a coated metal sheet, wherein the coating comprises less than 2.5 wt.-%, preferably less than 1 wt.-%, of the at least one polymer P1.
A roof system comprising:
i. A roof substrate (1),

ii. A roofing membrane (2) covering at least a portion of an upper major surface of the roof substrate (1),

iii. An edge metal flashing (3), wherein a portion of the roofing membrane (2) is trapped between the edge metal flashing (3) and the roof substrate (1), and

iv. A cover strip (4) or a self-adhering cover strip (5),

wherein the roof system further comprises a sealing strip (6) having upper and lower major surfaces limited between short and long edges, wherein the sealing strip (6) is adhesively bonded via its lower major surface to a portion of an upper major surface of the edge metal flashing (3) using a reactive adhesive (7) and wherein the cover strip (4) has upper and lower major surfaces limited between short and long edges and wherein a first long edge portion (8) of the lower major surface of the cover strip (4) is heat-welded to a portion of the upper major surface of the sealing strip (6) and a second long edge portion (8') of the lower major surface of the cover strip is heat-welded to a portion of an upper major surface of the roofing membrane (2),

or wherein the self-adhering cover strip (5) comprises a carrier layer (9) having upper and lower major surfaces limited by short and long edges and an adhesive layer (10) of a pressure sensitive adhesive coated directly to and covering at least a portion of the lower major surface of the carrier layer and wherein a first long edge portion (11) of the lower major surface of the carrier layer (9) is bonded to a portion of an upper major surface of the metal edge flashing (3) by the adhesive layer (10) and a second long edge portion (11') of the lower major surface of the carrier layer (9) is bonded to a portion of an upper major surface of the roofing membrane (2) by the adhesive layer (10).
The roof system according to claim 14 further comprising:
v. A sealant composition covering at least one of the long and/or short edges of the carrier layer (9).