METHODS OF MAKING ROOF LAMINATES WITH REMOVABLE PROTECTIVE SHEETS AND ROOF LAMINATES

A roof laminate (10) includes a roof membrane (12, 100, 200, 300) and a protective sheet (14, 114, 214, 314) removably affixed thereto. The surface (20) of the roof membrane (12, 100, 200, 300) can be protected from dirt, scratches and scrapes by a protective sheet (14, 114, 214, 314) which also provides other beneficial attributes that aid an installer. The membrane (12, 100, 200) and the sheet (14, 114, 214) are heat laminated together in the absence of adhesive and tackifiers. Alternatively, the membrane (12, 300) and the sheet (14, 314) are surface treated and then brought into contact with one another in the absence of adhesive and tackifiers. The sheet (14, 114, 214, 314)) may be single layer or include at least a first layer (30) directly secured to a second layer (32). The first layer (30) provides at least one of UV protection, anti-slip, and anti-glare to the roof laminate (10) and so aids the installer in at least one of those respects. The second layer (32) is removably affixed to the roof membrane (12, 100, 200, 300).

BACKGROUND

Membrane roofs are roofs that are covered with a polymeric sheet or membrane. These polymeric membranes can be, for example, polyvinyl chloride (PVC), thermoplastic olefin (TPO), or ethylene propylene diene monomer rubber (EPDM), as well as other materials. The polymeric membrane is positioned over a roof surface and held in place by fasteners, adhesive, or ballast. Adjacent membranes are bonded together along lap seams to form a unitary single sheet of the polymer covering the entire roof.

Generally, roof membranes are either white or black. Theoretically, the membranes could be basically any color. The choice of color may be for aesthetic purposes or to reduce energy costs by reflecting thermal energy. Regardless of color, the appearance following installation is of paramount importance both from an aesthetic standpoint and from a functional standpoint.

When replacing an existing roof, new sheeting is difficult to keep clean. In a re-roofing application, a section of the old roof covering is removed and new roof membrane is immediately installed in its place. This allows the roof to be fully covered each night. As subsequent sections of the old roof are removed, the roofers walk on the newly installed membrane. This can scratch and mar the new membrane.

While these membranes have generally been commercially successful, there remains a need for additional improvements to facilitate their installation and performance.

SUMMARY

Embodiments of the present invention are premised on the realization that during installation of a single-ply roofing membrane, the surface of the membrane can be protected from dirt, scratches and scrapes by a protective sheet which also provides other beneficial attributes that aid an installer. As an advantage, the protective sheet is adhered to the single-ply roofing membrane without adhesive.

To those and other ends, a roof laminate to be secured to a roof deck includes a roof membrane that has a first surface and a second surface and is configured to be secured to the roof deck. A protective sheet is removably affixed to the first surface in the absence of an adhesive and in the absence of a tackifier or other applied chemicals includes at least one layer directly secured to the roof membrane. The protective sheet is removably affixed to the roof membrane and is separable from the roof membrane when a force having a peel value in the range of 0.050 pound per inch to 20 pounds per inch (0.089 kilogram to 3.5 kilograms per linear centimeter) is applied to the protective sheet.

In one embodiment, a first layer is directly secured to a second layer, and the second layer is removably affixed to the roof membrane. One or both the first layer and the second layer aid the installer during installation.

In one embodiment, the protective sheet is removably affixed to the roof membrane and is separable from the roof membrane when a force having a peel value of at least 0.01 pounds per inch (0.002 kilogram per centimeter) is applied to the protective sheet.

According to one aspect, there is a method of manufacturing a roof laminate. The method includes heating one or both of a membrane and a protective sheet. While hot, the method further includes pressing the membrane and the protective sheet together in the absence of adhesive and in the absence of a tackifier or other applied chemicals between the membrane and the protective sheet. The pressure and heat being high enough to removably secure the protective sheet to the membrane but permits its removal following installation.

In one embodiment, pressing the membrane and the protective sheet together includes applying a pressure in the range of 30 to 300 pounds per linear inch (5.4 to 53.5 kilograms per linear centimeter) to the membrane and the protective sheet.

In one embodiment, pressing the membrane and the protective sheet together includes applying a pressure in the range of 30 to 100 pounds per linear inch (5.4 to 17.9 kilograms per linear centimeter) to the membrane and the protective sheet.

In one embodiment, pressing the membrane and the protective sheet together includes applying a pressure to the membrane and the protective sheet for 0.001 second to 2 seconds.

In one embodiment, heating includes heating at least one of the membrane and the protective sheet to a temperature between 100° F. (37.8° C.) and 400° F. (204° C.) while applying pressure in any one of the above mentioned ranges.

According to one aspect, there is a method of manufacturing a roof laminate. The method includes surface treating one or both of a membrane and a protective sheet. After treatment, the method further includes pressing the membrane and the protective sheet together in the absence of adhesive and in the absence of a tackifier or other applied chemicals between the membrane and the protective sheet.

In one embodiment, pressing the membrane and the protective sheet together includes applying a pressure in the range of 1 to 200 pounds per linear inch (0.2 to 36 kilogram per linear centimeter) to the membrane and the protective sheet.

In one embodiment, surface treating includes at least one of plasma treatment, coronal discharge, and flame treatment.

The objects and advantages of embodiments of the present invention will be further appreciated in light of the following detailed description and drawings in which:

DETAILED DESCRIPTION

To these and other ends and with reference toFIG. 1, a roof laminate10includes a single ply roof membrane12and a release sheet or protective sheet14. The roof laminate10is to be installed onto a roof, such as a roof deck16. In that regard, multiple roof laminates10may be positioned in an overlapping relationship (shown inFIGS. 5 and 6and described below) during installation of a new roof on the roof deck16. The roof membrane12includes a first surface18and a second surface20. The first surface18faces the roof deck16and may contact it during installation, and the second surface20is intended to be exposed to weather following installation and so faces in a direction away from the roof deck16. The roof laminate10may be installed on the roof deck16with mechanical fasteners (not shown), with an adhesive (not shown)(applied during installation or factory applied) between the membrane12and roof deck16, or by other means.

The protective sheet14includes a first surface22and a second surface24, which rests on and covers the second surface20of roof membrane12. The protective sheet14may be affixed directly to the roof membrane12. The protective sheet14is in continuous and direct contact with the roof membrane12. That is, no materials are placed between the protective sheet14and the roof membrane12. The protective sheet14is intended to be removed following installation of a new roof and thus temporarily protects the second surface20of the roof membrane12during installation of the roof laminate10on the deck16. For example, the protective sheet14may prevent damage to the roof membrane12due to roofing installers walking on the protective sheet14and not on the membrane12. Removing the protective sheet14exposes the second surface20of the roof membrane12. The protective sheet14is formed with multiple layers, each layer providing at least one beneficial characteristic designed to aid an installer and is described in detail below.

The roof membrane12can be formed from a polymer. By way of example only, the roof membrane12may be made of polyvinyl chloride (PVC), thermoplastic olefin (TPO), ethylene propylene diene monomer (EPDM), rubbers, polyethylene (PE), (PET), polypropylene (PP), as well as other polyolefins. While these are specific exemplary materials for the roof membrane12, it will be appreciated that there are other materials not specifically identified that may find utility as the roof membrane12. The roof membrane12can have a bottom fibrous surface referred to as fleeceback, which improves bond strength in a fully adhered system, which is with an adhesive applied between the fleeceback and the roof deck16. The roof membrane12is preferably white or slightly off-white, though it can be any color. Embodiments of the present invention are most useful when the membrane12is a lighter color, such as white or off-white.

The roof membrane12is generally rectangular and can be manufactured to a variety of sizes. By way of example only, the roof membrane12can be as narrow as 5 feet (about 1.5 meters) to as wide as 40 feet (12 meters). Length can be from 50 feet (15 meters) to 100 feet (30.5 meters) or more. The roof membrane12has a thickness effective for use as a roof cover, for example, from 20 mils to 160 mils (0.5 mm to 4.2 mm) thick, and by way of additional example from 40 mils to 160 mils (1 mm to 4.2 mm) thick. The roof membrane12is water insoluble and designed to withstand natural environmental conditions for prolonged periods of time, for example at least 15 years.

The multiple layers of the protective sheet14are polymeric sheets that can be formed from a variety of different polymers. One or all of the layers may be formed from a non-environmentally degradable polymer. These materials may include any one of the materials listed above for the roof membrane12and also include polyethylene (including low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE)), polypropylene (PP), polyamide (i.e., nylon), polyester, polyacrylate, polymethacrylate, polyvinylchloride (PVC), polyvinylidene chloride (PVDC), and combinations thereof.

While the protective sheet14may be a single layer, such as that shown and described in U.S. Pat. No. 8,833,037, in one embodiment, and with reference toFIG. 2, the protective sheet14may include layers30,32, which may appear as separate films or coatings that are stacked upon one another. For example, inFIG. 2, the protective sheet14consists of two layers30,32that are bonded together. Each layer30,32may provide the laminate10with a different characteristic designed to aid the installer. Although not shown, layer32may be stacked on layer30and so form the surface22of the protective sheet14. That is, the order of the layers30,32may be altered depending on the desired attribute of the surface22. Once the installation is complete, the layers30,32are removed. This may be achieved by removing both in a single operation that removes layers30and32. Alternatively, removal of layer30may be achieved before removal of layer32from the membrane12.

In one embodiment, the layer30may provide color to the protective sheet14. Although the protective sheet14can be clear, it is preferable that it be tinted with a color that is distinguishable from the color of the roof membrane12. For example, if the roof membrane12is white, the protective sheet14is preferably any color other than clear or white, such as green, red, blue or yellow. A pigment or dye may be added to the layer30and/or32during its manufacture to provide the color for the protective sheet14. In addition, and with reference toFIG. 6, by way of example, the color may vary across the width of the layer30. For example, the layer30may include at least two different colors. The color in the layer30may be utilized to produce text or other indicia or information in the protective sheet14. As shown, the protective sheet14may include advertising information but may also include instructions, warranty information, and other text/symbols.

With continued reference toFIG. 2, the other layer32of the layers30and32may provide UV protection for the protective sheet14, and for the roof laminate10prior to removal of the protective sheet14. This may be achieved for a short-term weather resistance, for example, a duration of 1 day to 2 years or until the sheet14is removed after installation. UV protection may be obtained by the addition of one or more antioxidants, UV absorber and light stabilizer additives, and light effective pigments to the layer32. By way of example only, antioxidants may include hindered phenols, thiosynergists, hydroxylamines, phosphates, and alpha-tocopherol. Commercially available antioxidants include Irganox® and Irgafos® from BASF; Anox®, Lowinox® and Weston® from Addivant; Songnox® from Songwon; Evernox® and Everfos® from Everspring; BNX® from Mayzo; Thanox® from Rianlon. In addition, or as an alternative, UV protection may be achieved by addition of UV absorbers and light stabilizers, which may include, for example, benzotriazole, hydroxybenzoate, benzophenone, triazine, and hindered amines of various molecular weights. These additives are commercially available from BASF under the brand names Tinuvin® and Chimassorb® and from Solvay under the brand name Cyasorb®, from Sabo under the brand name SaboSTAB®, from Songwon under the brand name of Songsorb®, from Mayzo under the brand name of BLS®, from Everspring under the brand name of EverSTAB®, from Rianlon under the brand of Thasorb®, and from Addivant under the brand of Lowilite. In addition, light reflective pigments can be used to screen UV light, which may include, for example, titanium dioxide. These pigments are commercially available as Ti-Pure® from Chemours, as Kronos® TiO2 from Kronos, as Tiona® from Cristal, as Troxide® from Huntsman, and as Tronox® TiO2 from Tronox.

In one embodiment and with reference toFIG. 3, the protective sheet14may include one or both of the layers30,32described above inFIG. 2. The protective sheet14may further include anti-slip layer34that is intended to be exposed during installation of the laminate10on the roof deck16. The anti-slip layer34is designed to improve traction, particularly with foot traffic. By way of example only, a static, dry coefficient of friction may be greater than 0.45 and a static wet coefficient of friction may be greater than 0.6. The coefficient of friction measurements may be completed according to the ASTM D1894-14 Standard Test Method for Static and Kinetic Coefficients Of Friction Of Plastic Film and Sheeting.

With reference toFIGS. 1 and 3, the anti-slip layer34may be formed in a pattern36in or on the protective sheet14, such as a diamond tread illustrated inFIG. 1. InFIG. 3, the pattern36may include raised areas40separated by recessed areas42. This localized relative thickness difference in the anti-slip layer34produces a physical texturing on the surface22of the protective sheet14. In addition, or as an alternative, the anti-slip layer34may include or be formed entirely by rubbery or tacky polymers, such as block copolymers (e.g., SIS and SBS), amorphous poly-alpha olefin, vinyl acetate/ethylene (VAE) and ethylene-vinyl acetate (EVA). These materials may be formed in a uniform coating on the layer30or32as the anti-slip layer34or they may be formed in discontinuous patterns, such as the raised and depressed areas40,42in the pattern36on the layer30.

With reference toFIG. 4, in one embodiment of the invention, the protective sheet14may include one or both of the layers30and32described above with regard toFIG. 2with an anti-glare layer44forming the surface22. However, rather than a three-layer protective sheet14, as shown, the protective sheet14may include one of layers30,32and the anti-glare layer44. The anti-glare layer44is designed to reduce reflection of light at any angle of observation that initially impinges on the surface22. In this way, the installation crew is not exposed to light reflection from the protective sheet14. The anti-glare layer44may be achieved by increasing surface roughness of the layer30to a range of from 5 μm to 200 μm.

Alternatively, the anti-glare layer44may be produced by a separate coating (not shown) on the layer30, which may be formed by low crystallinity polymers, such as amorphous poly-alpha olefin, vinyl acetate/ethylene (VAE) and ethylene-vinyl acetate (EVA), acrylic, or silicone. As shown inFIG. 7, the anti-glare layer44may include anti-glare regions46separated by regions48in a pattern58on the surface22. The anti-glare layer44may have an intermediate gloss of less than 20 gloss units (GU) when measured at 60° in accordance with the ASTM D2457-13 Standard Test Method for Specular Gloss of Plastic Films and Solid Plastics. In one embodiment, the layer34or layer44may have both anti-slip and anti-glare characteristics in the above-identified ranges.

With reference toFIGS. 2-4, the protective sheet including one or more of the layers30,32,34, and44may be made by co-extrusion, co-blowing, or a heat-lamination process, described below with reference toFIGS. 11 and 12. Advantageously, the laminate10may be produced without an adhesive between the roof membrane12and the protective sheet14. The laminate10may therefore be adhesive free. When installed and the protective sheet14is removed, no residual materials adhere to the roof membrane12. Dirt and other debris are less likely to stick to the exposed surface of the membrane12in the absence of residual adhesive. Moreover, the laminate10is of substantially less weight making it less strenuous to install.

To apply the roof membrane12over the roof deck16and with reference toFIGS. 5 and 6, two adjacent roof laminates50and52are laid down side by side over the roof deck16. The roof membrane12of first laminate50is fixed to the roof deck16, generally using adhesives (not shown) or fasteners (not shown). The second roof laminate52is rolled out and adhered to the roof deck16adjacent the first laminate50with an edge54of the second laminate52overlapping an edge56of the first laminate50. The overlapping edges54and56are adhered or welded to each other.

With the embodiment shown inFIGS. 5 and 6, an edge portion60of the protective sheet14on the first roof laminate50is pulled up enough to allow an edge62of the second protective sheet14to overlap the exposed edge56of the first laminate50. The overlapping edges54and56are then bonded together by heat or adhesive. As shown inFIG. 6, the edge portion60of the protective sheet14from the first roof laminate50is then folded back and rests over an overlapped portion64of the two membranes12.

As shown inFIG. 1, the protective sheet14covers the entire roof membrane12from edge to edge. However, as shown inFIG. 8, the protective sheet14may cover the entire membrane except for 4- to 12-inch (10 to 31 centimeters) portions on either edges66and70of the roof laminate10. Alternatively, as shown inFIGS. 1 and 9, the protective sheet14can include an overlap region72at which two separate protective sheets14may be bonded together.

InFIG. 10, perforations80,82may be formed alongside edges84and86. The perforations80,82allow strips90and92to be removed from the protective sheet14leaving the field portion94of the protective sheet14protecting the membrane12. These embodiments allow the adjacent membranes12to be bonded together while the field portion94, shown inFIG. 10, remains on the membrane12.

Once the roof is fully installed, all of the protective sheets14are pulled away from the membrane12leaving an exposed white or colored membrane surface free of scratches and dirt.

In one embodiment and with reference toFIG. 11, the roof laminate10is formed by heating a membrane100, which may be supplied via a stock roll102. As shown, the membrane100is pulled from the roll102according to arrow104around roller106and proximate heater110. The heater110may be an IR heater capable of heating the membrane100to a temperature of between 100° F. (37.8° C.) and 400° F. (204° C.). The temperature of the membrane100may be dependent on the material of the membrane100as well as other process conditions described below. By way of further example only, the heater110may heat the membrane100so that upon exiting a heat zone108, the membrane100has a temperature of about 240° F. (about 116° C.) (i.e., within a few degrees of 240° F. (116° C.), e.g., plus or minus 3° F. (plus or minus 1.7° C.)). The heater110heats the membrane100prior to forming the roof laminate10.

At the same time, a roll112is unwound and a sheet114from the roll112passes around roller116according to arrow120. Although not shown inFIG. 11, the sheet114may be a multilayer protective sheet14shown, for example, inFIGS. 2-4or a single layer sheet. Multilayer sheets may be preassembled prior to being assembled with the membrane100as shown inFIG. 11. In that regard, each of the sheet114and the membrane100contact one another at122. That is, at122the sheet114is stacked against the membrane100. No adhesive, tackifiers, or chemicals are applied to or between the sheet114and the membrane100. The sheet114is not intentionally stretched prior to or during contact with the membrane100at122. As an example, each of membrane100and the sheet114contact one another at122and pass through a nip roller124and so are pressed together to form the laminate10. The nip roller122may apply pressure in a range from 30 pounds per linear inch to 300 pounds per linear inch (5.4 kilograms to 54 kilograms per centimeter). By way of further example, the applied pressure may range from 30 pounds per linear inch to 100 pounds per linear inch (5.4 kilograms to 18 kilograms per linear centimeter). The stacked membrane100and the sheet114may experience the applied pressure for a controlled amount of dwell time. For example, the dwell time may be 0.001 second to 2 seconds, which may depend on the line speed. Once the protective sheet114is heat laminated to the membrane100, the roof laminate10is formed into a roll38(shown inFIG. 7). The laminate10is adhesive free (e.g.,FIG. 2).

In one embodiment, the line speed as is represented by arrows104and120may be in the range of 20 to 100 feet per minute (6 to 30 meters per minute). The rate at which each of the membrane100and sheet114are pulled from their respective rolls102,112may be the same. By way of further example only, the line speed may be from about 30 feet per minute (about 9 meters per minute) to about 33 feet per minute (about 10 meters per minute) (i.e., within a few feet per minute, plus or minus 2 feet per minute (0.6 meter per minute)).

In an alternative embodiment, and with reference toFIG. 12, the roof laminate10is formed by heating a membrane200, which may be supplied via a stock roll202. As shown, the membrane200is pulled from the roll202according to arrow204around drum or roller206. The roller206may be heated to a temperature of between 100° F. (37.8° C.) and 400° F. (204° C.) and so heat the membrane200while the membrane200is in contact with the roller206. In one embodiment, the roller206is set to a temperature of about 300° F. (about 149° C.) (i.e., within a few degrees, plus or minus 3° F. (−16.1° C.)). The temperature of the membrane200may be dependent on the material of the membrane200as well as other process conditions described below. The roller206heats the membrane200prior to forming the roof laminate10.

At the same time, a sheet214is pulled from a roll212and passes around roller216according to arrow220. Similar to sheet114ofFIG. 11, although not shown inFIG. 12, the sheet214may be a multilayer protective sheet14shown, for example, inFIGS. 2-4or a single layer sheet. Multilayer sheets may be preassembled prior to being assembled with the membrane200as shown inFIG. 12. The roller216may be heated to a temperature of between 100° F. (37.8° C.) and 400° F. (204° C.) and so heats the sheet214during contact. In one embodiment, the roller216is set to a temperature of about 300° F. (about 149° C.) (i.e., within a few degrees, plus or minus 3° F. (−16.1° C.)). The roller206and the roller216may be heated to different temperatures. The temperature of the sheet214may be dependent on the material of the sheet214as well as other process conditions described below. The roller216heats the sheet214prior to forming the roof laminate10.

Once heated, each of the sheet214and the membrane200contact one another at222. That is, at222the sheet214is stacked against the membrane200. No adhesive, tackifiers, or chemicals are applied to or between the sheet214and the membrane200. The sheet214is not intentionally stretched prior to or during contact with the membrane200at222. As an example, each of membrane200and the sheet214contact one another at222and pass through a nip roller224and so are pressed together to form the laminate10. The nip roller224may apply pressure in a range from 30 pounds per linear inch to 300 pounds per linear inch (5.4 kilograms per linear centimeter to 54 kilograms per linear centimeter). By way of further example, the applied pressure may range from 30 pounds per linear inch to 100 pounds per linear inch (5.4 kilograms per linear centimeter to 18 kilograms per linear centimeter). The stacked membrane200and the sheet214may experience the applied pressure for a controlled amount of dwell time. For example, the dwell time may be 0.001 second to 2 seconds, which may depend on the line speed. Once the protective sheet214is heat laminated to the membrane200, the roof laminate10is formed into a roll38(shown inFIG. 7). The laminate10is adhesive free (e.g.,FIG. 2).

In one embodiment, the line speed as is represented by arrows204and220may be in the range of 20 to 100 feet per minute (6.1 to 30.5 meters per minute). The rate at which each of the membrane200and sheet214are pulled from their respective rolls202,212may be the same. By way of further example only, the line speed may be from about 40 feet per minute (about 12.2 meters per minute) to about 45 feet per minute (about 13.7 meters per minute) (i.e., within a few feet per minute, plus or minus 2 feet per minute (0.61 meter per minute)).

Not being bound by theory, the protective sheet14may adhere to the membrane12via interdiffusion of polymer chains from the protective sheet14into the membrane12, from the membrane12into the protective sheet14, or from each of the protective sheet14and the membrane12into the other of the membrane12and the protective sheet14. That is, heat combined with the pressure may cause a blurring of the interface between the protective sheet14and the membrane12. The amount of interdiffusion adhesion may be dependent on the polymers of the protective sheet14and the membrane12as well as the temperature, pressure, and contact time under pressure at which the surfaces for each are brought into contact with one another to form an interface.

By way of example only and not limitation and with reference toFIGS. 13A, 13B, 13C, and 13D, amounts of interdiffusion adhesion are schematically illustrated at an interface96between a protective sheet88and a membrane98under different heat lamination conditions including at least one of a change in temperature of the protective sheet88and the membrane98and applied pressure. In general, the amount of interdiffusion adhesion increases from the condition shown inFIG. 13Ato the interdiffusion adhesion shown inFIG. 13D. As the amount of interdiffusion adhesion increases, a peel value, which is a measure of force required to separate the protective sheet88from the membrane98, also increases. A procedure for determining a peel value of separation forces between a protective sheet and a membrane is described below with reference to Example 2.

InFIG. 13A, no interdiffusion across the interface96is shown, and so the protective sheet88is only slightly adhered to the membrane98. Thus, a peel value between the protective sheet88and the membrane98with this configuration may be minimal and may be sufficient to resist separation only during handling. InFIG. 13B, the interface96may be represented by contact at the molecular level though there may still be little interdiffusion between the protective sheet88and the membrane98. Thus, a peel value between the protective sheet88and the membrane98may be greater than the configuration shown inFIG. 13A. By way of example only, a peel value may be at least 0.01 pounds per inch (0.002 kilograms per centimeter) and by way of additional example, in the range of 0.01 pounds per inch to 0.5 pounds per inch (0.002 kilograms to 0.009 kilogram per centimeter).

InFIG. 13C, which may represent the result of a heat lamination process, such as that described above, the interface96may include interdiffusion between the protective sheet88and the membrane98such that the interface96is no longer easily discerned. That is, molecules of the protective sheet88may extend across the interface96and into the membrane98. Similarly, molecules of the membrane98may extend across the interface96and into the protective sheet88. This configuration may provide a peel value in the range of 0.1 pounds per inch to 5 pounds per inch (0.02 kilograms per centimeter to 0.9 kilograms per centimeter). InFIG. 13D, the interface96may include interdiffusion between the protective sheet88and the membrane98. Like the interface96inFIG. 13C, the interface96shown inFIG. 13Dmay not be discernible. However, the interdiffusion inFIG. 13Dis greater than the interdiffusion illustrated shown inFIG. 13C. Thus, the penetration and intermingling of the polymers in the protective sheet88and the membrane98is increased such that the depth of penetration of the polymers across the interface96is increased. By way of example only, this configuration may provide a peel value in the range of 0.05 pounds per inch to 20 pounds per inch (0.009 kilogram per centimeter to 3.6 kilograms per centimeter).

As an alternative to a heat lamination process, for example those described above, the protective sheet14may be adhered to the membrane12via a process that produces physical adsorption, which may include Van der Waals interaction. This type of adhesion may be referred to as interfacial adhesion and may not result in interdiffusion. It is contemplated that if the surface properties of the protective sheet14and the membrane12are different, there may be an electrostatic attraction between the two surfaces. Electrostatic attraction may be due to ionic nature of the surfaces or formation of an electric double layer at the interface between the protective sheet14and the membrane12, which results in mutual attraction. Processes that may produce or enhance electrostatic interaction between surfaces may include plasma treatment of surfaces, coronal discharge treatment of the surfaces, or flame surface treatment. These processes may produce an interface such as that shown inFIG. 13AorFIG. 13B.

As an example, and with reference toFIG. 14, the roof laminate10is formed by surface treating a membrane300, which may be supplied via a stock roll302. As shown, the membrane300is pulled from the roll302according to arrow304around drum or roller306. Treatment at310may include any single one of plasma treatment, coronal discharge, or flame treatment on a surface of the membrane300. As examples, in atmospheric plasma treatment, the membrane300is exposed to a plasma formed by a plasma generator (not shown) (e.g., operated at 15 kHz and an intermediate voltage 300V) that is coupled to a plasma torch with a nozzle (rotating or static). The membrane300may be exposed to the plasma discharge from the nozzle at a distance of 2 mm (0.08 inch) to 20 mm (0.8 inch). In corona treatment, a high-voltage electrical discharge spans an air gap between an electrode and a dielectric. That discharge forms a corona and the surface of the membrane300is exposed to that corona. The power of the discharge can vary from 0.5 kW to 40 kW. In flame treatment, the surface of the membrane300is exposed to a burner unit. The burner unit may combust a natural gas-hair mixture (e.g. at a ratio of 9.6 to 1 to produce a sheet content of 38 Joules per cubic centimeter) with a flame of about 4 mm (about 0.2 inch) from a nozzle on the burner unit. An oxygen rich plasma treats the surface exposed to the flame. A distance between the nozzle and the surface of the membrane300may be 30 mm (1 inch) and exposure time may be varied from 0.02 second to 0.1 second.

At the same time, a sheet314is pulled from a roll312and passes around roller316according to arrow320and past a surface treatment process at322. Although not shown inFIG. 14, the sheet314may be a multilayer protective sheet14shown, for example, inFIGS. 2-4or a single layer sheet. Multilayer sheets may be preassembled prior to being assembled with the membrane300as shown inFIG. 14. Treatment at322may include any single one of plasma treatment, coronal discharge, or flame treatment or a combination of those on a surface of the sheet314. The treatment at322may be the same treatment as the treatment at310, though embodiments of the invention are not limited to the treatments being the same.

Once treated, each of the sheet314and the membrane300contact one another at324. That is, at324, the treated surface of the sheet314is brought into contact with the treated surface of the membrane300. No adhesive, tackifiers, or chemicals are applied to or between the sheet314and the membrane300. The sheet314is not intentionally stretched prior to or during contact with the membrane300at324. As an example, each of membrane300and the sheet314contact one another at324and pass through a nip roller326and so are pressed together to form the laminate10. The nip roller326may apply pressure in a range from 1 pounds per linear inch to 300 pounds per linear inch (0.2 kilograms per linear centimeter to 54 kilograms per linear centimeter). By way of further example, the applied pressure may range from 30 pounds per linear inch to 200 pounds per linear inch (5.4 kilograms per linear centimeter to 36 kilograms per linear centimeter). The stacked membrane300and the sheet314may experience the applied pressure for a controlled amount of dwell time. For example, the dwell time may be 0.001 second to 2 seconds, which may depend on the line speed. Once the protective sheet314is laminated to the membrane300, the roof laminate10is formed into a roll38(shown inFIG. 7). The laminate10is adhesive free (e.g.,FIG. 2).

In one embodiment, the line speed as is represented by arrows304and320may be in the range of 20 to 100 feet per minute (6.1 to 30.5 meters per minute). The rate at which each of the membrane300and sheet314are pulled from their respective rolls302,312may be the same. By way of further example only, the line speed may be from about 40 feet per minute (about 12 meters per minute) to about 45 feet per minute (about 14 meters per minute) (i.e., within a few feet per minute, plus or minus 2 feet per minute (0.6 meter per minute)).

As a prophetic example, a 60 mil by 10 foot (1.5 millimeter by 3 meters) PVC or TPO roofing membrane can be surface treated with plasma, corona, or flame treatment. A flexible PVC film may be similarly treated and brought into contact with the surface treated PVC or TPO membrane under an applied pressure of 1 pound per linear inch to 100 pounds per linear inch (0.2 kilograms per linear centimeter to 18 kilograms per linear centimeter). It is believed that this process will produce a peel value of 0.1 to 0.3 pounds per inch (0.02 to 0.0.05 kilogram per centimeter).

Examples 1 and 2

A roofing membrane of a 60 mil by 10 foot (1.5 millimeter by 3 meters) PVC sheet and a protective sheet of flexible PVC were heat laminated together with a process schematically shown inFIG. 11. The line speed was 30 feet per minute (9 meters/minute). The 60 mil (1.5 millimeter) PVC sheet had a temperature of 240° F. (116° C.) when exiting the heating zone. A nip pressure of 50 pounds per linear inch (8.9 kilograms per linear centimeter) was used to press the 60 mil (1.5 millimeter) PVC sheet and the PVC protective sheet together. The laminate had a peel value between the PVC protective sheet and the 60 mil (1.5 millimeter) PVC sheet of 1.0 pound per inch (0.18 kilogram per linear centimeter).

A roofing membrane of a 60 mil by 10 foot (1.5 millimeter by 3 meters) PVC sheet and a protective sheet of flexible PVC were heat laminated together with a process schematically shown inFIG. 11. The line speed was 33 feet per minute (10 meters per minute). The temperature for the 60 mil (1.5 millimeter) PVC sheet when exiting the heat zone108was changed in a periodic manner to map the peel value as a function of heat zone temperature. A nip pressure of 80 pounds per linear inch (14 kilograms per linear centimeter) was used to press the 60 mil PVC sheet and the PVC protective sheet together. The peel values of each laminate were measured and are tabulated in Table 1. Five samples of each laminate were manufactured.FIG. 16represents data of Table 1 in graphical form. The adhesion force between the protective film and roof membrane is primarily influenced by temperature, pressure, and contact time at temperature and pressure.

FIG. 16illustrates the temperature influence on adhesion in this example (i.e., fixed contact time and fixed pressure). It is contemplated that in a temperature range of 185° F. (85° C.) to 210° F. (98.9° C.), the molecular model would be close to that depicted inFIGS. 13B and 13C. In other words, there are some interaction and entanglement at the interface between polymer chains between the PVC sheet and PVC membrane. It is likewise contemplated that at temperatures over 210° F. (98.9° C.) there is an increase in entanglement between polymer chains of the sheet and the membrane. When polymer chain entanglement becomes significant, it is observed that it is increasingly difficult to distinguish the interface between the sheet and the membrane. This is believed to occur above 250° F. (121° C.) under the temperature and pressure conditions in the example.FIG. 13Dis believed to represent the interface at this combination of temperature, pressure, and time. As such, temperatures in the range of 210° F. (98.9° C.) to 235° F. (113° C.) are believed to provide sufficient entanglement/adhesion value for handling and installation but also permit removal of the protective sheet from the membrane. In contrast, the entanglement represented inFIG. 13Dmay present a problem for removal of the sheet after installation because of the difficultly in removing the sheet from the membrane.

A data plot from testing of five different specimens assembled in accordance with Example 2 is shown inFIG. 15. As shown, there is variability in adhesion between the specimens1-5. The peel value is determined as an average load for each specimen. The peel value above is an average peel value for the 5 specimens.

The procedure for measuring a peel value, as described herein, was as follows:(1) A 3-inch (7.6 centimeters) wide by 6-inch (15 centimeters) long specimen was cut from the prepared laminate.(2) Using a ruler, a line was drawn across the specimen 2 inches (5 centimeters) from one end along the 6-inch (15 centimeters) length.(3) The protective sheet was manually peeled from the membrane to the line to produce a tab leaving 4 inches (10 centimeters) of protective sheet adhered to the membrane.(4) The laminate was adhered to a 4-inch (10 centimeters) wide by 7-inch (18 centimeters) long at a support plate with tape opposite the tab.(5) The specimen was mounted in a 3365 Instron testing machine with a 20-pound (9 kilograms) load cell and 3-inch (8 centimeters) wide pneumatic grips.(a) The specimen was vertically mounted in the opposing grips so that the protective sheet was pulled in a direction substantially parallel to the support plate and to the membrane.(b) The support plate was mounted in one set of pneumatic grips and the tab was coupled to the opposing pneumatic grips with a piece of masking tape attached to the tab.(6) Following calibration of the load cell, the tab was pulled at a rate of 2 inches per minute (5 centimeters per minute). The peel value was calculated from the data shown inFIG. 15.

Examples 3 and 4

A roofing membrane of a 60 mil by 3-foot (0.914 meter) PVC sheet and a protective sheet of rigid PVC sheet were heat laminated together with a process schematically shown inFIG. 12. The heat drums were set to 300° F. (149° C.) for both the 60 mil (1.5 millimeters) PVC sheet and the rigid PVC sheet. The line speed was 42 feet per minute (12.8 meters per minute). A nip pressure of 160 pounds per linear inch (29 kilograms per linear centimeter) was used to press the 60 mil (1.5 millimeters) PVC sheet and the PVC protective sheet together. The roofing membrane had a peel value between the PVC protective sheet and the rigid 60 mil (1.5 millimeters) PVC sheet of 3.0 pound per inch (0.54 kilograms per linear centimeter).

A roofing membrane of a 60 mil by 3-foot (1.5 millimeters by 0.9 meter) PVC sheet and a protective sheet of semi-rigid PVC sheet were heat laminated together with a process schematically shown inFIG. 12. The sheet drums were set to 300° F. (149° C.) for both the 60 mil (1.5 millimeters) PVC sheet and the semi-rigid PVC sheet. The line speed was 42 feet per minute (12.8 meters per minute). A nip pressure of 160 pounds per linear inch (29 kilograms per linear centimeter) was used to press the 60 mil PVC sheet (1.5 millimeters) and the semi-rigid PVC protective sheet together. The roofing membrane had a peel value between the semi-rigid PVC protective sheet and the 60 mil (1.5 millimeters) PVC sheet of 1.0 pound per inch (0.18 kilogram per linear centimeter).

While the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in some detail, it is not the intention of the inventors to restrict or in any way limit the scope of the appended claims to such detail. Thus, additional advantages and modifications will readily appear to those of ordinary skill in the art. The various features of the invention may be used alone or in any combination depending on the needs and preferences of the user.