Conformable Preconditioned Adhesive Sealing Tape
An improved pressure sensitive flashing tape that is conformable over uneven or irregular surfaces for use in the construction industry, where a moisture and air seal having full adhesive contact to the adherend is required. The subject tape includes a topsheet layer and an adhesive underlayer. The topsheet is stabilized dimensionally as to tape length and width for ease in application, but is preconditioned with a plurality of diaphragm elements embossed into the topsheet and compacted under pressure so as to enable the tape to conform to raised and indented features, including lap joints, protruding screw heads, dents, holes, cracks and the like, in surfaces associated with flashing and associated building surfaces; thus improving weathertight sealing. The topsheet may also have fold lines disposed relative to the diaphragm elements so as to be complementary in function, the fold lines serving to further enhance conformability and adaptability during and after application.
CROSS REFERENCE TO RELATED APPLICATIONS
This application is related to and claims priority to U.S. Provisional Patent No. 61/796,873 entitled “Tape backing of pressure sensitive tape with embossed collapsed diaphragms that enhance adhesive conformance to rough surfaces and lap joints”, filed 23 Nov. 2012, which is herein incorporated in full by reference for all purposes.
FIELD OF THE INVENTION
The invention is directed to a flashing tape for weatherproofing, the tape having a topsheet layer and a pressure-sensitive adhesive underlayer. The topsheet is preconditioned with embossed, collapsed diaphragms that are surprisingly effective in conforming the tape to raised and indented features of surfaces, the preconditioned tape having a residual memory tension after installation that is less than the release tension of the adhesive.
Pressure sensitive adhesive tapes are utilized when applying flashing to create either an air or water seal. Performance is commonly inhibited by the phenomena referred to in the trade as “adhesive bridging” (or “tenting”). This phenomenon is easily demonstrated for example by placing a short piece of transparent general office tape (often referred to as “scotch tape”) on a flat surface of an adherend. Another piece of that same tape is then crossed at a 90 degree angle over the first piece of tape to double the thickness and forming a lap joint on either side edge. At the point where the second tape bridges up from the undersurface to cross over the first tape, a lap joint void will occur where the adhesive separates from the adherend. In practice, the initial application contact may be fully sealed by pressing the tape into the gap, but over time the tape retracts to its starting dimensions and the void regrows. The elastic memory “tension” or “elastic rebound” inherent in the stretched tape is greater than and defeats the adhesive bond strength. Vents and cavities grow where the adhesive separates, resulting in loss of weather seal. The separation is often accelerated at higher temperatures. Because of this, when a flashing tape is stretched during application, as over a lap joint, the tape progressively recovers to its unstretched form and, disadvantageously, forms unsealed gaps. Moisture or cold air can penetrate through the gaps. Adhesive bridging also occurs where tapes are applied with stretching over any rough or uneven surface.
Most pressure sensitive tapes are subject to adhesive bridging. However, the problem often is not easily evaluated because the tape overlayer(s) and the adhesive are not transparent, so that gaps in adhesion continuity are difficult to observe. Preferably, flashing tapes for the building construction industries should perform for years without weatherproofing seal failure, and thus slow creep elastic rebound and tension memory can lead to significant construction problems.
In general, flashing tapes are made by a roll-to-roll process. Properties of the film may differ in the machine direction (MD) corresponding to the process feed direction, and the cross direction (CD) across the roll. Tapes known in the art are preferred to be dimensionally stable for ease of installation, i.e., some dimensional stiffness is needed for handling. Many tapes utilize multilayer, pre-stretched film such as by Valeron or Hutamaki. The process re-orients polymer molecules in the film and limits later stretching in use. This type of high strength film is desirable in that it provides dimensional stability to the tape, minimizes adhesive bleed through, and is durable to abrasions.
Alternatively high density polyolefin, polypropylene and polyethylene films are used as barrier films. Typically these films range in thickness from 30.0 to 60.0 mils (0.00762-0.01524 cm). This type of pressure sensitive tape is referred to in the industry as a self-adhered flashing tape. Numerous well known brands of self-adhered flashing tape are made, and include Fortifiber, Protecto Wrap, and others. One such tape is described in US Pat. Publ. No. 2010/0285259, which is incorporated by reference by way of background on weatherproofing in construction.
In evaluating flashing tapes, it has been found that there are a few tapes that do not demonstrate significant adhesive bridging in the MD direction. There are several tapes that are creped by various methods so that the tape may be stretched in length during application without creating memory tension. These tapes are significantly more expensive than non-creped products. Since the material is creased across the full CD width of the tape, the tape is by design condensed together by as much as 60-70 percent in MD length. This allows the tape to be purposely stretched back toward its original length in a nonlinear fashion, and allows the tape to be fanned out around corners or arches. However, the lack of dimensional stability in MD length makes creped tapes unsuitable for many applications. Moreover, the volume of adhesive required to fill the pleated voids of the creases is substantial. For example, to achieve a final 20 mil (0.0508 cm) adhesive thickness, a 30-40 mil (0.0762-0.1016 cm) adhesive thickness may be required because the adhesive thins as the tape is stretched in length. Also, the manufacturing speed with creped tapes is significantly reduced, both in steps for pleating the overlayer and for applying the adhesive. An example of this type of product is described under EI Du Pont De Memours and Company's US Patent Publ. No. 2006/0083898, which discloses a self-adhering flashing system having high extensibility and low retraction.
U.S. Pat. No. 8,490,338, titled, “Self-Adhering Window Flashing Tape with Multi-Directional Drainage Plane” to Longo and Patent Application Publication US 2008/0307715 to Pufahl, provide for an exterior surface that is patterned to promote gravity drainage of water. This approach necessarily must form rigid dimples to facilitate water drainage from the tapes exterior exposed surface, and would not suggest a flaccid diaphragm construction. A construction that would allow the surfaces to deform or collapse would defeat the teachings because placing building siding and trim over the tape would flatten the drainage channels. Rigidly dimpled tapes will not reliably stretch or conform to seal over a rough or uneven surface.
It is desired to have a flashing tape that minimizes adhesive bridging while being both economical and suitable for weatherproofing applications with a wide variety of adhesives. It is desirable for such a tape to be dimensionally stable in length and width during installation, yet have minimal elastic rebound when applied over irregular and uneven surfaces. None of the flashing tapes known in the art directly address issues related to adhesive bridging, dimensional stability, and control of adhesive thickness in an economical manner. Thus, there is a need in the art for a flashing tape that overcomes the above disadvantages and limitations.
The invention is directed to improved flashing tapes for construction weatherproofing, the tapes having a weather-resistant layer or film, termed here a “topsheet”, and a smooth adhesive underlayer composed of pressure sensitive adhesive. The tapes are generally made by a roll-to-roll process. To improve the resistance of the tape to seal failures resulting from adhesive bridging, the topsheet is “preconditioned” during the manufacturing process by embossment with diaphragm elements at densities of 10 to 400 diaphragm elements per square inch, more preferably 25 to 200 diaphragm elements per square inch, each diaphragm having a collapsible wall. Stretching that occurs during manufacture as the film is rolled on embossment teeth or pits results in embossed diaphragm elements with thin, collapsible walls, the stretching process having exceeded the yield point of the film (without rupture).
Subsequent compression of the diaphragm elements improves the flexibility of the film. In a process termed “conditioning,” the diaphragms are compressed or collapsed in height. The result is a tape or sheet having an essentially uniform thickness and relatively smooth adhesive undersurface. Typically the diaphragm structures are compressed 20% to 70% but retain a capacity to expand or extend to their pre-conditioned dimensions without memory tension.
This preconditioning is surprisingly effective in enabling flashing tapes of the invention conform and adhere to raised and indented features of surfaces without tenting or adhesion bridging, features that include seams, nail or screw heads, holes, cracks, and surface irregularities commonly encountered in building construction. This benefit has been shown to be long-lasting, and is believed to be a permanent change in the structure of the tape:adherend combination. The improved performance results from the novel tape structure, the features of which include limited memory tension of an weather resistant topsheet having collapsed diaphragm elements, increased adhesion surface area of the topsheet, and localized stretchability for conforming to irregularities in the adherend surface, while retaining generally stable tape dimensions of length and width for ease of application.
Embossments that exceed the yield point of the film sheet material result in irreversible localized stretching and thinning of the film wall thickness around the diaphragm elements, and result in a tape having a residual memory tension that is less than the release tension of the adhesive bond. By providing an adhesive bond over a greater surface area that is greater than any memory tension storage capability of the tape, adhesive bridging is reduced or prevented. Advantageously, preventing or reducing elastic rebound and adhesive bridging results in inventive flashing tapes having better sealing over the building lifetime, as realized in tests reported here.
The embossed diaphragm elements have been stretched into the plastic region of a stress/strain plot for the topsheet film, and are thinner than the interconnecting strands at the junctions between the diaphragms. The interconnecting strands form a net that provides stability to the MD and CD dimension of the tape and limit its overall elasticity to a useable range. However, individual strands have a narrow individual structure and limited strength, and can be locally stretched (irreversibly) during installation. This allows the interconnecting strands to conform to undersurface features with minimal elastic rebound.
In alternate embodiments, diaphragm elements may be embossed in regular patterns of alternating concave and convex diaphragm elements. The adjacent concave and convex areas deform to a greater degree than each individual diaphragm alone, and have limited elastic rebound. By way of illustration, during installation of a tape of the invention over a screwhead, concave diaphragms are inverted and fuse with adjoining convex diaphragms so as to form a larger convexity conforming to the raised surface. The opposite is true for depressed areas of the adherend such as lap joints. Because the material is pre-yielded, little or no elastic memory results.
Variations in design of the ECD elements, including variations in size, pattern, separation, and depth, serve to optimize conformance and adhesion when applied to rough or uneven surfaces. The patterned embossed conditioned diaphragm (ECD) elements of the invention enhance the ability of the topsheet and adhesive to conform over rough surfaces and adhere, while maintaining reasonably consistent tape thickness. A preferred embodiment is a topsheet web having an embossed diaphragm pattern made of adjoining alternating convex and concave tetrahedron frustum diaphragm elements at a density of 25 to 200 diaphragm elements per square inch, where each diaphragm element has been irreversibly stretched beyond the yield point of the material by 5% or more and is readily collapsible.
Alternatively, the diaphragm elements are formed to be uniformly either concave or convex. A release liner may also be provided and optionally is used to receive the adhesive layer such that the topsheet is rolled against the adhesive with a release liner backing already in place.
In another embodiment, the performance of the flashing tape may be further enhanced due to a plurality of “fold lines” or “creases” created by the embossed pattern. The fold lines break the tendency of the topsheet to resist folding in multiple simultaneous dimensions. Synergically, by forming adjoining diaphragm elements in regular patterns or arrays, fold lines and creases may be formed in the cross direction (CD), in the machine direction (MD) or at one or more angles that are not perpendicular or parallel to the feed direction so as to better conform to surface features. The patterns are optionally arrayed to form a plurality of linear or curvilinear fold lines in crossed and intersecting directions such as triangular, diamond, or hexagonal patterns.
In a preferred embodiment, an arrayed pattern of alternating convex and concave tetrahedron frustum diaphragm elements provides un-compacted or flat fold lines across the tape width in the CD direction. In effect, the fold lines provide pre-creasing of the topsheet but no compaction. This pre-creasing allows the topsheet to be compacted in the MD direction in an accordion configuration with minimal residual elastic force. An important application of this structure is found in overcoming “fish mouth”, a communicating void that forms at the edge of a flashing tape when applied over a protrusion such as a screwhead.
Methods are also provided. In a first aspect, the invention is a roll-to-roll process for manufacturing a flashing tape, which includes steps for (a) embossing a precursor web of a polymeric material on a roller surface of an embossing roller, the precursor web having a first face, a second face, a thickness, a mid-thickness reference point centered therein, a width, and a linear dimension in the machine direction, the polymeric material having a yield point, the embossing roller surface having a regular pattern of adjoining three-dimensional pyramidal polyhedrons having a density of 20 to 400 polyhedra per square inch, more preferably 25 to 200 polyhedra per square inch, the polyhedra each having at least one positive or negative radial dimension greater than the thickness of the precursor web, at least one radial dimension having a radius relative to a rotational center of the embossing roller such that the yield point of the material is exceeded when pressingly contacted with the roller surface, thereby forming a topsheet web having a first side, a second side, and an array of adjoining diaphragm elements thereon, the array of diaphragm elements having an uncompacted height measured peak-to-peak thereof that is greater than the thickness of the precursor web and the diaphragm elements having an irreversibly stretched film wall thereof having a thickness that is less than the thickness of the precursor web; (b) extruding an uninterruptedly coating layer of a pressure-sensitive glue onto a release liner layer; (c) using a pinch roller having a pinch roller pressure adjusted so as to enable simultaneously:
- i) contacting the second side of the topsheet web with the continuous layer of the pressure-sensitive glue on the release liner;
- ii) compacting each the diaphragm element and film wall thereof to a compacted fractional height that is less than the uncompacted height;
and thereby form a conditioned flashing tape rollstock having a topsheet layer, a glue layer, and a release liner layer, the glue layer having a generally smooth external surface when the release liner is removed, the topsheet layer having diaphragm elements characterized by irreversibly stretched and compacted film walls that are generally flattened, crinkled, pliant and irresilient; and, (d) optionally forming smaller rolls from the rollstock by division thereof. In this instance the process of applying the glue layer and compacting the diaphragm cells may be performed in a single step. In selected aspects, the process may also include compacting the topsheet so that the compacted fractional height measured peak-to-peak is 20 to 70% of the uncompacted height. In another aspect, the pattern of adjoined three-dimensional pyramidal polyhedrons on the roller surface defines a pattern of fold lines there between. The fold lines further contribute to the pliancy of the product as will be described in more detail below. Other method variants are also described.
In another aspect, the invention is a flashing tape product by process, such that the product is produced by a method including: (a) irreversibly yielding a precursor web to form an array of unit diaphragm cells at a density of 10 to 400 diaphragm cells per square inch of web, more preferably 25 to 200 diaphragm cells per square inch of web, the array having a peak-to-peak height that is a multiple of the thickness of the precursor web and the diaphragm cells of the array having a film wall thickness that is a fraction of the thickness of the precursor web; thereby defining a topsheet intermediate; (b) compacting the diaphragm cells of the topsheet intermediate, thereby forming a conditioned topsheet intermediate having a peak-to-peak height that is 20 to 70% of the peak-to-peak height of the topsheet intermediate of step (a); (c) coating a bottom side of the conditioned topsheet intermediate with an uninterrupted glue layer; and thereby forming a flashing tape having a topsheet embossed with conditioned diaphragms and a glue layer coated thereunder. The product may be further characterized by evidence of a manufacturing step for sandwiching the glue layer between the conditioned topsheet intermediate and a release liner. Alternatively, self-wound rolls may be manufactured by applying a release formula so that the glue layer will not bond to a top side of the conditioned topsheet intermediate when the tape is rolled up, thereby eliminating the need for a release liner. Generally, products formed by these processes may include fold lines disposed between the unit diaphragm cells.
More broadly, or in other terms, the invention is a flashing tape for weatherproofing, the flashing tape including a weather-resistant topsheet overlayer and a weather-resistant adhesive underlayer, the topsheet overlayer having a regular array of embossed and compacted unit diaphragm cells formed from a feedstock film, the compacted unit diaphragm cells having pliant, crinkled, flattened, and irresilient walls such that the release tension of the adhesive is greater than the elastic memory tension of the unit diaphragm cells or clusters thereof. Clusters may behave cooperatively in sealing over fasteners and other defects. Cluster size is dependent on the construction features to be sealed and may be optimized by engineering diaphragm size, amplitude, wall thickness, shape, and other characteristics as described here.
In a currently preferred embodiment, the flashing tape comprises unit diaphragm cells that are engineered with dimensions selected for pliantly sealing over construction fasteners, lap joints and defects of commonly encountered sizes, the unit diaphragm cells having a size ranging from 5 diaphragm cells per linear inch to 20 diaphragm cells per linear inch, and more preferably about 25 to 200 diaphragm cells per square inch. Also currently preferred is a flashing tape having unit diaphragm cells characterized by a stretched embossment dimension of height that is a multiple of the original thickness of the feedstock web and a compacted “conditioned” dimension of height that is fractionally 20 to 70% of the peak-to-peak height of the embossments prior to conditioning.
The flashing tapes of the invention may be a component of a building sealing system or a fenestration unit. The flashing tapes may be installed on site at a building project, or may be pre-installed on modular units transported to the building site for final assembly.
The elements, features, steps, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings, in which presently preferred embodiments of the invention are illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustration and description only and are not intended to define limits of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The teachings of the present invention are more readily understood by considering the drawings, in which:
The drawing figures are not necessarily to scale. Certain features or components herein may be shown in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity, explanation, and conciseness. The drawing figures are hereby made part of the specification, written description and teachings disclosed herein.
NOTATION AND NOMENCLATURE
Certain terms are used throughout the following description to refer to particular features, steps or components, and are used as terms of description and not of limitation. As one skilled in the art will appreciate, different persons may refer to the same feature, step or component by different names. Components, steps or features that differ in name but not in function or action are considered equivalent and not distinguishable, and may be substituted herein without departure from the invention. Certain meanings are defined here as intended by the inventors, i,e., they are intrinsic meanings Other words and phrases used herein take their meaning as consistent with usage as would be apparent to one skilled in the relevant arts. The following definitions supplement those set forth elsewhere in this specification.
Adherend—The surface to which an adhesive adheres; also: one of the bodies held to another by an adhesive; an undersurface or substrate to which a flashing tape is applied.
Adhesive bridging (or tenting)—An area under a tape where the adhesive releases from the adherend, creating a void or break in the seal. Adhesive bridging is found due to movement of the adherend or more commonly due to the effect of elastic memory tension in areas where the tape has been stretched and the memory tension defeats the adhesive bond over time. Stretched tape will tend to return to a relaxed position in which the glue separates from the adherend and the memory tension is relieved. This tension may come from stretching the tape over a raised surface feature such as a screwhead, bending the tape over a lap joint and pressing the tape down into the junction, thermal expansion of the adherend (or the tape or the adhesive), or inadequate bond strength of the adhesive. While an initial seal may be formed, adhesive bridging manifests itself in open voids under the tape and resulting weatherseal failures over weeks, months or years.
Adjoining—in contact or located adjacently at a boundary or baseline, as of a pair of diaphragm elements having an adjoining or contiguous boundary. With reference to a pair of adjoining pyramidal polyhedrons of the embossments of the invention, indicates a base of a first polyhedron sharing an adjacent or contiguous edge with a base of a second polyhedron.
CD—The width of an adhesive tape or “Cross Direction” of the tape on the machine which it was made; the direction generally crosswise to the “machine direction” of the tape feed.
Diaphragm—A diaphragm is an area of the topsheet that is semi-flexible, having been stretched either positively or negatively out of the native plane of the precursor film by locally deforming the film beyond its yield point. References providing general background on embossment processes include U.S. Pat. No. 7,655,104 to McKenna and US Pat. Publ. No. 2010/0230857 to Muhs, and are incorporated herein in full by reference. Stretch deformation may be concentrated circumferentially around a tooth or depression of an embossment tool, or may be concentrated at the apex of the tool. Irreversible deformation results when the film thickness begins to yield and is thinned or “necks” as seen in the area of a stress-strain curve to the right of the elastic deformation region (
In a preferred embodiment, the “diaphragms” defined here are advantageously formed by embossing the precursor film with closely spaced regular arrays of teeth or depressions having the shape of a three-dimensional (concave or convex) pyramidal polyhedron, where at least one radius (“radius” being defined relative to a center of rotation of an embossment roller) of each polyhedral tooth or depression is greater than the thickness of the precursor film, and generally is a multiple thereof. One skilled in the art will recognize that the polyhedral features of a roller are not Platonic geometric forms, but are formed with a taper and shoulder radii so as to avoid rupture of the film during the embossment process. Pyramidal frustum shapes are contemplated, in particular tetrahedron frustum, hexagon frustum, square pyramid frustum, and diamond frustum shapes, without limitation thereto.
Embossed Conditioned Diaphragm (ECD)—Refers to a diaphragm that has been formed by an embossing process and also has been “conditioned” by a compression step that fractionally “compacts” or “collapses” the height of the embossed diaphragms. The product tape is formed by a method of embossing diaphragms using an embossing roller having convex teeth and/or concave depressions disposed on the roller surface. The peripheral wall of the diaphragm may be un-stretched while the center area of the diaphragm is stretched and thinned, or in other embodiments, the diaphragm's center is stretched and thinned while the peripheral wall retains more thickness. The plurality of ECD's in the topsheet may be in a pattern that is random or geometrically designed but is preferentially designed so as to include a regular pattern and fold lines.
The film forming the diaphragm element may be displaced either positively or negatively from the “relaxed” or “original” plane of the precursor topsheet. Conditioned diaphragms can be flexed or folded. The design force to move a conditioned diaphragm film will be less than the pressure required to move the original un-stretched material of the topsheet. The conditioning reduces the film's elastic memory tension to move in the third dimension back toward the original plane of the topsheet or extended beyond in the reverse original position of a diaphragm. Diaphragms can be distended or collapsed when conformed to an adherend. Conditioning by compression thins the embossed film back toward the original unconditioned plane of the precursor topsheet. The embossing process may result in an increase in film rigidity as compared to the same film in its precursor state, but subsequent compression results in making the embossed areas more flaccid and irresilient. The amplitude of ECD elements after tape fabrication, as controlled in the process, provides a balance between thickness of adhesive required for reliable seal, conformability for adhesion, handling characteristics, appearance and other design criteria. An ECD pattern allows multiple adjoined diaphragms to be moved cooperatively either positively or negatively so as to minimize the topsheet elastic memory tension on the corresponding adhesive—and thereby increase its ability to form and to maintain a seal. ECD patterns also provide fold lines where the topsheet memory is further reduced along adjoining perimeters of the ECD, allowing the film to contract in an accordion style with minimized elastic memory tension when flattened against the adherend. Advantageously the individual embossed area may be about 0.005 to 0.050 inches (0.0127-0.127 cm) in amplitude prior to conditioning and about 0.070 to 0.200 inches (0.1778-0.5080 cm) across. Variations from these parameters may be advantageous depending on the texture of the adherend. Advantageously, diaphragms minimize added adhesive cost while providing a significant increase in conformable surface.
Lap Joint—Where a tape crosses a first layer of similar tape applied to the same adherend. Lap joints are subject to seal loss where the second tape bridges the top surface of the first tape and the exterior surface of the underlying adherend.
MD—The linear dimension of an adhesive roll of tape or “Machine Direction” corresponding to the feed direction of the tape on the machine which it was made.
Pressure Sensitive Adhesive (PSA)—An adhesive that forms a bond with an adherend when pressure is applied to the outside surface of a tape. No solvent, water, or heat is needed to activate the adhesive. Some suitable adhesives include acrylic adhesives; butyl rubber or hybrid-butyl based adhesives, polymeric and rubberized asphalt adhesives. Other useful adhesives may include vinyl ether, styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene (SEBS), ethylene propylene-diene monomer, and combinations thereof, while not limited thereto. Advantageously hybrid acrylic, hybrid butyl rubber, butyl rubber, polymeric or rubberized asphalt based PSA adhesives are used. These adhesives are known to flow and may seal around penetrating fasteners when applied in layers thicker than 4 or 5 mils.
Topsheet—The top film layer of an adhesive tape. Generally this is a weather resistant exterior layer and is preferable an impervious material made of a nonwoven sheet such as a plastic film. Metal films and papers may also be used alone or in combination with a plastic layer. Exemplary materials include a polymer film, metal film, nonwoven fibrous polymer sheet or a combination operative to maintain an embossed pattern when exposed to temperatures as high as or about 200° F. (93.3° C.). Topsheets are generally substantially impermeable to water. Other materials useful in selected topsheet applications may include aluminum or other metal film; a non-woven sheet comprised of substantially continuous fibers, such as polyethylene, polypropylene, polyester, nylon and combinations thereof; a non-fibrous polymeric film, for example polyethylene, polypropylene, ethylene vinyl acetate, rubber, nylon, polyester, polyvinyl chloride or a combination thereof. In the case of a multilayer combination, the combined materials should have high resistance to delamination during installation and use. The topsheet may be impregnated or coated to lessen permeability and may be selected to be permeable to gases and water vapor. In manufacture, an adhesive is bonded to a topsheet so that the topsheet can be glued to a chosen adherend. In some tapes the topsheet is treated on one face so that an adhesive on another face will not stick to the treated surface, eliminating the need for a separate release liner during handling and installation.
Tetrahedron Frustum Diaphragms—As defined here, a tetrahedron frustum is a member of the set of geometric shapes termed “pyramidal polyhedrons”. A “tetrahedron” (plural: tetrahedra or tetrahedrons) is a polyhedron composed of four triangular faces, three of which meet at each corner or vertex. It has six edges and four vertices. A “diaphragm” is a thin film that is embossed to acquire the shape of the embossing tool, so that a diaphragm formed over a tetrahedron frustum-shaped tool has a generally tetrahedron frustum shape, but is hollow and merely the skin of the geometric solid on which it was formed. A diaphragm also lacks an enclosing surface corresponding to the base of a polyhedron, but otherwise the shape of an embossing tool, tooth or depression and the shape of the resulting diaphragm are referred to here, according to the context, by naming of the geometric shape they derive from. Analogously, the diaphragms of the invention include four sided pyramidal frustums, tapered blunt hexagons, conical frustums, and so forth, but a preferred form is that of a tetrahedron frustum. Arrays of polyhedrons may be formed in straight, curvilinear patterns, or waveforms, but in a yet more preferred an array of tetrahedron frustums is arranged in rows corresponding to alternatingly concave and convex polyhedral shapes sculpted into the embossing roll used to form them. While it is possible to mold or cast arrays and sheets of diaphragms, the most economical method of manufacture is by a roll-to-roll embossing process. Advantageously, by this method, fold lines between the rows may be formed in a single process step.
In general, unless otherwise explicitly stated the disclosed materials and processes may be alternately formulated to comprise, consist of, or consist essentially of, any appropriate components, moieties or steps herein disclosed. The disclosed materials and processes may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants, moieties, species and steps used in the prior art compositions or that are otherwise not necessary to the achievement of the function and/or objective of the present disclosure.
When the word “about” is used herein it is meant that the amount or condition it modifies can vary some beyond the stated amount so long as the function and/or objective of the disclosure are realized. The skilled artisan understands that there is seldom time to fully explore the extent of any area and expects that the disclosed result might extend, at least somewhat, beyond one or more of the disclosed limits. Later, having the benefit of this disclosure and understanding the concept and embodiments disclosed herein, a person of ordinary skill can, without inventive effort, explore beyond the disclosed limits and, when embodiments are found to be without any unexpected characteristics, those embodiments are within the meaning of the term about as used herein.
General connection terms including, but not limited to “connected,” “attached,” and “affixed” are not meant to be limiting and structures so “associated” may have other ways of being associated.
Relative terms should be construed as such. For example, the term “front” is meant to be relative to the term “back,” the term “upper” is meant to be relative to the term “lower,” the term “vertical” is meant to be relative to the term “horizontal,” the term “top” is meant to be relative to the term “bottom,” and the term “inside” is meant to be relative to the term “outside,” and so forth. Unless specifically stated otherwise, the terms “first,” “second,” “third,” and “fourth” are meant solely for purposes of designation and not for order or for limitation. Reference to “one embodiment,” “an embodiment,” or an “aspect,” means that a particular feature, structure, step, combination or characteristic described in connection with the embodiment or aspect is included in at least one realization of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment and may apply to multiple embodiments. Furthermore, particular features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments.
It should be noted that the terms “may”, “can” and “might” are used to indicate alternatives and optional features and only should be construed as a limitation if specifically included in the claims. It should be noted that the various components, features, steps, or embodiments thereof are all “preferred” whether or not it is specifically indicated. Claims not including a specific limitation should not be construed to include that limitation. The term “a” or “an” as used in the claims does not exclude a plurality.
“Conventional” refers to a term or method designating that which is known and commonly understood in the technology to which this invention relates.
Unless the context requires otherwise, throughout the specification and claims that follow, the term “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
The appended claims are not to be interpreted as including means-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase “means for.” Markush claims, if present, are recognized by a series of alternative selections joined by the “or” conjunction.
A “method” as disclosed herein refers to one or more steps or actions for achieving the described end. Unless a specific order of steps or actions is required for proper operation of the embodiment, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the present invention.
The invention is directed to a flashing or sealing tape for construction weatherproofing, the flashing tape having a topsheet overlayer and an adhesive underlayer, wherein the topsheet is embossed with a regular pattern of diaphragm elements that are then compressed such that the memory tension of the topsheet layer is engineered to be less than the adhesive tension of the adhesive: adherend bond. Advantageously, by embossing the topsheet with closely spaced “embossed collapsed diaphragm” (ECD) members at a density of about 25 to 200 diaphragms per square inch, a measureable improvement in sealing performance is demonstrated. Diaphragm members are found to operate cooperatively in a relaxed state and seal over protrusions, chips, lap joints and other irregularities commonly encountered in building construction without significant adhesion bridging over time. Fold lines in the designs and the crinkling that occurs during compression of the diaphragms also contributes to this effect, as will be described in more detail below.
The topsheet of the invention is comprised of a plurality of ECDs in an engineered pattern. Each ECD element formed in situ by an embossment and compression process. Each diaphragm is irreversibly stretched either positively or negatively out of the native plane of the precursor film by locally deforming the film beyond its yield point, thus thinning the enclosing film forming the diaphragm and rendering it pliant and irresilient. The pattern, size, amplitude and direction of the ECD's are designed to meet the level of conformity required to avoid adhesive bridging of the tape as installed. The diaphragms may be conjoined or spaced by reticula or web members which are not stretched or embossed; the interrelationship, size and orientation of the unstretched members are engineered to meet a desired level of dimensional stability suitable for processing and handling during installation.
By way of introductory illustration, when windows are installed in a structure, the window mounting flange is used as the interface with the building's weather resistive barrier to keep moisture out of the structure. The mounting flange is also used to secure the window to the structure, typically the mounting flange is screwed or nailed in place, such as with flat headed K-Lath screws or galvanized roofing nails. The head of the fastener forms a protrusion above the flat plane of the flange. Using conventional products, adhesive bridging, voids and fish mouth channels are formed around the fasteners. Because the window flange is typically about 1 inch (2.54 cm) in width, the edge of the fastener is about 0.5 inches (0.127 cm) or less from the edge of the flashing tape used to seal out water and air a good adhesive seal is essential. Adhesive bridging occurs at this location with almost all precursor tapes.
A similar problem occurs where conventional tapes are lapped at the corners of a window or door, and adhesive bridging again leads to communicating voids that break the weatherproof seal. This occurs immediately during installation, weeks, or months later as the elastic energy contracts the topsheet so as to separate the adhesive from the adherend.
In contrast, as shown in
Conformance is improved by the capacity of the closely spaced diaphragms to fold against each other (compress) where needed inside a corner and to expand around a corner. This folding capacity is a characteristic of the patterned diaphragm members and can be enhanced with fold lines formed in the topsheet during embossment. Smaller diaphragm members may also improve this performance. In general, for both protrusion-type defects and lap joint defects, the diaphragm pattern, size, spacing, and amplitude can be engineered to optimize sealing according to the expected size of the defects. A size of 20 to 400 ECD elements per square inch, more preferably 25 to 200 ECD elements per square inch, is useful for most standard construction applications in need of flashing or sealing tape.
As will be described in more detail, this view is of an intermediate in manufacture of the finished tape. Following formation of the embossments in the precursor film, compression rollers are used to reduce the height on the polyhedrons, resulting in a uniformly flatter and crinkled appearance. The fractional compression in the vertical dimension may be 20-70% of the original pyramidal height and is an independent engineering parameter of the ECD film.
The plan view of
For assembly of the topsheet to the completed tape, by way of example, a hybrid butyl blend adhesive layer 72 is first applied to a polyolefin release liner 73 in a continuous layer of about 0.015 inches (0.0381 cm) in generally uniform thickness. This ensures that when the release liner 73 is peeled away during installation, the adhesive 72 is exposed and has a smooth bottom surface. In other instances the topsheet may be coated first with adhesive and then the release liner nipped in to the adhesive. The topsheet 71 is then applied to the adhesive and compressed by a nip roller to a fractional height. The completed tape combination is then slit in widths from 2 inches (50.08 cm) to 36 inches (91.44 cm) in width, or as desired, and rolled on 3 or 5 inch (7.6 cm or 12.7 cm) cores in lengths of about 75 to 100 feet (22.86 m to 30.48 m). While not limiting thereto, the peak-to-peak amplitude of the compressed diaphragms after conditioning will be in the range of about 0.005-0.015 inches (0.0127-0.0381 cm), or about 20 to 70% of the stretched topsheet thickness prior to “conditioning”, as per the engineering needs of the application. Thus in some instances the topsheet layer is embossed with diaphragm features having vertical dimensions that are a multiple of its original thickness, and then compacted to be almost or essentially flat again. In this process the surface area of the topsheet is significantly expanded and the film walls are irreversibly stretched, thinned and crinkled. Rows may be separated by fold lines 78 for added compliancy during installation.
The topsheet precursor film may be a high density polypropylene and the adhesive an acrylic, asphalt, butyl, hybrid hotmelt or other polymer-based adhesives. Adhesives may include thermoplastic rubber resin adhesives, solvent-based rubber adhesives, and acrylic polymer based adhesives. Generally extrusion is a preferred method for applying an adhesive layer or film of a suitable thickness. In another embodiment the release liner may be perforated or split (e.g., kiss cut) to allow only portions of the adhesive to be exposed at one time so as to aid in installation.
As seen in
The embossed process intermediate is then forwarded to an adhesive extrusion line to combine the topsheet overlayer, adhesive underlayer, and an optional release liner layer into flashing tape rollstock. Depending in part on the heat levels required for adequate adhesive flow rates during extrusion, the release liner may be coated with adhesive (if the ECD film will not deform during the adhesive extrusion process, the topsheet may be coated with adhesive). After adhesive coating, the topsheet, adhesive and release liner are joined together in a sandwich, typically using a pinch roller operation. The pressure of the pinch rollers is needed to fully contact and bond the layers, but for manufacture of an ECD product, advantageously, a higher level of compression is applied by opposing pinch rollers so as to also compress and compact the diaphragm elements in one step. Thus the pinch rollers may have a dual roll in the ECD process, and pinch roller pressure level is adjusted to compact the diaphragms, increasing their pliancy and irresilience. In some instances, the pressure applied is sufficient to return the topsheet to a vertical profile approaching its original un-embossed thickness. Typically the pressure between the rollers will be adjusted to compress the embossments by a factor of 20 to 70% of their vertical dimension, while maintaining the desired adhesive thickness.
Variants on the process are possible. In-line cooling of the extruded adhesive may be needed before subsequent processing steps. A roller coated adhesive may be used instead of an extruded adhesive. In another variant of the process, if the tape is to be a self-wound product without a release liner, a release coating typically will be applied to the surface of the topsheet limiting adhesion of overlapping layers of tape in the roll. In self-wound products, the embossed film typically will be conditioned by compression through pinch rollers to form the ECD diaphragms either inline but subsequent to the embossing process or separately prior to the final tape fabrication steps. For product distribution, flashing tape rollstock may be trimmed and cut or slit into smaller individual rolls by methods known in the art.
In each of the cross-sectional views
A variety of patterns may be used in the design of ECD tapes of the invention. Patterns having triangular or hexagonal base geometry may be advantageous because of the added dimensionality of folding that is realized. While square and rectangular patterns will preferentially bend along a straight line, triangular and hexagonal patterns may bend (with expansion of unit diaphragm cells) along bent lines or circular outlines because the individual bending angle between the cells is not a right angle and because combinations of two or more cells can result in a variety of intermediate angles with a combined bending radius of the fold matching the required outline or bend of the underlying substrate. While regular patterns are generally preferred, fields of irregularly patterned elements may also find applications. The selection of pattern and pattern parameters relate to differing adherend rough surfaces. The film may be embossed in only a positive or negative direction from the original plane of the film, or in an alternating array of convex and concave elements as in the examples above, and arrayed patterns or random patterns depend on the tape's design criteria.
Alternatively, instead of central dimples and pits, smaller nested or compound polyhedral features may be embossed within diaphragm unit cell polyhedra. The net effect is to produce ECD elements having compound concavoconvex geometries and substantially increased surface area.
Samples of numerous flashing tapes available commercially were tested utilizing a test apparatus of
A second method was developed to demonstrate various pressure sensitive tapes performance related to adhesive bridging. Since the adhesive layer and the topsheet are not transparent it is difficult to evaluate the performance of the tape and in particular the areas of adhesive bridging. However, as shown in
A wide variety of flashing tapes having differing adhesive and topsheet compositions, including many tapes conventionally used in the construction industry for window and door installation, were tested to determine the degree to which adhesive bridging occurred. In addition, a wide variety of other topsheet materials were evaluated including mesh, fabric, film, aluminum, woven and non-woven materials and composites.
The test slides 400 of
A prior art pressure sensitive tape 603 is shown in
The above disclosure is sufficient to enable one of ordinary skill in the art to practice the invention, and provides the best mode of practicing the invention presently contemplated by the inventor. While above is a complete description of the preferred embodiments of the present invention, various alternatives, modifications and equivalents are possible. These embodiments, alternatives, modifications and equivalents may be combined to provide further embodiments of the present invention. Further, all foreign and/or domestic publications, patents, and patent applications cited herein, whether supra or infra, are hereby incorporated by reference in their entirety for all they teach. The inventions, examples, and embodiments described herein are not limited to particularly exemplified materials, methods, and/or structures. Various modifications, alternative constructions, changes and equivalents will readily occur to those skilled in the art and may be employed, as suitable, without departing from the true spirit and scope of the invention. Therefore, the above description and illustrations should not be construed as limiting the scope of the invention, which is defined by the appended claims.
INCORPORATION BY REFERENCE
All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and related filings are incorporated herein by reference in their entirety.
SCOPE OF CLAIMS
While the above is a complete description of selected embodiments of the present invention, it is possible to practice the invention use various alternatives, modifications, combinations and equivalents. In general, in the following claims, the terms used in the written description should not be construed to limit the claims to specific embodiments described herein for illustration, but should be construed to include all possible embodiments, both specific and generic, along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.
1. A flashing tape for weatherproofing, said flashing tape comprising a topsheet overlayer and an adhesive underlayer, the topsheet overlayer having a regular array of embossed and compacted unit diaphragm cells formed from a feedstock film, said compacted unit diaphragm cells having pliant and irresilient walls such that the release tension of the adhesive is greater than the elastic memory tension of the unit diaphragm cells or clusters thereof.
2. The flashing tape of claim 1, wherein said unit diaphragm cells are dimensioned for pliantly sealing over construction fasteners, lap joints and defects, said unit diaphragm cells having a size ranging from 5 diaphragm cells per linear inch to 20 diaphragm cells per linear inch, and more preferably about 25 to 200 diaphragm cells per square inch.
3. The flashing tape of claim 16, wherein said unit diaphragm cells are embossments of said topsheet and are characterized by a stretched dimension that is a multiple of the original thickness of said feedstock web and a compacted dimension that is fractionally 20 to 70% of the peak-to-peak height of the embossments of said array.
4. The flashing tape of claim 3, wherein said unit diaphragm cells are embossments having a triangular base or a hexagonal base.
5. The flashing tape of claim 1, wherein said flashing tape is a component of a building sealing system or fenestration unit.
6. A roll-to-roll process for manufacturing a flashing tape, which comprises
- (a) embossing a precursor web of a polymeric material on a roller surface of an embossing roller, said precursor web having a first face, a second face, a thickness, a mid-thickness reference point centered therein, a width, and a linear dimension in the machine direction, said polymeric material having a yield point, said embossing roller surface having a regular pattern of adjoining three-dimensional pyramidal polyhedrons having a density of 25 to 200 polyhedra per square inch, said polyhedra each having at least one positive or negative radial dimension greater than said thickness of said precursor web, said at least one radial dimension having a radius relative to a rotational center of said embossing roller such that said yield point of said material is exceeded when pressingly contacted with said roller surface, thereby forming a topsheet web having a first side, a second side, and an array of adjoining diaphragm elements thereon, said array of diaphragm elements having an uncompacted height measured peak-to-peak thereof that is greater than said thickness of said precursor web and said diaphragm elements having an irreversibly stretched film wall thereof having a thickness that is less than said thickness of said precursor web;
- (b) extruding an uninterruptedly coating layer of a pressure-sensitive glue onto a release liner layer;
- (c) using a pinch roller having a pinch roller pressure adjusted so as to enable simultaneously: i) contacting said second side of said topsheet web with said continuous layer of said pressure-sensitive glue on said release liner; ii) compacting each said diaphragm element and film wall thereof to a compacted fractional height that is less than said uncompacted height;
- thereby forming a conditioned flashing tape rollstock having a topsheet layer, a glue layer, and a release liner layer, said glue layer having a generally smooth external surface when said release liner is removed, said topsheet layer having diaphragm elements characterized by irreversibly stretched and compacted film walls that are generally flattened, crinkled, pliant and irresilient; and,
- (d) forming smaller rolls from said rollstock by division thereof.
7. The process of claim 6, wherein said compacted fractional height measured peak-to-peak is 20 to 70% of said uncompacted height.
8. The process of claim 6, further wherein said regular pattern of adjoining three-dimensional pyramidal polyhedrons on said roller surface defines a pattern of fold lines therebetween.
9. The process of claim 8, further comprising configuring said embossing roller to align said fold lines in the machine direction, the cross direction, or to intersect at an angle intermediate to the machine direction and the cross direction.
10. The process of claim 9, further comprising aligning said fold lines at intersecting angles defining the base of a triangle or a hexagon.
11. The process of claim 6, wherein said pyramidal polyhedrons are selected from concave pyramidal polyhedron, convex pyramidal polyhedron, or concavoconvex pyramidal polyhedron.
12. The process of claim 11, wherein said regular pattern comprises an array of alternatingly concave and convex pyramidal polyhedrons.
13. The process of claim 6, wherein said pyramidal polyhedrons are selected from:
- i) a concave or convex pyramidal frustum defining an isosceles triangular base;
- ii) a concave or convex pyramidal frustum defining an equilateral triangular base;
- iii) a concave or convex pyramidal frustum defining a right angle triangular base;
- iv) a concave or convex pyramidal frustum defining a diamond-shaped base;
- v) a concave or convex pyramidal frustum defining a square-shaped base;
- iv) a concave or convex pyramidal frustum defining a rectangle-shaped base;
- v) a concave or convex pyramidal frustum defining a hexagonal base.
14. A flashing tape product by process, produced by a method comprising:
- (a) irreversibly yielding a precursor web to form an array of unit diaphragm cells at a density of 10 to 400 diaphragm cells per square inch of web, more preferably 25 to 200 diaphragm cells per square inch of web, said array having a peak-to-peak height that is a multiple of the thickness of the precursor web and said diaphragm cells of said array having a film wall thickness that is a fraction of the thickness of the precursor web; thereby defining a topsheet intermediate;
- (b) compacting said diaphragm cells of said topsheet intermediate, thereby forming a conditioned topsheet intermediate having a peak-to-peak height that is 20 to 70% of the peak-to-peak height of the topsheet intermediate of step (a);
- (c) coating a bottom side of said conditioned topsheet intermediate with an uninterrupted glue layer; and,
- thereby forming a flashing tape having a topsheet embossed with conditioned diaphragms and a glue layer coated thereunder.
15. The product by process of claim 14, further comprising sandwiching said glue layer between said conditioned topsheet intermediate and a release liner.
16. The product by process of claim 14, further comprising applying a release formula so that said glue layer will not bond to a top side of said conditioned topsheet intermediate when said tape is rolled up, thereby eliminating the need for a release liner.
17. The product by process of claim 14, wherein said array comprises fold lines disposed between said unit diaphragm cells.
18. The product by process of claim 17, wherein said fold lines are disposed in a machine direction, a cross direction, or a crisscross direction.
19. The product by process of claim 17, wherein said fold lines are disposed to intersect at angles defining a triangular, hexagonal, square, rectangular, diamond, or circular unit cell.
20. The product by process of claim 17, wherein said fold lines define a reticulum of unyielded precursor web between said unit diaphragm cells.
International Classification: E04D 13/15 (20060101); E04F 19/02 (20060101);