Extruded polystyrene foam insulation laminates for pour-in-place concrete walls

By using a thermal insulation foam/film laminate wherein each major planar surface of a foam panel has a facer film bonded thereto that meets certain performance criteria rather than a foam panel by itself, composite walls that have a foam panel sandwiched between concrete layers can be made with fewer steps.

This invention relates generally to insulated building walls and more
 particularly to insulated concrete building walls.
 BACKGROUND OF THE INVENTION
 A known means of improving thermal resistance of exterior concrete building
 walls involves using thermally insulating plastic foam panels as exterior
 sheathing. While suitable for below ground applications, this means has
 shortcomings in above ground installation. For example, exposed thermal
 insulation panel portions can be unsightly. In addition, exposed thermal
 insulation panel portions may degrade as a result of the weather.
 An alternate means, which overcomes shortcomings due to exposed thermal
 insulation panel portions, provides a composite wall by embedding a
 thermal insulation panel between two layers of concrete. In building
 composite walls of this type, one begins with by setting into place
 spaced-apart rigid forms that define a cavity bounded by wall surfaces.
 One continues by placing a thermal insulation foam board having opposed
 major planar surfaces into the cavity to divide the cavity into two
 subcavities. Pouring concrete into the subcavities yields the composite
 wall after concrete curing and form removal. Punching connectors through
 the foam at approximately 12 inch (30.5 centimeter (cm)) intervals before
 pouring concrete into the subcavities forms a securely connected sandwich
 of the foam board between the concrete layers after the concrete has
 cured.
 In order to prevent distortion or bursting of the thermal insulation
 boards, a customary practice involves pouring the concrete in stages,
 alternating between subcavities to balance forces applied by the weight of
 the concrete on the opposite sides of the foam boards or panels. For
 example, a 9 foot wall (2.7 meters (m)) may be formed by pouring concrete
 into a subcavity on one side of the foam board to a height of about 3 feet
 (0.9 m), then pouring concrete into a second subcavity on the other side
 of the foam panel to a height of about 6 feet (1.8 m), then pouring
 concrete to a height of about 9 feet (2.7 m) in the first subcavity, and
 then filling the remainder of the second subcavity. Pouring the concrete
 for composite concrete and foam board walls in stages is undesirable
 because, at the conclusion of each stage, it is generally necessary to
 stop pouring concrete, reposition equipment, and begin pouring the next
 stage. These steps can add significantly to the time required to construct
 the composite walls. It would be more desirable if the cavities on the
 opposite sides of the thermal insulation board could be filled with
 concrete without regard to balancing forces applied by the weight of the
 concrete on the opposite sides of the insulation panel.
 SUMMARY OF THE INVENTION
 The invention provides an improved method of forming a composite wall
 comprising a thermal insulation foam board disposed between concrete
 layers, and to the resulting composite wall. The thermal insulation foam
 board has opposed, spaced-apart and generally parallel primary surfaces
 each of which has a thermal plastic facer film adhered thereto. Each facer
 film has a thickness of from 0.35 mils (10 micrometers (.mu.m) to 10.0
 mils (250 .mu.m), an ultimate elongation of less than (&lt;) 200 percent (%)
 in both machine and transverse directions, a yield tensile strength of at
 least (.gtoreq.) 7,000 pounds per square inch (psi) (48,400 kilopascals
 (kPa)) in both machine and transverse directions, and a 1% secant modulus
 .gtoreq.200,000 psi (1,380 megapascals (mPa)) in both machine and
 transverse directions. The facer films adhere to the panel with a peel
 strength of .gtoreq.100 grams per inch (gm/in) (39.4 gm/centimeter
 (gm/cm). Thermal insulation foam boards that have films bonded thereto and
 meet the above criteria are significantly stronger than thermal insulation
 foam boards that either lack such thermoplastic facer films or have facer
 films that fail such criteria.
 In accordance with the method of the invention, set rigid forms into place
 to define a thickness for the composite wall and circumscribe a cavity.
 Set the thermal insulation foam board described above into place between
 the forms to define two subcavities, each subcavity being defined by a
 form and a proximate primary surface of the thermal insulation foam board.
 Fill the subcavities are filled with concrete. Cure the concrete to form a
 composite wall in accordance with the invention.
 The significant improvement in the strength of the thermal insulation foam
 boards used in accordance with the method of this invention allows the
 concrete to be poured into the subcavities without regard to balancing
 forces applied by weight of the concrete against a primary surface of the
 insulation board. As a result, one subcavity can be completely filled to a
 height of, for example, 9 feet (2.7 m), while the subcavity on the other
 side of the insulation board remains unfilled, without causing significant
 distortion or rupture of the insulation panel The ability to fill the
 cavities with concrete without regard to balancing forces applied by the
 weight of the concrete can significantly reduce the time required to
 fabricate composite walls.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The composite wall 10 of this invention includes a thermal insulation foam
 board 12 disposed between concrete layers 14 and 15. Several (a plurality)
 connectors 18 extend through insulation foam board 12 and project into
 concrete layers 14 and 15. After concrete layers 14 and 15 have cured
 (solidified), connectors 18 function to securely sandwich board 12 between
 concrete layers 14, 15. Anchors 18 may take on any known shape or
 configuration and be made from any known material. Typical materials
 include thermoplastic materials, fiber reinforced thermoplastic materials,
 thermoset materials, fiber reinforced thermoset materials, steels, and
 stainless steels.
 Thermal insulation foam board 12 includes a plastic foam material panel 20,
 with opposing primary surfaces 21 and 23, and first and second
 thermoplastic facer films 22 and 24 adhered, respectively, to primary
 surfaces 21 and 23. First and second thermoplastic facer films 22 and 24
 each have a thickness of from 0.35 mils (10 .mu.m) to 10.0 mils (250
 .mu.m), an ultimate elongation &lt;200 % in both machine and transverse
 directions, a yield tensile strength .gtoreq.7,000 psi (48,400 kPa) in
 both machine and transverse directions, and a 1% secant modulus
 .gtoreq.200,000 psi (1,380 mPa). More preferably, each facer film has a
 yield strength .gtoreq.10,000 psi (69,000 kPa) in both machine and
 transverse directions. Adhesion between facer films 22 and 24 and
 corresponding primary surfaces 21 and 23 of panel 20 is sufficient to
 provide a peel strength .gtoreq.100 g/in (39.4 gm/cm).
 Composite wall 10 fabrication begins by setting into place, in spaced apart
 relationship, rigid forms 30, 31 to define a cavity and establish a
 desired thickness for the composite wall. Fabrication continues by placing
 thermal insulation foam board 12 into the cavity to define two
 subcavities. Form 30 and facer film 22 define one subcavity and form 31
 and facer film 24 define a second subcavity. Thermal insulation board 12
 preferably has a plurality of anchors or connectors 18 that pass through
 board 12 and extend beyond facer films 22 and 24 and into the respective
 subcavities. Fabrication concludes by filling the subcavities with
 concrete and allowing the concrete to cure (solidify). If desired, either
 subcavity may be completely filled with concrete before adding any
 concrete to the second subcavity. In addition, both subcavities may be
 filled simultaneously (or nearly so). Forms 30 and 31 may be, and
 desirably are, removed from composite wall 10 after concrete curing
 proceeds to a desired state.
 Facer films with a low yield tensile strength tend to exhibit tensile
 elongation in response to applied stress. A film/foam laminate formed by
 laminating such a facer film to opposing primary surfaces of a foam board
 responds to applied stress or impact by bending to a point where the
 laminate begins to fracture at the facer film/foam board interface. The
 facer film elongates over the fracture at the interface and allows
 fracture propagation to continue thereby resulting in ultimate failure of
 the board. Facer films with higher yield strength tend to have low tensile
 elongation in response to applied stress, and substantially inhibit, and
 prevent failure of, the laminate. An increasing facer film secant modulus,
 or stiffness, enhances overall laminate flexural modulus.
 Insulation foam board 12 must have facer films 22 and 24 adhered,
 respectively, to primary surfaces 21 and 23 and the facer films must have
 the properties described above together with a minimum facer film/board
 peel strength of 39.4 gm/cm in order to attain sufficient strength to
 allow concrete wall fabrication to proceed without requiring sequential,
 balanced concrete pours into the subcavities.
 The plastic facer film may be composed of any thermoplastic polymer as long
 as it meets the physical property criteria above and can be effectively
 (with a peel strength .gtoreq.39.4 gm/cm) laminated to the foam panel The
 polymer may be a polyolefin, an alkenyl aromatic polymer, a polyester, a
 polycarbonate, an acrylic polymer or a polyamide. Useful polyolefins
 include polyethylene and polypropylene. Useful polyethylenes include high
 density polyethylene, low density polyethylene, and linear low density
 polyethylene. The film may be non-oriented, uniaxially oriented, or
 biaxially oriented. Preferred facer films are biaxially oriented films of
 polyethylenes, polypropylene, polyesters, polystyrene, or polyamides. The
 film may be cross-linked or non-crosslinked. The film optionally contains
 conventional additives such as inorganic fillers, pigments, or colorants,
 antioxidants, ultraviolet stabilizers, fire retardants, and processing
 aids.
 The facer film may be any of a monolayer film, a coextruded multilayer film
 or a coated multiple-layer film. The facer film desirably has a thickness
 range of from 0.35 mil (10 .mu.m) to 10 mls (250 .mu.m). The range is
 preferably from 0.5 mils (13 .mu.m) to 2 mils (50 .mu.m). The facer film
 may be laminated to the present foam board by any conventional method. One
 method includes hot roll laminating a heat-activated adhesive layer on the
 facer film. Another involves liquid coating or spray coating a hot melt
 adhesive or liquid-based adhesive onto a facer film or a foam board prior
 to lamination. An adhesive melt may also be extruded onto the facer film
 or foam, or coextruded with either the facer film or the foam (preferably
 the facer film), prior to lamination. Adhesion between the facer film and
 the foam board must be sufficient to minimize, preferably eliminate,
 delaminating during impact or bending. Separation or slipping between the
 facer film and the foam panel at their interface substantially negates any
 strengthening effect the facer film might otherwise have. The adhesion or
 peel strength between the facer film and foam board or panel is preferably
 such that any failure occurs within the foam rather than in the film upon
 bending board or laminate 12. The peel strength is preferably sufficient
 to ensure that part or all of any skin on the foam adheres to the film and
 separates from the remainder of the foam when the film is peeled off the
 foam. An effective adhesive must therefore adhere to both the facer film
 and the foam board or substrate. The adhesion is desirably expressed as a
 peel strength .gtoreq.100 grams per inch (gm/in) (39.4 gm/cm) and
 preferably .gtoreq.250 gm/in (98.5 gm/cm), according to the 180 degree
 peel test (ASTM D-903).
 Materials suitable for use as an adhesive or in an adhesive layer include
 those adhesive materials known in the art as useful with plastic films and
 foams. They include olefin copolymers such as ethylene/vinyl acetate,
 ethylene/acrylic acid, ethylene/n-butyl acrylate, ethylene/methylacrylate,
 ethylene ionomers, and ethylene or propylene graft anhydrides. Other
 useful adhesives include urethanes, copolyesters and copolyamides, styrene
 block copolymers such as styrenetbutadiene and styrene/isoprene polymers,
 and acrylic polymers. The adhesives may be thermoplastic or curable
 thermoset polymers, and can include tacky, pressure-sensitive adhesives.
 The material chosen for use as an adhesive or in adhesive layers is
 preferably recyclable within the foam board manufacturing process. When
 recycled, the adhesive material desirably does not negatively impact the
 physical integrity or properties of the foam to a substantial degree.
 The foam panel or foam core stock of foam board 12 may comprise any
 insulation foam known in the art such as extruded polystyrene foam, molded
 expanded polystyrene foam, extruded polyolefin foam, expanded polyolefin
 bead or pellet foam, polyisocyanurate foam, and polyurethane foam. The
 foam panel is desirably an extruded polystyrene foam or a molded, expanded
 polystyrene foam (known in the industry as "MEPS"). Such foams are readily
 recyclable, and properly chosen or compatible thermoplastic facer films
 and adhesive materials are readily recyclable with the foams.
 Recyclability means the foams can be ground into scrap that can be melt
 processed with virgin polymer materials, blowing agents, and additives to
 form new foams. Further, the attractive appearance of the foams can be
 maintained by using transparent facer films and adhesive materials. The
 facer films also substantially enhance the strength of thin polystyrene
 foam boards useful in insulating sheeting applications, particularly
 boards having a thickness of 1/4 in. to 4 in. (6.4 millimeters (mm) to 100
 mm). The foam panel, irrespective of the insulation foam from which it is
 made, has a thickness that is desirably from 1 to 4 in. (25 to 100 mm),
 preferably from 2 to 4 in (50 to 100 mm), with acceptable results at a
 thickness of 2 to 3 inches (50 to 75 mm).
 The composite walls may be either symmetric or asymmetric. A symmetric wall
 has a foam core with equal thickness concrete layers on either side of the
 foam core. A "2+2+2" wall has, for example a 2 in. (50 mm) foam core
 sandwiched between two 2 in. (50 mm) concrete layers. Similarly, a "3+3+3"
 composite wall has a 3 in. (75 mm) foam core sandwiched between two 3 in.
 (75 mm) concrete layers. A "3+3+2" asymmetric wall has a 3 in. (75 mm)
 foam core sandwiched between a 3 in. (75 mm) concrete layer and a 2 in.
 (50 mm) concrete layer. These examples simply illustrate potential
 symmetric and asymmetric wall structures. Any number of variations are
 possible by changing the thickness of the foam layer, either or both of
 the concrete layers, or both. Composite walls having two or more foam core
 layers alternating with concrete layers are also possible if one desires
 very thick walls.
 Polystyrene foams may be derived from conventional alkenyl aromatic polymer
 materials. Suitable alkenyl aromatic polymer materials include alkenyl
 aromatic homopolymers and copolymers of alkenyl aromatic compounds and
 copolymerizable ethylenically unsaturated comonomers. The alkenyl aromatic
 polymer material may further include minor proportions of non-alkenyl
 aromatic polymers. The alkenyl aromatic polymer material may comprise one
 or more alkenyl aromatic homopolymers, one or more alkenyl aromatic
 copolymers, a blend of one or more of each alkenyl aromatic homopolymers
 and copolymers, or a blend of any of the foregoing with a non-alkenyl
 aromatic polymer. Regardless of composition, the alkenyl aromatic polymer
 material preferably comprises greater than (&gt;) 50, more preferably &gt;70
 weight percent (wt %) alkenyl aromatic monomer units, based on total
 alkenyl aromatic polymer material weight. Most preferably, the alkenyl
 aromatic polymer material comprises 100 wt % alkenyl aromatic monomer
 units.
 Suitable alkenyl aromatic polymers include those derived from alkenyl
 aromatic monomers such as styrene, alphamethylstyrene, ethylstyrene, vinyl
 benzene, vinyl toluene, chlorostyrene, and bromostyrene. A preferred
 alkenyl aromatic polymer is polystyrene. Minor amounts of
 monoethylenically unsaturated compounds such as two to six carbon atoms
 (C2-6) alkyl acids and esters, ionomeric derivatives, and C4-6 dienes may
 be copolymerized with an alkenyl aromatic monomer. Examples of
 copolymerizable monomers include acrylic acid, methacrylic acid,
 ethacrylic acid, maleic acid, itaconic acid, acrylonitrile, maleic
 anhydride, methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl
 acrylate, methyl methacrylate, vinyl acetate and butadiene. Preferred
 foams comprise substantially (i.e., &gt;95 wt %), and most preferably
 entirely, polystyrene.
 Preparing an extruded polymer foam generally involves heating a polymer
 material to form a heat-plastified or polymer melt material, incorporating
 a blowing agent therein to form a foamable gel, and extruding the gel
 through a die into a zone of lower pressure to form the foam. Prior to
 mixing with the blowing agent, the polymer material is typically heated to
 a temperature at or above its glass transition temperature, or for these
 polymers having sufficient crystallinity to have a melt temperature (Tm),
 near the Tm. "Near" means at, above, or below the Tm and largely depends
 upon where stable foam exists. The temperature desirably fall within 30
 degrees centigrade (.degree. c.) above or below the Tm. Blowing agent
 incorporation or mixing into the melt polymer material may occur by any
 means known in the art such as with an extruder, a mixer or a blender. The
 blowing agent is mixed with the polymer melt at an elevated pressure
 sufficient to prevent substantial expansion of the polymer melt and to
 generally disperse the blowing agent homogeneously therein. Optionally, a
 nucleator may be blended in the polymer melt or dry blended with the
 polymer material prior to heat plastification. The foamable gel is
 typically cooled to a lower temperature to optimize physical
 characteristics of the foam structure. The gel may be cooled in the
 extruder or other mixing device or in separate coolers. The gel is then
 extruded or conveyed through a die of desired shape to a reduced or lower
 pressure to form the foam structure. The zone of lower pressure is at a
 pressure lower than that in which the foamable gel is maintained prior to
 extrusion through the die. The lower pressure may be superatmospheric,
 subatmospheric (evacuated or vacuum), or at an atmospheric level.
 MEPS foams may be formed by expansion of pre-expanded beads containing a
 blowing agent. The expanded beads may be molded at the time of expansion
 to form articles of various shapes. Processes for making pre-expanded
 beads and MEPS foam articles are taught in Plastic Foams, Part II, Frisch
 and Saunders, pp. 544-585, Marcel Dekker, Inc. (1973) and Plastic
 Materials, Brydson, 5th ed., pp. 426-429, Butterworths (1989), the
 teachings of which are incorporated herein by reference.
 Polyurethane and polyisocyanurate foam structures are usually made by
 reacting two formulated components, commonly called an A-component and a
 B-component. Suitable formulated components comprise an isocyanate and a
 polyol.
 Polyurethane foams can be prepared by reacting the polyol and the
 isocyanate on a 0.7:1 to 1.1:1 equivalent basis. Polyisocyanurate foams
 can be advantageously prepared by reacting the polyisocyanate with a minor
 amount of polyol to provide 0.10 to 0.70 hydroxyl equivalents of polyol
 per equivalent of polyisocyanate. U.S. Pat. No. 4,795,763, the teachings
 of which are incorporated herein by reference discloses useful
 polyurethanes and polyisocyanurates and processes for making them.
 Blowing agent selection is not critical to the present invention. Blowing
 agents useful in making the foam board will vary depending upon the
 composition of the foam, and can include inorganic blowing agents, organic
 blowing agents and chemical blowing agents. Suitable inorganic blowing
 agents include carbon dioxide, argon, and water. Organic blowing agents
 include aliphatic hydrocarbons having 1-9 carbon atoms (C 1-9), C 1-3
 aliphatic alcohols, and fully and partially halogenated aliphatic C 1-4
 hydrocarbons. Particularly useful agents include n-butane, isobutane,
 n-pentane, isopentane, ethanol, HFC 22a, 1,1-difluoroethane (HFC-152a),
 1,1,1,2-tetrafluoroethane (HFC-134a), ethyl chloride,
 1,1-dichloro-1-fluoroethane (HFC-141b), and 1-chloro-1,1-difluoroethane
 (HFC-142b).
 Various additives may be incorporated in the foams such as inorganic
 fillers, pigments, antioxidants, and scavengers, ultraviolet absorbers,
 flame retardants, processing aids, extrusion aids.
 In addition, a nucleating agent may be added to a polymer melt in order to
 control foam cell size . Preferred nucleating agents include inorganic
 substances such as calcium carbonate, talc, clay, titanium dioxide,
 silica, barium stearate, diatomaceous earth, and mixtures of citric acid
 and sodium bicarbonate. Suitable nucleating agent amounts range from 0.01
 to 5 parts by weight per hundred parts by weight (phr) of a polymer resin.
 The preferred range is from 0.1 to 3 phr.
 Suitable polystyrene foams have a density of from 10 kilograms per cubic
 meter (kg/m3) to 150 kg/m3, preferably from 10 kg/m3 to 70 kg/m3 and most
 preferably from 25 kg/m3 to 50 kg/m3, as determined in accordance with
 ASTM D-1622-88. The polystyrene foams have an average cell size of from
 0.1 mm to 5.0 mm and preferably from 0.15 mm to about 1.5 mm as determined
 in accordance with ASTM D3576-77.
 The polyisocyanurate foams and polyurethane foams have a density of from 10
 kg/m3 to 150 kg/m3 and most preferably from 10 kg/m3 to 70 kg/m3 according
 to ASTM D-1622-88.The polyisocyanurate foams and polyurethane foams have
 an average cell size of from 0.05 mm to 5.0 mm and preferably from 0.1 mm
 to 1.5 mm according to ASTM D3576-77.
 The polystyrene foams may be closed cell or open cell, but are preferably
 closed cell Preferred polystyrene foams have a closed-cell content
 according to ASTM D2856-87, &gt;90%.
 The present foam board may be used to insulate a surface or an enclosure or
 building by applying the board to the same. Other useful insulating
 applications include in roofing, and refrigeration.
 The following examples illustrate, but do not limit, the present invention.
 Unless otherwise indicated, all percentages, parts, or proportions are by
 weight.
 EXAMPLES
 Prepare a foam laminate by hot-roll laminating a two-layer film (oriented
 polypropylene base layer, 2.times.10-3 mm thick, with an extrusion coated
 ethylene/vinyl acetate adhesive layer, 1.times.10-3 mm thick), using a
 Black Bros. Hot roll laminator, to each side of a 51 mm thick,
 1200.times.2400 mm extruded polystyrene foam sheet. Use a hot roll surface
 temperature of 190.degree. C., and a line speed of 10 meters/minute.
 Evaluate the laminate for breaking strength using a test designed to
 simulate forces applied against the foam laminate in an actual
 wall-pouring operation. Suspend the foam between two pieces of dimensional
 lumber (nominally 50 mm high.times.100 mm wide and 300 mm long), to
 provide a span of 220 mm between the pieces of lumber. Apply a single
 point force to the center of the foam at a rate of 30 pounds (13.6
 kilograms (kg)) of force per second. The control foam, with no film on it,
 falls at 110 kg of force. The laminated foam fails at 173 kg of force.
 This improvement of over 50% in the breaking strength of the foam
 translates to a significantly lower failure rate when concrete is poured
 around the foam when it is suspended between the forms of a pour-in-place
 concrete wall.
 While embodiments of the laminate foam board of the present invention have
 been shown with regard to specific details, it will be appreciated that,
 depending upon the manufacturing process and the manufacturer's desires,
 the present invention may be modified by various changes while still being
 fairly within the scope of the novel teachings and principles herein set
 forth.