Foamed thermoplastic polymer and wood fiber profile and member

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FIELD OF THE INVENTION

The invention relates to materials used in the fabrication of structural members or trim elements used in construction materials and fenestration units installed in residential and commercial architecture. More particularly, the invention relates to an improved profile or structural member that can be used as a direct replacement for wood and metal components having superior properties for fenestration, structural or construction purposes. The structural members of the invention can comprise sized lumber replacements and structural components with complex functional shapes such as wood and door rails, jambs, stiles, sills, tracks, stop and sash and miscellaneous trim elements. Further, the invention relates to structural components used in the fabrication of fenestration units such as windows and doors for commercial and residential architecture.

The structural components are made from an extruded composite polymer foam material. The structural components of the invention can form high strength joints in the construction assembly. The materials can be easily installed, adjusted, shimmed and trimmed with conventional fasteners and techniques. The components have thermal and mechanical properties rendering them durable yet easy to manufacture and install.

BACKGROUND OF THE INVENTION

Conventional industrial, commercial and residential architecture commonly involve the use of structural and nonstructural components in the assembly of useful units. Such components are often made from concrete, stone, wood, glass or metal. These materials are well known and are well understood in their applicability to construction purposes.

Wood has been milled into shaped structural components such as sized lumber, trim, post and beam and have also been used to form structural components that can be assembled with glass to form door and window units. Wood, lumber, trim, post, beam and assembled units comprising wood have obvious utility and are well adapted for many uses in many residential or commercial installations. However, the wood used in these applications, under certain circumstances, can have problems. Wood can deteriorate due to the effect of fungus and insect attack. Further, wood members also suffer from cost problems related to the availability of suitable for wood for construction purposes and require substantial upkeep comprising painting or staining. Metal, typically aluminum or steel, components are also often used in industrial, commercial and residential construction. Metal components can suffer from rust or corrosion problems and require their own particular construction skills and maintenance regimen. Vinyl polymeric materials have also been used in formation of structural members and for forming profiles in window and door assembly. Such vinyl materials typically comprise a major proportion of a vinyl polymer with a variety of additive materials that are used. Filled and unfilled (filled with additive materials such as fiber, inorganics, dye etc.) rigid and flexible thermoplastic materials have been extruded or injection molded into a variety of both structural and sealing materials. A thermoplastic polyvinyl chloride has been combined with wood members in the manufacture of PERMASHIELD.RTM. brand windows manufactured by Andersen Corporation for many years. This vinyl cladding technology is disclosed in Zaninni, U.S. Pat. Nos. 2,926,729 and 3,432,885. The technology disclosed in these patents involves the extrusion or injection molding of a thin polyvinyl chloride coating or envelope loosely formed around a shaped wooden structural member.

The polyvinyl chloride thermoplastic materials have also been combined with wood products to make extrusion materials. Initial efforts resulted in a material that can be directly extruded to form a member that has a modulus typically about 500,000 or less. Such members also failed to have adequate compressive strength, coefficient of thermal expansion, coefficient of elasticity, fastener retention or other useful properties required for use in many construction applications.

More recently, U.S. Pat. Nos. 5,486,553, 5,539,027, 5,406,768, 5,497,594, 5,441,801 and 5,518,677, assigned to Andersen Corporation, disclose the use of a thermoplastic such as polyvinyl chloride and wood fiber for the purpose of manufacturing a high strength composite material in the FIBREX.RTM. brand materials technology. Such composites are useful in the manufacture of a structural member such as a hollow profile that can be used in window and door manufacture. These materials have a high modulus (800,000 psi or more) and can be easily manufactured, assembled and installed. These unique high strength materials have had substantial success with respect to their use in window and door manufacture.

The PERMASHIELD.RTM. brand technology and the FIBREX.RTM. brand materials technology have substantial utility and have had substantial success in a variety of applications. Further extensions of thermoplastic polymer technology are useful for other applications. A need exists to obtain materials having enhanced properties.

BRIEF DISCUSSION OF THE INVENTION

We have found that a superior structural foamed material can be used to form a member which can be used as a replacement for stone, wood, glass and metal members. The member comprise a thermoplastic foam comprising a foamed composite comprising a thermoplastic polymer and a wood fiber. The wood fiber can be derived from either soft woods or evergreens or from hard woods commonly known as broad leaf deciduous trees. Soft woods are generally preferred for fiber manufacture because the resulting fibers are longer, contain high percentages of lignin and lower percentages of hemicellulose than hard woods. Additional fiber make-up can be derived from a number of secondary or fiber reclaim sources including bamboo, rice, sugar cane, and recycled fibers from newspapers, boxes, computer printouts, etc. One preferred source of wood fiber of this invention comprises the wood fiber product or by-product of sawing or milling soft woods. A quality fiber can be made by milling and a by-product of milling commonly known as sawdust or milling tailings can be used.

A large variety of thermoplastic polymer or resins can be used in the foamed composite materials of the invention. For the purpose of this application, a useful resin is a general term covering a thermoplastic that may or may not contain an additional filler or reinforcing material, other than wood fiber, that have mechanical, chemical and thermal properties suitable for use as structural components, machine components and chemical processing equipment components. We have found that the resins useful in the invention include both condensation polymeric materials and vinyl polymeric materials. The foamed material can provide improved thermal and physical properties. A large variety of vinyl polymeric materials can be used in the composite materials can be used in the composite materials of the invention. Useful vinyl polymers are polymers made by homopolymerization, copolymerization or terpolymerization methods. Condensation polymer resins can also be used in the composite materials of the invention.

The properties enhanced in the foamed composite include resistance to shrinkage, and improved COTE, compressive strength and fastener retention. Such a material display properties rendering the structural member ideal for industrial, commercial and household construction applications. The materials have acceptable thermal properties including a minimal coefficient of thermal expansion, minimal shrink and minimal heat distortion. Further, the materials can be easily manufactured, assembled into a useful structure and can be easily installed. For the purpose of this patent application the term "extrusion mass" indicates material processed by an extruder resulting in the foamed thermal plastic wood fiber composite. The extrusion mass can comprise a blend of powder, flaked or pelletized thermoplastic discrete wood fibers and a separate blowing agent each component mixed together to form a final extrusion mass. Alternatively, the extrusion mass can comprise a preformed pellet comprising thermoplastic, wood fiber and blowing agent preformed and a preextruded in a pellet composition. Alternatively, the extrusion mass can comprise a thermoplastic wood fiber pellet dry blended with a blowing agent. Alternatively, the extrusion mass can comprise the thermoplastic with the blowing agent dissolved or dispersed in the thermoplastic in the form of a pellet which is then blended with a separate wood fiber phase. In other words, the extrusion mass can comprise the thermoplastic, the wood fiber or the blowing agent in any useful form of an extrudable mass.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevated sideview of a typical sill stop used for the physical property testing discussed in the specification.

FIG. 2 is a direct sideview of a typical sill stop as used for the physical property testing discussed in the specification.

FIG. 3 is an isometric end view of a typical mull casing as used for the physical property testing discussed in the specification. These structures in FIGS. 1-3 are useful as components of fenestration units.

DETAILED DESCRIPTION OF THE INVENTION

Wood Fiber

The primary source for wood fiber of this invention comprises the wood fiber product or by-product of comminuting, sawing or milling wood materials, preferably soft woods. A quality fiber can be made by milling and a by-product of milling commonly known as sawdust or milling tailings can be used. Such wood fiber has a regular reproducible shape and aspect ratio. The fibers based on a random selection of about 100 fibers are commonly at least 0.05, preferably 0.1 mm in length, about 0.02 to 1 mm in thickness and commonly have an aspect ratio of at least 1.5. Preferably, the fibers are 0.1 to 5 mm in length with an aspect ratio between 2 and 7, preferably 2.5 to 6. The preferred fiber for use in this invention are fibers derived from processes common in the manufacture of windows and doors. Wooden members are commonly ripped or sawed to size in a cross grain direction to form appropriate lengths and widths of wood materials. The by-product of such sawing operations is a substantial quantity of sawdust. In shaping a regular shaped piece of wood into a useful milled shape, wood is commonly passed through machines which selectively removes wood from the piece leaving the useful shape. Such milling operations produces substantial quantities of sawdust or mill tailing by-products. Lastly, when shaped materials arc cut to size and mitered joints, butt joints, overlapping joints, mortise and tenon joints are manufactured from pre-shaped wooden members, substantial waste trim is produced. Such large trim pieces are commonly cut and machined to convert the larger objects into wood fiber having dimensions approximating sawdust or mill tailing dimensions. The wood fiber sources of the invention can be blended regardless of particle size and used to make the composite. The fiber stream can be pre-sized to a preferred range or can be sized after blending. Further, the fiber can be pre-pelletized before use in composite manufacture.

Such sawdust material can contain substantial proportions of compatible waste stream by-products. Such by-products include waste polyvinyl chloride or other thermoplastic or polymeric materials that have been used as coating, cladding or envelope on wooden members; recycled structural members made from thermoplastic materials or composites; polymeric materials from coatings; adhesive components in the form of hot melt adhesives, solvent based adhesives, powdered adhesives, etc.; paints including water based paints, alkyd paints, epoxy paints, etc.; preservatives, anti-fungal agents, anti-bacterial agents, insecticides, etc., and other waste streams common in the manufacture of wooden doors and windows. The total waste stream content of the wood fiber materials is commonly less than 25 weight percent (wt %) of the total wood fiber input into the composite product. Of the total waste recycle, approximately 10 wt % of that can comprise a thermoplastic. Commonly, the intentional recycle ranges from about 1 to about 25 wt %, preferably about 2 to about 20 wt %, most commonly from about 3 to about 15 wt % of contaminants based on the sawdust.

Moisture control is an important element of manufacturing a useful formed composite linear extrudate or pellet. Moisture can interfere with or change the constancy of the composite and the foamed product. Depending on the equipment used and processing conditions, control of the water content of the material can be important in forming a successful structural member substantially free of substantial changes in density, internal voids or surface blemishes. The concentration of water present in the sawdust during the formation of pellet or foaming of the linear extrudate when heated can flash from the surface of the newly extruded structural member and can come as a result of a rapid volatilization, form a steam bubble deep in the interior of the extruded member which can pass from the interior through the hot thermoplastic extrudate leaving a substantial flaw. In a similar fashion, surface water can bubble and leave cracks, bubbles or other surface flaws in the extruded member. Further, engineering resins that are moisture sensitive should be avoided. Water can react with some condensation polymers resulting in increased melt index (MI) (MI as measured by ASTM 1238) and reduced molecular weight (M.sub.n or M.sub.W).

Trees when cut depending on relative humidity and season can contain from 30 to 300 wt % water based on fiber content. After rough cutting and finishing into sized lumber, seasoned wood can have a water content of from 20 to 30 wt % based on fiber content. Kiln dried sized lumber cut to length can have a water content typically in the range of 8 to 12%, commonly 8 to 10 wt % based on fiber. Some wood source, such as poplar or aspen, can have increased moisture content while some hard woods can have reduced water content.

Because of the variation in water content of wood fiber source and the sensitivity of extrudate to water content control of water to a level of less than 8 wt % in the pellet based on pellet weight is important. For structural members extruded in non-vented extrusion process, the pellet should be as dry as possible and have a water content between 0.01 and 5%, preferably less than 1.5 wt %. When using vented equipment in manufacturing the extruded linear member, a water content of less than 8 wt % can be tolerated if processing conditions are such that vented extrusion equipment can dry the thermoplastic material prior to the final formation of the structural member at the extrusion head.

Thermoplastic Polymers, Hompolymers Copolymers and Polymeric Alloys

A large variety of thermoplastic polymer or resins can be used in the foamed composite materials of the invention. For the purpose of this application, a useful resin is a general term covering a thermoplastic that may or may not contain a filler or reinforcing material that have mechanical, chemical and thermal properties suitable for use as structural components, machine components and chemical processing equipment components. We have found that the resins useful in the invention include both condensation polymeric materials and vinyl polymeric materials. Included are both vinyl and condensation polymer resins, and alloys thereof, such as acrylonitrile-butadiene-styrene (ABS), polyacetyl resins, polyacrylic resins, fluorocarbon resins, nylon, phenoxy resins, polybutylene resins, polyarylether such as polyphenylether, polyphenylsulfide materials; polycarbonate materials, chlorinated polyether resins, polyethersulfone resins, polyphenylene oxide resins, polysulfone resins, polyimide resins, thermoplastic urethane elastomers and many other resin materials. Vinyl polymers are typically manufactured by the polymerization of monomers having an ethylenically unsaturated olefinic group. Condensation polymer resins are typically prepared by a condensation polymerization reaction which is typically considered to be a stepwise chemical reaction in which two or more molecules combined, often but not necessarily accompanied by the separation of water or some other simple typically volatile substance. If a polymer is formed, the process is called polycondensation.

Vinyl Polymers

A large variety of vinyl polymeric materials can be used in the composite materials can be used in the composite materials of the invention. Useful vinyl polymers are polymers made by homopolymerization, copolymerizati