CA2177412A1 - Thermoplastic blend material for capping or coating composite - Google Patents

Abstract

The invention relates to a layered profile thermoplastic extrusion. The profile of the invention comprises a thermoplastic composite core having an exterior layer comprising a material resistant to the damaging effects of the environment. The core comprises a thermoplastic polymer and an effective amount, to improve structural properties, of a cellulosic fiber.
The exterior layer comprises a blend of a thermoplastic polyvinyl chloride polymer composition and an effective structural and stabilizing amount of a polyvinylidene chloride polymer composition. The exterior layer can also comprise standard pigments, dyes and other process aids to produce an extruded exterior layer on the thermoplastic profile. The resulting profile comprising the core and exterior layer can be used as a high strength structural member in the manufacture of consumer and construction grade windows and doors. The exterior layer is uniquely resistant to the undesirable effects of sunlight, pollution, rain, wind and snow, freeze-thaw cycles and other harsh aspects of the environment.

Description

-Ln~IOPLASTIC BLEND MATERIAL FOR
CAPPING OR COATING COMPOSITE

Field of the Invention The invention relates to materials used for the fabrication of layered profiles or capped structural members used in residential and commercial architecture and preferably in the manufacture of windows and doors.
More particularly, the invention relates to an improved bilayer or multilayer structural member that can be used as a direct replacement for wood and metal components having superior weathering, aging and structural properties. The layered structural members of the invention can comprise sized member replacement or structural components of complex functional shapes such as window and door rails, jambs, styles, sills, tracks, stop sash and trim and elements such as grid cove, bead quarter round, etc.

Backqround of the Invention Conventional window and door manufacturers utilize structural members made commonly from hard and soft wood members, metal components, typically aluminum, and extruded thermoplastic materials. Residential window and door components are often manufactured from a number of specially shaped, milled wood products that are assembled with glass sheets to form typically double hung or casement windows and sliding door units. Some units are made from extruded polyvinyl chloride (vinyl) thermoplastic materials in preferred shapes. Such wood or vinyl window or door units are typically structurally sound and can be adapted for use in certain installations. However, such materials require maintenance and can have environmental degradation problems caused by insect attack or microbial attack on wood components and aging or environmental degradation when exposed to sunlight, heat, cold, freeze-thaw cycle and the natural environment. Metal windows and doors have been introduced into the market place, however, ~ 2 1 774 1 2 -such units made from extruded aluminum parts are often energy inefficient and transfer substantial quantities of heat from a heated exterior into a cold environment.
Extruded thermoplastic materials have been used in the manufacture of window and door components. Typically sealed edging grill and coatings have been manufactured from thermoplastic material. Thermoplastic polyvinyl chloride materials have been combined with wooden structural members in the manufacture of PERMASHIELD
windows manufactured by Andersen Corporation for many years. The technology performing the PERMASHIELD vinyl coated wooden window members is disclosed in Zanini, U.S. Patent Nos. 2,926,729 and 3,432,883. In the manufacture of PERMASHIELD brand windows, a polyvinyl chloride envelope or coating is extruded around the wooden member as it passes through an extrusion head or dye. Such coated members are commonly used as structural components in forming the window frame work, double hung or casement units.
Polyvinyl chloride has been a successful component in the manufacture of residential and commercial window and door units for many years. Polyvinyl chloride has always been considered to be relatively stable in a natural environment having acceptable resistance to weather including sunlight, rain, snow, freeze-thaw cycles and other aspects of the change in seasons. The purchasers of window and door units in both residential and commercial real estate are continuing to demand increased performance when compared to past achievements. One area highlighted for improvement in window and door manufacturer is the weatherability of extruded thermoplastic profiles. Any improvement in the resistance of the thermoplastic profile to the harsh effects of strong sun, rain, snow, wind, freeze-thaw cycles and other environmental conditions will be a welcome addition to the performance of known structural units. Polyvinyl chloride polymer compositions used in -such structural members have been known for many years to contain pigments and other stabilizers that render the polyvinyl chloride resistant to the undesirable impact of weather. These pigments and other stabilizing additives have been very successful in producing a quality polyvinyl chloride product. An increase in the properties of polyvinyl chloride is an important goal of thermoplastic research and development.
Recently, Hartley et al., U.S. Patent No. 5,284,710 has disclosed an improved thermoplastic material. The thermoplastic comprises a first layer comprising a mixture of an acrylic polymeric composition and a fluoropolymer polymeric composition and an inorganic pigment which is used to coat a second layer on a first member comprising a thermoplastic material. Hartley et al. disclose that the acrylic\fluoropolymer blend coating cooperates with the underlying thermoplastic (preferably polyvinyl chloride) layer to reduce UV-light induced polymer degradation when exposed to the environment in an outdoor application. Hartley et al.
disclose that the acrylic\fluoropolymer composite reduces loss in color, has improved stability, improved flexibility or strength. In our testing of the Hartley et al. material we have found the material to have substantial advantages, however, the market place appears to require improved performance when compared to the Hartley et al. structures. Summers et al., U.S.
Patent No. 4,183,777 disclosed an improved weather resistant product. The product comprises a substrate, extrudate and a capstock containing a polyvinyl chloride, a titanium dioxide pigment and a plasticizer.
Summers, U.S. Patent No. 4,247,506 teaches a method and apparatus for processing extruded thermoplastic materials showing the production of a siding profile extruded from a thermoplastic such as PVC, CPVC or ABS.
Ravinovitch et al., U.S. Patent No. 4,424,292 disclose a vinyl polymer composition containing a black infrared -reflecting pigment to stabilize the polymer against the undesirable aging properties of sunlight. The preferred pigments comprise Ferro Black (Cr2O3-Fe2O3). Wallen, U.S.
Patent No. 5,030,676 teaches a W stabilized polyvinyl chloride composition adapted for exterior use in house siding and window profiles. The stabilized polyvinyl chloride composition contains an organic impact modifier, at least one thermal dehydrohalogenation stabilizer and an ultraviolet stabilization system.
Bortnick et al., U.S. Patent No. 5,066,696 disclose stabilizing polymers such as acrylates, styrenics, polyvinyl chlorides and others with melamine type hindered aromatic amine stabilizer compositions.
Trabert et al., U.S. Patent No. 5,318,737 teach a thermoplastic composite having an underlying structural extrudate with a capstock comprising an acrylic thermoplastic. The capstock contains about 40 to 88 wt~
of an acrylic polymer having a molecular weight of at least about 125,000 daltons and from about 12 to 60 wt~
of an acrylate-based impact modifier resin. The modifier resin takes the form of discrete polymer particles dispersed in the acrylic thermoplastic layer.
Grunewalder et al., U.S. Patent No. 5,322,899 teach a layered extruded profile element. The profile contains a capstock layer comprising a fluoropolymer/acrylic polymer blend. The preferred polymer blend contains a major proportion of the fluoropolymer and minor proportions of the acrylic materials, pigments, lubricants and other additive components. Kelch et al., U.S. Patent No. 5,356,705 teach a laminated weatherable film capped siding material. The structure comprises a weatherable styrene acrylonitrile copolymer comprising an impact modifier comprising an olefinic elastomer or an acrylic elastomer.
There is a large body of art relating to polyvinyl chloride polymer compositions, polyvinyl-fluoropolymer compositions and blended materials comprising a halo -polymer and other additives and components. However, in view of this large body of prior art, significantly improved halo-polymer materials for environmentally stable structures have, as yet, not been disclosed. A
substantial need exists in providing a thermoplastic profile material having significantly improved resistance to the degrading effects of the environment.

summarY of the Invention We have found that significant improvements in weatherability and aging resistance to the degrading or discoloring effects of the environment can be achieved by forming structural profiles from a core thermoplastic polymer or composite thereof having a protective exterior layer comprising a binary blend of a polyvinyl chloride polymer composition with a polyvinylidene fluoride polymer composition. The portions of the profile exposed to the environment are manufactured with the exterior layer blend material. The exterior layer is surprisingly effective in protecting the profile as a whole from the undesirable effects of weather and the environment. We have found that the use of a major portion of a polyvinyl chloride and an effective amount, typically between about 1 and 45 wt~, of a polyvinylidene fluoride polymer composition in combination with other additives forms an exterior layer that is dimensionally stable and superior to other thermoplastic materials in resisting the degrading effects of weather and the environment. The polymer blend exterior layer bonds securely to the underlying thermoplastic, has a well matched thermal expansion coefficient, can be extruded at temperatures easily achieved in the extrusion of the composite core and is acceptable in terms of cost and other production considerations. For the purpose of this application, the term "polymer compositions" include homopolymers, copolymers, etc. and polymer materials containing stabilizing additives, pigments, dye, lubricants, reinforcing fibers, and other adjuvants.

Brief Diecueeion of the Drawin~s Figure 1 is a graphical representation of the color change of the cap stock material when exposed to xenon arc radiation exposure. The color change over thirty six months is shown. This test is an accelerated aging test that should yield results that correlate with actual exterior exposure results.
Figure 2 is a graphical representation of the color stability of various poly vinyl chloride, poly vinylidene chloride (PVC/PVDF) materials. The graph shows a parabola having a focus between 70~ and 80% PVC
(20~ and 30~) PVDF showing substantially enhanced stability.

Detailed Diecueeion of the Invention The improved layered profile structural member of the invention contain a core material comprising a thermoplastic polymer or a thermoplastic-cellulosic fiber composite having an exterior layer comprising a polymer blend comprising a major proportion of polyvinyl chloride and an effective stabilizing amount comprising about 0.1 to 45 wt~ of a polyvinylidene fluoride material. The exterior layer can comprise preferably about 5 to 40 wt~ of the polyvinylidene fluoride, most preferably about 20 to 35 wt~ for reasons of improved environmental resistance, manufacturing ease and manufacturing properties well matched between the exterior layer and the extruded core material.
The exterior layer comprises a polyvinyl chloride.
Polyvinyl chloride (PVC) is a common industrial thermoplastic. The polyvinyl chloride is compatible with many additive stabilizers, lubricants, and other polymers. PVC is known for use in rigid extruded ~' articles and can be used to make clear sheet or opaque pigmented materials. PVC is typically made by aqueous suspension polymerization or bulk polymerization techniques. Polyvinyl chloride polymer compositions useful in the extrusions of the invention comprise polymers having a molecular weight (Mn) of about 40,000 to 140,000, preferably about 7800 to 9800.
The core can be manufactured from a variety of known thermoplastic extrudable polymeric materials.
Typically polymer materials that can be used in structural units can be a core material. Known thermoplastic resins that can be used in such an application include polycarbonate acrylic polymers, acrylamide polymers, poly(acrylonitrile-butadiene-styrene) polymers, polyether ether ketone polymers, polyacrylonitrile, polyethylene, polypropylene, and other well known structural materials.

Polyvinylidene Fluoride Homo~olymer, Copolymers and Polymeric Blends The blend material obtains significantly improved heat distortion, impact resistance, and other mechanical properties including W and temperature stability due to the inclusion of a fluoropolymer composition. Such fluoropolymer compositions includethermoplastic, homopolymers or copolymers of vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, pentafIuoropropylene, hexafluoropropylene, and chlorotrifluoroethylene, as well as copolymers of these fluorinated monomers with one or more other monomers including any compatible copolymerized vinyl monomer such as ethylene, propylene, vinyl chloride, vinylidene chloride, acrylic acid, methylacrylic acid, methylacrylate, methylmethacrylate, and other similar acrylic monomers, etc. Further, mixtures of fluoropolymers can also be used in the blend composition if compatible. A preferred class of polyvinylidene fluoride homopolymers and copolymers are sold under the ` ` 2177412 -trade name KYNAR~ sold by Elf Adochem North America, Philadelphia, Pennsylvania. Similar materials are sold by Kureha, Solvay Polymers, Asai Glass and ICI Advanced Materials. Preferred polyvinylidene fluoride materials are polyvinylidene fluoride homopolymers and a copolymer of vinylidene fluoride with hexofluoropropylene.

Polyvinyl Chloride Homopolymer, Copolymers and Polymeric Blends Polyvinyl chloride is a common commodity thermoplastic polymer. Vinyl chloride monomer is made from a variety of different processes such as the reaction of acetylene and hydrogen chloride and the direct chlorination of ethylene. Polyvinyl chloride is typically manufactured by the free radical polymerization of vinyl chloride resulting in a useful thermoplastic polymer. After polymerization, polyvinyl chloride is commonly combined with thermal stabilizers, lubricants, plasticizers, organic and inorganic pigments, fillers, biocides, processing aids, smoke suppressants, flame retardants and other commonly available additive materials. Polyvinyl chloride can also be combined with other vinyl monomers in the manufacture of polyvinyl chloride copolymers. Such copolymers can be linear copolymers, branched copolymers, graft copolymers, random copolymers, regular repeating copolymers, block copolymers, etc. Monomers that can be combined with vinyl chloride to form vinyl chloride copolymers include a acrylonitrile; alpha-olefins such as ethylene, propylene, etc.; chlorinatedmonomers such as vinylidene dichloride, acrylate monomers such as acrylic acid, methylacrylate, methylmethacrylate, acrylamide, hydroxyethyl acrylate, and others; styrenic monomers such as styrene, alphamethyl styrene, vinyl toluene, etc.; vinyl acetate;
and other commonly available ethylenically unsaturated monomer compositions.
Such monomers can be used in an amount of up to -about 50 mol-~, the balance being vinyl chloride. Such blends or polymer alloys can be useful in manufacturing the pellet or linear extrudate of the invention. Such blends typically comprise two miscible polymers blended to form a uniform composition. Scientific and commercial progress in the area of polymer blends has lead to the realization that important physical property improvements can be made not by developing new polymer material but by forming polymer blends or blends. A
polymer blend at equilibrium comprises a mixture of two amorphous polymers existing as a single phase of intimately mixed segments of the two macro molecular components. Miscible amorphous polymers form glasses upon sufficient cooling and a homogeneous or miscible polymer blend exhibits a single, composition dependent glass transition temperature (Tg). Immiscible or non-alloyed blend of polymers typically displays two or more glass transition temperatures associated with immiscible polymer phases. In the simplest cases, the properties of polymer blends reflect a composition weighted average of properties possessed by the components. In general, however, the property dependence on composition varies in a complex way with a particular property, the nature of the components (glassy, rubbery or semi-crystalline), the thermodynamic state of the blend, and its mechanical state whether molecules and phases are oriented.
Polyvinyl chloride forms a number of known polymer blends including, for example, polyvinyl chloride/nitrile rubber; polyvinyl chloride and related chlorinated copolymers and terpolymers of polyvinyl chloride or vinylidine dichloride; polyvinyl chloride/alphamethyl styrene-acrylonitrile copolymer blends; polyvinyl chloride/polyethylene; polyvinyl chloride/chlorinated polyethylene and others.
The primary requirement for the underlying thermoplastic polymeric material is that it has sufficient thermopiastic properties to permit the -composition material or pellet to be extruded or injection molded in a thermoplastic process forming the rigid structural member. Polyvinyl chloride homopolymers copolymers and polymer alloys are available from a number of manufacturers including Geon, Vista, Air Products, Occidental Chemicals, etc. Preferred polymer materials include polyvinyl chloride homopolymer having a molecular weight (M~) of about 90,000 + 50,000, most preferably about 88,000 + 10,000, a CPVC polymer, an ABS polymer, etc.
The blend material of the invention can contain effective amounts, to obtain the benefits of known additives, preferably ranging from about 0.5 to about 10 parts by weight per each 100 parts by weight of the total blend composition of various compounding components known in the art. Such components include lubricants such as stearic acid, oxidized polyethylene, polypropylene, paraffin wax, metallic salts of fatty esters including mixtures, etc. Stabilizers for the polymer materials include barium/cadmium/zinc compounds and various organotins, for example, methyl, butyl, ontyltin carboxylates, mercapto-carboxylates, mercaptides, glycolates, thioglycolates, etc. Specific examples include dibutyl-S-S'-bis(isooxyl mercapto acetate), dibutyl tin dilaurate, with organotin di-isooxyl thioglycolates being preferred. Secondary stabilizers may include, for example, phosphates and metal salts of phosphoric acid. Specific examples of salts include water soluble alkaline metal phosphate salts, disodium hydrogen phosphate, orthophosphate such as mono, di and triorthophosphates of said alkaline metals, alkaline metal polyphosphates, tetrapolyphosphates, and similar condensed phosphate species. In addition, antioxidants may also be incorporated such as phenolics, BHT, BHA, various inhibitors such as substituted benzothiazoles, etc. can -be utilized to provide oxidation resistance, W
resistance, etc.
Various fillers, pigments and colorants can also be used in effective amounts. Examples of fillers include caesium carbonate clay silica, various silicates and talc. Examples of various pigments include rutile titanium dioxide, carbon black and the like.
Plasticizers may be included in any manner and amount when required by the end use. Plasticizers are well known in the art but are also set forth in "The Technology of Plasticizers", Sears and Darby, John Marley & Sons, New York, 1982, which are incorporated herein by reference.
The PVC/PVDF blend can be prepared in high speed powered mixing devices that can be operated at an effective melt blending temperature. High speed power mixing devices including a Banberry mixer extruder equipment. Once compounded, the mixed blend can be calendared, extruded, or injected, molded or processed in any suitable thermoplastic melt processing means.
The polymers can also be mixed with various additives, pigments, antioxidants, etc. in a high intensity mixer such as a Hershel mixer and then processed on an extruder into pellets or directly into a finished article by way of compounding extruder. In general, any conventional means of compounding melt processing, extruding, injection molding, etc. can be used to prepare the blend of the invention. The materials in the invention can be used in melt process equipment to form a variety of end use articles such as molded sheets, trays, structural members, appliance parts, cases, electric outlets, piping, automotive components, electronic components, etc.
The exterior layer of the extruded profiles of the invention can comprise a major proportion (greater than 50 wt~) of a polyvinyl chloride polymer composition.
The extruded material can also contain a minor -proportion tless than 50 wt~) of a polyvinylidene fluoride polymer composition in combination with optional additives including heat stabilizers, lubricants, UV absorbers, light stabilizers, pigments, impact modifiers, processing aids and other known additive materials. The exterior layer of the extruded profile of the invention can contain an additive or stabilizer that improves the resistance of the polymer material through the undesirable effects of visible and ultraviolet light. A variety of types of stabilizers can be used including organic salts of barium, cadmium and tin. Preferred salts are salts of carboxylic acids including maleic acid, phthalic acid or other similar organic carboxylic acids. Oxygen scavengers can be used to prevent oxygen catalyzed dehydrohalengenation.
Ultraviolet light absorbers are useful in improving the weatherability in light resistance of the exterior layer. Preferred ultraviolet light absorbers are derivatives of orthohydroxy benzophenone, orthohydroxy phenyl salycilate or 2-(ortho-hydroxyphenyl)benzotriazole.
Additives can also be used to prevent or suppress thermal oxidative degradation. Both hindered phenols and hindered aromatic amines, acting as labile hydrogen donors, can inhibit thermal degradation of a variety of polymer materials. Helpful materials that prevent thermal degradation and thermal oxidation include alkyl thiodipropionates, naphtholdisulfides, naphtholthioles, mercaptobenzothiazoles, benzothiazine, tris(para-nonylphenylphosphite), zinc dimethyldithiocarbamates,oxamides, oxanalides, benzotriazoles and others.
Thermoplastic materials are often formulated with lubricants (also known as mold release agents) to promote the ease of extrusion of the materials in extrusion dies. Such lubricants control or eliminate the tendency of the melt polymer to adhere to the surface of the dye or mold. Lubricants are diverse in terms of physical and chemical properties. Typical chemical classes include the long chain alkyl derivatives such as synthetic waxes comprising fatty esters, fatty acid, fatty acid methyl salts, fatty acid amides, fatty acid amines and fatty alcohols. Other natural products include petroleum waxes, vegetable waxes, animal waxes, cellulose derivatives, and polysaccharide. Synthetic polymer lubricants include silicone polymer materials, fluorocarbons and low molecular weight fluoropolymers including polytetrafluoroethylene (Teflon), poly(fluoroacrylate), polyfluoro-ethers and others. Fluorinated lubricant compounds include fluorinated fatty acids and alcohols such as perfluorolauric acid, perfluorostearic acid, etc. Lastly, inorganic lubricants are known including silicates, clays, silica, graphite and others.
The preferred extruded profile structural member of the invention contains a structural core comprising a polyvinyl chloride-cellulosic fiber composite. For the purpose of this invention, the term "core" connotes any shaped structural member including solid structural members, hollow structural members, structural members having a complex external shape, a variety of internal components including support webs, screw anchors, internal assembly components, etc. The core can also contain external features such as screen supports, hardware supports, decorative relief, or any other internal or external feature or structure useful in the manufacture of windows or doors. Such a core structure can be covered with the external layer comprising the PVC\PVDF material to preserve weatherability.
The core material is preferably made of a polyvinyl chloride cellulosic fiber composite. The polyvinyl chloride material used in the composite is recited above.
Cellulosic fibers used in the manufacture of the composite core of the invention can be obtained from a variety of ~ources of fiber. Virtually any fibrouQ
cellulo~ic material th~t can be converted into the preferred particle size and aspect ratios required for structural propertie~ can be used. However, a preferre~
fiber for use in the composites of the invent~on comprise cellulosic wood fibers. The wood f~ber can be derived from ~oft woods, evergreenQ, hard wood~, also commonly known as broad leaf deciduouQ tree~. The wood fiber can be made by abrading bulk wood ineo fibrouq component~ or by u~ing the sawdust by-product of a wood milling or cutting operations. Preferred wood fiber has a regular reprod~cible shape and a~pect ratio. The fibers are commonly about 0.1 to about 10 millimeters i~
length. The fibers al~o commonly have a minimum thickne~s of about 0.1 millimeters and are preferably between 0.01 and 3 millimeters in thickness. One i~portant aspect of the fibcr3 of the invention i9 aspect ratio (ratio of lenyth or width) which is typically greater than about 1.8. Preferably, the fiber dimensions are 1 to 10 millimeters ln length, 0.1 to 3 -millimeters in thickness having an aspect ratio of about 2 to 7.
The raw cellulosic fiber is commonly screened or otherwise classified to obtain a consistent fiber raw material having reliable length thickness and aspect ratio. The source of quality fiber with stable dimensions can significantly increase the structural properties as measured by Young's modulus and tensile strength.
We have found that in the manufacture of the composite materials of the invention that moisture control in the cellulosic fiber is important. Water is a natural component of all fiber sources and can range, depending on season and local climate, from 5 to 45 wt~
water based on the total weight of a cellulosic source.
We have found that the wood fiber used in the composite material should contain less than about 8~ water based on the wood fiber. The preferred water content of the extruded composite is as low as can be achieved by drying the wood fiber at any point in the process. The wood fiber can be dried prior to combination with the thermoplastic, the thermoplastic after combination can be dried prior to introduction into the extruder material or the heated mass of thermoplastic and fiber can be dried during shear processing or at any point in the extrusion process. The material can be exposed to vacuum or other processing conditions that can tend to optimize water removal. Commonly, thermoplastic composites used in the manufacture of the profiles in the invention are typically preformed into pellet materials. The preferred pellets for use in this invention contain less than 8 wt~, moisture less than 5~
moisture and preferably less than 3.5 wt~ moisture. The resulting extruded material can contain less moisture than the pellet moisture if processed to minimize water content.
Preferred blend of PVC and PVDF can be obtained in the form of powder chips or small pellets. The materials can be dry blended with other ingredients including W absorbers, lubricants, etc. and then pelletized in commonly available single or twin extruders at an appropriate temperature above the melting point of the resin materials in order to thoroughly mix the polymers and additive material into a uniform melt composition. The melt can be extruded through a dye forming spaghetti like strands or pellets (the strands are cut into segments). The preferred pellets are about 1-5 millimeters in diameter and about 1-10 millimeters long. The coextruded profiles of the invention having an exterior layer comprising the PVC-PVDF polymer allow layered on a polyvinyl chloride composite material were manufactured by coextruding the materials in twin screw equipment. The extruder was equipped with a dye capable of forming the exterior layer on the composite layer. The composite material can be extruded by the twin screw or single screw extruder at temperatures ranging from about 140C to 175C in a preferred profile for window or door manufacture. The exterior layer can be formed by coextruding onto the structural profile material derived from the blend pellets described above. The twin screw extruder for the PVC-PVDF material can be run at temperatures from about 150C to provide the blend material at extrusion rates similar to the profile composite. The PVC-PVDF material is extruded through a dye providing an exterior layer conforming in shape to the composite material. The exterior layer typically has a thickness of about 0.1 to 1.5 millimeters, preferably 0.03 to 0.8 millimeters and covers any portion of the extrudate exposed to the exterior environment. For PVC covering layers the exterior layer typically has a thickness of about 0.05 to 1.5 millimeters and covers any portion of the extrudate exposed to the exterior environment. The exterior layer -can cover a relatively small portion, 5-10~ of the exterior surface area of the profile, or can entirely cover 95-100~ of the exterior surface area. Any intermediate surface area required for environmental protection can be selected by the engineer. No adhesive layer is used between the exterior layer and the extruded profile. The appropriate shape of the laminate is maintained by vacuum gauging and cooled in a water bath to a controlled dimension. The extruded profile can then be cut and assembled into window or door units using conventional construction technology. It should be clearly understood that the shape of the dye used in the extrusion of the exterior layer and in the extrusion of the profile layer, is to be selected by the engineer for optimizing both the confirmation of the structural member to its end use and to ensure that the exterior layer covers portions of the profile requiring protection from the undesirable effects of the environment including ultraviolet light, degradation, heat and cooling cycles, etc.
The bi- or multilayer extrudate of the invention are typically made my coextrusion techniques including biextrusion, cocollandering, triextrusion which may incorporate an intermediate treatment adhesive or other bonding layer.

Extrusion Capping A lab scale twin screw extruder was used for the base portion of the product and a single screw, lab scale extruder was used for the capping. A PVC
Composite was used as the substrate material comprising 60 parts PVC and 40 parts wood fiber.

-Temperature Settings Main Twin Screw Extruder Barrel zone 1 180C

Die zone 1 172C

Screw oil 180C
Screw rpm 16.1 Feeder rpm 25 Single Screw Extruder - Kynar based materials Barrel zone 1 180C

Screw rpm 8 Single Screw Extruder - PVC only formula sarrel zone 1 148C

Screw rpm 8 Experimental The following experiments and data were developed to further illustrate the invention that is explained in detail above. The following information illustrates the 25 typical production formulation of the preferred exterior layer and the composition of the preferred core material. The data shows the unique stability of the material when exposed to accelerated aging testing. The following 29 30 examples and data shown in the examples and table contain a best mode.

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~ ` 2 1 774 1 2 We investigated a variety of capping co-extruded materials.
Kynar the Product It is supplied in 2 forms:
1. cubes - these process well through an extruder, without degrading, but do not readily accept pigmentation. Kynar cannot be processed using normal dispensing agents as they contaminate, and ultimately destroy the surface finish.
2. powders - these do not flow and bridge badly but do accept pigments.
solution - a 50/50 mix of powder and pellets are used to provide both pigment dispersion and the necessary flow characteristics (products 2800 and 2801).
adhesion - P.V.D.F. (Kynar) on its own, does not adhere to PVC very well and even less to PVC
composites. To lessen cost (for one thing) and to improve adhesion, Elf Atochem recommended the addition of Acrylic (Plexiglas) to partially solve this but as was later found - additional research into bonding media was required.
Elf Atochem Formula Kynar Flex 2800 series 61.6%
Acrylic - Plexiglas VS100 26.4 Pigment 12.0 100.0~
In processing this formula, we found several problems:
1. The coating was very "tacky" to the touch and was not vacuum sizable. It was later found that this tackiness -persisted until the surface had cooled and hardened in water.
2. Very poor adhesion was encountered with average tensile force (to pull off) as low as 6 lbs.
(right angle pull force over 1.625" width).
Accelerated Weathering The accelerated aging test is a well known testing protocol involving exposing a polymer structural material to a Xenon-arc device. This allows laboratory controlled conditions of light, heat and moisture to achieve accelerated degradation using radiation that is more intense than natural solar radiation. The spectrum produced by an artificial light source is extremely important in assuring that results correlate to real-time out door exposures. It can be demonstrated thatproperly filtered xenon lamps produce a spectral distribution that approximates nature more closely than other types of manufactured radiant sources. This is the primary reason the xenon device is the unit of choice over other alternatives such as Carbon arc devices or Fluorescent devices.
The exposure was conducted according to the test specification ASTM G26. The tests were conducted using Heraeus XENOTEST 1200 with low wavelength W filter.
Test cycle is 102 minutes light followed by 18 minutes light with water spray; 63+3C Black Panel Temperature with 50+5~ Relative Humidity maintained during the light-only phase. Source irradiance held at 100 W/m2 over the spectral range of 300 nm to 400 nm. With these conditions samples dosage is 80 W/m2 for the spectral range 300 nm to 385 nm. The normalized Southern Florida W Irradiance (26South) is 280 MJ/m2 for the spectral range 300 nm to 385 nm. (Quarterly Exposure, Heraeus DSET Laboratories, Inc. Fall 1992 Florida News W
Equivalent Year). Each hour of test exposure results in a dosage of 0.2884 MJ/m2.
Samples were rotated every 168 Hrs. Flat specimen -nominally 200 mil thick were cut to a surface dimension of 2.5" by 7" to properly fit the sample holder.
Chalk, color, gloss and visual data was collected every 140 MJ/m2 dosage interval.
Tape Chalk evaluations are performed in accordance with ASTM D4214-89, test method D.
Color measurements are performed on a HunterLab Ultrascan, spectrocolorimeter with a 6" integrating sphere reflectance specular excluded in accordance with ASTM D2244-89 and ASTM E308-90 with a 10 observer and lm; n~nt C. The specimen port is a circular and 1.25 inch in diameter with an 8 viewing angle and a beam diameter of 1.00 inch. The reduction of data is computed from the spectral data taken every lOnm over the wavelength range from 375nm to 750nm.
Gloss measurements are performed in accordance with ASTM D523-89 at an angle of 60 with a Byk Gardner Micro-Tri-Gloss portable glossmeter.
Inspections are performed on all specimens as per client instructions. Please refer to Appendix I of Test Reports for applicable standards used.
General Appearance Rating Other Criteria Rating 10-As Rec'd 8-Good 4-Poor 10-As Rec'd 8-Slight 4-Considerable 9-Excellent 6-Fair 2-V.Poor 9-V.Slight 6-Moderate 2-Severe In order to overcome the above problems a series of modified formulas were developed.

-K~nar/Acrylic Series - Ex. 1 Kynar 2800 25.0~
Kynar 2801 25.0%
Plexiglas VS100 50.0 TOTAL 100.0~
Pigment 12 phr Elf Atochem SuPplied - Ex. 2 Kynar 2800 series 61.6 10 Plexiglas VS100 26.4%
Pigment 12.0~
100 . 0%

70~ Kynar/30~ Acrylic - Ex. 3 Kynar 2800 35.0 Kynar 2801 35.0 Plexiglas VS100 30.0 100 . Og~
Pigment 12 phr Kynar/PVC Series - Ex. 4 Kynar 2800 35.0 Kynar 2801 35.0 PVC Geon 30.0 100.0~ resin =82.00 T634 3.0 phr 2.46 K120N 1.5 phr 1.23 D200 4.0 phr 3.28 AC165 0.3 phr 0.25 AC 629A 0.1 phr 0.80 Tinuvin 328 0.7 phr 0.57 Chimmasorb 944 0.3 phr 0.25 Pigment 12.0 phr 9.80 -Kynar/PVC - Ex. 5 PVC resin 70 Kynar 280130 T634 3.0 phr K120N 1.5 phr D200 4.0 phr AC165 0.3 phr AC629A 0.1 phr Tinuvin 3280.7 phr Chimmasorb 944 0.3 phr Pigment 12.0 phr Piqment System TerratoneShepherd Black lG 33.67 Shepherd Brown 19 38.99 Shepherd Brown 10 5.38 Tiona RCL4 (TiO2) 19.83 Kroma Red RO5097 2.13 100.00 SandtoneTiona RCL4 (TiO2) 62.15 Shepherd Brown 19 11.19 Shepherd Brown 10 11.11 Shepherd Yellow 193 7.42 Shepherd Black lG 6.81 Chroma Red RO5079 0.59 100.00 White (138) Tiona RCL4 (TiO2) 98.07%
Shepherd Black lG 0.74%
Shepherd Yellow 193 0.74%
Shepherd Yellow 195 0.37%
Kroma Red RO5097 0.08%
100 . 00%

Please note that the use of TiO2 is not limited to Tiona RCL4. The Dupont Product R102 (rutile) can be used with minimal color or performance shift as can Kronos 2071.

Method of Producing Pigments Because of the problem of airborne contamination all pigment blends were "tumbled" in an improvised jar mill. This appeared sufficient to provide a satisfactory product mix.

Method of Producing Capstock Material All capstock blends were produced in the laboratory Littleford high intensity mixer as follows:
1. Kynar/Acrylic Blends All products added at one time and blended for 5 minutes only with pigment included.
2. Kynar PVC Blends a) add PVC, Kynar and Stabilizer to mixer;
blend to 130F.
b) add all other additives except pigment;
blend to 140F.
c) add pigment and blend to 145F.
d) run mixture through a twin screw extruder at temperature settings of 205C (zone 1); 195C (zone 2); 185C (zone 3); 180C
(adapter) and 185C (die).

~ . 2177412 e) product extruded was then ground in a Cumberland grinder ready for the capping portion of the trial.

ADHESION TESTING
HESIOMETER
Principles of Operation: The Hesiometer is capable of evaluating intrinsic adhesion energy or practical adhesion. A hyper-sharp, hardened blade cuts through a coating to the multi-layer interface or the coating/substrate interface. An interfacial split is generated and projected forward of the blade cutting region. The energy required to perpetuate this interfacial splitting is a measure of adhesion.
Sample Preparation: All samples were cut to 7cm in length and 4cm in width. This was done to ensure proper fit in the machine. The submitted samples were also mechanically modified by defining a 5mm wide test area to eliminate edge effects. The modification was accomplished through the use of an exacto knife. The exacto knife was used to scribe parallel lines that penetrate down to the substrate. The distance between the parallel lines is the same as the width of the hesiometer blade.
OPeration: The hesiometer applies an empirically defined blade force, at an empirically defined angle, perpendicular to the sample travel. The blade is brought into contact with the sample until the applied force stabilizes to the set value. The transverse or cutting force is then measured as the sample moves perpendicular to the applied force.
The cutting force increases as the blade begins cutting through the coating. The cutting force levels out when the blade reaches the coating/substrate interface. A successful test has been completed when the blade reaches the coating/substrate interface. The transverse force curve, frictional force value, blade or sample width, and the coating removal distance are then recorded to the hesiometer software. The recorded values are used to calculate the energy per unit area.
The energy per unit area is a measure of practical adhesion.
Practical adhesion can be used to test samples of the same type. The tested samples can then be evaluated and compared to other samples of the same type using group statistics. This type of testing can develop guidelines for product quality analysis.
SPecific Test Conditions: A five millimeter wide flexible blade was employed at a 20 and 25 degree angle.
The applied loads on the blade were lN to 3N. Sample travel rate was five millimeters per minute in all cases.

HESIOMETER
1. Romulus II Universal Tester 2. Hesiometer Module 3. Quattro-pro software HESIOMETER
Table II shows the results of all the tested samples. Included in the table is the mean, standard deviation, and the minimum and maximum adhesion energy values.

-Table II. Hesiometer results for all submitted samples.
FO~ TION NFAN STD. DEV. MINIMUM MAXIM~M
3 70% Kynar N/A N/A N/A N/A
30% Acrylic 12 60% Kynar 732.25 138.73 602 901 40% Acrylic 9 60% Kynar 868.6 161.9 735 1142 40% Acrylic 6 70% Kynar 1003.2 515.31 379 1636 30% PVC
21 70% PVC 2511.3 742.12 1779 3437 30% Kynar 24 100% PVC 7427 700.02 6686 8077 HESIOMETER
According to table II, sample 03 appeared to have had the poorest adhesion energy. It was observed that when the sample was mechanically prepared for the hesiometer testing, the coating would detach. Samples 9 and 12 also appear to have low adhesion energy. During the testing of these samples, the coating would begin to remove from the substrate at a relatively large distance from the blade tip. This may be due to rigid characteristic of the coating which could contribute to the low adhesive strength of the material.
Sample 24 showed improved adhesive strength over the previous samples. After the testing was completed for these samples, it was observed that some of the coating was left on the substrate. This suggests the adhesive strength between the coating and the substrate was good. The adhesive strength of sample 24 also appeared to be good. During the testing of this sample, the coating and the substrate were removed. This prevented the adhesive strength of the coating from being determined. Instead, the adhesive strength of the substrate was recorded. However, this value is still of 217~412 -importance since it represents the good adhesive strength between the coating and the substrate.

HESIOMETER
The results of the hesiometer give the desired information about the adhesion energy between the coating and the substrate. According to the results, it may be assumed that sample 24 has the strongest coating adherence to the substrate.
The materials set forth above were tested for light stability using Xenum-arc testing protocol and adhesion testing. The results of the Xenum-arc light stability testing are summarized in figures 1 and 2. The poorest material, 100~ polyvinyl chloride, had substantial deltaE color changes over the twenty-four month time frame. The other formula had improved color changes.
However, of the other formulas, the 70~ PVC/30~ PVDF had superior Xenum-arc exposure stability when compared to the other materials.
The foregoing disclosure provides an explanation of the compositions and properties of the extruded profile manufactured from a composite core and an exterior layer. Many alterations, variations and modifications of the invention arising in the extruded profile material can be made by substitution of equivalent materials, rearrangement of the compositions, changes to the core structure, variations of the degree of coverage of the exterior layer and thickness of the layer.
Accordingly, the invention resides in the claims hereinafter appended.

Claims (11)

1. A capped extruded profile comprising:
(a) a core comprising a thermoplastic composite comprising a major proportion of a polyvinyl chloride polymer composition and about 1 to 40 wt% of a cellulosic fiber having an aspect ratio of about 1 to 10, and a minimum particle size of about 0.3 microns; and (b) an exterior layer comprising a polymer blend comprising a major proportion of a polyvinyl chloride polymer composition and about 1 to about 45 wt% of a polyvinylidene fluoride polymer composition and an effective amount of a pigment;
wherein the exterior layer is adhesively secure on the core and is resistant to environmental degradation.

2. The profile of claim 1 wherein the exterior layer comprises a major proportion of a polyvinyl chloride polymer composition and about 25 to 35 wt% of a polyvinylidene fluoride polymer composition.

3. The profile of claim 1 wherein the pigment comprises carbon black, titanium dioxide or mixtures thereof.

4. The profile of claim 1 wherein the composite comprises about 55 to 65 wt% of a polyvinyl chloride polymer composition and about 35 to 45 wt% of a wood fiber.

5. The profile of claim 1 wherein the profile comprises a structural member of a fenestration unit.

6. A capped extruded profile comprising:
(a) a core comprising a thermoplastic material comprising a major proportion of a thermoplastic polymer composition; and (b) an exterior layer comprising a polymer blend comprising a major proportion of a thermoplastic polyvinyl chloride polymer composition, about 1 to about 45 wt% of a polyvinylidene fluoride polymer composition and an effective amount of a pigment;
wherein the exterior layer is adhesively secure on the core and is resistant to environmental degradation.

7. The profile of claim 6 wherein the exterior layer comprises a major proportion of a polyvinyl chloride polymer composition and about 25 to 35 wt% of a polyvinylidene fluoride polymer composition.

8. The profile of claim 6 wherein the pigment comprises carbon black, titanium dioxide or mixtures thereof.

9. The profile of claim 6 wherein the profile comprises a structural member of a fenestration unit.

10. The profile of claim 6 wherein the thermoplastic core comprises a polyvinylchloride.

11. The profile of claim 6 wherein the thermoplastic core comprises an acrylonitrile-butadiene-styrene polymer, a chlorinated polyvinyl chloride.