Background of the Invention Texturing the surface of plastic extrusions is often difficult and may interfere with the extrusion process. Typically, texturing is performed as a separate process step after the extrusion step.

U. S. Pat. 4, 671, 913 to Gen et al. describes feeding an extruded sheet through cold press rolls followed by guide rolls, and then through embossing rolls.

U. S. patent 5, 164, 227 to Miekka describes a method for decoration of a paper or plastic sheeting where the coated sheet is heated to soften the coating and then decorated using embossing rollers to decorate the sheet. A remote heat source softens the sheet before embossing. As set forth, the surface of the embossing roller is hard and distortion resistant. g are described. The subsequent welding feature is used for butt welding the strips.

For many extrusions, especially hollow extrusions, the use of textured wheels tends to deform the surface and distort the profile itself since the profile requires support from the underside to resist the force of the wheels.

Typically, the texturing wheel also has to provide sufficient cooling to the

plastic surface so that the pattern is not diminished by subsequent operations such as calibrating. Texturing wheel or rollers also have an undesirable short repeat pattern which tends to be aesthetically objectionable. Use of rollers also requires that the surface speeds of the roller matches the surface speed of the extrudate so as to further complicate-the mechanism.

Hence, it desirable to provide for an improved apparatus and process for texturing a continuous extrusion with an extended or random pattern without applying undue pressure to the surface of the extrusion.

Summary of the Invention The apparatus of the present invention may advantageously be used for extended surface texturing over a large area. Since relatively low pressure is exerted, extruded hollow lineal type structures may be desirably surface textured. As a result, the apparatus is desirable for continuously applying surface texturing to a lineal type extrusion without distorting the extruded article.

In accordance with the present invention, there is provided an apparatus for texturing an outer surface of an extruded thermoplastic resin article comprising a calibrator having opposed and spaced apart sections for defining a gap therebetween for calibrating said extruded resin, said gap being determinative of a dimension of said article, an extruder for feeding a formable preshaped extruded thermoplastic resin into said gap, and a carrier for supporting a textured material being positioned for contacting resin extruded from said extruder prior to calibrating said extruded resin, said textured material imparting a pattern to said extruded thermoplastic resin article.

Description of the Drawings FIG. 1 is a schematic of the apparatus of the present invention showing an extruder, calibrator and carrier for the textured material ; FIG. 2 illustrates the profile of a hollow sheet.

Description of the Preferred Embodiment FIG. 1 shows an extrusion molding machine or extruder at 15. The extruder 15 has a housing 17 with a central barrel shape opening 19 with a helical screw 21 mounted for rotation about an axis. At one end of the opening, a hopper (not shown) is utilized for feeding material to be extruded into the rear portion of the screw 21. Helical threads mounted on the screw 21 are positioned for moving material from the rear portion of the screw to a forward portion through the opening 19. As the material or feedstock is conveyed along the screw 21, it is heated by frictional forces caused by rotation of the screw 21. It is also contemplated that an external heating source such as an electrical resistant heater may be provided to heat the extruder 15 which in turn heats the feedstock. The housing 17 or the screw 21 are parts of the extruder which may heated.

At the forward end of the housing 17 and spaced from the forward end of the screw 21, a gate or breaker plate 23 is mounted transverse to the flow of feedstock. The gate 23, which includes a plurality of openings 43 for the passage of feedstock, acts to create a back pressure which contributes to the mixing and heating of the feedstock and also serves to filter impurities from the feedstock.

A die body 25 which is mounted on the forward end of the housing 17.

The mounting is conventionally made by bolting or clamping a flange on the die body 25 to a flange on the housing 17. As illustrated in FIG. 1, the die body 25 includes a tapered central and axially aligned opening which

throttles the feedstock. At the a die outlet, a die plate 27, has an opening with the desired cross sectional shape of the lineal profile to be extruded.

It is also contemplated one or more layers may be coextruded or added at the end of the die 27. In coextrusion, additional extrudes may be provided for the additional layers. Another technique for adding a layer at the end of the die 27 is to include a capping plate which has an opening for the passage of capping layer. In this case, the outer layer may be of a weatherable material so as to resist the effects of UV radiation and moisture. Typically pressures within the extruder is in excess of 2, 000 lbs./sq. inch, and is preferably from 2, 000 to 5, 000. 1bs/sq. inch.

At the texturing station 41, the carrier or means 31 for feeding an elongated texturing material 47 imparts texturing to the outer surfaces of the sheet 44. In accordance with the present invention, a carrier 31 for textured material 47 is provided directly in the path of the melted thermoplastic material exiting the extruder 15 so that melted flowing material is fed directly into contact with textured material 47 prior to cooling.

As illustrated in FIG. 1, the carrier 31 which includes pulleys or rollers 49 is fixedly secured to a frame 44. The texturing material 47 may be in the form of endless belt which extends around rollers 49. The length of the repetitive pattern may be increased by increasing the length of the belt 47. The belt 47 can be made longer to provide longer repeat patterns if necessary by increasing the number of loops around additional rollers. It is also contemplated that the a non-repeating pattern may be achieved by having the carrier 31 be in the form of a roller which feeds a supply of pre-wound texturing material into the calibrator 29.

According to preferred embodiments, the carrier 31 is self feeding in that no additional drive wheels are needed to collect or move the texturing material 47. The momentary contact of the texturing material 47 with the

extrudate from the extruder 15 is sufficient to move the endless belt so that pulleys or drums of the endless belt need not be driven. Similarly, when tape unwound from a roll is utilized as the texturing material, is not necessary to drive the roll.

Refererence number 44 is a hollow profile sheet 44. The cross sectional profile of the hollow sheet 44 is illustrated in Fig. 2. Other cross sections are contemplated for the lineal extrusion, such as T, U and C cross sectional shapes. Uses for such lineal extrusions include window and door frames, supports, and framing material. The die plate 27 has a configuration permitting the formation of elongated hollow sections 46 as part of the sheet 44.

After contacting the texturing material 47, the extruded thermoplastic is calibrated at a calibration station or calibrator 29. Next, the extrusion 44 is cooled and solidified at a cooling station 61. The lineal extrusion 44 is drawn or pulled through the stations by a puller 71. A cutter mechanism (not shown) may be used to cut the lineal extrusion into proper lengths.

The texturing station 41 is positioned between the extruder 15 and the calibrating station 29. The distance between the extruder 15 and the calibrating station 29 is determined in part by the shape of the surface to be textured. Larger surface areas and more three dimensional texturing may require larger rollers and belts and even more than one belt may be needed so that increased distance may be required.

According to a preferred embodiment, a flexible belt is utilized so that good contact is maintained with the hot extrusion so that no drive is required for the belt pulley. Desirable, the belt does not influence the temperature of the melt surface either by using a material that exhibits poor thermal conductivity and mass or by controlling the belt and bottom roller temperature.

Cooling the texture by directing a fluid stream toward the texture is helpful for maintaining a clear texture through the calibrator. A variety of cooling fluids may be used depending on the material being processed. Air cooling of the texture as shown at 75. Fluid is directed at the texture through a nozzle or such as an air jet 75 mounted to direct cooling fluid or air at the surface. Some distortion of the hot profile may occur, but such distortion should not be severe enough to cause problems in the calibrator or changes in dimensions.

In the preferred apparatus, as illustrated in Fig. 1, the endless belt 47 is mounted on a frame which may be adjusted relative to the extrusion so as to adjust the pressure that is applied to the resin surface.

The texturing material 47 which may be in the form of a tape, web, belt, or even woven or non-woven fiber and is constructed of a flexible material that is stable under temperatures associated with extrusion. Screen type texturing material may be utilized. The material 47 includes raised surface portions in the form or projections and elongations which may be a random or ordered form. Random type projections are preferred for imparting a wood grain indent effect to the sheet or extrusion 44. The material 47 should be easily removed or substantially non-adherent to the surface of the extrusion. It is also contemplated that an additional roller (not shown) may be provided for transferring a colorant such as a dye to the surface of the texturing material to impart a variable coloration to the surface of the extrusion 44.

It is preferred to use a texturing material that retains its integrity through repeated contact with the extruded resin without build-up of resin on the belt. Preferred materials for the for the texturing material comprise fabric film or foil type materials.

Preferred fibers for such material include fibers of glass, graphite or carbon, metal materials, especially conductive metals drawn into wire, and polyamide polymers, which include polyamide-6 ; 6, 6 ; 11 and 12. KevlarX polyamide fiber of Du Pont de Nemours is preferred for its extremely high tensile strength and great resistance to elongation. A preferred material for construction of the belt is woven Kevlar@ cord. Additionally, strands of resistant fiber, such as Kevlar cord may be woven into the belt to give a random surface texture.

Highly conductive materials such as metal foils or fibers of steel, copper and nickel are also preferred for the texturing material. Poly fluoro hydrocarbon polymers, such as polytetrafluoroethylene (PTFE) such as Teflon@ resin fibers or films are also preferred. Conductive materials help cool the extrudate.

The vacuum calibrator 29 includes opposed and spaced apart sections 35, 37 for defining a gap 39 therebetween. The gap 39 is determinative of a dimension of the final article. Each of the opposing sections 35,37 include respective conformal surfaces which have a plurality of openings to draw the extrusion into contact with the surfaces which form the gap. The section 35,37 of the calibrator 29 is in the form of a closed container having perforations (not shown) facing the extrusion 44. The respective container section 35 or 37, is connected to a source of reduced pressure (not shown) so that an area of reduced pressure draws the extrusion 44 into contact with the calibrator 29.

The calibrator 29 servers to cool and shape the extrusion. The conforming surfaces of the calibrator 29 may have a variety of complex shapes.

A cooling section 61 includes a spray tank for cooling the extrusion.

The additional cooling provided by the cooling section 61 removes additional heat from the extruded article. A puller is illustrated at 71 and includes a pair of opposing tractor type belt mechanisms which grip the extrusion to pull the

extrusion. The puller 71 crates a stretching action as the melted article exits the extruder 17 and provides the force to pull the profile through the calibrator.

Reference number 44 refers to the extruded article which is shown as a hollow profile sheet 44. The profile of the hollow sheet 44 is illustrated in Fig.

2. Other cross sections for an extrusion are contemplated for such as T, U and C cross sectional shapes. Uses for such lineal extrusions include window and door frames, supports, and other framing material. The die plate 27 has a configuration permitting the formation of elongated hollow sections 46 as part of the sheet 44.

The extruded articles may have a variety of cross sectional shapes depending on the use. Fig. 2 illustrates a cross section of lineal extruded structure having centrally extending wall portion 57 in the form of a perpendicularly extending flange. The lineal profile illustrated includes one wall portion intersecting to form a hollow cross sectional profile. It is contemplated that the cross-section can comprise curved sections. The lineal structure is desirably utilized as a frame for an opening in a building.

Channel type structures may be utilized to hold stationary or moveable panels, as for example, a window pane or door. The calibrator 29 and the die body 25 are configured to prepare extrusions having various shapes.

The thermoplastic materials that can be employed in profile structure should be suitable for the geographical region in which the profile, when converted into a building product, would be used or depending upon the building code for the region. Typical thermoplastic materials are high temperature thermoplastics such as acrylonitrile-butadiene-styrene (ABS), polycarbonate, polycarbonate/ABS blend, a co-polycarbonate-polyester, acrylic-styrene-acrylonitrile (ASA), acrylonitrile- (ethylene-propylene diamine modified) -styrene (AES), polyalkylene terephthalate such as polybutylene

terephthalate (PBT) or polyethylene terephthalate (PET) or blends thereof, blends of polyphenylene ether/polyamide (NORYL GTX Registered TM from General Electric Company), blends of polycarbonate/polybutylene terephthalate and impact modifier (XENOY Registered TM resin from General Electric Company), blends of polycarbonate/PBT/PET, etc. , or blends thereof with other additives such as fillers, impact modifiers, pigments, stabilizer, reinforcing agents, etc. It is contemplated that PVC can also be use.

Polyamides useful in the present invention are well-known in the art.

Specific examples of polyamides are polyamide-6, polyamide-6, 6, polyamide- 11, polyamide-12, polyamide-6, 3, polyamide-6, 4, polyamide-6, 10 and polyamide-6, 12, as well as polyamides prepared from terephthalic acid and/or isophthalic acid and trimethylhexamethylenediamine ; from adipic acid and m-xylylenediamines ; from adipic acid, azelaic acid 2, 2-bis- (p- aminocyclohexyl) propane, and from terephthalic acid and 4, 4'- diaminodicyclohexylmethane.

Mixtures and/or copolymers of two or more of the foregoing discussed polymers or prepolymers thereof, respectively, are also within the scope of the present invention.