Abstract:
An elongated structural article, having a continuous profile extrusion with spaced apart layers defining a portion of a cavity filed filled with thermoplastic pre-expanded beads expanded with steam in-situ causing the beads to securely bond together and to the profile extrusion. The article is cut to a length forming ends having an exposed foam core. A system for manufacturing the article is also disclosed having a profile extrusion die for forming an axially profile defining a wall surrounding a cavity, a tubular shaping mold located axially downstream of the extrusion die sized to support a length of the profile as it passes there through. A bead dispenser is oriented to introducing pre-expanded beads into the profile cavity while within the shaping fixture and a steam tube is oriented downstream of the introduction of pre-expanded beads. Control valves regulate the flow of pre-expanded beads and steam into the profile cavity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 13/463,689 filed May 3, 2012, now U.S. Pat. No. 9,102,086, which, in turn, claims the benefit of U.S. provisional application Ser. No. 61/616,817 filed Mar. 28, 2012, the disclosures of which are hereby incorporated in their entirety by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The disclosed embodiments relate to in-situ foam core structural articles and methods of manufacture of profiles. 
       BACKGROUND 
       [0003]    Plastic processors who use profile extrusion methods continue to reduce the amount of plastic material used in every part made in order to reduce the cost of materials as well as increased the line speed of the extrusion equipment. Often, reducing the amount of material used results in weaker structural properties for the finished article. 
         [0004]    Profile extruders, even those initially producing sheet extrusions, can create an article having an internal cavity in the article during the extrusion process. When the article has the internal cavity, plastic processors will often improve the structural properties of the finished article by adding a microcellular foam to the cavity using either a chemical or physical blowing agent to expand the foam. 
         [0005]    Certain processes that create articles that, at least partially, fill the cavity extend the time periods for foaming and slow the line speed, which is not economically justified in view of the costly machine time. But, microcellular foaming does guarantee structural strength for profiles. Unless the profile wall uses a relatively thick, foam-filled, extruded plastic, the profile article will not be structural. In addition, in certain processes, the plastic material of the profile extruded article is different from the plastic material used for the foam core, rendering the article difficult to recycle. Recycling of articles after completion of their useful life is increasingly desirable for sustainability objectives as well as being included in certain regulations and specifications. 
       SUMMARY 
       [0006]    In at least one embodiment, an elongated article is recited having an elongated profile. The elongated profile includes a first layer having a periphery and a spaced apart and opposed second layer having a periphery. The first and second layers define a cavity therebetween. Within the cavity, an in-situ foam core is disposed. The in-situ foam core has a thermal bond to first and second layers. The first or second layer thickness ranges from 0.03 inches to 0.5 inches. The in-situ foam core density ranges from 1 lb/ft 3  to 25 lbs/ft 3 . 
         [0007]    In another embodiment, a method of manufacturing an elongated article is recited to include extruding a first and a second layer each having peripheries. The second layer is spaced apart from and opposed to the first layer. Together, they define a cavity between them. Into that cavity particles are dispensed. The particles are expanded with an expansion fluid to form an in-situ foam core and to thermally bond the in-situ foam core to the first and second layers. The first and second layers having the thermal bond to the in-situ foam core are shaped to form the article. 
         [0008]    In yet another embodiment, a method of manufacturing an elongated article is recited to include extruding a first elongated molten plastic arm having longitudinal axis and a second elongated molten plastic arm having a longitudinal axis. The first and second elongated molten arms are passed about a spider to form a profile defining a cavity. A plurality of particles is introduced into the cavity through a dispenser disposed co-linearly with at least one longitudinal axis. The profile is disposed into a mold having a downstream end. An expansion fluid is injected into the particles to expand the particles to form an in-situ foam core and thermally bond the in-situ foam core to the profile forming the elongated article. The first and second molten plastic arms when passing about the spider experience an average pressure drop from the spider maximum width to the downstream end that is constant within a range of +10 rel. % to −10 rel. % relative to the average pressure drop. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  schematically illustrates a method of producing a structural article having an in-situ foam core according to at least one embodiment; 
           [0010]      FIG. 2  schematically illustrates a structural hollow profile having in-situ foam core according to at least one embodiment; 
           [0011]      FIGS. 3A-3C  schematically illustrate a method producing a plastic structural article according to at least one embodiment; and 
           [0012]      FIGS. 4A-4B  schematically illustrate a method producing a plastic article according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0014]    Except where expressly indicated, all numerical quantities in the description and claims, indicated amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the present invention. Practice within the numerical limits stated should be desired and independently embodied. Ranges of numerical limits may be independently selected from data provided in the tables and description. The description of the group or class of materials as suitable for the purpose in connection with the present invention implies that the mixtures of any two or more of the members of the group or classes are suitable. The description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description and does not necessarily preclude chemical interaction among constituents of the mixture once mixed. The first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation. Unless expressly stated to the contrary, measurement of a property is determined by the same techniques previously or later referenced for the same property. Also, unless expressly stated to the contrary, percentage, “parts of,” and ratio values are by weight, and the term “polymer” includes “oligomer,” “co-polymer,” “terpolymer,” “pre-polymer,” and the like. 
         [0015]    It is also to be understood that the invention is not limited to specific embodiments and methods described below, as specific composite components and/or conditions to make, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the present invention and is not intended to be limiting in any way. 
         [0016]    It must also be noted that, as used in the specification and the pending claims, the singular form “a,” “an,” and “the,” comprise plural reference unless the context clearly indicates otherwise. For example, the reference to a component in the singular is intended to comprise a plurality of components. 
         [0017]    Throughout this application, where publications are referenced, the disclosure of these publications in their entirety are hereby incorporated by reference into this application to more fully describe the state-of-art to which the invention pertains. 
         [0018]      FIG. 1  schematically illustrates a method of producing a plastic structural article having an in-situ foam core according to at least one embodiment. An open-sided plastic extrusion profile  10  provided by a profile or sheet die extrusion (not shown) is schematically illustrated where a top portion  12  of the extrusion profile  10  is hingedly connected to fold over channel portion  14  when urged by shaping fingers (not shown) or other means known in the art to form a closed profile  16  while being pulled by a puller (not shown) under tension through a shaping and cooling line (not shown). 
         [0019]    During a time period when top  12  is open and not connected at both ends to channel  14 , a plurality of particles, such as pre-expanded beads  20 , are provided to channel  14  from a bead dispenser  18 . As the profile continues to move downstream from the profile extrusion die, an expansion fluid, such as steam  22  is provided from a steam source  24  into the pre-expanded beads  20 . Both the bead dispenser  18  and steam source  24  have valves  26  and  28 , respectively, to open and close bead dispenser  18  and steam source  24  controlling the flow of pre-expanded beads  20  and steam  22 . Steam  22  is vented prior to a time period when the profile forms a closed profile  16 . 
         [0020]    Closed profile  16  having rapidly expanding beads  32  as a result of the steam  22  causing the pre-expanded beads  20  to expand completely to their full expansion, enters a shaping fixture  30 . Shaping fixture  30  is sufficiently strong to contain expansion pressure of rapidly expanding beads  32  when forming an in-situ foam core  34 . In-situ foam core  34  has a thermal bond  42  to a wall  40  ( FIG. 2 ) of closed profile  16 . Thermal bond  42 , in at least one embodiment, includes a portion of wall  40  a portion of in-situ foam core  34 , and a co-mingled layer having both wall  40  and in-situ foam core  34 . 
         [0021]    In at least one embodiment, steam  22  injection has a frequency ranging from 2 inches of channel portion  14  longitudinal travel to 6 inches of channel portion  14  longitudinal travel. In another embodiment, steam  22  injection has a frequency ranging from 3 inches to 5 inches of channel portion  14  travel. 
         [0022]    It should be understood that a lubricant, such as a non-compressible-fluid, such as water, may be used to facilitate the transition of the closed profile  16  into shaping fixture  30 . Other fluids, including air and water, may be used to control the temperature of the open-sided plastic profile  10  prior to closed profile  16  having in-situ foam core  34 . A vacuum calibrator (not shown) may also be used to define the profile in shaping fixture  30 . 
         [0023]    Is also understood that while the single bead dispenser  18  is illustrated, certain embodiments may have a plurality of bead dispensers, and each bead dispenser may have pre-expanded beads  20  of identical or differing average diameters. It is further understood that while one steam source  24  is illustrated, certain embodiments may have a plurality of steam sources or multiple apertures along the steam source  24  shaft. In at least one embodiment steam sources  24  are spaced apart by a distance ranging from 2 inches to 6 inches: In another embodiment, steam sources  24  are spaced apart by a distance ranging from 3 inches to 5 inches. In another embodiment, steam sources  24  are spaced apart by a distance ranging from 3 inches to 5 inches of channel portion  14  travel. 
         [0024]    The steps of expanding the pre-expanded beads  20  are illustrated by U.S. patent application Ser. Nos. 13/358,181, 13/005,190, and 12/913,132 all of which are incorporated herein by reference. 
         [0025]    Turning now to  FIG. 2 , closed profile  16  having in-situ foam core  34  is schematically illustrated according to at least one embodiment. Closed profile  16  is formed using at least one of extrusion methods including profile, sheet, blown film extrusion, pulltrusion, and metal matrix composite extrusion. Wall  40  of closed profile  16  defines a cavity  44  into which a single density of pre-expanded beads  20  is expanded to form in-situ foam core  34 . Closed profile  16  having in-situ foam core  34  forms a structural article. In at least one embodiment, wall  40  comprises a plastic polymer composition when combined with in-situ foam core  34  forms a structural plastic article. In at least one embodiment, the structural plastic article is suitable for forming a structural assembly. It is understood that while a hexagonal-shaped structural article is illustrated in  FIG. 2 , any suitable shape having a cavity may be used without exceeding the scope or spirit of embodiments. Non-limiting examples of suitable shapes include an I-beam and a pipe. 
         [0026]    In at least one embodiment, wall  40  has a polymeric composition that is identical to the polymeric composition of in-situ foam core  34 , advantageously rendering the structural plastic article recyclable. A non-limiting example of such a recyclable structural plastic article includes one having wall  40  comprised of polyethylene and in-situ foam core  34  comprised of expanded polyethylene beads. In another embodiment, wall  40  has a polymeric composition that is sufficiently similar to the polymeric composition of in-situ foam core  34  to render still the structural article as recyclable. A non-limiting example of such a recyclable article having similar compositions between the wall  40  and the in-situ foam core  34  include having the wall  40  comprising acrylonitrile butadiene styrene (ABS) and in-situ foam core  34  comprising expanded polystyrene. 
         [0027]    In at least one embodiment, wall  40  thickness may range from 0.03 inches to 0.5 inches. In another embodiment, the thickness of wall  40  may range from 0.5 inches to 0.25 inches. 
         [0028]    In at least one embodiment, in-situ foam core  34  thickness may range from 0.15 inches to 6 inches. In another embodiment, in-situ foam core  34  thickness may range from 0.2 inches to 4 inches. In another embodiment, in-situ foam core  34  thickness may range from 0.5 inches to 1 inch. 
         [0029]    Closed profile  16 , in at least one embodiment, is formed of a composition of any extrudable-moldable composition. Non-limiting examples of the extrudable composition include, but is not limited to, a liquid silicone rubber, a synthetic rubber, a natural rubber, a liquid crystal polymer, a synthetic polymer resin, and a natural polymer resin. In another embodiment, closed profile  16  article is formed of a composition of a thermoplastic polymer, a thermoset polymer, or blends thereof having a viscosity ranging from 0.1 grams/10 min to 10 grams/10 min intended for use with profile extrusion. The viscosity is measured according to ASTM D-1238 at 190° C. with a 2.16 kg weight. In yet another embodiment, closed profile  16  article is formed of a composition of a polyolefin including polypropylene and polyethylene having a viscosity ranging from 1 grams/10 min to 8 grams/10 min. 
         [0030]    In at least one embodiment, the extrudable composition durometer may range from 35 Shore A to 80 Shore D when measured according to ASTM D 2240. In another embodiment, the extrudable composition durometer may range from 40 Shore A to 70 Shore D. 
         [0031]    In-situ foam core  34 , in at least one embodiment, is formed of a composition of any fluid-expandable material. Examples of fluid-expandable material include, but are not limited to, a polyolefin polymer composition, a biopolymer composition expandable bead, an alkenyl aromatic polymer or copolymer composition, a vinyl aromatic polymer resin composition, and a polystyrene polymer composition. In at least one embodiment, the polyolefin polymer composition includes polyolefin homopolymers; such as low-density; medium-density; and high-density polyethylenes; isotactic polypropylene; and polybutylene-1, and copolymers of ethylene or polypropylene with other polymerizable monomers such as ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and ethylene-ethyl acrylate copolymer, and ethylene-vinyl chloride copolymer. These polyolefin resins may be used alone or in combination. Preferably, expanded polyethylene (EPE) particles, cross-linked expanded polyethylene (xEPE) particles, polyphenyloxide (PPO) particles, biomaterial particles, such as polylactic acid (PLA), and polystyrene particles are used. In at least one embodiment, the polyolefin polymer is a homopolymer providing increased strength relative to a copolymer. It is also understood that some of the particles may be unexpanded, also known as pre-puff, partially, and/or wholly pre-expanded without exceeding the scope or spirit of the contemplated embodiments. 
         [0032]    Pre-expanded bead  20 , in at least one embodiment, is the resultant bead after the first expansion step of raw bead of a two-step expansion process for beads. During the first expansion step, raw bead is expanded to 2% to 95% of the fully expanded bead size. The fully expanded bead is the bead that forms in-situ foam core  34 . In another embodiment, pre-expanded bead  20  is result of the first expansion step where raw bead is expanded from 25% to 90% of the fully expanded bead size. 
         [0033]    A fluid for the second expansion step of the two-step expansion process for beads causes the pre-expanded beads to expand completely to form the fully expanded beads. An example of the fluid includes, but is not limited to, steam, 
         [0034]    Polyolefin beads and methods of manufacture of pre-expanded polyolefin beads suitable for making the illustrated embodiments are described in Japanese patents JP60090744, JP59210954, JP59155443, JP58213028, and US Pat. No. 4,840,973 all of which are incorporated herein by reference. Non-limiting examples of expanded polyolefins are ARPLANK® and ARPRO® available from JSP, Inc. (Madison Heights, Mich.). The expanded polypropylene, such as the JSP ARPRO™ EPP, has no external wall such as wall  40 . 
         [0035]    In at least one embodiment, in-situ foam core  34  density, after expansion by steam such a such as in  FIG. 1 , ranges from 0.21 lb/ft 3  to 25 lbs/ft 3 . In at least one embodiment, in-situ foam core  34  density, after expansion by steam such as in  FIG. 1 , ranges from 1.5 lbs/ft 3  to 15 lbs/ft 3 . In at least one embodiment, in-situ foam core  68  density, after expansion by steam such as in  FIG. 1 , ranges from 2 lbs/ft 3  to 9 lbs/ft 3 . In at least one embodiment, in-situ foam core  68  density, after expansion by steam such as in  FIG. 1 , ranges from 3 lbs/ft 3  to 6 lbs/ft 3 . 
         [0036]    Preferably, in at least one embodiment, steam-injected expanded polypropylene (EPP) has a density ranging from 0.2 lb/ft 3  to 20 lbs/ft 3 . In yet another embodiment, steam-injected EPP may have a density ranging from 1 lbs/ft 3  to 10 lbs/ft 3 . In yet another embodiment, steam-injected EPP may have a density ranging from 2 lbs/ft 3  to 8 lbs/ft 3 . In yet another embodiment, steam injected EPP may have a density ranging from 3 lbs/ft 3  to 6 lbs/ft 3 . 
         [0037]    In at least one embodiment, the structural article may be formed using an pultrusion process as schematically illustrated in  FIGS. 3A-3C . In this process, a plurality of fiberglass rovings  60  having a longitudinal axis, such as a roving doff, and a transverse axis, such as a mat creel (not shown), pass through an alignment guide  62  and enter a resin bath  64  having a curable resin, and are wetted while passing over a plurality of rollers  66 . The wetted fiberglass roving  68  passes through a die  70 . While consolidating, a closing profile  72  is formed as fiberglass rovings  60  exit die  70  forming a cavity  74 . Pre-expanded beads  20  are placed into the closing profile  72  from a bead dispenser  18 . Steam  22  from steam source  24  passes through valve  28  and is injected into pre-expanded beads  20  causing them to form fully-expanded beads  76 . The fully-expanded beads  76  are contained within closing profile  72  forming an in-situ foam core  78 . Closing profile  72  and in-situ foam core  78  form a structural article. The structural article is cured in a curing die  80  where heat is optionally applied by at least one heater  82 . The structural article is cross cut to length at a point at or beyond a puller (not shown) which is pulling fiberglass rovings  60  along the axis of the process. 
         [0038]    It is understood that placing pre-expanded beads into closing profile  72 , or any configuration having cross-woven reinforcements may require that placing of the pre-expanded beads  20  from bead dispenser  24  may be a discontinuous dispensing operation in order to avoid the cross-woven reinforcement. Bead dispenser  24  may include a reciprocating dispensing component which is configured to avoid the cross-woven reinforcement upon receiving a signal from a sensor such as an optical sensor, a proximity sensor, or a time sensor. 
         [0039]    In at least one embodiment, resin in resin bath  64  includes a thermoset polymer composition. Non-limiting examples of thermoset polymer composition include a polyester composition, a vinyl ester composition, an epoxy composition, and a phenolic composition. 
         [0040]    It is understood that while fiberglass rovings are illustrated, other reinforcements such as stitched rovings, aramid fibers, polyester fibers, carbon fibers, carbon fiber nanotubes fibers are contemplated within the scope and spirit of the embodiments. It is also understood that while rovings are illustrated, a reinforcement tow may be used. 
         [0041]    In certain embodiments of extrusion or pultrusion processes herein, other materials may be included in the compositions used for the profiles. Non-limiting examples of other materials include a filler, a catalyst, an initiator, an ultraviolet light inhibitor, an additive, an adjuvant, and a release agent. 
         [0042]    In at least one embodiment, in extrusion system  98  extrudes structural plastic articles, as schematically illustrated in  FIGS. 4A and 4B . Extrusion system  98  includes an extruder  100 , a spider  102  connected to a mold  104  by a connector  106  and a second connector  108 . Extruder  100  extrudes a molten plastic arm  110  is separated from a second molten plastic arm  112 , Molten passes about spider  102  until forming a profile  114  proximate to the entrance to mold  104 . Molten arms  110  and  112  defining a cavity  116  into which a dispenser  118  and a steam pin  120  are placed in a co-linear configuration relative to a longitudinal axis  122  of extruder  100 . Bead dispenser  118  and steam pin  120  pass through the spider  102  in a cavity  124  defined by the spider  102  walls. Bead dispenser  118  and steam pin  120  further pass through a cavity  126  defined by mold  104  walls. Steam pin  120  extends further into cavity  126  of mold  124  than bead dispenser  118 . 
         [0043]    Bead dispenser  118  transfers pre-expanded beads  128  from a bead source (not shown) proximate to extruder  100 . During the pressurization accompanying transfer of pre-expanded beads  128 , the pre-expanded beads  128  are compressed in the range of 10 volume percent to 70 volume percent in at least one embodiment. In another embodiment, pre-expanded beads  128  are compressed in the range of 25 volume percent to 50 volume percent. The compressed pre-expanded beads  128  are dispensed into cavity  126  of mold  104  and continue to travel downstream from the extruder  100 . Upon dispensing, the compressed pre-expanded beads  128  re-expand to approximately the size of the original pre-expanded beads  128 . Steam  130  from steam pin  120  is continuously provided to cavity  126  of mold  104  causing the re-expanded, pre-expanded beads  128  to expand fully forming fully expanded beads  132  comprising in-situ foam core  134 . 
         [0044]    In at least one embodiment, bead dispenser  118  and steam pin  120  are separate elements of extrusion system  98  and are co-linear with the longitudinal axis  122  of extruder  100 . In another embodiment, steam pin  120  is concentrically displaced inside bead dispenser  118 . Steam pin  120  may include telescoping segments, in at least one embodiment. In another embodiment, steam pin  120  has apertures (not shown) in steam pin  120  shaft, whether telescoping or not, in order to distribute steam broadly while minimizing the amount of separate steam pins  120 . 
         [0045]    In at least one embodiment, steam pin  120  and spider  102  are comprised of insulative material capable of preventing melting and/or premature expansion of pre-expanded beads  128 . In another embodiment, steam pin  120  and spider  102  have insulative coatings applied to surfaces exposed to pre-expanded beads  128 . 
         [0046]    Spider  102  has a shape configured have molten plastic arms  110  and  112  shaped to approximately the profile shape of mold  104  by the time molten plastic arms  110  and  112  pass the downstream end of spider  102 . Spider  102 , in certain embodiments, is configured to maintain constant pressure drop between the zone having maximum spider  102  width and the downstream end of spider  102 . In another embodiment, spider  102  is configured to maintain a pressure drop in a range of −10 relative percent to +10 relative percent of the average pressure drop from the widest point of spider  102  to the downstream end of spider  102 .