Abstract:
The method of producing a non-flammable synthetic wicker, that includes providing pellets incorporating polyethylene and flame retardant material; providing a screw conveyor means, introducing the pellets into the conveyor means and operating the conveyor means while heating the pellets, thereby forming a fluidized mixture and dispersing the flame retardant material throughout the mixture; extruding the fluidized and heated mixture in coherent strand form; cooling the extruded strand to partly solidify the strand; and winding the cooled strand, for use.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to production of synthetic wicker, and more particularly to non-flammable synthetic wicker. 
     In the past, wicker material, as for example is woven in sheets as for use in furniture, wall coverings, etc., was objectionable in that it could burn and become dangerous. Synthetic resinous wicker material was also subject to this objection. A need has arisen for a way or method to produce synthetic non-flammable wicker material, as for example attractively colored, safe, wicker strands. 
     SUMMARY OF THE INVENTION 
     It is a major object of the invention to provide method and means to meet the above referenced need. Basically, and in accordance with the invention the improved method now provided, for producing non-flammable synthetic wicker, includes the steps 
     a) providing pellets incorporating polyethylene and flame retardant material, 
     b) providing a screw conveyor means, introducing the pellets into the conveyor means and operating the conveyor means while heating the pellets, thereby forming a fluidized mixture and dispersing the flame retardant material throughout the mixture, 
     c) extruding the fluidized and heated mixture in coherent strand form, 
     d) cooling the extruded strand to partly solidify the strand, 
     e) and storing, such as winding the cooled strand, for use. 
     As will be seen, the referenced conveyor means may comprise twin conveyor screws meshing in response to screw rotation to progressively form and mix the fluidized mixture, for extrusion, with said flame retardant material thoroughly dispersed therein. 
     Another object includes use of a particularly advantageous retardant consisting of EB 4374, a product of Ciba Chemical Company, Switzerland, readily incorporated into the composition in small amounts for flame retardation of the ultimately formed wicker strands. 
     Yet another object includes initially providing the mixture introduced to auxiliary conveyor means in powder form, to form said pellets typically containing polyethylene, flame retardant and pigment; and additional pigment may then be added to the pellet feed to the auxiliary conveyor means to control the ultimate color of the produced wicker strand. 
     A further object includes the step or steps of extruding the fluidized and heated mixture in the form of multiple strands extending in side by side adherent relation, and having selected colorations. For this purpose, multiple extrusion dies may be provided, and to which the fluidized mixture or multiple mixtures may be respectively provided, for extruding selected coloration adjacent strands, as will be seen. 
     These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which: 
    
    
     
       DRAWING DESCRIPTION 
         FIG. 1  is a process equipment diagram, providing a flow chart; 
         FIG. 2  is a side elevation showing a wicker strand extruder; 
         FIG. 3  is a side elevation showing an extruded strand cooling bath device; 
         FIG. 4  is a side elevation showing a cooled wicker strand tensioner; 
         FIG. 5  is an end view taken on lines  5 - 5  of  FIG. 4 ; 
         FIG. 6  is a tensioned wicker strand winder, i.e. bobbin type wind up device; 
         FIG. 7  is a view showing an initial process for producing pellets; 
         FIGS. 7   a  and  7   b  are modifications; 
         FIG. 8  is a view showing a mesh of wicker as produced by the present invention; 
         FIG. 9  shows a wicker strand product comprising multiple strands adhered together; and 
         FIG. 10  shows multiple extrusions to produce the  FIG. 9  strand. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIGS. 1 and 2 , pellets produced from a powdered feed mixture are provided as in a hopper  10 . That mixture from which pellets are formed includes powdered synthetic resin, such as polyethylene, and powder form flame retardant material. Additional powder form materials in the mix include foaming agent; anti-oxidant; and pigment. Representative amounts of such materials for best results are as follows:
         about 95 weight percent polyethylene   about 2 to 4 weight percent EB 4374, a product of Ciba Chemical Company, Switzerland   about 0.1 to 0.2 weight percent foaming agent   about 1 to 2 weight percent pigment   about 1 to 2 weight percent anti-oxidant.       

     The flame retardant is compatible with the mix, and especially the resin, to impart non-flammable property to the ultimate wicker product. Examples of foaming agents include Hydrocerol, a product of Clariant Corporation, Muttenz, Switzerland; examples of pigment include iron oxide, cadmium, aluminum flakes and organic pigments produced by Clariant Corporation; and examples of anti-oxidant include products, such as Irganox B215, of Ciba Chemical Co., Switzerland. 
     The pellets are delivered downwardly at  20  to an extrusion apparatus  21 . The latter includes twin horizontal screws  22  driven in rotation and in meshing relation about horizontal axes, and within a barrel  23 , which may also extend horizontally. The pellets material is progressively combined and fed leftwardly by the screws, and simultaneously and progressively heated as by heating band  24  extending about the barrel along its length. The heated material is fed to a die  25 , from which it is extruded as a flexible, or fluidized (viscously flowable) coherent strand  26 , at elevated temperature T. The latter is typically between 180 degrees and 200 degrees, Celcius. 
     The screws  22  are for example driven in rotation by a motor drive  27  having an output shaft  27   a  coupled by belt  28  to input shaft  29   a  of a gear box  29 , operating to reduce the drive RPM to a level of about 60-70 RPM for rotating the screws. A stand  32  supports the above described equipment, as shown. 
     The next step, provided by cooler apparatus  35  (see  FIGS. 1 and 3 ) is to cool the leftwardly delivered and moving strand  26 , to partly solidify the strand. A cooling bath  36  is provided as is a horizontal tray  36   a . The strand moves leftwardly within the bath, entering it at  37  and emerging leftwardly at  38 . Strand temperature is thereby reduced as from about 190 to 40-60° Celcius. Apparatus cooling equipment may be provided as at  39 . Stand  40  supports the tray  36   a  and bath  36 , which may consist of water at about 35 degrees Celcius. 
     The emergent strand at  38   a  is subjected to tension, acting to haul or pull it leftwardly through or from the bath. For this purpose, the strand may be passed through appropriate means such as rolls at  48  of a hauling device  41  having motor driven elements  42   a  acting to rotate the rolls operating to haul the strand leftwardly, progressively immersed in the bath and then emergent. Elements  42  may be adjusted to effect hauling of the strand at selected speed, as for example between 30 and 40 inches per second, coinciding with speed of extrusion. 
     From the device  41 , the strand or strands at  38   b  is or are delivered to storage means  50 , that may include a winding bobbin or bobbins  51 . Strand directional pulleys are indicated at  52 , in  FIG. 6 . The strand or strands pass or passes beneath a tension bar  54  acting to tension the strand or strands wound on the bobbin or bobbins. Stand  55  supports bar  54 . 
       FIG. 7  shows an initial process to form “master batch” strand pellets at  67  and supplied to extruder  21 . A mixing and pellet forming means  61  and an extruder barrel  63  serve to receive, advance, and thoroughly mix the feed from a hopper  10   a , the powdered feed components being those referred to above. Discharge of the mix powder into the extruder is indicated at  20 . Use of a single screw conveyor provides assurance that the powdered mix components, and particularly the flame retardant EB4374, are thoroughly dispersed and uniformly distributed in the mix as it is heated and formed into the preliminary strand  64 . After cooling at  65 , as described above, and hauling at  66 , the strand is cut at  66   a  into pellets  67 , collected at  68 . Those pellets are then fed into hopper  10 , to be fed to extruder  21  for processing as described above in  FIG. 1 . Accordingly, the flame retardant is processed twice, in extruders  21  and  23 . 
       FIG. 7   a  is a more complete view of apparatus shown in  FIG. 7 . The powdered mix in hopper  90  is delivered to feeder  91 , from which the mix is fed to horizontal, rotating barrel  92 . Drive to rotate a screw convey  61  in that barrel includes a motor  93  and a gear box  94 , the screw rotating at an RPM between 40 and 65. Successive barrel zones are indicated at  61   a ,  61   b  and  61   c , with barrel heaters  61   aa ,  61   bb  and  61   cc , the temperature in zone  61   b  exceeding the temperature in zone  61   a , and the temperature in zone  61   c  exceeding that in zone  61   b . For example, see the following: 
     zone  61   a , about 170° C. to 180° C. 
     zone  61   b , about 180° C. to 185° C. 
     zone  61   c , about 190° C. 
     An extruder head  95  receives the heated, conveyed mix, and is typically heated to about 200° C.; a flange adapter  96  preceding that head is typically heated to about 210° C.; and the extrusion die or dies  97  are heated to about 180° C. to 200° C. 
     The heated, extruded strand  64  passes at  64   a  through water bath  65  for cooling, and is then air dried by dryer  98 . The strand is hauled at  66  and cut at  66   a  into pellets  67 , collected at  68 . 
       FIG. 7   b  shows a similar extrusion apparatus, with components having the same identifying numerals as are described in  FIG. 7   a.    
     It is found that a substantially uniform wicker product is thereby formed, in terms of wicker composition, durability, strength and appearance, as in a woven wicker product. A representative such product is shown at  68 , in  FIG. 8 . The wicker weaving step is indicated at  69  in  FIG. 1 . 
     Referring to  FIG. 9 , it shows multiple product strands  70 - 72  in cross section, each individually extruded and in side by side state as at interfaces  80  and  81 , to adhere to one another, prior to being cooled as a single strand  73 .  FIG. 10  shows multiple extruders  70   a - 72   a  extruding the strands  70 - 72  from dies  70   b - 72   b . Differently colored strands  70 - 72  may thereby be integrated into a multi-colored single product strand. The dies may be integrated as a single die having three discharge outlets or openings. The strand compositions differ, in that different pigments are added to the mixes forming the strands. Examples of such pigments are those referred to above. 
     Three said strands are simultaneously extruded in local linear side-by-side adherent relation with longitudinally linearly elongated wicker appearance, lateral spacing being maintained the same between outer two said strands at opposite sides of a medial strand, along the longitudinal length of the three strands, each of said three strands provided to be substantially rectangular in cross section with flat sides so that substantially the entireties of opposite flat sides of a medial strand cohere flatly to sides of the remaining two strands in conjunction with said extruding.