IL28865A - Integral extruded plastic net - Google Patents

Description

plastic net PLASTIC TEXTILE ACCESSGEIES THIS INVENTION relates to the extrusion of integral thermoplastic netting by methods and apparatus of the character for in our British Patent Specification According to the above specification the production for tubular netting is effected by extruding the thermoplastic material through circumferentially extending die means formed between a pair of extrusion members or dies referred to as die having surfaces adjacent the die means and in sliding contact with one another to form a bearing one or both of the die members being given continuous rotary or oscillatory The die means are supplied with thermoplastic material from a pressure supply chamber through feed vhich may be formed in or through one or both of the contacting surfaces of the die members and which communicate with the chamber and with the die the present invention may also be applied to the production of flat or sheet netting from rectilinear or arcuate dies as also described in the above An object of the present invention is to provide an improved net structure after molecular orientation of the net strands by stretching in known has a greater impact strength and tear strength than net structures fore of the same weight per unit area and the same mesh count transversely of the This improved net structure is achieved by extruding net strands of special as will be through die orifices of a corresponding the extrusion including cooling and of the extruded being substantially as In the accompanying drawings Figure 1 is a plan view of a portion of net according to the present invention with of the strands Figure 2 is a perspective view on an enlarged scale of a net intersection after orientation of a net structure according to the present Figure 3 a perspective view on an enlarged scale partly in section of the intersection shown in Figure 1 Figure is a on an enlarged scale of a die orifice for extruding one strand of a net structure as shown in Figure 1 and according to the present Figures 6 show the die orifice in Figure respectively extruding a mesh strand and conjointly with similar die orifice in register a net Figure 7 similar to Figure 4 of an alternative form die orifice according to the present and Figures 8 show various forms of suitable die orifice to extrude net structures according to the present In the net construction according to the present see for example Figure 1 and of which the intersection 1 of two strands 2 and 3 is shown in Figure each strand 2 or 3 comprises a base portion and one outlying portion The outlying portions after are continuously orientated throughout their whereas the base portions are orientated between the intersections 1 with unoriented intercepts at the tions The continuity of the outlying portions of the tively slender section is shown in Figures 2 and 3 together with the distribution of the thermoplastic from the base portions of the strands in the median plane M of the net to form an intersection joint of adequate strength involving a concentration 6 of the thermoplastic material in the median plane M between the pairs of strands 2 and A suitable die orifice 13 for extruding net which when stretched is as shown in Figures 1 to 3 is shown in Figure drawn against the outline of a conventional slot die The area of the die orifice 13 is substantially the same as that of the conventional die orifice ratio 12 to and comprises a triangular portion 15 for shaping the strand base portion and an outer portion 16 responsible for shaping the outlying portions 5 of the strands 2 or 3 as a rib or distinct from the base portion 15 of strand In the case of open slot when a die orifice 13 is separate as in Figure k strands 2 or 3 only are see Figure extrudate while when a pair of die orifices 13 passing in see Figure strand intersections 1 are the conjoint base portions 15 of the die orifices providing the concentration of material for the structure of the intersections 1 described Figure 7 shows detail of an alternative die orifice form 19 having a portion and two rib or portions and and Figures 8 to show a variety of still further alternative forms of suitable die orifices for carrying out the present Figures 8 and show strand having triangular base portions k and outlying portions 5 of rib or each of which feeds a die orifice o the face of the die the latter die orifices may open on to die face on the line of contact of die means or spaced a short distance The invention consists in an integral extruded thermoplastic which has molecularly oriented by stretching in known comprising two sets of strands and integral extruded wherein each strand comprises at least two distinct and demarcated linear a base portion adjacent the median plane of the net and one or more outlying portions extending from the base portion away from said plane and wherein the thermoplastic material in the outlying portion or portions is molecularly oriented throughout the continuous length of each strand and the thermoplastic material in the base portion is molecularly oriented between the net intersections leaving the two sets of strands connected together at their intersections by the unoriented intercepts of the base portions of the flange there being three portions the case of Figure 8 Figure 8 shows a flat base portion 4 having sloping ends and outlying portions or rib or extending outwardly at the same angle as the slope of the ends Figures 8 and show strands having triangular base portions 4 and outlying portions 5 of Figure 8 shows a strand having a lar base portion 4 and an inverted triangular section lying portion 5 and Figures 8 and show strands having outlying portions the distal ends of which have a rounded bead Different forms produce different net impact and tear strength and Test runs with the dies shown in Figures 4 and using a low density polyethylene having a density of and a melt flow index of gave the following results compared with the conventional die 14 shown drawn against the dies in Figures 4 and 7 TABLE Type of Die Strength Tear Strength Rectangular Die 226 7 3 Figure 4 862 Figure 7 96Ο The impact strength and tear strength in the above table were measured on conventional testing equipment Impact British Standards Methods of Testing BS Method Tear Elmendorf Tester TAPPI Specification It will be observed that the Figure 7 die gives a improvement in impact strength and a improvement in tear stren th over net extruded from a conventional die while insufficientOCRQuality

Claims (1)

1. CLAIMS An integral extruded net which has molecularly oriented by stretching in known sets strands and integral extruded wherein each strand comprises at least two distinct and linear a ortion adjacent the median plane the bet and one or more lying portions extending from the base portion away from said plane and wherein the thermoplastic material in the outlying portion or portions is molecularly oriented throughout continuous length of each strand and the thermoplastic material in base portio is molecularly oriented between the net intersections leaving the two sets of strands connected together at their intersections by unoriented cepts of the base portions of the An integral extruded thermoplastic net as claimed in Claim wherein the base portion o each strand is wide of the compared with the section of the or each outlying portion is narrow or includes a narrow part adjacent the base but is shallow in the direction away from the median plane the whereby at intersectio the of the base portions produces a concentration of the thermoplastic material in the median plane of the which concentration is composed of conjoined unoriented intercepts of the others wise base portions of the Integral extruded net structures which have been moleoularly oriented by stretching in known manner substantially as described with reference to the accompanying insufficientOCRQuality