JP2011104783A - Multilayer extrusion method for thermoplastic resin composition and covered wire/cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer extrusion method for thermoplastic resin compositions which can inexpensively manufacture a multilayer-structured extrusion molding by one extrusion molding machine and can surely raise the adhesion between layers in the extrusion molding and a covered wire/cable produced by the extrusion method. <P>SOLUTION: In the multilayer extrusion method for the thermoplastic resin composition, at least two kinds of the thermoplastic resin compositions A and B each of which is an extrusion material are supplied to one extrusion molding machine 1 equipped with a single axis screw 3 having a spiral structure flight 2 with a prescribed height on its periphery in the axial direction, conveyed simultaneously without being mixed through different passages 9 and 10 formed in the extrusion molding machine 1, and melt extrusion-molded respectively from the extrusion molding machine 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention can be applied, for example, as a method for insulating insulation of long electric wires and cables, and as a method for obtaining a long extruded product such as a plastic pipe having a multi-layer structure, and a multilayer extrusion of a thermoplastic resin composition. The present invention relates to a method and a covered electric wire / cable manufactured by the extrusion method.

  Conventionally, as a method of extruding a plurality of types of thermoplastic resin compositions of the same type or different types to obtain an extruded product having a multilayer structure, an extrusion molding machine uses a pellet-shaped thermoplastic resin composition as an extrusion material. Since it is necessary to melt and extrude for each type of extrusion material, a method is known in which multiple extrusion machines are placed on the extrusion line and extrusion is performed sequentially to obtain an extruded product with a multilayer structure. Currently, it is widely used.

  As an example of a multilayer structure extruded product, for example, there is a two-layer covered electric wire 1 ′ having a cross-sectional structure shown in FIG. 7. As is clear from the figure, this electric wire 1 ′ is formed by extrusion coating made of a thermoplastic resin composition of the same type or different from the extrusion coating layer (inner layer) 3 ′ made of a thermoplastic resin composition on the circumference of the conductor 2 ′. The layers (outer layers) 4 ′ are sequentially extruded. Moreover, in this electric wire 1 ', the contact interface (boundary) of the extrusion coating layer 3' which is an inner layer and the extrusion coating layer 4 'which is an outer layer is clearly distinguished. As shown in FIG. 8, the method of manufacturing the electric wire 1 ′ is such that the conductor 2 ′ traveling in the direction of arrow “a” is subjected to an extrusion coating layer by a first extruder 5 ′ disposed on the same manufacturing line. 3 'is coated, and the extrusion coating layer 4' is further coated by the second extruder 6 '. That is, this is a method of obtaining the electric wire 1 ′ having a two-layer covering structure by using two extruders 5 ′ and 6 ′.

  As can be seen from the production example of the electric wire 1 ′, in the conventional method of obtaining an extrusion molded article having a multilayer structure, the number of extrusion molding machines increases as the number of extrusion molding layers increases along with the type of thermoplastic resin composition as an extrusion material. Need to be increased. Alternatively, it is necessary to increase the number of manufacturing processes and use one extruder repeatedly.

  On the other hand, Patent Document 1 as a prior art document describes an extrusion molding machine provided with a single screw having a spiral structure flight having a predetermined height on an axial circumference as a foam insulated electric wire manufacturing apparatus. Has been.

  Further, in Patent Document 2, which is a prior art document, as a method for producing a foam insulated wire, two extruders each having the same single-screw as in Patent Document 1 are connected to one cross head. A method is described in which a head and a plastic containing no foaming agent and a plastic containing a foaming agent, which are melted and conveyed through the two extruders, are simultaneously extruded by the head, respectively.

JP-A-49-95189 Japanese Patent Application Laid-Open No. 64-67832

  According to the conventional method for obtaining an extruded product having a multilayer structure, it is necessary to increase the number of extruders on the same production line as the number of extruded layers increases along with the type of thermoplastic resin composition that is an extruded material. However, there is a problem that the equipment cost increases and the product cost increases accordingly. Further, in this case, it is necessary to control the operation of a plurality of extruders arranged on the same production line at the same time, and there is a problem that it is difficult to find the optimum operation control condition because the control parameters increase. is there. When this manufacturing condition is not appropriate, there is a problem that the adhesion between the layers of the extruded product extruded into a multilayer structure becomes insufficient.

  On the other hand, the extrusion molding machine described in Patent Document 1 is an extrusion molding machine provided with a single screw having a spiral flight having a predetermined height on the circumference in the axial direction. Therefore, when obtaining an extruded product having a multilayer structure (for example, a foam insulated wire having a two-layer covering structure), naturally, it is necessary to increase the number of extruders and arrange a plurality of extruders on the same production line. .

  Further, the extrusion molding machine described in Patent Document 2 is configured by connecting two extrusion molding machines to a single crosshead, respectively, to constitute the entire extrusion molding machine. This is not a simple addition of an extrusion molding machine, but the configuration is such that an extrusion molding machine is added.

  Therefore, in view of the above, an object of the present invention is to be able to manufacture an extrusion-molded article having a multilayer structure at a low cost with a single extruder, and to reliably improve the adhesion between the layers in the product. It is another object of the present invention to provide a multilayer extrusion method for a thermoplastic resin composition and a coated electric wire / cable manufactured by the extrusion method.

  In order to achieve the above object, the invention of claim 1 is directed to a single extrusion machine having a single screw having a spiral flight having a predetermined height on the circumference in the axial direction. A plurality of types of thermoplastic resin compositions are supplied, and the plurality of types of thermoplastic resin compositions are simultaneously conveyed without being mixed through separate flow paths provided in the extruder, and the extrusion molding is performed. Provided is a multilayer extrusion method for a thermoplastic resin composition characterized by melt-extruding the plurality of types of thermoplastic resin compositions from a machine.

  In the above, examples of the thermoplastic resin composition exhibiting fluidity upon heating include thermoplastic resin compositions such as polyethylene, polypropylene, polyethylene terephthalate, and polyvinyl chloride, and foaming agents and colorants for these thermoplastic resin compositions. The thermoplastic resin composition which added additives, such as, can be used. In particular, a thermoplastic resin composition made of polyethylene is preferable because the effect of the invention is remarkable when it is used. In this case, an additive such as a foaming agent or a colorant is azicarbonamide (ADCA). , Talc, etc., and can be used in an appropriate amount if desired.

  According to the multilayer extrusion method of this thermoplastic resin composition, by adopting the above-described configuration, in particular, one extrusion molding machine is supplied with a plurality of types of thermoplastic resin compositions, each of which is an extrusion material. These thermoplastic resin compositions are simultaneously conveyed without being mixed through separate flow paths provided in the extruder, and the plurality of types of thermoplastic resin compositions are melt-extruded from the extruder. Thus, an extruded product having a multilayer structure can be produced at a low cost with a single extruder, and the adhesion between the layers of the product can be reliably increased by simultaneously performing extrusion.

  The invention according to claim 2 is the multilayer extrusion of the thermoplastic resin composition according to claim 1, wherein the extrusion molding machine is provided with a single screw having a double spiral flight. Provide a method.

  In the above description, it is preferable that each of the flights having a double spiral structure is a full flight that is continuous (not intermittent) along the flight line. If it is such a full flight, the flow path (conveyance path) of an extrusion material can be separately formed along the flight line of a double spiral structure.

  According to this multilayer extrusion method of a thermoplastic resin composition, in addition to the above-described effects, the adoption of the above-described configuration allows the extrusion material to be extruded along the flight line of a double helical structure of a single screw in the extruder. Since the flow paths (conveyance paths) can be formed separately, the structure of this extrusion molding machine conveys two types of thermoplastic resin compositions, which are extrusion materials, simultaneously without mixing through separate flow paths. Thus, an extrusion-molded product having a two-layer structure can be easily produced at a low cost.

  The invention according to claim 3 is characterized in that a long extruded product obtained by extruding the plurality of types of thermoplastic resin compositions into a multilayer structure is obtained by the melt extrusion molding. A method for multilayer extrusion of a thermoplastic resin composition is provided.

  According to the multilayer extrusion method of this thermoplastic resin composition, in addition to the above effects, by adopting the above configuration, a long extruded product having a multilayer structure can be easily produced at low cost.

  The invention of claim 4 is characterized in that the plurality of types of thermoplastic resin compositions comprise at least two types of thermoplastic resin compositions and the same type of thermoplastic resin composition obtained by adding an additive thereto. A multilayer extrusion method for the thermoplastic resin composition according to claims 1 to 3 is provided.

  According to this multilayer extrusion method of a thermoplastic resin composition, in addition to the above effects, by adopting the above configuration, as a two-layer coated structure extrusion product including a foam layer, for example, a long extrusion molding such as a foam insulated wire The product can be easily manufactured at low cost.

  According to a fifth aspect of the present invention, there is provided a long extruded product produced by the extrusion method according to any one of the first to fourth aspects, wherein a plurality of types of thermoplastic resin compositions are coaxially extruded on the circumference of a conductor. A covered electric wire / cable is provided.

  According to this covered electric wire / cable, in addition to the above effects, by adopting the above configuration, a covered electric wire / cable made of a long extruded product having a multilayer structure can be easily and inexpensively manufactured. Moreover, in this coated electric wire / cable, the adhesion between the respective coated layers can be reliably increased.

  According to the multilayer extrusion method of the thermoplastic resin composition of the present invention and the coated electric wire / cable manufactured by this extrusion method, an extrusion-molded product having a multilayer structure can be manufactured at low cost with one extruder. And the adhesiveness between each layer in the product can be improved reliably.

It is a schematic explanatory drawing of the extrusion molding machine used for the multilayer extrusion method of the thermoplastic resin composition which concerns on one embodiment of this invention. 1 is a cross-sectional view and a vertical cross-sectional view of an extruded material dispensing jig attached to a rear end position of a single screw having a double spiral structure flight corresponding to the extruded material charging port in the extruder of FIG. It is. FIG. 2 is a cross-sectional view and a vertical cross-sectional view of an extrusion molding jig attached to a tip position of a single screw having a double spiral structure flight in the extruder of FIG. 1. It is a schematic explanatory drawing of the extrusion machine used for the manufacturing method of the covered electric wire and cable which concerns on one embodiment of this invention. It is a cross-sectional view of the covered electric wire and cable (two-layer covering foam insulated electric wire) manufactured by the manufacturing method of FIG. It is a cross-sectional view of the covered electric wire and cable (two-layer covering colored insulated electric wire) manufactured by the manufacturing method of FIG. It is a cross-sectional view of a conventional electric wire having a two-layer covering structure. It is a schematic explanatory drawing of the manufacturing method of the electric wire of the conventional 2 layer coating structure.

  Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. 1 to 6, but it goes without saying that the present invention is not limited to these embodiments.

  As described above, FIG. 1 is a schematic explanatory view of an extrusion molding machine used in a multilayer extrusion method for a thermoplastic resin composition according to an embodiment of the present invention. In this figure, an extrusion molding machine 1 includes a single-screw 3 having a double spiral structure flight 2 having a predetermined height on an axial circumference, and a cylindrical barrel 4, An extrusion material dispensing jig 7 is attached to the rear end position of the screw 3 corresponding to the extruded material inlets 5 and 6, and an extrusion molding jig 8 is attached to the distal end position of the screw 3. The single screw 3 in the barrel 4 in the configuration of the extrusion molding machine 1 is rotated together with the extrusion material distribution jig 7 and the extrusion molding jig 8, thereby allowing the extrusion material distribution jigs 5 and 6 to feed the extrusion material distribution jigs. The two types of thermoplastic resin compositions A and B supplied alternately into the barrel 4 through 7 are separated into separate flow paths in the extruder 1 provided along the double helical flight lines. (The flow path 9 indicated by the arrow A and the flow path 10 indicated by the arrow B) are simultaneously conveyed without being mixed, and the thermoplastic resin compositions A and B melted by heating in the conveyance process are further mixed. The melt extrusion molding is performed through the extrusion jig 8. Heating of the thermoplastic resin compositions A and B in the conveyance process can be performed by attaching a heater (not shown) to the outer periphery of the barrel 4.

  FIG. 2 is a cross-sectional view (right side view) and a longitudinal cross-sectional view (left side view) of an extruded material distribution jig 7 attached to the rear end position of the screw 3 corresponding to the extruded material input ports 5 and 6. ). As shown in FIG. 2, the extruded material distribution jig 7 has two types of thermoplastic resin compositions A and B fed from the extruded material feed ports 5 and 6, respectively, in the flow in the extruder 1. In order to alternately supply the passages 9 and 10, two passages 11 and 12 corresponding to the extruded material inlets 5 and 6 are provided by being shifted in the axial direction. Further, since the extruded material distribution jig 7 rotates together with the screw 3, the openings of the passages 11 and 12 communicate with the input ports 5 and 6 alternately every time the passages 11 and 12 rotate halfway. Thus, it is provided by being shifted in the circumferential direction. As a result, the cross-sectional view and vertical cross-sectional view of the extruded material dispensing jig 7 are as shown in FIG. The axial length of the extruded material distribution jig 7 is shorter in order to supply the thermoplastic resin compositions A and B fed from the extruded material inlets 5 and 6 to the flow passages 9 and 10 without delay. preferable. Various structures other than this can be adopted as the structure of the extruded material distribution jig 7.

  FIG. 3 is a cross-sectional view (right side view) and a vertical cross-sectional view (left side view) of the extrusion forming jig 8 attached to the tip position of the screw 3. As shown in FIG. 3, the extrusion jig 8 is used for melt extrusion molding the thermoplastic resin compositions A and B melted by heating without being mixed through the flow passages 9 and 10, respectively. The two extrusion ports 13 and 14 are provided corresponding to the flow paths 9 and 10. Since the extrusion molding jig 8 also rotates together with the screw 3, the extrusion molding ports 13 and 14 are spaced apart from each other in the radial direction so that the extruded products extruded through this do not collide and mix. Provided at intervals. As a result, the cross-sectional view and vertical cross-sectional view of the extrusion forming jig 8 are as shown in FIG. Various structures other than this can be adopted as the structure of the extrusion forming jig 8.

  According to the present embodiment, since continuous extrusion is possible, in order to take advantage of its merit, as an insulating coating method for long electric wires and cables, and long extruded products such as multilayered plastic pipes It is preferable to apply as a method of obtaining

  Further, according to the present embodiment, since two types of thermoplastic resin compositions A and B are melt-extruded with one extruder, each of the thermoplastic resin compositions A and B is extruded. It is preferable to employ one that does not have extremely different molding conditions. For example, as the thermoplastic resin compositions A and B, it is preferable to employ those having the same thermoplastic resin composition as the main component but different in the presence or absence of additives and the concentration of the main component. Or it is preferable to employ | adopt the thing which does not add a foaming agent or a coloring agent as one thermoplastic resin composition A, and the thing to which a foaming agent or a coloring agent was added as the other thermoplastic resin composition B.

(Manufacturing method of two-layer coated foam insulated wire)
A foam insulated wire 16 having a two-layer covering structure was manufactured using an extruder 15 shown in FIG. The basic structure of the extruder 15 is the same as that of the extruder 1 shown in FIG. Therefore, the same reference numerals are assigned to the members having the same names, and redundant description is omitted. In this extruder 15, the diameter (D) of the single screw 3 having the double spiral flight 2 is 45 mm, and the ratio of the screw length (L) to the diameter (D) (L / D) is 29.

  In this example, as the thermoplastic resin composition A as an extrusion material, pellet-shaped high-density polyethylene is used, and as the thermoplastic resin composition B as an extrusion material, the same kind of high-density polyethylene as pellets is added to the pellet. Each of which added 05 wt% foaming nucleating agent (ADCA) was used. In addition, as the conductor 17 for the foam insulated wire 16, a tin-plated wire having a conductor size of 24AWG (line / diameter: 0.51 mm) was used.

Further, in the embodiment using the extrusion molding machine 15 of FIG. 4, the conductor 17 is caused to travel in the direction of arrow a at a linear speed of 180 to 200 m / min on the cross head 18 provided so as to intersect the screw shaft. At the same time, N ₂ gas is injected into the barrel 4 from the gas inlet 19 penetrating the single screw 3 at a pressure of 36 to 38 MPa, and the temperature in the barrel 4 is set to 150 to 170 ° C. The thermoplastic resin composition B was foamed by a foaming method. At the crosshead 18, the thermoplastic resin composition B is extruded from the extrusion port 14 provided inside the extrusion molding jig 8 toward the conductor 17 passing through the crosshead 18, and the extrusion molding is performed. The thermoplastic resin composition A is extruded from an extrusion port 13 provided on the outside of the jig 8 and the foam layer 20 made of the thermoplastic resin composition B and the thermoplastic resin composition A are formed on the circumference of the conductor 17. A foamed insulated wire 16 having a two-layer covering structure having a cross-sectional structure shown in FIG.

  Incidentally, in the two-layer covered foam insulated wire 16 manufactured in this way, foaming of the coating layer is concentrated in the vicinity of the conductor 17, and the degree of foaming indicating the degree of foaming is about 50% of the entire coating layer. The surface coating layer had no foam and the surface was smooth. In the case where a foamed layer 20 and a non-foamed layer 21 are simultaneously extruded using one extruder 15 to produce a two-layer coated foam insulated wire having the same structure using two conventional extruders. Compared with, the foamed layer and the non-foamed layer were closely integrated, and the adhesion between the coating layers was significantly improved. Thereby, even when excessive bending is performed, the effect of preventing the peeling of the interface between the respective coating layers can be enhanced.

(Method for producing a two-layer coated colored insulated wire)
A colored insulated electric wire 22 having a two-layer covering structure shown in FIG. 6 was manufactured using an extruder 15 shown in FIG.

  In this example, the thermoplastic resin composition A as an extrusion material is pellet-shaped high-density polyethylene, and the thermoplastic resin composition B as an extrusion material is a pellet-shaped high-density polyethylene colored in blue. Density polyethylene was used respectively. Moreover, as the conductor 23 for the colored insulated wire 22, a tin-plated wire having a conductor size of 24AWG (line / diameter: 0.51 mm) was used.

In this example, N ₂ gas was not injected, and the conductor wire speed, barrel temperature, and screw structure were all the same as in Example 1.

  The cross-sectional structure of the colored insulated electric wire 22 having a two-layer covering structure obtained in this example is as shown in FIG. In this figure, 24 is an inner extrusion coating layer colored blue, and 25 is an outer extrusion coating layer. In addition, depending on the kind of colored electric wire, an outer extrusion coating layer may be colored.

  Incidentally, in the two-layer coated colored insulated electric wire 22 manufactured in this way, the same structure is obtained by simultaneously extruding the inner extrusion coating layer 24 and the outer extrusion coating layer 25 with one extruder 15. Compared with the case where the two-layer coated colored insulated electric wire was produced using two conventional extruders, the adhesion between the respective coating layers was remarkably improved. Thereby, even when excessive bending is performed, the effect of preventing the peeling of the interface between the respective coating layers can be enhanced.

DESCRIPTION OF SYMBOLS 1,15 Extruder 2 Flight 3 Single screw 4 Barrel 5,6 Extrusion material inlet 7 Extrusion material distribution jig 8 Extrusion jig 9, 10 Flow path A, B Thermoplastic resin composition 11, 12 Passage 13 , 14 Extrusion port 16 Foam insulated wire 17, 23 Conductor 18 Cross head 19 Gas inlet 20 Foamed layer 21 Non-foamed layer 22 Colored insulated wire 24 Extrusion coating layer on the inner side 25 Extrusion coating layer on the outer side

Claims (5)

  While supplying a plurality of types of thermoplastic resin compositions, each of which is an extruded material, to a single extrusion molding machine having a single screw having a spiral flight having a predetermined height on the circumference in the axial direction, These plural types of thermoplastic resin compositions are simultaneously conveyed without being mixed through separate flow paths provided in the extruder, and the plural types of thermoplastic resin compositions are respectively melted from the extruder. A multilayer extrusion method for a thermoplastic resin composition, characterized by performing extrusion molding.   The method for multilayer extrusion of a thermoplastic resin composition according to claim 1, wherein the extruder comprises a single screw having a double spiral flight.   3. The multilayer of the thermoplastic resin composition according to claim 1, wherein a plurality of types of thermoplastic resin compositions are extruded into a multilayer structure by the melt extrusion molding. Extrusion method.   4. The plurality of types of thermoplastic resin compositions are composed of at least two types of thermoplastic resin composition and the same type of thermoplastic resin composition obtained by adding an additive thereto. A multilayer extrusion method for a thermoplastic resin composition.   A coating comprising a long extruded product produced by the extrusion method according to any one of claims 1 to 4, wherein a plurality of types of thermoplastic resin compositions are each coaxially extruded on a circumference of a conductor. Electric wire / cable.

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