Extrusion Die for Cable

Abstract

The present invention relates to an extrusion die for manufacturing cables that can effectively suppress die drool at the exit of the extrusion die during the extrusion of an insulating layer or sheath layer for manufacturing cables, and increase extrusion productivity and improve the appearance quality of the product.

Description

Technology Field

[0001] The present invention relates to an extrusion die for manufacturing cables. More specifically, the present invention relates to an extrusion die for manufacturing cables that can effectively suppress die drool at the exit of the extrusion die during the extrusion of an insulating layer or sheath layer, etc., for manufacturing cables, and can increase extrusion productivity and improve the appearance quality of the product. Background Technology

[0002] Cables can generally be classified into power cables for power supply and communication cables for communication, and can generally be composed of at least one extruded layer extruded from a polymer material.

[0003] FIG. 1 illustrates a cross-sectional view of the basic structure of a power cable as an example of a cable manufactured by an extrusion process. The power cable (10) may be configured to include a conductor (1) for power transmission, an inner semiconducting layer (2) surrounding the conductor (1), an insulating layer (3) provided on the outside of the inner semiconducting layer (2) to perform an insulating function, an outer semiconducting layer (4) provided on the outside of the insulating layer (3), and a cable jacket (5) provided on the outside of the outer semiconducting layer (4).

[0004] The layers that sequentially wrap around the outside of the conductor (1) constituting this cable can be manufactured by extrusion or other methods using different materials to perform the function of each layer.

[0005] The inner semiconducting layer (2), the insulating layer (3), the outer semiconducting layer (4), and the cable jacket (5) may be formed by sequentially extruding them in separate extrusion processes or by extruding multiple layers in a single process using multiple extrusion. As an example of the latter, the inner semiconducting layer (2), the insulating layer (3), and the outer semiconducting layer (4) may be completed in a single extrusion process using triple extrusion, after which the cable jacket (5) may be extruded in a separate process.

[0006] Figure 2 shows a cross-sectional view of one example of an extrusion die used in a conventional cable extrusion process.

[0007] When the outer semiconducting layer of a cable or a cable jacket, etc., is formed by the extrusion of a polymer compound, as shown in FIG. 2, the extruded workpiece (c) is supported by a nipple (150') and passes through the inside of the extrusion die (100), and the extruded material (p') in the form of a molten polymer compound is applied to the surface, and then the extruded material (p') is cooled as it passes through the exit of the extrusion die (100) and is discharged to the outside, so that an extrusion layer (p) can be formed on the surface of the extruded workpiece (c).

[0008] Here, the inside of the extrusion die (100) is maintained at a high temperature and high pressure for the melting and coating of the extrusion material (p'), and as the extrusion work (c) coated with the extrusion material (p') is discharged to the outside at room temperature and pressure through the exit of the extrusion die (100), negative pressure is applied to the coated extrusion material (p'), causing the relatively low molecular weight components within the extrusion material (p') to be ejected to the outside of the extrusion material (p') and tenaciously adhere to the corners of the exit of the extrusion die (100), and such burr-shaped attachments are called die drool.

[0009] The above die rolls can adhere to the surface of the extruded product and degrade the product's appearance quality in the form of protrusions and foreign matter. Additionally, to remove the die rolls that cause quality degradation of the extruded product, the extrusion process must be stopped and the exit surface of the extrusion die must be cleaned manually, which leads to cost issues due to production stoppage.

[0010] Therefore, there is a need for an extrusion die for cable manufacturing that can effectively suppress die drool at the exit of the extrusion die during the extrusion of insulation and sheath layers for cable manufacturing and improve the extrusion appearance quality of insulation layers. The problem to be solved

[0011] The present invention aims to solve the problem of providing an extrusion die for manufacturing cables that can effectively suppress die drool at the exit of the extrusion die during the extrusion of an insulating layer or sheath layer for cable manufacturing, and increase extrusion productivity and improve the product appearance quality. means of solving the problem

[0012] To solve the above problem, an extrusion die for extruding a workpiece constituting a cable can be provided, comprising: an injection part through which an extrusion material is injected through the space between the inner surface of the extrusion die and the outer surface of a nipple that supports the workpiece and passes the workpiece into the extrusion die; a land part that applies the extrusion material injected into the extrusion die through the injection part to the surface of the workpiece; and an outlet part through which the workpiece coated with the extrusion material is discharged out of the extrusion die, wherein the inner surface of the land part is coated with a fluoropolymer.

[0013] In addition, at least a portion of the outer surface of the outlet portion connected to the land portion may be coated with fluoropolymer resin in a continuous manner with the inner surface of the land portion.

[0014] In addition, at least a portion of the injection part connected to the land part may be coated with fluoropolymer resin continuously with the inner surface of the land part.

[0015] Here, at least a portion of the outer surface of the outlet portion connected to the land portion and the inner surface of the injection portion may be coated with fluoropolymer resin continuously with the inner surface of the land portion.

[0016] In addition, the fluoropolymer may include one or more selected from the group consisting of polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), fluoroethylenepropylene (FEP), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), ethylenetetrafluoroethylene (ETFE), and ethylenechlorotrifluoroethylene (ECTFE).

[0017] In this case, the fluoropolymer may include one or more selected from the group consisting of polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), and fluoroethylenepropylene (FEP).

[0018] And, the land portion includes a first land portion connected to an injection portion and a second land portion disposed between the first land portion and the outlet portion, and

[0019] The inner diameter (D) of the second land portion may be 1.05 to 1.2 times the inner diameter (d) of the first land portion.

[0020] Here, the length (Lc) of the second land portion may be 2 / 15 to 1 / 3 of the total length (L) of the land portion.

[0021] In addition, the land portion may further include a third land portion having an inclined surface with an inner diameter that gradually increases along the extrusion direction between the first land portion and the second land portion.

[0022] Also, the angle of the inclined surface (θ) of the third land portion may be 10 to 30°.

[0023] Here, the fluoropolymer resin can be coated with a thickness of 20 to 50 μm.

[0024] In addition, the extrusion die may be made of steel or heat-treated steel.

[0025] In this case, the extruded material may include a polymer compound.

[0026] In addition, the extruded object may be one of the insulation layer of a power cable, an outer semiconducting layer surrounding the outer side of the insulation layer, or a cable jacket of a power cable.

[0027] Here, the land portion may have at least two steps so that the inner diameter expands sequentially between the injection portion and the outlet portion.

[0028] In addition, at least one of the above steps may be configured as an inclined surface having an inner diameter that expands in the direction of the exit section. Effects of the invention

[0029] The extrusion die for manufacturing cables according to the present invention has an excellent effect of improving the uniformity of the extrusion appearance and the transparency of the appearance of the insulation layer, etc., by coating the inner wall of the extrusion die with fluoropolymer and additionally designing the extrusion die outlet specifically to effectively suppress die-dough formation at the extrusion die outlet. Brief explanation of the drawing

[0030] Figure 1 shows a cross-sectional view of the basic structure of a power cable as an example of a cable manufactured by an extrusion process. Figure 2 shows a cross-sectional view of one example of an extrusion die used in a conventional cable extrusion process. FIG. 3 illustrates a cross-sectional view of an extrusion die according to the present invention used in a cable extrusion process. Figure 4 shows an enlarged view of the injection, land, and outlet structures of the extrusion die illustrated in Figure 3. FIG. 5 illustrates another embodiment regarding the structure of the injection section, land section, and outlet section of an extrusion die. Figures 6 to 14 are images of the extrusion products and a summary of the results under the extrusion conditions shown in Table 1 above. FIGS. 15 to 17 illustrate cross-sectional views of other embodiments of an extrusion die according to the present invention. Specific details for implementing the invention

[0031] Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete, and to ensure that the spirit of the present invention is sufficiently conveyed to those skilled in the art. Throughout the specification, the same reference numerals indicate the same components.

[0032] FIG. 3 illustrates a cross-sectional view of an extrusion die according to the present invention used in a cable extrusion process.

[0033] The extrusion process for manufacturing a cable may be performed as a multi-extrusion process, but for convenience of explanation and illustration, the extrusion die shown in FIG. 3 may be an extrusion die for forming a single extrusion layer, and the extrusion layer (p) may be a layer formed by extrusion, such as an outer semiconducting layer inside the cable or a cable jacket, for example, and the extruded material (c) introduced into the extrusion die (100) may be the conductor (1) of the cable, or a composition from the conductor (1) to the insulation layer (3) or a composition up to the outer semiconducting layer (4), but is not limited thereto.

[0034] In addition, the cable manufactured through the extrusion die is not limited to a power cable but may also be a communication cable, and the extrusion layer (p) can be interpreted as including any layer extruded through the extrusion die using a polymer compound, and the extruded object (c) can be understood as a configuration wrapped around the extrusion layer (p).

[0035] Hereinafter, an extrusion die according to the present invention will be described in detail with reference to FIG. 3 and below.

[0036] As illustrated in FIG. 3, the extrusion die (100) according to the present invention may have a structure including an injection part (110) through which an extrusion material (p') in the form of a polymer compound mixed with other additives in a polymer resin is injected through the space between the inner surface and the outer surface of a nipple (150) that supports the extrusion target (c) and passes it into the extrusion die (100); a land part (120) that applies the extrusion material injected into the extrusion die (100) through the injection part (110) to the surface of the extrusion target (c); and an outlet part (130) through which the extrusion target (c) coated with the extrusion material is discharged out of the extrusion die (100), and the inner surface of the land part (120) is characterized by being coated with fluoropolymer resin.

[0037] The extrusion die (100) may be operated at a high temperature and high pressure internally for melting and coating of the extrusion material, and the materials of the extrusion die (100) and the nipple (150) may be steel, heat-treated steel, etc. that can be operated at the high temperature and high pressure, and the extrusion material may have various molecular weights, viscosities, melt indices, etc.

[0038] Here, the high temperature may be above a temperature sufficient to melt the extruded material, for example, in the form of a polymer compound (p'), according to the melting point of the extruded material, for example, it may be 120 to 200°C, and the high pressure may be above a pressure sufficient to achieve adhesion between the extruded material when applying the extruded material to the surface of the extruded workpiece (c), for example, it may be 0.7 to 5 MPa.

[0039] In addition, to further improve the adhesion between the extruded material (c) and the extruded material (p') in the form of a molten polymer compound, the extruded material (c) may be preheated to, for example, 80 to 150°C by a torch or the like before being inserted into the extrusion die (100).

[0040] Meanwhile, the speed at which the extruded material (c) is introduced and discharged during extrusion in the extrusion die (100), i.e., the extrusion line speed, can be adjusted in various ways depending on the specifications of the extruded material (c), properties such as molecular weight, viscosity, melt index, etc. of the extrusion material, and the thickness of the extrusion layer formed, and, for example, can be 10 to 50 mpm.

[0041] In addition, the present invention was completed by experimentally confirming that when the cross-sectional shape of the land portion (120) of the extrusion die (100) is changed or a fluoropolymer is coated, die drool is not formed on the corner or open surface of the exit portion (130) during extrusion or is significantly reduced.

[0042] This effect is understood to be that the change in the cross-sectional shape of the land portion (120) of the extrusion die alleviates the rapid negative pressure change experienced by the extrusion layer (p), and the fluoropolymer coating improves the flowability of the extrusion material (p') by buffering the difference in thermal conductivity between the extrusion die (100) and the extrusion material, thereby suppressing the formation of diedrull.

[0043] Here, the thickness of the fluoropolymer coating may be, for example, 20 to 50 μm. The fluoropolymer may include, for example, polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), fluoroethylenepropylene (FEP), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), ethylenetetrafluoroethylene (ETFE), ethylenechlorotrifluoroethylene (ECTFE), etc., and preferably may include polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), fluoroethylenepropylene (FEP), etc.

[0044] The shape changes of the extrusion die and the fluoropolymer coating areas confirmed to be capable of suppressing die rolls will be explained sequentially below.

[0045] Figure 4 shows an enlarged view of the injection, land, and outlet structures of the extrusion die illustrated in Figure 3.

[0046] As illustrated in FIG. 4, the land portion (120) may include a first land portion (121) connected to the injection portion (110) and a second land portion (122) disposed between the first land portion (121) and the outlet portion (130), and the inner diameter (D) of the second land portion (122) may be configured to be larger than the diameter of the first land portion (121).

[0047] It was experimentally confirmed that the amount of daidrule can be significantly reduced solely by changing the diameter of the land portion.

[0048] The reason for the reduction in die roll due to the change in the inner diameter of the land portion or the step formed therefrom is presumed to be that the impact of negative pressure experienced by the extruded material when it is discharged to the outside at room temperature and atmospheric pressure through the extrusion die outlet is split and cushioned. Regarding the degree of change in the inner diameter of the land portion, specifically, it was confirmed that the inner diameter (D) of the second land portion is larger than the inner diameter (d) of the first land portion, and for example, it is preferable that the inner diameter (D) of the second land portion is about 1.05 to 1.2 times the inner diameter (d) of the first land portion.

[0049] The above land portion (120) is divided into a first land portion (121) and a second land portion (122) having different inner diameters, and has a structure in which the inner diameter increases along the extrusion direction, thereby buffering the negative pressure applied to the extrusion layer when the extruded workpiece (c) is discharged out of the extrusion die (100), so that the formation of die rolls in the outlet portion (130) can be further suppressed.

[0050] Here, the effect of suppressing diedrull formation can be maximized when the length (Lc) of the second land portion (122) is 2 / 15 to 1 / 3 of the total length (L) of the land portion (120). It was experimentally confirmed that when the length (Lc) of the second land portion (122) is less than 2 / 15 of the total length (L) of the land portion (120), the negative pressure buffering by the second land portion (122) is insufficient, and thus diedrull is formed at the outlet portion (130), and when the length (Lc) of the second land portion (122) is more than 1 / 3 of the total length (L) of the land portion (120), diedrull is formed at the outlet portion (130) due to a die swell phenomenon in which the extrusion layer expands.

[0051] FIG. 5 illustrates another embodiment regarding the structure of the injection section, land section, and outlet section of an extrusion die.

[0052] As illustrated in FIG. 5, the effect of suppressing the formation of a diedrull can be further enhanced by additionally including a third land portion (123) having an inclined surface with an inner diameter that gradually increases along the extrusion direction between the first land portion (121) and the second land portion (122) of the land portion (120). Here, the angle (θ) of the inclined surface may be, for example, 10 to 30°.

[0053] It was confirmed that the cushioning effect of negative pressure can be further enhanced by changing the inner diameter of the land portion of the extrusion die and simultaneously configuring the step formed according to the change in inner diameter as an inclined surface. For similar reasons, a method of configuring two or more steps according to the change in inner diameter of the land portion can also be applied. That is, although one step is formed in FIGS. 4 and FIGS. 5 respectively, a method of forming two or more steps, and a method of configuring at least one step as an inclined surface with an inner diameter that expands toward the exit portion, can also be applied.

[0054] In addition, to minimize diedrulls, it was confirmed that, in addition to methods of changing the inner diameter of the extrusion die or configuring the step difference resulting from the change in inner diameter as an inclined surface, coating the inner surface of the land portion with fluoropolymer resin is also highly effective in suppressing diedrulls. The fluoropolymer coating layer (f) is provided continuously across the entire area of ​​the first land portion (121), the second land portion (122), and the third land portion (123) to buffer the difference in thermal conductivity between the extrusion material and the land portion, thereby improving the flowability of the extrusion material (p') and minimizing diedrulls.

[0055] The experiment below tested whether die rolls occurred in extrusion dies under various conditions. Under the test conditions below, if there was a change in the inner diameter of the extrusion die, the change in inner diameter was limited to one time, and the extrusion die with added fluoropolymer coating was limited to a condition where the fluoropolymer coating was provided across the entire land area.

[0056] [test]

[0057] 1. Evaluation of die roll formation based on extrusion die design

[0058] The formation of die rolls during extrusion by an extrusion die designed as described in Table 1 below was evaluated.

[0059] [Table 1]

[0060]

[0061] As described in Table 1 above, Examples 1, 2, and Comparative Examples 2 to 5 are examples equipped with a second land portion formed by creating a step in the land portion, Examples 1 and 2 have a fluoropolymer coating applied to the entire inner surface of the land portion, Comparative Examples 1 to 7 have a fluoropolymer coating omitted, and Comparative Examples 1 and 6 are examples in which the experiment was conducted with an extrusion die not equipped with a third land portion having an inclined surface, and the material and dimensional conditions of each example are as described in Table 1 above.

[0062] D: Inner diameter of the second land section

[0063] d : Inner diameter of the first land section

[0064] Lc: Length of the second land section

[0065] L: Total length of the land portion

[0066] θ : Angle of the third land section

[0067] Figures 6 to 14 are images of the extrusion products and a summary of the results under the extrusion conditions shown in Table 1 above.

[0068] Among each example or comparative example, Example 1 and Comparative Example 4 underwent both short-term extrusion (5 minutes) and long-term extrusion (30 minutes) tests under the same conditions, while the remaining examples and comparative examples underwent only short-term extrusion (5 minutes) tests.

[0069] As illustrated and described in FIGS. 6 and 7, when extruding with the extrusion die of Examples 1 and 2 corresponding to the design according to the present invention, no die rolls were formed during both short-term extrusion (5 minutes) and long-term extrusion (30 minutes), and both the extrusion appearance quality and appearance transparency were excellent.

[0070] As shown in the results illustrated and described in FIGS. 8 to 14, when extruding with a comparative example extrusion die in which fluoropolymer (Teflon) is not coated on the inner surface of the extrusion mold land portion, it was confirmed that the occurrence of die rolls is reduced at an appropriate land ratio and angle when the length of each section of the land portion is adjusted.

[0071] In particular, in the case of Example 2, Comparative Example 6, and Comparative Example 7, where the extrusion material is polyethylene (PE) which can be used as an insulating layer material, it was confirmed that when the land portion of the extrusion die, etc., is coated with fluoropolymer, the transparency of the insulating layer surface appears differently depending on whether die rolls occur or whether there are lines or scratches on the surface of the insulating layer.

[0072] That is, in the case of Example 2, in which the land portion of the extrusion die was coated with fluoropolymer resin, the external transparency was excellent and no surface scratches caused by diedrulls occurred, but in the case of Comparative Examples 6 and 7, in which fluoropolymer resin coating was not performed, diedrulls were observed visually, or even if diedrulls were not observed visually, the external transparency was low and it was confirmed that many surface scratches caused by fine diedrulls occurred.

[0073] In addition, in the case of Example 1 and Comparative Examples 1 to 5, where the extrusion material is a polymer compound with polyvinyl chloride (PVC) as the base resin that can be used as the sheath layer material, it was easy to visually distinguish whether a die roll occurred near the extrusion die, whether there was gloss on the surface of the sheath layer, or whether scratches occurred.

[0074] In other words, it was confirmed that the extrusion quality of Example 1 was excellent, as no diedrolls visible to the naked eye occurred and the surface of the extrusion layer was formed smoothly without scratches. That is, while the extrusion quality is influenced by changes in cross-sectional shape, such as changes in the inner diameter of the land portion, it was confirmed that the occurrence of diedrolls is largely determined by the fluoropolymer coating on the land portion.

[0075] In addition, in the case of Examples 1 and 2, fluoropolymer coating was applied to the entire inner surface of the land portion, but although not included in the test in Table 1, it was confirmed that when fluoropolymer coating was applied only to a part of the area rather than the entire inner surface of the land portion, diedrulls were generated or the amount increased. Therefore, it was confirmed that when applying fluoropolymer coating to the extrusion die to minimize diedrull generation, it is desirable to apply it to at least the entire inner surface of the land portion.

[0076] FIGS. 15 to 17 illustrate cross-sectional views of other embodiments of an extrusion die according to the present invention.

[0077] Specifically, the embodiment illustrated in FIG. 15 illustrates an example in which a fluoropolymer coating layer (f) is continuously applied together with the land portion (120) to a part of the outer surface of the outlet portion (130) in addition to the land portion (120) in the extrusion die illustrated in FIG. 5, the embodiment illustrated in FIG. 16 illustrates an example in which a fluoropolymer coating layer (f) is continuously applied together with the land portion to a part of the inner surface of the injection portion (110) in addition to the land portion (120) in the extrusion die illustrated in FIG. 5, and the embodiment illustrated in FIG. 17 illustrates an example in which a fluoropolymer coating is continuously applied together with the land portion to a part of the outer surface of the outlet portion (130) and a part of the inner surface of the injection portion (110) in addition to the land portion (120) in the extrusion die illustrated in FIG. 5.

[0078] As described above, since the fluoropolymer coating can improve slip properties by buffering the difference in thermal conductivity between the extrusion die (100) and the extrusion material, it was confirmed that the flowability of the extrusion material can be improved by adding a fluoropolymer coating layer (f) from the injection section (110) to the outer surface of the outlet section (130) or the land section (120), which is the boundary area of ​​the part exposed to the outside at room temperature and atmospheric pressure where the negative pressure change applied to the extrusion layer is judged to be the greatest in addition to the land section of the extrusion die, thereby further reducing the die roll generated in the extrusion layer after extrusion.

[0079] As such, even when a fluoropolymer coating is applied to the outlet or injection portion of an extrusion die, it has been experimentally confirmed that the die reduction effect is lowered when there is a discontinuous region between the fluoropolymer coating of the land portion and the fluoropolymer coating. Therefore, it is desirable that the fluoropolymer coating be continuously provided over the entire inner surface of the land portion and at least a part of the outer surface of the outlet portion and / or at least a part of the inner surface of the injection portion.

[0080] In conclusion, according to the extrusion die of the present invention, by changing the shape of the land portion of the extrusion die to buffer the negative pressure change experienced by the extrusion layer, and continuously coating the extrusion die land portion, and further extending to the outlet portion and / or injection portion with fluoropolymer resin, it was confirmed that an excellent effect can be achieved in improving the extrusion uniformity and appearance transparency of the insulating layer or sheath layer by effectively suppressing die formation at the extrusion die outlet.

[0081] Although this specification has been described with reference to preferred embodiments of the present invention, those skilled in the art may modify and change the present invention in various ways without departing from the spirit and scope of the present invention as described in the claims below. Therefore, if a modified embodiment basically includes the components of the claims of the present invention, it should be considered to be included within the technical scope of the present invention. Explanation of the symbols

[0082] 100 : Extrusion die 150 : Nipple p : Extrusion layer c : extruded material

Claims

Claim 1 An extrusion die for extruding a workpiece constituting a cable, comprising: an injection portion through which an extrusion material is injected through a space between the inner surface of the extrusion die and the outer surface of a nipple that supports the workpiece and passes the workpiece into the extrusion die; a land portion for applying the extrusion material injected into the extrusion die through the injection portion to the surface of the workpiece; and an outlet portion through which the workpiece coated with the extrusion material is discharged out of the extrusion die, wherein the inner surface of the land portion is coated with a fluoropolymer, and the land portion includes a first land portion connected to the injection portion and a second land portion disposed between the first land portion and the outlet portion, wherein the inner diameter of the second land portion is larger than the inner diameter of the first land portion and a step is formed between the second land portion and the first land portion. Claim 2 An extrusion die for manufacturing a cable according to claim 1, characterized in that at least a portion of the outer surface of the outlet portion connected to the land portion is coated with fluoropolymer resin continuously with the inner surface of the land portion. Claim 3 An extrusion die for manufacturing a cable according to claim 1, characterized in that at least a portion of the injection part connected to the land part is coated with fluoropolymer resin continuously with the inner surface of the land part. Claim 4 An extrusion die for manufacturing a cable according to claim 1, characterized in that at least a portion of the outer surface of the outlet portion connected to the land portion and the inner surface of the injection portion are coated with fluoropolymer resin continuously with the inner surface of the land portion. Claim 5 An extrusion die for manufacturing a cable, characterized in that, in any one of claims 1 to 4, the fluoropolymer comprises one or more selected from the group consisting of polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), fluoroethylenepropylene (FEP), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), ethylenetetrafluoroethylene (ETFE), and ethylenechlorotrifluoroethylene (ECTFE). Claim 6 An extrusion die for manufacturing cables according to claim 5, characterized in that the fluoropolymer comprises one or more types selected from the group consisting of polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), and fluoroethylenepropylene (FEP). Claim 7 An extrusion die for manufacturing a cable, characterized in that, in claim 1, the inner diameter (D) of the second land portion is 1.05 to 1.2 times the inner diameter (d) of the first land portion. Claim 8 An extrusion die for manufacturing a cable, characterized in that, in claim 7, the length (Lc) of the second land portion is 2 / 15 to 1 / 3 of the total length (L) of the land portion. Claim 9 An extrusion die for manufacturing a cable according to claim 8, characterized in that the land portion further comprises a third land portion having an inclined surface with an inner diameter that gradually increases along the extrusion direction between the first land portion and the second land portion. Claim 10 An extrusion die for manufacturing a cable, characterized in that, in claim 9, the angle of the inclined surface (θ) of the third land portion is 10 to 30°. Claim 11 An extrusion die for manufacturing a cable, characterized in that, in any one of claims 1 to 4, the fluoropolymer is coated with a thickness of 20 to 50 μm. Claim 12 An extrusion die for manufacturing cables, characterized in that, in any one of claims 1 to 4, the extrusion die is made of steel or heat-treated steel. Claim 13 An extrusion die for manufacturing cables, characterized in that, in any one of claims 1 to 4, the extrusion material comprises a polymer compound. Claim 14 delete Claim 15 An extrusion die for manufacturing a cable, characterized in that, in any one of claims 1 to 4, the extruded object is one of an insulating layer of a power cable, an outer semiconducting layer surrounding the outer side of the insulating layer, or a cable jacket of a power cable. Claim 16 An extrusion die for manufacturing a cable, characterized in that, in any one of claims 1 to 4, the land portion has at least two steps such that the inner diameter is sequentially expanded between the injection portion and the outlet portion. Claim 17 An extrusion die for manufacturing cables according to claim 16, characterized in that at least one of the steps is configured as an inclined surface having an inner diameter that expands in the direction of the exit section.

Images