Coextruded multilayer article comprising continuous and discontinuous layers

Abstract

The present disclosure describes co-extruded multilayer articles including continuous layers and discontinuous layers, as well as systems and techniques for making co-extruded multilayer articles. For example, the present disclosure describes a co-extruded multilayer article comprising a body having a plurality of layers, where a first layer of the plurality of layers is formed from a first material and is continuous along a longitudinal axis of the body, and a second layer of the plurality of layers is formed from a second material and is co-extruded discontinuously along the longitudinal axis.

Description

[0001] This application is a divisional application of the Chinese invention patent application whose applicant is 3M Innovations Co., Ltd., whose application date is March 5, 2020, whose invention name is "Co-extruded multilayer article including continuous layers and discontinuous layers", and whose application number is 202080018868.8. Technical Field

[0002] The present disclosure relates to coextruded multilayer articles, including coextruded multilayer articles for use with insulated power cables. Background Art

[0003] The multilayer article comprises two or more material layers. Each layer can be selected to have unique chemical properties, electrical properties, mechanical properties, physical properties, or a combination thereof. In some examples, the multilayer article can be formed by multi-step injection molding, post-extrusion processing (such as material addition or material removal), or assembly of multiple layers. Generally speaking, extrusion is considered to be the manufacture of continuous shapes or contours, and a molding or forming process is required to manufacture discontinuous and intermittent 3D products. Both are well-known processes, and what is contemplated herein is a continuous process that can introduce intermittent features. See, for example, Stanley Middleman's Fundamentals of Polymer Processing, McGraw-Hill (1977) (Basic Principles of Polymer Processing, McGraw-Hill Group, 1977) and Ferdinand Rodriguez's Principles of Polymer Systems, Hemisphere Publishing Corp. (1982) (Principles of Polymer Systems, Hemisphere Publishing Corp., 1982). Coextrusion technology is also known. US 5,533,985 and US 6,135,992 describe tubing of varying stiffness for medical products, wherein the tubing is manufactured using a resin conditioning system and a coextrusion head. Summary of the invention

[0004] The present disclosure describes coextruded multilayer articles comprising at least one continuous layer and one discontinuous layer, and systems and techniques for making coextruded multilayer articles. The continuous layer comprises a first material, such as an electrically insulating polymer material, which may also contain a filler or a modifier, and the discontinuous layer comprises a different second material, such as a conductive material, an insulating material, a semiconductive material, or a high dielectric constant ("high-K") material. The position, geometry, and size of the discontinuous layer can be configured to provide selected chemical, electrical, thermal, optical, or mechanical properties. Compared to multilayer articles formed using other methods, coextruded multilayer articles can reduce manufacturing costs, reduce manufacturing time, improve control over the position, geometry, and size of the discontinuous layer, improve control over the longitudinal profile and / or axial profile of the discontinuous layer, and / or improve the uniformity of multiple articles.

[0005] In some examples, the present disclosure describes a coextruded multilayer article comprising a body having a plurality of layers, wherein a first layer of the plurality of layers is formed from a first material and is continuous along a longitudinal axis of the body, and a second layer of the plurality of layers is formed from a second material and is coextruded discontinuously along the longitudinal axis.

[0006] In some examples, the present disclosure describes a co-extruded multi-layer tube comprising a first layer and a second layer, the first layer extending continuously along a longitudinal axis from a first end edge of the tube to a second end edge of the tube, wherein the first layer comprises a first material defining an inner surface concentric with the longitudinal axis, and the second layer extending discontinuously along a portion of the inner surface of the first layer from the first end edge to the second end edge, wherein the second layer comprises a second material.

[0007] Although the exemplary body structures described herein include tubes or elongated tubular structures, in alternative embodiments, the body may include films, sheets, rods, fibers, or profiles.

[0008] In some examples, the present disclosure describes a co-extrusion system comprising: an outer die body including a first distal surface defining a first orifice transverse to a longitudinal axis, wherein the first orifice is fluidically coupled to a first flow channel; and an inner die body including a second distal surface defining a second orifice, the second orifice being concentrically positioned within the first orifice and fluidically coupled to the second flow channel; an inner pin extending from a proximal end to a distal end along the longitudinal axis and concentrically positioned within the second orifice, the inner pin including a proximal lip extending transverse to the longitudinal axis from an inner diameter less than a diameter of the second orifice to an outer diameter greater than a diameter of the second orifice; and a die forming surface extending distally from the proximal lip to a terminal edge, wherein the inner pin is movable between a first position configured to fluidly disengage the second orifice from the first orifice and a second position configured to fluidly couple the second orifice to the first orifice.

[0009] In some examples, the present disclosure describes a coextrusion method, the coextrusion method comprising flowing a first material from a first flow channel of an outer die body to a first orifice, the outer die body comprising a distal surface, the distal surface defining a first orifice transverse to a longitudinal axis. The method comprises extruding a portion of the first material from the first orifice to form a continuous layer, the continuous layer extending along the longitudinal axis and defining an inner surface concentric with the longitudinal axis. The method comprises flowing a second material from the first flow channel to an inner die body, wherein the inner die body comprises a second distal surface defining a second orifice, the second orifice being concentrically positioned within the first orifice and fluidly coupled to a second flow channel, wherein the second flow channel is fluidly coupled to a second extruder; and an inner pin, the inner pin being concentrically positioned within the second orifice and extending along the longitudinal axis from a proximal end to a distal end, the inner pin having a proximal lip extending transverse to the longitudinal axis from an inner diameter less than the diameter of the second orifice to an outer diameter greater than the diameter of the second orifice; and a die molding surface extending distally from the proximal lip to a terminal edge. The method includes controlling an internal pin from a first position, in which the second orifice is fluidly disengaged from the first orifice, to a second position, in which the second orifice is fluidly coupled to the first orifice. The method includes extruding a portion of the second material extending along a portion of the inner surface of the continuous layer. The method includes controlling the internal pin from the second position to the first position to form a discontinuous layer extending from a first end edge to a second end edge.

[0010] The details of one or more examples of the disclosure are shown in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1is a conceptual and schematic diagram showing a cross-sectional view of an exemplary coextrusion system for coextruding a multi-layer article.

[0012] Figure 2 is a conceptual diagram showing a portion of a coextrusion system including a die head having movable internal pins.

[0013] Figure 3A-3C is a conceptual diagram showing a die head of an exemplary coextrusion system including internal pins capable of operating in a rotational configuration.

[0014] Figure 4A and Figure 4B is a conceptual diagram showing an exemplary die head with a rotationally actuated internal pin.

[0015] Figure 5 is a conceptual diagram showing an exemplary die head of a coextrusion system using a mandrel.

[0016] Figure 6 is a conceptual diagram illustrating an exemplary portion of an insulated power cable including a cable and a cable joint including a coextruded multi-layer joint body.

[0017] Figure 7 is a conceptual diagram illustrating an exemplary portion of an insulated power cable including a cable and a cable joint including a coextruded multi-layer joint body.

[0018] Figure 8 is a flow chart illustrating an exemplary technique for making a coextruded multilayer article.

[0019] Figure 9A-9C as well as Figure 10-11 is a photograph showing an exemplary cable connector body including coextruded multiple layers including continuous layers and discontinuous layers.

[0020] It should be understood that embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. The figures are not necessarily drawn to scale. Like numbers used in the figures refer to like components. However, it should be understood that the use of numbers to refer to components in a given figure is not intended to limit the components labeled with the same number in another figure. DETAILED DESCRIPTION

[0021] The present disclosure describes a coextruded multilayer article including at least one continuous layer and one discontinuous layer, and a system and technology for manufacturing a coextruded multilayer article. The discontinuous layer is embedded in the continuous layer, at least partially embedded in the continuous layer, or formed adjacent to the continuous layer. The coextruded multilayer article can be formed in various shapes, sizes and profiles, such as in a tubular or substantially planar (film) form. In some examples, the coextruded multilayer article can be used for a cable joint or joint body ("joint body") or a cable terminal ("terminal"), collectively referred to as "cable accessories", for insulated power cables. The insulated power cable may include a component configured to transmit power (e.g., between about 600 volts (V) and about 1 kV, between about 1 kV and about 69 kV, or greater than about 69 kV) from a power source (e.g., a power station) to a power consumer (e.g., a distribution station, a business or a home). However, some insulated power cables may be configured to transmit power within any selected voltage and / or selected frequency range. Cable accessories may include a continuous layer comprising an electrically insulating polymer material and a discontinuous layer defining an electrode comprising a conductive material, a semiconductive material, or a high dielectric constant ("high-K") material. Failures of cables and cable accessories may occur as arcs or discharges across the cable or cable accessory due to thermal runaway of the connector, dielectric breakdown in the cable accessory, dielectric breakdown in the cable insulation, or interface breakdown (also known as internal tracking). Events leading to failures may include design flaws or defects introduced during the manufacturing process (e.g., flaws or defects in the electrodes defined by the discontinuous layers of the cable joint) or errors performed during installation or maintenance of the cable or cable accessory. Improved uniformity in the manufacture of cable accessories, improved control of the discontinuous layers that form the multilayer article, or both, may reduce failure events.

[0022] In some examples, the continuous layer is configured to surround the joint of the two cables to support and / or protect the joint. The discontinuous layer includes a material configured to enhance the performance of the joint, such as a conductive material, a semi-conductive material, an insulating material, or a high-K material. The end edge of the discontinuous layer is transverse to the longitudinal axis of the cable joint. The end edge may be discrete, such as a smooth edge profile in the longitudinal direction (or longitudinal direction, as used in film manufacturing) and a substantially uniform thickness in the axial direction. The longitudinal profile and / or axial profile of the end edge may include a shaped profile, such as a tapered profile or a rounded profile. In operation, the longitudinal profile and / or axial profile may reduce the concentration of electrical stress, reduce partial discharge events, or both. For example, the end edge of the discontinuous layer may be substantially free of tailing, trailing, flashing, or other distortions, otherwise an unwanted electric field may be generated, which may lead to electrical stress concentration, which may lead to partial discharge events or other failures of the device. As used herein, a partial discharge event refers to a current discharge that only partially bridges the gap between the electrodes of the cable (for example, this may be caused by a gas discharge in the gap of the cable). Compared to multilayer articles formed using other methods, coextruded multilayer articles can reduce manufacturing costs, reduce manufacturing time, improve control over the location, geometry and size of discontinuous layers, improve control over the longitudinal profile and / or axial profile of discontinuous layers, and / or improve the uniformity of multiple articles.

[0023] Figure 1 1 is a conceptual and schematic diagram showing a cross-sectional view of an exemplary coextrusion system 100 for coextruding a multilayer article 150. The coextrusion system 100 includes a first extruder 102 fluidly coupled to a die 104 via a first flow channel 106 and a second extruder 108 fluidly coupled to the die 104 via a second flow channel 110. The first extruder 102 and the second extruder 108 are configured to flow respective first and second materials through respective first and second flow channels 106 and 110. For example, the first extruder 102 and the second extruder 108 may include screw conveyors, plungers, or other mechanical components to drive the respective first and second materials through the respective first and second flow channels 106 and 110. In some examples, any one or more of the first extruder 102, the die 104, the first flow channel 106, the second extruder 108, or the second flow channel 110 may include a temperature sensor, a pressure sensor, or both, wherein the temperature sensor is configured to monitor the temperature of the material within the corresponding component of the co-extrusion system 100, and the pressure sensor is configured to monitor the pressure of the material within the corresponding component of the co-extrusion system 100.

[0024] In some examples, the first extruder 102, the second extruder 108, or both include respective heating devices configured to heat the material within the respective extruders. Controlling the temperature of the material within the first extruder 102, the second extruder 108, or both can improve control over the extrusion rate.

[0025] In some examples, the first extruder 102, the second extruder 108, or both include a corresponding pressure control device, which is configured to adjust the pressure in the corresponding extruder and / or at the corresponding outlet of the corresponding extruder, such as the first orifice 120 and / or the second orifice 126 (discussed below). The pressure control device may be configured to reduce the deadheading at the corresponding outlet of the corresponding extruder. The pressure control device may include, but is not limited to, one or more of the following: a dump valve, a ball valve, a pressure-actuated valve, a diverter valve, a gear pump, an accumulator head, an injection screw, or a device configured to control the pressure of the extrudate and / or reduce the deadheading at the corresponding outlet of the corresponding extruder. In some examples, the pressure control device may be fluidly coupled to a holding tank or a recirculation line, which is configured to recirculate the material back into the corresponding extruder. In some examples, the pressure control device may include a control device configured to automatically operate the pressure control device. For example, the control device may automatically open and close the valve to maintain the desired pressure range in the extruder. By controlling the pressure of the respective extruders, the coextrusion system 100 can better control the flow of material from the first extruder 102, the second extruder 108, or both.

[0026] The first extruder 102 and the second extruder 108 are configured to extrude the first material and the second material from the die 104 by forcing the first material and the second material through the die 104 (and optionally heating the first material and / or the second material) to form a section of the coextruded multilayer tube 150 extending along the longitudinal axis 122. The coextruded multilayer tube 150 may include an elongated tube having a continuous layer 152 of the first material and a plurality of periodic discontinuous layers 154 of the second material.

[0027] Continuous layer 152 defines inner surface 153. Discontinuous layer 154 can be mechanically and / or chemically bonded to continuous layer 152 at interface 157. For example, interface 157 can include an area where a second material is adhered to a first material by mechanical bonding (e.g., by an adhesive or mechanical interlock formed by a selected shape of interface 157) and / or chemical bonding (e.g., electrostatic forces between the first material and the second material at interface 157).

[0028] In some examples, at least one of the first material or the second material comprises a polymer that is substantially uniaxially aligned. For example, by extruding the first material and the second material, the polymer of the coextruded multilayer tube 150 may be substantially aligned with the longitudinal axis. In contrast, an injection molded polymer part may not have a polymer that is substantially uniaxially aligned. In some examples, the coextruded multilayer tube 150 has no subtractive manufacturing tool marks. Subtractive manufacturing tool marks may include ridges, valleys, or other surface defects introduced by processing materials from the article. In some examples, the coextruded multilayer tube 150 has substantially no parting lines. For example, a parting line may be formed on the article during the molding process, where, for example, two halves of the mold intersect to define the shape of the article. In some examples, the coextruded multilayer tube 150 has substantially no gate marks. For example, a gate mark may be formed on the article during the molding process, where, for example, a polymer material is injected into a mold that defines the shape of the article. In these ways, the coextruded multilayer tube 150 can be distinguished from a molded article, such as an injection molded article. Furthermore, the substantially uniaxially aligned polymers without subtractive manufacturing tool marks, parting lines, and / or gate marks can have a reduced number of defects or imperfections that adversely affect the performance of the article, for example, the control of electric fields in cable connector body applications. Additionally, the substantially uniaxially aligned polymers can be subjected to processes that further modify the orientation, such as drawing, tentering, folding, or stretching.

[0029] Each periodic discontinuous layer 154 includes a first end edge 155A and a second end edge 155B (collectively referred to as "end edges 155"). End edges 155 may include a selected longitudinal profile and an axial profile (e.g., relative to longitudinal axis 122). For example, the longitudinal profile may include a taper extending in the longitudinal direction. The axial profile may include the thickness of the discontinuous layer.

[0030] The first material and the second material may include a curable polymer material. In some examples, the first material includes an electrically insulating polymer material. In some examples, the first material includes at least one of a thermoplastic compound, polyvinyl chloride, polyethylene, a thermosetting compound, a cross-linked polyethylene, ethylene propylene rubber, silicone rubber, ethylene propylene diene monomer (EPDM), or a combination thereof. In some examples, the second material includes at least one of a conductive material, a semiconductive material, an insulating material, or a high-K material. In some examples, the second material includes a conductive filler, such as carbon black, which is impregnated in a polymer material, such as a thermoplastic compound, polyvinyl chloride, polyethylene, a thermosetting compound, a cross-linked polyethylene, ethylene propylene rubber, silicone rubber, ethylene propylene diene monomer (EPDM), or a combination thereof. Therefore, the first material and the second material may have differences in optical properties, physical properties, thermal properties, and electrical properties.

[0031] The die 104 includes an outer die body 114 and an inner die body 116. The outer die body 114 includes a first distal surface 118 defining a first orifice 120 transverse to the longitudinal axis 122. The outer diameter of the first orifice 120 can be selected based on the selected outer diameter of the coextruded multilayer tube 150. In some examples, the outer diameter of the first orifice 120 can be in the range of about 3 millimeters (mm) to about 50 centimeters (cm), or about 6.35 millimeters (mm) to about 15.24 centimeters (cm), such as about 2.54 cm to about 5.08 cm. The first orifice 120 is fluidly coupled to the first flow channel 106. In this way, the first extruder 102 can extrude the first material out of the first orifice 120 of the die 104.

[0032] The inner die body 116 includes a second distal surface 124 defining a second orifice 126. The second orifice 126 is concentrically positioned within the first orifice 120. The second orifice 126 is fluidly coupled to the second flow channel 110. In this way, the second extruder 108 can extrude the second material out of the second orifice 126 of the die head 104. The inner die body 116 also includes elements, such as an internal pin 128. The internal pin 128 extends from the proximal end 130 to the distal end 132 along the longitudinal axis 122. The internal pin 128 is concentrically positioned within the second orifice 126. In this way, the first orifice 120, the second orifice 126, and the internal pin 128 define an annular region from which the coextruded multilayer tube 150 is extruded.

[0033] In some examples, the inner pin 128 includes a proximal lip 134 and a die forming surface 136. The proximal lip 134 extends transversely to the longitudinal axis 122 from an inner diameter that is less than the diameter of the second orifice 126 to an outer diameter that is greater than the diameter of the second orifice 126. In some examples, the proximal lip may extend from the inner diameter to the outer diameter at an angle (such as an angle in the range of about 90 degrees to about 15 degrees) relative to the longitudinal axis. The inner pin 128 is movable between a first position and a second position, the first position being configured to fluidly disengage the second orifice 126 from the first orifice 120, and the second position being configured to fluidly couple the second orifice 126 to the first orifice 120. For example, the inner pin 128 may be coupled to an actuator 129. In this way, the inner pin 128 is configured to control the flow of the second material so that the coextrusion system 100 can extrude a continuous layer of the first material and a periodic discontinuous layer of the second material.

[0034] The die forming surface 136 extends distally from the proximal lip 134 to the terminal edge at the distal end 132 of the inner pin 128. In some examples, the die forming surface 136 may be substantially parallel to the longitudinal axis 122. In other examples, the die forming surface 136 may be dispersed from the longitudinal axis 122 at a selected angle or converged toward the longitudinal axis. For example, the die forming surface 136 may extend along a plane that intersects the longitudinal axis distally (or proximally) at an angle in the range of about 1 degree to about 80 degrees (such as about 30 degrees to about 60 degrees). In some examples, the die forming surface 136 includes a certain length, which is selected so that the extruded first material, the second material, or both maintain a selected shape. The length of the die forming surface 136 may be in the range of about 1.5 millimeters (mm) to about 150 mm (or greater), or about 1.5 mm to about 25.4 mm, such as about 3 mm to about 12.7 mm. In some examples, increasing the die forming surface length may result in an increase in the tailing of the discontinuous layer. To reduce tailing, the die molding surface may include a low surface energy coating known in the art. In some examples, the die molding surface 136 may include a substantially straight section and a tapered section. For example, the die molding surface 136 may include a first section extending from the proximal lip 134 substantially parallel to the longitudinal axis 122 for a length of about 3 mm, and a second section extending toward the longitudinal axis at an angle between about 30 degrees and about 60 degrees. In some examples, the first plane defined by the distal end 132 may be about 6 mm to the left of the second plane defined by the first distal surface 118 of the outer die body 114. The diameter of the terminal edge of the die molding surface 136 may correspond to the inner diameter of the extruded tube. In some examples, the diameter of the terminal edge of the die molding surface 136 may be in the range of about 2 mm to about 200 mm, or about 2.54 mm to about 101.6 mm, such as about 9 mm to about 31 mm or about 12.7 mm to about 25.4 mm. In some examples, the dimensions of the inner pins 128 may be selected to reduce tailing of the discontinuous layer 154 , control the edge profile of the discontinuous layer 154 , and / or improve bonding of the discontinuous layer 154 to the continuous layer 152 .

[0035] In some examples, the coextrusion system 100 includes a computing device 112 coupled to the first extruder 102, the second extruder 108, and the die 104. The computing device 112 is configured to control the extrusion process. For example, the computing device 112 may include one or more processors 113, one or more memory storage devices 115, and a communication interface 117. The one or more storage devices 115 may include a non-transitory computer-readable storage medium, which includes instructions that, when executed, cause the one or more processors 113 to control the coextrusion system 100 to extrude the coextruded multilayer tube 150. The one or more processors 113 may be communicatively coupled to the first extruder 102, the second extruder 108, and the die 104 via the communication interface 117, and are configured to control, for example, the feed rate of the first material and the second material from the respective first extruder 102 and the second extruder 108, the operating temperature of the first extruder 102 and / or the second extruder 108, and the position of the internal pin 128. In some examples, the communication interface 117 may include a user interface configured to output visual, audio, or semantic information to an operator and / or receive one or more commands from an operator to control operation of any one or more of the first extruder 102 , the second extruder 108 , and the die 104 .

[0036] although Figure 1 100 , but in some examples, the coextrusion system 100 may include a post-extrusion heater, a post-extrusion cooling bath, a post-extrusion cutting, or a combination thereof. For example, after extruding the coextrusion multilayer tube 150, a tubular heater such as a radiant heater may heat the coextrusion multilayer tube 150. Heating the coextrusion multilayer tube 150 may help to form a strong bond between the continuous layer 152 and the discontinuous layer 154 during curing. In some examples, after extruding the coextrusion multilayer tube 150 or after heating the coextrusion multilayer tube 150, the coextrusion multilayer tube 150 may be immersed in a cooling bath. In some examples, after extrusion, heating or cooling of the coextrusion multilayer tube 150, the coextrusion multilayer tube 150 may be cut into a selected length. In some examples, after cutting the coextrusion multilayer tube 150, each block may be heated under pressure, for example, in an autoclave to cure the curable elastomer.

[0037] Figure 2 A conceptual diagram of a portion of a coextrusion system 200 is shown, which includes a die head 204 having a movable element (e.g., internal pin 228). The coextrusion system 200 can be used in conjunction with the die head 204 described above with reference to Figure 1 The coextrusion system 100 is the same or substantially similar to the coextrusion system 100 described above, except for the differences described herein. Figure 1 Similar parts are denoted by reference numerals in Figure 1100 is added to the corresponding reference numerals in FIG. 2. For example, the coextrusion system 200 is configured to extrude the first material and the second material from the die head 204 to form a coextruded multilayer tube 250 extending along the longitudinal axis 222. The coextruded multilayer tube 250 includes a first continuous layer 252, a periodic discontinuous layer 254, and a second continuous layer 256. In some examples, the coextruded multilayer tube 250 may include the above-referenced Figure 1 The die head 204 includes an outer die body 214 and an inner die body 216. The outer die body 214 defines a first distal surface 218 and a first orifice 220 that is transverse to the longitudinal axis 222 and fluidically connected to the first flow channel 206. Figure 2 As shown, the co-extrusion system 200 is configured to extrude the first material and the third material from the first orifice 220 to form a first continuous layer 252 and a second continuous layer 256 , respectively.

[0038] The inner mold body 216 defines a second distal surface 224 and a second orifice 226, the second orifice 226 being fluidly coupled to the second flow channel 210. The inner mold body 216 includes an element, such as an inner pin 228. The inner pin 228 extends along the longitudinal axis 222 from the proximal end 230 to the distal end 232. The inner pin 228 is configured to slide along the longitudinal axis 222 in a proximal-distal direction, as indicated by arrow 231. In the most proximal position (e.g., the first position), the proximal lip 234 is configured to seal the second orifice 226 from the first orifice 220 by engaging with at least a portion of the second distal surface 224 of the inner mold body 216. In the most distal position (e.g., the second position), as shown in FIG. Figure 2 As shown, the proximal lip 234 moves distally of the second distal surface 224 to open the second orifice 226 to the first orifice 220. In this way, the internal pin 228 is configured to control the flow of the second material from the die 204.

[0039] Although reference Figure 1 and Figure 2 Axial movement is shown, but in some examples, internal pins of the coextrusion system may control the flow of the second material from the die by other means, such as a rotary valve. Figure 3A-3C 3 is a conceptual diagram showing a die head 304 of an exemplary coextrusion system 300 including an internal pin 328 operable in a rotational configuration. The coextrusion system 300 may be used in conjunction with the die head 304 of the exemplary coextrusion system 300 described above with reference to FIG. Figure 1 and Figure 2 The coextrusion systems 100 and 200 are identical or substantially similar, except for the differences described herein. Figure 1 and Figure 2 Similar parts are denoted by reference numerals in Figure 1 Add 200 to the corresponding reference numerals in Figure 2100 is added to the corresponding reference numerals in FIG. 1. The die head 304 includes an outer die body 314 and an inner die body 316. The outer die body 314 defines a first distal surface 318 and a first orifice 320 transverse to the longitudinal axis 322 and fluidly coupled to a first flow channel (not shown). The inner die body 316 defines a second distal surface (not shown) and a second orifice 326. The inner die body 316 includes an inner pin 328.

[0040] The inner pin 328 includes a fixed member 340 and a rotating member 342. The fixed member 340 defines a third orifice 344 that is fluidly coupled to the second orifice 326. The rotating member 342 defines a fourth orifice 346 that is fluidly coupled to the second flow channel 310. The rotating member 342 is rotatable in a radial direction about the longitudinal axis, as indicated by arrow 331. The rotating member 342 is controllable between a first position in which the third orifice 344 is fluidly coupled to the fourth orifice 346, as indicated by arrow 331. Figure 3C As shown, the third orifice 344 is not fluidly coupled to the fourth orifice 346 in this second position.

[0041] Although in Figure 3A-3C 1 is shown as a collet die, but in some examples, the rotationally actuated internal pin may include other rotationally actuated internal pins. Figure 4A and Figure 4B is a conceptual diagram illustrating an exemplary die head 404 having a rotationally actuated internal pin 428 . Figure 4A The inner pin 428 is shown in an open configuration (eg, second position). Figure 4B The inner pin 428 is shown in a closed configuration (eg, first position).

[0042] In some examples, the coextrusion system may use a mandrel to facilitate the formation of the coextruded multi-layer article. Figure 5 5 is a conceptual diagram showing an exemplary die head 504 of a coextrusion system 500 using a mandrel 505. The coextrusion system 500 can be used with the coextrusion system 500 described above with reference to Figures 1 to 4B The coextrusion systems 100, 200, 300 and 400 are the same or substantially similar to Figures 1 to 4B Similar parts are denoted by reference numerals in Figures 1 to 4B522 and 530. The coextrusion system 500 is configured to extrude a first material and a second material from a die 504 to form a section of a coextruded multilayer tube 550 extending along a longitudinal axis 522. The coextruded multilayer tube 550 includes a continuous layer 552 and a periodic discontinuous layer 554. The die 504 includes an outer die body 514 and an inner die body 516. The outer die body 514 defines a first distal surface 518 and a first orifice 520 that is transverse to the longitudinal axis 522 and fluidly connected to the first flow channel 506.

[0043] The inner mold body 516 defines a second distal surface 524 and a second orifice 526. The inner mold body 516 includes an element, such as an inner pin 528. The inner pin 528 extends along the longitudinal axis 522 from the proximal end 530 to the distal end 532. The inner pin 528 is configured to slide along the longitudinal axis 522 in a proximal-distal direction, as indicated by arrow 531. In the most proximal position (e.g., the first position), the proximal lip 534 is configured to seal the second orifice 526 from the first orifice 520 by engaging with at least a portion of the second distal surface 524 of the inner mold body 516. In the most distal position (e.g., the second position), as shown in FIG. Figure 5 As shown, the proximal lip 534 moves distally of the second distal surface 524 to open the second orifice 526 to the first orifice 520. In this way, the internal pin 528 is configured to control the flow of the second material from the die 504.

[0044] The coextrusion system 500 includes a mandrel 505 extending through the internal pin 528 of the die 504. In operation, when the coextrusion system 500 extrudes the coextruded multilayer tube 550, the mandrel 505 travels in the direction indicated by the arrow 507 at the same rate as the coextruded multilayer tube 550 is extruded. The mandrel 505 can promote the solidification of the coextruded multilayer tube 550 by maintaining the shape of the inner surface of the coextruded multilayer tube 550. In some examples, the mandrel 505 may include a coating that is configured to facilitate the removal of the mandrel 505 from the coextruded multilayer tube 550 after the coextruded multilayer tube 550 has been solidified. In some examples, the mandrel 505 can promote the solidification of the coextruded multilayer tube 550 by controlling the cooling rate of the coextruded multilayer tube 550. For example, the mandrel 505 can increase the cooling rate of the inner surface of the coextruded multilayer tube 550 or reduce the cooling rate of the coextruded multilayer tube 550 by keeping the heat longer than the coextruded multilayer tube 550 without the mandrel 505.

[0045] Figure 66 is a conceptual diagram showing an exemplary portion of an insulated power cable 600, which includes cables 602A and 602B (collectively referred to as "cable 602") and a cable joint 604 ("joint 604") including a co-extruded multilayer joint body 619. Insulated power cable 600 can be configured to transmit power of any suitable selected voltage and / or frequency underground, underwater, or suspended overhead. For example, insulated power cable 600 can transmit a voltage of 11 kV, 33 kV, 66 kV, or 360 kV. In some examples, insulated power cable 600 is configured to transmit "medium voltage" within a voltage range between about 12 kV and about 45 kV, for example, insulated power cable 600 may include a medium voltage cable. In some examples, insulated power cable 600 that transmits power between a power source and a substation can transmit a voltage of 360 kV or greater, which can be considered a "transmission grade voltage". In some examples, the insulated power cable 600 transmits voltages between 33 kV and 360 kV, which may be considered "sub-transmission grade voltages", and may provide power from a power source to an end user or customer (e.g., a customer utilizing relatively large amounts of power). In some examples, the insulated power cable 600 that transmits power between a distribution substation and a distribution transformer may transmit voltages less than 33 kV, which may be considered "distribution grade voltages". In some examples, the insulated power cable 600 transmits power between a distribution substation or a distribution transformer (e.g., a pad transformer or a pole transformer) and an end user or consumer (e.g., a home and business), and may transmit voltages between 360 volts and 240 volts, at which voltages the insulated power cable 600 may be referred to as a "secondary distribution line".

[0046] Cable 602 includes a shielded cable having multiple concentric (e.g., cylindrical) layers. In some examples, cable 602 includes a center conductor 606, a conductor shield 608, an insulator 610, an insulator shield 612, a shield 614 (e.g., a "metal shield"), and a jacket 616. In some examples, cable 602 may include different layers, fewer layers, or additional layers.

[0047] The center conductor 606 may include a conductive material, such as copper or aluminum. In some examples, the center conductor 606 includes a single solid conductor or a plurality of stranded conductors. The diameter (e.g., cross-sectional area) of the center conductor 606 may be based on the current that the cable 602 is designed to transmit. For example, the diameter of the center conductor 606 may be selected to transmit a current of at least about 15 amperes (A), such as at least about 120A, such as at least about 1,000A.

[0048] The conductor shield 608 may include a semiconductive polymer, such as a carbon black loaded polymer. The semiconductive polymer may have a bulk resistivity in the range of about 5 Ω-cm to about 100 Ω-cm. In some examples, the conductor shield 608 is physically and electrically coupled to the center conductor 606. For example, the conductor shield 608 may be disposed between the center conductor 606 and the insulator 610. The conductor shield 608 may provide a continuous conductive surface around the outside of the center conductor 606, which may reduce partial discharge that may otherwise be formed by the center conductor 606.

[0049] Insulation 610 includes polyethylene, such as cross-linked polyethylene (which may be abbreviated as PEX, XPE, or XLPE) or ethylene propylene rubber (EPR). The diameter or thickness of insulation 610 may be based on the voltage that cable 602 is designed to transmit.

[0050] The insulating shield 612 may include a semiconductive polymer similar to the conductor shield 608. The insulating shield 612 is disposed between the insulating member 610 and the shield 614. The insulating shield 612 may be coupled to the insulating member 610. In some examples, the insulating shield 612 is electrically coupled to the shield 614.

[0051] The guard 614 may include a conductive material, such as a metal foil, film, or wire. In some examples, the guard 614 may be referred to as a "ground conductor."

[0052] Jacket 616 is the outer layer of cable 602, which contains a plastic or rubber polymer, such as polyvinyl chloride (PVC), polyethylene (PE), or ethylene propylene diene monomer (EPDM). In some examples, jacket 616 can include an outer jacket configured to support and protect other layers of cable 602.

[0053] In some examples, the cable 602 can include additional layers, such as swellable or water-blocking materials placed within the conductor strands (eg, strand fillers) or between various layers within the cable 602 .

[0054] The connector 604 is configured to electrically and physically couple the cable 602A to the cable 602B. In some examples, the insulated power cable 600 may include a terminal instead of the connector 604, which is configured to electrically and physically couple the cable (e.g., cable 602A) to an electrical device, such as a transformer, a switchgear, an electrical substation, a business, a home, or other structure. In some examples, the insulated power cable 600 may include other cable accessories.

[0055] like Figure 6As shown, the joint 604 may include a joint body 619 and a connector 620. The connector 620 includes a cylindrical body having an outer surface extending from a first end edge to a second end edge opposite to the first end edge. Each end of the cylindrical body may be configured to receive a corresponding cable in the cable 602. For example, the first end edge and the second end edge of the connector 620 may each include a hole configured to receive the center conductor 606 of the cable 602. The hole may extend the entire length of the connector 620, so that the connector 620 includes a single hole or hollow area that traverses from the first end edge of the connector 620 to the surface of the second end edge of the connector 620. The connector 620 includes a conductive material, such as steel, copper, or aluminum. The diameter or thickness of the connector 620 may be based on the current that the insulated power cable 600 is designed to transmit or conduct and / or the specifications of the cable 602 that the joint 604 is configured to connect. In some examples, the connector 620 may connect more than two cables 602. An installer connecting two cables together can insert the center conductor of a first cable (e.g., cable 602A) into a hole at a first end edge of connector 620 and insert the center conductor of a second cable (e.g., cable 602B) into a hole at a second end edge of connector 620 and crimp connector 620 to electrically connect cables 602.

[0056] The joint body 619 includes a coextruded multilayer article 650. The coextruded multilayer article 650 extends along the longitudinal axis 601 and includes a continuous layer 652 and a discontinuous layer 654. The continuous layer 652 extends along the entire length of the joint body 619, for example, from the first end edge 657A to the second end edge 657B. The length of the joint body 619 can be selected to enable the continuous layer 652 to overlap at least a portion of the insulating shield 612.

[0057] The discontinuous layer 654 extends from the first end edge 655A to the second end edge 655B. In some examples, the discontinuous layer 654 can be mechanically and / or chemically bonded to the inner surface 653 of the continuous layer 652. For example, during coextrusion of the coextruded multilayer article 650, the polymer material of the discontinuous layer 654 can be mechanically and / or chemically bonded to at least a portion of the polymer material of the continuous layer 652. Additionally, in some embodiments, the exposed surfaces of the layers 652 and 654 can be substantially planar or coplanar when extruded, for example, where the layer 654 is formed on, embedded in, or partially embedded in the layer 652. Additionally, in other embodiments, the leading and / or trailing edges of the discontinuous layer 654 can have a substantially circular, elliptical, or wavy shape or pattern when viewed as a cross-section of a shaped article (e.g., a tube or film).

[0058] The length of discontinuous layer 654 may be selected to overlap selected layers of cable 602. For example, Figure 6 As shown, the discontinuous layer 654 may overlap a portion of the conductor 620 and the conductor shield 608. The overlapping layer and the amount of overlap may be configured to provide selected mechanical and / or electrical properties to the joint 604. For example, as described above with reference to Figure 1 As discussed, the discontinuous layer 654 can include a conductive or semiconductive material that can improve the transfer of current from the first cable 602A to the second cable 602B when in contact with the connector 620, the center conductor 606, and / or the conductor shield 608.

[0059] The terminal edges 655A and 655B of the discontinuous layer are transverse to the longitudinal axis of the joint 604. In some examples, the terminal edges 655A and 655B include discrete, smooth edge profiles in the longitudinal direction. In some examples, the terminal edges 655A and 655B include a substantially uniform thickness in the axial direction. In some examples, the longitudinal profile and / or axial profile of the terminal edges 655A and 655B may include a shaped profile. For example, Figure 6 As shown, the end edges 655A and 655B include tapered and rounded profiles. In operation, the longitudinal profile and / or the axial profile can reduce the concentration of electrical stress, reduce partial discharge events, or both. For example, the end edges 655A and 655B can be substantially free of tailing, trailing, flashing, or other distortions that may otherwise produce unwanted electric fields, which can lead to electrical stress concentrations that can lead to partial discharge events or other failure modes. In this way, the coextruded multilayer article 650 can reduce partial discharge events or other failure modes and increase the service life of the joint 604.

[0060] In some examples, the discontinuous layer 654 can include a high-K material that is configured to at least partially electrically insulate other layers of the header 604 (e.g., the continuous layer 652) from the connector 620, the center conductor 606, and / or the conductor shield 608. As such, the discontinuous layer 654 can be configured to electrically couple respective layers of the cable 602 to each other or to portions of the header 604, to electrically insulate respective layers of the cable 602 from each other or to portions of the header 604, or both.

[0061] In some examples, the connector 604 may include additional layers external to the continuous layer 652, such as a grounding conductor configured to electrically couple to a shield 614 of the cable 602 and / or a protective jacket configured to overlap the jacket 616 of the cable 602 to support and protect the connector body 619 from mechanical or environmental degradation.

[0062] Although shown as including one continuous layer and one discontinuous layer, joint 604 may include multiple continuous layers and multiple discontinuous layers. Multiple discontinuous layers may be adjacent or separated by one or more continuous layers. Multiple continuous layers may be adjacent or at least partially separated by one or more discontinuous layers. Each layer may be configured to provide selected mechanical properties and / or electrical properties.

[0063] Figure 7 700, which includes cables 702A and 702B (collectively referred to as "cables 702") and a cable joint 704 ("joint 704") including a coextruded multilayer joint body 719. The insulated power cable 700 may be similar to the insulated power cable 700 described above with reference to Figure 6 The insulated power cables 600 discussed are the same or substantially similar except for the differences described herein. For example, the cable 702 may include a center conductor 706 , a conductor shield 708 , an insulator 710 , an insulator shield 712 , a guard 714 , and a jacket 716 .

[0064] The co-extruded multilayer joint body 719 includes a plurality of discontinuous layers and a plurality of continuous layers. The plurality of discontinuous layers include a first discontinuous layer 722 and a second discontinuous layer 724, and the plurality of continuous layers include a first continuous layer 726 and a second continuous layer 728. The joint 704 or at least two or more layers of the joint 704 can be formed by co-extrusion. The two or more layers of the joint 704 formed by co-extrusion can reduce defects, such as misalignment of the layers or gaps in or between the layers, and / or improve the control of the longitudinal profile and / or axial profile of the layers. For example, the end edge of the discontinuous layer may be substantially free of tailing, trailing, flash or other distortions. Reducing defects and improving the control of the end edge profile of the layer can improve the function of the joint 704 by, for example, reducing electrical stress concentration, reducing local discharge events or both.

[0065] The first discontinuous layer 722 may include a semiconductive material, such as a carbon filled polymer. The second discontinuous layer 724 may include a conductive layer.

[0066] First continuous layer 726 may include a high-K material, an insulating material, or a relatively high resistance material that is not a perfect insulator. In some examples, first continuous layer 726 is configured to electrically isolate first discontinuous layer 722 and / or second discontinuous layer 724 from one or more other layers of joint 704 .

[0067] The second continuous layer 728 may include an insulating material, such as an elastomeric rubber (e.g., ethylene propylene diene monomer (EPDM)). By including the second discontinuous layer 724, the joint body 719 can better control the electric field compared to a joint body without the second discontinuous layer 724. For example, when current flows through the insulated power cable 700, the second discontinuous layer 724 can cause the electric field to develop more parallel to the longitudinal axis 701, which can produce an electric field substantially perpendicular to the longitudinal axis 701, compared to an insulated power cable without the second discontinuous layer.

[0068] In some examples, the connector 704 may include a ground conductor 730 that is configured to electrically couple the shield 714 of the cable 702. The ground conductor 730 may include a conductive material, such as a wire mesh, copper, or aluminum. In some examples, the connector body 719 may include a third continuous layer (not shown) between the connector 720 and the first discontinuous layer 722, so that the first discontinuous layer 722 may be electrically floating relative to the connector 720 or the ground conductor 730. In other words, in some examples, the first discontinuous layer 722 may be electrically isolated from the connector 720 and the ground conductor 730 and have a different potential than the connector 720 and the ground conductor 730. For example, when the connector 720 conducts AC current, the oscillating AC voltage in the connector 720 may generate a magnetic field, which in turn may induce AC current and voltage in the first discontinuous layer 722.

[0069] In some examples, the connector 704 can include a jacket 732 that is configured to overlap the jacket 716 of the cable 702 to support and protect the connector body 719 from mechanical or environmental degradation. For example, the jacket 732 can include one or more thermosets, thermoplastics, particulate-loaded nylon, acrylonitrile butadiene styrene, polyethylene, polypropylene, ethylene propylene diene monomer rubber, ethylene propylene rubber, polyvinyl chloride, or other materials configured to support, contain, and protect the connector 704 and / or the cable 702. In some examples, the jacket 732 can include an inner surface, such as an elastomer, that is configured to create a friction fit, such as an interference fit, between the jacket 732 and one or more layers of the cable 702. By supporting the cable 702, the jacket 730 can reduce wear caused by relative movement of the cable 702, such as wear on the connector 720.

[0070] The cable accessories described above may be manufactured using any suitable technique. Figure 8 is a flow chart illustrating an exemplary technique for manufacturing a coextruded multilayer article. Although the coextruded multilayer tube 150 is described with reference to the coextruded system 100 and the coextruded multilayer tube 150, Figure 8 The technique is shown, but the technique may be used with other systems and / or for making other coextruded multilayer articles, such as connector 704.

[0071] In some examples, although Figure 8 702, the connector 704, or both. Determining the circumference and / or diameter of the cable 702, the connector 704, or both can enable the selection of the diameter of the extrusion die 104 used to extrude the coextruded multilayer tube 150.

[0072] Figure 8 The illustrated technique includes flowing a first material from a first flow channel 106 of an outer mold body 114 to a first orifice 120 , the outer mold body including a first distal surface 118 defining the first orifice 120 transverse to a longitudinal axis 122 ( 802 ). Figure 8 The illustrated technique also includes extruding a portion of the first material from the first orifice 120 to form a continuous layer 152 that extends along the longitudinal axis 122 and defines an inner surface 153 (804) that is concentric with the longitudinal axis 122. In some examples, extruding the first material may include controlling the temperature of the first material or the pressure of the first material. For example, the temperature and / or pressure of the first material may be measured within the first extruder 102, the first flow channel 106, or the die 104. Measuring the temperature, volume rate (e.g., screw rpm), and / or pressure of the first material may enable control of the extrusion speed of the first material. For example, the extrusion speed may be proportional to the temperature of the first material, for example, via the viscosity of the first material, and / or proportional to the pressure of the first material. In some examples, extruding the first material may include measuring the extrusion rate of the first material by, for example, an optical or infrared camera. Thus, the technique may include controlling the extrusion speed of the first material by controlling the temperature of the first material, the pressure of the first material, or both.

[0073] Figure 8 The illustrated technique includes flowing the second material from the second flow channel 110 to the inner mold body (806). Figure 1 As discussed, the second distal surface 124 defines a second orifice 126 that is concentrically positioned within the first orifice 120 and fluidly coupled to the second flow channel 110. The second flow channel 110 is fluidly coupled to the second extruder 108. An internal pin 128 is concentrically positioned within the second orifice 126 and extends along the longitudinal axis 122 from a proximal end 130 to a distal end 132, the internal pin having a proximal lip 134 that extends transversely to the longitudinal axis 122 from an inner diameter that is less than the diameter of the second orifice 126 to an outer diameter that is greater than the diameter of the second orifice 126, and a die forming face 136 that extends distally from the proximal lip 134 to a terminal edge. As discussed above with reference to extruding a first material, the technique may include measuring and / or controlling the temperature and / or pressure of the second material to control the extrusion rate of the second material.

[0074] Figure 8The technique shown includes controlling the internal pin 128 from a first position to a second position (808). In the first position, the second orifice 126 is fluidly disengaged from the first orifice 120. In the first position, the second material may not be extruded from the die 104. In the second position, the second orifice 126 is fluidly connected to the first orifice 120. In the second position, the second material may be allowed to extrude from the die 104. In some examples, the technique includes controlling the movement speed of the internal pin 128 from the first position to the second position. By controlling the movement speed of the internal pin 128, the co-extruder system 100 can be configured to control the terminal edge profile of the discontinuous layer 154. For example, the movement speed of the internal pin 128 can be controlled relative to the extrusion rate of the first material (e.g., the continuous layer 152) to produce a selected edge profile, such as a straight line or a rounded tapered or discrete edge. In some examples, both the movement speed of the internal pin 128 and the extrusion rate of the first material can be controlled to produce a selected terminal edge profile. For example, when the inner pin 128 moves from the first position to the second position, the extrusion rate of the first material may be decreased or increased.

[0075] Figure 8 The illustrated technique includes extruding a portion of a second material extending along a portion of an inner surface 153 of a continuous layer 152 (810). In some examples, the technique may include measuring and / or controlling a temperature of the second material and / or a pressure of the second material to control an extrusion rate of the second material, similar to the control of an extrusion rate of the first material as discussed above. Controlling the extrusion rate of the second material relative to the extrusion rate of the first material may enable control of an axial profile of the discontinuous layer 154. For example, substantially similar extrusion rates of the first and second materials may result in a substantially uniform thickness (in an axial direction) of the discontinuous layer. In some examples, different extrusion rates of the first and second materials may result in a non-uniform thickness of the discontinuous layer. For example, the extrusion rate of the first material and the extrusion rate of the second material may be controlled to produce a convex or concave cross-sectional profile (e.g., relative to the longitudinal axis 122) of the discontinuous layer. By controlling the axial profile of the discontinuous layer 154, the co-extrusion system 100 may be configured to produce a cable joint (e.g., joint 704) having a selected electrical stress concentration or distribution.

[0076] Figure 8 The illustrated technique includes controlling the inner pin 128 from the second position to the first position to form a discontinuous layer 154 from the first end edge 155A to the second end edge 155B (812). Similar to the above discussion, controlling the inner pin 128 from the second position to the first position may include controlling the movement speed of the inner pin 128, the extrusion rate of the first material, and / or the extrusion rate of the second material, each independently or relative to one or more of each other to control the profile of the second end edge 155B of the discontinuous layer 154.

[0077] In some examples, the technology may include post-extrusion processing. For example, the technology may include heating the coextruded multilayer tube 150 by a tubular heater (such as a radiant heater). Heating the coextruded multilayer tube 150 may help to form a strong bond between the continuous layer 152 and the discontinuous layer 154 when solidifying. In some examples, after extruding the coextruded multilayer tube 150 or after heating the coextruded multilayer tube 150, the technology may include cooling the coextruded multilayer tube 150 by immersing it in a cooling bath. In some examples, after extrusion, heating or cooling of the coextruded multilayer tube 150, the technology may include cutting the coextruded multilayer tube 150 into a selected length. In some examples, after cutting the coextruded multilayer tube 150, the technology may include heating each block under pressure to solidify the curable polymer by, for example, an autoclave, a salt bath or other conventional curing techniques. In some examples, after cutting the coextruded multilayer tube 150 or heating each block, the technology may include material removal (e.g., grinding or cutting part of the material) or material addition (e.g., application of coating, injection molding, etc.).

[0078] Figure 9A-9C as well as Figure 10-11 1 is a photograph showing an exemplary cable connector body comprising a coextruded multilayer, the coextruded multilayer comprising a continuous layer and a discontinuous layer. In these photographs, the extruded tube is cut open to better show the inner surface structure and composition.

[0079] like Fig. 9A As shown, the cable connector body 900 is cut longitudinally and folded open to expose the continuous layer 952 and the discontinuous layer 954. As discussed above, the discontinuous layer 954 may include a conductive material, such as a polymer impregnated with carbon black. The end edges 955A and 955B of the discontinuous layers are substantially smooth and free of defects that may cause electrical stress concentration and / or partial discharge events during use. Fig. 9B As shown, a coextruded sample 960 is prepared in a manner similar to that described herein, the coextruded sample having a planar (transparent) continuous layer 962 and a discontinuous (dark) layer 964 formed thereon, wherein the exposed surface of layer 964 is substantially planar with the exposed surface of layer 962. In other aspects, the exposed surfaces can be coplanar with each other, wherein, for example, layer 964 can be partially or completely embedded in continuous layer 962. In other aspects, as Fig. 9C As shown, a coextruded sample 980 having a tube structure was prepared in a manner similar to that described herein, the coextruded sample having a transparent continuous outer layer 982 and a discontinuous dark inner layer 984 formed on the inner surface of the continuous layer.

[0080] As shown in these examples, and in the products and techniques described herein, according to another aspect of the present invention, the transition region of the coextruded product can be very sharp. For example, for a tubular product having an inner diameter of at least 2.5 cm or at least 5 cm, the length of the transition region where the inner surface layer changes from the first layer (e.g., continuous layer 962) to the second layer (e.g., layer 964) can be about 1 cm or less, preferably about 0.7 cm or less, so that the length to diameter (L / D) ratio can be about 0.3 or less, preferably about 0.25 or less.

[0081] like Fig.10 As shown, the cable connector body 1000 is cut longitudinally and folded open to expose the continuous layer 1052 and the discontinuous layer 1054. The first end edge 1055A is substantially smooth and free of defects that may cause electrical stress concentration and / or partial discharge events when in use. However, the second end edge 1055B includes a tail that may cause electrical stress concentration and / or partial discharge events when in use. To reduce the tail, as discussed above, the extrusion rate of the first material, the extrusion rate of the second material, the movement rate of the internal pin, or a combination thereof may be controlled. For example, Fig.11 The cable connector body 1100 is shown cut longitudinally and folded open to expose the continuous layer 1152 and the discontinuous layer 1154. After adjusting the extrusion rate of the first material, the extrusion rate of the second material, the movement rate of the internal pin, or a combination thereof to reduce the tailing of both the first end edge 1155A and the second end edge 1155B, the first end edge and the second end edge are substantially smooth and free of defects that can cause electrical stress concentration and / or partial discharge events when in use.

[0082] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A coextruded multilayer article comprising a body having a plurality of layers, wherein a first layer of the plurality of layers is formed of a first material and is continuous along a longitudinal axis of the body, wherein a second layer of the plurality of layers is formed of a second material and is discontinuously coextruded along the longitudinal axis with the first layer from the same annular region, and The body defines an elongated tube extending along the longitudinal axis, the first layer defines an inner surface concentric with the longitudinal axis, and the second layer is discontinuously disposed on the inner surface of the first layer concentric with the longitudinal axis and at least partially embedded in the first layer.

2. The coextruded multilayer article of claim 1, wherein the first material is different from the second material.

3. The coextruded multilayer article of claim 1, wherein at least one of the first material and the second material comprises a uniaxially aligned polymer.

4. The coextruded multilayer article of any one of claims 1 to 3, wherein the body is free of subtractive manufacturing tool markings.

5. The coextruded multilayer article according to any one of claims 1 to 3, wherein the body has no parting line.

6. The coextruded multilayer article according to any one of claims 1 to 3, wherein the body is free of gate marks.

7. The coextruded multilayer article according to any one of claims 1 to 3, wherein the coextruded multilayer article comprises a plurality of bodies, wherein the second layer is periodically discontinuous.

8. The coextruded multilayer article according to any one of claims 1 to 3, wherein the body is cut into predetermined lengths.

9. The coextruded multilayer article according to any one of claims 1 to 3, wherein the second layer is discontinuously disposed between the first layer and a third layer comprising a third material.

10. The coextruded multilayer article of claim 9, wherein the third material comprises a conductive material, a semiconductive material, or a high dielectric constant material.

11. The coextruded multilayer article of claim 9, further comprising a fourth layer comprising a fourth material, wherein the first layer is continuously disposed between the second layer and the fourth layer.

12. The coextruded multilayer article of claim 11, wherein the fourth layer comprises a continuous outer layer.

13. The coextruded multilayer article of any one of claims 1 to 3, wherein the second material comprises a conductive material, a semiconductive material, or a high dielectric constant material.

14. A coextruded multilayer article comprising: a first layer extending continuously along a longitudinal axis from a first terminal edge of the coextruded multilayer article to a second terminal edge of the coextruded multilayer article, wherein the first layer comprises a first material defining an inner surface concentric with the longitudinal axis; and a second layer extending along a portion of the inner surface of the first layer from a first terminal edge of the second layer to a second terminal edge of the second layer, wherein the second layer comprises a second material and is discontinuously coextruded with the first layer from the same annular region along the longitudinal axis, and the second layer is discontinuously disposed on the inner surface of the first layer concentric with the longitudinal axis and at least partially embedded in the first layer, Wherein the coextruded multilayer tube comprises a cable accessory, and wherein the second layer comprises an electrode centrally disposed in the cable accessory.

15. The coextruded multilayer article of claim 14, wherein at least one of the first material and the second material comprises a uniaxially aligned polymer.

16. The coextruded multilayer article of claim 14 or 15, wherein the coextruded multilayer article is free of subtractive manufacturing tool markings.

17. The coextruded multilayer article according to claim 14 or 15, wherein the coextruded multilayer article has no parting line.

18. The coextruded multilayer article according to claim 14 or 15, wherein the coextruded multilayer article is free of gate marks.

19. The coextruded multilayer article according to claim 14 or 15, wherein the coextruded multilayer article comprises a plurality of bodies, wherein the second layer is periodically discontinuous.

20. The coextruded multilayer article of claim 14 or 15, wherein the first material comprises an electrically insulating polymeric material.

21. The coextruded multilayer article of claim 14 or 15, wherein the second material comprises a conductive polymer material.

22. The coextruded multilayer article of claim 14 or 15, wherein the first terminal edge and the second terminal edge of the second layer are transverse to the longitudinal axis.

23. The coextruded multilayer article of claim 14 or 15, wherein the first terminal edge and the second terminal edge of the second layer are uniform in at least one of a longitudinal direction or an axial direction.

24. The coextruded multilayer article of claim 14 or 15, wherein the first layer is configured to engage a medium voltage cable.

25. The coextruded multilayer article according to claim 14 or 15, wherein the length of the coextruded multilayer tube is in the range of 5 cm to 200 cm.

26. The coextruded multilayer article according to claim 14 or 15, wherein the inner diameter of the coextruded multilayer tube is in the range of 0.2 cm to 15 cm, and wherein the outer diameter of the coextruded multilayer tube is in the range of 0.5 cm to 25 cm.

27. A coextruded multilayer article comprising a body having a plurality of layers, wherein a first layer of the plurality of layers is formed of a first material and is continuous along a longitudinal axis of the body, wherein a second layer of the plurality of layers is formed of a second material and is discontinuously coextruded along the longitudinal axis with the first layer from the same annular region, wherein the body is free of any manufacturing markings defining an edge of the second layer, and wherein the body defines an elongated tube extending along the longitudinal axis, the first layer defines an inner surface concentric with the longitudinal axis, and the second layer is discontinuously disposed on the inner surface of the first layer concentric with the longitudinal axis and at least partially embedded in the first layer.

28. A coextruded multilayer article comprising a body having a plurality of layers, wherein a first layer of the plurality of layers is formed of a first material and is continuous along a longitudinal axis of the body, wherein a second layer of the plurality of layers is formed of a second material and is periodically discontinuously coextruded with the first layer from the same annular region along the longitudinal axis, and wherein, The body defines an elongated tube extending along the longitudinal axis, the first layer defines an inner surface concentric with the longitudinal axis, and the second layer is discontinuously disposed on the inner surface of the first layer concentric with the longitudinal axis and at least partially embedded in the first layer.

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