High temperature, low scorch methods of making crosslinkable compound compositions

Abstract

This invention provides a method for manufacturing a crosslinkable compound composition under high temperature, low coking as defined herein, including coking-free conditions. The method includes melting and mixing a main stream at a temperature of 120.0°C to 150.0°C, wherein the main stream comprises one or more thermoplastic polyolefins and one or more antioxidants, but lacks a curing agent additive selected from the group consisting of peroxides and crosslinking aids; and injecting a combination of the curing agent additive comprising one or more organic peroxides and one or more crosslinking aids into a composite melt, and uniformly mixing them by melting and mixing one or more thermoplastic polyolefins, one or more antioxidants, one or more organic peroxides, and one or more crosslinking aids together. A method for manufacturing a crosslinkable compound composition and an article thereof is also provided.

Description

Technical Field

[0001] This technical field relates to methods for manufacturing crosslinkable compound compositions comprising thermoplastic polyolefins and additives, and to compositions manufactured thereby. Prior Technology

[0002] Thermoplastic polyolefins (TPOs), such as thermoplastic polyethylene (TPE), are polymeric hydrocarbons that melt and flow at "high temperatures," which here broadly refers to temperatures between 110°C and 190°C, depending on the specific TPO. Crosslinkable compound compositions include TPOs and additives such as antioxidants, fillers, colorants, and curing agents. Curing agents are compounds that initiate free radical crosslinking or increase the concentration of crosslinks thus created (sometimes referred to as crosslinking density). The characteristic of "crosslinkability" can be determined by compressing a sample of the crosslinkable compound composition into a substrate and measuring the maximum torque (MH). We define a "crosslinkable" compound composition as one having a maximum torque (MH) of at least 2.09 dN-m (1.85 lbf-in), preferably at least 2.26 dN-m (2.0 lbf-in), at 182°C, as determined by dynamic modulus rheology (MDR) testing according to ASTM procedure D5289.

[0003] Coking refers to the premature crosslinking of TPO during the initial melt treatment of TPO and additives to manufacture crosslinkable compound components. The sensitivity of a component to coking can be detected and measured by compressing a sample of the crosslinkable compound component into a substrate and measuring the time until coking occurs. We define "low coking" as a coking time (ts1) of at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, at 140°C, expressed as the time required to increase the minimum torque ("ML") by 1 unit (inch-pound) or 1.13 deciNewtons-meters (dN-m), as determined by dynamic modulus rheology (MDR) testing according to ASTM procedure D5289. We define "no coking" as a coking time (ts1) of greater than 150 minutes at 140°C, wherein the coking time (ts1) at 140°C is measured as described herein.

[0004] Coking is an industry-wide problem. It ultimately results in defects in finished articles. These defects can include cracks, gelling, or voids, and can cause mechanical failures in the finished articles. For example, when the crosslinkable compound composition used to manufacture the insulation layer of the conductive core in power cables (such as medium voltage (MV), high voltage (HV), or ultra-high voltage (EHV) power cables) is coked during the initial melting process, the insulation layer may end up with tiny cracks, voids, or gelling. This can lead to premature failure of the power cable.

[0005] Therefore, to prevent or minimize defects caused by coking during the initial melt treatment of TPO and additives, the method for manufacturing crosslinkable compound composition used in this technology includes (a) melt mixing of TPO melt with additives such as antioxidants, fillers and colorants, but not curing agent additives, to produce an intermediate melt without curing agent additives; (b) granulating the intermediate melt; (c) soaking the granules with curing agent additives (e.g., organic peroxides and crosslinking aids) at a temperature of 50°C to 90°C (i.e., below the melting temperature of TPO and below the decomposition temperature of organic peroxides) for 1 to 24 hours to obtain a crosslinkable compound composition in granular form; (d) melting the crosslinkable compound composition; (e) extruding the melt and shaping it into an article; and (f) curing the extruded and shaped article.

[0006] Known methods for manufacturing cable insulation include melt-blending polyolefin base resins to incorporate additives such as antioxidants to create a composite material, filtering the composite material, and subsequently granulating it to produce intermediate particulate compounds without free radical initiators (also known as crosslinking initiators). This is followed by impregnation or soaking of the free radical initiator and intermediate compound particles in an "immersion" tower to incorporate the free radical initiator and manufacture the cable insulation manufacturing compound. These methods require at least a mixer and an immersion tower; and the cable insulation manufacturing compound comprises a crosslinkable compound (also known as a thermoplastic, crosslinkable compound) in particulate form, which is crosslinked by downstream cable manufacturers during the manufacture of the cable itself. Therefore, bringing the intermediate fine particles or particles to a suitable temperature (e.g., around 70°C) and subsequently incorporating the free radical initiator includes immersion to physically mix them with the intermediate particles; the resulting fully formulated fine particles or particles are then immersed at a suitable temperature at which the free radical initiator will diffuse into the fine particles or particles over several hours until the particle surface is dry. Additional immersion may be required in the packaging box to achieve a uniform distribution of the free radical initiator within the particles. Soaking towers involve very bulky and expensive equipment, thereby limiting the feasibility of developing multiple composite sites or plants for manufacturing cable insulation compounds. Therefore, all materials in composite cable insulation compounds, such as those used to manufacture their crosslinkable granules, are still required without the use of or elimination of soaking towers. Fully formulated composite granules need to be cooled before transport; therefore, heating chambers (optional) and cooling devices (essential), such as fluidized beds or cooling tanks, are necessary for the previous methods.

[0007] Conventional polyolefin composite production lines used in the manufacture of cable insulation compounds cannot incorporate free radical initiators into the base resin. Instead, free radical initiators are incorporated by, for example, soaking the base resin in a soaking tower facility for extended periods, resulting in a costly process. Furthermore, the large volume of material in the facility poses a high risk of external contamination and requires numerous cleanrooms and personnel to handle the material. Not to mention the additional energy consumption during the processing, which results in a significant carbon footprint.

[0008] Furthermore, injecting radical initiators into the polymer melt in conventional compounding processes remains highly challenging because the radical initiators decompose and react under the conditions and time required for compounding the base resin and antioxidant (AO) additives. In manufacturing suitable cable insulation compounds, melting and mixing the polyolefin base resin and antioxidant (AO) additives to adequately distribute the AO additives, and more importantly, achieving acceptable high production rates, typically results in excessive melting temperatures of intermediate compounds, such as at or above 180°C. At these temperatures, the radical initiator decomposes, thereby producing undesirable chemical crosslinking reactions and unusable products.

[0009] A recent U.S. Patent Publication No. 2020 / 0199270A1 by Zhang et al. discloses a composition comprising a polyolefin polymer, an alkenyl-functionalized monocyclic organosilicon, and an organic peroxide. These compositions are used as coatings for conductors and cables, serving as insulators. While Zhang et al. generally refer to all materials in the mixed composition, the only method disclosed for incorporating the peroxide into the composition includes immersion. Summary of the Invention

[0010] According to embodiments of the present invention, the inventors have solved the problem of providing stable crosslinkable compound compositions for use as manufacturing compounds for cable insulations without requiring a soaking step to incorporate a crosslinking initiator into the composition. Embodiments of the present invention relate to manufacturing methods, particularly to high-temperature, low-coking (including no coking, defined herein as a coking time (ts1) greater than 150 minutes at 140°C, wherein the coking time (ts1) at 140°C is measured as described herein) methods for manufacturing crosslinkable compound compositions comprising thermoplastic polyolefins and additives. Methods for manufacturing crosslinked compositions and articles from crosslinkable compound compositions are also included.

[0011] A method is provided for manufacturing a crosslinkable compound composition at high temperature and low coking (including no coking, defined herein as a coking time (ts1) of more than 150 minutes at 140°C, wherein the coking time (ts1) at 140°C is measured as described herein). This method includes melting and mixing a main stream at a temperature of 120.0°C to 150.0°C, or alternatively 125°C to 149°C, wherein the main stream comprises one or more thermoplastic polyolefins and one or more antioxidants, but lacks a curing agent additive selected from the group consisting of peroxides and crosslinking aids; and injecting a combination of the curing agent additive comprising one or more organic peroxides and one or more crosslinking aids into a composite melt, and uniformly mixing them by melting and mixing one or more thermoplastic polyolefins, one or more antioxidants, one or more organic peroxides, and one or more crosslinking aids together. A method for manufacturing a crosslinkable compound composition and an article thereof is also provided. Simple Explanation of the Diagram

[0012] [Figure 1] Depicts a melt-mixing production line according to the present invention. [2]) Examples. [Figure 2] Depicts a melt-mixing production line according to the present invention. [2]) Alternative examples. [Figure 3] Depicts a melt-mixing production line for manufacturing the crosslinkable compound in the example of the present invention. [2]). Implementation

[0013] According to embodiments of the present invention, the inventors have solved the problem of providing stable, crosslinkable compound compositions for use as manufacturing compounds for cable insulations without requiring a soaking step to incorporate a crosslinking initiator into the composition. In some embodiments, the method incorporates a crosslinking initiator (such as a free radical generating compound, such as an organic peroxide) into the composition, wherein the free radical generating compound can be used to initiate carbon radical-based crosslinking of thermoplastic polyolefins, optionally utilizing unsaturated crosslinking aids. Embodiments of the present invention relate to manufacturing methods, particularly to high-temperature, low-coking (including no coking, defined herein as a coking time (ts1) of more than 150 minutes at 140°C, wherein the coking time (ts1) at 140°C is measured as described herein) methods for manufacturing crosslinkable compound compositions comprising thermoplastic polyolefins and additives. Methods for manufacturing crosslinked compositions and articles from crosslinkable compound compositions are also included. In some embodiments, the methods of the present invention and the crosslinkable compound compositions are lacking, i.e., they do not contain any acid additives. That is, no acidic compounds (such as Brønsted acid, sulfonic acid, and / or Lewis acid, such as added dialkyltin dicarboxylic acid) are added as components in the method or composition. Acid additives do not include acidic byproducts or acidic decomposition products, if any, which may be generated in situ from the reaction or decomposition of other components used herein. As described later, if necessary, amine retardant stabilizers (HAS) may be included in the method and composition to neutralize any potential in-situ generated acidic byproducts or acidic decomposition products.

[0014] A method is provided for manufacturing a crosslinkable compound composition at high temperature and low coking (including no coking, defined herein as a coking time (ts1) of more than 150 minutes at 140°C, wherein the coking time (ts1) at 140°C is measured as described herein). This method includes melting and mixing a main stream at a temperature of 120.0°C to 150.0°C, or alternatively 125°C to 149°C, wherein the main stream comprises one or more thermoplastic polyolefins and one or more antioxidants, but lacks a curing agent additive selected from the group consisting of peroxides and crosslinking aids; and injecting a combination of the curing agent additive comprising one or more organic peroxides and one or more crosslinking aids into a composite melt, and uniformly mixing them by melting and mixing one or more thermoplastic polyolefins, one or more antioxidants, one or more organic peroxides, and one or more crosslinking aids together. A method for manufacturing a crosslinkable compound composition and an article thereof is also provided.

[0015] For ease of cross-referencing, some embodiments of the present invention are described as numbered patterns.

[0016] Sample 1. A high-temperature, low-coking method for manufacturing a crosslinkable compound composition, the method comprising: injecting a combination of a curing agent additive comprising one or more organic peroxides and one or more crosslinking aids into a melt of an intermediate compound, the intermediate compound comprising one or more thermoplastic polyolefin polymers and one or more antioxidants (AO), but lacking one or more curing agent additives, wherein the melt is at a temperature of 120.0°C to 150.0°C; and rapidly mixing the curing agent additive into the melt in less than 60 seconds to manufacture a crosslinkable compound composition in the form of a homogeneous mixture of one or more thermoplastic polyolefins, antioxidants and curing agent additives.

[0017] Sample 2. The method of Sample 1, wherein the crosslinkable compound composition has: a coking time (ts1) of at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, at 140°C, described as the time required for an increase of 1 lbf-in or 1.13 decibels-meters (dN-m) from the minimum torque ("ML") at 140°C, as determined by dynamic modulus rheology (MDR) testing according to ASTM procedure D5289; and a maximum torque (MH) at 182°C that is at least 1.92 decibels-meters (dN-m; equal to at least 1.70 lbf-in) higher than the minimum torque (ML) at 182°C, preferably at 182°C MH is at least 1.92 dN-m higher than ML (at least 1.70 lbf-in higher), and at 182°C MH is at least 2.09 dN-m (1.85 lbf-in higher). 2.26 dN-m (2.0 lbf-in), preferably at least 2.26 dN-m (2.0 lbf-in), as determined by dynamic modulus rheology (MDR) testing according to ASTM procedure D5289.

[0018] State 3. The method of State 1 or State 2, wherein the crosslinkable compound composition is cooled to 100°C or lower, preferably 80°C or lower, within less than 5 minutes, and preferably further cooled to 30°C or lower within less than 6 hours.

[0019] 4. A method according to any one of 1 to 3, wherein the method is a high-temperature, low-coking method for continuously manufacturing crosslinkable compound components using a melt-blending production line, wherein the melt-blending production line includes a melt-blending apparatus and its downstream processing system, wherein the melt-blending apparatus has a preparation zone, an injection zone, and a mixing zone, wherein the preparation zone is configured to continuously prepare a melt stream of intermediate compounds and move the melt stream to the injection zone, wherein the injection zone has a feed point for continuously receiving the melt stream of intermediate compounds and one or more injection points for continuously injecting additives into the melt stream of intermediate compounds in the injection zone; and wherein the mixing zone has one or more mixing elements (e.g., one or more rotor blades or screws, and baffles as appropriate), which are configured to rapidly homogenize the injected additives (within 60 seconds or less) into the melt stream of intermediate compounds; and wherein the mixing zone is compatible with the injection zone. The method comprises: (A) continuously feeding a melt stream of an intermediate compound through the feed point into the injection zone of the melt mixing apparatus at a temperature of 120.0°C to 150.0°C, or 125°C to 149°C, the melt stream of the intermediate compound comprising a mixture of one or more thermoplastic polyolefin polymers and one or more antioxidants (AO), but lacking one or more curing agent additives selected from the group consisting of organic peroxides and crosslinking aids; wherein preferably, each of the one or more thermoplastic polyolefins is independently selected from the group consisting of: polyethylene homopolymers, ethylene / 1-butene copolymers, ethylene / 1-hexene copolymers, and ethylene / 1-octene copolymers; and more preferably, each of the one or more thermoplastic polyolefins is independently selected from the group consisting of low-density polyethylene polymers with a density ranging from 0.87 to 0.94. g / cm³, as measured according to ASTM D792, and with a melt flow index (I²) of 0 at 190°C / 2.16 kg.5 to 20 g / 10 minutes, as determined according to ASTM D1238; (B) a combination of curing agent additives comprising one or more organic peroxides and one or more crosslinking aids is continuously injected into the melt stream of the intermediate compound in the injection zone of the melt mixing apparatus via at least one of the one or more injection points; (C) the melt stream of the intermediate compound and the injected combination of curing agent additives are rapidly homogenized by melt mixing to produce a crosslinkable compound composition; and (D) the stream of the crosslinkable compound composition is continuously discharged from the melt mixing apparatus to a processing system, wherein the residence time of the combination of curing agent additives in the melt mixing apparatus is 60 seconds or less; and wherein the crosslinkable compound composition comprises: one or more A thermoplastic polyolefin polymer; one or more antioxidants; one or more organic peroxides; and one or more crosslinking aids; wherein the crosslinkable compound composition has: a coking time (ts1) of at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, at 140°C, described as the time required for an increase of 1 lbf-in or 1.13 decibels-meters (dN-m) from the minimum torque ("ML") at 140°C, as determined by dynamic modulus rheology (MDR) testing according to ASTM procedure D5289; and a torque at least 1.92 decibels-meters (dN-m) higher than the minimum torque (ML) at 182°C; equal to at least 1.70 decibels-meters (dN-m). The maximum torque (MH) at 182°C (1.70 lbf-in) is preferably at least 1.92 dN-m higher than the maximum torque (ML) at 182°C; and the MH at 182°C is at least 2.09 dN-m (1.85 lbf-in), more preferably at least 2.26 dN-m (2.0 lbf-in), as determined by dynamic modulus rheology (MDR) testing according to ASTM procedure D5289.

[0020] Version 5. The method of Version 4, wherein after step (d) the method includes either processing step (E)(i) or step (E)(II): (E)(i) wherein the processing system includes a cooling device and a granulation device, the granulation device being the same as or different from the cooling device, and step (E)(i) includes cooling and granulating the crosslinkable compound composition to produce its solid particles; or (E)(ii) wherein the processing system includes an annular coater device and a curing device, and step (E)(ii) includes coating a conductor, preferably a wire or optical fiber (optical fiber) with the crosslinkable compound composition to produce a coated conductor, and curing the coating to produce a cable including the conductor and an insulation layer at least partially surrounding the conductor, wherein the insulation layer includes the crosslinkable compound composition thus obtained, and the insulation material is in direct contact with the conductor or indirect contact via one or more intermediate layers (e.g., semiconductor layers).

[0021] State 6. The method of State 4 or State 5, the method comprising, prior to the injection step, preparing a melt stream of the intermediate compound by melting particles of the intermediate compound or by melting particles containing one or more thermoplastic polyolefins but lacking at least one of the one or more antioxidants, and mixing the molten thermoplastic polyolefin with the at least one of the one or more antioxidants.

[0022] Sample 7. The method of any one of Samples 4 to 6, wherein prior to the continuous injection of the combination of curing agent additives in step (B), the method further comprises: pumping a melt stream of the intermediate compound via a melt pump to create a pressurized melt stream; and subsequently melting and screening the pressurized melt stream of the intermediate compound via a first melt screen, the first melt screen being located upstream of all the injection points in the melt stream of the one or more for injecting the combination of curing agent additives into the intermediate compound; wherein the melt pump and the first melt screen are located upstream of all injection points in the injection zone of the melt mixing apparatus.

[0023] Sample 8. The method of any one of Samples 4 to 7, further comprising: adding a second thermoplastic polyolefin polymer to the melt flow of the intermediate compound at a point upstream of any injection point; and melt-mixing the second thermoplastic polyolefin polymer with the intermediate compound. Preferably, the weight ratio of the added second thermoplastic polyolefin polymer to the thermoplastic polyolefin polymer in the melt flow of the intermediate compound is in the range of 1:1 to 1:4.

[0024] Sample 9. The method of any one of Samples 4 to 8, wherein the one or more injection points for injecting the combination of curing agent additives into the melt stream of the intermediate compound include any or more of the following injection points (i) to (ix): (i) wherein the mixing zone of the melt mixing device has a distribution or kneading section, and the one or more injection points are located at the downstream end of the melt mixing device at the distribution mixing or kneading section; (ii) an injection point located downstream of the feed point of the injection zone downstream of the feeding step (A); (iii) wherein the melt mixing device sequentially includes a second melt screen and an independent melt pump, and The one or more injection points are located downstream of the second melt screen and upstream of the independent melt pump; (iv) wherein the melt mixing device sequentially includes the second melt screen, the independent melt pump and the second melt pump, and the one or more injection points are located between the independent melt pump and the second melt pump; or, (v) a combination of injection points (i) and (ii); (vi) a combination of injection points (i) and (iii); (vii) a combination of injection points (i) and (iv); (viii) a combination of any three of injection points (i) to (iv); or (ix) a combination of each of injection points (i) to (iv).

[0025] State 10. The method of any one of States 1 to 9, wherein it has any of the limitations (i) to (vii): (i) wherein the one or more antioxidants comprises two or more antioxidants, preferably a mixture of two or three antioxidants; or wherein the one or more crosslinking aids comprises an alkenyl-containing monocyclic organosiloxane; or wherein the one or more antioxidants comprises two or more antioxidants, preferably a mixture of two or three antioxidants, and the one or more crosslinking aids comprises an alkenyl-containing monocyclic organosiloxane; (ii) wherein the one or more crosslinking aids comprises an alkenyl-containing monocyclic organosiloxane of formula (I): [R1, R2SiO2 / 2]n(I), wherein the subscript n is an integer greater than or equal to 3; each R1 is independently (C2-C4)alkenyl or H2C═C(R1a)—C(═O)—O—(CH2). m—, wherein R 1a is H or methyl and a subscript, and m is an integer from 1 to 4; and each R 2 is independently H, (C 1-C 4) alkyl, phenyl, or the same as R 1; (iii) wherein the one or more organic peroxides comprise dicumyl peroxide or peroxides containing isopropylphenyl; (iv) limiting both (i) and (ii); (v) limiting both (i) and (iii); (vi) limiting both (ii) and (iii); (vii) limiting each of (i) to (iii).

[0026] Sample 11. The method of any of Samples 1 to 10, wherein a thermoplastic polyolefin is present, and the thermoplastic polyolefin has a density in the range of 0.87 to 0.94 g / cm³ as measured according to ASTM D792, and a melt index (I²) of 0.5 to 20 g / 10 min at 190°C / 2.16 kg as determined according to ASTM D1238 and expressed in grams eluted per 10 minutes; or wherein the one or more thermoplastic polyolefin polymers comprise one or more thermoplastic polyethylene polymers, preferably each of the one or more thermoplastic polyolefins is independently selected from the group consisting of: polyethylene homopolymers, ethylene / 1-butene copolymers, ethylene / 1-hexene copolymers, and ethylene / 1-octene copolymers; and more preferably, each of the one or more thermoplastic polyolefins is independently selected from the group consisting of low-density polyethylene polymers having a density range of 0.87 to 0.94 g / cm³. g / cm 3, as measured according to ASTM D792, and melt index (I 2) of 0.5 to 20 g / 10 min at 190°C / 2.16 kg, as measured according to ASTM D1238.

[0027] Sample 12. The method of any one of Samples 1 to 11, wherein the crosslinkable compound composition has a thermal elongation of less than 130%, preferably less than 100%, at 200°C as tested according to ICEA T-28-562a.

[0028] Sample 13. The method of any one of Samples 1 to 12, comprising: sampling the crosslinkable compound composition to obtain at least one sample thereof; using the sample to measure a coking time (ts1) at 140°C for at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, denoted as the time required for an increase of 1 ft-pound-in (lbf-in) or 1.13 decibels-newton-meters (dN-m) from the minimum torque ("ML") at 140°C, as determined by dynamic modulus rheology (MDR) testing according to ASTM procedure D5289; and using the sample to measure a maximum torque (MH) at 182°C that is at least 1.92 decibels-newton-meters (dN-m; equal to at least 1.70 lbf-in) higher than the minimum torque (ML) at 182°C, preferably MH at 182°C being at least 1.92 dN-m higher than ML (at least 1.70 lbf-in). 1 lbf-in); and MH at 182°C is at least 2.09 dN-m (1.85 lbf-in), preferably at least 2.26 dN-m (2.0 lbf-in), as determined by dynamic modulus rheology (MDR) testing according to ASTM procedure D5289.

[0029] Sample 14. The method of any one of Samples 1 to 13, the method comprising: molding a melt of the crosslinkable compound composition to form a molded crosslinkable compound composition, preferably extruding the melt of the crosslinkable compound composition into an insulating layer covering a conductive core; and curing the molded crosslinkable compound composition to manufacture an article comprising the crosslinkable compound composition, preferably curing the insulating layer to manufacture a power cable comprising the conductive core and the crosslinked insulating layer.

[0030] Sample 15. The method of any of Samples 1 to 14, wherein the method has one or more of the following limitations (a) to (g): (a) the melt mixing apparatus used in the method is a closed mixer or screw extruder; (b) the method during or before the rapid homogenization step (C) does not employ an active cooling step (e.g., via a heat exchanger device or cooling zone in the extruder apparatus), or allows the melt of the intermediate compound to be passively cooled from a temperature equal to or higher than 120°C to a temperature below 120°C, or from a temperature equal to or higher than 141°C to a temperature below 141°C; (c) the method independently has 0 wt% to less than 0.10 wt%, or does not include (i.e., lacks, i.e., 0 wt%). wt%) any of compounds (i) to (vi): (i) montmorillonite; (ii) hydroperoxide; (iii) N-nitroso-diarylamine; (iv) maleic diamide; (v) imine compound; and (vi) hydroquinone, wherein each wt% is based on the total weight of the combination of the intermediate compound and the curing agent additive; (d) limiting both (a) and (b); (e) limiting both (a) and (c); (f) limiting both (b) and (c); or (g) limiting each of (a), (b), and (c). Regarding limitation (b), cooling is permitted provided that the temperature of the melt flow of the intermediate compound is not lower than 120°C or lower than 125°C. Some such embodiments of the present invention do not contain either compound (i) or (ii); alternatively, both compound (i) and (vi); alternatively, both compound (ii) and (vi); alternatively, each of compounds (i), (ii), and (vi); alternatively, each of compounds (i), (ii), (v), and (vi); alternatively, any five of compounds (i) to (vi); alternatively, all compounds (i) to (vi). If any of compounds (i) to (vi) is found to have a char-delaying effect that may or may not be found, the minimum amount of such compound required to exhibit an effective char-delaying effect in the present method is expected to be at least 0.10 wt%, and possibly higher.

[0031] Examples of this method are continuous. This means that the feeding, injection, mixing, and discharging steps, and any processing steps of those examples, are operated without interruption (without stopping and restarting) for at least 50 minutes, or at least 60 minutes, or at least 6 hours, or at least 12 hours, or at least 24 hours. If sufficient quantities of the components (e.g., thermoplastic polyolefins, antioxidants, curing agent additives) are available, and if there is no power interruption (e.g., electrical loss), examples of this method are continuous and can operate indefinitely without interruption until one or more units of the melt-mixing production line need to be taken out of service for cleaning or repair. In typical manufacturing operations, examples of this method are continuous and can easily operate without interruption for 7 days, 4 weeks, or 6 months or longer.

[0032] A crosslinkable compound composition prepared by a high-temperature, low-coking (including no coking, which is defined herein as a coking time (ts1) of more than 150 minutes at 140°C, wherein the coking time (ts1) at 140°C is measured as described herein) method can be described as a "homogeneous mixture of crosslinkable compound compositions containing organic peroxides". The characteristic of a crosslinkable compound composition "containing organic peroxides" means that the composition has a crosslinking-effective amount of undecomposed organic peroxides sufficient to act as a free radical generator later during the method of curing the crosslinkable compound composition to manufacture the crosslinkable compound composition. "Crosslinking-effective amount" means the maximum torque (MH) at 182°C. The limitations described below are satisfied by the composition. The "homogeneous" state of the characteristic of a "homogeneous mixture" of a crosslinkable compound composition means that the crosslinkable compound composition has a uniform compositional distribution across its cross-section. The "mixing" state in the "homogeneous mixing" characteristic refers to the mechanical mixing of curing agent additives, including organic peroxides and crosslinking aids, into the melt flow of intermediate compound components by methods excluding soaking, wetting, grinding (e.g., twin-roll milling), calendering, or acoustic stirring.

[0033] In some embodiments of forms 1 to 15 of the foregoing embodiments, including any of the limitations (a) to (g), the combination of curing agent additives comprises an organic peroxide and two crosslinking aids. In some such embodiments, the organic peroxide is dicumyl peroxide. In some such embodiments, at least one of the two crosslinking aids is triallyl isocyanurate (“TAIC”) or 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-cyclotetrasiloxane (“vinyl-D4”). In some such embodiments, the organic peroxide is dicumyl peroxide, and the two crosslinking aids are TAIC and vinyl-D4.

[0034] This invention also claims crosslinkable compound compositions prepared by any of the methods described in samples 1 to 15. The crosslinkable compound compositions of this invention differ from comparative compound compositions in at least one property or composition. Comparative compound compositions are compounds containing all the same components as the crosslinkable compound compositions of this invention, but are manufactured by a different method in terms of the incorporation of one or more organic peroxides. The comparative compound compositions are prepared by a comparative method comprising: melt-mixing all the same components except for one or more organic peroxides to produce a secondary mixture; granulating the secondary mixture to produce its particles; and immersing the same one or more organic peroxides into the particles of the secondary mixture to produce a comparative compound composition in granular form. Due to the different manufacturing methods, the thermal history of the crosslinkable compound compositions of this invention differs from that of the comparative compound compositions. Therefore, due to the different thermal histories, the crosslinkable compound compositions of this invention may differ from the comparative compound compositions in at least one aspect selected from the group consisting of: component ratios; component concentrations; melt rheological properties; and mechanical properties. Advantageously, the method of the present invention can be more efficient, faster (i.e., more productive), and / or more cost-effective than comparative methods involving the soaking of one or more organic peroxides. The improved efficiency of the method of the present invention may include using fewer unit operations or less energy than comparative methods.

[0035] Unbound by theory, it is believed that the method of the present invention inherently provides evidence that the crosslinked compound composition has a ts1 of at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes at 140°C, which is low charring (including no charring, which is defined herein as a charring time (ts1) greater than 150 minutes at 140°C, wherein the charring time (ts1) at 140°C is measured as described herein), and inherently has a maximum torque (MH) at 182°C that is at least 1.92 dN-m (at least 1.70 lbf-in) higher than ML at 182°C, preferably at least 2.09 dN-m (1.85 lbf-in), and more preferably at least 2.26 dN-m (2.0 lbf-in). In this context, it is believed that at least one of one or more crosslinking aids is used independently as a tar-resistant additive (SRA) achieving a ts1 of at least 50 minutes, alternatively at least 60 minutes, and preferably at least 65 minutes at 140°C; or at least one of one or more crosslinking aids is used independently as a crosslinking booster additive (CBA) achieving maximum torque (MH) at 182°C, with a torque at 182°C at least 1.92 dN-m higher than ML (at least 1.70 lbf-in higher), and preferably at least 2.09 dN-m (1.85 lbf-in) at 182°C, more preferably at least 2.26 dN-m (2.0 lbf-in); or combinations thereof. One or more crosslinking aids may comprise or consist of the following crosslinking aids: a crosslinking aid used simultaneously as SRA and CBA; or two crosslinking aids, one used as SRA and the other as CBA. In some embodiments, one or more crosslinking aids are used as crosslinking aids for scorching resistant additives (SRA). In some embodiments, the maximum torque (MH) at 182°C is at least 1.92 dN-m higher (at least 1.70 lbf-in higher) than the maximum torque (ML) at 182°C, or the MH at 182°C is at least 2.26 dN-m (2.0 lbf-in), or from 2.37 dN-m (2.10 lbf-in) to 2.98 dN-m (2.64 lbf-in), or from 2.61 dN-m (2.31 lbf-in) to 2.96 dN-m (2.62 lbf-in).In some embodiments, one or more crosslinking aids are used as crosslinking aids for scorching resistant additives (SRA); the time to speed of reaction (ts1) at 140°C is at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes; and the maximum torque (MH) at 182°C is at least 2.26 dN-m (2.0 lbf-in), or from 2.37 dN-m (2.10 lbf-in) to 2.98 dN-m (2.64 lbf-in), or from 2.61 dN-m (2.31 lbf-in) to 2.96 dN-m (2.62 lbf-in).

[0036] Unbound by theory, it is believed that melt mixing temperatures from 120.0°C to 150.0°C, or from 125°C to 149°C, are exceptionally high for the use of organic peroxide systems. At 140°C, the time to coke (ts1) is at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, which is evidence of low coking (including no coking, defined herein as a coking time (ts1) greater than 150 minutes at 140°C, wherein the coking time (ts1) at 140°C is measured as described herein) in the method of the present invention. Furthermore, the maximum torque (MH) at 182°C is at least 1.92 dN-m (at least 1.70 lbf-in) higher than the ML at 182°C, or the MH at 182°C is at least 2.09 dN-m (1.85 lbf-in), more preferably at least 2.26 dN-m (2.0 lbf-in). (lbf-in), which is evidence of the crosslinkability of crosslinkable compound compositions produced by the method of the present invention.

[0037] As illustrated in the examples of the invention described later, the minimum torque ML at 182°C is typically 0.16 dN-m or 0.17 dN-m (0.14 lbf-in or 0.15 lbf-in), and when tested using a dynamic modulus rheometer (MDR) at 182°C according to ASTM procedure D5289, the torque increases to 2.44 dN-m to 2.95 dN-m (from 2.16 lbf-in to 2.61 lbf-in), depending on the specific example of the invention. Therefore, during the MDR test at 182°C, the torque rises from the ML value to the MH value, which is where the torque value tends to plateau or no longer increases. As illustrated in the examples of the invention, in some embodiments, the maximum torque (MH) at 182°C is at least 2.7 dN-m higher (at least 2.4 lbf-in higher) than the ML at 182°C.

[0038] The process of feeding one or more antioxidants and one or more thermoplastic polyolefins into the melt-mixing apparatus via one or more feed points to produce a main stream comprising one or more antioxidants and one or more thermoplastic polyolefins (collectively, components of the main stream) but lacking one or more curing agent additives selected from the group consisting of organic peroxides and crosslinking aids can be accomplished by any of the following methods. In one embodiment, at least one of the one or more antioxidants may be fed separately from at least one of the one or more thermoplastic polyolefins into the melt-mixing apparatus. In another embodiment, at least one of the one or more antioxidants and at least one of the one or more thermoplastic polyolefins may be pre-mixed together to form the combination thereof, and the combination may be fed into the melt-mixing apparatus. In another embodiment, when at least two antioxidants or at least two thermoplastic polyolefins or combinations thereof are present, it is applicable to feed at least one antioxidant and / or at least one thermoplastic polyolefin separately into the melt mixing apparatus and to feed at least one antioxidant and at least one thermoplastic polyolefin separately into the melt mixing apparatus.

[0039] According to embodiments of the present invention, injecting a combination of curing agent additives into the melt stream of an intermediate compound comprises injecting them into any one or more or all of the following injection points: (i) a distributed mixing or kneading section at the downstream end of a melt mixing apparatus, (ii) an injection point downstream of melt formation within the melt mixing apparatus itself, (iii) downstream of a melt screen located downstream of the melt mixing apparatus but upstream of a separate melt pump, preferably, (iv) upstream of a second melt pump located at the point downstream of (iii) both the separate melt pump and the melt screen, or (v) any combination thereof.

[0040] Preferably, to control the overall melt temperature of the intermediate compound, the method according to the invention further includes adding a solid thermoplastic polyolefin to the melt stream of the intermediate compound, such as at any point upstream or adjacent to all injection points, and melting and mixing the second feed. The weight ratio of the thermoplastic polyolefin in the second feed to the thermoplastic polyolefin in the main stream may be in the range of 1:1 to 1:4 or 1:1.5 to 1:4 or more preferably, 1:2 to 1:4.

[0041] Preferably, the density of the thermoplastic polyolefin in the method of the present invention ranges from 0.87 to 0.94 g / cm3, as measured according to ASTM D792, and the melt index (I2) is from 0.5 to 20 g / 10 min, as measured according to ASTM D1238 at 190°C / 2.16 kg and expressed in grams washed out every 10 minutes.

[0042] Preferably, one or more crosslinking aids in the method of the present invention comprise a monocyclic organosiloxane of formula (I): [R1,R2SiO2 / 2]n(I), wherein the subscript n is an integer greater than or equal to 3; each R1 is independently (C2-C4)alkenyl or H2C═C(R1a)—C(═O)—O—(CH2)m—, wherein R1a is H or methyl and a subscript, and m is an integer from 1 to 4; and each R2 is independently H, (C1-C4)alkyl, phenyl, or the same as R1, for example tetramethyl-tetravinyl-cyclotetrasiloxane, such as 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-cyclotetrasiloxane.

[0043] In another embodiment of the invention, the homogeneous thermoplastic polyolefin crosslinkable compound composition comprises: a thermoplastic polyolefin polymer, such as a low-density polyethylene polymer, for example having a density ranging from 0.87 to 0.94 g / cm³, as measured according to ASTM D792, and a melt index (I²) of 0.5 to 20 g / 10 min, or more preferably, 0.5 to 10 g / 10 min, as measured according to ASTM D1238 at 190°C / 2.16 kg, and described in grams eluted per 10 minutes; one or more antioxidants (AO), such as hindered phenols or hindered amines or mixtures thereof; one or more crosslinking aids, such as alkenyl-containing monocyclic organosiloxanes of formula (I): [R₁, R₂SiO₂ / ₂]ₙ(I), wherein the subscript n is an integer greater than or equal to 3; each R₁ is independently (C₂-C₄)alkenyl or H₂C═C(R₁, R₂, R₃, R₄)- ... R1a)—C(═O)—O—(CH 2) m—, wherein R1a is H or methyl and a subscript, and m is an integer from 1 to 4; and each R2 is independently H, (C 1-C 4)alkyl, phenyl, or the same as R1, preferably tetramethyl-tetravinyl-cyclotetrasiloxane; and one or more organic peroxides, such as dicumyl peroxide or peroxides containing isopropylphenyl, as crosslinking initiators. The composition may further include crosslinking aids, such as diallyl or triallyl crosslinking aids, such as triallyl isocyanurate (TAIC). The total amount of one or more antioxidants may be in the range of 0.01 wt.% to 1.5 wt.% or preferably 0.1 wt.% to 1 wt.% based on the total weight of the crosslinkable compound composition. The total amount of one or more organic peroxides may be based on the total weight of the crosslinkable compound composition and range from 0.1 wt.% to 2 wt.%, or preferably from 0.3 wt.% to 1.4 wt.%. The total amount of one or more crosslinking aids may be based on 0.1 wt.% to 5 wt.%, or preferably from 0.3 wt.% to 4 wt.%, or more preferably from 0.5 wt.% to 2 wt.%, all based on the total weight of the crosslinkable compound composition. The hindered phenol may be 2,6-bis(tert-alkyl)phenol, and the hindered amine may include a diradical secondary amine of the formula -C(alkyl)2-N(H)-C(alkyl)2- or a diradical tert-amine of the formula -C(alkyl)2-N(alkyl)-C(alkyl)2-.

[0044] Preferably, the crosslinkable compound composition according to the present invention has one or more of the following within one hour after melt mixing: (i) a coking time (ts1) of at least 51 minutes, or preferably at least 55 minutes, or even more preferably at least 65 minutes at 140°C, described as the time required to increase by 1 unit (inch-lbf) or 1.13 decibels-meters (dN-m) from the minimum torque ("ML"), as determined by dynamic modulus rheometer (MDR) test according to ASTM procedure D5289; (ii) a maximum torque (MH) of at least 2.26 dN-m (2.0 lbf-in) at 182°C, as determined by dynamic modulus rheometer (MDR) test according to ASTM procedure D5289; or (iii) a thermal elongation at 200°C of less than 100% according to ICEA T-28-562.

[0045] According to the present invention, a method of injecting peroxide and one or more crosslinking aids used as scorch-resistant additives (SRA) into the melt stream of a thermoplastic polyolefin polymer (such as low-density polyethylene polymer) immediately provides a homogeneous thermoplastic polyolefin crosslinkable compound, even before it cools down from the start of its processing. Injection during melt mixing, such as into a melt mixing apparatus, mixer, extruder, or kneader or its distributed mixing elements, eliminates the need for a melt cooling step or post-treatment with an initiator, producing a crosslinkable compound, such as granules or other raw materials, suitable for later use as a compound in the manufacture of cable insulation. The melt mixing method of the present invention always provides a fully formulated product without a melt cooling step or soaking of the polyolefin compound with a crosslinking initiator. The homogeneous thermoplastic polyolefin crosslinkable compound according to the present invention comprises a crosslinking initiator fully incorporated only during melt processing. The crosslinkable compound material of the present invention comprises a homogeneous thermoplastic polyolefin compound formed immediately after melt mixing. The composition or product according to the present invention comprises a crosslinkable homogeneous intermediate compound with a high scorch time. Therefore, the method of the present invention avoids the need for impregnation (soaking) facilities. The fully formulated products or homogeneous thermoplastic polyolefin crosslinkable compounds (such as granules) of this invention are storage-stable and allow for the manufacture of individual in-line articles in later stages, i.e., extrusion and molding into finished articles, such as cable insulation. In contrast to the homogeneous thermoplastic polyolefin crosslinkable compounds of this invention, thermoplastic polyolefin crosslinkable compounds prepared by dip mixing are not fully formulated, homogeneous, batch-stable, or even crosslinkable after melt mixing. In fact, dynamic modulus rheology (MDR) tests on the crosslinkable compound composition of this invention show that when the compound is prepared by dip mixing, initiators such as dicumyl peroxide (DCP) do not diffuse into the thermoplastic polyolefin matrix without additional heat treatment (e.g., at 70°C to 80°C for at least 2 hours) to remove the initiator from the granule surface; and even with heat treatment, the initiator requires time to fully diffuse into the polyolefin matrix. However, according to the present invention, DCP forms a uniform distribution in the polyolefin matrix immediately after melt mixing by redirecting the melt flow (mixing) and diffusion. Therefore, the present invention provides a crosslinkable compound having one or more of the following within one hour after melt mixing: (i) a coking time (ts1) of at least 51 minutes, or preferably at least 55 minutes, at 140°C, described as the time required to increase the minimum torque ("ML") by 1 unit (inch-lb) or 1.13 decibels-meters (dN-m), as determined by dynamic modulus rheology (MDR) testing according to ASTM procedure D5289; and / or (ii) a maximum torque (MH) of at least 2.26 dN-m (2.2 lbf-in) at 182°C, as determined by dynamic modulus rheology (MDR) testing according to ASTM procedure D5289.

[0046] All listed ranges are included and can be combined. For example, based on the total weight of the crosslinkable compound composition, the disclosed amount of organic peroxide is 0.1 wt.% to 2 wt.%, or preferably 0.3 wt.% to 1.4 wt.%, or preferably 0.4 wt.% to 1.2 wt.%, or preferably less than 0.5 wt.% to 1 wt.%, which will include 0.1 wt.% to 2 wt.%, or 0.1 wt.% to 1.4 wt.%, or 0.1 wt.% to 1.2 wt.%, or 0.1 wt.% to 1 wt.%, or 0.3 wt.% to 2 wt.%, or preferably 0.3 wt.% to 1.4 wt.%, or preferably 0.3 wt.% to 1.2 wt.%, or preferably 0.3 wt.% to 1 wt.%, or preferably 0.4 wt.% to 1.4 wt.%, or preferably 0.4 wt.%. wt.% to 1.2 wt.%, or preferably 0.4 wt.% to 1 wt.%, or preferably less than 0.5 wt.% to 1.4 wt.%, or preferably less than 0.5 wt.% to 1.2 wt.%, or preferably less than 0.5 wt.% to 1 wt.%, or preferably less than 0.3 wt.% to 0.4 wt.%, or preferably 0.3 wt.% to less than 0.5 wt.%, or preferably 0.4 wt.% to less than 0.5 wt.%, or 0.3 wt.% to 2 wt.%, or 0.4 wt.% to 2 wt.%, or less than 0.5 wt.% to 2 wt.%.

[0047] Unless otherwise specified, the temperature and pressure conditions are room temperature (23°C) and standard pressure (101.3 kPa), also referred to as "ambient conditions". Unless otherwise specified, all conditions include a relative humidity of 50% (RH).

[0048] Unless otherwise specified, any term containing parentheses shall alternatively refer to the entire term (as if the parentheses were present) and the term without parentheses, and combinations thereof. Thus, as used herein, the term "(meth)acrylate" and similar terms are intended to include acrylates, methacrylates and mixtures thereof.

[0049] As used herein, the term "ASTM" refers to the publications of ASTM International, Conshohocken, Pennsylvania, USA.

[0050] As used in this article, the term "ICEA" refers to publications of the American Society of Insulated Cable Engineers (Miamitown, Ohio, USA).

[0051] As used herein, the term "melt index" or "I²" refers to the result determined according to ASTM D1238 at 190°C / 2.16 kg, and is expressed in grams eluted per 10 minutes.

[0052] As used herein, the term "organic peroxide" refers to a peroxide having the structure R1—O—O—R2 or R1—O—O—R—O—O—R2, where R1 and R2 are each a hydrocarbon moiety, and R is an extended hydrocarbon moiety. As used herein, the term "hydrocarbyl" refers to a monovalent group (e.g., ethyl, phenyl) formed by removing a hydrogen atom from a hydrocarbon. As used herein, the term "hydrocarbylene" refers to a divalent group formed by removing two hydrogen atoms from a hydrocarbon.

[0053] As used herein, the term "polymer" means a macromolecular compound prepared by reacting (i.e., polymerizing) monomers of the same or different types, and includes homopolymers and copolymers. The term "copolymer" means a polymer prepared by polymerizing at least two different monomers as reactants, and includes copolymers prepared from two different monomers, as well as polymers prepared from more than two different monomers, such as trimers, tetramers (four different monomers), etc. As used herein, "homopolymer" means a polymer containing repeating units derived from monomers, but does not exclude residual amounts of other components used in the preparation of homopolymers, such as chain transfer agents.

[0054] As used herein, the term "solid" refers to a crystalline or amorphous substance that does not flow significantly under moderate pressure, has a certain ability to resist forces that would easily deform it, and maintains a certain size and shape under normal conditions.

[0055] As used in this article, the phrase "wt. %" represents weight percentage.

[0056] This invention proposes to provide homogeneous intermediate compounds via a single melt-mixing method, for example, using conventional melt-mixing equipment at temperatures up to the degradation temperature of the polymer. In the melt-mixing method of this invention, the temperature is maintained below 150°C, or preferably below 140°C, and above the melting point of the thermoplastic polyolefin polymer.

[0057] Pressure is required to push the melt through a screen in the screening step or through a die in the granulation step. Some melt-mixing devices that can be used in this method generate sufficient pressure to perform screening or granulation (i.e., they "generate sufficient pressure"). Other melt-mixing devices that can be used in this method do not generate sufficient pressure for screening and / or granulation (i.e., they generate sufficient pressure), where melt pumps or single-screw extruders can also be used to generate sufficient pressure. Therefore, melt-mixing devices may generate sufficient pressure for melt screening or granulation, but this is not necessary. Examples of melt-mixing devices that generate sufficient pressure for screening or granulation are single-screw extruders and some twin-screw extruders. Examples of melt mixing devices that do not generate sufficient pressure for screening or granulation include some twin-screw extruders, internal batch mixers (e.g., Farrel-Pomini Banbury and Kobelco Stewart Bolling mixers), co-rotating meshing twin-screw extruders not configured to generate sufficient pressure for melt screening or granulation, and counter-rotating non-meshing twin-screw extruders (e.g., Farrel FCM and LCM, Kobe Steel LCM, Japan Steel Works (JSW) Continuous Intensive Mixer (CIM) or CIMP).

[0058] Suitable melt mixing or melt mixing equipment includes at least one melt mixing device that moves from upstream to downstream in a melt flow, and further includes a distributed mixing element, which (i) is located within the melt mixing device, such as a gear mixer or gear mixing element, or (ii) serves as a melt pump located downstream of the melt mixing device, or (iii) both, and further includes a melt screening unit. The melt mixing equipment may further include a granulator or granulation die. Preferably, the melt mixing equipment includes two melt pumps, one located upstream of the melt screen and the other downstream of the melt screen.

[0059] To manufacture the homogeneous intermediate compound of this invention, a main feedstock of a thermoplastic polyolefin polymer and one or more antioxidants are melted and compounded or mixed in a melt mixing apparatus to produce a melt stream of the intermediate compound. To manufacture the homogeneous crosslinkable compound of this invention, a curing agent additive is injected and uniformly mixed by continuing to melt and mix the melt stream of the intermediate compound downstream of the melt mixing apparatus. When coupled with downstream mixing elements, suitable apparatus for manufacturing homogeneous melt compounds includes distributed mixing units or sections in an extruder, such as toothed mixing elements (TME, ZME, etc.) and kneading blocks, such as kneading blocks (forward, neutral, or reverse pumping), gear mixers, melt pumps, gear pumps, or foaming elements.

[0060] Injecting the combination of curing agent additives into the melt stream of the intermediate compound includes injecting it into an injection point at any of the following points: (i) a distributed mixing or kneading section downstream of the melt mixing apparatus, (ii) in the downstream production line of melt formation, which may be in the melt mixing apparatus itself, or (iii) upstream of a separate melt pump or other short mixing unit. The injection point is preferably located downstream of the melt screen and itself downstream of the melt pump. Preferably, the melt mixing apparatus includes a dual melt pump configuration, further including a second downstream melt pump and a melt screening device located between the melt pump and the second downstream melt pump; the two melt pumps span the melt screen. In the dual melt pump version, injecting the combination of curing agent additives includes melting the melt stream of the intermediate compound to form a pressurized melt stream, melting the pressurized melt stream of the intermediate compound, and injecting the combination of curing agent additives into the melt stream at an injection point downstream of the melt screen, which may be in or just upstream of the second downstream melt pump.

[0061] The injection point suitable for the curing agent additive combination may include both of the following: (i) a distributed mixing or kneading section at the downstream end of the melt mixing device and (ii) a downstream injection point formed by melting within the melt mixing device itself; and both of the following: (i) a distributed mixing or kneading section at the downstream end of the melt mixing device, and (iii) a melt screen located downstream of the melt mixing device but upstream of an independent melt pump; (i) a distributed mixing or kneading section at the downstream end of the melt mixing device, and (iv) an upstream of a second melt pump located at the point downstream of both the independent melt pump and the melt screen in (iii); Both: (ii) the injection point downstream of melt formation in the melt mixing apparatus itself and (iii) the injection point downstream of the melt screen located downstream of the melt mixing apparatus but upstream of the independent melt pump; or both: (ii) the injection point downstream of melt formation in the melt mixing apparatus itself and (iv) the injection point upstream of the second melt pump located downstream of both the independent melt pump and the melt screen in (iii); or both: (iii) the injection point downstream of the melt screen located downstream of the melt mixing apparatus but upstream of the independent melt pump and (iv) the injection point upstream of the second melt pump located downstream of both the independent melt pump and the melt screen in (iii).

[0062] Furthermore, the injection points for a suitable combination of curing agent additives may include all three of the following: (i) a distributed mixing or kneading section located at the downstream end of the melt mixing device, (ii) an injection point located downstream of the melt formation of the melt mixing device itself, and (iii) a melt screen located downstream of the melt mixing device but upstream of the independent melt pump; all three of the following: (ii) an injection point downstream of the melt formation of the melt mixing device itself, (iii) a melt screen located downstream of the melt mixing device but upstream of the independent melt pump, and (iv) an injection point upstream of a second melt pump located downstream of both the independent melt pump and the melt screen in (iii); all three of the following: (i) a distributed mixing or kneading section located at the downstream end of the melt mixing device, (iii) an injection point located downstream of the melt formation of the melt mixing device itself, and (iv) an injection point located upstream of the second melt pump located downstream of both the independent melt pump and the melt screen in (iii); Downstream of the melting mixing unit but upstream of the independent melting pump, and (iv) upstream of the second melting pump located downstream of both the independent melting pump and the melt screen in (iii); or all three of the following: (i) a distributed mixing or kneading section located at the downstream end of the melting mixing unit, (ii) an injection point located downstream of the melt formation of the melting mixing unit itself, and (iv) upstream of the second melting pump located downstream of both the independent melting pump and the melt screen in (iii); or all three of the following: (ii) an injection point downstream of the melt formation of the melting mixing unit itself, (iii) downstream of the melting mixing unit but upstream of the independent melting pump, and (iv) upstream of the second melting pump located downstream of both the independent melting pump and the melt screen in (iii).

[0063] Preferably, to control the overall melt temperature of the intermediate compound melt flow, the method of the present invention further includes adding a second solid feed of thermoplastic polyolefin polymer downstream of the main solid feed of the thermoplastic polyolefin polymer, such as at any point upstream of each injection point or near the furthest upstream injection point, and melt-mixing the second feed. By introducing the second polymer feed, such as at a weight ratio of 1:1 to 1:4, or preferably 1:2 to 1:4, to the initial polymer feed, the overall melt temperature of the intermediate compound and the resulting crosslinkable compound melt flow can be significantly reduced. The enthalpy-melting second polymer feed from the initial thermoplastic polyolefin polymer melt flow achieves improved temperature control of the melt, i.e., a reduction in melt temperature.

[0064] Suitable melt mixing apparatuses used according to the invention may include, for example, co-rotating meshing twin-screw extruders, batch mixers, counter-rotating non-meshing twin-rotor mixers (e.g., Farrel, FCM), or single-screw extruders. A wider range of compounding apparatuses may be used, wherein the method of the invention includes conveying a melt stream of intermediate compounds to a melt pump and upstream melt screening pressurizing the melt stream at any injection point (i.e., the location where the curing agent additive combination is injected into the melt stream). In this case, the melt mixing apparatus may include any of the aforementioned mixers, co-rotating meshing twin-screw extruders, internal batch mixers, or counter-rotating non-meshing twin-screw compound mixers. If the curing agent is not sufficiently, rapidly, and thoroughly incorporated into the melt by the described means, the resulting composition exhibits severe charring or decomposition of organic peroxides. For example, experiments conducted on a Banbury mixer with discharge at a melt temperature of 125°C and downstream addition of a curing agent additive combination resulted in severe charring rendering the compound unusable.

[0065] Suitable melt screening devices used according to the present invention may include, for example, continuous screening or filtration technologies, such as continuous discs, rotary screen changers, slide screen changers, double-bolt or chamber screen changers, or any candle, pleated candle, disc, cylinder or plate filter element, such as polymer gel, with a woven or non-woven filter medium capable of blocking particles with a size of 25 µm to 500 µm.

[0066] Suitable melt pumps used according to the invention may include any melt pump known in the art, such as MAAG, Farrel-Pomini, gear mixers, or appropriately modified to enhance the mixing dual-wheel pressure producing melt pump.

[0067] The present invention further provides a homogeneous thermoplastic polyolefin crosslinkable compound comprising a thermoplastic polyolefin, one or more antioxidants (AO), one or more crosslinking aids, and one or more free radical initiators. The composition may further comprise one or more crosslinking aids.

[0068] According to the present invention, the crosslinkable compound has a coking time (ts1) of at least 51 minutes, or preferably at least 55 minutes, at 140°C within one hour after melt mixing, described as the time required to increase by 1 unit (inch-lb) or 1.13 decibels-meters (dN-m) from the minimum torque ("ML"), as determined by dynamic modulus rheology (MDR) testing according to ASTM procedure D5289, and / or a maximum torque (MH) of at least 2.26 dN-m (2.2 lbf-in) at 182°C, or preferably at least 2.36 dN-m (2.3 lbf-in), as determined by dynamic modulus rheology (MDR) testing according to ASTM procedure D5289.

[0069] The terms "thermoplastic polyolefin" and "TPO" are used herein to refer to homopolymers made by polymerizing a single unsaturated hydrocarbon monomer and copolymers made by polymerizing two or more different unsaturated hydrocarbon monomers, wherein each unsaturated hydrocarbon monomer consists of carbon and hydrogen atoms. Examples of unsaturated hydrocarbon monomers are ethylene; propylene; (C4-C20)α-olefins; and 1,3-butadiene. In some embodiments, TPO is a polyethylene homopolymer or an ethylene / (C4-C20)α-olefin copolymer. (C4-C20)α-olefins are compounds of the formula H2C=C(H)-(CH2)qCH3, where the subscript q is an integer from 1 to 17. In some embodiments, (C 4-C 20) α-olefins are 1-butene, 1-hexene or 1-octene; alternatively, 1-butene or 1-hexene; alternatively, 1-octene; alternatively, 1-hexene; alternatively, 1-butene.

[0070] Suitable thermoplastic polyolefins may contain polymers prepared from ethylene monomers as the main (i.e., greater than 50 wt.%) monomer component, but other comonomers may also be used. The ethylene polymer may be an ethylene homopolymer or an ethylene / α-olefin ("α-olefin") copolymer, wherein the α-olefin monomer content is based on a total weight of at least 1 wt.%, at least 5 wt.%, at least 10 wt.%, at least 15 wt.%, at least 20 wt.%, or at least 25 wt.% of the total weight of the monomers used to manufacture the copolymer. Based on the weight of the copolymer, such copolymers may have an α-olefin content of less than 50 wt.%, less than 45 wt.%, less than 40 wt.%, or less than 35 wt.%. Suitable α-olefins may be C3-20 (i.e., having 3 to 20 carbon atoms) or C4-20 (i.e., having 4 to 20 carbon atoms), linear, branched, or cyclic α-olefins. Examples of C3-20 α-olefins include, for example, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene. α-olefins can also have cyclic structures, such as cyclohexane or cyclopentane, producing α-olefins such as 3-cyclohexyl-1-propylene (allylcyclohexane) and vinylcyclohexane. Illustrative ethylene / α-olefin endomers include ethylene / propylene, ethylene / butene, ethylene / 1-hexene, ethylene / 1-octene, ethylene / styrene, ethylene / propylene / 1-octene, ethylene / propylene / butene, ethylene / butene / 1-octene, and ethylene / butene / styrene. Furthermore, ethylene polymers can be used alone or in combination with one or more other types of ethylene polymers (e.g., blends of two or more ethylene polymers that differ from each other in monomer composition and content, catalytic methods of preparation, etc.). If an ethylene polymer blend is used, the polymer can be blended in any reactor or post-reactor process.

[0071] The ethylene polymer can be selected from the group consisting of low-density polyethylene (“LDPE”), linear low-density polyethylene (“LLDPE”), very low-density polyethylene (“VLDPE”), and combinations thereof. LDPE is typically a highly branched ethylene homopolymer and can be prepared via a high-compression process (i.e., HP-LDPE). LDPE suitable for use herein may have a density of 0.91 to 0.94 g / cm³, or, for example, at least 0.915 g / cm³ but less than 0.94 or less than 0.93 g / cm³. The polymer density provided herein is determined according to ASTM Method D792. LDPE suitable for use herein may have a melt index (I²) of less than 20 g / 10 min, or in the range of 0.1 to 10 g / 10 min, 0.5 to 5 g / 10 min, 1 to 3 g / 10 min, or 2 g / 10 min. The melt index provided herein is determined according to ASTM Method D1238. Unless otherwise specified, the melt index (also known as I²) is determined at 190°C and 2.16 kg. Generally, LDPEs have a wide molecular weight distribution (“MWD”), resulting in a high polydispersity index (“PDI”, or the ratio of weight average molecular weight to number average molecular weight). Ethylene polymers can be LLDPEs, such as polymers with a heterogeneous distribution of comonomers (e.g., α-olefin monomers) and characterized by short-chain branching. For example, LLDPEs can be copolymers of ethylene and α-olefin monomers with densities ranging from 0.916 to 0.925 g / cm³. Suitable LLDPEs for use herein may have melt indices (I²) ranging from 1 to 20 g / 10 min or 3 to 8 g / 10 min. Ethylene polymers can be VLDPEs, ultra-low density polyethylene, or ULDPEs. VLDPEs are typically ethylene polymers with a heterogeneous distribution of monomers (such as α-olefin monomers) and characterized by short-chain branching. For example, VLDPE may be a copolymer of ethylene and α-olefin monomers (such as one or more of the aforementioned α-olefin monomers). The VLDPE used herein may have a density in the range of 0.87 to 0.915 g / cm³. The VLDPE used herein may have a melt index (I²) in the range of 0.1 to 20 g / 10 min or 0.3 to 5 g / 10 min. Furthermore, the ethylene polymer according to the invention may comprise any combination of two or more of the aforementioned ethylene polymers.

[0072] The thermoplastic polyolefin polymers of this invention are manufactured by a wide variety of methods known in the art. The ethylene polymers of this invention can be prepared using any conventional or subsequently discovered manufacturing process for producing suitable ethylene polymers. Generally, polymerization can be carried out under Ziegler-Natta or Kaminsky-Sinn polymerization conditions known in the art, i.e., at temperatures from 0°C to 250°C, or 30°C, or 200°C, and at pressures from 100 to 10,000 atmospheres (1,013 MPa), preferably from 500 to 10,000 atmospheres. In most polymerization reactions, the molar ratio of polymerization catalyst to monomer is in the range of 10⁻¹²:1 to 10⁻¹:1 or 10⁻⁹:1 to 10⁻⁵:1.

[0073] In some embodiments, a melt stream comprising one or more antioxidants and one or more thermoplastic polyolefins (collectively referred to as the main stream components) but lacking one or more curing agent additives selected from the group consisting of organic peroxides and crosslinking aids, and an intermediate compound melt stream made therefrom (the intermediate compound comprising a mixture of one or more thermoplastic polyolefin polymers and one or more antioxidants (AO), but lacking one or more curing agent additives) contains no other polymers. In such embodiments, the polymer components of the main stream and the intermediate compounds made therefrom consist of one or more thermoplastic polyolefins. In such embodiments, the polymer components of the crosslinkable compound composition produced by the method of the present invention consist of one or more thermoplastic polyolefins and the polymer components of the crosslinkable compound composition made by curing the crosslinkable compound composition, the crosslinkable compound composition being independently composed of one or more thermoplastic polyolefins and / or crosslinked polyolefins made by curing the crosslinkable polyolefins.

[0074] In some embodiments, a main stream comprising one or more antioxidants and one or more thermoplastic polyolefins (collectively, the main stream components) but lacking one or more curing agent additives selected from the group consisting of organic peroxides and crosslinking aids, and a melt stream of an intermediate compound made therefrom (the intermediate compound comprising: a mixture of one or more thermoplastic polyolefin polymers and one or more antioxidants (AO), but lacking one or more curing agent additives) also contains a non-thermoplastic polyolefin polymer. Examples of polymers that are not thermoplastic polyolefins and may be included in these embodiments are ethylene / unsaturated carboxylic acid ester copolymers. Examples of usable ethylene / unsaturated carboxylic acid ester copolymers are ethylene / alkyl acrylate (EAA) copolymers, ethylene / alkyl methacrylate (EAMA) copolymers, and ethylene / vinyl acetate (EVA) copolymers. Examples of ethylene / alkyl acrylate copolymers are ethylene / methyl acrylate (EMA) copolymers, ethylene / ethyl acrylate (EEA) copolymers, and ethylene / butyl acrylate (EBA) copolymers. Examples of ethylene / alkyl methacrylate copolymers are ethylene / methyl methacrylate (EMMA) copolymers, ethylene / ethyl methacrylate (EEMA) copolymers, and ethylene / butyl methacrylate (EBMA) copolymers. In such embodiments, the polymeric component of the main stream and the intermediate compounds derived therefrom consist of one or more thermoplastic polyolefins and one or more ethylene / unsaturated carboxylic acid ester copolymers. The proportion of one or more ethylene / unsaturated carboxylic acid ester copolymers used in such embodiments of the main stream can be from 0.05 wt% to 20 wt%, or 0.10 wt% to 15 wt%, or 0.10 wt% to 5 wt% based on the total weight of the main stream, and the proportion of one or more ethylene / unsaturated carboxylic acid ester copolymers used in such embodiments of the intermediate compounds can be from 0.05 wt% to 20 wt%, or 0.10 wt% to 15 wt%, or 0.10 wt% to 5 wt% based on the total weight of the intermediate compounds. Examples of crosslinkable compound compositions produced by the method of the present invention also contain one or more ethylene / unsaturated carboxylic acid ester copolymers, and crosslinkable compound compositions produced by curing such examples contain their crosslinking products.

[0075] Suitable antioxidants (AO) may include tertiary amines, secondary or tertiary thiols, secondary or tertiary phenols, diphenols, triphenols and tetraphenols, or preferably, combinations of two or more of these. Examples of suitable antioxidants may include, for example, (4-(1-methyl-1-phenylethyl)phenyl)amine (e.g., NAUGARD 445, Addivant USA, Danbury, CT); 2,2-methylene-bis(4-methyl-6-tert-butylphenol) (e.g., VANOX MBPC, Vanderbilt Chemicals, New York, NY); 2,2-thiobis(2-tert-butyl-5-methyl)phenol (CAS No. 90-66-4); 4,4'-thiobis(2-tert-butyl-5-methylphenol), also known as 4,4'-thiobis(6-tert-butyl-m-cresol), CAS No. 96-69-5, LOWINOX TBM 6 antioxidant, Addivant); 2,2'-thiobis(6-tert-butyl-4-methylphenol) (CAS No. 90-66-4, commercial LOWINOX). TBP-6); Tris[(4-tert-butyl-3-hydroxy-2,6-dimethylphenyl)methyl)-1,3,5-triazine-2,4,6-trione (e.g., CYANOX 1790 antioxidant, Solvay Chemicals, Syracuse, NY); Neopentyltetra(3-(3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)propionate (e.g., IRGANOX 1010 antioxidant, CAS No. 6683-19-8); 2,2'-thiodiethylene glycol 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionate (e.g., IRGANOX 1035 antioxidant, CAS No. 41484-35-9, BASF, Ludwigshafen, DE); Distearate thiodipropionate (DSTDP); Dilaurate thiodipropionate (e.g., IRGANOX PS) 800 antioxidant); stearyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (e.g., IRGANOX 1076); 2,4-bis(dodecylthiomethyl)-6-methylphenol (IRGANOX 1726 antioxidant); 4,6-bis(octylthiomethyl)-o-cresol (e.g., IRGANOX 1520 antioxidant); and 2,3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyl]]propionhydrazine (IRGANOX 1024 antioxidant).Preferably, one or more antioxidants include 4,4'-thiobis(2-tributyl-5-methylphenol, also known as 4,4-thiobis(6-tributyl-m-cresol); 2,2'-thiobis(6-tributyl-4-methylphenol); tris[(4-tributyl-3-hydroxy-2,6-dimethylphenyl)methyl]-1,3,5-triazine-2,4,6-trione; distearate or dilaurate thiopropionate; or any combination of two or more thereof. More preferably, the antioxidant may be a combination of tris[(4-tributyl-3-hydroxy-2,6-dimethylphenyl)methyl]-1,3,5-triazine-2,4,6-trione and distearate thiopropionate.

[0076] Based on the total weight of the crosslinkable compound components, the total amount of one or more antioxidants may be from 0.01 wt.% to 1.5 wt.%, or from 0.05 wt.% to 1.2 wt.%, or from 0.1 wt.% to 1 wt.%.

[0077] According to the present invention, an ethylene polymer is used as a crosslinking initiator in combination with one or more organic peroxides. A suitable free radical initiator has a decomposition point at least as high as the melting point of the ethylene polymer and may contain any dialkyl, diaryl, dialkylaryl, or diaryl(di) peroxide having the same or different alkyl, aryl, alkylaryl, or aralkyl moieties. In the formula having the structure R1—O—O—R2 or R1—O—O—R—O—O—R2, R1 and R2 are each independently a hydrocarbon moiety, and R is an extended hydrocarbon moiety; R1 and R2 are each independently a C1 to C20 or C1 to C12 alkyl, aryl, alkylaryl, or aralkyl moiety; R can be a C1 to C20 or C1 to C12 alkylene, arylene, alkylenearyl, or arylene moiety; R, R1, and R2 can have the same or different numbers of carbon atoms, or any two of R, R1, and R2 can have the same number of carbon atoms, while the third has a different number of carbon atoms. Organic peroxides used herein include monofunctional peroxides and difunctional peroxides. As used herein, "monofunctional peroxide" means a peroxide having a single pair of covalently bonded oxygen atoms (e.g., having the structure R—O—O—R). As used herein, "difunctional peroxide" refers to a peroxide having two pairs of covalently bonded oxygen atoms (e.g., having the structure R—O—O—R—O—O—R). Difunctional or higher functional peroxides may be called co-crosslinking agents.

[0078] Exemplary organic peroxides include dicumyl peroxide (“DCP”), tributyl peroxybenzoate, di- and tert-pentyl peroxide (“DTAP”); isopropylisopropylphenyl tributyl peroxide; tert-butylisopropylphenyl peroxide; di- and tert-butyl peroxide; isopropylisopropylphenyl isopropylphenyl peroxide; di(isopropylisopropylphenyl) peroxide and mixtures thereof. Suitable difunctional peroxides may include bis(tributyl-peroxyisopropyl)benzene (“BIPB”), 2,5-bis(tributylperoxy)-2,5-dimethylhexane; 2,5-bis(tributylperoxy)-2,5-dimethylhexene-3; 1,1-bis(tributylperoxy)-3,3,5-trimethylcyclohexane; 4,4-butyl 4,4-bis(tributylperoxy)valerate; 2,5-bis(tributylperoxy)-2,5-dimethyl-3-hexyne; and mixtures of both or more thereof. Typically, only a single type of organic peroxide is used. Preferably, the organic peroxide is dicumyl peroxide, or a peroxide containing isopropylphenyl.

[0079] The crosslinkable compound composition according to the present invention may contain one or more organic peroxides in an amount based on the total weight of the crosslinkable compound composition, ranging from 0.1 wt.% to 2 wt.%, or preferably from 0.3 wt.% to 1.4 wt.%, or preferably from 0.4 wt.% to 1.2 wt.%, or preferably less than 0.5 wt.% to 1 wt.%.

[0080] Suitable crosslinking aids may comprise, for example, any monocyclic organosiloxane of formula (i): [R1,R2SiO2 / 2]n(i), wherein the subscript n is an integer greater than or equal to 3. Each 1 is independently (C2-C4)alkenyl or H2C═C(R1a)—C(═O)—O—(CH2)m—, wherein R1a is H or methyl and a subscript, and m is an integer from 1 to 4; and each R2 is independently H, (C1-C4)alkyl, phenyl, or the same as R1;

[0081] Suitable examples of crosslinking aids used in this invention may include, for example, any of the above formula (i), wherein: (i) each R1 is independently (C2-C3)alkenyl; and each R2 is independently H, (C1-C2)alkyl, or (C2-C3)alkenyl; (ii) each R1 is vinyl; and each R2 is independently (C1-C2)alkyl; (iii) each R1 is vinyl; and each R2 is methyl; (iv) each R1 is allyl; and each R2 is independently (C1-C2)alkyl; (v) each R1 is allyl; and each R2 is methyl; (vi) each R1 is independently H2C═C(R1a)—C(═O)—O—(CH2)m—, wherein R1a is H or methyl and a subscript, and m is an integer from 1 to 4; and each R 2 is independently H, (C1-C2)alkyl, or (C2-C3)alkenyl; (vii) each R1 is independently H2C═C(R1a)—C(═O)—O—(CH2)m—, where R1a is H and the subscript m is 3; and each R2 is independently (C1-C2)alkyl; (viii) each R1 is independently H2C═C(R1a)—C(═O)—O—(CH2)m—, where R1a is methyl and the subscript m is 3; and each R2 is independently (C1-C2)alkyl. More than one crosslinking aid may be used. Suitable crosslinking aids may include, for example, 2,4,6-trimethyl-2,4,6-trivinylcyclotrisiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 2,4,6,8,10-pentamethyl-2,4,6,8,10-pentavinylcyclopentasiloxane or tetramethyl-tetravinylcyclotetrasiloxane or mixtures thereof.

[0082] The amount of one or more crosslinking aids in the crosslinkable compound composition may be from 0.1 wt.% to 5 wt.%, or more preferably from 0.3 wt.% to 4 wt.%, or more preferably from 0.3 wt.% to 3.5 wt.%, such as, more preferably from 0.5 wt.% to 2 wt.%, all weights being based on the total weight of the crosslinkable compound composition.

[0083] Suitable crosslinking aids for use in this invention may comprise bifunctional and higher functional monomers capable of copolymerizing with ethylene polymers. Crosslinking aids may include polyallylic or polyvinyl crosslinking aids. As used herein, "polyallylic" means a compound having at least two dangling allyl functional groups, for example, triallyl compounds selected from the group consisting of: triallyl isocyanurate ("TAIC"), triallyl cyanurate ("TAC"), triallyl phenyltrimethacrylate ("TATM"), and mixtures of two or more thereof. Examples of suitable crosslinking aids include polyallyl crosslinking aids such as triallyl isocyanurate (“TAIC”), triallyl cyanurate (“TAC”), triallyl benzotriester (“TATM”), triallyl orthoformate, neopentyl tetral triallyl ether, triallyl citrate, and triallyl aconitate; vinyl or acrylic crosslinking aids such as ethoxylated bisphenol A dimethacrylate; trimethylolpropane triacrylate (“TMPTA”), trimethylolpropane trimethacrylate (“T…”) MPTMA, 1,6-hexanediol diacrylate, neopentyl terephthalate tetraacrylate, neopentyl terephthalate pentaacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate, and propoxylated glycerol triacrylate; vinyl-containing crosslinking aids, such as α-methylstyrene dimer ("AMSD"); polybutadiene having a high 1,2-vinyl content, and trivinylcyclohexane ("TVCH"); and other crosslinking aids, as described in U.S. Patent Nos. 5,346,961 and 4,018,852. Other crosslinking aids may have at least one N,N-diallylamide functional group, such as that disclosed in U.S. Patent No. 10,941,278 B2 to Cai et al. Preferably, the crosslinking aid is TAIC. Further examples of crosslinking aids are described in US 6,277,925 (e.g., allyl 2-allyl-phenyl ether and the like) and US US6143822 (e.g., 1,1-diphenylethylene, which may be unsubstituted or substituted).

[0084] The crosslinkable compound composition according to the present invention may contain one or more crosslinking aids in an amount ranging from 0.5 wt.% to 5 wt.%, or 0.7 wt.% to 3.5 wt.%, or 1.0 wt.% to 3 wt.%, or 1 wt.% to 2.5 wt.% based on the total weight of the crosslinkable compound composition.

[0085] Based on the total weight of the combination of curing agent additives present in the crosslinkable compound composition, the crosslinking aid may constitute at least 1 wt.%, at least 10 wt.%, at least 50 wt.%, at least 75 wt.%, or at most 50 wt.%, or at most 35 wt.%.

[0086] Crosslinkable compound compositions may also include hindered amine stabilizers (HAS), sometimes referred to as hindered amine light stabilizers (HALS). HAS are compounds with hindered amine functional groups that inhibit oxidative degradation. In some embodiments where HAS can also reduce acid-catalyzed degradation, acidic byproducts are generated in situ during the process. Acidic byproducts can be generated in situ by the reaction of antioxidants with oxygen. A suitable example of a HAS is a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidine-ethanol (CAS No. 65447-77-0, commercially available LOWILITE 62). Other examples of HAS include: (i) polymers of N,N'-bis(2,2,6,6,-tetramethyl-4-piperidinyl)-1,6-hexanediamine and 2,4,6-trichloro-1,3,5-triazine, reacted with N-butyl-1-butylamine and N-butyl-2,2,6,6-tetramethyl-4-piperidinylamine; (ii) poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]]); and (iii) Polymers of N,N'-bis(2,2,6,6-tetramethyl)-4-piperidinyl)-1,6-hexanediamine and 2,4-dichloro-6-(4-morpholinyl)-1,3,5-triazine. An alternative description of HAS (ii) is poly[(6-morpholino-s-triazine-2,4-diyl)[2,2,6,6-tetramethyl-4-piperidinyl)imino]-hexamethylene[2,2,6,6-tetramethyl-4-piperidinyl)imino]]. Other examples of HAS compounds can be found in J. Pospisil and PP Klemchuk, Oxidation Inhibition in Organic Materials, Volume II, pp. 2–8. HAS can be used alone or in combination of two or more of these compounds. In some embodiments, HAS is N,N'-1,6-hexamethylenedimethylbis(N-(2,2,6,6-tetramethyl-4-piperidinyl)-methoxyamine, which can be obtained from BASF using Uvinul 4050.

[0087] The term "montmorillonite" includes naturally occurring or synthetic styrene silicates, such as inorganic and organic montmorillonite. The term "hydroperoxide" refers to any compound having at least one functional group of the formula -OOH. The term N-nitroso-diarylamine refers to a compound of the formula ON-N-Ar2, where each Ar is independently an aryl group. The term "maleimide" (also known as "maleimide") refers to an N-substituted 1H-pyrrole-2,5-dione. The term "imine compound" refers to a compound having discrete carbon-nitrogen double bonds. The term "hydroquinone" refers to 1,4-benzenediol and substituted 1,4-benzenediol, wherein at least one of the six hydrogen atoms of 1,4-benzenediol is replaced by a different atom (such as a halogen atom) or by a functional group (such as a hydrocarbon group, an organic heterogroup, a hydroxyl group, an amino group, a thiol, or the like).

[0088] According to the present invention, Figures 1, 2, 3 and 4 show various versions of the melt mixing apparatus.

[0089] Figure 1 shows a method and apparatus according to the present invention for manufacturing components of conductors or cable insulation. Melt-mixing production line ( [2]) From upstream to downstream and from left to right, it includes the melting and mixing device ( [4]), in this case, it is a twin-screw extruder and a melt pump ( [6]), melt sieve ( [8]) and granulation mold (

[10] ). Melt mixing device ( [4]) Melt and blend base thermoplastic polyolefin (ethylene polymer) feed (

[12] ), including any antioxidant additives, and optionally, a combination of curing agent additives. Melt pump ( [6]) helps in melt screening ( [8]) Upstream pressure buildup itself helps in the distribution of curing agent additives and improves the cleanliness of crosslinkable compound products. Granulation mold (

[10] ) granulates the formulation into a ready-to-use form. Melt mixing device ( [4]) can be a twin-screw extruder, a batch mixer (Banbury mixer), a counter-rotating twin-rotor mixer (e.g., Farrel, FCM), or a single-screw extruder. Along the melt-mixing production line ( [2]), can be injected at any site (

[14] ) Injecting curing agent additives, including: i) injecting a melt mixing device (not shown) into or above a distribution mixing section (not illustrated). [4]), ii) melt mixing device ( [4]) and melt pump ( [6]) the transition between, or iii) direct injection into the melt pump ( [6]), or a combination thereof. Multiple injection sites can be used (

[14] ) Inject the required total amount of curing agent additive, with each injection site including a portion of the curing agent additive combination.

[0090] Figure 2 shows other methods and apparatus according to the present invention for manufacturing components of conductors or cable insulation. Melt-mixing production line ( [2]) From upstream to downstream and from left to right, it includes the melting and mixing device ( [4]), in this case, it is a twin-screw extruder, crossing the melt screen ( [8]) Two melting pumps ( [6]) and granulation mold (

[10] ). Melt mixing device ( [4]) Melt and blend base thermoplastic polyolefin (ethylene polymer) feed (

[12] ), including antioxidant additives, and optionally, a combination of curing agent additives. Upstream (left-hand) melt pump ( [6]) helps in melt screening ( [8]) Upstream pressure buildup itself improves the cleanliness of crosslinkable compound products. Downstream (right-hand) melt pump ( [6]) Disperse the curing agent additive into the intermediate compound. Granulation mold (

[10] ) granulates the formulation into a ready-to-use form. Melt mixing device ( [4]) can be a co-rotating meshing twin-screw extruder, an internal batch mixer (Banbury mixer), a counter-rotating twin-screw compound mixer (e.g., Farrel, FCM), or a single-screw extruder. The curing agent additive can be injected into one or more injection sites.

[14] ) includes i) melt sieve ( [8]) and downstream melt pump ( [6]) the transfer line between, or ii) directly injected into the downstream melt pump ( [6]) Two injection sites can be used (

[14] ), which allows multiple syringes (not shown) to inject the amount of curing agent additive to the required amount.

[0091] Figure 3 shows experimental melt-mixing production lines used in some examples. [2]), and from upstream to downstream and from left to right includes the extruder (

[20] ), polymer feed section (

[12] ), injection site for the combination of curing agent additives (

[14] ), melt sieve ( [8]) and granulation mold (

[10] ).

[0092] In a preferred embodiment of the extruder, a single-screw or twin-screw extruder has a feeder, a melting screw section, and a downstream mixing section, such as a kneading block or a gear mixer. The thermoplastic polyolefin polymer feed consisting of LDPE and antioxidants can be fed through a feeder at the upstream end of the extruder barrel; the curing agent additive can be injected at any of a variety of injection sites upstream of the downstream mixing section. Example

[0093] The following examples illustrate the invention. Unless otherwise specified, all parts and percentages are by weight, all temperatures are in degrees Celsius (°C), and all preparation and testing procedures are performed under ambient conditions of room temperature (23°C) and pressure (1 atm). In the following examples and Tables 1, 2, 3, and 4, the following abbreviations are used: DCP: dicumyl peroxide; LDPE: low-density polyethylene; MDR: dynamic modulus rheometer.

[0094] The following materials are used in the following examples (unless otherwise stated, all ingredients are used as is):

[0095] Antioxidant blend A: a mixture of 61.6 wt% distearate thiopropionate (DSTDP), 37.5 wt% tris[(4-tert-butyl-3-hydroxy-2,6-dimethylphenyl)methyl)-1,3,5-triazine-2,4,6-trione (available from Solvay Chemicals as an antioxidant in CYANOX 1790) and 0.9 wt% N,N'-1,6-hexadiylbis(N-(2,2,6,6-tetramethyl-4-piperidinyl)-methoxyamine (available from BASF as an antioxidant in Uvinul 4050).

[0096] Antioxidant blend B: 50 wt% 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionic acid 2,2'-thioethylenediester (Irganox 1035) and 50 wt% DSTDP.

[0097] Antioxidant blend C: 50 wt% of 4,4'-thiobis(2-tert-butyl-5-methylphenol) (Lowinox TBM-6) and 50 wt% of 3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyldecayl)-2H-1-benzopiperan-6-ol (Irganox E-201).

[0098] Antioxidant blend D: 50 wt% neopentyl tetroxide tetra(3-(3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)propionate (Irganox 1010) and 50 wt% DSTDP.

[0099] Antioxidant 1: Tris[(4-tert-butyl-3-hydroxy-2,6-dimethylphenyl)methyl)-1,3,5-triazine-2,4,6trione (CYANOX 1790).

[0100] Light-stabilizing amine 1: Poly{6-[(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino)} (Chimassorb 944).

[0101] Low-density polyethylene polymer 1 (LDPE1): Low-density polyethylene (LDPE) is used as a basic resin for the manufacture of compounds in the laboratory. Its density is 0.92 g / cc and its melt index (MI) is 1.9 dg / min (measured at 190°C with a 2.16 kg load).

[0102] Dicumyl peroxide: DI-CUP™ (DCP) initiator (Arkema, Paris, FR, white to pale yellow granular solid (melting point 38°C, specific gravity 1.02 g / cm³ at 25°C).

[0103] Crosslinking aid 1: Triallyl isocyanurate (TAIC).

[0104] Crosslinking aid 2: Monocyclic tetra(alkenyl-organosiloxane), its chemical name is 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-cyclotetrasiloxane ("[ViD] 4").

[0105] Crosslinking aid 3: allyl 2-allyl-phenyl ether.

[0106] Crosslinking aid 4: Triallyl cyanurate (TAC).

[0107] Crosslinking aid 5: α-methylstyrene dimer (AMSD).

[0108] Examples 1 to 4 (IE1 to IE4) of the present invention: The curing agent additive comprises one organic peroxide and two crosslinking aids. The formulations in Examples 1 to 4 of the present invention are manufactured by mixing LDPE1 and an antioxidant blend in the amount indicated by a Banbury mixer, and then granulating it (Gala pelletizing system, MAAG Group, Oberglatt, CH) to produce intermediate compounds in granular form. In Examples 1 to 4 of the present invention, the granules of the intermediate compound are then melt-mixed in a twin-screw extruder and a composite production line having the configuration shown in FIG3 and under the conditions shown in Table 2 below (e.g., 145°C) to obtain a melt stream of the intermediate compound; then, under the conditions shown in Table 2 (e.g., 145°C), a combination of organic peroxide DCP and crosslinking aid 1 (TAIC) and crosslinking aid 2 ([ViD] 4) is injected into the melt stream of the intermediate compound in the twin-screw extruder to produce the crosslinkable compound composition of Examples 1 to 4 (IE1 to IE4) of the present invention. In a composite production line, the melt screen includes screen components (20 / 150 / 60 / 20).

[0109] The examples shown in Table 3 below use the same components as those listed in Table 1 below. In the following example 1 of the invention, the indicator parameters of each formulation are measured at specified time intervals, starting immediately after the formulation product is manufactured.

[0110] Immersion: Compared to the method of the present invention, a widely used comparative method for adding organic peroxides and auxiliaries to thermoplastic polyolefins involves immersing the organic peroxide and auxiliaries in liquid form in heated thermoplastic polyolefin particles. In four non-inventive experiments, intermediate compound particles were heated in an oven at 70°C for at least 4 hours and then placed in 1000 mL wide-mouth glass jars. DCP and crosslinking aid 1 (TAIC) or crosslinking aid 2 (vinyl-D4), but not both (in contrast, both are used in IE1 to IE4), were premixed in proportion and then transferred to the glass jars using a syringe. The jars were shaken thoroughly and then placed on a stone rotisserie, which was run at 30 revolutions per minute (rpm) for 10 minutes. The resulting mixture was placed in an oven at 70°C overnight for immersion, and four non-inventive compound compositions were prepared. The non-inventive compound compositions were evaluated in the same manner as those evaluated in Examples 1 to 4 of the present invention. Data from the evaluation of the four non-inventive compound compositions are available upon request. Table 1: Insulation formula of Example 1 (IE1) of the present invention [Components] [Function] [quantity(] [wt.%] [)] Low-density polyethylene polymer LDPE1 Basic LDPE resin (0.920, 2.0 MI) 98.20 Antioxidant blends antioxidants 0.15 Crosslinking aid 1: TAIC Crosslinking agent 0.30 Crosslinking aid 2: Vinyl-D4 Crosslinking aids 0.85 dicumyl peroxide free radical initiators 0.50 [total]

[0100] Table 2: Continuous Process Conditions [Total Speed] [Feed rate of intermediate compound melt stream] [Injection Rate of Curing Agent Additives] [Screw speed] [Handheld thermocouple melting point] [Calculation of residence time for curing agent additives] Kg / hr (lb / hr) Kg / hr (lb / hr) g / min rpm ℃ Second 20.4 (45.00) 20.1 (44.26) 5.61 200 145 Less than 25 seconds

[0111] Test Methods: The following test methods were used in the various examples described below. Tables 3 and 4 provide the results of these test methods.

[0112] Stability Testing: In Examples 1 of the present invention in Table 3 below, Examples 1-1, 1-2, 1-3, and 1-4 (IE1-1 to IE1-4) each comprise an identical formulation sampled over time. Samples of each formulation were collected under the same processing conditions at different time intervals after the start of injecting the curing agent additive into the melt stream of the intermediate compound according to the present invention, and were tested to demonstrate product and process stability, as shown by the consistency of product properties produced in long-term continuous melt mixing operations. The long-term continuous melt mixing operation lasted 2 to 4 hours, typically 2 to 3 hours. The sample collection time intervals were as follows: for Example 1-1, samples were obtained approximately 15 minutes after the start of injecting the curing agent additive at the indicated rate; for Example 1-2, samples were obtained at the end of the first hour; for Example 1-3, samples were obtained at the end of the second hour; and for Examples 1 to 4, samples were obtained at the end of the third hour.

[0113] In the following examples, the substrates used for testing the crosslinkable compounds were manufactured in the following manner:

[0114] Preparation of the cured substrate: In the various examples of the present invention shown, WABASH™ GENESIS™ Steam Press with quenching and cooling capabilities is used to press and cure the particles. (For the comparative compound composition, particles were pressed and cured under pressure using a WABASH™ GENESIS™ Steam Press (Wabash MPI, Wabash, IN) with quenching cooling capability after immersion. The substrate was then subjected to specified tests. Curing for the thermal creep test involved melting the particles at 120°C in a compression mold (WABASH™ GENESIS™ Steam Press) at a low pressure of 3.5 MPa (500 psi) with a mold size of 203 mm × 203 mm (8 inches × 8 inches) × 1.3 mm (50 mil) for 3 minutes, followed by compression at 17 MPa (2500 psi) at the same temperature for 3 minutes; the mold was then opened, the substrate removed, and cut into four similarly sized fragments. In the test, the four fragments were then rearranged, placed back into the mold, melted at 120°C for 3 minutes at a low pressure of 3.5 MPa (500 psi), and then further compressed at 17 MPa (2500 psi) at the same temperature for 3 minutes.) The sample was then compressed for 3 minutes at the same temperature under high pressure (psi); subsequently, the press temperature was increased to 182°C and maintained for 12 minutes to cure the sample under high pressure. After curing, the mold was cooled to room temperature under high pressure at a rate of 15°C / min.

[0115] Preparation of uncured substrate: After soaking, the granules were pressed using a Wabash™ GENESIS™ Steam Press with quenching and cooling capabilities. For MDR testing: The granules were first melted at 120°C for 3 minutes under a low pressure of 3.5 MPa (500 psi), and then compressed again at the same temperature for 3 minutes under a high pressure of 17 MPa (2500 psi); the mold was then cooled to room temperature at 15°C / min under high pressure to form the uncured substrate.

[0116] Thermal Latency: Thermal latency measures the curing properties or degree of crosslinking of a crosslinkable compound; it can also indicate the degree to which a compound has not yet crosslinked. Thermal latency refers to the elongation of a cured sample of a given crosslinkable compound under load, and is measured according to ICEA T-28-562. The thermal latency test is performed at 200°C using a 20 N / cm² weight attached to the bottom of a 1.3 mm (50 mil) dog bone sample. This sample was cut from a self-cured substrate using a die-cutting machine according to ASTM D412 Type D and marked with two baselines, each 25.4 mm from the center of the sample. The sample is placed in a preheated oven at 200°C with the weight equal to the 20 N / cm² force attached to the bottom of each sample. After 15 minutes, the elongation (distance between the baselines) is measured and used to calculate the thermal latency. The weight is then removed from the sample. After 5 minutes in the oven, the sample is removed and left at room temperature for 24 hours. Measure the elongation (distance between baselines) again and use this value to calculate heat set. Test three samples and record the average thermal creep. An acceptable thermal creep result is 100% or lower. For thermal creep, the lower the percentage of elongation, the higher the degree of cross-linking of the material.

[0117] Dynamic Modulus Rheometer (MDR): The dynamic modulus rheometer (MDR) measures the curing properties of crosslinkable compounds. This instrument measures the torque response of a deformable material. As the material undergoes crosslinking, the torque response increases, eventually reaching a maximum torque ("MH") after the peroxide has reacted under the test conditions of time and temperature. The MH value indicates the degree of crosslinking of a given compound and should be high enough to produce a crosslinkable compound. MDR tests were performed using an Alpha Technologies MDR Model 2000 unit (Alpha Technologies, Hudson, OH) measured under shear, according to ASTM procedure D5289, "Standard Test 20 Method for Rubber – Property Vulcanization Using Rotorless Cure Meters." For the test, 2.56 cm (1 inch) diameter circles were cut from an uncured substrate with a thickness of 1.905 mm (75 mil), and two 1.905 mm (75 mil) circles were stacked together. Two stacked 1.905 mm (75 mil) spherical objects were tested at 182 °C for 12 minutes to obtain MH, and at 140 °C (typical extrusion melt temperature) for different durations to obtain ts1. Both tests were performed under 0.5 degree arc oscillation. MH is denoted as torque value when the curve tends to plateau. Ideally, MH should be above 2.26 dN-m or <2 lbf-in immediately after treatment and should not change over time. Coking time, or ts1, refers to the curing kinetics that can be used to assess resistance to premature crosslinking (coking). For coking time measurements, the stated value is the time required to increase by 1 unit (inch-lbf) or 1.13 minN-meters (dN-m) from the minimum torque ("ML"). An acceptable ts1 at 140 °C should be at least 51 min or longer. Longer ts1 is better. Following the equivalent definition, other coking measures such as ts0.5, ts2, ts5, etc. can be used. Table 3: Stability and test results of Example 1 of the present invention sampled at different time intervals 1, 2, 3 and 4. [Test Nature] [IE1-1] [IE1-2] [IE1-3] [IE1-4] Example 1 Sampling time (time interval after the start of curing agent additive injection), hours 0.25 1 2 3 High torque (MH) at 182°C, in Newton-meters (lbf-inches). 0.262 (2.32) 0.262 (2.32) 0.266 (2.35) 0.269 (2.38) Low torque ML at 182°C, in Newton-meters (lbf-inches) 0.016 (0.14) 0.016 (0.14) 0.017 (0.15) 0.017 (0.15) Coking time ts1 (minutes) at 140℃ 62.07 68.49 72.17 70.14 Thermal latent change at 200℃, % 73.6 82.53 61.59 64.11

[0118] As shown in Table 3 above, the crosslinkable compound composition of Example 1 of this invention closely matches the successful crosslinkable compounds produced through a significantly longer, labor-intensive soaking process; and, comparing Examples 1-4 of this invention with Examples 1-1, 1-2, and 1-3, the crosslinkable compound compositions remain consistent during melt mixing operations. Data including I10 melt index information, the difference between maximum and minimum torque, and long coking times all indicate that the method of this invention can stably produce the same product during long-term continuous melt mixing operations, and that the crosslinkable compound composition of this invention remains crosslinkable. Table 4: Coking and Curing Criteria [Element] [IE2] [IE3] [IE4] LDPE, 2MI 98.15 98.35 98 Antioxidant blends 0.15 0.15 0.15 Crosslinking aid 1: TAIC 0.2 0.4 0.4 Crosslinking aid 2: Vinyl-D4 1 0.6 0.85 dicumyl peroxide 0.5 0.5 0.6 [total] 100 100 100 [Testing Method] [2] [3] [4] High torque (MH) at 182°C, in Newton-meters (lbf-inches). 0.244 (2.16) 0.249 (2.2) 0.295 (2.61) Low torque ML at 182°C, in Newton-meters (lbf-inches) 0.016 (0.14) 0.016 (0.14) 0.017 (0.15) Coking time ts1 (minutes) at 140℃ 71.97 72.1 52.04 Thermal latent change at 200℃, % 82% 123% 73%

[0119] As shown in Tables 3 and 4 above, the crosslinkable compound compositions of Examples 1 to 4 of this invention provide char-resistant crosslinkable compound compositions with good product consistency and crosslinkability. As shown in the char time (ts1) tests in Tables 3 and 4 above, all crosslinkable compound compositions of this invention exhibit good char time and thermal creep results.

[0120] Predictive Examples 5 to 12 (IE5 to IE12): The procedures used for IE1 to IE4 are replicated, except for the following variations: the formulations are as described in Table 6 below (the curing agent additive contains one organic peroxide and one crosslinking aid), and the processing conditions are as described in Table 5 below. Except for the handheld thermocouple melting temperature of 125°C, the processing conditions in Table 6 are the same as those in Table 2 above. The crosslinkable compound compositions of IE5 to IE12 are then tested using MDR, and the predicted results are also shown in Table 6. Table 5: Predictive Continuous Processing Conditions for IE5 to IE12 [Total Speed] [Feed rate of intermediate compound melt stream] [Injection Rate of Curing Agent Additives] [Screw speed] [Handheld thermocouple melting point] [Calculation of residence time for curing agent additives] Kg / hr (lb / hr) Kg / hr (lb / hr) g / min rpm ℃ Second 20.4 (45.00) 20.1 (44.26) 5.6 200 125 25 to 50 Table 6: IE5-IE12 (predictive). Element IE5 IE6 IE7 IE8 IE9 IE10 IE11 IE12 LDPE1, 2MI 97.94 97.72 97.89 97.94 97.94 97.94 98.04 97.89 Antioxidant blend B 0.36 0 0.36 0 0 0 0 0 Antioxidant blend C 0 0.38 0 0 0 0 0 0 Antioxidant blend D 0 0 0 0 0 0 0.36 0.36 Antioxidant 1 (Cyanox 1790) 0 0 0 0.18 0.18 0.18 0 0 HALS1 0 0 0 0.18 0.18 0.18 0 0 Crosslinking aid 3 (allyl-2-allyl-phenyl ether) 0.20 0 0 0.20 0 0 0.20 0.35 Crosslinking aid 4 (TAC) 0 0.20 0 0 0 0 0 0 Crosslinking aid 5 (AMSD) 0 0 0.35 0 0.40 0.20 0 0 dicumyl peroxide 1.50 1.70 1.40 1.50 1.30 1.50 1.40 1.40 total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Predicted maximum torque MH at 182°C, in Newton-meters (lbf-inches). 2.8 3.2 2.7 3.0 2.0 2.8 2.8 2.5 The predicted minimum torque ML at 182°C, in Newton-meters (lbf-inches). 0.19 0.18 0.19 0.19 0.19 0.19 0.21 0.20 Predicted coking time ts1 (minutes) at 140℃ 79 69 84 78 130 91 69 90

[0121] Table 6 summarizes the prediction results. ML, MH, and TS1 are as defined elsewhere in this patent application. ML values ​​below 0.3 Nm indicate low viscosity after lamination and clearly indicate that the material is not cross-linked during lamination and the injection and mixing of additives and peroxides. These prediction results indicate examples of cross-linkable compound compositions obtained by direct injection of curing agents, examples that are expected to have not undergone detectable cross-linking, and predict that the cross-linkable compound compositions are suitable for the process of this invention.

[0122] 2: Melt Mixing Production Line 4: Melting and mixing device 6: Melting Pump 8: Melt screen 10: Granulation mold 12: Basic thermoplastic polyolefin (ethylene polymer) feed / polymer feed site 14: Injection site 20: Extruder

Claims

1. A high-temperature, low-coking method for manufacturing a crosslinkable compound composition, the method comprising: injecting a combination of a curing agent additive comprising one or more organic peroxides and one or more crosslinking aids into a melt of an intermediate compound, the intermediate compound comprising one or more thermoplastic polyolefin polymers and one or more antioxidants, but lacking the one or more curing agent additives, wherein the melt is at a temperature of 120.0°C to 150.0°C; and rapidly mixing the curing agent additives into the melt within less than 60 seconds to manufacture a crosslinkable compound composition as a homogeneous mixture of the one or more thermoplastic polyolefins, the antioxidants, and the curing agent additives; wherein the crosslinkable compound composition has: The coking time (ts1) of at least 50 minutes at 140°C is described as the time required for an increase of 1 ft-pound-in (lbf-in) or 1.13 decibels-newton-meters (dN-m) from the minimum torque ("ML") at 140°C, as determined by dynamic modulus rheometer (MDR) testing according to ASTM procedure D5289; and the maximum torque (MH) at 182°C that is at least 1.92 decibels-newton-meters (dN-m; equal to at least 1.70 lbf-in) higher than the minimum torque (ML) at 182°C; and the MH at 182°C is at least 2.09 dN-m (1.85 lbf-in), as determined by dynamic modulus rheometer (MDR) testing according to ASTM procedure D5289.

2. The method of claim 1, wherein the crosslinkable compound composition is cooled to 100°C or lower in less than 5 minutes.

3. The method of claim 1, wherein the method is a high-temperature, low-coking method for continuously manufacturing crosslinkable compound components using a melt-blending production line, wherein the melt-blending production line includes a melt-blending apparatus and a downstream processing system, wherein the melt-blending apparatus has a preparation zone, an injection zone, and a mixing zone, wherein the preparation zone is configured to continuously prepare a melt stream of an intermediate compound and move the melt stream to the injection zone, wherein the injection zone has a feed point for continuously receiving the melt stream of the intermediate compound and one or more injection points for continuously injecting additives into the melt stream of the intermediate compound in the injection zone; and wherein the mixing zone has one or more mixing elements configured to rapidly homogenize the injected additives into the melt stream of the intermediate compound within 60 seconds or less; and wherein the mixing zone may be the same as or downstream of the injection zone, the method comprising: (A) At a temperature of 120.0°C to 150.0°C, a melt stream of an intermediate compound is continuously fed into the injection zone of the melt mixing apparatus via the feed point, the melt stream of the intermediate compound comprising a mixture of: one or more thermoplastic polyolefin polymer melts and one or more antioxidants, but lacking one or more curing agent additives selected from the group consisting of organic peroxides and crosslinking aids; (B) A combination of curing agent additives comprising one or more organic peroxides and one or more crosslinking aids is continuously injected into the melt stream of the intermediate compound in the injection zone of the melt mixing apparatus via at least one of the one or more injection points; (C) The combination of the intermediate compound melt stream and the injected curing agent additive is rapidly homogenized within 60 seconds or less by melt mixing to produce the crosslinkable compound composition; and (D) The stream of the crosslinkable compound composition is continuously discharged from the melt mixing apparatus into the processing system, wherein the combination of the curing agent additive has a residence time of 60 seconds or less in the melt mixing apparatus; and wherein the crosslinkable compound composition comprises: one or more thermoplastic polyolefin polymers; one or more antioxidants; one or more organic peroxides; and one or more crosslinking aids; and wherein the crosslinkable compound composition has: The coking time (ts1) of at least 50 minutes at 140°C is described as the time required for an increase of 1 lbf-in or 1.13 decibels-meters (dN-m) from the minimum torque ("ML") at 140°C, as determined by dynamic modulus rheometer (MDR) testing according to ASTM procedure D5289; and the maximum torque (MH) at 182°C that is at least 1.92 decibels-meters (dN-m; equal to at least 1.70 lbf-in) higher than the minimum torque (ML) at 182°C; and the MH at 182°C is at least 2.09 dN-m (1.85 lbf-in), as determined by dynamic modulus rheometer (MDR) testing according to ASTM procedure D5289.

4. The method of claim 3, which, after step (D), includes a processing step (E)(i) or a step (E)(II): (E)(i) wherein the processing system includes a cooling device and a granulation device, the granulation device being the same as or different from the cooling device, and step (E)(i) includes cooling and granulating the crosslinkable compound composition to produce its solid particles; or (E)(ii) wherein the processing system includes an annular coater device and a curing device, and step (E)(ii) includes coating a conductor with the crosslinkable compound composition to produce a coated conductor, and curing the coating to produce a cable comprising the conductor and an insulation layer at least partially surrounding the conductor, wherein the insulation layer comprises a crosslinkable compound composition thus formed, and the insulation is in direct contact with the conductor or indirect contact via one or more intermediate layers.

5. The method of claim 3, comprising, prior to the injection step, preparing the melt stream of the intermediate compound by melting particles of the intermediate compound or by melting particles containing one or more thermoplastic polyolefins but lacking at least one of the one or more antioxidants, and mixing the molten thermoplastic polyolefin with the at least one of the one or more antioxidants.

6. The method of claim 3, wherein prior to the continuous injection of the combination of curing agent additives in step (B), the method further comprises: pumping the melt stream of the intermediate compound via a melt pump to create a pressurized melt stream; and subsequently melting and screening the pressurized melt stream of the intermediate compound via a first melt screen located upstream of the owner of one or more injection points for injecting the combination of curing agent additives into the melt stream of the intermediate compound; wherein the melt pump and the first melt screen are located upstream of all such injection points in the injection zone of the melt mixing apparatus.

7. The method of claim 3, wherein the one or more injection points for injecting the combination of curing agent additives into the melt stream of the intermediate compound comprise any or more of the following injection points (i) to (ix): (i) wherein the mixing region of the melt mixing apparatus has a dispensing or kneading section, and the one or more injection points are located at the dispensing or kneading section at the downstream end of the melt mixing apparatus; (ii) an injection point downstream of the feed point in the injection region downstream of the feeding step (A); (iii) wherein the melt mixing apparatus sequentially comprises a second melt screen and a separate melt pump, and the one or more injection points are located downstream of the second melt screen and upstream of the separate melt pump; (iv) wherein the melt mixing apparatus sequentially comprises a second melt screen, a separate melt pump and a second melt pump, and the one or more injection points are located between the separate melt pump and the second melt pump; or (v) a combination of injection points (i) and (ii); (vi) a combination of injection points (i) and (iii); (vii) A combination of injection points (i) and (iv); (viii) A combination of any three of injection points (i) to (iv); or (ix) A combination of any one of injection points (i) to (iv).

8. The method of claim 1, wherein the crosslinkable compound composition has a thermal elongation of less than 130% at 200°C as tested according to ICEA T-28-562a.

9. The method of claim 1, comprising: sampling the crosslinkable compound composition to obtain at least one sample thereof; using the sample to measure a coking time (ts1) of at least 50 minutes at 140°C, denoted as the time required for an increase of 1 lbf-in or 1.13 decibels-meters (dN-m) from the minimum torque ("ML") at 140°C, as determined by dynamic modulus rheometer (MDR) testing according to ASTM procedure D5289; and using the sample to measure a maximum torque (MH) at 182°C that is at least 1.92 decibels-meters (dN-m; equal to at least 1.70 lbf-in) higher than the minimum torque (ML) at 182°C; and an MH at 182°C that is at least 2.09 dN-m (1.85 lbf-in), as determined by dynamic modulus rheometer (MDR) testing according to ASTM procedure D5289.

10. The method of claim 1, having one or more of the following limitations (a) to (g): (a) the melt mixing apparatus used in the method is a closed mixer or a screw extruder; (b) the method does not employ an active cooling step during or before the rapid homogenization step (C), or allows the melt of the intermediate compound to be passively cooled from a temperature equal to or above 120°C to a temperature below 120°C; (c) the method independently has 0 wt% to less than 0.10 The following are wt% of any one of compounds (i) to (vi): (i) montmorillonite; (ii) hydroperoxide; (iii) N-nitroso-diarylamine; (iv) maleic diacetylimine; (v) an imine compound; and (vi) hydroquinone, wherein each wt% is based on the total weight of the combination of the intermediate compound and the curing agent additive; (d) limiting both (a) and (b); (e) limiting both (a) and (c); (f) limiting both (b) and (c); or (g) limiting each of (a), (b) and (c).

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