High-temperature, low-scorch method for producing a crosslinkable compound composition and the composition produced thereby.

Abstract

Provided is a high temperature, low scorch (including no scorch) method for making a crosslinkable compound composition, the method comprising melt blending a primary stream at a temperature between 120.0°C and 150.0°C, the primary stream comprising one or more thermoplastic polyolefins and one or more antioxidants, but lacking a curing additive selected from the group consisting of peroxides and crosslinking coagents, and injecting a combination of curing additives comprising one or more organic peroxides and one or more crosslinking coagents into the blended melt to homogeneously mix the one or more thermoplastic polyolefins, one or more antioxidants, one or more organic peroxides, and one or more crosslinking coagents by melt blending them together. Also provided are methods for making crosslinked compound compositions and articles of manufacture.

Description

[Technical Field]

[0001] This technical field relates to a method for producing a crosslinkable compound composition comprising a thermoplastic polyolefin and an additive, and to a composition produced thereby. [Background technology]

[0002] Introduction Thermoplastic polyolefins (TPOs), such as thermoplastic polyethylene (TPE), are polymer hydrocarbons that melt and flow at "high temperatures," broadly defined herein as temperatures between 110°C and 190°C, depending on the specific TPO. Crosslinkable compound compositions comprise TPOs and additives such as antioxidants, fillers, colorants, and curing agents, which are compounds that initiate free radical crosslinking or increase the concentration of crosslinks formed thereon (sometimes called crosslink density). The "crosslinkable" characteristic can be determined by compressing a sample of the crosslinkable compound composition into a plaque and measuring the maximum torque (MH). The inventors define a "crosslinkable" compound composition as 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 measured by a moving direometer (MDR) test according to ASTM procedure D5289.

[0003] Scorching is the premature crosslinking of TPO during the pre-melt processing of TPO with additives for the production of crosslinkable compound compositions. The susceptibility of a composition to scorching can be detected and measured by compressing a sample of the crosslinkable compound composition into a plaque and measuring the time to the onset of scorching. The inventors define "low scorching" as a scorching time (ts1) of at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, at 140°C, reported as the time required to increase 1 unit (inch-lb) or 1.13 decinewton-meter (dN-m) from the minimum torque ("ML") by a moving direometer (MDR) test according to ASTM Procedure D5289. The inventors define "no scorching" as having a scorching time (ts1) greater than 150 minutes at 140°C, where the scorching time (ts1) at 140°C is measured as described herein.

[0004] Scorching is an industrial problem. It ultimately creates defects in manufactured goods. These defects may include cracks, gels, or voids, which can lead to mechanical failure of the manufactured goods. For example, if a crosslinkable compound composition used to manufacture an insulating layer covering a conductive core in power cables, such as medium voltage (MV), high voltage (HV), or very high voltage (EHV) power cables, undergoes scorching during pre-melting, the insulating layer may ultimately develop small cracks, voids, or gels. This can cause premature failure of the power cable.

[0005] Therefore, in order to prevent or minimize defects caused by scorching during the pre-melting process of TPO with additives, a method used in the art to produce a crosslinkable compound composition includes: (a) a step of melt-blending a molten TPO with additives such as antioxidants, fillers, and colorants, rather than curing additives, to produce an intermediate molten material that does not contain curing additives; (b) a step of pelletizing the intermediate molten material; (c) a step of immersing the pellets in a curing additive (e.g., an organic peroxide and a crosslinking aid) at a temperature of 50°C to 90°C for 1 to 24 hours (i.e., below the melting temperature of TPO and below the decomposition temperature of the organic peroxide) to obtain a crosslinkable compound composition as pellets; (d) a step of melting the crosslinkable compound composition; (e) a step of extruding the molten material to form a manufactured article; and (f) a step of curing the extruded molded article.

[0006] A known method for manufacturing electrical cable insulation involves melt-compounding a polyolefin-based resin and incorporating additives such as antioxidants to produce a compound material, filtering the compound material, then pelletizing it to produce an intermediate pellet compound that does not contain a free radical initiator (also called a crosslinking initiator), and then impregnating or immersing the intermediate compound pellets with a free radical initiator in a “immersion” tower to incorporate the free radical initiator therein to produce a compound for manufacturing cable insulation. This method requires at least a compounder and an immersion tower, and the compound for manufacturing cable insulation includes a crosslinkable compound (also called a thermoplastic crosslinkable compound) in the form of pellets that are crosslinked when downstream cable manufacturers manufacture the cables themselves. Therefore, bringing the intermediate granules or pellets to a suitable temperature (e.g., around 70°C) and then incorporating the free radical initiator involves immersing them to physically mix them with the intermediate pellets. The resulting fully compounded granules or pellets are immersed for several hours at a suitable temperature for the free radical initiator to diffuse into the granules or pellets, until the surface of the pellets is dry. To achieve a uniform distribution of free radical initiators in the pellets, additional immersion in the packaging container may be necessary. Immersion towers involve very large and expensive equipment, thereby limiting the feasibility of developing multiple compounding sites or plants for producing compounds for cable insulation. Therefore, there is still a need to enable the compounding of all materials in the compounds for cable insulation without using or requiring an immersion tower, for example, to produce the crosslinkable pellets. The fully compounded pellets need to be cooled before they are transported, and therefore, conventional methods require a heating vessel (optional) and a cooling device such as a fluidized bed or cooling vessel (required).

[0007] Conventional polyolefin compounding lines for cable insulation compounds do not allow for the incorporation of free radical initiators into the base resin. Rather, free radical initiators are incorporated by immersion in the base resin, for example in immersion tower facilities, during long processing and handling periods, which results in a high-cost process. In addition, the large volume of material in the facility can lead to a high risk of external contamination, as well as the need for many cleanrooms and associated staff to handle the material. This, needless to say, results in energy consumption in additional processing, leading to significant carbon dioxide emissions.

[0008] Furthermore, in conventional compounding processes, injecting free radical initiators into polymer melts remains extremely difficult because the free radical initiators decompose and react under the conditions and time required to compound the base resin and antioxidant (AO) additives. In the production of suitable cable insulation compounds, the specific input energy (SEI) required to melt and mix the polyolefin base resin and antioxidant (AO) additives to properly distribute the AO additives and, more importantly, to achieve an acceptable high production rate, typically results in excessive melting temperatures of the intermediate compounds, e.g., above 180°C. At such temperatures, decomposition of the free radical initiators occurs, resulting in undesirable chemical crosslinking reactions and unusable products.

[0009] Zhang et al.'s recent U.S. Patent Publication 2020 / 0199270(A1) discloses a composition comprising a polyolefin polymer, an alkenyl-functionalized monocyclic organosiloxane, and an organic peroxide. The composition is found to have applications as a wire and cable coating acting as an insulator. While Zhang et al. generally refer to mixing all the materials in the composition, the only method disclosed for incorporating the peroxide into the composition involves immersion. [Overview of the project]

[0010] According to embodiments of the present invention, the inventors have solved the problem of providing a stable crosslinkable compound composition for use as a compound for manufacturing cable insulators that does not require a dipping step to incorporate a crosslinking initiator into the composition. Embodiments of the present invention relate to a method of production, in particular to a method of producing a crosslinkable compound composition comprising a thermoplastic polyolefin and additives, high temperature, low scorch (including no scorch), defined herein as a scorch time (ts1) of more than 150 minutes at 140°C, where the scorch time (ts1) at 140°C is measured as described herein. Also included are methods for producing crosslinked compositions and manufactured articles from the crosslinkable compound composition.

[0011] A method for producing a high-temperature, low-scorch (including no-scorch) crosslinkable compound composition is provided, wherein the scorch time (ts1) at 140°C is defined herein as exceeding 150 minutes, and the scorch time (ts1) at 140°C is measured as described herein, the method comprising: melt-blending a primary flow at a temperature of 120.0°C to 150.0°C or 125°C to 149°C, wherein the primary flow comprises one or more thermoplastic polyolefins and one or more antioxidants, but lacks curable additives selected from the group consisting of peroxides and crosslinking aids; and injecting a combination of curable additives comprising one or more organic peroxides and one or more crosslinking aids into the blunt mixture, thereby homogeneously mixing one or more thermoplastic polyolefins, one or more antioxidants, one or more organic peroxides, and one or more crosslinking aids together by melt-blending them. A method for producing a crosslinked compound composition and a manufactured article is also provided. [Brief explanation of the drawing]

[0012] [Figure 1] An example of a melt-mixing line 2 according to the present invention is shown. [Figure 2] An alternative example of the melt-mixing line (2) according to the present invention is shown. [Figure 3] This shows a melt compounding line (2) used to produce the crosslinkable compound in the examples of the present invention. [Modes for carrying out the invention]

[0013] According to embodiments of the present invention, the inventors have solved the problem of providing a stable crosslinkable compound composition for use as a compound for manufacturing cable insulators that does not require a dipping 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, and the free radical generating compound is useful for initiating carbon radical-based crosslinking of thermoplastic polyolefins, optionally together with an unsaturated crosslinking aid. Embodiments of the present invention relate to manufacturing methods, in particular high-temperature, low-scorch (including no-scorch) manufacturing methods, thermoplastic polyolefins, and additives, where the scorch time (ts1) at 140°C is defined herein as a scorch time of more than 150 minutes, and the scorch time (ts1) at 140°C is measured as described herein. Also included are methods for producing crosslinked compositions and manufactured articles from crosslinkable compound compositions. In some embodiments, the methods and crosslinkable compound compositions of the present invention lack, i.e., do not contain, any acid additives. In other words, acidic compounds such as Brønsted acids, including sulfonic acids, and / or Lewis acids, including added dialkyltin dicarboxylates, are not added as components of this method or composition. The acid additives do not include acidic by-products or acidic decomposition products that may be generated in situ by the reaction or decomposition of other components used herein. As described later, if necessary, hindered amine stabilizers (HAS) can be included in this method and composition to neutralize potentially situ-generated acidic by-products or acidic decomposition products.

[0014] A method for producing a high-temperature, low-scorch (including no-scorch) crosslinkable compound composition is provided, wherein the scorch time (ts1) at 140°C is defined herein as exceeding 150 minutes, and the scorch time (ts1) at 140°C is measured as described herein, the method comprising: melt-blending a primary flow at a temperature of 120.0°C to 150.0°C or 125°C to 149°C, wherein the primary flow comprises one or more thermoplastic polyolefins and one or more antioxidants, but lacks curing additives selected from the group consisting of peroxides and crosslinking aids; and injecting a combination of curing additives comprising one or more organic peroxides and one or more crosslinking aids into the blunt mixture, thereby homogeneously mixing the one or more thermoplastic polyolefins, one or more antioxidants, one or more organic peroxides, and one or more crosslinking aids together by melt-blending them. A method for producing a crosslinked compound composition and a manufactured article is also provided.

[0015] To facilitate cross-referencing, some embodiments of the present invention are described as numbered embodiments.

[0016] Embodiment 1. A high-temperature, low-scorch method for producing a crosslinkable compound composition, comprising: injecting a combination of one or more organic peroxides and one or more curable additives containing crosslinking aids into a molten intermediate compound containing one or more thermoplastic polyolefin polymers and one or more antioxidants (AOs) but not one or more curable additives, wherein the molten compound is heated to a temperature of 120.0°C to 150.0°C; and rapidly mixing the curable additives into the molten compound in less than 60 seconds to produce a crosslinkable compound composition as a homogeneous mixture of one or more thermoplastic polyolefins, antioxidants, and curable additives.

[0017] Embodiment 2. When the crosslinkable compound composition is determined by a moving direometer (MDR) test according to ASTM Procedure D5289, a scorching time (ts1) of at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, at 140°C, which is reported as the time required at 140°C for an increase of 1 foot-pound-inch (lbf-in) or 1.13 desinewton-meter (dN-m) from the minimum torque ("ML"), and by a moving direometer (MDR) test according to ASTM Procedure D5289 The method according to Embodiment 1, wherein, when determined, the maximum torque at 182°C (MH) is at least 1.92 decinewton-meters (dN-m; equal to at least 1.70 lbf-in) higher than the minimum torque at 182°C ("ML"), preferably MH is at least 1.92 dN-m (at least 1.70 lbf-in) higher than ML at 182°C, and 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).

[0018] Embodiment 3. The method according to Embodiment 1 or Embodiment 2, comprising cooling the crosslinkable compound composition to a temperature of 100°C or lower, preferably 80°C or lower, in less than 5 minutes, and further cooling it to a temperature of 30°C or lower, preferably in less than 6 hours.

[0019] Embodiment 4. A high-temperature, low-scorch method for continuously producing a crosslinkable compound composition using a melt-mixing line including a melt-mixing apparatus and a downstream processing system, wherein the melt-mixing apparatus has a preparation zone, an injection zone, and a mixing zone, the preparation zone is configured to continuously prepare a molten flow of an intermediate compound and move the molten flow to the injection zone, the injection zone has injection points for continuously receiving a molten flow of an intermediate compound and one or more injection points for continuously injecting additives into the molten flow of an intermediate compound in the injection zone, the mixing zone has one or more mixing elements (e.g., one or more rotor blades or screws, and optionally baffles) configured to rapidly homogenize the additives injected into the molten flow of an intermediate compound (in 60 seconds or less), and the mixing zone has, The method, which may be the same as the injection zone or downstream of the injection zone, is to (A) continuously supply a molten intermediate compound to the injection zone of the melt compounding apparatus via a supply point at a temperature of 120.0°C to 150.0°C or 125°C to 149°C, comprising a mixture of one or more thermoplastic polyolefin polymers and one or more antioxidants (AO), but without one or more curable additives selected from the group consisting of organic peroxides and crosslinking aids, wherein each of the one or more thermoplastic polyolefins is independently selected from the group consisting of polyethylene homopolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, and ethylene / 1-octen copolymer, and more preferably each of the one or more thermoplastic polyolefins has a concentration of 0.87 g / cm³ when measured according to ASTM D792. 3 ~0.94g / cm 3(B) Continuously supplying a combination of curable additives comprising one or more organic peroxides and one or more crosslinking aids to the molten flow of the intermediate compound in the injection zone of a melt compounding apparatus via at least one of one or more injection points; (C) Rapidly homogenizing the molten flow of the intermediate compound and the injected combination of curable additives by melt compounding the molten flow of the intermediate compound and the injected combination of curable additives to produce a crosslinkable compound composition; and (D) Continuously discharging the flow of the crosslinkable compound composition from the melt compounding apparatus to a processing system, wherein the combination of curable additives has a residence time of 60 seconds or less in the melt compounding apparatus, and the crosslinkable compound composition comprises one or more thermoplastic polyolefin polymers and one or more antioxidants. The crosslinkable compound composition comprises one or more organic peroxides and one or more crosslinking aids, and has a scorching time (ts1) of at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, at 140°C, which is reported as the time required at 140°C for an increase of 1 foot-pound-inch (lbf-in) or 1.13 decinewton-meters (dN-m) from the minimum torque ("ML") as determined by a moving direometer (MDR) test according to ASTM Procedure D5289, and a maximum torque (MH) at 182°C that is at least 1.92 decinewton-meters (dN-m; equal to at least 1.70 lbf-in) higher than the minimum torque ("ML") at 182°C, wherein the MH at 182°C is at least 2.09 dN-m (1.85 The method according to any one of embodiments 1 to 3, comprising continuously discharging at a rate of lbf-in, more preferably at least 2.26 dN-m (2.0 lbf-in).

[0020] Embodiment 5. The method according to Embodiment 4, wherein the process includes a processing step (E)(i) or a processing step (E)(II) after step (D), wherein in (E)(i), the processing system includes a cooling device and a pelletizing device (which may be the same as or different from the cooling device), and step (E)(i) includes cooling and pelletizing the crosslinkable compound composition to produce solid pellets thereof, or in (E)(ii), 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 (fiber optic), with the crosslinkable compound composition to produce a coated conductor, and curing the coating to produce a cable comprising the conductor and an insulating layer at least partially surrounding the conductor, wherein the insulating layer comprises the crosslinkable compound composition produced thereby, and the insulator is in direct contact with the conductor or indirectly in contact with it via one or more intervening layers (e.g., semiconductor layers).

[0021] Embodiment 6. The method according to Embodiment 4 or Embodiment 5, comprising, before the injection step, preparing a molten flow of the intermediate compound by either melting pellets of the intermediate compound or melting pellets containing one or more thermoplastic polyolefins but not containing at least one of one or more antioxidants, and mixing the molten thermoplastic polyolefin with at least one of one or more antioxidants.

[0022] Embodiment 7. The method according to any one of Embodiments 4 to 6, wherein, prior to step (B) of continuously injecting a combination of curable additives, the method further comprises pumping a molten flow of an intermediate compound through a melt pump to produce a pressurized molten flow, and then melt-screening the pressurized molten flow of the intermediate compound through a first molten screen located upstream of all one or more injection points for injecting a combination of curable additives into the molten flow of the intermediate compound, wherein the melt pump and the first molten screen are located upstream of all injection points in the injection zone of the melt compounding apparatus.

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

[0024] Embodiment 9. One or more injection points for injecting a combination of curable additives into the molten flow of the intermediate compound are the following injection points (i) to (ix): (i) one or more injection points in the distribution mixing or kneading section at the downstream end of the melting compound, when the mixing zone of the melting compound has a distribution or kneading section; (ii) an injection point downstream of the supply point in the injection zone downstream of the supply process (A); (iii) one or more injection points downstream of the second melting screen and upstream of the separate melting pump, when the melting compound sequentially includes a second melting screen and a separate melting pump. The method according to any one of embodiments 4 to 8, wherein (iv) when the melting and compounding apparatus sequentially comprises a second melting screen, a separate melting pump, and a second melting pump, one or more injection points located between the separate melting pump and the second melting pump, or (v) one or more of the following: 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) any three combinations of injection points (i) to (iv), or (ix) each of the combinations of injection points (i) to (iv).

[0025] Aspect 10. Limitations (i) to (vii): (i) One or more antioxidants contain a mixture of two or more antioxidants, preferably two or three antioxidants, or one or more crosslinking aids contain an alkenyl group-containing monocyclic organosiloxane, or one or more antioxidants contain a mixture of two or more antioxidants, preferably two or three antioxidants, and one or more crosslinking aids contain an alkenyl group-containing monocyclic organosiloxane; (ii) one or more crosslinking aids contain an alkenyl group-containing monocyclic organosiloxane of formula (I): [R 1 ,R 2 SiO 2 / 2 n (I) [where the subscript n is an integer of 3 or more, each R 1 is independently (C2-C4) alkenyl or H2C=C(R 1a )-C(=O)-O-(CH2) m -, where R 1a is H or methyl, the subscript m is an integer of 1 to 4, and each R 2 is independently H, (C1-C4) alkyl, phenyl, or the same as R 1 ; (iii) one or more organic peroxides contain dicumyl peroxide or a cumyl group-containing peroxide; (iv) both limitations (i) and (ii); (v) both limitations (i) and (iii); (vi) both limitations (ii) and (iii); (vii) any one of limitations (i) to (iii), the method according to any one of Aspects 1 to 9.

[0026] Aspect 11. There is one thermoplastic polyolefin, and the thermoplastic polyolefin has a density of 0.87 g / cm 3 to 0.94 g / cm 3 when measured according to ASTM D792.The density is in the range of [value missing] and, when determined according to ASTM D1238 and reported in grams eluted per 10 minutes, it has a melt index (I2) of 0.5 g / 10 min to 20 g / 10 min at 190°C / 2.16 kg, or one or more thermoplastic polyolefin polymers include one or more thermoplastic polyethylene polymers, preferably each of the one or more thermoplastic polyolefins is independently selected from the group consisting of polyethylene homopolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, and ethylene / 1-octene copolymer, and more preferably each of the one or more thermoplastic polyolefins has a melt index of 0.87 g / cm³ when measured according to ASTM D792. 3 ~0.94g / cm 3 The method according to any one of embodiments 1 to 10, independently selected from the group comprising low-density polyethylene polymers having a density in the range of and a melt index (I2) of 0.5 g / 10 min to 20 g / 10 min, as determined according to ASTM D1238 at 190°C / 2.16 kg.

[0027] Embodiment 12. The method according to any one of Embodiments 1 to 11, wherein the crosslinkable compound composition has a high-temperature creep elongation at 200°C of less than 130%, preferably less than 100%, as determined by testing in accordance with ICEA T-28-562a.

[0028] Embodiment 13. Sampling a crosslinkable compound composition to obtain at least one sample thereof, and using the sample, measuring a scorch time (ts1) at 140°C for at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, which is reported as the time required at 140°C for an increase of 1 foot-pound-inch (lbf-in) or 1.13 desimonewton-meter (dN-m) from the minimum torque ("ML") as determined by a moving dirometer (MDR) test according to ASTM Procedure D5289, and the test The method according to any one of embodiments 1 to 12, comprising: using a material, measuring that the maximum torque at 182°C (MH) is at least 1.92 decinewton-meters (dN-m; equal to at least 1.70 lbf-in) higher than the minimum torque at 182°C ("ML") as determined by a moving direometer (MDR) test in accordance with ASTM procedure D5289, and that 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).

[0029] Embodiment 14. The method according to any one of Embodiments 1 to 13, comprising: molding a molten crosslinkable compound composition to form a molded crosslinkable compound composition, preferably extruding the molten crosslinkable compound composition as an insulating layer covering a conductive core; curing the molded crosslinkable compound composition to manufacture a manufactured article containing the crosslinked compound composition, preferably curing the insulating layer to manufacture a power cable containing a conductive core and a crosslinked insulating layer.

[0030] Appearance 15. The following restrictions (a) to (g): (a) The melting and compounding apparatus used in this method is an internal mixer or a screw extruder; (b) This method does not use any process to actively cool the molten intermediate compound from a temperature of 120°C or higher to a temperature of less than 120°C, or from a temperature of 141°C or higher to a temperature of less than 141°C (for example, via a cooling zone in a heat exchanger or extruder apparatus) or a process to passively cool it during or before the rapid homogenization process (C); (c) This method independently contains 0% to less than 0.10% by weight of a compound (i) to (vi): (i) Montmol The method according to any one of embodiments 1 to 14, having (ii) one of lilonite, (iii) a hydroperoxide, (iv) an N-nitroso-diarylamine, (iv) a maleimide, (v) an imine compound, and (vi) a hydroquinone, or not having any of them (i.e., lacking them, i.e., 0% by weight) (where each % by weight is based on the total weight of the combination of the intermediate compound and the curable additive), (d) both of restrictions (a) and (b), (e) both of restrictions (a) and (c), (f) both of restrictions (b) and (c), or having one or more of each of restrictions (a), (b), and (c). With respect to restriction (b), cooling is permitted as long as the temperature of the molten flow of the intermediate compound does not drop below 120°C or below 125°C. Some such embodiments of the present invention do not include both compounds (i) and (ii), nor both compounds (i) and (vi), nor both compounds (ii) and (vi), nor each of compounds (i), (ii), and (vi), nor each of compounds (i), (ii), (v), and (vi), nor any five of compounds (i) to (vi), nor any of compounds (i) to (vi). If any of compounds (i) to (vi) are found to have an anti-scorching effect, whether found or not, the minimum amount of such compound required to exhibit effective anti-scorching in the method of the present invention is expected to be at least 0.10% by weight, and possibly higher.

[0031] Embodiments of this method are continuous. This means that the feeding, injecting, mixing, and discharging steps of these embodiments, as well as any processing steps, operate 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. Provided that sufficient quantities of components (e.g., thermoplastic polyolefins, antioxidants, curing additives) are available and there is no power outage (e.g., loss of power), embodiments of the continuous method can operate indefinitely without interruption until one or more pieces of equipment in the melt compounding line need to be shut down for cleaning or repair. In a typical manufacturing operation, embodiments of the continuous method can easily operate without interruption for 7 days, 4 weeks, or 6 months, or longer.

[0032] The crosslinkable compound composition is prepared by high-temperature low-scorch (including no scorch), defined herein as a scorch time (ts1) greater than 150 minutes at 140°C, where the scorch time (ts1) at 140°C is measured as described herein, and the method may be described as “organic peroxide-containing homogeneous mixed crosslinkable compound composition”. The “organic peroxide-containing” feature of the crosslinkable compound composition means that the composition has a sufficient crosslinking-effective amount of undegraded organic peroxide to act as a free radical generator during the method of subsequently curing the crosslinkable compound composition to produce the crosslinkable compound composition. “Crosslinking-effective amount” means the maximum torque (MH) at 182°C. This composition satisfies the limitations described below. The “homogeneous” aspect of the “homogeneous mixed” feature of the crosslinkable compound composition means that the crosslinkable compound composition has a uniform distribution of components throughout its cross-section. The "mixed" aspect of the "uniformly mixed" characteristic means that the curable additive, including the organic peroxide and crosslinking aid, is mechanically mixed into the molten flow of the intermediate compound composition by means of immersion, absorption, grinding (e.g., two-roll grinding), calendering, or by methods that do not involve acoustic stirring.

[0033] In some embodiments of aspects 1 to 15, including some of the above embodiments having any one of restrictions (a) to (g), the combination of curable additives comprises one organic peroxide and two crosslinking aids. In some 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-tetravinylcyclotetrasiloxane ("vinyl-D4"). In some such embodiments, the organic peroxide is dicumyl peroxide and the two crosslinking aids are TAIC and vinyl-D4.

[0034] The present invention also claims a crosslinkable compound composition manufactured by any one of the methods of embodiments 1 to 15. The crosslinkable compound composition of the present invention differs from the comparative compound composition in at least one property or component. The comparative compound composition contains all the same components as the crosslinkable compound composition of the present invention, but is manufactured by a different method with respect to the incorporation of one or more organic peroxides. The comparative compound composition is prepared by a comparative method comprising: melt-compounding all the same components except one or more organic peroxides to produce a second-to-last mixture; pelletizing the second-to-last mixture to produce pellets; and immersing the same one or more organic peroxides in the pellets of the second-to-last mixture to produce a comparative compound composition in pellet form. The thermal history of the crosslinkable compound composition of the present invention differs from that of the comparative compound composition due to the different method of manufacturing it. As a result of the different thermal histories, the crosslinkable compound composition of the present invention may differ from the comparative compound composition in at least one embodiment selected from the group consisting of: component proportions, component concentrations, melt rheological properties, and mechanical properties. Beneficially, the method of the present invention may be more efficient, faster (i.e., have higher productivity), and / or more cost-effective than comparative methods that involve immersion in 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 the comparative methods.

[0035] While not bound by theory, the present invention provides a method for producing a crosslinkable compound composition having essentially a ts1 of at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, at 140°C, which is evidence of low scorching (including no scorching), as defined herein as a scorching time (ts1) at 140°C greater than 150 minutes, and where the scorching time (ts1) at 140°C is measured as described herein in the method of the present invention, and where the maximum torque (MH) at 182°C is essentially at least 1.92 dN-m (at least 1.70 lbf-in) higher than the 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, at least one of the one or more crosslinking aids is considered to act independently as an anti-scorching additive (SRA) to achieve ts1 at 140°C for at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, or at least one of the one or more crosslinking aids acts independently as a crosslinking booster additive (CBA) to achieve 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 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), or a combination thereof. The one or more crosslinking aids may include, or consist of, one crosslinking aid that acts as both an SRA and a CBA, or two crosslinking aids, one acting as an SRA and the other as a CBA. In some embodiments, one or more crosslinking aids are crosslinking aids that act as anti-scorch additives (SRAs).In some embodiments, 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 2.26 dN-m (2.0 lbf-in), or 2.37 dN-m (2.10 lbf-in) to 2.98 dN-m (2.64 lbf-in), or 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 crosslinking aids that act as anti-scorch additives (SRAs), with a ts1 at 140°C of at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, and a maximum torque (MH) at 182°C of at least 2.26 dN-m (2.0 lbf-in), or 2.37 dN-m (2.10 lbf-in) to 2.98 dN-m (2.64 lbf-in), or 2.61 dN-m (2.31 lbf-in) to 2.96 dN-m (2.62 lbf-in).

[0036] While not bound by theory, melting and compounding temperatures of 120.0°C to 150.0°C, or 125°C to 149°C, are considered unusually high for use with organic peroxides, and a ts1 of at least 50 minutes, or at least 60 minutes, preferably at least 65 minutes, at 140°C is evidence of low scorching (including no scorching), as defined herein as a scorching time (ts1) at 140°C greater than 150 minutes, and a scorching time (ts1) at 140°C measured as described herein in the method of the present invention, with a maximum torque (MH) at 182°C at least 1.92 dN-m (at least 1.70 lbf-in) higher than ML at 182°C, or MH at 182°C at least 2.09 dN-m (1.85 lbf-in), preferably at least 2.26 dN-m (2.0 lbf-in), is considered evidence of the crosslinkability of the crosslinkable compound composition produced by the method of the present invention.

[0037] As shown in the embodiments of the present 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 using a moving dirometer (MDR) tested at 182°C according to ASTM procedure D5289, the torque increases from 2.44 dN-m to 2.95 dN-m (2.16 lbf-in to 2.61 lbf-in), depending on the specific embodiment of the present invention. Thus, during the MDR test at 182°C, the torque increases from the ML value to the MH value, where the torque value plateaus or no longer increases. As shown in the examples of the present invention, in some embodiments, the maximum torque (MH) at 182°C is at least 2.7 dN-m (at least 2.4 lbf-in) higher than the ML at 182°C.

[0038] The production of a primary flow containing one or more antioxidants and one or more thermoplastic polyolefins (collectively the primary flow components) but lacking one or more curable additives selected from the group consisting of organic peroxides and crosslinking aids, by supplying one or more antioxidants and one or more thermoplastic polyolefins to a melt compounding apparatus via one or more supply points, can be achieved by any one of the following methods: In one embodiment, at least one of the one or more antioxidants may be supplied to the melt compounding apparatus separately from at least one of the one or more thermoplastic polyolefins. 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 produce a combination thereof, which may then be supplied to the melt compounding apparatus. In another embodiment applicable when there are at least two antioxidants or at least two thermoplastic polyolefins or a combination thereof, at least one antioxidant and / or at least one thermoplastic polyolefin is supplied separately to the melt compounding apparatus, and a combination of at least one antioxidant and at least one thermoplastic polyolefin is supplied separately to the melt compounding apparatus.

[0039] According to this embodiment, injecting a combination of curable additives into the molten flow of an intermediate compound includes injecting them at any of the following injection points: (i) a distribution mixing or kneading section at the downstream end of the melting compounding apparatus, (ii) an injection point downstream of the melting formation in the melting compounding apparatus itself, (iii) a molten screen located downstream of the melting compounding apparatus but upstream of a separate molten pump, preferably (iv) an upstream of a second molten pump located at a point downstream of both the separate molten pump and the molten screen in (iii), or (v) one or more, or all, of any combination thereof.

[0040] Preferably, in order to control the overall melting temperature of the intermediate compound, the method according to the present invention further comprises adding a solid thermoplastic polyolefin as a second feed to the molten flow of the intermediate compound, for example, upstream of all injection points or at any adjacent point, and melting the second feed. The weight ratio of the thermoplastic polyolefin in the second feed to the weight of the thermoplastic polyolefin in the primary flow 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 thermoplastic polyolefin in the method of the present invention is measured according to ASTM D792 to 0.87 g / cm³. 3 ~0.94g / cm 3 It has a density in the range of [value missing], and when measured at 190°C / 2.16 kg according to ASTM D1238, it has a melt index (I2) of 0.5 g / 10 min to 20 g / 10 min, and is reported as grams eluted per 10 minutes.

[0042] Preferably, one or more crosslinking aids in the method of the present invention are of formula (I): [R 1 ,R 2 SiO 2 / 2 ] n (I) contains a monocyclic organosiloxane [wherein the formula, the subscript n is an integer greater than or equal to 3, and each R 1 These are independently (C2~C4) alkenyls or H2C=C(R 1a)-C(=O)-O-(CH2) m - and in the formula, R 1a is H or methyl, the subscript m is an integer from 1 to 4, and each R 2 These are independently H, (C1-C4) alkyl, phenyl, or R 1 It is the same as, for example, tetramethyl-tetravinyl-cyclotetrasiloxane such as 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-cyclotetrasiloxane.

[0043] In another aspect of the present invention, the homogeneous thermoplastic polyolefin crosslinkable compound composition is a thermoplastic polyolefin polymer, for example, 0.87 g / cm³ as measured according to ASTM D792. 3 ~0.94g / cm 3 A low-density polyethylene polymer having a density in the range of and a melt index (I2) of 0.5 g / 10 min to 20 g / 10 min, or preferably 0.5 g / 10 min to 10 g / 10 min, when measured at 190°C / 2.16 kg according to ASTM D1238, reported in grams eluted per 10 min, one or more antioxidants (AO), such as hindered phenol or hindered amine or a mixture thereof, and one or more crosslinking aids, for example, formula (I): [R 1 ,R 2 SiO 2 / 2 ] n Alkenyl group-containing monocyclic organosiloxane [wherein the formula, the subscript n is an integer of 3 or greater, and each R 1 These are independently (C2~C4) alkenyls or H2C=C(R 1a )-C(=O)-O-(CH2) m - and in the formula, R 1a is H or methyl, the subscript m is an integer from 1 to 4, and each R 2 These are independently H, (C1-C4) alkyl, phenyl, or R 1The composition comprises, preferably, tetramethyl-tetravinyl-cyclotetrasiloxane and one or more organic peroxides as crosslinking initiators, such as dicumyl peroxide or cumyl group-containing peroxides. The composition may further contain 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% to 1.5% by weight, or preferably 0.1% to 1% by weight, based on the total weight of the crosslinkable compound composition. The total amount of one or more organic peroxides may be in the range of 0.1% to 2% by weight, or preferably 0.3% to 1.4% by weight, based on the total weight of the crosslinkable compound composition. The total amount of one or more crosslinking aids may be in the range of 0.1% to 5% by weight, or preferably 0.3% to 4% by weight, or more preferably 0.5% to 2% by weight, all weight percentages are based on the total weight of the crosslinkable compound composition. The hindered phenol may be a 2,6-di(tertiary alkyl)phenol, and the hindered amine may contain a diradical secondary amino group of formula -C(alkyl)2-N(H)-C(alkyl)2- or a diradical tertiary amino group of formula -C(alkyl)2-N(alkyl)-C(alkyl)2-.

[0044] Preferably, within one hour after the completion of melt compounding, the crosslinkable compound composition according to the present invention has one or more of the following: (i) a scorch time (ts1) at 140°C of at least 51 minutes, preferably at least 55 minutes, or more preferably at least 65 minutes, as determined by a moving direometer (MDR) test according to ASTM Procedure D5289, reported as the time required to increase the minimum torque ("ML") by 1 unit (inch-lbf) or 1.13 decinewton-meter (dN-m); (ii) a maximum torque (MH) of at least 2.26 dN-m (2.0 lbf-in) at 182°C, as determined by a moving direometer (MDR) test according to ASTM Procedure D5289; or (iii) a high-temperature creep elongation of less than 100%, as determined at 200°C according to ICEA T-28-562.

[0045] According to the present invention, a method of injecting a peroxide and one or more crosslinking aids acting as anti-scorch additives (SRAs) into a molten flow of a thermoplastic polyolefin polymer, such as a low-density polyethylene polymer, immediately provides a homogeneous thermoplastic polyolefin crosslinkable compound, even before cooling from processing. Injection during molten compounding into a molten compounding apparatus, mixer, extruder or kneader or their distributing mixing elements does not require a molten cooling step or post-treatment with initiators to produce crosslinkable compounds such as pellets or other raw materials suitable for later use as cable insulation manufacturing compounds. The molten compounding method of the present invention consistently provides a fully compounded product without a molten cooling step or immersion of the polyolefin compound in a crosslinking initiator. The homogeneous thermoplastic polyolefin crosslinkable compound according to the present invention contains a crosslinking initiator that is fully incorporated only during molten processing. The crosslinkable compound material of the present invention contains a homogeneous thermoplastic polyolefin compound immediately after molten compounding. The composition or product according to the present invention contains a crosslinkable homogeneous intermediate compound with a high scorch time. Therefore, the method of the present invention avoids the need for impregnation (immersion) equipment. The fully compounded products of the present invention, such as pellets, or homogeneous thermoplastic polyolefin crosslinkable compounds are storage stable and allow for the production of separate in-line articles in later stages, i.e., separate extrusion and molding into manufactured articles such as cable insulators. In contrast to the homogeneous thermoplastic polyolefin crosslinkable compounds of the present invention, thermoplastic polyolefin crosslinkable compounds produced by immersion are not fully compounded, are not homogeneous, are not batch stable, or are not crosslinkable after melt compounding. In fact, moving direometer (MDR) testing of crosslinkable compound compositions such as those in the present invention shows that when the compound is produced by an immersion process, initiators such as dicumyl peroxide (DCP) do not diffuse into the thermoplastic polyolefin matrix without additional heat treatment (e.g., 70°C to 80°C for at least 2 hours) to remove the initiator from the surface of the pellet, and even with heat treatment, it takes time for the initiator to completely diffuse into the polyolefin matrix.However, according to the present invention, a uniform distribution of DCP is formed in the polyolefin matrix immediately after melt compounding by both reorientation (mixing) and diffusion of the molten flow. Accordingly, the present invention provides a crosslinkable compound having, within one hour after the completion of melt compounding, one of the following: (i) a scorch time (ts1) at 140°C of at least 51 minutes, or preferably at least 55 minutes, as determined by a moving direometer (MDR) test according to ASTM Procedure D5289, which is reported as the time required to increase by one unit (inch-lb) or 1.13 desinewton-meter (dN-m) from the minimum torque ("ML"), and / or (ii) a maximum torque (MH) at 182°C of at least 2.26 dN-m (2.2 lbf-in), as determined by a moving direometer (MDR) test according to ASTM Procedure D5289.

[0046] All cited ranges are comprehensive and combinable. For example, based on the total weight of the crosslinkable compound composition, the disclosed amounts of organic peroxides in the range of 0.1% to 2% by weight, or preferably 0.3% to 1.4% by weight, or preferably 0.4% to 1.2% by weight, or preferably 0.5% to less than 1% by weight, are 0.1% to 2% by weight, or 0.1% to 1.4% by weight, or 0.1% to 1.2% by weight, or 0.1% to 1% by weight, or 0.3% to 2% by weight, or preferably 0.3% to 1.4% by weight, or preferably 0.3% to 1.2% by weight, or preferably 0.3% to 1% by weight. It will include %, or preferably 0.4% to 1.4% by weight, or preferably 0.4% to 1.2% by weight, or preferably 0.4% to 1% by weight, or preferably less than 0.5% to 1.4% by weight, or preferably less than 0.5% to 1.2% by weight, or preferably less than 0.5% to 1% by weight, or preferably 0.3% to 0.4% by weight, or preferably 0.3% to less than 0.5% by weight, or preferably 0.4% to less than 0.5% by weight, or 0.3% to 2% by weight, or 0.4% to 2% by weight, or less than 0.5% to 2% by weight.

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

[0048] Unless otherwise specified, any term containing parentheses shall alternatively refer to the entire term as if it contained parentheses, the term without parentheses, and any combination of each alternative. Thus, as used herein, terms such as "(meth)acrylate" are intended to include acrylates, methacrylates, and mixtures thereof.

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

[0050] As used herein, the term "ICEA" refers to publications of the Insulated Cable Engineers Association, Miamitown, Ohio, USA.

[0051] As used herein, the terms “melt index” or “I2” refer to the result measured at 190°C / 2.16 kg in accordance with ASTM D1238, reported as grams eluted per 10 minutes.

[0052] The term "organic peroxide" as used herein refers to R 1 -OOR 2 , or R 1 -OOROOR 2 This shows a peroxide having the structure, where R 1 and R 2Each of the above is a hydrocarbyl moiety, and R is a hydrocarbylen moiety. As used herein, the term "hydrocarbyl" refers to a monovalent group (e.g., ethyl, phenyl) produced by removing a hydrogen atom from a hydrocarbon. As used herein, the term "hydrocarbylen" refers to a divalent group produced by removing two hydrogen atoms from a hydrocarbon.

[0053] As used herein, the term “polymer” means a high-molecular-weight compound prepared by reacting (i.e., polymerizing) the same or different types of monomers, 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 two or more different monomers, such as terpolymers, tetrapolymers (four different monomers), etc. As used herein, “homopolymer” refers to a polymer containing repeating units derived from a single monomer, but does not exclude residual amounts of other components used in the preparation of the homopolymer, such as chain transfer agents.

[0054] As used herein, the term “solid” means a crystalline or amorphous material that does not perceptibly flow under moderate stress, has a distinct ability to resist forces that tend to deform it, and retains a distinct size and shape under normal conditions.

[0055] As used herein, the term "weight %" refers to a percentage by weight.

[0056] The proposed invention provides a homogeneous intermediate compound by a single melt mixing method using a conventional melt compounding apparatus at a temperature up to the decomposition temperature of the polymer. In the melt mixing method of the present invention, the temperature is less than 150°C, preferably less than 140°C, and remains above the melting point of the thermoplastic polyolefin polymer.

[0057] Pressure is required to push the molten material through the screen in the screening process or through the die in the pelletizing process. Some molten compounding devices that may be used in this method generate sufficient pressure for screening or pelletizing (i.e., they are "sufficient pressure generators"). Other molten compounding devices that may be used in this method do not generate sufficient pressure for screening and / or pelletizing (i.e., they generate insufficient pressure), and in such embodiments, a molten pump or a single-screw extruder may also be used to generate sufficient pressure. Therefore, a molten compounding device may, but is not required to generate, sufficient pressure for molten screening or pelletizing. Examples of molten compounding devices that generate sufficient pressure for screening or pelletizing are single-screw extruders and some twin-screw extruders. Examples of melt mixing equipment that do not generate sufficient pressure for screening or pelletizing 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 pelletizing, 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] A suitable melt mixing or melt mixing apparatus moves from upstream to downstream of the melt flow and includes at least one melt mixing apparatus, further including (i) a melt mixing apparatus such as a gear mixer or gear mixing element, or (ii) a melt pump located downstream of the melt mixing apparatus, or (iii) both a melt mixing element, and further including a melt screening unit. The melt mixing apparatus may further include a pelletizer or pelletizing die. Preferably, the melt mixing apparatus includes two melt pumps, one located upstream of the melt screen and the other located downstream of the melt screen.

[0059] To produce the homogeneous intermediate compound of the present invention, a primary feed of a thermoplastic polyolefin polymer and one or more antioxidants are melt-blended or mixed in a melt-blended apparatus to produce a molten flow of the intermediate compound. To produce the homogeneous crosslinkable compound of the present invention, a curable additive is then injected and homogeneously mixed by continuing to melt-blended the molten flow of the intermediate compound at or downstream of the melt-blended apparatus. Suitable apparatus for producing a homogeneous molten compound includes a distribution mixer or segment within an extruder, such as a toothed mixing element (TME, ZME, etc.) and a kneading block (forward, neutral, or reverse pump transport), a gear mixer, a melt pump, a gear pump, or a kneading block such as a blister element, when connected to a downstream mixing element.

[0060] Injecting a combination of curable additives into the molten flow of the intermediate compound involves injecting them at any of the following injection points: (i) a distribution mixing or kneading section at the downstream end of the melt compounding apparatus, (ii) inline downstream of molten formation (this point may be within the melt compounding apparatus itself), or (iii) upstream of a separate molten pump or other short mixing apparatus. The injection point is preferably located downstream of a molten screen located downstream of the molten pump. Preferably, the melt compounding apparatus includes a twin molten pumping apparatus further comprising a second downstream molten pump and a molten screening apparatus located between the molten pump and the second downstream molten pump, with the two molten pumps straddling the molten screen. In the twin molten pumping version, injecting a combination of curable additives involves transporting the molten flow of the intermediate compound by the molten pumping to produce a pressurized molten flow, molten screening the pressurized molten flow of the intermediate compound, and injecting the combination of curable additives into the molten flow at an injection point downstream of the molten screen, which may be within or immediately upstream of the second downstream molten pump.

[0061] Suitable injection points for combinations of curable additives include: (i) the distribution mixing or kneading section at the downstream end of the melting apparatus and (ii) the injection point downstream of molten material formation in the melting apparatus itself; (i) the distribution mixing or kneading section at the downstream end of the melting apparatus and (iii) the downstream of the melting screen located downstream of the melting apparatus but upstream of a separate melting pump; (i) the distribution mixing or kneading section at the downstream end of the melting apparatus and (iv) the upstream of a second melting pump located downstream of both the separate melting pump and the melting screen in (iii); and (ii) in the melting apparatus itself (iii) Both the injection point downstream of the melt formation and the downstream of the melt screen located downstream of the melt mixing apparatus but upstream of a separate melt pump; (ii) Both the injection point downstream of the melt formation in the melt mixing apparatus itself and the upstream of a second melt pump located downstream of both the separate melt pump and the melt screen in (iii); or (iii) Both the downstream of the melt screen located downstream of the melt mixing apparatus but upstream of a separate melt pump and the upstream of a second melt pump located downstream of both the separate melt pump and the melt screen in (iv)

[0062] Furthermore, suitable injection points for combinations of curable additives are all three: (i) the distribution mixing or kneading section at the downstream end of the melting apparatus, (ii) the injection point downstream of molten material formation in the melting apparatus itself, and (iii) the downstream of the molten screen located downstream of the melting apparatus but upstream of a separate molten pump; (ii) the injection point downstream of molten material formation in the melting apparatus itself, (iii) the downstream of the molten screen located downstream of the melting apparatus but upstream of a separate molten pump, and (iv) the upstream of a second molten pump located downstream of both the separate molten pump and the molten screen in (iii); (i) the distribution mixing or kneading section at the downstream end of the melting apparatus, and (iii) the downstream of the molten screen located downstream of the melting apparatus but upstream of a separate molten pump. All three: (i) a distribution mixing or kneading section at the downstream end of the melting compound, (ii) an injection point downstream of the melting formation in the melting compound itself, and all three: (iv) an injection point downstream of the melting formation in the melting compound itself, and all three: (ii) an injection point downstream of the melting formation in the melting compound itself, and all three: (ii) an injection point downstream of the melting formation in the melting compound itself, (iii) an injection point downstream of the melting compound but located upstream of the separate melting pump, and all three: (iv) an injection point downstream of the melting formation in the melting compound itself, (iii) an injection point downstream of the melting compound but located upstream of the separate melting pump, and all three: (iv) an injection point downstream of the separate melting pump and all three: (iii) an injection point downstream of the melting formation in the melting compound itself, (iii) an injection point downstream of the melting formation in the melting compound, and all three: (iv) an injection point downstream of the melting formation in the melting compound itself, and all three: and all three: (iii) an injection point downstream of the melting formation in the melting compound itself, and all three: (iv) an injection point downstream of the melting formation in the melting compound, and all three: (ii) an injection point downstream of the melting formation in the melting compound itself, and all three: (iv) an injection point downstream of the melting formation in the melting compound, and all three: (iv) an injection point downstream of the melting formation in the melting compound, and all three: (iv) an injection point downstream of the melting formation in the melting compound, and all three: (iv) an injection point downstream of the melting formation in the melting compound, and all three: (iv

[0063] Preferably, to control the overall melting temperature of the intermediate compound melt stream, the method of the present invention further comprises adding a second solid feed of thermoplastic polyolefin polymer downstream of the first solid feed of thermoplastic polyolefin polymer, for example, at any point upstream of all injection points, or adjacent to the upstream injection point, and melting the second feed. By introducing the second polymer feed in a weight ratio of 1:1 to 1:4, or preferably 1:2 to 1:4, of the second polymer feed to the initial polymer feed, the overall melting temperature of the intermediate compound and the resulting crosslinkable compound melt stream can be significantly reduced. The enthalpy from the initial thermoplastic polyolefin polymer melt stream melts the second polymer feed, achieving improved temperature control over the melt, i.e., a reduced melting temperature.

[0064] Suitable melt compounding apparatuses for use in accordance with the present invention include, for example, co-rotating, meshing twin-screw extruders, batch mixers, counter-rotating, non-meshing twin-screw rotor mixers (e.g., Farrel, FCM), or single-screw extruders. A wider selection of compounding apparatuses can be used when the method of the present invention involves delivering a molten flow of the intermediate compound to a melt pump and melt-screening the pressurized molten flow upstream of an arbitrary injection point, i.e., a place for injecting a combination of curable additives into the molten flow. In such cases, the melt compounding apparatus may include any of the compounders listed above, co-rotating, meshing twin-screw extruders, internal batch mixers, or counter-rotating, non-meshing twin-screw compounding mixers. Without sufficiently rapid and complete incorporation of the curing agent into the molten material by the described means, the resulting compositions exhibited severe scorching or decomposition of the organic peroxide. For example, experiments with a comparative Banbury mixer, discharged at a melting temperature of 125°C and with the combination of curable additives added downstream, resulted in severe scorching and rendered the compound unusable.

[0065] Suitable molten material screening apparatuses for use in accordance with the present invention include, for example, continuous screening or filtration technologies such as continuous plates, rotary screen changers, slide plate screen changers, dual bolts, or chamber screen changers, or any candle, pleated candle, disc, cylinder, or plate filtration element having a woven or nonwoven filter material capable of blocking particles in the size range of 25 μm to 500 μm, such as polymer gels.

[0066] Suitable melting pumps for use in accordance with the present invention include any known in the art, such as MAAGs, Farrel-Pominis, gear mixers, or twin-gear pressure-generating melting pumps appropriately modified to facilitate mixing.

[0067] The present invention further provides a homogeneous thermoplastic polyolefin crosslinkable compound comprising a thermoplastic polyolefin, one or more antioxidants (AOs), 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, within one hour after the completion of melt compounding, the crosslinkable compound has a scorch time (ts1) at 140°C of at least 51 minutes, or preferably at least 55 minutes, which is reported as the time required to increase the minimum torque ("ML") by one unit (inch-lb) or 1.13 decinewton-meter (dN-m), as determined by a moving direometer (MDR) test according to ASTM Procedure D5289, and / or a maximum torque (MH) at 182°C of at least 2.26 dN-m (2.2 lbf-in), or preferably 2.36 dN-m (2.3 lbf-in), as determined by a moving direometer (MDR) test according to ASTM Procedure D5289.

[0069] The terms “thermoplastic polyolefin” and “TPO” are used herein to refer to homopolymers produced by polymerizing a single unsaturated hydrocarbon monomer, and copolymers produced by polymerizing two or more different unsaturated hydrocarbon monomers, each consisting of carbon atoms and hydrogen atoms. Examples of unsaturated hydrocarbon monomers include ethylene, propylene, (C4~C 20 ) alpha-olefin and 1,3-butadiene. In some embodiments, TPO is polyethylene homopolymer or ethylene / (C4~C 20 )It is an alpha-olefin copolymer. (C4~C 20 Alpha-olefins are given by the formula H2C=C(H)-(CH2) q It is a CH3 compound, where the subscript q is an integer from 1 to 17. In some embodiments, (C4-C 20 The alpha-olefin is 1-butene, 1-hexene, or 1-octene, or 1-butene or 1-hexene, or 1-octene, or 1-hexene, or 1-butene.

[0070] A suitable thermoplastic polyolefin may include a polymer prepared from an ethylene monomer as the main (i.e., more than 50% by weight) monomer component, but other comonomers may also be used. The ethylene polymer may be an ethylene homopolymer or an ethylene / alpha-olefin ("α-olefin") copolymer having an α-olefin comonomer content of at least 1% by weight, at least 5% by weight, at least 10% by weight, at least 15% by weight, at least 20% by weight, or at least 25% by weight, based on the total weight of the monomers used to produce the copolymer. Such copolymers may have an α-olefin content of less than 50% by weight, less than 45% by weight, less than 40% by weight, or less than 35% by weight, based on the weight of the copolymer. A suitable α-olefin is C 3~20 (i.e., having 3 to 20 carbon atoms), or C 4~20It may be a linear, branched, or cyclic α-olefin (i.e., having 4 to 20 carbon atoms). 3~20 Examples of α-olefins include, for example, propene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene. α-olefins also have cyclic structures such as cyclohexane or cyclopentane, which can result in α-olefins such as 3-cyclohexyl-1-propene (allylcyclohexane) and vinylcyclohexane. Exemplary ethylene / α-olefin interpolymers 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, catalyst preparation method, etc.). When ethylene polymer blends are used, the polymers may be blended by any in-reactor or post-reactor process.

[0071] Ethylene polymers can be selected from the group consisting of low-density polyethylene ("LDPE"), linear low-density polyethylene ("LLDPE"), very low-density polyethylene ("VLDPE"), and combinations of two or more thereof. LDPE is generally a highly branched ethylene homopolymer and can be prepared via a high-pressure process (i.e., HP-LDPE). Suitable LDPE for use herein is 0.91 g / cm³. 3 ~0.94g / cm 3 Within that range, or for example, at least 0.915 g / cm³ 3 However, if less than 0.94 or 0.93 g / cm³ 3It may have a density of less than . The densities provided herein are determined according to ASTM method D792. Suitable LDPEs for use herein may have a melt index (I2) of less than 20 g / 10 min, or in the range of 0.1 g / 10 min to 10 g / 10 min, 0.5 g / 10 min to 5 g / 10 min, 1 g / 10 min to 3 g / 10 min, or I2 of 2 g / 10 min. The melt index provided herein is determined according to ASTM method D1238. Unless otherwise stated, the melt index is determined at 190 °C and 2.16 kg (also known as I2). Generally, LDPEs have a broad molecular weight distribution ("MWD") and a high polydispersity index ("PDI", or "ratio of weight-average molecular weight to number-average molecular weight). Ethylene polymers may be LLDPEs such as polymers that have a heterogeneous distribution of comonomers (e.g., α-olefin monomers) and are characterized by short-chain branching. For example, LLDPE has a density of 0.916 g / cm³. 3 ~0.925g / cm 3 It may be a copolymer of ethylene and α-olefin monomer having a density in the range of 0.87 g / cm³. Suitable LLDPEs for use herein may have a melt index (I2) in the range of 1 g / 10 min to 20 g / 10 min, or 3 g / 10 min to 8 g / 10 min. The ethylene polymer may be VLDPE or ultra-low density polyethylene, or ULDPE. VLDPE is generally an ethylene polymer having a heterogeneous distribution of comonomers (e.g., α-olefin monomers) and is characterized by short-chain branching. For example, VLDPE may be a copolymer of ethylene monomer and α-olefin monomer, e.g., one or more of those α-olefin monomers mentioned above. Suitable VLDPEs for use herein have a density of 0.87 g / cm³. 3 ~0.915g / cm 3 It may have a density in the range of . VLDPE suitable for use herein may have a melt index (I2) in the range of 0.1 g / 10 min to 20 g / 10 min, or 0.3 g / 10 min to 5 g / 10 min. Furthermore, the ethylene polymer according to the present invention may include any two or more combinations of the above-mentioned ethylene polymers.

[0072] The thermoplastic polyolefin polymers of the present invention are produced by a wide variety of methods known in the art. Any conventional or future-discovered production processes for producing polyolefin polymers may be used to prepare the polyolefin polymers of this disclosure. Generally, polymerization can be achieved under conditions known in the art for Ziegler-Natta or Kaminski-Syn polymerization reactions, namely, temperatures of 0° to 250°C, or 30° or 200°C, and pressures of 100 atm to 10,000 atm (1,013 megapascals ("MPa")), preferably 500 atm to 10,000 atm. In most polymerization reactions, the molar ratio of polymerization catalyst to monomer is 10 -12 :1~10 -1 :1, or 10 -9 :1~10 -5 It is within the range of :1.

[0073] In some embodiments, the molten flow of the main stream, which includes one or more antioxidants and one or more thermoplastic polyolefins (collectively, the main stream components), but does not include one or more curable additives selected from the group consisting of organic peroxides and crosslinking aids, and the intermediate compound produced therefrom (the intermediate compound includes a mixture of one or more thermoplastic polyolefin polymers and one or more antioxidants (AO), but lacks one or more curable additives), does not include any other polymers. In such embodiments, the polymer components of the primary stream and the intermediate compound produced 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 produced by curing the crosslinkable compound composition consist independently of one or more thermoplastic polyolefins and / or crosslinkable polyolefins produced by curing them.

[0074] In some embodiments, the molten flow of the primary flow, which includes one or more antioxidants and one or more thermoplastic polyolefins (collectively, the components of the primary flow), but does not include one or more curing additives selected from the group consisting of organic peroxides and crosslinking aids, and the intermediate compound produced therefrom (the intermediate compound includes a mixture of one or more thermoplastic polyolefin polymers and one or more antioxidants (AO), but lacks one or more curing additives), also contains polymers that are not thermoplastic polyolefins. An example of a polymer that is not a thermoplastic polyolefin and may be included in these embodiments is ethylene / unsaturated carboxylic acid copolymer. Examples of ethylene / unsaturated carboxylic acid copolymers that may be used are ethylene / alkyl acrylate (EAA) copolymer, ethylene / alkyl methacrylate (EAMA) copolymer, and ethylene / vinyl acetate (EVA) copolymer. Examples of ethylene / alkyl acrylate copolymers are ethylene / methyl acrylate (EMA) copolymer, ethylene / ethyl acrylate (EEA) copolymer, and ethylene / butyl acrylate (EBA) copolymer. Examples of ethylene / alkyl methacrylate copolymers are ethylene / methyl methacrylate (EMMA) copolymer, ethylene / ethyl methacrylate (EEMA) copolymer, and ethylene / butyl methacrylate (EBMA) copolymer. In such embodiments, the primary flow polymer component and the intermediate compound produced therefrom consist of one or more thermoplastic polyolefins and one or more ethylene / unsaturated carboxylic acid copolymers. The proportion of one or more ethylene / unsaturated carboxylic acid copolymers used in such embodiments of the primary flow may be 0.05% to 20% by weight, or 0.10% to 15% by weight, or 0.10% to 5% by weight, based on the total weight of the primary flow, and the proportion of one or more ethylene / unsaturated carboxylic acid copolymers used in such embodiments of the intermediate compound may independently be 0.05% to 20% by weight, or 0.10% to 15% by weight, or 0.10% to 5% by weight, based on the total weight of the intermediate compound.Embodiments of the crosslinkable compound composition produced therefrom according to the method of the present invention also contain one or more ethylene / unsaturated carboxylic acid copolymers, and the crosslinkable compound composition produced by curing such embodiments contains the crosslinking product.

[0075] Suitable antioxidants (AOs) may include tertiary amines, secondary or tertiary thiols, secondary or tertiary phenols, bisphenols, trisphenols, and tetraphenols, or preferably a combination of two or more of these. Examples of suitable antioxidants 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-t-butylphenol) (e.g., VANOX MBPC, Vanderbilt Chemicals, New York, NY), 2,2'-thiobis(2-t-butyl-5-methyl)phenol (CAS No. 90-66-4), 4,4'-thiobis(2-t-butyl-5-methylphenol), also known as 4,4'-thiobis(6-tert-butyl-m-cresol), CAS No. 96-69-5, LOWINOX TBM 6 antioxidant, Addivant), and 2,2'-thiobis(6-t-butyl-4-methylphenol) (CAS No. 90-66-4, commercially available 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), Pentaerythritol tetrakis(3-(3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)propionate) (e.g., IRGANOX 1010 antioxidant, CAS number 6683-19-8), 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanoate 2,2'-thiodiethanediyl ester (e.g., IRGANOX 1035 antioxidant, CAS number 41484-35-9, BASF, Ludwigshafen, DE), distearyl thiodipropionate (DSTDP), dilauryl thiodipropionate (e.g., IRGANOX PS800 antioxidant), stearyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate (e.g., IRGANOX 1076), 2,4-bis(dodecylthiomethyl)-6-methylphenol (IRGANOX 1726 antioxidant), 4,These are 6-bis(octylthiomethyl)-o-cresol (e.g., IRGANOX1520 antioxidant) and 2,3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyl]]propionohydrazide (IRGANOX1024 antioxidant). Preferably, one or more antioxidants include 4,4'-thiobis(2-t-butyl-5-methylphenol) (also known as 4,4'-thiobis(6-tert-butyl-m-cresol)), 2,2'-thiobis(6-t-butyl-4-methylphenol), tris[(4-tert-butyl-3-hydroxy-2,6-dimethylphenyl)methyl]-1,3,5-triazine-2,4,6-trione, distearyl thiodipropionate, or dilauryl thiodipropionate; or any combination of two or more of these. More preferably, the antioxidant may be a combination of tris[(4-tert-butyl-3-hydroxy-2,6-dimethylphenyl)methyl]-1,3,5-triazine-2,4,6-trione and distearyl thiodipropionate.

[0076] The total amount of one or more antioxidants may be 0.01% to 1.5% by weight, or 0.05% to 1.2% by weight, or 0.1% to 1% by weight, based on the total weight of the crosslinkable compound composition.

[0077] According to the present invention, an ethylene polymer is combined with one or more organic peroxides as crosslinking initiators. Suitable free radical initiators may include any dialkyl, diaryl, dialkaryl, or dialkyl(di)peroxide having a decomposition rate at least as high as the melting point of the ethylene polymer and having the same or different alkyl, aryl, alkaryl, or aralkyl moieties. Structure: R 1 -OOR 2 , or R 1 -OOROOR 2 In an equation having R 1 and R 2 Each of these is independently a hydrocarbyl moiety, R is a hydrocarbylene moiety, and R 1 and R2 Each of these is independently C1~C 20 Or C1~C 12 The alkyl, aryl, alkaryl, or aralkyl moiety is C1-C11. 20 Or C1~C 12 It can be an alkylene, arylene, alkalirene, or aralkylene moiety, R, R 1 , and R 2 It may have the same or different number of carbon atoms, or R, R 1 , and R 2 Any two of these atoms may have the same number of carbon atoms, but the third may have a different number of carbon atoms. Suitable organic peroxides for use herein include monofunctional and difunctional peroxides. As used herein, “monofunctional peroxide” refers to a peroxide having a pair of covalently bonded oxygen atoms (e.g., having the structure ROOR). As used herein, “difunctional peroxide” refers to a peroxide having two pairs of covalently bonded oxygen atoms (e.g., having the ROOROOR structure). Difunctional or more functional peroxides may be called cocrosslinking agents.

[0078] Exemplary organic peroxides include dicumyl peroxide (“DCP”), tert-butyl peroxybenzoate, di-tert-amyl peroxide (“DTAP”), isopropyl cumyl t-butyl peroxide, t-butyl cumyl peroxide, di-t-butyl peroxide, isopropyl cumyl cumyl peroxide, di(isocyanate) peroxide, and mixtures of two or more thereof. Suitable difunctional peroxides include bis(t-butyl-peroxyisopropyl) benzene (“BIPB”), 2,5-bis(t-butylperoxy)-2,5-dimethylhexane, 2,5-bis(t-butylperoxy)-2,5-dimethylhexane-3, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, butyl4,4-di(tert-butylperoxy) valerate, 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexyne, and mixtures of two or more thereof. In many cases, only a single type of organic peroxide is used. Preferably, the organic peroxide is dicumyl peroxide or a cumyl group-containing peroxide.

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

[0080] Suitable crosslinking aids include, for example, formula (I): [R 1 ,R 2 SiO 2 / 2 n (I) may include any monocyclic organosiloxane, wherein the subscript n is an integer of 3 or more, and each R 1 is independently (C2-C4) alkenyl or H2C=C(R 1a )-C(=O)-O-(CH2) m -, wherein R 1a is H or methyl, the subscript m is an integer of 1 to 4, and each R 2 ​is independently H, (C1-C4)alkyl, phenyl, or R 1 is the same as

[0081] Suitable examples of crosslinking aids for use in the present invention include, for example, any of the above formulas (I), where (i) each R 1 is independently a (C2-C3)alkenyl group and each R 2 is independently H, a (C1-C2)alkyl group, or a (C2-C3)alkenyl group, (ii) each R 1 is vinyl and each R 2 is independently a (C1-C2)alkyl group, (iii) each R 1 is vinyl and each R 2 is methyl, (iv) each R 1 is allyl and each R 2 is independently a (C1-C2)alkyl group, (v) each R 1 is allyl and each R 2 is methyl, (vi) each R 1 is independently H2C=C(R 1a )-C(=O)-O-(CH2) m -, wherein R 1a is H or methyl, the subscript m is an integer from 1 to 4, and each R 2 is independently H, a (C 1 -C 2 )alkyl group, or a (C 2 -C 3 )alkenyl group, (vii) each R 1 is independently H2C=C(R 1a )-C(=O)-O-(CH2) m -, wherein R 1a is H, the subscript m is 3, and each R 2 is independently a (C1-C2)alkyl group, (viii) each R 1 is independently H2C=C(R 1a )-C(=O)-O-(CH2) m -, wherein R 1a is methyl, the subscript m is 3, and each R 2Each of these is independently a (C1-C2) alkyl group. Two or more crosslinking aids can be used. Suitable crosslinking aids 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 is 0.1% to 5% by weight, preferably 0.3% to 4% by weight, or preferably 0.3% to 3.5% by weight, for example, preferably 0.5% to 2% by weight, and all weights are based on the total weight of the crosslinkable compound composition.

[0083] Suitable crosslinking aids for use in the present invention may include bifunctional and more functional monomers that can copolymerize with ethylene polymers. Crosslinking aids may include polyallyl or polyvinyl crosslinking aids. As used herein, “polyallyl” means a trialyl compound selected from the group consisting of compounds having at least two pendant allyl functional groups, such as triallyl isocyanurate ("TAIC"), triallyl cyanurate ("TAC"), triallyl trimellitate ("TATM"), and mixtures of two or more of these. Examples of suitable crosslinking agents include polyallyl crosslinking agents, e.g., triallyl isocyanurate ("TAIC"), triallyl cyanurate ("TAC"), triallyl trimellitate ("TATM"), triallyl orthoformate, pentaerythritol triallyl ether, triallyl citrate, and triallyl aconitate; vinyl or acrylic crosslinking agents, e.g., ethoxylated bisphenol A dimethacrylate; trimethylolpropane triacrylate ("TMPTA"), trimethylolpropane trimethyl acrylate ("TMPTMA"), 1 Examples include ,6-hexanediol diacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate, and propoxylated glyceryl triacrylate; vinyl-containing crosslinking aids, such as α-methylstyrene dimer ("AMSD"); polybutadiene with a high 1,2-vinyl content, and trivinylcyclohexane ("TVCH"); and other crosslinking aids as described in U.S. Patents No. 5,346,961 and No. 4,018,852. Further crosslinking aids may have at least one N,N-diallylamide functional group, as disclosed in U.S. Patent No. 10,941,278(B2) by Cai et al. Preferably, the crosslinking aid is TAIC. Further examples of crosslinking aids are described in U.S. Patent No. 6,277,925 (e.g., allyl-2-allyl-phenyl ether) and U.S. Patent No. 6,143,822 (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% to 5% by weight, or 0.7% to 3.5% by weight, or 1.0% to 3% by weight, or 1% to 2.5% by weight, based on the total weight of the crosslinkable compound composition.

[0085] The crosslinking aid can consist of at least 1% by weight, at least 10% by weight, at least 50% by weight, at least 75% by weight, or up to 50% by weight, or up to 35% by weight, based on the total weight of the combination of curing additives present in the crosslinkable compound composition.

[0086] The crosslinkable compound composition may also contain a hindered amine stabilizer (HAS), sometimes called a hindered amine light stabilizer (HALS). A HAS is a compound having a sterically hindered amino functional group that inhibits oxidative degradation. In some embodiments, the HAS can also reduce acid-catalyzed degradation, and in these embodiments, the acidic byproduct is generated in situ during the process. The acidic byproduct can be generated in situ by the reaction of an antioxidant with oxygen. A suitable example of a HAS is a polymer having dimethyl butanediate, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidine-ethanol (CAS number 65447-77-0, commercially available LOWILITE62). Other examples of HAS include (i) N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-polymer having 1,6-hexanediamine, 2,4,6-trichloro-1,3,5-triazine, reaction products with N-butyl-1-butanamine and N-butyl-2,2,6,6-tetramethyl-4-piperidineamine, and (ii) poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5- Examples include polymers of 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) 1,6-hexanediamine, N,N'-bis(2,2,6,6-tetramethyl)-4-piperidinyl), and 2,4-dichloro-6-(4-morpholinyl)-1,3,5-triazine. An alternative description for HAS(iii) is poly[(6-morpholino-s-triazine-2,4-diyl)[2,2,6,6-tetramethyl-4-piperidinylimino]-hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)imino]]. Other examples of HAS compounds can be found on pages 2-8 of Volume II of *Oxidation Inhibition in Organic Materials* by J. Pospisil and PPKlemchuk. HAS may be used alone or in combination of two or more compounds.In some embodiments, HAS is N,N'-1,6-hexanediirbis(N-(2,2,6,6-tetramethyl-4-piperidinyl)-formamide, which is available from BASF as Uvinul 4050.

[0087] The term "montmorillonite" includes inorganic montmorillonite and natural or artificial phyllosilicates such as oranomontmorillonite. The term "hydroperoxide" means any compound having at least one monovalent functional group of the formula -OOH. The term "N-nitroso-diarylamine" means a compound of the formula ON-N-Ar2, where each Ar is independently an aryl group. The term "maleimide" (also called "maleinimide") means N-substituted 1H-pyrrole-2,5-dione. The term "imine compound" means a compound having a distinct carbon-nitrogen double bond. The term "hydroquinone" means 1,4-benzenediol and substituted 1,4-benzenediol, where 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 hydrocarbyl group, organoheteryl group, hydroxyl, amino, or thiol.

[0088] Various modifications of the melting and mixing apparatus according to the present invention are shown in Figures 1, 2, 3, and 4.

[0089] Figure 1 shows a method and apparatus according to the present invention for manufacturing a conductor or cable insulation composition. The molten compounding line (2) moves from left to right upstream to downstream and includes a molten compounding apparatus (4), in this case a twin-screw extruder, a molten pump (6), a molten screen (8), and a pelletizing die (10). The molten compounding apparatus (4) melts and mixes a base thermoplastic polyolefin (ethylene polymer) feed (12) containing optional antioxidant additives and optionally a combination of curable additives. The molten pump (6) helps build pressure upstream of the molten screen (8), which in turn promotes the distribution of curable additives and improves the cleanliness of the crosslinkable compound product. The pelletizing die (10) pelletizes the formulation into a ready-to-use form. The molten compounding apparatus (4) may be a twin-screw extruder, a batch mixer (Banbury mixer), a reverse-rotor mixer (e.g., Farrel, FCM), or a single-screw extruder. Along the melt-mixing line (2), the curable additive can be injected at any injection site (14), including i) a distribution mixing section (not shown) or a melt-mixing apparatus (4) above it, ii) a transition between the melt-mixing apparatus (4) and the melt pump (6), or iii) a direct melt pump (6), or a combination thereof. A desired total amount of curable additive can be injected using multiple injection sites (14), each containing a portion of the combination of curable additives.

[0090] Figure 2 shows other methods and apparatus according to the present invention for manufacturing conductor or cable insulation compositions. The molten compounding line (2) moves from left to right upstream to downstream and includes a molten compounding apparatus (4), in this case a twin-screw extruder, two molten pumps (6), a molten screen (8), and two molten pumps (6) that cross a pelletizing die (10). The molten compounding apparatus (4) melts and mixes a base thermoplastic polyolefin (ethylene polymer) feed (12) containing antioxidant additives and optionally a combination of curable additives. The upstream (left) molten pump (6) helps build pressure upstream of the molten screen (8) and itself improves the cleanliness of the crosslinkable compound product. The downstream (right) molten pump (6) disperses the curable additives into the intermediate compound. The pelletizing die (10) pelletizes the formulation into a ready-to-use form. The melting and compounding apparatus (4) may be a co-meshing twin-screw extruder, an internal batch mixer (Banbury mixer), a counter-rotating twin-screw compounding mixer (e.g., Farrel, FCM), or a single-screw extruder. The curable additive may be injected into one or more injection sites (14), including i) a transition line between the melting screen (8) and the downstream melting pump (6), or ii) direct injection into the downstream melting pump (6). Both injection sites (14) may be used so that multiple injectors (not shown) can inject an amount that totals a desired amount of curable additive.

[0091] Figure 3 shows an experimental melt-mixing line (2) used in some of the examples, moving from left to right upstream to downstream, and includes an extruder (20), a polymer supply section (12), an injection section (14) for a combination of curable additives, a melt screen (8), and a pelletizing die (10).

[0092] In a preferred example of an extruder, a single-screw or twin-screw extruder has a feeder, a molten screw section, and a downstream mixing section such as a kneading block or a gear mixer. A thermoplastic polyolefin polymer feed consisting of LDPE and antioxidants can be supplied via a feeder at the upstream end of the extruder barrel, and curable additives can be injected at any of the various injection sites upstream of the downstream mixing section. [Examples]

[0093] The present invention is illustrated by the following examples. Unless otherwise specified, all parts and percentages are by weight, all temperatures are in degrees Celsius (°C), and all preparation and test procedures are carried out under ambient conditions of room temperature (23°C) and pressure (1 atm). In the following examples and in Tables 1, 2, 3, and 4, the following abbreviations are used: DCP: dicumyl peroxide, LDPE: low-density polyethylene, MDR: moving dirometer.

[0094] The following materials were used in the following examples (unless otherwise noted, all ingredients were used as received).

[0095] Antioxidant blend A: A mixture of 61.6 wt% distearyl thiodipropionate (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 antioxidant CYANOX 1790), and 0.9 wt% N,N'-1,6-hexanediirbis(N-(2,2,6,6-tetramethyl-4-piperidinyl)-formamide (available from BASF as Uvinul 4050).

[0096] Antioxidant blend B: 50% by weight of 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropionic acid 2,2'-thiodiethanediyl ester (Irganox 1035) and 50% by weight of DSTDP.

[0097] Antioxidant blend C: 50% by weight of 4,4'-thiobis(2-t-butyl-5-methylphenol) (Lowinox TBM-6) and 50% by weight of 3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-ol (Irganox E-201).

[0098] Antioxidant blend D: 50% by weight of pentaerythritol tetrakis(3-(3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)propionate (Irganox 1010) and 50% by weight of DSTDP.

[0099] Antioxidant 1: Tris[(4-tert-butyl-3-hydroxy-2,6-dimethylphenyl)methyl)-1,3,5-triazine-2,4,6-trione)(CYANOX1790).

[0100] Hindered amine light stabilizer 1: Poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidiyl)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) was used as the base resin when preparing the compound in the laboratory. It has a density of 0.92 g / cc and a melt index (MI) of 1.9 dg / min (measured at 190°C with a load of 2.16 kg).

[0102] Dicumyl peroxide: DI-CUP(trademark) (DCP) initiator (Arkema, Paris, FR), white to pale yellow granular solid (melting point 38°C, specific gravity 1.02 g / cm³ at 25°C) 3 ).

[0103] Crosslinking agent 1: Triaryl isocyanurate (TAIC).

[0104] Crosslinking aid 2: Chemical name 2,4,6,8-tetramethyl2,4,6,8-tetravinylcyclotetrasiloxane ("[ Vi A monocyclic tetra (alkenylorganosiloxane) having D]4).

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

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

[0107] Crosslinking agent 5: Alpha-methylstyrene dimer (AMSD).

[0108] Examples 1-4 of the present invention (IE1-IE4): The curable additive comprises one organic peroxide and two crosslinking aids. The formulations in Examples 1-4 of the present invention below were prepared by mixing LDPE1 and an antioxidant blend in the indicated amounts in a Banbury mixer and pelletizing them (Gala pelletizing system, MAAG Group, Oberglatt, CH) to produce intermediate compounds in pellet form. In Examples 1-4 of the present invention, the pellets of the intermediate compounds were then melt-blended in a twin-screw extruder and blending line having the configuration shown in Figure 3 under the conditions shown in Table 2 below (e.g., 145°C) to obtain a molten flow of the intermediate compounds, and then organic peroxide DCP and crosslinking aid 1 (TAIC) and crosslinking aid 2 ([ Vi The combinations of [D]4) were injected into the molten flow of the intermediate compound in a twin-screw extruder under the conditions shown in Table 2 (e.g., 145°C) to produce the crosslinkable compound compositions of the present invention for Examples 1-4 (IE1-IE4). In the compounding line, the molten screen included screen packs (20 / 150 / 60 / 20).

[0109] The examples shown in Table 3 below use the same compositions as those listed in Table 1 below. In Example 1 of the present invention below, the parameters shown for each formulation were measured at the indicated time intervals, starting immediately after the compounded product was manufactured.

[0110] Immersion: In contrast to the method of the present invention, a widely used comparative method for adding organic peroxides and crosslinking aids to thermoplastic polyolefins involves immersing the organic peroxides and crosslinking aids in liquid form into heated pellets of thermoplastic polyolefins. In four non-inventive experiments, intermediate compound pellets were heated in an oven at 70°C for at least 4 hours and then placed in 1000 mL wide-mouthed glass jars. DCP and mixtures containing either crosslinking aid 1 (TAIC) or crosslinking aid 2 (vinyl-D4), or without both aids (in contrast to IE1-IE4 which used both aids), were pre-mixed proportionally and then transferred to the glass jars using syringes. The jars were shaken thoroughly and then placed on a ceramic tumbler, which was run at 30 revolutions per minute (rpm) for 10 minutes. The resulting mixtures were immersed overnight in an oven at 70°C to produce four non-inventive compound compositions. The non-inventive compound compositions were evaluated in the same manner as in which Examples 1-4 of the present invention were evaluated. Data from the evaluation of four non-inventive compound compositions are available upon request.

[0111] [Table 1]

[0112] [Table 2]

[0113] Test Method: The following test methods were used in the various examples below. Tables 3 and 4 below provide the results of the test methods.

[0114] Stability Testing: In Example 1 of the present invention shown in Table 3 below, each of Examples 1-1, 1-2, 1-3, and 1-4 (IE1-1 to IE1-4) of the present invention contains one identical formulation sampled over time. Samples of each formulation were collected under the same processing conditions and tested at different time intervals after initiation of the injection of the curable additive into the molten flow of the intermediate compound according to the present invention to demonstrate product and process stability, as indicated by the consistency of product properties produced over long continuous molten compounding runs. Long continuous molten compounding runs last from 2 to 4 hours, typically from 2 to 3 hours. The sample collection time intervals were as follows: For Example 1-1 of the present invention, a sample was taken approximately 15 minutes after initiation of the injection of the curable additive, added at the indicated rate. For Example 1-2 of the present invention, a sample was taken at the end of the first hour. For Example 1-3 of the present invention, a sample was taken at the end of the second hour, and for Example 1-4 of the present invention, a sample was taken at the end of the third hour.

[0115] Plaques of crosslinkable compounds for testing in the following examples were prepared by the following method.

[0116] Preparation of cured plaques: In various embodiments of the present invention as shown, pellets were pressed and cured using a WABASH® GENESIS® Steam Press with rapid cooling capability. (For comparative compound compositions, immersed pellets were pressed under pressure and cured using a WABASH® GENESIS® Steam Press (Wabash MPI, Wabash, IN) with rapid cooling capability. The plaques were then subjected to the shown tests. Curing for high-temperature creep tests was performed using a compression mold WABASH® GENESIS® Steam Press.) The process involved melting the pellets at 120°C in a press. The mold dimensions were 203mm x 203mm (8 inches x 8 inches) x 1.3mm (50 mils), and the pellets were compressed under a low pressure of 3.5 MPa (500 psi) for 3 minutes, followed by a further 3 minutes under a high pressure of 17 MPa (2500 psi) at the same temperature. The mold was opened, the plaque was removed from the mold, and it was cut into four similarly sized pieces. In the test, the four pieces were then rearranged and returned to the mold, melted at 120°C under a low pressure of 3.5 MPa (500 psi) for 3 minutes, and then compressed under a high pressure of 17 MPa (2500 psi) at the same temperature for a further 3 minutes. The press temperature was then increased to 182°C and held for 12 minutes to cure the sample under high pressure. After curing, the mold was cooled to room temperature at 15°C / min under high pressure.

[0117] Preparation of uncured plaque: The immersed pellets were pressed using a Wabash® GENESIS® Steam Press with rapid cooling capabilities. For the MDR test, the pellets were first melted at 120°C under a low pressure of 3.5 MPa (500 psi) for 3 minutes, and then compressed at the same temperature under a high pressure of 17 MPa (2500 psi) for another 3 minutes. The mold was cooled to room temperature at 15°C / min under high pressure to form the uncured plaque.

[0118] High-temperature creep: High-temperature creep measures the curing performance or degree of crosslinking of a crosslinkable compound, which can also indicate the extent to which the compound is not yet crosslinked. High-temperature creep refers to the tensile deformation of a cured specimen of a given crosslinkable compound under load and is measured according to ICEA T-28-562. The high-temperature creep test is performed by applying a load of 20 N / cm to the lower end of a 1.3 mm (50 mil) dogbone specimen cut from a cured plaque using a die cutter according to ASTM D412 Type D. 2 The weight was attached and marked with two benchmark lines, and the test was performed at 200°C, with each line 25.4 mm apart in the center of the sample. The sample was placed in an oven preheated to 200°C and subjected to a pressure of 20 N / cm². 2 A weight equal to the force was attached to the bottom of each sample. After 15 minutes, the elongation (distance between reference lines) was measured and used to calculate the high-temperature creep. The weight was removed from the sample. After 5 minutes in the oven, the sample was removed and left at room temperature for 24 hours. The elongation (distance between reference lines) was measured again, and this value was used to calculate the hot hardening. Three samples were tested, and the average high-temperature creep was reported. An acceptable high-temperature creep result is 100% or less. For high-temperature creep, the lower the % elongation, the more crosslinking the material undergoes.

[0119] Moving Direometer (MDR): A moving direometer (MDR) allows for the measurement of the curing properties of crosslinkable compounds. The instrument measures the torque response of a material under deformation. As the material undergoes crosslinking, the torque response increases and eventually reaches the maximum torque ("MH") after the peroxide has reacted under the time and temperature test conditions. The MH value indicates the level of crosslinking of a given compound and must be high enough to produce a crosslinkable compound. The MDR test was performed under shear using an Alpha Technologies Rheometer, MDR Model 2000 unit (Alpha Technologies (Hudson, OH)) according to ASTM Procedure D5289, "Standard Test 20 Method for Rubber-Property Vulcanization Using Rotorless Cure Meters". For the test, a circle with a diameter of 2.56 cm (1 inch) was cut from an uncured plaque with a thickness of 1.905 mm (75 mils), and two of the 1.905 mm (75 mils) circles were stacked together. Two stacked 1.905 mm (75 mil) circles were tested at 182°C for 12 minutes to obtain MH, and then tested at 140°C (typical extrusion melting temperature) for various lengths of time to obtain ts1. Both tests were performed with an arc vibration of 0.5 degrees. MH is reported as the torque value when the curve reaches a plateau. Preferably, MH is greater than 2.26 dN-m or <2 lbf-in immediately after processing and does not change over time. Scorch time or ts1 refers to an index of the curing reaction rate useful for evaluating resistance to premature crosslinking (scorch). For scorch time measurements, the reported value is the time required to increase 1 unit (inch-lbf) or 1.13 decinewton-meter (dN-m) from the minimum torque ("ML"). An acceptable ts1 at 140°C should be at least 51 minutes. The longer the ts1, the better. Other scorch metrics such as ts0.5, ts2, and ts5 can be used according to equivalent definitions.

[0120] [Table 3]

[0121] As shown in Table 3 above, the crosslinkable compound composition of the present invention in Example 1 closely matches the successful crosslinkable compound produced through a much longer, labor-intensive immersion process, and when comparing Examples 1-4 of the present invention with Examples 1-1, 1-2, and 1-3 of the present invention, the crosslinkable compound composition remains consistent throughout the duration of the melt compounding operation. All of this data, including I10 melt index information, the delta between the maximum and minimum torques, and the long scorch time, demonstrates that the method of the present invention can consistently produce the same product during long, continuous melt compounding operations, and that the crosslinkable compound composition of the present invention remains crosslinkable.

[0122] [Table 4]

[0123] As shown in Tables 3 and 4 above, the crosslinkable compound compositions of Examples 1 to 4 of the present invention provide scorch-resistant crosslinkable compound compositions with good product consistency and crosslinkability. As shown in the scorch time (ts1) tests in Tables 3 and 4 above, all of the crosslinkable compound compositions of the present invention exhibit good scorch time and high-temperature creep results.

[0124] Predictive Examples 5-12 of the present invention (IE5-IE12): The procedure used in IE1-IE4 is repeated, with the following changes: the formulations are as shown in Table 6 below (the curable additives include one organic peroxide and one crosslinking aid), and the processing conditions are as shown in Table 5 below. The processing conditions in Table 6 are the same as those in Table 2 above, except that the handheld thermocouple melting temperature is 125°C. Next, the crosslinkable compound compositions of IE5-IE12 are tested with MDR, and the predicted results are also shown in Table 6.

[0125] [Table 5]

[0126] [Table 6]

[0127] Table 6 summarizes the predicted results. ML, MH, and TS1 are as defined elsewhere in this patent application. An ML value of less than 0.3 Nm indicates low viscosity after compounding, clearly indicating that the material is not crosslinked during compounding and the injection and mixing of additives and peroxides. These predicted results result in embodiments of crosslinkable compound compositions in which direct injection of curing agents is expected to have resulted in no detectable amount of crosslinking, and predict the suitability of the crosslinkable compound compositions for use in the process of the present invention.

Claims

1. A high-temperature, low-scorch method for continuously producing a crosslinkable compound composition, wherein the method is The method uses a melt compounding line including a melt compounding apparatus and a downstream processing system, wherein the melt compounding apparatus has a preparation zone, an injection zone, and a mixing zone, the preparation zone is configured to continuously prepare a molten flow of an intermediate compound and move the molten flow to the injection zone, the injection zone has a supply point for continuously receiving the molten flow of the intermediate compound and one or more injection points for continuously injecting additives into the molten flow of the intermediate compound in the injection zone, and the mixing zone has one or more mixing elements configured to rapidly homogenize the additives injected into the molten flow of the intermediate compound, and the method is (A) Continuously supplying a molten flow of the intermediate compound to the injection zone of the melt compounding apparatus via the supply point at a temperature of 125.0°C to 149.0°C, The molten flow of the intermediate compound, A molten material of one or more low-density polyethylene polymers having a density in the range of 0.91 g / cm³ to 0.94 g / cm³ as measured according to ASTM D792, and a melt index (I²) of 0.5 g / 10 min to 5 g / 10 min as determined according to ASTM D1238 at 190°C / 2.16 kg, It contains one or more antioxidants and a mixture thereof, It does not contain one or more curing additives selected from the group consisting of organic peroxides and crosslinking aids, and is supplied continuously. (B) Continuously injecting a combination of a curable additive comprising dicumyl peroxide, triallyl isocyanurate, and 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane into the molten flow of the intermediate compound in the injection zone of the melt compounding apparatus via at least one of the one or more injection points, (C) Rapidly homogenizing the combination of the molten flow of the intermediate compound and the injected curable additive by melt-blending them to produce the crosslinkable compound composition as a homogeneous mixture, (D) Continuously discharge the flow of the crosslinkable compound composition from the melt compounding apparatus to the processing system, wherein the combination of curable additives has a residence time of less than 25 seconds within the melt compounding apparatus, The crosslinkable compound composition comprises one or more low-density polyethylene polymers, one or more antioxidants, dicumyl peroxide, triallyl isocyanurate, and 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane. A method wherein the crosslinkable compound composition has a scorch time (ts1) of at least 50 minutes at 140°C, which is reported as the time required at 140°C for an increase of 1 foot-pound-inch (lbf-in) or 1.13 decinewton-meter (dN-m) from the minimum torque ("ML") as determined by a moving direometer (MDR) test according to ASTM Procedure D5289, and a maximum torque (MH) at 182°C that is at least 1.92 decinewton-meter (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).

2. The aforementioned crosslinkable compound composition The method according to claim 1, having a scorch time (ts1) of at least 60 minutes at 140°C and a maximum torque (MH) of at least 2.26 dN-m at 182°C, as determined by a moving direometer (MDR) test according to ASTM procedure D5289.

3. The method according to claim 1 or 2, comprising cooling the crosslinkable compound composition to a temperature of 100°C or less in less than 5 minutes.

4. The method according to claim 1 or 2, wherein the one or more mixing elements include one or more rotor blades or screws.

5. The method according to claim 1, wherein step (D) is followed by a processing step (E)(i) or step (E)(ii), wherein in E(i), the processing system includes a cooling device and a pelletizing device which may be the same as or different from the cooling device, and step (E)(i) includes cooling and pelletizing the crosslinkable compound composition to produce solid pellets, or in (E)(ii), 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 which includes the conductor and an insulating layer which at least partially surrounds the conductor, wherein the insulating layer includes the crosslinkable compound composition produced therefrom, and the insulator is in direct contact with the conductor or indirectly in contact with it via one or more intervening layers.

6. The method according to claim 1, further comprising, before step (B), preparing the molten flow of the intermediate compound by either melting pellets of the intermediate compound or melting pellets containing one or more low-density polyethylene polymers but not containing at least one of the one or more antioxidants, and mixing the molten low-density polyethylene polymers with at least one of the one or more antioxidants.

7. Prior to step (B) in which the combination of curing additives is continuously injected, the method is performed The molten flow of the intermediate compound is pumped through a melting pump to produce a pressurized molten flow. The process further includes: melt screening the pressurized melt flow of the intermediate compound through a first melt screen located upstream of all of the one or more injection points for injecting the combination of curable additives into the melt flow of the intermediate compound; The method according to claim 1, wherein the melting pump and the first molten material screen are located upstream of all the injection points in the injection zone of the melting and mixing apparatus.

8. The second low-density polyethylene polymer is added to the molten flow of the intermediate compound at a point upstream of any injection point. The method according to claim 1, further comprising melt-blending the second low-density polyethylene polymer with the intermediate compound, wherein the weight ratio of the added second low-density polyethylene polymer to the weight of the intermediate compound with respect to the weight of the low-density polyethylene polymer in the molten flow is in the range of 1:1 to 1:

4.

9. The one or more injection points for injecting the combination of curable additives into the molten flow of the intermediate compound are the following injection points (i) to (ix): (i) If the mixing zone of the melting and compounding apparatus has a distribution mixing section or a kneading section, one or more injection points located in the distribution mixing section or the kneading section at the downstream end of the melting and compounding apparatus, (ii) an injection point located downstream of the supply point in the injection zone, (iii) When the melting and mixing apparatus is equipped with a second melting screen and a separate melting pump in sequence, one or more injection points located downstream of the second melting screen and upstream of the separate melting pump, (iv) When the melting and mixing apparatus is equipped with a second melting screen, the separate melting pump, and the second melting pump in sequence, one or more injection points located between the separate melting pump and the second melting pump, (v) Combinations of injection points (i) and (ii), (vi) Combinations of injection points (i) and (iii), (vii) Combinations of injection points (i) and (iv), (viiii) Any three combinations of injection points (i) to (iv), or The method according to claim 1, comprising (ix) one or more of each combination of injection points (i) to (iv).

10. The method according to claim 1 or 2, wherein the one or more antioxidants comprises a mixture of two or three antioxidants.

11. Each of the one or more low-density polyethylene polymers is 0.915 g / cm³ as measured according to ASTM D792. ３ ~0.93 g / cm ３ Density in the range of , and melt index (I) of 1 g / 10 min to 3 g / 10 min as determined according to ASTM D1238 at 190°C / 2.16 kg ２ The method according to claim 1 or 2, having )

12. The method according to claim 1 or 2, wherein the crosslinkable compound composition has a high-temperature creep elongation of less than 130% at 200°C as determined by a test in accordance with ICEA T-28-562a.

13. To obtain at least one sample of the crosslinkable compound composition, Using the aforementioned sample, measure the scorch time (ts1) at 140°C for at least 50 minutes, which is reported as the time required at 140°C for an increase of 1 foot-pound-inch (lbf-in) or 1.13 decinewton-meter (dN-m) from the minimum torque ("ML") as determined by a moving direometer (MDR) test according to ASTM procedure D5289, The method according to claim 1 or 2, comprising measuring, using the sample, the maximum torque (MH) at 182°C which is at least 1.92 desinewton-meters (dN-m; equal to at least 1.70 lbf-in) higher than the minimum torque ("ML") at 182°C and at least 2.09 dN-m (1.85 lbf-in) as determined by a moving direometer (MDR) test according to ASTM procedure D5289.

14. The molten crosslinkable compound composition is extruded as an insulating layer covering a conductive core, The method according to claim 1 or 2, comprising curing the insulating layer to manufacture a power cable including the conductive core and the crosslinked insulating layer.

15. The following restrictions (a) to (g): (a) The melting and compounding apparatus used in the above method is a screw extruder, (b) The method does not involve a step of actively cooling the molten flow of the intermediate compound from a temperature of 120°C or higher to a temperature of less than 120°C, or a step of passively cooling it, during or before step (C). (c) The method contains, independently, one of the compounds (i) to (vi): (i) montmorillonite, (ii) hydroperoxide, (iii) N-nitrosodiarylamine, (iv) maleimide, (v) imine compound, and (vi) hydroquinone, in an amount of 0% to less than 0.10% by weight, based on the total weight of the combination of the intermediate compound and the curing additive. (d) Both restrictions (a) and (b), (e) Both restrictions (a) and (c), (f) Both restrictions (b) and (c), or (g) Restrictions (a), (b), and (c), The method according to claim 1 or 2, comprising one or more of the above.

Images