High-temperature, low-scorch method for producing crosslinkable compound composition and 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] TECHNICAL FIELD The technical field relates to methods for producing crosslinkable compound compositions comprising thermoplastic polyolefins and additives, and the compositions produced thereby. [Background technology]

[0002] Introduction Thermoplastic polyolefins (TPOs), such as thermoplastic polyethylenes (TPEs), are polymeric hydrocarbons that melt and flow at "high temperatures," which herein broadly means temperatures between 110°C and 190°C, depending on the particular TPO. Crosslinkable compound compositions include TPOs and additives, such as antioxidants, fillers, colorants, and curing agents, which are compounds that initiate free radical crosslinks or increase the concentration of crosslinks formed thereby (sometimes referred to as crosslink density). The characteristic of being "crosslinkable" can be determined by compression molding a sample of the crosslinkable compound composition into a plaque and measuring the maximum torque (MH). We define a "crosslinkable" compound composition as one that has a maximum torque (MH) of at least 2.09 dN-m (1.85 lbf-in) at 182°C, preferably at least 2.26 dN-m (2.0 lbf-in), as measured by the Moving Die Rheometer (MDR) test according to ASTM procedure D5289.

[0003] Scorch is the premature crosslinking of TPO during pre-melt processing of TPO with additives to produce a crosslinkable compound composition. The susceptibility of a composition to scorch can be detected and measured by compression molding a sample of the crosslinkable compound composition into a plaque and measuring the time to onset of scorch. We define "low scorch" as a scorch time (ts1) of at least 50 minutes, alternatively at least 60 minutes, and preferably at least 65 minutes at 140°C, reported as the time required for an increase of one unit (inch-lb) or 1.13 deciNewton-meter (dN-m) from the minimum torque ("ML") as determined by a moving die rheometer (MDR) test according to ASTM procedure D5289. We define "scorch-free" as having a scorch time (ts1) of greater than 150 minutes at 140°C, where the scorch time (ts1) at 140°C is measured as described herein.

[0004] Scorch is an industrial problem. It ultimately creates defects in manufactured articles. The defects may include cracks, gels, or voids, which may lead to mechanical failure of the manufactured article. For example, if a crosslinkable compound composition used to manufacture an insulating layer covering a conductive core in a power cable, such as a medium voltage (MV), high voltage (HV), or extra high voltage (EHV) power cable, is subjected to scorch during pre-melt processing, the insulating layer may end up with small cracks, voids, or gels. This may cause premature failure of the power cable.

[0005] Therefore, in order to prevent or minimize defects caused by scorch during pre-melt processing of TPO with additives, a method used in the art to prepare a crosslinkable compound composition includes the steps of: (a) melt compounding a melt of TPO with additives such as antioxidants, fillers, and colorants, but not with curable additives, to prepare an intermediate melt without curable additives; (b) pelletizing the intermediate melt; (c) immersing the pellets in curable additives (e.g., organic peroxides and crosslinking coagents) at a temperature of 50°C to 90°C for 1 hour to 24 hours (i.e., below the melting temperature of TPO and below the decomposition temperature of organic peroxides) to obtain a crosslinkable compound composition as pellets; (d) melting the crosslinkable compound composition; (e) extruding the melt to form a manufactured article; and (f) curing the extruded molded article.

[0006] A known method for producing electric cable insulation involves melt compounding polyolefin-based resins to incorporate additives such as antioxidants to produce a compounded material, filtering the compounded material, then pelletizing to produce an intermediate pellet compound that does not contain a free radical initiator (also called a crosslinking initiator), followed by impregnating or dipping the intermediate compound pellets with a free radical initiator in a "dipping" tower to incorporate the free radical initiator therein to produce a compound for producing cable insulation. This method requires at least a compounder and a dip tower, the compound for producing cable insulation containing a crosslinkable compound (also called a thermoplastic crosslinkable compound) in the form of pellets that crosslink when the downstream cable manufacturer produces the cable itself. Thus, the intermediate granules or pellets thereof are brought to a suitable temperature (e.g., around 70° C.) and then incorporating the free radical initiator involves dipping them to physically mix them with the intermediate pellets. The resulting fully compounded granules or pellets are soaked 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. Additional soaking may be required in the packaging container to achieve uniform distribution of the free radical initiator in the pellets. The soaking towers include very large and expensive equipment, thereby limiting the feasibility of developing multiple compounding sites or plants for producing the compound for cable insulation. Therefore, there remains a need to enable the compounding of all materials in the compound for cable insulation, for example, to produce crosslinkable pellets thereof, without using or needing a soaking tower. The fully compounded compound pellets need to be cooled before their transport, and therefore the conventional method requires a heating vessel (optional) and a cooling device (necessary), such as a fluidized bed or a cooling vessel.

[0007] Conventional polyolefin compounding lines for cable insulation manufacturing compounds do not allow the incorporation of free radical initiators into the base resin. Rather, the free radical initiators are incorporated in the base resin by soaking it, for example, in soaking tower equipment, in long-term processing and handling, which results in a high-cost process. In addition, the large amount of material in the equipment may result in a high risk of external contamination, as well as the need to have many clean rooms and related staff to process the material. This, of course, results in energy consumption in additional processing leading to a large carbon dioxide footprint.

[0008] Furthermore, injecting free radical initiators into polymer melts in conventional compounding processes remains very 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 energy input (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 usually results in excessive melting temperatures of the intermediate compounds, such as 180°C or higher. At such temperatures, decomposition of the free radical initiators occurs, which results in undesirable chemical crosslinking reactions and unusable products.

[0009] Recent U.S. Patent Publication No. 2020 / 0199270(A1) to Zhang et al. discloses a composition comprising a polyolefin polymer, an alkenyl-functional monocyclic organosiloxane, and an organic peroxide. The composition finds use as a wire and cable coating that acts as an insulator. Although Zhang et al. generally refer to mixing all materials in the composition, the only method disclosed for incorporating the peroxide into the composition involves immersion. Summary of the Invention

[0010] According to an embodiment 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 insulation that does not require a soaking step to incorporate a crosslinking initiator into the composition. An embodiment of the present invention relates to a method of manufacture, in particular a method of manufacture of a high temperature, low scorch (including no scorch) crosslinkable compound composition comprising a thermoplastic polyolefin and an additive, the scorch time (ts1) being defined herein as greater than 150 minutes at 140° C., where the scorch time (ts1) at 140° C. is measured as described herein. Also included are methods of manufacture of crosslinked compositions and articles of manufacture from the crosslinkable compound composition.

[0011] A method is provided for producing a high temperature, low scorch (including no scorch) crosslinkable compound composition, defined herein as a scorch time (ts1) at 140°C greater than 150 minutes, where the scorch time (ts1) at 140°C is measured as described herein, the method comprising melt blending a primary stream at a temperature of 120.0°C to 150.0°C, alternatively 125°C to 149°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, 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, the one or more antioxidants, the one or more organic peroxides, and the one or more crosslinking coagents by melt blending them together. Also provided are methods for producing crosslinked compound compositions and articles of manufacture. [Brief description of the drawings]

[0012] [Figure 1] 1 shows an example of a melt compounding line 2 according to the present invention. [Diagram 2] 1 shows an alternative example of a melt compounding line (2) according to the present invention. [Diagram 3] 1 shows a melt compounding line (2) used to produce crosslinkable compounds in the examples of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 cable insulation manufacturing compound that does not require a soaking step to incorporate a crosslinking initiator into the composition. In some embodiments, the method incorporates a crosslinking initiator, such as a free radical generator compound, such as an organic peroxide, into the composition, which is useful, optionally with an unsaturated crosslinking coagent, to initiate carbon radical-based crosslinking of thermoplastic polyolefins. Embodiments of the present invention relate to a method of manufacture, particularly a method of manufacture of a high temperature, low scorch (including no scorch), defined herein as a scorch time (ts1) of greater than 150 minutes at 140° C., where the scorch time (ts1) at 140° C. is measured as described herein, a method of manufacture of a crosslinkable compound composition comprising a thermoplastic polyolefin and an additive. Also included are methods of manufacture of crosslinked compositions and articles of manufacture from the crosslinkable compound composition. In some embodiments, the method and crosslinkable compound composition of the present invention are devoid, i.e., do not include, any acid additive. That is, acidic compounds such as Bronsted acids, such as sulfonic acids, and / or Lewis acids, such as added dialkyltin dicarboxylates, are not added as components of the method or composition. Acid additives do not include acidic by-products or acidic decomposition products that may be generated in situ by reaction or decomposition of other components used herein. As described below, hindered amine stabilizers (HAS) can be included in the method and composition, if desired, to neutralize acidic by-products or acidic decomposition products potentially generated in situ.

[0014] A method is provided for producing a high temperature, low scorch (including no scorch) crosslinkable compound composition, defined herein as a scorch time (ts1) at 140°C greater than 150 minutes, where the scorch time (ts1) at 140°C is measured as described herein, the method comprising melt blending a primary stream at a temperature of 120.0°C to 150.0°C, alternatively 125°C to 149°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, 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, the one or more antioxidants, the one or more organic peroxides, and the one or more crosslinking coagents by melt blending them together. Also provided are methods for producing crosslinked compound compositions and articles of manufacture.

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

[0016] Aspect 1. A high temperature, low scorch method of producing a crosslinkable compound composition, the method comprising: injecting a combination of curable additives including one or more organic peroxides and one or more crosslinking coagents into a melt of an intermediate compound including one or more thermoplastic polyolefin polymers and one or more antioxidants (AOs) but not including one or more curable additives, the melt being at a temperature between 120.0°C and 150.0°C; and rapidly mixing the curable additives into the melt in less than 60 seconds to produce the crosslinkable compound composition as a homogenous mixture of one or more thermoplastic polyolefins, antioxidants, and curable additives.

[0017] Aspect 2. The crosslinkable compound composition has a scorch time (ts1) of at least 50 minutes, alternatively at least 60 minutes, preferably at least 65 minutes at 140°C, 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 a minimum torque ("ML"), as determined by the Moving Die Rheometer (MDR) Test in accordance with ASTM Procedure D5289; and a maximum torque (MH) at 182°C, as determined, 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, preferably, the MH is at least 1.92 dN-m higher (at least 1.70 lbf-in higher) than the ML at 182°C, and the MH at 182°C is at least 2.09 dN-m (1.85 lbf-in), more preferably at least 2.26 dN-m (2.0 lbf-in).

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

[0019] Aspect 4. A high temperature, low scorch method for continuously producing a crosslinkable compound composition using a melt compounding line including a melt compounding apparatus and a downstream processing system, the melt compounding apparatus having a preparation zone, an injection zone, and a mixing zone, the preparation zone configured to continuously prepare a melt stream of an intermediate compound and move the melt stream to the injection zone, the injection zone having an injection point for continuously receiving the melt stream of the intermediate compound and having one or more injection points for continuously injecting an additive into the melt stream of the intermediate compound in the injection zone, the mixing zone having one or more mixing elements (e.g., one or more rotor blades or screws, and optionally baffles) configured to rapidly (in 60 seconds or less) homogenize the additive injected into the melt stream of the intermediate compound, the mixing zone having The method may be the same as the injection zone or downstream of the injection zone, comprising: (A) continuously feeding, at a temperature of from 120.0°C to 150.0°C, alternatively from 125°C to 149°C, a melt stream of an intermediate compound comprising a mixture of a melt of one or more thermoplastic polyolefin polymers and one or more antioxidants (AO), but not including one or more curing additives selected from the group consisting of organic peroxides and crosslinking coagents, via a feed point into an injection zone of a melt compounding apparatus, 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, more preferably each of the one or more thermoplastic polyolefins has a viscosity of less than 0.87 g / cm, as measured according to ASTM D792. 3 ~0.94g / cm 3and 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; (B) continuously injecting a combination of curable additives comprising one or more organic peroxides and one or more crosslinking coagents into the molten stream of intermediate compounds in an injection zone of the melt compounding device via at least one of the one or more injection points; (C) rapidly homogenizing the molten stream of intermediate compounds and the injected combination of curable additives by melt blending to produce a crosslinkable compound composition; and (D) continuously discharging the stream of crosslinkable compound composition from the melt compounding device to a processing system, wherein the combination of curable additives has a residence time of 60 seconds or less in the melt compounding device, and the crosslinkable compound composition is selected from the group consisting of one or more thermoplastic polyolefin polymers and one or more antioxidants. one or more organic peroxides, and one or more crosslinking coagents, wherein the crosslinkable compound composition has a scorch time (ts1) at 140°C, 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"), of at least 50 minutes, alternatively at least 60 minutes, and preferably at least 65 minutes, 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, as determined by the Moving Die Rheometer (MDR) Test in accordance with ASTM Procedure D5289, and wherein the MH at 182°C is at least 2.09 dN-m (1.85 4. The method of any one of aspects 1-3, comprising continuously discharging a pressure of at least 2.26 dN-m (2.0 lbf-in), more preferably at least 2.0 lbf-in.

[0020] Aspect 5. The method of aspect 4, comprising after step (D) a processing step (E)(i) or step (E)(II), in which in (E)(i) the processing system comprises a cooling device and a pelletizing device (which may be the same as or different from the cooling device), and in which step (E)(i) comprises cooling and pelletizing the crosslinkable compound composition to produce solid pellets thereof, or in which in (E)(ii) the processing system comprises an annular coater and curing device, and in which step (E)(ii) comprises 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, the insulating layer comprising the crosslinkable compound composition produced therefrom, and the insulating layer being in direct contact with the conductor or indirect contact with the conductor through one or more intervening layers (e.g., semiconducting layers).

[0021] Example 6. The method of example 4 or example 5, comprising, prior to the injecting step, preparing a molten stream of the intermediate compound by either melting pellets of the intermediate compound or melting pellets comprising the one or more thermoplastic polyolefins but not including at least one of the one or more antioxidants, and mixing the molten thermoplastic polyolefin with at least one of the one or more antioxidants.

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

[0023] Embodiment 8. The method of any one of embodiments 4-7, further comprising adding a second thermoplastic polyolefin polymer to the melt stream 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 melt stream of the intermediate compound ranges from 1:1 to 1:4.

[0024] Aspect 9. The one or more injection points for injecting the combination of curable additives into the melt stream of the intermediate compound are selected from the following injection points (i) to (ix): (i) one or more injection points in a distributive mixing or kneading section at a downstream end of the melt compounding apparatus when the mixing zone of the melt compounding apparatus has a distributive or kneading section; (ii) at an injection point downstream of the feed point of the injection zone downstream of the feeding step (A); (iii) one or more injection points downstream of the second melt screen and upstream of the separate melt pump when the melt compounding apparatus sequentially comprises a second melt screen and a separate melt pump. (iv) one or more injection points located between the separate melt pump and the second melt pump when the melt compounding apparatus comprises, in sequence, a second melt screen, a separate melt pump, and a second melt pump; or (v) a combination of injection points (i) and (ii); (vi) a combination of injection points (i) and (iii); (vii) a combination of injection points (i) and (iv); (viii) a combination of any three of injection points (i) through (iv); or (ix) a combination of each of injection points (i) through (iv).

[0025] Aspect 10. Restrictions (i) to (vii): (i) the one or more antioxidants include a mixture of two or more antioxidants, preferably two or three antioxidants, or the one or more crosslinking coagents include an alkenyl group-containing monocyclic organosiloxane, or the one or more antioxidants include a mixture of two or more antioxidants, preferably two or three antioxidants, and the one or more crosslinking coagents include an alkenyl group-containing monocyclic organosiloxane; (ii) the one or more crosslinking coagents are represented by the formula (I): [R 1 ,R 2 SiO 2 / 2 ] n (I) alkenyl-containing monocyclic organosiloxane, 1 are 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 from 1 to 4, and each R 2 are independently H, (C1-C4) alkyl, phenyl, or R 1 (iii) the one or more organic peroxides include dicumyl peroxide or a cumyl group-containing peroxide; (iv) both of limitations (i) and (ii); (v) both of limitations (i) and (iii); (vi) both of limitations (ii) and (iii); or (vii) each of limitations (i)-(iii).

[0026] Embodiment 11. There is one thermoplastic polyolefin, the thermoplastic polyolefin having a viscosity of 0.87 g / cm as measured according to ASTM D792. 3 ~0.94g / cm 3and a melt index (I2) at 190° C. / 2.16 kg, as determined in accordance with ASTM D1238 and reported in grams dissolved per 10 minutes, of 0.5 g / 10 min to 20 g / 10 min; or the one or more thermoplastic polyolefin polymers comprise one or more thermoplastic polyethylene polymers, preferably each of the one or more thermoplastic polyolefins is independently selected from the group consisting of polyethylene 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 (I2) of 0.87 g / cm or less, as measured in accordance with ASTM D792. 3 ~0.94g / cm 3 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 of 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%, by testing according to ICEA T-28-562a.

[0028] Aspect 13. Sampling a crosslinkable compound composition to obtain at least one sample thereof, and using the sample to measure a scorch time (ts1) of at least 50 minutes, alternatively at least 60 minutes, preferably at least 65 minutes at 140°C, 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 a minimum torque ("ML"), as determined by a moving die rheometer (MDR) test in accordance with ASTM procedure D5289, at 140°C, and and measuring, using the material, 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, the MH at 182°C being at least 2.09 dN-m (1.85 lbf-in), more preferably at least 2.26 dN-m (2.0 lbf-in), as determined by a Moving Die Rheometer (MDR) test according to ASTM procedure D5289.

[0029] Aspect 14. The method of any one of aspects 1-13, comprising molding a melt of the crosslinkable compound composition to form a molded crosslinkable compound composition, preferably extruding the melt of the crosslinkable compound composition as an insulating layer covering a conductive core, and curing the molded crosslinkable compound composition to produce an article of manufacture comprising the crosslinked compound composition, preferably curing the insulating layer to produce a power cable comprising a conductive core and a crosslinked insulating layer.

[0030] Aspect 15. The following limitations (a) to (g): (a) the melt compounding device used in the method is an internal mixer or a screw extruder; (b) the method does not use a step of actively cooling (e.g., via a heat exchanger device or a cooling zone in an extruder device) or a step of passively cooling the melt of the intermediate compound from a temperature of 120° C. or more to a temperature of less than 120° C. or from a temperature of 141° C. or more to a temperature of less than 141° C. during or prior to the rapid homogenization step (C); (c) the method does not use a step of actively cooling (e.g., via a heat exchanger device or a cooling zone in an extruder device) or a step of passively cooling the melt of the intermediate compound from a temperature of 120° C. or more to a temperature of less than 141° C. The method of any one of aspects 1-14, wherein the intermediate compound is either free of (i.e., devoid of, i.e., 0 wt%) any one of (i.e., 0 wt%), (wherein each wt% is based on the total weight of the combination of the intermediate compound and the curable additive), (d) both of limitations (a) and (b), (e) both of limitations (a) and (c), (f) both of limitations (b) and (c), or one or more of each of limitations (a), (b), and (c). With respect to limitation (b), cooling is permitted as long as the temperature of the molten stream of the intermediate compound does not fall below 120°C, alternatively below 125°C. Some such embodiments of the invention do not include both compounds (i) and (ii), or both compounds (i) and (vi), or both compounds (ii) and (vi), or each of compounds (i), (ii), and (vi), or each of compounds (i), (ii), (v), and (vi), or any five of compounds (i)-(vi), or all of compounds (i)-(vi). If any of compounds (i)-(vi) are found to have a scorch inhibition effect, which may or may not be found, the minimum amount of such compound required to exhibit effective scorch inhibition in the method of the invention is expected to be at least 0.10 wt.%, and possibly higher.

[0031] The process embodiments are continuous. This means that the feeding, injection, mixing, and discharge steps of these embodiments, as well as any processing steps, operate uninterrupted (without stopping and restarting) for at least 50 minutes, alternatively at least 60 minutes, alternatively at least 6 hours, alternatively at least 12 hours, alternatively at least 24 hours. If sufficient amounts of ingredients (e.g., thermoplastic polyolefin, antioxidant, curative additive) are available and there is no interruption (e.g., loss of power), continuous process embodiments can operate uninterrupted indefinitely until one or more pieces of equipment in the melt compounding line need to be taken out of service for cleaning or repair. In a typical manufacturing operation, continuous process embodiments can easily operate uninterrupted for 7 days, 4 weeks, or 6 months, or longer.

[0032] The crosslinkable compound composition is produced by high temperature low scorch (including no scorch), defined herein as a scorch time (ts1) of more than 150 minutes at 140°C, and the scorch time (ts1) at 140°C is measured as described herein, and the method may be described as an "organic peroxide-containing homogeneously mixed crosslinkable compound composition." The "organic peroxide-containing" feature of the crosslinkable compound composition means that the composition has a crosslinking effective amount of undecomposed organic peroxide sufficient to act as a free radical generator during the process of subsequently curing the crosslinkable compound composition to produce the crosslinked compound composition. "Crosslinking effective amount" means the maximum torque (MH) at 182°C. The composition meets the limitations described below. The "homogenous" aspect of the "homogenously 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" feature means that the curable additives, including the organic peroxide and the crosslinking coagent, are mechanically mixed into the molten stream of the intermediate compound composition by a method that does not include immersion, absorption, milling (e.g., two-roll milling), calendaring, or acoustic agitation.

[0033] In some embodiments of aspects 1-15, including some embodiments thereof described above having any one of limitations (a)-(g), the curable additive combination includes one organic peroxide and two coagents. In some embodiments, the organic peroxide is dicumyl peroxide. In some such embodiments, at least one of the two coagents is triallyl isocyanurate ("TAIC") or 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-cyclotetrasiloxane ("vinyl-D4"). In some such embodiments, the organic peroxide is dicumyl peroxide and the two coagents are TAIC and vinyl-D4.

[0034] The present invention also claims a crosslinkable compound composition produced by the method of any one of aspects 1-15. 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 of the same components as the crosslinkable compound composition of the present invention, but the comparative compound composition is produced 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 that includes melt blending all of the same components except the one or more organic peroxides to produce a penultimate mixture, pelletizing the penultimate mixture to produce pellets thereof, and impregnating the same one or more organic peroxides into the pellets of the penultimate mixture to produce the comparative compound composition in pellet form. The thermal history of the crosslinkable compound composition of the present invention differs from the thermal history of the comparative compound composition due to the different method of producing it. Thus, as a result of the different thermal history, the crosslinkable compound composition of the present invention can differ from the comparative compound composition in at least one aspect selected from the group consisting of: component ratios, component concentrations, melt rheological properties, and mechanical properties. Advantageously, the methods of the invention may be more efficient, faster (i.e., have higher productivity), and / or more cost-effective than comparative methods that involve one or more organic peroxide soaks. The improved efficiency of the methods of the invention may include using fewer unit operations or less energy than the comparative methods.

[0035] Without being bound by theory, it is believed that the method of the present invention produces a crosslinkable compound composition that essentially has a ts1 at 140°C of at least 50 minutes, alternatively at least 60 minutes, preferably at least 65 minutes, which is evidence of low scorch (including no scorch), defined herein as a scorch time (ts1) at 140°C of greater than 150 minutes, the scorch time (ts1) at 140°C being measured as described herein for the method of the present invention, and essentially has a maximum torque (MH) at 182°C of at least 1.92 dN-m (at least 1.70 lbf-in) higher than the ML at 182°C, preferably an MH at 182°C of at least 2.09 dN-m (1.85 lbf-in), more preferably at least 2.26 dN-m (2.0 lbf-in). In this context, it is considered that at least one of the one or more crosslinking coagents independently acts as a scorch prevention additive (SRA) to achieve a ts1 of at least 50 minutes, alternatively at least 60 minutes, preferably at least 65 minutes at 140°C, or at least one of the one or more crosslinking coagents independently acts as a crosslinking booster additive (CBA) to achieve a maximum torque (MH) at 182°C of 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), more preferably at least 2.26 dN-m (2.0 lbf-in) at 182°C, or a combination thereof. The one or more crosslinking coagents may comprise or consist of one crosslinking coagent acting as both an SRA and a CBA, or may comprise or consist of two crosslinking coagents, one acting as an SRA and the other as a CBA. In some embodiments, the one or more crosslinking coagents are crosslinking coagents that act as anti-scorch additives (SRA).In some embodiments, the maximum torque (MH) at 182°C is at least 1.92 dN-m higher (at least 1.70 lbf-in higher) than the ML at 182°C, or 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, the one or more coagents are coagents that act as scorch prevention additives (SRA) and have a ts1 at 140°C of at least 50 minutes, alternatively 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), alternatively from 2.37 dN-m (2.10 lbf-in) to 2.98 dN-m (2.64 lbf-in), alternatively from 2.61 dN-m (2.31 lbf-in) to 2.96 dN-m (2.62 lbf-in).

[0036] Without being bound by theory, it is believed that melt compounding temperatures of 120.0°C to 150.0°C, alternatively 125°C to 149°C, are unusually high for use with organic peroxides, and that a ts1 at 140°C of at least 50 minutes, alternatively at least 60 minutes, and preferably at least 65 minutes, is evidence of low scorch (including no scorch), defined herein as a scorch time (ts1) at 140°C of greater than 150 minutes, the scorch time (ts1) at 140°C being measured as described herein of the method of the present invention, and a maximum torque (MH) at 182°C of at least 1.92 dN-m (at least 1.70 lbf-in) higher than the ML at 182°C, or an MH at 182°C of at least 2.09 dN-m (1.85 lbf-in), preferably at least 2.26 dN-m (2.0 lbf-in), is evidence of crosslinkability of the crosslinkable compound composition produced by the method of the present invention.

[0037] As shown in the inventive examples below, 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 using a moving die rheometer (MDR) testing 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 particular inventive example. Thus, during the course of 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 by the inventive examples, in some embodiments, the maximum torque (MH) at 182°C is at least 2.7 dN-m higher (at least 2.4 lbf-in higher) than the ML at 182°C.

[0038] Feeding one or more antioxidants and one or more thermoplastic polyolefins to a melt compounding device via one or more feed points to produce a primary stream comprising one or more antioxidants and one or more thermoplastic polyolefins (collectively components of the primary stream) but lacking one or more curing additives selected from the group consisting of organic peroxides and crosslinking coagents can be accomplished by any one of the following methods. In an embodiment, at least one of the one or more antioxidants may be fed to the melt compounding device 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 premixed together to produce a combination thereof, and this combination may be fed to the melt compounding device. In another embodiment applicable when at least two antioxidants or at least two thermoplastic polyolefins or a combination thereof are present, at least one antioxidant and / or at least one thermoplastic polyolefin is fed separately to the melt compounding device, and a combination of at least one antioxidant and at least one thermoplastic polyolefin is fed separately to the melt compounding device.

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

[0040] Preferably, to control the overall melt temperature of the intermediate compound, the process according to the invention further comprises adding solid thermoplastic polyolefin as a second feed to the melt stream of the intermediate compound, for example at any point upstream or adjacent to all of the injection points, and melt blending the second feed. The weight ratio of thermoplastic polyolefin in the second feed to the weight of thermoplastic polyolefin in the primary stream may range from 1:1 to 1:4, or from 1:1.5 to 1:4, or more preferably from 1:2 to 1:4.

[0041] Preferably, the thermoplastic polyolefin in the process of the present invention has a modulus of 0.87 g / cm3 as measured according to ASTM D792. 3 ~0.94g / cm 3 and has a melt index (I2) of 0.5 g / 10 min to 20 g / 10 min measured at 190° C. / 2.16 kg according to ASTM D1238, reported in grams dissolved per 10 minutes.

[0042] Preferably, the one or more crosslinking coagents in the process of the present invention have the formula (I): [R 1 ,R 2 SiO 2 / 2 ] n (I) wherein the subscript n is an integer of 3 or greater, and each R 1 are 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 from 1 to 4, and each R 2 are independently H, (C1-C4) alkyl, phenyl, or R 1

[0043] , for example, tetramethyl-tetravinyl-cyclotetrasiloxanes such as 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-cyclotetrasiloxane.

[0043] In another embodiment according to the present invention, the homogeneous thermoplastic polyolefin crosslinkable compound composition is a thermoplastic polyolefin polymer having a crosslinkability of, for example, 0.87 g / cm as measured according to ASTM D792. 3 ~0.94g / cm 3 and a melt index (I2) of from 0.5 g / 10 min to 20 g / 10 min, or preferably from 0.5 g / 10 min to 10 g / 10 min, as measured at 190° C. / 2.16 kg according to ASTM D1238, reported in grams dissolved per 10 minutes, one or more antioxidants (AO), such as hindered phenols or hindered amines or mixtures thereof, and one or more crosslinking coagents, such as those represented by formula (I): [R 1 ,R 2 SiO 2 / 2 ] n where the subscript n is an integer of 3 or more, and each R 1 are 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 from 1 to 4, and each R 2 are independently H, (C1-C4) alkyl, phenyl, or R 1is the same as], preferably tetramethyl-tetravinyl-cyclotetrasiloxane, and one or more organic peroxides, such as dicumyl peroxide or cumyl group-containing peroxides, as a crosslinking initiator. The composition may further comprise a crosslinking coagent, such as a diallyl or triallyl crosslinking coagent, such as triallyl isocyanurate (TAIC). The total amount of the one or more antioxidants may range from 0.01% to 1.5% by weight, or preferably from 0.1% to 1% by weight, based on the total weight of the crosslinkable compound composition. The total amount of the one or more organic peroxides may range from 0.1% to 2% by weight, or preferably from 0.3% to 1.4% by weight, based on the total weight of the crosslinkable compound composition. The total amount of the one or more crosslinking coagents may range from 0.1% to 5% by weight, or preferably from 0.3% to 4% by weight, or more preferably from 0.5% to 2% by weight, all weight percentages being 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 comprise a diradical secondary amino group of the formula -C(alkyl)2-N(H)-C(alkyl)2- or a diradical tertiary amino group of the formula -C(alkyl)2-N(alkyl)-C(alkyl)2-.

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

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

[0046] All recited ranges are inclusive and combinable. For example, disclosed amounts of organic peroxide ranging from 0.1 wt% to 2 wt%, or preferably 0.3 wt% to 1.4 wt%, or preferably 0.4 wt% to 1.2 wt%, or preferably 0.5 wt% to less than 1 wt%, based on the total weight of the crosslinkable compound composition, can be used to describe 0.1 wt% to 2 wt%, or 0.1 wt% to 1.4 wt%, or 0.1 wt% to 1.2 wt%, or 0.1 wt% to 1 wt%, or 0.3 wt% to 2 wt%, or preferably 0.3 wt% to 1.4 wt%, or preferably 0.3 wt% to 1.2 wt%, or preferably 0.3 wt% to 1 wt%. %, or preferably 0.4% 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 indicated, temperature and pressure conditions are room temperature (23°C) and standard pressure (101.3 kPa), also referred to as "ambient conditions." In addition, all conditions include 50% relative humidity (RH) unless otherwise stated.

[0048] Unless otherwise specified, any term containing parentheses refers alternatively to the entire term as if the parentheses were present, and to the term without the parentheses, and to combinations of each alternative. Thus, as used herein, a term such as "(meth)acrylate" is intended to include acrylate, methacrylate, 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 a publication of the Insulated Cable Engineers Association, Miamitown, Ohio, USA.

[0051] As used herein, the term "melt index" or "I2" refers to the results measured in accordance with ASTM D1238 at 190°C / 2.16 kg and reported in grams dissolved per 10 minutes.

[0052] As used herein, an "organic peroxide" is defined as an R 1 -OOR 2 , or R 1 -OOROOR 2 wherein R 1 and R 2Each of is a hydrocarbyl moiety and R is a hydrocarbylene moiety. As used herein, the term "hydrocarbyl" refers to a monovalent group (e.g., ethyl, phenyl) prepared by removing a hydrogen atom from a hydrocarbon. As used herein, the term "hydrocarbylene" refers to a divalent group made by removing two hydrogen atoms from a hydrocarbon.

[0053] As used herein, the term "polymer" refers to a polymeric compound prepared by reacting (i.e., polymerizing) monomers of the same or different types, including homopolymers and copolymers. The term "copolymer" refers to a polymer prepared by polymerization of at least two different monomers as reactants, including copolymers prepared from two different monomers, as well as polymers prepared from more than two different monomers, such as terpolymers, tetrapolymers (four different monomers), etc. As used herein, "homopolymer" refers to a polymer that contains repeat 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" refers to a crystalline or amorphous material that does not flow appreciably under moderate stress, has a definite ability to resist forces tending to deform it, and retains a definite size and shape under normal conditions.

[0055] As used herein, the phrase "wt. %" stands for weight percent.

[0056] The proposed invention provides homogeneous intermediate compounds by a single melt mixing process using, for example, conventional melt compounding equipment at temperatures up to the decomposition temperature of the polymer. In the melt mixing process of the present invention, the temperature is below 150°C, or preferably below 140°C, and remains above the melting point of the thermoplastic polyolefin polymer.

[0057] Pressure is required to push the melt through a screen in the screening process or through a die in the pelletizing process. Some melt compounding devices that can be used in the present method generate sufficient pressure to perform screening or pelletizing (i.e., they are "sufficient pressure generating"). Other melt compounding devices that can be used in the present method do not generate sufficient pressure for screening and / or pelletizing (i.e., they generate insufficient pressure), and in that embodiment, a melt pump or single screw extruder can also be used to generate sufficient pressure. Thus, a melt compounding device may generate sufficient pressure for melt screening or pelletizing, but does not have to do so. Examples of melt compounding devices that generate sufficient pressure for screening or pelletizing are single screw extruders and some twin screw extruders. Examples of melt compounding equipment that do not generate sufficient pressure for screening or pelletizing are some twin screw extruders, internal batch mixers (e.g., Farrel-Pomini Banbury and Kobelco Stewart Bolling mixers), co-rotating intermeshing twin screw extruders that are not configured to generate sufficient pressure for melt screening or pelletizing, and counter-rotating non-intermeshing 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 compounding or melt mixing device includes at least one melt compounding device, moving from upstream to downstream of the melt flow, and further includes distributive mixing elements, either (i) within the melt compounding device, such as a gear mixer or gear mixing element, or (ii) as a melt pump located downstream of the melt compounding device, or (iii) both, and further includes a melt screening unit. The melt mixing device may further include a pelletizer or pelletizing die. Preferably, the melt mixing device 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 supply of thermoplastic polyolefin polymer and one or more antioxidants are melt compounded or mixed in a melt compounding device to produce a melt stream of intermediate compound. To produce the homogeneous crosslinkable compound of the present invention, a curing additive is then injected and homogeneously mixed by continuing to melt compound the melt stream of intermediate compound at the downstream end or downstream of the melt compounding device. Suitable devices for producing homogeneous molten compounds include distributive mixing devices or segments in extruders, such as toothed mixing elements (TME, ZME, etc.) and kneading blocks (forward, neutral or reverse pumping), gear mixers, melt pumps, gear pumps or kneading blocks such as blister elements, when coupled with downstream mixing elements.

[0060] Injecting the combination of curable additives into the melt stream of intermediate compounds includes injecting them into either (i) a distributive mixing or kneading section at the downstream end of the melt compounding device, (ii) in-line downstream of the melt formation (this point can be in the melt compounding device itself), or (iii) an injection point upstream of a separate melt pump or other short mixing device. The injection point is preferably located downstream of a melt screen located downstream of the melt pump. Preferably, the melt compounding device includes a twin melt pump device further including a second downstream melt pump and a melt screening device located between the melt pump and the second downstream melt pump, the two melt pumps straddling the melt screen. In the twin melt pump version, injecting the combination of curable additives includes melt pumping the melt stream of intermediate compounds to produce a pressurized melt stream, melt screening the pressurized melt stream of intermediate compounds, and injecting the combination of curable additives into the melt stream at an injection point downstream of the melt screen, which can be in or immediately upstream of the second downstream melt pump.

[0061] Suitable injection points for the curable additive combination include: (i) both a distributive mixing or kneading section at the downstream end of the melt compounding device, and (ii) an injection point downstream of the melt formation in the melt compounding device itself; (i) both a distributive mixing or kneading section at the downstream end of the melt compounding device, and (iii) downstream of the melt screen downstream of the melt compounding device but upstream of a separate melt pump; (i) a distributive mixing or kneading section at the downstream end of the melt compounding device, and (iv) upstream of a second melt pump at a point downstream of both the separate melt pump and the melt screen in (iii); (ii) in the melt compounding device itself. (ii) an injection point downstream of the melt formation in the melt compounding apparatus itself and (iv) upstream of a second melt pump at a point downstream of both the separate melt pump and the melt screen in (iii); or (iii) both downstream of the melt screen downstream of the melt compounding apparatus but upstream of the separate melt pump and (iv) upstream of a second melt pump at a point that is downstream of both the separate melt pump and the melt screen in (iii).

[0062] Further, suitable injection points for the curable additive combination include all three of: (i) a distributive mixing or kneading section at the downstream end of the melt compounding device; (ii) an injection point downstream of the melt formation in the melt compounding device itself; and (iii) downstream of a melt screen located downstream of the melt compounding device but upstream of a separate melt pump; (ii) an injection point downstream of the melt formation in the melt compounding device itself; (iii) downstream of a melt screen located downstream of the melt compounding device but upstream of a separate melt pump; and (iv) upstream of a second melt pump located at a point downstream of both the separate melt pump and the melt screen in (iii). and (iv) upstream of a second melt pump located at a point downstream of both the separate melt pump and the melt screen in (iii); all three of: (i) a distributive mixing or kneading section at the downstream end of the melt compounding apparatus, (ii) an injection point downstream of the melt formation in the melt compounding apparatus itself, and upstream of a second melt pump located at a point downstream of both the separate melt pump and the melt screen in (iv)(iii); or all three of (ii) an injection point downstream of the melt formation in the melt compounding apparatus itself, (iii) downstream of a melt screen located downstream of the melt compounding apparatus but upstream of the separate melt pump, and upstream of a second melt pump located at a point downstream of both the separate melt pump in (iv)(iii) and the melt screen in (iii).

[0063] Preferably, in order to control the overall melt temperature of the melt stream of the intermediate compound, 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 most upstream injection point, and melt compounding the second feed. By introducing the second polymer feed, such as at a weight ratio of the second polymer feed to the initial polymer feed of 1:1 to 1:4, or preferably 1:2 to 1:4, the overall melt temperature of the melt stream of the intermediate compound and the resulting crosslinkable compound 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., reduced melt temperature.

[0064] Suitable melt compounding equipment for use according to the present invention can include, for example, co-rotating intermeshing twin screw extruders, batch mixers, counter-rotating non-intermeshing twin rotor mixers (e.g., Farrel, FCM), or single screw extruders. If the method of the present invention includes delivering a melt stream of intermediate compounds to a melt pump and melt screening the pressurized melt stream upstream of any injection point, i.e., the location for injecting the combination of curing additives into the melt stream, a wider selection of compounding equipment can be used. In such cases, the melt compounding equipment can include any of the compounders listed above, co-rotating intermeshing twin screw extruders, internal batch mixers, or counter-rotating non-intermeshing twin screw compounding mixers. Without sufficiently rapid and complete incorporation of the curing agent into the melt by the described means, the resulting compositions showed severe scorching or decomposition of the organic peroxide. For example, experiments with a comparative Banbury mixer with discharge at a melt temperature of 125° C. and downstream addition of the combination of curing additives resulted in severe scorching, rendering the compound unusable.

[0065] Melt screening equipment suitable for use in accordance with the present invention can include, for example, continuous screening or filtration techniques such as continuous plate, rotary screen changers, sliding plate screen changers, dual bolt or chamber screen changers, or any candle, pleated candle, disk, cylinder, or flat plate filtration element having a woven or non-woven filter medium capable of rejecting particles in the size range of 25 μm to 500 μm, such as, for example, a polymer gel.

[0066] Melt pumps suitable for use in accordance with the present invention can include any known in the art, such as a MAAG, Farrel-Pomini, gear mixer, or a twin gear pressure generating melt pump 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 coagents, and one or more free radical initiators. The composition may further comprise one or more crosslinking coagents.

[0068] According to the present invention, within one hour after melt compounding is completed, the crosslinkable compound has a scorch time (ts1) at 140°C, reported as the time required for an increase of one unit (inch-lb) or 1.13 deciNewton-meter (dN-m) from the minimum torque ("ML"), as determined by the Moving Die Rheometer (MDR) Test according to ASTM Procedure D5289, of at least 51 minutes, or preferably at least 55 minutes, and / or a maximum torque (MH) at 182°C, as determined by the Moving Die Rheometer (MDR) Test according to ASTM Procedure D5289, of at least 2.26 dN-m (2.2 lbf-in), or preferably 2.36 dN-m (2.3 lbf-in).

[0069] The terms "thermoplastic polyolefin" and "TPO" are used herein to refer to homopolymers, which are made by polymerizing a single unsaturated hydrocarbon monomer, and to copolymers, which are made by polymerizing two or more different unsaturated hydrocarbon monomers, each of which consists of carbon and hydrogen atoms. Examples of unsaturated hydrocarbon monomers are ethylene, propylene, (C4-C 20 ) alpha-olefin, and 1,3-butadiene. In some embodiments, the TPO is a polyethylene homopolymer or an ethylene / (C4-C 20 ) alpha-olefin copolymer. (C4-C 20 ) Alpha-olefins have the formula H2C=C(H)-(CH2) q CH3, 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, alternatively 1-butene or 1-hexene, alternatively 1-octene, alternatively 1-hexene, or alternatively 1-butene.

[0070] Suitable thermoplastic polyolefins may include polymers prepared from ethylene monomer as the primary (i.e., greater than 50 wt%) monomer component, although 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 wt%, at least 5 wt%, at least 10 wt%, at least 15 wt%, at least 20 wt%, or at least 25 wt%, based on the total weight of monomers used to make the copolymer. Such copolymers may have an α-olefin content of less than 50 wt%, less than 45 wt%, less than 40 wt%, or less than 35 wt%, based on the weight of the copolymer. Suitable α-olefins include C 3~20 (i.e., having 3 to 20 carbon atoms), or C 4~20(i.e., having 4 to 20 carbon atoms), linear, branched or cyclic α-olefins. 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. The α-olefins may also have cyclic structures, such as cyclohexane or cyclopentane, resulting 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, the 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 by monomer composition and content, catalyst preparation method, etc.). When a blend of ethylene polymers is used, the polymers may be blended by any in-reactor or post-reactor process.

[0071] The ethylene polymer may 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 may be prepared via a high pressure process (i.e., HP-LDPE). LDPE suitable for use herein has a viscosity of 0.91 g / cm 3 ~0.94g / cm 3 or, for example, at least 0.915 g / cm 3 but less than 0.94 or 0.93 g / cm 3The LDPE may have a density of less than 20 g / 10 min. The densities provided herein are determined according to ASTM method D792. The LDPE suitable for use herein may have a melt index (I2) of less than 20 g / 10 min, or in the range of 0.1 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 an 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, LDPE has a broad molecular weight distribution ("MWD") resulting in a high polydispersity index ("PDI", or ratio of weight average molecular weight to number average molecular weight"). The ethylene polymer may be an LLDPE, such as a polymer having a non-uniform distribution of comonomers (e.g., α-olefin monomers) and characterized by short chain branching. For example, LLDPE has a density of 0.916 g / cm 3 ~0.925g / cm 3 The LLDPE suitable for use herein may have a melt index (I2) ranging from 1 g / 10 min to 20 g / 10 min, or from 3 g / 10 min to 8 g / 10 min. The ethylene polymer may be a VLDPE or very low density polyethylene, or ULDPE. VLDPE is generally an ethylene polymer with a non-uniform distribution of comonomers (e.g., α-olefin monomers) and is characterized by short chain branching. For example, the VLDPE may be a copolymer of ethylene and α-olefin monomers, such as one or more of those α-olefin monomers mentioned above. The VLDPE suitable for use herein may have a melt index (I2) ranging from 0.87 g / cm 3 ~0.915g / cm 3 The VLDPE suitable for use herein may have a melt index (I2) in the range of from 0.1 g / 10 min to 20 g / 10 min, or from 0.3 g / 10 min to 5 g / 10 min. Still further, the ethylene polymer according to the present invention may comprise a combination of any two or more of the ethylene polymers set forth above.

[0072] The thermoplastic polyolefin polymers of the present invention are manufactured by a wide variety of methods known in the art. Any conventional or hereafter discovered production process for producing polyolefin polymers may be used to prepare the polyolefin polymers of the present disclosure. In general, polymerization can be accomplished under conditions known in the art for Ziegler-Natta or Kaminsky-Sinn polymerization reactions, i.e., temperatures of 0° to 250° C., or 30° or 200° C., and pressures of 100 atmospheres to 10,000 atmospheres (1,013 megapascals ("MPa")), preferably 500 atmospheres to 10,000 atmospheres. In most polymerization reactions, the molar ratio of polymerization catalyst to monomer is between 10 and 200° C. -12 :1~10 -1 :1 or 10 -9 :1~10 -5 :1 range.

[0073] In some embodiments, the melt stream of the main stream, which comprises one or more antioxidants and one or more thermoplastic polyolefins (collectively, the main stream components), but does not comprise one or more curing additives selected from the group consisting of organic peroxides and crosslinking coagents, and the intermediate compounds produced therefrom (the intermediate compounds comprise a mixture of one or more thermoplastic polyolefin polymers and one or more antioxidants (AO), but lack one or more curing additives), does not comprise any other polymer. In such embodiments, the polymer components of the main stream and the intermediate compounds 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 crosslinked compound composition produced by curing the crosslinkable compound composition consist independently of one or more thermoplastic polyolefins and / or crosslinked polyolefins produced by curing the same.

[0074] In some embodiments, the melt stream of the primary stream containing one or more antioxidants and one or more thermoplastic polyolefins (collectively, components of the primary stream), but not containing one or more curing additives selected from the group consisting of organic peroxides and crosslinking coagents, and the intermediate compound produced therefrom (the intermediate compound contains a mixture of one or more thermoplastic polyolefin polymers and one or more antioxidants (AO), but lacks one or more curing additives) also contains a polymer that is not a thermoplastic polyolefin. An example of a polymer that may be contained in these embodiments that is not a thermoplastic polyolefin is an ethylene / unsaturated carboxylic acid ester copolymer. Examples of ethylene / unsaturated carboxylic acid ester copolymers that may be used are ethylene / alkyl acrylate (EAA) copolymers, ethylene / alkyl methacrylate (EAMA) copolymers, and ethylene / vinyl acetate (EVA) copolymers. Examples of ethylene / alkyl acrylate copolymers are ethylene / methyl acrylate (EMA) copolymers, ethylene / ethyl acrylate (EEA) copolymers, and ethylene / butyl acrylate (EBA) copolymers. Examples of ethylene / alkyl methacrylate copolymers are ethylene / methyl methacrylate (EMMA) copolymer, ethylene / ethyl methacrylate (EEMA) copolymer, and ethylene / butyl methacrylate (EBMA) copolymer. In such embodiments, the polymeric components of the primary stream and the intermediate compounds produced therefrom comprise one or more thermoplastic polyolefins and one or more ethylene / unsaturated carboxylic acid ester copolymers. The proportion of one or more ethylene / unsaturated carboxylic acid ester copolymers used in such embodiments of the primary stream may be 0.05% to 20% by weight, alternatively 0.10% to 15% by weight, alternatively 0.10% to 5% by weight, based on the total weight of the primary stream, and the proportion of one or more ethylene / unsaturated carboxylic acid ester copolymers used in such embodiments of the intermediate compounds may independently be 0.05% to 20% by weight, alternatively 0.10% to 15% by weight, alternatively 0.10% to 5% by weight, based on the total weight of the intermediate compounds.Crosslinkable compound composition embodiments produced therefrom according to the methods of the present invention also contain one or more ethylene / unsaturated carboxylic acid ester copolymers, and crosslinked compound compositions produced by curing such embodiments contain the crosslinked product thereof.

[0075] Suitable antioxidants (AO) may include tertiary amines, secondary or tertiary thiols, secondary or tertiary phenols, bisphenols, trisphenols and tetraphenols, or preferably, combinations 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), 2,2'-thiobis(6-t-butyl-4-methylphenol) (CAS No. 90-66-4, commercially available from 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-hydroxybenzenepropanoic acid 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), 4,6-bis(octylthiomethyl)-o-cresol (e.g., IRGANOX 1520 antioxidant), and 2,3-bis[[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyl]]propionohydrazide (IRGANOX 1024 antioxidant). Preferably, the one or more antioxidants may 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 a combination of any two or more thereof. 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 the one or more antioxidants can be from 0.01 wt % to 1.5 wt %, or from 0.05 wt % to 1.2 wt %, or from 0.1 wt % to 1 wt %, based on the total weight of the crosslinking compound composition.

[0077] According to the present invention, the ethylene polymer is combined with one or more organic peroxides as crosslinking initiators. Suitable free radical initiators have a decomposition at least as high as the melting point of the ethylene polymer and may include any dialkyl, diaryl, dialkaryl, or diaralkyl (di)peroxide having the same or different alkyl, aryl, alkaryl, or aralkyl moieties. Structure: R 1 -OOR 2 , or R 1 -OOROOR 2 In the formula having the formula 1 and R 2 each is independently a hydrocarbyl moiety, R is a hydrocarbylene moiety, and R 1 and R2 Each of C1 to C 20 Or C1~C 12 R is an alkyl, aryl, alkaryl, or aralkyl moiety, and R is a C-C 20 Or C1~C 12 R, R can be an alkylene, arylene, alkarylene, or aralkylene moiety. 1 , and R 2 may have the same or different number of carbon atoms, or R, R 1 , and R 2 Any two of the peroxides may have the same number of carbon atoms, but the third has 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 structure ROOROOR). Difunctional or higher functionality peroxides may be referred to as co-crosslinkers.

[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 can 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, butyl 4,4-di(tert-butylperoxy)valerate, 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexyne, and mixtures of two or more thereof. In most cases, only a single type of organic peroxide is used. Preferably, the organic peroxide is dicumyl peroxide or a peroxide containing a cumyl group.

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

[0080] Suitable crosslinking coagents include, for example, those represented by the formula (I): [R 1 ,R 2 SiO 2 / 2 ] n (I), where the subscript n is an integer of 3 or greater, and each R 1 are 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 from 1 to 4, and each R 2are independently H, (C1-C4) alkyl, phenyl, or R 1 is the same as:

[0081] Suitable examples of crosslinking coagents for use in the present invention can include, for example, any of the above formula (I), wherein: (i) each R 1 are 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 an aryl group, and each R 2 is independently a (C1-C2) alkyl group; (v) each R 1 is an aryl group, and each R 2 is methyl; (vi) each R 1 are independent, 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 are independent of each other, H, (C 1 ~C 2 ) alkyl group, or (C 2 ~C 3 (vii) each R 1 are independent, 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 are independent, H2C=C(R 1a )-C(=O)-O-(CH2) m -, wherein R 1a is methyl, the subscript m is 3, and each R 2are independently (C1-C2) alkyl. Two or more crosslinking coagents can be used. Suitable crosslinking coagents include, for example, 2,4,6-trimethyl-2,4,6-trivinyl-cyclotrisiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-cyclotetrasiloxane, 2,4,6,8,10-pentamethyl-2,4,6,8,10-pentavinyl-cyclopentasiloxane, or tetramethyl-tetravinyl-cyclotetrasiloxane, or mixtures thereof.

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

[0083] Suitable crosslinking coagents for use in the present invention can include difunctional and higher functional monomers that can be copolymerized with ethylene polymers. Crosslinking coagents can include polyallyl or polyvinyl crosslinking coagents. As used herein, "polyallyl" refers to a compound having at least two pendant allyl functional groups, such as a triallyl compound selected from the group consisting of triallyl isocyanurate ("TAIC"), triallyl cyanurate ("TAC"), triallyl trimellitate ("TATM"), and mixtures of two or more thereof. Examples of suitable crosslinking coagents include polyallyl crosslinking coagents, such as triallyl isocyanurate ("TAIC"), triallyl cyanurate ("TAC"), triallyl trimellitate ("TATM"), triallyl orthoformate, pentaerythritol triallyl ether, triallyl citrate, and triallyl aconitate; vinyl or acrylic crosslinking coagents, such as ethoxylated bisphenol A dimethacrylate; trimethylolpropane triacrylate ("TMPTA"), trimethylolpropane trimethyl acrylate ("TMPTMA"), 1,2-diphenyl ether ("1,2,3-tetramethylphenyl ether) and 1,2,3-tetramethylphenyl ether ("1,2,3-tetramethylphenyl ether). ,6-hexanediol diacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, and propoxylated glyceryl triacrylate; vinyl-containing coagents such as α-methylstyrene dimer ("AMSD"); polybutadiene with high 1,2-vinyl content, and trivinylcyclohexane ("TVCH"); and other coagents as described in U.S. Patents 5,346,961 and 4,018,852. Still other coagents may have at least one N,N-diallylamide functional group, as disclosed in U.S. Patent No. 10,941,278 (B2) to Cai et al. Preferably, the coagent is TAIC. Further examples of crosslinking coagents are described in U.S. Pat. No. 6,277,925 (such as allyl 2-allyl-phenyl ether) and U.S. Pat. No. 6,143,822 (such as 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 coagents in an amount ranging from 0.5% by weight to 5% by weight, or from 0.7% by weight to 3.5% by weight, or from 1.0% by weight to 3% by weight, or from 1% by weight to 2.5% by weight, based on the total weight of the crosslinkable compound composition.

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

[0086] The crosslinkable compound composition may also include a hindered amine stabilizer (HAS), sometimes referred to as a hindered amine light stabilizer (HALS). HAS is a compound that has a sterically hindered amino functional group and inhibits degradation by oxidation. In some embodiments, the HAS can also reduce acid-catalyzed decomposition, and these embodiments are those in which acidic by-products are generated in situ during the process. The acidic by-products can be generated in situ by reaction of the antioxidant with oxygen. An example of a suitable HAS is butanedioic acid dimethyl ester, polymer with 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)-polymers with 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-piperidinamine, (ii) poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5- triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6 hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]]), and (iii) polymers with 1,6-hexanediamine, N,N'-bis(2,2,6,6-tetramethyl)-4-piperidinyl)-, 2,4-dichloro-6-(4-morpholinyl)-1,3,5-triazine. An alternative description of 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 in Oxidation Inhibition in Organic Materials, Volume II, by J. Pospisil and P.P.Klemchuk, pages 2 to 8. The HAS may be used alone or in combination of two or more.In some embodiments, the HAS is N,N'-1,6-hexanediylbis(N-(2,2,6,6-tetramethyl-4-piperidinyl)-formamide, available as Uvinul 4050 from BASF.

[0087] The term "montmorillonite" includes natural or artificial phyllosilicates such as inorganic montmorillonite and oranomontmorillonite. The term "hydroperoxide" refers to any compound having at least one monovalent functional group of the formula -OOH. The term N-nitroso-diarylamine refers to a compound of the formula ON-N-Ar2, where each Ar is independently an aryl group. The term "maleimide" (also called "maleinimide") refers to N-substituted 1H-pyrrole-2,5-diones. The term "imine compounds" refers to compounds having separate carbon-nitrogen double bonds. The term "hydroquinone" refers to 1,4-benzenediol and substituted 1,4-benzenediols, where at least one of the six hydrogen atoms of the 1,4-benzenediol is replaced by a different atom, such as a halogen atom, or by a functional group, such as a hydrocarbyl group, an organoheteryl group, a hydroxyl, an amino, or a thiol.

[0088] Various variations of the melt mixing apparatus according to the present invention are shown in FIGS.

[0089] FIG. 1 displays a method and apparatus according to the invention for producing a conductor or cable insulation composition. The melt compounding line (2), moving from left to right in an upstream to downstream direction, includes a melt compounding device (4), in this case a twin screw extruder, a melt pump (6), a melt screen (8) and a pelletizing die (10). The melt compounding device (4) melts and mixes the base thermoplastic polyolefin (ethylene polymer) feed (12) containing any antioxidant additives and optionally a combination of curative additives. The melt pump (6) helps to build pressure upstream of the melt screen (8), which itself promotes distribution of the curative additives and improves the cleanliness of the crosslinkable compound product. The pelletizing die (10) pelletizes the formulation into a ready-to-use form. The melt compounding device (4) can be a twin screw extruder, a batch mixer (Banbury mixer), a counter-rotating twin rotor mixer (e.g., Farrel, FCM), or a single screw extruder. Along the melt compounding line (2), the curable additives may be injected at any injection site (14), including: i) at the melt compounding device (4) at or above a distributive mixing section (not shown), ii) at the transition between the melt compounding device (4) and the melt pump (6), or iii) directly at the melt pump (6), or combinations thereof. Multiple injection sites (14), each containing a portion of the curable additive combination, may be used to inject the total amount of curable additives desired.

[0090] FIG. 2 displays another method and apparatus according to the invention for producing a conductor or cable insulation composition. The melt compounding line (2) includes a melt compounding device (4), in this case a twin screw extruder, two melt pumps (6), a melt screen (8) and two melt pumps (6) that span a pelletizing die (10) from upstream to downstream. The melt compounding device (4) melts and mixes the base thermoplastic polyolefin (ethylene polymer) feed (12) containing an antioxidant additive and optionally a combination of curative additives. The upstream (left) melt pump (6) helps build pressure upstream of the melt screen (8), which itself improves the cleanliness of the crosslinkable compound product. The downstream (right) melt pump (6) disperses the curative additives into the intermediate compound. The pelletizing die (10) pelletizes the formulation into a ready-to-use form. The melt compounding device (4) can be a co-intermeshing 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 curative additives can be injected at one or more injection sites (14), including i) in the transition line between the melt screen (8) and the downstream melt pump (6), or ii) directly into the downstream melt pump (6). Both injection sites (14) may be used so that multiple injectors (not shown) can inject amounts that add up to the desired amount of curative additive.

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

[0092] In a preferred example of an extruder, a single or twin screw extruder has a feeder, a melt screw section, and a downstream mixing section such as a kneading block or gear mixer. The thermoplastic polyolefin polymer feed consisting of the LDPE and antioxidant can be fed via a feeder at the upstream end of the extruder barrel, and the curative additives can be injected at any of a variety of injection sites upstream of the downstream mixing section. EXAMPLES

[0093] The following examples illustrate the invention. Unless otherwise indicated, all parts and percentages are by weight, all temperatures are in degrees Celsius (°C), and all preparation and testing procedures are carried out at ambient conditions of room temperature (23°C) and pressure (1 atm). In the following examples and Tables 1, 2, 3, and 4, the following abbreviations have been used: DCP: dicumyl peroxide, LDPE: low density polyethylene, MDR: moving die rheometer.

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

[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 as CYANOX 1790 antioxidant from Solvay Chemicals), and 0.9 wt. % N,N'-1,6-hexanediylbis(N-(2,2,6,6-tetramethyl-4-piperidinyl)-formamide (available as Uvinul 4050 from BASF).

[0096] Antioxidant Blend B: 50 wt% 3,5-bis(1,1 dimethylethyl)-4-hydroxybenzenepropionic acid 2,2'-thiodiethanediyl ester (Irganox 1035) and 50 wt% 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 wt% pentaerythritol tetrakis(3-(3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)propionate (Irganox 1010) and 50 wt% DSTDP.

[0099] Antioxidant 1: Tris[(4-tert-butyl-3-hydroxy-2,6-dimethylphenyl)methyl)-1,3,5-triazine-2,4,6-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 in the preparation of 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™ (DCP) initiator (Arkema, Paris, FR, a white to pale yellow granular solid (melting point 38° C., specific gravity 1.02 g / cm at 25° C.) 3 ).

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

[0104] Crosslinking agent 2: Chemical name 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-cyclotetrasiloxane ("[ Vi D]4").

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

[0106] Coagent 4: Triallyl cyanurate (TAC).

[0107] Coagent 5: alpha-methylstyrene dimer (AMSD).

[0108] Inventive Examples 1-4 (IE1-IE4): The curable additive comprises one organic peroxide and two crosslinking coagents. The formulations in the following Inventive Examples 1-4 were prepared by mixing LDPE1 and an antioxidant blend in the amounts shown in a Banbury mixer and pelletized (Gala pelletizing system, MAAG Group, Oberglatt, CH) to produce intermediate compounds in the form of pellets. In Inventive Examples 1-4, the pellets of the intermediate compounds were then melt compounded in a twin-screw extruder and compounding line having the configuration shown in FIG. 3 under the conditions shown in Table 2 below (e.g., 145° C.) to obtain a melt stream of the intermediate compounds, which was then mixed with the organic peroxide DCP and crosslinking coagent 1 (TAIC) and crosslinking coagent 2 ([ Vi D]4) was injected into the melt stream of the intermediate compound in a twin-screw extruder under the conditions (e.g., 145°C) shown in Table 2 to produce the crosslinkable compound compositions of the present invention in Examples 1 to 4 (IE1 to IE4) of the present invention. In the compounding line, the melt screen contained a screen pack (20 / 150 / 60 / 20).

[0109] The examples shown in Table 3 below use the same compositions as listed in Table 1 below. In Inventive Example 1 below, the parameters indicated 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 of adding organic peroxide and coagent to thermoplastic polyolefin involves immersing the organic peroxide in liquid form and the coagent in liquid form into warm pellets of thermoplastic polyolefin. In four non-inventive experiments, the intermediate compound pellets were heated in a 70°C oven for at least 4 hours and then placed in 1000 mL wide-mouth glass jars. The compositions containing DCP and either coagent 1 (TAIC) or coagent 2 (vinyl-D4), and without both coagents (as opposed to IE1-IE4, which used both coagents), were premixed in proportion and then transferred to the glass jars using a syringe. 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 placed in a 70°C oven overnight to soak, producing four non-inventive compound compositions. The non-inventive compound compositions were evaluated in the same manner as inventive Examples 1-4 were evaluated. Data from the evaluation of four non-inventive compound compositions are available upon request.

[0111] [Table 1]

[0112] [Table 2]

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

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

[0115] Plaques of the crosslinking compounds for testing in the following examples were prepared in the following manner.

[0116] Preparation of Cured Plaques: In various inventive examples as indicated, pellets were pressed and cured using a WABASH™ GENESIS™ Steam Press with quenching capability. (For comparative compound compositions, the pellets after immersion were pressed and cured under pressure using a WABASH™ GENESIS™ Steam Press with quenching capability (Wabash MPI, Wabash, Ind.). The plaques were then subjected to the tests indicated. Curing for high temperature creep testing was performed using a compression mold WABASH™ GENESIS™ Steam Press with quenching capability. The test included melting the pellets at 120°C in a press. The mold dimensions were 203 mm x 203 mm (8 in x 8 in) x 1.3 mm (50 mils) and compressed under a low pressure of 3.5 MPa (500 psi) for 3 minutes, then under a high pressure of 17 MPa (2500 psi) for an additional 3 minutes at the same temperature. The mold was opened and the plaque removed from the mold and cut into four similarly sized pieces. The four pieces were then rearranged and placed back in the mold, melted under a low pressure of 3.5 MPa (500 psi) at 120°C for 3 minutes, then compressed under a high pressure of 17 MPa (2500 psi) for an additional 3 minutes at the same temperature. The temperature of the press was then increased to 182°C and held for 12 minutes to cure the samples under high pressure. After curing, the mold was cooled to room temperature at 15°C / min under high pressure.

[0117] Preparation of green plaques: The pellets after dipping were pressed using a Wabash™ GENESIS™ Steam Press with quenching capability. For MDR testing, the pellets were first melted at 120° C. under low pressure of 3.5 MPa (500 psi) for 3 minutes and then compressed at the same temperature under high pressure of 17 MPa (2500 psi) for an additional 3 minutes. The mold was cooled to room temperature under high pressure at 15° C. / min to form the green plaques.

[0118] High Temperature Creep: High temperature creep measures the cure performance or degree of crosslinking of a crosslinkable compound, which can also indicate the extent to which the compound has not yet been crosslinked. High temperature creep refers to the elongation deformation under load of a cured specimen of a given crosslinkable compound and is measured according to ICEA T-28-562. The high temperature creep test is performed by applying a 20 N / cm load to the bottom end of a 1.3 mm (50 mil) dog bone specimen cut from a cured plaque using a die cutter according to ASTM D412 Type D. 2 The specimen was placed in a preheated oven at 200°C and subjected to a 20N / cm weight and two benchmark lines were marked, each line 25.4mm apart in the center of the specimen. 2 A weight equal to a force of 0.01 mm was attached to the bottom of each sample. After 15 minutes, the elongation (distance between the reference lines) was measured and used to calculate the hot creep. The weights were removed from the samples. After 5 minutes in the oven, the samples were removed and left at room temperature for 24 hours. The elongation (distance between the reference lines) was measured again and this value was used to calculate the hot set. Three samples were tested and the average of the hot creep was reported. An acceptable hot creep result is 100% or less. For hot creep, the lower the % elongation, the more crosslinked the material is.

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

[0120] [Table 3]

[0121] As shown in Table 3 above, the inventive crosslinkable compound composition of Inventive Example 1 closely matches the successful crosslinkable compound produced via the much longer labor-intensive soaking process, and comparing Inventive Examples 1-4 to Inventive Examples 1-1, 1-2, and 1-3, the crosslinkable compound composition remains consistent over the duration of the melt compounding run. All of this data, including I10 melt index information, delta between maximum and minimum torque, and long scorch time, shows that the inventive method can consistently produce the same product during long continuous melt compounding runs, and that the inventive crosslinkable compound composition 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) test in Tables 3 and 4 above, all of the crosslinkable compound compositions of the present invention show good scorch time and high temperature creep results.

[0124] Inventive Prophetic Examples 5-12 (IE5-IE12): The procedure used for IE1-IE4 is repeated, except for the following changes: the formulation is as set forth in Table 6 below (the curing additive includes one organic peroxide and one crosslinking coagent), and the processing conditions are set forth 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. The crosslinking compound compositions of IE5-IE12 are then 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. ML values ​​less than 0.3 Nm indicate low viscosity after compounding, clearly indicating that the material is not crosslinked during compounding and injection and mixing of coagents and peroxides. These predicted results result in an embodiment of the crosslinkable compound composition in which direct injection of the curing agent is expected to not undergo a detectable amount of crosslinking, predicting the suitability of the crosslinkable compound composition for use in the process of the present invention.

Claims

Claim 1 A high-temperature, low-scorch method for manufacturing a crosslinkable compound composition, the method comprising: injecting a combination of curable additives comprising one or more organic peroxides and one or more crosslinking aids into a melt of an intermediate compound comprising one or more thermoplastic polyolefin polymers and one or more antioxidants but not comprising the one or more curable additives, the melt being at a temperature of 120.0°C to 150.0°C; rapidly mixing the curable additives into the melt in less than 60 seconds to produce the crosslinkable compound composition as a homogeneous mixture of the one or more thermoplastic polyolefins, the antioxidant, and the curable additives. Claim 2 The crosslinkable compound composition has: a scorch time (ts1) of at least 50 minutes at 140°C, 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 die rheometer (MDR) test according to ASTM procedure D5289; 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 as determined by a moving die rheometer (MDR) test according to ASTM procedure D5289, and the MH at 182°C is at least 2.09 dN-m (1.85 lbf-in). The method according to claim 1. Claim 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. Claim 4 The method is a high-temperature low-scorch method for continuously producing a crosslinkable compound composition using a melt compounding line including a melt compounding apparatus and a processing system downstream thereof, the melt compounding apparatus having a preparation zone, an injection zone, and a mixing zone, the preparation zone being configured to continuously prepare a melt stream of an intermediate compound and move the melt stream to the injection zone, the injection zone having an injection point for continuously receiving the melt stream of the intermediate compound and one or more injection points for continuously injecting an additive into the melt stream of the intermediate compound in the injection zone, the mixing zone having one or more mixing elements configured to rapidly homogenize the additive injected into the melt stream of the intermediate compound in 60 seconds or less, the mixing zone may be the same as the injection zone or downstream of the injection zone, and the method comprises continuously supplying a melt stream of an intermediate compound at a temperature of 120.0 °C to 150.0 °C to the injection zone of the melt compounding apparatus through the supply point, wherein the melt stream of the intermediate compound is a mixture of a melt of one or more thermoplastic polyolefin polymers and one or more antioxidants, and does not contain one or more curable additives selected from the group consisting of organic peroxides and crosslinking aids, and continuously supplying continuously injecting a combination of one or more organic peroxides and one or more crosslinking aids as a curable additive through at least one of the one or more injection points into the melt stream of the intermediate compound in the injection zone of the melt compounding apparatus continuously injecting a combination of one or more organic peroxides and one or more crosslinking aids as a curable additive through at least one of the one or more injection points into the melt stream of the intermediate compound in the injection zone of the melt compounding apparatus rapidly homogenizing in 60 seconds or less by melt compounding the melt stream of the intermediate compound and the injected combination of curable additives to produce the crosslinkable compound composition continuously discharging 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 in the melt compounding apparatus of 60 seconds or less the crosslinkable compound composition comprises the one or more thermoplastic polyolefin polymers, the one or more antioxidants, the one or more organic peroxides, and the one or more crosslinking aids, and the crosslinkable compound composition When determined by a Moving Die Rheometer (MDR) test in accordance with ASTM procedure D5289, the scorch time (ts1) of at least 50 minutes at 140 °C, 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”), and When determined by a Moving Die Rheometer (MDR) test in accordance with ASTM procedure D5289, having a maximum torque (MH) at 182 °C that is at least 1.92 decinewton-meter (dN-m; equivalent to at least 1.70 lbf-in) higher than the minimum torque (“ML”) at 182 °C, and the MH at 182 °C being at least 2.09 dN-m (1.85 lbf-in), continuously discharging, the method according to claim 1 or 2.

5. After step (D), including processing step (E)(i) or step (E)(II), 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 its 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 including the conductor and an insulating layer at least partially surrounding the conductor, the insulating layer including a crosslinked compound composition produced therefrom, and the insulator being in direct contact with the conductor or in indirect contact via one or more intervening layers, the method according to claim 4.

6. Before the injection step, preparing the melt flow of the intermediate compound by either melting the pellets of the intermediate compound or melting the pellets containing the one or more thermoplastic polyolefins but not containing at least one of the one or more antioxidants, and mixing the melted thermoplastic polyolefins with at least one of the one or more antioxidants, the method according to claim 4.

7. Before step (B) of continuously injecting the combination of the curable additives, the method Pumping the melt stream of the intermediate compound through a melt pump to produce a pressurized melt stream; then, melt screening the pressurized melt stream of the intermediate compound through a first melt screen upstream of all of the one or more injection points for injecting the combination of curable additives into the melt stream of the intermediate compound. The method according to claim 4, wherein the melt pump and the first melt screen are located upstream of all of the injection points in the injection zone of the melt compounding apparatus.

8. Adding a second thermoplastic polyolefin polymer to the melt stream of the intermediate compound at a point upstream of any injection point; and melt compounding the second thermoplastic polyolefin polymer and the intermediate compound. Preferably, the weight ratio of the second thermoplastic polyolefin polymer added to the weight of the thermoplastic polyolefin polymer in the melt stream of the intermediate compound is in the range of 1:1 to 1:

4. The method according to claim 4.

9. The one or more injection points for injecting the combination of curable additives into the melt stream of the intermediate compound are the following injection points (i) to (ix): (i) When the mixing zone of the melt compounding apparatus has a distribution or kneading section, the one or more injection points in the distribution mixing section or the kneading section at the downstream end of the melt compounding apparatus; (ii) Those at an injection point downstream of the supply point in the injection zone downstream of the supply step (A); (iii) When the melt compounding apparatus sequentially includes a second melt screen and a separate melt pump, one or more injection points downstream of the second melt screen and upstream of the separate melt pump; (iv) When the melt compounding apparatus sequentially includes a second melt screen, a separate melt pump, and a second melt pump, one or more injection points located between the separate melt pump and the second melt pump, or (v) A combination of injection points (i) and (ii); (vi) A combination of injection points (i) and (iii); (vii) A combination of injection points (i) and (iv); (viii) A combination of any three of injection points (i) to (iv), or The method according to claim 4, comprising any one or more of each combination of injection points (i) to (iv).

10. The following restrictions (i) to (vii): (i) The one or more antioxidants include a mixture of two or more antioxidants, preferably two or three antioxidants, or the one or more crosslinking aids include an alkenyl group-containing monocyclic organosiloxane, or the one or more antioxidants include a mixture of two or more antioxidants, preferably two or three antioxidants, and the one or more crosslinking aids include an alkenyl group-containing monocyclic organosiloxane, (ii) The one or more crosslinking aids include a compound of formula (I): [R １ , R ２ SiO ２／２ ｎ (I)​ An alkenyl group-containing monocyclic organosiloxane as described above [wherein, the subscript n is an integer of 3 or more, and each R １ is independently (C ２ to C ４ ) alkenyl or H ２ C═C(R １ａ )-C(═O)-O-(CH ２ ), and in the formula, R ｍ is H or methyl, the subscript m is an integer of 1 to 4, and each R １ａ is independently H, (C ２ to C １ to C ４ ) alkyl, phenyl, or the same as R １ )], (iii) The one or more organic peroxides include dicumyl peroxide or a cumyl group-containing peroxide, (iv) Both of the restrictions (i) and (ii), (v) Both of the restrictions (i) and (iii), (vi) Both of the restrictions (ii) and (iii), (vii) The method according to claim 1 or 2, having any one of each of the restrictions (i) to (iii).

11. There is one thermoplastic polyolefin, and the thermoplastic polyolefin has a density in the range of 0.87 g / cm ３ to 0.94 g / cm ３ as measured according to ASTM D792, and a melt index (I ２ ) of 0.5 g / 10 min to 20 g / 10 min at 190 °C / 2.16 kg as determined according to ASTM D1238 and reported in grams eluted per 10 minutes, or The one or more thermoplastic polyolefin polymers include the one or more thermoplastic polyethylene polymers, preferably each of the one or more thermoplastic polyolefins is independently selected from the group consisting of polyethylene homopolymers, ethylene / 1-butene copolymers, ethylene / 1-hexene copolymers, and ethylene / 1-octene copolymers, more preferably each of the one or more thermoplastic polyolefins has a density in the range of 0.87 g / cm ３ to 0.94 g / cm ３ and a melt index (I ２ ) of from 0.5 g / 10 min to 20 g / 10 min as determined according to ASTM D1238 at 190 °C / 2.16 kg, the method according to claim 1 or 2, selected independently from the group comprising low density polyethylene polymers having

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

13. Sampling the crosslinkable compound composition to obtain at least one sample thereof, Using the sample, when determined by a moving die rheometer (MDR) test according to ASTM procedure D5289, measuring a scorch time (ts1) of at least 50 minutes at 140 °C, 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"), Using the sample, when determined by a moving die rheometer (MDR) test according to ASTM procedure D5289, 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, Measuring that the MH at 182 °C is at least 2.09 dN-m (1.85 lbf-in), the method according to claim 1 or 2.

14. Forming a crosslinkable compound composition by molding a melt of the crosslinkable compound composition, preferably extruding the melt of the crosslinkable compound composition as an insulating layer coating a conductive core, and Manufacturing a manufactured article comprising a crosslinked compound composition by curing the formed crosslinkable compound composition, preferably manufacturing a power cable comprising the conductive core and a crosslinked insulating layer by curing the insulating layer, the method according to claim 1 or 2.

15. The following restrictions (a) to (g): (a) the melt compounding apparatus used in the method is an internal mixer or a screw extruder; (b) the method does not use a step of actively cooling or passively cooling the melt of the intermediate compound from a temperature of 120 °C or higher to a temperature lower than 120 °C during or before the rapid homogenization step (C); (c) the method independently has from 0 wt% to less than 0.10 wt% of any one of compounds (i) to (vi): (i) montmorillonite, (ii) hydroperoxide, (iii) N-nitroso-diarylamine, (iv) maleimide, (v) imine compound, and (vi) hydroquinone (where each wt% is based on the total weight of the combination of the intermediate compound and the curable additive); (d) both restrictions (a) and (b); (e) both restrictions (a) and (c); (f) both restrictions (b) and (c), or one or more of each of restrictions (a), (b), and (c), the method according to claim 1 or 2.

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