Method for crosslinking moisture-curing polymer compositions

Abstract

A method for crosslinking a moisture-curable polymer composition comprises the following steps: producing a moisture-curable polymer composition of a silane-functionalized polyolefin and an expandable flame retardant mixture, wherein the expandable flame retardant mixture comprises piperazine pyrophosphate and a phosphoric acid compound in an amount of 15% to 55% by weight, based on the total weight of the expandable flame retardant mixture. The method also comprises the step of using the expandable flame retardant mixture to catalyze a moisture-induced crosslinking reaction of the silane-functionalized polyolefin to form a moisture-curable polymer composition.

Description

[Technical Field]

[0001] This disclosure relates to moisture-curable polymer compositions, and more specifically, to methods for crosslinking such moisture-curable polymer compositions.

[0002] Introduction Crosslinked polyolefin compositions are used in a variety of applications where heat resistance and good mechanical properties are desired. Crosslinking of polyolefins converts thermoplastic compositions into thermosetting compositions, which increases their resistance to deformation and flow at high temperatures because the polymer chains are linked together, unlike in thermoplastic compositions. There are various industrially implemented physical and chemical methods for crosslinking polymer compositions, including vulcanization for peroxide-induced crosslinking, crosslinking based on electron beam irradiation, and moisture-induced crosslinking using silane functionalization. Silane crosslinking of polymer compositions utilizing silane functionalization of polymers typically requires the use of silanol condensation catalysts such as tin-based dibutyltin dilaurate and / or strong acids such as sulfonic acids. The presence of moisture in such formulations is undesirable and should therefore be avoided, as it can lead to premature crosslinking during melt extrusion and adversely affect the final material properties. Moisture-induced crosslinking of formulations occurs in subsequent processes after the manufacture of the article, due to the diffusion of water into the article. A polymer composition is typically considered crosslinked if it exhibits a gel content of 10% by weight or more, as measured according to ASTM D2765.

[0003] Expanding compounds can be used in polymer applications as halogen-free flame retardant ("HFFR") fillers. For example, U.S. Patent Application Publication 2003 / 0088000A1 discloses the use of expanding compounds with polymer systems such as polypropylene. Expanding compounds often contain pentaerythritol (as a char-forming agent), which is dehydrated to produce water, presumably in the presence of an acid or acid source (e.g., ammonium polyphosphate, a typical component of expanding compounds), and this can then cause premature crosslinking during melt extrusion of compositions containing silane-functionalized polymers. For this reason, these expanding compounds have not been previously used in silane crosslinking systems. Formula 1 of Applied Catalysis A:General 253(2003)29-32 shows the production of water from acid-catalyzed dehydration of pentaerythritol. Furthermore, expanding compounds have not been shown to have catalytic activity for water-induced crosslinking of silane-functionalized polyolefins.

[0004] Considering the above, it is remarkable to discover a method for crosslinking silane-functionalized polyolefins using an expandable flame retardant mixture that does not undergo premature crosslinking during melt extrusion. Even more remarkable is the evidence of catalytic activity against moisture-induced crosslinking of the compound after melt extrusion. [Overview of the Initiative]

[0005] This disclosure provides a moisture-curable polymer composition and a method for crosslinking a silane-functionalized polyolefin using a mixture of expandable flame retardants. The silane-functionalized polyolefin is preferably a silane-functionalized ethylene-based polymer.

[0006] The inventors of this disclosure have discovered that certain expandable compounds can function as catalysts for crosslinking silane-functionalized polyolefins without the need for additional or conventional catalysts. Specifically, it has been found that a mixture of expandable flame retardants containing piperazine pyrophosphate and a phosphate compound catalyzes a water-induced silane crosslinking reaction, thereby producing a crosslinked polymer composition having a gel content of 10% by weight or more, as measured according to ASTM D2765. Although not bound by theory, it is thought that acid-water curing catalysts may be generated during the thermal dissociation of phosphate compounds.

[0007] A method for crosslinking a moisture-curable polymer composition is provided, comprising the steps of: producing a moisture-curable polymer composition of a silane-functionalized polyolefin and an expandable flame retardant mixture, wherein the expandable flame retardant mixture comprises piperazine pyrophosphate and a phosphoric acid compound in an amount of 15% to 55% by weight, based on the total weight of the expandable flame retardant mixture; and catalyzing a moisture-induced crosslinking reaction of the silane-functionalized polyolefin using the expandable flame retardant mixture to form a moisture-curable polymer composition.

[0008] According to another feature of this disclosure, the step of catalyzing a water-induced crosslinking reaction is carried out in a water bath at a temperature above 50°C, or in a gaseous atmosphere having a temperature of 15°C or higher and a relative humidity of 10% or higher, as measured according to ASTM E337.

[0009] According to another feature of this disclosure, the moisture-curable polymer composition comprises 10% to 99% by weight of a silane-functionalized polyolefin, based on the total weight of the moisture-curable polymer composition, wherein the silane-functionalized polyolefin is a silane-functionalized ethylene-based polymer.

[0010] According to another feature of this disclosure, the silane-functionalized ethylene polymer contains 0.1% to 5.0% by weight of silane groups, based on the total weight of the silane-functionalized ethylene polymer.

[0011] According to another feature of the present disclosure, the silane is vinyltrimethoxysilane.

[0012] According to another feature of the present disclosure, the moisture-curable polymer composition contains 1 wt% to 90 wt% of an expandable flame retardant mixture based on the total weight of the moisture-curable polymer composition.

[0013] According to another feature of the present disclosure, the polymer composition contains 1 wt% to 30 wt% of an expandable flame retardant mixture based on the total weight of the moisture-curable polymer composition.

[0014] According to another feature of the present disclosure, the expandable flame retardant mixture contains 25 wt% to 45 wt% of a phosphoric acid compound based on the total weight of the expandable flame retardant mixture.

[0015] According to another feature of the present disclosure, the phosphoric acid compound is selected from the group consisting of melamine polyphosphate, ammonium polyphosphate, or a combination thereof.

[0016] According to another feature of the present disclosure, the moisture-curable polymer composition does not contain dibutyltin dilaurate and sulfonic acid.

Mode for Carrying Out the Invention

[0017] As used herein, the term "and / or" means that when used in a list of two or more items, any one of the listed items can be used by itself or any combination of two or more of the listed items can be used. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone, B alone, C alone, A and B in combination, A and C in combination, B and C in combination, or A, B, and C in combination.

[0018] Unless otherwise stated, all ranges include the endpoints.

[0019] Unless otherwise indicated with a hyphenated two-digit test method number, the test method refers to the most recent test method as of the priority date of this document. References to test methods include both references to the testing association and the test method number. Test method organizations are referred to by one of the following abbreviations: ASTM refers to ASTM International (formerly the American Society for Testing and Materials), EN refers to European Norm, DIN refers to the German Institute for Standardization (Deutsches Institut fuer Normung), and ISO refers to the International Organization for Standardization.

[0020] moisture-curable polymer composition This disclosure generally pertains to moisture-curable polymer compositions. These moisture-curable polymer compositions include a silane-functionalized polyolefin and a mixture of expandable flame retardants. The moisture-curable polymer compositions may exhibit a density of 1.70 g / cc or less, as measured according to ASTM D792. For example, a moisture-curable polymer composition may exhibit a density of 1.70 g / cc or less, or 1.65 g / cc or less, or 1.60 g / cc or less, or 1.55 g / cc or less, or 1.50 g / cc or less, or 1.45 g / cc or less, or 1.40 g / cc or less, or 1.30 g / cc or less, or 1.20 g / cc or less, or 1.10 g / cc or less, or 1.00 g / cc or less, or 0.99 g / cc or less, or 0.98 g / cc or less, or 0.97 g / cc or less, or 0.96 g / cc or less, or 0.95 g / cc or less, or 0.94 g / cc or less, when measured according to ASTM D792. According to various examples, the moisture-curable polymer composition does not contain dibutyltin dilaurate and sulfonic acid.

[0021] Silane-functionalized polyolefins "Silane-functionalized polyolefin" is a polymer containing silane and polymerized α-olefin in an amount of 50% by weight or more, or more than half, based on the total weight of the silane-functionalized polyolefin. "Polymer" means a macromolecular compound prepared by reacting (i.e., polymerizing) the same or different types of monomers. As described above, the moisture-curable polymer composition contains silane-functionalized polyolefin. The polyolefin contains polymerized α-olefin and optionally unsaturated esters.

[0022] Silane-functionalized polyolefins may include copolymers of α-olefins and silanes (i.e., α-olefin / silane copolymers), silane-grafted polyolefins, and / or combinations thereof. "α-olefin-silane copolymers" are formed by copolymerization of an α-olefin (e.g., ethylene) and a hydrolyzable silane monomer (e.g., vinylsilane monomer) such that the hydrolyzable silane monomer is incorporated into the polymer chain backbone before the polymer is incorporated into a moisture-curable polymer composition. "Silane-grafted polyolefins" or "Si-g-PO" may also be formed by a Sioplas process, where the hydrolyzable silane monomer is grafted onto the base polyolefin backbone by a process such as extrusion before the polymer is incorporated into a polymer composition.

[0023] In examples where the silane-functionalized polyolefin is a copolymer of an α-olefin and a silane, the silane-functionalized polyolefin is prepared by copolymerizing at least one α-olefin with a hydrolyzable silane monomer. In examples where the silane-functionalized polyolefin is a silane-grafted polyolefin, the silane-functionalized polyolefin is prepared by grafting one or more hydrolyzable silane monomers onto an α-olefin backbone.

[0024] Silane-functionalized polyolefins, when measured using Fourier transform infrared (FTIR) spectroscopy, contain 90% or more by weight, or 91% or more by weight, or 92% or more by weight, or 93% or more by weight, or 94% or more by weight, or 95% or more by weight, or 96% or more by weight, or 97% or more by weight, or 97.5% or more by weight, or 98% or more by weight, or 98.5% or more by weight, or 99% or more by weight, while simultaneously containing 99.5% or less by weight, or 99% or less by weight, or 98% or less by weight, or 97% or less by weight, or 96% or less by weight, or 95% or less by weight, or 94% or less by weight, or 93% or less by weight, or 92% or less by weight, or 91% or less of α-olefins and optionally unsaturated esters. α-olefins are C2, or C3-C4, or C6, or C8, or C 10 , or C 12 , or C 16 , or C 18 , or C 20 The α-olefins may include, for example, ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. The unsaturated esters may be alkyl acrylates, alkyl methacrylates, or vinyl carboxylates.

[0025] When measured using FTIR spectroscopy, silane-functionalized polyolefins are found to have a total weight of 0.1% by weight, or 0.3% by weight, or 0.5% by weight, or 0.8% by weight, or 1.0% by weight, or 1.2% by weight, or 1.5% by weight, or 1.6% to 1.8% by weight, or 2.0% by weight, or 2.3% by weight, or 2.5% by weight, or 3.0% by weight, or 3.5% by weight, or 4.0% by weight, or 4.5% by weight. It may contain silane in amounts of 5.0% by weight or less, or 4.5% by weight or less, or 4.0% by weight or less, or 3.5% by weight or less, or 3.0% by weight or less, or 2.5% by weight or less, or 2.4% by weight or less, or 2.3% by weight or less, or 2.0% by weight or less, or 1.8% by weight or less, or 1.6% by weight or less, or 1.4% by weight or less, or 1.2% by weight or less, or 1.0% by weight or less, or 0.8% by weight or less, or 0.6% by weight or less.

[0026] Silane-functionalized polyolefins, when measured by ASTM D792, have concentrations of 0.850 g / cc, or 0.860 g / cc, or 0.875 g / cc, or 0.880, or 0.890 g / cc to 0.900 g / cc, or 0.910 g / cc, or 0.915 g / cc, or 0.920 g / cc, or 0.930 g / cc, or 0.940 g / cc, or 0.950 g / cc, or 0.960 g / cc, or 0.965 g / cc, while on the other hand, At the same time, it may have a density of 0.970 g / cc or less, or 0.960 g / cc or less, or 0.950 g / cc or less, or 0.940 g / cc or less, or 0.930 g / cc or less, or 0.920 g / cc or less, or 0.910 g / cc or less, or 0.900 g / cc or less, or 0.890 g / cc or less, or 0.880 g / cc or less, or 0.870 g / cc or less, or 0.860 g / cc or less.

[0027] Silane-functionalized polyolefins may have a melt index when measured according to ASTM D1238 under conditions of 190°C / 2.16 kg weight, which is reported as the number of grams dissolved per 10 minutes (g / 10 min). The melt index of silane-functionalized polyolefins is 0.5 g / 10 min or more, or 1.0 g / 10 min or more, or 1.5 g / 10 min or more, or 2.0 g / 10 min or more, or 2.5 g / 10 min or more, or 3.0 g / 10 min or more, or 3.5 g / 10 min or more, or 4.0 g / 10 min or more, or 4.5 g / 10 min or more, while simultaneously being 50.0 g / 10 min or less, or 45.0 g / 10 min or less, or 40.0 g / 10 min or less, or 35.0 g / 1 It may be 0 minutes or less, or 30.0g / 10 minutes or less, or 25.0g / 10 minutes or less, or 20.0g / 10 minutes or less, or 15.0g / 10 minutes or less, or 10.0g / 10 minutes or less, or 5.0g / 10 minutes or less, or 4.5g / 10 minutes or less, or 4.0g / 10 minutes or less, or 3.5g / 10 minutes or less, or 3.0g / 10 minutes or less, or 2.5g / 10 minutes or less, or 2.0g / 10 minutes or less, or 1.5g / 10 minutes or less, or 1.0g / 10 minutes or less.

[0028] A "hydrolyzable silane monomer" is a silane-containing monomer that effectively copolymerizes with α-olefins (e.g., ethylene) to form α-olefin / silane copolymers (e.g., ethylene / silane copolymers), or grafts onto α-olefin polymers (i.e., polyolefins) to form Si-g-PO, thereby enabling subsequent crosslinking of silane-functionalized polyolefins. A representative but not limited example of a hydrolyzable silane monomer has structure (I),

[0029] [ka] In the formula, R 1 x is a hydrogen atom or a methyl group, x is 0 or 1, n is an integer from 1 to 4, or 6, or 8, or 10, or 12, and each R 2 However, independently, hydrolyzable organic groups, such as alkoxy groups having 1 to 12 carbon atoms (e.g., methoxy, ethoxy, butoxy), aryloxy groups (e.g., phenoxy), araloxy groups (e.g., benzyloxy), aliphatic acyloxy groups having 1 to 12 carbon atoms (e.g., formyloxy, acetyloxy, propanoyloxy), amino groups or substituted amino groups (e.g., alkylamino, arylamino), or lower alkyl groups having 1 to 6 carbon atoms, provided that three R's are present. 2One of the groups is alkyl. The hydrolyzable silane monomer can copolymerize with an α-olefin (such as ethylene) in a reactor, such as a high-pressure process, to form an α-olefin-silane copolymer (i.e., a reactor copolymer). In the example where the α-olefin is ethylene, such a copolymer is referred to herein as an ethylene-silane copolymer. The hydrolyzable silane monomer can be grafted onto a polyolefin (such as polyethylene) using an organic peroxide, such as 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, to form Si-g-PO or in-situ Si-g-PO. In-situ Si-g-PO is formed by a process such as the MONOSIL® process, in which the hydrolyzable silane monomer is grafted onto the backbone of the polyolefin during extrusion of the composition to form a coated conductor, as described, for example, in U.S. Patent No. 4,574,133.

[0030] The hydrolyzable silane monomer may include a silane monomer containing an ethylenically unsaturated hydrocarbyl group, such as vinyl, allyl, isopropenyl, butenyl, cyclohexenyl, or gamma (meth)acryloxyallyl group, and a hydrolyzable group, such as a hydrocarbyloxy, hydrocarbonyloxy, or hydrocarbylamino group. The hydrolyzable group may include methoxy, ethoxy, formyloxy, acetoxy, propionyloxy, and alkyl or arylamino groups. In a specific example, the hydrolyzable silane monomer is an unsaturated alkoxysilane, which can be grafted onto a polyolefin or copolymerized with an α-olefin (such as ethylene) in a reactor. Examples of the hydrolyzable silane monomer include vinyltrimethoxysilane (VTMS), vinyltriethoxysilane (VTES), vinyltriacetoxysilane, and gamma-(meth)acryloxypropyltrimethoxysilane. With respect to structure (I), for VTMS, x = 0, R 1 = hydrogen, and R 2 = methoxy, for VTES, x = 0, R 1= Hydrogen, and R 2 = For ethoxy and vinyltriacetoxysilane, x=0, R 1 =H and R 2 = Acetoxy

[0031] Examples of suitable ethylene-silane copolymers are commercially available as SI-LINK® DFDA-5451 NT and SI-LINK® AC DFDB-5451 NT, respectively, from The Dow Chemical Company, Midland, Mich.

[0032] The moisture-curable polymer composition may contain 10% to 99% by weight of silane-functionalized polyolefin. For example, the moisture-curable polymer composition may contain 10% or more by weight, or 15% or more by weight, or 20% or more by weight, or 25% or more by weight, or 30% or more by weight, or 35% or more by weight, or 40% or more by weight, or 45% or more by weight, or 50% or more by weight, or 55% or more by weight, or 60% or more by weight, or 65% or more by weight, or 70% or more by weight, or 75% or more by weight, or 80% or more by weight, or 85% or more by weight, or 90% or more by weight, or 95% or more by weight, based on the total weight of the moisture-curable polymer composition. It contains silane-functionalized polyolefins in amounts of 98% by weight or more, while simultaneously containing 99% by weight or less, 95% by weight or less, 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, 45% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight or less, 25% by weight or less, or 20% by weight or less.

[0033] Ethylene-based polymers The polyolefins in silane-functionalized polyolefins may be ethylene-based polymers. Furthermore, ethylene-based polymers may be silane-functionalized and used as blending components in formulations. Ethylene-based polymers may be non-polar or polar ethylene-based polymers. As used herein, the term “non-polar” as used in relation to polymers means containing 0.1% by weight or less of polar monomers or comonomers, as measured using nuclear magnetic resonance ("NMR"), Fourier transform infrared ("FTIR") spectroscopy, or X-ray fluorescence (XRF) techniques. As used herein, an “ethylene-based” polymer is a polymer in which more than 50% by weight of monomers is ethylene, but other comonomers may also be used. A description of "ethylene-based" polymers (both polar and nonpolar) can be found in Patel, R., "Types and Basics of Polyethylene," In: Mark A. Spalding and Ananda M. Chatterjee (eds.), Handbook of Industrial Polyethylene and Technology, Chapter 4, Scrivener, 2017, pp. 105-138. Polar ethylene-based polymers may include ethylene and one or more unsaturated esters (e.g., alkyl acrylate, alkyl methacrylate, or vinyl carboxylate). Ethylene-based polymers may include ethylene and one or more C3-C3 esters such as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene. 20It may include α-olefin comonomers. Ethylene polymers may have a unimodal or multimodal molecular weight distribution and may be used alone or in combination with one or more other types of ethylene polymers (e.g., a blend of two or more ethylene polymers having different monomer compositions and content, catalyst preparation methods, molecular weights, molecular weight distributions, densities, etc.). When a blend of ethylene polymers is used, the polymers may be blended by any in-reactor or post-reactor process. The term "multimodal polymer" refers to a polymer characterized by having at least two distinct peaks in a gel permeation chromatography (GPC) chromatogram showing the molecular weight distribution of the composition. Therefore, the collective term multimodal polymer includes bimodal polymers having two main fractions: a first fraction which may be a low molecular weight fraction and / or component, and a second fraction which may be a high molecular weight fraction and / or component.

[0034] When ethylene-based polymers are measured using NMR, FTIR spectroscopy, or XRF, they are found to contain 50% or more by weight, 60% or more by weight, 70% or more by weight, 80% or more by weight, 85% or more by weight, 90% or more by weight, or 91% or more by weight, or 92% or more by weight, or 93% or more by weight, or 94% or more by weight, or 95% or more by weight, or 96% or more by weight, or 97% or more by weight, or 97.5% or more by weight, or 98% or more by weight, or 98.5% by weight. The ethylene may be present in amounts of 100% or less by weight, or 99% or more by weight, or 99.5% or more by weight, while simultaneously being present in amounts of 100% or less by weight, 99.5% or less by weight, or 99% or less by weight, 98.5% or less by weight, or 98% or less by weight, or 97% or less by weight, or 96% or less by weight, or 95% or less by weight, or 94% or less by weight, or 93% or less by weight, or 92% or less by weight, or 91% or less by weight, or 90% or less by weight, or 85% or less by weight, or 80% or less by weight, or 70% or less by weight, or 60% or less by weight. Other units of ethylene polymers include unsaturated esters (e.g., alkylacrylic acid, alkylmethacrylic acid, or vinyl carboxylic acid), or α-olefins (e.g., propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene, etc., C3, C4, C6, or C8, or C 10 , or C 12 , or C 16 , or C 18 , or C 20 Examples include α-olefins.

[0035] Ethylene-based polymers can have densities ranging from 0.850 g / cc to 0.970 g / cc when measured according to ASTM D792. For example, ethylene-based polymers, when measured according to ASTM D792, may have densities of 0.850 g / cc or more, 0.860 g / cc or more, or 0.870 g / cc or more, or 0.880 g / cc or more, or 0.890 g / cc or more, or 0.900 g / cc or more, or 0.900 g / cc or more, or 0.910 g / cc or more, or 0.915 g / cc or more, or 0.920 g / cc or more, or 0.921 g / cc or more, or 0.922 g / cc or more, or 0.925 g / cc or 0.928 g / cc or more, while simultaneously having densities of 0.970 g It may have a density of less than or equal to / cc, less than or equal to 0.960 g / cc, less than or equal to 0.950 g / cc, or less than or equal to 0.940 g / cc, less than or equal to 0.930 g / cc, or less than or equal to 0.925 g / cc, or less than or equal to 0.920 g / cc, or less than or equal to 0.915 g / cc, or less than or equal to 0.910 g / cc, or less than or equal to 0.900 g / cc, or less than or equal to 0.890 g / cc, or less than or equal to 0.880 g / cc, or less than or equal to 0.870 g / cc, or less than or equal to 0.865 g / cc, or less than or equal to 0.860 g / cc, or less than or equal to 0.855 g / cc.

[0036] Ethylene-based polymers may have a melt index when measured according to ASTM D1238 under conditions of 190°C / 2.16 kg weight, which is reported as grams of elution per 10 minutes (g / 10 min). The melt index of ethylene-based polymers is considered to be 0.3 g / 10 min or higher, or 0.5 g / 10 min or higher, or 1.0 g / 10 min or higher, or 1.5 g / 10 min or higher, or 2.0 g / 10 min or higher, or 2.5 g / 10 min or higher, or 3.0 g / 10 min or higher, or 3.5 g / 10 min or higher, or 4.0 g / 10 min or higher, or 4.5 g / 10 min or higher, or 5.0 g / 10 min or higher, or 5.5 g / 10 min or higher, or 6.0 g / 10 min or higher, while simultaneously being 30.0 g / 10 min or lower, or 25. It may be 0g / 10 min or less, or 20.0g / 10 min or less, or 15.0g / 10 min or less, or 10.0g / 10 min or less, or 6.0g / 10 min or less, or 5.5g / 10 min or less, or 5.0g / 10 min or less, or 4.5g / 10 min or less, or 4.0g / 10 min or less, or 3.5g / 10 min or less, or 3.0g / 10 min or less, or 2.5g / 10 min or less, or 2.0g / 10 min or less, or 1.5g / 10 min or less, or 1.0g / 10 min or less, or 0.5g / 10 min or less.

[0037] Ethylene polymers may be polar ethylene polymers. As used herein, the term “polar” in relation to polymers means containing 0.1% by weight or more of polar monomers or comonomers, as measured using NMR, FTIR spectroscopy, or XRF techniques. Other units of ethylene polymers may be derived from one or more polymerizable monomers, including but not limited to polar monomers such as unsaturated esters. Acids may be acrylic acid and methacrylic acid. Unsaturated esters may be alkyl acrylates, alkyl methacrylates, or vinyl carboxylates. Alkyl groups may have 1 to 8 carbon atoms or 1 to 4 carbon atoms. Carboxylate groups may have 2 to 8 carbon atoms or 2 to 5 carbon atoms. Examples of acrylates and methacrylates include, but are not limited to, ethyl acrylate, methyl acrylate, methyl methacrylate, t-butyl acrylate, n-butyl acrylate, n-butyl methacrylate, and 2-ethylhexyl acrylate. Examples of vinyl carboxylates include, but are not limited to, vinyl acetate, vinyl propionate, and vinyl butanoate. Polar ethylene polymers typically have a high level of long-chain branching.

[0038] The density of polar ethylene polymers, when measured according to ASTM D792, can range from 0.925 g / cc to 0.985 g / cc. For example, the density of polar ethylene polymers, when measured according to ASTM D792, can be 0.925 g / cc or more, or 0.930 g / cc or more, or 0.935 g / cc or more, or 0.940 g / cc or more, 0.945 g / cc or more, or 0.950 g / cc or more, or 0.955 g / cc or more, or 0.960 g / cc or more, or 0.965 g / cc or more, or 0.970 g / cc or more, or 0.975 g / cc or more, or 0.980 g / cc or more. On the other hand, it may also be 0.985 g / cc or less, or 0.980 g / cc or less, or 0.975 g / cc or less, or 0.970 g / cc or less, or 0.965 g / cc or less, or 0.960 g / cc or less, or 0.955 g / cc or less, or 0.950 g / cc or less, or 0.945 g / cc or less, or 0.940 g / cc or less, or 0.935 g / cc or less, or 0.930 g / cc or less.

[0039] The moisture-curable polymer composition may contain 0% to 40% by weight of an ethylene-based polymer, which is not silane-functionalized. The silane-unfunctionalized ethylene-based polymer may be added alone and / or as part of a masterbatch of a swellable flame retardant mixture. For example, the moisture-curable polymer composition may contain 0% or more by weight, or 1% or more by weight, or 5% or more by weight, 10% or more by weight, or 15% or more by weight, or 20% or more by weight, or 25% or more by weight, or 30% or more by weight, or 35% or more by weight, while simultaneously containing 40% or less by weight, or 35% or less by weight, or 30% or less by weight, or 25% or less by weight, or 20% or less by weight, or 15% or less by weight, or 10% or less by weight, or 5% or less by weight of an ethylene-based polymer.

[0040] Halogen-free flame retardant Moisture-curing polymer compositions may contain halogen-free flame retardants. Halogen-free flame retardants can inhibit, suppress, or delay flame generation. As used herein, "halogen-free" and similar terms mean that the flame retardant filler has no halogen content, or substantially no halogen content, i.e., contains less than 10,000 mg of halogen per kg of flame retardant filler as measured by ion chromatography (IC) and similar analytical methods. Halogen content below this amount is considered insignificant to the effectiveness of the flame retardant filler, for example, in coated conductors (also called insulated wires). Examples of halogen-free flame retardants suitable for use in moisture-curing polymer compositions include, but are not limited to, swelling flame retardants and other halogen-free flame retardants, metal hydrates (e.g., aluminum hydroxide, magnesium hydroxide), metal carbonates, red phosphorus, silica, alumina, brucite (a mineral form of magnesium hydroxide), metal oxides (e.g., zinc oxide, calcium oxide, magnesium oxide, titanium oxide), carbon nanotubes, talc, clay, organically modified clay, calcium carbonate, zinc borate, antimony trioxide, wollastonite, mica, ammonium octamolybdate, frit, hollow glass microspheres, swelling materials, or compounds, swelling graphite, and combinations thereof. In one embodiment, another halogen-free flame retardant is selected from fillers having a hydroxyl moiety (e.g., metal hydrate) and / or a hydroxyl group (e.g., silica). In one embodiment, the metal hydrate of the halogen-free flame retardant may be selected from the group consisting of aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, iron hydroxide, copper hydroxide, and combinations thereof. In one embodiment, another halogen-free flame retardant is selected from the group consisting of metal hydrates, metal oxides, silica, and combinations thereof. The halogen-free flame retardant may optionally be surface-treated (coated) with silane, saturated or unsaturated carboxylic acids with 8 to 24 carbon atoms or 12 to 18 carbon atoms, or metal salts of acids, or other substances.Exemplary surface treatments are described in U.S. Patents 4,255,303, 5,034,442, 7,514,489, U.S. Patent Application Publication 2008 / 0251273, and International Publication 2013 / 116283. Alternatively, silanes, acids, or salts may be added to the composition in similar amounts, rather than using a surface treatment procedure. Other surface treatments known in the art, including titanates, phosphates, and zirconates, may also be used.

[0041] Examples of commercially available halogen-free flame retardants suitable for use in moisture-curing polymer compositions include, but are not limited to, APYRAL® 40CD aluminum hydroxide from Nabaltec AG, MAGNIFIN® H5 magnesium hydroxide from Magnifin Magnesiaprodukte GmbH & Co KG, Microcarb 95T ultrafine and treated calcium carbonate from Reverte, and combinations thereof.

[0042] The moisture-curable polymer composition is defined as having a concentration of 0% by weight, or 0.1% or more by weight, or 0.5% or more by weight, or 1% or more by weight, or 3% or more by weight, or 5% or more by weight, or 7% or more by weight, or 10% or more by weight, or 12% or more by weight, or 14% or more by weight, or 16% or more by weight, or 18% or more by weight, or 20% or more by weight, or 22% or more by weight, or 24% or more by weight, or 26% or more by weight, or 28% or more by weight, or 30% or more by weight, or 32% or more by weight, or 34% or more by weight, or 36% or more by weight, or 38% or more by weight, or 40% or more by weight, or 42% or more by weight, or 44% or more by weight, or 46% or more by weight, or 48% or more by weight, based on the total weight of the moisture-curable polymer composition. It may contain a halogen-free flame retardant at a concentration of 50% or more by weight, or 48% or less by weight, or 46% or less by weight, or 44% or less by weight, or 42% or less by weight, or 40% or less by weight, or 38% or less by weight, or 36% or less by weight, or 34% or less by weight, or 32% or less by weight, or 30% or less by weight, or 28% or less by weight, or 26% or less by weight, or 24% or less by weight, or 22% or less by weight, or 20% or less by weight, or 18% or less by weight, or 16% or less by weight, or 14% or less by weight, or 12% or less by weight, or 10% or less by weight, or 7% or less by weight, or 5% or less by weight, or 3% or less by weight, or 1% or less by weight, or 0.5% or less by weight.

[0043] Expandable flame retardant mixture The moisture-curing polymer composition contains an expandable flame retardant mixture as an HFFR filler. The expandable flame retardant mixture may contain piperazine pyrophosphate and a phosphoric acid compound. The expandable flame retardant mixture may contain 45% to 85% by weight of piperazine pyrophosphate based on the total weight of the expandable flame retardant mixture. For example, the expandable flame retardant mixture may contain 45% or more by weight, or 50% or more by weight, or 55% or more by weight, or 60% or more by weight, or 65% or more by weight, or 70% or more by weight, or 75% or more by weight, or 80% or more by weight, while simultaneously containing 85% or less by weight, or 80% or less by weight, or 75% or less by weight, or 70% or less by weight, or 65% or less by weight, or 60% or less by weight, or 55% or less by weight, or 50% or less by weight, or 45% or less by weight of piperazine pyrophosphate.

[0044] The expandable flame retardant mixture may contain 15% to 55% by weight of a phosphorus compound, based on the total weight of the expandable flame retardant mixture. For example, the expandable flame retardant mixture may contain 15% or more by weight, or 20% or more by weight, or 25% or more by weight, or 30% or more by weight, or 35% or more by weight, or 40% or more by weight, or 45% or more by weight, or 50% or more by weight, while simultaneously containing 55% or less by weight, or 50% or less by weight, or 45% or less by weight, or 40% or less by weight, or 35% or less by weight, or 30% or less by weight, or 25% or less by weight, or 20% or less by weight of a phosphorus compound.

[0045] Phosphate compounds may consist of one or more materials. Phosphate compounds may be salts formed by the reaction of phosphoric acid or polyphosphate with an amine. Phosphate compounds may be selected from melamine polyphosphate (a reaction product of melamine and polyphosphate), ammonium polyphosphate (a reaction product of ammonia and polyphosphate), or a combination thereof.

[0046] The expandable flame retardant mixture may contain a flame retardant synergistic agent in an amount of 0% to 20% by weight, based on the total weight of the expandable flame retardant mixture. For example, an expandable flame retardant mixture may contain, based on the total weight of the expandable flame retardant mixture, 0% or more by weight, or 0.5% or more by weight, or 1.0% or more by weight, or 2% or more by weight, or 3% or more by weight, or 4% or more by weight, or 5% or more by weight, or 6% or more by weight, or 7% or more by weight, or 8% or more by weight, or 9% or more by weight, or 10% or more by weight, while simultaneously containing 20% ​​or less by weight, or 18% or less by weight, or 16% or less by weight, or 14% or less by weight, or 13% or less by weight, or 12% or less by weight, or 11% or less by weight, or 10% or less by weight, or 9% or less by weight, or 8% or less by weight, or 7% or less by weight, or 6% or less by weight, or 5% or less by weight, or 4% or less by weight, or 3% or less by weight, or 2% or less by weight, or 1% or less by weight, or 0.5% or less by weight, or 0% by weight, as a flame retardant synergist. The flame retardant synergist in the expandable flame retardant mixture may be a silicone component (e.g., silicone gum, but not limited to silicone gum). The flame retardant synergist in the expandable flame retardant mixture may be a metal oxide. In one embodiment, the flame retardant synergist in the expandable flame retardant mixture is zinc oxide.

[0047] Furthermore, the moisture-curable polymer composition contains an expansive flame retardant mixture in an amount of 1% to 90% by weight, based on the total weight of the polymer composition. For example, the polymer composition may contain 1% or more by weight, or 5% or more by weight, or 7% or more by weight, or 10% or more by weight, or 15% or more by weight, or 20% or more by weight, or 25% or more by weight, or 30% or more by weight, or 31% or more by weight, or 35% or more by weight, or 40% or more by weight, or 45% or more by weight, or 50% or more by weight, or 55% or more by weight, or 60% or more by weight, or 65% or more by weight, or 70% or more by weight, or 75% or more by weight, or 80% or more by weight, or It may contain an expandable flame retardant mixture in an amount of 85% by weight or more, while simultaneously containing 90% by weight or less, or 85% by weight or less, or 80% by weight or less, or 75% by weight or less, or 70% by weight or less, or 65% by weight or less, or 60% by weight or less, or 55% by weight or less, less, 50% by weight or less, or 45% by weight or less, or 40% by weight or less, or 35% by weight or less, or 31% by weight or less, or 30% by weight or less, or 25% by weight or less, or 20% by weight or less, or 15% by weight or less, or 10% by weight or less, or 5% by weight or less.

[0048] additives A moisture-curable polymer composition may contain one or more additives. Non-limiting examples of suitable additives include antioxidants, colorants, corrosion inhibitors, lubricants, ultraviolet (UV) absorbers, or stabilizers, anti-blocking agents, moisture scavengers (including hydrolyzable silane monomers), silanol condensation catalysts, flame retardants, coupling agents, compatibilizers, plasticizers, fillers, processing aids, propylene polymers (including polypropylene homopolymers, random copolymer polypropylenes, and impact copolymer polypropylenes, as well as homopolymers and copolymers), and combinations thereof. Compatibilizers include, but are not limited to, anhydrous-modified ethylene polymers (e.g., anhydrous-modified ethylene plastomers or elastomers).

[0049] Moisture-curing polymer compositions may contain antioxidants. Non-limiting examples of suitable antioxidants include phenolic antioxidants, thio-based antioxidants, phosphoric acid-based antioxidants, and hydrazine-based metal deactivators. Suitable phenolic antioxidants include high molecular weight hindered phenols, methyl-substituted phenols, phenols having substituents with primary or secondary carbonyl compounds, and polyfunctional phenols such as sulfur and phosphorus-containing phenols. Typical hindered phenols include 1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, pentaerythrityltetrakis-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, n-octadecyl-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 4,4'-methylenebis(2,6-tert-butyl-pheno Examples include 4,4'-thiobis(6-tert-butyl-o-cresol), 2,6-di-tert-butylphenol, 6-(4-hydroxyphenoxy)-2,4-bis(n-octyl-thio)-1,3,5-triazine, di-n-octylthio)ethyl 3,5-di-tert-butyl-4-hydroxy-benzoate, and sorbitol hexa[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionate]. The polymer composition may include pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), which is commercially available from BASF as Irganox® 1010. A non-limiting example of a preferred methyl-substituted phenol is isobutylidenebis(4,6-dimethylphenol). A non-limiting example of a suitable hydrazine-based metal deactivator is oxalylbis(benzylidene hydrazide).The moisture-curable polymer composition may contain an antioxidant in an amount of 0% by weight, or 0.001% by weight, or 0.01% by weight, or 0.02% by weight, or 0.05% by weight, or 0.1% by weight, or 0.2% by weight, or 0.3% by weight, or 0.4% to 0.5% by weight, or 0.6% by weight, or 0.7% by weight, or 0.8% by weight, or 1.0% by weight, or 2.0% by weight, or 2.5% by weight, or 3.0% by weight, based on the total weight of the moisture-curable polymer composition.

[0050] Moisture-curing polymer compositions may contain ultraviolet (UV) absorbers or stabilizers. A non-limiting example of a suitable UV stabilizer is a hindered amine light stabilizer (HALS). A non-limiting example of a suitable HALS is 1,3,5-triazine-2,4,6-triamine, N,N-1,2-ethanediylbis-N-3-4,6-bisbutyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amino-1,3,5-triazine-2-ylaminopropyl-N,N-dibutyl-N,N-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-1,5,8,12-tetrakis[4,6-bis(n-butyl-n-1,2,2,6,6-pentamethyl-4-piperidylamino)-1,3,5-triazine-2-yl]-1,5,8,12-tetraazadodecane (which is commercially available from SABO SpA (Levate, Italy) as SABO® STAB UV-119). In one embodiment, the composition contains 0% by weight, or 0.001% by weight, or 0.002% by weight, or 0.005% by weight, or 0.006% to 0.007% by weight, or 0.008% by weight, or 0.009% by weight, or 0.01% by weight, or 0.2% by weight, or 0.3% by weight, or 0.4% by weight, or 0.5% by weight, or 1.0% by weight, or 2.0% by weight, or 2.5% by weight, or 3.0% by weight of a UV absorber or stabilizer, based on the total weight of the composition.

[0051] The moisture-curing polymer composition may contain processing aids. Non-limiting examples of suitable processing aids include oils, organic acids (e.g., stearic acid), and metal salts of organic acids (e.g., zinc stearate). In one embodiment, the composition contains 0% by weight, or 0.01% by weight, or 0.02% by weight, or 0.05% by weight, or 0.07% by weight, or 0.1% by weight, or 0.2% by weight, or 0.3% by weight, or 0.4% to 0.5% by weight, or 0.6% by weight, or 0.7% by weight, or 0.8% by weight, or 1.0% by weight, or 2.0% by weight, or 2.5% by weight, or 3.0% by weight, or 5.0% by weight, or 10.0% by weight, or 20.0% by weight, of the total weight of the composition, of the processing aids.

[0052] The moisture-curable polymer composition may contain additives in amounts of 0% or more by weight, or 0.001% or more by weight, or 0.002% or more by weight, or 0.005% or more by weight, or 0.006% or more by weight, or 0.008% or more by weight, or 0.009% or more by weight, or 0.01% or more by weight, or 0.2% or more by weight, or 0.3% or more by weight, or 0.4% or more by weight, or 0.5% or more by weight, or 1.0% or more by weight, or 2.0% or more by weight, or 3.0% or more by weight, or 4.0% or more by weight, or 5.0% or more by weight, or 10.0% or more by weight, or 15.0% or more by weight, or 20.0% or more by weight, or 30% or more by weight, or 40% or more by weight, or 50% or more by weight, based on the total weight of the moisture-curable polymer composition.

[0053] Crosslinking of moisture-curing polymer compositions This disclosure also relates to a method for crosslinking a moisture-curable polymer composition to form a moisture-curable polymer composition. Such a method comprises the step of preparing a moisture-curable polymer composition of a silane-functionalized polyolefin and an expandable flame retardant mixture, wherein the expandable flame retardant mixture comprises piperazine pyrophosphate and a phosphoric acid compound in an amount of 15% to 55% by weight, based on the total weight of the expandable flame retardant mixture. After the moisture-curable polymer composition has been prepared, it may be crosslinked to form a moisture-curable polymer composition.

[0054] A moisture-curable polymer composition can be converted to a moisture-curable polymer composition by using an expandable flame retardant mixture to catalyze a moisture-induced crosslinking reaction of a silane-functionalized polyolefin to form a moisture-curable polymer composition. As used herein, the term “moisture-curing” means that the curing process is carried out in the presence of water, and that water is a necessary component in the curing process. For example, the step of catalyzing the moisture-induced crosslinking reaction may be carried out in a water bath at a temperature above 50°C, or in a gaseous atmosphere having a temperature of 15°C or higher and a relative humidity of 10% or higher, as measured according to ASTM E337. The gaseous atmosphere may be air at room temperature and room humidity, for example, 23°C and 50% relative humidity.

[0055] The curing process is carried out by the condensation reaction of hydrolyzable silane monomers in silane-functionalized polyolefins. The condensation reaction of hydrolyzable silane monomers results in crosslinking of the polymer chains of the silane-functionalized polyolefin chains, thereby causing the curing of the silane-functionalized polyolefin. Although such a reaction can occur in the presence of water, practical manufacturing and engineering considerations in the production of moisture-curable polymer compositions often indicate the use of catalysts to increase the rate of the condensation reaction and ultimately accelerate the curing of the moisture-curable polymer composition. As described above, acid-moisture curing catalysts can be produced during the thermal dissociation of phosphorylated compounds, which is thought to lead to an increase in the rate of the moisture curing reaction. Such characteristics are advantageous for a variety of reasons. Firstly, the fact that a swellable flame retardant mixture can also be used as a catalyst is advantageous in that fewer distinct components are required, thus simplifying the production and eliminating the complexity of the formulation of moisture-curable polymer compositions. Secondly, because the expandable flame retardant mixture does not contain materials such as tin and other substances of potential concern, the resulting moisture-curing polymer composition may face less regulatory pressure.

[0056] moisture-curing polymer composition A moisture-curing polymer composition exhibits one or more of the following properties: a peak tensile strength of 4 megapascals (MPa) or more, as measured according to ASTM D638; a tensile elongation at break of 50% or more, as measured according to ASTM D638; a gel content of 10% or more, as measured according to ASTM D2765; and a hot creep of 175% or less, as measured according to UL 2556 section 7.9. A moisture-curing polymer composition may exhibit a peak tensile strength of 4 MPa or more, or 6 MPa or more, or 8 MPa or more, or 10 MPa or more, or 12 MPa or more, or 14 MPa or more, or 16 MPa or more, or 18 MPa or more, as measured according to ASTM D638, while simultaneously exhibiting a peak tensile strength of 20 MPa or less, or 18 MPa or less, or 16 MPa or less, or 14 MPa or less, or 12 MPa or less, or 10 MPa or less, or 8 MPa or less, or 6 MPa or less. For example, a moisture-curing polymer composition may exhibit a tensile elongation at break of 50% or more, or 75% or more, or 100% or more, or 125% or more, or 150% or more, or 175% or more, or 200% or more, or 225% or more, or 250% or more, or 275% or more, or 300% or more, or 325% or more, or 350% or more, or 375% or more, while simultaneously exhibiting a tensile elongation at break of 400% or less, or 375% or less, or 350% or less, or 325% or less, or 300% or less, or 275% or less, or 250% or less, or 225% or less, or 200% or less, or 175% or less, or 150% or less, or 125% or less, or 100% or less, or 75% or less, when measured according to ASTM D638. Moisture-curing polymer compositions may exhibit a gel content of 10% or more, or 20% or more, or 30% or more, or 40% or more, or 50% or more, or 60% or more, or 70% or more, as measured according to ASTM D2765. For example, moisture-curing polymer compositions may exhibit hot creep of 175% or less, or 150% or less, or 125% or less, or 100% or less, or 75% or less, or 50% or less, or 25% or less, as measured according to UL 2556 Section 7.9.

[0057] Insulated conductor This disclosure also provides a coated conductor. The coated conductor comprises a conductor and a coating on the conductor, the coating comprising a moisture-curing polymer composition. The moisture-curing polymer composition is at least partially disposed around the conductor to produce the coated conductor. The conductor may include a conductive metal and / or an optical waveguide. The coated conductor may, in other words, be known as a wire, optical fiber, cable, or other connector.

[0058] A moisture-curing polymer composition is placed on and / or around a conductor to form a coating. The coating may be one or more inner layers, such as an insulating layer. The coating may cover the conductor entirely or partially, or otherwise surround or enclose it. The coating may be the sole component surrounding the conductor as an insulator or jacket. Alternatively, the coating may be one layer of a multilayer jacket or sheath enclosing the conductor. The coating may be in direct contact with the conductor. The coating may be in direct contact with the insulating layer surrounding the conductor.

[0059] The insulated conductor can pass the UL-2556 horizontal combustion test. [Examples]

[0060] Test method Melt Index: The melt index (MI) value was measured according to ASTM D1238, using a load of 2.16 kg or 21.6 kg at 190°C or 150°C.

[0061] Density was measured according to ASTM D792, Method B, or calculated as follows: For a given composition, the "mL per 100 grams" of each component or element is the "weight %" of that component, expressed in g / cm³. 3 It was obtained by dividing by its density. The individual values ​​of "mL per 100 grams" for each component were added together to obtain the total value of "mL per 100 grams" for that particular formulation. Next, the number "100" (representing the total weight % of all components in that formulation) was divided by the total value of "mL per 100 grams" to obtain the "calculated density" of that particular formulation in g / cm³. 3The densities obtained were the same or similar. For measurement, the samples were prepared according to ASTM D 1928. The samples were prepared by compression molding as described above. Using ASTM D792, Method B, the samples were pressed for 40 hours and then density measurements were performed.

[0062] The hot creep (also known as hot creep elongation) of a polymer composition (i.e., the coating removed from an insulated wire, i.e., a coated conductor) is measured under a fixed stress (0.2 MPa) at a specific temperature (either 250°C, 200°C, or 150°C) according to UL 2556 Section 7.9 and ICEA-T-28-562-2003. A lower hot creep measurement indicates a higher degree of crosslinking.

[0063] For coated conductors, the tensile peak stress (also known as tensile strength) and tensile strain at fracture (also known as tensile elongation) of the polymer composition are measured according to Underwriter's Laboratory ("UL") 2556, Section 3.5, at a displacement rate of 20 inches (508 mm) / min, 23°C, and 50% relative humidity. The average of four or five measurements is taken. Each test specimen is prepared by removing the polymer composition coating (insulator) from a coated conductor without damaging the coated conductor.

[0064] Tensile properties are also measured in extruded tapes and compression-molded samples made from polymer compositions at a displacement rate of 20 inches (508 mm) per minute (using Type IV dogbone-shaped test specimens obtained from tapes and compression-molded samples), according to ASTM D638-14.

[0065] The gel content of the polymer composition (i.e., the coating removed from the insulated wire, i.e., the coated conductor) was determined by extraction with the solvent decahydronaphthalene (decalin) under boiling conditions for 6 hours, according to ASTM D2765. A higher gel content indicates a higher degree of crosslinking.

[0066] Silane Test: X-ray fluorescence spectroscopy ("XRF") is used to determine the weight percentage (Wt%) of silicon atoms (Si) in the ethylene-silane copolymer test sample, and then the unit weight percentage of the silane comonomer is calculated. Using a Buehler SimpliMet 300 automated embedding machine preheated to 115.6°C for 3 minutes (240°F), the powder form of the test sample is pressed for 1 minute under 8.3 megapascals (MPa; 1,200 lbs / square inch (psi)) to form a plaque with a thickness of approximately 6 mm, and the plaque is cooled to 25°C. The Si atom content of the plaque is analyzed by wavelength-dispersive XRF using a wavelength-dispersive X-ray fluorescence spectrometer from PANalytical Axios. The Si atom content is determined by comparing the line intensity of the XRF spectrum with a calibration curve of Si atom content established using polymer standards of known Si atom concentrations, which are individually measured using activation analysis (NAA) or inductively coupled plasma (ICP) methods. The weight percentage of hydrolyzable silyl group comonomers (i.e., the weight percentage of hydrolyzable silyl groups) in ethylene-silane copolymers is calculated using the weight percentage of Si atoms measured by XRF and the molecular weight of at least one silane comonomer derived from the hydrolyzable silyl group. For hydrolyzable silyl groups derived from vinyltrimethoxysilane (VTMS), the molecular weight of VTMS (148.23 g / mol) is used. To calculate the hydrolyzable silyl group content of ethylene-silane copolymers (weight percentage of hydrolyzable silyl group comonomer units), the weight percentage of Si atoms ("C") obtained by XRF and the following formula: p=C * Using (m / 28.086)(1 / 10000ppmw), in the formula, *∫ represents multiplication, ∫ / represents division, p is the weight % of hydrolyzable silyl groups in the ethylene-silane copolymer, C is the weight of Si atoms in parts per million (ppmw) (XFR), m is the molecular weight in g / mol of the silane comonomer derived by the hydrolyzable silyl groups, 28.086 is the atomic weight of the silicon atom, and 10000 ppmw is 1 part by weight in 1.00 wt%. For example, if XRF indicates 379 ppmw of Si atoms in the ethylene-silane copolymer and the comonomer used to produce the ethylene-silane copolymer is VTMS with a molecular weight of 148.23 g / mol, then the wt% comonomer content is 0.20 wt%. To calculate the molar percentage of hydrolyzable silyl group comonomer units in the ethylene-silane copolymer of the silane comonomer used, use the calculated wt% of hydrolyzable silyl group comonomer units in the ethylene-silane copolymer and the following formula: G=100 * (p / m) / [(p / m)+(100.00wt%-p) / 28.05g / mol], in the formula, *The symbol (x) represents multiplication, where G is the mole percent (mol%) of hydrolyzable silyl groups in the ethylene-silane copolymer. p is the weight percent of hydrolyzable silyl groups in the ethylene-silane copolymer, and m is the molecular weight in g / mol of the silane comonomer from which the hydrolyzable silyl groups are derived, with 28.05 g / mol being the molecular weight of the monomer ethylene (H2C=CH2). For example, if the comonomer content is 2.0 wt% and the comonomer is VTMS, then p=2.0 wt%, m=148.23 g / mol, and G=0.38 mol%. If the comonomer content is 5.0 wt% and the comonomer is VTMS, then p=5.0 wt%, m=148.23 g / mol, and G=0.99 mol%. When preparing ethylene-silane copolymers using two or more silane comonomers with different molecular weights, the molecular weight used to calculate the total molar percentage of all hydrolyzable silyl groups in the ethylene-silane copolymer is the weighted average molecular weight of the comonomers. The weighting can be determined by the proportion of comonomers supplied to the reactor. Alternatively, it can be determined by NMR spectroscopy of the ethylene-silane copolymer to determine the relative amounts of different comonomer units in the copolymer when each hydrolyzable silyl group is bonded to different types of carbon atoms (e.g., tertiary carbon atoms versus secondary carbon atoms), or by Fourier transform infrared (FT-IR) spectroscopy calibrated to provide quantification of different types of comonomers.

[0067] Crystallinity Test: The melting peak, and percentage (%) and weight percentage (Wt%) crystallinity of the ethylene polymer at 23°C are determined using a differential scanning calorimeter (DSC) instrument, DSC Q1000 (TA Instruments). (A) Baseline Calibration DSC Instrument. Use the software calibration wizard. Obtain the baseline by heating the cell from -80°C to 280°C with no sample in the aluminum DSC pan. Then, use a sapphire standard according to the instructions of the calibration wizard. Analyze 1-2 milligrams (mg) of fresh indium sample by heating the standard sample to 180°C, cooling to 120°C at a cooling rate of 10°C / min, then holding the standard sample isothermally at 120°C for 1 minute, and then heating the standard sample from 120°C to 180°C at a heating rate of 10°C / min. (B) The indium standard sample is determined to have a heat of fusion of 28.71 ± 0.50 joules (J / g) per gram and a melting onset of 156.6° ± 0.5°C. DSC measurements are then performed on the test sample using a baseline-calibrated DSC instrument. The semicrystalline ethylene polymer test sample is pressed into a thin film at a temperature of 160°C. 5-8 mg of the test sample film is weighed into an aluminum DSC pan. The pan is sealed by pressing the lid onto it to ensure a sealed atmosphere. The covered pan is placed in a DSC cell, the cell is equilibrated at 30°C, then heated to 190°C at a rate of approximately 100°C / min, the sample is held at 190°C for 3 minutes, the sample is cooled to -60°C at a rate of 10°C / min to obtain the cooling curve heat of fusion (Hf), and the sample is held isothermally at -60°C for 3 minutes. Next, the sample is reheated to 190°C at a rate of 10°C / min to obtain a second heating curve for the heat of fusion (ΔHf). Using the second heating curve, -20°C (ethylene homopolymer, copolymer of ethylene and hydrolyzable silane monomer, and 0.90 g / cm³) 3 (For ethylene alpha-olefin copolymers of the above density), or -40°C (Ethylene and unsaturated ester copolymer, and 0.90 g / cm³) 3The "total" heat of fusion (J / g) is calculated by integrating from the heat of fusion (ΔHf) of the second heating curve to the end of melting. The "room temperature" heat of fusion (J / g) from 23°C (room temperature) to the end of melting is calculated by using a second heating curve and descending vertically at 23°C. The "total crystallinity" (calculated from the "total" heat of fusion) and the "crystallinity at room temperature" (calculated from the heat of fusion at 23°C) are measured and reported. Room temperature refers to 23°C. Crystallinity is measured and reported as the percentage (%) or weight percentage (W%) crystallinity of the polymer from the second heating curve heat of fusion (ΔHf) of the test sample and its normalization relative to the heat of fusion of 100% crystalline polyethylene, where % crystallinity or W% crystallinity = (ΔHf) * 100%) / 292J / g, where ΔHf is defined above. * The symbol ∫ represents mathematical multiplication, the symbol ∫ represents mathematical division, and 292 J / g is the literature value for the heat of fusion (ΔHf) of 100% crystalline polyethylene.

[0068] material The materials used in the examples ("IE") and comparative examples ("CE") of the present invention are provided below.

[0069] ESC is an ethylene-silane copolymer containing a moisture scavenger, characterized by a melt index of 1.5 g / 10 min (190°C; 2.16 kg), a density of 0.922 g / cc, a copolymer VTMS content of 1.6 wt% (0.31 mol%), and a crystallinity of 46.8 wt% at 23°C. ESC is available from The Dow Chemical Company (Midland, Michigan).

[0070] CAT MB is a silanol condensation catalyst masterbatch (a blend of thermoplastic ethylene polymer, antioxidants, and approximately 3% by weight of dibutyltin dilaurate) developed for use in conjunction with moisture-curing ethylene-silane copolymers, and is commercially available from The Dow Chemical Company (Midland, MI) as SI-LINK® DFDA-5481 NT.

[0071] POLAR is a polar ethylene ethyl acrylate copolymer (ethylene-based polymer) with a density of 0.930 g / cc, a melt index of 1.3 g / 10 min (190°C; 2.16 kg), and an ethyl acrylate content of 15% by weight. POLAR is commercially available from The Dow Chemical Company (Midland, MI, United States) as IAMPLIFY® EA 100 Functional Polymer.

[0072] NPEP1 is a nonpolar linear low-density polyethylene, LLDPE (i.e., an ethylene-based polymer), having a density of 0.920 g / cc and a melt index of 3.5 g / 10 min (190°C; 2.16 kg), and is commercially available from The Dow Chemical Company (Midland, MI, United States) as DOW® LLDPE 1648.

[0073] NPEP2 is a non-polar polyolefin elastomer (i.e., an ethylene-based polymer) with a density of 0.870 g / cc and a melt index of 5 g / 10 min (190°C; 2.16 kg), and is commercially available from The Dow Chemical Company (Midland, MI, United States) as ENGAGE® 8200.

[0074] COMP is a compatibilizer for anhydrous-modified ethylene elastomers (ethylene-based polymers) and is commercially available from The Dow Chemical Company (Midland, MI) as FUSABOND® N216.

[0075] HFFR1 is uncoated aluminum hydroxide (ATH) and is commercially available from Nabeltec AG (Schwandorf, Germany) as APYRAL® 40 CD.

[0076] HFFR2 is magnesium hydroxide (MDH) treated with stearic acid at a maximum of 1% by weight, and is commercially available from Europiren BV (Rosterdam, NL) as ECOPIREN 3.5 LC.

[0077] IFRM is a halogen-free flame retardant (HFFR) that is an expandable flame retardant mixture consisting of 65% by weight of piperazine pyrophosphate and 35% by weight of melamine polyphosphate, with a nitrogen content of ≥19%, a phosphorus content of ≥17.0%, and a water content of ≤0.2%. Piperazine pyrophosphate has a density of 1.74 g / cc, and melamine polyphosphate has a density of 1.85 g / cc, which means that the density of IFRM is 1.78 g / cc. IFRM is commercially available as JNPTM-2-3 from CENTURY MULTECH, INC (Flushing, NY, United States).

[0078] GPS is a combination of ultra-high molecular weight silicone gum and fumed silica in pellet form, and is commercially available from Wacker Chemie AG (Munich, Germany) as GENIOPLAST® Pellet S.

[0079] AO1 is pentaerythritol tetrakis[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate, which is commercially available from BASF (Ludwigshafen, Germany) as IRGANOX™ 1010.

[0080] AO2 is distearyl thiodipropionate (C 42 H 82 It is O4S and is commercially available from Struktol (OH, United States) as MORSTILLETM 18C DSTDP.

[0081] MDAO is a bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazine that functions as a metal deactivator and antioxidant. MDAO is marketed by BASF Corporation (Florham Park, NJ, United States) as IRGANOX® MD 1024 FF.

[0082] MD is FUTURECHEM® OABH (oxalylbis(benzylidene)hydrazide), which functions as a metal deactivator. MD is commercially available from FutureFuel Chemical Company (Missouri, USA).

[0083] LSAO is C 132 H 250 N 32 It functions as a hindered amine light stabilizer and antioxidant. LSAO is commercially available from SABO Spa (Italy) as CHIMASSORB® 119 FL.

[0084] CAT is dibutyltin dilaurate and functions as a silanol condensation catalyst when used in combination with alkoxysilane-functionalized polymers. CAT has CAS number 77-58-7 and is commercially available from PMC Organometallix (Mount Laurel, NJ, US) as FASCAT® 4202.

[0085] OTS is octyltriethoxysilane, which functions as a moisture scavenger and is commercially available from SiVance LLC, of ​​Milliken & Co (USA) as PROSIL® 9202. It is useful in combination with alkoxysilane-functionalized polymers.

[0086] Sample preparation The sample formulations for Masterbatch 1 (MB1) shown in Table 1 were prepared using a Brabender mixer equipped with a cam rotor. A bowl volume of 420 mL was obtained by filling the bowl to 70% of its volume at a rotor speed of 50 rpm and a set temperature of 125°C. The HFFR packing material (IFRM) was dried in a vacuum oven at 60°C for 16 hours before use. The ethylene polymer(s) were allowed to flow in the mixing bowl for 5 minutes before adding the other components. The order of addition was ethylene polymer(s), antioxidant(s), IFRM, and other additives. When adding the various solid components, the mixing blade speed was reduced to approximately 20 rpm. After adding all components, mixing was performed for 5 minutes.

[0087] The procedure used to prepare the sample formulation for Masterbatch 2 (MB2) was the same as that for MB1, except that (a) a rollerblade was used at a rotor speed of 40 rpm, resulting in a bowl volume of 350 mL; (b) a set temperature of 150°C was used; (c) all components were added and mixed for 10 minutes; and (d) the IFRM was not dried before use.

[0088] The procedure used to prepare the sample formulation for Masterbatch 3 (MB3) was the same as that for MB2, except that the order of addition was as follows: ethylene polymer(s), COMP2, GPS, antioxidant(s), MD, HFFR4, HFFR5, IFRM, OTS, and CAT.

[0089] Each of the molten blend compositions MB1-MB3 was removed from the mixing bowl and compressed at 120°C and 500 psi (3.4 MPa) for 5 minutes to form a 75 mil (1.905 mm) thick plaque / sheet, which was then cut into strips using a guillotine and fed into a pelletizer to produce "chips". These "chips" were then processed into a Brabender with a Maddock mixing screw with a 25:1 length-to-diameter (L / D) ratio, operating at 40 rpm with set temperature profiles of 140°C / 145°C / 150°C / 155°C across Zone 1, Zone 2, Zone 3, and head / die (using 40 / 60 / 100 mesh screen packs). The material was introduced into a 3 / 4” extruder. The composition was processed into strands and then converted into pellets using a pelletizer. The catalyst masterbatch was pre-dried in a vacuum oven at 70°C for 16-24 hours, and then packaged in vacuum-sealed foil bags until use. Where appropriate, plaques of 75 mil (1.905 mm) or 125 mil (3.175 mm) thickness were prepared for property testing by compression molding at 500 psi (3.4 MPa) at 150°C for 3 minutes, followed by 2500 psi (17.2 MPa) at 150°C for 3 minutes, and then cooled to 30°C at a pressure of 2500 psi (17.2 MPa).

[0090] Coated conductors were prepared using the sample formulations for IE1 to IE11 and CE1 shown in Table 2. For IE1 to IE11, this was done by melt-blending one of MB1 to MB3 with ESC (ethylene-silane copolymer) in the proportions shown in Table 2, using the experimental procedure described below. For IE2, CAT MB was also melt-blended by extrusion. CE1 was prepared by melt-blending CAT MB with ESC in the proportions shown in Table 2, using the experimental procedure described below.

[0091] Physical blends (in plastic bags) were prepared from pellets of IE1 and IE2:ESC, MB1, and / or CAT MB. The pellet blend was fed into a Brabender 3 / 4” extruder equipped with a Maddock screw with a length-to-diameter (L / D) ratio of 25:1, and melt-extruded to apply a coating (insulating layer) with a nominal wall thickness of 30 mils (0.762 mm) to 14 AWG solid copper conductors of the following dimensions: nominal diameter of the conductor: 0.064 inches (1.626 mm); nominal outer diameter of the insulating wire: 0.124 inches (3.150 mm). The set temperature profiles across the extrusion zone were 165°C, 170°C, 175°C, and 180°C at the head / die. A 40 / 40 mesh screen pack was used, the screw speed was 40 rpm, and the discharge belt speed was 8 ft / min (2.4 m / min). The resulting melt temperature was approximately 188–189°C in both cases.

[0092] IE3 to IE10 and CE1 were the same as IE1 and IE2, except that (a) MB2 was used; (b) CE1 was prepared without any of MB1 to MB3; (c) the set temperature profiles across the extrusion zone were 145°C, 150°C, 155°C, and 160°C at the head / die; (d) the screw speed was approximately 40 to 41 rpm and the output belt speed was approximately 8.5 ft / min (2.6 m / min); and (e) the resulting melt temperature was approximately 165 to 166°C in all cases.

[0093] IE11: (a) Use MB3; (b) Feed the pellet blend into a Brabender 1 1 / 4” extruder with a Maddock screw with a length-to-diameter ratio (L / D) of 20:1, and melt-extrude to produce a coating (insulating layer) with a nominal wall thickness of 55 mil (1.397 mm) and the following dimensions of 4 mm 2Applied to (ca.11 AWG) stranded tin-copper conductors: Nominal diameter of conductor: 0.090 inches (2.286 mm); Nominal outer diameter of insulating wire: 0.200 inches (5.080 mm); (c) The discharge belt speed was approximately 9.5 ft / min (2.9 m / min); (d) The resulting melting temperature was approximately 169°C; otherwise, it was the same as IE3 to IE10.

[0094] result Table 1 provides composition and performance data for the masterbatch material ("MB") used in forming the embodiments of the present invention. Table 2 provides composition data for IE1-IE11 and CE1. Table 3 provides performance data for moisture-cured embodiments of IE1-IE11 and CE1. NA means that identified data for the sample could not be measured.

[0095] [Table 1] NA: Not applicable

[0096] [Table 2]

[0097] [Table 3] Regarding Table 3, the "characteristics after moisture curing" were measured at 23°C and 50% relative humidity for one week. * , or ** Except for those marked as such, the insulated wires (i.e., coated conductors) were subsequently cured in a 90°C water bath for 24, 72, or 96 hours, and the results were determined. Hot creep measurements were performed at a test temperature of 150°C in all cases (IE1-IE11, and CE1). * The material was cured at 23°C and 50% relative humidity, then tested for 6 months, followed by 24-hour tests in a 90°C water bath. **After curing at 23°C and 50% relative humidity, the material was tested for one month, followed by a 24-hour test in a 90°C water bath.

[0098] Referring to Tables 2 and 3, CE1 represents a conventional formulation that requires a so-called water-curing (silanol condensation) catalyst for crosslinking in order to achieve a high gel content and therefore exhibit satisfactory high-temperature creep performance (<175% hot creep). In contrast to CE1, compositions IE1 and IE3-IE10 were surprisingly able to achieve sufficiently high gel content without the use of a catalyst and / or pass the hot creep test after curing in a hot water bath. Furthermore, the compositions of the present invention passed the hot creep test even when the gel content, as measured by decalin extraction, was relatively low. Without the use of a catalyst at all, examples of the present invention containing a relatively high filler amount of IFRM required 24 hours of curing in a 90°C water bath to exceed the hot creep passing requirement after initial curing for about one week under ambient conditions of 23°C and 50% relative humidity. By extending the curing time in the hot water bath to 96 hours, even formulations of the present invention containing relatively small amounts of IFRM were able to reliably pass the hot creep test. These characteristics indicate that the moisture-induced crosslinking of the silane-functionalized polyolefin occurred after melt blending by extrusion (i.e., melt extrusion).

[0099] Hot creep data (IE2 and IE11) clearly demonstrate that the expansive flame retardant mixture is compatible with conventional moisture-curing catalysts (such as dibutyltin dilaurate and Lewis acids) used in such formulations to enable silane crosslinking of the resulting HFFR composition. This characteristic is advantageous because such conventional catalysts can be incorporated into the formulation of the present invention to significantly reduce curing time.

Claims

1. A method for crosslinking a moisture-curing polymer composition, wherein the method comprises the following steps: A step of producing a moisture-curable polymer composition of a silane-functionalized polyolefin and a mixture of expandable flame retardants, wherein the expandable flame retardant mixture comprises piperazine pyrophosphate and 15% to 55% by weight of a phosphoric acid compound based on the total weight of the expandable flame retardant mixture. A method comprising the step of using the aforementioned expandable flame retardant mixture to catalyze a moisture-induced crosslinking reaction of the silane-functionalized polyolefin to form a moisture-curing polymer composition.

2. The method according to claim 1, wherein the step of catalyzing the moisture-induced crosslinking reaction is carried out in a water bath at a temperature above 50°C, or in a gaseous atmosphere having a temperature of 15°C or higher and a relative humidity of 10% or higher, as measured according to ASTM E337.

3. The method according to claim 1 or 2, wherein the moisture-curable polymer composition comprises 10% to 99% by weight of the silane-functionalized polyolefin based on the total weight of the moisture-curable polymer composition, and the silane-functionalized polyolefin is a silane-functionalized ethylene-based polymer.

4. The method according to claim 3, wherein the silane-functionalized ethylene polymer contains 0.1% to 5.0% by weight of silane, based on the total weight of the silane-functionalized ethylene polymer.

5. The method according to claim 4, wherein the silane is vinyltrimethoxysilane.

6. The method according to any one of claims 1 to 5, wherein the moisture-curing polymer composition comprises 1% to 90% by weight of the expanding flame retardant mixture, based on the total weight of the moisture-curing polymer composition.

7. The method according to claim 5, wherein the polymer composition comprises 1% by weight to 30% by weight of the expandable flame retardant mixture, based on the total weight of the moisture-curing polymer composition.

8. The method according to any one of claims 1 to 7, wherein the expandable flame retardant mixture contains 25% to 45% by weight of the phosphoric acid compound based on the total weight of the expandable flame retardant mixture.

9. The method according to any one of claims 1 to 8, wherein the phosphoric acid compound is selected from the group consisting of melamine polyphosphate, ammonium polyphosphate, or a combination thereof.

10. The method according to any one of claims 1 to 9, wherein the moisture-curable polymer composition does not contain dibutyltin dilaurate and sulfonic acid.

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