Flame-retardant polymer composition

Abstract

The polymer composition comprises 10 to 80 weight percent of a silane-grafted ethylene polymer, based on the total weight of the polymer composition. The silane-grafted ethylene polymer has a silane content of 0.40 to 1.50 mole percent, based on the total moles of the silane-grafted ethylene polymer, and the ethylene polymer used to make the silane-grafted ethylene polymer has a polar comonomer content of less than 15 weight percent, based on the total weight of the ethylene polymer. The polymer composition also comprises 10 to 80 weight percent of a flame-retardant filler, based on the total weight of the polymer composition.

Description

[Background technology]

[0001] Technical Field The present disclosure relates to polymer compositions, and more particularly to flame retardant polymer compositions.

[0002] Introduction Polymer compositions using polyolefins and flame-retardant materials, either halogenated or halogen-free flame retardants (HFFRs), are useful for forming insulation and jackets for coated conductors used in applications where flame retardancy is important. Halogen-free flame retardancy is typically achieved by diluting the concentration of flammable polyolefin materials and adding hydrated mineral fillers to the formulation, which decompose below the polymer's decomposition temperature when exposed to heat. The decomposition of the hydrated mineral fillers releases water, which removes heat, one of the primary factors in fire (the others being fuel and oxygen). Traditional HFFR-containing polymer compositions are used in buildings, trains, cars, or anywhere people may be present.

[0003] The use of HFFRs in polymer compositions has many drawbacks, most of which stem from the relatively high levels of HFFRs required to meet flame retardant specifications. HFFR loadings of 60 or 65 weight percent in polyolefins are not uncommon. This HFFR loading adversely affects the density, flexibility, and mechanical properties of coated conductors made using the polymer compositions.

[0004] One approach to addressing the issues associated with high HFFR loadings is to use a silane-grafted polyolefin elastomer as the carrier polyolefin for the HFFR. For example, International Publication No. 2017218280(A1) ("'280 Publication") discloses the use of a polymer composition comprising a silane-grafted polyolefin elastomer and an HFFR, the elastomer having a wide range of silane concentrations. However, the use of a silane-grafted polyolefin elastomer with an HFFR presents its own set of complications. For example, the chemical reaction between the silane and the hydroxyl groups of the HFFR / moisture is not fully understood, making premature crosslinking difficult to avoid. Furthermore, the effect of the grafted silane on the flame performance of cables made with polymer compositions containing HFFR is unclear, and the '280 Publication is silent regarding the flame performance of the cables (coated conductors or insulated wires).

[0005] Given the uncertainty in cable fire performance based on silane concentration and high HFFR loading, it is surprising to discover a critical silane concentration range for silane-grafted ethylene polymers in polymer compositions that maximizes the fire performance of coated conductors made with the compositions. Summary of the Invention

[0006] The present disclosure provides polymer compositions having a critical silane concentration range for silane-grafted ethylene polymers that maximizes the combustion performance of coated conductors made with the polymer compositions.

[0007] The inventors of the present application have discovered that polymer compositions comprising a silane-grafted ethylene polymer having a grafted silane content of 0.40 mol % to 1.50 mol %, based on the total moles of the silane-grafted ethylene polymer, a flame retardant material, optionally a silicone, optionally an antioxidant, and optionally a silanol condensation catalyst, can be used to form coated conductors that exhibit acceptable filler-weighted char length ("FWCL") values, as described in more detail below.

[0008] Evaluating the flame performance of coated conductors with high flame retardant loadings, especially high HFFR loadings, is important from the perspective of achieving desired cable flame performance while minimizing any loss in mechanical properties of the polymer composition as a result of the high flame retardant loading. One method for determining the flame performance of coated conductors using polymer compositions with high flame retardant loadings is to measure the effectiveness of the flame retardant in reducing the length of char formed using the Fire-Flow Curve Limit (FWCL) standard in International Electrotechnical Commission test 60332-1-2:2004. Generally, a value of less than 15 cm*% on the FWCL standard is considered desirable. The present inventors surprisingly discovered that the measured FWCL value is a function of the silane concentration of the silane-grafted ethylene polymer used to make the polymer composition with high flame retardant loading. Even more surprisingly, it has been discovered that a critical grafted silane content of 0.40 mol% to 1.50 mol%, based on the total moles of silane-grafted ethylene polymer, enables coated conductors formed from high flame retardant loading polymer compositions to exhibit values ​​of less than 15 cm*% on the FWCL basis.

[0009] The polymer compositions of the present invention are particularly useful in making coated conductors.

[0010] According to a first aspect of the present disclosure, a polymer composition comprises 10 wt% to 80 wt% of a silane-grafted ethylene polymer, based on the total weight of the polymer composition, wherein the silane-grafted ethylene polymer has a silane content of 0.40 mol% to 1.50 mol%, based on the total moles of the silane-grafted ethylene polymer, and the ethylene polymer used to make the silane-grafted ethylene polymer has a polar comonomer content of less than 15 wt%, based on the total weight of the ethylene polymer; and 10 wt% to 80 wt% of a flame-retardant filler, based on the total weight of the polymer composition.

[0011] According to a second aspect of the present disclosure, the polymer composition further comprises one or more of 1 wt % to 5 wt % of a silicone, based on the total weight of the polymer composition, and 0.001 wt % to 10.0 wt % of a silanol condensation catalyst, based on the total weight of the polymer composition.

[0012] According to a third aspect of the present disclosure, the silane-grafted ethylene polymer has a silane content of 0.40 mol % to 0.94 mol %, based on the total moles of the silane-grafted ethylene polymer.

[0013] According to a fourth feature of the present disclosure, the silane-grafted ethylene polymer has a density of 0.860 g / cc to 0.930 g / cc, as measured according to ASTM D-792.

[0014] According to a fifth feature of the present disclosure, the flame-retardant filler is a halogen-free flame-retardant filler.

[0015] According to a sixth feature of the present disclosure, the silane grafts of the silane-grafted ethylene polymer are units derived from hydrolyzable silane monomers of structure (I), wherein R 1 is a hydrogen atom or a methyl group, x is 0 or 1, n is an integer of 1 to 4, or 6, or 8, or 10, or 12, and each R 2 are independently a hydrolyzable organic group, for example, an alkoxy group having 1 to 12 carbon atoms (e.g., methoxy, ethoxy, butoxy), an aryloxy group (e.g., phenoxy), an araryloxy group (e.g., benzyloxy), an aliphatic acyloxy group having 1 to 12 carbon atoms (e.g., formyloxy, acetyloxy, propanoyloxy), an amino group or a substituted amino group (e.g., alkylamino, arylamino), or a lower alkyl group having 1 to 6 carbon atoms, provided that three R 2 Provided that no more than one of the groups is alkyl.

[0016] According to a seventh aspect of the present disclosure, the hydrolyzable silane is selected from the group consisting of vinyltrimethoxysilane and vinyltriethoxysilane.

[0017] According to an eighth aspect of the present disclosure, the flame-retardant filler includes at least one of magnesium hydroxide, aluminum trihydrate, calcium carbonate, hydrated calcium silicate, and hydrated magnesium.

[0018] According to a ninth feature of the present disclosure, a coated conductor includes a conductor and the polymer composition of any one of features 1-8 positioned at least partially around the conductor, the coated conductor exhibiting a filler-weighted char length metric of less than 15 cm*%.

[0019] According to a tenth feature of the present disclosure, the coated conductor has a filler-weighted char length standard value of 1 cm*% to 10 cm*%. DETAILED DESCRIPTION OF THE INVENTION

[0020] As used herein, the term "and / or," when used with a list of two or more items, means that any one of the listed items can be used alone, 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.

[0021] Unless otherwise stated, all ranges are inclusive of the endpoints.

[0022] Test methods refer to the most current test method as of the priority date of this document unless a date is indicated with a two-digit number separated by a hyphen along with the test method number. References to test methods include both a reference to the testing society 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 Deutsches Institut fur Normung, and ISO refers to the International Organization for Standards.

[0023] As used herein, the term weight percent ("wt %") refers to the weight percentage that a component represents of the total weight of the polymer composition, unless otherwise specified. The term mole percent ("mol %") refers to the ratio of moles of a component to the total moles of the item in which the component is present.

[0024] Unless otherwise specified herein, density is measured according to ASTM D792, Method B. Results are reported in grams (g) per cubic centimeter (g / cc).

[0025] Unless otherwise specified herein, Melt index (MI) was measured in accordance with ASTM D1238, Condition 190°C / 2.16 kilogram (kg) weight, and is reported in grams dissolved per 10 minutes (g / 10 min).

[0026] "Polymer" means a macromolecular compound prepared by polymerizing monomers, whether of the same or different type. Thus, the generic term polymer encompasses the terms homopolymer, interpolymer, and copolymer.

[0027] "Ethylene polymer" means a polymer containing units derived from ethylene. Ethylene polymers typically contain at least 50 mole percent units derived from ethylene. Polyethylene is an ethylene polymer.

[0028] polymer composition The present disclosure relates to a polymer composition. The polymer composition includes a silane-grafted ethylene polymer and a flame-retardant filler. The polymer composition may also include a silicone. As described in more detail below, the polymer composition may be used in the manufacture of coated conductors.

[0029] Ethylene polymer The terms "silane-grafted ethylene polymer," "silane-grafted polyethylene," "Si-g-PE," and the like refer to ethylene polymers prepared by a process in which silane functional groups are grafted onto the backbone of the ethylene polymer, as described, for example, in U.S. Pat. Nos. 3,646,155 or 6,048,935.

[0030] The ethylene polymer (from which the silane-grafted ethylene polymer is formed) has a silane-grafted ethylene polymer content of 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, or 91 mol% or more, or 92 mol% or more, or 93 mol% or more, or 94 mol% or more, or 95 mol% or more, or 96 mol% or more, or 97 mol% or more, or 97.5 mol% as determined by nuclear magnetic resonance (NMR) or Fourier transform infrared (FTIR) spectroscopy. The ethylene polymer may comprise 100 mol% or less, or 99.5 mol% or less, or 99 mol% or more, or 98 mol% or more, or 99 mol% or more, while simultaneously comprising 100 mol% or less, or 99.5 mol% or less, or 99 mol% or less, or 98 mol% or less, or 97 mol% or less, or 96 mol% or less, or 95 mol% or less, or 94 mol% or less, or 93 mol% or less, or 92 mol% or less, or 91 mol% or less, or 90 mol% or less, or 85 mol% or less, or 80 mol% or less, or 70 mol% or less, or 60 mol% or less ethylene. Other units of the ethylene polymer may be C3-C4, or C6, or C8, or C 10 , or C 12 , or C16 , or C 18 , or C 20 The α-olefins may include, for example, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Other units of the ethylene polymer (from which the silane-grafted ethylene polymer is formed) may be derived from one or more polymerizable monomers, including, but not limited to, polar monomers such as unsaturated esters. The unsaturated esters may be alkyl acrylates, alkyl methacrylates, or vinyl carboxylates. The alkyl groups may have 1 to 8 carbon atoms or 1 to 4 carbon atoms. The 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.

[0031] The ethylene polymer from which the silane-grafted ethylene polymer is formed can be an ultra-low density polyethylene, or a linear low density polyethylene, or a high density polyethylene, or an ethylene-ethyl acrylate copolymer, or an ethylene-vinyl acetate copolymer, and the density of the ethylene polymer, as measured by ASTM D792, is 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 0.904 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 to 0.930 g / cc or more, may be 0.935 g / cc or more, while simultaneously being 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 0.935 g / cc or less, or 0.930 g / cc or less, or 0.925 g / cc or less, or 0.920 g / cc or less, or 0.915 g / cc or less, or 0.910 g / cc or less, or 0.905 g / cc or less, or 0.900 g / cc or less.

[0032] The melt index of the ethylene polymer is 0.5 g / 10 min or greater, or 1.0 g / 10 min or greater, or 1.5 g / 10 min or greater, or 2.0 g / 10 min or greater, or 2.5 g / 10 min or greater, or 3.0 g / 10 min or greater, or 3.5 g / 10 min or greater, or 4.0 g / 10 min or greater, or 4.5 g / 10 min or greater, or 10.0 g / 10 min or greater, or 18 g / 10 min or greater, while simultaneously being 30.0 g / 10 min or less, or 25.0 g / 10 min or less. g / 10 min or less, or 20.0 g / 10 min or less, or 18.0 g / 10 min or less, or 15.0 g / 10 min or less, or 10.0 g / 10 min or less, or 5.0 g / 10 min or less, or 4.5 g / 10 min or less, or 4.0 g / 10 min or less, or 3.5 g / 10 min or less, or 3.0 g / 10 min or less, or 2.5 g / 10 min or less, or 2.0 g / 10 min or less, or 1.5 g / 10 min or less, or 1.0 g / 10 min or less.

[0033] Ethylene polymers can be homopolymers or homopolymers. Homogeneous ethylene polymers have a polydispersity index (i.e., molecular weight distribution) in the range of 1.5 to 3.5, a substantially uniform comonomer distribution, and are characterized by a single, relatively low melting point as measured by differential scanning calorimetry (DSC). Substantially linear ethylene copolymers (SLEPs) are homogeneous ethylene polymers.

[0034] As used herein, "substantially linear" means that the bulk polymer is substituted, on average, with from about 0.01 long chain branch / 1000 total carbons (including both backbone and branch carbons) to about 3 long chain branches / 1000 total carbons, preferably from about 0.01 long chain branch / 1000 total carbons to about 1 long chain branch / 1000 total carbons, more preferably from about 0.05 long chain branch / 1000 total carbons to about 1 long chain branch / 1000 total carbons, and especially from about 0.3 long chain branch / 1000 total carbons to about 1 long chain branch / 1000 total carbons.

[0035] "Long chain branching" or "long chain branched" (LCB) means a chain length of at least one (1) carbon less than the number of carbons in the comonomer, as opposed to "short chain branching" or "short chain branched" (SCB), which means a chain length of two (2) fewer than the number of carbons in the comonomer. For example, a substantially linear polymer of ethylene / 1-octene has a backbone with long chain branches at least seven (7) carbons in length, but it also has short chain branches that are only six (6) carbons in length, while a substantially linear polymer of ethylene / 1-hexene has long chain branches at least five (5) carbons in length, but also has short chain branches that are only four (4) carbons in length. LCB means 13 They can be distinguished from SCBs using C nuclear magnetic resonance (NMR) spectroscopy and, to a limited extent, can be quantified using, for example, the method of Randall in the case of ethylene homopolymers (Rev. Macromol. Chem. Phys., C29(2&3). p. 285-297). However, as a practical matter, the current 13C NMR spectroscopy cannot identify long chain branch lengths greater than about six (6) carbon atoms, and therefore this analytical technique cannot distinguish between seven (7) and seventy (70) carbon branches. LCBs can be as long as the polymer backbone.

[0036] U.S. Patent No. 4,500,648 states that the LCB frequency is calculated using the equation LCB=b / M w (where b is the weight average number of LCBs per molecule, M w where ρ is the weight average molecular weight. The molecular weight average and LCB properties are determined by gel permeation chromatography (GPC) and intrinsic viscosity methods.

[0037] One measure of the SCB of an ethylene copolymer is its short-chain branching distribution index (SCBDI), also known as the composition distribution branching index (CDBI), which is defined as the weight percent of polymer molecules having a comonomer content within 50 percent of the median total molar comonomer content. The SCBDI or CDBI of a polymer is readily calculated from data obtained from techniques known in the art, such as temperature-rising elution fractionation (TREF), as described, for example, in Wild et al., Journal of Polymer Science, Poly. Phys. Ed., Vol. 20, p. 441 (1982), or as described in U.S. Pat. No. 4,798,081. The SCBDI or CDBI of the substantially linear ethylene polymers useful in the present invention typically exceeds about 30 wt.%, or 50 wt.%, or 80 wt.%, or 90 wt.%.

[0038] "Polymer backbone" or simply "backbone" refers to an individual molecule, and "bulk polymer" or simply "polymer" refers to the product resulting from a polymerization process; in the case of a substantially linear polymer, the product may include both polymer backbones with and without LCBs. Thus, "bulk polymer" includes all backbones formed during polymerization. For a substantially linear polymer, not all backbones will have LCBs, but a sufficient number will have LCBs such that the average LCB content of the bulk polymer positively affects melt rheology (i.e., melt fracture properties).

[0039] SLEPs and methods for their preparation are more fully described in US Pat. No. 5,741,858 and US Pat. No. 5,986,028.

[0040] The polydispersity index is calculated as Mw / Mn. Mw is defined as the weight-average molecular weight, and Mn is defined as the number-average molecular weight. The polydispersity index is measured according to the following technique: Polymers are analyzed by gel permeation chromatography (GPC) on a Waters 150°C high-temperature chromatography unit equipped with three linear mixed-bed columns (Polymer Laboratories (10 micron particle size)) operated at a system temperature of 140°C. The solvent is 1,2,4-trichlorobenzene, from which an approximately 0.5 wt% solution of the sample is prepared for injection. The flow rate is 1.0 milliliters per minute (mm / min), and the injection size is 100 microliters (μL). Molecular weight determination is estimated using narrow molecular weight distribution polystyrene standards (from Polymer Laboratories) in combination with their elution volumes. The equivalent polyethylene molecular weight is determined by deriving the following equation using appropriate Mark-Houwink coefficients for polyethylene and polystyrene (as described by Williams and Ward in Journal of Polymer Science, Polymer Letters, Vol. 6, (621) 1968, which is incorporated herein by reference): M polyethylene = (a) (M polystyrene) b

[0041] In this formula, a=0.4316 and b=1.0. The weight average molecular weight Mw is calculated by the formula:

number

[0042] Typical catalyst systems for preparing homogeneous ethylene polymers include metallocene and constrained geometry catalyst (CGC) systems, which are used to prepare SLEP.

[0043] The ethylene polymer may be a copolymer of ethylene and one or more alpha-olefins (α-olefins) having 3 to 12 carbon atoms or 3 to 8 carbon atoms. The α-olefin may be one or more of 1-butene, 1-hexene, and 1-octene. The ethylene polymer may contain units derived from three or more different monomers. For example, the third comonomer may be another α-olefin, or a diene such as ethylidene norbornene, vinyl norbornene, butadiene, 1,4-hexadiene, or dicyclopentadiene, or a polar material such as an unsaturated ester. The ethylene polymer used to prepare the silane-grafted ethylene polymer may have a polar comonomer content of less than 15 wt%, or 10 wt%, or 5 wt% or less, or 3 wt% or less, or 1 wt% or less, or 0 wt%, based on the total weight of the ethylene polymer. An exemplary polar comonomer is ethyl acrylate.

[0044] Specific examples of ethylene polymers useful in the present invention include homogeneously branched linear ethylene / alpha-olefin copolymers (e.g., TAFMER™ from Mitsui Petrochemical Co., Ltd. and EXACT™ from Exxon Chemical Company), and homogeneously branched substantially linear ethylene / alpha-olefin polymers (e.g., AFFINITY™ plastomers and ENGAGE™ elastomers available from Dow Chemical Company).

[0045] Hydrolyzable Silane Monomer A "hydrolyzable silane monomer" is grafted onto the ethylene polymer to produce the silane-grafted ethylene polymer. Any hydrolyzable silane or mixture of such hydrolyzable silanes that effectively grafts onto the ethylene polymer (thus allowing for subsequent crosslinking of the silane-grafted ethylene polymer) can be used. A representative, but non-limiting example, of a hydrolyzable silane monomer has the structure (I): [ka] In the formula, R 1 is a hydrogen atom or a methyl group, x is 0 or 1, n is an integer of 1 to 4, or 6, or 8, or 10, or 12, and each R 2 are independently a hydrolyzable organic group, for example, an alkoxy group having 1 to 12 carbon atoms (e.g., methoxy, ethoxy, butoxy), an aryloxy group (e.g., phenoxy), an araryloxy group (e.g., benzyloxy), an aliphatic acyloxy group having 1 to 12 carbon atoms (e.g., formyloxy, acetyloxy, propanoyloxy), an amino group or a substituted amino group (e.g., alkylamino, arylamino), or a lower alkyl group having 1 to 6 carbon atoms, provided that three R 2 Provided that no more than one of the groups is alkyl.

[0046] The hydrolyzable silane monomer may include a silane monomer containing an ethylenically unsaturated hydrocarbyl group, such as a 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, proprionyloxy, and alkyl or arylamino groups. In a specific example, the hydrolyzable silane monomer is an unsaturated alkoxysilane and can be grafted onto an ethylene polymer. Examples of hydrolyzable silane monomers 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 ethoxysilane and vinyltriacetoxysilane, x=0, R 1 =H, and R 2 = acetoxy.

[0047] Free Radical Initiators Hydrolyzable silane monomers can be grafted onto ethylene polymers using a free radical initiator to form Si-g-PE. Examples of free radical initiators include peroxides, azo compounds (i.e., compounds with a diazinyl moiety), and / or ionizing radiation. The free radical initiator can be an organic peroxide such as dicumyl peroxide, di-tert-butyl peroxide, t-butylbenzoyl peroxide, benzoyl peroxide, cumene hydroperoxide, t-butyl peroctoate, methyl ethyl ketone peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, lauryl peroxide, and t-butyl peracetate. An example of an azo compound is azobisisobutyronitrile.

[0048] The amount of initiator used can be 0.04 wt% or more, or 0.06 wt% or more, based on the total combined weight of the ethylene polymer, hydrolyzable silane monomer, and initiator, while simultaneously being 1.00 wt% or less, 0.50 wt% or less, 0.30 wt% or less, 0.15 wt% or less, or 0.10 wt% or less. The weight ratio of hydrolyzable silane monomer to initiator can be 5:1 to 70:1 or 10:1 to 30:1. For certain polymers containing unsaturation, grafting without the use of any initiator may be possible, utilizing radicals generated by heat and shear.

[0049] Silane grafting of ethylene polymers Typically, the ethylene polymer is grafted with a hydrolyzable silane monomer before mixing the silane-grafted ethylene polymer (Si-g-PE) with the flame-retardant filler. Alternatively, Si-g-PE can be formed in situ by a process such as the MONOSIL process, in which a hydrolyzable silane monomer is grafted onto the backbone of the ethylene polymer during extrusion of the polymer composition to form a coated conductor, as described, for example, in U.S. Pat. No. 4,574,133. The ethylene polymer, hydrolyzable silane monomer, and free-radical initiator are mixed using known equipment and techniques and subjected to a grafting temperature of 120°C to 270°C. Typically, the mixing equipment is a BANBURY™ mixer or similar mixer, or a single-screw or twin-screw extruder. Other extruders, such as counter-rotating twin-screw extruders, kneaders, planetary extruders, and multi-screw extruders, can also be used. Two or more of the above mixers and extruders can also be used in tandem.

[0050] Silane-grafted ethylene polymer The silane-grafted ethylene polymer has the same density range as the pre-grafted ethylene polymer. The melt index of the silane-grafted ethylene polymer, as measured in accordance with ASTM D1238, is 0.1 g / 10 min or greater, or 0.3 g / 10 min or greater, or 0.5 g / 10 min or greater, or 1.0 g / 10 min or greater, or 1.5 g / 10 min or greater, or 2.0 g / 10 min or greater, or 2.5 g / 10 min or greater, or 3.0 g / 10 min or greater, or 3.5 g / 10 min or greater, or 4.0 g / 10 min or greater, or 4.5 g / 10 min or greater, or 10.0 g / 10 min or greater, or 18 g / 10 min or greater, or 20 g / 10 min or greater, or 30 g / 10 min or greater, or 40 g / 10 min or greater, while simultaneously being 5. It may be 0.0g / 10min or less, 40.0g / 10min or less, 30.0g / 10min or less, or 25.0g / 10min or less, or 20.0g / 10min or less, or 18.0g / 10min or less, or 15.0g / 10min or less, or 10.0g / 10min or less, or 5.0g / 10min or less, or 4.5g / 10min or less, or 4.0g / 10min or less, or 3.5g / 10min or less, or 3.0g / 10min or less, or 2.5g / 10min or less, or 2.0g / 10min or less, or 1.5g / 10min or less, or 1.0g / 10min or less.

[0051] The silane-grafted ethylene polymer has a silane content of 0.40 mol% to 1.50 mol%, based on the total moles of the silane-grafted ethylene polymer. For example, the silane-grafted ethylene polymer may have a silane content of 0.40 mol% or more, or 0.41 mol% or more, or 0.42 mol% or more, or 0.43 mol% or more, or 0.44 mol% or more, or 0.45 mol% or more, or 0.46 mol% or more, or 0.47 mol% or more, or 0.48 mol% or more, or 0.49 mol% or more, or 0.50 mol% or more, or 0.52 mol% or more, or 0.54 mol% or more, or 0.56 mol% or more, or 0.58 mol% or more, based on the total moles of the silane-grafted ethylene polymer. 0.60 mol% or more, or 0.62 mol% or more, or 0.64 mol% or more, or 0.66 mol% or more, or 0.68 mol% or more, or 0.70 mol% or more, or 0.72 mol% or more, or 0.74 mol% or more, or 0.76 mol% or more, or 0.78 mol% or more, or 0.80 mol% or more, or 0.82 mol% or more, or 0.84 mol% or more, or 0.86 mol% or more, or 0.88 mol% or more, or 0.90 mol% or more, or 0.92 mol% or more, or 0.94 mol% or more, or 0.96 mol% or more, or 0.9 8 mol% or more, or 1.00 mol% or more, or 1.10 mol% or more, or 1.20 mol% or more, or 1.00 mol% or more, or 1.30 mol% or more, or 1.40 mol% or more, while simultaneously 1.50 mol% or less, or 1.40 mol% or less, or 1.30 mol% or less, or 1.20 mol% or less, or 1.10 mol% or less, or 1.00 mol% or less, or 0.99 mol% or less, or 0.98 mol% or less, or 0.96 mol% or less, or 0.94 mol% or less, or 0.92 mol% or less, or 0.90 mol% or less, 0.88 mol% or less, or 0.86 mol% or less, or 0.84 mol% or less, or 0.82 mol% or less, or 0.80 mol% or less, or 0.78 mol% or less, or 0.76 mol% or less, or 0.74 mol% or less, or 0.72 mol% or less, or 0.70 mol% or less, or 0.68 mol% or less, or 0.66 mol% or less, or 0.64 mol% or less, or 0.62 mol% or less, or 0.60 mol% or less, or 0.58 mol% or less, or 0.56 mol% or less, or 0.54 mol% or less, or 0.52 mol% or less, or 0.It may have a silane content of 50 mol% or less, or 0.49 mol% or less, or 0.48 mol% or less, or 0.47 mol% or less, or 0.46 mol% or less, or 0.45 mol% or less, or 0.44 mol% or less, or 0.43 mol% or less, or 0.42 mol% or less, or 0.41 mol% or less.

[0052] The silane-grafted ethylene polymer can have a silane content of 1.8 wt% to 5.0 wt%, based on the total weight of the silane-grafted ethylene polymer. For example, the silane content can be 1.8 wt% or more, or 2.0 wt% or more, or 2.2 wt% or more, or 2.4 wt% or more, or 2.6 wt% or more, or 2.8 wt% or more, or 3.0 wt% or more, or 3.2 wt% or more, or 3.4 wt% or more, or 3.6 wt% or more, or 3.8 wt% or more, or 4.0 wt% or more, or 4.2 wt% or more, or 4.4 wt% or more, or 4.6 wt% or more, or 4.8 wt% or more. At the same time, it may be 5.0% by weight or less, or 4.8% by weight or less, or 4.6% by weight or less, or 4.4% by weight or less, or 4.2% by weight or less, or 4.0% by weight or less, or 3.8% by weight or less, or 3.6% by weight or less, or 3.4% by weight or less, or 3.2% by weight or less, or 3.0% by weight or less, or 2.8% by weight or less, or 2.6% by weight or less, or 2.4% by weight or less, or 2.2% by weight or less, or 2.0% by weight or less.

[0053] The polymer composition can comprise 10 wt% to 80 wt% of the silane-grafted ethylene polymer, based on the total weight of the polymer composition. For example, the polymer composition can comprise 10 wt% or more, or 12 wt% or more, or 14 wt% or more, or 15 wt% or more, or 16 wt% or more, or 17 wt% or more, or 18 wt% or more, or 19 wt% or more, or 20 wt% or more, or 21 wt% or more, or 22 wt% or more, or 23 wt% or more, or 24 wt% or more, or 25 wt% or more, or 26 wt% or more, or 27 wt% or more, or 28 wt% or more, or 29 wt% or more, or 30 wt% or more, or 35 wt% or more, or 40 wt% or more, or 45 wt% or more, or 50 wt% or more, or 55 wt% or more, or 60 wt% or more, or 65 wt% or more, or 70 wt% or more, or 75 wt% or more, while simultaneously comprising 80 wt% or more of the silane-grafted ethylene polymer, based on the total weight of the polymer composition. % or less, or 75% or less, or 70% or less, or 65% or less, or 60% or less, or 55% or less, or 50% or less, or 45% or less, or 40% or less, or 35% or less, or 30% or less, or 29% or less, or 28% or less, or 27% or less, or 26% or less, or 25% or less, or 24% or less, or 23% or less, or 22% or less, or 21% or less, or 20% or less, or 19% or less, or 18% or less, or 17% or less, or 16% or less, or 15% or less, or 14% or less, or 13% or less, or 12% or less, or 11% or less by weight of the silane-grafted ethylene polymer.

[0054] Flame-retardant filler The flame-retardant filler can inhibit, suppress, or delay the onset of a flame. In some examples, the flame-retardant filler can be halogen-free. As used herein, terms such as "halogen-free" indicate that the flame-retardant filler has no or substantially no halogen content, i.e., contains less than 10,000 mg / kg of halogen, as measured by ion chromatography (IC) or a similar analytical method. Halogen content below this amount is not considered significant to the effectiveness of the flame-retardant filler, for example, in coated conductors.

[0055] Examples of flame-retardant fillers suitable for use in the polymer composition include, but are not limited to, halogenated materials, metal hydroxides, red phosphorus, ammonium polyphosphate, silica, alumina, titanium dioxide, carbon nanotubes, talc, clay, organically modified clay, calcium carbonate, zinc oxide, zinc molybdate, zinc sulfide, zinc borate, antimony trioxide, wollastonite, mica, ammonium octamolybdate, frit, hollow glass microspheres, expandable compounds, expandable graphite, and combinations thereof. Halogen-free examples of flame-retardant fillers may include at least one of magnesium hydroxide, aluminum trihydrate, calcium carbonate, hydrated calcium silicate, aluminum hydroxide, and magnesium hydrate. Commercially available examples of flame-retardant fillers suitable for use in the polymer composition include, but are not limited to, APYRAL™ 40CD available from Nabaltec AG, Schwandorf, Germany, and FR-20-100 from Israel Chemicals Ltd. of Tel Aviv-Yafo, Israel.

[0056] The flame-retardant filler can be optionally surface-treated (coated). The surface treatment can be with a saturated or unsaturated carboxylic acid having 8 to 24 carbon atoms or 12 to 18 carbon atoms, or a metal salt of the acid. Alternatively, the acid or salt can simply be added to the polymer composition in a similar amount, rather than using a surface treatment procedure. Other surface treatments, including silanes, titanates, phosphates, and zirconates, can also be utilized. Other surface treatments not disclosed herein can also be used.

[0057] The polymer composition may include the flame-retardant filler in an amount of 10% to 80% by weight, based on the total weight of the polymer composition. For example, the polymer composition may include 10% by weight or more, or 15% by weight or more, or 20% by weight or more, or 25% by weight or more, or 30% by weight or more, or 35% by weight or more, or 40% by weight or more, or 45% by weight or more, or 50% by weight or more, or 55% by weight or more, or 60% by weight or more, or 65% by weight or more, or 70% by weight or more, or 75% by weight or more, while simultaneously including 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, or 50% by weight or less, or 45% by weight or less, or 40% by weight or less, or 35% by weight or less of the flame-retardant filler, based on the total weight of the polymer composition.

[0058] silicone The polymer composition may contain 1% to 5% by weight of silicone (also called polysiloxane). The silicone may be linear, branched, reactive, and / or non-reactive. The silicone may be used in its native form (including but not limited to polydimethylsiloxane and silicone gum), as a masterbatch in a carrier polymer, or as a so-called "powder resin modifier" (e.g., DOWSIL™ Si powder resin modifier), or a combination thereof. For example, the polymer composition may comprise silicone at a concentration of 1 wt% or more, or 1.5 wt% or more, or 2 wt% or more, or 2.5 wt% or more, or 3 wt% or more, or 3.5 wt% or more, or 4 wt% or more, or 4.5 wt% or more, while simultaneously 20 wt% or less, or 15 wt% or less, or 10 wt% or less, 7 wt% or less, or 5 wt% or less, or 4.5 wt% or less, or 4.0 wt% or less, or 3.5 wt% or less, or 3.0 wt% or less, or 2.5 wt% or less, or 2.0 wt% or less, or 1.5 wt% or less.

[0059] additives The polymer composition may include one or more additives. Non-limiting examples of suitable additives include antioxidants, colorants, corrosion inhibitors, lubricants, silanol condensation catalysts, ultraviolet (UV) absorbers or stabilizers, antiblocking agents, flame retardants, coupling agents, compatibilizers, plasticizers, fillers, processing aids, and combinations thereof.

[0060] The polymer composition may contain an antioxidant. Non-limiting examples of suitable antioxidants include phenolic antioxidants, thio antioxidants, phosphate antioxidants, and hydrazine metal deactivators. Suitable phenolic antioxidants include polyfunctional phenols such as high molecular weight hindered phenols, methyl-substituted phenols, phenols with primary or secondary carbonyl substituents, and sulfur- and phosphorus-containing phenols. Representative hindered phenols include 1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, pentaerythrityl tetrakis-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, n-octadecyl-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 4,4'-methylenebis(2,6-tert-butyl-phenol), and methyl-substituted phenols. Examples of suitable methyl-substituted phenols include 4,4'-thiobis(6-tert-butyl-o-cresol), 2,6-di-tert-butylphenol, 6-(4-hydroxyphenoxy)-2,4-bis(n-octylthio)-1,3,5-triazine, di-n-octylthio)ethyl 3,5-di-tert-butyl-4-hydroxybenzoate, and sorbitol hexa[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The polymer composition may include pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), commercially available from BASF as Irganox™ 1010. A non-limiting example of a suitable methyl-substituted phenol is isobutylidenebis(4,6-dimethylphenol). A non-limiting example of a suitable hydrazine-based metal deactivator is oxalyl bis(benzylidene hydrazide). The polymer composition can contain from 0 wt%, or 0.001 wt%, or 0.01 wt%, or 0.02 wt%, or 0.05 wt%, or 0.1 wt%, or 0.2 wt%, or 0.3 wt%, or 0.4 wt% to 0.5 wt%, or 0.6 wt%, or 0.7 wt%, or 0.8 wt%, or 1.0 wt%, or 2.0 wt%, or 2.5 wt%, or 3.0 wt% of the antioxidant, based on the total weight of the polymer composition.

[0061] The polymer composition may include a silanol condensation catalyst, such as a Lewis acid and a base, and a Bronsted acid and a base. The "silanol condensation catalyst" promotes crosslinking of silane-functionalized polyolefins through hydrolysis and condensation reactions. A Lewis acid is a chemical species that can accept an electron pair from a Lewis base. A Lewis base is a chemical species that can donate an electron pair to a Lewis acid. Non-limiting examples of suitable Lewis acids include dibutyltin dilaurate (DBTDL), dimethylhydroxytin oleate, dioctyltin maleate, di-n-butyltin maleate, dibutyltin diacetate, dibutyltin dioctoate, stannous acetate, stannous octoate, and various other organometallic compounds, such as lead naphthenate, zinc caprylate, and cobalt naphthenate. Non-limiting examples of suitable Lewis bases include primary, secondary, and tertiary amines. Non-limiting examples of suitable Bronsted acids include methanesulfonic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, or alkylnaphthalenesulfonic acid. The silanol condensation catalyst can include a blocked sulfonic acid. The blocked sulfonic acid can be as defined in U.S. Patent Application Publication No. 2016 / 0251535(A1) and can be a compound that generates a sulfonic acid in situ upon heating, optionally in the presence of moisture or alcohol. Examples of blocked sulfonic acids include amine-sulfonate salts and sulfonic acid alkyl esters. The blocked sulfonic acid can consist of a carbon atom, a hydrogen atom, one sulfur atom, three oxygen atoms, and optionally a nitrogen atom. These catalysts are typically used in moisture-curing applications. The polymer composition comprises from 0, or 0.001, or 0.005, or 0.01, or 0.02, or 0.03 to 0.05, or 0.1, or 0.2, or 0.5, or 1.0, or 3.0, or 5.0, or 10 weight percent of a silanol condensation catalyst, based on the total weight of the polymer composition. The silanol condensation catalyst is typically added to an article-making extruder (such as during cable production) so that the silanol condensation catalyst is present during the final melt extrusion process.In this manner, the silane-functionalized polyolefin may be crosslinked to some extent before the silane-functionalized polyolefin exits the extruder, and crosslinking is completed after the silane-functionalized polyolefin exits the extruder when it is exposed to moisture (e.g., a sauna, hot or cold bath) and / or humidity typically present in the environment in which the silane-functionalized polyolefin is stored, transported, or used.

[0062] The silanol condensation catalyst can be included in the catalyst masterbatch blend, with the catalyst masterbatch being included in the composition. Non-limiting examples of suitable silanol condensation catalyst masterbatches include those sold under the SI-LINK™ trade name by The Dow Chemical Company, including SI-LINK™ DFDB-5480 NT, SI-LINK™ DFDA-5481 NT, and SI-LINK™ AC DFDA-5488 NT. In one embodiment, the composition contains from 0 wt%, or 0.001 wt%, or 0.01 wt%, or 0.5 wt%, or 1.0 wt%, or 2.0 wt%, or 3.0 wt%, or 4.0 wt% to 5.0 wt%, or 6.0 wt%, or 7.0 wt%, or 8.0 wt%, or 9.0 wt%, or 10.0 wt%, or 15.0 wt%, or 20.0 wt%, of a silanol condensation catalyst masterbatch, based on the total weight of the composition.

[0063] The polymer composition may include an ultraviolet (UV) light absorber or stabilizer. A non-limiting example of a suitable UV stabilizer is a hindered amine light stabilizer (HALS). Non-limiting examples of suitable HALS include 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-triazin-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-triazin-2-yl]-1,5,8,12-tetraazadodecane (commercially available as SABO™ STAB UV-119 from SABO SpA, Levate, Italy). In one embodiment, the composition contains from 0 wt.%, or 0.001 wt.%, or 0.002 wt.%, or 0.005 wt.%, or 0.006 wt.% to 0.007 wt.%, or 0.008 wt.%, or 0.009 wt.%, or 0.01 wt.%, or 0.2 wt.%, or 0.3 wt.%, or 0.4 wt.%, or 0.5 wt.%, or 1.0 wt.%, or 2.0 wt.%, or 2.5 wt.%, or 3.0 wt.% of a UV absorber or stabilizer, based on the total weight of the composition.

[0064] The composition may include a processing aid. Non-limiting examples of suitable processing aids include oils, organic acids (such as stearic acid), and metal salts of organic acids (such as zinc stearate). In one embodiment, the composition contains 0 wt%, or 0.01 wt%, or 0.02 wt%, or 0.05 wt%, or 0.07 wt%, or 0.1 wt%, or 0.2 wt%, or 0.3 wt%, or 0.4 wt% to 0.5 wt%, or 0.6 wt%, or 0.7 wt%, or 0.8 wt%, or 1.0 wt%, or 2.0 wt%, or 2.5 wt%, or 3.0 wt%, or 5.0 wt%, or 10.0 wt%, or 20.0 wt%, of the processing aid, based on the total weight of the composition.

[0065] The composition may contain 0 wt% or more, or 0.001 wt% or more, or 0.002 wt% or more, or 0.005 wt% or more, or 0.006 wt% or more, or 0.008 wt% or more, or 0.009 wt% or more, or 0.01 wt% or more, or 0.2 wt% or more, or 0.3 wt% or more, or 0.4 wt% or more, or 0.5 wt% or more, or 1.0 wt% or more, or 2.0 wt% or more, or 3.0 wt% or more, or 4.0 wt% or more, or 5.0 wt% or more, or 10.0 wt% or more, or 15.0 wt% or more, or 20.0 wt% or more, or 30 wt% or more, or 40 wt% or more, or 50 wt% or more of the additive, based on the total weight of the polymer composition.

[0066] Masterbatch The silane-grafted ethylene polymer, the flame retardant, and one or more of the additives can be combined as a premixed masterbatch. Such masterbatches are typically formed by dispersing the flame retardant and additives in an inert plastic resin. The masterbatch is conveniently formed by melt compounding.

[0067] To reduce or eliminate the possibility of scorch, which may be caused by moisture present in or associated with the components, such as fillers, one or more of the components or masterbatches may be dried prior to compounding or extrusion, or the mixture of components or masterbatches may be dried after compounding or extrusion. The present compositions may be prepared in the absence of a silanol condensation catalyst for long shelf life, which may be added as a final step in the manufacture of cable structures (coated conductors) by extrusion processes.

[0068] coated conductor The present disclosure also provides a coated conductor. The coated conductor includes a conductor and a coating on the conductor, the coating including the polymer composition. The polymer composition is at least partially disposed around the conductor to produce the coated conductor. The conductor may include a conductive metal.

[0069] The method for making a coated conductor includes mixing a polymer composition in an extruder and heating to at least the melting point of the silane-grafted ethylene polymer to form a polymer melt blend, and then coating the polymer melt blend onto a conductor. The term "on" includes direct or indirect contact between the polymer melt blend and the conductor. The polymer melt blend is in an extrudable state.

[0070] The polymer composition is disposed on and / or around a conductor to form a covering. The covering can be one or more inner layers, such as an insulating layer. The covering can completely or partially cover or otherwise surround or encase the conductor. The covering can be the only component surrounding the conductor. Alternatively, the covering can be one layer of a multi-layer jacket or sheath that encases the conductor. The covering can be in direct contact with the conductor. The covering can be in direct contact with an insulating layer that surrounds the conductor.

[0071] The coated conductor may exhibit a FWCL value of less than 15 cm*% as specified below. For example, the coated conductor may exhibit a filler weighted char length value of 0.5 cm*% or more, or 1 cm*% or more, or 2 cm*% or more, or 3 cm*% or more, or 4 cm*% or more, or 5 cm*% or more, or 6 cm*% or more, or 7 cm*% or more, or 8 cm*% or more, or 9 cm*% or more, or 10 cm*% or more, or 11 cm*% or more, or 12 cm*% or more, or 13 cm*% or more, or 14 cm*% or more, while simultaneously less than 15 cm*%, or 14 cm*% or less, or 13 cm*% or less, or 12 cm*% or less, or 11 cm*% or less, or 10 cm*% or less, or 9 cm*% or less, or 8 cm*% or less, or 7 cm*% or less, or 6 cm*% or less, or 5 cm*% or less, or 4 cm*% or less, or 3 cm*% or less, or 2 cm*% or less, or 1 cm*% or less. [Example]

[0072] Test Method VTMS Content of Si-g-PE: The VTMS content of Si-g-PE was measured using neutron activation analysis (NAA). Samples were prepared from portions of Si-g-PE that had been vacuum-stripped at 55°C for 24 hours. Si standards were prepared in similar vials from NIST-traceable standard solutions. The standards were diluted to the same volume as the samples using pure water. A blank sample of water was also prepared. The samples, standards, and blanks were then analyzed according to the standard NAA procedure for Si, "Global-SOP-01101.02." Specifically, irradiation during NAA was performed for 3 minutes at 250 kW reactor power. An HPGe detector set was used, with a waiting time of 9 minutes and a counting time of 270 seconds. The Si concentration was calculated as a weight percent using Canberra software and comparative techniques. Typical measurement uncertainties ranged from 2% to 5% relative values, with a detection limit of less than 90 ppm. All Si measured by NAA was determined from doped vinyltrimethoxysilane (C5H5H5). 12 The VTMS content (wt %) was back-calculated using stoichiometry, assuming it was from the ethylene / comonomer (O3Si). Knowing the wt % of VTMS and the wt % of ethylene and other comonomers (e.g., octene, ethyl acrylate) used to make the ethylenic polymer, the mole % VTMS was calculated using the following equation:

number

[0073] FWCL Value: The FWCL value of a coated conductor is determined by first conducting International Electrotechnical Commission test 60332-1-2:2004, which defines a procedure for testing the resistance of a single vertical coated conductor to vertical flame propagation. Test 60332-1-2:2004 measures the length of char ("char length") that forms on the coated conductor during the test. The FWCL value is calculated by multiplying the char length in centimeters by the weight percent of flame-retardant filler present in the polymer composition used to form the coated conductor and dividing by 100.

[0074] material The materials used in the examples are provided below.

[0075] POE1 is an ethylene polymer made with 1-octene (10.3 mol%) as a comonomer, having a density of 0.88 g / cc as measured in accordance with ASTM D792 and a melt index of 18 g / 10 min at 190°C / 2.16 kg as measured in accordance with ASTM D1238. POE1 has a polar comonomer content of 0 wt%. POE1 is commercially available from The Dow Chemical Company, Midland, MI.

[0076] POE2 is an ethylene polymer made with 1-octene (5.6 mol%) as a comonomer, having a density of 0.902 g / cc as measured in accordance with ASTM D792 and a melt index of 30 g / 10 min at 190°C / 2.16 kg as measured in accordance with ASTM D1238. POE2 has a polar comonomer content of 0 wt%. POE2 is commercially available from The Dow Chemical Company, Midland, MI.

[0077] Polar PE1 is an ethylene polymer made with ethyl acrylate (18 wt. % ethyl acrylate) as a comonomer, having a melt index of 6 g / 10 min at 190° C. / 2.16 kg measured according to ASTM D1238. Polar PE1 has a polar comonomer content of 18 wt. %. Polar PE1 is commercially available from The Dow Chemical Company, Midland, MI.

[0078] Polar PE2 is an ethylene polymer made with ethyl acrylate (21 wt% ethyl acrylate) as a comonomer, having a melt index of 21 g / 10 min at 190°C / 2.16 kg as measured in accordance with ASTM D1238. Polar PE2 has a polar comonomer content of 21 wt%. Polar PE2 is commercially available from The Dow Chemical Company, Midland, MI.

[0079] LDPE is a low density polyethylene (ethylene polymer) having a density of 0.918 g / cc as measured in accordance with ASTM D792 and a melt index of 8 g / 10 min at 190°C / 2.16 kg as measured in accordance with ASTM D1238. LDPE has a polar comonomer content of 0 wt%. LDPE is commercially available from The Dow Chemical Company, Midland, MI.

[0080] Vinyltrimethoxysilane (VTMS), CAS number 2768-02-7, is commercially available from Sigma-Aldrich, St. Louis, MO, at 98% purity.

[0081] 2,5-Bis(tert-butylperoxy)-2,5-dimethylhexane (DBPH), CAS number 78-63-7, is a peroxide commercially available from Sigma-Aldrich, St. Louis, MO.

[0082] SC is a silanol condensation catalyst masterbatch developed for use in combination with moisture-curable ethylene-silane copolymers and is commercially available as SI-LINK™ DFDB-5480 NT from The Dow Chemical Company, Midland, MI.

[0083] OBC is an olefin block copolymer having a density of 0.877 g / cc as measured in accordance with ASTM D792 and a melt index of 15 g / 10 min at 190° C. / 2.16 kg as measured in accordance with ASTM D1238. OBC is commercially available as INFUSE™ 9817 from The Dow Chemical Company, Midland, MI.

[0084] The compatibilizer is a maleic anhydride grafted ethylene vinyl acetate copolymer, commercially available as FUSABOND™ C250 from The Dow Chemical Company, Midland, MI.

[0085] The filler is magnesium hydroxide (HFFR) and is commercially available as FR-20-100 from Israel Chemicals Ltd. of Tel Aviv-Yafo, Israel.

[0086] AO1 is a sterically hindered phenolic antioxidant with the chemical name pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), commercially available as IRGANOX™ 1010 from BASF (Ludwigshafen, Germany).

[0087] AO2 is distearyl thiodipropionate, commercially available as NAUGARD™ DSTDP from Addivant, Danbury, CT.

[0088] OBH is oxalyl bis(benzylidene)hydrazide and is commercially available from Sigma-Aldrich, St. Louis, MO.

[0089] The silicone is DOWSIL™ Si Powdered Resin Modifier 4-7081, commercially available from The Dow Chemical Company, Midland, MI.

[0090] OTS is octyltriethoxysilane, commercially available as PROSIL™ 9202 from SiVance LLC of Milliken & Co.

[0091] Sample preparation Silane functionalization of ethylene polymers was performed using a 26 mm co-rotating twin-screw extruder (ZSK-26 from Coperion Corp.). The extruder consisted of 15 barrels (60 L / D). The maximum screw speed was 1200 revolutions per minute (rpm), and the maximum motor power was 40 horsepower. The extruder was equipped with a "loss-in-weight feeder" to feed the base resin. For all samples, the silane (VTMS) and DBPH (peroxide) were pre-blended in a 20:1 weight ratio and metered into the extruder using an Eldex scale at barrel 5. The run rate was 4.54 kg / h, and the screw speed was 300 rpm. Barrel temperatures were set at 150 °C for barrels 2-4, 230 °C for barrels 6-10, 190 °C for barrels 11-12, and 160 °C for barrels 12-15 and the adapter / die. The first barrel section was purged with 10-15 standard cubic feet per hour of nitrogen to maintain an inert atmosphere and minimize oxidation. A vacuum (50795.8 Pa) was applied to barrel 13. Strands were produced using a two-hole die and cut into pellets with a strand cutter. The silane-grafted material was then dried in a hood using nitrogen for approximately 4-6 hours, vacuum-sealed in aluminum foil bags to prevent exposure to moisture, and stored for further testing. The vacuum-stripped samples were subjected to grafting measurements using neutron activation analysis (NAA). Table 1 shows the silane content of the silane-functionalized ethylene polymers used in the examples. [Table 1]

[0092] Flame retardant masterbatches ("FRMB") were formed by combining the materials in Table 2. FRMB was made by combining magnesium hydroxide and other raw ingredients with OBC in a BRABENDER™ mixer equipped with a cam blade at a rotor speed of 40 rpm and a jacket (mixing bowl set) temperature of 160°C. After all other raw ingredients were uniformly mixed, the FRMB liquid additive was added. The FRMB was mixed for 15 minutes after fluxing, flattened in a press, cooled, and chopped into small pieces. The pieces were extruded at 40 rpm in a 25:1 single-screw extruder equipped with a dual mixing head using a 150°C / 160°C / 170°C / 180°C profile through a 20 / 40 / 60 US mesh / inch screen pack, and the resulting strands were chopped into small pellets. [Table 2]

[0093] All masterbatches were dried in a vacuum oven before wire production. FRMB pellets were placed in a 60°C oven for 48 hours to remove moisture. The silane-grafted ethylene polymer, FRMB, and silanol condensation catalyst were then physically blended in the specific ratios shown in Table 3. The blend was then melt-mixed during extrusion to fabricate wire structures on 10 AWG solid copper wire with a nominal wall thickness of 1.524 mm. The wire production unit included a BRABENDER™ 19.05 mm extruder with a variable speed drive, a 24:1 polyethylene screw without a mixing head, a BRABENDER™ crosshead wire die, a laboratory water-cooled trough with air wipes, a laser micrometer, and a variable speed wire puller. Wire samples were extruded using a temperature profile of 140°C / 155°C / 165°C / 165°C (zone 1, zone 2, zone 3, and overall head / die) and a 40 / 40 mesh screen pack at a 40 rpm screw speed and a take-up speed of approximately 2.44 m / min.

[0094] The extruded coated conductors were cured for 2 days in a water bath at 90° C. After further conditioning at 23° C. and 50% relative humidity for 72 hours, the cured coated conductors were tested according to International Electrotechnical Commission test 60332-1-2:2004 to calculate FWCL values.

[0095] result Table 3 shows the compositions of Comparative Examples ("CE") 1-6 and Inventive Examples ("IE") 1-10, as well as the associated FWCL values. [Table 3]

[0096] As can be seen from Table 3, it was surprisingly discovered that the measured FWCL values ​​are a function of the silane content (grafted VTMS) of the Si-g-PE used to make the polymer composition and the type of ethylene polymer used to make the Si-g-PE. Surprisingly, when Polar PE1 or Polar PE2 is used to make the Si-g-PE, substantially poorer flammability performance of the coated conductor is obtained (reflected in FWCL values ​​of 15 cm*% or greater). Even more surprisingly, it was discovered that at silane contents below 0.40 mol%, the coated conductor exhibits FWCL values ​​of 15 cm*% or greater, while at silane contents above 0.40 mol%, FWCL values ​​below 15 cm*% (when Polar PE1 or Polar PE2 is not Si-g-PE) are obtained, indicating that 0.40 mol% is a critical silane content. FWCL values ​​of less than 15 cm*% are obtained with grafted VTMS (silane content) values ​​up to 0.94 mol% (when Polar PE1 or Polar PE2 is not Si-g-PE), and it is believed that this relationship extends up to 1.50 mol%.

Claims

1. 1. A polymer composition comprising: 10 wt% to 40 wt%, based on the total weight of the polymer composition, of a silane-grafted ethylene polymer, the silane-grafted ethylene polymer having a silane content of 0.40 mol% to 1.50 mol%, based on the total moles of the silane-grafted ethylene polymer, and the ethylene polymer used to make the silane-grafted ethylene polymer has a polar comonomer content of less than 15 wt%, based on the total weight of the ethylene polymer; 30% to 70% by weight of a flame retardant filler, based on the total weight of the polymer composition; 1 wt % to 5 wt % of a polysiloxane, based on the total weight of the polymer composition; comprising 1. A polymeric composition, wherein the flame retardant filler comprises at least one of magnesium hydroxide, aluminum trihydrate, calcium carbonate, hydrated calcium silicate, and hydrated magnesium.

2. The polymer composition of claim 1, further comprising 0.001 wt % to 10.0 wt % of a silanol condensation catalyst based on the total weight of the polymer composition.

3. 3. The polymer composition of claim 1 or 2, wherein the silane-grafted ethylene polymer has a silane content of 0.40 mole % to 0.94 mole %, based on the total moles of the silane-grafted ethylene polymer.

4. The polymer composition of any one of claims 1 to 3, wherein the silane-grafted ethylene polymer has a density of from 0.860 g / cc to 0.930 g / cc as measured according to ASTM D-792.

5. The silane graft of the silane-grafted ethylene polymer has the general formula: 【Chemical 1】 [In the formula, R １ 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 are independently hydrolyzable organic groups, provided that three R ２ 5. The polymer composition according to claim 1, wherein the units are derived from a hydrolyzable silane monomer of the formula: [provided that not more than one of the groups is alkyl].

6. 6. The polymer composition of claim 5, wherein the hydrolyzable silane monomer is selected from the group consisting of vinyltrimethoxysilane and vinyltriethoxysilane.

7. A conductor; and the polymer composition of any one of claims 1 to 6 positioned at least partially around the conductor, wherein the coated conductor exhibits a filler-weighted char length metric of less than 15 cm*%.

8. 8. The coated conductor of claim 7, wherein the filler weighted char length criteria is between 1 cm*% and 10 cm*%.

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