Polymeric compositions comprising moisture cure catalysts

Abstract

A polymeric composition includes a silane-functionalized polyolefin and a moisture cure catalyst. The moisture cure catalyst includes 20 wt% to 70 wt% of bismuth carboxylate based on the total weight of the catalyst and 30 wt% to 80 wt% of carboxylic acid based on the total weight of the catalyst. The carboxylic acid is in excess of the coordination number of bismuth.

Description

POLYMERIC COMPOSITIONS COMPRISING MOISTURE CURE CATALYSTS BACKGROUNDField of the disclosureThe disclosure generally relates to polymeric compositions and more specifically to polymeric compositions comprising moisture cure catalysts.IntroductionSilane functionalized ethylene-based polymers are used in the formation of moisture-curable polymeric compositions. Such polymeric compositions are used to fabricate wires and cables (including low-voltage cable constructions) and may be utilized as either a jacket for the cable or as electrical insulation. The silane contains hydrolysable groups and may be grafted onto the ethylene -based polymer or copolymerized with ethylene to form the silane functionalized ethylene-based polymers. The silane facilitates crosslinking of the polymeric composition generally through moisture-induced cure. The crosslinking of the polymeric composition is often referred to as “curing.” Such a curing is accomplished with the formation of siloxane bonds via hydrolysis and condensation reactions aided by moisture cure catalysts. In practice, curing takes place in a humid environment (such as water or steam bath at elevated temperatures, or even at ambient conditions of room temperature and humidity) such that the water permeates into the polymeric composition and reacts with the hydrolysable silane groups in the presence of the moisture cure catalyst.The effectiveness of a moisture cure catalyst is often judged by its ability to cure the moisture-curable polymeric composition to a specific mechanical property within a set period of time. A moisture-curable polymeric composition is sufficiently cured if it exhibits a storage modulus (G’) at 130°C and 0.025 rad / s of 0.040 MPa or greater after curing in a humid environment (such as for 4 or more hours in a 90°C water bath) and exhibits a hot creep at 150°C with 0.2 MPa applied stress of 175% or less after curing in a humid environment (such as for 4 or more hours in a 90°C water bath).Traditional catalysts for moisture cure reactions include tin-based moisture catalysts. For the tin-based catalysts, the most used catalyst is Dibutyltin dilaurate (“DBTDL”). Such tin-based moisture catalysts are under enhanced regulatory scrutiny and alternatives with comparable performance and enhanced EH&S profile are desired. Others have attempted to create tin-free catalyst solutions. For example, United States patent application publicationnumber 2005 / 0171315 (“the ‘315 publication’’) discloses the use of a curable composition comprising a reactive silicon group-containing organic polymer (A) and a carboxylic acid (B). The ‘315 publication in paragraph

[0111] discloses “preferably that a content of a metal carboxylate (such as bismuth neodecanoate) formed between a carboxylic acid and a metal atom of more than 208 in atomic weight in the curable composition of the present invention is less than 0.1 parts by weight in relation to 100 parts by weight of the organic polymer (A). More preferably, the metal carboxylate formed between a carboxylic acid and a metal atom of more than 208 in atomic weight is not contained substantially.” The ‘315 publication further explains in paragraph

[0112] that “[t]he carboxylic acid (B) of the present invention has an effect to improve the curing activity of the curable composition of the present invention” but is silent with respect to how much additional carboxylic acid should be present in any mixture with the metal carboxylate. The inclusion of carboxylic acid, however, is not without its own problems. Carboxylic acids can react with silanol thereby reducing the overall curability of the polymer. Further, the carboxylic acid may phase separate from the polymeric composition and carry catalyst or other necessary components with it thereby also reducing the overall curability of the polymer.In view of the foregoing, it would be surprising to discover a moisture-curable polymeric composition comprising greater than 0.1 parts metal carboxylate in a mixture with carboxylic acid of specified amount that exhibits a storage modulus (G’) at 130°C and 0.025 rad / s of 0.040 MPa or greater after curing for 4 or more hours in a 90°C water bath and exhibits a hot creep at 150°C with 0.2 MPa applied stress of 175% or less after curing in a humid environment (such as for 4 or more hours in a 90°C water bath).SUMMARY OF THE DISCLOSUREThe inventors of the present application have discovered a moisture-curable polymeric composition comprising greater than 0.1 parts metal carboxylate in a mixture with carboxylic acid of specified amount that exhibits a storage modulus (G’) at 130°C and 0.025 rad / s of 0.040 MPa or greater after curing for 4 or more hours in a 90°C water bath and exhibits a hot creep at 150°C with 0.2 MPa applied stress of 175% or less after curing in a humid environment (such as for 4 or more hours in a 90°C water bath).The invention is a result of discovering that a catalyst comprising bismuth carboxylate in a mixture with a free carboxylic acid is an effective moisture cure catalyst for a moisture-curable polymeric composition when the catalyst comprises 30 wt% or greater (and no morethan 80 wt%) of carboxylic acid based on the total weight of the catalyst. This range is surprising for several reasons. First, in that the moisture cure catalyst remains effective even when additives having base characteristics are present in the moisture-curable polymeric compositions. Such additives include ultra-violet stabilizers (for example, hindered amine light stabilizers), pigments (including carbon black and red colorants) and fillers (the latter include metal hydroxides). Thus, the minimum and maximum permissible amounts of carboxylic acids in mixtures with metal carboxylates (that are used as moisture cure catalysts for moisture-curable polymeric compositions) are important considerations that have hitherto not been disclosed in the prior art. Second, despite the inclusion of 30 wt% or greater of carboxylic acid, the polymeric composition does not exhibit reductions in the overall curability of the polymer as highlighted above.According a feature of the present disclosure, a polymeric composition includes a silane-functionalized polyolefin; and a moisture cure catalyst, comprising: 20 wt% to 70 wt% of bismuth carboxylate based on the total weight of the catalyst; and 30 wt% to 80 wt% of carboxylic acid based on the total weight of the catalyst, wherein the carboxylic acid is in excess of the coordination number of bismuth.According to another feature of the present disclosure, the silane-functionalized polyolefin exhibits one or more of (i) to (iv): (i) the silane-functionalized polyolefin has a density of 0.910 g / cc to 0.940 g / cc as measured according to ASTM D792; (ii) the silane-functionalized polyolefin has a melt index of 0.1 g / lOmin. to 10 g / lOmin. as measured according to ASTM D1238; (iii) the silane-functionalized polyolefin is an a-olefin and silane copolymer; and (iv) the silane-functionalized polyolefin is a silane-grafted polyolefin.According to another feature of the present disclosure, the silane-functionalized polyolefin exhibits each of (i), (ii) and (iv).According to another feature of the present disclosure, the polymeric composition comprises 0.10 wt% to 5.0 wt% of the moisture cure catalyst based on the total weight of the polymeric composition.According to another feature of the present disclosure, the carboxylic acid comprises from 8 to 14 carbons.According to another feature of the present disclosure, the carboxylic acid comprises one or more of neodecanoate, ethyl hexanoate, and combinations thereof.According to another feature of the present disclosure, the carboxylic acid is neodecanoate.According to another feature of the present disclosure, the moisture cure catalyst comprises from 40 wt% to 60 wt% of carboxylic acid based on the total weight of the moisture cure catalyst.According to another feature of the present disclosure, the moisture cure catalyst comprises from 40 wt% to 50 wt% of carboxylic acid based on the total weight of the moisture cure catalyst.According to another feature of the present disclosure, a coated conductor, includes the polymeric composition positioned around the conductor.DETAILED DESCRIPTIONAs used herein, the term “and / or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. 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.All ranges include endpoints unless otherwise stated.Test methods refer to the most recent test method as of the priority date of this document unless a date is indicated with the test method number as a hyphenated two-digit number. References to test methods contain both a reference to the testing society and the test method number. Test method organizations are referenced by one of the following abbreviations: ASTM refers to ASTM International (formerly known as American Society for Testing and Materials); EN refers to European Norm; DIN refers to Deutsches Institut fur Normung; and ISO refers to International Organization for Standards.Polymeric CompositionThe present disclosure is directed to a polymeric composition. The polymeric composition comprises a silane functionalized polyolefin and a moisture cure catalyst. The moisture cure catalyst comprises bismuth carboxylate and a carboxylic acid.The polymeric composition may exhibit a storage modulus (G’) at 130°C and 0.025 rad / s of 0.040 MPa or greater as measured according to Oscillatory Shear Rheology Testing. For example, the polymeric composition, after curing may exhibit a storage modulus (G’) at 130°C and 0.025 rad / s of 0.040 MPa or greater, or 0.060 MPa or greater, or 0.080 MPa or greater, or 0.100 MPa or greater, or 0.120 MPa or greater, or 0.140 MPa or greater, or 0.160 MPa or greater, or 0.180 MPa or greater, or 0.200 MPa or greater, or 0.220 MPa or greater, or0.240 MPa or greater, while at the same time, 0.260 MPa or less, or 0.240 MPa or less, or 0.220 MPa or less, or 0.200 MPa or less, or 0.180 MPa or less, or 0.160 MPa or less, or 0.140 MPa or less, or 0.120 MPa or less, or 0.100 MPa or less, or 0.080 MPa or less, or 0.060 MPa or less as at 130°C and 0.025 rad / s measured according to Oscillatory Shear Rheology Testing.The polymeric composition may exhibit a hot creep of 175% or less as measured according to Hot Creep Testing after curing for 4 hours in a 90°C water bath. For example, the polymeric composition may exhibit a 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 Hot Creep Testing after curing for 4 hours in a 90°C water bath.Silane-Functionalized PolyolefinA “silane -functionalized polyolefin” is a polymer that contains silane and equal to or greater than 50 wt %, or a majority amount, of polymerized a-olefin, based on the total weight of the silane -functionalized polyolefin. “Polymer” means a macromolecular compound prepared by reacting (i.e., polymerizing) monomers of the same or different type. As noted above, the polymeric composition comprises the silane-functionalized polyolefin. The polyolefin comprises polymerized a-olefins and optionally unsaturated esters.The silane-functionalized polyolefin may include an a-olefin and silane copolymer (i.e., a-olefin / silane copolymer), a silane-grafted polyolefin, and / or combinations thereof. An “a-olefin and silane copolymer” is formed from the copolymerization of an a-olefin (such as ethylene) and a hydrolyzable silane monomer (such as a vinyl silane monomer) such that the hydrolyzable silane monomer is incorporated into the backbone of the polymer chain prior to the polymer's incorporation into the polymeric composition. A “silane-grafted polyolefin” or “Si-g-PO” may be formed by the Sioplas process in which a hydrolyzable silane monomer is grafted onto the backbone of a base polyolefin by a process such as extrusion, prior to the polymer's incorporation into the polymeric composition.In examples where the silane-functionalized polyolefin is an a-olefin / silane copolymer, the silane-functionalized polyolefin is prepared by the copolymerization of at least one a-olefin and 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 on to the a-olefin backbone.The silane-functionalized polyolefin comprises 90 wt% or greater, or 91 wt% or greater, or 92 wt% or greater, or 93 wt% or greater, or 94 wt% or greater, or 95 wt% or greater, or 96 wt% or greater, or 97 wt% or greater, or 97.5 wt% or greater, or 98 wt% or greater, or 98.5 wt%or greater, or 99 wt% or greater, while at the same time, 99.5 wt% or less, or 99 wt% or less, or 98 wt% or less, or 97 wt% or less, or 96 wt% or less, or 95 wt% or less, or 94 wt% or less, or 93 wt% or less, or 92 wt% or less, or 91 wt% or less of a-olefin and optional unsaturated ester based on a total weight of the silane functionalized polyolefin as measured using Fourier-Transform Infrared (FTIR) Spectroscopy. The a-olefin may include C2, or C3 to C4, or Ce, or Cs, or C10, or C12, or C16, or Cis, or C20 a-olefins, such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-l -pentene, and 1 -octene. The unsaturated ester can be an alkyl acrylate, alkyl methacrylate, or vinyl carboxylate.The silane-functionalized polyolefin may comprise from 0.1 wt%, or 0.3 wt%, or 0.5 wt%, or 0.8 wt%, or 1.0 wt%, or 1.2 wt%, or 1.5 wt%, or 1.6 wt% to 1.8 wt%, or 2.0 wt%, or 2.3 wt%, or 2.5 wt%, or 3.0 wt%, or 3.5 wt%, or 4.0 wt%, or 4.5 wt%, while at the same time, 5.0 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 2.4 wt% or less, or 2.3 wt% or less, or 2.0 wt% or less, or 1.8 wt% or less, or 1.6 wt% or less, or 1.4 wt% or less, or 1.2 wt% or less, or 1.0 wt% or less, or 0.8 wt%, or 0.6 wt% or less of silane based on a total weight of the silane functionalized polyolefin as measured using FTIR Spectroscopy.The silane-functionalized polyolefin has a density from 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 at the same time, 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 as measured by ASTM D792.The silane-functionalized polyolefin may have a melt index as measured according to ASTM D1238 under the conditions of 190°C / 2.16 kilogram (kg) weight and is reported in grams eluted per 10 minutes (g / 10 min). The melt index of the silane-functionalized polyolefin may be 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, while at the same time, 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 / 10 min or less, or 30.0 g / 10 min or less, or 25.0 g / 10 min or less, or 20.0 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.A “hydrolyzable silane monomer” is a silane-containing monomer that will effectively copolymerize with an a-olefin (e.g., ethylene) to form an a-olefin / silane copolymer (such as an ethylene / silane copolymer), or graft to an a-olefin polymer (i.e., a polyolefin) to form a Si-g-PO, thus enabling subsequent crosslinking of the silane -functionalized polyolefin. A representative, but not limiting, example of a hydrolyzable silane monomer has structure (I):Structure (I)in which R1is a hydrogen atom or 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 R2independently is a hydrolyzable organic group such as an alkoxy group having from 1 to 12 carbon atoms (e.g., methoxy, ethoxy, butoxy), an aryloxy group (e.g., phenoxy), an araloxy group (e.g., benzyloxy), an aliphatic acyloxy group having from 1 to 12 carbon atoms (e.g., formyloxy, acetyloxy, propanoyloxy), an amino or substituted amino group (e.g., alkylamino, arylamino), or a lower-alkyl group having 1 to 6 carbon atoms, with the proviso that not more than one of the three R2groups is an alkyl. The hydrolyzable silane monomer may be copolymerized with an a-olefin (such as ethylene) in a reactor, such as a high-pressure process to form an a-olefin-silane copolymer (“i.e., a reactor copolymer”). In examples where the a-olefin is ethylene, such a copolymer is referred to herein as an ethylenesilane copolymer. The hydrolyzable silane monomer may also be grafted to a polyolefin (such as a polyethylene) by the use of an organic peroxide, such as 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, to form a Si-g-PO or an in-situ Si-g-PO. The in-situ Si-g-PO is formed by a process such as the MONOSIL™ process, in which a hydrolyzable silane monomer is grafted onto the backbone of a polyolefin during the extrusion of the present composition to form a coated conductor, as described, for example, in US 4,574,133.The hydrolyzable silane monomer may include silane monomers that comprise an ethylenically unsaturated hydrocarbyl group, such as a vinyl, allyl, isopropenyl, butenyl, cyclohexenyl or gamma (meth)acryloxy allyl group, and a hydrolyzable group, such as, for example, a hydrocarbyloxy, hydrocarbonyloxy, or hydrocarbylamino group. Hydrolyzable groups may include methoxy, ethoxy, formyloxy, acetoxy, proprionyloxy, and alkyl orarylamino groups. In a specific example, the hydrolyzable silane monomer is an unsaturated alkoxy silane, which can be grafted onto the polyolefin or copolymerized in-reactor with an a-olefin (such as ethylene). Examples of hydrolyzable silane monomers include vinyltrimethoxysilane (VTMS), vinyltriethoxysilane (VTES), vinyltriacetoxysilane, and gamma-(meth)acryloxy propyl trimethoxy silane. In context to Structure (I), for VTMS: x = 0; R1= hydrogen; and R2= methoxy; for VTES: x = 0; R1= hydrogen; and R2= ethoxy; and for vinyltriacetoxysilane: x = 0; R1= H; and R2= acetoxy.Examples of suitable ethylene-silane copolymers are commercially available as SI-LINK™ DFDA-5451 NT and SI-LINK™ AC DFDB-5451 NT, each available from The Dow Chemical Company, Midland, Mich.The polymeric composition may comprise from 10 wt% to 99 wt% of the silane-functionalized polyolefin. For example, the polymeric composition comprises 10 wt% or greater, or 15 wt% or greater, or 20 wt% or greater, or 25 wt% or greater, or 30 wt% or greater, or 35 wt% or greater, or 40 wt% or greater, or 45 wt% or greater, or 50 wt% or greater, or 55 wt% or greater, or 60 wt% or greater, or 65 wt% or greater, or 70 wt% or greater, or 75 wt% or greater, or 80 wt% or greater, or 85 wt% or greater, or 90 wt% or greater, or 95 wt% or greater, or 98 wt% or greater, while at the same time, 99 wt% or less, or 95 wt% or less, or 93 wt% or less, or 90 wt% or less, 85 wt% or less, or 80 wt% or less, 75 wt% or less, or 70 wt% or less, 65 wt% or less, or 60 wt% or less, or 55 wt% or less, or 50 wt% or less, or 45 wt% or less, or 40 wt% or less, or 35 wt% or less, or 30 wt% or less, or 25 wt% or less, or 20 wt% or less of the silane-functionalized polyolefin based on the total weight of the polymeric composition.In view of the foregoing, the silane-functionalized polyolefin may exhibit one or more of (i) to (iv): (i) the silane-functionalized polyolefin has a density of 0.910 g / cc to 0.940 g / cc as measured according to ASTM D792; (ii) the silane-functionalized polyolefin has a melt index of 0.1 g / lOmin. to 10 g / lOmin. as measured according to ASTM D1238; (iii) the silane-functionalized polyolefin is an ethylene-silane copolymer; and (iv) the silane-functionalized polyolefin is a silane-grafted ethylene-based polymer. In a specific example, the silane-functionalized polyolefin exhibits each of (i), (ii) and (iv).Moisture Cure CatalystThe polymeric composition includes the moisture cure catalyst. As highlighted above, the moisture cure catalyst comprises both bismuth carboxylate and carboxylic acid. The term bismuth carboxylate means a salt of bismuth and one or more carboxylic acids. The bismuth carboxylate may include bismuth (iii) ethylhexanoate, bismuth (iii) neodecanoate, bismuthbenzoate, bismuth acetate, bismuth oxalate, bismuth oleate, bismuth stearate and combinations thereof.The polymeric composition may comprise from 0.10 wt% to 5.0 wt% of the moisture cure catalyst based on the total weight of the polymeric composition. For example, the polymeric composition may comprise 0.1 wt% or greater, or 0.2 wt% or greater, or 0.3 wt% or greater, or 0.4 wt% or greater, or 0.5 wt% or greater, or 0.6 wt% or greater, or 0.7 wt% or greater, or 0.8 wt% or greater, or 0.9 wt% or greater, or 1.0 wt% or greater, or 2.0 wt% or greater, or 3.0 wt% or greater, or 4.0 wt% or greater, while at the same time, 5.0 wt% or less, or 4.0 wt% or less, or 3.0 wt% or less, or 2.0 wt% or less, or 1.0 wt% or less, or 0.9 wt% or less, or 0.8 wt% or less, or 0.7 wt% or less, or 0.6 wt% or less, or 0.5 wt% or less, or 0.4 wt% or less, or 0.3 wt% or less, or 0.2 wt% or less of the moisture cure catalyst based on the total weight of the polymeric composition.The moisture cure catalyst may comprise 20 wt% to 70 wt% of bismuth carboxylate based on the total weight of the moisture cure catalyst. For example, the moisture cure catalyst may comprise 20 wt% or greater, or 25 wt% or greater, or 30 wt% or greater, or 35 wt% or greater, or 40 wt% or greater, or 45 wt% or greater, or 50 wt% or greater, or 55 wt% or greater, or 60 wt% or greater, or 65 wt% or greater, while at the same time, 70 wt% or less, or 65 wt% or less, or 60 wt% or less, or 55 wt% or less, or 50 wt% or less, or 45 wt% or less, or 40 wt% or less, or 35 wt% or less, or 30 wt% or less, or 25 wt% or less of the bismuth carboxylate based on the total weight of the moisture cure catalyst.The polymeric composition may comprise from 0.1 wt% to 3.0 wt% of the bismuth carboxylate based on the total weight of the polymeric composition. For example, the polymeric composition may comprise 0.1 wt% or greater, or 0.2 wt% or greater, or 0.3 wt% or greater, or 0.4 wt% or greater, or 0.5 wt% or greater, or 0.6 wt% or greater, or 0.7 wt% or greater, or 0.8 wt% or greater, or 0.9 wt% or greater, or 1.0 wt% or greater, or 1.5 wt% or greater, or 2.0 wt% or greater, or 2.5 wt% or greater, while at the same time, 3.0 wt% or less, or 2.5 wt% or less, or 2.0 wt% or less, or 1.5 wt% or less, or 1.0 wt% or less, or 0.9 wt% or less, or 0.8 wt% or less, or 0.7 wt% or less, or 0.6 wt% or less, or 0.5 wt% or less, or 0.4 wt% or less, or 0.3 wt% or less, or 0.2 wt% or less of the bismuth carboxylate based on the total weight of the polymeric composition.The moisture cure catalyst also comprises the carboxylic acid. The carboxylic acid is in excess of the coordination number of bismuth. As used herein, the term “in excess of the coordination number of bismuth’’ means that there is “free” carboxylic acid in the moisture cure catalyst which is unbound, uncoordinated, or otherwise disassociated with the bismuth orbismuth carboxylate in the catalyst. The carboxylic acid may comprise methanoic acid, ethanoic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, ethanedioic acid, propanedioic acid, butanedioic acid, pentanedioic acid, neodecanoate, ethyl hexanoate, decanoic acid, octanoic acid, naphthenic acid, 2-ethylhexanoic acid, stearic acid, oleic acid, other carboxylic acids and combinations thereof. According to various examples, the carboxylic acid comprises from 8 to 14 carbons.The moisture cure catalyst comprises 30 wt% to 80 wt% of carboxylic acid based on the total weight of the moisture cure catalyst. For example, the moisture cure catalyst may comprise 30 wt% or greater, or 35 wt% or greater, or 40 wt% or greater, or 45 wt% or greater, or 50 wt% or greater, or 55 wt% or greater, or 60 wt% or greater, or 65 wt% or greater, or 70 wt% or greater, or 75 wt% or greater, while at the same time, 80 wt% or less, or 75 wt% or less, or 70 wt% or less, or 65 wt% or less, or 60 wt% or less, or 55 wt% or less, or 50 wt% or less, or 45 wt% or less, or 40 wt% or less, or 35 wt% or less of the carboxylic acid based on the total weight of the moisture cure catalyst.The polymeric composition may comprise from 0.1 wt% to 3.0 wt% of the carboxylic acid based on the total weight of the polymeric composition. For example, the polymeric composition may comprise 0.1 wt% or greater, or 0.2 wt% or greater, or 0.3 wt% or greater, or 0.4 wt% or greater, or 0.5 wt% or greater, or 0.6 wt% or greater, or 0.7 wt% or greater, or 0.8 wt% or greater, or 0.9 wt% or greater, or 1.0 wt% or greater, or 1.5 wt% or greater, or 2.0 wt% or greater, or 2.5 wt% or greater, while at the same time, 3.0 wt% or less, or 2.5 wt% or less, or 2.0 wt% or less, or 1.5 wt% or less, or 1.0 wt% or less, or 0.9 wt% or less, or 0.8 wt% or less, or 0.7 wt% or less, or 0.6 wt% or less, or 0.5 wt% or less, or 0.4 wt% or less, or 0.3 wt% or less, or 0.2 wt% or less of the carboxylic acid based on the total weight of the polymeric composition.AdditivesThe polymeric composition may comprise additional additives in the form of antioxidants, cross-linking co-agents, cure boosters and scorch retardants, processing aids, coupling agents, ultraviolet stabilizers (including UV absorbers), antistatic agents, additional nucleating agents, slip agents (i.e., silicone gums), lubricants, viscosity control agents, tackifiers, anti-blocking agents, surfactants, extender oils, acid scavengers, anti-drip agents (e.g., ethylene vinyl acetate) and metal deactivators. The polymeric composition may comprise from 0.01 wt% to 20 wt% of one or more of the additional additives.The UV light stabilizers may comprise hindered amine light stabilizers (“HALS”) and UV light absorber (“UVA”) additives. Representative UVA additives include benzotriazole types such as TINUVIN 326™ light stabilizer and TINUVIN 328™ light stabilizer commercially available from BASF, Inc. Blends of HAL’s and UVA additives are also effective.The antioxidants may comprise hindered phenols such as tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydro-cinnamate)]methane; bis[(beta-(3,5-ditert-butyl-4-hydroxybenzyl) methylcarboxy ethyl)] -sulphide, 4,4'-thiobis(2-methyl-6-tert-butylphenol), 4,4'-thiobis(2-tert-butyl-5-methylphenol), 2,2'-thiobis(4-methyl-6-tert-butylphenol), and thiodiethylene bis(3,5-di-tert-butyl-4-hydroxy)-hydrocinnamate; phosphites and phosphonites such as tris(2,4-di-tert-butylphenyl)phosphite and di-tert-butylphenyl-phosphonite; thio compounds such as dilaurylthiodipropionate, dimyristylthiodipropionate, and distearylthiodipropionate; various siloxanes; polymerized 2,2,4-trimethyl-l,2-dihydroquinoline, n,n'-bis(l,4-dimethylpentyl-p-phenylenediamine), alkylated diphenylamines, 4,4’-bis(alpha, alpha-dimethylbenzyl)diphenylamine, diphenyl-p-phenylenediamine, mixed di-aryl-p-phenylenediamines, and other hindered amine anti-degradants or stabilizers.The processing aids may comprise metal salts of carboxylic acids such as zinc stearate or calcium stearate; fatty acids such as stearic acid, oleic acid, or erucic acid; fatty amides such as stearamide, oleamide, erucamide, or N,N'-ethylene bis-stearamide; polyethylene wax; oxidized polyethylene wax; polymers of ethylene oxide; copolymers of ethylene oxide and propylene oxide; vegetable waxes; petroleum waxes; non-ionic surfactants; silicone fluids, polysiloxanes, fluoropolymers, and / or fluoroelastomers.CompoundingThe components of the polymeric composition can be added to a batch or continuous mixer for melt blending. The components can be added in any order or first preparing one or more masterbatches for blending with the other components. The melt blending may be conducted at a temperature above the highest melting polymer but lower than the maximum compounding temperature of 285°C. The melt-blended composition can then either be delivered to an extruder or an injection-molding machine or passed through a die for shaping into the desired article, or converted to pellets, tape, strip or film or some other form for storage or to prepare the material for feeding to a next shaping or processing step. Optionally, if shaped into pellets or some similar configuration, then the pellets, etc. can be coated with an anti-block agent to facilitate handling while in storage.Examples of compounding equipment that may be used include internal batch mixers, continuous single or twin-screw mixers, or kneading continuous extruders. The type of mixer utilized, and the operating conditions of the mixer, will affect properties of the composition such as viscosity, volume resistivity, and extruded surface smoothness.CableThe polymeric composition may be utilized in a cable. In some examples, the cable may be a coated conductor. In other examples, the cable may be a fiber optic cable. In coated conductor examples, the coated conductor includes a conductor and a coating on the conductor, the coating including the polymeric composition. The polymeric composition is at least partially positioned around the conductor to produce the coated conductor. The conductor may comprise a conductive metal or an optically transparent structure.In optical fiber cable examples, the cable comprises a conductor and the polymeric composition is positioned around the conductor. The polymeric composition may be in the form of a buffer tube, one or more jacketing layers on the cable, and / or as other components in the cable. The conductor may include optical fibers or other transmissive components.ExamplesMaterialsThe following materials were used in the formation of the inventive examples (“IE”) and the comparative examples (“CE”).Si-PO is an ethylene and vinyltrimethoxysilane copolymer having 1.5 wt% of vinyltrimethoxysilane based on the total weight of the polymer, density of 0.922 g / cc and a melt index of 1.5 g / 10 min (190°C / 2.16 kg). Si-PO is commercially available as SI-LINK™ DFDA-5451 from The Dow Chemical Company, Midland Michigan.LLDPE is a linear low-density polyethylene with a density of 0.920 g / cc and a melt index of 0.65 g / 10 min (190°C / 2.16 kg). LLDPE is commercially available as DFH 2065 from The Dow Chemical Company, Midland, Michigan.MCI is dibutyl tin dilaurate (DBTDL) and is commercially available from Sigma-Aldrich, St. Louis Missouri.MC2 is bismuth neodecanoate and is commercially available from Sigma-Aldrich, St. Louis Missouri.MC3 is bismuth neodecanoate and is commercially available as REAXIS™ C3208 from Reaxis, McDonald, Pennsylvania.MC4 is bismuth neodecanoate and is commercially available as BiCAT™ 8118 from The Shepard Chemical Company, Cincinnati, Ohio.MC5 is bismuth neodecanoate and is commercially available as Borchi Kat™ 315 from Borchers Americas Inc., Westlake Ohio.Table 1 provides the metal, metal carboxylate and free acid content of MC1-MC5.Table 1Sample PreparationThe samples were prepared by first forming a masterbatch including the moisture catalyst in a linear low-density polyethylene and then compounding it with a silane functionalized polyolefin. Master batch (MB) formation was performed on a Rheometer Services Inc. rs7500 drive unit with a Techmix 6 bowl with Roller-type rotors. A nitrogen purge was used throughout when possible. The LLDPE was fluxed at 130 °C and 40 revolutions per minute (“rpm”). Once melted, a nitrogen purged line was placed in the headspace and the polymer allowed to flux for 2 additional minutes. The moisture cure catalyst being used was added dropwise from a tared syringe, while maintaining nitrogen flow. Mixing was continued for 2 minutes after addition was complete. The slab was quickly removed from the mixer and allow to cool in a canister under nitrogen flow before storing in a moisture proof bag with desiccant.After formation of the masterbatch, the polymeric composition was made. 13.0 g of Si-PO was compounded with 0.68 g (5 wt%) of catalyst masterbatch (“MB”) in a 15 cubic centimeter Xplore microcompounder with nitrogen purge. The microcompounder barrel was first heated to 135 °C and speed set to 40 rpm. Under recirculation, the Si-PO was added as pellets via a plunger and allowed to flux for 2 minutes. The MB was then added via plunger and the polymeric composition allowed to compound for another 4 minutes. The polymericcomposition was then extruded. A slab was pressed in a heated carver press in a 75 mm x 75 mm chase at 150 °C. Thickness of the compression molded plaques was 1.3 mm. Bars for hot creep testing were punched using a 11 mm x 60 mm custom die on a clicker press prior to curing and discs for rheology were manually punched using an 8 mm steel die. Some discs for rheology testing were set aside and not cured as a control. Samples were placed in a temperature-controlled water bath with lid set at 90 °C. Finally, samples were removed at 4 hours for both hot creep and rheology testing.Test MethodsOscillatory Shear Rheology Testing: Oscillatory shear rheology was measured on a TA DHR-3 rheometer with ETC environmental control oven and an 8 mm parallel plate geometry. Samples were tested after curing 4 hours in a 90°C water bath. Testing was performed at 130 °C under a nitrogen atmosphere. Discs were loaded and several Newtons (N) of normal force applied to achieve good contact before backing off to 0.5-1 N. A strain sweep was first performed at 1 rad / s to determine LVR strain range. Ultimately, all frequency sweeps were performed at 0.1% strain (within LVE). Frequency sweeps were collected between 100-0.025 rad / s. The value of the storage modulus (G’) at 0.025 rad / s was extracted for reporting and taken to be proportional to the crosslink density. The frequency value was chosen to emphasize the effect of covalent crosslinks and give a better dynamic range than at higher frequencies where entanglements and other effects have a large influence on G’.Hot Creep Testing: All samples were run in triplicate. Sample bars were removed from the water bath, dried, and allowed to cool. The samples were then marked with benchmarks 25 + / - 2.5 mm apart (perpendicular to pulling) with a pen. Specimen was completely at rest when marked. The thickness and width were measured to calculate cross-sectional area in mm2. A weight proportional to the cross-sectional area of sample was applied according to equation 1:Weight (g) = width (mm) * thickness (mm) * 20.4 g / mm2Eq. (1)The weight includes all components clamped on the bottom side of specimen and be within + / -2g from calculated. The clamp was placed approximately 10 mm from the benchmark. The sample and its associated testing apparatus was placed in a recirculating air oven set at 150 °C for 15 minutes at applied stress of 0.2 MPa. At the end of the test, the benchmarks were measured in place without cooling or relaxing the specimen. The hot creep elongation value was then calculated according to equation 2Hot creep elongation [%] = 100*(Dfinai-Dinitiai) / Dinitiai Eq. (2)ResultsTable 2 provides the compositional, thermal and rheological data of the CE1-CE3 and IE1-IE5.Table 2It can be seen in table 2 that using a moisture catalyst comprising bismuth carboxylate and carboxylic acid in excess of the coordination number of bismuth is able to effectively cure silane functionalized polyolefins such that the resulting polymeric compositions achieve the targeted thermal and rheological properties. CE1 and CE2 demonstrate that DBTDL is an effective catalyst that can achieve the targeted properties, but it is facing enhanced regulatory scrutiny. CE3 demonstrates that although bismuth carboxylate can catalyze the silane crosslinking reaction, without free acid in excess of bismuth’s coordination number it is unable to meet the targeted thermal and rheological properties. IE1 -IE5 demonstrate that moisture cure catalysts with 30 wt% to 80 wt% of carboxylic acid such that the carboxylic acid is in excess of the coordination number of bismuth are effective catalysts. Specifically, the increasing amount of free uncoordinated acid in the moisture cure catalyst provides increasing G' and decreasing hot creep values thereby demonstrating an improved cure with increased free acid content when the metal complex (e.g., bismuth carboxylate) is unchanged (see IE1, IE2 and IE4).

Claims

CLAIMSWhat is claimed is1. A polymeric composition, comprising :a silane-functionalized polyolefin; anda moisture cure catalyst, comprising:20 wt% to 70 wt% of bismuth carboxylate based on the total weight of the catalyst; and30 wt% to 80 wt% of carboxylic acid based on the total weight of the catalyst, wherein the carboxylic acid is in excess of the coordination number of bismuth.

2. The polymeric composition of claim 1, wherein the silane-functionalized polyolefin exhibits one or more of (i) to (iv):(i) the silane-functionalized polyolefin has a density of 0.910 g / cc to 0.940 g / cc as measured according to ASTM D792;(ii) the silane-functionalized polyolefin has a melt index of 0.1 g / lOmin. to 10 g / lOmin. as measured according to ASTM D1238;(iii) the silane-functionalized polyolefin is an a-olefin and silane copolymer; and (iv) the silane-functionalized polyolefin is a silane-grafted polyolefin.

3. The polymeric composition of claim 2, wherein the silane-functionalized polyolefin exhibits each of (i), (ii) and (iv).

4. The polymeric composition of any one of claims 1-3, wherein the polymeric composition comprises 0.10 wt% to 5.0 wt% of the moisture cure catalyst based on the total weight of the polymeric composition.

5. The polymeric composition of one of claims 1 -4, wherein the carboxylic acid comprises from 8 to 14 carbons.

6. The polymeric composition of any one of claims 1-5, wherein the carboxylic acid comprises one or more of neodecanoate, ethyl hexanoate, and combinations thereof.

7. The polymeric composition of any one of claims 1-6, wherein the carboxylic acid is neodecanoate.

8. The polymeric composition of any one of claims 1 -6, wherein the moisture cure catalyst comprises from 40 wt% to 60 wt% of carboxylic acid based on the total weight of the moisture cure catalyst.

9. The polymeric composition of any one of claims 1 -6, wherein the moisture cure catalyst comprises from 40 wt% to 50 wt% of carboxylic acid based on the total weight of the moisture cure catalyst.

10. A coated conductor, comprising:a conductor; andthe polymeric composition of any one of claims 1-9 positioned around the conductor.

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