CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. patent application serial 61/140,247, filed on December 23, 2008, the entire content of which is incorporated by reference herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None

FIELD OF THE INVENTION

[0001] This invention relates to an ambient temperature (e.g., about 1O ⁰ C to about 3O ⁰ C) and ambient humidity (e.g., about 30% to about 70% relative humidity (RH)) curing polymer compositions and to novel or crosslinking processes curing catalysts used therein. More specifically, the invention relates to crosslinkable polymer compositions containing a silane- functional polymer and at least one silanol condensation catalyst.

BACKGROUND OF THE INVENTION

[0002] It is known to crosslink different polymers through the use of crosslinked or coupling agents. Crosslinking improves properties of the polymer such as its mechanical strength and heat resistance. Polymers normally considered to be thermoplastics, and not crosslinkable, can also be crosslinked by introducing crosslinkable groups into the polymer. An example thereof is the crosslinking of polyolefins, such as polyethylene. A silane compound can be introduced as a crosslinkable group, e.g. by grafting the silane compound onto the prepared polyolefin, or by copolymerization of the polyolefinic and the silane compound.

[0003] Silane-crosslinkable polymers, and compositions comprising those polymers, are well known in the art, e.g., USP 6,005,055, WO 02/12354 and WO 02/12355. The polymer is typically a polyolefin, e.g., polyethylene, into which one or more unsaturated silane compounds, e.g., vinyl trimethoxysilane, vinyl triethoxysilane, vinyl dimethoxyethoxysilane, etc., have been incorporated. The polymer is crosslinked upon exposure to moisture typically in the presence of a catalyst. Silane crosslinked polymers have a myriad of uses, particularly in the preparation of insulation coatings in the wire and cable industry.

[0004] The crosslinking of polymers with hydrolysable silane groups is carried out by so- called moisture curing. In a first step, the silane groups are hydrolyzed under the influence of water, resulting in the splitting-off of alcohol and the formation of silanol groups. In a second step, the silanol groups are crosslinked by a condensation reaction splitting off water. In both steps, a so-called silanol condensation catalyst is used as catalyst.

[0005] Prior-art silanol condensation catalysts include carboxylates of metals, such as tin, zinc, iron, lead and cobalt; organic bases; inorganic acids; and organic acids. Dibutyl tin diacetate, dioctyl tin dilaurate, stannous acetate, stannous caprylate, lead naphthenate, zinc caprylate, cobalt naphthenate, ethyl amines, dibutyl amine, hexylamines, pyridine, inorganic acids, such as sulphuric acid and hydrochloric acid, as well as organic acids, such as toluene sulphonic acid, acetic acid, stearic acid and maleic acid exemplify prior art silanol condensation catalysts.

[0006] Although the above silanol condensation systems, and in particular ones based on tin carboxylates e.g., di-n-butyltin dilaurate (DBTDL) and reactor based silane/α-olefin copolymers, are frequently used in the crosslinking of polymer compositions containing silanol groups, they are disadvantageous in some respects. Thus, efforts are being made to find silanol condensation systems reducing or obviating these disadvantages.

[0007] For instance, prior-art silanol condensation catalysts function satisfactorily only at elevated temperatures in the order of 80-100 ⁰ C and give a poor performance at normal ambient temperature and relative humidity, e.g., room temperature (lOoC to 30oC) and 30% RH to 70% RH. In many contexts, such as the production of cable insulation, low voltage (LV) wire insulation, or water pipe circulation, it is desirable that the silane-containing polymer composition can be crosslinked at room temperature without the use of water baths or steam cabinets. The degree of crosslinking of the polymer composition is measured as the gel content after crosslinking at a certain temperature for a certain period of time. It is desirable that crosslinking at room temperature for four days should result in a gel content of at least 65% and a catalyst loading of 1 mmol/kg composition. Alternatively, crosslinking can be measured by hot creep. Hot Creep here and in the example is maximum elongation under load found in the hot set test described in IEC 60811-2-1 International Standard when performed at 200 ⁰ C. See also ICEA T-28-562 "Test Method for Measurement of Hot Creep of Polymeric Insulations. This is not achieved by existing silanol condensation catalysts, and it would therefore be a considerable step forward to provide a silanol condensation catalyst meeting this requirement.

SUMMARY OF THE INVENTION

[0008] According to this invention, silane crosslinkable polymer compositions comprise (i) at least one silane-functional polymer, e.g., silane-grafted copolymer, and mixtures thereof, and (ii) a catalytic amount of at least one substituted, preferably poly-substituted, aromatic sulfonic acid (PASA). Catalyst blends are also contemplated.

DETAILED DESCRIPTION OF THE INVENTION

[0009] All references to the Periodic Table of the Elements refer to the Periodic Table of the Elements published and copyrighted by CRC Press, Inc., 2003. Also, any references to a Group or Groups shall be to the Group or Groups reflected in this Periodic Table of the Elements using the IUPAC system for numbering groups. Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percents are based on weight and all test methods are current as of the filing date of this disclosure. For purposes of United States patent practice, the contents of any referenced patent, patent application or publication are incorporated by reference in their entirety (or its equivalent US version is so incorporated by reference) especially with respect to the disclosure of synthetic techniques, product and processing designs, polymers, catalysts, definitions (to the exjent not inconsistent with any definitions specifically provided in this disclosure), and general knowledge in the art.

[0010] The numerical ranges in this disclosure are approximate, and thus may include values outside of the range unless otherwise indicated. Numerical ranges include all values from and including the lower and the upper values, in increments of one unit, provided that there is a separation of at least two units between any lower value and any higher value. As an example, if a compositional, physical or other property, such as, for example, molecular weight, viscosity, melt index, etc., is from 100 to 1,000, it is intended that all individual values, such as 100, 101, 102, etc., and sub ranges, such as 100 to 144, 155 to 170, 197 to 200, etc., are expressly enumerated. For ranges containing values which are less than one or containing fractional numbers greater than one (e.g., 1.1, 1.5, etc.), one unit is considered to be 0.0001, 0.001, 0.01 or 0.1, as appropriate. For ranges containing single digit numbers less than ten (e.g., 1 to 5), one unit is typically considered to be 0.1. These are only examples of what is specifically intended, and all possible combinations of numerical values between the lowest value and the highest value enumerated, are to be considered to be expressly stated in this disclosure. Numerical ranges are provided within this disclosure for, among other things, the density, melt index, and various temperatures and other process ranges.

[0011] The terms "comprising", "including", "having" and their derivatives are not intended to exclude the presence of any additional component, step or procedure, whether or not the same is specifically disclosed. In order to avoid any doubt, all compositions claimed through use of the term "comprising" may include any additional additive, adjuvant, or compound whether polymeric or otherwise, unless stated to the contrary. In contrast, the term, "consisting essentially of excludes from the scope of any succeeding recitation any other component, step or procedure, excepting those that are not essential to operability. The term "consisting of excludes any component, step or procedure not specifically delineated or listed. The term "or", unless stated otherwise, refers to the listed members individually as well as in any combination. [0012] A catalyst of this invention comprises a component of the formula (I):

ArSO ₃ H (I) or a hydrolyzable precursor thereof, Ar being a substituted aryl group, and the total compound containing 10-28 carbon atoms. Preferably, the aryl group is an alkyl-substituted benzene ring with the alkyl substituent containing 8-20 carbon atoms.

[0013] The catalysts of the compositions of this invention are preferably poly-substituted aromatic sulfonic acid (PASA) catalysts. A PASA catalyst of this invention may be introduced e.g., as a component of a catalyst masterbatch or deployed during polymer extension. Various other approaches to mixing, admixing, or commingling the selected reactants will be readily apparent in view of this disclosure. The preferred PASA catalysts of this invention are of formula (II):

HSO ₃ Ar-R ₁ (R _x ) ₁₁₁ (II)

Where in a first instance: m is 1 to 3; R, is (CH ₂ ) _n CH ₃ ; n is 0 to 3; Each R _x is the same or different than Ri ; and Ar is an aromatic moiety; and

Where in a second instance: m is 0 to 3; R ₁ is (CH ₂ ) _n CH ₃ ; n is greater than 20;

Each R _x is the same or different than Ri ; and Ar is an aromatic moiety.

[0014] The catalysts of the second instance demonstrate lower water solubility than the catalysts of the first instance (the longer the length of the Ri alkyl chain and the more alkyl chains on the aromatic moiety, the more compatible the catalyst is with the organic media of the polymer). The catalysts of the first instance, however, are readily prepared as sulfonated derivatives of alkylated toluene, ethyl benzene and xylene materials.

[0015] The aromatic moiety can be heterocyclic, e.g., a pyridine or quinoline, but preferably is benzene or naphthalene. The catalysts of the second instance include α-olefin sulfonates, alkane sulfonates, is ethionates (ethers or esters of 2-hydroxyethylsulfonic acid also known as isethionic acid), and propane sulfone derivatives, e.g., oligomers or copolymers of acrylamide propane sulfonic acid. While the maximum value of n is limited only by practical considerations such as economics, catalyst mobility and the like, preferably the maximum value of n is 80, more preferably 50. The PASA typically comprises from 0.01 to 1, preferably from 0.03 to 0.5 and more preferably from 0.05 to t 0.2, weight percent of the composition based upon the total weight of the composition.

[0016] Further preferred substituted aromatic sulfonic acid catalysts are selected from the group consisting of:

(i) An alkylated naphthalene monosulfonic acid substituted with 1-4 alkyl groups wherein each alkyl group is a linear or branched alkyl with 5-20 carbons with each alkyl group being the same or different and wherein the total number of carbons in the alkyl groups is in the range of 20 to 80 carbons; (ii) An arylalkyl sulfonic acid wherein the aryl is phenyl or naphthyl and is substituted with 1-4 alkyl groups wherein each alkyl group is a linear or branched alkyl with 5-20 carbons with each alkyl group being the same or different and wherein the total number of carbons in the alkyl groups is in the range of 12-80;

(iii) a derivative of (i) or (ii) selected from the group consisting of an anhydride, an ester, an acetylate, an epoxy blocked ester and an amine salt thereof which is hydrolyzable to the corresponding alkyl naphthalene monosulfonic acid or the arylalkyl sulfonic acid;

(iv) a metal salt of (i) or (ii) wherein the metal ion is selected from the group consisting of copper, aluminum, tin and zinc.

[0017] The invention is further directed to a process for crosslinking silane functional polyolefins by adding an alkylated naphthalene monosulfonic acid or an arylalkyl sulfonic acid or a hydrolyzable derivative thereof or a metal salt thereof as a crosslinking catalyst. [0018] The number of carbons in each substituent alkyl group of the alkylated naphthalene and the arylalkyl group will depend on their size and degree of branching. For alkylated naphthalene monosulfonic acids and the derivatives thereof, the total number of carbons in the alkyl groups is in the range of 20-80. The number of carbons in each alkyl group is in the range of 5-20, preferably the alkyl group on the naphthalene ring is a linear or branched alkyl with 10- 18 carbons, and most preferably a linear alkyl of 10 to 18 carbons. Preferably, the number of alkyl groups on the naphthalene rings is 2 or 3. Most preferably, the total number of carbons in the alkyl groups on the naphthalene rings is in the range of 24 to 50. For arylalkyl sulfonic acids, the aryl group may be phenyl or naphthyl, preferably phenyl, substituted with at least two alkyl groups with the total number of carbons in the alkyl group(s) being 12-80, preferably 24-50. Each of the alkyl groups may be same or different, and preferably the alkyl group is linear with 5-20 carbons, preferably 9-14 carbons.

[0019] The crosslinking catalyst may be a mixture of alkylated naphthalene monosulfonic acids or a mixture of the arylalkyl sulfonic acids.

[0020] The derivative of the alkylated naphthalene monosulfonic acid or arylalkyl sulfonic acid is selected from the group consisting of the anhydrides, esters, acetylates, epoxy-blocked esters and amine salts thereof which are hydrolyzable to the corresponding alkylated naphthalene monosulfonic acid or the arylalkyl sulfonic acid. Examples of such derivatives include sulfonic acid anhydrides, alkyl sulfonic acid esters, epoxy blocked sulfonic acids, acetylated sulfonic acids, and amine salts of the alkylated naphthalene monosulfonic acids or arylalkyl sulfonic acids. The sulfonic acid group of the epoxy-blocked sulfonic acid is reacted with an epoxide to provide a beta-hydroxy sulfonic acid ester. Suitable epoxy compounds for preparing an epoxy- blocked sulfonic acid include diglycidyl ethers of bisphenol A or bisphenol F; diglycidyl ethers of a glycol, such as ethylene glycol, propylene glycol or butanediol; monoglycidyl ethers of Ci to C ₁₈ alpha-olefin epoxides and 1,2-epoxycyclohexane.

[0021] The derivatives of the sulfonic acid crosslinking catalysts of the present invention may be prepared from the sulfonic acid in accordance with procedures well known in the art. The process for making an ester or acetylate typically involves condensation of the sulfonic acid group with a hydroxy functioning group such as an alcohol, or an acetyl alcohol. The anhydride of a sulfonic acid is prepared by heating a sulfonic acid compound to remove H ₂ O causing two sulfonic acid groups to condense to form an anhydride. The epoxy blocked esters are prepared by reacting the sulfonic acid with an epoxy compound. The metal salt of the alkylated naphthylene monosulfonic acid or the arylalkyl sulfonic acid can be prepared from the corresponding sulfonic acid using well known procedures. The process typically involves reaction of the corresponding sulfonic acid with a metal oxide or metal hydroxide in a suitable solvent such as methanol. The amine salt is prepared by reacting ammonia or an alcohol amine with the sulfonic acid group.

[0022] For the metal salts of alkylated naphthalene monosulfonic acid, the metal or arylalkyl acid salt is selected from the group consisting of aluminum, tin, copper, and zinc. Particularly preferred are zinc, tin, and aluminum, In one particularly preferred embodiment of the invention the catalyst is the zinc salt of a predominantly dinonylnaphthalene monosulfonic acid. In another preferred embodiment, the crosslinking catalyst is the zinc salt of a mixture of didodecylnaphthalene monosulfonic acid, tridodecylnaphthalene monosulfonic acid and tetradodecylnaphthalene monosulfonic acid, or a zinc salt of (tetradecylphenyl) tetradecyl sulfonic acid.

[0023] Although the presence of metal ions may not provide a lower electro-conductivity, the metal salts, of the present invention are highly compatible with polyethylene and form a single phase therewith. [0024] The silane crosslinking catalysts useful in the invention are alkylated naphthalene monosulfonic acids as well as their corresponding derivatives and metal salts and arylalkyl sulfonic acids as well as their corresponding derivatives and metal salts.

[0025] In a preferred embodiment of the invention, the catalyst is a mixture of didodecylnaphthalene monosulfonic acid and tridodecylnaphthalene monosulfonic acid and tetradodecyl-naphthalene sulfonic acid wherein the ratio of di, tri, and tetra-alkylated naphthalene sulfonic acids is in a ratio of 2: 1 : 1.

[0026] The silanol condensation catalyst is distinguished by being a benzene or naphthalene sulphonic acid that is sufficiently lipophilic to be compatible with the polymer composition to be crosslinked, e.g. polyethylene containing hydrolysable silane groups. To achieve such lipophilicity, the hydrocarbon group of the alkylaryl sulphonic acid must have a certain size and must, e.g. in the case where the acid is a benzene sulphonic acid, have an alkyl substituent containing at least 8 carbon atoms, as indicated in the foregoing. If the alkyl group does not have such a size that the lipophilicity requirement is met, the catalyst is not compatible with the polymer composition but will be released therefrom upon crosslinking in aqueous solution, thus impairing crosslinking efficiency.

[0027] In the silanol condensation catalyst of formula I, Ar preferably is an alkyl-substituted aryl group containing a benzene or naphthalene ring, substituted by an alkyl group, the size of which is 8-20 carbon atoms in the benzene case and 4-18 carbon atoms in the naphthalene case. Due to commercial availability, it is most preferred that the aryl group is a benzene ring, substituted with an alkyl substituent containing 12 carbon atoms.

[0028] The currently most preferred compounds of formula I are dodecyl benzene sulphonic acid and tetrapropyl benzene sulphonic acid.

[0029] The silanol condensation catalyst may also be a precursor of a compound of formula I, i.e. a compound that is converted by hydrolysis to a compound of formula I. Such a precursor is the acid anhydride of the sulphonic acid compound of formula I. Another instance is a sulphonic acid of formula I that has been provided with a hydrolysable protective group, e.g. an acetyl group, which can be removed by hydrolysis to give the sulphonic acid of formula I. [0030] According to the invention, the amount of silanol condensation catalyst present in the crosslinkable polymer composition generally is in the order of 0.0001-3% by weight, preferably 0.001-2% by weight and most preferably 0.005-1% by weight, as based on the amount of silanol- group containing polymers in the composition. It will be appreciated that the effective amount of catalyst depends on the molecular weight of the catalyst. Thus, a smaller amount is required of a catalyst having a low molecular weight, than of a catalyst having a high molecular weight. [0031] The catalyst is preferably added to the crosslinkable polymer in the form of a master batch, i.e., mixed with a polymer, such as a homo- or copolymer of ethylene, e.g. LDPE, EEA or EBA containing 3-30% by weight of alkyl acrylate comonomer. The master batch contains a minor amount of the catalyst, generally 0.02-5% by weight, preferably 0.05-2% by weight. [0032] The catalyst may be used in the crosslinkable polymer composition alone or combined with other silanol condensation catalysts, such as other catalysts of the formula I or conventional silanol condensation catalysts, e.g. carboxylic acid salts of the metals tin, zinc, iron, lead and cobalt; hydrolysis products of alkyl tin trichlorides; organic bases; inorganic acids; and organic acids.

[0033] The silane crosslinkable polymer compositions of this invention comprise (i) at least one silane-functionalized or silane functional polymer, e.g., a silane derivatized α-olefinic polymer, and (ii) a catalytic amount of at least one substituted aromatic sulfonic acid, preferably PASA. Silane-functionalized olefinic polymers include but are not limited to silane- functionalized polyethylene, polypropylene, etc., and various blends of these polymers. Preferred silane-functionalized olefinic polymers include (i) the copolymers of ethylene and a hydrolysable silane, (ii) a copolymer of ethylene, one or more C ₃ or higher α-olefins or unsaturated esters, and a hydrolysable silane, (iii) a homopolymer of ethylene having a hydrolysable silane grafted to its backbone, and (iv) a copolymer of ethylene and one or more C ₃ or higher α-olefins or unsaturated esters, the copolymer having a hydrolysable silane grafted to its backbone. Each of these groups is described in greater detail below.

[0034] Polyethylene polymer as here used is a homopolymer of ethylene or a copolymer of ethylene and a minor amount of one or more α-olefins of 3 to 20 carbon atoms, preferably of 4 to 12 carbon atoms, and, optionally, a diene or a mixture or blend of such homopolymers and copolymers. The mixture can be either an in situ blend or a post-reactor (or mechanical) blend. Exemplary α-olefins include propylene, 1-butene, 1-hexene, 4-methyl-l-pentene and 1-octene. Examples of a polyethylene comprising ethylene and an unsaturated ester are copolymers of ethylene and vinyl acetate or an acrylic or methacrylic ester. [0035] The polyethylene can be homogeneous or heterogeneous. Homogeneous polyethylenes typically have a polydispersity (Mw/Mn) of about 1.5 to about 3.5, an essentially uniform comonomer distribution, and a single, relatively low melting point as measured by differential scanning calorimetry (DSC). The heterogeneous polyethylenes typically have a polydispersity greater than 3.5 and lack a uniform comonomer distribution. Mw is weight average molecular weight, and Mn is number average molecular weight.

[0036] The polyethylenes have a density in the range of 0.850 to 0.970 g/cc, preferably in the range of 0.870 to 0.950 g/cc. They also have a melt index (I ₂ ) in the range of 0.01 to 2000, preferably 0.05 to 1000 and more preferably 0.10 to 50, g/10 min. If the polyethylene is a homopolymer, then its I ₂ is 0.5 to 5.0 g/10mm, preferably 0.75 to 3 g/10 min. The I ₂ is determined under ASTM D-1238, Condition E and measured at 190 C and 2.16 kg.

[0037] The polyethylenes used in the practice of this invention can be prepared by any process including high-pressure, solution, slurry and gas phase using conventional conditions and techniques. Catalyst systems include Ziegler-Natta, Phillips, and the various single-site catalysts, e.g., metallocene, constrained geometry, etc. The catalysts are used with and without supports.

[0038] Useful polyethylenes include low density homopolymers of ethylene made by high pressure processes (HP-LDPE), linear low density polyethylenes (LLDPE), very low density polyethylenes (VLDPE), ultra low density polyethylenes (ULDPE), medium density polyethylenes (MDPE), high density polyethylene (HDPE), and metallocene and constrained geometry copolymers.

[0039] High-pressure processes are typically free radical initiated polymerizations and conducted in a tubular reactor or a stirred autoclave. In the tubular reactor, the pressure is within the range of 25,000 to 45,000 psi and the temperature is in the range of 200 to 35O ⁰ C. In the stirred autoclave, the pressure is in the range of 10,000 to 30,000 psi and the temperature is in the range of 175 to 250 ⁰ C.

[0040] Copolymers comprised of ethylene and unsaturated esters are well known and can be prepared by conventional high-pressure techniques. The unsaturated esters can be alkyl acrylates, alkyl methacrylates, or vinyl carboxylates. The alkyl groups typically have 1 to

8 carbon atoms, preferably 1 to 4 carbon atoms. The carboxylate groups typically have 2 to

8 carbon atoms, preferably 2 to 5 carbon atoms. The portion of the copolymer attributed to the ester comonomer can be in the range of 5 to 50 percent by weight based on the weight of the copolymer, preferably in the range of about 15 to about 40 percent by weight. Examples of the acrylates and methacrylates are ethyl acrylate, methyl acrylate, methyl methacrylate, t-butyl acrylate, n-butyl acrylate, n-butyl methacrylate, and 2-ethylhexyl acrylate. [0041] Examples of the vinyl carboxylates are vinyl acetate, vinyl propionate, and vinyl butanoate. The melt index of the ethylene/unsaturated ester copolymers is typically in the range of 0.5 to 50 g/10min, preferably in the range of 2 to 25 g/10min.

[0042] The VLDPE or ULDPE is typically a copolymer of ethylene and one or more α-olefins having 3 to 12 carbon atoms, preferably 3 to 8 carbon atoms. The density of the VLDPE or ULDPE is typically in the range of 0.870 to 0.915 g/cc. The melt index of the VLDPE or ULDPE is typically in the range of 0.1 to 20 g/10min, preferably in the range of 0.3 to 5 g/10min. The portion of the VLDPE or ULDPE attributed to the comonomer(s), other than ethylene, can be in the range of 1 to 49 percent by weight based on the weight of the copolymer, preferably in the range of 15 to 40 percent by weight.

[0043] A third comonomer can be included, e.g., another α-olefin or a diene such as ethylidene norbornene, butadiene, 1 ,4-hexadiene or a dicyclopentadiene. Ethylene/propylene copolymers are generally referred to as EPRs, and ethylene/propylene/diene terpolymers are generally referred to as an EPDM. The third comonomer is typically present in an amount of 1 to 15 percent by weight based on the weight of the copolymer, preferably present in an amount of 1 to 10 percent by weight. Preferably the copolymer contains two or three comonomers inclusive of ethylene.

[0044] The LLDPE can include VLDPE, ULDPE, and MDPE, which are also linear, but, generally, have a density in the range of 0.916 to 0.925 g/cc. The LLDPE can be a copolymer of ethylene and one or more α-olefins having 3 to 12 carbon atoms, preferably 3 to 8 carbon atoms. The melt index is typically in the range of 1 to 20 g/10min, preferably in the range of 3 to 8 g/10min. HDPE, MDPE, blends of polyethylene(s) LLDPE/LDPE, high (e.g., 3-10) and low (0.5 to 0.9) melt index materials will readily be suggested to one skilled in this art. [0045] Any polypropylene may be used in these compositions. Examples include homopolymers of propylene, copolymers of propylene and other olefins, and terpolymers of propylene, ethylene, and dienes (e.g. norbornadiene and decadiene). Additionally, the polypropylenes may be dispersed or blended with other polymers such as EPR or EPDM. Suitable polypropylenes include thermoplastic elastomers (TPE), thermoplastic olefins (TPO) and thermoplastic vulcanates (TPV). Examples of polypropylenes are described in Polypropylene Handbook: Polymerization, Characterization, Properties, Processing, Applications 3-14, 113-176 (E. Moore, Jr. ed., 1996).

[0046] A silane-functional polymer of this invention is preferably a graft polymer of a silane- functional group grafted onto, e.g., polyethylene. Preferred polyethylene reactants are LLDPE or LDPE having a density in the range of 0.90 to 0.94 g/cc. The grafted silane component (if a graft polymer is used) should generally comprise about 0.5 to about 5% by weight, preferably 1.0% to 2.0% by weight of the graft polymer.

[0047] It is to be understood that the silane-functional group can be bound to or incorporated into the backbone or to-be-cross-linked-polymer (to create a silane-functional polymer) in various ways. Whether a graft polymer or silane/α-olefin copolymer is used will depend upon the end use of the cross-linked material and its physical characteristics. For example, silane- functional copolymer (as distinguished from graft polymer) will generally have silane-functional groups that are less sterically hindered than their graft-polymer analogies. Both chemical and processing equipment issues (as well as the resulting cross-linked polymer's characteristics) will be considered in deciding upon which of the various synthetic routes to use. [0048] Vinyl alkoxysilanes (e.g., vinyltrimethoxysilane and vinyltriethoxysilane) are suitable silane compounds for grafting or copolymerization to form the silane-functionalized olefinic polymer. Copolymers of ethylene and vinyl silanes may also be used. Examples of suitable silanes are vinyltrimethoxysilane and vinyltriethoxysilane. Such polymers are typically made using a high-pressure process. Ethylene vinylsilane copolymers are particularly well suited for moisture-initiated crosslinking.

[0049] The compositions of this invention may contain other components such as antioxidants, colorants, corrosion inhibitors, lubricants, anti-blocking agents, flame retardants, and processing aids. Suitable antioxidants include (a) phenolic antioxidants, (b) thio-based antioxidants, (c) phosphate-based antioxidants, and (d) hydrazine-based metal deactivators. Suitable phenolic antioxidants include methyl-substituted phenols. Other phenols, having substituents with primary or secondary carbonyls, are suitable antioxidants. One preferred phenolic antioxidant is isobutylidene bis(4,6-dimethylphenol). One preferred hydrazine-based metal deactivator is oxalyl bis(benzylidiene hydrazine). These other components or additives are used in manners and amounts known in the art. For example, the antioxidant is typically present in amount between 0.05 and 10 weight percent based on the total weight of the polymeric composition.

[0050] In one embodiment, the invention is a fabricated article such as a wire or cable construction prepared by applying the polymeric composition over a wire or cable, e.g., by extrusion. Other constructions include fiber, film, foam, ribbons, tapes, adhesives, footwear, apparel, packaging, automotive parts, refrigerator linings and the like. The composition may be formed, applied and used in any manner known in the art.

[0051] In another embodiment, the invention is a process of curing a composition comprising a silane-crosslinkable polymer using a PASA. The cure can be effected in any one of a number of known processes and under a variety of conditions.

SPECIFIC EMBODIMENTS

[0052] The formulations given in Table 1 were extruded into wires as 30 mil of insulation on a 14AWG conductor. Systems (1, 2 and 5) are compositions typical of ambient curing (AC) systems In order to have a back to back comparison of the performance of impact of base resin and catalyst a formulation using the DBTDL (Sn Masterbatch 1 in Table 1) was prepared in conjunction with the commercial system 5. Also, in order to evaluate the cure performance of the grafted copolymer with a sulfonic acid based catalyst Grafted copolymer 1 was extruded with SA masterbatch 1. This is listed as System 3 in the table below.

[0053] First, the cure rate of each system was evaluated at typical sauna conditions by immersing them into a 7O ⁰ C water bath. It was found that the System 1 system took 360 minutes to cure while each of the ambient curing Systems 2 and 5 took 30 and 90 minutes respectively. Under these conditions it is found that System 3 cures ten times faster than the copolymer based System 1 using the same level of DBTDL catalyst and is cured within 30 minutes. This makes it cure at a similar rate as System 5 the sulfonic acid based catalyst system. System 3 was found to take merely 20 minutes to cure.

[0054] Cure rates of each system were then evaluated at a cooler than room ambient temperature condition (15 ⁰ C, 70% RH) to identify performance at a conditions where A cabler typically loseS the ability to economically wait for cables to cure with existing AC systems. It was found that the two ambient curing systems (Systems 2 and 5) took 14 days and 10 days respectively to fully cure, while the non-ambiently curing System 1 did not show any significant cure within 21 days. System 4 cured faster, requiring only 3.5 days. However, System 3 i.e., a system of this invention, cured a surprisingly 3.5 times faster more and was cured within 1 day. Therefore, System 3 has demonstrated a surprising and unexpectedly improved cure rate performance at lower temperatures by using a sulfonic catalyst acid in conjunction with a grafted resin, than by using a DBTDL based catalyst with System 5 resin.

Table 1

Formulations Made to Evaluate the Performance of Reactor Copolymer 1 vs Grafted Copolymer 1

Sn Masterbatch 1 is a catalyst masterbatch containing 2.5% of DBTDL and additional antioxidants.

SA Masterbatch 1 is catalyst masterbatch containing 2.8% of a sulfonic acid based catalyst and additional antioxidants.

Reactor copolymer 1 is a commercially available reactor based high pressure copolymer from Dow Chemical (1.5 melt index LDPE), it contains -1.5% by wt. of VTMS.

Sn Masterbatch 2 is a catalyst masterbatch containing 0.25% of DBTDL and additional antioxidants and flame retardants.

Grafted copolymer 1 is a LLDPE grafted with ~ 1.5% VTMS via reactive extrusion with peroxide.