WO2009149001A1 - Procédé pour inhiber une vulcanisation dans des compositions réticulables - Google Patents

Procédé pour inhiber une vulcanisation dans des compositions réticulables Download PDF

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WO2009149001A1
WO2009149001A1 PCT/US2009/045808 US2009045808W WO2009149001A1 WO 2009149001 A1 WO2009149001 A1 WO 2009149001A1 US 2009045808 W US2009045808 W US 2009045808W WO 2009149001 A1 WO2009149001 A1 WO 2009149001A1
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polymer
radicals
composition
temperature
alkoxyamine
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PCT/US2009/045808
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WO2009149001A9 (fr
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Timothy J. Person
Robert F. Eaton
Jeffrey M. Cogen
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Union Carbide Chemicals & Plastics Technology Llc
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/16—Nitrogen-containing compounds
    • C08K5/32—Compounds containing nitrogen bound to oxygen
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/16—Nitrogen-containing compounds
    • C08K5/34—Heterocyclic compounds having nitrogen in the ring
    • C08K5/3412—Heterocyclic compounds having nitrogen in the ring having one nitrogen atom in the ring
    • C08K5/3432—Six-membered rings
    • C08K5/3435—Piperidines

Definitions

  • the present disclosure is directed to scorch retard ant crosslinkable compositions and methods for inhibiting premature crosslinking of same.
  • Premature crosslinking or "scorch'" during compounding and/or processing is a major difficulty in the use of free radical initiators such as peroxides and/or azo compounds in the crosshnkirig applications of elastomeric and/or thermoplastic materials.
  • Scorch occurs when the free radical initiator undergoes thermal decomposition. This initiates a crosslinking reaction that may proceed in an uncontrolled manner and create gel particles in the mass of the thermoplastic material. Gel particles adversely impact the homogeneity of the crosslinked polymer, hi addition, scorch results in high melt viscosities for the thermoplastic material which makes processing difficult and requires undesired increases in processing energy.
  • THMI 3 O and 4-hydroxy TEMPO are volatile and exhibit blooming and/or sweat-out during processing- TEMPO and 4-hydroxy TEMPO are incompatible with many polymers that are crosslinked (EPDM, LDPbI, LLPE, FlDPE) and also have a tendency to adversely affect the color of the thermoplastic material.
  • Desirable would be a scorch retardant with improved processing properties such as reduced volatility, reduced blooming and sweat-out, the scorch retardant being compatible with crosslinkable polymers.
  • the present disclosure is directed to scorch retardant compositions and methods for controlling polymer crosslinking.
  • the compositions and methods of the present disclosure permit in situ creation of nitroxyl radicals within a crosslinkable polymeric composition. This provides a seorch-retardant crosslinking composition that has reduced volatility and experiences reduced blooming and sweat-out during processing when compared to crosslinkable compositions containing TEMPO-bascd scorch retardants, for example.
  • a method for controlling polymer crosslinking includes heating a composition to a processing temperature.
  • the composition includes a crosslinkable polymer, a free radical initiator, and an alkoxy amine.
  • the method includes producing nitroxy] radicals from the alkoxyamine when the temperature is less than or equal to the processing temperature.
  • the method further includes forming polymer radicals from the crosslinkable polymer with the free radical initiator. Crosslinking of the polymer radicals is prevented with the nitroxy] radicals.
  • the nitroxyl radicals cap the polymer radicals which prevents the polymer radicals from bonding, or crosslinking, to each other.
  • the nitroxyl radicals are produced with cleavage of the aikoxyamine at a temperature less than the decomposition temperature for the free radical initiator.
  • the alkoxyamine is selected to have a half-life that is less than the half-life of the free radical initiator at the processing temperature.
  • the method entails cleaving the alkoxyamine into nitroxyl radicals at a faster rate than free radical initiator decomposition. This ensures that (1) in situ formation of the nitroxyl radicals occurs before polymer radicals are formed and/or (2) in situ nitroxyl radical generation occurs at a faster rate than polymer radical formation.
  • the method includes dissolving the alkoxyamine (cither partially or fully) in the crosslinkable polymer. This advantageously reduces the volatility of the nitroxyl radicals cleaved from the alkoxyamine during processing.
  • the method includes cleaving carbon-centered radicals from the alkoxyamine. The carbon-centered radicals are cleaved at a temperature less than or equal to the processing temperature, The alkoxyamine is selected so that the carbon-centered radicals have sufficient reactivity to cap with the polymer radicals and prevent crossJinking.
  • the alkoxyamine provides two types of scorch retardants: (i) the nitroxyl radicals and (ii) the carbon- centered radicals.
  • a single alkoxyamine molecule caps at least one polymer radical and may cap at least two polymer radicals,
  • another method for controlling polymer crosslinking includes heating a composition to a processing temperature.
  • the composition includes a crossli ⁇ kable polymer and a free radical initiator.
  • the composition also includes a hydroxylamine.
  • the method includes forming polymer radicals from the crosslinkable polymer with the free radical initiator and preventing erosslinking of the polymer radicals with the hydroxylamine.
  • the hydroxy iamine donates a hydrogen atom from the hydroxyl group.
  • the hydrogen atom subsequently caps a polymer radical. Donation of the hydrogen atom converts the hydroxylamine into a nitroxyl radical which also caps a polymer radical,
  • a single hydroxylamin ⁇ molecule caps at least one polymer radical and may cap at least two polymer radicals.
  • the method includes producing the hydroxylamine in situ from the alkoxyamine by way of an elimination reaction. This occurs at a temperature less than or equal to the processing temperature.
  • a method for retarding scorch in a crosslinkable polymer includes extruding a crosslinkable composition.
  • the crosslinkable composition includes a crosslinkable polymer, a free radical initiator, and an alkoxyamine.
  • the method includes decomposing the free radical initiator.
  • the initiator radicals abstract hydrogen from the backbone of the crosslinkable polymer to form polymer radicals.
  • the method further includes cleaving nitroxyl radicals from the aikoxyamine. Provision of the nitroxyl radicals in the composition prevents crosslinking of the polymer radicals during the extrusion process.
  • the nitroxyl radicals cap the polymer radicals thereby preventing the polymer radicals from crosslinking.
  • the method further includes crosslinking the polymer after extrusion has occurred.
  • the crosslinkable composition is heated to an extrusion temperature.
  • the method further includes cleaving the alkoxyamine at a temperature below or equal to the extrusion temperature.
  • alkoxyamine cleavage occurs before polymer radicals are formed.
  • the alkoxyamine cleavage occurs at a faster rate than decomposition of the free radical initiator.
  • the alkoxyamine is cleaved into nitroxyl radicals and carbon- centered radicals.
  • the carbon-centered radicals bond to the polymer radicals during the extrusion to prevent polymer erosslinking.
  • a scorch-r ⁇ iardant erosslinking composition includes a crosslinkable polymer and a free radical initiator, ' [ " he free radical initiator has a decomposition temperature.
  • the scorch-retardant erosslinking composition also includes an alkoxyamine. The alkoxyamine lias a cleaving temperature that is less than the free radical initiator decomposition temperature.
  • the alkoxyamine has the following structure (V).
  • the alkoxyamine has a half-life less than the half-life of the free radical initiator at the decomposition temperature.
  • the free radical initiator decomposes and forms polymer radicals.
  • the polymer radicals bond to the alkoxyamine cleavage products, namely, nilroxyl radicals, carbon-centered radicals, and combinations thereof. This further prevents erosslinking during the extrusion process.
  • the erosslinking composition may he heated after extrusion to crosslink polymer radicals and form a crosslinked polymer.
  • An advantage of the present disclosure is the provision of an improved scorch retard an L
  • An advantage of the present disclosure is the in situ formation of a scorch retard ant within a crossiinkable polymer composition.
  • a further advantage is the in situ formation of two scorch retardants within a erosslinkahle polymer corn position,
  • An advantage of the present disclosure is the provision of a scorch retard ant which yields a functional group that grafts to the crosslinkable polymer to provide the crosslinked polymer useful functionality.
  • An advantage of the present disclosure is the capability to process thermally initiated crosslinkablc polymers at higher processing temperatures with increased outputs and without scorch.
  • An advantage of the present disclosure is the provision of a multi-functional alkoxyamine scorch retardant.
  • any numerical range recited herein includes all values from the lower value and the upper value, in increments of one unit, provided that there is a separation of at least two units between any lower value and any higher value.
  • a compositional, physical or other property such as, for example, molecular weight, melt index, etc.
  • a compositional, physical or other property such as, for example, molecular weight, melt index, etc.
  • a compositional, physical or other property such as, for example, molecular weight, melt index, etc.
  • sub ranges such as 100 to 144, 1 55 to 1 70, 197 to 200. etc.
  • any numerical range recited herein includes any value or subrange within the staled range. Numerical ranges have been recited, as discussed herein, in reference to density, weight percent of component, molecular weights and other properties.
  • aromatic ' ' or aryl refers to a polyatomic, cyclic, ring system containing (4 ⁇ -H2) ⁇ -electrons, wherein ⁇ is an integer greater than or equal to 1.
  • composition includes a mixture of materials which comprise the composition, as well as reaction products and decomposition products formed from the materials of the composition.
  • polymer is a macromolecular compound prepared by polymerizing monomers of the same or different type.
  • Polymer includes homopolymers, copolymers, terpolymers, interpolymers, and so on.
  • interpolymcr' means a polymer prepared by the polymerization of at least two types of monomers or comononiers.
  • copolymers which usually refers to polymers prepared from two different types of monomers or comonomers, although it is often used interchangeably with "interpolymer” to refer to polymers made from three or more different types of monomers or comonomers ⁇
  • terpolymers which usually refers to polymers prepared from three different types of monomers or comonomers
  • tctrapolymers which usually refers to polymers prepared from four different types of monomers or comonomers
  • 'monomer ' " or “comonomcr” are used interchangeably, and they refer to any compound with a polym ⁇ rizable moiety which is added to a reactor in order to produce a polymer.
  • a method for controlling polymer crosslinking includes;? heating a composition to a processing temperature.
  • the composition includes a crosslinkabie polymer, a free radical initiator, and an alkoxyaminc.
  • the method further include? producing nitroxyl radicals from the aikoxyamine at a temperature less than or equal to the processing temperature.
  • At the processing temperature at least some tree radical initiation occurs, the free radical initiator forming free polymer radicals (or polymer radicals) from the crosslinkabie polymer.
  • the method further includes preventing the polymer radicals from crosslhiLing. Crosslink prevention occurs by way of the presence of the nitroxyl radicals.
  • the processing temperature may be a temperature to enable compounding, melting blending, or extruding the composition, either alone, or with other components, (n other words, the process may be a compounding process, a melting blending process, and/or an extrusion process performed at a temperature (i e., the processing temperature) whereby the crossliiiLabic polymer is sufficiently melted and/or softened such that the processing operation may be performed.
  • the processing temperature may be from about 80 0 C to about 250°C (or any value or subrange therebetween), or from about 120 0 C to about 160°C,
  • the composition includes a crosslinkabie polymer, a free radical initiator, and an alkoxyamme
  • the crosslinkabie polymer is a thermoplastic and/or elastomeric polymer which can be crosslirtked for "cured") through the action of the free radical initiator, In Rubber World, "Elastomer Crosslbiking with Diperoxyketah, " October, 1983, pp.26-32, Rubber and Plastic News,, and "Organic Peroxides for Rubber Crosdinking, " Sep 29, 1980, pp. 46-50, the crosshnking action and er ⁇ sslinkabie polymers are described. Suitable crosslinkabie polymers are described in Modern Plastics Encyclopedia 89. pages 63-67 and 74-75.
  • Noniimiting examples of suitable erosslinkable polymers include linear low density polyethylene, low density polyethylene, high density polyethylene, medium density polyethylene, ultra low density polyethylene, chlorinated polyethylene, ethylene-propylene-diene t ⁇ rpoiymcrs (EPDM), ethyf ⁇ ne-viny!
  • acetate copolymers ethylene-propylene copolymers, silicone rubber, ehlorosulphonated polyethylene, fluoroelastomers, natural rubber (NR), polyisoprcne (SR), poly butadiene (BR), acrylomt ⁇ le-butadiene copolymers (NBR) or styrene- butadiene copolymers (SBR), slyrene-acrylonitrile. aerylonitrile-butadiene-styrene, and any combination, or blend of the foregoing.
  • the urosslinkable polymer is a polyethylene.
  • the composition includes a tree radical initiator. Upon thermal decomposition, the free radical initiator produces free radicals which facilitate the crosslinking reaction. Representative of this class of compounds are the peroxides, such as die organic peroxides, and the azo initiators. Suitable free radical initiators used as crosslinking agents are the dialkyl peroxides and dipcroxyketal initiators. These compounds are described in the Encyclopedia of Chemical Technology, 3 fd edition, Vol. 17, pp 27-90 (1982).
  • nonlimiting examples of suitable free radical initiators are: dicumyl peroxide, di-t-butyl peroxide, t-butyi cumyi peroxide. 2,5-dim ⁇ thyl-2,5- di(t-butylperoxy)-hexane, 2,5 ⁇ dimethyl-2,5-di(t-amylperoxy)-hexane, 2,5-dimetby[ ⁇ 2,5-di(t- butylperoxy)hexyne-3, 2,5-dimethyl-2,5 ⁇ di(t-amylperoxy)hexyne ⁇ 3, ⁇ ,c»di[(t-butylperoxy)- isopropyij-b ⁇ n/ene, di-t-amyi peroxide, l,3.5-tri-[(t-b ⁇ tylperoxy)-isopropyi]ben/.ene, 1 ,3- dirnet
  • nonlimiting examples of suitable free radical initiators include: 1 ,l-di(t-butyl ⁇ eroxy) ⁇ 3,3,5-trim ⁇ thylcyclohcxane,
  • peroxide initiators e.g., 00-t-butyl-O-hydrogen-mono ⁇ eroxysuccinate; (iO-t- amyl-O-hydrogen-moRoperoxysuceinate and/or azo initiators e.g.. 2,2'-azobis-(2- acetoxypropan ⁇ ).
  • azo initiators e.g.. 2,2'-azobis-(2- acetoxypropan ⁇
  • free radicals can form from shear energy, heat or radiation.
  • the amount of free radical initiator present in the composition can vary with the minimum amount being sufficient to afford the desired range of erosslinking,
  • the minimum amount of free radical initiator is at least about 0.02 wi%, or at least about 0,05 wt%, or at least about 0.1, wt% based upon the weight of the crosslinkabi ⁇ polymer(s).
  • the maximum amount of free radical initiator in the composition can vary, and it is typically determined by such factors as cost, efficiency and degree of desired crosslinking. The maximum amount may be less than about 20 wi%, or less than about 15 wt%. or less than about 10, wt% based upon the weight of the crosslinkable poiymer(s).
  • the free radical initiator may be liquid or neat.
  • liquid free radical initiator may be sprayed onto crosslinkable polymer pellets or granules to coat them prior to extrusion compounding. This provides increased production efficiency and eliminates physical handling of hazardous compounds.
  • the composition includes an alk ⁇ xyamine.
  • the alkoxyamine may be an open chain amine or a cyclic amine having the following structure (A):
  • R is a group selected from an alkyl, an alkenyl, an arylalkyi, an arylalke ⁇ yl, a cycloalkyl, a cycloalkenyi, substituted derivates thereof, or combinations thereof.
  • the amine is derived from a cyclic amine.
  • Suitable cyclic amines include 2,2,6,0-tetram ⁇ thylpiperidinoxyl (TBMPO) and 4-hydroxy-2,2, ⁇ , ⁇ - tetramethylpiperidinoxyl (4-hydroxy TEMPO) and substituted/unsubstitutcd derivatives thereof.
  • j TBMPO has the chemical structural formula of ( ⁇ ): (I)
  • the alkoxyamin ⁇ has the chemical structural formula of (111):
  • R is a group selected from an alkyl. an alkenyl, an arylalkyl, an arylaikenyl, a cycloalkyl, a cycloalkenyl, substituted derivates thereof, or combinations thereof.
  • Nitroxyl radicals are produced from the alkoxyamine at a temperature less than or equal to the processing temperature. Nitroxyl production occurs by way of a cleavage reaction and/or an elimination reaction.
  • the aikoxyamine of formula (111) undergoes thermal cleavage to break the O R bond.
  • the alkoxyamine cleavage reaction is shown in the chemical equation of
  • the R group may be selected to form an O R bond having a desired bond strength.
  • the R group is a carbon-centered radical providing the alkoxyaniin ⁇ with a
  • the R group is selected so that the O — C bond breaks at or below the processing temperature and/or at or below the decomposition temperature of the free radical initiator.
  • the alkoxyamine undergoes thermal cleavage to produce or otherwise generate nitroxyl radicais (as well as carbon-centered radicals) in situ, In situ generation of nitroxy ] radicals carries several advantages.
  • the R-group of the aikoxyar ⁇ ine may be selected to provide an alkoxyaminc with reduced volatility or no volatility when added to the crosslinkable polymer. This is particularly beneficial when compared to TEMPO-based scorch retardants which experience volatility problems during processing.
  • the R-group may be selected to provide the alkoxyamine with a molecular weight which permits partial solubility or full solubility of the alkoxyamine in the crosslinkablc polymer. This advantageously reduces blooming.
  • Bloom refers to the migration of an ingredient of a crosslinkable composition to the surface of the crosslinkable polymer or the crosslinked polymer. Bloom can cause formation of a thin coating of a thermosetting polymeric mixture to the surface of an article, and typically occurs within a few hours after crosslinking. Bloom can impair the aesthetic appearance of crosslinked polymeric articles. Bloom can also interfere with the ability to bond or adhere materials to the crosslinked polymeric articles. With the presence of the alkoxyamine, the present composition exhibits less bloom compared to crosslmkabl ⁇ compositions containing TKM PO or a TEMPO derivative.
  • the alkoxyamine does not adversely affect the color of the crosslinkable polymer as do scorch retardants containing TEMPO or a TE- MPO derivative.
  • the free radical initiator decomposes into free iadicais 1 he initiator free radicals extract or abstrdct hydrogen atoms from the backbone ol the erosslmkable polymer (hydrogen abstraction). This results m the formation of free polymer radicals (or polymer radicals)
  • hydrogen abstr action points provide bonding sites ior the polymer radicals to crosslink.
  • cap or ' ' "capping” as used herein, is the act of controlling (or terminating) the growth of free radical polymerization by bonding or interacting with the abstraction site
  • the nitroxyi radicals react faster with the polymer radicals than the polymer radicals react with each other
  • the nitroxyi radicals readily ''cap" the polymer radicals before crosslinkinp can occur.
  • the K-groi ⁇ is selected so the alkoKyamine cleavage temperature is less than the decomposition temperature of the free radical initiator This ensures that nitroxyi radicals (and carbon-centered radicals) are present in the composition before decomposition of the free radical. I hus, by selecting a suitable R-grou ⁇ , the cleavage temperature for the alkoxyamme can be tailored as desired.
  • the alkoxyamine and-'or the decomposition temperature is selected such that the alkoxyamine cleaves at a faster rate than the free radical initiator decomposes
  • the aikoxyarnine can be tailored (by way of R-group selection, foi example) so that the kinetics of alkoxyamine cleavage occur at a faster rate than decomposition of the free radical initiator
  • the aikoxy amine may be selected such that its half-life is less than the half-lite ol the free radical initiator at the processing temperature and/or the decomposition temper ature,
  • hall-life' ' is the lime required to reduce the original content of a composition by 50% at a given temperature fhus
  • the structure of the alkoxyamine may be tailored so that the cleavage kinetics accommodate the properties of the crossiinkable polymer and/or the processing parameters oi the crosslinking operation,
  • the amount of alkoxyaraine present in the composition is dependent upon the type of free radical initiator decom
  • the composition includes alkoxyamin ⁇ in an amount sufficient to provide from about 0.5 r ⁇ ol ⁇ to about 5.0 r ⁇ ole excess R-group radicals compared to the expected moles of polymer radicals formed via free radical initiation.
  • the amount of alkoxyamine may be selected to ensure no crossiinking occurs during processing, such as during extrusion, for example.
  • the amount of alkoxyamine may be selected to ensure that crossiinking does not occur for a desired time period.
  • the amount of alkoxyamine in the composition may be selected to ensure that no erossHrsking occurs for about 1 minute to about 30 minutes once the processing temperature is reached. Crossiinking may then proceed after this time period.
  • the carbon-centered radical functions as a scorch r ⁇ tardant.
  • the R-group of the alkoxyamine may be selected so that the carbon-centered radical has sufficient reactivity to bond with the polymer radicals.
  • the R group may be selected so that the carbon-centered radical provides a desired functionality when bonded to (or grafted to) the polymer.
  • the alkoxyamine is a T ⁇ MPO-isopropylbenzen ⁇ component having the chemical structural formula (V) shown below.
  • the alkoxyamin ⁇ cleaves into a nitroxyl radical (as discussed above) and a dimethyl benzyl radical as shown in the chemical structure fVD,
  • the functional group derived from the carbon centered radical may provide the crosslinked polymer with useful properties.
  • the carbon centered radical can incorporate polymer terminal unsaturaiion sites to increase the erossiinking efficiency for subsequent free-radical crossiinking.
  • the carbon centered radical can include conjugated aromatic structures incorporating polymer terminal unsaturation sites to provide insulation and improved ability to mitigate space-charge build-up (a problem in cable applications) in the crosslinked polymer.
  • the carbon centered radical can include polar functionalities which incorporate the polymer terminal unsaturation sites to provide resistance to "water-treeing" (also known as wet-electrical aging) in the cross ) iaked polymer.
  • incorporación of other polar groups and/or aromatic functional groups by way of the carbon centered radical and into the crosslinked polymer can provide the crosslinked polymer adhesive properties and/or electrical tree r ⁇ tardance.
  • the crosslinked polymer with one or more of the aforesaid properties finds application in cable coatings/insulation, and DC and/or AC cables in particular.
  • the R-group may be selected so that the carbon-centered radical (1 ) has sufficient reactivity to cap the polymer radicals and (2) provide a desired functionality to the crosslinked polymer (i. e. , insulation, adhesion, heat resistance, etc.)
  • another method for controlling polymer crossiinking includes heating a composition to a processing temperature.
  • the composition includes a crosslinkable polymer and a free radical initiator as discussed above.
  • the composition also includes a hydroxy] amine.
  • the method includes forming polymer radicals from the crosslirikable polymer with the free radical initiator and preventing crossiinking of the polymer radicals with the hydroxylamine, 356j
  • the hydroxy iarnine may be added before, during or after the heating or before, during or after the forming.
  • the method includes adding tbe hydroxy] amine to the composition before the composition is healed.
  • the hydroxy lamine can be an open chain or a cyclic structure that incorporates the following structure (VII),
  • the hydroxy! group of the hydroxy lamine is a hydrogen atom donor.
  • the donated hydrogen atom caps a polymer radical abstraction site to prevent crosslinking. This converts the hydroxyjarnine into a nitroxyl radical which also prevents crosslinking by capping an abstraction site as discussed above.
  • a single molecule of hydroxylaminc caps at least one, or ai least two, or two or more, abstraction sites.
  • the number of abstraction sites a hydroxylamine molecule may cap is influenced by reaction efficiency and/or the scorch retarding ability of the derivative aik ⁇ ne.
  • the hydroxylamine caps at least two polymer radicals.
  • the method includes producing the nitroxyl radical from the hydroxylamine and capping a polymer radical with the nitroxyl radical.
  • the nitroxyl radical is formed at a temperature less than or equal to the processing temperature.
  • the method includes capping a polymer radical with a hydrogen atom from the hydroxy! group.
  • the hydrogen atom is formed at a temperature less than or equal to the processing temperature
  • the method includes capping at least one, or at least two, or two or more polymer radicals with a single hydroxylamine molecule (i.e., one polymer radical capped with the nitroxyl radical and another polymer radical capped with the hydrogen;. If In an embodiment, the hydroxylamin ⁇ has the following structure (VHl).
  • the hydroxyiaraine is formed in the composition in situ.
  • the composition includes an alkoxyaminc as discussed above.
  • the method includes heating the composition (which includes crosslinkabie polymer, free radical initiator, and alkoxyamine) to a processing temperature and producing hydroxylamine from the alkoxyamine at a temperature less than or equal to the processing temperature.
  • the free radical initiator forms polymer radicals from the crosslinkabie polymer. Crosslinking of the polymer radicals is prevented by the hydroxylamine.
  • the alkoxyamine produces or otherwise generates hydroxylamine (and nilro ⁇ yl radicals) by way of an elimination reaction.
  • the alkoxyamine thermally decomposes and undergoes an elimination reaction (disproportionation) yielding the hydroxy iamine and an alkene as shown in the chemical reaction (IX) below.
  • the hydroxylamine donates a hydrogen atom to cap a polymer radical abstraction site and produce a nitroxyl radical as discussed above,
  • the bydroxylarnine resulting from alkoxyamine disproportionalion caps at least one, or at least two, or two or more polymer radicals as discussed above.
  • Additives can be added to the composition either before or during processing.
  • the amount of additive is usually in the range of about 0.01 to about 50 percent by weight based on the weight of the composition.
  • Nonlimiting additives include ultraviolet absorbers, antistatic agents, pigments, carbon black, dyes, fillers, slip agents, fire retardants, plasticizers, stabilizers, processing aids, lubricants, smoke inhibitors, halogen scavengers, flow aids, lubricants, water tree inhibitors such as polyethylene glycol, viscosity control agents, foaming and d ⁇ ibaraing agents, cure boosters, antioxidants, UV absorbers, light stabilizers, metal deactivators, phosphites, phosphonit ⁇ s, hydroxylamines, nitrones.
  • thi ⁇ syncrgists co-stabilizers, nucleating agents, fillers, reinforcing agents, emulsit ⁇ ers, pigments, theology additives, catalysts, flow- control agents, optica! brighteners, llameproofmg agents, antistatic agents, blowing agents, and monomelic eo-agents such as triallylcyanurate, allyldigiycolearbonatc, triallyiisocyanurate, trimethylolpropane, diallylether, trimethylolpropane trimetbacryiate, and various allyiic compounds and any combination of the foregoing. Methacrylatc and acrylatc compounds may also be added separately to the various polymers identified above.
  • a method for retarding scorch in a crosslinkable composition includes extruding a crosslinkable composition.
  • the crosslinkable composition includes a crosslinkable polymer, a free radical initiator, and an alkoxyaminc. Extrusion occurs at a temperature greater than or equal to the decomposition temperature of the free radical initiator. Decomposition of the free radical initiator forms polymer free radicals.
  • the method includes producing nitroxyl radicals from the alkoxy amine before formation of the polymer free radicals. Nitroxyl radical production may occur by way of cleavage and/or elimination as discussed above,
  • the method also includes preventing crosslinking of the polymer radicals with the nitroxyl radicals during the extruding.
  • the method also includes crosslinking the polymer radicals after the extrusion.
  • the components of the crossHnkable composition may be added directly to the extruder to b ⁇ compounded, mclled and extruded.
  • Any suitable extruder may be used to extrude the composition.
  • suitable extruders include single or twin screw extruders, single-layer extruders, two-layer co-extruders, or three layer co-extruders.
  • a typical extruder has a hopper at its upstream end and a die with an outlet at its downstream end. The hopper feeds into a barrel, which contains a screw.
  • the screw portion of the extruder includes heating zones which may heal the composition to a temperature from about 110 0 C to about 210 0 C (or any value or subrange therebetween).
  • the extruder outlet may feed the extrudate into another heating zone. Crosslinking may occur in this post-extrusion heating zone.
  • the present crosslinkabl ⁇ composition may be prepared by mixing the components (the crossiinkable polymer, the free radical initiator, the alkoxyamine, and any desired additive(sj) in a mixer and kneading at or above the melt temperature of the crossiinkable polymer but below the decomposition temperature of the free radical initiator,
  • suitable mixers include a B anbury mixer, a continuous mixer, and/or a roller.
  • the kneaded material is then granulated or pelietizcd,
  • the palletized material may then be fed into the extruder.
  • all of the components and additives except the free radical initiator can be processed in this manner. These initiator-free pellets may be fed into the extruder along with liquid free radical initiator.
  • the extrusion temperature is greater than or equal to the decomposition temperature of the free radical initiator.
  • the method includes selecting an alkoxyamine having a cleavage temperature less than the decomposition temperature of the free radical initiator. Consequently, the alkoxyamine cleaves into nitroxyl radicals before the free radical initiator decomposes.
  • the nitroxyl radicals in the composition cap any hydrogen-abstracted polymer strands while the composition is in the extruder. This prevents crosslinking of the polymer radicals during extrusion.
  • the cleaving of the alkoxyamine occurs at a faster rate than the decomposition rate for the free radical initiator.
  • the alkoxyamine has a half-life that is less than the half-life of the free radical initiator.
  • the rate of formation of the nitroxyl radicals is greater than the rate of formation of the initiator free radicals, This ensures that sufficient nitroxyl radicals are present to cap the polymer radicals and prevent crosslinking during extrusion.
  • the alkoxyamine may be cleaved into nitroxyl radicals and carbon-centered radicals as discussed above.
  • the R.- group of the alkoxyamine may be selected so that the carbon-centered radicals have the capability to function as a scorch retardant and cap the polymer radicals.
  • the atkoxyamin ⁇ is present in an amount to ensure that Sittle or no crossiinking occurs during extrusion
  • the composition includes alkoxyamine in an amount sufficient to provide from about 0.5 mole to about 5.0 mole excess R- group radicals compared to the expected moles of polymer radicals formed via free radical initiation.
  • the extrudate is led to a heating zone and is heated to crosslink the crosslinkable composition and form a crosslinked polymer.
  • the crossiinking temperature may be from about 100 0 C to about 300 0 C (or any value or subrange therebetween).
  • the crosslinkable composition is molded into articles after extrusion and before and/or during crossiinking.
  • the crosslinkable composition may be heat cured for a time sufficient to obtain the desired degree of crossiinking.
  • the heat curing has a temperature -time relationship which is primarily dependent on the polymeric compound and the free radical initiator present, but that relationship may be affected by other ingredients in the formulation.
  • the customary cure time is typically about 3 to 8 half-lives of the free radical initiator. This may be varied based on the exact properties desired in the final product.
  • the cure time is inversely related to the temperature.
  • Compositions employing the free radical initiators disclosed herein heat cure at a temperature-time relation from about 12O 0 C to about 200°C and about 0.5 to about 30 minutes.
  • the heat cure may be carried out in any- conventional fashion such as mold cures, oil bath cures (where oil does not harm the polymeric compound), oven cures, steam cures, and hot metal salt bath cures.
  • a scorch-re tardant crossHrrking composition is provided.
  • the erosslinJking composition includes a crosslinkahle polymer, a free radical initiator, and an aikoxyaraine, Tbe free radical initiator has a decomposition temperature.
  • the alkoxyamine has a cleaving temperature that is less than the decomposition temperature
  • the crosslinkabl ⁇ polymer, the free radical initiator, and the alkoxyamine may be any respective component as discussed above.
  • the aikoxyamine has a half-life less than the half-life of the free radical initiator at the decomposition temperature.
  • the crosslinkabl ⁇ composition contains polymer radicals that are bonded to nitroxyl radicals and/or carbon- e ⁇ nt ⁇ rcd radicals formed by way of the alkoxyarm ' ne cleavage.
  • the aikoxyamine present in the crosslitiking composition has the structure as previously shown in structural formula (V) and further shown below.
  • the carbon-centered radicals are dimethyl benzyl radicals.
  • the benzyl functional groups bond to or cap the polymer radicals when the crosslinkable composition is at the decomposition temperature.
  • the erosslinkable composition may be molded or extruded into crosslinked articles such as wire, electric cables, and/or insulation.

Abstract

L'invention concerne des procédés et des compositions pour commander la réticulation d'un polymère. La composition de réticulation comprend un polymère réticulable, un déclencheur de radicaux libres, et une amine. L'amine est une alcoxyamine ou une hydroxylamine. La composition de réticulation est chauffée jusqu'à une température de traitement. L'amine subit une réaction de clivage à la température de traitement ou en dessous de celle-ci pour produire des radicaux nitroxyle in situ. Le déclencheur de radicaux libres forme des radicaux polymériques à la température de traitement. Les radicaux nitroxyle formés in situ coiffent les radicaux polymériques pour commander la réticulation.
PCT/US2009/045808 2008-06-06 2009-06-01 Procédé pour inhiber une vulcanisation dans des compositions réticulables WO2009149001A1 (fr)

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US61/059,414 2008-06-06

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EP2995631A1 (fr) 2014-09-12 2016-03-16 Borealis AG Procédé de production de copolymères greffés à un squelette de polyoléfine

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WO2002010226A1 (fr) * 2000-07-28 2002-02-07 Tesa Ag Materiaux adhesifs de contact acrylate presentant une faible repartition moleculaire
WO2002024761A1 (fr) * 2000-09-25 2002-03-28 Ciba Specialty Chemicals Holding Inc. Methode de polymerisation radicalaire controlee dans une dispersion aqueuse
US20030149205A1 (en) * 2002-02-01 2003-08-07 Callais Peter A. High-solids coatings resins via controlled radical polymerization
WO2005059048A1 (fr) * 2003-12-10 2005-06-30 Ciba Specialty Chemicals Holding Inc. Compositions de revetement contenant des agents d'ecoulement prepares par polymerisation a radicaux nitroxyle
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WO2000014135A1 (fr) * 1998-09-03 2000-03-16 Ciba Specialty Chemicals Holding Inc. Greffe de monomeres non satures en ethylene sur des polymeres
WO2002010226A1 (fr) * 2000-07-28 2002-02-07 Tesa Ag Materiaux adhesifs de contact acrylate presentant une faible repartition moleculaire
WO2002024761A1 (fr) * 2000-09-25 2002-03-28 Ciba Specialty Chemicals Holding Inc. Methode de polymerisation radicalaire controlee dans une dispersion aqueuse
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WO2005059048A1 (fr) * 2003-12-10 2005-06-30 Ciba Specialty Chemicals Holding Inc. Compositions de revetement contenant des agents d'ecoulement prepares par polymerisation a radicaux nitroxyle
WO2007025885A1 (fr) * 2005-08-30 2007-03-08 Ciba Specialty Chemicals Holding Inc. Polymères obtenus par polymérisation radicalaire exercée par le nitroxyle

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Publication number Priority date Publication date Assignee Title
EP2995631A1 (fr) 2014-09-12 2016-03-16 Borealis AG Procédé de production de copolymères greffés à un squelette de polyoléfine
WO2016038177A1 (fr) 2014-09-12 2016-03-17 Borealis Ag Procédé de production de copolymères greffés sur un squelette de polyoléfine
US10392460B2 (en) 2014-09-12 2019-08-27 Borealis Ag Process for producing graft copolymers on polyolefin backbone

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