CA2116784A1

CA2116784A1 - Article and method for bonding to an elongate object

Info

Publication number: CA2116784A1
Application number: CA002116784A
Authority: CA
Inventors: Jozef Albert Gustaff Doucet
Original assignee: Individual
Current assignee: Commscope Connectivity Belgium BVBA
Priority date: 1991-10-23
Filing date: 1992-10-22
Publication date: 1993-04-29
Also published as: EP0610279A1; JPH07500057A; FI941880A0; FI941880A; WO1993008012A1; GB9122512D0

Abstract

A wraparound polymer-laminated fabric sleeve (2) that is heat-recoverable at least in part is provided with electrical heating means (8, 10, 12) along one longitudinal edge and both annular ends of the wrapped sleeve. Electrical current is passed through the heating means (8, 10, 12) to recover at least part of the sleeve and to bond it to an underlying substrate.

Description

2 -1 - 21 16 7 8 !1 PCT/GB92/01937 Descri~tion This in~en~ion relat~s to a hea~ recoverable wraparound art~cle r for bond~g to aIl ob~ect such as a pipe, eg to seal agains~ in~ess of wate~ ~o protect aga~st p~ysical dam~ge or to make a ~oint between the ob~ect and aDother ob~ec~. In par~icular. ~che in~e~tion relates to :;
a wraparolmd art~cle ~cluding heatiI~g meaIls along at leas~ o~e long~ al edge and alc)ng t~e circu~feren~al edges as considered in the wrapp~d con~gura~o~.

A wrapar~und ~cle includ~g hea~g means along 'chree edge~ is known from D~:-A-3712356. This descr~bes a sheet of ~;
thermoplastic material for covering a ~o~nt between plas~c pipes in which the sheet is pr~ided w~th at least two parallel heating wires on three edg~ r~gion~. The ar~cle is not heat recovera~le.
.

A heat-reco~rera~le a~a~le is one whose d~erlsio~l c~n~tion can be made to cha~ge substantlally when sub~ected to heat tre~tmen~. A he~t-reco~e~able ar~cle will usually reco~rer towards an orig~al shape from ~vhich it has previously been : ~ ~ deformed but the term as used herein also ineludes ar~cles w~ch adopt a new conflguration when su~ected to heat treatment, e~en if it has not pr~viou~ly been deformed.
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HLeat-recoYerable ~cles are well }m~wn ~nd may be used ~n t~e se~g o pipe ~oints. the repair of polymeric coatings on pipes arld s~m~lar structures. the protection f~om chemical ~d physical at~ack of pipes and ot~er s~ucb~res. o~ten metaLlic. Th~y IIlay also be used to ~eal cable splices.

When a ~oint ~5 made between two leng~hs of ther~ly insula~ed steel pipe. a~ used for e~ca~ple ~n a district he~ffng system.
the insula~ion is remaved (~plcally In the factory) from the end .: .

Wo 93/08012 PCI/GW2/01937 regions o~6~ng~ of pipe in order that the insulation is not burnt when the pipes are ~oined. for example by welding. After the weld has been comple~ed. the ~aninsul~ted portion of the pipe in the region of the joint must be reinsulated in order to minimise heat loss.
It ~s important ~ha~ the insulation in $he re~ion of the ~oint is sealed against mois~ure ~ngress which migh~ otherwise eause degradation of the insu~a~don. not only ~n the 3O~nt region but possibly also along the plpes to ~ome dl~tance f~om the ~oint. arld cause also corro~on of the pipe~.
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Severe physical c~rlstraint$ are placed upon the seal of t~e insul~ at a ~o~ betwee~ Insulated pipes in a distr;lct heaffng ~y~tem. As a result of i~equent and w~de temperature cy~ng, the plpe c~ be sub~ected to ~x:p~ion and con~as~on cydes and to lo~ ud~al and transv~se m=en~s. For example~ lt ha~ been determ~ed that forces of up to lON.mm~2 can be exerted on the outer protecthre ~acket of aD in~ulated pipe as a result of temperature c~rcles e~erie~ced ~ a plpe ~ Ynnter before ~t 18 burled. The se~l ~usS be abl~ ~tad~these cy~les ~d movemen~s wlt:hout bre~g. Fbrth~ ~ is preferred that the 5eal be able to -wiehstand ffle preS~eB :exerted when the ca~i~y arourld ~he insul~ted port~on of p~pe ls relnsulated bY~r ~aming in situ.

One ~pproach '~hat ~ha~; met wit~ conxidera~le succes~ is the su~ect of GB-A-2108~i25. In one aspect it involves creating a fle~fible ~seal. be~en the ~sula'don surroundlng each p~pe and a rigid casing which spans the unlnsulated por~on of pipe. by means of a heat- :
rec~vable polymeric~sb~e co~ted w~th a sealant. To pFeValt m~vemeIlt of:the sealant coated s~eve of (}B-~-2l08625 re~a~ve to ~e pipe. the sle~ve is pro~ided wi~ adhe5~ve m~terial at spe~fled regions to bond ~e sleeve to the p~pe insulation ~d to ~e cas~slg.

Ano~; approæh wh~ch has met with considerable success is described ln EP-B-245067. This des~r~bes a ~gid sy~tem for sealing the insula~on al: a pipe Joint which is sufflcien~y strong to wlthstand the forces encountered durlng lnstallation wl~out stretchlng or WO 93/OB012 ~ 8 ~ pcr/GB92lol937 ., 3--fle~nng to any sign~ficant extent. or breaking. E;P-B-0245067 describes an article comprising a heat recoverable polvmeric layer~ a layer of bondirlg matenal ~or forming a bond between the recoYerable material and the ob~ect, and a larninar me~al heating elemen~ having a pluralit~r of apertures through its th~ckness inbuilt in one of the layers. The sleeve is multlwrapped for some embodiments. especially for large pipe or cable cove~g, so t~a~ it builds up a th~ckness of.
~or ~mple, from O.S ~o 3.5 mm. lncreased thic~ness enhances the s~en~, which is reguired of a r~gld seal.

We have c~scove~ed ~at par~cular advanLtage~ can be achi~ed by provl~ng a heat re~erable fabric wraparo~nd sleeYe, preferably impreg~ated or eoated wlth~ polymeric materlal,, which ~leeve 1s pr~rlded ~lth heat~$lg mean~ in or on ~ts in~er surface. along at least three edges. be~g one lo~gl~edge and botb annular edge~
when t~e sle~ve is ~n its wrapp~d con~gurat~o~.

The e~dstence~ o~ heat-recoverable ~ c sle~es is krl~wn.
E~ference may be made~: for exa~ple~, to EP-A-0~16393, GB~A-2133639, GB~-2133740. GB-~-21343~4, C;B~-21356~2. GB-~-21358~6 and GB-A-213942. the di~osures of which are incorporated herein by refer~ce.

Thus the prese~t invention provltles a wraparound ar~ele for ~oncllng to an elorlgate obJect such as a pipe or cable or for ma~ng, :: or bonding to, a ~o~t or spllce be~weer~ such a~dcles. the article ~: co~prl~fflg a layer of a fabrlc t~a~ is heat-recoverable, preferably heat shrlnkable. ~t leas~ in part~, whlch is in the for~ of a sheet ~at can be apped arouIld the ob~ect. aDd which is provlded with elect~ical hea~g ~e~s in andlor o~ its inner ~ e when Yvrapped. along at least three edges of the shee~, being at least one of ~e lon~tudinal edges aT~d bo~ an!lular edges when the shee~: is in lts wrapped conflg~
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WO 93~08012 PCltGB92/01937 2,~ lG7 ~4 -4-One. some or all of the healing means can be at least partially embedded ~ the reco~rerable fabnc. or ~hey can lie on the surface of the fabric layer.

The electrical he~ting rneans may be of any suitable type. For example an open mesh of the type descnbed in EP-53-Q245067 can be used. Such a s~cruc~ure c~ a~van~ageously follow the recoYery of the slee~e. In another embodiment certain fibres of the fabr~c may be conduc~re, or extra conduc~re fl~res or w~res can be inserted in the fabric and connected to a power supply to act as he~t~ng elements.
For ~ple~ c0nduc~ve copper w~ may be inserted. Mi~ures of di~erent hea~g means naay be used. Elec~ical power to the electr~cal he~g means tWhich heat by I2R heat~ng a~ a result of e~ecbical ~e~t pa~sage) may be p~rided by ~y su~table electrodes. For OEample. metal s~ips or conduc~lre braid ~ips may be ~ed to, or ~n~exwoven ~, the fabric.

~ e sle~e preferably also comprises a bonding layer, on i~s inner surface lwhen w~pped) at leas~ e reg~on of ~e hea~Lng ~ -means. l?~ef~ab~ he bond~ng layer c~mprises a~y o~ thg mater~als m~ti~ed f~r the boIlding layer of EP-B~24506~, ~e di~closure of which i~ incorpora~d herein by refere~ce.
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The bonding material may be selected from mate~als whlch :pro~de arl adhesive bond and: ~rom mate~s which pro~ride a fusion bond. The selection ~ depend on the :m~tenals of the recoverable l~yer and on:the ob~ect to which ~ is ~o bond. Pre~erably the bonding ma~erlal ~ be heat-ac~vatable. t~at is for example a mater~al w~ch can pr~vlde a fi~sion; bond. or ~ a material wh~ch provide~ an adheshre bo~d (ie. asl adhesive) a hot-melt ~&esi~e or a heat-curable adhe~ive.
has the adtrantage of p~lding an ar~cle w~th a layer of bonding m~ter~ that is 1~1:ent uD'Lil t~e heati~g elemeIlt is powered in order to cause ~ yer o reeo~erable ma~erial to recover and to ac~ate the borlding matenal~ a~d wh~ch ls t~e~efore particularly con~renient du~ing storage arld during manipulation of the article prior to inst~Llatiorl.

wo 93/080l2 pcr/Gss2/ol937 5 211678~

A heat-acti~ratable adhesive (as the te.,l~ is used herein) forms a bond that is based on chesI~ical and physical interaccions which are initiated when the adhesive is in its liquid phase and are retained on solidi~cation, Examples of hot-melt adhesives which may be used as bonding mater~al in the article of the invent~on are disclosed in US-418177~ and US-4018733, w~ich disclose formula~ons comprising polyam~des modii~ed wlth hydrocarbon waxes. and Ix~tures of acidic et~ylene polymers and tac~ers. Also su~table are composi~ons based on etheylene vinyl-acetate copolymers. bIended with h~rdro~on waxes ~nd optionally butyl rubber. A par~cularly preferred adbesive. especially for use on untreated surfaces and in low temperature applicatlons. is that disclosed in GB-A-2075991.
whlc~ IS a blend of a polya~de. an acryli~ rubber and preferabl~ a small amount of arl e~ylene/acry~ic acid/bu~ri acrylate terpolymer.
In order to obta~n satlsfactory shear performances in such adhesives.
it may be ad~lantageous to cross-l~ e adhesiYe. although the degree of c~ss-~g must not be so high as to reduce the abllit~r of t}se adhesive to l~quify. and tl~ to flow and to wet the ob~ect to be bonded. and therefore to form a bond to the ob~ect wlth good ped skengt~.
:
A fuslon bond ~as the term is used hereln) on the other hand is one that ls based on physical interac~ons lni~ated by intimate contact between compa~ble materlals in thei ~isco-elastic state. and is more akin to a weld. ln m~y Ibut not all) cases. compatib~lity of two or more polymeric composi~ons arises from substan~al amounts of comm= recurring units in the polymers of the mate~ials. such as for ~le whe~ ~t least 50~6. preferably at least 70%. of the recurrfng units of a~ polymer of a flrst csmposltion are the same as at ~least 50%, preferably at:least 70%, of ~he recurring units of a polymer of the ot}ler co~post~on. these percentages being based on the total nu~ber of recurTir~g units.
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Polymerie mate~ t}lat may be used for the fusion bonding layer ~nclude. for example po~eth~lene, polypropylene. polybutene.

W093/08012 ~'~,.6~S4 -6- PCI/GB92/01937 copolvmers of ethylene~ propylene. butene and hexene. copolvrners of ethylene w~th ethyl acrylate. ~rinyl acetate, acrylic acid. methacrylic acid, acrylic esters or methacrylic esters in which polyethylene predominates, blends of these polymers. and blends of these polymers w~th elastomers~
, :', We have found ~hat a slee~e af a certain thlckness when made from the recoverable fabric of the present in~renffon pro~ides the same strength eg parffcular~ ag~st internal or external pressure. or aga~nst tensile stre~ a much thl~lcer sleeve made from a recover~le sleeYe of the mater~al described irl EP-B-0245067. For many appl~ ons ~ is very desirable s~nce lt allows the the~mal mass of the ar~ciie to be le~s than tha~ of t~e he~ted reglon of the p~pes so that, if the ~ lcle during heat reco~ery rea~hes hlg~
temperature~ d~ to the ~oint ls m~mised. Thl~ 1s par~cularly usefi~l ~n the ca~e of d~s~dct he~g pipe ~oirlts a~ explained below.

~ Di6t~ hca~ng pipes 1 yp~cally compdses a een~al steel plpe1, an outer~ thick insula~on and aD outer pol~meric coa~g. I~ loi~g such plpe~ the :9tcel: iS bared aDd a weld made. It is ~en necessa~y tQ make good t~e iDsula~oIl. Tbls may be done by Sl~Ollndi~lg the outer p~bmer~c coadngs on e~t~er slde of the plslt with a casirlg (one o r mul~-p~ sealed to the polymerlc coverlng, ~nd then i~nmed~ately adding~foam lnto the~ annular gap around the steel pipes in ;~the ~oi~t reglon wlthin:the ca~ing. The ~pes of foams used callydecompose~at~tempaturesofabout140Corhig~er.
Therefore if a heat recoverable sleeYe ~s used during the reinsulation of: ~strlct; heat~g ~oints.~ er as a sin~e part casing or as seals onto a r~gld: cas~ng,~ t~en t~ tnstaller must ensure that the sleeve does not heat to temperature~ at wh~ch the foam w~ll decc~mpose. In situat~ons where the ~cknes~ of ~e sleeve is high. s~ that the thermal ~ass~of the sleeve is greater than th~t of the region of the pipe wh~ch }~ durlng the :ins~ ation. then it is ~rery dffl~cult to con~ol o~rer-hea~dng of the sleeve and consequent dam~ge to the foam. Thus the present applica~on, which allo~ws the use of ~inner d hence l~wer t~ermal mass sleeves. provides signi~cant : .

WO 93~08012 P~/GB92/01937 7 21167~1 advantages compared to the pnor arc soiutions. Preferably ~he sleeve used has a wall thickness less ~an that of ~e pipes to be joined.
preferably less ~ 0.75 times the wall thickne~s of the pipes to be joined. As an exa~ple~ according to our ~ven~on a sleeve of appro~dmately 1.7 mm ~ckness can provide appro~dmately the same strength ~when tested by a~dal pull out of a 160mm diameter, 0~5m length tubular ar~cle) as a double wrap slee~re according to EP-B-0245067 of about 3.2 mm total thickness. ~gh s~e~gth slee~es are par~cularly required where large pipes are used, eg of the order of 400 mm diameter or larger. p~ci~lar~y if subiect to high stress d~ng ~nstallatio~s. Suc~ stresses may be generated for ea~mple when a p~pe line is ~g la~d i n soil. This typical3y takeB several days so ~e ~oints may be ~osed to night/day temperature cycles wh~ch may create stres~ on tbe~)Di~lts.

In a preferred embodiment according to ~che invention part o}~r of the fabr~c is heat recoverable, pre~erably heat shrinkable.
preferablyrad~ . a ces~tral nrtllarre~on oft~e sleev~
when ~ l~cs wrapped- co~tlon is not ~ieat re~overable. Tbis may be ashl~, for example. ~ a wea:ve, by arran~g for the flbres ~n :the w~ ~to run ~==P~I~ and ~o provide rows of heat recoverable fl~*es at eithe~ end of the wr~ped ~lee~re and non-heat-recovable, ie. heat stable flbres in the central region. The use of a fabric according to the ~nven~on, par~cularly one ha~g a central h~t:stable sec~on has~been found to be a par~cularly advantageous structure in appllcatlons where the ar~cle is sub~ected to stress eg when empl~yed as a 30int be~cween distr~ct hea~ng pipes, slnce the sleeve is able to "glve" a small amoun~ due to straigbtening of f~bres ~de~ tension and~ rdax~tlon of fibres when tension is released. Such stralgh~é~ng and relaxadon occurs due to the nature of the fab~ic. in which. at least ir~ the unrec~rered state. ~bres pass o~er arld under each: o~er in a shallow slllulso~dal con~guraffon and hence, unless in a ~rery ffgbfweave or other fabrlc con~gurat~on. car~ straighten and tigbten in response to stresses.
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WO 93/08012 PCI/GBg2/01937 8- ;
The fle~bility of a joint between district heating pipes pro~ridea by the use of a he~t recoverable fabric also forms part of the present ~:
inYention. ThUS another aspect of ~he irl~ention prt~rides a method of reinsulating a bared ~oint bel:ween district hea~ng pipes each of which co~pr~ses a ce~tral pipe ha~ring an outer insulation. the me~hod compr~sing ~1) pos~oning a wraparound article either to bridge the insulation on e~ther side of the pipes or to bridge from a pipe to a central cas~g position~d over the ~oint. t~e ~cle comprising a wraparound ~abxic sleelre ~vhlch has end annular regions which are radially heat ~hrlnl~le, d a ceiltral tubular portio~ which is radlally l~eat stable.
and ~21 a~ply~g hea~ to shr~; the ends of the ~r~cle.

whereby aft~ shrinkage tbe sle~e i5 longitudinally ~ble.
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Ihe slee~e co~pri~es a ~absic. which i~elf pre~erably comprlses recoverable. prcferably cros~-l~kedt f~br@s arranged in one of t~ warp or t~e weft of t~e fab~ic. so tha~ ~e f~ic ls :recovera~le ir~ subseantlally ne directlon. Preferab~r ~ls is the circumferen~ direc~on whe~ the sle~ve is in a wrapped conlguratlosl. .

l~e term "fibre" as used herei~ includes filaments eOg.
mono~lament~ or ~ents, and a~so staple fibres, and tapes.
Th~ fabr~cs used iD;the articles accord1ng:to the in~ren~on preferably :~
empl~r the heat-shrinkàble fibres in the ~orm of fllaments. espec~ y mo~of~l~ents. In ~a~other preferred embodiment 1:he recoverabillty ~is hi~est. espedally preferably significarlt~y highest. in the direction of tl~e rec~YeraWe ~bres.

Cross-lin~g of the fibres enables the ~abric ~:o be heated aboYe their recovery temperature wit~out mel~ing. Higher recoYery ratios ~an be a~ie~red w~t~ cross-linked flbres thar~ would be possible with -W0 93/08012 ~ 2 I 1 6 7 8 ~ Pcr/GBg2~01g37 non-cross-lirlked stretched fibres. and in addition fabric containing cross-l~nked ~bres is not so sensitiYe ~o overheating.

As examples. any of t~e fabrics descnbed in EP-B~0116393.
EP-B-024398S. EP-~-0430377. :E:P-A-022S152. US 4816328~ US
4816309, U.K. Pa~e~t ~pplicatlon Pllblication Nos. 2133639, 2133740. 2134334. 2135632. 2135836 and 2139142 carl be used ~n the article and method of the presen~ rentlon.

Whllst the ~abric may be tlsed alone. it is often ad~tag~ous for it to be emplc~red in con~ tlon wlth an adhesive or seala~t or ot3her po~lc m~te~ ~t reIlders ~t ~ubs~antially impe~v~ous to fluids~
the ~e~lve. sealallt or o~er mater~al either being a~pl~d in sib~
whOEl the fabr~s~ 18 ~stalled or applled in the ~actory. Thus~ for e~ple, ~e fab~c may be ~mpregnated Y i~ a curable adbe~ve composltio~, e.g a ~le epoxy composi~on and espeeially an ~3ptlo~ b-staged ~pox~ re~ bat is c~ed by me~s of a pol~mide, arl ar~hydrlde ~r an ~so~ate al~holl~bL other mate~ials may be used ~u~h ~ ph~c~ resins~ or i~te/phe~llc re~. The re~i$ L may y be lamlna~d on to t~e f~bFic or ~t may be employed i~
partlculate fo~ as desc~ed in U.K Pate~c Pub~at~o~ 0. :21~300.
Alte~ an adheshre suc~ ~ a h~t-~elt adhe~i~e and espec~lly an ad~e~1ve based :on a polyam~de or anL e~ylene-~nyl aceta~e copolyme~ may be appl~ed el~her to the ~ c or to ~e substg~te during~nstalla'don.
, P~os~ preferably, howeYer~ the heat-reco~rerable fabric is used ~n comb~ lon wl'lh a matrix polymer layer which softens when he~ted to aecommodate recovery of the fabric. to ~orm a s~gle co~po~ite stru~ture.

The heat-recover~le fabric is pre~era~ly bonded to. mo~
preferably. c~mbedded in. the polymer matrix mater~al. At or abo~re the reco~r~ry temperature of the flb~es. the polymer mat~ix material sh~uld be capable o~ limi~ed flow under pressure so that it ~etains the in~egri~ o ~e composite struch~re without substan~lly imped~g :

W093/08012 2~ 4 -10- PCr/GB92/01937 recovery of the fibres. It preferably has. at the aforesaid temperature.
an elongat~on to break of greater than 50%. most preferably greater than 100%, and a ~O% secant modulus of pre~erabl~r greater than 100%, and a 20% secant modulus of preferably at least 5 X 1O-2 MPa.
most preferably at least lo-l MPa, measured at a strain rate of 300%M per mirlute.

The ab~Lt~ of the matr~x materlal to flow ~hen heated need ~ot necessarlly apply afte~ recovery. T~us, for ~ple. the polymer matrix mate~lal may eventually c~e to a the~mo~et Oll hea~g, although it is p~eerred that th:e cure rate is suf~c~ently slow under the reeo~ y cond~t~ons not to af~ect adYersel~ e above men~isned physlc~l prop~le~ of ~he polymer ma~ material du~ g t~e rec~y of the flb~es. Th~s, ~or example~ t~e po~mer form~g tbe ma~ materlal may con~ain graft2d hydrol~ab~e ~llane g~up5 whlch are capa~le of cross-~g t~e m;~te~al subsequently i~ the p~seslee of moisbure. Alten~ the mat~lx materlal may include a po~mer. preferabb a rubbcr ar~d espe~all~ a~ylle n~bber, w~eh eor~ s ep~ group~: and a roo~ tgmperab~e insoluble cur~ng agent e.g. dl~a~diamlde. Preférred mal~ materlals are descr~bed in U.
Patent ~ppllcation Publicat~on No. 2135632. Thus a partieular~y ; ` ~ pre~eITed slee~e eomprlse~ a ~ompos~te structure of a heat-:~ recove~We fabrle a~d~ a polyme~ mam~ mate~al ehar~c~r~ed in .
(a) the hea~-reco~erable fab~c comprises fibres that wil~
recover when heated. ~: fl~re~ ~g a recove~y s~ess Y of at least 5 x lO-~2 MPa at a temperab~re above their c~y~talline melting Sransitlon temperaturc: and (b~ t~e polymer mat~i~ material has an elongat~o~
temperature profEle such tbat there e~dsts a tempera~ure O wh~ch is at~ or ab~e ~e crysta~ne meltlng transltlon temperature of the flbres at whlch temperature ~t~e poIymer matrix materiaI has an elong~a~on to break of greater ehan 20% snd a 20% secane modulus X

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: ', WO 93/08012 pcr/GB92/ol937 211 678~
of a~ leas~ 10-2 MPa (measured at a strain rate of 3~0% per minutes~, and at which temperature the inequali~ (1) is satisfied:

(1-~) is less than orle.
Y R

wherein R is ~e mearl effective vo~ume fra~on of he~t-recoverable ~:
fibre~ in ~e compo~ite structure along a glven d~eeffoIl baS@Cl 0~ t~e . ~:
total ~rohLme o~ t~e compo~te s~:ructure. or rele~t p~rtlon thereof.

Ihe ~abric ca~ be ~t~d, W~ " noIl-wo~en~ braided. or ~che l~e. It is prefOEred ~t ~che fiab~ic 1~ a woven ~abric. Ihe ~abrlc can be wove~
in a~ ~u~table p~ or =ple, twlll~ bro~en twill. ~a~n~ satee~. :
I~o, EalaiD" ~op $ack. sa~k and vaho~ e c~mlbi~tio~ in si~le or ~ul~ple p~r ~eave~ for ~ple two or three ply weavesr The c may be lmitted if des~ed, eit~er ~ k~i~ted or weft ~nitted.
Whe~e ~ f~ric ~s~ a brald the tlYms '~arp" and 1~ are ~o$
strl~b app~ le. but whe~3L used i~ ~h~s Sped~ R t~ey cas~ be co~sld~ed t~ r~ate to braid~ b~r arbltaIy sele~ioIl of ~Ibre dire~i~s.

~he fablic m~y CD}ltai~l 0~1}31' heat-recove~Lble flbre~, o~ as is ~:
prefe~ed i~ m~y colltain bo~ heat -re~overable f~bres a~d non he~t- :
recaverable flbr~s. I~ may al~o compIise conduc~ve ~bres ~h~ch naay provlde th~ heati~g me~,: ~e ~bres may be = ged i~ any patt~rn irl aceorda~ce wlt}l~e ~n~e~on~ but it i~ especially --pre~erred th~t all t~e ~b~e~ ~end~ng Irl the dire~on of t~e rec~le fi~re~ are recoverable. a~d t~at all the o~e~ flbre~ ~e norl-h~t-rec~le. Where the ~a:b~ic i~ en it preferab~ has heat-rec~rable fibre~ ~ one direc~oIl and d~si~all~ heat stable ~res iIi ~e ot~er directio~ so t}lat t~e fabric as a w~ole is reco~able i~ a 8i~ e dirCC~t)Il O~lly. WhOEe the fàb~ic is ~ted. if sric i~iade sQlely ~m heat reco~rerable ~bre~ ~t will be r~coverable ~ dlmension~. b~t if. ~s is preferred ~ is kn~tted from a he~-stable flb~ and a ~eat-rec~erable fibre ~Lhat is either warp or weft inserted. it will be recove~able in only one direc~on.

wo 93/08012 2 ~ ~ 6~ 8 ~ ~12 - PCI /GB92/11 1937 The reco~erable fibres preferably form part of the fabric itself.
T~e recoverable fibres may instead be additional. and be incorporated, for example, inser~ed after production of the ~asic fabrio.

Sin~larly, if coIlductive ~bres are included, they may form part t~e fabrlc i~self or be add~onal. and ~neorporated. for e~ample ~n~e~ed after produc~on of the baslc fabric.

The flbres are preferably formed ~rom a polymerlc heat-recaverable maLterial which recover when heated to over and above th~ rec~ emperature. By "~he r~co~rery te~per~ture" of p~lymesic heat-recoverable ~t~lal~ 1~ mearlt t~t ~e~perature at ~lch the recovegy of ~e polymerlc materlal ~ill go substantlally to comple~o~. In general~ the ree~e~y temperature w~ll be ~he ~ e mel~g transltlon t~mperature if the polymer ~s ery~talli~e or ~e ~ tra$~ffl~ temperature if the polymer ls amorp~ous.
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The he~t-recoverable flb~res are preferabl~ ~rmed ~om a polymerl~ mat~ial that ~mparts good physical prope~es and. in part~cular. good creep re~ ce to ~e f~br~s. Olef~n polymers such a~ polyethylene and e~lene copolymers. pol~amides. polyesters~ :
a~rylic pol~rmers ~d other polymers may be employed and pregerably ~hvse t~at are capable of: be~ng cros~-l~ked. A par~cul~ly preferred polymerlc material for ~e flbres i~ ba~ed o~ polye~ylene ha~ring a ~enslqr of fi~m 0.94 t~ 0.97Jgms/cc~ a weig~ average molecular glat ~ ~f ~om :80 ~ 103 t~ 200 X 1~ and a number a~erage molecular wdgbt Mn of firom 15 X 103 to 30 X 103.

Pr~fera~ly the recovery ~emperature of $he fibres is 60C or more. mosf~ from 809C to 250C ~uch a~, for çxample, 120 to 150C.

WO 93/08012 21 1 6 7 ~ ~ pcr/GBs2/ols37 When ~he ~ibre is cross-linked bv irradi~tion it is convenient to incorporate the cross-linking step into manufacture of the fibre.
The ~bre ean be extruded, s~retched at a temperature below its melting tempera~ure, preferably by an amount of from 800 to 2000%, :
then sub~ected to irra~atlon to effect cross-link~g. A less prefe~Ted way of maki~g t:he ~bre is to ~de the ~bre. irradiate to cross-link.
then heat the ~bre, preferably to above ~ts ~eltlng temperature.
stretchlng t~e fibre, and then COQI~Ilg the stretched flbre. High density polyethylene flbres are preferably ~rad~ated with a dose of ~om about 5 to about 3S megarads. preferably ~om about 5 to about ~ ::
2S megarads and ~n par~cuiar ~om about 7 to about 18 megarads.
especially firom 10 to about 18 meds. Usually the gel content of -the cross-linked flbre ~s gre~ter than 20~6, preferably greater tban 30%. most preferaby greater than 40%. In prac~dce. gel contents ~:
greater ~ 90% a~e not easlly achlevable. Fibres produced i~ ~Lhis way can have a hi~h strength after reco~y.
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Any sultable: ~: may be used for any norl heat-~bres i~cluded~ e fabrlc. As~e~nples there may be menelo~ed glass bre. polyester.Rayon:~Iraoe Mar~). cotton and tinsel metal.

Pa~ of all of the hea~ recov~y~ fabric may be lined u~ith a bon~ng layer as aforesaid such as an adhesive for bondlng to ob~ects and/or~ bonding the~overlapping longltud~al edges~ of the ar~cle. in the~:wrapped conflgura!~on. to each~o~er. Alterrathely bonding may be by fusion.: The preferred: steps and order in which bond~g is carried out:is~descr~bed ~ respect of the ~method according to the inven~on. : :

Th~s ~other aspect of ~e invent~on provides a me~od of c~ering n elongate ob~e~t or bonding two such ob~ects in end to end relat~onshl,p us~ng a u~raparound ar~cle accordirlg to the first aspect of the ~nventlon. t~e method comprising connect~ng the hea~cing means to a power:suppl~r to heat and to recover those reg~ons into contact wi~ the underlylng ob~ect.

WO93/08012 ~ 6 18 4 14- pcr/GBs2/ol937 Pre~rably the article is wrapped around Jche ob~ec~ so that longitudinal edges o~Te~lap and electrical power applied initially to the electrical heat~ng means on the at least one longitudinal edge to bond the edges to each other. Then. the longltudinal seal ha~ring been made. heat is pre~erably applied to the hea'dng means at the end~ to complete the seal. In a prefelTed method for joining two elonga~e ob~ects or for co~e~ing a ~oixlt be~wee~ the two elongate ob~ects" the a~cle ~ wrapped arou~d a piece of relea~e paper po~ttoned arou~d one of ~e elongate ob~ects. before heat is appl~ed to t~e hea~ng mean~ on t~e longitudinal edge,. The underlying pipe or cable 'lherefore act~ as a support. The loIlgltud~nally sealed article i~ then prefesably slid from the release paper, which is rem~ved.
Then electr~al po~r is preferab~ supplled to t~e ~l~lar heating means at eac~ e~d of the wrapped ar~cle to co~plete ~e seal.
Where t~e artlcle i5 used to.loin two elongate ob~ects. ~t ls preferably wrap~ed around ~ piece of release paper on one of ~e ob~ec~ to one side of the Jolnt. before heat is applied to ~e hea~dng mea~s O~ e lw~ al edge. Ihe ar~cle ca~ t~en s~ply be pu~hed over the ~oislt b~o~ e~e dectrlcal~ power i~ supplled to ~e annular hea~dng mean~ to cog~plete the seal. Thls i~ made pos~ible becau~e of t}~e prese~ce of the rele~se paper.

The ~et~od according to the ~mre~ation is par~icularly appllcable where :t~e ob~ect~s ~ pipes or cables or ~oints ~erebetween~ p~e~ably distrlet heating pipes or ~oints therebet~een .

mbod~s of the ~vention w~ll now be descr~bed. by way of example. w~th referenc~ to 'che accompanying ~aw~ngs. wherein:-Flgure 1 sho~vs a first ar~cle acc~rding to the i~yeIltiorl:

Fig~ s 2 and 3 show se~uen~al steps in the installaffon of .

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WO 93/08012 pcr/GBg2/ol937 -~lI678~
F~gures 4 and 5 show other em~odimen~s o ar~lcle according to the i~ven'don Referring to ~he drawings Figure 1 show~ a first artlcle acco~g to the inveIltlorL. The ar~cle comprises a fabric sle~e 2 wh~ch is lamina~ed with a polymer matrlx (not shown). The slee~e 2 has lo~gU:udinal edges 4 arld circumferen~al edge~ 6 v~ewed when ::
the sleeve i~ ~ it~ wrapped con~gurat~on as sh~wn. The longitudi~al edge~ 4 can be overlapped in order to hold the ~paround ar~cle in a tubular closed cor~i~tlon. ~e sleeve also comprlses three hea~dng eleme~ 8, 10 and 12 ~n the fon~ of copper meshe~ :;
e~tendlng al~g one longltu~ edge and both circumferentlial clr lar edges of the sleeve 2. The me~ heater 15 also covered on ~ts ~n~lde s~ce ~vi~ a bonding layOE a~ de~cribed ~ EP-E~-0~245~367.
~vhlch bonds t~e mesh heater to t~e ~ ic sle~ve 2. arld ~ use, will bond the aleeve 2 to tbe underly~g elo~gate ob~ect. II1 the drawlngs the mesh heater~ are not ~h~ n detall. a~d ~he bond~ng layer is not shown (for s~plLcity). Ihe ar~cle al~s) comp~lse~ two elongate elecrode~ 14 ~g along e~ o~ the` lo~gitud~al edges o~
sle~ve 2. a~d fi~the~ elonge~e ekstrodes 16 ~t~d~ng arolmd the cl_=lere~l edges of ~e sleeve 2.

Th~ construct~on of ~e fab~c is such as to prQ~rlde e~r~u~e~t~al sh~ge at the e~ds only of the sle~re. Thus i~ two e~rcumferenUal zoIles at t~e ends of the slee~ 2. beneath the mesh hesters 10 and 12. t~e sleeve compr~ses heat shrinkable polyethlene fl~res e~endl~g~ the cirn~ferexltial direction~ while in the circumfe~tlal ~r~ctioIl in tbe entral reglon bet:weeIl the two end ~gions of l~e sleeve 2 the sleeve comp~ses non-shrin~able po~r~thyle~e f~bre~. In the longltudinal d~eetion t~oughout. the ~fabrie comprise~ a ml.cta~ of ~lass ffbres and non-shrinkable po~retlyle~e ~bres. The e~fest of this cDns~uc~on is that if electrieal ci~T~nt is applied to tbe me~h heater it eau~es the shrinkabb polyet~ylene flbre~ at t~e en~ regi~ns in contact ~nth mesh hea~ers 10 asld 12 to:shrlnk. whi:le ~he een~al reg~on be~veen e encl regio~s of $he slecve does not shrink. When electrical , WO 93/08012 ~ " 16 Pcr/cs92lolg37 current is applied to the mesh heater 8 it causes che ~onding layer ad~acent to that mesh heater to bond to the overlapp~ng edges of the sleeve, although there is no longitudinal shrinkage. ~:

Figures 2 ~nd 3 are seque~tial steps showing the instaL1ation of 'che article.

In Figure 2 the sleeve 2 is showIl wrapped ar3und two district ::
heat~ng pipe~ 18 and ao wh~ch h~ve been ~oined toget}ler by a weld 21~. Each of the di~trlct heat~g pipes I8 and 20 comp~lses an inner steel pipe 22 arld an out~r ~tion 24. The steel pipes 22 are welded at 21. but t~e insula~on 24 around t~at reg~n has belslg bared. It ls ~at reg~o~ ~h~ t i~ necessary to r~nsulate. The sleev~ a ~B posi~ed to orle side: of the weld 21. I~ 1~ po~ orled around a release paper a6 wrapped around the outer ins~on 24 of o~e o~ ~e pipe~ 18. The l~ngltu~al edg~s of t~e sleeve 2 are ov~apped. ~d ~he~ ele~t:r~e~ 16 are con~ectetl ~o a 5Upp]y of power 80 that elç~rlcal curr~nt ~ t~r~u~h the ~esh heater 8~
y hea~g t~e b~d~ng layer a~acalt t~t me~ hea~ 8. aDd thereby for3DIng a seal between t~e lox~ dlnal edges of ~e ~abrie ~leeve 20 Fai~lc sleeve 2 is therefore at ~s stage in ~e shape o~ a tub~ar sleeve. arld this ls the~ slid f~om the release paper 26 over : t~e ~eld region 21 which~ls to be reinsulat~d. The ~v~tage of form~ig ~e longltudinal ~eal to one side o~ the ~oirlt ~er a release p~per 26 is th~ the pipe to one side of the ~oint pro~ndes a ~uppo~ ~-fo~ t~e sleeve while the longltud~ seal is made. The lo~gitudin~l seal eoul~ be ~ade ~ the slee~e 2 posi'doned arousld t~e bared reglon sround weld~ 21, but ~ thls were done it wo~ld be desirable to include an i~sert support member while t~e long~tud~nal seal were : made.

After t~e sleeYe 2: has been slid from the release paper into positiorl o~er t~e bared region around weld 21. elec~:ric~l power needs to be supplied to effect heat shrlnkage of the end reglons of ~ .
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Wo 93/080l2 - 1 7 ? 1 1 6 7 ~ ~ pcr/s:iBs~/ol937 the sleeve 2. When the sleeve has been slid in~o position the edges of ::
slee~e 2 o~erlap the insulation 24 on either side of the bared weld regi~n. Electrodes 16 are then discosmected from the power supply and eleetrodes 14 connected to opposite l:erminals on ~he power s~pp~y. Th~S causes elec~ical current to flow through mesh heaters 10 and lZ at either end of the sleeve ~. This hea~ ef~ec~ shrinkage of ~e reco~rerable f~bres in those reglons of the f~bric sleeve 2.
there~y e~ec~ing radial he~t silrinkage of t~e ends of the sleeve 2.
Also t~e heat applied ac~ rates the bonding layer ad~aceIlt ~e mesh heaters 10 and 12 in the end regions of ~e slee~r~. allowing the slee~e 2 to fon~ a tl~t bond to ~e ~nsulation 24 on eit~er slde of the b~ed weld re~on 21. Ihus ~e fab~c slee~re 2 is sealed to the dlstrl~t he~dng plpes 18 and 18 on eit~er side of ~e weld 21. The seal~d s~tem lS sh~ clearly in F~gure 3.

Figure 4 sh~s an alternati~ cle accord~g ~o ~e present i~renlion. ~ dl~ers f~om tlle a~cle show~ in F~gure 1 irl ~hat t~e me~h heater~ 8. 10 arld 12 are replaced by corlductlve ~bres or w~es eg. copper ~vire~ g along the lo~l~ al edge and a~ou~d the end~ of t~e sle~e~2. These are i~dica~ed a~ 8', 10' aDd 12'.
These co~duc~e ~ir~s or flbres may be interwaverl into the fab~c 2, or they :may form par~ of the fab~c 2 itself. Thus ~ ~e end reg~ons of the ~leeYe 2 the fab~c comprises polyethylene heat shrinkable fibres, in the ~lrcumferen~al dlrec~on a~d in the cen~ral reg~on.
between the ends of sleeve 2. polye~chlerle non-shrinkable f~bres are arranged ~ the ~rcumferent~al dlrection. ~lass fIbres e~ctend in th~ :
lo~gltud~nal d~re~tion throug}lout. A~ for t~e embodiment of figures 1-3 this means that the ce~tral region betweerl t;he t~o zones at the e~ds will not be heat rec~erable. Simllarly along the lon~tudinal edge of ~e sleeve where ~e mesh heater was posi~oned ~n ~he a~cle vf Figure l. the mesh is replaced by conductive wires eg copper WiJreB or by conduc~e fibres.
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bre arrangement can be easily manu~actured by a wea.re : ~ in whi~h t~e weft ~ctends longltudinall~- and the warp ex~ends clrcumfentlally :~round the sle~ve.

wo 93/0801~ pcr/Gs92/ol937 ~6~'~4 18-For the embodiments of Figure 4 the electrodes 14 and 16 are positioned as i~ Figure 1. In this case when electrodes 16 are connected to a power supply they ca~se hea~ng of the copper wlre or conductive f~bres 8' along the longitudinal edges of the sleeve 2.
When electrodes 14 are connected to the powcr supply they cause hea'dng of the copper wires or conduct~ve flbres 10', 12' extending arotmd the c~rcumference a~ the ends of the sleeves. The installation steps of the slee~re of F~es 4 are the same as that for the sleeYe of Figure 1 to 3. the longlt~dinal seal being formed before the circumferen~al seals.

F~ure 5 ~hows a *~rther embodiment of ~r~cle according to t~e inven~on. The flbre ~nd wire stn}cture of Flgure 5 is similar to that of E4~ure 4. le it lnclude~ hea~ng wlres 8'. 10' and 12' interw~ven in the fabrlc stru~e along t~e edges. Howcver in this case ~vhere t~e wlres o~ conductive flbres 8' o~rerlap ~vith the w~res or conduc~ bres lO'~and 12' th~y make electrical contact ~vith ea~h ot~ ~ (~n tbe embodlme~t ~of Flgure 4 th~y do not). Ihi~ is s}w~m at con~s 28 and 30:of~ . Ihu~ ln t~ ca~e. onlg two electrodes ~32: and 34~are pruv~ded. belng eonnected to ~flbres 10' and :~
12' re~ at the opposlte eorners of:the wrapped s~eeve 2 fro~ e:omers 28 ar~d: 30.: When tbe sleeve is wrapped an~ power suppl~ed -to :the deet~odes. eleetr~cal cl~rrent: therefore flows. say f~ ~ele~trode 32. through condue~e w~res~or flbres 10'. then throug~ eonductiye ~bres ~or ~wlres 8'. and fln~lly tbrough eonduet~e flbres: 12'.~ Ihus by;this~a~rangement stmultaneous Ion~tudinal and ti~l seals are: made.

It ls also envisaged ~at a U-shaped mesh heater could be used -in the e~mbodlmen~ of Figure 5 to prov~de heating means 8'. 10' and 12'. ~n place of the conduct~ve fibres or wires.
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Claims

1. A wraparound article for bonding to an elongate object such as a pipe or cable or for making, or bonding to, a joint or splice between such articles, the article comprising a layer of fabric that is heat-recoverable at least in part, which is in the form of a sheet that can be wrapped around the object, and which is provided with electrical heating means in and/or on its inner surface when wrapped, along at least three edges of the sheet, being at least one of the longitudinal edges of both annular edges when the sheet is in its wrapped configuration.

2. An article according to claim 1, wherein at least one of the heating means is at least partiallly embedded in the surface of the sheet.

3. An article according to claim 1, wherein at least one of the heating means lies on the surface of the fabric layer.

4. An article according to any preceding claim, wherein at least one of the heating means comprises conductive wire or fibres forming part of, or inserted into the interstices of the fabric.

5. An article according to any preceding claim, having a wall thickness in the range 2 to 15mm.

6. An article according to any preceding claim which is heat recoverable only in part.

7. An article according to claim 6, wherein a central tubular region of the sleeve, when in its wrapped configuration is not heat-recoverable.

8. A method of covering an elongate object or bonding two such objects in end to end relationship using a wraparound article according to any preceding claim, the method comprising connecting the heating means to a power supply to heat and to recover those regions into contact with the underlying object.

9. A method according to claim 8, in which the article is wrapped around the object so that longitudinal edges overlap and electrical power applied initially to the electrical heating means on the at least one longitudinal edge to bond the edges to each other.

10. A method according to claim 9, for joining two pipes or cables, or for covering a joint between two pipes, or cables wherein the article is wrapped around a piece or release paper, preferably on one object to one side of the joint before heat is applied to the heating means on the longitudinal edge.

11. A method according to claims 9 or 10, wherein electrical power is the supplied to the annular heating means at each end of the wrapped article.

12. A method according to claim 11, when dependent on claim 10, wherein the article is pushed over the joint before the electrical power is supplied to the annular heating means.

13. A method according to any of claims 10 to 12, wherein the objects are pipes or cables or joints therebetween, preferably district heating pipes or a joint therebetween.

14. A method according to any of claims 10 to 13, wherein the thermal mass of the article is less than the thermal mass of that part of the pipe which is heated by the heating means.

15. An method according to any preceding claim , wherein the wall thickness of the article is less than the wall thickness of the pipe, preferably less than 0.75 times the thickness of the pipe.

16. An article or method according to any preceding claim, which is at least partially heat shrinkable, preferably radially heat shrinkable when the article is in its wrapped configuration.

17. A method of reinsulating a bared joint between district heating pipes each of which comprises a central pipe having an outer insulation, the method comprising (1) positioning a wraparound article either to bridge the insulation on either side of the pipes or to bridge from a pipe to a central casing positioned over the joint, the article comprising a wraparound fabric sleeve which has end annular regions which are radially heat shrinkable, and a central tubular portion which is a radially heat stable, and (2) applying heat to shrink the ends of the article, whereby after shrinkage the sleeve is longitudinally flexible.