CA2148833A1

CA2148833A1 - Electrically bondable layer to cover an opening

Info

Publication number: CA2148833A1
Application number: CA002148833A
Authority: CA
Inventors: Johannes Maria Cordia; Dirk Raymond Jozef Baert; Marcel Paul Cristens; Karl Heylighen; Jozef Albert Gustaaf Doucet; Jan Lodewijk Maria Frans Ghislain Vansant
Original assignee: Individual
Current assignee: Commscope Connectivity Belgium BVBA
Priority date: 1992-11-20
Filing date: 1993-11-05
Publication date: 1994-06-09
Also published as: FI952452A0; PL172669B1; PL308961A1; FI952452A; EP0676995A1; JPH08503429A; KR950704106A; WO1994012338A1

Abstract

2148833 9412338 PCTABScor01 A hole in a pipe or polymeric casing associated with a district heating system is sealed by means of a polymeric patch that comprises a backing layer (2), a heat-activatable bonding layer (4) for securing the patch to the pipe or casing, and an electrically heatable layer (4). A further polymeric layer (8) may be included in the patch remote from the backing layer (2) when the substrate itself is not polymeric. The layers may be separate, or one layer may perform more than one function. Tooling (Figure 5) may also be provided to enhance the sealing of the hole when using the patch and method of the invention.

Description

WO 94/12338 - 1 2 1 4 8 ~ ~ 3 PCT/GB93/0228$ $ - ~
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Electrically Bondable Laver to Cove} an Opening This invention relates to an article comprising an electrically heatable laver which itself bonds, or which activates a separa~e bondable layer, tO cover an opening in a polymeric, preferably tubular, substrate such as a pipe or a casing, to a method of covering such an opening, and to a tool which may be used ~or installing such an article. ~ -,, '~
Articles comprising electrically heatable bondable, e.g. fusible, ~ -~
layers are known. EP-A-0157640, for example, describes a method of Joining, repairing, reinforcing or otherwise modifving a polymeric substrate bv placing a tubular conductive polymeric ar~icle, preferabl~
one comprising sintered UHI`~fWPE (Ultra High Molecular Weight Polyethylene) adjacent the substrate, and passing electrical current ~ ~ -through the article to heat it and to cause the article to adhere directly (e.g.by fusion) or indirectly (e.g. by an insert) to the substrate. In one , ~;
embodiment, described in Figure 11 of EP-A-0157640, a hole in a plastic pipe , - -is repa~red using a non-~eat-recoverable, sintered conductive polvmeric - ~;
patch comprising a material that is compatible with the pipe material. This patch is placed over the hole, and kept in place by means of a tape.
Electrical current is passed through the patch so it softens and fuses to the pipe.

Another article also relating to an electrically heatable fusible laver is described in WO-A-88/06517. l~is describes a method of joining articles together with the aid of a conductive polymeric article which comprises smtered ultra high molecular weight polyethylene. The article is typically provided in tape form and positioned, and electrically powered, between -~
two polvmeric substrates to bond those substrates to each other. - ~-A known reference describillg a separate fusible layer and 2'"
electrically heatable layer is GB-A-2076489. T~is describes an impingement , layer which may be a thermoset~ing resin adjacent a heating eleme~t in the form of a metal ~vire braid. This is used to connect pipes or to repair a '~ -leaking pipe. ~
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Og4/12338 21~8~3 ~3 ~ PcT/Gsg3/o228 All aspects of the present invention are particularly applicable for covering an opening in a casing used in join-ing district heating pipes.
This opening rnay be a hole of closed outer section, or a longitudinal slit t along the casing. Distnct heating pipes typically consist of a steel ~ ' transport pipe, insulated by a foam usually polyurethane, and an outer polyethylene jacket. When these pipes are joined, a length of insulation is first removed in order that a joint can be easily made; The joints are usually made by welding, and the heat re~uired would damage any insulation close to the weld line. After welding the pipes have to be made ~ ~
good again across the weld, preferably in a water-proof manner. One vay -`
of doing this is to encase the e.Yposed regions within a casing ~e.g. within two mating half cylindrical shells) and then injecting a curable insulating -material e.g. polvurethane foam into the casing through an injection hole left in the casing for that purpose. The casing may then be sealed to the insulation on either side thereof. The foamLng hole must then also be ~;
sealed to prevent ~vater damage to the insùlating material. One method of doing this is first to install a mastic plug in the hole, and then to position aprotection sleeve over the mastic plug. Such a pro~ection sleeve may comprise an irradiated modified polyolefin backing coated on the inside ' -with a hot melt adhesive and carrying on the outside a thermo indicating paint. This type of sleeve is sold by the company Raychem under the trademark FOPS. It is installed by heating with a gas torch to activate the adhesive, and then applying pressure to the sleeve using a hand-held ~ -compressible plunger to press the sleeve against the casing. Although this method is successful, one problem is that heat applied by the gas torch to activate the adhesive may liberate gasses within the polyurethane foam, and unless pressure is applied and the installation carefully controlled, this nav lead to lifting of the FOPS protection sleeve.

We have discovered a new method that can be used tO re-cover a hole, inter alia a foaming hole in a casing surrounding thermally insulated pipe, ~vhich method involves the use of an electrically heatable layer and a heat-activatable bondable layer, which may or may not be the same layer. 2''- ' We have also discovered new articles that can be used in that method, and a ~;
ne-vinstailationtooiing. .

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WO 94/lD38 3 21 ~ 8 8 ~ 3 PCTlGs93lo228s A first aspect of the invention provides a method of covering a hole in a polvmenc, preferablv tubular, substra~e such as a pipe or casing, comprising:

(a) positioning a laminar polvmeric patch comprising~
'' ':.: . ' (i) a backing layer ~ii) a heat activatable bondable layer ~;
~iii) an electrically heatable laver and ~-, tiv) a further polymeric laver positioned remote from the backing layer, ~
~. .,.~.
over the hole in the pol,vmeric substrate so that the further polvmeric layer lies within the opening in the substrale, and so that at least a portion -of the bondable layer is in contact ~vith a surface of the substrate; and (b) passing electrical current through the electrically heatable laver for a time, and at a watt density, sufficient to heat the bondable layer tO
bond it to the substrate.
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The method according to the flrst aspect of the invention generally ~ -envisages using a continuous patch to completely sealingly cover the hole in the substrate. However this aspect of the invention also encompasses ; , the possibilit~ that the patch ~ncorporates a valve e.g. a pressure valve, ~ -~vhich is installed via the patch into the hole in the substrate. Therefore -the te~m "covering a hole" is intended to include such a va~ve installation. ;~
Such a patch might be used, for e,Yample to install a pressure access valve . -onto the jacket of a cable or a pipeline. A specific application is described later in the specification.
~ ' .. .
It is envisaged that the further layer and the heat activatable bondable layer may be the same layers i '" "`'~
A second aspect o~ the present invention provides a method of covering a hole in a polymeric preferably tubular substrate such as a pipe "or casing, compnsing: ' . ~
'. ' ,:

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2 1 ~ 8 8 3 3 (a) positioning a laminar pol~meric pa~ch comprising a backing layer,a heat-activa~able bondable laver, ~nd an eiectrically heatable layer over ! ~- ~
the hole so that it covers the opening and overlaps the substrate in the area ' ;
around the opening, and so that the bondable layer lies in contact with the substrate; and -:
(b) passing electrical current through the electrically heatable layer for a time and at a watt densitv sufflcient to hea`t the bondable layer to bond it to the substrate, but so that the temperature within the substrate remains ~ ~-below 100C, preferably below 90C, especially preferablv below 80C.

In the prior art applications, for e.Yample, where a gas torch is used to apply a relatively thin FVPS patch over a hole in a distnct heating casing, it is known for temperatures inside the substrate to exceed 80C, 90C or even 100C. This may lead to problems of lifting of the patch as described earlier, especially where a relatively thin patch is used.
Therefore methods according to the invention whereby the electrical heating method res~ricts the heating to the bond line region can be used in applications where the prior art solution using a gas torch cannot be used, or is less desired. In particular preferred embodiments of al} aspects of the invention the patch according to the invention is thicker than the previously used FOPS, and/or is applied with an e.Yternal supporting installation tool, bvth of which factors also reduce or elim~nate the problem ~;
of lifting of the patch.

Referring specifica~ly to the insulated pipe application, a third aspect of the invention provides a method of sealing a joint between two insulated pipes, the insulation of each of which ends short of the joint, the method comp~ising: ;

(a) positioning a polymeric casing containing a fluid-entry hole aroundthe e.~posed portions of the pipe to bridge the cut-back insulations, and sealing the ends of the casing ro the cut back insulations;

(b) filling the casing through the fl--id entry hole with a pourable composition, for e,Yample polvure~hane, which solidi~ies after positioning in the casing; ;

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'`~' WO 94/12338 21 4 8 8 3 3 PCT/Gs93/02285 ... :.:.

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(c) positioning a laminar polymeric patch comprising a backing laver, a heat-activatable bondable laY~r, and an electrically heatable layer, over the fluid entry hole so that it covers the hole and overlaps the casing in the area around the hole, and so that the bondable layer lies adjacent to the casing; and ~ -. . ~

~d) passing el~ctrlcal currellC through the electrically hèatable layer to heat and thereby to bond the bond~ble layer to the casing.

The pourable composition ~vhich later solidifies may, for example, comprise a curable composition, e.g. a polvurethane foam. The pourable composition may solidify immediately on positioning in the casing, or some time thereafter. The pourable composition rnav be one which gives off gasses if heated to temperatures above 80C, 90C or 100C.

In the first, second and third aspects of the invention, the heat-activatable bondable layer and the electrically heatable layer may be separate layers or may be provided by the same single layer. Where a ,-single layer is used this single layer preferably comprises a conductive polymer layer. The conductive polymer is preferably a polymer matrix comprising a conductive carbon black filler. It may also or instead comprise a polymer matrix with other metal fiIlers. Preferably it comprises sintered ultra high molecular weight polyethylene con~aining carbon blac~ filler dispersed at the boundaries of the coalesced particles of the sintered ultra high molecular weight polyethylene particles, as described for example, in ~'-A-0157640, the disclosure of which is incorporated herein by reference. As another e,Yample a single fusible and - ~;
electrically heatable layer may comprlse a mat of carbon fibre, or a metal `
mesh.
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In other embodiments separate layers may be used for the bondable layer and the electrically heatable layer. For example a metal mesh layer may be used for the electrically heatable layer. In other embodiments wherein the heat-activatable bondable layer and the electrically heatable laver are separate layers, there maybe preferably additionally provided two electrodes which are in electrical contact with ~he electrically heatable layer, preferably sandwiched between the separate bondable and heatable lavers. ~-'-~
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., :, WO 94112338 PCT1GB93/02285 ~:

2~48833 ,, ~ , .....
The bondable layer, ~vhether or not it is also the electrically heatable layer, is preferably a fusible laver. Such a layer may comprise a non cross-linked polyethylene laver, for example. Other suitable materials ~ ~ -include pol,vpropylene, polybutene, copolymers of ethylene, propylene, -butene and hexene, copolymers of ethylene with ethyl acrylate, vinyl acetate, acrylic acid, methacrvlic acid, acrylic esters or me~hacrylic esters in which polyethylene predominates, biends of these polymers, and blends of these polvmers with elastomers. When the fusiblè laver is the same layer as the electrically heatable layer, it may coInprise a conductive polymeric material, preferably comprising a matrix of sintered UHMWPE -containing a conductive filler preferably carbon blac~;.
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A definition of "fusible layer" appears later in the specification. - -As an alternative the electrically heatable bondable layer may -comprise a layer which provides an adhesive bond. Preferably such a matenal is a hot melt adhesive or a heat curable adhesive. E~amples of hot-melt adhesives that may be used include formulations comprising polyamides modified with hydrocarbon waxes, and mixtures of acidic ethylene polymers and tackifiers. Also suitable are compositions based on ethylene vinyl-acetate copolymers, blended with hydrocarbon waxes and -optlonally buyle rubber. One sui~able adhesive is described in G~A- ~
207599I. It comprises a blend of a polyamide, an acrylic rubber, and ~ ~-preferablv a small amount of an ethylene/acrylic acid/butyl ac~ylate terpolymer. The hot melt adhesive may be cross-linked, though the degree of cross-linking must not be so high as to reduce the abilitv of the adhesive to liquefy, and thereby to flow and to wet.

Preferably the heat activatable bondable layer and the electrically heatable layer (being the same or separate layers) project beyond the ~ ;
edges of the backing layer. This allows separately applied electrodes to be brought easily into contact ~vith the electrically heatable }ayer, e.g. on an installation tool. Details of this are given later in the specification. ~
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A further layer ~similar or the same as that used according to ~he :~
first aspect of the invention) may also be included, on the side of the patch .

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WO 94/12338 pcTlGs93lo228s ~7~ 21~8833 I't~

remote from the backing layer, in embodimen~s according to the second and third aspect of the invention.
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In certain applications ~-~here an electrically heatable layer separate from the bondable layer is used ~e.g. a metal mesh or a mat of carbon ;
fibre), the backing layer 3nd the bondable layer mav be provided by the sd~ne layer. For e:~ample the order of layers may be: co~nmon backing and ~-bondable layer; electrically heatable layer, further layer.

Also in other applications the further layer and the bondable layer may be provided by a common layer. ~ndeed the electrically heatable `--layer, the further layer and the bondable laver mav be provided by a common laver. -:
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A fourth aspect of the invention also provides use of a laminar -polymeric patch comprising a polvmeric backing layer, a heat activatable bondable layer, an electrically heatable layer and a further polvmeric ;
layer to cover an opemng in a polymeric substrate, wherein the further polymeric layer is shaped and sized to fit within the opening in the substrate. ~, A fifth aspect of the invention provides the use of a laminar ~ ~`
polymeric patch comprising a polymeric backing layer, a bondable layer and an electrically heatable laver to cover a hole in a polymeric substrate, ~herein the patch is positioned to cover the hole and electAcal current is --supplied for a time and at a ~vatt density sufficient to heat the bondable layer to fuse the fusible layer to the casing, but so that the temperature within the casing remains below 100C, preferably below 90C, especiallv - -preferably below 80C.

Where the further polymeric layer is used, it is preferably smaller in surface area than the bondable laver and is positioned so that the said further layer projects within the opening and at least the bondable layer and preferably all the other layers cover the opening and overlap the substrate in the area around the opening, wi~h the bondable layer in contact with rhe substrate ~ `-;-, i WO 94/12338 PCT/GB93/02285 ~ -2 1 ~ 8 ~ 3 3 - 8 ~
Another possibility, vhere the further layer is also the bondable, preferably fusible laver, is for the further layer to be a close fit in the I -opening, and for there to be no overlapping of the region around the opening, by the bondable layer if not all the layers, a~d for the edges of the further bondable layer tO ~preferably fuse to) bond to the edge of the opening in the substrate. -Preferably, however, the palch according~ to the invention is used in methods so that it spans an opening and overl!aps a~ area of the substrate ;~
in a region around the opening. When heat~ls applied to the electrically heatable laver by passage of electrical current, this a~Tangement means that the portion of the heatable layer lying over the opening is only heat-sunk by the adjacent layer(s~ making up the patch, vhereas in the region around the opemng i.e. over the substrate but beneath the patch, the heatable layer of the patch is also heat-sunk bv the substrate itself. ;Therefore, according to the first and fourth aspects of the invention and preferred methods and uses of patches according to other aspects of the invention, the patch also comprises a further pol,vmeric layer positioned on the opposite side of the fusible layer from the backing layer. This is preferably shaped and sized substantially to correspond to the shape and size of the hole in the substrate or casing. Y~hen the further layer is present methods and uses of the patch according to the invention preferably also comprise the step of positioning the patch so that the said further layer of the patch projects within the opening in the substra~e or casing. This further layer acts, in use, as a heat sink preventing any overheating of the central region of the patch. Advantageously it may also act as a locating member to locate the patch in the correct position.

The provision of a heat sink in this way is an important feature of t ~ .
the present invention. ? ,~

Preferably the further layer is so shaped and sized that it is a close -fit in the hole ~hereby when bonding occurs there is partial bonding (e.g.
welding) of the further layer lwhich is preferably fusible) to the ~ `
substrate, e.g. the edge of the further layer to the inside edge of the hole in the substrate. `

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WO 94/12338 214 8 8 3 3 PCT/GB93/022B5 ~ ~ -Generally the arrangement is such that passage of electrical current causes the bondable layer of the patch ro bond to the ou~ermost surface of the tubular substrate. However other configurations are possible in which this is not the case. For example, ~vhere a further layer is used that is a close fit in the opening, electrodes mav be arranged so that the only heated surface is the edge of the further layer which bonds to the inside edge of ~ -the opening in the substrate. This could be achi~ved, for example, for a circular further layer, using a first disc shaped electrode on the inside -major surface of the further layer, and an annular electrode on the upper ;~surface corresponding to the outer edgè of the further laver. Therefore when the words "bonding or fusing to the substrate" are used no limitation is implied as tO which surface of the substrate is intended. It is preferablv the outer surface, but need not be.
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As mentioned above a technical advantage of the invention is that, since electrical heating is used, heat is supplied only in the bond line area 1-over a small area. This is useful in typical dist~ict heating pipe joints, and in pressurised pipe applications where the temperature within a casing surrounding the pipes must be kept low if a live seal around the pipes is to ~ `
be made. For these and other applications the energy input (which is in~er alia both time and temperature dependant) is preferably kept to the minimum possible while achieving the temperature re~uired to effect the said fusion. ~ -Another advantage of supplying heat at the bond line electricallv rather than e~cternally by a gas torch is that thicker, and conse~uently stronger bac~ing layers can be used. This allows the patch to withstand higher pressures through the hole from within the casing both during installation, and in service life, without ballooning, lifting or bursting. , -The invention also provides, in another aspect a laminar polymeric patch suitable for use in the methods of the present invention, comprising: ' (a) a polymeric backing layer tuld ~b) a conductive polvmeric layer which is both fusible and electricaIl~
conductive, t~hich projécts beyond at least part of the ed~e of the backing . :.,.

, Wo 94/12338 ~ .883 3 10 PCT/Gs93/022~s laver, ~vhich is less than half as thick, preferablv less than one quarter as thick as the backing layert and ~c) preferably an additional further layer smaller than the conductive ~ ¦
layer a~d positioned on the suTface of the conductive polymer layer that is remote from the backing laver. ~ ~-In preferred aspects of the invention, the;fusible electrically conc}uctive layer comprises conductive sinte e~ UHMWPE containing a carbon blacl~ filler. Preferably the fusible electrically conductive layer is -pre-bonded to the backing layer.

The present invention can be used to cover openings of any shape.
~n one e,~:ample the opening is in the form of a hole of closed outer section, e.g. a foaming hole in a district heating pipe casing. In another embodiment the opening is and elongate slit e.Ytending along at least part, preferably along the encire length of a polymeric casing.

Preferablv the patch is rectilinear, and both the backing layer and ~ -~
the conductive polymeric layer are also rectilinear, and the conductive polymeric layer projects beyond opposite sides of the backing layer. This design is preferred for easy installation using an installation tool according to the invention as descnbed in more detail later in the --specification. Depending orl the shape of the opening e.g. a hole such as a -foaming hole, or a longitudinal slit, the rectilinear pa~ch may have one side significantly longer than the other side. ~ -,.. -The patch according to rhe present invention is preferably also -provided with a further polymeric layer as described above with reference to earlier aspects of the invention.

According to the present invention electrical current is passed through the electrically heatable layer to heat, and thereby to bond the ~ ~
bondable layer to the substrate. Preferably ~he bondable layer is fusible ' ~-`
and the heat applied fuses the fusible layer to the substrate. The terms "to fuse" and "fusible layer" etc are used herein tO mean that sufficient molecular compatibility e.~asts between the element and the substrate outer surface that a bond forms which will provide mechanical performance ~''`',.

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equal to or greater than that of the substrate. This may be through ~;
viscoelastic contact as defined bvJ N Anand in Adhesion 1, 1969, pages 16 through 73 and Adhesion 2, 1970. pages 16 through 77, or a process of molecular diffusion across the pol~qner/polymer interface, such that, within the interfacial region there is a continuous gradient of one polymer ~ ,in the other.

The fusible layer fuses to the substrate and thereby bonds the -backing layer (~vhich is preferably pre-bonded thereto either directly or via an intermediate separate heatable layer) to the substrate. According to the article aspect of this invention the fusible layer is preferably at most 1/2 times, preferably at most 1/~ times the thickness of the backing layer.
This is also preferred for all aspects of the invention. The backing layer therefore provides the necessarv strength to act as a protection sleeYe, and the fusible layer provides a bonding layer for the backing layer. As an e.carnple the backing laver ma~ comprise cross-linked HDPE. the backing ;
layer is preferably not heat reco-~erable, a heat recoverable article being one whose dimensional configuration may be made to change when subjected to an appropriate treatment, as well known in the art.

The present invention, in all its aspects, can be used to span i ;
significant sized holest e.g. ~pically holes? of closed outer section, with a transverse dimension (e.g. diameeer of circular holes) of at least IS mm, even at least 20 mm or even at least 25 mm, or longitudinal slits, of width ~, ;
8, 10, 15, 70 or 2~ mm. that e.~end partially or even completely along the ' ~- ~
length of the substrate, which may be substantially cylindrical and of I -polymeric material.
,.
The patch according to the invention may also be provided with melt ~`
flow indicators to show when the bondable layer has heated to a ¦- -sufficiently high temperature to bond tO the substrate. These may r `'.
conveniently be formed by ~orming cylindrical pop-up indica~ors t}~ough the patch, by drilling with an annular bore drill alms~st through the : --backing layer. This presents snlbs of bac~ing layer connected by a narrow neck of mate2~al to the bo~dable layer. Especially vhen the bondable layer , i-is a fusible layer, when this fusible, conductive layer heats, it melts that -neck of material, and flows into the bore causing the stubs to l'pop-up"

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WO 94/12338 21 ~ 8 ~ 3 3 1 ~ PCT/GB93/0~285 !~

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above the surface of the patch and indicate that sufficient bonding has occurred. .
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As mentioned above the bondable layer and the electrically heatable layer may be the same or separare layers. An advantage obtained when they are the same layer, e.g. a fusible conductive polymeric layer, is that by appropriate electrode arrangement there are then no discrete conductive parts e.g. metal parts acting as electrical busses or electrodes separating the backing layer from the substra~e~.and interfering with the fusion process. .. `

An appropriate electroding arrangement which inter alia achieves `
the above advantage is provided by the tooling used in the method according to another aspect of the invention which provides a method of ~-installing a patch comprising a backing layer, an electrica~ly heatable layer, and a heat activatable bondable lave~ over an opening in a polymenc substrate, comprisin~g: ;

(a) positioning the patch so that it covers the hole and the bondable layer is in contact with the substrate; : ~
;.~ -.
~b) positioning a tool comprising a support, nvo electrodes, and a flxing member over the patch so that the support lies o~rer the patch and the nvo ~:~
electrodes ~re in electrical con~act wi~h the electrically heatable layer;
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(c) a~Tanging the fi,~cing member to secure the support and the electrodes against the patch; and (d) passing electrical current via the electrodes through the electrically heatable layer to bond the bondable layer of the patch to the substrate. . ;
~ .
Preferably, the patch also comprises a backing layer and the .
electrically heatable layer projects beyond the edges of the backing layer r "'.'`.
and the tool is positioned so the electrodes contact those projecting portions ; .
of the electrically heatable laver. ~- ;
.:
Where "electrical con~act" between electrodes and the electrically ;
hea~able layer is referred to, this may be direc~ contact, i.e. the electrodes : .'.
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WO 94tl2338 pcTlGs93lo2285 ~ ~
` ~13- 21~8833 mav be contaeted ~ga~ns~ the electrically heatable laver. Alternativel~
conductive bus bars may be included between the electrical1y heatable layer and the electrodes to enhance the electrical current flow to the electrical heatable laver. ~ ~;

Preferably the polymeric substrate is a substantially cylindrical ; -casing or housing and the tool support is arranged IO conform to the surface of the substrate when fixed by the fix~ng member. The tool support ~ `
may, for e,cample, comprise a series of articulated rigid blocks. Instead, a continuous fleYible support may be used. These arrangements allow the -patch to be curved around the substrate surface and the tool support tO
press down on that patch over itS entire surface. Preferably the fixing ~--member comprises a s~rip that can be tightened around the cvlindrical housing.
.''~ .`.
The tooling mav be provided with melt flow indicator risers in line with those in the patch (if present) so that the pop-up of the indicator ~-activates an aligned riser rod in the tooling. As an alternative, electrical ~ ~
power may be supplied at a predeterrr~ined voltage a~d for a predetermined ;time and then the tool removed to view the underlying indicators in the patch (which would not be visible with the tool still present). Preferably - ` -the current is passed for a sufficient time and at a sufficient voltage to provide a watt density of at least 3W/cm2 to activate the melt flow - ~ `
indicators. ~ --,, ., ,~

As an alternative the tooling may comprise component parts 1 -including a plate, e.g. an insulating layer, caIT~ing two electrodes, e.g. of --`
copper. Preferably a metal plate is also included that is electrically "
insulated from the electrodes but in thermal contact with electrode- i ca~ying plate so that it is the~mally heated as the patch heats. The electr~cal insulation of the metal plate from the elec~rodes is necessa~y to ' ~, prevent a short circuit through the metal plate, rather than electI~cal current passage, and hence heating through a patch. Preferably a further backing insulating component is also included. The component parts are -preferably held together by metal screws or the like. These screws ? ,.` ~, preferably pass into the electrodes, and can therefore conveniently be used as a means of cormection to the power source ~or pro~iding power to `
the electrically heatable layer. The electrode car~ying plate is preferably :. .

: ,,' ' 2~L 4883~

placed. in use, inwardly of the other components. It may be provided ~ith a release layer, e.g. a Teflon layer or sheet, to facilitate removal of the toolafter the patch has been installed.

The tooling is preferably held in place by ~eans of a fi~ng member such as a tightening strap or the like positioned over the further backing insulating componerlt. The metal plate functlons to transfer the clamp~ng force of the fi~ang member over the widcl;t of the tool. It may also serve to enhance uniform heat distribution over the patch surface, and to prevent overheating and distortion of any release layer present on the electrode-caITying plate. The furrher backing insulating component functions to hold the metal plate in position. It may also serve as a guide for holding the fi,~ing member ~e.g. tightening strap) if used. ~
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It will be appreciated that the patch and the materials and relationships of its various layers may be as herein described with respect to the other aspects of the present invention.

Where the electrically heatable layer and the bondable layer are separate layers the electroding can be effected in a similar manner to that described above whereby the heatable layer projects beyond the sides of the backing layer and a separate removable tool is installed above the patch to contact the electrically heatable layer dlmng the installation -.. ....
process. ~:-'.~ .':..
Alternatively integral electrodes may be included in the patch itself. -;
As an e~Yample elongate electrodes, e.g. strips of braid may be incorporated in the patch in electAcal contact wit~ the electrically heatable layer. For -~ -e.Yample they may be embedded between the backing layer and the heatable layer, or between the bondable layer and the heatable layer. , -. .
It is also possible to use a separate plugging mass, e.g. of mastic for ~ .
plugging the hole in the substrate prior to application of the patch.
Where separate heatable and bondable layers are used the tvpi~
. ~
dimensions for the backing layer and the bondable layer are as follows: `
Bac};ing layer 1-1.5 mm thick, e.g. about 1.75mm thick; bondable layer 0.15-0.35mm thick, e.g. about O.~Smm thick.

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WO 94/12338 2 I ~ 8 8 ~ 3 PcT/GBg3loæ85 ,. '., . - 1 ~ - , . .
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In a particularly preferred ernbodimen~ of the presenl invention, the insulation tooling and the patch are preferably provided with an electrical safety feature wherebv power can not accidentally be applied to the e.~cposed electrodes of the tooling, and in the absence of deliberate sabotage, can only be applied to the electrodes on the tooling when the tooling is positioned over ~and preferably fi,~;ed firmly over) the patch.
I~his is preferably achieved by provi~ing contact points o~l the tooling and the patch which when mated allow electrical current to flow to the ~
electrodes of the tooling. As an exarrlple, the mated electrical contacts may -;
activate a switch, e.g. a solenoid switch, which ~n turn activates or opens the electAcal circuit feeding the electrodes of the installation tooling.
The inven~ion also provides a kit of par~s comprising:
(a) a laminar polvmer patch comprising (i) a bacl;ing laver (ii) a heat activatable bonding layer (iii) an electrically heatable layer and (iv) a further polymenc layer positioned remo~e from the backing layer and ~-,:

(b) an installation tOOlLng comprising a support, two electrodes and a fi,~ng member.
.
The patch and/or the tooling of this l;it of parts preferably have the features rnentioned above and in the appended claims with reference to the said meehods according to the invention.
The invention also provides a kit of parts for fo~ning a substantially ~ -cylindrical casing of closed cross-section, suitable for use in a district heating joint, the kit comprising: -C~ ' ' ..
~ . .:- .
a) a iongitudinal slit polymeric cylindrical casing; and b) an elongate patch comprising an electrically hea~able layer and a hea~ activatable bondable lavert the patch being positionable over the slit in the casi~g and bondable to the casing to cover the slit.

WO 94/12338 2~ 3 PCT/GB93/02285 In one embodiment according to the invention the patch is adapted to carry an access member, e.g. a valve, for access through the hole over vhich the patch is positioned. Thus the inner wall of the hole in the patch ~ ;
may be provided for e,YarnpIe ~vith a valve base. A sealing means may also be incorporated to seal the valve base to the ~atch, e.g. to the said further ~;
layer on the patch. The invention may be particularly advantageous for such an application where it is desired to m~nimise the heat time or amount applied to the substrate, e.g. vhere appl~'ng the valve to a cable jacket containing conductor parts insulated with a lemperature sensitive layer ~`
(e.g. PE layer~. For such an application the invention is advantageous since a relativelv small mass is heated during the installation cycle. -., F~nbodiments of the present invention will now be described, bv wa~
of e,Yarnple, with reference to the accompanying drawings wherein:
,,.-.,.,.~
Figure 1 is a side cross-sectional view through a patch according to and usable in methods according to the invention;
. . ' . ' Figure ~ d 3 are top plan and bottom plan views of the patch of Figure 1; ;

Figure ~ is a cross-sectional view showing a foam filled casing conta~ning a hole that is covered by the patch o~ Figures 1-3 `

Figure 5 is a side view of an installa~ion tool for installing the patch of Figures 1 to 3 on the casing of Figure 4; ~
......
. .
Figure 6 is a cross-sectional view through Figure 5;
,~, ...
Figure 7 is a plan view of the tool of Figures ~ and 6;

Figures 8a, 8b and 8c are plan views of component parts of an al~emative installation tool for installing the patch of Figures 1 to 3 on the casing of Figure 4; and Figure 9 is a sectional v ie v through the assembled components of ~ ~
Figures 8a, 8b and 8c along line A-A; ;
" :~

WO 94/12338 21 ~ 8 8 3 3 pcTlGs93lo2285 i~ ~

~ -Figures 10 and 11 are inside and outside views respectively of an ~-installation tooling and patch respectively, incolporating additional safetv features;

Figures 12, 13 and 14 are a longitudinal section, a oss-section and a tol~ view of a second embodiment according tO the invention, whi;~h can be used to cover a longitudinal slit e,Ytending along a polvmer casing as shown in Figure 15; and ''''' '' Figures 16 to 18 shows a patch incorporating a value base being -installed in a hole in a jacketed cable. `-. . .
Figures 19 and 20 show another embodiment of patch that can be ,~;
used in the present invention. ;`-~ .
Refernng now tO the drawings, Figures 1, 7 and 3 show a patch according to the invention comprising a HDPE baclcing l~yer 2, bonded to a sintered UHh~WPE conductive polymeric fusible layer 4. Both layers 2 and 4 `.
are rectangular. The long edges of the rectangular conductive layer 4 are ~-longer than those of the backing layer 2, but their short edges are the same ^`
length. This means that the conductive polymeric layer projects out beyond opposite edges of the backing layer to provide two exposed strips 6 !~ . .
at either end thereof. On the opposite side of the conductive layer ~ from the backing layer 2, a central disc shaped layer 8 of HDPE is provided. Its function as described later is to loca~e the patch in a hole in a casing and also to act as a heat sink.
.-:
These Figures also indicate melt flow indicators in the form of s~bs , ~ -10 made by using a annular bore drill to drill almost through the backing layer at discrete points on the patch. At those point cylindrical stubs 10 of backlng layer material are connected by a narrow neck of material 12 tO
the fusible layer. W~en heated by the conductive layer ~ these regions ~ -melt, releasing the stubs 10. Flow of fusib~e layer ~} into the bore then causes the stubs 10 to pop-up indicating that fusion is complete.
~:
- Figures 1 to 3 also show a fastening pin 13 projecnng up from the backing layer. This i5 to fasten the inst~llation tool as described later.
. .
~` ' Wo 94/12338 21 4~3 3 - 18 - PCT/Gs93l~228s ~

Figure ~ is a sectional vie.~/ showing a steel pipe 1~ surrounded by polvurethane foam 16 and an outer casing 18. The casing 18 contains a circular hole 20 through which the foam 16 was previously inserted. The p~tch of Figures 1 to 3 has been installed over the hole, the disc 8 sitting ! .
within the hole and the conductive fusible layer having being heated to fuse it to the surface of casing ~. Th~ di~c 8 acts as a centring disc and alse.as a heat sink during this operation. Since heat is electrically applied onlv the bond line is heated and the risk of gasses being }iberated from the polyurethane foam 16 is minimised. The indicators 10 have popped up to ~ -show fusion is complete. These are now indicated as 10'. -.~ .
Figures ~ to 7 show a tool for installing the patch of Figures 1 to 3 to the installed position shown in Figure ~. It comprises a tool support 27 `~ -comprising articulated segmented pressure blocks 74. The articulation is -along lines parallel to the aYis of the casing, so that the segments also e,Ytend parallel to the aYis of the casing. The articulation allows the blocks -24 to bend arc,und the casing 18 of Figure 3 while retaining firm pressure ;
on the patch. The blocks are tightened around the casing 18 by means of a tightening strap 26 which pass around the circumference of the casing.
The strap may simply to tied to itself, or an opening 28 e,Ytending pa~Lllel to -:
the axis of the casing may be provided in the tool support 22 through which the strap 26 is passed and fixed. Elongate electrodes 30 extend along the end segmen~s of the tool support.

The tool has a stepped profile 32 so that the segmented central regions lie above the backing layer conductive fusible layer part of the patch, while the electrodes lie directly on the conductive layer. This arrangement avoids any metallic parts remaining in the final installed patch.
-. . .
If desired the tool may also be provided with pop-up risers 34 that correspond in position to the indicators on the patch, so that the po~up action is translated through the installation tool. , -The tool is positioned over fastening pin 13 on the patch so that ;
electrodes 30 overlie the exposed conductive stAps 6 of the patch, and the pop-up risers 34 line up with the indicators 10 of the patch. Then ''.

, ~. .
......

WC) ~4/12338 21 4 8 PCT/Gs93l02285 : - 19-- ~33 ~ -. ., electrodes 30 are powered to pass current to, and heat the entire conductive ;~-polymeric layer ~ causing fusion to the substrate as described above.

Figures 8a, b, c and Figure ~ show an alternative tool that can be used for inst~lling the patch. The tool is provided in three component parts S0, 52 and 5~ (see Figs 8a, 8b, 8c respectively). -`

Component part S0 provides a backing plate and comprises a polymeric insulating material. It contains a depression ~6 in its inward facing surface to receive component part 52, and a feed through and guide S9 (see Fig 9) for receiving a tightening strap to hold the tool in place on -:
the patch. It also contains holes ~ to receive screws which hold the tool together and act as power connections as descnbed later.
,...
Component part 52 is a spring steel ~netal plate that fits within the depressions ~6 of component ~0. Its functions are inter alia to spread the ` -force introduced by the tightening strap fed through guide 59, and to help :
to spread the heat generated in the patch uniformly. The metal plate 5 7 . ,-also contains screw holes 60 to receh~e the screws and bolts 70 that hold the component parts of the ~ool together and to receive the electrode contact ``
pins 71 (held in housings 73) - see Figure 9, which act as a power connection. Insulating washers 62 are also provided with each hole 60.

Final component part ~. which is positioned adjacent the patch in use comprises a layer 6~ of electrically insulat~ng mateAal on which are mounted copper bar electrodes 66. The layer 6~ and copper electrodes 66 contain holes therethrough to receive the screws bolts and contact pins 70, 71, 73. A Teflon release laver 68 (not shown in Fig 9) extends between the copper electrodes 66, facilitate removal of the tool from the patch after installation.

The component parts ~, S~ and 56 are assembled so that part 5 1 is ~ -sandwiched between parts ~2 and 55. Part ~6, in use, lies against the paech so that the electrodes 66 overlie the e,Yposed conductive strips 6 of ehe patch , ~ ~;
in the manner descnbed with reference to Figures S to 7, and so that the ~-Teflon patch 68 overlies the remainder of the patch, and part ~ is ~-;
outermost. ~ insulation cap / ~ covers bolt hole 70 through which no -contact pin protrudes.

'.

WQ 94/1~338 PCT/Gsg3/02285 - ~a- , 33 , : :

f :
In this second embodiment of installation tool the component paI tS
~,0, 52 and 54 provide the "support" referred to in the claims. As with the previous installation tool this tool must be fixed over the patch and onto a I :
polymeric substrate using a fi~ang member. r, `~

Figures 10 and 11 sho-~ additional electrical safety features that can be incorporated into the tooling e.g. the tooling of Figures 8 and 9 and patch to avoid inadvertent powering of the tooli~ig when not in place over the patch.

Referring to Figure 10 ~vhere like reference numerals are used for like parts referred to in Figures 8 and 9, the tooling comprises, on its underside, additional contact elements 80. These provide a first pair of safety-contact-elements.
, Refen~rlg now to Figure 1 I this shows the outside view of the patch of figures 1 and 2 with the additional features of a second pair of safety contact elements 82. ;

F~ements 80 (on the tooling) and 82 (on the patch) are arranged to contact each other when the tooling is firmly clamped over the patch, thereby completing a low voltage electncal circuit that activates a solenoid switch (not shown), which in turn allows the circuit powering the electrodes 66 of the tooling to be activated. This additional safety feature --means that power can only be applied to the exposed contact electrodes of :~
the tooling when it is clamped over the patch (or by deliberate sabotage by -shor~ing the contact points).

Figures 12,13 and 15 show an elongate patch which can be used to cover an opening in the form of a longitudinal slit e~tending along the length of a polyrneric casing. As ~n the peIvious embodLments the patch 40 comprises a polyethylene backing layer 4~ and a sintered UHMWPE layer 44. Both laYers 42 and 44 are rectangular. Their long edges are significantly longer than their short edges because of the application of the patch to cover a longinldinal slit in a polymer casing. The long edges of lavers ~2 and 44 are ~he same length, and the shor~ edges of layer 42 are shorter than those of layer ~ so that ~he conductive polymer layer ~4 ;

. ~:
'~

Wo 94/12338 2 1 4 8 8 3 3 PcT/Gs93lo2z8s projects out beyond the backing layer ~2 on two long edges 46. Bus bars ~8 e.Ytend along these edges ~6. Indicators SO to show when ~usion has taken place are also provided, as in the previous embodiment.

Figure 15 sho~vs a polymer casing 52 with a longitudinal slit the edges of which are indicated by dotted lines 54. The patch 40 of Figures 12, l 3 and 14 is positioned to cover the slit 5~. A tool similar to that previouslydescribed, but appropriately shaped, is applied so that electrodes contact the bus bars 48~ Then power is supplied to fuse layer 46 to the casing ~2 on either side of the slit.

Figure 16 is a cross-sectional view through a patch of the type shown in Figures 1-3 provided with a valve base 84 which extends through a hole centrally punched in the patch. (In Figure 16, parts like those used in the patch of Figures 1-3 are referenced with lilce reference numbers).
The embodiment also includes a sealLng Ang 86 between the valve base and the further polymeric layer 8 of the patch, an insulating tube 88 extending within the inner walls of the hole in the patch, and a washer and nut 9O
holding the inserted valve base in the patch. The outwardly facing end 92 of the valve base 84 is a hollow cylindricàl foIm provided with screw threads on itS outer surface to receive a v~lve.

Figure 17 shows an alternative form of patch for incorporating a valve piece. In this case the baclcing layer 2, ~urther layer 8 and insulating tube 88 of Figure l 6 are replaced by a single injection moulded piece 2' in which is embedded the conductive layer 4. The valve piece is not shown in Figure 17 for simplicity, but is incorpora~ed ~n the patch in the same way as for Figure 16.

Figure 18 shows the patch of Figure 17 incorporatillg a valve inserted into a hole 94 in a polymeric jacketed bundle of c~les 96. When power is applied (in the manner described with reference to the earlier Figures), fusioII occurs over the area indicated in the figures by arrows W. ~ `

Figure 19 shows an al~e~native embodiment of patch that can be used in the methods accord~ng to the inven :ion. ln this case a separate electrically heatable layer 42 and f~sible layer 44 are provided. The heatabie laver 42 is a metal mesh e.g. copper. The fusible layer compnses ~ ~ 4 ~ ~ 3 " PcT/Gns3lo228s l' polyethylene. A heat stable backing layer ~0 covers part of the surface of layer 42. It does not cover opposed edges which are therefore exposed for application of a separate installation tool comprising electrodes, e.g. as descr~bed in Figures 5-7, or similar, tO be brought into contact with the mesh 42. Layers 42 and 44 are coterminous. The backing layer comprises ~, cross-linked high density polyethyiene. It is not expa~ded and hence not heat recoverable. ~ ' . ~ , Figure 20 shows an alternative embodiment in which three separate layers, the backing layer 46 and the heater layer 48 and the fusible layer 50 are provided all coterminous with each other. Elongate electrodes 52 are provided as part of the patch, sandwiched between heater layer 48 and bacl;ing sheet 46, or weaving through heater layer 48. The electrodes may be connected to a source of electrical power to provide power tO the heater ~8. Layers ~6, ~8 and ~0 comprise the same materials as described for Figure 19.

EYampie As an example, a patch of the type shown in Figures 1-3 was made according to the following method. The following components were ~-provided:
.
a) A backing layer (2) manufactured from a W-resistant pipe grade high density polyethvlene, type 3408, as defined in ASTM D1248 and ASTM
D2513. This material has the following properties:
:
(i) density (23C) 0.941-0.959 g/cm3, typically Q.954 g/cm3.
(ii) Melt Flow ~ndex (190C, 2160g load) 0.4-1 g/10min, typically 0.596 g/10min (iii) tensile strength (23C, cross head speed 50mm/min) 22 ~vIpa or more, typically 25 MPa (iv) ultimate elongation ~23C, cross head speed 50mm/min) 500~o or more, typically 800%.
s-, The dimensions of ;the ~acking layer were 50mm x 50mm x 3 mm thick. Cylindrical pop up indicator cha~nels were made through this bachng ~ mm in diameter.

:

WO 94/1~138 2 1 ~ 8 8 3 3 PCTIGr~3/~2285 ¦ ~ ~

.t, 1, J b) A fusible, electrically heatable layer (4) manufactured from 3 electrically conductive (carbon black loaded) ultra high molecular weight polyethylene, with a molecular weight greater than ~ x 106 g~mol. This material has the following properties: i I `,(ii) tensile strength ~23C), 0.93 - 0.94 g/cm3, typically 0.935 g/cm3 ~iii) ultimate elongation (23C, cross head speed SOmm/min) of 350% or more, typically 3~5%
(iv) ult~mate elongation (150C, cross head speed SOmm/min) of 1000%ormore, tvpically llSO'Yo.

The dimensions of the fusible, electAcally heatable layer (4) were SOmm x 70mm x 3mm thick.
.

c) A further layer 98) made of the same mateAal as that of the backing la~er (Z). Ihis was circular, of diameter 25mm, and thickness 3 mm.

The above three elements were positioned in a laminating mould in the order and relative position shown in Figure 1. A pressure of 4 bars/cm2 was applied and electrical power passed through the electrically heatable fusible layer from a Z7W stlpply for a few seconds to cause prelamination of the component parts of the patch to each other.

.

Claims

1. A method of covering a hole in a polymeric, preferably tubular, substrate such as a pipe or casing, comprising:

(a) positioning a laminar polymeric patch comprising:

(i) a backing layer (ii) a heat-activatable bondable layer (iii) an electrically heatable layer and (iv) a further polymeric layer positioned remote from the backing layer, over the hole in the polymeric substrate so that the further polymeric layer lies within the hole in the substrate, and so that at least a portion of the bondable layer is in contact with a surface of the substrate; and (b) passing electrical current through the electrically heatable layer for a time, and at a watt density, sufficient to heat the bondable layer to bond it to the substrate.

2. A method of sealing a joint between two insulated pipes, the insulation of each of which ends short of the joint, the method comprising:

(a) positioning a polymeric casing containing a fluid-entry hole around the exposed portions of the pipe to bridge the cut-back insulations, and sealing the ends of the casing to the pipe insulations;

(b) filling the casing through the fluid entry hole with a pourable composition which solidifies after positioning in the casing;

(c) positioning a laminar polymeric patch comprising a backing layer, a heat-activatable bondable layer, and an electrically heatable layer, over the fluid entry hole so that it covers the hole and overlaps the casing in the area around the hole, and so that the bondable layer lies adjacent to the casing; and (d) passing electrical current through the electrically heatable layer to heat and thereby to bond the fusible layer to the casing.

3. Use of a laminar polymeric patch comprising a polymeric backing layer, a heat-activatable bondable layer, an electrically heatable layer and a further polymeric layer to cover an opening in a polymeric substrate, wherein the further polymeric layer is shaped and sized to fit within the hole in the substrate, preferably as a close fit.

4. A laminar polymeric patch suitable for use in methods according to any of the preceding claims, comprising:

(a) a polymeric backing layer and (b) a conductive polymeric layer which is both fusible and electrically conductive, which projects beyond at least part of the edge of the backing layer, which is less than half as thick, preferably less than one quarter as thick as the backing layer, and;

(c) preferably an additional further layer, smaller than the conductive layer and positioned on the surface of the conductive polymer layer that is remote from the backing layer.

5. A method of installing a patch comprising a backing layer, an electrically heatable layer, and a heat activatable bondable layer over a hole in a polymeric substrate, comprising:

(a) positioning the patch so that it covers the opening and the bondable layer is in contact with the substrate;

(b) positioning a tool comprising a support, two electrodes, and a fixing member over the patch so that the support lies over the patch and the two electrodes are in electrical contact with the electrically heatable layer;

(c) arranging the fixing member to secure the support and the electrodes against the patch; and (d) passing electrical current via the electrodes through the electrically heatable layer to bond the bondable layer of the patch to the substrate

6. A method according to claim 5, wherein the tool is provided on its inward facing surface with one or more first-safety-contacts, and the patch is provided on its outward facing surface with one or more second-safety-contacts, wherein securement of the fixing member causes contact between the said first and second safety contacts, and wherein in the absence of such contact, electrical power can not be supplied to the said electrodes on the tooling.

7. A kit of parts for forming a substantially cylindrical casing of closed cross-section, suitable for use in a district heating joint, the kit comprising:

a) A longitudinal slit polymeric cylindrical casing; and b) an elongate patch comprising an electrically heatable layer and a heat activatable bondable layer, the patch being positioned over the slit in the casing and bondable to the casing to cover the slit.

8. A kit of parts according to claim 7, wherein the elongate patch also comprises a backing layer, and the electrically heatable layer projects beyond the edges of the backing layer so that a tool carrying electrodes can be brought into electrical contact with the exposed parts of the electrically heatable layer.

9. A kit of parts according to claim 7 or 8, wherein the electrically heatable layer and the heat activatable bondable layer are provided by a single conductive polymeric layer.

10. A method or kit of parts according to any preceding claim wherein the patch is provided with, or adapted to receive, a valve, preferably a pressure access valve, to allow controlled access of fluid through the hole in the polymeric substrate.