CA1328802C - Heat recoverable article - Google Patents
Heat recoverable articleInfo
- Publication number
- CA1328802C CA1328802C CA000616170A CA616170A CA1328802C CA 1328802 C CA1328802 C CA 1328802C CA 000616170 A CA000616170 A CA 000616170A CA 616170 A CA616170 A CA 616170A CA 1328802 C CA1328802 C CA 1328802C
- Authority
- CA
- Canada
- Prior art keywords
- fabric
- layer
- article
- fibres
- recoverable
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- Lining Or Joining Of Plastics Or The Like (AREA)
- Laminated Bodies (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A heat-recoverable article suitable for enclosing a telecommunications cable splice comprises a recoverable fabric cover and a strengthening layer laminated to a sur-face of the fabric cover.
A heat-recoverable article suitable for enclosing a telecommunications cable splice comprises a recoverable fabric cover and a strengthening layer laminated to a sur-face of the fabric cover.
Description
DESCRIPTION
HEAT ~ECOVERABLE ARTICLE
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This invention relates to a heat recoverable fa~ric article.
I Heat recoverable articles which are based on fabrics are i' described in the following patent puklications European q' Patent Application Publication Nos. 0116393 (MPo790), 0116391 (RKlSs), 0117026 (RK176), 0115905 (RK177), 0116392(RK178), 016390 (RK179), 0117025 (RK181), 0118260 (RK189zO, 0137648 (RK205), 0153823 (RK228), 0175554 (RK246), US Patent No.
4816326 (RK273), and US Patent No. 4900596 (RK289).
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~, The manufacture of heat recoverable articles from j~ fabrics containing heat recoverable fibres can have a ~:
number of advantages as compared with conventional heat- -~
shrinkable products, including for example ease of manu-facture, since no subsequent expansion ~tep is ;:
J ~ necsssary, improved mechanical properties such as ten- -~
slle strength, abrasion resistance and split re~istance, and :the ability to introduce very high strength heat stable fibres into the articles, all of which enable heat recoverable fabrics to be employed in ~ield-~ :
~-- hitherto considered-lnapproprlate for heat shrinkable ~: product3.
1 ~ ~ : ,, The~heat reooverable fabrics described in the prior 1~ art have many application~, for exa~ple covering, mecha-,. .. .
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i nically protecting, electrically screening, and environ-mentally sealing objects enclosed by the fabric. Far many of those applications it is partlcularlY desirable ~ for the fabric to provide an enclocure which is imper-ii vious to the ingress of water, moisture or other liquid.
An example of such an application iq where the fabric i~
to provide protection Or junctions in elongate substra-tes, such as splice in cables, particularlY in telecom-i munications cableq. It is frequently necessary to protect such junctions against the environment in order than the cables or other substrates may continue to function properly. Protection generally has to be pro-vided against moisture, corrosive chemicals as well as insect and animal damage etc. The intention when enclosing a junction such as cable splice is to make good the original cable insulation and it is generally `~! required that the life-time of the seal provided by the new enclosure be comparable to that of the original cable insulation. The material of the enclosure must provide a highly resistant barrier for a considerable period of time.
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For many applications, for example in many telecom-munications distribution cables an ability to retain pres~ure is also important. This may be required simply --as an indication of completeness of environmental sealing, or because the cables are pre~surised during use. Where cables are pressurised in use, the pre3suri-sation may be continual, or be applied temporarily, for example to te~t the article.
Various tests have been devi3ed to measure the abi-lity of an article to retain a pressure. The tests are known as "cycling testsn, and typically involve cycling , .
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the article at a constant preqqure between predetermined temperature limits. To pass the te~t the article must not leak after a predetermined number of cycles.
. ~ , '~ The ability of an article to re~ain pre~ure depends both on the poro_ity of the article, that its perviousnesq to air, and also on its ability to ; withstand hoop ~tre~ses generated by pres~ure within the ~qleeve. Each o~ these factor3 is oow discussed.
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A fabric material iq inherently pervious to air because of the intertices between the fibres making up the fabric. Thus in the fabric based articles of the ~il prior art it i~ known to pro~ide the fa~ric with mean~
.';3' ~or re~dering the fabric substantially impervious when the fabric is recovered. The means for rendering the fabric substantially impervious i9 typically in the form ~1 of a polymeric material used in conJunction with, bonded -` ~! to, or extending through the fabric. The polymeric ,~ material is typically applied as a laminate layer on one or both side~ of the fabric, or as a matrix through i which the fibre extends.
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The ability of an article to withstand hoop ~3 stre ses generated by pressure within the sleeve depends 3 on the components making up the wall of the article. It is wi~h regard to this factor that recoverable fabrics have been found to be particularly successful, with the fibres which make up the fabric providing a good resi~tance to those hoop stresses.
It has been found that by appropriate choice of the J material for the fibres of the fabric, the design of fabric used, and the material of the polymeric matrix it has been possible to make fabric sleeve3 of small thickness which are able to resist high pres~ures ,, .
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without significant ballooning or creep. EPA 0112390 (RK179) for example describes such a recoverable fabric artlcle having excellent pressure retention and imper_ viousness to air.
Heat recoverable Pabric article3 are also described in the prior art which are coated internally with a layer of adhesive. This is generallly provided to bond the ~abric to the underlying ob~ect. The adhesive is typically a heat activated adhesive, for example a hot melt adhesive, which is activated by the heat applled to recover the fabric article.
~ here an internal lining of adhe9ive i9 use~, the fabric and polymeric matrix used in con~unction with the fabric i9 advantageously chosen 80 that on recovery of the fabric, and activation of the adhesive, the adhesive stays on the inside of the article and does not pas3 through the fabric to the outside of the article. If the polymeric matrix material is wea~ and/or the ~ interstices in the fabric, between the fibres of the -i~ fabric, are large, then adhesive may pass, or bur~t, out of the article. The appearance of adhesive on the out-ide of the article as a re~ult of this i9 referred to in this specification as "adhesive burst-through~.
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~e have discovered that the performance of a fabric, recoverable article can be significantly ~;
improved by laminating a strengthening layer on the heat recoverable fabric, and that thi~ has a number of con-sequential advantages. In particular we have found that the presence of strenthening layer can improve (1) the ability of the article to retain pressure, ~2) the abi-lity of the article to resi3t adhe~ive burst through on recovery of the fabric (when the fabric is used in con- ;
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~ 1328802 .: :
_ 5 _ junction with an inner lining of adhesive, (3~ the barrier to moisture vapour transmission (MVT) of the article (by appropriate choice of material for the strengthening layer) and (4) the creep performance of the article.
' These improvements have a number of consequential advantages. In particular it enables fabric designs to be used which are more open in design than has hitherto been thought desirable. Where reference is made to the openness or closeness of a fabric design it refers to the density of the fibres, that is the number of fibres per inch in the fabric~ For example an open weave design will have less fibres per inch in its weft and/or warp than a closer weave design.
According to one aspect of the present invention there is provided a heat-recoverable article for covering a i substrate which comprises a fabric, a polymeric material ¦~ bonded to or extending through the fabric, and a strengthening layer comprising a metal and having a moisture vapour transmission value of less than 1 g/m2/day, the ~j strengthening layer being laminated to the fabric directly or via an intermediate member.
According to another aspect of the invention, there is provided a method of making a heat-recoverable article which comprises: (a) providing a laminate, by adhering a polymeric -~ material to at least one surface of a fabric or by providing a polymeric material through which the fabric extends; (b) providing recovsrability by a method which comprises: (i) providing in step (a) a fabric from fibres that are recoverable, or (ii) deforming the fabric, (c) laminating a strengthening layer to the fabric directly or via an ' intermediate member.
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- 5a -According to a further aspect of the invention, there is provided a method of protecting a cable splice which comprises: (a) making a heat-recoverable article by a method according to any preceding claim, (b) enclosing the splice my means of the heat-recoverable article, ~c) heating the article to cause it to recover.
~In one particular embodiment the strengthening layer -used comprises a metal foil. In this respect it is noted that the use of metal foil liners in heat recoverable non-fabric articles is known from the prior art. GB 1604379 (B034), for example, describes a heat recoverable polymeric sleeve comprising a liner of a continuous metal foil. The metal is sufficiently thin that it does not buckle and adopt a shape exhibiting peaks and troughs under the conditions of recovery. Thicknesses of 10 - 25 microns are stated to be preferred. However this reference does not mention heat recoverable fabrics and does not address the problems with which this specification is concerned.
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Preferably the heat recoverable article iq a tubu_ lar or wraparound article and the strengthening layer is laminated to the internal surface of the article.
The provision of a strengthening layer improveq the ability of the article to retain pressure, since as men-tioned above the ability of a fabric article to retain preqsure depends inter alia on its abilitY to withstand hoop ~tresse~, and the inclu~ion of the strengthening layer means that at least some of hoop stre3ses generated within the article are accommodated by the , strengthening layer rather than by the fabric. This i means that the ~abric per se has to accommodate less of the noop stresses. Consequently, to achieve an article having a given ability to withstand hoop stresses, a weaker fabric (that is one that is itself less able to withstand hoop stresses), can be used in an article ~! accsrding to the invention, than would be necessary in article of the prior art, which does not have a strengthening layer.
' The ability of the fabric per se to withstand hoop ¦ ~tresses depends inter alia on the density of fibres in the fabric, particularly the density of fibres extending in the direction of the hoop ~tre~es. Thuq since the fabric per ~e has to withstand lower hoop stres~e~ it i9 possi~le to use more open fabrics than had hitherto been possible to achieve an article having a given overall ability to withstand hoop stresses. In particular the invention enables a recoverable fabric to be made which has sufficient ability to retain pre~sure to pass the pressure/tempeature cycling texts referred to above using fabri¢s which are less densely fabricated than hitherto thought de~irable, for example having an opti-cal coverage less than 90~ and even less than 70S.
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The ability to use open fabric~ ha~ a number of advantages. First fabrication speeds are increa~ed~-since less fibres need to be interlinked per unit area o~ fabric. Also design flexibility i~ improved since it allows fabric designs to be used which inherently have an open structure (low optical coverage), for example WIWK (weft in~erted warp knittlng) and leno weave.
Also more open fabrics can achieve higher recovery ratios.
Preferably a fabric is used with heat reco~erable fibres such as polyolefin fibres in one of the warp and weft and heat stable fibres such as glass in the other of the warp and weft. Some embodiments of the inven~lon have less than 90, some less than 80, even less than 70 heat recoverable fibres per inch, and some embodiments have less than 12, even less than 8 heat stable fibres per inch.
A mentioned above the ability of an article to retain pressure depends also on the porosity or per-viousness to air of the article. Advantageously the strengthening layer comprise3 a material that is itself impervious to air, to improve the imperviousness of the article. Moi~t preferably, however, the fabric, like the ~abric in the prior art, has associated therewith means for rendering it subi~tantially impervious when reco-vered. Preferably the means for rendering the fabric, substantially impervious comprises a polymeric material which i9 adhered to at least one, preferably both sur-faces of the fabric, or is a polymeric matrix through which the fabric extends. Suitable materials are desoribed in European Patent Application No. 0116393 (MP0790).
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, Examples of suitable polymeric materials to render the fabric lmperviou~ include thermoplastic and ela~to-meric materials. Examples of thermoplastic material~
include: ethylene/vinyl acetate copolymer~, ethylene/ethylene acrylate copoly~er~, LLDPE, LDPE, MDPE, HDPE, polypropylene, polybutylene, polye9ters~
polyamides, polyetheramides, perfluoroethylene/ethylene copolymers, and polyvinylidene fluoride. The following i~ a list o~ preferred of preferred elastomeric materials: ABS block copolymer~, acrylic~ including acrylate~, methacrylate~ and their copolymers, high vinyl acetate copolymer~ with ethylene, polynorbornene, ~olyurethanes and ~ilicone ela3tomers.
Where a polymeric material is used to render the fabric 9ubstantially imperviou~, the polymeric material on the outslde of the tabric i9 preferably cross-linked to prevent it dripping or running during heat recovery, particularly during heat recovery by means of a torch.
Preferably the polymeric material on the inside of the article is not cross;linked, so it can flow on recovery to provide a bond to the ad~acent strengthening layer on recovery.
Preferred embodiments according to the invention comprise a recoverable fabric cover, a 3trengthening layer laminated to the surface of the fabric, and a layer of adhesive coating the surface of the strengthening layer facing away from the fabric.
Preferably the article is tubular or wraparound and the layers from the out~ide to inside are fabric (with - -polymer matrix of laminates if present), strengthening layer, adhesive. The adhesive is preferably heat acti-vatable, for example a hot melt adhe~ive, such as a polyamide or EVA. The heat activatable adhesive pre_ ,, , ~ .
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_ 9 _ ferably has3 a viscosity in the range of 40 - 150 pre_ ferably 60 - 80 Pa.3 at 160 C, and a flow temperature in the range 80 - 120C, preferably 95 - 110C. A
~3uitable polyamide adhesive, which is disclo3ed in UK
patent publication 2075991, contains up to 10S, pre-ferably up to 1~ of an acrylic rubber and has excel}ent adhesion to untreated polyethylene, and good low tem-perature flexibility. The activation temperature of the adhesive i~ preferably chosen to correspond to the s3ingle recovery temperature of the fabric, so that the single step of heating achieves both recovery and bonding. The adhesive need not extend over the entire urface of the fabric.
~ When a lining of adhesive i9 used the strengthening j layer i9 preferably sufficiently strong at the recovery ~ temperature of the fabric to prevent adhesive burst 3 through. The strengthening layer i9 preferably also impermeable to the passage of adhesive through its thickness. Thi3 means that when the fabric recovers the ~- adhesive stays on the inside of the article and the ~ activated adhesive cannot pas3s through the strengthening i layer into contact with the fabric. ~-~f` .-In the absence Or a strengthening layer adhe~ive 3`~ burst through is worse for open fabric de~igns because the mo're open de~igns have larger interstices through which the adhesive may burst. In the absence of a ~ -strengthening layer, adhesive burst_through may be a ~ problem even when the fabric is used in con~unction with `3,~ a polymeric matrix material, since at the recovery tem-'~ perature the polymeric material may soften and therefore -have a sufficiently low viscosity to be punctured by the adhesive as it bursts through the interstices of the , .!: ~ .
~ fabric. -, - , -, ,,~ .. . .
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~ o --The use of a strengthening layer that is strong enough to prevent adhesiYe burst_through, maintaini~g tke adhe~ive on its inner 3urface, therefore enable_ more open fabric de~igns to be used than had hitherto been thought desirable, without the risk of adhesive ''. burqt-through.
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Thus desirable pressure retention and adhe~ive burst-through resistance can be obtained u~ing more open fabrics than has hitherto been possible.
,, The strengthening layer can also be chosen 90 that it improve~ the barrier to moisture vapour transmission l (M~T~ of the ar~icle.
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In the prior art recoverable fabric articles a ; small amount o~ moisture vapour tran~mission (MVT) can occur through the thickness of the article even when the ~;~ fabric i3 used in conjunction with a polymeric matrix.
~I Thiq i3 because polymeric materials are inherently i slightly permeable to moisture. Also water moisture, or other liquid ingre~s into the article may occur 3 through the fibres themselves. This may be the case if the fabric used is one which inciudes fibres which can ~,,!~ themselves transmit water or moisture or other liquid along their length (for example glass), if the fabric ¢on~truction is such that a free end of a fibre i9 accessible to the ?iquid. In the~e case~ water may enter the interior of the tubular article, by entering ~ fir~t the free end of the fibre, then migrating along -~j the length of the fibre, from which it may then pass ~i into the interior of the article. Thi-q a particular ;, problem if the poIymeric material used in conJunction with the fabric is laminated to the outer ~urface only of the fabric, or even when laminated on both sides or : . .
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1, extending aQ a matrix through the fabric, when the internal ~urface of the polymeric material (lying within the fabric) 1~ damaged in some way allowing a pathway for liquid to pas~ to the interior of the sleeve.
Due to the pos~ibility of ~ome moi~ture ingre~
into the fabric articles of the prior art, for some applications it is usual to include silica gel packages within the articles to ab~orb that moisture.
Ac¢ording to the present invention a strengthening layer having a low (preferably sub~tantially zero) MVT
value may be used to improve the barrier to MVT of the article. ~ence recoverable fabric artlc~les ha~ing better I MVT properties than has hitherto been po~sible can be i made, and the need to include silca gel drying packed in article~ may be avoided. Where MVT value3 are quoted in this Specification they are measured at room tem-'i perature.
The article according to the invention has surpri-i singly been found to have improved creep performance as compared to comparative examples without a strengthening , layer. In general the amount of creep occuring for the -article with the ~trengthening layer is approximately half that of articles without a strengthening layer.
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Preferred features of the strengthenlng layer, and a~sociated layers, which provide the advantages of the present invention will now be di~cus~ed. -~
Preferably the strengthening layer has a tensile strength of at least 10 MPa more preferably at least 13 MPa, e~pecially at ~east 16 MPa at 100C, and a tensile ~trength of at least 30 MPa at room temperature. The tensile strength is particularly important in improving t ~' '.
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_ 12 -pres~qure retention, in preventing adhe~ive bur~t through, and alqo in improving creep performance.
The flow temperature of the qtrengthening layer compared to the recovery temperature of the fabric, and al30 the viqcosity of the strengthening layer at the recovery temperature are important parameters, par-ticularly where it is deqired to stop adhesive burst ! through. If the strengthening layer flows on recovery, or if the viscosity of the strengthening layer i8 too low at the recovery temperature, the strengthening layer may be punctured by the adhesive. Preferably the ~trengthening layer has a flow temperature which i9 at `! least 40C, more preferably at least 6~C higher than the recovery temperature of the fabric. Preferably the l strengthening layer has a melt ~low index which is substantially zero, measured at 190C under 2.16 Rg.
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Preferably the strengthening layer compri~es a ' material that has a low MVT value, especially for ;~ applicationq where it i9 important to have low moisture -i vapour transmission from the exterior to iaterior of the article. Preferably the strengthening layer comprise~ a ~, material having an MVT value less than 1g/m2/day, more preferably less than 0.3g/m2/day.
~' While it is desirable that the ~trengthening layer ~, is strong, and have a high tensile 3trength, it must also be able to accommodate the configurational change of the article on recovery of the sleeve. Thi~ is pre-ferably achieved by making the strengthening layer 90 - that it can corrugate longitudinally, and preferably also uniformly on shrinkage of the fabric to accommodate -~ the configuration change of the article.
~3 One parameter which is considered important to determine the ability of the strengthening layer to ,'f '' !
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accommodate changes in the configuration of the article by forming itself into corrugations is the stiffness-of the strengthening layer. The term stiffness i9 appli-cable to both homogeneous and heterogeneous material~
and where several layer~ are present is dependent on the inherent stiffnesq of the separate layers as well as their respective thickness. Stiffness measurements are I considered particularly relevant for the ~trengthening ; layer of the present invention since it is envisaged that multilayer strengthening layers could be used.
Preferred stiffness values were determined for the strengthening layer of the present invention using Jl British Standard ~es~ BS 2782 (Part 3 method 332A 197~).
The stiffness of the strengthening layer mea~ured according to this method is preferably less than 10 N/m, ' more preferably less than 6 N/m measured at room -~ temperature. At 100C the stiffness is preferably at most 6 N~m, more preferably at most 1.5 N/m.
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The ~trengthening layer preferably corrugates on , recovery, preferably uniformly. Preferably the ^~-i strengthening layer is not pre~cored or pretreated in any other way to enhance the corrugation. Preferably the ~trengthening layer i such that the recovery forces exerted on it by the recovering fabric cause it to form corrugations having a height in the range of 1.0 to 1.3 mm, preferably about 1.16 mm, and a tip to tip diqtance of about 1 to 2.5 mm, preferably about 1.7 mm.
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f According to the invention the ~trengtheing mem-! ber is laminated to the fabric. This includes the strengthening member being directly laminated to the fabric, and al~o the lamination being via an inter-mediate member. For example, where, aq i~ preferred, a .
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_ 14 -polymeric material i9 used in con~uction with the fabric to render it ~ub~tantially impervious, and that po1y- -meric material extends, or i9 laminated to the inner ~urface of the fabric, the ~trengthening layer may be bonded directly to that polymeric material, which in turn is bonded to the fabric.
Preferably the strengthening layer remain~ lami-nated to the fabria even after recovery that is no dis_ bonding which would cause an air gap between the fabric and the strengthening layer occurs. Disbonding is disadvantageous ~or a number of rea~ons. For exa~ple, the transfer of hoop ~tresses from the fabric to the strengthening layer i~ reduced, reducing the ability of the article to retain pressure, ingreq~ of water may occur, for example at the edges, adhesive bur~t through may occur for example at the edges, and where the strengthening layer corrugates on recovery, the corru8a-tion may be lnhomogeneous.
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In order that the strengthening layer remains lami-nated to the fabric before, during and after recovery, a layer of meltable material is preferably provided bet-ween the ~abric and the strengthening layer whlch is molten at the reaovery temperature of the fabric. This enables the strengthening layer to corrugate within the meltable material durlng recovery, and ensure~ that, after recovery, the meltable material has flowed to fill the trough~ in the corrugated ~trengthening member.
Thus there i8 no air gap between the fabric and the trengthening layer before, during or after recovery.
Preferably the meltable material has a melt flow index in the range 0.1 - 10, more preferably 4-7, mea~ured at 190C under 2.16 Kg. The meltable material may be, fGr -example, a copolymer. The melt flow index of the -, ' .
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; meltable material should not be 90 high that it can burc3-t through the interticeq of the 3fabric. Hence ~he preferred upper limit of 10.
Pre~erably the strengthening layer iq provided on both its maJor ~qurfaces with a meltable material, pre-ferably as defined above. ThuJ the strengthening layer corrugates in a matrix of meltable material. The pre_ sence of the meltable material on one, or preferably both sides of the strengthening layer enhance~3 the uni-~ormity of the corrugation of the strengthening layer.
The meltable material between the fabric and the strengthçning layer iq preferably select~d to form a good bond between thoqe layers. -The meltable layer between the fabric and the qtrengthening layer preferably has a thickness in the -~
range of 20-30 microns. The meltable layer on the sur-Pace of the ~trengthening layer facing away from the ~- fabric preferably has a thickneq~ in the range 20-30 ~ microns.
;3 ~ Particularly if the layer of meltable material bet--~ ween the strengthening layer and the fabric is too thick, and the melt flow index too high, the meltable layer may burst through the fabric.
The ability of the meltable material to flow to ~ill the space between the corrugated ~trengthening member and the fabric, and pre~erably the proviqion of a i meltable matrix on which the strengthening layer corru-~ gateY, i~ thought to be important in improving the creep ;1 characteristics of the article. In this respect it is noted that it is surprising that a corrugated member can, in fact, improve the creep resistance of the article.
,, . ' _ 16 -The ~trengthening layer may comprise a single layer or two or more layers of different materials. Where two or more layer~ are used each of the required properties of the strengthening layer may be provided by any one of i the layeri~ of by a combination of the layerS. For example where a layer having high tensile strength and low MVT value is required two layers together may be used, one having the required high tensile strength and j the other having the required low MVT value. The pre_ ferred tensile strength may be achieved, for example, using a layer of mylar or biaxially stretched nylon.
The preferred low MVT value may be achieved for example using a metal layer, for exa~ple aluminlum; Thu~ a pre-ferred strengthening layercomprises a layer of MylarlM or nylon bonded, on one or both sides, to a layer of metal 1 such as aluminium. The layer(s) of metal may be pro-1 vided, for example, in the form of a foil or as a very I thin metal deposited layer.
Where a support layer ~uch as mylar or nylon, and a metal foil layer are u~ed either layer may be nearest the fabric. Preferably the mylar or nylon is nearest the fabric to achieve the ~trongest bond between the fabric and the strengthening layer.
The overall thickness of the strengthenin~ layer i~
preferably in the range 5 to 100 microns, more preferbly in the range 7 to 35 microns. Where a metal layer or ` layers is used in combination with a support layer, the $ support layer preferably has a thickness in the range about 8-25 microns, for example about 12 - 15 microns.
Where the metal layer is provided as a foil it pre_ ferably has a thickness about 5-15 microns, for example about 9-12 microns. Where the metal is provided a~ a deposited layer or layers this preferably has a . ~ .
. - , _ 17 _ thickness o~ abouS 3-500 Ang~troms. Where a metal deposited layer i9 used, it i~ preferably provided on both sides of the support layer.
The construction of the fabric will now briefly be oonsidered, although it is envlsaged that any weave or knit or non-woven agglomeration of any fibreq may be used. For the pre~ent purpose~ the term weave i9 to include braids 9 ~ince the products are similar although t^ne methods of production are different. Recoverability is preferably provided by weaving or knitting fibres that are already recoverable. Alternatively it may be provided by deforming a fabric woven or knitted from dime~3ionalIy ~table fibres. EXamples of i~uitable reco-verable fabrics are described in European Patent Application No. 84300059.7 (MP0790).
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' Different effects, in term~ of for example, final ¦ reaovery ratio, strength and flexibility, will result from different types of weave or knit even if the same ~ fibres are u~ed. Example~ of type of weave include ji~ plain, twill, broken twill, herring bone satin, sateen, i~ leno, hop sack, sack, mat and combinations of these.
The weave may be single ply, or multiple ply weaves may be used. A particular advantage of the present inven-t tion i~ that high performance articles can be made from fabri~ of open-design, examples of such fabrics in¢luding WIWK, and leno weave.
~i The fibres used to produce the recoverable fabric ~i may be monofilament3, multifilament~, spun staple yarns or tapes. Examples of polymeric ~aterials that may be ! used for the recoverable fibres include polyolefinq, ~uch as polyethylene (e3pecialy HDPE) and polypropylene, polyamide~, polye~ter~ and fluoropolymers suoh a~ FEP, ~ 1 .
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,, " . , , . ~. ., ,., .. ., . . , . .. , . . ~ . . . -ethylene perfluoro copolymer, polyvinylidine fluoride and TFE copolymers. The recovery temperature, by which , we mean the temperature at which recovery will go substantially to completion, is pre~erably 60C or more, more preferably from 80-250C, most preferably from 120-150C.
A non-recoverable fibre may be used an a reinfor-cement or supplement to the recoverble fibre3, or may constitute the ma~or component in one or more dimensions ' of the fabric. The following non-recoverable materials may be regarded as illustrative: glassflbres, carbon ;- fibres, wires or other metal fibres, polye9ters, aroma-,3 'tiC polymers'such as'a'romatic polyamides' for e'xample j Kevlar (trade name), imides and ceramics.
'' The article according to the invention may be made in tubular form or wraparound form. Wraparound articles i are preferred ~ince they can be installed around ~-sub~trates having no free ends. This is particularly useful when a splice in a telephone cable is to be i enclosed after the repair of only a few of the many con-ductors it contains, since if the artiole is tubular, the entire cable has to be severed for installation.
Wraparound products are al90 useful where spaoe is ~ limited.
s Where a wraparound sleeve i3 used an elongate flap '~
may be provided beneath the longitudinal slit of the ~' sleeve to from the seal. Thls may be provided as a separate entity or attached to on side of the sleeve.
The flap preferably also includes a strengthening layer.
The technique3 by which the sleeve may be held in the wrapped configuration in any suitable way. Firstly, ~: .
-~ 9 a lap or other bond may be made between oppoising edgec of the ~heet, optionally with a patch to prevent peçl-back. In a qecond possibility, some meanq which penetrates the fabric may be uised, for example istitching, stapling, riveting, or pre-ini3erted catchei A third method of closure involves forming the edge~ of ; the slee~e in isiuch a way that they may be held together by isome form of clamping means, such as the C-shaped channel diqclosed in UK Patent No. 1155470, or by a reuseable tool.
Preferred forms of cloisiure for the article are dei3cribed in European Patent No. 0116391.
In a pa~tlcularly preferred embodiment the fabrl~ 1i3 J folded back on itsielf at each longitudinal edge to 1 accommodate rods, preferably nylon rods, running along J the length of the article. The rodis and overlying fabric are held together by the closure channel.
Where this type of cloisure is uisied the i3trengthening layer advantageously extends to the longi-i tudinal edgesi of the article and the channel grips the j strengthening layer with the fabric. Thi3 substan_ tially preventis the strengthening layer pulling out from ; the longitudinal edges of the article at the closiure.
l Also, the strengthening layer substantially preventsi j adhes~ve burst through in the rod region.
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; For many applications it is desirable to include a liner within the sleeve. The liner preferably hai3 a central region of larger cross-section, and end 3ections of ismall crosisi-section which provide tranisitions to the subistrate. The liner typically comprii3eiis tapered fingers at the endis which provide the transitions. The liner provideis support and mechanical rigidity to the .. ..
,, article. The use of a liner with a fabric is described, for example in European Patent Application No.
ô4300057.1 (RK169). The liner typically comprises a metal such as aluminium, for example in the form of half shells.
, Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:
Figure 1 i9 a perspective view of an article according to the invention.
Figure 2 iq cross_~ection through ~-A of Figure , Figure 3 is a cross-section through the article of Figure 1 and 2, after recovery ., .
Figure 4 is an enlarged view of part of the cro3s-section of Figure 3 ~ Figure 5 i8 an end view of another article - according to the invention.
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Figure 6 is an enlarged view of the clo~ure portion of the article of Figure 4.
Figure 7 is a schematic view showing part of a pre-ferred process for making an article according to the invention.
Figure 8 i~ a cross-sectional view of an apparatus used to te~t adhesive burst through of articles according to the invention and other .' ' .
i Figure 9 is a graph showing creep behaviour of ~; article according to the invention and others.
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132~802 Figure 1 qhows a wraparound article 2, according to the invention. Longitudinal edges 4 of the article are thickened and can be held together by a channel shaped closure 6. The article 2 comprise_ a laminate struc-turç. Thiq i~ ~hown in Figure 2 which is a croqs-section through A-A of the article of Figure 1. The structure compri~eq a fabric 8, which is a weave comprising high denqity polyethylene heat recoverable fibreq 1Q and heat stable glasq fibres 12. The reco-verable fibreq 10 are in the weft of the fabric and extend around the circumference of the article. The glas3 fibres 12 are in the warp and extend along the length of the article. The fabric recovers at a tem-perature of about 110-135 C. A layer of poly~eric material i9 laminated on both sides of the fabric. The outermost layer 14 (facing outwards of the article is cross-linked by irradiating it to a beam dose of 12 MRads. This restricts the tendency of layer 14 to flow during recovery. Inner layer 16 is uncross-linked.
This i~ explained later. Strengthening layer 18 is laminated to the inner surface of the inner laminate layer 16. On recovery polymeric layer 16 which i9 not cross-linked flows and enhances bonding to the strengthening layer 18. This is why it is not cross-linked.
Th~e strengthening layer 18 itself comprises two layers, which are respectively a layer of aluminium (20) and a support layer of mylar (22). To either side of these layers are bonded copolymer hot melt adhesive layers 24 and 26. Adhesive layer~ 24 bonds the strengthening layer lô to the inner laminate layer 16 both before and after recovery. Adhesive layer 26 bond~
the article to the underlying obJect after recovery~
Adhesive layers 24 and 26 have a flow temperature of ,, , ,, .
about 200 C. They also have a melt flow index of about 5 at 190C ~easured at 2.16 Kg. Thus at the recove-ry temperature of the fabric strengthening layer 18 buckles in layers 24 and 26, the adhesive layer 24 flowing to fill any gaps between the strengthening layer 18 and the fabric 8. A final layer of a Polyamide adhesive 25 i~
provided on the surface of adhesive layer 26. Thi3 i9 to bond the article 2 to the underlying ob~ect.
., Figureq 3 and 4 ~how the article after recovery onto an object such as a oable 27. The recoverable fibre~ 10 have shrunk pulling the glass fibre~ 12 cloqer together. The ~trengthening layer 18 has buckled or ~ corrugated to accommodate the reduction in size of the ,'! article. Adhesive layer 24 has flowed to fill the trough~ in the buckled or corrugated layer 18 so that the strengthening layer 18 remains laminated to fabric 8. Adhesive layers 26 and 25 have flowed to fill the gap between the strengthening layer 18 and cable 27 ~ Figures 5 and 6 show another wraparound article ! according to the invention. The material of the article f is the qame as that de~cribed in Figures 1 to 3, but the material at the longitudinal edges of the article is i~ wrapped around nylon rods 28 which extend along the ~ length of the sleeve. The strengthening layer 18 wraps '7~ with the fabric 8. Closure channel 6 is positioned over the rods and holds the longitudinal edges in close con-formity. A ~eparate flap 29 is used to seal the gap underneath the channel 6. Thi~ may instead be secured to one side of the wrapped article. This also contain3 strengthening layer 18.
., Figure 7 illustrates part of a preferred process for making an article according to the invention. Fir~t ~.
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a recoverable fabric i~ made, e.g. woven, from heat recoverable and optionally other fibres. The fabric i~
then preferably irradiated to cro~s_link it, then a layer of low den~ity polyethylene material laminated on one side. That fabric i~ preferably wound on roller~ 30 with the ~ingle polymeric laminate layer which wlll form the outer layer 14 of the article on the inner surface of the roller (i.e. facing the bottom of the diagram as it is drawn from the roller). This fabric is then fed ~l to another set of rollers 32 where a second layer of low density polyethylene is laminated on the other side of the fabric from a hopper This form~ the inner lami-, nate layer 16. Simultaneously the ~trengthening layer `'7 18 is laminated on top of the polymeric layer i6, being fed from roller~ 34. The lamination process is completed by rollers 36. Longitudinal edge~ of the fabric may be formed into the shape shown in Figure 3, a ~, flap secured if desired, then the article cut to length.
` -'1 - Examples Adhesive Burst Through Comparative tests were carried out to qhow the effect of a ~trengthening layer on adhesive burst through for a number of samples. A specific apparatus and te~t was devi~ed to measure tendency of the samples ~! to suffer adhesive burst through. The test is now explained with reference to Figure 8, and is carried out ~ as follows:
;~'7~ Test sample 42 is positioned between a silicone rubber membrane 44 of thickness 3 mm and a metallic ~ screen 46 having a penetration factor of 55S. An adhe--,~ sive sheet 48 of size 40 mm x 40 mm and thickness 0.5 -~' , ~ i ':'. ' "",",, .,,,S~ , ",1"~ "~ ""." ' 1.,". ~,'. ' .. ,,~ ,.. - : - , . . ., .. ., .. .,,, . ,. , ~, .. . . . . . . ... .
0.9 mm lie~ between the Qilicone rubber membrane 44 and the metallic screen 46. The above members are clamped between top and bottom aluminium plates 50 and 52 with the penetrable metal screen ad~acent to the top plate.
A viton 0-ring 5~ seals between the silicone rubber membrane 44 and the bottom plate 52. Top and bottom plate~ 50 and 52 contain equal sized circular apertures 56 and 58 which lie one above the other. Screws 60 con-nect plates 50 and 52, and these are tightened to secure members 42, 44, 46, 48 and 54 between them.
The circular aperture 56 and 58 in plates 50 and 52 are 50 mm in diameter. The top aperture 56 is exposed to the atmocphere. The bottom aperture 58 is in com-munication with a reservior which can be pressurised to test the sample. Pressurisation causes the silicone rubber member 44 to press against the adhesive tending to force it through the sample 42 and the metal screen 46.
The apparatus containing the test sample i~ placed in an oven and heat stabilised at 150C for one hour.
After stabilisation the pressure is increased by incre- -ment~ of 10 kPa until adhesive burst through i~
observed. This is recorded. The test is carried out at , 150C since this is about the temperature used for reco_ - very o'f typical reaoverable fabrics, and hence the tem-perature at which adhesive burst through would occur in ;~ practice.
.,~',~ ., ~. The test was carried out for a number of different fabric de~igns. Each fabric was provided with a poly-meric material to render it impervious. The polymeric material was provided as a laminate of low density polyethelene on both sides of the fabric. Each layer was 0.1 to 0.5 mm thick.
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Examples 2, 3, 5, 7, 9 and 11 are comparative examples which do not use a strengthenlng layer.
Examples 1, 4, 6, 8 and 10 are articles according to the invention. Each include~ a strengthening layer which is a laminate with the following construction:
biaxial stretch nylon - thickness 15 microns (nearest the fabric) ~ . .
aluminium foil - thickness 12 microns (furthest from fabric) Also a layer of hot melt adhesive copolymer thicknes~ 35 microns i9 provided between the fabric anq the strengt~ening layer, and a layer of hot melt copo-lymer thickness 25 microns is provided on the surface of the strengthening layer ~acing away from the fabric.
! The total copolymer~nylon/aluminium~copolymer laminate .7 i8 that supplied by UCB under the trade name SidamilTM.
The strengthening layer used in examples 1,4, 6, 8 and 10 has an MFI value of substantially zero.
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Table 1 EX NO MATERIAL FABRIC DESIGN LAMINATION STRENGTHENING PRESSURE TO
~ONSTRUCTION . LAYER CAUSE EURST
(See Key) THROUGH kPa 1 A WIWK one side yes 400 2 A WIWK both side~ no 85 3 A WIWK one ~ide no 50 4 B Twill 2 both sides ye~ 400 B Twill 2 both side3 no 210 6 B Broken Twill both side~ yes 400 i B Broken Twill b.oth sides no 205 .
8 B Satin 4 both sides yes 400 9 B Satin 4 both sides no 135 C Broken Twill both sides yes 400 11 ¦ ¦ ~ck~n ~wlll ¦ both 91dea ¦ o ¦ 7ZO
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Material Con~truction K~y A 4 bundles of 5 and 7 bundle~ of 4 heat recoverable high density polyethylene fibres = ~8 fibres per inch in weft and 6 glas~ f~breq per inch in warp.
B 18 bundles of 4 heat recoverable high density polyethylene fibreq = 72 heat recoverable fibres per inch in weft 9 glas~ fibres per inch in warp.
C. Fibrillated 16 inqertion~ of 2 flat embossed fibrillated heat recoverable high densith polyethy-; ~ene-fibreq per inch in the we~t, 9 glas~ fibres per inch in the warp The results clearly show that adhesive burst through is reduced significantly for all fabric types by including a strengthening layer. Much higher force~ are needed to cause burst through when a strengthening layer ~ i~ used.
; A second test wa~ carried out to ~how the effect of the melt flow index of the ~trengthening laye of the ability of the material to resist adhesive burst through.
In each case the fabric desi~n was design B a~
above. Each fabric was provided with a polymer material ~ to render it impervious. The polymeric material wa~
;~ provided as a laminate of low density polyethylene on both ~ides o~ the fabric. Each layer was 0.1 to 0.5 mm thick.
The results, as shown in Table 2 below, show that even when the strengthening layer has a very low melt :: .
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- 2~ -flow index, of the order of 0.3, the pre~qure to cause adhe~ive bur~t through i~ signi~icantly reduced, compared to the pre~sure required u~ing the SML layer of Example~ 1, 4, 6, 8 and 10 in which the strengthening layer ha~ an MFI value of sub~tantially zero.
For applications in whlch adhesive bur~t through is unacceptable the material~ of examples 12 - 15 are not preferred for the strengthening layer.
Table 2 EX N0 Material of Melt Flow Pre~ure to Strengthening layer Index cau~e adhe~ive bur~t through KPa 12Elvax 670TM 0.28 125 . (supplied by Dupont) 13DPD 6182 0.26 130 ~: .
'. (~upplied by Union Carbide) 14CxA 2002 6.67 100 ~, (supplied by Dupont) -~ 15Plexar 100TM 0.64 130 upplied by DSM) -,.1,~ "~ ' ' .
~. Creep behaviour ~
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A comparative test wa~ alqo carried out to deter- :-mine the tendency of articles with and without - ' -strengthening layer to creep. The fabric con~truction ,' used in each oase wa~ that of type ~B~ given above. -The following sample~ were used.
l, 16 Without a strengthening layer `, 17 With a strengthening layer of P~T/copolymer ,' coated on one ~ide with 9 micron aluminium '~ layer 18 As example 17 but with a 500- Angstrom ~`
thick aluminium layer in place of 9 mic,ron ~, thick layer i! The sa~ples were recovered, causing the ~, strengthening layer when present to or corrugate, and `~ then sub~ected to creep testing at 60C under an inter-nal pressure of 70 kPa for approximately one month. The ,' '~ results are set out in the graph (Figure 9).
It can be seen that the addition of the I strengthening layer significanntly reduce~ the creep of the article. For example the sample without a ~trengthening layer (Example 12 creep~ more than 14~ in ,, 30 days, while those with strengthening layers ,'~ creep less than 7b. The performance is thus about twice ,~ as good with a strengthening layer.
It is thought surprising that the presence of the strengthening layer can improve creep performance, even 1,~ though it is corrugated.
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HEAT ~ECOVERABLE ARTICLE
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This invention relates to a heat recoverable fa~ric article.
I Heat recoverable articles which are based on fabrics are i' described in the following patent puklications European q' Patent Application Publication Nos. 0116393 (MPo790), 0116391 (RKlSs), 0117026 (RK176), 0115905 (RK177), 0116392(RK178), 016390 (RK179), 0117025 (RK181), 0118260 (RK189zO, 0137648 (RK205), 0153823 (RK228), 0175554 (RK246), US Patent No.
4816326 (RK273), and US Patent No. 4900596 (RK289).
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~, The manufacture of heat recoverable articles from j~ fabrics containing heat recoverable fibres can have a ~:
number of advantages as compared with conventional heat- -~
shrinkable products, including for example ease of manu-facture, since no subsequent expansion ~tep is ;:
J ~ necsssary, improved mechanical properties such as ten- -~
slle strength, abrasion resistance and split re~istance, and :the ability to introduce very high strength heat stable fibres into the articles, all of which enable heat recoverable fabrics to be employed in ~ield-~ :
~-- hitherto considered-lnapproprlate for heat shrinkable ~: product3.
1 ~ ~ : ,, The~heat reooverable fabrics described in the prior 1~ art have many application~, for exa~ple covering, mecha-,. .. .
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i nically protecting, electrically screening, and environ-mentally sealing objects enclosed by the fabric. Far many of those applications it is partlcularlY desirable ~ for the fabric to provide an enclocure which is imper-ii vious to the ingress of water, moisture or other liquid.
An example of such an application iq where the fabric i~
to provide protection Or junctions in elongate substra-tes, such as splice in cables, particularlY in telecom-i munications cableq. It is frequently necessary to protect such junctions against the environment in order than the cables or other substrates may continue to function properly. Protection generally has to be pro-vided against moisture, corrosive chemicals as well as insect and animal damage etc. The intention when enclosing a junction such as cable splice is to make good the original cable insulation and it is generally `~! required that the life-time of the seal provided by the new enclosure be comparable to that of the original cable insulation. The material of the enclosure must provide a highly resistant barrier for a considerable period of time.
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For many applications, for example in many telecom-munications distribution cables an ability to retain pres~ure is also important. This may be required simply --as an indication of completeness of environmental sealing, or because the cables are pre~surised during use. Where cables are pressurised in use, the pre3suri-sation may be continual, or be applied temporarily, for example to te~t the article.
Various tests have been devi3ed to measure the abi-lity of an article to retain a pressure. The tests are known as "cycling testsn, and typically involve cycling , .
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the article at a constant preqqure between predetermined temperature limits. To pass the te~t the article must not leak after a predetermined number of cycles.
. ~ , '~ The ability of an article to re~ain pre~ure depends both on the poro_ity of the article, that its perviousnesq to air, and also on its ability to ; withstand hoop ~tre~ses generated by pres~ure within the ~qleeve. Each o~ these factor3 is oow discussed.
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A fabric material iq inherently pervious to air because of the intertices between the fibres making up the fabric. Thus in the fabric based articles of the ~il prior art it i~ known to pro~ide the fa~ric with mean~
.';3' ~or re~dering the fabric substantially impervious when the fabric is recovered. The means for rendering the fabric substantially impervious i9 typically in the form ~1 of a polymeric material used in conJunction with, bonded -` ~! to, or extending through the fabric. The polymeric ,~ material is typically applied as a laminate layer on one or both side~ of the fabric, or as a matrix through i which the fibre extends.
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The ability of an article to withstand hoop ~3 stre ses generated by pressure within the sleeve depends 3 on the components making up the wall of the article. It is wi~h regard to this factor that recoverable fabrics have been found to be particularly successful, with the fibres which make up the fabric providing a good resi~tance to those hoop stresses.
It has been found that by appropriate choice of the J material for the fibres of the fabric, the design of fabric used, and the material of the polymeric matrix it has been possible to make fabric sleeve3 of small thickness which are able to resist high pres~ures ,, .
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without significant ballooning or creep. EPA 0112390 (RK179) for example describes such a recoverable fabric artlcle having excellent pressure retention and imper_ viousness to air.
Heat recoverable Pabric article3 are also described in the prior art which are coated internally with a layer of adhesive. This is generallly provided to bond the ~abric to the underlying ob~ect. The adhesive is typically a heat activated adhesive, for example a hot melt adhesive, which is activated by the heat applled to recover the fabric article.
~ here an internal lining of adhe9ive i9 use~, the fabric and polymeric matrix used in con~unction with the fabric i9 advantageously chosen 80 that on recovery of the fabric, and activation of the adhesive, the adhesive stays on the inside of the article and does not pas3 through the fabric to the outside of the article. If the polymeric matrix material is wea~ and/or the ~ interstices in the fabric, between the fibres of the -i~ fabric, are large, then adhesive may pass, or bur~t, out of the article. The appearance of adhesive on the out-ide of the article as a re~ult of this i9 referred to in this specification as "adhesive burst-through~.
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~e have discovered that the performance of a fabric, recoverable article can be significantly ~;
improved by laminating a strengthening layer on the heat recoverable fabric, and that thi~ has a number of con-sequential advantages. In particular we have found that the presence of strenthening layer can improve (1) the ability of the article to retain pressure, ~2) the abi-lity of the article to resi3t adhe~ive burst through on recovery of the fabric (when the fabric is used in con- ;
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~ 1328802 .: :
_ 5 _ junction with an inner lining of adhesive, (3~ the barrier to moisture vapour transmission (MVT) of the article (by appropriate choice of material for the strengthening layer) and (4) the creep performance of the article.
' These improvements have a number of consequential advantages. In particular it enables fabric designs to be used which are more open in design than has hitherto been thought desirable. Where reference is made to the openness or closeness of a fabric design it refers to the density of the fibres, that is the number of fibres per inch in the fabric~ For example an open weave design will have less fibres per inch in its weft and/or warp than a closer weave design.
According to one aspect of the present invention there is provided a heat-recoverable article for covering a i substrate which comprises a fabric, a polymeric material ¦~ bonded to or extending through the fabric, and a strengthening layer comprising a metal and having a moisture vapour transmission value of less than 1 g/m2/day, the ~j strengthening layer being laminated to the fabric directly or via an intermediate member.
According to another aspect of the invention, there is provided a method of making a heat-recoverable article which comprises: (a) providing a laminate, by adhering a polymeric -~ material to at least one surface of a fabric or by providing a polymeric material through which the fabric extends; (b) providing recovsrability by a method which comprises: (i) providing in step (a) a fabric from fibres that are recoverable, or (ii) deforming the fabric, (c) laminating a strengthening layer to the fabric directly or via an ' intermediate member.
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- 5a -According to a further aspect of the invention, there is provided a method of protecting a cable splice which comprises: (a) making a heat-recoverable article by a method according to any preceding claim, (b) enclosing the splice my means of the heat-recoverable article, ~c) heating the article to cause it to recover.
~In one particular embodiment the strengthening layer -used comprises a metal foil. In this respect it is noted that the use of metal foil liners in heat recoverable non-fabric articles is known from the prior art. GB 1604379 (B034), for example, describes a heat recoverable polymeric sleeve comprising a liner of a continuous metal foil. The metal is sufficiently thin that it does not buckle and adopt a shape exhibiting peaks and troughs under the conditions of recovery. Thicknesses of 10 - 25 microns are stated to be preferred. However this reference does not mention heat recoverable fabrics and does not address the problems with which this specification is concerned.
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Preferably the heat recoverable article iq a tubu_ lar or wraparound article and the strengthening layer is laminated to the internal surface of the article.
The provision of a strengthening layer improveq the ability of the article to retain pressure, since as men-tioned above the ability of a fabric article to retain preqsure depends inter alia on its abilitY to withstand hoop ~tresse~, and the inclu~ion of the strengthening layer means that at least some of hoop stre3ses generated within the article are accommodated by the , strengthening layer rather than by the fabric. This i means that the ~abric per se has to accommodate less of the noop stresses. Consequently, to achieve an article having a given ability to withstand hoop stresses, a weaker fabric (that is one that is itself less able to withstand hoop stresses), can be used in an article ~! accsrding to the invention, than would be necessary in article of the prior art, which does not have a strengthening layer.
' The ability of the fabric per se to withstand hoop ¦ ~tresses depends inter alia on the density of fibres in the fabric, particularly the density of fibres extending in the direction of the hoop ~tre~es. Thuq since the fabric per ~e has to withstand lower hoop stres~e~ it i9 possi~le to use more open fabrics than had hitherto been possible to achieve an article having a given overall ability to withstand hoop stresses. In particular the invention enables a recoverable fabric to be made which has sufficient ability to retain pre~sure to pass the pressure/tempeature cycling texts referred to above using fabri¢s which are less densely fabricated than hitherto thought de~irable, for example having an opti-cal coverage less than 90~ and even less than 70S.
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The ability to use open fabric~ ha~ a number of advantages. First fabrication speeds are increa~ed~-since less fibres need to be interlinked per unit area o~ fabric. Also design flexibility i~ improved since it allows fabric designs to be used which inherently have an open structure (low optical coverage), for example WIWK (weft in~erted warp knittlng) and leno weave.
Also more open fabrics can achieve higher recovery ratios.
Preferably a fabric is used with heat reco~erable fibres such as polyolefin fibres in one of the warp and weft and heat stable fibres such as glass in the other of the warp and weft. Some embodiments of the inven~lon have less than 90, some less than 80, even less than 70 heat recoverable fibres per inch, and some embodiments have less than 12, even less than 8 heat stable fibres per inch.
A mentioned above the ability of an article to retain pressure depends also on the porosity or per-viousness to air of the article. Advantageously the strengthening layer comprise3 a material that is itself impervious to air, to improve the imperviousness of the article. Moi~t preferably, however, the fabric, like the ~abric in the prior art, has associated therewith means for rendering it subi~tantially impervious when reco-vered. Preferably the means for rendering the fabric, substantially impervious comprises a polymeric material which i9 adhered to at least one, preferably both sur-faces of the fabric, or is a polymeric matrix through which the fabric extends. Suitable materials are desoribed in European Patent Application No. 0116393 (MP0790).
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, Examples of suitable polymeric materials to render the fabric lmperviou~ include thermoplastic and ela~to-meric materials. Examples of thermoplastic material~
include: ethylene/vinyl acetate copolymer~, ethylene/ethylene acrylate copoly~er~, LLDPE, LDPE, MDPE, HDPE, polypropylene, polybutylene, polye9ters~
polyamides, polyetheramides, perfluoroethylene/ethylene copolymers, and polyvinylidene fluoride. The following i~ a list o~ preferred of preferred elastomeric materials: ABS block copolymer~, acrylic~ including acrylate~, methacrylate~ and their copolymers, high vinyl acetate copolymer~ with ethylene, polynorbornene, ~olyurethanes and ~ilicone ela3tomers.
Where a polymeric material is used to render the fabric 9ubstantially imperviou~, the polymeric material on the outslde of the tabric i9 preferably cross-linked to prevent it dripping or running during heat recovery, particularly during heat recovery by means of a torch.
Preferably the polymeric material on the inside of the article is not cross;linked, so it can flow on recovery to provide a bond to the ad~acent strengthening layer on recovery.
Preferred embodiments according to the invention comprise a recoverable fabric cover, a 3trengthening layer laminated to the surface of the fabric, and a layer of adhesive coating the surface of the strengthening layer facing away from the fabric.
Preferably the article is tubular or wraparound and the layers from the out~ide to inside are fabric (with - -polymer matrix of laminates if present), strengthening layer, adhesive. The adhesive is preferably heat acti-vatable, for example a hot melt adhe~ive, such as a polyamide or EVA. The heat activatable adhesive pre_ ,, , ~ .
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_ 9 _ ferably has3 a viscosity in the range of 40 - 150 pre_ ferably 60 - 80 Pa.3 at 160 C, and a flow temperature in the range 80 - 120C, preferably 95 - 110C. A
~3uitable polyamide adhesive, which is disclo3ed in UK
patent publication 2075991, contains up to 10S, pre-ferably up to 1~ of an acrylic rubber and has excel}ent adhesion to untreated polyethylene, and good low tem-perature flexibility. The activation temperature of the adhesive i~ preferably chosen to correspond to the s3ingle recovery temperature of the fabric, so that the single step of heating achieves both recovery and bonding. The adhesive need not extend over the entire urface of the fabric.
~ When a lining of adhesive i9 used the strengthening j layer i9 preferably sufficiently strong at the recovery ~ temperature of the fabric to prevent adhesive burst 3 through. The strengthening layer i9 preferably also impermeable to the passage of adhesive through its thickness. Thi3 means that when the fabric recovers the ~- adhesive stays on the inside of the article and the ~ activated adhesive cannot pas3s through the strengthening i layer into contact with the fabric. ~-~f` .-In the absence Or a strengthening layer adhe~ive 3`~ burst through is worse for open fabric de~igns because the mo're open de~igns have larger interstices through which the adhesive may burst. In the absence of a ~ -strengthening layer, adhesive burst_through may be a ~ problem even when the fabric is used in con~unction with `3,~ a polymeric matrix material, since at the recovery tem-'~ perature the polymeric material may soften and therefore -have a sufficiently low viscosity to be punctured by the adhesive as it bursts through the interstices of the , .!: ~ .
~ fabric. -, - , -, ,,~ .. . .
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~ o --The use of a strengthening layer that is strong enough to prevent adhesiYe burst_through, maintaini~g tke adhe~ive on its inner 3urface, therefore enable_ more open fabric de~igns to be used than had hitherto been thought desirable, without the risk of adhesive ''. burqt-through.
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Thus desirable pressure retention and adhe~ive burst-through resistance can be obtained u~ing more open fabrics than has hitherto been possible.
,, The strengthening layer can also be chosen 90 that it improve~ the barrier to moisture vapour transmission l (M~T~ of the ar~icle.
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In the prior art recoverable fabric articles a ; small amount o~ moisture vapour tran~mission (MVT) can occur through the thickness of the article even when the ~;~ fabric i3 used in conjunction with a polymeric matrix.
~I Thiq i3 because polymeric materials are inherently i slightly permeable to moisture. Also water moisture, or other liquid ingre~s into the article may occur 3 through the fibres themselves. This may be the case if the fabric used is one which inciudes fibres which can ~,,!~ themselves transmit water or moisture or other liquid along their length (for example glass), if the fabric ¢on~truction is such that a free end of a fibre i9 accessible to the ?iquid. In the~e case~ water may enter the interior of the tubular article, by entering ~ fir~t the free end of the fibre, then migrating along -~j the length of the fibre, from which it may then pass ~i into the interior of the article. Thi-q a particular ;, problem if the poIymeric material used in conJunction with the fabric is laminated to the outer ~urface only of the fabric, or even when laminated on both sides or : . .
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1, extending aQ a matrix through the fabric, when the internal ~urface of the polymeric material (lying within the fabric) 1~ damaged in some way allowing a pathway for liquid to pas~ to the interior of the sleeve.
Due to the pos~ibility of ~ome moi~ture ingre~
into the fabric articles of the prior art, for some applications it is usual to include silica gel packages within the articles to ab~orb that moisture.
Ac¢ording to the present invention a strengthening layer having a low (preferably sub~tantially zero) MVT
value may be used to improve the barrier to MVT of the article. ~ence recoverable fabric artlc~les ha~ing better I MVT properties than has hitherto been po~sible can be i made, and the need to include silca gel drying packed in article~ may be avoided. Where MVT value3 are quoted in this Specification they are measured at room tem-'i perature.
The article according to the invention has surpri-i singly been found to have improved creep performance as compared to comparative examples without a strengthening , layer. In general the amount of creep occuring for the -article with the ~trengthening layer is approximately half that of articles without a strengthening layer.
.1~ .
Preferred features of the strengthenlng layer, and a~sociated layers, which provide the advantages of the present invention will now be di~cus~ed. -~
Preferably the strengthening layer has a tensile strength of at least 10 MPa more preferably at least 13 MPa, e~pecially at ~east 16 MPa at 100C, and a tensile ~trength of at least 30 MPa at room temperature. The tensile strength is particularly important in improving t ~' '.
'~/ ' '' ,"
, ~ .
_ 12 -pres~qure retention, in preventing adhe~ive bur~t through, and alqo in improving creep performance.
The flow temperature of the qtrengthening layer compared to the recovery temperature of the fabric, and al30 the viqcosity of the strengthening layer at the recovery temperature are important parameters, par-ticularly where it is deqired to stop adhesive burst ! through. If the strengthening layer flows on recovery, or if the viscosity of the strengthening layer i8 too low at the recovery temperature, the strengthening layer may be punctured by the adhesive. Preferably the ~trengthening layer has a flow temperature which i9 at `! least 40C, more preferably at least 6~C higher than the recovery temperature of the fabric. Preferably the l strengthening layer has a melt ~low index which is substantially zero, measured at 190C under 2.16 Rg.
~ .
Preferably the strengthening layer compri~es a ' material that has a low MVT value, especially for ;~ applicationq where it i9 important to have low moisture -i vapour transmission from the exterior to iaterior of the article. Preferably the strengthening layer comprise~ a ~, material having an MVT value less than 1g/m2/day, more preferably less than 0.3g/m2/day.
~' While it is desirable that the ~trengthening layer ~, is strong, and have a high tensile 3trength, it must also be able to accommodate the configurational change of the article on recovery of the sleeve. Thi~ is pre-ferably achieved by making the strengthening layer 90 - that it can corrugate longitudinally, and preferably also uniformly on shrinkage of the fabric to accommodate -~ the configuration change of the article.
~3 One parameter which is considered important to determine the ability of the strengthening layer to ,'f '' !
. ~ .
accommodate changes in the configuration of the article by forming itself into corrugations is the stiffness-of the strengthening layer. The term stiffness i9 appli-cable to both homogeneous and heterogeneous material~
and where several layer~ are present is dependent on the inherent stiffnesq of the separate layers as well as their respective thickness. Stiffness measurements are I considered particularly relevant for the ~trengthening ; layer of the present invention since it is envisaged that multilayer strengthening layers could be used.
Preferred stiffness values were determined for the strengthening layer of the present invention using Jl British Standard ~es~ BS 2782 (Part 3 method 332A 197~).
The stiffness of the strengthening layer mea~ured according to this method is preferably less than 10 N/m, ' more preferably less than 6 N/m measured at room -~ temperature. At 100C the stiffness is preferably at most 6 N~m, more preferably at most 1.5 N/m.
.i :
The ~trengthening layer preferably corrugates on , recovery, preferably uniformly. Preferably the ^~-i strengthening layer is not pre~cored or pretreated in any other way to enhance the corrugation. Preferably the ~trengthening layer i such that the recovery forces exerted on it by the recovering fabric cause it to form corrugations having a height in the range of 1.0 to 1.3 mm, preferably about 1.16 mm, and a tip to tip diqtance of about 1 to 2.5 mm, preferably about 1.7 mm.
'I .
f According to the invention the ~trengtheing mem-! ber is laminated to the fabric. This includes the strengthening member being directly laminated to the fabric, and al~o the lamination being via an inter-mediate member. For example, where, aq i~ preferred, a .
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1328802 ~:
_ 14 -polymeric material i9 used in con~uction with the fabric to render it ~ub~tantially impervious, and that po1y- -meric material extends, or i9 laminated to the inner ~urface of the fabric, the ~trengthening layer may be bonded directly to that polymeric material, which in turn is bonded to the fabric.
Preferably the strengthening layer remain~ lami-nated to the fabria even after recovery that is no dis_ bonding which would cause an air gap between the fabric and the strengthening layer occurs. Disbonding is disadvantageous ~or a number of rea~ons. For exa~ple, the transfer of hoop ~tresses from the fabric to the strengthening layer i~ reduced, reducing the ability of the article to retain pressure, ingreq~ of water may occur, for example at the edges, adhesive bur~t through may occur for example at the edges, and where the strengthening layer corrugates on recovery, the corru8a-tion may be lnhomogeneous.
.~
In order that the strengthening layer remains lami-nated to the fabric before, during and after recovery, a layer of meltable material is preferably provided bet-ween the ~abric and the strengthening layer whlch is molten at the reaovery temperature of the fabric. This enables the strengthening layer to corrugate within the meltable material durlng recovery, and ensure~ that, after recovery, the meltable material has flowed to fill the trough~ in the corrugated ~trengthening member.
Thus there i8 no air gap between the fabric and the trengthening layer before, during or after recovery.
Preferably the meltable material has a melt flow index in the range 0.1 - 10, more preferably 4-7, mea~ured at 190C under 2.16 Kg. The meltable material may be, fGr -example, a copolymer. The melt flow index of the -, ' .
; :
; meltable material should not be 90 high that it can burc3-t through the interticeq of the 3fabric. Hence ~he preferred upper limit of 10.
Pre~erably the strengthening layer iq provided on both its maJor ~qurfaces with a meltable material, pre-ferably as defined above. ThuJ the strengthening layer corrugates in a matrix of meltable material. The pre_ sence of the meltable material on one, or preferably both sides of the strengthening layer enhance~3 the uni-~ormity of the corrugation of the strengthening layer.
The meltable material between the fabric and the strengthçning layer iq preferably select~d to form a good bond between thoqe layers. -The meltable layer between the fabric and the qtrengthening layer preferably has a thickness in the -~
range of 20-30 microns. The meltable layer on the sur-Pace of the ~trengthening layer facing away from the ~- fabric preferably has a thickneq~ in the range 20-30 ~ microns.
;3 ~ Particularly if the layer of meltable material bet--~ ween the strengthening layer and the fabric is too thick, and the melt flow index too high, the meltable layer may burst through the fabric.
The ability of the meltable material to flow to ~ill the space between the corrugated ~trengthening member and the fabric, and pre~erably the proviqion of a i meltable matrix on which the strengthening layer corru-~ gateY, i~ thought to be important in improving the creep ;1 characteristics of the article. In this respect it is noted that it is surprising that a corrugated member can, in fact, improve the creep resistance of the article.
,, . ' _ 16 -The ~trengthening layer may comprise a single layer or two or more layers of different materials. Where two or more layer~ are used each of the required properties of the strengthening layer may be provided by any one of i the layeri~ of by a combination of the layerS. For example where a layer having high tensile strength and low MVT value is required two layers together may be used, one having the required high tensile strength and j the other having the required low MVT value. The pre_ ferred tensile strength may be achieved, for example, using a layer of mylar or biaxially stretched nylon.
The preferred low MVT value may be achieved for example using a metal layer, for exa~ple aluminlum; Thu~ a pre-ferred strengthening layercomprises a layer of MylarlM or nylon bonded, on one or both sides, to a layer of metal 1 such as aluminium. The layer(s) of metal may be pro-1 vided, for example, in the form of a foil or as a very I thin metal deposited layer.
Where a support layer ~uch as mylar or nylon, and a metal foil layer are u~ed either layer may be nearest the fabric. Preferably the mylar or nylon is nearest the fabric to achieve the ~trongest bond between the fabric and the strengthening layer.
The overall thickness of the strengthenin~ layer i~
preferably in the range 5 to 100 microns, more preferbly in the range 7 to 35 microns. Where a metal layer or ` layers is used in combination with a support layer, the $ support layer preferably has a thickness in the range about 8-25 microns, for example about 12 - 15 microns.
Where the metal layer is provided as a foil it pre_ ferably has a thickness about 5-15 microns, for example about 9-12 microns. Where the metal is provided a~ a deposited layer or layers this preferably has a . ~ .
. - , _ 17 _ thickness o~ abouS 3-500 Ang~troms. Where a metal deposited layer i9 used, it i~ preferably provided on both sides of the support layer.
The construction of the fabric will now briefly be oonsidered, although it is envlsaged that any weave or knit or non-woven agglomeration of any fibreq may be used. For the pre~ent purpose~ the term weave i9 to include braids 9 ~ince the products are similar although t^ne methods of production are different. Recoverability is preferably provided by weaving or knitting fibres that are already recoverable. Alternatively it may be provided by deforming a fabric woven or knitted from dime~3ionalIy ~table fibres. EXamples of i~uitable reco-verable fabrics are described in European Patent Application No. 84300059.7 (MP0790).
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' Different effects, in term~ of for example, final ¦ reaovery ratio, strength and flexibility, will result from different types of weave or knit even if the same ~ fibres are u~ed. Example~ of type of weave include ji~ plain, twill, broken twill, herring bone satin, sateen, i~ leno, hop sack, sack, mat and combinations of these.
The weave may be single ply, or multiple ply weaves may be used. A particular advantage of the present inven-t tion i~ that high performance articles can be made from fabri~ of open-design, examples of such fabrics in¢luding WIWK, and leno weave.
~i The fibres used to produce the recoverable fabric ~i may be monofilament3, multifilament~, spun staple yarns or tapes. Examples of polymeric ~aterials that may be ! used for the recoverable fibres include polyolefinq, ~uch as polyethylene (e3pecialy HDPE) and polypropylene, polyamide~, polye~ter~ and fluoropolymers suoh a~ FEP, ~ 1 .
.~ - .
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,, " . , , . ~. ., ,., .. ., . . , . .. , . . ~ . . . -ethylene perfluoro copolymer, polyvinylidine fluoride and TFE copolymers. The recovery temperature, by which , we mean the temperature at which recovery will go substantially to completion, is pre~erably 60C or more, more preferably from 80-250C, most preferably from 120-150C.
A non-recoverable fibre may be used an a reinfor-cement or supplement to the recoverble fibre3, or may constitute the ma~or component in one or more dimensions ' of the fabric. The following non-recoverable materials may be regarded as illustrative: glassflbres, carbon ;- fibres, wires or other metal fibres, polye9ters, aroma-,3 'tiC polymers'such as'a'romatic polyamides' for e'xample j Kevlar (trade name), imides and ceramics.
'' The article according to the invention may be made in tubular form or wraparound form. Wraparound articles i are preferred ~ince they can be installed around ~-sub~trates having no free ends. This is particularly useful when a splice in a telephone cable is to be i enclosed after the repair of only a few of the many con-ductors it contains, since if the artiole is tubular, the entire cable has to be severed for installation.
Wraparound products are al90 useful where spaoe is ~ limited.
s Where a wraparound sleeve i3 used an elongate flap '~
may be provided beneath the longitudinal slit of the ~' sleeve to from the seal. Thls may be provided as a separate entity or attached to on side of the sleeve.
The flap preferably also includes a strengthening layer.
The technique3 by which the sleeve may be held in the wrapped configuration in any suitable way. Firstly, ~: .
-~ 9 a lap or other bond may be made between oppoising edgec of the ~heet, optionally with a patch to prevent peçl-back. In a qecond possibility, some meanq which penetrates the fabric may be uised, for example istitching, stapling, riveting, or pre-ini3erted catchei A third method of closure involves forming the edge~ of ; the slee~e in isiuch a way that they may be held together by isome form of clamping means, such as the C-shaped channel diqclosed in UK Patent No. 1155470, or by a reuseable tool.
Preferred forms of cloisiure for the article are dei3cribed in European Patent No. 0116391.
In a pa~tlcularly preferred embodiment the fabrl~ 1i3 J folded back on itsielf at each longitudinal edge to 1 accommodate rods, preferably nylon rods, running along J the length of the article. The rodis and overlying fabric are held together by the closure channel.
Where this type of cloisure is uisied the i3trengthening layer advantageously extends to the longi-i tudinal edgesi of the article and the channel grips the j strengthening layer with the fabric. Thi3 substan_ tially preventis the strengthening layer pulling out from ; the longitudinal edges of the article at the closiure.
l Also, the strengthening layer substantially preventsi j adhes~ve burst through in the rod region.
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; For many applications it is desirable to include a liner within the sleeve. The liner preferably hai3 a central region of larger cross-section, and end 3ections of ismall crosisi-section which provide tranisitions to the subistrate. The liner typically comprii3eiis tapered fingers at the endis which provide the transitions. The liner provideis support and mechanical rigidity to the .. ..
,, article. The use of a liner with a fabric is described, for example in European Patent Application No.
ô4300057.1 (RK169). The liner typically comprises a metal such as aluminium, for example in the form of half shells.
, Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:
Figure 1 i9 a perspective view of an article according to the invention.
Figure 2 iq cross_~ection through ~-A of Figure , Figure 3 is a cross-section through the article of Figure 1 and 2, after recovery ., .
Figure 4 is an enlarged view of part of the cro3s-section of Figure 3 ~ Figure 5 i8 an end view of another article - according to the invention.
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Figure 6 is an enlarged view of the clo~ure portion of the article of Figure 4.
Figure 7 is a schematic view showing part of a pre-ferred process for making an article according to the invention.
Figure 8 i~ a cross-sectional view of an apparatus used to te~t adhesive burst through of articles according to the invention and other .' ' .
i Figure 9 is a graph showing creep behaviour of ~; article according to the invention and others.
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132~802 Figure 1 qhows a wraparound article 2, according to the invention. Longitudinal edges 4 of the article are thickened and can be held together by a channel shaped closure 6. The article 2 comprise_ a laminate struc-turç. Thiq i~ ~hown in Figure 2 which is a croqs-section through A-A of the article of Figure 1. The structure compri~eq a fabric 8, which is a weave comprising high denqity polyethylene heat recoverable fibreq 1Q and heat stable glasq fibres 12. The reco-verable fibreq 10 are in the weft of the fabric and extend around the circumference of the article. The glas3 fibres 12 are in the warp and extend along the length of the article. The fabric recovers at a tem-perature of about 110-135 C. A layer of poly~eric material i9 laminated on both sides of the fabric. The outermost layer 14 (facing outwards of the article is cross-linked by irradiating it to a beam dose of 12 MRads. This restricts the tendency of layer 14 to flow during recovery. Inner layer 16 is uncross-linked.
This i~ explained later. Strengthening layer 18 is laminated to the inner surface of the inner laminate layer 16. On recovery polymeric layer 16 which i9 not cross-linked flows and enhances bonding to the strengthening layer 18. This is why it is not cross-linked.
Th~e strengthening layer 18 itself comprises two layers, which are respectively a layer of aluminium (20) and a support layer of mylar (22). To either side of these layers are bonded copolymer hot melt adhesive layers 24 and 26. Adhesive layer~ 24 bonds the strengthening layer lô to the inner laminate layer 16 both before and after recovery. Adhesive layer 26 bond~
the article to the underlying obJect after recovery~
Adhesive layers 24 and 26 have a flow temperature of ,, , ,, .
about 200 C. They also have a melt flow index of about 5 at 190C ~easured at 2.16 Kg. Thus at the recove-ry temperature of the fabric strengthening layer 18 buckles in layers 24 and 26, the adhesive layer 24 flowing to fill any gaps between the strengthening layer 18 and the fabric 8. A final layer of a Polyamide adhesive 25 i~
provided on the surface of adhesive layer 26. Thi3 i9 to bond the article 2 to the underlying ob~ect.
., Figureq 3 and 4 ~how the article after recovery onto an object such as a oable 27. The recoverable fibre~ 10 have shrunk pulling the glass fibre~ 12 cloqer together. The ~trengthening layer 18 has buckled or ~ corrugated to accommodate the reduction in size of the ,'! article. Adhesive layer 24 has flowed to fill the trough~ in the buckled or corrugated layer 18 so that the strengthening layer 18 remains laminated to fabric 8. Adhesive layers 26 and 25 have flowed to fill the gap between the strengthening layer 18 and cable 27 ~ Figures 5 and 6 show another wraparound article ! according to the invention. The material of the article f is the qame as that de~cribed in Figures 1 to 3, but the material at the longitudinal edges of the article is i~ wrapped around nylon rods 28 which extend along the ~ length of the sleeve. The strengthening layer 18 wraps '7~ with the fabric 8. Closure channel 6 is positioned over the rods and holds the longitudinal edges in close con-formity. A ~eparate flap 29 is used to seal the gap underneath the channel 6. Thi~ may instead be secured to one side of the wrapped article. This also contain3 strengthening layer 18.
., Figure 7 illustrates part of a preferred process for making an article according to the invention. Fir~t ~.
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`:'' ` ': '' . . .' . :` , , . ' ,' ~ ~ . : " `' :,: . ` ' ,- ' .... ` . , ;' ' : ' , : .
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a recoverable fabric i~ made, e.g. woven, from heat recoverable and optionally other fibres. The fabric i~
then preferably irradiated to cro~s_link it, then a layer of low den~ity polyethylene material laminated on one side. That fabric i~ preferably wound on roller~ 30 with the ~ingle polymeric laminate layer which wlll form the outer layer 14 of the article on the inner surface of the roller (i.e. facing the bottom of the diagram as it is drawn from the roller). This fabric is then fed ~l to another set of rollers 32 where a second layer of low density polyethylene is laminated on the other side of the fabric from a hopper This form~ the inner lami-, nate layer 16. Simultaneously the ~trengthening layer `'7 18 is laminated on top of the polymeric layer i6, being fed from roller~ 34. The lamination process is completed by rollers 36. Longitudinal edge~ of the fabric may be formed into the shape shown in Figure 3, a ~, flap secured if desired, then the article cut to length.
` -'1 - Examples Adhesive Burst Through Comparative tests were carried out to qhow the effect of a ~trengthening layer on adhesive burst through for a number of samples. A specific apparatus and te~t was devi~ed to measure tendency of the samples ~! to suffer adhesive burst through. The test is now explained with reference to Figure 8, and is carried out ~ as follows:
;~'7~ Test sample 42 is positioned between a silicone rubber membrane 44 of thickness 3 mm and a metallic ~ screen 46 having a penetration factor of 55S. An adhe--,~ sive sheet 48 of size 40 mm x 40 mm and thickness 0.5 -~' , ~ i ':'. ' "",",, .,,,S~ , ",1"~ "~ ""." ' 1.,". ~,'. ' .. ,,~ ,.. - : - , . . ., .. ., .. .,,, . ,. , ~, .. . . . . . . ... .
0.9 mm lie~ between the Qilicone rubber membrane 44 and the metallic screen 46. The above members are clamped between top and bottom aluminium plates 50 and 52 with the penetrable metal screen ad~acent to the top plate.
A viton 0-ring 5~ seals between the silicone rubber membrane 44 and the bottom plate 52. Top and bottom plate~ 50 and 52 contain equal sized circular apertures 56 and 58 which lie one above the other. Screws 60 con-nect plates 50 and 52, and these are tightened to secure members 42, 44, 46, 48 and 54 between them.
The circular aperture 56 and 58 in plates 50 and 52 are 50 mm in diameter. The top aperture 56 is exposed to the atmocphere. The bottom aperture 58 is in com-munication with a reservior which can be pressurised to test the sample. Pressurisation causes the silicone rubber member 44 to press against the adhesive tending to force it through the sample 42 and the metal screen 46.
The apparatus containing the test sample i~ placed in an oven and heat stabilised at 150C for one hour.
After stabilisation the pressure is increased by incre- -ment~ of 10 kPa until adhesive burst through i~
observed. This is recorded. The test is carried out at , 150C since this is about the temperature used for reco_ - very o'f typical reaoverable fabrics, and hence the tem-perature at which adhesive burst through would occur in ;~ practice.
.,~',~ ., ~. The test was carried out for a number of different fabric de~igns. Each fabric was provided with a poly-meric material to render it impervious. The polymeric material was provided as a laminate of low density polyethelene on both sides of the fabric. Each layer was 0.1 to 0.5 mm thick.
. ' ,' .
Examples 2, 3, 5, 7, 9 and 11 are comparative examples which do not use a strengthenlng layer.
Examples 1, 4, 6, 8 and 10 are articles according to the invention. Each include~ a strengthening layer which is a laminate with the following construction:
biaxial stretch nylon - thickness 15 microns (nearest the fabric) ~ . .
aluminium foil - thickness 12 microns (furthest from fabric) Also a layer of hot melt adhesive copolymer thicknes~ 35 microns i9 provided between the fabric anq the strengt~ening layer, and a layer of hot melt copo-lymer thickness 25 microns is provided on the surface of the strengthening layer ~acing away from the fabric.
! The total copolymer~nylon/aluminium~copolymer laminate .7 i8 that supplied by UCB under the trade name SidamilTM.
The strengthening layer used in examples 1,4, 6, 8 and 10 has an MFI value of substantially zero.
., . ~ .
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, , ,' '. -' '' ' ' ' ' ' '', : ' ' '' ' ' ', ~ ' ' '. '; " ."' ' '': '' '` ' ' , : . '-~328802 _ 26 -The requltq are set out in Table 1 below:
Table 1 EX NO MATERIAL FABRIC DESIGN LAMINATION STRENGTHENING PRESSURE TO
~ONSTRUCTION . LAYER CAUSE EURST
(See Key) THROUGH kPa 1 A WIWK one side yes 400 2 A WIWK both side~ no 85 3 A WIWK one ~ide no 50 4 B Twill 2 both sides ye~ 400 B Twill 2 both side3 no 210 6 B Broken Twill both side~ yes 400 i B Broken Twill b.oth sides no 205 .
8 B Satin 4 both sides yes 400 9 B Satin 4 both sides no 135 C Broken Twill both sides yes 400 11 ¦ ¦ ~ck~n ~wlll ¦ both 91dea ¦ o ¦ 7ZO
. ~
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Material Con~truction K~y A 4 bundles of 5 and 7 bundle~ of 4 heat recoverable high density polyethylene fibres = ~8 fibres per inch in weft and 6 glas~ f~breq per inch in warp.
B 18 bundles of 4 heat recoverable high density polyethylene fibreq = 72 heat recoverable fibres per inch in weft 9 glas~ fibres per inch in warp.
C. Fibrillated 16 inqertion~ of 2 flat embossed fibrillated heat recoverable high densith polyethy-; ~ene-fibreq per inch in the we~t, 9 glas~ fibres per inch in the warp The results clearly show that adhesive burst through is reduced significantly for all fabric types by including a strengthening layer. Much higher force~ are needed to cause burst through when a strengthening layer ~ i~ used.
; A second test wa~ carried out to ~how the effect of the melt flow index of the ~trengthening laye of the ability of the material to resist adhesive burst through.
In each case the fabric desi~n was design B a~
above. Each fabric was provided with a polymer material ~ to render it impervious. The polymeric material wa~
;~ provided as a laminate of low density polyethylene on both ~ides o~ the fabric. Each layer was 0.1 to 0.5 mm thick.
The results, as shown in Table 2 below, show that even when the strengthening layer has a very low melt :: .
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- 2~ -flow index, of the order of 0.3, the pre~qure to cause adhe~ive bur~t through i~ signi~icantly reduced, compared to the pre~sure required u~ing the SML layer of Example~ 1, 4, 6, 8 and 10 in which the strengthening layer ha~ an MFI value of sub~tantially zero.
For applications in whlch adhesive bur~t through is unacceptable the material~ of examples 12 - 15 are not preferred for the strengthening layer.
Table 2 EX N0 Material of Melt Flow Pre~ure to Strengthening layer Index cau~e adhe~ive bur~t through KPa 12Elvax 670TM 0.28 125 . (supplied by Dupont) 13DPD 6182 0.26 130 ~: .
'. (~upplied by Union Carbide) 14CxA 2002 6.67 100 ~, (supplied by Dupont) -~ 15Plexar 100TM 0.64 130 upplied by DSM) -,.1,~ "~ ' ' .
~. Creep behaviour ~
,. ~ .
A comparative test wa~ alqo carried out to deter- :-mine the tendency of articles with and without - ' -strengthening layer to creep. The fabric con~truction ,' used in each oase wa~ that of type ~B~ given above. -The following sample~ were used.
l, 16 Without a strengthening layer `, 17 With a strengthening layer of P~T/copolymer ,' coated on one ~ide with 9 micron aluminium '~ layer 18 As example 17 but with a 500- Angstrom ~`
thick aluminium layer in place of 9 mic,ron ~, thick layer i! The sa~ples were recovered, causing the ~, strengthening layer when present to or corrugate, and `~ then sub~ected to creep testing at 60C under an inter-nal pressure of 70 kPa for approximately one month. The ,' '~ results are set out in the graph (Figure 9).
It can be seen that the addition of the I strengthening layer significanntly reduce~ the creep of the article. For example the sample without a ~trengthening layer (Example 12 creep~ more than 14~ in ,, 30 days, while those with strengthening layers ,'~ creep less than 7b. The performance is thus about twice ,~ as good with a strengthening layer.
It is thought surprising that the presence of the strengthening layer can improve creep performance, even 1,~ though it is corrugated.
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Claims (19)
1. A method of making a heat-recoverable article which comprises: (a) providing a laminate, by adhering a polymeric material to at least one surface of a fabric or by providing a polymeric material through which the fabric extends; (b) providing recoverability by a method which comprises: (i) providing in step (a) a fabric from fibres that are recoverable, or (ii) deforming the fabric; (c) laminating a strengthening layer to the fabric directly or via an intermediate member, wherein said strengthening layer comprises a metal and has a moisture vapour transmission value of less than 1 g/m2/day.
2. A method according to claim 1, in which recoverability is provided by a method which comprises providing in step (a) a fabric from fibres that are recoverable.
3. A method according to claim 1, in which recoverability is provided by a method which comprises deforming the fabric.
4. A method according to claim 1, 2 or 3, in which the strengthening layer is laminated via a polymeric layer that is lamitated to the fabric.
5. A method according to claim 1, 2 or 3, in which a layer of polymeric material is laminated to each surface of the fabric.
6. A method according to claim 5, in which a layer of polymeric material is cross-linked and a layer of polymeric material is not cross-linked.
7. A method according to any one of the claims 1 to 3 or 6, in which the fabric includes fibres which can themselves transmit water or moisture or other liquid along their length.
8. A method according to any one of claims 1 to 3 or 6, in which the strengthening material is laminated via an intermediate member comprising a meltable material in which the stengthening material corrugates on recovery of the article.
9. A method according to any one of claims 1 to 3 or 6, in which the article comprises a wrap-around sleeve, the method additionally comprising forming edges of the sleeve in such a way that they may be held together by some form of clamping means.
10. A method according to claim 9, in which the fabric is folded back on itself at each longitudinal edge to accommodate rods.
11. A method according to claim 10, in which the stengthening layer extends to the longitudinal edges of the article such that a closure channel can grip the strengthening layer with the fabric.
12. A method according to any one of claims 1 to 3, 6, 10, or 11, in which non-recoverable fibre constitutes the major component in one or more dimensions of the fabric of the heat-recoverable article.
13. A method according to any one of claims 1 to 3, 6, 10 or 11, in which the fabric comprises a weave or knit or non-woven agglomeration of fibres.
14. A method according to any one of claims 1 to 3, 6, 10 or 11, in which fibres of the fabric comprise polyolefin fibres and glass fibres.
15. A method according to any one of claims 1 to 3, 6, 10 or 11, in which the fabric of the article has heat-recoverable fibres, and non-heat-recoverable fibres as a reinforcement or supplement to the heat-recoverable fibres.
16. A method according to any one of claims 1 to 3, 6, 10 or 11, in which the strengthening layer comprises a metal.
17. A method according to claim 16, in which the strengthening layer comprises a metal foil having a thickness of from 5 - 15 microns or a deposited metal having a thickness of 100 - 500 Angstroms.
18. A method according to any one of claims 1 to 3, 6, 10, 11 or 17, in which the strengthening layer has a tensile strength of at least 10 MPa at 100°C and/or a stiffness measured according to BS 2782 of less than 10 N/m at room temperature.
19. A method of protecting a cable splice which comprises:
(a) making a heat-recoverable article by a method according to any one of claims 1 to 3, 6, 10, 11 or 17, (b) enclosing the splice by means of the heat-recoverable article, (c) heating the article to cause it to recover.
(a) making a heat-recoverable article by a method according to any one of claims 1 to 3, 6, 10, 11 or 17, (b) enclosing the splice by means of the heat-recoverable article, (c) heating the article to cause it to recover.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000616170A CA1328802C (en) | 1986-10-20 | 1991-09-23 | Heat recoverable article |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB868625126A GB8625126D0 (en) | 1986-10-20 | 1986-10-20 | Heat recoverable article |
| GB8625126 | 1986-10-20 | ||
| CA000549561A CA1303952C (en) | 1986-10-20 | 1987-10-19 | Heat recoverable article |
| CA000616170A CA1328802C (en) | 1986-10-20 | 1991-09-23 | Heat recoverable article |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000549561A Division CA1303952C (en) | 1986-10-20 | 1987-10-19 | Heat recoverable article |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1328802C true CA1328802C (en) | 1994-04-26 |
Family
ID=25671557
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000616170A Expired - Lifetime CA1328802C (en) | 1986-10-20 | 1991-09-23 | Heat recoverable article |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1328802C (en) |
-
1991
- 1991-09-23 CA CA000616170A patent/CA1328802C/en not_active Expired - Lifetime
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |
Effective date: 20110426 |